Highly efficient synthesis of diethyl carbonate via one-pot reaction from carbon dioxide, epoxides and ethanol over KI-based binary catalyst system

Abstract

The synthesis of diethyl carbonate (DEC) directly from carbon dioxide, ethylene oxide (EO), and ethanol via one-pot reaction is reported for the first time. The effects of catalyst species and reaction variables on the synthetic performance of DEC were systematically studied. The integration of easily available KI and sodium ethoxide as homogeneous binary catalyst system was found to be very active for the one-pot reaction, and 63.6% of the DEC yield could be achieved under relatively mild reaction conditions (443K, 3MPa CO2 initial pressure, 2h). The byproduct of 2-ethoxyethanol, which is predominantly formed via alcoholysis of EO by ethanol through ring-opening reaction, was produced with small amount (<5%) under optimized conditions. Additionally, the thermodynamic evaluation reveals that the standard molar enthalpy of one-pot reaction is exothermic (ΔrHmθ=−19.70 kcal/mol<0). In comparison with the direct synthesis of DEC from CO2 and ethanol, the involvement of EO facilitates the formation of DEC, simultaneously with glycol produced. This strategy could also be successfully expanded to terminal epoxide substrates. Furthermore, a possible mechanism of the reaction was proposed on the basis of experimental results. This method provides a highly effective way to produce DEC via directly chemical utilization of CO2 and shows promising application in the manufacture of diethyl carbonate on an industrial scale.