Determination and modeling of solid–liquid equilibrium for ternary system of 3,4-dichloronitrobenzene + 2,3-dichloronitrobenzene + methanol

• Solid-liquid equilibrium of 3,4/2,3-dichloronitrobenzene + methanol were determined.
• The ternary phase diagrams were constructed at three temperatures.
• The ternary phase diagrams were correlated and calculated by NRTL and Wilson model.

The solid–liquid phase equilibrium for ternary system of 3,4-dichloronitrobenzene + 2,3-dichloronitrobenzene + methanol were determined experimentally by the method of isothermal solution saturation at temperatures of 283.15 K, 293.15 K and 303.15 K under pressure of 101.3 kPa. According to the obtained solubility data, the isothermal phase diagrams of the system were constructed. At each temperature, there were two pure solid phases formed, which were confirmed by Schreinemakers' wet residue method and corresponded to pure 3,4-dichloronitrobenzene and pure 2,3-dichloronitrobenzene. The crystallization regions of pure 3,4-dichloronitrobenzene and pure 2,3-dichloronitrobenzene increased with decreasing in temperature. The crystalline region of 2,3-dichloronitrobenzene was larger than that of 3,4-dichloronitrobenzene at the same temperature, and increased rapidly as the temperature increase. The data of solid–liquid phase equilibrium were correlated with NRTL model and Wilson model. The calculated solubility data with NRTL model agreed well with the experimental values. The mutual solubility data and ternary phase diagrams for the system were of great significance for optimizing the purification procedure of 3,4-dichloronitrobenzene and 2,3-dichloronitrobenzene.

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