High pressure phase equilibrium for δ-tocopherol + CO2

Vapour-liquid equilibrium compositions were measured for mixtures of delta-tocopherol and carbon dioxide, at pressures from 9 up to 27 MPa, and four temperatures between 306 and 333 K. The system exhibits liquid-liquid equilibrium at high pressures, similarly to previous results for mixtures of alpha-tocopherol with carbon dioxide. The results were correlated with the Peng-Robinson equation of state, using the Panagiotopoulos-Reid combination rules. Comparison of the solubilities of delta-tocopherol and alpha-tocopherol in supercritical carbon dioxide was performed using Chrastil's equation to correlate the data. The number of solvent CO2 molecules per solute molecule was calculated in both cases. An enthalpy of solvation per mole of CO2 of -10 kJ mol(-1) was obtained. (C) 2003 Elsevier B.V. All rights reserved.