Thermal solid–solid interaction and physicochemical properties of CuO–Fe2O3 system

Abstract

A series of single and mixed oxides of CuO–Fe2O3 was prepared by thermal treatment of pure and mixed copper and ferric nitrate solids at 350–1000°C. The thermal behaviour of the single and binary salts has been studied using the thermal analysis (TG-DTG) technique. The thermal products were characterised using the X-ray diffraction analysis. The results revealed that copper and ferric nitrates decomposed to CuO and Fe2O3 at about 400°C, respectively, in the Cu–Fe mixtures. The presence of ferric oxide in the mixture prevents the reduction process of CuO to Cu2O. Crystalline copper ferrite phase was detected at 750 and 1000°C as a result of solid–solid interaction between CuO and Fe2O3. The presence of excess of CuO in the mixture stimulates the formation of well crystalline copper ferrite phase while excess of Fe2O3 hinders the previous process. The catalytic activity of the obtained pure and mixed oxides was measured using the decomposition of hydrogen peroxide at 30–50°C. It was found that the mixed oxide solids have catalytic activity higher than single oxides preheated at 350 and 550°C. The rise in precalcination temperature to 750 and 1000°C brought about a drastic decrease in the activity of mixed solids because of formation of copper ferrite phase and/or sintering process.