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

摘要

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.