Efficient Separation of 1,2-Dimethoxyethane and Water via [EMIM][AC]-Based Extraction: From Multi-scale Solvent Screening to Process Simulation

Abstract

The separation of 1,2-dimethoxyethane (DME) from water is a critical step in chemical engineering but remains challenging due to the formation of stable azeotropes. Traditional separation methods often suffer from high energy consumption and solvent volatility, necessitating the development of greener and more efficient alternatives. In this study, a systematic multi-scale screening strategy—combining thermodynamic predictions, quantum chemical (QC) calculations, and process simulation—was established to identify optimal ionic liquids (ILs) for DME/H2O separation. Specifically, the selectivity of 190 ILs was predicted using the Conductor-like Screening Model for Real Solvents (COSMO-RS) model, followed by experimental validation of liquid-liquid equilibrium (LLE). The screening results identified 1-ethyl-3-methylimidazolium acetate ([EMIM][AC]) as the most promising candidate. QC analysis revealed that the superior performance of [EMIM][AC] originates from strong hydrogen bonding interactions between the anion and water molecules, which was corroborated by Independent Gradient Model based on Hirshfeld partition (IGMH) and Bader's Atoms-in-Molecules (AIM) analyses. Experimental data confirmed that [EMIM][AC] exhibits significantly higher distribution coefficients compared to 1-ethyl-3-methylimidazolium diethyl phosphate ([EMIM][DEP]). Furthermore, techno-economic analysis via Aspen Plus demonstrated that the [EMIM][AC]-based extraction process reduced the total annual cost (TAC) by 25.1% and gas emission costs by 14.1% compared to the conventional dimethyl sulfoxide (DMSO) extractive distillation process. This work not only presents a cost-effective and environmentally friendly process for DME purification but also provides theoretical insights into the molecular mechanisms of IL-based separations.