The Role of Promoter Atoms in Cobalt-Molybdenum and Nickel-Molybdenum Catalysts

Topsøe, Henrik; Topsøe, Nan‐Yu; Sørensen, Ole Henning; Candia, Roberto; Clausen, Bjerne S.; Pedersen, E.; Nevald, R.

doi:10.1021/bk-1985-0279.ch014

Cited by 22 publications

(23 citation statements)

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“…In addition to this structural evolution, we show in what follows how the magnetic properties of the edges are influenced. On the one hand, this analysis confirms how important it is to consider spin polarization in DFT calculations to correctly describe the edge states for Me = Cr, Fe, Mn, and Co. On the other hand, it enables to make the bridge with experimental data available on CoMoS systems. − As we recently reported, MeMoS nanolayers exhibit magnetic properties particularly for Me = Cr, Mn, and Fe and to a less extend for V and Co, which depend on the edge . Apparently, magnetic effects on the other phases are far less pronounced; hence, we focus here on Cr, Fe, Mn, and Co.…”

Section: Resultssupporting

confidence: 71%

Combined Experimental and Theoretical Molecular Approach of the Catalytically Active Hydrotreating MoS₂ Phases Promoted by 3d Transition Metals

et al. 2019

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High-throughput synthesis combined with a surface organometallic (coordination) chemistry approach is used to prepare in a systematic way a series of 40 metal-promoted (Me)–MoS2 active phases supported on amorphous silica alumina with various Me/Mo ratios (0–0.5). The intrinsic catalytic activity in a model reaction, namely, toluene hydrogenation, evaluated also by a high-throughput method shows a well-marked Me/Mo optimal ratio corresponding to an improved catalytic activity with respect to the MoS2 reference for Me = Fe, Co, and Ni. In contrast, no impact is observed for Zn, while a negative impact on the activity is observed for Ti and Cu. To rationalize these results, the thermodynamic stabilities, local structures, and magnetic properties of the Me atoms at the edges of the MoS2 nanocrystallite are examined by the density functional theory (DFT) calculations. The calculated edge energy descriptor unambiguously categorizes the different types of MeMoS mixed phases. Optimal intermediate edge energies are found for CoMoS, NiMoS, and to a lesser extent for FeMoS, whereas too high or too low edge energies are found for Me = Ti, V, Cu, and Zn, which is consistent with the observed catalytic trends with the varying Me/Mo ratio. The location of Fe in close vicinity of the MoS2 phase is highlighted by scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy analysis which is in agreement with the DFT prediction of the stability of Fe at MoS2 edges. Finally, we propose to extend the edge energy descriptor to WS2-based catalysts and to other sulforeductive conditions.

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Section: Resultssupporting

confidence: 71%

Combined Experimental and Theoretical Molecular Approach of the Catalytically Active Hydrotreating MoS₂ Phases Promoted by 3d Transition Metals

et al. 2019

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“…In this case, their study suggested that the magnetic susceptibility gradually increased with the Co/Mo ratio and as a result d M became larger. For the magnetic properties of cobalt species on the catalyst, Topsøe et al previously reported that the magnetic susceptibility of Co 9 S 8 was much smaller than that of the Co-Mo-S phase [14]. Recently, Okamoto et al reported that the Co-Mo-S phase was antiferromagnetic, while Co 9 S 8 was diamagnetic [9].…”

Section: Effect Of the Co/mo Ratiomentioning

confidence: 99%

“…This fact suggests that 129 Xe NMR will be an useful technique for analysis of a magnetic property of cobalt on sulfided Co-Mo/Al 2 O 3 catalyst. For the magnetic property of cobalt on the catalyst, Topsøe et al previously measured the magnetic susceptibility of supported or unsupported Co-Mo catalysts and investigated the chemical state of cobalt on the catalyst [14]. Recently, Okamoto et al reported that the Co-Mo-S phase was antiferromagnetic, while Co 9 S 8 was diamagnetic [9].…”

Section: Introductionmentioning

confidence: 99%

129Xe NMR analysis of sulfided Co-Mo/Al2O3 catalyst

Hagiwara

Ebihara

Urasato

et al. 2005

Applied Catalysis A: General

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“…Previous studies Co _ Mo _ S phase 4),5) . This model is closely related to using 57 Co Mössbauer spectroscopy proposed that the the antiferromagnetic property of cobalt in the so-called ＂Co _ Mo _ S phase＂ was formed by sulfidation Co _ Mo _ S phase 6) and mainly corresponds with other and functioned as the catalytic active site for hydrofindings using ab initio DFT (density functional theory) desulfurization 1),2) . In the Co _ Mo _ S phase model, calculations of the Co _ Mo _ S phase 7) .…”

Section: Introductionmentioning

confidence: 83%

Characterization of Co-Mo/Al2O3 Hydrodesulfurization Catalyst by 129Xe NMR Spectroscopy

和彦

2008

J. Jpn. Petrol. Inst.

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The present study evaluated 129 Xe NMR spectroscopy for the analysis of Co _ Mo/Al2O3 hydrodesulfurization catalyst. This study also reconsidered the conventional interpretation of 129 Xe NMR spectroscopy that had been used for zeolite micropore analysis. The chemical shift δ of an observed 129 Xe NMR peak varied nonlinearly against the amount of adsorbed xenon N for sulfided Mo/Al2O3 catalyst. In contrast, δ was almost constant against N for dried catalyst. This result suggests that the nonlinear variation of δ against N is mainly caused by electronic interactions between xenon and coordinatively unsaturated sites on the edge of MoS2 crystallites. In addition, the xenon diffusibility δ0 calculated from 129 Xe NMR spectra gradually increased with sulfidation temperature and approached the maximum value at more than 673 K, indicating that δ0 is closely related to the formation of MoS2 crystallites on the surface. δ0 became gradually larger with the cobalt loading and reached the maximum value at 5.7 mass％ for sulfided Co _ Mo/Al2O3 catalyst. On the other hand, δ0 increased from 0 mass％ to 2.4 mass％ and was almost constant at more than 2.4 mass％ for sulfided Co/Al2O3 catalyst. This observation is mainly caused by the differences in the magnetic susceptibility between Co _ Mo/Al2O3 catalyst and Co/Al2O3 catalyst after sulfidation. In other words, the formation of the antiferromagnetic Co _ Mo _ S phase causes increased magnetic susceptibility that greatly affects δ0. The slight decrease of δ0 at 7.3 mass％ for sulfided Co _ Mo/Al2O3 catalyst is closely related to the formation of Co9S8 prior to that of the Co _ Mo _ S phase. These findings strongly suggest that δ0 obtained from 129 Xe NMR spectroscopy is a sensitive indicator of the amount of the Co _ Mo _ S phase. Furthermore, the relative hydrodesulfurization activity of various Co _ Mo/Al2O3 catalysts was roughly correlated with δ0. This result also demonstrates that 129 Xe NMR spectroscopy is useful for analysis of the Co _ Mo _ S phase on Co _ Mo/Al2O3 hydrodesulfurization catalyst.

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The Role of Promoter Atoms in Cobalt-Molybdenum and Nickel-Molybdenum Catalysts

Cited by 22 publications

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Combined Experimental and Theoretical Molecular Approach of the Catalytically Active Hydrotreating MoS₂ Phases Promoted by 3d Transition Metals

Combined Experimental and Theoretical Molecular Approach of the Catalytically Active Hydrotreating MoS₂ Phases Promoted by 3d Transition Metals

129Xe NMR analysis of sulfided Co-Mo/Al2O3 catalyst

Characterization of Co-Mo/Al<sub>2</sub>O<sub>3</sub> Hydrodesulfurization Catalyst by <sup>129</sup>Xe NMR Spectroscopy

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The Role of Promoter Atoms in Cobalt-Molybdenum and Nickel-Molybdenum Catalysts

Cited by 22 publications

References 0 publications

Combined Experimental and Theoretical Molecular Approach of the Catalytically Active Hydrotreating MoS2 Phases Promoted by 3d Transition Metals

Combined Experimental and Theoretical Molecular Approach of the Catalytically Active Hydrotreating MoS2 Phases Promoted by 3d Transition Metals

129Xe NMR analysis of sulfided Co-Mo/Al2O3 catalyst

Characterization of Co-Mo/Al<sub>2</sub>O<sub>3</sub> Hydrodesulfurization Catalyst by <sup>129</sup>Xe NMR Spectroscopy

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Combined Experimental and Theoretical Molecular Approach of the Catalytically Active Hydrotreating MoS₂ Phases Promoted by 3d Transition Metals

Combined Experimental and Theoretical Molecular Approach of the Catalytically Active Hydrotreating MoS₂ Phases Promoted by 3d Transition Metals