Ni-WOx催化剂上正辛烷加氢异构化反应性能的研究

采用浸渍法制备Ni-WOx催化剂,在常压连续流动固定床反应器上考察了Ni-WOx催化剂上正辛烷加氢异构化的催化性能。讨论了焙烧温度、Ni的含量、还原条件和反应条件对催化剂性能的影响,对Ni-WOx催化剂进行了XRD和BET表征。实验结果表明,在Ni-WOx催化剂上,焙烧温度为800℃,还原温度为525℃,反应温度为275℃,Ni-WOx催化剂对正辛烷异构化反应的转化率达到58.17%,同时其异构化选择性达到87.33%。通过XRD表征推测催化剂的活性相主要为WO2,正辛烷在Ni-WOx催化剂上是按照传统的双功能机理进行反应的。     

La-Ni-Al合金中镍的测定

镍离子本身具有鲜艳的兰绿色,这一特性可用于镍的测定.文章结合La-Ni-Al合金中镍的测定方法研究,重点考察了本色光度法测镍的相关条件,设计了La-Ni-Al合金中镍的分析方法.方法具有高选择性、准确、简便、快速、经济的优点.     

不同预热温度WC增强镍基合金堆焊层的微结构演化与摩擦学性能

目的 研究不同预热温度(200、400 ℃)条件下硬质颗粒增强镍基合金堆焊层的微观组织结构演化机理,以及对其力学性能、磨损性能的影响规律。方法 采用等离子弧焊接技术在42CrMo钢基体表面堆焊硬质WC颗粒增强镍基强化层,利用X射线衍射(XRD)、扫描电子显微镜(SEM)、硬度计和摩擦磨损试验机,分析不同预热温度堆焊层的物相组成、微观组织形貌、力学性能和磨损性能,建立堆焊层制备工艺–微观组织结构–力学性能–磨损性能之间的强映射关系。结果 堆焊层主要由γ-Ni/Fe、WC、W2C、M7C3、M23C6、Ni2W4C、Cr3C2等物相组成,在预热温度200 ℃下堆焊层二次碳化物析出较少,发生了严重的WC颗粒沉降现象;在预热温度400 ℃下,堆焊层析出了大量的二次碳化物,WC颗粒沉降减弱,组织均匀性提高。在400 ℃下预热,相较于200 ℃下预热,堆焊层的磨损质量减少了51.85%,磨损率减少了51.89%。结论 高预热温度和长保温时间可促进WC颗粒界面反应,驱动大面积二次碳化物的析出,有效缓解WC颗粒沉降,改善凝固组织中WC颗粒的分布均匀性,从而显著提高堆焊层的硬度和耐磨性。     

Renewable hydrogen production from steam reforming of glycerol (SRG) over ceria-modified γ-alumina supported Ni catalyst

Excess crude glycerol derived as a by-product from biodiesel industry prompts the need to valorise glycerol to value-added chemicals. In this context, catalytic steam reforming of glycerol (SRG) was proposed as a promising and sustainable alternative for producing renewable hydrogen (H₂). Herein, the development of nickel (Ni) supported on ceria-modified mesoporous γ-alumina (γ-Al₂O₃) catalysts and their applications in catalytic SRG (at 550–750 °C, atmospheric pressure and weight hourly space velocity, WHSV, of 44,122 ml·g⁻¹·h⁻¹ (STP)) is presented. Properties of the developed catalysts were characterised using many techniques. The findings show that ceria modification improved Ni dispersion on γ-Al₂O₃ catalyst support with highly active small Ni particles, which led to a remarkable catalytic performance with the total glycerol conversion (ca. 99%), glycerol conversion into gaseous products (ca. 77%) and H₂ yield (ca. 62%). The formation rate for H₂ production (14.4 × 10⁻⁵ mol·s⁻¹·g⁻¹, TOF (H₂) = 3412 s⁻¹) was significantly improved with the Ni@12Ce-Al₂O₃ catalyst, representing nearly a 2-fold increase compared with that of the conventional Ni@Al₂O₃ catalyst. In addition, the developed catalyst also exhibited comparatively high stability (for 12 h) and coke resistance ability.     

Composite Electrodes for Electrochemical Supercapacitors

Manganese dioxide nanofibers with length ranged from 0.1 to 1 μm and a diameter of about 4–6 nm were prepared by a chemical precipitation method. Composite electrodes for electrochemical supercapacitors were fabricated by impregnation of the manganese dioxide nanofibers and multiwalled carbon nanotubes (MWCNT) into porous Ni plaque current collectors. Obtained composite electrodes, containing 85% of manganese dioxide and 15 mass% of MWCNT, as a conductive additive, with total mass loading of 7–15 mg cm⁻², showed a capacitive behavior in 0.5-M Na₂SO₄ solutions. The decrease in stirring time during precipitation of the nanofibers resulted in reduced agglomeration and higher specific capacitance (SC). The highest SC of 185 F g⁻¹ was obtained at a scan rate of 2 mV s⁻¹ for mass loading of 7 mg cm⁻². The SC decreased with increasing scan rate and increasing electrode mass.     

搬运镍始极片的专用堆垛台设计

通过对冶金工业中镍始极片的堆垛要求进行分析,并参考所配合使用的搬运机械手的运作规律,设计了一个自由度为2的镍始极片堆垛台。堆垛台主要由旋转底座、升降部分和挡杆等零部件组成。它可以实现360°旋转（每次可转90°）和升降的功能,从而可以满足镍始极片整齐堆垛的要求。另外,该堆垛台不仅可以运用在镍始极片的堆垛上,还适用于其他同类物品。利用这一装置可以大大减轻工人的劳动强度,改善工人的劳动条件,从而大大提高生产效率。     

Chlorination of bromide-containing waters: Enhanced bromate formation in the presence of synthetic metal oxides and deposits formed in drinking water distribution systems

Bromate formation from the reaction between chlorine and bromide in homogeneous solution is a slow process. The present study investigated metal oxides enhanced bromate formation during chlorination of bromide-containing waters. Selected metal oxides enhanced the decay of hypobromous acid (HOBr), a requisite intermediate during the oxidation of bromide to bromate, via (i) disproportionation to bromate in the presence of nickel oxide (NiO) and cupric oxide (CuO), (ii) oxidation of a metal to a higher valence state in the presence of cuprous oxide (Cu₂O) and (iii) oxygen formation by NiO and CuO. Goethite (α-FeOOH) did not enhance either of these pathways. Non-charged species of metal oxides seem to be responsible for the catalytic disproportionation which shows its highest rate in the pH range near the pK_a of HOBr. Due to the ability to catalyze HOBr disproportionation, bromate was formed during chlorination of bromide-containing waters in the presence of CuO and NiO, whereas no bromate was detected in the presence of Cu₂O and α-FeOOH for analogous conditions. The inhibition ability of coexisting anions on bromate formation at pH 8.6 follows the sequence of phosphate >> sulfate > bicarbonate/carbonate. A black deposit in a water pipe harvested from a drinking water distribution system exerted significant residual oxidant decay and bromate formation during chlorination of bromide-containing waters. Energy dispersive spectroscopy (EDS) analyses showed that the black deposit contained copper (14%, atomic percentage) and nickel (1.8%, atomic percentage). Cupric oxide was further confirmed by X-ray diffraction (XRD). These results indicate that bromate formation may be of concern during chlorination of bromide-containing waters in distribution systems containing CuO and/or NiO.     

Copolymerization of methyl methacrylate with 4‐vinylpyridine initiated by a novel Ni(II)α‐Benzoinoxime complex

Copolymerizations of methyl methacrylate (MMA) with 4‐vinylpyridine (4VP) were performed from different monomer feed ratios in 1,4‐dioxan at 30°C under free radical initiation experimental conditions, using Ni(II)α‐Benzoinoxime complex as initiator. The obtained copolymers (PMMA4VP) were examined by FTIR and ¹H NMR spectroscopies. The composition of these copolymers was calculated, using ¹H NMR spectra and elemental analysis. Monomer reactivity ratios were estimated from Fineman–Ross (FR, r_m = 0.550, r_v = 1.165) and Kelen–Tudos (KT, r_m = 0.559, r_v = 1.286) linearization methods, as well as nonlinear error in variables model (EVM) method using the RREVM computer program (RREVM, r_m = 0.559, r_v = 1.264). These values suggest that MMA‐4VP pair copolymerizes randomly. ¹H NMR spectra provide information about the stereochemistry of the copolymers in terms of sequence distributions and configurations. These results showed that the age of the Ni complex has an impact not only on its activity towards polymerization reactions but also on the features of the corresponding copolymers, whereas the chemical composition was insensitive to this prominent factor. The mechanism of MMA‐4VP copolymerization is consistent with a radical process as supported by microstructure and molecular weight distribution studies. Thermal behaviours of these copolymers were investigated by differential scanning calorimetry and thermogravimetric analysis. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

钢铁中温光亮化学镀镍新工艺

研究了一种镜面光亮化学镀镍新工艺,优选了镀液配方及工艺条件.该工艺采用有机酸多络合体系,中温酸性化学光亮镀镍.试验表明,该镀层耐蚀性好、结合力强、硬度大、光洁度高,镀层镜面光亮,且光亮剂A无毒,减少了环境污染.     

Properties of Ferrite-Filled Natural Rubber Composites

Nickel zinc ferrite (Ni-ZnFe₂O₄)-filled natural rubber (NR) composite was prepared at various loading of ferrite. The tensile properties included in this study were tensile strength, tensile modulus and elongation at break. The tensile strength and elongation at break of the composites increased up to 40 parts per hundred rubber (phr) of ferrite and then decreased at higher loading whereas the tensile modulus was increased gradually with increasing of ferrite loading. Scanning electron microscopy (SEM) was used to determine the wettability of filler in rubber matrix. From the observation, the increase of filler loading reduced the wettability of the filler. Thermal stability of the composites was conducted by using a thermogravimetry analyser (TGA). The incorporation of ferrite in NR composites enhanced the thermal stability of NR composites. The swelling test results indicate that the swelling percentage of the composites decreased by increasing of ferrite loading. The initial permeability, μ_i and quality factor, Q of magnetic properties of NR composites achieved maximum value at 60 phr of ferrite loading for frequency range between 5000–40,000 kHz. The maximum impedance, Z _max of the NR composites was at the highest value at 80 phr ferrite loading for frequency range between 200–800 MHz.