Low-temperature SCR of NO with NH₃ over biomass char supported highly dispersed Mn–Ce mixed oxides

Series of catalysts with Mn–Ce mixed oxides loaded onto biomass char (BC) modified by nitric acid were prepared via impregnation method. And these catalysts were used for the selective catalytic reduction (SCR) of NO with NH₃. Mn–Ce (7:3)/BC catalysts with loading 6% (mass ratio) Mn–Ce oxides showed the best NO conversion ratio of 99.2% at 175 °C. The changes of the microstructure, phase composition, metal valence state and functional groups were investigated through SEM, BET, XRD, XPS and FT-IR. It showed that nitric acid modification could increase surface acidic functional groups of biomass char. And surface functional groups on BC could increase NH₃ and NO adsorption capacity. In the denitration process, oxygen was transferred from CeO₂ to Mn₂O₃, which could promote the cyclic catalytic reaction rate, then significantly enhanced the NO conversion in the Mn–Ce/BC catalysts. Based on the experimental results and theoretical analysis, the synergetic mechanism model of surface functional groups on the surface of BC, Mn and Ce on the catalysts was set up.