Hydrodesulfurization of 4,6-dimethyldibenzothiophene over Pt, Pd, and Pt–Pd catalysts supported on amorphous silica–alumina

The activities and selectivities of Pt, Pd, and Pt–Pd supported on amorphous silica–alumina (ASA) in the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DM-DBT) were investigated. The ASA-supported catalysts had much higher activities than alumina-supported catalysts, due to the creation of electron-deficient metal particles. Pd had a high hydrogenation activity for 4,6-DM-DBT, but the removal of sulfur from 4,6-DM-DBT and its HDS intermediates occurred faster over Pt than over Pd. Comparison of two Pt/ASA catalysts with different Pt loadings showed that the metal dispersion strongly influenced the product selectivity. Larger metal particles led to relatively faster hydrogenation and slower C–S bond breaking. Bimetallic Pt–Pd catalysts were much more active than the monometallic constituents, indicating that the metal particles were alloyed. Acid-catalyzed cracking and isomerization occurred especially over Pt/ASA.