Effect of gamma-irradiation on surface and catalytic properties of Co3O4 doped with NiO

Abstract

NiO-doped Co3O4 samples precalcined at 500 °C were subjected to various doses of γ-rays within the range 0.2-1.6 MGy. The particle size and BET-surface areas of different samples were determined using XRD and nitrogen adsorption at -196 °C. The catalytic reactions studied were conversion of ethanol and isopropanol at 250-400 °C using a micropulse technique and H2O2 decomposition in aqueous solution at 30-50 °C. The results revealed that the γ-irradiation brought a significant decrease in the particle size of Co3O4 phase with subsequent increase in the SBET surface areas. The treatment brought also a progressive decrease in the total conversion of both alcohol (dehydration and dehydrogenation) falling to a minimum value (about 20% of its initial activity) at a dose of 0.8 MGy. The catalysts retain their initial activity upon exposure to a dose of 1.6 MGy. On the other hand, the catalytic activity in H2O2 decomposition of the investigated system decreased progressively by increasing the dose of γ-rays and the catalysts lost more than 90% of their initial activity upon exposure to a dose of 1.6 MGy.