Characterization of Nb-Containing MnO x −CeO2 Catalyst for Low-Temperature Selective Catalytic Reduction of NO with NH3

The reactivity in the selective catalytic reduction of the individual and binary components of NbO x −MnO x −CeO2 catalysts has been studied with coated cordierite monoliths in the temperature range of 150−450 °C. FTIRS, DRIFTS, TA, XRD, BET, and XAS have been used to elucidate the structural and catalytic properties. The results confirmed the contribution of the manganese oxides, particularly to the low-temperature NO-to-NO2 oxidation reaction. The significant increase of the surface acidity as a result of niobium oxide addition has been established. The data obtained revealed also the strong interaction between the manganese and niobium catalytic active sites. This phenomenon leads to a very good distribution of the oxidizing and acidic sites in the catalyst structure and also diminishes the unselective NH3 oxidation at higher temperatures. However, in order to keep the low-temperature catalytic activity, an excess of manganese relative to the niobium content is needed.