LOW-TEMPERATURE COPPER INTERCALATION IN SODIUM VANADIUM OXIBRONZE - PREPARATION AND CHARACTERIZATION

The vanadium oxibronze alpha'-NaV2O5 reacts with CuCl2 in water at 373 K affording a new compound, Cu0.5V2O5(H2O)0.5, WhiCh has a high surfa ce area for such an unsupported phase. The overall process is describe d as the replacement of two sodium ions by one copper ion and one wate r molecule. Structural and chemical investigations by visible and IR s pectroscopy, X-ray powder diffraction, thermal analyses, and oxidation studies are described. It is suggested that the metastable structure Of Cu0.5V2O5(H2O)0.5 is reminiscent of the lamellar character of the p recursor phase alpha'-NaV2O6. Heat treatment under inert atmosphere fi rst leads to amorphization via dehydration with an activation energy o f 110 kJ mol-1, then to the beta'-Cu0.5V2O5 phase formation at 973 K. The oxidizing properties vs hydrogen and carbon monoxide are compared with those of related compounds. For carbon monoxide oxidation, the te mperature of carbon dioxide formation follows the order V2O5 > alpha'- NaV2O5 > beta'-Cu0.5V2O5 > CuO/V2O5 > Cu0.5V2O5. Therefore the presenc e of copper involves a greater lability of the oxygen atoms of the V2O 5 lattice. This effect is enhanced with the new compound Cu0.5V2O5. Pr eliminary results in the catalytic decomposition of 2-propanol show th at Cu0.5V2O5 is selective for the oxidative dehydrogenation route wher eas the other compounds are also active for dehydration.