Application of nanoporous graphene membranes in natural gas processing: Molecular simulations of CH₄/CO₂, CH₄/H₂S and CH₄/N₂ separation

Nanoporous graphene is a very promising gas separation membrane with ultrahigh permeability and selectivity. We demonstrate from molecular dynamics insights that the nanoporous graphene membranes with appropriate pore size and geometry can achieve high permeability and selectivity for separating CH₄/CO₂, CH₄/H₂S and CH₄/N₂ mixtures. For the 12-graphene-ring-units nanopores functionalized by N and H atoms, the permeance of CO₂, H₂S and N₂ are on the order of 10⁵-10⁶GPU (gas permeation unit); the selectivity of permeating gases (i.e. CO₂, H₂S and N₂) over the non-permeating gases (i.e. CH₄) is as high as 10². The separation performance of the nanoporous graphene membranes for the three gas mixtures far surpasses the upper bond of the conventional polymer membranes. We anticipate that the development of nanoporous graphene membranes will provide a novel and high efficiency membrane separation technology for the natural gas processing and other gas separation processes in the industries.