DE1965645A1 - Process for the production of straight-chain fatty acids - Google Patents

Description

Henkel & Cie GmbH Düsseldorf, the 2 * ». 12th 1969

Patent department at Henkelstrasse 67

Dr. E / P

Patent application

D 3942
"Process for the production of straight-chain fatty acids"

The invention relates to a method for producing straight-chain, Saturated aliphatic carboxylic acids with more than 4 carbon atoms due to alkali melting of oxygen-containing compounds and subsequent conversion of the alkali salts into the free acids.

Several processes are already known by which higher carboxylic acids can be produced by alkali melting of oxygen-containing secondary products of petrochemical raw materials. The reaction has been proposed in particular for mixtures of substances from the oxo synthesis. However, the resulting process products always contain larger amounts of branched-chain carboxylic acids, even if hydroformylation products of _α- olefins are used as raw materials, since these also result in products that are always more or less large amounts of branched, by CO addition in the 2-position contain resulting connections. In order to obtain the straight-chain carboxylic acids from these raw materials, either a laborious separation of the starting material or the end products is necessary. An embodiment of the alkali melt has also already been proposed in which the straight-chain fractions of the oxo synthesis product are selectively oxidized to carboxylic acids. However, this procedure also has the fundamental disadvantage that only part of the petrochemical raw material originally used can be converted into straight-chain carboxylic acids. Produce a further possibility, straight-chain fatty acids by alkali fusion oxygen-containing compounds is to use straight-chain fatty alcohols of the organoaluminum synthesis as starting materials.

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. Since this method of production is due to the multi-stage synthesis route the starting material is extremely complex, this method of operation has not acquired any technical importance. In addition, starting from these raw materials, only carboxylic acids with an even number of carbon atoms are accessible.

It has now been found that unbranched higher 1,2-diols or their full or partial esters with lower aliphatic carboxylic acids by alkali melt smoothly into the alkali salts the straight-chain carboxylic acids shorter by one carbon atom get convicted.

The starting materials mentioned can be obtained easily and in high yields from the straight-chain o-olefins which are available on an industrial scale and originate from cracking or building processes. Direct one-step hydroxylation of the o-olefins with HJD ₂ or mixtures of H ₃ O ₂ and carboxylic acids or with peracids or by epoxidation of the olefins and subsequent hydrolytic cleavage provides a simple way of producing the starting materials to be used according to the invention.

The invention accordingly provides a process for the preparation of exclusively straight-chain aliphatic carboxylic acids with more than k carbon atoms by alkali melting of oxygen-containing compounds and subsequent conversion of the alkali metal salts obtained into the free acids, which is characterized in that unbranched, 6-30 ° C. -Atom-containing, 1,2-diols and / or their full or partial esters with aliphatic, 1 - 4 C-atoms, carboxylic acids used *

Examples of suitable starting materials are: n-1,2-hexanediol, n-Heptanediol-1,2, n-Octanediol-1,2, n-Undecanediol-1,2, n-Dodecanediol-1,2, n-Tetradecanediol-1,2, n-Heptadecanediol-i, 2,

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n-octadecanediol-1,2, n-eicosanediol-1,2, n-pentacosanediol-1,2, n-Triacontanediol-1,2 and their full and / or partial esters with formic acid, acetic acid, propionic acid and n- and i-butyric acid, e.g. l-formoxy-2-hydroxy-n-heptane, 1,2-diacetoxy-n-octadecane, l-formoxy-2-hydroxy-n-eieosan, 1-propoxy-2-hydroxy-n-pentacosan, l-butoxy-2-hydroxy-n-triacontane.

The starting materials can be used individually or as a mixture with one another. You can also choose from their manufacture Contain originating admixtures, e.g. unreacted olefin, paraffinic hydrocarbons, lower carboxylic acids and Catalyst components.

Particularly suitable starting materials are those crude products obtained by hydroxylating the α-olefins with preformed or in situ peracids such as peracetic acid or its solutions, formic acid / H ₃ O ₂ or acetic acid / sulfuric acid / HpOp mixtures in a manner known per se have been. According to another aspect, the invention thus relates to a process for the production of exclusively straight-chain aliphatic carboxylic acids with more than 4 carbon atoms from corresponding unbranched α-olefins, which is characterized in that unbranched α-olefins with 6-30 carbon atoms are combined with the said hydroxylating agents are converted in a manner known per se, the crude reaction product is subjected to an alkali melt and the alkali metal salts obtained are converted into the free acids. Examples of the α-olefins to be used as starting materials in this procedure are: n-hexene-1, n-octene-1, n-undecene-1, n-dodecene-1, n-tetradecene-1, n-heptadecene-1, n-Octadecen-1, n-Eicosen-1, n-Pentacosen-1, n-Triaconten-1 and their mixtures with one another or with paraffinic hydrocarbons. These starting materials can also contain additives that originate from production.

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The hydroxylation can be carried out in manner known per se from the literature, for example by reacting a mixture of a-01efin and formic acid or with 2-3 wt -% sulfuric acid tigern offset acetic acid with stirring and cooling to about 60 ° C with the calculated amount of hydrogen 30. added and the reaction mixture is kept at 60 ° C. until no more peroxide can be detected. In order to avoid an uneconomical excess consumption of alkali metal hydroxide, it is advisable to then remove the carboxylic acid. The crude product obtained in this way can then be subjected directly to the alkali melt.

The alkali melt is advantageously carried out under pressure, it being possible to use pressures in the range from 1 to 300 atmospheres. In the case of a discontinuous procedure, depending on the design of the apparatus, the one developed during the implementation can be used Leave hydrogen in the reactor. In the case of continuous operation, one will generally relax the developed Prefer gases and work in the range of lower pressures.

The reaction can in principle be carried out with all alkali metal hydroxides or their mixtures. For economic However, sodium and potassium hydroxide, which can also be used as a mixture, are preferred for reasons.

It is advisable to add water to the reaction mixture, preferably in amounts of 0.5 to 50% by weight, based on the alkali metal hydroxide used. It has been found to be particularly advantageous that additions of 1-15 parts by weight of water, based on the dried alkali metal hydroxide, are sufficient. In this case , the oxidative dehydration begins at around 170 ° C.

For complete conversion of the starting material, stoichiometric amounts of alkali metal hydroxide are basically required, ie per mole of diol 2, per mole of diol partial ester 3 and per mole of full diol ester k moles of alkali metal hydroxide.

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However, in contrast to the results obtained with the alkali melting of monohydric fatty alcohols, it was found that that the yield can be increased significantly if you use an excess of alkali metal hydroxide, which is preferably the.1,1 to 3 times and especially 1.5 to 2.5 times the stoichiometric required amount works.

The applicable to the alkali melt temperatures depend, inter alia on the starting material, each employed an alkali metal hydroxide or alkali metal hydroxide mixture, and water content of the Re- "action mixture. The procedure is generally in the range of 170 36O ⁰ C. Under these conditions, the reaction is generally after about Completed 1-3 hours.

The reaction mixture can be worked up in such a way that that it is introduced into water, any unsaponifiable components present are removed in a known manner and removed from the aqueous Solution that releases free carboxylic acids by adding dilute mineral acids. In general, there is no need for intermediate cleaning, since the process products have an extremely high degree of purity and virtually no by-products available. . (

The carboxylic acids separated from the acidified solutions can then in a conventional manner, for. B. by distillation, getting cleaned. However, this cleaning is not necessary for many use products for the reasons mentioned above.

The advantage that can be achieved with the invention consists in particular in the fact that a raw material which is new for this reaction has been developed for the synthesis of straight-chain carboxylic acids and which can be produced directly from -olefins in a simple manner. Ale Another advantage dee procedure is considered "that the implementation of practically proceeds quantitatively and uniformly, that almost gives homologous free fatty acids. In addition, it should be emphasized

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that the high purity fatty acids produced in this way are particularly color-stable and practically free from by-products, In addition, the process offers the advantage of a wide range of variations, since the selection of appropriate starting materials Fatty acids of any desired chain length can be produced.

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Henkel & CIe GmbH s · »· 7« "Pat« ntonm «iduna d 3942 Examples example 1

2.023 kg (10 mol) of 1,2-n-dodecanediol, 840 g (21 mol) of sodium hydroxide and 20 g of water (2.4% by weight, based on sodium hydroxide) were thoroughly homogenized and placed in a 10 l nickel autoclave equipped with a stirrer brought in. After displacing the air by purging with nitrogen, the reaction mixture was heated to 320 ° C. over 2.2 hours. The oxidative dehydrogenation ä began, as was recognized by the spontaneous rise in pressure, at 185 ° C. The pressure of the resulting hydrogen was maintained at 130 atm by repeatedly draining. After no further pressure increase could be detected with a further increase in temperature above 270 ° C., the heating was switched off. After cooling to 100 ° C., the reaction mixture was admixed with enough water that an approximately 15% aqueous soap solution resulted. The solution was acidified with 20% sulfuric acid and the crude fatty acid which had separated out was separated off. The yield of fatty acid was 73 % of theory, based on the diol used. The fatty acid had the following key figures: ■ '

Acid number OH number Iodine number found 295 0.9 calculated 301

The fatty acid was then worked up by distillation.

The main run (boiling point 98 - 102 ° C, 0.05 mm Hg) was gas

• examined chromatographically and showed the following composition

2,5Jf n-decanoic acid, 9 ^, X% n-undecanoic acid, 3.4 % n-dodecanoic acid,

To determine the unsaponifiable content in the reaction mixture

An aliquot was made of the aqueous soap solution

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Amount extracted with gasoline (boiling range 65 - 85 ° C) * t χ. The benssine extracts were washed free of alkali and the gasoline was distilled off after drying. The distillation residue was weighed and showed a proportion of unsaponifiable material of 6.9 % (based on the diol used).

Example 2

2.023 kß (10 mol) of n-dodecanediol-1,2, 1.6 kg (10 mol) of sodium hydroxide and 190 g of water (11.9% by weight, based on NaOH) were in a 10 1 nickel autoclave with stirring in the course heated to 300 ° C from 2.3 hours. The reaction started at 170.degree. C. and was practically complete at 270.degree. The reaction pressure rose to 280 atmospheres in the course of the reaction. The cooled reaction mixture was worked up as described in Example 1. 1.7 * 1 kg of n-undecanoic acid were obtained, which corresponds to a yield of 93 % of theory, based on the diol used. The fatty acid had an acid number of 300.

Example 3

177 g (1.5 mol) of 1,2-hexanediol, 180 g (4.5 mol) of sodium hydroxide and 11 g of water (6.1% by weight, based on NaOH) were placed in a 1 liter nickel autoclave stirring in the course _of: heated hour to 290 ° C. The oxidative dehydrogenation took place in the temperature range 185-280 ° C. The reaction pressure rose to 180 atmospheres in the course of the reaction. After gluing the reaction product in water and acidifying it with dilute sulfuric acid, 151 g of n-valeric acid were obtained. The yield was 99 % of theory.

Key figures of the obtained valeric acid:

Acid number OH number Jodeahl 536 2.8 / 0

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Example M

1 kg of a C ^ ~ C ^ g-n-alkanediol-1,2-mixture of the middle Molecular weight 275, 465 g (11.6 mol) sodium hydroxide and 46 g water (9.9% by weight based on NaOH) were in the course of

Heated to 315 ° C for 2 hours. The oxidative dehydrogenation took place in the temperature range 180-290 ° C at a maximum pressure of 135 atm. A fatty acid mixture with the following key figures was obtained in a yield of 88 % of theory:

Acid number OH number Iodine number found 227 2.6 0.6 calculated 228 - - Example 5

2.51 kg of 30% hydrogen peroxide were added in portions to a mixture of 3.367 kg (20 mol) of n-dodecene-1 and 17,198 iiger formic acid over the course of one hour and while cooling to 25-40 ° C. The reaction mixture was then stirred at 60 ° C. for 12.5 hours. The excess formic acid was distilled off until the temperature of the distillation residue rose to above 105.degree. After cooling, the distillation residue was mixed with 3.26 kg of sodium hydroxide and 183 g of water (7.9% by weight, based on NaOH) and introduced into a 10 l nickel autoclave. After excluding air by purging the autoclave with nitrogen, the mixture was heated to 300 ° C. in the course of 2.8 hours. The oxidative dehydrogenation took place in the temperature range 175-260 ° C. The pressure rose to 242 atmospheres during the reaction. In the work-up of the reaction mixture, which was carried out as in Example 1, 3.28 kg of n-undecanoic acid were obtained. This corresponds to a yield of 84 % of theory, based on the olefin used.

Analogous results were obtained when the hydroxylation of the olefin was carried out with peracetic acid.

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Claims (5)

Henkel & Cie GmbH s. »« Iq mr Potemannniduna d 39IJ2 PATENT CLAIMS Ij Process zxxv Production of exclusively straight-chain ^ -eiliphatic carboxylic acids with more than ¹ I C atoms by alkali melting of oxygen-containing compounds and subsequent conversion of the alkali salts obtained into the free acids, characterized in that the starting materials are unbranched, 6-30 C atoms, 1,2-diols and / or their full or partial esters with aliphatic carboxylic acids containing 1 - k carbon atoms are used. 2. A process for producing exclusively straight-chain aliphatic carboxylic acids having more than ¹ J C-atoms of the corresponding unbranched a-01efinen, characterized in that unbranched α- olefins _m i ^ 6-30 carbon atoms with preformed or in situ generated peracids, such as Peracetic acid and its solutions, formic acid / HpOg or acetic acid / sulfuric acid / HpOp mixtures are hydroxylated in a manner known per se, the crude reaction product is subjected to an alkali melt and the alkali metal salts obtained are converted into the free acids. 3. The method according to claim 1 and 2, characterized in that the alkali melt carried out in the pressure range 1 - 300 atü will. 4. The method according to claim 1 to 3 »characterized in that that the alkali hydroxide is used in an excess, which is preferably 1.1 to 3 times and in particular 1.5 to 2.5 times the stoichiometrically required amount. -I- 109829/191 1 Henkel & CIe GmbH S.It. lliur Puf.ntanm.ldune D 39 ^ 2 5. The method according to claim 1 to ¹ I, characterized in that the alkali melt with the addition of 0.5 to 50, preferably 1 to 15 Gevr.-Ϊ water, based on the alkali hydroxide used, is carried out. H e η k e 1 & C i e GmbH • i.Y Jl. ■ ^ * 7 · . Arnold /) (Dr. Haas) (Dr 109829/1911