Preparation and characterization of thermally stable porous ceria aggregates formed via a sol-gel process of ultrasonically dispersed cerium(IV) isopropoxide

Porous ceria aggregates of submicron size were obtained from cerium(IV) isopropoxide via a two-step sol-gel process. In the first step, dispersion of the cerium(TV) isopropoxide in isopropanol media was achieved by ultrasonic radiation, where limited hydrolysis occurred and resulted in the formation of a stable dispersant gel phase. In the second step, the resultant dispersions were mixed under stirring with a neutral (water-isopropanol) or basic (aqueous ammonium hydroxide-isopropanol) solution where complete hydrolysis took place. The structural and morphological characteristics of the uncalcined (dried at 120degreesC) and the calcined (at 650degreesC for 3h in static air) materials were investigated by TGA, XRD, FTIR, SEM and nitrogen adsorption techniques. It was found that the type of media affected both the particle texture and the morphology. For the calcined materials, porous textural aggregates with specific surface areas of 33.1 and 44.2m(2) g(-1) were measured for the materials obtained via neutral and basic preparations. In addition, smaller particle size, higher mesoporous area and higher aggregation morphology were found for the material produced from the preparation in base. The preservation of surface area and porosity for the calcined materials was explained as a result of the aggregated morphology which was greater for the material produced in base. (C) 2004 Elsevier Inc. All rights reserved.