The Study On Tests And Kinetic Modeling For NH₃-SCR Over Cu-zeolite Catalysts

In order to reduce NO_x emissions from mobile sources,in response to the new requirements for NO_x and N₂O proposed by the National VI emission regulations,It is of great significance to study the NO_x an N₂O emissions in the rear of the NH₃-SCR system of diesel vehicles.However,the mechanism of N₂O formation during the NO conversion of the catalyst is still unclear.Therefore,N₂O generation experiment and building NH₃-SCR dynamic model are important research topics.In this paper,the SCR simulation reaction system was built to simulate the engine test bench.The effects of reaction temperature,space velocity,NH₃/NO ratio and other factors on the activity of Cu-zeolite Catalysts were studied by the NH₃-SCR simulation reaction system.At the same time,the AVL Boost software was used to establish a one-dimensional kinetic model of NH₃-SCR,which clarified the SCR reaction mechanism,and provided a basis for the development of Cu-zeolite Catalystss with a wider active temperature window and higher NO_x conversion activity.In the SCR simulation reaction system,the catalyst performance tests under different schemes were conducted.It was found that during the NH3-SCR catalytic reduction reaction,the Cu-based catalyst exhibited higher performance denitration capability,and had the advantage of meeting the national VI emission standard.The test results show that the NO conversion activity of the Cu-zeolite Catalysts is most affected by temperature,and the catalyst activity gradually increases with increasing temperature;The NO conversion rate of the Cu-zeolite Catalysts increases first and then fluctuates around the stable value as the ammonia-nitrogen ratio increases;The NO conversion rate of Cu-zeolite Catalysts is less affected by space velocity,and it increases slightly with the increase of space velocity and then decreases.All Cu-zeolite Catalystss will inevitably be accompanied by side reactions that generate N₂O during the SCR reaction.Among them,the N₂O production of the Cu-zeolite Catalysts is most affected by temperature,and the N₂O production of the Cu-zeolite Catalysts is less affected by the ammonia-nitrogen ratio and space velocity.The NH₃-SCR one-dimensional kinetic model was optimized by AVL Workspace software based on genetic algorithm to optimize parameters such as activation energy and pre-finger factor of each elementary reaction.Finally,a comprehensive comparison of test results and prediction results confirms that the optimized SCR model can accurately predict the NO and N₂O emissions of the Cu-zeolite Catalysts under the actual conditions of the NH₃-SCR system.