JP2022042339A - Method for producing p-dichlorobenzene - Google Patents

Abstract

To provide a method for producing p-dichlorobenzene that has a small amount of unreacted chlorine to occur in a reaction system having a phenothiazine compound as a cocatalyst, which has high selectivity of p-dichlorobenzene.SOLUTION: A method for producing p-dichlorobenzene includes a chlorination step of supplying an aromatic raw material containing at least one of benzene and monochlorobenzene, chlorine, a Lewis acid, and a phenothiazine compound that has been chlorinated beforehand to a reactor, causing a reaction between the aromatic raw material and the chlorine, and producing p-dichlorobenzene.SELECTED DRAWING: None

Description

The present invention relates to a method for producing p-dichlorobenzene.

p-dichlorobenzene has applications in engineering plastics and the like, and is a compound having high industrial value. p-Dichlorobenzene is generally produced by a method of substituting benzene or monochlorobenzene with chlorine molecules to chlorinate benzene or monochlorobenzene using Lewis acid as a catalyst.

As a method for producing p-dichlorobenzene, the reaction generally proceeds only with Lewis acid. However, the selectivity of the target p-dichlorobenzene is low, and the para / ortho ratio is about 1.5 (para ratio 60%). The addition of a co-catalyst is effective in improving para-selectivity, and the para / ortho ratio is 3.3 (para ratio 77%) due to the addition of sulfur-based small molecule compounds.
It is described in Non-Patent Document 1 that the improvement is to a certain extent. Therefore, it is considered that it is produced in the market in this way.

Further, Patent Document 1 describes a production method using 10H-phenothiazine-10-carboxylic acid phenyl esters as a co-catalyst in addition to using Lewis acid as a main catalyst.

Patent Document 2 describes a production method using phenothiazines as a co-catalyst in addition to using aluminum chloride as a Lewis acid.

Patent Document 3 describes a production method using 10-halocarbonyl-10H-phenothiazines as a co-catalyst in addition to using Lewis acid as a catalyst.

International Publication No. 97/434041 Pamphlet Japanese Unexamined Patent Publication No. 2004-91440 Japanese Unexamined Patent Publication No. 2010-100571

Yu. A. Serguchev, I. I. Chernobaev, Theor. Exp. Chem., 46, No.2, 102-106 (2010)

However, from the viewpoint of productivity, it is desired to put it into practical use in a phenothiazine-based compound having higher paraselectivity (para ratio of more than 80%).

In the method for producing p-dichlorobenzene, it is generally preferable that all chlorine supplied as a raw material is consumed and unreacted chlorine is not generated. This is preferable from various viewpoints such as a viewpoint of reducing the separation and purification cost of chlorine and a viewpoint of pressure control of the reactor in the chlorination reaction. In addition, hydrogen chloride produced by the reaction when chlorine is consumed is a valuable resource and can be sold as a product. From this point as well, it is preferable that all chlorine is consumed and unreacted chlorine is not generated.

However, in Patent Documents 1 to 3, unreacted chlorine generated by the production method is not considered at all. For example, in the method for producing p-dichlorobenzene described in Patent Document 3, 7 volumes by volume of unreacted chlorine is generated.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to produce p-dichlorobenzene having a small amount of unreacted chlorine generated in a reaction system using a phenothiazine compound that produces a high para ratio as a co-catalyst. To provide a method.

In order to solve the above problems, the method for producing p-dichlorobenzene according to one aspect of the present invention is pre-chlorinated with an aromatic raw material containing at least one of benzene and monochlorobenzene, chlorine and Lewis acid. It comprises a chlorination step of supplying the phenothiazine compound to the reactor and reacting the aromatic raw material with the chlorine to produce p-dichlorobenzene.

According to one aspect of the present invention, it is possible to realize a method for producing p-dichlorobenzene with a small amount of unreacted chlorine generated.

<Terminology>
As used herein, "chlorination" typically refers to chlorination by a substitution reaction. Further, in the present specification, "nuclear chlorination" typically refers to chlorination in which a hydrogen atom directly bonded to a benzene ring of benzene and chlorobenzenes is replaced by a chlorine atom. As used herein, "pre-chlorinated" means that the subject described by this term is already chlorinated in the context in which it is used.

In the present specification, "less unreacted chlorine" means that the chlorine concentration is usually 2 ppm or less, preferably 1 ppm or less, particularly preferably 1 ppm or less in the gas component generated from the reaction solution after the step, unless otherwise specified. It means that chlorine is not detected.

In the present specification, "chlorobenzenes" refers to monochlorobenzene, o-dichlorobenzene, m-dichlorobenzene, dichlorobenzenes composed of p-dichlorobenzene, 1,2,4-trichlorobenzene and the like, unless otherwise specified. Refers to trichlorobenzenes.

As used herein, the term "chloride of chloride" refers to the average value of the number of chlorine atoms bonded to one molecule of a compound, and the molar fraction (mol%) of each component of benzene and chlorobenzene is benzene. It is calculated by multiplying 0, monochlorobenzene by 1, dichlorobenzenes by 2, and trichlorobenzenes by 3 and dividing the total value by 100.

In the present specification, the "benzene-equivalent concentration" refers to the concentration when it is assumed that all the benzene and chlorobenzene contained in the solution are benzene, and specifically, it is equal to the total number of moles of benzene and chlorobenzene. Refers to the concentration of a particular component relative to the weight of benzene in moles.

In the method for producing p-dichlorobenzene according to one aspect of the present invention, an aromatic raw material containing at least one of benzene and monochlorobenzene, chlorine, Lewis acid, and a prechlorinated phenothiazine compound are supplied to a reactor. It comprises a chlorination step of reacting the aromatic raw material with the chlorine to produce p-dichlorobenzene. The reaction is a nuclear chlorination reaction of aromatic raw materials. By using a phenothiazine compound chlorinated in advance as a co-catalyst in the chlorination step, unreacted chlorine can be reduced while maintaining high paraselectivity in the nuclear chlorination reaction of aromatic raw materials. In particular, if all the chlorine supplied as a raw material is consumed and unreacted chlorine is not generated, it is not necessary to introduce and maintain a detoxification treatment facility for the remaining chlorine. Therefore, it is particularly preferable that all chlorine is consumed and unreacted chlorine is not generated.

Hereinafter, the method for producing p-dichlorobenzene according to one aspect of the present invention will be described in detail for each step.

<Preliminary chlorination process>
The method for producing p-dichlorobenzene according to one aspect of the present invention may include a pre-chlorination step before the chlorination step. The pre-chlorination step is a step of reacting a phenothiazine compound with chlorine in the presence of Lewis acid to obtain a solution containing a pre-chlorinated phenothiazine compound. Hereinafter, the reaction may be referred to as prechlorination. The solution obtained in the pre-chlorination step (hereinafter, may be referred to as a pre-chlorination solution) is a Lewis acid that acts as a catalyst in the subsequent chlorination step and a pre-chlorinated phenothiazine compound that acts as a co-catalyst (hereinafter,). , May be referred to as a chlorinated phenothiazine compound). Therefore, the prechlorinated solution can be used as it is as a supply system for the catalyst and the co-catalyst in the subsequent chlorination step, and does not require an operation for separation and purification.

(Chlorinated phenothiazine compound)
The chlorinated phenothiazine compound obtained in this step may be any compound having a chlorinated phenothiazine skeleton. The chlorinated phenothiazine compound is preferably a compound represented by the following formula (I) (hereinafter, may be referred to as compound (I)) from the viewpoint of activity as a co-catalyst.

In the formula (I), m and p are integers of 0 or more and 4 or less, n is an integer of 0 or more and 5 or less, and m + n + p is 1 or more. Here, since it is important that the phenothiazine skeleton is chlorinated from the viewpoint of improving the reaction rate, it is preferable that m + p is 1 or more.

When the compound of the formula (I) is obtained as the chlorinated phenothiazine compound, the precursor of the chlorinated phenothiazine compound used as a raw material to be chlorinated in the preliminary chlorination step is preferably represented by the following formula (II). It is a compound (hereinafter, may be referred to as compound (II)).

In formula (II), q is an integer of 0 or more and 5 or less. When p and m of the formula (I) are 0, q is smaller than n of the formula (I).

The compound represented by the formula (II) is particularly suitable as a precursor of the chlorinated phenothiazine compound because it is easy to handle. The phenothiazine compound is particularly preferably a compound having q = 0 in the formula (II) from the viewpoint of availability as a commercially available synthetic raw material and production cost.

The amount of the phenothiazine compound used in the prechlorination step can be 10 mol or less, preferably 5 mol or less, more preferably 2 mol or less, relative to 1 mol of Lewis acid. By satisfying this range, the prechlorination reaction of the phenothiazine compound can be suitably promoted. The amount of the phenothiazine compound used in the preliminary chlorination step can be 0.4 mol or more, preferably 0.6 mol or more, and more preferably 0.75 mol or more with respect to 1 mol of Lewis acid. .. By satisfying this range, the amount of the phenothiazine compound contained in the preliminary chlorination solution and the pre-chlorinated phenothiazine compound can be increased.

In the prechlorination step, the phenothiazine compound may be supplied in a lump sum, may be continuously supplied, or may be supplied in a plurality of times. When the concentration of Lewis acid in the reaction solution is high, the phenothiazine compound and the chlorinated phenothiazine compound are decomposed. Therefore, it is preferable to control the concentration of Lewis acid in the reaction solution to a certain concentration or less. When the concentration of Lewis acid is controlled to be low as described above, it is preferable to reduce the initial concentration of the preferable phenothiazine compound according to the concentration of Lewis acid. Therefore, when it is desired to improve the concentration of the final phenothiazine compound, it is preferable to supply the compound in a plurality of times.

The phenothiazine compound can act as a co-catalyst for the nuclear chlorination reaction of benzene and monochlorobenzene even if it is not chlorinated. Therefore, even when the prechlorinated solution contains an unchlorinated phenothiazine compound, the prechlorinated solution can be suitably used as a co-catalyst supply system in the subsequent chlorination step. Of course, it is more preferable to increase the ratio of the chlorinated phenothiazine compound as much as possible.

(Lewis acid)
Lewis acid is considered to form a complex with the phenothiazine compound in the prechlorination step and act as a catalyst for the prechlorination of the phenothiazine compound. The Lewis acid used at this time also acts as a catalyst for the nuclear chlorination reaction of benzene and monochlorobenzene in the subsequent chlorination step. Therefore, direct use of the prechlorinated solution for the nuclear chlorination reaction of benzene and monochlorobenzene is preferable because the residual Lewis acid and the chlorinated phenothiazine compound can be used without separation and purification. Further, in the preliminary chlorination step, Lewis acid in the form of a complex with the chlorinated phenothiazine compound can be obtained. The Lewis acid in the form of forming the complex is preferable because it works suitably as a catalyst for carrying out the nuclear chlorination reaction of the aromatic raw material with high paraselectivity in the subsequent chlorination step.

Examples of Lewis acid include ferric chloride, aluminum chloride, antimony chloride and the like. As the Lewis acid, ferric chloride and aluminum chloride are preferable, and ferric chloride is more preferable, from the viewpoint of reducing the environmental load due to the waste liquid of the production method.

(chlorine)
Chlorine is a source of chlorine atoms that react with phenothiazine compounds in the prechlorination step.

The amount of chlorine used in the prechlorination step can be set in a timely manner depending on the composition of the reaction solution of the reaction system. Here, when compound (I) is used as the chlorinated phenothiazine compound, when the nuclear chlorination reaction of benzene and monochlorobenzene using compound (I) and Lewis acid is carried out, the reaction rate is generally the phenothiazine compound. It is thought that the more chlorinated, the higher the tendency. Since the chlorination reaction of the phenothiazine compound is a competitive reaction with chlorobenzenes as a solvent, it is preferable that the chlorobenzenes as a solvent have a high chloride content from the viewpoint of improving the chlorination degree of the phenothiazine compound.

On the other hand, when the chloride content of chlorobenzenes is high (specifically, when the chloride content exceeds 2), the chlorination rate of chlorobenzenes as a solvent is significantly reduced, so that the compound (II) does not generate unreacted chlorine. ) And compound (I) become difficult to chlorinate.

Therefore, in the preliminary chlorination step, it is preferable to further increase the chloride content of the compound (I) under the condition that unreacted chlorine is not generated. From the above viewpoint, the method is not particularly limited as long as the compound (II) is chlorinated, but the chlorobenzenes in the reaction solution may have a chloride content of 1.1 to 2.5, which is preferable. It is 1.3 to 2.2, more preferably 1.5 to 2.1. The amount of chlorine used is such that chlorobenzenes and phenothiazine compounds in the reaction solution are chlorinated to adjust the chlorobenzenes to the desired chloride content.

(Reaction solvent)
In the prechlorination step, any reaction solvent known in the art can be supplied as the reaction solvent, but the reaction solvent is preferably composed only of benzene and chlorobenzenes. Since benzene and chlorobenzene also act as raw materials to be chlorinated in the subsequent chlorination step, they do not need to be separated and purified after the chlorination step and are suitable as reaction solvents. The reaction solvent is more preferably a mixture of o-dichlorobenzene and at least one of benzene and monochlorobenzene. Since o-dichlorobenzene is liquid at room temperature and inexpensive, it is suitable as a reaction solvent. Further, since benzene and monochlorobenzene have higher reactivity with chlorine than dichlorobenzenes, they easily react with chlorine that did not react with the phenothiazine compound in the preliminary chlorination step. Therefore, by adding benzene and monochlorobenzene as reaction solvents, it is possible to suppress the generation of unreacted chlorine in the prechlorination step. From the viewpoint of reactivity with chlorine, it is more preferable to use monochlorobenzene in addition to o-dichlorobenzene as the reaction solvent.

When o-dichlorobenzene and monochlorobenzene are used as reaction solvents, the mixing ratio of o-dichlorobenzene to monochlorobenzene can be 0.5 or more, preferably 1 or more. By using a mixing ratio in this range, the prechlorination reaction of the phenothiazine compound can be suitably promoted. The mixing ratio of o-dichlorobenzene to monochlorobenzene can be 50 or less, preferably 20 or less. By using a mixing ratio in this range, it is possible to suitably suppress the generation of unreacted chlorine in the prechlorination step.

The amount of the reaction solvent used in the prechlorination step can be 5 g or more, preferably 10 g or more, and more preferably 20 g or more with respect to 1 g of Lewis acid. By using an amount of the reaction solvent in this range, the concentration of Lewis acid can be controlled to be small, and the decomposition of the phenothiazine compound can be suitably suppressed. The amount of the reaction solvent used in the preliminary chlorination step may be 1000 g or less, preferably 500 g or less, and more preferably 200 g or less with respect to 1 g of Lewis acid. By using a reaction solvent in an amount in this range, the prechlorination reaction of the phenothiazine compound can be suitably promoted.

(Reaction condition)
The temperature at which the pre-chlorination step is performed is not particularly limited as long as the pre-chlorination reaction proceeds. The temperature at which the prechlorination step is performed can be 20 ° C. or higher, preferably 25 ° C. or higher, and more preferably 30 ° C. or higher. By performing the pre-chlorination step at a temperature in this range, the speed of the pre-chlorination reaction can be increased. The temperature at which the prechlorination step is performed can be 120 ° C. or lower, preferably 100 ° C. or lower, and more preferably 80 ° C. or lower. By performing the preliminary chlorination step at a temperature in this range, the decomposition of the phenothiazine compound and the chlorinated phenothiazine compound can be suitably suppressed.

The time for performing the pre-chlorination step is not particularly limited as long as the pre-chlorination reaction proceeds. The time for performing the prechlorination step can be 0.1 hours or more, preferably 0.5 hours or more, and more preferably 1 hour or more. The time for performing the preliminary chlorination step may be 24 hours or less, preferably 16 hours or less, and more preferably 8 hours or less.

The pre-chlorinated solution obtained in the pre-chlorination step may be subjected to the pre-chlorination step again by supplying the phenothiazine compound and chlorine. When one pre-chlorination step is one cycle, the pre-chlorination step may be performed for two or more cycles. From the viewpoint of simplifying the operation of the pre-chlorination step, the pre-chlorination step can be 20 cycles or less, preferably 10 cycles or less, and more preferably 5 times or less.

In the pre-chlorination step, the chlorination degree of the obtained pre-chlorination solution can be 2.5 or less, preferably 2.2 or less, and more preferably 2.1 or less. When the chloride content is in this range, the generation of unreacted chlorine in the preliminary chlorination step can be suitably suppressed.

<Chlorination process>
The method for producing p-dichlorobenzene according to one aspect of the present invention includes a chlorination step. In the chlorination step, an aromatic raw material containing at least one of benzene and monochlorobenzene, chlorine, Lewis acid, and a prechlorinated phenothiazine compound are supplied to a reactor, and the aromatic raw material and the chlorine are used. Is a step of reacting to produce p-dichlorobenzene. By using Lewis acid as a catalyst and a pre-chlorinated phenothiazine compound as an auxiliary catalyst, the nuclear chlorination reaction of the aromatic raw material can be suitably promoted and the generation of unreacted chlorine can be suppressed. Hereinafter, aromatic raw materials, chlorine, Lewis acid, and pre-chlorinated phenothiazine compounds may be collectively referred to as raw materials.

(Aromatic raw material)
The aromatic feedstock can be a precursor of the target product, p-dichlorobenzene, and comprises at least one of benzene and monochlorobenzene. In addition to benzene and monochlorobenzene, the aromatic raw material may be any ratio of dichlorobenzenes consisting of o-dichlorobenzene, m-dichlorobenzene and p-dichlorobenzene, and trichlorobenzenes such as 1,2,4-trichlorobenzene. May be included in.

As each component contained in the aromatic raw material, a commercially available product may be used or a manufactured product may be used. For example, benzene or monochlorobenzene separated from the reaction solution in the chlorination step may be subjected to the chlorination step again.

(chlorine)
In the chlorination process, chlorine is a source of chlorine atoms in the nuclear chlorination reaction of aromatic raw materials.

As the chlorine, a commercially available product may be used, or a chlorine produced by electrolysis of an aqueous sodium chloride solution or the like may be used.

As a method of supplying chlorine to the reactor, gaseous chlorine may be directly blown into the reactor, or chlorine previously dissolved in another raw material may be supplied to the reactor.

(Lewis acid)
Lewis acid is a catalyst in the chlorination process. Examples of Lewis acid include ferric chloride, aluminum chloride, antimony chloride and the like. As the Lewis acid, ferric chloride and aluminum chloride are preferable, and ferric chloride is particularly preferable, from the viewpoint of reducing the environmental load of the waste liquid of the production method.

When the pre-chlorination step is performed, the Lewis acid used in the chlorination step may be the same Lewis acid as the Lewis acid used in the pre-chlorination step, or may be a different Lewis acid, but operability. From the viewpoint of, it is preferable to use the same Lewis acid.

When the pre-chlorination step is performed, the Lewis acid supplied in the pre-chlorination step may be only one contained in the pre-chlorination solution, or is additionally supplied in addition to the pre-chlorination solution. It may be a thing.

It is preferable that the Lewis acid to be additionally supplied is supplied after being mixed with an aromatic raw material such as benzene or chlorobenzene in advance. As a result, Lewis acid can be uniformly dispersed in the reaction solution.

(Pre-chlorinated phenothiazine compound)
The prechlorinated phenothiazine compound is a compound that acts as a co-catalyst in the chlorination step. As the prechlorinated phenothiazine compound, a commercially available product may be used as long as it can be purchased, or a manufactured compound, for example, a compound (II) which is a raw material used in the preliminary chlorination step in the present specification. ) May be synthesized and subjected to a preliminary chlorination step to prechlorinate the phenothiazine compound. The prechlorinated phenothiazine compound is preferably a compound represented by the above formula (I) from the viewpoint of its action as a co-catalyst.

Since it is important that the phenothiazine skeleton of the pre-chlorinated phenothiazine compound used in the chlorination step is chlorinated to some extent from the viewpoint of improving the reaction rate, the chloride level of the pre-chlorinated phenothiazine compound (phenothiazine compound). The number of chlorine atoms in it) is preferably 4 or more. By using a pre-chlorinated phenothiazine compound in this range as a co-catalyst, the reaction rate of the nuclear chlorination reaction of the aromatic raw material can be increased.

(Reaction mode)
In the chlorination step, the aromatic raw material, Lewis acid, and the pre-chlorinated phenothiazine compound may be mixed together in a reactor and then supplied with chlorine to carry out the reaction in a batch manner. Further, in the chlorination step, the reaction may be continuously carried out by continuously supplying the aromatic raw material, chlorine, Lewis acid, and the pre-chlorinated phenothiazine compound to the reactor. Performing the reaction continuously is advantageous from the viewpoint of productivity and operability because p-dichlorobenzene, which is the target product, can be continuously obtained without interrupting the reaction. When the reaction is carried out continuously in the chlorination step, the chlorination step includes a continuous reaction step, preferably including a reaction liquid forming step before the continuous reaction step.

[Reaction solution forming step]
The reaction solution forming step is a step of supplying a raw material to a reactor to form a reaction solution in order to form a reaction solution capable of performing a steady reaction in the subsequent continuous reaction step.

The raw materials to be supplied can be those described above.

As a method for forming the reaction solution, any method known to those skilled in the art can be used. As a method for forming the reaction solution, for example, (i) an aromatic raw material, Lewis acid, and a prechlorinated phenothiazine compound are mixed in a reactor, and then chlorine is supplied while measuring the chloride content of the reaction solution. Methods, (ii) a method of supplying an aromatic raw material, chlorine, Lewis acid, and a pre-chlorinated phenothiazine compound to a reactor in a batch and allowing a certain period of time to elapse, and the like are not limited thereto.

In the reaction solution forming step, the temperature of the reaction solution can be 20 ° C. or higher, preferably 40 ° C. or higher. The temperature of the reaction solution can be 100 ° C. or lower, preferably 70 ° C. or lower.

In the reaction solution forming step, the chloride content of the reaction solution after formation can be 1.1 or more, preferably 1.2 or more. The chloride content of the reaction solution after formation may be 2.5 or less, preferably 2.0 or less.

[Continuous reaction process]
The continuous reaction step is a step of continuously reacting the aromatic raw material with chlorine by continuously supplying the raw material to the reactor.

The raw materials to be supplied can be those described above.

In the continuous reaction step, it is preferable to supply all the raw materials continuously, but a part of the raw materials may be supplied intermittently.

In the continuous reaction step, in order to keep the environment inside the reactor in a steady state and simplify the operation, it is preferable to adjust the supply amount of the raw material so that the concentration of each component of the reaction solution is kept constant. The supply amount of the raw material may be constant or may change with time, and is preferably constant.

In the continuous reaction step, it is preferable to continuously or intermittently withdraw the reaction solution in the reactor in order to keep the environment in the reactor in a steady state and simplify the operation. The extraction method is not particularly limited as long as it does not affect the chlorination reaction, and may be extracted by, for example, a liquid level control by overflow and opening / closing of a valve, a pump or the like.

(Supply system)
Hereinafter, in the chlorination step, the system of the raw material supplied to the reactor is referred to as a supply system, and the system of the reaction solution extracted from the reactor is referred to as a generating system.

The chloride content of the aromatic raw material contained in the supply system can be 0.01 or more, preferably 0.03.
The above is more preferably 0.05 or more. Considering the production of p-dichlorobenzene, it is advantageous to have a lower chloride content, but it may not be possible to supply only benzene (0 chloride content) due to the inclusion of a prechlorinated solution. .. In addition, when the chloride content is high to a certain extent, the reaction rate decreases, and the amount of benzene and monochlorobenzene converted to p-dichlorobenzene in the supply system, which is the original target product, decreases. Not suitable for. From this point of view, the chloride content of the entire supply system can be 1.95 or less, preferably 1.85 or less, and more preferably 1.75 or less.

The benzene-equivalent concentration of Lewis acid contained in the supply system can be 200 ppm or more, preferably 300 ppm or more, and more preferably 400 ppm or more. The benzene-equivalent concentration of Lewis acid contained in the supply system can be 2000 ppm or less, preferably 1500 ppm or less, and more preferably 1200 ppm or less. A high concentration of Lewis acid improves the reaction rate, but reducing the amount of Lewis acid used can reduce the number of operations for separating and purifying Lewis acid. Further, as described later, it is preferable that the molar ratio of the pre-chlorinated phenothiazine compound, which is a co-catalyst, to Lewis acid is at least a certain level in order to enhance paraselectivity. From such a viewpoint, the reduction of the amount of Lewis acid is also an advantageous condition for the reduction of the amount of the phenothiazine compound chlorinated in advance.

The amount of the pre-chlorinated phenothiazine compound contained in the feed system can be 0.4 mol or more, preferably 0.7 mol or more, and more preferably 0.9 mol or more with respect to 1 mol of Lewis acid. be. When the amount of the prechlorinated phenothiazine compound is in this range, the paraselectivity of the nuclear chlorination reaction of the aromatic raw material can be enhanced. The amount of the pre-chlorinated phenothiazine compound contained in the feed system can be 5 mol or less, preferably 2 mol or less, more preferably 1.7 mol or less, relative to 1 mol of Lewis acid. When the amount of the phenothiazine compound chlorinated in advance is in this range, the reaction rate of the chlorination reaction can be increased.

The amount of chlorine contained in the supply system can be appropriately adjusted according to the desired chloride content of the generating system.

(Generating system)
The chloride content of the product system obtained in the chlorination step can be 1.1 or more, preferably 1.2 or more, more preferably, from the viewpoint of increasing the yield of the target product, p-dichlorobenzene. Is 1.3 or higher. The chloride content of the generating system obtained in the chlorination step can be 2.0 or less, preferably 1.9 or less, and more preferably 1.8 or less, from the viewpoint of reducing unreacted chlorine.

(Reaction condition)
The reaction temperature in the chlorination step can be 20 ° C. or higher, preferably 30 ° C. or higher, more preferably 40 ° C. or higher, from the viewpoint of increasing the reaction rate. The reaction temperature in the chlorination step can be 120 ° C. or lower, preferably 100 ° C. or lower, and more preferably 70 ° C. or lower, from the viewpoint of reducing the decomposition of the prechlorinated phenothiazine compound.

The reaction time of the chlorination step (corresponding to the residence time of the reaction solution when the step is continuously performed) can be 0.5 hours or more from the viewpoint of sufficiently advancing the chlorination reaction, which is preferable. Is 8 hours or more, more preferably 24 hours or more. Further, industrially, since it is assumed that the continuous chlorination step is performed while preparing the preliminary chlorination solution, the reaction time of the chlorination step is set from the viewpoint of efficiently obtaining p-dichlorobenzene. A longer time is preferable, and there is no particular upper limit such as several days to several months.

<Summary>
The present invention can also be expressed as follows.

In the method for producing p-dichlorobenzene according to an embodiment of the present invention, an aromatic raw material containing at least one of benzene and monochlorobenzene, chlorine, Lewis acid, and a prechlorinated phenothiazine compound are used as a reactor. It comprises a chlorination step of feeding and reacting the aromatic raw material with the chlorine to produce p-dichlorobenzene.

According to the above configuration, by converting a phenothiazine compound having high paraselectivity into a prechlorinated compound and using it as a co-catalyst, p-dichlorobenzene having high paraselectivity and less unreacted chlorine generated is produced. Can be manufactured.

In the method for producing p-dichlorobenzene according to an embodiment of the present invention, the aromatic raw material, the chlorine, the Lewis acid, and the pre-chlorinated phenothiazine compound are continuously supplied in the chlorination step. ..

According to the above configuration, p-dichlorobenzene can be continuously obtained, which is advantageous from the viewpoint of productivity and operability.

In the method for producing p-dichlorobenzene according to an embodiment of the present invention, the Lewis acid is ferric chloride.

According to the above configuration, the environmental load due to the waste liquid of the production method can be reduced as compared with other Lewis acids such as antimony chloride, which may be toxic.

In one embodiment of the present invention, in the method for producing p-dichlorobenzene, the prechlorinated phenothiazine compound is a compound represented by the following formula (I).

(In the formula (I), m and p are integers of 0 or more and 4 or less, n is an integer of 0 or more and 5 or less, and m + n + p is 1 or more.)
According to the above configuration, when Lewis acid is used as the main catalyst, the catalytic activity is higher when the pre-chlorinated phenothiazine compound is used as the co-catalyst than when the unchlorinated phenothiazine compound is used. Therefore, the reaction rate of chlorination of aromatic raw materials can be increased.

In one embodiment of the present invention, the method for producing p-dichlorobenzene is a solution containing the pre-chlorinated phenothiazine compound by reacting the phenothiazine compound with chlorine in the presence of Lewis acid before the chlorination step. Includes a pre-chlorination step to obtain.

According to the above configuration, the prechlorinated phenothiazine compound and Lewis acid form a complex. The complex can realize high paraselectivity in the chlorination reaction of aromatic raw materials.

In the method for producing p-dichlorobenzene according to an embodiment of the present invention, the phenothiazine compound used for producing the pre-chlorinated phenothiazine compound is a compound represented by the following formula (II).

(In the formula (II), q is an integer of 0 or more and 5 or less, and when p and m of the formula (I) are 0, q <n.)

According to the above configuration, the phenothiazine compound which is the raw material of the pre-chlorinated phenothiazine compound can be easily handled.

In one embodiment of the present invention, the method for producing p-dichlorobenzene is q = 0 in the above formula (II).

According to the above configuration, the manufacturing cost of the manufacturing method can be reduced.

In one embodiment of the present invention, the method for producing p-dichlorobenzene supplies the phenothiazine compound in a plurality of times in the preliminary chlorination step.

According to the above configuration, the concentration of the prechlorinated phenothiazine compound can be increased while reducing the decomposition of the phenothiazine compound.

In one embodiment of the present invention, the method for producing p-dichlorobenzene comprises using monochlorobenzene as a part of the reaction solvent in the prechlorination step.

According to the above configuration, it is possible to suppress the generation of unreacted chlorine in the preliminary chlorination step.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention.

P-dichlorobenzene is produced by the production methods described in Examples 1 and 2 and Comparative Example 1, the amount of benzene and chlorobenzene contained in the supply system and the production system, and the unreacted chlorine released from the production system. The amount of benzene was measured.

〔Measuring method〕
The amounts of benzene and chlorobenzenes in the solution were measured by gas chromatography.

(Conditions for gas chromatography)
Gas chromatograph: Shimadzu gas chromatograph Colon: Agilent Technology Capillary column Column temperature: 50 ° C to temperature rise Program inlet temperature: 250 ° C
Detector temperature: 270 ° C

In the following description, the "para ratio" represents the ratio of p-dichlorobenzene to the total amount of dichlorobenzene in the solution after the reaction. Further, the "produced para ratio" represents the ratio of p-dichlorobenzene produced by the reaction to the total amount of dichlorobenzene produced by the reaction. The p-dichlorobenzene content (kg) in the solution before and after the reaction was set to Xp1 and Xp2, respectively, and the o-dichlorobenzene content (kg) in the solution before and after the reaction was set to Xo1 and Xo2, respectively. The m-dichlorobenzene content (kg) in the solution before and after the reaction is set to Xm1 and Xm2, respectively, and the para ratio of the solution and the para ratio of the reaction are defined as the following formulas.
Para ratio (%) = Xp2 / (Xp2 + Xo2 + Xm2) x 100
Generated para ratio (%) = (Xp2-Xp1) / ((Xp2-Xp1) + (Xo2-Xo1) + (Xm2-Xm1)) × 100

[Example 1]
In Example 1, the following (A) preliminary chlorination step by a method of collectively adding a phenothiazine compound (10H-phenothiazine-10-carboxylic acid phenyl ester (hereinafter, may be referred to as compound (III))). And (B) chlorination step including (B-1) reaction liquid forming step and (B-2) continuous reaction step were carried out.

(A) Preliminary chlorination process The raw materials shown in Table 1 were mixed together. The chloride content of the mixed solution was 1.605. At a reaction temperature of 40 ° C., chlorine was blown at a flow rate of 12 kg / h for 0.75 hours and then at a flow rate of 14 kg / h for 3.3 hours to chlorinate compound (III). Then, the precipitate was removed to obtain a prechlorinated solution having the composition shown in Table 1. The chlorination degree of the obtained preliminary chlorination solution was 2.02. Further, from the analysis by liquid chromatography, it was estimated that the obtained compound (I) had a chloride degree of 3 to 6, and the average chloride degree of the compound (I) was about 4.

(B) Chlorination step (B-1) Reaction solution forming step An aromatic raw material consisting of 32.3 kg of benzene, 155.6 kg of monochlorobenzene, 0.1 kg of m-dichlorobenzene, and 7.7 kg of p-dichlorobenzene, and chloride. 38 g of dichlorobenzene and 30.1 kg of the prechlorinated solution obtained in step (A) were supplied to the reactor and mixed. In the obtained mixed solution, the chloride degree was 0.92, the concentration of ferric chloride was 567 ppm (the benzene equivalent concentration was 800 ppm), and it was assumed that the chlorinated compound (I) (average chloride degree 4). The concentration of (case) was 2145 ppm (concentration in terms of benzene was 3014 ppm). At a reaction temperature of 50 ° C., the chlorine flow rate is gradually increased from 6 kg / h to the mixed solution at 10-minute intervals, and after 30 minutes, chlorine is blown into the mixed solution at a flow rate of 22 kg / h for about 3.2 hours to chlorinate the aromatic raw material. did. No unreacted chlorine was detected during the reaction. The chloride content of the obtained reaction solution was 1.43. Table 2 shows the contents of each component of the aromatic raw material and chlorine in the solution before and after blowing chlorine. The para ratio of the reaction solution obtained after injecting chlorine was 72.1%, and the para ratio of the nuclear chlorination reaction was 82.0%.

(B-2) Continuous reaction step About 24 kg of the reaction solution obtained in the step (B-1) was withdrawn from the reactor, and the amount of the liquid was adjusted. In the reactor, at 50 ° C., as a supply system, benzene at a flow rate of 17.2 kg / h, monochlorobenzene at a flow rate of 1.4 kg / h, ferric chloride at a flow rate of 4 g / h, and a step ( The prechlorinated solution obtained in A) was supplied at a flow rate of 4 kg / h. As a result, the concentration of ferric chloride in terms of benzene was adjusted to be about 800 ppm in the entire supply system. The ferric chloride was supplied as a mixture with a part of benzene or monochlorobenzene. While supplying the above components, the chlorine flow rate was gradually increased from 6 kg / h at 10-minute intervals, and after 30 minutes, chlorine was blown at a flow rate of 22 kg / h to carry out a continuous reaction. The chloride content of the reaction solution during the continuous reaction was maintained at about 1.45.

During the continuous reaction, about 10 kg of the reaction solution was intermittently withdrawn from the reactor about every 0.3 hours to keep the liquid volume substantially constant. The extracted reaction solution was used as a generating system. Here, it is possible to assume that a steady state (a state in which the composition of the reaction solution is constant) is reached after a sufficient time has elapsed from the start of the continuous reaction. Here, the composition of the generating system was estimated assuming that the composition of the reaction solution at the end of the reaction (10 hours after the start of the continuous reaction) was in a steady state, and was calculated as shown in the table below.

During the 10-hour continuous reaction, no unreacted chlorine was detected in the gas generated from the reaction system. The generating para ratio of the production system was 72.8%, and the generating para ratio of the nuclear chlorination reaction was 82.3%.

[Example 2]
Example 2 includes (B) chlorine, which comprises (A) a preliminary chlorination step by a method of adding the phenothiazine compound in three portions, (B-1) a reaction solution forming step, and (B-2) a continuous reaction step. The chemical conversion process was carried out.

(A) Preliminary chlorination step Compound (III) 2.72 kg, monochlorobenzene 11.2 kg, o-dichlorobenzene 87.8 kg, and ferric chloride 1.84 kg were mixed. At this point, the chlorination of the scar solution was 1.86. Chlorine was blown in at a reaction temperature of 45 ° C. at a flow rate of 8 kg / h for 1.3 hours. Then, 0.91 kg of compound (III), 3.68 kg of monochlorobenzene, and 1.33 kg of o-dichlorobenzene were added. Chlorine was blown in at a reaction temperature of 45 ° C. at a flow rate of 8 kg / h for 0.4 hours. Then, 0.91 kg of compound (III), 3.67 kg of monochlorobenzene, and 1.33 kg of o-dichlorobenzene were added. Chlorine was blown in at a reaction temperature of 45 ° C. at a flow rate of 8 kg / h for 0.4 hours. Then, the precipitate was removed to obtain a prechlorinated solution having the composition shown in Table 4. The chlorination degree of the obtained preliminary chlorination solution was 2.01. Further, from the analysis by liquid chromatography, it was estimated that the obtained compound (I) had a chloride degree of 3 to 6, and the average chloride degree of the compound (I) was about 4.

(B-1) Reaction solution forming step Benzene 40.0 kg, monochlorobenzene 187.7 kg, m-dichlorobenzene 0
.. An aromatic raw material consisting of 1 kg, p-dichlorobenzene 6.8 kg, and o-dichlorobenzene 0.6 kg, 31 g of ferric chloride, and 7.86 kg of the prechlorinated solution obtained in step (A) were used in a reactor. Supplied and mixed. In the resulting mixed solution, the chloride was 0.82, the ferric chloride concentration was 519 ppm (benzene equivalent concentration was 700 ppm), and the chlorinated compound (assuming an average chloride of 4) (assuming an average chloride of 4). The concentration of I) was 1723 ppm (the benzene-equivalent concentration was 2343 ppm). At a reaction temperature of 50 ° C., the chlorine flow rate is gradually increased from 6 kg / h to the mixed solution at 10-minute intervals, and after 30 minutes, chlorine is blown into the mixed solution at a flow rate of 22 kg / h for about 4.5 hours to chlorinate the aromatic raw material. did. The chloride content of the obtained reaction solution was 1.45. Table 5 shows the contents of each component of the aromatic raw material and chlorine in the solution before and after blowing chlorine. The para ratio of the reaction solution obtained after injecting chlorine was 79.7%, and the para ratio of the nuclear chlorination reaction was 82.1%.

(B-2) Continuous reaction step About 65 kg of the reaction solution obtained in the step (B-1) was withdrawn from the reactor, and the amount of the liquid was adjusted. In the reactor, at 50 ° C., as a supply system, benzene at a flow rate of 16.7 kg / h, monochlorobenzene at a flow rate of 0.8 kg / h, ferric chloride at a flow rate of 3 g / h, and a step ( The prechlorinated solution obtained in A) was supplied at a flow rate of 0.78 kg / h. As a result, the concentration of ferric chloride in terms of benzene was adjusted to be about 700 ppm in the entire supply system. The ferric chloride was supplied as a mixture with a part of benzene or monochlorobenzene. While supplying the above components, chlorine was blown in at a flow rate of 22 kg / h to carry out a continuous reaction. The chloride content of the reaction solution during the continuous reaction was maintained at about 1.45.

During the continuous reaction, about 10 kg of the reaction solution was intermittently withdrawn from the reactor about every 0.35 hours to keep the liquid volume substantially constant. The extracted reaction solution was used as a generating system. Here, it is possible to assume that a steady state (a state in which the composition of the reaction solution is constant) is reached after a sufficient time has elapsed from the start of the continuous reaction. Here, the composition of the reaction solution at the end of the reaction (5 hours after the start of the continuous reaction) was estimated as the composition of the generating system assuming a steady state, and was calculated as shown in the table below.

No unreacted chlorine was detected in the generating system during the 5-hour continuous reaction. The producing para ratio of the production system was 79.9%, and the production para ratio of the nuclear chlorination reaction was 82.6%.

Subsequently, the components of the supply system were changed to reduce the concentration of ferric chloride, and the continuous reaction step was continued. Specifically, in the reactor, at 50 ° C., as a supply system, benzene at a flow rate of 16.7 kg / h, monochlorobenzene at a flow rate of 0.7 kg / h, and p-dichlorobenzene at a flow rate of 0.1 kg / h. At a flow rate of 0.5 kg / h for o-dichlorobenzene, at a flow rate of 3 g / h for ferric chloride, and at a flow rate of 0.66 kg / h for the prechlorinated solution obtained in step (A). Supplied in. As a result, the concentration of ferric chloride in terms of benzene was adjusted to be about 600 ppm in the entire supply system. The ferric chloride was supplied as a mixture with a part of benzene or monochlorobenzene. While supplying the above components, chlorine was blown in at a flow rate of 22 kg / h to carry out a continuous reaction. The chloride content of the reaction solution during the continuous reaction was maintained at about 1.45. Here, it is possible to assume that a steady state (a state in which the composition of the reaction solution is constant) is reached after a sufficient time has elapsed from the start of the continuous reaction. Here, the composition of the generating system was estimated assuming that the composition of the reaction solution at the end of the reaction (16 hours after the start of the continuous reaction) was in a steady state, and was calculated as shown in the table below.

During the continuous reaction, about 10 kg of the reaction solution was intermittently withdrawn from the reactor about every 0.35 hours to keep the liquid volume substantially constant. The extracted reaction solution was used as a generating system.

No unreacted chlorine was detected in the generating system during the continuous reaction for 16 hours after changing the supply system. The generating para ratio was 79.9%, and the generating para ratio of the nuclear chlorination reaction was 82.2%.

[Comparative Example 1]
Comparative Example 1 is a production method in which a nuclear chlorination reaction of an aromatic raw material is carried out by using a phenothiazine compound as a co-catalyst without chlorination in advance.

(B) Chlorination step (B-1) Reaction liquid formation step From benzene 32.9 kg, monochlorobenzene 222.1 kg, m-dichlorobenzene 0.1 kg, p-dichlorobenzene 11.4 kg, o-dichlorobenzene 0.8 kg The aromatic raw material, 0.41 kg of compound (III), and 0.175 kg of ferric chloride were supplied to the reactor and mixed. In the obtained mixed solution, the chloride degree is 0.86, the ferric chloride concentration is 652 ppm (benzene equivalent concentration is 900 ppm), and the concentration of compound (III) is 1534 ppm (benzene equivalent concentration is 2110 ppm). there were. At a reaction temperature of 60 ° C., the chlorine flow rate was gradually increased from 6 kg / h to the mixed solution at 10-minute intervals, and after 30 minutes, chlorine was blown into the mixed solution at a flow rate of 22 kg / h for 4.6 hours to chlorinate the aromatic raw material. .. The chloride content of the obtained reaction solution was 1.45. Table 8 shows the contents of each component of the aromatic raw material and chlorine in the solution before and after blowing chlorine. The para ratio of the reaction solution obtained after injecting chlorine was 82.9%, and the para ratio of the nuclear chlorination reaction was 82.0%.

(B-2) Continuous reaction step About 80.5 kg of the reaction solution obtained in the step (B-1) was withdrawn from the reactor, and the amount of the liquid was adjusted. O -Dichlorobenzene chloride throughout the supply system while supplying dichlorobenzene at a flow rate of 0.1 kg / h, compound (III) at a flow rate of 0.042 kg / h, and ferric chloride at a flow rate of 0.018 kg / h. The concentration of ferric ferric in terms of benzene was adjusted to be about 900 ppm. Chlorine was blown in at a flow rate of 22 kg / h to carry out a continuous reaction. The chloride content of the reaction solution during the continuous reaction was maintained at about 1.45. Here, it is possible to assume that a steady state (a state in which the composition of the reaction solution is constant) is reached after a sufficient time has passed from the start of the continuous reaction, but since the reaction was stopped in 6 hours. The composition of the reaction solution at the end of the reaction was estimated as the composition of the generating system assuming a steady state, and was calculated as shown in the table below.

During the continuous reaction, about 10 kg of the reaction solution was intermittently withdrawn from the reactor about every 0.3 hours to keep the liquid volume substantially constant. The extracted reaction solution was used as a generating system.

From the generating system, 0.7 ppm of unreacted chlorine was detected after 3 hours of reaction time, and 4.6 ppm of unreacted chlorine was detected after 6 hours of reaction time. In Comparative Example 1, since unreacted chlorine was detected, the continuous reaction was stopped in 6 hours. After 6 hours, the producing para ratio of the production system was 82.6%, and the production para ratio of the nuclear chlorination reaction was 82.5%.

In Examples 1 and 2 using the prechlorinated phenothiazine compound as a co-catalyst, the same production para ratio was obtained, and unreacted chlorine was not detected. On the other hand, in Comparative Example 1 in which the phenothiazine compound was used as a co-catalyst without chlorination in advance, unreacted chlorine was detected even though the concentration of ferric chloride as the main catalyst used was high. In addition, although the reaction temperature of the continuous reaction step was 10 ° C. lower than that of Comparative Example 1 in Examples 1 and 2, unreacted chlorine was detected in Examples 1 and 2 unlike Comparative Example 1. There wasn't. From these facts, it can be seen that the reaction rate of the nuclear chlorination reaction of the aromatic raw material was remarkably improved by using the phenothiazine compound chlorinated in advance as a co-catalyst.

Further, comparing Example 1 and Example 2, in Example 2 in which the phenothiazine compound was divided and added in the preliminary chlorination step, the ratio of o-dichlorobenzene in the preliminary chlorination solution was reduced and higher. It was found that a phenothiazine compound pre-chlorinated at a concentration can be obtained. If o-dichlorobenzene used as a solvent can be reduced in the prechlorination step, o-dichlorobenzene contained in the finally obtained production system can also be reduced, and o-dichlorobenzene can be reduced during separation and purification. It has the effect of reducing the separation cost of.

In the following Reference Example 1 and Reference Comparative Example 1, the solvent used in the preliminary chlorination step was examined.

[Reference Example 1]
Add 6.0 g of compound (III), 180 g of o-dichlorobenzene, 32.6 g of monochlorobenzene and 4.0 g of ferric chloride to a 300 mL four-necked flask, and add 6 L / h of chlorine while stirring at a reaction temperature of 45 ° C. It was blown in and chlorinated compound (III).

When the gas analysis generated from the reaction solution was performed after 45 minutes and 85 minutes, unreacted chlorine was not detected, and the chlorine reaction rate was calculated to be 100%.

[Reference Comparative Example 1]
3.0 g of compound (III), 180 g of o-dichlorobenzene and 2.0 g of ferric chloride were added to a 300 mL four-necked flask, and 3 L / h of chlorine was blown into the flask at a reaction temperature of 45 ° C. with stirring to compound (III). Was chlorinated.

Similarly, when gas analysis was performed and the chlorine reaction rate was measured, it was 83% after 30 minutes and 44% after 60 minutes. From this, it can be seen that in Reference Comparative Example 1, a large amount of unreacted chlorine was generated.

From the results of Reference Example 1 and Reference Comparative Example 1, the effect of reducing the generation of unreacted chlorine by coexisting a compound susceptible to a nuclear chlorination reaction in the solvent in the preliminary chlorination step, such as monochlorobenzene. It turns out that it plays.

The present invention can be used for the production of p-dichlorobenzene.

Claims (9)

An aromatic raw material containing at least one of benzene and monochlorobenzene, chlorine, Lewis acid, and a prechlorinated phenothiazine compound are supplied to a reactor, and the aromatic raw material and the chlorine are reacted to p. -A method for producing p-dichlorobenzene, which comprises a chlorination step to produce dichlorobenzene. The method for producing p-dichlorobenzene according to claim 1, wherein in the chlorination step, the aromatic raw material, the chlorine, the Lewis acid, and the pre-chlorinated phenothiazine compound are continuously supplied. The method for producing p-dichlorobenzene according to claim 1 or 2, wherein the Lewis acid is ferric chloride. The method for producing p-dichlorobenzene according to any one of claims 1 to 3, wherein the prechlorinated phenothiazine compound is a compound represented by the following formula (I).

(In the formula (I), m and p are integers of 0 or more and 4 or less, n is an integer of 0 or more and 5 or less, and m + n + p is 1 or more.) 1. The method for producing p-dichlorobenzene according to item 1. The method for producing p-dichlorobenzene according to claim 5, wherein the phenothiazine compound used for producing the pre-chlorinated phenothiazine compound is a compound represented by the following formula (II).

(In the formula (II), q is an integer of 0 or more and 5 or less, and when p and m of the formula (I) are 0, q <n.) The method for producing p-dichlorobenzene according to claim 6, wherein in the formula (II), q = 0. The method for producing p-dichlorobenzene according to any one of claims 5 to 7, wherein the phenothiazine compound is supplied in a plurality of divided portions in the preliminary chlorination step. The method for producing p-dichlorobenzene according to any one of claims 5 to 8, which comprises using monochlorobenzene as a part of the reaction solvent in the prechlorination step.