Showing papers by "Takashi Kubota published in 2004"
TL;DR: In this article, the effect of boron addition was studied on the hydrodesulfurization (HDS) of thiophene over MoS 2 /B/Al 2 O 3 and CoMoS 2, which was prepared by a CVD technique using Co(CO) 3 NO as a precursor of Co. The catalysts were characterized by means of NO adsorption and TEM.
70 citations
TL;DR: In this paper, the authors showed that a selective formation of Co atoms in a CoMoS phase is achieved by means of a CVD technique using Co(CO)3NO.
50 citations
Hokkaido University of Education1, Kobe University2, Saitama University3, Kyoto University4, Kyoto Institute of Technology5, Kogakuin University6, Tottori University7, Shimane University8, Tokyo Institute of Technology9, Kitami Institute of Technology10, Muroran Institute of Technology11, Nagoya University12
TL;DR: The effect of preparation conditions on the platinum metal dispersion and the effect of dispersion on turnover frequencies (TF) of several representative reactions was investigated in this article, where the authors found that high dispersion of platinum was achieved without extra modification for the catalyst preparation method and an attentive pretreatment brought high reproducible results in platinum dispersions.
Abstract: To obtain a broad understanding of the effect of preparation conditions on the platinum metal dispersion and the effect of dispersion on turnover frequencies (TF) of several representative reactions, we prepared platinum-supported alumina catalysts by impregnation methods in which preparation conditions were fixed or not fixed using certain alumina Platinum dispersions on the alumina catalysts were determined by several methods Catalytic activities for combustion of propane, oxidation of CO, hydrogenations of ethylene and naphthalene, hydrodechlorination of 1,1,1-trichloroethane, hydrodesulfurization of thiophene, and hydrocracking of hexane were compared based on the TF of these reactions The following results were obtained: (i) high dispersion of platinum was achieved without extra modification for the catalyst preparation method; (ii) an attentive pretreatment brought high reproducible results in platinum dispersions; (iii) the catalytic activities for combustion of propane, hydrodesulfurization of thiophene and hydrogenation of naphthalene were affected by starting materials of platinum; (iv) the relation between the TF and platinum dispersion was negative in all reactions tested except hydrocracking of hexane
35 citations
TL;DR: In this article, the solvent effect on the enantioselective hydrogenation of α,β-unsaturated carboxylic acids has been studied using cinchonidine-modified Pd/TiO 2 catalysts with different Pd dispersions.
Abstract: The solvent effect on the enantioselective hydrogenation of α,β-unsaturated carboxylic acids has been studied using cinchonidine-modified Pd/TiO 2 catalysts with different Pd dispersions. The structure sensitivity observed in the hydrogenation of ( E )-2,3-diphenyl-2-propenoic acid was found to depend on the property of the solvent used, especially in the dispersion range lower than 0.2. In the solvents with low polarity, the optimal Pd dispersions are much lower than those observed in polar and protic solvents. The catalysts with the lowest dispersions, however, exhibit unexpectedly poor selectivities irrespective of the solvent employed. With the reactions of smaller aliphatic acids: ( E )-2-methyl-2-pentenoic acid and ( E )-2-methyl-2-butenoic acid, the Pd dispersion dependencies are much milder and independent of the solvents. These variations of the structure sensitivity could be explained by the difference in the steric interference of the metal surface with the modifier–substrate adduct in different solvents.
28 citations
TL;DR: In this paper, the atomic structure of a single crystal basal plane was examined by ultra-high vacuum scanning tunneling microscopy (UHV-STM) and a number of crater structures with diameters ranging from 5 to 9nm were observed on pristine as well as on high-temperature (473 K) resulfided surfaces.
Abstract: Atomic structure of a natural molybdenite (MoS 2 ) single crystal basal plane was examined by ultra-high vacuum scanning tunneling microscopy (UHV-STM). Numbers of crater structures with diameters ranging from 5 to 9 nm were observed on pristine as well as on high-temperature (473 K) resulfided surfaces. Atomic structures within these craters were continuous from the surrounding terrace, with no step structures at the rims of the craters. Atoms in the bottom of the craters showed higher corrugations compared to the terrace atoms, indicating higher electronic density of states in the craters. Its implication on hydrotreating activity over curved MoS 2 nanoparticles is discussed.
12 citations
TL;DR: Porous smectite-type clays containing cobalt atoms in lattice, (MST(Co)), were synthesized with a hydrothermal method as discussed by the authors, which showed higher activities for the hydrodesulfurization of thiophenic compounds (thiophene and benzothiophene).
5 citations