High-pressure interfacial tensions for nitrogen + ethanol, or hexane or 2-methoxy-2-methylbutane: A comparison between experimental tensiometry and Monte Carlo simulations

Abstract

Interfacial tension (IFT) data have been characterized for three binary systems composed by a pure liquid (i.e., ethanol or hexane or 2-methoxy-2-methylbutane) under a pressurized nitrogen atmosphere. Experimental measurements have been carried out in a high-pressure pendant drop tensiometer over the temperature range of 303–353K and over the pressure range of 0.1–15MPa.According to experimental results, the interfacial tensions of the binary mixtures decrease as temperature and/or pressure increase. Particularly, the decrease of interfacial tensions with increasing pressure at isothermal conditions evidences adsorption of nitrogen at the liquid surface, a behavior that was clearly corroborated by analyzing the trend of the calculated Gibbs adsorption isotherms.The measured data have been favorably compared with predictions obtained from Monte Carlo simulations appropriately performed in an NpNAT ensemble, case in which intra- and inter-molecular interactions were represented by a TraPPE-UA united-atom force field. Particularly, molecular simulation results coherently predict the overall trend observed in the IFT experimental data and, from a microscopic viewpoint, provide a clear explanation about the observed preferential adsorption of nitrogen at the liquid surface.