GB647903A - Separation of close-boiling alcohols from aqueous liquid mixtures by distillation - Google Patents

Abstract

<PICT:0647903/III/1> Water-soluble alcohols of different molecular weights, which have close-boiling aqueous azeotropes, are separated from each other by passing the mixture, which may also contain other oxygenated organic compounds such as ketones, into the side of a fractionating column, and introducing water into the top of the column to make the water content of the internal reflux at least 65 mol. per cent and sufficient to alter the relative volatilities of the components of the feed-mixture so that a dilute aqueous solution of the alcohol of lowest molecular weight, free from the other organic components of the feed mixture, is withdrawn from the base of the column while vapours of the other components are withdrawn overhead. In an example, a mixture containing ethyl alcohol, isopropyl alcohol, methyl ethyl ketone and water was fed at 52 volumes per hour between the sections (each of 30- plates) of a fractionating column; and 2100 volumes per hour of water at 90 DEG C. was introduced into the top of the column. The reflux ratio was somewhat higher than 30 : 1. After equilibrium was reached, no detectible concentration of isopropyl alcohol or of methyl ethyl ketone was found in the aqueous ethyl alcohol bottoms. Other examples describe the separation of ethyl alcohol from the products of a Fischer synthesis. When more than one component is required to be separated in a pure state, apparatus such as that shown is employed. An aqueous mixture of narrow boiling-range containing ethyl alcohol, isopropyl alcohol, tertiary butyl alcohol and methyl ethyl ketone is fed through inlet 44 into column 41; and water is introduced into the column through inlet 45. Dilute aqueous ethyl alcohol is withdrawn through line 50 and passed to column 51 where it is concentrated; a distillate containing about 96 per cent ethyl alcohol, 4 per cent water and less than 0.1 per cent of other organic compounds, being obtained through line 57. The distillate from column 41 is passed through line 58 into column 42 where a water concentration of 90-99 mol. per cent is maintained in the internal reflux by adding water through line 62. Dilute aqueous isopropyl alcohol, free from butyl alcohol and M.E.K., is withdrawn through line 64 and concentrated in column 65. Similarly, columns 43 and 78 are used for the separation and concentration of tertiary butyl alcohol. The water withdrawn from the bottoms of columns 51, 65 and 78 is pumped back to columns 41, 42 and 43, respectively. The separation of alcohols from an olefin hydration reaction, and from a hydrocarbon oxidation reaction is referred to. Specification 598,346 is referred to.