Effect of Mn on selective catalytic reduction of NOx by NH3 from Rare earth tailings and mechanistic analysis

Abstract In order to obtain good performance of low temperature denitration catalyst, we modified manganese on rare earth tailings by impregnation method, and investigated the effect of manganese modification on the denitrification performance of rare earth tailings by X-ray diffraction, Brunauer-Emmett-Teller, Temperature program reduction, Temperature-programmed desorption of ammoniaand X-ray photoelectron spectroscopy characterisation methods. The results showed: The optimum amount of manganese-modified rare earth tailings was 5 mass fraction, and the denitrification efficiency reached up to 78 percent at 200 degrees centigrade. The addition of manganese resulted in the appearance of uniformly dispersed MnO x on the catalyst surface, and the new component interacted with iron and cerium in the minerals to promote the redox cycle and greatly enhance the redox capacity of the catalyst. It also increased the content of Fe 3+ and adsorbed oxygen on the surface, which led to the increase of Brønsted acid sites and the generation of more Mn 3+ and Mn 4+ , which promoted the selective catalytic reduction reaction, but the strong oxidizing ability of manganese resulted in the low selectivity of N 2 . From the in situ IR results, NO in the Mn-modified catalyst mainly participates in the reaction as monodentate nitrate to promote the SCR reaction, following the L-H mechanism.