The dependence of the interfacial tension of binary mixtures composed of acid gases and n-alkanes has been investigated by molecular simulations. Two-phase Monte Carlo (MC) calculations have been performed to predict the interfacial tension of CO 2 +n-butane, CO 2 +n-decane, and H 2 S+n-pentane mixtures at different pressures. The phase densities and phase compositions of these different mixtures have been calculated from both of the two-phase Monte Carlo and Gibbs Ensemble Monte Carlo (GEMC) simulation methods. The comparison among the simulation data, the experimental measurements, and the parachor theory demonstrates the efficiency of molecular simulations for the prediction of the pressure dependence of the interfacial tension for binary mixtures. Such results demonstrate the capability of molecular simulation techniques to complete sets of available experimental data by generating some so-called pseudo-experimental data. Additionally, the molecular description of the interface has shown specific local arrangements of the CO 2 at the decane surface.

We report molecular simulations of oil-water liquid-liquid interfaces by using atomistic and coarse grained (CG) MARTINI force fields. We also apply the electronic continuum (EC) model to the MARTINI force field for the calculation of the interfacial tension of oil/water-salt systems. In a first step, we propose to calculate the interfacial tensions using thermodynamic and mechanical definitions of hydrocarbon-water interfacial systems modified by the addition of salts and alcohol. We also establish here the order of magnitude of the long-range corrections to the interfacial tension in fluid-fluid interfaces. Whereas the atomistic models are able to reproduce quantitatively the interfacial tension and the coexisting densities of oil-water systems, the coarse-description shows some deviations in the prediction of the interfacial tensions. Nevertheless, the physical features of these liquid-liquid interfaces are well-captured by this CG description. The CG force field offers then a very challenging alternative that will require however a more developed calibration of the parameters on the basis of liquid-liquid properties.