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 zFe-CexMny 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 degrees C and GHSV = 50,000 h-1, with the peak value of 98% at 150 degrees 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 zFe-CexMny catalysts. These findings are helpful for the development of high-performance low-temperature deNOx catalysts.

Automated summary

The low-temperature deNOx performance of various zFe-CexMny catalysts was evaluated in this study. The 4FeMn7Ce3 catalyst with 4 wt% Fe based on Mn7Ce3 showed the best deNOx performance, achieving over 90% deNOx efficiency at temperatures of 120-220 degrees C. Fe doping resulted in uniform distribution of the oxide on the catalyst's surface, promoting the valence cycle and producing more Mn4+ and Ce3+ species for optimal low-temperature deNOx. The presence of Lewis acid sites on the catalyst's surface enhanced the formation of amide species, facilitating the deNOx reaction. Both E-R and L-H mechanisms were observed in the deNOx process of zFe-CexMny catalysts. These findings are valuable for the development of high-performance low-temperature deNOx catalysts.