GB640581A - A process for the purification of ketones by distillation - Google Patents

Abstract

<PICT:0640581/III/1> Crude ketone containing secondary alcohol, aldehydic material, water, and hydrocarbons having higher boiling points than the ketone, is fed into a fractionation zone and the aldehydic material is either withdrawn as vapour or converted into higher boiling compounds by introducing a suitable reagent, the bottoms from the fractionating zone are passed to a second fractionating zone from which a liquid side stream is withdrawn from a point where the concentration of hydrocarbons is high, while substantially pure ketone vapours are withdrawn overhead and aqueous alcohol is withdrawn at the base; the side stream is scrubbed with water and the hydrocarbons are then separated from the aqueous solution of ketone and alcohol so obtained; this aqueous solution is passed into the first fractionating zone. The process is applicable to the purification of acetone, methyl ethyl ketone, mesityl oxide, acetonyl acetone, cyclohexanone, and acetophenone; and is particularly useful in removing olefine-polymers, formed by undesirable side reactions in the dehydrogenation of secondary alcohols, from the crude ketone. Crude acetone containing 0.02 per cent aldehydes and 0.19 hydrocarbons, obtained by the oxidation of isopropanol, is passed through heat-exchanger 3 and line 2 into column 4 which contains 30 to 40 bubble trays. Acetone vapours containing 2.4 per cent aldehydes and 6 per cent hydrocarbons, are withdrawn from the head of the column and condensed; the condensate being partly eliminated from the system and partly returned as reflux to the column. The liquid withdrawn from the base of column 4 contains 0.2 per cent hydrocarbon-polymers, and is passed through line 17 into column 19 which contains 35 to 45 bubble trays. Liquid amounting to 0.2 to 0.3 of the charge to column 19 is continuously withdrawn from the zone of high polymer concentration therein, by means of one or more lines 21, 22, 23. This liquid is passed into accumulator 28 and is then forced together with water introduced at line 33, through mixing-coil 32. The mixture is allowed to separate in chamber 36; the polymer is eliminated from the system through line 41, and the aqueous layer is passed to column 4 via lines 37 and 39. The heads from column 19, which contain 99.6 per cent acetone, may either be condensed and, except for reflux, eliminated from the system; or they may be still further purified in column 62. Aqueous isopropyl alcohol is withdrawn from the base of column 19. A dilute solution of sodium hypochlorite or other alkali hypohalite, in an amount not substantially in excess of that equivalent to the aldehydic material, may be added through line 76 into accumulator 8 at the head of column 4; in which case the reaction mixture is passed into column 4 through line 11 and light hydrocarbons are vented through line 13. The reaction products are eliminated from the system at the base of column 19 (salts) and also through line 41 (chloroform). Specification 392,652 is referred to.