Low-temperature DeNOx characteristics and mechanism of the Fe-doped modified CeMn selective catalytic reduction catalyst

Low-temperature deNOx selective catalytic reduction (SCR) catalysts are of great significance to prolong catalyst life and reduce flue gas temperature. In this work, the low-temperature deNOx performance of different zFeCexMny catalysts was investigated on a simulated flue gas fixed-bed experimental bench. BET, XRD, XPS, NH3-TPD, and in situ FT-IR were used to characterize the physical-chemical properties of the samples. The optimum ratio and deNOx mechanism of the catalysts were explored. The results show 4FeMn7Ce3 doped with 4 wt% Fe based on Mn7Ce3 has the best deNOx performance. Its deNOx efficiency is over 90% at 120–220 °C and GHSV = 50,000 h−1, with the peak value of 98% at 150 °C. The Fe doping makes the oxide distributed uniformly on the catalyst's surface, promotes the valence cycle of the catalyst, yields more Mn4+ and Ce3+ species, and prompts the optimal deNOx temperature to the low temperature direction. Meanwhile, Lewis acid sites on the catalyst's surface are enhanced, which can promote the amide species formation that is beneficial for the deNOx reaction. Combined with in situ FTIR, the E-R mechanism and the L-H mechanism coexist in the deNOx process of zFeCexMny catalysts. These findings are helpful for the development of high-performance low-temperature deNOx catalysts. •4FeMn7Ce3 catalyst can achieve >90% of deNOx efficiency at 120–220 °C.•Abundant Ce3+ and Fe3+ play a key role in protecting active Mn4+ and increasing Oα concentration.•The Lewis acid site is stronger than the Bronsted acid site in the deNOx process.•The deNOx mechanism of 4FeMn7Ce3 obeys both L-H and E-R mechanism.