Enhancing effect of Cu and Sn doping on low-temperature catalytic activity and operating temperature window of γ-Fe2O3 in NH3-SCR of NOx

gamma-Fe2O3 and Cu/Sn doped gamma-Fe2O3 catalysts were prepared and applied for the NH3-SCR of NOx. It is discovered that doping gamma-Fe2O3 with Cu or Sn can promote its low-temperature catalytic performance and H2O + SO2 resistance. In a broad temperature range of 150-330 degrees C, over 80% denitration efficiency can be obtained with Cu/gamma-Fe, which has the best low-temperature catalytic performance. These catalysts were characterized by many characterization techniques including BET, SEM, XRD, Raman, NH3-TPD, H-2-TPR, XPS, and in situ DRIFT. The results indicate that the doping of Cu and Sn can enlarge the specific surface area while not changing the crystal structure of the catalysts. Among these catalysts, Cu/gamma-Fe exhibits the strongest surface acidity and low-temperature redox capacity. Furthermore, Cu/gamma-Fe possesses the highest concentration of Fe3+ and surface chemisorbed oxygen, which enhances the NO oxidation to NO2. All of the mentioned above factors will facilitate its superior low-temperature catalytic activity. Finally, the E-R reaction route is mostly followed by gamma-Fe2O3, while both the E-R and L-H reaction routes are obeyed by Cu/gamma-Fe and Sn/gamma-Fe.