JPH0237909B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high-quality aminophenols from divalent phenols. More specifically, aminophenols and unreacted divalent phenols are efficiently separated from a reaction mixture obtained by reacting divalent phenols with ammonia in the absence of a catalyst or in the presence of a water-soluble catalyst to produce high-grade aminophenols. and unreacted 2
This invention relates to a method for circulating phenols into a reaction system.

Aminophenols have traditionally been widely used as intermediates for medicines, agricultural chemicals, azo dyes, antioxidants, and photographic agents, and have recently been used as raw materials for polyimide and polyamide heat-resistant resins. It is an extremely useful compound industrially. A method for producing aminophenols by reacting divalent phenols with ammonia without a catalyst or in the presence of a catalyst is known, but at that time, the reaction mixture contains other than the target aminophenols. It contained many unreacted divalent phenols and by-products. Without efficient separation of these components, especially when used in medicines, agricultural chemicals, etc., high-quality medicines, agricultural chemicals, etc. could not be produced due to these impurities. Therefore, conventionally, a special purification process was required. Several methods have been proposed for separating aminophenols, unreacted dihydric phenols, and/or by-products from the reaction mixture to obtain purified aminophenols. For example, (i) JP-A No. 48-28429 discloses that 2
A liquid-liquid extraction method using a water-diisopropyl ether solvent for crude aminophenols obtained by the reaction of phenols and ammonia is described.

(ii) GB 1228568 describes a process in which crude p-aminophenol is contacted with liquid aliphatic, cycloaliphatic or aromatic ketones.

(iii) GB 1028078 describes a process for washing crude p-aminophenol obtained by catalytic hydrogenation of nitrobenzene under acidic conditions with an aliphatic alcohol, preferably isopropanol.

(iv) British Patent No. 1324787 states that crude p.
- A liquid-liquid extraction method of aminophenol with benzene, toluene, xylenes, and acetic esters and a water solvent is described.

(v) British Patent No. 1291642 discloses that crude p.
-aminophenol carbon tetrachloride, 1,1,1
-A liquid-liquid extraction method using trichloroethane, 1,1-dichloroethane and a water solvent is described.

(vi) JP-A-55-69543 describes a method for extraction by bringing an aqueous solution of crude p-aminophenol into contact with an aromatic amine.

Therefore, the present inventors conducted additional experiments on these separation and purification methods, and although each method was found to have a purification effect to some extent, the separation of aminophenols from divalent phenols and/or byproducts was still insufficient. In addition, I learned that methods (i) to (vi) are unsatisfactory in terms of yield. That is, in the method (i) above, since the solubility of aminophenols and divalent phenols in water is high, the separation efficiency of aminophenols and divalent phenols is low, and furthermore, the loss of aminophenols is low. This resulted in poor yield and was economically disadvantageous. Also, (ii) above
Method (vi) is basically applied to p-aminophenol obtained by catalytic hydrogenation of nitrobenzene under acidic conditions, and is applied to p-aminophenol obtained by the reaction of divalent phenols and ammonia. Since the by-products are fundamentally different from aminophenols, it has been difficult to separate the aminophenols from unreacted divalent phenols and/or by-products.

Therefore, as a result of various studies on separation and purification methods that do not have the above-mentioned drawbacks, the present inventors have found that a reaction mixture obtained by reacting divalent phenols and ammonia without a catalyst or in the presence of a water-soluble catalyst is distilled. The distillate obtained by removing heavy components is catalyzed with specific aliphatic ethers while maintaining its molten state to precipitate and separate the aminophenols. After recovering the aminophenols, The inventors have discovered that the above object can be achieved by circulating the bottoms obtained by distilling the group ether into the reaction system, and have arrived at the present invention. In the present invention, aminophenols, unreacted divalent phenols, and/or byproducts can be efficiently separated from the reaction mixture,
Furthermore, the aminophenols obtained by separation are of high quality and have the advantage that the bottoms obtained by distilling off aliphatic ethers can be recycled as they are to the reaction system. That is, the present invention involves reacting divalent phenols with ammonia without a catalyst or in the presence of a water-soluble catalyst, separating aminophenols and unreacted divalent phenols from the reaction mixture after the reaction, and In a method of recycling recovered divalent phenols in a reaction, the distillate obtained by removing heavy components from the reaction mixture after the reaction is distilled is heated to a boiling point of 60°C or higher while maintaining its molten state. and is brought into contact with an aliphatic ether that is substantially incompatible with the aminophenols, the aminophenols are precipitated and separated, the aminophenols are recovered, and then the aliphatic ether is distilled off, This method for producing aminophenols is characterized by circulating this bottoms liquid through a reaction system.

In the method of the present invention, specific examples of divalent phenols used as reaction raw materials include catechol, resorcinol, hydroquinone, 2-
Methylhydroquinone, 4-methyl-resorcin, 5-methyl-resorcin, 5-isopropylresorcin, 3-methyl-catechol, 4-methylcatechol, 4-tert-butylresorcin, 4
Among these divalent phenols, it is preferable to use divalent phenols without substituents, and the method of the present invention is particularly applied to resorcinol or hydroquinone. It is preferable. Further, the ammonia used in the present invention can be used as aqueous ammonia or liquid ammonia. The proportion of ammonia used is preferably in the range of 0.5 to 10 moles per mole of divalent phenols.
If it is less than 0.5 mol, the production of heavy components will increase, and if it exceeds 10 mol, the recovery load of ammonia will be significant, which will be extremely disadvantageous to the production of aminophenols, which is not preferable.

In the present invention, the reaction between divalent phenols and ammonia can be carried out without a catalyst or in the presence of a catalyst. Examples of the catalyst include known water-soluble catalysts, such as various ammonia compounds, ammonium chloride, ammonium sulfate, and ammonium phosphate. Further, although the reaction is carried out under an ammonia atmosphere, it is also possible to carry out the reaction under an inert gas atmosphere such as argon, helium, or nitrogen.

In the present invention, after the completion of the above-mentioned reaction, the reaction product mixture is optionally distilled to remove ammonia, etc. contained therein, and then the heavy substances contained in the reaction mixture are further removed. A distillate containing aminophenols and unreacted dihydric phenols obtained by separating the phenols by distillation or the like is brought into contact with a specific aliphatic ether while maintaining its molten state. Unreacted divalent phenols and/or by-products (e.g. aromatic diamines) are dissolved in aliphatic ethers, and the target aminophenols are substantially incompatible with aliphatic ethers and are separated. becomes possible. The aminophenol layer in a molten state and the unreacted divalent phenol-containing aliphatic ether layer may be separated into liquid-liquid as they are, or if necessary, by cooling this mixed layer while stirring, The precipitated aminophenols can also be efficiently recovered by precipitating the aminophenol layer while solidifying it and performing an over-operation or the like. The aliphatic ethers used here have a boiling point of 60°C or higher and are substantially incompatible with the aminophenols, such as dichloroethyl ether, dichloroisopropyl ether, isopropyl ether, n- Examples include butyl ether, diisoamyl ether, ethylene glycol diethyl ether, and the like. Preferably, especially n-
Butyl ether and diisoamyl ether are selected. The amount of aliphatic ether used in the present invention varies depending on the target impurity or the composition of the reaction solution, but an amount of 0.5 to 10 times the amount of aminophenol by weight is sufficient. After the aminophenols are separated from the reaction mixture by the method described above, the aliphatic ether layer is removed by distillation or the like and recycled to the distillation extraction system. Also, leave the canned liquid as is.
It can be recycled to the reaction system.

In the case of the distillate containing the aminophenols and the aliphatic ethers, the melting temperature of the distillate,
Depending on the boiling point of the aliphatic ether used, it can be carried out under increased pressure, normal pressure, or reduced pressure.

After contacting the distillate containing the aminophenols with the aliphatic ethers, the separated and recovered aminophenols can be dried under reduced pressure to form a product depending on the purpose of use. The product is purified by distillation, etc.

Next, the method of the present invention will be specifically explained with reference to Examples, but the method is not limited thereto.

Example 1 110 g (1.0 mol) of resorcinol was placed in a 500 c.c. stainless steel autoclave (with rotary stirrer).
91.2 g of 28% aqueous ammonia (1.5 mol of ammonia) was charged, and after purging with N ₂ , the temperature was raised to 240° C. and an amination reaction was carried out for 3 hours. After the reaction is complete, remove excess ammonia by purging while cooling.
The reaction mixture was taken out. As a result of gas chromatography (GC) analysis, it was found that 44.0 g of resorcinol and 55.7 g of m-aminophenol were contained.

This reaction mixture was transferred to a 300 c.c. three-necked pear-shaped flask, and water was first distilled off under a reduced pressure of 100 mmHg, followed by distillation to remove heavy components under 5 mmHg. As a result of GC analysis, the amount of distilled resorcin m-aminophenol was 41.8 g and 53.0 g, respectively.

Subsequently, this distillate and 200 g of n-butyl ether as a solvent were charged into a separable flask (No. 1) and brought into contact with each other at 120°C under _N2 flow for 15 minutes while maintaining the molten state of the distillate, and then cooled to 30°C. , m-aminophenol was precipitated.
After separating the precipitated crystals from the liquid by filtration, add another 200 g of n-butyl ether.
The mixture was brought into melt contact at 120°C for 15 minutes, and the same operation as the first time was carried out to obtain crystals of m-aminophenol. The weight of the crystals dried at 60℃ under reduced pressure is 45.3g.
The purity of m-aminophenol is 99.3%.
It was hot.

Using the entire amount of the n-butyl ether layer from which the m-aminophenol obtained above was separated,
The solvent was distilled off under reduced pressure of 200 mmHg to recover unreacted resorcinol. The resulting still liquid contained 41.7 g of resorcinol and m-aminophenol.
It contained 7.9g. 68.3 g of new resorcin was added to the recovered resorcin, 91.2 g of 28% aqueous ammonia was charged, the mixture was replaced with _N2 , and an amination reaction was carried out at 240°C for 3 hours. Thereafter, the same procedure as above was carried out to obtain a reaction mixture. Resorcinol as a result of GC analysis
It contained 44.5g and 63.1g of m-aminophenol, and the first reaction could be reproduced.

Example 2 The same procedure as in Example 1 was carried out except that 200 g of diisoamyl ether was used as the solvent in Example 1 to obtain 46.0 g of m-aminophenol crystals with a purity of 98.8%. Furthermore, the purity is determined by distilling these crystals under reduced pressure of 5 mmHg.
42.3 g of 99.9% m-aminophenol could be obtained.

The diisoamyl ether layer obtained above was subjected to the same operation as in Example 1 to obtain resorcinol.
40.8 g of m-aminophenol and 7.5 g of m-aminophenol were recovered, and 69.2 g of resorcinol and 91.2 g of 28% aqueous ammonia were newly charged thereto, and the reaction was carried out in the same manner as in Example 1. Resorcinol as a result of GC analysis
A reaction mixture containing 44.2 g of m-aminophenol and 62.8 g of m-aminophenol was obtained, and the first reaction could be reproduced.

Comparative Example 1 Resorcinol 41.8 obtained in the same manner as in Example 1
g, a distillate containing 53.0 g of m-aminophenol.
Dissolve in 100g of water at 70℃, and at this temperature 200g of n.
- Extraction was repeated twice with butyl ether to obtain an aqueous layer, which was cooled to 20°C to precipitate m-aminophenol. The precipitated crystals were collected by filtration and dried at 60°C under reduced pressure, resulting in crystals with a purity of 93.2%.
Obtained 38.8g. It was clear that the method of the present invention was significantly superior in both the purity and recovery rate of m-aminophenol.

Example 3 110 g (1.0 mol) of hydroquinone in a 500 c.c. stainless steel autoclave (with rotary stirrer)
91.2 g of 28% aqueous ammonia (1.5 mol of ammonia) was charged, and after purging with N ₂ , the temperature was raised to 240° C. and an amination reaction was carried out for 2 hours. After the reaction was completed, excess ammonia was removed by purging while cooling, and the reaction mixture was taken out. As a result of GC analysis,
Hydroquinone 32.6g and p-aminophenol
It contained 57.8g.

This reaction mixture was transferred to a 300 c.c. three-necked pear-shaped flask, and water was first distilled off under a reduced pressure of 200 mmHg, followed by distillation to remove heavy components under 2 mmHg. As a result of GC analysis, the distilled hydroquinone and p-aminophenol were 30.8g each.
It weighed 53.1g.

Subsequently, this distillate and 300 g of diisoamyl ether as a solvent were charged into a separable flask (1) and brought into contact with each other at 170°C under _N2 flow for 15 minutes while maintaining the molten state of the distillate, and then heated at 30°C.
The mixture was cooled to a temperature of 100.degree. C. to precipitate p-aminophenol. After separating the precipitated crystals from the liquid by filtration,
Further, 300 g of diisoamyl ether was newly charged and brought into melt contact at 170°C for 15 minutes, and the same operation as the first time was carried out to obtain crystals of p-aminophenol. The weight of the crystals dried at 60° C. under reduced pressure was 44.1 g, and the purity of p-aminophenol was 99.4%.

Using the entire amount of the diisoamyl ether layer from which the p-aminophenol obtained above was separated,
The solvent was distilled off under reduced pressure of 200 mmHg to recover unreacted hydroquinone. The resulting still liquid contained 29.8 g of hydroquinone and 8.9 g of p-aminophenol. 80.2g of new hydroquinone was added to this recovered hydroquinone, and 91.2g of 28% ammonia water was added to _N2.
After substitution, amination reaction was carried out at 240°C for 2 hours. Thereafter, the same procedure as above was performed to obtain a reaction mixture.
As a result of GC analysis, 31.8g of hydroquinone and p-
It contained 66.3g of aminophenol and was able to reproduce the first reaction.

Claims (1)

[Claims] 1. Divalent phenols and ammonia are reacted without a catalyst or in the presence of a water-soluble catalyst, and after the reaction is completed, aminophenols and unreacted 2.
In a method of separating and recovering divalent phenols and recycling the recovered divalent phenols in the reaction,
After the completion of the reaction, heavy components are removed from the reaction mixture by distillation to obtain a distillate, and while maintaining the molten state, the distillate has a boiling point of 60°C or higher and the aminophenols. After recovering the aminophenols by precipitation separation by bringing them into contact with aliphatic ethers that are substantially incompatible with the aminophenols, distilling off the aliphatic ethers, and then circulating this bottoms to the reaction system. A method for producing aminophenols, characterized by: 2. The method for producing aminophenols according to claim 1, wherein the aliphatic ether is n-butyl ether or diisoamyl ether. 3. The method for producing aminophenols according to claim 1, wherein the divalent phenols are resorcinol or hydroquinone.