Study On Selective Catalytic Reduction Of NO_x By Oxygenated Organic Compounds

Selective catalytic reduction(SCR)is an important method for the control of NOx emissions from diesel vehicles.Oxygenated organic alcohols has a certain advantage in the reductants,and zeolite-based catalysts are considered to be SCR catalysts with application prospective.In this paper,alcohols were selected as reducing agents,and the effect of alcohols on the reduction of NOx on molecular sieve catalysts was investigated for the first time.In this paper,Cu/ZSM-5,BE A,SUZ-4 and SAPO-34 were prepared by using Cu as the active component.The effects of copper metal loading,molecular sieve species,reductant type,preparation method,H2O and SO2 on the catalytic performance of catalyst were studied.And catalysts were further analyzed by XRD,H2-TPR,BET,XPS and other characterization.Among them,SAPO-34 molecular sieve raw powder was synthesized with different aluminum source and templates.The main conclusions are as follows:While ethanol as reductant,the NOx conversion of ZSM-5,BEA,SUZ-4 was the highest with 5%copper loading,and the nitrogen selectivity of ZSM-5,BEA,SUZ-4 was the best with 3%copper loading;When ethanol and butanol reductant had the same concentration,the ratio of carbon and nitrogen had a great influence on the catalytic activity.The higher the ratio of carbon and nitrogen,the better the catalytic activity.For 5%Cu/ZSM-5 and 5%Cu/BEA,tert-butyl alcohol as reductant had better catalytic activity and nitrogen selectivity.For 5%Cu/SUZ-4,n-butanol had the highest NOx conversion.The type of zeolites had a great influence on the catalytic performance of catalysts with the same reductant.Comparing ZSM-5,BEA and SUZ-4,Cu/ZSM-4 had excellent catalytic performance at low temperature while Cu/SUZ-4 had excellent catalytic performance at high temperature.The introduction of water vapor could improve the NOx conversion rate of ZSM-5,BEA and SUZ-4 catalyst,especially the low temperature catalytic activity.At the same time,it reduced N2 selectivity of the catalyst at high temperature.Water had little effect on Cu/SAPO-34.Cu/SUZ-4 and Cu/SAPO-34 catalysts had relatively better resistance to sulfur.SAPO-34 crystallized best by using pseudo-boehmite as aluminum source and TEA as template.As a carrier,the Cu modification was carried out by rotating impregnation method and the ion exchange method.It was found that the former had better catalytic performance due to the presence of more Cu2+ active sites.The effect of space velocity and oxygen concentration on Cu/SAPO-34 prepared by rotating impregnation method were further studied.It was found that oxygen concentration had little effect on its catalytic activity,which may be due to the higher concentration of the reductant.The catalytic activity and the N2 selectivity at high temperatures decreased with the increasing of space velocity.Cu/SAPO-34 synthesized with the introduction of CuO by in situ synthesis method had a relatively good catalytic activity due to its large specific surface area.