Preparation of mesoporous TiO2 by the sol-gel method assisted by surfactants

Mesoporous titania was obtained by gelation of tetraisopropyl orthotitanate in aqueous or alcoholic solutions with addition of a cationic or anionic surfactant. The gels were dried and calcined to obtain the oxides. The dried samples and the oxides were characterized by thermal analysis, N₂- adsorption measurements, infrared spectroscopy, X-ray diffraction and titration with n-butylamine. The effect of the type of surfactant, the chain length of the surfactant and the synthesis method on the textural and surface characteristics of the oxides obtained has been investigated. Cationic surfactants such as dodecyltrimethylammoniumbromide and cetyltrimethylammoniumbromide are effective in controlling the pore size and in increasing the pore volume and the surface area. On the contrary, the sodium dodecylsulphate employed as an anionic surfactant is not incorporated to the hydrous titanium oxide network. The use of a surfactant in the preparation enhances the acid strength of the surface sites of the titanium oxide formed.