超细态CuO-ZnO-Al２Ｏ３催化剂的CＯ２＋Ｈ２反应性能

研究了草酸盐凝胶共沉淀法和碳酸氢铵并流共沉淀法对催化剂的表面形貌、晶相结构和还原性能的影响,结果表明草酸盐凝胶共沉淀法制备的催化剂表面比较规整,Cu、Zn、Al组分混合均匀。考察了Cu∶Zn比例与催化剂反应性能的关系,当Cu∶Zn接近1时,甲醇的选择性和产率最高,还原后的Cu颗粒度对甲醇产率有较大的影响。     

Preparation of aluminum ultrafine particles by anodizing aluminum foil in acidic electrolyte containing chloride ions

Anodization of aluminum in acidic electrolyte containing chloride ions was used to prepare aluminum ultrafine particles (Al UFPs) for the first time. In addition, the influence of different acid electrolyte was investigated and the mechanism of generating Al UFPs is analyzed. It is found that the pitting corrosion of chloride ions plays an important role in preparing Al UFPs and the acidification of the electrolyte is in favor of the preparation. Al UFPs with different shape and size distribution were obtained via changing the type of acid. Finally, the model of generating Al UFPs via this method is proposed.     

Characterization of polyethylene/kaolin composites by polymerization filling with Cp2ZrCl2/MAO catalyst system

In this work, the preparation and characterization of metallocene‐catalyzed polyethylene (PE)/kaolin composites were presented. The composites was prepared by the so‐called polymerization‐filling method in which the PE matrix was formed directly on the kaolin surface by ethylene polymerization with the prefixed Cp₂ZrCl₂/methylaluminoxane (MAO) catalyst system on the kaolin surface. SEM, FTIR, and DMA were carried out to characterize the composites. The experimental results showed the new composites had homogeneous distribution of kaolin particles in the PE matrix and strong interfacial interaction between the PE matrix and kaolin particles. At the molecular level, the interfacial interaction caused the decrease of the mobility of PE molecular chains. In addition rheological testing showed that the introduction of kaolin by polymerization filling could improve the rheological behavior of prepared composites. The relationship between the rheological behaviors and the interfacial conditions were discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2913–2921, 2002     

Catalytic properties of ultrafine molybdenum-cerium oxide particles prepared by the sol-gel method

The structure and catalytic properties of ultrafine Mo-Ce oxide particles prepared by the sol-gel method have been studied by using X-ray diffraction, transmission electron microscopy, temperature-programmed reduction, laser Raman spectroscopy and microreactor tests. It has been shown that for selective oxidation of toluene to benzaldehyde the ultrafine Mo-Ce oxide particles exhibit higher catalytic activity than the larger oxide particles prepared by a conventional coprecipitation method. The unique catalytic properties of ultrafine Mo-Ce oxide particles may be correlated not only to the interaction between molybdenum oxide and cerium oxide, but also to the higher reactivity of lattice oxygen species in the ultrafine oxide matrix. This revised version was published online in July 2006 with corrections to the Cover Date.     

Application of non-fluorescent carbon particles as scavengers for heavy metal ions: A waste utilisation approach

In the preparation of fluorescent carbon nanoparticles, formation of non-fluorescent carbon particles (CPs) as waste matter is indispensible. This work is introducing CPs as adsorbents for some toxic metal ions in aqueous medium. CPs were characterised and their particle size, surface area, porosity, morphology etc. were compared with their parent material (charcoal). The effects of the initial metal ion concentration, contact time and pH on adsorption were undertaken. Adsorption data were evaluated for Langmuir and Freundlich isotherm models. The adsorption capacities (mg/g) of Ni²⁺, Pb²⁺, Zn²⁺, Co^2+, Cd²⁺ and Cu²⁺ were 85, 76, 75, 67, 58 and 46, respectively.     

Palladium on carbon nanofibers grown on metallic filters as novel structured catalyst

A novel composite material based on carbon nanofibers (CNF) grown on sintered metal fibers (SMF_Inconel) filter was investigated for its favorable properties as catalytic support. The CNF were formed directly over the SMF_Inconel by thermal (650 °C) chemical vapor deposition of ethane–hydrogen mixture. The CNF/SMF_Inconel composite consists of metal fibers entangled by CNF network of microns thickness and strongly anchored to the metal surface. The properties of the CNF/SMF_Inconel were controlled by the synthesis conditions. The CNF coating reduced the filter porosity and decreased the material permeability, but the pressure drop during the gas passage through the reactor remained low for CNF fraction <10%. Palladium was deposited on CNF previously activated by boiling in hydrogen peroxide. The activity and selectivity of Pd°/CNF/SMF_Inconel catalysts were tested in the selective hydrogenation of acetylene and compared with Pd supported on activated carbon fibers (Pd°/ACF). The TOF was one order of magnitude higher for Pd°/CNF/SMF_Inconel as compared to Pd°/ACF. This effect was attributed to a strong metal-support interaction of Pd°-nanoparticles with the graphitized CNF. The reaction was found to be structure sensitive leading to a decrease of TOF for the Pd°-particles <3 nm.     

不同变质程度超微煤粉对重金属离子的吸附性能

重金属离子由于具有毒性、难以生物降解且可在生物体内累积,严重威胁人类的身体健康。吸附是去除重金属离子的一种可行有效的方法。本文选择褐煤、烟煤、无烟煤3种变质程度不同的煤种,通过高能球磨获得超微煤粉。研究了3种超微煤粉对水溶液中Ni²⁺和Cr⁶⁺的吸附动力学与热力学以及投加量与pH值对吸附效果的影响。结果表明3种煤粉对Ni²⁺、Cr⁶⁺的吸附量均随时间的增加而增加,并且Ni²⁺的处理效果明显好于Cr⁶⁺,在180min时褐煤、无烟煤与烟煤对Ni²⁺、Cr⁶⁺的吸附量分别为3.906mg/g、3.582mg/g、2.983mg/g和1.953mg/g、1.774mg/g、0.487mg/g。3种煤粉对两种重金属离子的吸附均符合二级吸附动力学和Freundlich等温式,随着投加量与pH值的增加,去除效果增加,在相同条件下,褐煤的吸附效果优于烟煤与无烟煤。     

New carbon composites containing ultrafine Fe,Co, or Ni particles. 1. Facile synthesis by pyrolysis of organometallic polymers

Uniformly dispersed, air-stable carbon composites containing ultrafine α-Fe, Co, or Ni particles were obtained by a careful two-step thermal degradation of a copolymer of acrylonitrile (AN) and 2,4-hexadienyl-[tri(carbonyl)iron] acrylate. Carbonization yields were 45–55% and metal particle size ranged from 80 to 120 nm. Analogous degradation of the acrylonitrile copolymer with CoCl₂(AN)₂, CoCl₂(4-vinylpyridine)₂, or Ni(bis-styrene carboxylate) gave similar composites containing β-Co (18 nm), β-Co (55 nm), or cubic Ni (52 nm) particles, respectively, with lower carbonization yields. Other salient features noted for the metal-containing composites are progressive graphitization promoted by catalysis of nascent metal species at low temperature, microporous structures with surface areas of 75 and 55 m² g^?1 for Co and Ni composites, respectively, high electrical conductivities (10–10² S cm^?1), ferromagnetism, and catalysis in the decomposition of H₂O₂.     

Synthesis of carbon nanotubes on carbon fibers by means of two-step thermochemical vapor deposition

The present study aimed at development of a method for synthesizing multi-walled carbon nanotubes (CNTs) on carbon paper substrates (CP) at densities as high as those so far reported for CNTs formed on quartz substrates. Applying conditions optimized for CNTs synthesis on quartz substrates, in which CP was heated at 1073 K, being placed parallel to the flow of m-xylene/ferrocene vapor, resulted in formation of extremely few deposits on CP. Forced vapor flow through the CP greatly improved the frequency and homogeneity of deposition of the Fe-bearing nanoparticles, but these became encapsulated by carbon and deactivated. The addition of H₂S to the vapor further enhanced nanoparticle deposition. Moreover, it enabled the subsequent formation of CNTs at densities as high as 2-6 × 10⁹ cm⁻². In order to realize such high population densities, it was found essential to perform CVD in a two-stage sequence commencing with nanoparticles deposition at 1073 K followed by the formation and growth of CNTs at 1273 K, with the H₂S concentration in the vapor phase optimized throughout within a range of 0.014-0.034 vol%.     

增材制造连续碳纤维增强金属基复合材料性能

采用增材制造工艺方法进行具有高比强度、密度小等优良性能连续碳纤维增强金属基复合材料的直接制备。研究了连续碳纤维表面改性、路径搭接率、打印喷头温度、基板温度、打印速度等过程处理方法及工艺参数对所制备金属基复合材料抗拉强度的影响。研究结果表明,对连续碳纤维原材料实施表面改性处理,可以实现制备过程中熔融金属基体与连续碳纤维之间的良好浸润复合,以提高复合材料的抗拉强度;增大路径搭接率,可以有效提高增材制造复合材料内部纤维的体积占比,从而增大其抗拉强度;升高打印喷头温度、基板温度、打印速度,可以减小熔融金属表面张力,提高其流动性,并有利于沉积层间实现良好重熔,从而有效避免在已沉积层表面裂纹处和路径搭接区凹坑处形成气孔缺陷,进一步提升复合材料的抗拉强度。     

负载钌的氮掺杂石墨烯催化剂的制备及应用

利用人工合成的蒙脱石做硬模板,以插层的邻菲罗啉-钌络合物为前体,在惰性气氛下热解后用氢氟酸和盐酸刻蚀除去蒙脱石模板制备出负载钌纳米粒子的氮掺杂石墨烯催化剂(Ru-NG)。Ru-NG具有与模板蒙脱石类似的层状石墨烯结构,C、N、O及Ru元素在其上分布均匀。Ru-NG中钌的含量随钌前体的加入量的增加而增加,但受蒙脱石片层的物理限域作用及与含氮物种的配位作用,钌纳米粒子的粒径却无显著变化,且粒径均一,平均粒径在1.2～1.4 nm范围内。与传统浸渍-还原法制备的活性炭负载的Ru催化剂相比,Ru-NG在二氧化碳加氢生成甲酸反应中表现出优异的催化活性。     

Synthesis of ruthenium-embedded nitrogen-doped graphene for carbon dioxide hydrogenation

Two-dimensional (2D) layered materials have attracted great interest in the energy storage and catalysis field due to their graphene-like structure and excellent performance. Ruthenium-embedded nitrogen-doped graphene (Ru-NG) have been obtained by a novel method, using montmorillonite as hard template and Ru-phenanthroline chelate as precursor. After calcination in N₂ atmosphere at 800℃, Ru-NG were obtained and further characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and nitrogen sorption. Ru-NG have 2D layered structure just like the montmorillonite template, and C, N, O and Ru are homogeneously distributed on them. The average sizes of Ru nanoparticles do not change much with the increasing of Ru content, and they keep at about 1.2 to 1.4 nm. The XPS results indicate that phenanthroline has been successfully transformed to nitrogen-doped carbon during pyrolysis, and the peaks at 398.5, 400.1 and 401.5 eV suggest the presence of pyridine-like, pyrrole-like and quaternary nitrogen atoms, respectively. Compared with the Ru catalyst supported on activated carbon prepared by the traditional impregnation-reduction method, Ru-NG exhibits excellent catalytic activity in the reaction of hydrogenation of carbon dioxide to formic acid.     

The conductivity behavior of multi‐component epoxy,metal particle,carbon black,carbon fibril composites

Following the previous studies of epoxy/silver conductive composites, a detailed investigation of the influence of ethylene glycol on the resulting resistivity of various composites was carried out. Ethylene glycol was found to have a catalytic effect on the curing process of the epoxy resin, verified by differential scanning calorimetry studies. The accelerated curing process diminishes settling of the metal particles and therefore results in better and more uniform conductivities. High temperature curing of the composites was found to have a similar effect on the conductivity. The conductivity behavior of some other composites, such as epoxy/nickel, epoxy/nickel/carbon fibrils, and epoxy/carbon black/carbon fibrils, were also studied. The structure–property relations were better understood through scanning electron microscopy observations. Silver and nickel particles were found to perform differently in the cured epoxy, showing different percolation concentrations and conductivity levels. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1706–1713, 2002     

The influence of fuel type on carbon deposition over precious metal containing motorcycle catalysts

The influence of fuel type on carbon deposition over precious metal containing motorcycle catalysts was studied by SEM, EPMA, XPS, TG-DTA and FTIR. The results show that the carbonaceous species are in the form of C_xH_y if the vehicle is fueled with MTBE blended gasoline, whereas the carbonaceous species are C_xH_yO for blended ethanol fuel. The majority of the carbonaceous species are deposited on the PM sites. Further, aromatic rings, alkyl groups and their partial oxidation products are found in the carbonaceous deposit.     

Enantioselective hydrogenation of ethyl pyruvate catalysed by Pt/graphite: Superior performance of sintered metal particles

A 5% Pt/graphite catalyst has been sintered in 5% H₂/Ar at 400, 500, 600, 700, 800, and 1000 K and cinchonidine-modified samples used to catalyse enantioselective ethyl pyruvate hydrogenation at 293 K and 30 bar pressure. Changes in catalyst morphology on sintering have been investigated by high resolution electron microscopy and cyclic voltammetry. The as-received catalyst contained small Pt particles aggregated into clusters. As the temperature was raised these clusters disaggregated; the resulting small particles grew, first showing enhanced crystallinity and better defined step and terrace topography, and later progressive faceting. Ultimately the particles were large and hexagonal. These processes were accompanied by a loss of surface area and a reduction in catalytic activity. Enantiomeric excess rose from 43% for as-received material to 63% for catalyst sintered at 700 K, and declined for higher sintering temperatures. The particle size distribution for the optimal catalyst peaked at 8 nm and most particles were substantially faceted. Chiral performance is interpreted in terms of enhanced enantioselectivity provided by edge sites in the Pt surface. Modification of chiral kink sites by alkaloid, to give diastereomeric enantioselective sites may have further enhanced the enantioselectivity. The investigation provides clear objectives for future catalyst design.     

Synthesis and characterization of SiC ultrafine particles by means of sol-gel and carbothermal reduction methods

A modified sol–gel method is proposed for the preparation of silicon carbide ultrafine powders. In this method, tetraethoxysilane (TEOS) and saccharose are used for preparing a binary carbonaceous silicon xerogel, and ferric nitrate is employed in the sol–gel process as a catalyst. The influence of processing parameters such as temperature of reaction and mass ratio of C to Si (C/S_i =0.5, 0.7, 1) on the synthesis of SiC particles were studied. After purification, the SiC sample was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectrum, Fourier transform infrared spectroscopy, differential thermal analysis (DTA) and thermo- gravimetric analysis (TGA). The results show that the SiC ultrafine particles were fully formed at reaction temperature of 1450 °C by employing the mass ratio of C/S_i =1. This is confirmed by the obtained pattern from XRD and the Si–C absorption bands of SiC in the FTIR.     

Floating catalyst chemical vapor infiltration of nanofilamentous carbon reinforced carbon/carbon composites – Integrative improvement on the mechanical and thermal properties

Nanofilamentous carbon (NFC) reinforced carbon/carbon composites were produced by floating catalyst chemical vapor infiltration with ferrocene content ranging 0–2.0?wt%. The NFCs and increased graphitization degree led to an improvement on the mechanical and thermal properties. An excellent combination of high strength and thermal conductivity (TC), and low coefficient of thermal expansion (CTE) was reached by adding 0.5–0.8?wt% catalyst. When the content exceeded 0.8wt%, the strength and TC were decreased by the limited NFC growth and matrix transited from rough laminar to isotropic pyrocarbon. After the treatment of 2500?°C, the strength and CTE decreased whereas the TC was increased. With the catalyst contents at 0.5–0.8?wt%, the flexural and shear strength retention ratios achieved a high value of 73.1–74.5 and 79.1–79.4%, respectively, and the in-plane and out-of-plane TCs exhibited maxima of 339.1 and 72.5?W/(m?K). Relatively low CTE was obtained at 2.0?wt% catalyst owing to the increased amount of cracks and pores.