Exploring the potential of hydrophobic deep eutectic solvents for bioethanol separation using DFT and COSMO-RS model

Bioethanol has sparked significant interest as a promising energy source due to its green nature and sustainability. However, the separation of bioethanol presents considerable challenges. Deep eutectic solvents (DESs), as alternatives to conventional solvents, have shown efficient separation capabilities in various separation processes. However, selection of an ideal DES for a specific task always remains a challenge. In the present study, fifteen different hydrophobic DESs have been screened by employing COSMO-RS model. Three DESs (1,2-Decanediol: Thymol, Atropine: Thymol, and Lauric acid: Lidocaine) showing the best separation performance for ethanol from water were selected. DFT simulations have unveiled interaction mechanisms, emphasizing hydrogen bonding. Molecular electrostatic potential (MEP) analysis has identified the possible interaction sites for binding. Thermodynamic stabilities of the DES-ethanol complexes are elucidated through energy decomposition analysis (EDA) and second-order perturbation energies. Quantum theory of atoms in molecules (QTAIM) and interaction region indicator (IRI) analyses corroborate the existence of electrostatic interactions, predominantly in the form of hydrogen bonding, between ethanol and DESs. The significance of robust hydrogen bonding in driving ethanol separation is underscored through core-valence bifurcation (CVB) index analysis. The findings of this study yield a robust and practical methodology for choosing the most suitable DES, thereby enhancing the efficacy of ethanol separation from fermentation broths. This outcome offers a valuable and efficient approach that holds considerable promise for advancing the field of bioethanol production and refining processes.