Hydrodesulfurization of 4,6-dimethyldibenzothiophene over Pt, Pd, and Ptx2013;Pd catalysts supported on amorphous silicax2013;alumina
摘要
The activities and selectivities of Pt, Pd, and Ptx2013;Pd supported on amorphous silicax2013;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 Cx2013;S bond breaking. Bimetallic Ptx2013;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.