Synthesis of Unsymmetrical Alkyl Carbonate from Diethyl Carbonate and Benzyl Alcohol with N-Doped Carbon-Supported Iron Oxide Catalysts

Abstract

Developing simple and efficient heterogeneous catalysts for transesterification of dialkyl carbonates with alcohols is very significant for achieving green syntheses of unsymmetrical alkyl carbonates. Here, a set of N-doped carbon material (NCM)-supported iron oxides was prepared for catalytic application in transesterification of diethyl carbonate (DEC) with benzyl alcohol to synthesize benzyl ethyl carbonate (BEC). Various characterization results demonstrated that introducing a small amount of iron salts onto the NCM support generated a number of weak Lewis acidic centers after the impregnation–calcination process. The condition-optimized catalyst named 6.0%Fe2O3/NCM-600 displayed very high catalytic activity, selectivity and stability in the transesterification reaction, showing 95% conversion of benzyl alcohol and 98% selectivity to benzyl ethyl carbonate under mild conditions, much better than iron oxide catalysts supported on other carriers (active carbon, SiO2 and Al2O3). The weak-to-medium Lewis acidic sites derived from the interaction between the highly dispersed Fe2O3 and NCM support were the main active centers, while the neighboring basic N-containing groups of NCM might also have promoted the activation of the reagents, thus synergistically catalyzing the transesterification of DEC with alcohols to generate unsymmetrical alkyl carbonates.