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This paper reports the use of a differential dissolution stoichiographic method for determining the phase composition of catalysts for ammine borane hydrolysis and hydrothermolysis [1, 2]. Cu1–xFe2+xO4 copper ferrite samples were prepared using layer-by-layer combustion, dried, and then calcined at different temperatures. We describe conditions that make it possible to detect and quantitatively determine various phases in the composition of amorphous and crystalline materials with the spinel structure and compare differential dissolution and X-ray diffraction results. [ABSTRACT FROM AUTHOR]

The synthesis of fine vanadium-carbide (VC0.88) powder is considered. To produce the vanadium carbide, vanadium(III) oxide is reduced by means of carbon nanofiber in an induction furnace with an argon atmosphere. The carbon nanofiber is produced by the catalytic decomposition of light hydrocarbons. The specific surface of the carbon nanofiber is very high: ~150000 m2/kg, as against ~50000 m2/kg for soot. The impurity content in the carbon nanofiber is 1 wt %. By analysis of the phase diagram of the V-C system, the batch composition and the upper temperature limit in carbide formation may be determined such that vanadium carbide is formed as powder. Thermodynamic analysis yields the initial temperature at which the vanadium( III) oxide is reduced in a furnace with different CO pressures. The characteristics of the vanadium carbide are determined by the following methods: X-ray phase and elementary analysis; pycnometric analysis; scanning electron microscopy with local energy dispersion X-ray microanalysis (EDX); low-temperature nitrogen adsorption with subsequent determination of the specific surface by the BET method; sedimentation analysis; and synchronous thermogravimetric analysis and differential scanning calorimetry (TG/DSC). The material obtained with optimal reduction parameters consists of a single phase: vanadium carbide VC0.88. The powder particles are predominantly clumped together in aggregates. The mean size of the particles and aggregates is 9.2-9.4 μm, with a broad size distribution. The specific surface of the samples is 1800-2400 m2/kg. Oxidation of vanadium carbide begins at about 430°C and is practically over at 830°C. Optimal synthesis requires stoichiometric proportions of the reagents in the production of vanadium carbide VC0.88 at 1500-1600°C, with 20-min holding. In this process, carbon nanofiber effectively produces the carbide as the reduction product. The vanadium(III) oxide is reduced practically completely to VC0.88. [ABSTRACT FROM AUTHOR]

Hydrogen-generating solid-state NaBH4 composite are promising systems for storing and transporting hydrogen intended for use in low-temperature proton-exchange membrane fuel cells. Catalysts are introduced into the composites to ensure the generation of hydrogen at ambient temperatures. In this work, the effect of the synthesis conditions for cobalt catalyst on the gas generation rate is analyzed. It is found that the efficiency of hydrogen generation depends on the nature of the cobalt salt and pH of the aqueous solution of the salt in which the active component precursor is reduced under the action of sodium borohydride because these factors determine the composition, degree of dispersion, and magnetic behavior of the cobalt systems. It is found that the highest rate of gas generation—505 cm3/min per gram of the composite with a hydrogen content of 8.4 wt %—is observed for a sample reduced with sodium borohydride in a hydrochloric acid solution of cobalt chloride with a pH of 1.3. The results can be used to develop effective inexpensive cobalt catalysts for the production of hydrogen from pelletized solid-state NaBH4 composite. [ABSTRACT FROM AUTHOR]

The reaction properties of Rh/TiO2 sodium tetrahydroborate hydrolysis catalysts reduced directly in the reaction medium depend on the temperature at which they were calcined. Raising the calcination temperature to 300°C enhances the activity of the Rh/TiO2 catalysts. Using diffuse reflectance electronic spectroscopy, photoacoustic IR spectroscopy, and chemical and thermal analyses, it is demonstrated that, as RhCl3 is supported on TiO2 (anatase), the active-component precursor interacts strongly with the support surface. The degree of this interaction increases as the calcination temperature is raised. TEM, EXAFS, and XANES data have demonstrated that the composition and structure of the rhodium complexes that form on the titanium dioxide surface during different heat treatments later determine the state of the supported rhodium particles forming in the sodium tetrahydroborate reaction medium. [ABSTRACT FROM AUTHOR]

Purification of emulsions of 1,2-dichlorobenzene (1,2-DCB) by carbon-based adsorbent catalysts has been studied. The cycle of purification includes: (1) adsorption of 1,2-DCB from the aqueous phase and (II) reductive regeneration by hydrodechlorination of the adsorbed 1,2-DCB by molecular hydrogen in the liquid phase. 1,2-DCB adsorption from aqueous solutions has been found to proceed by the mechanism of volume filling of pores. The rate of hydrodechlorination was shown to correlate with the particle size of the active component: the finer the particles, the higher the activity of the adsorbent catalyst. Pd/FAS with an average Pd particle size of 2.8 nm was found to be the most efficient catalyst., (Copyright © 2014 Elsevier B.V. All rights reserved.)