The effect of temperature upon the permeation of oxygen, nitrogen and their binary gas mixtures through carbon membranes was investigated by using a dual control volume grand canonical molecular dynamics method. A two-dimensional slit was used instead of a one-dimensional pore, and a novel iteration was introduced in order to overcome the difficulty of ignoring the effect of permeation side pressure and composition on gas transport. The results showed that both oxygen and nitrogen followed a Knudsen diffusion mechanism when they permeated through carbon membranes as pure components. In this case, nitrogen had a rather higher permeability than did oxygen. However, oxygen had a higher permeability than nitrogen due to competitive adsorption at low temperature when their mixtures flowed through membranes. In addition, the pore width strongly affected the permeability; especially when the pore was very small, and molecular sieving predominated in the separation of oxygen and nitrogen. At high temperatures, adsorption hardly affected the separation of oxygen and nitrogen.

Effect of Temperature on the Permeation and Separation of Oxygen and Nitrogen in Carbon Membranes: a Non-Equilibrium Molecular Dynamics Simulation Study. Wang, S.M., Yu, Y.X., Gao, G.H.: Acta Chimica Sinica, 2006, 64[11], 1111-5