Phase equilibrium of fish oil ethyl esters with supercritical carbon dioxide

Phase equilibrium measurements for 13 different fatty acid ethyl ester mixtures were performed in the temperature range of 40-80 degrees C and in the pressure range of 9-25 MPa with supercritical CO2. These complex mixtures represent various fractions of separation experiments and cover a wide concentration range. Numerous components were lumped into five pseudocomponents on the basis of the chain length representing more than 95 wt.% of all components. Distribution coefficients were calculated from the experimental data, Binary and ternary equilibrium data were correlated using the Peng-Robinson equation of state [1] in combination with the Melhem mixing rule [2]. Fitting of temperature dependent interaction parameters thr a system containing three components as a maximum, leads to a medium average absolute deviation of 1.3 x 10(-2). Prediction of partition coefficients in multi component systems needs an empirical model in order to keep the computational effort reasonable. The molecular weight and an exponential decay equation are used in this model to calculate the partition coefficients for each pseudocomponent. A medium average absolute deviation of 5.3 x 10(-3) results from this model. (C) 1999 Elsevier Science B.V. All rights reserved.