LAUSR

Abstract Currently, selective catalytic reduction (SCR) of NOx with NH3 in the presence of alkali metal ions by using vanadium-free catalysts is still a big challenge for the removal of NOx for stationary sources. In this work, improved reduction of NOx with NH3 in the presence of alkali metal ions over novel Fe-doped manganese oxide octahedral molecular sieve (OMS-2) catalysts has been demonstrated and the promotional effects of Fe have been clarified. The Fe-doped OMS-2 (Fe-OMS-2) catalysts exhibited excellent NH3-SCR activity, improved N2 selectivity and enhanced alkali resistance. The X-ray absorption fine structure spectroscopy (XAFS) results indicated that the trapped K+ ions could make the catalyst structure more stable. In situ diffuse reflectance infrared transform spectroscopy (in situ DRIFTs) results revealed that the Fe doping could enhance adsorption of NH3 species and adsorb various types of NOx species namely monodentate nitrate, bridged nitrate, bidentate nitrate and chelating nitrite. These formed intermediates on the Fe-OMS-2 catalysts were more reactive and thus more effectively participated in the SCR reactions. Superior alkali resistance of the Fe-OMS-2 catalysts was due to improved redox species, more acid sites and stronger adsorption of NOx species. The present investigations in this work may lead to an alternative development of high-performance non-vanadium catalysts for alkali-resistant NOx reduction.