Prediction of ß-Carotene Solubility at Supercritical Conditions Using Regular Solutions Theory

The objective of this paper is to model the extraction of carotenoid with supercritical carbon dioxide as the solvent used. Experimental data for the high pressure vapor-liquid phase equilibrium of the binary system carbon dioxide-carotenoid are reviewed for the elevated temperature 313.15, 323.15, 333.15 K and pressure up to 500 bar. The experimental data were correlated and modeled using Redlich-Kwong equation of state and regular solution methods. The use of equation of state as an empirical correlation for collating and predicting liquid-liquid and liquid-dense fluid equilibria is discussed. It is concluded that the estimation of some of the parameters required for these calculations would be difficult if the solute (carotenoid) was a complex substance about which little was known apart from its structural formula. An alternative procedure is to apply activity coefficient expression of the regular solution theory type to each phase. Calculations along these lines are described and the physical basis for applying these methods under the relevant conditions discussed. The regular solution theory approach in particular has been found to be encouraging for the mutual miscibility calculations for heavy components (such as carotenoid) particularly substances sensitive to temperature, though the interaction parameters for the prediction activity coefficients must be regarded as pressure dependent.