Monoxide Oxidation on Modified Nickel Oxide Catalysts

Carbon Monoxide Oxidation on Modified Nickel Oxide Catalysts 

Such a proof of the carbon monoxide oxidation was first given by one of us (28). It is very important to remark that the catalysts containing impurities were prepared by firing together in air at 600°C. for 3 hr. a mechanical mixture of the required components in adequate proportions. As pointed out by Fensham (54), this is much too low a temperature to ensure homogeneous solid solutions. Consequently, when a catalyst is described as NiO + 0.1% Li2O, there is no assurance that this nominal composition is realized at all either in the surface layer or in the bulk of the sample. As will be shown, this reservation is quite essential. 

The main features of this investigation are the following. First, a deactivation process similar to that observed on the pure nickel oxide was found on the modified catalysis as well, with the same logarithmic law to represent its evolution with time. Second, the kinetic equations which were found to fit the data on pure nickel oxide also apply to the modified catalysts. Thus there is a low-temperature mechanism operative between 100° and 180°C. For all the samples assembled in Table II, the activation energies were practically the same, about 2 kcal./mole and essentially equal to the value for pure nickel oxide. This indicates that, for this particular mechanism of the reaction, the added ions and the semiconductivity changes do not affect directly the catalytic process. 

Activation Energies for Carbon Monoxide Oxidation on Nickel Oxide Catalysis 

This again confirms the reasoning presented above, according to which loosely adsorbed mobile oxygen which does not exchange electrons with the catalyst, or does so in a restricted sort of way, is the essential partner for the surface reaction. 

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VI. Carbon Monoxide Oxidation on Modified Nickel Oxide Catalysts.. 68... 

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