Mechanistic and performance insights into low-temperature NH3-SCR based on Ce-modified Mn-Ti catalysts

Abstract

In this study, Mn-Ti supported Ce catalysts (derived from manganese tailings) were synthesized by coprecipitation method. The denitration performance and SO2 resistance of the catalysts were investigated. The results showed that introducing Ce oxides into Mn-Ti catalyst improved the low temperature catalytic performance, with almost 100% NO conversion at 225 °C. Additionally, the N2 selectivity was improved due to the decrease in lattice oxygen. The modified catalyst also presented excellent SO2 resistance, with around 80% NO conversion after 10 h of SO2 injection. The modified catalyst had higher ratios of Mn4+ and Mn3+ species, stronger surface acidity, and more redox properties than the Mn-Ti catalyst, which improved NH3-SCR performance. After SO2 poisoning, the surface Lewis acidity decreased and the surface Brønsted acidity became stronger, indicating that the loss of Lewis acidity might cause the decrease of NO conversion. Moreover, the nitrate species on Mn-Ti catalyst were less than those on Mn-Ce-Ti catalyst in the presence of SO2, suggesting that doping Ce into Mn-Ti catalyst retained more oxidation performance after being poisoned by SO2.