An optimized highly active and thermo-stable oxidation catalyst Pd/Ce-Zr-Y/Al2O3 calcined at superhigh temperature and used for C3H8 total oxidation

A series of supported catalysts Pd/Ce-Zr-Y/Al2O3 with different Y loadings (0%, 2%, 5%, 10% by weight) were prepared by ultrasonic-assisted impregnation, and employed for C3H8 total oxidation. It is found that these catalysts possess high catalytic activity and high thermal stability even after calcination at 1100 degrees C, especially for the one promoted by 5% Y. In addition, this catalyst also exhibits best water-vapor resistance performance. The results of H-2-TPR and XPS show that the addition of proper amount of Y to Pd/Ce-Zr/Al2O3 can enhance the interaction between Pd species and the support, thus increasing the dispersion of Pd species. The TEM, TPHD and CO pulse chemisorption results conformably reveal that the catalyst Pd/Ce-Zr-Y/Al2O3 containing 5% Y possesses the highest Pd dispersion as compared with others. However, excessive amounts of Y lead to remarkable decrease of BET surface area, lowering the dispersion of Pd species and weakening the interaction between Pd species and support; as a result, the catalyst exhibits lower oxidation activity. Combined with all the results of catalytic oxidation performance, water-vapor resistance performance and multiple characterizations, it is concluded that the Pd/Ce-Zr-Y/Al2O3 catalyst containing 5% Y possesses the greatest application potential for the catalytic removal of hydrocarbon pollutants released by engines during cold-start period. (C) 2012 Elsevier Ltd. All rights reserved.