CH615148A5 - Process for the preparation of pure 1-nitroanthraquinone - Google Patents

Description

615 148

2nd

PATENT CLAIMS

1. A process for the preparation of pure 1-nitroanthraquinone, characterized in that anthraquinone is nitrated in at least 85% nitric acid at temperatures from -20 to + 65 ° C and at molar ratios of nitric acid: anthraquinone of over 20: 1, the If the anthraquinone conversion exceeds 50%, the reaction is stopped by cooling the reaction mixture to temperatures below 20 ° C. and / or adjusting the mole fraction of the nitric acid in the reaction mixture to a value of less than 0.86, the 1-nitroanthraquinone then fails by adjusting the molar fraction of the nitric acid to a value of 0.7 to 0.4 and / or lowering the temperature to below 20 ° C., separating the precipitated 1-nitroanthraquinone and subjecting it to vacuum distillation.

2. The method according spoke 1, characterized in that nitriding at temperatures from -10 to + 35 ° C.

3. The method according to claim 1 or 2, characterized in that nitrating at a molar ratio of nitric acid: anthraquinone from 25 to 100: 1.

4. The method according to claim 1, characterized in that the reaction is terminated at an anthraquinone conversion of 80 to 100%.

5. The method according to any one of claims 1 to 4, characterized in that the molar fraction of the nitric acid is adjusted to a value of less than 0.86 by adding water, adding dilute nitric acid and / or distilling off concentrated nitric acid.

6. The method according to any one of claims 1 to 5, characterized in that the 1-nitroanthraquinone precipitates out by the molar fraction of the nitric acid by distilling off nitric acid and / or by dilution with water and / or by adding dilute nitric acid to one Sets the value from 0.7 to 0.4.

7. The method according to any one of claims 1 to 6, characterized in that the vacuum distillation is carried out in the presence of stable in the distillation and inert to the nitroanthraquinone, which boil between 100 and 350 ° C.

DE-OS 2 343 978 describes a process for the preparation of pure 1-nitroanthraquinone, which is characterized in that anthraquinone in at least 90% nitric acid at a temperature of at least 0 ° C., in particular at least 45 ° C., is preferred at 55 to 75 ° C, and with molar ratios of nitric acid to anthraquinone of less than 20: 1, in particular 6: 1 to 15: 1, nitrated, the reaction with an anthraquinone conversion of at least 50%, in particular at 80-100% , terminates in that the reaction mixture is cooled to temperatures below 30 ° C. and / or the molar fraction of the nitric acid is adjusted to a value of less than 0.86, for example by adding water and / or distilling off nitric acid, which causes 1-nitroanthraquinone to fail that the mole fraction of the nitric acid is subsequently reduced to a value of by distilling off nitric acid and / or by diluting with water and / or by adding dilute nitric acid 0.7 to 0.4 and / or the temperature is reduced to below 20 ° C, the precipitated 1-nitroanthraquinone is removed and a vacuum distillation, if appropriate in the presence of solvents which are stable during the distillation and are inert towards the nitroanthraquinones and which are between 100 and 'Boil 350 ° C, subject.

Here and below, mole fraction always means that of nitric acid in the respective total mixture according to the following equation

V hno3 = nHNo3 / (nnNo3 + nN + nH2o)

n = number of moles

N = nitroanthraquinone derivatives and anthraquinone

A disadvantage of this process is that molar ratios of nitric acid to anthraquinone and / or nitroanthraquinones can occur, which make certain procedural and safety-related measures necessary and may therefore require considerable additional effort. The present invention has for its object to avoid this disadvantage.

A process has now been found for the preparation of pure 1-nitroanthraquinone, which is characterized in that anthraquinone is nitrated in at least 85% nitric acid at temperatures from −20 to + 65 ° C. with molar ratios of nitric acid: anthraquinone of over 20: 1, the reaction is stopped at an anthraquinone conversion of more than 50%, in particular from 80 to 100%, by cooling the reaction mixture to temperatures below 20 ° C. and / or the molar fraction of the nitric acid, preferably by adding water, adding dilute Nitric acid and / or distilling off concentrated nitric acid, to a value of less than 0.86, which 1-nitroanthraquinone then precipitates out by subsequently breaking down the mole fraction of the nitric acid, preferably by distilling off nitric acid and / or by diluting with water and / or by adding dilute nitric acid to a value of 0.7 to 0.4 and / or the temperature to below 20 ° C lowered, the precipitated 1-nitroanthraquinone is separated off and subjected to vacuum distillation, if appropriate in the presence of solvents which are stable during the distillation and are inert towards the nitroanthraquinone and boil between 100 and 350.degree.

The preferred temperatures at which the nitriding can be carried out are temperatures from -10 to + 35 ° C. All molar ratios up to 500: 1 are possible as molar ratios of nitric acid-anthraquinone above 20: 1, with molar ratios of nitric acid: anthraquinone between 25 to 100: 1 being preferred. Molar ratios of 30 to 80: 1 are particularly preferred.

The nitriding can generally be carried out in a conventional reaction apparatus, such as a flow tube, boiler cascade or boiler, in a continuous or discontinuous mode of operation. In order to obtain the greatest possible yield of 1-nitroanthraquinone in a continuous procedure, a pronounced plug flow or Reynolds number of more than 2300 should be achieved in the case of the flow tube, and an ideal residence time spectrum should be achieved in the case of a cascade or kettle. The reaction should advantageously be adiabatic or partially adiabatic, but can of course also be carried out isothermally.

The stopping of the reaction depends on the molar fraction of the nitric acid in the mixture and also on the temperature. Lower mole fractions must then be set at higher temperatures than at low temperatures.

It is nitrided at a molar ratio of over 20: 1. The nitriding can be stopped, for example, by setting a lower molar ratio and, if appropriate by cooling, certain temperatures by rapidly distilling off concentrated nitric acid. For example, you can set the following conditions:

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615 148

Molar ratio temperature molar fraction

19: 1 at most -5 ° C 0.871

15: 1 at most +5 ° C 0.847

10: 1 at most + 15 ° C 0.793

6: 1 at most + 30 ° C 0.694

At higher temperatures, the mole fractions should be set smaller, for example as follows:

temperature

Molar ratio

Breakwater

Acid concentration

65 ° C

18: 1

0.615

86%

45 ° C

18: 1

0.692

90%

25 ° C

18: 1

0.758

93%

65 ° C

10: 1

0.702

91.5%

45 ° C

10: 1

0.744

93.5%

25 ° C

10: 1

0.791

95.5%

65 ° C

5: 1

0.733

95.5%

45 ° C

5: 1

0.754

96.5%

25 ° C

5: 1

0.775

97.5%

The acid concentration results from the mole fraction through the equation for the mole fraction given at the beginning.

If the nitration is stopped, for example by adding water and / or distilling off nitric acid, the following conditions can be set, for example:

Molar ratio temperature molar fraction acid concentration

112: 1 25 ° C 0.76 92%

54: 1 65 ° C 0.65 87%

45: 1 50 ° C 0.78 93%

40: 1 40 ° C 0.72 90.5%

25: 1 65 ° C 0.59 84%

Similar to stopping the reaction, the cleaning operation associated with the crystallization is dependent on the temperature and the mole fraction of the nitric acid in the nitriding mixture. Since the nitric acid has a relatively high vapor pressure at higher temperatures, it should be more expedient to filter off the crystals at room temperature or at temperatures ^ 30 °. The amounts and concentrations of nitric acid required for the cleaning operation depend on which impurities and how much they should be removed. If, for example, 10% by weight (5% by weight) of anthraquinone are to be separated from the nitroanthraquinone mixture obtained according to the invention, z. B. the acid concentrations to approx. 93% (82%), 84% (78%), 80% (76%) or 76% (72%) and accordingly the mole fractions to yhno3 = 0.69 (0.53), 0.58 (0.49), 0.52 (0.47). or 0.46 (0.42) can be set.

The same naturally applies to the separation of 2-nitroanthraquinone from such nitroanthraquinone mixtures. For example, if approximately 8% by weight of 2-nitroanthraquinone and less than 3% by weight of anthraquinone are to be separated off, z. B. for acid concentrations of approx. 80, 78, 76 or 72% mole fractions of} 'hno3 = 0.51; 0.49; 0.47 or 0.42 can be set.

In order to only have to accept the smallest possible loss of separation of 1-nitroanthraquinone, large mole fractions should be used at relatively high acid concentrations. H. small molar ratios can be set. Correspondingly, at relatively low acid concentrations, small mole breaks, i.e. H. large molar ratios can be set.

The separation loss of 1-nitroanthraquinone in the process according to the invention is smaller, the greater the amount of appropriately diluted nitric acid. However, large amounts of dilute nitric acid are generally uneconomical, since the nitric acid has to be distilled and possibly concentrated again. However, it has been shown that enough pure 1-nitroanthraquinone is obtained for the next process step if 90-72% nitric acid is used for the crystallization and the associated purification and the mole fractions are correspondingly upgraded between 1 / hno3 = 0.70 and sets 0.42.

To stop the reaction and the subsequent cleaning operation, the following combination options result for the method according to the invention:

If the reaction is stopped by adding a little water and / or by distilling off nitric acid and / or by cooling the reaction mixture, the addition of water and / or dilute nitric acid and / or by distilling off nitric acid can be used to precipitate 1- Nitroanthraquinone set the required mole fraction.

If a molar ratio of the nitration products and the unreacted anthraquinone to nitric acid of ^ 12: 1 is reached by distillation or if nitration is carried out at these molar ratios, the 1-nitroanthraquinone precipitated at temperatures of gl5 ° C can be separated from the by-products in the filtrate. These by-products can be almost completely precipitated from the filtrate if a mole fraction of less than 0.4 z. B. by diluting with water or by partially or completely distilling off the nitric acid. This precipitated and separated off mixture of the by-products contains almost all of the 2-nitroanthraquinone. This can be isolated in a relatively pure form if the precipitation described above is carried out in a fractional manner. The nitric acid freed from the organic products can, for example, be returned to the process after concentration or as a diluent.

The 1-nitroanthraquinone precipitated from the nitric acid by the process according to the invention is obtained in crystalline form and can be filtered off relatively easily (for example using a rotary, plane or pressure filter). After briefly washing with dilute nitric acid, the filter cake can be washed neutral with water in the usual manner and dried, or it can be freed of nitric acid directly (if appropriate in vacuo) (for example a current or contact dryer). The 1-nitroanthraquinone thus dried is then subjected to vacuum distillation, in particular rectification.

This vacuum distillation is carried out in a manner known per se.

The temperatures and pressures given below reflect the conditions at the top of the distillation apparatus.

The distillation is carried out between 200 and 400 ° C at 0.5 to 100 torr, in particular at 235 to 330 ° C and 1.5 to 50 torr, preferably at 245 to 315 ° C and 2.5 to 35 torr. The process can be carried out either batchwise or continuously. It proves to be particularly favorable to carry out the distillation at temperatures between 265 and 300 ° C. and a vacuum of 5 to 20 torr.

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615 148

4th

A special variant of the process according to the invention "consists in that the prepurified product, together with a solvent boiling at 100 to 300 ° C., is stable under distillation conditions and inert to the product, for example high-boiling hydrocarbons or silicone oils, among the Distilled conditions above and the 1-nitroanthraquinone crystallized from the condensate separated by known methods.

The method according to the invention can, for. B. in the form of the following variants:

version 1

The nitration is stopped by passing the entire reaction mixture to an evaporator, e.g. B. a contact thin film or falling film evaporator, and the necessary part of nitric acid - conveniently quickly - distilled off and the mixture in the sump in a crystallizer either cools to temperatures below 15 ° C and / or by adding water or dilute nitric acid the 1-nitroanthraquinone precipitates and separates in a separator. The by-products dissolved in the filtrate can be precipitated either by dilution with water or by distilling off the nitric acid. The nitric acid freed from organic products can be separated into a high and low percentage nitric acid via a column, the high percentage nitric acid again being used for nitration and the low percentage nitric acid for crystallization.

The precipitated 1-nitroanthraquinone is freed from nitric acid, in particular by direct drying, if appropriate under reduced pressure, and subjected to a high vacuum rectification.

Variant 2

Depending on the molar ratio, the nitration is stopped in a cooling unit by cooling down to temperatures below 25 ° C. The 1-nitroanthraquinone is precipitated by subsequent dilution of the reaction mixture with water and / or dilute nitric acid and / or by cooling the reaction mixture to below 15 ° C. and separated off in a separating device. The further purification of the 1-nitroanthraquinone and the processing of the filtrate are carried out according to variant 1.

Variant 3

The nitration is stopped in a mixing vessel by adding a little water or dilute nitric acid. The reaction mixture is then brought to a mole fraction of less than 0.7 by adding dilute nitric acid or further amounts of water and / or by distilling off corresponding amounts of nitric acid. The precipitated 1-nitroanthraquinone is separated off. The further purification of 1-nitroanthraquinone and the work-up of the filtrate are carried out as described under variant 1. Of course, combinations of these variants are also possible.

It has been shown that 1-nitroanthraquinone which has a purity of 99% and more can be obtained by the process according to the invention.

According to the method according to the invention there are no molar ratios of nitric acid to anthraquinone and / or nitroanthraquinone which are particularly complex in terms of safety.

In the following examples, the molar ratio always means that of nitric acid: anthraquinone. Unless stated otherwise, the product which has crystallized out is separated off at room temperature. The yield always relates to the anthraquinone used. The temperature information is always given in ° C. All batches carried out and described here can also be carried out continuously.

Examples

1. 20.8 g of anthraquinone are stirred in 2.15 liters of 98% nitric acid for 42 minutes at -20 ° C. Then 255 g of ice are added very quickly and 1.72 liters of 98% nitric acid are distilled off (crystallizing acid 70%, y = 0.40). The precipitated product is filtered off, washed with a little 70% nitric acid, dried in vacuo and fractionally distilled at 6 torr and 267 ° C. top temperature. 21.5 g of 100% pure 1-nitroanthraquinone are obtained (85% of theory).

2. 20.8 g of anthraquinone are dissolved in 851 ml at -10 ° C

98% nitric acid stirred for 15 minutes. 634 ml of 98% nitric acid are then distilled off very rapidly in vacuo at −10 ° C. and 108.3 ml of water are added (crystallizing acid 73%, y = 0.43). The crystallized product is filtered off, washed with a little 70% nitric acid, dried in vacuo and distilled at 5 Torr and 264 ° C top temperature. 20.0 g of 99.6% pure 1-nitroanthraquinone are obtained (78.7% of theory).

3. 20.8 g of anthraquinone are stirred at -10 ° C in 425.2 ml of 98% nitric acid for 19 minutes. Thereafter, 395.8 ml of 98% nitric acid are distilled off very quickly in vacuo at -10 ° C. and 69.5 ml of 70% nitric acid (crystallizing acid 76.7%, y = 0.47) are added.

After filtration, washing with a little 70% nitric acid and drying, the mixture is distilled at 10 torr and 282 ° C. top temperature: 19.9 g of 99.6% pure 1-nitroanthraquinone (78.3% of theory).

4. 208 g of anthraquinone are nitrated in 851 ml of 98% nitric acid at -10 ° C for 500 minutes. Then 490 ml of 98% nitric acid are quickly distilled off in vacuo. The product precipitated by adding 1.44 liters of 70% nitric acid is filtered off (crystallizing acid 75%, y = 0.45), washed with a little 75% nitric acid, dried at 140-180 ° C. under normal pressure and at 5 Torr and 263 ° C top temperature distilled. 161 g of 99% pure 1-nitroanthraquinone (63.0% of theory) are obtained.

5. 208 g of anthraquinone are nitrated in 2.13 liters of 98% nitric acid at 0 ° C. within 17 minutes. The reaction is stopped by cooling to −20 ° C. and the product which has precipitated out by adding 1.12 liters of water (crystallizing acid 72% y = 0.42) is filtered off at room temperature, washed with 74% nitric acid, dried and at 274 ° C top temperature, 7 Torr distilled:

191 g 99% pure 1-nitroanthraquinone (74.7% of theory).

6. 20.8 g of anthraquinone are nitrided in 2.15 liters of 98% nitric acid for 20 minutes at -20 ° C. The reaction is stopped at −20 ° C. by adding 635 ml of 70% nitric acid. The product which precipitated out during the rapid distillation of 2.144 liters of 98% nitric acid was filtered off at room temperature (crystallizing acid 70%, y = 0.40) and distilled at 25 torr and 250 ° C. top temperature / 308 ° bottom temperature. 17.5 g of 99.8% pure 1-nitroanthraquinone (69% of theory) are obtained in the bottom.

The mixture of 1-nitroanthraquinone and anthraquinone obtained as a distillate can be used again in the nitration.

7. A mixture of 2.08 kg of anthraquinone and 17.02 liters of 98% nitric acid / hour, cooled to -10 ° C., is continuously reacted in a flow tube with a residence time of 7.5 minutes at a temperature of + 20 ° C. To stop the reaction, the reaction mixture is passed immediately after leaving the reactor in an evaporator (e.g. thin-film, circulating or falling film evaporator), where 13.8 liters / hour of 99% nitric acid are removed in vacuo5

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615 148

be lated. While the distilled nitric acid is reused for nitration, the bottom product is placed in a crystallization container into which 5.1 liters of 70% nitric acid are added per hour (crystallizing acid 79.4%, y = 0.51). The crystallized product is separated off with the aid of a rotary pressure filter or a flat filter (or a centrifuge), after which it is subsequently washed briefly with 70% nitric acid, freed from nitric acid in a vacuum, melted and subjected to vacuum rectification at 5 Torr and a top temperature of 269 ° C . io

The yield of 99.5% pure 1-nitroanthraquinone is 1.74 kg / hour (68.4% of theory).

The anthraquinone derivatives dissolved in the mother liquor are freed from nitric acid by distillation, and the nitric acid leaving the head is rectified. The 99% is used for nitration, the 70% nitric acid for crystallization (or concentrated).

8. 20.8 g of anthraquinone are nitrated at 65 ° for 130 minutes in 387.8 ml of 88% nitric acid. The reaction is stopped by adding 467.6 ml of 70% nitric acid. The product crystallized out by distilling off 220 ml of 100% nitric acid and cooling to room temperature (crystallizing acid 70%, = 0.4) is filtered off, washed with 70% nitric acid and distilled after vacuum drying at 8 torr and 273 ° C. top temperature;

17.8 g of 99.2% pure 1-nitroanthraquinone (69.8% of theory).