Adsorptive Desulfurization Using Rare Earth Exchanged Zeolite Y: A Comparative Study

Sulfur emissions pose a serious risk to human health and the environment. Adsorptive desulfurization using ion-exchanged Y zeolites has proven to be a promising alternative to the traditional hydrodesulfurization process. Cu in Y (CuY) has proven to be an effective sorbent of sulfur molecules in fuels, even in the presence of aromatics. It was also demonstrated that Cu performs remarkably well when paired with Ce (CuCeY), a rare earth (RE). This study explores the potential of using other REs such as Lanthanum (La), Samarium (Sm), and Neodymium (Nd) ion exchanged in Y zeolite alone or paired with Cu on the adsorption of heavy sulfur molecules in the presence of aromatics. RE and CuRE ion-exchanged Y and mesoporous Y (SAY) zeolites were synthesized, characterized, and tested for the adsorption of Benzothiophene (BT) and dibenzothiophene (DBT). Characteristic adsorption modes such as σ-bonding and π-complexation, previously found in CuCeY, were observed in all the CuREY samples. Rietvield refinement was used to determine the location and composition of metal cations in the zeolite structure and it was shown that all of the REs prefer the inner sites of Y, while Cu occupies sites in the supercage. The synergy between Cu and the REs varies, with Ce showing the strongest synergistic interaction with Cu compared to the other rare earths. The results of this study provide insight into the role of various metals in zeolite Y for sulfur adsorption.