(51f) Prediction of the Water/Oil Interfacial Tension from Molecular Simulations Using the Coarse Grained SAFT-γ Mie Force Field

This work is framed within the Ninth Industrial Fluid Properties Simulation Challenge, with the aim of assessing the capability of molecular simulation methods and force fields to accurately predict the interfacial tension of oil-water mixtures at high temperatures and pressures. The current challenge focuses on predicting the liquid-liquid interfacial tension of binary mixtures of dodecane + water, toluene + water and a 50:50 (wt%) mixture of dodecane + toluene in water for a range of temperatures and pressures. In our methodology, we use coarse-grained intermolecular models with a top-down technique where an accurate equation of state is used to link the experimentally observed macroscopic properties of a fluid to the force-field parameters. The state-of-the-art version of the statistical associating fluid theory (SAFT) for potentials of variable range as reformulated in the Mie incarnation is employed here. Interfacial tensions are calculated through a direct method, where an elongated simulation cell is sampled through molecular dynamics in the isobaric-isothermal constant area ensemble (NPzzAT). The coarse-grained nature of the force field allows for the accelerated calculation of relative large systems. The interfacial
properties of the pure components are described with an error of less than 5% over the whole fluid range. The binary interaction parameters needed for the accurate description of the interfacial properties are obtained from a fit interfacial tensions of the constituent binaries at lower pressures and temperatures and is taken as a constant for all conditions and mixtures studied.