On the Physical Insight into the Barotropic Effect in the Interfacial Behavior for the H₂O + CO₂ Mixture

Abstract

Practice-based experimental reviews have unambiguously shown that the experimental efforts for determining and understanding in detail the dependence of the interfacial tension (IFT) of the H2O + CO2 system at high pressure are limited by the well-known mass density inversion. This phenomenon entails that the CO2-rich phase becomes denser than the H2O-rich phase. Additionally, there are often inconsistencies among the existing literature data, thereby making it challenging to propose predictive models to complement densities and IFT in the regions where experimental measurements are difficult or even impossible to access. In this contribution, the mass density inversion effect on IFT is corroborated by coarse-grained molecular dynamics simulations employing the SAFT-γ-Mie force field, combined with the density gradient theory. The mass density inversion due to gas enrichment is revealed to be an important switch that controls the slope in the IFT curve and also the conformation of minimum and maximum accumulation on the interfacial population of species, which interestingly implies simultaneous desorption and adsorption along the interfacial zone.

Bulk and Interfacial Properties of the Decane + Water System in the Presence of Methane, Carbon Dioxide, and Their Mixture

“…It is interesting to note that the IFT shows a nonmonotonic dependence on pressure in the CO 2 +water system and, at low pressures, it decreases with pressure as discussed in previous studies. 47,53,54 Also, for a given pressure, the IFT decreases almost linearly with increasing temperature and increasing mole fraction of carbon dioxide x CO 2 . It can be seen that, independent of the mole fraction of CO 2 , the slope of the IFT versus temperature plot varies from about −0.09 to −0.07 mN/(m K) in the pressure range 30−100 MPa (see Figure S17).…”

Interfacial behavior of the decane + brine + surfactant system in the presence of carbon dioxide, methane, and their mixture

“…Note that the IFT of the water + CH 4 /CO 2 and brine + CH 4 /CO 2 systems depends nonmonotonically on pressure. [72][73][74][75][79][80][81][82][83][84][85][86][87][88] Furthermore, the IFTs of the alkane + water + CH 4 /CO 2 and alkane + brine + CH 4 /CO 2 systems increased with decreasing x CH 4 /x CO 2 . Here, the influence of methane was found to be less pronounced than that of carbon dioxide.…”

“…38,40 Details of the interfacial behavior of the water + CH 4 /CO 2 and brine + CH 4 / CO 2 systems have been described by us and others. [72][73][74][75][80][81][82][83][84][86][87][88] Here the enrichment of the interfacial region with CH 4 and CO 2 depends nonmonotonically on pressure. Note that the behavior of the IFT can be further understood by means of the Gibbs adsorption equation:…”

“…38,39 For the water + CH 4 /CO 2 and brine + CH 4 /CO 2 systems, a minimum was found in the IFT versus pressure plot when the surface excess of CH 4 /CO 2 changes sign from positive to negative. 73,75,84,85 Furthermore, for the alkane + water and alkane + water + CH 4 /CO 2 systems, the solubilities of decane/ CH 4 /CO 2 in the water-rich phase and water in the decane-rich phase were very low. 38,92,93 The solubility of CH 4 /CO 2 in the water-rich phase was found to decrease with the addition of salt (salting-out effect).…”

Molecular dynamics of liquid–liquid equilibrium and interfacial properties of aqueous solutions of methyl esters

“…The coexistence densities can be calculated from the density profiles in the regions at which liquids are homogeneous, i.e., averaging the appropriate central homogeneous liquid slabs in each phase excluding the interfacial region. See the works of Algaba et al, 53,54 Garrido et al, 31 and Mejı ´a et al 55 for further details. Coexistence densities of both phases as obtained from MD simulations are summarized in Table 5.…”