Preparation, Characterization And Catalytic Behaviors Of Ce_xZr_1-xO₂

In nowadays, air pollution by the exhaust emission from automotive engine is brought the human attention. Catalytic eliminate car exhaust is proved to be an effect route to control pollution from the automotive emission. CexZr1-xO2solid solution plays an important role in the three-way catalyst used in car due to its unique oxygen storage capacity. The performance of the three-way catalyst is maximized in the exhaust gas conditions close to the stoichiometric point, for CexZr1-xO2solid solution can maintain the air-fuel (A/F) ratios around this point through oxygen storage or release. So improve the amount of oxygen storage capacity and thermal stability of CexZr1-xO2solid solution can increase the efficiency of the three-way catalyst to save noble metal and reduce cost.In this thesis, the synergistic effect of the noble metal, CexZr1-xO2solid solution, Al2O3was investigated to find out their effect about the oxygen storage capacity and the performance of the three-way catalyst. Three different methods (citrate method, urea homogeneous precipitation method, sol co-precipitation) were used to prepare CZA nanocomposite. The obtained CZA was used to prepare1%pd/CZAatalyst by incipient wetness method. Then the catalyst was investigated by means of H2temperature-programmed Reduction (H2-TPR), Brunauer-Emmett-Teller (BET) specific surface area (SSA) and X-ray diffraction (XRD), Transmission electron microscope (TEM) to character the property of redox, thermal stability, crystal structure, oxygen storage capacity and catalytic activity for CO oxidation.The result indicates that the Pd supported on Ceo.5Zro.5O2solid solution can improve the OSC of Ceo.5Zro.5O2solid solution, for the interface of the Pd-CeZr can facilitate oxygen migration from Ceo.5Zro.5O2solid solution. The CZA prepared by three methods were proved to be nanocomposite structure and have good thermal stability. In the oxygen storage capacity aspect, the optimal proportion of Al doped in CZA is5,10,5for citrate method, urea homogeneous precipitation method, sol co-precipitation, respectively. CZA prepared by citrate acid sol-gel method had the highest oxygen storage capacity (717.5μmol/g-CeO2).