Fundamentals of xylene adsorptive separation

Abstract

Coadsorption of liquid p-xylene, m-xylene, o-xylene and ethylbenzene with toluene on the KBaX and KY zeolites was studied at 40, 65 and 90℃. The KBaX zeolite adsorbed p-xylene more than the other aromatics, and 0-xylene was the least adsorbed species at high xylene/toluene m ole ratios. However, at low xylene/toluene m ole ratios, o-xylene was the most adsorbed aromatic. This may be due to the o-xylene molecular structure and affinity between each aromatic and the zeolite. The KY zeolite adsorbed p-xylene more than the other aromatics, and o-xylene was the least adsorbed aromatic at higher xylene/toluene m ole ratios. At low xylene/toluene m ole ratios, unlike the KBaX zeolite, the KY zeolite adsorbed about the same amount of the C8 aromatics. The KY zeolite had an ability to adsorb more C8 aromatics than the KBaX zeolite did. As the adsorption process is exothermic, the zeolites adsorbed all the species less at higher temperature. But, at the full capacity of both zeolites, temperature had very little effect on the selectivity of p-xylene relative to the other C8 aromatics and toluene. The KBaX and KY zeolites selectively adsorbed p-xylene more than toluene w hile they adsorbed more toluene than the other C8 aromatics.