Newsome David A, Sholl David S
Department of Chemical Engineering, Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213, USA.
J Phys Chem B. 2005 Apr 21;109(15):7237-44. doi: 10.1021/jp044247k.
The diffusive transport of molecules through nanoporous membranes is determined by both intracrystalline diffusion and mass transport resistances associated with entering and leaving the membrane material. We compare two methods for assessing the relative importance of these resistances based on atomically detailed descriptions of the membrane material. For extremely thin membranes, net transport can be assessed using dual control volume grand canonical molecular dynamics (DCV-GCMD). We show that previous implementations of this technique may have been influenced by nonisothermal effects in interfacial regions and suggest a simple remedy to this situation. We also introduce an approximate method that uses information only from equilibrium MD simulations, which avoids the significant computational expense associated with DCV-GCMD. This approximate method can be used to rapidly assess the importance of interface-related resistances to mass transport over broad ranges of membrane operating conditions. This method will be useful in allowing a rapid determination of whether these interface resistances are significant in practical experimental situations. These two methods are compared by considering the transport of CH(4) and CF(4) through defect-free silicalite membranes.
分子通过纳米多孔膜的扩散传输由晶体内扩散以及与进出膜材料相关的传质阻力共同决定。我们基于膜材料的原子级详细描述，比较了两种评估这些阻力相对重要性的方法。对于极薄的膜，可以使用双控制体积巨正则分子动力学（DCV-GCMD）来评估净传输。我们表明，该技术以前的实现方式可能受到界面区域非等温效应的影响，并针对这种情况提出了一种简单的补救方法。我们还引入了一种仅使用平衡分子动力学（MD）模拟信息的近似方法，该方法避免了与DCV-GCMD相关的巨大计算成本。这种近似方法可用于在广泛的膜操作条件范围内快速评估界面相关传质阻力的重要性。该方法将有助于快速确定在实际实验情况下这些界面阻力是否显著。通过考虑CH(4)和CF(4)通过无缺陷硅沸石膜的传输来比较这两种方法。
