Synthesis of unsupported Co-Mo hydrodesulfurization catalysts with ethanol-water mixed solvent: Effects of the ethanol/water ratio on active phase composition, morphology and activity

Co-Mo sulfide catalysts with different particle size and structures were prepared in ethanol-water mixed solvent followed by a low-temperature sulfurization process, and were tested in dibenzothiophene hydrodesulfurization . The effects of the ethanol/water ratio on the particle size of precursors, active phase composition, active site number, morphology, and hydrodesulfurization activity of the final catalysts were investigated. The atomic ratio of Co/Mo and active phase morphology of catalysts closely relate to the dielectric constant of ethanol-water mixed solvent. Appropriate dielectric constant favors the formation of (Co)MoS 2 slabs with shorter length (∼ 5.0 nm) and higher stacking number (∼ 4.3 layers), resulting in more coordinatively unsaturated sites, especially in the corner sites. The catalytic activity not only depends on the active sites of CoMoS phase, but also on that of Co 9 S 8 and MoS 2 phases because of synergistic effect. For MoS 2 and CoMoS phases, the corner sites show higher direct desulfurization activity than the edge sites.