Study of natural zeolites for hydrogen purification: CO2 adsorption capacity and kinetic mechanism

Hydrogen is considered a promising alternative fuel. However, its use requires a high degree of purity achieved through purification processes. Adsorption is considered one of the most important techniques for purification. This study investigates the CO₂ adsorption capacity and kinetic mechanism of natural zeolite to understand carbon dioxide adsorption behavior under various operating conditions. Multicomponent breakthrough curves of a mixture of H 2 /CO/CH 4 /CO 2 were obtained at different pressures and gas flow rates. Additionally, comprehensive analyses of CO 2 adsorption equilibrium and kinetics were conducted. The adsorption isotherm data were fitted with different model equations. Freundlich, Sips and Toth models providing the best fit, indicating the heterogeneous nature of the adsorbent surfaces. The carbon dioxide adsorption kinetic was analysed using different kinetic models , obtaining that the adsorption process involves both physical and chemical interactions. The limiting step of the diffusion process is intraparticle diffusion, although a sequence of linear sections observed in the qt vs. t 1/2 plots indicates the presence of multiple mass transfer mechanisms, such as diffusion through the boundary layer.