Influence of Temperature on the Binary Adsorption of Ethane and Ethene on FAU Zeolites

The aim of this article is to examine the adsorptive separation of ethane and ethene and to discuss interactions occurring during adsorption in detail. Therefore, fixed-bed adsorption experiments of the pure components and binary mixtures on zeolites NaX, NaY, and CaNaX were performed in the temperature range between -20 and -75 degrees C and at partial pressures from 5 to 450 Pa. The ideal adsorbed solution theory (IAST) based on the pure component isotherms is applied to analyze the difference in interactions between pure component and mixture adsorption. The results show a clear preference of the zeolites for ethene since cations form strong interactions with ir- electrons. In the mixture, strong competition for the limited adsorption sites occurs at the lowest temperatures, resulting in ethane being displaced by ethene. IAST provides good results in predicting the two-component adsorption. Small deviations between the IAST prediction and the isotherms from mixture measurements reveal a change in interactions during adsorption from the mixture compared to pure component adsorption. Zeolite NaX, which has the highest aluminum content and the largest number of accessible cations, shows the highest capacity and best separation efficiency at low temperatures.