Solubility of protocatechuic acid, sinapic acid and chrysin in supercritical carbon dioxide

Solubility data of some phenolic compounds of industrial interest, such as protocatechuic acid (3,4-dihydroxybenzoic acid), chrysin (5,7-dihydroxyflavone) and sinapic acid (3,5-dimethoxy-4-hydroxycinnamic acid) in supercritical carbon dioxide were determined at pressures of 200, 300 and 400 bar and temperatures of 40, 50 and 60 degrees C. Experimental data were correlated with semi-empirical Chrastil model and thermodynamic modeling using the Peng-Robinson equation of state with classical mixing rule. The critical properties, acentric factor, and vapor pressure of these compounds were estimated by group contribution methods. The solubility values followed a similar tendency, with higher solubility with increasing temperature and pressure, and no crossover pressure in the range studied. However, a crossover pressure around 150 bar was observed when extrapolating the solubility data by the Chrastil equation, which is in agreement with values reported in the literature for phenolic compounds, thereby indicating the consistency of the solubility experimental data. (C) 2016 Elsevier B.V. All rights reserved.