Phase equilibria for the mixtures of the deep eutectic solvent L-menthol plus thymol plus CO2 at high pressure

The Vapour-Liquid Equilibrium (VLE) of different mixtures of CO2 +L-menthol, CO2 + thymol and CO2 + Lmenthol + thymol has been determined at 35, 40, 50 and 60 degrees C and pressures up to 220 bar using a variable volume view cell. Menthol + Thymol form a deep eutectic solvent (DES) mixture at a 1:1 molar ratio. For selected conditions, the composition of the vapour phase was determined by 1H NMR. By interpolation of the experimental values, ternary diagrams were built. The mutual solubility between CO2 and DES decreased as the proportion menthol:thymol approached the eutectic composition (1:1). Mutual miscibility also decreased with temperature and increased with pressure. The composition of the mixture of menthol + thymol (1:1) does not remain stable at 60 degrees C but it does at lower temperatures. The intermolecular interactions between menthol and thymol are responsible for this behaviour. The PengRobinson equation of state was used to correlate the results with promising results. (c) 2023 The Author(s). Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering Chemistry. This is an open access article under the CC BY license (http://creativecommons.org/ licenses/by/4.0/).