SCR of NO with CH4 over Fe/Ga2O3-Al2O3 and the mechanism

The selective catalytic reduction of NO with methane (SCR-CH4) is a very promising alternative method, however, the catalysts reported showed low catalytic activity for SCR-CH4. In order to improve the catalytic activity and resistance to H2O of the catalysts, Fe was introduced to modify the Ga2O3-Al2O3. The xFe/Ga2O3-Al2O3 catalysts were prepared with the co-precipitation method, and the SCR-CH4 performance was investigated. It was found that Fe improved the catalytic activity at medium and high temperatures, the N-2 selectivity, and the resistance to H2O. Among all catalysts, the 5Fe/Ga2O3-Al2O3 catalyst achieved NO conversion of 76% and N-2 selectivity of 100% at 500 degrees C, and still maintained NO conversion of more than 60% in the presence of 5% H2O. Several characterization techniques, XRD, N-2 adsorption-desorption, XPS, UV-Vis, H-2-TPR, Py-IR, etc., were used to explore the relationship between the catalytic activity and structure. The results showed that after the doping of Fe, the pore diameter was increased, resulting in a promotion in the resistance to H2O. In addition, the redox properties and Lewis acid content of the catalysts were promoted by the Fe species, where the isolated Fe3+ species contribute to the catalytic activity at medium and high temperatures. In situ DRIFTS revealed that NO, CH4, and O-2 were adsorbed and reacted on the catalyst surface to form various nitrates, formate, and R-NCO species, where O-2 can promote the formation of bidentate nitrates.