Solubilities of adipic acid in binary cyclohexanone + cyclohexanol, cyclohexane + cyclohexanol, and cyclohexane + cyclohexanone solvent mixtures

The solubilities of adipic acid in cyclohexanone  +  cyclohexanol mixtures at (303.15–349.45) K, in cyclohexane  + cyclohexanol mixtures at (304.15–339.45) K, and in cyclohexane + cyclohexanone mixtures at (304.85–342.45) K were determined at atmospheric pressure by the dynamic method. Experimental results show that when solvent composition remains constant, solubilities of adipic acid in the studied binary mixed solvents increase monotonically with temperature increasing, and when temperature remains constant, solubilities of adipic acid decrease monotonically with the increasing mass fraction of cyclohexane in cyclohexane + cyclohexanol and cyclohexane + cyclohexanone mixture. However, the measured solubility firstly increases monotonically with the increasing mass fraction of cyclohexanone in cyclohexanone + cyclohexanol mixtures and then reaches the maximum solubility at the mass fraction of cyclohexanone at 0.4. When the mass fraction of cyclohexanone was bigger than 0.40, the solubility of adipic acid decreased with the increasing mass fraction of cyclohexanone. There exists a maximum-solubility effect. Further, both the NRTL equation and the Apelblat equation were used to correlate the experimentally determined solubilities. A fairly good agreement was obtained between the correlated solubilities with the experimental observations. Thermodynamic quantities of dissolution were calculated by the Clark and Glew equation, including dissolution enthalpy, entropy, Gibbs energy and isobaric heat capacity for adicip acid in cyclohexane + cyclohexanol, cyclohexane + cyclohexanone, and cyclohexanone + cyclohexanol solvent mixtures .