Development of Acidity on Sol-Gel Prepared TiO2-SiO2 Catalysts

Three different TiO2-SiO2 gels (Xerogel, Carbogel and Aerogel) are more active acid catalysts than other reference samples used here. As deduced from FTIR, XRD and XANES studies, the structural properties of these gels are quite different to each other, thus revealing the strong influence of the drying treatment. It is found that the degree of Si-O-Ti linking and the surface acidity follows the same trend (X 〉 C 〉 A). We conclude that supercritical drying at 600 K and 190 bars can induce Ti leaching followed by redeposition in the narrower pores of the gel. These effects modify both the textural and surface chemical properties of the resulting material.