Iron-based Oxide Catalyst For The Selective Catalytic Reduction Of NO With NH₃

NOxis one of the pollutants causing the greenhouse effect, acid rain and ozonedepletion, and has had a serious impact on economic development, ecological balanceand people's lives. Currently selective catalytic reduction of NO with (NH3-SCR) isthe most effective technique for the removal of Nitrogen Oxide(NOx,x=1,2). Thecommercial catalyst is mainly vanadium-based catalyst (V2O5-WO3(MoO3)/TiO2).Although the catalyst has been industrialized for many years, there are some problems:narrow temperature windows, toxicity of vanadium pent-oxide to environment andhuman health, and higher activity for oxidation of SO2to SO3.In this paper, non-toxic to the environment and low-cost iron-based oxidecatalysts were prepared for selective catalytic reduction of NO by ammonia. Byadjusting the content of Ce and W, the catalysts with best catalytic performance werescreened.The samples were characterized by SEM, BET, XRD, NH3-TPD andH2-TPR to investigage the structural feature. The effect of calcination temperature andcatalytic reaction conditions on the catalytic activity was studied.(1) A series of FeaWbOxcatalysts were prepared by co-precipitation and theresults showed that the catalyst with the Fe/W molar ratio of4/1exhibited the bestcatalytic activity with above90%NO conversion in the te mperature range from250oC to400oC under the space velocity of75,000h-1. The Fe4WOxcatalyst alsoshowed high tolerance to SO2and H2O in the test condition. The characterizationresult showed that the strong interaction between Fe and W, the large specific surface,and the strong acidity were the main reasons for the iron-tungsten mixed oxidecatalyst to acquire the high catalytic activity.(2) A series of Fe4WCeyOxcatalysts were prepared by co-precipitation and theresults showed that Fe4WCeOx(y=1) catalyst had best catalyst performance in thetemperature range from150oC to350oC. The oxygen concentration and mole ratio ofNH3/NO had an important role in the catalytic reaction. The Fe4WCeOxcatalyst alsoshowed higher tolerance to SO2and H2O than Fe4WOx.The characterization resultshowed that Fe?W?Ce had a high level of dispersion or the amorphous form andFe4WCeOxcatalyst had not the largest surface area. The result implied the surfacearea was not the main factor leading to the high activities of different mixed oxides. The doping of Ce could reduce the amount of acid, which was not conducive to hightemperature denitration reaction.