Temperature programmed reduction studies of nonpyrophoric Raney nickel catalysts

Temperature programmed reduction studies have revealed that the surface of nonpyrophoric Raney nickel catalysts is covered by readily reduceable nonstoichiometric metaloxygen structures. A method is suggested to calculate kinetic reaction parameters on the basis of analyzing the shape of one of the TPR curves.

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Structural studies of nickel-based Raney catalysts

Electron microscopy and Mössbauer spectroscopy studies of nickel-based Raney catalysts have revealed that the catalysts are formed through the successive aggregation of their structural elements. Catalyst particles are covered by a thin layer of nickel oxide.

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Investigation of the pore structure of Raney nickel catalysts

Ar and N₂ adsorption and capillary condensation studies at 77.4 and 84K on Raney nickel catalysts modified by Ti, V, Cr, Mn, Zr, Mo, Ta, W, Re and on BAU char coal show that at 77.4K, in pores with d_eff>100Å, argon exists in the solid state.

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Ar N₂ 77,4 84°K - , Ti, V, Cr, Mn, Zr, Mo, Ta, W, Re , d>100 Å 77,4 °K .

     

Studies of the structure of multicomponent Raney nickel catalysts

Genesis and structure of Raney nickel catalysts modified by Mo, Fe and Ca have been studied by XPS, SIMS and Auger and electron microprobe methods. It has been established that these catalysts are inhomogeneous and their structure can be described by models accounting for the interaction and localization character of metal components, their oxides and hydroxides.

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, - Ni-, Mo, Fe Ca. , , , .

     

Kinetics and mechanism of the hydrogenation of substituted anthraquinones on Raney nickel catalysts

The rate and direction of the hydrogenation of anthraquinone has been established to depend considerably on the nature and position of the substituent as well as on the structure and phase composition of the catalyst. The selectivity of the process is increased by introducing electronaccepting substituents into the anthraquinone molecule or upon doping the Ni–Al alloy by additives increasing the M–H bond energy.

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, . Ni–Al , M–H, .

     

Study of vanadium distribution in supported V?Mg catalysts by XPS and SIMS

The catalyst surface is occupied predominantly by mono- and bilayer vanadium oxide species, vanadium being mainly in the form of polylayer species that occupy a small part of the surface.

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Surface studies of halloysite nanotubes by XPS and ToF‐SIMS

This report provides detailed experimental results of thermal and surface characterization on untreated and surface‐treated halloysite nanotubes (HNTs) obtained from two geographic areas. Surface characterization techniques, including XPS and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) were used. ToF‐SIMS surface analysis experiments were performed with both atomic and cluster ion beams. Higher ion yields and more high‐mass ions were obtained with the cluster ion beams. Static ToF‐SIMS spectra were analyzed with principal component analysis (PCA). Morphological diversities were observed in the samples although they mainly contained tubular structures. Thermogravimetric data indicated that aqueous hydrogen peroxide solution could remove inorganic salt impurities, such as alkali metal salts. The amount of grafting of benzalkonium chloride of HNT surface was determined by thermogravimetic analysis. PCA of ToF‐SIMS spectra could distinguish the samples mined from different geographical locations as well as among surface‐treated and untreated samples. Copyright © 2010 John Wiley & Sons, Ltd.     

Reusable,magnetic Raney nickel based palladium catalysts for the Heck coupling in aqueous media

Russian Chemical Bulletin - Hybrid materials based on Pd- and Cu-doped Raney nickel appeared to be highly efficient catalysts for the Heck reaction in aqueous media in the absence of organic...     

XPS and SIMS investigations on plasma-treated glass surfaces

Commercially available float-glass samples were exposed to ion bombardment in an HF-plasma. This should form an SiO₂-rich layer close to the surface of the samples. From XPS-investigations it was found that treatment times between 2 and 4 min in Ar plasma lead to a pronounced depletion of alkalis. Further FAB-SIMS depth profiles gave additional information about the extension of the layers with altered stoichiometry.     

Hydrogenation of nitrobenzonitriles using Raney nickel catalyst

2-, 3-, 4-Nitrobenzonitriles were hydrogenated using Raney nickel catalyst in the environment of two different solvents (methanol and dioxane). The position of the nitro group relative to the nitrile group plays the dominant role in the course of hydrogenation. The nearer the substituent to the nitrile group is, the larger is its effect. 3- and 4-nitrobenzonitriles were hydrogenated to their primary amines, in contrast to 2-nitrobenzonitrile, which was transformedvia intramolecular oxidation to 2-aminobenzamide. During hydrogenation, numerous intermediates were formed. The choice of the solvent is another significant parameter affecting the course of hydrogenation.     

X-ray diffraction study of Raney nickel catalyst structure

X-ray diffraction studies have revealed that the modification of Raney nickel catalysts by iron leads to formation of Ni–Fe solid solution, whereas modification by chromium and titanium produces Cr₂O₃ and TiO₂. The higher dispersity of chromium — and especially of titanium-promoted catalysts is ascribed to the interaction of nickel with oxide components.

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, Ni–Fe, Cr₂O₃ TiO₂-, . , , .

     

XPS studies of the surface of Sn?Sb?O catalysts

Electronic state of the cations of Sn–Sb catalysts has been investigated by the XPS method. The established change in the charge of tin and antimony ions is ascribed to the interaction between catalyst components during its formation. It has been found that the surface of Sn–Sb–O catalysts accumulates antimony, which accounts for their high selectivity in partial oxidation of olefin.

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Surface characterization (XPS and SIMS) of emersed polybithiophene electrodes

Emersed polybithiophene (pbT) films, doped at different levels with ClO₄⁻, have been prepared by both discharging fully charged samples and charging fully discharged samples. The different strengths of two surface techniques, e.g. x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS), have been fully exploited in the analysis of emersed pbT samples. XPS has been used to assess the relative atomic concentrations of species from substratum, dopant and, for the first time, solvent (acetonitrile). Curve analysis has been employed, where necessary, to discern between different chemical environments of the same atom. Different chemical environments for acetonitrile molecules have been observed in different samples. The higher surface sensitivity of static SIMS and variable-angle XPS has been employed to distinguish between double layer and more deeply located mobile species. The participation of all mobile species (anions, cations and solvent molecules) to the charging-discharging process and the direction of migration of them at the different stages of the process have been assessed and found to be in good agreement with previous reports.