Effect On Storage Process Of No_x Emission From Diesel Engine Of Nsr Catalyst

NO_x storage and reduction?NSR?technology has the advantages of no additional addition of reducing agent,high removal efficiency and is considered as one of the effective solutions for solving the NO_x emission of diesel engines.The key to NSR's technology is the highly active catalyst material.Study found that Mn exhibited a variety of valences in the catalyst which was beneficial to increase the NO oxidation capacity of the catalyst.This is expected to promote the NO_x storage performance of NSR catalysts.In this paper,Mn was used as a co-catalyst to prepare composite NSR catalysts with different Mn loadings by sol-gel method and impregnation method.The physicochemical properties of the catalyst were characterized by X-ray diffraction?XRD?,Brunauer-Emmett-Teller specific surface area?BET?and Scanning Electron Microscope/Energy Dispersive Spectrometer?SEM/EDS?;by use In-suit DRIFTs and programmed temperature desorption?NO_x-TPD?test to evaluated the catalyst's storage and reduction activity.Then based on the simulated gas experimental platform,the effects of different temperatures,Mn loading,O₂ concentration and NO concentration on the storage performance of the catalyst were studied.At the same time,H₂O was added to the exhaust gas components to further explore the anti-H₂O performance of the catalyst.Finally,the effects of different storage times on the storage performance of the catalysts were investigated with periodic storage reduction tests.The main work content and conclusions are as follows:?1?A series of NSR catalysts with different Mn loadings were prepared and characterized by XRD,BET and SEM/EDS.The results show that the overall crystallization conditions of NSR catalysts with different Mn loadings are good,Ba exists mainly in the form of BaCO₃,Mn elements coexist in the form of Mn³⁺and Mn⁴⁺,and Ce mainly exists in an amorphous structure.The specific surface area of the catalyst decreased after Mn loading.The dispersion of the components is relatively uniform.As the Mn loading increases,a large number of porous pore structures appear on the surface of the catalyst.This facilitates the contact between the active components and the exhaust components of the engine,thereby increasing the reactivity of the catalyst surface.?2?In-suit DRIFTs test results show that the Mn load has a certain influence on the storage path of the catalyst,and promotes the conversion of the"nitrite"pathway to the"nitrate"pathway after the temperature rises.The NO_x-TPD test results show that compared with NO₂,the adsorbed NO has higher thermal stability.The desorption peak temperatures for NO and NO₂ were 450°C and 380°C,respectively.?3?The simulated gas test results show that at 350°C,the storage efficiency of the catalyst is highest,reaching 83.70%,and the NO_x adsorption is 695.45?mol/gcat.The NO_x storage capacity of the catalysts is as follows:8Mn>10Mn>6Mn>4Mn>2Mn>0Mn.In the presence of O₂,the catalyst has better NO oxidation capacity,which promotes the storage reaction of the catalyst to react with the"nitrite"pathway and the"nitrite"pathway to achieve rapid adsorption storage.The NO_x storage efficiency of the catalyst and the NO_x adsorption amount are negatively correlated with the NO concentration.The lean/rich time has a great influence on the NO_x storage performance of the catalyst.Under the 60s-60s mode,the NO_x storage efficiency of the catalyst is 87.14%,and it has the best storage capacity.In the presence of H₂O,NO oxidation was inhibited to NO₂,which led to a slight decrease in the NO_x storage efficiency of the catalyst.