Molecular Insights on the CH4/CO2 Separation in Nanoporous Graphene and Graphene Oxide Separation Platforms: Adsorbents versus Membranes

A Khakpay and F Rahmani and S Nouranian and P Scovazzo, JOURNAL OF PHYSICAL CHEMISTRY C, 121, 12308-12320 (2017).

DOI: 10.1021/acs.jpcc.7b03728

Molecular dynamics simulations were performed to gain fundamental molecular insights on the concentration-dependent adsorption and gas transport properties of the components in a CH4/CO2 gaseous mixture in single-and double layered nanoporous graphene (NPG) and graphene oxide (NPGO) separation platforms. While these platforms ate promising for a variety of separation applications, much about the relevant gas separation mechanisms in these systems is still unexplored. Based on the gas adsorption results in this work, at least two layers of CO2 are formed on the gas side of both NPG and NPGO, while no adsorption is observed for pure CH4 on the single-layered NPG. In contrast, increasing the CH4 concentration in the CH4/CO2 mixture leads to an enhancement of the CH4 adsorption on both separation platforms. The through-the-pore diffusion coefficients of both CO2 and CH4 increase with an increase in the CH4. concentration for all NPG and NPGO systems. The permeance of CO2 is smaller than that of CH, suggesting the NPG and NPGO platforms are more suitable as CO2 adsorbents or membranes for the CH4/CO2 (rather than the CO2/CH4) separation. The highest observed selectivities for the CH4/CO2 separation in the NPG and NPGO platforms are about 5 and 6, respectively.

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