Adsorption of CO2, CH4, and N-2 was investigated using pulse concentration chromatography on polystyrene functionalized by covalently attached diethanolamine, dimethylamine, imidazole, and N-methyl piperazine. The adsorption equilibrium constants at different temperatures were estimated by fitting the experimental chromatograms into a non-linear equilibrium dispersive chromatography model using gPROMS. Axial dispersion was found to be the controlling mechanism for dispersion of the chromatograms. The heat of adsorption and corresponding equilibrium selectivities were determined from the adsorption equilibrium constants. The imidazole based adsorbent showed the highest affinity for CO2.