Improvements in or relating to a process for separating acetone and methanol from complex mixtrues by extractive distillation

摘要

PICT:0715191/III/1 Methanol is separated from mixtures containing acetone and other organic compounds containing oxygen, by subjecting the mixture to extractive distillation using water as solvent in such an amount that the concentration of water in the liquid at any point of the fractionating column is at least 50 mol. per cent., maintaining the temperature at the head of the column at 60 DEG -80 DEG C. and the temperature at the base of the column at 85 DEG -105 DEG C., removing a distillate containing acetone and other organic compounds from the head of the column, and withdrawing an aqueous solution of methanol from the base of the column. A mixture containing acetone (80 per cent.), methanol (2 per cent.), aldehydes of average molecular weight 56.5 (14 per cent.), esters (3 per cent., as methyl acetate), and water was introduced through line 2 at the 45th plate of a 60 plate fractionating column 4; and water (1.9 volumes per unit volume of feed) was added to the top of the column through line 6. The temperatures of the top and bottom of the column were maintained at 76 DEG and 101 DEG C. respectively. An aqueous solution containing 1.2 weight per cent. of methanol was withdrawn from the base of column 4 through line 8, and introduced into column 10. Pure methanol was obtained from the head of column 10. The water obtained as bottoms in column 10 was partially recycled to the top of column 4. The overhead stream from column 4, which contained less than 0.05 per cent. methanol, was introduced through line 22 on to the 45th plate of p plate of a 60 plate fractionating column 24. Water, 15 volumes per unit volume of feed, was introduced into the top of column 24 through line 26; and the temperatures at the top and bottom of this column were maintained at 53 DEG and 96 DEG C. respectively. An aqueous solution containing 3.2 weight per cent. of acetone was withdrawn from the base of column 24 through line 32, and introduced into column 34. Substantially pure acetone was taken-off from the head of column 34. Water was withdrawn from the base of column 34, and partially recycled to the top of column 24. The overhead stream from column 24 comprised water and substantially all the impurities, viz. acetaldehyde, propionaldehyde, butyraldehyde, and methyl acetate. In a modification, the initial extractive distillation is carried out to obtain a purified aqueous solution of methanol and acetone as bottoms; and this solution is then subjected to further extractive distillation to separate methanol and acetone. Specification 660,773 is referred to.