DE2309378C2 - Process for the production of anthraquinones by drying aroylbenzoic acids - Google Patents

Description

The invention relates to a process for the production of anthraquinones by drying aroylbenzoic acids at a temperature above the melting point of the acid to be dried and cyclization of the dried, liquid aroylbenzoic acids in the form of a melt.

The ring closure reactions of o-aroylbenzoic acids with removal of water to form anthraquinone and its Derivatives at elevated temperatures in media such as oleum, sulfuric acid or polyphosphoric acid be carried out, require in terms of yield of end product, economy and ease of use Operating mode the starting materials in the form of dried powders. Also in other syntheses with these Starting materials, it is necessary to dry them in order to achieve optimal results. It's from Ullmanns Encyklopadie der technischen Chemie, Volume 1, pages 563 to 609 and Fiat Final Report No. 13/3, Volume II, pages 39,42,47 known, the drying of solids below and above the boiling point of water or des to make adsorbed organic solvent. Such powders are always dried considerably below the melting point of the solid.

You can z. B. the hydrous aroylbenzoic acids in electric dryers, paddle dryers or spray towers dry. If o-aroylbenzoic acids are used later as starting materials for ring closure reactions, The dry product is usually stored in barrels and bunkers before it enters the cycling process is fed. Since the powder cools down on storage, it has to be renewed in the event of ring closure reactions be heated. The dry, powdery acids tend to harden, stick and

Baked, they often lose their loose consistency and pourability, they agglomerate and clump together Transport, baked on pipe and vessel walls and can no longer or only with difficulty dose. The addition of the dry powders to the ring closure reactors is time consuming and for continuous Unsuitable operating mode All of these difficulties increase, especially on an industrial scale. operation the costs; more operating personnel and expensive systems are required for monitoring and control Form of conveying, filtering and weighing devices. In addition, the energy costs are continuous Drying processes in which the products are obtained as a powder, high because the drying temperatures are low must remain, because the products tend to stick, especially at higher temperatures. The discontinuous Dryer, e.g. B. paddle dryers, require more operating personnel when filling and emptying the units. For physiological reasons, powdery, dry o-aroylbenzoic acids are generally handled only possible with dust masks, as the products are often very irritating to the mucous membranes and, if necessary can also cause allergies.

It has now been found that anthraquinones can be obtained by drying moist aroylbenzoic acids general formula

R ²

COOH

in which the individual radicals R ¹ and R ^{2 can be} identical or different and each represent a hydrogen atom, an alkyl radical with 1 to 6 carbon atoms, a cyclohexyl radical, an aralkyl radical with 7 to 12 carbon atoms or a phenyl radical, a chlorine atom or a bromine atom, R ¹ can also mean a phenyl radical fused to the adjacent nucleus, advantageously obtained at elevated temperature and subsequent cyclization, if the drying is carried out at a temperature above the melting point of the acid, the dried, liquid aroylbenzoic acids thus obtained are obtained in the form of the melt fed to a cyclization medium and cyclized there.

Compared to the known processes, the process according to the invention results in a simpler and more economical way of drying aroylbenzoic acids in a better space-time yield. So the result of the melt drying (solid with 20 wt .-% water) z. B. 75 kg of dry chlorobenzoylbenzoic acid per m ^{2 of} apparatus area and hour compared to about 8 kg of dry chlorobenzoylbenzoic acid per m ^{2 of} apparatus area and hour by known drying methods in a commercially available paddle dryer. The complex transport of powders is avoided, the process is better and fully automatically controllable and regulatable. Handling and dosing of the substances are simplified, the products are no longer filled and filled by hand. A dust nuisance for the staff is avoided. The capacity of corresponding ring closure reactors can be increased considerably, as drying and

Transport of melts is much easier and faster. A heating of cooled, powdery o-Aroylbenzoic acids are avoided, which is also a simpler plant of higher capacity enables. On the other hand, they are usually the Melting of the aroylbenzoic acids is stable for a long time at the correspondingly high temperature, so that the liquid melts can also be stored. The inventive method allows just in large-scale operation a continuous mode of operation of the drying and the entire synthesis route the production of anthraquinone, requires fewer operating personnel and cleaning operations and saves expensive storage and transport systems. With regard to the previously used to dry aroylbenzoic acids used, significantly lower temperatures, it is surprising that at the high drying temperatures of the process according to the invention side reactions, e.g. B. ring closure to quinones, cleavage of Carboxyl groups, do not occur to any significant extent.

The claimed process is technically valuable because it is simpler and cheaper than the previously used processes with drying cabinets, Venuleth and the like. A lot of manual work (weighing and filling of the powder, transport to the ring closure boiler, entry into the boiler) is reduced to a simple flow measurement of the molten benzoylbenzoic acid. _{It is surprising that no significant decarboxylation (CO 2} elimination) is observed during melt drying and in all operations before the ring closure to form the anthraquinone. The production of anthraquinones is therefore surprisingly improved in a technically advantageous manner.

Also could not be expected that by means of the corresponding melting temperature with the help of the Heat of reaction, the cyclization temperature can be adjusted so that the energy for the Cyclization is saved and the cyclization faster than with powdery starting materials runs.

Suitable starting materials are, for. B. o-Benzoylbenzoic acid, o-naphthoylbenzoic acid. o-naphthoylnaphthoic acid; 4'-ethyl-, 2 ', 4'-dimethyl-, 4'-chlorine, 4'-methyl-, 2 ', 4'-dichloro-, 3'-bromo-, 4'-n-hexyl-, 4'-tert-butyl-, 4'-Cyclohexyl-, 4'-benzyl-, 4'-phenyl-o-benzoylbenzoic acid and correspondingly substituted in the o-position 2-methyl, 2,4-dichloro, 2,3,4-trichloro, 4-benzyl-. 4-phenyl-, 2-bromo-o-benzoylbenzoic acid.

In general, the absorbed or entrained water is removed during drying, but it can also other absorbed or entrained solvents which are inert under the reaction conditions, e.g. B. alkanols such as methanol, ethanol; aromatic X.ohlenwassei substances such as benzene, toluene, xylenes; Halogenated hydrocarbons such as chlorobenzene, trichlorethylene; Ethers such as diethyl ether; or corresponding mixtures separated will. Correspondingly, there are solvent residues from the production of the acids during drying severed. It is expedient to first pass through a large excess of solvent or water mechanical means, e.g. B. suction, centrifugation, decanting or filtering the starting material, remove. Appropriately get starting materials with 80 to 2, in particular with 30 to 20 wt .-% solvent, preferably water, for drying.

Kneaders, for example, are used as dryers. Rotary drum dryers, cylinder dryers, trough dryers, preferably paddle dryers, tunnel dryers, agitator dryers or stirred kettles, in question. The drying is generally performed at a temperature from 1 to 180 ,, preferably carried out for 2 to 30 ⁰ C above the melting point of the Aroylbenzoesäure, without pressure, under pressure or negative pressure, continuously or discontinuously. For example, as drying temperatures such. B. in the case of o-benzoylbenzoic acid temperatures of 135 to 145 ° C, for o-naphthoylbenzoic acid from 160 to 170 ° C, for o-chlorobenzoylbenzoic acid from 145 to 155 ° C, for toluyibenzoic acids 135 to 145 ° C, for p-ethylbenzoylbenzoic acid from 115 to 125 ° C preferred.

The inventive method is used for drying o-aroylbenzoic acids before the cyclization, for example in reactors with cyclization media such as oleum, sulfuric acid or polyphosphoric acid, used e.g. B. in the following procedure: the moist o-aroylbenzoic acid, which is usually 15 contains up to 25 wt .-% water, is from a storage vessel with the help of an entry device, for. B. Worm or a cellular wheel, into one with o-aroylbenzoic acid heated to drying temperature filled and heatable container added; stat; in a stirred tank can be used to melt the acid The required energy is also supplied by pumping the liquid acid through a heat exchanger will. The water getting into the stirred tank with the starting material evaporates and the liquid, dry melt can be drawn off at the bottom of the stirred tank, depending on the addition will. The temperature in the stirred tank is kept constant by appropriate controls. the Melt is intensively stirred or pumped through a heat exchanger. The formed water vapor is separated directly with the exhaust gas or by condensation. The dry, hot melt can be stored or conveniently fed directly to the cyclization stage. The addition can carried out discontinuously, expediently the required amount of melt in a measuring vessel measures and allows the cyclization reactor to run or with nitrogen fed to the cyclization reactor. However, it is advantageous to feed the melt with the aid of a metering device, ζ. Β. a dosing piston pump or Centrifugal pump with volume flow control to the reactor. The cyclization process is controlled expediently so that the temperature of the liquid melt is just chosen so that with the help of the Heat of reaction sets the cyclization temperature; no additional energy is required from the outside are supplied, and it becomes a faster compared to the reaction with powdery starting materials Cyclization achieved. Aroylbenzoic acid can also be used in whole or in part in the form of its powder remove the water by drying, the highly dehydrated or anhydrous powder obtained in this way melt and cyclize the melt in the cyclization medium. For the reasons mentioned above, however, is one Such a way of working is more cumbersome and uneconomical.

The dried aroylbenzoic acids which can be prepared by the process of the invention are valuable starting materials for the manufacture of dyes and pesticides.

The parts listed in the following examples are parts by weight.

Example 1 (Fig. 1)

One part per hour of o-chlorobenzoylbenzoic acid with a water content of 20% by weight is continuously added from a container 5 via a screw 6 to the stirred tank 1, in which 5 parts of liquid melt have been placed. In the stirred tank 2, 5 parts of the starting material are exemplified. The melt is maintained at a temperature of 150 ⁰ C.. The water vapor escaping via line 15 (0.2 parts per hour) is condensed in container 4 with water from feed line 21. The stirred kettles 1 and J are connected in a communicating manner via the pipeline 11, and the melt is further dried in the kettle 2. When the measurement template 3 is filled (one part per hour in portions) via the line 12, the valve 8 is closed. When the valve 9 is opened, only post-dried melt from boiler 2 enters the receiver 3. The venting takes place via outlet 23; Heating steam is supplied through lines 22. From receiver 3, the melt (150 ^° C.) is allowed to run (one part per hour) into the cyclization reactor 7 via line 13 and valve 10, in which oleum is previously charged via line 14. The temperature in the cyclization reactor 7 is adjusted to the desired reaction temperature of 150 ° C. through the addition of the hot melt and the heat of reaction released. The aroylbenzoic acids are cyclized to the corresponding anthraquinones in the customary manner by known processes.

B e i s ρ i e I 2 (A b b. 2)

30th

From the container 5, 2 parts per hour of water-moist o-toluylbenzoic acid (25% by weight of water) are continuously added to the stirred tank 1 heated with steam via a screw 6. The resulting water vapor (0.5 parts per hour) is condensed in container 4. The ventilation takes place via outlet 23; Heating steam is supplied through lines 22. 0.4 parts of starting material are placed in the stirred tank 1. The drying temperature is maintained at 140 ⁰ C. Via the pump 16, 2 parts per hour of melt are fed to the cyclization reactor 17, to which oleum is simultaneously added via the line 19. The cyclization product emerges via line 20. The aroylbenzoic acids are cyclized to the corresponding anthraquinones in the customary manner by known processes.

Example 3 (Fig. 3)

From a container 5, 0.5 parts per hour of o-benzoylbenzoic acid with 30% by weight of water are continuously fed into the receiver 1 filled with 3 parts of melt via a screw 6. To supply heat, a pump 16 circulates 10 parts per hour of melt via heat exchanger 18. The temperature of the melt in the original 1 is set to 140 ⁰ C. The ventilation takes place via outlet 23; Heating steam is supplied through lines 22. In the partial flow, dried melt is fed to the cyclization reactor 17 via the control valve 9. In the cyclization reactor 17, the dried starting material is cyclized in the oleum fed in via line 19. The cyclization product leaves the cyclization reactor 17 via line 20. 0.15 parts per hour of steam escape from receiver 1 and are condensed in container 4. The aroylbenzoic acids are cyclized to the corresponding anthraquinones in the customary manner by known processes.

Example 4 (Fig. 1)

Analogously to Example 1, 3 parts per hour of 1-naphthoyl-o-benzoic acid with a water content are added continuously dried from 20 wt .-% in the melt. The drying temperature is 165 ° C. 0.6 parts per Hour water vapor are condensed. From the template 3 3 parts per hour of melt are the Cyclization reactor 7 charged with sulfuric acid monohydrate is supplied. By adding the hot The cyclization temperature of 140 ° C. is set in the melt. The cyclization of the aroylbenzoic acids too the corresponding anthraquinones are carried out in the customary manner by known processes.

For this purpose 3 sheets of drawings

Claims (1)

Claim: Process for the production of anthraquinones !! by drying moist aroylbenzoic acids the general formula in which the individual radicals R ¹ and R ^{2 can be} identical or different and each represent a hydrogen atom, an alkyl radical with 1 to 6 carbon atoms, a cyclohexyl radical, an aralkyl radical with 7 to 12 carbon atoms or a phenyl radical, a chlorine atom or a bromine atom, R ¹ can also mean a phenylene radical fused to the adjacent core, at elevated temperature and subsequent cyclization, characterized in that the drying is carried out at a temperature above the melting point of the acid, the thus obtained dried, liquid aroylbenzoic acids in the form of the melt one Cyclization medium fed and cyclized there.