JP2946944B2 - Method for producing alkylaminophenols - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an alkylaminophenol. More specifically,
The present invention relates to a method for producing an alkylaminophenol, which is capable of efficiently separating and recovering an alcohol used as a reaction solvent, and is therefore extremely advantageous from an industrial viewpoint and a viewpoint of resource conservation.

[0002]

2. Description of the Related Art A technique for producing an alkylaminophenol by reacting an aminophenol with an aldehyde in the presence of hydrogen and a hydrogenation catalyst using an alcohol as a solvent is known (for example, Japanese Patent Application Laid-Open No. 62-258346).
Reference). In this technique, a large amount of alcohol is used as a reaction solvent, and the alcohol is usually recovered in a state containing an aldehyde. However, how to efficiently regenerate this alcohol, that is, separation of the aldehyde from the alcohol, is required. How to do it was a big problem. That is, when separating and recovering high-purity alcohol from a mixed solution of aldehyde and alcohol having relatively close boiling points, there is a problem that an expensive distillation facility having high resolution is required. In contrast, Japanese Patent Application Laid-Open No. 2-188
No. 540 discloses a method in which the pH of an alcohol solution is adjusted to a range of 7 to 12 to change the specific volatility of aldehyde and alcohol, followed by distillation. However, this method has a problem that separation of the aldehyde from the alcohol is not sufficient, and a high-resolution distillation facility is required to remove a small amount of the aldehyde remaining in the alcohol. There is a problem that part of the aldehyde becomes heavy under alkaline conditions and blocks piping and the like.

[0003]

SUMMARY OF THE INVENTION In view of the above situation, the problem to be solved by the present invention is to solve the problems of the prior art and to reduce the use of alkylphenols starting from aminophenols and aldehydes. A production method in which the alcohol used as a reaction solvent can be efficiently separated and recovered, and there is no accumulation of insolubles due to heavy substances in the distillation apparatus, and therefore, stable continuous operation over a long period of time is possible. Another object of the present invention is to provide a method for producing alkylaminophenols, which is extremely advantageous from an industrial viewpoint and a viewpoint of resource protection.

[0004]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have reached the present invention. That is, the present invention relates to a method for producing alkylaminophenols using aminophenols and aldehydes as starting materials, and relates to a method for producing alkylaminophenols including the following steps. Reaction step: a step of reacting aminophenols and aldehydes to form alkylaminophenols using alcohol as a reaction solvent in the presence of hydrogen and a hydrogenation catalyst First distillation step: reacting the reaction solution obtained in the reaction step Subjected to distillation to obtain an alcohol solution containing aldehyde as a distillate,
Step of obtaining a solution containing alkylaminophenols as the main component as the bottom liquid Alkali treatment step: 0.2 to 5.0 parts by weight per 100 parts by weight of the aldehyde-containing alcohol solution obtained in the first distillation step. Step of converting aldehyde to aldol by adding and mixing parts by weight of alkali Neutralizing step: step of neutralizing the mixture obtained in the alkali treatment step Second distillation step: neutralizing solution obtained in the neutralizing step Alcohol having a higher boiling point than the alcohol used as a reaction solvent used in the reaction step, aldehydes, ketones, subjected to distillation in the presence of at least one solvent selected from the group consisting of esters, is a reaction solvent Process of distilling alcohol

The details will be described below. The reaction step of the present invention is a step of reacting an aminophenol with an aldehyde in the presence of hydrogen and a hydrogenation catalyst using alcohol as a reaction solvent to produce an alkylaminophenol.

[0006] Aminophenols specifically include o
-Aminophenol, m-aminophenol, p-aminophenol and the like. Aldehydes are acetaldehyde, propionaldehyde, butyraldehyde,
Aliphatic aldehydes such as valeraldehyde; cyclic aldehydes such as cyclohexylaldehyde and furfural;
Examples thereof include aromatic aldehydes such as benzaldehyde and p-tolualdehyde.

[0007] The resulting alkylaminophenols are
N-monoalkylaminophenols such as N-ethylaminophenol, N-propylaminophenol, N-butylaminophenol, N-benzylaminophenol, etc., which are determined by the aminophenols and aldehydes used; , N-diethylaminophenol, N, N-dipropylaminophenol, N, N
And N, N-dialkylaminophenols such as -dibutylaminophenol, N, N-diamylaminophenol, N-ethyl-N-butylaminophenol and N-ethyl-N-amylaminophenol.

[0008] As the alcohol as a reaction solvent,
Examples include methanol, ethanol, propanol, butanol, amyl alcohol, hexyl alcohol, cyclohexyl alcohol and the like.

The ratio of aminophenols and aldehydes to be reacted is usually 0.8 to 3.0 in terms of the molar ratio of aminophenols / aldehydes. As the reduction catalyst, platinum and / or palladium supported on activated carbon is used. The reaction temperature is usually from room temperature to 150 ° C., the reaction pressure is usually from ^{2 to} 30 kg / cm ² G, and the reaction time is usually from 30 to
360 minutes.

In the first distillation step of the present invention, the reaction solution obtained in the reaction step is subjected to distillation to obtain an aldehyde-containing alcohol solution as a distillate and an alkylaminophenol as a main component as a bottom liquid. This is the step of obtaining a solution. The conditions for the distillation are not particularly limited, and usually, the column bottom temperature is 40 ° C.
To 200 ° C., and the pressure at the top of the column is in the range of 50 to 400 Torr. The reaction solution obtained in the reaction step is preferably separated and removed by a filtration or the like before the first distillation step.

The alkali treatment step of the present invention is to add and mix 0.2 to 5.0 parts by weight of alkali per 100 parts by weight of the alcohol solution containing aldehyde obtained in the first step. This is the step of converting aldehyde to aldol. Examples of the alkali include sodium hydroxide and potassium hydroxide. The amount of the alkali used is 0.2 to 5.0 parts by weight, preferably 0.2 to 3.0 parts by weight, per 100 parts by weight of the alcohol solution containing aldehyde. If the amount is too small, the reaction from the aldehyde to the aldol does not proceed sufficiently,
Therefore, the separation of the aldehyde from the alcohol becomes insufficient. On the other hand, if the amount is too large, insolubles are generated due to the heavy aldehyde, and the amount of acid used in the subsequent neutralization step increases, which is uneconomical. Note that the alkali may be added as a solid, but it is preferable to add the alkali as an aqueous solution or an alcohol solution from the viewpoint of operability. The concentration of the alkali at this time is not particularly limited.

The processing temperature in this step is usually 20 to 100
° C, preferably 30 to 80 ° C. If the temperature is too low, the reaction of the aldehyde to the aldol will not proceed sufficiently, while if the temperature is too high, the generation of insolubles due to the heavier aldehyde may increase. Processing time of 0.5 to 10 hours is usually sufficient. In this step, the aldehyde is converted to an aldol, but a part of the aldol further reacts with the aldehyde to become a heavy substance. Then, the heavy matter is removed by a characteristic later step of the present invention.

The neutralization step of the present invention is a step of neutralizing the mixture obtained in the alkali treatment step. Examples of the acid used for neutralization include organic acids such as formic acid, acetic acid, propionic acid and oxalic acid, and inorganic acids such as hydrochloric acid, sulfuric acid and phosphoric acid. When an inorganic acid is used as the acid, an inorganic salt generated by the neutralization may precipitate. In this case, it is necessary to remove the inorganic salt by filtration after the neutralization. From this viewpoint, it is preferable to use an organic acid that does not require a filtration operation. The pH after neutralization is preferably adjusted to the pH of the salt to be produced, that is, it is preferable to completely neutralize the alkali used in the previous step, but if 80% or more of the alkali used is neutralized, There is no particular problem, and the pH is usually in the range of 5 to 12. If the neutralization step is omitted without using the present invention, heavy substances will be generated in the subsequent distillation step.

The second distillation step of the present invention means that the neutralized liquid obtained in the neutralization step is converted into an alcohol, aldehyde, ketone or ester having a boiling point higher than that of the reaction solvent used in the reaction step. In the presence of at least one solvent selected from the group consisting of (hereinafter, referred to as "high boiling point solvent").
This is a step of distilling an alcohol which is a reaction solvent for distillation. The boiling point difference between the high boiling point solvent and the alcohol to be separated and recovered depends on the equipment used for distillation.
It is preferable that it is above. For example, when the alcohol to be separated and recovered is methanol, as a high boiling point solvent,
Butanol and amyl alcohol are preferred. Especially,
For a methanol solution containing acetaldehyde,
One of the most suitable embodiments is to use n-butanol as a high boiling point solvent. The distillation method may be any of normal pressure and reduced pressure, and may be any of a batch type and a continuous type.

As a method for causing a high boiling point solvent to coexist,
A high boiling point solvent may be added before the alkali treatment step, before the neutralization step, or before the second distillation step. When the alcohol solution containing aldehydes already contains a high-boiling solvent, it is not necessary to add a high-boiling solvent thereafter. The high-boiling solvent may be reused repeatedly. The amount of the high boiling point solvent to be coexisted is usually 0.1 to 10.0 parts by weight, preferably 0.5 to 5.0 parts per 100 parts by weight of the solution to which the high boiling point solvent is added.
Parts by weight. When the addition amount is too small, the effect of suppressing the accumulation of heavy substances in the distillation column is insufficient, while when the addition amount is excessive, the cost of the high boiling point solvent and the amount of heat required for distillation are reduced. It is uneconomical.

The aldol and heavy substances generated in the alkali treatment step are dissolved in a high boiling point solvent and removed as a bottom liquid. In addition, without performing the present invention, when distillation is performed in the absence of a high boiling point solvent, heavy substances generated in the alkali treatment step are deposited at various parts of the distillation apparatus, and the distillation apparatus is clogged, resulting in a long period of time. Stable continuous operation is not possible.

The reaction alcohol to be separated and recovered in this way is recovered as a distillate from or near the top of the distillation column in the second distillation step, and this alcohol is of high purity substantially containing no aldehyde. And can be used again in the reaction step. The target product, alkylaminophenols, is recovered as a bottom liquid in the first distillation step, and is separated and purified by distillation.

[0018]

Next, the present invention will be described by way of examples. Example 1 In a 5 L autoclave made of SUS with a stirrer, 1855 g of methanol, 16.4 g of 5% platinum-supported activated carbon catalyst,
327 g (3.0 mol) of m-aminophenol was charged, and the hydrogen pressure was kept constant at 10 kg / cm ² ,
675 g of a methanol solution (6.9 mol of acetaldehyde) containing 45% by weight of acetaldehyde and acetic acid 2.
0 g (0.033 mol) was added continuously over 1 hour. After the addition of acetaldehyde was completed, the mixture was kept at the same temperature for another 150 minutes, then cooled, the reaction solution was extracted from the autoclave, and the catalyst was separated by filtration.
870 g of a reaction solution was obtained. The reaction solution was distilled using a simple distillation apparatus at 250 Torr and a bottom temperature of 45 to 100 ° C., to obtain 2371 g of a crude methanol solution containing 1.0% by weight of acetaldehyde as a distillate.

Next, 1500 g of the above crude methanol solution was placed in a 3 L flask equipped with a stirrer, a reflux condenser and a thermometer.
And 20.0 g of a 30% by weight aqueous sodium hydroxide solution (6.0 g of sodium hydroxide, weight ratio of alcohol solution containing aldehydes / alkali = 100 / 0.4), and heated and stirred at 60 ° C. for 4 hours. After cooling, the solution was analyzed by gas chromatography.
0% by weight remained. The obtained alkali treatment liquid was treated with 6
Neutralize to pH = 8.9 with 5% by weight acetic acid aqueous solution, and further add 1.5 parts by weight of n-
22.8 g of butanol was added as a high boiling point solvent, and batch distillation was performed under normal pressure using an Oldershaw distillation column having 10 theoretical plates. As a distillate from the top of the distillation column, 1302 g of methanol containing 0.12% by weight of acetaldehyde and containing no n-butanol was obtained. The methanol recovery at this time was 91.0% (provided that methanol recovery = (weight of methanol in distillate) / (weight of methanol in distillation raw material) × 100). Further, in the bottom of the distillation column, n-butanol and water were separated, but no insoluble content was observed.

Comparative Example 1 To an alcohol solution containing an aldehyde used in Example 1, 22.9 g of n-butanol was added without performing alkali treatment, and using an Oldershaw distillation column having 10 theoretical plates, The batch distillation was performed as it was. Distillation was performed so that the recovery of methanol was 90.0%, and 1.1% by weight of acetaldehyde was present in the distillate.
No separation of the aldehyde from the alcohol was performed.

COMPARATIVE EXAMPLE 2 Except that the amount of a 30% by weight aqueous sodium hydroxide solution was changed to 5.0 g (sodium hydroxide 1.5 g, alcohol solution containing aldehydes / alkali weight ratio = 100 / 0.1). The procedure was performed in the same manner as in Example 1. The concentration of acetaldehyde after the alkali treatment was 0.40% by weight. Thereafter, neutralization and n-butanol addition were performed, and batch distillation was performed using an Oldershaw distillation column having 10 theoretical plates. As a result, the concentration of acetaldehyde in the distilled alcohol was as high as 0.42% by weight.

Comparative Example 3 The same operation as in Example 1 was carried out except that the neutralization treatment was not performed. The acetaldehyde concentration in the distilled alcohol was 0.1
Although it was as low as 1% by weight, precipitation of a heavy substance-like solid which was not dissolved in the can solution was observed in the still.

Comparative Example 4 A treatment was carried out in the same manner as in Example 1 except that n-butanol which was a high boiling point solvent was not added. The concentration of acetaldehyde in the distilled alcohol was as low as 0.12% by weight, but precipitation of a solid which did not dissolve in the bottom liquid in the still was observed.

Example 2 Same as Example 1 except that the amount of the 30% by weight aqueous sodium hydroxide solution was changed to 250 g (75 g of sodium hydroxide, weight ratio of alcohol solution containing aldehydes / alkali = 100 / 5.0). It went to. Although the concentration of acetaldehyde after the alkali treatment was as low as 0.04% by weight, solids which did not dissolve in the treatment liquid were observed around 3 hours after the treatment. Thereafter, the precipitated solid was neutralized without filtration, n-butanol as a high boiling point solvent was added, and batch distillation was performed using an Oldershaw distillation column having 10 theoretical plates. The acetaldehyde concentration in the mixture was as low as 0.05% by weight, and no precipitation of insoluble components was found in the still.

Example 3 Example 3 was repeated except that methanol solution containing 50% by weight of n-butyraldehyde was replaced by 1038 g (7.2 mol of n-butyraldehyde) of methanol containing 50% by weight of n-butyraldehyde. The reaction step and the first distillation step were carried out in the same manner as in 1 to obtain 3235 g of a crude methanol solution containing 0.5% by weight of n-butyraldehyde. In this, n-butanol by-produced in the reaction step is 1.1.
% (N-butanol 35.6 g).

In a 3 L flask equipped with a stirrer, reflux condenser and thermometer, 1500 g of the above crude methanol solution and 30 g
A 100% by weight aqueous sodium hydroxide solution (30.0 g of sodium hydroxide, an alcohol solution containing aldehydes / alkali weight ratio = 100 / 2.0) was added, and the mixture was heated to 60 ° C.
For 4 hours. After cooling, analysis by gas chromatography revealed that 0.08% by weight of n-butyraldehyde remained. The obtained alkali-treated solution was neutralized to pH = 8.9 with a 65% by weight aqueous acetic acid solution, and subjected to batch distillation under normal pressure using an Oldershaw distillation column having 10 theoretical stages. As a distillate from the top of the distillation column, 1354 g of methanol containing 0.11% by weight of n-butyraldehyde and containing no n-butanol was obtained. The methanol recovery at this time was 95.0%. Further, in the bottom liquid of the distillation column, n-butanol and water were separated, but no insoluble content was observed.

Example 4 In the same manner as in Example 3, the reaction step and the first distillation step were each performed in five batches, and 16500 g of a crude methanol solution was obtained. This contained 0.4% by weight of n-butyraldehyde and 2.0% by weight of n-butanol. Next, a stirrer,
In a 5 L flask equipped with a reflux condenser and a thermometer, the above crude methanol solution was added at a rate of 470 ml / Hr and a 30% by weight aqueous sodium hydroxide solution 28 g / Hr (sodium hydroxide 8.4 g / Hr, containing aldehydes). (Alcohol solution / alkali weight ratio = 100 / 2.3), and the mixture was continuously supplied for 30 hours and stirred at 60 ° C. At this time, the liquid volume in the flask was set to 4.5 L, and the residence time was set to 9 hours. After the treatment liquid was cooled, it was analyzed by gas chromatography. As a result, 0.11% by weight of n-butyraldehyde remained. The obtained alkali-treated solution was neutralized to a pH of 8.9 with a 65% by weight aqueous acetic acid solution, and continuous distillation was carried out at normal pressure and a reflux ratio of 0.5 under normal pressure using an Oldershaw distillation column having 30 theoretical plates. Time went on. Analysis of the distillate from the top of the distillation column revealed that n-butyraldehyde contained 0.11 to 0.14% by weight on average,
Also, n-butanol was not detected throughout the entire period. The average recovery of methanol at this time was 91.5%. Further, n-butanol and water were separated in the distillation still throughout the period, but no insolubles were observed.

The following can be understood from the above results. In all of the examples according to the invention, the separation of the aldehyde from the alcohol is sufficient and there is no accumulation of insolubles (heavy matter) in the distillation column. On the other hand, in Comparative Example 1 in which the alkali treatment step of the present invention was omitted, no aldehyde was separated from alcohol at all. In Comparative Example 2 where the amount of alkali added was too small, the separation of aldehyde from alcohol was insufficient. In Comparative Example 3 in which the neutralization step of the present invention was omitted, insolubles were precipitated in the liquid in the still. In Comparative Example 4 in which the high boiling point solvent was not added, an insoluble component was precipitated in the kettle liquid in the distillation kettle.

[0029]

As described above, according to the present invention, there is provided a method for producing alkylaminophenols using aminophenols and aldehydes as starting materials, in which alcohol used as a reaction solvent can be efficiently separated and recovered. That there is no accumulation of insolubles due to heavy substances in the distillation column, and thus continuous stable operation is possible over a long period, which is extremely advantageous from the industrial viewpoint and the viewpoint of resource protection.
A method for producing an alkylaminophenol can be provided.

Claims (1)

(57) [Claims] 1. A method for producing an alkylaminophenol starting from an aminophenol and an aldehyde, comprising the following steps: Reaction step: a step of reacting aminophenols and aldehydes to form alkylaminophenols using alcohol as a reaction solvent in the presence of hydrogen and a hydrogenation catalyst First distillation step: reacting the reaction solution obtained in the reaction step Subjected to distillation to obtain an alcohol solution containing aldehyde as a distillate,
Step of obtaining a solution containing alkylaminophenols as the main component as the bottom liquid Alkali treatment step: 0.2 to 5.0 parts by weight per 100 parts by weight of the aldehyde-containing alcohol solution obtained in the first distillation step. Step of converting aldehyde to aldol by adding and mixing parts by weight of alkali Neutralizing step: step of neutralizing the mixture obtained in the alkali treatment step Second distillation step: neutralizing solution obtained in the neutralizing step Alcohol having a higher boiling point than the alcohol used as a reaction solvent used in the reaction step, aldehydes, ketones, subjected to distillation in the presence of at least one solvent selected from the group consisting of esters, is a reaction solvent Process of distilling alcohol