Solubility and Thermodynamic Modeling of Dimethyl Terephthalate in Pure Solvents and the Evaluation of the Mixing Properties of the Solutions

In this work, the solubility of dimethyl terephthalate (DMT) in alcohols (methanol, ethanol, n-propanol, i-propanol, n-butanol, and i-butanol), esters (ethyl acetate, i-propyl acetate, n-propyl acetate, n-butyl acetate, n-amyl acetate, and methyl propionate), ketones (acetone, methyl ethyl ketone, and cyclohexanone), acetonitrile, and chloroform was experimentally determined. The solubility of DMT in these solvents follows the order: chloroform > esters and ketones > acetonitrile > alcohols and increases with increasing temperature. The solubility of DMT as a function of temperature has been regressed in terms of three semiempirical models (modified Apelblat, λh, and three-parameter Van't Hoff) and two activity coefficient models (Wilson and nonrandom two-liquid), which gave a maximum relative average deviation of 2.32% and a maximum root-mean-square deviation of 31.63 × 10–5. Better fittings were obtained with the activity coefficient models. In addition, the mixing properties (Gibbs energy, enthalpy, entropy, as well as activity coefficients and reduced excess enthalpy at infinitesimal concentration) were evaluated using the Wilson model.