Abstract
The main purposes of this study are to evaluate the performance of graphene membranes in the separation/purification of hydrogen from nitrogen from a theoretical point of view using the molecular dynamic (MD) simulation method, and to present details about molecular mechanisms of selective gas diffusion through nanoscale pores of graphene membranes at the simulated set conditions. On the other hand, permeance and perm-selectivity are two significant parameters of such a membrane that can be controlled by several variables such as pressure gradient, pore density, pore layer angles etc. Hence, in this work, the hydrogen and nitrogen permeating fluxes as well as the H2/N2 ideal perm-selectivity are investigated from a theoretical point of view in a two-layer nanoporous graphene (NPG) membrane through classical MD simulations, wherein the effects of pressure gradient, pore density, and pore angle on the NPG membrane performance are evaluated and discussed. Simulation outcomes suggest that hydrogen and nitrogen permeating fluxes increase as a consequence of an increment of pressure gradient across the membrane and pore density.
Highlights
The increasing demand for highly efficient operations resulted in increased global willingness to embrace membrane technology as a potential long-term solution to mitigate the emission of gases that contribute to global warming
To evaluate the pore density effect on graphene membrane performance, the second and third cases of nanoporous graphene (NPG) models are defined as illustrated in Figure 2a,b, respectively
A run series of simulations based on molecular dynamic (MD) method was performed to evaluate the effects of imperative parameters on NPG membrane performance in terms of gas permeating flux and H2 /N2 ideal perm-selectivity, as presented
Summary
The increasing demand for highly efficient operations resulted in increased global willingness to embrace membrane technology as a potential long-term solution to mitigate the emission of gases that contribute to global warming. Method [17,18,19,20], could be useful to achieve a better understanding of the effects of several parameters for the design and performance of graphene membranes and specific features and constraints like the need to obtain as pure high-purity hydrogen as possible. To this purpose, the MD tool is a feasible method to simulate detailed gas flow characteristics of a membrane system. In the present work, as a first approach, a two-layer graphene membrane cell is theoretically studied by applying the MD method to investigate the effects of the most important design parameters such as pore density and pore angles on graphene membrane performance in terms of hydrogen permeating flux and H2 /N2 ideal perm-selectivity, during various pressure gradients
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