Effect of WO3 content on the catalytic activity of CeO2-ZrO2-WO3 for selective catalytic reduction of NO with NH3

A series of CeO2-ZrO2-WO3 catalysts (CZW) was prepared by the hydrothermal method. The effect of WO3 content on their catalytic properties for selective reduction of NOx with NH3 was investigated. The catalysts were characterized by X-ray diffraction, N2 sorption, H2 temperature-programmed reduction, NH3 temperature-programmed desorption and NO temperature-programmed desorption techniques. It was shown that WO3 existed as amorphous species in the CZW. Introduction of WO3 in the CZW dramatically enhanced its surface acidity and gave rise to strongly adsorbed NO species, consequently increasing the catalytic activity. In addition, appropriate amounts of WO3 also increased the surface area and improved the reduction behavior of the catalyst. Compared to the CeO2-ZrO2, the CZW with 20% WO3 not only exhibited high resistivity to SO2, but also had a wider reaction temperature window. It showed a NOx conversion of > 90% at the space velocity of 60000 h−1 in the temperature range of 200–463°C.