Insights into the low-temperature NH3-SCR of NO performance and mechanism over manganese tailings-derived catalyst

Abstract

Manganese carbonate ore is ascertained as the most abundant manganese ore in China, while its mining and beneficiation generated a large amount of manganese tailings which is regarded as a hazardous waste. Owing to great catalytic performance of manganese oxides, it is double-benefit to employ manganese tailings as catalyst to eliminate harmful nitrogen oxides from flue gas. In this study, the effects of calcination temperature on the low-temperature denitration performance and physicochemical properties of manganese tailings were systematically investigated via XRF, XRD, XPS, H2-TPR, NH3-TPD and DRIFTS, aiming at exploring the effective utilization of manganese tailings. The results revealed the best catalytic activity can be obtained at a calcination temperature of 500 °C with over 95 % NO conversion attained in the denitration temperature range of 75–225 °C. Lower calcination temperature led to the incomplete decomposition of MnCO3, while higher calcination temperature led to the decrease in specific surface area, surface acidity and oxidation performance. The denitration reaction was followed by Eley-Rideal pathway, in which the absorbed NH3 species was reacted with the gaseous NO and NO2. Based on the results in this study, the effective utilization of manganese tailings for NO emission reduction could promise for wide applications.