GB698617A - Improved method of separating by distillation the components of aqueous mixtures containing methanol and ethanol - Google Patents

Abstract

<PICT:0698617/III/1> Aqueous ethanol which contains methanol, e.g. a sulphite or sulphate lye, is freed from methanol by a two-stage rectification process; a mixture comprising methanol, water and between 20 to 60 per cent by weight of ethanol is withdrawn as distillate from the first rectification column, and this distillate is then rectified in a second column to strip out the methanol and give aqueous ethanol, free from methanol, as bottoms. An acidic mixture of methanol, water and about 12 per cent ethanol, supplied through pipe 1, is preheated in condenser 6 and then introduced through pipe 2 on to the top plate of column 3 which contains sixteen plates. Column 3 is surmounted by column-section 4 which contains five to seven plates; and neutralizing lye is introduced through pipe 16. Alcohol-free wash is discharged from the sump of column 3 through pipe 5. All the condensate from condensers 6 and 7 is refluxed to section 4, from which a neutral solution containing methanol, water and 25 to 50 per cent of ethanol is withdrawn through pipe 9 and introduced into the side of fractionating-column 10, 11. This column has about 40 plates below the feed-inlet. The condensed distillate from the head of the column, which contains methanol, ethanol and water, is partly returned to the head of the column, and partly withdrawn through line 14. Aqueous ethanol free from methanol, is obtained from the sump of column 10 through pipe 15. The ternary mixture withdrawn from the head of column 11 may be fractionated to give methanol as "heads" and aqueous ethanol as "bottoms"; and the latter may be refluxed to column 10, 11, after adjustment of its composition to ensure that the relative concentration of the ethonal in the total feed to the column, conforms with the invention. Fusel oil and/or other impurities may be withdrawn as a side-stream from column 10, 11.