High-pressure phase equilibrium and modeling of CO₂ + eucalyptol binary system

The use of supercritical carbon dioxide technology to improve extractive and industrial processes using green solvents such as eucalyptol (1,8-cineol) requires knowledge of phase equilibrium and thermophysical properties under different pressure, temperature and composition conditions. This work presents the phase equilibrium data for the CO₂ (1) + eucalyptol (2) binary system. The synthetic visual method was employed with CO₂ molar fractions ranging from 0.60 to 0.99 in the temperature range of 313.15 to 333.15 K. For this system, vapor-liquid equilibrium (VLE) with bubble point (BP) and dew point (DP) was visually identified between 5.31 and 12.76 MPa, with the mixture’s critical point observed near a CO₂ molar fraction of 0.95. The system exhibited lower critical solution temperature (LCST) behavior, with transition pressures increasing with temperature. The Peng-Robinson equation of state with the van der Waals mixing rule (PR_vdW) was employed to correlate the experimental data, providing a satisfactory representation of the equilibrium data. These results provide a relevant thermodynamic model for understanding the phase behavior of this system under high pressure and supercritical conditions, supporting its potential technological applications.