Precise tuning the CoMoOx/Al2O3 and CoMoSx/Al2O3 interfacial structures for efficient hydrodesulfurization of dibenzothiophene

Abstract In this work, we studied how the oxidic CoMoOx/Al2O3 and sulphurated CoMoSx/Al2O3 interfacial structures determine catalytic efficiency in selective hydrodesulfurization (HDS) of dibenzothiophene (DBT). To achieve this goal, we first synthesized the γ-Al2O3 materials of unique morphologies through the ionic liquid-assisted hydrothermal process under different conditions. The resulting γ-Al2O3 hexagonal plates (HP) and stacked hexagonal plates (SHP) are single crystallites with the dominant (1 1 0) and (1 1 1)/(1 0 0) facet structures, respectively; whereas the Al2O3 rods show polycrystalline feature. Through impregnation of Mo/Co salts of different loadings, the various CoMoOx precursors were generated on the different Al2O3 facets owing to the distinct interaction: mostly the two-dimensional (2D) poly-/mono-meric MoOx species together with the three-dimensional (3D) MoO3 on the Al2O3 (1 1 0) facet vs. the quasi 2D polymeric MoOx species on the Al2O3 polycrystalline facet. Such structural difference further affected the sulfidation of the MoCoOx as well as the quantity of active MoCoSx entities on different γ-Al2O3 supports: 10Mo3CoSx/Al2O3-HP had the highest level of MoCoOx sulfidation thus a much higher fraction of MoS2 plus Co9S8/CoMoS species whereas less quantity of partially sulphurated CoMoOxS2/CoOx together with SOx2-species. All the distinct interfacial domains of the sulphurated catalysts reasonably account for significantly different efficiency in HDS of DBT. Surface MoS2/CoMoS/Co9S8 species of the highest content over the Al2O3 (1 1 0) facet correspond to the highest DBT areal conversion rate and TOF value, owing to the enhanced MoS2-Co9S8 and MoS2-CoMoS conjunction and synergism.