COSMO-RS assisted solvent screening for liquid-liquid extraction of mono ethylene glycol from aqueous streams

Separation of polar mixtures from water is one of the most energy consuming operations in industry, because of the high heat of vaporization of water. Avoiding evaporation of water by applying liquid-liquid extraction instead of (multi-effect) evaporation can yield large energy-savings. The distribution of mono ethylene glycol and the co-extraction of water are key parameters that depend on the characteristics of the solvent. We here report on the solvent screening for mono ethylene glycol (MEG) extraction from water to maximize the distribution coefficient (D-MEG) and selectivity (S) of MEG over water. To speed-up the screening process and avoid unnecessary experiments, COSMO-RS was used to predict the LLE performance of both real and hypothetical solvents for the extraction of MEG from aqueous streams. Based on the sigma-electron density-profile analysis, hypothetic tetraoctyl ammonium carboxylate, phosphinate and boronate ILs were considered as potentially interesting. These ILs were tailor made and evaluated in LLE experiments. They outperformed other solvents tested thus far with D-MEG up to 0.45, and S up to 3.2 vs D-MEG = 0.08 and S = 1.5 for alpha-terpineol. (C) 2012 Elsevier B.V. All rights reserved.