Effect of Mn and Ce oxides on low-temperature NH3-SCR performance over blast furnace slag-derived zeolite X supported catalysts

Several Mn and/or Ce oxides on blast furnace slag-derived (BFS-derived) zeolite X catalysts were prepared to investigate their low-temperature NH3-SCR performance. It was found that Mn-Ce/X catalyst had the highest NO conversion of nearly 98% at 250 ? and excellent N-2 selectivity of nearly 100% during 75-175 ?. The co addition of Ce and Mn could inhabit the growth of crystal grains, resulting in the increase of surface area and the generation of Mn-Ce double active sites. Besides, high concentration of Mn4+ and Mn3+ could promote oxidation of NO to NO2 accelerating the fast-SCR reaction and high concentration of Ce4+ could form more oxygen vacancies on Mn-Ce/X catalyst. In addition, the Mn-Ce/X catalyst had large acid amount and high redox ability owing to the co-existed Mn-Ce double active sites on zeolite catalyst and the co-effect of Mn-Ce oxides and zeolite X. Furthermore, the decomposition of NH4NO3 species on Mn/X catalyst led to the low N-2 selectivity at higher temperature. While NH2NO and NH4NO(2) intermediates on Mn-Ce/X catalyst played a vital part in NH3- SCR reaction and prevented the generation of N2O, and Mn-Ce/X catalyst provided more Mn-Ce active sites for the reaction between NO3- species and gaseous NO, accelerating SCR catalytic reaction.

Automated summary

The effects of different Mn and/or Ce oxides on blast furnace slag-derived zeolite X catalysts were investigated for low-temperature NH3-SCR performance. It was found that the Mn-Ce/X catalyst exhibited the highest NO conversion and N2 selectivity, along with large acid amount and high redox ability. The addition of Mn and Ce inhibited crystal grain growth and generated double active sites, promoting the SCR catalytic reaction.