Enhanced yields of diethyl carbonate via one-pot synthesis from ethanol, carbon dioxide and butylene oxide over cerium (IV) oxide

摘要

There is a considerable industrial interest towards short-chain dialkylcarbonate production technologies due to their attractive properties and apparent commercial applications. Over the years, dimethyl carbonate (DMC), in contrast to diethyl carbonate (DEC), was mainly explored in seeking novel synthesis ideas in academic investigations. Therefore, this work has been devoted to the synthesis of diethyl carbonate. The preliminary results showed that the formation of DEC via direct route starting from ethanol and carbon dioxide (CO2) is limited by the reaction equilibrium and therefore thermodynamics of the reaction has been estimated. Consecutively, butylene oxide was introduced to the reaction system as a dehydrating agent in order to overcome thermodynamic constrains and shift the equilibrium towards diethyl carbonate production. The underlying reason for choosing a longer chain epoxide (i.e. butyl instead of e.g. propyl) was the acute toxicity of short-chain epoxides. A 9-fold enhancement in DEC yield compared to the method without any water removal was achieved over cerium (IV) oxide (CeO2) in the presence of butylene oxide at 180 °C and 9 MPa of total final pressure unequivocally indicating that butylene oxide is an efficient chemical water trap. The highest obtained yield of diethyl carbonate was 2.5 mmol, corresponding to ethanol conversion of 15.6% and selectivity to DEC 10% on ethanol basis. Moreover, kinetic studies were conducted facilitating understanding of the reaction pathway and influence of various parameters on the reaction.