Kinetic and in situ infrared spectroscopic studies were conducted during the investigation of the effect of methyl-naphthalene (mNpht) on the oxidation of meta-dichlorobenzene (m-DCB) over a 3.6 wt.% V2O5/TiO2 catalyst. A gradual decrease in the conversion of m-DCB was observed with time on stream in the presence of mNpht. This deactivation was more pronounced at lower temperatures and higher mNpht inlet concentrations. The results Of ill Situ FTIR studies indicate the accumulation of carbonaceous species oil the catalyst surface. The catalyst can regain its activity towards the oxidation of m-DCB upon removal of mNpht from the reaction gas mixture. The rate of regeneration depends oil temperature and the amount of carbon accumulated on the catalyst surface. (C) 2004 Elsevier B.V. All rights reserved.