Amination of Polyethylene Glycol to Polyetheramine over the Supported Nickel Catalysts

Surface nickel (NiO _x ) species, surface NiAl _x O _y compound, and NiO crystallites are present on the Ni/Al₂O₃ catalysts, and the ratio of these nickel species is dependent on the nickel loading. Surface nickel interacts with the TiO₂ support to form a surface nickel titanate compound (NiTiO _x ) which has a lower reducibility. The weak interaction between the surface nickel and the silica support results in the formation of NiO crystallites on the SiO₂ surface. The Ni/Al₂O₃ and Ni/TiO₂ catalysts contain new surface Lewis acid sites and the amount of surface Lewis acid sites increases with increasing nickel concentration. The Ni/SiO₂ catalysts have no sign of the presence of the surface Lewis acid sites. Only the Ni/Al₂O₃ catalysts have shown the ammonia adsorption at temperature of 200°C. Supported nickel on alumina catalysts possess the highest amination conversion, and the amine yield increases with increasing nickel loading up to 15% and starts to level off. By comparing amination catalysis with quantitatively TPR studies of the H₂ consumed of the Ni/Al₂O₃ catalysts, it appears that the dispersed nickel species are the active sites for amination. In addition, the amination product is mainly the secondary amine due to the presence of water.     

Pulse study of methane partial oxidation to syngas over SiO2-supported nickel catalysts

Methane was pulsed over pure CuO and NiO as well as Cu/La₂O₃ and Ni/La₂O₃ catalysts at 600° C. Results indicate that the mechanisms for methane activation over copper and nickel are quite different. Over CuO, methane is converted to CO₂ and H₂O, most likely via the combustion mechanism; whereas metallic copper does not activate methane. Over NiO in the presence of metallic nickel sites, methane activation follows the pyrolysis mechanism to give CO, CO₂, H₂ and H₂O. Similar results were obtained over the Cu/La₂O₃ and Ni/La₂O₃ catalysts. XRD investigations indicate that copper and nickel existed as CuLa₂O₄ and LaNiO₃ respectively in the La₂O₃-supported catalysts. The effect of La₂O₃ on the activation of methane is discussed.     

Synthesis of spherical NiO nanoparticles using a solvothermal treatment with acetone solvent

Nanometer-sized nickel oxide (NiO) particles were synthesized by thermal reactions with nickel (II) carbonate as a metal-containing precursor and four solvents: water, ethanol, butanol, and acetone. The optimal reaction conditions to obtain spherical NiO were determined to be the acetone solvent, nickel carbonate precursor, and a reaction temperature and time of 200 °C and 48 h, respectively. TEM images revealed perfectly spherical NiO nanoparticles of size ranging from 2.0 to 10.0 nm in the acetone solvent. The reaction mechanism for the formation of the NiO nanoparticles is proposed based on a pathway of chelated Ni complex during crystal growth. Although metallic Ni was also formed from reactions using the two alcoholic solvents, the Ni(OH)₂ structure remained in the water solvent after thermal treatment.     

Ni–Nb–O mixed oxides as highly active and selective catalysts for ethene production via ethane oxidative dehydrogenation. Part I: Characterization and catalytic performance

This work demonstrates the high potential of a new class of catalytic materials based on nickel for the oxidative dehydrogenation of ethane to ethylene. The developed bulk Ni–Nb–O mixed oxides exhibit high activity in ethane ODH and very high selectivity (∼90% ethene selectivity) at low reaction temperature, resulting in an overall ethene yield of 46% at 400 °C. Varying the Nb/Ni atomic ratio led to an optimum catalytic performance for catalysts with Nb/Ni ratio in the range 0.11–0.18. Detailed characterization of the materials with several techniques (XRD, SEM, TPR, TPD-NH₃, TPD-O₂, Raman, XPS, electrical conductivity) showed that the key component for the excellent catalytic behavior is the Ni–Nb solid solution formed upon the introduction of niobium in NiO, evidenced by the contraction of the NiO lattice constant, since even small amounts of Nb effectively converted NiO from a total oxidation catalyst (80% selectivity to CO₂) to a very efficient ethane ODH material. An upper maximum dissolution of Nb⁵⁺ cations in the NiO lattice was attained for Nb/Ni ratios ⩽0.18, with higher Nb contents leading to inhomogeneity and segregation of the NiO and Nb₂O₅ phases. A correlation between the specific surface activity of the catalysts and the surface exposed nickel content led to the conclusion that nickel sites constitute the active centers for the alkane activation, with niobium affecting mainly the selectivity to the olefin. The incorporation of Nb in the NiO lattice by either substitution of nickel atoms and/or filling of the cationic vacancies in the defective nonstoichiometric NiO surface led to a reduction of the materials nonstoichiometry, as indicated by TPD-O₂ and electrical conductivity measurements, and, consequently, of the electrophilic oxygen species (O⁻), which are abundant on NiO and are responsible for the total oxidation of ethane to carbon dioxide.     

Plasma treatment of polymethyl methacrylate to improve surface hydrophilicity and antifouling performance

Surface modification of polymethyl methacrylate (PMMA) by O₂/CF₄ plasma is investigated to improve hydrophilicity and antifouling performance of PMMA. The PMMA surface before and after treatment is characterized by atomic force microscopy, contact angle measurement, and X-ray photoelectron spectroscopy. Antifouling properties are evaluated by protein adsorption and bacterial adhesion experiments using Staphylococcus aureus in vitro. Higher O₂ content in the mixture gas promotes hydrophilicity of the plasma-treated PMMA, while a hydrophobic surface forms at higher CF₄ content. Modifying PMMA improves antifouling performance regardless of the O₂/CF₄ volume ratio, and this improvement increases with rising CF₄ content in O₂/CF₄ plasma working gas. Functional groups C O and C F are detected in O₂/CF₄ plasma-treated PMMA surface and the ratio of C O to C F can be controlled by the O₂/CF₄ volume ratio in the plasma working gas.     

Effect of calcination temperature on catalyst reducibility and hydrogenation reactivity in rice husk ash–alumina supported nickel systems

Nickel catalysts supported on rice husk ash–alumina (Ni/RHA–Al₂O₃) were prepared by an incipient wetness impregnation method. Characterization included TGA, DSC, TPR, XRD, and BET. Results show that the decomposition of the nickel compound to nickel oxide was complete above 500 °C. The TPR analysis revealed a strong interaction between nickel and support, and a decrease in reducibility of NiO with increasing calcination temperature. The XRD analysis of Ni/RHA–Al₂O₃ catalyst precursors demonstrated the presence of spinel. It also showed that the size of crystallites in the supported NiO first decreased with increase in calcination temperature up to 700 °C, and then increased due to phase transformation of nickel oxide to spinel. The pores are mesopores and their meshy surface structure was not affected by calcination temperature in the range investigated. The catalytic activity was tested by CO₂ hydrogenation with an H₂/CO₂ ratio of 4/1 at 500 °C. The CO₂ conversion and CH₄ yield for CO₂ hydrogenation over 15 wt% Ni/RHA–Al₂O₃ catalyst were almost independent of calcination and reduction temperatures. Copyright © 2004 Society of Chemical Industry     

Die entscheidende Mitwirkung der Metall- und Sauerstoffionen von Nickeloxid beim Ablauf der Oxidation von o-Xylol

The Decisive Cooperation of Metal and Oxygen Ions of Nickel Oxide During the Oxidation of o-Xylene As can be concluded from the experimental results at 450°C in the reaction mixtures consisting of N₂ O₂-o-Xylene, both nickel oxide pure and doped with Li₂O or In₂O₃ is unsuited as catalyst for the oxidation of o-xylene to phthalic anhydride. In contrast to NiO which ionosorbs both oxygen and o-xylene, NiO Li₂O, a strong ionosorbent for o-xylene, prevents the ionosorption of oxygen because of the large concentration of holes. Since gaseous oxygen does not react with ionosorbed o-xylene but a reduction of nickel oxide to metallic nickel has been observed in spite of the fact of enough oxygen in the gas phase it can be assumed that o-xylene is forced to remove oxygen ions from the NiO lattice under generation of oxygen-ion vacanxies and nickel atoms. The predominant portions of the reaction products are H₂O and CO₂. With undoped nickel oxide and NiO In₂O₃ which were not reduced under the same experimental conditions, the reaction products had roughly the same composition. The reduction of NiO Li₂O however will be prevented in a gas mixture with a high oxygen pressure which oxidizes the formed nickel atoms on the surface of NiO Li₂O to nickel oxide making possible the entrance of oxygen from the gas phase and, therefore, the oxidation of o-xylene. A turbulent motion of a 2-component catalyst powder from NiO-1mole% Li₂O covered with ionosorbed o-xylene and ZnO-1mole% In₂O₃ covered with ionosorbed oxygen in the same gas mixture resulted in the same reaction products as in the presence of sole NiO Li₂O under simultaneous reduction of nickel oxide. From that we can conclude that the oxidation of o-xylene by oxygen ions of NiO occurs more easily than the reaction with ionosorbed oxygen on ZnO In₂O₃ which obviously seems to be bounded too strongly. This result is also confirmed by the prevention of the oxidation of gaseous o-xylene in the presence of only ZnO In₂O₃. Finally, the operation of the carrier catalyst V₂O₅/TiO₂ which is employed for the oxidation of o-xylene to phthalic anhydride will be prevented to a large extent in simultaneous presence of nickel oxide either pure or doped with Li₂O and In₂O₃ in roughly the same amount. This result can be mentioned as a proof for the interaction of a 2-component catalyst the mechanism of which is at present not satisfactorily understood.     

N2O Decomposition Catalysed by Transition Metal Ions

The ignition processes for the catalytic partial oxidation of methane (POM) to synthesis gas over oxidic nickel catalyst (NiO/Al₂O₃), reduced nickel catalyst (Ni⁰/Al₂O₃), and Pt-promoted oxidic nickel catalyst (Pt–NiO/Al₂O₃) were studied by the temperature-programmed surface reaction (TPSR) technique. The complete oxidation of methane usually took place on the NiO catalyst during the CH₄/O₂ reaction, even with a pre-reduced nickel catalyst, and Ni⁰ is inevitably first oxidized to NiO if the temperature is below the ignition temperature. It is above a certain temperature that Ni⁰ is formed again, which leads to the start of the POM. The POM can be initiated at a much lower temperature on a Pt–NiO catalyst because of Pt promotion of the reduction of NiO. The POM in a fluidized bed can be easily initiated due to the addition of Pt.     

Nucleation of metal clusters on plasma treated multi wall carbon nanotubes

The influence of a preliminary RF-plasma treatment of the multi wall carbon nanotube (MWCNTs) surface on the resulting overlayer morphology (dispersion, shape and size of metal clusters) formed by thermally evaporating Ag, Ni or Au atoms is studied. RF plasma treatments successfully bind polystyrene, oxygen, amine and fluorine chemical groups depending on the type of gas used for the treatment (styrene, O₂, Ar, NH₃ or CF₄) of the MWCNT surface. Transmission electron microscopy (TEM) analysis showed that the dispersion and size of the metal particles on MWCNT surface depend on the gas type used for plasma treatment, on the nature of the evaporated metal, on the MWCNT curvature and on the evaporation time.     

On the development of metallic inert anode for molten CaCl2–CaO System

Some fundamental aspects related to inert anode development in molten CaCl₂–CaO were investigated based on thermodynamic analysis, electrochemistry of metals and solubility of oxide measurements. The Gibbs free energy change of several key anodic reactions including electro-stripping of metals, electro-formation of metallic oxides, electro-dissolution of metallic oxides as well as oxygen and chlorine evolution was calculated and documented, for the first time, as a reference to develop metallic inert anode in chloride based melts. The anodic behaviors of typical metals (Ni, Fe, Co, Mo, Cu, Ag, and Pt) in the melt were investigated. The results confirmed the thermodynamic stability order of metals in the melts and revealed that surface oxide formation can increase the stability of the electrodes in CaO containing melt. Furthermore, solubility of several oxides (NiO, Fe₂O₃, Cr₂O₃, Co₃O₄, NiFe₂O₄) in pure CaCl₂ or CaCl₂–CaO melts was measured to evaluate the stability of oxide coating or a cermet inert anode in the melt. It was found that the solubility of NiO decreased with increasing CaO concentration, while that of Fe₂O₃ increased. Ni coated with NiO film had much higher stability during anodic polarization.     

Surface energy of the plasma treated Si incorporated diamond-like carbon films

Surface energy and surface chemical bonds of the plasma treated Si incorporated diamond-like carbon films (Si-DLC) were investigated. The Si-DLC films were prepared by r.f. plasma assisted chemical vapor deposition using benzene and diluted silane (SiH₄/H₂ = 10:90) as the precursor gases. The Si-DLC films were subjected to plasma treatment using various gases like N₂, O₂, H₂ and CF₄. The plasma treated Si-DLC films showed a wide range of water contact angles from 13.4° to 92.1°. The surface energies of the plasma treated Si-DLC films revealed a high polar component for O₂ plasma treated Si-DLC films and a low polar component for CF₄ plasma treated Si-DLC films. The CF₄ plasma treated Si-DLC films indicated the minimum surface energy. X-ray photoelectron spectroscopy (XPS) revealed that the polarizability of the bonds present on the surface explains the hydrophilicity and hydrophobicity of the plasma treated Si-DLC films. We also suggest that the O₂ plasma treated surface can provide an excellent hemocompatible surface from the estimated interfacial energy between the plasma treated Si-DLC surface and human blood.     

Corrosion of nickel in sodium sulphate-sodium chloride melts. Part I

The corrosion behaviour of Ni in molten Na₂SO₄, NaCl, and in mixtures of these two salts, at 900° C, in laboratory air and under O₂+SO₂/SO₃ atmospheres has been examined by electrochemical curves and topochemical analysis of corrosion products.Ni passivity in pure Na₂SO₄ was observed under potentiodynamic and potentiometric conditions, the passive film corresponding to NiO. Passivity was not so easy to achieve in chloride melts as in sulphate alone, but once a thick oxide film forms on the specimen, the Cl^– addition is accompanied by an increase in the film stability. The inhibiting role of NaCl on Ni in the passive-transpassive area was also evidenced. In opposition, halide additions (especially those up to 25%) increased the dissolution current densities of Ni in the active region. These higher dissolution rates are represented by the equation Ni₃S₂+4NaCl+1/2 O₂ = 2NiCl₂+2Na₂S + NiO which is also suggested as a critical factor in the Ni passivation.The passive capability found for Ni in Na₂SO₄/NaCl melts, in air, is destroyed by SO₃ atmospheres. This corrosion-stimulation is due to the SO₃ role in promoting reactions such as NiS + 3O^2– = Ni²⁺+SO₃+8e which would be potential-determining at the Ni surface until Ni²⁺ precipitates or the conjugate oxygen cathodic reduction process takes place. Microprobe analysis also evidenced S penetration which might be the reason for the Ni embrittlement.The polarization curves for Ni in pure NaCl showed the lack of a passive region; occurrence of extensive intergranular attack was also indicated by metallographic observation. The observed dissolution must occur at the expense of the Ni interactions with the species which intervene in the reaction equilibrium between O₂ and molten NaCl (O₂, Cl^–, Cl₂ and O^2–) as well as with the Na⁺ cations, as has been discussed elsewhere. Its self-sustaining nature is enhanced by the continuous reduction of the nickel ion content of the melt by NiCl₂ evaporation.     

The electrodepositions of copper and nickel from trifluoroacetate-H2O baths

In the present study, the electrodepositions of copper from the Cu(CF₃COO)₂CF₃COOHH₂O bath and nickel from the Ni(CF₃COO)₂NH₄ClH₂O bath, were studied.In the copper electrodeposition from Cu(CF₃COO)₂ (100 g/l)CF₃COOH(0.1 N)H₂O bath, the cathode current efficiency showed about 100% and the anode current efficiency showed over 100% at low cd. In the nickel electrodeposition from Ni(CF₃COO)₂ (200 g/lH₄Cl(15.0 g/l)H₂O bath, the efficiencies of the cathode and anode were about 100%. The range of current density to obtain bright and smooth copper and nickel deposits were 4.0 ～ 24 A/dm², 5.0 ～ 16 A/dm² respectively, and the cross-section of the electrodeposits showed a granular structure.The rates of the electrodeposition of copper and nickel from the above-mentioned baths were controlled by the charge-transfer reaction in the same way as in the reaction in non-aqueous solution[1, 2].     

Temperature-programmed reduction of NiOWO3/Al2O3 Hydrodesulphurization catalysts

Temperature-programmed reduction patterns are reported of NiO/Al₂O₃, WO₃/Al₂O₃, and NiOWO₃/Al₂O₃ catalysts, and of bulk oxides relevant to these catalysts. At loadings below 10% NiO and 19% WO3 nickel and tungsten are present as disperse species and no bulk oxides are found on the support. Tungsten forms a stable monolayer species which is extremely difficult to reduce. At high temperatures of reduction tungsten metal is formed without the intermediate formation of WO₂. Several nickel species were detected in the supported catalysts, and their characters and amounts depend on the loading and the temperature of calcination. After calcination at low temperatures and at low loadings (2% NiO) nickel is incorporated in the surface layers of the support; at higher loadings a NiO like species is formed which is more difficult to reduce than bulk NiO because of the interaction with the aluminium ions of the support. A high temperature of calcination favours the formation of a diluted spinel phase at the expense of the surface phases. In NiOWO₃/Al₂O₃ catalysts a fraction of nickel is present in a mixed NiWOAl phase which is formed by incorporation of nickel in a tungsten containing surface layer. At high temperatures of calcination some disperse NiWO₄ is formed. It is shown that there are two causes for a strong interaction between nickel species and the support: incorporation of nickel ions in the surface layers of the support during impregnation, and solid-state diffusion during calcination of the catalysts. The nickel containing species which are the precursor to the active phases in sulfided HDS catalysts are identified as the nickel species in the surface layers of the support in NiO/Al₂O₃ samples, and the NiWOAl phase in NiOWO₃/Al₂O₃ catalysts.     

Characterization of highly dispersed Ni/Al2O3 catalysts by EXAFS analysis of higher shells

The size and morphology of Ni/Al₂O₃ catalysts in the oxidic, reduced, and passivated state were determined by EXAFS analysis of the higher shells around the Ni atoms. In the oxidic state, the Ni cations were present in small NiO_x particles with predominant (111) plane. Below 4.5 wt% Ni loading, the NiO_x particles consisted of one Ni layer, and of two or three Ni layers above 4.5 wt% Ni. A Ni–Al contribution was observed in samples with low Ni loading. The layer which is in contact with the Al₂O₃ surface is affected by the support surface and its structure is highly distorted, while the other layers were not distorted and have a structure similar to that in bulk NiO. In the reduced state, the number of Ni metal atoms in the reduced Ni particles was smaller than 100 with a narrow distribution below a loading of 15.6 wt% Ni. Above this loading, the particle size suddenly increased and the distribution became wider. The distances and Debye–Waller factors were similar to those of bulk nickel which suggested a weak interaction between the particles and the support. In the passivated state, Ni kernels with 20–40 metal atoms were covered by a one layer thick NiO skin. This revised version was published online in June 2006 with corrections to the Cover Date.     

Spark plasma sintering technique for reaction sintering of Al2O3/Ni nanocomposite and its mechanical properties

Al₂O₃/Ni nanocomposites were prepared by spark plasma sintering (SPS) using reaction sintering method and the mechanical properties of the obtained nanocomposites are reported. The starting materials of Al₂O₃–NiO solid solution were synthesized from aluminum sulfate and nickel sulfate. These Al₂O₃–NiO powders were changed into Al₂O₃ and Ni phases during sintering process. The obtained nanocomposites showed high relative densities (>98%). SEM micrographs showed homogeneously dispersed Ni grains in the matrix. The 3-point strength and the fracture toughness of the composites significantly improved from 450 MPa in the monolithic α-Al₂O₃ to 766 MPa in the 10 mol% (2.8 vol.%) Ni nanocomposite and from 3.7 to 5.6 MPa m^1/2 in 13 mol% (3.7 vol.%) Ni nanocomposite. On the other hand, Young's modulus and Vickers hardness of the nanocomposites were mostly same as those of the monolithic α-Al₂O₃.     

Cyclophosphazene-containing Polymers as Imprint Lithography Resists

We present the evaluation of a cyclophosphazene-containing polymer as a patternable resist for imprint lithography. Hexamethacryloxybutoxycyclotriphosphazene layers containing small amounts of photoinitiator can be applied to silicon wafers substrates by spin coating techniques and cured photochemically to give tough, network polymer thin films. The films were characterized by FT-IR. Thin films approximately 200 nm in thickness were subjected to anisotropic O₂ and CF₄ plasmas and the etch rates were determined. The polymer films etch at a rate of 21 Å/s in CF₄ plasma, and as low as 1.6 Å/s in O₂ plasma, which is comparable or lower than the rates observed with commercially available silicon-containing photoresists. The surface chemical composition was surveyed by X-ray photoelectron spectroscopy, which gave results consistent with the formation of an etch resistant phosphorus-rich layer during reaction with O₂ plasma. The polymer was processed by nano-contact molding imprint lithography and replicated 200 nm period test patterns. This report is the first demonstration of a cyclophosphazene-containing polymer as a resist candidate for high-resolution lithography.     

Characteristics of NiO films prepared by atomic layer deposition using bis(ethylcyclopentadienyl)-Ni and O<Subscript>2</Subscript> plasma

Plasma-enhanced atomic layer deposition (PEALD) is well-known for fabricating conformal and uniform films with a well-controlled thickness at the atomic level over any type of supporting substrate. We prepared nickel oxide (NiO) thin films via PEALD using bis(ethylcyclopentadienyl)-nickel (Ni(EtCp)₂) and O₂ plasma. To optimize the PEALD process, the effects of parameters such as the precursor pulsing time, purging time, O₂ plasma exposure time, and power were examined. The optimal PEALD process has a wide deposition-temperature range of 100–325 °C and a growth rate of 0.037±0.002 nm per cycle. The NiO films deposited on a silicon substrate with a high aspect ratio exhibited excellent conformality and high linearity with respect to the number of PEALD cycles, without nucleation delay.     

Evaluation of electroactive intermediate states in anodic O2 evolution at chemically formed nickel oxide: Comparison with behaviour at nickel metal anodes

The behaviour of the kinetically involved intermediate states arising in the electrocatalysis of anodic oxygen evolution at chemically formed, high-area nickel oxide (NiO·OH) films on nickel metal as substrate is examined by means of analysis of potential (V) decay transients, following interruption of anodic polarization currents at various overpotentials. The potential decay behaviour is treated in terms of the dependence ofV(t) on log (time,t), and of ln (–dV/dt) as f[V(t)]. The pseudocapacitance associated with the potential-dependence of the coverage or surface density of the overpotential-deposited species involved as intermediates in the reaction at the oxide electrode surface is evaluated jointly from the potential decay and Tafel polarization behaviour, following procedures developed recently.In anodic O₂ evolution on oxide surfaces, such as NiO·OH, the intermediate states in the kinetics of the reaction are to be identified as OH or O species coupled with potential-dependent Ni(III) and Ni(IV) oxidation states of nickel, and the surface density of these states can be evaluated experimentally.The results obtained for anodic O₂ evolution on the chemically formed nickel oxide films are compared with the behaviour at anodically formed thin oxide films on nickel metal.     

The Effect of Nickel on the Conversion of Amorphous Iron(III) Hydroxide into more Crystalline Iron Oxides in Alkaline Media

The effect of nickel (Ni) on the transformation of amorphous iron(III) hydroxide into more crystalline iron oxides has been followed using X-ray powder diffraction and chemical analysis. One aim of this study was to determine the fate of Ni that had been co-precipitated with amorphous iron(III) hydroxide as the amorphous phase recrystallised. Ni/amorphous iron(III) hydroxide co-precipitates transformed into Ni substituted α-FeOOH or α-Fe₂O₃, NiFe₂O₄ and α-3Ni(OH)₂.2H₂O in alkaline media. The type of reaction products formed depended on the concentration of Ni in the system and on the pH. Ni retarded the crystallisation of amorphous iron(III) hydroxide by stabilising the co-precipitate both against dissolution leading to α-FeOOH and against the internal rearrangement process which leads to α-Fe₂O₃. Chemical analysis showed that Ni was incorporated into the structure of α-FeOOH to a maximum level of 5.5 mol% and into the structure of α-Fe₂O₃ to up to 7 mol%. Excess Ni was adsorbed on the surface of the iron oxide or taken up by NiFe₂O₄ or the pure Ni phase. The b₀ dimension of the unit cell increased from 0.9960 nm for α-FeOOH to 0.9965 nm for α-FeOOH with 5.5 mol% Ni substitution. The same maximum level of Ni could be incorporated in the α-FeOOH structure in the presence of either Mn (up to 8 mol%) or Co (up to 7 mol%).