| In 2019,the total emission of four pollutants from motor vehicles nationwide was 16.038 million tons,of which carbon monoxide(CO),nitrogen hydride(HC),nitrogen oxides(NOx)and soot particulate matter(PM)emissions exceeded 90%.Among them,diesel vehicle NOx emissions exceed 80%of total vehicle emissions,and PM emissions exceed 90%of total vehicle emissions.To this end,in response to the emission of diesel vehicle pollutants,my country promulgated the National VI emission regulations at the end of 2016,which have stricter regulations and requirements for PM and NOx emissions from diesel engines.Catalytic particulate filter(CDPF)technology is currently an effective tool for reducing diesel engine PM emissions and meeting diesel engine emission regulations.Among them,the most critical point is to choose a catalyst with high catalytic activity,low cost and wide application.Cerium dioxide(CeO2)is widely used in the treatment of automobile exhaust due to its excellent oxygen storage capacity(OSC)and redox(Redox),and it is doped with potassium(K)and iron(Fe)with strong redox properties.Copper(Cu)and other elements form a solid solution of cerium potassium iron and cerium potassium copper rich in oxygen vacancies to enhance its catalytic performance.In addition,the choice of the catalyst carrier is very critical to the performance.The three-dimensional ordered macroporous structure carrier is considered to have the characteristics of a neatly arranged structure,high mechanical strength,multiple pores,high specific surface area,and easy surface modification.It is one of the best carriers for catalysts;nano-microsphere carrier has the characteristics of high degree of dispersion,small particle size,high mechanical strength and high specific surface area.It is also a catalyst carrier with strong comprehensive performance.This paper analyzes the catalyst activity from the influence of different morphology supports on the catalytic activity of the catalyst,as well as the size changes of the cerium-based catalyst lattice structure and nanoparticle morphology under the doping of Fe,Cu and K.Thermogravimetric analysis(TG-DTG)was used to detect the catalytic activity of the catalyst.Using SEM,X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),Raman spectroscopy(Raman)and other characterization methods to detect the physical and chemical properties of the catalyst,providing a solid theory for the development of high-performance PM catalysts in accordance with.The specific research content of this article is as follows:1.Develop an experimental program,prepare polymethyl methacrylate(PMMA)colloidal crystal microspheres by a modified emulsifier-free emulsion polymerization method,add ethyl orthosilicate to fill to obtain 3DOM-SiO2 carrier;diatomaceous earth and nano The microsphere carrier was obtained by high-temperature modification,and finally a CeKM(M:Cu,Fe)composite catalyst with 3DOM-SiO2,diatomaceous earth and nano-microspheres as the carrier was prepared by the impregnation method.The composition of two different elements,Fe and Cu,doped with cerium potassium as a substrate is compared and analyzed.Among them,the ion solubility ratio of Ce:K:M is 8:1:1.Compare the two different elements of Fe and Cu.The effect of doping on the catalytic performance of cerium potassium-based catalysts.2.The physical and chemical performance parameters of CeKM(M:Cu,Fe)composite catalyst were characterized and analyzed by XRD,Raman,FTIR,XPS and SEM.The characterization results show that the nano-microsphere CeKFe catalyst has good advantages in terms of specific surface area,particle size,oxygen vacancy concentration,and redox properties.3.Based on the CeKFe catalyst with the best catalytic performance,a CeKFe catalyst with three-dimensional ordered macroporous structure and nano-microsphere structure as the carrier was prepared.Compared the catalytic activity of the two catalysts,the nano-microsphere CeKFe catalyst has better performance.Dispersion performance,smaller particle size and more oxygen defect sites,its catalytic activity is higher than the three-dimensional ordered macroporous structure CeKFe catalyst.In this thesis,the two main factors affecting the catalyst,namely the physical and chemical properties and morphological structure of the catalyst,have been studied,and the nano-microsphere cerium potassium iron and nano-microsphere cerium potassium iron catalysts with high catalytic performance and low cost have been successfully prepared.,Can be widely used in diesel engine after-treatment system,and has a strong effect on the removal of soot particles.It is also conducive to the protection of the ecological environment while complying with the national VI emission regulations. |
