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

Abstract

γ-Fe₂O₃ and Cu/Sn doped γ-Fe₂O₃ catalysts were prepared and applied for the NH₃-SCR of NOx. It is discovered that doping γ-Fe₂O₃ with Cu or Sn can promote its low-temperature catalytic performance and H₂O + SO₂ resistance. In a broad temperature range of 150–330 °C, over 80% denitration efficiency can be obtained with Cu/γ-Fe, which has the best low-temperature catalytic performance. These catalysts were characterized by many characterization techniques including BET, SEM, XRD, Raman, NH₃-TPD, H₂-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/γ-Fe exhibits the strongest surface acidity and low-temperature redox capacity. Furthermore, Cu/γ-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 γ-Fe₂O₃, while both the E–R and L–H reaction routes are obeyed by Cu/γ-Fe and Sn/γ-Fe.