US2425878A - Oxidation of lower aliphatic alcohols - Google Patents

Description

Aug. 19, 1947. D. c. Hum; ,8

I OXIDATION OF LOWER ALIPHATIC ALCOHOLS Filed July 8, 1944 I 6* I9 METER 'n 5 P I 8 /CONDENSER STEAM I f 21 i 9 P I} SEPARATOR 24 ,-OXIDATION V UNIT Z I ,-PACKED 12 22v SCRUBBER RECEIVER y 2 RECEIVER .17 oxuuzms MEDIUM DAWD L I HVVENTOR BY I fifln'w -bz ATT YS Patented Aug. 19, 1947 OXIDATION OF LOWER ALIPHATIC 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. 543,999

6 Claims.

This invention relates to the direct oxidation of organic compounds, particularly the oxidation of hydroxy compounds such as lower aliphatic alcohols oxidized directly to acids.

As pointed out in my U. S. Patent No. 2,287,- 803 prior art oxidation processes have required the employment of relatively high temperatures such as 300 C. or 400 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 converting ethanol to acetic acid, before my invention it was considered necessary to first dehydrogenate all of the ethanol and thereafter the aldehyfiic 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. S. Patent No. 2,287,803 I have described a process for a more direct oxidation of organiccompounds. While the process of my patent 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. 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. S. Patent 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 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 to the polyh'ydroxy alcohols and 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 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 the number of carbon atoms in the alcohol molecule, but also to a difierent 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 and aldehydes 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 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, yields of the desired end products are not nearly as high as those obtained by my process.

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 below 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 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 or a different aldehyde, may be efficiently 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 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 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 4, are cooling jackets provided with inlets for cooling medium as at 6 and I.

The upper part of the unit was provided with a 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, I and B; outlets are provided at ll, [2, and 13.

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 [4 which is connected with a temperature-controlled feed supply [6. 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 drawoif conduit I8 which leads throu h condenser l9 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 26 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 effluents.

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 economica 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 the rare earth elements listed in the periodic table and included in the group consisting of cerium, neodymium, lanthanum, praseodymium, illinium, samarium, holmium, europium, erbium, gadolinium, thulium, terbium, ytterbium, dysprosium, and lutecium, 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 aforelnentioned, 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 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 cerium, neodymium, or other acetate, depending upon the particular metal or metals employed. Further typical examples of metal derivatives which might be employed for producing the catalyst solution are lanthanum acetate, terbium acetate, ytterbium acetate, dysprosium acetate, and lutecium acetate.

While the aforementioned metal derivatives maybe 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 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 valencev 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 vary from around 0 C. 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 a rare earth metal compound as already described has been treated and brought to a starting temperature, usually above room temperature but below about 100 C., the organic compound to be oxidized may be supplied to the process.

and to esters in addition to the main product of the oxidation, while the major portion of the remaining alcohol was left unchanged. As indicated, while at normal atmospheric pressure, a temperature under 150 C. 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 That is, referring to the attached drawing, the 10 at atmospheric pressure. oxidation column 2 is filled with thetkciatalysil; liquid Under preferred operating conditions as, for fi p s e Or more rare ear me a CO I example, when air is used as the oxidant, this pounds of the type described dissolved in the 501- may be supplied under some pressure and, if devent and maintained at the desired temperature. sired, th substantial excess may be The y y p d to be OXidiZed is t 5 ployed, although for normal operations merely an zlizicedcinttg the ociliidation P590 58 t tll (fi i l excess is required that is, such an amount that a an 6 0X1 g me 111m, usua y a few per cent of oxygen will be present in the h h p xy en 01' ozone m be pl y effluents. In the event of the use of other oxiand appear to render the catalyst solution more dants such as relatively pure oxygen and ozone, active, but are not necessary), and the compound smaner amounts are r quired and may be supoxidized 313 0 2 mg geslljedfgxldatlon P plied under substantial pressure to cause them 110 S, as W1 e 9501 e erema fully to permeate the entire catalyst solution.

Assuming that the oxidation product is a liquid, Th xid tion of any given alcohol in accorda portion thereofmay be volatilized or pumped ance it my process may be accomplished by fie'it iteilttii l32 32333522 03???2 20? activating the i lg g the by means of a singe a e y e or b a luralit of lected in receiver 22. The unconsumed gases (as aldehydes' For example in oxigizing ethy1yal nitrogen when air is used as oxidizing medium), 601101, I may employ acetaldehyde propionalde unoxidized organic compounds and the l1l e comhyde, or WWI-aldehyde alone or two or more of Ponents, uncondensed: pass through conduit them. Moreover, I may oxidize ethyl alcohol, 3322? iirttfiifififlii fai titiflldi'iltt alcohol butyl alcohol or m1 alcohol, by employing any one or more of aldehydes such as i ggigg gg f ggg lgfigs be employed or other acetaldehyde, propionaldehyde, butyraldehyde, The operation of my process to convert an or- F so :Iowever, t clh as acetaldehyde 1s ganic compound such as ethyl alcohol, p-ropyl al- In many ances F reach aivallable and has cohol, butyl alcohol or other aliphatic hydroxy a 10W bollmg 110mb, It would pleferably be mcompounds to the desired acids and the function ployed along with alcohols $11011 as tyl 9 601101, of the various rare earth metals as aldehyde actiyl alcohol, and the like, as representing the vated catalysts is quite clearly illustrated by the 40 most economical procedure, as well as tending to data appearing in the following table: lower the boiling points and permit the function- Percent Grams Percent E M t 1 M amgle g o a t S1511 Grams Alcohol Fed ofFlga kc. Yieclgigo Acid or Acids h 1A1 s90 94 100 HOA. iiiiij: ritfitita f? ??P $-Z 33g 9 A5. HOA

o 1', o [3- R IIIII 'o'iii ill'fiij 3, 870 fir niei itt yni 895 90.1 90%HOBu, 5% HOPI, 5% HOAc.

The foregoing examples were carried out in ing of the process at the lowest practical temperapparatus as indicated in the attached drawing atures. and at a temperature between 30 C. and Q, As already indicated, the pressure may be varalthou h a wider ran e of temperatures, such as ied over wide limits without basically changing g g 50 C. to 150 C. could be employed satisfacthe process. However, since the process functorily. It will be observed from the above table tions satisfactorily undernormal atmospheric that I have employed a relatively small amount pressures, I prefer to operate under such condiof the metal acetate in the catalyst solution in the tions. In some instances, such as for saturating examples given, but this may be varied rather the catalyst solution with oxygen, I may apply widely. For example, I may use anywhere from a few pounds pressure up to 2 or 3 atmospheres 1 or 2% of the metal acetate up to 12% or more.

While the foregoing examples are illustrative of preferred embodiments of my invention, it will be evident that many modifications therein may be made within the scope of the inventive concept involved and that various other catalysts included within the group of rare earth metals or compounds thereof may be employed. 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 lower acids 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 assure a suflicient supply of aldehyde in the catalyst solution to obtain the desired catalyst activity. By operating at these higher temperatures and pressures, larger amounts of alcohol maybe converted per 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 7 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 compounds, such as hydroxy alcohols exemplifled 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 metal of the rare earth metal group 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 metal of the rare earth metal group 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 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 atemperature 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 cerium 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 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 neodyminum salt in an aliphatic acid with an aldehyde and a gaseous oxidizing medium to form an active catalyst solution, introducing ma terial amounts of a lower aliphatic alcohol and a lower aliphatic aldehyde into the activated cata lyst 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 metal of the rare earth metal group 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 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 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 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 FOREIGN PATENTS Number Country Date 111,050 Australia July 25, 1940

Images