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Recently, some works claim that hydrophobic deep eutectic solvents could be prepared based on menthol and monocarboxylic acids. Despite of some promising potential applications, these systems were poorly understood, and this work addresses this issue. Here, the characterization of eutectic solvents composed of the terpenes thymol or l­(−)-menthol and monocarboxylic acids is studied aiming the design of these solvents. Their solid–liquid phase diagrams were measured by differential scanning calorimetry in the whole composition range, showing that a broader composition range, and not only fixed stoichiometric proportions, can be used as solvents at low temperatures. Additionally, solvent densities and viscosities close to the eutectic compositions were measured, showing low viscosity and lower density than water. The solvatochromic parameters at the eutectic composition were also investigated aiming at better understanding their polarity. The high acidity is mainly provided by the presence of thymol in the mixture, while l­(−)-menthol plays the major role on the hydrogen-bond basicity. The measured mutual solubilities with water attest to the hydrophobic character of the mixtures investigated. The experimental solid–liquid phase diagrams were described using the PC-SAFT equation of state that is shown to accurately describe the experimental data and quantify the small deviations from ideality.

Vegetable oils can be deacidified by liquid-liquid extraction. The difference in polarity between the triglycerides, the principal components of the oil, and the solvent guarantees the formation of two phases and permits the removal of free fatty acids. A knowledge of the equilibrium between the phases of such systems is important, however, if adequate equipment for the implementation of the process is to be designed. The present paper establishes experimental data for systems of canola oil, oleic acid, and alcohols, subsequently adjusting the NRTL and UNIQUAC models to them for the calculation of activity coefficients. The results show the good descriptive quality of the models.

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