Abstract

Among other compounds, hexanal and ethyl-2-methyl are relevant substances that define the nature and quality of fruits flavors and aromas, like in apple juice flavor. Conceptualization, design and modeling of alternative processes to concentrate fruit essences, as those that use compressed carbon dioxide (CO2), require reliable and accurate phase equilibria information. Isothermal vapor + liquid equilibria was measured for binary systems CO2 + hexanal and CO2 + ethyl 2-methylbutyrate at temperatures of 313.2, 323.2 and 333.2 K, and at pressures from 2 to 15 MPa. The measurements were carried in a apparatus with methodology based on a static–analytic method [1]. The composition of the vapor phase was measured with a gas chromatograph, for liquid phase a gravimetric method with a cold trap for the phase separation and a wet test meter to measure the CO2 content was used. The validation of the experimental data measured was carried out verified a selected thermodynamic consistency test, and by estimating the combined uncertainties for the reported CO2 composition for the vapor phase < 0.005 mol/mol, and for the liquid phase < 0.001 mol/mol [2]. Information from literature for data of vapor + liquid equilibria was found for the system CO2 + hexanal at 323.2 K, 353.2 K and 383.2 K [3]. Differences between this work and previously reported at 323.2 K are < 1.2 % in vapor phase, and < 13 % for liquid phase, attributed to the different experimental methodologies used. For the system CO2 + ethyl 2-methylbutyrate there is no information in literature about phase equilibria data at high-pressure. Experimental data was properly correlated using the Peng-Robinson equation state, with the conventional quadratic mixing rule and two adjustable parameters, and with Wong-Sandler mixing rule [4] with the Non Random Two Liquid model for the calculation of the excess Gibbs free energy.