Raney Ni催化二亚糠基丙酮加氢制取长链烷烃前驱体的特性研究

采用Raney Ni为催化剂,考察了反应温度、压力、时间和溶剂对二亚糠基丙酮加氢制取长链烷烃前驱体催化性能的影响。结果表明,Raney Ni对二亚糠基丙酮具有很好的低温加氢性能,升高反应温度和压力均有利于加氢反应的进行,但过高的温度反而不利于加氢反应。在50℃和2.5 MPa下反应2 h,二亚糠基丙酮转化率达99.5%以上,饱和加氢产物的总选择性达到80.8%。此外,加氢中间产物的变化结果表明,二亚糠基丙酮的双键加氢容易程度为,烯键>呋喃环双键>C=O双键。Raney Ni 在甲醇溶剂中的加氢性能明显高于在四氢呋喃、环己烷或水溶剂中的加氢性能。     

高镍负载量Ni/SiO2和低镍负载量Ni-Ce/SiO2催化CO甲烷化的比较研究

采用等体积浸渍法制备了高镍负载量的13%Ni/SiO₂(13Ni/Si)催化剂和低镍负载量的7%Ni-2%Ce/SiO₂(7Ni-2Ce/Si)催化剂.通过N₂物理吸附、XRD、FT-IR、TEM、H₂-TPR/TPD等技术对催化剂进行表征,在连续流动微反装置上考察了催化剂的CO甲烷化活性.结果表明,在7Ni-2Ce/Si催化剂中NiO、CeO₂和SiO₂之间产生的相互作用,改变了Ni-O-Si键的化学环境,促进了氧化镍物种的分散和还原,进而提高了催化剂的活性比表面积,同时在催化剂表面形成了新的中等强度的CO吸附中心.与高镍负载量的13Ni/Si催化剂相比,低镍负载量的7Ni-2Ce/Si表现出更高的CO吸附能力和甲烷化活性.常压下,在CO体积分数1%和空速7 000 h^-1的反应条件下,低镍负载量的7Ni-2Ce/Si催化剂上CO完全甲烷化最低温度为230 ℃,比高镍负载量的13Ni/Si低了30 ℃.     

Ni Nanoparticles: Mild and Efficient Catalyst for the Chemoselective Synthesis of 2-Arylbenzimidazoles, 2-Arylbenzothiazoles,and Azomethines

A new and efficient method has been developed for the synthesis of biologically significant 2-arylbenzimidazoles, 2-arylbenzothiazoles, and azomethines using recyclable and inexpensive polyvinyl pyrrolidone (PVP)–stabilized Ni nanoparticles in ethylene glycol at room temperature in excellent yields.     

Cu/Ni助催化剂对TiO2光催化制取苯酚性能的影响

以TiO₂纳米粒子为主催化剂, 采用“浸渍-还原法”构筑了铜、镍共负载的二氧化钛基光催化系统。以苯为起始原料, H₂O₂为氧化剂, 研究了Cu/Ni助催化剂对TiO₂可见光催化制取苯酚性能的影响并对Cu/Ni助催化剂的作用机制进行了探讨。结果表明, 在可见光照射下, 纯TiO₂纳米粒子对苯氧化制取苯酚反应没有催化活性。铜、镍的引入可以明显地增强TiO₂可见光催化制取苯酚的活性。当使用负载有铜、镍的TiO₂作为催化剂时, 苯酚的产率可达到18%。结果还表明Cu、Ni之间存在着很强的协同作用。在该协同作用下, Cu、Ni共负载的TiO₂纳米粒子表现出了较单一金属负载的TiO₂纳米粒子高得多的光催化活性。     

GRAFT COPOLYMERIZATION OF METHYL ACRYLATE ONTO CHITOSAN INITIATED BY POTASSIUM DIPERIODATONICKELATE (IV)

ABSTRACT

A novel redox system, potassium diperiodatonickelate [Ni (IV)]‐chitosan, was employed to initiate the graft copolymerization of methyl acrylate (MA) onto chitosan in alkali aqueous solution. The effects of reaction variables such as monomer concentration, initiator concentration, reaction time, pH and temperature were determined. By means of a series of copolymerization, the grafting conditions were optimized. The maximum grafting percentage obtained was 404.1% when 0.3 g chitosan was copolymerized with 1.8 mL monomer at 35°C for 5 hours with [Ni (IV)]=9.4×10^?4 M and the total volume was 20 mL. Ni (IV)-chitosan system is found to be an efficient redox initiator for this graft copolymerization. A single electron transfer mechanism is proposed to explain the formation of radicals and the initiation. The grafted copolymers were characterized by IR and X-ray diffraction diagrams. The thermal stability of chitosan and chitosan-g-PMA was studied by thermogravimetric analysis (TGA).     

Combination of Dispersive Liquid‐Liquid Microextraction with Flame Atomic Absorption for Determination of Trace Ni and Co in Water Samples and Vitamin B12

A dispersive liquid‐liquid microextraction method based on the dispersion of 1,2‐dichlorobenzene as an extraction solvent into an aqueous phase in the presence of ethanol as a dispersive solvent for the preconcentration of Co²⁺ and Ni²⁺ ions is discussed. 1‐Nitroso 2‐naphtol was used as a chelating agent prior to the extraction and the preconcentrated analyte was determined by flame atomic absorption spectrometry. The effect of various experimental parameters including the extraction and dispersive solvent type and volume, pH, amount of the chelating agent, etc. on the microextraction and complex formation was investigated for finding the optimum conditions. The enhancement factors were about 61.9 and 51.8, the calibration graphs were linear in the range of 10‐150 μgL^?1 and 10‐250 μgL^?1 with detection limits of 2.42 μgL^?1 and 1.59 μgL^?1, and RSD (n = 5) of 3.08% and 2.17% for cobalt and nickel, respectively. The method was successfully applied to the determination of Co and Ni in water and vitamin B₁₂.     

In situ variable temperature X-ray diffraction studies on the transformations of nano-precursors to La-Ni-O phases

In situ variable temperature XRD (VT-XRD) measurements on the transformation of nano-precursors to LaNiO phases are presented. Experimental results showed that LaNiO₃ and La₂NiO₄ phases were formed at ca. 700 °C via the reaction of La₂O₃ and NiO (from the initial nano-precursors), where a relatively low temperature of 700 °C was found for the synthesis of La₂NiO₄. The formation of La₃Ni₂O₇ at higher temperature (up to 1150 °C) appeared to proceed through a further reaction of La₂NiO₄ with unreacted NiO, whilst the formation of La₄Ni₃O₁₀ (at 1075 °C) proceeded via a further decomposition of LaNiO₃. Although phase pure La₃Ni₂O₇ and La₄Ni₃O₁₀ were not directly obtained under the processing conditions herein, the results of this study allow for a better understanding of formation pathways, particularly for the higher order La-Ni-O phases.     

Carbon dioxide reforming of methane on monolithic Ni/Al2O3-based catalysts

Nickel-alumina catalysts supported on cordierite monoliths of honeycomb structure surpass essentially the conventional granulated ones with respect to the output in carbon dioxide reforming of methane. Adjusting the surface acid-base properties of catalysts by introduction of alkali metal (Na, K) oxides inhibits the carbonization and as a result, improves the operational stability of these catalysts. An effect of promotion of nickel-alumina based composite doped by lanthanum oxide is found. This effect, caused by an additional route for the CO2 activation on Ni-La2O3/Al2O3/cordierite catalyst, is displayed in increase of methane conversion under conditions of an oxidant excess.     

第一原理计算在铁(镍)基超导体中的应用

铁(镍)基超导体的发现引起了凝聚态物理界的广泛兴趣和关注.第一原理计算以其快速、准确等优点在铁(镍)基超导研究过程中做出了巨大贡献.文章主要介绍了第一原理计算在该研究领域所取得的成果,其中包括电子结构计算,磁性基态的寻找和解释,声子谱和电声子耦合,以及关联效应在该类材料中的作用等.文章还简略介绍了目前的研究现状以及存在的问题,分析了未来的研究方向和可能的解决办法.     

Magnetic properties of one-dimensional embedded nickel nanostructures in gold nanowires

Magnetic nanostructures of nickel embedded in gold were successfully fabricated by electrochemical deposition in porous alumina templates. Structural characterization of the samples confirmed the formation of pure phase, crystalline multi-segmented Au-Ni-Au nanowires. Magnetic characterization of the wires reveals that ferromagnetism arises as a result of Ni embedded in Au segments. An interesting behavior of coercivity was observed that showed a rapid decrease of coercivity for smaller Ni segments while a monotonic decrease was found for the larger segments. Finally, the saturation magnetization of the wires exhibited a slower increase for smaller Ni segments while a sharp increase was observed for larger Ni segments.