JP4803911B2 - Method for producing 4,4'-dibromobiphenyl - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a process for producing 4,4′-dibromobiphenyl, and more specifically, bromine and biphenyl are reacted in a reaction solvent to obtain 4,4′-dibromobiphenyl crude crystal, and then the crude crystal The slurry was recrystallized by heating and cooling without separating 4,4′-dibromobiphenyl from the slurry containing 4,4′-dibromobiphenyl to obtain pure crystals of 4,4′-dibromobiphenyl. , 4'-dibromobiphenyl.
[0002]
[Prior art]
4,4′-dibromobiphenyl can be hydrolyzed to 4,4′-dihydroxybiphenyl and further oxidized to 4,4′-dicarboxybiphenyl, which is It is useful as a raw material for producing oxidation stabilizers, dye intermediates and resins such as polyesters, polyepoxides, polyurethanes and polycarbonates, and is used for copolymers such as organic silicon and oxide films. Further, N, N, N ′, N′-tetraphenylbenzidine obtained by reacting 4,4′-dibromobiphenyl with a secondary amine can be used as a raw material compound such as organic electroluminescence. Furthermore, the insect growth regulator ethyl-4- (isopropylphenyl) benzoate can be produced from 4,4'-dibromobiphenyl, and 4,4'-dibromobiphenyl is extremely useful for agrochemicals, polymers, and dyes. It is a highly potent compound.
[0003]
There are various methods for producing 4,4′-dibromobiphenyl. When biphenyl and bromine are used as raw materials, a method of brominating biphenyl with bromine using a catalyst in a solvent, There is a method of reacting biphenyl with bromine without using a catalyst.
[0004]
For example, US Pat. No. 3,518,316 discloses that 4,4′-dibromobiphenyl is prepared by reacting 2.1 moles of bromine with 1 mole of biphenyl in the presence of sulfur dioxide in the range of −40 to −5 ° C. A manufacturing method is disclosed. In the examples, bromine is added to an anhydrous sulfur dioxide solvent containing biphenyl at a temperature of -6 ° C over 65 minutes. Since the temperature is lowered by hydrobromic acid generated when the solvent is stirred, the reaction temperature is maintained at −22 ° C. for 6 hours after the addition of bromine, and then the hydrogen bromide is removed to raise the temperature. When the temperature reaches −10 ° C., the solvent is filtered. In the example, this gives 4,4′-dibromobiphenyl in 92.2% yield.
[0005]
JP-A-55-64532 uses a compound having a dielectric constant of 6.5 or more as a solvent, such as o-dichlorobenzene, nitrobenzene, or a specific halogenated saturated aliphatic hydrocarbon. A method for producing 4,4′-dibromobiphenyl by reacting biphenyl and bromine in a reaction solvent is disclosed. The present invention is a method for producing 4,4′-dibromobiphenyl at room temperature and normal pressure without using a catalyst. The reason why a solvent having a dielectric constant of 6.5 or more is used as a reaction solution is excellent in yield. It is. In Example 6 of this publication, dichlorobenzene was used as a solvent, and a liquid mixture of bromine and dichlorobenzene was added dropwise over 1 hour while maintaining the temperature at 30 to 35 ° C. The reaction is carried out for 5 hours while maintaining the same temperature. Next, a 10% aqueous sodium hydroxide solution is added to the reaction system at 50 ° C. or less, neutralizing excess bromine and dissolved hydrogen bromide, cooling the reaction product to 10 to 15 ° C., filtering, washing with water and drying. Thus, 4,4′-dibromobiphenyl (primary crystal) was obtained. Then, after distilling and concentrating the solvent from the filtrate, the mixture was cooled in the same manner, filtered, washed with water and dried to obtain secondary crystals of 4,4′-dibromobiphenyl. The yield in terms of charged biphenyl is 80.0%.
[0006]
On the other hand, Japanese Patent Application Laid-Open No. 1-1479740 discloses a method of reacting biphenyl and bromine in a halogenated hydrocarbon solvent using an elemental element of antimony, titanium, tin or zinc or a compound thereof as a catalyst. ing. When a nitro compound is used as a solvent, it generates intense heat when adding bromine to biphenyl, and it is difficult to control the reaction when carried out on a large scale, so the use of halogenated hydrocarbons as a solvent prevents severe heat generation. Is. On the other hand, when halogenated hydrocarbons are used, many of them stop at monobromobiphenyl, so that by-product formation of isomers is prevented by addition of a catalyst. In the examples of the publication, 1,2-dichloroethane, 1,1,1-trichloroethane, chloroform, chlorobenzene and the like are used, bromine is dropped into the solvent at a temperature of 30 to 35 ° C. in the presence of a catalyst, and then the liquid temperature is changed. The temperature was raised to 38-50 ° C. and aged for 5 hours, then the reaction solution was cooled to 0 ° C., a bromine treating agent was added dropwise, the crystals were filtered, washed with water, dried in vacuo, and 4,4′-dibromobiphenyl Have gained. In addition, 4,4′-dibromobiphenyl is also obtained from the organic phase separated from the filtrate.
[0007]
[Problems to be solved by the invention]
4,4′-Dibromobiphenyl is a compound that is widely used as described above, and when used as a raw material compound for pharmaceuticals and agricultural chemicals, a product purity of 99% by mass or more is required. However, it is generally difficult to easily produce a product having such purity. For example, in the method of US Pat. No. 3,518,316, in the reaction, in the presence of water, bromine is changed to hydrogen bromide and sulfur dioxide is changed to sulfuric acid to cause a decrease in yield. Therefore, care must be taken not to mix water. Further, when bromine is added to biphenyl, if the temperature is out of the above temperature range, an isomer is by-produced and the yield is lowered.
[0008]
Further, in the methods described in JP-A Nos. 55-64532 and 1-1479740, separation from the reaction solution, washing with water, drying, and separation of the target product from the filtrate in order to obtain the desired product, Drying or the like is necessary, and the isolation operation of the target product is extremely complicated. In addition, since a catalyst is used in Japanese Patent Application Laid-Open No. 1-1479740, a separation operation between the catalyst and 4,4′-dibromobiphenyl, which is the target product, is required, and the number of production steps is further increased. Since 4,4′-dibromobiphenyl is a useful raw material, it is preferable that it can be produced in a high yield. However, the above method does not satisfy them.
[0009]
[Means for Solving the Problems]
The present inventor has studied in detail a process for producing 4,4′-dibromobiphenyl by reacting biphenyl with bromine in a reaction solvent without using a catalyst, and as a result, while suppressing by-product formation of isomers. 4,4'-dibromobiphenyl can be produced in high yield, and pure crystals can be obtained by recrystallizing the target product simply by raising the temperature and cooling the specific temperature in the solvent. 4,4'-dibromobiphenyl can be produced, and the solvent after separation of the target product can be reused as a reaction solvent for biphenyl and bromine. However, since it can be recovered as 4,4′-dibromobiphenyl in the next reaction system, it was found that the yield could be further improved, and the present invention was completed. That is, the present invention provides the following (1) to (5).
[0010]
(1) Biphenyl and bromine are reacted in a reaction solvent to precipitate crude 4,4′-dibromobiphenyl as crude crystals in the reaction solvent, and then the slurry containing the crude crystals is heated and cooled to recrystallize. And 4,4′-dibromobiphenyl pure crystals, to obtain 4,4′-dibromobiphenyl.
[0011]
(2) Reaction of biphenyl and bromine in the reaction solvent and precipitation of crude 4,4′-dibromobiphenyl crystals at a temperature of −5 to 50 ° C. After precipitation of the crude crystals, the slurry is heated to a temperature of 80 to The method for producing 4,4′-dibromobiphenyl as described in (1) above, wherein pure crystals are obtained by heating to 130 ° C. and then cooling.
[0012]
(3) The 4,4′-dibromo as described in (1) or (2) above, wherein after the precipitation of the crude crystals, bromine remaining in the slurry is removed, and then the slurry is heated and cooled. A method for producing biphenyl.
[0013]
(4) The reaction solvent after fractionating pure crystals from the slurry is reused as a reaction solvent for the reaction of biphenyl and bromine, according to any one of (1) to (3) above Of 4,4′-dibromobiphenyl.
[0014]
(5) The reaction solvent is benzene, monochlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, monobromobenzene, o-dibromobenzene, m-dibromobenzene, p-dibromobenzene, bromochlorobenzene. The method for producing 4,4′-dibromobiphenyl according to any one of (1) to (4) above, which is any one or more.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
In the first aspect of the present invention, biphenyl and bromine are reacted in a reaction solvent to precipitate crude 4,4′-dibromobiphenyl as crude crystals in the reaction solvent, and then the slurry containing the crude crystals is heated and cooled. And recrystallizing to obtain 4,4′-dibromobiphenyl pure crystals, which is a method for producing 4,4′-dibromobiphenyl.
[0016]
There is recrystallization as a method for purifying a crude product obtained in the form of crystals, and heating and cooling operations are generally performed in a solvent. Recrystallization is a process in which a target solution in a solvent is heated to form a saturated solution, which is then cooled and the solute is precipitated again as crystals from the difference in solubility due to temperature differences, and purified to leave a small amount of impurities in the solvent. It is. For this reason, it is usual to use a solvent different from the reaction solvent because of the difference in solubility between the starting compound and the target compound in the specific solvent. In particular, when biphenyl and bromine are reacted to produce 4,4′-dibromobiphenyl, the temperature of the solution rises due to the heat of reaction. For this reason, it is necessary to select an optimal reaction solvent in relation to a solvent with a small calorific value, a raw material compound or a target compound, reactivity with by-products, etc., and the types of reaction solvents that can be conventionally used are limited. Is. Therefore, it has not been known at all that the reaction solvent in which 4,4′-dibromobiphenyl is precipitated is recrystallized by heating and cooling to obtain 4,4′-dibromobiphenyl having higher purity as crystals. However, in the present invention, by finding reaction conditions and optimum recrystallization conditions, recrystallization is performed using a reaction solvent containing crude crystals, and a highly pure 4,4′-dibromobiphenyl can be produced extremely simply. be able to. Hereinafter, the present invention will be described in detail.
[0017]
First, as a reaction solvent that can be used in the present invention, biphenyl is dissolved, 4,4′-dibromobiphenyl is precipitated as crystals in the solvent, and does not react with the raw material compound or the target compound. It does not decompose even when the temperature rises during crystallization. Examples of such a reaction solvent include benzene, monochlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, monobromobenzene, o-dibromobenzene, m-dibromobenzene, p-dibromobenzene, bromochlorobenzene and the like. There is. In the present invention, one of these can be used alone, or two or more can be used in combination. In the present invention, benzene, monochlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, monobromobenzene, o-dibromobenzene, m-dibromobenzene, p-dibromobenzene, bromochlorobenzene are used alone. It is preferable. Of these, monochlorobenzene is preferably used alone. 4.4'-dibromobiphenyl is excellent in selectivity, and by-products such as 4-bromobiphenyl, 2,4'-dibromobiphenyl, 3,4'-dibromobiphenyl are dissolved during recrystallization. It is because it is excellent in efficiency.
[0018]
In general, the reaction solvent, bromine, and biphenyl are charged into a reactor equipped with a cooling device. Biphenyl as a reaction raw material is dissolved in the reaction solvent at a concentration of 20 to 80 mass / volume%, more preferably 30 to 70 mass / volume%, particularly preferably 40 to 60 mass / volume%. If it exceeds 80% by mass / volume, temperature control during the reaction with bromine becomes difficult, and the purity of the target product may be reduced during recrystallization. On the other hand, if it is less than 20% by mass / volume, the yield may be lowered.
[0019]
In addition, the molar ratio (bromine / biphenyl) of bromine and biphenyl used as a reaction raw material is 2.0 to 3.0, more preferably 2.4 to 2.8, and particularly preferably 2.5 to 2.6. It is. If it is less than 2.0, not only the yield of the target product is lowered, but also the amount of monobromide is increased, which may lower the purity. On the other hand, if it exceeds 3.0, by-products increase and purification may be difficult. At this time, the bromine and the reaction solvent to be used do not need to be subjected to treatment such as dehydration. In the present invention, since the reaction is carried out in a hydrophobic reaction solvent such as benzene or monochlorobenzene, even if water is mixed, the reaction itself proceeds quickly in these reaction solvents, such as decomposition of bromine by water. This is because there are few side effects. Thus, since the pretreatment of the used raw material is not necessary, the target product can be efficiently produced.
[0020]
When bromine and biphenyl are mixed, reaction heat is generated. Since the 4,4′-dibromobiphenyl isomer is by-produced by the generated heat, it is preferable to keep the reaction solution at a low temperature. When mixing bromine and diphenyl, the reaction solution is preferably at a temperature of −5 to 50 ° C., preferably Is limited to −5 to 20 ° C., more preferably 0 to 15 ° C., and particularly preferably 5 to 10 ° C. For example, when monochlorobenzene is used as a reaction solvent, the liquid temperature decreases due to heat of dissolution when biphenyl is dissolved in the reaction solvent, and when bromine is added dropwise thereto, the liquid temperature gradually increases due to reaction heat. Therefore, the temperature is controlled in a reactor equipped with a cooling device. Conventionally, bromine is added dropwise to biphenyl in order to prevent a sudden exotherm, but in the present invention, if the above temperature range can be maintained, biphenyl is added to a reaction solvent such as monochlorobenzene, and then bromine is added to the stock solution. It may be dropped as it is, or biphenyl may be added to a reaction solvent such as monochlorobenzene in which bromine is dissolved in advance, and there is no limitation on the blending order. In this case, the reaction solvent can be used not only to dissolve biphenyl but also to dissolve bromine. In addition, since hydrogen bromide is by-produced by mixing with the reaction solvent, bromine and biphenyl, it can be recovered by introducing it into the collection liquid from the upper part of the reactor.
[0021]
In the present invention, the addition of a catalyst is not required. This is because by reacting in a specific reaction solvent such as monochlorobenzene, 4,4′-dibromobiphenyl can be produced with high selectivity without adding a catalyst.
[0022]
Next, a reaction solution in which biphenyl and bromine are mixed in a reaction solvent such as monochlorobenzene is heated to a temperature in the range of -5 to 50 ° C, preferably 15 to 50 ° C, more preferably 15 to 40 ° C, particularly 20 to 38. Maintain at ℃ and age. This is because the bromination of biphenyl proceeds and crude crystals of 4,4′-dibromobiphenyl are precipitated in the reaction solvent. At this time, there is no limitation on the aging time, and it is sufficient that a crude crystal of 4,4′-dibromobiphenyl which is the target product is sufficiently precipitated. Generally, it is 8 to 36 hours, more preferably 12 to 24 hours, particularly 16 to 20 hours. The temperature at the time of aging may be the same as the temperature at the time of mixing the reaction solvent, bromine, and biphenyl. However, in order to promote the reaction, it is preferable to keep the temperature higher than this. Therefore, it is more preferable to maintain the time for adjusting the reaction solution, that is, the time for mixing with the reaction solvent, biphenyl and bromine at a temperature of -5 to 20 ° C and then to maintain the temperature at 15 to 40 ° C for aging.
[0023]
By such adjustment and aging of the reaction solution, 4,4′-dibromobiphenyl crude crystals are precipitated in the reaction solvent. The purity of the crude crystals is 96 to 97% by mass, and the by-products are 3 to 4% by mass of monobromobiphenyl, and 0.1 to 0.3% by mass of other isomers of 4,4′-dibromobiphenyl. It is.
[0024]
Then, excess bromine contained in the reaction solvent is removed. As a method for removing such bromine, a conventionally known method can be employed. For example, a slurry containing crude crystals (in this specification, a reaction solvent after precipitation of 4,4′-dibromobiphenyl crystals is used to remove the crystals. Excess bromine and hydrogen bromide may be removed by adding an alkaline substance such as sodium hydroxide at 50 ° C. or lower (referred to as “slurry” with or without) (Japanese Patent Laid-Open No. 55-64532). The slurry containing the crude crystals may be cooled to 0 ° C., and bromine treating agents (bromine removing agents) such as sodium hydroxide and sodium bisulfite may be added thereto to remove bromine present in the slurry. (JP-A-1-149740) or sulfurous acid or sodium bisulfite may be added to remove excess bromine (JP-A-1-311035). In the present invention, as the bromine treatment method, the slurry is cooled to a temperature of -5 to 20 ° C., and then sulfurous acid, an aqueous sodium sulfite solution, and the like are treated using a neutralized amount of bromine.
[0025]
In the present invention, the slurry after addition of the bromine remover is heated to a temperature of 80 to 130 ° C., more preferably 90 to 120 ° C., particularly 100 to 105 ° C., to thereby add 4,4′-dibromobiphenyl into the slurry. Dissolve. Thereafter, when cooled, 4,4′-dibromobiphenyl of high purity is precipitated. If the heating temperature is lower than 80 ° C., the purity of the target product may be lowered. On the other hand, if the temperature exceeds 130 ° C., the target product is not further dissolved and is useless. In addition, when an aqueous solution is used as a bromine treating agent, or when water is contained in bromine and the reaction solvent, it may be difficult to heat to a temperature higher than the boiling point of the reaction solvent used by the azeotropic phenomenon, There is no particular problem as long as the temperature can be raised to the above range.
[0026]
In the present invention, the slurry is cooled after the temperature is raised to the above temperature, but there is no limitation on the cooling temperature, the cooling rate, the cooling time, etc. as long as the target product is precipitated. In general, the slurry may be cooled to room temperature in 2 to 3 hours.
[0027]
In the present invention, high-purity 4,4′-dibromobiphenyl is precipitated in the slurry by the above treatment, and by-products are dissolved in the slurry, whereby high-purity 4,4′-dibromobiphenyl is obtained in a crystalline form. be able to. The bromine remover added to remove bromine and the reaction compound with bromine are dissolved in the aqueous phase in the slurry, and the target 4,4′-dibromobiphenyl is precipitated in the solvent phase in the slurry. If the solvent phase is separated, 4,4′-dibromobiphenyl crystals can be separated. The fractionation of 4,4′-dibromobiphenyl pure crystals from the slurry can also be carried out by other conventionally known methods. The purity of the pure crystals at this time is 99.5 to 99.8% by mass, and by-products are 0.1 to 0.5% by mass of monobromobiphenyl and other isomers of 4,4′-dibromobiphenyl. Is 0.1 to 0.2% by mass.
[0028]
In addition, in order to further refine | purify the 4,4'- dibromobiphenyl obtained by recrystallization, it can also recrystallize again in another solvent or the same fresh reaction solvent.
[0029]
In the present invention, a solvent obtained by fractionating pure crystals can be reused as a reaction solvent for the reaction between biphenyl and bromine. In the present invention, a specific reaction solvent is heated to the above specific temperature to recrystallize the target product, thereby suppressing the production of by-products and decomposition of the target product. It has been found that reaction solvents such as chlorobenzene and monochlorobenzene can be used stably without being brominated and can be reused. The present invention is based on the very simple principle of utilizing the activity of bromine itself and brominating the 4th and 4'-positions of biphenyl with bromine, so that the reaction solution may also be brominated. high. However, in the present invention, the reaction solvent used by the treatment under the above-mentioned specific conditions is not brominated by the raw material compound, and is decomposed by the product, by-product, reaction heat or recrystallization And can be reused very stably. This is the same even when a treatment agent for removing bromine and hydrogen bromide is added prior to recrystallization. In addition to the above-mentioned method for recrystallizing using the above reaction solution as it is to obtain a higher purity target product, the present invention further contributes to an increase in productivity of the target product 4,4′-dibromobiphenyl. It has become.
[0030]
In order to reuse the solvent after fractionating pure crystals (also referred to as “crystallization mother liquor”) as a reaction solvent, the above-mentioned molar ratio of diphenyl to bromine and the concentration of diphenyl in the solvent can be maintained. An insufficient amount of the reaction solvent may be added to the crystallization mother liquor. At this time, the crystallization mother liquor may contain monobromobiphenyl, 2,4′-dibromobiphenyl, 3,4′-dibromobiphenyl, and further 4,4′-dibromobiphenyl. Originally, since the present invention is excellent in the selectivity of 4,4′-dibromobiphenyl, the abundance of by-products is extremely small. For example, monobromobiphenyl is the target product in the following reaction system, 4,4′- This is because the desired product 4,4′-dibromobiphenyl, which becomes dibromobiphenyl and dissolves in the crystallization mother liquor, can improve the yield by reuse. Moreover, the crystallization mother liquor is excellent in that it can be used as it is without being subjected to distillation, decolorization, column treatment, dehydration or the like.
[0031]
The 4,4′-dibromobiphenyl obtained by the present invention has a very high purity, and when other derivatives are synthesized by a conventional method, a high-purity target product can be obtained. For example, 4,4′-dihydroxybiphenyl is a compound useful as an oxidation stabilizer for resins, dye intermediates, and resin production raw materials such as polyesters, polyepoxides, polyurethanes, and polycarbonates. Various methods for synthesizing 4,4′-dihydroxybiphenyl are also known. Examples of such a method include a method described in JP-A-52-36057 and a method described in JP-A-55-17304. Specifically, according to the description in JP-A-55-17304, 4,4′-dibromobiphenyl is hydrolyzed in an alkaline aqueous solution in the presence of a copper compound catalyst, and a by-product is removed from the alkaline aqueous solution containing the reaction product. Extraction is carried out with alcohols or ketones that are hardly or insoluble in water, then the aqueous alkali solution is neutralized with mineral acid, extracted with the same reaction solvent as above, and then crystallized. According to the present invention, since 4,4′-dibromobiphenyl, which is a raw material of 4,4′-dihydroxybiphenyl, can be produced with high purity, 4,4′-dihydroxy can be produced in a high yield using the compound. Biphenyl can be synthesized.
[0032]
For the same purpose as the above 4,4′-dihydroxybiphenyl, 4,4′-dibromobiphenyl produced by the present invention was partially hydrolyzed by a conventionally known method to give 4-bromo-4′-hydroxybiphenyl. It is also possible to produce 4,4′-dihydroxybiphenyl by a known method to produce 4,4′-dicarboxybiphenyl. These compounds are all useful as intermediates for organic EL applications, pharmaceuticals, and agricultural chemicals.
[0033]
【Example】
Hereinafter, the present invention will be described in detail by way of examples.
Example 1
In a 500 liter GL reactor, 154 liters of monochlorobenzene and 77 kg (500 mol) of powdered biphenyl were charged and stirred to dissolve. While maintaining the temperature of the solution at 0 to 12 ° C., 208 kg (1300 mol) of bromine was added dropwise over 1 hour and 30 minutes. The generated hydrogen bromide was recovered by introducing it into a receiver filled with water from the top of the reactor. After the completion of the dropwise addition, the solution was gradually warmed and aged at 20 ° C. for 20 hours. Subsequently, the liquid temperature was raised to 38 ° C. and aged for 1 hour. In the solution, 4,4′-dibromobiphenyl crude crystals were precipitated. The 4,4′-dibromobiphenyl content of the crude crystals was 97.0% by mass.
[0034]
Next, the slurry containing the crude crystals was cooled to 0 ° C. and 23.2% by mass of Na ₂ SO _Three Excess bromine was removed by adding 162.8 kg of aqueous solution. Next, the slurry was heated to 100 ° C. and immediately cooled. The precipitated crystals were collected by centrifugation and dried with a conical dryer. The crystals were 99.8% by mass of 4,4′-dibromobiphenyl, and the yield based on biphenyl was 94%. In addition, the crystallization mother liquor after centrifugation is 160 kg, monobromobiphenyl is 2 mass / volume%, and other isomers of 4,4′-dibromobiphenyl are 0.5-1 mass / volume%, 4,4 '-Dibromobiphenyl was 4% by mass / volume.
[0035]
The purity of 4,4′-dibromobiphenyl and the content of each component in the crystallization mother liquor were measured by gas chromatography.
[0036]
(Example 2)
Example 1 except that 9.4 kg of monochlorobenzene was newly added to 160 kg of the crystallization mother liquor obtained in Example 1 to make a total of 169.4 kg in place of 154 liters of monochlorobenzene of Example 1. In the same manner as described above, 4,4′-dibromobiphenyl was obtained. The 4,4′-dibromobiphenyl content of the crude crystals was 96.5% by mass. The purity of the crystal obtained by recrystallization was 99.8% by mass of 4,4′-dibromobiphenyl, and the yield based on biphenyl was 96%. The crystallization mother liquor was 158 kg, monobromobiphenyl was 2 mass / volume%, the other 4,4′-dibromobiphenyl isomer was 0.5-1 mass / volume%, 4,4′-dibromobiphenyl. Was 3% by mass / volume.
[0037]
(Example 3)
Example 1 except that 11.4 kg of monochlorobenzene was newly added to 158 kg of the crystallization mother liquor obtained in Example 2 instead of 154 liters of monochlorobenzene of Example 1, and a total of 169.4 kg was used. In the same manner as described above, 4,4′-dibromobiphenyl was obtained. The 4,4′-dibromobiphenyl content of the crude crystals was 96.8% by mass. The purity of the crystal obtained by recrystallization was 99.8% by mass of 4,4′-dibromobiphenyl, and the yield based on biphenyl was 97%. The crystallization mother liquor was 158 kg, monobromobiphenyl was 2 mass / volume%, the other 4,4′-dibromobiphenyl isomer was 0.5-1 mass / volume%, 4,4′-dibromobiphenyl. Was 2.5% by mass / volume.
[0038]
Example 4
A 500-liter GL reactor was charged with 208 kg (1300 mol) of bromine, and 77 kg (500 mol) of powdered biphenyl dissolved in 154 liters of monochlorobenzene while maintaining the temperature of the solution at 0 to 12 ° C. Except that it was added dropwise over a period of 30 minutes, the same operation as in Example 1 was performed to obtain 4,4′-dibromobiphenyl crude crystals. The 4,4′-dibromobiphenyl content of the crude crystals was 97.0% by mass.
[0039]
Further, the slurry containing the crude crystals was treated in the same manner as in Example 1 to obtain 4,4′-dibromobiphenyl pure crystals. The purity was 99.8% by mass, and the yield based on biphenyl was 94%. The crystallization mother liquor is 160 kg, monobromobiphenyl is 2 mass / volume%, the other 4,4′-dibromobiphenyl isomers are 0.5-1 mass / volume%, 4,4′-dibromobiphenyl. Was 4% by mass / volume.
[0040]
(Example 5)
A 500-liter GL reactor was charged with 208 kg (1300 mol) of bromine dissolved in 54 liters of monochlorobenzene, and 77 kg (500 mol) of powdered biphenyl was added to this while maintaining the temperature of the solution at 0 to 12 ° C. A crude crystal of 4,4′-dibromobiphenyl was obtained in the same manner as in Example 1 except that a solution dissolved in 100 liters of monochlorobenzene was added dropwise over 1 hour 30 minutes. The 4,4′-dibromobiphenyl content of the crude crystals was 97.0% by mass.
[0041]
Further, the slurry containing the crude crystals was treated in the same manner as in Example 1 to obtain 4,4′-dibromobiphenyl pure crystals. The purity was 99.8% by mass, and the yield based on biphenyl was 94%. The crystallization mother liquor is 160 kg, monobromobiphenyl is 2 mass / volume%, the other 4,4′-dibromobiphenyl isomers are 0.5-1 mass / volume%, 4,4′-dibromobiphenyl. Was 4% by mass / volume.
[0042]
(Example 6)
A 500-liter GL reactor was charged with 77 kg (500 mol) of powdered biphenyl dissolved in 100 liters of monochlorobenzene, and 208 kg (1300 mol) of bromine was added to this while maintaining the temperature of the solution at 0 to 12 ° C. A crude crystal of 4,4′-dibromobiphenyl was obtained in the same manner as in Example 1 except that a solution dissolved in 54 liters of monochlorobenzene was added dropwise over 1 hour 30 minutes. The 4,4′-dibromobiphenyl content of the crude crystals was 96.7% by mass.
[0043]
Further, the slurry containing the crude crystals was treated in the same manner as in Example 1 to obtain 4,4′-dibromobiphenyl pure crystals. The purity was 99.8% by mass, and the yield based on biphenyl was 94%. The crystallization mother liquor is 160 kg, monobromobiphenyl is 2 mass / volume%, the other 4,4′-dibromobiphenyl isomers are 0.5-1 mass / volume%, 4,4′-dibromobiphenyl. Was 4% by mass / volume.
[0044]
【The invention's effect】
According to the present invention, 4,4′-dibromobiphenyl is produced by reacting biphenyl and bromine as raw materials in a reaction solvent of any one of benzene and benzene derivatives, while suppressing by-products such as isomers. The reaction solvent can be heated and cooled to recrystallize 4,4′-dibromobiphenyl, which can be produced with high purity. For this reason, it has been common to recrystallize using a reaction solvent different from the reaction solution. However, the recrystallization process is simply performed without separating the crude crystals, and the high purity 4,4′- Dibromobiphenyl can be produced. Moreover, since the reaction solvent can be stably recovered without decomposition or the like under the reaction conditions, the crystallization mother liquor after obtaining 4,4′-dibromobiphenyl by recrystallization is used again as a reaction solution of biphenyl and bromine. Can be used. For this reason, even if monobromobiphenyl is present, it can be converted to the target 4,4′-dibromobiphenyl in the next step, so that the yield can be further improved.

Claims (5)

Biphenyl and bromine are reacted in a reaction solvent to precipitate crude 4,4′-dibromobiphenyl as crude crystals in the reaction solvent;
Next , without separating the crude crystals, the slurry containing the crude crystals is recrystallized by heating and cooling to obtain 4,4′-dibromobiphenyl pure crystals. A method for producing dibromobiphenyl. Reaction of biphenyl and bromine in the reaction solvent and precipitation of crude 4,4′-dibromobiphenyl crude crystals were performed at a temperature of −5 to 50 ° C. After the crude crystals were precipitated, the slurry was heated to a temperature of 80 to 130 ° C. The method for producing 4,4'-dibromobiphenyl according to claim 1 , wherein the pure crystal is obtained by cooling after heating. The method for producing 4,4'-dibromobiphenyl according to claim 1 or 2 , wherein bromine remaining in the slurry is removed after the precipitation of the crude crystals, and then the slurry is heated and cooled. The reaction solvent after fractional pure crystals from the slurry, characterized in that it re-used as the reaction solvent for reaction of the biphenyl and bromine, according to claim 1 4,4 Method for producing '-dibromobiphenyl. The reaction solvent is any one of benzene, monochlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, monobromobenzene, o-dibromobenzene, m-dibromobenzene, p-dibromobenzene and bromochlorobenzene. and characterized in that species or more, the production method of 4,4'-dibromo-biphenyl according to any one of claims 1 to 4.