Effects of γ irradiation and lithium doping on the catalytic activity of nickel-aluminum mixed oxides

Abstract

The catalytic activity of pure NiO and Ni-Al mixed oxides subjected to various doses of γ irradiation was investigated using the oxidation of CO with O₂ at various temperatures. The effect of lithium doping on the catalytic activity of Ni-Al was also investigated. The results obtained revealed that γ irradiation of pure NiO using doses up to 10 Mrad effected a decrease of 45% in its catalytic activity which suffered a further slight change when the dose was increased to 20 Mrad. The activity of Ni-Al mixed oxide was modified in a somewhat complicated manner by γ irradiation. Doses of 5 – 10 Mrad produced an increase of 34% in its catalytic activity and a dose of 15 Mrad caused a drastic decrease in its activity of 57%. Increasing the dose of 20 Mrad produced a slight increase in the catalytic activity of the mixed oxide solid.

The modifications in the catalytic activity of pure NiO and mixed oxide solids arising from γ irradiation were attributed to an induced removal of chemisorbed O₂ in the case of pure NiO and to a possible increase in the [Ni]/[Al] ratio, especially in the outermost surface layers, of the mixed oxide catalyst.

Lithium doping was found to cause a significant increase in the catalytic activity of Ni-Al mixed oxide which was attributed to the increase in the amount of chemisorbed O₂ and to an increase in the [Ni]/[Al] ratio.