| Solubility is the basic data for the crystallization process. It is important for the optimization of the crystallization process and the prediction of the yield. The thermodynamic model which studys on the solid-liquid equilibrium before is often ignore the impact of temperature on the heat capacity or take it as a constant. The thermodynamic model which established in this paper considers the impact of temperature on the heat capacity has important theoretical significance. m-phthalic acid has wide use which is the important materials for the produce of acid modified polyester, unsaturated polyester, alkyd resin and so on. It is mainly prepared by air-oxidation in liquid-phase, which select acetic acid as solvent. But acetic acid has serious corrosion for the equipment. So, determine the solubility of m-phthalic acid in other solvent is important for the improvement of the product process. In this paper, we use the equilibrium method to determine the solubility in methanol,1-propanol, 2-propanol,1-butanol,2-butanol,1-pentanol,1-hexnaol seven pure solvent and acetone+water, acetone+ethanol two mixed solvent. Using the thermodynamic model established in this paper to correlation the solubility data in the pure solvent get the relationship between temperature and heat capactity:â–³Cp=24.5013+0.273993(621.2-T), the maximal ARD% is 0.79%. Based on Wilson equation and solid-liquid equilibrium equation using the solubilities of m-phthalic acid in pure solvent to predict the solubilities that in the mixtured one and compare it to the experimental data. The prediction of solubility is in two cases. The first is ignore the influence of temperature toâ–³CP; the second is consider the influence of teperature toâ–³CP. The result is that the prediction results of the second one is better than the first one. The ARD% of m-Phthalic acid in acetone+water, acetone+ethanol is reduced from 66.70% and 54.20% to 64.66% and 19.59% respectively.
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