The influence of Lewis and Bronsted acid sites on the performance Of V2O5/TiO2 and V2O5-WO3/TiO2 catalysts in the total oxidation of o-dichlorobenzene was investigated. Catalytic activity of these materials resulted strongly affected by their acidic properties. The presence of Bronsted acid sites significantly increases the o-DCB conversion but also leads to the uncompleted degradation of chlorinated compounds, promoting the formation of partial oxidation products, as dichloromaleic anhydride. On the contrary, Lewis acid sites, acting as absorbing sites, promote the further oxidation of intermediates to CO and CO2, without any by-products desorption. Furthermore, the presence of water in the feed-stream was proven to decrease o-DCB conversion but also to play a positive role on process selectivity, increasing COx production. Plausible reasons for this effect are the reduction of Bronsted acid sites and the hydrolysis of anhydride during wet tests. (c) 2008 Elsevier B.V. All rights reserved.