Journal of Thermal Analysis, Vol. 38 (1992) 2631-2638 THERMAL BEHAVIOUR OF HIGH SURFACE AREA V2Os/TiO2 CATALYSTS M. Turco 1, G. Bagnasco ~, L. Lisi ~and P. Ciambelli 2 1 DIPARTIMENTO DI INGEGNERIA CHIMICA, UNIVERSITA DI NAPOLI "FEDERICO II", P. LE TECCHIO 80125 NAPOLI, ITALY. 2 DIPARTIMENTO DI INGEGNERIA CHIMICA ED ALIMENTARE, UNIVERSITA DI SALERNO, 84084 FISCIANO (SA), ITALY Thermal analysis (TG and DTA) was employed for the characterization of V2Os/TiO2 catalysts supported on high surface urea TiO2. The results obtained are consistent with a uniform spreading of vanadium oxide on TiO2 surface for V205 content less than 15% by weight. The presence of V205 on the surface of TiO2 affects the anatase-rutile phase transition lowering the temperature at which it occurs. DTA measurements, performed on catalysts after many months from the preparation, show the appearance of an exothermic peak in the range 2g0~176 This signal has been related to the oxidation of V(IV) to V(V) on the catalyst surface. Catalysts characterization, performed by chemical analysis and FT-IR spectroscopy, has confirmed this interpretation. It has been suggested that a slow modification of the catalyst occurs, leading to an increase of the V(IV) content during the time. Keywords: high surface urea, V2Os/TiO2 catalysts Introduction V205/TiO2 systems are the most effective catalysts for selective catalytic reduction (S.C.R.) of nitrogen oxides with ammonia [1]. The best performances are obtained with catalysts having a V205 content not exceeding monolayer coverage [2]. Recent studies have shown that the interaction between V205 and TiO2 leads to the formation of vanadium oxide species having specific catalytic properties towards NO reduction [3-5]. John Wiley & Sons, Limited,Chichester Akad~miai Kiad6, Budapest