Excess volume, isothermal compressibility, isentropic compressibility and speed of sound of carbon dioxide+n-heptane binary mixture under pressure up to 70 MPa. II. Molecular simulations

Abstract

Molecular simulations have been performed in this work to provide a microscopic understanding of the experimental results of asymmetric supercritical binary mixtures of carbon dioxide and n-heptane published in the first article of the series [Bazile et al. J. Supercrit. Fluids 140, 218 (2018)]. Interestingly, molecular simulations results compared well with experimental data on density, isothermal compressibility, speed of sound, isentropic compressibility and the corresponding excess properties. In addition, using Kirkwood-Buff theory, computed partial molar volumes are found to be consistent with those obtained indirectly from experimental data. In particular, the negative value of partial molar volume of n-heptane at infinite dilution close to CO2 critical conditions is well captured, confirming the occurrence of a clustering phenomenon at such conditions. Last, computed properties of the cluster indicates a weak cluster with a radius of about 3 nm and a residence time of the CO2 molecules in the cluster of about 25 ps.