Abstract
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 degrees 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 degrees C. The results revealed that pure basic copper carbonate decomposed to CuO at 300 degrees C and to Cu(2)O at temperature above 950 degrees C, where as pure ammonium vanadate decomposed to (NH(4))(2)V(6)O(16) and NH(4)V(4)O(10) as an intermediate compound at 250 and 350 degrees C before the formation of V(2)O(5) at 450 degrees C. CuO enhanced the formation of V(2)O(5) at 300 degrees C. A series of copper vanadate phases were detected, Cu(5)V(2)O(10), Cu(2)V(2)O(7) and Cu(3)V(5)O(4), for the mixtures 3Cu:1V, 1Cu:1V and 1Cu:3V preheated at 750 degrees 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 degrees C. The catalytic activity of mixed CuO-V(2)O(5) 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 degrees C. This might be attributed to restriction of catalytically active constituents. (C) 2008 Elsevier B.V. All rights reserved.