Plasma-assisted CO2 reforming of methane over Ni-based catalysts: Promoting role of Ag and Sn secondary metals

Carbon dioxide (CO₂) and methane (CH₄) are the primary greenhouse gases (GHGs) that drive global climate change. CO₂ reforming of CH₄ or dry reforming of CH₄ (DRM) is used for the simultaneous conversion of CO₂ and CH₄ into syngas and higher hydrocarbons. In this study, DRM was investigated using Ag–Ni/Al₂O₃ packing and Sn–Ni/Al₂O₃ packing in a parallel plate dielectric barrier discharge (DBD) reactor. The performance of the DBD reactor was significantly enhanced when applying Ag–Ni/Al₂O₃ and Sn–Ni/Al₂O₃ due to the relatively high electrical conductivity of Ag and Sn as well as their anti-coke performances. Using Ag–Ni/Al₂O₃ consisting of 1.5 wt% Ag and 5 wt% Ni/Al₂O₃ as the catalyst in the DBD reactor, 19% CH₄ conversion, 21% CO₂ conversion, 60% H₂ selectivity, 81% CO selectivity, energy efficiency of 7.9% and 0.74% (by mole) coke formation were achieved. In addition, using Sn–Ni/Al₂O₃, consisting of 0.5 wt% Sn and 5 wt% Ni/Al₂O₃, 15% CH₄ conversion, 19% CO₂ conversion, 64% H₂ selectivity, 70% CO selectivity, energy efficiency of 6.0%, and 2.1% (by mole) coke formation were achieved. Sn enhanced the reactant conversions and energy efficiency, and resulted in a reduction in coke formation; these results are comparable to that achieved when using the noble metal Ag. The decrease in the formation of coke could be correlated to the increase in the CO selectivity of the catalyst. Good dispersion of the secondary metals on Ni was found to be an important factor for the observed increases in the catalyst surface area and catalytic activities. Furthermore, the stability of the catalytic reactions was investigated for 1800 min over the 0.5 wt% Ag-5 wt% Ni/Al₂O₃ and 0.5 wt% Sn-5 wt% Ni/Al₂O₃ catalysts. The results showed an increase in the reactant conversions with an increase in the reaction time.     

Effect of heat treatment and zircon addition on the properties of low-cement castables based on recycled alumina grog

In this investigation, low-cement castables were prepared using 70% alumina grog aggregates obtained from crushed alumina brick waste. The aggregates were thermally treated at 1550 °C for 3 h. Four types of low-cement castables were prepared with various types of aggregates (alumina grog with or without thermal treatment) and fillers (with or without zircon addition), and they were evaluated in terms of their physical, thermal, and chemical properties. Microstructural analysis via scanning electron microscopy (SEM) was performed on the castables before and after slag attack. Compared to the other fabricated castables, the thermally treated alumina grog castables with zircon showed better physical properties, such as a higher bulk density, cold crushing strength, and modulus of rupture and a lower apparent porosity and water absorption. In addition, they had a higher positive linear thermal expansion, refractoriness under load, permanent linear change, and hot modulus of rupture. The results of the SEM with energy dispersive X-ray analysis of the prepared castables confirmed that the mullite and anorthite phases were predominant when zircon was not added and the zircon–mullite phase additionally appeared upon the incorporation of zircon. A quantitative elemental analysis via X-ray fluorescence spectroscopy was employed to determine the composition of the castables. X-ray diffraction analysis showed that the alumina grog castables had a high mullite and low anorthite content, and the thermally treated alumina grog had a high anorthite, low mullite, and high zircon content. The improvement in the mechanical and thermo-mechanical properties of the castables with thermally treated alumina grog and added zircon can be attributed to the formation of the zircon–mullite phase with a low mullite phase content.     

Cu-Mg/Al_2O_3催化乙醇和乙二胺合成N-乙基乙二胺

在固定床反应器内,乙醇和乙二胺经分子间催化胺化反应合成了N-乙基乙二胺(NEED),考察了一系列铜系催化剂的活性,并筛选出催化性能较好的Cu-Mg/A l2O3催化剂;通过X射线衍射和透射扫描电子显微镜方法表征了助剂Mg对Cu/A l2O3催化剂的改性作用;考察了助催化剂Mg含量、反应温度、反应压力、进料量和乙二胺含量等对Cu-Mg/A l2O3催化剂性能的影响。实验结果表明,Cu-Mg/A l2O3催化剂具有很好的活性和选择性;在200℃、3.0MPa、质量分数20%的乙二胺乙醇溶液、进料量1.0mL/m in的条件下,乙二胺的转化率为71.56%,产物NEED的选择性和收率分别为92.62%和69.86%;经过20 d的连续使用表明,Cu-Mg/A l2O3催化剂具有良好的稳定性。     

Processing of Yttria-Alumina Coated Silicon Nitride Slips by Slip Casting

Si₃N₄powders coated with 6 wt% Y₂O₃and 4 wt% Al₂O₃were prepared by coprecipitation. The resulting powders were dispersed in water at different pH values and with addition of various amounts of ammonium polyacrylate (NH₄PA) to produce 32 vol% slips. The influence of the amount of NH₄PA solution added and pH on the rheological properties of 32 vol% coated Si₃N₄slips were studied. In addition, the sintered density of cast samples was determined and related to the degree of slip dispersion. The adsorption of the NH₄PA on the coated particle surface was rather high and the surface became saturated near 0.86 mg/m²at pH 9.2. High NH₄PA concentrations (1.7–3 wt%) were necessary to obtain well dispersed 32 vol% coated Si₃N₄slips at pH 9.2. The best stabilization was obtained with the addition of 2.3 wt% NH₄PA; in this condition, the viscosity reached a minimum value of 35 mPa.s at 100 s^–1. The slip viscosity increased with increasing pH from 9.2 to 10.2. Slips with low viscosities gave a more dense packing of cast samples and consequently higher sintered density values.     

NaY晶化母液制备硅铝胶的技术探讨

在导向剂法合成Y型分子筛的工艺下，晶化母液中SiO₂的含量为50～55g/l,Na₂O含量为20～25g/l，相当于模数为1.65～2.58的稀水玻璃，将晶化母液分离处理后，在晶化母液中加入一定量的硫酸铝溶液使硅沉淀,经过滤和水洗后即可制备出合格的硅铝胶，以便进行重新利用。     

Asymmetric Hydrogenation of Activated Ketones on Platinum: Relevant and Spectator Species

The heterogeneous enantioselective hydrogenation of activated ketones over chirally modified platinum is reviewed with emphasis on identifying the role of the various species observed in this catalytic system. The past years have witnessed a continuous broadening of the scope of this catalytic system including new reactants and modifiers affording over 97% ee. New reaction pathways have been uncovered and the kinetic and mechanistic studies have been faced with a number of complicating factors caused by spectator species and interactions in solution and on the Pt surface. The previously proposed mechanistic models are critically assessed in the light of these new findings.     

氧化铝生产过程结疤溶解的研究

针对氧化铝生产过程结疤现象。研制出一种新型清洗溶剂，溶垢率可达95%，清洗效果达到《工业设备化学清洗质量标准》要求。     

Al2O3对镁铬耐火材料致密化的影响

为了提高镁铬耐火材料的烧结性能,通过考察气孔率、体积密度和常温耐压强度与Al2O3加入量之间的关系,讨论了Al2O3添加剂对两种不同镁铬耐火材料致密化的影响.结果表明,镁铬耐火材料的骨料不同,Al2O3对其烧结性能和致密化的影响也不一样.     

氧化铝/锌合金复合材料界面的SEM观察

利用挤压铸造制备氧化铝／锌合金复合材料，在扫描电镜（ＳＥＭ）上观察复合材料的界面。结果表明，在复合材料中纤维与基体间存在致密界面层，合金元素通过适当的化学反应可改善纤维与基体间的结合；在凝固过程中，纤维／基体界面上的硅在共晶体的共生生长过程中起了领先相作用，导致复合材料的共晶转变是由铝硅共晶转变和锌铝共晶转变两者组成。     

Anodising potential influence on well-ordered nanostructures formed by anodisation of aluminium in sulphuric acid

High-density structures with relatively well-ordered nanopore arrays have been obtained by the self-ordering growth of nanopores occurring during anodisation of aluminium in sulphuric acid. The resulting array of well-ordered nanopores strongly depends on an applied voltage of anodising, temperature and a procedure of synthesis. Regular arranged hexagonal arrays on aluminium with a relatively uniform pore diameter, interpore distance, and depth of pores exceeding 90 μm, can be formed by the self-ordering two-step anodising at 1 °C. The interpore distance and the pore diameter were evaluated on anodised aluminium layers obtained at different cell potentials ranging from 15 to 25 V. The detailed analyses of their uniformity were performed from SEM images. The analysis of a pore arrangement defects was made from SEM top view images taken on samples anodised at various cell potentials. The defect maps, known as Delaunay triangulations, of the arrangement of about 1000 pores were constructed for different applied anodising potentials. The percentage of pores that are not six-fold coordinated by the neighbouring pores indicates the percentage of defected surface.