Catalytic activity of Ce^IVO₂/Ce₂^IIIO₃-silica mesoporous composite materials for oxidation and esterification reactions

Bifunctional catalytic performance of various ceria-containing mesoporous silica samples have been investigated for oxidation as well as acid-catalyzed esterification reactions under mild conditions. Hexagonal (p6mm) and cubic (Ia3d) ordered mesoporous silica materials with incorporated Ce^IVO₂ were synthesized with high Ce content and successfully reduced to Ce₂^IIIO₃-silica species under H₂ gas flow. Small angle X-ray scattering (SAXS) analysis of the samples shows ordered patterns of the materials studied. The surface area and porosity of the samples were determined from N₂ adsorption isotherms. Both the oxidation states of ceria have been proved as highly efficient catalysts for liquid phase oxidation of numerous hydrocarbons like cyclohexene, styrene, benzyl alcohol, and xylene and so on at room temperature under solvent-free conditions, whereas Lewis basicity of cerium oxide has been explored for esterification reaction of various alcohols like benzyl alcohol, octanol, and decanol and so on using acetic acid under mild conditions. The surface acidic sites present on both Ce^IVO₂-silica and Ce₂^IIIO₃-silica composites have been measured and compared by ammonia-TPD analysis performed at 393K. The reusability and heterogeneity of the catalysts with minimum loss have also been examined under identical conditions.