GEORGEITE AND AZURITE AS PRECURSORS IN THE PREPARATION OF CO-PRECIPITATED COPPER-ZINC OXIDE CATALYSTS

Georgeite, a recently identified basic copper carbonate mineral, can be synthesised in aqueous solutions from copper salts. It has now been shown that a zincian georgeite (i.e. georgeite with some substitution of copper by zinc) is formed by precipitation with sodium carbonate in copper-zinc systems. Conversion of zincian georgeite to a malachite phase in an aqueous medium occurs more slowly than the equivalent conversion of pure copper georgeite. The possibility of georgeite formation as a precursor to malachite in the manufacture of copper/zinc catalysts is discussed: it is suggested that the blue/green colour transition seen during the ageing of precipitated copper/zinc catalyst precursors can be attributed to the conversion of georgeite to malachite. Synthetic azurite materials, with and without zinc inclusion, were prepared from aqueous suspensions of georgeite with azurite seeding under 40 bar carbon dioxide. These were used as precursors to prepare active copper/zinc catalysts but their performance was inferior to that of a conventional catalyst.