Fluid phase behavior of ethylene glycol + water mixtures (at operating conditions of the first-stage esterification reactors for PET synthesis) by molecular simulations and activity coefficient (γ-φ) method

Phase-equilibria of binary mixtures for ethylene glycol (EG) + water mixtures are predicted by employing molecular simulations and the activity coefficient (γ-φ) method. The temperature-composition (T-x-y) diagram at 99.6 kPa and the pressure-composition (P-x-y) diagram of EG + water mixtures at 395.15 K have been generated using the Gibbs ensemble Monte Carlo simulations and the activity coefficient (γ-φ) method for comparison with that reported in literature. The phase diagram of this system at the operating conditions (405.3 kPa) in the first-stage esterification reactor used in the manufacture of poly(ethylene terephthalate), PET, (from terephthalic acid and EG) has been predicted using both the approaches. These results can be used to improve the design of separators and reactors used in PET synthesis.