High Efficient CO₂ Separation at High Pressure by Grain-Boundary-Controlled CHA Zeolite Membrane Investigated by...

The CO₂ permeability and selectivity of CHA-type zeolite membranes in the separation of a CO₂/CH₄ mixture gas at high pressure were evaluated using non-equilibrium molecular dynamics (NEMD). It was found that in a perfectly crystalline, defect-free CHA membrane, the adsorption of CH₄, which diffuses slowly in the pores, hinders CO₂ permeation. Therefore, an increase in the amount of CH₄ adsorbed at high pressure decreases the CO₂ permeability and significantly reduces the CO₂ selectivity of the CHA membrane. CHA membranes with grain boundaries parallel to the permeation direction were found to show higher CO₂ selectivity than perfectly crystalline CHA membranes at high pressure, as the blocking effect of CH₄ on CO₂ permeation occurring within the grain boundary is not significant. This paper is the first to show that the CO₂ permeability of CHA membranes with controlled grain boundaries can exceed the intrinsic performance of fully crystalline zeolite membranes at high pressure.