Immobilized Pd on a NHC functionalized metal–organic framework MIL-101(Cr): an efficient heterogeneous catalyst in Suzuki−Miyaura coupling reaction in water

A novel Pd−NHC functionalized metal–organic framework (MOF) based on MIL-101(Cr) was synthesized and used as an efficient heterogeneous catalyst in the C-C bond formation reactions. Using this heterogeneous Pd catalyst system, the Suzuki−Miyaura coupling reaction was accomplished well in water, and coupling products were obtained in good to excellent yields in short reaction time. The Pd−NHC−MIL-101(Cr) was characterized using some different techniques, including Fourier transform-infrared, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy, inductively coupled plasma and elemental analysis. The microscopic techniques showed the discrete octahedron structure of MIL-101(Cr), which is also stable after chemical modification process to prepare the catalyst system. The TEM images of the catalyst showed the existence of palladium nanoparticles immobilized in the structure of the catalyst, while no reducing agent was used. It seems that the NHC groups and imidazolium moieties in the structure of the MOF can reduce Pd (II) to Pd (0) species. This modified MOF substrate can also prevent aggregation of Pd nanoparticles, resulting in high stability of them in organic transformation. The Pd−NHC−MIL-101(Cr) catalyst system could be simply extracted from the reaction mixture, providing an efficient synthetic method for the synthesis of biaryls derivatives using the aforementioned coupling reaction. The Pd−NHC−MIL-101(Cr) catalyst could be recycled in this organic reaction with almost consistent catalytic efficiency.     

Pd/MIL-101的制备及非均相催化吲哚C-H活化

水热合成MIL-101,过量浸渍法吸附Pd(OAc)_2,原位还原Pd~(2+)制得Pd/MIL-101催化剂.采用XRD、XPS、SEM、ICP、HRTEM和N_2吸/脱附实验对其结构进行表征,催化剂Pd纳米粒子尺寸在1.5~2.5 nm之间,含量为1.5%.催化实验表明,Pd/MIL-101能高效催化吲哚C_2位芳基化,对于活性较差的溴代芳烃,也能得到中等以上的收率,催化剂循环5次后仍能保持较高的反应活性,发展了吲哚C_2位衍生物的简单、高效的合成方法.     

Selective palladium-loaded MIL-101 catalysts

Palladium nanoparticles (NPs) of different mean particle size have been synthesized in the host structure of the porous coordination polymer (or metal-organic framework: MOF) MIL-101. The metal-organic chemical vapor deposition method was used to load MIL-101 with the Pd precursor complex [(η(5)-C(5)H(5))Pd(η(3)-C(3)H(5))]. Loadings higher than 50 wt.% could be accomplished. Reduction of the Pd precursor complex with H(2) gave rise to Pd NPs inside the MIL-101 (Pd@MIL-101). The reduction conditions, especially the temperature, allows us to make size-conform (size of the Pd NPs correlates with the size of the cavities of the host structure of MIL-101) and undersized Pd NPs. The Pd@MIL-101 samples were characterized by X-ray diffraction, IR spectroscopy, Brauner-Emmett-Teller (BET) analysis, elemental analysis, and transmission electron microscopy (TEM). Catalytic studies, hydrogenation of ketones, were performed with selected Pd@MIL-101 catalysts. Activity, selectivity, and recyclability of the catalyst family are discussed.     

金属有机骨架材料MIL-53(Al)负载纳米Pd颗粒：一种CO氧化的活性催化剂

通过等体积浸渍法制备了金属有机骨架材料MIL-53(Al) (MIL：Materials of Institut Lavoisier)负载纳米Pd催化剂. 采用X射线衍射(XRD)、透射电子显微镜(TEM)和X射线光电子能谱(XPS)等手段对催化剂的结构进行了表征. 催化剂在反应前后XRD衍射峰保持不变,说明载体MIL-53(Al)具有良好的稳定性. 采用TEM对催化剂进行表征,结果表明,MIL-53(Al)的多孔晶体结构有助于形成高度分散的纳米Pd颗粒,样品2.7% (w) Pd/MIL-53 中Pd颗粒的平均粒径为2.21 nm. 该催化剂在CO氧化反应中表现出较高的催化活性,115 ℃达到完全转化. 同时催化剂可循环使用,多次反应后催化活性和催化剂结构都保持稳定.     

MIL-101(Cr)-NH2负载Pd低温催化糠醛高选择性加氢生成四氢糠醇

随着资源枯竭和环境污染严重问题的凸显,生物质转化的研究越来越多,特别是生物质催化裂解制备生物燃料及高附加值的化学品.糠醛是一种半纤维素酸解的产物,也是生产糠醇、四氢糠醇、2-甲基呋喃、环戊酮等的重要原料.其中四氢糠醇既可以用于生产其他高附加值化学品,也可以用作生物燃料或者燃料添加剂.虽然Pd/MFI,Ni/SiO2,Pd-Ir/SiO2等催化剂均可用于糠醛选择加氢制备四氢糠醇,但是反应通常在高温高压条件下进行.为此我们希望找到一种在温和条件下使用的高效催化剂.MOF多孔材料具有丰富的孔道结构、极高的比表面积、表面可修饰的特点,还可与其他客体发生相互作用,进而影响催化性能.因此本课题组合成了一种含有氨基的MOF材料MIL-101(Cr)-NH2,进一步利用表面氨基吸附Pd的氯酸盐前体,经还原直接制得负载型催化剂Pd@MIL-101(Cr)-NH2,并用于糠醛选择加氢反应.本文采用X射线粉末衍射(PXRD)、热重分析(TG)、N2物理吸附-脱附、透射电镜(TEM)等手段表征了所制的MOFs和催化剂.通过将MIL-101(Cr)-NH2和不同Pd@MIL-101(Cr)-NH2的XRD谱与标准谱图对比,发现MIL-101(Cr)-NH2已成功合成,并在催化剂制备过程中和反应之后仍然保持稳定.TG结果表明,所制备MIL-101(Cr)-NH2在低于350 ℃C时结构不会被破环.MIL-101(Cr)-NH2的比表面积可达到1669 m2g?1,孔容达1.35 cm3g?1,从而为Pd纳米粒子均匀分散在载体上提供了可能性.各Pd@MIL-101(Cr)-NH2样品的TEM照片我们看出,Pd纳米粒子可均匀分散在MIL-101(Cr)-NH2上,粒径为3?4 nm.对比实验表明,氨基与金属的相互作用有利于Pd纳米粒子分散均匀.将Pd@MIL-101(Cr)-NH2用于糠醛选择加氢反应时,在40 ℃C,2 MPa H2的温和条件下,反应6 h后糠醛完全转化为四氢糠醇其选择性接近100%.表现出比文献报导的更加优异的催化性能.这得益于高度均匀分散的Pd纳米粒子,以及催化剂载体与Pd纳米粒子的配位作用和π-π相互作用.结果还表明当高于80℃C反应时,即有副产物生成,进一步提高反应温度会促进环戊酮的生成.可见,Pd@MIL-101(Cr)-NH2所表现的低温高加氢活性对提高四氢糠醇选择性至关重要.     

A new Brønsted acid MIL-101(Cr) catalyst by tandem post-functionalization; synthesis and its catalytic application

A new heterogeneous Brønsted solid acid catalyst was prepared by tandem post-functionalization of MIL-101(Cr) and utilized for acetic acid esterification and alcoholysis of epoxides under solvent-free conditions. First, MIL-101(Cr) was functionalized with pyrazine to achieve MIL-101(Cr)-Pyz. Afterwards, the nucleophilic reaction of MIL-101(Cr)-Pyz with 1,3-propane sultone and next acidification with diluted sulfuric acid gave MIL-101(Cr)-Pyz-RSO₃H Brønsted solid acid catalyst. Various characterization methods such as Fourier transformation infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), elemental analysis (CHNS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersiveX-ray(EDX) spectroscopy, thermal analysis (TGA/DTA), acid–base titration, and N₂ adsorption/desorption analysis were employed to fully characterize the prepared catalyst. The catalyst showed high activity compared to unmodified MIL-101(Cr) in both catalytic acetic acid esterification and alcoholysis of epoxides. It can also be readily isolated from the reaction mixture and reused three times without major decrease in its activity.     

Metal organic framework–organic polymer monolith stationary phases for capillary electrochromatography and nano-liquid chromatography

In this study, metal organic framework (MOF)–organic polymer monoliths prepared via a 5-min microwave-assisted polymerization of ethylene dimethacrylate (EDMA), butyl methacrylate (BMA), and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) with the addition of various weight percentages (30–60%) of porous MOF (MIL-101(Cr)) were developed as stationary phases for capillary electrochromatography (CEC) and nano-liquid chromatography (nano-LC). Powder X-ray diffraction (PXRD) patterns and nitrogen adsorption/desorption isotherms of these MOF–organic polymer monoliths showed the presence of the inherent characteristic peaks and the nano-sized pores of MIL-101(Cr), which confirmed an unaltered crystalline MIL-101(Cr) skeleton after synthesis; while energy dispersive spectrometer (EDS) and micro-FT-IR spectra suggested homogenous distribution of MIL-101(Cr) in the MIL-101(Cr)–poly(BMA–EDMA) monoliths. This hybrid MOF–polymer column demonstrated high permeability, with almost 800-fold increase compared to MOF packed column, and efficient separation of various analytes (xylene, chlorotoluene, cymene, aromatic acids, polycyclic aromatic hydrocarbons and trypsin digested BSA peptides) either in CEC or nano-LC. This work demonstrated high potentials for MOF–organic polymer monolith as stationary phase in miniaturized chromatography for the first time.     

Influence of Pore Structure and Metal-Node Geometry on the Polymerization of Ethylene over Cr-Based Metal–Organic Frameworks

Metal–organic frameworks (MOFs) have received increasing interest as solid single-site catalysts, owing to their tunable pore architecture and metal node geometry. The ability to exploit these modulators makes them prominent candidates for producing polyethylene (PE) materials with narrow dispersity index (Ð) values. Here a study is presented in which the ethylene polymerization properties, with Et₂AlCl as activator, of three renowned Cr-based MOFs, MIL-101(Cr)-NDC (NDC=2,6-dicarboxynapthalene), MIL-53(Cr) and HKUST-1(Cr), are systematically investigated. Ethylene polymerization reactions revealed varying catalytic activities, with MIL-101(Cr)-NDC and MIL-53(Cr) being significantly more active than HKUST-1(Cr). Analysis of the PE products revealed large Ð values, demonstrating that polymerization occurs over a multitude of active Cr centers rather than a singular type of Cr site. Spectroscopic experiments, in the form of powder X-ray diffraction (pXRD), UV/Vis-NIR diffuse reflectance spectroscopy (DRS) and CO probe molecule Fourier transform infrared (FTIR) spectroscopy corroborated these findings, indicating that indeed for each MOF unique active sites are generated, however without alteration of the original oxidation state. Furthermore, the pXRD experiments indicated that one major prerequisite for catalytic activity was the degree of MOF activation by the Et₂AlCl co-catalyst, with the more active materials portraying a larger degree of activation.     

Matrices based on meso antibacterial framework

In this paper, the synthesis of three types of porous materials (PMs) (porous Fe₃O₄, MIL-101 metal-organic framework (MOF), and MCM-41 mesoporous silica) by hydrothermal method was performed. The incorporation of Ag nanoparticles (Ag NPs) was carried out after the synthesis reaction of supports in MCM-41 and MIL-101 MOF. Ag core@ porous Fe₃O₄ core–shell system was prepared via a one-pot hydrothermal method. Ag-MIL-101 was obtained using Urtica dioica leaf extract as the green solvent and reducing agent. The antibacterial activity of Ag-PM nanocomposites (NCs) was investigated on both Gram-negative and Gram-positive bacteria. The size of the silver NPs was determined to be 12 and 30 nm in MCM-41 and MIL-101 MOF, respectively. The diameter of Ag core in Ag@Fe₃O₄ shell was ~135 nm. The antibacterial activity of Ag-PMs was in the order Ag-MCM-41 > Ag-MIL-101 > Ag core@Fe₃O₄ shell. The loading percent of Ag NPs in MCM-41 (84%) was more than that in MIL-101 (53%) and Fe₃O₄ (31%). The release of Ag⁺ ions from Ag-MCM-41, Ag-MIL-101, and Ag@Fe₃O₄ NCs was 46, 2, and 1 ppm, respectively. The release of the Ag⁺ ions and, consequently, the antibacterial activity of NCs depend on the uniform distribution, particles size, and the absence of aggregation of Ag NPs in PMs.     

苯部分加氢制环己烯新型Ru-B/MOF催化剂

制备了多种金属-有机骨架(MOF)材料,采用浸渍-化学还原法制备了非晶态Ru-B/MOF催化剂,考察了它们在苯部分加氢反应中的催化性能.催化性能评价结果表明,这些催化剂的初始反应速率(r0)顺序为Ru-B/MIL-53(Al)Ru-B/MIL-53(Al)-NH2Ru-B/UIO-66(Zr)Ru-B/UIO-66(Zr)-NH2Ru-B/MIL-53(Cr)Ru-B/MIL-101(Cr)Ru-B/MIL-100(Fe),环己烯初始选择性(S0)顺序为Ru-B/MIL-53(Al)≈Ru-B/MIL-53(Cr)Ru-B/UIO-66(Zr)-NH2Ru-B/MIL-101(Cr)Ru-B/MIL-53(Al)-NH2Ru-B/UIO-66(Zr)≈Ru-B/MIL-100(Fe).催化性能最好的Ru-B/MIL-53(Al)催化剂上的r0和S0分别为23 mmol·min-1·g-1和72%.采用多种手段,对催化性能差异最为显著的Ru-B/MIL-53(Al)和Ru-B/MIL-100(Fe)催化剂的物理化学性质进行了表征.发现MIL-53(Al)载体能够更好地分散Ru-B纳米粒子,粒子的平均尺寸为3.2 nm,而MIL-100(Fe)载体上Ru-B纳米粒子团聚严重,粒径达46.6 nm.更小的粒径不仅能够提供更多的活性位,而且也有利于环己烯选择性的提高.对Ru-B/MIL-53(Al)催化剂的反应条件进行了优化,在180°C和5 MPa的H2压力下,环己烯得率可达24%,展示了MOF材料用作苯部分加氢催化剂载体的良好前景.     

Pt/MIL-101(Cr)在肉桂醛选择性加氢反应中的催化性能

采用简单易行的浸渍法将Pt纳米粒子负载到MIL-101(Cr)上, 制备了Pt/MIL-101(Cr)催化剂, 并对其在肉桂醛选择性加氢反应的催化性能进行了研究。XRD、N₂吸附、TEM和催化性能的研究结果表明, Pt的负载量对负载于MIL-101(Cr)上Pt纳米粒子的尺寸及所制备催化剂对肉桂醇的选择性有很大影响。低Pt负载量(1.0wt%)的Pt/MIL-101(Cr)较其他MOFs和无机材料在肉桂醛选择性加氢反应中表现出了高的催化性能, 在优化的反应条件下肉桂醛转化率和对肉桂醇的选择性可分别达96.5%和86.2%。Pt/MIL-101(Cr)催化剂具有良好的稳定性。Pt/MIL-101(Cr)所表现出的优良的催化性能同MIL-101(Cr)载体的孔道结构及其表面性质密切相关。     

Pt/MIL-101(Cr)在肉桂醛选择性加氢反应中的催化性能

采用简单易行的浸渍法将Pt纳米粒子负载到MIL-101(Cr)上,制备了Pt/MIL-101(Cr)催化剂,并对其在肉桂醛选择性加氢反应的催化性能进行了研究。XRD、N₂吸附、TEM和催化性能的研究结果表明,Pt的负载量对负载于MIL-101(Cr)上Pt纳米粒子的尺寸及所制备催化剂对肉桂醇的选择性有很大影响。低Pt负载量(1.0%)的Pt/MIL-101(Cr)较其他MOFs和无机材料在肉桂醛选择性加氢反应中表现出了高的催化性能,在优化的反应条件下肉桂醛转化率和对肉桂醇的选择性可分别达96.5%和86.2%。Pt/MIL-101(Cr)催化剂具有良好的稳定性。Pt/MIL-101(Cr)所表现出的优良的催化性能同MIL-101(Cr)载体的孔道结构及其表面性质密切相关。     

Influence of the Base on Pd@MIL‐101‐NH2(Cr) as Catalyst for the Suzuki–Miyaura Cross‐Coupling Reaction

The chemical stability of metal–organic frameworks (MOFs) is a major factor preventing their use in industrial processes. Herein, it is shown that judicious choice of the base for the Suzuki–Miyaura cross‐coupling reaction can avoid decomposition of the MOF catalyst Pd@MIL‐101‐NH₂(Cr). Four bases were compared for the reaction: K₂CO₃, KF, Cs₂CO₃ and CsF. The carbonates were the most active and achieved excellent yields in shorter reaction times than the fluorides. However, powder XRD and N₂ sorption measurements showed that the MOF catalyst was degraded when carbonates were used but remained crystalline and porous with the fluorides. XANES measurements revealed that the trimeric chromium cluster of Pd@MIL‐101‐NH₂(Cr) is still present in the degraded MOF. In addition, the different countercations of the base significantly affected the catalytic activity of the material. TEM revealed that after several catalytic runs many of the Pd nanoparticles (NPs) had migrated to the external surface of the MOF particles and formed larger aggregates. The Pd NPs were larger after catalysis with caesium bases compared to potassium bases.     

CO2在氨基改性MIL-101(Cr)中吸附的分子模拟

采用实验与分子模拟结合的方法研究298 K下CO₂在氨基改性得到的MIL-101（Cr）-NH₂和MIL-101（Cr）-ED（ED：乙二胺）上的吸附性能。比较MIL-101（Cr）、MIL-101（Cr）-NH₂和MIL-101（Cr）-ED的吸附等温线与吸附热的结果,表明采用直接合成改性法得到的MIL-101（Cr）-NH₂比采用合成后再改性得到的MIL-101（Cr）-ED有更高的CO₂吸附容量。进一步比较密度分布图和径向密度分布曲线,分析CO₂在氨基改性MIL-101（Cr）中的吸附位,表明在低压下CO₂首先吸附在MIL-101（Cr）微孔的超级四面体中,随着吸附压力的增大逐渐填充到更大的孔中。氨基的存在增加了CO₂的吸附位点,使MIL-101（Cr）-NH₂具有较高CO₂吸附容量;同时MIL-101（Cr）-ED中的ED分子的存在增加了CO₂的吸附位点,使MIL-101（Cr）-ED也具有较高CO₂吸附容量;但是MIL-101（Cr）-ED中的ED分子占据了MIL-101（Cr）中Cr的吸附位点,使Cr对CO₂的吸附强度减弱,同时可吸附位点少于MIL-101（Cr）-NH₂,导致其对CO₂的吸附容量少于MIL-101（Cr）-NH₂。     

CO2在氨基改性MIL-101(Cr)中吸附的分子模拟

采用实验与分子模拟结合的方法研究298 K下CO_2在氨基改性得到的MIL-101(Cr)-NH_2和MIL-101(Cr)-ED(ED:乙二胺)上的吸附性能。比较MIL-101(Cr)、MIL-101(Cr)-NH_2和MIL-101(Cr)-ED的吸附等温线与吸附热的结果,表明采用直接合成改性法得到的MIL-101(Cr)-NH_2比采用合成后再改性得到的MIL-101(Cr)-ED有更高的CO_2吸附容量。进一步比较密度分布图和径向密度分布曲线,分析CO_2在氨基改性MIL-101(Cr)中的吸附位,表明在低压下CO_2首先吸附在MIL-101(Cr)微孔的超级四面体中,随着吸附压力的增大逐渐填充到更大的孔中。氨基的存在增加了CO_2的吸附位点,使MIL-101(Cr)-NH_2具有较高CO_2吸附容量;同时MIL-101(Cr)-ED中的ED分子的存在增加了CO_2的吸附位点,使MIL-101(Cr)-ED也具有较高CO_2吸附容量;但是MIL-101(Cr)-ED中的ED分子占据了MIL-101(Cr)中Cr的吸附位点,使Cr对CO_2的吸附强度减弱,同时可吸附位点少于MIL-101(Cr)-NH_2,导致其对CO_2的吸附容量少于MIL-101(Cr)-NH_2。     

Molecular Encapsulation of Trimeric Chromium Carboxylate Clusters in Metal–Organic Frameworks and Propylene Sorption

Oxo-bridged trimeric chromium acetate clusters [Cr₃O(OOCCH₃)₆(H₂O)₃]NO₃ have been encapsulated for the first time in the mesoporous cages of the chromium terephthalate MIL-101(Cr). The isolated clusters in MIL-101(Cr) have increased affinity towards propylene compared to propane, due to generation of a new kind of pocket-based propylene-binding site, as supported by DFT calculations.     

Novel Synthesis of Cu-Schiff Base Complex@Metal-Organic Framework MIL-101 via a Mild Method: A Comparative Study for Rapid Catalytic Effects

The use of metal complex immobilized/decorated porous materials as catalysts has found various applications. As such, finding a new and mild method for synthesis of metal complex immobilized over porous material is of great interest. Immobilized porous materials for styrene oxidation were reported in this work. Immobilized porous material of Cu-Schiff base complex @MIL-101 were described, in which immobilized Cu-Schiff base complex within super cage of a metal-organic framework (MOF)-based porous material, chromium (III) terephthalate MIL-101. They were systematically characterized by using elemental analysis, powder X-ray diffraction, fourier transform infrared spectroscopy, N₂ absorption-desorption, and so on, also used as catalyst for the selective oxidation of styrene to benzaldehyde. Comparatively, the immobilized heterogeneous catalyst of Cu-Schiff base complex@MIL-101 acted as an efficient heterostructure catalyst in the oxidation of styrene to benzaldehyde up to six cycles, and showed superior activity for styrene oxidation over MIL-101.     

五乙烯六胺改性金属有机骨架材料MIL-101(Cr)对CO_2的吸附性能

采用溶剂热法合成金属有机骨架材料MIL-101(Cr),用回流法将五乙烯六胺(PEHA)负载到MIL-101(Cr)孔道中的不饱和金属位点上,使用扫描电镜、粉末X射线衍射、氮气物理吸附、元素分析和傅里叶变换红外光谱等表征手段考察材料的结构和形貌,测试氨基改性前后的MIL-101(Cr)在25℃、不同压力下对CO_2的吸附效果。结果表明,负载0.24 m L五乙烯六胺后的MIL-101(Cr)对CO_2的吸附效果最好,在25℃、常压下对CO_2的饱和吸附量可达58.944 mg/g,相比未负载五乙烯六胺的MIL-101(Cr)吸附量(CO_2饱和吸附量为44.208 mg/g)增加了33%。随着吸附压力的增加,MIL-101(Cr)和0.24PEHAM IL-101(Cr)对CO_2的饱和吸附量逐渐增加,当吸附压力为1.1 MPa时,两者的吸附量分别为1 147.59和1 256.74 mg/g,表明该类材料在高压下对CO_2有着良好的吸附效果。     

磺酸功能化金属-有机骨架吸附脱氮性能

以硝基甲烷为溶剂,采用三氟甲磺酸酐(Tf2O)和浓硫酸对金属有机骨架材料MIL-101(Cr){Cr3F(H2O)2O[(O2C)-C6H4-(CO2)]3nH2O(n~25)}进行磺酸功能化修饰,使其孔壁配体上形成磺酸基团.通过改变MIL-101(Cr)、Tf2O和浓硫酸的摩尔配比,得到含有不同磺酸基团数量的S-MIL-101(Cr),对磺化后的材料进行了X射线衍射(XRD)、傅里叶变换红外(FTIR)、氮气物理吸附、酸碱电位滴定以及热重分析(TGA)表征.结果表明,磺酸功能化后MIL-101(Cr)的孔道结构仍然保持,比表面积和孔径有所下降,表面磺酸基团的数量根据磺化程度的不同从0.21到0.42 mmol g-1不等.将磺酸功能化后的MIL-101(Cr)用于液体燃料的吸附脱氮,发现磺酸功能化能够增强MIL-101(Cr)与含氮化合物的相互作用,有利于其对碱性氮化物的吸附脱除.相对于未经磺化的样品,按照摩尔配比n(MIL-101(Cr)):n(H2SO4):n(Tf2O)=1:3:4.5反应得到的磺酸功能化MIL-101(Cr)对喹啉和吲哚的吸附量提高较大,其对喹啉和吲哚的Langmuir最大吸附量分别提高了12.2%和6.3%.通过乙醇洗涤,吸附剂可再生,经过三次再生之后的吸附剂对模拟燃料中含氮化合物的吸附量没有明显的降低.