Preparation And Properties Of Diesel Particulate Filter Supported Ordered Macroporous Metal Oxide

With the increasing popularity of motor vehicles,the environmental problems they brought are becoming more and more serious.Compared with gasoline vehicles,the amount of soot from diesel exhaust is about 30-100 times higher,which indicates that it is essential to remove soot effectively in diesel exhaust emission aftertreatment system.Recently,Diesel Particulate Filter(DPF)represented by wall-flow honeycomb ceramics have been widely used in diesel engine exhaust control systems and are considered to be the most effective diesel particulate matter control technology.The continuous accumulation of soot will cause the reduction of combustion efficiency and energy waste.Therefore,it is a hot research topic to develop a novel Catalytic Diesel Particulate Filter(CDPF)to effectively reduce the oxidation temperature of the soot and effectively regenerate DPF in engine operation cycle.Cerium-based oxide catalysts and perovskite oxide catalysts are widely investigated in the field of environmental catalysis,especially soot oxidation catalysis.The cerium oxide catalyst has the characteristics of high reserve,good thermal stability,large oxygen storage capacity,and excellent redox resistance.By doping with other atoms,better soot catalytic activity and more outstanding thermal stability can be obtained on cerium based catalysts.By atomic doping,their electronic structure,active site valence and thermal stability of perovskite oxide catalysts could also be regulated to produce high catalytic activities for soot oxidation.The three-dimensional ordered macroporous structure could increase the effective contact area between the soot and the catalyst,thereby promoting the low temperature oxidation of soot.In this thesis,we successfully prepared three-dimensional ordered macroporous cerium oxide and perovskite oxide loaded particle filter with wall flow cordierite as the substrate.Oxygen vacancies were produced in the cerium-zirconium system by reducing agent NaBH4,and the relationship between oxygen vacancies and catalytic activities for soot oxidation were explored.(1)Combined with sol-gel method and template method,three-dimensional ordered macroporous cerium oxide and perovskite oxide particle filter based on DPF were successftully prepared.The macroporous structure is regular,tightly arranged,uniform in size and excellent thermal stability and mechanical stability;(2)The three-dimensional ordered macroporous loaded particle filter exhibits significantly better soot catalytic oxidation activity than the powdered catalyst.Both the macroporous structure and active components affect the soot catalytic oxidation performance.A series of characterization such as X-ray photoelectron spectroscopy,hydrogen temperature-programmed reduction and oxygen temperature-programmed desorption reveals that high concentration of Ce3+,adsorption of oxygen and oxygen vacancies,and low temperature redox and active oxygen species are its source of excellent catalytic activity;(3)oxygen vacancies rich catalysts have better soot catalytic oxidation activity.The relationship between soot oxidation activity and oxygen vacancies has been quantitatively and qualitatively analyzed by X-ray photoelectron spectroscopy,electron paramagnetic resonance,and Raman spectroscopy.