Ultrahighly Dispersed Titanium Oxide on Silica : Effect of Precursors on the Structure and Photocatalysis

Abstract
The effect of precursor on the dispersion and catalytic performance of titanium oxide supported on silica has ben investigated. The catalysts were prepared by a simple impregnation method with three kinds of titanium complexes of different ligands (bis(isopropyato)-bis(pivaroylmethanato) : DPM, acetylacetonato : ACAC, tetrakis(isopropylato) : IPRO) with the aim of preparing ultrahighly dispersed titanium oxide on silica. The XAFS study revealed that titanium species in the catalyst prepared from the complex with DPM ligand was a mononuclear species of an almost regular tetrahedral TiO₄. The species prepared from the complex with ACAC ligand was also mononuclear but the titanium ion was coordinated by five oxygen atoms. The complex with IPRO ligand resulted in preparation of a catalyst containing some aggregated titanium species. These catalysts exhibited a remarkable difference in photooxidation of propane.