Diffusion coefficients of supercritical carbon dioxide and its mixtures using molecular dynamic simulations

Molecular dynamic simulations have been evaluated for systems containing supercritical carbon dioxide to predict high-pressure diffusion coefficients of binary mixtures. Diffusion coefficients of high boiling compounds in supercritical fluids are important for the design of supercritical extractors, separators and reactors. Since high-pressure experiments are time intensive and difficult to perform, molecular simulations could prove a useful framework to obtain thermodynamic properties; however, their reliability is still in question. In this work, an NVT ensemble single site model molecular dynamic simulation using gear predictor corrector algorithm has been applied to calculate diffusion coefficients of carbon dioxide, naphthalene, 2,6-dimethylnaphthalene and 2,7-dimethylnaphthalene in supercritical carbon dioxide system at 317.5 K. The Lennard-Jones (12-6) and the Coulomb potential function have been combined into an intermolecular potential function to measure the binary molecular interaction. The simulation results of the diffusion coefficients are being compared with similar experimental data near the critical points. The calculated diffusion coefficients for each system behaved as a monotonic decreasing function of the molar density and the molecular simulations results, and the selected experimental data are in good agreement.