Characterization of Nb-Containing MnOx-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 NbOx-MnOx-CeO2 catalysts has been studied with coated cordierite monoliths in the temperature range of 150-450 degrees 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.