Showing papers by "Takashi Kubota published in 2000"
TL;DR: In this paper, the catalytic performance and structures of multicomponent MoVNbTe oxides have been studied to find the correlation among the performance, active phases, and preparation conditions.
86 citations
TL;DR: In this paper, Fe 3+ cation species are preferentially formed below 2.8 Fe nm −2 by ion exchange with the surface OH groups of ZrO 2.
43 citations
TL;DR: In this paper, the enantioselective hydrogenation of the C=C double bond in (E)-α-phenylcinnamic acid has been studied with different supported Pd catalysts prepared by a precipitation-deposition method and modified with cinchonidine.
Abstract: The enantioselective hydrogenation of the C=C double bond in (E)-α-phenylcinnamic acid has been studied with different supported Pd catalysts prepared by a precipitation-deposition method and modified with cinchonidine. The influences of the support materials and the texture, Pd loadings, precipitation procedures, and reduction conditions on the hydrogenation activity and enantioselectivity are described. The texture of the supports has a decisive influence on the behavior of the resulting catalysts, especially when it is pre-reduced at elevated temperatures. Nonporous titania with a relatively small specific surface area was found to be the most suitable. The use of a large excess amount of precipitant resulted in an increase in the amount of residual Na and in a drastic decrease in the amount of residual Cl, leading to a remarkable increase in the activity. The elimination of both the residual Na and Cl from the catalyst precursor was found to be preferable for the enantioselectivity. A considerable inc...
33 citations
TL;DR: In this paper, the metal oxide−support interactions in ZrO2-supported Fe oxide catalysts as a function of calcination temperature were revealed by means of 57Fe Mossbauer spectroscop...
Abstract: To reveal the metal oxide−support interactions in ZrO2-supported Fe oxide catalysts as a function of calcination temperature, 5 wt % Fe/ZrO2 was characterized by means of 57Fe Mossbauer spectroscop...
29 citations
TL;DR: In this paper, Zeolite-supported highly dispersed Co sulfide clusters are synthesized using Co(CO)3 (NO) as a precursor, and the amount of Co inCoSx/zeolite anchored by a CVD technique increases as the Al/Si ratio of the zeolite increases, whereas the activity per Co atomdecreases for thiophene hydrodesulfurization.
Abstract: Zeolite-supported highly dispersed Co sulfide clusters are synthesized using Co(CO)3 (NO) as a precursor. The amount of Co inCoSx/zeolite anchored by a CVD technique increases as the Al/Si ratio of the zeolite increases, whereas the activity per Co atomdecreases for thiophene hydrodesulfurization (HDS). When an Na-exchanged USY zeolite is used, the Co sulfide catalyst shows a muchhigher HDS activity than a conventional Co—Mo/Al2 O3 catalyst. It is considered from XAFS and NO adsorption techniques that thehigh HDS activity of CoSx/USY-Na is due to an extremely high dispersion of Co sulfide clusters.
15 citations
TL;DR: In this article, it was revealed by means of XPS, XRF and EXAFS that catalytically active Co-Mo sulfide species are thermally stable Co2Mo2S6 clusters possessing a thiocubane structure.
Abstract: Intrazeolite Co-Mo binary sulfide clusters are synthesized using metal carbonyl techniques and used for the HDS of thiophene. It is revealed by means of XPS, XRF and EXAFS that catalytically active Co-Mo sulfide species are thermally stable Co2Mo2S6 clusters possessing a thiocubane structure. With Mo, Co and Co-Mo sulfides synthesized in Pd-NaY, Pd promotes the HDS activity of Co2Mo2S6 clusters through hydrogen activation. Full development of the catalytic synergy between Co and Mo is strongly suggested to require both cus Co and Mo sites.
2 citations