JPH0678305B2 - Method for producing N-methyl-2-pyrrolidone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field] N-methyl-2-pyrrolidone is non-toxic, chemically stable, and
It is used as a solvent having excellent heat resistance and is also useful as an intermediate for various organic syntheses, and the demand thereof has been greatly expanded in recent years.

In addition, N-methyl-2-pyrrolidone, especially recently polyphenylene sulfide, polyimide, polyether ketone,
Since it is widely used as a solvent for polymerization and film forming of highly functional resins such as aramid, and particularly high purity is required for these applications, the development of an advantageous manufacturing method of high quality is desired. .

The present invention relates to an improvement in the method for producing N-methyl-2-pyrrolidone.

[Prior Art] It is conventionally known that N-methyl-2-pyrrolidone can be produced by the following various methods.

i) A method by reacting γ-butyrolactone with monomethylamine.

ii) A method in which a methylation reagent such as methyl halide or methyl alcohol is allowed to act on 2-pyrrolidone to cause a methylation reaction in the presence of a catalyst to convert an NH bond into an N-CH ₃ bond.

iii) A method of catalytic hydrogenation of N-methylimide of maleic acid or succinic acid.

iv) A method by hydrogenolysis of N-hydroxymethyl-2-pyrrolidone.

Of these, the method i) is most commonly used industrially. That is, this method is
In terms of reaction yield and also from the viewpoint of product quality, it has extremely advantageous conditions for practical use in that it does not use raw materials such as corrosive catalysts. [Kirk Othmer Encyclopedia of Chemical Technology
Chemical Technology), Willie Interscience Publications, Joan Willie &
Published by Wiley Intersience Publication, John Wiley
& Sons (1984) Volume 19 Page 517 and Ullmann
Ulwann Encyclopedia of Industrial Chemistr
y, VCH VerlagsgesellschaftmbH, (1985) A4 Volume 495-
Page 498).

However, during the reaction between γ-butyrolactone and monomethylamine, the decomposition and disproportionation reaction of methylamine occurs, a small amount of dimethylamine, trimethylamine, and ammonia are produced, and they are reacted in excess mole (monomethylamine / γ-butyrolactone> 1). Therefore, they are dissolved in excess monomethylamine and discharged out of the reaction system.

Therefore, this method has a drawback that the unit consumption of monomethylamine is high and that dimethylamine, trimethylamine, and ammonia, which are by-produced from excess monomethylamine, are consumed and circulated in the reaction after purification.

[Problems to be Solved by the Invention] The present inventors have studied in detail the reaction of γ-butyrolactone with secondary amines and tertiary amines. -Reacting with butyrolactone
Generates N, N-dimethyl-γ-hydroxybutyric acid amide, ammonium salt of γ-hydroxybutyric acid, etc.
Above all, it is close to the condition for producing N-methyl-2-pyrrolidone by the reaction of γ-2-pyrrolidone and monomethylamine.
It has been found that when heated above ℃, these compounds can be de-methanolized and eventually converted into N-methyl-2-pyrrolidone.

It is an object of the present invention to provide a method for producing N-methyl-2-pyrrolidone using monomethylamine including dimethylamine and trimethylamine without lowering yield and quality.

That is, the present invention is intended to provide an advantageous treatment method of secondary and tertiary amines, which are by-products in the production of N-methyl-2-pyrrolidone by the reaction of γ-butyrolactone and monomethylamine. Yes, simplifying the purification process of recycled monomethylamine by finally converting to N-methyl-2-pyrrolidone while maintaining particularly high quality,
It seeks to improve its economic efficiency.

[Means for Solving Problems] Reaction of γ-butyrolactone and monomethylamine at 230 ° C.
When the reaction is carried out at the above temperature in the presence of excess monomethylamine, the monomethylamine is decomposed and disproportionated under the reaction conditions, and a small amount of dimethylamine and trimethylamine, and further unreacted monomethylamine containing ammonia is by-produced.
These are circulated in the reaction system together with the water produced in the reaction, and γ-is formed with the monomethylamine newly introduced into the reaction system.
It is characterized by reacting with butyrolactone.

At this time, it is necessary to select specific reaction conditions so that the secondary amine and the tertiary amine react with γ-butyrolactone to finally convert into high quality N-methyl-2-pyrrolidone.

As a result of intensive research, the present inventors have found reaction conditions that can achieve this object, and completed the present invention.

That is, the present invention is a method for producing N-methyl-2-pyrrolidone by reacting γ-butyrolactone and monomethylamine in the presence of an excess amount of monomethylamine,
Excess monomethylamine containing dimethylamine and trimethylamine, which are by-produced during the production process, is separated from the reaction mixture, and the separated product is directly recycled to the reaction system, and water is added to the production reaction system in the range of 3 to γ-butyrolactone. N-characterized by adding 5 times mol and reacting dimethylamine and / or trimethylamine with γ-butyrolactone together with monomethylamine at a reaction temperature of 240 to 265 ° C.
It comprises a method for producing methyl-2-pyrrolidone.

In the production method of the present invention, the presence of water is essential, and the reaction temperature is 240 to 265 ° C.

The amount of water used in the present invention needs to be 3 to 5 times the molar amount of γ-butyrolactone.

If the amount of water used is less than 3, the reaction rate becomes slow, and if it exceeds 5, the reverse reaction of the reaction product to γ-butyrolactone increases and the content of γ-butyrolactone in the product N-methyl-2-pyrrolidone increases. .

The present inventors have found that the manufacturing process of the present invention proceeds according to the following reaction formula.

That is, dimethylamine and trimethylamine and γ-
The reaction of the following formula with butyrolactone in the presence of water:
It proceeds at a temperature of 0 ° C or higher. In the formula, R is a methyl group (-C
Representing the H _3).

It is considered that the dealcohol decomposition of the dimethylamine and trimethylamine adducts shown here proceeds stepwise.

Alcohol was detected in the reaction solution of the present invention, and in the case of dimethylamine and trimethylamine, it was observed that N-methyl-γ-oxybutyric acid amide (I) was produced as an intermediate step. To reach N-methyl-2-pyrrolidone, it is presumed that it always goes through (I).

The reaction conditions under which the reaction proceeds are almost the same as the reaction conditions for producing N-methyl-2-pyrrolidone by the reaction of pure monomethylamine and γ-butyrolactone, that is, 220 ° C or higher and 350 ° C or lower. .

However, more suitable reaction conditions exist in order to meet strict quality requirements such as purity and color tone of N-methyl-2-pyrrolidone, and a reaction temperature of 240 ° C to 265 ° C and the presence of appropriate water are required. is there.

In the manufacturing method of the present invention, in order to satisfy both of these, 240
It is necessary to carry out the reaction in the temperature range of ~ 265 ° C.

In this temperature range, a sufficiently high reaction rate and a sufficient product quality can be ensured.

If the reaction temperature exceeds the range of the present invention, the color tone of the important product tends to be deteriorated because the sequential reaction increases and a by-product is produced.

In the production method of the present invention, dimethylamine and trimethylamine, which are by-products, are consumed by reacting with γ-butyrolactone under the condition that N-methyl-2-pyrrolidone is produced by the reaction of monomethylamine and γ-butyrolactone. It is not accumulated in the inside. That is, as the accumulated amount of dimethylamine and trimethylamine by-produced under specific reaction conditions increases, the amount consumed by reaction in the reaction system also increases, so that a steady concentration is maintained under each reaction condition and dimethylamine The accumulated amount in the reaction system does not gradually increase with the continuous operation time.

The present invention, in the coexistence of water, by appropriately selecting the reaction temperature, by-product dimethylamine and trimethylamine N-methyl-2-while suppressing the re-decomposition into γ-butyrolactone and the by-product of coloring impurities to a minimum. Since it can be converted to pyrrolidone, its economic effect is great.

The small amount of by-produced alcohol can be separated and reused in the amine production process by reaction with ammonia.

[Examples] The effects of the present invention are described below with reference to Examples, but the present invention is not limited thereto.

Example 1 γ was added to 10 SUS-316L autoclaves equipped with an induction rotating machine.
-Butyrolactone, monomethylamine and water were added,
N-methyl-2-pyrrolidone was produced by a batch operation.

The production conditions were a molar ratio of monomethylamine / γ-butyrolactone of 1.08, and a molar ratio of H ₂ O / γ-butyrolactone.
The reaction was carried out at a reaction temperature of 255 ° C. and a residence time of 3 hours. The reaction product solution was fractionated and purified by combining three Oldershaw distillation columns.

In the first tower, most of the water and excess monomethylamine were withdrawn to the top of the tower, the bottom liquid was further separated in the second tower to separate water, and then purified and distilled in the third tower to remove N-methyl- 2-Pyrrolidone was extracted and used as a product.

In this case, when the amine aqueous solution extracted from the top of the first tower was analyzed, the content of monomethylamine was 3.51% by weight, but it further contained 3700 ppm of dimethylamine, 162 ppm of trimethylamine, and 733 ppm of ammonia.

The total amount of this distillate, γ-butyrolactone and monomethylamine were supplied to carry out the second reaction by adjusting the molar ratio to the value of the first reaction. As a result, the concentration of monomethylamine in the amine aqueous solution extracted from the top of the first tower was 3.56% by weight, dimethylamine was 3500 ppm, and trimethylamine was 168 pp.
m, Ammonia 663ppm and the change of concentration is small, especially when the concentration of amines other than monomethylamine and ammonia is assumed to be completely inactive, it becomes twice as much as the case of the first reaction. Despite being predicted,
It is clear that it has not actually changed.

During this period, no substantial change was observed in the N-methyl-2-pyrrolidone yield based on γ-butyrolactone and the quality of N-methyl-2-pyrrolidone.

The N-methyl-2-pyrrolidone thus obtained had a purity of 99.9% by weight, a coloring degree of APHA10, and a γ-butyrolactone content of 0.02% by weight.

Example 2 N-Methyl-2-pyrrolidone was produced by reacting in the same manner as in Example 1 except that the monomethylamine / γ-butyrolactone molar ratio was changed to 1.7 and the reaction temperature was changed to 260 ° C.

The reaction time was 5 hours. The concentration of monomethylamine in the aqueous amine solution distilled from the top of the first tower was 6.80% by weight, the concentration of dimethylamine was 2.16% by weight, the concentration of trimethylamine was 1.76% by weight, and the concentration of ammonia was Was 0.63% by weight.

Next, the total amount of this distillate, γ-butyrolactone and monomethylamine were additionally supplied to carry out a second reaction.

At this time, the molar ratio of methylamine / γ-butyrolactone is
The reaction conditions were adjusted to 1.11 and the other reaction conditions were the same as those of the first reaction.

As a result of analysis, the distillate from the top of the first tower was found to have a monomethylamine concentration of 4.70% by weight, a dimethylamine concentration of 2.04% by weight, a trimethylamine concentration of 1.83% by weight, and an ammonia concentration of 0.57% by weight.

Compared to the 1st time, there is little change in concentration between each amine including monomethylamine, and γ-butyrolactone standard
There was an increase in N-methyl-2-pyrrolidone yield and there was no substantial change in the quality of N-methyl-2-pyrrolidone. Dimethylamine, part of trimethylamine is N-methyl-
It was confirmed that it was changed to 2-pyrrolidone.

The results are shown in the table below.

Reference example γ in the presence of water from dimethylamine and trimethylamine
The conditions for reacting with -butyrolactone to form N-methyl-2-pyrrolidone were investigated by model experiments.

i) Dimethylamine was reacted with γ-butyrolactone to obtain N, N-dimethyl-γ-oxybutyric acid amide, which was decomposed by heating to measure the formation of methanol and N-methyl-2-pyrrolidone.

This decomposition reaction did not proceed at a temperature of 210 ° C, and some γ-butyrolactone was detected due to the reverse reaction to the starting material, but N-methyl-2-pyrrolidone was formed above 220 ° C, especially above 240 ° C. Was confirmed.

Furthermore, when the temperature was raised to 255 ° C, the case of dimethylamine was almost the same as the dehydration ring closure (N-methyl-2-pyrrolidone) of N-methyl-γ-oxybutyric acid amide in the case of monomethylamine. Of the ring closure reaction of.

ii) The same experiment was conducted for trimethylamine.

In this case, methanol is detected at a temperature of 220 ° C or higher, but N-methyl-γ-oxybutyric acid amide, N, N-
It was confirmed that dimethyl-γ-oxybutyric acid amide was produced and that N-methyl-2-pyrrolidone was produced at a temperature of 240 ° C or higher.

However, the amount of N-methyl-2-pyrrolidone produced was not as high as that of monomethylamine or dimethylamine at the reaction temperature of 255 ° C.
It was found to be significantly lower than in the reaction of -butyrolactone.

Comparative Example N-Methyl-2-pyrrolidone was produced in the same manner as in Example 1, except that the molar ratio of water to 1 mol of γ-butyrolactone in the second reaction was changed to 8.5. The color tone of N-methyl-2-pyrrolidone was good with APHA10, but γ
-Butyrolactone content from 0.02% to 0.23% by weight
Was increasing.

EFFECT OF THE INVENTION Conventionally, in a process of producing N-methyl-2-pyrrolidone by reacting γ-butyrolactone and an excess amount of monomethylamine, dimethylamine, trimethylamine and ammonia by-produced under reaction conditions are separated and removed. Excess monomethylamine can be recycled to the reaction system without any recycling.

Under the reaction conditions selected according to the present invention, the recycled dimethylamine and trimethylamine are effectively consumed by reacting with γ-butyrolactone, so that these by-products do not accumulate in the reaction process and the concentration is constant. Can be maintained at.

INDUSTRIAL APPLICABILITY The present invention eliminates the need for equipment and energy consumption for purifying monomethylamine, and makes it possible to rationalize the manufacturing process.

Further, there is an advantage that the quality of the N-methyl-2-pyrrolidone product obtained by the present invention is not substantially affected.

Claims (1)

[Claims] 1. A method for producing N-methyl-2-pyrrolidone by reacting γ-butyrolactone with monomethylamine in the presence of an excess amount of monomethylamine, wherein dimethylamine and trimethylamine produced as by-products during the production process are used. The excess monomethylamine contained is separated from the reaction mixture, the separated product is recycled to the reaction system as it is, and water is added to the production reaction system in an amount of 3 to 5 times mol of γ-butyrolactone.
At a reaction temperature of ~ 265 ° C, dimethylamine and / or trimethylamine together with γ-
A method for producing N-methyl-2-pyrrolidone, which comprises reacting with butyrolactone.