Solubility of cinnamic acid in supercritical carbon dioxide and subcritical 1,1,1,2-tetrafluoroethane: Experimental data and modelling

To promote the extraction of natural cinnamic acid with supercritical and subcritical fluids, the solubility of cinnamic acid was measured respectively in supercritical carbon dioxide (SCCO2) by the dynamic method and in subcritical 1,1,1,2-tetrafluoroethane (sub-R134a) by the static method. The experiments were performed at temperatures from 308 K to 328 K and pressures of 9.0, 11.0, 13.0, 15.0, and 18.0 MPa. The solubility of cinnamic acid in SCCO2 and sub-R134a were compared by calculating the enhancement factor (delta), which indicated that the value of delta in sub-R134a is greater than that in SCCO2;meanwhile, the entrainment factor (psi), which describes the influence of co-solvent (ethanol, ethyl acetate and n-pentane) on the cinnamic acid solubility in SCCO2, showed that the solubility of cinnamic acid in SCCO2 increased with the co-solvent polarity increasing. Six semi-empirical models (Chrastil, A-L, K-J, S-S, M-S-T, and Bartle) were used to correlate cinnamic acid solubility in binary system (cinnamic acid + SCCO2 or sub-R134a) and four models (Gonzalea, Sovova, Tang and Sauceau) were used to correlate cinnamic acid solubility in ternary system (cinnamic acid + SCCO2+co-solvent). The enthalpy values of cinnamic acid, including Delta H-total, Delta H-sub. and Delta H-sub., were estimated through Chrastil and Bartle models; and the partial molar volume of cinnamic acid was calculated by K-J model. A new model was proposed on the basis of the molecular association theory and verified by 47 solid solutes solubility in SCCO2 or sub-R134a with satisfactory correlation results. (C) 2018 Elsevier B.V. All rights reserved.