Determination of diffusion coefficient of C2H6 and CO2 in hydrocarbon solvents by molecular dynamics simulation

Abstract

In this paper, the diffusion coefficients of C2H6 and CO2 in various hydrocarbon solvents have been determined using molecular dynamics simulation at different temperatures and atmospheric pressure. Effect of force field type and number of cell molecules on MD simulation results were investigated. The optimum number of molecules in amorphous cell was obtained and it was found that COMPASS force field showed the best result in comparison with the other investigated force fields forces (Universal, Dreiding, Cvff, and Pcff). In addition, the diffusion coefficients of ethane and CO2 were found to comply with the Stokes–Einstein equation. These coefficients were calculated from the slope of mean square displacement (MSD) curves. Temperature changes also showed an increasing effect on the diffusion coefficients and the activation energies (Ea) and pre-exponential constants (D0) for C2H6 diffusion in heptane and hexane solvents were obtained using Arrhenius theory. The simulated results indicated a good agreement with the experimental data for C2H6 in heptane, hexane, octane, dodecane, and hexadecane solvents and CO2 in hexadecane solvent.