Journal of Supercritical Fluids, Vol.138, 238-246, 2018
Solubility of caffeic acid in CO2 + ethanol: Experimental and predicted data using Cubic Plus Association Equation of State
This work evaluated the solubility of caffeic acid (CA) in mixtures of supercritical carbon dioxide (scCO(2)) and ethanol at different temperatures (313, 323 and 333 K), pressures (20, 30 and 40 MPa) and concentrations of ethanol (2.2, 5.4 and 10.2 mol%). The Soave-Redlich-Kwong and Cubic Plus Association (CPA) equations of state were used to correlate the binary mixture data and to predict the ternary system data. CA solubility in ethanol is approximately 106 times higher than its solubility in pure scCO(2). By using 10.2 mol% ethanol in scCO(2), CA solubility increased 30,000 times at 313 K and 20 MPa. Both models provided reasonable descriptions of the experimental data for the binary systems. However, CPA-EoS can better describe the strong interactions between acid molecules and ethanol, and can predict that the addition of small amounts of ethanol to scCO(2) provides a large increase in CA solubility.