Photocatalytic Degradation of Toluene in the Gas Phase : Relationship between Surface Species and Catalyst Features

Photocatalytic activity of com. and home-made samples was tested for gaseous toluene degrdn. using 2 irradn. sources, UV and solar. Humidity effect on toluene degrdn. is discussed. Catalyst deactivation (due to high toluene concn. [1000 ppm]) and subsequent regeneration, by water washing, were analyzed. Highest degrdn. and corresponding kinetic consts. were achieved for anatase/brookite composite samples; com. catalysts (including P25 Degussa) exhibited lower efficiency. Various adsorbed arom. species (benzoic acid [the major surface product], hydroquinone, benzylic alc., benzaldehyde, cresols) obtained by washing exhaust catalysts were analyzed by HPLC. Parallel results were achieved by Fourier transform IR attenuated total reflectance (FTIR-ATR) spectroscopy. The presence of different photodegrdn. surface species for the various photocatalysts suggested the occurrence of different reaction pathways, depending on fine physicochem. features of specific TiO2 adopted in the reaction.