Chemical Assembly Prepared By Automobile Exhaust Catalysts

Pollution of automobile exhaust has already attracted people's widespread attention. The main pollutant in the automobile exhaust may cause acidic rain and photochemical smog, pollute environment severely and endanger people's health. Therefore, controlling of automobile exhaust pollution has already become an urgent task today. Aiming at the fluid of the source of exhaust pollution, converter is equipped in the discharging pipe that makes pollutant harmless. However, in the case of cold-start, it is useless. According to this, making use of the characteristics of the small thermal capacity of metal-based supports, metal honeycomb supports are prepared by anodic oxidizing technology and are made them assemble catalytic component of purification of automotive exhaust in order to solve the problem of pollution during the cold start in the research.High purity aluminum foils are used as the starting materials and are anodized by anodic oxidizing technology in the constant voltage. The nanometer anodic alumina membranes (AAMs) were both prepared in the sulfuric and oxalic acid solution. During the preparation of AAMs, the factors affecting its pore diameter, such as technique of electropolishing, anodization time, anodization voltage, the type of electrolyst, temperature in the cell and the proportion of etching solution were investigated, and make sure that the optimal processes were: in 0.3 mol /L oxalic acid under 40V, anode oxidize aluminum foil for 4 hours, then chemical etch in the phosphoric acid solution of which the content is 5%, and then anode oxidize in the same condition for 2 hours, and finally erode in a mixture of 6% phosphoric acid and 1.8% chromic acid, at the volume proportion of 5:1.The Pd-AAMs catalyst samples were prepared by impregnation method, that is,using AAMs and PdCl2 as carriers and active component respectively. The factors affecting the catalytic activities, such asconcentration of PdCl2, times of impregnation, calcinations temperature,reactive temperature etc. have been investigated, when AAMs were immersed in the 1% PdCl2 solution for four times, and then calcined in the 600 C,the catalytic materials for purifying automobile exhaust are finally obtained, and when the optional reaction temperature is the range of 140~250 C of reaction temperature. The conversion rate of CO can arrive 92%.The Pd-CeO2-AAMs catalyst samples were also prepared by impregnation method, in which AAMs, PdCl2 and Ce(NO3)3 are used as starting materials. The factors affecting the Pd-CeO2-AAMs catalytic activities, such as the concentration of Ce(NO3)3, fluid capacity of simulated automobile exhaust and reaction temperature have been investigated. What's more, their thermal stabilities also have been discussed. The results showed that catalytic activities increased little with the growing of CeO2 under relatively low temperature. When reaction temperature was over 200 C, the contents of CeO2 in the catalysts seemed have no effect on their activities. Moreover, the thermal stabilities of Pd-CeO2-AAMs were improved with the concentrations of CeO2.