Modeling aspirin and naproxen ternary solubility in supercritical CO2/alcohol with a new Peng–Robinson EOS plus association model

A new version of the Peng–Robinson equation of state (PR EOS) is developed through the use of Wertheim's thermodynamic perturbation theory of associating fluids and statistical associating fluid theory (SAFT). The new equation is characterized by two temperature-independent parameters, namely, association strength and association volume, which account for the association interactions between associating molecules. In this work, we employed the equation to model aspirin and naproxen solubility enhancement obtained in the ternary supercritical CO2/alcohol systems, where the original PR EOS has resulted in large and negative binary interaction parameters between the polar solute and polar cosolvent. Calculated results show that the Peng–Robinson EOS plus association model gives better performance to correlate these ternary solubility data over the ranges of temperature, pressure and cosolvent concentration investigated than its conventional form that uses temperature-dependent parameters.