Molecular Dynamics Simulation of the Separation of CH4/CO2 by Nanoporous Graphene

The processes involved in the separation of gaseous CH4/CO2 mixtures using a nanoporous graphene membrane were simulated using a molecular dynamics method, and the effects of three functional modifications (i.e., N/H, all H, and N/-CH3 modifications) in the nanopores were analyzed. The results showed that the gas molecules could form an adsorption layer on the surface of the graphene. The adsorption intensity of the CO2 molecules was higher than that of the CH4 molecules. The functional modifications in the nanopores not only reduced the permeable area, but also improved the adsorption intensity of the gas molecules by changing the potential distribution of atoms at the edge of nanopores, and therefore affecting the permeability and selectivity of the gas mixture being separated by the nanoporous graphene membranes. Furthermore, the permeability of the CO2 molecules was as high as 10(6) GPU (1 GPU=3.35x 10(-10) mol.s(-1).m(-2).Pa-1), which was far greater than those of the existing polymer gas separation membranes. These results therefore demonstrate that nanoporous graphene membranes could be used in an extensive range of applications in industrial gas separation processes, such as natural gas processing and CO2 capture.