GB348282A - Improvements in the separation of anhydrous organic acids from their aqueous solutions - Google Patents

Abstract

Monobasic organic acids of the aliphatic series, other than acetic acid, are separated from their aqueous solutions by extraction with a solvent which is insoluble or only slightly soluble in water, has a boiling point higher than that of the acid and does not form an azeotropic mixture therewith, followed by dehydration of the extract with an entrainer which forms with water an azeotropic mixture having a minimum boiling point lower than that of the mixture formed by water and the solvent, as in the parent Specification. The acid vapours may be used to heat the dehydrating column as in Specification 300,246, [Class 32, Distilling &c.]; and the extraction stage may be carried out in the vapour phase, as in Specification 301,415, [Class 32, Distilling &c.]. The solvent may be separated from the acid by the use of an accessory liquid forming with the acid a minimum boiling point mixture as in Specification 317,462, [Class 32, Distilling &c.]. Aqueous propionic acid is extracted with amyl propionate, and the extract is dehydrated by distillation with ethyl propionate. The propionic acid may be separated from the amylpropionate by distillation with a petroleum fraction of B.P. 138-140 DEG C., with which the acid forms an azeotropic mixture. Aqueous formic acid is extracted with amyl formate, and dehydrated with propyl formate; the formic acid is separated from the amyl formate in azeotropic mixture with normal heptane.ALSO:Monobasic organic acids of the aliphatic series, other than acetic acid, are separated from their aqueous solutions by extraction with a solvent which is insoluble or only slightly soluble in water, has a boiling point higher than that of the acid, and does not form an azeotropic mixture therewith, followed by dehydration of the extract with an entrainer which forms with water an azeotropic mixture having a minimum boiling point lower than that of the mixture formed by water and the solvent, as in the parent Specification. The acid vapours may be used to heat the dehydrating column as in Specification 300,246, [Class 2 (iii), Dyes &c.]; and the extraction stage may be carried out in the vapour phase, as in Specification 301,415, [Class 2 (iii), Dyes &c.]. The solvent may be separated from the acid by the use of an accessory liquid forming with the acid a minimum boiling-point mixture as in Specification 317,462, [Class 2 (iii), Dyes &c.]. Aqueous propionic acid is extracted with amyl propionate, and the extract is dehydrated by distillation with ethyl propionate. The propionic acid may be separated from the amyl propionate by distillation with a petroleum fraction of B.P. 138-140 DEG C., with which the acid forms an azeotropic mixture. Aqueous formic acid is extracted with amyl formate, and dehydrated with propyl formate; the formic acid is separated from the amyl formate in azeotropic mixture with normal heptane.