Modification and adsorptive denitrification of NaY molecular sieve

NaY molecular sieve, modified by NH⁺₄, Zn²⁺, Cu²⁺, Cr³⁺ metallic cations, were characterized by X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR) and nitrogen adsorption. XRD and FT-IR results indicated that the crystalline structure of the Y molecular sieve was not changed after modification. The average pore size, Brunauer-Emmett-Teller (BET) surface area and the pore volume of CrY was smaller than other modified molecular sieves. CrY had some mesopores. The modified molecular sieve was used to adsorb nitrogen from simulated fuel containing quinoline. The molecular size of quinoline, calculated by using density functional theory (DFT), was 0.711 6 nm×0.500 2 nm, implying that the quinoline can not access easily to the 0.74 nm microporous pores of Y molecular sieve. The denitrification performance of modified catalysts was in the order: CrY, CuY, ZnY and NH₄Y, which implying that the absorption denitrification performance of modified Y molecular sieve related to valence state of metal ion. The result showed that the effects of absorption time on denitrification removal at modified Y molecular sieve by same valence metal ions were showed the same trend and the higher the valence, the higher the denitrification removal. Adsorption temperature had little influence on the denitrification removal by using CrY and NH₄Y molecular sieve could be used at room temperature. The adsorption removal of quinoline by CuY and ZnY increased with the increasing temperature. The calcination had effects on the denitrification performance of CrY. The XRD measurement showed that the skeleton of CrY molecule sieve had been burned down and had almost totally lost its denitrification capability.