Hydrodesulfurization of 4,6-dimethyldibenzothiophene over Pt supported on γ-Al₂O₃, SBA-15, and HZSM-5

The promoting effect of an acidic support on the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (DMDBT) was studied by comparing the activity and selectivity of Pt/HZSM-5 with those of Pt/γ-Al₂O₃ and Pt/SBA-15. Pt/γ-Al₂O₃ and Pt/SBA-15 hydrogenated DMDBT fast to the intermediate hexahydro-4,6-dimethyldibenzothiophene and removed sulfur from DMDBT somewhat slower, giving 3,3′-dimethylbiphenyl. The dodecahydro-4,6-dimethyldibenzothiophene intermediate was not observed, indicating that it was very quickly desulfurized. The conversion of DMDBT over Pt/HZSM-5 was low, probably because of the high hydrocracking of the decane solvent and coking of the catalyst by the cracking products. Decreasing the bifunctional hydrocracking by lowering the temperature was not successful, because of a too low HDS activity. Poisoning of the acid sites by co-feeding pyridine suppressed the hydrocracking, but brought the HDS activity down to the level of Pt on a non-acidic support like SBA-15.