Journal of Catalysis, Vol.178, No.1, 299-308, 1998
The synthesis and characterization of mesoporous high-surface area ceria prepared using a hybrid organic/inorganic route
The synthesis, characterization, and proposed formation mechanism of mesoporous high surface area ceria is described. It is shown that the reaction of cerium salts under basic conditions with ammonia in the presence of a cationic surfactant results in the precipitation of a gelatinous hydrous cerium oxide/surfactant mixture, which after drying and calcination gives pure, high surface area, fluorite-structured CeO2. Although ceria does not show long range mesoscopic organization, it exhibits a broad arrangement of mesopores in the region 20-80 Angstrom with a maximum located at around 35-40 Angstrom. HRTEM detected very small crystalline CeO2 particles with an approximate dimension of 20-50 Angstrom. This ceria shows enhanced textural and thermal resistance features compared with ceria prepared by conventional routes. Surface areas in excess of 200 m(2)/g are obtained after calcination at T = 723 K, which drop to ca 40 m(2)/g after calcination at T > 1173 K; this highlights its better potential to operate as a catalyst support or promoter under medium/high temperature range. It is suggested that the cationic surfactant does not act as a true templating agent but as a surface-area enhancer by incorporation into the hydrous oxide and lowering of the surface tension of water in the pores during drying.