DE1054984B - Process for the rearrangement of benzene carboxylic acids into terephthalic acid - Google Patents

Description

Process for the rearrangement of benzenecarboxylic acids into terephthalic acid It has been found that the alkali salts of benzene polycarboxylic acids, the more contained as two carboxyl groups in the molecule, in the alkali salts of terephthalic acid can be converted by adding them to a mixture with alkali metal salts of benzoic acid Heated temperature above 3000 C. The salts obtained can be used in a known manner processed on terephthalic acid or on its derivatives, such as halides or esters will.

The reaction is essentially based on an inter- or intramolecular one Change of position of the carboxyl groups on the benzene ring. The im Mixture of existing alkali salts of benzenecarboxylic acids with three to six carboxyl groups pass into the alkali salts of terephthalic acid, while this is also mixed Any alkali benzoate present is also converted into an alkali salt of terephthalic acid will. The mixture of alkali metal benzoate and the alkali metal salts is expediently prepared of the benzene polycarboxylic acids so that the number of per benzene ring in the reaction mixture the average carboxyl groups present is approximately the same as in the one to be prepared Carboxylic acid, d. h., one uses z. B. for the production of terephthalates from alkali metal benzoates and alkali salts of benzene tricarboxylic acids, the two salts are expediently im equimolecular ratio, while in the implementation of hexacarboxylic acids Alkali salts with benzoates to terephthalate in order to moderate to 1 mole of hexacarboxylic acid Salt applies 4 moles of benzoate.

Suitable benzene polycarboxylic acids are, for. B. hemimellite, trimellite and trimesic acid, mellophanic, prehnitic and pyromellitic acid and benzene pentacarboxylic acid and mellitic acid. They are made by known methods, for example by oxidation of alkylbenzenes or by oxidative degradation of higher, if necessary alkylated ring systems, or from carbon-containing substances such as graphite, hard coal, Brown coal, peat, wood, lignin, coal extracts, tars, pitch, asphalt, coke, Petroleum residues and their transformation products, in particular through treatment with nitric acid. Also naturally occurring benzenecarboxylic acids with at least three carboxyl groups, e.g. B. honey stone occurring as a mineral are suitable.

The acids or their mixtures are used in the form of their alkali salts, in the usual way, for. B. by reaction in solvents or by melting together the acids or their anhydrides with alkali metal compounds, e.g. B. alkali carbonates, oxalates or hydroxides. The salts of sodium are preferred and potassium. It is technically possible in itself, also the corresponding lithium, Process rubidium, cesium and thatlium salts. However, these salts usually separate for economic reasons. You can achieve particularly good results with the salts of potassium.

The conversion takes place by heating to a temperature above 3000 C. It is advantageous to work between about 340 to 4000 C. A higher temperature than 450.0 C is generally not very suitable, since then it is already to a greater extent Decomposition occurs.

It is advantageous to mix the starting materials well, e.g. in a stirred vessel, in a rotary kiln or in a fluidized bed. Oxygen is kept appropriate remote during the implementation, on the other hand, inert gases, especially carbon dioxide and nitrogen, or solid substances such as sand, coke grit and metal shavings are present be. Instead of the alkali salts of the aromatic carboxylic acids, mixtures can also be used the acids with potassium carbonates, hydroxides or oxalates. The presence full of water during the heat treatment is undesirable because it reduces the yields be reduced. It is therefore advisable to start the starting materials at around 110 to 3000 C, advantageously at about 15 (4 "C, expediently in the reaction vessel itself) to dry.

The reaction takes place at normal or elevated pressure, e.g. B. at about 10, 20 or 100, 200 and more atmospheres.

The reaction is triggered by catalysts, especially through metals or metal compounds, e.g.

[eren oxides, hydroxides, salts or organometallic compounds accelerated. The most effective rivets are cadmium and zinc. These may as free Sletalle and in addition to the compounds already mentioned above in the form of Iodides, chlorides, 3romides, fluorides, sulfates, phosphates, carbonates, acetates, soaps, Benzoates, phthalates, isophthalates, rerephthalate and also in the form of their salts with the: benzene polycarboxylic acids to be processed according to the invention are used. The Älenge of the catalog authors can be up to 15 weight percent metal, lied to the entire approach. However, even if you use it, you get considerably less \ close excellent results.

The acids of their salts in The usual way, for example, you can separate the mixture in a solvent. c. B. dissolve in water, separate undissolved components .Ind optionally the acid or acidic salts with acids or acid anhydrides, such as sulfuric acid, hydrochloric acid, Precipitate carbonic acid, sulphurous acid and organic acids or with acidic salts and detach. The unreacted aromatic carboxylic acids can be extracted from the liquor recovered and reused. The salts or those obtained from them Free acids can be processed into acid derivatives in a known manner, e.g. B. on the technically valuable Terephthalsäuredimethyle ster.

Example 1 15 g of an equimolar mixture of potassium benzoate and the tripotassium salt of hemimellitic acid and 0.75 g of Cd 0 were in a glass vessel by means of an aluminum block in a stream of CO2 at normal pressure 5 minutes to 4500 C heated. The reaction product was boiled with water, and the solution after hydrochloric acid is added to hot filtration.

The precipitated terephthalic acid was washed out several times with hot water and then dried at 130.degree. 7.05 g of terephthalic acid were obtained. The terephthalic acid had an acid number of 673; the one via the terephthalic acid dichloride Wanted dimethyl terephthalate had a melting point of 1400 C.

Example 2 A mixture of 2.5 g of potassium benzoate and 5 g of the tripotassium salt of hemimellitic acid, 7.5 g of dipotassium phthalate (Alol ratio 1: 1: 2) and 0.75 g CdO was as indicated in Example 1. in the C O2 stream at normal pressure for 5 minutes heated to 4500 C. The reaction product was worked up in the manner described and yielded 7.05 g of terephthalic acid.

Example 3 A mixture of 5 g of potassium benzoate and 10 g of the tripotassium salt the trimellitic acid (alcohol ratio 1: 1) with 0.75 g of CdO was as in Example 1 described, heated to 4500 ° C. for 11/2 hours. When working up the reaction product 5.7 g of terephthalic acid were obtained.

Example 4 In a roller autoclave with a capacity of 200 cm3, 40 g of a Mixture of potassium benzoate and the tetrapotassium salt of pyromellitic acid in a molar ratio 2: 1 together with 1.3 g of cadmium fluoride heated to 410 "C for 2 hours. At the beginning of the Test 45 at C O2 were injected. At 4100 C the was Pressure 125 at The crude product obtained, weighing 36 g, was dissolved in water and filtered and precipitating with mineral acid 16.2 g of terephthalic acid. From the mother liquor were still 1.2 g of pyromellitic acid recovered.

Example 5 15 g of a mixture of potassium benzoate and the tetrapotassium salt of pyromellitic acid in a molar ratio of 2: 1 were mixed with 0.45 g of cadmium fluoride wide test tube given. The latter was carried out for 5 minutes using an aluminum block heated to 4500 C (temperature measurement in the aluminum block). During the trial dry C O2 was passed over. The crude product weighing 13.8 g was in Worked up in the manner described and yielded 2.95 g of terephthalic acid. From the Mother liquor was still 1.4 cm of pyromellitic acid isolated.

Example 6 A mixture of 11.8 g of the tetrapotassium salt of mellophanic acid and 9.3 g of potassium benzoate (corresponding to a molar ratio of 1: 2) and 0.6 g of cadmium fluoride was heated to 4200 C for 2 hours in a roller autoclave with a capacity of 200 cm3. At the start of the experiment, 50 at C O2 were injected. The final pressure at 4200 ° C. was 150 at. The product obtained, weighing 19.0 g, was made in the manner described Worked up and gave 9.3 g of terephthalic acid.

Example 7 A starting mixture made from carbon oxidation products was used produced mixture of benzene polycarboxylic acids, the 39 tri- and 610/0 tetracarboxylic acids contained. This mixture was neutralized with potassium hydroxide and added to the aqueous solution of potassium salts given so much potassium benzoate that in the mixture per benzene nucleus two Carboxyl groups were present. The aqueous solution was evaporated and the with 1500 C dried residue mixed with 3 0 / o cadmium fluoride. 40 g of this mixture were heated to 430 "C for 1 1/2 hours in a 200 cm roller autoclave. At the beginning of the experiment, 40 at C O2 were injected. At 4300 C the pressure was 144 at. The reaction product obtained, weighing 33.9 g, resulted in work-up in the manner described 14.4 g of terephthalic acid. A same approach, the t / 2 Heating to 4200 C at 20 at C O2 for an hour gave a yield of 11.0 g of terephthalic acid.

Example 8 12.5 g of pyromellitic acid, obtained by carbon oxidation, were neutralized with potassium hydroxide, the tetrapotassium salt with potassium benzoate in a molar ratio Mixed 1: 2 and, after adding 0.75 g of cadmium fluoride t / 2 hour, heated to 4300 ° C. At the beginning of the experiment, 50 at C O2 were injected. The pressure at 4300 ° C was 116 at. The reaction product, which weighed 32.9 g, was converted into 13.6 g of terephthalic acid obtain. 3.79 g of pyromellitic acid were obtained from the mother liquor from the terephthalic acid precipitation recovered.

Example 9 27.0 g of the pentapotassium salt of benzene pentacarboxylic acid, obtained by oxidation of 9-acetyloctohydroanthracene, were with 26.5 g of potassium benzoate (Nole ratio 1 3) and 1.6 g fine cadmium fluoride grind and Heated to 4400 C for 1/2 hour in a roller autoclave. Before the start of the experiment, 50 at carbon dioxide. In the course of the reaction the pressure rose to 160 at. After cooling under carbon dioxide and working up the reaction product were 25.0 g of terephthalic acid were obtained.

13 e i s p i e 1 10 25.4 g of the hexapotassium salt of ellithic acid, obtained by oxidation of dodecahydrotriphenylene, were with 28.6 g of potassium benzoate (Molar ratio 1: 4) and 1.6 g of cadmium fluoride finely ground and placed in a roller autoclave Heated to 4400 ° C. for 3 hours. Before the start of the experiment, there was 60 atmospheres of carbon dioxide pressed into the autoclave. When working up the reaction product were 22.3 g terephthalic acid obtained.

Example 11 A mixture of 10.0 g tripotassium trimesinate, 5.0 g potassium benzoate, 30.0 g of anhydrous potassium carbonate and 3.0 g of cadmium fluoride were placed in a rolling autoclave with a capacity of 200 cm3. Then 50 atm of nitrogen were injected and the autoclave was heated to 420 ° C. for 3 hours. A pressure of 160 at a. After cooling and letting down the pressure, the reaction mixture was in 500 cm3 Dissolved water and filtered the solution. The filtrate was at the boiling point with Acidified hydrochloric acid.

The precipitated terephthalic acid was filtered off in the heat and washed with hot water. The yield was 5.1 g.

Example 12 A mixture of 10.0 g tripotassium trimesinate, 5.0 g potassium benzoate and 30.0 g of potassium carbonate was in the absence of atmospheric oxygen in a roller autoclave from 200 cm3 capacity in a carbon dioxide atmosphere to above the critical one Heated temperature of this gas. Then 50 atmospheres of carbon dioxide were expressed and heated to 4200 C for 5 hours. This resulted in a pressure of 149 at. The reaction product was worked up in the manner described in Example 11. 1.8 g of terephthalic acid were obtained.

Example 13 A mixture of 10.0 g tripotassium trimesinate, 5.0 g potassium benzoate, 30.0 g of potassium carbonate and 3.9 g of anhydrous zinc fluoride were made in the same manner as in Example 12 heated to 4200 ° C. for 5 hours under carbon dioxide pressure. The work-up the reaction mixture yielded 4.1 g of terephthalic acid.

Example 14 A mixture of 4.9 g of the pentapotassium salt of benzene pentacarboxylic acid, 4.8 g potassium benzoate, 30.0 g anhydrous potassium carbonate and 5.0 g anhydrous zinc fluoride was placed in a rolling autoclave of 200 cm3 capacity and under one Carbon dioxide initial pressure of 50 at 3 hours heated to 420 "C. This set a maximum pressure of 140 at. The work-up of the reaction product, which done in the usual manner gave 4.7 g of terephthalic acid.

Example 15 A mixture of 10.0 g tripotassium trimesinate, 4.0 g lithium benzoate, 30.0 g of anhydrous potassium carbonate and 3.0 g of cadmium fluoride were used in the same Place in a rolling autoclave with a capacity of 200 cm3 as in Example 12 heated to an initial carbon dioxide pressure of 50 at for 5 hours at 4200 C. The reaction product was worked up in the usual way and yielded 5.7 g of terephthalic acid.

Example 16 A mixture of 10.0 g tripotassium trimesinate, 4.5 g sodium benzoate, 30.0 g of potassium carbonate and 3.0 g of cadmium fluoride were placed in a rolling autoclave with 200 cm3 capacity given. Then 50 at of carbon dioxide were above the critical temperature of this gas and the autoclave at 4200 for 5 hours C heated. The reaction mixture was worked up in the manner described above. 4.1 g of terephthalic acid were obtained.

Example 17 A mixture of 10.0 g of the tripotassium salt of trimesic acid, 4.5 g sodium benzoate, 30.0 g anhydrous sodium carbonate and 3.0 g cadmium fluoride was placed in a rolling autoclave with a capacity of 200 cm3. Subsequently were 50 atm of carbon dioxide above the critical temperature of this gas. The reaction mixture was heated to 4200 ° C. for 5 hours, with a maximum pressure set from 170 at. The work-up, which took place in the usual way, provided 0.6 g of terephthalic acid.

PATENT CLAIM: 1. Process for rearrangement of benzene carboxylic acids in terephthalic acid, characterized in that the alkali metal salts of benzoic acid are used in a mixture with the alkali salts of benzene polycarboxylic acids, which have more than two carboxyl groups contained in the molecule, heated to a temperature above 3000 C and the reaction mixture processed in a known manner on terephthalic acid or optionally on its derivatives.

Claims (1)

2. The method according to claim 1, characterized in that mixtures processed, in which there are on average two carboxyl groups on a benzene ring meet. 3. The method according to claim 1 and 2, characterized in that one potassium salts are used as alkali salts. 4. The method according to claim 1 to 3, characterized in that one heating in the presence of inert gases such as carbon dioxide or nitrogen, and expediently carried out under pressure. 5. The method according to claim 1 to 4, characterized in that one heating in the presence of metals or metal compounds, in particular of those of cadmium or zinc. Older patents considered: German Patent No. 1 014982.