3.3. Separation of CO2 from CH4/CO2 gas mixture in a fixed bed column
under atmospheric pressure Even though the adsorption capacity of the AC-DEA at high pressure is greater than that at atmospheric pressure, the adsorption of CO2 molecules from the CH4/CO2 gas mixture was first investigated under atmospheric pressure as the atmospheric adsorption is less energy-intensive. The breakthrough curves of CO2 adsorption on the impregnated AC under atmospheric pressure are shown in Fig. 5. The breakthrough curves were relatively dispersed compared to those associated with physical adsorption. That is, the time from the breakthrough point to the saturation point was longer than that in the breakthrough curve of physical adsorption with favorable isotherms. The shape of the breakthrough curves were similar to those reported in the literature for amine loaded zeolites [21], amine-impregnated commercial AC [48] and amine functionalized activated alumina [4]. Broad breakthrough curves are associated with intraparticle mass transfer resistance [49]. Therefore, the shape of the breakthrough curves indicated that the impregnated amines increased the intraparticle mass transfer resistance of the AC.