ACIDITY STUDIES OF TITANIA SILICA MIXED OXIDES

A series of titania-silica mixed oxides were prepared by co-precipitation and sol-gel methods. The mole fraction of titanium was varied from 0 to 1. The effects of preparation method and chemical composition on the physical properties and acidity profiles of mixed oxides were examined. While pure silica was non-acidic and titania contained only Lewis acid sites, Bronsted acidity was created by the Ti-O-Si interaction in the binary oxides. Samples containing a titania : silica mole ratio of 9 : 1 possessed the largest amount of Bronsted acidity. The generation of acid sites and the stability of the oxide was a strong function of preparation method. With all preparation methods, higher calcination temperatures increased crystallinity and decreased the total number of acid sites.