Effect of Entrainer Thermodynamic Properties on the Separation of Ternary Mixtures Containing Two Minimum Boiling Azeotropes by Extractive Distillation

Generally, the selection of an entrainer in extractive distillation depends on relative volatility, but our previous research shows that relying on relative volatility alone may not achieve the best economic and environmental benefits in the process. In this work, the effects of different entrainers on the separation process of ternary mixtures containing two minimum boiling azeotropes by extractive distillation were studied using a dichloromethane (DCM)/methanol (MeOH)/water system as an example. Taking the gas emission and total annual cost as objectives, the separation processes of eight entrainers in the DCM/ MeOH/water system were optimized and compared by a multiobjective optimization method. The optimization results show that 1,3-propanediol had the best economic and environmental benefits, although its relative volatility was not the best. The limitations of screening entrainers by relying on relative volatility alone were demonstrated. To achieve optimal economic and environmental benefits, entrainer screening needs to consider the relative volatility, thermodynamic properties of the entrainers, and possible thermal integration schemes. This work provides a reference for the screening of entrainers and process design in extractive distillation processes.