Effect of cation exchange on hydrogen adsorption property of mordenite for isotope separation

Zeolite easily exchanges its cation to another. As a result, pore size changes easily. Cation-exchanged mordenite type zeolite (MOR) has been reported to have comparatively good isotope separation capability at temperatures higher than 77 K. However, correlations between adsorption capacities, adsorption rate, cation variety, and cation exchange ratio have not been clearly indicated. In this work, the cation (Na+) of synthetic mordenite type zeolite (Na-MOR) was exchanged by alkaline metal ion or alkaline earth ion (e.g., Li+, K+, Mg2+ and Ca2+). Then, adsorption capacities of H2 and D2 were investigated at 77 K, 159 K, 175 K and 195 K. Adsorption capacities on Li-MOR and Ca-MOR became larger than that of Na-MOR at a low-pressure range, while that of K-MOR became smaller. Micro-pore size indicated that only K-MOR was clearly shifting to smaller size. In the case of alkaline metal, cations with lower atomic numbers may lead to increased adsorption capacities.