Catalytic performance of Sn/Al2O3 catalysts prepared by impregnation (IM) and sol-gel (SG) method for selective catalytic reduction of NOx by propene under lean bum condition were investigated. The physical properties of catalyst were characterized by BET, XRD, XPS and TPD. The results showed that NO2 had higher reactivity than NO to nitrogen, the maximum NO conversion was 82% on the 5% Sn/Al2O3 (SG) catalyst, and the maximum NO2 conversion reached nearly 100% around 425 degreesC. Such a temperature of maximum NO conversion was in accordance with those of NOx, desorption accompanied with O-2 around 450degreesC. The activity of NO reduction was enhanced remarkably by the presence of H2O and SO2 at low temperature, and the temperature window was also broadened in the presence of H2O and SO2, however the NO, desorption and NO conversion decreased sharply on the 300 ppm SO2 treated catalyst, the catalytic activity was inhibited by the presence of SO2 due to formation of sulfate species (SO42-) on the catalysts. The presence of oxygen played an essential role in NO reduction, and the activity of the 5% Sn/Al2O3 (SG) was not decreased in the presence of large oxygen. (C) 2004 Elsevier B.V. All rights reserved.