High-pressure vapor + liquid equilibria for the binary system CO2 + (E)-2-hexenal

Abstract

The isothermal vapor + liquid equilibria of carbon dioxide + (E)-2-hexenal (a key apple aroma) was measured using a visual equilibrium cell with an analytic methodology. The selected isotherms were (313.2, 323.2 and 333.2) K, and the pressures assessed ranged from (2.2–9.8) MPa. The thermodynamic consistency of the experimental data was verified, and the uncertainties of the molar fractions of the vapor and liquid phases were estimated. The density and dynamic viscosity of pure (E)-2-hexenal were measured at 101.13 kPa and temperatures from (292.2–353.2) K. Two equations of state were selected to model the vapor + liquid equilibria. The Peng-Robinson with two different mixing rules, and the Perturbed Chain - Statistical Associating Fluid Theory. The phase envelopes showed a critical pressure, detected at carbon dioxide molar fractions ≥ 95 % mol∙mol−1.