Abstract:

The suffidation process of Mo/Al_2O_3, Mo/TiO_2-Al_2O_3, Co/Al_2O_3 t Co/TiO_2Al_2O_3, Co-Mo/Al_2O_3 and Co-Mo/TiO_2-Al_2O_3 samples were studied by using "in - situ" XPS techniques. The results show that for alumina-supported catalysts with lower Mo orCo loading (less than 0.05 g MoO_3/gAl_2O_3 or 0.03 g CoO/gAl_2O_3 respectively) the Mo andCo sulfides can not be formed. While the catalysts supported on the TiO_2-modified aluAnna, the sulfidatrion of Mo/TiO_2-Al_2O_3 catalysts is much easier than that of Mo/Al_2O_3catalysts. The highly dispersed cobolt oxidic species are very difficult to the Co/Al_2O_3 catalysts be sulfided even at 400 ℃, while the sulfidation of Co_3O_4crystallite is much easier. The TiO_2-modified alumina doed not affect the sulfidation of the Co/Al_2O_3 catalysts in the form of higher dispersion, but has a significant influence on the sulfidation of Co_3O_4 crystallite. The activity measurements of thiophene hydrodesulfurization (HDS) indicate that a good correlation exists between the degree of sulfidation and HDS activity for both Co-Mo/Al_2O_3 and Co-Mo/TiO_2-Al_2O_3 catalysts. The HDS activity and sulfidation degree of Co-Mo catalysts can be increased remarkly as using the TiO_2-modified alumina carrier.

Key words: "in-situ", XPS, TiO₂-modified alumina carrier, Co-M0/TiO₂-Al₂O₃ catalysts, Degree of sulfidation, HDS activity