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 m esoporous high surface area ceria is described. It is shown that the r eaction of cerium salts under basic conditions with ammonia in the pre sence of a cationic surfactant results in the precipitation of a gelat inous hydrous cerium oxide/surfactant mixture, which after drying and calcination gives pure, high surface area, fluorite-structured CeO2. A lthough ceria does not show long range mesoscopic organization, it exh ibits a broad arrangement of mesopores in the region 20-80 Angstrom wi th a maximum located at around 35-40 Angstrom. HRTEM detected very sma ll crystalline CeO2 particles with an approximate dimension of 20-50 A ngstrom. This ceria shows enhanced textural and thermal resistance fea tures compared with ceria prepared by conventional routes. Surface are as 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 hig hlights its better potential to operate as a catalyst support or promo ter under medium/high temperature range. It is suggested that the cati onic surfactant does not act as a true templating agent but as a surfa ce-area enhancer by incorporation into the hydrous oxide and lowering of the surface tension of water in the pores during drying. (C) 1998 A cademic Press.