Phase equilibria and excess enthalpy for tetrahydrofuran + 2-methylpyrazine, tetrahydrofuran + 2-methylpyridine and 2-methylpyridine + 2-methylpyrazine: Experimental measurement and predictive modeling

Knowledge about the vapor–liquid equilibrium (VLE) behavior of systems containing 2-methylpyridine or 2-methylpyrazine is limited in the literature, despite their industrial importance. In this study, consistent VLE data for mixtures of tetrahydrofuran + 2-methylpyrazine and 2-methylpyridine + 2-methylpyrazine at 50 and 75 kPa, as well as the system of tetrahydrofuran + 2-methylpyridine at 50, 75, and 101 kPa are presented. The excess molar enthalpy (H^E) of these binaries has been measured using an isothermal flow calorimeter at 298.15 K and 101 kPa. The vapor pressure data of the pure components were measured and correlated over the temperature range between 294 and 405 K. The measured VLE and H^E data were successfully correlated with NRTL, UNIQUAC, and Wilson activity coefficient models. In addition, the acquired VLE and H^E were compared with those predicted by COSMO-RS and different predictive group contribution (GC) based models, including the original UNIFAC, UNIFAC-Dortmund, Volume Translated Peng-Robinson (VTPR) and Predictive Soave–Redlich–Kwong (PSRK). A satisfactory agreement was observed between the calculated results and experimental VLE data for all predictive methods; however, these models exhibited lower accuracy in predicting H^E compared to VLE. Attained phase equilibria were checked for thermodynamic consistency using Wisniak's l-W and Van Ness methods. All binaries exhibit nearly ideal behavior.