Sulfation of the 1%Pt-1%Sn/gamma-Al2O3 catalyst, resulted in an enhancement of the conversion of NO and C3H8 during the C3H8-NO-O-2 reaction. IR study showed the formation of bulk aluminum sulfate and surface tin sulfate. The presence of tin sulfate in the catalyst enhances C3H8 oxidation by probably conferring on Pt atoms a stronger partial positive charge than in the case of sulfated 1%Pt/Al2O3. The improvement of NO conversion on 1%Pt-1%Sn/gamma-Al2O3 is explained on the basis of the enhancement of NO oxidation to NO2 induced by Sn surface species over the catalyst. (C) 2002 Elsevier Science B.V. All rights reserved.