Determination and modeling of binary and ternary solid–liquid phase equilibrium for the systems formed by adipic acid, urea and diethylene glycol

•Solid–liquid equilibrium formed by adipic acid, urea and diethylene glycol were determined.•The binary and ternary phase diagrams were constructed.•The phase diagrams were correlated and predicted using Wilson and NRTL model.•Densities of equilibrium liquore were obtained and correlated with an empirical equation.

Solid–liquid phase equilibrium data for binary (adipic acid + diethylene glycol) and (urea + diethylene glycol) systems at temperatures from (298.15–333.15) K and ternary (adipic acid + urea + diethylene glycol) system at temperatures of 298.15 K, 313.15 K and 333.15 K were determined herein under pressure of 101.3 kPa. The corresponding solids formed in the ternary system were confirmed by Schreinemakers' method of wet residue. Three isothermal phase diagrams were constructed in terms of the measured mutual solubility data. Two pure solids were formed at each temperature, which corresponded to pure adipic acid and pure urea. The crystallization region of urea was smaller than that of adipic acid at each temperature. NRTL model and Wilson model were used to correlate the obtained solubility data, and the interaction parameters' values of adipic acid-urea were acquired. The calculated solubility with the two models agreed well with the experimental values.

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