GB800763A - Purification of acetone - Google Patents

Abstract

Crude substantially phenol-free acetone obtained by the acid-catalysed decomposition of cumene hydroperoxide is purified by distillation in a fractionating column in the presence of an aqueous solution of an alkali metal hydroxide with removal of pure acetone as the overhead stream from the column. The crude acetone may be fed continuously into the column at an intermediate point and the aqueous alkali introduced at a point substantially below the column top. The aqueous alkali is suitably used in a concentration of about 1-25 w./v. per cent and at a feed rate of 5-1 gals. per hour for crude acetone rates of 5-10 gals. per minute. In examples: (1) a crude acetone fraction obtained by neutralization and then distillation of the acid catalyzed decomposition of cumene hydroperoxide in acetone (see Group IV (b)), is stripped of the bulk of aldehydic impurities and then introduced on to the 38th tray of a 55-tray column while aqueous NaOH is added at the 34th tray; a pure acetone fraction is removed overhead and a wet acetone is removed from the 20th tray and recycled to the decomposition zone; (2) the stripped acetone of (1) is fed with aqueous NaOH on to the 34th tray of the column operated under slight vacuum and specification acetone is distilled off; similar results are obtained when the aqueous NaOH is introduced a few trays above or below the acetone feed point.ALSO:Crude substantially phenol-free acetone obtained by the acid catalysed decomposition of cumene hydroperoxide is purified by distillation in a fractionating column in the presence of an aqueous solution of an alkali metal hydroxide with removal of pure acetone as the overhead stream from the column. The crude acetone, containing aldehydes, esters, acetals, mesityl oxide and sulphur compounds as impurities may be fed continuously into the column at an intermediate point and the aqueous caustic alkali solution introduced at a point substantially below the column top. Preferably, however, the aqueous alkali solution is added to the crude acetone immediately prior to its entering the fractionating column or prior to a preliminary stripping of the crude acetone of aldehyde impurities in a stripping column. The aqueous caustic alkali is suitably used in a concentration of about 1-25 w/v per cent and at a feed rate of 5-1 gallons per hour for crude acetone rates of 5 to 10 gallons per minute. In examples: (1) a cumene hydroperoxide concentrate containing some a :a -dimethylbenzyl alcohol, aceto phenone and cumene is continuously decomposed in a reaction medium of acetone and sulphuric acid under acetone reflux and product is withdrawn, neutralized and then distilled to recover a crude acetone fraction. Pure phenol is recovered from the residue. The crude acetone fraction is stripped of aldehydic impurities and then introduced into the 38th tray of a 55-tray column while aqueous NaOH is added at the 34th tray; a pure acetone fraction is removed as overheads and a wet acetone is removed from the 20th tray is recycled to the decomposition stage; (2) the stripped crude acetone of (1) is fed together with aqueous NaOH on to the 34th tray of the column operated under slight vacuum and specification acetone is distilled off; this process may be carried out with similar results by introducing the aqueous NaOH a few trays above or below the acetone feed point.