JPS60228446A - Recovery of aromatic amine - Google Patents

Abstract

PURPOSE:Aromatic amines are extracted aqueous solutions containing the same with a solvent mainly consisting of tetrahydrofuran, the extract is washed with aqueous ammonia to remove electrolytes with high distribution ratio to aromatic amines whereby aromatic amines are recovered. CONSTITUTION:The extraction of aromatic amines is carried out from an aqueous solution or dispersion containing the same using an extractant containing mainly tetrahydrofuran, preferably ammonia and/or electrolytes such as ammonium halide or alkali metal halide at 0-100 deg.C. the resultant extract is rinsed with aqueous ammonia, preferably more than 10wt% concentration at 40-90 deg.C to recover aromatic amines.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering aromatic amines that combines extraction with a novel oil agent and washing of the extract.

Conventionally, methods for producing aromatic amines include a reduction method in which aromatic nitroamines are reduced.4. Amination methods are known in which aromatic halides such as aromatic cibarides are reacted with ammonia in the presence of water using a catalyst mainly composed of copper compounds.

However, especially in the case of the amination method, the reaction product solution containing the aromatic amine obtained in this way, for example, the reaction product solution when producing phenylenediamine using dichlorobenzene as the aromatic halide, does not contain the target substance. In addition to certain phenylene diamines, unreacted substances such as dichlorobenzene and ammonia, intermediate products such as chloroaniline, by-products such as chlorobenzene, adolin, phenol, ammonium chloride, and heavy substances, and copper used as a catalyst. This results in an aqueous solution or suspension containing the compound. Furthermore, before separating the aromatic amine from the reaction product liquid, in order to separate the catalyst consisting of a copper compound, an alkali metal hydroxide or an alkaline earth metal hydroxide is added to precipitate the copper compound, The reaction product liquid becomes an aqueous solution or aqueous suspension having an extremely complex composition containing, in addition to those mentioned above, alkali metal halides, alkaline earth metal halides, and the like. Extraction is a common method for separating the target substance, aromatic amine, from these complex reaction product liquids.

However, aromatic amines do not dissolve unless they are used in highly polar solvents, and such solvents also have high solubility in water, so they are often unsuitable as extractants, and various studies are required to select an extractant. It is.

As a result of these studies, for example, Japanese Patent Application Laid-Open No. 51-598
In Publication No. 24, aniline and 0 are added as extractants to the reaction product solution.
- A method for extracting and separating phenylenediamine using aromatic amines such as chloroaniline and 0-toluidine is disclosed. However, aniline and 0-toluidine have a specific gravity close to that of water, and it takes time to separate them into an extract and a raffinate. On the other hand, 0-chloroaniline is an intermediate of 0-phenylenediamine; Although it is suitable for production, it is not preferable to use it as an extractant in the production of m,p-phenylenediamine.

Also, Japanese Patent Publication No. 55-33707, No. 55-337
No. 08 and No. 55-. Publication No. 33709 discloses a method for extracting phenylenediamine from a reaction product liquid with an aliphatic alcohol having 3 to 4 carbon atoms. Although this method does not have the above-mentioned drawbacks, the distribution ratio [in the extract liquid] is The concentration of aromatic amines (wt%)/concentration of aromatic amines in the raffinate (wt%)] is still not sufficiently high, and heavy substances increase during the distillation process to recover the extractant from the extract. When phenylenediamine is recovered by rectification after removing the extractant from the extract, there is a problem that the recovered phenylenediamine turns black in the air.

Furthermore, U.S. Patent No. 4,193,938 proposes a method of extracting phenylenediamine from a reaction product solution using a chlorinated carbon solvent having 1 carbon atom, such as methylene chloride, chloroform, or carbon tetrachloride. Although this method has a relatively high partitioning rate in the case of methylene chloride, it involves a decomposition reaction in the process of distilling the extract extracted using these solvents to remove the extractant, and it produces a large number of unidentified by-products. may occur. This is probably because chlorinated carbon solvents such as methylene chloride are hydrolyzed in this step and the products cause secondary reactions.

The present invention has been made against the above background, and has a high partitioning ratio to aromatic amines and an extractant when recovering aromatic amines from an aqueous solution or suspension containing aromatic amines. Extraction using a new extractant that is easy to recover,
The object of the present invention is to provide a method for recovering aromatic amines that combines washing of the extract.

That is, in the present invention, when recovering aromatic amines from an aqueous solution or aqueous suspension containing aromatic amines, after extracting using an extractant containing tetrahydrofuran as a main component, the obtained extract is extracted with aqueous ammonia. The present invention provides a method for recovering aromatic amines, which is characterized by washing.

The extraction material used in the recovery method of the present invention is an aqueous solution or suspension containing an aromatic amine. For example, as described above, an aromatic halide and ammonia are mixed in the presence of water with a catalyst mainly containing a copper compound. It can be obtained by an amination method using

Examples of aromatic halides used in this amination method include chlorobenzene, dichlorobenzene, trichlorobenzene, chloroaniline, dichloroaniline, chlornitrohenzene, and dichloronitrobenzene. Preferred aromatic halides include can include chlorobenzene, dichlorobenzene, chloroaniline, and trichlorobenzene. These aromatic halides can be used in combination.

The amount of ammonia used is preferably 2 to 25 mol, particularly preferably 4 to 20 mol, per gram-atom of halogen which requires amination of the aromatic halide.

Further, the amount of water used is preferably 30 to 70% by weight, particularly preferably 4% by weight, based on the weight sum of both ammonia and water.
It is 5 to 65% by weight.

Furthermore, the amount of the copper compound to be used is preferably 0.01 to 0.4 g-atom, particularly preferably 0.02 to 0.2 g-atom in terms of copper atom per mole of aromatic halide.
It is an atom. Copper compounds used as catalysts include copper oxides, hydroxides, copper halides, etc., especially cuprous oxide, cupric oxide, cupric hydroxide,
Cupric halides and cupric halides are preferred, and mixed hydroxides, mixed oxides, or mixed halides of copper and alkaline earth metals are also preferred catalysts. When the copper compound contains an alkaline earth metal such as calcium, the content is preferably 10 gram atoms or less, particularly preferably 0.1 to 5 gram atoms, per 1 gram atom of copper.

The reaction temperature between the aromatic halide and ammonia is preferably 170 to 250°C, particularly preferably 200 to 240°C.
'C, and the reaction time is usually 2 to 40 hours. When the reaction is carried out continuously, two or more reactors are preferably connected in series so that the residence time of the reaction solution in the reactor becomes the desired reaction time.

Examples of aromatic amines produced in this manner include chloraniline, phenylenediamine, chlorphenylenediamine, and triaminohenzene.

After the reaction is completed, the reaction product solution obtained is preferably 20 to 8
0°C1, particularly preferably 30 to 700C, and if necessary, return the reaction system to normal pressure to remove ammonia in the reaction product liquid as a gas and reduce the pressure during operation in the following steps. However, it is not necessary to remove ammonia from the reaction product liquid at normal pressure.

In the recovery method of the present invention, an aqueous solution or aqueous suspension containing an aromatic amine obtained by the above-mentioned amination method is used as an extraction material, and the aromatic amine is extracted using tetrahydrofuran as an extraction agent.

During extraction, it is preferable that ammonia and/or an electrolyte be present in the extract, which can improve the layer separation between the extract and the extractant.

Such ammonia may be utilized by allowing unemitted ammonia present in the extract to exist as is, or by newly mixing ammonia. Moreover, such an electrolyte is an electrolyte that is water-soluble and does not react with aromatic amines. Such electrolytes include ammonium halides such as ammonium chloride produced as a by-product in the reaction of the amination method, alkali metal halides such as sodium chloride, potassium chloride, sodium bromide, and potassium bromide, calcium chloride, and calcium bromide. , alkaline earth metal halides such as magnesium chloride and magnesium bromide, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkali metal sulfates such as sodium sulfate, and water-soluble substances such as copper chloride and iron chloride. Examples include water-soluble metal sulfates such as halogenated metal salts and copper sulfate. If an electrolyte is present as a by-product from the reaction in the extract, there is no need to newly mix the electrolyte. The amount of ammonia and/or electrolyte in the extract is preferably 5 parts by weight or more, particularly 7 parts by weight or more and 50 parts by weight or less, based on 100 parts by weight of water in the extract.

When the reaction product liquid obtained by the amination method is used as an extract, ammonia and/or electrolyte within this range is usually present in the extract without adding ammonia and/or electrolyte.

Tetrahydrofuran used as extract may contain water, but if water is contained in large amounts, it may be necessary to reduce the concentration of ammonia and/or electrolytes in the extract, and also reduce the actual amount of extract. Therefore, the water content is preferably within a range that does not impair the layer separation during extraction, generally from 0 to 20% by weight. In addition, tetrahydrofuran contains 30% by weight of alcohols with 3 to 6 carbon atoms in the main chain such as propatool, butanol, pentanol, and hexanol, and other organic solvents such as aniline, aniline derivatives, propyl ether, and butyl ether.
It may be contained in amounts below.

The extraction agent/extractant ratio during extraction is changed as appropriate depending on the type and amount of aromatic amine, ammonia, electrolyte, etc. in the extract, but is usually 0.5 to 5 (weight ratio).

Further, for extraction, continuous countercurrent liquid-liquid extraction is preferably employed from the viewpoint of efficiency, but a batch extraction method may also be employed. When 5 parts by weight or more of ammonia and/or electrolyte are present in the extract, the extraction temperature is generally 10 to 100°C, but when the amount of ammonia and/or electrolyte present is less than 5 parts by weight. The extraction temperature is preferably 50 to 100°C from the viewpoint of layer separation between the extract and the raffinate.

The extractant and the target aromatic amine are separated and recovered from the extract obtained by extraction by distillation, crystallization, or other means. When extracts are processed by distillation, crystallization, etc., small amounts of electrolytes such as ammonium halides dissolved in the extracts may cause trouble during the process. For example, when trying to remove the extractant from the extract by distillation, the ammonium halide decomposes due to heating and reacts with the coexisting aromatic amine to form ammonia and the hydrogen halide salt of the aromatic amine. Hydrogen halide salts of aromatic amines adhere to the lower part of the distiller when heated and become sticky and solid, which tends to cause blockage in the distiller.

For this reason, in the present invention, before removing the extractant from the extract obtained by such extraction by means such as distillation and separating aromatic amines, aqueous ammonia, preferably aqueous ammonia, preferably at a concentration of 1O2 or higher, is used. , particularly preferably 10 to 40
By washing with aqueous ammonia at a concentration of % by weight,
The amount of electrolytes such as ammonium halides in the extract is significantly reduced or substantially eliminated.

If the concentration of ammonia water is less than 10% by weight, the layer separation between the extract and ammonia water during washing tends to deteriorate. The ammonia water may also contain tetrahydrofuran in a soluble range.

Although a batch type extractor such as a mixer/settler type can be used for this washing operation, it is preferable to use a continuous extractor, particularly preferably a continuous countercurrent liquid-liquid extractor. The weight ratio of ammonia water/extraction liquid during washing is preferably 0°05 to 0.5, and the washing temperature is preferably 10 to 100°C, particularly preferably 40 to 900°C.
It is.

The ammonia water used to wash the extract contains electrolytes such as ammonium halides as well as a certain amount of aromatic amines, but this is returned to the extraction process and treated in the same way as the extractant, using the extractant tetrahydrofuran. The recovery rate of aromatic amines can be increased by extracting the aromatic amines again.

To give a specific example of such an aromatic amine recovery method, for example, when combined with a countercurrent liquid-liquid extraction column, the extraction material is supplied to the middle stage, the extractant to the bottom of the column, and aqueous ammonia to the upper part of the column. The feed ratio of feedstock, extractant, and ammonia water is approximately 1:1 by weight.
0.5 to 5: 0.025 to 2.5, and the extract can be obtained from the top of the column and the raffinate can be obtained from the bottom of the column.

A crude aromatic amine can be obtained by separating tetrahydrofuran and water from the extract that has been washed with aqueous ammonia in a cold manner.

The crude aromatic amine obtained in this way has a low content of electrolytes such as ammonium halides and virtually no electrolytes, and can be easily processed by either the recrystallization method (crystallization method) or the rectification method. High purity aromatic amines can be easily obtained. Particularly in the rectification method, there is little cold residue and the residue has fluidity under cold conditions, making it easy to carry out the distillation.

If the extract contains electrolytes such as ammonium halides because washing with ammonia water is not performed,
During rectification, for example, ammonium chloride decomposes and ammonia gas is generated, causing flooding, and the generated hydrogen chloride creates aromatic amine hydrochloride, which further causes a condensation reaction of aromatic amines and removes heavy substances. bring about an increase.

On the other hand, an alkali metal hydroxide and/or an alkaline earth metal hydroxide is added to the raffinate obtained from the extraction to precipitate a copper compound mainly consisting of copper oxide and/or copper hydroxide. By this, copper compounds in the raffinate can be separated.

The raffinate after extraction contains ammonium halides, ammonia, extraction agents, etc. in addition to copper ions, and further contains small amounts of aromatic amines and unreacted raw materials that remain after extraction. Therefore, if necessary, extractants, aromatic amines, unreacted raw materials, etc. are removed by azeotropic distillation, steam distillation, or other methods.

Then, while thoroughly stirring this raffinate, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide and/or
Or, by adding an alkaline earth metal hydroxide such as magnesium hydroxide or calcium hydroxide, preferably an alkali metal hydroxide, the copper compound in the raffinate is made mainly of copper oxide and/or copper hydroxide. Precipitates as a copper compound.

In this copper compound precipitation step, when using an alkali metal hydroxide or a combination of an alkali metal hydroxide and an alkaline earth metal hydroxide, these are thoroughly stirred after addition, and the pH is preferably 10 or higher, particularly preferably. By making the solution basic with a pH of 12 or higher and at a temperature of preferably 50'C or higher, particularly preferably boiling, most of the copper compound is precipitated as copper oxide, and at the same time the ammonium halide contained in the solution is precipitated. Decomposes and produces ammonia.

The precipitated copper compound can be easily separated and recovered by filtration or the like. This recovered copper compound is
It has almost the same catalytic activity as copper oxide, copper hydroxide, and copper halide, and can be reused as a catalyst in an amination method.

In the copper compound precipitation step, when alkaline earth metal hydroxides are mainly used, they are preferably added to the raffinate in an amount of 1 molar equivalent per gram of ammonium ions, and the pH is adjusted to 5.5 to 5.5. 9.5, particularly preferably 6.0 to 7.0. In this case, heating and stirring alone may not result in sufficient precipitation of the copper compound. At this time, ammonia in the raffinate is removed by passing air, nitrogen gas, or other non-reactive, non-condensable gas into the liquid, or by a gentle process to promote the precipitation of the copper compound. In this case, the copper compound co-precipitates with the alkaline earth metal hydroxide, making it impossible to obtain a highly pure copper compound. However, it is absolutely acceptable for the catalyst to contain alkaline earth metals, and if the content is within the preferred range, the reaction rate can be increased by reusing the recovered copper compound as a catalyst. may increase.

Note that when using an alkali metal hydroxide or when using an alkali metal hydroxide and an alkaline earth metal hydroxide together, a non-condensable gas may be passed in order to promote the precipitation of the copper compound. Since the filtrate after separating the precipitated copper compounds contains only a very small amount of copper compounds, it can be easily treated by ordinary dehydration treatments such as activated sludge treatment and activated carbon treatment. In addition, when the reaction product liquid obtained by the amination method is used as an extraction material,
When recovering the copper compound, which is a catalyst, present in the reaction product solution, the copper compound is precipitated by adding a large amount of alkali metal hydroxide and/or alkaline earth metal hydroxide prior to extraction, and then filtered. , can also be recovered. In this case, the filtrate becomes the extract, and the extract further contains an alkali metal halide and an alkaline earth metal halide. However, this method has a problem in that the precipitated copper compound becomes colloidal and cannot be easily separated by filtration.

As described above, the recovery method of the present invention improves the layer separation property during extraction by extracting an aromatic amine-containing aqueous solution or aqueous suspension with a novel extractant mainly composed of tetrahydrofuran. It has a high distribution rate for aromatic amines, and most of the electrolytes such as ammonium halides in the extract can be removed by washing the extract with aqueous ammonia, making it an extremely useful method for recovering aromatic amines. It is valid.

Furthermore, this recovery method has the advantage that, after extraction, the extraction agent tetradrofuran in the extract can be removed very easily by distillation, with almost no generation of heavy substances. Furthermore, aromatic amines, especially phenylenediamine, obtained by rectification after distilling off tetrahydrofuran from the extract obtained by the recovery method of the present invention are said to be unlikely to cause coloration such as blackening even when stored in air. It has characteristics.

Although the extraction material used in the recovery method of the present invention is mainly the reaction product liquid obtained by the amination method, it goes without saying that the extraction material is not limited thereto.

The present invention will be explained in more detail below with reference to Examples.

Example 450 g of p-dichlorobenzene, 40
1125 g of wt% ammonia water and 21 g of cupric oxide were charged, the temperature was raised to 7210 oC, and the reaction was carried out for 5 hours.

After the reaction, the autoclave was cooled to 60'C, and the valve was opened little by little while stirring to release excess ammonia gas. After lowering the internal pressure of the autoclave to normal pressure, a portion of the reaction solution was analyzed and the reaction rate was 99.8%.
The selectivity was 92.0% for p-phenylenediamine, 4.0% for p-chloroaniline, and 0.0% for aniline. It was 8%.

330 cc of water was added to this liquid, and the mixture was transferred to a separate container and stored. The operation up to this point was performed 5 times, and the reaction product liquids for the 5 times were mixed. Note that the reason why water was added to the reaction product liquid is that the concentration of p-phenylenediamine is so high that it tends to precipitate.

The p-phenylenediamine contained in this liquid is 16.
5% by weight, ammonium chloride was 17.0% by weight.

Next, using a vertically vibrating countercurrent liquid-liquid extraction device with an inner diameter of 15 mm and an effective height of 2 m, 1.3 kg of tetrahydrofuran containing 6% water by weight and 0.0% aqueous ammonia of 14% by weight were added to 1 kg of the reaction product liquid. Extraction and washing were performed by supplying 3 kg. That is, aqueous ammonia was supplied from the upper part of the column of the extractor, extraction material was supplied from the upper part of the column to a position of 1/3, and tetrahydrofuran as an extraction agent was supplied from the lower part of the column.

The p-phenylenediamine contained in the washed extract obtained from the top of the extraction device was fed 1i (7) 99.8
%, and the extraction rate of ammonium chloride was 1.2%.

Next, the obtained extract was distilled to remove tetrahydrofuran and water, and further rectified at 40 Torr to obtain purified p-phenylenediamine. This p-phenylenediamine was left in dry air at room temperature for 30 days without causing any discoloration. In addition, the residue after rectification of p-phenylenediamine is small, and the residue is 10
It had fluidity at 06C or higher and was easy to post-process.

On the other hand, the raffinate obtained from the bottom of the extractor is passed through a thinner to distill off tetrahydrofuran, and then 50% by weight of sodium hydroxide is added dropwise to remove I)H from the raffinate.
I set it to 2.5. When this raffinate was boiled again, a large amount of ammonia gas was generated and black copper oxide was precipitated. After the generation of ammonia gas was completed, an air blowing tube was introduced into the raffinate, and bubbling was performed at 90° C. for 30 minutes, followed by cooling. By filtering this liquid, the copper content in the raffinate liquid was recovered as copper oxide with a recovery rate of 99%.

Comparative Example 1 The experiment up to extraction and washing was carried out in the same manner as in Example, except that 20% by weight saline solution was used instead of 4% by weight ammonia water. The p-phenylenediamine contained in the washed extract obtained from the top of the extraction device is 99.9% of the supplied amount.
%, and the extraction rate of ammonium chloride was 2.1%.

The obtained extract was distilled to remove tetrahydrofuran and water, and further rectified at 40 Torr to obtain p-phenylenediamine. There was a considerable amount of residue after rectification of p-phenylenediamine, and it did not have fluidity even at temperatures above 100'C. After analyzing this residue,
It was a heavy substance mainly consisting of common salt, phenylenediamine hydrochloride, and a condensate of p-phenylenediamine. In addition, the rectifier can part and the lower part of the tower are dirty with a lot of deposits.
In particular, deposits on the can part caused problems with heat transfer.

Patent applicant: Japan Synthetic Rubber Co., Ltd. Agent: Patent Attorney, Self-Attorney: Shigetaka

Claims (1)

[Claims] ■When recovering aromatic amines from aqueous solutions or suspensions containing aromatic amines, it is recommended to extract them using an extractant containing tetrahydrofuran as a main component and then wash the resulting extract with aqueous ammonia. Characteristic method for recovering aromatic amines.