Pressure swing adsorption (PSA) and temperature swing adsorption are potential techniques for removing CO2 from high-pressure fuel gas streams. Natural zeolites are suitable candidate sorbents for use in the PSA process. Studies of volumetric gas adsorption Of CO2, N-2, and O-2 on three natural zeolites, with different major cations, were conducted at 25 degreesC up to a pressure of 300 psi (2 x 10(6) Pa). Preferential adsorption Of CO2 was observed with all three zeolites. The natural zeolite with the highest sodium content and highest surface area showed the highest CO2 adsorption capacity. Competitive gas adsorption studies also showed that the zeolite with the highest sodium content gave the best separation Of CO2 from the gas mixtures. Contact time did not affect the extent of adsorption of the zeolites. Temperature-programmed desorption studies indicated that the majority of the physically adsorbed CO2 was desorbed at room temperature, while some strongly bound CO2 was desorbed at 115 degreesC.