SCR And Soot Oxidation Catalytic Performance Of Cu/ZSM-5 Catalyst With Different Copper Valence

Nitrogen oxides(NOx) and particulate matter(PM) are the most serious pollutants from diesel engines, and Selective Catalytic Reduction(SCR) technology and Particulate Oxidation Catalyst(POC) are the most potential technologies for NOx and PM after-abatement. Modified zeolite catalysts not only possess the excellent selectivity of NOx reduction at low temperature, but could lower the oxidation temperature of PM obviously, and have great potential for the application on SCR and POC technologies of diesel engines. The series of Cu/ZSM-5 zeolite catalysts with different metal valence state and contents were synthesized in the present work according to solid state ion exchange(SSIE) methods, and advanced characterization methods where performed to exhibit the physi-chemical properties, SCR activities and the catalytic performance for these catalysts in PM oxidation. Investigations will bring great benefits in theoretical aspects to the development of new SCR and POC catalyst.The main research contents and results obtained are listed as follows:The series of modified high loading Cu/ZSM-5 zeolite catalysts were prepared using SSIE methods. The introduction of Cu does not destroy the pore structure of zeolites, and the Cu species loaded in zeolite catalyst system can perform varieties of morphologies dispersing uniformly. When the mass fraction of Cu loaded is more than 15%, the aggregation phenomenon appears on the surface of zeolite catalyst as CuCl state.For series of Cu(i) ZSM-5 catalysts, the catalytic activities of SCR catalyst ascend with the increase of the Cu loadings at high temperature. The Cu loadings do not obviously promote the SCR activities when the percentage of loading is more than 11%. However, the SCR activities at low temperature are improved with the increase of Cu loading, but this improvement becomes unapparent when the loading percentage exceeds 13%. For series of Cu(ii) ZSM-5 catalysts, Cu loadings have little effect on the SCR activities at high temperature, but at low temperature the catalytic activities of SCR catalyst ascend with the increase of the Cu loadings, till the loading percentage exceeds 13%. At 13% Cu loading, all zeolite catalysts modified by Cu with different valence states exhibit the excellent temperature ranges of SCR activities and the lowest SCR ignition temperature.Cu species introduced with different valence states can address the promotion of PM catalytic oxidation and PM-NOx simultaneously removal for zeolite catalysts, and the capabilities of the catalysts for PM catalytic oxidation have a declining trend after an initial increase. Cu modified zeolite catalysts with 11% Cu loading at different valence state possess the most excellent catalytic activity for PM oxidation.Compared to series of Cu(ii)/ZSM-5 with the same Cu loading, the Cu(i)/ZSM-5 catalysts demonstrate the better activities for SCR and PM oxidation under the same reaction conditions.