Phase Equilibrium Measurements for the System Clove (Eugenia caryophyllus) Oil + CO2

Abstract

Phase equilibria data for the system formed by clove oil + CO2 were measured at pressures from 58.3 to 108.1 bar and temperatures of 303.2, 313.2, and 328.2 K. The phase equilibrium experiments (cloud points) were performed using a high-pressure variable-volume view cell. The phase transitions were visually recorded as bubble or dew points. The clove oil used in the present work was extracted with carbon dioxide at 150 bar and 298.2 K, and it consisted of a mixture of the following mass fractions: eugenol (75.5%), β-caryophyllene (12.1%), eugenol acetate (11.0%), and α-humulene (1.40%). Liquid−liquid−vapor equilibria were observed at 303.2 and 308.2 K, and liquid−vapor equilibria were observed at 313.2, 318.2, and 328.2 K. The phase equilibria data were modeled assuming the system to be a pseudobinary system. The Peng−Robinson equation of state with the quadratic mixing rule was used. The experimental data were fitted using the simulated annealing minimization method. Two different procedures were employed: (i) the phase stability was calculated using the Helmholtz free energy and the interval analysis, and (ii) the phase equilibrium was calculated using the Gibbs free energy, which was solved with the simulated annealing method. The model described quantitatively the experimental data.