Phase behaviour and interfacial properties of ternary system CO2 + n-butane plus n-decane: coarse-grained theoretical modelling and molecular simulations

Abstract

This work illustrates the application of a three-party approach based on theoretical modelling, molecular dynamic (MD) simulations and available experimental data for describing the phase equilibrium and interfacial properties for the ternary system: carbon dioxide + n-butane + n-decane and its corresponding binary sub-systems at 344.3 K. Specifically, a coarse-grained force field is employed for both theoretical predictions and MD. The interfacial region is described by the square gradient theory where the homogenous Helmholtz energy density contribution is provided by the Statistical Associated Fluid Theory equation of state for potentials of variable range for molecules conformed of segments interacting through the Mie potential (SAFT-VR Mie) and MD simulations in the canonical ensemble where the molecules are represented by a coarse-grained Mie force field. The novelty here is that both the theory and the simulations uniquely share the same underlying intermolecular potentials; hence, the experimental data are employed to verify both the theory and simulations. In this schema, the ternary mixture is full predictive as its parameters are only based on pure fluids parameters and binary interactions. It is observed that the phase equilibria and the interfacial properties are equally well represented by the used approach. Keywords. Author Keywords:Square gradient theory; molecular dynamics; hydrocarbon mixtures; CO2; SAFT. KeyWords Plus:EQUATION-OF-STATE; SURFACE-TENSION; CARBON-DIOXIDE; N-ALKANES; SIMULTANEOUS PREDICTION; FLUID INTERFACES; CUBIC EQUATIONS; BINARY-MIXTURES; GRADIENT THEORY; CLIMATE-CHANGE