CeO2 grafted with different heteropoly acids for selective catalytic reduction of NOx with NH3

Abstract

The CeO2 catalysts grafted with heteropoly acid (i.e., HPA) could enhance their catalytic performance for selective catalytic reduction of NOx with NH3 (NH3-SCR). In comparison to HSiW/CeO2, HPMo/CeO2, and commercial V2O5-WO3/TiOx catalysts, HPW/CeO2 catalysts showed the best SCR performance. XPS and DRIFTS demonstrated that the amount of HPA on HPW/CeO2 was more than those on HSiW/CeO2 and HPMo/CeO2. H2-TPR results indicated that reducibility of HPMo/CeO2 was stronger than those of HSiW/CeO2 and HPW/CeO2, resulting in the high-temperature performance loss. According to kinetic results, below 250 °C, kSCR-ER and kSCR-LH of HPW/CeO2 were higher than those of HSiW/CeO2, meanwhile kside of both HSiW/CeO2 and HPW/CeO2 were low. Therefore, HPW/CeO2 had the better SCR performance than HSiW/CeO2. As NH3 was completely consumed, SCR activity depended on the ratio of SCR reaction in the consumption of NH3. The selectivity of SCR reaction, NSCR reaction, and C–O reaction of HSiW/CeO2 were almost the same as those of HPW/CeO2 above 250 °C, resulting in the NOx conversion of HPW/CeO2 was basically the same as that of HSiW/CeO2 above 250 °C. Due to the lowest kSCR-ER and kSCR-LH, and highest kside, NOx conversion of HPMo/CeO2 was the worst compared to HSiW/CeO2 and HPW/CeO2 catalysts.