Permeation dynamics of small molecules through silica membranes: Molecular dynamics study

The permeation of He, CO 2 , and N 2 through a thin silica membrane was investigated using molecular dynamics. The permeance of He follows Knudsen flow. The permeation of CO 2 is higher than the estimated value from Knudsen theory. Inside the pore, CO 2 , tends to be parallel to the pore wall. This orientation is suitable for diffusion. In contrast, N 2 , shows lower permeance compared to the value from Knudsen theory. The molecules present perpendicular orientations inside the pore wall, which reduces their diffusion. In mixed CO 2 /N 2 , gas simulation, the selective permeation of CO 2 relative to N 2 was observed.