Investigation of toluene-methyl isobutyl ketone mixed solvents as extractants for efficient separating ethylene carbonate from ethylene glycol

Background

The separation of value-added glycerol carbonate, versatile commercial ethylene glycol (EG), and residual ethylene carbonate (EC) is crucial for further application after transesterification of glycerol and EC. However, the EC and EG form an azeotropic mixture, which cannot be separated by conventional distillation methods.

Methods

To separate EC-EG azeotropic mixture, a mixed extractant of toluene and methyl isobutyl ketone (MIBK) was developed to extract EG and EC by liquid-liquid extraction. The selection of suitable extractants with high selectivity (S) and distribution coefficient (D) is key to achieving efficient separation. Herein, to evaluate the feasibility of extractive separation of EG and EC, the corresponding liquid−liquid equilibrium (LLE) data were measured at 313.2 K under atmospheric pressure.

Significant findings

The mixed extractant showed higher D than toluene alone and higher S than MIBK alone, which makes it a more suitable extractant for separating the EC-EG mixture. In addition, the radial distribution function showed that the peak height g(r) between extractants (MIBK and toluene) and EC (1.58–1.83) was higher than that between extractants and EG (1.01–1.15), suggesting that toluene and MIBK preferentially extracted EC from the EC-EG mixture. Herein, this study provided an effective strategy for separating EC and EG after transesterification of glycerol and EC.