Isothermal vapor–liquid equilibrium of R170 + n-perfluorooctane at 308–338 K: Measurement, equation of state modelling, and molecular simulation

Abstract

Isothermal vapor–liquid equilibrium data are presented for the R170+n-perfluorooctane system. Measurements were performed at five isotherms ranging from 308.45 to 338.43K and were undertaken using a “static-analytic” type apparatus, with sampling of the equilibrium phases via a moveable capillary sampler (ROLSI™). The uncertainties in the measurements of temperature, pressure, and phase compositions were within 0.036K, 0.0058MPa, and less than 0.02molmol−1 respectively. The VLE data were correlated with the Peng–Robinson equation of state, incorporating the Mathias–Copeman α function. The Wong–Sandler mixing rule with the non-random two-liquid (NRTL) activity coefficient model and the classical one-fluid mixing rule were used. The Wong–Sandler mixing rule represents the experimental data more accurately than the classical mixing rule. These measurements have also been compared to results obtained from isobaric–isothermal Gibbs ensemble Monte Carlo molecular simulations. Very good agreement between experiment and simulation was obtained, although systematic under-estimation of the experimental vapor compositions was observed. The simulations further validate the transferability of an existing optimum Lennard–Jones cross-parameter set. Radial distribution functions for the liquid phase were calculated and show that R170 molecules tend to cluster around each other, while the CF2 groups on n-perfluorooctane molecules show the least preference for mutual proximity.