Modeling high-pressure vapor–liquid equilibrium of limonene, linalool and carbon dioxide systems

The research reported in this study is focused on modeling high-pressure phase behavior for CO2–limonene and CO2–linalool. A modified Peng–Robinson equation of state was applied to calculate vapor–liquid equilibrium using five different mixing rules obtained by incorporating activity coefficient models. The methodologies proposed by Heidemann–Kokal, Wong–Sandler and LCVM were used coupled with NRTL, UNIQUAC and UNIFAC models. A comparative analysis of the generated models was done for the binary systems and the best model was chosen to describe phase behavior of the system CO2–limonene–linalool. An isothermal flash calculation was applied to investigate selectivity and yield simultaneously for this ternary system in order to understand better the process parameters governing supercritical CO2 deterpenation of citrus peel oil. The results showed that to obtain good separation between limonene and linalool at 50°C and pressures from 80 to 90 bar a high CO2/oil ratio is needed. As this ratio decreases, the process can be operated at 60 and 70°C over the same pressure range with equivalent performance.