The Simultaneous Purification Of PM And NO_x From Diesel Engines Over 3DOM Oxide Catalysts

In recent years,the application of after-treatment catalytic technology has been attracted much attention from researchers due to the increasingly rigorous emission standards.A novel catalytic simultaneous purification approach of PM（particulates matter）and NO_x is proposed in this work,which can replace the otherwise separate catalytic diesel particulate filters（DPF）and NH₃ selective catalytic reduction（SCR）steps,is designed for achieving the simultaneous high-performance abatement of PM and NO_x in a single catalytic converter.This approach is quite cost-effective because it can simplify the exhaust system to lower the pressure drop and reduce the system volume and mass.Catalysts were prepared with three-dimensionally ordered macroporous（3DOM）architecture in this work,to enlarge the effective contact area between soot and active species.NH₃ was added in the simultaneous purification system to provide a reductant in the lean-burning atmosphere for oxynitride reduction.To obtain an excellent purification capability,the catalysts were modified by introducing the active transition metal oxides to 3DOM carrier.Combining the analysis of textural properties and the intrinsic features of catalysts,3DOM Ce_xTi_1-xO₂ catalysts,3DOM M_0.05-Ce_0.1Ti_0.9O₂ and3DOM M_0.05/Ce_0.1Ti_0.9O₂（M=Cd,Co,Cu,Fe,Mn）catalysts,3DOM LDO and 3DOM M_0.05/LDO（M=Ce,Co,Mn）catalysts,3DOM Cu-Fe LDO and 3DOM M/Cu-Fe LDO（M=Ce,Co,Mn）catalysts were designed and prepared.Diverse characterization methods were used to analyze their properties and In-situ DRIFTS was used to inverstigate the simultaneous mechanism of purification of PM and NO_x.The main research contents and results are as follows:1.3DOM Ce_xTi_1-xO₂ and 3DOM Ce_xTi_1-xO₂-2（x=0.1,0.3,0.5,0.7,0.9）oxide catalysts,were prepared by colloidal crystal template method.The modified 3DOM Ce_0.1Ti_0.9O₂-2 oxide catalyst provided the T_m（temperature of maximum CO₂concentration）at 579 ℃ and NO conversion in the range of 250-450 ℃ is kept above70%.The catalyst performance is intensified by the ordered macroporous structure and amorphous modified method.The specific 3DOM architecture,E-R reaction mechanism,high specific surface area and the ample acid are related to the catalyst performance of3DOM Ce_0.1Ti_0.9O₂-2 sample.2.3DOM M_0.05-Ce_0.1Ti_0.9O₂ and 3DOM M_0.05/Ce_0.1Ti_0.9O₂（M=Cd,Co,Cu,Fe,Mn）catalysts.3DOM Cu_0.05/Ce_0.1Ti_0.9O₂ catalyst exhibited the T_mvalue at 472 ℃ and above70%NO conversion in the range of 250-400 ℃,maximun NO conversion is 85%in305 ℃.The mobility of particulates is promoted in 3DOM architecture;E-R reaction mechanism is proposed in high temperature by In-situ DRIFT results and the ample acid sites are related to the catalyst performance of Cu_0.05/Ce_0.1Ti_0.9O₂ catalyst.3.A series of 3DOM Mg-Al layered double oxides（LDO）sample were prepared by colloidal crystal template method.Best preparation method was selected to obtain the specific 3DOM LDO architecture,then 3DOM M_0.05/LDO（M=Ce,Co,Mn）catalyst were prepared by incipient-wetness impregnation method.The 3DOM M_0.05/LDO catalyst improved the performance for PM combustion but the catalyst performance of NO conversion is kept below 25%,it is ascribed to the inert support of 3DOM Mg-Al LDO.4.A series of 3DOM Cu-Fe LDO catalysts and 3DOM M/Cu-Fe LDO（M=Ce,Co,Mn）catalysts,were prepared by colloidal crystal template method and incipient-wetness impregnation method.The 3DOM Ce/Cu-Fe LDO catalyst provided the the T_mvalue at 473 ℃ and above 50% NO conversion in the 200-400 ℃ temperature range,maximun NO conversion is 85%in 305 ℃.N₂ selectivity is promoted to a out-standing level.The catalyst performance has been intensified by the unique 3DOM-LDO structure and supported active metal oxides.