Catalytic properties of CuO/CeO2-Al2O3 catalysts for low concentration NO reduction with CO

Abstract

Cu/CeAl catalysts with different Ce/Al molar ratios were prepared for low concentration NO removal by CO in the presence of O2 and SO2. The flash and used catalysts were characterized by XRD, BET, XPS, H2-TPR, CO-TPD, NO-TPD, in situ DRIFTS and catalytic properties for NO + CO model reaction. Cu/CeAl catalysts with appropriate ceria doping contents showed excellent catalytic performance and superior resistance to O2 and SO2. Ceria was conducive to reduce the active temperature and improve N2 selectivity. Cu/Ce0.1Al catalyst had stable NO conversion over 90% within the temperature range from 330 °C to 650 °C. After incorporation of Ce4+, CeO2 replaced Al2O3 and gradually became the major phase structure in XRD, specific surface area and pore volume decreased with Ce content increasing. Based on XPS analysis, the synergistic interaction of Ce3+ + Cu2+ ↔ Ce4+ + Cu+ was beneficial to generate oxygen vacancies, improving the reducing property and adsorption capacity. Therefore, the reduction temperature in H2-TPR and desorption temperature in TPD both shifted to low temperature. Moreover, the characterizations of used Cu/Ce0.1Al-A catalyst were almost unchanged with flash catalyst. The reaction over Cu/Ce0.1Al catalyst was an Eley-Rideal (E-R) mechanism according to the CO and NO co-adsorption in situ DRIFTS results.