SAFT-γ force field for the simulation of molecular fluids 6: Binary and ternary mixtures comprising water, carbon dioxide, and n-alkanes

Abstract

The SAFT-γ coarse graining methodology (Avendaño et al., 2011) is used to develop force fields for the fluid-phase behaviour of binary and ternary mixtures comprising water, carbon dioxide, and n-alkanes. The effective intermolecular interactions between the coarse grained (CG) segments are directly related to macroscopic thermodynamic properties by means of the SAFT-γ equation of state for molecular segments represented with the Mie (generalised Lennard-Jones) intermolecular potential (Papaioannou et al., 2014). The unlike attractive interactions between the components of the mixtures are represented with a single adjustable parameter, which is shown to be transferable over a wide range of conditions. The SAFT-γ Mie CG force fields are used in molecular-dynamics simulations to predict the challenging (vapour + liquid) and (liquid + liquid) fluid-phase equilibria characterising these mixtures, and to study phenomena that are not accessible directly from the equation of state, such as the interfacial properties. The description of the fluid-phase equilibria and interfacial properties predicted with the SAFT-γ Mie force fields is in excellent agreement with the corresponding experimental data, and of comparable if not superior quality to that reported for the more sophisticated atomistic and united-atom models.