Correlation of steroid solubilities in supercritical carbon dioxide

Abstract

A correlation for the solubilities of cholesterol, stigmasterol, ergosterol, pregosterone, and lauric acid is developed. The correlation employs the Patel-Teja cubic equation of state (EOS). The mixture energy parameter of the EOS, am, is determined by a UNIFAC group contribution model at an infinite pressure limit. The excluded volume parameter of the EOS, bm, is evaluated by the van der Waals mixing rule with an excluded volume correction term. New group interaction parameters of the UNIFAC model involving carbon dioxide are reported, and our calculation results are compared with those obtained from other methods. The accuracy of the mixing model with excluded volume correction is shown to be superior to the traditional van der Waals mixing rules with optimally adjusted binary parameters.