Method for synthesizing 2-vinylpyridine through one-pot method

Abstract

The invention discloses a method for synthesizing 2-vinylpyridine by a one-pot method, which comprises the following step: by taking 2-methylpyridine and paraformaldehyde as raw materials and water as a solvent, synthesizing the 2-vinylpyridine by a one-pot reaction under the catalysis of a basic catalyst. According to the invention, 2-methylpyridine and paraformaldehyde are taken as initial raw materials, the raw materials are simple and easy to obtain, the production cost is reduced, and water is taken as a solvent, so that the use of a large amount of organic solvents is avoided, and the influence on environmental pollution is small. In the reaction, a basic catalyst such as triethylamine is used as a catalyst, a small amount of sodium hydroxide solid is added in the reaction process, the basic catalyst enables the whole system to be in an alkaline environment, and sodium hydroxide improves the depolymerization efficiency of paraformaldehyde and promotes the dehydration process of the reaction, so that the selectivity and yield of 2-vinylpyridine are improved.

Description

Technical Field

[0001] The invention belongs to the field of chemical industry and pesticides, relates to a preparation method of 2-vinylpyridine, and specifically relates to a method for synthesizing 2-vinylpyridine by a "one-pot method". Background Art

[0002] 2-vinylpyridine is widely used and is an important intermediate for the synthesis of pesticides and medicines. For example, 2-vinylpyridine can be used to synthesize styrene butadiene latex, which is widely used in rubber products such as high-strength tires, pressure-resistant hoses, and conveyor belts. In the pharmaceutical industry, 2-vinylpyridine can be used to manufacture drugs such as closiperine and betidine hydrochloride. 2-vinylpyridine is a colorless or slightly yellow liquid at room temperature. It is sensitive to light and heat and is prone to polymerization, so an inhibitor needs to be added during storage.

[0003] The main preparation method of 2-vinylpyridine is as follows:

[0004] (1) 3-methoxypropionitrile and acetylene are used as raw materials, and 2-methoxyethylpyridine is synthesized under the catalysis of a tetrahydrofuran solution of sodium indene, and then catalytic cracking and separation are performed to obtain 2-vinylpyridine. Although the raw materials of this method are cheap and easy to obtain, the tetrahydrofuran solution of sodium indene is used as a catalyst, the preparation process is complicated, the pungent odor is strong and it is toxic.

[0005] (2) Using acrylonitrile and acetylene as raw materials and a soluble organic cobalt salt as a catalyst, 2-vinyl pyridine is obtained by reaction at a temperature of 150°C. Although the route of this method is simple, the preparation process of the catalyst is cumbersome.

[0006] (3) Using 2-(2-methoxyethyl)pyridine as a raw material, under the catalysis of potassium carbonate / alumina solid superbase catalyst, the methanol is cracked and removed at a temperature of 220 to 260°C and a vacuum degree of -0.045 to 0.095 MPa to obtain 2-vinylpyridine. This method involves a catalytic cracking process and is relatively complex to operate; in addition, it needs to be carried out at a high temperature, which increases the problems of equipment wear and energy consumption.

[0007] (4) 2-methylpyridine and polyformaldehyde are used as raw materials, KOH-modified HZSM-5 molecular sieve (silicon-aluminum ratio 25) is used as catalyst, the temperature is raised to 335°C, and 2-vinylpyridine is synthesized in a fixed bed reactor. The conversion rate of 2-methylpyridine is 80.26%, and the selectivity of 2-vinylpyridine is 97.59%. The catalyst used in this method takes a long time to prepare and binders, extrusion aids, etc. need to be added during the preparation process. The operation process is complicated and the cost is high. In addition, high-temperature reaction is required, and the equipment energy consumption is high. Summary of the invention

[0008] The purpose of the present invention is to provide a method for preparing 2-vinylpyridine in view of the problems existing in the prior art. The method of the present invention is simple to operate, has a green and environmentally friendly production process, and has high product selectivity and yield.

[0009] To achieve the above object, the present invention adopts the following technical solution:

[0010] A method for synthesizing 2-vinylpyridine by a "one-pot method" comprises: using 2-methylpyridine and polyformaldehyde as raw materials, using water as a reaction solvent, and synthesizing 2-vinylpyridine by a one-pot reaction under the catalysis of an alkaline catalyst.

[0011] The mass ratio of 2-methylpyridine to paraformaldehyde is 6:1 to 37.5:1, preferably 9:1 to 15.5:1, and most preferably 9:1 to 9.5:1.

[0012] Specifically, the mass ratio of 2-methylpyridine to paraformaldehyde is 6:1, 9:1, 9.3:1, 9.5:1, 15.5:1, 30:1, and 37.5:1.

[0013] The molar ratio of the 2-methylpyridine to the alkaline catalyst is 1:0.009 to 1:0.5, preferably 1:0.009 to 1:0.05, and most preferably 1:0.009 to 1:0.01.

[0014] The alkaline catalyst is selected from one or more of triethylamine, potassium tert-butoxide, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), potassium carbonate, and potassium hydroxide, preferably triethylamine.

[0015] The reaction temperature is 140-200°C, preferably 140-180°C.

[0016] The reaction time is 18 to 24 hours, preferably 18 to 20 hours.

[0017] As a preferred technical solution of the method for synthesizing 2-vinylpyridine by the "one-pot method" of the present invention, it also includes: adding a small amount of sodium hydroxide during the reaction process to improve the depolymerization efficiency of the polyformaldehyde and promote the dehydration process of the reaction. If sodium hydroxide is not added, the dehydration process of the reaction cannot proceed and the depolymerization rate of the polyformaldehyde is reduced, resulting in a decrease in the yield and selectivity of the product.

[0018] Preferably, 2-methylpyridine, paraformaldehyde, water and an alkaline catalyst are mixed, and the temperature is gradually raised to the reaction temperature. After the paraformaldehyde is dissolved, a small amount of sodium hydroxide is added.

[0019] The molar ratio of sodium hydroxide to 2-methylpyridine is 0.1:1 to 0.2:1, preferably 0.2:1.

[0020] As a preferred technical scheme of the method for synthesizing 2-vinylpyridine by the "one-pot method" described in the present invention, the method also includes: after the reaction is completed, the reaction solution is allowed to stand and separate into layers, the organic phase is collected, and the organic phase is subjected to vacuum distillation at a temperature of 90° C. and a pressure of about 1 kPa, and a fraction of 60 to 75° C. is collected to obtain pure 2-vinylpyridine.

[0021] As a preferred technical solution of the method for synthesizing 2-vinylpyridine by the "one-pot method" described in the present invention, it also includes: adding a polymerization inhibitor to the obtained 2-vinylpyridine for storage.

[0022] The polymerization inhibitor is selected from one or more of methylene blue, hydroquinone, and polymerization inhibitor 701; preferably methylene blue.

[0023] As a specific implementation scheme of the method for synthesizing 2-vinylpyridine by the "one-pot method" of the present invention, the method comprises: using 2-methylpyridine and paraformaldehyde as raw materials and water as a reaction solvent, mixing 2-methylpyridine, paraformaldehyde, water and an alkaline catalyst, gradually heating to a reaction temperature, stirring while heating, and adding a small amount of solid sodium hydroxide after the paraformaldehyde is dissolved, and generating a 2-vinylpyridine solution by a one-pot reaction under the catalytic action of the alkaline catalyst.

[0024] The beneficial effects of the present invention are as follows:

[0025] The invention uses 2-methylpyridine and paraformaldehyde as starting raw materials, the raw materials are simple and easy to obtain, the production cost is reduced, water is used as a solvent, a large amount of organic solvents are avoided, and the impact on environmental pollution is small. In the reaction, a basic catalyst such as triethylamine is used as a catalyst, and a small amount of sodium hydroxide solid is added during the reaction process. The basic catalyst makes the whole system an alkaline environment, and the sodium hydroxide improves the depolymerization efficiency of the paraformaldehyde and promotes the dehydration process of the reaction, thereby improving the selectivity and yield of 2-vinylpyridine.

[0026] Compared with the acidic catalyst currently used, the present invention uses an alkaline catalyst, and the reaction system has a relatively small degree of corrosion on equipment.

[0027] In addition, the preparation method of the present invention is simple, the equipment requirements are simple, the reaction conditions are mild, and it complies with green and environmentally friendly process production. DETAILED DESCRIPTION

[0028] The present invention will now be further described in conjunction with specific embodiments. The following embodiments are intended to illustrate rather than further limit the present invention.

[0029] Example 1

[0030] 93g (1mol) 2-methylpyridine and 10g paraformaldehyde were added to a high-pressure reactor, and then 1g (0.01mol) triethylamine and 6g deionized water were added, and the temperature was gradually raised to 180°C, and mechanical stirring was performed while the temperature was raised until the paraformaldehyde was dissolved, and then 8g (0.2mol) sodium hydroxide solid was added, and the temperature was kept at 180°C for reaction, and the reaction process was monitored by gas chromatography. The reaction was performed for 20 hours, at which time, the selectivity of 2-vinylpyridine was 98.7% and the yield was 85.2%. After the reaction was completed, the reaction solution was cooled to room temperature, allowed to stand and decompose, and the organic phase was collected. The organic phase was subjected to vacuum distillation at a temperature of 90°C and a pressure of about 1kPa for 4 hours, and the 60-75°C fraction was collected to obtain pure 2-vinylpyridine.

[0031] Example 2

[0032] 93g 2-methylpyridine and 10g paraformaldehyde were weighed and added to a high-pressure reactor, and then 1.12g potassium tert-butoxide and 6g deionized water were added, and the temperature was gradually raised to 180°C, and mechanical stirring was performed while the temperature was raised until the paraformaldehyde was dissolved, and then 8g (0.2mol) of sodium hydroxide solid was added, and the reaction was kept at 180°C. The reaction process was monitored by gas chromatography, and the reaction was performed for 20 hours. At this time, the selectivity of 2-vinylpyridine was 48.1% and the yield was 39.3%. After the reaction was completed, the reaction solution was cooled to room temperature, allowed to stand and decompose, and the organic phase was collected. The organic phase was subjected to vacuum distillation for 4 hours at a temperature of 90°C and a pressure of about 1kPa, and the 60-75°C fraction was collected to obtain pure 2-vinylpyridine.

[0033] Example 3

[0034] 93g 2-methylpyridine and 10g paraformaldehyde were weighed and added to a high-pressure reactor, and then 1.52g DBU and 6g deionized water were added, and the temperature was gradually raised to 180°C, and mechanical stirring was performed while the temperature was raised until the paraformaldehyde was dissolved, and then 8g (0.2mol) of sodium hydroxide solid was added, and the temperature was kept at 180°C for reaction, and the reaction process was monitored by gas chromatography. The reaction was performed for 20 hours, at which time, the selectivity of 2-vinylpyridine was 50.2% and the yield was 45.4%. After the reaction was completed, the reaction solution was cooled to room temperature, allowed to stand for stratification, and the organic phase was collected. The organic phase was subjected to pressure distillation at a temperature of 90°C and a pressure of about 1kPa for 4 hours, and the 60-75°C fraction was collected to obtain pure 2-vinylpyridine.

[0035] Example 4

[0036] 93g of 2-methylpyridine and 10g of paraformaldehyde were weighed and added to a high-pressure reactor, and then 1.38g of potassium carbonate and 6g of deionized water were added, and the temperature was gradually raised to 180°C, and mechanical stirring was performed while the temperature was raised until the paraformaldehyde was dissolved, and then 8g (0.2mol) of sodium hydroxide solid was added, and the temperature was kept at 180°C for reaction, and the reaction process was monitored by gas chromatography. The reaction was performed for 20 hours, at which time, the selectivity of 2-vinylpyridine was 47.2% and the yield was 38.2%. After the reaction was completed, the reaction solution was cooled to room temperature, allowed to stand for stratification, and the organic phase was collected. The organic phase was subjected to vacuum distillation for 4 hours at a temperature of 90°C and a pressure of about 1kPa, and the 60-75°C fraction was collected to obtain pure 2-vinylpyridine.

[0037] Example 5

[0038] 93g of 2-methylpyridine and 10g of paraformaldehyde were weighed and added to a high-pressure reactor, and then 0.56g of potassium hydroxide and 6g of deionized water were added, and the temperature was gradually raised to 180°C, and mechanical stirring was performed while the temperature was raised until the paraformaldehyde was dissolved, and then 8g (0.2mol) of sodium hydroxide solid was added, and the temperature was kept at 180°C for reaction, and the reaction process was monitored by gas chromatography. The reaction was performed for 20 hours, at which time, the selectivity of 2-vinylpyridine was 55.3% and the yield was 48.0%. After the reaction was completed, the reaction solution was cooled to room temperature, allowed to stand for stratification, and the organic phase was collected. The organic phase was subjected to vacuum distillation for 4 hours at a temperature of 90°C and a pressure of about 1kPa, and the 60-75°C fraction was collected to obtain pure 2-vinylpyridine.

[0039] Example 6

[0040] 93g (1mol) 2-methylpyridine and 6g paraformaldehyde were weighed and added to a high-pressure reactor, and then 1g (0.01mol) triethylamine and 6g deionized water were added, and the temperature was gradually raised to 180°C, and mechanical stirring was performed while the temperature was raised until the paraformaldehyde was dissolved, and then 8g (0.2mol) sodium hydroxide solid was added, and the temperature was kept at 180°C for reaction, and the reaction process was monitored by gas chromatography. The reaction was performed for 20 hours, at which time, the selectivity of 2-vinylpyridine was 78.8%, and the yield was 75.8%. After the reaction was completed, the reaction liquid was cooled to room temperature, allowed to stand for stratification, and the organic phase was collected. The organic phase was subjected to vacuum distillation at a temperature of 90°C and a pressure of about 1kPa for 4 hours, and the 60-75°C fraction was collected to obtain pure 2-vinylpyridine.

[0041] Example 7

[0042] 93g (1mol) 2-methylpyridine and 3.1g paraformaldehyde were weighed and added to a high-pressure reactor, and then 1g (0.01mol) triethylamine and 6g deionized water were added, and the temperature was gradually raised to 180°C, and mechanical stirring was performed while the temperature was raised until the paraformaldehyde was dissolved, and then 8g (0.2mol) sodium hydroxide solid was added, and the temperature was kept at 180°C for reaction, and the reaction process was monitored by gas chromatography. The reaction was performed for 20 hours, at which time, the selectivity of 2-vinylpyridine was 65.9% and the yield was 46.4%. After the reaction was completed, the reaction solution was cooled to room temperature, allowed to stand and decompose, and the organic phase was collected. The organic phase was subjected to vacuum distillation at a temperature of 90°C and a pressure of about 1kPa for 4 hours, and the 60-75°C fraction was collected to obtain pure 2-vinylpyridine.

[0043] Example 8

[0044] 93g (1mol) 2-methylpyridine and 10g paraformaldehyde were weighed and added to a high-pressure reactor, and then 5g (0.05mol) triethylamine and 6g deionized water were added, and the temperature was gradually raised to 180°C, and mechanical stirring was performed while the temperature was raised until the paraformaldehyde was dissolved, and then 8g (0.2mol) sodium hydroxide solid was added, and the temperature was kept at 180°C for reaction, and the reaction process was monitored by gas chromatography. The reaction was performed for 20 hours, at which time, the selectivity of 2-vinylpyridine was 62.4%, and the yield was 52.4%. After the reaction was completed, the reaction liquid was cooled to room temperature, allowed to stand for stratification, and the organic phase was collected. The organic phase was subjected to vacuum distillation at a temperature of 90°C and a pressure of about 1kPa for 4 hours, and the 60-75°C fraction was collected to obtain pure 2-vinylpyridine.

[0045] Example 9

[0046] 93g (1mol) 2-methylpyridine and 10g paraformaldehyde were weighed and added to a high-pressure reactor, and then 10g (0.1mol) triethylamine and 6g deionized water were added, and the temperature was gradually raised to 180°C, and mechanical stirring was performed while the temperature was raised until the paraformaldehyde was dissolved, and then 8g (0.2mol) sodium hydroxide solid was added, and the temperature was kept at 180°C for reaction, and the reaction process was monitored by gas chromatography. The reaction was performed for 20 hours, at which time, the selectivity of 2-vinylpyridine was 60.8%, and the yield was 51.6%. After the reaction was completed, the reaction liquid was cooled to room temperature, allowed to stand for stratification, and the organic phase was collected. The organic phase was subjected to vacuum distillation at a temperature of 90°C and a pressure of about 1kPa for 4 hours, and the 60-75°C fraction was collected to obtain pure 2-vinylpyridine.

[0047] Comparative Example 1

[0048] 93 g (1 mol) of 2-methylpyridine and 10 g of paraformaldehyde were added to a high-pressure reactor, and then 6 g of deionized water was added. The temperature was gradually raised to 180° C., and mechanical stirring was performed while the temperature was raised until the paraformaldehyde was dissolved. 8 g (0.2 mol) of solid sodium hydroxide was added, and the temperature was kept at 180° C. The reaction progress was monitored by gas chromatography. The reaction was continued for 20 hours. At this time, the selectivity of 2-vinylpyridine was 36.6%, and the yield was 30.2%.

[0049] Although the embodiments of the present invention have been specifically described in the above examples, it should be understood by those skilled in the art that these are only for illustration, and that various changes or improvements to the technical solutions and implementation methods of the present invention, without departing from the essence and scope of the present invention, fall within the scope of the present invention. The protection scope of the present invention can be defined by the claims.

Claims

1. A method for synthesizing 2-vinylpyridine by a "one-pot method", characterized in that: include: 2-vinylpyridine is synthesized by a one-pot reaction using 2-methylpyridine and polyformaldehyde as raw materials and water as solvent under the catalysis of an alkaline catalyst; wherein the alkaline catalyst is selected from one or more of triethylamine, potassium tert-butoxide, 1,8-diazabicyclo[5.4.0]undec-7-ene, potassium carbonate and potassium hydroxide.

2. The method for synthesizing 2-vinylpyridine by a "one-pot method" according to claim 1, characterized in that: The mass ratio of the 2-methylpyridine to the paraformaldehyde is 6:1 to 37.5:

1.

3. The method for synthesizing 2-vinylpyridine by a "one-pot method" according to claim 2, characterized in that: The mass ratio of the 2-methylpyridine to the paraformaldehyde is 9:1 to 15.5:1, preferably 9:1 to 9.5:

1.

4. The method for synthesizing 2-vinylpyridine by a "one-pot method" according to claim 1, characterized in that: The molar ratio of the 2-methylpyridine to the alkaline catalyst is 1:0.009 to 1:0.

5.

5. The method for synthesizing 2-vinylpyridine by a "one-pot method" according to claim 4, characterized in that: The molar ratio of the 2-methylpyridine to the alkaline catalyst is 1:0.009 to 1:0.05, preferably 1:0.009 to 1:0.

01.

6. The method for synthesizing 2-vinylpyridine by a "one-pot method" according to claim 1, characterized in that: The alkaline catalyst is triethylamine.

7. The method for synthesizing 2-vinylpyridine by a "one-pot method" according to claim 1, characterized in that: The reaction temperature is 140-200° C. and the reaction time is 18-24 hours.

8. The method for synthesizing 2-vinylpyridine by a "one-pot method" according to claim 7, characterized in that: The reaction temperature is 140-180° C. and the reaction time is 18-20 hours.

9. The method for synthesizing 2-vinylpyridine by a "one-pot method" according to claim 1, characterized in that: A small amount of sodium hydroxide is added during the reaction; the molar ratio of the sodium hydroxide to 2-methylpyridine is 0.1:1 to 0.2:

1.

10. The method for synthesizing 2-vinylpyridine by a one-pot method according to claim 1, characterized in that: With 2-methylpyridine and paraformaldehyde as raw materials and water as reaction solvent, 2-methylpyridine, paraformaldehyde, water and an alkaline catalyst are mixed, the temperature is raised to the reaction temperature, and stirring is performed while the temperature is raised. After the paraformaldehyde is dissolved, sodium hydroxide is added to generate a 2-vinylpyridine solution through a one-pot reaction.