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

The y Ce- x Mn/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 NH 3 (NH 3 -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 SO 2 poisoning than the Ce-free 4Mn/Fe-PILC sample. The loading of ceria not only increased the concentrations of the active Mn 4+ species and chemisorbed oxygen (O ads ) species, but also improved redox ability of the 4Ce-4Mn/Fe-PILC sample. After sulfur dioxide poisoning, the concentrations of the active Mn 4+ and O ads 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 NH 3 intermediates (i.e., monodentate nitrite and bridging nitrate), and protected the main active Mn 4+ species. Therefore, the samples containing ceria possessed better resistance to SO 2 poisoning.