JP3533352B2 - Method for purifying 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for purifying industrially produced 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile which is useful as a fungicide for agricultural and horticultural use. . More specifically, the present invention relates to 2,4,5,6-tetrachloro
TECHNICAL FIELD The present invention relates to a novel purification method for reducing the content of hexachlorobenzene as an impurity contained in a trace amount in industrial products of 1,3-benzenedicarbonitrile.

[0002]

[Background art and its problems] 2,4,5,6-tetrachloro-
A large amount of 1,3-benzenedicarbonitrile is used as a raw material for agricultural and horticultural germicides (generic name: chlorothalonil, trade name: Daconyl (registered trademark)). 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile is the starting material
It is industrially manufactured at a low cost by a method of heating 1,3-benzenedicarbonitrile to vaporize it, and then chlorinating it by using chlorine gas at a high temperature with activated carbon as a catalyst.

Under the reaction conditions of the above production method, the chlorination reaction of 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile excessively proceeds in a part of the reaction system, resulting in hexachlorobenzene. Is a by-product. The hexachlorobenzene content of industrially produced 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile is usually 500 ppm.
Hexachlorobenzene is toxic even though the amount is as follows, so that further reduction of the content is strongly demanded.

Conventionally, attempts have been made to reduce the content of hexachlorobenzene in industrial products by improving the chlorination conditions, but there is a limit to this. In addition, there is no known economically useful purification method for removing a small amount of hexachlorobenzene as an impurity from industrially produced 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile. Has not been done.

As a conventional purification method, for example, a mixture of 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile and hexachlorobenzene as an impurity is added under normal pressure or reduced pressure. 2,4,5,6-Tetrachloro-1,3-benzenedicarbonitrile can be mentioned as a method of heating above the melting point or above the boiling point and performing fractional distillation for purification. When heated above the melting point of 6-tetrachloro-1,3-benzenedicarbonitrile, decomposition or polymerization of 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile occurs in the system, There is a very undesirable problem of obtaining by-products.

Another conventional purification method is a method utilizing a recrystallization method. In the case of this purification method,
It utilizes the difference in solubility depending on the temperature when the system temperature is raised once and then cooled, but 2,4,5,6-tetrachloro-
There is a problem that a large amount of 1,3-benzenedicarbonitrile remains on the filtrate side. To obtain a high yield, it is necessary to further concentrate the filtrate to precipitate 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile. There is a problem in that hexachlorobenzene in the recrystallization solvent is in a state of being concentrated to a higher concentration than in the first purification, and the efficiency is significantly lower than in the first purification. Furthermore, there is a problem that purification requires a long time because a plurality of purification steps are performed, and that equipment and labor are required for recovery and purification of the solvent from the filtrate obtained in each purification step.

Therefore, there is a demand for a more efficient energy-saving and resource-saving type refining method for industrially produced 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile.

[0008]

OBJECT OF THE INVENTION The present invention is useful as a fungicide for agriculture and horticulture.
It is an object of the present invention to provide an efficient purification method capable of reducing the content of hexachlorobenzene as an impurity contained in a small amount in an industrial product of 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile. Has an aim.

[0009]

SUMMARY OF THE INVENTION 2,4,5,6-Tetrachloro-1,3 according to the present invention
-The purification method of benzenedicarbonitrile is 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile (hereinafter,
"Compound (A)") in an amount of 95% by weight or more and hexachlorobenzene as an impurity of 50% or more.
The crude mixture (I) containing an amount of 0 ppm or less at 90 to 220 ° C.
At a temperature of 1 to 1000 mmHg and solid and gas phases
Maintain coexisting purification system, 10% by weight of the unpurified mixture
By separating and removing the following amount as a gaseous substance (B), hexachlorobenzene contained as an impurity in the unpurified mixture is removed in an amount of 20% by weight or more to obtain high purity.
The feature is that 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile is obtained.

Further, 2,4,5,6-tetrachloro according to the present invention
The method for purifying -1,3-benzenedicarbonitrile is 2,4,5,6.
-Tetrachloro-1,3-benzenedicarbonitrile (hereinafter,
"Compound (A)") and contains hexachlorobenzene as an impurity with respect to Compound (A).
The crude mixture (II) containing 500 ppm or less and containing chlorine and / or hydrogen chloride is maintained at a temperature of 90 to 220 ° C. in a purification system in which a solid phase and a gas phase coexist. A mixture containing 10% by weight or less of the compound (A) in the mixture is separated and removed as a gaseous substance (C) to remove hexachlorobenzene contained as an impurity in the unpurified mixture in an amount of 20% by weight or more. Then, high-purity 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile is obtained.

[0011] Purification methods for both said, the purification system, nitrogen, air, water, chlorine, hydrogen chloride, while circulating any one or more of a mixture of carbon dioxide, the 90 ~ 200 ° C.
It is preferable to carry out at temperature .

[0012]

[0013]

DETAILED DESCRIPTION OF THE INVENTION The method for purifying 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile according to the present invention will be specifically described below. 2,4,5,6-Tetrachloro-1,3-benzenedicarbonitrile used in the purification method of the present invention is a known compound, and an agricultural and horticultural fungicide (generic name:
Chlorothalonil, trade name: Daconyl (registered trademark)) is produced in large quantities as a drug substance.

As described above, this compound is a starting material 1,
It is industrially manufactured at a low cost by heating 3-benzenedicarbonitrile to vaporize it, and then chlorinating it with activated carbon as a catalyst at a high temperature and using chlorine gas. Usually, by adjusting the chlorination conditions, the amount of hexachlorobenzene in this industrial product is 500 ppm or less with respect to 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile.

The present inventor has determined the content ratio of hexachlorobenzene as an impurity contained in 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile produced industrially at low cost. We have diligently studied the purification method to reduce the amount.
Further, since this industrial product is produced by a chlorination reaction using chlorine gas and is mixed with chlorine and / or hydrogen chloride, a product from which this chlorine and / or hydrogen chloride has been removed (unpurified mixture (I) ) And the unpurified product that is not removed (unpurified mixture (II)) were investigated.

As a result, the crude mixture (I) or (I
The present invention has been completed by finding that it is possible to effectively reduce hexachlorobenzene by simply maintaining the purification system containing I) under predetermined conditions and removing the obtained gas. The purification method of the unpurified mixture (I) is industrially produced, and 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile (compound (A)) is contained in an amount of 95% by weight or more. In addition to containing 50% of hexachlorobenzene as an impurity
It includes a step of maintaining the purification system at a temperature of 80 ° C. or higher and a melting point of the compound (A) or lower under a pressure of 1 to 1000 mmHg, the unpurified mixture containing 0 ppm or less.

At this time, 10 parts by weight of the crude mixture (I)
% Or less, preferably 5% by weight or less, more preferably 2% by weight or less is separated and removed as the gaseous substance (B). As a result, hexachlorobenzene contained as an impurity in the unpurified mixture (I) is 20 wt% or more, preferably 30 wt% or more, more preferably 40 wt% or more, and particularly
Removed in an amount of 40 wt% or more and 90 wt% or less, for example, 200 ppm
The following, preferably 40ppm or less, more preferably containing 20ppm or less hexachlorobenzene, high purity 2,4,
5,6-Tetrachloro-1,3-benzenedicarbonitrile is obtained.

The method for purifying the unpurified mixture (II) is industrially produced and contains 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile (compound (A)), and An unpurified mixture (II) containing hexachlorobenzene as an impurity in an amount of 500 ppm or less with respect to the compound (A) and containing chlorine and / or hydrogen chloride at 80 ° C. or higher and below the melting point of the compound (A). The process includes maintaining the purification system at the temperature of.

At this time, 10% by weight or less, preferably 5% by weight or less of the compound (A) in the unpurified mixture (II),
More preferably, a mixture containing 2% by weight or less is separated and removed as a gaseous substance (C). As a result, hexachlorobenzene contained as an impurity in the unpurified mixture (II) is 20 wt% or more, preferably 30 wt% or more, more preferably 40 wt% or more, and particularly 40 wt% or more 90 wt%
High-purity for industrial use, removed in the following amounts:
For example, 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile containing 200 ppm or less, preferably 40 ppm or less, more preferably 20 ppm or less of hexachlorobenzene is obtained.

It should be noted that, in any purification method, 40 weight
It is possible to remove hexachlorobenzene in excess of%,
During the purification operation, 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile is vaporized and removed together with hexachlorobenzene, so 2,4,5,6-tetrachloro-1,3- Loss of 3-benzenedicarbonitrile is less than 10% by weight, preferably 5
The amount of hexachlorobenzene to be removed is determined so that it is not more than 2% by weight, more preferably not more than 2% by weight.

In any of these purification methods, nitrogen, air, water, chlorine, hydrogen chloride, carbon dioxide, an organic compound (preferably a halogenated organic compound, more preferably a halogenated organic compound) which is a gas under the above-mentioned purification conditions is used in the purification system. It is preferable to conduct it while circulating any one or a mixture of a plurality of chlorinated organic compounds). These circulating gases act to promote the vaporization of hexachlorobenzene by lowering the concentration of vaporized hexachlorobenzene in the system.

Further, the separated and removed gaseous substance (B) or gaseous substance (C) is subjected to a treatment such as cooling or dissolution in an appropriate solvent outside the purification system in order to facilitate handling. It is preferably made into a liquid, a solution and / or a solid and then recovered. The purification method of the present invention is a method of maintaining a purification system in which a solid phase and a gas phase coexist under predetermined conditions. When an industrial product is obtained as a solid, this system heats the solid at a temperature below the melting point of 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile and vaporizes a part of the solid. Obtained with
When an industrial unrefined product is obtained as a gas, the gas is 2,4,5,6-
This can be achieved by cooling to a temperature below the melting point of tetrachloro-1,3-benzenedicarbonitrile and solidifying a part of the gas.

In such a system, the distribution of each component into each phase is not in an equilibrium state, and rate processes such as solidification, sublimation, and diffusion of hexachlorobenzene proceed in parallel between both phases, so that each component's The ratio of distribution to the solid phase / gas phase depends on the maintenance conditions of the purification system, such as the properties such as the particle size of 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile, temperature, pressure, and the gas to be circulated. It varies depending on the amount. Therefore, it is extremely difficult to predict the operating conditions required to reach the purification target purity within a certain period of time. For example, when a part of the solid is vaporized, the particle size of 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile is large, the temperature as a maintenance condition is low, the pressure is high, When the amount of the circulating gas is small, purification tends to take a long time. When part of the gas is solidified, the loss of 2,4,5,6-tetrachloro-1,3-benzenedicarbonyl tends to increase especially when the temperature is high and the amount of flowing gas is large. is there.

In addition, chlorine and / or hydrogen chloride and hexachlorobenzene and 2,4,5,6-tetrachloro-
In a system in which a plurality of gas components such as 1,3-benzenedicarbonitrile are mixed, the solid phase / gas phase distribution state becomes complicated. Under such circumstances, it is very difficult to predict effective purification conditions. In the present invention, the temperature as a maintenance condition of the purification system, the pressure and the presence or absence of gas to be circulated, of sufficient purity for industrial applications, 2,
Given the purification method for obtaining 4,5,6-tetrachloro-1,3-benzenedicarbonitrile, preferable conditions for performing the treatment within 24 hours will be specifically described.

When an industrial product is obtained as a solid, the purification system containing the solid is heated under predetermined conditions to vaporize a part of the solid to obtain the purification system. In a system in which no gas is passed through this purification system, the pressure during heating is 1 to 760 mmHg, preferably 3 to 760 mmHg, and more preferably 40 to 760 mmHg. The heating temperature is 80 ℃ or higher and 2,4,5,6-tetrachloro
The temperature is not higher than the melting point of -1,3-benzenedicarbonitrile, preferably 90 to 220 ° C, more preferably 100 to 200 ° C. Under these conditions, the most preferable combination is, for example, when the heating pressure is 3 to 40 mmHg, the heating temperature is 90%.
~ 180 ℃, heating temperature is 100 ~ 220 ℃ in the case of heating pressure of 40 ~ 760 mmHg.

Further, in the system in which gas is circulated in the purification system,
The pressure during heating is 1 to 1000 mmHg, preferably 40 to 1000 mmHg
g, more preferably 700 to 900 mmHg. The heating temperature is 8
A temperature not lower than 0 ° C and not higher than the melting point of 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile, preferably 80 to 220
C., more preferably 90 to 200.degree. The most preferable combination is a heating temperature of 80 to 200 ° C when the heating pressure is 40 to 700 mmHg, and a heating temperature of 100 to 200 ° C when the heating pressure is 700 to 900 mmHg.

When the industrial product is obtained as a gas, the purification system is 2, 4,
Cooling to below the melting point of 5,6-tetrachloro-1,3-benzenedicarbonitrile, solidifying part of the gas, and further increasing the system pressure to 700-900 mmHg and the temperature to 2,4,5,6. -Tetrachloro-1,3-benzenedicarbonitrile is maintained at a melting point or lower, preferably 80 to 220 ° C, more preferably 90 to 200 ° C for purification.

As described above, according to the method for purifying 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile of the present invention, industrially produced 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile is purified. 6-tetrachloro-
To remove more than 20% by weight of hexachlorobenzene from 1,3-benzenedicarbonitrile, keep the loss of 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile below 10% by weight. It becomes possible to do it.

[0029]

INDUSTRIAL APPLICABILITY The present invention is 2,4,5,6-tetrachloro industrially produced in large quantities as a raw material for agricultural and horticultural fungicides (generic name: chlorothalonil, trade name: Daconyl (registered trademark)).
Disclosed is a novel purification method capable of reducing the content of harmful impurities such as hexachlorobenzene contained in -1,3-benzenedicarbonitrile.

According to this purification method, industrially advantageous,
The content of the above-mentioned harmful impurities, hexachlorobenzene, can be reduced.

[0031]

The present invention will be described in more detail below with reference to examples. However, these are merely examples for explanation, and the scope of the present invention is determined by the description of the claims. Yes, and is not limited by the description below. In addition, in each example, the content of hexachlorobenzene was quantified by an internal standard method and an absolute calibration curve method using HPLC.

[0032]

Example 1 2,4,5,6-Tetrachloro-1,3-benzenedicarbonitrile (100 g) containing hexachlorobenzene (85 ppm) was added to a 1000 ml flask, and the pressure was reduced to 3 mmHg using a rotary evaporator. Below, it heated at 110 degreeC for 3 hours. A solidified mixture (7.2 g) was obtained from the sublimed gas. Purified as a residue 2,4,5,6-tetrachloro-1,3
-Benzenedicarbonitrile (92.7 g; yield 92.7%) was obtained, the residue containing hexachlorobenzene (38 ppm).

The results are shown in Table 1.

[0034]

Example 2 2,4,5,6-Tetrachloro-1,3-benzenedicarbonitrile (100 g) containing hexachlorobenzene (85 ppm) was added to a 1000 ml flask, and the pressure was reduced to 3 mmHg using a rotary evaporator. Below, it heated at 130 degreeC for 4 hours. A solidified mixture (9.2 g) was obtained from the sublimed gas. Purified as a residue 2,4,5,6-tetrachloro-1,3
-Benzenedicarbonitrile (90.7 g; yield 90.7%) was obtained, the residue containing hexachlorobenzene (39 ppm).

The results are shown in Table 1.

[0036]

Example 3 2,4,5,6-Tetrachloro-1,3-benzenedicarbonitrile (100 g) containing hexachlorobenzene (85 ppm) was added to a 1000 ml flask, and the pressure was reduced to 3 mmHg using a rotary evaporator. Below, it heated at 140 degreeC for 2 hours. A solidified mixture (8.6 g) was obtained from the sublimed gas. Purified as a residue 2,4,5,6-tetrachloro-1,3
-Benzenedicarbonitrile (91.3 g; yield 91.3%) was obtained, the residue containing hexachlorobenzene (44 ppm).

The results are shown in Table 1.

[0038]

Example 4 2,4,5,6-Tetrachloro-1,3-benzenedicarbonitrile (100 g, hereinafter "starting weight") containing hexachlorobenzene (HCB) (85 ppm, hereinafter referred to as "starting HCB content") ) Is added to a 1000 ml flask, and a rotary evaporator is used to reduce the pressure to 1 mm at 120 ° C. under a reduced pressure of 3 mmHg.
Heated for hours. A solidified mixture (1.0 g) was obtained from the sublimed gas, which contained hexachlorobenzene (545 pp).
m) was contained. Purified 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile as a residue (99.0 g; yield 99.
0%) was obtained, and the residue was hexachlorobenzene (52 p
pm). The results are shown in Table 1.

Further, the obtained residue was added to a 1000 ml flask and heated at 130 ° C. for 1 hour under reduced pressure of 3 mmHg using a rotary evaporator. A solidified mixture (0.5 g) was obtained from the sublimed gas which contained hexachlorobenzene (1009 ppm). Purified 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile (98.5 g; yield based on starting weight 98.5%) was obtained as a residue. The residue contained hexachlorobenzene (45 ppm). The results are shown in Table 1.

Furthermore, the obtained residue was added to a 1000 ml flask and heated at 140 ° C. for 1 hour under reduced pressure of 3 mmHg using a rotary evaporator. A solidified mixture (3.3 g) was obtained from the sublimed gas which contained hexachlorobenzene (260 ppm). Purified 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile (95.2g; yield 95.2% based on starting weight) was obtained as a residue.
The residue contained hexachlorobenzene (37 ppm). The results are shown in Table 1.

Further, the obtained residue was added to a 1000 ml flask and heated at 150 ° C. for 1 hour under reduced pressure of 3 mmHg using a rotary evaporator. A solidified mixture (2.1 g) was obtained from the sublimed gas which contained hexachlorobenzene (265 ppm). Purified 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile (93.1 g; yield based on starting weight 93.1%) was obtained as a residue.
The residue contained hexachlorobenzene (25 ppm). The results are shown in Table 1.

[0042]

Example 5 2,4,5,6-Tetrachloro-1,3-benzenedicarbonitrile (100 g) containing hexachlorobenzene (85 ppm) was added to a 1000 ml flask, and the pressure was reduced to 40 mmHg using a rotary evaporator. Below, it heated at 170 degreeC for 1 hour. Mixture (1.4g) solidified from sublimed gas
Was obtained, which contained hexachlorobenzene (715 ppm). Purified as a residue 2,4,5,6-tetrachloro-
1,3-Benzenedicarbonitrile (98.6 g; yield 98.6%) was obtained and the residue contained hexachlorobenzene (43 ppm).

[0043]

Example 6 Purification by adding air 100 parts of 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile (100 g) containing hexachlorobenzene (85 ppm) were added.
Add it to a 0 ml flask, and while passing air to continuously remove the gas generated in the system, remove it at 40 mmHg and 140 ° C.
Heated for hours. A solidified mixture (7.8 g) was obtained from the sublimed gas, which was hexachlorobenzene (206 p
pm). Purified 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile as a residue (92.1 g; yield 92.
1%) was obtained, and this residue was converted to hexachlorobenzene (36 p
pm).

The results are shown in Table 1.

[0045]

Example 7 Purification by Adding Nitrogen 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile (100 g) containing hexachlorobenzene (36 ppm) was added to 100 parts.
While adding to a 0 ml flask and passing nitrogen through the system at a flow rate of 300 ml / min to continuously remove the gas generated in the system out of the system,
It heated at 760 mmHg and 140 degreeC for 1 hour. A solidified mixture (3.5 g) was obtained from the sublimed gas which contained hexachlorobenzene (435 ppm). Purified 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile (96.5g; yield 96.5%) was obtained as a residue, and this residue contained hexachlorobenzene (21ppm). .

The results are shown in Table 1.

[0047]

Example 8 Purification with addition of nitrogen 100 2,2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile (100 g) containing hexachlorobenzene (95 ppm) was added.
Add it to a 0 ml flask and pass nitrogen at a flow rate of 1400 ml / min to continuously remove the gas generated in the system from the system,
It heated at 0 mmHg and 140 degreeC for 1 hour. A solidified mixture (1.5 g) was obtained from the sublimed gas. Purified 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile (98.5g; yield 98.5%) was obtained as a residue, and this residue contained hexachlorobenzene (50ppm). .

The results are shown in Table 1.

[0049]

Example 9 2,4,5,6-Tetrachloro-1,3-benzenedicarbonitrile containing purified hexachlorobenzene (197 ppm, hereinafter referred to as "starting HCB content 2") to which nitrogen was added (100 g, hereinafter " (Starting weight 2 ") was added to a 1000 ml flask, and nitrogen was passed at a flow rate of 300 ml / min to continuously remove the gas generated in the system out of the system, and the mixture was heated at 760 mmHg and 140 ° C. for 1 hour. A solidified mixture (3.5 g) was obtained from the sublimed gas which contained hexachlorobenzene (1958 ppm). Purified 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile (96.5g; yield 96.5%) was obtained as a residue, and this residue contained hexachlorobenzene (151ppm). . The results are shown in Table 1.

Further, the obtained residue was added to a 1000 ml flask and nitrogen was passed at a flow rate of 300 ml / min to continuously remove the gas generated in the system out of the system, while the temperature was 760 mmHg and 140 ° C.
It was heated for 2 hours. A solidified mixture (3.5 g) was obtained from the sublimed gas which contained hexachlorobenzene (1963 ppm). Purified as a residue 2,4,5,6
-Tetrachloro-1,3-benzenedicarbonitrile (93.0g;
A yield of 93.0% based on a starting weight of 2) was obtained. The residue contained hexachlorobenzene (127 ppm). The results are shown in Table 1.

The results of Examples 1-9 are shown in Table 1. Using 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile containing a certain amount of hexachlorobenzene, heat it at a specified pressure, a specified temperature and a specified time for the purification system. Attempts were made to reduce the content of hexachlorobenzene. In addition,
As the circulating gas, air is used in the sixth embodiment, and air is used in the seventh, eighth, ninth
Then, nitrogen was used.

[0052]

[Table 1]

* TCIPN represents 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile. The yield based on the total weight of Examples 4 and 9 before the first-stage purification is shown. ** For Examples 4 and 9, the reduction rate after each stage purification is shown based on the amount of HCB (hexachlorobenzene) before the first stage purification. Table 1 reveals that the hexachlorobenzene content in the gas to be removed is extremely high under the conditions of the invention. For example, in Example 4, when the gaseous substance (1.0 g) was sublimated in the first step, about 40% of hexachlorobenzene was sublimated. Further, for example, in Example 5, about 50% of hexachlorobenzene is sublimated by sublimating the gaseous substance (1.4 g). The method for purifying 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile according to the present invention is an industrially extremely advantageous method, and hexachlorobenzene can be efficiently reduced.

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Claims (4)

(57) [Claims] 1. 95% of 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile (hereinafter referred to as “compound (A)”)
The unpurified mixture (I) containing hexachlorobenzene as an impurity in an amount of 500 ppm or less in addition to an amount of not less than 1% by weight is used as a solid phase mixture at a temperature of 90 to 220 ° C and a pressure of 1 to 1000 mmHg.
And maintaining a purification system in which a gas phase coexists, and an amount of 10% by weight or less of the unpurified mixture is a gaseous substance (B).
20% by weight of hexachlorobenzene contained as an impurity in the unpurified mixture by separating and removing as
High-purity 2,4,5,6-tetrachloro-1,3 is removed by the above amount.
-Characterized by obtaining benzenedicarbonitrile,
A method for purifying 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile. The method according to claim 2, wherein the purification process, the purification system, nitrogen, air, water, chlorine, hydrogen chloride, while circulating any one or more of a mixture of carbon dioxide, <br at a temperature of 90 ~ 200 ° C. The purification method according to claim 1, which is performed. 3. Containing 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile (hereinafter referred to as "compound (A)") and containing hexachlorobenzene as an impurity in the compound (A). To an unpurified mixture containing less than 500 ppm and containing chlorine and / or hydrogen chloride (I
I) is maintained at a temperature of 90 to 220 ° C. in a purification system in which a solid phase and a gas phase coexist, and a mixture containing 10% by weight or less of the compound (A) in the unpurified mixture is converted into a gaseous substance (C). Hexachlorobenzene, which is contained as an impurity in the unpurified mixture in an amount of 20% by weight or more, is obtained as high purity 2,4,5,6-tetrachloro-1,3-benzene. A method for purifying 2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile, which comprises obtaining dicarbonitrile. The method according to claim 4, wherein the purification process, the purification system, nitrogen, air, water, chlorine, hydrogen chloride, while circulating any one or more of a mixture of carbon dioxide, <br at a temperature of 90 ~ 200 ° C. The purification method according to claim 3, which is performed.