Fu, Yi-lu, Jing Tu, Pei-yan Lin. EFFECT OF CERIA ON Pd/CeO2-Al203 THREE WAY CATALYSTS
Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, P. R. China (fulin@ustc.edu.cn)
Three-way catalysts (TWC) have been used for catalytic control of three main pollutants in automobile exhaust that needs both reduction of NOx and oxidation of HC and CO. The effect of ceria doping to Pd-only catalysts with different ceria and Pd contents on the TWC activities was investigated. The surface structure of Pd/CeO2-Al2O3 was studied by XPS and TPD-MS methods. It is confirmed that the increase of Pd content is of benefit to the TWC activities. The thermal stability and the lean-burn property are significantly promoted by pre-doping the alumina with appropriate amount of ceria before the Pd impregnation. The presence of CeO2 makes Pd(+2) easily to be reduced to Pd(0). There is a stronger dissociation adsorption of NO on Pd/CeO2-Al2O3 than on Pd/Al2O3. The "oxygen storage "speciality of CeO2 and the oxygen spillover from Pd to the oxygen vacancies in Ce(+3) may promote the dissociation adsorption of NO on Pd in the presence of oxygen.