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

CeO 2 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 SO 2 resistance. Novel Cr doped CeO x catalysts were synthesized by solid phase method and used for NH 3 -SCR of NO x at middle-low temperature. The effect of Cr addition on the SCR performance and physicochemical properties of CeO 2 catalyst was investigated by activity test and characterizations. Among the tested catalysts, Cr(0.4)-CeO x catalyst exhibited excellent NO x removal efficiency, with >90% NO conversion within 180–300 °C, 100% NO conversion at 220 °C and outstanding SO 2 resistance at 240 °C under 100 or 600 ppm SO 2 . The characterizations results revealed that Cr modified CrCeO x 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)-CeO x catalyst followed Eley-Rideal mechanism and active –NH 2 was the major intermediate species. After sulfuration, Cr(0.4)-CeO x still exhibited excellent SCR activity due to the increase of Cr 6+ , Ce 3+ and O α concentration and the formation of Cr–O–Ce bond, new Brønsted acid site and more crystallized Cr 2 O 3 .