JP2001213815A - Method for producing para-dichlorobenzene - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of obtaining high chlorination ratio, readily carrying out treatment of unreacted chlorine gas in discharged hydrochloric acid gas, effectively utilizing hydrochloric acid gas as by-product and making selection ration of p-DCB high when producing p-DCB by chlorinating benzene or monochlorobenzene. SOLUTION: This method for producing para-dichlorobenzene comprises a main reaction process for producing para-dichlorobenzene by chlorinating benzene and/or monochlorobenzene with chlorine gas by using zeolite as a catalyst and a subsidiary reaction step for reacting a part or all of hydrochloric acid gas containing unreacted chlorine gas discharged from the main reaction process with benzene and/or monochlorobenzene by using zeolite as a catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for chlorinating benzene and / or monochlorobenzene using zeolite as a catalyst to obtain paradichlorobenzene (hereinafter referred to as "p-DC").
More specifically, the present invention relates to a method for producing p-DCB rationally by increasing the chlorine conversion by a two-step reaction comprising a main reaction step and a side reaction step.

[0002]

2. Description of the Related Art p-DCB is a polyphenylene sulfide (PPS) which is one of engineering plastics whose demand is rapidly growing in recent years. It is a compound with extremely high industrial value as a raw material.

[0003] Conventionally, there has been known a production method of p-DCB in which benzene and / or monochlorobenzene is subjected to liquid-phase chlorination using a Lewis acid such as ferric chloride or antimony pentachloride as a catalyst. Ferric chloride has a high activity and a chlorine conversion of 99.
Unreacted chlorine in hydrochloric acid gas by-produced reaches 99% or more, and only a trace amount remains. On the other hand, the selectivity of the target para-substituted product is at most about 60%, and a large amount of ortho-, meta-substituted product, trichlorobenzene and the like are by-produced.

As a method for selectively producing p-DCB, Japanese Patent Publication No. 63-12450 discloses a method using L-type zeolite as a catalyst. Here, potassium-exchanged KL-type zeolite is used to obtain a p-DCB selectivity of 90% or more.

[0005] JP-A-2-45431, JP-A-2-45431
No. 45432 discloses that a KL type zeolite is used as a catalyst,
A method for producing p-DCB by a liquid phase continuous chlorination reaction at a reaction temperature of 70 ° C. using a gas lift reactor is disclosed. The chlorine conversion rate in this method is relatively high at the initial stage of the reaction, 99.90 to 99.97%, but after 400 hours from the start of the reaction, the chlorine conversion rate is 99.4 to 99.9.
%, And unreacted chlorine is reduced to 0.6 to 0.1%.
It remains. JP-A-63-166434 discloses a method for producing p-DCB using a molded zeolite catalyst having improved catalyst separability, and this method facilitates handling of the catalyst. . However, the chlorine conversion is as low as 98 to 99%, and there is much unreacted chlorine gas.

JP-A-63-258436 discloses that benzene is chlorinated to monochlorobenzene using a Lewis acid catalyst such as ferric chloride in a first reactor, and then the Lewis acid catalyst is removed. After that, the method further discloses chlorination using a zeolite catalyst in a second reactor to obtain p-DCB, and introducing hydrochloric acid gas containing unreacted chlorine gas discharged at this time into the first reactor. .

In this method, the selectivity of p-DCB can be increased, and the conversion of chlorine through the first and second reactions is increased. Then, the desired p-DCB is obtained from the second reactor. However, since the catalysts used for the first reaction and the second reaction are different, it is essential to avoid the mixture. Here, a method for removing the Lewis acid type catalyst from the first reaction solution is not shown, but usually, water or an alkaline aqueous solution is used.
Washing is performed more than one step. At this time, the operation becomes extremely complicated due to precipitation of iron hydroxide and the like. Disposal of iron compounds and accompanying chlorine compounds also requires careful precautions in environmental conservation. Further, in order to prevent the deactivation of the zeolite catalyst in the second reaction, it is necessary to perform a dehydration operation of the reaction solution after washing and removing the catalyst, and the apparatus and operation are further complicated. Further, the p-DCB selectivity can be increased in the second reaction using the zeolite catalyst, but the p-DCB selectivity is low in the first reaction using the Lewis acid type catalyst. Therefore, when the chlorination rate in the first reaction increases, the p-DCB selectivity through the first and second reactions decreases.

As described above, the Lewis acid type catalyst has a high reaction activity and can achieve a very high level of chlorine conversion, but the selectivity of useful p-DCB is as low as about 60%. In contrast, zeolite catalysts increase the selection of useful p-DCB by about 9
Although it can be reduced to 0%, the catalytic activity is relatively low, the chlorine conversion rate is 98 to 99%, and even if it is devised, it is 99 to 99.9%, and the unreacted chlorine gas in the discharged hydrochloric acid gas is 1000 to 20000 p.
pm and a large amount of pm, which requires complicated post-processing.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to overcome the above-mentioned conventional problems, and to produce p-DCB by chlorinating benzene and monochlorobenzene, to have a high chlorine conversion rate and to remove the exhausted hydrochloric acid gas. It is an object of the present invention to provide a method which can easily treat unreacted chlorine gas therein, can effectively utilize by-product hydrochloric acid gas, and can increase the selectivity of p-DCB.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that there is no catalyst having high selectivity other than zeolite. The study in a two-step reaction in which a side reaction step was added to the reaction step was advanced. As a result, it was found that by using zeolite as a catalyst in both the main reaction step and the side reaction step, trace chlorine gas in by-product hydrochloric acid gas can be efficiently used for chlorination even in a zeolite having originally low catalytic activity, and the present invention was found. It was completed.

That is, the present invention provides a main reaction step for producing benzene and / or monochlorobenzene by chlorine gas using zeolite as a catalyst to produce paradichlorobenzene, and an unreacted chlorine gas discharged from the main reaction step. This is a method for producing p-DCB, comprising a side reaction step of reacting benzene and / or monochlorobenzene with zeolites using a part or all of hydrochloric acid gas as a catalyst.

Hereinafter, the present invention will be described in more detail.

In the present invention, it is essential to use zeolite as a catalyst in the reaction step. Examples of the zeolite to be used include L-type, Y-type, ZSM-5, offretite, erionite, ferrierite, X-type, omega, and mordenite, and any of them can be used. Further, these zeolites may be ion-exchanged to an alkali metal such as Li, K and Na, or an alkaline earth metal such as Mg and Ca by a known method. Among these zeolites, L-type is preferably used because of high p-DCB selectivity and relatively high chlorine conversion, and KL-type zeolite obtained by ion-exchanging L-type zeolite with K is preferable. Used.

As the zeolite to be used, both powders and molded bodies can be used, but molded bodies having a size of 10 to 250 μm are preferred, and the operability is remarkably improved. Examples of the shape include a columnar shape, a spherical shape, and an irregular-shaped granular shape. A spherical shape is preferable, and driving operability and handleability are improved. When zeolite is used as a molded body, granulation may be performed. As a granulation method, a rolling granulator, a spray granulator, or the like is preferably used.

The amount of zeolite used in the reaction step is not particularly limited, but is preferably in the range of 3 to 30% by weight based on the total amount of the reaction solution. Outside this range, if the amount is less than 3% by weight, the catalytic activity may decrease and the productivity may slightly decrease. If the amount exceeds 30% by weight, the catalyst viscosity is high, but the slurry viscosity is high and the operability is reduced. In some cases, when a zeolite molded body is used as a catalyst, its abrasion may increase.

In the present invention, the chlorinated substances as raw materials are benzene and monochlorobenzene, and may be not only benzene and monochlorobenzene alone, but also a mixture of both. Furthermore, dichlorobenzene,
Higher chlorinated substances such as trichlorobenzene may be contained.

A part or all of the reaction solution in the side reaction step may be recycled to the main reaction step. Main reaction step,
Since zeolite is used as a catalyst in the side reaction step, circulation from the side reactor to the main reactor becomes possible, and the flexibility and operation operability of the process are further improved. During the circulation, part or all of the zeolite as a catalyst may flow.

The chlorine gas used in the present invention may be industrial chlorine gas or chlorine gas containing a gas that does not participate in the reaction such as nitrogen and air. From the viewpoint of effective utilization, the gas not involved in these reactions is 10% by volume based on the total amount of chlorine gas.
Or less, more preferably 5% by volume or less, particularly preferably 1% by volume or less.

The reaction conditions in the main reaction step will be described. The reaction temperature is not particularly limited.
A range of 130 ° C. is preferred. When the reaction temperature is lower than 40 ° C., increasing the chlorination rate may increase the viscosity or decrease the reaction rate. If the temperature exceeds 130 ° C., it is considered that the solubility of chlorine decreases, and the amount of unreacted chlorine gas may increase.

The residence time of chlorination in the main reaction step varies depending on the reactor and is not fixed, but is usually 1 to 10 hours, preferably 2 to 8 hours, and sufficient chlorination is possible. If this time is short, the chlorine conversion may decrease, and if it is too long, the productivity per reactor volume may decrease.

The chlorination may be of a batch type, but a continuous type is preferred in terms of productivity and operability. The reactor may be of a tank type or a tower type.

It is preferable that the chlorination rate in the main reaction step is a condition that the reaction chlorine is 1.3 to 1.7 mol per mol of benzene nucleus. If the chlorination rate is less than 1.3 mol, the productivity of p-DCB may not be sufficient, and the chlorination rate may be 1.7.
If it exceeds mol, polychlorinated substances and impurities may increase.
The chlorine conversion in the main reaction step is usually 99.0 to 9
Unreacted chlorine gas in the discharged hydrochloric acid gas is 2%.
00 to 10000 ppm. Further, p-DCB as a product is obtained from the main reaction step, and its selectivity is about 9%.
0%, and p-DCB is obtained in high yield.

Next, in the side reaction step, the reaction of benzene and / or monochlorobenzene with zeolite using a part or all of hydrochloric acid gas containing unreacted chlorine gas discharged from the main reaction step as a catalyst is described. Required. The zeolite used as a catalyst in the secondary reaction step may be of a different type from the zeolite used in the primary reaction step, but when the resulting product is circulated between the secondary reaction step and the primary reaction step, The same zeolite is preferable in consideration of mixing.

In the side reaction step, the chlorinated substances used as raw materials are benzene and monochlorobenzene, and may be not only benzene and monochlorobenzene alone, but also a mixture of both. Furthermore, higher chlorinated substances such as dichlorobenzene and trichlorobenzene may be contained in the raw materials. Further, a part of the main reaction step liquid may be circulated to the side reaction step.

In the sub-reaction step, part or all of hydrochloric acid gas containing unreacted chlorine gas discharged from the main reaction step is used as chlorine gas. Further, in order to increase the chlorine conversion through the main reaction step and the side reaction step, it is preferable to use all of them, and the chlorine conversion can be easily increased to 99.99% or more. In addition, the concentration of unreacted chlorine gas in the discharged hydrochloric acid gas can be easily reduced to 100 ppm or less, and even 50 ppm or less, so that even if post-treatment is unnecessary or necessary, very simple treatment is sufficient. This blowing speed or rate of introduction of hydrogen chloride gas is not particularly limited, the amount of gas calculated in the standard state relative reaction volume of the main reaction step, 10~200m ³ / m ³ · H
r, i.e., it is preferably in the range of 10 to 200 per hour (gas / liquid volume ratio), further 20 to 100 m ³ / m ³
-The range of Hr is preferable. Within this range, chlorination can be performed at a high conversion without reducing the reaction activity.

The amount of zeolite used as a catalyst in the side reaction step is not particularly limited as in the main reaction step, but the concentration can be lower than that in the main reaction step, and 1 to 30% by weight, and A range of 2 to 20% by weight is preferred. When the amount is out of this range, if the amount is less than 1% by weight, the catalytic activity may be reduced and the productivity may be reduced.
If it is higher than this, the operability may decrease or the wear of the catalyst may increase.

Although the reaction temperature in the side reaction step is not particularly limited, it can be operated at a temperature somewhat lower than that of the main reaction step.
The temperature is preferably from 0 to 120C, more preferably from 50 to 80C.

The reaction in the side reaction step may be a batch system or a continuous system, but a continuous system is preferred in terms of productivity and operability.
Further, the reaction apparatus may be any of a tank type and a tower type,
When a tower type is adopted, a bubble column type can also be applied.

It is preferable that the chlorination rate in the side reaction step is 1.7 mol or less of reaction chlorine per 1 mol of benzene nucleus. Even if the chlorination rate is 1.7 or more, a high chlorine conversion rate can be obtained, but polychlorinated substances and impurities may increase.

FIG. 1 shows the basic structure of the present invention as an example of the above-described method of manufacturing p-DCB. As shown in FIG. 1, zeolite is used as a catalyst, which is a feature of the present invention, in the main reactor and the sub-reactor.
-DCB is obtained.

[0031]

According to the present invention, the following effects can be obtained.

(1) A high chlorine conversion is obtained, and the treatment of unreacted chlorine is unnecessary or can be greatly reduced.

(2) By-product hydrochloric acid gas can be utilized as high-quality hydrochloric acid without removing unreacted chlorine gas and by simple processing even if it is removed.

(3) High value-added p-DCB can be obtained at a high selectivity, and the productivity is greatly improved as compared with the conventional method.

(4) The zeolite and the reaction solution used as the catalyst may be mixed between the main reaction step and the side reaction step, and the operability is high.

(5) The catalyst life is long, the amount of waste catalyst is extremely small, the washing of the paradichlorobenzene reaction solution is simple, the amount of washing wastewater is small, and the amount of chlorinated organic matter in the wastewater is extremely small. Few. Therefore, it is advantageous in environmental conservation.

[0037]

EXAMPLES Next, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1 A 4.5 cm diameter turbine blade made of SUS, a glass reactor equipped with a reflux condenser (total internal volume: 1.6 L, upper part: inner diameter 12c)
m, height 8 cm, lower part: inner diameter 8 cm, height 16 cm, classification weir / prevent catalyst outflow), to carry out a continuous two-stage liquid-phase chlorination reaction. That is, 75 g of spherical KL-type zeolite having a particle diameter of 40 to 150 μm and benzene 900 g are charged into the main reactor, and 50 g of KL-type zeolite and 900 g of benzene same as those charged into the main reactor are charged into the sub-reactor. At a stirring rotation speed of 200 rpm, supply of chlorine to the main reactor was started at a rate of 1.6 mol / hour. The temperature of the main reactor gradually rises from 80 ° C., and when it reaches 120 ° C. after 2 hours, unreacted chlorine gas-containing by-product hydrochloric acid gas (Cl ₂ : in hydrochloric acid gas) discharged from the main reactor Was passed through a coiled condenser cooled to 10 ° C., and then blown into the sub-reactor from the bottom at a rate of 36 (gas / liquid volume ratio) per hour. At the same time, feed (benzene / monochlorobenzene =
72.3 / 27.7 (weight ratio) at a rate of 100 g / hour, and the reaction temperature was maintained at 60 ° C. Further, the reaction solution overflowing from the sub-reactor is passed through a 500 cm ³ static stabilization tank, and the KL-type zeolite that has partially flowed out is sedimented and separated, and then continuously supplied to the main reactor to perform a two-stage continuous chlorination reaction for 24 hours. went. The average chlorine concentration in the by-product hydrochloric acid gas discharged from the sub-reactor was 0.0020% by volume, and the average chlorine conversion through the main reactor and the sub-reactor was 99.9980%. The average conversion of chlorine in the main reactor was 99.54%, p-D
The CB selectivity was constant at 86.6%. Table 1 shows the conditions and results obtained in the main reaction step, and Table 2 shows the conditions and results obtained in the side reaction step.

[0039]

[Table 1]

[0040]

[Table 2]

Example 2 The procedure of Example 1 was repeated, except that the temperature of the sub-reactor was set at 80 ° C. The average chlorine concentration in the by-product hydrochloric acid gas discharged from the sub-reactor was 0.0044% by volume, and the average chlorine conversion through the main reactor and the sub-reactor was 99.9956%. The p-DCB selectivity of the reaction solution obtained in the main reaction was 86.6%. Table 1 shows the conditions and results obtained in the main reaction step, and Table 2 shows the conditions and results obtained in the side reaction step.

Example 3 The procedure of Example 2 was repeated except that the temperature of the sub-reactor was set at 40 ° C. The average chlorine gas concentration in the secondary hydrochloric acid gas discharged from the sub-reactor was 0.0025% by volume, and the chlorine conversion through the main reactor and the sub-reactor was 99.9975%. The p-DCB selectivity of the reaction solution obtained in the main reaction was 86.6%. Table 1 shows the conditions and results obtained in the main reaction step, and Table 2 shows the conditions and results obtained in the side reaction step.

Example 4 The procedure of Example 1 was repeated except that the temperature of the sub-reactor was 90 ° C. The average chlorine gas concentration in the by-product hydrochloric acid gas discharged from the sub-reactor was 0.010% by volume, and the average chlorine conversion through the main reactor and the sub-reactor was 99.990%. The p-DCB selectivity of the reaction solution obtained in the main reaction was 86.6%. Table 1 shows the conditions and results obtained in the main reaction step, and Table 2 shows the conditions and results obtained in the side reaction step.

Example 5 Raw materials (benzene / monochlorobenzene = 7) to the sub-reactor
2.3 / 27.7 (weight ratio)) and 156 g / hour, and chlorine was supplied to the main reactor at a rate of 2.5 mol / hour. The average conversion of chlorine in the main reactor was 99.34%. The average chlorine gas concentration in the by-product hydrochloric acid gas discharged from the sub-reactor was 0.0049% by volume, and the average chlorine conversion through the main reactor and the sub-reactor was 99.9951%. The p-DCB selectivity of the reaction solution obtained in the main reaction was 86.5%. Table 1 shows the conditions and results obtained in the main reaction step, and Table 2 shows the conditions and results obtained in the side reaction step.

Example 6 Raw materials (benzene / monochlorobenzene = 7) to the sub-reactor
2.3 / 27.7 (weight ratio)) and 200 g / hour of chlorine and 3.2 mol / hour of chlorine to the main reactor were supplied in the same manner as in Example 1. The average conversion of chlorine in the main reactor was 99.15%. The average chlorine gas concentration in the by-product hydrochloric acid gas discharged from the sub-reactor was 0.0077% by volume, and the average chlorine conversion through the main reactor and the sub-reactor was 99.99923%. The p-DCB selectivity of the reaction solution obtained in the main reaction was 86.5%. Table 1
Shows the conditions and results of the main reaction step, and Table 2 shows the conditions and results of the sub-reaction step.

Example 7 The procedure of Example 1 was repeated, except that the temperature of the main reactor was changed to 100 ° C. The average conversion of chlorine in the main reactor was 99.
92%. The average chlorine concentration in the by-product hydrochloric acid gas discharged from the sub-reactor was 0.0006% by volume, and the average chlorine conversion through the main and sub-reactors was 99.99994%. The p-DCB selectivity of the reaction solution obtained in the main reaction was 87.0%. Table 1 shows the conditions and results obtained in the main reaction step, and Table 2 shows the conditions and results obtained in the side reaction step.

Comparative Example 1 In a reactor similar to the main reactor of Example 1, benzene 900 was added.
g and 75 g of the same KL-type zeolite as in Example 1, and the starting material (benzene / monochlorobenzene = 72.3 / 27.7 (weight ratio)) was added under the conditions of a reaction temperature of 120 ° C.
A single-stage reaction of only the main reaction in Example 1 was performed by continuously supplying chlorine at a rate of 1.6 mol / hour at 0 g / hour. The average conversion of chlorine was 99.54%. The average chlorine gas concentration in the by-product hydrochloric acid gas was 0.46% by volume,
Post-treatment of by-produced hydrochloric acid gas was required, and the operation became complicated. The p-DCB selectivity of the obtained reaction solution was 86.6%. Table 3 shows the conditions used and the results.

[0048]

[Table 3]

As is evident from Table 3, the chlorine conversion by the one-stage reaction is lower than the chlorine conversion by the two-stage reaction as in the examples, and it is understood that the reaction is insufficient with the one-stage reaction. .

Comparative Example 2 (First reaction) Benzene 900 was placed in the same reactor as in Example 1.
g, 0.45 g of ferric chloride, and the reaction temperature was 60 ° C.
Under the condition of a stirring rotation speed of 230 rpm, a ferric chloride concentration of 3
78 ppm / hour of benzene of 00 ppm and chlorine were continuously supplied at a rate of 1.0 mol / hour (setting Cl ₂ / benzene (nucleus) molar ratio = 1.0), and 6 kg of a reaction solution containing monochlorobenzene as a main component was supplied. Obtained. The composition of this reaction solution was benzene: 15.6% by weight, monochlorobenzene: 54.8.
% By weight, dichlorobenzene: 29.4% by weight (p-DCB in dichlorobenzene: 17.8% by weight), and trichlorobenzene: 0.2% by weight. The average conversion of chlorine was as high as 99.9999% or more, and the p-DCB selectivity was as low as 60.2%.

(Second reaction) Water was added to the reaction solution, mixed and settled, and the ferric chloride as a catalyst was removed by extraction with water, then neutralized with a dilute aqueous sodium hydroxide solution, and washed with water.
Finally, after dehydration by distillation, 1150 g of the reaction solution was charged into the reactor used in the first reaction, 75 g of the same KL type zeolite as used in Example 1 was added, and the mixture was stirred at 120 ° C. and 200 rpm for stirring. , 150 g /
Time, chlorine is continuously supplied at a rate of 0.8 mol / hour,
Chlorination was performed until the molar ratio of l ₂ / benzene (nucleus) was 1.6. The composition of the reaction solution in the steady state was as follows: benzene: 1.6% by weight, monochlorobenzene: 14.8% by weight, dichlorobenzene: 82.7% by weight (p-D in dichlorobenzene).
CB: 65.0% by weight), trichlorobenzene: 0.9
% By weight. The p-DCB selectivity was 77.9% and the average conversion of chlorine was 99.50%.

Table 3 shows the conditions used and the results.

As is clear from Table 3, in the first reaction without using zeolite as a catalyst, the selectivity for p-DCB was low, and the selectivity remained low even when zeolite was used as a catalyst after the second reaction. You can see that.

[Brief description of the drawings]

FIG. 1 is an example showing a basic configuration of the present invention. In the figure,
Benzene, monochlorobenzene, p,
o, m-dichlorobenzene, zeolite, and the like.

FIG. 2 is a view showing a method of Comparative Example 2, in which Comparative Example 2 does not introduce by-product HCL gas containing unreacted Cl ₂ into the first reactor.

[Explanation of symbols]

 CB: Monochlorobenzene

Claims (7)

[Claims] A main reaction step for producing paradichlorobenzene by chlorinating benzene and / or monochlorobenzene with chlorine gas using zeolite as a catalyst,
Production of p-dichlorobenzene characterized by comprising a sub-reaction step in which part or all of hydrochloric acid gas containing unreacted chlorine gas discharged from the main reaction step is reacted with benzene and / or monochlorobenzene using zeolite as a catalyst. Method. 2. Hydrochloric acid gas containing unreacted chlorine gas discharged from the main reaction step is supplied to the side reaction step at a rate of 20 to 10 per hour.
The method for producing paradichlorobenzene according to claim 1, wherein the introduction is performed at a blowing rate of 0 (gas / liquid volume ratio). 3. The para-dichlorobenzene according to claim 1, wherein hydrochloric acid gas containing unreacted chlorine gas discharged from the main reaction step is blown into the sub-reaction step to react at 80 ° C. or lower. Manufacturing method. 4. The process for producing paradichlorobenzene according to claim 1, wherein the reaction solution obtained in the side reaction step is circulated to the main reaction step. 5. The process for producing paradichlorobenzene according to claim 1, wherein the zeolite used in the main reaction step is the same as the zeolite used in the side reaction step. 6. The method according to claim 1, wherein the zeolite is an L-type zeolite. 7. The method according to claim 1, wherein the concentration of chlorine in the hydrochloric acid gas discharged in the side reaction step is 50 ppm or less.
7. The method for producing paradichlorobenzene according to any one of claims 1 to 6.