Molecular Dynamics Simulation of Diffusion and Structure of Some n-Alkanes in near Critical and Supercritical Carbon Dioxide at Infinite Dilution

Abstract

The diffusion coefficients of n-alkanes (from CH4 to C14H30) in near critical and supercritical carbon dioxide at infinite dilution have been studied by molecular dynamics simulation. The simulation results agree well with experiment, which suggests that the simulation method is a powerful tool to obtain diffusion coefficients of solutes in fluids at high pressures. The local structures of such fluids are further investigated by calculating radial distribution functions and coordination numbers. Meanwhile, the dihedral, end-to-end distance and radius of gyration, which are calculated to characterize the flexibility of n-alkanes, are used to reasonably explain the abnormal trends on radial distribution functions and coordination numbers. Moreover, it is found that the flexibility effects on diffusion in pure n-alkanes and infinitely dilute n-alkane/CO2 system are different. The differences in MD simulation results of molecular diffusion in such systems could be qualitatively explained by the flexibility.

A molecular dynamics investigation into the adsorption behavior inside {001} kaolinite and {1014} calcite nano-scale channels: the case with confined hydrocarbon liquid, acid gases, and water

“…The results are in good agreement to previous reports on pure hydrocarbons (modeled using United-Atom or All-Atom force fields) (Feng et al 2013;Ferguson et al 2009;Thomas et al 2006). Comparison against the bulk-configuration results shows reduction in these properties, which is more conspicuous for longer chain hydrocarbons.…”

Molecular dynamics simulation of diffusion coefficients and structural properties of some alkylbenzenes in supercritical carbon dioxide at infinite dilution

“…It is worth mentioning that we had ever studied the diffusion coefficients and structural properties of n-alkane in scCO 2 at infinite dilution by MD simulation at 10.5 MPa and in the temperature range of 299 K to 323 K. 42 In order to investigate the influence of benzene ring on flexibility of these two different systems, we also carried out the simulation of the Ph-C n /CO 2 system at 323 K and 10.5 MPa by above-mentioned simulation way. The computed mean endto-end distance of these two systems are listed in Table III and plotted in Fig.…”

Molecular dynamics simulation of diffusion coefficients and structural properties of ketones in supercritical CO2 at infinite dilution

“…With respect to computer simulations, they are very useful for investigating dynamic, structural and thermodynamic properties, allowing researchers to complement other existing studies and get valuable information not directly obtained by experiment [21,[27][28][29] as, for instance, radial distribution functions, coordination numbers, and energetic data.…”

“…During the last decades, the MD simulation techniques opened avenues in the prediction of thermo-physical properties, under equilibrium and non-equilibrium conditions, of a wide variety of systems [21,[28][29][30][31]. The information acquired from microscopic computations is 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 vital for the development of reliable and robust macroscopic models, which means that MD simulation and phenomenological modeling may complement each other.…”

“…In recent years, some authors successfully performed classical MD simulation for calculation of organic molecules in SC-CO 2 [21,28,[32][33], taking advantage of the accurate potential functions available in the literature. More than replacing or incrementing measurements, MD is also very desired to unveil and interpret experimental trends observed.…”