Phase behaviour and interfacial properties of ternary system CO₂ + n-butane + 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.

Experimental measurements and theoretical modeling of high-pressure mass densities and interfacial tensions of carbon dioxide + n-heptane + toluene and its carbon dioxide binary systems

“…For the vapor phase, Zhang et al [38] reported bulk densities at 308.15 K and over the pressure range from (5.94 to 10.19) MPa and Kalra et al [39] reported the density at the following conditions: 310. 29 The density of liquid phase has been reported by Poehler and Kiran [41] at the isothermal range (323 to 423) K and in a broad pressure range (9.85 to 65.07) MPa, and Zirrahi et al [42] In terms of IFT, a search of the DECHEMA [35] and Landolt-Börnstein data bases [45] reveals that the CO 2 + n-C 7 H 16 binary mixture is the only mixture where interfacial tensions have been previously reported. Specifically, Niño Amézquita et al, [46], Jaeger et al, [47] and Zolghadr et al, [48] reported interfacial tension as a function of temperature and pressure that cover the temperature and pressure ranges from 313.15 to 393.15 K and from 0.1 to 11.2 MPa, respectively.…”

“…[16,17,20,21,22,23,24,25,26,27,28]). Furthermore, molecular simulations based either on Molecular Dynamics or Monte Carlo schemes have also been employed [16,29,30]. As it was previously showed (see for instances Refs.…”

“…As it was previously showed (see for instances Refs. [16,17,29]), a complete description of bulk phase and interfacial properties, including IFT, are obtained when experimental determinations are combined with theoretical models and/or molecular simulations. This interrelated combination provides a route to extrapolate the experimental data to extreme conditions, exploring unmeasurable quantities such as interfacial concentration along the interfacial region, surface activity, etc.…”

“…As part of our ongoing research work, which is devoted to the description of interfacial properties for CO 2 + n-alkanes mixtures [16,17,20,21,22,29], this work is focused on the experimental determination and theoretical modeling of bulk phase equilibrium densities and interfacial tensions of the CO 2 + {nheptane (n-C 7 H 16 ) + toluene (C 7 H 8 )} or CO 2…”

Interfacial properties of binary Lennard-Jones mixtures by molecular simulation and density gradient theory

“…In water-alcohols mixtures 45 , as well as dimethylformamidealkanes mixtures 46 , component densities were found which were up to 10 times higher than the highest corresponding component density in the bulk phase. Only minor enrichments are reported for mixtures of alkanes 26,47 , mixtures of poly(dimethylsiloxane)-acid gases 48 , mixtures of carbon dioxide-sulfur dioxide, mixtures of carbon dioxide-hydrogen sulfide 49,50 , mixtures of acetone-nitrogen and of acetone-oxygen 16 , mixtures of R32 and R290 41 . A strong enrichment is reported in many cases where the VLE exhibits a wideboiling behavior 3,14,15,28,31,32,36,37,40,51 .…”