Study on the enhancement mechanism of low-temperature SCR performance of ammonium persulfate coupled transition metal oxides modified carbon-based catalysts

In recent years, carbon-based catalysts have received extensive attention in the field of NH₃-SCR due to their unique advantages. In order to improve the performance of low-temperature NH₃-SCR of carbon-based catalysts, V/OAC, Fe/OAC, Mn/OAC and Cu/OAC carbon-based catalysts were prepared by oxidizing and coupling transition metal oxides with ammonium persulfate. The mechanism of SCR performance enhancement of modified carbon-based catalysts was investigated by means of catalytic activity test, physical adsorption, FT-IR, XPS, NH₃-TPD, H₂-TPR, EPR and other characterization methods. The results show that ammonium persulfate oxidation can introduce a large number of acidic oxygen-containing functional groups to the surface of activated carbon support, promote the formation of oxygen vacancy in transition metal oxides, and improve the surface acidity and redox performance of carbon-based catalysts, therefore the low temperature NH₃-SCR performance of the carbon-based catalyst was improved. In particular, we found that oxidation of ammonium persulfate can induce the formation of lower valence states of transition metal elements (V, Fe, Mn, Cu ). Therefore, after oxidative modification of ammonium persulfate, the performance of V/OAC and Fe/OAC catalysts with low-priced metals in active components conducive to NH₃-SCR reaction is significantly improved, the NO conversion of VO_x/OAC and FeO_x/OAC catalysts at 100 ℃ increased from 18.2% to 34.8% and from 34.2% to 55.6%, respectively; while the performance of Mn/OAC and Cu/OAC catalysts with high-priced metals in active components conducive to NH₃-SCR reaction is limited, the conversion of NO at 100 ℃ only increased from 61.4% to 70.4% and from 61.3% to 69.7%. This work summarized the regulatory effect of ammonium persulfate oxidation modification on the surface metal states of carbon-based catalysts, which is helpful to deeply understand the regulation law of physical and chemical properties of carbon-based catalysts by oxidative modification of ammonium persulfate, and provide guidance and reference for the development of high-efficiency carbon-based denitrification catalysts.