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Dive into the research topics where Toshihiko Osaki is active.

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Featured researches published by Toshihiko Osaki.


Journal of Non-crystalline Solids | 2001

Maintenance of large surface area of alumina heated at elevated temperatures above 1300 °C by preparing silica-containing pseudoboehmite aerogel

Tatsuro Horiuchi; Toshihiko Osaki; Toyohiko Sugiyama; Kenzi Suzuki; Toshiaki Mori

Abstract Silica-containing pseudoboehmite aerogel was prepared so that the surface area of alumina was maintained large after heating at elevated temperatures. Below 1300 °C, depending on the amount of silica added, the prepared samples transformed to γ-, δ-, and θ-alumina with columnar shaped particles, but not to α-alumina. As a result of the suppression of the phase transformation, heated samples had large pore volume (0.6–1.8 cm 3 / g ) and large surface area (70–300 m 2 / g ) . After heating at 1400 °C, while complete transformation to α-alumina occurred for 2.5 and 10 wt% silica with the additional formation of mullite for the latter, θ-alumina still remained present up to 5 wt% silica. When there was no formation of mullite, the surface area was quite large (23–37 m 2 / g ) . The cause for the maintenance of large surface area of alumina was discussed from the structure of the starting alumina source and the effect of the added silica.


Catalysis Letters | 2000

A comparative study of reactions of methanol over catalysts derived from NiAl- and CoAl-layered double hydroxides and their Sn-containing analogues

S. Velu; Kenzi Suzuki; Toshihiko Osaki

Ni- and Co-based catalysts derived from NiAl- and CoAl-layered double hydroxides were tested in four kinds of reactions of methanol, namely decomposition of methanol (DCM), partial oxidation of methanol (POM), steam reforming of methanol (SRM), and oxidative steam reforming of methanol (OSRM), for the purpose of H2 production for fuel cells. H2, CO and/or CO2 were the predominant products with minor amounts of dimethyl ether (DME) and CH4 depending on the reaction temperature. Among the four kinds of reactions tested, the OSRM reaction was found to be more effective in terms of MeOH conversion and H2 selectivity over these catalysts. Higher selectivity of H2 and CO2 with only traces of CO could be obtained at about 100% methanol conversion around 300 °C in the OSRM reaction over the catalyst derived from CoAl-LDH. Substitution of a part of Al by Sn in the NiAl- and CoAl-LDH systems was found to be inhibiting the methanol conversion. On the other hand, the selectivities to DME and CH4 were declined with a consequent increase in the selectivity to H2. In addition, considerable amount of formaldehyde was also noticed, especially over the catalyst derived from CoAlSn-LDH at lower reaction temperatures. The observed difference in the catalytic performance upon Sn incorporation was attributed to an improved redox capability of the Ni- and Co-based oxide catalysts, as determined by temperature-programmed reduction (TPR) experiments.


Journal of Materials Science | 2002

Synthesis and characterization of CuO containing mesoporous silica spheres

Lianzhou Wang; S. Velu; Shinji Tomura; F. Ohashi; Kazutaka Suzuki; M. Okazaki; Toshihiko Osaki; Masaki Maeda

A new series of mesoporous silica spheres containing nanodispersed copper oxides were synthesized in H2O/EtOH/ammonia solution at room temperature. The mesoporous structures were characterised using X-ray powder diffraction and N2 adsorption-desorption techniques. Scanning electron micrograph and transmission electron micrograph revealed that the MCM-41 particles have spherical morphologies. The DTA curve of pure MCM-41 exhibited a sharp single exothermic peak between 290°C and 340°C, while a broad peak with several shoulders in the temperature range between 180°C and 380°C was observed for Cu-MCM-41, indicating the possible complexation of Cu2+ with surfactants adhering to the inner surfaces of the mesopores. Electron paramagnetic resonance spectra of uncalcined samples revealed that Cu2+ ions are in an octahedral or distorted octahedral coordination with nitrogen ligands of the surfactant while in the calcined samples they are coordinated with oxygen of the MCM-41 framework. The redox properties of samples were examined by a temperature-programmed reduction and N2O passivation method. The results indicate that CuO with increasing particle size could be formed in the mesoporous materials with increasing Cu contents, and this decreased the reducibility of the resulting CuO.


Catalysis Letters | 1997

CH4/CD4 isotope effect on the reaction of adsorbed hydrocarbon species in CO2-reforming over Ni/Al2O3 catalyst

Toshihiko Osaki; Tatsuro Horiuchi; Kenzi Suzuki; Toshiaki Mori

By replacing CH4 with CD4, the isotope effect on the reaction of adsorbed hydrocarbon species with CO2 over Ni/Al2O3 catalyst was studied using pulse surface reaction rate analysis (PSRA). The first-order rate constant for this step was 1.45 times larger for CH4 than for CD4. The observed isotope effect suggests that the reaction of adsorbed hydrocarbon species with CO2 (or adsorbed oxygen) is rate-controlling for the reforming of CH4.


Reaction Kinetics and Catalysis Letters | 2003

Catalytic hydrogenation of C60 on transition metals

Toshihiko Osaki; Tomoki Hamada; Yutaka Tai

The catalytic hydrogenation of C60 on Ru, Rh and Ir produced C60H18 mainly, while Pd, Pt, Co and Ni catalysts gave C60H36 principally. Very little activity was observed on Au and Fe. The higher hydrogenated fullerene obtained on Pd, Pt, Co and Ni was ascribed to the smaller % d-character of the metallic bond, on which the fullerene and hydrogen may more strongly be adsorbed.


Journal of Sol-Gel Science and Technology | 2017

Effect of ethylene glycol on structure, thermal stability, oxygen storage capacity, and catalytic CO and CH4 oxidation activities of binary CeO2–Al2O3 and ternary CeO2–ZrO2–Al2O3 cryogels

Toshihiko Osaki

Porous and homogeneous cryogels of binary ceria-alumina (CA) and ternary ceria-zirconia-alumina (CZA) were prepared from cerium nitrate, zirconium (IV) dinitrate oxide hydrate, and aluminium sec-butoxide by a one-pot sol–gel technique in an aqueous system and subsequent freeze drying, and effect of ethylene glycol (EG) used for chelation of cerium ions on structure, thermal stability, reducibility, oxygen storage capacity, and catalytic carbon monoxide and methane oxidation activities of the catalysts was investigated. EG did not significantly affect surface area, pore volume, mean pore size, and surface morphology of the catalysts after calcination and subsequent oxidative/reductive atmosphere heating at 900 °C. Whereas use of EG resulted in much finer particles of cerium oxides and ceria-zirconia solid solution for CA and CZA, respectively, distributed throughout alumina with high dispersion. X-ray diffraction (XRD) and Raman spectra suggested that while a cubic CeO2 phase was observed for CA after the oxidative heating regardless of whether or not EG was employed, finely-divided cerium oxides or crystalline CeAlO3 were respectively obtained after the reductive heating depending on whether EG was respectively used or not used. As for CZA, while a pseudo-cubic t″ phase was seen after the reductive heating regardless of whether EG was used or not, mixed phases of pseudo-cubic t″ and cubic or a cubic one were respectively observed after the oxidative heating depending on whether EG was respectively employed or not employed. The solid solubility of zirconia in ceria was improved by EG for CZA. The oxygen storage capacity and catalytic CH4 and CO oxidation activities were also enhanced by employing EG for both catalysts, which was ascribed fundamentally to the finer particles of cerium oxides and ceria-zirconia solid solution for CA and CZA, respectively, although CO oxidation on CA was unimproved by EG after the reductive heating.Graphical Abstract


Reaction Kinetics, Mechanisms and Catalysis | 2015

Superior thermal stability and oxygen storage capacity of ceria nanoparticles dispersed on alumina cryogel

Toshihiko Osaki; Kiho Yamada; Koji Watari; Koji Tajiri

Cerium-dispersed alumina cryogel was prepared from cerium nitrate and aluminum sec-butoxide by a combination of one-pot sol–gel with freeze drying. The cryogel catalyst exhibited higher thermal stability of ceria and larger oxygen storage capacity than the corresponding xerogel and impregnation catalysts. The better stability and capacity were owing to the homogeneous distribution of cerium in boehmite gel by the one-pot synthesis of cerium-boehmite gel, and also to the suppression of aggregation of the cerium during the subsequent elimination of water from frozen gel by sublimation. As a result, cerium was finely dispersed and stabilized throughout the alumina cryogel, retarding the sintering of ceria at high temperatures. The destruction of fine structures of the catalyst at high temperatures was less pronounced on the cryogel, which also contributed to the stability of ceria.


Catalysis Letters | 2012

Palladium-alumina Cryogel with High Thermal Stability and CO Oxidation Activity

Toshihiko Osaki; Kiho Yamada; Koji Watari; Koji Tajiri; Saori Shima; Takeshi Miki; Yutaka Tai

Palladium-alumina cryogel was prepared from palladium nitrate and aluminum sec-butoxide through a sol–gel processing and subsequent freeze drying. The cryogel showed higher thermal stability of palladium and catalytic CO oxidation activity than the corresponding xerogel and impregnation catalysts. The superior stability and activity were ascribed to the uniform distribution of palladium ions in the boehmite gel by the one-pot preparation of palladium-boehmite co-gel, and also to the suppression of transfer and aggregation of the metal during the subsequent freeze drying. As a result palladium ions were finely distributed and stabilized throughout the alumina cryogel support, which consequently suppressed the sintering of palladium at elevated temperatures.Graphical Abstract


Advances in Science and Technology | 2006

The Catalysis of NiO-Al2O3 Aerogels for the Methane Reforming by Carbon Dioxide

Toshihiko Osaki; Toshiaki Mori

The aerogels of nickel-alumina system have been synthesized from aluminum triisoprppoxide and nickel glycoxide by sol-gel and subsequent supercritical drying, and the catalysis of NiO-Al2O3 aerogels for the methane reforming by carbon dioxide have been examined. The aerogel catalysts showed higher activity for the reforming than the impregnation catalysts prepared by a conventional impregnation method, on the other hand, the carbon deposition was much less significant on the aerogel catalysts than on the impregnation catalysts. By TEM and XRD observations, it was found for aerogel catalysts that fine nickel particles were formed throughout the alumina aerogel support with high dispersion. This resulted in not only higher catalytic reforming activity but also much less coking activity. The suppression of catalyst deactivation during the reforming was ascribed to the retardation of both carbon deposition and sintering of nickel particles on alumina aerogel support.


Reaction Kinetics and Catalysis Letters | 2003

The hydrogenolysis of C60 and C70

Toshihiko Osaki; Toshiyuki Tanaka; Yutaka Tai

Temperature-programmed reaction (TPR) of C60 and C70 with H2 was carried out on nickel in order to investigate the thermal stability of the fullerenes in the catalytic hydrogenation. The TPR profiles showed two methanation peaks and the corresponding weight decrease above 420°C, indicating the hydrogenolysis to CH4.

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Yutaka Tai

National Institute of Advanced Industrial Science and Technology

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Koji Tajiri

National Institute of Advanced Industrial Science and Technology

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Koji Watari

National Institute of Advanced Industrial Science and Technology

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Kiho Yamada

National Institute of Advanced Industrial Science and Technology

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Saori Shima

National Institute of Advanced Industrial Science and Technology

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Takeshi Miki

National Institute of Advanced Industrial Science and Technology

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Kenzi Suzuki

National Institute of Advanced Industrial Science and Technology

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Kiho Nagashima

National Institute of Advanced Industrial Science and Technology

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Tatsuro Horiuchi

National Institute of Advanced Industrial Science and Technology

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