The structure of a cobalt-boron catalyst obtained by reduction of cobalt chloride in an aqueous solution of sodium borohydride at ambient temperature has been investigated by TEM HR, XPS, EXAFS and Xray diffraction method. It was found that nanoparticles of the forming catalyst consisted of a core and a shell. The oxygen-containing compounds (cobalt hydroxide and cobalt borates) mainly reside in the shell. In spite of the amorphous state of the catalyst the EXAFS and X-ray diffraction analysis indicated the presence of ferromagnetic clusters with the shortest Co-Co distance of about 2.5 angstrom and coordination number of 2.7 which are regularly distributed within the core with average separations of 5.8 angstrom. The presence in the catalyst of the Co-B bonds, a short Co-Co distance and the absence of long Co-Co distances (4.3 and 4.8 angstrom) as well as the presence of boron bound to hydrogen allows suggestion to be made that stabilization of the cobalt tetramers occurs due to the presence of a boron-hydrogen structure formed by BH4- ions upon the reduction of cobalt chloride. To substantiate the above model of the active phase of the cobalt-boron catalyst the OFT method with a PBE functional in the plane-wave basis has been employed which showed that the ferromagnetic tetramers may exist within a boron-hydrogen matrix isolated from the surrounding medium by an oxygen-containing shell. (C) 2017 Elsevier B.V. All rights reserved.

The activity of cobalt–boron catalysts in sodium borohydride hydrolysis has been correlated with change of structure in the active component of the catalysts upon their thermal treatment. It was shown that at temperatures to 300 °C there takes place loss of water and hydrogen from the catalysts without noticeable changes in activity. At temperatures above 300 °C the amorphous cobalt boride particles undergo crystallization to produce metallic cobalt with a hexagonal structure and this is seemingly the cause of the substantial fall in the rate of hydrogen generation in the presence of cobalt–boron catalysts.

Trimetallic Co-Ni-Mo catalysts with different Co and Ni content (Co3Ni0, Co1.8Ni1.2, Co1.5Ni1.5, Co1.2Ni1.8 and Co0Ni3) were studied. Catalysts were characterized by HRTEM, XPS, EXAFS and XANES methods. It was shown that all catalysts contain metals preferentially in the form of sulfide active component with the structure that is similar to Co-Mo-S phase. Co-Mo and Ni-Mo catalysts contain active component in the form of Co-Mo-S and Ni-Mo-S phases respectively. Trimetallic catalysts were shown to contain mixed Ni-Co-Mo-S phases. Catalytic tests showed that the catalyst with 1.8% Co, 1.2% Ni and 10% Mo has the highest activity in hydrotreating of VGO. The highest activity of the catalyst is proposed to be provided by the formation of mixed Ni-Co-Mo-S phase. (C) 2015 Elsevier B.V. All rights reserved.

The structure and catalytic properties of catalysts modified by gallium and indium Pd/Sibunite for liquid-phase hydrogenation of acetylene were studied. The nature of introduced modifier (M: gallium, indium) and molar ratio of Pd:M was shown to affect strongly on the catalytic activity and selectivity of the samples. The highest activity in series under study is observed for 0.5%Pd-0.16%Ga/Sibunite, which is connected with formation of some amount of joint Pd-Ga phase.

A series of catalysts Pd/Sibunit and Pd–Ga/Sibunit were prepared by impregnation with joint solutions of palladium and gallium nitrates in ethanol. The state of the active component and catalytic properties of the samples were studied in the liquid-phase hydrogenation of acetylene. The EXAFS method showed that the active component in the gallium-modified catalysts exists in the form of a non-stoichiometric Pd–Ga solid solution. The activity of the catalysts was found to be determined by the ratio Pd:Ga. It was shown that at the molar ratios Ga:Pd>0.5:1, the catalytic activity is reduced by blocking the surface of the bimetallic particles by gallium oxide.

A study of unique archaeological organic material from the burials of the aristocracy of the Xiongnu people (Noin-Ula, Nothern Mongolia) is performed by means of X-ray fluorescent analysis with synchrotron radiation (SRXRF), micro-SRXRF, X-ray absorption (XAFS), scanning electron microscopy, and high-resolution X-ray computed tomography.

The burials of famous X iongnu people are a unique source of information about X iongnu culture, due to the variety of organic findings. SRXRF analysis of hair, clay, bones, teeth and woollen cloth was carried out. An anomalously high copper content was observed in all hair samples, whereas the levels of copper in bone and clay were low. To define the hair morphology and the elemental distribution in the hair cross‐section, high‐resolution X ‐ray computed tomography ( HRXCT ) and energy‐dispersive spectroscopy ( EDS ) with scanning electron microscopy ( SEM ) were used. The X ‐ray absorption fine‐structure method ( XAFS ) was applied to determine the local copper environment. The majority of the copper species in the hair and enamel samples are present as Cu 2+ cations in a distorted octahedral (4 + 2) coordination, surrounded by light ligands (oxygen/nitrogen). A similar distorted octahedral coordination is typical for both inorganic mixed oxide/hydroxide C u nanosystems and metal–organic C u complexes (with oxygen/nitrogen).

The structural characteristics and catalytic properties of Pd/Sibunit and Pd-Ga/Sibunit catalysts for the liquid-phase hydrogenation of acetylene prepared via impregnation of joint alcoholic precursor solutions are studied. A surface film of gallium oxide covering the surfaces of bimetallic particles forms on a sample modified with gallium, leading to partial blocking of its active centers. This explains the lower activity and selectivity to ethylene of Pd-Ga/Sibunit catalyst, relative to Pd/Sibunit.

The catalytic characteristics of Pd/Ga 2 O 3 samples in the liquid-phase hydrogenation of acetylene to ethylene are studied. The structure of the catalyst’s components before and after the reaction is examined by EXAFS spectroscopy. The activity of the original (after drying) samples results from the reduction of the original palladium oxide to a metallic state in the reaction medium. According to EXAFS, the catalysts reduced at 200°C contain small amounts of Pd-Ga alloy that was preserved in the reaction medium during the liquid-phase hydrogenation of acetylene and presumably increased the activity and selectivity of the samples.

Co-Mo/Al2O3 catalysts were prepared using bimetallic complexes consisting of ethylenediamine and polybasic carboxylic acid ligands coordinated to cobalt and molybdenum, respectively. The structures of the complex compounds remained unchanged upon initial adsorption to alumina. However, the chemical composition, morphology of the Co-Mo-S phase and thiophene hydrogenolysis activity of the catalysts were dependent on the pretreatment temperature before sulphidation. Nitrogen, a product of ligand decomposition, significantly inhibited catalytic activity. To attain the maximum thiophene hydrogenolysis activity, a 400 degrees C pretreatment was necessary. At this temperature, most of the nitrogen was removed, but the formation of Co and Mo compounds, which transform into low activity compounds during sulphidation, was not observed. (C) 2013 Elsevier B.V. All rights reserved.

Despite the abundance of available experimental techniques, the X-ray absorption spectroscopy often remains the only acceptable means for solving a number of problems: studying X-ray amorphous substances, determining the phase composition at a lower concentration limit for impurity samples, determining the valence state of a chemical element in the case of a low content thereof in the sample (mass percent quota). The present review reports the theory and examples of successful applying the methods of EXAFS and XANES to solve complicated problems.

Model low-percentage metal oxide palladium catalysts are prepared from acetate complexes of Pd and Mn to study the nature of the activity and the genesis of nanostructured membrane catalyst Pd-Mn systems. A comprehensive study of the prepared model precursor compounds; specific features of their metal components in gels and oxides; and the genesis of the active component, local structure, and charge state is performed by EXAFS and XANES. Possible versions of structural models for the stabilization of metals on oxide supports aare discussed.

Catalysts of liquid-phase hydrogenation of acetylene deposited on the oxides of aluminium, gallium, and indium were studied. According to the results of catalytic tests and examination using the physical methods, decoration of the active component by partially reduced support is observed in Pd/Ga2O3 and Pd/In2O3 catalysts. An increase in the atomic catalytic activity for the samples deposited on gallium and indium oxides can be connected with the change of the electron density of the active component or with the formation of bimetallic phases.

As the catalytic cycle for electrochemical hydrogen generation includes cobalt(I, II, and III)-containing clathrochelate species, we performed a detailed study of their electronic structure. The Co K-edge spectra demonstrated a lowering of the Co Is ionization potentials from cobalt(III) complexes to their cobalt(II)-containing analogs and then to the cobalt(I) clathrochelates. The absence of pre-edge structure and specific peculiarities suggested a high symmetry of the N-6-coordination polyhedra of an encapsulated cobalt(I) ion. The Co 2p core-level spectra contained very weak shakeup satellites, suggesting a hybridization of the cobalt-localized 3d orbitals and the valent orbitals of their encapsulating ligands, while the binding energy Co 2p(3/2) increased with a formal oxidation state of an encapsulated cobalt ion(I, II, or III) from 780.5-780.8 eV and 780.9-781.2 eV to 781.8-782.2 eV. The Cl 2p, C 1s, N 1s, O 1s, B Is, and Co 2p core-level spectra and data of X-ray absorption near edge structure (XANES) proved that both the electronic and spatial structures of the highly conjugated polyene macrobicyclic ligands are affected by the metal-localized redox processes. The nature of these encapsulating ligands influenced the redox characteristics of the caged metallocenters, allowing them to adopt unusual catalytically active oxidation state.

Studies concerning supported aluminum-palladium catalysts obtained via surface self-propagating thermal synthesis (SSTS) for the selective liquid-phase hydrogenation of acetylene into ethylene in the presence of CO were performed. According to the results of catalytic testing, in the case of running the reaction at 60 degrees C the SSTS catalysts are inferior to the samples prepared in a conventional manner. At a temperature of 90 degrees C, the catalyst prepared via SSTS with using citric acid as a fuel additive is almost similar to the sample prepared via traditional method, in the catalytic properties thereof. According to the results obtained by EXAFS and XPS, the original SSTS catalysts contain palladium in oxidized and reduced forms, whose ratio depends on the nature and content of the fuel additive. It has been found that palladium oxide in SSTS catalysts can be quickly reduced under the reaction conditions to produce zero-valent Pd, which is indicated by the results of studying the SSTS catalysts before and after the reaction by means of EXAFS.

The technique of Surface Self-propagating Thermal Synthesis (SSTS) was used to prepare Pd/γ-Al2O3/fiber glass (FG) catalysts for selective liquid-phase hydrogenation of acetylene in the presence of CO. The results of XRD SR analysis (in synchrotron radiation) in combination with the technique of arrested combustion shed new light on the dynamic of phase transformations in the systems under study and variation in the size of diffraction-active crystallites. The catalytic performance of synthesized catalysts was found to be close to that of similar conventionally prepared catalysts. The EXAFS and TEM data afforded to estimate the variation in relative amounts of Pd0 and PdO in synthesized catalysts. In the course of selective hydrogenation, PdO rapidly (<15 min) reduced to Pd0.

The state of palladium deposited on carbon nanofibers (CNFs) with stacked structure in 0.04–0.5wt% concentration was studied by XRD, electron microscopy and EXAFS. Palladium was found to exist as single atoms attached to CNF in the samples with Pd concentration 0.2wt% or less. Most probable location of Pd atoms according to EXAFS data was analysed using quantum-chemical calculation.

Model catalysts Pd/Ga2O3 of selective liquid-phase hydrogenation of acetylene to ethylene were prepared by impregnation of β-Ga2O3 with a palladium nitrate solution with following drying and reduction in a hydrogen flow at 200°C. A part of the samples was then calcined in an argon flow at 200–500°C. The as-prepared samples were tested in the reaction of selective liquid-phase hydrogenation of acetylene. EXAFS was used to study structure of the catalyst components. Based on the EXAFS data it was found that Pd–Ga alloys present in the subsurface region of Pd particles. The presence of these alloys increases activity and selectivity of catalysts. The alloys are decomposed by calcination in inert atmosphere following decrease in catalytic activity.

Monoslab HNb 3 O 8 supported on MgO was obtained; the changes of the structure of HNb 3 O 8 after exfoliation and after aniline adsorption were detected.