Patent GB-684968-A (GB)
Title: Separating organic oxygen compounds from aqueous mixtures by extractive distillation
IPC: C07C45/83
Filed: 1950-03-24
Abstract: <PICT:0684968/III/1> Ethanol is recovered from aqueous mixtures containing isopropanol and at least one other oxygenated organic compound, e.g. methyl ethyl ketone, by subjecting the mixture to fractional distillation in a column supplied with 100-150 B.t.u. of heat per pound of bottoms, introducing water into the column countercurrent to the flow of vapour so that the concentration of water in the liquid at any point in the column is in the range 90 to 99 mol per cent, and maintaining the head and base temperatures in the respective temperature range 73 DEG -88 DEG C and 90 DEG -98 DEG C.  The bulk of the ethanol is withdrawn as aqueous bottoms while the isopropanol and the other oxygenated organic compounds, together with about 1-10 per cent of the ethanol, are taken overhead.  An aqueous solution containing ethanol and isopropanol in the ratio of about 30 to 1, together with methyl ethyl ketone, methyl propyl ketone, ethyl acetate and butyraldehyde, obtained by hydrogenation of carbon monoxide in the presence of a fluidized iron catalyst, is introduced through line 2 into 65-plate column 4.  The column is supplied with water through line 6, the water-concentration therein being maintained at about 95 mol per cent; while the top and bottom temperatures are maintained at 76 DEG C and 96 DEG C respectively. Aqueous ethanol containing only about 10 parts per million of isopropanol, is withdrawn through line 8 and concentrated in column 10 from which the purified ethanol/water azeotrope is with drawn from the base of column 10 is in part rejected through line 17 and in part recycled to column 4 through line 18.  The overhead fraction from column 4 which contains isopropanol, M.E.K., M.P.K., ethyl acetate, butyraldehyde and about 1.3 per cent of the ethanol originally present in the feed, is introduced through line 20 into column 22 which is supplied with water through lines 27 and 24 to maintain 95 mol per cent of water therein.  The heat input to column 22 is 90 B.t.u. per pound of bottoms while the head and base temperatures are 71 DEG C and 85 DEG C respectively.  The overhead stream withdrawn through line 26 contains butyraldehyde and ethyl acetate; while the bottom stream consists of an aqueous solution of isopropanol, M.E.K., M.P.K., and ethanol, which is fed through line 30 into column 32. This column is supplied with water through line 35 to maintain 95 to 99 mol per cent of water in the upper part of the column.  An aqueous side-stream containing ethanol and isopropanol at a temperature between 92 DEG C and 99 DEG C is withdrawn through line 38, while the two ketones are withdrawn overhead (74 DEG C) and water is withdrawn as bottoms (part being recycled to column 22 through line 24).  The ketones may be dehydrated and then separated by conventional fractional distillation.  The side-stream is introduced into column 40 where another extractive distillation takes place; water being introduced through line 42 while the head and base temperatures are maintained at 80.6 DEG C and 97 DEG C respectively.  The isopropanol/water azeotrope is taken off overhead; and aqueous ethanol is withdrawn as bottoms and recycled through line 50 to column 4.  Specification 647,903 is referred to.