Study On The Use Of Zeolite In Selective Catalytic Reduction Of NO_x With Propane

NOx has a close relationship with the formation of acid rain and phot °Chemical smog,and the study of its removal has attracted great attentions of academic community.The most ideal way to efficiently remove NOx in car exhaust is using its exhaust HC compounds as a reducing agent.However,due to toxic content of V in the traditional deNOx catalysts,it is necessary and urgent to develop alternative efficient catalysts.In present work,various zeolite catalysts were modified by bimetallic species and applied for C3H8-SCR.The modified zeolite catalyst with excellent catalytic performance was thereafter obtained through a large number experiments.Secondly,this paper evaluates the activity of the monolithic catalyst prepared by using it as the catalyst powder,and makes a basic research to improve its catalytic efficiency.Finally,the preparation of Cu/SSZ-13 and its C3H8-SCR activity evaluation study provide a reference for the dynamic synthesis of SSZ-13.In present work,Cu modified zeolite catalysts with different morphologies(ZSM-5,BEA,MOR,MCM-49,Y,ZSM-35,SUZ-4 and SAPO-34)were prepared by impregnation method.By comparing the relatecatalytic activity of C3H8-SCR,it was found that ZSM-5 and BEA exhibit much higher activity than other topologied zeolites.Cu/ZSM-5 and Cu/BEA showed the bestactivity as the Cu loading was 5%.Through a series of characterization,it was found that the higher activity of Cu/ZSM-5 and Cu/BEA was related to the large amount of Cu2+ ions acting as active sites.On the basis of 5%Cu loading zeolite samples,present work further loaded another metal(Ce,Zr and Zn)on the Cu based zeolite samples through impregnation method.The activity measurement results suggested that addition of Zn can significantly improve the catalytic activity and its water and sulfur resistances.For Cu/ZSM-5,the optimum loading amount of Zn was 1%with an active temperature window of 300 ?-750 ?.For Cu/BEA,its optimum Zn loading was 5%with a active temperature window of 350 ?-700 ?.The characterizations revealed that the addition of Zn can make CuO species well dispersed on the surface of zeolite catalysts;and was also helpful to polarize C-H bond of C3H8 reluctant,thereby greatly improving catalytic behavior of Cu/ZSM-5 and Cu/BEA.Additionally,changing oxygen concentration(2%?7%)had a slight influence on the activity of Cu-Zn/ZSM-5 and Cu-Zn/BEA,which can also main higher activity.5%Cu-1%Zn/ZSM-5 was loaded onto cordierite.The synthesis parameters,indlucing surface active agents(Tianjing powder,ethylene glycol and polyethylene glycol 4000)and their additions,the amounts of binder(silica sol and aluminum sol)and cordierite(400 cpsi,200 cpsi and 100 cpsi),were taken into account to evlauted their influences on the catalyst activity.Finally,it was concluded that when polyethylene glycol 4000 was used as the surfactant;the mass ratio of molecular weight to the original powder was 0.2:1;the silica sol was used as the binder;and 400 cpsi cordierite was chose as the carrier;the catalysts have a best acvity.In present work,SSZ-13 microporous molecular sieve catalysts were synthesized by static method and dynamic method respectively with choline chloride as template.Comparing to the static method,the crystallinity of SSZ-13 synthesized by dynamic method was relatively lower.Characterization showed that much more CuO species were formed on the surface of Cu/SSZ-13 synthesized through dynamicmethod.This also constituted the main reason of lower C3H8-SCR activity of Cu/SSZ-13 with respect to that of Cu/SSZ-13 prepared by static method.