Propane/propylene separation by adsorption using Cu⁺ on faujasite zeolites

Abstract

Effects of three different reduction environments on the preparation of Cu(I)X and Cu(I)Y zeolites and their adsorption selectivities towards propylene were investigated. NaX and NaY zeolites were ion exchanged with ammoniacal copper solution before they were reduced with 1 h of ammonia flow, 2 h of ammonia flow, or 1 h of hydrogen flow. Results from inductively couple plasma indicated that there was an incomplete exchange between Cu+ and Na+, which may be from the limitation of this preparation method. The x-ray photoelectron spectroscopy results showed that all reduction methods provided the zeolite with the amount of Cu+ and Cu²⁺. The breakthrough study was used to investigate the propylene adsorption of the prepared zeolites. Although the results showed that the zeolites selectively adsorbed propylene, which was contributed by the π-complex formation between the Cu+ and propylene, it was postulated in this work that there must be a certain exchange degree in the zeolites for the effects of the π-complexation to show any noticeable preferential adsorption towards propylene. The spent zeolites were regenerated and tested for their reusability. It was shown that there was a decrease in the adsorption capacities of the regenerated zeolites. In addition, Cu+ on the Cu(I)Y zeolite was less stable and more susceptible than that on the Cu(I)X zeolite.