Description of the Co9S8-MoS2 interface: Insights for explaining the cobalt promoting effect in hydrodesulfurization sulfide catalysts

Abstract

Hydrodesulfurization (HDS) catalysts are still a crucial part of the refining industrial strategy to achieve clean petroleum cuts, respecting regulations in terms of sulfur amount. Even if the promoting effect of cobalt or nickel over MoS2-based catalysts has been extensively studied for decades providing satisfactory description of the promotion, electronic by nature, through the formation of the so-called CoMoS phase, discrepancy still persist when comparing the CoMoS model with the previous description of the synergy for unsupported Co/MoS2 systems through the so-called synergy by contact model. This review summarizes the advancements made, both experimentally and through DFT calculations, to address this discrepancy, considering the description of Co9S8/MoS2 interfacial models. Different aspects will be described, including transmission electron microscopy characterization of the interface, the DFT construction of the interfacial model, and its consequences in terms of electronic structure, transition state (TS) energies for the dibenzothiophene HDS reaction, as well as the spin dependence of TS energies for various MoS2 edge sites. Finally, potential new advancements coming from the description of Co9S8/MoS2 interfacial models will be presented. This review accomplishes the pressing need for a wide-ranging and swift introduction to HDS using Co-promoted MoS2 to guide the development of nextgeneration catalysts for fuel production.