DE1072979B - Process for the preparation of saturated aliphatic mono- and / or dicarboxylic acids - Google Patents

Description

Process for the preparation of saturated aliphatic mono- and or or dicarboxylic acids It has been found that formic acid esters can be converted into carbonic acids Can isomerize if you can with a carbonyl-forming metal of VI., VII. or VIII. Group of the Periodic Table or with a compound of such a metal and with a halogen, a halogen compound or mixtures of these substances, is advantageous in the presence of a carrier and preferably an activator, under the pressure of a Inert gases from 20 to 700 atm at a temperature between 150 and 3000 C, preferably between 230 and 2600 C, heated.

The reaction follows the general equation Suitable esters are the formic acid esters of primary, secondary and tertiary mono- or polyhydric saturated aliphatic, cycloaliphatic or araliphatic alcohols, such as methanol, ethanol, butanol, isobutanol, hexanol, 2-ethylhexanol, benzyl alcohol, isopropanol, sec-butanol, octanol-2, tert-butyl alcohol, ethylene glycol, 1,4-butanediol, 1,6-hexanediol, glycerine and 1,2,4-butanediol. The esters are prepared in a manner known per se.

Of the carbonyl-forming metals, especially those of Iron group, preferably nickel and cobalt, applied. But also chromium, molybdenum, Tungsten, manganese and rhenium are suitable. Used by the compounds of these metals one advantageous the halides. The metals or their compounds are used appropriately in amounts of 2 to 104/0, based on the formic acid ester.

Iodine is expediently used as the halogen.

Bromine and chlorine have a less favorable effect, while compounds of halogens one another, like iodine chloride and iodine bromide, are again good catalysts. That applied halogen is after completion of the reaction in the form of organic halogen compounds and halide ions. For the anti-effectiveness of the other halogen compounds the same order of precedence applies as for the elements themselves. One can also use organic halogen compounds, use such as ethyl bromide or iodobenzene, or hydrohalic acids or their salts, for example the halides of carbonyl-forming metals. The halogen or the Halogen compound is expediently used in an amount of 1 to 3 percent by weight, based on the formic acid ester, too.

As activators that increase the reaction rate and the yield increase, there are compounds of bismuth, antimony and, to a lesser extent, of Bors into consideration. Bismuth iodide is preferably used, expediently in an amount from 0.1 to 1 percent by weight, based on the formic acid ester. Instead of Costly bismuth iodide is just as good at bismuth oxide and hydriodic acid use.

The catalysts can, if appropriate with the activator, on supports be upset. Suitable carriers are e.g. B. activated carbon, silica strands, fused silica, Zeolites, aluminum oxide, pumice stone or bentonite. The carrier is expediently soaked with an aqueous solution of a compound of the carbonyl-forming metal in question and the activator and removes the water by gentle heating under reduced pressure Pressure. But it is also possible to use the porous, large-surface material together with the carbonyl-forming metal or its compound, the halogen compound or the halogen compound and to add the activator to the formic acid ester. The use of a carrier allows isomerization to take place at a lower temperature, i.e. H. under gentler Conditions to perform and is particularly suitable for continuous execution of the procedure.

Suitable inert gases are inert gases such as carbon monoxide and carbon dioxide and nitrogen, or mixtures thereof. The protective gases force the decomposition of the reaction products or the starting materials back. Even a pressure of 20 at is effective in this sense, however, it is expedient to use 50 to 250at. The isomerization takes place at a temperature between 150 and 3000 C, preferably between 230 and 2600 C instead. Higher temperatures are not recommended because they favor decarboxylation.

The process is carried out, for example, by using the formic acid ester, the prepared support or the carbonyl-forming metal or its compound, the activator and the substance with a large surface area and the halogen or halogen compound in a pressure vessel under the desired pressure of the selected protective gas on the Reaction temperature heated. The reaction time depends on the temperature and is generally 1 to 12 hours. The pressure vessel is released and the resulting ones are separated Acids from the catalyst, e.g. B. by extraction with a volatile organic Solvent recovered by distillation and the reaction product leaves behind.

The new process generally gives a mixture of isomers Carboxylic acids. In this way, n-butyl formate is produced side by side with n-valeric acid and 2-methylbutyric acid, from butanediol-1,4-diformate adipic acid and 2-methylglutaric acid. In the conversion of diols into dicarboxylic acids, which are used in the manufacture of polyesters and polyamides are used, is an advantageous application of the new process. The content of branched dicarboxylic acids modifies the properties of the high molecular weight Products of further processing in a much desired manner.

The parts mentioned in the following examples are parts by weight.

Example 1 500 parts of n-butyl formate and 370 parts of granules Activated carbon containing 40/0 nickel iodide and 1 0 / o bismuth iodide (manufactured by Soaking the coal with the aqueous solutions and evaporating the water) filled in a pressure vessel. 40 atmospheres of carbon dioxide are injected and the mixture is heated to 2,400 C. After 10 hours, the reaction mixture is allowed to cool and the pressure is released.

The activated charcoal is extracted with acetone and the solution is distilled. The fraction boiling between 170 and 1900 C is removed. It has an acid number from 500 to 520 and is colored red-brown due to a low content of iodine. The iodine is removed by shaking with a little silver or copper oxide and distilled once more under reduced pressure.

310 parts of a carboxylic acid mixture are obtained, which is 75 to 800 parts Boiling at C / 10 Torr and, according to gas chromatographic analysis, from 52.50 / 0 n-valeric acid and 46.7% consists of 2-methylbutyric acid.

Similar results are obtained when using nitrogen, Nitrogen-Carbon Dioxide, Nitrogen-Carbon Monoxide, and Carbon Monoxide-Carbon Dioxide as a protective gas.

Example 2 500 parts of n-butyl formate are heated in a pressure vessel, 25 parts of "moon nickel" powder, 20 parts of iodine, 10 parts of bismuth iodide and 370 parts of granulated Activated carbon (grain size 4 to 6 mm) under a carbon monoxide pressure of 150 at 10 hours to 2400 ° C. Work up as described in Example 1 and 360 parts are obtained of a carboxylic acid mixture consisting of 53.9% 2-methylbufic acid and 46.10 / 0 n-valeric acid consists.

The preparative separation of the mixture is expediently achieved by Distillation of the methyl esters.

The n-valeric acid methyl ester has a boiling point of 1280 C, while the methyl 2-methyl butyrate passes over at 114 to 1150 C.

Example 3 500 parts of 1,4-butanediol diformate and 500 parts of silica strands, The 40 parts nickel iodide and 10 parts bismuth iodide are placed in a pressure vessel heated to 2400 C for 7 hours under a carbon monoxide pressure of 200 at. One extracts the silica strands with methanol or tetrahydrofuran and recover the solvent back by distillation. The monocarboxylic acids are removed from the residue with petroleum ether shaken out. This gives 78 parts of monocarboxylic acids, mainly n-valeric acid. The remaining dicarboxylic acids are separated from the same by recrystallization Amount of water or by heating with five times the amount of benzene. In both cases the 2-methylglutaric acid remains in solution. This gives 280 parts of adipic acid and from the concentrated mother liquor 106 parts of 2 methylglutaric acid.

Example 4 500 parts of 1,4-butanediol are mixed with 25 parts Nickel powder, 20 parts of iodine, 10 parts of bismuth iodide and 370 parts of granulated activated carbon (Grain size 4 to 6 mm) under a carbon dioxide pressure of 40 at 12 hours on 2450 C heated. The charcoal is extracted with acetone, the solvent is evaporated and obtained by recrystallizing the residue from water with the addition of activated charcoal 310 to 330 parts of adipic acid. Only small amounts of 2-methylglutaric acid fall as by-products and n-valeric acid.

Example 5 500 parts of 1,4-butanediol diformate are produced in a press with 380 parts of activated carbon, which contains 45 parts of nickel iodide and 10 parts of bismuth iodide, heated to 2400 C for 7 hours under a carbon monoxide pressure of 180 at. One proceeds as described in Example 3, and receives 88 parts of a mixture of n-valeric acid and 2-methylbutyric acid, 68 parts of 2-methylglutaric acid and 308 parts of adipic acid.

A reaction time of 6 hours is obtained under otherwise identical conditions 64.5 parts of C5 monocarboxylic acids, 61 parts of 2-methylglutaric acid and 337 parts of adipic acid. If the reaction time is even shorter, the starting material has not yet been converted among the reaction products.

Example 6 In a pressure vessel made of corrosion-resistant material there are 1000 parts of butanediol-i, 4-diformate with 50 parts of "moon nickel" powder, 20 parts of iodine, 10 parts of bismuth iodide and 25 parts of 700% hydriodic acid. You press on 80 atmospheres of carbon monoxide and heat to - 2500 C. Then you increase the Pressurize to 200 atm by injecting nitrogen and continue heating for 2 hours long gone.

It is allowed to cool, relaxed, flushed several times with nitrogen, and suction removes the solid constituents and receives 480 parts of crude adipic acid (melting point 140 up to 1420 C). 30 parts of formic acid can be obtained from the oily filtrate by distillation and water, 70 parts of n-valeric acid and 75 parts of 2-methylglutaric anhydride. Recrystallization from benzene is obtained from the distillation residue still 152 parts of adipic acid and 30 parts of 2-methylglutaric acid.

Example 7 A mixture of 80 parts of methyl formate, 5 parts Cobalt iodide, 1 part iron (III) chloride and 0.5 part bismuth iodide is applied after pressing of 50 at carbon dioxide and 450 at carbon monoxide heated to 2650 C for 3 hours. To the cooling is relaxed and flushed with nitrogen. One sucks off, distilled through a silver column that retains traces of iodine and receives 54 parts of acetic acid.

Example 8 1000 parts of benzyl formate (kr.5 86 to 890 C) are mixed with 40 parts of "moon nickel" powder, 20 parts of iodine and 10 parts of bismuth iodide and fills the mixture in a pressure vessel. After injecting 50 atmospheres of carbon monoxide, it heats the vessel is raised to 2400 C and the pressure is increased by forcing in more carbon monoxide to 200 atm. After 3 hours, the vessel is allowed to cool and it is relaxed. The educated Nickel carbonyl is flushed out with nitrogen at 40 to 450.degree.

The bismuth iodide and the iodine are separated off from the reaction mixture and the remaining 930 parts of the reaction mixture under reduced pressure distilled. At a pressure of 0.3 mm Hg, in addition to a fraction of 210 parts, which passes between 93 and 1100 C and consists of a brown oil, 640 parts a fraction distilling between 110 and 1300 C. The latter solidifies when it cools down (F. = 42 to 590 C) and gives 570 parts of phenylacetic acid after another distillation from bp 24 = 122 to 1240 C and F. = 70 to 710 C. The distillate has an acid number of 400 and corresponds to a 970% phenylacetic acid.

The preliminary fraction that passes between 93 and 1100 C at 0.3 mm Hg pressure contains the unreacted starting material.

Example 9 35 parts of nickel powder formed by thermal decomposition obtained from nickel tetracarbonyl are in a print according to together with 800 parts of pentaerythritol tetraformate, 20 parts of iodine and 8 parts of bismuth iodide heated to a pressure of 195 at carbon monoxide and heated to 240 bis for 4 hours Held at 2450 C. During the reaction, the pressure rises to about 220 to 230 atm. After 4 hours let the vessel cool down and relax it. The nickel carbonyl formed in the reaction flushed out with nitrogen. The reaction mixture is filtered through vacuum separated into a solid and an oily part. The solid residue that too still contains some of the catalyst components, is extracted with hot water. The methane-tetraacetic acid crystallizes out of the aqueous solution (m.p. = 190 up to 2100 C [disarmed]). The product has an acid number from 812 to 815 and corresponds to an 820 / own acid. Obtained by recrystallization of the crude product from water 22 parts of a methane-tetraacetic acid with a melting point of 238 to 2420 C (measured with the so-called Koflerbank).

The oily portion of the reaction mixture, which weighs 648 parts, contains methane-tetraacetic acid, essentially dissolved as anhydride, and decarboxylated Descendants. The dicarboxylic acids with cis-positioned carboxy groups can be passed through Treat with a barium chloride solution to separate as salts. From the remaining The 2 ', 2'-dimethylbutyric acid can be obtained by distillation (acid number 482; Kp.12 = 90 to 920 C).

Claims (2)

PATENT CLAIMS: 1. Process for the production of saturated aliphatic Mono- and / or dicarboxylic acids, characterized in that formic acid esters are used saturated aliphatic, cycloaliphatic or araliphatic mono- or polyvalent Alcohols with a carbonyl-forming metal of the VI., VII. Or VIII. Group of the Periodic table or with a compound of such a metal, preferably one Halide, and with a halogen, a halogen compound or mixtures thereof Substances, advantageously in the presence of a carrier and preferably an activator, under the pressure of an inert gas of 20 to 700 atm to a temperature between 150 and 3000 C, preferably between 230 and 260 ° C, heated and optionally resulting mixture of isomeric carboxylic acids in a known manner into the individual components separates. 2. The method according to claim 1, characterized in that as carbonyl-forming metals cobalt and nickel and bismuth iodide as an activator.