A new apparatus to measure the vapour-liquid equilibria of low-volatility compounds with near-critical carbon dioxide. Experimental and modelling results for carbon dioxide+ n-butanol, +2-butanol, +2-butyl acetate and +vinyl acetate systems

• Published in: The Journal of supercritical fluids 1997-10, Vol.11 (1), p.1-14
• Main Authors: Stevens, R.M.M, Shen, X.M, de Loos, Th.W, de Swaan Arons, J
• Format: Article
• Language: English
• Subjects: Alkanols; Equations of state; Esters; Experimental method; Solubility data; Supercritical carbon dioxide
• ISSN: 0896-8446; 1872-8162
• DOI: 10.1016/S0896-8446(97)00032-6

A new apparatus has been developed for the experimental determination of vapour-liquid equilibria in systems containing low-volatility compounds and near-critical carbon dioxide. The apparatus combines the advantages of the gas saturation method with those of a circulation method. An air-lift-functioning draft tube is used in the centre of the equilibrium cell to increase contact time between solute and solvent. The apparatus is tested by measuring the vapour-liquid equilibrium (VLE) of the system CO 2+1-butanol at 313.2 and 333.2 K and at pressures up to 11 MPa. For the systems CO 2+2-butanol, CO 2+vinyl acetate and CO 2+2-butyl acetate, VLE data were measured at pressures up to 10 MPa and at the temperatures of 303.2, 313.2 and 333.2 K. The measured mole fractions of the low-volatility compound in carbon dioxide have an accuracy better than 3%. The solubility isotherms were modelled using the PRSV EOS with Wong-Sandler mixing rules and the LCVM model. It is shown that the solubility of the low-volatility compounds in carbon dioxide can be predicted well with the PRSV-WS EOS (NRTL-G E-model) using the fit parameters obtained from bubble point measurements. The PRSV-WS predicts the solubilities better than the LCVM model (t-mPR EOS with an adapted UNIFAC-G E-model).