Molecular Dynamics Simulation of Straight-chain Alkanes Adsorption and Diffusion in Zeolite

Molecular dynamics simulations were applied to calculate self-diffusion coefficients (D i,self) and heats of adsorption for ethane, propane and n-butane. Simulations were done in temperature range of 300- 525 K for various concentrations inside the pores of silicalite type zeolite. Calculated values of selfdiffusion coefficients and heats of adsorption resulted from the current work, were in better agreement with experimental estimated values found in literature than those resulted from simulations reported by other authors. For instance, at temperature of 300K and loading of 5 molecules/unit cell, self- diffusion coefficients of 16.56×10^-5, 7.62×10^-5 and 5.81×10^-5 cm2/s were calculated for C2H6, C3H8 and n- C4H10 respectively was compared to experimental reported values of 10×10^-5, 9×10^-5 and 6×10^-5 cm^2/s. At the same conditions, adsorption energies of 9.2, 11.48, and 13.66 kcal/mol. were calculated for ethane, propane, and n-butane respectively, while the experimental reported values found to be6.93, 9.7 and 12.7 kcal/mol. Simulations showed that the diffusion decreases when loading increases and the heats of adsorptions were increase by molecular weight of hydrocarbons for all adsorbates studied.