Adsorption Kinetics and Equilibria of Carbon Dioxide, Ethylene, and Ethane on 4A(CECA) Zeolite

Abstract

The adsorption kinetics and equilibria of pure carbon dioxide (CO2), ethylene (C2H4), and ethane (C2H6) on 4A(CECA) commercial zeolite have been measured over the temperature range T = (293.15 to 353.15) K using a glass-vacuum volumetric device. The adsorption rates of the gases were measured automatically via a custom acquisitions data card that was capable of registering pressure and time (t) data five times per second in the first period for t = (0 to 180) s, simultaneously. All of the gases showed a decreasing adsorption affinity and isosteric heat of adsorption in the order CO2 > C2H4 > C2H6. Unlike CO2, an activated diffusion for C2H4 and C2H6 for low t was observed. The adsorption activation energy for ethane Ea = (14.6 ± 0.2) kJ·mol−1 was found to be slightly higher than that for ethylene Ea = (13.8 ± 1) kJ·mol−1. The dual Langmuir model described the CO2 adsorption isotherms, whereas those for C2H4 and C2H6 were fitted with the Sips equation at (293.15 and 323.15) K. The three gases were reversibly adsorbed, and the adsorption selectivity for gas binary mixtures decreased in the sequence CO2/C2H6 > C2H4/C2H6 > CO2/C2H4. The obtained results indicate that 4A(CECA) zeolite could be a good candidate for separating these binary gas mixtures at 293.15 K.