Decomposition of hydrogen peroxide on a two-component NiO-CdO catalyst and the effect of ionizing radiation on its catalytic properties

1979 ◽  
Vol 44 (4) ◽  
pp. 1015-1022 ◽  
Author(s):  
Viliam Múčka
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Peroxide ◽  
Catalytic Activity ◽  
Nickel Oxide ◽  
Catalytic Properties ◽  
Cadmium Oxide ◽  
Chemisorb Oxygen ◽  
Composition Region ◽  
Chemisorbed Oxygen ◽  
Two Component

The catalytic properties of two-component catalyst nickel oxide-cadmium oxide with the proportions of the components covering the whole composition region 0-100% were examined by studying the decomposition of hydrogen peroxide in aqueous solution on it. In the range 0-25 mol.% CdO, cadmium oxide is found to affect infavourably the ability of nickel oxide to chemisorb oxygen. The amount of the chemisorbed oxygen increases several times on gamma irradiation of the samples. The effect of cadmium oxide on the catalytic activity of the system shows up in fresh samples only indirectly via the changed amount of the oxygen chemisorbed. In older samples the initial catalytic activity of the system is changed, which can be explained based on the concept of bivalent catalytic centres in terms of the co-action of the catalytic centres of the two oxides, which are in equilibrium. The irradiation of the system under study speeds up the processes leading to the establishing of this equilibrium which is thermally very stable, and results in a substantial increase of the catalytic activity of the samples investigated.

Decomposition of hydrogen peroxide on cerium dioxide-nickel oxide two-component catalysts and the effect of ionizing radiation on them

1984 ◽  
Vol 49 (1) ◽  
pp. 14-24 ◽  
Author(s):  
Viliam Múčka
Keyword(s):  
Heat Treatment ◽  
Hydrogen Peroxide ◽  
Ionizing Radiation ◽  
Nickel Oxide ◽  
Cerium Dioxide ◽  
Catalytic Properties ◽  
Specific Activity ◽  
Ion Pairs ◽  
Composition Region ◽  
Two Component

Some physical and catalytic properties of cerium dioxide-nickel oxide two-component catalysts have been studied over the entire composition region, employing the decomposition of hydrogen peroxide in aqueous solution as a model catalytic process. The two oxides have been found to affect each other, particularly for NiO contents of 9.1 and 96.7 mol%; the mutual influencing, the nature of which in the conditions applied remains unaffected by heat treatment of the sample or by its exposition to ionizing radiation, is manifested by the nonmonotonic dependences of the oxidation power and of the specific activity of the catalysts on their composition. This can be interpreted in terms of the concept of bivalent catalytic centres, assuming that for nickel oxide the centres consist of Ni2+-Ni3+ ion pairs, for cerium dioxide they consist of Ce3+-Ce4+ ion pairs, and that in the region of the mutual influencing , Ni2+-Ce4+ ion pairs play a major role. Within the scope of this concept, the increase in the oxidation power of all the catalysts in question and a simultaneously decrease in the specific activity of the pure nickeloxide exposed to ionizing radiation can be explained in terms of the ionization effect.

Decomposition of hydrogen peroxide on a mixed NiO-MgO catalyst and the effect of ionizing radiation on the catalyst

1979 ◽  
Vol 44 (4) ◽  
pp. 1003-1014 ◽  
Author(s):  
Viliam Múčka
Keyword(s):  
Heat Treatment ◽  
Hydrogen Peroxide ◽  
Catalytic Activity ◽  
Room Temperature ◽  
View Point ◽  
Composition Region ◽  
Catalyst Composition ◽  
Chemisorbed Oxygen ◽  
Two Component ◽  
Nonlinear Relation

The decomposition of hydrogen peroxide in aqueous solution was studied on the NiO-MgO two-component catalyst, which occurs as solid solution in the whole composition region (0-100% component fractions). The results indicate that the mutual influencing of the two oxides shows up predominantly in the different amount of oxygen chemisorbed on the surface, which may be due to the different particle size of the various catalysts. The catalytic activity of the samples, being proportional to the amount of chemisorbed oxygen, is thus in a nonlinear relation to the catalyst composition. From the view point of the concept of bivalent catalytic centres, the catalytic activity can be thus assumed to be controlled by the concentration of the minor donor reaction centres constituted by the Ni3+ ions. In addition, catalytic centres of another kind, probably charge one, take part in the catalytic activity of the system in question. The two kinds of catalytic centres can be affected by the temperature of calcination during the preparation of the oxides, their heat treatment, and also by gamma-irradiation of the system. The equilibrium state of the two kinds of catalytic centres is attained rather slowly at room temperature.

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.

Decomposition of hydrogen peroxide on nickel oxide-molybdenum trioxide two-component catalysts and effect of gamma radiation and neutrons on them

1981 ◽  
Vol 46 (8) ◽  
pp. 1876-1885 ◽  
Author(s):  
Viliam Múčka
Keyword(s):  
Hydrogen Peroxide ◽  
Catalytic Activity ◽  
Gamma Radiation ◽  
Nickel Oxide ◽  
Molybdenum Trioxide ◽  
Surface Concentration ◽  
Major Constituent ◽  
Initial Stage ◽  
Two Component ◽  
Negative Effect

Decomposition of hydrogen peroxide in aqueous solution was studied on nickel oxide-molybdenum trioxide two-component catalysts with various proportions of the constituents covering the entire region of 0-100% of one component. The systems were found to comprise the two oxides and, in the region of 18-92 mol.% MoO3, a small quantity of nickel molybdate, which, however, does not affect appreciably their catalytic activity. A change in the kinetics of the reaction was found in its initial stage, which is probably associated with surface reduction of Mo6+ ions (major catalytic centres) to ions in lower oxidation state (minor centres) whose surface concentration determines the catalytic activity. The nickel oxide present probably accelerates this process, obviously occuring also during the ageing of the catalysts. In the regions of very low contents of one component the catalytic activity is determined by that of the major constituent, but is appreciably affected by the admixture oxide. In the range of 15 mol.% MoO3 both oxides contribute significantly to the catalytic activity; the activity is rather high, which is explained in terms of the concept of bivalent catalytic centres. In addition to the minor centres constituted by Ni3+ and probably also Mo5+ ions, determining the catalytic activity of the system, catalytic centres of another kind also take part in the reaction; these may be associated with structure defects on the catalyst surface. The greatest part play these centres in catalysts with roughly equal proportions of the two constituents. Neither the mutual influencing of the two components of the system nor the mechanism of the testing reaction alters on prior irradiation of the system by gamma radiation or by neutrons. The irradiation, however has a negative effect on the catalytic activity of the sample with 2.7 mol.% MoO3, both kinds of catalytic centres (of charge and structure nature, respectively) being probably affected. In the case of catalyst with 76.2 mol.% MoO3, radiation of both kinds induces increase in the catalytic activity; this is probably due to the establishment of a new equilibrium of the charge defects acting as catalytic centres in the reaction in question.

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