High-performance Fe-Cu composite oxide for selective catalytic reduction of NOx with NH3: Driving of Cu on α-Fe2O3

Abstract

One kind of driving of Cu on α-Fe2O3 was successfully created for removing NOx. It brought excellent low-temperature performance, high N2 selectivity and strong water and sulfur resistance. The concrete process was that Cu2+ ions entered into the crystal lattice of Fe2O3, forming solid solution with Cu-O-Fe structure and further changed the property of Fe2O3. On the one hand, Cu2+ ions adjusted the electrophilicity of Fe3+ species, thereby facilitating the generation and adsorption of NO2, nitrate and nitrite species and increasing Lewis acid sites. The increase of NH3 and NOx adsorbed species on the catalyst surface conduced to excellent low-temperature NH3-SCR activity. On the other hand, the regulation of Cu brought abundant lattice defects to Fe2O3 which strengthened the redox ability and generated oxygen vacancy. It led to the growth of surface adsorbed oxygen, which was crucial for the “fast SCR” reaction. In-situ DRIFTS results revealed that the NH3 on Lewis acid sites preferred to react with weakly adsorbed NO2 through Langmuir-Hinshelwood (L-H) mechanism over the Fe-Cu composite oxide catalyst. Meanwhile, the NH3 on Lewis acid sites was also able to react with monodentate nitrates, bidentate nitrates and nitrites through L-H reaction mechanism. This work provided a new inspiration for the construction of green and efficient catalysts to remove NOx in the practical industrial applications.