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

Abstract

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 (C 2 H 4 ), ethane (C 2 H 6 ) and carbon dioxide (CO 2 ) onto untreated natural clinoptilolite/heulandite volcanic tuff (Cp) from Villa de Reyes (San Luis Potosí, México) and onto cation-exchanged clinoptilolite samples (Cp–H and Cp–Na) have been measured over the temperature range 0–240 °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 CO 2 > C 2 H 4 > C 2 H 6 . A very slow adsorption process and a large proportion of irreversible adsorption were observed for both hydrocarbons onto Cp at 20 °C. The irreversible adsorption of C 2 H 4 decreased with increasing temperature, with a small irreversible adsorption being detected at 240 °C. Both Cp at 240 °C and Cp–Na at 0 °C could be promising adsorbents for the separation of C 2 H 4 /C 2 H 6 mixtures, while Cp–H may be recommended for the separation at 20 °C at times less than 100 s. The high adsorption selectivity toward CO 2 of Cp and Cp–Na at all the experimental temperatures studied enables these samples to be recommenced for the purification of C 2 H 4 and C 2 H 6 contaminated with CO 2 .