Solubility of caffeic acid in CO2 + ethanol: Experimental and predicted data using Cubic Plus Association Equation of State

• Published in: The Journal of supercritical fluids 2018-08, Vol.138, p.238-246
• Main Authors: Bitencourt, Raphaela G., Palma, André M., Coutinho, João A.P., Cabral, Fernando A., Meirelles, Antonio J.A.
• Format: Article
• Language: English
• Subjects: 3,4-Dihydroxycinnamic acid; Cosolvent; Phase equilibrium; Soave-Redlich-Kwong; Supercritical carbon dioxide; Thermodynamic modeling
• ISSN: 0896-8446; 1872-8162
• DOI: 10.1016/j.supflu.2018.04.008

[Display omitted] •CA solubility in CO2 + ethanol at 20–40 MPa, 313–333 K and 2–10 mol% ethanol.•Comparison between thermodynamic modeling using SRK and CPA equations.•By adding 10.2 mol% ethanol to scCO2, CA solubility increased up to 30,000 times.•CPA model showed good ability to predict the ternary system data. This work evaluated the solubility of caffeic acid (CA) in mixtures of supercritical carbon dioxide (scCO2) 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 scCO2. By using 10.2 mol% ethanol in scCO2, 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 scCO2 provides a large increase in CA solubility.