(481a) High Pressure Fluid Phase Behavior of Two Essential Oil Systems with CO2

From numerous studies on binary and ternary mixtures with carbon dioxide as the near-critical component, it became apparent that the fluid phase behavior of these systems can be quite complex. For instance, with many solutes carbon dioxide shows a second liquid phase. In processing essential oils, we are dealing with complex mixtures of organic constituents of which many of them may show fluid multiphase behavior with carbon dioxide, of course, depending on temperature, pressure and composition of the system. Therefore, it has to be expected that also essential oils may show such a complex multiphase behavior. This study reports on phase equilibrium experiments of two essential oils, namely eucalyptus and alecrim oil in the presence of carbon dioxide as the near-critical solvent. It has been established that both oils show liquid-liquid immiscibility with carbon dioxide with all characteristics of type-III fluid phase behavior in the classification of Van Konynenburg and Scott. Although both essential oils have a completely different molecular composition, it was found that only minor differences occurred in their fluid phase behavior.