Experiments with a mathematical model were performed for pure CO2 feed adsorption on activated carbon up to high pressure (30 kg/cm(2) . G) by using H-2 pressurization and vacuum purge to study adsorption steps in vacuum pressure swing adsorption and atmospheric pressure swing adsorption. All on-line real data from transmitters and instruments were obtained using the automatic control and data acquisition system. The maximum breakthrough time and the initial constant pattern were investigated under changing process variables. The maximum breakthrough times were found out under the limiting conditions and compared between two desorption methods using vacuum purge and atmospheric blowdown. The initial constant pattern occurred when the interstitial velocity approached certain values. The occurrence of the maximum breakthrough curves was strongly related with the formation of the initial constant pattern. From the nonisothermal and nonadiabatic model with the linear driving force model and the temperature-dependent Langmuir isotherms, the effects of the mass and heat transfer parameters on the adsorptive process were examined. The possibility of predicting the breakthrough curves was confirmed by monitoring the temperature propagation profiles, At high pressure the overall heat transfer coefficient had a larger effect on the adsorptive process than the overall mass transfer coefficient.