Researcher Profile and Settings

Master

Affiliation (Master)

• Faculty of Engineering　Applied Chemistry　Chemical Engineering

Affiliation (Master)

• Faculty of Engineering　Applied Chemistry　Chemical Engineering

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Profile and Settings

Affiliation

• Hokkaido University, Graduate School of Engineering, Professor, Dr.

Profile and Settings

• Name (Japanese)

  Kikuchi

• Name (Kana)

  Ryuji

• Name

  200901081849939848

Alternate Names

https://cse-lab.eng.hokudai.ac.jp/
https://apchem.eng.hokudai.ac.jp/en/lab/chemical-system-engineering/

Affiliation

• Hokkaido University, Graduate School of Engineering, Professor, Dr.

Achievement

Research Interests

• CO2 utilization   Electrolytic synthesis   太陽電池   エネルギーシステム   環境触媒   触媒燃焼   燃料電池   

Research Areas

• Manufacturing technology (mechanical, electrical/electronic, chemical engineering) / Chemical reaction and process system engineering
• Nanotechnology/Materials / Energy chemistry
• Manufacturing technology (mechanical, electrical/electronic, chemical engineering) / Catalytic processes and resource chemistry
• Nanotechnology/Materials / Composite materials and interfaces
• Nanotechnology/Materials / Basic physical chemistry

Research Experience

• 2022/04 - Today 北海道大学大学院工学研究院 応用化学部門 教授
• 2008/04 - 2022/03 東京大学大学院工学系研究科 化学システム工学専攻 准教授
• 2007/04 - 2008/03 京都大学大学院工学研究科 物質エネルギー化学専攻 准教授
• 2003/12 - 2007/03 京都大学大学院工学研究科 物質エネルギー化学専攻 助教授
• 2001/10 - 2003/11 京都大学大学院工学研究科 物質エネルギー化学専攻 助手
• 2000/04 - 2001/09 Kyushu University Interdisciplinary Faculty of Engineering Sciences
• 1998/10 - 2000/03 東京大学大学院工学系研究科 化学システム工学専攻 博士研究員
• 1997/04 - 1998/09 スイス連邦工科大学チューリッヒ校 プロセス工学専攻 博士研究員

Education

• 1994/04 - 1997/03  The University of Tokyo
• 1992/04 - 1994/03  東京大学大学院工学系研究科化学エネルギー工学専攻
• 1990/04 - 1992/03  The University of Tokyo  The Faculty of Engineering
• 1988/04 - 1990/03  The University of Tokyo

Awards

• 2022/05 石油学会 論文賞 Y. Kobayashi, M. Sohmiya, S. Tada, R. Kikuchi, “Low-Temperature Synthesis of Single Phase Intermetallic NiZn Nanopowder in a Molten LiCl-KCl with a CaH2 as a Reducing Agent”, Journal of the Japan Petroleum Institute, 63(6), 380-387 (2020).
  
• 2015/09 化学工学会 論文賞
   R. Kikuchi, M. Yokoyama, S. Tada, A. Takagaki, T. Sugawara, S. T. Oyama, “Novel Nickel Catalysts based on spinel-type mixed oxides”, J. Chem. Eng. Japan, 47, 530-535 (2014)
• 2008/05 石油学会 奨励賞
   炭化水素の接触部分酸化ならびに固体酸化物形燃料電池アノード用複合酸化物触媒の開発
• 2008/03 触媒学会 奨励賞
   高耐熱性銅系スピネル触媒の調製に関する研究
• 1999 化学工学会 The Researcher賞
  

Published Papers

• Low-Temperature CO2 Methanation over Ru Nanoparticles Supported on Monoclinic Zirconia

  Shohei Tada, Tomona Jinushizono, Kenya Ishikawa, Shinta Miyazaki, Takashi Toyao, Ken-ichi Shimizu, Masahiko Nishijima, Noriko Yamauchi, Yoshio Kobayashi, Ryuji Kikuchi

  Energy & Fuels 2024/02/01
• High-pressure in situ X-ray absorption fine structure measurements for hydrogenation of CO₂ to methanol over Zn-doped ZrO₂

  Shohei Tada, Kazumasa Oshima, Tastuya Joutsuka, Masahiko Nishijima, Ryuji Kikuchi, Tetsuo Honma

  Catalysis Science & Technology 2044-4753 2024 

  During CO₂ hydrogenation under pressurised conditions, slight distortions were observed in the Zn structure. Our DFT calculations revealed that the adsorption of CO₂ at Zr⁴⁺ sites near Zn species can induce these structural distortions.
• Optimal mixing method of ZnZrO and MOR-type zeolite to prepare a bifunctional catalyst for CO2 hydrogenation to lower olefins

  Shohei Tada, Hiroka Kinoshita, Duanxing Li, Masahiko Nishijima, Harune Yamaguchi, Ryuji Kikcuhi, Noriko Yamauchi, Yoshio Kobayashi, Kenta Iyoki

  Advanced Powder Technology 2023/10
• Direct conversion of carbon dioxide and steam into hydrocarbons and oxygenates using solid acid electrolysis cells

  Naoya Fujiwara, Shohei Tada, Ryuji Kikuchi

  iScience 105381 - 105381 2589-0042 2022/11
• An in situ DRIFTS study on nitrogen electrochemical reduction over an Fe/BaZr_0.8Y_0.2O_3−δ-Ru catalyst at 220 °C in an electrolysis cell using a CsH₂PO₄/SiP₂O₇ electrolyte

  Yao Yuan, Naoya Fujiwara, Shohei Tada, Ryuji Kikuchi

  RSC Advances 12 (14) 8474 - 8476 2022 

  In situ DRIFTS measurements of an Fe/BZY-Ru cathode catalyst in an electrolysis cell using a CsH2PO4/SiP2O7 electrolyte were carried out in a mixed N-2-H-2 gas flow under polarization. The formation of N2Hx species was confirmed under polarization, and an associative mechanism in the electrochemical NRR process was verified.
• Electrochemically promoted ammonia synthesis on an Fe/BaZr_0.8Y_0.2O_3−δ catalyst at ambient pressure

  Yao Yuan, Shohei Tada, Ryuji Kikuchi

  Sustainable Energy & Fuels 6 (2) 458 - 465 2398-4902 2022 

  Electrochemically promoted nitrogen reduction on solid-state electrolytes is a promising approach for synthesising ammonia (NH3) under mild conditions. In this study, yttrium-doped barium zirconate (BZY) was chosen as a solid-state electrolyte owing to its high chemical stability and NH3 production on an Fe/BZY catalyst was investigated under open-circuit conditions and polarised conditions in a N-2-H-2 gas mixture at 500 degrees C and ambient pressure. NH3 production was enhanced under applied voltages, and the highest production rate of 3.07 x 10(-9) mol (s cm(2))(-1) was achieved under polarised conditions. The reaction rates were observed to change gradually as the reaction progressed, both in the open-circuit state and under applied voltages. This slow response of the NH3 production rate was modelled, and the electrochemical promotion of NH3 production was explained by the gradual removal of H adatoms from the catalyst and the resultant increase in N adsorption sites. The modelling result indicated that a higher ratio of adsorbed nitrogen atoms (N*) to adsorbed hydrogen atoms (H-s) contributed to accelerating the NH3 production rate.
• Hydrodeoxygenation of benzofuran on novel CoPdP catalysts supported on potassium ion exchanged ultra-stable Y-zeolites

  William J. Movick, Gwang-Nam Yun, Vibin Vargheese, Kyoko K. Bando, Ryuji Kikuchi, S. Ted Oyama

  Journal of Catalysis 403 160 - 172 0021-9517 2021/11
• Dimethyl Ether Steam Reforming Utilizing Cu-based Catalysts Derived from Mg_1–xCu_xAl₂O₄ and γ-Al₂O₃

  Shohei TADA, Fumito OTSUKA, Ryuji KIKUCHI

  Journal of the Japan Petroleum Institute 64 (5) 226 - 237 1346-8804 2021/09/01 

  Dimethyl ether (DME) steam reforming reaction is a sequential reaction of DME hydrolysis (catalyst: solid acid) followed by methanol steam reforming (catalyst: Cu-based catalyst). Combination of the catalysts can produce H-2 from DME and H2O in one pass. DME hydrolysis proceeds slowly at low temperatures, so the catalyst for DME steam reforming must be operated at relatively high temperatures (300-400 degrees C). Since this temperature range is higher than that of the typical methanol steam reforming reaction (200-300 degrees C), a methanol steam reforming catalyst must be developed to operate at 300 degrees C or higher, with high activity and durability. This study focused on spinel-type oxide MgAl2O4, which has a high surface area and high durability, and found a new catalyst precursor, Mg1-xCuxAl2O4. Spinel-type oxide-supported Cu catalyst was synthesized by reducing the catalyst precursor with H-2. The synthesized Cu catalyst combined with gamma-Al2O3, which is a solid acid catalyst, exhibited high DME steam reforming reaction activity. The optimum ratio of the Cu catalyst and gamma-Al2O3 was in the range of 1 to 2 by weight. This catalyst can be regenerated by calcining in air.
• Effect of Sm Doping on CO2-to-Methanol Hydrogenation of Cu/Amorphous-ZrO2 Catalysts

  Taihei Yamamura, Shohei Tada, Ryuji Kikuchi, Kakeru Fujiwara, Tetsuo Honma

  The Journal of Physical Chemistry C 125 (29) 15899 - 15909 1932-7447 2021/07/29 

  A series of 14 wt % Cu/Sm2O3/a-ZrO2 (a-: amorphous) catalysts for CO2-to-methanol hydrogenation were prepared by a coimpregnation method. When the Sm loading was 5-6 mol %, the CO2 conversion reached the maximum value (10.1% for 5 mol % catalyst and 9.4% for 6 mol % catalyst). In contrast, methanol selectivity decreased monotonically from 79% to 67% as the Sm loading increased from 0 to 7 mol %. Among the prepared catalysts, the 5-6 mol % Sm-doped Cu/a-ZrO2 catalyst exhibited the highest methanol production rate of 3.7 mmol g(cat)(-1) h(-1), which was ca. 20% greater than that with no Sm dopant (3.1 mmol g(cat)(-1) h(-1)), at 1.0 MPa and 230 degrees C with a space velocity = 6 L(STP) g(cat)(-1) h(-1). When we took into consideration the results of temperature-programmed reduction by H-2, X-ray diffraction, and X-ray photoelectron spectroscopy, doping Sm species into Cu/a-ZrO2 increased the number of surface-dispersed Cu2+, resulting in the high dispersion of Cu nanoparticles, as well as an increase in the number of the active sites (interfacial sites between Cu and a-ZrO2). Furthermore, according to the temperature-programmed desorption of CO2, Sm doping promoted CO2 adsorption on the catalysts and simultaneously activated CO,. The negative effect of Sm doping is a drop in methanol selectivity. In other words, it results in an improvement in methanol decomposition to CO. An excess amount of Sm led to Cu sintering. The main active sites (Cu-ZrO2 interface) are expected to be destroyed by sintering the Cu particles, in other words, losing the interaction between Cu and a-ZrO2. Therefore, since the above-mentioned positive effect and negative effect coexist, there is an optimum value for the amount of Sm doping.
• Promotion of Hydrogen Oxidation and Methane Dry Reforming Over Ni-SDC Anode by Basic Oxide Additives

  Ryuji Kikuchi, Tomohiro Mishina, Taro Kayamori, Naoya Fujiwara, Shohei Tada

  ECS Transactions 103 (1) 1615 - 1624 1938-5862 2021/07/09
• Low-temperature chemical synthesis of intermetallic TiFe nanoparticles for hydrogen absorption

  Yasukazu Kobayashi, Shohei Yamaoka, Shunta Yamaguchi, Nobuko Hanada, Shohei Tada, Ryuji Kikuchi

  International Journal of Hydrogen Energy 46 (43) 22611 - 22617 0360-3199 2021/06 

  Nanosizing of TiFe hydrogen storage alloy is conducted to facilitate its activation. Here, pure intermetallic TiFe nanoparticles (45 nm) were prepared using chemical reduction of oxide precursors at 600 °C, which is the lowest temperature ever used in chemical synthesis. This was achieved using a strong reducing agent (CaH2) in a molten LiCl. When used for hydrogen absorption, the obtained nanoparticles surprisingly exhibited almost no hydrogen absorption. The results demonstrated that TiFe nanoparticles are more difficult to activate than the bulk powder because the oxidized surface layers of the nanoparticles become stabilized, which prevents the morphological change necessary for their activation.
• Correction to What Are the Best Active Sites for CO₂ Methanation over Ni/CeO₂?

  Shohei Tada, Hironori Nagase, Naoya Fujiwara, Ryuji Kikuchi

  Energy & Fuels 35 (9) 8441 - 8441 0887-0624 2021/05/06
• What Are the Best Active Sites for CO2 Methanation over Ni/CeO2?

  Shohei Tada, Hironori Nagase, Naoya Fujiwara, Ryuji Kikuchi

  Energy & Fuels 35 (6) 5241 - 5251 2021/03/18
• How to scrutinize adsorbed intermediates observed by in situ spectroscopy: Analysis of Coverage Transients (ACT)

  S. Ted Oyama, Gwang-Nam Yun, So-Jin Ahn, Kyoko K. Bando, Atsushi Takagaki, Ryuji Kikuchi

  Journal of Catalysis 394 273 - 283 0021-9517 2021/02 

  The understanding of catalytic mechanisms is enhanced by the observation of surface intermediates at reaction conditions using spectroscopic techniques, but this is insufficient, as the observed species may not be involved in the reaction. This work describes a general method of analysis of hydrogenation or oxidation reactions which uses transient spectroscopic data to determine whether an adsorbed species is a reactive intermediate or a spectator on the surface. The assumptions and limitations of the method are summarized. Although the technique is approximate, it is easy to implement, and provides order-of-magnitude estimates of the rate of reaction of an intermediate. The method consists of measuring the change of coverage of the species with time, dθ/dt, during adsorption in inert gas or at reaction conditions. An example is given with the hydrodeoxygenation of the model compound γ-valerolactone (GVL) using a Ni2P/MCM-41 catalyst, one of the most effective catalysts reported for the transformation. The reaction is relevant to the upgrading of bio-oil derived from pyrolysis of lignocellulosic feedstocks. The kinetics of the reaction and observation by in situ infrared spectroscopy of adsorbed GVL and its transformation to pentanoic acid are consistent with a Langmuir-Hinshelwood mechanism. Analysis by in situ transient X-ray absorption fine structure shows that the adsorbed GVL is a true reaction intermediate.
• Hydrogen Production by Steam Electrolysis in Solid Acid Electrolysis Cells

  Naoya Fujiwara, Hironori Nagase, Shohei Tada, Ryuji Kikuchi

  ChemSusChem 14 (1) 417 - 427 2021/01/07
• Porous intermetallic Ni2XAl (X = Ti or Zr) nanoparticles prepared from oxide precursors

  Yasukazu Kobayashi, Shohei Tada, Ryuji Kikuchi

  Nanoscale Advances 2021
• Ammonia synthesis using Fe/BZY–RuO₂ catalysts and a caesium dihydrogen phosphate-based electrolyte at intermediate temperatures

  Yao Yuan, Shohei Tada, Ryuji Kikuchi

  Materials Advances 2 (2) 793 - 803 2021 

  In this study, we developed an Fe2O3/BZY (yttrium-doped barium zirconate)-RuO2 (Fe/BZY-RuO2) cathode catalyst, which was applied to the electrochemical synthesis of NH3 using a proton-conducting electrolyte, CsH2PO4/SiP2O7, at 220 degrees C and ambient pressure. The highest faradaic efficiency of 7.1% was achieved at -0.4 V (vs. open-circuit voltage (OCV)) and the highest NH3 yield rate of 4.5 x 10(-10) mol (s cm(2))(-1) was achieved at -1.5 V (vs. OCV). We also successfully detected N2H4 and NH3 at -0.2 V (vs. OCV), which indicated that the N-2 reduction proceeded via an associative mechanism. A potentiostatic pulse experiment was conducted under a feed of Ar or N-2 in the cathode at different applied voltages to investigate the N-2 reduction reaction (NRR) mechanism. A model was developed to fit the current response of the potentiostatic pulse experiment, which comprised the decomposition of adsorbed intermediates on the surface of the cathode catalyst, diffusion of H in the cathode catalyst, and an electrical double layer. The results revealed that the rate constant estimated by the model for the decomposition of intermediates, such as NH or N2H, was lowest at -0.2 V, where N2H4 was detected. The fitting results also indicated that the NRR proceeded via an associative mechanism at lower applied voltages, while a dissociative mechanism dominated at higher applied voltages.
• Development of CO2-to-Methanol Hydrogenation Catalyst by Focusing on the Coordination Structure of the Cu Species in Spinel-Type Oxide Mg1–xCuxAl2O4

  Shohei Tada, Fumito Otsuka, Kakeru Fujiwara, Constantinos Moularas, Yiannis Deligiannakis, Yuki Kinoshita, Sayaka Uchida, Tetsuo Honma, Masahiko Nishijima, Ryuji Kikuchi

  ACS Catalysis 10 (24) 15186 - 15194 2020/12/18
• Low-temperature Synthesis of Single Phase Intermetallic NiZn Bulk Nanopowder in Molten LiCl–KCl with CaH2 Reducing Agent

  Yasukazu KOBAYASHI, Minoru SOHMIYA, Shohei TADA, Ryuji KIKUCHI

  Journal of the Japan Petroleum Institute 63 (6) 380 - 387 1346-8804 2020/11/01
• Dimethyl ether synthesis from CO2-H2 mixture over Cu/amorphous-ZrO2 mixed with FER-type zeolite

  Kazumasa OSHIMA, Shiori NAKAJIMA, Shohei TADA, Ryuji KIKUCHI, Shigeo SATOKAWA

  Journal of the Japan Petroleum Institute 63 (6) 388 - 393 1346-8804 2020/11/01 

  Combinations of Cu-based catalysts and acidic zeolite were investigated for dimethyl ether (DME) production from a mixture of CO2 and H-2. The physical mixture of Cu/a-ZrO2 (a-: amorphous) catalyst and protonated FER-type zeolite produced a higher yield of DME than that of a Cu/ZnO/Al2O3 catalyst and FER-type zeolite at high pressure of 1.0 MPa. Cu/a-ZrO2 catalyst showed relatively low activity in terms of undesirable CO formation, and the FER-type zeolite combined with the Cu/a-ZrO2 catalyst had good activity for methanol dehydration, leading to the high yield of DME. DME selectivity over the combination catalyst of Cu/a-ZiO(2) and FER reached almost 40 %.
• Calcium-Modified Ni-SDC Anodes in Solid Oxide Fuel Cells for Direct Dry Reforming of Methane

  Tomohiro Mishina, Naoya Fujiwara, Shohei Tada, Atsushi Takagaki, Ryuji Kikuchi, Shigeo Ted Oyama

  Journal of The Electrochemical Society 167 (13) 0013-4651 2020/09/30 

  Direct internal reforming is one of the promising methods of utilizing hydrocarbon fuels in solid oxide fuel cells (SOFCs). Among direct internal reforming technologies, dry reforming of methane (DRM) is attracting attention as an alternative to steam reforming of methane. In this study, a cermet material composed of nickel and samarium-doped ceria (Ni-SDC) was investigated as an SOFC anode for the direct internal DRM operation. Compared to a conventional nickel-yttria-stabilized zirconia (Ni-YSZ) anode, the Ni-SDC anode showed superior current-voltage characteristics. However, poor carbon balances were recorded in anode outlet gas analysis, indicating coke formation on the Ni-SDC anode. The addition of calcium to the Ni-SDC anode was also tested. Measured anode outlet gas compositions suggested that the calcium addition suppressed coke formation, while the power generation performance of the pristine Ni-SDC anode was maintained. Microscopic observations showed that a certain part of the calcium additive existed as CaO particles on the anode surface, which could be responsible for the improved coking resistance.
• Effects of Porosity and Ni/Al Molar Ratio in Ni–Al Oxide Precursors on Porous Intermetallic Nickel Aluminide Nanopowders Prepared by Chemical Route

  Yasukazu Kobayashi, Shohei Tada, Ryuji Kikuchi

  JOURNAL OF CHEMICAL ENGINEERING OF JAPAN 53 (9) 562 - 568 0021-9592 2020/09/20
• Simple chemical synthesis of ternary intermetallic ReNi2Si2 (RE = y, La) nanoparticles in molten LiClCaH2 system

  Kobayashi, Y., Tada, S., Kikuchi, R.

  Materials Transactions 61 (5) 1037 - 1040 1345-9678 2020/05/01
• Synthesis of silica membranes by chemical vapor deposition using a dimethyldimethoxysilane precursor

  S. Ted Oyama, Haruki Aono, Atsushi Takagaki, Takashi Sugawara, Ryuji Kikuchi

  Membranes 10 (3) 2020/03 

  Silica-based membranes prepared by chemical vapor deposition of tetraethylorthosilicate (TEOS) on γ-alumina overlayers are known to be effective for hydrogen separation and are attractive for membrane reactor applications for hydrogen-producing reactions. In this study, the synthesis of the membranes was improved by simplifying the deposition of the intermediate γ-alumina layers and by using the precursor, dimethyldimethoxysilane (DMDMOS). In the placement of the γ-alumina layers, earlier work in our laboratory employed four to five dipping-calcining cycles of boehmite sol precursors to produce high H2 selectivities, but this took considerable time. In the present study, only two cycles were needed, even for a macro-porous support, through the use of finer boehmite precursor particle sizes. Using the simplified fabrication process, silica-alumina composite membranes with H2 permeance > 10−7 mol m−2 s−1 Pa−1 and H2 /N2 selectivity >100 were successfully synthesized. In addition, the use of the silica precursor, DMDMOS, further improved the H2 permeance without compromising the H2 /N2 selectivity. Pure DMDMOS membranes proved to be unstable against hydrothermal conditions, but the addition of aluminum tri-sec-butoxide (ATSB) improved the stability just like for conventional TEOS membranes.
• Flame spray pyrolysis makes highly loaded Cu nanoparticles on ZrO2 for CO2-to-methanol hydrogenation

  Tada, S., Fujiwara, K., Yamamura, T., Nishijima, M., Uchida, S., Kikuchi, R.

  Chemical Engineering Journal 381 122750 - 122750 2020/02
• Simple chemical synthesis of intermetallic Pt2Y bulk nanopowder

  Yasukazu Kobayashi, Shohei Tada, Ryuji Kikuchi

  Materials Advances 1 (7) 2202 - 2205 2020 

  Intermetallic Pt2Y bulk nanopowder (2.9 m² g⁻¹, 28 nm) was chemically synthesized with approachable common chemicals and facilities.

• Ru nanoparticles supported on amorphous ZrO2 for CO2 methanation

  Hironori Nagase, Rei Naito, Shohei Tada, Ryuji Kikuchi, Kakeru Fujiwara, Masahiko Nishijima, Tetsuo Honma

  Catalysis Science & Technology 10 (14) 4522 - 4531 2044-4753 2020 

  The influence of support materials and preparation methods on CO₂ methanation activity was investigated using Ru nanoparticles supported on amorphous ZrO₂ (am-ZrO₂), crystalline ZrO₂ (cr-ZrO₂), and SiO₂.

• Direct electrochemical synthesis of oxygenates from ethane using phosphate-based electrolysis cells

  Yusuke Honda, Naoya Fujiwara, Shohei Tada, Yasukazu Kobayashi, Shigeo Ted Oyama, Ryuji Kikuchi

  Chemical Communications 2020
• Mesoporous intermetallic NiAl nanocompound prepared in a molten LiCl using calcium species as templates

  Kobayashi, Y., Tada, S., Kikuchi, R.

  Chemistry Letters 49 (4) 2020
• Regeneration behavior of reforming catalysts based on perovskite oxides LaM0.95Rh0.05O3 (M: Cr, Co, Fe) by redox treatment

  Tada, S., Ono, T., Kikuchi, R.

  Fuel 269 2020
• Power-to-gas systems utilizing methanation reaction in solid oxide electrolysis cell cathodes: a model-based study

  Fujiwara, N., Tada, S., Kikuchi, R.

  Sustainable Energy and Fuels 4 (6) 2020
• Influences of particle size and crystallinity of highly loaded CuO/ZrO2 on CO2 hydrogenation to methanol

  Kakeru Fujiwara, Shohei Tada, Tetsuo Honma, Hiro Sasaki, Masahiko Nishijima, Ryuji Kikuchi

  AIChE Journal 65 (12) 0001-1541 2019/12
• Gas Separation Silica Membranes Prepared by Chemical Vapor Deposition of Methyl-Substituted Silanes

  Harumi Kato, Sean-Thomas B. Lundin, So-Jin Ahn, Atsushi Takagaki, Ryuji Kikuchi, S. Ted Oyama

  MEMBRANES 9 (11) 2019/11 [Refereed][Not invited]
   

  The effect on the gas permeance properties and structural morphology of the presence of methyl functional groups in a silica membrane was studied. Membranes were synthesized via chemical vapor deposition (CVD) at 650 degrees C and atmospheric pressure using three silicon compounds with differing numbers of methyl- and methoxy-functional groups: tetramethyl orthosilicate (TMOS), methyltrimethoxysilane (MTMOS), and dimethyldimethoxysilane (DMDMOS). The residence time of the silica precursors in the CVD process was adjusted for each precursor and optimized in terms of gas permeance and ideal gas selectivity criteria. Final H-2 permeances at 600 degrees C for the TMOS-, MTMOS-, and DMDMOS-derived membranes were respectively 1.7 x 10(-7), 2.4 x 10(-7), and 4.4 x 10(-8) mol center dot m(-2)center dot s(-1)center dot Pa-1 and H-2/N-2 selectivities were 990, 740, and 410. The presence of methyl groups in the membranes fabricated with the MTMOS and DMDMOS precursors was confirmed via Fourier-transform infrared (FTIR) spectroscopy. From FTIR analysis, an increasing methyl signal in the silica structure was correlated with both an improvement in the hydrothermal stability and an increase in the apparent activation energy for hydrogen permeation. In addition, the permeation mechanism for several gas species (He, H-2, Ne, CO2, N-2, and CH4) was determined by fitting the gas permeance temperature dependence to one of three models: solid state, gas-translational, or surface diffusion.
• Effects of Cu Precursor Types on the Catalytic Activity of Cu/ZrO₂ toward Methanol Synthesis via CO₂ Hydrogenation

  Shohei Tada, Kazumasa Oshima, Yoshihiro Noda, Ryuji Kikuchi, Minoru Sohmiya, Tetsuo Honma, Shigeo Satokawa

  Industrial & Engineering Chemistry Research 58 (42) 19434 - 19445 0888-5885 2019/10/23 

  This paper presents the influence of different types of copper precursors on CO2-to-methanol hydrogenation over copper nanoparticles on amorphous ZrO2. Here, we chose copper nitrate hydrate, copper acetate hydrate, and a copper ammine complex as the precursor. A copper-acetate-based catalyst, which was precalcined at 350 degrees C, was more active and selective toward methanol than were the other catalysts. Regardless of the different copper precursors, after calcining a mixture of a copper precursor and amorphous ZrO2 at 350 degrees C, surface-dispersed Cu2+ species ([CuO4] square planes) were partly formed on amorphous ZrO2. The Cu2+ species was reduced by H-2 to form Cu-0 nanoparticles (<5 nm). This paper reports that using copper acetate monohydrate as a copper precursor leads to the greater number of active sites (Cu-0-ZrO2 interfacial sites) compared with the other precursors.
• Fabrication and Evaluation of Trimethylmethoxysilane (TMMOS)-Derived Membranes for Gas Separation

  Yoshihiro Mise, So-Jin Ahn, Atsushi Takagaki, Ryuji Kikuchi, Shigeo Ted Oyama

  MEMBRANES 9 (10) 123  2019/10 [Refereed][Not invited]
   

  Gas separation membranes were fabricated with varying trimethylmethoxysilane (TMMOS)/tetraethoxy orthosilicate (TEOS) ratios by a chemical vapor deposition (CVD) method at 650 degrees C and atmospheric pressure. The membrane had a high H-2 permeance of 8.3 x 10(-7) mol m(-2) s(-1) Pa-1 with H-2/CH4 selectivity of 140 and H-2/C2H6 selectivity of 180 at 300 degrees C. Fourier transform infrared (FTIR) measurements indicated existence of methyl groups at high preparation temperature (650 degrees C), which led to a higher hydrothermal stability of the TMMOS-derived membranes than of a pure TEOS-derived membrane. Temperature-dependence measurements of the permeance of various gas species were used to establish a permeation mechanism. It was found that smaller species (He, H-2, and Ne) followed a solid-state diffusion model while larger species (N-2, CO2, and CH4) followed a gas translational diffusion model.
• High-performance anode for solid acid fuel cells prepared by mixing carbon substances with anode catalysts

  Tada, S., Tajima, S., Fujiwara, N., Kikuchi, R.

  International Journal of Hydrogen Energy 44 (48) 26545 - 26553 0360-3199 2019/10
• Novel SOFC Anodes Using Pyrochlore-Type Mixed Conducting Materials

  Ryuji Kikuchi, Tomohito Sasouzaki, Shohei Tada

  ECS Transactions 91 (1) 1881 - 1888 1938-6737 2019/07/10
• Hydrogen Oxidation Activity of SOFC Anodes with Metal Oxide Addition

  Naoya Fujiwara, Taro Kayamori, Tomohiro Mishina, Shohei Tada, Yasukazu Kobayashi, Ryuji Kikuchi

  ECS Transactions 91 (1) 1837 - 1844 1938-6737 2019/07/10
• Oxidative Coupling of Methane in Solid Oxide Electrolysis Cell

  Shu Kodama, Ryuji Kikuchi, Naoya Fujiwara, Shohei Tada, Yasukazu Kobayashi, Shigeo Ted Oyama

  ECS Transactions 91 (1) 2697 - 2705 1938-6737 2019/07/10
• Combined in Situ XAFS and FTIR Study of the Hydrodeoxygenation Reaction of 2-Methyltetrahydrofuran on Ni 2 P/SiO 2

  Iino, A., Takagaki, A., Kikuchi, R., Oyama, S.T., B, o, K.K.

  Journal of Physical Chemistry C 123 (13) 7633 - 7643 1932-7447 2019/04/04
• Infrared spectroscopic studies of the hydrodeoxygenation of γ-valerolactone on Ni2P/MCM-41

  Gwang-Nam Yun, So-Jin Ahn, Atsushi Takagaki, Ryuji Kikuchi, S. Ted Oyama

  Catalysis Today 323 54 - 61 0920-5861 2019/02 

  The hydrodeoxygenation (HDO) of the cyclic five-membered ester gamma-valerolactone (GVL) was studied on a Ni2P/MCM-41 catalyst. The activation of the passivated catalyst in H-2 was followed by in situ near-edge X-ray absorption spectroscopy (NEXAFS) which indicated reduction of the catalyst after 3 h at 550 degrees C. In situ infrared measurements under reactive H-2 and inert N-2 showed the presence of adsorbed GVL and pentanoic acid (PA) as the most abundant surface intermediates. The results supported a previous reaction network that showed that ring-opening of GVL to produce pentanoic acid was the rate-determining step. This was confirmed by transient infrared measurements which showed that the number of CH2 groups in the adsorbed species increased under H-2 flow, consistent with PA formation but not an alkoxide. The results provide understanding of the key steps in the reaction mechanism.
• Silica-supported chromia-titania catalysts for selective formation of lactic acid from a triose in water

  Atsushi Takagaki, Hiroshi Goto, Ryuji Kikuchi, S. Ted Oyama

  Applied Catalysis A: General 570 200 - 208 0926-860X 2019/01 

  A variety of silica-supported metal oxide catalysts were prepared by the incipient wetness impregnation method and were used for the conversion of dihydroxyacetone to lactic acid. A titanium oxide catalyst with Bronsted acid sites was selective to an intermediate, pyruvaldehyde and a chromium oxide catalyst with Lewis acid sites was selective to lactic acid. The co-impregnation of chromium- and titanium oxides with different ratios accelerated the reaction rate and improved the lactic acid yield up to 80% at 130 degrees C. Pyridine-adsorbed Fourier-transform infrared spectroscopy indicated that the silica-supported mixed oxides had both Bronsted acid and Lewis acid sites and the trend of the Lewis/Bronsted ratio was close to that of selectivity to lactic acid. Diffuse reflectance UV vis spectroscopy showed that the silica-supported chromia-titania catalyst composed of isolated Cr and Ti species in tetrahedral coordination. Kinetic analysis revealed that the two critical rate constants, pyruvaldehyde formation and lactic acid formation, for the chromia-titania catalyst were much higher than those of the titania and chromia catalysts.
• Effects of ball-milling treatment on physicochemical properties and solid base activity of hexagonal boron nitrides

  Shoichiro Namba, Atsushi Takagaki, Keiko Jimura, Shigenobu Hayashi, Ryuji Kikuchi, S. Ted Oyama

  Catalysis Science & Technology 9 (2) 302 - 309 2044-4753 2019 

  Hexagonal boron nitride solid base catalysts were prepared by simple ball-milling at various rotation speeds of a commercial low-surface area boron nitride.

• Low Ni-Containing Cermet Anodes of Solid Oxide Fuel Cells with Size-Controlled Samarium-Doped Ceria Particles

  Naoya Fujiwara, Tatsushi Minami, Ryuji Kikuchi, Atsushi Takagaki, Takashi Sugawara, Shohei Tada, Shigeo Ted Oyama

  Journal of The Electrochemical Society 166 (12) F716 - F723 0013-4651 2019
• Oxidative dehydrogenation of ethane using ball-milled hexagonal boron nitride

  Honda, Y., Takagaki, A., Kikuchi, R., Oyama, S.T.

  Chemistry Letters 47 (9) 1090 - 1093 0366-7022 2018/09/05
• Effects of pressure, contact time, permeance, and selectivity in membrane reactors: The case of the dehydrogenation of ethane

  Ahn, S.-J., Yun, G.-N., Takagaki, A., Kikuchi, R., Oyama, S.T.

  Separation and Purification Technology 194 197 - 206 1383-5866 2018/04
• Synthesis and characterization of a silica-alumina composite membrane and its application in a membrane reactor

  Naoki Kageyama, Atsushi Takagaki, Takashi Sugawara, Ryuji Kikuchi, S. Ted Oyama

  SEPARATION AND PURIFICATION TECHNOLOGY 195 437 - 445 1383-5866 2018/04 

  Hydrothermally stable silica-alumina composite membranes were synthesized through chemical vapor deposition (CVD) of tetraethylorthosilicate (TEOS) and aluminium tri-sec-butoxide precursor at 923 K on porous alumina supports. The membranes showed high hydrogen permselectivity (order of 10(-7) mol m(-2) s(-1)Pa(-1)) comparable to that of pure silica membranes but with superior hydrothermal stability, and were used in a membrane reactor. The permeation of small gas species (H-2, He, Ne) was well explained by a solid-state diffusion mechanism, involving jumps of the permeating species between solubility sites. The permeation mechanism of large gas molecules (CH4, CO2, N-2) was explained by the gas translation mechanism involving large pore defects. Steam methane reforming (SMR) on a Ni/MgO-SiO2 catalyst was carried out at 923 K in the membrane reactor and in a conventional packed-bed reactor. The membrane contributed to an increase in the hydrogen production rate by the selective extraction of hydrogen from the reaction zone.
• Mechanochemical Decomposition of Crystalline Cellulose in the Presence of Protonated Layered Niobium Molybdate Solid Acid Catalyst

  Furusato, S., Takagaki, A., Hayashi, S., Miyazato, A., Kikuchi, R., Oyama, S.T.

  ChemSusChem 11 (5) 888 - 896 1864-5631 2018/03/09
• Synthesis and characterization of hydrogen selective silica membranes prepared by chemical vapor deposition of vinyltriethoxysilane

  So-Jin Ahn, Gwang-Nam Yun, Atsushi Takagaki, Ryuji Kikuchi, S. Ted Oyama

  JOURNAL OF MEMBRANE SCIENCE 550 1 - 8 0376-7388 2018/03 

  Hydrogen-selective silica membranes were prepared on a macroporous alumina support by chemical vapor deposition (CVD) of vinyltriethoxysilane (VTES) at 873 K at atmospheric pressure. The membrane had a high H-2 permeance of 5.4 x 10(-7) mol m(-2) s(-1) Pa-1 with H-2 selectivity over CO2, N-2, CO and CH4 of 95, 170, 170 and 480, respectively. In situ Fourier transform infrared (FTIR) measurements after CVD on an alumina disk at the same conditions as for the membrane preparation showed that the vinyl groups remained in the silica structure. The VTES-derived membrane had higher hydrothermal stability than a pure tetraethoxyorthosilicate (TEOS)-derived silica membrane, during exposure to 16 mol% water vapor at 872 K for 72 h. The temperature dependence of the permeance of various molecules (He, Ne, H-2, CO2, N-2, CO, CH4) before and after hydrothermal treatment gave information about the mechanism of permeance and the structure of the membrane. The membrane was composed of a contiguous silica network through which small species permeated by a solid-state mechanism and a small number of pores through which the large molecules diffused. The silica-based structure became more compact after hydrothermal treatment with decreasing permeance of small molecules (He, Ne, H-2), while small pores were enlarged increasing permeance of large molecules (CO2, N-2, CO, CH4). Calculation results for the small species based on a mechanism involving jumps of the permeating species between solubility sites showed lower activation energy and larger jump distances than those of a TEOS-derived silica membrane. The retention of the vinyl groups in the structure mostly associated with the defect pores resulted in interactions with CH4 and CO2, so that these species permeated by a surface diffusion mechanism.
• Development of Solid Oxide Electrolysis Cell Cathodes for Direct Methanation in CO₂/H₂O Co-electrolysis

  Naoya Fujiwara, Ryuji Kikuchi, Atsushi Takagaki, S. Ted Oyama

  Grand Renewable Energy Proceedings 225 - 228 2018 [Not refereed][Not invited]
  
• Preface to the special issue for the 5th Asian conference on innovative energy & environmental chemical engineering (ASCON-IEEChE) 2016

  Kameyama, H., Kikuchi, R., Hirao, M., Sakurai, M., Fushimi, C., Qian, E., Tsuru, T., Kai, T.

  Journal of Chemical Engineering of Japan 51 (9) 711 - 711 2018
• Utilization of hexagonal boron nitride as a solid acid–base bifunctional catalyst

  Shusaku Torii, Keiko Jimura, Shigenobu Hayashi, Ryuji Kikuchi, Atsushi Takagaki

  Journal of Catalysis 355 176 - 184 0021-9517 2017/11 

  This work explores the use of hexagonal boron nitride (h-BN), a graphite-like compound, as a novel catalyst with base and acid functionalities. For use as a solid catalyst, the layered structure of h-BN was disrupted by ball-milling, exposing boron and nitrogen edge sites as well as increasing the surface area from 3 to ca. 400 m(2) g(-1). Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and proton magic-angle spinning nuclear magnetic resonance spectroscopy (H-1 MAS NMR) indicated simultaneous and adjacent formation of amino and hydroxyl groups by milling, which function as Bronsted base and acid sites, respectively. Analysis using color indicator reagents and pyrrole-adsorbed H-1 MAS NMR results revealed that the ball-milled h-BN had basic sites of strength +9.3 > H_ >= +7.2, comparable to those of KY zeolite. Measurements of P-31 MAS NMR of adsorbed trimethylphosphine oxide indicated that the ball-milled h-BN had weak acid sites, comparable to those in HY zeolite. Despite its weak basicity, the ball-milled h-BN showed high activity and selectivity toward beta-nitroalkenes for the nitroaldol reaction (Henry reaction) and the Knoevenagel condensation, whereas nontreated h-BN did not show activity. The nitroaldol reaction was considered to proceed in two steps: the abstraction of a proton from nitro methane by the amino group and the formation of an imine followed by a nucleophilic attack of the deprotonated nitromethane. Kinetic isotope effect experiments using (D)-substituted nitromethane revealed that the first step was the rate-determining step. Several nitroaldol reactions using a variety of monosubstituted benzaldehydes indicated that electron-donating groups enhanced the activity, suggesting that the formation of adjacent base and acid sites is responsible for it. This study shows the high catalytic activity of BN, a solid catalyst with moderate basicity and weak acidity. (C) 2017 Elsevier Inc. All rights reserved.
• Hydrogenation of 2,5-dimethylfuran on hexagonal-boron nitride- and silica-supported platinum catalysts

  Hiroshi Goto, Atsushi Takagaki, Ryuji Kikuchi, S. Ted Oyama

  APPLIED CATALYSIS A-GENERAL 548 122 - 127 0926-860X 2017/11 

  Hydrogenation of furanic compounds is one of the important reactions for upgrading of bio-oils and production of diesel fuels. Platinum catalysts supported on amorphous silica and hexagonal boron nitride (h-BN) were prepared by incipient wetness impregnation and subsequent reduction, and were used for the vapor-phase hydrogenation of 2,5-dimethylfuran in hydrogen at atmospheric pressure and a temperature range of 150-350 degrees C. For the same amount of Pt loading (1 wt%), the particle size of Pt supported on h-BN was larger than that on silica, resulting in a lower amount of CO chemisorption for Pt/BN than that for Pt/SiO2. Using the same amount of active sites, Pt/BN exhibited a 3-fold higher turnover frequency than Pt/SiO2 for the hydrogenation of 2,5-dimethylfuran whereas both catalysts gave similar product distributions with high selectivity to 2-hexanone at any conversion and low selectivity to n-hexane at high conversion. Contact time studies of 2,5-dimethylfuran hydrogenation on Pt/BN suggested that 2,5-dimethylfuran formed the ring-opening product, 2-hexanone and the ring-saturation product, 2,5-dimethyltetrahydrofuran in parallel, with the rate of the direct furan ring-opening being 9-fold higher than that of the furan ring-saturation.
• Comparison of phosphide catalysts prepared by temperature-programmed reduction and liquid-phase methods in the hydrodeoxygenation of 2-methylfuran

  Jianwen Zhang, Kazuki Matsubara, Gwang-Nam Yun, Huidong Zheng, Atsushi Takagaki, Ryuji Kikuchi, S. Ted Oyama

  APPLIED CATALYSIS A-GENERAL 548 39 - 46 0926-860X 2017/11 

  Two types of Ni2P/SiO2 were prepared by different methods, a conventional method involving temperature programmed reduction (TPR) and a liquid-phase synthesis (LP). Both methods resulted in phase-pure materials with the Ni2P hexagonal phase, but the sample prepared by TPR had lower particle size (7 nm) than the sample prepared by LP synthesis (25 nm). The samples were tested in the gas-phase hydrodeoxygenation of 2-methyl-furan (2-MF) in H-2 at 0.5 MPa and 250-450 degrees C, and it was found that the Ni2P/SiO2-TPR gave higher conversions and turnover frequencies than the Ni2P/SiO2-LP. It was conjectured that the difference in activity was due to the higher phosphorus content of the sample prepared by TPR, and this was confirmed by measurements of the P/Ni ratio by x-ray photoelectron spectroscopy. The main products formed by the two catalysts were 2-pentanone and n-pentane and small amounts of 1-pentanol and 2-pentanol. Contact time measurements on the Ni2P/SiO2-TPR sample indicated that 2-pentanone was a primary product, the pentanols were intermediary compounds, and the n-pentane was a final product. Kinetic measurements on the Ni2P/SiO2-LP revealed orders of 0.6 for the 2-MF and 0.5 for H2, consistent with adsorption of both reactants on the catalyst and a surface reaction between the adsorbed species. TPR was also employed to prepare a Cu3P/SiO2 sample. Although a phase-pure material was formed, the substance showed very low activity for the HDO of 2-MF.
• Ammonia synthesis at intermediate temperatures in solid-state electrochemical cells using cesium hydrogen phosphate based electrolytes and noble metal catalysts

  Shota Kishira, Geletu Qing, Shuya Suzu, Ryuji Kikuchi, Atsushi Takagaki, Shigeo Ted Oyama

  International Journal of Hydrogen Energy 42 (43) 26843 - 26854 0360-3199 2017/10
• Overcoming pressure drop losses in membrane reactors by semi-batch operation

  Kageyama, N., Hacarlioglu, P., Takagaki, A., Kikuchi, R., Oyama, S.T.

  Separation and Purification Technology 185 175 - 185 1383-5866 2017/09
• Hydrodeoxygenation of γ-valerolactone on bimetallic NiMo phosphide catalysts

  Gwang-Nam Yun, So-Jin Ahn, Atsushi Takagaki, Ryuji Kikuchi, S. Ted Oyama

  Journal of Catalysis 353 141 - 151 0021-9517 2017/09 

  A series of supported Ni-Mo-P alloy catalysts was studied for the catalytic hydrodeoxygenation (HDO) of the cyclic five-membered ester gamma-valerolactone (GVL-C5H8O2) as a model compound for pyrolysis oil. Alloy formation in Ni-Mo-P was indicated by X-ray diffraction analysis and X-ray absorption near-edge spectroscopy, which showed systematic shifts with composition. The number of active sites of each metal species was estimated by factor analysis combining CO-uptake measurements and infrared (IR) spectra of adsorbed CO. It was found that the catalytic activity followed the order: Ni2P/MCM-41 > NiMo(3:1)P/MCM-41 > NiMo(1:1)P/MCM-41 congruent to (Ni2P + MoP)/MCM-41 > NiMo (1:3)P/MCM-41 > MoP/MCM-41, whereas the normalized turnover frequency based on Ni sites were similar for all the catalysts, while retaining the same order. It is concluded that adjacent surface Ni atoms are the main active sites involved in the rate-determining step (rds). The Mo-containing catalysts produced more 1-pentanol and C5 hydrocarbons than Ni2P/MCM-41, indicating that while the exposed Ni sites governed catalytic activity, Mo sites controlled the selectivity to C5 hydrocarbons. Thus, steps following the rds were influenced by Mo sites, leading to preferences for different reaction pathway during the HDO of gamma-valerolactone. The study reveals that the catalytic behavior of NiMoP catalysts can be tuned by the relative proportion of Ni and Mo sites. (C) 2017 Elsevier Inc. All rights reserved.
• CsH5(PO4)2/quartz fiber thin membranes for intermediate temperature fuel cells and electrochemical synthesis of ammonia

  Qing, G., Sukegawa, K., Kikuchi, R., Takagaki, A., Oyama, S.T.

  Journal of Applied Electrochemistry 47 (7) 803 - 814 0021-891X 2017/07
• Properties of Yttrium-Doped Barium Zirconate (BZY)-Hematite Mixed Ionic-Electronic Conductor

  Yao Yuan, Ryuji Kikuchi, Atsushi Takagaki, Shigeo Ted Oyama

  ECS Transactions 78 (1) 451 - 459 1938-6737 2017/05/30
• Ni-SDC Based Cermets for Direct Dry Reforming of Methane on SOFC Anode

  Tomohiro Mishina, Kazuyuki Miya, Ryuji Kikuchi, Takashi Sugawara, Atsushi Takagaki, Shigeo Ted Oyama

  ECS Transactions 78 (1) 1161 - 1167 1938-6737 2017/05/30
• Investigation of Solid Oxide Electrolysis Cell Electrodes for Methane Synthesis

  Naoya Fujiwara, Ryuji Kikuchi, Atsushi Takagaki, Takashi Sugawara, Shigeo Ted Oyama

  ECS Transactions 78 (1) 3247 - 3256 1938-6737 2017/05/30
• Gas Diffusion Electrode with Large Amounts of Gas Diffusion Channel Using Hydrophobic Carbon Fiber: For Oxygen Reduction Reaction at Gas/Liquid Interfaces

  Tada, S., Privatananupunt, P., Iwasaki, T., Kikuchi, R.

  Journal of Electrochemical Energy Conversion and Storage 14 (2) 2381-6872 2017/05/01 

  For a gas diffusion cathode for oxygen reduction reaction (ORR) in aqueous alkaline electrolyte, it is important to create networks for O2 gas diffusion, electronic conduction, and liquid-phase OH− transport in the cathode at once. In this study, we succeeded to fabricate a promising cathode using hydrophobic vapor grown carbon fibers (VGCF-Xs), instead of hydrophobic carbon blacks (CBs), as additives to its active layer (AL). Mercury porosimetry, as well as electrochemical impedance spectroscopy, showed that porosity of the cathode gradually increased with increasing the amount of the carbon fibers. In other words, addition of larger amount of the carbon fibers creates better O2 gas diffusion channels. Also, the activation polarization resistance for the ORR increased as the carbon fibers' amount from 0 to 0.03–0.04 g and then dropped. In consequence, the cathode with 0.03 g of the carbon fibers exhibited the highest ORR performance among the prepared cathodes.
• Permeation properties of silica-zirconia composite membranes supported on porous alumina substrates

  Ahn, S.-J., Takagaki, A., Sugawara, T., Kikuchi, R., Oyama, S.T.

  Journal of Membrane Science 526 409 - 416 0376-7388 2017/03
• P-37 Hydrodeoxygenation of gamma valerolactone (GVL) on transition metal phosphides

  Yun Gwang-Nam, Ahn So-Jin, Takagaki Atsushi, Kikuchi Ryuji, Oyama S. Ted

  Proceedings of the Conference on Biomass Science 一般社団法人 日本エネルギー学会 12 123 - 124 2017 

  The catalytic hydrodeoxygenation (HDO) of the cyclic five-membered ester gamma-valerolactone (GVL-C5H8O2) on a series of supported metal phosphide and bimetallic phosphide catalysts was studied at 0.5 MPa. Comparison of activities was based on turnover frequencies calculated from surface metal atoms determined from the chemisorption of CO at 50 °C. It was found that catalytic activity followed the order: Ni₂P/MCM-41 >> CoP/MCM-41 >> Pd/Al₂O₃ ≈ MoP/MCM-41 > WP/MCM-41 in mono metallic phosphide catalyst and Ni₂P/MCM-41 > NiMo(3:1)P/MCM-41 > NiMo(1:1)P/MCM-41 > NiMo(1:3)P/MCM-41 > MoP/MCM-41 in bimetallic phosphide catalysts. On all catalysts ring opening of the lactone to produce pentanoic acid was the main initial step with subsequent hydrogenation to form pentanal. On Ni₂P/MCM-41, CoP/MCM-41 and Pd/Al₂O₃ this was followed mainly by decarbonylation to produce CO and saturated C4 hydrocarbons. On MoP/MCM-41 and WP/MCM-41 the principal subsequent step was deoxygenation to produce unsaturated C5 hydrocarbons. The bimetallic phosphide catalysts presented performance as pure compounds depending on the metal ratio, but slightly enhanced production of C5 hydrocarbons. A possible reaction network is proposed based on product selectivity.

• Hydrodeoxygenation of gamma-valerolactone on transition metal phosphide catalysts

  Gwang-Nam Yun, Atsushi Takagaki, Ryuji Kikuchi, S. Ted Oyama

  Catalysis Science & Technology 7 (1) 281 - 292 2044-4753 2017 

  The catalytic hydrodeoxygenation (HDO) of the cyclic five-membered ester gamma-valerolactone (GVL-C₅H₈O₂) on a series of supported metal phosphide catalysts and a commercial Pd/Al₂O₃ catalyst was studied at 0.5 MPa.

• Supported fluorocarbon liquid membranes for hydrogen/oxygen separation

  Taichiro Yamaguchi, Atsushi Takagaki, Takashi Sugawara, Ryuji Kikuchi, S. Ted Oyama

  JOURNAL OF MEMBRANE SCIENCE 520 272 - 280 0376-7388 2016/12 

  Photocatalytic water splitting is an environmentally-friendly method for hydrogen formation, but usually H-2 and O-2, are produced together, so separation is needed. This paper describes the separation of the gases with supported liquid membranes. The permselective liquids were various perfluorocarbon-based fluids, Dimethyl perfluorosebacate ((CF2)(6)(COOCH3)(2)), ethyl perfluorononanoate (CF3(CF2)(7)COOC2H5), perfluoro(perhydrophenanthrene) (C14P24) and 1H,1H,2H,2H-perfluorodecyl acrylate (CF3(CF2)(7)(CH2)(2)OCOCH=CH2). It was found that the perfluorodecyl acrylate-based liquid membrane showed the highest performance with H-2 permeance of 2.4 x 10(-9) mol m(-2) s(-1) Pa-1 (6700 barrers) and a H-2/O-2 selectivity of 10. The permeance properties of H-2 and O-2 were measured by a time-lag technique and respective diffusivities of 1.1 x 10(-9) and 6.7 x 10(-9) m(2) s(-1) and solubilities of 2.7 x 10(-4) and 4.1 x 10(-5) mol m(-3) Pa-1, were obtained. The lifetime of the membrane was over 48 h, which was much longer than that of other perfluorocarbon-based liquid membranes. The membrane was also stable at humid conditions. (C) 2016 Elsevier B.V. All rights reserved.
• Kinetic and Infrared Spectroscopy Study of Hydrodeoxygenation of 2-Methyltetrahydrofuran on a Nickel Phosphide Catalyst at Atmospheric Pressure

  Bui, Phuong, Takagaki, Atsushi, Kikuchi, Ryuji, Oyama, S. Ted

  Acs Catalysis 6 (11) 7701 - 7709 2155-5435 2016/11/04
• Steam Reforming of Dimethyl Ether over Composite Catalysts of Supported Transition Metal Oxides and Cu/ZnO/Al₂O₃

  Fumito OTSUKA, Shohei TADA, Ryuji KIKUCHI

  Journal of the Japan Petroleum Institute 公益社団法人 石油学会 59 (6) 293 - 298 1346-8804 2016/11/01 

  Several supported transition metal oxides (X/Y, X＝WO₃, Nb₂O₅, Y＝Al₂O₃, TiO₂, SiO₂) were investigated as solid acid catalysts for hydrolysis of dimethyl ether (DME). Among the transition metal oxide catalysts tested, Nb₂O₅/Al₂O₃ showed the highest catalytic activity in the temperature range appropriate for DME steam reforming. Using several types of Nb₂O₅/Al₂O₃ samples, the effects of Nb₂O₅ loading amounts and calcination temperature on the catalytic activity were studied to enhance the hydrolysis activity. XRD patterns showed AlNbO₄ phase appeared when the calcination temperature was over 800 °C. The BET surface area decreased for the increase in the calcination temperature. For Nb₂O₅/Al₂O₃, the acid amount increased consistently with the Nb₂O₅ loading amounts up to 25 wt%, and it became almost constant for the further increase in the Nb₂O₅ loadings. 25 wt% Nb₂O₅/Al₂O₃ catalyst calcined at 500 °C exhibited the highest catalytic activity for DME hydrolysis, and consequently steam reforming of DME was carried out over the Nb₂O₅/Al₂O₃ mixed with Cu/ZnO/Al₂O₃. It was found that an optimal ratio of Cu/ZnO/Al₂O₃ to Nb₂O₅/Al₂O₃ was 1, which resulted in higher catalytic activity for steam reforming of DME than a mixture of Cu/ZnO/Al₂O₃ and γ-Al₂O₃.

• Metal Phosphide-Based Novel Anodes for Intermediate Temperature Fuel Cells

  Ryuji Kikuchi, Takahiro Ataku, Atsushi Takagaki, Shigeo Ted Oyama

  ECS Transactions 75 (14) 931 - 937 1938-5862 2016/08/22 

  In this study, metal phosphides such as Ni₂P, CoP, FeP, WP, and MoP were investigated as novel anode catalysts for intermediate temperature fuel cells. Composite electrolytes composed of CsH₂PO₄ and SiP₂O₇, the metal phosphates, and a commercial Pt/C electrode were used as the electrolyte, anode, and cathode, respectively, and power generation characteristics were evaluated at 220ºC as H₂-O₂ fuel cells. The anode performance was compared based on the electrochemical surface area of each anode determined by cyclic voltammetry. Among the phosphide anodes, the MoP catalyst exhibited excellent current-voltage characteristics, and demonstrated a potential as an anode catalyst superior to the Pt/C catalyst.
• Interfacial interaction and melting point depression of CsH5(PO4)(2) in CsH5(PO4)(2)/SiO2 composites

  Qing, Geletu, Kikuchi, Ryuji

  Solid State Ionics 289 133 - 142 0167-2738 2016/06
• Effect of contact time, reaction temperature, and reactant pressure on reaction sequences: The case of guaiacol hydrodeoxygenation on Ni phosphide catalysts

  Shigeo Oyama, Pengfei Yang, Atsushi Takagaki, Ryuji Kikuchi

  ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 251 0065-7727 2016/03 [Refereed][Not invited]
  
• Interfacial conduction mechanism of cesium hydrogen phosphate and silicon pyrophosphate composite electrolytes for intermediate-temperature fuel cells

  Kikuchi, Ryuji, Ogawa, Akari, Matsuoka, Takuya, Takagaki, Atsushi, Sugawara, Takashi, Oyama, S. Ted

  Solid State Ionics 285 160 - 164 0167-2738 2016/02
• Stability of CsH5(PO4)(2)-based composites at fixed temperatures and during heating-cooling cycles for solid-state intermediate temperature fuel cells

  Geletu Qing, Ryuji Kikuchi, Atsushi Takagaki, Takashi Sugawara, Shigeo Ted Oyama

  JOURNAL OF POWER SOURCES 306 578 - 586 0378-7753 2016/02 

  This work reports the stability of CsH5(PO4)(2)-based composites at fixed temperatures (158 degrees C and 210 degrees C) and during three heating cooling cycles (106 degrees C -> 158 degrees C -> 106 degrees C). Composites of CsH5(PO4)(2) and SiO2 prepared by pressing the corresponding powders were stable at fixed temperatures, but were not stable during repeated heating and cooling due to the structural damage or existence of CsH5(PO4)(2) particles that were not highly dispersed in the silica matrix. Composites of CsH5(PO4)(2) and SiP2O7 absorbed a large amount of water into the electrolyte inner phase and formed a paste. The absorbed water had a significant influence on the electrolyte conductivity. Doped glasses of CsH5(PO4)(2), which had an interconnected silica matrix with 5-12 nm pores filled with CsH5(PO4)(2), exhibited stable conductivity both at fixed temperatures and during three heating-cooling cycles. From these findings, it was concluded that matrices with both strong interfacial interaction with CsH5(PO4)(2) and interconnected structure were important to the preparation of CsH5(PO4)(2)-based composites with high stability. (C) 2015 Elsevier B.V. All rights reserved.
• Steam Reforming of Dimethyl Ether over Composite Catalysts of Supported Transition Metal Oxides and Cu/ZnO/Al2O3

  Otsuka, Fumito, Tada, Shohei, Kikuchi, Ryuji

  Journal of the Japan Petroleum Institute 59 (6) 2016
• Methane synthesis in solid oxide electrolysis cells - study on cathode materials

  Fujiwara Naoya, Kikuchi Ryuji, Takagaki Atsushi, Oyama S. Ted

  Proceeding of Annual/Fall Meetings of the Japan Petroleum Institute 公益社団法人 石油学会 2016 13 - 13 2016 

  再生可能エネルギーを用いた水と二酸化炭素からのメタン合成は、間欠的な再生可能エネルギーの貯蔵法や、化石燃料に頼らない燃料の合成法として注目されている。本研究では、固体酸化物形電解セルを用いたメタン合成に着目し、カソード材料の検討を行った。ニッケルをイットリア安定化ジルコニアやサマリウム添加セリアに担持させた電極や、活性の向上を期待してこれらの材料に貴金属を添加した電極の性能について、報告する。
• Anode materials for direct dry reforming of methane on SOFC anode

  Mishina Tomohiro, Miya Kazuyuki, Takagaki Atsushi, Oyama Shigeo Ted, Kikuchi Ryuji

  Proceeding of Annual/Fall Meetings of the Japan Petroleum Institute 公益社団法人 石油学会 2016 14 - 14 2016 

  
  
• 2-1-2 Nickel catalysts supported on mixed ionic and electronic conductive materials for CO₂ reforming of methane

  KIKUCHI Ryuji, SEKI Shiori, TAKAGAKI Atsushi, OYAMA S. Ted

  Proceedings of the Annual Conference of The Japan Institute of Energy 一般社団法人 日本エネルギー学会 25 24 - 25 2016 

  Solid Oxide Fuel Cells (SOFC) operating at high temperatures are one of the most efficient electrochemical devices for power generation. For the efficient recovery of exhaust heat from SOFC stacks, external steam reforming of hydrocarbon fuels such as methane is generally employed in commercial SOFC systems. In this study, dry reforming reaction (DR) is proposed as the external reforming because it does not need steam generators and enables to use carbon dioxide as reactant in the anode gas. Supported Ni catalysts have been investigated by using several support materials of different oxygen ion conductivity and basicity. Among the prepared catalysts, Ni/La_0.3Sr_0.7TiO_3-δ (LST) was found to exhibit excellent activity for DR. In order to improve the catalytic activity and tolerance to carbon deposition, post treatment and basic additives were examined for Ni/LST.

• Upgrading of pyrolysis bio-oil using nickel phosphide catalysts

  Koike, Natsume, Hosokai, Sou, Takagaki, Atsushi, Nishimura, Shun, Kikuchi, Ryuji, Ebitani, Kohki, Suzuki, Yoshizo, Oyama, S. Ted

  Journal of Catalysis 333 115 - 126 0021-9517 2016/01
• Ammonia synthesis by N2 and steam electrolysis in solid-state cells at 220°C and atmospheric pressure

  Qing, G., Kikuchi, R., Kishira, S., Takagaki, A., Sugawara, T., Oyama, S.T.

  Journal of the Electrochemical Society 163 (10) E282 - E287 0013-4651 2016
• Efficient Epimerization of Aldoses Using Layered Niobium Molybdates

  Atsushi Takagaki, Shogo Furusato, Ryuji Kikuchi, S. Ted Oyama

  ChemSusChem 8 (22) 3769 - 3772 1864-5631 2015/11 

  Both non-acidic LiNbMoO6 and strongly acidic HNbMoO6 efficiently catalyze the epimerization of sugars including glucose, mannose, xylose, and arabinose in water. The reactions over these oxides reached almost equilibrium within a few hours where yields of corresponding epimers from glucose, xylose, and arabinose were 24-29%. The layered mixed oxides functioned as heterogeneous catalysts and could be reused without loss of activity, whereas bulk molybdenum oxide MoO3 was completely dissolved during the reaction. A C-13 substitution experiment showed that the reaction proceeds through a 1,2-rearrangement mechanism. The surface Mo octahedra were responsible for the activity. The layered HNbMoO6 could also afford mannose from cellobiose through hydrolysis and successive epimerization.
• Role of trace chlorine in Ni/TiO2 catalyst for CO selective methanation in reforrnate gas

  Shimoda, Naohiro, Shoji, Daiki, Tani, Kazunori, Fujiwara, Masashi, Urasaki, Kohei, Kikuchi, Ryuji, Satokawa, Shigeo

  Applied Catalysis B-Environmental 174 486 - 495 0926-3373 2015/09
• Kinetic and spectroscopic studies of catalytic mechanisms: Hydrodeoxygenation of biomass feedstocks on transition metal phosphides

  Shigeo Oyama, Ayako Iino, Jieun Shin, Phoung Bui, Atsushi Takagaki, Ryuji Kikuchi, Kyoko Bando

  ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 250 0065-7727 2015/08 [Refereed][Not invited]
  
• CsH2PO4/Epoxy Composite Electrolytes for Intermediate Temperature Fuel Cells

  Qing, G., Kikuchi, R., Takagaki, A., Sugawara, T., Oyama, S.T.

  Electrochimica Acta 169 219 - 226 0013-4686 2015/07
• Low Ni-Containing Anodes Using Titanate-Based Perovskites for Methane Direct Internal Reforming Power Generation

  Ryuji Kikuchi, Daisuke Minori, Atsushi Takagaki, Takashi Sugawara, Shigeo Ted Oyama

  ECS Transactions 68 (1) 1489 - 1498 1938-5862 2015/06/02 

  In this study titanate-based perovskite anodes containing Ni such as Ni-La_xSr_1-xTiO₃ (LST) have been investigated as anodes for direct internal reforming solid oxide fuel cells, which directly utilize hydrocarbons as fuels in the anode. Catalytic activity tests of Ni-titanate cermets were carried out in methane steam reforming, and Ni-LST exhibited comparable activity to Ni-YSZ (yttria-stabilized zirconia). It was found that moderate power generation performance was observed over Ni-LST prepared by the impregnation method when the Ni content was decreased to 10 wt%, whereas almost no current was attained over Ni-YSZ for the decrease in the Ni content. The 10 wt%Ni-LST anode prepared by the impregnation method exhibited stable power generation characteristics in severe direct internal reforming operation at steam-to-carbon ratio of 0.1 at 1000 ºC under a constant current load of 200 mA cm^-2.
• Mixed matrix membranes using SAPO-34/polyetherimide for carbon dioxide/methane separation

  Messaoud, Souha Belhaj, Takagaki, Atsushi, Sugawara, Takashi, Kikuchi, Ryuji, Oyama, S. Ted

  Separation and Purification Technology 148 38 - 48 1383-5866 2015/06
• The optimal point within the Robeson upper boundary

  Castro-Dominguez, Bernardo, Leelachaikul, Pornravee, Messaoud, Souha Belhaj, Takagaki, Atsushi, Sugawara, Takashi, Kikuchi, Ryuji, Oyama, S. Ted

  Chemical Engineering Research & Design 97 109 - 119 0263-8762 2015/05
• Active Sites in Ni2P/USY Catalysts for the Hydrodeoxygenation of 2-Methyltetrahydrofuran

  Cho, Ara, Takagaki, Atsushi, Kikuchi, Ryuji, Oyama, S. Ted

  Topics in Catalysis 58 (4-6) 219 - 231 1022-5528 2015/04
• Production of Phenol and Cresol from Guaiacol on Nickel Phosphide Catalysts Supported on Acidic Supports

  Oyama, S. Ted, Onkawa, Tatsuki, Takagaki, Atsushi, Kikuchi, Ryuji, Hosokai, Sou, Suzuki, Yoshizo, B, o, Kyoko K.

  Topics in Catalysis 58 (4-6) 201 - 210 1022-5528 2015/04
• Alkylamine-silica hybrid membranes for carbon dioxide/methane separation

  Messaoud, Souha Belhaj, Takagaki, Atsushi, Sugawara, Takashi, Kikuchi, Ryuji, Oyama, S. Ted

  Journal of Membrane Science 477 161 - 171 0376-7388 2015/03
• Study on solid oxide fuel cell anodes for direct CO2 reforming power generation

  Kikuchi Ryuji, Miya Kazuyuki, Takagaki Atsushi, Sugawara Takashi, Oyama S. Ted

  Proceeding of Annual/Fall Meetings of the Japan Petroleum Institute 公益社団法人 石油学会 2015 138 - 138 2015 

  固体酸化物形燃料電池は高温作動のため、燃料極上で直接炭化水素を直接改質し、電池反応における発熱を化学エネルギーに変換し、発電効率を高めることが可能である。これまでは主に水蒸気改質について検討が行われてきたが、本研究では直接ドライリフォーミング可能な燃料極材料について検討した結果を報告する。
• Mechanistic study and catalyst development for selective carbon monoxide methanation

  Tada, S., Kikuchi, R.

  Catalysis Science & Technology 5 (6) 3061 - 3070 2044-4753 2015 

  As for selective CO methanation over heterogeneous catalysts, numerous investigations of the reaction mechanism and catalyst development are reviewed.

• CsH5(PO4)(2) doped glass membranes for intermediate temperature fuel cells

  Qing, Geletu, Kikuchi, Ryuji, Takagaki, Atsushi, Sugawara, Takashi, Oyama, Shigeo Ted

  Journal of Power Sources 272 1018 - 1029 0378-7753 2014/12
• Development of inorganic-organic hybrid membranes for carbon dioxide/methane separation

  Shunsuke Suzuki, Souha Belhaj Messaoud, Atsushi Takagaki, Takashi Sugawara, Ryuji Kikuchi, S. Ted Oyama

  JOURNAL OF MEMBRANE SCIENCE 471 402 - 411 0376-7388 2014/12 

  Membrane separation processes are attractive for the removal of carbon dioxide from natural gas since they consume less energy than conventional methods such as amine absorption and pressure swing adsorption. In this work inorganic-organic hybrid membranes were prepared employing chemical vapor deposition (CVD) of tetraethylorthosilicate (TEOS) and 3-aminopropyltriethoxysilane (APTES) as silica and amino-silica precursors. They were deposited on the surface of a porous alumina support at high temperature using oxygen as a co-reagent. The objective was to enhance the permeance of CO2 by placing amine groups on the surface of the membrane. The APTES/(TE0S+APTES) ratio R was varied from 0% to 10000 in order to find an optimum composition for the separation of the CO2 from CH4. The best membrane was found to have a ratio R of 20% with a CO2 permeance of 2.3 x 10(-7) mol m(-2) s(-1) Pa-1 and an ideal CO2/CH4 selectivity of 40 at 393 K and 0.10 MPa of partial pressure difference.The transport mechanism for CO2 permeation was surface diffusion and for CH4 passage was gastranslation. The pore size of the membrane was evaluated by Tsuru`s method revealing a pore size of 0.44 nm. The results are significant because the permeance level is above that necessary for commercial use, the selectivity is adequate to produce a pipeline quality natural gas (purity > 2.4%), and the permeating gas is CO2 which allows retention of methane at high pressure. (C) 2014 Elsevier B.V. All rights reserved.
• Long-term durability of Ni/TiO2 and Ru-Ni/TiO2 catalysts for selective CO methanation

  Tada, Shohei, Kikuchi, Ryuji, Wada, Katsuya, Osada, Kazuo, Akiyama, Kazuya, Satokawa, Shigeo, Kawashima, Yoshimi

  Journal of Power Sources 264 59 - 66 0378-7753 2014/10
• Effect of metal addition to Ru/Ti02 catalyst on selective CO methanation

  Tada, Shohei, Kikuchi, Ryuji, Takagaki, Atsushi, Sugawara, Takashi, Oyama, S. Ted, Satokawa, Shigeo

  Catalysis Today 232 16 - 21 0920-5861 2014/09
• Kinetic and spectroscopic studies of catalytic mechanisms: Hydrodeoxygenation of biomass feedstocks on transition metal phosphides

  Ted S. Oyama, Ayako Iino, Jeun Shin, Phuong Bui, Ara Cho, Atsushi Takagaki, Ryuji Kikuchi, Kyoko K. Bando

  ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 248 0065-7727 2014/08 [Refereed][Not invited]
  
• Decomposition of crystalline cellulose by ball-milling in the presence of layered niobium molybdate solid acid

  Atsushi Takagaki, Shogo Furusato, Shigenobu Hayashi, Ryuji Kikuchi, S. Ted Oyama

  ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 248 0065-7727 2014/08
• Effect of Ru and Ni ratio on selective CO methanation over Ru-Ni/TiO 2

  Tada, S., Minori, D., Otsuka, F., Kikuchi, R., Osada, K., Akiyama, K., Satokawa, S.

  Fuel 129 219 - 224 0016-2361 2014/08
• Novel Nickel Catalysts Based on Spinel-Type Mixed Oxides for Methane and Propane Steam Reforming

  Ryuji Kikuchi, Misato Yokoyama, Shohei Tada, Atsushi Takagaki, Takashi Sugawara, S. Ted Oyama

  JOURNAL OF CHEMICAL ENGINEERING OF JAPAN 47 (7) 530 - 535 0021-9592 2014/07 

  Novel nickel catalysts based on magnesium aluminate spinel-type mixed oxides are developed as hydrocarbon reforming catalysts for hydrogen supply to polymer electrolyte fuel cells. The spinel catalysts were prepared by co-precipitation and the Pechini method, and the spinels prepared by the former method exhibited higher activity for methane steam reforming. The effect of spinel composition, Mg1-xNixAl2O4 (x = 0.17, 0.35, 0.50, 0.70, 1) was investigated on the activity and resistance to carbon deposition in steam reforming reaction. The turnover frequency for methane steam reforming at a steam-to-carbon (S/C) ratio of 2 increased with increase in the x value from 0.17 to 0.35, and then gradually decreased with further increase in the nickel content. The carbon deposition tolerance of the spinel catalysts was examined in propane steam reforming at S/C = 1 and 600 degrees C. The propane conversion during the reaction was ca. 98% over all catalysts tested, and the amount of deposited carbon, determined as carbon dioxide by temperature programmed oxidation, was least at x = 0.17, which is 1/8 of that deposited on a conventional Ni/gamma-Al2O3 catalyst. The spinels with x <= 0.5 exhibited smaller amounts of carbon deposition, and thus superior tolerance to deactivation.
• Promotion of CO2 methanation activity and CH4 selectivity at low temperatures over Ru/CeO2/Al2O3 catalysts

  Tada, Shohei, Ochieng, Ochieng James, Kikuchi, Ryuji, Haneda, Takahide, Kameyama, Hiromichi

  International Journal of Hydrogen Energy 39 (19) 10090 - 10100 0360-3199 2014/06
• Kinetic studies of hydrodeoxygenation of 2-methyltetrahydrofuran on a Ni2P/SiO2 catalyst at medium pressure

  Iino, Ayako, Cho, Ara, Takagaki, Atsushi, Kikuchi, Ryuji, Oyama, S. Ted

  Journal of Catalysis 311 17 - 27 0021-9517 2014/03
• Intercalation-Controlled Cyclodehydration of Sorbitol in Water over Layered- Niobium- Molybdate Solid Acid

  Morita, Yuya, Furusato, Shogo, Takagaki, Atsushi, Hayashi, Shigenobu, Kikuchi, Ryuji, Oyama, S. Ted

  Chemsuschem 7 (3) 748 - 752 1864-5631 2014/03
• Perfluorooctanol-based liquid membranes for H-2/O-2 separation

  Leelachaikul, Pornravee, Castro-Dominguez, Bernardo, Takagaki, Atsushi, Sugawara, Takashi, Kikuchi, Ryuji, Oyama, S. Ted

  Separation and Purification Technology 122 431 - 439 1383-5866 2014/02
• P-36 Development of the pretreatment method for cellulose saccharification by milling with solid acid catalysts

  FURUSATO Shogo, TAKAGAKI Atsushi, KIKUCHI Ryuji, OYAMA S. Ted

  Proceedings of the Conference on Biomass Science 一般社団法人日本エネルギー学会 9 124 - 125 2014 

  Scission of β-1,4-glycosidic linkage in cellulose was promoted under solvent-free ball milling mixing with a layered metal oxide, HNbMoO_6. 72% yields of water-soluble sugars were obtained after ball milling for 24 hours. Most of the resultant water-soluble sugars were produced not via successive degradation of oligosaccharides but via direct decomposition of cellulose long chains. Selectivity of monosaccharide, glucose was improved by powerful milling using stainless reactor. Addition of a small amount of solvent such as water and DMSO afforded the highest yield, and addition of water decreased formation of anhydrosugars in contrast to addition of DMSO.
• P-04 Hydrodeoxygenation of Model Compounds of Pyrolysis Oil by using Base Metal Phosphide Catalysts

  TAKAGAKI Atsushi, IINO Ayako, ONKAWA Tatsuki, KOIKE Natsume, KIKUCHI Ryuji, OYAMA S. Ted

  Proceedings of the Conference on Biomass Science 一般社団法人日本エネルギー学会 9 60 - 61 2014 

  The crude bio-oil contains a high proportion of oxygen and for their effective use hydrodeoxygenation (HDO) is required. Base metal phosphides such as Ni_2P and CoP exhibited remarkable activity for HDO of pyrolysis model compounds, 2-methyltetrahydrofuran (2MTHF) and guaicol. Ni_2P/SiO_2 catalyst could deoxygenate 2MTHF and guaiacol into corresponding compounds, n-pentane and benzene. Kinetics indicate 2MTHF and hydrogen are competitively adsorbed on surface via Langmuir-Hinshelwood mechanism. The presence of water vapor did not affect the performance of the catalyst. Furthermore, the 2MTHF HDO activity of Ni_2P/SiO_2 remained unchanged for 30 h reaction.
• 3-8-1 Mechanochemical Decomposition of Cellulose by Layered Metal Oxide Solid Acid

  TAKAGAKI Atsushi, FURUSATO Shogo, KIKUCHI Ryuji, OYAMA S.Ted

  Proceedings of the Annual Conference of The Japan Institute of Energy 一般社団法人日本エネルギー学会 23 120 - 121 2014 

  An efficient decomposition of cellulose has been demonstrated by mechanochemical reaction. The ball-milling of microcrystalline cellulose in the presence of a layered metal oxide, HNbMoO6 afforded 72% yield of water-soluble sugars including cello-oligomers and their anhydro-sugars whereas that in the absence of the catalyst gave negligible yield (1%). The addition of a slight amount of water improves product yields and decreases selectivity for anhydro-sugars.
• 2-1-2 Acid catalysts for hydrogen production via steam reforming of dimethyl ether

  KIKUCHI Ryuji, OTSUKA Fumito, TADA Shohei, TAKAGAKI Atsushi, SUGAWARA Takashi, S. Ted OYAMA

  Proceedings of the Annual Conference of The Japan Institute of Energy 一般社団法人日本エネルギー学会 23 34 - 35 2014 

  Acid catalysts with moderate acidity based on Nb_2O_5/Al_2O_3 have been developed for dimethyl ether (DME) hydrolysis as a first step of steam reforming of DME. The activity for DME hydrolysis was enhanced as the loading of Nb_2O_5 on Al_2O_3 as well as the acid amount of Nb_2O_5/Al_2O_3 was increased. Physical mixture of Nb_2O_5/Al_2O_3 and a commercial Cu catalyst exhibited higher DME conversion than that of Al_2O_3 and the commercial one.
• Preparation of Ru nanoparticles on TiO2 using selective deposition method and their application to selective CO methanation

  Tada, S., Kikuchi, R.

  Catalysis Science & Technology 4 (1) 26 - 29 2044-4753 2014
• CsH2PO4/Polyvinylidene Fluoride Composite Electrolytes for Intermediate Temperature Fuel Cells

  Qing, Geletu, Kikuchi, Ryuji, Takagaki, Atsushi, Sugawara, Takashi, Oyama, Shigeo Ted

  Journal of the Electrochemical Society 161 (4) F451 - F457 0013-4651 2014
• Supported perfluorotributylamine liquid membrane for H-2/O-2 separation

  Castro-Dominguez, Bernardo, Leelachaikul, Pornravee, Takagaki, Atsushi, Sugawara, Takashi, Kikuchi, Ryuji, Oyama, S. Ted

  Journal of Membrane Science 448 262 - 269 0376-7388 2013/12
• Fabrication of Low Ni-Containing SOFC Anode Using Mixed Ionic and Electronic Conductors

  Ryuji Kikuchi, Tatsushi Minami, Atsushi Takagaki, Takashi Sugawara, Shigeo Ted Oyama

  ECS Transactions 57 (1) 1201 - 1210 1938-5862 2013/10/06 

  Typical anodes of solid oxide fuel cell consist of a cermet of electronic conductor such as Ni and oxygen ion conductor such as yttria-stabilized zirconia, and have porous structure to enlarge reaction sites. It has been recognized that volume expansion of the Ni species during redox cycle can damage the anode structure and that sintering of the Ni species results in degradation of power generation characteristics. One possible approach for lessening these undesirable effects is to reduce the amount of Ni in the anode, whereas reduced Ni amount in turn decreases the anodic reaction sites. In this study, Ni-SDC (samaria-doped ceria) cermet was prepared by changing SDC particle size and Ni content, and I-V and AC impedance measurement were conducted to evaluate the electrochemical processes that influence the performance of the anode by introducing ΔZ'spectra. It was found that large SDC particles were effective in reducing ohmic overpotential even with low Ni content, and that the conductivity change in the anode with Ni content can be explained by percolation theory.
• Perfluorocarbon-based supported liquid membranes for O-2/N-2 separation

  Castro-Dominguez, B., Leelachaikul, P., Takagaki, A., Sugawara, T., Kikuchi, R., Oyama, S. T.

  Separation and Purification Technology 116 19 - 24 1383-5866 2013/09
• Study of Ru-Ni/TiO2 catalysts for selective CO methanation

  Shohei Tada, Ryuji Kikuchi, Atsushi Takagaki, Takashi Sugawara, S. Ted Oyarria, Kohei Urasaki, Shigeo Satokawa

  APPLIED CATALYSIS B-ENVIRONMENTAL 140 258 - 264 0926-3373 2013/08 

  The removal of CO from reformate streams by selective CO methanation was investigated over TiO2 supported Ru-Ni bimetallic and monometallic catalysts. The combination of Ru and Ni enhanced CO methanation at low temperatures. The introduction of Ni into Ru/TiO2 decreased the CO2 conversion rate at 260 degrees C from 10 to 7.3 mu mol min(-1) g(cat)(-1). The use of Ru and Ni, thus, expands the temperature range of selective CO methanation. Transmission electron microscopy and temperature programmed reduction by H-2 confirmed that Ru species were in close proximity to Ni species on Ru-Ni/TiO2, indicating a decrease in direct contact between Ru and TiO2. Fourier transform infrared spectroscopy techniques revealed that the decomposition of the formate species, formed during CO2 methanation, is slow over Ru-Ni/TiO2, in contrast to Ru/TiO2. (C) 2013 Elsevier B.V. All rights reserved.
• N2O Pulse Titration of Ni/alpha-Al2O3 Catalysts: A New Technique Applicable to Nickel Surface-Area Determination of Nickel-Based Catalysts

  Tada, Shohei, Yokoyama, Misato, Kikuchi, Ryuji, Haneda, Takahide, Kameyama, Hiromichi

  Journal of Physical Chemistry C 117 (28) 14652 - 14658 1932-7447 2013/07/18
• Effects of preparation conditions of Ni/TiO2 catalysts for selective CO methanation in the reformate gas

  Kohei Urasaki, Yuta Tanpo, Yuta Nagashima, Ryuji Kikuchi, Shigeo Satokawa

  APPLIED CATALYSIS A-GENERAL 452 174 - 178 0926-860X 2013/02 

  Selective CO methanation in the reformate gas over Ni/TiO2 catalyst was carried out. Nickel metal salts (nitrate, sulfate, acetate, chloride and formate) used as a precursor of nickel, calcination temperatures (400-700 degrees C), reduction temperatures (350-650 degrees C) and nickel contents (1-30 wt%) affected to the CO methanation activity and CO/CO2 selectivity over the obtained Ni/TiO2 catalysts. The appropriate nickel precursors were nitrate and acetate and suitable calcination and reduction temperatures were 400-500 degrees C and 450-550 degrees C, respectively. An increase of nickel contents in the Ni/TiO2 catalysts improved to the CO methanation activity. Reverse water gas shift reaction activity was extremely low regardless of nickel contents. As a result, temperature window of Ni/TiO2 catalyst was constant and it could be shifted to desired position by changing nickel content. (C) 2012 Elsevier B.V. All rights reserved.
• Extraordinary activity of nanodispersed bimetallic nife phosphide catalysts for the conversion of a biomass model compound

  S. Ted Oyama, Ara Cho, Jieun Shin, Atsushi Takagaki, Ryuji Kikuchi

  Technical Proceedings of the 2013 NSTI Nanotechnology Conference and Expo, NSTI-Nanotech 2013 1 444 - 447 2013 

  The present work deals with the development of new catalysts, transition metal phosphides, which have outstanding activity for hydrodeoxygenation of pyrolysis oil. The study is significant as it leads to the production of high-energy content liquid fuels. Pyrolysis of biomass is a thermal conversion process that produces liquid fuels and chemicals, and is a promising technology to compete with and eventually replace non-renewable fossil fuels. The model substrate 2-methyltetrahydrofuran is studied by kinetic and spectroscopic methods to uncover the important steps involved in the reaction. On the most active catalyst, Ni2P, the studies indicate that the rate-determining step involves a single Ni atom. In situ infrared measurements are used to identify adsorbed reactive intermediates during reaction and give support for the reaction mechanism. The studies are important because they allow understanding of reactivity at a nanoscale level and lead to the design of more active catalysts.
• Dehydration of sugar alcohols in water using layered metal oxides

  Morita Yuya, Takagaki Atsushi, Hayashi Shigenobu, Kikuchi Ryuji, Oyama S. Ted

  Proceeding of Annual/Fall Meetings of the Japan Petroleum Institute 公益社団法人 石油学会 2013 20 - 20 2013 

  ソルビトールはセルロースを加水分解、水素還元によって得られる糖アルコールであり、木質系バイオマス由来原料として重要である。本研究では、ソルビトールの水中脱水反応を、層状金属酸化物を用いて行った。HNbMoO6やHTaMoO6は各種固体酸、液体硫酸よりも高いソルビトール転化率、高いソルビタン選択率を示した。この反応経路を見積もり、反応速度定数と活性化エネルギーを求め、副生成物の生成抑制のための条件を提案した。
• Ligand and ensemble effects in bimetallic NiFe phosphide catalysts for the hydrodeoxygenation of 2-methyltetrahydrofuran

  Ara Cho, Jieun Shin, Atsushi Takagaki, Ryuji Kikuchi, S.Ted Oyama

  Topics in Catalysis 55 (14-15) 969 - 980 1022-5528 2012/10 [Refereed][Not invited]
   

  A series of supported nickel-iron phosphide catalysts were used to study the hydrodeoxygenation (HDO) of 2-methyltetrahydrofuran (2-MTHF), a model compound for biomass-derived pyrolysis oil. The catalysts were prepared by incipient wetness impregnation of the active components onto potassium ion-exchanged USY zeolites followed by temperature-programmed reduction. The samples were denoted as Ni2P/KUSY, NiFeP(3:1)/KUSY, NiFeP(1:1)/KUSY, NiFeP(1:3)/KUSY, and FeP/KUSY, where the numbers in parenthesis are the Ni:Fe molar ratios. The results of the studies can be understood from ensemble and ligand effects. X-ray diffraction analysis indicated the presence of alloys in the mixed composition samples, and this was supported by CO chemisorption and infrared measurements. Uptakes of CO decreased as the iron content increased, suggesting that iron present on the surface of the catalysts blocked chemisorption sites. Fourier transform infrared (FTIR) measurements showed a single peak for linearly adsorbed CO whose intensity decreased with Fe content, in agreement with the uptake results. Moreover, the FTIR peak shifted monotonically consistent with a ligand effect in an alloy formed in the Ni 2P and FeP particles. The reactivity in 2-MTHF HDO was studied at 250-325 °C and 0.5 MPa and it was found that the conversion was highest for the Ni 2P/KUSY sample and decreased steadily with Fe content. However, the turnover frequency did not change significantly, indicating that the rate-determing step was activation of 2-MTHF on single Ni sites. The selectivity at low conversion (3 %) changed from mostly n-pentane and n-butane for Ni 2P/KUSY to mostly 1-pentanol for the ironcontaining samples, suggesting that in subsequent steps an ensemble effect was operational with the iron influencing the reaction chemistry. At high conversion (70 %) all the samples produced mostly n-pentane and n-butane. © Springer Science+Business Media, LLC 2012.
• Ni/CeO2 catalysts with high CO2 methanation activity and high CH4 selectivity at low temperatures

  Shohei Tada, Teruyuki Shimizu, Hiromichi Kameyama, Takahide Haneda, Ryuji Kikuchi

  International Journal of Hydrogen Energy 37 (7) 5527 - 5531 0360-3199 2012/04 [Refereed][Not invited]
   

  CO2 methanation was performed over 10 wt%Ni/CeO2, 10 wt%Ni/α-Al2O3, 10 wt%Ni/TiO2, and 10 wt%Ni/MgO, and the effect of support materials on CO2 conversion and CH4 selectivity was examined. Catalysts were prepared by a wet impregnation method, and characterized by BET, XRD, H2-TPR and CO2-TPD. Ni/CeO2 showed high CO2 conversion especially at low temperatures compared to Ni/α-Al2O 3, and the selectivity to CH4 was very close to 1. The surface coverage by CO2-derived species on CeO2 surface and the partial reduction of CeO2 surface could result in the high CO2 conversion over Ni/CeO2. In addition, superior CO methanation activity over Ni/CeO2 led to the high CH4 selectivity. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.
• Studies of hydrodeoxygenation on transition metal phosphates

  S. Ted Oyama, Phuong Bui, Dan Li, Ara Cho, Ayako Lino, Jieun Shin, Atsushi Takagaki, Ryuji Kikuchi

  ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 243 0065-7727 2012/03 [Refereed][Not invited]
  
• Hydrodeoxygenation of 2-methyltetrahydrofuran on a Ni2P/SiO2 catalyst

  Iino Ayako, Cho Ara, Sugawara Takashi, Takagaki Atsushi, Kikuchi Ryuji, Oyama S. Ted

  Proceeding of Annual/Fall Meetings of the Japan Petroleum Institute 公益社団法人 石油学会 2012 67 - 67 2012 

  バイオマスの利便性を向上するための方法の一つとして、木質バイオマスを不活性ガス中で高温にし、熱分解油(バイオオイル)を得る方法がある。熱分解油は含酸素有機化合物を多量に含み、燃料としての質が劣っているため、熱分解油から酸素を取り除くことが必要である。本研究では2-メチルテトラヒドロフランをモデル含酸素有機化合物としリン化ニッケル触媒上での水素化脱酸素機構を検討した。また、市販のパラジウムアルミナ触媒と触媒の活性・特性を比較した。
• Dimethyl ether steam reforming under daily start-up and shut-down (DSS)-like operation over CuFe2O4 spinel and alumina composite catalysts

  Naohiro Shimoda, Hiroki Muroyama, Toshiaki Matsui, Kajornsak Faungnawakij, Ryuji Kikuchi, Koichi Eguchi

  Applied Catalysis A: General 409-410 91 - 98 0926-860X 2011/12 [Refereed][Not invited]
   

  The durability of the CuFe2O4 spinel and γ-Al2O3 composite catalysts for steam reforming of dimethyl ether (DME) was evaluated at 375 °C for 120 h under the daily start-up and shut-down (DSS) operation. No degradation could be observed for the catalyst subjected to the cooling-heating process in O2 atmosphere. On the other hand, the catalyst performance was significantly degraded by the cooling-heating process in steam atmosphere due to the deactivation of the acid sites on γ-Al2O3 for DME hydrolysis reaction, leading to the loss of DME steam reforming activity. The higher amount of coke formation was also observed over the catalysts exposed to steam during the cooling-heating process, as compared with the catalysts exposed to O2 or without DSS operation. The degraded catalyst could be recovered by the heat treatment in air at 375 °C, since the active sites of γ-Al 2O3 were regenerated and the coke deposits were removed. Interestingly, the catalytic activity of the regenerated catalysts for methanol steam reforming was higher than the fresh one because of an increase in the metal surface area of Cu species after the regeneration treatment. © 2011 Elsevier B.V. All rights reserved.
• Effect of reduction pretreatment and support materials on selective CO methanation over supported Ru catalysts

  Tada, Shohei, Kikuchi, Ryuji, Urasaki, Kohei, Satokawa, Shigeo

  Applied Catalysis a-General 404 (1-2) 149 - 154 0926-860X 2011/09
• Stable Equilibrium Shift of Methane Steam Reforming in Membrane Reactors with Hydrogen-selective Silica Membranes

  Akamatsu, Kazuki, Murakami, Takuya, Sugawara, Takashi, Kikuchi, Ryuji, Nakao, Shin-ichi

  Aiche Journal 57 (7) 1882 - 1888 0001-1541 2011/07
• Reaction Sites of Mixed Conductor Anodes in Solid Oxide Fuel Cells

  Ryuji Kikuchi, Takaaki Okamoto, Kazuki Akamatsu, Takashi Sugawara, Shin-ichi Nakao

  ECS Transactions 35 (1) 1707 - 1715 1938-5862 2011/04/25 

  Pt pattern anodes with defined TPB length were prepared on the surface of YSZ or SDC (Samaria-doped ceria) interlayer deposited on an YSZ disk, in order to investigate the reaction sites of SOFC anodes consisting of mixed conductor oxides. The electrode resistance was measured by AC impedance method under different conditions and assigned to reaction resistances by fitting to an equivalent circuit. The dependence of the reaction resistances was investigated by varying operation temperature, hydrogen partial pressure, and the number of the Pt electrode patterns. The impedance in the Nyquist plots was fitted by two semicircles at low and high frequency, and the high frequency arc was assigned to the anodic reactions nearby the TPB. For the same TPB length, the conductivity determined from the high frequency arc for the Pt electrodes on the SDC layer was almost ten times as large as that on the YSZ layer.
• Review on Mechanisms of Gas Permeation through Inorganic Membranes

  S. Ted Oyama, Mariko Yamada, Takashi Sugawara, Atsushi Takagaki, Ryuji Kikuchi

  Journal of the Japan Petroleum Institute The Japan Petroleum Institute 54 (5) 298 - 309 1346-8804 2011 

  The major mechanisms of gas permeation through solid membranes are described and the applicable equations describing the permeance are presented. The mechanisms depend on the relative size of the permeating molecules and the diameter of the pores. As pore size decreases the operable mechanisms are Hagen-Pouiselle flow, Knudsen diffusion, surface diffusion, gas-translation, and finally solid-state diffusion. The Hagen-Pouiselle mechanism involves flow through large pores, while the Knudsen mechanism involves collision of molecules with the walls of pores of intermediate size. Surface diffusion deals with movement of molecules trapped in the potential field of the walls of pores of relatively small size, while gas-translation involves molecules that can escape the field, but are constrained by the small pores. Finally, solid-state transport comprises dissolution and transport by diffusion within the solid. These mechanisms are illustrated for hydrogen permeance with the use of two membranes, an alumina membrane with intermediate sized pores and a silica on alumina membrane of dense structure.
• A study of various zeolites and CuFe(2)O(4) spinel composite catalysts in steam reforming and hydrolysis of dimethyl ether

  Shimoda, N., Faungnawakij, K., Kikuchi, R., Eguchi, K.

  International Journal of Hydrogen Energy 36 (2) 1433 - 1441 0360-3199 2011/01 [Refereed][Not invited]
  
• Dehydrogenation of Methylcyclohexane To Produce High-Purity Hydrogen Using Membrane Reactors with Amorphous Silica Membranes

  Oda, Kazunori, Akamatsu, Kazuki, Sugawara, Takashi, Kikuchi, Ryuji, Segawa, Atsushi, Nakao, Shin-ichi

  Industrial & Engineering Chemistry Research 49 (22) 11287 - 11293 0888-5885 2010/11/17
• Preparation of Monodisperse Chitosan Microcapsules with Hollow Structures Using the SPG Membrane Emulsification Technique

  Akamatsu, Kazuki, Chen, Wei, Suzuki, Yukimitsu, Ito, Taichi, Nakao, Aiko, Sugawara, Takashi, Kikuchi, Ryuji, Nakao, Shin-ichi

  Langmuir 26 (18) 14854 - 14860 0743-7463 2010/09/21
• Supported and free-standing sulfonic acid functionalized mesostructured silica films with high proton conductivity

  Supplit, R., Sugawara, A., Peterlik, H., Kikuchi, R., Okubo, T.

  European Journal of Inorganic Chemistry 2010 (25) 3993 - 3999 1434-1948 2010/09
• Selective Methanation of CO in Reformate Gas over Ni/TiO2 Catalyst

  Kohei Urasaki, Yuta Tanpo, Tomoki Takahiro, Jayaraj Christopher, Ryuji Kikuchi, Toshinori Kojima, Shigeo Satokawa

  CHEMISTRY LETTERS 39 (9) 972 - 973 0366-7022 2010/09 

  Selective methanation of CO was performed over Ni/TiO2. CO in reformate gas was completely removed at 150-300 degrees C. The CH4 concentration in the outlet gas could be maintained below 1% in the entire temperature region because Ni/TiO2 suppressed the CO2 methanation reaction. It can be considered that the formation of CO by the reverse water-gas-shift reaction is blocked by the application of TiO2 to the support of Ni catalyst and that it results in the high CO/CO2 selectivity of Ni/TiO2.
• Effect of Support Materials on the Selective Methanation of CO over Ru Catalysts

  Kohei Urasaki, Ken-ichiro Endo, Tomoki Takahiro, Ryuji Kikuchi, Toshinori Kojima, Shigeo Satokawa

  TOPICS IN CATALYSIS 53 (7-10) 707 - 711 1022-5528 2010/06 

  Selective methanation of CO in the reformate gas (CO/CO2/H-2/H2O = 0.175/17.9/70.9/11.1) proceeded over Ru catalysts supported on metal oxides and zeolites. CO was selectively methanated at wide temperature ranges (200-275 A degrees C) over Ru/gamma-Al2O3, Ru/TiO2 Ru/H-Y and Ru/H-beta catalysts. Higher Ru contents in Ru/gamma-Al2O3 improved the selective CO methanation rate.
• Limiting mechanisms in catalytic steam reforming of dimethyl ether

  Faungnawakij, K., Shimoda, N., Viriya-empikul, N., Kikuchi, R., Eguchi, K.

  Applied Catalysis B: Environmental 97 (1-2) 21 - 27 0926-3373 2010/06 [Refereed][Not invited]
  
• Preparation of silver nanoparticles using the SPG membrane emulsification technique

  Kakazu, Emiri, Murakami, Takuya, Akamatsu, Kazuki, Sugawara, Takashi, Kikuchi, Ryuji, Nakao, Shin-ichi

  Journal of Membrane Science 354 (1-2) 1 - 5 0376-7388 2010/05
• Three Preparation Methods for Monodispersed Chitosan Microspheres Using the Shirasu Porous Glass Membrane Emulsification Technique and Mechanisms of Microsphere Formation

  Akamatsu, Kazuki, Kaneko, Daisaku, Sugawara, Takashi, Kikuchi, Ryuji, Nakao, Shin-ichi

  Industrial & Engineering Chemistry Research 49 (7) 3236 - 3241 0888-5885 2010/04/07
• Degradation and regeneration of copper-iron spinel and zeolite composite catalysts in steam reforming of dimethyl ether

  Shimoda, N., Faungnawakij, K., Kikuchi, R., Eguchi, K.

  Applied Catalysis a-General 378 (2) 234 - 242 0926-860X 2010/04
• Development of Cu-Fe based spinel oxide catalysts for water gas shift reaction

  Shimoda Naohiro, Muroyama Hiroki, Matsui Toshiaki, Kikuchi Ryuji, Eguchi Koichi

  Proceeding of Annual/Fall Meetings of the Japan Petroleum Institute 公益社団法人 石油学会 2010 155 - 155 2010 

  炭化水素系燃料からの固体高分子形燃料電池への水素供給プロセスにおいてCO低減プロセスである水性ガスシフト反応は非常に重要な反応である。これまで我々は、Cu-Fe、Cu-Mnスピネル触媒が高いシフト活性を示すこと、アルミナと混合したCu-Feスピネル触媒を高温で空気中焼成することで触媒活性が向上することを報告している。本研究では、Cu-Feスピネル酸化物への第三成分添加効果ならびに熱処理効果について検討し、活性ならびにDSS条件下での耐久性の優れたシフト触媒の開発を試みた。
• Development of supported bimetallic catalysts for selective CO methanation

  Tada Shohei, Kikuchi Ryuji, Takagaki Atsushi, Sugawara Takashi, Oyama S. Ted, Urasaki Kohei, Satokawa Shigeo

  Proceeding of Annual/Fall Meetings of the Japan Petroleum Institute 公益社団法人 石油学会 2010 150 - 150 2010 

  PEFC用水素製造プロセスにおける微量のCO除去方法として、COメタン化反応が注目を集めている。しかし改質ガス中に共存するCO₂が同時にメタン化すると熱暴走する危険性があることが問題である。そこでCOメタン化選択性を向上させる必要がある。今までにCOメタン化反応に対する担体効果を調べており、Ru/TiO₂触媒が高いCOメタン化選択性を示した。今回は活性種に金属を添加することで、COメタン化選択性の高い担持二元金属触媒を開発する。
• 膜乳化法を用いたキトサン中空マイクロカプセルの合成と架橋法が中空構造に与える影響

  赤松 憲樹, 陳 為, 鈴木 幸光, 伊藤 大知, 菅原 孝, 菊地 隆司, 中尾 真一

  化学工学会 研究発表講演要旨集 公益社団法人 化学工学会 2010 894 - 894 2010
• Development of Novel Proton Conductors Consisting of Solid Acid/pyrophosphate Composite for Intermediate-temperature Fuel Cells

  Toshiaki Matsui, Hiroki Muroyama, Ryuji Kikuchi, Koichi Eguchi

  JOURNAL OF THE JAPAN PETROLEUM INSTITUTE JAPAN PETROLEUM INST 53 (1) 1 - 11 1346-8804 2010/01 [Refereed][Not invited]
   

  Fuel cells are attractive energy conversion devices with high efficiencies and low emissions, and many studies have been conducted so far. Among them, fuel cells operating at 200-600°C are promising technologies which combine the many advantages of high- and low-temperature fuel cells. However, they have not been developed due to the lack of good ionic-conductors with high thermal stability at intermediate temperatures. Recently, we have developed new proton-conductive electrolytes consisting of solid acid and pyrophosphate, and evaluated their electrochemical, structural and thermal properties at intermediate temperatures. For the composite based on CsH₂PO₄/SiP₂O₇, the interfacial chemical reaction between CsH₂PO₄ and SiP₂O₇ during heat-treatment gave rise to the formation of a new phase of CsH₅(PO₄)₂. The temperature dependence of conductivity for this composite was different from that for pure CsH₂PO₄, and the maximum conductivity achieved was 44 mS·cm⁻¹ at 266°C. Using potassium and rubidium salts, MH₂PO₄ (M = K, Rb), as the solid acids for the composite electrolytes, analogous phenomena were confirmed despite the alkaline metal. Operation of a fuel cell employing CsH₂PO₄/SiP₂O₇-based composite electrolyte (thickness: ca. 1.3 mm) was demonstrated at 200°C and generated electricity up to 220 mA·cm⁻² at 0.2 V. CsH₅(PO₄)₂ composites with SiP₂O₇ and SiO₂ were fabricated, and the composite effects were investigated at intermediate temperatures based on conductivity measurement, thermal analysis, and wettability evaluation. The melting and dehydration processes of CsH₅(PO₄)₂ in composites were different depending on the matrix species. The composite with SiP₂O₇ matrix showed the highest conductivity of all composites. The conductivity of the composites appears to correlate with the wettability between the components as examined by contact angle measurement. These findings should be attributed to the differences in the interfacial interactions between CsH₅(PO₄)₂ and the matrix.
• Activation of LSM Electrode Related to the Potential Oscillation under Cathodic Polarization

  Kota Murakami, Toshiaki Matsui, Ryuji Kikuchi, Hiroki Muroyama, Koichi Eguchi

  JOURNAL OF THE ELECTROCHEMICAL SOCIETY ELECTROCHEMICAL SOC INC 157 (6) B880 - B884 0013-4651 2010 [Refereed][Not invited]
   

  Solid oxide fuel cells with the conventional configuration of Ni-ytttria-stabilized zirconia (Ni-YSZ) YSZ (La,Sr) MnO 3±δ (LSM) have been reported to exhibit performance improvement in the initial discharge operation, which is attributed to the activation of LSM. In this study, the time course of potential for LSM was monitored under cathodic polarization to precisely analyze this enhancement. A characteristic phenomenon of potential oscillation was found during the constant current loading. Regardless of electrolyte materials and LSM composition, the potential was oscillated with a frequency of ca. 0.67 Hz soon after current passing. The potential oscillation appeared under the following conditions: (i) at low partial pressure of oxygen, (ii) at high cathodic current loading, and (iii) for an LSM electrode with low porosity. The amplitude of oscillation reduced with the elapsed time of cathodic polarization and then disappeared. The microscopic observation revealed that the structural change in the LSM electrode after cathodic polarization is responsible for the disappearance of potential oscillation. These findings suggest that the potential oscillation originates in the mass-transfer limitation, oxygen diffusion, and densified electrode. © 2010 The Electrochemical Society.
• Nano-structural changes of SnO2-supported palladium catalysts by redox treatments

  Kamiuchi Naoto, Muroyama Hiroki, Matsui Toshiaki, Kikuchi Ryuji, Eguchi Koichi

  Applied Catalysis a-General 379 (1-2) 148 - 154 0926-860X 2010 [Refereed][Not invited]
   

  The structural changes in Pd/SnO2 catalyst upon redox treatments were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). In the as-calcined catalyst, the fine particles of palladium species with the amorphous and the well-cyrstallized states were highly dispersed on the surface of SnO2 support due to the strong chemical interaction. The heat-treatment at 200 °C in hydrogen induced the reduction of palladium species and the particle growth, resulting in the formation of the well-crystallized Pd particles. Some peculiar structures, called the core-shell structure and the particle intrusion structure, were formed by the reduction at 400 °C. After the reoxidation treatment, the core-shell structure disappeared while the particle intrusion structure remained. Furthermore, the decrease in the mean particle diameter was confirmed in the reoxidized catalyst. The proposed formation mechanism of the unique structures from TEM observation was supported by the combination of XRD and XPS measurements. © 2010 Elsevier B.V. All rights reserved.
• Catalytic combustion of ethyl acetate and nano-structural changes of ruthenium catalysts supported on tin oxide

  Kamiuchi Naoto, Mitsui Tomohiro, Muroyama Hiroki, Matsui Toshiaki, Kikuchi Ryuji, Eguchi Koichi

  Applied Catalysis B-Environmental 97 (1-2) 120 - 126 0926-3373 2010 [Refereed][Not invited]
   

  Correlation between the catalytic activity and the nano-structure of ruthenium catalyst supported on tin oxide was investigated. As-calcined Ru/SnO2 catalyst exhibited high catalytic activity for ethyl acetate combustion despite its low surface area of ca. 5.0 m2 g-1. The catalytic activity was degraded by the reduction treatment at 400 °C, whereas it was partially restored by the subsequent reoxidation treatment at 400 °C. To elucidate the variation in the catalytic activity, the ruthenium catalysts heat-treated under reductive or oxidative condition were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). In the as-calcined catalyst, it was revealed that the fine particles with the small contact angles were well-dispersed on the surface of tin oxide support. In the deactivated catalyst treated at 400 °C under a reductive atmosphere, the large particles of intermetallic compounds with the core-shell structure were clearly observed. On the other hand, upon the reoxidation treatment at 400 °C the particles with the core-shell structure disappeared accompanied with the appearance of the nano-sized particles. Accordingly, it was clarified that the catalytic activity was strongly influenced by the structural changes of active sites such as sintering and redispersion. © 2010 Elsevier B.V. All rights reserved.
• Activation of Pt/SnO2 catalyst for catalytic oxidation of volatile organic compounds

  Kamiuchi Naoto, Mitsui Tomohiro, Yamaguchi Nobutada, Muroyama Hiroki, Matsui Toshiaki, Kikuchi Ryuji, Eguchi Koichi

  Catalysis Today 157 (1-4) 415 - 419 0920-5861 2010 [Refereed][Not invited]
   

  The catalytic combustion of toluene over tin oxide-supported metal catalysts (Pt/SnO2, Pd/SnO2, Ru/SnO2, and Rh/SnO2) was studied. As a result, the Pt/SnO2 catalyst exhibited the highest activity. The activity of Pt/SnO2 catalyst is expected to originate from the strong chemical interaction between platinum and tin oxide. The correlation between the nano-structure and catalytic activity in the oxidation of ethyl acetate was investigated for the Pt/SnO2 catalysts treated under a reducing or an oxidative atmosphere. For the transmission electron microscopy image of the as-calcined Pt/SnO2 catalyst, the fine particles composed of platinum species was highly dispersed on the surface of SnO2 support. After the reduction treatment at 400 °C, the peculiar core-shell structure was formed. It is noted that the particles with this structure disappeared by the reoxidation treatment in air, and the redispersion of nano-particles was confirmed. The particles with the core-shell structure were observed again after the second reduction treatment for the reoxidized catalyst. The catalytic activities of ethyl acetate combustion over Pt/SnO2 catalysts were deteriorated and activated, corresponding to the nano-structural changes induced by the reduction-oxidation treatments. © 2010 Elsevier B.V. All rights reserved.
• Crystal structure and surface species of CuFe2O4 spinel catalysts in steam reforming of dimethyl ether

  Faungnawakij, Kajornsak, Shimoda, Naohiro, Fukunaga, Tetsuya, Kikuchi, Ryuji, Eguchi, Koichi

  Applied Catalysis B-Environmental 92 (3-4) 341 - 350 0926-3373 2009/11 [Refereed][Not invited]
  
• Stability enhancement in Ni-Promoted Cu-Fe spinel catalysts for dimethyl ether steam reforming

  Faungnawakij, K., Kikuchi, R., Fukunaga, T., Eguchi, K.

  Journal of Physical Chemistry C 113 (43) 18455 - 18458 1932-7447 2009/10 [Refereed][Not invited]
  
• Catalytic performance enhancement by heat treatment of CuFe(2)O(4) spinel and gamma-alumina composite catalysts for steam reforming of dimethyl ether

  N. Shimoda, K. Faungnawakij, R. Kikuchi, T. Fukunaga, K. Eguchi

  APPLIED CATALYSIS A-GENERAL 365 (1) 71 - 78 0926-860X 2009/08 [Refereed][Not invited]
   

  The influence of heat treatment on catalytic activity and durability for steam reforming of dimethyl ether (DME SR) over the composite catalysts of CuFe(2)O(4) spinel and gamma-Al(2)O(3) was investigated. The heat treatment in air after mixing of CuFe(2)O(4) and Al(2)O(3) improved the activity and durability of the composite catalysts for DME SR. The treatment temperature range of 700-800 degrees C is most effective to enhance the catalytic performance. According to XRD and TPR analyses, the new phase of Cu-Fe-AlO(4) Was produced by solid-state reaction at the interface between CuFe(2)O(4) and Al(2)O(3) after heat treatment, leading to high catalytic performance. This new active phase also formed over the composites of pre-reduced CuFe(2)O(4) and Al(2)O(3), due to the re-construction of Cu-Fe spinel by the heat treatment. (C) 2009 Elsevier B.V. All rights reserved.
• Reforming activity and carbon deposition on cermet catalysts for fuel electrodes of solid oxide fuel cells

  Koichi Eguchi, Kentaro Tanaka, Toshiaki Matsui, Ryuji Kikuchi

  CATALYSIS TODAY ELSEVIER SCIENCE BV 146 (1-2) 154 - 159 0920-5861 2009/08 [Refereed][Not invited]
   

  The activities of cermet catalysts composed of Ni and oxides for steam reforming of methane were investigated for internal reforming of solid oxide fuel cells. For all catalysts studied, the reaction attained almost equilibrium above 500 °C at the space velocity of 20,000 l kg-1 h-1. The kinetic-controlled reaction and difference in activity among the catalysts were observable at S.V. = 60,000 l kg-1 h-1. The reforming activity was higher for Ni-YSZ (YSZ: yttria-stabilized zirconia) than Ni-ScSZ (ScSZ: scandia-stabilized zirconia), whereas the highest activity was attained on Ni/Al2O3. However, the catalyst performance was degraded with carbon deposition in the course of the reaction. The tolerance to carbon deposition and, therefore, the life of the catalyst was significantly affected by the oxide material in the cermet. The carbon deposition was most rapid on Ni/Al2O3. The high loading of Ni also facilitated the deposition on the Ni-YSZ and Ni-ScSZ catalysts. It is noted that the carbon deposition rate was significantly smaller for Ni-ScSZ than the case of the Ni-YSZ. © 2009 Elsevier B.V. All rights reserved.
• Microstructural Transformation with Heat-Treatment of Aluminum Hydroxide with Gibbsite Structure

  Tomohiro Mitsui, Toshiaki Matsui, Ryuji Kikuchi, Koichi Eguchi

  BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN CHEMICAL SOC JAPAN 82 (5) 618 - 623 0009-2673 2009/05 [Refereed][Not invited]
   

  Aluminum hydroxide with gibbsite structure was prepared, and the microstructural transformation of the sample heat-treated at various temperatures was investigated. The sample was characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), thermogravimetry and differential thermal analysis (TG-DTA), and BET surface area. The shape of the grains in the prepared sample was hexagonal prism-like morphology. The prepared sample kept a metastable state of alumina phase at higher temperatures than the commercially available gibbsite powders. The prepared gibbsite grains underwent characteristic structural change depending on the calcination temperature. The transformation of the surface morphology was initiated at 400 °C, leading to the formation of cracks with the direction parallel to the basal plane. After calcination at 1200 °C, a large number of grooves were formed on the surface of the lateral planes. The specific structural change of gibbsite induced by the heat treatment was strongly related to the topotactic dehydration from gibbsite and subsequent phase transition to aluminum oxides.
• Low-Temperature Complete Oxidation of Ethyl Acetate Over CeO2-Supported Precious Metal Catalysts

  Tomohiro Mitsui, Toshiaki Matsui, Ryuji Kikuchi, Koichi Eguchi

  TOPICS IN CATALYSIS SPRINGER/PLENUM PUBLISHERS 52 (5) 464 - 469 1022-5528 2009/05 [Refereed][Not invited]
   

  Catalytic combustion of ethyl acetate was investigated over various CeO2-supported precious metal catalysts prepared by impregnation method, and the effect of reduction treatment on the activity was examined. Among the catalysts tested, Ru/CeO2 achieved the highest activity for ethyl acetate combustion, and the activity was almost unchanged by the heat treatment in a hydrogen atmosphere. In the cases of Pt/CeO2, Pd/CeO2, and Rh/CeO2, the catalytic activity was enhanced by the reduction treatment at 400 °C, though the activity of the reduced catalysts was still inferior to that of Ru/CeO2. It was confirmed by temperature-programmed reduction that the reduction of the ruthenium species was initiated at the lowest temperature among the CeO2-supported precious metals. The precious metal species reducible at lower temperatures should be responsible for the high activity in the complete oxidation of ethyl acetate. © Springer Science+Business Media, LLC 2009.
• X-ray photoelectron spectroscopy characterization of copper-iron spinel as a catalyst for steam reforming of oxygenated hydrocarbon

  Faungnawakij, Kajornsak, Kikuchi, Ryuji, Eguchi, Koichi

  Scripta Materialia 60 (8) 655 - 658 1359-6462 2009/04 [Refereed][Not invited]
  
• Sudden Deterioration in Performance During Discharge of Anode-supported Solid Oxide Fuel Cells

  Toshiaki Matsui, Jin-young Kim, Ryuji Kikuchi, Koichi Eguchi

  ELECTROCHEMISTRY ELECTROCHEMICAL SOC JAPAN 77 (2) 123 - 126 1344-3542 2009/02 [Refereed][Not invited]
   

  The stability of the anode-supported solid oxide fuel cell consisting of Ni-YSZ|YSZ|LSM was examined at 800°C by monitoring the current density at a constant terminal voltage of 0.5 V. Although stable power generation was possible within initial 60 min, gradual decrease and subsequent sudden drop in current density were observed: a series of this behavior was different from that observed in limiting current density. This behavior is suggested to be one of the degradation factors related with transport of gas species in the pores of the electrode. In response to performance deterioration, a drastic increase in ohmic loss and impedance was confirmed soon after the discharge operation. It is noted, however, that the deteriorated performance was reversibly recovered depending on the holding time under the open-circuit condition. Analogous phenomena occurred with the cell consisted of Ni-YSZ|YSZ|Ce_0.8Sm_0.2O_1.9|La_0.6Sr_0.4Co_0.2Fe_0.8O₃, indicating that the cause of the sudden deterioration was in the anode side.
• ジメチルエーテル水蒸気改質用Cuスピネルコンポジット触媒へのNi添加効果

  菊地 隆司, 霜田 直宏, Faungnawakij Kajornsak, 福永 哲也, 松井 敏明, 河島 俊一郎, 江口 浩一

  化学工学会 研究発表講演要旨集 公益社団法人 化学工学会 2009 41 - 41 2009
• Electrochemical Hydrogen Production from Carbon Monoxide and Steam with a Cell Employing CsH2PO4/SiP2O7 Composite Electrolyte

  Hiroki Muroyama, Toshiaki Matsui, Ryuji Kikuchi, Koichi Eguchi

  JOURNAL OF THE ELECTROCHEMICAL SOCIETY ELECTROCHEMICAL SOC INC 156 (12) B1389 - B1393 0013-4651 2009 [Refereed][Not invited]
   

  Electrochemical hydrogen pumping was investigated with a cell consisting of a CsH2 PO4 / SiP2 O7 composite electrolyte at 200°C. When humidified hydrogen was fed to the anode, the evolution rate of hydrogen at the cathode obeyed Faraday's law up to a current density of 1000 mA cm-2. In this system, the water-gas shift reaction (WGSR) was promoted electrochemically at the anode during polarization with a feed of humidified carbon monoxide. The overpotential was much higher in humidified carbon monoxide than in humidified hydrogen. With the reactor for the catalytic WGSR located upstream of the anode gas, the overpotential significantly depended on the temperature and space velocity of the reactor. The bilayered electrode composed of a Cu spinel oxide and a Pt catalyst exhibited a low overpotential at low current densities due to the formation of hydrogen over the Cu spinel catalyst. © 2009 The Electrochemical Society.
• Sintering and redispersion of platinum catalysts supported on tin oxide

  Kamiuchi Naoto, Taguchi Keiichi, Matsui Toshiaki, Kikuchi Ryuji, Eguchi Koichi

  Applied Catalysis B-Environmental 89 (1-2) 65 - 72 0926-3373 2009 [Refereed][Not invited]
   

  CO oxidation activities of platinum/tin oxide catalysts prepared by impregnation have been investigated in relation with their nano-structural changes in various reduction-oxidation treatments. Variously treated Pt/SnO2 catalysts were characterized by XRD, XPS, and TEM. In 1 wt.% Pt/SnO2 catalyst calcined at 400 °C, crystallized fine particles of Pt were highly dispersed on SnO2 due to strong chemical interaction between two components. After the heat-treatment in a reducing atmosphere, the sintered Pt particles with grown size were frequently observed. Furthermore, unique texture of particles with core-shell structure was produced in the catalyst exposed in air after the reduction treatment at 400 °C. These large particles with the peculiar shape were re-dispersed by the reoxidation treatment at 400 °C to fine particle with similar size to the as-calcined catalysts. The reversibility of the microstructural changes between growth and redispersion of deposited particles was confirmed after the several reduction-oxidation cycles. It was revealed that the structural changes on the interface of Pt/SnO2 catalysts were closely related to the catalytic activity for CO oxidation. © 2008 Elsevier B.V. All rights reserved.
• Electrochemical CO Oxidation and Microstructure in Pt/Co3O4-Based Catalysts

  Matsui Toshiaki, Kamiuchi Naoto, Fujiwara Katsuhiko, Kikuchi Ryuji, Eguchi Koichi

  Journal of the Electrochemical Society 156 (7) K128 - K133 0013-4651 2009 [Refereed][Not invited]
   

  The metal-support interaction in a platinum catalyst supported on cobalt oxide (Pt/ Co3 O4) was investigated. In the as-calcined catalysts prepared by the impregnation method, platinum particles were highly dispersed on the surface of cobalt oxide with the strong interaction. The as-calcined catalysts were sensitive to the reduction treatment. After the pretreatment with hydrogen, the formation of the intermetallic compound of Pt3 Co was observed, accompanied with a significant change in the surface composition and microstructure. Furthermore, the reduced surface species were readily oxidized after exposure to an oxidizing atmosphere. These behaviors were induced by the strong chemical interaction between platinum and cobalt oxide. As a model case study, the electrocatalytic activity for CO oxidation was studied for the applications to polymer electrolyte fuel cells. © 2009 The Electrochemical Society.
• Catalytic hydrogen production from dimethyl ether over CuFe2O4 spinel-based composites: Hydrogen reduction and metal dopant effects

  Faungnawakij, K., Kikuchi, R., Fukunaga, T., Eguchi, K.

  Catalysis Today 138 (3-4) 157 - 161 0920-5861 2008/11 [Refereed][Not invited]
  
• Influence of the supporting matrix on the electrochemical properties of CsH5(PO4)(2) composites at intermediate temperatures

  Hiroki Muroyama, Toshiaki Matsui, Ryuji Kikuchi, Koichi Eguchi

  JOURNAL OF PHYSICAL CHEMISTRY C AMER CHEMICAL SOC 112 (39) 15532 - 15536 1932-7447 2008/10 [Refereed][Not invited]
   

  Proton-conductive CsH5(PO4)2 composites with various pyrophosphate and silica matrices (e.g., SiP2O 7, TiP2O7, and SiO2, etc.) were synthesized, and the composite effects were investigated at intermediate temperatures based on the electrochemical measurement, thermal analysis, and contact angle measurement. The melting and dehydration processes of CsH 5(PO4)2 in composites depended on the matrix species. The composite with SiP2O7 matrix exhibited the highest conductivity among all composites in the temperature range investigated. This result indicates that the conductivity of composites was affected by the pyrophosphate unit and the metal species in the crystalline structure of the pyrophosphate. The conductivity of composites appears to correlate with the compatibility between the components examined by contact angle measurement. These differences in electrochemical and physical properties should be attributed to the interfacial interaction between CsH5(PO 4)2 and the matrix. © 2008 American Chemical Society.
• Formation of layered Al2O3 and its inhibitory effect on the sintering of supported platinum particles

  Tomohiro Mitsui, Toshiaki Matsui, Hitoshi Miyata, Takaaki Kanazawa, Ichiro Hachisuka, Ryuji Kikuchi, Koichi Eguchi

  APPLIED CATALYSIS A-GENERAL ELSEVIER SCIENCE BV 348 (1) 121 - 128 0926-860X 2008/09 [Refereed][Not invited]
   

  The sintering behavior of Pt particles on layered Al2O3 was investigated. Layered Al2O3 was prepared by calcination of a commercially available aluminum hydroxide. The growth of Pt particles on layered Al2O3 was suppressed even in an oxidizing atmosphere at above 1000 °C, and the particle size was greatly affected by the pore diameter of the layered Al2O3. On the other hand, the particle size of platinum on γ-Al2O3 was drastically increased. The diameters and the supported states of Pt particles were evaluated by transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), and chemisorption of carbon monoxide. The platinum particles in a highly dispersed state were captured in the pores of layered Al2O3, so the space for the particles for aggregation or migration was limited. © 2008 Elsevier B.V. All rights reserved.
• Steam reforming on Ni-samaria-doped ceria cermet anode for practical size solid oxide fuel cell at intermediate temperatures

  Mitsunobu Kawano, Toshiaki Matsui, Ryuji Kikuchi, Hiroyuki Yoshida, Toru Inagaki, Koichi Eguchi

  JOURNAL OF POWER SOURCES ELSEVIER SCIENCE BV 182 (2) 496 - 502 0378-7753 2008/08 [Refereed][Not invited]
   

  Direct internal and external reforming operations on Ni-samaria-doped ceria (SDC) anode with the practical size solid oxide fuel cell (SOFC) at intermediate temperatures from 600 to 750 °C are carried out to reveal the reforming activities and the electrochemical activities, being compared with the hydrogen-fueled power generation. The cell performance with direct internal and external steam reforming of methane and their limiting current densities were almost the same irrespective of the progress of reaction in the methane reformate at 700 and 750 °C. The durability test for 5.5 h at 750 °C with direct internal reforming operation confirmed that the cell performance did not deteriorate. The operation temperature of the cell controlled the reforming activities on the anode, and the large size electrode gave rise to high conversion due to the slow space velocity of the steam reforming. Direct internal steam reforming attained sufficient level of conversion for SOFC power generation with methane at 700 and 750 °C on the large Ni-SDC cermet anode. © 2008 Elsevier B.V. All rights reserved.
• Investigation on the power generation and electrolysis behavior of Ni-YSZ/YSZ/LSM cell in reformate fuel

  Chuan-Gang Fan, Tatsuya Iida, Kota Murakami, Toshiaki Matsui, Ryuji Kikuchi, Koichi Eguchi

  JOURNAL OF FUEL CELL SCIENCE AND TECHNOLOGY ASME-AMER SOC MECHANICAL ENG 5 (3) 031202  1550-624X 2008/08 [Refereed][Not invited]
   

  The bigger drop of open circuit voltage (OCV) for a degraded or damaged cell unit will make it consume the electricity generated by other cells of the solid oxide fuel cell stack to electrolyze the exhaust gas. In this article, the degradation behaviors of Ni-YSZ/YSZ (0.5 mm thick)/ La0.6 Sr0.4 MnO3δ cell sample caused by exhaust of hydrocarbon fuel were studied by solid oxide electrolysis cell method. I-V curve and impedance spectra measurements were carried out to investigate the polarization feature of the electrodes during power generation and electrolysis at 1000° C with gas mixtures of H2-CO2, CO-CO2, and H2-H2O at the Ni-YSZ working electrode (WE) as well as oxygen at La0.6 Sr0.4 MnO3-δ counterelectrode. In case of H2-CO2 couple, It was found that the increase of CO2 only depressed the OCV due to the increase of oxygen partial pressure (Po2) at the WE side, and the characteristics of the cell were more influenced by the H2O produced during power generation. In the case of CO-CO2, more CO produced during electrolysis would lead to the carbon deposition, which can result in the increase of polarization resistance by the reduction of the active site (triple phase boundary). In the case of H2-H2O couple, the polarization contribution was different for both power generation and electrolysis. The former likely contributed from concentration polarization since its nature of producing H2O, and the latter mainly contributed to the active site polarization as compared with that from concentration polarization due to its nature of consuming H2O. Copyright © 2008 by ASME.
• Cu-based spinel catalysts CuB2O4 (B = Fe, Mn, Cr, Ga, Al, Fe0.75Mn0.25) for steam reforming of dimethyl ether

  Faungnawakij, Kajornsak, Shimoda, Naohiro, Fukunaga, Tetsuya, Kikuchi, Ryuji, Eguchi, Koichi

  Applied Catalysis a-General 341 (1-2) 139 - 145 0926-860X 2008/06 [Refereed][Not invited]
  
• Support effect on complete oxidation of volatile organic compounds over Ru catalysts

  Tomohiro Mitsui, Kazuki Tsutsui, Toshiaki Matsui, Ryuji Kikuchi, Koichi Eguchi

  APPLIED CATALYSIS B-ENVIRONMENTAL ELSEVIER SCIENCE BV 81 (1-2) 56 - 63 0926-3373 2008/05 [Refereed][Not invited]
   

  Catalytic combustion of ethyl acetate, acetaldehyde, and toluene was investigated on various supported Ru catalysts prepared by the impregnation method, and the effect of reduction treatment on the activity was examined. Among the as-calcined catalysts tested, Ru/CeO2 showed the highest activity for all tests regardless of the pre-treatment in hydrogen atmosphere. The catalytic activity of Ru/SnO2 was significantly degraded by the reduction treatment, whereas the activity of Ru/ZrO2 and Ru/γ-Al2O3 was enhanced. To reveal these phenomena, the as-calcined and reduced catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), transmission electron microscopy (TEM), and BET surface area. The dispersion of ruthenium on the supports was evaluated by chemisorption methods of carbon monoxide. The catalytic activity was strongly related to ruthenium species easily oxidizable and reducible at low temperatures. Such ruthenium species were loaded on CeO2 in a highly dispersed state, resulting in the highest activity. © 2008 Elsevier B.V. All rights reserved.
• Temperature and humidity dependence of the electrode polarization in intermediate-temperature fuel cells employing CsH2PO4/SiP2O7-based composite electrolytes

  Shuichi Yoshimi, Toshiaki Matsui, Ryuji Kikuchi, Koichi Eguchi

  JOURNAL OF POWER SOURCES ELSEVIER SCIENCE BV 179 (2) 497 - 503 0378-7753 2008/05 [Refereed][Not invited]
   

  The polarization behaviors of platinum electrode were investigated with a single cell employing CsH2PO4/SiP2O7-based composite electrolyte. The electrochemical measurements were conducted in the temperature range of 180-240 degrees C under various humidity conditions. The cell performance was enhanced during several discharge cycles, and then the steady state was attained. The active triple phase boundary (TPB) appears to be spontaneously formed. The polarization behaviors for both anode and cathode were strongly affected by the electrolyte conductivity due to its humidity dependence. In accordance with this tendency, the maximum performance was achieved at 220 degrees C in 30% humidified condition whereas the deterioration was observed at 240 degrees C. Throughout the analysis, however, the performance limitation was mainly due to cathodic polarization at every condition. The cathodic overpotential showed a linear dependence against the log of current density at each temperature, which can be expressed as a Tafel equation. Then, the influence of steam concentration and temperature on the electrochemical kinetics was also discussed. (C) 2008 Elsevier B.V. All rights reserved.
• Deactivation and regeneration behaviors of copper spinel-alumina composite catalysts in steam reforming of dimethyl ether

  Faungnawakij, Kajomsak, Fukunaga, Tetsuya, Kikuchi, Ryuji, Eguchi, Koichi

  Journal of Catalysis 256 (1) 37 - 44 0021-9517 2008/05 [Refereed][Not invited]
  
• Preparation of sulfur-tolerant NO_x storage-reduction catalysts based on Pt-Li₂O/TiO₂ and effect of Al₂O₃ addition to TiO₂ on catalyst performance

  Kikuchi Ryuji, Suzuki Shunkei, Matsui Toshiaki, Eguchi Koichi

  Proceeding of Annual/Fall Meetings of the Japan Petroleum Institute 公益社団法人 石油学会 2008 39 - 39 2008 

  これまでにPt-Li₂O/TiO₂がSO₂共存下で優れたNO_x吸収放出特性を示し、高いSO₂被毒耐性を持つことを報告した。本報告ではPt-Li₂O/TiO₂の調製法およびアルミナの添加効果を検討した。アルコキシド法でPt-Li₂O/TiO₂を調製することによりNO_x吸収量が増加した。また、アナターゼ相のTiO₂が高いNO_x吸収能を示すこと、Al₂O₃の添加により耐熱性が向上し、より高温での再生が可能となることを見いだした。
• ジメチルエーテル水蒸気改質用Cuスピネルコンポジット触媒の活性劣化および再生挙動

  菊地 隆司, 霜田 直宏, Faungnawakij Kajornsak, 福永 哲也, 松井 敏明, 河島 俊一郎, 江口 浩一

  化学工学会 研究発表講演要旨集 公益社団法人 化学工学会 2008 176 - 176 2008
• Pt/SnO2によるCO酸化反応:酸化還元処理の効果

  菊地 隆司, 田口 圭一, 松井 敏明, 江口 浩一

  化学工学会 研究発表講演要旨集 公益社団法人 化学工学会 2008 737 - 737 2008
• Transmission Electron Microscopic Observation on Reduction Process of Copper-Iron Spinel Catalyst for Steam Reforming of Dimethyl Ether

  Koichi Eguchi, Naohiro Shimoda, Kajornsak Faungnawakij, Toshiaki Matsui, Ryuji Kikuchi, Syunichiro Kawashima

  Applied Catalysis B: Environmental 80 (1-2) 156 - 167 0926-3373 2008 [Refereed][Not invited]
   

  The reduction process of copper-iron spinel oxide, which is active for steam reforming of dimethyl ether after mixing with alumina, has been investigated by a transmission electron microscope (TEM), scanning TEM (STEM), and energy dispersive X-ray (EDX) analyzer. The catalyst preparation was started from formation of well-sintered CuFe2O4 by calcination in air at 900 °C. After reduction of CuFe2O4 with hydrogen at 250 °C, metallic copper grains were developed on reduced spinel surface by the phase separation from the oxide. Strong chemical interaction between deposited Cu and reduced spinel oxide was expected from their intimate interfacial contact and lattice matching. The reduced sample contained metallic Cu, reduced spinel, and spinel oxide with super-lattice structure. Partial elimination of Cu and lattice oxygen resulted in formation of pores in and between the oxide grains. The size of the deposited Cu particle and Cu grain was largely distributed. After heating at higher temperature of 350 °C, the large spinel oxide particles are decomposed into small particles via formation of cracks. The resultant catalyst powder was very porous and consisted of very small particles of Cu, iron oxide, and spinel oxide. STEM-EDX analyses clarified the phase separation process of metallic Cu and iron oxide from host CuFe2O4 upon reduction. © 2007 Elsevier B.V. All rights reserved.
• Catalytic abatement of acetaldehyde over oxide-supported precious metal catalysts

  Tomohiro Mitsui, Kazuki Tsutsui, Toshiaki Matsui, Ryuji Kikuchi, Koichi Eguchi

  APPLIED CATALYSIS B-ENVIRONMENTAL ELSEVIER SCIENCE BV 78 (1-2) 158 - 165 0926-3373 2008/01 [Refereed][Not invited]
   

  Catalytic combustion of acetaldehyde was investigated on various oxide-supported metal catalysts prepared by impregnation method. Among the as-calcined catalysts tested, SnO2-supported precious metal catalysts showed the highest activity at low temperatures despite low BET surface area, whereas the catalytic activity of the SnO2-supported samples was significantly degraded by reduction treatment in H2 atmosphere. The catalytic activity of ZrO2- and CeO2-supported metal catalysts was improved by reduction treatment, as compared with the as-calcined catalysts. Among the reduced catalysts, ZrO2-supported metal catalysts exhibited the highest activity for acetaldehyde combustion. To reveal these phenomena, all the catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), and BET surface area. The catalytic activity was strongly related to the surface species easily reducible at low temperatures. Over the as-calcined SnO2-supported catalysts, Pt particles were highly dispersed and the existence of platinum species reducible at room temperature was inferred from XPS and TPR, which disappeared by the H2 reduction treatment, leading to deterioration of the activity. On the other hand, over the ZrO2- and CeO2-supported samples, precious metal species were reduced to metallic state by the H2 reduction treatment and stabilized to maintain the enhanced catalytic activity under oxidative atmosphere during acetaldehyde combustion. © 2007 Elsevier B.V. All rights reserved.
• Carbon deposition over Ni-ScSZ anodes subjected to various heat-treatments for internal reforming of solid oxide fuel cells

  Toshiaki Matsui, Tatsuya Iida, Ryuji Kikuchi, Mitsunobu Kawano, Toru Inagaki, Koichi Eguchi

  JOURNAL OF THE ELECTROCHEMICAL SOCIETY ELECTROCHEMICAL SOC INC 155 (11) B1136 - B1140 0013-4651 2008 [Refereed][Not invited]
   

  The influence of the preparation condition of Ni-scandia-stabilized zirconia (Ni-ScSZ) cermet on the tolerance to carbon deposition was investigated in the wide temperature range of 800-1000°C. The mixture of NiO-ScSZ was subjected to preheat-treatments prior to use as a cermet electrode. Although the inhibitory effect of ScSZ in Ni-based cermet for carbon deposition is well known, the present study revealed that the preparation method and firing condition influenced the carbon deposition behavior. The Ni-ScSZ cermet obtained from the oxide mixture heated at 1400°C showed peculiar behavior to carbon deposition. The initial carbon deposition rate at 800-900°C for this sample was larger than that at 1000°C, whereas other samples exhibited a reduction in deposition rate with decreasing temperature. The cubic phase stabilization in ScSZ was confirmed for the sample treated at 1400°C, though ScSZ was in the rhombohedral phase before the heat-treatment with NiO. These results suggested that a strong interaction between NiO and ScSZ was induced by the high-temperature heat-treatment. © 2008 The Electrochemical Society.
• Correlation between conduction behavior of CsH5(PO4)(2) and thermal history

  Hiroki Muroyama, Toshiaki Matsui, Ryuji Kikuchi, Koichi Eguchi

  JOURNAL OF THE ELECTROCHEMICAL SOCIETY ELECTROCHEMICAL SOC INC 155 (9) B958 - B962 0013-4651 2008 [Refereed][Not invited]
   

  The influence of thermal cycle on the conduction behavior of CsH 5(PO4)2 was investigated. The temperature dependence of the conductivity was examined in two consecutive heating processes with different sequential operations under a dry atmosphere. In the second heating, the conduction behavior was significantly affected by the thermal history. This phenomenon could be explained consistently by the results from X-ray diffraction (XRD) and thermal analyses of CsH5(PO 4)2. When the sample was heated at the melting point of CsH5(PO4)2 and then rapidly cooled, the diffraction lines of CsH5(PO4)2 and the condensed phosphates were observed in the XRD pattern. The differential scanning calorimetry and thermogravimetry-differential thermal analysis were conducted in the heating-cooling process under various experimental conditions. It was noted that the crystallization temperature of CsH5(PO 4)2 was strongly dependent on the extent of dehydration. © 2008 The Electrochemical Society.
• Effect of Thermal Treatment on Activity and Durability of CuFe(2)O(4)-Al(2)O(3) Composite Catalysts for Steam Reforming of Dimethyl Ether

  Faungnawakij, Kajornsak, Kikuchi, Ryuji, Shimoda, Naohiro, Fukunaga, Tetsuya, Eguchi, Koichi

  Angewandte Chemie-International Edition 47 (48) 9314 - 9317 1433-7851 2008 [Refereed][Not invited]
  
• A comparative study of solid acids in hydrolysis and steam reforming of dimethyl ether

  Kajornsak Faungnawakij, Ryuji Kikuchi, Toshiaki Matsui, Tetsuya Fukunaga, Koichi Eguchi

  APPLIED CATALYSIS A-GENERAL ELSEVIER SCIENCE BV 333 (1) 114 - 121 0926-860X 2007/12 [Not refereed][Not invited]
   

  The catalytic performances of solid acids (Al2O3 derived from bayerite (PBT), γ-Al2O3 (ALO8), ZSM-5, H-mordenite, and TiO2) in hydrolysis of dimethyl ether (DME) to methanol have been investigated. The stronger and the larger acid sites give rise to higher conversion in hydrolysis; however, fast degradation due to coking and low quality of product are observed. The acid strength of the solid acids is as follows: H-mordenite > ZSM-5 > PBT, ALO8 > TiO2. The apparent activation energies of DME hydrolysis over H-mordenite, ZSM-5, PBT, ALO8, and TiO2 were determined as 73, 76, 101, 146, and 186 kJ mol-1, respectively. Next, steam reforming of dimethyl ether over composites of the solid acid and copper iron spinel was evaluated for hydrogen production. The composites of alumina and Cu spinel are active and durable to produce H2-rich reformate with CO2 as the major products along with trace amounts of CO. The Cu content of 13.3-17.7 wt% in the composites was optimum in terms of reforming performance. Alumina-spinel composites are superior to zeolite-spinel ones with regard to stability. Increasing the steam-to-carbon ratio obviously suppresses the catalyst degradation. © 2007 Elsevier B.V. All rights reserved.
• Nanoscopic observation of strong chemical interaction between Pt and tin oxide

  Naoto Kamiuchi, Toshiaki Matsui, Ryuji Kikuchi, Koichi Eguchi

  JOURNAL OF PHYSICAL CHEMISTRY C 111 (44) 16470 - 16476 1932-7447 2007/11 [Refereed][Not invited]
   

  Platinum catalysts supported on tin oxide were prepared by the impregnation method and were treated in several conditions. The change of their structure by the treatment was investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. In the as-prepared catalyst, platinum particles with their mean size of ca. 3 nm were highly dispersed on SnO2 supports. After the treatment in reduction atmosphere, the intermetallic compounds ascribed to PtSn and Pt3Sn were formed, and the growth of particle by aggregation was observed. Moreover, the particles with core - shell nanostructure were observed in the catalyst reduced at higher temperatures. It was revealed that the core - shell structure was formed by the phase separation of Sn species from the intermetallic compound particles when the catalyst was treated by mild reoxidation such as exposure to air. On the other hand, after the reoxidation treatment, the mean particle size of the metal particle became smaller and crystallized in the unique particle morphology. After reoxidation at higher temperatures, the intermetallic compounds disappeared, and morphology of platinum particles observed in the as-prepared catalyst was regenerated. These structural changes in the interface between platinum and SnO2 should be related to the unusual CO adsorptive property of Pt/SnO2.
• Electrochemical properties of MH2PO4/SiP2O7-based electrolytes (M = alkaline metal) for use in intermediate-temperature fuel cells

  Muroyama, H., Kudo, K., Matsui, T., Kikuchi, R., Eguchi, K.

  Solid State Ionics 178 (27-28) 1512 - 1516 0167-2738 2007/11 [Refereed][Not invited]
  
• Hydrogen production from dimethyl ether steam reforming over composite catalysts of copper ferrite spinel and alumina

  Faungnawakij, Kajornsak, Tanaka, Yohei, Shimoda, Naohiro, Fukunaga, Tetsuya, Kikuchi, Ryuji, Eguchi, Koichi

  Applied Catalysis B-Environmental 74 (1-2) 144 - 151 0926-3373 2007/06 [Not refereed][Not invited]
  
• 無機酸素酸塩を用いた中温作動燃料電池用電解質の開発

  菊地 隆司, 室山 広樹, 松井 敏明, 江口 浩一

  化学工学会 研究発表講演要旨集 公益社団法人 化学工学会 2007 489 - 489 2007
• Thermodynamic analysis of carbon formation boundary and reforming performance for steam reforming of dimethyl ether

  Faungnawakij, K., Kikuchi, R., Eguchi, K.

  Journal of Power Sources 164 (1) 73 - 79 0378-7753 2007/01 [Not refereed][Not invited]
  
• Degradation Behavior of Ni-ScSZ Cermet anode under various humidified conditions for solid oxide fuel cells

  Toshiaki Matsui, Hiroki Fujii, Akira Ozaki, Tomoya Takeuchi, Ryuji Kikuchi, Koichi Eguchi

  JOURNAL OF THE ELECTROCHEMICAL SOCIETY ELECTROCHEMICAL SOC INC 154 (12) B1237 - B1241 0013-4651 2007 [Not refereed][Not invited]
   

  Nickel-scandia-stabilized zirconia (Ni-ScSZ) cermet is one of the promising anodes for use in intermediate-temperature solid oxide fuel cells. Although ScSZ exhibits higher oxide-ion conductivity than yttria stabilized zirconia, the aging effects depending on the doping-concentration results in a decrease in conductivity. However, recent extensive research has clarified that the electrolyte with >10 mol % Sc2 O3 shows no decrease in conductivity. In this study, therefore, 10 mol % Sc2 O3 - ZrO2 (10ScSZ) was used as the ionic conductor in the cermet anode. The degradation behaviors under various humidified conditions were investigated at 800°C on the basis of partial pressure of oxygen under both open-circuit and discharge conditions. The degradation was judged from the impedance spectra before and after oxidative treatments, such as a continuous discharge or an exposure to highly humidified fuel under the open-circuit condition. The Ni-10ScSZ cermet exhibited both reversible and irreversible changes in impedance spectra, depending on the steam concentration and passed current densities. It is noted that, even under the open-circuit condition, the irreversible degradation has occurred with supplying a gaseous mixture of 10% H2 -20% H2 O- N2 balance (p O2 =1.72× 10-18 atm), whereas the reversible change in interfacial resistance was observed in the case of 10% steam concentration (p O2 =4.29× 10-19 atm). © 2007 The Electrochemical Society.
• Preparation and characterization of CO-tolerant Pt and Pd anodes modified with SnO2 nanoparticles for PEFC

  Tatsuya Takeguchi, Yuri Anzai, Ryuji Kikuchi, Koichi Eguchi, Wataru Ueda

  JOURNAL OF THE ELECTROCHEMICAL SOCIETY ELECTROCHEMICAL SOC INC 154 (11) B1132 - B1137 0013-4651 2007 [Not refereed][Not invited]
   

  The Pd/C and Pt/C anodes modified with SnO2 nanoparticles for the polymer electrolyte fuel cell (PEFC) were investigated using pure and 500 ppm CO-contaminated H-2 as fuel gas. Modification of the Pd/C anode with SnO2 nanoparticles enhanced the cell performance in pure H-2, while modification of the Pt/C anode a little lowered the performance. The effect of SnO2 addition on the performances of the cell with the Pd anode in CO-contaminated H-2 was examined. The cell voltage with the Pd/SnO2/C anode in 500 ppm CO-contaminated H-2 was 0.41 V at a current density of 0.2 A/cm(2), while that in pure H-2 was 0.59 V. The Pd/SnO2/C anode exhibited good tolerance to CO poisoning, since the anode adsorbed CO more weakly. Neither electrochemical oxidation of CO nor shift reaction contributed to the CO tolerance of the Pd/SnO2/C anode.
• Direct internal steam reforming at SOFC anodes composed of NiO-SDC composite particles

  Mitsunobu Kawano, Toshiaki Matsui, Ryuji Kikuchi, Hiroyuki Yoshida, Toru Inagaki, Koichi Eguchi

  JOURNAL OF THE ELECTROCHEMICAL SOCIETY ELECTROCHEMICAL SOC INC 154 (5) B460 - B465 0013-4651 2007 [Not refereed][Not invited]
  
• Internal reforming of SOFCs - Carbon deposition on fuel electrode and subsequent deterioration of cell

  Tatsuya Iida, Mitsunobu Kawano, Toshiaki Matsui, Ryuji Kikuchi, Koichi Eguchi

  JOURNAL OF THE ELECTROCHEMICAL SOCIETY ELECTROCHEMICAL SOC INC 154 (2) B234 - B241 0013-4651 2007 [Not refereed][Not invited]
   

  Several cermet anode materials were investigated for direct internal reforming operation of solid oxide fuel cells. The effects of steam and discharge conditions were examined for internal reforming operation with propane as a hydrocarbon fuel. Even at high steam-to-carbon (S/C) ratio, power generation characteristics with Ni-yttria-stabilized zirconia (YSZ) were deteriorated during internal reforming operation with propane at 1000°C, possibly due to carbon formation at low current densities, whereas stable generation behavior was observed for the cells with Ni-scandia-stabilized zirconia (ScSZ) or Ni-samaria-doped ceria (SDC) anode by feeding propane at low SC=0.8. The carbon deposition rate was measured for several cermet anode materials by feeding dry or humidified methane by the gravimetric technique. The carbon deposition rate over Ni-ScSZ was lower than Ni-YSZ, leading to better generation performance with propane at low S/C. Ni-SDC showed the highest carbon deposition rate among the cermets investigated, even for humidified methane. This implies that carbon formed over Ni-SDC could be effectively removed upon power generation. © 2006 The Electrochemical Society.
• Preparation of silica-modified TiO2 and application to dye-sensitized solar cells

  Hoshikawa, Toyohisa, Ikebe, Tsugio, Yamada, Masashi, Kikuchi, Ryuji, Eguchi, Koichi

  Journal of Photochemistry and Photobiology a-Chemistry 184 (1-2) 78 - 85 1010-6030 2006/11 [Not refereed][Not invited]
  
• Thermodynamic evaluation of methanol steam reforming for hydrogen production

  Faungnawakij, Kajornsak, Kikuchi, Ryuji, Eguchi, Koichi

  Journal of Power Sources 161 (1) 87 - 94 0378-7753 2006/10 [Not refereed][Not invited]
  
• Effect of reduction-oxidation treatment on the catalytic activity over tin oxide supported platinum catalysts

  Toshiaki Matsui, Takeoh Okanishi, Katsuhiko Fujiwara, Kazuki Tsutsui, Ryuji Kikuchi, Tatsuya Takeguchi, Koichi Eguchi

  SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS ELSEVIER SCI LTD 7 (6) 524 - 530 1468-6996 2006/09 [Not refereed][Not invited]
   

  In precious metal-oxide catalyst system, the support materials strongly affect the catalytic activity. Especially the term of strong metal-support interaction is well known: Tauster et al. reported that partially reducible oxide such as titanium oxide could modify the chemisorption of H2 and CO [S.J. Tauster, S.C. Fung, R.L. Garten, J. Am. Chem. Soc. 100 (1978) 170; S.J. Tauster, S.C. Fung, J. Catal. 55 (1978) 29; S.J. Tauster, S.C. Fung, R.T.K. Baker, J.A. Horsley, Science 211 (1978) 1121.]. It was also demonstrated that this interaction could modify the catalytic activity of precious metals in different reactions. Accordingly, elucidating these phenomena will be the useful guide for the development of new class of active catalysts. Thus, we had focused on the chemical interaction between platinum and oxide and reported several results. Tin oxide supported platinum catalysts were heat-treated under oxidizing or reducing atmospheres at various temperatures, and their catalytic activity for methane combustion and electrochemical oxidation of CO was investigated. The resulting catalysts exhibited the peculiar microstructure and catalytic activity because of the metal-support interaction. © 2006 NIMS and Elsevier Ltd.
• Composite effects of silicon pyrophosphate as a supporting matrix for CsH5(PO4)2 electrolytes at intermediate temperatures

  Toshiaki Matsui, Tomokazu Kukino, Ryuji Kikuchi, Koichi Eguchi

  Electrochimica Acta 51 (18) 3719 - 3723 0013-4686 2006/05/05 

  The proton-conductive electrolytes of CsH5(PO4)2/SiP2O7 composites were synthesized, and composite effects of silicon pyrophosphate as a supporting matrix at intermediate temperatures were investigated by comparing the properties of CsH5(PO4)2/SiO2 composite. Although both composites showed similar thermal stability, the temperature dependence of the conductivity was quite different each other; the conductivity of the composite electrolyte of CsH5(PO4)2/SiP2O7 was about one-order magnitude higher at every temperature investigated and the maximum conductivity achieved was 116 mS cm-1 at 230 °C. These results suggested that the interfacial interaction between the proton-conductor phase of CsH5(PO4)2 and the matrix of SiP2O7 played an important role in the proton conduction mechanism. © 2005 Elsevier Ltd. All rights reserved.
• Electrochemical oxidation of CO over tin oxide supported platinum catalysts

  T Matsui, K Fujiwara, T Okanishi, R Kikuchi, T Takeguchi, K Eguchi

  JOURNAL OF POWER SOURCES 155 (2) 152 - 156 0378-7753 2006/04 [Refereed][Not invited]
   

  Tin oxide supported platinum catalysts (Pt/SnOx) for use in polymer electrolyte fuel cells were prepared, and their electrochemical oxidation of CO was investigated. From the XPS measurements of Pt/SnOx catalysts, it was found that the binding energy of Pt showed no change compared to bulk Pt, regardless of tin oxide addition. In accordance with this result, CO-stripping voltammograms for Pt/SnOx catalysts revealed that the peak potential for the pre-adsorbed CO oxidation was almost the same value of Pt/C catalyst. However, the onset potential of CO oxidation shifted negatively compared to PtRu/C catalyst, indicating an enhancement of CO tolerance of Pt/SnOx catalysts. (c) 2005 Elsevier B.V. All rights reserved.
• Impedance analysis for dye-sensitized solar cells with a reference electrode

  Hoshikawa, T, Kikuchi, R, Eguchi, K

  Journal of Electroanalytical Chemistry 588 (1) 59 - 67 0022-0728 2006/03 [Not refereed][Not invited]
  
• Novel anode materials for multi-fuel applicable solid oxide fuel cells

  Ryuji Kikuchi, Naotsugu Koashi, Toshiaki Matsui, Koichi Eguchi, Truls Norby

  Journal of Alloys and Compounds 408-412 622 - 627 0925-8388 2006/02/09 

  New anode materials based on Fe-doped CaTiO3 and ruthenium were examined to enhance the fuel flexibility of SOFCs. An optimum weight ratio between NiO and Ca(Fe)TiO3, RuO2 and YSZ (yttria-stabilized zirconia) was determined for Ni-Ca(Fe)TiO3 and Ru-YSZ anodes, respectively, and sintering temperature was investigated to achieve high power generation characteristics. The Ni-Ca(Fe)TiO3 anode of NiO:Ca(Fe)TiO3 = 4:1 sintered at 1300 °C showed better current-voltage characteristics than those sintered at 1200 and 1400 °C, which was comparable to Ni-YSZ anode. When a constant current of 200 mA/cm 2 was applied by feeding a gas mixture of methane, H2O, and N2 at steam-to-carbon (S/C) ratio of 1.6 at 1000 °C, terminal voltage over SOFCs with the Ni-Ca(Fe)TiO3 and Ru-YSZ anode was stable in 20 h, whereas that over Ni-YSZ decreased significantly. The catalytic activity of the anode materials for carbon formation was evaluated by methane decomposition rate measurements. Carbon deposition rates over the Ni-Ca(Fe)TiO3 and Ru-YSZ were found to be lower than that over Ni-YSZ, possibly leading to the stable power generation at the low S/C ratio. © 2005 Elsevier B.V. All rights reserved.
• Effects of electrolyte in dye-sensitized solar cells and evaluation by impedance spectroscopy

  Hoshikawa, T., Ikebe, T., Kikuchi, R., Eguchi, K.

  Electrochimica Acta 51 (25) 2006
• Effects of electrolyte in dye-sensitized solar cells and evaluation by impedance spectroscopy

  Hoshikawa, T., Ikebe, T., Kikuchi, R., Eguchi, K.

  Electrochimica Acta 51 (25) 2006
• Development of NO sorbents tolerant to sulfur oxides

  Yamamoto, K., Kikuchi, R., Takeguchi, T., Eguchi, K.

  Journal of Catalysis 238 (2) 2006
• Development of NO sorbents tolerant to sulfur oxides

  Yamamoto, K, Kikuchi, R, Takeguchi, T, Eguchi, K

  Journal of Catalysis 238 (2) 2006
• Intermediate-temperature fuel cell employing CsH2PO 4/SiP2O7-based composite electrolytes

  Toshiaki Matsui, Tomokazu Kukino, Ryuji Kikuchi, Koichi Eguchi

  Journal of the Electrochemical Society 153 (2) 0013-4651 2006 

  The proton-conductive electrolytes based on CsH2 PO4 SiP2 O7 composites with various molar ratios were synthesized, and their structural and electrochemical properties were investigated at intermediate temperatures. The interfacial chemical reaction between CsH2 PO4 and SiP2 O7 took place during the heat-treatment at 220°C, resulting in the formation of CsH5 (PO4) 2 phase for the composition at CsH2 PO4: SiP2 O7 =2:1-1:5. The resulting composites showed high proton conductivity with no conductivity jump inherent in CsH2 PO4, and the maximum conductivity achieved was 66 mS cm-1 at 272°C. The fuel cell employing CsH2 PO4 SiP2 O7 -based composite electrolyte (molar ratio 1:2, thickness 1.8 mm) was demonstrated at 220°C and showed good performance. It was possible to generate electricity up to 150 mA cm-2, and the maximum power density was 44 mW cm-2. © 2005 The Electrochemical Society. All rights reserved.
• Composite effect on the structure and proton conductivity for CsHsO 4 electrolytes at intermediate temperatures

  Hiroki Muroyama, Toshiaki Matsui, Ryuji Kikuchi, Koichi Eguchi

  Journal of the Electrochemical Society 153 (6) 0013-4651 2006 

  Proton-conductive electrolytes of CsHS O4 composite were synthesized, and the influence of the matrix on their structure and proton conductivity was investigated at intermediate temperatures. As the supporting matrix, heat-treated TiOS O4 hydrate was used. When the matrix heat-treated at 300°C was employed, formation of new phases was observed in the composite during the heat-treatment at 200°C due to the interfacial chemical reaction between CsHS O4 and the matrix. The resulting composite with a suitable composition exhibited higher conductivity than pure CsHS O4 with linear temperature dependence. This anomalous behavior is quite different from that of the pure CsHS O4, which exhibits the "conductivity jump" at ca. 140°C because of the phase transition. © 2006 The Electrochemical Society.
• 固体酸化物形燃料電池の燃料多様化の検討

  菊地 隆司, 飯田 達也, 松井 敏明, 江口 浩一

  化学工学会 研究発表講演要旨集 公益社団法人 化学工学会 2006 651 - 651 2006
• Chemical interaction between Pt and SnO2 and influence on adsorptive properties of carbon monoxide

  T Okanishi, T Matsui, T Takeguchi, R Kikuchi, K Eguchi

  APPLIED CATALYSIS A-GENERAL 298 181 - 187 0926-860X 2006/01 [Refereed][Not invited]
   

  The adsorption and catalytic properties of Pt/SnO2 were investigated as a model catalyst system that undergoes strong chemical interaction upon reduction-oxidation treatment. The surface platinum on Pt/SnO2 adsorbed very little CO at room temperature after reduction with hydrogen at 400 degrees C. This chemical interaction was found to be related with the reaction between precious metal and reduced tin oxide support. The Pt/SnO2 particles after reduction treatment were composed of a core/shell structure where the core of Pt was covered with an oxide shell. An X-ray diffraction pattern of Pt/SnO2 sample after reduction at 400 degrees C contained some lines attributed to intermetallic compounds, such as PtSn2 and PtSn4. The Pt/SnO2 catalyst was employed for a fuel electrode of a polymer electrolyte fuel cell and compared with the conventional Pt/C catalyst. Both catalysts were degraded with the presence of CO in hydrogen. However, the degradation of Pt/SnO2 with 100 ppm CO was insignificant as compared with that of Pt/C. (c) 2005 Elsevier B.V. All rights reserved.
• Influence of solid-acid catalysts on steam reforming and hydrolysis of dimethyl ether for hydrogen production

  Faungnawakij, K, Tanaka, Y, Shimoda, N, Fukunaga, T, Kawashima, S, Kikuchi, R, Eguchi, K

  Applied Catalysis a-General 304 (1) 40 - 48 2006 [Refereed][Not invited]
  
• Electrochemical properties and chemical stabilities of (NH4)2SO4/TiO2 composites at intermediate temperatures

  Hiroki Muroyama, Toshiaki Matsui, Ryuji Kikuchi, Koichi Eguchi

  Solid State Ionics 176 (31-34) 2467 - 2470 0167-2738 2005/10 [Refereed][Invited]
   

  A proton-conductive electrolyte of (NH4)2SO 4/TiO2 composite was synthesized, and its proton conductivity and chemical stability at intermediate temperatures were investigated. In the composite, partial decomposition of (NH4) 2SO4 occurred at around 250 °C, and the resulting materials showed high proton conductivity. The highest conductivity achieved was 15 and 35 mS cm-1 under dry and wet atmospheres at 250 °C, respectively. The temperature dependences of the conductivity were almost reversible in any conditions investigated, and the composite was relatively stable. Under a hydrogen atmosphere, however, the reduction of (NH4)2SO4 phase occurred and the formation of H2S was observed. © 2005 Elsevier B.V. All rights reserved.
• Determination of dispersion of precious metals on CeO2- containing supports

  Takeguchi, T., Manabe, S., Kikuchi, R., Eguchi, K., Kanazawa, T., Matsumoto, S., Ueda, W.

  Applied Catalysis A: General 293 (1-2) 91 - 96 0926-860X 2005/09
• Proton conductivity and stability of Cs2HPW12O40 electrolyte at intermediate temperatures

  Kukino, T, Kikuchi, R, Takeguchi, T, Matsui, T, Eguchi, K

  Solid State Ionics 176 (23-24) 1845 - 1848 0167-2738 2005/07
• An Intermediate Temperature Proton-Conducting Electrolyte Based on a CsH2PO4 / SiP2O7 Composite

  T. Matsui, T. Kukino, R. Kikuchi, K. Eguchi

  Electrochemical and Solid-State Letters 8 (5) A256 - A258 1099-0062 2005/05/01 

  A proton-conductive electrolyte based on a CsH2PO 4/SiP2O7 composite was synthesized, and its electrochemical properties were investigated in the temperature range of 110-287°C. Addition of SiP2O7 as supporting matrix brought about the structural change of conduction phase, CsH2PO 4, into CsH5(PO4)2. The resultant composite electrolyte showed high thermal stability and conductivity under 30% H2O/Ar atmosphere. The maximum conductivity achieved was 44 mS cm-1 at 266°C. Furthermore, the temperature dependence of the conductivity showed no conductivity-jump inherent in the CsH2PO 4-based composite. © 2005 The Electrochemical Society. All rights reserved.
• Steam reforming of dimethyl ether over composite catalysts of gamma-Al2O3 and Cu-based spinel

  Tanaka, Y, Kikuchi, R, Takeguchi, T, Eguchi, K

  Applied Catalysis B-Environmental 57 (3) 211 - 222 0926-3373 2005/05
• Impedance analysis for dye-sensitized solar cells with a three-electrode system

  Hoshikawa, T, Yamada, M, Kikuchi, R, Eguchi, K

  Journal of Electroanalytical Chemistry 577 (2) 339 - 348 1572-6657 2005/04
• Partial oxidation of CH4 and C3H8 over hexaaluminate-type oxides

  Kikuchi, R., Iwasa, Y., Takeguchi, T., Eguchi, K.

  Applied Catalysis A: General 281 (1-2) 61 - 67 0926-860X 2005/03
• Impedance analysis of internal resistance affecting the photoelectrochemical performance of dye-sensitized solar cells

  Hoshikawa, T, Yamada, M, Kikuchi, R, Eguchi, K

  Journal of the Electrochemical Society 152 (2) E68 - E68 0013-4651 2005
• Influence of preparation method and additive for Cu-Mn spinel oxide catalyst on water gas shift reaction of reformed fuels

  Tanaka, Y, Takeguchi, T, Kikuchi, R, Eguchi, K

  Applied Catalysis a-General 279 (1-2) 59 - 66 0926-860X 2005/01
• Characteristics of anodic polarization of solid oxide fuel cells under pressurized conditions

  R Kikuchi, T Yano, T Takeguchi, K Eguchi

  SOLID STATE IONICS 174 (1-4) 111 - 117 0167-2738 2004/10 [Refereed][Not invited]
   

  AC impedance measurements were carried out under pressurized conditions by using a Ni-Y2O3-stabilized zirconia (YSZ)/YSZ half cell in order to investigate anodic polarization at high-pressure conditions. AC impedance spectra were measured at 900 and 1000 degreesC in H-2-H2O system with a constant H-2/H2O ratio, or a constant partial pressure of H-2 or H2O for different total pressures of 1 to 10 atm. At high pressures, the resistance characterized by the semicircle at high frequency was lowered, whereas that at low frequency was raised. A model based on one-dimensional diffusion was developed to estimate concentration polarization based on the impedance measurements, and activation polarization was evaluated using a linear current-potential relation derived from the Butler-Volmer equation. The activation overvoltage was at most 40 mV at 10 mA/cm(2), irrespective of the total pressure. Concentration polarization was computed to increase as the total pressure was raised, whereas it was almost constant for temperature change. Large voltage drop at small current densities was calculated for the system with low partial pressure of oxygen. (C) 2004 Elsevier B.V. All rights reserved.
• SOx sorption-desorption characteristics by ZrO2-based mixed oxides

  Kikuyama, S, Miura, A, Kikuchi, R, Takeguchi, T, Eguchi, K

  Applied Catalysis a-General 259 (2) 191 - 197 0926-860X 2004/03
• Development of solid oxide fuel cells and the component materials

  Koichi Eguchi, Ryuji Kikuchi

  Fuel Cell Science, Engineering and Technology - 2004 419 - 425 2004 

  In addition to the high conversion efficiency, the solid oxide fuel cell (SOFC) is quite attractive from the viewpoint of fuel flexibility, especially the possibility of internal reforming of methane and other hydrocarbons for power generation. The systems with several kW to tens kW-class modules have been successfully operated and tested in Japan. The SOFC systems with internal steam reforming reaction over a Ni-YSZ anode or pressurized condition have been tested as a suitable operation mode. Methane internal reforming proceeded without deterioration with time, whereas the power generation with ethane and ethylene suffered from carbon deposition even at high steam-to-carbon ratio. Carbon deposition region and equilibrium partial pressure of oxygen in the C-H-O diagram were estimated from the thermodynamic data. Reduced temperature SOFC operation is another approach, especially for small scale applications, in which scandia-stabilized zirconia, lanthanum gallate, or rare earth-doped ceria were employed as candidate for the electrolyte.
• Strong chemical interaction between PdO and SnO2 and the influence on catalytic combustion of methane

  Takeguchi, T., Takeoh, O., Aoyama, S., Ueda, J., Kikuchi, R., Eguchi, K.

  Applied Catalysis A: General 252 (1) 205 - 214 0926-860X 2003/10/08
• Effect of precious metal addition to Ni-YSZ cermet on reforming of CH4 and electrochemical activity as SOFC anode

  Takeguchi, T, Kikuchi, R, Yano, T, Eguchi, K, Murata, K

  Catalysis Today 84 (3-4) 217 - 222 0920-5861 2003/09
• Partial oxidation of methane over Ni catalysts based on hexaaliminate- or perovskite-type oxides

  Utaka, T, Al-Drees, SA, Ueda, J, Iwasa, Y, Takeguchi, T, Kikuchi, R, Eguchi, K

  Applied Catalysis a-General 247 (1) 125 - 131 0926-860X 2003/07
• CO removal from reformed fuels over Cu and precious metal catalysts

  T Utaka, T Takeguchi, R Kikuchi, K Eguchi

  APPLIED CATALYSIS A-GENERAL 246 (1) 117 - 124 0926-860X 2003/06 [Refereed][Not invited]
   

  Cu-Al2O3-ZnO and supported precious metal catalysts were investigated for CO removal from reformed fuels. Supported Ru catalysts readily converted CO in the reformed fuel via formation of CH4, Supported Pt catalysts, especially Pt/Al2O3, under 200degreesC demonstrated high CO conversion (ca. 93%) without formation of methane. The Cu-Al2O3-ZnO catalyst also had a high activity (ca. 88%) comparable to that of Pt/Al2O3 without methanation under 200degreesC. CO removal by shift reaction was promoted for the catalysts with large adsorption of H2O. In concentrated CO conditions, the Cu-Al2O3-ZnO catalyst was superior to PUAl2O3 for CO removal due to high activity for the shift reaction. A small amount of oxygen (1.3%) added to reformed fuels accelerated the shift reaction over the Cu-Al2O3-ZnO catalyst. The additive effect is ascribed to thermal activation of the shift reaction with heat supplied by CO and H-2 Oxidation and to facilitating dissociation of adsorbed H2O with adsorbed oxygen. (C) 2003 Elsevier Science B.V. All rights reserved.
• Water gas shift reaction for the reformed fuels over Cu/MnO catalysts prepared via spinel-type oxide

  Tanaka, Y, Utaka, T, Kikuchi, R, Takeguchi, T, Sasaki, K, Eguchi, K

  Journal of Catalysis 215 (2) 271 - 278 0021-9517 2003/04/25
• Water gas shift reaction over Cu-based mixed oxides for CO removal from the reformed fuels

  Tanaka, Y, Utaka, T, Kikuchi, R, Sasaki, K, Eguchi, K

  Applied Catalysis a-General 242 (2) 287 - 295 0926-860X 2003/03
• High temperature catalytic combustion of methane and propane over hexaaluminate catalysts: NOx emission characteristics

  Kikuchi, R., Tanaka, Y., Sasaki, K., Eguchi, K.

  Catalysis Today 83 (1-4) 2003
• High temperature catalytic combustion of methane and propane over hexaaluminate catalysts: NOx emission characteristics

  Kikuchi, R, Tanaka, Y, Sasaki, K, Eguchi, K

  Catalysis Today 83 (1-4) 2003
• CO removal from reformed fuel over Cu/ZnO/Al2O3 catalysts prepared by impregnation and coprecipitation methods

  Tanaka, Y, Utaka, T, Kikuchi, R, Sasaki, K, Eguchi, K

  Applied Catalysis a-General 238 (1) 11 - 18 0926-860X 2003/01
• NOx sorption-desorption mechanism of ZrO2-based oxide

  Kikuyama, S, Matsukuma, I, Takeguchi, T, Kikuchi, R, Eguchi, K, Sasaki, K, Anpo, M, Onaka, M, Yamashita, H

  Science and Technology in Catalysis 2002 145 247 - 250 0167-2991 2003
• Catalytic combustion of volatile organic compounds on supported precious metal catalysts

  Takeguchi, T., Aoyama, S., Ueda, J., Kikuchi, R., Eguchi, K.

  Topics in Catalysis 23 (1-4) 159 - 162 1022-5528 2003
• Catalytic activity of oxide-supported Pd catalysts on a honeycomb for low-temperature methane oxidation

  Kikuchi, R, Maeda, S, Sasaki, K, Wennerstrom, S, Ozawa, Y, Eguchi, K

  Applied Catalysis a-General 239 (1-2) 169 - 179 0926-860X 2003/01
• Characteristics of anodic polarization of solid oxide fuel cells under pressurized conditions

  R Kikuchi, T Yano, T Takeguchi, K Eguchi

  SOLID OXIDE FUEL CELLS VIII (SOFC VIII) 2003 (7) 720 - 727 2003 [Refereed][Not invited]
   

  AC impedance measurements were carried out under pressurized conditions using a Ni-YSZ/YSZ half-cell to investigate anodic polarization at high-pressure conditions. AC impedance spectra were measured at 900degrees and 1000degreesC in H-2-H2O system with a constant H-2/H2O ratio, or a constant partial pressure of H-2 or H2O for different total pressures of 1 to 10 atm. At high pressures, the resistance characterized by the semicircle at high frequency decreased, while that at low frequency increased. Carbon deposition condition was examined thermodynamically for pressurized conditions. Typical operating conditions for solid oxide fuel cells such as S/C = 1 and 1000degreesC, in which carbon deposition is expected at I atm, are out of the carbon deposition region when the total pressure is raised.
• Low-temperature methane oxidation over oxide-supported Pd catalysts: Inhibitory effect of water vapor

  Kikuchi, R., Maeda, S., Sasaki, K., Wennerstr{\"o}m, S., Eguchi, K.

  Applied Catalysis A: General 232 (1-2) 23 - 28 0926-860X 2002/06
• A role of components in Pt-ZrO2/Al2O3 as a sorbent for removal of NO and NO2

  Kikuyama, S, Matsukuma, I, Kikuchi, R, Sasaki, K, Eguchi, K

  Applied Catalysis a-General 226 (1-2) 23 - 30 0926-860X 2002/03/28
• Direct-Alcohol/Hydrocarbon SOFCs : Comparison of Power Generation Characteristics for Various Fuels

  Kazunari SASAKI, Hideaki KOJO, Yuuichi HORI, Ryuji KIKUCHI, Koichi EGUCHI

  Electrochemistry 電気化学会 70 (1) 18 - 22 1344-3542 2002/01/05
• Effect of preparation methods on NOx removal ability by sorption in Pt-ZrO2-Al2O3

  Kikuyama, S, Matsukuma, I, Kikuchi, R, Sasaki, K, Eguchi, K

  Applied Catalysis a-General 219 (1-2) 107 - 116 0926-860X 2001/10
• Thick-film coating of hexaaluminate catalyst on ceramic substrates and its catalytic activity for high-temperature methane combustion

  Kikuchi, R, Takeda, K, Sekizawa, K, Sasaki, K, Eguchi, K

  Applied Catalysis a-General 218 (1-2) 101 - 111 0926-860X 2001/09
• Prediction of dynamic heat transfer of a 2-D bubble column using ANNs

  Hasegawa, T., Chen, W., Kuramoto, K., Kikuchi, R., Tsutsumi, A.

  Journal of Chemical Engineering of Japan 34 (9) 2001
• 3-2. Catalytic Combustion over Hexaaluminate Catalysts and Oxide-Supported Pd Catalysts on a Honeycomb

  EGUCHI Koichi, KIKUCHI Ryuji, MAEDA Shingo, SASAKI Kazunari, OZAWA Yasushi

  Proceedings of the Annual Conference of The Japan Institute of Energy 一般社団法人日本エネルギー学会 10 275 - 278 2001
• The Latest Frontiers of Bubble Columns and Slurry Bubble Columns. Prediction of Dynamic Heat Transfer of a 2-D Bubble Column Using ANNs.

  Tatsuya Hasegawa, Wei Chen, Koji Kuramoto, Ryuji Kikuchi, Atsushi Tsutsumi, Kentaro Otawara

  KAGAKU KOGAKU RONBUNSHU The Society of Chemical Engineers, Japan 27 (4) 461 - 465 0386-216X 2001 

  The instantaneous local heat transfer rates in a 2-D bubble column were measured by using a hot wire probe. An artificial neural network (ANN) was applied to correlate the fluctuation of heat transfer rates with dynamic motions of bubble and liquid. The optimal structure of the artificial neural network was determined for the prediction of heat transfer rates. The trained ANN model gives a good prediction of dynamic heat transfer with errors of less than 5%.
• Nonlinear Phenomena. Nonlinear Hydrodynamics of Three-Phase Reactors.

  TAKATOSHI YANO, RYUJI KIKUCHI, ATSUSHI TSUTSUMI, KUNIO YOSHIDA, MIROSLAV PUNCOCHÁR, JIRI DRAHOŠ

  KAGAKU KOGAKU RONBUNSHU The Society of Chemical Engineers, Japan 25 (4) 530 - 534 0386-216X 1999 

  In the present study, nonlinear hydrodynamic behavior of bubbles and particles in a gas-liquid-solid three-phase reactor is characterized by deterministic chaos analysis in terms of correlation dimension. The embedding method is used to determine correlation dimension from the series of the time intervals between successive optical signals triggered by bubbles or particles. The axial and radial distributions of correlation dimensions are examined and the effect of superficial gas velocity on correlation dimensions for gas and solid phases is investigated.
  In the bubbly flow regime, with increasing axial position the correlation dimensions for the gas phase increase to reach a maximum and slightly drop at the center of the column. On the other hand, in the churn-turbulent flow regime, the correlation dimension of the gas phase has a minimum at the middle of the column. The correlation dimensions of solid phase are 1-2 lower than those of gas phase, and decrease with axial positions. Uniform radial distributions of both gas and solid phases are observed except near the wall.
• Stochastic analysis of bubble and particle motions in a 2-D three-phase reactor.

  Ryuji Kikuchi, Atsushi Tsutsumi, Kunio Yoshida

  JOURNAL OF CHEMICAL ENGINEERING OF JAPAN 公益社団法人 化学工学会 30 (2) 202 - 209 0021-9592 1997 

  The bubble and particle frequencies in a 2-D gas-liquid-solid three-phase reactor were measured with a novel optical transmittance probe using a narrow laser beam. The signals for the gas and solid phases were extracted separately based on the differences in the shape and voltage level of the signals. The power spectral densities of the extracted time series data for both phases were then calculated. All the power spectra were found to exhibit a continuous spectrum and exponential decay in the high-frequency region. Comparison between the power spectra of both phases indicates that these can be classified into three frequency regions: the low frequency region where most of the peaks were found to be common to both the gas and solid phases and no component intrinsic to the solid phase was found; the frequency region between 10 and 35 Hz where the components intrinsic to each of the gas and solid phases were found; and the region above 35 Hz where the components intrinsic to the solid phase were only observed. No significant change of the power spectrum intrinsic to the gas phase was observed with the gas velocity, whereas the component of the power spectrum of the solid phase, especially in the high-frequency region, showed a dependence on the gas velocity. These results indicate that although bubble rising motion affects the dominant frequency of the solid phase, the bubble dynamics were almost independent of the local solid flow structure.
• Fractal aspect of hydrodynamics in a three-phase fluidized bed

  Ryuji Kikuchi, Atsushi Tsutsumi, Kunio Yoshida

  Chemical Engineering Science 51 (11) 2865 - 2870 0009-2509 1996/06

MISC

• Outside front cover: Simple chemical synthesis of intermetallic Pt2Y bulk nanopowder

  Yasukazu Kobayashi, Shohei Tada, Ryuji Kikuchi  Materials Advances  1-  (7)  2141  -2141  2020/07  [Refereed][Not invited]
  
• Low Ni-containing Anodes Using Titanate-based Perovskites for Methane Direct Internal Reforming Power Generation

  菊地 隆司  触媒  57-  (3)  136  -142  2015/06
• リン化ニッケル触媒を用いた熱分解バイオオイルの合成

  小池夏萌, 高垣敦, 菊地隆司, OYAMA S. Ted, 細貝聡, 鈴木善三, 西村俊, 海老谷幸喜  日本エネルギー学会大会講演要旨集  23rd-  78  -79  2014/07/14  [Not refereed][Not invited]
   

  Nickel phosphide has shown to be a highly active catalyst for hydrodeoxygenation of bio-oil model compounds such as furan or phenolic compounds. To investigate the effectiveness of the catalyst in actual bio-oil production, catalytic hydrodeoxygenation of fast pyrolysis oil derived from woody biomass was examined. The upgraded bio-oil was remarkably deoxygenated compared to the pyrolysis oil without upgrading.
• Fabrication of Low Ni-Containing Anodes for Solid Oxide Fuel Cells

  菊地 隆司  化学工学  78-  (7)  455  -457  2014/07
• Design, Fabrication, and Experimentation with Energy Conversion Devices

  KIKUCHI Ryuji  化学工学 = Chemical engineering  76-  (6)  354  -357  2012/06/05
• Support effect on Ni/TiO_2 catalyst in selective methanation of CO in reformed gas

  URASAKI K., TANPO Y., NAGASHIMA Y., KIKUCHI R., KOJIMA T., SATOKAWA S.  觸媒 = Catalyst  53-  (2)  80  -82  2011/03/10
• Heat treatment effect and durability of Cu-based spinel composite catalysts for dimethyl ether steam reforming under DSS-like conditions

  SHIMODA Naohiro, MUROYAMA Hiroki, MATSUI Toshiaki, KIKUCHI Ryuji, EGUCHI Koichi  触媒  52-  (6)  402  -404  2010  [Refereed][Not invited]
  
• 改質ガス中のCO選択メタン化反応用Ru触媒への担体の影響

  浦崎浩平, 遠藤健一朗, 高廣智基, 菊地隆司, 小島紀徳, 里川重夫  石油学会年会講演要旨  52nd-  95  2009/05/19  [Not refereed][Not invited]
  
• Effect of High Current Loading on the Performance Enhancement of SOFCs

  K. Murakami, H. Muroyama, T. Matsui, R. Kikuchi, K. Eguchi  SOLID OXIDE FUEL CELLS 11 (SOFC-XI)  25-  (2)  517  -524  2009  [Not refereed][Not invited]
   

  Solid Oxide Fuel Cells (SOFCs) with a conventional configuration, Ni-YSZ vertical bar YSZ vertical bar LSM, exhibit a continuous improvement of performance during the operation for initial several tens of hours to several weeks until the cathode is completely activated for oxygen reduction. However, the power generation performance is required to be stable in a short period of time for the practical application. In this study, we investigated the effect of high current loading on the stabilization of cell performance. The time course of terminal voltage was recorded at high current densities, where the cell operated as an oxygen pumping. The terminal voltage abruptly increased at first current loading and then achieved a stable value within several hours. The termination of performance enhancement in fuel cell operation by this current treatment was confirmed. No degradation by loading the current density up to 5.0 A/cm(2) for a short time was confirmed in the impedance of both electrodes.
• Development of thermally stable copper spinel-alumina composite catalysts for steam reforming of dimethyl ether

  KIKUCHI Ryuji  觸媒 = Catalyst  50-  (6)  480  -481  2008/09/10
• Formation of layered Al_2O_3 and inhibitory effect on sintering of supported platinum particles

  MITSUI Tomohiro, MATSUI Toshiaki, MIYATA Hitoshi, KANAZAWA Takaaki, HACHISUKA Ichiro, KIKUCHI Ryuji, EGUCHI Koichi  觸媒 = Catalyst  50-  (6)  490  -492  2008/09/10
• Electrode polarization characteristics of solid oxide fuel cells under pressurized conditions

  Toshiaki Matsui, Makoto Futamiua, Ryuji Kikuchi, Koichi Eguchi  ECS Transactions  7-  (1 PART 1)  851  -858  2007/12/01  [Not refereed][Not invited]
   

  Polarization characteristics of both anode and cathode were investigated under pressurized conditions as basic information for solid oxide fuel cell/gas turbines hybrid systems. The influences of partial pressure of reactant gases on interfacial conductivity were examined at 1000°C in the total pressure range of 100-300 kPa by using a conventional single cell employing YSZ tubular electrolyte. For both electrodes, the two arcs were observed in the impedance spectra and the impedance was reduced with an increase in partial pressure of reactant gases. For anode, the interfacial conductivity at high frequencies was independent of the P(H2O) whereas it depended on the P(H2) in the low P(H2O)/P(H2) ratio under an open circuit condition. On the other hand, in the case of cathode, the interfacial conductivity at low frequencies was proportional to P(O2)1/4, whereas that at high frequencies it was independent of P(O2). ©The Electrochemical Society.
• Behavior of carbon deposition on fuel electrode and subsequent deterioration of cell performance during internal reforming operation of SOFCs

  Toshiaki Matsui, Tatsuya Iida, Mitsunobu Kawano, Mitsunobu Kawano, Toru Inagaki, Ryuji Kikuchi, Koichi Eguchi  ECS Transactions  7-  (1 PART 2)  1437  -1445  2007/12/01  [Not refereed][Not invited]
   

  Several cermet anodes were investigated for direct internal reforming operation of solid oxide fuel cells. The effects of steam and discharge conditions were examined for internal reforming operation with propane as a hydrocarbon fuel. Even at high steamto-carbon (S/C) ratios, power generation characteristics with Ni-YSZ deteriorated during internal reforming operation with propane at 1000°C, due to carbon formation at low current densities, whereas stable generation was observed for the cells with Ni-ScSZ or Ni-SDC anode by feeding propane at low S/C = 0.8. Carbon deposition rate was measured for several cermets by feeding dry or humidified methane by the gravimetric technique The carbon deposition rate over Ni-ScSZ was lower than over Ni-YSZ, leading to better generation performance with propane at low S/C. Ni-SDC showed the highest carbon deposition rate among the cermets investigated, even for humidified methane. This implies that carbon formed over Ni-SDC could be effectively removed upon power generation. © The Electrochemical Society.
• Effect of redox treatment on nano-scopic modification of Pt/SnO_2 interface and the catalytic activity for CH_4 and CO oxidation

  KIKUCHI Ryuji, KAMIUCHI Naoto, TSUTSUI Kazuki, MITSUI Tomohiro, MATSUI Toshiaki, EGUCHI Koichi  触媒 = Catalysts & Catalysis  49-  (6)  459  -461  2007/09/05
• Activation Process of Solid Oxide Fuel Cells under Polarization Conditions

  R. Kikuchi, K. Murakami, M. Futamura, T. Matsui, K. Eguchi  SOLID OXIDE FUEL CELLS 10 (SOFC-X), PTS 1 AND 2  7-  (1)  1251  -1260  2007  [Not refereed][Not invited]
   

  Power generation characteristics were improved during electrical loading on the cells with Zr-containing electrolyte and La-containing cathode, mainly because of decrease in the resistance of the cathode. On the contrary, the resistance of anode was slightly decreased, and thus the cell activation can be derived from cathode and/or cathode/electrolyte interface. LSM/YSZ/Pt was fabricated and the impedance between LSM and reference electrode was measured. The impedance was reduced by cathodic current treatment for ca. 60 min in air, whereas increased by anodic current treatment. Reversible behavior of the impedance was observed for cathodic and anodic current treatments. In addition, oscillation in cathode potential during current loading was observed depending on the partial pressure of oxygen. From these experimental results, it is inferred that the oscillation behavior and cell activation process can be related to redox of manganese species by current passage in the proximity of the three-phase boundary.
• Direct Internal Steam Reforming at SOFC with Anode Prepared Using NiO-SDC Composite Particles

  M. Kawano, T. Matsui, R. Kikuchi, H. Yoshida, T. Inagaki, K. Eguchi  SOLID OXIDE FUEL CELLS 10 (SOFC-X), PTS 1 AND 2  7-  (1)  1455  -+  2007  [Not refereed][Not invited]
   

  The dependence of anode catalytic activities on the fuel species and the operating temperatures was investigated for use in the direct internal steam-reformed power generation. The SOFCs employing Ni-SDC cermet anode fabricated from the NiO-SDC composite particles were operated in the temperature range of 700-1000 degrees C by feeding the humidified hydrogen and methane as fuels. The cell performances with humidified hydrogen fuel were higher than those with humidified methane fuel at every operation temperature. The performances at 700 and 800 degrees C were much lower than that at 1000 degrees C when the humidified methane fuel was supplied. Considering the results of the electrochemical characterization and the microstructural observation of anode, the methane conversion and the deposited carbon appeared to significantly affect the cell performances.
• Cu系スピネル触媒によるジメチルエーテルの水蒸気改質

  菊地隆司, 霜田直宏, Kajornsak Faungnawakij, 田中洋平, 竹口竜弥, 福永哲也, 河島俊一郎, 江口浩一  触媒  48-  (6)  458  -460  2006/09  [Refereed][Not invited]
  
• Electrochemical performance of (La, Sr)(Co, Fe)O3- (Ce, Sm)O3 composite cathodes for low temperature solid oxide fuel cells

  Ryuji Kikuchi, Makoto Futamura, Toshiaki Matsui, Koichi Eguchi, Jun Ichiro Kugai, Kazuki Furusho, Masatoshi Shimomura, Kazuo Hata  Proceedings - Electrochemical Society  PV 2005-07-  1674  -1683  2005/12/01  [Not refereed][Not invited]
   

  La0.6Sr0.4Co0.2Fe0.8O 3 (LSCF) - Ce0.7Sm0.3O3 (SDC) composite cathodes were investigated for demonstration of SOFCs working at reduced-temperatures of ca. 800°C. Interlayer of SDC or Ce 0.7Gd0.3O3 (GDC) was inserted between the composite cathode and Sc0.10Ce0.01Zr0.89O 2-α (ScSZ) electrolyte to achieve stable operation. Ni-ScSZ was used as anode. The performance of the composite cathode and the effect of the interlayer were evaluated based on current-voltage and impedance measurements. It was found that insertion of SDC and GDC interlayers was effective in improving power generation characteristics, and especially the SDC interlayer resulted in better performance. In the case of the GDC interlayer, the GDC/LSCF-SDC interface could be responsible for inferior performance to the cell with the SDC interlayer, possibly due to poor adhesion in the GDC/LSCF-SDC interface.
• Influence of steam concentration on the degradation behavior of reversible solid oxide fuel cells

  Toshiaki Matsui, Akira Ozaki, Ryuji Kikuchi, Koichi Eguchi  Proceedings - Electrochemical Society  PV 2005-07-  621  -626  2005/12/01  [Not refereed][Not invited]
   

  The degradation behavior of reversible SOFCs was investigated under various steam concentration atmospheres in the power generation and electrolysis processes. In the power generation process at high steam concentration, a sudden drop in terminal voltage was observed and cell performance degraded. After H2 treatment to the degraded cell, performance recovered but not to the initial level. This result indicated that the irreversible degradation proceeded only partially. On the other hand, during electrolysis, terminal voltage increased continuously while applying a constant current under low steam concentration. This behavior brought about irreversible degradation at both electrodes and suggested interfacial reaction and microstructural destruction.
• 技術情報 CO吸着を抑える電極の開発

  菊地 隆司, 江口 浩一, 竹口 竜弥  燃料電池  5-  (1)  85  -89  2005
• Determination of dispersion of Precious metal on Ce-containing metal oxides

  TAKEGUCHI Tatsuya, MANABE Shinsuke, KIKUCHI Ryuji, EGUCHI Koichi, KANAZAWA Takaaki, MATSUMOTO Shinichi, UEDA Wataru  触媒 = Catalysts & Catalysis  46-  (6)  483  -485  2004/09/10
• Solid oxide fuel cell as a multi-fuel applicable power generation device

  R Kikuchi, K Eguchi  JOURNAL OF THE JAPAN PETROLEUM INSTITUTE  47-  (4)  225  -238  2004/07  [Not refereed][Not invited]
   

  The solid oxide fuel cell (SOFC) has high conversion efficiency, and is quite attractive from the viewpoint of fuel flexibility, especially the possibility of internal reforming of methane and other hydrocarbons for power generation. The high temperature operation of SOFCs allows the reform of hydrocarbon fuels on the fuel electrode internally in a SOFC module. The power generation characteristics of SOFCs with internal steam reforming of methane were investigated. Steam reforming over a Ni-YSZ (yttria-stabilized zirconia) cermet catalyst attained almost the equilibrium conversion and selectivity in a fixed bed reactor at 1000degreesC. Internal reforming of hydrocarbons was incomplete because of the limited contact time with the thick layer of the Ni cermet electrode. Therefore, the fuel cell supplied with pre-reformed gas to the anode always produced a lower terminal voltage due to insufficient conversion of the fuel compared with that supplied with post-reformed gas at a given current density. Methane internal reforming proceeded without deterioration with time, whereas power generation with ethane and ethylene was deteriorated by carbon deposition even at high steam-to-carbon ratio. The carbon deposition region and equilibrium partial pressure of oxygen in the C-H-O diagram were estimated from thermodynamic data. The characteristics of CH4 steam reforming, carbon deposition, and power generation with Ni-YSZ cermet anodes modified by MgO, CaO, SrO, CeO2, and precious metals were examined. CaO addition was effective for suppressing carbon deposition and promoting CH4 steam reforming, although the anode electrochemical activity was slightly deteriorated. Ru and Pt addition enhanced steam reforming and suppressed carbon deposition without deteriorating the anode electrochemical activity. The impedance related to gas diffusion was significantly reduced by precious metal additions, indicating that the stability of the anode catalyst was considerably improved since no carbon was deposited.
• Evaluation of Dye-sensitized Solar Cells by Comparing Impedance Spectra and I-V Curves of the Cells

  HOSHIKAWA Toyohisa, KIKUCHI Ryuji, EGUCHI Koichi  Ceramics Japan  39-  (6)  455  -458  2004/06/01
• 中温作動型燃料電池のための無機酸素酸塩電解質の開発 (特集 中低温型FC用電解質膜およびMEAの開発状況)

  江口 浩一, 菊地 隆司, 松井 敏明  燃料電池  4-  (1)  14  -16  2004
• Catalyst and Life Cycle Assessment

  TAKEGUCHI TATSUYA, KIKUCHI RYUJI  触媒 = Catalysts & Catalysis  45-  (4)  339  -339  2003/06/10
• Water gas shift reaction of reformed fuel over supported Ru catalysts

  T Utaka, T Okanishi, T Takeguchi, R Kikuchi, K Eguchi  APPLIED CATALYSIS A-GENERAL  245-  (2)  343  -351  2003/06  [Refereed][Not invited]
   

  Precious metal catalysts (Ir, Pd, Pt, Rh and Ru) supported on Al2O3 and Ru catalysts on CeO2, La2O3, MgO, Nb2O5, Ta2O5, TiO2, V2O5 and ZrO2 were investigated for water gas shift reaction of reformed gas. Ru/V2O3 catalyst reduced at 400 degreesC in H demonstrated the highest activity for the shift reaction without producing methane. The activities for the shift reaction over Ru catalysts supported on different oxides were not correlated with BET surface area or Ru dispersion, but the activity depended on the chemical character of oxide supports. The catalyst supported on a strongly basic or acid oxide is not effective for the shift reaction. In the same series of catalysts like Ru/V2O3, the activity systematically changed with BET surface area and Ru dispersion. (C) 2002 Elsevier Science B.V. All rights reserved.
• Effect of Additive to Ni-YSZ Cermet on Reforming of CH_4 and Electrochemical Activity as SOFC Anode

  TAKEGUCHI Tatsuya, YANO Tatsuya, KANI Yukimune, KIKUCHI Ryuji, EGUCHI Koichi  触媒 = Catalysts & Catalysis  45-  (2)  86  -88  2003/03/10
• SO_x sorption-desorption characteristics by Cu-Zr oxide

  MIURA Asako, KIKUYAMA Suzue, TAKEGUCHI Tatsuya, KIKUCHI Ryuji, EGUCHI Koichi  触媒 = Catalysts & Catalysis  45-  (2)  95  -97  2003/03/10
• Catalytic autothermal reforming of methane and propane over supported metal catalysts

  S. Ayabe, H. Omoto, T. Utaka, R. Kikuchi, K. Sasaki, Y. Teraoka, K. Eguchi  Applied Catalysis A: General  241-  (1-2)  261  -269  2003/02/20  [Not refereed][Not invited]
   

  Catalytic autothermal reforming of methane and propane over supported metal catalysts has been investigated in the present study. The carbon deposition region and the heat balance of the reaction have been determined from the equilibrium calculations. The sequence of the activities of the 2wt.% metal on alumina support for autothermal reforming of methane was Rh> Pd> Ni> Pt> Co. The catalytic activity of 10wt.% Ni/Al2O3 was higher than that of the 2wt.% Rh/Al2O3. The activity of Ni was significantly lowered by the preferential oxidation of the catalyst in the reactant gas at low temperatures. Although little carbon deposition was observed for the autothermal reforming of methane in the deposition-free region expected from the equilibrium, a large amount of carbon deposition was observed for the propane autothermal reforming even in the steam-rich conditions. The deposited carbon possessed fibrous morphology. The catalytic autothermal reforming appears to be initiated by decomposition of hydrocarbon at the inlet zone then the reforming reaction subsequently proceeded in the catalyst bed. © 2002 Elsevier Science B.V. All rights reserved.
• Fuel flexibility in power generation by solid oxide fuel cells

  K Eguchi, H Kojo, T Takeguchi, R Kikuchi, K Sasaki  SOLID STATE IONICS  152-  411  -416  2002/12  [Not refereed][Not invited]
   

  Power generation characteristics of solid oxide fuel cell (SOFC) with internal steam reforming of hydrocarbons were investigated. Steam reforming reaction over a Ni-YSZ cermet catalyst attained almost the equilibrium conversion and selectivity in the fixed bed reactor at 1000 degreesC. The conversion of internal reforming of hydrocarbons was incomplete because of the limited contact time with a thick layer of the Ni cermet electrode. Therefore, the fuel cell supplied with pre-reforming gas to the anode always gave rise to a lower terminal voltage because of the insufficient conversion of fuel compared with that supplied with post-reforming gas at a given current density. Methane internal reforming proceeded without deterioration with time, whereas the power generation with ethane and ethylene suffered from carbon deposition even at high steam-to-carbon ratio. Carbon deposition region and equilibrium partial pressure of oxygen in the C-H-O diagram were estimated from the thermodynamic data. The effect of the gas composition in the power generation characteristics, especially, difference in reactivity between H-2 and CO2 was investigated. The H-2-H2O and CO-CO2 fuel systems led to almost the same open circuit voltage at the same H-2/H2O and CO/CO2 ratios at 1000 degreesC. as expected from the thermodynamic equilibrium. The output voltage in a discharge condition was always higher for H-2- H2O than for CO-CO2 at every current density. (C) 2002 Elsevier Science B.V. All rights reserved.
• Study on steam reforming of CH4 and C-2 hydrocarbons and carbon deposition on Ni-YSZ cermets

  T Takeguchi, Y Kani, T Yano, R Kikuchi, K Eguchi, K Tsujimoto, Y Uchida, A Ueno, K Omoshiki, M Aizawa  JOURNAL OF POWER SOURCES  112-  (2)  588  -595  2002/11  [Not refereed][Not invited]
   

  Equilibrium partial pressure of oxygen and the boundary of carbon deposition region were calculated in the C-H-O phase diagram at temperatures ranging from 400 to 1000 degreesC. The open circuit voltage for the solid oxide fuel cell (SOFC) was directly connected to the calculated partial pressure of oxygen at higher temperatures. These calculations suggested that the development of the anode catalyst without carbon deposition was one of the most promising ways to achieve high efficiency in SOFC because the amount of added water could be reduced. The characteristics of steam reforming of methane and carbon deposition on Ni-Y2O3-stabilized zirconia (Ni-YSZ) cermets anodes were examined. The effect of MgO, CaO, SrO and CeO2 addition to Ni-YSZ cermets on their catalytic activity and carbon deposition was investigated. Although, the CaO addition slightly deteriorated the electrochemical activity as anode, the CaO addition was effective in suppressing carbon deposition and promoted steam reforming of CH4. (C) 2002 Elsevier Science B.V. All rights reserved.
• スピネル型酸化物を経由するCu/MnOの調製および水性ガスシフト反応活性

  田中 洋平, 宇高 俊匡, 菊地 隆司, 竹口 竜弥, 佐々木 一成, 江口 浩一  触媒  44-  (6)  419  -421  2002/09/10
• Impedance analysis of electronic transport in dye-sensitized solar cells

  T Hoshikawa, R Kikuchi, K Sasaki, K Eguchi  ELECTROCHEMISTRY  70-  (9)  675  -680  2002/09  [Not refereed][Not invited]
   

  The ac impedance spectroscopy was applied to dye-sensitized solar cells with TiO2, or Nb2O5 as the semiconductor electrode. It was found that the impedance spectra consisted of three or four semicircles in the Nyquist representation. The arc with a characteristic frequency of a few hundred Hz was attributable to the electron transport between the semiconductor particles or within the particles, the arc at a few Hz to the electron transport at the electrode/dye/electrolyte interface, and the arc at the frequency in the order of 10(-1) Hz to the reduction of the electrolyte at the Pt electrode/electrolyte interface. The resistance of the arc at a few Hz decreased as the amount of the dye adsorbed on the TiO2 electrode and the irradiation intensity increased. When the Nb2O5 particles with large BET surface area were used as the electrode, the internal resistance of the solar cell was lowered; especially the shrinkage of the arcs in diameter at a few hundred Hz and a few Hz was significant.
• Development of zirconia-based oxide sorbents for removal of NO and NO2

  Matsukuma, I, S Kikuyama, R Kikuchi, K Sasaki, K Eguchi  APPLIED CATALYSIS B-ENVIRONMENTAL  37-  (2)  107  -115  2002/06  [Not refereed][Not invited]
   

  Zirconia-based oxide sorbents for NOx has been investigated to clarify the role of additives. Addition of yttria to Mn-Zr oxide improved the sorption capacity due to enhanced basicity and larger surface area. A small amount of transition metal oxide as additives was effective in promoting the sorption-desorption capability. A small addition of Mn or Co to ZrO2 was effective in achieving reversible sorption and desorption of NOx due to their activity as a reduction-oxidation catalyst. These oxides were active for the oxidation of NO to nitrate ions via NO2 in an oxidizing atmosphere and reduction of nitrate ions in the presence of a gaseous reductant. The NOx sorptive capacities of Mn-containing sorbents were significantly deteriorated in dilute SO2. The NOx sorption capacity of 0.5 wt.% Co/ZrO2 was lowered only slightly in the initial stage of NO2 sorption with dilute SO2. (C) 2002 Elsevier Science B.V. All rights reserved.
• Current-voltage characteristics and impedance analysis of solid oxide fuel cells for mixed H-2 and CO gases

  K Sasaki, Y Hori, R Kikuchi, K Eguchi, A Ueno, H Takeuchi, M Aizawa, K Tsujimoto, H Tajiri, H Nishikawa, Y Uchida  JOURNAL OF THE ELECTROCHEMICAL SOCIETY  149-  (3)  A227  -A233  2002/03  [Not refereed][Not invited]
   

  Current-voltage (I-V) characteristics and electrode impedance of a tubular-type solid oxide fuel cell (SOFC) were analyzed for mixed fuel gases, consisting mainly of CO, H-2, H2O, and a carrier gas, as simulated reformed gas of hydrocarbons or coal gas. I-V characteristics of a single cell were measured as a function of various operational parameters including the H-2-to-CO ratio, the type of carrier gas such as He, N-2, and Ar, the temperature, the fuel-to-carrier gas ratio, and the water vapor concentration. It has been experimentally confirmed that the use of CO-rich gases results in comparable performance to that of H-2-rich gases and thus mixed gas such as coal gas is useful as a SOFC fuel. We have found, for the first time, that the I-V characteristics depend on the carrier gas, indicating the importance of gas transport in porous anodes for anodic polarization. The change in cell voltage by varying fuel compositions was mainly caused by the change in anode impedance associated with a low frequency semicircle in a Cole-Cole impedance plot at 1000degreesC. The fuel gas compositions in thermodynamic equilibrium were calculated and compared with the initial gas compositions, suggesting the importance of water vapor concentration to control the equilibrium H-2-to-CO ratio for CO-rich fuel gases. (C) 2002 The Electrochemical Society.
• Characterization of nonlinear dynamics in a circulating fluidized bed by rescaled range analysis and short-term predictability analysis

  R Kikuchi, A Tsutsumi  CHEMICAL ENGINEERING SCIENCE  56-  (23)  6545  -6552  2001/12  [Not refereed][Not invited]
   

  In the present study, nonlinear hydrodynamic behavior of a circulating fluidized bed with a riser 0.10 m in inner diameter and 10 m in height was characterized in terms of the Hurst exponent and V statistic obtained by the R/S analysis, as well as Mann-Whitney statistic determined by short-term predictability analysis. Hurst exponent, the maximum V statistic and Mann-Whitney statistic were estimated for time series of the local heat transfer rate measured by a hot-wire probe in three radial positions at the height of 6.0 m from the riser bottom. The effects of superficial gas velocity and circulating solid mass flux on the gas-solid flow behavior in the CFB were examined based on the statistics. The Mann-Whitney statistic estimated for the time series was lower than the 99% rejection threshold for the null hypothesis, indicating that the gas-solid flow behavior in the CFB is statistically distinguishable from linearly correlated noise. Radial distributions of the Hurst exponent and Mann-Whitney statistic were found to become flatter as circulating solid mass flux increased. This result indicates that the gas-solid flow structure becomes more uniform and deterministic with increasing circulating solid mass flux. The variation of the maximum V statistic toward circulating solid mass flux appeared to be similar to that of the Hurst exponent. (C) 2001 Elsevier Science Ltd. All rights reserved.
• Pt-ZrO_2-Al_2O_3系酸化物のNOx吸収 - 放出反応機構の検討と残留塩素の影響

  喜久山 鈴恵, 松熊 和泉, 竹口 竜弥, 江口 浩一, 菊地 隆司, 佐々木 一成  触媒  43-  (6)  422  -424  2001/09/10
• Pd 系燃焼触媒のハニカム担持と燃焼特性

  菊地 隆司, 小沢 靖, 前田 真吾, 佐々木 一成, 江口 浩一  触媒  43-  (2)  109  -109  2001/03/10
• Nonlinear modeling of chaotic dynamics in a circulating fluidized bed by an artificial neural network

  Y Nakajima, R Kikuchi, K Kuramoto, A Tsutsumi, K Otawara  JOURNAL OF CHEMICAL ENGINEERING OF JAPAN  34-  (2)  107  -113  2001/02  [Not refereed][Not invited]
   

  In this study, an artificial neural network (ANN) was trained to model dynamic behavior of pressure fluctuations measured in a circulating fluidized bed with a riser having an inner diameter of 0.10 m and a height of 10 m, The ability of the neural network model to approximate the dynamic behavior is examined by comparing time-averaged characteristics, power spectra, and chaotic features of time series measured and generated by the ANN, It is found that dynamic behavior of the original time series is captured well by the ANN, and that the ability of the ANN for generation improves with the number of iterations.
• Design and scale-up methodology for multi-phase reactors based on non-linear dynamics

  A Tsutsumi, R Kikuchi  APPLIED ENERGY  67-  (1-2)  195  -219  2000/09  [Not refereed][Not invited]
   

  Multi-phase reactors exhibit chaotic behaviors due to the highly turbulent motions of bubbles and phase interactions, leading to the formation of a complex spatio-temporal flow structure. The instantaneous motions of bubbles and wakes were studied by local measurements of bubble and particle-velocity fluctuations, bubble-wake structure, bubble shape and orientation. The chaotic dynamics of bubble and particle motions in multi-phase reactors were characterized in terms of the correlation dimension obtained by the deterministic chaos analysis for the series of time intervals between successive bubbles or particles by means of the embedding method. Three different methods, the deterministic chaos analysis, the short-term predictability analysis and the rescaled range (R/S) analysis, were applied to the non-linear dynamics of multi-phase reactors. The scale-up effect in the dynamic behavior of multi-phase reactors was investigated by using columns of different diameters. In addition, the non-linear hydrodynamic motions of bubbles and particles in multi-phase reactors have been modeled by means of an ANN (Artificial Neural Network) trained with time series data of voidage fluctuations for gas and solid phases. By successively adapting its output to input, the ANN can generate time-series data for any superficial gas velocity. The bifurcation diagrams of both bubble and particle motions generated by the trained ANN demonstrated that the ANN is capable of predicting and modeling the chaotic dynamics of multi-phase reactors. (C) 2000 Elsevier Science Ltd. All rights reserved.
• 9-4. Long-Term Strategy up to 2100 for Construction of a New Energy System in the Next Century

  KIKUCHI Ryuji, EGUCHI Koichi, TSUTSUMI Atsushi  日本エネルギー学会大会講演要旨集  (9)  257  -260  2000/08/02
• Thermochemical Recuperative Combined Cycle with Methane-Steam Reforming Combustion

  Ryuji Kikuchi, Kenji Essaki, Atsushi Tsutsumi, Shoichi Kaganoi, Hideki Kurimura, Takashi Sasaki, Takashi Ogawa  Kagaku Kogaku Ronbunshu  26-  (2)  257  -262  2000  [Not refereed][Not invited]
   

  Thormochemical recuperative combined cycles with methane-steam reforming are proposed for improving their thermal efficiency and for peak-load leveling. For targeting higher thermal efficiency, a cycle with methane-steam reforming reaction heated by gas turbine exhaust was analyzed. The inlet temperature of gas turbine was set at 1,350°C. Low-pressure steam extracted from a steam turbine is mixed with methane, and then this mixture is heated by part of the gas turbine exhaust to promote a reforming reaction. The rest of the exhaust heat is used to produce steam, which drives steam turbines to generate electricity. The effect of steam-to-methane ratio (S/C) on thermal efficiency of the cycle, as well as on methane conversion, is investigated by using the ASPEN Plus process simulator. The methane feed rate was fixed at constant and S/C ratio was varied from 2.25 to 4.75. Methane conversion shows an increasing trend toward the ratio and has a maximum value of 17.9% at S/C=4.0. Thermal efficiency for the system is about 51%, which is 1% higher than that calculated for a conventional 1,300 °C class combined cycle under similar conditions. A thermochemical recuperative combined cycle is designed for peak-load leveling. In night-time operation from 20: 00 to 8: 00 it stores hydrogen produced by methane steam reforming at S/C=3.9 to save power generation. The gas turbine inlet temperature is 1,330°C. In daytime operation from 8: 00 to 20: 00 the chemically recuperated combined cycle operated at S/C=2.0 is driven by the mixture of methane and the stored hydrogen. The output at night-time operation decreases down to 0.70 of that for a combined cycle operated at constant load with the same methane feed rate, whereas daytime operation generated power 1.26 times larger than that of the combined cycle. © 2000, The Society of Chemical Engineers, Japan. All rights reserved.
• Characterization of Circulating Fluidized Bed Fluid Dynamics by Deterministic Chaos Theory

  KIKUCHI R.  CFB Technology  pp107-112-  107  -112  1999  [Not refereed][Not invited]
  
• Diagnosis of chaotic dynamics of bubble motion in a bubble column

  R Kikuchi, T Yano, A Tsutsumi, K Yoshida, M Puncochar, J Drahos  CHEMICAL ENGINEERING SCIENCE  52-  (21-22)  3741  -3745  1997/11  [Not refereed][Not invited]
   

  The motion of bubbles in a two-dimensional bubble column was characterized by the deterministic chaos analysis of time-series data of bubble frequency, measured locally by an optical transmittance probe with a narrowed He-Ne laser beam. To diagnose the dynamics of bubble motion, three different methods were applied to the series of time intervals between two successive bubble passages: (i) the correlation dimensions were estimated from the reconstructed attractors, (ii) using the short-term predictability analysis, the deterministic and random features in the bubble motion were characterized in terms of Mann-Whitney statistic, and (iii) the value of the Hurst exponent was computed using the rescaled range (RIS) analysis. All three parameters were found to show consistent and significant changes at the transition between homogeneous bubble flow and heterogeneous churn-turbulent flow. These results indicate that at low velocity the motion of bubbles in the bubble column is deterministic chaotic whereas at high gas velocity the random-like motion of bubbles becomes significant. (C) 1997 Elsevier Science Ltd.
• Low-temperature methane oxidation over oxide-supported Pd catalysts on metal and ceramic honeycombs

  Applied Catalysis A: General  in press-  [Not refereed][Not invited]
  
• NOx Emission in high-temperature catalytic combustion of methane and propane over hexaaluminate catalysts

  Catalysis Today  in press-  [Not refereed][Not invited]
  

Books etc

• Nb2O5を用いた色素増感太陽電池の開発

  色素増感太陽電池の最新技術、シーエムシー出版 2001

Association Memberships

• SOFC研究会   化学工学会   石油学会   触媒学会   米国機械学会   The Electrochemical Society   固体イオニクス討論会   日本エネルギー学会   日本化学会   電気化学会   日本機械学会   水素エネルギー協会   

Research Projects

• Electrochemical Promotion of Ammonia Synthesis in Electrolysis Cells with High Conversion Efficiency

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

  Date (from‐to) : 2020/04 -2023/03 

  Author : 菊地 隆司, 久保田 純

   

  本年度は、Fe/バリウムジルコネート（BZY）系のアンモニア合成電極触媒における、アンモニア合成過程の検討を行った。電流遮断法による電極表面吸着種の解析、赤外分光法による電極表面吸着種の解析、および電圧印加によるアンモニア合成の促進効果に対する温度の影響を検討した。まず、電解質にプロトン伝導体のリン酸塩固体電解質を用いた220℃でのアンモニア合成において、電流遮断法を適用した。この方法では、電圧を印加しアンモニア合成が進行している状況から、電圧を開回路電圧に変更することで、電極表面上の吸着種が分解する際の逆電流を測定した。窒素をアンモニア合成電極に供給した場合には、アルゴンを供給した場合（水素発生反応）と応答電流の挙動が異なり、反応中間体であるN2Hxの分解による電流が流れる可能性が示唆された。これを確認するために、電圧印加状態でアンモニア合成電極の表面吸着種をFT-IRでその場観察した。電圧を印加することでN2Hxの生成に対応する吸収ピークが現れ、電気化学的な作用によりN2の還元が進み、窒素分子にプロトンもしくは水素原子が付加してから窒素原子間の結合が解離しアンモニアが生成する、associative機構で反応が進行することを強く示唆する結果が得られた。一方で、電解質にプロトン伝導体のBZY、電極触媒にFe/BZYを用いて500℃で電圧印加しアンモニアを合成したところ、アンモニア合成速度が徐々に増加するという結果が得られた。電圧印加を止めたところ、アンモニア合成速度は緩やかに減少した。この緩やかな変化は、200℃での印加の場合と大きく異なり、また、電極材料の還元のような時間スケールの現象よりも変化が緩やかであった。500℃では電圧印加によるアンモニア合成促進の機構が、200℃の場合と大きく異なることが分かった。
• Li recovery with pseudocapacitive electrode in fluidized bed cell

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Research (Exploratory)

  Date (from‐to) : 2017/06 -2020/03 

  Author : Sugimoto Wataru

   

  The purpose of this study is to establish the concept of lithium recovery using a slurry of pseudocapacitive material for redox flow CDI (capacitive de-ionization). The study consisted of two schemes. The first work package was related to materials development and mechanistic understanding of the proposed concept. The electrochemical properties of a half-cell with a porous electrode slurry in the presence of a redox active species dissolved in the aqueous electrolyte. A new fast reversible process where the active species are trapped in a high concentration in micropores was elucidated. The second work package involved the study of the proposed concept with a slurry flow in a membrane-electrode assembly using LiMn2O4 slurry, and it was found that LiMn2O4 fine particles selectively adsorb Li ions.
• 固体電解質を用いた電解セルの電極触媒高性能化によるアンモニア合成システムの開発

  国立研究開発法人科学技術振興機構：戦略的創造研究推進事業

  Date (from‐to) : 2014/10 -2020/03 

  Author : 菊地隆司
• Development of metal phosphides as a novel anode material and application to intermediate-temperature fuel cells

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

  Date (from‐to) : 2016/04 -2019/03 

  Author : Kikuchi Ryuji, TADA Shohei, QING Geletu

   

  Metal phosphides are active for H-H bond dissociation, thermally and chemically stable, and electronically conductive comparable to metals. Because of these features, metal phosphides are expected as electrode materials in fuel cells. In this study, metal phosphides such as Ni2P, CoP, FeP, WP, and MoP have been investigated as anode catalysts for intermediate temperature fuel cells, and power generation characteristics were evaluated at 220℃ as H2-O2 fuel cells. The anode performance is in the following order: MoP > WP > FeP > CoP > Ni2P. In addition, MoP and WP exhibited higher current density per electrochemical surface area than commercial Pt/C. Carbon materials such as carbon black or carbon nano-fiber mixed in the anode were found effective to reduce polarization resistances derived from the anodic reaction and gas diffusion in the anode, leading to better power generation performance. In addition, CO tolerance of MoP and WP anodes was proved by using 1%CO/H2 gas.
• Study on reaction site formation at the interface of metal and mixed ionic and electronic conductive oxides and their application to electrochemical devices

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

  Date (from‐to) : 2013/04 -2016/03 

  Author : Ryuji KIKUCHI

   

  The effect of transport properties of mixed ionic and electronic conductors (MIEC) on reaction site formation at the interface of metal and MIEC was studied and their application to anodes of fuel cells was conducted. To clarify the influences of MIEC transport properties on anodic reaction characteristics, several types of MIEC with different particle sizes and crystallinity were investigated systematically for the anodes with various mixing ratio of metals to MIEC. It was found that the anodic overpotential was decreased for the increase in the electric conductivity of MIEC when the oxygen ion conductivity remained sufficiently high. In addition, MIEC oxides of high electronic conductivity realized a new method for anode fabrication by infiltration of Ni into a scaffold of the MIEC.
• 固体高分子形燃料電池実用化戦略的技術開発 要素技術開発 定置用燃料電池改質系触媒の基盤要素技術開発

  独立行政法人新エネルギー・産業技術総合開発機構：固体高分子形燃料電池実用化戦略的技術開発

  Date (from‐to) : 2008/10 -2014/03 

  Author : 菊地隆司
• バイオマスの接触分解によるバイオオイル製造触媒の研究開発

  農林水産省：地域活性化のためのバイオマス利用技術の開発

  Date (from‐to) : 2010/10 -2012/03 

  Author : 菊地隆司
• High performance inorganic hollow fiber membranes for hydrogen production with reaction-generated separation driving force

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

  Date (from‐to) : 2010 -2012 

  Author : OYAMA Shigeo ted, KIKUCHI Ryuji

   

  This project deals with the development of advanced membranes for enhancing the performance of catalytic systems by coupling of transport and reaction processes. The studies were performed with amorphous silica membranes prepared by depositing the permselective components onto porous alumina supports with intermediate layers that have high hydrogen permeance and selectivity. Comparison studies with packed-bed reactor (PBR) and membrane reactor (MR) operation showed that higher conversions and hydrogen molar flows were obtained in the MRs for all pressures studied. A criterion for the required permeance for industrial applications is developed.
• Novel composite electrolytes using hetero-interfacial effect and their application to electrochemical devices

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

  Date (from‐to) : 2010 -2012 

  Author : KIKUCHI Ryuji

   

  Novel composite electrolytes based on phosphate and oxide matrix were investigated for intermediate fuel cells operative at 200-300°C, and the promotional effect of the hetero-interface between the conductive phase and matrix was examined. Interfacial conductive phase was formed between phosphate and SiO2 treated with phosphoric acid, leading to an increase in the conductivity. CsH5(PO4)2/SiO2 composite membrane employing silica fiber membrane as a matrix with a thickness of 70 and 150 μm was fabricated and applied to an electrolyte for an intermediate-temperature fuel cell, which demonstrated good performance of 105 mW cm-2 at 200°C due to a low area specific resistance of 0.32 Ω cm2, and was stable at 200°C under a constant current load of 100 mA cm-2 for 50 h.
• Hydrogen production and separation processes employing proton conductor and water-gas shift reaction catalyst

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

  Date (from‐to) : 2007 -2009 

  Author : EGUCHI Koichi, KIKUCHI Ryuji, MATSUI Toshiaki

   

  Electrochemical hydrogen pumping was investigated with a cell consisting of CsH_2PO_4/SiP_2O_7 composite electrolyte at 200℃. When humidified carbon monoxide was fed to the anode, the evolution rate of hydrogen at the cathode obeyed the Faraday's law. In this system, the water gas shift reaction was promoted electrochemically at the anode during polarization. The overpotential was much higher in humidified carbon monoxide than in humidified hydrogen. The Cu spinel catalyst located upstream of anode gas reduced anodic overpotential at low current densities due to the formation of hydrogen over the catalyst.
• 固体酸化物形燃料電池における高温反応場形成の科学

  日本学術振興会：科学研究費助成事業 特定領域研究

  Date (from‐to) : 2007 -2008 

  Author : 菊地 隆司, 松井 敏明

   

  固体酸化物形燃料電池(SOFC)は作動温度が高く、総合エネルギー変換効率の優れた魅力的な発電システムである。一方で、構成材料が限られており、特に、高温発電下においては構成材料の凝集、材料同士の反応が起こりやすく、反応場である電極/電解質界面の制御は重要な課題である。通電効果として知られている分極時の界面状態変化については、発電性能および長期安定性に大きな影響をおよぼすことが知られているものの、その現象の本質はまだ明確になっていない。本研究ではこの点に着目し、SOFCの高温電極反応場における界面形成と発電性能に及ぼす影響について研究した。これまでに通電による発電性能の向上は空気極/電解質界面および空気極に起因し、La_<0.6>Sr_<0.4>MnO_<3-δ>(LSM)電極をカソード分極した際、通電初期に電位の振動が発現することを報告した。この振動現象は時間の経過と共に消滅することや、LSM電極に供給するガスの酸素分圧に依存することを明らかにしている。本年度は、この振動現象について更に検対し、電極の多孔度、電解質やLSMの組成が通電効果および発電特性におよぼす影響について検討した。LSM電極の気孔率が小さい場合に電位の振動が確認され、気孔率が大きい場合には振動現象はみられなかった。これは、気孔率が小さい場合は三相界面に酸素が十分に供給されず、濃度過電圧の変化に対応して電位の振動が現れ、通電によりLSM粒子径が職大して電極微構造が変化した結果、空孔が大きくなり、三相界面に酸素が十分に供給されたことで、振動現象が消滅したと考えられる。また振動の周期と振幅はLSMの組成に依存したことから、振動現象は通電によるMn種の還元と酸素による再酸化を反映していると考えられる。また単結晶YSZ(100)を電解質に用いた場合、振動現象が観察されたが、SDC(Samarium-doped ceria)場合では観測されなかった。これは、電解質材料によって電極との焼き付け状態が異なり、電極電解質界面の微構造が異なるためであると考えられる。
• 固体酸化物形燃料電池における高温反応場界面形成の科学

  日本学術振興会：科学研究費助成事業 特定領域研究

  Date (from‐to) : 2005 -2006 

  Author : 菊地 隆司, 松井 敏明

   

  固体酸化物形燃料電池(SOFC)は作動温度が高く、総合エネルギー変換効率の優れた魅力的な発電システムである。通電効果として知られている分極時の界面状態変化については、発電性能および長期安定性に大きな影響をおよぼすことが知られているものの、その現象の本質はまだ明確になっていない。本研究ではこの点に着目し、SOFCの高温電極反応場における界面形成と発電性能に及ぼす影響について研究を進めた。アノード、またはアノード/電解質界面は、発電特性が劣化する方向にのみ変化することが分かつた。通電による発電性能の向上は、ランタンを含む空気極とジルコニアを含む電解質を組みあわせた場合に、空気極または空気極/電解質界面に起因することが、インピーダンス解析の結果明らかになった。この性能向上は通電開始後数時間経過後に見られる時間スケールでおこった。空気極/電解質または空気極での通電効果を検討するために、対極にPtを用いたセルで通電効果の検証をしたところ、空気極-参照極間の電位差がある一定値以上になると、端子電圧が一定周期で振動し、電極性能が活性化する現象が見られた。活性化と振動現象が見られる電位差は、測定雰囲気の酸素分圧に依存し、また、カソーディック-アノーディックに電流を流す方向を変えると可逆性があることを見いだした。このような振動現象は他に報告されておらず、活性化との関連が深いことから、現象の解明が通電効果の本質の解明に重要であると考えられる。この振動現象は数十秒から数分のスケールで起こり、測定雰囲気の酸素分圧によること、可逆性があることから、空気極材料の酸素不定比性や酸素欠陥の生成と消滅、もしくは空気極中に含まれる遷移元素の酸化還元が深く関与していると考えられ、空気極における酸素還元反応の活性と密接に関連していると思われる。
• Basic Sorption-Desorption Characteristics of NOx and SOx by Mixed Oxide Sorbents

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

  Date (from‐to) : 2004 -2005 

  Author : EGUCHI Koichi, KIKUCHI Ryuji

   

  Sulfur-tolerant NO sorbents based on Pt/TiO_2 were developed by adding base oxide additives such as M_xO_y (M= Li, Na, K, Cs, Sr, Bo, La). The base oxide additives were effective in improving the NO sorption capacity of Pt/TiO_2 under both SO_2-free and SO_2-containing atmosphere. Under SO_2-containing atmosphere, the NO uptake during sorption reaction for 6 h was not affected over Pt-Li_2O/TiO_2, whereas it was significantly deteriorated over the other sorbents. TPD spectra of H_2S in H_2 after sorption reaction of 6h in SO_2-containing atmosphere showed SO_2 stored on Pt-Li_2O/TiO_2 was released at the lowest temperature. In addition to weak basicity of lithium compared to other additives, Li_2TiO_3 formed over Pt-Li_2O/TiO_2 could lead to instability of the sulfates on Pt-Li_2O/TiO_2, giving rise to desorption of sulfur-containing species at the lowest temperature. In situ FT-IR indicated formation of bulk-like sulfate that needs high temperature to decompose was slow over Pt-Li_2O/TiO_2, which also contributed to the excellent SO_2-tolerance of Pt-Li_2O/TiO_2. NO and NO_2 sorption characteristics were simulated using continuously-stirred tank reactor model. Model parameters included in the model were determined by series of experiments. In these experiments, the following findings were obtained : 1) NO_x uptake was raised by increasing W/F (catalyst weight/gas flow rate) and the concentration of NO and NO_2, 2) NO_x uptake was increased upon feeding NO_2 due to limitation of oxidation of NO to NO_2, 3) NO_x uptake was proportional to W/F during NO_2 sorption reaction. NO and NO_2 sorption curves were successfully simulated by the model, and NO_x uptake was well predicted for various operating conditions. The NO_x concentration at position x in the axial distance in the reactor and operation time t, represented as V_x, t, was expressed as a function of NO_x inlet concentration V_ and surface coverage θ(t), V_= exp(- 1.75θ)V_(1-θ)-0.0242 exp(2.00θ)θ.
• 複素インピーダンス解析に基づく色素増感太陽電池構成成分の評価方法の確立

  日本学術振興会：科学研究費助成事業 特定領域研究

  Date (from‐to) : 2003 -2004 

  Author : 江口 浩一, 菊地 隆司

   

  標準的な色素増感太陽電池のインピーダンス測定の結果、オーミックな抵抗成分R_0と界面電荷移動に起因する円弧成分ω_1〜ω_4の少なくとも5種類の抵抗成分が内部抵抗成分として存在することをこれまでに明らかにしている。このうちω_2は、作用極におけるTiO_2粒子間の電子移動に帰属されるが、一方で、対極のPt触媒活性により影響を受けることが明らかとなり、作用極および対極両方の成分を含むことが示唆された。まず、オープンセルに参照極を導入した三極式のセルを作製し、作用極および対極のインピーダンスを分離したところ、ω_2は対極のインピーダンスにもあらわれ、作用極におけるTiO_2粒子界面の電子移動に起因する成分だけでなく、対極の影響も受けることが判明した。しかしながら、オープンセルを用いると、電解質の厚みが大きく、実際の色素増感太陽電池のとの対応が十分でないため、サンドイッチ型セルに参照極の導入を試みた。参照極として、白金黒付きφ0.2mm白金線を使用し、スペーサーにより通常よりも電極間距離を若干大きくしたサンドイッチ型セルに導入して、作用極および対極のインピーダンスを分離した。ω_2は対極側のインピーダンススペクトルにも現れ、また対極のPt量を変化させることにより、その大きさが変化した。したがって、対極のω_2成分は、対極のPt/電解質界面における電子移動過程に帰属できるものと考えられる。この結果、作用極および対極のω_2に対する寄与を分離できるようになり、色素増感太陽電池の内部抵抗要因の詳細な解析が可能となった。
• 中温作動燃料電池のための無機酸素酸塩電解質の開発と発電特性

  新規産業創造型提案公募制度

  Date (from‐to) : 2002 -2004
• 固体高分子形燃料電池用耐CO披毒SnO2担持貴金属系アノード電極の開発

  新規産業創造型提案公募制度

  Date (from‐to) : 2002 -2004
• 化学物質およびエネルギー同時生産のための固体酸化物燃料電池型反応器の開発

  日本学術振興会：科学研究費助成事業 若手研究(B)

  Date (from‐to) : 2002 -2004 

  Author : 菊地 隆司

   

  固体酸化物を電解質として用いた燃料電池型反応器において、合成ガス(CO+H_2)と電力の同時生産をおこなう電力化学物質同時生産システムの構築を目的とし、燃料極について研究を行った。メタンの部分酸化反応条件では、電極上に炭素が析出し、電極性能劣化を引き起こすため、炭素析出を抑制する燃料極の開発が重要である。 FeをドープしたCaTiO_3(以下FCT)を新規燃料極材料として検討し、化学的安定性をX線回折により評価し、また電極微構造の電子顕微鏡観察を行い、電極作製条件の最適化を行った。この材料はプロトンおよび酸素イオン導電性を示し、導電性が高いため、燃料極のNi量を低減し炭素析出をおさえられる可能性がある。これまでにNi-FCTとYSZ電解質との焼成温度は1300℃がもっとも良いことを報告しているが、この温度での熱処理前後では、X線回折パターンに変化は見られず、高温処理後も化学的に安定であることが分かった。焼成温度を1400℃にしても同様に安定であることが示唆された。NiとFCTの重量比が、NiO:FCT=1:1もしくは4:1において、電極表面観察および発電試験を行ってきたが、さらにNiO:FCT=7:3、6:4、4:6、3:7において電極を調製した。このうちNiO:FCT=4:6がもっとも微細な電極構造をとった。開回路電圧はNiO:FCT=1:1の場合と同様の値が得られ、メタンの部分酸化反応に対応する開回路電圧となったが、電流値は1/10程度となり、著しく性能は低くかった。したがって、NiO:FCT=1:1、1300℃焼成試料が最適条件であると分かった。 SOFCモデルにより、燃料の電極上での直接内部改質と、外部燃料改質との熱効率の比較をした。内部改質では熱エネルギーが余剰になる傾向があり、部分的に燃料を外部改質し、のこりの燃料を直接電極上で改質する方が、発電効率が向上することがわかった。
• Mechanism of carbon nanotube formation on metal supported on zirconia-based fine particles

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)

  Date (from‐to) : 2002 -2004 

  Author : TAKEGUCHI Tatsuya, SADAKANE Masahiro

   

  Reduction behaviors of NiO-modified large surface area CeO_2-ZrO_2, CaO-ZrO_2 solid solutions, YSZ and ZrO_2 were examined by the temperature-programmed reduction technique to evaluate the interaction between NiO particles and supports. Particle sizes of NiO were controlled by changing the calcination temperature of supports. The ZrO_2 showed week interaction with NiO particles, while CeO_2-ZrO_2 showed strong interaction with NiO particles. The NiO particles having strong interaction with the support showed high stability for partial oxidation of methane, while the NiO particles having weak interaction produced a large amount of carbon nanotube in low temperature range. However, when NiO particles were reduced at high temperature, the NiO particles having weak interaction with supports became larger ; therefore, carbon nanotube was not formed effectively. On the other hand, when NiO particles having strong interaction with supports were reduced at high temperature, nano-sized Ni particles were formed and carbon nanotube was effectively produced.
• Efficient and Flexible SOFC System

  国際共同研究

  Date (from‐to) : 2001 -2003
• 超小型ガスタービン・高度分散エネルギーシステム

  ＪＳＴ戦略的創造研究推進制度（研究チーム型） （戦略的基礎研究推進事業：ＣＲＥＳＴ）

  Date (from‐to) : 1999 -2003
• Fuel Reforming and CO Removal for Transportable Hydrogen Production Systems

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

  Date (from‐to) : 1999 -2001 

  Author : EGUCHI Koichi, SEKIZAWA Koshi, KIKUCHI Ryuji, TAKEGUCHI Tatsuya

   

  Fuel Cells are highly efficiency devices, which use hydrogen as fuel, since the cells can directly convert chemical energy to electronic energy. In particular, polymer electrolyte fuel cells are compact and transportable ; therefore, they can beused in cars and houses. In transportable system, hydrogen must be produced on site. In this study, hydrogen productions form methanol and hydrocarbons were investigated. For hydrogen synthesis from methanol, supported Cu catalyst was used. For low loading catalyst, catalyst activity strictly depended on the support. The Cu catalyst supported on ZnAl_2O_4 with high surface area showed high activity. They had two kinds of active sites. One was an XRD-detectable species which showed high TOF and, the other was an XRD undetectable species which showed low TOF. Next partial oxidation of methane was conducted on Ni catalysts supported on hexaaluninate mixed oxide. Ni species was supported by the reduction of the mixed oxide at 800℃. It showed high activity and high stability even at high temperature range. CO removals from reformed methanol and hydrocarbon gasses were conducted on Cu-Al_2O_3-ZnO catalyst in the presence of small amount of oxygen. Oxygen promoted the CO removal, and enhanced CO removal in particular at low temperature of 150℃. Generation experiment was conducted on solid oxide fuel cell, inside of which methane was reformed with steam. CaO, SrO, and CeO_2 addition to Ni-YSZ cermet reduced the carbon formation rate. Deactivation for steam reforming was suppressed by the CaO addition. Performance of Ca-containing Ni-YSZ for Electrode catalyst was slightly lower than parent Ni-YSZ and showed stable activity.
• Development of new sorbent material for reversible removal of air pollutants using catalytic reactions

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B).

  Date (from‐to) : 1998 -2000 

  Author : EGUCHI Koichi, KIKUCHI Ryuji, HABA Masaaki, TAKEGUCHI Tatsuya

   

  It was earnestly desired to develop the effective removal methods or harmful compounds such as NO_X and HCl in the exhaust gases as pollutants. However, it was very difficult to convert these pollutants to harmless compounds on catalysts, because some components in the exhaust gases poisoned the catalyst. In this project, we tried to develop the solid oxide sorbents on which these pollutants were absorbed, concentrated, and reversibly released. We prepared ZrO_2-based sorbents such as Pt-ZrO_2/Al_2O_3 and MnO_y-ZrO_2, On these sorbents NO was catalytically oxidized to nitrate ions, and they moved to the Zr sites. The effect of calcinations temperature and preparation procedures on their NO_X removal capacity was investigated. When H_2PtCl_6 was used as starting materials, high temperature calcination was necessary to remove residual chlorine on the surface of the sorbent. The residual chlorine was not removed by at low temperature calcinations. We found out that when Cl-free compound was used as starting materials, the removal capacity was enhanced by high dispersion of Pt. The ZrO_2-Al_2O_3 support prepared by the coprecipitation method was impregnated with Pt(NO_2)_2(NH_3)_2 solution, and this catalyst showed highest activity in this project. Although ZrO_2-Al_2O_3 did not store NO, it stored NO_2 obtained by oxidation of NO.We found out that catalysts played an important role in store and release reactions at high velocity. While NO removal reaction needed relatively a larger amount of Pt, NO_2 removal reaction needed a trace amount of relatively inactive compounds such as Co and Mn, which enhanced both store and release reactions.