MnOx-CeO2 catalysts synthesized by solution combustion synthesis for the low-temperature NH3-SCR

MnOx-CeO2 catalysts with different compositions have been investigated as catalysts for low temperature SCR by preparing a series of samples by the Solution Combustion Synthesis (SCS) method. Variable amounts of two different organic fuels (glycine and citric acid) with respect to the stoichiometry of synthesis were investigated. The samples were characterized by XRD, BET, H2-TPR, XPS, FESEM and their catalytic activity tested for NOx abatement in the range of temperature of interest (120-350 °C). By varying the synthesis parameters it was possible to obtain catalysts different in terms of structure, morphology, specific surface area, Mn average oxidation state as well as superficial content of Mn, Ce and O atoms. These features were correlated with the resulting catalytic performances in the SCR reaction and compared to pure MnOx phases obtained through the same synthesis method. All the developed catalysts were considerably active in the temperature range investigated and could be considered suitable for the low-temperature SCR process. The sample with the higher content of manganese oxide obtained with glycine in below-stoichiometric amount showed the best performance in terms of NOx conversion and N2 yield, likely due to the high reducibility as well as the presence of Mn3O4 phase.