TiO 2–SiO 2 mixed oxides prepared by a combined sol–gel and polymer inclusion method

Abstract

Titania–silica mixed oxides were prepared by the sol–gel method from tetraethylorthosilicate (TEOS) and titanium (IV) isopropoxide (TTIP) as precursors. This paper reports the preparation of mixed oxides of different composition, incorporating the biopolymer chitosan to the precursor mixed sol, producing a hybrid xerogel. Drying and calcining of this xerogel leads to the formation of inorganic networks of different structure with surface areas in the range of 305–524 m 2/g. The reactions were carried out with magnetic stirring (4 h) and under ultrasound (20 kHz, 180 W, 1 h) using a small amount of water, HCl as catalyst, and the solvent was 2-methoxyethanol, which has the ability to coordinate with TTIP and decrease its rate of hydrolysis. The materials obtained were characterized by Nitrogen physisorption, FTIR, XPS, XRD, 29Si-NMR, DTA-TGA thermal analysis, and TEM. It was found that an increase in chitosan concentration decreases the surface area and increases average pore diameter, and that ultrasound causes a finer and more homogeneous structure together with changes in the surface area.