Excellent low temperature NH3-SCR and NH3-SCO performance over Ag-Mn/Ce-Ti catalyst: Evaluation and characterization

Abstract

Low temperature SCR has been a promising technology due to the diverse load in coal-fired plants. However, ammonia escape problem could be more serious at low temperature on account of the condensation of NH4HSO4, resulting in deactivation of SCR catalyst and equipment corrosion. NH3-SCO technology could oxidize slip ammonia to harmless N2. Hence, it is important to develop a novel catalyst with high SCR and SCO efficiency at low temperature to remove NOx and slip NH3 and achieve the stable operation of SCR system. In this work, a combined sol-gel and impregnation method was used to synthetize different Aga−Mn/Ce-Ti (a = 2%, 5%, 8%) catalysts and applied in NOx and slip NH3 removal at low temperature. The activity measurement confirmed that Ag5-Mn/Ce-Ti catalyst exhibited an excellent low-temperature performance. At 150–300 °C, its NO conversion was 100%, NH3 conversion was above 95% and N2 selectivity was more than 90%. Moreover, considering the oxidation of slip ammonia, Ag5-Mn/Ce-Ti catalyst also exhibited above 90% NH3 conversion at 200–350 °C in the absence of NO. The catalytic performance could also be kept at a high level under the existence of SO2 and H2O. The characteristic results revealed that Ag and Mn modification could not apparently change the phase structure and could decrease the BET area to some extent. In addition, Ag-Mn/Ce-Ti catalyst possessed stronger and more surface acidic sites and contributed to better NH3 adsorption capacity. Besides, there was more chemisorbed oxygen on Ag-Mn/Ce-Ti catalyst resulting from the interactions among Ag, Mn and Ce oxides, which was responsible for its better redox property.