JP4000721B2 - Process for producing 2,2,6,6-tetramethyl-4-oxopiperidine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing 2,2,6,6-tetramethyl-4-oxopiperidine (hereinafter abbreviated as TAA). In detail, it is related with the simple manufacturing method of TAA which can obtain a highly purified 2,2,6,6-tetramethyl-4-oxopiperidine with a high yield.
[0002]
[Prior art]
TAA is a compound useful as a raw material for polymer light stabilizers, pharmaceuticals and the like. As a method for producing TAA, in the presence of a catalyst, at least one selected from acetone and acetone condensates and ammonia, 2, 2, A method using a reaction crude liquid obtained by reacting at least one selected from 4,4,6-pentamethyl-2,3,4,5-tetrahydropyrimidine (hereinafter abbreviated as ACN) is known. .
[0003]
As a method for producing TAA from the reaction crude liquid obtained by the above method, (1) a method of adding a strong alkaline aqueous solution such as sodium hydroxide or potassium hydroxide, then removing the aqueous layer and distilling the oil layer, or (2) After adding an aqueous alkali solution, an organic solvent is added to extract and separate the product, and the resulting extract is made into a crude product by distillation, followed by crystallization, and the resulting crude crystal is washed with an organic solvent. A method (Japanese Patent Laid-Open No. 4-154663) and the like are known.
[0004]
However, in the method (1), TAA tends to be thermally decomposed during distillation of the oil layer, and the yield may be lowered. Further, the method (2) has a problem that crystallization and accompanying solid-liquid separation are necessary, and the manufacturing process is complicated and the operation becomes complicated.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a reaction crude liquid obtained by reacting at least one selected from acetone and acetone condensate with ammonia in the presence of a catalyst, or 2,2,4,4,6-pentamethyl-2. 2,2,6,6-tetramethyl-4-oxopiperidine using a crude reaction solution obtained by reacting 1,3,4,5-tetrahydropyrimidine in the presence of water, comprising high-purity TAA An object of the present invention is to provide a simple method that can be produced in a high yield.
[0006]
As a result of intensive studies to solve such problems, the present inventors have added an alkaline aqueous solution to the reaction crude liquid to extract and remove the catalyst from the oil layer, added a specific aqueous solution to the oil layer, washed the oil layer, and distilled. According to a simple method including the steps, it was found that the thermal decomposition of TAA during distillation can be suppressed and TAA can be produced in a high yield, and the present invention has been completed.
[0007]
[Means for Solving the Problems]
That is, the present invention provides a reaction crude liquid obtained by reacting at least one selected from acetone and acetone condensate with ammonia in the presence of a catalyst, or 2,2,4,4,6-pentamethyl-2. 2,2,6,6-tetramethyl-4-oxopiperidine using a reaction crude liquid obtained by reacting 3,4,5-tetrahydropyrimidine in the presence of water,
(1) An alkaline aqueous solution is added to the reaction crude liquid to extract and remove the catalyst from the oil layer,
(2) Next, a weak alkaline aqueous solution is added to the oil layer to wash the oil layer,
(3) Next, the step of distilling the oil layer to obtain 2,2,6,6-tetramethyl-4-oxopiperidine gives 2,2,6,6-tetramethyl-4-oxo This is a method for producing piperidine.
DETAILED DESCRIPTION OF THE INVENTION
[0008]
Hereinafter, the present invention will be described in detail.
The present invention includes (1) adding an alkaline aqueous solution to the reaction crude liquid to extract and remove the catalyst from the oil layer, (2) then adding a weak alkaline aqueous solution to the oil layer to wash the oil layer, (3) The method includes the step of distilling the oil layer to obtain 2,2,6,6-tetramethyl-4-oxopiperidine.
[0009]
The reaction crude liquid used in the present invention is obtained by reacting at least one selected from acetone and acetone condensate with ammonia in the presence of a catalyst. Examples of the catalyst include inorganic acids, carboxylic acids, sulfonic acids, ammonium salts thereof (JP-A 63-222157), ammonium thiocyanate (JP-A 63-10761), and hydrazine hydrochloride (special No. 54-112873), cumyl chloride (JP-A-1-233272), ammonium hydrogen sulfate (JP-A-2-145570), ammonium tetrafluoroborate (JP-A-5-86030), etc. Can be mentioned. Examples of the condensate of acetone include diacetone alcohol, mesityl oxide, phorone, isophorone, and triacetone dialcohol.
[0010]
The reaction crude liquid can also be obtained by reacting 2,2,4,4,6-pentamethyl-2,3,4,5-tetrahydropyrimidine (ACN) in the presence of water. The ACN is obtained by a condensation reaction of acetone and ammonia. The reaction solution obtained by the condensation reaction can be isolated and used, or the reaction solution can be used as it is. The reaction is preferably performed in the presence of the above-described catalyst because the reaction time can be shortened.
[0011]
Examples of the alkaline aqueous solution used in the step (1) include a strong alkaline aqueous solution such as a sodium hydroxide aqueous solution and a potassium hydroxide aqueous solution, or a weak alkaline aqueous solution such as sodium carbonate, sodium hydrogen carbonate, potassium carbonate, and potassium hydrogen carbonate. In order to extract and remove the catalyst from the oil layer, it is preferable to use a strong alkaline aqueous solution because the salting-out effect can be enhanced. The alkali concentration of the aqueous alkali solution is preferably close to the saturation solubility at the extraction temperature. For example, it is preferably about 40 to 50% for an aqueous sodium hydroxide solution. If the solubility is higher than the saturation solubility, crystals may precipitate and the liquid separation property may decrease. On the other hand, if the solubility is too low, the salting-out effect may decrease and the catalyst extraction and removal efficiency may decrease. The addition amount of the alkaline aqueous solution is usually an amount that is equimolar or more to the catalyst contained in the reaction crude liquid, and is preferably an amount that is about 1 to 3 mol times. Even if an amount exceeding 3 mol times is added, not only an effect commensurate with the added amount cannot be obtained, but also problems such as an increase in the size of the equipment and an increase in wastewater treatment load occur.
[0012]
The extraction removal process in the step (1) may be usually performed at a temperature equivalent to the temperature of the condensation reaction. From the standpoint of extraction efficiency and suppression of TAA decomposition, the temperature is preferably about 10 to 90 ° C, more preferably 10 to 70 ° C.
[0013]
In carrying out the step (1) of the present invention, the reaction crude liquid is put into a vessel equipped with a stirring blade, an aqueous alkali solution is added while stirring to extract the catalyst from the oil layer to the water layer, and then left to stand for liquid separation. The aqueous layer may be removed from the lower layer of the container.
[0014]
Examples of the weak alkaline aqueous solution used in the step (2) include weak alkaline aqueous solutions such as sodium carbonate, sodium hydrogen carbonate, potassium carbonate, and potassium hydrogen carbonate. The alkali concentration of the weak alkaline aqueous solution is preferably close to the saturation solubility at the extraction temperature. For example, it is preferably about 45 to 55% for a potassium carbonate aqueous solution. When the solubility is higher than the saturation solubility, crystals may precipitate and the liquid separation property may be lowered. When the strong alkaline aqueous solution is used in the step (1), the removal efficiency of the strong alkaline component in the oil layer may be lowered if the weak alkaline aqueous solution concentration in the step (2) is too low.
[0015]
The addition amount of the weak alkaline aqueous solution is 1 weight or less, preferably 0.2 to 1 weight times the addition amount of the alkaline aqueous solution added in the step (1). Even if an amount exceeding 1 times the weight is added, not only the effect corresponding to the added amount is not obtained, but also problems such as an increase in the size of the facility and an increase in wastewater treatment load occur. When a strong alkaline aqueous solution is used in the step (1), when the amount of the weak alkaline aqueous solution added in the step (2) is less than 0.2 times, a strong alkaline component may remain in the oil layer after extraction. is there.
[0016]
The extraction and removal treatment in the step (2) may be usually performed at a temperature equivalent to the temperature of the condensation reaction. From the standpoint of extraction efficiency and suppression of TAA decomposition, the temperature is preferably about 10 to 90 ° C, more preferably 10 to 70 ° C.
[0017]
In carrying out the step (2) of the present invention, a weak alkaline aqueous solution is added to the oil layer obtained in the step (1) while stirring to wash the oil layer, and then allowed to stand for liquid separation. What is necessary is just to remove an aqueous layer. Moreover, you may repeat operation of a process (2) as needed.
[0018]
The distillation in the step (3) may be performed using a known distillation apparatus, and is usually preferably performed under reduced pressure because the distillation efficiency can be improved and the thermal decomposition of TAA can be suppressed. The distillation apparatus may be either a batch type or a continuous type.
[0019]
When performing step (3) of the present invention, the oil layer obtained in step (2) (hereinafter abbreviated as oil layer after washing) is usually placed in a vessel equipped with a cooling tube and distilled under reduced pressure. Good. The fraction is divided into mixed fractions such as unreacted acetone and water, and mixed fractions such as acetone condensate, ACN and TAA. A mixed fraction such as unreacted acetone and water is recycled as a raw material for the reaction crude liquid. Moreover, you may refine | purify further using well-known methods, such as redistillation and crystallization, as needed.
[0020]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to these Examples. The yield was calculated as follows.
TAA simple distillation yield X (%) during recovery of mixed fractions such as unreacted acetone and water = (TAA content in B + TAA content in C) / (TAA content in A) × 100
TAA simple distillation yield Y (%) during recovery of mixed fraction such as acetone condensate, ACN and TAA = (TAA content in D + TAA content in E) / (TAA content in C) × 100
Simple distillation overall TAA yield (%) = X × Y / 100
[In the formula, A is an oil layer after washing, B is a mixed fraction such as unreacted acetone and water after washing and oil layer distillation, C is a simple distillation pot solution after oil layer distillation after washing, and D is acetone after distillation of C. Condensate, mixed fraction such as ACN and TAA, E represents a simple distillation still liquid after distillation of C. ]
[0021]
Example 1
Preparation of reaction crude:
A 1000 ml autoclave was charged with 650.0 g of acetone, 14.3 g of ammonium chloride catalyst, and 20.0 g of water, and 38.8 g of ammonia gas was added over 2.5 hours at a reaction temperature of 60 ° C., and 1.0 hour at 60 ° C. After aging, the ammonia gas in the autoclave was extracted, and further aged at 60 ° C. for 1.5 hours. After cooling, 708.9 g of a crude reaction liquid was obtained.
[0022]
Example 2
401.0 g of the crude reaction solution prepared in the same manner as in Example 1 was placed in a separable flask equipped with a stirring blade, 35.3 g of 48% aqueous sodium hydroxide solution was added, and the mixture was stirred at 60 ° C. for 10 minutes and allowed to stand for 10 minutes. After liquid separation, 67.9 g of a washing water layer was recovered from the lower layer.
[0023]
Next, 55.1 g of a 49% aqueous potassium carbonate solution was added to the residual oil layer, followed by liquid separation at 60 ° C. for 10 minutes with stirring and 10 minutes after standing, and 60.0 g of a washing water layer was recovered from the lower layer. Next, 55.0 g of a 49% aqueous potassium carbonate solution was added to the residual oil layer, and the mixture was allowed to stand for 10 minutes with stirring at 60 ° C., followed by liquid separation for 10 minutes. 26 g was obtained. After this washing, the oil layer was analyzed by gas chromatography, and production of 107.6 g of TAA was confirmed.
[0024]
After this washing, 299.5 g of oil layer (TAA content 93.6 g) was placed in a 500 ml flask equipped with a condenser, and was distilled at 100 ° C. in an oil bath at a vacuum of 760 Torr for 1.5 hours. 143.2 g (TAA content 0.8 g) of a mixed fraction such as water and 156.2 g (TAA content 92.6 g) of a simple distillation kettle liquid were obtained. Next, 142.8 g (TAA content 84.6 g) of the simple distillation kettle liquid after recovering the mixed fraction such as unreacted acetone and water is heated to 170 ° C. in an oil bath, and gradually vacuumed from 760 to 120 Torr. By increasing the temperature, 121.3 g of a mixed fraction such as acetone condensate, ACN and TAA (TAA content 79.6 g) was obtained in 4.5 hours. At this time, 18.8 g (TAA content 4.7 g) was recovered from the flask as a single distillation pot liquid. TAA simple distillation balance during recovery of mixed fractions such as unreacted acetone and water is 99.9%, and TAA single distillation balance during recovery of mixed fractions such as acetone condensate, ACN and TAA is 99.6%, The simple distillation overall TAA balance was 99.5%.
[0025]
Example 3
400.6 g of the crude reaction solution prepared in the same manner as in Example 1 was placed in a separable flask equipped with a stirring blade, 35.3 g of a 49% potassium carbonate aqueous solution was added, and the mixture was allowed to stand at 60 ° C. for 10 minutes and left for 10 minutes. Then, 56.3 g of a washing water layer was recovered from the lower layer.
[0026]
Next, 55.2 g of a 49% potassium carbonate aqueous solution was added to the residual oil layer, and the mixture was allowed to stand for 10 minutes with stirring at 60 ° C. for 10 minutes, followed by liquid separation. Further, 55.1 g of a 49% potassium carbonate aqueous solution was added to the residual oil layer, and the mixture was allowed to stand for 10 minutes with stirring at 60 ° C. for 10 minutes, followed by liquid separation. 4 g was obtained. After this washing, the oil layer was analyzed by gas chromatography to confirm the production of 104.6 g of TAA.
[0027]
After this washing, 298.0 g (TAA content 88.7 g) of the oil layer was put into a 500 ml flask equipped with a condenser, and the temperature was set to 100 ° C. in an oil bath, and unreacted acetone, water, and the like at a vacuum degree of 760 Torr and 1.5 hours. The mixed fraction 138.7g (TAA content 0.7g) was obtained. Next, the oil bath temperature was raised to 170 ° C., and the degree of vacuum was gradually increased from 760 to 180 Torr, and 130.9 g of a mixed fraction of acetone condensate, ACN, TAA, etc. in 4 hours (TAA content: 74.5 g) ) At this time, 27.1 g (TAA content: 12.9 g) was recovered from the flask as a single distillation pot liquid. The TAA content in these three fractions was 88.0 g. The single distillation overall TAA yield was 99.3%.
[0028]
Comparative Example 1
400.0 g of the crude reaction solution prepared in the same manner as in Example 1 was placed in a separable flask equipped with a stirring blade, 34.4 g of a 48% aqueous sodium hydroxide solution was added, and the mixture was stirred at 62 ° C. for 10 minutes and left for 10 minutes. Liquid separation was performed, and 60.6 g of a washing water layer was recovered from the lower layer.
[0029]
Next, 55.4 g of a 48% sodium hydroxide aqueous solution was added to the residual oil layer, and the mixture was allowed to stand for 10 minutes with stirring at 62 ° C. for 10 minutes, followed by liquid separation. Further, 55.2 g of 48% sodium hydroxide aqueous solution was added to the residual oil layer, and the mixture was allowed to stand for 10 minutes with stirring at 62 ° C. for 10 minutes, followed by liquid separation, and 61.1 g of the washing water layer was recovered from the lower layer. .9 g was obtained. After washing, the oil layer was analyzed by gas chromatography to confirm the formation of 97.9 g of TAA.
[0030]
After this washing, 296.6 g of oil layer (TAA content 90.8 g) was put into a 500 ml flask equipped with a condenser, and the temperature was raised to 100 ° C. in an oil bath, and the degree of vacuum was gradually increased from 760 to 300 Torr. As a result, 126.1 g of a mixed fraction such as unreacted acetone and water (TAA content 0.4 g) was obtained. Next, the oil bath temperature was raised to 170 ° C., and the degree of vacuum was gradually increased from 760 to 80 Torr. A mixture fraction of acetone condensate, ACN, TAA and the like 135.8 g (TAA content) in 4.5 hours. 75.2 g) was obtained. At this time, 30.4 g (TAA content: 3.0 g) was recovered from the flask as a single distillation pot liquid. The TAA content in these three fractions was 78.6 g. The single distillation overall TAA yield was 86.5%.
[0031]
【The invention's effect】
As described in detail above, the present invention is a reaction crude liquid obtained by reacting ammonia with at least one selected from acetone and a condensate of acetone in the presence of a catalyst, or 2, 2, 4, 4, An alkaline aqueous solution is added to the reaction crude liquid obtained by reacting 6-pentamethyl-2,3,4,5-tetrahydropyrimidine in the presence of water to extract and remove the catalyst from the oil layer, and a specific aqueous solution is added to the oil layer to remove the oil layer. This is a simple production method including the steps of washing and then distilling, which can suppress the thermal decomposition of TAA during the distillation, and is highly pure 2,2,6,6-tetramethyl-4-oxopiperidine ( TAA) can be produced in a high yield, and its industrial utility value is great.

Claims (3)

Reaction crude liquid obtained by reacting ammonia with at least one selected from acetone and acetone condensate in the presence of a catalyst, or 2,2,4,4,6-pentamethyl-2,3,4,5 A process for producing 2,2,6,6-tetramethyl-4-oxopiperidine using a crude reaction solution obtained by reacting tetrahydropyrimidine in the presence of water,
(1) An alkaline aqueous solution is added to the reaction crude liquid to extract and remove the catalyst from the oil layer,
(2) Next, a weak alkaline aqueous solution is added to the oil layer to wash the oil layer,
(3) Next, the step of distilling the oil layer to obtain 2,2,6,6-tetramethyl-4-oxopiperidine gives 2,2,6,6-tetramethyl-4-oxo A method for producing piperidine. 2. The 2, 2, 6 according to claim 1, wherein the weak alkaline aqueous solution used in (2) is at least one selected from the group consisting of sodium carbonate, sodium hydrogen carbonate, potassium carbonate, and potassium hydrogen carbonate. , 6-tetramethyl-4-oxopiperidine. The method for producing 2,2,6,6-tetramethyl-4-oxopiperidine according to claim 1 or 2, wherein the alkaline aqueous solution used in (1) is a strong alkaline aqueous solution.