Co@N-石墨烯/C催化甲苯衍生物氧化胺化研究

核壳结构纳米催化剂的发展一直备受化学家的关注.我们通过热解碳担载乙酸钴和1,10-菲哕啉复合物制备出具有核壳结构的氮掺杂石墨烯包裹钴催化剂,并对其进行了系统的表征和催化性能研究.研究发现,该催化剂在TBHP和H2共存的条件下,在催化硝基苯和甲苯的选择性还原-氧化胺化合成N-烷基化胺反应中展现出较好的催化性能和良好的官能团耐受性.透射电镜表征表明氧化钴纳米颗粒被厚度约1.12～1.87 nm的含氮石墨烯壳包裹.X射线光电子能谱表征发现壳层中的石墨烯氮和作为核的氧化钴纳米颗粒间具有较明显的相互作用.我们对催化体系的普适性以及反应机理也进行了较为系统的研究.     

Co@N-石墨烯/C催化甲苯衍生物氧化胺化研究（英文）

核壳结构纳米催化剂的发展一直备受化学家的关注.我们通过热解碳担载乙酸钴和1,10-菲啰啉复合物制备出具有核壳结构的氮掺杂石墨烯包裹钴催化剂,并对其进行了系统的表征和催化性能研究.研究发现,该催化剂在TBHP和H_2共存的条件下,在催化硝基苯和甲苯的选择性还原-氧化胺化合成N-烷基化胺反应中展现出较好的催化性能和良好的官能团耐受性.透射电镜表征表明氧化钴纳米颗粒被厚度约1.12~1.87 nm的含氮石墨烯壳包裹.X射线光电子能谱表征发现壳层中的石墨烯氮和作为核的氧化钴纳米颗粒间具有较明显的相互作用.我们对催化体系的普适性以及反应机理也进行了较为系统的研究.     

超临界二氧化碳中羰基钴催化的端基炔烃环三聚反应研究

原子经济性良好的炔烃[2+2+2]环加成反应与绿色溶剂超临界二氧化碳相结合,是一个符合绿色化学原则的环境友好反应过程.建立了一个纯超临界二氧化碳介质中八羰基二钴催化的端基炔烃环三聚反应体系,在优化的反应条件下,以较高产率选择性地制备1,2,4-三取代苯衍生物.优化了催化剂用量、二氧化碳压力、反应温度及时间等反应条件,讨论了反应物料及催化剂在超临界二氧化碳介质中的溶解性和相行为,提出了端基炔烃环三聚反应机理,并将反应底物从C≡C键拓展至C≡N键,对超临界二氧化碳介质中炔-腈环加成反应进行了初步探索.优化出的炔烃环三聚催化反应体系无需使用有机助溶剂和各类助剂,底物适应性好,产物选择性高,为合成1,2,4-三取代苯衍生物提供了一种绿色合成方法.     

聚乙二醇双丙烯酸酯在超临界二氧化碳中的光聚合研究

探索了聚乙二醇双丙烯酸酯在超临界二氧化碳中发生光聚合反应制备聚合物颗粒的过程.方法为向充满超临界二氧化碳的高压反应釜中,同时喷射二氧化碳与聚乙二醇双丙烯酸酯及光引发剂的溶液,溶液与二氧化碳形成均匀的喷雾并进一步通过反溶剂作用与超临界二氧化碳形成分散体系,当同步进行紫外光照射时,单体可以在超临界二氧化碳中发生光聚合.结果证明此方法是可行的,得到了聚合物微颗粒.研究了不同溶剂及反应原料用量对产物粒径分布的影响.采用不同溶剂,将改变反应原料及产物在超临界二氧化碳中的溶解度,进而改变产物的粒径分布;反应原料用量增加,其在超临界二氧化碳中的溶解度减小,导致产物粒径分布较宽。     

氢化物发生-原子荧光光谱法测定氧化钴中痕量铅

样品经HCl消解,加入硫氰酸钾 草酸 邻菲啰啉混合液抑制大量钴的干扰,在K3Fe(CN)6氧化体系下,实现了无需分离大量钴直接进行氧化钴中痕量铅的氢化物-原子荧光光谱法测定.回收率为91%～107%,检出限为0.56μg/L,线性范围0～80μg/L.用该方法分析氧化钴样品中的Pb,方法简便,结果准确,应用前景良好.     

离子交换法合成钴酸锌纳米空心材料及磁性

采用所合成的四氧化三钴纳米立方颗粒作为前驱体,在相对低温的水热条件下,通过反应体系中自身存在的扩散作用和离子交换作用,可控制备了钴酸锌纳米空心材料。利用SEM、TEM、EDS和XRD等测试方法对样品进行了形貌、结构、组成和物相的表征。结果表明,所得钴酸锌纳米盒粒径均匀,分散度好;钴酸锌纳米盒颗粒大小约为20nm,整个纳米盒为单晶。研究了钴酸锌纳米盒的生长机理。对所制备的材料进行了磁学性质测试,结果显示,尖晶石型结构钴酸盐纳米材料的磁性大小可以通过改变实验条件而加以调变。     

超临界二氧化碳在高分子合成及加工领域的应用

重点概述了近年来超临界二氧化碳作为环境友好介质在高分子合成与加工方面研究的新进展,具体介绍了在超临界二氧化碳中丙烯酸的合成及疏水改性方面所做的工作,并在此基础上,展望超临界二氧化碳作为高分子合成介质的前景。     

在二乙烯三胺体系中含钴磷酸铝分子筛新相的合成

在二乙烯三胺体系中, 以磷酸、氢氧化铝、正硅酸乙脂、乙酸钴为原料, 在水热条件下合成出含钴磷酸铝分子筛新相, 我们把它们分别命名为CoAPSO-101和CoAPO-101型分子筛。X射线粉未衍射分析表明, 这两种分子筛具有六方对称结构, 酸洗脱及分析实验数据表明, 在该分子筛中金属钴有两种形式存在, 一种是骨架钴, 一种有非骨架钴, 同时吸附数据表明, 这两种分子筛均属于小孔结构。     

Co-MCM-41的表征及其催化苯乙烯环氧化性能

 分别采用模板剂离子交换法(TIE法)、水热合成法(DHT法)及浸渍法合成了Co-MCM-41,此催化剂能够在无共还原剂存在条件下催化以氧气为氧化剂的烯烃环氧化反应. 另外考察了催化剂的结构特别是钴的存在状态与催化性能之间的关系,以期能够弄清催化环氧化反应中催化剂活性位的本质. X射线衍射及N2吸附-脱附等结果证实,当导入分子筛中的钴的量在2.2%以下时,所有的Co-MCM-41均具有规整排列的六方孔道结构. 漫反射光谱和H2程序升温还原等结果表明,通过TIE法合成的样品中钴主要以孤立态钴离子(single-site Co(Ⅱ))形式存在,而以DHT法合成的样品中钴主要以微晶态Co2SiO4形式存在,浸渍法合成的样品中则存在大量颗粒状氧化钴. 催化反应结果表明,当钴含量均接近1.0%时,采用 TIE法合成的样品的苯乙烯转化率为45%,而用DHT法和浸渍法合成的样品的苯乙烯转化率均低于30%. 考虑到氧化钴和Co2SiO4的低活性以及DHT法和浸渍法合成样品中可能存在一小部分孤立态钴离子,我们推测MCM-41中的孤立态钴离子是催化活化分子氧发生环氧化反应的高效活性位.     

超临界二氧化碳介质中的有机反应*

本文主要介绍了超临界近5年来超临界二氧化碳中的有机反应研究的最新进展,包括加氢反应、氧化反应、羰基化反应、碳碳键形成反应、酯化反应和酶催化反应的研究现状;同时,还介绍了超临界二氧化碳作为反应底物用于合成碳酸酯和氨基甲酸酯的研究进展;并对未来的发展进行了展望。     

Synthesis and Characterization of Cobalt-Carbon Core-Shell Microspheres in Supercritical Carbon Dioxide System

The synthesis of cobalt-carbon core-shell microspheres in supercritical carbon dioxide system was investigated. Cobalt-carbon core-shell microspheres with diameter of about 1 μm were prepared at 350 oC for 12 h in a closed vessel containing an appropriate amount of bis(cyclopentadienyl)cobalt powder and dry ice. Characterization by a variety of techniques, including X-ray powder diffraction, X-ray photoelectron spectroscopy, Transmission electron microscope, Fourier transform infrared spectrum and Raman spectroscopy analysis reveals that each cobalt-carbon core-shell microsphere is made up of an amorphous cobalt core with diameter less than 1 μm and an amorphous carbon shell with thickness of about 200 nm. The possible growth mechanism of cobalt-carbon core-shell microspheres is discussed, based on the pyrolysis of bis(cyclopentadienyl)cobalt in supercritical carbon dioxide and the deposition of carbon or carbon clusters with odd electrons on the surface of magnetic cobalt cores due to magnetic attraction. Magnetic measurements show 141.41 emu/g of saturation magnetization of a typical sample, which is lower than the 168 emu/g of the corresponding metal cobalt bulk material. This is attributed to the considerable mass of the carbon shell and amorphous nature of the magnetic core. Control of magnetism in the cobalt-carbon core-shell microspheres was achieved by annealing treatments.     

直流电弧自催化合成β-SiC纳米线

采用C,Si和SiO₂为反应原料,利用直流电弧法制备出长直的β-SiC纳米线。纳米线的直径为100～200 nm,长度为10～20 μm,并且沿着<111>方向生长。通过X射线衍射(XRD)、扫描电子显微术(SEM)、透射电子显微术(TEM)、拉曼光谱等手段,对β-SiC纳米线进行表征。探讨了β-SiC纳米线自催化气-液-固(VLS)生长机制。     

Sol-Gel Route to Direct Formation of Silica Aerogel Microparticles Using Supercritical Solvents

A simple and versatile method to obtain silica aerogel particles based on the hydrolysis and subsequent condensation of silicon alkoxides in supercritical fluids is proposed. This microparticle production route reduces the number of steps of traditional microparticle sol-gel processing.A case example is explained in more detail. Spherical and fiber silica morphologies were obtained by a one step method using a sol-gel process with supercritical acetone as a solvent. Particle size was controlled by varying the relative amounts of alkoxysilane, water and acetone. The resulting materials are influenced by a large number of experimental parameters; it has been observed that a quite relevant one is the supercritical fluid venting rate. The morphology of the particles was characterized by electron microscopy (SEM and TEM) and Atomic Force Microscopy (AFM). Alternatively, a low temperature synthesis can be performed by using supercritical carbon dioxide as solvent and formic acid as condensation agent.     

Green synthesis and characterization of cobalt oxide nanoparticles and its electrocatalytic behavior

Green synthesis of pure cobalt oxide nanoparticles (CoO-NPs) in aqueous medium has been carried out using gelatin. The main advantage of using gelatin as a stabilizing agent is that it provides long-term stability for nanoparticles by preventing particles agglomeration. The particles have been characterized using X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EADX), and thermogravimetric analysis (TGA). TEM image shows the formation of CoO-NPs with average particle size of 28 nm which agrees well with the XRD data. Cobalt oxide nanoparticles modified carbon paste electrode (CoO-NPs/CPE) displayed excellent electrochemical catalytic activities towards the oxidation of glucose. The electrocatalytic response showed a wide linear range of 7–1000 µM, as well as its experimental limit of detection can be achieved 5.3 µM. The modified electrode for glucose determination is of the property of simple preparation, good stability and high sensitivity.     

Phonon properties of nanosized MnWO4 with different size and morphology

Highly hierarchical barlike and flowerlike MnWO₄ microcrystals have been synthesized for the first time by a hydrothermal method, where ethanolamine (EA) and cetyltrimethylamonnium bromide (CTAB) play important roles in directing growth and self-assembly of these structures. The possible formation process has been proposed. In addition, platelike nanosized MnWO₄ was also synthesized by annealing of a precursor obtained by coprecipitation method. The obtained samples were characterized by XRD, SEM, TEM, Raman and IR methods. Raman spectra showed relatively weak dependence on particle size and morphology of the particles. In contrast to this behavior, IR-active bands showed pronounced shifts and changes in relative intensities on particle size and the morphology. Origin of this behavior is discussed.     

PtRu/carbon nanotube nanocomposite synthesized in supercritical fluid: a novel electrocatalyst for direct methanol fuel cells

Platinum/ruthenium nanoparticles were decorated on carbon nanotubes (CNT) in supercritical carbon dioxide, and the nanocomposites were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). TEM images show that the particles size is in the range of 5-10 nm, and XRD patterns show a face-centered cubic crystal structure. Methanol electrooxidation in 1 M sulfuric acid electrolyte containing 2 M methanol were studied onPtRu/CNT (Pt, 4.1 wt%; Ru, 2.3 wt%; molar ratio approximately Pt/Ru = 45:55) catalysts using cyclic voltammetry, linear sweep voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. All the electrochemical results show that PtRu/CNT catalysts exhibit high activity for methanol oxidation which resulted from the high surface area of carbon nanotubes and the nanostructure of platinum/ruthenium particles. Compared with Pt/CNT, the onset potential is much lower and the ratio of forward anodic peak current to reverse anodic peak current is much higher for methanol oxidation, which indicates the higher catalytic activity of PtRu/CNT. The presence of Ru with Pt accelerates the rate of methanol oxidation. The results demonstrated the feasibility of processing bimetallic catalysts in supercritical carbon dioxide for fuel cell applications.     

Cu2O微晶的可控制备及可见光催化亚甲基蓝降解性能

以醋酸铜为铜源, 柠檬酸钠为形貌导向剂, 乙二醇和水为溶剂, 采用溶剂热法制备了立方状形貌的Cu₂O微晶. 利用X射线衍射(XRD)、 X射线光电子能谱( XPS)、 扫描电子显微镜(SEM)、 透射电子显微镜(TEM)和紫外-可见漫反射光谱(UV-Vis DRS)等对Cu₂O微晶进行了表征. 结果表明, 在柠檬酸钠与醋酸铜摩尔比为1.0时, 于180 ℃反应5 h可以制备出尺寸分布在0.6~1.5 μm间的均一立方状形貌Cu₂O微晶. 研究了该微晶对亚甲基蓝(MB)在可见光下降解反应的光催化性能. 结果表明, 在H₂O₂存在下, Cu₂O微晶(0.3 g/L)在100 min内对30 mg/L MB溶液的降解率可以达到98%. 该催化剂经过8次循环使用对MB的降解率仍保持在96%以上, 展现了较高的催化活性及良好的稳定性. 通过活性物种的分析对催化体系的光催化机理进行了推测.     

Synthesis of TiO2 photocatalysts in supercritical CO2 via a non-hydrolytic route

Nanoscaled TiO2 powders with narrow size dispersion were prepared in supercritical carbon dioxide via non-hydrolytic acylation/deacylation of titanium alkoxide precursors with or without tris-fluorination. The microstructures of these powders were characterized by spectroscopic (FTIR, TGA, and XRD), microscopic (SEM or TEM), and surface area (BET) measurements. Photocatalytic oxidation of 1-octanol on these calcined TiO2 powders and on commercial T805 TiO2 suspended in aerated supercritical carbon dioxide revealed relative reactivity controlled by the powder microstructures. Calcined TiO2 prepared from titanium(IV) isopropoxide and trifluoroacetic anhydride was effectively dispersed in aerated supercritical carbon dioxide under stirring and exhibited high photocatalytic oxidation activity.     

ZIF67衍生硫化钴/多孔碳复合催化剂的制备及其电催化性能

采用离子交换法与热处理相结合的方法,以ZIF67为前驱体,硫代乙酰胺为硫源,制备出硫化钴/多孔碳(CoS/C)复合催化材料,并探讨了硫化时间对复合催化剂的形貌、结构及其氧还原(ORR)性能的影响。采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射仪(XRD)、N2吸附-脱附测定仪、X射线光电子能谱分析(XPS)、拉曼光谱仪(Raman)和旋转圆盘电极(RDE)技术表征催化剂的物理特征和电催化性能。研究结果显示,在碱性条件下该复合催化剂具有与20%(w/w)的商业Pt/C催化剂相媲美的ORR活性,其半波电位仅比Pt/C催化剂低31 mV。随着硫化时间的增加,硫化钴颗粒逐渐增大,催化剂中碳材料的无序程度出现先减小后增大的趋势。在硫化时间为10 min时,复合催化剂在0.1 mol·L-1KOH中表现出良好的电催化活性,且在ORR过程中复合催化剂的平均转移电子数可达到3.72,接近于4,说明氧气在该催化剂表面发生的是四电子转移过程。     

Hydrothermal Syntheses of CuO,CuO/Cu2O,Cu2O,Cu2O/Cu and Cu Microcrystals Using Ionic Liquids

In this paper, CuO, CuO/Cu₂O, Cu₂O, Cu₂O/Cu and Cu microcrystals were synthesized via a hydrothermal method by mixing Cu(NO₃)₂·3H₂O and NaOH together in the presence of an ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate([BMIM]BF₄) or 1-butyl-3-methylimidazolium chloride([BMIM]Cl). The structures and the morphologies of the obtained products were characterized by means of X-ray diffractometer(XRD), field-emission scanning electron microscopy/energy-dispersive spectroscopy(FESEM/EDS), transmission electron microscopy/selected area electron diffraction(TEM/SAED) and Raman spectroscopy. The result of XRD indicates that Cu₂O and Cu microcrystals are cubic phase and the Raman spectra confirm the presence of carbon. The results of FESEM and TEM images show Cu₂O microcrystals as rule cubes of 2 μm in length and Cu particles of 5 μm in diameter. According to the difference between crystal structures, bi-component and single component products were synthesized by adjusting the reaction conditions. A possible formation mechanism of Cu₂O and Cu was proposed in[BMIM]BF₄.