Phase behavior of systems consisting of supercritical carbon dioxide and eucalyptus or rosemary essential oil

From experimental studies in literature, it has been proven that the phase behavior of supercritical carbon dioxide with pure or mixed solvents or solutes may not be simple, and in many cases, a second liquid phase appears. In this work, we considered the phase behavior of supercritical carbon dioxide with two essential oils, namely, eucalyptus oil and rosemary oil. We investigated the phase behavior of each system of CO2 + eucalyptus oil and CO2 + rosemary oil separately, and we observed that both systems form a second liquid phase. We measured the bubble point pressures of both systems for five different concentrations of CO2, and also the three phase line of liquid-liquid-vapor of these systems. Based on the observed upper solution critical points, we concluded that the phase behavior of these two systems is Type-III based on the Scott and Van Konynenburg phase classification.