Precise tuning the CoMoOx/Al2O3 and CoMoSx/Al2O3 interfacial structures for efficient hydrodesulfurization of dibenzothiophene
In this work, we studied how the oxidic CoMoO x /Al 2 O 3 and sulphurated CoMoS x /Al 2 O 3 interfacial structures determine catalytic efficiency in selective hydrodesulfurization (HDS) of dibenzothiophene (DBT). To achieve this goal, we first synthesized the γ-Al 2 O 3 materials of unique morphologies through the ionic liquid-assisted hydrothermal process under different conditions. The resulting γ-Al 2 O 3 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 Al 2 O 3 rods show polycrystalline feature. Through impregnation of Mo/Co salts of different loadings, the various CoMoO x precursors were generated on the different Al 2 O 3 facets owing to the distinct interaction: mostly the two-dimensional (2D) poly-/mono-meric MoO x species together with the three-dimensional (3D) MoO 3 on the Al 2 O 3 (1 1 0) facet vs. the quasi 2D polymeric MoO x species on the Al 2 O 3 polycrystalline facet. Such structural difference further affected the sulfidation of the MoCoO x as well as the quantity of active MoCoS x entities on different γ-Al 2 O 3 supports: 10Mo3CoS x /Al 2 O 3 -HP had the highest level of MoCoO x sulfidation thus a much higher fraction of MoS 2 plus Co 9 S 8 /CoMoS species whereas less quantity of partially sulphurated CoMoO x S 2 /CoO x together with SO x 2- species. All the distinct interfacial domains of the sulphurated catalysts reasonably account for significantly different efficiency in HDS of DBT. Surface MoS 2 /CoMoS/Co 9 S 8 species of the highest content over the Al 2 O 3 (1 1 0) facet correspond to the highest DBT areal conversion rate and TOF value, owing to the enhanced MoS 2 -Co 9 S 8 and MoS 2 -CoMoS conjunction and synergism.
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