Fe-Mn Mixed Oxide Catalysts Synthesized by One-Step Urea-Precipitation Method for the Selective Catalytic Reduction of NO (x) with NH3 at Low Temperatures

A range of Fe-Mn mixed oxide catalysts, Fe alpha Mn1-alpha O (x) (alpha = 1, 0.25, 0.33, 0.50, 0 mol%) were prepared via one-step urea-precipitation method and applied to the selective catalytic reduction (SCR) of nitric oxide (NO (x) ) with NH3. The Fe0.33Mn0.66O (x) catalyst showed the highest activity in the NH3-SCR process within a broad operation temperature range (75-225 degrees C) with 90% NO (x) conversion. Series of characterization have been taken to investigate the physical and chemical properties of the catalysts. The BET results evidenced that the doping of iron species increased the surface area of the catalyst effectively, and this structure could provide more acid sites and active sites on the surface of catalysts for SCR reaction. X-ray powder diffraction results and Raman spectroscopy indicate that the active Mn and Fe species were in poorly crystalline or amorphous states which could increase lattice defects and oxygen vacancies on the surface of Fe0.33Mn0.66O (x) catalyst. The X-ray photoelectron spectra results suggested that more surface-adsorbed oxygen (O-A), Fe3+, Mn4+ species existed on the surface of the Fe0.33Mn0.66O (x) catalyst compared with that of MnO (x) and FeO (x) catalysts, which is favorable to the NH3-SCR performance. Analysis by in situ Fourier transform infrared spectroscopy (FTIR) suggested that Fe-doping can enhance the absorption and the activation ability of NO which could promote the catalytic performance in the SCR process.