Abstract
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.
Highlights
Glycols and glycol ethers are widely used as additives in food and cosmetics industries
In work [4] it has been noted that calculation of the parameters of eutectics and azeotrope mixtures used in technological processes of crystallization and rectification is complicated by the absence of accurate data on enthalpies of phase transitions of individual components
Molar enthalpy of vaporization ΔHev at normal boiling point of a pure component for homology series of alkanes, alcohols, acids, glycols, and glycol ethers is expressed as a function of the number of carbon atoms N, relative molecular mass M, normal boiling temperature Tb, and the universal gas constant R: The following relation is proposed for these members of different homology series: H
Summary
Glycols and glycol ethers are widely used as additives in food and cosmetics industries. Systems containing glycols and glycol ethers in mixtures with water, alkanes, and salts are actively studied [1,2,3]. These systems are the subjects of the current work because experimental and theoretical foundation for their application is lacking. There should be thermodynamic models that would be able to predict properties of pure components and phase equilibrium in systems containing glycols and glycol ethers with high accuracy. In work [4] it has been noted that calculation of the parameters of eutectics and azeotrope mixtures used in technological processes of crystallization and rectification is complicated by the absence of accurate data on enthalpies of phase transitions of individual components
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