PROCESS FOR PRODUCING 4,4'-DICHLORODIPHENYL SULFONE

Abstract

The invention relates to a process for producing 4,4′-dichlorodiphenyl sulfone, comprising: (I) reacting thionyl chloride, chlorobenzene and aluminum chloride forming an intermediate reaction product and hydrogen chloride; (II) mixing aqueous hydrochloric acid and the intermediate reaction product to obtain an organic phase comprising 4,4′-dichlorodiphenyl sulfoxide and an aqueous phase; (III) cooling the organic phase to a temperature below the saturation point of 4,4′-dichlorodiphenyl sulfoxide to obtain a suspension; (IV) solid-liquid-separation of the suspension to obtain crystallized 4,4′-dichlorodiphenyl sulfoxide, and mother liquor; (V) washing the crystallized 4,4′-dichlorodiphenyl sulfoxide with a carboxylic acid to obtain carboxylic acid-wet 4,4′-dichlorodiphenyl sulfoxide; (VI) reacting the washed 4,4′-dichlorodiphenyl sulfoxide and an oxidizing agent in a carboxylic acid as solvent to obtain a reaction mixture comprising 4,4′-dichlorodiphenyl sulfone and carboxylic acid; (VII) separating the reaction mixture comprising 4,4′-dichlorodiphenyl sulfone and carboxylic acid into a residual moisture comprising 4,4′-dichlorodiphenyl sulfone as crude product and a liquid phase comprising carboxylic acid.

Claims

1.-15. (canceled)

16. A process for producing 4,4′-dichlorodiphenyl sulfone, comprising: (I) reacting thionyl chloride, chlorobenzene and aluminum chloride in a molar ratio of thionyl chloride:chlorobenzene:aluminum chloride of 1:(6 to 9):(1 to 1.5) at a temperature from 0 to below 20° C., forming an intermediate reaction product and hydrogen chloride; (II) mixing aqueous hydrochloric acid and the intermediate reaction product at a temperature from 70 to 110° C. to obtain an organic phase comprising 4,4′-dichlorodiphenyl sulfoxide and an aqueous phase; (III) cooling the organic phase comprising the 4,4′-dichlorodiphenyl sulfoxide to a temperature below the saturation point of 4,4′-dichlorodiphenyl sulfoxide to obtain a suspension comprising crystallized 4,4′-dichlorodiphenyl sulfoxide; (IV) solid-liquid-separation of the suspension to obtain a residual moisture comprising solid 4,4′-dichlorodiphenyl sulfoxide comprising crystallized 4,4′-dichlorodiphenyl sulfoxide and solvent, and mother liquor; (V) washing the residual moisture comprising solid 4,4′-dichlorodiphenyl sulfoxide with a carboxylic acid to obtain carboxylic acid-wet 4,4′-dichlorodiphenyl sulfoxide; (VI) reacting the carboxylic acid-wet 4,4′-dichlorodiphenyl sulfoxide and an oxidizing agent in a carboxylic acid as solvent to obtain a reaction mixture comprising 4,4′-dichlorodiphenyl sulfone and carboxylic acid; (VII) separating the reaction mixture comprising 4,4′-dichlorodiphenyl sulfone and carboxylic acid into a residual moisture comprising 4,4′-dichlorodiphenyl sulfone as crude product and a liquid phase comprising carboxylic acid. (VIII) optionally working up the residual moisture comprising 4,4′-dichlorodiphenyl sulfone.

17. The process according to claim 16, wherein separating the reaction mixture in (VII) comprises: (VII a) mixing the reaction mixture with water in a gastight closed vessel to obtain a liquid mixture, wherein the amount of water mixed to the reaction mixture in (VII.a) is such that the amount of water in the liquid mixture is from 10 to 60 wt % based on the total amount of the liquid mixture; (VII b) cooling the liquid mixture obtained in (VII.a) to a temperature below the saturation point of 4,4′-dichlorodiphenyl sulfone by (i) reducing the pressure in the gastight closed vessel to a pressure at which the water starts to evaporate, (ii) condensing the evaporated water by cooling (iii) mixing the condensed water into the liquid mixture in the gastight closed vessel, to obtain a suspension comprising crystallized 4,4′-dichlorodiphenyl sulfone; (VII c) carrying out a solid-liquid-separation of the suspension to obtain the residual moisture comprising 4,4′-dichlorodiphenyl sulfone and the liquid phase comprising the carboxylic acid.

18. The process according to claim 17, wherein the pressure is reduced in (i) until the suspension has cooled down to a temperature from 10 to 30° C.

19. The process according to claim 16, wherein in (VIII) the residual moisture comprising 4,4′-dichlorodiphenyl sulfone is washed with an aqueous base and then with water to obtain a first purified 4,4′-dichlorodiphenyl sulfone.

20. The process according to claim 19, wherein the aqueous base after being used for washing is mixed with a strong acid and a phase separation is carried out in which an aqueous phase and an organic phase comprising the carboxylic acid are obtained.

21. The process according to claim 16, wherein the carboxylic acid is at least one aliphatic C.sub.6 to C.sub.10 carboxylic acid.

22. The process according to claim 16, wherein cooling of the organic phase comprising 4,4′-dichlorodiphenyl sulfoxide in (III) is carried out in a gastight closed vessel by (III a) reducing the pressure in the gastight closed vessel; (III b) evaporating solvent; (III c) condensing the evaporated solvent by cooling; (III d) returning the condensed solvent into the gastight closed vessel.

23. The process according to claim 16, wherein the residual moisture comprising 4,4′-dichlorodiphenyl sulfone or the first purified 4,4′-dichlorodiphenyl sulfone, if the residual moisture comprising 4,4′-dichlorodiphenyl sulfone is washed, is further processed by: (A) dissolving the residual moisture comprising 4,4′-dichlorodiphenyl sulfone or the first purified 4,4′-dichlorodiphenyl sulfone in an organic solvent in which 4,4′-dichlorodiphenyl sulfone has a solubility of 0.5 to 20% at 20° C. to obtain a solution; (B) cooling the solution to a temperature below the saturation point of 4,4′-dichlorodiphenyl sulfone to obtain a suspension comprising crystallized 4,4′-dichlorodiphenyl sulfone; (C) carrying out a solid-liquid separation to obtain residual moisture comprising 4,4′-dichlorodiphenyl sulfone and a mother liquor; (D) washing the residual moisture comprising 4,4′-dichlorodiphenyl sulfone with an organic solvent in which 4,4′-dichlorodiphenyl sulfone has a solubility of 0.5 to 20% at 20° C.; (E) optionally repeating steps (B) to (D); (F) drying the 4,4′-dichlorodiphenyl sulfone; (G) optionally working up and recycling into the dissolving (A) at least a part of the mother liquor and optionally the organic solvent in which 4,4′-dichlorodiphenyl sulfone has a solubility of 0.5 to 20% at 20° C. used for washing by distillation.

24. The process according to claim 16, wherein the liquid phase comprising carboxylic acid obtained in (VII) is purified by distilling a part of the liquid phase comprising carboxylic acid; stripping low boilers from at least a part of the liquid phase comprising carboxylic acid; and recycling the purified carboxylic acid into the reaction (VI).

25. The process according to claim 16, wherein the residual moisture comprising solid 4,4′-dichlorodiphenyl sulfoxide obtained in (IV) is washed with solvent.

26. The process according to claim 16, wherein the mother liquor obtained in (IV) is concentrated and at least a part of the concentrated mother liquor is recycled into the cooling of the organic phase comprising 4,4′-dichlorodiphenyl sulfoxide (III).

27. The process according to claim 16, wherein the amount of carboxylic acid in the reaction (VI) is such that the weight ratio of 4,4′-dichlorodiphenyl sulfoxide to carboxylic acid is at least 1:2.

28. The process according to claim 16, wherein the oxidizing agent is a peroxide.

29. The process according to claim 16, wherein a liquid mixture comprising chlorobenzene and carboxylic acid is withdrawn from the washing (V) and the liquid mixture comprising chlorobenzene and carboxylic acid is separated into a first stream comprising substantially chlorobenzene and a liquid phase comprising substantially carboxylic acid.

30. The process according to claim 16, wherein the organic phase comprising 4,4′-dichlorodiphenyl sulfoxide obtained in (II) is separated off and washed with water at a temperature from 70 to 110° C. before cooling in (III).

Description

EXAMPLES

Example 1 (Production of 4,4′-dichlorodiphenyl sulfoxide)

[0235] 5.5 mol aluminum chloride and 40 mol chlorobenzene were fed into a stirred tank reactor as first reactor. 5 mol thionyl chloride were added to the reaction mixture in 160 min. The reaction in the first reactor was carried out at 10° C. Hydrogen chloride produced in the reaction was withdrawn from the process. After finishing the addition of thionyl chloride the reaction mixture was heated to 60° C.

[0236] After finishing the reaction in the first reactor the resulting reaction mixture was fed into a second stirred tank reactor which contained 3400 g hydrochloric acid with a concentration of 11 wt %. The second stirred tank reactor was heated to a temperature of 90° C. After 30 min the mixing was stopped and the mixture separated into an aqueous phase and an organic phase.

[0237] The aqueous phase was withdrawn and the organic phase was washed with 3000 g water while stirring at 90° C. After washing, stirring was stopped and the mixture separated into an aqueous phase and an organic phase.

[0238] The aqueous phase was removed and the organic phase was subjected to a distillation. Monochlorobenzene was distilled from the organic phase until saturation was reached at about 88° C. (monitored via a turbidity probe, distillation conditions: 200 mbar(abs)). The organic phase was cooled by reducing the pressure until the temperature reached 30° C.

[0239] By the cooling a suspension was obtained containing crystallized DCDPSO. The suspension then was filtrated to obtain a filter cake comprising crystallized DCDPSO, which was washed with 550 g monochlorobenzene.

[0240] The combined mother liquor and the monochlorobenzene which was used for washing were subjected to a distillation. In the distillation monochlorobenzene was removed until the amount of combined mother liquor and washing filtrate was reduced to 25 wt %. The distillation was operated at a bottom temperature of 90° C. and 200 mbar(abs).

[0241] While the distilled monochlorobenzene was reused in the next batch as starting material, 80 wt % of the obtained bottom product were transferred into the crystallization of the next batch.

[0242] After washing with monochlorobenzene, the thus obtained monochlorobenzene-wet filter cake comprising crystallized DCDPSO was washed with 300 g n-heptanoic acid and filtrated to obtain n-heptanoic acid wet DCDPSO as filter cake.

[0243] The filtrate was subjected to distillation yielding a top fraction of monochlorobenzene and a bottom fraction comprising n-heptanoic acid and DCDPSO. The bottom fraction was topped up with fresh n-heptanoic acid and reused in the next filtration. The distillation was operated at a bottom temperature of 140° C. and 100 mbar(abs).

[0244] The 4,4′-dichlorodiphenyl sulfoxide yield in the steady state was 1232 g which corresponds to a yield of 91.3%.

[0245] The n-heptanoic acid wet DCDPSO had a purity of 89.7 wt %, containing 8.9 wt % n-heptanoic acid, 0.8 wt % monochlorobenzene, 0.3 wt % 4,4′-dichlorodiphenylsulfide and 0.3 wt % 2,4′-dichlorodiphenylsulfoxide.

Example 2 (Production of 4,4′-dichlorodiphenyl sulfone)

[0246] 1113 g of the n-heptanoic acid wet 4,4′-dichlorodiphenyl sulfoxide were dissolved in 2900 g n-heptanoic acid and heated to 90° C. 7.2 g sulfuric acid were added to the solution. Over a period of 3 h and 10 min 143 ml H.sub.2O.sub.2 were added to the solution with a constant feed rate. During the reaction the temperature in the vessel was controlled to 90° C. by wall cooling, whereby the temperature in the reactor was determined to be 97 to 99° C. After finishing this step, the reactor was stirred for 15 minutes at a temperature of 97° C. Then, a second amount of 7 ml H.sub.2O.sub.2 was added within 10 minutes. After completing the H.sub.2O.sub.2 dosage the temperature of the solution was raised to 100° C. The reactor was stirred for 20 minutes at a temperature of 100° C.

[0247] To the resulting reaction mixture comprising DCDPS and n-heptanoic acid, 881 g water were added with a temperature of 97° C. The thus obtained mixture was cooled by reducing the pressure according to the cooling profile shown in table 1.

TABLE-US-00001 TABLE 1 cooling profile time ]h] temperature [° C.] pressure [mbar] 0:00 97 760 0:50 81 380 01:15 90 580 1:45 90 580 2:45 81 370 3:40 61.5 175 4:35 43 70 6:00 18 980

[0248] A suspension comprising 2480 g n-heptanoic acid and DCDPS was obtained by this process.

[0249] The suspension then was filtered at ambient temperature to obtain a filter cake comprising about 80 wt % DCDPS, 16 wt % n-heptanoic acid and 4 wt % water. The mother liquor which was separated off the filter cake in the filtration process contained about 78 wt % n-heptanoic acid, 20 wt % water and about 2.5 wt % DCDPS. For filtering the suspension, a glass nutsche was used which was covered with a Sefar® Tetex DLW 17-80000-SK 020 Pharma filter cloth. For filtering, an absolute pressure of 500 mbar was set below the nutsche. After filtration, the filter cake was treated with dry air for 30 s.

Example 3 (Washing the DCDPS with an Aqueous Base and Water)

[0250] The filter cake obtained in example 2 then was washed with 2 kg of diluted NaOH 5%. For washing a pressure of 750 mbar(abs) were set to the filtrate side of the nutsche.

[0251] Washing with diluted NaOH was followed by washing with 1.5 kg water. For washing with water a pressure of 500 mbar(abs) were set to the filtrate side of the nutsche. Subsequently the filter cake was treated for 30 seconds with dried air.

[0252] After washing and treating with dried air, the filter cake contained about 20 wt % water and 0.24 wt % n-heptanoic acid. The final filter cake mass was 1369 g.

[0253] The mother liquor obtained in the filtration process was subjected to a phase separation. By phase separation, 482 g aqueous phase and 2712 g organic phase were obtained.

Example 4 (Purifying of the DCDPS)

[0254] 500.4 g of the filter cake obtained in example 3 containing 115 g water and containing about 0.24% n-heptanoic acid and about 240 ppm isomers of 4,4′-DCDPS were suspended into 1385 g methanol. This mixture was heated to a temperature of 100° C. in a closed vessel. The temperature was kept at 100° C. for 2 h and 20 min. Then the pressure in the vessel was reduced and methanol started to evaporate. Evaporation of methanol resulted in crystallization of the DCDPS. The temperature in the vessel was reduced linearly with a rate of 10 Kelvin per hour until a temperature of 10° C. was reached. After this temperature was reached, the vessel was vented until ambient pressure was achieved. The thus obtained mixture of crystallized DCDPS and methanol was filtered in a filter nutsche. By this filtration a wet filter cake which weighted 613.5 g was obtained. The wet filter cake was washed with fresh 400 g methanol. Afterwards, the washed wet filter cake was dried for 5 hours in a Rotavapor® rotary evaporator with a wall temperature of 130° C. The thus obtained product had the following composition:

[0255] 99,987% 4,4′-DCDPS

[0256] 120 ppm methanol

[0257] 90 ppm DCDPS-isomers

[0258] <20 ppm remaining carboxylic acid.

Example 5 (Working Up the Solvent Used in the DCDPS-Production)

[0259] The organic phase obtained by phase separation of the mother liquor in example 3 was mixed with 269 g of 50% sulfuric acid. This mixture was combined with the mother liquor obtained in the filtration in example 2. This combined mother liquor then was separated in two streams. One stream was subjected to distillation and one stream to stripping. After distillation and stripping, respectively, the resulting purified carboxylic acid streams were combined again. The combined mother liquor had the following composition:

[0260] 0.715 wt % monochlorobenzene, 0.02 wt % dodecane, 0.003 wt % n-heptanoic acid methyl ester, 0.026 wt % valeric acid, 0.315 wt % n-hexanoic acid, 95.02 wt % n-heptanoic acid and 3.5 wt % water.

[0261] Distillation

[0262] 310 g of the combined mother liquor were fed into a batch distillation column with 10 trays and distilled with a bottom temperature of 160° C., and a top temperature of 135° C. at a pressure of 52 mbar (abs) for about 4.5 h. The carboxylic acid obtained by this distillation had the following composition:

[0263] 0.014 wt % monochlorobenzene, 0.002 wt % dodecane, 0.0 wt % n-heptanoic acid methyl ester, 0.005 wt % valeric acid, 0.185 wt % n-hexanoic acid, and 99.52 wt % n-heptanoic acid. Stripping

[0264] 2627 g of the combined mother liquor with a temperature of 88° C. were provided in a buffer vessel and continuously fed into a stripping column with a feed rate of 66 ml/min.

[0265] The stripping column had 10 trays and the crude carboxylic acid was fed on top into the stripping column and 150 NL per hour nitrogen were fed into the stripping column at the bottom as stripping gas. The pressure in the stripping column was set to 300 mbar.

[0266] After stripping, the carboxylic acid was continuously removed from the stripping column and had the following composition:

[0267] 0.456 wt % monochlorobenzene, 0.018 wt % dodecane, 0.003 wt % n-heptanoic acid methyl ester, 0.025 wt % valeric acid, 0.333 wt % n-hexanoic acid, 95.36 wt % n-heptanoic acid, and 0.42 wt % water.

[0268] The purified carboxylic acid (unified from stripping and distillation) was fed back into the oxidation reaction and contained 0.41 wt % monochlorobenzene, 2.2 wt % 4,4′-DCDPS, 0.54% 2,4′-DCDPS, about 600 ppm lactones, 4000 ppm n-hexanoic acid, 240 ppm valerian acid, 100 ppm esters, and 160 ppm dodecane.