Pure and Multicomponent Adsorption Equilibrium of Carbon Dioxide, Ethylene, and Propane on ZSM-5 Zeolites with Different Si/Al Ratios

Abstract

Experimental adsorption isotherms of pure carbon dioxide, ethylene, and propane as well as their mixtures have been obtained on three samples of ZSM-5 zeolite of different atomic Si/Al ratios (15, 29, and 60) over the pressure range 0−100 kPa. The data are given at temperatures of 281, 293, and 308 K (pure data) and 293 K (binary and ternary data). Changes in the zeolite selectivity with its Si/Al ratio were observed for the pure components, with an increase in the loading of polar molecules, like carbon dioxide and ethylene, as the atomic Si/Al ratio decreases. The selectivity, however, was nearly constant for propane. The characteristic equilibrium curve was obtained for each adsorbent, and a good fit of the equilibrium data was obtained for all adsorbates at the three temperatures. Some equilibrium overadsorption and displacement effects with large deviations from the ideal behavior including binary azeotropes were found for the mixtures of polar and nonpolar compounds. Thus, ethylene and carbon dioxide are displaced by propane, showing a maximum in their individual adsorption isotherms in the binary mixtures. The Si/Al ratio of the zeolite was found to modify the azeotrope and overadsorption effects.