Catalytic Performance of Noble Metals Supported on Mesoporous Silica MCM-41 for Hydrodesulfurization of Benzothiophene

摘要

The catalytic performances of noble metals (Pt, Rh, Pd, Ru) supported on mesoporous silica MCM-41 were investigated for the hydrodesulfurization (HDS) of benzothiophene (BT). The order of HDS activities of noble metal/MCM-41 catalysts was Pt>Rh>Pd》Ru. Pt/MCM-41 catalyst showed high HDS activity, which was higher than that of commercial CoMo/Al_2O_3 catalyst. The supported noble metal catalysts were characterized by TEM, XRD, hydrogen adsorption and benzene hydrogenation. The order of dispersion of noble metal on MCM-41 was Rh>Pt>Pd>Ru, which was not the same as that of HDS activities. On the other hand, the order of the activities of noble metal/MCM-41 catalysts for benzene hydrogenation was Pt>Rh>Pd>Ru. The hydrogenation activity of Pt/MCM-41 catalyst was regenerated after H_2S treatment, but the activities of other catalysts were not regenerated. Thus, high hydrogenation activity and sulfur tolerance are important factors to prepare highly active noble metal/MCM-41 catalysts. Pt/MCM-41 catalyst showed remarkably high and stable activity for the HDS of BT, but Pt/SiO_2 catalyst, with similar Pt dispersion on MCM-41, showed low activity which decreased with time on stream. Since MCM-41 showed higher acidity than SiO_2, hydrogenation activity and sulfur tolerance of Pt/MCM-41 catalyst were higher than those of Pt/SiO_2 catalyst. The results of FT-IR analysis indicated that the strength of interaction between BT and MCM-41 was stronger than that of SiO_2, suggesting that both acid sites of MCM-41 and Pt particles in the Pt/MCM-41 catalyst act as active sites for the HDS of BT. Furthermore, FT-IR spectra of BT adsorbed on Pt/MCM-41 revealed that BT interacts with the silanol group on the MCM-41 surface rather than the Pt surface. Therefore, we concluded that the high HDS activity of Pt/ MCM-41 catalyst could be attributed to the high hydrogenation activity of Pt and the acidity of the support.