Investigation of the formation process of nanosized particles of Ru(III)

^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.     

Sol–gel synthesis,characterization and catalytic activity of mesoporous γ-alumina prepared from boehmite sol by different methods

In this study, boehmite sols were used as alumina precursors for preparing mesoporous γ-aluminas by two different methods. In one case polyethylenimine was used as a structure-directing agent, and in another case ultrasound treatment was applied. Nitrogen physisorption showed that aluminas that had been prepared by these methods demonstrated different porous structures. The sample obtained without additional treatment had closely packed spherical particles and pores had ink-bottle neck morphology. Ultrasound treatment led to the transformation of ink-bottle pores into cylindrical form and to the increase in surface area and pore volume. Aluminas prepared using polyethylenimine as a template showed larger cylindrical wormhole-like mesopores with a broader pore size distribution, high surface area and pore volume. Catalytic tests showed that textural properties as well as crystallite size were very important parameters of synthesized samples which affected the catalytic activity in the methanol dehydration reaction. It was found that γ-Al₂O₃ prepared by ultrasound treatment had large crystallite size and demonstrated high catalytic activity.     

Interaction of platinum and molybdophosphoric heteropoly acid under conditions of catalyst preparation for benzene oxidation to phenol with an O2-H2 gas mixture

The transformations of platinum and a heteropoly acid (HPA) in binary systems prepared from H₂PtCl₆ or H₂PtCl₄ and H₃PMo₁₂O₄₀ 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_mO_xH_y) (H_3+p PMo _12?p ^VI Mo _p ^V O₄₀) (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 PMo₁₂O₄₀] (I _s) (n = 0.3?0.8) and [Pt _n ⁰ PMo ₁₂ ^red O₄₀] (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_mO_xH_y). (H₃PMo₁₂O₄₀), where n = 0.3?0.8, m = 0.2?1, and x = 3?0, (I _solid) were obtained. The I _solid/SiO₂ supported samples were prepared by impregnating SiO₂ 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/SiO₂ 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 O₂-H₂-N₂ mixture.     

On the possible discovery of intercalated carbonate anions via the analysis of 13C NMR spectra of graphite-like carbon materials

Analysis of ¹³C NMR spectra of graphite-like carbon materials shows that pyrolytic carbon, being a part of carbon-carbon composites, contains carbonate ions that are probably intercalated between the graphite-like layers of composites as in the case of layered double hydroxides.     

The structure of porous carbon formed in the chemical dehydrohalogenation of halogenated polymers followed by thermal treatment

The possibility of preparing carbonaceous materials with a developed microporous structure by low-temperature dehydrohalogenation of carbon-chain halogenated polymers under the action of a strong base followed by thermal treatments (carbonation in an inert atmosphere and activation in an oxidative medium) was demonstrated for the example of the polyvinyl chloride-polyvinylidene chloride system.     

New carbon-carbonaceous composites for catalysis and adsorption

Properties, structural features, and basic principles for the synthesis of some new carbon-carbonaceous composite materials (CCM) originating at the Boreskov Institute of Catalysis are discussed. The CCM are synthesized via chemical growth of carbon deposits in a pre-formed porous carbon matrix. Among the CCM are: Sibunit produced by supporting pyrocarbon (PC) on carbon black granules, carbon filaments (CFC) produced by decomposition of CH₄ over Ni or Ni–Cu catalysts, CFC on Sibunit, CFC on ultradispersed diamond, and systems such as CFC/CFC, PC/CFC, etc. Basic mechanisms of structure and texture formation of CCM and some of their properties as adsorbents and catalyst supports are reported.     

Modifying the functional cover of the γ-Al2O3 surface using organic salts of aluminum

A method is suggested for modifying the surface properties of alumina without changing its chemical composition. The sorption of aluminum complexes with organic acid ligands on the γ-Al₂O₃ surface is reported. The thermal decomposition of the adsorbed oxalate complexes yields supported aluminum oxide compounds on the surface of the initial support. This modifies the functional cover of the γ-Al₂O₃ surface, altering the proportions of different types of surface hydroxyl groups, reducing their total number, and lowering the concentration of weak Lewis acid sites.     

Synthesis of Pd/C Catalysts: Approaches to Regulating the Structure of Active Sites toward Achieving High Selectivity in Hydrogenation of Organic Compounds

Russian Journal of General Chemistry - The methods for regulating the physicochemical and catalytic properties of Pd/C compositions by varying their synthesis conditions were reviewed. The effect...     

Structure of polynuclear palladium(II) hydroxocomplexes and the mechanism of their adsorption by carbon materials

Adsorption of polynuclear palladium(ii) hydroxocomplexes (PHC) by carbon materials (CM) was studied. It was found that PHC are adsorbed from aqueous solutions without a change in their chemical composition and are composed of clusters (<10 A) with metalmetal distances typical of the PdO chain structure. Three-dimensional ordered particles with the PdO structure were formed upon adsorption of PlIC on carbon materials at room temperature or after the PHC suspension was dried in air at 400 °C (the size of the particles was 15 and 25 A, respectively). Calculation of the electron-microscopic images of the adsorbed PHC with atomic resolution based on crystal structure modeling showed that PdO particles containing -100 palladium atoms is the final product after drying of the adsorbed PHC.Translated fromIzvesfiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1366–1372, June, 1996.