Active and Stable Supported MnO <i> _x </i> -CeO <i> _x </i> Mixed Oxide Catalysts for Low-Temperature NH ₃ -SCR-DeNO <i> _x </i>

The influence of the composition of MnOx-CeOx catalysts for low-temperature NH3-SCR-DeNOx supported on TiO2 doped with different contents of SiO2 on the conversion of NOx, the yield of N2O, and the stability in the presence of SO2 and water were investigated. The dual redox cycle of MnOx and CeOx shifts the reduction temperature obtained by TPR-H2 and the conversion of NOx during NH3-SCR-DeNOx to lower temperatures by roughly 25 K for MnOx-CeOx/TiO2-4SiO2 with nMn/nCe = 4 compared to MnOx/TiO2-4SiO2. Above 473 K, the increased redox abilities cause an increased oxidation of NH3 and formation of N2O. Doping the support with SiO2 suppresses the oxidation of NH3 to N2O above 573 K with no significant influence on the conversion of NOx in the absence of water. Water adsorption at 433 K reveals that the addition of 4.4 wt % SiO2 reduces the water uptake by about 70% compared to the pure TiO2 support, leading to improved resistance toward water poisoning during NH3-SCR-DeNOx. The protective effect of CeOx for MnOx in the presence of SO2 results in a highly active and stable low-temperature NH3-SCR-DeNOx catalyst for exhaust gas treatment in stationary power plants.