Orientation Effect of DDR Zeolite Membrane for the Separation of CO2 and H2

Abstract

Zeolite is one of the most popular adsorbent due to its uniform pore structure as well as superior thermal, mechanical and chemical stabilities. In the separation of CO2 and H2 via membrane-based technology, since the kinetic diameter of H2 is quite smaller than that of CO2, the adsorbent is required to have distinctive pore size and adsorptive property. DDR zeolite having 6 and 8-membered ring windows in different orientations could be employed for the separation of these gas molecules. In this study, the orientation effect of DDR zeolite membrane on CO2 separation was investigated via molecular dynamics (MD) simulation and density functional theory (DFT) calculation. We considered two slab models, perpendicular to (001) and (101) surfaces, where adsorbed gas molecules pass through 6- and 8-membered ring windows. In the (001) slab model, both CO2 and H2 molecules undergo high-energy barrier, thereby impeded permeabilities. In contrast, in the (101) slab model, CO2 was facilitatively diffused with good permeance, resulting in high H2/CO2 separation performance. Through this study, the effectiveness of the oriented zeolite membrane in CO2 separation was shown.