PREPARATION AND PROPERTIES OF NANOPHASE (Ce, Zr, Pr)O2-DOPED ALUMINA COATING ON CORDIERITE CERAMIC HONEYCOMB FOR THREE-WAY CATALYSTS

Nanophase (Ce, Zr, Pr)O2-doped alumina coatings were prepared by impregnating the cordierite ceramic honeycomb in the sol or in the slurry of already calcined powder, respectively. The effects of preparation methods on the crystal phase, texture, oxygen storage capacity (OSC), reducibility, surface morphology and thermal stability of coatings were investigated by X-ray diffraction (XRD), the Brunauer Emmet Teller (BET) method, the oxygen pulsing technique, H2-temperature-programmed reduction (H2-TPR) and scanning electron microscopy (SEM). These nanophase (Ce, Zr, Pr)O2-doped alumina coatings were used as supports to prepare Pd-only three-way catalysts, and evaluated with respect to catalytic activities. The results indicate that the nanophase (Ce, Zr, Pr)O2-doped alumina coatings prepared by the two methods have high thermal stability. However, the coating derived from the sol shows better crystalline structure, texture, reducibility and oxygen storage capacity than the coating derived from the slurry. SEM observation shows that the morphology of the coating derived from the sol is uniform and smooth. The Pd-only catalyst derived from the sol exhibits high three-way catalytic activity at low temperature and thermal stability, suggesting a great potential for applications.