Application of Mixed Solvent To Achieve an Energy-Saving Hybrid Process Including Liquid-Liquid Extraction and Heterogeneous Azeotropic Distillation

There is a binary azeotrope in the propylene glycol methyl ether dehydration system. The traditional process to separate propylene glycol methyl ether and water is a high-energy consumption issue. To save energy, a novel hybrid process consisting of heterogeneous azeotropic distillation and liquid-liquid extraction is proposed to separate the binary mixture using a mixed solvent, which is proposed. The process is optimized to achieve a minimum total annual cost (TAC). The optimal mixed solvent is 70 mol % chloroform and 30 mol % 2-ethylhexanoic acid. The hybrid process using the mixed solvent shows a better performance than the previous work in terms of both environmental impact and economy. The optimal process reduced CO2 emissions from 27.5% to 26.7% in the TAC compared with using a single solvent. Thermodynamic efficiency was improved from 8.55% to 10.15%. The mixed solvent is promising for recovering propylene glycol methyl ether.