DE1028984B - Process for the production of aromatic di- and polycarboxylic acids - Google Patents

Description

Process for the production of aromatic di- and polycarboxylic acids The alkali salts of aromatic carboxylic acids can be obtained by heating to a higher temperature convert into the corresponding salts of other aromatic carboxylic acids. After this A number of processes can be created, some of them from easily accessible starting materials Manufacture technically valuable products, e.g. B. terephthalic acid, trimesic acid, 1 \ aphthalene-2,6-dicarboxylic acid, 4,4'-diphenyldicarboxylic acid and others. Next to it will be in some cases the corresponding carboxyl group-free cyclic products as by-products Get connections. This procedure is at different high pressures or also without pressure, expediently using an inert protective gas and optionally in the presence of catalytically active metals or metal compounds.

It has now been found that the salts of polyvalent metals of aromatic mono- or dicarboxylic acids can also be converted into the salts of other aromatic carboxylic acids, in particular of di- and polycarboxylic acids, by heating to a higher temperature, which can optionally be converted into the free ones by methods known per se Allow acids or their derivatives to be converted. In many cases, the process according to the invention gives rise to other main or By-products than in the conversion of the alkali salts. Often those dicarboxylic or polycarboxylic acids are formed in which at least two carboxyl groups are in o-position to one another. So z. 13. Obtain phthalic acid from benzoic acid.

Salts serve as the starting material for the process according to the invention of aromatic mono- or dicarboxylic acids, e.g. B. salts of benzoic acid, a- and ß-Naplithoesätire, the diphenylmonocarboxylic acids, also salts of phthalic acid, isophthalic acid, Terephthalic acid, naphthalic acid and other naphthalenedicarboxylic acids, also the Diphenic acid and other diphenyldicarboxylic acids. Also salts of mono- or dicarboxylic acids, in which the carboxyl groups are on another aromatic ring system, e.g. B. anthracene, 1,4-diphenylbenzene, diphenylmethane or benzophenone are suitable as starting material for the process according to the invention. It can too Mixtures of aromatic carboxylic acids are used, such as are used, for. B. by oxidation obtained from crude xylene mixtures or from coal by various known methods will. In the case of those used as starting material for the process according to the invention In addition to the carboxyl groups, the aromatic ring can also contain other carboxylic acids Carry substituents, e.g. B. alkyl radicals, insofar as this does not result in a decomposition of the Molecule already occurs below the reaction temperature. As starting materials Serving carboxylic acids are in the form of their salts with polyvalent metals for the method according to the invention is used. The salts are particularly suitable Alkaline earth metals, e.g. B. the salts of magnesium. Calcium, strontium or barium. Furthermore, the salts of other polyvalent metals, such. B. of aluminum, Zinc, cadmium, iron and other heavy metals are suitable. Instead of the salts It is also possible to use reaction mixtures which produce such salts. Mixtures of carboxylic acid anhydrides and acid-binding metal compounds, z. B. metal carbonates or metal oxides., Suitable. These mixtures do not need to be present in the stoichiometric ratio. One or the other component can be used in excess. The salts or salt mixtures to be processed are preferably processed in as dry a condition as possible.

It has been shown that the reaction according to the invention by the presence is favored by catalysts. Metals, such as, in particular, serve as catalysts Zinc, cadmium, mercury, lead and iron, and compounds of these metals, e.g. B. their oxides or their salts with inorganic or organic acids. Suitable Salts include carbonates, bicarbonates, halogeilides, sulfates, phosphates, Acetates, formates, oxalates and fatty acid salts or the salts of those mentioned Metals with those acids which are used as starting material for the invention Reaction can be used or which arise in this reaction, e.g. B. their benzoates or phthalates. The amount of catalysts and can vary within wide limits to 15, preferably 0.5 to 5 percent by weight, based on the Reaction mixture ,. be. The catalysts mentioned can also be used in conjunction with known carriers, e.g. B. kieselguhr can be used.

In addition to these catalysts, the reaction according to the invention can be carried out in the presence inert liquid or solid additives are carried out, e.g. B. in the present of sand, metal powder, metal shavings, kieselguhr, activated carbon, _ finely divided aluminum oxide, finely divided silica or inert salts such as sodium sulfate. By these additives will in many cases affect the mechanical properties of the reaction mixture improved. Instead of solid, inert liquids, inert liquids, which do not decompose under the conditions used are used.

In some cases it is also useful to make the heating of the salts more aromatic Carry out mono- or dicarboxylic acids in the presence of acid-binding agents, e.g. B. in the presence of carbonates, bicarbonates or oxalates of the alkali, alkaline earth or other metals.

Because the presence of oxygen during heating usually adversely affecting the yields, it is appropriate to carry out the reaction in the presence of a carry out inert protective gas. Carbon dioxide is best suited for this purpose, but also other inert gases, e.g. B. nitrogen or methane can be used. It is advantageous to carry out the reaction under increased pressure.

The reaction according to the invention usually takes place at one temperature 200 and 300 ° C. The optimal reaction temperature depends on the one used Starting materials different. Although you can at a temperature of up to about 500 ° C work, but it is often useful to have a reaction temperature below = 150 ° C to use, as undesirable side reactions at too high a temperature, such as z. B. ketonization or charring can occur.

When carrying out the reaction according to the invention, it can be avoided local overheating and the resulting decomposition as well as prevention the caking of the reaction mixture may be useful, the reaction mixture in motion to keep. This can e.g. B. by working in stirred vessels, shaking or rolling autoclaves take place. The uniform heating can also be brought about by works in a thin layer, whereby the reaction material is movably or immovably stored can be. However, good yields are obtained even without these measures if one ensures that strong local overheating is avoided.

The reaction mixtures are worked up in a manner known per se Way. You can z. B. by treating the crude reaction products with dilute Mineral acids win the free acids, which are then purified in a known manner will. Another option is to use the crude reaction products by treatment with an aqueous alkali metal carbonate solution in the alkali salts of the Can convert formed aromatic di- or polycarboxylic acids. Out of the solution The free acids or their acidic salts pass through the alkali salts Acidification with an inorganic or organic acid precipitate in a known manner. It is also possible to acidify with the help of carbon dioxide with or without pressure perform. The free acids can be due to their different solubility or volatility separated and isolated in pure form and optionally in their Derivatives, e.g. B. their halides or esters, are converted. A separation or Cleaning can also be carried out in a known manner by removing the acids esterified and the esters obtained are distilled or fractionated. Example 1 In a 0.21 capacity autoclave was charged with 37.9 g of barium benzoate. Of the The autoclave was evacuated and then about 180 g of carbon dioxide from a pressure bottle filled. The mixture was then heated to 350 ° C. for 10 hours. (In this and in the following Examples, the temperature was measured with a thermal element, which was in the middle of the powdery reaction mixture.) This turned out a pressure of about 1580 at. After cooling and relaxing it became raw Reaction product, which weighed 37.5 g, with a solution of 20 g of potassium carbonate in 500 boiled in water. The barium carbonate formed was filtered off and the aqueous solution acidified with hydrochloric acid. After cooling to room temperature the acid which had crystallized out was filtered off and the mother liquor was extracted with ether. The crystals obtained after evaporation of the ether were with those from the aqueous Solution obtained combined, from the mixture the benzoic acid with chloroform pulled out and recovered in this way 9.65 g of benzoic acid. The residue of 8.0 g consisted of phthalic acid. Example 2 In an autoclave with a capacity of 0.2 l 37.9 g barite benzoate mixed with 2 g cadmium fluoride and 190 g carbon dioxide Heated to 350 ° C for 10 hours. A pressure of about 2000 at was established. After letting down and cooling down, the reaction product, which weighed 32.6 g, was boiled with a solution of 25 g of potassium carbonate in 500 ccm of water. The resulting Barium carbonate was filtered off and the aqueous solution acidified with hydrochloric acid. Upon cooling, initially 3 g of an acidic potassium salt of an aromatic one crystallized Polycarboxylic acid that has not been identified. From the 1lutterlauge were obtained by crystallization and extraction with ether 11.75 g of phthalic acid. example 3 In an autoclave with a capacity of 0.21, 33.0 g of strontium benzoate were mixed heated to 330 ° C. for 10 hours with 2 g of mercury (II) chloride and 180 g of carbon dioxide. This resulted in a pressure of 1850 at. After relaxing and cooling down the reaction product with a solution of 20 g of potassium carbonate was about -100 ccm of water boiled. The resulting strontium carbonate was filtered off and the aqueous solution acidified with hydrochloric acid. After standing for some time at room temperature the separated phthalic acid was filtered off and the mother liquor finite ether extracted. The total amount of this way through crystallization and extraction obtained phthalic saturation was 14.0 g.

Example 4 In an autoclave with a capacity of 0.21, 37.9 g of barium benzoate, mixed with 2 g of mercury (11) chloride, and 190 g of carbon dioxide were heated to 330 ° C. for 10 hours. A pressure of about 2000 at was established. The reaction product was boiled with a solution of 20 g of potassium carbonate in about 400 cc of water. The barium carbonate formed was filtered off and hydrochloric acid was added to the hot solution until it became strongly acidic. Here, 0.6 g of terephthalic acid crystallized out, which was filtered off while hot. Then the solution was up. Cooled to room temperature and extracted after separation of the crystallized phthalic acid with ether. The total amount of phthalic acid obtained was 10.1 g. Example 5 8 g 11Iagnesiuinoxide, 45,2-benzoic anhydride and 4- of the double salt KZ Cd FZ Cl. were mixed in a ball mill. The mixture was heated together with 170 g of carbon dioxide in an autoclave with a capacity of 0.21 at 300 ° C. for 10 hours. This resulted in a pressure of about 2000 at. After cooling and releasing the pressure, the reaction product was boiled with a solution of 30 g of potassium carbonate in 500 ccm of water. The resulting basic magnesium carbonate was filtered off and the solution was acidified with hydrochloric acid while hot. Here, 0.65 g of terephthalic acid crystallized out. which were filtered off hot. By crystallization and extraction with ether in the manner described in Example 1, 5.3 g of phthalic acid were obtained from the solution. In addition, 16.9 g of ßenzoic acid was recovered. Example 6 37.9 g of barium benzoate and 2 g of cadmium fluoride were mixed in a ball mill and the mixture was heated at 350 ° C. for 5 hours in a roller autoclave of 0.21 capacity. At the beginning of the experiment, 50 atmospheres of carbon dioxide were injected. The final pressure at 350 ° C. was 160 atm. After cooling and releasing the pressure, the reaction product, which weighed 29.7 g, was boiled with a solution of 30 g of potassium carbonate in 400 cc of water. The barium carbonate formed and the catalyst were filtered off and the solution was acidified with hydrochloric acid while hot. This crystallized out 0.95 g of terephthalic acid, which was filtered off while hot. From the cooled mother liquor, 11.65 g of a mixture of organic acids with an acid number of 625 were obtained by crystallization and extraction with ether in the manner described in Example 1. 2.55 g of benzoic acid were separated from the mixture by extraction with chloroform. The remainder of 9.1 g consisted of a mixture of phthalic acid and isophthalic acid (in a ratio of 68.4 to 31.6%). Example ? 37.9 g of barium benzoate, 19.75 g of arium carbonate and 2.5 g of cadmium fluoride were mixed in a ball mill. The mixture was heated to 350 ° C. for 5 hours in a roller autoclave with a capacity of 0.2 l. At the beginning of the experiment, 50 atmospheres of carbon dioxide were injected, the final pressure at 350 ° C. was 160 atmospheres. The reaction product, which weighed 54.8 g, was boiled with a solution of 50 g of potassium carbonate in 500 cc of water. After filtering off the barium carbonate and the catalyst, the hot solution was acidified with hydrochloric acid and then filtered hot. 1.95 g of terephthalic acid were obtained. A total of 13.6 g of organic acids with an acid number of 628 were isolated from the cooled mother liquor by crystallization and extraction with ether. 2.96 g of benzoic acid were separated therefrom by extraction with chloroform. The residue of 10.64 g consisted of 62.5% phthalic acid and 37.5% isophthalic acid. Example 8 A mixture of 37.9 g of barium benzoate and 2 g of cadmium fluoride was heated to 320 ° C. for 5 hours in a roller autoclave with a capacity of 0.2 l. At the beginning of the experiment, 5 atmospheres of carbon dioxide were injected. The final pressure at 320 ° C. was 20 atm. The reaction product, which weighed 36.6 g, was boiled with a solution of 40 g of potassium carbonate in 500 cc of water. The barium carbonate formed was filtered off and the solution acidified with hydrochloric acid. By crystallization and extraction with ether, 20.95 g of a mixture of organic acids were obtained, which consisted of 75% benzoic acid and 25% phthalic acid. EXAMPLE 9 A mixture of 42.3 g of calcium benzo and 2 g of cadmium fluoride was heated to 400 ° C. for 4 hours in a roller autoclave with a capacity of 0.2 l. At the beginning of the experiment, 50 atmospheres of carbon dioxide were injected. The final pressure at 400 ° C. was 160 atm. The reaction product, which weighed 31.1 g, was boiled with a solution of 35 g of potassium carbonate in 500 cc of water. The calcium carbonate formed was filtered off and the solution was acidified with hydrochloric acid while hot. 3.15 g of terephthalic acid crystallized out and were filtered off while hot. From the cooled mother liquor, crystallization and extraction with ether gave 21.1 g of a mixture of organic acids which contained 1.3.7 g of benzoic acid and 6.4 g of ortho and isophthalic acid. The ratio between ortho and isophthalic acid, as determined by infrared spectroscopy, was about 1 : 3. The total yield of dicarboxylic acids was accordingly 9.55 g. Example 10 A mixture of 37.9 g of barium benzoate and 2.0 g of cadmium fluoride was heated to 340 ° C. at normal pressure in a stream of carbon dioxide for 3 hours. The reaction product, weighing 31.85 g, was boiled with a solution of 35 g of potassium carbonate in 500 cc of water. The barium carbonate formed was filtered off and the solution acidified with hydrochloric acid. By crystallization and extraction with ether, 8.62 g of benzoic acid and 5.93 g of phthalic acid were isolated. The phthalic acid was found to be free of isophthalic acid by infrared analysis.

When repeating the described experiment with extension the reaction time from 3 to 6 hours were 6.32 g of benzoic acid and 7.48 g of phthalic acid obtain.

Example 11 A mixture of 38 g of strontium benzoate and 1.5 g of cadmium fluoride was heated to 350 ° C. for 4 hours in an autoclave under a carbon dioxide pressure of 10 atm, which was kept constant with the aid of a pressure relief valve. The reaction product, weighing 32.45 g, was worked up in the manner described above. 9.72 g of phthalic acid and 6.43 g of benzoic acid were isolated. Example 12 A mixture of 400g and 24g Bariumbenzoat cadmium fluoride was filled in a pan made of sheet steel. The tub was placed in an autoclave with a capacity of 7 liters. The air in the Autoldav was displaced by multiple flushes with carbon dioxide. Subsequently were. 10 at carbon dioxide pressed on. The autoclave was then heated to 370 ° C. for 3 hours, the pressure being kept constant at 10 atm. The excess gas was passed through a cooler, then through two washing bottles with tetralin and finally through a cold trap, which was cooled to -55 ° C. with a cold mixture.

Subsequent to the heating, the carbon dioxide and the gases formed during the reaction were carefully released from the still hot autoclave through the cooler, the washing bottles and the cold trap, flushing with carbon dioxide. By fractional distillation of the contents of the washing bottles and the cold trap, 39 g of pure benzene were obtained. The solid reaction products were worked up in the manner described above. 96.2 g of phthalic acid were obtained and 73.2 g of benzoic acid were recovered. Example 13 In an autoclave a mixture of. 50 g of barium isophthalate and 3 g of cadmium fluoride were heated to 440 ° C. for 4 hours at a constant pressure of 10 atmospheres of carbon dioxide. The crude reaction product, which weighed 46.25 g, was dissolved in water, insoluble matter filtered off and acidified with hydrochloric acid. The organic acids which precipitated out were filtered off. The mother liquor was extracted with ether. The residue obtained on evaporation of the ether was combined with the acid which was precipitated first. By determining the acid number and by infrared analysis, it was found that the acid mixture isolated in this way consisted of 13.8 g of isophthalic acid, 3.9 g of hemimellitic acid and small amounts of phthalic acid. Example 14 In an autoclave with a capacity of 600 ccm, a mixture of 60 g of Ba, riumphtha.lat and 3 g of cadmium fluoride was heated to 420 ° C. for 15 hours. Before starting, the heating was done. 350 g of liquid carbon dioxide were poured into the autoclave, which resulted in a pressure of about 1200 atm at the reaction temperature. The reaction product was worked up in the manner described. Acidification with hydrochloric acid and subsequent extraction with ether gave a mixture of aromatic carboxylic acids. By determining the acid number and infrared analysis, it was found that this mixture consisted of 21.8 g of phthalic acid and 6.75 g of hemimellitic acid. Example 15 In an autoclave with a capacity of 600 ccm, a mixture of 38.7 g of barium benzoate and 9.5 g of zinc benzoate was heated to 380 ° C. for 5 hours. At a temperature of 120 ° C., 650 atmospheres of carbon dioxide were injected with a compressor, which gave a pressure of about 1200 atmospheres at the reaction temperature. The reaction product, which weighed 35 g, was worked up in the manner described and gave 2.75 g of terephthalic acid and 9.0 g of phthalic acid. 4 g of the benzoic acid used were recovered.

Claims (3)

PATENT CLAIMS: 1. Process for the production of aromatic di- and polycarboxylic acids or their salts or derivatives, characterized in that the alkaline earth salts of aromatic mono- or dicarboxylic acids in the presence of inert ones Gases, such as carbon dioxide, and possibly more catally effective in the presence of them : Metals or metal compounds heated to a temperature between 200 and 500 ° C and optionally convert the salts obtained into the free ones in a manner known per se Acids or their derivatives transferred. 2. The method according to claim 1, characterized in that because the heating is carried out under increased pressure. 3. The method according to claim 1 and 2, characterized in that the catalysts used are cadmium, zinc, mercury, Iron and lead or compounds of these metals are used.