GB356787A - Process for the production of concentrated aliphatic acids - Google Patents

Abstract

In the concentration of acetic, propionic, butyric, and other lower acids by distilling with an added liquid (termed an entraining liquid) which forms with water an azeotropic mixture boiling at a lower temperature than the acid, the aqueous acid and the entraining liquid are brought into the form of a homogeneous mixture prior to the distillation. The dilute acid and entraining liquid may be mixed with concentrated acid, for instance they may be each introduced into the heated concentrated acid in such proportions that the mixture does not separate into layers. The dilute acid and entraining liquid may be introduced continuously into a heated mixture of concentrated acid and entraining liquid in a still, which is preferably provided with a rectifying column, and the entraining liquid which separates from the condensate is returned to the still, concentrated acid being withdrawn from the still and treated in an auxiliary distillation p column to separate anhydrous acid. Or dilute acid, entraining liquid, and concentrated acid in proportions to form a homogeneous mixture, may be introduced into a distilling column, an azeotropic mixture of water and entraining liquid passing off at the top and concentrated acid being withdrawn at the bottom without needing an auxiliary column. If desired the dilute acid, entraining liquid and concentrated acid may be mixed in a separate vessel, the mixture being withdrawn continuously and fed to a distillation column for instance at a point one-third from the bottom, an auxiliary column being unnecessary. In all cases the column may be provided with a dephlegmator or other device for returning a part of the condensate to the column, and the heat of the vapour and of the concentrated acid may be utilized for instance to heat the dilute acid and the entraining liquid. Suitable entraining liquids are hydrocarbons such as benzene or xylene, halogenated hydrocarbons such as trichlorethylene and ethylene dichloride and esters such as ethyl, propyl, and butyl acetates or mixtures of such bodies.ALSO:In the concentration of acetic, propionic, butyric and other lower aliphatic acids by distilling with an added liquid (termed an entraining liquid) which forms with water an azeotropic mixture boiling at a lower temperature than the acid, the aqueous acid and the entraining liquid are brought into the form of a homogeneous mixture prior to the distillation. The dilute acid and entraining liquid may be mixed with concentrated acid, for instance they may be each introduced into the heated concentrated acid in such proportions that the mixture does not separate into layers. The dilute acid and entraining liquid may be introduced continuously into a heated mixture of concentrated acid and entraining liquid in a still, which is preferably provided with a rectifying column, and the entraining liquid which separates from the condensate is returned to the still, concentrated acid being withdrawn from the still and treated in an auxiliary distillation column to separate anhydrous acid. Or dilute acid, entraining liquid, and concentrated acid in proportions to form a homogenous mixture, may be introduced into a distilling column, an azeotropic mixture of water and entraining liquid passing off at the top and concentrated acid being withdrawn at the bottom without needing an auxiliary column. If desired the dilute acid, entraining liquid and concentrated acid may be mixed in a separate vessel, the mixture being withdrawn continuously and fed to a distillation column, for instance at a point one third from the bottom, an auxiliary column being unnecessary. In all cases the column may be provided with a dephlegmator or other device for returning a part of the condensate to the column, and the heat of the vapour and of the concentrated acid may be utilized for instance to heat the dilute acid and/or the entraining liquid. Suitable entraining liquids are hydrocarbons such as benzene or xylene, halogenated hydrocarbons such as trichlorethylene and ethylene dichloride and esters such as ethyl, propyl and butyl acetates or mixtures of such bodies.