CREATION OF HIGHLY ACTIVE NOBLE METAL HDS CATALYSTS SUPPORTED ON UNIFORM MESOPOROUS MATERIALS AND MECHANISM FOR HIGH ACTIVITY APPEARANCE

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The order of noble metals (NM) supported on mesoporous silica MCM-41 for the hydrodesulfurization (HDS) of thiophene at 350℃ was Pt.>Pd>Rh.>>Ru. This order is related to that of n-butane selectivity in the products of thiophene HDS reaction. This result indicates that hydrogen is activated on NM to form spillover hydrogen.On the other hand, thiophene is activated on acid site (silanol group, Si-OH) on MCM-41. The spillover hydrogen formed on NM attacks the thiophene molecule activated on acid site of MCM-41 in the HDS of thiophene. It was suggested that high dispersion of NM on MCM-41 to form spillover hydrogen and the enhancement of surface acidity of MCM-41 is very important to develop highly active NM/MCM-41-based HDS catalysts. The surface modification of MCM-41 with metal oxides (MOx), especially alumina, was performed to enhance the acidity of MCM-41 and the dispersion of MCM-41. The catalytic activity of Pt supported on Al_2O_3-modified MCM-41 (Pt/Al_2O_3-MCM-41) was remarkably higher than that of Pt/MCM-4l. In this research program, new highly active Pt/Al_2O_3-MCM-41 HDS catalysts was developed for HDS of organic sulfur compounds in the petroleum feedstocks.