Preparation Of DPF Efficient Catalyst And Its Catalytic Performance For Soot Combustion

Diesel vehicles are more and more popular due to their superior efficiency,low fuel consumption and durability.However,diesel engine pumps a lot of soot pollution into atmosphere,which has became a serious social problem.Diesel particulate filter?DPF?combined with catalyst is considered to be the most direct and efficient method to eliminate soot pollution.In our previous study,the Mn-Ce catalyst with high activity at low temperature is synthesized by citrate sol-gel method,but the poor themal stability of the catalyst is main obstacle for its industial application.Therefore,it is need to further improve the themal stability and catalytic activity of Mn-Ce catalyst through modifying the preparation method.The main results in this paper were as follows:1.A series of MnCe catalysts with different crystal sizes and morphology characteristics are synthesized by molten salts method,and their catalytic activities for soot combustion are evaluated by the TG technology.XRD,SEM,BET and H₂-TPR are used to investigate the texture and redox properties of samples.The results show that Mn-Ce oxides can be fast crystallized and nucleated in the composite molten salt solution,espeicial in the melten salt solution with three components due to its lower melting point,which result in high dispersion of particles with nano-size.The synthesized samples show the higher low-temperature catalytic activity for soot combustion.2.Alkalis?K,Rb and Cs?and ZrO₂ in appropriate amount are introduced into Mn-Ce nanocrystalline to improve the themal stability and activity for soot combustion.It is found that alkali metal oxides can highly disperse on the surface of the MnCe oxides,and absorb large amount of CO₂ from air,resulting in high content of suface oxygen speices which is benefit to the catalytic combustion of soot.In addition,the alkali metal oxides,especially for Cs₂O,will enter into the bulk phase of Mn-Ce nanocrystalline and form a tubular structure inside the crystalline grain,which well transfer the active oxygen from MnCe to soot as the O_x^-transfer channel during high temperature reaction.