Separation of low molecular weight alcohols from water with deep eutectic solvents: Liquid-liquid equilibria and process simulations

Low molecular weight alcohols such as ethanol, propanol and butanol are currently gaining attention owing to their complete combustion and higher calorific value. These low molecular weight alcohols are obtained by ABE (acetone-butanol-ethanol) fermentation, where they are produced within an aqueous phase. Extraction is contemplated as one of the effective methods for the separation of these lower alcohols from aqueous phase through a solvent. The solvent explored here relates to the formulation of Deep Eutectic Solvent (DES) comprising of DL-menthol (Hydrogen Bond Donor) + decanoic acid (Hydrogen Bond Acceptor). The current work adopts a multiscale approach leading with DES preparation and subsequent batch scale Liquid-Liquid Equilibria (LLE) measurement and finally concludes through process simulation studies. The experimental LLE data of DES (1)-Alcohol (2)-Water (3) gave a higher affinity towards alcohol and lower solubility with water. The experimental results were thereafter regressed with the NRTL model using the additional constraint where a positive tangent plane distance is imposed for all the tie lines within the Gibbs energy of mixing (G(m)) surface. The average absolute RMSD values correlated via NRTL and COSMO-SAC model were found to be 0.003 and 0.008 respectively. A flow sheet with a hybrid extraction-distillation system is then proposed and simulated for the solvent recovery, scale-up and cost analysis. (C) 2021 Elsevier B.V. All rights reserved.