JPH0635434B2 - Method for producing N- (α-hydroxyethyl) pyrrolidone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in an industrial production method of N- (α-hydroxyethyl) pyrrolidone.

N- (α-hydroxyethyl) pyrrolidone is, for example,
It is a useful raw material to give N-vinylpyrrolidone according to the following reaction formula.

[Prior Art] A secondary cyclic amide is reacted with acetaldehyde to produce N-
Methods for producing (α-hydroxyethyl) cyclic amides are known. For example, Japanese Patent Publication No. 45-14283 discloses the second
The primary cyclic amide and acetaldehyde are reacted by liquid-liquid contact in the presence of an acidic or basic catalyst to obtain an N- (α-hydroxyethyl) cyclic amide, which is then thermally decomposed to produce N-vinylamide. A method is disclosed.

[Problems to be solved by the invention]

However, this method has a problem that the yield of N- (α-hydroxyethyl) pyrrolidone produced is low. That is, for example, in Example 3 of the above patent publication, only the yield of N-vinylpyrrolidone, which is the final product, is described, but N- (vinylhydroxypyrrolidone) is decomposed into N-vinylpyrrolidone by thermal decomposition of Even if it is assumed that the conversion rate is 100 mol%, the problem is that the yield of N- (α-hydroxyethyl) pyrrolidone is only about 50 mol%.

An object of the present invention is to solve the above-mentioned problems of the conventional method and to provide a method capable of producing N- (α-hydroxyethyl) pyrrolidone in a significantly high yield.

[Means for solving problems]

The object is to react 2-pyrrolidone and acetaldehyde in the presence of a weakly basic salt catalyst consisting of a strong base and a weak acid having a pKa value of 4 to 15, and thus N- (α-of the present invention. Achieved by the method for producing hydroxyethyl) pyrrolidone.

Hereinafter, the present invention will be described in detail.

The catalyst used in the present invention has a strong base and a pKa value of 4 to 15
It is a weakly basic salt consisting of a weak acid. Where the pKa value is
It means a value of 0.01 mol / aqueous solution concentration at 25 ° C. Examples of such weakly basic salts include, for example, strong bases of hydroxides such as lithium, sodium or potassium and organic acids, phenols, sulfurous acid, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, Examples thereof include salts with weak acids such as phosphoric acid, carbonic acid, boric acid and metasilicic acid. Of these, particularly preferred weakly basic salts are potassium carbonate, sodium carbonate,
Examples thereof include potassium phosphate, sodium phosphate, potassium pyrophosphate, sodium pyrophosphate and the like.

The ratio of the catalyst to be used is generally selected from the range of 0.0001 to 10 mol% relative to 2-pyrrolidone, but the suitable range depends on the supply mode of the starting acetaldehyde to the reaction system. That is, in the case of supplying acetaldehyde in a gaseous form (this gaseous supply method means removing acetic acid, which is a decomposition product present in acetaldehyde, before use), it is preferable to use 2-pyrrolidone.
It is selected from the range of 0.001 to 1 mol%, more preferably 0.01 to 0.5 mol%. On the other hand, when acetaldehyde is supplied in a liquid state in which acetic acid is present, it is preferable to take the presence of acetic acid into consideration as follows. That is, the amount of acetic acid in acetaldehyde is X mol% relative to 2-pyrrolidone, and the use ratio of the catalyst is preferably X + 0.
It is selected from the range of 001 to 2 mol%, more preferably X + 0.01 to 2 mol%. When the amount of the catalyst is less than this, the reaction continuity is remarkably lowered, and when the amount of the catalyst is more than this, the reaction rate of 2-pyrrolidone is lowered.

The reaction temperature is generally -10 to 60 ° C, preferably 0 to 50 ° C.
Selected from the range of. When carried out at a temperature of 60 ° C. or higher, decomposition of N- (α-hydroxyethyl) pyrrolidone as a product and condensation of acetaldehyde occur,
When carried out at a temperature of -10 ° C or lower, the reaction becomes extremely slow.

The reaction of 2-pyrrolidone and acetaldehyde can be carried out without solvent or in the presence of a solvent, but when carried out at a melting point (25 ° C.) or lower of 2-pyrrolidone, in the presence of a solvent capable of dissolving 2-pyrrolidone. It is preferably carried out. Examples of the solvent include water; alcohols such as methanol and ethanol; aromatic hydrocarbons such as benzene, toluene and xylene; ethers such as ether and tetrahydrofuran; esters such as ethyl acetate. The amount of the solvent used is usually appropriately selected from the range of 0.01 to 5 times by weight with respect to 2-pyrrolidone.

The molar ratio of acetaldehyde to 2-pyrrolidone is
Generally, the range of 0.7 to 2.0, preferably 0.9 to 1.6 is suitable. When the molar ratio is smaller than the above range, the selectivity of N- (α-hydroxyethyl) pyrrolidone based on 2-pyrrolidone and acetaldehyde is high, but the reaction rate of 2-pyrrolidone decreases, and the molar ratio is larger than the above range. If 2
-The reaction rate of pyrrolidone increases, but the selectivity of N- (α-hydroxyethyl) pyrrolidone based on acetaldehyde decreases.

Further, the yield can be further increased by precipitating N- (α-hydroxyethyl) pyrrolidone generated during the reaction and then continuing the reaction. The precipitation of N- (α-hydroxyethyl) pyrrolidone in such a case is usually carried out in the same reaction tank in which the reaction of 2-pyrrolidone and acetaldehyde is carried out, but the precipitation may be carried out in a different reaction tank. .

When the reaction is carried out in the same reaction tank, the reaction rate of 2-pyrrolidone is 50 to 97 mol%, preferably 60 to 97 mol%, and more preferably 70 to 97 mol%, and then -20
Crystals are precipitated by cooling to -25 ° C, preferably 0 to 10 ° C, or adding a small amount of N- (α-hydroxyethyl) pyrrolidone as a crystal nucleus, or by using these in combination. That is, when the reaction rate of 2-pyrrolidone is 60 mol% or less, it is difficult to precipitate crystals, and when it is 97 mol% or more, crystal precipitation is easy, but the reaction rate of 2-pyrrolidone is 97%. A large excess of acetaldehyde must be used to raise it to more than mol%, which is disadvantageous.

When N- (α-hydroxyethyl) pyrrolidone is deposited in different reaction vessels, a small excess of acetaldehyde is added to 2-pyrrolidone, and the reaction rate of 2-pyrrolidone is 50 to 90 mol%, preferably 60 to 90 mol%. When it reaches 90 mol%, it is sent to a reaction tank for precipitating N- (α-hydroxyethyl) pyrrolidone, or acetaldehyde is added to 2-pyrrolidone in an equal amount or less, and N- (α-hydroxyethyl) pyrrolidone Is sent to a reaction tank for precipitation, and acetaldehyde is further added so that the total amount of added acetaldehyde is in a small excess with respect to 2-pyrrolidone,
Precipitate N- (α-hydroxyethyl) pyrrolidone.

When the crystals are precipitated, it is preferable to use a dispersion medium that disperses the crystals of N- (α-hydroxyethyl) pyrrolidone without dissolving them.

The crystallization dispersion medium may be coexistent at the start of the reaction, or may be added immediately before the crystal precipitation. However, when the reaction is carried out at 25 ° C. or less to precipitate crystals, a dispersion medium in which 2-pyrrolidone is dissolved and crystals of N- (α-hydroxyethyl) pyrrolidone are dispersed without being dissolved is used at the start of the reaction. It is preferable to coexist. As the dispersion medium, 2-pyrrolidone and N- (α-hydroxyethyl)
Cyclohexane, hexane, which is difficult to dissolve pyrrolidone,
Aliphatic hydrocarbons such as heptane; aromatic hydrocarbons such as benzene, toluene and xylene that dissolve 2-pyrrolidone but hardly dissolve N- (α-hydroxyethyl) pyrrolidone; ethers such as ether and tetrahydrofuran;
Examples thereof include esters such as ethyl acetate. The amount of the dispersion medium used is usually appropriately selected from the range of 0.2 to 3 times the weight of 2-pyrrolidone.

Further, the yield of N- (α-hydroxyethyl) pyrrolidone can be improved by cooling and supplying acetaldehyde instead of adding crystal nuclei.

〔Example〕

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist. In addition, "%" is "% by weight" unless otherwise specified.

Example 1 Trap in which a small amount of fluid paraffin was put in the exhaust pipe of a 200 m four-necked flask equipped with an agitator having a fluororesin agitator, a gas introduction pipe, a thermometer and an ice-cooled cooling pipe equipped with an exhaust pipe Connected. Also equipped with a needle valve
Approximately 55 acetaldehyde in a 100m pressure-resistant glass container
g was collected, the needle valve was closed, and the gas introduction tube of the flask was connected with a fluororesin tube.

Add 85.1 g of 2-pyrrolidone and potassium carbonate to the flask.
0.05 g (0.036 mol% relative to 2-pyrrolidone) was charged, and the mixture was vigorously stirred while being kept warm in a water bath at 30 ° C. on the other hand,
The pressure-resistant glass container was kept warm at 30 ° C., the needle valve was opened, and acetaldehyde was blown into the reaction solution in a gaseous form through the gas introduction tube of the flask. Meanwhile, the trap containing the fluid paraffin was observed, and the reaction was performed while adjusting the needle valve so that acetaldehyde was supplied to the maximum in a gaseous state without leaking from the trap.

It took 3.5 hours to supply 44.1 g of acetaldehyde.

After completion of the supply, the reaction solution was analyzed by liquid chromatography to find that the reaction rate of 2-pyrrolidone was 89.5 mol% and the selectivity of N- (α-hydroxyethyl) pyrrolidone based on 2-pyrrolidone was 99.8 mol%. It was

Examples 2 to 6 The reaction was carried out in the same manner as in Example 1 except that the type and amount of catalyst and the amount of acetaldehyde used were changed to the compounds and values shown in Table 1. The results are shown in Table 1 below.

Example 7 A small amount of flowing paraffin was put in the exhaust pipe of a 500 m four-necked flask equipped with a stirrer having a stirring blade made of fluororesin, a gas introduction pipe, a thermometer and an ice cooling condenser equipped with an exhaust pipe. Connected the trap. In addition, about 300 m of pressure-resistant glass container equipped with a needle valve is used for acetaldehyde.
g was collected, the needle valve was closed, and the gas introduction tube of the flask was connected with a fluororesin tube.

127.7 g (1.5 mol) of 2-pyrrolidone in the flask
0.075 g (0.036 mol% relative to 2-pyrrolidone) of potassium carbonate was added, the temperature was kept at 28 ° C., and the mixture was vigorously stirred. On the other hand, keeping the pressure-resistant glass container at 30 to 40 ° C.,
The needle valve was opened, and acetaldehyde was blown into the reaction solution in a gaseous form through the gas introduction tube of the flask. Meanwhile, the trap containing the fluid paraffin was observed, and the reaction was performed while adjusting the needle valve so that acetaldehyde was supplied to the maximum in a gaseous state without leaking from the trap.

The internal temperature rose to 30 ° C. due to the heat generation. It took 3.5 hours to supply 78.9 g (1.79 mol) of acetaldehyde.

After completion of the supply, the reaction solution was analyzed by liquid chromatography to find that the reaction rate of 2-pyrrolidone was 95.9 mol%,
The selectivity of N- (α-hydroxyethyl) pyrrolidone based on 2-pyrrolidone was 100 mol%.

The flask was further cooled to 5 ° C. with stirring, and 5 mg of N- (α-hydroxyethyl) pyrrolidone was added as a crystal nucleus. After 10 minutes, the reaction solution became white crystals and solidified. When the product was analyzed by liquid chromatography, the reaction rate of 2-pyrrolidone was 99.0 mol% and the selectivity of N- (α-hydroxyethyl) pyrrolidone based on 2-pyrrolidone was 100 mol%.

Example 8 A trap containing a small amount of liquid paraffin was connected to an exhaust pipe of a 500 m four-necked flask equipped with a stirrer having a stirring blade made of fluororesin, a gas introduction pipe, a thermometer and an exhaust pipe. Approximately 100 g of acetaldehyde was collected in a 300 m pressure-resistant glass container equipped with a needle valve, and connected to the gas introduction tube of the flask with a fluororesin tube.

122.7 g (1.5 mol) of 2-pyrrolidone in the flask
0.15 g (0.072 mol% relative to 2-pyrrolidone) of potassium carbonate was added, the temperature was kept at 28 ° C., and the mixture was vigorously stirred. On the other hand, keeping the pressure-resistant glass container at 30 to 40 ° C.,
The needle valve was opened, and acetaldehyde was blown into the reaction solution in a gaseous form through the gas introduction tube of the flask. Meanwhile, the trap containing the liquid paraffin was observed, and the reaction was performed while adjusting the needle valve so that acetaldehyde was supplied to the maximum in a gaseous state without leaking from the trap.

The internal temperature rose to 30 ° C. due to the heat generation. It took 3.5 hours to supply 67.4 g (1.53 mol) of acetaldehyde.

The flask was further cooled to 5 ° C. with stirring, and 5 mg of N- (α-hydroxyethyl) pyrrolidone was added as a crystal nucleus. After 10 minutes, the reaction solution became white crystals and solidified. When the product was analyzed by liquid chromatography, the reaction rate of 2-pyrrolidone was 96.7 mol% and the selectivity of N- (α-hydroxyethyl) pyrrolidone based on 2-pyrrolidone was 100 mol%.

Example 9 A small amount of fluid paraffin was put in the exhaust pipe of the four-necked flask of 1 equipped with a stirrer having a stirring blade made of fluororesin, a gas introduction pipe, a thermometer and an ice cooling condenser equipped with an exhaust pipe. Connected the trap. Also equipped with a needle valve 30
Approximately 55 g of acetaldehyde in a 0 m pressure-resistant glass container
Was collected, the needle valve was closed, and the gas introduction tube of the flask was connected with a fluororesin tube.

In the flask, 85.1 g (1 mol) of 2-pyrrolidone and potassium carbonate 0.15 g (0.11 mol% based on 2-pyrrolidone)
And 155.8 g (1.8 weight times of 2-pyrrolidone) of cyclohexane were added, and the mixture was vigorously stirred while being kept warm in a water bath at 28 ° C. On the other hand, the pressure-resistant glass container is placed at 30 to 40 ° C.
The temperature was kept at 1, the needle valve was opened, and acetaldehyde was blown into the reaction solution in a gaseous form through the gas introduction tube of the flask. Meanwhile, the trap containing the fluid paraffin was observed, and the reaction was performed while adjusting the needle valve so that acetaldehyde was supplied to the maximum in a gaseous state without leaking from the trap.

To supply 45.2 g (1.03 mol) of acetaldehyde
It took 3.5 hours. The internal temperature rose to 30 ° C. due to the heat generation.

Further, the flask was cooled to 8 ° C. with stirring, and 5 mg of N- (α-hydroxyethyl) pyrrolidone was added as a crystal nucleus. After 10 minutes, the reaction liquid crystallized and became a slurry because of cyclohexane. Since the temperature rose to 26 ° C, the mixture was cooled to 8 ° C and stirred for 1 hour. When the product was analyzed by liquid chromatography, the reaction rate of 2-pyrrolidone was 99.3 mol%, and N- (α-based on 2-pyrrolidone was used.
Hydroxyethyl) pyrrolidone selectivity is 100 mol%
Met.

Examples 10 to 12 The reaction was carried out in the same manner as in Example 9 except that the amounts of 2-pyrrolidone used, the amount of catalyst, the amount of acetaldehyde used, the amount of solvent, and the reaction temperature were changed to the values shown in Table 2. It was The results are shown in Table 2 below.

Example 13 85.1 g in a 200 m four-necked flask equipped with a stirrer having a stirring blade made of fluororesin, a thermometer, and an ice cooling condenser
(1.0 mol) of 2-pyrrolidone and 0.138 g (0.10 mol% relative to 2-pyrrolidone) of potassium carbonate were added, and the mixture was vigorously stirred while being kept warm in a 28 ° C water bath. On the other hand, 45.8 g (1.04 mol; acetic acid contained was 0.02 mol% with respect to 2-pyrrolidone) of acetaldehyde containing 250 ppm of acetic acid was placed in a dropping funnel and added in four portions every 50 minutes. Due to the heat generation, the internal temperature rose to 44 ° C.

After completion of the dropping, the reaction mixture was analyzed by liquid chromatography to find that the reaction rate of 2-pyrrolidone was 91.6 mol% and the selectivity of N- (α-hydroxyethyl) pyrrolidone based on 2-pyrrolidone was 100 mol%. there were.

The reaction mixture was cooled to 6 ° C. with stirring to form 5 crystal nuclei.
When N- (α-hydroxyethyl) pyrrolidone (mg) was added, the reaction solution became white crystals and solidified after 10 minutes. When the product was analyzed by liquid chromatography, the reaction rate of 2-pyrrolidone was 99.2 mol% and the selectivity of N- (α-hydroxyethyl) pyrrolidone based on 2-pyrrolidone was 95.0 mol%.

Example 14 The reaction was performed in the same manner as in Example 13 except that the amounts of potassium carbonate used, the concentration of acetic acid contained in acetaldehyde, and the amount of acetaldehyde used were changed to the values shown below. The results before and after crystallization are shown below.

Amount of potassium carbonate used: 0.606 g (based on 2-pyrrolidone
0.439 mol%) Acetic acid concentration in acetaldehyde; 55.44 ppm Acetaldehyde usage; 45.4 g (1.03 mol) Acetic acid in acetaldehyde; 0.2 per 2-pyrrolidone
419 mol% Before crystallization: 2-pyrrolidone reaction rate 89.0 mol% N- (α-hydroxyethyl) pyrrolidone selectivity of 100 mol% based on 2-pyrrolidone After crystallization: 2-pyrrolidone reaction rate 95.7 mol% 2 Selectivity of N- (α-hydroxyethyl) pyrrolidone based on pyrrolidone: 100 mol% Comparative Example 1 85.1 g in a 200 m four-necked flask equipped with a stirrer having a stirring blade made of fluororesin, a thermometer and a reflux condenser. Of 2
-Pyrrolidone and 44.1 g of acetaldehyde were added and stirred vigorously. 0.3 g of sodium hydroxide (0.75 mol% relative to 2-pyrrolidone) was added, and the mixture was reacted under reflux for 30 minutes while maintaining the temperature at 70 ° C.

After the reaction, the product was analyzed by liquid chromatography to find that the reaction rate of 2-pyrrolidone was 27.5 mol%,
The selectivity of N- (α-hydroxyethyl) pyrrolidone based on pyrrolidone was 42.8 mol%.

Comparative Example 2 A small amount of liquid paraffin was put into an exhaust pipe of a 200 m four-necked flask equipped with a stirrer having a stirring blade made of fluororesin, a gas introduction pipe, a thermometer and an ice-cooled cooling pipe equipped with an exhaust pipe. Connected the trap. In addition, about 100 m of acetaldehyde is placed in a 100 m pressure-resistant glass container equipped with a needle valve.
5 g was collected, the needle valve was closed, and the gas introduction tube of the flask was connected with a fluororesin tube.

In this flask, 85.1 g of 2-pyrrolidone and polyphosphoric acid 1.
3 g was added, and the mixture was vigorously stirred while being kept warm in a water bath at 30 ° C. On the other hand, keeping the pressure-resistant glass container at 30 ° C.,
The needle valve was opened, and acetaldehyde was blown into the reaction solution as a gas through the gas introduction tube of the flask. Meanwhile, the trap containing the fluid paraffin was observed, and the reaction was performed while adjusting the needle valve so that acetaldehyde was supplied to the maximum in a gaseous state without leaking from the trap.

It took 3.5 hours to supply 44.1 g of acetaldehyde.

After the supply of acetaldehyde was completed, the reaction solution was analyzed by liquid chromatography to find that the reaction rate of 2-pyrrolidone was 87.1 mol% and the selectivity of N- (α-hydroxyethyl) pyrrolidone based on 2-pyrrolidone was 43.7 mol%. .

Comparative Example 3 Comparative Example 2 except that 2 g of 35% hydrochloric acid (1.9 mol% based on 2-pyrrolidone) was used instead of 1.3 g of polyphosphoric acid.
When the reaction was carried out in the same manner as in, the reaction rate of 2-pyrrolidone was 80 mol%, and the selectivity of N- (α-hydroxyethyl) pyrrolidone based on 2-pyrrolidone was 17.9 mol%.

〔The invention's effect〕

As is clear from the above results, the method for producing N- (α-hydroxyethyl) pyrrolidone according to the present invention has a reaction rate of the starting material 2-pyrrolidone and selection of N- (α-hydroxyethyl) pyrrolidone as compared with the conventional method. Greatly improve any of the rates. That is, the reaction rate of 2-pyrrolidone 72 to 9
6 mol% and a selectivity of N- (α-hydroxyethyl) pyrrolidone based on 2-pyrrolidone of 81 to 100 mol% can be achieved, and N- (α-hydroxyethyl) pyrrolidone was precipitated during the reaction. After that, by continuing the reaction, the reaction rate of 2-pyrrolidone is 95 to 99.8 mol% and 2 by using only a small excess of acetaldehyde.
-It has an industrially significant effect that the selectivity of N- (α-hydroxyethyl) pyrrolidone based on pyrrolidone of 95 to 100 mol% can be achieved.

Claims (3)

[Claims] 1. 2-pyrrolidone and acetaldehyde,
N- (α-characterized in that the reaction is carried out in the presence of a weakly basic salt catalyst consisting of a strong base and a weak acid having a pKa value of 4 to 15.
Process for producing hydroxyethyl) pyrrolidone. 2. The production method according to claim 1, wherein the reaction temperature is in the range of 0 to 50 ° C. 3. The N- (α-hydroxyethyl) pyrrolidone produced in the course of the reaction is precipitated, and then the reaction is allowed to continue.
The manufacturing method according to the item.