JPH0438742B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to a method for purifying N,N-diethylaminophenols. N,N-diethylaminophenols are industrially extremely important compounds as intermediates for heat-sensitive and pressure-sensitive paper dyes, xanthene dyes, fluorescent dyes, and the like.

<Prior art> Conventionally, as a method for synthesizing N,N-diethylaminophenols, nitrobenzene is used as a starting material to obtain sodium methanate, which is ethylated with ethyl chloride or diethyl sulfate, and then the desired product is obtained as alkaline fusion. A method for obtaining the desired product by reacting dihydric phenols with diethylamine in the presence of an acid catalyst. A method for obtaining the desired product by ethylating aminophenols with ethyl chloride or diethyl sulfate in the presence of an alkali salt. How to obtain it is known.

This method is the so-called alkaline fusion method, which generates a large amount of wastewater and sludge.
The process is also long, making it an extremely unattractive method from an industrial perspective.

The method involves using an excess amount of diethylamine in the presence of an acid catalyst at high temperature and pressure, but the yield of N,N-diethylaminophenols is low and there are many by-products. In addition, it is necessary to recover excess diethylamine, and there is also the problem of material corrosion, making this method extremely difficult from an industrial perspective.

Although the method uses an alkali salt as a deoxidizing agent, it is accompanied by corrosion of the material, and it is difficult to separate the chloride produced after the reaction and the N,N-diethylaminophenols produced. The refining process generates a large amount of wastewater, making the process quite complicated.

In addition, in both methods, when recovering N,N-diethylaminophenols, neutralization treatment with acid or alkali is always necessary, and because the compounds contain amino groups, it is difficult to determine the end point of neutralization. Furthermore, when purifying N,N-diethylaminophenols, it has not been possible to use a distillation method due to their thermal instability. Therefore, there was naturally a limit to the quality of N,N-diethylaminophenols.

That is, N,N-diethylaminophenols obtained by conventional methods generally have a brown appearance because they contain a small amount of tar (heavy content), which often impairs their commercial value.

In addition, after the reductive alkylation reaction of aminophenols and acetaldehyde, the N,N-diethylaminophenols recovered by distillation are
However, in recent years, the demand for N,N-diethylaminophenols as dyes for heat-sensitive and pressure-sensitive paper has increased, and the quality is not necessarily satisfactory. Depending on the application, there has been an increasing demand for N,N-diethylaminophenols with higher purity and less coloring.

<Problems to be Solved by the Invention> The present invention solves the drawbacks of these conventional techniques, such as the generation of a large amount of waste water, sludge, and corrosion of materials, and also provides high-quality N, N −
The purpose is to obtain diethylaminophenols in high yield.

<Means for solving the problems> The present inventors have developed a high-quality N,N solution to replace the conventional method.
- As a result of intensive studies on a new method for producing diethylaminophenols, we found that the aminophenols and acetaldehyde are subjected to a reductive alkylation reaction, and after the reaction is completed, the catalyst is separated, and the resulting reaction liquid is distilled and recovered from the crude N, N-diethylaminophenols are brought into contact with water under an inert gas atmosphere, and then cooled to precipitate and recover N,N-diethylaminophenols, which is extremely advantageous industrially and has a high yield. Moreover, it has been found that high-quality N,N-diethylmethaminophenols can be obtained.

That is, the present invention involves subjecting aminophenols and acetaldehyde to a reductive alkylation reaction in the presence of an organic solvent, a catalyst, and hydrogen, and after the completion of the reaction, separating the catalyst. In purifying N,N-diethylaminophenols, water and crude N,N-diethylaminophenols are brought into contact with each other under an inert gas atmosphere, and then N,N-diethylaminophenols are precipitated by cooling. The present invention relates to a method for purifying N,N-diethylaminophenols, which is characterized by recovering N,N-diethylaminophenols. This will be explained in detail below.

Specifically, the aminophenols of the present invention include ortho-aminophenol, meta-aminophenol, para-aminophenol, etc., and meta-aminophenol is particularly preferred. N,N-diethylaminophenols specifically refer to N,N-
These include diethyl orthoaminophenol, N,N-diethylmeta-aminophenol, N,N-diethylpara-aminophenol, and N,N-diethylmeta-aminophenol is particularly preferred.

In the method of the present invention, the reductive alkylation reaction can be easily carried out by a conventional method, that is, by charging aminophenols, an organic solvent, and a catalyst, and continuously supplying acetaldehyde under hydrogen pressure. can. Usually, the organic solvent used is an aliphatic alcohol such as methanol, ethanol, or propanol, and the catalyst used is one having reductive alkylation ability, such as platinum, palladium, or nickel. The amount of acetaldehyde used is
Usually 2.1 to 1 mole of aminophenols
4 times the molar amount, and the amount of organic solvent used is 1 to 20 parts by weight per 1 part by weight of aminophenols, and the amount of catalyst is 0.005 to 0.1 part by weight per 1 part by weight of aminophenols. used.

The reaction temperature is room temperature to 150°C, and the hydrogen pressure is not particularly limited, but usually 20 kg/cm ² G or less is sufficient.

Further, after the reductive alkylation reaction, a method for distilling and recovering crude N,N-diethylaminophenols from the reaction solution obtained by separating the catalyst is as follows:
Usually, first, while maintaining the temperature of canning at 160℃ or less,
Unreacted acetaldehyde and organic solvent are substantially removed by distillation, and then the bottoms after substantially removing unreacted acetaldehyde and organic solvent are heated to N,N- Diethylaminophenols can be easily obtained by distillation.

The rough N, N obtained by the method described above
- A feature of the present invention for purifying diethylaminophenols is that water and crude N,N are purified under an inert gas atmosphere.
- After bringing the N,N-diethylaminophenols into contact with each other, the N,N-diethylaminophenols are precipitated and recovered by cooling.

The amount of water used is usually 1 to 10 parts by weight per 1 part by weight of the crude N,N-diethylaminophenol. The inert gas is usually preferably nitrogen, argon or helium.

The contact of crude N,N-diethylaminophenols with water in the present invention is usually carried out by adding the molten crude N,N-diethylaminophenols recovered by distillation to water that has been previously placed under an inert gas atmosphere while stirring. You can make it work by doing this. The temperature at which the water is maintained at this time may be higher than or lower than the temperature at which the N,N-diethylaminophenols melt, but preferably, after adding the crude N,N-diethylaminophenols, once the N,N-diethylaminophenols are - It is more preferable from the viewpoint of impurity removal to bring the mixture into contact at a temperature higher than the melting temperature of the diethylaminophenols. The temperature at which N,N-diethylaminophenols melt is defined as the amount of impurities contained in the crude N,N-diethylaminophenols, the crude N,N-
Although it varies depending on the ratio of diethylaminophenols and water used, the temperature is usually 50°C or higher.

The contact between the crude N,N-diethylaminophenols and water can be carried out either batchwise or continuously. The crude N,N-diethylaminophenols are brought into contact with water under stirring and then cooled in a conventional manner to crystallize and precipitate the N,N-diethylaminophenols. At this time, it is more preferable to add seed crystals for smoother crystallization. Precipitated N,N
- Diethylaminophenols are recovered by conventional over-operation methods such as reduced pressure, increased pressure, and centrifugation. Further, the recovered cake of N,N-diethylaminophenols is dried to produce a product, for example.

As described above, according to the method of the present invention, N,N-diethylaminophenols are obtained as a high-quality pale yellowish white to pale pink solid without any of the problems seen in the conventional method, and in good yield. I am now able to do it.

Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

<Example> Example 1 (Obtaining crude N,N-diethyl meta-aminophenol) Meta-aminophenol 163.7g (1.5 mol) and methanol were placed in a SUS 5 autoclave equipped with a stirrer.
1814gr, 4.1gr of 5% platinum-carbon as a catalyst was charged, and the reductive alkylation reaction was carried out at 40°C under a constant hydrogen pressure of 10Kg/cm ² G and while continuously supplying 165.2gr (3.75 mol) of acetaldehyde over 5 hours. Summer.
After the continuous introduction of acetaldehyde was completed, the temperature was maintained for an additional 20 minutes and then cooled, and the catalyst was over-separated to obtain a reaction liquid.

Next, while continuously feeding the reaction solution obtained in the reductive alkylation reaction into a pear-shaped flask placed in an oil bath, vacuum distillation was performed to remove unreacted aldehyde and methanol. The reaction solution was continuously fed for 3 hours, and after the feeding was completed, it was concentrated in batches to substantially remove aldehyde and methanol. During this period, the operating pressure was kept constant at 300 mmHg, and the temperature of the bottoms was kept below 120°C.
Distillation was stopped when the bottom liquid temperature reached 120°C.

Subsequently, in order to distill and recover crude N,N-diethylmethaminophenol from the bottoms obtained by removing acetaldehyde and methanol, vacuum was applied in batches at a constant pressure of 3 mmHg.
Distillation was carried out. When the temperature of the bottom liquid reached 170℃, the distillation operation was stopped and the resulting liquid crude N,N
-diethylmethaminophenol was fed to the next purification step.

(Purification of N,N-diethylmethaminophenol) 400g of sewage under nitrogen atmosphere was charged into a separable flask (1) equipped with a stirrer, a buffer, a thermometer, and a condenser, and the temperature was set at 50°C. Charge 100g of liquid crude N,N-diethylmethaminophenol into this, then raise the internal temperature to 65°C, confirm that the N,N-diethylmethaminophenol has melted, and then start cooling while stirring. did. When 0.1g of seed crystals were added at an internal temperature of 60°C, N,N-diethylmethaminophenol began to precipitate from around 57°C. Crystallization was completed by cooling to an internal temperature of 30° C. at a cooling rate of approximately 0.2 to 0.3° C./min, and a cake of N,N-diethylmethaminophenol was recovered by filtration under reduced pressure.

The resulting cake was dried at 40° C./30 mmHg for 2 hours to obtain 98.4 gr of granular product. As a result of gas chromatography analysis (hereinafter referred to as GC analysis),
The purity was 99.8%, and as a result of gel permeation analysis (hereinafter referred to as GPC analysis), it contained no tar and the product had a clean pale yellow-white appearance.

Reference Example 1 Purification of N,N-diethylmethaminophenol in the same manner as in Example 1 using 100g of crude N,N-diethylmethaminophenol obtained in the same manner as in Example 1 and 400g of n-heptane as a solvent. I did this.

The resulting cake was dried at 40° C./30 mmHg for 2 hours to obtain 98.1 gr of a granular product. As a result of GC analysis, the purity is 99.7%, and as a result of GPC analysis,
It contained no tar, and the product had a clean, pale pink appearance.

Reference Example 2 N,N-diethylmethaminophenol was purified using 100g of crude N,N-diethylmethaminophenol obtained in the same manner as in Example 1 and 400g of n-hexane as a solvent. Under N ₂ atmosphere, while stirring at an internal temperature of 60° C., liquid crude N,N-diethyl metaaminophenol was added and cooling started. When 0.1gr of seed crystals were added at an internal temperature of 58°C, N,N-diethylmethaminophenol began to precipitate around 56°C. Approximately 0.2
Crystallization was completed by cooling to an internal temperature of 25°C at a cooling rate of ~0.3°C/min. A cake was obtained by over-operation, and then a granular product was obtained by drying at 40℃/30mmHg for 2 hours.
Got 98.6gr. As a result of GC analysis, the purity was 99.5%.
Also, as a result of GPC analysis, it does not contain tar.
The appearance of the product was a beautiful pale pink color.

<Effects of the invention> N,N-diethylaminophenols are produced by reductive alkylation reaction of aminophenols and acetaldehyde, and the crude N,N-diethylaminophenols distilled and recovered from the reaction solution are inactivated. The N,N-diethylaminophenol is brought into contact with water in a gas atmosphere and cooled to precipitate the N,N-diethylaminophenol.
This is an industrial method for producing N-diethylaminophenols. According to the method of the present invention, problems such as material corrosion, generation of a large amount of waste water, and product quality are significantly improved compared to conventional methods, and N,N-diethylaminol is extremely industrially advantageous. Phenols can be produced.

Claims (1)

[Scope of Claims] 1. Aminophenols and acetaldehyde are subjected to a reductive alkylation reaction in the presence of an organic solvent, a catalyst, and hydrogen, and after the reaction is completed, the catalyst is separated and recovered by distillation from the resulting reaction liquid. In purifying crude N,N-diethylaminophenols,
N,N-diethylamino, characterized in that the crude N,N-diethylaminophenols are brought into contact with water in an inert gas atmosphere, and then the N,N-diethylaminophenols are precipitated and recovered by cooling. Method for purifying phenols. 2 Aminophenols are meta-aminophenol, N,N-diethylaminophenols are N,
A method for purifying N,N-diethylaminophenol according to claim 1, which is N-diethylmethaminophenol.