高温煤气脱硫 Ⅰ.铁基脱硫剂的相态特征和活性

用穆斯堡尔谱考察了氧化铁脱硫剂在高温煤气中还原及硫化时的铁形态变化规律。在反应开始阶段，原脱硫剂中的α-Fe2O3即被迅速还原成Fe3O,Fe3O4可进一步还原转化成α-Fe。反应初期Fe3O4和α-Fe都参与脱硫反应，其中α-Fe具有较高的脱硫活性，对整个脱硫过程而言α-Fe是主要的脱硫活性相。铁化合物与硅铝氧化物载体间存在相互作用，形成磁微 晶颗粒及少量γ-Fe。在高温煤气条件下，FeS是唯一的铁硫化物，θ－Fe3C则是α－Fe转化中的主要产物。适量的θ－F e3C对脱硫有促进作用。     

LaAl1-xFexO3/Al2O3/FeCrAl催化剂的制备及其对甲烷燃烧的催化性能

 以FeCrAl合金薄片为载体,以LaAl1-xFexO3为活性组分,以Al2O3为过渡层,制备了LaAl1-xFexO3/Al2O3/FeCrAl金属基整体式催化剂,并用XRD和SEM等方法对催化剂的物相和形貌进行了表征,对催化剂上甲烷催化燃烧活性进行了评价. 结果表明,催化剂物相中有LaAl1-xFexO3型钙钛矿及 α-Al2O3 和 γ-Al2O3; 催化剂的颗粒小于2 μm, 并且颗粒的尺寸及形貌与LaAl1-xFexO3中的Fe/Al摩尔比有关; 催化剂样品对甲烷催化燃烧活性的大小顺序为LaAl0.3Fe0.7O3/Al2O3/FeCrAl＞LaFeO3/Al2O3/FeCrAl＞LaAl0.5Fe0.5O3/Al2O3/FeCrAl＞LaAl0.7Fe0.3O3/Al2O3/FeCrAl＞LaAlO3/Al2O3/FeCrAl.     

沉淀铁催化剂在F-T合成反应过程中的物相变化

 采用元素分析、X射线衍射和穆斯堡尔谱等手段研究了喷雾干燥沉淀Fe-Cu-K/SiO2催化剂在F-T合成反应过程中的物相变化. 结果表明,新鲜催化剂样品主要由α-Fe2O3组成,且81.1%的α-Fe2O3粒径小于13.5 nm. 随着反应时间的延长,催化剂表面碳沉积物的含量逐渐增多,不饱和度逐渐增大; χ-Fe5C2的含量逐渐增多,Fe3O4的含量逐渐减少并趋于稳定. 超顺磁Fe3+的含量呈先增加后减少的变化趋势. 由于碳沉积物是由CO生成的,而χ-Fe5C2是由α-Fe2O3经Fe3O4生成的,故催化剂表面碳沉积物的生成先于χ-Fe5C2的生成.     

Al掺杂α-Fe2O3材料的制备、表征和气敏特性

采用均相沉淀法制备了纯α-Fe2O3(300 ℃煅烧)和Al掺杂α-Fe2O3(300和400 ℃煅烧), 使用SEM, XRD, ICP和红外光谱等手段进行表征, 并利用气敏仪测试无水乙醇和90＃汽油在不同条件下对材料的响应性能. 结果表明, 微量Al掺杂不改变α-Fe2O3材料的物相, 但会阻碍晶粒生长, 使颗粒变小及Fe2O3晶格间隙中的铁原子数目增多, 材料的导电率增大, 从而显著提高材料的气敏性能. Al掺杂α-Fe2O3对乙醇的响应性能优于对汽油的响应性能, 在乙醇气氛中, 材料对湿度仍然不敏感. 经400 ℃煅烧的Al掺杂α-Fe2O3稳定性较好, 可作为检测乙醇气体的半导体气敏材料.     

γ′-Fe_4N纳米晶薄膜的磁性及热稳定性研究

采用直流磁控溅射方法,在Si(100)单晶衬底上获得了γ′-Fe4N纳米晶薄膜样品.将样品在真空中分别于300,400,500,600,700和800℃下进行热处理,利用XRD,SEM和VSM等测试手段对样品的结构、形貌和磁性进行表征.结果表明,热处理温度在300～500℃时,在γ′-Fe4N纳米晶粒的界面处形成了Fe8N包裹层,600℃时,Fe8N包裹层转变为α-Fe,当热处理温度≥700℃时,样品全部转变为α-Fe.γ′-Fe4N薄膜样品在600℃以下温度热处理可保持其主相γ′-Fe4N的结构稳定,而其软磁性能并未发生明显的减弱.     

不同晶化度γ-FeOOH的合成及其液相转化研究

进行了空气氧化Fe(OH)2悬浮液, EDTA作用下可见光诱导, 不同温度(14～20 ℃)制备不同晶化度γ-FeOOH的研究, 进行了其沸腾回流液相转化历程的探讨. 结果表明: 随温度的升高, γ-FeOOH的晶化程度变差; 而γ-FeOOH的晶化程度越差, 在液相沸腾回流时就越易转化成α-Fe2O3, 反之则易转化为α-FeOOH. 在pH近中性, 微量Fe(II)存在条件下低晶态的γ-FeOOH可以快速转化为均匀球形的α-Fe2O3.     

Fe2O3/YSZ-γ-Al2O3催化剂在甲烷催化燃烧中的催化性能研究

以Fe2O3为活性组分，γ-Al2O3，ZrO2-γ—Al2O3及YSZ—γ—Al2O3(YSZ是用Y2O3稳定ZrO2的催化剂载体)为载体，制备了3种甲烷燃烧催化剂．其中以YSZ—γ—Al2O3为载体的催化剂催化性能最好．XPS检测发现．ZrO2和Y2O3的存在可以增加和稳定Fe2O3的表面浓度，同时也可减弱Fe2O3与γ—Al2O3之间的相互作用．Fe2O3质量分数为10％的Fe2O3／YSZ—γ—Al2O3催化剂具有最佳的催化活性．XRD测试结果表明．该催化剂的活性与Fe2O3在载体上的分散状况有关．     

不同制备方法和反应条件对Fe_2O_3形貌和晶型转变的影响

研究了吸附相反应技术、浸渍法以及沉淀法制备Fe2O3的过程中,反应环境的变化对粒子形貌和晶型转变过程的影响。当吸附层是主要反应场所时,生成的粒子与SiO2表面以较强的化学键键合,焙烧过程中Fe2O3的晶型变化和粒子团聚被有效地抑制,焙烧后Fe2O3粒子维持稳定的γ-Fe2O3晶型和高分散的小粒子。而在乙醇体相中反应生成的粒子,仅通过物理作用与SiO2表面结合,不能有效抑制其向α-Fe2O3晶型的转变和粒子的团聚。吸附相反应制备过程中,当水量持续增加或者体系温度升高,反应环境逐渐从吸附层向乙醇体相中转变,SiO2对Fe2O3晶型转变的抑制作用减弱,从而导致样品中逐渐出现α-Fe2O3晶型。     

纳米Al2O3颗粒对纯Fe液诱导凝固过程的分子动力学模拟

采用分子动力学(MD)方法模拟了不同半径大小的纳米Al2O3颗粒夹杂在三个温度下(1750、1730和1710K)对纯Fe液的诱导凝固过程,并分析了作为诱导核心的纳米Al2O3颗粒的结构演变及其对Fe原子体系的凝固过程的影响.发现在诱导过程中,纳米Al2O3颗粒的内部保持较好的晶型结构,仅表面原子有结构变形;诱导凝固的Fe原子主要为面心立方(fcc)和密排六方(hcp)原子;纳米Al2O3颗粒的尺寸越大,发生诱导凝固的温度越高;诱导凝固得到的Fe晶体的晶格取向受纳米Al2O3颗粒在Fe液中的漂移程度影响.     

LaPO4∶Eu3+—Fe3O4光-磁复合材料的合成与性能研究

采用2步水热法合成了LaPO4∶Eu3+-Fe3O4复合材料.在LaPO4∶Eu3+-Fe3O4复合材料中,LaPO4∶Eu3+为单斜晶相,呈纳米棒状,纳米棒的直径和长度分别为20~100nm和0.2~1μm;Fe3O4为正交晶相、呈20~30nm的颗粒状,Fe3O4粒子紧紧附着在LaPO4∶Eu3+纳米棒的表面;样品的磁性和发光性质研究表明所合成的LaPO4∶Eu3+—Fe3O4复合材料既具有发光性质又具有磁性.     

Fe3O4的X射线微结构特征与催化活性间的关系

湿法工艺制备的不同晶型Fe2O3, 经水煤气还原后Fe3O4的X射线衍射微结构特征, 用分析微应变和晶粒尺寸的Voigt函数单峰分析法进行了测定。Fe3O4微应变大小同催化活性间存在一种对应关系。γ-Fe2O3还原的Fe3O4比α型还原的有更大的晶格畸变, 在325℃, 500空速条件下, CO转化率达97%以上, 比后者高出30%多。这种畸变结构在工业催化反应条件下能长期稳定, 但经600℃高温处理后, 畸变减小,活性下降。湿法工艺可以获得具有不同活性的Fe3O4前身, γ-Fe2O3与Fe3O4晶体结构上的类似, 使它在还原过程中, 能把这种高活性的结构状态保留下来。     

Reaction products and kinetics of the reaction of NO2 with γ-Fe2O3

The reaction of NO(2) with Fe(2)O(3) has relevance for both atmospheric chemistry and catalysis. Most studies have focused on hematite, α-Fe(2)O(3), as it is the thermodynamic stable state of iron oxide; however, other forms of Fe(2)O(3) naturally occur and may have different chemistries. In this study, we have investigated the reaction products and kinetics for NO(2) reacting with γ-Fe(2)O(3) powder using diffuse reflectance infrared Fourier transform spectroscopy and compared the results to those of previous studies of NO(2) reacting with α-Fe(2)O(3). Both α- and γ-Fe(2)O(3) produce surface-bound nitrate at the pressures examined in this study (24-212 mTorr); surface-bound nitrite products are observed at all pressures for γ-Fe(2)O(3) whereas nitrite was only observed on α-Fe(2)O(3) at lower pressures. Surface-bound NO(+) and Fe-NO products are observed on γ-Fe(2)O(3), which have not been observed with α-Fe(2)O(3). The reaction kinetics show a first-order dependence on NO(2) pressure and this is used to support the hypothesis of unimolecular reaction of adsorbed NO(2) with the γ-Fe(2)O(3) surface as the slow step in the reaction mechanism. The difference in product formation between NO(2) reacting with γ-Fe(2)O(3) and previous studies of α-Fe(2)O(3) illustrate the fact that care must be taken in generalizing reactivity of different polymorphs.     

基于溶液配位化学过程调控的中空单晶氧化铁纳米材料

本文简要综述了本课题组近年来在单晶氧化铁空心纳米结构制备与生长机理研究方面的相关工作.通过采用磷酸根与硫酸根的双阴离子调节,结合反应时间、反应温度等条件的改变,实现了对α-Fe2O3单晶空心纳米结构形貌、尺寸和表面结构的良好调控,并提出一种针对非层状结构纳米环/纳米管新颖生长机理,即"配位辅助的定向溶解机理".以所制备的α-Fe2O3为前驱体,采用气相还原方法,成功制备得到了系列单晶Fe3O4和γ-Fe2O3管状及环状纳米结构,并对单个Fe3O4纳米环的磁学行为进行了考察.     

γ-Fe(2)O(3) and Fe(3)O(4) magnetic hierarchically nanostructured hollow microspheres: Preparation, formation mechanism, magnetic property, and application in water treatment

In this paper, we report the preparation of γ-Fe(2)O(3) and Fe(3)O(4) magnetic hierarchically nanostructured hollow microspheres by a solvothermal combined with precursor thermal conversion method. These γ-Fe(2)O(3) and Fe(3)O(4) magnetic hierarchically nanostructured hollow microspheres were constructed by three-dimensional self-assembly of nanosheets, forming porous nanostructures. The effects of experimental parameters including molar ratio of reactants and reaction temperature on the precursors were studied. The time-dependent experiments indicated that the Ostwald ripening was responsible for the formation of the hierarchically nanostructured hollow microspheres of the precursors. γ-Fe(2)O(3) and Fe(3)O(4) magnetic hierarchically nanostructured hollow microspheres were obtained by the thermal transformation of the precursor hollow microspheres. Both γ-Fe(2)O(3) and Fe(3)O(4) hierarchically nanostructured hollow microspheres exhibited a superparamagnetic property at room temperature and had the saturation magnetization of 44.2 and 55.4emu/g, respectively, in the applied magnetic field of 20 KOe. Several kinds of organic pollutants including salicylic acid (SA), methylene blue (MB), and basic fuchsin (BF) were chosen as the model water pollutants to evaluate the removal abilities of γ-Fe(2)O(3) and Fe(3)O(4) magnetic hierarchically nanostructured hollow microspheres. It was found that γ-Fe(2)O(3) hierarchically nanostructured hollow microspheres showed a better adsorption ability over SA than MB and BF. However, Fe(3)O(4) hierarchically nanostructured hollow microspheres had the best performance for adsorbing MB.     

Hydration/expansion and cation charge compensation modulate the Brønsted basicity of distorted clay water

This letter addresses how iron redox cycling and the hydration properties of the exchangeable cation influence the Br?nsted basicity of adsorbed water in 2:1 phyllosilicates. The probe pentachloroethane undergoes facile dehydrochlorination to tetrachloroethene, attributed to increases in the Br?nsted basicity of near-surface hydrating water molecules following the reduction of structural Fe(III) to Fe(II). This dehydrochlorination process is studied in the presence of Na(+)- or K(+)-saturated Upton montmorillonite [(Na0.82 (Si7.84 Al0.16)(Al3.10 Fe(3+)0.3 Mg0.66) O20 (OH)4] or ferruginous smectite [(Na0.87 Si7.38 Al0.62)(Al1.08) Fe(3+)2.67 Fe(2+)0.01 Mg0.23) O20 (OH)4]. The effect of iron redox cycling on pentachloroethane dehydrochlorination is studied using reduced or reduced and reoxidized smectite samples saturated with Na+ (fully expanded clay) or K+ (fully collapsed clay). Variations in the clay Br?nsted basicity following Na+ -for- K+ exchange are explained by cationic charge compensation or interlayer hydration/expansion imposed by the nature of the exchangeable cation. Inverse relations between K+ fixation and clay water content as well as trends in pentachloroethane transformation indicate that increases in the Br?nsted basicity result from increases in the clay hydrophilicity and shifts in the local activity of distorted clay water. Potassium fixation causes partially collapsed smectites bearing low amounts of structural Fe(II) to have a similar reactivity to that of fully expanded smectites (Na+ form) bearing higher amounts of structural Fe(II). In particular, the conversion of up to 80% of the pentachloroethane to tetrachloroethane by K+ -saturated, reoxidized Upton was explained because the fixation of K+ causes nonreversible expansion and incomplete reoxidation of structural Fe(II), which contributes to the stabilization of charge density near sites bearing Fe(II). Higher pentachloroethane conversions by Upton montmorillonite over ferruginous smectite, however, suggest that charge dispersion rather than site specificity contributes predominantly to clay reactivity. Thus, clay interlayer hydration/expansion imposed by the nature of the exchangeable cation alters water dissociation and proton exchange in Fe(II)-Fe(III) phyllosilicates susceptible to iron redox cycling.     

γ-Fe2O3纳米粉的低热固相制备及其电磁损耗特性(英)

The Fe(OH)₃ precursor was prepared by solid -state reaction with Fe(NO₃)₃·9H₂O, NaOH and dispersed poly-ethylene glycol at low heating temperature(25 ℃). Synthesis of iron oxide (γ-Fe₂O₃) nanoparticle was achieved by thermal decomposition of Fe(OH)₃·xH₂O precursor. The nanoparticle was characterized by TG-DTA, X-ray diffra-ction, TEM etc. The results showed that the nanoparticle was composed of γ-Fe₂O₃ and was a better absorber for electromagnetic wave within the low frequency band.     

聚乙烯醇对碳纳米管负载氧化铁影响的研究

采用液相化学沉积法制备了碳纳米管负载的Fe2O3. TEM观察发现， 添加聚乙烯醇作为表面活性剂可以实现碳纳米管对Fe2O3的有效负载， 未添加聚乙烯醇两者出现物相分离. 聚乙烯醇均匀吸附在碳纳米管表面, 增强碳纳米管在水溶液中的分散, 其疏水基团与碳纳米管以范德华力结合, 其亲水基团与Fe2O3·nH2O结合, 对碳纳米管有效负载Fe2O3起到了桥梁作用. 在样品煅烧过程中, 聚乙烯醇熔融后均匀地包裹在碳纳米管表面上, 进一步阻止了两者在煅烧过程中的物相分离.     

Morphology- and phase-controlled iron oxide nanoparticles stabilized with maleic anhydride grafted polypropylene

About phase: Ferromagnetic γ-Fe(2) O(3) nanowires (left in the figure) with a saturation magnetization (M(s) ) of 54.0?emu?g(-1) and coercivity of 518?Oe at room temperature, and superparamagnetic hollow α-Fe(2) O(3) nanoparticles (right) with a room-temperature M(s) of 2.9?emu?g(-1) were synthesized by the thermal decomposition of [Fe(CO)(5) ] but with the stabilizing action of maleic anhydride grafted polypropylene.     

三维有序大孔α-Fe2O3的制备及电化学性能研究

通过聚苯乙烯(PS)胶晶模板法合成了三维有序大孔(3DOM) α-Fe2O3, 运用扫描电镜、热重分析、X射线衍射、电化学充放电等多种方法对其结构和性能进行了表征和研究. SEM表明PS 胶晶模板和3DOM α-Fe2O3呈周期性排列. 合成的3DOM α-Fe2O3为三维有序多孔网状结构, 具有球型和六边形的孔隙形貌, 其孔径大小约为(115±10) nm; 孔壁由α-Fe2O3纳米晶粒组成, 壁厚为20～30 nm. XRD图谱表明经过煅烧除去模板后, 形成了纯α-Fe2O3相. 当3DOM α-Fe2O3作为锂离子电池负极材料时, 首次放电充电容量分别高达1880和1130 mAh•g－1, 20次循环后可逆容量依然高达631 mAh•g－1, 库仑效率大于90%.