Copper and chrome oxide were co-impregnated on mordenites and characterized by XRD, ESR, and H-2-TPR. The catalysts, subjected to a H-2/O-2 redox cycle at 500 degrees C and 750 degrees C, were examined for combustion of methane and acetone, and for NO decomposition. An easily reducible Cr-Cu oxide complex was formed by the addition of chrome oxide to copper oxide on the mordenites after the redox treatment (H-2/O-2) at 500 degrees C. However, the redox treatment at 750 degrees C transformed the oxide complex to copper chromate. No difference was found in the activity of NO decomposition between CuO/mordenite and CuO-Cr2O3/mordenite redox-treated at 500 degrees C. For both methane oxidation and NO decomposition, maximum activity appeared at CuO(7)-Cr2O3(7)/mordenite redox-treated at 750 degrees C, resulting in the formation of copper chromate. Dealumination also increased the activities, and the maximum activity appeared at a silica/alumina ratio of 20-30.