The permeation of He, Co2 and N2 through a thin silica membrane was investigated using molecular dynamics. The permeation of He involved Knudsen flow. The permeation of CO2 was higher than the estimated value for Knudsen theory. Within the pore, CO2 tended to be parallel to the pore wall. This orientation was suitable for diffusion. In contrast, N2 exhibited a lower permeation compared to the value for Knudsen theory. The molecules had perpendicular orientations inside the pore wall, which reduced their diffusion. In mixed CO2/N2 gas simulations, the selective permeation of CO2 relative to N2 was observed.

Permeation Dynamics of Small Molecules Through Silica Membranes: Molecular Dynamics Study. Takaba, H., Mizukami, K., Kubo, M., Fahmi, A., Miyamoto, A.: AIChE Journal, 1998, 44[6], 1335-43