Priority Separation of Phenols with Deep Eutectic Solvents from an Acetonitrile-Extractable Portion of a Shale Oil: Experimental and Computational

Several liquid deep eutectic solvents (DESs) at room temperature were screened and used to extract phenols from an acetonitrile-extractable portion (ANEP) of the oil from oil shale pyrolysis. Among choline chloride (CC)/ethylene glycol (EG) with lowest viscosity and neutral oil entrainment (molar ratio = 1:3) was selected as an optimal DES for isolating phenols from ANEP. As a result, the CC/EG-extractable portion contains 56.7% of oxygen-containing aromatics, among which phenols account for 75.1% by magnetically stirring the isometric mass mixture of ANEP and the CC/EG at room temperature and 500 rpm for 0.5 h. Intermolecular interaction energy and type between different DESs and solutes were calculated by molecular dynamics simulation, independent gradient model analysis, energy decomposition analysis based on the force field, and electrostatic potential analysis to uncover the mechanism for the priority separation of phenols. The result shows that the DES that contains polar HBD with lower viscosity and carbon number and asymmetric HBA with shorter alkyl chains, e.g., CC/EG, could strongly interact with phenols by the strong hydrogen bond, X-H···π and/or cation/anion···π compared to other aromatics.