In situ generation of superbasic sites on mesoporous ceria and their application in transesterification

Abstract

Mesoporous solid superbases have high potentials for applications as environmentally benign catalysts in diverse reactions, whereas their preparation remains a challenge. In the present study, an in situ functionalization strategy was designed to fabricate mesoporous solid superbases based on the hard-templating synthetic system of mesoporous ceria. Sodium and potassium modified mesoporous ceria (NaMC and KMC) were successfully prepared, and structural and basic properties were characterized by various methods. The obtained materials exhibit well-expressed mesostructure and superbasicity with a high strength of 27.0. The basic solutions (namely NaOH and KOH aqueous solutions) play a double role by removing the silica template SBA-15 and functioning as the guests. Therefore, sodium and potassium can be coated onto mesoporous ceria formed in situ. This strategy allows the fabrication and functionalization of mesoporous ceria in one step, which avoids the destruction of mesoporous ceria in post-modification. The obtained mesoporous solid superbases also exhibit excellent catalytic performance in dimethyl carbonate (DMC) synthesis. The yield of DMC can reach 64.6% in 4 h over NaMC, which is apparently higher than those over the samples derived from post-modification (28.9%), nonmesoporous ceria (10.8%), as well as the conventional solid base magnesia (7.6%).