JPH069513A - Production of alkylaminophenols - Google Patents

Abstract

PURPOSE:To produce an alkylaminophenol extremely advantageous in terms of industrial points and resources preservation by efficiently separating and recovering an alcohol used as a reaction solvent and continuously performing a stable operation for a long period of time. CONSTITUTION:An aminophenol is reacted with an aldehyde in the presence of hydrogen and a hydrogenating catalyst in an alcohol as a reaction solvent at normal temperature to 150 deg.C under 2-30kg/cm<2>G pressure to form an alkylaminophenol. The obtained reaction solution is distilled at 40-200 deg.C column bottom temperature under 50-400Torr column top pressure to give an aldehyde- containing alcohol solution as a distillate and a solution consisting of the objective compound as a column bottom solution. 0.2-5.0 pts.wt. alkali based on 100 pts.wt. of the solution is added to the distillate of the previous process, the aldehyde is converted to an aldol and neutralized. The prepared neutralized solution is distilled in the presence of a solvent (e.g. alcohols or aldehydes) having a boiling point higher than that of the alcohol as the solvent for the reaction to distill the alcohol as the solvent for the reaction.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing alkylaminophenols. For more details,
The present invention relates to a method for producing alkylaminophenols, which is capable of efficiently separating and recovering the alcohol used as a reaction solvent, and is therefore extremely advantageous from the industrial viewpoint and resource conservation viewpoint.

[0002]

2. Description of the Related Art A technique is known in which an alcohol is used as a solvent in the presence of hydrogen and a hydrogenation catalyst to react an aminophenol with an aldehyde to produce an alkylaminophenol (for example, JP-A-62-258346).
(See the official gazette). In this technique, a large amount of alcohol is used as a reaction solvent, and the alcohol is usually recovered in a state of containing the aldehyde. How to efficiently regenerate this alcohol, that is, separation of the aldehyde from the alcohol How to do it was a big problem. That is, in the case of separating and recovering highly pure alcohol from a mixed solution of aldehyde and alcohol having relatively close boiling points, there is a problem that expensive distillation equipment having high resolution is required. On the other hand, JP-A-2-188
Japanese Patent No. 540 discloses a method in which the relative volatility of an aldehyde and an alcohol is changed by adjusting the pH of an alcohol solution in the range of 7 to 12, and then distilled. However, this method has a problem that the separation of the aldehyde from the alcohol is not sufficient, and in order to remove a small amount of the aldehyde remaining in the alcohol, a distillation facility having high resolution is required, and Under alkaline conditions, part of the aldehyde becomes a heavy substance, and there is a problem that it blocks pipes and the like.

[0003]

In view of the present situation, the problem to be solved by the present invention is to solve the problems of the prior art and to provide alkylaminophenols starting from aminophenols and aldehydes. In the production method, the alcohol used as the reaction solvent can be efficiently separated and recovered, and insolubles due to heavy substances are not accumulated in the distillation apparatus, and thus continuous stable operation is possible for a long period of time. That is, the point is to provide a method for producing an alkylaminophenol, which is extremely advantageous from the industrial point of view and the point of view of resource protection.

[0004]

The present inventors have arrived at the present invention as a result of intensive studies to solve the above problems. That is, the present invention relates to a method for producing an alkylaminophenol starting from an aminophenol and an aldehyde, which is a method for producing an alkylaminophenol including the following steps. Reaction step: a step of reacting aminophenols with aldehydes to produce alkylaminophenols in the presence of hydrogen and a hydrogenation catalyst using alcohol as a reaction solvent First distillation step: The reaction liquid obtained in the reaction step Subjected to distillation to obtain an alcohol solution containing an aldehyde as a distillate,
Step of obtaining a solution containing alkylaminophenols as a main component as a bottom liquid Alkali treatment step: 0.2 to 5.0 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 Neutralization step: Step of neutralizing mixed solution obtained in alkali treatment step Second distillation step: Neutralization solution obtained in neutralization step, Alcohol having a boiling point higher than that of the reaction solvent used in the reaction step, which is a reaction solvent subjected to distillation in the presence of at least one solvent selected from the group consisting of aldehydes, ketones, and esters. Process of distilling alcohol

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

Aminophenols are specifically 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;
Aromatic aldehydes such as benzaldehyde and p-tolualdehyde are exemplified.

The alkylaminophenols obtained are
Depending on the aminophenols and aldehydes used, specifically, N-monoalkylaminophenols such as N-ethylaminophenol, N-propylaminophenol, N-butylaminophenol and N-benzylaminophenol; N , N-diethylaminophenol, N, N-dipropylaminophenol, N, N
Examples include N, N-dialkylaminophenols such as -dibutylaminophenol, N, N-diamylaminophenol, N-ethyl-N-butylaminophenol and N-ethyl-N-amylaminophenol.

The alcohol used as the reaction solvent is
Examples thereof 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 molar ratio of aminophenols / aldehydes. As the reducing catalyst, platinum and / or palladium supported on activated carbon is used. The reaction temperature is usually room temperature to 150 ° C., the reaction pressure is usually ^{2 to} 30 kg / cm ² G, and the reaction time is usually 30 to
It is 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 alcohol solution containing an aldehyde as a distillate and an alkylaminophenol as a main component as a bottom liquid. Is a step of obtaining a solution. The distillation conditions are not particularly limited, and the column bottom temperature is usually 40
˜200 ° C., tower top pressure 50˜400 Torr. The reaction solution obtained in the reaction step is preferably separated and removed by filtration or the like before being subjected to the first distillation step.

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

The treatment temperature in this step is usually 20 to 100.
C., preferably 30 to 80.degree. If the temperature is too low, the reaction of aldehyde to aldol does not proceed sufficiently, while if the temperature is too high, insoluble matter may be generated due to the heavy aldehyde. A treatment time of 0.5 to 10 hours is usually sufficient. By this step, the aldehyde is converted to aldol, but part of the aldol further reacts with the aldehyde to become a heavy product. Then, the heavy material is removed by the later step which is a characteristic of the present invention.

The neutralization step of the present invention is a step of neutralizing the mixed solution 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 formed by neutralization may precipitate, and 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 filtration. The pH after neutralization is preferably that of the salt 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 5-12. If the neutralization step is omitted without the use of the present invention, heavy substances are generated in the subsequent distillation step.

The second distillation step of the present invention means an alcohol, an aldehyde, a ketone or an ester having a boiling point higher than that of the alcohol used as the reaction solvent 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 subjecting to distillation and distilling off alcohol which is a reaction solvent. 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, but is 20 ° C.
The above is preferable. For example, as the high boiling point solvent when the alcohol to be separated and recovered is methanol,
Butanol, amyl alcohol and the like are preferable. In particular,
For a methanol solution containing acetaldehyde,
It is one of the optimal modes to use n-butanol as a high boiling point solvent. The distillation method may be atmospheric pressure or reduced pressure, and may be batch type or continuous type.

As a method of coexisting a high boiling point solvent,
The 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 the aldehyde already contains the high boiling point solvent, it is not necessary to add the high boiling point solvent after that. The high boiling point 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 by weight per 100 parts by weight of the solution to which the high boiling point solvent is added.
Parts by weight. If the addition amount is too small, the effect of suppressing the accumulation of heavy substances in the distillation column is insufficient, while if the addition amount is too large, from the viewpoint of the cost of the high boiling point solvent and the amount of heat required for distillation. It is uneconomical.

The aldol and heavy substances produced in the alkali treatment step are dissolved in a high boiling point solvent and removed as a bottom liquid. Incidentally, when the distillation is carried out in the absence of a high-boiling-point solvent without according to the present invention, heavy substances produced in the alkali treatment step are deposited in various places of the distillation apparatus, clogging of the distillation apparatus occurs, and it occurs for 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 the top of the distillation column or its vicinity in the second distillation step, and this alcohol is of high purity containing substantially no aldehyde. However, it can be used again in the reaction step. The target product, alkylaminophenols, is recovered as a bottom liquid in the first distillation step and separated and purified by distillation.

[0018]

EXAMPLES Next, the present invention will be described with reference to examples. Example 1 In a 5 L autoclave made of SUS equipped with a stirrer, methanol 1855 g, 5% platinum-supported activated carbon catalyst 16.4 g,
Charge 327 g (3.0 mol) of m-aminophenol, keep the hydrogen pressure constant at 10 kg / cm ² , and keep at 40 ° C.
675 g of a methanol solution containing 45% by weight of acetaldehyde (acetaldehyde 6.9 mol) and acetic acid 2.
0 g (0.033 mol) was added continuously over 1 hour. After the addition of acetaldehyde was completed, the temperature was kept at the same temperature for another 150 minutes, then cooled, the reaction solution was taken out from the autoclave, and the catalyst was separated by filtration.
870 g of reaction liquid was obtained. The reaction solution was distilled using a simple distillation apparatus at 250 Torr and a can 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.
Then, 20.0 g of a 30 wt% sodium hydroxide aqueous solution (6.0 g of sodium hydroxide, alcohol solution containing aldehydes / alkali weight ratio = 100 / 0.4) was charged, and the mixture was heated and stirred at 60 ° C. for 4 hours. After cooling, when analyzed by gas chromatography, acetaldehyde was 0.1
0% by weight remained. The obtained alkaline treatment liquid was added to 6
The solution was neutralized to pH = 8.9 with a 5% by weight aqueous acetic acid solution, and n-equivalent to 1.5 parts by weight with respect to 100 parts by weight of the solution after neutralization.
22.8 g of butanol was added as a high boiling point solvent, and batch distillation was performed under atmospheric pressure using an Oldershaw distillation column with 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 rate at this time was 91.0% (however, methanol recovery rate = (weight of methanol in distillate) / (weight of methanol in distillation raw material) × 100). In addition, n-butanol and water were separated in the bottom liquid of the distillation column, but no insoluble matter was observed.

Comparative Example 1 The alcohol solution containing the aldehyde used in Example 1 was not subjected to alkali treatment, 22.9 g of n-butanol was added, and an Oldershaw distillation column with 10 theoretical plates was used. It was batch distilled as it was. When the methanol was distilled so that the recovery rate was 90.0%, 1.1% by weight of acetaldehyde was present in the distillate,
No separation of the aldehyde from the alcohol has taken place.

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

Comparative Example 3 The procedure of Example 1 was repeated except that no neutralization treatment was performed. The acetaldehyde concentration in the distilled alcohol is 0.1
Although it was as low as 1% by weight, precipitation of a heavy substance-like solid which was not dissolved in the bottom liquid was observed in the distillation pot.

Comparative Example 4 The same treatment as in Example 1 was carried out except that the high boiling point solvent n-butanol was not added. The acetaldehyde concentration in the distilled alcohol was as low as 0.12% by weight, but precipitation of solids that were not dissolved in the can solution was observed in the distillation still.

Example 2 Same as Example 1 except that the amount of 30% by weight sodium hydroxide aqueous solution was 250 g (sodium hydroxide 75 g, alcohol solution containing aldehydes / alkali weight ratio = 100 / 5.0). I went to. The concentration of acetaldehyde after the alkali treatment was as low as 0.04% by weight, but precipitation of a solid that was not dissolved in the treatment liquid was observed from about 3 hours after the treatment. Then, the precipitated solid was neutralized without filtering, n-butanol as a high boiling point solvent was added, and batch distillation was performed using an Oldershaw distillation column with 10 theoretical plates. The acetaldehyde concentration was as low as 0.05% by weight, and no insoluble matter was found in the distillation still.

Example 3 Example 3 except that 1038 g of a methanol solution containing 50% by weight of n-butyraldehyde (7.2 mol of n-butyraldehyde) was used instead of the methanol solution containing 45% by weight of acetaldehyde. 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. Among these, n-butanol by-produced in the reaction step was 1.1.
% (N-butanol 35.6 g) was contained.

In a 3 L flask equipped with a stirrer, a reflux condenser and a thermometer, 1500 g and 30 g of the above crude methanol solution were added.
Add 100 g of a weight% sodium hydroxide aqueous solution (sodium hydroxide 30.0 g, alcohol solution containing aldehydes / alkali weight ratio = 100 / 2.0), and add 60 ° C.
The mixture was heated and stirred for 4 hours. After cooling, it was analyzed by gas chromatography to find 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 batch distillation was performed under atmospheric pressure using an Oldershaw distillation column with 10 theoretical plates. 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. At this time, the methanol recovery rate was 95.0%. Further, n-butanol and water were separated in the bottom liquid of the distillation column, but no insoluble matter was observed.

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

From the above results, the following can be understood. In all the examples according to the present invention, the aldehyde was sufficiently separated from the alcohol, and insoluble matter (heavy substances) was not accumulated in the distillation column. On the other hand, in Comparative Example 1 in which the alkali treatment step of the present invention was omitted, the aldehyde was not separated from the alcohol at all. Moreover, in Comparative Example 2 in which the amount of alkali added was too small, the separation of the aldehyde from the alcohol was insufficient. Further, in Comparative Example 3 in which the neutralization step of the present invention was omitted, insoluble matter was precipitated in the pot liquid in the distillation pot. Further, in Comparative Example 4 in which the high boiling point solvent was not added, insoluble matter was precipitated in the kettle liquid in the distillation kettle.

[0029]

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

Claims (1)

[Claims] 1. A method for producing an alkylaminophenol starting from an aminophenol and an aldehyde, which comprises the following steps. Reaction step: a step of reacting aminophenols with aldehydes to produce alkylaminophenols in the presence of hydrogen and a hydrogenation catalyst using alcohol as a reaction solvent First distillation step: The reaction liquid obtained in the reaction step Subjected to distillation to obtain an alcohol solution containing an aldehyde as a distillate,
Step of obtaining a solution containing alkylaminophenols as a main component as a bottom liquid Alkali treatment step: 0.2 to 5.0 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 Neutralization step: Step of neutralizing mixed solution obtained in alkali treatment step Second distillation step: Neutralization solution obtained in neutralization step, Alcohol having a boiling point higher than that of the reaction solvent used in the reaction step, which is a reaction solvent subjected to distillation in the presence of at least one solvent selected from the group consisting of aldehydes, ketones, and esters. Process of distilling alcohol