DE2343964C3 - Process for the production of naphthalene-1,4,5,8-tetracarboxylic acid - Google Patents

Description

Cl

Cl

HOOC COOH

100% ENT ₃
in 13% oleum

—— ■ >

130 "C

The yield by this process is approx. 50% of theory. Th., Based on the expensive pyrene. In the synthesis Large amounts of waste are produced, the disposal of which is associated with costs. So z. Am the second stage 1850 kg of 20% oleum used per 100 kg of halogenation product, which is worked up again Need to become.

A process has now been established for the preparation of naphthalene-1,4,5,8-tetracarboxylic acid or its dianhydride found, which is characterized in that one is a peri-acenaphthindenone of the general Formula (I)

in which R denotes hydrogen or an alkyl group with 1-4 C atoms, in an aliphatic carboxylic acid with 1-4 C atoms as solvent with nitric acid, optionally with the use of oxygen, in the presence of oxidation catalysts at temperatures above 100 "C, the reaction product obtained is isolated and this optionally in a manner known per se by dissolving in I.
HOOC COOH

Alkali and precipitation with an acid in naphthalenetetracarboxylic acid convicted.

Of the known starting materials, the peri-acenaphthindenone-7 (R = H) can be obtained by treating the Na compound of; rj? -oxyvinyl] - [acenaphthenyl- (5) -] - ketones with conc. Sulfuric acid obtained (DT-PS 4 89 571). Perindenones of the formula (I) with R = alkyl, the one advantageous according to patent application P 22 09 692.0 by reacting the corresponding j3-ketocarboxylic acid fluoride obtained with acenaphthene in liquid hydrogen fluoride are for example

S-methyl-peri-acenaphthindenone ^ .S-ethyl-peri-

acenaphthindenone-7,

S-propyl-peri-acenaphthindenone- ?,

S-butyl-peri-acenaphthindenone- ?.
The aliphatic carboxylic acid, which serves as a selective solvent or as a diluent, can be used in concentrations above 50% by weight, preferably 80-100% by weight, in particular 90-100% by weight - remainder water. The quantitative ratio is 1 to 10, preferably 4 to 8 parts by weight of aliphatic carboxylic acid to one part of peri-indenone. Acetic acid is preferred. Other suitable aliphatic carboxylic acids are e.g. B. formic acid, propionic acid and butyric acid. They serve as a solvent in which the compounds of the formula (I) are soluble, so that a homogeneous solution can be assumed, but in which the naphthalene-1,4,5,8-tetiacarboxylic acid or naphthalene-1,4,5,8-carboxylic acid or

their anhydrides are insoluble, so they precipitate and can be easily separated by filtration.

At the same time, however, the aliphatic carboxylic acid also serves as a diluent for the nitric acid used, so that concentrated nitric acid can also be used without nitration in occur to a noticeable extent.

The nitric acid is used in the absence of oxygen in amounts of 7 to 14, preferably 12 to 12 mol / mol of indenone.When elemental oxygen is supplied at the same time, this molar ratio can be reduced to 1 to 6 mol, preferably 1.5 to 4, in particular 2 to 4 will. To obtain a completely oxidized product, at least 2 moles of HNO3 / MOI indenone should be used. Products that are not completely oxidized can be post-oxidized in a manner known per se _{after they have been isolated with KMnO 4 in an alkaline solution.} The nitric acid used can be used in any concentration. In order not to unnecessarily dilute the solvent, the carboxylic acid, however, it is preferred to use concentrated, ie at least 60%, especially 90 to 100%, HNO ₃ . In the case of discontinuous work, it can be initially charged in its entirety, but it is preferred to add it in portions or continuously.

Oxidation catalysts which can be used per se are those known from the literature, in particular Cobalt, manganese, copper, vanadium and molybdenum catalysts, in a manner known per se, preferably in the form of, for. B. their oxides, especially their salts. So can cobalt and manganese in shape their nitrates, acetates or carbonates are used, vanadium z. B. as ammonium vanadate, fresh Precipitated vanadium pentoxide or vanadyl acetylaectonate, molybdenum as molybdenum hexacarbonyl, freshly precipitated Molybdenum oxide, as molybdenum tetrabromide or as a heteropoly acid with cobalt or manganese. the Oxidation catalysts can be used alone or, preferably, in combination. When Vanadium and a mixture of cobalt, manganese and vanadium have proven to be particularly effective. Surprisingly adding small amounts of molybdenum compounds results in a cleaner end product. The concentration of metal ions in cobalt and manganese can be 0.2-40 mg atom / 1 carboxylic acid, preferably 0.8-20 mg-atom / l, particularly preferably 2-8 mg-atom / l. Vanadium can be in one concentration from 0.2-40 mg-atom / l, preferably 0.4-20 mg-atom / l and particularly preferably 2-10 mg atom / 1, be applied. A mixture of cobalt, manganese and vanadium leads to particularly high Conversions with high purity of the reaction product, such as a mixture of 2 mg-atom cobalt and 2 mg-atom manganese and 6 - 8 mg-atom vanadium / l aliphatic carboxylic acid.

Small additions of molybdenum (0.3 mg-atom to 2 mg-atom / 1) to the above-mentioned catalysts promote the completeness of oxidation. This is particularly the case with semicontinuous or fully continuous processes of importance, as there are already traces of incompletely oxidized products, which are difficult to remove can be eliminated, have an adverse effect on the quality of dyes from the naphthalene tetracarboxylic acid getting produced.

If nitric acid and oxygen are used at the same time, the oxygen required for oxidation can be increased in pure form or mixed with an inert gas,

z. B. with nitrogen (as air). His If a pure tetraacid product is to be obtained, the amount corresponds to at least the stoichiometric one Amount that is required after taking into account the nitric acid used. Since the oxidation, for example, for the Case of S-methyl-peri-acenaphthinderion-? according to the following reaction equation (based on the dianhydride as the sole reaction product)

• 5

35

40

45

55

60

₈ +13 [O]

13 oxygen equivalents are required, the use of, for example, 2 mol HNO3 (decomposition to N2O and H ₂ O) results in a stoichiometric oxygen requirement of 4.5 mol O2 / MOI indenone or about 100 normal liters O ₂ (at normal pressure and temperature). In general, however, an excess of oxygen of from 10 to 400% or more is used, the upper limit not being critical. A 20 to 200% excess of oxygen is preferably used, with the excess of oxygen being more in the upper part of the stated intervals when air is used.

The reaction may advantageously ⁰ C to 240 ⁰ C in Tenipaaturbereich of '2O, preferably from 140 ° C to 20O ⁰ C, in particular from 150'C to 180 ⁰ C is performed. If the oxidation is carried out continuously, the preferred temperatures are in the upper range of the intervals mentioned.

The pressure in the reactor is chosen in a manner known per se above the vapor pressure of the aliphatic carboxylic acid at the reaction temperature, i.e. generally above 2 ata. The upper Limit is not critical and essentially depends on technical requirements. Preferably chooses depending on the reaction temperature, pressures of 3 to 30, in particular 4 to 20, ata. This With the appropriate oxygen supply, pressures can easily be regulated by adjusting the exhaust valve. The Process can be carried out batchwise or continuously. When carried out in batches all reactants can be initially charged and then brought to the reaction temperature while passing oxygen through them. In the representation Larger amounts of naphthalenetetracarboxylic acid, however, it is recommended that the nitric acid only during the Pump in the reaction to the extent that it is consumed in order to achieve its stationary concentration as possible to keep it low. This is supposed to cause a nitration of the naphthalene ring and possibly the formation of explosive mixtures of organic compounds and nitric acid are avoided.

For the batch preparation of the naphthalenetetracarboxylic acid, the method is preferably as follows carried out that the solutions of peri-indenone or HNOj in z. B. acetic acid simultaneously and from each other be pumped separately into the reactor, in which the metal catalyst and acetic acid are in the desired reaction temperature. The nitric acid can also be used undiluted without acetic acid be pumped in. The metal catalyst can also

as a solution or dispersion in the carboxylic acid with a third pump «! be pressed in. It is important for the desired course of the reaction that an intensive mixing of the reactants in the liquid phase and the gas phase is ensured during the entire reaction time, which z. B. can be accomplished by vigorous stirring of the reaction mixture and / or passing through the required oxygen. The use of a shaking reactor is also possible. The material for the vessel walls of ι ο pressure reactors are z. B. tantalum, titanium or enamel is particularly suitable. The reaction temperature should be at least 130-140 ⁰ C, since the strongly exothermic oxidation reaction at lower temperatures, e.g. B. 100-120 ⁰ C, sometimes does not start immediately, ts which can lead to heat build-up that is difficult to control when inserted. During the pumping in of the reactor, 1 to 1.5 times the theoretically required amount of oxygen is fed into the reactor and, at the same time, exhaust gas is withdrawn via a cooler in order to remove the CO2, CO, N2 and N2O formed and to maintain the reaction pressure. Even at 150 ^° C. the reaction takes place quickly and almost completely, so that the pumping in can take place in about 2 hours. The temperature is increased with continued introduction of oxygen at 150- 170 ⁰ C then expedient wherein further reacted over a period of for example 30 minutes to 3 hours, optionally with the addition of a small amount of nitric acid, not quite durchoxydierte intermediates.

Right at the beginning of the reaction, the exhaust gas contains a high percentage of N ₂ O and less N _{2 in} addition to a little CO and a lot of CO ₂ (see Table 1). After the reaction has ended, more than 99% of the nitric acid has generally been consumed.

The only low steady-state concentration of HNO3 and NO2 in the reactor leads to less corrosion of the reactor walls than z. B. from the mix Nitric acid / acetic acid would be expected.

The reaction can also be carried out continuously in such a way that for better utilization of the oxygen graze several reactors connected in series as a cascade.

The reaction material - for the most part microcrystalline naphthailintetracarboxylic acid anhydride or dianhydride in z. B. acetic acid - is suctioned off or centrifuged, washed with acetic acid and dried.

It can be used in a manner known per se for cleaning and thus for complete conversion into naphthalene-1,4,5,8-tetracarboxylic acid in alkali, preferably in dilute sodium hydroxide solution, and with an acid, preferably Hydrochloric acid or sulfuric acid, can be precipitated again as naphthalenetetracarboxylic acid. To avoid renewed anhydride formation is particularly the last operation at low temperatures, preferably at Room temperature.

In many cases, however, the crude product can already be used as such. To determine its quality, it can be converted into indanthrene scarlet in a known manner with o-phenylenediamine. The crude yield ^r from the resulting F arbstoffausbeute translates to the Naphtrialin-tetracarboxylic acid dianhydride. The values given for dianhydride in the examples were obtained in this way.

The acetic acid or the aliphatic carboxylic acid of the filtrate can be reused as the reaction medium will. Since it is practically free of nitric acid, the water of reaction can be safely removed by distillation be, for example, an azeotrope of 97% water and 3% acetic acid is distilled off and then optionally the acetic acid itself can be distilled over in pure form.

The process according to the invention means a considerable technical advance compared to the process of technology (pyrene) through the use of a cheaper and easily accessible starting material (in particular 5-methyl-peri-acenaphthindenone-7) and through the good yield of very pure end product. Its particular advantages are in the almost complete absence of difficult to recycle or environmentally harmful waste products. Furthermore, the combined use of HNO ₃ and oxygen only requires relatively small amounts of nitric acid, which also saves costs and considerably reduces the risk of explosions and enables better utilization of the reactor volume, so that the process as a whole is highly economical.

The process is also new and its feasibility was surprising. It is already known, alkylated aromatic compounds with oxygen and / or with nitric acid to aromatic To oxidize carboxylic acids. Because of the special chemical properties of peri-acenaphthindenones of formula (I), however, these processes failed when attempting to convert naphthalenetracarboxylic acid from these compounds to manufacture.

The "Amoco process" is known to be particularly effective for oxidation with oxygen or air. is prepared at the terephthalic acid by oxidation of p-XyIoIs with air in 95% acetic acid at 190-205 ⁰ C. The reaction pressures are between 12 and 28 atmospheres. The catalyst used is a combined system consisting of cobalt acetate, manganese acetate, tetrabromoethane and ammonium bromide (US Pat. No. 10 81 445 and 29 62 361). This process can also be used, for example, to oxidize acenaphthene to 1,8-naphthalenedicarboxylic acid. However, the application of these conditions to 5-methyl-peri-acenaphth indenone-7 did not lead to the formation of naphthalenetetracarboxylic acid, but rather black microcrystals, insoluble in glacial acetic acid and soluble in alkali, of the composition Ci ₆ H ₆ Oi of the following structure:

Ί //

Λ Α

HOOC

The oxidation of alkyl aromatic compounds using dilute aqueous HNO ₃ has also been described. z. B. for xylenes in German patents 8 20 308 and 10 51 840, for p-cymene and p-di-iso-propylbenzene in DT-AS 10 46017 and DTAS 11 55 111. The oxidation of these compounds leads to Formation of terephthalic acid. In the examples given, temperatures of 240-260 ³ C are required for the oxidation of p-xylene, and for the oxidation of

p-cymene and p-di-iso-propylbenzene 260-280 ° C. With these high temperatures are accompanied by high pressures of 50-100 ata, which is expensive Make pressure equipment necessary. In addition, the concentration of nitric acid should be at least 10% as only then can the oxidation be terminated within a useful time. With the necessary At high temperatures, nitric acid places very high demands on the resistance of the reactor material. Working under these conditions is associated with ι ο great technical difficulties.

However, these known processes cannot be applied to the peri-indenones of the formula (I), since the compounds decompose at such high temperatures and the naphthalene structure is broken down to the benzene nucleus under such extreme oxidation conditions. 5-Methyl-peri-acenaphth-indenone-7 can be compared most closely with p-di-iso-propylbenzene because of its 4 CC bonds that have to be cleaved. However, while the p-di-iso-propylbenzene according to the information in DT-AS 11 55 111 ^{must be oxidized with 40% aqueous nitric acid at 260-280 0} C, it is possible according to the process according to the invention, 5-methylperi-acenaphth- Indenon-7 can be oxidized with only 2% by weight nitric acid in glacial acetic acid at 135-145 ° C in a smooth reaction to give naphthalene-tetracarboxylic acid di-anhydride. This is all the more remarkable as the oxidative degradation and cleavage of the alkyl groups z. B. with the S-methyl-peri-acenaphth-indenon-? significantly more difficult than with p-Di- ^; .sopropylbenzene, because the starting product contains two condensed rings and there is always the danger that the oxidation will stabilize at the intermediate stage of a ketone or diketone, as is the case with oxidation with oxygen alone in the presence of metal catalysts is.

From this it can be seen that the oxidation of peri-acenaphthindenones of the formula (1) is not in Analogous to the oxidation of simple alkylated aromatic compounds such as toluene, xylene or diisopropylbenzene, can be seen, but that this class of compounds is the discovery of new reaction possibilities and required the development of new reaction conditions.

The fact that there are obviously peculiar differences in the reaction mechanism between the oxidation of indenones 4S in glacial acetic acid with nitric acid and oxygen in the presence of oxidation catalysts and the oxidation of alkyl aromatics with aqueous nitric acid is particularly illustrated by the composition of the exhaust gases ) from the oxidation of p-diisopropylbenzene with 40% nitric acid at 260 ^° C. (DT-PS 11 55 111) compared with an exhaust gas (B) according to the process according to the invention (Example 7). The numbers mean% by volume.

table

NOj NO N2O N2 CO CO2

A. - 14.0 58.0 0.9 4.0 4.0 19.1 B. 25.0 0.2 0.0 11.3 75 5.4 50.6

The comparison shows that in the process according to the invention even in the presence of excess Oxygen nitric acid is consumed practically quantitatively and is essentially N2O and N2 form.

The invention is illustrated by the following examples.

example 1

In a 2-1 stand-alone car, the one with chrome-nickel-molybdenum steel (Remanit HC) and equipped with a magnetic stirrer, 800 ml Glacial acetic acid, 1.5 g cobalt acetate tetrahydrate, 50 g 5-methylperi-acenaphth-indenone-7 (80%) and 31.5 g of pure nitric acid. The supply of oxygen was increased to 10 Nl / h (Nl / h = Normal liters of gas per hour), the pressure was regulated to 1.1 ata by means of the exhaust valve, then it was below Stirring heated to the reaction temperature of 150 ° C. The exhaust gas (approx. 10 Nl / h) was via a pressure cooler removed and measured with a gas meter. After 4 hours the reaction mixture was cooled, relaxed and the contents of the autoclave filtered. The filter residue was washed with acetic acid and at 80 ° C / 150 Torr. The yield was 28.7 g of yellow ocher powder, corresponding to 25.3 g of naphthalene-tetracarboxylic acid dianhydride (51.8% of theory).

Comparative example 1 (Amoco process)

In an autoclave, as described in Example 1, 900 ml of glacial acetic acid, 13 g of cobalt acetate tetrahydrate, 2.6 g of manganese acetate tetrahydrate, 0.3 g of ammonium bromide, 2.0 g of tetrabromoethane and 50 g of 5-methyl-peri-acenaphth-indenone-7 (88%) and proceed as described in Example 1. The reaction temperature was 210 ° C., the pressure 14 ata, the reaction time 10 h, the amount of oxygen and exhaust gas about 5 Nl / h. the The yield of the reaction product was 45.9 g of a black powder insoluble in glacial acetic acid in alkali is soluble and according to elemental analysis, IR spectrum and titration the composition C ^ HöOs and the following Structural formula has:

60

Example 2

In an autoclave, as in the example! 1, 800 ml of glacial acetic acid, 1.5 g of cobalt acetate tetrahydrate, 3.0 g of ammonium metavanadate, dissolved in 30 g of pure nitric acid and 50 g of 5-methyl-peri-acenaphth-indenon-7 (92%) were presented and proceed as described in example 1. The reaction ^{temperature was 150 D} C, the pressure 11 ata, the reaction time 5.5 h, the amount of oxygen and exhaust gas about 10 Nl / h.

The yield was 39.1 g of ocher-colored small crystals, corresponding to 35.6 g of naphthalene tetracarbon acid dianhydride (63.4% of theory).

Example 3

In an autoclave, as described in Example 1, 800 ml of glacial acetic acid and 1.0 g of ammonium metavanada were placed

709 617/288

dissolved in 30 g of pure nitric acid and 50 g of 5-methylperi-acenaphth-indenone-7 (93%) and proceed as described in Example 1. The reaction temperature was 15O ⁰ C, the pressure is 5 ata, the reaction time is 3.5 hours, the oxygen and the exhaust gas amount is about 10 Nl / h.

The yield was 33.5 g of ocher brown fine crystals, corresponding to 30.1 g of naphthalene-tetracarboxylic acid dianhydride (53.2% of theory).

Example 4

As described in Example 1, 800 ml of glacial acetic acid, 1.0 g of ammonium metavanadate dissolved in 30 g of pure nitric acid and 50 g of 5-methyl-peri-acenaphthindenon-7 were submitted (95%) and oxidized, the reaction temperature was 180 ⁰ C, the pressure 1.1 ata, the reaction time 2.5 h, the amount of oxygen and exhaust gas approx. 10 Nl / h.

The yield was 44.4 g of ocher-colored, fine crystals, corresponding to 40.7 g of naphthalene-tetracarboxylic acid dianhydride (70.5% of theory).

Example 5

As described in Example 1, 800 ml of glacial acetic acid, 1.0 g of ammonium metavanadate, dissolved in 30 g of pure nitric acid, and 50 g of 5-methyl-peri-acenaphth-indenone-7 (92%) were initially charged and oxidized ⁰ C, the pressure 11 ata, the reaction time 2 h, the amount of oxygen and exhaust gas about 10 Nl / h.

The yield was 39.8 g of olive-curly, fine crystals, corresponding to 36.1 g of naphthalene-tetracarboxylic acid dianhydride (64.2% of theory).

Example 6

As described in Example 1 In an autoclave, 300 ml of glacial acetic acid and 1.0 g of vanadyl acetylacetonate were initially then was heated with stirring to 160 ⁰ C. By a pump A (pump and supply pipe is heated to 70 ⁰ C) were then dissolved in 400 ml glacial acetic acid, by a pump B 30 50 g of 5-methyl-peri-acenaphth-indenone-7 (ig 96%) g of HNO ₃ in 200 ml of glacial acetic acid was metered in uniformly and at the same time for one hour. The pressure was kept at 8 ata, the amount of oxygen and exhaust gas was approx. 20 Nl / h.

Stirring was then continued under the same conditions for 1.5 hours. The yield was 44.7 g of light, loose, crystalline powder, corresponding to 42.0 g of naphthalenetetracarboxylic acid dianhydride (71.7% of theory). The absolute remaining amount of HNO ₃ in glacial acetic acid was 0.24 g.

An exhaust gas sample taken during the first hour had the following composition:

O2 NO2 N2O N2 CO CO2

Vol.% 60 0.2 6.0 3.3 3.2 29

Example 7

As in Example 6, the following were submitted: 300 ml of glacial acetic acid. 1.0 g of cobalt acetate tetrahydrate 1.0 g of manganese acetate tetrahydrate 2.0 g of vanadyl acetylacetonate A: 200 g of 5-methyl-periacenaphth-indenone-7 (93.5%) in 500 ml of fish vinegar were pumped in for 2 hours B: g HNO ₃ (96%) in 240 ml glacial acetic acid. The reaction temperature was 140 ° C. and the pressure 10 ata. The amount of oxygen and the exhaust gas were set to approx. 50 Nl / h

the temperature is increased to 170 ^° C. and the mixture is subsequently stirred for a further 3 hours with an amount of oxygen and exhaust gas of about 20 standard l / h.

The yield was 179.8 g of a very light ocher powder, corresponding to 168.5 g of naphthalene-tetracarboxylic acid dianhydride (73.9% of theory). The absolute remaining amount of HNO ₃ in glacial acetic acid was 0.9 g. One during de; The exhaust gas sample taken when pumping in had the following composition:

O2 NO2 N2O N2 CO CO2

Vol-% 25.0 0.2 11.3 7.5 5.4 50.6

Example 8

As in Example 6, the following were submitted: 300 ml of glacial acetic acid, 0.5 g of cobalt acetate tetrahydrate, 0.5 g of manganese acetate-te-

trahydrate, 2.0 g vanadyl acetylacetonate, 0.2 g molybdenum nexacarbonyl. There were 3 hours einge- ^{_Ρ ο υ} = Τ / ^Ρ - \ ^{Λ: 200g 5} - ^meth yl-peri-acenaphth-indenone-7 Wi ^{m 40} ° ^{ml Eisess'} g and B: 120 g of HNO ₃ (96% ) in 240 ml glacial acetic acid. The reaction temperature was 135 ° C

the pressure 7 ata. The amount of oxygen and the exhaust gas were adjusted to approx. 60 Nl / h The reaction temperature was pumped in to 145.degree increased and with an oxygen and exhaust gas quantity of approx. 15 Nl / h needle-stirred for a further 2 hours.

te was 164.2 g of ocher-colored powder, corresponding to ii £ f ^Na P ^hthali n-tetracaibonic acid dianhydride (663%

Example 9 (oxidation with HNO ₃ without oxygen)

As in Example 6, the following were presented: 300 ml of glacial acetic acid, 1.5 g cobalt acetate tetrahydrate, 1.5 g manganese acetate tetrahydrate, 1.5 g of vanadyl acetylacetonate

pumped in during 2 hours A: 50 g = 0.227 mol of s-methyl-peri-acenaphth-indenone-? (90%) in 500 ml of glacial acetic acid and B: IHg = ,, 82MoI HNO ₃ in 240 ml of tis acetic acid. The reaction temperature was 150 ° C. The pressure was low during the reaction and was at 11 ata

kept constant by exhaust gas extraction. After completion of the Einpumpens was stirred μ under the same conditions for 20 minutes α ^ ö ^{S, booty was 32} ^ g of brown powder, corresponding "<? w 5 ' Ä _x ^{Na Phthalin} tetracarboxylic acid dianhydride

so (52.3% dTh.). The absolute remaining amount of HNO ₃ in glacial acetic acid was 13 g of ⁶

Example 10 (oxidation with HNO ₃ and air)

ϊηίη,

^before placed: 300 ml glacial acetic acid, v ^ ³¹¹ ^^ ¹ ^ S manganese acetate-te-vanadyl acetylacetonate, 0.1 g molybdenum

^It ™ ^ά ™ ^for 3 hours - ™ * ⁵ - ^Met hyl-peri-acenaphth-indenon-7

^?) V ο ^"1 ', ^{and B ElSessig. 120} S HNO ₃ in 240 ml ig The reaction temperature was 140 ⁰ C., the pressure 15 ata Instead of pure oxygen was

on ciTsSMUh ^{ie air} - ^{and the} ab ^ "ies were made L ^ ^e ! ⁿ after the termination of the

^{dle Reaktionstem} Peratur to 170 ⁰ C.

; ^ft · ^{and exhaust gas volume of 50 N1 / h}

The yield was 168.2 g of ocher-colored, finely crystalline powder, corresponding to 157.3 g of naphthalene-tetracarboxylic acid dianhydride (71.6% of theory).

Example 11

g of the crude naphthalene-tetra-carboxylic acid product obtained according to Example 6 were suspended in 300 ml of water at room temperature, with a
Solution of 6 g of NaOH in 100 ml of water added, the
Mixture then heated to the boil and hot ι ο

filtered through a folded filter to a clear solution. After cooling the filtrate to room temperature, was 20% aqueous hydrochloric acid is added dropwise to this with stirring until the solution has a pH of 1 had achieved. After standing for about 2 hours; The product crystallized out was mixed off sucks, washed with water and dried over calcium chloride at room temperature. This resulted in 10.8j pure, pale ocher-colored naphthalene-1,4,5,8-tetra carboxylic acid.

- λ in

Claims (1)

'■ f Claim: Process for the production of naphthalene-1,4E8-tetracarboxylic acid or its dianhydride, characterized in that that a peri-acenaphthindenone of the general formula (I) R is hydrogen or an alkyl group having 1-4 carbon atoms, in an aliphatic carboxylic acid having 1-4 carbon atoms as solvent with nitric acid, optionally with the addition of oxygen, in the presence of oxidation catalysts at temperatures above 100 ⁰ C is oxidized, the reaction product obtained is isolated and this is optionally converted into naphthalene-tetracarboxylic acid in a manner known per se by dissolving in alkali and precipitating with an acid. The invention relates to a method for the technology is operated is in principle in Preparation of naphthalene-1,4,5,8-tetracarboxylic acid 25 Fierz-David, Basic operations of the or their anhydrides. Naphthalenetetracarboxylic acid is an important preliminary paint product. Your representation in three stages, starting from pyrene, as it is still in today Farbenchemie, 1952, Verlag Springer, Vienna, described.