US2425879A - Oxidation of alcohols - Google Patents

Description

Aug. 19, 1947. c, HULL 2,425,879

OXIDATION OF ALCOHOLS Filed July 8, 1944 METER conosnscn 27 STE-AM 9 L23 SEPARATOR oxmmon UNIT 2* PACKED 2T? 22 SCRUBBER RECEIVER JJW Y f r JJJ 2e 44 RECEIVER OXIDIZING MEDIUM D V") C, HULL V DVVENTUR v A Ys Patented Aug. .19, 1947 UNITED STATES PATENT OFFICE OXIDATION OF ALCOHOLS David 0. Hull, Kingsport, Tenn assignor to Eastman Kodak Company, Rochester, N. Y., a

corporation of New Jersey Application July .8, 1944, Serial No. 544,000 4 Claims. (01. 260-531) verting ethanol to acetic acid, before my invention it was considered necessary to first dehydrogenate 2 polyhydroxy alcohols and similar organic compounds, invention is to provide a direct oxidation process which may be operated at relatively low tem-v peratures and under ordinary pressure conditions, yet give very satisfactory yields of the desired oxidation products. Still another object is to provide a direct oxidation process for the conversion'of alcohols to acids wherein the alcohol may be converted, not only to an acid having a number of carbon atoms corresponding to a 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 all of the ethanol and thereafter the aldehydic other than normal atmospheric conditions, dehydrogenation product was converted to the namely, under either superatmospheric or reacid which, as can be seen, involves a number of duced pressures. steps. A further object is to provide a direct oxida- Carrying out oxidation processes in accordance tion proc s tha m y be pl d to i h with the prior art possesses a number of disadalcohols alone or mixtures of alcohols and aldevantages exemplified, for example, by the required hydes, or other types of mixtures. A still further use of relatively high temperatures. Also there object is to provid a direct, low-temperature may in some instances be the disadvantag of oxidation process which may be applied to various polymerization of the products and of the startmixtures of alcohols and aldehydes' wherein both ing materials accompanied by low yields and the alcohol and the aldehyde are converted into other losses.

In my U. S. Patent 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 in relatively few steps, it involves the utilization of metals having an atomic number from 25 to 29.. t

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 certan other catalytic materials which may be employed in direct oxidation processes in a manner akin to the procedure set forthin my U. S. Patent 2,287,803, which not only permits obtaining direct oxidation, 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 be applied, not only to the monohydroxy alcohols, but also td the useful oxidation products. 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 the direct conversion of alcohols alone, or alcohols in various admixtures, into useful oxidation products. A still further object is to provide methods for producing the 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 dehydrogenation products further treated. In any event, prior art 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, involves dangers of loss from polymerization or other undesired reactions. Also apparatus destruction 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 Another and particular object of this Another object is denser l9 into separator 2|.

temperatures, even temperatures substantially below 100 0., 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 usually require any heat input but generates sufficient 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 ora different aldehyde, may be efllciently treated by my novel process and catalyst to give very high yields 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 de tail 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 forcarrying out my process.

Referring to the drawing, 2 represents an exidation unit which may comprise any of several different constructions. For example, the preferred external construction would, in a large di-' ameter 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 tree 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 4 are, cooling jackets provided with inlets for cooling medium as at 6 and I.

The upper part of the unit was provided similar Jacket 8; however, in this jacket, rather than cooling 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, 1 and 6; outlets are provided at l|.l2,and|3.

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 em ployed, 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 11 for oxidizing medium.

,The upper part of the unit is provided with a drawoff conduit l8 which leads through con- 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 24.

The aforementioned scrubber is provided with a receiver 26 at the lower part thereof a d V t with a conduit 21 from the upper part thereof, which may lead through a meter or other device for measuring and testing the eflluents.

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.

1 have found that silver may be incorporated in acidic solutions and that thes 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 will be chosen which is easily soluble under the conditions of the process. For example, assuming that it is desired to convert an aliphatic a1- coho1 such as ethanol or butanol directly to the corresponding aliphatic acid, the derivative of the catalyst metal may be silver acetate.

While the aforementioned metal derivative may be employed in various organic liquids,

which are solvents therefor, for simplicity of operation and minimizing the necessity of complivfor several hours.

- cated 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 alcoholdirectly 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 preparing the catalyst solution other liquids could be employed, as for example, organic esters and the like such as butyl or ethyl acetate.

In an 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,

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 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 heated air. The temperature 'of treatment, however, may varyfrom around 0C up to the boiling point of the particular liquid present. In other words the-solution is maintained under liquid phase conditions.

It is also preferred to incorporate the oxidizing 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 silver as already described has been treated and brought than their lowest That is, referring to the attached drawing, the

oxidation column 2 is filled with the catalyst liquid comprising silver acetate dissolved in the solvent and maintained at the desired temperature. The hydroxy compound to be oxidized is introduced into the oxidation process through conduit I 4 and the oxidizing mediunnusually 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 l8 through the condenser i9 where condensables are condensed out to be col-,- lected in receiver 22. The unconsumed gases (as nitrogen when air is used as oxidizing medium), unoxidized organic compounds and the like components, u ncondensed,pa ss through conduit 23 into scrubber 24 where they are recovered. While only a single scrubbingunit has been indicated, a plurality of such units may be employed or other recovery devices utilized.

The operation of my process to convert-an organic compound such as ethyl alcohol, propyl alcohol, butyl alcohol or other: aliphatic hydroxy compounds to the desiredacidsandthe function of the metal compound as aldehyde activated catalyst is quite clearlyillustrated by the data the oxidation, while the major portion of the remaining alcohol was left unchanged. As indicated, while at normal atmospheric pressure, a temperature under 100 C. appears to be'quite satisfactory, the particular temperature selected will be determined largely by reference to the particular alcohol tobe oxidized and. whether the process is to be operated under pressure or merely at atmospheric pressure. For example, in the case of ethyl, propyl, or butyl alcohol, I prefer a temperature range of C. to 50 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 an excess is required; that is, such an amount that a few per cent of oxygen will be present in the eiliuents. In the event of the use of other oxidants such as relatively pureoxygen 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. Forlgexample, in oxidizing ethyl alcohol, I may 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,

appearing in the following table:' and so on. However, inasmuch as acetaldehyde Q Percent Grams Percent Percent Grams Grams Percent Grams Grams Example 533 g g A HAO HGBu' Conversion HOP! 23, 25: HOAc fig g so}. Fed Produced to HOBu it Produced Produced ROM:

1 Ag s 234.4 124 12.3 4.32 14.5 6 {c at Percent Metal I Metal Salt Grams of Examples Acetate in cat.v lrams Alcohol Fed HA0 Fed Yie'lgclldto Acid or Acids n x 3.5 560 EthylAlc 375 91.8 100% Acetic. ,III Ag 2.7 876NormallropylAlc.... 880 85.3 90% HOPr, 10% HOAc.

The foregoing examples were carried out in apparatus as indicated in the-attached drawing and at a temperature between 30 C. and C., .althou h a'*wider range'of temperatures, such -5 C. to 150C. could be employed satisfactorily.

It will be observed from theabove table that I'.

have employed a relatively small amount of the metal acetate in thecatalyst solution in the examples given, but'this' may be varied rather widely. For example, I mayuse anywhere from i 1 or 2% of the'metal acetate upto 12% or more. While the foregoing examples are illustrative of preferred embodiments of -xmy invention, it will be evident that many modifications therein may be made within the scope of the inventive concept involved. As previously, indicated, the silver catalyst may be used under the conditions outlined above for the conversion of various aliphatic alcohols to acids. It 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 lower acids and to .esters in addition to the mainproduct of 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 representing the most economical procedure, as well as tending to lower the boiling-points and permit the functioning of the'process at the lowest practical temperatures.

As already indicated, the pressure, may be varied over wide limits without basically changing the process. 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 suillcient supply of aldehyde in the catalyst solution to obtain the desired catalyst activity. By

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 illustrativeflof some of the materials to which my low temperature liquid phase process may be applied, but variousjother compounds, such as hydroxy alcohols exemplified by glycols, may be treated in a comparable man ner. 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 silver 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 recovering the aliphatic acid produced.

aldehyde during its treatment with the gaseous oxidizing medium such that the solution is'main-- tained 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 silver in an aliphatic acid with an aldehyde and a gaseous oxidizing medium to form an active catalyst solution, introducing material 3. The process of claim 2'1n.which the catalyst, alcohol and aldehyde is maintained during its treatment with the gaseous oxidizing medium at a temperature of 30 C. to C.

4. 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 silver 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 c'atalyst 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.

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, 194(

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