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

Abstract Breakthrough curves of non-trace H 2 –D 2 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 D 2 in H 2 –D 2 mixtures and at the same ones of H 2 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 H 2 and D 2 in the packed column. This dynamic model of adsorption takes in account the characteristics of the separation factor of D 2 /H 2 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 D 2 replacing H 2 adsorbed in advance is larger than that of H 2 replacing D 2 adsorbed. This difference can be interpreted by assuming that desorption of molecules adsorbed in advance is the rate-determining process of replacement adsorption.