Designed synthesis of highly active CeO2-ZrO2-Al2O3 support materials with optimized surface property for Pd-only three-way catalysts

Abstract

In this work, a series of CeO2-ZrO2-Al2O3 (CZA) support materials were prepared by co-precipitation method combing with hydrothermal treatment at different temperatures. Then their supported Pd-only three-way catalysts (TWCs) were prepared, characterized and compared with commercial Pd/CZAS catalyst. It is found that the catalytic performance of Pd-only TWCs shows a strong dependence on the surface properties rather than the bulk structures of CZA supports. Higher hydrothermal temperatures promote the self-assemble of Al2O3 into nanorods, and the formation of CeO2-ZrO2 (CZ) solid solution with larger crystal size, which widens the pore size distribution of CZA and improves the thermal stability of CZ nanoparticles with lower growth rate, respectively. However, the specific surface area, surface oxygen vacancies and surface Ce content of CZA decrease with hydrothermal temperature rising, which in return decreases the activity of the Pd/CZA catalysts. While it should also be noted that all the as prepared Pd/CZA exhibit better activity than the commercial Pd/CZAS, and the T50 (temperature for 50% conversion) for CO, NO, C3H6, C3H8 over Pd/CZA100 are 48 °C, 30 °C, 26 °C and 31 °C lower than those for Pd/CZAS, respectively. It further indicates that highly active Pd-only TWCs could be constructed by optimizing the surface properties of CZA support via hydrothermal treatment at modern temperature.