Preparation of Ag+ modified NaY molecular sieve and its 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、FT-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303、323、343 K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: 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. -
图 1 AgY分子筛12T团簇模型和优化后的氮化物3D模型结构
Figure 1 AgY molecular sieve 12T cluster model and optimized nitride 3D model structure
图 4 AgY和NaY分子筛的N2吸附-脱附等温曲线
Figure 4 N2 adsorption-desorption curves of AgY and NaY molecular sieves
图 5 吸附温度对AgY分子筛吸附脱除模拟燃料中吡啶、苯胺、喹啉的影响
Figure 5 Effect of adsorption temperature on the adsorption and removal of pyridine, aniline, and quinoline from model fuels by AgY molecular sieve
图 6 AgY分子筛12T团簇吸附吡啶、苯胺、喹啉的构型示意图
Figure 6 Configuration diagram of AgY molecular sieve 12T cluster adsorption for aniline, pyridine, and quinoline
(Numbers in the figure are the distances between the N atoms in the nitride and the Ag atoms in the AgY molecular sieve; units are nm)
图 7 吡啶、苯胺、喹啉分子的前线轨道示意图
Figure 7 Frontline orbitals of pyridine, aniline and quinoline molecules
图 8 不同温度下AgY分子筛吸附脱吡啶、苯胺、喹啉的等密度分布
Figure 8 Isodensity distribution diagram of adsorbed adsorption of pyridine, aniline and quinoline on AgY molecular sieve at different temperatures
图 9 吸附时间对AgY分子筛吸附脱除模拟燃料中吡啶、苯胺、喹啉的影响
Figure 9 Effect of adsorption time on the adsorption and removal of pyridine, aniline, and quinoline from model fuels by AgY molecular sieve
图 10 吡啶、苯胺、喹啉与AgY分子筛中Ag原子的径向分布函数
Figure 10 Radial distribution function between pyridine, aniline, quinoline and Ag atom in AgY molecular sieve
图 11 AgY分子筛吸附脱除模拟燃料中吡啶、苯胺、喹啉的吸附等温线拟合
Figure 11 Adsorption isotherms fitting of pyridine, aniline and quinoline in model fuels on AgY molecular sieve
图 12 AgY分子筛吸附脱除模拟燃料中吡啶、苯胺、喹啉的动力学拟合曲线
Figure 12 Kinetic fitting curve of adsorption and removal of pyridine, aniline, and quinoline from model fuels using AgY molecular sieve
表 1 NaY和AgY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 from model fuels
Project NaY AgY Adsorption capacity/（mg·g−1） 51.26 62.60 Removal rate/% 57.69 70.46 
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表 2 AgY分子筛团簇吸附吡啶、苯胺、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
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表 3 吡啶、苯胺、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
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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 Model parameter values of the adsorption for pyridine, aniline, and quinoline on the AgY molecular sieve with three adsorption models
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
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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−1) ∆S/(kJ·mol−1·K−1) ∆H/(kJ·mol−1) Pyridine 303 K −28.76 0.18 28.39 323 K −33.40 343 K −36.04 Aniline 303 K −8.437 0.055 8.228 323 K −9.537 343 K −10.637 Quinoline 293 K −3.273 0.020 2.587 313 K −3.673 333 K −4.073 Note: ΔG is Gibbs free energy; ΔH is enthalpy change; ΔS is entropy change.
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表 6 准一级和准二级动力学模型拟合相关参数
Table 6 Parameters fitted with 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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