Preparation of Ag⁺ modified NaY molecular sieve and its adsorption and denitrogenation properties

An AgY molecular sieve modified by Ag⁺ ion was characterized by XRD, FT-IR and N₂ adsorption and desorption and used to the adsorption denitrogenation from model fuels containing pyridine, aniline and quinoline basic nitrides. The adsorption capacity for N with the AgY molecular sieve was obviously better than that with the NaY molecular sieve. The effects of adsorption temperature and adsorption time on the adsorption capacity of three kinds of nitrides by AgY molecular sieve were investigated. The experimental results show that the adsorption capacity for N is aniline>quinoline>pyridine. To study the adsorption mechanism of AgY, the 12T cluster model of AgY molecular sieve was established by Materials Studio software and the adsorption of three kinds of nitride molecules on the AgY molecular sieve was simulated at 303 K, 323 K and 343 K. The adsorption energy, the distance between the active center and pyridine, aniline and quinoline molecules, the frontier orbit, the isodensity distribution, the radial distribution function and other relevant parameters were calculated. The calculated results show that the adsorption of aniline by AgY molecular sieve is better than that of quinoline and pyridine, which is consistent with the experimental results. Moreover, the adsorption is mainly the chemical adsorption, and the S and W sites of AgY molecular sieve are the main adsorption sites. The results of isothermal adsorption show that the adsorption of pyridine on the AgY follows the Langmuir-Freundlich mixed adsorption model, and the adsorption of aniline and quinoline follows the Freundlich adsorption model. The results of adsorption kinetics and thermodynamics show that the adsorption of pyridine on the AgY molecular sieve conforms to the quasi-second-order kinetic model, while the adsorption of aniline and quinoline conforms to the quasi-first-order kinetic model, and all adsorption processes are spontaneous entropy increasing process.