Effect of gamma-irradiation on surface and catalytic properties of nano crystalline Fe2O3/CuO system

ABSTRACT

Ferric/copper mixed oxides samples having the formula 0.25Fe2O3/CuO were prepared by thermal decomposition of their mixed hydroxides at 400 °C. The mixed hydroxides were prepared by cooprecipitation method using iron and copper nitrates solution using NaOH at pH = 8. The obtained solid was exposed to different doses of gamma-rays varying between 0.2 MGy and 1.6 MGy. The techniques employed were XRD, nitrogen adsorption measurements at -196 °C and ethanol and isopropanol conversion using micropulse technique at temperatures between 250-400 °C. The results obtained revealed that the investigated system consisted of nano crystalline CuO [major phase] and poorly crystalline Fe2O3 as a minor phase. The exposure to gamma-irradiation resulted in a measurable decrease a the crystallite size of CuO [major phase], a dose of 1.6 MGy brought about a significant drop in the crystallite size from 31.4 to 19.2 nm. This treatment led also to a progressive increase in the BET=surface area to an extent proportional to the dose of gamma-rays employed. The investigated solid samples acted as dehydration catalysts converting ethanol and isopropanol into ethene and propene, respectively. Their activity was found to increase by increasing the dose of gamma-rays reaching to a maximum limit at a dose of 0.4 MGy. However, a dose of 0.8 MGy led to a sudden drop in the catalytic activity of various solids which retained most of their initial activity upon exposure to a dose of 1.6 MGy. The results obtained were discussed in terms of the role of gamma-rays in modifying the chemistry of the surface of the treated solids and the decrease in the crystallite size with subsequence increase in their SBET