US1982160A - Manufacture of acetic acid from alcohol - Google Patents

Description

Patented Nov. 27, 1934 UNITED STATES MANUFACTURE OF ACETIC ACID FROM ALCOHOL Henri Martin Gninot, Melle, France, assignor to Usines De Melle, Melle, Deux- Sevres, France No Drawing. Application September 5, 1933, Serlal No. 688,258. In France September 16,

Claims.

It is known that there exists a method of estimating alcohol by oxidation by means of potassium bichromate, the alcohol being quantitatively converted into acetic acid by fixation of the quan- 5 tity of oxygen strictly corresponding to the conversion:

In this method of estimation, one contents one- 19 self with determining the consumption of oxidizing agent in order to deduce therefrom the alcohol that was present in the liquid treated, without in addition endeavouring to estimate or to isolate the acid that is formed.

On the other hand, it has also been proposed to oxidize alcohol into acetic acid by electrolysis with leaden anodes (Takayama, J. Soc. Chem. Ind. 1926, No. 9, p. 129 B.) However, under these conditions the yield of acetic acid does not exceed 20 80%; as for the yield of utilization of the current, it does not exceed 75%. It is possible to improve the working a little, especially when the temperature is increased, by operating in the presence of chromic salts; however, the reaction of the destruction of the acetic acid under the influence of the current, which destruction is more pronounced the greater the concentration of the acid, has a limiting effect on the favourable action of these salts.

9 Moreover, the leaden anodes used for the electrolysis are attacked little by little owing to the presence of large quantities of acid in the solution treated.

According to the present invention, the alcohol is oxidized with almost quantitative yields by I duced and submitting the spent solution containing the reduced salts to the action of electrolysis to bring the salts back to the desired degree of oxidation in order to enable them to exert a fresh action on the alcohol.

For this purpose, one commences by causing a solution of an oxidizing salt, as for example potassium bichromate to act upon a hydro-alcoholic solution so as to have, after the reaction, as small an excess of oxidizing solution as possible. The dilute acetic solution obtained in this way is then treated in the cold in an extraction battery of known type by a solvent such as ethyl acetate or a mixture of benzene and methylethyl ketone or any other solvent which is only slightly sensitive to the action of the small quantity of, oxidizing agent that may remain in solution. In this connection it should be observed incidentally that ethyl acetate does not at first sight appear to be suitable because it is partially oxidized by the bichromate even in the cold; however, this is not a disadvantage, because, in the courseof the;r.e-'- action, the alcohol that is momentarily liberated by the oxidizing solution is converted into acetic acid, so that, in order to compensate the losses of ethyl acetate thus caused, it is sufficient, dur- 66 ing the subsequent separation of the anhydrous acid by distillation, to re-esterify a fraction of the acid that corresponds to the quantity formed to a minor degree at the expense of the ethyl acetate. 70

In all cases, the extract of acetic acid in the solvent is distilled ,by the known azeotropic method; the acid is separated in the anhydrous form whilst the recovered solvent can be repeatedly used indefinitely.

As for the spent aqueous solution leaving the extraction battery, it may, without disadvantage, contain a small proportion of acetic acid, the latter having the property of resisting sufliciently well in a very dilute, solution the subsequent operations of electrolytic oxidation carried out with a view to the regeneration of the oxidizing agent (Takayama, Zoc. cit). This possibility of contenting oneself with an exhaustion that is not far advanced and is consequently fairly inexs5 pensive forms one of the advantages and one of the features of the invention.

Thus the aqueous solution, that has been roughly freed from acetic acid and from solvent and that contains chromous salts, is then treated, advantageously by electrolysis, with a view to the regeneration of the original chromic solution. Here also, thanks to the indefinitely repeated use of the same batch of oxidizing solution, it is in no way essential to carry the operation to the end as is usually necessary in the manufacture of chromates. There is thus obtained a very high yield of utilization of the oxygen produced by the current, which yield is of the order of 95% to 98%.

The solution of chromic acid which is regenerated in this way is then used again for oxidizing fresh quantities of alcohol and so on. The small quantity of acetic acid, which had originally escaped the action of the solvent, is wholly in the regenerated chromic solution, so that there are finally obtained very high yields of direct conversion of alcohol into acetic acid. In practice, these yields vary from 90 to 99%.

The alcohol that is used as initial material can, no

without disadvantage, contain certain impurities, such as aldehydes, ethyl acetate, etc., which are converted into acetic acid by oxidation.

It is possible, without departing from the scope of the invention, to apply the method to other a1coholse. g. propyl'alcohol. With the higher alcohols, the molecule is split up and acids of lower molecular weight are obtained. Also instead of potassium bichromate, there may be used other oxidizing agents which are capable of quantitatively converting the alcohols into corresponding acidse. g. potassium permanganate used in a suitable proportion.

What I claim is:-

1. The method of manufacturing organic acids from alcohols, consistingin treating the alcohol with an oxidizing agent capable of regeneration by electrolysis, extracting the produced acid by a solvent, regenerating the residual spent oxidizing agent by electrolysis for re-use, and separating the acid-solvent mixture into acid and solvent.

2. The method of manufacturing organic acids from alcohols, consisting in treating the alcohol with an oxidizing agent capable of regeneration by electrolysis, extracting the produced acid by a solvent, regenerating the residual spent oxidizing agent by electrolysis, re-using the regenerated agent in the process, separating the acid-solvent mixture by azeotropic distillation into acid and solvent, and re-using the recovered solvent in the process.

3.- The method of manufacturing organic acids from alcohols, consisting in treating the alcohol with an aqueous solution of a bichromate salt, extracting the produced acid by a solvent not materiallyafiected by said salt, regenerating the residual spent salt solution by electrolysis for reuse, and separating the acid-solvent mixture by azeotropic distillation into acid and solvent and re-using the recovered solvent in the process. 4. The method of maufacturing organic acids from alcohols, consisting in treating the alcohol withan aqueous-solution of a bichromate salt, extracting the produced acid by ethyl acetate, regenerating the residual spent salt solution by electrolysis for re-use and separating the acid from the ethyl acetate by azeotropic distillation and re-using the latter in the process.

5. The method of manufacturing organic acids from alcohols, consisting in treating the alcohol with an aqueous solution of a biohromate salt, extracting the produced acid by a mixture of benzene and methylethyl ketone, regenerating the residual spent salt solution by electrolysis for reuse and separating the acid from said mixture by azeotropic distillation and re-using the mixture in the process.

' 6. The method of manufacturing acetic acid from ethyl alcohol, consisting in treating the alcohol with an oxidizing agent capable of regeneration by electrolysis, extracting the produced acid by a solvent, regenerating the residual spent agent by electrolysis for re-use and separating the acidsolvent mixture into acid and solvent.

7. The method of manufacturing acetic acid from ethyl alcohol, consistingin treating the alcohol' with an aqueous solution of a bichromate salt, extracting the acetic acid by a solvent, regenerating the spent salt solution by electrolysis, separating the acetic acid from the solvent by azeotropic distillation and re-using the latter in the process.

8. The method of manufacturing acetic acid from ethyl alcohol, consisting in treating the alcohol with an aqueous solution of a bichromate salt, extracting the acetic acid by ethyl acetate, regenerating the spent salt solution by electrolysis, re-

using the regenerated solution in the process, separating the acetic acid from the ethyl acetate by azeotropic distillation, and re-using the recovered ethyl acetate in the process.

9. The method of manufacturing acetic acid from ethyl alcohol, consisting in treating the alcohol with an aqueous solution of a bichromate salt, extracting the acetic acid by a mixture of benzene and methylethyl keto'ne, regenerating the spent salt solution by electrolysis, re-using the regenerated solution in the process, separating the acetic acid from the benzene and methylethyl ketone by azeotropic distillation, and reusing the recovered benzene and methylethyl ketone in the process.

10. The method of manufacturing acetic acid from ethyl alcohol, consisting in treating the alcohol with an aqueous solution of oxidizing agent capable of regeneration by electrolysis, roughly extracting the produced acetic acid by a solvent not materially affected by said oxidizing agent, separating the acid from the solvent by azeotropic distillation, regenerating by electrolysis the spent oxidizing agent containing any unextracted acid,

and re-using the regenerated agent together with said unextracted acid in the process;

HENRI MARTIN GU'INOT.