Control of the Texture of Titania−Silica Mixed Oxides Prepared by Nonhydrolytic Sol−Gel

Abstract

A series of titania−silica xerogels was prepared using nonhydrolytic sol−gel routes. The parameters explored were the nature of the oxygen donors (alkoxides or diisopropyl ether), the amount of liquid phase in the gel, the titanium content, the reaction time, and the reaction temperature. The samples were characterized using FT-Raman, FTIR, and DRUV−Vis spectroscopy, XRD, TGA, and N2 physisorption. Spectroscopic data indicated a molecular scale dispersion of the Ti atoms. The titania−silica nonhydrolytic xerogels were mesoporous with specific surface areas up to 1040 m2 g-1 and pore volumes up to 1.53 cm3 g-1. The mesoporous texture of the xerogels is ascribed to the high degree of condensation of nonhydrolytic gels, which prevents complete pore collapse during the evaporation of solvent. The average pore diameter could be adjusted in the 2−6 nm range by changing the volume fraction of liquid phase, reaction time, or reaction temperature.