The structure of the cobalt sulfide phase in carbon-supported Co and Co-Mo sulfide catalysts as studied by exafs and xanes

Bouwens, Smam Stephan; Koningsberger, DC Diek; Beer, De; Prins, R.

doi:10.1007/bf00765354

Cited by 44 publications

(32 citation statements)

References 16 publications

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“…The mean size of the CoS2 crystallites was determined at ≈ 48 nm using the Scherrer's formula. The XANES spectrum reported for CoS2 in Figure S2 displays the characteristic broad spectral shape of cobalt sulfide species with no white line [45,46]. The ill-defined pre-edge structure assigned to transition from cobalt 1s atomic level to 3d molecular orbitals hybridized with metal p states is characteristic of the octahedral symmetry in which cobalt atoms are embedded in the CoS2 structure [45,46].…”

Section: Raman Characterization Of Bulk Co9s8mentioning

confidence: 99%

“…The XANES spectrum reported for CoS2 in Figure S2 displays the characteristic broad spectral shape of cobalt sulfide species with no white line [45,46]. The ill-defined pre-edge structure assigned to transition from cobalt 1s atomic level to 3d molecular orbitals hybridized with metal p states is characteristic of the octahedral symmetry in which cobalt atoms are embedded in the CoS2 structure [45,46]. A satisfactory simulation of the EXAFS signal in the 1-4 Å R-space (Figure S3, Table S1) has been obtained using the crystallographic distances reported for CoS2 [44].…”

Section: Raman Characterization Of Bulk Co9s8mentioning

confidence: 99%

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First in situ temperature quantification of CoMoS species upon gas sulfidation enabled by new insight on cobalt sulfide formation

et al. 2021

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Insights into the cobalt sulfide formation upon sulfidation (10% H2S/H2) of cobalt-based materials with 4 wt % CoO supported on alumina or silica were obtained by Quick-X-ray absorption spectroscopy monitoring analysed by multivariate curve regression analysis. A common pathway is evidenced involving the formation of supported defective CoS2 species transformed around 200-250°C into supported Co9S8 species. Upon cooling down under sulfiding atmosphere, a reverse transition towards CoS2 was observed by XAS multivariate analysis and supported by Raman analysis. This reverse transition is sensitive to the Co9S8 crystallite size: the smaller the Co9S8 nanoparticles the higher the amount of formed CoS2 after cooling. The knowledge gained on the sulfidation of monometallic cobalt-based catalysts has been used in order to isolate the X-ray absorption spectrum of the CoMoS active species formed during the sulfidation of a calcined cobalt-promoted HDS catalyst. The evolution of the concentration of the CoMoS species upon temperature increase is determined for the first time, together with those of the pristine oxidic CoMo catalyst and CoS2 and Co9S8 supported species. Although the conversion of Co9S8 into CoS2 is still observed for the HDS catalyst when temperature is decreased under H2S/H2 atmosphere, no change of the CoMoS percentage is evidenced.

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Section: Raman Characterization Of Bulk Co9s8mentioning

confidence: 99%

Section: Raman Characterization Of Bulk Co9s8mentioning

confidence: 99%

First in situ temperature quantification of CoMoS species upon gas sulfidation enabled by new insight on cobalt sulfide formation

et al. 2021

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“…The exact position of the Co or Ni atoms at the edges of the MoS 2 crystallites in the Co-Mo-S structure has still to be established, although informative EXAFS and XANES results have been published by Topsoe et al [6] and by Bouwens et al [7][8][9][10]. Since the beryllium windows of the in-situ EXAFS cell used in our investigations [7][8][9][10] contained a small amount of Ni, the Co EXAFS k-range which could be measured for Co-MoS 2 catalysts was somewhat limited.…”

Section: Introductionmentioning

confidence: 99%

“…Since the beryllium windows of the in-situ EXAFS cell used in our investigations [7][8][9][10] contained a small amount of Ni, the Co EXAFS k-range which could be measured for Co-MoS 2 catalysts was somewhat limited. Therefore we decided to study the Ni K edge EXAFS spectra of Ni-MoS2/C catalysts.…”

Section: Introductionmentioning

confidence: 99%

Exafs study of the local structure of Ni in Ni-MoS2/C hydrodesulfurization catalysts

et al. 1990

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To study the local structure of the Ni promoter atom, the Ni and Mo K edge EXAFS spectra of Ni-MoSz/C hydrodesulfurization catalyst were measured in an in-situ EXAFS cell at 77 K. The Ni atom is situated in a square pyramid of five S atoms at a distance of 2.21 from the S atoms. In addition an EXAFS contribution due to a Mo atom at 2.82 A from the Ni atom could be identified. This local structure indicates that the Ni atoms are situated on top of the S 4 squares at the MoS 2 edges in millerite-type Ni sites. The Ni atoms are situated in the planes of the Mo atoms and not in the intercalation plane midway between successive MoS 2 sandwich layers.

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“…Such a change is more pronounced for the Co/C, in which also Co9S 8 is formed, than for the Co-Mo/C catalysts. In this respect it is important to mention also the results recently obtained by Bouwens et al [25] via characterization of a Co(4.1)/C and Co(1.5)-Mo(7.7)/C catalyst by means of EXAFS and XANES. They found that as a result of sulfidation similar Cophases are formed in these catalysts i.e.…”

Section: Discussionmentioning

confidence: 84%

So-called “Co-Mo-S” phase observed in carbon-supported Co and Co-Mo sulfide catalysts by Mössbauer emission spectroscopy

et al. 1989

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The structure of the cobalt sulfide phase in carbon-supported Co and Co-Mo sulfide catalysts as studied by exafs and xanes

Cited by 44 publications

References 16 publications

First in situ temperature quantification of CoMoS species upon gas sulfidation enabled by new insight on cobalt sulfide formation

First in situ temperature quantification of CoMoS species upon gas sulfidation enabled by new insight on cobalt sulfide formation

Exafs study of the local structure of Ni in Ni-MoS2/C hydrodesulfurization catalysts

So-called “Co-Mo-S” phase observed in carbon-supported Co and Co-Mo sulfide catalysts by Mössbauer emission spectroscopy

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