Gas-phase photo-oxidation of toluene using nanometer-size TiO2 catalysts

A modified sol–gel process was used to prepare nanostructured TiO2 catalysts of controlled particle size (i.e. 6, 11, 16 and 20 nm). The influence of the TiO2 particle size in the gas phase photocatalytic oxidation of toluene was investigated under both dry and humid conditions. The main products of reaction were carbon dioxide and water, although small amounts of benzaldehyde were also detected. The smaller particle size (i.e. 6 nm) lead to higher conversion and complete mineralization of toluene into CO2 and H2O. Both electronic and structural effects (i.e. size and ensemble effects) are responsible for the excellent performance of 6 nm TiO2 catalyst for toluene photo-degradation. The structural differences between 6 nm TiO2 and larger catalysts were analyzed using EPR spectroscopy.