Promotion effect of Cr addition on the activity and SO2 tolerance of CeOx catalysts for the NH3-SCR at middle-low temperature

Abstract

CeO2 as selective catalytic reduction (SCR) catalyst has attracted wide attention due to its abundant surface acidity and excellent oxygen storage/release capacity. However, its further implication was hindered owing to insufficient catalytic activity and SO2 resistance. Novel Cr doped CeOx catalysts were synthesized by solid phase method and used for NH3-SCR of NOx at middle-low temperature. The effect of Cr addition on the SCR performance and physicochemical properties of CeO2 catalyst was investigated by activity test and characterizations. Among the tested catalysts, Cr(0.4)-CeOx catalyst exhibited excellent NOx removal efficiency, with >90% NO conversion within 180–300 °C, 100% NO conversion at 220 °C and outstanding SO2 resistance at 240 °C under 100 or 600 ppm SO2. The characterizations results revealed that Cr modified CrCeOx catalyst could effectively increase BET surface area, pore volume, surface acidity and redox capacity. In situ DRIFTS indicated that SCR reactions over Cr(0.4)-CeOx catalyst followed Eley-Rideal mechanism and active –NH2 was the major intermediate species. After sulfuration, Cr(0.4)-CeOx still exhibited excellent SCR activity due to the increase of Cr6+, Ce3+ and Oα concentration and the formation of Cr–O–Ce bond, new Brønsted acid site and more crystallized Cr2O3.