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

Abstract

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.

Impact of Metal Content on the Deactivation of a Bifunctional Hydrocracking Catalyst

“…The used methods are analogous to the one described elsewhere. 47 The catalytic tests were carried out in a high-throughput fixed bed reactor unit in the presence of H 2 S (generated by decomposition of DMDS) under hydrogen pressure. Catalyst samples were sulfided in situ.…”

Impact of Feedstock Properties on the Deactivation of a Vacuum Gas Oil Hydrocracking Catalyst

“…To evaluate the hydrogenating function, the activity was determined by quantifying the hydrogenated products during toluene hydrogenation. The methodology used is described elsewhere . An equivalent protocol was followed regarding the acid function but using the hydroconversion of n -heptane as model reaction.…”

“…The methodology used is described elsewhere. 57 An equivalent protocol was followed regarding the acid function but using the hydroconversion of n-heptane as model reaction. The catalytic tests were carried out in a fixed bed reactor unit in the presence of H 2 S (generated by the decomposition of DMDS) under hydrogen pressure.…”

Electronic structures of the MoS2/TiO2(anatase) heterojunction: influence of physical and chemical modifications at the 2D- or 1D-interfaces

“…13,14 Due to the low-cost, high stability and abundance of the 2H-MoS 2 and anatase-TiO 2 materials, MoS 2 /TiO 2 heterostructure has been the subject of numerous studies 15,16 combining the efficient photocatalytic proporties of TiO 2 17,18 with the wellknown catalytic activity of MoS 2 for the activation, conversion and production of various molecules. 19,20 MoS 2 may act as a cocatalyst with the aim to harvest the photogenerated charges in order to avoid the recombination of the electrons and holes photogenerated in TiO 2 . The charge carriers collected and the active sites of MoS 2 offers a large range of applications (degradation of organic pollutants, 21,22 CO 2 reduction, 23 Hydrogen Evolution Reaction 24 .…”