Study on low⁃temperature NH3 -SCR activity of manganese metal organic framework catalyst modified by transition metal

MnFeOx ， MnNiOx and MnCeOx were synthesized by impregnating the precursor material of Mn - MOF (metal⁃organic framework) with transition metal nitrate solution. Low temperature selective catalytic reduction (SCR) activity and sulfur resistance of MnMeOx catalyst were investigated. The results showed that the MnFeOx and Mn⁃ NiOx catalysts had the best low⁃temperature NH3 -SCR denitration performance and sulfur resistance when the space velocity was 30 000 h-1. The working window ranges of their denitration efficiency greater than 90% were 100-250 °C and 125 - 275 °C respectively. The doping of cerium did not significantly improve the denitration performance of the catalyst. The results of different space velocity tests showed that the space velocity had a significant effect on the performance of the catalysts. The larger the space velocity the lower the denitration efficiency of the catalysts，but the variation of space velocity had less effect on the amount of N2 O production. The physicochemical properties of the doped catalysts were studied by X-ray powder diffraction (XRD)，scanning electron microscope (SEM)，N2 ad⁃ sorption⁃desorption，X-ray photoelectron spectroscopy (XPS)，Hydrogen temperature⁃programmed reduction perform⁃ ance test (H2 -TPR)，and Ammonia temperature⁃programmed desorption test (NH3 -TPD). The results showed that the doping of Fe or Ni increased the specific surface area of the catalyst，changed the formation process of MnOx crystal during Mn-MOF sintering，and increased Mn4+ and surface oxygen on the catalyst surface. Doping metal ions improved the redox performance of the catalyst and increased the active center of the catalyst. In contrast，the do⁃ ping of cerium element reduced the specific surface area and surface oxygen content of the catalyst，inhibited the redox performance and the formation of surface active sites，resulting in poor denitration activity. The results showed that ap⁃ propriate nitrate impregnation Mn-MOF could prepare an efficient low⁃temperature NH3 -SCR denitration catalyst.