Carbonate door in the NaKA zeolite as the reason of higher CO2 uptake relative to N2

Theoretical calculations are performed on a model zeolite A where sodium ions have successively been exchanged with potassium. Using both isolated cluster and periodic DFT calculations, we made an attempt to explain how the chemisorbed carbonate species in the material contribute to the exceptionally high CO2 over N-2 selectivity of nearly 200 found in recent experiments [Liu et al. [1]] with the zeolite NaKA as adsorbent to capture and separate carbon dioxide from a gas mixture containing nitrogen. We have shown that the high carbonate forming at the potassium positions in the 8R windows (KII) results in a larger 8R window diameter potentially enhancing the CO2 uptake if adsorption is measured for individual gases. Crown Copyright (C) 2012 Published by Elsevier Inc. All rights reserved.