Molecular dynamics study of gas permeation through amorphous silica network and inter-particle pores on microporous silica membranes
Molecular dynamics study of gas permeation through amorphous silica network and inter-particle pores on microporous silica membranes
复制标题
DOI：
10.1080/00268970310001649383
复制
发表时间：
2004-01
影响因子：
1.7
通讯作者：
Tomohisa Yoshioka;T. Tsuru;M. Asaeda
中科院分区：
文献类型：
--
作者：
Tomohisa Yoshioka;T. Tsuru;M. Asaeda
采用边界驱动的非平衡态分子动力学模拟方法研究了气体通过微孔无定形二氧化硅膜的渗透机理。制备了两种类型的二氧化硅膜，一种是通过随机原子去除，另一种是通过常规的孔挖掘程序。前者是一个致密的膜，作为由二氧化硅聚合物形成的网络孔的模型，后者具有一个贯穿的圆柱形孔，模拟粒子间的孔。He、H2和Ne通过密度为1.7和1.8 g cm−3的网络模型的渗透率随着温度的降低而增加，而在密度更大的模型中观察到活化渗透。从克努森模型预测的渗透性能的偏差变得更大，随着膜密度的增加，作为分子筛效应的结果。H2通过直径为0.6 nm的圆柱形孔的渗透率大于他在所有温度下检查的预测由克努森模型，和更大的相互作用的CO2与孔表面产生了更大的温度依赖性曲线的渗透率相比，他和H2。几种气体的模拟渗透性能与实际微孔二氧化硅膜的实验数据一致，表明由二氧化硅网络相的小开口和较大的颗粒间孔组成的微孔结构模型的定性有效性。
A boundary driven non-equilibrium molecular dynamics simulation method was used to study gas permeation mechanisms through microporous amorphous silica membranes. Two types of silica membranes were prepared, one by random atom-removing and the other by regular pore-digging procedures. The former was a dense membrane that served as a model for network pores formed by silica polymers and the latter had a penetrating cylindrical pore which simulated an inter-particle pore. The permeances of He, H2 and Ne through network models with densities of 1.7 and 1.8 g cm−3 increased with decreasing temperature, while activated permeation was observed for the denser models. Deviations in the permeation properties from those predicted by the Knudsen model became greater with increasing membrane density as the result of molecular sieving effects. The permeance of H2 through a cylindrical pore 0.6 nm in diameter was greater than that for He at all temperatures examined as predicted by the Knudsen model, and the greater interaction of CO2 with the pore surface yielded a larger temperature-dependency curve for permeance, compared to He and H2. The simulated permeation properties of several gases were in agreement with experimental data on actual microporous silica membranes, indicating the qualitative validity of the microporous structure model composed of small openings in a silica network phase and larger inter-particle pores.