| 摘要 |
1,181,479. Fine sized alumina. W. R. GRACE & CO. 10 June, 1968 [12 June, 1967], No. 27541/68. Heading C1A. Alumina particles having a particle size of 0À02 to 2 microns are prepared by feeding an aluminium oxide or salt into a size-reduction apparatus, e.g. a fluid energy mill operated above 500‹ F. Aluminium nitrate, sulphate and hydrous alumina can be used in the form of solids, solutions, and in the case of alumina, slurries. Aluminium salts are preferably acidified to pH 1 to 2 before treatment, or neutralized with ammonia, and the mixture milled, or the mixture filtered, and the alumina filter cake milled. The aluminas formed by the invention have surface areas above 5M<2>/gm., but it is possible by varying the conditions of milling to produce gamma aluminas having surface areas of 150 to 200 M<2>/gm. and alpha aluminas with surface areas of 20 to 100 M<2>/gm. |
