This work presents first results of an EXAFS study of a model flotation system – the xanthate/zinc sulphate in aqueous solution, initial solutions of zinc sulphate and reference bulk samples. All EXAFS spectra (Zn-K edge) of the samples studied (both in solution and deposition) were recorded at EXAFS station of Siberian Synchrotron Terahertz Radiation Center (SSTRC, Novosibirsk) based on VEPP-3 storage ring. Some differences of local structure of initial solution of zinc sulfate (∼10-2 mol/l) compared to the bulk reference sample were found. The presence of different Zn-O forms were proposed. For the model flotation system - xanthate/zinc sulphate in aqueous solution, the Zn-S forms were predominantly found. The structural determination of interaction forms existing in aqueous solution and deposition were carried out in comparison with the initial bulk and reference samples. All possible structural models were discussed. A preliminary structural analysis has done. Perspectives of the used approach are shown.

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.

SAXS and EXAFS were applied to study genesis of polynuclear zirconium hydroxyspecies in pillaring solutions as dependent upon the zirconium concentration, addition of alkaline-earth chlorides and aging. After the montmorillonite clay pillaring, the structure of zirconium nanopillars was characterized by applying X-ray structural analysis, UV-Vis, FTIRS of adsorbed CO and nitrogen adsorption isotherms. Main pillaring species appear to be nanorods comprised of several Zr4 tetramers. Basic structural features of the tetramers are preserved in zirconia nanoparticles fixed between alumosilicate layers in pillared clays. In calcined samples, those nanoparticles contain only bridging hydroxyls and/or oxygen anions responsible for bonding within pillars and between pillars and clay sheets.

This work is devoted to a structural study of a highly dispersed Pd nanosystem, which is stabilized in the TiO2 matrix, by XAFS spectroscopy. Nanocomposite was prepared from bimetallic PdCo(μ-OOCMe)4(NCMe) precursor followed by processing in several ways: calcination in air and in argon and microwave irradiation. The local structure of Pd catalysts formed by different methods was studied. Possible structural models were considered in detail.

The possibility of controlling the state of platinum deposited on the support surface via minor changes in the catalyst preparation procedure is demonstrated using a series of highly dispersed Pt/γ-Al2O3 catalysts with different particle size of the active component. Dispersity, local structure and electronic state of supported platinum were examined by a combination of high resolution transmission electron microscopy and X-ray absorption spectroscopy (EXAFS/XANES). It was shown that various platinum species can be obtained on the surface of the support: bulk or surface Pt(II) or Pt(IV) oxides, mixed metal-oxide structures, bulk particles of metallic platinum, and two-dimensional surface Pt0 particles strongly interacting with the support.

This work is concerned with the study of Au specimens produced by gold deposition on nanosized mixed oxides (alumina, ceria, zirconia) prepared by the sol-gel method using organometallic precursors. According to X-ray absorption near edge structure, extended X-ray absorption fine structure, transmission electron microscopy data, and ultraviolet-visible and X-ray photoelectron spectroscopy measurements, mixed Al-Ce-Zr oxides are quite effective for stabilization of different gold specimens. The samples pre- treated in hydrogen at 150°C are characterized by the presence of gold Au 3+ cations located on the surface in slightly disordered octahedral oxygen coordination. Metallic gold nanoparticles with a size of about 2 nm and gold clusters were found in the samples treated in hydrogen at 300°C.

This work is concerned with the study of Au specimens produced by gold deposition on nanosized mixed oxides (alumina, ceria, zirconia) prepared by the sol-gel method using organometallic precursors. According to X-ray absorption near edge structure, extended X-ray absorption fine structure, transmission electron microscopy data, and ultraviolet-visible and X-ray photoelectron spectroscopy measurements, mixed Al-Ce-Zr oxides are quite effective for stabilization of different gold specimens. The samples pre- treated in hydrogen at 150A degrees C are characterized by the presence of gold Au3+ cations located on the surface in slightly disordered octahedral oxygen coordination. Metallic gold nanoparticles with a size of about 2 nm and gold clusters were found in the samples treated in hydrogen at 300A degrees C.

Recently great efforts are being devoted to develop new methods of preparation of high-disperse Pd–CeO2 containing nanosystems stabilized on an oxide matrix. A new approach of synthesis consists in using the heterometallic PdII2CeIV2(μ-OOCMe)12(H2O)2 complex as a precursor to anchor Pd nanoparticles on the surface of γ-alumina in direct contact with CeO2. The present work is devoted to a structural study of this disperse Pd–CeO2 containing nanosystem after oxidative or reductive pretreatments in comparison with monometallic alumina-supported samples by XAFS and TEM. A strong interaction between Pd and ceria in the catalyst produced in the studied system affects reducibility of both PdO and CeO2, which in turn results in an increased low-temperature activity in CO oxidation along with a dramatic change of the ignition–extinction curve.

This work is devoted to a structural study of the finely dispersed nanosized gold species supported on nanosized mixed oxides prepared by the sol–gel method. An analysis of the XANES (Au-L3) spectra has revealed mainly Au3+ cations located on the oxide matrix surface in distorted octahedral coordination for the catalysts reduced at 150°C. For the catalysts reduced at 300°C, a highly distorted metallic gold species has been mainly found, within the method limitation. The synthesized catalysts have also been characterized by transmission electron microscopy (TEM), BET, X-ray diffraction (XRD) and XPS.

V.V. Kriventsov, I.L. Simakova, A. Simakov, E. Smolentseva, F. Castillon, M. Estrada, E. Vargas, D.P. Ivanov, B.N. Novgorodov, D.I. Kochubey, S. Fuentes Boreskov Institute of Catalysis, Novosibirsk, 630390 (Russia) CNYN-Universidad Nacional Autónoma de México, Ensenada, B.C., 22800 (México) Posgrado de Física de Materiales de CICESE, Ensenada, B.C., 22800 (México) Posgrado de Nanomateriales de UABC, Ensenada, B.C., 22800 (México)

Recently, great efforts are devoted to develop new methods of preparation of high-disperse Pd-containing nanosystems (composed of metal and/or oxide substance) stabilized on oxide matrix. New approach of synthesis is usage of PdCo(μ-OOCMe)4(NCMe) complex and Ti(OBu)4 as precursors to anchor Pd on the surface of oxide matrix surface in a highly dispersed form. The present work is devoted to the structural study of this high-disperse Pd-containing nanosystem by the XAFS spectroscopy. The strong interaction between Pd and Co cations takes place in the studied system. Seemingly, Co cations incorporate into TiO2 oxide matrix, forming mixed oxides. This allows to anchor Pd cations, with the formation of the palladium oxide structures, modified by interaction with Co and Ti cations. These compounds are non-stochiometric and have typical structural features of mixed oxides. All possible structural models are discussed in detail.

17O, 35Cl, 133Cs NMR spectroscopy, static magnetic susceptibility measurements, EXAFS, UV spectroscopy, pH measurements, and electron microscopy are applied to investigate alkaline hydrolysis of aqueous K2[RuCl5H2O]. It is found that on addition of a base ligand substitution is accompanied by polycondensation processes which afford filament structures consisting of Ru(OH)4Cl2 octahedra bonded by single OH-bridges. When polynuclear compounds are sorbed on the surface of carbonic substrates, the filaments aggregate into nanosized particles which have a diameter of approximately 2.0 nm with a narrow size distribution.

The transformations of platinum and a heteropoly acid (HPA) in binary systems prepared from H 2 PtCl 6 or H 2 PtCl 4 and H 3 PMo 12 O 40 were studied using IR and UV-VIS spectroscopy, elemental analysis, XPS, EXAFS, TPR, and HREM. The calcination of platinum chloride with the HPA to 450°C resulted in the formation of a platinum salt of the HPA along with decomposition products (mixture I ). The reduction of calcined samples containing Pt: HPA = 1: 1 with hydrogen at 300°C (mixture II ) followed by exposure to air resulted in the regeneration of the HPA structure. The resulting solid samples of Pt 1− n 0 Pt n II Cl m O x H y ) (H 3+ p PMo 12− p VI Mo p V O 40 ) ( III ) contained platinum and molybdenum in both oxidized and reduced states. The following association species were isolated from mixtures I and II by dissolving in water: [Pt n II PMo 12 O 40 ] ( I s ) ( n = 0.3−0.8) and [Pt n 0 PMo 12 red O 40 ] ( II s ) ( n ≈ 1). Under exposure to air, the solutions of I s were stable (pH ∼2), whereas Pt met was released from II s . After the drying of I s , the solid association species (Pt n II Cl m O x H y ). (H 3 PMo 12 O 40 ), where n = 0.3−0.8, m = 0.2−1, and x = 3−0, ( I solid ) were obtained. The I solid /SiO 2 supported samples were prepared by impregnating SiO 2 with a solution of I s and drying at 100°C. Platinum metal particles of size ∼20 Å and a mixed-valence association species of platinum with the HPA were observed after the reduction of I solid /SiO 2 with hydrogen at 100–250°C. These samples were active in the gas-phase oxidation of benzene to phenol at 180°C with the use of an O 2 -H 2 -N 2 mixture.

Approaches to design of zirconia pillared clays via control of the properties of pillaring species in solutions were elaborated. Structural features of pillars and Pt + Cu active components fixed at these nanoparticles were shown to determine catalytic properties of pillared clays in NO x selective reduction by hydrocarbons in the oxygen excess.

The reaction of the tetranuclear complex of composition Pd-4(CO)(4)(CF3COO)(4) (I) with nitrogen monoxide (NO) was studied. The reaction involves the replacement of all the coordinated carbonyl groups with nitrosyl groups accompanied by redox transformations to give the tetranuclear complex Pd-4(NO)(4)(CF3COO)(4) (II). Complex II is structurally similar to the starting complex I, which was confirmed by elemental analysis, IR spectroscopy, and EXAFS. Complex II is unstable in aromatic solvents (benzene and toluene) and decomposes to form the trinuclear complex Pd-3(NO)(2)(CF3COO)(4)(TolH)(2) (III) and metallic palladium. X-ray diffraction analysis showed that the metal atoms in complex III form a linear chain in which each terminal atom is linked to the central atom via two bridging trifluoroacetate groups. The nitrosyl ligands are coordinated to the terminal palladium atoms in a bent end-on fashion. The scheme of the transformation of tetranuclear complex II into trinuclear complex III is proposed. This scheme was confirmed by quantum-chemical calculations.

The reaction of tetranuclear Pd4(μ-COOCH3)4(μ-CO)4 cluster (1a) with p- and o-chloronitrosobenzenes was found to give dinuclear nitrosoamide complexes, Pd2(OAc)2(p-ClC6H4N[p-ClC6H3NO])2 (4) and Pd2(OAc)2(o-ClC6H4N[o-ClC6H3NO])2 (5), respectively. The formation of complexes 4 and 5 is accompanied by evolution of CO2, resulting from oxidation of CO coordinated in cluster 1. Complexes 4 and 5 were characterized by elemental analysis and IR and 1H NMR spectroscopy; their structures were studied by EXAFS. The reactions of dinuclear complex 4 with molecular hydrogen and CO were studied. The major products of reduction of 4 with hydrogen include metallic palladium, acetic acid, cyclohexanone, and molecular nitrogen. Treatment of complex 4 with CO under mild conditions (1 atm, 20 °C) affords p-chlorophenyl isocyanate.

The reaction of tetranuclear Pd4(μ-COOCH3)4(μ-CO)4 cluster (1a) with p- and o-chloronitrosobenzenes was found to give dinuclear nitrosoamide complexes, Pd2(OAc)2(p-ClC6H4N[p-ClC6H3NO])2 (4) and Pd2(OAc)2(o-ClC6H4N[o-ClC6H3NO])2 (5), respectively. The formation of complexes 4 and 5 is accompanied by evolution of CO2, resulting from oxidation of CO coordinated in cluster 1. Complexes 4 and 5 were characterized by elemental analysis and IR and 1H NMR spectroscopy; their structures were studied by EXAFS. The reactions of dinuclear complex 4 with molecular hydrogen and CO were studied. The major products of reduction of 4 with hydrogen include metallic palladium, acetic acid, cyclohexanone, and molecular nitrogen. Treatment of complex 4 with CO under mild conditions (1 atm, 20 °C) affords p-chlorophenyl isocyanate.

The nearest environment of europium atoms in borate-germanate glass of composition La 3 Gd 10 Eu(BO 3 ) 6 (GeO 4 ) 2 O 8 was studied by EXAFS spectroscopy, and the Eu-O distances were determined. The structural data on the isostructural compound Gd 14 (BO 3 ) 6 (GeO 4 ) 2 O 8 of similar composition were used for the construction of models. It was established that a europium atom is surrounded by eight oxygen atoms, and the Eu-O distance in the glass was equal to ∼2.45 Å. These characteristics are close to the values in the crystals of the corresponding solid solutions.