Reduction of two-component CuO–Cr2O3 mixed oxides and their catalytic activity

1992 ◽  
Vol 70 (7) ◽  
pp. 1914-1916 ◽  
Author(s):  
V. Múčka
Keyword(s):  
Activation Energy ◽  
Hydrogen Peroxide ◽  
Mixed Oxides ◽  
Catalytic Properties ◽  
Mutual Influence ◽  
Test Reaction ◽  
Hydrogen Peroxide Decomposition ◽  
Physico Chemical ◽  
Peroxide Decomposition ◽  
Two Component

The reduction with hydrogen of the two-component mixed oxides CuO–Cr2O3 containing various amounts of both components in the whole range from 0 to 100% was studied, as well as some physico-chemical and catalytic properties. The hydrogen peroxide decomposition served as a test catalytic reaction. A significant effect of the reduction on the rate constant of the test reaction was found, as well as on the value of its apparent activation energy. Pronounced changes were observed, especially in the border ranges of the composition. This fact may be connected with the mutual influence of both components in the catalyst.

Hydrogen peroxide decomposition on a non-irradiated and gamma pre-irradiated NiO-U3O8 catalyst

1981 ◽  
Vol 46 (8) ◽  
pp. 1886-1897 ◽  
Author(s):  
Viliam Múčka
Keyword(s):  
Hydrogen Peroxide ◽  
Gamma Rays ◽  
Catalytic Properties ◽  
Chemical Properties ◽  
Oxidation States ◽  
Hydrogen Peroxide Decomposition ◽  
Physico Chemical ◽  
Peroxide Decomposition ◽  
Charge Interaction ◽  
Observed Behaviour

This paper deals with some physico-chemical properties of a two component catalyst NiO-U3O8, prepared with varying ratio of both components. Special interest was given to the catalytic properties - tested by decomposition of aqueous solution of hydrogen peroxide. The study presented evidence of mutual charge interaction between both components of the catalyst. This enables one to explain the observed behaviour of the studied system on the basis of the principle of bivalent sites. A pre-irradiation of a catalyst by gamma rays leads to significant increase of the oxidation states of both catalyst components.

Hydrogen peroxide decomposition on a two-component CuO-Cr2O3 catalyst

1988 ◽  
Vol 53 (8) ◽  
pp. 1636-1646 ◽  
Author(s):  
Viliam Múčka ◽  
Kamil Lang
Keyword(s):  
Hydrogen Peroxide ◽  
Catalytic Activity ◽  
Extreme Values ◽  
Catalytic Properties ◽  
Active Components ◽  
Catalytic Systems ◽  
Heterogeneous Catalytic ◽  
Peroxide Decomposition ◽  
Two Component ◽  
Catalytically Active

Some physical and catalytic properties of the two-component copper(II)oxide-chromium(III)oxide catalyst with different content of both components were studied using the decomposition of the aqueous solution of hydrogen peroxide as a testing reaction. It has been found that along to both basic components, the system under study contains also the spinel structure CuCr2O4, chromate washable by water and hexavalent ions of chromium unwashable by water. The soluble chromate is catalytically active. During the first period of the reaction the equilibrium is being established in both homogeneous and heterogeneous catalytic systems. The catalytic activity as well as the specific surface area of the washed solid is a non-monotonous function of its composition. It seems highly probable that the extreme values of both these quantities are not connected with the detected admixtures in the catalytic system. The system under study is very insensitive with regard to the applied doses of gamma radiation. Its catalytic properties are changed rather significantly after the thermal treatment and particularly after the partial reduction to low degree by hydrogen. The observed changes of the catalytic activity of the system under study are very probably in connection with the changes of the valence state of the catalytically active components of the catalyst.

Decomposition of hydrogen peroxide on nickel oxide-manganese sesquioxide two-component catalysts and effect of ionizing radiation on them

1981 ◽  
Vol 46 (8) ◽  
pp. 1860-1875 ◽  
Author(s):  
Viliam Múčka
Keyword(s):  
Hydrogen Peroxide ◽  
Catalytic Activity ◽  
Nickel Oxide ◽  
Surface Area ◽  
Chemical Properties ◽  
Unit Surface Area ◽  
Hydrogen Peroxide Decomposition ◽  
Specific Catalytic Activity ◽  
Peroxide Decomposition ◽  
Two Component

The catalytic and some physico-chemical properties were studied of nickel oxide-manganese sesquioxide two-component catalysts with various proportions of the constituents. Decomposition of hydrogen peroxide in aqueous solution with the initial concentration 1.2 mol l-1 served as testing reaction. The catalyst components affect each other; the effect, being highest in the region of 20-30 mol.% manganese sesquioxide, brings about an enhanced dispersity of the system, with the result of increased surface area, increased amount of overstoichiometric oxygen and deficit in chemical analysis. Furthermore, the mutual component influencing appears in the specific catalytic activity of the system and in the amount of overstoichiometric oxygen per unit surface area, which is highest at 85 mol.% Mn2O3. A model of the mechanism is suggested for the reaction under study, based on the concept of bivalent catalytic centres, assuming that during the reaction, the high valency manganese species are gradually reduced as far as divalent manganese; this accounts for the occurrence of the observed two or three stages of hydrogen peroxide decomposition. Neither the mechanism of interaction of the two oxides nor the mechanism of the hydrogen peroxide decomposition changes on prior gamma irradiation of the catalyst. However, the irradiation affects markedly the catalytic activity of the system, the effect for catalyst of different composition being qualitatively different. Within the suggested concept of the reaction mechanism, the observed changes can be interpreted in terms of formation of non-eqilibrium charge carriers (electrons) resulting from the ionization both in the surface layer and in the catalyst bulk; after stabilization on the surface, the carriers may serve as adsorption centres for chemisorption of oxygen or may recombine with the catalytic centres of the reaction under study.

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