Thermodynamic insights into bio-based solvent separations: phase equilibria and excess enthalpy of binary mixtures γ -valerolactone (GVL) and Xylene isomers

ABSTRACT This study examines the thermodynamic behavior of binary systems containing the green solvent γ-valerolactone (GVL) and p -xylene or o -xylene. The measurements of the isobaric vapor-liquid equilibrium (VLE) were performed at 50.0 kPa and 70.0 kPa; furthermore, the excess molar enthalpies (H E ) were determined at 298.15 K for the binary mixtures. The experimental H E results were positive across the entire composition range, suggesting that the addition of non-polar aromatic rings disrupts the self-interactions of the polar lactone in GVL. The absence of azeotropic behavior in these systems allows for a straightforward distillation process. We confirmed the consistency of the VLE data through Van Ness and L–W thermodynamic tests. The correlation of the experimental data was performed using a simultaneous regression of VLE and H E employing the Wilson, NRTL, and UNIQUAC activity coefficient models. Experimental data were compared with predictions from the UNIFAC and UNIFAC-DMD group contribution models and the COSMO-RS quantum chemical model. COSMO-RS with the TZVPD-FINE parameterization level displayed better predictive accuracy than all other models studied and its validity was further confirmed through retrospective testing on several additional GVL-containing binary mixtures, including toluene, ethylbenzene, water, and alcohols.