Cu/zeolite catalysts have been prepared by wet impregnation and characterized by N-2 physisorption, EPR, H-2-TPR and NH3-TPD methods. The Cu content was varied to optimize the loading as well as surface acidity. Optimized Cu/zeolite catalysts showed high surface acidity and excellent activity in the selective catalytic reduction (SCR) of NO with NH3. Furthermore, Cu/zeolite catalysts showed high SCR activity even after doping with potassium (0-500 mu mol/g) compared to a commercial vanadium catalyst which deactivated at lower potassium content. Fresh and deactivated catalysts were further examined to investigate the redox and acidic properties of the catalysts. The poisoning resistivity seems to be due to a combination of high surface area and strong acidity of the Cu/zeolite catalysts. The catalysts might be attractive alternatives to conventional catalysts for deNO(x) of flue gases from biomass fired power plants and other stationary industrial installations. (c) 2010 Elsevier B.V. All rights reserved.