JPH0443899B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is currently used as a soil fungicide.
This invention relates to a method for producing pentachloronitrobenzene (hereinafter abbreviated as PCNB), which is widely used as

More specifically, the present invention uses nitrobenzene and/or polychloronitrobenzenes to
When producing PCNB, a chlorination reaction is carried out at low temperatures to produce hexachlorobenzene (hereinafter abbreviated as HCB).
The present invention relates to a method for producing PCNB that suppresses by-products of PCNB.

[Conventional technology]

In recent years, soil environmental pollution caused by pesticides and their contaminants has become a problem worldwide, and PCNB, which is used as a soil disinfectant, is no exception. Supply of PCNB is strongly desired.

For example, in the United States, the U.S. Environmental Protection Agency
In April 1982, revised standards for PCNB registration were established, stipulating that new technology should be implemented to reduce the HCB content in PCNB to 0.5% by weight or less from March 1983 onwards.

Conventionally, a typical method for industrially obtaining PCNB is to nitrate pentachlorobenzene (U.S. Patent No. 4026955, No. 4057590, No. 4147732).
), a method for nitrating hexachlorobenzene via sodium pentachlorothiophenolate (US Pat. No. 4,461,918), and a method for chlorinating nitrobenzene or chloronitrobenzene [East German Patent No. 10655, Himichieskaya Promschuren] Nostii (Khim.Prom.) 44
(5), 334-7 (1968) (Russ)] is known.

However, although the first method has the possibility of producing PCNB with a relatively low HCB content, there is a problem in that high-purity pentachlorobenzene as a raw material is not always commercially available. The second method of using hexachlorobenzene as a raw material is difficult to call a realistic method because the raw material itself is designated as a highly toxic specified chemical substance. The third chlorination method is
Although it is considered to be the most industrially advantageous method for producing PCNB, it also has the drawback that HCB is most likely to be produced as a by-product.

[Problem that the invention seeks to solve]

The object of the present invention is to
Industrially advantageous for suppressing the amount of HCB produced
The purpose of the present invention is to provide a method for manufacturing PCNB.

[Means and actions for solving problems]

The present inventors focused on the third chlorination method for starting materials, which does not have any industrial problems, and conducted extensive studies to solve the above problems. Although the above literature does not describe the amount of HCB by-produced in the chlorination reaction, experiments conducted by the present inventors under the exemplified reaction conditions revealed that a large amount of HCB was produced as a by-product. It was recognized that under the described reaction conditions, industrial production of PCNB with a low HCB content could not be expected.

The present inventors have investigated factors such as reaction temperature, catalyst amount, and solvent amount in the chlorination reaction of nitrobenzene and/or polychloronitrobenzenes in the presence of a chlorosulfonic acid solvent and an iodo catalyst.
As a result of a detailed study of the relationship with the amount of HCB produced, we found that among the various factors, the most dominant influence on the production of HCB is the reaction temperature, such as raw materials, amount of catalyst,
When the amount of solvent and concentration of solvent are fixed at the optimal conditions, the relationship between reaction temperature, amount of HCB produced, and reaction time is as follows.
The present invention was completed by discovering that the relationship shown in Figure 1 exists and that by carrying out the chlorination reaction at a low reaction temperature of 50°C or less, the by-product of HCB can be suppressed.

That is, the present invention provides a by-product of hexachlorobenzene, which is characterized by carrying out a chlorination reaction of nitrobenzene and/or polychloronitrobenzenes using chlorine in the presence of chlorosulfonic acid and an iodine catalyst at a temperature of 50°C or lower. This is a method for producing pentachloronitrobenzene.

In the chlorination reaction according to the production method of the present invention,
If the reaction temperature is set above 50℃, PCNB
Although the reaction time required for production can be significantly shortened compared to low-temperature reactions, the overchlorination reaction from PCNB to HCB progresses, and the production of HCB increases rapidly as the reaction temperature rises.

On the other hand, if the chlorination reaction is carried out at a low reaction temperature of 50° C. or lower, the reaction time will naturally become longer.

Initially, the longer reaction time is due to
There are more opportunities for PCNB to come into contact with chlorine, and PCNB
As a result, PCNB
It was expected that HCB production would increase from 50
At temperatures below ℃, HCB production was suppressed to a low level.

This means that when the reaction temperature exceeds 50°C, there is no big difference in the reaction rate from tetrachloronitrobenzenes to PCNB and the reaction rate from PCNB to HCB at the same temperature, and there is no significant difference in the reaction rate from PCNB to HCB at the same temperature.
The perchlorination reaction from PCNB to HCB progresses sequentially and easily, and the content of HCB increases in the product PCNB. However, in chlorination at a low temperature range of 50°C or less, the reaction rate from tetrachloronitrobenzenes to PCNB also decreases, but the reaction rate from PCNB to HCB is extremely decreased, so the reaction between the two decreases. A large difference in rate occurs, and the ratio of reaction rates is approximately 200-300:1.

As a result, it is presumed that by lowering the temperature, it becomes possible to significantly suppress the perchlorination reaction to HCB, although the reaction time for PCNB production takes longer.

As can be seen from Figure 1, in order to obtain PCNB with an HCB content of 0.4% by weight or less, the HCB content must be 50% or less.
To obtain PCNB below 0.3 wt%, the reaction temperature is 30
It can be done at temperatures below ℃.

Nitrobenzene and/or in the method of the present invention
Alternatively, the ratio of the amounts of polychloronitrobenzenes and chlorosulfonic acid used is 1:1 to 1:20, preferably 1:2 to 1:5. When the amount of chlorosulfonic acid is less than 1:1, PCNB of nitrobenzene and/or polychloronitrobenzenes
The reaction rate is slow, and the operability of stirring and stirring is poor.

If the amount of chlorosulfonic acid is more than 1:20, it is not preferable because it increases cost and decreases volumetric efficiency.

In addition, the solvent chlorosulfonic acid is highly hygroscopic,
Reacts with water to produce sulfuric acid and hydrogen chloride, and in some cases sulfuric acid and chlorosulfonic acid are mixed in the liquid phase.The concentration range is 50 to 100% by weight, preferably 70 to 100%.
Weight%. If it is less than 50% by weight, the reaction rate to PCNB will be significantly slowed, which is not preferable.

The amount of iodine used as a catalyst is 0.1% to 10% by weight, preferably 0.5 to 5% by weight based on nitrobenzene and/or polychloronitrobenzenes.
Weight%.

In this case, if it is less than 0.1% by weight, the reaction rate will be slow, which is not preferred in practice. Moreover, if it exceeds 10% by weight, the cost will increase, which is industrially disadvantageous.

Chlorination is carried out at any suitable reaction temperature of 0 to 50°C, but 10 to 40°C is practically preferred. 50
As shown in Figure 1, when the temperature exceeds ℃, HCB by-products rapidly increase. If the temperature is below 0°C, the reaction rate is slow and it is not practical.

The reaction time is determined by the amount of catalyst used and the temperature, but a practically preferred reaction time is in the range of about 10 hours to 60 hours.

It is optional whether chlorine is blown into the liquid or onto the liquid surface, and the chlorine injection method may be carried out depending on the reaction rate.

At the beginning of the reaction, considerable heat is generated, so sufficient cooling is required.

Since PCNB crystals precipitate as the reaction progresses, efficient stirring is required, and as long as this purpose is achieved, the type of stirrer is arbitrary.

After a compositional analysis is performed and the reaction reaches a predetermined degree of completion, the produced PCNB crystals are separated using a conventional liquid/solid separation method. The separated PCNB crystals are washed with sulfuric acid, further washed with water, and dried to form a product.

The separated liquid contains chlorosulfonic acid and can be reused as the next reaction solvent.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Nitrobenzene 184.5g, chlorosulfonic acid 570g
Chlorine gas was blown into a mixture of g, 98% sulfuric acid, 57 g, and iodine at a flow rate of 59 g/hour, and the mixture was heated at 30°C.
The reaction was allowed to proceed for 45 hours.

The reaction solution was filtered at room temperature and the residue was separated. Thereafter, the slag was washed with 98% sulfuric acid, and then poured into water in a beaker. Add slag to water in a beaker, 5%
After washing with carbonated soda water and water in that order, drying, 0.25
385 g of PCNB containing % by weight of HCB (gas chromatography analysis) was obtained (yield: 87% by weight).

Example 2 145.3 g of nitrobenzene, 25 g of m-chloronitrobenzene, 55 g of new chlorosulfonic acid, Example 1
680 g of solvent obtained by separating the reaction solution, 1.0 iodine
Chlorine gas was blown into the mixture at a flow rate of 51 g/hour, and the mixture was reacted at 30° C. for 45 hours.

The reaction solution was filtered to separate the residue. 98% slag
After washing with sulfuric acid, it was filtered and poured into water in a beaker. Add the slag in the beaker to water, 5% carbonated soda water,
After successively washing with water and drying, 392 g of PCNB containing 0.35% by weight of HCB was obtained (yield: 99.1% by weight).

Example 3 Nitrobenzene 209g, chlorosulfonic acid 846.5g
Chlorine gas was passed at a flow rate of 68 g/hour into a mixed solution of 94 g of 98% sulfuric acid, and 5.0 g of iodine, and the reaction was carried out at 10° C. for 60 hours.

The reaction solution was filtered, and the residue was washed with 98% sulfuric acid, filtered, and poured into water in a beaker. Water slag, 5
% caustic soda, then washed with water and then dried.
388g of PCNB containing 0.2% by weight of HCB was obtained (yield
74.6% by weight).

Example 4 Nitrobenzene 135.3g, chlorosulfonic acid 920g
Chlorine was blown at a flow rate of 44 g/hour into a mixture of 6.5 g of iodine and 6.5 g of iodine to cause a reaction at 0°C. The reaction solution was filtered, the residue was separated, and the residue was washed with 98% sulfuric acid and filtered.

The slag was poured into water in a beaker, washed with water, 5% soda water, and water in that order, and then dried.
223g of PCNB containing 0.16% by weight of HCB was obtained (yield: 68% by weight).

Example 5 Nitrobenzene 61.5g, chlorosulfonic acid
Chlorine gas was blown into the mixture of 105.3 g, 98% sulfuric acid 11.7 g, and iodine 0.37 g at a flow rate of 20 g/hour.
The reaction was carried out for 25 hours while maintaining the reaction temperature at 40°C.

The reaction solution was filtered, and the residue was washed with 98% sulfuric acid, filtered, and poured into water in a beaker. After washing the slag in the beaker with water, 5% bicarbonate of soda water, and water in that order, dry it and add PCNB containing 0.35% by weight of HCB.
127.6g was obtained (yield 86.5% by weight).

Example 6 2,5-dichloronitrobenzene 96.0g, chlorosulfonic acid 190g, 98% sulfuric acid 19g, iodine 0.37
Chlorine gas was blown into the mixture at a flow rate of 20 g/hour, and the mixture was reacted at 30° C. for 25 hours. The reaction solution was filtered at room temperature and the residue was separated. Next, the slag was washed with 98% sulfuric acid, and then poured into water in a beaker. In a beaker, mix the slag with water, 5% carbonated soda water,
Washed with water and then dried, 0.27% by weight HCB
135.8 g of PCNB containing PCNB was obtained (yield 92% by weight).

Comparative example 1 73.8g of nitrobenzene, chlorosulfonic acid
40% chlorine gas in a mixed solution of 184.5g and 0.6g of iodine
The reaction temperature was maintained at 60° C. for 9.5 hours.

The reaction solution was filtered at room temperature, the residue was washed with 98% sulfuric acid, and the residue was poured into water in a beaker.
Wash the slag in a beaker with water, 5% soda water, and water in that order, then dry it to remove 2.54% by weight of HCB.
150g of PCNB was obtained (yield: 85% by weight).

Comparative example 2 Nitrobenzene 61.0g, chlorosulfonic acid 155g
34.5 g of chlorine gas in a mixture of 0.5 g of iodine
The mixture was blown in at a flow rate of g/hour, and the reaction temperature was maintained at 80°C for 9 hours.

The reaction solution was filtered at room temperature, the residue was washed with 98% sulfuric acid, and the residue was poured into water in a beaker.
Wash the slag in a beaker with water, 5% soda water, and water in that order and dry it, containing 10.6% by weight of HCB.
118g of PCNB was obtained (yield: 80% by weight).

〔Effect of the invention〕

The manufacturing method according to the present invention uses industrially easily available raw materials, and reduces the content of undesirable HCB, which is produced in large amounts as a by-product in conventional PCNB manufacturing, at 50°C.
By carrying out the chlorination reaction below, the amount can be reduced to a very small amount, which is extremely excellent industrially.

[Brief explanation of the drawing]

Figure 1 shows that 3.4 parts of chlorosulfonic acid is added as a solvent to 1 part of nitrobenzene, and 0.6% by weight of iodine is added as a catalyst to nitrobenzene.
This figure shows the relationship between the reaction temperature, the amount of HCB produced as a by-product, and the reaction time when PCNB is produced by chlorination.

Claims (1)

[Claims] 1 Chlorination reaction of nitrobenzene and/or polychloronitrobenzenes using chlorine in the presence of chlorosulfonic acid and an iodine catalyst at 50°C
A method for producing pentachloronitrobenzene that suppresses the by-product of hexachlorobenzene, the method being carried out at the following temperature.