Investigation of Mn doped perovskite La-Mn oxides for NH3-SCR activity and SO2/H2O resistance.

[Display omitted] • Mn doped La-Mn oxides show excellent SCR activity and SO 2 /H 2 O resistance. • SCR activity decreases but N 2 selectivity increases in the presence of SO 2 /H 2 O. • Mn doping changes some of Mn3+ at B-site to Mn4+ and some at A-site to Mn2+. • The formation of sulfate increases acidity strength and improves N 2 selectivity. • After SO 2 /H 2 O resistance, decrease of Mn4+ and oxygen species weakens redox. A series of Mn doped perovskite La-Mn oxides were prepared and characterized systematically·NH 3 -SCR activity and the resistance to SO 2 and/or H 2 O were evaluated. The results showed that LM-1.4 catalyst displays excellent LT SCR activity and wide window (80% NO x conversion in 100–300 °C). In the presence of SO 2 and H 2 O, LM-1.4 catalyst can also achieve about 95% NOx conversion and N 2 selectivity in long-term testing and good SCR activity (above 80% NOx conversion in 145–300 °C) in the cycles. The Mn doped La-Mn oxides have S BET of 86 m2/g and V total of 0.27 cm3/g, but some Mn oxides do not enter the perovskite framework and form Mn 3 O 4 and MnO 2. Mn substituted A-site La ions in perovskite La-Mn oxides changes some of Mn3+ at the B-site in LaMnO 3 to Mn4+ and some at the A-site to Mn2+. Doping of Mn can change redox properties of perovskite La-Mn oxides, but after the resistance testing in the presence of SO 2 and H 2 O, the decrease of Mn4+ content and active oxygen species on the catalyst surface can weaken the redox properties of La-Mn oxides. Mn doping increases significantly the adsorption amount of NH 3 , but the formation of sulfate increases the strong acidity of the catalyst. Mn doping can also accelerate the decomposition of ammonium sulfate, resulting in an improvement of SO 2 -resistance. [ABSTRACT FROM AUTHOR]