Lucie Coniglio

Phase Equilibria Measurements and Modeling of EPA and DHA Ethyl Esters in Supercritical Carbon Dioxide

Abstract A high pressure, variable-volume visual cell was used to perform static measurements of phase equilibria involving carbon dioxide and two different fatty acid ethyl esters: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) ethyl esters. Six temperatures ranging from 303.15 to 353.15 K were selected. In a second step, our data were compared with predictions obtained by two group contribution based models previously published. Both models are able to predict with quite high accuracy our data whatever the temperature.

Prediction of supercritical fluid-liquid equilibria for carbon dioxide and fish oil related compounds through the equation of state — excess function (EOS-gE) approach

Abstract This paper compares the correlative and predictive abilities of three forms of models based on the approach which combines an equation of state (EOS) with a gE-model in an EOS framework. In particular, the MHV1 mixing rule with a quadratic mixing rule for the mixture b parameter, the LCVM method and a variation of the LCVM method have been investigated. Estimation of supercritical fluid-liquid (SCFL) phase behavior of mixtures involving carbon dioxide and ethane as the “light” compound and fatty acid esters (carbon number > 10) and hydrocarbons (n-Alkanes) as the “heavy” compounds have been considered. Finally, a generalized expression for the mixture α-parameter, from which several other mixing rules (including the ones investigated in this paper) can be derived, is presented. The derivation of the MHV1 mixing rule and the LCVM method from the generalized expression is given together with the estimated phase equilibria.

Use of heat capacities for the estimation of cubic equation-of-state parameters-application to the prediction of very low vapor pressures of heavy hydrocarbons

Abstract Improvement in the prediction of very low vapor pressures is checked by introducing heat capacity data into the estimation of cubic equation-of-state (EOS) parameters. As the key parameter is the temperature-dependent parameter a, several expressions (mainly of exponential form) were investigated. All of them were chosen in order to show a consistent behavior for the two considered properties (vapor pressures and heat capacities). The cubic EOS used as an illustration is of the Peng–Robinson type applied to heavy hydrocarbons. No satisfactory refinement in the prediction of the very low vapor pressures was observed in comparison with the results obtained by extrapolating the EOS from medium to very low pressures. This work has, however, the following benefits: (1) to point out the changes that should be made to improve these predictions; (2) to inform on the accuracy that may be obtained if vapor pressures of heavy organic compounds are predicted from heat capacity data as the sole alternative for estimating the temperature-dependent parameter a of a cubic EOS; (3) to confirm the reliability of the cubic group-contribution (GC)-based EOS proposed by Coniglio et al. [Ind. Eng. Chem. Res. 39 (2000) 5037] when extrapolated for modeling crude oils or gas condensates encountered in the petroleum industry.