In this work the activity and deactivation of optimized titania nanoparticles (TNPs) as photo-catalyst for the abatement of mixtures of important volatile organic compounds (VOCs): ethylene, propylene, toluene has been investigated. The TNPs photo-catalyst was synthesized in a vortex reactor by means of a sol-gel process with controlled operating parameters and was optimized by controlling the calcination time and temperature. These optimized TNPs were used in powder, thin film, pellets and in honeycomb shapes. The conversion results were compared with those of the individual pollutants in order to conduct a mechanistic analysis also on the basis of a simple kinetics assessment. The TNPs photo-catalyst performance was also compared with that of the commercially available Degussa P25 TiO2. The effects of temperature and moisture content were investigated on both the adsorption and on the catalytic conversion of the individual VOCs and their mixture in order to define the optimal operating conditions to adopt. Adsorption phenomena were found to control the performance of the photo-catalyst, especially when VOC mixtures were treated. Furthermore, deactivation of the TNPs and Degussa P25 photocatalysts was investigated by means of FT-IR characterization of these photocatalysts after activity tests of the individual VOCs and their mixture. Different by-products, adsorbed on the active sites of the photocatalysts, polyethylene/polypropylene, aldehydes, carboxylic acids, alcohols and adsorbed toluene itself were found to be responsible for the deactivation of the catalysts as a function of the catalyst operating conditions. (C) 2011 Elsevier B.V. All rights reserved.