Molecular Modeling and Simulation of Vapor-Liquid Equilibria of Ethylene Oxide, Ethylene Glycol, and Water as Well as their Binary Mixtures

Mixtures containing ethylene oxide are technically highly relevant but hazardous so that typically only few reliable experimental data are available. They are therefore interesting candidates for the application of molecular modeling and simulation to predict thermodynamic properties. The industrially most important ethylene oxide containing mixtures are those with water and ethylene glycol. An excellent molecular model for ethylene oxide is available from prior work. Because the molecular models for water from the literature do not yield satisfactory results for the vapor-liquid equilibrium over a wide temperature range, a new water model is developed. Furthermore, also a new molecular model for ethylene glycol is developed. The models for ethylene glycol and water show mean unsigned deviations with respect to experimental data, considering the whole temperature range from triple point to critical point, of 0.8 and 1.1% for the saturated liquid density, 4.8 and 7.2% for the vapor pressure, and 13.4 and 2.8% for the enthalpy of vaporization, respectively. Vapor-liquid equilibria of all three binary mixtures are determined by molecular simulation, and in general, a good agreement is found with the available experimental data. The models can be used for subsequent predictions at other conditions.