JPH0543519A - Production of 2,6-dichloro-4-nitroaniline - Google Patents

Abstract

PURPOSE:To obtain 2,6-dichloro-4-nitroaniline useful as a raw material for azo-type disperse dye and insecticide in high selectivity, yield and efficiency on an industrial scale using nearly quantitative amount of chlorine while suppressing the formation of by-product. CONSTITUTION:2,6-Dichloro-4-nitroaniline (DCNA) is produced by chlorinating p-nitroaniline (PNA) with chlorine gas in an aqueous solution of hydrochloric acid having a hydrochloric acid concentration of >=25wt.%. In the above process, the reaction temperature is adjusted to 40-60 deg.C and the introduction rate of chlorine gas is maintained to 0.1-0.3mol/h based on 1 mol of PNA until the chlorination degree reaches 60-80% and, thereafter, the reaction temperature is lowered to <=40 deg.C and the introduction rate of chlorine gas is decreased to <=1/2 of the above rate. Preferably, the filtrate of residual hydrochloric acid left after the filtration of DCNA is circulated and reused as it is after the completion of the reaction to suppress the by-production of 2-chloro-4-nitroaniline and 2,4-dichloro-6-nitroaniline and obtain DCNA in high efficiency at a yield of >=90% and a purity of >=97%.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is 2,6-dichloro-4-
It relates to a method for producing nitroaniline. More specifically, p-
It relates to an improved process for the chlorination of nitroaniline to produce 2,6-dichloro-4-nitroaniline.

[0002]

2. Description of the Related Art 2,6-Dichloro-4-nitroaniline is a compound useful as a raw material for azo disperse dyes and insecticides. BACKGROUND ART Conventionally, a technique in which 2,6-dichloro-4-nitroaniline (hereinafter abbreviated as DCNA) is produced by chlorination of p-nitroaniline (hereinafter abbreviated as PNA) is generally known. The manufacturing method is shown below.

A method of chlorinating with a chlorine gas in a low-concentration aqueous hydrochloric acid solution (1.8N) under low or high temperature conditions [J. Chem. Soc. 93, 1772]. -5 (190
8))]. Medium temperature hydrochloric acid solution (4.5-6N), high temperature (9
Method of chlorinating with chlorine gas under conditions of 5 to 110 ° C. [Japanese Patent Publication No. 62-12787]. A method of chlorinating in a high-concentration aqueous hydrochloric acid solution (5 to 12 N) in the presence of an alkylbenzenesulfonic acid (or its salt) and an alkylnaphthalenesulfonic acid (or its salt, a formalin condensate) [JP-A-56-36435]. .. A method of chlorinating in the presence of ligninsulfonic acid (or a salt thereof) or a dialkylsulfosuccinic acid ester in a mineral acid [JP-A-62-70345]. A method of chlorinating with chlorine gas in hydrochloric acid and glacial acetic acid [J. Che.
m. Soc. 93, 1772-5 (1908))]. A method of using sulfuryl chloride as a chlorinating agent in monochlorobenzene [Japanese Patent Laid-Open No. 50-46633].

However, in the above production method, the yield is low (37%) when the reaction is carried out under a low temperature condition and in a hydrochloric acid aqueous solution having a relatively low concentration (1.8N). Further, when the reaction is carried out under a high temperature condition and in a dilute aqueous hydrochloric acid solution (0.25N), the yield is substantially improved (75%), but the yield is low and it is not industrial. Further, since the solubility of PNA in a dilute hydrochloric acid aqueous solution is low, it is not industrial in terms of volume efficiency.

In the above-mentioned production method, the purity of DCNA in the product is as low as 82 to 90%, and 2-chloro-4-nitroaniline (hereinafter abbreviated as OCPNA) which is a reaction intermediate.
Of 1,4-dichloro-6-nitroaniline (hereinafter abbreviated as DCONA), which is considered to be a rearrangement product of a nitro group, is not only present as a by-product. Therefore, in order to obtain high-purity DCNA, it is necessary to carry out purification such as recrystallization.

In the above-mentioned production method and method, alkylbenzene sulfonic acid, alkylnaphthalene sulfonic acid, lignin sulfonic acid and the like are added in catalytic amounts, but as a result of additional tests, chlorination progresses in the middle despite introduction of chlorine gas. And a product rich in OCPNA and PNA is obtained. From this, it is not preferable to improve the volumetric efficiency by adding the additive, because the purity of the product is lowered. Further, these additives may remain in the product, which is not preferable from the viewpoint of quality deterioration.

In the above-mentioned production method, the product DCNA is dissolved in hydrochloric acid-glacial acetic acid, so that the yield is low, and if an attempt is made to improve the yield, an extraction operation or the like is required, which is not preferable because the process becomes complicated.

In the above-mentioned production method, as a result of additional tests, various by-products were many, and therefore the purity of DCNA obtained was 80%.
It was confirmed that the degree was low. In particular, DCONA, which is considered to be a rearranged product of a nitro group, was contained as a byproduct in an amount of about 10%. Therefore, purification such as recrystallization is required, which complicates the process, which is not preferable.

In all of these conventional methods (from the above-mentioned production methods), the product contains a large amount of reaction intermediate OCPNA or nitro group rearrangement product DCONA, etc. Was difficult to obtain.

Further, in the conventional method using chlorine gas as a chlorinating agent, the reaction efficiency of chlorine is poor, and chlorine gas must be used in excess of the stoichiometric amount in the actual reaction. If the chlorine gas used in excess is released into the atmosphere, it will seriously damage the environment, and if it is to be reused, a chlorine recovery device or the like is required, which is not industrially preferable.

As described above, the conventionally known method for producing DCNA by chlorination of PNA is not always industrially satisfactory in terms of yield, quality, and chlorination efficiency of the chlorinating agent.

[0012]

Problems to be Solved by the Invention PNA is chlorinated to obtain D
It is an object of the present invention to provide a method for producing a target DCNA with high yield and high selectivity in the method for producing CNA.

[0013]

The present inventors have attempted to improve productivity in a method for producing DCNA by chlorinating PNA, and also to leave residual OCPNA which is a reaction intermediate and rearrangement of nitro group. As a result of diligent study on a method for producing a desired DCNA with a high yield and a high selectivity by suppressing the by-product of DCONA which is considered to be a substance as much as possible, chlorine is introduced in a method of chlorinating with chlorine gas in concentrated hydrochloric acid. The inventors have found that the object can be achieved by devising the speed and the reaction temperature, and have completed the present invention.

That is, the present invention relates to a method of chlorinating PNA in an aqueous hydrochloric acid solution with chlorine gas, which comprises:
A method for producing DCNA, which comprises reacting chlorine gas in a stoichiometric amount to produce high-purity DCNA, and more specifically, PNA is treated with chlorine in an aqueous hydrochloric acid solution having a hydrochloric acid concentration of 25% by weight or more. In the method of producing DCNA by chlorinating using gas, the reaction temperature is 40 to 60 ° C. and the chlorine gas introduction rate is P until the chlorination proceeds to 60 to 80%.
DC in which the range of 0.1 to 0.3 mol / h with respect to 1 mol of NA is set, and then the flow rate is reduced to ½ or less of the flow rate and the reaction temperature is set to 40 ° C. or lower.
It is a manufacturing method of NA.

The present invention will be described in more detail below. The method for producing DCNA of the present invention is characterized in that PNA is chlorinated in an aqueous hydrochloric acid solution having a hydrochloric acid concentration of 25% or more at a temperature of 60 ° C. or less using chlorine gas. PNA has the highest solubility in a 15% hydrochloric acid aqueous solution, but in a hydrochloric acid aqueous solution having a concentration of less than 25%, a large amount of by-product DCONA as an isomer and OCPNA as a reaction intermediate remain, which is not preferable.

On the other hand, in a high concentration hydrochloric acid aqueous solution of 25 to 30%, the residual OCPNA in the product can be suppressed, and DCN
A's selectivity is improved, and DCONA's byproduct is 1.5-2%
Can be suppressed. Further, with concentrated hydrochloric acid having a hydrochloric acid concentration of 30% or more, the production of DCONA is suppressed to less than 1.5%, and highly pure DCNA can be produced.

The second feature of the present invention is that the introduction rate of chlorine gas is set to PNA1 until the chlorination rate reaches 60 to 80%.
The amount is between 0.1 and 0.3 mol / h with respect to mol, and thereafter, the flow rate is reduced to 1/2 or less of the flow rate.
The introduction rate of chlorine is 0.3 mol / mol PNA 1 mol /
If it is larger than h, chlorine is discharged from the reaction solution without reaction and bubbles are generated, so that the volumetric efficiency is lowered, which is not preferable. OCP, which is an intermediate if the amount of chlorine used is small
NA remains and the yield decreases. Using excess chlorine also reduces the yield. As for the amount of chlorine used, it is usually preferable to use a stoichiometric amount of chlorine.

Excess chlorine accelerates the perchlorination reaction or oxidation reaction of DCNA and lowers the selectivity and the purity, which is not preferable. Moreover, even if the chlorination rate becomes 60 to 80%,
If the reaction is carried out while keeping the chlorine introduction rate within the range of 0.1 to 0.3 mol / h with respect to 1 mol of PNA, unreacted chlorine will be discharged to the outside of the system, so excess chlorine will be required, Is also not desirable.

The third feature of the present invention is that the reaction temperature is 40 to 60 ° C. until the reaction proceeds to 60 to 80%, and then 40 ° C. or lower. First, PNA is suspended in a reaction medium which is an aqueous hydrochloric acid solution, and the obtained suspension is heated to the reaction condition temperature of the present invention, whereby PNA is mostly dissolved in the reaction medium. Next, while maintaining the temperature at 40 to 60 ° C., chlorine gas is introduced into the reactor by using a dip tube, and the temperature is lowered to 40 ° C. or lower when the reaction proceeds 60 to 80% on the way.

The amount of chlorine used is usually stoichiometric.
If the amount of chlorine used is small, the intermediate OCPNA remains and the yield decreases. Using excess chlorine also reduces the yield. In practice, it is preferred to use a stoichiometric amount of chlorine. If the reaction is carried out at a temperature higher than 60 ° C, bubbles will be generated due to unreacted chlorine and the bubbles will be discharged out of the system, which is not preferable. If the temperature is lower than 30 ° C, the quality of the product is deteriorated, which is not preferable. It is preferable to carry out the reaction under the above-mentioned reaction conditions because almost no unreacted chlorine is generated and the quality of the product is not deteriorated.

The fourth feature of the present invention is that the hydrochloric acid filtrate recovered in the reaction is recycled to the next reaction as it is. The product DCNA is poorly soluble and precipitates under the reaction conditions. After the reaction is completed, the precipitate is filtered. The precipitate can be obtained as high-purity DCNA simply by washing with water and drying,
The filtered mother liquor can be recycled as it is. The quality of DCNA obtained when this hydrochloric acid mother liquor is circulated and used as is is comparable to that when fresh hydrochloric acid is used, and the yield is slightly improved as compared with fresh hydrochloric acid. The DCNA of the product has a very high purity, and a DCNA having a yield of 90% or more and a purity of 97% or more can be obtained simply by filtering, washing with water and drying.

[0022]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples. Example 1 70.6 g (0.511 mol) of PNA and 35 in a reactor
% 812 g hydrochloric acid was introduced. The suspension was heated to about 50 ° C. with stirring. While keeping the temperature at 50-55 ℃,
Chlorine gas was introduced into the apparatus at a molar ratio of 0.20 to PNA / h using an immersion tube. After 8 hours, the chlorine gas was stopped, the temperature was cooled to about 30 ° C., and chlorine gas was introduced at a 0.07 mol ratio / h for 8 hours while maintaining the temperature at 30 to 35 ° C. After filtration, the product is heated to 55 ° C. in 300 warm water.
g once, and 280 g of room temperature water 5 times.
Upon drying, 95.7 g of product was obtained. The yield in terms of purity was 89.1%.

The analysis results of the obtained product are shown below. DCNA 98.5% DCONA 1.2% The amount of chlorine collected without reaction was 1.9 g (0.05 mol ratio based on PNA).

Example 2 The same procedure as in Example 1 was repeated except that 650 g of the reaction filtrate of Example 1 and 162 g of 35% hydrochloric acid were used in place of 812 g of 35% hydrochloric acid in Example 1, and 98.0 g of the product was obtained.
Got The yield in terms of purity was 91.3%.

The analysis results of the obtained product are shown below. DCNA 98.5% DCONA 1.3% Chlorine collected unreacted was 0.6 g (0.01 mol ratio to PNA). In addition, the recycling was repeated 6 times, but there was almost no change with a purity conversion yield of 90 to 93% and a DCNA purity of 98.0 to 99.0%.

Comparative Example 1 [Similar Method to Japanese Examined Patent Publication No. 62-12787] The same procedure as in Example 1 was repeated except that 15% hydrochloric acid was used in place of 35% hydrochloric acid.
4.6 g was obtained. The yield in terms of purity was 62.1%.

The analysis results of the obtained product are shown below. DCNA 69.5% DCONA 1.2% OCPNA 5.5% The amount of chlorine collected unreacted was 2.0 g (0.06 mol ratio to PNA).

Comparative Example 2 The same procedure as in Example 1 was carried out except that the reaction temperature was maintained at 50 to 55 ° C. and chlorine gas was introduced into PNA at a molar ratio of 0.34 / h for 9 hours. , Product 92.
4 g was obtained. The yield in terms of purity was 84.5%.

The analysis results of the obtained product are shown below. DCNA 96.7% DCONA 3.0% Chlorine collected without reaction was 45.8 g (1.3 mol ratio to PNA).

Comparative Example 3 [Additional Test of JP-A-56-36435] In Example 1, 547.8 g of 35% hydrochloric acid was used, and demol N (formalin condensation product of naphthalene sulfonic acid) was used.
2.8 g was added, the reaction temperature was maintained at 50 to 55 ° C., and chlorine gas was introduced at a 0.56 mol ratio with respect to PNA for 4 hours.
Got The yield in terms of purity was 72.6%.

The analysis results of the obtained product are shown below. DCNA 88.3% DCONA 2.5% OCPNA 9.1% PNA 0.1% The amount of chlorine collected unreacted was 6.0 g (0.17 mol ratio to PNA).

Comparative Example 4 The procedure of Example 1 was repeated, except that the reaction temperature was maintained at 50 to 55 ° C. and chlorine gas was introduced into PNA at a molar ratio of 0.20 / h for 21 hours. , Product 8
0.1 g was obtained. The yield in terms of purity was 64.6%.

The analysis results of the obtained product are shown below. DCNA 85.3% DCONA 2.6% OCPNA 11.8% The amount of chlorine collected without reaction was 64.9 g (1.8 mol ratio to PNA).

Comparative Example 5 [Additional Test of Japanese Patent Laid-Open No. 50-46633] 72.5 g (0.53 mol) of PNA and 430 g of monochlorobenzene were introduced into the reactor. This solution was heated to about 70 ° C. with stirring, and while maintaining the temperature at 70 to 73 ° C., 165 g (1.22 mol, 2.3) of sulfuryl chloride.
(3 molar ratio / PNA) was added dropwise over 2 hours. Then, the mixture was kept at 75 ° C. and stirred for 1.5 hours. 30 after the reaction
After cooling to 0 ° C., adding 60 ml of water, neutralizing with a 16% aqueous sodium hydroxide solution, and then performing steam distillation.
The residue of the kettle was collected by filtration, washed with water and dried to give the product 99.0.
g was obtained. The yield in terms of purity was 74.5%.

The analysis results of the product are shown below. DCNA 82.3% DCONA 7.5%

[0036]

INDUSTRIAL APPLICABILITY By the method of the present invention, the target DCNA can be obtained with high selectivity and high yield by suppressing the by-product DCONA, and it is an industrially efficient production method by using almost theoretical amount of chlorine. ..

Front page continuation (72) Inventor Ryuichi Mita 30 Asmuta-cho, Omuta-shi, Fukuoka Mitsui Toatsu Chemical Co., Ltd.

Claims (2)

[Claims] 1. P-nitroaniline is chlorinated using a chlorine gas in a hydrochloric acid aqueous solution having a hydrochloric acid concentration of 25% by weight or more,
In the method for producing 2,6-dichloro-4-nitroaniline, the reaction temperature is 40 to 60 ° C and the introduction rate of chlorine gas is 1 mol of p-nitroaniline until chlorination proceeds to 60 to 80%. 0.1 to 0.3 mol / h, and thereafter, the flow rate is reduced to ½ or less of the flow rate, and at the same time, the reaction temperature is set to 40 ° C. or less.
Process for producing 6-dichloro-4-nitroaniline. 2. The method according to claim 1, wherein the hydrochloric acid filtrate obtained after filtering out the precipitated 2,6-dichloro-4-nitroaniline after the reaction is circulated as it is.