The enhanced performance of a CeSiOx support on a Mn/CeSiOx catalyst for selective catalytic reduction of NOx with NH3

Abstract

A series of Mn/CeSiO_x catalysts were prepared by the wet impregnation method and used for selective catalytic reduction of NO with NH₃. As can be seen from the experimental results, the Mn/CeSiO_x catalyst with a Ce/Si molar ratio of 2/1 showed excellent low-temperature SCR activity, high N₂ selectivity and excellent SO₂ and H₂O tolerance. The relationship between the CeSiO_x support and the SCR performance of Mn/CeSiO_x (2 : 1) catalyst was investigated based on the characterization results of N₂ adsorption, XRD, XPS, H₂-TPR, NH₃-TPD and in situ DRIFT. The strong interaction between Ce and Si resulted in the good dispersion of Mn species on the support; correspondingly, the redox ability and NH₃ adsorption capacity were greatly enhanced. The results of in situ DRIFT study revealed that the NH₃-SCR reactions over Mn/CeO₂ and Mn/CeSiO_x (2 : 1) mainly obeyed both the E–R mechanism and the L–H mechanism. Furthermore, the formation of more Mn⁴⁺ and chemisorbed oxygen greatly facilitates the oxidation of NO to NO₂, as a result, promoting the low-temperature SCR performance of Mn/CeSiO_x (2 : 1).