Comparison of the adsorption dynamics of air on zeolite 5A and carbon molecular sieve beds

Adsorption and desorption in zeolite 5A and CMS beds were compared by using a ternary mixture (N2/ O2/Ar; 78 : 21 : 1 vol%). Because the breakthrough curves for both beds show a tail by temperature variance, a non-isothermal mathematical model was applied to the simulation of adsorption dynamics. The LDF model with a constant rate parameter was enough to predict the experimental breakthrough and temperature curves of an equilibrium separation bed, while the modified LDF model with a concentration-dependent parameter should be applied to a kinetic separation bed. In the CMS bed initially saturated with He, Ar was the first breakthrough component with N2 following after a short interval. Then, after a long interval, the breakthrough of O2 occurred with a broad roll-up due to its fast diffusion rate and the relatively slow diffusion rate of N2. In the CMS bed initially saturated with O2, the breakthrough curves of O2 and N2 showed a very broad shape because of the slow diffusion of N2 into CMS. In the zeolite 5A bed, the breakthrough time sequence was Ar, O2, and N2 at very close time intervals. After the sharp roll-ups of O2 and Ar, the variation of the breakthrough curves was negligible. The inflection of the temperature profile in the zeolite 5A bed was caused by the crossover of the O2 and N2MTZs, while in the CMS bed it was caused by the difference in the diffusion rates of O2 and N2.