The effect of SO2 addition on the oxidation of ethyl acetate, ethanol, propane and propene, over Pt/gamma -Al2O3 and Pt/SiO2 has been investigated. The reactants (300-800 vol, ppm) were mixed with air and led through the catalyst bed. The conversions below and above light-off were recorded both in the absence and in the presence of 1-100 vol. ppm SO2. For the alumina-supported catalyst, the conversion of ethyl acetate, ethanol and propane was promoted by the addition of SO2, while the conversion of propene was inhibited. The effect of SO2 was reversible, i.e. the conversion of the reactants returned towards the initial values when SO2 was turned off. However, this recovery was quite slow. The oxidation of propane was inhibited by water, both in absence and presence of SO2. For the silica-supported catalyst no significant effect of SO2 could be observed on the conversion of ethyl acetate, ethanol or propane, whereas the conversion of propene was inhibited by the presence of SO2. In situ FTIR measurements revealed the presence of surface sulphates on the Pt/gamma -Al2O3 catalyst with and after SO2 addition. It is proposed that these sulphate groups enhance the oxidation of propane, ethyl acetate and ethanol by creating additional reaction pathways to Pt on the surface of the Pt/gamma -Al2O3 catalyst. (C) 2001 Elsevier Science B.V. All rights reserved.