Thermal characterization of individual and mixed basic copper carbonate and ammonium metavanadate systems

The thermal behaviour of individual and mixed solids, with different molar ratios, of basic copper carbonate and ammonium metavanadate was reported. The pure and mixed solids were thermally treated at 300, 500, 750 and 1000 °C. The thermal products at various calcination temperatures were characterized by means of thermal analyses (TG–DTG–DTA), X-ray diffraction (XRD) and electron spin resonance (ESR) techniques. The catalytic activity of all solids was measured using hydrogen peroxide decomposition at 30, 40 and 50 °C. The results revealed that pure basic copper carbonate decomposed to CuO at 300 °C and to Cu2O at temperature above 950 °C, where as pure ammonium vanadate decomposed to (NH4)2V6O16 and NH4V4O10 as an intermediate compound at 250 and 350 °C before the formation of V2O5 at 450 °C. CuO enhanced the formation of V2O5 at 300 °C. A series of copper vanadate phases were detected, Cu5V2O10, Cu2V2O7 and Cu3V5O4, for the mixtures 3Cu:1V, 1Cu:1V and 1Cu:3V preheated at 750 °C, respectively. These phases were formed as a result of solid–solid interactions between copper and vanadium oxides. The calcination temperature and the composition of the Cu–V mixtures affect the degree of crystallinity and pattern intensities of different phases detected at treatment temperatures ranged between 300 and 1000 °C. The catalytic activity of mixed CuO–V2O5 was found to be greater than that of single oxides obtained at the same calcination temperatures. This might be attributed to increase in the concentration of active sites by creation of new ion pairs. No measurable catalytic activity was observed for all solids calcined at 750 and 1000 °C. This might be attributed to restriction of catalytically active constituents.