JP4029447B2 - Method for producing 2-chloro-1,4-bistrichloromethylbenzene - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing 2-chloro-1,4-bistrichloromethylbenzene by subjecting 2-chloroparaxylene and chlorine to side chain chlorination reaction under light irradiation, and is industrially particularly effective in high yield. The present invention relates to a process for producing 2-chloro-1,4-bistrichloromethylbenzene which can be advantageously produced.
[0002]
[Prior art]
2-Chloro-1,4-bistrichloromethylbenzene (hereinafter abbreviated as “CBTB”) is useful as an intermediate for pharmaceuticals and agricultural chemicals and also as an intermediate for various industrial chemicals. It is a very important compound as an intermediate in the production of 2-chloroterephthalic acid chloride used as a monomer in the production of functional polymers such as aromatic polyamides and aromatic polyesters.
[0003]
As a method for producing this CBTB, first of all, a direct chlorination method in which chlorine is directly introduced into the aromatic nucleus of 1,4-bistrichloromethylbenzene is known (Japanese Patent Laid-Open No. 4-31551). In this method, 1,4-bistrichloromethylbenzene is synthesized by photochlorination of para-xylene under irradiation with ultraviolet light, and this 1,4-bistrichloromethylbenzene is then combined with chlorine in the presence of ferric chloride. The reaction is carried out, and the resulting reaction mixture is distilled under reduced pressure to obtain the desired CBTB.
[0004]
However, in the direct chlorination method of 1,4-bistrichloromethylbenzene, the concentration of the target CBTB in the reaction mixture is extremely low, less than 40% by weight, and is contained as an impurity in the CBTB and the reaction mixture. The unreacted 1,4-bistrichloromethylbenzene has a high boiling point and melting point, and it is not economical and industrially difficult to separate and purify CBTB by distillation.
[0005]
Further, as a second method for producing CBTB, there is known a side chain chlorination method of 2-chloroparaxylene in which a side chain methyl group of 2-chloroparaxylene is chlorinated (JP-A-4-327557). ). In this method, paraxylene and chlorine are reacted in the presence of ferric chloride, 2-chloroparaxylene is separated from the reaction mixture by distillation, and ultraviolet light containing ultraviolet light is irradiated into the obtained 2-chloroparaxylene. Under the reaction temperature of 120 ° C., 1.25 times equivalent of chlorine gas was blown in for 15 hours to react, and it was reported that CBTB with a gas chromatography analysis purity of 97.8% was obtained. .
[0006]
However, in this method, when the target CBTB is used as a raw material for producing 2-chloroterephthalic acid chloride, it is used as a monomer for producing a functional polymer. The concentration of 3-chloro-4-dichloromethylbenzotrichloride and 2-chloro-4-dichloromethylbenzotrichloride (hereinafter, these may be collectively referred to as “benzal form”) of the reaction intermediates remaining in However, since the boiling point and melting point of CBTB are very high, it is difficult to separate and remove these benzal bodies in the distillation purification process of CBTB, and the side chain chlorine of 2-chloroparaxylene It is necessary to control the concentration of these benzal bodies to 100 ppm or less in the chemical reaction step.
[0007]
Further, similarly, JP-A-8-188551 was obtained by reacting paraxylene and chlorine in the presence of ferric chloride, and separating 2-chloroparaxylene from the reaction mixture by distillation. While irradiating ultraviolet light in 2-chloroparaxylene under the conditions of a reaction temperature of 100 to 155 ° C. and a chlorine gas of 1.10 times equivalent, gradually reducing the chlorine blowing rate as the chlorination reaction proceeds, 31 Blowing in for 5 hours, reacting until the concentration of the benzal body is 100 ppm or less, CBTB 90.1 wt% and 3,4-dichlorobenzotrichloride (hereinafter abbreviated as “3,4-DCBT”) 9.9 It has been reported that a reaction product having a composition by weight is obtained.
[0008]
However, in these methods, since it is necessary to chlorinate until the concentration of the reaction intermediate benzal is 100 ppm or less, the amount of by-produced 3,4-DCBT, which is a perchlorinated byproduct, increases. Accordingly, there was a problem that the yield of the side chain chlorination reaction was lowered.
[0009]
[Problems to be solved by the invention]
Therefore, the present inventors have intensively studied a method capable of producing 2-chloro-1,4-bistrichloromethylbenzene (CBTB) with high yield and industrially advantageously. The inventors have found a method that can suppress the formation of 3,4-DCBT as a perchlorination by-product as much as possible in the side chain chlorination reaction of chloroparaxylene, and have completed the present invention.
[0010]
Accordingly, an object of the present invention is to produce 2-chloro-1,4-bistrichloromethyl capable of producing CBTB in high yield and industrially advantageously by side chain chlorination reaction of 2-chloroparaxylene. The object is to provide a method for producing benzene.
[0011]
[Means for Solving the Problems]
That is, in the present invention, 2-chloro-1,4- bistrichloromethylbenzene is produced by subjecting 2-chloroparaxylene and chlorine to side chain chlorination reaction at a reaction temperature of 90 to 160 ° C. under light irradiation. In this side chain chlorination reaction , when the degree of chlorination, which shows the average number of hydrogen atoms of two methyl groups in 2 - chloroparaxylene , is replaced by chlorine atoms, reaches 5.0 to 6.0. 2-chloro-1,4-bistrichloromethylbenzene which lowers the reaction temperature of the side chain chlorination reaction in the range of 20 to 90 ° C. and controls the reaction temperature at the end of the reaction until the end of the reaction to 70 to 140 ° C. It is a manufacturing method.
[0012]
In the present invention, 2-chloroparaxylene used as a raw material may be produced by any method as long as it has high purity with respect to paraxylene and dichloroparaxylene, but preferably paraxylene and dichloroparaxylene. The 2-chloroparaxylene is preferably obtained by distilling a reaction mixture of paraxylene and chlorine.
[0013]
This reaction between paraxylene and chlorine is a nuclear chlorination reaction in the liquid phase of paraxylene. In the presence of a Lewis acid catalyst such as aluminum chloride, antimony chloride, zinc chloride, ferric chloride, etc., the raw material paraxylene This is done by blowing chlorine gas into the inside.
[0014]
For the nuclear chlorination reaction of para-xylene, either a batch method or a continuous method can be adopted, and the Lewis acid catalyst used is preferably ferric chloride because it is easy to handle and economical. The amount of the catalyst used is 0.005 to 5% by weight, preferably 0.01 to 1% by weight, based on para-xylene as a raw material. When the amount of the catalyst used is less than 0.005% by weight, the reaction rate is remarkably slow. On the other hand, when the amount used is more than 5% by weight, the by-product of perchlorate such as a dichloro compound increases, which is not preferable.
[0015]
Furthermore, in the nuclear chlorination reaction of para-xylene, the reaction temperature is usually 20 to 160 ° C., preferably 30 to 60 ° C. If the reaction temperature is too low, the reaction rate is lowered, which is not economical. If it is too high, the by-product of perchlorate such as dichloro is increased, which is not preferable. Further, the amount of chlorine used in the reaction is 0.3 times mol or more, preferably 0.8 to 1.5 times mol with respect to the raw material paraxylene. If the amount of chlorine to be used is small, the yield per cycle is lowered, and if it is too high, the by-product of perchlorates such as dichloro is increased, which is not preferable. The nuclear chlorination reaction of para-xylene can be performed without using a solvent, but a reaction solvent such as carbon tetrachloride may be used as necessary.
[0016]
In the nuclear chlorination reaction of para-xylene, a distillation method is usually employed as a method for purifying 2-chloropara-xylene from the obtained reaction mixture, and it may be a continuous type or a batch type. In distilling and purifying 2-chloroparaxylene, reducing the impurity concentration of 2-chloroparaxylene obtained, especially the total impurity concentration of paraxylene and dichloroparaxylene to 100 ppm or less, the reflux ratio management and the fraction switching point management The reflux ratio is 3 or more, preferably 5 or more, and the fraction switching point is an impurity concentration of 500 ppm or less, preferably 300 ppm or less.
[0017]
Unreacted para-xylene is recovered by this distillation purification, and this unreacted para-xylene is preferably recycled by recycling it to the nuclear chlorination reaction step. Perchlorate is removed from the bottom of the column as a high boiler.
[0018]
The 2-chloroparaxylene used in the next side chain chlorination reaction should preferably have a purity of 99.9% by weight or more, more preferably 99.99% by weight or more. And dichloroparaxylene become 1,4-bistrichloromethylbenzene and dichloro-1,4-bistrichloromethylbenzene, respectively, by the side chain chlorination reaction, and separation and removal thereof are difficult and remain as impurities in the product CBTB. At this stage, the total impurity concentration of paraxylene and dichloroparaxylene is preferably reduced to 100 ppm or less.
[0019]
The side chain chlorination reaction of 2-chloroparaxylene thus obtained is carried out by blowing chlorine gas into 2-chloroparaxylene under light irradiation with a mercury lamp or the like. The reaction form in this side chain chlorination reaction may be batch or continuous and can be carried out without using a solvent, but a reaction solvent such as carbon tetrachloride can also be used if necessary.
[0020]
In this side chain chlorination reaction, in order to suppress the formation of 3,4-DCBT as a perchlorination byproduct as much as possible, the reaction temperature at the end of the reaction is 70 to 140 ° C., preferably 80 to It is necessary to control to 120 ° C. Here, the end of the side chain chlorination reaction in which the reaction temperature is controlled to 70 to 140 ° C. is an average value of how many hydrogen atoms of two methyl groups in the raw material 2-chloroparaxylene are substituted with chlorine atoms. Is understood as from the time when the degree of chlorination reaches 5.0 to 6.0, preferably 5.4 to 5.9 to the end of the reaction. If the reaction temperature at the end of the reaction is lower than 70 ° C, the chlorine reaction rate decreases and the reaction time becomes undesirably long. If the reaction temperature exceeds 140 ° C, the production of perchlorinated byproducts is effectively suppressed. The problem that it is not possible arises.
[0021]
The reaction temperature in the side chain chlorination reaction is usually 90 to 160 ° C. from the initial stage to the middle stage of the reaction, shortening the time required to complete the reaction, and at the same time allowing the by-production of perchlorinated by-products. In terms of suppression, it is preferably carried out at a reaction temperature of 100 to 150 ° C. If the reaction temperature from the initial stage to the middle stage of the reaction is lower than 90 ° C., there is a problem that the reaction rate is lowered and it is not economical. There arises a problem that it decreases and causes the generation of impurities.
[0022]
In the present invention, the degree of chlorination used as an indicator of the degree of progress of the side chain chlorination reaction is an average of how many hydrogen atoms of two methyl groups in the raw material 2-chloroparaxylene are substituted with chlorine atoms. Since it is a value indicated by a value, it is theoretically determined in the range of 0 to 6, and the target CBTB has a chlorination degree of 6. However, since this CBTB is further chlorinated and becomes a perchlorinated byproduct, 3,4-DCBT, in the present invention, this 3,4-DCBT is assumed to be a compound having a chlorination degree of 7 and is chlorinated. Calculate the degree.
[0023]
In addition, in the side chain chlorination reaction of 2-chloroparaxylene, the reaction end is rate-limiting, and excessive supply of chlorine increases the amount of unreacted chlorine in the exhaust gas and promotes the generation of impurities. Therefore, it is preferable to reduce the chlorine supply amount as the reaction proceeds. And the usage-amount of chlorine should just be more than a theoretical amount, However, Preferably the range of 1.1-1.6 times mole of theoretical amount is good. If the amount of chlorine used exceeds 1.6 times the theoretical amount, formation of 3,4-DCBT as a perchlorinated byproduct is promoted, which is not preferable.
[0024]
Furthermore, in the side chain chlorination reaction of 2-chloroparaxylene, in the obtained reaction mixture, in addition to the target CBTB and the perchlorinated by-product 3,4-DCBT, a benzal compound which is a reaction intermediate (3-chloro-4-dichloromethylbenzotrichloride and 2-chloro-4-dichloromethylbenzotrichloride) are included, but these benzal bodies are used as a raw material for producing 2-chloroterephthalic acid chloride. When used, it becomes 3-chloro-4-dichloromethylbenzoic acid chloride or 2-chloro-4-dichloromethylbenzoic acid chloride as an impurity of 2-chloroterephthalic acid chloride in its production process, and its purity reduction or yield It is better to reduce as much as possible during the side chain chlorination reaction of 2-chloroparaxylene. And it is preferably carried out side-chain chlorination reaction until the concentration of benzal body becomes 100ppm or less. For this reason, in the side chain chlorination reaction of 2-chloroparaxylene, the reaction mixture is preferably analyzed by gas chromatography in the course of the reaction to determine the end point of the reaction.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
In the side chain chlorination reaction of 2-chloroparaxylene, the production of 3,4-DCBT, which is a perchlorination byproduct, begins at the end of the reaction when the degree of chlorination exceeds 5.0 to 6.0. It increases as the degree of conversion progresses.
[0026]
Therefore, in the method of the present invention, from the time when the chlorination degree reaches 5.0 to 6.0, preferably 5.4 to 5.9, until the end of the reaction, preferably 3-chloro-4 which is a reaction intermediate. -The reaction temperature at the end of the reaction until the end of the reaction when the concentration of the benzal compound consisting of dichloromethylbenzotrichloride and 2-chloro-4-dichloromethylbenzotrichloride is 100 ppm or less and the reaction is terminated. The reaction temperature is controlled to be in the range of 70 to 140 ° C. by reducing the reaction temperature from 90 to 160 ° C. by 20 to 90 ° C.
[0027]
According to the present invention, in this way, in the side chain chlorination reaction of 2-chloroparaxylene, the reaction temperature at the end of the reaction is controlled to a temperature lower than the reaction temperature at the beginning of the reaction or at the middle of the reaction. CBTB can be produced in a high yield and industrially advantageously without unnecessarily lengthening the reaction time up to.
[0028]
【Example】
Hereinafter, preferred embodiments of the present invention will be described in detail based on examples and comparative examples.
[0029]
Example 1
A reaction vessel was charged with 7436 g (70.00 mol) of para-xylene and 1.5 g (0.02 wt%) of ferric chloride and introduced with stirring while bubbling chlorine gas at a rate of 5.5 g / min. The mixture was reacted at a reaction temperature of 40 to 50 ° C. for 14 hours.
The amount of chlorine used was 4761 g (67.15 mol), and the chlorine reaction rate was 99.9% by weight.
[0030]
Moreover, as a result of analyzing the obtained reaction mixture by gas chromatography after the completion of the reaction, the composition of the reaction mixture was as follows: unreacted paraxylene 15.6%, 2-chloroparaxylene 69.7%, and Dichloroparaxylene was 14.7%.
[0031]
9728 g of the reaction mixture thus obtained was distilled under reduced pressure at a reflux ratio of 3 using a rectification column having 10 theoretical plates with a conventional method to obtain a fraction having a boiling point of 116 to 117 ° C./116 mmHg.
The obtained fraction was 5568 g (39.54 mol, yield: 56.6% by weight) of 2-chloroparaxylene having a purity of 99.99% by weight.
[0032]
Next, 563 g (4.00 mol) of 2-chloroparaxylene obtained above was charged into a reaction vessel and introduced while bubbling chlorine gas at a reaction temperature of 140 ° C. and under the following flow rate under irradiation with a high-pressure mercury lamp. Then, a side chain chlorination reaction of 2-chloroparaxylene was performed. The introduction of chlorine gas is 2.5 g / min for the first 4 hours, 2.0 g / min for the next 4 hours, 1.0 g / min for the next 4 hours, and then 0.5 g / min. The introduction speed was changed.
[0033]
Further, in this side chain chlorination reaction, the chlorination degree and reaction intermediates 3-chloro-4-dichloromethylbenzotrichloride and 2-chloro-4-dichloromethyl which are time-dependent by gas chromatography during the process. The concentration of benzotrichloride (benzal form) was measured, and when the chlorination degree reached 5.4, the reaction temperature was lowered to 80 ° C., and when the concentration of benzal form became 100 ppm or less. The reaction was terminated to obtain 1352 g of a reaction mixture (yield 94.6% based on 2-chloroparaxylene as a raw material).
[0034]
The total reaction time was 40.0 hours, the reaction time until the reaction temperature was lowered from 140 ° C. to 80 ° C. was 24 hours from the start of the reaction, and the total chlorine usage was 2130 g (30.04 mol). The average chlorine reaction rate was about 80%.
Moreover, as a result of analyzing the obtained reaction mixture by gas chromatography, the composition was a gas chromatograph percentage, 2-chloro- 1, 4- bistrichloromethylbenzene (CBTB) 97.2%, and 3, 4- dichloro. Benzotrichloride (3,4-DCBT) was 2.8%.
[0035]
Example 2
The above example was used except that 563 g (4.00 mol) of 2-chloroparaxylene obtained in Example 1 was used and the reaction temperature was lowered to 100 ° C. when the chlorination degree reached 5.4. The side chain chlorination reaction of 2-chloroparaxylene was carried out in the same manner as in Example 1 to obtain 1345 g of a reaction mixture (yield 92.2% based on the raw material 2-chloroparaxylene).
[0036]
The total reaction time was 38.0 hours, the reaction time until the reaction temperature was lowered from 140 ° C. to 100 ° C. was 24 hours from the start of the reaction, and the total chlorine consumption was 2070 g (29.20 mol). The average chlorine reaction rate was about 82%.
Moreover, as a result of analyzing the obtained reaction mixture by gas chromatography, the composition was CBTB: 95.2% and 3,4-DCBT: 4.8% in terms of gas chromatography.
[0037]
Example 3
The above example was used except that 563 g (4.00 mol) of 2-chloroparaxylene obtained in Example 1 was used and the reaction temperature was lowered to 120 ° C. when the chlorination degree reached 5.4. The side chain chlorination reaction of 2-chloroparaxylene was carried out in the same manner as in case 1 to obtain 1342 g of reaction mixture (yield 90.9% with respect to the raw material 2-chloroparaxylene).
[0038]
The total reaction time was 33.0 hours, the reaction time until the reaction temperature was lowered from 140 ° C. to 120 ° C. was 24 hours from the start of the reaction, and the total chlorine usage was 1920 g (27.08 mol). The average chlorine reaction rate was about 89%.
Moreover, as a result of analyzing the obtained reaction mixture by the gas chromatography, the composition was CBTB: 94.1% and 3,4-DCBT: 5.9% by the gas chromatography percentage.
[0039]
Comparative Example 1
Except for using 563 g (4.00 mol) of 2-chloroparaxylene obtained in Example 1 above and maintaining the reaction temperature at 140 ° C. from the start of the reaction to the end of the reaction, the same as in the case of Example 1 above. Then, the side chain chlorination reaction of 2-chloroparaxylene was performed to obtain 1334 g of a reaction mixture (yield of 88.2% based on 2-chloroparaxylene as a raw material).
[0040]
The total reaction time was 31.5 hours, the total amount of chlorine used was 1875 g (26.45 mol), and the average chlorine reaction rate was about 91%.
Moreover, as a result of analyzing the obtained reaction mixture by gas chromatography, the composition was CBTB: 91.8% and 3,4-DCBT: 8.2% in percentage by gas chromatography.
[0041]
Example 4
The above example was used except that 563 g (4.00 mol) of 2-chloroparaxylene obtained in Example 1 was used and the reaction temperature was lowered to 100 ° C. when the chlorination degree reached 4.8. The side chain chlorination reaction of 2-chloroparaxylene was carried out in the same manner as in case 1 to obtain 1338 g of reaction mixture (yield 91.8% relative to the raw material 2-chloroparaxylene).
[0042]
The total reaction time was 47.0 hours, the reaction time until the reaction temperature was lowered from 140 ° C. to 100 ° C. was 15 hours from the start of the reaction, and the total amount of chlorine used was 2340 g (33.00 mol). The average chlorine reaction rate was about 73%.
Moreover, as a result of analyzing the obtained reaction mixture by gas chromatography, the composition was CBTB: 95.3% and 3,4-DCBT: 4.7% in percentage by gas chromatography.
[0043]
Example 5
The above example was used except that 563 g (4.00 mol) of 2-chloroparaxylene obtained in Example 1 was used and the reaction temperature was lowered to 100 ° C. when the chlorination degree reached 5.2. The side chain chlorination reaction of 2-chloroparaxylene was carried out in the same manner as in case 1 to obtain 1346 g of a reaction mixture (yield 92.4% based on the raw material 2-chloroparaxylene).
[0044]
The total reaction time was 41.0 hours, the reaction time until the reaction temperature was lowered from 140 ° C. to 100 ° C. was 21 hours from the start of the reaction, and the total chlorine usage was 2160 g (30.47 mol). The average chlorine reaction rate was about 79%.
Moreover, as a result of analyzing the obtained reaction mixture by gas chromatography, the composition was CBTB: 95.3% and 3,4-DCBT: 4.7% in percentage by gas chromatography.
[0045]
Example 6
The above example was used except that 563 g (4.00 mol) of 2-chloroparaxylene obtained in Example 1 was used and the reaction temperature was lowered to 100 ° C. when the chlorination degree reached 5.9. The side chain chlorination reaction of 2-chloroparaxylene was carried out in the same manner as in case 1 to obtain 1346 g of a reaction mixture (yield 90.3% relative to the raw material 2-chloroparaxylene).
[0046]
The total reaction time was 34.0 hours, the reaction time until the reaction temperature was lowered from 140 ° C. to 100 ° C. was 29 hours from the start of the reaction, and the total chlorine usage was 1980 g (27.93 mol). The average chlorine reaction rate was about 87%.
Moreover, as a result of analyzing the obtained reaction mixture by the gas chromatography, the composition was CBTB: 93.2% and 3,4-DCBT: 6.8% by the gas chromatography percentage.
[0047]
【The invention's effect】
According to the present invention, 2-chloroparaxylene side chain chlorination reaction that can be easily and inexpensively produced industrially enables high yield and industrially advantageous 2-chloro-1, 4-Bistrichloromethylbenzene can be produced.

Claims (4)

When producing 2-chloro-1,4- bistrichloromethylbenzene by subjecting 2-chloroparaxylene and chlorine to side chain chlorination reaction under light irradiation at a reaction temperature of 90 to 160 ° C. , this side chain chlorination reaction When the chlorination degree reaches an average value of 5.0 to 6.0 indicating how many hydrogen atoms of two methyl groups in 2 - chloroparaxylene are replaced by chlorine atoms, the above side chain chlorination reaction Of 2-chloro-1,4-bistrichloromethylbenzene, wherein the reaction temperature at the end of the reaction until the end of the reaction is controlled at 70-140 ° C. Method. The method for producing 2-chloro-1,4-bistrichloromethylbenzene according to claim 1 , wherein the total impurity concentration of paraxylene and dichloroparaxylene in 2-chloroparaxylene is 100 ppm or less. The production of 2-chloro-1,4-bistrichloromethylbenzene according to claim 1 or 2 , wherein the side chain chlorination reaction is carried out until the concentration of the benzal body, which is a reaction intermediate in the reaction mixture, becomes 100 ppm or less. Method. The production of 2-chloro-1,4-bistrichloromethylbenzene according to any one of claims 1 to 3 , wherein 2-chloroparaxylene is obtained by distilling a reaction mixture of paraxylene and chlorine. Method.