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

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