Thermodynamic analysis of phase equilibria in the system cyclohexane-methanol

The phase diagram of cyclohexane-methanol was thermodynamically modeled in the range of 150 less than or equal to T/K less than or equal to 360 and at a pressure of 1 bar on the basis of available experimental data. The Gibbs energy functions of four pure solid and two mixture phases were taken into consideration. The liquid phase was described by a model based on mole fraction statistics and the simplified assumption of methanol tetramers mixed with cyclohexane monomers. The gas phase was treated as a nonideal mixture with a Gibbs energy modeled on the basis of the virial coefficient formalism considering only monomers. The Gibbs energies of the two solid modifications of pure methanol, as well as pure cyclohexane, were fixed using literature data. The pressure dependence of the Gibbs energies of the liquid and solid phases were neglected. The complete T-x phase diagram including gas/ liquid equilibria as well as p-x phase diagrams in the range of 20 and 55 degrees C were calculated. Experimental and calculated data were found to agree reasonably well.