A PROCESS FOR WORKING UP WATER CONTAINING 4,4'-DICHLORODIPHENYL SULFOXIDE AND/OR 4,4'-DICHLORODIPHENYL SULFONE AS IMPURITIES

Abstract

The invention relates to a process for working up water containing 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone as impurities, comprising: (a) mixing the water containing 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone as impurities with an organic solvent in which 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone have a solubility of at least 0.5 wt % based on the amount of 4,4′-dichlorodiphenyl sulfoxide and/or 4, 4′-dichlorodiphenyl sulfone and organic solvent at 20° C., which forms a two-phase system with water and which can be stripped from water with a stripping gas and subsequently separating the obtained mixture into an aqueous phase and an organic phase, and (b) stripping the organic solvent from the aqueous phase with a stripping gas.

Claims

1.-17. (canceled)

18. A process for working up water containing 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone as impurities, comprising: (a) mixing the water containing 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone as impurities with an organic solvent in which 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone have a solubility of at least 0.5 wt % based on the amount of 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone and organic solvent at 20° C., which forms a two-phase system with water and which can be stripped from water with a stripping gas and subsequently separating the obtained mixture into an aqueous phase and an organic phase, and (b) stripping the organic solvent from the aqueous phase with a stripping gas.

19. The process according to claim 18, wherein the water containing 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone as impurities accrues in a process for producing 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone or in a process using 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone.

20. The process according to claim 18, wherein in (a) 0.10 to 5 kg organic solvent per kg water containing 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone as impurities are used.

21. The process according to a claim 18, wherein the organic solvent is chlorobenzene.

22. The process according to claim 18, wherein the stripping gas is steam.

23. The process according to claim 22, wherein for stripping the organic solvent from the water containing 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone as impurities 0.05 to 0.7 kg steam per kg water containing 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone as impurities are used.

24. The process according to claim 18, wherein the water containing 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone as impurities additionally comprises at least one of chlorobenzene, hydrogen chloride, alkali metal sulfates, metal chlorides, carboxylic acids or alcohols.

25. The process according to claim 24, wherein the amount of chlorobenzene in the water containing 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone as impurities is in the range from 0.01 to 3 wt % based on the total amount of water containing 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone as impurities.

26. The process according to claim 24, wherein the amount of hydrogen chloride in the water containing 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone as impurities is in the range from 1 to 12 wt % based on the total amount of the water containing 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone as impurities.

27. The process according to claim 24, wherein the metal chloride is AlCl.sub.3 and the amount of AlCl.sub.3 in the water containing 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone as impurities is in the range from 10 to 30 wt % based on the total amount of the water containing 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone as impurities.

28. The process according to claim 24, wherein the amount of carboxylic acids in the water containing 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone as impurities is in the range from 1 ppm to 10 wt %.

29. The process according to claim 18, wherein the aqueous phase has a temperature in the range from 70 to 150° C. during stripping.

30. The process according to claim 18, wherein mixing and phase separation (a) is carried out at a temperature in the range from 10 to 100° C.

31. The process according to a claim 18, wherein mixing and phase separation (a) is carried out in at least two steps.

32. The process according to claim 18, wherein after mixing and phase separation, the aqueous phase contains less than 10 ppm 4,4′-dichlorodiphenyl sulfoxide and/or 4,4′-dichlorodiphenyl sulfone.

33. The process according to claim 18, wherein stripping (b) is carried out in a column with at least two theoretical plates.

34. The process according to claim 18, wherein gaseous components being withdrawn from the stripping are condensed and recycled into a process for producing 4,4′-dichlorodiphenyl sulfoxide or into a process for producing 4,4′-dichlorodiphenyl sulfone.

Description

[0122] An illustrative embodiment of the invention is shown in the figure and explained in more detail in the following description. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the disclosure in unnecessary detail.

[0123] FIG. 1 shows a flow diagram of an embodiment of the inventive process,

[0124] FIG. 2 shows a flow diagram of an extraction carried out in two steps,

[0125] In the process shown in FIG. 1, polluted water 1 containing DCDPSO and/or DCDPS as impurities is collected in a buffer container 3. From the buffer container, the polluted water 1 is fed into an extraction 5 where the polluted water 1 is mixed with an organic solvent, particularly chlorobenzene, as extractant 7 and subsequently separated into an organic phase and an aqueous phase. In the extraction 5, DCDPSO and/or DCDPS is separated off the polluted water.

[0126] The extraction 5 can be carried out in any suitable apparatus for a liquid-liquid extraction. Suitable apparatus for example are columns or mixer-settler. Preferably, the extraction 5 is carried out in a mixer settler. Preferably, the extraction 5 is carried out in at least two steps as shown in FIG. 2, wherein for each step a separate extraction apparatus is used. Thereby, each extraction step can be carried out in a different type of extraction apparatus. However, it is preferred to use only one type of apparatus for each extraction step, particularly a mixer-settler.

[0127] The extraction 5 preferably is carried out at a temperature in the range from 70 to 110° C. and at ambient pressure.

[0128] From the extraction 5 water depleted in DCDPSO and/or DCDPS 9 and organic solvent enriched in DCDPSO and/or DCDPS 11 are withdrawn. If the organic solvent is chlorobenzene, the organic solvent enriched in DCDPSO and/or DCDPS 11 for example is returned into the production process of DCDPSO, particularly into the hydrolysis of the intermediate reaction product which was obtained by reacting chlorobenzene and thionyl chloride in the presence of aluminum chloride.

[0129] The water depleted in DCDPSO and/or DCDPS 9 is subjected to stripping 13. By stripping 13, organic solvent is separated off the water depleted in DCDPSO and/or DCDPS. For stripping 13, steam 15 is brought into contact with the water depleted in DCDPSO and/or DCDPS. Stripping 13 preferably is carried out in a stripping column in which the water depleted in DCDPSO and/or DCDPS and the steam flow in counter current. During stripping the steam is brought into intense contact with the water depleted in DCDPSO and/or DCDPS. Stripping is carried out at a temperature in the range from 80 to 120° C. To achieve this temperature, it is possible to provide a heat exchanger 17 in the line 19 through which the water depleted in DCDPSO and/or DCDPS flows from the extraction 5 to the stripping 13. If the extraction 5 is carried out at the same temperature at which stripping is carried out, it is not necessary to provide the additional heat exchanger 17. In this case it generally is sufficient to insulate the line through which the heated water depleted in DCDPSO and/or DCDPS 9 flows from the extraction 5 to the stripping 13. Alternatively, it is also possible to use the heat of the water depleted in DCDPSO and/or DCDPS 9 for heating the water which is fed into the stripping 13. For using the heat of the water depleted in DCDPSO and/or DCDPS 9 for heating the water which is fed into the stripping 13, any suitable indirect heat exchanger can be used through which the water depleted in DCDPSO and/or DCDPS and the water which is fed into the stripping can flow in separate channels, for example a tube bundle heat exchanger, a plate heat exchanger or a spiral heat exchanger. The water depleted in DCDPSO and/or DCDPS and the water which is fed into the stripping may flow in counter-current flow, co-current flow or cross-flow. Using the heat of the water depleted in DCDPSO and/or DCDPS for heating the water which is fed into the stripping has the additional advantage that the water depleted in DCDPSO and/or DCDPS is cooled.

[0130] If an additional buffer container is provided in which the water depleted in DCDPSO and/or DCDPS 9 is collected before being fed into the stripping 13, it is possible to temper the buffer container to heat the water depleted in DCDPSO and/or DCDPS to the temperature at which the stripping 13 is carried out. For tempering, the buffer container may comprise a double jacket or a heating coil through which a heating medium or cooling medium flows or with an electrical heating or with a combination of at least two thereof. A cooling particularly is necessary when the extraction 5 is carried out at a higher temperature than the stripping 13. However, it is preferred to either operate extraction 5 and stripping 13 at the same temperature or stripping 13 at a higher temperature than the extraction 5.

[0131] From the stripping, a gaseous stream 21 containing steam and vaporized organic solvent and a liquid stream 23 containing water depleted in DCDPSO and/or DCDPS and organic solvent are obtained. If the organic solvent is chlorobenzene, the gaseous stream 21 preferably is subjected to condensation 25 and then recycled into the production process of DCDPSO, particularly in a washing step of the organic phase obtained by phase separation of the reaction product which is obtained by reacting chlorobenzene and thionyl chloride in the presence of aluminum chloride forming an intermediate reaction product and hydrolysis of the intermediate reaction product in the presence of aqueous hydrogen chloride to form DCDPSO.

[0132] The liquid stream 23 obtained by stripping, which contains the water depleted in DCDPSO and/or DCDPS and organic solvent can be withdrawn from the process and introduced in a water purification plant before draining in the environment.

[0133] FIG. 2 shows a flow diagram of an extraction process in two steps.

[0134] If the extraction 5 is carried out in two steps, the polluted water 1 is fed into a first mixing unit 101. In the first mixing unit 101, the polluted water is mixed with the organic solvent as extractant. The first mixing unit 101 preferably can be heated, for example by a double jacket 103 or a heating coil which is not shown here. The mixture of polluted water and extractant then is fed into a first phase separation unit 105 in which the water and the extractant are separated in an aqueous phase 106 and an organic phase 115.

[0135] The first mixing unit 101 and the first phase separation unit 105 preferably are a mixing chamber and a settling chamber of a first mixer-settler.

[0136] From the first phase separation unit 105 the aqueous phase 106 is fed into a second mixing unit 107. Further, organic solvent is fed into the second mixing unit 107 as extractant 7. The organic solvent and the aqueous phase are mixed in the second mixing unit 107 and the thus obtained mixture is fed into a second phase separation unit 109. As for the first step, also the second mixing unit 107 preferably can be heated, for example by a double jacket 108 or heating coil which is not shown here. Further, also the second mixing unit 107 and the second phase separation unit 109 preferably are a mixing chamber and a settling chamber of a second mixer-settler. In the second phase separation unit 109, the mixture obtained in the second mixing unit 107 is separated into a second aqueous phase 111 and a second organic phase 113.

[0137] The second organic phase 113 is fed into the first mixing unit 101 as extractant. The second aqueous phase 111 is withdrawn from the extraction as water depleted in DCDPSO and/or DCDPS 9 which is fed into the stripping 13.

[0138] The organic phase 115 withdrawn from the first phase separation unit 105 is the organic solvent containing DCDPSO and/or DCDPS 11 and is recycled into the production process of DCDPSO if the organic solvent is used in the process for producing DCDPSO.

EXAMPLES

Example 1

[0139] 249 g polluted water withdrawn from the hydrolysis of a process for producing DCDPSO, containing 107 ppm DCDPSO and 25 g chlorobenzene were agitated in a 1-liter vessel at 90° C. and 1000 rpm. After stopping agitating, the mixture separated into an organic phase and an aqueous phase. Samples of the aqueous phase were taken after one minute settling time. 8 ppm DCDPSO were analyzed in the sample.

Example 2

[0140] 237 g polluted water withdrawn from the hydrolysis of a process for producing DCDPSO, containing 107 ppm DCDPSO and 49 g chlorobenzene were agitated in a 1-liter vessel at 90° C. and 1000 rpm. After stopping agitating, the mixture separated into an organic phase and an aqueous phase. Samples of the aqueous phase were taken after one minute settling time. 5 ppm DCDPSO were analyzed in the sample. After phase separation, the aqueous phase was mixed again with 40 g chlorobenzene. After stopping mixing, the mixture separated into an organic phase and an aqueous phase. A sample of the aqueous phase taken after 1 minute settling time contained <2 ppm DCDPSO.

Example 3

[0141] In a continuous mixer-settler apparatus 11 kg/h polluted water withdrawn from the hydrolysis of a process for producing DCDPSO, containing 280 ppm DCDPSO were mixed at 80° C. in an agitated vessel of 1 liter volume at 1200 rpm with 1.7 kg/h chlorobenzene and separated in a verti-cal phase separator with a load of 9 m.sup.3/(m.sup.2h). A sample was taken from the aqueous phase withdrawn from the phase separator. The sample contained 6 ppm DCDPSO.

Example 4

[0142] In a bubble cap column a continuous polluted water stream of 10 kg/h with a chlorobenzene inlet concentration of 802 mg/L and a temperature of 99° C. was stripped with 0.8 kg/h steam, resulting in a steam to polluted water ratio of 0.08 kg/kg. The steam had an inlet temperature of approximately 120° C. The column was operated in counter current mode. To avoid heat losses the column was heated. After stripping, the water depleted in chlorobenzene had a chlorobenzene concentration of 19 mg/L.