Research On Catalytic Emission Reduction Technology Of Automobile Exhaust

With the development of the automobile industry,automobile exhaust has become an important source of urban air pollution.At present,the most effective way to control automobile exhaust is to install a catalytic converter.The increasingly stringent automobile emission standards pose challenges to traditional catalysts.It is necessary to study new catalysts to further purify automobile exhaust.In this paper,a purification device is designed and a new type of catalyst is installed in the device.The device can be installed in the exhaust pipe of a car to further purify the car exhaust.Aiming at the temperature of the automobile exhaust pipe,an automobile exhaust catalyst with higher low temperature activity is prepared.The catalytic activity of automobile exhaust catalysts is closely related to the properties of oxygen storage materials.The oxygen storage material with good performance adjusts the air-fuel ratio,reduces the oxygen fluctuation,and improves the catalytic efficiency of the catalyst.The development of high-performance oxygen storage materials is one of the effective means to improve the catalytic efficiency of automobile exhaust.The catalyst adopts zirconium and cerium solid solution as the carrier;lanthanum,yttrium,and praseodymium are used as catalyst additives;nano-alumina is used as the coating of the catalyst;Cu O is used as the active component of the catalyst.In this paper,a rare earth metal modified cerium-zirconium solid solution was prepared by co-precipitation method,and nano-alumina and active component Cu were loaded by impregnation method.Catalytic activity tests were carried out under laboratory conditions,and the results showed that the catalysts modified with binary and ternary rare earth metals in an appropriate ratio performed better than those modified with single-component rare earth metals.When the amounts of La,Y,and Pr dopants are 6%,3%,and 3%,respectively,the catalytic performance of the catalyst is the best.The ignition temperature of the catalyst for CO,NOx and CH is 125℃,255℃,250℃;the complete conversion temperature is 150℃,300℃,280℃.The specific surface area of the fresh catalyst is as high as 198.4 m~2/g,and the specific surface area can still reach 68.3 m~2/g after aging at 900℃.The addition of rare earth metal Y can improve the low temperature catalytic activity of the catalyst,and the addition of rare earth metal Pr can,improve the high temperature stability of the catalyst.Compared with the precious metal Pd catalyst,the low temperature catalytic activity of the catalyst for CO is much lower than that of Pd.Use VESTA for modeling and VASP software for first-principle calculations.The calculation results show that the cerium-zirconium solid solution modified by the three rare earth elements of cerium,zirconium and lanthanum has the best oxygen storage and release performance,followed by the cerium-zirconium solid solution modified by lanthanum and yttrium,and the cerium-zirconium solid solution modified by lanthanum-praseodymium has the worst oxygen storage performance.The formation energies of the three rare-earth metal doping modification systems of La,Y,and Pr are very low,and La,Y,and Pr can easily enter the cerium-zirconium solid solution crystal lattice.The adsorption energy of Cu O for CO、NO is lower than that of precious metal Pd,and CuO is easier to adsorb CO、NO.