Preparation and Characterization of Spherical Mesoporous CeO2-Al2O3 Composites with High Thermal Stability

Spherical mesoporous CeO2-Al2O3 composites containing 2, 5, and 8 wt % ceria have been prepared by an oil-drop sol-gel method. A mixed alumina-ceria hydrosol and hexamethylenetetramine Solution were mixed together and added dropwise into a hot oil column where spherical gel particles were formed due to surface tension. The spherical gel particles were then aged, washed, dried, and calcined at 600, 960, or 1200 degrees C. The resulting materials were characterized by X-ray diffraction, nitrogen adsorption-desorption, and temperature-programmed desorption of ammonia. At 1200 degrees C sinteiing of pure alumina is severe, whereas the presence of ceria prevents the alumina from sintering, so that the CeO2-Al2O3 composites have much larger BET surface areas than pure alumina. Addition of ceria also leads to an increase in the number of strong acid sites and the total number of acid sites compared with pure alumina. These results show that the spherical mesoporous CeO2-Al2O3 composites prepared in this way are suitable supports for high temperature catalytic processes.