Mo and NiMo catalysts supported on SBA-15 modified by grafted ZrO2 species: Synthesis, characterization and evaluation in 4,6-dimethyldibenzothiophene hydrodesulfurization

A series of ZrO2-containing mesoporous SBA-15 supports and their respective Mo and NiMo catalysts were prepared to study the effect of zirconia loading on the characteristics of Ni and Mo species and their catalytic activity in 4,6-dimethyldibenzothiophene hydrodesulfurization (HDS). ZrO2-containing SBA-15 solids with different metal loadings (up to 23 wt% of ZrO2) were prepared by chemical grafting at room temperature. Supports and catalysts were characterized by N2 physisorption, XRD, UV–vis DRS, TPR, chemical analysis, and HRTEM. The incorporation of zirconia into the SBA-15 support provides better dispersion to the deposited molybdenum species, increasing the effective surface of the MoS2 phase. Mo and NiMo catalysts supported on SBA-15 materials showed an increase in catalytic activity in 4,6-dimethyldibenzothiophene HDS with zirconia loading in the support. Unpromoted Mo catalysts were active in the formation of hydrogenated intermediates of 4,6-DMDBT, namely tetrahydro- and hexahydrodimethyldibenzothiophenes; however, they were not able to realize efficient sulfur elimination from these intermediates with the formation of desulfurized products. Addition of the Ni promoter resulted in a further increase in Mo dispersion, as well as in the acceleration of C–S bond cleavage in hydrogenated intermediates of 4,6-DMDBT, improving the overall kinetics of the HYD pathway of HDS.