A series of different transition metals (V, Co, Cr, Mn, Fe, Ni, Cu and Zn) promoted H-ZSM-5 catalysts were prepared by impregnation method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The catalytic activity of these catalysts was evaluated for the selective catalytic reduction (SCR) of NO with NH3 as reductant in the presence of oxygen. The results revealed that the catalytic activity of Cu-ZSM-5 nanocatalyst for NO conversion to N-2 was 80% at 300 degrees C, which was the best among various promoted metals. Design of experiments (DOEs) with Taguchi method was employed to optimize NH3-SCR process parameters such as NH3/NO ratio, O-2 concentration, and gas hourly space velocity (GHSV) over Cu-ZSM-5 nanocatalyst at 250 and 300 degrees C. Results showed that the most important parameter in NH3-SCR of NO is O-2 concentration; followed by NH3/NO ratio and GHSV has little importance. The NO conversion to N-2 of 63.1% and 94.86% was observed at 250 degrees C and 300 degrees C, respectively under the obtained optimum conditions. (C) 2015 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.