Preparation of Highly Dispersed Anchored Catalysts by Photochemical Activation of Adsorbed Species and Their Photocatalytic Activities

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Photochemical activation of various transition metal compounds adsorbed on innert support surfaces is expected to be a promising method to prepare highly dispersed welldefined catalysts. In this research, the advantage of this method to prepare the highly dispersed anchored oxide catalysts and their photocatalytic activities have been investigated for the systems of TiCl_4, MoCl_5, and VoCl_3 adsorbed on porous Vycor glass.Especially, highly dispersed anchored vanadium oxide catalysts have been first prepared by using facile reaction of the photochemically activated VoCl_3 molecules with surface OH groups on Vycor glass. Anchored vanadium oxides prepared by the prepsent photochemical method exhibit a higher activity for the photocatalytic isomerization reaction of 2-butene and much higher yields in the phosphorescence, as compared with those obtained for the vanadium oxides prepared by conventional impregnation method. A good linear relationship between the yields of photocatalytic isomerization and the yields of phosphorescence from the charge transfer excited triplet state of the surface vanadyl species in tetrahedral coordination is obtained, indicating that not only the surface vanadyl species paly a significant role in the photocatalytic reaction on vanadium oxide catalysts, but also a photochemical activation method of adsorbed compounds leads to the higher photocatalytic activity due to their higher dispersion of metal oxides than impregnation method.