JP6773448B2 - Method for producing high-purity 2,5-dichloro-p-xylene - Google Patents

Description

The present invention relates to a method for producing high-purity 2,5-dichloro-p-xylene.

2,5-Dichloro-p-xylene (hereinafter, also referred to as "25DCPX") has been proposed to be used as a substitute for polyphenylene sulfide, which is a highly functional resin, and p-dichlorobenzene, which is a raw material for polyphenylsulfone. 25DCPX can be synthesized by reacting p-xylene with chlorine gas in the presence of a catalyst. In this synthetic method, the production of chloro-p-xylene other than 25DCPX, which is a by-product, is unavoidable, and in particular, 2,3-dichloro-p-xylene (hereinafter, also referred to as 23DCPX), which is an isomer of 25DCPX, is produced. Generate a lot.

In the above synthesis method, a method of reducing the amount of 23DCPX that is not the target compound is being studied, and a type of reaction catalyst and a method of using a co-catalyst together are also being studied. For example, in Example 1 of Patent Document 1, when p-xylene is chlorinated using ferrous sulfide as a catalyst, a reaction is produced in which the production ratio of 25DCPX and 23DCPX is 25DCPX: 23DCPX = 77.1: 15.6. It is described that a product was obtained, and that the reaction product was mixed with isopropyl alcohol at about 60 ° C., then cooled and crystallized to obtain 25 DCPX having a purity of 93.5%.
Further, in Example 2 of Patent Document 2, the production ratio of 25DCPX and 23DCPX is 25DCPX: by chlorinating p-xylene using antimony trichloride as a catalyst and bis (p-chlorophenyl) sulfide as a co-catalyst. It is described that a reaction product of 23DCPX = 80.9: 13.8 was obtained, and that when this reaction product was crystallized with isopropyl alcohol, 25DCPX was obtained with a purity of 90% or more. ..

Special Publication No. 59-53246 Special Publication No. 60-26773

In recent years, in order to enhance the function of synthetic resin and obtain a resin material having higher performance, 25DCPX used as a raw material is required to have a high purity of 99.9% or more. However, the purity of 25DCPX obtained by the conventional method including the techniques described in Patent Documents 1 and 2 is only about 95%.

Since chlorination of p-xylene is a sequential reaction in which chlorine is sequentially introduced, as described above, in addition to the target 25DCPX and its isomer (23DCPX), a plurality of types of chloro having a different number of chlorines from 25DCPX. A mixture with chemical-p-xylene is produced. Among them, monochloro-p-xylene, trichloro-p-xylene and tetrachloro-p-xylene have a large difference in boiling point from 25DCPX and can be easily separated from 25DCPX by distillation treatment. However, 23DCPX, which is an isomer of 25DCPX, has a boiling point close to that of 25DCPX, and it is not easy to separate and remove 23DCPX by distillation. Although it is possible to increase the purity of 25DCPX by the recrystallization treatment, it is still necessary to repeat the recrystallization treatment in order to achieve the desired high purity. In this case, the purification loss is large and the yield deteriorates.

Therefore, the present invention provides a method for producing high-purity 2,5-dichloro-p-xylene capable of obtaining high-purity 2,5-dichloro-p-xylene having a purity of 99.9% or more in high yield. Is the subject.

In view of the above problems, the present inventors have repeatedly studied the degree of chlorination in the chlorination reaction of p-xylene and the combination of the catalyst and the co-catalyst in producing 2,5-dichloro-p-xylene. As a result, a specific combination was adopted for the catalyst and co-catalyst used in the chlorination reaction, and the degree of chlorination in the chlorination reaction (the number of moles of chlorine replaced with 1 mol of p-xylene) was increased to a specific range. In this case, it was found that the produced 23DCPX can be changed to a trichloro compound preferentially over 25DCPX. That is, in the presence of a specific catalyst and a co-catalyst, the present inventors raise the degree of chlorination to a specific level and carry out a chlorination reaction of p-xylene to produce a dichloro-p-xylene isomer. It has been found that 23DCPX can be preferentially chlorinated to a trichloro form, and as a result, the proportion of 23DCPX in the isomer ratio of dichloro-p-xylene can be effectively reduced while ensuring a sufficient absolute amount of 25DCPX. It was. Trichloro-p-xylene has a large difference in boiling point from dichloromethane, and both can be easily separated by distillation. Therefore, the desired high-purity 25DCPX can be obtained in a small number of separation treatment steps, and the yield of the high-purity 25DCPX can be greatly increased.
The present invention has been completed based on these findings.

That is, the above problem was solved by the following means.
[1]
In the presence of a catalyst composed of ferric chloride and / or antimony trichloride and a co-catalyst composed of diarylsulfide, p-xylene is reacted with chlorine to bring the p-xylene to a degree of chlorination of 2.2 to 2.6. The resulting reaction product is subjected to (I) distillation treatment or (II) combination of distillation treatment and recrystallization treatment to achieve 2,5-dichloro-p-xylene having a purity of 99.9% or more. A method for producing high-purity 2,5-dichloro-p-xylene, which comprises obtaining.
[2]
The method for producing high-purity 2,5-dichloro-p-xylene according to [1], wherein the diaryl sulfide is diphenyl sulfide.
[3]
The high according to [1] or [2], wherein the reaction product obtained by chlorination having a degree of chlorination of 2.4 to 2.6 is subjected to the distillation treatment of (I). A method for producing pure 2,5-dichloro-p-xylene.
[4]
[1] or [2], wherein the reaction product obtained by chlorination having a degree of chlorination of 2.2 to 2.3 is subjected to the following steps (a) and (b). A method for producing high-purity 2,5-dichloro-p-xylene.
Step (a)
A step of separating a dichloroparaxylene mixture containing 2,5-dichloro-p-xylene and 2,3-dichloro-p-xylene from the reaction product by a distillation treatment, and a step (b).
A step of obtaining 2,5-dichloro-p-xylene having a purity of 99.9% or more from the dichloroparaxylene mixture by recrystallization treatment.
[5]
In the method for producing high-purity 2,5-dichloro-p-xylene, the yield of high-purity 2,5-dichloro-p-xylene having a purity of 99.9% or more is higher than that of p-xylene used as a raw material. The method for producing high-purity 2,5-dichloro-p-xylene according to any one of [1] to [4], which is 30% or more.
[6]
Obtaining 2,5-dichloro-p-xylene having a purity of 99.9% or more from the chloro-p-xylene mixture obtained by the method for producing the chloro-p-xylene mixture according to (i) or (ii) below. A method for producing high-purity 2,5-dichloro-p-xylene, which comprises the above.
(I)
In the presence of a catalyst composed of ferric chloride and / or antimony trichloride and a co-catalyst composed of diarylsulfide, p-xylene is reacted with chlorine to bring the p-xylene to a degree of chlorination of 2.4 to 2.6. In the peak area ratio of the gas chromatograph, the ratio of 2,5-dichloro-p-xylene in the total chloro-p-xylene is 40% or more, and the ratio of 2,3-dichloro-p-xylene is 0. A method for producing a chloro-p-xylene mixture, which comprises obtaining a chloro-p-xylene mixture having a content of 3% or less.
(Ii)
In the presence of a catalyst composed of ferric chloride and / or antimony trichloride and an auxiliary catalyst composed of diarylsulfide, p-xylene is reacted with chlorine to bring the p-xylene to a degree of chlorination of 2.2 to 2.3. In the peak area ratio of the gas chromatograph, the ratio of 2,5-dichloro-p-xylene in the total chloro-p-xylene is 65% or more, and the ratio of 2,3-dichloro-p-xylene is 10%. characterized in that to obtain the following chlorination -p- xylene mixtures, prepared how the chlorination -p- xylene mixtures.

In the present specification, "%" and "part" representing the composition, purity, amount used, and yield are based on moles unless otherwise specified.

According to the method for producing high-purity 25DCPX of the present invention, high-purity 2,5-dichloro-p-xylene having a purity of 99.9% or more can be obtained in good yield and operationally efficiently.

Preferred embodiments of the present invention will be described below.
<Method for producing high-purity 2,5-dichloro-p-xylene>
As described above, by the chlorination reaction of p-xylene that reacts p-xylene with chlorine in the presence of a catalyst (and co-catalyst), the target 25DCPX, its isomer 23DCPX, and chlorine A mixture with chloro-p-xylene (monochromo-p-xylene, trichloro-p-xylene and tetrachloro-p-xylene) having different numbers of substitutions (hereinafter referred to as chloro-p-xylene mixture) is produced. To.
In the method for producing high-purity 25DCPX of the present invention, ferric chloride and / or antimony trichloride is used as a catalyst, and diarylsulfide is used as a co-catalyst. By reacting p-xylene with chlorine in the presence of these catalysts and co-catalysts under chlorination conditions of 2.0 to 2.8 degree of chlorination, a sufficient amount of 25DCPX can be produced, and at the same time, 25DCPX. 23DCPX, which is an isomer of the above, can be preferentially converted into a trichloroform. As a result, the purity of the chlorination reaction product (mixture of p-xylene dichlorooxide and trichlorooxide), which is easily separated, is 99 by simply distilling the product, or by performing the recrystallization treatment in addition to the distillation treatment, for example, once. It is possible to obtain 25 DCPX of 9.9% or more. That is, the desired extremely high-purity 25DCPX can be obtained in a high yield.

-Catalyst-
In the chlorination reaction in the present invention, ferric chloride and / or antimony trichloride is used as a catalyst. That is, ferric chloride may be used as a catalyst, antimony trichloride may be used, or ferric chloride and antimony trichloride may be used in combination.
In the present invention, the amount of the catalyst used with respect to 100 parts of p-xylene as a substrate is preferably 0.01 to 10.0 parts, more preferably 0.01 to 1 part.
The present invention employs a catalytic system that combines ferric chloride and / or antimony trichloride, which is a catalyst, with diarylsulfide, which is a co-catalyst, which will be described later.

-Cocatalyst-
The aryl group in the diarylsulfide used as a co-catalyst is preferably a phenyl group or a substituted phenyl group. As the substituent in such a substituted phenyl group, a halogen atom (fluorine, chlorine, bromine, iodine) or a lower alkyl group having 1 to 4 carbon atoms is preferable. In the present invention, since the co-catalyst itself is chlorinated during the chlorination reaction, inexpensive and easily available diphenyl sulfide can be used. In addition, when it is simply referred to as "diphenyl sulfide" in this specification, it means an unsubstituted diphenyl sulfide.
In the chlorination reaction in the present invention, the ratio of the amount of the catalyst used and the amount of the co-catalyst used is preferably a molar ratio of catalyst: co-catalyst = 1:10 to 10: 1, more preferably 1: 5 to 5: 1. Preferably, 1: 2 to 2: 1 is even more preferable.

-Reaction conditions-
The reaction temperature in the chlorination reaction in which p-xylene is reacted with chlorine is usually 15 to 100 ° C, more preferably 15 to 60 ° C. Chlorine can be carried out using gaseous or liquid chlorine.
The reaction time in the chlorination reaction varies depending on the reaction scale and the capacity of the chlorine blowing facility, but is usually 2 to 40 hours.
In the present invention, the chlorination reaction can be carried out in the absence of a solvent, or if necessary, a stable solvent can be used under the reaction conditions of the present invention. Examples of the solvent that can be used include halogenated hydrocarbons such as dichloromethane, chloroform, 1,2-dichloroethane, and 1,2-dichloropropane, trifluoromethylbenzene, p-chlorotrifluoromethylbenzene, and o-chlorotrifluoro. Fluorine-based aromatic hydrocarbons such as methylbenzene can be mentioned. These can be used alone or in combination of two or more. When a solvent is used, the amount of the solvent used per mole of p-xylene is preferably 100 ml or more, more preferably 200 to 2000 ml.

In the chlorination reaction of the present invention, the degree of chlorination (the number of moles of chlorine substituted with 1 mol of p-xylene as a substrate) is 2.0 to 2.8. The degree of chlorination is preferably 2.1 to 2.7, more preferably 2.2 to 2.6.
Further, the degree of chlorination can be appropriately adjusted within the above range according to the separation treatment method for purifying 25DCPX to a purity of 99.9% or more. For example, when it is desired to obtain 25DCPX having a purity of 99.9% or more only by distillation treatment, the degree of chlorination is 2.4 to 2.8 (preferably 2.4 to 2.7, more preferably 2.4 to 2.4). 2.6) is preferable. By doing so, the content of 25DCPX in the chlorination-p-xylene mixture obtained by the chlorination reaction (that is, the ratio of 25DCPX to the total chloro-p-xylene) is 40% or more (preferably 45% or more). , More preferably 48% or more), and the content of 23DCPX can be highly reduced to 0.3% or less (preferably 0.2% or less, more preferably 0.1% or less). .. Therefore, it is possible to obtain 25 DCPX having a purity of 99.9% or more in an excellent yield only by the distillation treatment.
Further, when the 25DCPX is separated by combining the distillation treatment and the recrystallization treatment, the degree of chlorination is preferably 2.0 to 2.3. By chlorinating within the range of this degree of chlorination, the content of 25DCPX in the obtained chlorophyll-p-xylene mixture is increased to 65% or more (preferably 70% or more), and the content of 23DCPX is increased. The amount can be reduced to 10% or less (preferably 8.5% or less, more preferably 7.0% or less, still more preferably 6.0% or less). As a result, 25 DCPX having a purity of 99.9% or more can be obtained in a high yield by a separation treatment that combines a distillation treatment and a recrystallization treatment. The separation treatment of 25DCPX, which is a combination of the above distillation treatment and recrystallization treatment, preferably comprises the following steps (a) and (b).

Step (a)
A step of separating the dichloroparaxylene mixture containing 25DCPX and 23DCPX from the chlorochlorinated-p-xylene mixture by a distillation treatment, and step (b).
A step of separating 2,5-dichloro-p-xylene from the dichloroparaxylene mixture by a recrystallization treatment.

A method (distillation treatment, recrystallization treatment) for separating 25DCPX from the reaction product (chloroidation-p-xylene mixture) obtained by the chlorination reaction will be described.
(Distillation)
The method of distillation treatment is not particularly limited, and a normal method can be adopted. For example, distillation is performed under reduced pressure in a facility equipped with a rectification column to distill from the top of the column. 25DCPX can be separated by controlling the distillate at the temperature at the top of the column and separating it from the monochloroform.

(Recrystallization treatment)
The method for separating 25DCPX by recrystallization is also not particularly limited, and a usual method can be adopted. As the recrystallizing solvent, for example, an alcohol is preferable, a lower alcohol having 5 or less carbon atoms is more preferable, and any one selected from methanol, ethanol, 1-propanol, 2-propanol and various isomers butanol is more preferable, and 2-propanol is more preferable. Is particularly preferable. The amount of the recrystallization solvent is preferably 0.25 to 10.0 g, more preferably 0.5 to 5.0 g per 1 g of the crude product of 25 DCPX.

The yield of 25DCPX having a purity of 99.9% or more obtained by the method for producing high-purity 25DCPX of the present invention is based on p-xylene used as a raw material (when the number of moles of p-xylene is 100%). 30% or more is preferable, 35% or more is more preferable, and 40% or more is further preferable.
The above yield is a value calculated by the following formula.
Yield (%) = 100 x (number of moles of 25DCPX with 99.9% purity) / (number of moles of p-xylene used as a raw material)

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not construed as being limited thereto.
The measurement was performed according to the method shown below.
-Measurement of purity and composition ratio of crude product-
The purity and composition ratio were measured by the following measuring device and measuring conditions.
・ Measuring device: Gas chromatography (detector: FID)
Purity (%): (peak area of 25DCPX / total area of all peaks) × 100
-Composition ratio (%): (peak area of each chloro-p-xylene / total area of all peaks) x 100

Example 1
To 3900 g (36.7 mol) of p-xylene in a 5000 ml round bottom flask, 5.96 g (0.036 mol) of ferric chloride and 6.84 g (0.036 mol) of diphenylsulfide were added under stirring. It was. Then, the temperature of the stirring mixture was raised to 30 ° C., and at the same temperature, 6772 g of gaseous chlorine was blown over for 35 hours. The temperature was gradually raised to about 60 ° C. based on the solidification temperature of the reaction mixture. Table 1 below shows the measured values of the degree of chlorination and the ratio of 25DCPX and 23DCPX during that period. As a result of analyzing the reaction mixture (hereinafter referred to as crude product) after completion of the reaction by gas chromatography, it was found to have the following composition.
(Composition ratio of crude product)
Degree of chlorination (number of moles of chlorine replaced with 1 mole of p-xylene) 2.58
25DCPX 50.0%
23DCPX 0.02%
Trichloro-p-xylene 42.7%
Tetrachloro-p-xylene 7.4%
The crude product was purged with nitrogen to remove hydrogen chloride and residual chlorine, and then distilled. The distillation treatment was carried out using a 20-stage rectification column, and 25 DCPX was distilled off from the top of the column under reduced pressure. The distillate was controlled at the column top temperature to obtain 2611 g (yield 40.6% with respect to p-xylene) of 25 DCPX having a purity of 99.97%.

Example 2
To 330 g (3.1 mol) of p-xylene in a 500 ml round bottom flask, 0.50 g (0.003 mol) of ferric chloride and 0.58 g (0.003 mol) of diphenylsulfide were added under stirring. It was. Then, the temperature of the stirring mixture was raised to 30 ° C., and 521 g of gaseous chlorine was blown at the same temperature over 8 hours. The temperature was gradually raised to about 60 ° C. based on the solidification temperature of the reaction mixture. After the chlorination reaction, the crude product was analyzed by gas chromatography and found to have the following composition.
(Composition ratio of crude product)
Degree of chlorination (number of moles of chlorine replaced with 1 mole of p-xylene) 2.21
25DCPX 74.5%
23DCPX 5.1%
Trichloro-p-xylene 19.9%
Tetrachloro-p-xylene 0.5%
The crude product was subjected to nitrogen purging and distillation treatment in the same manner as in Example 1 to obtain 255.6 g of crude 25DCPX having a purity of 93.9%. To this, 281.8 g of isopropyl alcohol was added and heated to 60 ° C. to dissolve the crystals, and then cooled to 19 ° C. for crystallization to produce 187 g (yield 53.4%) of 25DCPX having a purity of 99.9%. Obtained.

Example 3
To 40 g (0.38 mol) of p-xylene in a 100 ml round bottom flask, 0.09 g (0.0004 mol) of antimony trichloride and 0.07 g (0.0004 mol) of diphenylsulfide were added under stirring. .. Then, the temperature of the stirring mixture was raised to 30 ° C., and at the same temperature, gaseous chlorine was blown over for 7 hours. The temperature was gradually raised to about 60 ° C. based on the solidification temperature of the reaction mixture. After the chlorination reaction, the crude product was analyzed by gas chromatography and found to have the following composition.
(Composition ratio of crude product)
Degree of chlorination (number of moles of chlorine replaced with 1 mole of p-xylene) 2.48
25DCPX 54.0%
23DCPX 0.01%
Trichloro-p-xylene 39.2%
Tetrachloro-p-xylene 6.8%

Comparative Example 1
In Example 3, 0.065 g (0.0004 mol) of ferric chloride was used instead of antimony trichloride, and 0.10 g (0.0004 mol) of dioctyl sulfide was used instead of diphenyl sulfide, and the chlorine blowing time was set. The reaction was carried out in the same manner as in Example 3 except that the change was made from 7 hours to 5 hours. The degree of chlorination was 2.06, and the ratio of 25DCPX to 23DCPX was 25DCPX: 23DCPX = 79.8: 20.4. Further, as a result of analyzing the crude product when chlorine was blown for 2 hours by the same method and the degree of chlorination was 2.75 by gas chromatography, it was found to have the following composition.
(Composition ratio of crude product with chlorination degree 2.75)
25DCPX 31.71%
23DCPX 1.83%
Trichloro-p-xylene 56.50%
Tetrachloro-p-xylene 9.70%
As much as 1.83% of 23DCPX remained in the crude product. With this, it is not possible to obtain 25 DCPX having a purity of 99.9% or more by distillation. Moreover, the content of the target 25DCPX is very small as compared with Examples 1 and 2. Recrystallization increased the purity, but it was clear that the yield was very low, and no further separation was performed.

Comparative Example 2
In Example 3, chlorination was carried out in the same manner as in Example 3 except that 0.0004 mol of ferric chloride and sulfur powder were used instead of antimony trichloride and diphenyl sulfide. The degree of chlorination was 1.28 in 2 hours, and the ratio of 25DCPX to 23DCPX was 25DCPX: 23DCPX = 84.0: 16.0. Further, as a result of analyzing the crude product when chlorine was blown for 6 hours by the same method and the degree of chlorination was 2.82 by a gas chromatograph method, it was found to have the following composition.
(Composition ratio of crude product with chlorination degree 2.82)
25DCPX 28.30%
23DCPX 0.05%
Trichloro-p-xylene 56.27%
Tetrachloro-p-xylene 14.12%
This crude product can be distilled to 25DCPX having a purity of 99.9% or higher. However, it was clear that the yield was very low and no further separation was performed.

As described above, in Comparative Example 1 in which dioctyl sulfide was used as a co-catalyst, 23 DCPX was contained in the crude product as much as 1.83% even if the degree of chlorination was increased to 2.75, and the purity was 99. It is not possible to obtain 25 DCPX of 9% or more. Further, since the amount of 25DCPX produced is small, when the purity of 25DCPX is increased by recrystallization, the yield of 25DCPX is low and the production efficiency is inferior.
Further, in Comparative Example 2 using sulfur powder as a co-catalyst, it is possible to obtain 25 DCPX having a purity of 99.9% or more by distillation. However, in this case as well, the yield is low and the production efficiency is inferior.
On the other hand, in Example 1, in the presence of the catalyst and co-catalyst specified in the present invention, the chlorination reaction of p-xylene was carried out under the chlorination condition of 2.58 degree of chlorination, and then 25DCPX was separated. .. As shown in Table 1, it was found that when the degree of chlorination was 2 or more, the isomer 23DCPX disappeared rapidly and the selectivity of 25DCPX improved. Further, at a chlorination degree of 2.58, the compositions of 25DCPX and 23DCPX in the crude product became 50.0% and 0.02%, and a high yield of 25DCPX having a purity of 99.97% was obtained only by a simple distillation treatment. I was able to get it at.
Further, in Example 2, in the presence of the catalyst and the co-catalyst specified in the present invention, the chlorination reaction of p-xylene was carried out under the chlorination condition of 2.21 degree of chlorination, and then 25DCPX was separated. In this case, when the amount of 25DCPX produced in the crude product was high (74.5%), the amount of 23DCPX produced could be reduced to 5.1%, and the trichloro and tetrachloro compounds were removed by distillation. After that, by subjecting it to a recrystallization treatment, 25 DCPX having a purity of 99.9% could be obtained in a high yield.
In Example 3, 25 DCPX was synthesized by performing a chlorination reaction of p-xylene under chlorination conditions of a chlorination degree of 2.48 in the presence of the catalyst and co-catalyst specified in the present invention. The content of 23DCPX in the obtained crude product could be 0.01%, and the content of 25DCPX could be 54.0%. Therefore, as in Example 1, 25 DCPX having a purity of 99.9% or more can be obtained in a high yield only by a simple distillation treatment.

Reference Example 1 and Comparative Examples 3 to 5
The results of confirming the effectiveness of other Lewis acids (catalysts) and cocatalysts are summarized in Table 2 below. Here, Reference Example 1 is an intermediate analysis result of Example 1.

In Comparative Example 3 in which aluminum trichloride was used as the catalyst, the selectivity of 25DCPX and 23DCPX was worse than that in the case of using iron chloride in Reference Example 1 due to the chlorination reaction, and it is clear that the absolute yield of 25DCPX was inferior. is there.
Further, in Comparative Examples 4 and 5 in which cuprous chloride and zinc chloride were used as catalysts, dichloroization due to the chlorination reaction of p-xylene was very slow, and the production efficiency was inferior.
As described above, 25DCPX having a purity of 99.9% or more is obtained by chlorinating p-xylene at a degree of chlorination within the range specified in the present invention by using a combination of a specific catalyst and a co-catalyst specified in the present invention. Can be obtained in good yield.

Claims (6)

In the presence of a catalyst composed of ferric chloride and / or antimony trichloride and a co-catalyst composed of diarylsulfide, p-xylene is reacted with chlorine to bring the p-xylene to a degree of chlorination of 2.2 to 2.6. The resulting reaction product is subjected to (I) distillation treatment or (II) combination of distillation treatment and recrystallization treatment to achieve 2,5-dichloro-p-xylene having a purity of 99.9% or more. A method for producing high-purity 2,5-dichloro-p-xylene, which comprises obtaining. The method for producing high-purity 2,5-dichloro-p-xylene according to claim 1, wherein the diaryl sulfide is diphenyl sulfide. The high purity 2 according to claim 1 or 2, wherein the reaction product obtained by chlorination having a degree of chlorination of 2.4 to 2.6 is subjected to the distillation treatment of (I). , 5-Dichloro-p-xylene production method. The high amount according to claim 1 or 2, wherein the reaction product obtained by chlorination having a degree of chlorination of 2.2 to 2.3 is subjected to the following steps (a) and (b). A method for producing a purity of 2,5-dichloro-p-xylene.
Step (a)
A step of separating a dichloroparaxylene mixture containing 2,5-dichloro-p-xylene and 2,3-dichloro-p-xylene from the reaction product by a distillation treatment, and a step (b).
A step of obtaining 2,5-dichloro-p-xylene having a purity of 99.9% or more from the dichloroparaxylene mixture by recrystallization treatment. In the method for producing high-purity 2,5-dichloro-p-xylene, the yield of high-purity 2,5-dichloro-p-xylene having a purity of 99.9% or more is higher than that of p-xylene used as a raw material. The method for producing high-purity 2,5-dichloro-p-xylene according to any one of claims 1 to 4, which is 30% or more. Obtaining 2,5-dichloro-p-xylene having a purity of 99.9% or more from the chloro-p-xylene mixture obtained by the method for producing the chloro-p-xylene mixture according to (i) or (ii) below. A method for producing high-purity 2,5-dichloro-p-xylene, which comprises the above.
(I)
In the presence of a catalyst composed of ferric chloride and / or antimony trichloride and a co-catalyst composed of diarylsulfide, p-xylene is reacted with chlorine to bring the p-xylene to a degree of chlorination of 2.4 to 2.6. In the peak area ratio of the gas chromatograph, the ratio of 2,5-dichloro-p-xylene in the total chloro-p-xylene is 40% or more, and the ratio of 2,3-dichloro-p-xylene is 0. A method for producing a chloro-p-xylene mixture, which comprises obtaining a chloro-p-xylene mixture having a content of 3% or less.
(Ii)
In the presence of a catalyst composed of ferric chloride and / or antimony trichloride and an auxiliary catalyst composed of diarylsulfide, p-xylene is reacted with chlorine to bring the p-xylene to a degree of chlorination of 2.2 to 2.3. In the peak area ratio of the gas chromatograph, the ratio of 2,5-dichloro-p-xylene in the total chloro-p-xylene is 65% or more, and the ratio of 2,3-dichloro-p-xylene is 10%. A method for producing a chloro-p-xylene mixture, which comprises obtaining the following chloro-p-xylene mixture.