Vapor–liquid equilibrium data for the hexafluoroethane + carbon dioxide system at temperatures from 253 to 297 K and pressures up to 6.5 MPa

Abstract

Isothermal vapor–liquid equilibrium data have been measured for the hexafluoroethane (R-116) + carbon dioxide (R-744) binary system at six temperatures between 253.29 and 296.72 K, and at pressures from 1.051 to 6.45 MPa. The three remarkable peculiarities of this system are: (1) the existence of azeotropic behavior and critical azeotropy, (2) the splitting of phase envelope into two parts at high temperatures and (3) the proximity of bubble and dew curves in the whole range of compositions at all temperatures investigated. The experimental method used in this work to measure VLE data is of the “static-analytic” type, taking advantage of two pneumatic capillary samplers (Rolsi™, Armines’ patent) developed in the CEP/TEP laboratory. The data were obtained with uncertainties within ±0.01 K, ±0.0015 MPa and ±1.6% for molar compositions. The isothermal P, x, y data are well represented with the Peng–Robinson equation of state using the Mathias–Copeman alpha function and the Wong–Sandler mixing rules involving the NRTL model.