High Efficient CO 2 Separation at High Pressure by Grain-Boundary-Controlled CHA Zeolite Membrane Investigated by Non-Equilibrium Molecular Dynamics.

The CO 2 permeability and selectivity of CHA-type zeolite membranes in the separation of a CO 2 /CH 4 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 CH 4 , which diffuses slowly in the pores, hinders CO 2 permeation. Therefore, an increase in the amount of CH 4 adsorbed at high pressure decreases the CO 2 permeability and significantly reduces the CO 2 selectivity of the CHA membrane. CHA membranes with grain boundaries parallel to the permeation direction were found to show higher CO 2 selectivity than perfectly crystalline CHA membranes at high pressure, as the blocking effect of CH 4 on CO 2 permeation occurring within the grain boundary is not significant. This paper is the first to show that the CO 2 permeability of CHA membranes with controlled grain boundaries can exceed the intrinsic performance of fully crystalline zeolite membranes at high pressure.