Effect of Samarium doping on the activity and sulfur resistance of Ce/MnFeO catalyst for low-temperature selective catalytic reduction of NO by ammonia

The self-made MnFeOx catalysts doped with cerium and samarium were prepared by impregnation method for low-temperature selective catalytic reduction by NH3. In this work, the surface properties of the series of MnFe-based catalysts were studied. The results indicate Sm-modified catalyst have superior low-temperature SCR activity; NOx conversion maintained at nearby to 100% at 90–240 °C. In addition, The N2 selectivity of Sm doping remains above 80% in the range of 60–150 °C. In SO2 poisoning test, the NOx conversion can be remained >90% after 10 h of reaction. The XPS, NH3-TPD and H2-TPR results show the catalyst with Sm doping enhances the acid sites and oxidation catalytic sites of mixed oxides serves for improving oxygen vacancies and transfer electrons. In situ DRIFTS results show that NOx is more easily adsorbed on the surface after Sm doping, which provided favorable conditions for the NH3-SCR reaction to proceed. The reaction at the catalyst surface will follow the L-H reaction mechanism by transient reaction test.