The selective catalytic reduction of NO by propene in the presence of excess oxygen has been studied over catalysts based on Co-Pt supported on ZSM-5. Pure Pt based catalysts are highly active, but produce large amounts of N2O. Bimetallic Co-Pt/ZSM-5 catalysts with low Pt contents (0.1 wt.%) show a synergistic effect by combining high stability and activity of Pt catalysts with the high N-2 selectivity of Co catalysts. The lower selectivity to N2O is attributed to its selective conversion over Co. The catalysts also showed high water and sulfur tolerance above 350 degreesC. (C) 2001 Elsevier Science B.V. All rights reserved.