Activation Mechanism of Hydrogen and Organosulfur Compounds over Supported Noble Metal Hydrodesulfurization Catalysts

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The order of noble metals (MM) supported on mesoporous silica MCM-41 for the hydrodesulfurization (HDS) of thiophene at 350℃ was Pt>Pd>Rh>>Ru. This order is corresponded to that of n-butane formation in the HDS of thiophene, indicating that hydrogen is activated on MM to form spillover hydrogen.On the other hand, thiophene is activated on silanol groups (Si-OH) on MCM-41. The spillover hydrogen formed on NM attacks the thiophene molecule activated on MCM-41 in the HDS of thiophene. These results suggested that the high dispersion of NM on MCM-41 to form spillover hydrogen and the enhancement of surface acidity of MCM-41 is important in order to design highly active NM/MCM-41 catalysts for the HDS reaction. The surface modification of MCM-41 with alumina was performed to enhanced the acidity of MCM-41 and the NM dispersion on MCM-41. The catalytic activity of NM, especially Pt, supported on Al_2O_03 modified MCM-41 (Pt/Al_2O_3-MCM-41) for the HDS of thiophene was remarkably higher than Pt/MCM-41. In this work, new highly active Pt/Al_2O_3-MCM-41 catalyst has been successfully developed for the HDS of organosulfur compounds contained in the petroleum feedstocks.