Liquid-vapor and liquid-liquid-vapor equilibria in the ternary system ethane + limonene + linalool

To investigate the potential of replacing supercritical carbon dioxide by supercritical ethane in the deterpenation of citrus essential oils, the phase behavior of the ternary system ethane + limonene + linalool was determined experimentally. The measurements were made with a synthetic method in which at any desired temperature, the pressure was varied for a mixture of fixed overall concentration, until a phase change was observed visually. The molar concentration of ethane was fixed at a constant value of 98% in all the experiments, leaving the ratios of limonene to linalool as variables ranging from 0 to 1. Equilibria between the vapor and liquid phases were measured within temperature and pressure ranges of 293-363 K and 3-9 MPa, respectively. It was observed that limonene had higher solubility than linalool in supercritical ethane, with the difference in solubility increasing with temperature. In contrast to the ternary system with carbon dioxide, the ternary system with ethane, limonene and linalool exhibited liquid-liquid phase splitting, resulting in the presence of a three-phase liquid-liquid-vapor region. This occurred in the linalool-rich side of the phase diagram. Experimental values of the upper and lower critical endpoints of the three-phase region, in addition to normal critical points of two-phase equilibria are presented. From the experimental results, it can be concluded that the system ethane + linalool + limonene shows type-V fluid phase behavior according to the classification of van Konynenburg and Scott.