Interfacial barriers of H2 and O2 transport through RHO, SAS, and NPT zeolites with eight-membraned ring

JS Song and L Zhang and SY Cai and L Shi, INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER, 166, 109210 (2025).

DOI: 10.1016/j.icheatmasstransfer.2025.109210

Molecular simulations were extensively performed to investigate effects of thickness, framework flexibility on interfacial resistances of H2 and O2, alongside separation performance of three eight-membraned ring (8MR) zeolite (RHO, SAS, and NPT) membranes for H2/O2 being analyzed and compared. The corrected diffusivities of H2 and O2 increase with finite thickness and ultimately reach their maximum values in infinite frameworks, whereas the interfacial resistance contributes a smaller percentage to the total resistance. Attributed to stronger adsorbate- adsorbent interactions, larger kinetic diameter, higher energy barriers, and heavier molecular weight, O2 molecules experience much enhanced interfacial resistance and critical membrane thickness in comparison with H2. The average pore apertures and areas of flexible 8MR windows both follow order SAS > RHO > NPT. Therefore, O2 and H2 diffuse more rapidly in rigid RHO and NPT zeolites compared to their flexible counterparts. This trend is consistently observed for O2 in SAS zeolite, while H2 exhibits an opposite transport behavior under identical conditions. Adsorption capacity of zeolites is RHO >= NPT > SAS. Owing to the strongest kinetic selectivity, NPT zeolite achieves an average selectivity of 15.36, which is over three times higher than RHO and SAS. Consequently, NPT zeolite demonstrates superior performance in separating H2/O2 mixtures.

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