2009 Volume 52 Issue 2 Pages 42-50
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/Al2O3 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 H2S 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/SiO2 catalyst, with similar Pt dispersion on MCM-41, showed low activity which decreased with time on stream. Since MCM-41 showed higher acidity than SiO2, hydrogenation activity and sulfur tolerance of Pt/MCM-41 catalyst were higher than those of Pt/SiO2 catalyst. The results of FT-IR analysis indicated that the strength of interaction between BT and MCM-41 was stronger than that of SiO2, 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.