Hydrous aluminas and aluminas produced by electrolysis

摘要

880,580. Making pure alumina electrolytically. SPENCE & SONS Ltd., PETER. May 24, 1960 [June 5, 1959], No. 19268/59. Class 41. Pure alumina or hydrated alumina is made by electrolysing a solution of an organic acid or a salt thereof, using pure aluminium as one or both electrodes. As organic acid formic, acetic or oxalic acid is used, and as the saltforming base ammonia, aluminium, quaternary bases, or amines. The pure aluminium used as electrode is pre-treated with alkali, acid or abrasives. In examples, the electrolyte consists of ammonium acetate, or formic acid and piperidine or n-butylamine, using as electrodes aluminium and platinum, or both aluminium. In the presence of organic bases bayerite is formed. The aluminium anode is preferably surrounded by a porous pot to avoid contamination with particles of metal. By maintaining temperature above 72‹ C., boehmite is formed. The precipitated alumina is then separated, washed and dried.