Improved sulfur dioxide resistance of the Mn/Fe-PILC catalyst by the doping of ceria in the selective catalytic reduction of NO with NH3

Abstract

The yCe-xMn/Fe-PILC (x and y are the nominal weight percentages of Mn and Ce, respectively; x = 4.0 wt%, y = 2.0, 4.0, and 6.0 wt%) catalysts were prepared using the impregnation method. Physicochemical properties of the as-prepared materials were measured by means of the XRD, SEM, BET, TPR, XPS, TGA-DSC, and in situ DRIFTS techniques, and their catalytic activities for the selective catalytic reduction of NO with NH3 (NH3-SCR) at low temperatures were evaluated. The 4Ce-4Mn/Fe-PILC sample showed the highest NO conversion of 95% at 350 ℃ and better resistance to SO2 poisoning than the Ce-free 4Mn/Fe-PILC sample. The loading of ceria not only increased the concentrations of the active Mn4+ species and chemisorbed oxygen (Oads) species, but also improved redox ability of the 4Ce-4Mn/Fe-PILC sample. After sulfur dioxide poisoning, the concentrations of the active Mn4+ and Oads species in the ceria-loaded samples were decreased by less extents than those in the ceria-free sample. The in situ DRIFTS results further demonstrated that the doping of ceria increased the amount of the acid sites, enhanced the formation of NH3 intermediates (i.e., monodentate nitrite and bridging nitrate), and protected the main active Mn4+ species. Therefore, the samples containing ceria possessed better resistance to SO2 poisoning.