Manganese-niobium mixed oxide catalyst for the selective catalytic reduction of NOx with NH3 at low temperatures

A series of manganese-niobium mixed oxide (Mn-Nb) catalysts were prepared by homogeneous precipitation method and tested for low temperature selective catalytic reduction of NOx with NH3 (NH3-SCR). These catalysts were characterized by N-2 adsorption, X-ray diffraction, H-2-TPR, X-ray photoelectron spectroscopy, NOx-TPD and NH3-TPD. Among the series of Mn-Nb catalysts, Mn2Nb1Ox calcined at 500 degrees C exhibited the best catalytic activity. MnOx had stronger redox capability than Mn2Nb1Ox, resulting in lower N-2 selectivity due to the unselective oxidation of NH3 at relatively high temperatures. The addition of Nb to MnOx enhanced the acidity, especially the Bronsted acidity, which is responsible for the low temperature SCR activity. The combination of MnOx with strong redox capability and NbOx with high acidity simultaneously led to high NOx conversion and N-2 selectivity over the Mn2Nb1Ox catalyst. (C) 2014 Elsevier B.V. All rights reserved.