Adsorption kinetic behaviour of pure CO2, N2 and CH4 in natural clinoptilolite at different temperatures

The adsorption kinetics of pure CO2, N-2 and CH4 on a natural clinoptilolite (ZSL) sample from Villa de Reyes (San Luis Potosi, Mexico) were measured at different temperatures using a glass, high-vacuum volumetric system. The ability of the natural zeolite to adsorb these gases depended on the gas-adsorbent contact time, t. For short values of t, the gas adsorption uptakes decreased in the order CO2 >> N-2 > CH4. However, for long t values, the adsorption uptakes decreased in the sequence CO2 >> CH4 > N-2. It was established that the activation energies (kJ/mol) for the adsorption process increased in the following order CO2 (15) < N-2 (18) < CH4 (40), correlating fairly well with the increasing order of kinetic diameter (Angstrom) of the molecules: CO2 (3.3) < N-2 (3.64) < CH4 (3.8). In comparison to the ZSL sample, the rate of adsorption of N-2 and CH4 on H-ZSL increased and the total adsorption capacity decreased. The ZSL sample may be recommended as an effective adsorbent for the separation of CO2/CH4 and N-2/CH4 mixtures.