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3577825 
Journal Article 
Solubility of Terephthalic Acid in Subcritical Water 
Takebayashi, Y; Sue, K; Yoda, S; Hakuta, Y; Furuya, T 
2012 
Yes 
Journal of Chemical and Engineering Data
ISSN: 0021-9568
EISSN: 1520-5134 
57 
6 
1810-1816 
WOS:000305356300023 
The solubility of terephthalic acid (TPA) in subcritical water was measured as a function of the temperature from (349 to 547) K at a pressure of 10.0 MPa. A semibatch flow apparatus was developed for the solubility measurement. N-Methylpyrrolidone was used as a good solvent for collection of TPA saturated in subcritical water without deposition upon cooling. The solubility of TPA in water showed an exponential increase with increasing temperature from 1.25.10(-5) at 349 K to 2.99.10(-2) at 547 K. The aqueous solubility of TPA was found to be lower than those of m- and o-phthalic acids by one and three orders of magnitude, respectively. The Gibbs free energy of solution (Delta G(sol)) as well as the enthalpic and entropic components (Delta H-sol and T Delta S-sol) were calculated from the temperature dependence of the solubility. The thermodynamic analysis showed that the Delta G(sol) gradually decreases with increasing temperature, as a result of the competition between a large increase in Delta H-sol and a large decrease in -T Delta S-sol. The Delta G(sol) value decreased in the order of (p-phthalic acid) > (m-phthalic acid) > (o-phthalic acid) due to a decrease in -T Delta S-sol, whereas Delta H-sol showed a small variation among the three isomers.