Distribution of Cu Ions in Lanthanum-Modified CuHY Zeolite and Its Influence on Adsorption Desulfurization Performance

The Cu-loaded CuHY and CuLaHY zeolites were prepared by an incipient wetness method under nitrogen gas atmosphere. The samples were characterized by X-ray diffraction (XRD), N(2) adsorption, NH(3) temperature-programmed desorption, and X-ray photoelectron spectroscopy. The crystalline structure and the distribution of Cu(2+) cations in the cages of Y zeolite were determined by XRD. The adsorption desulfurization performance of the zeolites was investigated for model diesel containing dibenzothiophene (DBT). The results showed that most of Cu species from the precursor CuCl(2) was ion-exchanged with the HY and LaHY zeolites. For the La(3+)-modified CuHY zeolite (Cu-LaHY), the Cu(2+) cations entering the supercages of the zeolite coordinated with both skeleton-oxygen atoms and water molecules, and thus being firmly situated at the sites Sri and Sill in the supercages. For the CuHY zeolite, however, Cu(2+) cations entering the supercages were only near the sites S(II) and S(III) in the supercages. A very small percentage of CuCl molecules was highly scattered in the cages of the Y zeolite, with no definite position. The Cu(2+) cations at the sites S(II) and S(III) in the supercages adsorbed DBT molecules in the model diesel were the centers of adsorption desulfurization. The desulfurization capacity of the CuLaHY zeolite was better as compared with the CuHY zeolite. However, naphthalene molecules will result in competitive adsorption with DBT molecules if there are naphthalene molecules in the model diesel