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Kubota, Takeshi; Okamoto, H.; Okamoto, Yasuaki

doi:10.1023/a:1019021706546

Cited by 14 publications

(16 citation statements)

References 13 publications

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“…A similar transformation of Co sulfide clusters to Co 2+ cations was observed on evacuation at 673 K for the Co sulfide clusters prepared from Co(CO)3NO adsorbed in H + -type USY 103) . As a result, we employed Co(CO)3NO adsorbed on Na + -exchanged zeolite to prepare thermally stable intrazeolite Co sulfide clusters 103) . Sulfidation of Co(CO)3NO/NaY resulted in CoSx/Na-zeolite (S/Co = 1.0) 85), 103) .…”

Section: Intrazeolite Co Sulfide Clusterssupporting

confidence: 68%

“…This was recently confirmed by the magnetic properties of CoSx/NaY 104) . Based on EXAFS analysis, the Co _ Co coordination number of Co sulfide species in CoSx/NaX (3Co/SC) was lower than that in CoSx/NaY in spite of higher Co loading 103) . It is likely that the stronger interaction between Co precursor and zeolite framework oxygen causes better dispersion of Co sulfide clusters or higher distortion in the structure.…”

Section: Intrazeolite Co Sulfide Clustersmentioning

confidence: 98%

“…As a result, we employed Co(CO)3NO adsorbed on Na + -exchanged zeolite to prepare thermally stable intrazeolite Co sulfide clusters 103) . Sulfidation of Co(CO)3NO/NaY resulted in CoSx/Na-zeolite (S/Co = 1.0) 85), 103) . The loading of Co increased as the Si/Al ratio decreased or basic strength of the zeolite increased 103) .…”

Section: Intrazeolite Co Sulfide Clustersmentioning

confidence: 99%

“…Sulfidation of Co(CO)3NO/NaY resulted in CoSx/Na-zeolite (S/Co = 1.0) 85), 103) . The loading of Co increased as the Si/Al ratio decreased or basic strength of the zeolite increased 103) . This is a consequence of the increasing interaction strength between Co(CO)3NO molecules and the zeolite framework oxygens with increasing basic strength.…”

Section: Intrazeolite Co Sulfide Clustersmentioning

confidence: 99%

“…The dispersion of the Co sulfide species was examined by XAFS 103) . EXAFS analysis of CoSx/NaY (2Co/SC) indicated that Co sulfides are highly dispersed to form dimer species like the Mo sulfide clusters in MoSx/NaY.…”

Section: Intrazeolite Co Sulfide Clustersmentioning

confidence: 99%

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Preparation and Characterization of Co-Mo Model Sulfide Catalysts for Hydrodesulfurization

Okamoto

2003

J. Jpn. Petrol. Inst.

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Development of highly active hydrodesulfurization (HDS) catalysts is one of the most urgent problems in the petroleum industry. Better characterization and understanding of the nature of HDS catalysts on the molecular scale are of great importance for the rational design of highly active HDS catalysts. Our approaches for this purpose involve the fabrication of model catalysts using metal carbonyls to overcome the difficulties caused by the heterogeneity of practical catalysts. One of our new approaches uses the synthesis of intrazeolite homogeneous Mo, Co and Co _ Mo sulfide clusters with well defined structures. The local structure of intrazeolite Mo sulfide dimer clusters, Mo2S4, depends on the composition of the host zeolite. Thermally stabilized Co2Mo2S6 binary sulfide clusters, which show catalytic synergies between Co and Mo for thiophene HDS, with a thiocubane type structure are formed in zeolite. The intrinsic HDS activity of Co sulfide clusters depends on the host zeolite. The hydrode-selenium reaction of selenophene, combined with an extended X-ray absorption fine structure (EXAFS) study, over Mo2S4 and MoS2 clusters suggests a microscopic HDS reaction mechanism. More practical modeling of Co _ Mo sulfide catalysts using a selective preparation method of CoMoS phases supported on refractory oxides is established to understand the nature of practical HDS catalysts. No effects of the support are found with the CoMoS phase supported on Al2O3, TiO2 and ZrO2, whereas the CoMoS phase supported on SiO2 shows a higher intrinsic activity. The fraction of the CoMoS phase accessible to NO adsorption is elucidated, based on the number of the CoMoS phase in the model catalyst, suggesting a new model of the CoMoS structure. The maximum potential HDS activity of Co(Ni) _ Mo(W) catalysts is evaluated by using Co(CO)3NO as a probe molecule. Such model catalysts provide important information about the effects of the catalyst preparation and additives, the catalyst structure and the fundamental aspects of HDS catalysts such as microscopic reaction mechanisms and structure-reactivity relationship.

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Section: Intrazeolite Co Sulfide Clusterssupporting

confidence: 68%

Section: Intrazeolite Co Sulfide Clustersmentioning

confidence: 98%