In this study, carbon deposition process on activated carbon (AC) in order to produce carbon molecular sieve (CMS) is simulated using molecular dynamics simulation. The proposed activated carbon for simulation includes micropores with different characteristic diameters and lengths. Three different temperatures of 773K, 973K, and 1273K are selected to investigate the optimum deposition temperature. Simulation results show that the carbon deposition process at 973 K creates the best adsorbent structure. While at lower temperature some micropore openings blocked with carbon atoms, at higher temperature the number of deposited carbons on the micropores does not change significantly. Also, carbon deposition process conform pseudo-second-order kinetic model with an endothermic behavior. Moreover, to evaluate sieving property of adsorbent products, nitrogen and oxygen adsorption on the initial and final adsorbent products are examined. Results show that there is not any considerable difference between the equilibrium adsorption amounts of nitrogen and oxygen on the initial and final adsorbents especially at low pressure (P < 10 atm). Although, adsorption kinetics curves of these gases change significantly after carbon deposition process in comparison to the initial sample. These observations indicate that the final adsorbent has high selectivity towards oxygen compared with the nitrogen, so it can be named as a carbon molecular sieve. All simulated results are in good agreement with experiments.

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