Hydrogen-bonding of hfcs with Dimethyl Ether: evaluation by isothermal VLE measurements

Following our study on the Hydrogen-bonding of HFCs with dimethyl ether, the VLE (P-T-x-y) data for the pentafluoroethane (R125) + dimethyl ether (RE170) and R125 + propane (R290) systems are measured at 258.15 K, 273.15 K, 288.15 K and 303.15 K by means of an apparatus based on the vapour recirculation. The estimated accuracies of measured data are ±0.02 K for temperature, ±1 kPa for pressure, ±0.002 in mole fraction for both liquid and vapour phase by gas-chromatographic analysis. The R125+RE170 system shows strong negative deviations from the Raoult's law. The deviations are attributed to H-bonding between oxygen of RE170 as proton acceptor and hydrogen of R125 as proton donor. The H-bonding for the R125+RE170 system is estimated through the homomorphic concept, evaluating the physical interaction through excess Gibbs energy of the homomorphic R125+propane system. The data for R125+propane system were reduced by means of a RKS EoS with classical mixing rules. To improve the reduction for the system R125+RE170, the Huron-Vidal mixing rule and NRTL model for the excess energy were used, while the virial equation of state was applied to calculate the fugacity of the vapour phase.