Deep desulfurization of model gasoline by selective adsorption over Cu–Ce bimetal ion-exchanged Y zeolite

Abstract

Adsorbents were successfully prepared by liquid-phase ion-exchange of Y zeolites with Cu, Ce and combined Cu–Ce metal ions. The adsorbents were characterized by means of X-ray diffraction (XRD), N2-adsorption specific surface area measurements (BET), Fourier transform infrared (FT-IR), H2 temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) techniques. The adsorptive desulfurization properties of the adsorbents were studied in a fixed-bed unit through a model gasoline which was made up of 1-octane solution of refractory sulfur compounds (such as thiophene and benzothiophene) and certain amounts of toluene, pyridine or cyclohexene. Results indicate that CuICeIVY not only has a high sulfur adsorption capacity similar to CuIY but also has a high selectivity for sulfur compounds similar to CeIVY. For each sorbent, the selectivity of adsorption of sulfur compounds from liquid solutions followed the order: benzothiophene>thiophene. The effect on the metal ion-exchanged Y zeolites for sulfur removal was in the order: pyridine>cyclohexene>toluene. The high selectivity of CuICeIVY for sulfur removal can be attributed to the synergistic interaction between Cu+ and Ce4+. The CuICeIVY zeolite binds organic sulfur compounds through two types of adsorption modes: π-complexation and direct coordination (S–M) interaction.