Effects of sulfur compounds on the hydrogenation and isomerization of 1-hexene over a sulfided CoMo catalyst for hydrodesulfurization

Abstract

The transformation of olefins is crucial to the hydrodesulfurization (HDS) of fluid catalytic cracking (FCC) gasoline. The reactivity of 1-hexene was studied over a sulfided CoMo/Al₂O₃ catalyst. Effects of hydrogen sulfide (H₂S) and three organic sulfur compounds on 1-hexene transformation were also investigated. As for the hydroconversion of 1-hexene, the double-bond isomerization (ISOM) of 1-hexene proceeded readily at lower temperatures while the hydrogenation (HYD) of 1-hexene and its isomers predominated at higher temperatures. The inhibiting effect of H₂S on both isomerization and hydrogenation reactions resulted in the decline in 1-hexene HYD conversion. The saturation rate of 1-hexene increased sharply when H₂S content decreased to below 100 μg g⁻¹ S. It was also found that thiophene (T), 2-methylthiophene (2MT) and 3-methylthiophene (3MT) strongly inhibited the hydrogenation of 1-hexene. Furthermore, the inhibiting effect on 1-hexene HYD reaction originated from H₂S generated by organic sulfide desulfurization. More isomerization products were obtained in the presence of sulfur compounds, probably attributable to the inhibition of sulfur compounds on the hydrogenation of 1-hexene and its isomers.