Study On Catalytic Properties Of Modified Mn/ZSM-5 Catalysts In The Fast SCR Reaction

Nitrogen oxides has huge damages.Fast SCR reaction occurs by raising the proportion of NO2 in nitrogen oxides,which can accelerate the process of catalytic reduction of NOx.So it has great significance to develop effective Fast SCR catalysts with low cost.Mn/ZSM-5 catalyst with 12%Mn loadings was prepared through incipient impregnation method.Based on it,we prepared Mn-Fe/ZSM-5 and Mn-Ce/ZSM-5 catalysts with varying amounts of iron doping or cerium doping.ICP,BET,XRD,H2-TPR,NH3-TPD and XPS were employed to characterize the properties of the catalysts and their catalytic activities in Fast SCR and NO oxidation were evaluated.It turned out that the addition of Fe promoted the dispersion of active components and the reaction between active sites and nitrate ions.The strong interaction between Mn and Fe increased the ratio of Mn4+,created more oxygen vacancy and active lattice oxygen.Among all the tested catalysts,Mn-Fe(0.490)/Z catalyst exhibited the highest catalytic activity in Fast SCR,achieving 96.15%NOx conversion at 100? and near-stable 100%conversion at between 150-250?.However,an excessive iron loading amount led to the agglomeration of active components and accelerate the oxidation of NH3.Furthermore,Mn-Fe(0.490)/Z catalyst also exhibited better performance in NO oxidation than Mn/ZSM-5,achieving maximum NO conversion of 55.88%at 300?,in contrast,NO conversion using Mn/ZSM-5 at 300? was only 30.05%.The addition of Ce improved the dispersion of active components and the strong interaction between Mn and Ce increased the amount of Mn4+and Ce3+,created more oxygen vacancy and active lattice oxygen.Among all the tested catalysts,Mn-Ce(0.458)/Z catalyst exhibited the highest catalytic activity in Fast SCR,achieving 93.48%NOx conversion at 150? and near-stable 100%conversion at between 200-350?.However,an excessive cerium loading amount led to the agglomeration of active components,decrease the specific surface area and lower the dispersion.Furthermore,Mn-Ce(0.458)/Z catalyst also exhibited better performance in NO oxidation than Mn/ZSM-5,achieving maximum NO conversion of 56.5%at 350?.