NaY分子筛的改性及吸附脱氮性能

Modification and adsorptive denitrification of NaY molecular sieve

采用离子交换法用NH+4、Zn2+、Cu2+、Cr3+阳离子改性Na Y分子筛,并利用XRD、FT-IR和低温N2吸附-脱附等方法对改性的分子筛进行了表征。XRD和FT-IR表征结果表明,改性后的分子筛骨架完好。Cr改性Y分子筛(Cr Y)的比表面积、孔体积及平均孔径均较小,但存在部分介孔。研究了改性分子筛对含喹啉模拟燃料的吸附脱氮,喹啉分子尺寸的模拟结果为0.711 6 nm×0.500 2 nm,说明其并不易进入Y型分子筛0.74 nm的微孔。吸附脱氮结果表明,Cr Y的脱氮效果最好,Cu Y和Zn Y次之,NH4Y效果最差,改性分子筛的吸附脱氮性能与金属离子的价态有关,同价金属离子改性后的分子筛,吸附时间对其影响趋势相同,且金属离子价态越高,改性分子筛的吸附脱氮性能越好。吸附温度对Cr Y和NH4Y分子筛吸附脱除喹啉的影响不大,可在室温下使用,但高温有利于Cu Y和Zn Y吸附脱氮。XRD表征结果表明,焙烧后Cr Y分子筛骨架已完全塌陷失去了绝大部分吸附脱氮性能。

Na Y 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 Cr Y was smaller than other modified molecular sieves.Cr Y 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 the0.74 nm microporous pores of Y molecular sieve.The denitrification performance of modified catalysts was in the order： Cr Y,Cu Y,Zn Y and NH4 Y,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 Cr Y and NH4 Y molecular sieve could be used at room temperature.The adsorption removal of quinoline by Cu Y and Zn Y increased with the increasing temperature.The calcination had effects on the denitrification performance of Cr Y.The XRD measurement showed that the skeleton of Cr Y molecule sieve had been burned down and had almost totally lost its denitrification capability.