Mo-doped mesoporous silica for thiophene hydrodesulfurization: Comparison of materials and methods

The mesoporous silica APMS-30 was compared to MCM-41 and MCM-48 as a substrate for the hydrodesulfurization (HDS) of thiophene with H-2. Mo was introduced to these materials by four methods: dry impregnation of the calcined silica with MoO3, wet impregnation with aqueous (NH4)(6)Mo7O24.4H(2)O, "reactive" impregnation with MoCl3 in toluene, or in situ addition of (NH4)(6)Mo7O24.4H(2)O to the reaction mixture (APMS-30 only). Mo loading was approximately 6 wt % (Si/Mo = 24). Samples were characterized by chemical analysis, XRD, N-2 physisorption, SEM, and TEM. All samples were active for HDS and showed decreasing catalytic performance as a function of time, generally leveling out at total thiophene conversions between 22.8% and 57.4% after 75 min. Mo-APMS-30 showed the highest conversions, although Mo-MCM-48 synthesized by dry impregnation had slightly higher total conversion. Product distributions showed a shift from more hydrogenated to less hydrogenated C-4 compounds as conversion decreased, and low amounts Of C-1, C-2, and C-3, compounds indicated that hydrocarbon cracking did not occur to a significant degree. Surface area did not appear to be a significant factor in catalytic performance.