| 摘要 |
Hydrous alumina is prepared from solid, finely divided aluminium and liquid water, by scouring a mixture of hydrous alumina and unreacted aluminium in an aqueous medium until substantially all the particles in the mixture have a size of less than 50 microns and there is more than 95% conversion, the mixture before scouring containing at least 1% of aluminium-containing particles having a size of more than 50 microns. The mixture may be scoured until more than 99% of the aluminium is converted to alumina, by means of a colloid mill with a clearance of 0.001 to 0.003 inches, and the starting material may have a surface area of 75,000 to 1,000,000 square millimetres per gram and more than 5% of the particles may have failed to pass through a 325 mesh sieve. The process may be carried out at an acid or basic pH, in the presence of a lower, non-oxidizing fatty acid, e.g. formic acid. Before scouring, the conversion of aluminium may have stopped with less than 95% of the aluminium converted. |
