GB455325A - Improvements in or relating to the concentration of aliphatic acids - Google Patents

Abstract

<PICT:0455325/IV/1> In extraction processes for concentrating aliphatic acids from cellulose esterification processes by means of solvents, sludge is removed from the apparatus by admitting the vapour of a solvent or partial solvent and draining away the condensed solvent. The extraction of acetic acid, for example, may be effected by passing the dilute acid through a column made of or lined with stainless steel, glass, bronze or the like in countercurrent with a solvent such as phenol ethers, ethylene chloride, or mixtures of petroleum ether, kerosene or benzol with ethyl ether, ethyl acetate, chloroform, or acetone oil; and the column may contain Raschig rings or other packing material. In the apparatus described aqueous acid from 1 is fed to columns 10, 11, 12, any of which may be cut out for cleaning. Each column has an upper part 13 in which the liquid phases separate, a packed part 14, and a bottom part 15 with sight glasses 16. The bottom sections of columns 10, 11 are connected by pipes 17, 18 to the acid-feed pipes at the top of columns 11, 12 respectively, and from the bottom section of column 12 is connected to a tank 22, still 23 and dephlegmator 24. Solvent from a tank 25 is supplied to the columns in counter-current to the aqueous acid and the extract is collected in a tank 30 from which it passes by a pipe 34 to a still head 35 from which it may be returned to the tank 25 or preferably is passed through a preheater 36 to a still 38 which has a fractionating column 43. Concentrated acid is led to a tank 40, and the vapour of the solvent is condensed at 68 and returned to the tank 25. When a column is to be cleaned, it is cut out of the circuit by the appropriate valves and the liquids are drained away into a tank 50. Concentrated acid or other solvent for the sludge is vaporized in a still 53 and admitted to the column by way of a pipe 54, the condensate and sludge being received in a tank 63 where much of the sludge separates out, the remainder being led to the tank 51 or to the still 53. The process may be applied to the extraction of formic, propionic, and butyric acids. The extraction process may be that described in Specification 454,891. The Specification as open to inspection under Sect. 91 is described generally for the concentration of aliphatic compounds and mentions aqueous acids obtained by distillation or fermentation of fruits or plants or other industrial processes, and aqueous solutions of aliphatic anhydrides. This subject-matter does not appear in the Specification as accepted.