Trimetallic NiMoW and CoMoW catalysts supported on SBA-15 modified with titania or zirconia for deep hydrodesulfurization

Abstract

SBA-15, Ti-SBA-15 and Zr-SBA-15 were used to prepare trimetallic CoMoW and NiMoW catalysts in order to inquire into the effect of the support’s composition on the catalytic performance in deep hydrodesulfurization (HDS). Supports and catalysts were characterized by N2 physisorption, X-ray diffraction, temperature-programmed reduction, scanning electron microscopy (SEM-EDX) and high-resolution transmission electron microscopy. The catalytic activity was determined in the simultaneous HDS of dibenzothiophene and 4,6-dimethyldibenzothiophene. The most important characteristics of the SBA-15 material were preserved in the titania and zirconia-containing supports and the trimetallic catalysts. The deposited metal oxide species (NiO, CoO, MoO3 and WO3) were well-dispersed. NiMoW catalysts were substantially more active in deep HDS than the corresponding CoMoW ones. Titania and zirconia addition to the supports resulted in higher HDS activity of NiMoW and CoMoW catalysts, being this effect larger for the Ni-promoted samples. The NiMoW/Zr-SBA-15 catalyst was the most active for the elimination of sulfur from both dibenzothiophene and 4,6-dimethyldibenzothiophene. Its activity was twice higher than that of the NiMoW/SBA-15 analog. This was attributed to the high dispersion of the deposited metal species in the sulfided NiMoW/Zr-SBA-15 sample. Regarding the catalysts’ selectivity, it depended more strongly on the promoter used than on the support’s chemical composition.