Synthesis of mesoporous Ti-inserted SBA-15 and CoMo/Ti-SBA-15 catalyst for hydrodesulfurization and hydrodearomatization

Ti-inserted ordered mesoporous silica SBA-15 (Ti-SBA-15) synthesized by original microwave-assisted method as a support was used to prepare CoMo catalysts to develop a new catalyst with high hydrodesulfurization (HDS) and controlled hydrodearomatization (HDA) activities. The activity tests of catalysts were carried out by using a pressurized fixed-bed flow reactor. 4,6-Dimethyldibenzothiophene (4,6-DMDBT), 1-methylnaphthalene, and phenanthrene were used as model reactants in HDS and HDA, respectively. CoMo/Ti-SBA-15 catalyst showed about 1.35 times of HDS activity and half of HDA activity of CoMo/SBA-15 catalyst. The results of XRD, FT-IR and Si-29-NMR reveal that titanium was successfully inserted into silica framework of SBA-15, and the SBA-15 mesoporous structure was maintained after insertion of titanium. The reduction of molybdenum from Mo6+ to Mo4+ readily occurred with incorporation of titanium, resulting in an increase in Mo4+ species and CoMoS phase on sulfided catalysts. This enhanced the HDS activity of CoMoTiSBA15 catalyst. Moreover, the presence of Ti3+ on CoMo/Ti-SBA-15 was observed, suggesting that TiMoS was formed and played a role as new active sites. CoMoS active slabs with shorter length and higher stacking layer were formed on CoMo/Ti-SBA-15 comparing with CoMo/SBA-15, resulting in the low HDA activity of the former.