Hydrogen Isotope (H₂ and D₂) Sorption Study of CHA-Type Zeolites

Using either single H₂ and D₂ or H₂-D₂ mixed gases, the sorption abilities of CHA (chabazite)-type zeolites ion-exchanged with K, Na, or Ca were studied at 77, 201, and 250 K. The LTA (Linde Type A) (3A) and FAU (faujasite)-type zeolites were also examined for comparison. The pore diameters in these materials were found to decrease on the order of FAU > Ca-CHA > [K-CHA, Na-CHA, and LTA(3A)]. The quantities of D₂ adsorbed on these zeolites were larger than the amounts of H₂. At higher temperatures, the CHA-type zeolites having smaller pores exhibited superior D₂/H₂ selectivity compared with the LTA(3A) and FAU, suggesting that hydrogen isotope separation using zeolites is affected by pore size.