Deep eutectic solvents as extraction media for azeotropic mixtures

The separation of azeotropic mixtures is an “old” engineering problem that cannot be solved by simple distillation processes. One of the current ways to overcome this problem is to use other types of processes, such as extractive/azeotropic distillation or liquid–liquid extraction, where entrainers or extraction solvents are applied. Liquid–liquid extraction processes have been emerging as appealing alternatives because they do not require high amounts of energy, volatile organic compounds or high pressures. In this work, deep eutectic solvents (DES) are tested as extraction solvents in the liquid–liquid separation of azeotropic mixtures. For this study three different DES, all based on choline chloride, were used for the liquid–liquid separation of an azeotropic mixture of heptane + ethanol at 25 °C. The feasibility of DES as extraction solvents was assessed by the determination of their selectivities and distribution coefficients, and compared with the literature. The data obtained show that DES surpass the performance of existing extraction solvents, leading to an increase in efficiency and a reduction in energy consumption of the overall process.