Breakthrough curves of non-trace H2–D2 mixture replacement adsorption with SZ-13X packed column at 77.4 K

Breakthrough curves of non-trace H2–D2 mixture replacement adsorption with a synthetic zeolite SZ-13X packed column at a cryogenic temperature of 77.4 K were measured at several concentrations of D2 in H2–D2 mixtures and at the same ones of H2 in these mixtures, and were analyzed by the curve-fitting with the curves estimated from a model of non-trace two-component mass-flow balances of H2 and D2 in the packed column. This dynamic model of adsorption takes in account the characteristics of the separation factor of D2/H2 in adsorption equilibrium depending on the composition in adsorbed phase. Experimental curves show a slight but certain variation with increase in the concentration of a subjective component in the isotope mixtures. It is demonstrated here that these behaviors can be approximated closely by the numerical curves. The curve-fitting analysis brings an interesting result that the overall mass-transfer coefficient of D2 replacing H2 adsorbed in advance is larger than that of H2 replacing D2 adsorbed. This difference can be interpreted by assuming that desorption of molecules adsorbed in advance is the rate-determining process of replacement adsorption.