Unusual positive effect of SO2 on Mn-Ce mixed-oxide catalyst for the SCR reaction of NOx with NH3

A high-performance denitration catalyst based on Mn-Ce mixed-oxide derived from a specific Mn/Ce pre-cursorwas fabricated by solvothermal method. It exhibited outstanding low-temperature activity, which achieved above 90% NOx conversion in the temperature of 150-310 degrees C. Remarkably, Mn-Ce mixed-oxide demonstrated a much better SO2 tolerance, in which the NOx conversion increased from 92.6% to 97.8% at 150 degrees C after introducing 200 ppm SO2. The synthesized Mn-Ce mixed-oxide has a porous structure with abundant chemisorbed oxygen spices and exposed active sites. In addition, the increased acidity and redox capacity enhanced the catalytic activity after introducing SO2. Meanwhile, the injection of SO2 separates NH3 adsorption sites from oxidation agents, inhibiting the unwanted oxidization of ammonia to nitrogen oxides. Furthermore, the reaction pathway on Mn-Ce mixed-oxide proved to be the L-H mechanism based on in situ DRIFTS. Thus, the synthesized Mn-Ce mixed oxide demonstrated an excellent denitration performance and the especially high SO2 tolerance, showing great potential for low-temperature NH3-SCR.