JPH0448788B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for producing trichloroaniline. Specifically, it is a method for obtaining highly pure trichloroaniline in high yield from trichloroaniline hydrochloride obtained by chlorinating aniline hydrochloride.

Trichloraniline is useful as a raw material for azo dyes, insecticides, fungicides, herbicides, photographic magenta couplers, and the like.

Conventionally, in a method for producing trichloroaniline by chlorinating aniline, aniline is generally used in the form of a hydrochloride to prevent side reactions. That is, after suspending the hydrochloride of aniline in an organic solvent and supplying chlorine to the solution to obtain the hydrochloride of trichloroaniline, this is separated,
A method is known in which the hydrochloride is then brought into contact with water to dehydrochloride it to obtain trichloroaniline.

However, in the above method, problems arise in that the trichloroaniline obtained by dehydrochlorination is colored and the yield and purity are reduced. One possible way to solve this problem is to wash the trichloroaniline hydrochloride with a clear organic solvent before dehydrochloridizing it, but it is difficult to effectively prevent the development, and the effect of the washing is limited. In order to improve the performance, a large amount of organic solvent is required, and this method cannot necessarily be said to be industrially satisfactory.

The present invention was made in view of the above problem, and by removing chlorine present in the hydrochloride slurry of trichloroaniline obtained by chlorination, the side reactions in the dehydrochlorination of the hydrochloride can be completely prevented. To provide a method for producing trichloroaniline, which can prevent coloring and obtain high purity trichloroaniline without coloration in high yield.

That is, the present invention chlorinates aniline hydrochloride in an organic solvent to obtain trichloroaniline hydrochloride, and removes substantially the entire amount of dissolved chlorine from the slurry containing the obtained trichloroaniline hydrochloride, The method for producing trichloroaniline is characterized in that the hydrochloride of trichloroaniline is then dechlorinated to obtain trichloroaniline.

The organic solvent used in the present invention is not particularly limited as long as it can suspend the aniline hydrochloride and does not adversely affect the chlorination described below. Chlorinated hydrocarbons are generally preferred. Specific examples include carbon tetrachloride, chloroform, methylene chloride, perchlorethylene, and ethylene dichloride, among which carbon tetrachloride is most preferred. In addition to this, acetic acid is also preferably used.

In the present invention, the hydrochloride of aniline may be obtained by any method, but it is generally preferable to react the aniline with hydrogen chloride in an organic solvent to form the hydrochloride. As the above reaction conditions, known conditions are applied as they are. For example, it is most common to feed hydrogen chloride in gaseous form into the organic solvent at a temperature below 40°C, preferably below 30°C. In order to solubilize the aniline hydrochloride produced in this case and to facilitate the chlorination reaction described below, alcohols such as methanol and ethanol, ketones such as acetone, etc. are added to the organic solvent during or after the reaction. of polar solvent is recommended. In this case, the appropriate amount of the polar solvent used is 0.5 to 10% by volume based on the organic solvent.

The aniline hydrochloride is then chlorinated to form trichloroaniline hydrochloride. For the above-mentioned chlorination, known conditions may be employed without particular restriction. That is,
10 to 10 to a theoretical amount in an organic solvent containing the hydrochloride of aniline at below 30°C, preferably below 25°C.
A common method is to blow in 50% excess chlorine gas. The trichloroaniline hydrochloride produced has extremely low solubility in organic solvents, and the liquid after the reaction becomes a slurry.

The most important feature of the present invention is that substantially the entire amount of dissolved chlorine is removed from the trichloroaniline hydrochloride slurry obtained by chlorination. In the present invention, "removing substantially the entire amount of dissolved chlorine" means removing dissolved chlorine to such an extent that it is not detected by normal analysis.
In other words, the present invention claims that extremely small amounts of chlorine remaining in the hydrochloride of trichloroaniline obtained separately have a great effect on the coloring of the trichloroaniline obtained, the reduction in yield, etc. when the hydrochloride is dechlorinated. This was done based on knowledge, and by removing the chlorine in the slurry, it was possible to completely prevent the above problem. Therefore, the hydrochloride of trichloroaniline from which dissolved chlorine has been removed can be dehydrochlorinated without particularly precise treatment such as washing, and highly purified and uncolored trichloroaniline can be obtained in high yield.

The method for removing dissolved chlorine from the slurry containing the hydrochloride of trichloroaniline is not particularly limited, and it is possible to substantially eliminate the chlorine dissolved in the organic solvent adhering to the surface of the separated hydrochloride. I wish I could. Note that free hydrogen chloride is present together with chlorine in the slurry after chlorination, and may be removed at the same time as the chlorine removal process. However, even after hydrogen chloride is almost completely removed, chlorine remains in the slurry in an amount that adversely affects dehydrochlorination. Therefore, even after the hydrogen chloride in the slurry is removed, it is necessary to sufficiently remove chlorine. The above method for removing dissolved chlorine is preferably carried out by degassing the slurry. The general degassing method is to degas the hydrochloride slurry as it is, but
After concentrating the slurry, or by further removing the organic solvent, a method of degassing the cake-like trichloroaniline hydrochloride may be carried out as necessary. Further, the means for the degassing treatment is not particularly limited, but generally employed are a method of heating, a method of blowing inert gas such as nitrogen or carbon dioxide, a method of reducing pressure, or a combination thereof. Among the above methods, the method using heating is most preferred.

In the degassing method by heating, the heating temperature is 30 to 60
The temperature is preferably 35 to 50°C. heating temperature
If the temperature is 60°C or higher, the dissolution of trichloroaniline hydrochloride in the solvent will increase, resulting in a decrease in the amount of trichloroaniline obtained. When the mother liquor is reused, dissolved trichloroaniline is undesirably subjected to further chlorination, causing an increase in by-products. In the degassing method using reduced pressure, the appropriate pressure is 10 to 200 Torr, preferably 20 to 100 Torr.

On the other hand, the removal of dissolved chlorine makes it possible to recirculate and use the mother liquor consisting of an organic solvent obtained when the hydrochloride of trichloroaniline is separated from the slurry as the organic solvent for dissolving aniline. do. That is, the above treatment effectively prevents a trace amount of chlorine dissolved in the mother liquor from denaturing the aniline dissolved in the mother liquor, and allows the organic solvent as the mother liquor to be circulated without any hindrance. It is. Therefore, in the method of the present invention, among the embodiments in which dissolved chlorine is removed from the slurry of trichloroaniline hydrochloride, the embodiment in which the slurry is treated as it is is preferable because the separated mother liquor can be directly recycled and used. Of course, the same effect can be obtained by subjecting the mother liquor separated before removing dissolved chlorine to the above-mentioned treatment.

In addition, when a polar solvent is added to solubilize the hydrochloride of aniline in an organic solvent, contacting the mother liquor from which dissolved chlorine has been removed with water at a ratio of 20 to 200% by volume is effective for denaturation of aniline. prevent,
It is also preferable because it can prevent a decrease in the chlorination reaction rate.

In the present invention, trichloroaniline hydrochloride from which dissolved chlorine has been removed is brought into contact with water to dehydrochloride it, thereby obtaining uncolored, highly pure trichloroaniline in good yield.

EXAMPLES Hereinafter, Examples will be shown to explain the present invention more specifically, but the present invention is not limited to these Examples.

Example 1 600 ml of carbon tetrachloride, 20 ml of methanol, and 60 g of aniline were placed in a 1-4 neck round bottom flask equipped with a thermometer, stirring bar, gas inlet tube, and condenser.
(0.645 mol) was charged. Hydrogen chloride gas was passed through at 150 ml/min for 106 minutes in a water bath at 15°C. During this time,
The reaction solution temperature was 15 to 23°C, and aniline was precipitated as aniline hydrochloride. Next, add 150ml of chlorine gas.
The reaction mixture was heated for 5 hours and 47 minutes at a temperature of 100 min to produce trichloraniline hydrochloride. During this time, the slurry temperature was 18-25°C. Immediately after stopping the chlorine gas supply, raise the temperature of the water bath to raise the slurry temperature.
It was heated to 40-43°C for 10 minutes and degassed. No dissolved chlorine was detected after deaeration. After degassing, the slurry was cooled to room temperature and filtered under reduced pressure using a nutsutier, and further filtered while washing the crude trichloroaniline hydrochloride with 100 ml of carbon tetrachloride to obtain 110 g of crude trichloroaniline hydrochloride and 650 ml of carbon tetrachloride liquid. Ta. The crude trichloroaniline hydrochloride was dehydrochlorinated with 300 ml of water and dried to obtain 105 g (0.534 mol) of white, powdered trichloroaniline. The purity of this thing is
It was 99.2%.

Example 2 Trichloroaniline was obtained in the same manner as in Example 1, except that 650 ml of carbon tetrachloride solution after separating crude trichloroaniline hydrochloride was washed with 600 ml of water and then recycled as a solvent for aniline. The obtained trichloroaniline was 104 g (0.529 mol) and was in the form of a white powder. Moreover, the purity was 99.1%.

Comparative Example 1 Trichloroaniline was obtained in the same manner as in Example 1, except that the slurry of trichloroaniline hydrochloride was not deaerated. The obtained trichloroaniline was 98.2 g (0.499 mol) and was in the form of a slightly reddish brown powder. Moreover, the purity was 95.3%.

In addition, in the above method, 650 ml of carbon tetrachloride solution after separating crude trichloroaniline hydrochloride was mixed with 600 ml of water.
Trichloroaniline was obtained in the same manner, except that after washing with ml of water, the solution was recycled as a solvent for aniline. As a result, the trichloraniline obtained was 68g.
(0.346 mol), and the powder had a reddish brown color. In addition, the purity was poor at 78.1%.

Example 3 Trichloroaniline was obtained in the same manner as in Example 1, except that the trichloroaniline hydrochloride slurry was stirred for 30 minutes at 30° C. under a reduced pressure of 100 Torr to degas it. Note that no chlorine was detected in the slurry after degassing. The obtained trichloraniline is
The amount was 102 g (0.519 mol) and was in the form of a white powder. In addition, the purity of the above trichloroaniline is 99.1
It was %.

Example 4 In Example 1, the trichloroaniline hydrochloride slurry was kept at 30°C, and nitrogen was added to it at a rate of 150 ml'min.
Trichloroaniline was obtained in the same manner except that it was degassed by blowing for 120 minutes. Note that no chlorine was detected in the slurry after deaeration.

As a result, the trichloraniline obtained was 104
g (0.529 mol), and was in the form of a white powder.
Moreover, the purity was 98.9%.

Example 5 In Example 1, the trichloroaniline hydrochloride slurry was filtered to separate trichloroaniline hydrochloride, and then heated at 45°C for 10 minutes to degas it.
Trichloroaniline was then obtained in the same manner except that it was washed with 100 ml of carbon tetrachloride. After degassing, no chlorine was detected in the trichloroaniline hydrochloride cake.

The trichloraniline obtained was 101.0g (0.514
mole) and was in the form of a white powder. Also,
The purity of the above trichloroaniline was 98.8%.

Further, the separated liquid was heated at 40 to 43° C. for 10 minutes to degas it, and then recycled as a solvent in the production of trichloroaniline, but there was almost no decrease in the yield or purity of the trichloroaniline obtained.

Claims (1)

[Claims] 1. Chlorinate the hydrochloride of aniline in an organic solvent to obtain the hydrochloride of trichloroaniline, remove substantially the entire amount of dissolved chlorine from the obtained slurry containing the hydrochloride of trichloroaniline, and then remove the hydrochloride of trichloroaniline. A method for producing trichloroaniline, which comprises dehydrochlorinating the hydrochloride of to obtain trichloroaniline.