Direct Observation by EXAFS of Selenophene Chemisorption by Sulphide Hydrodesulphurization Catalysts

Startsev, A. N.; Shkuropat, S. A.; Кривенцов, В. В.; Kochubey, D.I.; Zamaraev, K. I.

doi:10.1070/mc1991v001n01abeh000004

Cited by 15 publications

(6 citation statements)

References 4 publications

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“…At such a low temperature only physisorption or possibly chemisorption can take the place of selenophene on sulfur atoms, which, as already discussed by the authors, cannot be seen with EXAFS. The disagreement between the study of Medicie et al and the findings of Startsev et al (also obtained at room temperature) therefore still remains unless the latter catalysts were pretreated, for example, with hydrogen, although this was not mentioned.…”

Section: Discussionmentioning

confidence: 87%

“…A precise description of the structural position of the sulfur vacancies and of their immediate surrounding is still lacking. 15 To achieve a more precise description of the active sites, the investigation with EXAFS of the adsorption of selenophene (a structural analogue of thiophene) on a HDS catalyst by Startsev et al 26 was very promising. EXAFS can distinguish Se of the reactant from the structural S atoms, which allows one to study the behavior of the heteroatom of the reactant within the metal sulfide.…”

Section: Introductionmentioning

confidence: 99%

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Structure and Nature of the Active Sites in CoMo Hydrotreating Catalysts. An EXAFS Study of the Reaction with Selenophene

et al. 1997

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The genesis of sulfur vacancies on sulfided (Co)Mo/Al 2 O 3 catalysts was studied with EXAFS at the reaction temperature (673 K) in a H 2 and H 2 /thiophene gas atmosphere. For Mo no significant changes in the sulfur coordination were observed for either the Co-promoted or the unpromoted sample. The experiments indicated that in Co-promoted Mo/Al 2 O 3 vacancies are primarily formed on the Co atom. The sulfur coordination of the cobalt changed from 6.0 to 5.2 upon reduction with H 2 , followed by a slight increase to 5.4 by treatment with H 2 /thiophene. The reaction of selenophene (a structural analogue of thiophene) in hydrogen with sulfided (Co)Mo/Al 2 O 3 catalysts was also investigated with EXAFS. It was possible to monitor the incorporation of Se in the metal sulfide phase. Characterization of the promoted catalyst after HD-Se at 473 K showed that Se was exclusively coordinated to the Co atoms. In contrast, data obtained after HD-Se at 673 K revealed that the Se atoms were located in the position of the bridging sulfur atoms between Co and Mo. Accordingly, a structural model is proposed that involves two types of active sites for hydrodesulfurization on the sulfided Co-promoted Mo catalyst. The first type consists of a sulfur vacancy that is only associated with the promoter atoms, which is created at low temperatures. At higher temperatures, a second type of site is produced by removal of sulfur atoms that are bonded to both Co and Mo atoms.

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Section: Discussionmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Structure and Nature of the Active Sites in CoMo Hydrotreating Catalysts. An EXAFS Study of the Reaction with Selenophene

et al. 1997

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“…This was confirmed in particular by experiments on the adsorption of selenophene (a thiophene analogue). 325 The vacancies available in the Co x Mo 17x S 2AEd phase are involved in the following reactions: Mo 4+ +Co 2+ + & + S 2À + HSR Mo 3+ +Co 3+ + SH À +SR À , Mo 3+ +Co 3+ + SH À +SR À + H2 Mo 3+ +Co 3+ + 2SH À + HR, Mo 3+ +Co 3+ + 2SH À Mo 4+ +Co 2+ + & + S 2À + H2S.…”

Section: S 2àmentioning

confidence: 99%

Heterogeneous hydrogenation catalysts

Navalikhina¹,

Крылов²

1998

Russ. Chem. Rev.

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“…For this reason, it is usually assumed that the active sites are also located there. This model is also supported by EXAFS spectra of the Mo K edge, which are recorded during the adsorption of selenophene at the catalyst at room temperature [6]. However, for monometallic MoS 2 catalysts, the corresponding data are absent.…”

Section: Introductionmentioning

confidence: 98%

Activity of MoSe2/Al2O3 catalysts in decomposition of thiophene and selenophene

Kochubey

Rogov

Babenko

2007

React Kinet Catal Lett

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The rate of thiophene decomposition was shown to be independent of the type of chalcogens used in catalysts МоХ 2 /Al 2 O 3 , where Х = S, Se. On the contrary, the rate of selenophene decomposition was shown to be higher on catalysts MoSe 2 than that on MoS 2 . This observation suggests that the decomposition proceeds on anion vacancies. The decomposition of either thiophene over MoSe 2 or selenophene over MoS 2 results in the formation of partially substituted chalcogenides. At that, the molar ratios of the substituted chalcogen to Mo were shown to coincide in both cases. The fact that the rate of the thiophene decomposition does not depend on the degree of anion exchange indicates that the decomposition is not associated with hydrogenolysis.

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Direct Observation by EXAFS of Selenophene Chemisorption by Sulphide Hydrodesulphurization Catalysts

Cited by 15 publications

References 4 publications

Structure and Nature of the Active Sites in CoMo Hydrotreating Catalysts. An EXAFS Study of the Reaction with Selenophene

Structure and Nature of the Active Sites in CoMo Hydrotreating Catalysts. An EXAFS Study of the Reaction with Selenophene

Heterogeneous hydrogenation catalysts

Activity of MoSe2/Al2O3 catalysts in decomposition of thiophene and selenophene

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