Preparation Of Cerium-based Oxides And Catalytic Properties For Purification Of Automobile Exhausts

While the development of the automobile industry promotes the convenience of people’s lives,it emits a large amount of harmful pollutant gases,causing serious environmental pollution problems,and also causing great harm to the human body.Therefore,controlling the emission of automobile exhaust pollutants has become a crucial issue at present.Three Way Catalytic Technology(TWC)is currently the world’s mainstream technology for controlling automobile exhaust pollution,which can effectively eliminate NOx,HC,and CO in exhaust gas.As the main pollutant of lean-burn gasoline vehicle exhaust,NOx can be effectively removed through NOx Storage-Reduction(NSR)technology.The specific surface area of cerium-based oxide will be reduced by sintering under a high temperature environment and lead to degradation of catalytic performance.The preparation process of ultrasonic spray pyrolysis is simple and efficient,and cerium-based oxide materials with large specific surface areas can be prepared.The oxygen storage capacity is conducive to improving the catalytic activity.Because precious metals are scarce in resources and expensive,it is particularly important to increase the utilization rate of precious metals,reduce manufacturing costs,and save resources.Studies have found that highly dispersed Pt/CeO2 catalysts can be obtained by atom trapping method,but the catalytic effect is poor,the reduction operation treatment can improve the catalytic activity.This paper studied the effects of different preparation methods(co-precipitation method,ultrasonic spray pyrolysis method),different calcination temperature,addition of block copolymer P123,and high temperature aging treatment on the specific surface area,redox performance,and oxygen storage performance of CeO2.It is found that a series of cubic fluorite phase CeO2 has been successfully prepared under different preparation conditions.Compared with the traditional co-precipitation method,the ultrasonic spray pyrolysis method has a larger specific surface area and better oxygen storage.Oxygen performance shows that CeO2 prepared by ultrasonic spray pyrolysis method is more conducive to adjusting the oxygen value in automobile exhaust gas,and plays a role in expanding the working window of air-fuel ratio.On the basis of the ultrasonic spray pyrolysis method,it was found that the addition of block copolymer P123 significantly increased the specific surface area,which in turn affected the oxygen storage and release performance of the material.The high temperature aging treatment results show that the ceria prepared by the ultrasonic spray pyrolysis method still has a higher specific surface area,which indicating that it has excellent high temperature stability.On the basis of the prepared high-performance ceria material,a highly dispersed Pt/CeO2 catalyst was prepared by the atom trapping method.XRD characterization found that highly dispersed on the ceria carrier.It was also found that after loading Pt,the high-temperature sintering of ceria was effectively suppressed.The samples were tested for dynamic oxygen storage performance,three-way catalytic activity test,NO oxidation activity,NSR activity test,etc.It was found that the catalytic activity of the Pt/CeO2 catalyst was poor.It was further subjected to reduction treatment(275 ℃,400 ℃),found that the redox ability of the sample after the reduction operation treatment has been improved,and was found that the TWC and NSR activity of the sample after the reduction operation treatment was also greatly improved.Compare different reduction temperatures,the higher activity of the sample was found 400 ℃reduction process,indicating that increasing the reduction temperature would further increase the catalytic activity.We have fully improved the utilization of precious metals while ensuring high catalytic performance.