JPH082863B2 - Method for producing high-purity 4,4'-dihydroxydiphenyl sulfone - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing 4,4′-dihydroxydiphenyl sulfone (hereinafter referred to as “4,4′-DDS”).

Conventional technology and its problems In recent years, 4,4′-DDS has an increasing demand in the field of chemical industry such as fibers and resins, and further, in order to improve product quality in each field, 4,4′-DDS having an extremely high purity is used. 4'-DDS is required. For this reason, it is desired to produce 4,4'-DDS in high yield and high purity as the manufacturing apparatus becomes larger.

As a method for producing 4,4′-DDS, a method is known in which a phenol and a sulfonating agent are dehydrated in the presence of a solvent such as dichlorobenzene that dissolves the above-mentioned raw material and produced 4,4′-DDS. ing. However, when the dehydration reaction is carried out in a solvent as in the method, the isomer 2,4′-dihydroxydiphenyl sulfone (hereinafter, “2,4′-DDS”, which is a target product of 4,4′-DDS is a byproduct. 20 to 30 in the resulting crude product due to having an isomerization equilibrium in the dissolved state between
As much as 4,4'-DDS is contained as an impurity by weight,
-Lower purity and yield of DDS. Also recently
It is also recognized that trihydroxytriphenyldisulfone (hereinafter referred to as "tri-form") is by-produced together with the above 2,4'-DDS.

Therefore, as a method for obtaining 4,4′-DDS in high purity and high yield, the present inventors first dehydrate phenol and sulfuric acid in the presence of a solvent, and then gradually remove the solvent from the reaction solution. While removing it, isomerize the by-product 2,4'-DDS to 4,4'-DDS (hereinafter, simply "DDS" means 4,4'-DDS and 2,4'-DDS) The high purity 4,4'-DDS
A method of manufacturing (Japanese Patent Publication No. 55-8972) was proposed.
The above method utilizes the difference in the solubility of 4,4'-DDS and 2,4'-DDS in a solvent and gradually removes the solvent to obtain 4,4'-DDS.
Of the by-product 2,4'-DDS to 4,4'-DDS and the purity of 4,4'-DDS And to improve the yield. However, according to the above method, the reaction product solidifies from the molten state as the solvent is removed, resulting in a viscous solid with no fluidity, and therefore a special stirring device excellent in mechanical strength is required for production. Become. Therefore, it is difficult to increase the size of the manufacturing apparatus associated with mass production.

The present inventors have also proposed a method of using an aromatic sulfonic acid as a catalyst in carrying out the above dehydration reaction or dehydration reaction and isomerization reaction (JP-A-61-243059 and JP-A-61-2430).
No. 60 bulletin). According to these methods, not only the reaction time of dehydration reaction and / or isomerization reaction can be shortened, but also 2,4′-DDS by-produced in the dehydration reaction step and the tri-form produced in the dehydration reaction and isomerization reaction step Can be suppressed by-product. However, the suppression of the production of by-products becomes more prominent,
Further reduction of the reaction time is desired. Moreover, the above method cannot overcome the difficulty in handling the viscous product in the isomerization reaction.

On the other hand, recently, 2,4'-DDS produced by dehydration reaction of phenol and sulfuric acid under heating in the presence of an aliphatic hydrocarbon suspending agent and an azeotropic agent is converted into 4,4'-DDS. A method for isomerization (Japanese Patent Laid-Open No. 64-9970) has also been proposed. However, in the above-mentioned method, the progress of the dehydration reaction is slow, and the tendency becomes remarkable particularly in the latter stage of the reaction, and the reaction requires a long time. Moreover, it is difficult to complete the reaction even if it takes a long time,
It is difficult to sufficiently increase the yield of 4,4'-DDS with respect to the used sulfuric acid. Purity and yield are confused in the above publication, the yield of 4,4'-DDS is not indicated, and the yield with respect to sulfuric acid is not indicated correctly. In fact, the result of tracing the third embodiment in which the present inventors have obtained the best result shows that
At the beginning of the reaction, the dehydration reaction proceeds smoothly, but the amount of water distilled off decreases with the progress of the reaction, and the amount of water distilled decreases extremely after 1 hour after heating to 170 ° C, and the reaction proceeds after 2 hours. Has stopped. In order to proceed the reaction, the distilled phenol was returned to the system and the azeotropic agent was added several times to proceed the reaction, but the reaction proceeded remarkably slowly and was used even after a reaction time as long as 16 hours and 20 minutes. In addition, 4,4'-DDS could only be obtained in a yield of about 80% with respect to sulfuric acid, and the reaction could not proceed further. Further, the reaction system easily causes aggregation and precipitation, and in order to prevent this, it is necessary to use a powerful stirring device. In addition, the aliphatic hydrocarbon-based suspending agent has a high boiling point, and it is necessary to use an azeotropic agent in combination in order to proceed the dehydration reaction while removing water out of the system. Since it is a multi-component system, the management and operation during the reaction and recovery must be complicated. Further, the product is colored in blackish brown and is hardly decolorized during purification, so that only a product having a low commercial value can be obtained.

The present inventor, as a result of proceeding with research in view of the current state of the art as described above, uses mesitylene as a reaction medium in carrying out the dehydration reaction, and carries out the reaction while suspending DDS produced in mesitylene. In some cases, the by-product of 2,4′-DDS can be significantly suppressed, and only with the dehydration reaction, a purity of about 90% by weight or more
It was found that 4'-DDS can be obtained in high yield.
After further dehydration reaction, the reaction product was converted into 2,4'-DDS by 4,4'-DDS.
The isomerization of 2,4'-DDS to 4,4'-DDS can be carried out in a short time by heating the isomerization temperature above the isomerization temperature to give higher purity and higher yield. It was found that 4,4'-DDS can be obtained. Based on these discoveries, we filed a patent application for Japanese Patent Application No. 1-239523.

Means for Solving the Problems An object of the present invention is to provide a method which is a further advance of the above-mentioned prior invention.

The object of the present invention is to further reduce the production of by-products in the dehydration reaction and shorten the dehydration reaction time to achieve extremely high purity.
It is an object of the present invention to provide a method for producing 4,4'-DDS in an even higher yield.

Another object of the present invention is to provide a method for suppressing by-production of a tri-form in an isomerization reaction process to obtain a highly pure 4,4'-DDS in a high yield.

That is, in the present invention, when a phenol and a sulfonating agent are dehydrated to produce 4,4′-DDS, DDS produced by using mesitylene as a reaction medium is reacted while being suspended in mesitylene and the reaction system. Within the general formula (1) [Wherein X represents a halogen atom or an alkyl group having 1 or 2 carbon atoms, n represents 0, 1 or 2 and m represents 2 or 3], and an aromatic polysulfonic acid represented by the formula is present. And a method for producing high-purity 4,4′-DDS. In addition, the present invention, after the dehydration reaction, in the state of DDS suspended in mesitylene and / or (2) in the solid state from which the liquid was removed, 2,4'-DDS to 4,4'-DDS High purity 4,4'-D characterized by further heating above the isomerization temperature to proceed the isomerization reaction of the by-product 2,4'-DDS to 4,4'-DDS
It relates to the manufacturing method of DS.

According to the research conducted by the present inventor, the dehydration reaction of phenol and a sulfonating agent in the presence of the aromatic polysulfonic acid represented by the general formula (1) does not substantially dissolve the reaction product DDS. When the generated DDS is allowed to proceed in mesitylene while being suspended in mesitylene, the reaction proceeds remarkably quickly, and the dehydration reaction can be completed in a shorter time than in the conventional case. It was found that not only the by-product of ′ -DDS can be suppressed more significantly, but also the by-product of the avian body is suppressed, and it can be reduced to substantially zero depending on the reaction conditions. As a result, in a preferred embodiment, it is possible to obtain 4,4′-DDS with a purity of about 97% by weight or more and a yield of about 96% or more only by the dehydration reaction. The suspension state of the above reaction system can be stably maintained by using an ordinary stirring device and does not require a strong stirring device.First, since the reaction medium is a single component of mesitylene, it does not require special management and is easy. The reaction can be allowed to proceed and recovered. Also,
The resulting 4,4'-DDS is pink to light brown and can be easily decolorized during purification.

According to the research conducted by the present inventor, the DDS suspended in the mesitylene produced by the dehydration reaction is in a suspended state as it is, or in a suspended state after removing a part of the liquid before the isomerization reaction. In addition, while the liquid fraction was distilled off in the course of the isomerization reaction, while precipitating DDS crystals, the crystals were co-suspended and heated above the isomerization temperature to produce a byproduct 2,4′-DDS 4,4 ′. -When proceeding to the isomerization to DDS, it can be isomerized with an ordinary stirring device without agglomeration and precipitation, and in the isomerization reaction process, the liquid is distilled off to convert DDS from the suspended state to the solid state. Even if the isomerization reaction is performed, the liquid content is removed by removing the liquid content before the isomerization reaction.
Even when the isomerization reaction is carried out in the solid state, DDS can be isomerized in the state of a smooth crystal powder, and therefore does not require a special stirring device and is of extremely high purity in a simple operation.
It has been found that it becomes possible to obtain 4'-DDS in a yield almost equivalent to the theoretical value, and mass production of 4,4'-DDS can be easily carried out industrially. Moreover, the aromatic polysulfonic acid added in the dehydration reaction step is adsorbed by the DDS crystals and exists in the isomerization reaction system, and this suppresses the by-product of the tri-form in the isomerization reaction step.

As the sulfonating agent in the present invention, various sulfonating agents capable of introducing a sulfonyl group into phenol can be widely used, and examples thereof include concentrated sulfuric acid, anhydrous sulfuric acid, fuming sulfuric acid, chlorosulfonic acid, and phenolsulfonic acid.
Concentrated sulfuric acid is more preferred.

In the dehydration reaction, for example, when sulfuric acid is used as a sulfonating agent, first, phenol and sulfuric acid react with each other to intermediately generate phenolsulfonic acid, and the generated phenolsulfonic acid reacts with phenol to generate DDS. . The reaction proceeds while producing water as a by-product. When phenolsulfonic acid, which is an intermediate when sulfuric acid is used as a sulfonating agent, is used, DDS is produced only by the latter reaction.

In the method of the present invention, the use ratio of the phenol and the sulfonating agent is not particularly limited, but if the former is too small with respect to the latter, the yield decreases, and if it is excessive, 4,4 Due to the solubility of'-DDS in phenol
The content ratio of 2,4'-DDS increases, which is not preferable. Therefore, it is usually most preferable to use both at or near the stoichiometric ratio. For example, when 2 mol of phenol reacts with 1 mol of a sulfonating agent such as sulfuric acid or chlorosulfonic acid, 1.9 to 2.5 mol of phenol is more preferable, and more preferably 1.95 to 2.3 mol with respect to 1 mol of a sulfonating agent. It is recommended to use about a mole. Further, when a sulfonating agent and phenol react in an equimolar manner like phenolsulfonic acid, phenol is added to 1 mol of phenolsulfonic acid.
It is preferable to use about 0.9 to 1.5 mol, and more preferably about 0.95 to 1.3 mol.

In the present invention, DD is produced by dehydrating phenol and a sulfonating agent using mesitylene as a reaction medium.
It is essential to allow the reaction to proceed while suspending S in mesitylene.

Mesitylene (1,3,5-trimethylbenzene) is 165 ℃
Has a boiling point of, and the raw material dissolves under the reaction conditions of the present invention, but the DDS formed is 4,4'-DDS and 2,4'-
DDS is practically insoluble. The amount of mesitylene used is not particularly limited as long as it is at least a liquid amount having a fluidity sufficient to stir the reaction system. That is, an excess amount may be used as long as it is at least a liquid amount capable of maintaining the suspension state of DDS produced in the reaction system until the end of the dehydration reaction. However, from the economical aspect, it is usually 0.3-by weight with respect to the amount of phenol.
It is preferably about 5 times, more preferably about 0.5 to 2 times. Moreover, when mesitylene is used as the reaction medium, it is 120 to 165 ° C.
The dehydration reaction can be carried out at a relatively low temperature.

As the aromatic polysulfonic acid represented by the general formula (1) used in the present invention, conventionally known ones can be widely used as long as they are stable in the reaction system without participating in the dehydration reaction. 1,3-disulfonic acid, chlorobenzene-2,4-disulfonic acid, bromobenzene-2,4-
Disulfonic acid, fluorobenzene-2,4-disulfonic acid, toluene-2,4-disulfonic acid, ethylbenzene-
2,4-disulfonic acid, benzene-1,3,5-trisulfonic acid, chlorobenzene-2,4,6-trisulfonic acid, bromobenzene-2,4,6-trisulfonic acid, fluorobenzene-2, 4,6-trisulfonic acid, toluene-2,4,6-trisulfonic acid, ethylbenzene-2,4,6-trisulfonic acid and the like can be mentioned. Among the above aromatic polysulfonic acids, especially benzene-1,3-disulfonic acid and benzene-1,
3,5-trisulfonic acid is preferred. In the present invention, these aromatic polysulfonic acids may be used alone or in combination of two or more. The amount of the aromatic polysulfonic acid used is not particularly limited as long as it is used in a catalytic amount and can be appropriately selected from a wide range, but is usually about 0.5 to 10 mol%, more preferably 2% with respect to the sulfonating agent. ~ 5
It is recommended to use about mol%. Even if the amount of the aromatic polysulfonic acid used is increased, it does not adversely affect the reaction, but from the economical viewpoint, it is preferably 10 mol% or less. Such aromatic sulfonic acid may be a commercially available product, or a crude product obtained by synthesizing benzene, halogenated benzene or alkylbenzene and a sulfonating agent according to a conventional method, or a purified product thereof. In the present invention, since the above aromatic polysulfonic acid can exert a desired effect even when used in a small amount, there is almost no economical problem even if the aromatic polysulfonic acid is discarded after the reaction, but it is separated from the target product as necessary. It can be reused later.

In the present invention, the dehydration reaction can be easily carried out according to a conventional method, and is usually carried out while azeotropically distilling by-produced water together with mesitylene under stirring to separate and remove water and reflux mesitylene. At this time, the dehydration reaction usually proceeds at about 120 ° C or higher, and the temperature of the reaction system rises from 140 ° C to about the boiling point of mesitylene (165 ° C) as the reaction progresses. Since mesitylene can be azeotropically distilled with water produced as a by-product to remove the water out of the system, it is not necessary to use any other azeotropic agent. Since the reaction medium is a single component of mesitylene, the reaction operation and recovery operation are easy. The suspension state of the reaction system can be maintained by using an ordinary stirring device without aggregation or precipitation, and no special stirring device is required. The termination of the reaction can be easily known by stopping the by-product of water. According to the present invention, the dehydration reaction proceeds remarkably rapidly and is completed in only a few hours, usually 3 to 5 hours. With the progress of the dehydration reaction, 2,4′-DDS is by-produced, but if the temperature of the reaction system is higher than the isomerization temperature, 4,4′-DDS will be produced.
-Isomerized to DDS. That is, the reaction proceeds to some extent, and in the steps, the dehydration reaction and the isomerization reaction proceed in parallel.

The slurry-like reaction mixture thus obtained is distilled at a liquid content, or if necessary, at a temperature which is easy to handle, for example,
After lowering the temperature to about 100 ℃, solid-liquid separation can be easily performed by decantation, excess, etc. The solid obtained is a dry, finely crystalline powder mixture. Further, for example, by purging the reaction mixture into caustic soda water to form an aqueous solution in which the product is dissolved as a sodium salt and then leaving it to stand still, it is possible to easily perform liquid separation separation into an upper phase mesitylene and a lower phase aqueous solution.
Further, the sodium salt aqueous solution obtained by purging the aqueous solution or the crystalline powder mixture into caustic soda water is subjected to activated carbon filtration and salting out for decolorization as necessary to obtain 4,4′-D.
If only the monometal salt of DS is precipitated and isolated, and then purified by acid treatment, it can be isolated and obtained as a 4,4'-DDS high-purity purified product (these purification methods are described in, for example, JP-A-64). -50855). On the other hand, the mesitylene separated from the product as described above is colorless and transparent and can be reused as it is.

After performing the dehydration reaction as described above, DDS
In a suspended state and / or in a state where the liquid content of the reaction system is removed to give a solid, and heated to a temperature above the isomerization temperature to produce a by-product 2.
By advancing the isomerization reaction of 4'-DDS to 4,4'-DDS, 4,4'-DDS can be obtained with higher purity and higher yield. The above isomerization reaction is carried out in a state where DDS is suspended in mesitylene or in a solid state from which mesitylene has been removed.In mesitylene, it can be easily agitated with an ordinary agitator without causing aggregation or precipitation. Can be isomerized to
Further, the solid from which the liquid component has been removed can be subjected to isomerization with an ordinary stirring device in the state of a smooth and easy-to-stir crystal powder, and no special special stirring device is required. Further, in the suspension or solid state reaction system during the isomerization reaction, phenolsulfonic acid produced as a reaction intermediate of the dehydration reaction or used as a sulfonating agent, and the general formula (1) used in the degreasing reaction process Aromatic polysulfonic acid of the present exists in a state of being adsorbed on DDS, and these act well as an acid catalyst for promoting the isomerization reaction. Suppress life. As a result, the above-mentioned isomerization reaction usually takes 2 to 4 hours.
It is completed in about an hour, and 4,4'-DDS can be obtained in a higher yield.

In the present invention, when proceeding with isomerization in a state where DDS is suspended, it may be carried out as it is after the dehydration reaction, or while removing a part of the liquid or distilling the liquid. it can. In the latter case, the liquid may be distilled off in the course of the isomerization reaction to isomerize DDS as a solid, or all the liquid may be distilled off at the same time as the completion of the isomerization reaction. In the case of, it is not necessary to perform a separate drying step. It is also possible to remove the liquid component prior to the isomerization reaction and make DDS a solid to be subjected to the isomerization reaction.

The method for removing the liquid component is not particularly limited, and known methods may include, for example, a method of evaporating under a normal pressure or a reduced pressure, an overpressure, and the like.

In the present invention, the isomerization reaction in the suspension state is usually carried out in the same reactor following the dehydration reaction with stirring under normal pressure or reduced pressure, but it may be carried out in another reactor. . The reaction temperature is about 120 ° C or higher, more preferably 1
It is about 40-165 ℃. Stirring can be easily performed even when the liquid is distilled off, and the suspension state of the reaction system can be kept good.

In the present invention, when proceeding the isomerization reaction in the solid state from the beginning of the reaction, the reaction mixture after the dehydration reaction,
For example, it is carried out by heating the solid obtained by solid-liquid separation according to the past method, decantation method, flash drying method or the like. The above solid is in the state of a smooth, fine crystal powder, and isomerization proceeds in that state. Further, when the isomerization is carried out in a suspension state while distilling off the liquid fraction as described above, and substantially all of the liquid fraction is distilled off before the completion of the isomerization reaction, the obtained solid is It is also possible to continue heating to complete the isomerization reaction.

In the present invention, when the product obtained by performing the isomerization reaction under reduced pressure is taken out as a solid under normal pressure, it is preferable to use an inert gas such as nitrogen in order to prevent air oxidation of the product.

The isomerization reaction in solid form is carried out in a closed or open container under normal pressure or reduced pressure at about 120 to 200 ° C, more preferably
It is heated to about 140 to 180 ° C and stirred if necessary. When the above isomerization reaction is allowed to proceed with stirring, it can be easily carried out by an ordinary powder handling device such as a vacuum dryer. In the present invention, the isomerization reaction may be carried out in the air, but it is preferably carried out in an atmosphere of an inert gas such as nitrogen.

The product thus obtained is a liquid crystal-free fine-grained powdery mixture containing 4,4′-DDS in high purity, and the yield of 4,4′-DDS is remarkable. It will be expensive.
The obtained crystal powder mixture can be easily made into a purified product of 4,4'-DDS by the above-mentioned appropriate purification method, for example, the method described in JP-A-64-50855, if necessary.

Examples The following examples are given to further clarify the features of the present invention.

The compositions of products in Examples and Comparative Examples were confirmed by high performance liquid chromatography.

Example 1 To a mixture of 197.6 g (2.10 mol) of phenol, 200 ml of mesitylene and 11.9 g (0.05 mol) of benzene-1,3-disulfonic acid, 100.0 g (1.00 mol) of 98.1% sulfuric acid was added dropwise with stirring. Then, the temperature was raised by heating in an oil bath, and the reaction product began to boil at around 145 ° C. and distillation started. The distillate was condensed with a condenser and separated into two phases with a trap. The upper organic phase was continuously returned to the reaction system. Approximately 4 hours after the distillation started, the temperature of the reaction system was 165 ° C., and the amount of water in the lower phase removed by the trap was 38 ml, and both were constant. The composition of the product thus obtained has a weight ratio of 4,4′-DDS: 2,4 ′.
-DDS = 97.9: 2.1. The yield was 99.2% with respect to sulfuric acid as a total of the above two components, and was 97.1% with 4,4′-DDS.

Example 2 In Example 1, benzene-1,3-disulfonic acid 0.05
A product was obtained in the same manner except that 0.05 mol of benzene-1,3,5-trisulfonic acid (containing 20% disulfonic acid) was used instead of mol. The composition of the obtained product is 4,
4'-DDS: 2,4'-DDS = 97.5: 2.5. The yield was 99.3% with respect to sulfuric acid as a total of the above two components.
-DDS was 96.8%.

Example 3 Benzene-1,3-disulfonic acid 0.05 in Example 1
A product was obtained in the same manner except that 0.05 mol of chlorobenzene-2,4-disulfonic acid (containing 40% of monosulfonic acid) was used instead of the mol. The composition of the obtained product was 4,4'-DDS: 2,4'-DDS: tri isomer = 96.8: 3.0: 0.2 by weight. The yield was 99.2% with respect to sulfuric acid as a total of the above three components, and was 96.0% with 4,4′-DDS.

Example 4 Benzene-1,3-disulfonic acid 0.05 in Example 1
A product was obtained in the same manner except that 0.05 mol of toluene-2,4-disulfonic acid was used instead of mol. The composition of the obtained product was 4,4′-DDS: 2,4′-DDS: tri body = 9 by weight.
It was 6.6: 3.0: 0.4. The yield was 99.2% with respect to sulfuric acid as a total of the above three components, and was 95.8% with 4,4′-DDS.

Example 5 Following the same operation as in Example 1, the reaction system was charged with 12
0 ml was collected, and the mixture was kept stirred under reflux at 165 ° C. for 3 hours. The composition of the obtained product was 4,4′-DDS: 2,
4'-DDS = 98.1: 1.9. The yield was 99.3% with respect to sulfuric acid as a total of the above two components, and 97.4% with 4,4′-DDS.
Met.

Example 6 Following the same operation as in Example 1, the oil bath temperature was changed to 165 ° C.
It was fixed for 30 minutes, and by adjusting the degree of vacuum of the reaction system, it took 30 minutes to recover substantially all of the liquid content. Then, the pressure was returned to normal pressure, and the temperature of the oil bath was kept at 165 ° C. and the temperature was kept for 3 hours to complete the isomerization reaction. The composition of the obtained product is 4,
4'-DDS: 2,4'-DDS = 98.8: 1.2. The yield was 99.5% with respect to sulfuric acid as a total of the above two components, and was 4,4 '.
-DDS was 98.3%.

Comparative Example 1 A product was obtained in the same manner as in Example 1 except that benzene-1,3-disulfonic acid was not used and the reaction was carried out for about 5 hours after the start of distillation. The composition of the product obtained is
Weight ratio of 4,4′-DDS: 2,4′-DDS: tri body = 89.3: 9.0: 1.7
Met. The yield was 96.2 in total for the above three components, based on sulfuric acid.
%, And 85.9% in 4,4′-DDS.

Comparative Example 2 100.0 g phenol (1.06 mol), 139 ml ISOPAR
H (trademark, saturated aliphatic hydrocarbon), and as an azeotropic agent 8.
7 ml of ISOPAR E (trademark, saturated aliphatic hydrocarbon) was added to a 250 ml three-necked flask (under N ₂ atmosphere) equipped with a thermometer, a dropping funnel, a mechanical stirrer, an oil bath, and a sampling port and a Dean-Stark trap. ).

52.1 g of sulfuric acid (0.53 mol) was added drop by drop at 100 ° C. for 30 minutes.

Next, the temperature of the reaction mixture was raised to start the reaction. The distillate contains a considerable amount of phenol in addition to water and the azeotropic agent, and since phenol does not dissolve in the azeotropic agent, the azeotropic agent phase, the phenol-saturated aqueous phase and the water-saturated phenol are trapped more than the upper phase in the trap. It was divided into three phases. The amount of distillate gradually decreased with the progress of the reaction, and the amount of distillate drastically decreased 1 hour after the temperature was raised to 170 ° C., and almost completely stopped in 2 hours, and the reaction was stopped. At this stage, the total amount of by-product water was 10 g, and the reaction rate was low.

Therefore, in order to reduce the loss of a considerable amount of phenol distilled out of the system, the phenol phase is returned to the system, and the azeotropic agent is added to the system several times to react while maintaining the reaction medium composition. Was advanced.

The composition of the final product obtained 16 hours and 20 minutes after the start of heating was 4,4′-DDS: 2,4′-DDS: tri isomer = 95.1: 2.9: 2.0. The yield of 4,4'-DDS with respect to sulfuric acid was 80%.

The reaction could not proceed any further.

Claims (2)

[Claims] 1. When dehydrating a phenol and a sulfonating agent to produce 4,4'-dihydroxydiphenylsulfone, the reaction is carried out while suspending dihydroxydiphenylsulfone produced using mesitylene as a reaction medium in mesitylene. With the general formula in the reaction system [Wherein X represents a halogen atom or an alkyl group having 1 or 2 carbon atoms, n represents 0, 1 or 2 and m represents 2 or 3], and an aromatic polysulfonic acid represented by the formula is present. And a method for producing high-purity 4,4'-dihydroxydiphenyl sulfone. 2. After the dehydration reaction according to claim 2, in a state in which dihydroxydiphenyl sulfone is suspended and / or in a state in which substantially all of the liquid component is removed to give a solid, 2.
Further heating of 4'-dihydroxydiphenylsulfone to isomerization temperature of 4,4'-dihydroxydiphenylsulfone to a temperature higher than the isomerization temperature of 2,4'-dihydroxydiphenylsulfone
A process for producing high-purity 4,4'-dihydroxydiphenyl sulfone, which comprises advancing an isomerization reaction to 4,4'-dihydroxydiphenyl sulfone.