Effect of gamma-irradiation on surface and catalytic properties of nanocrystalline CuO, NiO and Fe2O3 supported on alumina

The effect of γ-irradiation on surface and catalytic properties of CuO/Al2O3, NiO/Al2O3 and Fe2O3/Al2O3 was investigated. The techniques employed were XRD, nitrogen adsorption at -196 deg C and catalytic conversion of ethanol and isopropanol at 250-400 deg C using micropulse technique. The results showed that the supported solids being calcined at 400 deg C consisted of well crystallized CuO, NiO, Fe2O3 and AlOOH phases. The AlOOH crystallized into a poorly crystalline γ-Al2O3 upon heating at 600 deg C. All phases present in different solids calcined at 400 and 600 deg C showed that these solids are of nanocrystalline nature measuring an average crystallite size between 6 and 85 nm. The crystallite size of crystalline phases present was found to be much affected by the dose of γ-rays and the nature of the metal oxide. This treatment resulted in a progressive increase in the specific surface area reaching to a maximum limit at a dose of 0.8 MGy. The dose of 1.6 MGy exerted a measurable decrease in the SBET. A radiation dose of 0.2 to 0.8 MGy brought about a progressive significant decrease in the catalytic activity of all the catalytic systems investigated. All the catalytic systems retained their high activity upon exposure to a dose of 1.6 MGy. The rise in precalcination temperature of the systems investigated from 400 to 600 deg C brought about a measurable increase in their catalytic activity in the conversion of alcohols. (author)