Solid-liquid equilibrium for the ternary 2-naphthaldehyde + 2-methyl-1,4-naphthoquinone + ethanol system: Determination, correlation and molecular simulation

In this work, the solubility of 2-methyl-1,4-naphthoquinone (2-MNQ, Vitamin K3) and its by-product 2-naphthaldehyde in binary and ternary systems was studied. Three phase diagrams were established based on the experimental solubility data. Each ternary phase diagram contains three crystallization regions (pure 2-MNQ, pure 2-naphthaldehyde and mixture of 2-MNQ and 2-naphthaldehyde), two co-saturated curves and one co-saturated point. The crystalline region of 2-MNQ is larger than that of 2-naphthaldehyde at three temperatures (283.15, 293.15 and 303.15) K. The solubility of the binary (2-MNQ + ethanol and 2-naphthaldehyde + ethanol) system was correlated by λh equation, modified Apelblat equation and NRTL model. The ternary (2-MNQ + 2-naphthaldehyde + ethanol) system was correlated by NRTL model. The calculated values agree well with the determined solubility data. Interaction energy between solute and solvent molecules were calculated to illustrate the solubility behavior of 2-MNQ and 2-naphthaldehyde in ethanol. RDF shows that when adding pure 2-naphthaldehyde in solution of 2-MNQ + ethanol, the interaction between 2-MNQ and ethanol molecules will become stronger, which leads to an increase in solubility of 2-methyl-1,4-naphthoquinone. This study can provide basic data and theoretical foundation for the separation process.