Selective Catalytic Reduction of NO with NH3 over MnOx-CeO2-WO3-ZrO2: Effect of Calcination Temperature

MnOx-CeO2-WO3-ZrO2 catalysts were prepared by co-precipitation and calcined at various temperatures (500, 600, 700, and 800 C). The effect of calcination temperature on their performance in the selective catalytic reduction (SCR) of NO with ammonia in the presence of O-2 and H2O was investigated. The structural and physicochemical characterization of the catalysts were performed by N-2 adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), NH3 temperature-programmed desorption (NH3-TPD), and CO pulse reaction. The results show that the low temperature activity decreased with an increase in the calcination temperature, which is due to a decrease in the amount of surface chemisorbed oxygen and acid sites. As the calcination temperature increased the high temperature activity first increased and then decreased, which is contrary to the variation found for the most readily releasable oxygen on the catalyst surface. The catalyst calcined at 700 degrees C exhibited good low temperature activity and had the widest reaction temperature window. The light-off temperature (50% NO conversion) was 189 degrees C for this catalyst and the NO conversion was 80%-100% between 218 and 431 degrees C at a space velocity of 90000 h(-1).