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

吸附在载体内表面的各种过渡金属化合物的光化学活化有望成为制备高分散、高稳定性催化剂的一种有前途的方法。本研究以TiCl4、MoCl5、VoCl3为载体，考察了该方法制备高分散锚定氧化物催化剂的优势及其光催化活性，特别是首次利用Vycor玻璃表面羟基与光化学活化的VoCl3分子反应制备了高分散锚定氧化钒催化剂。与常规浸渍法制备的钒氧化物相比，目前的光化学方法制备的固载氧化钒对2-丁烯的光催化异构化反应具有更高的活性，磷光产率也更高。光催化异构化反应产率与表面钒物种的电荷转移激发三态磷光产率之间存在良好的线性关系，表明表面钒物种不仅在氧化钒催化剂上的光催化反应中起重要作用，而且吸附化合物的光化学活化方法比浸渍法制备的金属氧化物分散度更高，从而使其具有更高的光催化活性。

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.