DE3134133A1 - Process for the preparation of naphthalene-1,4,5,8-tetracarboxylic acid by co-oxidation - Google Patents

Abstract

The invention relates to a process for the preparation of naphthalene-1,4,5,8-tetracarboxylic acid by oxidation of pyrene. The latter is treated with a low molecular weight carbonyl compound and oxygen in the presence of a catalyst and the resulting intermediate is reacted with chlorine in aqueous-alkaline solution. Most importantly, the process according to the invention makes it possible to avoid the procedural difficulties and serious environmental concerns which are associated with the disposal of substantial quantities of concentrated sulphuric acid which has hitherto been used as the solvent for the pyrene oxidation.

Description

Process for the production of naphthalene-1,4,5,8-tetra-

carboxylic acid by co-oxidation naphthalene-1,4,5,8-tetracarboxylic acid - hereinafter referred to as "tetra acid" for short - is an important precursor for colorants, which are characterized by particularly high lightfastness. So are through implementation obtain valuable dyes and pigments with aromatic diamines.

Several methods are known to use pyrene in a multi-step process to oxidize to tetraacid with halogens and sulfur trioxide (Fierz-David, Fundamental Operations der Farbenchemie, Verlag Springer, Vienna 1952). Have these procedures the disadvantage that it is carried out in concentrated sulfuric acid as a solvent will. This results - apart from procedural difficulties - the need to dispose of the very considerable amounts of sulfuric acid.

A process has now been found in which pyrene is converted into tetraacid is oxidized, whereby no sulfuric acid is required.

According to the invention, the alkali salts are naphthalene-1,4,5,8-tetracarboxylic acid produced by oxidation of pyrene by ds pyrene in a first Stage with a low molecular weight carbonyl compound and oxygen in the presence cines catalyst treated and the intermediate in a second stage with Reacts chlorine in an aqueous alkaline solution.

From the alkali salt of tetraacid, which is easily soluble in water, can then be done in a simple and known manner - optionally after previous filtration and / or clarification with the help of activated carbon - precipitate the tetraacid by acidification. The tetraacid obtained in this way or the mono- or dianhydride which may also have formed after drying, is of sufficient quality and purity for the production of Colorants.

Preferred embodiments of the invention are described in greater detail below explained: The low molecular weight carbonyl compounds usually used for Such cooxidations used compounds are used, such as Methyl ethyl ketone, but preferably acetaldehyde.

The oxidation of the low molecular weight carbonyl compound is formed the corresponding carboxylic acid, in the case of acetaldehyde, acetic acid. It is beneficial Add acetic acid from the start as a solvent.

Pyrene dissolves relatively well in warm acetic acid, so that the Oxidation can be carried out in a homogeneous solution. However, one can take advantage of this Save considerable amounts of solvent by first pouring the pyrene into the just necessary amount of hot resp.

boiling acetic acid dissolves and then by cooling to the oxidation temperature a fine crystal suspension is produced with vigorous stirring.

For the reaction mixture, i.e. preferably for the acetic acid solution or The catalyst, preferably a metal compound, is added to the suspension has the task the one that is too slow for technical purposes Accelerate oxidation of pyrene with the compounds mentioned. As such Oxidation catalysts are heavy metal salts, especially compounds the metals chromium, manganese, iron, cobalt, nickel or copper or mixtures thereof. The salts of the reaction medium formed or

lower alkanecarboxylic acid used, i.e. preferably the acetates, since this does not introduce any foreign anions into the reaction system, whereby the work-up is facilitated. Small amounts of foreign anions interfere Reaction however not. The addition of cobalt and / or manganese acetate.

Small amounts of the catalysts are sufficient; 0.0n5 are preferred up to 0.1 g atom (metal) per mole of pyrene used.

The molar ratio of pyrene to acetaldehyde is expediently between 1: 3 and 1:30, preferably from 1: 6 to 1:20.

If a lower alkanecarboxylic acid is used as the reaction medium is, the carbonyl compound) is expediently the pyrene solution or suspension ill admixed with the carboxylic acid.

The temperature of the co-oxidation is expediently between room temperature and the boiling point of the reaction medium and is adjusted, if necessary, by cooling. A temperature of about 40 to 90 ° C. is advantageous.

The oxygen required for the co-oxidation can be in pure form or ih the form of air are introduced into the reactor. The reaction proceeds, in particular in the presence of a lower carboxylic acid such as acetic acid, under normal pressure, however A slight overpressure of up to about 10 bar has proven to be beneficial. Particularly A mode of operation in which the oxygen partial pressure is about 2 bar is advantageous amounts to.

The reaction solution from the first stage can be used directly in the second Stage are post-oxidized, but the reaction medium is advantageous more or less completely separated. This separation is expediently carried out in a thin-film or falling film evaporator.

The recovered carboxylic acid can go into the first oxidation stage to be led back.

Post-oxidation with chlorine in an aqueous alkaline medium is expedient in the temperature range from about 40 to 700C.

A particularly advantageous embodiment is that per Mol originally used pyrene about 10 mol of aqueous sodium or potassium hydroxide solution and about 8 moles of aqueous sodium or potassium hypochlorite solution ("sodium hypochlorite") will. At about 40 to 50 ° C., the reaction solution is then extracted from the first stage, from which the carboxylic acid is more or less completely separated off, registered. The addition of Alkali.laucje ensures that the pH value does not drop below 10. After raising the temperature to around 60 "C, that time Hypochlorite solution added as it is consumed. The end point can be known in Manner, e.g. by spotting on potassium iodide starch paper. The solution is then light yellow-orange and can optionally by filtration be clarified.

The hypochlorite solution can also be in the oxidation kettle before or during the reaction can be produced by introducing chlorine into alkali lye. If enough Alkali for the formation of the salt of the tetraacid can be present by introduction of chlorine in the aqueous solution, i.e. without the addition of further alkali, the oxidation be accomplished satisfactorily.

The solution of the alkali salt of tetraacid thus obtained can be as follows to be worked up to the free tetraacid: Excess hypochlorite is with Sodium sulfite destroyed and then acidified to a pH of about 1.

Here, hydrochloric acid is preferred because of the chlorine ions that are already present. The mixture is then heated to the boil. The precipitated tetraacid is Sucked off, washed with water to remove the hydrochloric acid and dried. That The predominant part of the product is then the monoanhydride of tetraacid.

In the following example, percentages relate to weight, if nothing else is given.

Example In a glass autoclave (1 l), 60.6 g (0.3 mol) of pyrene, the solution of 2.0 g (0.008 mol) of cobalt acetate tetrahydrate in 250 g of glacial acetic acid and 220 g (5.0 mol) of acetaldehyde were added.

The mixture is heated to 70 ° C. under an overpressure of 5 bar nitrogen and when this temperature is reached, oxygen is introduced, with an exhaust gas stream is regulated by 15 lih. An exothermic reaction sets in immediately; the temperature is kept at 80900C by cooling the autoclave jacket. After 4 hours it is the reaction ended. The acetic acid is distilled off from the brown reaction solution and the residue (92.2 g) in a solution of 200 g of KOH and 600 g of sodium hypochlorite (Chlorine content 13% 1.1 mol hypochlorite) entered.

The solution is heated to 50 ° C. and by adding sodium hypochlorite solution constantly oxidizing and kept above plant 10 by consuming more KOH. After adding about 0.5 kg of sodium hypochlorite, the mixture is filtered.

The filter cake (22.7 g) consists essentially of unreacted Pyrene and a little cobalt oxide. The dark red filtrate is made by adding more Chlorine bleach lightened to a yellow color. Finally it is heated to 709C, Excess hypochlorite destroyed with sodium hydrogen sulfite and treated with conc. Salts acid acidified to pH 1.

The naphthalenetetracarboxylic acid falls in the heat as a monoanhydride in the form of small crystals that are suctioned off, washed with water and heated to 70 "C be dried in a stream of air.

Yield: 27.4 g (32.0% of theory, based on the pyrene used) Narjhthwalintetracarbonsäuremonoanhydrid.

Claims (10)

PATENT CLAIMS Process for the production of naphthalene-1,4,5,8-tetracarboxylic acid by oxidation of pyrene, characterized in that the pyrene with a low molecular weight Treated carbonyl compound and oxygen in the presence of a catalyst and the intermediate is reacted with chlorine in an aqueous alkaline solution. 2. The method according to claim 1, characterized in that as low molecular weight carbonyl compound acetaldehyde is used. 3. The method according to claim 1 and 2, characterized in that one acetic acid is added as a solvent. 4. The method according to claim 1 to 3, characterized in that one a heavy metal salt is used as a catalyst. 5. The method according to claim 1 to 4, characterized in that one cobalt and / or manganese acetate is used as a catalyst. 6. The method according to claim 1 to 5, characterized in that one 3 to 30 moles of lower carbonyl compound are used per mole of pyrene. 7. The method according to claim 1 to 6, characterized in that one 6 to 20 moles of acetaldehyde are used per mole of pyrene 8. Procedure according to Claim 1 to 7, characterized in that the co-oxidation with oxygen 40 to 900C and the oxidation with chlorine at 40 to 70 ° C. 9.Verfahren according to claim 1 to 8, characterized in that one the co-oxidation is carried out at an oxygen partial pressure of up to 10 bar. 10. The method according to claim 1 to 9, characterized in that one the reaction medium is largely separated off before the reaction with chlorine.