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 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 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.

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

1984 ◽  
Vol 49 (10) ◽  
pp. 2231-2240 ◽  
Author(s):  
Viliam Múčka
Keyword(s):  
Heat Treatment ◽  
Hydrogen Peroxide ◽  
Catalytic Activity ◽  
Nickel Oxide ◽  
Cerium Dioxide ◽  
Catalyst Activity ◽  
Fast Neutrons ◽  
Entire Region ◽  
Catalyst Composition ◽  
Cerium Iv Ammonium Nitrate

Physical characteristics of nickel oxide-cerium dioxide catalysts and their catalytic activity in the decomposition of hydrogen peroxide were studied over the entire region of catalyst composition. The systems under study, prepared from cerium(III) nitrate, were compared with those prepared previously from cerium(IV) ammonium nitrate, and the properties of the catalysts were found to be affected considerably by the nature of the precursor used. Nevertheless, in spite of the differences the catalytic reaction on the catalysts of the two series seems to proceed on catalytic centres of the same kind, the extent to which the centres operate being dependent on the catalyst composition. The changes in the catalyst activity brought about by sample ageing, heat treatment, or previous exposition to gamma or beta rays or fast neutrons can be accounted for, in terms of the bivalent catalytic centres concept, by interaction of the catalytic centres with oxygen or the radiation applied.

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.

The kinetics of reduction of nickel oxide-cerium dioxide mixed systems with hydrogen and the effect of ionizing radiation on it

1984 ◽  
Vol 49 (10) ◽  
pp. 2241-2251 ◽  
Author(s):  
Milan Pospíšil ◽  
Igor Petrecký
Keyword(s):  
Nickel Oxide ◽  
Maximum Rate ◽  
Cerium Dioxide ◽  
Effect Of Temperature ◽  
Composition Region ◽  
System Composition ◽  
Radiation Induced ◽  
Kinetics Of ◽  
Mixed Systems ◽  
Kinetics Of Reduction

The reduction with hydrogen is studied thermogravimetrically over the temperature region of 260-500 °C for nickel oxide-cerium dioxide mixed systems of various composition. The overall rate of reduction increases and the maximum rate of reduction of nickel oxide decreases with increasing cerium dioxide content as a result of two counteracting processes occurring on the reaction interface and conditioned by the presence of the finely dispersed unreducible component. The dependence of the degree of reduction α on time t obeys the relation (α + 0.3)/(1 - α) = Aekt over the entire system composition region. Previous exposition of the samples to gamma does of 100 and 500 kGy from a 60Co source or to a fast neutron dose of 400 Gy from a 252Cf source results in a decrease in the rate of reduction for region with excess nickel oxide, but as the concentration of cerium dioxide is increased, inversion of the radiation-induced effect takes place and the rate of reduction becomes higher than for the initial, unexposed samples. The effect of temperature and system composition on the phenomena under study is examined and discussed.

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