DE1056598B - Process for the preparation of aromatic or aromatic-heterocyclic di- and / or tricarboxylic acids or their salts - Google Patents

Description

Process for the preparation of aromatic or aromatic heterocyclic Di- and / or tricarboxylic acids or their salts As already found earlier, aromatic di- and polycarboxylic acids or their salts can be produced by that one salts of aromatic monocarboxylic acids in a mixture with salts of aromatic polycarboxylic acids, which contain more than two carboxyl groups in the molecule, to a temperature above Heated at 3000 C and optionally converted the salts thus obtained into the free acids. In this reaction there is migration of carboxyl groups from one molecule on the other hand, and possibly also a rearrangement of the carboxyl groups within of the molecule instead, so that, for example, from 1 mole of potassium benzoate and 1 mole of des Potassium salt of a benzenetricarboxylic acid, 2 moles of potassium terephthalate can be obtained can.

It has now surprisingly been found that carboxyl groups can also be introduced into carboxyl-free aromatic compounds or into aromatic-heterocyclic compounds if they are used in the absence of significant amounts of oxygen and with the exclusion of water with alkali salts of aromatic or aromatic-heterocyclic carboxylic acids at elevated temperature, under pressure as well as reacting in the presence of suitable catalysts. In the reaction according to the invention, all or some of the carboxyl groups of the carboxylic acids used as starting material are transferred to the compound free of carboxyl groups. According to the process according to the invention, for example, from benzene and the potassium salt of pyromellitic acid, potassium terephthalate is obtained according to the following equation: The free acids or their derivatives can be obtained in a known manner from the salts obtained in this way.

Suitable starting materials for the process according to the invention Carboxyl group-free connections are z. B. aromatic hydrocarbons such as Benzene, naphthalene, diphenyl and other polynuclear aromatic compounds.

Also carboxyl group-free aromatic-heterocyclic compounds can serve as starting material for the new process. Below are some Heterocyclic compounds are understood to have one or more heteroatoms in the ring included and which, due to their chemical behavior, have an "aromatic" character ascribes. Such compounds are e.g. B. pyridine, quinoline, isoquinoline, thiophene, Thionaphthene, a, a-dipyridyl, and others. m.

Aromatic carboxylic acids, which according to the invention in the form of their alkali salts with the aromatic or aromatic-heterocyclic hydrocarbons mentioned are brought to implementation, are z. B. benzene carbanic acids, especially hemimellitic, Trimellitic and trimesic acid, mdlophanic, prehnitic and pyromellitic acid, benzene pentacarboxylic acid and mellitic acid. Mixtures of such polycarboxylic acids can also be used. Mono- or dicarboxylic acids of benzene can also be used for the carboxylation of heterocyclic acids Connections are used. Such a way of working is often expedient, because benzoic acid and phthalic acids are technically easily accessible substances are. The benzene carboxylic acids mentioned are produced by known processes, for example by oxidation of alkylbenzenes or by oxidative degradation of higher, optionally alkylated ring systems. You can also choose from carbonaceous StoKen, such as B. graphite and carbon, by oxidation z. B. with nitric acid or can be obtained with oxygen.

Other aromatic polycarboxylic acids suitable for the process according to the invention derive from polynuclear aromatic ring systems, such as. B. the a- and , B-naphthoic acid, naphthalic acid, diphenic acid, naphthalenetricarboxylic acid-1,4,5 and for naphthalene-1,4,5,8-tetracarboxylic acid. Also aromatic heterocyclic ones Carboxylic acids, e.g. B. pyridinarboxylic acids are equally suitable to come but in general, for economic reasons, they are less suitable as starting materials.

The acids mentioned or their mixtures are used for the inventive Process used in the form of their alkali salts. The salts of potassium are preferred processed, because you get particularly good results with these. The rubidium and cesium salts, which give equally good yields, come from economic ones Reasons less in question.

The main catalysts for the process according to the invention are Cadmium and its compounds suitable, e.g. B. the oxide or the salts with organic or organic acids, also organometallic or complex compounds of the Cadmiums. Also some other metals, especially zinc and mercury, as well as compounds these metals come into question.

To carry out the method according to the invention, it is necessary exclude the presence of large amounts of oxygen. So you work in the presence of a suitable protective gas, preferably in the presence of carbon dioxide negative pressure. Other protective gases, for example nitrogen or argon, can also be used can be used, optionally mixed with carbon dioxide.

It is also useful for carrying out the method according to the invention necessary to exclude the presence of water. There are therefore all starting materials preferably used in a carefully dried state. To the presence too small amounts of water that are either still present in the starting materials or which can form through secondary or decomposition reactions can be ruled out with certainty, It is advantageous to add those substances to the reaction mixture which are under the applied reaction conditions are able to bind water or with it implement without disturbing the actual reaction. Such substances can be chemical be of very different nature. Suitable are e.g. B. Carbides of various metals, such as aluminum carbide, or also carbides of the alkaline earth or alkali metals, such as calcium carbide. Other compounds of the metals mentioned, e.g. B. their nitrides or boards or Cyanates, particularly potassium cyanate, can also be used, for example elemental silicon or boron, or various compounds of these elements, under other silicon tetraphenvl.

The reaction according to the invention generally starts at one temperature above 3000 C. The optimal reaction temperature depends on the one used Starting materials different. The upper temperature limit is determined by the decomposition temperature given the starting materials or the reaction products.

Working up the reaction mixtures is usually simple. The unreacted aromatic or aromatic-heterocyclic hydrocarbons can be recovered. In the technical implementation of the process can the hydrocarbon are circulated. The same goes for that for Use of protective gas, e.g. B.

Carbon dioxide, which, if necessary after appropriate cleaning, can also be used again. Likewise, other additives, such. B. the catalyst, use several times.

In many cases, the process according to the invention is technical valuable aromatic or aromatic-heterocyclic dicarboxylic acids or their salts, such as terephthalic acid, naphthalene-2,6-dicarboxylic acid or isocinchomeronic acid. Other aromatic carboxylic acids, e.g. B. trimesic acid.

Example 1 40.6 g of the tetrapotassium salt of pyromellitic acid was obtained with 4.0 g of cadmium fluoride and 10.0 g of aluminum carbide by grinding in a ball mill intimately mixed together with 325 cm3 of benzene in an autoclave with a capacity of 600 cm3 filled. The contents of the autoclave were then heated to 4250 ° C. for 15 hours. Before the start of heating, so much carbon dioxide was injected that it was at the reaction temperature a pressure of 1400 at was set. The solid reaction products became after cooling and releasing the pressure in the autoclave from excess benzene and dissolved in water.

The solution was filtered and the filtrate at 90 to 1000 C with ~ Acidified hydrochloric acid. The precipitated terephthalic acid was filtered hot, with Washed out with hot water and then dried at 1400 C. The yield was 23.35 g. 3.8 g of pyromellitic acid were obtained from the mother liquor by extraction with ether recovered.

Example 2 40.6 g of the tetrapotassium salt of pyromellitic acid, 3.0 cadmium terephthalate and 5.0 g aluminum carbide were mixed in a ball mill and together with 325 cm3 of benzene in an autoclave with a capacity of 600 cm3 25 Heated to 4100 ° C. for hours. At the beginning of the experiment, so much carbon dioxide was in pressed the autoclave that a pressure of about 1500 at resulted at the reaction temperature.

The solid reaction products were as described in Example 1 Way worked up. 19.2 g of terephthalic acid were obtained. From the mother liquor 5.4 g of pyromellitic acid could be recovered.

Example 3 32.4 g of the tripotassium salt of hemimellitic acid, 2.0 g Cadmium fluoride and 5.0 g of aluminum carbide were mixed in a ball mill and then together with 325 cm3 of benzene in an autoclave with a capacity of 600 cm3 Heated to 4100 C for 16 hours. At the beginning of the experiment there was so much carbon dioxide pressed into the autoclave that a pressure of about 1500 at resulted. The solid reaction products were as described in Example 1 Way worked up.

17.05 g of terephthalic acid were obtained. From the mother liquor were Recovered 2.6 g of tricarboxylic acid.

Example 4 40.6 g of the tetrapotassium salt of pyromellitic acid was obtained with 4.0 g cadmium fluoride and 10.0 g aluminum carbide (grain size <0.06 mm) in one Ball mill mixed and then put together in an autoclave of 600 cm8 capacity heated to 4250 C for 15 hours with 300 cm3 of benzene. At the beginning of the experiment 150 atm of nitrogen pressed onto the autoclave. The final pressure at 4250 ° C. was 720 at.

The solid reaction products were prepared in the manner described above. worked up, whereby 4.65 g of terephthalic acid were obtained. From the mother liquor were made by crystallization and extraction with ether in total 19.2 g of pyromellitic acid recovered.

Example 5 40.6 g of the tetrapotassium salt of pyromellitic acid was obtained with 4.0 g of cadmium fluoride and 11.2 g of powdered silicon in a ball mill mixed and placed in an autoclave of 600 cm8 capacity together with 290 cm3 Benzene heated to 4250 C for 15 hours. At the beginning of the experiment there was so much carbon dioxide pressed into the autoclave that a pressure of 1500 at set. The solid reaction products were as described in Example 1 Way worked up. 12.25 g of terephthalic acid were obtained. After cooling down the mother liquors were total by crystallization and extraction with ether 12.65 g of pyromelldic acid recovered.

Example 6 A mixture of 40.6 g of the tetrapotassium salt of pyromellitic acid, 100 g of naphthalene, 10.0 g of aluminum carbide and 4.0 g of cadmium chloride was in one Autoclave with a capacity of 600 cm3 heated to 4250 C for 15 hours. At the beginning of The experiment was so much carbon dioxide that a reaction temperature Pressure from 1450 at was created. After cooling, the reaction product was comminuted and digested with acetone to bring excess naphthalene into solution. Of the undissolved residue was dissolved in hot water and filtered. The filtrate was acidified in the heat with hydrochloric acid. The precipitated naphthalene-2,6-dicarboxylic acid was washed with hot washing water and with alcohol. The yield was 13.2 G. 13.3 g of pyromellitic acid were obtained from the mother liquor by extraction with ether recovered.

Example 7 A mixture of 40.6 g of the tetrapotassium salt of pyromellitic acid, 200 cc anhydrous pyridine, 10.0 g aluminum carbide and 2.0 g cadmium fluoride was used Heated in an autoclave with a capacity of 600 cm3 at 4100 C for 16 hours. to At the beginning of the experiment, so much carbon dioxide was injected that at the reaction temperature a pressure of 660 at was created. After cooling, the reaction product was from Filtered off excess pyridine and dissolved in hot water. The solution was filtered and the filtrate acidified with hydrochloric acid at the boiling point.

8.4 g of terephthalic acid precipitated out and were separated off. the end the mother liquor was converted into 11.85 g of isocinchomeronic acid by crystallization and extraction with ether and 6.95 g of unreacted pyromellitic acid were obtained.

Example 8 A mixture of 48.4 g of dipotassium phthalate, 250 cc anhydrous Pyridine, 10.0 g aluminum carbide and 2.5 g cadmium fluoride were in an autoclave with a capacity of 600 cm8 heated to 4100 C for 16 hours. At the beginning of the experiment so much carbon dioxide was injected that a pressure was reached at the reaction temperature from 1300 at. After cooling, the excess was removed from the reaction product Filtered off pyridine and dissolved in hot water. The solution was filtered and the filtrate is acidified with hydrochloric acid at the boiling point. This gave 20.8 g of terephthalic acid obtain. After cooling, apart from the mother liquor, crystalline sation- and obtained by extraction with ether a total of 6.55 g of isocinchomeronic acid.

Example 9 A mixture of 32.0 g of potassium benzoate, -250 cm3 of pyridine, 10.0 g of aluminum carbide (grain size <0.06 mm) and 2.0 g of cadmium fluoride were used in heated to 4200 C for 16 hours in an autoclave with a capacity of 600 cm3. At the start so much carbon dioxide was injected during the experiment that at reaction temperature a print of 1450 at was created. After cooling, the reaction product was in 11 dissolved water and filtered. The filtrate was concentrated to 300 cm3 and again filtered.

It was then acidified with hydrochloric acid at the boiling point. Of the The resulting precipitate weighed 4.5 g and consisted of terephthalic acid. From the Mother liquor was obtained by crystallization and extraction with ether 6.0 g of isocinchomeronic acid obtain.

Example 10 A mixture of 40.6 g of the tetrapotassium salt of pyromellitic acid, 4.0 g of cadmium fluoride, 10.0 g of amorphous boron, and 325 cm8 of benzene were placed in an autoclave with a capacity of 600 cm3 heated to 4250 C for 15 hours. At the beginning of the experiment so much carbon dioxide was injected that at the reaction temperature a pressure of 1350 at. After cooling, the reaction product, which was a weight of 59.4 g, worked up in the manner described above. There were here 26.2 g of terephthalic acid were obtained. By extracting the mother liquor with ether furthermore, 2.5 g of pyromellitic acid can be recovered.

Example 11 A mixture of 34.2 g of the tetrasodium salt of pyromellitic acid, 2.0 g of cadmium fluoride, 10.0 g of amorphous boron and 250 cm3 of dry pyridine were in heated to 4300 C for 16 hours in an autoclave with a capacity of 600 cm3. At the start so much carbon dioxide was injected during the experiment that at reaction temperature a pressure of 840 at was created. The reaction product, which weighed 46.8 g, was in worked up in the manner described above.

This gave 4.5 g of terephthalic acid. From the mother liquor 2.9 g of a mixture of pyridinedi- and tricarboxylic acid crystallized on cooling the end. Example 12 A mixture of 40.6 g of tetrapotassium pyromellitate, 4.0 g of zinc chloride, 10.0 g silicon and 300 cm3 anhydrous pyridine was in an autoclave of 600 cm3 capacity heated to 4100 C for 20 hours. At the beginning of the experiment was so much carbon dioxide is pressed in that at the reaction temperature a pressure of 1440 at was created. After cooling and letting down the pressure, the excess pyridine was decanted off and the solid reaction product, which weighs 57.0 g, is worked up in the manner described. This gave 12.7 g of terephthalic acid. From the mother's length became through Crystallization and extraction with ether obtained 11.2 g of isocinchomeronic acid.

Claims (1)

PATENT CLAIM 1. Process for the production of aromatic or aromatic - Heterocyclic di- and / or tricarboxylic acids or their salts, characterized in that, that one carboxyl group-free aromatic or aromatic-heterocyclic compounds with Alkali salts of aromatic or aromatic heterocyclic carboxylic acids in the absence significant amounts of oxygen and water and in the presence of such substances, which Binding water or being able to react with water at a temperature above 3000 C under pressure in the presence of a protective gas and in the presence of metal catalysts converts and, if necessary, converts the salts obtained into the free acids 2. Process according to Claim 1, characterized in that the catalysts used are the Metals Cadmium or zinc or their compounds are used. 3. The method according to claim 1 and 2, characterized in that one Carbides, in particular aluminum carbide, are used as water-binding agents. 4. The method according to claim 1 and 2, characterized in that one elemental silicon or boron is used as a water-binding agent. 5 The method according to claim 1 to 4, characterized in that one carbon dioxide is used as a protective gas.