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

dl-γ-Tocopherol is one of the four homologues compounds also known as vitamin E. Tocopherols are present in all four forms (α-, β-, γ-, δ-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-γ-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-α-tocopherol/methanol and reasonable agreement between the two systems, using for both the same thermodynamic model, behaviour of the ternary system dl-α-tocopherol/dl-γ-tocopherol/methanol has been predicted.