Adsorption of C2H4, C2H6 and CO2 on Cation-exchanged Clinoptilolite

As a means of assessing their possible applications in the separation and purification of the gases concerned, the adsorption kinetics and equilibrium of pure ethylene (C2H4), ethane (C2H6) and carbon dioxide (CO2) onto untreated natural clinoptilolite/heulandite volcanic tuff (Cp) from Villa de Reyes (San Luis Potosi, Mexico) and onto cation-exchanged clinoptilolite samples (Cp-H and Cp-Na) have been measured over the temperature range 0-240 degrees C using a glass high-vacuum volumetric device. Some of the results have been compared with those obtained on a commercial synthetic zeolite 4A (CECA). The adsorption rates of the various gases were measured automatically via a custom acquisition data card capable of registering pressure and time data simultaneously. All the samples showed a decreasing adsorption affinity in the order CO2 > C2H4 > C2H6. A very slow adsorption process and a large proportion of irreversible adsorption were observed for both hydrocarbons onto Cp at 20 degrees C. The irreversible adsorption of C2H4 decreased with increasing temperature, with a small irreversible adsorption being detected at 240 degrees C. Both Cp at 240 degrees C and Cp-Na at 0 degrees C could be promising adsorbents for the separation of C2H4/C2H6 mixtures, while Cp-H may be recommended for the separation at 20 degrees C at times less than 100 s. The high adsorption selectivity toward CO2 of Cp and Cp-Na at all the experimental temperatures studied enables these samples to be recommenced for the purification of C2H4 and C2H6 contaminated with CO2.