Supercritical fractionation of Agathosma (buchu) essential oil. Part I: Measurement of binary phase equilibria

Abstract

The value of essential oils can be improved by removing the potentially unstable compounds, such as monoterpene hydrocarbons (MT), in a process known as deterpenation. In order to determine the feasibility of deterpenation using supercritical CO2, the phase behaviour of the pure components in CO2 must be known. Phase equilibria data of most components found in buchu essential oil in supercritical CO2 are not available in the literature. In this study, the phase equilibria of binary systems pulegone + CO2, diosphenol + CO2, terpinen-4-ol + CO2 and limonene + CO2 were measured between 308 K and 358 K, and at solute mass fractions between 0.0147 and 0.638, using a static synthetic view cell. The data were modelled using Chrastil's equation and separation factors determined. Oxygenated terpenes (OT) are significantly less soluble than MT, especially at the higher temperatures, indicating the possibility of separation.