High pressure phase behaviour of ternary systems containing CO2 + fatty acid methyl esters

Abstract

High pressure bubble- and dewpoint data were measured for ternary mixtures of CO2 + methyl palmitate + (methyl stearate or methyl oleate). The reported data were measured in the range T=308−348 K, p=7.1−21.8 MPa, and total solute (fatty acid methyl ester) mass fractions ranging from 0.020 to 0.618 g⋅g−1. The phase transition pressures in all the mixtures increase monotonically as temperature increases. Investigation of the ternary phase behaviour indicates that the differences observed between the binary CO2 + methyl stearate and CO2 + methyl oleate systems due to the presence of a C=C bond on methyl oleate, are translated to the ternary mixtures. The phase transition pressures also decrease almost linearly as the amount of methyl palmitate increases suggesting no significant interactions between the solutes. Prediction of the ternary data with the CPA equation of state are in good agreement with the experimental data provided binary CO2 + solute interaction parameters are fitted.