Deep desulfurization of gasoline using ion-exchange zeolites: Cu(I)- and Ag(I)-beta

Solid adsorbents Cu(I) and Ag(I) metal exchanged beta zeolites were prepared by solid-state ion-exchange (SSIE) method. Crystallographic structure of the prepared adsorbents has been characterized by XRD analysis. The texture of the prepared adsorbents was investigated using N₂ sorption. Pyridine IR measurements have been carried out to investigate the nature of the acid sites of the adsorbents. The deep-desulfurization performance of such adsorbents has been evaluated through fixed-bed adsorption technique with model gasoline containing thiophene and benzothiophene at ambient temperature and pressure. The obtained results revealed that the breakthrough capacities of Cu(I)- and Ag(I)-beta zeolite with the optimized Cu⁺ or Ag⁺ content are 0.239 mmol S/g and 0.237 mmol S/g, respectively. The remaining sulfur in the desulfurized gasoline is less than 1 ppmw. Their desulfurization capacity for actual FCC gasoline blend is reduced about 30% due to the competitive adsorption from olefins and aromatics. However, The capacity regeneration of Cu(I)- and Ag(I)-beta zeolite sorbents was carried out for 9 times. It is more than 95% recovery of desulfurization after the first regeneration, and it keeps little reduction after subsequent 8 times of regeneration. Such studies included the effect factors on desulfurization performance, such as metal exchange content, SiO₂/Al₂O₃ ratio, acidity, and other texture properties of the zeolite etc.