US2425882A - Oxidation of lower aliphatic alcohols - Google Patents

Description

Patented 'Aug. 19, 1947 UNITED STATES PATENT OFFICE OXIDATION OF LOWER ALIPHATIC ALCOHOLS David 0. Hull, Kingsport, Tenn., assignor to Eastman Kodak Com corporation of New J pany, Rochester, N. Y., a ersey Application July 8, 1944, Serial No. 544,003

. 6 Claims. 1 This invention relates to thedirect oxidation of organic compounds, particularly the oxidation of hydroxy compounds such as lower aliphatic alcohols oxidized directly to acids. 7

As pointed out in my U. S. Patent No. 2,287,803 prior art oxidation processes have required the employment of relatively hightemperaturessuch as 300 C. or 100 C. and the application of several steps. In other words, the oxidation either has not been direct, or if there has been direct conversion, the yields have been very. low. For example, considering prior art procedure for con verting ethanol to acetic acid, before my invention it was considered necessary to first dehydrogenate all of the ethanol and thereafter the aldehydic dehydrogenation product was 'converted to the acid which, as can be seen, involves a number of steps.

Carrying out oxidation processes in accordance I use or relatively high temperatures. Also there may in some instances be the disadvantage of i with the prior art possesses a number of disad vantages exemplified, for example, by the required polyhydroxy alcohols and other similar organic compounds. Another and particular object of this invention is to provide a direct oxidation process which may be operated at relatively low temperatures and under ordinary pressure conditions, yet give very satisfactory yields of the desired oxidation products. Still another object is to provides. direct oxidation process for the conversionof alcohols to acids wherein the alcohol may be converted, not only to an acid having a number of carbon atoms corresponding to the number of carbon atoms in the alcohol molecule,

but also to a different acid. A still further object is to Provide a, process which may be operated underother than normal atmospheric conditions, namelyfunder either superatmospherlc or reduced pressures.

A further object is to provide a direct oxidation process that may be applied to either alcohols alone or mixtures of alcohols and aldehydes, or other types of mixtures.

' process which may be applied to various mixtures polymerization of the products and of 'the start-"- ing materials accompanied by low yields'andother After further investigation I have. found thatthere are certain other catalytic materials which may be employed in direct oxidation processes in a manner akin to the procedure set forth in my of alcohols and aldehydes wherein both the alcohol and the. aldehyde are converted into useful goxidation products. Another object is to provide a direct oxidation process, particularly adapted to the treatment of alcohols such as butyl alcohol and the like wherein, not only may butyric acid be obtained, but contents of other acids.

A further object is to provide novel catalysts containing liquids particularly adapted for employment in the aforesaid types of processes for U. 8. Patent No. 2,287,803 which, not only permits obtaining directoxidation, but permits the production of a relativelylarger variety of products than has heretofore been obtainable.

This invention has for one object to provide a process for the direct oxidation of organic compounds. Another object is to provide a direct oxidation process which is particularly valuable for the direct conversion of lower aliphatic alcohols to lower aliphatic acids in substantially a single step. Still another object, however, is to provide a process which may also be applied to, not only the monohydroxy alcohols, but to the the direct conversion of alcohols alone, or alcohols in various admixtures, into useful oxidation products. A still further object is to provide methods for producingithe catalysts as well as for activating and utilizing the catalysts.

As already indicated, prior to my invention if an alcohol were to be oxidized it was generally first dehydrogenated and then the dehydrogena tion products further treated. In any event prior art processes as applied to alcohols usually invalve the utilization of temperatures in excess of 300 C., which, not only requires substantial heat input but, due to the higher. temperatures and other conditions required in handling chemicals,

involves dangers of loss from polymerization or other undesired reactions. Also apparatus de struction may be more severe.

- I have found that contrary to such procedure an organic compound, exemplified in particular by a hydroxy compound as a lower aliphatic alcohol, may be directly oxidized at relatively low temperatures, even temperatures substantially A still further object is' to provide a direct, low-temperature oxidation below 100 C., with any of the usual oxidizing mediums of which the commonest one, namely air, may be readily utilized in my process. Also my process, after it is placed in operation, does not usualh' require any heat input but generates suflicient heat itself to maintain the reaction. Not only may single organic compounds be treated, but various mixtures of the organic compounds may be treated. For example, I have found that a mixture comprising a lower aliphatic alcohol, together with a corresponding or a different aldelnrde, may be efliciently treated by my novel process and catalyst to give very high yields of aliphaticacid. By my process and choice of catalyst it is possible to obtain one or more acids in the oxidation procedure. The foregoing features. as well as features of treating various mix,- tures under different conditions, will be set forthin detail hereinafter.

While the oxidation procedure may be carried out in the apparatus described in my U. S. Patent No. 2,287,803, for convenience of consideration and for a better understanding of the present invention reference will be made to the attached drawing. The single figure thereof may be considered a semi-diagrammatic side elevation view showing a general apparatus arrangement which could be employed for carrying out my process.

Referring to the drawing, 2 represents an oxidation unit which may comprise any of several different constructions. For example, the preferred external construction would, in a large diameter unit, be in accordance with H'asche Patent 2,159,988. However, the construction may be a sieve plate column, bubble plate column, or other comparable arrangement for permitting the contact of an oxidizing medium containing free oxygen with the material to be oxidized. In the unit shown in the attached figure the column merely comprises an elongated open column of relatively narrow dimensions. Attached to the lower part of the unit at 3 and l. are cooling 4 a receiver 28 at the lower part thereof and vent conduit 21 from the upper part thereof, which may lead through a meter or other device for measuring and testing the eiiluents.

There may also be associated with the apparatus thermometers or other temperature controlling devices or various exchangers for recovering heat or otherwise faclhtating or rendering the operation of the process more economical, or permitting it to be operated with automatic control. in these respects.

I have found that certain metal compounds. as for example, salts derived from group V metals included in the group consisting of vanadium, bismuth, tantalum, antimony, arsenic and columbium may be incorporated in acidic solutions and that these solutions will function as a catalyst medium for the direct oxidation of organic compounds. That is, an alcohol alone or an alcohol and other organic compounds to be oxidized, may be passed into a catalyst solution. as aforementioned, in the presence of an oxidizing medium containing free oxygen and the alcohol may be directly oxidized to acid, as will be observable from the specific data which follow.

In preparing catalyst solutions for use in the present process, any convenient source of the metal may be employed, such as salts, oxides, or other derivatives thereof. Preferably, a derivative wil1 be chosen which is easily soluble under the conditions of the process. For example, assuming that it is desired to convert an aliphatic alcohol such as ethanol or butanol directly to the corresponding aliphatic acid, the derivative of the catalyst metal may, for example, be a compound such as vanadium, bismuth, tantalum,

- antimony, arsenic and columbium jackets provided with inlets for cooling medium as at 8 and l.

The upper part of the unit was provided with a similar Jacket I; however, in this Jacket, rather .ll, l2, and I3.

As indicated, if desired in place of the external jackets, coils may be included within the unit and in large-size units such arrangement wherein internal coils, or both coils and jackets are employed, may be desirable.

The lower part 'of the unit is provided with a plurality of inlet conduits, namely, inlet conduit H which is connected with a temperature-controlled feed supply It. Also leading into the lower part of the unit is an inlet conduit i! for oxidizing medium.

The upper part of the unit is provided with a drawofi conduit I! which leads through condenser l9 into separator 2!. This separator has attached thereto a receiver 22 for condensate and a branch conduit 23 through which non-condensables may be conducted to the scrubber 2|.

The aforementioned scrubber is provided with While the aforementioned metal derivatives may be employed in various organic liquids, which are solvents therefor, for simplicity of operation and minimizing the necessity of complicated separations I prefer to dissolve the catalyst compound in a liquid principally composed of one of the materials which is to be produced in the process. For'example, in the event my process were to be applied in converting butyl alcohol directly into butyric acid I would preferably dissolve the catalyst compound in an aliphatic .acid such as butyric acid, although propionic or acetic acid could also be used. However, for initially preparting the catalyst solution other liquids could be employed, as for example, organic esters and the like such as butyl or ethyl acetate.

In any event, irrespective of the exact metal compound and the liquid that the compound is dissolved in, the catalyst solution would be given a vigorous oxidation treatment such as blowing with a substantial amount of air, usually for a period of at least 5 or 10 minutes, and if desired, for several hours. This treatment would be accompanied by'the introduction of an aldehyde along with the oxidizing medium which functions to convert the metal ions of the catalyst metal into a higher state of valence than their lowest valence. The treatment may be accompanied by heating obtained in any convenient manner, such as by flowing a heating medium in the jackets or coils in association with the oxidation unit or by introducing heating air. The temperature of treatment, however, may vary from around 0 C. .up to the boiling point of the particular liquid present. Inother words the solution is maintained under liquid phase conditions.

It is also preferred to incorporate the oxidiz- Hence, my invention is not to be restricted ing medium into the catalyst liquid under at least atmospheric pressure as this permits the inclusion of a larger amount of oxidizing medium and fully saturates the catalyst liquid.

After the catalyst liquid containing a group V metal compound as already described has been treated and brought to a starting temperature, usually above room temperature but below about 100 0., the organic compound to be oxidized may be supplied to the process.

That is, referring to the attached drawing, the oxidation column 2 is filled with the catalyst liquid comprising oneor more of the group V metal compounds of the type described dissolved in the solvent and maintained at the desired temperature. The hydroxy compound to be oxidized is introduced into the oxidation process through conduit l4 and the oxidizing medium, usually air (although pure oxygen or ozone may be employed and appear to render the catalyst solution more active, but are not necessary), and the compound oxidized to one or more desired oxidation products, as will be described hereinafter.

Assuming that the oxidation product is a liquid,

a portion thereof may be volatilized or pumped off through conduit it through the condenser 20- where condensables are condensed out to be collected in receiver 22. The unconsumed gases (as nitrogen when air is used as oxidizing medium), unoxidized organic compoxmds and the like components, uncondensed, pass through conduit 23 into scrubber 14 where they are recovered. While only a single scrubbing .unit has been indicated. a plurality of such units may be employed or other recovery devices utilized.

The operation of my process to convert an or- Uanic compound such as ethyl alcohol, propyl alcohol, butyl alcohol, or other aliphatic hydroxy compounds to the desired acids and the function of the group V metals as aldehyde activated catalysts is quite clearly illustrated by the data appearing in the folowing table:

product of the oxidation, while the tion of the remaining alcohol was left unchanged. As indicated, while at normal atmospheric pressure, a temperature under 100 0. appears to be quite satisfactory, the particular temperature selected will be determined largely by reference to the particular alcohol to be oxidized and whether the process is to be operated under pressure or merely at atmospheric pressure. For example, although I find a temperature range of -5 C. to 90 C. satisfactory for the oxidation of butyl alcohol to butyric acid, if ethyl or propyl alcohol is to be converted by my process, with or without butyl alcohol, I prefer a temperature range of C. to C.

Under preferred operating conditions as, for example, when air is used as the oxidant, this may be supplied under some pressure and, if desired, a rather substantial excess may be employed, although for normal operations merely major poran excess is required; that is, such an amount that a few per cent of oxygen will be present in the eilluents. In the event of the use of other oxidants such as relatively pure oxygen and ozone, smaller amounts are required and may be supplied under substantial pressure to cause them fully to permeate the entire catalyst solution.

The oxidation of any given alcohol in accordance with my process may be accomplished by activating the catalyst metal in the solution by means of a single aldehyde or by a plurality of aldehydes. For example, in oxidizing ethyl alcohol, Imay employ acetaldehyde, propionaldehyde, or butyraldehyde alone or two or more of them. 'Moreover, I may oxidize ethyl alcohol. propyl alcohol, butyl alcohol, or amyl alcohol by employing any one or more of aldehydes such as acetaldehyde, propionaldehyde, butyraldehyde.

and so on. However, inasmuch as acetaldehyde is in many instances most readily available and has a low boiling point, it would preferably be employed along with other alcohols such as butyl alcohol, amyl alcohol, and the like, as represent- Percent G B t l Grams Grams Grams Percent Percent Metal A ta Metal Salt HAc BOBu HOP: Conversion Conversion m m Cat. 001. Feed rm. rm. to HOBu to Hon- Bismuth 1 m 2,016 350.2 41.1 sso 1.1 Vsuadium-.-.-..-. 1.7 420 1,260 217.3 75.2" 43-4 18.1

The foregoing examples were carried out in apparatus as indicated in the attached drawing and at a. temperature between 30 C. and 50 (3., although a wider range of temperatures, such as -5 C. to 90"v C. could be employed satisfactorily. It will be observed from the above table that I have employed a relativel small amount of the metal acetate in the catalyst solution in the examples given, but this may be varied rather widely. For examples, I may use anywhere from 1 or 2% of the metal acetate up to 12% or more.

While the foregoing examples are illustrative of prefered embodiments of my invention, it will be evident that many modifications therein may be made within the scope of the inventive concept involved. As previously indicated, these catalysts may be used under the conditions outlined above for the conversion of various aliphatic alcohols to acids. They may be employed in the form of a single salt or mixtures of salts of any desired organic acid or acids.

In the above examples, there was some small percentage of alcohol converted to acetic acid I and some to butyl esters in addition to the main ing the most economical procedure, as well as tending to lower the boiling points and permit the functioning of the process at the lowest practical tem tures.

As alre dy indicated, the pressure may be varied over wide limits without basically changing the prbcess. However, since the process functions satisfactorily under normal atmospheric pressures I prefer to operate under such conditions. In some instances, such as for saturating the catalyst solution with oxygen, I may apply a few pounds pressure up to 2 or 3 atmospheres for this purpose. Also, as indicated, the process functions very well at temperatures of 5 C. to 50 or 70 C. and normal atmospheric pressure. However, by raising the temperature above the range indicated to C., for example,

the pressure should be increased in order to asbe correspondingly reduced as the amount of alcohol fed was increased. In general, it may be said that I prefer to carry out the process under liquid phase conditions and at a temperature of 30 C. to 70 C.

One valuable aspect of the present invention is that acids having fewer carbon atoms than the alcohol being oxidized may be directly produced, and the proportion of these other acids to the acid having the same number of carbon atoms as the alcohol being oxidized may be varied by choice of the particular catalyst.

It is apparent from the foregoing that my invention is applicable to the direct oxidation of the various organic compounds, particularly hydroxy compounds such as various alcohols. The foregoing data are merely illustrative of some of the materials to which my low temperature liquid phase process may be applied, but various other ccmpounds, such as hydroxy alcohols exemplified by glycols. may be treated in a comparable manner. Hence, I do not wish to be restricted in my invention except insofar as is necessitated by the prior art and the spirit of the appended claims.

What I claim and desire to secure by Letters Patent of the United States is:

1. A process for the direct oxidation of a lower aliphatic alcohol to obtainthe corresponding aliphatic acid, which comprises .treating a solution of a metal ion of a group V metal selected from the group consisting of vanadium, bismuth, tantalum, antimony, arsenic and columbium in an aliphatic acid with an aldehyde and a gaseous oxidizing medium to form an active catalyst solution, introducing material amounts of a lower aliphatic alcohol and a lower aliphatic aldehyde into the activated catalyst solution, oxidizing the alcohol of the resulting solution of catalyst, alcohol and aldehyde to the corresponding acid by treating said solution with a gaseous oxidizing medium, maintaining the temperature of the solution of catalyst, alcohol and aldehyde during its treatment with the gaseous oxidizing medium such that the solution is maintained in the liquid phase, and subsequently recovering the aliphatic acid produced.

2. A process for the direct oxidation of a lower aliphatic alcohol to obtain the corresponding aliphatic acid, which comprises treating a solution of a metal ion of a group V metal selected from the group consisting of vanadium, bismuth, tan talum, antimony, arsenic and columbium in an aliphatic acid with an aldehyde and a gaseous oxidizing medium to form an active catalyst solution, introducing material amounts of a lower aliphatic alcohol and a lower aliphatic aldehyde into the activated catalyst solution, oxidizing the alcohol of the resulting solution of catalyst, alcohol and aldehyde to the corresponding acid by treating said solution with a gaseous oxidizing medium, maintainin the temperature of the solution of catalyst, alcohol and aldehyde during its treatment with the gaseous oxidizing medium such that the solution is maintained in the liquid phase at a temperature of from C. to 100 C., and subsequently recovering the aliphatic acid produced,

3. The process of claim 2 in which the catalyst, alcohol and aldehyde is maintained during its treatment with the gaseous oxidizing medium at a temperature of 30 C. to 70 C.

4. A process for the direct oxidation of a lower aliphatic alcohol to obtain a lower aliphatic acid. which comprises treating a solution of a bismuth salt in an aliphatic acid with an aldehyde and a gaseous oxidizing medium to form an active catalyst solution, introducing material amounts of a lower aliphatic alcohol and a lower aliphatic aldehyde into the catalyst solution, oxidizing the alcohol of the resulting solution of catalyst, alcohol and aldehyde to the corresponding acid by treating said solution with a gaseous oxidizing medium, maintaining the temperature of the solution of catalyst, alcohol and aldehyde during its treatment with the gaseous oxidizing medium such that the solution is maintained in the liquid phase at a temperature below C.. and subsequently recovering the aliphatic acid produced.

5. A process for the direct oxidation of a lower aliphatic alcohol to obtain the corresponding aliphatic acid, which comprises treating a solution of a vanadium salt in an aliphatic acid with an aldehyde and a gaseous oxidizing medium to form an active catalyst solution, introducing material amounts of a lower aliphatic alcohol and a lower aliphatic aldehyde into the catalyst solution, oxidizing the alcohol of the resulting solution of catalyst, alcohol and aldehyde to the corresponding acid by treating said solution with a gaseous oxidizing medium, maintaining the temperature of the solution of catalyst, alcohol and aldehyde during its treatment with the gaseous oxidizing medium such that the solution is maintained in the liquid phase at a temperature :below 100 C. and subsequently recovering the aliphatic acid produced.

6. A process for the direct oxidation of a lower aliphatic alcohol to obtain an acid mixture containing a major proportion of an acid corresponding to the alcohol being oxidized and a minor proportion of an acid having a less number of carbon atoms than the alcohol, which comprises treating a solution of a metal ion of a group V metal selected from the group consisting of vanadium, bismuth, tantalum, antimony, arsenic and columbium in an aliphatic acid with an aldehyde and a gaseous oxidizing medium to form an active catalyst solution, introducing material amounts of a lower aliphatic alcohol and a lower aliphatic aldehyde into the catalyst solution, oxidizing the alcohol of the resulting solution of catalyst, alcohol and aldehyde to the corresponding acid by treating said solution with a gaseous oxidizing medium, maintaining the temperature of the solution of catalyst, alcohol and aldehyde during its treatment with the gaseous oxidizing medium such that the solution is maintained in the liquid phase at a temperature of -50 C. to C., and subsequently recovering the aliphatic acid produced.

DAVID C. HULL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,285,914 Drossbach June 9, 1942 2,263,607 Bludworth Nov. 25, 1941 2,287,803 Hull June 30, 1942 2,265,948 Loder Dec. 9,1941

FOREIGN PATENTS Number Country Date 111,050 Australia July 25, 1940 Dettifieete of Deflection Patent No. 2,425,882. August 19, 1947'.

DAVID C. L

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Column 8, line 57, for 50 C. to 150 (3.; read 5 0'. to 150 0.; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 30th day of September, A. D. 19%.

it; ME

THOMAS F. i PHYQ Assistant @ommz'estooer of Patenteu

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