Recent Research Progress of Branched and Functional Branched Polyethylene Prepared Using Ni- and Pd–Based Catalysts

In this paper, the recent development of branched and functional branched polyethylene prepared using Ni- and Pd-based catalysts are reviewed. The influence of ligand species, steric effect, electronic effect and polymerization condition on branching density of resultant polymer prepared using Ni- and Pd-based catalysts is discussed. In addition, the review is also focused on functional branched polyethylene produced by copolymerization of ethylene and polar monomer and copolymerization mechanism.     

Methanol Steam Reforming Over NiAl and Ni (M) Al Layered Double Hydroxides (M = Au, Rh, Ir) Derived Catalysts

This paper deals with an experimental investigation concerning steam reforming of methanol at 280, 340 and 380 °C over NiAl and Ni (Au, Rh or Ir)Al layered double hydroxides (LDHs) derived catalysts. Incorporation of noble metal ions into the NiAl-LDH framework was evidenced by XRD, TGA and TEM techniques. High selectivity to H₂ and CO₂ with less than 5% (volume) CO and trace CH₄ was observed over the NiAl-LDH catalyst. Whereas CO and H₂ are major products at lower temperatures after addition of Au, Rh and Ir to the NiAl-LDH system. They are significantly reduced with the concomitant increase in CH₄ and CO₂ as the temperature increased.     

Catalytic hydrogenation of insoluble organic matter of CS2/Acetone from coal over mesoporous HZSM-5 supported Ni and Ru

Four supported catalysts, nickel and ruthenium on a HZSM-5 support, were prepared by equal volume impregnation and in-situ decomposition of carbonyl nickel. The properties of catalysts were investigated by catalytic hydro-conversion of 2,2′-dinaphthyl ether as the model compound and extraction residue of Naomaohu lignite as the sample under an initial H₂ pressure of 5 MPa and temperature at 150 °C. According to the catalytic hydro-conversion results of the model compound, Ni−Ru/HZSM-5 exhibited the best catalytic performance. It not only activated H₂ into H···H, but also further heterolytically split H···H into immobile H^‒ attached on the acidic centers of Ni−Ru/HZSM-5 and relatively mobile H⁺. Catalytic hydro-conversion of the extraction residue from Naomaohu lignite was further examined over the optimized catalyst, Ni−Ru/HZSM-5. Detailed molecular compositions of products from the extraction residue with and without hydrogenation were characterized by Fourier transform infrared spectroscopy and gas chromatography/mass spectrometry. The analytical results showed that the oxygen-containing functional groups in products of hydrogenated extraction residue were obviously reduced after the catalytic treatment. The relative content of oxygenates in the product with catalytic treatment was 18.57% lower than that in the product without catalytic treatment.     

Highly dispersed and confined Ni/MMO catalyst synthesized in a rotating packed bed for hydrogenation of maleic anhydride

Catalytic hydrogenation of maleic anhydride (MA) into succinic anhydride (SA) is one of the most important transformations in synthetic organic chemistry. Herein, we firstly synthesized well-dispersed nickel particles confined by mixed metal oxides (Ni/MMO) derived from in situ transformation of Ni-Al hydrotalcite in a rotating packed bed (RPB) to catalyze this process. A series of Ni/MMO catalysts (63 wt%–89 wt% Ni) were effectively fabricated and the structure–activity relationship was established. Results showed that a Ni/MMO catalyst (82 wt% Ni) with substantial surface defect sites and the highest Ni surface area among the prepared Ni/MMO catalysts, demonstrates the highest activity with ~100% MA conversion and ~100% selectivity to SA under 25°C within 77 min. This is, to our knowledge, the highest conversion and selectivity under room temperature to date. Moreover, the Ni/MMO catalyst prepared by RPB has higher specific surface area and Ni surface area, therefore possessing a higher hydrogenation rate compared to that by stirred tank reactor (1.69 vs. 1.36, 10⁻³·mol_MA/g_cat/min). These results will provide an attractive option of the catalysts for MA hydrogenation, and a novel strategy for synthesizing nickel catalyst derived from Ni-Al hydrotalcite.     

Copolymerization of norbornene with norbornene terminated polystyrene macromonomer in the presence of Ni-based/MAO catalytic systems

Copolymerization of -norbornenyl polystyrene macromonomer (NBE-PS) with norbornene (NBE) using Ni-based catalysts in combination with methylaluminoxane (MAO) was investigated. The nature of the catalyst, the of the polystyrene macromonomer as well as the [NBE-PS]/[NBE] ratio have been shown to be important parameters to obtain graft copolymers with high NBE-PS incorporation (up to 43 wt%). The compatibilization ability of these graft copolymers has been checked for PS/PNBE blends. The length of the grafts was proved not to be an important parameter to consider compatibilization of the PS/PNBE blend.     

枝晶间距对镍基单晶合金蠕变性能的影响

为了研究枝晶间距对镍基单晶合金组织与蠕变性能的影响,采用不同抽拉速率制备出两种不同枝晶间距的单晶镍基合金.通过蠕变性能测试及组织形貌观察,研究了枝晶间距对合金成分偏析及蠕变性能的影响.结果表明,随着合金枝晶间距的减小,元素成分偏析程度降低,且在相同热处理条件下,枝晶间距较小的合金具有较好的蠕变性能.合金在稳态蠕变期间的变形机制是位错攀移越过筏状γ′相,而蠕变后期的变形机制是位错在基体中滑移和切入筏状γ′相.蠕变断裂后,在试样不同区域筏状γ′相具有不同的形貌,在远离断口区域,筏状γ′相与应力轴方向垂直,而在近断口区域,筏状γ′相尺寸及扭曲程度均增加.     

基于损伤力学的含夹杂粉末高温合金FGH96低周裂纹萌生寿命预测

研究FGH96粉末高温合金中夹杂物对低周疲劳寿命的影响,提出基于损伤力学理论的低周裂纹萌生寿命预测模型,在建立损伤演化方程后提出损伤表征参数.对含夹杂物和不含夹杂物的粉末高温合金试样在530℃和600℃下进行疲劳试验,并对具有椭圆形、半椭圆形、多边形和条形表面/亚表面夹杂物的试样进行模型验证,然后通过有限元模拟进行应力...     

Effect of Supports and Promoters on the Performance of Ni-Based Catalysts in Ethanol Steam Reforming

Ethanol steam reforming (ESR) is one of the potential processes to convert ethanol into valuable products. Hydrogen produced from ESR is considered as green energy for the future and can be an excellent alternative to fossil fuels with the aim of mitigating the greenhouse gas effect. The ESR process has been well studied, using transition metals as catalysts coupled with both acidic and basic oxides as supports. Among various reported transition metals, Ni is an inexpensive material with activity comparable to that of noble metals, showing promising ethanol conversion and hydrogen yields. Additionally, different promoters and supports were utilized to enhance the hydrogen yield and the catalyst stability. This review summarizes and discusses the influences of the supports and promoters of Ni-based catalysts on the ESR process.     

Effects of yttrium on wettability and interactions between molten superalloy and SiO2-based ceramic core

In order to obtain high-quality superalloy castings, the wettability and interactions between superalloy melts with various Y contents and SiO₂-based ceramic cores were investigated at 1823 K. The results indicated that the wettability and interface reactions were affected by the content of Y in the alloy. For the alloys with Y content less than 0.011 wt%, no Y-oxide was found at the interface, but HfO₂, Al₂O₃ and ZrO₂ phases were formed, and the wetting angle dropped slightly. However, different Y-oxides precipitated at the alloy-ceramic interface for the alloys with Y content more than 0.017 wt%, and the wetting angle dropped sharply. When the content of Y was 0.017 and 0.025 wt%, Al₂O₃, Y₃Al₂(AlO₄)₃, HfO₂ and ZrO₂ phases were formed at the interface. When the content of Y was 0.1 wt%, YAlO₃, Y₃Al₅O₁₂, Y₄Al₂O₉, HfO₂ and ZrO₂ phases were formed. The formation of different reaction products was mainly caused by the change of Y activity (a_Y) in the alloy. The reaction between Y and SiO₂ could improve the wettability of the system apparently.     

对一种组合式钎料的试验分析

针对一种以固定牌号使用的俄罗斯组合式钎料ВПР11-40H进行了试验分析，结果表明，该钎料表现出不同于一般钎料的熔化特性，对不锈钢及高温合金薄壁件具有较弱的溶蚀作用，适用于不等间隙、较大间隙钎缝以及薄壁零件的钎焊，对采用该钎料钎焊GH3044和GH3039接头的性能测试结果表明，接头具有满意的室温和高温性能。