State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China.
Phys Chem Chem Phys. 2015 Sep 28;17(36):23619-26. doi: 10.1039/c5cp03195h.
We identify the inhibition effect of a non-permeating gas component on gases permeating through the nanoporous graphene membranes and reveal its mechanisms from molecular dynamics insights. The membrane separation process involves the gas mixtures of CH4/H2 and CH4/N2 with different partial pressures of the non-permeating gas component (CH4). The results show that the permeance of the H2 and N2 molecules decreases sharply in the presence of the CH4 molecules. The permeance of the N2 molecules can be reduced to as much as 64.5%. The adsorption of the CH4 molecules on the graphene surface weakens the surface adsorption of the H2 and N2 molecules due to a competitive mechanism, accordingly reducing the permeability of the H2 and N2 molecules. For the N2 molecules with stronger adsorption ability, the reduction of the permeance is greater. On the other hand, the CH4 molecules near the nanopore have a blocking effect, which further inhibits the permeation of the H2 and N2 molecules. In addition, we predict the selectivity of the nanopore by using density functional theory calculations. This work can provide valuable guidance for the application of nanoporous graphene membranes in the separation of the gas mixtures consisting of permeating and non-permeating components with different adsorption abilities.
我们从分子动力学的角度出发，确定了非渗透气体成分对通过纳米多孔石墨烯膜渗透气体的抑制作用，并揭示了其机制。膜分离过程涉及 CH4/H2 和 CH4/N2 等不同分压的非渗透气体成分（CH4）的气体混合物。结果表明，当存在 CH4 分子时，H2 和 N2 分子的渗透率会急剧下降。N2 分子的渗透率可降低至 64.5%。由于竞争机制，CH4 分子在石墨烯表面的吸附会削弱 H2 和 N2 分子的表面吸附，从而降低 H2 和 N2 分子的渗透率。对于吸附能力更强的 N2 分子，渗透率的降低更大。另一方面，纳米孔附近的 CH4 分子具有阻塞作用，进一步抑制了 H2 和 N2 分子的渗透。此外，我们还通过密度泛函理论计算预测了纳米孔的选择性。这项工作可为纳米多孔石墨烯膜在分离具有不同吸附能力的渗透和非渗透成分的气体混合物中的应用提供有价值的指导。
