Ternary phase equilibria for mixtures of supercritical methanol + c18 fatty acid, methyl esters + 2,5,7,8-tetramethyl-2-(5,9,13-trimethyltetradecyl) chroman-6-ol (α-tocopherol)

Ternary phase equilibrium data for methanol + C18 fatty acid, methyl esters + 2,5,7,8-tetramethyl-2-(5,9,13-trimethyltetradecyl)chroman-6-ol (α-tocopherol) were measured at (523 and 548) K and (6 and 8) MPa. The experimental results indicated that the two-phase region shrinks with increasing pressure. Additionally, temperature has the opposite influence to that of pressure; i.e., the two-phase area expands with temperature. The experimental data were correlated using the Peng-Robinson equation of state (PR EOS). An exponent-type mixing rule was adopted for the energy parameter of the PR EOS. The binary parameters for methanol + C18 fatty acid, methyl esters and methanol + 2,5,7,8-tetramethyl-2-(5,9,13-trimethyltetradecyl)chroman-6-ol pairs in the mixing rules were determined from the phase equilibrium data for the binary systems. For the C18 fatty acid, methyl esters + 2,5,7,8-tetramethyl-2-(5,9,13- trimethyltetradecyl)chroman-6-ol pair, the data for the ternary system were used for the determination of the binary parameters. The correlated results with the exponent-type mixing rule are more accurate than those in the case of the conventional mixing rule. The experimental data can be used for designing the supercritical methanol process for producing biofuel and tocopherols from soybean oil byproducts. Notably, this work is the first to report the ternary phase equilibrium data of methanol + C18 fatty acid, methyl esters + 2,5,7,8-tetramethyl-2-(5,9,13-trimethyltetradecyl)chroman-6-ol at high temperatures and pressures.