Preparation and characterization of aluminosilicate supports with a synthesized layer of catalytic filamentous carbon: I. Synthesis of carbon nanofibers on a supported nickel catalyst

The synthesis of catalytic filamentous carbon (CFC) on a Ni catalyst supported by homogeneous precipitation onto the surface of aluminosilicate ceramic supports (honeycomb monoliths, ceramic foam, glass foam, and haydite) was studied. The effects of CFC synthesis conditions (the catalyst concentration on a support, the pyrolysis temperature of a propane-butane mixture, and the composition of the gas mixture) on the specific surface areas of supports, the yield of carbon, and the morphology of a surface CFC layer were examined. As found by scanning electron microscopy, the uniformity of distribution and the size of carbon nanofibers synthesized depended on the conditions of their synthesis. The resulting CFC-containing supports were tested as adsorbents for the immobilization of enzymatically active substances (individual enzymes, cell membranes, and microorganisms) in order to prepare highly stable heterogeneous catalysts for biotechnology and biocatalysis.     

Preparation and characterization of aluminosilicate supports with a synthesized layer of catalytic filamentous carbon: II. Synthesis of carbon nanofibers on a supported cobalt catalyst

The synthesis of a layer of catalytic filamentous carbon (CFC) on a Co catalyst supported by homogeneous precipitation onto the surface of aluminosilicate supports (ceramic foam and vermiculite) was studied. The effects of CFC layer synthesis conditions (the catalyst concentration on a support, the pyrolysis temperature of a propane-butane mixture, and the composition of the gas mixture) on the specific surface areas of supports, the yield of carbon (g C)/(g Co)), and the morphology of a surface CFC layer were examined. It was found that, in the case of ceramic foam, the concentration of cobalt hydroxide precipitated on the surface was lower by a factor of 15 and the yield of carbon was higher by a factor of 20–40 than those in vermiculite. The specific surface areas of supports, the yield of carbon, and the amount of synthesized carbon increased as the pyrolysis temperature of a propane-butane mixture was increased from 500 to 600°C. As found by scanning electron microscopy, the carbon content increased with pyrolysis temperature because of an increase in the length of carbon nanofibers. The properties (activity and stability) of biocatalysts prepared by the adsorption immobilization of a recombinant protein having glucose isomerase activity on CFC-Co-containing supports (ceramic foam and vermiculite) were studied.     

Preparation and characterization of supports with a synthesized layer of catalytic filamentous carbon: IV. Synthesis of carbon nanofibers on a Co/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst

A comparative study of the synthesis of carbon layers, including catalytic filamentous carbon, on the surface of various alumina modifications was made. The synthesis was performed by the pyrolysis of alkanes (a propane-butane mixture) on Co/Al₂O₃ supported catalysts. The texture characteristics (specific surface area and pore structure) of the starting supports and adsorbents with a synthesized carbon layer were studied. The surface morphology of Co/Al₂O₃ catalysts and the synthesized carbon deposits was studied by scanning electron microscopy. It was found that carbon nanofibers were formed only on the catalysts prepared by the homogeneous precipitation of Co compounds onto the surface of macroporous α-Al₂O₃, whereas carbon deposits on mesoporous aluminum oxides did not exhibit a pronounced fibrous structure. The applicability of C/Co/Al₂O₃ carbon-containing adsorbents to the immobilization of the nitrile hydratase enzyme and the preparation of a biocatalyst for acrylonitrile hydration to acrylamide was considered.     

Formation of a supported cobalt catalyst for the synthesis of carbon nanofibers on aluminum oxide

Comparative studies of the effect of the physicochemical characteristics of a support (aluminum oxide) on the formation of a supported Co catalyst and its activity in the pyrolysis of alkanes (propane-butane) were performed. The effect of the crystalline modification of alumina on the yield of catalytic filamentous carbon (CFC) ((g CFC)/(g Co)) was studied. The surface morphologies of Co-containing catalysts and synthesized carbon deposits were studied by scanning electron microscopy. It was found that carbon deposits with a well-defined nanofiber structure were synthesized by the pyrolysis of a propane-butane mixture in the presence of hydrogen at 600°C on supported Co catalysts prepared by homogeneous precipitation on macroporous corundum (α-Al₂O₃). The yield of CFC was no higher than 4 (g CFC)/(g Co). On the Co catalyst prepared by homogeneous precipitation on mesoporous Al₂O₃, the intense carbonization of the initial support; the formation of cobalt aluminates; and, as a consequence, the deactivation of Co⁰ as a catalyst of FC synthesis occurred. The dependence of the yield of CFC on the preheating temperature (from 200 to 800°C) of Co catalysts before pyrolysis was studied. It was found that, as the preheating temperature of supported Co/Al₂O₃ catalysts was increased, the amount of synthesized carbon, including CFC, decreased because of Co⁰ deactivation due to the interaction with the support and coke formation.     

Preparation and characterization of nanoporous carbon supports on a nickel/sibunit catalyst

A nanoporous composite carbon material was developed; this material was prepared by the synthesis of catalytic filamentous carbon (CFC) on a Ni catalyst supported onto the Sibunit carbon support. The texture characteristics (specific surface area and pore structure) of this material were studied. The effects of the conditions of supporting bivalent nickel compounds from aqueous or water-ethanol solutions in the presence of urea and the pretreatment of the parent Sibunit (oxidation and reduction) on the yield of synthesized carbon were considered. The distribution of Ni inside a Sibunit granule was studied using energy dispersive X-ray microanalysis. The surface morphology of the Ni/Sibunit catalyst, as well as the synthesized carbon layer, was studied by scanning electron microscopy. It was found that a maximum yield of carbon (50–60 g/(g Ni)) was obtained on the precipitation of nickel compounds from water-ethanol solutions with an ethanol concentration of 5 to 50 vol %. The preliminary surface oxidation or reduction of the parent Sibunit resulted in a considerable decrease in the yield of carbon (by a factor of 2 or more). The parent Sibunit phase occurred within the prepared nanoporous carbon material, whereas a shell formed by CFC occurred on the outside.     

Synthesis and characterization of nickel catalysts supported on different carbon materials

Nickel catalysts supported on various carbon materials such as multiwall carbon nanotubes, shortened length carbon nanotubes, graphite and amorphous carbon were synthesized, characterized and tested in cyclohexene hydrogenation reaction. We have found that carbon nanotube supports are superior to graphite and amorphous carbon both in terms of catalytic activity and stability.     

Ketiminate supported aluminum(III) complexes: Synthesis, characterization and reactivity

The reaction of LLi, (L = [RNC(Me)CHC(Me) = O] (R = C₂H₄NEt₂)), with AlCl₃ at −78 °C forms the mono-ketiminate product, LAlCl₂, 1, while the same reaction at 0 °C affords the bis-ketiminate complex, [{(LH)₂AlCl}(Cl₂)], 2, Reduction of 1 with Li^o, K^o or Mg^o yielded an unusual dimeric aluminum(III) species, [L′AlCl]₂, 3, where C-C coupling of the ligand backbone is observed.     

Synthesis of nickel nanoparticles and carbon encapsulated nickel nanoparticles supported on carbon nanotubes

Nickel nanoparticles were prepared and uniformly supported on multi-walled carbon nanotubes (MWCNTs) by reduction route with CNTs as a reducing agent at 600 °C. As-prepared nickel nanoparticles were single crystalline with a face-center-cubic phase and a size distribution ranging from 10 to 50 nm, and they were characterized by transmission electron microscopy (TEM), high-resolution TEM and X-ray diffraction (XRD). These nickel nanoparticles would be coated with graphene layers, when they were exposed to acetylene at 600 °C. The coercivity values of nickel nanoparticles were superior to that of bulk nickel at room temperature.     

Synthesis of carbon nanofibers by catalytic pyrolysis of ethylene and methane on hydrides of intermetallic compounds of lanthanum with nickel

Carbon nanofibers were synthesized by the pyrolysis of ethylene and methane on hydrides of intermetallides LaNi_nH_x (n = 2, 3, 5; x = 0.1–4). The influence of parameters of the synthesis (temperature and the ratio of gases in an Ar: H₂: C₂H₄ (CH₄) mixture) on the structure of nanofibers thus formed was studied. Hydrides of nickel intermetallides are more efficient catalytic systems than metallic nickel. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2210–2214, October, 2005.     

Synthesis of catalytic filamentous carbon on a nickel/graphite catalyst and a study of the resulting carbon-carbon composite materials in microbial fuel cells

The carbon-carbon composite materials obtained via the synthesis of catalytic filamentous carbon (CFC) on a Ni/graphite supported catalyst in the process of the pyrolysis of C₃–C₄ alkanes in the presence of hydrogen were systematically studied. The effects of the following conditions on the catalytic activity expressed as the yield of carbon (g CFC)/(g Ni) and on the character of CFC synthesis on graphite rods were studied: procedures for supporting Ni(II) compounds (impregnation and homogeneous precipitation), the concentrations of impregnating compouds (nickel nitrate, urea, and ethyl alcohol) in solution, graphite treatment (oxidation) conditions before supporting Ni(II) compounds, and the pyrolysis temperature of C₃–C₄ alkanes in the range of 400–600°C. Optimum conditions for preparing CFC/graphite composite materials, which are promising for use as electrodes in microbial fuel cells (MFCs), were chosen. The electrochemical characteristics of an MFC designed with the use of a CFC/graphite electrode (anode) and Gluconobacter oxydans glycerol-oxidizing bacteria were studied. The morphology of the surfaces of graphite, synthesized CFC, and also bacterial cells adhered to the anode was studied by scanning electron microscopy.     

Preparation and characterization of modified aluminum oxide catalysts

The formation of individual and modified high-purity aluminum oxides (γ-Al₂O₃) prepared from aluminum alcoholates was studied. In the study of the hydrolysis of aluminum alcoholates and modified (Zr, Ti, and Si) aluminum alcoholates, it was found that an increase in the chain length of the alkoxy group and an increase in the aging temperature or aging time in mother liquor resulted in a decrease in the concentration of an amorphous phase, an increase in the concentration of a pseudoboehmite phase, and an improvement in its crystal structure. Hydrolysis in alkaline (a 0.5 wt % solution of ammonia) or neutral solutions made it possible to obtain samples with an almost 100% pseudoboehmite content. At the same time, the samples prepared by hydrolysis in an acidic solution (a 0.1 M solution of HCl) contained a considerable amount of an amorphous phase. It was found that the specific rate of dehydration of n-butanol on the modified aluminum oxide samples linearly decreased with the concentration of donor sites and linearly increased with the concentration of acceptor sites, whose concentration was measured using the spin probe method.     

Kinetics of the catalytic transformation of isobutene into methacrylonitrile with NO on supported nickel oxide aerogel

Kinetic studies of the nitroxidation of isobutene by NO show that the reaction follows a redox mechanism in the temperature range of 300–400°C. This mechanism implies an interaction between dehydrogenated isobutene -allyl radical and atomic nitrogen due to the decomposition of NO by the reduced catalyst, which is then reoxidized.

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NO , 300–400°C. - , NO , .

     

Synthesis, characterization and formation process of transition metal oxide nanotubes using carbon nanofibers as templates

Mono and binary transition metal oxide nanotubes could be synthesized by the immersion of carbon nanofiber templates into metal nitrate solutions and removal of the templates by heat treatment in air. The transition metal oxide nanotubes were composed of nano-crystallites of metal oxides. The functional groups on the carbon nanofiber templates were essential for the coating of these templates: they acted as adsorption sites for the metal nitrates, ensuring a uniform metal oxide coating. During the removal of the carbon nanofiber templates by calcination in air, the metal oxide coatings promoted the combustion reaction between the carbon nanofibers and oxygen.     

Formation of a nickel catalyst on the surface of aluminosilicate supports for the synthesis of catalytic fibrous carbon

Conditions for the homogeneous precipitation of nickel hydroxide in the presence of urea onto the surface of aluminosilicate honeycomb monoliths, which were prepared based on clay, talc, and amorphous aluminum hydroxide, were examined. Factors affecting the concentration of supported nickel (synthesis time, starting solution concentrations, loaded amount of the support, and support calcination temperature) were studied. The possibility of supporting nickel hydroxide onto the surface of cellular ceramic foam, glass foam, and haydite was demonstrated. The morphology of nickel hydroxide particles, nickel metal particles on support surfaces, and carbon coatings synthesized in the course of the catalytic pyrolysis of a propane-butane mixture was studied by scanning electron microscopy.     

Preparation and characterization of helical carbon/silica nanofibers with lamellar mesopores on the surfaces

Helical 1,2-ethylene-silica nanofibers with lamellar mesopores on the surfaces and twisted rod-like mesopores inside were prepared according to literature procedures. After carbonization, helical carbon/ silica nanofibers with lamellar mesopores on the surfaces and twisted rod-like micropores inside were obtained. The morphologies and pore architectures of the carbon]silica nanofibers were characterized using transmission electron microscopy, field-emission scanning electron microscopy, powder X-ray diffraction and N2 sorptions. Although the mesopores inside shrank into micropores, the helical nanostructure remained. Moreover, several carbon/silica nanofibers with lamellar mesopores on the surfaces and concentric circular micropores inside were also obtained. After being calcined in air, helical silica nanofibers with lamellar mesopores on the surfaces and twisted rod-like micropores inside were produced as well.     

Some physico-chemical and catalytic properties of nickel(II) oxide promoted with gadolinium(III) oxide

Chemical and phase compositions of NiO–Gd₂O₃ catalysts have been studied. It has been found that the Gd₂O₃ dopant retards the sintering of NiO and increases its deviation from stoichiometry. Catalytic activity for CO oxidation does not change monotonically with an increase in Gd₂O₃ content in the catalysts.

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NiO–Gd₂O₃ . , Gd₂O₃ NiO - . Gd₂O₃ .

     

Fe2O3/Al2O3催化氧化苯偶姻制备苯偶酰

考察了几种常用载体负载金属氧化物催化分子氧氧化苯偶姻制备苯偶酰的性能 ，发现氧化铁、三氧化二铝催化活性较高，稳定性较好。以吡啶为溶剂，用483K下 活化的含铁14．8％的氧化铁／三氧化二铝作催化剂，当其用量为苯偶姻用量20％ （质量分数），253K下反应1h,苯偶酰平均产率98．1％。用IR，MS，和^1H NMR光 谱对其结构进行了表征。     

高比表面积介孔氧化镍制备及表征

采用硝酸镍和草酸为原料,采用固态热分解法制备得到高比表面积的介孔Ni O纳米粒子,考察了原料的用量,热处理的温度,热处理的时间对孔结构的影响。用X射线衍射、透射电镜、扫描电镜和N2吸附-脱附技术对材料的物化性质进行了表征。结果表明:硝酸镍和草酸1∶1混合均匀、400℃灼烧4 h得到的介孔Ni O粒子的孔结构为最发达的蠕虫状介孔结构,比表面积和孔容分别达到236 m2·g-1和0.42 cm3·g-1。     

Fabrication and characterization of silver nanostructures conformal coating layer onto electrospun N6 nanofibers with improved physical properties

In this communication, colloidal silver (Ag) nanostructures were synthesized and deposited directly onto electrospun nylon 6 (N6) fibers without using surface modifier in the form of an ultrathin conformal coating layer via a hydrothermal treatment. The morphological, structural, and thermal properties of the Ag/N6 nanocomposite membranes were analyzed by field-emission scanning electron microscopy (FESEM), X-ray diffraction, X-ray photoelectron spectroscopy, and differential scanning calorimetry (DSC). FESEM imaging showed that the Ag coating on individual N6 nanofibers was continuous, uniform, and compact. A DSC study of the nanocomposites illustrated a strong interfacial adhesion of the Ag layer with N6 nanofiber surfaces via strong hydrogen bonds. A possible mechanism for hydrogen bond formation during the hydrothermal process was proposed. Further, it was found that the transition of the meta-stable γ-form into the thermodynamically more stable α-form of N6 structure was achieved; therefore, the hydrothermal process did not cause chain degradation.     

Synthesis and studies on dichloro iodo triphenylphosphine oxide nickel(III)

A new compound of nickel(III), [Ni(OPPh₃)Cl₂I] has been prepared by the action of nitrosyl chloride or chlorine gas on [Ni(PPh₃)₂I₂]. Various physical studies of the compound are reported.