Hydrodesulfurization of Dibenzothiophene over siliceous MCM-41-Supported Catalysts

摘要

High-performance hydrodesulfurization (HDS) catalysts wre prepared by depositing Ni-Mo species over siliceous MCM-41. HDS of dibenzothiophene (DBT), one of the most refractory sulfur-containing moleculles in petroleum, was used to evaluate the activity of the prepared catalysts. The Ni-Mo/MCM-41 showed better performance than the Co-Mo/MCM-41 in the HDS of DBT catalyzed by Co-Mo/MCM-41. The optimum HDS activity was observed at a Ni/Mo atomic ratio of 0.75, similar to Co-Mo/MCM-41 catalysts but higher than the conventional gamma-Al_2O_3-supported catalysts. The higher optimal Ni/Mo ratio may be attributed to the higher dispersion of the active species and to generation of more Ni-Mo pairs on the surface of MCM-41. The high performance of the prepared Ni-Mo(0.75)/MCM-41 catalyst was confirmed by the HDS of 4-methyldibenzothiophene, 4,6-dimethyldibenzothiophene, and a high-sulfur diesel. The ~35S isotopetracer investigation revealed that sulfur atoms accommodated on the surface after HDS could be released only by the introduction of a sulfur-containing compound, indicating that sulfur-atom exchange between sulfur-containing molecules and the active sites is involved in the HDS reaction. Accordingly, a reaction mechanism for HDS is proposed.