Effects of Nd-modification on the activity and SO2 resistance of MnOx/TiO2 catalysts for low-temperature NH3-SCR

Abstract

MnO_x/TiO₂ (MnTi) and Nd-modified MnO_x/TiO₂ (MnNdTi) were prepared via a coprecipitation method. The used samples were obtained by exposing the fresh catalysts to 50 ppm SO₂ stream at 210 °C for 3 h and 6 h, respectively. Comparative investigations were performed on the fresh and used catalysts to identify the nature of improvement effects. As a result, the addition of Nd could improve the low temperature SCR activity of MnO_x/TiO₂ due to the enhanced redox property and more surface active species. SO₂ resistance tests revealed that MnTi was deactivated quickly in 3 h, while MnNdTi still retained 80% of NO_x conversion and deactivated in 6 h, implying that the SO₂ resistance of MnNdTi was greatly enhanced. The main reason for the improvement of the SO₂ resistance of MnNdTi was that the sulfation of the Mn active species was inhibited by the preferential reaction between SO₂ and NdO_x.