G. L. Elizarova

Detoxication of water containing 1,1-dimethylhydrazine by catalytic oxidation with dioxygen and hydrogen peroxide over Cu- and Fe-containing catalysts

Abstract A number of Cu- and Fe-hydroxide containing catalysts, supported on oxide carriers, were prepared to provide the removal of 1,1-dimethylhydrazine from aqueous solutions via its oxidation by hydrogen peroxide and air oxygen. The Cu-containing samples as well as Fe/ZSM-5 are the most active catalysts in this reaction. The reaction products were analyzed by gas chromatography and UV–Vis spectroscopy. The effect of nature of the oxidizer and catalyst, pH and temperature on both the reaction rate and product composition was studied.

Polyhedral silsesquioxanes as precursors of tailor-made heterogeneous catalyst centres: I. Water oxidation

Fe-, Ni-, Cu- and Mn-polyhedral oligometallasilsesquioxanes containing (PhSiO 1.5 ) 12 (MO) n L-fragments (where L=ROH, H 2 O; n=6 for Fe, Ni, Mn and n=4 for Cu; Ni 2 Fe 2 - and Ni 4 Cu 2 -complexes were also used) have been used for the preparation of heterogeneous catalysts to investigate the influence of structural factors on the catalytic properties of the hydroxides of these metals. SAXS have been used for the characterization of the distribution of complexes associated in the solution and on the supports surface. It was found that the complex distribution on the carbon support (soot) is close to monomolecular. The highest O 2 yields have been obtained when Fe 6 /C were used as catalysts. It has been found that supports have a strong influence on the catalytic properties of supported complexes

Kinetics and mechanism of water catalytic oxidation by a Ru3+(bpy)3 complex in the presence of colloidal cobalt hydroxide

Kinetics of the catalytic oxidation of water to molecular oxygen by a tris(bipyridyl) Ru(III) complex is studied in the presence of colloidal cobalt hydroxide stabilized by starch. Oxidant consumption follows the first-order rate law with respect to the oxidant concentration. The dependence of the apparent rate constant of this process on the catalyst concentration, initial oxidant concentration, and initial concentration of its reduced form was determined. The dependence of the oxygen yield on H+ at pH 7–11 and a catalyst concentration of 10-7-10-3 mol1 is studied. An intermediate product of the reaction was found, which is probably a bridged peroxo complex of cobalt. The kinetic scheme and mechanism of the reaction is proposed, which agree with experimental observations.

Reactivity of the Peroxo Complexes of Copper(II) Hydroxide

In the interaction with H2O2 in an alkaline medium, Cu(OH)2 forms terminal Cu–OOH and bridging peroxo complexes with the μ-1,1 and μ-η2:η2 structures. It was found that the terminal peroxide is active in the reactions of H2O2 decomposition, diphenol oxidation, and nitrile conversion into acid amides. The promoting effect of ammonia on these reactions was found. A possible mechanism is discussed.

The role of peroxo complexes in the catalytic decomposition of H2O2 in the presence of Cu(II) hydroxides

The catalytic decomposition of hydrogen peroxide is studied in the presence of colloidal and silicagel-supported Cu(OH)2. Copper peroxo complexes with different activities were identified. The reaction is molecular without radical formation. The mechanisms of H2O2 decomposition are discussed.

Iron Hydroxides—New Catalysts for Oxidation Reactions in Aqueous Solutions

The catalytic decomposition of H2O2 in the presence of SiO2-supported amorphous and colloidal FeO(OH) is studied. An inactive Fe(IV) compound and a Fe(III) peroxo complex are found in the hydroxide composition. Possible mechanisms are discussed for H2O2 decomposition involving no free radicals. It is shown that lower hydrocarbons are oxidized in the systems, and their presence changes both the kinetics of H2O2 decomposition and the behavior of Fe(IV) and the peroxo complex.

Stationary kinetics of light olefin oxidation by hydrogen peroxide in aqueous alkali solutions in the presence of Fe(III) oxide

The steady-state kinetics of ethylene and propylene oxidation by hydrogen peroxide in the presence of Fe(III) oxide in aqueous solutions with the permanent adding of H2O2 to the reaction medium was studied. The use of an original method for the study of the steady-state reaction kinetics with gas chromatographic detection of substrate consumption from the gas phase made it possible to estimate the apparent rate constants of ethylene oxidation, the ratio of the rate constants of propylene and ethylene oxidation, the reaction orders with respect to the substrate and oxidant concentration, the dependence of the apparent rate constant of ethylene oxidation on the catalyst weight and on the pH of solution, and the apparent activation energy of the process under condition of substrate distribution between the gas and liquid phases. It was found that the kinetic isotope effect in ethylene oxidation is almost absent when completely deuterated ethylene is used.