Preparation of Ag + modified NaY molecular sieve and their adsorption and denitrogenation properties
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摘要: 采用Ag + 改性NaY分子筛成功制备了AgY分子筛,利用XRD射线衍射、IR、N2吸附脱附对NaY和AgY分子筛进行了表征,并用于吸附脱除模拟燃料中吡啶、苯胺、喹啉碱性氮化物,AgY分子筛的吸附能力明显优于NaY分子筛。考察了吸附温度、吸附时间对AgY分子筛吸附三种氮化物的影响,实验结果表明吸附能力均为:苯胺>喹啉>吡啶,为了进一步研究其吸附机理,采用Materials Studio软件建立了AgY分子筛12T团簇模型并在303K、323K、343K下模拟三种氮化物分子在AgY分子筛上的吸附,计算了吸附能、活性中心与吡啶、苯胺、喹啉分子的距离、前线轨道、等密度分布、径向分布函数等相关参数,计算结果也表明AgY分子筛对苯胺的吸附优于喹啉,优于吡啶,与实验结果一致,且吸附以化学吸附为主,AgY分子筛S位和W位为主要吸附位。吸附等温线研究结果表明,AgY分子筛对吡啶的吸附符合Langmuir-Freundlich混合吸附模型,对苯胺、喹啉的吸附符合Freundlich吸附模型。吸附动力学和吸附热力学结果表明,AgY分子筛对吡啶的吸附符合准二级动力学模型,对苯胺、喹啉的吸附符合准一级动力学模型,吸附是自发的熵增过程。
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关键词:
- AgY分子筛 /
- 吸附脱氮 /
- Materials Studio /
- 分子动力学模拟
Abstract: AgY molecular sieve was successfully prepared by using Ag + to modify NaY molecular sieve. The NaY and AgY molecular sieve were characterized by XRD, IR and N2 adsorption and desorption, and were used for adsorption and removal of pyridine, aniline and quinoline basic nitrides in simulated fuel. The adsorption capacity of AgY molecular sieve was obviously better than that of 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 showed that the adsorption capacity was as follows: aniline > quinoline > pyridine, In order to further 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 AgY molecular sieve was simulated at 303 K, 323 K and 343 K.The adsorption energy, distance between the active center and pyridine, aniline and quinoline molecules, frontier orbit, isodensity distribution, radial distribution function and other relevant parameters were calculated. The calculated results also showed that the adsorption of aniline by AgY molecular sieve was better than that of quinoline and pyridine, which was consistent with the experimental results. Moreover, the adsorption was mainly chemical adsorption, and the S and W sites of AgY molecular sieve were the main adsorption sites. The results of adsorption isotherm showed that the adsorption of pyridine by AgY was consistent with Langmuir-Freundlich mixed adsorption model, and the adsorption of aniline and quinoline was consistent with Freundlich adsorption model. The results of adsorption kinetics and thermodynamics showed that the adsorption of pyridine by AgY molecular sieve conforms to the quasi-second-order kinetic model, and the adsorption of aniline and quinoline conforms to the quasi-first-order kinetic model, the adsorption was a spontaneous entropy increase process. -
表 1 NaY和AgY分子筛吸附脱除模拟燃料中吡啶的脱氮性能
Table 1 Denitrification performance of NaY and AgY molecular sieves for adsorption and removal of pyridine in simulated fuels
Project NaY AgY Adsorption capacity(mg·g−1) 51.26 62.60 removal rate(%) 57.69 70.46 表 2 AgY分子筛团簇吸附苯胺、吡啶、喹啉的吸附能
Table 2 Adsorption Energy of AgY Molecular Sieve Clusters for Aniline, Pyridine, and Quinoline
Project Adsorption complex
energy / eVAdsorbent energy / eV Adsorbed molecule
energy / eVAdsorption energy / eV AgY adsorbed Pyridine −172864.913 −166114.168 −6749.488 1.257 AgY adsorbed aniline −310406.903 −302585.559 −7818.546 2.798 AgY adsorbed quinoline −177043.348 −166113.821 −10927.236 2.291 表 3 苯胺、吡啶、喹啉与AgY分子筛活性中心的距离d(Ag-N)和前线轨道能量值
Table 3 Distance d (Ag-N) and Frontline Orbital Energy Values of Aniline, Pyridine, Quinoline and AgY Molecular Sieve Active Centers
Project HOMO /eV LUMO /eV △E /eV d(Ag-N)/ nm AgY adsorbed Pyridine −5.960 −2.575 3.385 3.410 AgY adsorbed aniline −4.569 −1.710 2.859 2.328 AgY adsorbed quinoline −7.198 −3.135 4.063 2.777 表 4 三种吸附模型拟合AgY分子筛吸附模吡啶、苯胺、喹啉的相关参数值
Table 4 Three adsorption models fitting the relevant parameter values of AgY molecular sieve adsorption models for pyridine, aniline, and quinoline
Temperature Langmuir Freundlich Langmuir-Freundlich qm KL × 105 R2 n KF R2 qm Ka × 105 n R2 Pyridine 303 K 142.9 10.788 0.926 0.508 0.639 0.934 291.6 1.769 0.658 0.986 323 K 185.6 8.302 0.925 0.572 0.607 0.935 600.4 0.576 0.652 0.980 343 K 171.2 8.955 0.915 0.559 0.253 0.926 592.3 0.497 0.634 0.982 Aniline 293 K 650.5 7.055 0.985 0.811 0.168 0.991 305 24 1.276 0.972 313 K 733.7 5.929 0.983 0.828 0.144 0.989 320 20 1.172 0.970 333 K 637.5 6.937 0.983 0.811 0.144 0.990 320 20 1.176 0.974 Quinoline 303 K 2770 1.302 0.986 0.923 0.065 0.987 265 26 1.441 0.947 323 K 1223 3.280 0.989 0.885 0.092 0.992 250 30 1.502 0.956 343 K 1092 3.790 0.989 0.877 0.099 0.992 269 28.3 1.445 0.965 表 5 热力学模型拟合的相关参数
Table 5 Relevant parameters for thermodynamic model fitting
Project ΔG(KJ/mol) ∆S(KJ/mol·K) ∆H(KJ/mol) Pyridine 303K −28.76 0.18 28.39 323K −33.40 343K −36.04 Aniline 303K −8.437 0.055 8.228 323K −9.537 343K −10.637 Quinoline 293K −3.273 0.020 2.587 313K −3.673 333K −4.073 (ΔG is Gibbs free energy, ΔH is enthalpy change, ΔS is entropy change) 表 6 准一级和准二级动力学模型拟合相关参数
Table 6 Parameters related to fitting of Quasi-first-order and Quasi-second-order kinetic models
Project Quasi-first-order kinetic equation Quasi-second-order kinetic equation Qe K1 R2 Qe K2 R2 Pyridine 30.162 0.197 0.986 32.252 0.013 0.993 Aniline 79.003 0.473 0.997 82.137 0.022 0.994 Quinoline 63.012 2.936 0.975 64.234 0.627 0.969 -
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