GB407656A - Process for the working up of aqueous solutions of organic acids in particular of acetic acid - Google Patents

Abstract

<PICT:0407656/III/1> Aqueous acids such as acetic, lactic, and valeric acids are extracted with a solvent, and the extract is distilled with an alcohol so as to produce a concentrated acid and an ester in any desired proportion. The solvent employed for the extraction may be of higher or lower boiling point than the acid and may be the ester to be produced, and in the distillation this may pass off with the water as an azeotropic mixture. An acid catalyst such as sulphuric acid may be employed for the esterification. In an example, fermentation acetic acid from a tank A is passed by a pipe 1 to a packed extraction column 3, and ethyl acetate from a tank B is led by a pipe 2 to the lower part of the column. The extract is taken by pipes 4, 11, to the upper part of a column 12, ethyl acetate vapour passing off by pipes 14, 15, 16 to a condenser 17. Concentrated acid containing some ethyl acetate leaves the column by a pipe 19 and passes to a column 20, ethyl acetate returning by pipes 21, 22 to the column 12, while acetic acid flows to a cooler 41. That portion of the acetic acid which does not leave the column 12 at 19 passes by an overflow 25 into the lower column 13 to which sulphuric acid is fed from a vessel C by pipes 27, 29 and ethyl alcohol is fed from a vessel D through a pipe 30 and evaporator 31, the alcohol vapour rising through the acid in the column 13. Ethyl acetate passes through 25 into the column 12 and so to the condenser 17. The sulphuric acid leaving the bottom of the column 13 is cooled at 34 and may be returned to the tank C. The effluent from the column 3 passes by a tube 5 into a column 6 into which steam is blown at 7, ethyl acetate being recovered in a condenser 9. In another example, dilute acetic acid is extracted with amyl acetate, the extract being led to the top of the column 13, acetic acid, amyl acetate, and water vapours escaping at 25 into the column 12 into which amyl alcohol and sulphuric acid are fed. Most of the amyl acetate is withdrawn at the bottom of the column 13. Acetic acid, water and amyl acetate vapours pass from the top of the column 12 by pipes 14, 47 into a column 48, acetic acid passing to a cooler 52 and amyl acetate and water vapour passing to a condenser 17. Steam can be blown in at 49 to remove any remaining amyl acetate. The rest of the amyl acetate formed in the column 12 flows in liquid phase together with the sulphuric acid by pipe 19 into the column 20. In another example, lactic acid is extracted with ethyl ether and the ether distilled off from this extract. Part of the lactic acid is drawn off and freed from remaining ether, and the rest is treated with vapour of ethyl alcohol for the production of ethyl lactate, a catalyst being unnecessary.ALSO:Aqueous acids such as acetic, lactic and valeric acids are extracted with a solvent, and the extract is distilled with an alcohol so as to produce a concentrated acid and an ester in any desired proportion. The solvent employed for the extraction may be of higher or lower boiling point than the acid and may be the ester to be produced, and in the distillation this may pass off with the water as an azeotropic mixture. An acid catalyst such as sulphuric acid may be employed for the esterification. In an example, fermentation acetic acid from a tank A is passed by a pipe 1 to a packed extraction column 3, and ethyl acetate from a tank B is led by a pipe 2 to the lower part of the column. The extract is taken by pipes 4, 11 to the upper part of a column 12, ethyl acetate vapour passing off by pipes 14, 15, 16 to a condenser 17. Concentrated acid containing some ethyl acetate leaves the column by a pipe 19 and passes to a column 20, ethyl acetate returning by pipes 21, 22 to the column 12, while acetic acid flows to a cooler 41. That portion of the acetic acid which does not leave the column 12 at 19 passes by an overflow 25 into the lower column 13 to which sulphuric acid is fed from a vessel C by pipes 27, 29 and ethyl alcohol is fed from a vessel D through a pipe 30 and evaporator 31, the alcohol vapour rising through the acid in the column 13. Ethyl acetate passes through 25 into the column 12 and so to the condenser 17. The sulphuric acid leaving the bottom of the column 13 is cooled at 34 and may be returned to the tank C. The effluent from the column 3 passes by a tube 5 into a column 6 into which steam is blown at 7, ethyl acetate being recovered in a condenser 9. In another example, dilute acetic acid is extracted with amyl acetate, the extract being led to the top of the column 13, acetic acid, amyl acetate and <PICT:0407656/IV/1> water vapours escaping at 25 into the column 12 into which amyl alcohol and sulphuric acid are fed. Most of the amyl acetate is withdrawn at the bottom of the column 13. Acetic acid, water and amyl acetate vapours pass from the top of the column 12 by pipes 14, 47 into a column 48, acetic acid passing to a cooler 52 and amyl acetate and water vapour passing to a condenser 17. Steam can be blown in at 49 to remove any remaining amyl acetate. The rest of the amyl acetate formed in the column 12 flows in liquid phase together with the sulphuric acid by pipe 19 into the column 20. In another example, lactic acid is extracted with ethyl ether and the ether distilled off from this extract. Part of the lactic acid is drawn off and freed from remaining ether, and the rest is treated with vapour of ethyl alcohol for the production of ethyl lactate, a catalyst being unnecessary.