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.