The effect of temperature variation on the breakthrough curve in the bed packed by zeolite 5A was studied theoretically in the isothermal, adiabatic and nonisothermal- nonadiabatic systems. The H₂/CO(70/30 volume %) mixture which is two major components of coke oven gas was used as a feed gas. The commercial ADSIM/SU program was used for the simulation incorporating the mass, energy and momentum balances with linear driving force and Langmuir-Freundlich isotherm models. The validity of nonisothermal-nonadiabatic model used in this study was confirmed by using the nonisothermal experimental breakthrough curve obtained from the bench scale bed. The tailing of breakthrough curve in the nonisothermal-nonadiabatic condition occurred due to the decrease of temperature profile in the small scale bed by the feed gas. In the case of the pilot scale bed, the temperature profile and breakthrough curve under the nonisothermal-nonadiabatic condition showed similar behavior with those under the adiabatic condition because of the adiabatic effect of the adsorbent in the bed. Since the dynamics of adsorption bed is affected by the temperature variation in the bulk .separation, the isothermal model makes large errors predict the breakthrough curve.