Effects of Sm modification on biochar supported Mn oxide catalysts for low-temperature NH₃-SCR of NO

In this study, Samarium (Sm) modification over Mn oxide biochar (BC)-based catalysts was synthesized and the activity of low-temperature selective catalytic reduction with NH₃ (LT NH₃-SCR) of NO was measured. Varies in surface area and pore volume, structure, morphology, and surface chemistry of Sm-modified Mn/BC catalyst were investigated to analyze the effect of Sm on the physiochemical properties on catalyst. The Sm(0.2)-Mn/BC catalyst showed the highest NH₃-SCR activity with the NO conversion of 85% at 200 °C and best N₂ selectivity in a broad temperature range of 75–250 °C. Doping with Sm species, Mn⁴⁺ + Mn³⁺/Mnⁿ⁺ and O_α/O_β increased greatly, and the surface adsorbed oxygen were enhanced in Sm(0.2)-Mn/BC catalyst, which could promote the oxidation of NO, the NO conversion and N₂ selectivity. In addition, weak and medium acid increased markedly after the Sm species added on catalysts, causing more active sites for SCR reaction. The NH₃-SCR reaction of Sm(0.2)-Mn/BC catalyst followed the L-H mechanism, and the generation of intermediate –NH₂, NH₄⁺ species and the N_xO_y species were observed which played vital part in the LT NH₃-SCR reaction.