JPH10109947A - Production of halogenated benzene - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a halogenated benzene, by which the halogenated benzene useful as an intermediate for medical and agrochemical preparation, liquid crystal, polymerization catalyst, etc., in industrially obtained in a high yield and high purity by performing a decarbonation reaction of a halogen-substituted benzenecarboxylic acid by using a basic catalyst. SOLUTION: In this method for producing a halogenated benzene, (A) a halogen-substituted benzenecarboxylic acid of the formula [X is a halogen such as F; (m) is 1-5; (n) is 1-4; 2<=(m+n)<=6] in the presence of (B) a basic catalyst such as an alkali (ne earth) metal compound and, if necessary, (C) a sulfate catalyst such as a metal sulfate are decarboxylated by heating in (D) a solvent (e.g. the one having >=1.0 dipole moment of the molecule and 100-500 deg.C boiling point), for example, at a temp. of 80-300 deg.C. Further, the reaction is performed by using 0.01-1mol component B and 0.001-10mol component C based on 1mol component A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing halogenated benzene. The halogenated benzene provided by the present invention is useful as an intermediate for pharmaceuticals, pesticides, liquid crystals or polymerization catalysts.

[0002]

2. Description of the Related Art A method for producing halogenated benzene is disclosed in British Patent Publication No. 2,122,190, in which a halogen-substituted benzene carboxylic acid is heated to 20 ° C. or more in a solvent, particularly an aprotic polar solvent, to remove it. A method for performing a carbonic acid reaction is described. The reaction is carried out in dimethylformamide, but the yield and the like are not described. In addition, when a reaction is carried out using a polar solvent such as ethylene glycol, it takes time to increase the yield.

[0003] Japanese Patent Application Laid-Open No. 64-25787 discloses a nitrogen-containing organic base which does not contain a hydrogen atom directly hydrogen-bonded to a nitrogen atom and has no heterocyclic aromatic attribute. A method of heating a halogen-substituted benzene carboxylic acid in a mixture of non-polar organic solvents to carry out a decarboxylation reaction is described. A similar method is disclosed in
No. 65120. However, the solvent used is expensive and is not preferred in terms of economy.

[0004] JP-A-7-145063 describes a method for decarboxylating pentafluorobenzoic acid from alkanolamines. However, alkanolamines are solid at ordinary temperature, the reaction raw materials are not uniform at the beginning of the reaction, and it is difficult to control the reaction.

[0005]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method capable of industrially producing halogenated benzene and obtaining it with a high yield and a high purity.

[0006]

The above object is achieved by the following (1).
(10).

(1) A process for producing halogenated benzene, which comprises subjecting a halogen-substituted benzene carboxylic acid to a decarboxylation reaction by heating in a solvent in the presence of a basic catalyst.

(2) The production method according to (1), wherein the dipole moment of the solvent molecule is 1.0 or more.

(3) The method according to the above (1), wherein the solvent has a boiling point of 100 ° C. or more at normal pressure.

(4) The method according to the above (1), wherein the amount of the basic catalyst is 0.01 to 1 mol per 1 mol of the halogen-substituted benzenecarboxylic acid.

(5) The method according to (1), wherein the basic catalyst is an alkaline earth and / or alkaline earth metal compound.

(6) The method according to (1), wherein the halogenated benzenecarboxylic acid is continuously added to the reaction system during the reaction, and the halogenated benzene is continuously extracted from the reaction system.
The production method described in 1.

(7) The above (1), wherein a decarboxylation reaction is carried out in the presence of a sulfate catalyst as a catalyst.
The production method described in 1.

(8) The sulfate catalyst is obtained by neutralizing sulfuric acid contained in a halogen-substituted benzenecarboxylic acid obtained by hydrolyzing a halogenated benzenecarbonitrile using an aqueous sulfuric acid solution (7). The production method described in 1.

(9) (i) A halogenated benzenecarbonitrile is hydrolyzed using an aqueous sulfuric acid solution to obtain a halogen-substituted benzenecarboxylic acid. (Ii) Then, sulfuric acid contained in the halogen-substituted benzenecarboxylic acid is removed. The production method according to the above (1), comprising neutralizing and further (iii) subjecting the neutralized halogen-substituted benzenecarboxylic acid to a decarboxylation reaction.

(10) The method according to the above (1), wherein the halogen-substituted benzenecarboxylic acid is pentafluorobenzoic acid and the halogenated benzene is pentafluorobenzene.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, as one embodiment (A) of the method for producing halogenated benzene according to the present invention,
The decarboxylation reaction is carried out by heating a halogen-substituted benzenecarboxylic acid in a solvent in the presence of a basic catalyst.

The halogen-substituted benzenecarboxylic acid as a starting material in the production method according to the embodiment (A) is not particularly limited, but is preferably represented by the following formula (I):

[0019]

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(In the above formula, X represents a halogen atom. However, the type of X is not limited to one, and any type can be selected within the range of the number m. In the formula, X is at least one fluorine atom, more preferably X is all fluorine atoms, and m is 1
N is an integer of 1 to 4, and 2 ≦ m + n ≦ 6
Is a number that satisfies ) Is a halogen-substituted benzenecarboxylic acid. The product, halogenated benzene, is not particularly limited, but preferably has the following formula (II):

[0021]

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(In the above formula, X represents a halogen atom. However, the kind of X is not limited to one, and any kind can be selected within the range of the number m. Is a halogenated benzene represented by the formula: wherein at least one of X is a fluorine atom, more preferably all of X are fluorine atoms, and m is an integer of 1 to 5.
Examples of the preferred halogen-substituted benzene carboxylic acid represented by the general formula (I) and the halogenated benzene represented by the general formula (II) include those shown in Table 1 below. Among them, pentafluorobenzoic acid is preferable as the halogenated benzenecarboxylic acid, and pentafluorobenzene is preferable as the halogenated benzene.

[0023]

[Table 1]

The starting materials are not particularly limited, and those produced by a conventionally known method can be widely used. In the present invention, the following formula (II) which is a method of the embodiment (C) described below is used.

[0025]

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(In the above formula, X represents a halogen atom. However, the type of X is not limited to one, and any type can be selected within the range of m. Is that at least one of X is a fluorine atom, more preferably all of X is a fluorine atom, m is an integer of 1 to 5, n is an integer of 1 to 4, and satisfies 2 ≦ m + n ≦ 6 It is preferable to use a product obtained by hydrolyzing a halogenated benzenecarbonitrile represented by the following formula (1) with an aqueous sulfuric acid solution. Such halogenated benzenecarbonitrile includes pentafluorobenzonitrile, 2,4,6-trifluorobenzonitrile, tetrafluorophthalonitrile, 1,4-difluoropyromellitonitrile and the like. Of these, pentafluorobenzonitrile is preferred.

The solvent used in the production method according to the embodiment (A) is preferably a polar solvent, particularly preferably a polar solvent having a molecular dipole moment of 1.0 or more. A polar solvent having a moment of 2.0 or more is preferred. The upper limit of the dipole moment of the molecule is not particularly limited, but is preferably 6.0 or less. Further, among the polar solvents, any solvent can be used as long as it can be separated from the halogenated benzene by distillation.
Solvents having a temperature of at least 00 ° C are preferred, and those having a boiling point of at least 130 ° C are particularly preferred. The upper limit of the boiling point is not critical as long as it can dissolve the basic catalyst and the halogen-substituted benzenecarboxylic acid, but is preferably 500 ° C. or lower, more preferably 300 ° C. or lower.

Examples of the solvent include ethylene glycol (dipole moment: 2.31, boiling point: 197.5)
° C), ethylene glycol monoethyl ether (dipole moment 2.08, boiling point 135.6 ° C), 1.3-propanediol (dipole moment 2.55, boiling point 21)
4.4 ° C.), diethylene glycol (dipole moment 2.31, boiling point 245.7 ° C.), diethylene glycol monomethyl ether (dipole moment 1.60, boiling point 194.1 ° C.), triethylene glycol (dipole moment 5.58) , Boiling point 288.0 ° C), polyhydric alcohols such as glycerin (dipole moment 2.56, boiling point 290.0 ° C), 1-butanol (dipole moment 1.75, boiling point 117.7 ° C), 1-butanol Alcohols such as octanol (dipole moment 1.76, boiling point 195.2 ° C.), water (dipole moment 1.82, boiling point 10
0 ° C.), among which ethylene glycol is particularly preferred from the viewpoints of economy and physical properties.

The amount of the solvent used is 10 to 20 parts by weight based on 100 parts by weight of the halogen-substituted benzene carboxylic acid.
00 parts by weight, preferably 20 to 1000 parts by weight.
It is preferred to use parts by weight. If the amount of the solvent is less than the above range, it becomes difficult to control the reaction, and if the amount is too large, the productivity is deteriorated, which is not preferable.

The basic catalyst used in the production method according to the embodiment (A) includes sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, potassium hydrogen carbonate,
Alkali metal compounds such as sodium carbonate and potassium carbonate and / or alkaline earth metal compounds such as calcium hydroxide, magnesium hydroxide, calcium carbonate and magnesium carbonate are preferred, and alkaline earth metal compounds are particularly preferred. Particularly, among them, it is preferable to use calcium hydroxide, calcium carbonate, and the like from the viewpoint of economy and physical properties. The basic catalyst is preferably used in an amount of 0.01 to 1 mol, more preferably 0.05 to 0.5 mol, per 1 mol of the halogen-substituted benzenecarboxylic acid. When the use amount of the basic catalyst is less than the above range, the reaction rate is decreased and productivity is deteriorated, which is not preferable. When the use amount is more than the above range, a side reaction such as a hydroxylation reaction proceeds. Therefore, it is not preferable.

The reaction temperature (the above heating condition) for the decarboxylation reaction in the production method according to the embodiment (A) is usually 8
Although it can be carried out at 0 ° C. or higher, it is preferably carried out in the range of 80 to 300 ° C., and more preferably in the range of 100 to 200 ° C. When the reaction temperature is high, the reaction proceeds at a stretch and control becomes difficult. When the reaction temperature is low, the reaction rate is decreased and productivity is deteriorated, which is not preferable.

The method for isolating the halogenated benzene obtained by the production method according to the embodiment (A) can be easily carried out by distillation. When to isolate,
The reaction can be carried out either during the reaction or after the reaction. The solvent remaining after isolating the halogenated benzene can be recycled.

In the production method according to the embodiment (A), a halogen-substituted benzenecarboxylic acid is continuously added to the reaction system during the reaction by using a halogenated benzene and a solvent which can be separated by distillation. The reaction can be carried out continuously while extracting the benzene chloride. By performing such a reaction, it is possible to prevent the reaction temperature from gradually lowering due to halogenated benzene generated during the reaction, and it is possible to maintain the reaction temperature at a constantly high state and to carry out the reaction efficiently. became.

Next, as another embodiment (B) of the method for producing a halogenated benzene according to the present invention, as a catalyst, a sulfate, preferably ammonia, sulfuric acid of an alkali metal or an alkaline earth metal is used. The decarboxylation reaction is carried out in the presence of at least one kind of catalyst selected from salts. The sulfate catalyst acts as a co-catalyst for the basic catalyst.

The production method according to the embodiment (B) is the same as the production method according to the embodiment (A) described above, except that a sulfate catalyst is used in combination with the basic catalyst.

Examples of the sulfate catalyst include ammonium sulfate, sodium sulfate, potassium sulfate, rubidium sulfate, cesium sulfate, magnesium sulfate, calcium sulfate, strontium sulfate, and barium sulfate.

The amount of the sulfate catalyst used is 0.001 to 10 per mol of the halogen-substituted benzenecarboxylic acid.
It is preferably used in moles, particularly preferably 0.01 to 1 mole. When the amount of the sulfate catalyst used is less than the above range, the effect as a catalyst is reduced, which is not preferable. When the amount is large, undesirably, a large amount of the sulfate is required to be treated after completion of the reaction. .

Further, in another embodiment (C) of the present invention, (i) a halogenated benzenecarboxylic acid is obtained by hydrolyzing a halogenated benzenecarbonitrile as a starting material using an aqueous sulfuric acid solution, (Ii) Then, sulfuric acid contained in the halogen-substituted benzenecarboxylic acid is neutralized, and (iii) the neutralized halogen-substituted benzenecarboxylic acid is subjected to a decarboxylation reaction. Thus, in the embodiment (C), the decarboxylation reaction can be carried out in a system using a sulfate catalyst in combination as in the other embodiments (B) described above. By doing so, it becomes possible to use the reaction solution containing sulfate as it is for the decarboxylation reaction without isolating the halogen-substituted benzenecarboxylic acid as the starting material. That is, it is possible to use the obtained halogen-substituted benzenecarboxylic acid for the decarboxylation reaction without requiring a step of removing sulfuric acid from the obtained halogen-substituted benzenecarboxylic acid and a step of drying the halogen-substituted benzenecarboxylic acid from which sulfuric acid has been removed.

The method of the hydrolysis reaction is not particularly limited, and the hydrolysis can be carried out in a 30 to 90% by weight aqueous sulfuric acid solution at a temperature of 100 to 180 ° C.

The sulfates after neutralization of sulfuric acid in the above embodiment (C) include those present in the form of at least one of ammonia, an alkali metal and an alkaline earth metal, Those that exist in the form of biological ammonium sulfate can be used.

Examples of the basic neutralizing agent used for neutralizing sulfuric acid include alkali metal compounds such as sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate, potassium carbonate and / or the like.
Alternatively, alkaline earth metal compounds such as calcium hydroxide, magnesium hydroxide, calcium carbonate, and magnesium carbonate are preferred, and alkaline earth metal compounds are particularly preferred. Particularly, among them, it is preferable to use calcium hydroxide, calcium carbonate, and the like from the viewpoint of economy and physical properties.
The amount of the basic neutralizing agent used is theoretically sufficient to neutralize the sulfuric acid in the system, but since these can be used as a basic catalyst for the decarboxylation reaction, There is no particular problem even if an appropriate amount or more is used. As a preferred method, a basic neutralizing agent equivalent to sulfuric acid is added to neutralize sulfuric acid, and then subjected to a decarboxylation reaction. Thereafter, an amount of the basic catalyst required for the decarboxylation reaction is added. The preferred amount of the basic catalyst is the same as in the case of the embodiment (A). Further, as the sulfate obtained by neutralizing sulfuric acid, at least one kind of ammonia, alkali metal and alkaline earth metal, for example, ammonium sulfate, sodium sulfate,
Examples include potassium sulfate, rubidium sulfate, cesium sulfate, magnesium sulfate, calcium sulfate, strontium sulfate, barium sulfate and the like. The amount of sulfate present after neutralization is the same as in the case of Embodiment (B).

[0042]

Next, the production method of the present invention will be described in more detail with reference to examples.

Example 1 13.90 g (66 mmol) of pentafluorobenzoic acid and ethylene glycol 4 were added to a distillation apparatus equipped with a stirrer.
0 g and calcium hydroxide 0.82 g (11 mmo
l) was added, and the mixture was heated to 140 ° C. and reacted for 4 hours while extracting pentafluorobenzene formed.
Pentafluorobenzene obtained by distillation is 10.2
0 g (61 mmol), the yield was 92.6%, and the purity was 99.0% or more as measured by gas chromatography.

Example 2 The reaction solution obtained by distilling pentafluorobenzene in Example 1 was cooled to room temperature, and pentafluorobenzoic acid was added.
90 g (66 mmol) were added. Thereafter, the mixture was heated to 160 ° C. and reacted for 3 hours while extracting pentafluorobenzene formed. 10.52 g (63 mmol) of pentafluorobenzene obtained by distillation had a yield of 95.6% and a purity of 99.0% or more as measured by gas chromatography.

Example 3 13.90 g (66 mmol) of pentafluorobenzoic acid and ethylene glycol 4 were added to a distillation apparatus equipped with a stirrer.
0 g and calcium carbonate 2.50 g (25 mmol)
And heated to 120 ° C. to carry out a reaction for 8 hours while extracting pentafluorobenzene formed. 10.27 g of pentafluorobenzene obtained by distillation
(61 mmol), the yield was 93.2%, and the purity was 99.0% or more as measured by gas chromatography.

Example 4 13.90 g (66 mmol) of pentafluorobenzoic acid and ethylene glycol 4 were added to a distillation apparatus equipped with a stirrer.
0 g and calcium hydroxide 0.82 g (11 mmo
l) was added thereto, and the mixture was heated to 140 ° C. to extract the generated pentafluorobenzene. The reaction was performed while adding pentafluorobenzoic acid corresponding to the number of moles of the extracted pentafluorobenzene to the reaction solution. The amount of pentafluorobenzoic acid added was 10.0 g and the reaction time was 6 hours. The pentafluorobenzene obtained by distillation was 17.70 g (106 mmol), and the yield was 93.5.
%, Purity was measured by gas chromatography,
It was 99.0% or more.

Example 5 13.90 g (66 m) of pentafluorobenzoic acid was placed in a three-necked flask equipped with a stirrer, a cooling reflux tube and a thermometer.
mol), 40 g of ethylene glycol and 0.82 g (11 mmol) of calcium hydroxide.
The reaction was carried out for 6 hours while the reaction temperature was gradually lowered from 0 ° C. to 110 ° C. at the end of the reaction. After the completion of the reaction, pentafluorobenzene was separated by distillation. 8.02 g (48 mm) of pentafluorobenzene obtained by distillation was obtained.
ol), the yield was 72.8%, and the purity was 99.0% or more as measured by gas chromatography. Although the starting material pentafluorobenzoic acid remains in the solution after distillation, the solution can be recycled for the next reaction.

Comparative Example 1 13.90 g (66 mmol) of pentafluorobenzoic acid and 0.82 g (11 mmol) of calcium hydroxide were added to a distillation apparatus equipped with a stirrer, heated to 140 ° C., and reacted for 4 hours. . No distilled pentafluorobenzene was found, and no pentafluorobenzene was produced in the reaction solution.

Comparative Example 2 13.90 g (66 mmol) of pentafluorobenzoic acid and 40 g of ethylene glycol were added to a distillation apparatus equipped with a stirrer, heated to 140 ° C., and the reaction was carried out for 7 hours while extracting pentafluorobenzene produced. Done. The pentafluorobenzene obtained by distillation is 3.
56 g (21 mmol), the yield was 32.3%, and the purity was 99.0 or more as measured by gas chromatography. Example 6 In a distillation apparatus equipped with a stirrer, 10.00 g (0.057 mol) of 2,4,6-trifluorobenzoic acid, 30 g of ethylene glycol and 0.50 g of calcium hydroxide were added.
(0.0065 mol) and heated to 160 ° C.
The reaction was carried out for 5 hours while extracting the generated 1,3,5-trifluorobenzene. 1, obtained by distillation
7.13 g (0.05%) of 3,5-trifluorobenzene
4mmol), the yield was 94.7%, and the purity was 99.0% or more as measured by gas chromatography.

Example 7 In a distillation apparatus equipped with a stirrer, 10.00 g (0.057 mol) of 2-chloro-6-fluorobenzoic acid, 1,3
-40 g of propanediol and 0.1 g of calcium hydroxide.
82 g (0.011 mol) was added, and the mixture was heated to 170 ° C. and reacted for 6 hours while extracting the generated 1-chloro-3-fluorobenzene. 1 obtained by distillation
-Chloro-3-fluorobenzene 6.95 g (0.0
53 mol), the yield was 93.4%, and the purity was 99.0% or more as measured by gas chromatography.

Example 8 10.00 g (0.042 mol) of 3,4,5,6-tetrafluorophthalic acid was placed in a distillation apparatus equipped with a stirrer.
60 g of diethylene glycol and 0.85 g (0.011 mol) of calcium hydroxide were added, and the mixture was heated to 220 ° C. and reacted for 6 hours while extracting generated 1,2,3,4-tetrafluorobenzene. The amount of 1,2,3,4-tetrafluorobenzene obtained by distillation was 5.25 g (0.035 mol), and the yield was 83.3.
%, Purity was measured by gas chromatography,
It was 99.0% or more.

Example 9 A three-necked flask equipped with a stirrer, a thermometer and a cooling reflux tube was charged with 50 g of pentafluorobenzonitrile (0.26 m
ol) and 250 g of a 65% by weight aqueous sulfuric acid solution, and the mixture was reacted under reflux for 15 hours. After cooling to room temperature, the precipitated pentafluorobenzoic acid was filtered to obtain 98.0 g of a cake. When the cake was analyzed, 90% by weight of pentafluorobenzoic acid, 5.0% by weight of sulfuric acid, and 0.1% by weight of ammonium sulfate were used.
It contained 6% by weight and 2.6% by weight of water. 1.82 g (0.8%) of calcium hydroxide was added to 49.0 g of the obtained cake.
025 mol) was added to neutralize the sulfuric acid.

The above cake containing calcium sulfate obtained by neutralizing sulfuric acid in a distillation apparatus equipped with a stirring apparatus.
8 g (44.1 g of pentafluorobenzoic acid (0.21 m
ol)), 150 g of ethylene glycol and 2.55 g (0.03 g) of calcium hydroxide as a basic catalyst.
4 mol), and the mixture was heated to 140 ° C. and reacted for 4 hours while extracting pentafluorobenzene produced. The pentafluorobenzene obtained by distillation is 3
3.2 g (0.20 mol), the yield was 95.0%, and the purity was measured by gas chromatography.
0% or more.

Example 10 A three-necked flask equipped with a stirrer, a thermometer and a cooling reflux tube was charged with 50 g (0.26 m) of pentafluorobenzonitrile.
ol) and 250 g of a 65% by weight aqueous sulfuric acid solution, and the mixture was reacted under reflux for 15 hours. After cooling to room temperature, the precipitated pentafluorobenzoic acid was filtered to obtain 98.0 g of a cake. When the cake was analyzed, 90% by weight of pentafluorobenzoic acid, 5.0% by weight of sulfuric acid, and 0.1% by weight of ammonium sulfate were used.
It contained 6% by weight and 2.6% by weight of water. To 49.0 g of the obtained cake, 1.0 g (0.0%) of sodium hydroxide was added.
25 mol) was added to neutralize the sulfuric acid.

The above cake containing sodium sulfate obtained by neutralizing sulfuric acid in a distillation apparatus equipped with a stirring apparatus.
0 g (pentafluorobenzoic acid 44.1 g (0.21 m
ol)), 150 g of ethylene glycol, and 0.74 g of calcium hydroxide as a basic catalyst (0.01 g).
0 mol), and the mixture was heated to 140 ° C. and reacted for 4 hours while extracting pentafluorobenzene formed. The pentafluorobenzene obtained by distillation is 3
2.9 g (0.20 mol), the yield was 94.1%, and the purity was measured by gas chromatography.
0% or more.

Example 11 In Example 1, a catalyst other than calcium hydroxide was used.
The same procedure was performed except that 0.87 g (6.6 mmol) of ammonium sulfate was added. The obtained pentafluorobenzene was 10.30 g (62 mmol) and the yield was 9
3.3%, and the purity was 99.0% or more as measured by gas chromatography.

[0057]

In the production method of the present invention, the decarboxylation of the halogen-substituted benzenecarboxylic acid is carried out by heating in a solvent in the presence of a basic solvent, so that the halogenated benzene can be obtained in high yield and high yield. Obtained on an industrial scale in purity.

Furthermore, in the production method of the present invention, the decarboxyl group of the halogen-substituted benzenecarboxylic acid is heated in a solvent in the presence of a basic catalyst and a sulfate catalyst, for example, to obtain a halogen-substituted benzene. Carboxylic acid is obtained by hydrolyzing halogenated benzenecarbonitrile using an aqueous sulfuric acid solution, and is used for decarboxylation after neutralizing sulfuric acid of the halogen-substituted benzenecarboxylic acid containing sulfuric acid. Thus, the halogenated benzene can be obtained in a high yield and high purity on an industrial scale under a simpler production process.

Claims (5)

[Claims] 1. A method for producing a halogenated benzene, comprising subjecting a halogen-substituted benzene carboxylic acid to a decarboxylation reaction by heating in a solvent in the presence of a basic catalyst. 2. The process according to claim 1, wherein the halogen-substituted benzenecarboxylic acid is continuously added to the reaction system during the reaction, and the halogenated benzene is continuously extracted from the reaction system. 3. The method according to claim 1, wherein the decarboxylation reaction is carried out in the presence of a sulfate catalyst as a catalyst. 4. A method of (i) hydrolyzing a halogenated benzenecarbonitrile using an aqueous sulfuric acid solution to obtain a halogen-substituted benzenecarboxylic acid, and (ii) subsequently removing a sulfuric acid contained in the halogen-substituted benzenecarboxylic acid. 2. The method according to claim 1, further comprising (iii) subjecting the neutralized halogen-substituted benzenecarboxylic acid to a decarboxylation reaction. 5. The method according to claim 1, wherein the halogen-substituted benzenecarboxylic acid is pentafluorobenzoic acid, and the halogenated benzene is pentafluorobenzene.