ENTHALPY OF PHASE TRANSITION AND PREDICTION OF PHASE EQUILIBRIA IN SYSTEMS OF GLYCOLS AND GLYCOL ETHERS

The PCEAS model was used to study the liquid-solid and liquid-vapor phase transitions at constant pressure in systems containing glycols and glycol ethers. This method is based on minimizing the excess Gibbs energy over the solvation parameter, which takes into account the processes of association of molecules in various phases. To compute the diagrams, the data on enthalpy and phase transition temperatures of pure components are required, while the information about the interactions in the binary system is not necessary. We present analytical expressions for the enthalpy of vaporization and enthalpy of melting of glycols and glycol ethers obtained with the theory of similarity using molecular weight, critical temperature, temperature of the triple point, and the number of carbon atoms in the molecule as the parameters. In the absence of information about the critical temperature, the enthalpy of vaporization may be calculated using the boiling point value. It is shown that the prediction of the enthalpy of melting and enthalpy of vaporization allows us to calculate of the phase diagram, as well as the azeotropic and eutectic parameters in water-glycol ether and glycol ether-alkane systems.