Improvement of SO2 resistance of Cu-SSZ-13 with polyoxometalates in selective catalytic reduction of NOx

Abstract

Nitrogen oxides (NOx) are harmful to the environment and human health. Cu-SSZ-13 catalyst plays a crucial role in selective catalytic reduction of NOx with NH3 benefiting from its good activity and structure stability. However, the sulfur resistance of Cu-SSZ-13 needs to be improved. Therefore, polyoxometalates (POMs) with strong acidity and strong oxidizing are chosen to enhance the catalytic performance of Cu-SSZ-13. Among them, Cu–CePW sample has better structural stability and the best NOx conversion rate over 95% between 250 and 450 °C and the best resistance to water vapor and SO2 up to about 90%. Besides, Ce and W species increases the amount of acid sites on the surface of sample especially at low temperature, and Ce species activates the Cu species in the catalyst and protects the active sites in the presence of SO2. Furthermore, Cu–CePW possesses both Lewis acid sites and Brønsted acid sites at the same time, and the reaction mechanism of Cu–CePW in NH3-SCR reaction involved both L-H mechanism and E-R mechanism.