An investigation of trichloroethylene photocatalytic oxidation on mesoporous titania-silica aerogel catalysts

Freestanding blocks of mesoporous, titania-silica aerogel catalyst were prepared and tested for gas phase photocatalytic oxidation of trichloroethylene (TCE) in a new photoreactor where the reactant gases flow through the aerogel block. The intimate contact between the reactants and catalyst resulted in a higher conversion. TS01 aerogel was prepared by ethanol supercritical drying, and contained nanometer-sized crystalline domains of anatase TiO2 (i.e., TiOTi sites) within an amorphous SiOTi and SiOSi network. The TS02 aerogel prepared by CO2 supercritical drying remained amorphous even after high temperature treatment, and analysis indicated that the TiOSi is the predominant site on this catalyst. The reaction results indicated that only the TS01 aerogel containing anatase TiO2 was active, but the formation of dichloroacetaldehyde on the amorphous SiOSi sites led to a rapid catalyst deactivation. However, a stable catalyst was obtained after these sites were passivated by ozone pretreatment under ultraviolet (UV) irradiation. The TS01 aerogel catalysts exhibited an average conversion of 30% and a quantum yield of 0.27 at a TCE concentration of 56 ppm, feed flow rate of 40 sccm and UV irradiation of 710 μW cm−2.