US2425881A - Oxidation of lower aliphatic alcohols - Google Patents

Description

pounds.

oxidation process which is particularly valuable Patented Aug. 19, 1947 UNITED STATES PATENT OFFICE.

OXIDATION OF LOWER ALIPHATIC ALCOHOLS David C. Hull, Kingsport, Tenn., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application July 8, 1944, Serial No. 544,002

6 Claims. (Cl. 260-531) .verting ethanol to acetic acid, before my invention it was considered necessary to first dehy- I 'drogenate 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 with the prior art possesses a number 'of disadvantages exemplified, for example, by the required use of relatively high temperatures. Also there may in some instances be the disadvantage of polymerization of the products and of the starting materials accompanied by low yields and other losses.

In my U. 8. Patent No. 2,287,803 I have described a process for a more direct oxidation of organic compounds. While the process of my application functions very satisfactorily and gives good yields inrelatively few steps, it involves the utilization of metals having an atomic number from 25 to'29. It is, therefore, apparent that it is desirable, particularly under present conditions. to develop a process in order that other metals may be employed and the process improved in' other respects, as will be apparent from the description which follows.

After further investigation I have found that there are certain other catalytic materials which may be employed in direct oxidation processes in a manner akin to the procedure set forth in my U. 8. Patent No. 2,287,803 which, not only permits obtaining direct oxidation, but permits the production of a relatively larger variety of products than has heretofore been obtainable.

This invention has for one object to provide a process for the direct oxidation of organic com- Another object is to provide a direct provide a process which may also be applied to,

not only the monohydroxy alcohols, but to the 2 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 de--,

sired oxidation products. Still another object is to provide a direct oxidation process for the conversion of alcohols to acids wherein the alco hol 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 under other than normal atmospheric conditions, namely, under either superatmospheric 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. A still further object is to provide a direct, low-temperature oxidation process which may be applied to various mixtures of alcohols andaldehydes wherein both the alcohol and the aldehyde are converted into useful oxidation 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 em ployment in the aforesaid types of processes for the direct conversion of alcohols alone, or alcohols in various admixtures, into useful oxidation prodart processes as applied to alcohols usually involve 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, in-

volves dangers of loss from polymerization or other undesired reactions. Also apparatus destruction may be 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 auaaei below 100' 0., with any of the usual oxidizing of aliphatic acid. 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 mixtures under different conditions, will be set forth in detail hereinafter.

While the oxidation procedure maybe 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 dliferent constructions. For example, the preferred external construction would, in a large diameter unit, be in accordance with Hasche 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 6, are cooling jackets provided with inlets for cooling medium as at 6 and l.

The upper part of the unit was provided with a similar jacket 8; however, in this jacket, rather than coolin medium some heating medium may be circulated in the event that high boiling components are being directly oxidized or the reaction temperature is to be held lower than that which would maintain a constant volume of catalyst. Inasmuch as the construction is substantially the same, however, the mechanical construction would be approximately the same and an inlet provided at 9, l and 6; outlets are provided at H, 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 M which is connected with a temperature-controlled feed supply l6. Also leading into the lower part of the unit is an inlet conduit H for oxidizing medium.

The upper part of the unit is provided with a drawofl conduit I8 which leads through con- 7 denser {9 into separator 2|. This separator has attached thereto a receiver 22 for condensate and a branch conduit 23 through which noncondensables may be conducted to the scrubber The aforementioned scrubber is provided with 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-emuents.

There may also be'associated with the apparatus thermometers or other temperature controlling devices or various exchangers for recovering heat or otherwise facilitating or rendering the operation of the process more economical, or permitting it to be operated with automatic control. Hence, my invention is not to be restricted in these respects.

I have found that certain metal compounds, as for example, salts derived from group IV metals included in the group consisting of tin, lead,

thorium, titanium, germanium, zirconium and hafnium may be incorporated in acidic solutions and that these solutions will function as acatalyst medium for the direct oxidation of organic compounds. That is, an'alcohol alone or an alcohol and other organic compounds to be oxidlzed, 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 will 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 be a compound such as tin acetate, lead acetate, thorium acetate, titanium acetate, germanium acetate, zirconium acetate, 40 and hafnium acetate.

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 butyrlc 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 preparing 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 o manner, such as by flowing a heating medium in the jackets or coils in association with the oxidation unit or by introducing heated air. The

temperature of treatment, however, may vary from around 0 C. up to the boiling point of the particular liquid present. In other -words the It is also preferred to incorporate the oxidizing medium into the catalyst liquid under at least atmospheric pressure as this permits the inclupercentage of alcohol converted to acetic acid and some to butyl esters in addition to the main product of the oxidation, while the major portion of the remaining alcohol was left unchanged. As

5 indicated, while at normal atmospheric ressure, sion of a larger amount of oxidizing medium and' .a temperature under 100 C. appears to be quite fully saturates the catalyst liquid. satisfactory, the particular temperature selected After the catalyst liquid containing a group IV will be determined largely by reference to the metal compound as already described, has been particular alcohol to be oxidized and whether the treated and brought to a starting temperature, process is to be operated under pressure or merely usually above room temperature but below about at atmospheric pressure. For example, although 100 C., the organic compound to be oxidized'may I ilnd a temperature range of C. to 90 C. be supplied to the process. satisfactory for the oxidation of butyl alcohol to That is, referring to the attached drawing, the butyric acid, it ethyl or ropyl alcohol is to be conoxidation column 2 is filled with the catalyst 16 verted by my process, with or without butyl liquid comprising one or more of the group IV alcohol, I prefer a temperature range of 30 C. metal compounds of the type described dissolved to 50 C. in the solvent and maintained at the desired Under preferred operating conditions as, for temperatur The hy y compoun to be oxiexample, when air is used as the oxidant, this dizied is introduced into the oxidation process 20 may be supplied under some pressure and, if through conduit l and e oxidizing e desired, a rather substantial excess may be ems y a t u h pu e x en or ozone may ployed, although for normal operations merely an be mp oy and pp l to r r the Catalyst excess is required; that is, such an amount that solution more active, but are not necessary), and a few per t of oxygen i be present in t t e mpoun o idi to v r more r eflluents. In the event of the use of other oxioxldation products, as will be described hereinm such as relatively pure oxygen and ozone aftersmaller amounts are required and may be sup- Assumme that Oxidation Product is pliedunder substantial pressure to cause them Portien thereof may be voletilized fully to permeate the entire catalyst solution. Pumped ofi'through conduit through the e The oxidation of any given alcohol in accorddenser l9 where condensables are condensed out ance with my process may be accomplished by to be collected m receiver The unconsumed activating the catalyst metal in the solution by gases (as nitrogen when air is used as oxidizing means of a Single aldehyde or by a plurality, of medium), unoxidized organlcdcompourrlids ailld the aldehydes For example, in oxidizing ethyl ab like components, uncondense ,pass t roug concohol, I may employ acetaldehyde pmpmnalde duit 23 into scrubber 24 where they are recovhyde, or butyraldehyde alone or two or more of ered. While only a single scrubbing unit has them Moreover I ma 0 x1 dize em I ale hol been indicated, a plurality of such units may be 1 h l b l 1 1 1 employed or other recovery devices utilized. propy e0 0 y \1 Y a 00 0 or amy a co 0 y The operation of my process to convert an or- 40 employmg any one or more of aldehydes Such as ganic compound such as ethyl alcohol, propyl acetaldehyde, propionaldehyde, butyraldehyde, alcohol, but l alcohol, or other aliphatic hydroxy d so However. inasmuch s a ld yde compounds t t desired acids and t function is in many instances most readily available and of the group IV metals as aldehyde activated has a 10W 00111118 p it would Preferably be catalysts is quite clearly illustrated by the data employed 0 8 w t other a c s s h as butyl appearing i th following t bl alcohol, amyl alcohol, and the like, as represent- Pcrcent SBHWI Grams G ams firsili ls CPercenit CPercent than; Me PM its that a... .Zttti era-s2 s .a 500 17.43 2. 0 5. 01 or titer... 4.5 :52 704 27.3 N n 6.53

The foregoing examples were carried'out in ap- H s t st mi al pr ur s. a; w l as paratus as indicated inthe attached drawing and M tending to lower the boiling points an permit at a temperature between 30 C. and C., 91- thefunctioning of the process at the lowest praciilgough a ggi dgr ranlgjegef temfieragurisi, fsucch rials te l lipegetuiretsl. t d th b .to .cou emp oye sa s ac or y. & y n we e 6 Pressure y 8 It will be observed from the above table that I varied over wide limits without basically h n have employed a relatively small amount of the 00 mg the process. However, since the process funcmetal acetate in the catalyst solution in the extions satislfactotrilyt under t g p g amples given, but this may be varied rather wide- P e s D 0 Opera 8 under e 00!! ly. For example, I may use anywhere from 1 or tions. In some instances, such asfor saturating 2% of the metal acetate up to 12% or more. P the catalyst solution with oxygen, I may apply a While the foregoing examples are illustrative few p unds p su up t 2 or 3 at osph r s for of preferred embodiments of my invention, it will this purpose. Also, as indicated, the process evidlent that many modiflfcagions therein may iunscttions vgery vzlell at ttlemperatullles of -5 C.

ma e wit n the scope o e inven ive con- 0 or an norma a mosp eric pressure. cept involved. As previously indicated, these However, by raising the temperature above the catalysts may be used under the conditions-outrange indicated to 90 C., for example, the preslined above for the conversion of various alisure should be increased in order to assure a sumphatic alcohols to acids. They may be employed cient supply of aldehyde in the catalyst solution in the form of a single salt or mixtures of salts to obtain the desired catalyst activity. By operof any desired organic acid or acids. ating at these higher temperatures and pressures,

In the above examples, there was some small larger amounts of alcohol may be converted per the alcohol of the resulting solution of Pass per unit of time. Under such procedure the aldehyde feed would be 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 compound 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 compounds, 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 obtain the corresponding aliphatic acid, which comprises treating a solution of a metal ion of a group IV metal selected from the group consisting of tin, lead, thorium. titanium; germanium, zirconium, and hafnium 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 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 IV metal selected from the group consisting of tin, lead, thorium, titanium, germanium, zirconium, and hafnium 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 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 from C. to 100 0., 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 the corresponding aliphatic acid, which comprises treating a solution of a lead salt in an aliphatic acid with an aldehyde and a gaseous oxidizing medium to form an active catalyst solution, introducing material amounts 5 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 treatmentwith the gaseous oxidizing medium such that the 'solution is maintained in the liquid phase at a temperature below 100 0.. 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 thorium 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 activated catalyst solution, oxidizing the alcohol 01' 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 (7., and subsequently recovering the aliphatic acid produced.

6. A process for'the direct oxidation of a lower aliphatic alcohol to obtain an acid mixture con-- taining 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 IV metal selected from the group consisting of tin, lead, thorium, titanium, germanium, zirconium, and hafnium in an aliphatic acid with 45 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 50 resulting solution of catalyst, alcohol and aldehyde 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 55 medium such that the solution is maintained in the liquid phase at a temperature of 5 C. to 100 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 Q FOREIGN PATENTS Number Country Date 1i1,050 Australia July 25, 1940

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