Deactivation of π-complexation adsorbents by hydrogen and rejuvenation by oxidation

The pi -complexation sorbents are the best sorbents for bulk olefin/paraffin separation and purification of normal alpha -olefins. Hydrogen produced during cracking operations would remain in small or trace amounts in the process streams. The effect of hydrogen exposure on Ag+-exchanged Y zeolite (AgY) and monolayer-dispersed AgNO3/SiO2 (pi -complexation sorbents) on olefin adsorption was studied by using accelerated tests. Hydrogen exposure could severely deactivate the pi -complexation sorbents for adsorption of ethylene, 1,3-butadiene, and 1-butene. XPS analysis indicated that the Ag+ ion responsible for pi -complexation was partially reduced, hence, the deactivation. It was found that the deactivated sorbents could be rejuvenated by mild oxidation. The reoxidation of the H-2-exposed AgY samples were carried out under different oxidation conditions to locate the optimum conditions. The treatment of the H-2-exposed samples to 0.13 atm of O-2 in He at 350 degreesC for 0.5 h was the best reoxidation condition achieved in this study.