Measurement and correlation of the solubility of 4-methylbenzoic acid in (methanol + acetic acid) binary solvent mixtures

Data on corresponding solid-liquid equilibrium of 4-methylbenzoic acid in (methanol + acetic acid) binary solvent mixtures are essential for industrial design and further theoretical studies. In this study, the solubility of 4-methylbenzoic acid was measured in (methanol + acetic acid) binary solvent mixtures in the temperature ranging from 283.15 to 333.15 K by the analytical stirred-flask method under atmospheric pressure. The results obtained from these measurements were fitted using the modified Apelblat equation, the combined nearly ideal binary solvent/Redlich-Kister (CNIBS/R-K) equation and the Jouyban-Acree equation, respectively. All the equations were proven to give good representations of the experimental data. The experiment results indicated that the solubility of 4-methylbenzoic acid in the binary solvent increased with increasing temperature, decreases with increasing methanol content, but the increments with temperature differed from different methanol contents. The Redlich-Kister (CNIBS/R-K) equation was more accurate than the other two equations owning to its lowest value of the overall MD. In addition, the thermodynamic properties of the solution process, including the Gibbs energy, enthalpy, and entropy were calculated by the van't Hoff analysis. The experimental data and model parameters would be useful for optimizing the process of purification of 4-methylbenzoic acid in industry.