Effect of ethanol on supercritical CO2 solvent densities

The development of new industrial applications in the pharmaceutical, food, and cosmetic fields uses supercritical carbon dioxide as a solvent or antisolvent in their processes for extracting non-polar molecules. Ethanol (EtOH) is added in small quantities to isolate a polar molecule during a unit operation by solubilization or precipitation. Density measurements in pure carbon dioxide (CO2) and in binary CO2-EtOH mixtures with mass compositions (wCO2 = 0.99 and wCO2 = 0.98) were carried out using a vibrating tube densimeter. The isotherms were determined at temperatures of 303, 308, and 313 K, above the critical temperature, and for a pressure range from 5 to 10 MPa. Fine modeling around the critical point was performed using cubic equations of state with two or three parameters (Peng-Robinson and Coquelet-El Abbadi-Houriez EoS). The Huron-Vidal mixing rule coupled with the NRTL model was employed. To enhance the prediction around the critical point of pure carbon dioxide and binary CO2-EtOH mixtures, White's correction method was used. The results for pure supercritical carbon dioxide show modeling performance with a deviation of 5.8% around the critical point.