JP2692769B2 - Organic solvent recovery method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing chloranil by chlorinating hydroquinone under mild conditions and then recovering water used as a solvent or an organic solvent which is incompatible with hydrochloric acid.

BACKGROUND OF THE INVENTION Chloranil is an industrially important compound as an intermediate for pesticides and dyes. The present inventors have continued research on a method for producing high-purity chloranil having high bulk specific gravity, which is easy to handle, under mild conditions and simple operations. As a result, the above object can be achieved by reacting hydroquinone with chlorine in a heterogeneous mixed solvent of water or hydrochloric acid and an organic solvent which is not compatible with them, and has already been proposed (Patent No. 2017115). . In the above method, the organic solvent which is incompatible with water or hydrochloric acid can be reused without any treatment, but it was found that impurities were accumulated and the purity of chloranil was affected with repeated reuse. A method for removing these impurities to recover an organic substance has not been known so far, but it is a usual method to recover an organic solvent by distillation. Regarding the organic solvent in which chlorine and hydrochloric acid are dissolved after the chlorination reaction, water or dissolved chlorine and hydrochloric acid are brought into contact with an alkaline aqueous solution to remove chlorine and hydrochloric acid,
Generally, it is recovered by distillation.

However, chlorine, hydrochloric acid, chloranil and by-products at the time of chloranil production are dissolved in the organic solvent after the production of chloranil. And the problem of corrosion by hydrochloric acid arises. In addition, when an alkaline aqueous solution equimolar to chlorine and hydrochloric acid dissolved in an organic solvent was brought into contact with the above organic solvent, an organic substance insoluble in both phases at the interface between the aqueous phase and the organic solvent phase (hereinafter, this Is called a meniscus.)

Means for Solving the Problems As a result of diligent studies on a method for recovering an organic solvent which is incompatible with water or hydrochloric acid after producing chloranil by a simple method, the present inventors It was found that the meniscus generated when an alkaline aqueous solution was brought into contact with an organic solvent that is incompatible with water and hydrochloric acid was derived from chloranil and its by-products, and further from the chlorinated product of the solvent. They have found that these compounds can decompose metal chlorides and organic substances containing almost no chlorine by contacting with excess alkali, and the meniscus generated thereby can be minimized. Furthermore, it was found that the meniscus generated at this time can be easily removed by bringing it into contact with an oxidizing agent, and the present invention has been completed. That is, the present invention is to produce chloranil by reacting hydroquinone with chlorine in a heterogeneous mixed solvent of water or hydrochloric acid and an organic solvent incompatible with them to produce chloranil, and separate chloranil from the organic solvent incompatible with water or hydrochloric acid. After that, an alkaline aqueous solution which is more than twice the molar amount of chlorine and hydrochloric acid dissolved in an organic solvent incompatible with water or hydrochloric acid is contacted with the organic solvent incompatible with water or hydrochloric acid. It is a method of recovering an organic solvent. The organic solvent which is not compatible with water or hydrochloric acid used in the present invention is an organic solvent which does not form a homogeneous phase with water or hydrochloric acid at an arbitrary ratio and is separated into two phases. Specific examples of such an organic solvent include chlorobenzene, o-dichlorobenzene, and m.
-Dichlorobenzene, p-dichlorobenzene, 1,2,
3-trichlorobenzene, 1,2,4-trichlorobenzene, fluorobenzene, o-difluorobenzene, m
-Halogenated aromatic hydrocarbons such as difluorobenzene, 1,2,3-trifluorobenzene and 1,2,4-trifluorobenzene; nitro group-substituted aromatic hydrocarbons such as nitrobenzene; methylene chloride, chloroform, tetrachloride Carbon, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,
Examples thereof include halogenated aliphatic hydrocarbons such as 1,2,2-tetrachloroethane. Among these organic solvents, chlorobenzene, o-dichlorobenzene, m-
Dichlorobenzene, p-dichlorobenzene, 1,2,3
-Halogenated aromatic hydrocarbons such as trichlorobenzene and 1,2,4-trichlorobenzene are preferably used.
These solvents may be used alone or as a mixture of two or more. The concentration of hydrochloric acid which is another solvent in the present invention is not particularly limited, and hydrochloric acid up to 37% by weight can be used, but when hydrochloric acid having a too low concentration is used, the product chloranil may be colored. Therefore, it is usually preferable to be 5% by weight or more.
When water is used as another solvent, chlorine dissolves into hydrochloric acid during the chlorination reaction of hydroquinone. The mixing ratio of the organic solvent and hydrochloric acid is not particularly limited, but in order to make the obtained chloranil have a high bulk density, the organic solvent / hydrochloric acid (volume ratio) is in the range of 0.1 to 10, and further 0.5 to 5 The range is more preferable. The concentration of hydroquinone in the heterogeneous mixed solvent varies depending on the composition of the heterogeneous mixed solvent, the type of organic solvent, and the stirring effect, but is generally 0.
It is preferable to select from the range of 5 to 40% by weight. The chlorination reaction of hydroquinone is performed by dissolving hydroquinone in a heterogeneous mixed solvent and then blowing chlorine gas. The reaction temperature may be usually selected in the range of 25 ° C. to the boiling point of the heterogeneous mixed solvent, preferably 50 to 100 ° C. The total amount of chlorine gas used is usually 6 to 9 mol per 1 mol of hydroquinone. Although the amount of this chlorine gas is about 20% or more in excess of the theoretical amount, in actual production, it may be determined by analyzing the composition of the reaction product. Thus, after chloranil is produced by chlorination of hydroquinone, chloranil is separated. For separation of chloranil, known means such as centrifugation and sedimentation can be adopted. In the present invention, an alkaline aqueous solution that is at least twice the molar amount of chlorine and hydrochloric acid dissolved in an organic solvent that is incompatible with water or hydrochloric acid is contacted with the organic solvent that is incompatible with water or hydrochloric acid. As the type of alkali used as the above alkaline aqueous solution, known compounds can be used without particular limitation. Generally, alkali metal and alkaline earth metal hydroxides and carbonates can be preferably used.
Specific examples thereof include sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, calcium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate and the like. In particular, among these alkalis, strong alkalis such as sodium hydroxide, potassium hydroxide and calcium hydroxide are preferably used because they rapidly decompose chloranil and by-products in the organic solvent. These alkalis may be used alone or as a mixture of two or more kinds without any problem.
The amount of alkali used in the present invention must be 2 times or more, and preferably 3 times or more, the moles of chlorine and hydrochloric acid dissolved in an organic solvent incompatible with water or hydrochloric acid. . 2 for alkali and chlorine and hydrochloric acid
When the amount is less than twice the molar amount, the organic substances contained in the organic solvent cannot be sufficiently decomposed, mechanics are generated, and the reuse of the organic solvent becomes impossible. Since there is no problem even if the amount of alkali is too large, the upper limit may be arbitrarily determined for economic or other reasons. The amount of the alkaline aqueous solution is not particularly limited, but may be selected from the range of 10 to 200 parts by volume with respect to 100 parts by volume of the organic solvent to be treated. In the present invention, the alkaline aqueous solution is
Although it depends on the organic solvent to be treated, the alkali concentration is preferably 2.5 to 30% by weight, and the amount of the aqueous solution is preferably 20 to 100 parts by volume with respect to 100 parts by volume of the organic solvent to be treated. The temperature at which the alkaline aqueous solution and the organic solvent are brought into contact with each other is not particularly limited, but if the temperature is too high, the alkali decomposition of the organic solvent occurs, so 0 ° C to 100 ° C.
C., preferably in the range of 5 to 80.degree. In the present invention, it is preferable that the organic solvent is brought into contact with the above-mentioned alkaline aqueous solution and then further brought into contact with an oxidizing agent. Even if a meniscus is generated due to the contact between the organic solvent and the alkaline aqueous solution, the oxidizing agent has a function of eliminating the generated meniscus. In addition to the meniscus extinguishing effect, the oxidizing agent also has the effect of decolorizing the alkaline aqueous solution colored by being brought into contact with the organic solvent. The oxidizing agent is not particularly limited as long as it is a compound having an oxidizing power, but a gas or a water-soluble oxidizing agent is preferable in consideration of operability during and after the treatment with the oxidizing agent. Specific examples thereof include water-soluble oxidizing agents such as hydrogen peroxide solution, sodium hypochlorite aqueous solution, potassium hypochlorite aqueous solution, sodium hypobromite aqueous solution, and potassium hypobromite aqueous solution; chlorine and bromine. , And gases such as oxygen and ozone. The above-described decolorizing effect of the oxidizing agent is remarkable for the oxidizing agent having a strong oxidizing power, and when it is desired to eliminate the meniscus and also decolorize the alkaline aqueous solution, use an oxidizing agent having a strong oxidizing power such as hydrogen peroxide. You can easily reach the goal.
The amount of oxidant used is not particularly limited, but if a large amount is used, surplus oxidant must be reduced. Therefore, the oxidizing agent may be added little by little, and the use of the oxidizing agent may be stopped when the meniscus disappears. The temperature at which the oxidant is brought into contact with the organic solvent is not particularly limited, but normally, the oxidant having a strong oxidizing power may be brought into contact at a low temperature, and the oxidant having a weak oxidizing power may be brought into contact at a high temperature, generally 0 to 80. It is preferred to choose between ° C. The organic solvent thus recovered may be reused as it is, or may be reused after further rectifying by distillation.

According to the present invention, the organic solvent after chloranil production can be recovered under mild conditions and by a simple operation.
The organic solvent thus recovered can be used again for producing chloranil.

The following examples are given, but the present invention is not limited to these examples. Example 1 400 ml of o-dichlorobenzene, 400 ml of 25% hydrochloric acid, and hydroquinone 8 were placed in a four-necked flask equipped with a central stirrer with blades, a condenser, a thermometer, and a chlorine gas introduction tube.
1.6 g (0.74 mol) were charged, and this mixture was
The mixture was heated to 0 ° C. to introduce chlorine gas. Chlorine gas 26
2.7 g (3.71 mol) was introduced over 4 hours and 10 minutes, and then the chlorine supply rate was reduced to half and further 1
57.6 g (2.22 mol) of chlorine was introduced. 50
After cooling to ℃, the hydrochloric acid phase is separated, and warm water at 50 ℃ 20
0 ml was added and stirred for 10 minutes, and the aqueous phase was separated. Repeat this operation and add 200 ml of warm water to add 1
After stirring for 0 minute, chloranil and the mixed solvent were separated by centrifugation. The separated mixed solvent was separated into an aqueous phase and an o-dichlorobenzene phase. Fresh o-dichlorobenzene was added to the o-dichlorobenzene obtained by this series of operations to make 400 ml, chlorination of hydroquinone was carried out in the same manner as above, and the same post-treatment operation was carried out. Then, the same operation was repeated for the obtained o-dichlorobenzene, and this operation was repeated 10 times in total. The chlorine and hydrochloric acid dissolved in 100 ml of red-orange o-dichlorobenzene (purity 96.0%) thus obtained was 0.0
It was 2 mol. 100 ml of this o-dichlorobenzene
Was added to a four-necked flask equipped with a central stirrer equipped with a blade, a thermometer and a dropping funnel, and 100 ml (0.25 mol) of a 10 wt% sodium hydroxide aqueous solution was added.
Stirred for 0 minutes. After stirring, the mixture was allowed to stand for 30 minutes to obtain 98 ml of a colorless and transparent o-dichlorobenzene phase containing a small amount of meniscus and a phase containing an aqueous sodium hydroxide solution.
From this solution, only the o-dichlorobenzene phase is separated,
When subjected to the above chlorination reaction of hydroquinone, there was no problem in the reaction. Further, a solution consisting of 98 ml of a colorless and transparent o-dichlorobenzene phase containing a small amount of meniscus and a phase containing an aqueous solution of sodium hydroxide obtained by the same operation as described above was 30% without separating.
When 2 ml of hydrogen peroxide solution was added and the temperature was raised to 50 ° C. and stirred for 30 minutes, the meniscus disappeared and 100 ml of o-
Dichlorobenzene was recovered (purity 98.0%). When the above chlorination reaction of hydroquinone was carried out using the recovered o-dichlorobenzene, there was no problem in the reaction. In addition, the aqueous phase containing the aqueous sodium hydroxide solution was hardly colored. Example 2 By changing the alkaline aqueous solution to 100 ml (0.18 mol) of a 10% by weight potassium hydroxide aqueous solution and carrying out the same operation as in Example 1 and contacting with o-dichlorobenzene, 98 ml containing a small amount of meniscus. Only the colorless and transparent o-dichlorobenzene phase of was separated. When the chlorination reaction of hydroquinone was carried out using this solution, there was no problem in the reaction. In addition, a solution consisting of 98 ml of a colorless and transparent o-dichlorobenzene phase containing a small amount of meniscus and a phase containing an aqueous solution of potassium hydroxide obtained by exactly the same operation as described above was added to a solution containing 30% hydrogen peroxide without separation. 2m
When 1 was added and the temperature was raised to 50 ° C. and stirred for 30 minutes, the meniscus disappeared and 100 ml of o-dichlorobenzene was recovered (purity 98.3%). When the above chlorination reaction of hydroquinone was carried out using the recovered o-dichlorobenzene, there was no problem in the reaction. In addition, the aqueous phase containing the aqueous potassium hydroxide solution showed almost no coloring. Example 3 15% by weight aqueous potassium carbonate solution 1
After changing to 00 ml (0.11 mol) and contacting with o-dichlorobenzene by the same operation as in Example 1, only 98 ml of a yellow o-dichlorobenzene phase containing a small amount of meniscus was separated. When the chlorination reaction of hydroquinone was carried out using this solution, there was no problem in the reaction. In addition, 98 ml obtained by the same operation as above
The solution consisting of the yellow o-dichlorobenzene phase and the phase containing the aqueous potassium carbonate solution was added to 2 ml of 30% hydrogen peroxide solution without separating the liquid, and the temperature was raised to 50 ° C. and stirred for 30 minutes, the meniscus disappeared. Then, 100 ml of o-dichlorobenzene was recovered (purity 97.5%). When the above chlorination reaction of hydroquinone was carried out using the recovered o-dichlorobenzene, there was no problem in the reaction. In addition, the aqueous phase containing the aqueous potassium carbonate solution showed almost no coloring. Example 4 After the contact treatment with an alkaline aqueous solution was carried out in the same manner as in Example 1, 23 ml of a 5% sodium hypochlorite aqueous solution was added as an oxidizing agent, and the mixture was stirred at 45 ° C. for 30 minutes. Then, 100 ml (purity 98.0%) of colorless and transparent o-dichlorobenzene was recovered. At this time, the color of the aqueous phase containing the alkaline aqueous solution was yellow. When the chlorination reaction of hydroquinone was carried out using the recovered o-dichlorobenzene, there was no problem in the reaction. Example 5 After contact treatment with an alkaline aqueous solution was carried out in the same manner as in Example 1, 4.0 g of sodium hydroxide (0.1 mo)
l) was added and the temperature was raised to 50 ° C., and chlorine gas was added to this solution to 4 times.
When introduced at a rate of 5 ml / min for 30 minutes to generate sodium hypochlorite in the system for oxidation treatment, the meniscus disappeared completely, and colorless and transparent o-dichlorobenzene was recovered (purity 98. 0%). At this time, the color of the aqueous phase containing the alkaline aqueous solution was brown. When the chlorination reaction of hydroquinone was carried out using the recovered o-dichlorobenzene, there was no problem in the reaction. Comparative Example 1 The alkaline aqueous solution was changed to 100 ml (0.025 mol) of a 1% by weight aqueous sodium hydroxide solution, and contacted with o-dichlorobenzene in the same manner as in Example 1. After stirring, the mixture was allowed to stand for 1 hour, but a large amount of meniscus was dispersed throughout the solution, and the interface between the o-dichlorobenzene phase and the aqueous phase could not be discriminated at all. Further, 2 ml of 30% hydrogen peroxide solution was added to this solution and the temperature was raised to 50 ° C. and stirred for 30 minutes, but the meniscus did not disappear and the interface could not be discriminated. Therefore, o-dichlorobenzene could be finally recovered by removing the meniscus by vacuum filtration. (Purity: 96.5%) The separated aqueous phase remained black and was hardly decolorized.

Claims (1)

(57) [Claims] 1. Hydroquinone is reacted with chlorine in a heterogeneous mixed solvent of water or hydrochloric acid and an organic solvent incompatible with them to produce chloranil, and chloranil is separated from the organic solvent incompatible with water or hydrochloric acid. After that, an alkaline aqueous solution which is more than twice the molar amount of chlorine and hydrochloric acid dissolved in an organic solvent incompatible with water or hydrochloric acid is brought into contact with the water or an organic solvent incompatible with hydrochloric acid. Solvent recovery method.