Study On Microwave Catalytic Removal Of Nitrogen Oxides Over Cu-ZSM-5-based Microwave Catalysts

Nitrogen oxide(NO_x),one of the atmospheric pollutants,were harm to environment and human body.Efficient denitration has become an important issue in environmental protection.The new nitrogen oxide emissions concentration limits was discussed in the Emission standard of Air Pollutants for Thermal Power Plants which was less than 100 mg/m3(123 ppm).This standard,which was far more than the United States's and Europe's,became the most strict standards.It faced enormous pressure and difficulty to execute the new standard strictly.So,it had realistic significance to indagate efficient denitration technology.Cu-ZSM-5 catalyst was the best catalyst for denitration at low temperature and it also the most active object to indagate.Although NO direct decomposition was feasible in the thermodynamic,the activation energy of reaction as high as 364 kJ/mol.So,Looking for a highly efficient catalyst or energy to reduce reaction energy barrier could be a new way of denitration.In recent years,it has been discussed that microwave inaddition existing "the heating effect".Beyond that,it still existed other special effects such as accelerating chemical reaction,improving the reaction selectivity and the total yield and so on.Therefore,it may be a new way by using microwave technology and denitration echnology to remove NO efficiently.In this paper,the Cu-ZSM-5 catalysts were prepared by the method of ion exchange.Their activity for NO removal was tested in the new microwave catalytic reactor which was designed by our research.And the conclusion of the experiment as follows:NO conversion rate in the microwave radiation condition was up to 82%at 180?,and that was significantly higher than conventional heating condition's over Cu-ZSM-5 catalyst.The catalyst modified by CuO can increase the temperature of catalyst bed and activity.The NO conversion rate was up to 99%at 380?,and the existence of O2 had no influence on denitration over CuO-Cu-ZSM-5 catalyst.The catalyst modified by AC can increase the temperature of catalyst bed and activity.The NO conversion rate was up to 99.23%in the conditions of rich oxygen and 800 W microwave power.The existence of O2 was beneficial to denitration over AC-Cu-ZSM-5 catalyst.Cu-ZSM-5 catalysts direct decomposition NO reaction's dynamics was analysed.The different kinds of dynamic model were verified.It has been demonstrated that Cu-ZSM-5 catalyst microwave catalytic denitration's data was more in line with the dynamic model putting forward by Tomasic.Based on this model,the reaction activation energy for denitration were calculated.Cu-ZSM-5 catalyst in microwave mode decomposition NO activation energy E=25.0 kJ.mol-1,pre-exponential factor A=42.6;Cu-ZSM-5 catalyst in conventional heating mode decomposition NO activation energy E = 75.6 kJ.mol-1,pre-exponential factor A = 0.19;CuO-Cu-ZSM-5 catalyst in microwave mode decomposition NO activation energy E = 19.5 kJ.mol-1,pre-exponential factor A = 15.839.The reducing of activation energy E and the increasing of pre-exponential factor A demonstrated that Microwave has Microwave Catalytic effect just as Photocatalysis.