某些有机物在氧化物载体表面的自发单层分散

自发单层分散原理已在载负型催化剂制备、再生等方面得到越来越广泛的应用[1，2]．许多氧化物和盐类可以在载体表面形成单层分散或亚单层分散．有些分散物与载体混合后在低于其熔点的温度下处理，就可以自发分散到载体表面[1，3]．这一现象通过XRD、LRS、XPS、SIMS、ISS、EXAFS     

金属氧化物在γ-Al2O3上单层分散的表面对称模型

提出了一个分散在γ－Ａｌ２Ｏ３表面的金属氧化物单层结构的表面对称模型，该模型认为金属氧化物单层结构到下规则：（１）金属氧化物的氧负离子将尽量保持与所在表面层的氧负离子相同的排列方式；（２）金属离子将根据所在表面层金属离子排布的对称性取与之相适应的排布方式；（３）金属子和氧负离子都对分散层的结构有影响。     

氯化钙在粗孔硅胶上的单层分散研究

由于氨合成反应平衡的限制,使得冷冻分离氨的能量消耗较大[1].开发一种对氨比对H2、N2具有更高吸附能力和很强选择性的吸附剂,实现一次循环即获得纯氨产品,由此达到节能降耗的目的.     

氯化亚铜在活性炭载体表面单层分散的密度泛函理论计算

 应用量子化学计算方法研究了活性炭载体表面CuCl活性组分的单层分散行为. 以C16H10,C13H9和C12H12原子簇模型模拟活性炭表面,用密度泛函理论中的B3LYP方法计算得到了CuCl在活性炭表面分散的活性位、稳定构型、相互作用能以及单层分散阈值. 结果表明,CuCl以铜端垂直附着在活性炭表面的顶位和桥位上,相互作用能为76.84～80.79 kJ/mol,单层分散阈值为0.471 g/g. 而XRD测得的单层分散阈值为0.467 g/g,与量子化学计算的结果一致; 按照密置单层模型计算得出的单层分散阈值为0.941 g/g,远大于实验测定结果. 因此,应用量子化学计算方法可以得到活性炭表面活性组分单层分散的丰富信息,并能确定活性组分的单层分散阈值.     

蔗糖在MCM-48表面的自发单层分散

采用液相浸渍法研究了蔗糖在中孔MCM-48表面的自发单层分散. 用X射线衍射(XRD)相定量分析法, 测定了蔗糖在MCM-48上的最大分散容量, 并用差热分析、N2吸附技术对制备的样品进行表征. 结果表明, 在蔗糖与MCM-48的质量比小于1.1时, 蔗糖在MCM-48表面能自发分散成单层. 当蔗糖/MCM-48 质量比为0.8时, MCM-48的比表面积由初始的998 m2·g-1降至114 m2·g-1, 孔径由原来的2.7 nm降至2.0 nm, 孔容由0.76 cm3·g-1降至0.11 cm3·g-1. 当蔗糖与MCM-48的质量比超过1.1时, MCM-48的比表面积迅速减小至10 m2·g-1以下. 这是因为蔗糖分子大小和MCM-48孔径相差不大, 导致蔗糖在MCM-48表面分散时出现孔道堵塞.     

金属氧化物在γ－Al_2O_3上单层分散的表面对称模型

提出了一个分散在γ－Ａｌ２Ｏ３表面的金属氧化物单层结构的表面对称模型．该模型认为金属氧化物单层结构符合以下规则：（１）金属氧化物的氧负离子将尽量保持与所在表面层的氧负离子相同的排列方式；（２）金属离子将根据所在表面层金属离子排布的对称性取与之相适应的排布方式；（３）金属离子和氧负离子都对分散单层的结构有影响．根据这些规则，对一价、二价、三价和六价金属氧化物的分散单层的具体形态进行了讨论．该模型预测的单层分散阈值与实验值符合得很好．提出了单层分散状态为一种中间状态的观点     

单层分散CuOx对甲苯催化燃烧作用的研究

考察了一系列在不同温度下制备的Cu/Al2O3催化剂对苯催化燃烧的性能,并利用X-射线粉末衍射（XRD）、X-射线光电子能谱（XPS）、程序升温还原（TPR）对催化剂进行了表征．结果表明：低于单层分散的CuO具有可在低温还原的特性．在低于单层分散阈值的范围内,随着CuO负载量的增加催化剂活性加．超过单层分散阈值,催化剂...     

MgO-ZrO_2共沉淀体系的结构表征及单层分散现象

用共沉淀法制备了一系列MgO-ZrO2复合氧化物,用XRD、XPS、BET、DTA、EXAFS和TEM等进行了表征.结果表明,500℃与600℃下焙烧得到的MgO-ZrO2复合氧化物,在ZrO2高含量一端,MgO倾向于固溶到ZrO2中,最大固溶量可达到1:1(摩尔比);固溶达到饱和后,MgO开始在固溶体表面分散,并析出单独的MgO晶粒;在MgO高含量端,少量的ZrO2以分散态存在于MgO的表面,并使其表面性质发生较明显的变化.这些结果表明,在共沉淀法制备的MgO-ZrO2样品中,在一定相对含量范围内,会出现一种组分在另一种组分或由两种组分形成的固溶体上的单层分散现象.     

盐类和氧化物在载体上自发单层分散研究新进展

 盐类和氧化物在载体上自发单层分散的现象和原理自被发现以来在国内外得到了广泛认同，国内外这方面的工作越来越多．我们从国内外同行近年发表的上百篇有关论文中，选择一部分内容加上我们的部分工作做一个简单的综述，介绍有关自发单层分散原理在基础研究和应用两个方面的新进展．     

Dispersion and Structure Studies of Molybdenum Oxide on Anatase TiO2

X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS) were used to characterize the structure of the mixture of molybdenum oxide and anatase calcined at 723 K. The resuits indicate that molybdenum oxide can disperse onto the surface of anatase (TiO2) and the dispersion threshold is 11.2 mg in per gram of MoO3 or 4.8 Mo atoms/nm^2 TiO2. When the coment of MoO3 is below the dispersion threshold, MoO3 species is in highly dispersed state interacting strongly with TiO2 support and in discrete tetrahedral coordination. [MoO4], on the surface of TiO2. When the MoO3 loading is above this value, MoO3 exists in both dispersed phase and crystalline phase. MoO3 in dispersed phase is still a discrete [MoO4] tetrahedron; MoO3 in crystal phase is in octahedral coordination.     

A Solution-Phase Chemical Approach to a New Crystal Structure of Cobalt

Kinetic control of crystal growth in the presence of a coordinating ligand is critical for the formation of a new structure of elemental cobalt (ε-cobalt, the unit cell with the two different types of cobalt atoms is shown), which was discovered upon analyzing the metallic powder produced by the thermal decomposition of [Co₂(CO)₈] in solution in the presence of trioctylphosphane oxide [TOPO, Eq. (1)].     

氧化铁在TiO2上的分散状态及其物理化学表征

采用(NH_4)_3[Fe(C_2O_4)_3]·xH_2O稀水溶液含浸,Fe(NO_3)_3·9H_2O水溶液饱和浸渍以及Fe(AcAc))_3的甲苯溶液热吸附方法制备了在TiO_2(锐钛矿)上分散的氧化铁体系。用多种物理化学手段进行了表征,结果表明由含浸和热吸附法制备的样品中,负载组分FeO_x很容易充分分散或单层分散,这些单层物种很难被XRD,FTIR-DRS或LRS所检测,单层分散的Fe~(3+)处于高自旋态,具有较小的正交畸变配位对称性,但不是孤立四面体的配位结构,没有发现置换Fe~(3+)的存在。实验结果还表明,由XPS的电子结合能数据鉴别Fe~(3+)和TiO_2表面相互作用的强弱是困难的,充分分散的FeO_x表面物种在973K的还原温度下其Fe~(2+)尚不能被进一步还原,在TiO_2(锐钛矿)表面上单层分散的Fe—O多面体仍然是丁烯ODH反应的有效活性位。单层型催化剂的选择性不同于晶相a-Fe_2O_3,且与是否存在气相氧密切相关。     

Synthesis,Spectra, Thermal Analysis and Crystal Structure of Trans-Bis(2-Pyridinepropanol)Bis (Saccharinato)Cobalt(II)

The title complex, [Co(pypr)₂(sac)₂] (pypr = 2-pyridinepropanol and sac = saccharinate), has been prepared and characterized by elemental analysis, electronic and FTIR spectra, magnetic susceptibility measurements, thermal analysis and X-ray diffractometry. The complex crystallizes in triclinic space group PI with a = 8.1836(2), b = 10.0062(2), c = 10.4989(3) Å, α = 90.474(1), β = 107.989(1) and γ = 110.923(1)°. The cobalt(II) ion sits on a center of symmetry and is octahedrally coordinated by two pypr and two sac ligands. Both pypr and sac ligands occupy the trans positions of the coordination octahedron. The two pypr ligands are neutral and act as bidentate N- and O-donor ligands forming two symmetry-related seven-membered chelate rings around the cobalt(II) ion, while both sac ligands are O-coordinated through the carbonyl oxygen atoms. On heating the endothermic removal of two pypr ligands occurs in the first stages of decomposition and at higher temperatures the Co/sac intermediate decomposes to Co₃O₄ and finally to CoO.     

酞菁钴/纳米铁复合颗粒的结构与微波电磁特性

一些铁磁性金属及其合金超细粉末,具有比饱和磁化强度高、易于合成与粒径可控等优点,因此被广泛应用于磁流体、电磁流变液、微波吸收材料等领域,但由抗氧化性差、密度较大等主要缺点而使其应用受到限制,采用有机／无机复合技术可制备具有有机包覆层的有机／无机复合颗粒,不仅可以增强铁磁性颗粒的抗氧化性,减小了密度,而且可以提高与有机基体的亲和性,为该类材料向更高层次发展提供了可能。     

Phosphoraneiminato Complexes of Manganese and Cobalt with Heterocubane Structure

The phosphoraneiminato complexes [MnBr(NPEt₃)]₄ ( 1 ) and [M₄Br₅{NP(NMe₂)₃}₃] with M = Mn ( 2 ) and M = Co ( 3 ) are prepared by melting reactions from the anhydrous metal dibromides with the silylated phosphaneimines Me₃SiNPR₃ (R = Et, NMe₂) in the presence of potassium fluoride. All complexes are characterized by crystal structure analyses. 1 forms an only slightly distorted Mn₄N₄ heterocubane skeleton with an approximate T_d symmetry and short Mn…Mn distances of average 295.7 pm. In the structures of 2 and 3 one μ₃-NPEt₃ ligand of 1 is replaced by one bromine atom with μ₃-function. This leads to the novel heterocubane type M₄N₃Br with approximate C₃ symmetry. The deformation of the cubic skeleton leads to metal-metal distances of different lengths, i. e. 292.7 and 323.6 pm in 2 and 274.4 and 306.2 pm in 3 . Temperature dependent magnetic susceptibility measurements between 300 and 5 K on 1 have shown that strong antiferromagnetic coupling exists between the Mn(II) ions with S = 5/2, with a large negative Weiss constant of Θ = –694 K.     

Impact of Oxygen Vacancy on Band Structure Engineering of n-p Codoped Anatase TiO2

Doping with various impurities is an effective approach to improve the photoelectrochemical properties of TiO₂. Here, we explore the effect of oxygen vacancy on geometric and electronic properties of compensated (i.e. V-N and Cr-C) and non-compensated (i.e. V-C and Cr-N) codoped anatase TiO₂ by performing extensive density functional theory calculations. Theoretical results show that oxygen vacancy prefers to the neighboring site of metal dopant (i.e. V or Cr atom). After introduction of oxygen vacancy, the unoccupied impurity bands located within band gap of these codoped TiO₂ will be filled with electrons, and the position of conduction band offset does not change obviously, which result in the reduction of photoinduced carrier recombination and the good performance for hydrogen production via water splitting. Moreover, we find that oxygen vacancy is easily introduced in V-N codoped TiO₂ under O-poor condition. These theoretical insights are helpful for designing codoped TiO₂ with high photoelectrochemical performance.     

四核钴羰基簇合物的合成和晶体结构

用Co₂(CO)₈与有机杂环二硫代次膦酸盐SP(C₆H₄OR)(S)N(C₆H₅)NC(Me)(R=Me,Et)反应,得到两类4个含S,P桥基配体的四核钴羰基簇合物Co₄(CO)₁₀(μ₄-S)[μ₄-P(C₆H₄OR)](1:R=Me;3:R=Et)和Co₄(CO)₁₀(μ₃-S)[μ₂-P(C₆H₄OR)N(C₆H₅)NC(Me)](2:R=Me,4:R=Et).在反应中,前配体中的PS键以及C-S,P-S,P-N键劈开,产生的分子片与金属钴原子配位,组建成新的羰基钴簇.对这4个簇合物进行了元素分析,IR,¹HNMR和MS谱学表征,并测定了簇合物4的晶体结构,该晶体属单斜晶系,P2₁/c空间群,晶胞参数a=1.9065(4)nm,b=1.0081(2)nm,c=1.6663(3)nm,β=97.36(3)°,V=3.1704(11)nm₃,Z=4,D_c=1.743g/cm³.Co1Co3Co4呈三角形分布,其中Co-Co平均键长为0.251nm,而Co₂在该三角平面的一侧,Co2-Co3键为0.269nm.该簇合物分子骨架为三角钉型结构,每个Co原子的立体几何均为变形八面体,但配位环境各不相同.     

分散聚合技术及其研究进展

介绍了分散聚合体系中各组分及反应条件对反应过程和最终产物性能的影响,简要归纳了分散聚合成核机理、稳定机理及其反应动力学,并着重阐述了近年来分散聚合发展的新技术以及制备的功能微球在各领域的应用等方面的研究进展.分散聚合与其它非均相聚合方法相比,是制备粒径范围在1-10μm且单分散性较好的聚合物微球的有效方法.最近,许多新思路不断引入分散聚合体系,如采用水和超临界CO2作为分散介质,尝试微波和辐射引发聚合以及按照活性聚合机理进行反应等.     

Synthesis,Crystal Structure,and Electrochemistry of Iron and Cobalt Complexes Supported by a Pentadentate Amine‐bis(phenolate) Ligand

The pentadentate amine‐bis(phenolate) ligand 6,6′‐(dipyridin‐2‐ylmethylazanediyl)bis(methylene)bis(2,4‐dimethylphenol) (H₂L) was prepared and characterized. This ligand readily coordinates with Fe^III or Co^III ions, and the resulting complexes [Fe^IIILCl] ( 1 ) and [Co^IIIL(H₂O)]Cl ( 2 ) were characterized by elemental analysis. X‐ray structural studies show that the ligand in complexes 1 and 2 acts as a pentadentate ligand, leaving one coordination side of the transition metal available for exogenous ligands such as chloride ion ( 1 ) or water ( 2 ) ligand, and the central metal atoms are hexacoordinate in a similar distorted octahedral arrangement. Electrochemical studies reveal that each of the complexes exhibits multiple redox processes in the potential window investigated. Complex 1 shows one reversible oxidative event at 0.32 V and one quasi‐reversible reduction event at –1.03 V, while the complex 2 displays one reversible oxidative event at 0.18 V and one quasi‐reversible reduction at –0.64 V.