The Effect Of Templates And Ion Modification On The Reaction Mechanism Of NO In The SCR Over Cu-SSZ-13

The Cu-SSZ-13 zeolite catalyst is the most promising catalysts in diesel denitration.It mainly contains two kinds of synthesis methods:ion-exchanged and one-pot synthesis.One step synthesis is competitively compared with ion exchange method because its synthetic route is very cheap,but one step synthesis method can not entirely replace ion exchange method.The biggest difference between two kinds of preparation methods is the templates.Different templates have different effect on the NO oxidation process in NH3-SCR,but this is unclear.Otherwise,the Cu activity in CHA cage has an excellent low temperature activity,we need to study the one step synthesis can whether or not obtain the Cu activity in CHA cage and why it has an excellent low temperature activity.In this paper,we combine the quantum chemical calculation and experiment method to study the effect about template on active sites and its property.Furthermore,we study the effect about active sites on the NO adsorption reaction process in NH3-SCR.The H2-TPR and DFT calculation results show that:(1)The Cu-SSZ-13 by ion-exchanged has the Cu active site in the CHA cage.When the Cu species are in the CHA cage,NO and O2 are more conducive to form the NO2.(2)The Cu-SSZ-13 by one-pot synthesis and modified have the Cu active sites on the six-membered ring and eight-membered ring.When the Cu active sites are on the six-membered ring and eight-membered ring,NO and O2 are more conducive to form the nitrate.So,different preparation methods may lead to different Cu active sites,and further different Cu active sites lead to the different NO oxidation process.We also studied the effect about the Ce/Cu-SSZ-13 to the oxidizing ability of NO in the NH3-SCR using experiment and theoretical calculation methods.The effect about Ce/Cu-SSZ-13 to the oxidizing ability of NO mainly reflects in the activation reaction of O2.Ce is better than Cu in the activation of O2 to make it being a highly active adsorbed oxygen.The reaction energy barrier of Cu activate O2 required is 117.3 kJ/mol,however the reaction energy barrier of Ce activate O2 required is only 67.3 kJ/mol.The reaction energy barrier of Ce activate O2 is much less than the reaction energy barrier of Cu activate O2.The conversion frequency TOF of NO oxidation reaction about whether containing Ce is contrasted.The conversion frequency TCF of NO oxidation reaction become fast when Ce join the reaction.