High pressure vapour-liquid equilibria for the mixture DL-γ-tocopherol/methanol

DL-gamma-Tocopherol is one of the four homologues compounds also known as vitamin E. Tocopherols are present in all four forms (alpha-, beta-, gamma-, delta-tocopherol) in many natural sources and extraction design of purification processes used for their enrichment needs detailed knowledge of the phase equilibrium behaviour. Experimental vapour-liquid equilibrium data (pressure-composition isotherms) for the binary system DL-gamma-tocopherol/methanol at four temperatures 473 K, 498 K, 523 K, 543 K and pressures up to 12 MPa are presented. The measurements were carried out in a static constant volume high-pressure apparatus. Different cubic equations of state and mixing rules were used to model the data. A modified Redlich-Kwong-Soave EOS gives the better correlation. On the basis of the new experimental data and those for the system DL-alpha-tocopherol/methanol and reasonable agreement between the two systems, using for both the same thermodynamic model, behaviour of the ternary system DL-alpha-tocopherol/DL-gamma-tocopherol/methanol has been predicted. (C) 1999 Elsevier Science B.V. All rights reserved.