INFLUENCE OF PREPARATION METHODS ON THE TEXTURE AND STRUCTURE OF TITANIA-SUPPORTED ON SILICA

Deposition of titanium over a silica support was performed by three methods: precipitation with TiCl4 and ammonium hydroxide in aqueous solution; impregnation with titanium(IV) isopropoxide in isopropyl alcohol; grafting with a solution of TiCl4 in hexane. Samples were characterized by BET, XPS, zeta potential, DRS, XRD, SEM and EPMA. The method of deposition influences deeply the morphology and dispersion of the coated oxide. With the precipitation method, TiO2 is deposited at the external surface of the silica. Impregnation provides the best external superficial dispersion of titania allowing the formation of small crystallites at its surface. The grafting method gives the best internal TiO2 dispersion with formation of large crystallites at the external surface of silica. A strong interaction is found between titanium and silicon. This work also draws attention to the many analytical techniques needed to characterize the TiO2-coated supports.