TBABr-based deep eutectic mixtures as efficient catalytic medium for the cycloaddition reaction between CO2 and epoxides

Abstract

The production of cyclic carbonates from CO₂ and epoxides is one of the most investigated strategies for the chemical utilization of CO₂ as renewable carbon source. In this work different tetrabutylammonium bromide (TBABr)-based deep eutectic mixtures were prepared and tested as catalytic systems for the cycloaddition reaction between CO₂ and propylene oxide. Best results were obtained for TBABr:Glycerol deep eutectic system. The operating conditions (reaction temperature, CO₂ pressure and TBABr:Glycerol molar ratio) on propylene carbonate formation was studied. The catalytic activity of DES (TBABr: Gly (1:5)) was also tested for different epoxides resulting in the corresponding cyclic carbonates in good yields, the exceptions were cyclohexene oxide and limonene oxide, which are more difficult to activate owing to an increased steric hindrance. Finally, the reusability of the catalytic medium was investigated using supercritical CO₂ extraction as a second step for product separation from the reaction mixture.