Comparison of the morphology and reactivity in HDS of CoMo/HMS, CoMo/P/HMS and CoMo/SBA-15 catalysts

Mesoporous HMS and SBA-15 materials were synthesized using dodecylamine and pluronic triblock copolymer as surfactants, respectively. The P-modified HMS material (P/HMS) was prepared by incipient wetness impregnation of calcined HMS substrate with aqueous solutions of H3PO4. The influence of support (HMS, P/HMS, SBA-15) and metal loading on both bulk and surface structures of calcined and sulfided CoMo catalysts were studied by a variety of techniques (N2 adsorption–desorption, XRD, TPD–NH3, TGA, FT-IR of NO adsorption, HRTEM, XPS). Textural data of the oxide catalysts confirm that sequential impregnation with Mo, Co salt solutions followed by calcination does not destroy the mesoporous structure of these materials. There is only a minimal blocking of the host pore systems by the widely-dispersed metal oxides located inside them. XPS analysis of the sulfided catalysts revealed that Co3Mo10/HMS catalyst shows lower Mo exposure than on its Co3Mo10/SBA-15 counterpart. Notwithstanding the catalytic response of HMS- and SBA-15-supported catalysts in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) was similar. It was also observed that the Co3Mo10/P/HMS sample show a drop in activity with respect to Co3Mo10/HMS sample due to the strong decrease in the specific surface area and a large surface concentration of unsulfided Co2+ species on the former sample. The increase of total metal content from 15 to 19.5 wt.% (Co4.5Mo15/P/HMS) led to catalyst, which behaves a little better in DBT conversion than a commercial CoMoP/Al2O3 catalyst in the target reaction.