Patent GB-655698-A (GB)
Title: Separation of oxygenated organic compounds by distillation
IPC: C07C45/80
Filed: 1948-09-15
Abstract: Neutral non-alcoholic oxygenated organic compounds such as aldehydes, ketones and esters are removed from a mixture containing at least two normal primary aliphatic C1 to C5 alcohols together with branched-chain aliphatic alcohols, e.g. a mixture obtained by Fischer <PICT:0655698/III/1> synthesis, by introducing the mixture into a fractionating zone at an intermediate point and adding water or aqueous liquid to the upper section of the zone so as to maintain an internal reflux having a water content in the range of 65 to 99 mol. per cent in the zone; the actual proportion being adjusted to alter the relative volatilities of the components of the mixture so as to take off an aqueous distillate containing the neutral non-alcoholic oxygenated compounds and preferably the branched-chain alcohols also, from the head of the zone, while a purified aqueous solution containing the bulk of the normal primary alcohols present in the feed, is withdrawn as bottoms. Any organic acids present in the feed are, unless previously separated, also present in the bottoms.  A sample of a water layer from a Fischer synthesis containing alcohols (84.6 mol. per cent on a water-free bases), aldehydes and ketones (11.2 mol. per cent), esters (0.2 mol. per cent) and acid (4 mol. per cent) was distilled in a one-inch I.D. column having 30 perforated plates above and 30 plates below the feed point, the rate of feed being 440 c.c. per hour; and 930 c.c. of water per hour was introduced at the top of the column to maintain 96.8 mol. per cent water on the top plate.  Operating in this manner, 19 volume per cent of the organic matter in the feed was taken overhead, including all the esters, about 97 per cent of the carbonyls, and most of the secondary and tertiary alcohols.  The apparatus shown is used in a modification where the aqueous layer from a Fischer synthesis is, prior to extractive distillation, freed from acids and divided into two separate acid-free fractions.  The crude aqueous layer is fed through line 105 into column 101 where it is subjected to ordinary fractionation to remove overhead the alcohols, aldehydes, ketones and esters, leaving aqueous acid as bottoms.  The overhead is passed through line 111 to column 202 where it is subjected to ordinary fractionation to take overhead nearly all the constituents boiling below n-butyl alcohol; while n-butyl alcohol and all constituents boiling above it together with some n-propyl alcohol, sec. and iso-butyl alcohols, are taken off as bottoms. The overhead from column 202 is passed into the middle of column 204, and the bottoms into the middle of column 207.  Columns 204 and 207 are supplied, through lines 205 and 208 respectively, with portions of the dilute acids from the base of column 101 so that there is 90 volume per cent of water on the plates of both columns.  Aldehydes, ketones, esters, hydrocarbons, acetals and ethers are withdrawn from the tops of columns 204 and 207.  A purified aqueous solution of low-boiling alcohols is withdrawn from the base of column 204, while a purified aqueous solution of the higher boiling alcohols is withdrawn from the base of column 207.  An aqueous solution of a salt of sodium, potassium or ammonium may also be used instead of pure water as extractant. Specification 647,903 is referred to.