Removal of bromobutanone from acetic acid

Acetic acid can be prepared in high conversions and selectively by the oxidation of liquid n-butane at temperatures of from 120 DEG C. up to 230 DEG C. in the presence of an acetic acid solution containing bromine ions in combination with ions of cobalt or cobalt and manganese. The debutanized effluent of such oxidation consists mainly of acetic acid and water but also contains esters and ketones boiling lower than acetic acid, some higher carbon content aliphatic acids and metal salts boiling higher than acetic acid and rather small amounts of 3-bromo-2-butanone which, although boiling higher than acetic acid, cannot be separated by simple distillation as can be the other non-acetic acid organic impurities. The present inventive technique for removal of said bromo-ketone has for its concept the use of a combination of cryogenic crystallization and removal of adhering mother liquor which can be practiced continuously in known apparatus devised for other fractional crystallizations.