Solubility Determination, Modeling, and Preferential Solvation of Terephthalaldehydic Acid Dissolvend in Aqueous Solvent Mixtures of Methanol, Ethanol, Isopropanol, and N-Methyl-2-pyrrolidone

The present work mainly reports the terephthalaldehydic acid solubility in aqueous solutions of methanol, ethanol, isopropanol, and NMP, which was achieved through a steady-state method covering a temperature range from 283.15 to 323.15 K under 101.1 kPa. The terephthalaldehydic acid solubility increased positively as the mass fraction of methanol (ethanol, isopropanol, and NMP) increased for the investigated mixtures of methanol (ethanol, isopropanol, and NMP) and water. At the same temperature and mass fraction of methanol (ethanol, isopropanol, and NMP), the mole fraction solubility of terephthalaldehydic acid was higher in the NMP and water mixture than in the other three mixtures. The solid equilibrating with saturated liquor was indentified through X-ray power diffraction, which showed no crystal transition, polymorphic transformation, or solvate formation. Three models, the Van't Hoff-Jouyban-Acree, Jouyban-Acree, and Apelblat-Jouyban-Acree, were used here to correlate the obtained solubility data. The back-calculated values were in good agreement with the determined ones. The values of RAD and RMSD were, respectively, no greater than 3.63% and 6.66 x 10(-4). Preferential solvation of terephthalaldehydic acid in the four mixtures was analyzed by employing the method of inverse Kirkwood-Buff integrals. The preferential solvation parameter delta x(1,3) by NMP (methanol, ethanol, or isopropanol; 1) is positive within the composition range of 0.16 < x(1) < 1 for NMP, 0.32 < x(1) < 1 for methanol, and 0.25 < x(1) < 1 for ethanol and isopropanol. As it can be speculated that in the regions where terephthalaldehydic acid is preferentially solvated by NMP (methanol, ethanol, or isopropanol), terephthalaldehydic acid acts as a Lewis acid with NMP (methanol, ethanol, or isopropanol) molecules.