Generally, the common adsorption processes of air separation are divided into two categories: The first category is consists of processes which make use of zeolites as nitrogen adsorbent under the equilibrium conditions and oxygen is a process product. The second one contains processes which utilize Carbon Molecular Sieves (CMSs) as oxygen adsorbent. Zeolite 13X is the most commonly adsorbent used in the air separation for oxygen production. In this work, nitrogen adsorption behavior on zeolite 13X bed is simulated. Desorption and adsorption dynamics of zeolite 13X was investigated in order to study the behavior of this zeolite. The simulation results showed that the high Roll-up Phenomena occurs for oxygen than nitrogen. There is a large mass transfer zone (MTZ) for zeolite 13X. Therefore, the adsorption rate of zeolite 13X is high. The main drop of nitrogen concentration in the outlet of zeolite 13X occurs at the time of about 125 seconds. Nitrogen concentration in the outlet of zeolite 13X approaches zero after about 180 seconds. Keywords: