Characterization and Modeling of the Liquid Phase of Deep Eutectic Solvents Based on Fatty Acids/Alcohols and Choline Chloride

The solid-liquid equilibria phase diagrams of eight eutectic systems formed by choline chloride and fatty acids, or fatty alcohols, were measured to characterize the non-ideality of the liquid phase of these deep eutectic solvents (DES), and to evaluate the best modelling approaches to their description. Most of these systems are shown to present only slight deviations to ideal behavior, resulting from a fine balance of the hydrogen bonding between the hydroxyl/carboxylic groups with the chloride anion, and the interactions present in the pure compounds. The phase diagrams measured were modelled with an associative EoS and a gE model. As EoS the perturbed-chain statistical associating fluid theory (PC-SAFT) was used, and this model was able to accurately describe the experimental data and to provide reliable estimates of the eutectic points using just a single binary temperature dependent interaction parameter, that often correlates with the acid/alcohol chain length. The performance of PC-SAFT was furthe...