研究者データベース

大友 亮一(オオトモ リヨウイチ)
地球環境科学研究院 物質機能科学部門 機能材料化学分野
准教授

基本情報

所属

  • 地球環境科学研究院 物質機能科学部門 機能材料化学分野

職名

  • 准教授

学位

  • 博士(工学)(東京工業大学)

ホームページURL

科研費研究者番号

  • 10776462

J-Global ID

研究キーワード

  • バイオマス   ゼオライト   触媒   

研究分野

  • ナノテク・材料 / 無機物質、無機材料化学

研究活動情報

論文

  • Taichi Nakamura, Yuichi Kamiya, Ryoichi Otomo
    Microporous and Mesoporous Materials 333 111743 - 111743 2022年03月
  • Haruka Aihara, Sou Watanabe, Atsuhiro Shibata, Lina Mahardiani, Ryoichi Otomo, Yuichi Kamiya
    PROGRESS IN NUCLEAR ENERGY 139 2021年09月 [査読有り]
     
    To prevent unexpected accidents at nuclear facilities caused by accumulated ammonium nitrate in an aqueous liquid waste containing ammonium salts and nitric acid, NH4+ in the liquid waste must be decomposed under mild reaction conditions. In this study, we investigated the oxidative decomposition of NH4+ with O-3 at 333 K in the presence of a homogeneous Co2+ catalyst and Cl in the wide pH range of the test solution. The reaction behavior was greatly affected by pH of the test solution. In a basic solution at pH 12, high conversion of NH4+ was obtained even in the absence of Co2+ and Cl, and the main product was NO3. However, Co2+ and Cl in the solution greatly enhanced the decomposition rate of NH4+ in acidic to mild basic solutions (pH 1-8), while only low conversion of NH4+ was observed unless both Co2+ and Cl were present. For the reaction with Co2+ and Cl in the solutions, NH4+ was transformed mainly into chloramines (NHxCl3 x, x = 1-3) by the reaction with HClO, which was formed by the reaction of Cl with O-3 catalyzed by the homogeneous Co2+ catalyst, and led to the high decomposition rate of NH4+. Cl suppressed the formation of the precipitate CoO(OH) during the reaction and consequently the Co2+ catalyst stably existed in the reaction solution, which was another reason for the high decomposition rate of NH4+ in the presence of Cl. Owing to the swift decomposition of NH4+ under mild reaction conditions and small formation of secondary waste, the oxidative decomposition of NH4+ in the presence of the homogeneous Co2+ catalyst and Cl is suitable and applicable for the treatment of the aqueous liquid waste containing ammonium salts and nitric acid.
  • Ichiro Yamane, Kota Sato, Ryoichi Otomo, Takashi Yanase, Akira Miura, Taro Nagahama, Yuichi Kamiya, Toshihiro Shimada
    NANOMATERIALS 11 4 2021年04月 [査読有り]
     
    A metal-organic framework (MOF) consisting of Cu-benzenetricarboxylic acid was processed under ultrahigh pressure (5 GPa) and at temperature of up to 500 degrees C. The products were characterized with TEM, FTIR, and XAFS. The decomposition of the MOF started at 200 degrees C at 5 GPa. This temperature was much lower than that in the vacuum. Single-nanometer Cu nanoparticles were obtained in carbon matrix, which was significantly smaller than the Cu particles prepared at ambient pressure. The catalytic activity for Huisgen cycloaddition was examined, and the sample processed at 5 GPa showed a much improved performance compared with that of the MOF-derived Cu nanoparticles prepared without high pressure.
  • Philip Anggo Krisbiantoro, Tomokazu Togawa, Koki Kato, Jieqiong Zhang, Ryoichi Otomo, Yuichi Kamiya
    CATALYSIS COMMUNICATIONS 149 2021年01月 [査読有り]
     
    Al2O3-supported precious metal catalysts were tested for the oxidative decomposition of NH4+ in water with O-3 and the effects of support on the catalytic activity of Pd were investigated. Pd/CeO2 was found to be the best catalyst in terms of activity, selectivity and stability and was more active and selective than Co3O4, which is one of the best catalysts reported so far. The reaction proceeded only in the presence of Cl-. The moderate value of the d-band center relative to the Fermi level of Pd was found to be favorable for the activation of reactants, leading to a high catalytic performance.
  • Nuryono Nuryono, Dikki Miswanda, Satya Candra Wibawa Sakti, Bambang Rusdiarso, Philip Anggo Krisbiantoro, Nastiti Utami, Ryoichi Otomo, Yuichi Kamiya
    MATERIALS CHEMISTRY AND PHYSICS 255 2020年11月 [査読有り]
     
    It is keenly desired to develop an environmentally benign and highly stable magnetic adsorbent for efficient recovery of Au(III) ion from an acidic solution. In the present study, we investigated the synthesis of magnetic adsorbents that the magnetic particles, which was prepared from natural iron sand, were modified with silica layer on which chitosan was fixed through 3-chloropropyltrymethoxysilane (CPTMS) by a sol-gel process. Since the magnetic particles were almost completely covered with the silica layer and chitosan was tightly fixed on it through CPTMS, the adsorbent was highly stable in an acidic solution with pH 3 or lower. Excess CPTMS significantly lowered the adsorption capacity for Au(III) ion, while lead to little improvement in the stability. Thus, 1 mmol of CPTMS against 4 mmol of chitosan gave the best magnetic adsorbent in terms of stability and adsorption capacity, of which the maximum was 112 mg g(-1) for Au(III) ion at pH 5. The adsorbent showed high selectivity of Au(III) adsorption in the solution containing Cu(II) and Zn(II), and was reusable for two times keeping high selectivity without fatal decline in the adsorption performance. The magnetic adsorbent was separable from the solution simply with an external magnet, while the modification caused a slight decrease of the saturated magnetization.
  • Kazutaka Hashimoto, Ryoichi Otomo, Yuichi Kamiya
    CATALYSIS SCIENCE & TECHNOLOGY 10 18 6342 - 6349 2020年09月 [査読有り]
     
    A series of Sn-substituted strontium ferrates SrFe1-xSnxO3-delta(x= 0, 0.25, 0.50, 0.75 and 1.0) were prepared by the polymerized complex method. The influence of the substitution of Fe in SrFeO(3-delta)with Sn on structural, redox, and catalytic properties was investigated. X-ray diffraction and(57)Fe Mossbauer analyses revealed that the partial substitution of Fe with Sn expanded the lattice of the perovskite-type structure, leading to elongation of Fe-O bonds. The partial substitution resulted in the decline of the particle size and the increase of the specific surface area. H-2-TPR and TG measurements in a H(2)or O(2)flow indicated that the partial substitution significantly accelerated the redox rates of Fe at 500 degrees C. Due to the increased surface area and enhanced redox properties, the partially substituted SrFe(1-x)Sn(x)O(3-delta)showed higher catalytic activity than SrFeO(3-delta)for the combustion of benzene.
  • Marina Kobune, Dai Takizawa, Jun Nojima, Ryoichi Otomo, Yuichi Kamiya
    CATALYSIS TODAY 352 204 - 211 2020年08月 [査読有り]
     
    Pollution of groundwater with NO3- is a serious problem in the world. While catalytic reduction of NO3- over Pd-bimetallic catalysts including Cu-Pd and Sn-Pd is a promising method for purification of the groundwater, the use of precious metal is a major obstacle for practical applications. In the present study, we applied Ni/Al2O3 for the catalytic reduction of NO3- and compared the catalytic performance with that of unsupported Ni catalyst. The reaction rate over 5 wt.% Ni/Al2O3 was about 5 times higher than that of the unsupported Ni catalyst, based on unit weight of catalyst. While the unsupported Ni catalyst was completely deactivated in low partial pressure of H-2 (=0.75 atm) and high concentration of NO3- (= 800 ppm), Ni/Al2O3 was still active even under less reductive conditions ([NO3-](0)= 800 ppm and P(H-2) = 0.5 atm). The unsupported Ni catalyst had the Ni-0 particles formed by the reduction of NiO with H-2 at 310-420 degrees C. On the other hand, 5 wt.% Ni/Al2O3 possessed the Ni-0 particles formed from NiAl2O4 on Al2O3 by the reduction with H-2 above 450 degrees C. It is plausible that those Ni-0 particles had different properties, giving different catalytic properties. The Ni loadings for Ni/Al2O3 had a significant impact on the catalytic properties. The reaction orders with respect to both NO3- and H-2 were 0.8 for 5 wt.% Ni/Al2O3, while those were 0 and -0.2, respectively, for 10 wt.% Ni/Al2O3. On 10 wt.% Ni/Al2O3, there were two kinds of the Ni degrees particles, which were formed by low (310-420 degrees C) and high (above 450 degrees C) temperature H-2 reductions. Unlike the Pd-bimetallic catalysts, the reduction of NO3- over Ni/Al2O3 did not proceed through NO2-.
  • Toshiki Miyazato, Nuryono Nuryono, Mrina Kobune, Bambang Rusdiarso, Ryoichi Otomo, Yuichi Kamiya
    JOURNAL OF WATER PROCESS ENGINEERING 36 2020年08月 [査読有り]
  • Philip Anggo Krisbiantoro, Tomokazu Togawa, Lina Mahardiani, Haruka Aihara, Ryoichi Otomo, Yuichi Kamiya
    APPLIED CATALYSIS A-GENERAL 596 2020年04月 [査読有り]
     
    In this study, the reaction mechanisms for ozonation of ammonia nitrogen in the presence of Co3O4 or MgO were investigated. For the reaction over Co3O4, Cl- in the reaction solution was indispensable and ClO- was formed by a non-catalytic oxidation of Cl-. Co3O4 promoted the reaction of NH4+ with ClO- to give the products including NO3-, chloramines and gaseous products. In contrast, Cl- was unnecessary for the reaction with MgO. pH of the reaction solution was maintained at around 9 throughout the reaction owing to partial dissolution of MgO. Ammonia nitrogen was decomposed to mainly NO3(-) by non-catalytic radical reaction involving OH center dot, which was formed by the reaction of OH- with O-3 in weakly basic solution. To keep the reaction solution weakly basic, H+ formed with the decomposition of NH4+ was neutralized. As a result, about the same amount of Mg2+ as that of decomposed ammonia nitrogen was dissolved.
  • Wontae Kim, Loida O. Casalme, Taiki Umezawa, Fuyuhiko Matsuda, Ryoichi Otomo, Yuichi Kamiya
    CHEMISTRY LETTERS 49 1 71 - 74 2020年01月 [査読有り]
     
    A method to create adjacent acid-base pair sites, which are carboxyl and amino groups, respectively, on silica through hydrolysis of pre-anchored amide is proposed. This method can produce an adjacent acid-base pair site. The catalyst showed excellent catalytic performance for aldol condensation of 4-nitrobenzaldehyde with acetone, overwhelming the catalyst having only amino group and an acid-base catalyst prepared in a conventional manner.
  • Masanori Nagao, Sayaka Misu, Jun Hirayama, Ryoichi Otomo, Yuichi Kamiya
    ACS APPLIED MATERIALS & INTERFACES 12 2 2539 - 2547 2020年01月 [査読有り][通常論文]
     
    Alongside TiO2, Magneli-phase titanium suboxide having the composition of TinO2n-1 is a kind of attractive functional materials composed of titanium. However, there still remain problems to be overcome in the synthesis of titanium suboxide; the existing synthesis methods require high temperature typically over 1000 degrees C and/or postsynthesis purification. This study presents a novel approach to synthesis of titanium suboxide nanoparticles through solid-phase reaction of TiO2 with TiH2. Crystal phases of titanium suboxide were easily controlled by changing TiO2/TiH2 molar ratios in a TiO2-TiH2 mixed precursor, and a series of titanium suboxide nanoparticles including Ti2O3, Ti3O5, Ti4O7, and Ti8O15 were successfully obtained. The reaction of TiO2 with TiH2 proceeded at a relatively low temperature due to the high reactivity of TiH2, giving titanium suboxide nanoparticles without any postsynthesis purification. Ti2O3 nanoparticles and TiO2 were applied as solid acid catalysts for reaction of furfural with 2-propanol. Ti2O3 showed a high catalytic activity and high selectivity for acetalization of furfural, while TiO2 showed only poor activity for transfer hydrogenation of furfural. The difference in catalytic properties is discussed in terms of the acid properties of Ti2O3 and TiO2.
  • Ryoichi Otomo, Momo Fujimoto, Masanori Nagao, Yuichi Kamiya
    MOLECULAR CATALYSIS 475 2019年10月 [査読有り][通常論文]
     
    Various metal oxides (MgO, Al2O3, SiO2, TiO2, ZrO2, Nb2O5, and CeO2) were treated with NH3 for incorporating nitrogen into the structure of metal oxides. The pristine and NH3-treated metal oxides were used as solid base catalysts for isomerization of glucose to f7ructose in water. SiO2 and Nb2O5 showed a large increment of nitrogen content by the treatment with NH3. FT-IR study on NH3-treated SiO2 revealed that NH3 reacted with terminal silanol groups and siloxane bonds to form Si-NH2 and Si-NH-Si groups. Meanwhile, nitrogen was incorporated into bulk crystal of Nb2O5, causing amorphization of the crystal. Of all the samples, pristine and NH3-treated MgO showed highest catalytic activity for the isomerization of glucose. However, the selectivity to fructose was low due to subsequent reactions of formed fructose. Catalytic activity of Al2O3 and SiO2 was increased by the treatment with NH3, while that of the other metal oxides was not affected. Particularly, the catalytic activity of SiO2 emerged after the treatment with NH3 and was enhanced by increasing the temperature for the treatment up to 800 degrees C. While fructose was consumed by subsequent reactions over MgO, decreasing the selectivity, such reactions of fructose were not noticeable over NH3-treated SiO2. Consequently, NH3-treated SiO2 showed higher selectivity to fructose and gave higher carbon balance than MgO.
  • Nuryono Nuryono, Ani Qomariyah, Wontae Kim, Ryoichi Otomo, Bambang Rusdiarso, Yuichi Kamiya
    MOLECULAR CATALYSIS 475 2019年10月 [査読有り][通常論文]
     
    Modifications of propylsulfonic acid-fixed Fe3O4@SiO2 with three organosilanes (C-2, C-8, and phenyl) were investigated to develop a magnetically separable solid acid catalyst active for hydrolysis of ethyl acetate in excess water. Among the organosilanes, triethoxy(octyl)silane was the best modifier for improvement in catalytic activity, with activity of approximately twice that of the unmodified catalyst. The catalytic activity was comparable to those of Cs2.5H0.5PW12O40 and H3PW12O40 anchored on hydrophobic SBA-15 if compared per acid sites, though the acid strength of sulfonic acid was much weaker than that of H3PW12O40. High hydrophobicity over the surface and around the acid sites created by the octyl group was responsible for the high catalytic activity and the high stability in water. In addition to the improvement in catalytic activity, modification with the octyl group provided high stability for repeated uses of the catalyst in the reaction and there was little decrease in activity over at least four reuses. The catalyst was easily separated from the reaction solution by application of an external magnetic field.
  • Xinyi Ji, Yunan Wang, Tsubasa Fujii, Ryoichi Otomo, Junko N. Kondo, Toshiyuki Yokoi
    CHEMISTRY LETTERS 48 9 1130 - 1133 2019年09月 [査読有り]
     
    A method for estimating the location of Ti atoms in zeolite framework has been developed based on the difference in catalytic activity for epoxidation of 1-hexene and 2-methyl-2-pentene. We have found that the Ti distribution in the MWW framework can be controlled by its preparation method; Ti atoms introduced into the framework by the post-synthesized method were selectively located at narrow space, i.e., 10-membered ring (10MR) channels and the proportion of Ti atoms located in large space, i.e., supercages and 12MR side pockets on the crystal exterior was low.
  • Jun Hirayama, Kei-ichiro Yasuda, Sayaka Misu, Ryoichi Otomo, Yuichi Kamiya
    CATALYSIS SCIENCE & TECHNOLOGY 9 15 4017 - 4022 2019年08月 [査読有り]
     
    In the present study, we investigated the influence of the addition of O-2 to the H-2 reactant stream during the hydrogenation of NO2- in water on the catalytic performances of Al2O3-supported precious metal catalysts including Pd, Pt, Ir, Rh, and Ru with 0.3 mmol g(-1) of the metal. Pd/Al2O3 showed high selectivity for N-2 irrespective of the presence and absence of O-2, and Rh and Ru/Al2O3 were inactive towards the hydrogenation of NO2- even in the absence of O-2. In contrast, while Pt/Al2O3 showed high selectivity for NH3 (90%) in the absence of O-2 (P-H2 = 0.2 atm and P-O2 = 0 atm), the product drastically changed to N-2 with 93% selectivity when O-2 was added (P-H2 = 0.2 atm and P-O2 = 0.1 atm). Since Pt/Al2O3 was completely inactive towards the oxidation of NH3 with O-2 in water under the reaction conditions, oxidative decomposition of the formed NH3 was not the reason for the high selectivity for N-2 in the presence of O-2. Kinetic analysis of the reaction in the absence and presence of O-2 and studies on the effects of the Pt size suggested that hydrogen atoms activated on the Pt particles were mainly consumed by O-2 upon H2O formation in the presence of O-2. We concluded that the inactivation of the Pt sites active for NH3 formation and furthermore the change in the function of the sites to N-2 formation caused by the O-2 addition lead to the drastic change in the selectivity from NH3 to N-2 in the presence of O-2.
  • Shuhei Yasuda, Atsuki Iwakura, Jun Hirata, Mitsuru Kanno, Wataru Ninomiya, Ryoichi Otomo, Yuichi Kamiya
    CATALYSIS COMMUNICATIONS 125 43 - 47 2019年05月 [査読有り]
     
    Gas-phase oxidation of methacrolein to methacrylic acid was carried out over an acid-modified Cr2O3/SiO2 catalyst. While only total oxidation occurred over bare Cr2O3/SiO2, the acid-modified Cr2O3/SiO(2 )showed catalytic activity for the formation of methacrylic acid. In particular, H3PW12O40 strong Bronsted acid was the most effective modifier for improving both activity and selectivity. The interface between Cr2O3 and H3PW12O40 particles on SiO2 appears to be responsible for the formation of active sites for the selective formation of methacrylic acid. The strong Bronsted acid would help the activation of methacrolein through rendering it more electrophilic, which is a key step for the formation of methacrylic acid over the present catalyst.
  • Ryoichi Otomo, Ryota Osuga, Junko N. Kondo, Yuichi Kamiya, Toshiyuki Yokoi
    APPLIED CATALYSIS A-GENERAL 575 20 - 24 2019年04月 [査読有り][通常論文]
     
    Ion-exchange of an Al-rich zeolite beta, synthesized by organic structure-directing agent-free method (Beta-OF), was studied for application as a base catalyst. While the as-synthesized Beta-OF in Na-form itself had base sites and showed moderate catalytic activity for Knoevenagel condensation, the ion-exchange with Cs+ improved the catalytic activity. For Knoevenagel condensation of benzaldehyde with ethyl acetoacetate, the catalytic activity of Beta-OF ion-exchanged with Cs+ largely surpassed that of the conventional zeolite beta with less Al content. CO2-TPD and IR observation with chloroform as a probe molecule revealed that the Cs-exchanged Beta-OF had strong base sites comparable to Cs-exchanged Y zeolite. Base strength of Beta-OF was stronger than that expected by Sanderson's theory. A local high density of Al atoms in the framework of Beta-OF resulted in the unexpected base property and high catalytic activity.
  • Ryoichi Otomo, Chiaki Yamaguchi, Daiki Iwaisako, Shun Oyamada, Yuichi Kamiya
    ACS SUSTAINABLE CHEMISTRY & ENGINEERING 7 3 3027 - 3033 2019年02月 [査読有り]
     
    Catalytic properties of metal phosphates were investigated for gas-phase dehydration of 1,2-propanediol to propanal in the presence and absence of steam in the temperature range of 150-340 degrees C. Boron, aluminum, and nickel phosphates showed promising catalytic activity for the dehydration reaction. Especially, boron phosphate showed outstanding catalytic activity at a low reaction temperature and high selectivity to propanal without formation of competitive dehydration products such as acetone and allyl alcohol. The catalytic activity of boron phosphate was remarkably enhanced in the presence of steam cofed with 1,2-propanediol. The additional steam was also favorable for promoting hydrolysis of dioxolane, which is a byproduct formed through acetalization of propanal, resulting in the high yield of propanal over 95%. Boron phosphate showed more durable catalytic activity and much higher yield of propanal than conventional solid acid catalysts such as ZSM-5, silica-alumina and niobium oxide that have been reported to be active for the dehydration of 1,2-propanediol.
  • Shuhei Yasuda, Jun Hirata, Mitsuru Kanno, Wataru Ninomiya, Ryoichi Otomo, Yuichi Kamiya
    APPLIED CATALYSIS A-GENERAL 570 164 - 172 2019年01月 [査読有り][通常論文]
     
    Role of steam in selective oxidation of methacrolein with molecular oxygen over H3PMo12O40 catalyst was investigated. Addition of steam to feed gas significantly enhanced both catalytic activity and selectivity to methacrylic acid, which were fivefold and twice increases, respectively, under the optimal steam pressure (P-H2O = 0.13 atm). Kinetic analysis demonstrated that the addition of steam caused 200-fold increase in the pre-exponential factor for the formation of methacrylic acid, leading to the significant increase in the activity. The steam in the feed gas varied hydrous state of H3PMo12O40 under the reaction conditions, while did not alter redox property, molecular and crystalline structures, and surface area of the catalyst. In the presence of steam at 573 K, three H2O per one H3PMo12O40 were absorbed and hydrated protons like [H3O](+) were formed in the bulk of H3PMo12O40. Methacrolein was adsorbed on the surface of the hydrous catalyst, but not on anhydrous one at all. Based on the results, it was concluded that activation of methacrolein readily occurred on the catalyst in the presence of steam, leading to the significant increase in the pre-exponential factor. Quantum chemical calculation supported the smooth activation of methacrolein by the reaction with [H3O](+) without any transition state.
  • Ryoichi Otomo, Toshiki Nishitoba, Rota Osuga, Yusuke Kunitake, Yuichi Kamiya, Takashi Tatsumi, Toshiyuki Yokoi
    JOURNAL OF PHYSICAL CHEMISTRY C 122 2 1180 - 1191 2018年01月 [査読有り][通常論文]
     
    A series of MCM-68 zeolites with different Si/Al ratios were prepared by treatment with nitric acid and compared with beta zeolites. Speciation of aluminum and location of acid sites changed depending on the Si/Al ratio. The location of Bronsted acid sites in MCM-68 samples was able to be classified by FT-IR measurements with pyridine and 2,6-di-tert-butylpyridine as probe molecules, and the number of Bronsted acid sites was quantified according to the locations. For high-aluminum MCM-68, Bronsted acid sites were broadly distributed in both the 12-ring channel and 10-ring windows as well as inside the supercage. The Bronsted acid sites in the 12-ring channel were easily removed by the acid treatment, and consequently, high-silica MCM-68 had Bronsted acid sites predominantly in the 10-ring windows and inside the supercage. Al-27 MQMAS NMR spectra of high-silica MCM-68 showed two specific peaks assignable to T6 and T7 sites, which did not face the 12-ring channel, forming the Bronsted acid sites highly tolerant to the acid treatment. MCM-68 catalysts showed better catalytic performance in dehydration of sorbitol than beta, mordenite, and ZSM-5. Large void spaces at the intersection of 12- and 10-ring channels and inside the supercage for MCM-68 made it easy to take bulky transition states in the dehydration of sorbitol, resulting in its high catalytic performance.
  • Turgen Biligetu, Yong Wang, Toshiki Nishitoba, Ryoichi Otomo, Sungsik Park, Hiroshi Mochizuki, Junko N. Rondo, Takashi Tatsumi, Toshiyuki Yokoi
    JOURNAL OF CATALYSIS 353 1 - 10 2017年09月 [査読有り][通常論文]
     
    The distribution of Al atoms in ZSM-5 has been recognized as an important factor in catalytic activity. Here, ZSM-5 zeolites were synthesized from synthetic gels containing various alcohols, including straight- and branched-chains alcohols. The effect of the alcohols in the synthetic gel on the Al distribution in the MFI framework was investigated based on (27)AI MAS NMR, Co(II) ion UV-vis DRS, and constraint index value. Thus synthesized ZSM-5 zeolites were applied to catalysts for the cracking of n-hexane and the methanol-to-olefins (MTO) reactions in order to investigate the impact of the Al distribution on the catalytic properties. A unique Al distribution in the MFI framework was achieved by the use of trimethylolethane (TME) in combination with Na cations, and thus-prepared ZSM-5 catalyst showed a long catalytic life for both the cracking of n-hexane and the MTO reaction. (C) 2017 Elsevier Inc. All rights reserved.
  • Ryoichi Otomo, Toshiyuki Yokoi
    MICROPOROUS AND MESOPOROUS MATERIALS 224 155 - 162 2016年04月 [査読有り][通常論文]
     
    To date, many types of zeolites have been successfully synthesized without using any organic structure directing agent (OSDA). However, so-called "OSDA-free synthesis of zeolites" including Beta often gives a low product yield. The present study shows that hydrothermal synthesis using precursor suspension with a high-aluminum content substantially improved the yield in the OSDA-free synthesis of Beta zeolite. By means of monitoring time course changes of solid products in detail, it was found that the crystallization proceeded through the "solution-mediated mechanism" in which the amount of aluminosilicate species (not silicate species alone) in the mother solution determined the product yield. Synthesis parameters such as silica raw material, alkalinity, and seed crystal were optimized, achieving similar to 80% yield based on SiO2. (C) 2015 Elsevier Inc. All rights reserved.
  • Yong Wang, Ryoichi Otomo, Takashi Tatsumi, Toshiyuki Yokoi
    CATALYSIS SURVEYS FROM ASIA 20 1 1 - 12 2016年03月 [査読有り][通常論文]
     
    The catalytic cracking of n-hexane for producing light olefins on Beta zeolite synthesized under organic structure-directing agent free conditions (OFB) was carried out as a model reaction of naphtha cracking. The Al-rich H-form OFB (HOFB) catalyst exhibited a short catalytic life and a low selectivity to propylene even at the lower reaction temperature of 773 K, due to its high acid amount. Dealumination of HOFB by ammonium hexafluorosilicate (AHFS) treatment and followed by nitric acid treatment resulted in the increase in the catalytic life and propylene selectivity, regardless of the reaction temperatures ranging from 773 to 923 K. This could be attributed to the lower amount of the acid sites especially the Lewis acid sites, which suppressed the secondary reactions of propylene and butenes and the hydride transfer to form coke. For example, the HOFB-AHFS(0.5 M)-HNO3(6 h) catalyst showed a very high selectivity of ca. 41 C-% to propylene even at nearly 100 % n-hexane conversion, at the higher reaction temperature of 923 K.
  • Yong Wang, Ryoichi Otomo, Takashi Tatsumi, Toshiyuki Yokoi
    MICROPOROUS AND MESOPOROUS MATERIALS 220 275 - 281 2016年01月 [査読有り][通常論文]
     
    This work deals with the dealumination of organic structure-directing agent (USDA) free beta (OFB) zeolite by different methods to change its acid amount and enhance its catalytic performance in n-hexane cracking. The OFB zeolite was pre-treated with ammonium hexafluorosilicate (AHFS) solution, steaming, or concentrated NH4NO3 (ca. 10 M) followed by calcination at high temperature. Then, thus pre-treated OFB samples can be effectively dealuminated by acid treatment with the structure retained. The H-form OFB (HOFB) and dealuminated OFB (DOFB) catalysts were characterized by using X-ray diffraction, N-2 adsorption-desorption, SEM, ICP, NH3-TPD, Si-29 and Al-22 MAS NMR, and pyridine adsorption FT-IR. In the catalytic cracking of n-hexane, the DOFB catalysts showed a higher propylene selectivity and a longer catalytic life than the parent Al-rich HOFB catalyst. This would be attributed to the lower amount of acid sites, especially the Lewis acid sites, which suppressed the secondary reaction of propylene and butenes and the hydride transfer to form coke. (C) 2015 Elsevier Inc. All rights reserved.
  • Ryoichi Otomo, Ulrich Mueller, Mathias Feyen, Bilge Yilmaz, Xiangju Meng, Feng-Shou Xiao, Hermann Gies, Xinhe Bao, Weiping Zhang, Dirk De Vosh, Toshiyuki Yokoi
    CATALYSIS SCIENCE & TECHNOLOGY 6 3 713 - 721 2016年 [査読有り][通常論文]
     
    Zeolites synthesized without any organic structure-directing agent (OSDA) have several advantages over conventional zeolites synthesized with OSDAs. Their Al-rich compositions, however, are sometimes not suitable for applications as catalysts. In the present study, post-synthetic modification was performed using an Al-rich Beta zeolite synthesized without any OSDAs (designated as "Beta.OF)") to obtain high-silica Beta zeolites. We have successfully developed a facile post-synthetic method for tuning the Al content of Beta(OF) with the *BEA-type structure retained by calcination at >750 degrees C followed by acid treatment. Solid-state Si-29 and Al-27 MAS NMR analyses revealed that during calcination, framework Al atoms were isomorphously substituted with Si atoms to form high-silica frameworks and concomitant extra-framework Al species. The stability of the obtained frameworks against acid treatment was evaluated in terms of the framework Al content, finding that the framework with the Si/Al ratio higher than 12 is well stabilized enough for acid treatment. Thus, dealuminated Beta(OF) zeolites with high-silica compositions were found to be effective catalysts for the methanol-to-olefin (MTO) reaction; particularly, the Beta zeolite with the Si/Al ratio of 112 maintained the conversion of methanol over 90% with selectivity to C-2-C-4 olefins over 70% even at 40 hours on stream at WHSV = 3.2 h(-1).
  • Ryoichi Otomo, Ryota Kosugi, Yuichi Kamiya, Takashi Tatsumi, Toshiyuki Yokoi
    CATALYSIS SCIENCE & TECHNOLOGY 6 8 2787 - 2795 2016年 [査読有り][通常論文]
     
    Sn-Beta was post-synthetically modified with various cations such as Li+, Na+, K+, Cs+, and NH4+. During the modification process, the ion-exchange of the cations with silanol groups occurred along with a reversible change between "closed" and "open" Sn sites through hydrolysis of the Si-O-Sn bonds. The IR study showed that Sn-Beta had weak Bronsted acid sites, which were passivated by the ion-exchange, in addition to the Lewis acid sites and that surprisingly, basic sites were formed on the modified zeolites. The ion-exchange with a small amount of Li+, Na+ and NH4+ was effective for suppressing side-reactions, leading to an improvement in selectivity to caprolactone in the Baeyer-Villiger oxidation of cyclohexanone with H2O2. The modification of Sn-Beta with such cations also effectively enhanced the catalytic activity in the Baeyer-Villiger oxidation of 2-adamantanone.
  • Ryoichi Otomo, Toshiyuki Yokoi, Takashi Tatsumi
    CHEMCATCHEM 7 24 4180 - 4187 2015年12月 [査読有り][通常論文]
     
    Organic structure-directing agent (OSDA)-free zeolite Beta with high Al content exhibit remarkably high catalytic performance in the conversion of glucose to 5-hydroxymethylfurfural (HMF) by virtue of their appropriate acid properties; specifically, a sufficient number of Lewis acid sites were generated by calcination of the NH4-form zeolite, while the original BrOnsted acid sites were substantially maintained, with both acid sites being in close proximity. The OSDA-free Beta catalyst, having a large number of BrOnsted acid sites and sufficient Lewis acid sites, showed superior catalytic performance to a physical mixture of each type of acid catalyst with a similar number of each acid site. This behavior could be ascribed to the high reactivity and slow intrazeolitic diffusion of fructose. The structure of the Al species active in the isomerization of glucose to fructose is discussed based on relationships between catalytic activities and changes in Al species by the calcination, changes that were observed by Al-27 magic-angle spinning (MAS) NMR and IR spectroscopies.
  • Ryoichi Otomo, Toshiyuki Yokoi, Takashi Tatsumi
    APPLIED CATALYSIS A-GENERAL 505 28 - 35 2015年09月 [査読有り][通常論文]
     
    Dehydration of sorbitol to isosorbide in water was studied using various types of aluminosilicate zeolites as heterogeneous catalyst. Among the zeolite catalysts tested, the 'BEA-type aluminosilicate zeolite (beta) showed a remarkably high catalytic performance; especially, beta zeolite with the Si/Al ratio of 75, designated as beta(75), gave an isosorbide yield as high as 80%. We have found that the three-dimensional large pore structure is favorable for enhancing the diffusion of sorbitol and the products. In addition, beta with a low Al content exhibited a higher catalytic activity than that with a high Al content, despite the small number of acid sites. The reason for this high catalytic activity is ascribed to hydrophobicity of the catalyst surface. Hydrothermal stability is another critical factor in determining the catalytic performance. The influence of reaction parameters such as temperature and the catalyst amount was investigated. The beta(75) proved to be reusable without loss of activity after calcination at 550 degrees C. (C) 2015 Elsevier B.V. All rights reserved.
  • Ryoichi Otomo, Takashi Tatsumi, Toshiyuki Yokoi
    Catalysis Science & Technology 5 8 4001 - 4007 2015年 [査読有り]
     

    Beta zeolite having both Lewis and Brønsted acid sites universally promoted direct conversion of various types of saccharides into furfurals.

  • Yunan Wang, Toshiyuki Yokoi, Ryoichi Otomo, Junko N. Kondo, Takashi Tatsumi
    APPLIED CATALYSIS A-GENERAL 490 93 - 100 2015年01月 [査読有り][通常論文]
     
    Sn-containing mesoporous silica nanospheres (Sn-MSNSs) with uniform crater-like mesopores were successfully synthesized by a direct synthetic method. The effects of Sn content and calcination temperature on the structural properties of Sn-MSNSs were investigated. Moreover, the catalytic performance of SnMSNSs in the Baeyer-Villiger (BV) oxidation of bulky cyclic ketone with hydrogen peroxide (H2O2) was studied. Compared with Sn-MCM-41, which possessed long mesopores, Sn-MSNSs with high hydrophobicity provided by high-temperature calcination exhibited much higher activity in the BV oxidation of bulky cyclic ketone, 2-adamantanone. (C) 2014 Elsevier B.V. All rights reserved.
  • Ryoichi Otomo, Toshiyuki Yokoi, Junko N. Kondo, Takashi Tatsumi
    APPLIED CATALYSIS A-GENERAL 470 318 - 326 2014年01月 [査読有り][通常論文]
     
    To improve the catalytic performance of Beta zeolite in the direct transformation of glucose into 5hydroxymethylfurfural (HMF), effects of calcination and steam treatment on the structure of Al atoms in the framework and acid properties of Beta zeolite were examined in detail. 27Al MAS NMR measurement and IR observation revealed that a part of Si-O-Al bonds in the framework were cleaved to form Al species out of the *BEA framework during the treatments and these species showed Lewis acidity. Especially, when the ammonium-type Beta was calcined over 700 degrees C or treated with steam (50 kPa in N2 balance) over 500 degrees C, the amount of Lewis acid sites was increased at the expense of Bronsted acid sites. Thus prepared Beta zeolite catalysts having a sufficient amount of Lewis acid sites were found to be effective bifunctional catalysts in synthesis of HMF from glucose; for example, Beta zeolite prepared by the calcination at 750 degrees C showed 55% selectivity to HMF at 78% conversion of glucose. We clarified the roles of Lewis and Bronsted acid sites on the Beta zeolite in the direct transformation of glucose to HMF. Furthermore, the reaction mechanism for the isomerization of glucose was investigated by means of isotope experiment using deuterated glucose. Finally, reusability of the Beta zeolite was also investigated. (C) 2013 Elsevier B.V. All rights reserved.
  • Takeshi Suzuki, Toshiyuki Yokoi, Ryoichi Otomo, Junko N. Kondo, Takashi Tatsumi
    APPLIED CATALYSIS A-GENERAL 408 1-2 117 - 124 2011年11月 [査読有り][通常論文]
     
    Various sulfated metal oxides were tested as solid acid catalyst for the dehydration of xylose to furfural under milder conditions. On the basis of our findings that sulfated tin oxide exhibited the highest catalytic activity, the effects of the content of SO42- group and the calcination temperature on the structural properties and catalytic performance were investigated, and the reusability of the sulfated tin oxide catalyst was evaluated. The acid property on the sulfated tin oxide catalyst was characterized by in situ FT-IR observations of the CO-adsorbed sample. Finally, the reaction mechanism of dehydration of xylose over the SO42-/SnO2 catalyst was considered. (C) 2011 Elsevier B.V. All rights reserved.

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  • ナノ環境材料化学特論Ⅰ
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 環境科学院
    キーワード : 触媒化学、環境修復、グリーンケミストリー、大気化学、オゾン層、オゾンホール、光化学オキシダント、反応速度論 Catalytic chemistry, Environmental remediation, Green sustainable chemistry, Atmospheric chemistry, Ozone layer, Ozone hole, Photochemical oxidant, Chemical kinetics
  • 化学Ⅰ
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 原子の構造、原子軌道、化学結合、混成軌道、物質の三態、電解質溶液


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