Vapor-Liquid Equilibria, Excess Enthalpy, and Density of Aqueous γ-Valerolactone Solutions

Thermodynamic measurements were made for the binary mixture of water + γ-valerolactone (GVL) and for pure GVL to facilitate the development of the technology of lignin removal from lignocellulosic biomass (Fang, W.; Sixta, H. Advanced Biorefinery based on the Fractionation of Biomass in γ - Valerolactone and Water. ChemSusChem 2015, 8, 73-76). The density and vapor pressure of pure GVL as a function of temperature were measured and correlated for a wide range of the temperatures and pressures. Isothermal vapor-liquid equilibrium (VLE) data of the binary mixture of water + GVL were measured at 350.2 K with a static total pressure apparatus. Absence of an azeotrope was confirmed by circulation still measurements with diluted GVL solutions. Excess molar enthalpy (h^E) of the mixture for the whole range of mole fractions including infinite dilution was measured using a SETARAM C80 calorimeter equipped with a flow mixing cell at 322.6 and 303.2 K. The VLE and h^E data were used for the optimization of UNIQUAC and NRTL activity coefficient model parameters. The experimental results are compared herein with those predicted by COSMO-RS and UNIFAC-Dortmund models. The water + GVL binary mixture shows positive deviation from Raoult's law.