The effect of tungsten and barium on the thermal stability Of V2O5/TiO2 catalyst for NO reduction by NH3 was examined over a fixed bed flow reactor system. The activity of V2O5/SUlfated TiO2 catalyst gradually decreased with respect to the thermal aging time at 600 degrees C. The addition of tungsten to the catalyst surface significantly enhanced the thermal stability Of V2O5 catalyst supported on sulfated TiO2. On the basis of Raman and XRD measurements, the tungsten on the catalyst surface was identified as suppressing the progressive transformation of monomeric vanadyl species into crystalline V2O5 and of anatase into rutile phase of TiO2. However, the NO removal activity Of V2O5/sulfated TiO2 catalyst including barium markedly decreased after a short aging time, 6 b at 600 degrees C. This may be due to the transformation of vanadium species to inactive V-O-Ba compound by the interaction with BaO which was formed by the decomposition of BaSO4 on the catalyst surface at high reaction temperature of 600 degrees C. The addition of SO2 to the feed gas stream could partly restore the NO removal activity of thermally aged V2O5/sulfated TiO2 catalyst containing barium. (c) 2005 Elsevier B.V. All rights reserved.