THERMODYNAMIC MODELING OF HIGH-PRESSURE PHASE EQUILIBRIA FOR THREE ESSENTIAL OIL+CARBON DIOXIDE SYSTEMS

摘要

In this work, the thermodynamic modeling of high-pressure phase equilibrium data of essential oils present in three odoriferous plants (clove buds, eucalyptus and Lippia sidoides) in carbon dioxide is presented. The proposed estimation method uses the volatile oil composition obtained by supercritical fluid extraction for modeling solid-vapor equilibria (SVE), Based on the chemical composition of the volatile oil and using a group contribution method, a pseudo component is defined. The thermodynamic model combines the cubic Peng-Robinson equation of state (PR-EOS) with the van der Waals (VDW), Non-Quadratic Generalized (NQG) and Wong-Sandler-UNIQUAC (WS-UNIQUAC) mixing rules. The fugacity coefficient is obtained numerically by differentiating the pressure with respect to the mole numbers, allowing the combination of any EOS with any mixing rule and eliminating the need for the cumbersome analytical determination. Parameter estimation is performed by using a modified Marquardt method with an objective function that includes the gas phase concentration. The results demonstrate that, in spite of the simplifying assumptions, the model quantitatively describes the experimental data.