Zeolites are microporous, crystalline materials. They are capable of selectively adsorbing CO2, suggesting potential applications for carbon capture and natural gas purification processes. Cations are present within aluminum-substituted zeolites. They are essential to the adsorption process as they often either block gases from diffusing within the material or become strong adsorption sites. CO2’s quadrupole allows for a distinct interaction with the zeolite framework, sometimes resulting in the selective adsorption of CO2. In particular, within zeolite Na-RHO, CO2 bypasses the thermally fluctuating cation, while gases such as N2 and CH4 are blocked from entering the adsorption sites. Examining the cations’ role within the zeolite is essential to our understanding of the selective adsorption demonstrated by zeolites. In this project, we used Molecular Dynamics (MD) simulations to investigate the behavior of the sodium cations within zeolites RHO and MFI and the effect of aluminum substitutions on cation position. We used both classical MD simulations and computationally demanding, but very accurate, ab-initio MD simulations. Experimental data are used to validate our ab-initio MD results, and then both experimental and ab-initio MD data are used to evaluate the performance of our classical models. The classical potential CLAYff produced results in agreement to those using quantum calculations in significantly less computational time and therefore is the one we will continue to use, in addition to ab-initio MD, to further examine the behavior of sodium cations within zeolites RHO and MFI.

Cation behavior within zeolites

2019 Spring National Meeting

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