Thermodynamic properties of five biofuel-relevant compounds at infinite dilution in water

In this work, thermodynamic behavior of five biomass-derived compounds, namely furfural, 2-methylfuran, 2,5-dimethylfuran, methyl vinyl ketone, and allyl alcohol, in highly dilute aqueous solutions has been experimentally investigated. Using the inert gas stripping technique, their air-water partition coefficients (Kaw) and limiting activity coefficients γ1∞ were measured at several temperatures in the range from (273 to 333) K. Except for the furans, infinite dilution partial molar excess enthalpies and volumes were further determined as functions of temperature from (288 to 318) K by tandem flow mixing calorimetry and vibrating-tube densimetry, which in turn allowed reliable derivation of respective heat capacities and expansivities. In addition, densities of all five pure liquids and viscosities of furfural and allyl alcohol were also measured in the range from (288 to 318) K. For each compound, the vapor-liquid equilibrium and (when measured) calorimetric data of this work together with some relevant data reported previously in the literature were simultaneously correlated by a three-parameter model equation providing adequate simultaneous description of all information involved. As a result, recommended thermodynamically consistent temperature dependences of Kaw and γ1∞ of superior accuracy were thus established in the range from the melting point to the normal boiling point of water. The variation of Kaw and γ1∞ with temperature and solute molecular structure along with related energetic functions of dissolution and hydration of the examined compounds were overviewed and briefly discussed.