Separation of ethylene glycol and ethylene glycol diacetate azeotropic mixture with a heterogeneous extraction distillation process

The vapor-liquid equilibria of binary mixtures of ethylene glycol diacetate (EGDA) + o-chlorotoluene (OCT) and EGDA + cyclohexylbenzene (CHB), and the liquid-liquid equilibria (LLE) in ternary mixtures of ethylene glycol (EG) + EGDA + o-chlorotoluene and EG + EGDA + cyclohexylbenzene are measured in this work. The new data have been described with the NRTL thermodynamic model. The heterogeneous extractive distillation and liquid-liquid phase separation process for the investigated systems are then simulated using the Aspen Plus software and the adjusted thermodynamic model. The influence of key process parameters such as the ratio of solvent flow rate to feed flowrate, the plate number and the reflux ratio on the separation process are analyzed in detail, and the optimal process parameters are determined. An economic and environmental study of the process is then performed. It is found that the two extractants (o-chlorotoluene and cyclohexylbenzene) can achieve a good EG + EGDA azeotrope separation. The purities of both EG and EGDA products are greater than 99.50 wt% in the two processes. The predicted selectivity obtained with o-chlorotoluene is higher than the one obtained with cyclohexylbenzene process. However, the cyclohexylbenzene process is found to be was more environmentally friendly, and the utility costs and CO₂ emissions of are lower. This work brings new insights in the design and optimization for the separation of EG and EGDA azeotropic mixtures.