The influence of preparation method on the physicochemical properties of titaniasilica aerogels: part two
Faculty of Sciences. Chemistry
Boston, Mass. :Kluwer Academic
Journal of porous materials. - Boston, Mass.
, p. 541-549
University of Antwerp
Titaniasilica aerogels with different titania content were prepared. Four preparation methods differing mainly in approach to precursors hydrolysis were applied, while only three of them allowed total hydrolysis of silica precursor before titania precursor was added. The preparation of mixed products of titania and silica hydrolysis precursors containing gels was followed by high temperature supercritical drying (HTSCD) and thermal treatment at 500 °C. Obtained mixed oxides in form of aerogels were characterized by BET surface areas up to 1000 m2/g, mesopore volumes up to 1.6 cm3/g and bulk densities as low as 0.04 g/cm3. Even 18 h lasting aging did not allow to produce narrow diameter range mesoporous materials, their broad pore diameter distributions resulted in average pore sizes varying from 10 to nearly 30 nm. XRD measurements proved the presence of anatase crystalline form of titania, while silica was present in amorphous form. SEM studies indicated presence of isolated titania particles on titaniasilica surface while joint hydrolysis method was applied. Titaniasilica aerogels obtained by the simultaneous hydrolysis of precursors and the impregnation method showed high photocatalytic activity in degradation of salicylic acid in water. Activities of these mesoporous photocatalysts were higher than commercial P25 Degussa TiO2. Comparison of activity of pure TiO2 (P25 Degussa) and aerogels indicates higher utilization of titania present in mesoporous mixed oxides.