VOC's abatement: Photocatalytic oxidation of toluene in vapour phase on anatase TiO₂ catalyst

Photocatalytic oxidation of toluene has been carried out in a gas-solid regime by using polycrystalline anatase TiO₂. A fixed bed continuous photoreactor of cylindrical shape was used for performing the photoreactivity runs; the Pyrex glass photoreactor was irradiated by a medium pressure Hg lamp. Air containing toluene and water vapours in various molar ratios was fed to the photoreactor. Toluene was mainly photooxidised to benzaldehyde although benzene, benzyl alcohol and traces of benzoic acid and phenol were also detected. The presence of oxygen was essential for the occurrence of the photoreaction while water played an important role in the maintainance of the catalytic activity. The results obtained in a preliminary Fourier transform infrared (FT-IR) investigation indicate that toluene is weakly stabilised on the TiO₂ particles by hydrogen-bonding between the aromatic ring and surface hydroxyl groups.