Correlating the solubility behavior of fatty acids, mono-, di-, and triglycerides, and fatty acid esters in supercritical carbon dioxide

The knowledge of the solubility behavior of different Lipid classes in supercritical carbon dioxide (SCCO2) is of great importance in the design of SCCO2 fractionation, extraction, and reaction processes. Solubility data from the literature for binary mixtures of SCCO2 and pure lipids (fatty acids, mono-, di-, and triglycerides, and fatty acid esters) were correlated using Chrastil's equation to determine the effect of compound properties (molecular weight and polarity) and operating conditions (density of CO2, pressure, and temperature) on the solubility behavior. The physical state of the lipid solute had a significant effect on model parameters and, hence, the solubility behavior. An isothermal increase in the pressure and a temperature increase at constant CO2 density led to an increase in solubility for all the compounds studied. Retrograde solubility behavior was observed for liquid solutes, whereas the solid solutes were in the nonretrograde region under the examined conditions. In a homologous series, solubility decreased with an increase in the molecular weight and polarity. The effect of solute proper ties on solubility was observed to be dependent on operating conditions. The solubility behaviors of pure lipid classes outlined in this study are intended to provide the basis for further study of complex multicomponent lipid mixtures in supercritical processes.