Preparation of titania-impregnated silica aerogels and their application to removal of benzene in air

Silica-titania aerogels were prepared by impregnating titanium tetraisoprop oxide modified with acetylacetone into a silica alcogel followed by supercr itical drying. The effects of the impregnation conditions, the supercritica l drying medium (ethanol, 2-propanol or CO2) and the calcination temperatur e on the homogeneity of the aerogel and the nature of the impregnated titan ia were investigated. Aerogels prepared in this way had large specific surf ace areas and maximum titanium contents of ca. 32 at%. Ethanol and CO2 drie d samples were homogeneous, but 2-propanol dried samples were inhomogeneous because of the extraction of impregnated titania. Ethanol and 2-propanol d ried samples contained anatase particles of < 10 nm agglomerated into clust ers of 100-300 nm size, whereas CO2 dried samples contained amorphous titan ia. Their application to the removal of benzene from air was attempted. Eth anol dried samples possessed excellent benzene adsorption capacities and th e adsorbate could be decomposed to CO2 by photocatalytic reaction.