Effect of gas molecule affinities on CO₂ separation from the CO₂/N₂ gas mixture using inorganic membranes as investigated by molecular dynamics simulation

Applying molecular dynamics simulation and computer graphics methods we have investigated the dynamic behavior of the separation process of CO₂ from the CO₂/N₂ gas mixture in inorganic membranes at high temperatures. We have demonstrated that the permeation dynamics follows the Knudsen diffusion mechanism in our model system that has a slit-like pore of 6.3 Å. We have analyzed the effect of affinities of gas molecules for the membrane wall on the permeation to predict the optimal affinity strength for high selectivity of CO₂. Our results indicate that in the model with the 600 K and 200 K affinities for CO₂ and N₂, respectively, we can obtain a high selectivity of CO₂ even if the temperature is 1073 K. It is also shown that there is an optimal range for the CO₂ affinity for the membrane wall to achieve good separation, which was estimated as the range of 400-600 K in our system, if the affinity of N₂ is always weaker than that of CO₂.