研究者総覧

高橋 亮治 (タカハシ リョウジ)

  • 大学院理工学研究科 環境機能科学専攻 教授
Last Updated :2020/10/13

研究者情報

学位

  • 博士(工学)(京都大学)

ホームページURL

J-Global ID

研究キーワード

  • 細孔内分子輸送の定量的評価   マイクロリアクターおよび分離材の一体作製   触媒反応プロセスの開発   固体触媒の調製   無機多孔体の合成   

研究分野

  • ナノテク・材料 / 複合材料、界面
  • ものづくり技術(機械・電気電子・化学工学) / 触媒プロセス、資源化学プロセス
  • ナノテク・材料 / エネルギー化学
  • ナノテク・材料 / 無機物質、無機材料化学
  • ナノテク・材料 / 無機・錯体化学
  • ナノテク・材料 / 無機材料、物性

経歴

  • 2006年 - 2007年  愛媛大学大学院理工学研究科 環境機能科学専攻Graduate School of Science and Engineering, Chemistry and Biology
  • 2007年  愛媛大学大学院理工学研究科 環境機能科学専攻Graduate School of Science and Engineering, Chemistry and Biology
  • 2004年 - 2006年  千葉大学工学部 共生応用化学科Faculty of Engineering, Department of Applied Chemistry and Biotechnology
  • 1998年 - 2004年  千葉大学工学部 物質工学科Faculty of Engineering
  • 1997年 - 1998年  千葉大学工学部 応用化学科Faculty of Engineering
  • 1996年 - 1997年  京都大学
  • 1995年 - 1996年  京都大学

学歴

  •         - 1996年   京都大学   工学研究科   材料化学専攻
  •         - 1996年   京都大学   Graduate School, Division of Engineering
  •         - 1993年   京都大学   工学研究科   工業化学専攻
  •         - 1993年   京都大学   Graduate School, Division of Engineering
  •         - 1991年   京都大学   工学部   工業化学科
  •         - 1991年   京都大学   Faculty of Engineering

所属学協会

  • ゼオライト学会   ゾルゲル学会   日本化学会   触媒学会   日本セラミックス協会   

研究活動情報

論文

  • Takuma Nemoto, Yasuhiro Yamada, Fumiya Sato, Ryoji Takahashi, Satoshi Sato
    Molecular Catalysis 473 2019年08月 研究論文(学術雑誌) 
    © 2019 Elsevier B.V. Vapor-phase dehydration of 1,3-butanediol was performed over Yb2O3-ZrO2 catalysts in an ambient nitrogen atmosphere. Catalysts were prepared by a hydrothermal (HT) method as well as a coprecipitation method. The Yb2O3-ZrO2 sample prepared by HT was confirmed to be crystallites of oxygen-defected type cubic Yb2Zr2O7, while the as-prepared coprecipitation sample was amorphous. The HT samples had high specific surface areas as ca. 40 m2 g−1 even after calcined at temperatures higher than 800 °C, whereas the coprecipitation samples without HT was readily sintered at the high temperatures. The best catalytic performance was obtained over HT Yb2O3-ZrO2 catalyst calcined at 900 °C: the total selectivity to unsaturated alcohols was higher than 95% at a 1,3-butanediol conversion of 82% at 325 °C. The structure of active sites and the reaction mechanism of the dehydration of 1,3-butanediol were discussed. We proposed that an oxygen defect site on the stable (111) face of cubic Yb2Zr2O7 would provide an active site, and that Zr4+, Yb3+, and O2- exposed on the defect could coordinate with a 1,3-butanediol molecule to form a tridentate coordination structure, which possibly initiate the dehydration to produce unsaturated alcohols through a base-acid concerted mechanism.
  • Yovita Djohan, Tomoki Azukizawa, Patmawati, Kotaro Sakai, Yuki Yano, Fumiya Sato, Ryoji Takahashi, Masafumi Yohda, Mizuo Maeda, Noriho Kamiya, Tamotsu Zako
    Biomaterials Science 7 1801 - 1804 2019年05月 
    © The Royal Society of Chemistry 2018. Here we report a novel aspect of molecular chaperone prefoldin (PFD) as a biomaterial in the biocatalytic synthesis of gold nanoparticles (AuNPs) using glycerol dehydrogenase (GLD). We found that PFD could inhibit the aggregation of AuNPs during the biosynthesis, leading to the formation of AuNPs with controlled size distribution.
  • Shota Ohtsuka, Takuma Nemoto, Rikako Yotsumoto, Yasuhiro Yamada, Fumiya Sato, Ryoji Takahashi, Satoshi Sato
    Applied Catalysis A: General 575 48 - 57 2019年04月 研究論文(学術雑誌) 
    © 2019 Elsevier B.V. Vapor-phase catalytic dehydration of butanediols (BDOs) such as 1,3-, 1,4-, and 2,3-butanediol was investigated over yttria-stabilized tetragonal zirconia (YSZ) catalysts as well as monoclinic zirconia (MZ). BDOs were converted to unsaturated alcohols with some by-products over YSZ and MZ. YSZ is superior to MZ for these reactions in a view point of selective formation of unsaturated alcohols. Calcination temperature of YSZ significantly affected the products selectivity as well as the conversion of BDOs: high selectivity to unsaturated alcohols was obtained over the YSZ calcined at high temperatures over 800 °C. In the conversion of 1,4-butanediol at 325 °C, the highest 3-buten-1-ol selectivity of 75.3% was obtained over the YSZ calcined at 1050 °C, whereas 2,3-butanediol was less reactive than the other BDOs. In the dehydration of 1,3-butanediol at 325 °C, in particular, it was found that a YSZ catalyst with a Y2O3 content of 3.2 wt.% exhibited an excellent stable catalytic activity: the highest selectivity to unsaturated alcohols such as 2-buten-1-ol and 3-buten-2-ol over 98% was obtained at a conversion of 66%. Structures of active sites for the dehydration of 1,3-butanediol were discussed using a crystal model of tetragonal ZrO2 and a probable model structure of active site was proposed. The well-crystalized YSZ inevitably has oxygen defect sites on the most stable surface of tetragonal ZrO2 (101). The defect site, which exposes three cations such as Zr4+ and Y3+, is surrounded by six O2− anions. The selective dehydration of 1,3-butanediol to produce 3-buten-2-ol over the YSZ could be explained by tridentate interactions followed by sequential dehydration: the position-2 hydrogen is firstly abstracted by a basic O2− anion and then the position-1 hydroxyl group is subsequently or simultaneously abstracted by an acidic Y3+ cation. Another OH group at position 3 plays an important role of anchoring 1,3-butanediol to the catalyst surface. Thus, the selective dehydration of 1,3-butanediol could proceed via the speculative base-acid-concerted mechanism.
  • Ikuya Yamada, Ikuya Yamada, Kentaro Shiro, Naoaki Hayashi, Shogo Kawaguchi, Takateru Kawakami, Ryoji Takahashi, Tetsuo Irifune
    Journal of Asian Ceramic Societies 5 2 169 - 175 2017年06月 [査読有り]
     研究論文(学術雑誌) 
    © 2017 The Ceramic Society of Japan and the Korean Ceramic Society Crystal structures and electronic transformations of quadruple iron perovskite solid solution Ca 1−x Sr x Cu 3 Fe 4 O 12 (x = 0.2, 0.4, 0.6, and 0.8) have been investigated by synchrotrons X-ray powder diffraction, Mössbauer spectroscopy, and magnetization measurements. For x = 0.2, a charge disproportionation transition (2Fe 4+  → Fe 3+  + Fe 5+ ) occur simultaneously with electron charge transfers from Fe to Cu below ∼200 K, as well as CaCu 3 Fe 4 O 12 . In contrast, negative thermal expansions derived from continuous electron charge transfers from Cu and Fe are observed for x = 0.6 and 0.8 at low temperatures below room temperature, as in SrCu 3 Fe 4 O 12 , followed by charge disproportionation transitions. A two-phase coexistence is observed at low temperature below ∼200 K for x = 0.4, indicating that the phase boundary locates in the vicinity of this composition. We have discovered that the Fe–O bond lengths are closely related to their covalency which were estimated from Mössbauer isomer shift parameters. The Fe–O bond covalency plays a crucial role in the types of electronic phase transitions for the Ca 1−x Sr x Cu 3 Fe 4 O 12 and R 3+ Cu 3 Fe 4 O 12 (R: trivalent rare earth metal ions, Y, La–Lu) systems, where the two different low-temperature electronic phases are separated by a common isomer shift value of ∼0.17 mm s −1 .
  • Fumiya Sato, Hitoshi Shiokai, Yusuke Yano, Masatoshi Sugiura, Ryoji Takahashi
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 125 10 737 - 741 2017年 [査読有り]
     研究論文(学術雑誌) 
    Rare earth hydroxide nitrates are prepared from rare earth nitrates by hydrothermal treatment. Three crystal phases, M(OH) 3 (M1), M-2(OH)(5.14)(NO3)(0.86)center dot H2O (M2), and M4O(OH)(9)NO3 (M4) are identified. The crystal phase systematically changes from M1 to M4 through M2 with decreasing radius of rare earth cation. Morphology of nanocrystal depends on the crystal phase. M1 and M4 phases grow to be nanorod, and M2 to nanoplate. (C) 2017 The Ceramic Society of Japan. All rights reserved.
  • Ryoji Takahashi, Akiko Onishi, Fumiya Sato, Makoto Kuramoto
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 125 10 742 - 746 2017年 [査読有り]
     研究論文(学術雑誌) 
    Bimodal porous alumina was prepared from the solution with aluminum chloride and 1,2-propylene oxide by adding propylene glycol oligomers (PPG). Because of hydrophobic nature of PPG, the addition of PPG induces phase separation during sol-gel reaction, and macroporous morphologies are formed by fixing transitional structure of phase separation. Since ethanol works as a co-solvent, the macropore size of the obtained gel can be increased by decreasing ethanol content. Change in the concentration of other constituents such as PPG has also an effect to control morphologies through changing the timing of phase separation and sol-gel transition. (C) 2017 The Ceramic Society of Japan. All rights reserved.
  • Masaki Saito, Tamotsu Zako, Ryoji Takahashi, Youji Shimazaki
    Chemistry Letters 45 11 1241 - 1243 2016年11月 [査読有り]
     研究論文(学術雑誌) 
    © 2016 The Chemical Society of Japan. In this study, we firstly report inhibition of amyloid β 42 (Aβ 42 ) fibrillation, which is related to the progression of Alzheimer's disease, by digestion using proteases, combined with Aβ 42 isolation using an immunoaffinity membrane. Especially, digestion of Aβ 42 with carboxypeptidase Y (CPY) is effective for the inhibition of Aβ 42 fibrillation, indicating that carboxy-terminal digestion of Aβ 42 is efficient for the prevention of its fibrillation. The combinational method of the immunoaffinity membrane with CPY digestion is applicable to suppress Aβ 42 fibrillation.
  • Ikuya Yamada, Hidenobu Etani, Makoto Murakami, Naoaki Hayashi, Takateru Kawakami, Masaichiro Mizumaki, Shigenori Ueda, Hideki Abe, Klaus-Dieter Liss, Andrew J. Studer, Tomoatsu Ozaki, Shigeo Mori, Ryoji Takahashi, Tetsuo Irifune
    INORGANIC CHEMISTRY 53 21 11794 - 11801 2014年11月 [査読有り]
     研究論文(学術雑誌) 
    A novel quadruple perovskite oxide CeCu3Fe4O12 has been synthesized under high-pressure and high-temperature conditions of 15 GPa and 1473 K. (57)Fe Mossbauer spectroscopy displays a charge disproportionation transition of 4Fe(3.5+) -> 3Fe(3+) + Fe5+ below similar to 270 K, whereas hard X-ray photoemission and soft X-ray absorption spectroscopy measurements confirm that the Ce and Cu valences are retained at approximately +4 and +2, respectively, over the entire temperature range measured. Electron and X-ray diffraction studies reveal that the body-centered cubic symmetry (space group Im3(_), No. 204) is retained at temperatures as low as 100 K, indicating the absence of any types of charge-ordering in the charge-disproportionated CeCu3Fe4O12 phase. The magnetic susceptibility and neutron powder diffraction data illustrate that the antiferromagnetic ordering of Fe ions is predominant in the charge-disproportionated CeCu3Fe4O12 phase. These findings suggest that CeCu3Fe4O12 undergoes a new type of electronic phase in the ACu(3)Fe(4)O(12) series and that the melting of the charge-ordering in CeCu3Fe4O12 is caused by the substantial decrease in the Fe valence and the resulting large deviation from the ideal abundance ratio of Fe3+:Fe5+ = 1:1 for rock-salt-type charge-ordering.
  • Ikuya Yamada, Mikiko Ochi, Masaichiro Mizumaki, Atsushi Hariki, Takayuki Uozumi, Ryoji Takahashi, Tetsuo Irifune
    INORGANIC CHEMISTRY 53 14 7089 - 7091 2014年07月 [査読有り]
     研究論文(学術雑誌) 
    A novel perovskite oxide, CaCu3Rh4O12, has been synthesized under high-pressure and high-temperature conditions (15 GPa and 1273 K). Rietveld refinement of synchrotron X-ray powder diffraction data indicates that this compound crystallizes in a cubic AA(3)'B4O12-type perovskite structure. Synchrotron X-ray absorption and photoemission spectroscopy measurements reveal that the Cu and Rh valences are nearly trivalent. The spectroscopic analysis based on calculations suggests that the appropriate ionic model of this compound is Ca2+Cu3 similar to 2.8+Rh4 similar to 3.4+O12, as opposed to the conventional Ca2+Cu32+Rh44+O12. The uncommon valence state of this compound is attributed to the relative energy levels of the Cu 3d and Rh 4d orbitals, in which the large crystal-field splitting energy of the Rh 4d orbitals is substantial.
  • Ikuya Yamada, Hidenobu Etani, Kazuki Tsuchida, Shohei Marukawa, Naoaki Hayashi, Takateru Kawakami, Masaichiro Mizumaki, Kenya Ohgushi, Yoshihiro Kusano, Jungeun Kim, Naruki Tsuji, Ryoji Takahashi, Norimasa Nishiyama, Toru Inoue, Tetsuo Irifune, Mikio Takano
    INORGANIC CHEMISTRY 52 23 13751 - 13761 2013年12月 [査読有り]
     研究論文(学術雑誌) 
    Unusual electronic phase transitions in the A-site ordered perovskites LnCu(3)Fe(4)O(12) (Ln: trivalent lanthanide ion) are investigated. All LnCu(3)Fe(4)O(12) compounds are in identical valence states of Ln(3+)Cu(3)(2+)Fe(4)(3.75+)O(12) at high temperature. LnCu(3)Fe(4)O(12) with larger Ln ions (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb) show an intersite charge transfer transition (3Cu(2+) + 4Fe(3.75+) -> 3Cu(3+) + 4Fe(3+)) in which the transition temperature decreases from 360 to 240 K with decreasing Ln ion size. In contrast, LnCu(3)Fe(4)O(12) with smaller Ln ions (Ln = Dy, Ho, Er, Tm Yb, Lu) transform into a charge-disproportionated (8Fe(3.75+) -> 5Fe(3+) + 3Fe(5+)) and charge-ordered phase below similar to 250-260 K The former series exhibits metal-to-insulator, antiferromagnetic, and isostructural volume expansion transitions simultaneously with intersite charge transfer. The latter shows metal-to-semiconductor, ferrimagnetic, and structural phase transitions simultaneously with charge disproportionation. Bond valence calculation reveals that the metal-oxygen bond strains in these compounds are classified into two types: overbonding or compression stress (underbonding or tensile stress) in the Ln-O (Fe-O) bond is dominant in the former series, while the opposite stresses or bond strains are found in the latter. Intersite charge transfer transition temperatures are strongly dependent upon the global instability indices that represent the structural instability calculated from the bond valence sum, whereas the charge disproportionation occurs at almost identical temperatures, regardless of the magnitude of structural instability. These findings provide a new aspect of the structure-property relationship in transition metal oxides and enable precise control of electronic states by bond strains.
  • Yu Kawasaki, Syota Takase, Yutaka Kishimoto, Takashi Ohno, Ikuya Yamada, Kentaro Shiro, Ryoji Takahashi, Kenya Ohgushi, Norimasa Nishiyama, Toru Inoue, Tetsuo Irifune
    JOURNAL OF THE KOREAN PHYSICAL SOCIETY 63 3 640 - 643 2013年08月 [査読有り]
     研究論文(学術雑誌) 
    We have investigated the successive magnetic phase transitions of the A-site ordered perovskite LaMn3Cr4O12 by measuring La-139 nuclear magnetic resonance (NMR) spectra. The successive magnetic transitions are revealed by a very small but clear increase in the full width at half maximum (FWHM) of the La-139 NMR signal at T (M2) = 150 K and by the disappearance of the signal due to the line broadening at temperatures below T (M1) = 50 K. These two magnetic transitions are associated with independent orderings within the Cr-site sublattice at T (M2) and within the Mn-site sublattice at T (M1). Regarding the magnetic structure of the Cr-site sublattice at temperatures below T (M2), the cancellation of internal fields at the La site, ruling out ferromagnetic and multi-q antiferromagnetic structures, is consistent with the typical antiferromagnetic structure for perovskites, such as G-, A- and C-type orders. The uncanceled internal field at the La site at temperatures below T (M1) is also consistent with these typical antiferromagnetic structures in the Mn-site sublattice. The differences in the temperature dependences of the Knight shift K(T) and the bulk susceptibility chi(T) are consistently explained by the independent magnetic orderings of the Cr- and the Mn-site sublattices and the cancellation of internal field originating from the Cr-site sublattice at the La site at temperatures below T (M2).
  • Hidenobu Etani, Ikuya Yamada, Kenya Ohgushi, Naoaki Hayashi, Yoshihiro Kusano, Masaichiro Mizumaki, Jungeun Kim, Naruki Tsuji, Ryoji Takahashi, Norimasa Nishiyama, Toru Inoue, Tetsuo Irifune, Mikio Takano
    Journal of the American Chemical Society 135 16 6100 - 6106 2013年04月 [査読有り]
     研究論文(学術雑誌) 
    A novel iron perovskite YCu3Fe4O12 was synthesized under high pressure and high temperature of 15 GPa and 1273 K. Synchrotron X-ray and electron diffraction measurements have demonstrated that this compound crystallizes in the cubic AA′3B4O 12-type perovskite structure (space group Im3Ì..., No. 204) with a lattice constant of a = 7.30764(10) Å at room temperature. YCu 3Fe4O12 exhibits a charge disproportionation of 8Fe3.75+ → 3Fe5+ + 5Fe3+, a ferrimagnetic ordering, and a metal-semiconductor-like transition simultaneously at 250 K, unlike the known isoelectronic compound LaCu3Fe4O 12 that currently shows an intersite charge transfer of 3Cu 2+ + 4Fe3.75+ → 3Cu3+ + 4Fe3+, an antiferromagnetic ordering, and a metal-insulator transition at 393 K. This finding suggests that intersite charge transfer is not the only way of relieving the instability of the Fe3.75+ state in the A3+Cu 2+ 3Fe3.75+ 4O12 perovskites. Crystal structure analysis reveals that bond strain, rather than the charge account of the A-site alone, which is enhanced by large A 3+ ions, play an important role in determining which of intersite charge transfer or charge disproportionation is practical. © 2013 American Chemical Society.
  • Mikiko Ochi, Ikuya Yamada, Kenya Ohgushi, Yoshihiro Kusano, Masaichiro Mizumaki, Ryoji Takahashi, Shunsuke Yagi, Norimasa Nishiyama, Toru Inoue, Tetsuo Irifune
    Inorganic Chemistry 52 7 3985 - 3989 2013年04月 [査読有り]
     研究論文(学術雑誌) 
    An A-site-ordered perovskite LaCu3Pt3.75O 12 was synthesized by replacing Ca2+ with La3+ in a cubic quadruple AA′3B4O12-type perovskite CaCu3Pt4O12 under high-pressure and high-temperature of 15 GPa and 1100 C. In LaCu3Pt 3.75O12, 1/16 of B-site cations are vacant to achieve charge balance. The B-site deficiencies were evidenced by crystal structure refinement using synchrotron X-ray powder diffraction, hard X-ray photoemission spectroscopy, and soft X-ray absorption spectroscopy, leading to the ionic model La3+Cu2+3Pt4+3.75O 2-12. Magnetic susceptibility data for this compound indicated a spin-glass-like behavior below Tg = 3.7 K, which is attributed to disturbance of the antiferromagnetic superexchange interaction by the B-site deficiencies. © 2013 American Chemical Society.
  • Kentaro Shiro, Ikuya Yamada, Naoya Ikeda, Kenya Ohgushi, Masaichiro Mizumaki, Ryoji Takahashi, Norimasa Nishiyama, Toru Inoue, Tetsuo Irifune
    INORGANIC CHEMISTRY 52 3 1604 - 1609 2013年02月 [査読有り]
     研究論文(学術雑誌) 
    Novel A-site ordered perovskites CaPd3Ti4O12 and CaPd3V4O12 were synthesized under high-pressure and high-temperature of 15 GPa and 1000 degrees C. These compounds are the first example in which a crystallographic site in a perovskite-type structure is occupied by Pd2+ ions with a 4d(8) low spin configuration. The ionic models for these compounds were determined to be Ca(2+)pd(2+)3Ti(4)(4+)O(12) and Ca-2+Pd-2+V-3(4)+O-4(12) by structural refinement using synchrotron X-ray powder diffraction, hard X-ray photoemission, and soft X-ray absorption spectroscopy. Magnetic susceptibility, electrical resistivity, and specific heat measurements demonstrated diamagnetic insulating behavior for CaPd3Ti4O12 in contrast to the Pauli-paramagnetic metallic nature of CaPd3V4O12.
  • Toshiaki Abe, Shouhei Anan, Fumiya Watanabe, Ryoji Takahashi, Yoshifumi Ikoma
    Materials Science Forum 750 244 - 247 2013年 [査読有り]
     研究論文(国際会議プロシーディングス) 
    Au-catalyzed growth of nanocrystalline Si by pulse jet chemical vapor deposition hasbeen investigated. Au thin film was first deposited on thermally oxidized Si(100), then CH3SiH3pulse jets were irradiated onto the Au/SiO2/Si(100) surface. The irradiation of the CH3SiH3 jets at1150 °C resulted in circular patterns with a diameter of ~40 μm on the sample surfaces. In thecenter of the circular patterns, agglomerations of Au were observed. It was found that the oxidelayer was etched and that nanocrystalline Si with diameters ~500 nm was formed in the circularpatterns. These results indicate that the nanocrystalline Si was grown by the VLS process in whichSi atoms were supplied from the oxide layer, Si substrate, and CH3SiH3 molecules. © (2013) Trans Tech Publications, Switzerland.
  • Olim Ruzimuradov, Suvon Nurmanov, Yumi Kodani, Ryoji Takahashi, Ikuya Yamada
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 64 3 684 - 693 2012年12月 [査読有り]
     研究論文(学術雑誌) 
    Macroporous gels with bicontinuous morphology in micrometer range were prepared in a titania-silica system containing 5 and 7.6 mass % titania using tetraethoxysilane and four kinds of Ti precursors, two titanium alkoxides, titanium chloride and titanium sulfate, under coexistence of poly(ethylene glycol) (PEG) with an average molecular weight of 20,000. In all the systems with different Ti precursors, the addition of PEG induced phase separation, and the macroporous morphology was formed when the transitional structure of phase separation was frozen-in by sol-gel transition of inorganic components. However, we can see large differences in phase separation tendency and Ti dispersion in silica network depending on the Ti precursors used. When titanium alkoxides were added into pure silica sol-gel system, phase separation tendency largely decreased, so that low temperature reaction was necessary for macropore formation. When we used titanium salts, on the other hand, phase separation tendency does not change much from pure silica system. The difference has been tentatively attributed to the difference in the mixing level of Ti in silica network. Although titania tended to aggregate when titanium alkoxides were used as precursors, Ti could be well dispersed in silica gel matrix when acetylacetone was added in the alkoxide system or when titanium salts were used as Ti precursors.
  • S. J.E. Carlsson, G. Rousse, I. Yamada, H. Kuriki, R. Takahashi, F. Lévy-Bertrand, G. Giriat, A. Gauzzi
    Physical Review B - Condensed Matter and Materials Physics 84 9 2011年09月 [査読有り]
     研究論文(学術雑誌) 
    We studied the structural, magnetic, and electronic properties of the geometrically frustrated layered AuCrS2 system by means of x-ray and neutron powder diffraction, specific heat, dc magnetization, and dc electrical resistivity measurements. The room-temperature structural refinement is consistent with a hexagonal centrosymmetric R-3m symmetry and with formal valence states Au+ and Cr3+, where the Cr3+ ions form a regular triangular lattice within the hexagonal planes. On cooling, we observe a first-order structural phase transition to a monoclinic C2/m symmetry concomitant to an antiferromagnetic order at TN = 47 K. The atomic displacements associated with this transition stretch the triangular lattice, thus suppressing the geometric frustration. This accounts for the magnetic order observed and gives evidence of a large magnetoelastic coupling. The refined magnetic structure is commensurate and consists of double ferromagnetic chains along the stretching direction with μ = 2.54 μB/Cr3+ the residual frustration stabilizes an elegant pattern of alternate ferromagnetic and antiferromagnetic intra- and interplane couplings between adjacent chains. The electrical transport of our sintered powder samples is found to be semiconducting-like with ρ300K ∼ 157 Ωcm and an activation energy of 0.38 eV. © 2011 American Physical Society.
  • S. J. E. Carlsson, G. Rousse, I. Yamada, H. Kuriki, R. Takahashi, F. Levy-Bertrand, G. Giriat, A. Gauzzi
    PHYSICAL REVIEW B 84 9 2011年09月 [査読有り]
     研究論文(学術雑誌) 
    We studied the structural, magnetic, and electronic properties of the geometrically frustrated layered AuCrS2 system by means of x-ray and neutron powder diffraction, specific heat, dc magnetization, and dc electrical resistivity measurements. The room-temperature structural refinement is consistent with a hexagonal centrosymmetric R-3m symmetry and with formal valence states Au+ and Cr3+, where the Cr3+ ions form a regular triangular lattice within the hexagonal planes. On cooling, we observe a first-order structural phase transition to a monoclinic C2/m symmetry concomitant to an antiferromagnetic order at T-N = 47 K. The atomic displacements associated with this transition stretch the triangular lattice, thus suppressing the geometric frustration. This accounts for the magnetic order observed and gives evidence of a large magnetoelastic coupling. The refined magnetic structure is commensurate and consists of double ferromagnetic chains along the stretching direction with mu = 2.54 mu B/Cr3+; the residual frustration stabilizes an elegant pattern of alternate ferromagnetic and antiferromagnetic intra-and interplane couplings between adjacent chains. The electrical transport of our sintered powder samples is found to be semiconducting-like with rho(300K) similar to 157 Omega cm and an activation energy of 0.38 eV.
  • Ikuya Yamada, Kazuki Tsuchida, Kenya Ohgushi, Naoaki Hayashi, Jungeun Kim, Naruki Tsuji, Ryoji Takahashi, Masafumi Matsushita, Norimasa Nishiyama, Toru Inoue, Tetsuo Irifune, Kenichi Kato, Masaki Takata, Mikio Takano
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 50 29 6579 - 6582 2011年 [査読有り]
     研究論文(学術雑誌)
  • Hironobu Nishino, Ryoji Takahashi, Satoshi Sato, Toshiaki Sodesawa
    Journal of Non-Crystalline Solids 356 43 284 - 290 2010年09月 [査読有り]
     研究論文(学術雑誌) 
    Silica gel samples with macropores were prepared from solutions of silicate and poly(vinyl alcohol) (PVA), where macropores were formed by fixing a transitional structure of phase separation. Among the silica sources tested, tetraethoxysilane (TEOS), colloidal silica and water glass, only the system with water glass shows phase separation and forms macroporous silica gel. In the system with TEOS, ethanol formed during hydrolysis of TEOS becomes good solution and stabilizes the system not to induce phase separation. In the system with colloidal silica, dense structure of silica is probably not suitable for controlling phase separation and gelation. In the system with water glass, driving force of phase separation is considered to be a repulsive interaction between solvent molecules and PVA interacting with silica surface and the solution separates into a phase rich in solvent and that rich in silica and PVA. One of the features in the water glassPVA system is insensitivity of macropore size against compositional change in the solution, i.e. macroporous morphology in the resultant silica gel hardly changes by changing the composition ratio in the solution. This would be an advantage in the preparation of well-defined macroporous silica from water glass, whose composition varies among the product lot number, because reproducibility in macroporous morphology is ensured regardless of the lot number of the water glass. © 2004 Elsevier B.V.
  • Ikuya Yamada, Yuka Takahashi, Kenya Ohgushi, Norimasa Nishiyama, Ryoji Takahashi, Kohei Wada, Takehiro Kunimoto, Hiroaki Ohfuji, Yohei Kojima, Toru Inoue, Tetsuo Irifune
    INORGANIC CHEMISTRY 49 15 6778 - 6780 2010年08月 [査読有り]
     研究論文(学術雑誌) 
    A novel A-site ordered perovskite CaCu3Pt4O12 was synthesized under high pressure and high temperature of 12 GPa and 1250 degrees C. CaCu3Pt4O12 is the first perovskite in which the B site is fully occupied by Pt4+. The crystal structure refinement based on the synchrotron powder X-ray diffraction data shows that CaCu3Pt4O12 crystallizes in the space group Im (3) over bar (cubic) with a lattice constant of a = 7.48946(10) angstrom. The magnetic susceptibility data show the antiferromagnetic transition at T-N = 40 K, which is attributed to the magnetic ordering of Cu2+ spins with S = 1/2.
  • Masayuki Numata, Ryoji Takahashi, Ikuya Yamada, Kazuki Nakanishi, Satoshi Sato
    APPLIED CATALYSIS A-GENERAL 383 1-2 66 - 72 2010年07月 [査読有り]
     研究論文(学術雑誌) 
    Ni/TiO2 with bimodal pore structure was prepared from nickel nitrate and titanium alkoxide by a sol-gel process under acidic conditions in the presence of formamide. The Ni/TiO2 has continuous macropores which are formed by fixing the transitional structure of phase separation. Although the addition of nickel nitrate in the sol-gel reaction of titanium alkoxide steeply decreases the phase separation tendency, the macropore size can be controlled by changing the composition of preparation. The Ni/TiO2 prepared by sol-gel has higher dispersion of Ni compared with that prepared by impregnation, and shows catalytic activity for the selective hydrogenation of crotonaldehyde: selectivity in the hydrogenation of C=C bond is much higher than that of C=O bond over sol-gel-derived Ni/TiO2. (C) 2010 Elsevier B.V. All rights reserved.
  • Ryoji Takahashi, Ikuya Yamada, Aiko Iwata, Naoya Kurahashi, Satoshi Yoshida, Satoshi Sato
    APPLIED CATALYSIS A-GENERAL 383 1-2 134 - 140 2010年07月 [査読有り]
     研究論文(学術雑誌) 
    Dehydration of 1,4-butanediol (14BDO) was investigated over indium oxide. Over the indium oxide prepared by precipitation, both conversion of 14BDO and selectivity to unsaturated alcohol, 3-buten-1-ol (3B1ol), increase with the increase in calcination temperature of indium oxide irrespective of the decrease in the specific surface area. The maximum values of 79.6% conversion and 79.0% selectivity to 3B1ol are obtained over indium oxide calcined at 900 degrees C. The values are much higher than the activities of commercial indium oxide. The activities of indium oxide depend on the shape of particles. Indium oxides prepared by the precipitation are composed of particles with diameter of 10-70 nm. The size and shape of particles change by calcination: spherical shape at low temperature of <800 degrees C varies to angular one at >800 degrees C with a slight growth of particle size. The change in the shape of the particles means that indium oxide crystallites calcined at >800 degrees C mainly expose 222 facets. The dehydration reaction of 14BDO to 3B1ol is preferentially promoted over 222 surface of bixbyite structure. (C) 2010 Elsevier B.V. All rights reserved.
  • Ryoji Takahashi, Satoshi Sato, Yasuhide Kojima, Toshiaki Sodesawa, Ikuya Yamada, Daisuke Nishi, Katsuhiro Muramatsu, Hidenori Yahiro, Hiroyuki Yamaura, Naoki Mikami
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 118 1376 295 - 299 2010年04月 [査読有り]
     研究論文(学術雑誌) 
    Phase separation in an acidic aqueous solution with sodium silicate and sodium dodecyl sulfate (SDS) was investigated. The solution separated into silica-rich and SDS-rich phases during condensation of silica components. During the phase separation, the transition structure was fixed by gelation, resulting in mutually continuous morphology. The addition of a small amount of water-miscible organic solvents, such as methanol, ethanol, 1-propanol, and 1-butanol, into the reacting solution greatly decreases both viscosity and phase separation tendency of the solution. In the system with high concentration of strong acid. SDS molecules form wormlike micelles, which not only increase viscosity of the solution hut also play an important role in the phase separation in the solution because the to of wormlike micelles increases apparent molecular weight of SDS and decreases mixing entropy. The decrease in the viscosity by the addition of organic solvents suggests that wormlike in become small in the presence of organic solvent molecules. Consequently, the addition of appropriate amount of organic solvent is effective for controlling phase separation tendency and size of the resulted macropores in the system with SDS through the change in the structure of the micelles. (C) 2010 The Ceramic Society of Japan All rights reserved
  • Masaki Akiyama, Satoshi Sato, Ryoji Takahashi, Kanichiro Inui, Masahiro Yokota
    APPLIED CATALYSIS A-GENERAL 371 1-2 60 - 66 2009年12月 研究論文(学術雑誌) 
    The vapor-phase reaction of glycerol was performed over copper metal catalysts at ambient hydrogen pressure. Glycerol was converted into 1,2-propanediol (1,2-PDO) through the dehydration into hydroxyacetone, followed by the hydrogenation into 1,2-PDO. The yield of 1,2-PDO was limited up to 80% at a constant temperature of 190 degrees C because of a trade-off problem between the dehydration and the hydrogenation. The dehydration needs relatively high reaction temperatures, whereas the hydrogenation favors low temperatures and high hydrogen concentration. We developed an efficient process during which glycerol was converted into 1,2-PDO with yield higher than 96% in hydrogen flow at gradient temperatures; the dehydration into hydroxyacetone was catalyzed at ca. 200 degrees C, and the following hydrogenation into 1,2-PDO was completed at ca. 120 degrees C. The developed process controls the thermodynamic equilibrium of the second-step hydrogenation. (C) 2009 Elsevier B.V. All rights reserved.
  • Takashi Nozawa, Satoshi Sato, Ryoji Takahashi
    Springer (Kluwer Academic Publishers)Topics in Catalysis 52 6-7 609 - 617 2009年06月 研究論文(学術雑誌) 
    The dehydration of 1,3-butanediol was investigated over CeO2-ZrO2 catalysts prepared by impregnation at temperatures of 325-375 A degrees C. Pure CeO2 selectively catalyzed the dehydration of 1,3-butanediol to form 3-buten-2-ol and 2-buten-1-ol, while pure ZrO2, which was less active than pure CeO2, catalyzed the dehydration to 3-buten-1-ol. In the CeO2/ZrO2 catalyst in which CeO2 was supported on zirconia, the presence of a small amount of CeO2 suppressed the formation of 3-buten-1-ol and induced the dehydration of 1,3-butanediol to form 3-buten-2-ol and 2-buten-1-ol and the subsequent dehydrogenation of 3-buten-2-ol to form 3-buten-2-one and butanone. The activity would be related to the redox features of CeO2. The monoclinic phase of zirconia support decreased while the cubic CeO2 phase increased as CeO2 content was increased. In contrast, in the ZrO2/CeO2 catalyst in which ZrO2 was supported on cubic CeO2, only the cubic CeO2 phase was observed and ZrO2 species appeared in the form of a solid solution of CeO2-ZrO2 with fluorite structure. Regardless of zirconia loading, ZrO2 species did not affect the catalytic activity of ZrO2/CeO2, which was controlled by CeO2 species.
  • Satoshi Sato, Ryoji Takahashi, Mika Kobune, Hirotomo Inoue, Yusuke Izawa, Hironobu Ohno, Kazunari Takahashi
    APPLIED CATALYSIS A-GENERAL 356 1 64 - 71 2009年03月 研究論文(学術雑誌) 
    Vapor-phase catalytic dehydration of 1,4-butanediol was investigated over rare earth oxides (REOs) calcined at different temperatures. In the dehydration of 1,4-butanediol over RECs, 3-buten-1-ol was mainly produced, together with tetrahydrofuran (THF). Weakly basic heavy RECs, such as DY(2)O(3), Ho(2)O(3), Er(2)O(3), Tm(2)O(3), Yb(2)O(3), Lu(2)O(3), and Y(2)O(3), showed high selectivity to 3-buten-1-ol, while strongly basic light RECs, such as La(2)O(3), Pr(6)O(11), Nd(2)O(3), Sm(2)O(3), and Eu(2)O(3), produced more THF and gamma-butyrolactone. Heavy REOs exhibited different catalytic activities in the dehydration of 1,4-butanediol depending on their crystal structures. Cubic C-type RECs selectively produced 3-buten-1-ol; in particular, cubic Er(2)O(3), Yb(2)O(3), and Lu(2)O(3) showed the highest formation rates of 3-buten-1-ol. Since the formation rate of 3-buten-1-ol was suppressed over Er(2)O(3) in acidic CO(2) or basic NH(3) carrier gas flow, it is probable that the active centers for the formation of 3-buten-1-ol are composed of both basic and acidic sites. (C) 2008 Elsevier B.V. All rights reserved.
  • Satoshi Sato, Ryoji Takahashi, Mika Kobune, Hiroshi Gotoh
    APPLIED CATALYSIS A-GENERAL 356 1 57 - 63 2009年03月 研究論文(学術雑誌) 
    l Basic properties of rare earth oxides (REOs) calcined at different temperatures were investigated. During the calcination process, the crystal structures of Lu, Yb, Tm, Er, Y, Ho, and Dy oxides transformed from monoclinic to cubic with increasing calcination temperature, while those of Sc Ce La Pr Nd Sm Eu Gd, and Tb oxides showed no change at temperatures below 1100 degrees C No acidic sites were observed in the. measurement of NH(3) adsorbed on the REOs at 25 degrees C. CO(2) was adsorbed on the REOs: CO(2) desorption peaks were observed depending on the strength of the basic sites. Light REOs, such as La(2)O(3) Pr(6)O(11), Nd(2)O(3), and Sm(2)O(3), had surface basic sites from which CO(2) desorbed at temperatures below 500 degrees C, as well as structural carbonate that decomposed above 500 degrees C. Heavy REOs, such as Dy(2)O(3), Ho(2)O(3), Y(2)O(3), Er(2)O(3), Tm(2)O(3), Yb(2)O(3), and Lu(2)O(3), had weak basic sites. The basic properties of REOs are attributed to lanthanide contraction: the strength of the basic sites decreases with decreasing radius of the rare earth cation. (C) 2008 Elsevier B.V. All rights reserved.
  • Hirotomo Inoue, Satoshi Sato, Ryoji Takahashi, Yusuke Izawa, Hironobu Ohno, Kazunari Takahashi
    APPLIED CATALYSIS A-GENERAL 352 1-2 66 - 73 2009年01月 研究論文(学術雑誌) 
    Vapor-phase catalytic dehydration of 1,4-butanediol was investigated over rare earth oxides supported on ZrO(2). In the dehydration of 1,4-butanediol, 3-buten-1-ol was mainly produced, together with tetrahydrofuran (THF) and gamma-butyrolactone. The heavy group of rare earth oxides, such as Dy(2)O(3), Ho(2)O(3), Er(2)O(3), Tm(2)O(3), Yb(2)O(3), and Lu(2)O(3), supported on monoclinic ZrO(2) showed higher selectivity to 3-buten-1-ol than pure monoclinic ZrO(2) and supported light rare earth oxides. such as La(2)O(3) and Pr(6)O(11). Supported Yb(2)O(3) catalysts dispersed on other oxides, such as alumina, silica, and tetragonal ZrO(2) catalyze the formation of THF. X-ray diffraction (XRD) measurements reveal that cubic Yb(2)O(3) crystallites dispersed on monoclinic ZrO(2) provide active sites in the dehydration of 1,4-butanediol to produce 3-buten-1-ol. (C) 2008 Elsevier B.V. All rights reserved.
  • Satoshi Sato, Masaki Akiyama, Ryoji Takahashi, Takayoshi Hara, Kanichiro Inui, Masahiro Yokota
    APPLIED CATALYSIS A-GENERAL 347 2 186 - 191 2008年09月 研究論文(学術雑誌) 
    The vapor-phase reaction of triols and diols was performed over copper metal catalysts. Triols, such as 1,2,3-propanetriol (glycerol) and 1,2,3- and 1,2,4-butanetriols, were dehydrated to afford corresponding hydroxyketones, while 1,2-propanediol was dehydrogenated to form hydroxyacetone. Supported copper as well as pure copper metal was an effective catalyst for the dehydration of glycerol to produce hydroxyacetone under inert conditions. in hydrogen flow, however, copper catalyzed the hydrogenation of hydroxyacetone as well as hydrogenolysis to produce ethylene glycol. Alumina-supported copper showed the highest catalytic activity with hydroxyacetone selectivity of >90 mol% at ambient pressure of nitrogen and 250 degrees C. Copper metal provides an active site for the dehydration of glycerol. We propose a reaction mechanism for the dehydration of glycerol to form hydroxyacetone. (C) 2008 Elsevier B.V. All rights reserved.
  • 村松 克洋, 高橋 亮治, 山田 幾也, 山浦 弘之, 八尋 秀典, 佐藤 智司
    日本セラミックス協会 年会・秋季シンポジウム 講演予稿集 2008 0 683 - 683 公益社団法人 日本セラミックス協会 2008年 [査読有り]
     
    水ガラスから調製した二元細孔シリカゲルを構造規定在としてのテトラプロピルアンモニウムイオン共存下で水蒸気処理を行うことにより、マクロ孔構造を維持したゼオライト成形体を合成した。生成した試料は、相分離の過渡構造を凍結して得られたマクロ孔、ゼオライト結晶子間隙に相当するメゾ孔、ゼオライト格子内のミクロ孔が階層的に配列した三元細孔構造を有していることが確認された。シリカゲルの水蒸気処理の際の結晶化挙動は、構造規定材濃度や水蒸気処理温度などの処理条件の他に、シリカゲルのメゾ孔サイズやマクロ孔のサイズにも依存して変化することがわかった。マクロ孔構造を維持したまま結晶化するのに最適な条件を決定した。また、得られたゼオライトの固体触媒としての物性評価を行った。
  • Moises Fernandez, Andre Pampel, Ryoji Takahashi, Satoshi Sato, Dieter Freude, Joerg Kaerger
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 10 28 4165 - 4171 2008年 研究論文(学術雑誌) 
    Magic-angle spinning pulsed field gradient nuclear magnetic resonance (MAS PFG NMR) was applied for selective self-diffusion measurements of acetone -n-alkane (C(6) up to C(9)) mixtures in nanoporous silica gel. Two specimens of silica gel with mean pore sizes of about 4 and 10 nm are considered. In the smaller pores, the n-alkane diffusivities are by about one and the acetone diffusivities by about two orders of magnitude smaller than in the larger pores. In addition, the acetone diffusivities in the narrow-pore specimen exhibit a pronounced oscillation with increasing chain length of the solvent n-alkanes: the diffusivities of acetone dissolved in odd-carbon number n-alkanes exceed those of acetone dissolved in even-carbon number n-alkanes by about 50%! These findings reproduce the tendencies observed in previous macroscopic release studies (Phys. Chem. Chem. Phys. 2003, 5, 2476) and suggest the formation of acetone -n-alkane complex-like assemblages in the narrow-pore silica gel.
  • Mika Kobune, Satoshi Sato, Ryoji Takahashi
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 279 1 10 - 19 2008年01月 研究論文(学術雑誌) 
    Vapor-phase catalytic reactions of several reactants were investigated over CeO2 with different particle sizes, and the surface-structure sensitivity, i.e. crystal plane dependency, was discussed. The particle size of CeO2 was regulated by the calcination temperature. In.dehydration of 1,4-butanediol and 1,3-butanediol into unsaturated alcohols, and ketonization of propanoic acid, the activities increased with increasing the CeO2 particle size. CeO2 {111} facets became predominant on the large particles. This indicates that CeO2 {111} facets have active sites for the reactions of butanediols and of propanoic acid. Therefore, dehydration of 1,4-butanediol and 1,3-butanediol, and ketonization of propanoic acid are categorized into surface-structure-sensitive reaction. The structure-sensitive reactions have feature that the main product is formed with high selectivity at temperatures lower than 400 degrees C. In contrast, activities of dehydration of 2-heptanol, methylation of phenol with methanol, and ketonization of propanal and 1-propanol were independent of the CeO2 particle size. These reactions are categorized into structure-insensitive reaction. (c) 2007 Elsevier B.V. All rights reserved.
  • Satoshi Sato, Ryoji Takahashi, Naoki Yamamoto, Eiji Kaneko, Hirotomo Inoue
    APPLIED CATALYSIS A-GENERAL 334 1-2 84 - 91 2008年01月 研究論文(学術雑誌) 
    Dehydration of 1,5-pentanediol was investigated over ZrO(2) and Yb(2)O(3) catalysts at 300-450 degrees C. 1,5-Pentanediol was converted into 4-penten-1-ol together with tetrahydropyran over monoclinic ZrO(2) at temperatures <400 degrees C, and the selectivity to 4-penten-1-ol exceeded 50 mol%. Modification of ZrO(2) with Li ions increased the selectivity to 4-buten-1-ol up to 70 mol%. Yb(2)O(3) also effectively worked as a catalyst in the dehydration of 1,5-pentanediol into 4-buten-1-ol at temperatures <425 degrees C. Especially, Yb(2)O(3) with cubic structure showed higher than 75 mol% selectivity to 4-penten-1-ol. (c) 2007 Elsevier B.V. All rights reserved.
  • Ryoji Takahashi, Satoshi Sato, Toshiaki Sodesawa, Yasuhide Kojima, Naoki Mikami
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 115 1348 882 - 887 2007年12月 研究論文(学術雑誌) 
    Bimodal porous silica gel with both macropores and mesopores was prepared from water glass (WG) in the presence of low-molecular-weight surfactant, sodium dodecyl sulfate (SDS), by inducing phase separation during sol-gel reaction. The macroporous morphology was controlled by changing starting composition and gelation temperature: the change in the concentration of SDS was effective to control connectivity of macropores and silica gel skeleton in micrometer size, and the gelation temperature significantly affected macropore size. From the change in morphology with the concentration of SDS, it is considered that a homogeneous reacting solution separated into a phase of SDS and that of polymerized silica in contrast to other silica-surfactant systems, where phase separation proceeds between solvent and surfactant associated with silica gel surface. It is also suggested that SDS forms associated complex or micelle in aqueous acidic solution, and the formation of such structure plays an important role in the phase stability. We also controlled mesopore structures in the macroporous silica gel by aging as-geled samples under basic conditions.
  • Satoshi Sato, Ryoji Takahashi, Toshiaki Sodesawa, Ai Igarashi, Hirotomo Inoue
    APPLIED CATALYSIS A-GENERAL 328 2 109 - 116 2007年09月 研究論文(学術雑誌) 
    Vapor-phase reaction of 1,3-butanediol was investigated over rare earth oxide (REO) catalysts. In the reaction of 1,3-butanediol, dehydration and decomposition of 1,3-butanediol occurred simultaneously at 325 degrees C. The formation of unsaturated alcohols such as 3-buten-2-of and trans-2buten-l-ol was predominant over CeO(2), Sc(2)O(3), and Tm(2)O(3), while 1,3-butanediol was preferentially decomposed over the other REOs. Especially, light REOs such as La(2)O(3), Pr(6)O(1) >, Nd(2)O(3), and Sm(2)O(3), catalyzed decomposition of 1,3-butanediol into 2-propanol, propanone, methanol, and ethanol. Basic and acidic properties of REOs were measured with temperature-programmed desorption (TPD) of adsorbed CO(2) and NH(3), respectively. The surface character of REOs was basic but not acidic. Both strength and number of basic sites of REOs increased with increasing ionic radius of rare earth cation in the REO except CeO(2): light REOs were more basic. The decomposition of 1,3-butanediol would be attributed to the basicity of catalyst. In the reaction of 1,3-butanediol as well as 1,4-butanediol, the catalytic function of REOs will be discussed in connection with lanthanide contraction. (c) 2007 Elsevier B.V All rights reserved.
  • Naoki Shinozaki, Ryoji Takahashi, Satoshi Sato, Toshiaki Sodesawa
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 43 3 275 - 282 2007年09月 研究論文(学術雑誌) 
    The bending strength and the Young's modulus of bimodal porous silica gels having different porosity were evaluated. The porosity of the gel increased by aging the gel under basic conditions, and decreased with increasing the calcination temperature. The mesopores disappeared on calcination at 1,050 degrees C, whereas continuous macropores retained their morphology up to 1,050 degrees C for all the samples. Both the bending strength and the Young's modulus of the bimodal porous silica gels were expressed as power-law functions of the bulk density, and no effect of bimodal pore structures on mechanical properties was observed. We also found linear correlation between the bending strength and the elasticity. The bimodal porous silica had higher strength and elastic modulus compared with other porous materials at the same porosity probably due to the presence of homogeneous micrometer-scale macropores.
  • Eriko Tsukuda, Satoshi Sato, Ryoji Takahashi, Toshiaki Sodesawa
    CATALYSIS COMMUNICATIONS 8 9 1349 - 1353 2007年09月 研究論文(学術雑誌) 
    Dehydration of glycerol to produce acrolein was performed over several solid acids. Supported heteropoly acids were effective as a catalyst for the dehydration of glycerol. The catalytic activity depended on the types of heteropoly acid and on the size of the mesopores in the silica support. Silicotungstic acid supported on silica with mesopores of 10 nm showed the highest catalytic activity with the acrolein selectivity of > 85 mol% at an ambient pressure and 275 degrees C. (c) 2006 Elsevier B.V. All rights reserved.
  • Satoshi Sato, Ryoji Takahashi, Hiromitsu Fukuda, Kanichiro Inui
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 272 1-2 164 - 168 2007年07月 研究論文(学術雑誌) 
    Vapor-phase dehydrogenation of 1,3-butanediol into 4-hydroxy-2-butanone was examined over copper catalysts modified with ZnO, ZrO2, Al(2)O3, and MgO. 4-Hydroxy-2-butanone was efficiently produced by the dehydrogenation of 1,3-butanediol over pure Cu and Cu/ZnO catalysts. However, the selectivity to 4-hydroxy-2-butanone decreases with increasing conversion of 1,3-butanediol, while the selectivity to butanone increases. Addition of Al2O3 and ZrO2 to the catalysts decreases the selectivity to 4-hydroxy-2-butanone because of the enhancement of dehydration of 4-hydroxy-2butanone into 3-buten-2-one and the following hydrogenation into butanone. An addition of basic MgO increases the formation of propanone via the retro-aldol reaction of 4-hydroxy-2-butanone. (c) 2007 Elsevier B.V. All rights reserved.
  • Ai Igarashi, Satoshi Sato, Ryoji Takahashi, Toshiaki Sodesawa, Mika Kobune
    CATALYSIS COMMUNICATIONS 8 5 807 - 810 2007年05月 研究論文(学術雑誌) 
    Vapor-phase catalytic dehydration of 1,4-butanediol was investigated over lanthanide oxides at 375 degrees C. Tetrahydrofaran (THF) and 3-buten-1-ol were competitively produced from 1,4-butanediol: oxides of light rare earth dominantly catalyze cyclization to THF, while oxides of heavy rare earth such as Tb, Er, and Yb effectively catalyze dehydration to 3-buten-1-ol. In particular, Yb(2)O(3) shows the most efficient catalytic activity in the formation of 3-buten-1-ol with the selectivity higher than 80 mol%, which depends on the structure of Yb(2)O(3). (c) 2006 Elsevier B.V. All rights reserved.
  • Ryoji Takahashi, Satoshi Sato, Toshiaki Sodesawa, Takaya Goto, Katsuhiro Matsutani, Naoki Mikami
    MATERIALS RESEARCH BULLETIN 42 3 523 - 531 2007年03月 研究論文(学術雑誌) 
    The bending strength of amorphous silica gels with bimodal pore structure was evaluated by changing macropore morphology and porosity, where the macropore morphology was controlled by inducing phase separation during gelation of silicate solution and the porosity was controlled by changing aging conditions and calcination temperature. At the same porosity, the bending strength was decreased for gels with larger macropores. In this preparation of bimodal porous silica gels, however, samples with large macropores also had many small particles in the macropores. Therefore, the decrease in bending strength with increasing macropore size was attributed to the presence of the particles that contributed to increasing bulk density but not bending strength. A power law applies to the bending strength and the bulk density of gels with the same macropore morphology, where the exponent depends on the morphology. (C) 2006 Elsevier Ltd. All rights reserved.
  • Ryoji Takahashi, Satoshi Sato, Satoshi Tomiyama, Tomoya Ohashi, Norifuml Nakamura
    MICROPOROUS AND MESOPOROUS MATERIALS 98 1-3 107 - 114 2007年01月 研究論文(学術雑誌) 
    Ni/SiO2 catalysts with bimodal pore structure were prepared by the sol-gel method of silicon tetraethoxide and nickel nitrate in the presence of poly(ethylene oxide) (PEO) and urea. The presence of PEO was effective to induce phase separation during the sol-gel process, and through-macropores interconnected three-dimensionally were formed by fixing transitional structure of the phase separation. After gelation, the as-prepared wet gel was aged at 80 degrees C for decomposition of urea in order to increase pH of the solution within the gel. This pH increase led both the ripening of silica gel network through dissolution-reprecipitation and homogeneous deposition of nickel hydroxide. As a result, Ni could be dispersed highly in the silica network. In addition to the high dispersion of Ni, thus prepared Ni/SiO2 has typical bimodal pore structure with size-controllable macropores and mesopores. The bimodal porous Ni/SiO2 also had high thermal stability and showed steady catalytic activity in CO2-reforming of methane at 700 degrees C. (C) 2006 Elsevier Inc. All rights reserved.
  • Osamu Nagashima, Satoshi Sato, Ryoji Takahashi, Toshiaki Sodesawa, Tetsu Akashi
    APPLIED CATALYSIS A-GENERAL 312 175 - 180 2006年09月 研究論文(学術雑誌) 
    Cycloketonization of dimethyl hexanedioate into cyclopentanone was investigated over pure CeO2 at a temperature between 350 and 475 degrees C. The conversion of the diester increased with raising the reaction temperature. The selectivity to cyclopentanone, however, decreased whenever the conversion increased. The major by-product other than methanol was 2-methylcyclopentanone. It was found that methylation of cyclopentanone with methanol into 2-methylcyclopentanone proceeded over CeO2. The decrease in the selectivity to cyclopentanone at high conversion was mainly caused by a consecutive reaction of cyclopentanone into 2-methylcyclopentanone due to alkylation with methanol. (C) 2006 Elsevier B.V. All rights reserved.
  • Ryoji Takahashi, Satoshi Sato, Toshiaki Sodesawa, Yuta Haga, Kei Kobayashi, Souta Watanabe, Masanari Ishizuki, Katsuhiro Matsutani, Naoki Mikami
    CHEMISTRY LETTERS 35 9 1078 - 1079 2006年09月 研究論文(学術雑誌) 
    A catalytic reactor using a capillary column with CU/SiO2 layer on its inner surface was prepared by injecting a silica sol containing Cu ions in a fused silica capillary and by subsequent gelation under the conditions controlled in order to deposit silica gel uniformly on the inner wall of the capillary. Its catalytic activity was demonstrated in the hydrogenation of propene by constructing a pulse reactor using the catalyst capillary and a separation capillary with pure silica gel layer.
  • Naoki Ichikawa, Satoshi Sato, Ryoji Takahashi, Toshiaki Sodesawa
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 256 1-2 106 - 112 2006年08月 研究論文(学術雑誌) 
    Catalytic reaction of 1,3-butanediol over solid acids such as SiO2-Al2O3, Al2O3, ZrO2 and TiO2 was investigated. The catalytic activities of these acids were in good coincidence with their acid properties: strong acid catalysts, SiO2-Al2O3 and Al2O3, catalyzed dehydration of 1,3-butanediol at the reaction temperature below 250 degrees C, while weak acid catalysts, ZrO2 and TiO2, required the temperature above 325 degrees C to activate 1,3-butanediol. SiO2-Al2O3 catalyzed the dehydration of 1,3-butanediol into unsaturated alcohols, and consecutively dehydrated them into 1,3-butadiene. 4-Methyl-1,3-dioxane, which is the acetal compound of 1,3-butanediol and formaldehyde, was obtained with high selectivity over Al2O3. Several compounds were produced over TiO2 and ZrO2 owing to the side reactions such as dehydrogenation and hydrogenation. The characteristics in the reaction were discussed in connection with other reactions of monoalcohols and of the produced unsaturated alcohols. (c) 2006 Elsevier B.V All rights reserved.
  • Ryoji Takahashi, Satoshi Sato, Toshiaki Sodesawa, Hironobu Nishino, Akiyuki Yachi
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 114 1329 421 - 424 2006年05月 [査読有り]
     研究論文(学術雑誌) 
    Monolithic polycrystalline zeolites with through-macropores were prepared by steam treatment of bimodal porous silica gel monolith in the presence of tetrapropylammonium hydroxide, where the bimodal porous silica gel was prepared by inducing phase separation during sol-gel process. The silica skeleton with mesopores was transformed into polycrystalline zeolites maintaining continuous macropore morphology and monolithic shape. In the zeolites, there are three different pores arranged hierarchically: through-macropores originally existed in the precursor silica gel, small macropores at interstitial of zeolite crystallites, and micropores in zeolite framework.
  • N Ichikawa, S Sato, R Takahashi, T Sodesawa, H Fujita, T Atoguchi, A Shiga
    JOURNAL OF CATALYSIS 239 1 13 - 22 2006年04月 研究論文(学術雑誌) 
    The adsorption of 1,3-butanediol on ail oxygen-defect site of a CeO2(111) surface was investigated with density functional theory (DFT) and paired interacting orbital (PIO) calculations in connection with the investigation of a CeO2(111) stoichiornetric surface. At theoxygen-defect site, two adsorption structures were obtained by DFT Calculations. In the structures, the two oxygen atoms of the OH groups interact with exposed Cc cations at the oxygen-defect site. The adsorption structures at the oxygen-defect site are more stable than that on the stoichiometric surface. In the most stable adsorption structure, one hydrogen atom of the 2-position niethylene group interacts with the third Cc cation at the oxygen-defect site of the CeO2(111) surface. We confirmed the elongation of two C-O bonds and one C-H bond of the 2-position methylene group in the most stable adsorption Structure. We also executed PIO calculations of 1,3-butanediol-CeO2(111) systems to analyze interacting orbitals. In-phase interaction between the two oxygen atoms in 1,3-butanediol and Cc cations was observed, indicating that the 13-butanediol molecule is anchored by two O-Ce bonds. Out-of-phase interactions between O and C atoms at 1-position and between H and C atorns at 2-position were confirmed. (c) 2006 Elsevier Inc. All rights reserved.
  • Satoshi Sato, Ryoji Takahashi, Toshiaki Sodesawa, Daiji Shin, Naoki Ichikawa, Katsuyuki Ogura
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 79 4 649 - 655 2006年04月 研究論文(学術雑誌) 
    SiO2-coated Al2O3 powders were prepared by depositing hydrolyzed tetraethoxysilane (TEOS) on Al(OH)(3) and gamma-Al2O3 at 40 degrees C. In the preparation using Al(OH)(3) with a specific surface area (SA) of ca. 40 m(2) g(-1) as a support, loading of silica deposited on the Al(OH)3 was saturated at 80 mg g(alumina)(-1). Ammonium nitrate, a catalyst for the hydrolysis of TEOS, increased silica loading linearly with increasing the amount of TEOS charged, while the silica aggregated on the Al(OH)(3). At temperatures of > 300 degrees C, the core Al(OH)(3) coated with aggregated silica was fragmented into a mixture of small particles of pure alumina and silica-alumina diminishing small particles with a large SA of > 400 m(2) g(-1). The small surface area of the support Al(OH)(3) is ineffective in generating active acid sites. In the deposition of silica on gamma-Al2O3 with a SA of 450 m(2) g(-1), however, silica loading increased with increasing the amount of TEOS charged at 40 degrees C without using ammonium nitrate. Silicate species with thinner layer structures uniformly covered the gamma-Al2O3 surface. The SiO2-covered gamma-Al2O3 showed higher catalytic activity than the SiO2-Al2O3 prepared from Al(OH)(3) did.
  • M Otsuda, R Takahashi, S Sato, T Sodesawa, M Ishizuki, K Matsutani, N Mikami
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 114 1327 282 - 285 2006年03月 研究論文(学術雑誌) 
    Production method of spherical silica beads with macropores was investigated from water glass. Spherical beads with continuous macropores were obtained by inducing phase separation in sol droplets in an organic solvent, and the diameter of beads was controlled between 0.7 and 2.8 mm by changing volume of droplets. The macroporous silica beads have dense external surface layer with thickness of ca. 2 mu m. The surface layer was removed by soaking the wet gel in I mol dm(-3) HIF solution for 10 s before drying.
  • Makoto Otsuda, Ryoji Takahashi, Satoshi Sato, Toshiaki Sodesawa, Masanari Ishizuki, Katsuhiro Matsutani, Naoki Mikami
    Journal of the Ceramic Society of Japan 114 1327 282 - 285 2006年 [査読有り]
     研究論文(学術雑誌) 
    Production method of spherical silica beads with macropores was investigated from water glass. Spherical beads with continuous macropores were obtained by inducing phase separation in sol droplets in an organic solvent, and the diameter of beads was controlled between 0.7 and 2.8 mm by changing volume of droplets. The macroporous silica beads have dense external surface layer with thickness of ca. 2μm. The surface layer was removed by soaking the wet gel in 1 mol dm-3 HF solution for 10s before drying.
  • N Yamamoto, S Sato, R Takahashi, K Inui
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 243 1 52 - 59 2006年01月 研究論文(学術雑誌) 
    Dehydration of 1,4-butanediol was investigated over ZrO2 at temperatures of 325-375 degrees C. Modification of ZrO2 with a small amount of sodium hydroxide greatly enhanced the selectivity to 3-buten-1-ol. Temperature-programmed desorption of adsorbed NH3 and CO2 elucidated acidity and basicity of the catalysts, respectively. The number of acidic sites on the ZrO2 decreased with increasing Na content, and disappeared at Na content of 1.0 mol%, whereas the number of basic sites increased with increasing Na content. In the relationship between Na content and the selectivity to products, selectivities to tetrahydrofuran and gamma-butyrolactone simply increased with the number of acidic and basic sites, respectively. However, the selectivity to 3-buten-1-ol was maximized at an appropriate Na content. 3-Butan-1-ol is possibly formed by acid-base-concerted catalysis of monoclinic ZrO2 in the dehydration of 1,4-butanediol. (c) 2005 Elsevier B.V. All rights reserved.
  • A Igarashi, N Ichikawa, S Sato, R Takahashi, T Sodesawa
    APPLIED CATALYSIS A-GENERAL 300 1 50 - 57 2006年01月 研究論文(学術雑誌) 
    Dehydration of butanediols into unsaturated alcohols was investigated over CeO2 with different particle sizes. The size was controlled by the calcination temperature. Catalytic performance in the dehydration of 1,3-butanediol is greatly affected by the particle size. The selectivity to unsaturated alcohols such as 3-buten-2-ol and trans-2-buten-1-ol increases with increasing the particle size, while decomposition of 1,3-butanediol into methanol and ethanol is catalyzed by CeO2 With small particles. In contrast, in the reaction of 1,4-butanediol, cyclization products such as tetrahydrofuran and gamma-butyrolactone increases with decreasing the particle size, instead of the decomposition into methanol and ethanol. CeO2 {111} facets became predominant on the large particles, whereas different surfaces such as {100} and {110} facets were exposed on the small CeO2 particles. In the dehydration of butanediols, CeO2 has structure-sensitive catalysis: CeO2 {111} facets have active sites for the formation of unsaturated alcohols, and the other surfaces catalyze the side reactions such as decomposition of 1,3-butanediol and cyclization of 1,4-butanediol. (c) 2005 Elsevier B.V. All rights reserved.
  • Ryoji Takahashi, Satoshi Sato, Toshiaki Sodesawa, Hironobu Nishino, Akiyuki Yachi
    Journal of the Ceramic Society of Japan 114 1329 421 - 424 2006年 研究論文(学術雑誌) 
    Monolithic polycrystalline zeolites with through-macropores were prepared by steam treatment of bimodal porous silica gel monolith in the presence of tetrapropylammonium hydroxide, where the bimodal porous silica gel was prepared by inducing phase separation during sol-gel process. The silica skeleton with mesopores was transformed into polycrystalline zeolites maintaining continuous macropore morphology and monolithic shape. In the zeolites, there are three different pores arranged hierarchically: through-macropores originally existed in the precursor silica gel, small macropores at interstitial of zeolite crystallites, and micropores in zeolite frame-work.
  • R Takahashi, S Sato, T Sodesawa, Y Haga, M Ishizuki, K Matsutani, N Mikami
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 113 1321 634 - 636 2005年09月 [査読有り]
     研究論文(学術雑誌) 
    Glass capillaries with silica gel layer on the inner surface were prepared by applying phase separation during sol-gel reaction of tetraethyl orthosilicate in the presence of poly (ethylene glycol) with number-average molecular weight of 20000. According to this technique, we can coat the internal surface with uniform silica gel layer for silica capillary with diameter up to 0.1 mm. In the gas chromatographic analysis of hydrocarbons using the capillary column with silica gel layer, light hydrocarbons up to C4 can be analyzed with high resolution and within short experimental time at ambient temperature.
  • S Sato, R Takahashi, T Sodesawa, H Fukuda, T Sekine, E Tsukuda
    CATALYSIS COMMUNICATIONS 6 9 607 - 610 2005年09月 研究論文(学術雑誌) 
    Synthesis of alpha-hydroxyketones from 1,2-diols over copper catalysts modified with ZnO, Al2O3 and ZrO2 was investigated. 1-Hydroxy-2-butanone was efficiently produced by the dehydrogenation of 1,2-butanediol over Cu-Zn-Zr-Al-O catalysts: the highest activity was obtained at the molar ratio of CuO:ZnO:ZrO2:Al2O3 = 12:1:2:2. Several alpha-hydroxyketones were produced by the dehydrogenation of 1,2-diols with carbon chain of C3-C6. (c) 2005 Elsevier B.V. All rights reserved.
  • R Takahashi, S Sato, T Sodesawa, T Goto, K Matsutani, N Mikami
    MATERIALS RESEARCH BULLETIN 40 7 1148 - 1156 2005年07月 研究論文(学術雑誌) 
    Silica gels with both macropores and mesopores were prepared from water glass by fixing transitional structure of phase separation, and their strength was investigated. Pore structure of the gels was controlled by changing gel-preparation compositions, aging conditions and calcination temperature. Strength of the gels varies depending on the mesopore volume. At the same time, porosity of the gels decreases with decreasing mesopore volume, and correlation between strength and porosity is recognized like other porous systems. The strength of the bimodal porous silica gel is somewhat larger than that in literature for the silica aerogel with similar porosity. (c) 2005 Elsevier Ltd. All rights reserved.
  • N Yamamoto, S Sato, R Takahashi, K Inui
    CATALYSIS COMMUNICATIONS 6 7 480 - 484 2005年07月 研究論文(学術雑誌) 
    Catalytic dehydration of 1,4-butanediol was investigated over ZrO2 with monoclinic crystal phase at temperatures of 275-425 degrees C. In the reaction, 3-buten-1-ol was effectively produced together with tetrahydrofuran (THF) over ZrO2 at 300-375 degrees C. 3-Buten-1-ol and THF were produced competitively, and the yield of 3-buten-1-ol increased with increasing the contact time. Formation of by-products such as 2-buten-1-ol, 2-butenal, and 1-butanol was suppressed over ZrO2 at 325 degrees C. (C) 2005 Elsevier B.V. All rights reserved.
  • R Takahashi, S Sato, T Sodesawa, S Tomiyama
    APPLIED CATALYSIS A-GENERAL 286 1 142 - 147 2005年05月 研究論文(学術雑誌) 
    Ni/SiO2 catalysts with Ni content up to 50 wt.% were prepared by depositing nickel hydroxides in a sol-gel-derived wet silica gel, where nickel hydroxides were produced by the increase in pH due to the decomposition of urea. The Ni dispersion in the resulting catalysts is relatively high, and increases monotonically with increasing Ni content up to 40 wt.%. The Ni/SiO2 catalysts have large volume and large-sized mesopores at <= 20 wt.% Ni-loading, and have high thermal stability. In the CO2-reforming of methane, the catalytic activity proportionally increases with increasing Ni content at reaction temperatures between 500 and 900 degrees C. High and steady catalytic activity is achieved when we use the Ni/SiO2 catalysts with Ni content of 20 wt.% under the reaction conditions of high space-time velocity and high temperature. (c) 2005 Elsevier B.V. All rights reserved.
  • R Takahashi, S Sato, T Sodesawa, M Shizukuishi, K Morofuji, K Ogura
    JOURNAL OF NON-CRYSTALLINE SOLIDS 351 10-11 826 - 832 2005年04月 研究論文(学術雑誌) 
    Change in the local structure of aluminum cations was investigated during the preparation of silica-alumina mixed-oxide by coprecipitation from a solution of tetraethyl orthosilicate (TEOS) and aluminum nitrate. In the mixture of hydrolyzed TEOS and aluminum nitrate, aluminum cations exist as aqua complex, and promote hydrolysis and condensation of TEOS. When precipitates are formed by adding ammonia, Al-O-Si bonds are formed accompanied with the change in coordination number of Al cations from 6 to 4. At the same time, acid centers, whose number agrees with the number of Al cations, are generated on the surface of the precipitates. A silica-alumina catalyst prepared by coprecipitation with excess ammonia shows high activity in the cracking of cumene. Dispersion of Al in it, is also high, and this would be the reason of the high activity. © 2005 Elsevier B.V. All rights reserved.
  • N Ichikawa, S Sato, R Takahashi, T Sodesawa
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 231 1-2 181 - 189 2005年04月 研究論文(学術雑誌) 
    CeO2 has specific catalytic activity for the selective dehydration of 1,3-diols to unsaturated alcohols. In order to clarify the catalytic mechanism. quantum calculation based on the paired interacting orbital (PIO) theory was adopted to 1,3-butanediol-CegO(18) cluster systems. Strong attractive interaction was observed between 1,3-butanediol and oxygen-defected CeO2 (111), where three in-phase interactions were confirmed between H atom at 2-position in 1,3-butanediol and Cc cation and between two OH groups and other Cc cations. In addition, out-of-phase interaction between H and C atom at 2-position was induced by the in-phase interaction between H atom and Cc cation at appropriate coordinate of 1,3-butanediol. The PIO results suggest that the dehydration of 1,3-diols initiates from the abstraction of H atom at 2-position in 1,3-butanediol adsorbed on an oxygen defect site on CeO2 (111) with tridentate coordination. (c) 2005 Elsevier B.V. All rights reserved.
  • S Sato, R Takahashi, T Sodesawa, M Koubata
    APPLIED CATALYSIS A-GENERAL 284 1-2 247 - 251 2005年04月 研究論文(学術雑誌) 
    Palladium catalysts loaded on bimodal porous silica were examined in the liquid-phase hydrogenation of 2-butenal at 0 degrees C and a hydrogen pressure of 1.1 MPa. The sizes of mesopores and macropores of the silica support are controllable in the range of 4-23 nm and 0.5-25 mu m, respectively. The macropores provide effective paths of mass transfer, and the mesopores present effective surfaces for dispersion of metals. The catalytic activity of Pd-silica with bimodal porous structure depends on the size of mesopores and macropores as well as on the particle 14 size of the support silica. The most active Pd-silica catalyst, with mesopores of 12 run and macropores of 2 mu m, shows much higher activity than does a commercial palladium carbon catalyst without macropores. The results indicate that the diffusion process inside the catalyst particles dominantly determines the reaction rate in the hydrogenation. (c) 2005 Elsevier B.V. All rights reserved.
  • O Nagashima, S Sato, R Takahashi, T Sodesawa
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 227 1-2 231 - 239 2005年03月 研究論文(学術雑誌) 
    The ketonization of propanoic acid to form 3-pentanone over CeO2-based composite oxides at temperatures of 300-425 degreesC was investigated. A CeO2-based solid solution, CeO2-Mn2O3, was effective for the ketonization. The citrate process was the most appropriate method for preparing, a well-dispersed solid solution. In the ketonization of propanoic acid with another linear carboxylic acid, an asymmetric ketone together with two symmetric ketones was formed, and the ketone composition was approximated by a binomial distribution. The reactivity of the carboxylic acid was slightly decreased as its chain length was increased. In contrast to linear aliphatic acids, branched acids were less reactive. Methyl group substituents at the alpha- and beta-positions of carboxylic acids decreased their reactivities in both homo- and cross-ketonization. The lack of an alpha-hydrogen or the increase in steric hindrance was surmised to be the cause of the decrease in reactivity. (C) 2004 Elsevier B.V. All rights reserved.
  • R Takahashi, K Nakanishi, N Soga
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 33 2 159 - 167 2005年02月 研究論文(学術雑誌) 
    Structural rearrangement of sol-gel-derived silica gel by aging under basic conditions was investigated using small angle X-ray scattering (SAXS) and Si-29 nuclear magnetic resonance (NMR). A wet silica gel prepared under acidic conditions had a fractal nature, and many unreacted silanols remained on the surface. During aging of the gel in ammonia solution, additional Si-O-Si bonds rapidly formed, whereas the change in mesoscale structure gradually proceeded. This result was compared with that of simulation modeling the Ostwald ripening, i.e. dissolution from positive curvature and reprecipitation on negative curvature. In the simulation, structural change in a cluster from fractal nature to particle aggregates was well visualized in 2-dimmensional square lattice. Both scattering profiles calculated from the model clusters and the change in average coordination number of monomers in the cluster well agreed with the experimental SAXS and NMR results, respectively. This agreement strongly ensures us that structural change by aging under basic conditions proceeds through the Ostwald ripening. The mesopore size as well as mesopore volume in calcined silica gel is determined by the shrinkage degree during drying and calcination. The sample aged in basic solution restrains the shrinkage because of the growth of particulate structure, and retains large size and volume of pores.
  • A Yachi, R Takahashi, S Sato, T Sodesawa, K Uma, K Matsutani, N Mikami
    JOURNAL OF NON-CRYSTALLINE SOLIDS 351 4 331 - 339 2005年02月 研究論文(学術雑誌) 
    Monolithic silica gel with macropores was prepared in the solution of water glass and polyacrylic acid (HPAA) by freezing transitional structures of phase separation. In the system, phase separation proceeds between silica polymers and HPAA, so that the porous morphology varies from closed macropores to particle aggregates through bicontinuous morphology, where both macropores and silica skeleton are three-dimensionally interconnected, with increasing HPAA/silica ratio. In addition, we can control the macropore size in bicontinuous morphology by varying the concentration of both silica and HPAA, or by changing the molecular weight of HPAA. The pore size distribution is quite sharp indicating the presence of pores with the same size all through the monolithic samples. (C) 2004 Elsevier B.V. All rights reserved.
  • R Takahashi, S Sato, T Sodesawa, Y Tomita
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 113 1313 92 - 96 2005年01月 [査読有り]
     研究論文(学術雑誌) 
    Thermal properties of bimodal porous silica and silica-zirconia with humidity control ability are investigated in order to clarify their potential as a multi-functional building material. Thermal conductivity of the silica decreases with increasing the porosity of the silica, and 0.06 W m(-1)K(-1) is achieved when the porosity exceeds 90%. The silica shows thermal resistance of ca. 800degreesC, which is much higher than conventional thermal insulators. The thermal resistance can be improved by the addition of zirconia: a silica-zirconia sample maintains its high porosity up to 1050degreesC. Thus, the bimodal porous silica and silica-zirconia are expected to be a thermal insulator with humidity control and thermal resistance abilities.
  • Ryoji Takahashi, Satoshi Sato, Toshiaki Sodesawa, Yuta Haga, Masanari Ishizuki, Katsuhiro Matsutani, Naoki Mikami
    Journal of the Ceramic Society of Japan 113 1321 634 - 636 2005年 研究論文(学術雑誌) 
    Glass capillaries with silica gel layer on the inner surface were prepared by applying phase separation during sol-gel reaction of tetraethyl orthosilicate in the presence of poly (ethylene glycol) with number-average molecular weight of 20000. According to this technique, we can coat the internal surface with uniform silica gel layer for silica capillary with diameter up to 0.1 mm. In the gas Chromatographic analysis of hydrocarbons using the capillary column with silica gel layer, light hydrocarbons up to C4 can be analyzed with high resolution and within short experimental time at ambient temperature.
  • Ryoji Takahashi, Satoshi Sato, Toshiaki Sodesawa, Yumiko Tomita
    Journal of the Ceramic Society of Japan 113 1313 92 - 96 2005年 研究論文(学術雑誌) 
    Thermal properties of bimodal porous silica and silica-zirconia with humidity control ability are investigated in order to clarify their potential as a multi-functional building material. Thermal conductivity of the silica decreases with increasing the porosity of the silica, and 0.06 W m -1K-1 is achieved when the porosity exceeds 90%. The silica shows thermal resistance of ca. 800°C, which is much higher than conventional thermal insulators. The thermal resistance can be improved by the addition of zirconia: a silica-zirconia sample maintains its high porosity up to 1050°C. Thus, the bimodal porous silica and silica-zirconia are expected to be a thermal insulator with humidity control and thermal resistance abilities.
  • R Takahashi, S Sato, T Sodesawa, K Arai, M Yabuki
    JOURNAL OF CATALYSIS 229 1 24 - 29 2005年01月 研究論文(学術雑誌) 
    Bimodal porous silica-alumina catalysts with both continuous macropores and mesopores were prepared from tetraethyl orthosilicate in the presence of polyethylene oxide, and the effectiveness of macropores in vapor-phase dehydration of 2-propanol was evaluated by the comparison with silica-alumina having no macropores. The reaction rate of dehydration varies depending on the particle size and the presence of macropores as well as reaction temperature. For more detail data processing, diffusion coefficients in pores at each reaction temperature were theoretically calculated by assuming molecular diffusion and Knudsen diffusion for catalysts with and without macropores, respectively. Then, we compare the catalyst effectiveness factors obtained experimentally with the theoretical curve. The experimental data well agree with theoretical prediction. The results clearly show that the macropores with interconnected structure effectively work as pathways for rapid diffusion and improve the reaction kinetics. (C) 2004 Elsevier Inc. All rights reserved.
  • N Ichikawa, S Sato, R Takahashi, T Sodesawa
    CATALYSIS COMMUNICATIONS 6 1 19 - 22 2005年01月 研究論文(学術雑誌) 
    Dehydration of 4-hydroxy-2-butanone (HB) to 3-buten-2-one (MVK) was investigated. Anatase-TiO2 exhibited excellent activity for the dehydration of HB with 98.8 mol% MVK yield. The highest activity was obtained at 160 degreesC, and deactivation was rarely observed over anatase-TiO2. HB decomposes into propanone above 240 degreesC, and the MVK selectivity decreases with increasing temperature. High acidity of catalysts causes deactivation because of strong interaction between MVK and acid sites that induces polymerization. Weak acid sites are efficient for the dehydration of HB to MVK. (C) 2004 Elsevier B.V. All rights reserved.
  • S Sato, R Takahashi, T Sodesawa, NT Honda
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 221 1-2 177 - 183 2004年11月 研究論文(学術雑誌) 
    Dehydration of several 1,3-diols into unsaturated alcohols was investigated over pure CeO2 at 325-425 degreesC. 1,3-Diols are more reactive than other diols and monoalcohols over CeO2. In the dehydration of 1,3-propanediol, 1,3-butanediol, 3-methyl-1,3-butanediol, 2,4-pentanediol, and 2-methyl-2,4-pentanediol, unsaturated alcohols are selectively produced at 325 degreesC. In the dehydration of 2-methyl-1,3-propanediol, the corresponding unsaturated alcohol is produced with low selectivity: decomposition simultaneously proceeds. TPR experiment reveals that active CeO2 surface is maintained at high valence of Ce4+ in the water-producing reaction. It is speculated that redox nature between Ce4+-Ce3+ affects the dehydration of 1,3-diols. (C) 2004 Elsevier B.V. All rights reserved.
  • R Takahashi, S Sato, T Sodesawa, M Yoshida, S Tomiyama
    APPLIED CATALYSIS A-GENERAL 273 1-2 211 - 215 2004年10月 研究論文(学術雑誌) 
    Nickel catalysts supported on silica-zirconia mixed oxides were prepared by homogeneous precipitation in sol-gel-derived wet silica gel. Their structural properties and catalytic performance in steam-reforming of methane were investigated from the viewpoint of steam resistance. Ni/SiO2 without zirconia readily loses its catalytic activity during the reaction because the coarsening of silica that occurs in the presence of high-temperature steam hinders the active surface of Ni. The addition of zirconia drastically increases the steam resistance of silica. Ni/SiO2-ZrO2 catalyst shows steady activity in steam-reforming of methane without any changes in pore structure. (C) 2004 Elsevier B.V. All rights reserved.
  • Y Tomita, R Takahashi, S Sato, T Sodesawa, M Otsuda
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 112 1309 491 - 495 2004年09月 [査読有り]
     研究論文(学術雑誌) 
    Humidity control ability of monolithic bimodal porous silica gel prepared from water glass in the presence of poly (acrylic acid) was investigated from the viewpoints of both equilibrium and kinetic aspects. The humidity, at which adsorption-release of water vapor occurred reversibly, was systematically controlled by changing the mesopore size. The equilibrium adsorption amount of water was as high as 0.7 g per gram of silica. In addition, the presence of macropores made it possible to quickly response for humidity change by the adsorption-release cycle because of rapid gas diffusion in monolithic gel body. These features are quite attractive as a material for humidity control in the airtight buildings.
  • R Takahashi, S Sato, T Sodesawa, T Azuma
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 31 1-3 373 - 376 2004年08月 研究論文(学術雑誌) 
    The comparison of bimodal pore structures between silica gels prepared from silicon alkoxide and from water glass was performed based on the results of phase separation tendency, mesopore formation, and atomic scale observation using Si-29 NMR. Macropore structure could be controlled for both the raw material systems by inducing phase separation. Although the gelation in the water glass system is much faster than that in the silicon alkoxide system, there is little difference in the atomic scale structure, mesopore evolution during processing, and phase separation tendency. The results suggest that the obtained bimodal porous silica from water glass is essentially the same as that from silicon alkoxide. Because of the low cost of water glass, water- glass- derived bimodal porous silica is applicable to industrial use.
  • S Sato, R Takahashi, T Sodesawa, N Yamamoto
    CATALYSIS COMMUNICATIONS 5 8 397 - 400 2004年08月 研究論文(学術雑誌) 
    Catalytic dehydration of 1,4-butanediol was investigated at temperatures of 200-450 degreesC. In the dehydration of 1,4-butanediol, homoallyl alcohol such as 3-buten-1-ol is produced over pure CeO2. The formation of 3-buten-1-ol is followed by the stepwise dehydration to 1,3-butadiene. CeO2 can produce 3-buten-1-ol without catalyzing the further dehydration: the maximum selectivity of 68.1 mol% and the yield of 59.7% are attained at 400 degreesC. (C) 2004 Elsevier B.V. All rights reserved.
  • N Ichikawa, S Sato, R Takahashi, T Sodesawa, K Inui
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 212 1-2 197 - 203 2004年04月 研究論文(学術雑誌) 
    Synthesis of gamma-butyrolactone (GBL) from 1,4-butanediol (BDO) over copper-based catalysts with ZnO, Al2O3 and ZrO2 was investigated. Catalytic activity of copper was greatly affected by the additive oxides. The highest activity was obtained at a catalyst molar ratio of CuO:ZnO:ZrO2:Al2O3 = 6:1:2:2. ZrO2 showed the highest additive effect for the GBL synthesis with enhancing dehydrogenation ability of metallic Cu and enlarging Cu surface area. Al2O3 enlarged Cu surface area, whereas a large amount of tetrahydrofuran (THF) was formed over the acid sites of Al2O3 surface, and ZnO reduced the THF yield. The reaction pathway from BDO to GBL was also clarified: BDO was initially dehydrogenated to 4-hydroxybutanal, which was immediately hemiacetalized to 2-hydroxytetrahydrofuran, followed by the dehydrogenation to GBL over metallic Cu. (C) 2003 Elsevier B.V. All rights reserved.
  • H Nishino, R Takahashi, S Sato, T Sodesawa
    JOURNAL OF NON-CRYSTALLINE SOLIDS 333 3 284 - 290 2004年03月 研究論文(学術雑誌) 
    Silica gel samples with macropores were prepared from solutions of silicate and poly(vinyl alcohol) (PVA), where macropores were formed by fixing a transitional structure of phase separation. Among the silica sources tested, tetraethoxysilane (TEOS), colloidal silica and, water glass, only the system with water glass shows phase separation and forms macroporous silica gel. In the system with TEOS, ethanol formed during hydrolysis of TEOS becomes good solution and stabilizes the system not to induce phase separation. In the system with colloidal silica, dense structure of silica is probably not suitable for controlling phase separation and gelation. In the system with water glass, driving force of phase separation is considered to be a repulsive interaction between solvent molecules and PVA interacting with silica surface and the solution separates into a phase rich in solvent and that rich in silica and PVA. One of the features in the water glass-PVA system is insensitivity of macropore size against compositional change in the solution, i.e. macroporous morphology in the resultant silica gel hardly changes by changing the composition ratio in the solution. This would be an advantage in the preparation of well-defined macroporous silica from water glass, whose composition varies among the product lot number, because reproducibility in macroporous morphology is ensured regardless of the lot number of the water glass. (C) 2004 Elsevier B.V. All rights reserved.
  • R Takahashi, S Sato, T Sodesawa, A Haga, H Nishino
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 112 1302 99 - 103 2004年02月 [査読有り]
     研究論文(学術雑誌) 
    Pressure loss in gas flow in three-dimensionally interconnected macropores in silica gel rods was investigated. In the preparation of the silica gel, the continuous macropores are formed by inducing phase separation in a solution containing tetraethoxysilane (TEOS) and poly (ethylene oxide) (PEO), and subsequent freezing of its transitional structures by gelation. Average macropore size of the silica gels was systematically controlled from 25 to 0.6 mum by changing PEO content in the solution without affecting porous morphology. The pressure loss in gas flow in the continuous macropores can be approximated with a simple straight channels model, and well reproduced with the Hargen-Poiseuille's equation without any correction, in contrast to that in columns packed with micrometer-size particles, which show substantial higher pressure loss than the continuous macropores. The low flow resistance in the macroporous silica rods would be attributed to the absence of necks in flow pathways.
  • Yumiko Tomita, Ryoji Takahashi, Satoshi Sato, Toshiaki Sodesawa, Makoto Otsuda
    Journal of the Ceramic Society of Japan 112 1309 491 - 495 2004年 研究論文(学術雑誌) 
    Humidity control ability of monolithic bimodal porous silica gel prepared from water glass in the presence of poly (acrylic acid) was investigated from the viewpoints of both equilibrium and kinetic aspects. The humidity, at which adsorption-release of water vapor occurred reversibly, was systematically controlled by changing the mesopore size. The equilibrium adsorption amount of water was as high as 0.7 g per gram of silica. In addition, the presence of macropores made it possible to quickly response for humidity change by the adsorption-release cycle because of rapid gas diffusion in monolithic gel body. These features are quite attractive as a material for humidity control in the airtight buildings.
  • Ryoji Takahashi, Satoshi Sato, Toshiaki Sodesawa, Akihiro Haga, Hironobu Nishino
    Journal of the Ceramic Society of Japan 112 1302 99 - 103 2004年 研究論文(学術雑誌) 
    Pressure loss in gas flow in three-dimensionally interconnected macropores in silica gel rods was investigated. In the preparation of the silica gel, the continuous macropores are formed by inducing phase separation in a solution containing tetraethoxysilane (TEOS) and poly (ethylene oxide) (PEO), and subsequent freezing of its transitional structures by gelation. Average macropore size of the silica gels was systematically controlled from 25 to 0.6 μm by changing PEO content in the solution without affecting porous morphology. The pressure loss in gas flow in the continuous macropores can be approximated with a simple straight channels model, and well reproduced with the Hargen-Poiseuille's equation without any correction, in contrast to that in columns packed with micrometer-size particles, which show substantial higher pressure loss than the continuous macropores. The low flow resistance in the macroporous silica rods would be attributed to the absence of necks in flow pathways.
  • R Takahashi, S Sato, T Sodesawa, M Suzuki, N Ichikuni
    MICROPOROUS AND MESOPOROUS MATERIALS 66 2-3 197 - 208 2003年12月 研究論文(学術雑誌) 
    A Ni/SiO2 with high Ni content over 50 wt% in NiO form was prepared from a solution of TEOS, nickel nitrate and citric acid. The additive citric acid contributes both the formation of mesopores and increase in the Ni dispersion. The Ni/SiO2 has large mesopores with size of 5-10 nm. The mesopores are formed by eliminating citric acid from the silica-Ni-citric acid composite with small shrinkage, i.e. the spaces occupied with citric acid in the composite directly turn to pores after elimination. Although large shrinkage in pores occurs when the composite is calcined in air, the calcination in an inert atmosphere is effective to suppress the shrinkage during calcination. In addition to the controlled large mesopores, high Ni dispersion is achieved in the Ni/SiO2. Nickel citrate formed in the as-prepared silica-Ni-citric acid composite effectively suppresses the aggregation of Ni species during drying because of low crystallization ability of nickel citrate. Furthermore, the following calcination in an inert atmosphere has an additional effect to increase Ni dispersion. Thus prepared samples keep small Ni particle size even at high Ni content of approximate to 50 wt% after reduction at 500 degreesC, and show high Ni surface area over 30 m(2) g(-1). (C) 2003 Elsevier Inc. All rights reserved.
  • S Takenaka, S Sato, R Takahashi, T Sodesawa
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 5 21 4968 - 4973 2003年11月 研究論文(学術雑誌) 
    MgO and NiO-MgO with large mesopores were prepared by using the corresponding nitrates and carboxylic acids. Their pore structures were characterized by N-2 adsorption, and reduced Ni-MgO samples were used in the liquid-phase hydrogenation of ketone. The mesopore size of MgO was controllable with the alkyl-chain length of the carboxylic acid in the range between 13 and 38 nm. The mesopores are located at the MgO interparticles. In the hydrogenation of 4-heptanone to 4-heptanol, the catalytic activity of the Ni-MgO, which had mesopores at 11 nm, prepared using dodecanoic acid was higher than that of a commercial Raney Ni with mesopores around 4 nm, while the Ni surface of the Ni-MgO was lower than that of a Raney Ni catalyst. At an optimum regulated size of mesopores, the Ni-MgO catalyst would show high catalytic activity satisfying both rapid mass transfer of the reactants and high dispersion of Ni metals on the catalyst surface.
  • Y Kamimura, S Sato, R Takahashi, T Sodesawa, T Akashi
    APPLIED CATALYSIS A-GENERAL 252 2 399 - 410 2003年10月 研究論文(学術雑誌) 
    Vapor-phase synthesis of 3-pentanone from 1-propanol over CeO2-Fe2O3 catalysts was investigated, and the reaction pathway was discussed in comparison with the reactions of propanal and n-propyl propionate over the CeO2-Fe2O3. 1-Propanol was preferentially converted into 3-pentanone over the CeO2-Fe2O3 catalysts at 450 degreesC, and propanal, 3-hydroxy-2-methylpentanal, and n-propyl propionate were observed as by-products. The addition of Fe2O3 to CeO2 enhances the ability of CeO2 for the catalytic dehydrogenation of 1-propanol to propanal without losing the ability for the dimerization of propanal. The turnover frequency (TOF) based on a basic site varies with Fe content. Both the selectivity-conversion curves and similarity in the TOF between the reactants of 1-propanol at 450 degreesC and propanal at 400 degreesC suggest that propanal is an initial intermediate converting into the final product, 3-pentanone. The formation of 3-pentanone from 1-propanol over the CeO2-Fe2O3 proceeds via aldol addition of propanal into 3-hydroxy-2-methylpentanal, followed by the decomposition into 3-pentanone, while n-propyl propionate is formed as a mere by-product. (C) 2003 Elsevier B.V. All rights reserved.
  • T Akashi, S Sato, R Takahashi, T Sodesawa, K Inui
    CATALYSIS COMMUNICATIONS 4 8 411 - 416 2003年08月 研究論文(学術雑誌) 
    CeO2-based binary oxides catalyzed the cyclization of 1,6-hexanediol into cyclopentanone at temperatures of 400-475 degreesC. CeO2-based solid solution with Mn content of 20 mol% shows the highest catalytic activity, both conversion and selectivity, while both pure CeO2 and Mn2O3 have the cyclization ability of 1,6-hexanediol. Cyclopentanone is produced with the maximum selectivity of 80.9 mol% over CeO2-MnOx solid solution catalyst at 450 degreesC. As byproducts, cyclohexanone, cyclopentylmethanol, 1-hexanol, and hexanal are observed in the cyclization. Low concentration of 1,6-hexanediol would be preferable in the catalytic operation because dimerized products are observed at high concentration of 1,6-hexanediol. (C) 2003 Elsevier B.V. All rights reserved.
  • S Takenaka, R Takahashi, S Sato, T Sodesawa, F Matsumoto, S Yoshida
    MICROPOROUS AND MESOPOROUS MATERIALS 59 2-3 123 - 131 2003年05月 研究論文(学術雑誌) 
    Mesoporous SnO2 with controlled pore size was prepared by calcination of the precursors containing stearic acid (STA). The vaporization of STA promoted the crystallization of SnO2 at low temperature. Crystallization accompanied with the vaporization of STA at low temperature allowed SnO2 crystallites to aggregate loosely to form mesopores. The SnO2 consisted of the aggregates of crystallites, and the mesopores were located at intercrystallites. The pore size and crystallite size of the mesoporous SnO2 increased with increasing calcination temperature (T-c). The specific surface area decreased with increasing T-c, while the pore volume showed little change in the range of T-c. The crystal growth of SnO2 during calcination at high T-c provided large mesopores at interparticles. (C) 2003 Elsevier Science Inc. All rights reserved.
  • S Sato, R Takahashi, T Sodesawa, N Honda, H Shimizu
    CATALYSIS COMMUNICATIONS 4 2 77 - 81 2003年02月 研究論文(学術雑誌) 
    CeO2 catalyzed the selective dehydration of 1,3-diols into allylic alcohols at temperatures 300-375degreesC. In the dehydration of 1,3-propanediol over pure CeO2, 2-propen-1-ol is produced with the maximum selectivity of 98.9 mol% at 325degreesC. In the dehydration of 1,3-butanediol, 2-buten-1-ol and 3-buten-2-ol were produced with the sum of the selectivity > 99 mol% over CeO2, which showed attractive catalytic performance without decay at temperatures <375degreesC. In the reactions of 2-buten-1-ol, 1,2- and 1,4-butanediol, little dehydrated products were detected over the CeO2. (C) 2002 Elsevier Science B.V. All rights reserved.
  • S Tomiyama, R Takahashi, S Sato, T Sodsawa, S Yoshida
    APPLIED CATALYSIS A-GENERAL 241 1-2 349 - 361 2003年02月 研究論文(学術雑誌) 
    Silica-supported nickel (Ni/SiO2) catalysts were prepared by homogeneous precipitation of nickel hydroxide in a wet silica gel derived from a sol-gel process (HPG). Their microstructures and their catalytic performance for the CO2-reforming of CH4 were investigated in comparison with those of Ni/SiO2 prepared by a conventional incipient wet impregnation process (IMP). The HPG process consists of two successive steps: gelation of silica in the presence of nickel nitrate and urea at 20degreesC, followed by aging at higher temperature, typically at 80degreesC,to induce thermal decomposition of the urea. The nickel metal surface area of the HPG catalysts was larger than that of IMP catalysts at each calcination temperature. Nickel species in HPG catalysts are expected to be entrapped in the network of silica with high dispersion, while those in IMP catalysts are expected to aggregate on the surface of silica. The characteristic structure in HPG catalysts is considered to be formed through concurrence of dissolution-reprecipitation of silica and entrapment of nickel species into the network. Such processes are promoted in a basic condition led by NH3 formation during thermal decomposition of urea at 80degreesC. The amount of carbon deposited and the catalytic deactivation degree in HPG catalysts were smaller than those in IMP catalysts. Thermal stability of HPG catalysts was much higher than that of IMP catalysts and catalytic activities of the former were higher than those of the latter. This originates in the highly-dispersed nickel metal particles in the rigid network of silica for HPG catalysts. (C) 2002 Elsevier Science B.V. All rights reserved.
  • S Takenaka, R Takahashi, S Sato, T Sodesawa, T Uematsu
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 111 1 16 - 23 2003年01月 [査読有り]
     研究論文(学術雑誌) 
    Mesoporous zirconia was prepared by the hydrolysis of zirconium tetrapropoxide (ZTP). Crystal structure of zirconia was controlled by using different hydrolysis procedures. A large amount of water and subsequent calcination led to the formation of mesoporous monoclinic zirconia with the pore size of 20 nm, while nonporous tetragonal zirconia was prepared with a small amount of water. Mesoporous tetragonal zirconia with controlled pore size was prepared from ZTP and carboxylic acids with different alkyl-chain length. The average pore size of the tetragonal zirconia increased from 4.8 to 7.5 nm with increasing alkyl-chain length of carboxylic acids. A complex of ZTP and carboxylic acid formed a hexagonal mesophase at the molar ratio of carboxylic acid to ZTP greater than or equal to 1.5. The lattice parameter of the hexagonal mesophase increased with increasing alkyl-chain length of carboxylic acid. The hexagonal mesophase, however, disappeared when the precursor melted over 58degreesC. The calcined zirconia consisted of the aggregates of crystallites, and the mesopores were located at interparticles. The appropriate coordination state and alkyl-chain length of carboxylic acid are probably effective in preparing mesoporous tetragonal zirconia and controlling the mesopores.
  • R Takahashi, S Sato, T Sodesawa, T Ikeda
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 5 11 2476 - 2480 2003年 研究論文(学術雑誌) 
    The liquid-phase diffusion coefficient of several ketones within mesopores was estimated by measuring the change in UV absorbance of mesoporous plates immersed in a solvent. Monolithic plates of silica gel with different mesopore sizes at ca. 4 and 10 nm were used for the measurement after their pore surface had been modified with trimethylsilyl groups. In the modified silica plates, the diffusion coefficient of ketones, Dp(,) decreases with increasing the molecular size of the solvent, whereas little dependence is observed on the molecular size of solutes. This indicates that diffusivity of the solute in the mesopores is determined by the diffusivity of the solvent. A zigzag tendency (i.e. the D-p in alkane solvents with an odd number of carbons is larger than those with an even number of carbons) was observed in the small pores with a diameter of ca. 4 nm. The zigzag in Dp can explain a similar zigzag trend in the reaction rate observed only in the small mesopores of the Raney nickel catalyst with a diameter of 3.8 nm in the hydrogenation of several ketones.
  • Shoichi Takenaka, Ryoji Takahashi, Satoshi Sato, Toshiaki Sodesawa, Takayoshi Uematsu
    Journal of the Ceramic Society of Japan 111 1289 16 - 23 2003年 研究論文(学術雑誌) 
    Mesoporous zirconia was prepared by the hydrolysis of zirconium tetrapropoxide (ZTP). Crystal structure of zirconia was controlled by using different hydrolysis procedures. A large amount of water and subsequent calcination led to the formation of mesoporous monoclinic zirconia with the pore size of 20 nm, while nonporous tetragonal zirconia was prepared with a small amount of water. Mesoporous tetragonal zirconia with controlled pore size was prepared from ZTP and carboxylic acids with different alkyl-chain length. The average pore size of the tetragonal zirconia increased from 4.8 to 7.5 nm with increasing alkyl-chain length of carboxylic acids. A complex of ZTP and carboxylic acid formed a hexagonal mesophase at the molar ratio of carboxylic acid to ZTP ≥ 1.5. The lattice parameter of the hexagonal mesophase increased with increasing alkyl-chain length of carboxylic acid. The hexagonal mesophase, however, disappeared when the precursor melted over 58°C. The calcined zirconia consisted of the aggregates of crystallites, and the mesopores were located at interparticles. The appropriate coordination state and alkyl-chain length of carboxylic acid are probably effective in preparing mesoporous tetragonal zirconia and controlling the mesopores.
  • S Sato, R Takahashi, T Sodesawa, R Tanaka
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 76 1 217 - 223 2003年01月 研究論文(学術雑誌) 
    Fine particles of SiO2-coated Fe2O3 were prepared by depositing silica on an iron(III) hydroxide precipitate using tetraethoxysilane (TEOS). The silica deposition proceeded under mild conditions at 20 degreesC; crystallization hardly occurred and silica loading was controlled by the amount of TEOS charged, whereas the precipitate crystallized to a mixture of FeO(OH) and alpha-Fe2O3 under hydrothermal conditions. The specific surface area of the SiO2-coated Fe2O3 increased with silica loading, and exceeded 280 m(2) g(-1) even after calcination at 500 degreesC. The silicate species deposited on the precipitate of iron(III) hydroxide prevented the primary particles from agglomerating during calcination, resulting in the high surface area and hard reducibility of the SiO2-Fe2O3.
  • D Shin, S Sato, R Takahashi, T Sodesawa
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 110 12 1097 - 1099 2002年12月 [査読有り]
     研究論文(学術雑誌) 
    Various metal oxides coated with a thin silica layer were prepared by two different liquid-phase deposition methods; one is the deposition of silica on the corresponding metal hydroxides using tetraethyl orthosilicate (TEOS), and the other is the hydrothermal treatment of the metal hydroxides with silica glass in basic solution. The TEOS treatment is more effective for depositing silica on the precursor hydroxides than the hydrothermal treatment employing the process of dissolution-deposition of silica. The. silica-coated metal oxides of MgO, Fe2O3, NiO, Y2O3, ZrO2, SnO2, and Dy2O3 have high specific surface areas > 200 m(2)g(-1) after heating at 773 K.
  • S Sato, R Takahashi, T Sodesawa, N Ichikuni, H Amano
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 75 10 2297 - 2304 2002年10月 研究論文(学術雑誌) 
    Fine particles Of SiO2-coated Ni metal were prepared by depositing silica on a Ni(OH)(2) precipitate in a dissolution-deposition process of silica glass under hydrothermal conditions, followed by calcination and reduction. A fresh precipitate of Ni(OH)(2) was heated with a NaOH solution containing several pieces of silica glass chips in a pressure vessel at 100 degreesC. Silica components dissolved from the glass chips were deposited on the Ni(OH)(2) precipitate, and the silica loading increased with increasing the hydrothermal period. Even after calcination at 500 degreesC, a specific surface area of the resulting SiO2-NiO increased with silica loading, and exceeded 200 m(2) g(-1). SiO2-NiO, reduced at 500 degreesC, had a metal surface area as high as 22 m(2) g(-1). In contrast to the fact that pure Ni(OH)(2) readily aggregates during heating, the SiO2-coated Ni(OH)(2) particles are protected from agglomerating during the hydrothermal process, calcination, and reduction.
  • M Yabuki, R Takahashi, S Sato, T Sodesawa, K Ogura
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 4 19 4830 - 4837 2002年 研究論文(学術雑誌) 
    Amorphous silica alumina catalysts were prepared in the sol gel reaction of tetraethoxysilane in the presence of aluminium nitrate and various organic additives, and the effects of the additives on both pore formation and acid-site generation were investigated. Macropores with bicontinuous morphology are formed in the system with poly(ethylene oxide) (PEO) with an average molecular weight of 10 0000, when a transitional structure of spinodal decomposition is fixed by sol gel transition of inorganic components. In the systems with other organic additives with low molecular weight, such as ethylene glycol oligomers and citric acid, silica alumina is provided with only mesopores. Although their mesopore structures are not affected by organic additives, the catalytic activity varies depending on the kind of organic additives. It is found that organic additives with the ability to increase the interaction between silica oligomers and aluminium cations increase the dispersion of Al in the silica network, resulting in high catalytic activity in the cracking of cumene. PEO interacts with both silica and aluminium cations in the sol gel solution, so that macroporous silica alumina prepared in the presence of PEO shows excellent catalytic activity.
  • R Takahashi, S Sato, T Sodesawa, H Nishida
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 4 15 3800 - 3805 2002年 研究論文(学術雑誌) 
    The diffusion coefficient of nickel nitrate dissolved in water in porous silica plates with different pore size was measured to investigate the effect of pore size on the liquid-phase diffusion resistance. The pore-diffusion coefficient of nickel nitrate varied with the pore size of the silica gel. In pores of diameter > 5 nm, the diffusion resistance can be ignored, and the pore-diffusion coefficient varies proportionally to the porosity of the silica plates. In pores of diameter < 5 nm, however, the diffusion resistance increases rapidly with decreasing pore diameter. A microporous silica shows the largest diffusion resistance: the pore-diffusion coefficient in micropores is less than 0.01 of the diffusion coefficient in an unbounded system.
  • HL Tsai, S Sato, R Takahashi, T Sodesawa, S Takenaka
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 4 14 3537 - 3542 2002年 研究論文(学術雑誌) 
    The liquid-phase hydrogenation of ketones was investigated over Raney nickel and Ni-MgO catalysts with known pore structures: the effects of the sizes of the reactant and solvent on the catalytic activity were examined at 0degreesC at a hydrogen pressure of 1.1 MPa to discuss the mass transfer of reactants/products and solvents within the mesopores. The catalytic activity decreases linearly with increasing reactant molecular size in the hydrogenation of both aliphatic and aromatic ketones with an acetyl group, such as acetone, butan-2-one, heptan-2-one, nonan-2-one, undecan-2-one, acetophenone, 4'-methylacetophenone, 4'-ethylacetophenone, and 4'-n-propylacetophenone. In the hydrogenation of ketones such as acetone, cyclohexanone, and heptan-4-one in linear alkane solvents, the catalytic activity decreases with the increasing length of the carbon chain of the solvent, and a zigzag phenomenon, i.e. the catalytic activity in alkane solvents with an odd number of carbons in the chain is higher than in those with an even number of carbons, is observed for larger reactants in smaller pores. Neither the activity drop nor the zigzag tendency appears for smaller reactants reacted in sufficiently large mesopores. It can be concluded that strong resistance for the mass transfer of larger reactants in smaller mesopores explains the difference in the catalytic hydrogenation reactivity of reactant diffusing through solvent in a mesoporous catalyst.
  • Daiji Shin, Satoshi Sato, Ryoji Takahashi, Toshiaki Sodesawa
    Journal of the Ceramic Society of Japan 110 1288 1097 - 1099 2002年 研究論文(学術雑誌) 
    Various metal oxides coated with a thin silica layer were prepared by two different liquid-phase deposition methods one is the deposition of silica on the corresponding metal hydroxides using tetraethyl orthosilicate (TEOS), and the other is the hydrothermal treatment of the metal hydroxides with silica glass in basic solution. The TEOS treatment is more effective for depositing silica on the precursor hydroxides than the hydrothermal treatment employing the process of dissolution-deposition of silica. The silica-coated metal oxides of MgO, Fe2O3, NiO, Y2O3, ZrO2, SnO2, and Dy2O3 have high specific surface areas > 200 m2g-1 after heating at 773 K.
  • R Takahashi, S Sato, T Sodesawa, M Kato, S Takenaka, S Yoshida
    JOURNAL OF CATALYSIS 204 2 259 - 271 2001年12月 研究論文(学術雑誌) 
    Structural formation of Ni/SiO2 in a solution exchange method, where Ni was supported on silica by exchanging the solution in wet silica gel derived from tetraethoxysilane under acidic conditions, and its catalytic property were investigated. In the preparation of Ni/SiO2, the dispersion of Ni is largely dominated by aggregation in drying, while mesopore structure in the silica support can be controlled to similar to4 nm by exchanging the solution with strong acids. When aqueous nickel nitrate solution is used in the solution exchange, large nickel nitrate crystals are formed within the gel matrix during drying. They decompose into aggregates of NiO crystallites, with sea-island distribution during calcination. On the other hand, the use of citric acid together with nickel nitrate in the solution exchange effectively inhibits the aggregation of Ni species in drying through the formation of nickel citrate, which barely crystalizes in drying. In calcination, the nickel citrates decompose into NiO particles, and their distribution in the silica matrix becomes homogeneous. Additionally, the use of citric acid and calcination in an inert atmosphere has another effect, decreasing the particle size of NiO and Ni. Consequently, we can prepare Ni/SiO2 catalyst with high Ni surface area at high Ni content, which shows superior catalytic activity in the hydrogenation of benzene. (C) 2001 Elsevier Science.
  • R Takahashi, S Sato, T Sodesawa, H Nishida
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 109 10 840 - 845 2001年10月 [査読有り]
     研究論文(学術雑誌) 
    The liquid-phase diffusion coefficient of nickel nitrate in wet silica gels with different Si content as well as in mesoporous silica gel was measured by the flow-cell method, where absorbance of a gel plate placed in a flow cell was monitored as a function of time. For diffusion in the mesoporous silica gel with pore diameter of 12 run, the tortuosity was as low as 1.2, suggesting that the liquid-phase diffusion of nickel nitrate is not restricted in the large mesopores. In contrast, the diffusion coefficient in wet silica gels monotonously decreased with increasing Si content in the gels, and the tortuosity in the wet gel, 1.7-3.5, was larger than that in the mesoporous silica gel. The wet gel is considered to consist of crosslinked polymeric network of silica. The tortuosity in the wet gel would vary depending on the mesh size in the network and on the number of free side chain.
  • R Takahashi, S Sato, T Sodesawa, K Suzuki, M Tafu, K Nakanishi, N Soga
    JOURNAL OF THE AMERICAN CERAMIC SOCIETY 84 9 1968 - 1976 2001年09月 研究論文(学術雑誌) 
    Phase separation in a sol-gel process of SiO2-ZrO2 in the presence of polyethylene oxide is investigated. An amorphous gel with interconnected macroporous morphology is obtained when phase separation and sol-gel transition concur to fix a transitional structure of spinodal decomposition. Macropore size, together with connectivity of the pores and gel skeleton, can be controlled precisely by selecting an appropriate starting composition for preparation at a zirconium content less than or equal to 11.7 mol%. The macroporous gel retains additional mesopores < 4 nm and exhibits typical bimodal pore size distribution. The addition of ZrO2 in SiO2 improves the thermal stability of both macroporous and mesoporous structures.
  • S Takenaka, R Takahashi, S Sato, T Sodesawa
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 109 8 712 - 714 2001年08月 [査読有り]
     研究論文(学術雑誌) 
    A porous titania film was prepared on a glass substrate by a spin-coating technique from the precursor solution containing titanium tetraisopropoxide and stearic acid. Stearic acid formed a 2 : 2 complex with titanium in the dried film, and the complex melted before decomposition. Before the coating of the precursor solution, methylsilane precoating on the hydrophilic glass surface was effective in preparing a uniform film because of hydrophobicity of the complex melt. The resultant film was transparent and composed of anatase after heating at 500 degreesC. Micrometer-scale rough surface with aggregates of secondary particles composed of primary crystallites was observed in the film, and mesopores seem to be located at the inter-crystallites. It is probable that decomposition of stearic acid and aggregation of anatase crystallites occur simultaneously to provide the porous structure during heating.
  • R Takahashi, S Sato, T Sodesawa, A Yachi
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 109 7 577 - 579 2001年07月 [査読有り]
     研究論文(学術雑誌) 
    An amorphous silica with distinct bimodal pore structure containing both macropores and mesopores was prepared from an acidified solution of water glass in the presence of poly(acrylic acid) by inducing phase separation together with gelation. Both of pore sizes of the macropores and the mesopores can be controlled in the ranges from 1 to 10 mum and from 4 to 30 mm, respectively.
  • R Takahashi, S Sato, T Sodesawa, N Nakamura, S Tomiyama, T Kosugi, S Yoshida
    JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 1 2 169 - 176 2001年06月 研究論文(学術雑誌) 
    A Ni/SiO2 catalyst was prepared by homogeneous precipitation of nickel hydroxide in a sol-gel-derived wet silica gel. The preparation process consists of two successive steps: gelation of silica in the presence of nickel nitrate and urea at 50 degreesC, followed by aging at higher temperature, typically at 80 degreesC, to decompose the urea. The decomposition of urea increases the pH of the solution in the wet gel, leading to the concurrence of structural rearrangement of silica gel and deposition of nickel species. As a result, the structure of the silica changes from a ramified polymeric network into particle aggregates that entrap the nickel cations in the particles. The resulting Ni/SiO2 contains large mesopores that have high thermal stability up to 1000 degreesC and highly dispersed Ni metal particles with typical crystallite size of 4 nm even at high Ni content at 20 wt%.
  • R Takahashi, S Sato, T Sodesawa, M Yabuki
    JOURNAL OF CATALYSIS 200 1 197 - 202 2001年05月 研究論文(学術雑誌) 
    An amorphous silica-alumina catalyst with distinct bimodal pore structure was prepared by sol-gel reactions of tetraethoxysilane (TEOS) and aluminum nitrate in the presence of poly(ethylene oxide) (PEO). It contains macropores effective for rapid molecular transportation and mesopores providing a large specific surface area of similar to 600 m(2) g(-1). The pore size distribution of the macropores is sharp and its average diameter varies from 0.3 to 5 mum by altering the starting compositions such as water/TEOS and PEO/TEOS weight ratios. The macropores are formed when transitional morphologies of spinodal decomposition are fixed by sol-gel transition of inorganic components, and their size is controlled by altering the timing of the onset of spinodal decomposition and gelation. A change in the starting composition would affect this timing. In addition to macropores, silica-alumina has a large number of Bronsted acid sites, and shows excellent catalytic activity in the cracking of cumene. PEO would have the effect of increasing the uniformity of Al atoms in the silica network, which would be a cause of the formation of Bronsted acid sites. (C) 2001 Academic Press.
  • S Sato, R Takahashi, T Sodesawa, C Kobayashi, A Miura, K Ogura
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 3 5 885 - 890 2001年 研究論文(学術雑誌) 
    A supported type of silica-alumina catalyst prepared by depositing alumina on silica was treated under steaming conditions. Physical properties of the silica-alumina were characterized by the N-2 adsorption-desorption isotherm, small-angle X-ray scattering and solid-state NMR measurements. The particle size and the mean pore size increased slightly with increasing steam pressure up to 2.0 MPa. The specific surface area of the silica-alumina steamed at 2.0 MPa was half of that before steaming. The number of four-coordinate Al ions increased with increasing steam pressure and was saturated at a steam pressure of 0.5 MPa. Temperature-programmed desorption of chemisorbed 2,6-dimethylpyridine elucidated that the number of Bronsted acid sites is maximized at 0.5 MPa.
  • H Amano, S Sato, R Takahashi, T Sodesawa
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 3 5 873 - 879 2001年 研究論文(学術雑誌) 
    The dehydrogenation of cyclohexene over carbon deposited on alumina, C/Al2O3, which was prepared by contacting hydrocarbons such as cyclohexane, cyclohexene and cyclohexanone with alumina surface at greater than or equal to 823 K, was investigated under non-oxidative conditions. The deposited carbon was identified as condensed aromatic hydrocarbon with graphite-like structure in the results of XRD and C-13 NMR measurements. It was found that the dehydrogenation activity was generated on alumina by carbon deposition: the dehydrogenation of cyclohexene proceeded over C/Al2O3 at 773 K, while the isomerization to methylcyclopentenes proceeded over pure alumina without carbon. The selectivity to dehydrogenated products such as benzene and 1,3-cyclohexadiene was maximized at a specific carbon content. The disproportionation of cyclohexene into benzene and cyclohexane proceeded over C/Al2O3 above the specific carbon content. Unpaired electrons observed in the EPR measurement are related to the ratio of dehydrogenation and disproportionation, whereas the dehydrogenation activity is not related with the unpaired electron content.
  • R. Takahashi, S. Sato, T. Sodesawa, H. Nishida
    Journal of the Ceramic Society of Japan 109 1274 840 - 845 2001年 研究論文(学術雑誌) 
    The liquid-phase diffusion coefficient of nickel nitrate in wet silica gels with different Si content as well as in mesoporous silica gel was measured by the flow-cell method, where absorbance of a gel plate placed in a flow cell was monitored as a function of time. For diffusion in the mesoporous silica gel with pore diameter of 12 nm, the tortuosity was as low as 1.2, suggesting that the liquid-phase diffusion of nickel nitrate is not restricted in the large mesopores. In contrast, the diffusion coefficient in wet silica gels monotonously decreased with increasing Si content in the gels, and the tortuosity in the wet gel, 1.7-3.5, was larger than that in the mesoporous silica gel. The wet gel is considered to consist of crosslinked polymeric network of silica. The tortuosity in the wet gel would vary depending on the mesh size in the network and on the number of free side chain.
  • S. Takenaka, R. Takahashi, S. Sato, T. Sodesawa
    Journal of the Ceramic Society of Japan 109 1272 712 - 714 2001年 研究論文(学術雑誌) 
    A porous titania film was prepared on a glass substrate by a spin-coating technique from the precursor solution containing titanium tetraisopropoxide and stearic acid. Stearic acid formed a 2 : 2 complex with titanium in the dried film, and the complex melted before decomposition. Before the coating of the precursor solution, methylsilane precoating on the hydrophilic glass surface was effective in preparing a uniform film because of hydrophobicity of the complex melt. The resultant film was transparent and composed of anatase after heating at 500°C. Micrometer-scale rough surface with aggregates of secondary particles composed of primary crystallites was observed in the film, and mesopores seem to be located at the inter-crystallites. It is probable that decomposition of stearic acid and aggregation of anatase crystallites occur simultaneously to provide the porous structure during heating.
  • R. Takahashi, S. Sato, T. Sodesawa, A. Yachi
    Journal of the Ceramic Society of Japan 109 1271 577 - 579 2001年 研究論文(学術雑誌) 
    An amorphous silica with distinct bimodal pore structure containing both macropores and mesopores was prepared from an acidified solution of water glass in the presence of poly(acrylic acid) by inducing phase separation together with gelation. Both of pore sizes of the macropores and the mesopores can be controlled in the ranges from 1 to 10 μm and from 4 to 30 nm, respectively.
  • R Takahashi, S Sato, T Sodesawa, M Kato, S Yoshida
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 19 1-3 715 - 718 2000年12月 研究論文(学術雑誌) 
    Structural formation process of Ni/SiO2 and Cu/SiO2 catalysts prepared by solution exchange of wet silica gel was investigated. Microstructures of Cu/SiO2 and Ni/SiO2 were quite different from each other. In the case of Cu/SiO2, Cu particles with diameter of ca. 3-5 nm dispersed homogeneously at less Cu content, and the particle size of Cu as well as pore size of silica gel support increased with increasing Cu content. In the Ni/SiO2, the Ni particles with diameter of ca. 6-10 nm gathered densely to form aggregates in silica matrix resulting in sea-island structure, whereas the size of Ni particle slightly increased with increasing Ni content. The difference in the structure of the metal-silica composites is probably caused by the difference in interaction between silica gel network and metal ions during drying and heating processes.
  • S Takenaka, R Takahashi, S Sato, T Sodesawa
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 19 1-3 711 - 714 2000年12月 研究論文(学術雑誌) 
    Mesoporous titania with regulated pore size as well as high specific surface area was prepared from titanium alkoxide and various carboxylic acids with different alkyl-chain length [CH3(CH2)(n)COOH : n = 0-20]. Although the pore size and pore volume of titania changed slightly at n < 10, they increased with increasing the alkyl-chain length of carboxylic acid at n greater than or equal to 10. Each carboxylic acid forms a complex with titanium alkoxide in an organic-inorganic precursor, while the precursor prepared by using carboxylic acid with n greater than or equal to 10 consists of a lamella-type mesophase. The interplanar distance of the lamella structure increases with increasing the alkyl-chain length of carboxylic acid. During calcination, the lamella structure collapses together with the combustion of organic moieties and titania particles crystallized to anatase aggregate to provide pores. Although carboxylic acid does not act as a true template, the formation of the lamella-type mesophase in the precursor plays an important role in controlling the pore size of titania.
  • R Takahashi, S Sato, T Sodesawa, M Kawakita, K Ogura
    JOURNAL OF PHYSICAL CHEMISTRY B 104 51 12184 - 12191 2000年12月 研究論文(学術雑誌) 
    The pore formation process of silica gel from tetraethoxysilane in the presence of citric acid (CA) was investigated. The silica gel prepared by pyrolysis of a composite of CA and silica had high specific surface area, ca. 1000 m(2) g(-1) and its pore volume increased linearly with increasing CA content. In addition, the average pore size successively increased from the micropore range to the mesopore range of ca. 10 nm with the increase in the CA content. The silica and the CA-silica composite were amorphous without long-range ordering. In the composite, amorphous CA and polymeric silica gel are mixed on a nanometer scale without the aid of specific chemical bonding, except for weak hydrogen bonding. Because of the nature of the composite, the silica gel network becomes rigid through the additional formation of Si-O-Si bonds during heating, irrespective of the existence of CA. Therefore, the bulky structure is retained without shrinkage after elimination of CA, and silica gel with high specific surface area and pore volume results. Thus, CA is considered to provide mesopores as a template.
  • S Sato, R Takahashi, T Sodesawa, K Yuma, Y Obata
    JOURNAL OF CATALYSIS 196 1 195 - 199 2000年11月 研究論文(学術雑誌) 
    A Cu metal surface was evaluated by a novel technique combining temperature-programmed reduction (TPR) measurement with N2O oxidation. The technique consists of three steps: the usual TPR measurement, the oxidation of the Cu surface by N2O, and the subsequent TPR measurement. The surface Cu oxidized by N2O was determined as a ratio of the peak area of the second TPR profile to that of the first one. It was found that bulk oxidation gradually proceeds after surface oxidation even at 30 degreesC. After the surface oxidation, the Cu2O produced by N2O oxidation varied with N2O exposure time (t) and had a linear correlation with ta at temperatures below 100 degreesC. The linear correlation in the parabolic plot proves that bulk oxidation proceeds through the diffusion process, and the Y-intercept corresponds to the surface oxidation. Both the dispersion and the Cu metal surface area of the sample were calculated from the intercept in the parabolic plot for the Cu2O produced by N2O oxidation. In addition, we found that a very large Cu metal surface area, as high as 32 m(2) g(cat)(-1), was created on a Cu-MgO catalyst through a citrate process using a molten mixture of copper nitrate, magnesium nitrate, and citric acid. (C) 2000 Academic Press.
  • S Sato, R Takahashi, T Sodesawa, S Tanaka, K Oguma, K Ogura
    JOURNAL OF CATALYSIS 196 1 190 - 194 2000年11月 研究論文(学術雑誌) 
    Preparation of high-surface-area SiO2-ZrO2 by deposition of silicate species on zirconia under hydrothermal conditions in an aqueous ammonia solution was investigated. A fresh precipitate of ZrO(OH)(2) was heated in a pressure vessel with several pieces of quartz glass tube at 100 degreesC. In the measurement of ICP-AES and solid-state Si-29 NMR, it was elucidated that a silica component dissolved from the glass in the basic solution was deposited on the ZrO(OH)(2) precipitate and that the silica content increased with increasing hydrothermal period. The resulting SiO2-ZrO2 had a specific surface area higher than 240 m(2) g(-1) even after calcination at 500 degreesC. In contrast to the pure ZrO2 particles readily aggregating, the silicate species deposited on the surface of ZrO2 particles prevented the agglomeration of the primary particles during calcination, resulting in high-surface-area SiO2-ZrO2. (C) 2000 Academic Press.
  • S Sato, R Takahashi, T Sodesawa, F Nozaki, XZ Jin, S Suzuki, T Nakayama
    JOURNAL OF CATALYSIS 191 2 261 - 270 2000年04月 研究論文(学術雑誌) 
    Liquid-phase hydrogenation of cyclohexanone, acetone, 2-butanone, 3-pentanone, and 4-heptanone to the corresponding secondary alcohols was investigated over various porous Ni catalysts at 0 degrees C under a hydrogen pressure of 1.1 MPa. Pore size distributions as well as Ni surface area of Ni-MgO catalysts, which were prepared from a melt of the corresponding nitrates and citric acid, with high Ni contents of 60-80 wt% were controlled by the calcination temperature of the precursors. For the hydrogenation of acetone, reaction rate constants were directly proportional to the Ni surface areas of the catalysts, and Raney nickel which had the largest Ni surface area showed the highest reaction rate. For the hydrogenation of other reactants larger than acetone in molecular size, however, rate constants do not have a simple linear correlation with Ni surface area. Ni-MgO catalysts with large mesopores exhibited reaction rates higher than those of Raney nickel catalysts with the largest Ni surface areas. Assuming that diffusion of both reactants and products is restricted in small pores such as in Raney nickel, we tried to evaluate an effective pore size for the liquid-phase mass transfer in porous materials by a novel approach analyzing reaction rate data coupled with pore size distribution and hydrogen chemisorption data. Cumulative Ni surface areas were calculated by multiplying the Ni surface area by a fraction of cumulative surface area located in pores larger than a specific size to the total surface area, and relationship between the cumulative Ni surface areas and the reaction rate constants were examined. It was found that the rate constants for the hydrogenation of 2-butanone, cyclohexanone, 3-pentanone, and 4-heptanone were proportional to cumulative Ni surface areas in pores larger than critical sizes of 2.0, 2.3, 3.2, and 3.7 nn in radius, respectively. It has been consequently elucidated that the mass transfer of the reactants is restricted in pores smaller than a critical size that depends on the size of the reactants. (C) 2000 Academic Press.
  • K Nakanishi, R Takahashi, T Nagakane, K Kitayama, N Koheiya, H Shikata, N Soga
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 17 3 191 - 210 2000年03月 [査読有り]
     研究論文(学術雑誌) 
    By inducing a phase separation parallel to the sol-gel transition of alkoxy-derived silicate systems, gels with well-defined macroporous structure can be prepared. Depending on the post-gelation treatment such as aging and solvent exchange, the final pore structure in the nanometer range of dried and heat-treated gels exhibits a considerable variation. With an aim of completely controlling the hierarchical pore structure in the discrete size ranges of nanometers and micrometers, systematic experimental studies have been performed. The macroporous nature of the wet gels allows an efficient solvent exchange process compared with conventional gels only with mesopores. In addition, the surface chemistry of the wet gel skeleton affects the mesopore formation process by the solvent exchange to a great extent. The median size of mesopores larger than 5 nm can be controlled by adjusting the basic solvent exchange conditions such as pH value, temperature and bath ratio for any kind of macroporous silica gel. On the other hand, the control of pore volume independent of the mesopore size is possible only in the system incorporated with the micelle-forming surfactant. Some examples of the effects of controlled mesopores on the analytical performance of monolithic-type chromatographic columns are also presented.
  • Y Kamimura, S Sato, R Takahashi, T Sodesawa, M Fukui
    CHEMISTRY LETTERS 3 232 - 233 2000年03月 研究論文(学術雑誌) 
    Formation of 3-pentanone via oxidative dimerization of 1-propanol was investigated over CeO2-based solid solution with various metal oxides. An addition of Fe2O3 into CeO2 greatly enhanced the 3-pentanone formation, and both 1-propanol conversion and 3-pentanone selectivity were maximized at Fe content of 20 mol%. It was found that the CeO2-Fe2O3 effectively works as a catalyst for the formation of symmetric ketones such as 3-pentanone, 4-heptanone, 5-nonanone, etc.
  • R Takahashi, S Sato, T Sodesawa, M Suzuki, K Ogura
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 73 3 765 - 774 2000年03月 研究論文(学術雑誌) 
    A microporous silica gel was prepared by a sol-gel process in the presence of ethylene glycol (EG) and its oligomers (oligoEG), and the pore formation process was investigated by using NMR and TG-DTA. The micropore volume changed with the polymerization degree of oligoEG, and showed a minimum at the trimer of EG. An attractive interaction between silanol and organic additives plays a key role in micropore formation: the interaction inhibits the bond formation of Si-O-Si during drying and heating, and heterogeneous domains which convert into micropore are formed after the combustion of additives. There are two kinds of interaction: one is eater (Si-OR) bond formation of a silanol with an end hydroxy group of additives; the other is hydrogen bonding between a silanol and an ether oxygen of additives. The former interaction is significant for EG. With increasing length of oligoEG, however, the former interaction rapidly disappears, while the latter becomes stronger. Because of a minimum in the combination of these interactions, the minimal volume of the micropore is observed.
  • N Nakamura, R Takahashi, S Sato, T Sodesawa, S Yoshida
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 2 21 4983 - 4990 2000年 研究論文(学術雑誌) 
    Silica-supported nickel catalysts with both macropores and mesopores were prepared in an alkoxide-derived sol-gel process in the presence of poly(ethylene oxide) (PEO) with an average molecular weight of 100000. In this process, the interconnected macroporous morphology is formed when transitional structures of spinodal decomposition are frozen by the sol-gel transition of silica. The addition of nickel into a silica-PEO system has negligible effect on the morphology formation suggesting that phase separation in the nickel-containing system proceeds by repulsive interaction between the solvent and PEO adsorbed on the silica, as observed in the system without nickel. In gel formation, it was found that the Ni was distributed selectively in mesopores in the silica gel skeleton as fine particles rather than aggregated in macropores. It is considered that PEO interacts with both silica and nickel cations. The interaction between PEO and Ni makes nickel distribute in the silica phase and keeps Ni from aggregation during drying, resulting in a high dispersion of Ni.
  • R Takahashi, S Sato, T Sodesawa, Y Kamomae
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 2 6 1199 - 1204 2000年 研究論文(学術雑誌) 
    A novel technique for the measurement of the diffusion coefficient of a solute in a transparent wet-gel monolith was developed by analyzing the decay behavior of the absorbance of the gel plate in a flow cell. The diffusion coefficient of a Ni(NO3)(2) in a wet silica gel is estimated by fitting the absorbance-time data with an exponential function. The efficiency of the technique was ensured by testing the effects of several measurement conditions, such as the flow rate of the external solution and the thickness of the gel plate. The diffusion coefficient of Ni(NO3)(2) in wet silica gel is 6.0x10(-10) s(-1) at 20 degrees C, which is ca. 60% of that in bulk solution. The data suggest that the silica gel network allows relatively fast transport of the liquid phase.
  • R Takahashi, K Nakanishi, N Soga
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 17 1 7 - 18 2000年01月 研究論文(学術雑誌) 
    Growth behavior of silica in an acid catalyzed sol-gel process from silicon alkoxide in the presence of poly(ethylene oxide), PEO, was investigated by in situ small angle X-ray scattering, SAXS, and Si-29 NMR measurements. The results of SAXS, that aggregation and gel formation behaviors of silica were affected by the presence of PEO, suggested a strong attractive interaction between silica oligomers and PEO. A possible reaction scheme of silica in the presence of PEO is as follows; (1) PEO and small silica oligomers coexist in the solution without specific interaction just after hydrolysis of the silicon alkoxide. (2) With the progress of condensation, a ramified aggregated complex between PEO and silica oligomers is formed, which is characterized by larger apparent value of radius of gyration and smaller fractal dimension than in the PEO-free system. (3) After gelation, the fractal dimension of scatterers remains to be smaller than that in the PEO-free system, because PEO associated with the silica network inhibits aggregation within the gel networks. Furthermore, PEO inhibits the condensation in the aging and in the drying process, leading to less strongly crosslinked dry gel. A temporal maximum in the time evolution of R-g was observed for the samples separated into two phases with their characteristic domain size being larger than several micrometers. This is considered to be a phenomenon related to increase and divergence of correlation length near and at the critical point.
  • A Oyane, M Minoda, T Miyamoto, R Takahashi, K Nakanishi, HM Kim, T Kokubo, T Nakamura
    JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 47 3 367 - 373 1999年12月 研究論文(学術雑誌) 
    The surfaces of ethylene-vinyl alcohol copolymer (EVOH) substrates were modified with silanol (Si-OH) groups, and their apatite forming ability was examined in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma or in a solution with ion concentrations 1.5 times those of SBF (1.5SBF). The surface modification of EVOH was carried out by reacting 3-iso-cyanatopropyltriethoxysilane, followed by hydrolysis of the ethoxysilyl groups into Si-OH groups. However, no apatite formation was observed on the EVOH substrate thus modified, even after 3 weeks in SBF and 1.5SBF. The Si-OH modified EVOH substrate was further modified by hydrolysis and polycondensation of tetraethyoxysilane (TEOS). It was found that the apatite forms on the TEOS-modified substrate within 3 weeks in 1.5SBF. These results suggest that the presence of a large amount of Si-OH groups (i.e., a cluster of Si-OH groups) on the substrate is prerequisite to apatite formation in the body environment. Apatite-EVOH composites prepared by this process might be useful as hard tissues substitutes. (C) 1999 John Wiley & Sons, Inc.
  • R Takahashi, S Sato, T Sodesawa, M Kawakita
    CHEMISTRY LETTERS 10 1107 - 1108 1999年10月 研究論文(学術雑誌) 
    Pore size and pore volume of an amorphous silica with high specific surface area, ca, 1000 m(2)g(-1), can be controlled in meso scale by using citric acid as a template in sol-gel reaction of tetraethoxysilane.
  • S Sato, R Takahashi, T Sodesawa, K Matsumoto, Y Kamimura
    JOURNAL OF CATALYSIS 184 1 180 - 188 1999年05月 研究論文(学術雑誌) 
    Vapor-phase alkylation of phenol with l-propanol was investigated over CeO(2M)gO catalysts prepared utilizing a molten mixture of the corresponding nitrates and citric acid. The CeO2-MgO had a stable catalytic activity at 475 degrees C, and had an excellent selectivity to 2-propylphenol, higher than 82% based on phenol. Although a portion of the 2-propylphenol produced was decomposed into o-cresol and 2-ethylphenol, a sum of selectivities to the monoalkylated phenols exceeded 97%. During the alkylation, propanal and 3-pentanone was observed. In the results of l-propanol conversion without phenol, it was found that l-propanol was dehydrogenated to propanal and that the propanal produced was dimerized to 3-hydroxy-2-methylpentanal via aldol addition, followed by the deformylation into 3-pentanone. Namely, in the reaction of phenol and 1-propanol, the propylation of phenol and the dehydrogenation of 1-propanol occurred concurrently over the CeO2-MgO. The pure CeO2, having both the redox property with Ce4+-Ce3+ and weak basic sites, catalyzed both the propylation of phenol and the 1-propanol transformation into 3-pentanone, while the pure MgO with strong basicity was less active for the 1-propanol transformation and had a low reaction rate in the alkylation. The reaction mechanism of the ortho-propylation over the CeO2-MgO catalyst is speculated as follows. The ortho position of phenol adsorbed perpendicularly on weak basic sites of the catalyst is selectively alkylated by 1-propanol, which is possibly activated in the form of 1-hydroxypropyl radical on CeO2 species rather than as a form of n-propyl cation. The redox property of CeO2 is probably attributed to the homolitic activation of 1-propanol to produce 1-hydroxypropyl radical. (C) 1999 Academic Press.
  • R Takahashi, S Sato, T Sodesawa, M Kato, T Yoshii
    CHEMISTRY LETTERS 4 305 - 306 1999年04月 研究論文(学術雑誌) 
    Particle size of NiO in silica with well defined mesoporous structure can be controlled from 3.5 to 10 nm regardless of NiO content up to 30 wt% by solution exchange of wet silica gel derived from sol-gel process. Ni surface area of samples reduced at 500 degrees C can be enlarged by decreasing the NiO particle size. resulting in 30 m(2)g(-1) at 30 wt% loading. The catalysts showed superior activities for gas-phase hydrogenation of benzene.
  • R Takahashi, S Takenaka, S Sato, T Sodesawa, K Ogura, K Nakanishi
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS 94 20 3161 - 3168 1998年10月 研究論文(学術雑誌) 
    A mesoporous titania was prepared from titanium tetraisopropoxide and stearic acid (STA). The pore size of the titania increases linearly from ca. 5 to 15 nm with increase in the STA/Ti ratio (X) for X < 1.5, while the change becomes negligible for X > 1.5. A mol equivalent of STA coordinates with Ti atom forming a bidentate carboxy group and excess STA forms propyl stearate. Upon calcination, the propyl stearate is removed at a lower temperature by vaporization, and does not affect the pore structure of the titania. The Ti-STA precursor has the layered structure of the Ti-STA complex, whose interplanar distance increases with increasing STA content, while the mesoporous titania is composed of aggregates of crystallites of anatase. During calcination of the precursor, decomposition of the complex and crystallization of anatase occur concurrently. The crystallization process is considered to be affected by the interplanar distance of the layered structure in the precursor, so that both the pore size and the pore volume increase with increase in the STA/Ti ratio.
  • R Takahashi, K Nakanishi, N Soga
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 106 8 772 - 777 1998年08月 研究論文(学術雑誌) 
    Gels with interconnected porous morphology in micrometer range have been prepared in a silica-zirconia system containing 12.7 mass% of zirconia from metal alkoxides under coexistence of poly(ethylene oxide) (PEO) with an average molecular weight of 100000. The porous structure was formed when the transitional structure of spinodal decomposition was frozen-in by sol-gel transition of inorganic components. In the system, the driving force of phase separation was considered to be the repulsive interaction between solvent and PEO associated on inorganic oligomers. Although the addition of zirconium alkoxide has an effect to decrease the domain size of dried gel by the increase of condensation rate, the domain size could be controlled in the sizes ranging from 0.2 to 30 mu m by adjusting the compositions of other constituents in the reacting solution.
  • S Sato, S Oimatsu, R Takahashi, T Sodesawa, F Nozaki
    CHEMICAL COMMUNICATIONS 22 2219 - 2220 1997年11月 研究論文(学術雑誌) 
    The pore size distribution of TiO2 can be controlled by changing the molar ratio;of stearic acid to titanium tetraisopropoxide.
  • R Takahashi, K Nakanishi, N Soga
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 8 1-3 71 - 76 1997年 研究論文(学術雑誌) 
    Gels with interconnected domain morphologies in the micrometer-range have been prepared in the silica-zirconia system. The domain formation kinetics in the gelling solution have been examined. Growth of an ordered structure on the length scale of micrometers, for which the kinetics are interpreted as spinodal decomposition, was observed by time-resolved light scattering measurements. The remarkable feature of the silica-zirconia system was that a time-dependent decrease of the wavelength of compositional fluctuations was observed. This occurred in the early stage, probably because the fast condensation reaction which was induced by the addition of zirconia, lead to a substantial change in quench depth on a timescale similar to that of the growth of concentration fluctuations. In the following stage, the coarsened domain structure was frozen-in by the sol-gel transition as the permanent morphology.
  • R TAKAHASHI, K NAKANISHI, N SOGA
    JOURNAL OF NON-CRYSTALLINE SOLIDS 189 1-2 66 - 76 1995年08月 研究論文(学術雑誌) 
    For silica gels with interconnected macropore morphology, the pore structure in the micrometer and nanometer size ranges has been investigated. The pore size distribution of dried gel in nanometer-range was influenced by the conditions of aging and solvent exchange treatments in the wet state, whereas only the drying behavior of macropore structure was affected by those conditions. These variations are explained by the occurrence of swelling and microscopic phase separation, the degree of which is determined by the solvent quality, of the gel networks. Small-angle X-ray scattering results confirmed the structural change in the wet state. The difference in thermal evolution behavior of nanopore structure with solvent exchange was also examined in relation to the difference in size of the structural unit.
  • Ryoji Takahashi, Kazuki Nakanishi, Naohiro Soga
    Faraday Discussions 101 249 - 263 1995年 [査読有り]
     研究論文(学術雑誌) 
    Small-angle X-ray scattering (SAXS) together with nitrogen adsorption, have been employed to analyse the pore-structure evolution behaviour, on the nanometre scale, by varying solvent-exchange treatment for silica gels having bicontinuous interconnected macropores. For the gels prepared in the system containing poly(acrylic acid), the difference in SAXS profile between gels immersed in ethanol and 1 mol dm-3 nitric acid was small in the wet state, but was considerably enlarged on drying. The dried gel immersed in ethanol exhibited a mass fractal feature, while that immersed in 1 mol dm-3 nitric acid was non-fractal up to several nanometres. The evolution behaviour during heat-treatment also differed, leading to a smaller size and lower volumes of the pores in the former gel. These variations in pore structures are explained by the occurrence of swelling in ethanol, and microscopic phase separation in 1 mol dm-3 nitric acid solution. However, for gels prepared in the system containing poly(ethylene oxide), the difference in profiles of similarly treated dried gels was not so evident, possibly because the progress of microscopic phase separation was restricted by the adsorbed organic polymer on silanols of the gel matrix. On the other hand, a significant increase in the average pore size, as well as the pore volume, was observed by solvent exchange in basic conditions, irrespective of the kind of polymer or catalyst used for gel preparation. This effect is interpreted as a coarsening process through a dissolution and reprecipitation mechanism. The time evolution of the Porod slope, as well as its dependence on the solution pH in the wet state, were monitored by in situ SAXS measurements. The steep increase of the Porod slope accompanied by the extension of the power-law region in the wet state indicated reorganization within the silica gel structures.
  • R Takahashi, K Nakanishi, N Soga
    FARADAY DISCUSSIONS 101 249 - 263 1995年 研究論文(学術雑誌) 
    Small-angle X-ray scattering (SAXS) together with nitrogen adsorption, have been employed to analyse the pore-structure evolution behaviour, on the nanometre scale, by varying solvent-exchange treatment for silica gels having bicontinuous interconnected macropores. For the gels prepared in the system containing poly(acrylic acid), the difference in SAXS profile between gels immersed in ethanol and 1 mol dm(-3) nitric acid was small in the wet state, but was considerably enlarged on drying. The dried gel immersed in ethanol exhibited a mass fractal feature, while that immersed in 1 mol dm(-3) nitric acid was non-fractal up to several nanometres. The evolution behaviour during heat-treatment also differed, leading to a smaller size and lower volumes of the pores in the former gel. These variations in pore structures are explained by the occurrence of swelling in ethanol, and microscopic phase separation in 1 mol dm(-3) nitric acid solution. However, for gels prepared in the system containing poly(ethylene oxide), the difference in profiles of similarly treated dried gels was not so evident, possibly because the progress of microscopic phase separation was restricted by the adsorbed organic polymer on silanols of the gel matrix. On the other hand, a significant increase in the average pore size, as well as the pore volume, was observed by solvent exchange in basic conditions, irrespective of the kind of polymer or catalyst used for gel preparation. This effect is interpreted as a coarsening process through a dissolution and reprecipitation mechanism. The time evolution of the Pored slope, as well as its dependence on the solution pH in the wet state, were monitored by in situ SAXS measurements. The steep increase of the Pored slope accompanied by the extension of the power-law region in the wet state indicated reorganization within the silica gel structures.
  • K NAKANISHI, H KOMURA, R TAKAHASHI, N SOGA
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 67 5 1327 - 1335 1994年05月 研究論文(学術雑誌) 
    Phase separation and gelation behaviors have been studied for the acid-catalyzed. alkoxide-based silica systems containing poly(ethylene oxide) (PEO) with an average molecular weight of 100000. Gels with micrometer range interconnected porous morphology were obtained similarly to the systems containing other water-soluble polymers, in which the structure development by the spinodal decomposition and the gel forming process take place concurrently. In spite of the morphological similarity, the thermogravimetric analysis revealed that the reacting solution decomposed into phases one rich in PEO and the other rich in solvent. Macropore volume of gels depended mainly on the amount of solvent phase.
  • K NAKANISHI, R TAKAHASHI, N SOGA
    JOURNAL OF NON-CRYSTALLINE SOLIDS 147 291 - 295 1992年10月 研究論文(学術雑誌) 
    Pore characteristics of silica gels prepared by the polymer-incorporated alkoxide-based sol-gel process have been investigated. Micrometer-range Pore sizes could be controlled by changing several reaction parameters, such as molecular weight or concentration of polymer or reaction temperature, that affect the domain formation process due to an occurrence of phase separation during a gel-forming reaction. The volume fraction and size distribution of nanometer-range pores after a heat treatment were varied by different solvent exchange treatments of a wet gel.

書籍

  • 目的を達成するためのゾル-ゲル法における構造制御ノウハウ集
    技術情報協会 2003年

講演・口頭発表等

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    第123回触媒討論会 2019年03月 ポスター発表
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    2018年 日本化学会中国四国支部大会 2018年11月 ポスター発表
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    2018年 日本化学会中国四国支部大会 2018年11月 ポスター発表
  • 半導体基板上での多孔性薄膜をマスキング剤としたCNT成長制御  [通常講演]
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    2018年 日本化学会中国四国支部大会 2018年11月 ポスター発表
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    田中 元気, 高橋 亮治, 佐藤 文哉
    2018年 日本化学会中国四国支部大会 2018年11月 ポスター発表
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    第122回触媒討論会 2018年09月 ポスター発表 北海道教育大学函館校
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    The 8th Tokyo Conference on Advanced Catalytic Science and Technology (TOCAT8) 2018年08月 ポスター発表
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    Fumiya SATO, Ryoji TAKAHASHI
    The 8th Tokyo Conference on Advanced Catalytic Science and Technology (TOCAT8) 2018年08月 ポスター発表
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    2017年日本化学会中国四国支部大会 2017年11月 口頭発表(招待・特別) 鳥取大学 日本化学会中国四国支部
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    田中 元気, 高橋 亮治, 佐藤 文哉
    第11回触媒道場 2017年09月 ポスター発表
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    第120回 触媒討論会 2017年09月 口頭発表(一般) 愛媛大学 触媒学会
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    第120回 触媒討論会 2017年09月 口頭発表(一般) 愛媛大学 触媒学会
  • 希土類硝酸水酸化物の結晶相:希土類カチオン半径の影響と硝酸添加効果  [通常講演]
    佐藤文哉, 高橋亮治
    第55回セラミックス基礎科学討論会 2017年01月 口頭発表(一般) 岡山コンベンションセンター 日本セラミックス協会基礎科学部会
  • プロピレンオキシド(PO)を用いたアルミナ多孔体形成における相分離挙動  [通常講演]
    大西瑛子, 高橋亮治, 佐藤文哉
    第55回セラミックス基礎科学討論会 2017年01月 口頭発表(一般) 岡山コンベンションセンター 日本セラミックス協会基礎科学部会
  • Sm・Y複合硝酸水酸化物の合成と平均カチオン半径に対する結晶相および粒子形態変化  [通常講演]
    佐藤 文哉, 石橋 拓宗, 高橋 亮治
    日本セラミックス協会 第29回秋季シンポジウム 2016年09月 口頭発表(一般) 広島大学 日本セラミックス協会
  • シリカをハードテンプレートとした活性炭の作製  [通常講演]
    松井 智也, 高橋 亮治, 佐藤 文哉
    日本セラミックス協会 第29回秋季シンポジウム 2016年09月 口頭発表(一般) 広島大学 日本セラミックス協会
  • ポリプロピレングリコールを用いたアルミナ多孔体  [通常講演]
    大西 瑛子, 高橋 亮治, 佐藤 文哉
    日本セラミックス協会 第29回秋季シンポジウム 2016年09月 ポスター発表 広島大学 日本セラミックス協会
  • シリカジルコニア多孔体中のジルコニア局所構造と酸特性  [招待講演]
    高橋 亮治
    第10回九州シンクロトロン光研究センター研究成果報告会 2016年08月 口頭発表(招待・特別) サンメッセ鳥栖 九州シンクロトロン光研究センター
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    佐藤 文哉, 高橋 亮治
    日本セラミックス協会 2016年年会 2016年03月 ポスター発表 早稲田大学 日本セラミックス協会
  • シリカゲルを鋳型とした連続貫通細孔を有する活性炭の作製  [通常講演]
    松井智也, 高橋亮治, 佐藤文哉
    2015年日本化学会中国四国支部大会 2015年11月 ポスター発表 岡山大学 日本化学会中国四国支部
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    小玉修身, 佐藤文哉, 高橋亮治
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    松井智也, 高橋亮治, 佐藤文哉
    第116回触媒討論会 2015年09月 口頭発表(一般) 三重大学 触媒学会
  • Pore size control of silica-templated activated carbon  [通常講演]
    松井智也, 高橋亮治, 佐藤文哉
    触媒学会西日本支部第6回触媒科学研究発表会 2015年06月 ポスター発表 愛媛大学 触媒学会(西日本支部)
  • Effect of ZrO2 addition in SiO2 on stability and acidic properties  [通常講演]
    山田賢一郎, 高橋亮治, 佐藤文哉
    触媒学会西日本支部第6回触媒科学研究発表会 2015年06月 ポスター発表 愛媛大学 触媒学会(西日本支部)
  • Synthesis and crystal growth of Al rich Cu-Al based layered double hydroxides using sol-gel method  [通常講演]
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    触媒学会西日本支部第6回触媒科学研究発表会 2015年06月 ポスター発表 愛媛大学 触媒学会(西日本支部)
  • Investigation of active species on the ketonization of carboxylic acid over lanthanum oxide  [通常講演]
    菊地啓太, 佐藤文哉, 高橋亮治
    触媒学会西日本支部第6回触媒科学研究発表会 2015年06月 ポスター発表 愛媛大学 触媒学会(西日本支部)
  • SiO2にZrO2を添加した時の構造安定性と酸特性に与える影響  [通常講演]
    山田 賢一郎, 高橋 亮治, 佐藤 文哉, 大西 真史
    日本セラミックス協会 2015年年会 2015年03月 口頭発表(一般) 岡山大学 日本セラミックス協会
  • Structural control of activated carbon using porous silica as a template  [招待講演]
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    2015 International Symposium on Advanced Materials and Optoelectronics 2015年01月 口頭発表(招待・特別) 佐賀大学
  • 酸化ランタンを用いたカルボン酸のケトン化反応における活性を示す構造の検討  [通常講演]
    菊地啓太, 佐藤文哉, 高橋亮治
    第114回触媒討論会 2014年09月 口頭発表(一般) 広島大学 触媒学会
  • 希土類硝酸水酸化物の結晶相とモルフォロジーとの関連性の検討  [通常講演]
    佐藤文哉, 高橋亮治, 山田幾也
    日本セラミックス協会 第27回秋季シンポジウム 2014年09月 口頭発表(一般) 鹿児島大学 日本セラミックス協会
  • Pore size control of silica-templated activated carbon  [通常講演]
    松井智也, 高橋亮治, 佐藤文哉
    触媒学会西日本支部第6回触媒科学研究発表会 2014年06月 ポスター発表 愛媛大学 触媒学会(西日本支部)
  • Effect of ZrO2 addition in SiO2 on stability and acidic properties  [通常講演]
    山田賢一郎, 高橋亮治, 佐藤文哉
    触媒学会西日本支部第6回触媒科学研究発表会 2014年06月 ポスター発表 愛媛大学 触媒学会(西日本支部)
  • Synthesis and crystal growth of Al rich Cu-Al based layered double hydroxides using sol-gel method  [通常講演]
    小玉修身, 佐藤文哉, 高橋亮治
    触媒学会西日本支部第6回触媒科学研究発表会 2014年06月 ポスター発表 愛媛大学 触媒学会(西日本支部)
  • Investigation of active species on the ketonization of carboxylic acid over lanthanum oxide  [通常講演]
    菊地啓太, 佐藤文哉, 高橋亮治
    触媒学会西日本支部第6回触媒科学研究発表会 2014年06月 ポスター発表 愛媛大学 触媒学会(西日本支部)
  • 二元細孔多孔質炭素材料の作製  [通常講演]
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    日本化学会 第94春季年会 2014年03月 口頭発表(一般) 名古屋大学 日本化学会

MISC

産業財産権

受賞

  • 2005年 触媒学会 平成16年度触媒学会奨励賞
     JPN 
    受賞者: 高橋亮治

共同研究・競争的資金等の研究課題

  • 階層構造を有する有機無機複合多孔体の作製と機能制御
    日本学術振興会:科研費 基盤研究C
    研究期間 : 2014年04月 -2017年03月 
    代表者 : 高橋 亮治

委員歴

  • 2013年04月 - 2016年03月   触媒学会西日本支部   代議員

社会貢献活動

  • 第120回触媒討論会実行委員
    期間 : 2017年09月12日 - 2017年09月14日
    役割 : 運営参加・支援
    主催者・発行元 : 触媒学会
  • 無機先端材料科学 非常勤講師
    期間 : 2017年09月06日 - 2017年09月07日
    役割 : 講師
    主催者・発行元 : 滋賀県立大学工学研究科 材料科学専攻
  • 無機先端材料科学 非常勤講師
    期間 : 2016年09月15日 - 2016年09月16日
    役割 : 講師
    主催者・発行元 : 滋賀県立大学工学研究科 材料科学専攻
  • 無機先端材料科学 非常勤講師
    期間 : 2015年08月10日 - 2015年08月11日
    役割 : 講師
    主催者・発行元 : 滋賀県立大学工学研究科 材料科学専攻
  • 第6回触媒科学研究発表会+触媒技術セミナー(1) 実行委員長
    期間 : 2015年06月12日 - 2015年06月12日
    役割 : 運営参加・支援
    主催者・発行元 : 触媒学会西日本支部

愛媛大学教員活動実績

教育活動(B)

担当授業科目(B01)

  • 2019, 前期, 学部, 化学入門
  • 2019, 前期, 学部, 化学入門
  • 2019, 前期, 学部, 無機化学Ⅰ
  • 2019, 前期, 学部, 卒業研究Ⅰ
  • 2019, 前期, 学部, 無機固体化学Ⅰ
  • 2019, 前期, 修士, 分子科学課題演習I
  • 2019, 前期, 学部, 無機化学I
  • 2019, 前期, 学部, 無機固体化学I


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