Vapor–Liquid Equilibrium Data Measurements and Modeling for the Methane + Perfluorohexane System from 293.39 to 333.38 K

This study presents vapor–liquid equilibrium (VLE) data for the methane + perfluorohexane system across five isotherms (293.39 to 333.38 K) with pressures up to 6.669 MPa. The experimental data were obtained via a “static-analytical” based setup incorporating a Rapid Online Sampler Injector (ROLSI) for sampling of equilibrium phases and a gas chromatograph (GC) for analyzing phase composition. Expanded uncertainties for temperature (T), pressure (P) and phase compositions (x, y) are estimated within 0.07 K, 0.011 MPa, and 0.020, 0.030, respectively. The experimental VLE data were regressed via the direct method using both the Peng–Robinson and the Soave–Redlich–Kwong equations of state. In each case, the Mathias–Copeman α function was employed, and the calculations were performed using either the Wong–Sandler or the predictive Soave-Redlich-Kwong mixing rule in combination with the nonrandom two-liquid activity coefficient model. The model parameters were refined using a simplex algorithm optimized through the flash calculation objective function. The calculated average absolute deviation (AADxy) and bias (Biasxy) values between the measured data and the models were both below 4%, indicating satisfactory data regression. Comparative analysis of the CO2 + C6F14, C2H6 + C6F14 and CH4 + C6F14 systems highlights C6F14’s strong selectivity as a physical solvent for C2H6 and CO2 over CH4.