TiO2/SiO2 photocatalysts at low levels of loading:: preparation, structure and photocatalysis

The effect of precursor on the dispersion and photocatalytic performance of titanium oxide supported on silica has been investigated. The catalysts were prepared by a simple impregnation method with three kinds of titanium complexes of different ligands (dipyvaroylmethanato (DPM), acetylacetonato (acac), isopropoxide (O-iPr)) abbreviated to D-TS, A-TS, and I-TS. The UV/Vis diffuse reflectance, Raman, XAFS spectroscopic study showed that surface titanate of D-TS is isolated TiO4 species, and that of I-TS is a mixture of rutile and anatase crystallites. The surface state of A-TS is the intermediate between D-TS and I-TS. TiO2/SiO2 samples were more active than bulk TiO2 and partial oxidation selectivity of TiO2/SiO2 samples are higher than that of TiO2 in photo-oxidation of propane. Products distribution over TiO2/SiO2 was drastically varied with the surface titanates. The activity for photo-assisted selective catalytic reduction (SCR) of NO with ammonia was found for D-TS. (C) 2002 Elsevier Science B.V. All rights reserved.