Separating Krypton (Kr) from Xenon (Xe) is a challenging task and a highly relevant issue during the treatment of spent nuclear fuel. Once separated, both of these gases can find a broad range of functional applications. For instance, Xe has been widely used in lighting, medical applications, and semiconductor industry. Kr has been successfully employed in nuclear magnetic resonance spectroscopy. The conventional approach to separate these two gases is fractional distillation at cryogenic temperatures, which is an energy intensive process. In this respect, microporous crystalline membranes have emerged as a promising and less energy intensive alternative to separate this challenging gas mixture.<br/>Herein we demonstrate the separation ability of microporous crystalline zeolite (SAPO-34), MOF (ZIF-8), and AlPO (AlPO-18) membranes for Kr/Xe gas mixtures. SAPO-34 membranes displayed the best overall separation performance, while AlPO-18 membranes displayed the highest Kr permeances. We identified the key factors affecting both the separation selectivity and permeance. For these three distinctive types of microporous materials, the presence of rigid micropores with size lying between Kr and Xe atomic sizes, lower Xe/Kr uptakes (adsorption selectivity), and lower concentration of non-selective pores led to the highest observed s Kr/Xe separation selectivities among these three microporous crystals. The Kr permeances for these three microporous crystalline membranes decreased exponentially as membrane thickness increased.

Crystalline molecular sieve membranes for Kr/Xe separation

256th National Meeting (2018)

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