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US 2892858 A
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United States Patent PRODUCTION OF ALCOHOLS Karl Ziegler, Muelheim, Ruhr, Germany No Drawing. Application July 27, 1955 Serial No. 524,798
Claims priority, application Germany August 7, 1954 17 Claims. (Cl. 260-448) This invention relates to and has as its object, the production of alcohols from organic aluminum compounds.
In accordance with the invention, it has been found that aluminum hydrocarbons containing a methylene radical bound to the aluminum, will undergo autooxidation when contacted with oxygen forming aluminum alcoholates which are readily decomposed with water and/or acids into primary alcohols. Alumina in practically, pure form may be recovered as a by-product of the reaction.
While it was known that certain organic metal compounds as, for example, alkyl and aryl compounds of the alkali metals, magnesium, zinc, boron, etc., would react vigorously with oxygen, the oxidation would not proceed smoothly and generally several reaction products were obtained as a result of the oxidation. Furthermore, the reaction products obtained from the oxidation of the various difierent compounds would vary widely from each other and it was not possible to predict or foresee how the oxidation of the organic aluminum compounds in accordance with the invention, would proceed.
The starting aluminum hydrocarbons, in accordance with the invention, may be any of the known aluminum hydrocarbons containing a methylene radical bound to the aluminum as, for example, aluminum trialkyls or aluminum alkyl hydrides. These aluminum compounds may be represented by the general formula in which R and R represent hydrogen or a hydrocarbon radical such as an alkyl radical and in which may be in the form of a hydrocarbon ring.
These aluminum hydrocarbons may be readily and economically prepared as, for example, in accordance with the method of co-pending applications, Serial No. 484,576 filed January 27, 1955 and Serial No. 524,797 filed July 27, 195 5, now Patent No. 2,835,689.
As a result of the oxidation of these aluminum hydro carbons, aluminum alcoholates are formed which correspond in structure to the starting aluminum hydrocarbons except that an oxygen atom is interposed between the organic radical and the aluminum. 7
Starting aluminum hydrocarbons may also be obtained in accordance with West German Patents Nos. 917,006 and 889,229. In accordance with these German patents,
higher molecular trialkyl aluminum compounds are built up from triethyl aluminum by reaction with ethylene. As
the alcohol ultimately produced in accordance with the invention corresponds to the organic radical portion connected to the aluminum in the starting aluminum aluminum to form aluminum hydrocarbons having an,
organic radical portion corresponding to the a-olefines. It is thus possible, in accordance with the invention, to convert olefines into the corresponding primary alcohols. Thus, for example, the a-olefines obtained from the cracking of the higher boiling fractions of the Fischer-Tropsch synthesis, may be converted into the corresponding alcohols.
Prior to the instant invention, it was not, as a rule, possible to obtain primary alcohols directly from olefines as, for example, by the addition of water. In accordance with the present invention, however, olefines may be very easily converted via the corresponding aluminum compound into primary alcohols. In this manner, in accordance with the invention, in mation of many known alcohols, it a very large number of completely have not been literature.
The formation of the aluminum hydrocarbon from the olefine in accordance with application Serial No. 524,797 filed July 27, 1955 which are subsequently converted into the alcohol by the oxidation and decomposition, in accordance with the invention, is merely effected by contacting an aluminum hydrocarbon having a methylene is possible to produce novel alcohols which previously produced nor described in the radical connected to the aluminum as, for example, tri-- isobutyl aluminum with an olefine at a temperature between about 50 and C. The olefines used for this purpose may be any olefine having a terminal double bond, cyclo olefines having 4, 5, 7 and 8 carbon atoms and at least one R C=CH group in the ring and fulvenes. When starting, in accordance with the invention, with aluminum hydrocarbons in which the aluminum has all its valence linkages bound to hydrocarbons, as may be represented by the formula omR AICH2R CHgR in which R is a hydrocarbon radical, during the course of the auto-oxidation, in accordance with the invention, the compounds pass successively into OOHZR OCH R Al-CHgR AlOCHgR CHgR 01113 and OCHzR AlOCH2R OCH2R The oxidation forming the first two types of compounds,
takes place extremely rapidly while the oxidation forming the third type of re-oxidation at ordinary or even slightly increased temperatures. It is therefore preferable to effect the auto addition to the for-' compound requires a rather lengthy oxidation initially with a gas containing only a small amount of oxygen as, for example, nitrogen to which only a small amount of air has been added and to gradually increase the oxygen concentration during the course of the reaction until finally pure oxygen is present in the final stage. The gases used for the oxidation should be extensively dried since otherwise due to side reactions, hydrocarbon radicals as such in non-oxidized form can prematurely split off the aluminum resulting in a decrease in yield. For effecting the oxidation, the oxidizing gases may be maintained in circulation and oxygen may be added at some point in the circuit.
The temperature of the oxidation may vary widely as, for example, between temperatures of minus 20 and plus 150 C. It is more practical to use temperatures between and 100 C. with temperatures between about 3.0 and 60 C. being preferred.
In many cases, the aluminum alcoholates produced by the oxidation of the aluminum hydrocarbons, are liquids of rather low viscosity. In such cases, the auto-oxidation may be elfected using undiluted starting aluminum hydrocarbons. While proceeding in such a manner, however, it is necessary to be particularly careful at the start of the reaction in determining the oxygen content of the oxidizing gas mixture. In other cases, it is advisable to effect the oxidation in the presence of solvents, as, for example, primary aliphatic or aromatic hydrocarbons.
As mentioned, the starting aluminum hydrocarbons may be in the form of monohydrides and monohydrides may be formed to a greater or lesser extent when producing the aluminum hydrocarbons have the three hydrocarbon radicals bound to the aluminum.
When oxidizing and decomposing these monohydrides, in accordance with the invention, to form alcohols, the yield is substantially less than proceeding with the aluminum hydrocarbons having three hydrocarbon radicals bound to the aluminum since in the case of the monohydrides, a maximum of two mols of alcohol can be theoretically produced per mol of monohydride. In operation, however, it is not even possible to obtain this reduced theoretical yield since the first resultant product of the oxidation is a hydroperoxide, i.e., an aluminum compound having an OOH group bound to the aluminum which contains a mobile hydrogen atom which then releases a hydrocarbon radical from the aluminum in the form of an unoxidized hydrocarbon further reducing the ultimate yield of alcohol by about one-third.
Losses of this type may be avoided by using a starting aluminum hydrocarbon which contains a minimum quantity of hydride. The formation of hydrides may be kept at a minimum when preparing the aluminum hydrocarbons, by various methods. Thus, for example, when preparing the starting aluminum hydrocarbons in accordance with US. patent application Serial No. 524,797 an excess of olefine may be used in the reaction and then this excess may be removed under as gentle conditions as possible at the lowest possible temperature, or the first oxidation in accordance with the invention may be etlected in the presence of this excess olefine and the olefine may be subsequently separated from the formed aluminum alcoholate by distillation.
It is often desirable, particularly when using more expensive olefines to completely convert these olefines into the alcohols via the alcoholate without the use of an excess. In such cases, the olefines may be converted into the corresponding aluminum hydrocarbons using an ex-- cess of the initial aluminum hydrocarbon which is re acted with the olefine as, for example, triisobutyl aluminum. Under these conditions, however, monohydrides are formed since the triisobutyl aluminum readily loses an isobutyl radical while hot forming diisobutyl' alumi num monohydride, After treatment of the olefine with the triisobutyl aluminum, it is therefore advisable to again treat the reaction product prior to the oxidation in accordance with the invention, with a less expensive olefine which may, for example, be isobutylene, at the lowest. possible temperature in order to convert. all the AlH bonds present in the reaction mixture into Al-R bonds and, in particular, when using isobutylene to isobutyl radicals. As side products there is then produced upon the oxidation-decomposition, in accordance with the invention, a certain quantity of isobutyl alcohol. On the other hand, however, the conversion of the olefine employed corresponding to the desired reaction product into the alcohol takes place substantially more easily than if this after-treatment were omitted and if quantities of aluminum monohydrides were present.
It is of particular advantage that the oxidation, in accordance with the invention, may be efiected in the presence of inert hydrocarbons. It is thus possible when converting the olefines ultimately to be converted to alcohols, in accordance with the invention, into the starting aluminum hydrocarbons, to use hydrocarbon mixtures which consist only in part of these olefines. The
aluminum hydrocarbons formed will therefore be formed in admixture with these inert hydrocarbons. Accordingly, the oxidation in accordance with the invention, is efiected using this entire mixture and after the oxidation, the formed aluminum alcoholates may easily be separated from the other hydrocarbons by distillation, possibly under vacuum. The aluminum alcoholates are generally difiiculty volatile and remain as the distillation residue. This distillation residue which is substantially free from the other hydrocarbons, may then be directly converted into the desired alcohols, free of the hydrocarbons with water and/ or acids. This obtaining of the hydrocarbonfree alcohol in a simple manner is a substantial advantage as compared with the known methods for the conversion of olefines into oxygen-containing compounds as, for example, in accordance with the so-called oxosynthesis. As is well known, hydrocarbon mixtures may not be used in the oxo process. if pure reaction products are desired since it is not possible to separate the aldehydes formed in the oxo process from the hydrocarbons with the same boiling point by distillation alone.
The following examples are given by way of illustration and not limitation:
Example 1 Nitrogen was blown through 366 grams tri-n-octyl aluminum prepared by the process of patent application, Serial No. 524,797 and triisobutyl aluminum in a recycle apparatus. Oxygen was carefully added to the circuit in such a manner that the oxygen content in the circulating gas was about 5%. The aluminum tri-n-octyl warmed up and the reaction vessel used was cooled from the outside. As the heat given off in the reaction vessel became smaller, the oxygen content in the circulating stream was increased first of all to 10 to 20% and finally pure oxygen was employed. The oxidation required 3 to 8 hours depending on the intensity of the cooling. Towards the end, the absorption of oxygen slowed down greatly. The apparatus was so arranged that the oxygen absorption was under control and the operation discontinued when no more oxygen had been absorbed for at least one-halt hour to one hour. The gases used were very carefully dried by a good drying agent, for example, potassium hydroxide heated to 400 0., dried and applied to pumice stone or magnesium perchlorate. During the oxidation,
the aluminum trioctyl which initially had a thin liquid consistency became viscous, but the reaction could be carried out without difliculty. The thick, oily aluminum octylate finally obtained was decomposed by the addition of water with heating. Thereupon the octyl alcohol formed was distilled over by steam distillation. The oil which passed over with the distillate was separated and I dried over potassium carbonate. Distillation, preferably in a vacuum, was then effected. There were obtained 320to 350-grams of the primary normal octyl alcohol.
having an entirelyconstant boiling point of 81.5/8 mm. and of excellent odor.
As residue of the steam distillation, there were obtained an aluminum hydroxide paste from which the aluminum hydroxide could easily be separated in the known manner by filtration orcentrifuging, and can thereupon be convetted by the removal of water into an alumina of very high purity.
Example 2 A solution of tri phenyl-ethyl aluminum in hexane is first of all prepared in accordance with Example 3 of patent application Serial No. 524,797 and then oxidized in the manner described in Example 1. The treatment carried out in the manner indicated in Example 1 results in the formation of phenylethyl alcohol of a boiling point of 98-10l C./ 8 mm. or 220 at ordinary pressure, which corresponds to the value given in the literature. The yield is about 70% of the theoretical quantity.
' Example 3 To 10 kgs. of a product obtained by the cracking of higher Fischer-Tropsch paratfins and having a boiling point of ISO-230 Cfwith an olefine content determined by bromine titration of 8 moles of olefine per kilogram and an tat-olefine content determined spectroscopically in infrared light of 5.8 moles per kilogram, there were added 3 kilograms aluminum triisobutyl. The mixture was thereupon converted, in accordance with Example 5 of patent application Serial No. 524,797 at 120-130 C. in vacuum into the aluminum compound. The solution of the aluminum hydrocarbons formed in the inert accompanying substances of the OL-OIefiIICS was then transferred into a high cylindrical iron vessel provided on the outside with water cooling and thereupon very thoroughly dried air was blown through, first of all cautiously, and thereupon continuously more intensively. The cooling of the reaction mixture and the gas velocity were so regulated that the temperature as far as possible did not exceed +30 C. Finally, the temperature was increased to 50 C. and oxidation was continued for about 2 hours with pure oxygen. The solution obtained in this manner of the aluminum compounds of the alcohols produced was thereupon transferred into a distilling vessel and freed as completely as possible from the hydrocarons by heating under vacuum. If importance is placed on the absolute freedom of the alcohols to be obtained from hydrocarbons, after the hydrocarbons have been driven ofi, superheated vapors of a hydrocarbon of relatively low boiling point, for instance, benzene, can be blown through the liquid aluminum alcoholate remaining in the residue, whereupon the last traces of higher hydrocarbons still adhering to the liquid aluminum alcoholate will be driven oil, or a very effective continuously operating thin-layer vacuum evaporator may be used to drive off the hydrocarbons.
In each case, there is obtained the oily alcoholate which is then advisedly further treated by decomposition with water in accordance with Example 1. The higher boiling fractions of the alcohols obtained are finally separated from the aluminum hydroxide paste by distillation with superheated steam under a vacuum. The aluminum hydroxide paste can be very readily converted back into pure alumina by calcining. The entire organic portions of the distillate are collected.
The quantity of crude alcohols to be obtained depends somewhat on the initial olefines employed. In one special case, there were obtained, for example, 6 kilograms of crude alcohol which could be further split up by fractional vacuum distillation. The individual fractions to be obtained in this connection depend, of course, on the sharpness of the hydrocarbon cut introduced. With an introduced fraction of a boiling point of 180- 6 230 0., there were regularly still presentsmall portions of C -olefines so that the first alcohol obtained upon dis tillation in an effective column in vacuum, is customarily the primary octyl alcohol. By further distillation on an efiective column, there can be obtainedone after the other all primary straight-chain fatty alcohols having 9 to 16 carbon atoms, with which however, if a hydrocarbon prepared by Fischer-Tropsch synthesis is initially used, there are also admixed certain quantities of methylbranched fatty alcohols. The pure primary fatty alcohols, praticularly the higher carbon atoms, can readily be caused to crystallize from the corresponding fractions by cooling and then removed by suction filtering or centrifuging.
Example 4 Example 5 118 grams of the aluminum compound obtained from 1-vinylcyclohexene-( 3) were diluted with 200 cc. octane and subjected to oxidation in accordance with'Examp'le 1. Upon working-up there is obtained tetrahydrophenylalcohol of the following formula: 1
This alcohol is a colorless oil of a to 107 C./15 mm.; n =1.4831.
From limonene and camphene there can be obtained in a simple manner the alcohol having the formul Example 6 patent application Serial No. 524,797, filed July 27, 1955, i
with aluminumtriisobutyl into the aluminum compound 12 Al CHg-O which is then oxidized with 600 cc. of toluene, diluted in the manner described in the other examples, and there are obtained 300 gm. of the alcohol 12 H O-QHg-C members having 12 or more 20 carbon atoms with a maximum boiling point of aseassa alcohol is a colorless oil of a boiling point of hydrocarbon having a radical bound to the aluminum in methylene linkage therewith, at a temperature between -20 and 150 C. thereafter decomposing the aluminum alcoholate formed with a member selected from the group consisting of water and acid, and recovering the primary alcohol formed.
2. Process according to claim 1, in which said contactingisjeiiected in the presence of a solvent.
1 3.-Processaccording to claim 2, in which said solvent is a? member selected from the group consisting of aliphatic and aromatic hydrocarbons.
4. Process according to claim 1, in which said contacting with oxygen is effected by contacting the aluminumhydrocarbon with a gas having a low oxygen content, and increasing the oxygen content of the gas during said contacting until the gas has a high oxygen content.
5. Process according to claim 1, in which said contacting is effected at a temperature between about 20 to l50 C.
j 6. Process according to claim 1, in which said contactingisefiected at a temperature between about and 100 ,C.
7. Process according to claim 1, in which said contacting is efiected at a temperature at 30 to 60 C.
8. Process according to claim 1, in which an aluminum hydrocarbon is substantially free from aluminum hydride.
9. Process according to claim 1, in which said aluminum hydrocarbon contains aluminum hydride and which includes contacting the aluminum hydrocarbon with an olefine prior to said contacting with oxygen.
10. Process according to claim 9, in which said olefine is isobutylene.
' ll. Process according to claim 1, in which said aluminum hydrocarbon is in admixture with hydrocarbons and which includes after said contacting with oxygen, distilling oi the hydrocarbons from the formed aluminum alcoholate prior to said decomposition.
12. Process for the production of aluminum alcoholates which comprises contacting with oxygen an aluminum hydrocarbon having a radical bound to the aluminum in methylene linkage therewith at a temperature between about --20 to C., and recovering the aluminum alcoholate formed.
13. Process according to claim 12, in which said contacting is effected with a gas mixture containing a, low. oxygen content, and in which the oXYgcn content of the gas mixture is increased during said contacting until the gas mixture has a high oxygen content.
14. Process for the production of primary alcohols from olefines which comprises contacting an aluminum hydrocarbon with an olefine having a terminal'double bond, at a temperature between about 50 and 150 C., thereafter contacting the aluminum hydrocarbon formed by displacement of the initial hydrocarbon radical with a hydrocarbon radical corresponding to the olefine with oxygen at a temperature between about -20 and +150 C., decomposing the aluminum alcoholate formed with a member selected from the group consisting of water and acid, and recovering the primary alcohol formed.
15. Process according to claim 14, in which said start ing aluminum hydrocarbon is triisobutyl aluminum and in which said olefine is an olefine other than isobutylene.
16. Process according to claim 14, in which said olefine is present in admixture with other hydrocarbons and which includes distilling oil the hydrocarbons from the formed aluminum alcoholate prior to said decomposition. Y
17. A process for the production of primary alcohols having the general formula ROH which comprises contacting with molecular oxygen under anhydrous conditions an aluminum trialkyl compound having the general formula AlR wherein R is an alkyl group containing at least two carbon atoms hitting a radical bound to the aluminum in methylene linkage therewith, at an oxidizing reaction temperature maintained at less than about, 150 C. and hydrolyzing the aluminum trialkoxides formed and recovering the primary alcohols thus produced.
References Cited in the file of this patent UNITED STATES PATENT OFFICE CERTIFICATE OF CQRRECTEQN Patent Noo 2392,8523 June 139, 1959 Karl Ziegler It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.
Column 2, line 46, for "RgC 'CH" ree C GH a Signed and sealed this 3rd day of November 1959,
KARL HG AXLINE Atteszing Officer RGBERT C. WATSGN Commissioner of Patents