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Molecular Simulation Study of Transport and Separation of Gas through Nanoporous Graphene Membranes

Abstract : Nanoporous graphene membranes are gaining attention in the field of separation processes. Regarding gas separation, perm-selective membranes technology consumes less energy than other conventional technologies. Due to nanoporous graphene’s atomic thickness, controllable pore size in the range of molecular diameters, mechanical and chemical stability, it is considered as one of the most favorable membrane material for industrial gas separation applications. For instance, in the context of natural gas production and air separation, the separation of CH4/CO2, N2/O2 mixtures would greatly benefit from this kind of new materials. With the rapid development in graphene fabrication technology, breakthroughs in nanoporous graphene membranes are expected in the next few years and quite sufficient data can be found in publications. However,there is no accurate theory that can predict gas permeation and separation factor quantitively.In this work, we show that gas permeation through single-layer nanoporous graphene membranes can be divided into three regimes: molecular sieving, crossover regime and effusion. We propose a theoretical framework to explain the mechanisms and predict the diffusive transport coefficient. In our framework, the transport coefficient is related to the parameters which can be computed from the potential of mean force (PMF) between permeating gas molecules and the membrane atoms. By means of Equilibrium (EMD) and Non Equilibrium (NEMD) molecular dynamics simulations, we explore the permeation of pure compounds through nanoporous graphene membranes exhibiting differentpore sizes and geometry. We also investigate the effect of thermodynamic conditions (pressure and temperature) on the transport coefficient. Simulated transport coefficients are in good agreement with the predictions of our theory over the whole range of permeation regimes. Furthermore, based on the knowledge acquired on the permeation of pure compounds, we define the concept of selectivity. By comparing the results of molecular simulations performed with gas mixtures, we show in which cases the results weobtained for pure compounds, and consequently our theoretical framework, allow us to predict the selectivity of mixtures.
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Submitted on : Thursday, February 18, 2021 - 11:31:11 AM
Last modification on : Friday, February 19, 2021 - 3:27:56 AM

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  • HAL Id : tel-03145287, version 1

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Juncheng Guo. Molecular Simulation Study of Transport and Separation of Gas through Nanoporous Graphene Membranes. Chemical and Process Engineering. Université de Pau et des Pays de l'Adour, 2020. English. ⟨NNT : 2020PAUU3029⟩. ⟨tel-03145287⟩

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