Hydrodesulfurization pathway of 4,6-dimethyldibenzothiophene through isomerization over Y-zeolite containing CoMo/Al₂O₃ catalyst

Hydrodesulfurization (HDS) reactivity of a refractory sulfur species, 4,6-dimethyldibenzothiophene (4,6-DMDBT), was examined over a Y-zeolite containing CoMo/Al₂O₃ (CoMo/Al₂O₃-zeolite), conventional CoMo/Al₂O₃, and NiMo/Al₂O₃. Isomerization and considerable transalkylation of 4,6-DMDBT into 3,6-DMDBT and into trior tetramethyldibenzothiophenes, respectively, were observed characteristically over CoMo/Al₂O₃-zeolite catalyst. Migration of methyl groups enhances the HDS reactivity of the refractory sulfur species by diminishing the steric hindrance. Among the catalysts examined, CoMo/Al₂O₃-zeolite exhibited the best activity for HDS of the gas oil through the effective desulfurization of refractory alkyldibenzothiophenes.