Sm-modified Mn-Ce oxides supported on cordierite as monolithic catalyst for the low-temperature reduction of nitrogen oxides

Abstract

Nitrogen oxides (NOx) are typical atmospheric pollutants that harm the environment and human body, and selective catalytic reduction (SCR) with NH3 is one of the most effective technologies to deal with NOx emissions at present. In this work, a monolithic catalyst, Sm-modified Mn-Ce composite oxides (Sm-MnCe) supported on cordierite (CC), is prepared by impregnation for the first time, and their denitration (de-NOx) performance in NH3-SCR reaction is evaluated in detail. The results show that 0.1Sm-MnCe/CC (Sm/Mn mole ratio is 0.1) has the best de-NOx efficiency with above 80 % NOx conversion from 60° to 270°C, and the high NOx conversion can be maintained within 15 h in the presence of 100 ppm SO2. It is found that appropriate introduction of Sm increases the specific surface area and acid sites, improves the redox environment, elevates the content of Mn4+ on the catalyst surface, which are conducive to the improvement of catalytic activity. In addition, the interaction between active components (Sm, Mn and Ce) also plays a positive role for the excellent de-NOx activity. It is revealed by in-situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) that the NH3-SCR reaction over the 0.1Sm-MnCe/CC catalyst follows Eley-Rideal (E-R) and Langmuir-Hinshel (L-H) mechanisms. This work provides ideas for the preparation and modification of monolithic catalysts, which is conducive to promoting the practical industrial application of low-temperature SCR de-NOx technology.