Influence of modifications on the deep desulfurization behavior of NaY and Na13X zeolites in gasoline

NaY and Na13X zeolites were modified by different modification manners including H+ modification, metal ion modification (Cu2+, Ni2+, or Ce3+), and H+ modification followed by metal ion modification to investigate their deep desulfurization behavior in gasoline. The sorbents were characterized by X-ray diffraction, FTIR of chemisorbed pyridine, N-2 adsorption, and scanning electron microscope (SEM). The desulfurization performance of these sorbents was evaluated in model gasoline containing thiophene and cyclohexane with thiophene concentration of 500mg/L, and the results were analyzed to investigate the effect of preparation methods on adsorption desulfurization behavior. The result indicates that H+ modification or metal ion modification could all improve the desulfurization performance of both NaY and Na13X zeolites, except for Na13X modified by Cu2+ and Ni2+. For Cu2+ or Ni2+ ion exchanging, the crystal structure of Na13X would be destroyed, resulting in a much lower desulfurization efficiency than that of the parent Na13X. The desulfurization efficiency of sorbents prepared via H+ modification followed by metal ion modification is higher than that of sorbents prepared by single H+ modification or single metal ion modification, because the former is more conducive to improve the content of metal elements on the sorbents than the latter. In addition, the increase of the specific surface area and pore volume of the sorbents would directly lead to the improvement of desulfurization performance of the sorbents. Compared with Na13X, the H+ modification on NaY zeolite can significantly enhance the desulfurization performance of the sorbents. Among those prepared sorbents, the CuHY has the highest desulfurization efficiency. The influence of thiophene concentration (100-1000mg/L) on desulfurization efficiency of CuHY sorbent was evaluated. The results indicate that the desulfurization efficiency of CuHY sorbent is nearly 100% at room temperature, when the thiophene concentration is lower than 300mg/L. Moreover, its desulfurization behavior could be described by Langmuir isothermal equation.