Method for synthesizing 2-vinylpyridine by using solid acid catalyst

Abstract

The application discloses a method for synthesizing 2-vinylpyridine by using a solid acid catalyst, and comprises the following steps: taking 2-methylpyridine and an aqueous formaldehyde solution as raw materials, and generating 2-vinylpyridine by using a solid acid catalyst in a fixed bed reactor. 2‑ The solid acid catalyst is selected from one or more of H-ZSM-5 molecular sieve, HY molecular sieve, WO3 / ZrO2, SO4 2‑ / TiO2 and γ-Al2O3. The application uses a fixed bed reactor, takes 2-methylpyridine and an aqueous formaldehyde solution as starting raw materials, and uses a solid acid catalyst such as γ-Al2O3 to catalytically and efficiently synthesize 2-vinylpyridine, thereby improving the conversion rate of 2-methylpyridine and the selectivity of 2-vinylpyridine. The raw materials are simple and easy to obtain, and the production cost is reduced. The method has simple synthesis steps, reduces equipment loss and reduces wastewater discharge in the reaction process, and meets the requirements of green and environment-friendly process production.

Description

Technical Field

[0001] This invention belongs to the fields of chemical engineering and pesticides, and relates to a method for the synthesis of 2-vinylpyridine by solid acid catalysis. Background Technology

[0002] Pyridine and its derivatives are important intermediates in the synthesis of pesticides and pharmaceuticals. Pesticides containing pyridine rings are not only highly effective, low in toxicity, and have a long duration of action, but also exhibit good biocompatibility with humans and other organisms. 2-Vinylpyridine, as an important pyridine derivative, has wide applications in industry, medicine, and agriculture. In the rubber industry, 2-vinylpyridine can copolymerize with butadiene and styrene to form styrene-butadiene-pyridine latex, a key raw material for high-strength tires, pressure-resistant hoses, and hiking boots. In the pharmaceutical field, 2-vinylpyridine can be used to prepare pharmaceutical intermediates such as chlorpyrifos and betamethrin hydrochloride, as well as film coating materials for tablets. In the pesticide field, 2-vinylpyridine can be used to prepare the highly effective and low-toxicity insecticide imidacloprid, while its derivatives can be used to prepare flupyradifurone, pymetrozine, etc.

[0003] Currently, the main methods for preparing 2-vinylpyridine include the following three:

[0004] (1) Using quinoline as the reaction solvent, pyridylacrylic acid, copper powder and hydroquinone were mixed together and refluxed for 1.5 h under a nitrogen atmosphere. The yield of 2-vinylpyridine was 65.7%. The preparation of pyridylacrylic acid, the raw material used in this method, is complicated and the yield is not high.

[0005] (2) Using acrylonitrile and acetylene as raw materials, organocobalt salt as catalyst, and toluene as reaction solvent, 2-vinylpyridine is obtained by reaction at 150℃. Although this synthesis method is simple, acrylonitrile is highly toxic and pollutes the environment; organocobalt salt is expensive; the reaction requires a large amount of toluene, generating a large amount of wastewater, which is not in line with green chemistry.

[0006] (3) Using 2-methylpyridine and formaldehyde as raw materials, 2-vinylpyridine is obtained by a strong acid (sulfuric acid or phosphoric acid) catalytic reaction at a temperature of 230℃. In this method, the strong acid will corrode the reaction pipeline, and the yield and conversion rate are low. The conversion rate of 2-methylpyridine is 37%, and the yield of 2-vinylpyridine is 33%, which is not conducive to industrial production. Summary of the Invention

[0007] The purpose of this invention is to address the problems existing in the prior art by providing a method for the solid acid catalytic synthesis of 2-vinylpyridine. This method has simple steps, high raw material conversion rate, high product selectivity, and reduces equipment wear and wastewater discharge, thus conforming to green production processes.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for synthesizing 2-vinylpyridine using solid acid catalysis includes: reacting 2-methylpyridine and an aqueous formaldehyde solution in a fixed-bed reactor under the action of a solid acid catalyst to generate 2-vinylpyridine.

[0010] The formaldehyde aqueous solution has a mass fraction of 35% to 40%.

[0011] The molar ratio of 2-methylpyridine to formaldehyde is 1:1 to 1:12, preferably 1:2 to 1:2.5.

[0012] The solid acid catalyst is selected from commercially available H-ZSM-5 molecular sieve, HY molecular sieve, WO3 / ZrO2, and SO4. 2- / ZrO2、SO4 2- One or more of / TiO2 and γ-Al2O3, preferably γ-Al2O3.

[0013] The solid acid catalyst was pre-activated in a muffle furnace at 500°C for 5 hours.

[0014] The mass hourly space velocity (mass hourly space velocity) of the solid acid catalyst (the ratio of the total flow rate (g / h) of the 2-methylpyridine and formaldehyde aqueous solution to the mass of the solid acid catalyst) is 0.1 h⁻¹. -1 ~2h -1 Preferably 0.8h -1 ~1h -1 .

[0015] The reaction temperature is 180–380°C, preferably 220–360°C.

[0016] After the reaction was completed, the reaction solution was subjected to atmospheric distillation at a temperature of about 95℃, and the fraction at about 65-80℃ was collected to obtain pure 2-vinylpyridine.

[0017] When the conversion rate of 2-methylpyridine decreases to about 10-15%, the solid acid catalyst is activated and regenerated. The activation and regeneration process involves first washing the solid acid catalyst with methanol until the washing liquid is clear and transparent, and then purging it with high-temperature air at about 450°C for 4-5 hours.

[0018] Even after 2 to 5 activations and regenerations, the solid acid catalyst can still maintain a high conversion rate of 2-methylpyridine and a high selectivity for 2-vinylpyridine.

[0019] A specific embodiment of the solid acid catalytic synthesis of 2-vinylpyridine according to the present invention includes: filling an activated solid acid catalyst into a fixed-bed reactor; preparing a mixed solution of 2-methylpyridine and formaldehyde aqueous solution; heating the fixed-bed reactor to the reaction temperature, pumping the mixed solution into the fixed-bed reactor from the bottom, and efficiently preparing 2-vinylpyridine by a single continuous reaction under the catalytic action of the solid acid catalyst; activating and regenerating the solid acid catalyst 2 to 5 times, and recycling it for catalyzing the reaction of 2-methylpyridine and formaldehyde to prepare 2-vinylpyridine.

[0020] The single continuous reaction time is 16 to 32 hours, preferably 16 to 26 hours.

[0021] The beneficial effects of this invention are as follows:

[0022] This invention employs a fixed-bed reactor, using 2-methylpyridine and formaldehyde aqueous solution as starting materials, and utilizes solid acid catalysts such as γ-Al2O3 to efficiently synthesize 2-vinylpyridine, thereby improving the conversion rate and selectivity of 2-methylpyridine.

[0023] The raw materials used in this invention are simple and readily available, which reduces production costs.

[0024] The method of this invention has simple synthesis steps, reduces equipment wear and wastewater discharge, and conforms to green and environmentally friendly industrial production processes. Detailed Implementation

[0025] The technical solution of the present invention will now be further described with reference to specific embodiments. The following embodiments are intended to illustrate rather than to further limit the present invention.

[0026] Example 1

[0027] γ-Al2O3 was activated in a muffle furnace at 500°C for 5 hours.

[0028] 18g of activated γ-Al₂O₃ catalyst was packed into the pipes of a fixed-bed reactor. 259g of 2-methylpyridine and 477.2g of formaldehyde aqueous solution (35% by mass) were weighed and mixed to obtain a mixed solution. The fixed-bed reactor was heated to 350℃ and the solution was flowed at a rate of 0.30mL / min (mass space velocity of 1h⁻¹). -1 The mixed solution was pumped from the bottom of the fixed-bed reactor into the fixed-bed reactor for reaction. The reaction liquid was collected from the top outlet of the fixed-bed reactor. The reaction process was monitored by gas chromatography. After 2 hours of reaction, the conversion rate of 2-methylpyridine was 86.2% and the selectivity of 2-vinylpyridine was 95.4%. After a single continuous reaction of 24 hours, the conversion rate of 2-methylpyridine dropped to 12.8% and the selectivity of 2-vinylpyridine dropped to 91.3%.

[0029] Activation and regeneration of the γ-Al₂O₃ catalyst: The reaction was stopped, and the temperature was allowed to drop to room temperature. The reaction solution was drained, and methanol was pumped in to wash the γ-Al₂O₃ catalyst until the washing solution was clear and transparent. Then, the catalyst was purged with air at 450°C for 4-5 hours to complete the activation and regeneration. After each activation and regeneration, the same ratio of 2-methylpyridine to formaldehyde aqueous solution, the same flow rate, the same temperature, and the same single continuous reaction time were used. The γ-Al₂O₃ catalyst was activated and regenerated three times. In the fourth catalytic preparation of 2-vinylpyridine, the reaction time was 2 hours, the conversion rate of 2-methylpyridine was 75.4%, and the selectivity of 2-vinylpyridine was 90.6%.

[0030] After a single continuous reaction is completed, the reaction liquid is collected and distilled at atmospheric pressure at a temperature of about 95℃ for 4 hours. The fraction at about 65-80℃ is collected to obtain pure 2-vinylpyridine.

[0031] Example 2

[0032] H-ZSM-5 molecular sieve (silicon-to-aluminum ratio 25, particle size 2-3 mm) was activated in a muffle furnace at 500℃ for 5 hours.

[0033] 21g of activated H-ZSM-5 molecular sieve was packed into the pipes of a fixed-bed reactor; 259g of 2-methylpyridine and 477.2g of formaldehyde aqueous solution (mass fraction 35%) were weighed and mixed to obtain a mixed solution; the fixed-bed reactor was heated to 350℃ and the solution was flowed at a flow rate of 0.35mL / min (mass space velocity of 1h). -1 The mixed solution was pumped from the bottom of the fixed-bed reactor into the fixed-bed reactor for reaction. The reaction liquid was collected from the top outlet of the fixed-bed reactor. The reaction process was monitored by gas chromatography. After 2 hours of reaction, the conversion rate of 2-methylpyridine was 45.5% and the selectivity of 2-vinylpyridine was 75%. After a single continuous reaction of 24 hours, the conversion rate of 2-methylpyridine dropped to 9.2% and the selectivity of 2-vinylpyridine dropped to 52.2%.

[0034] Activation and regeneration of H-ZSM-5 molecular sieve: The reaction was stopped, and the temperature was allowed to drop to room temperature. The reaction solution was drained, and methanol was pumped in to wash the H-ZSM-5 molecular sieve until the washing solution was clear and transparent. Then, the sieve was purged with air at 450℃ for 4-5 hours to complete the activation and regeneration. After each activation and regeneration, the same ratio of 2-methylpyridine to formaldehyde aqueous solution, the same flow rate, and the same single continuous reaction time were used. After three activation and regeneration cycles, in the fourth catalytic preparation of 2-vinylpyridine, the reaction time was 2 hours, the conversion rate of 2-methylpyridine was 26.4%, and the selectivity of 2-vinylpyridine was 50.6%.

[0035] After a single continuous reaction is completed, the reaction liquid is collected and distilled at atmospheric pressure at a temperature of about 95℃ for 4 hours. The fraction with a boiling point of about 65-80℃ is collected to obtain pure 2-vinylpyridine.

[0036] Example 3

[0037] HY molecular sieve (silicon-to-aluminum ratio 25, particle size 2-3 mm) was activated in a muffle furnace at 500℃ for 5 hours.

[0038] 21g of activated HY molecular sieve was packed into the pipes of a fixed-bed reactor; 259g of 2-methylpyridine and 477.2g of formaldehyde aqueous solution (mass fraction 35%) were weighed and mixed to obtain a mixed solution; the fixed-bed reactor was heated to 350℃ and the solution was flowed at a flow rate of 0.35mL / min (mass space velocity of 1h). -1 The mixed solution was pumped from the bottom of the reactor into a fixed-bed reactor for reaction. The reaction liquid was collected from the top outlet of the fixed-bed reactor. The reaction process was monitored by gas chromatography. After 2 hours of reaction, the conversion rate of 2-methylpyridine was 73.6% and the selectivity of 2-vinylpyridine was 80.2%. After a single continuous reaction of 24 hours, the conversion rate of 2-methylpyridine dropped to 12.1% and the selectivity of 2-vinylpyridine dropped to 75.3%.

[0039] Activation and regeneration of HY molecular sieve: The reaction was stopped, and the temperature was allowed to drop to room temperature. The reaction solution was drained, and methanol was pumped in to wash the HY molecular sieve until the washing solution became clear and transparent. Then, the sieve was purged with air at 450°C for 4-5 hours to complete the activation and regeneration. After each activation and regeneration, the same ratio of 2-methylpyridine to formaldehyde aqueous solution, the same flow rate, and the same single continuous reaction time were used. After three activation and regeneration cycles, the fourth catalytic preparation of 2-vinylpyridine was carried out over 2 hours, achieving a 2-methylpyridine conversion rate of 52.4% and a 2-vinylpyridine selectivity of 65.3%.

[0040] After a single continuous reaction is completed, the reaction liquid is collected and distilled at atmospheric pressure at a temperature of about 95℃ for 4 hours. The fraction at about 65-80℃ is collected to obtain pure 2-vinylpyridine.

[0041] Example 4

[0042] The WO3 / ZrO2 catalyst (WO3 content 15%, particle size 3-4 mm) was activated in a muffle furnace at 500℃ for 5 hours.

[0043] 18g of activated WO3 / ZrO2 catalyst was packed into the pipes of a fixed-bed reactor. 259g of 2-methylpyridine and 477.2g of formaldehyde aqueous solution (35% by mass) were weighed and mixed to obtain a mixed solution. The fixed-bed reactor was heated to 350℃ and the solution was flowed at a rate of 0.30mL / min (mass space velocity of 1h).-1 The mixed solution was pumped from the bottom of the reactor into a fixed-bed reactor for reaction. The reaction liquid was collected from the top outlet of the fixed-bed reactor. The reaction process was monitored by gas chromatography. After 2 hours of reaction, the conversion rate of 2-methylpyridine was 80.7% and the selectivity of 2-vinylpyridine was 86.1%. After a single continuous reaction of 24 hours, the conversion rate of 2-methylpyridine dropped to 9.6% and the selectivity of 2-vinylpyridine dropped to 84.3%.

[0044] Activation and regeneration of the WO3 / ZrO2 catalyst: The reaction was stopped, and the temperature was allowed to drop to room temperature. The reaction solution was drained, and methanol was pumped in to wash the WO3 / ZrO2 catalyst until the washing solution was clear and transparent. Then, the catalyst was purged with air at 450℃ for 4-5 hours to complete the activation and regeneration. After each activation and regeneration, the same ratio of 2-methylpyridine to formaldehyde aqueous solution, the same flow rate, and the same single continuous reaction time were used. The WO3 / ZrO2 catalyst was activated and regenerated three times. In the fourth catalytic reaction to prepare 2-vinylpyridine, the reaction time was 2 hours, the conversion rate of 2-methylpyridine was 66.2%, and the selectivity of 2-vinylpyridine was 74.5%.

[0045] After a single continuous reaction is completed, the reaction liquid is collected and distilled at atmospheric pressure at a temperature of about 95℃ for 4 hours. The fraction at about 65-80℃ is collected to obtain pure 2-vinylpyridine.

[0046] Example 5

[0047] SO4 2- / ZrO2 catalyst (SO4) 2- (Content 10%, particle size 3-4mm) was activated in a muffle furnace at 500℃ for 5 hours.

[0048] 18g of activated SO4 was filled into the pipes of the fixed-bed reactor. 2- For the ZrO2 catalyst, weigh 259 g of 2-methylpyridine and 477.2 g of formaldehyde aqueous solution (mass fraction 35%), mix them to obtain a mixed solution; heat the fixed-bed reactor to 350 °C, and flow at a rate of 0.30 mL / min (mass space velocity 1 h⁻¹). -1 The mixed solution was pumped from the bottom of the reactor into a fixed-bed reactor for reaction. The reaction liquid was collected from the top outlet of the fixed-bed reactor. The reaction process was monitored by gas chromatography. After 2 hours of reaction, the conversion rate of 2-methylpyridine was 82.7% and the selectivity of 2-vinylpyridine was 88.1%. After a single continuous reaction of 24 hours, the conversion rate of 2-methylpyridine dropped to 11.6% and the selectivity of 2-vinylpyridine dropped to 85.2%.

[0049] For SO4 2- / ZrO2 catalyst activation and regeneration: Stop the reaction, wait for the temperature to drop to room temperature, drain the reaction liquid, and pump in methanol to replace SO4. 2- The ZrO2 catalyst was washed until the washing solution became clear and transparent, then activated and regenerated by purging with air at 450°C for 4-5 hours. After each activation and regeneration, the same ratio of 2-methylpyridine to formaldehyde aqueous solution, the same flow rate, and the same single continuous reaction time were used. SO4 2- When the ZrO2 catalyst was activated and regenerated three times, and the fourth catalytic reaction to prepare 2-vinylpyridine took 2 hours, the conversion rate of 2-methylpyridine was 70.1% and the selectivity of 2-vinylpyridine was 75.6%.

[0050] After a single continuous reaction is completed, the reaction liquid is collected and distilled at atmospheric pressure at a temperature of about 95℃ for 4 hours. The fraction at about 65-80℃ is collected to obtain pure 2-vinylpyridine.

[0051] Example 6

[0052] SO4 2- / TiO2 catalyst (SO4) 2- (Content 10%, particle size 3-4mm) was activated in a muffle furnace at 500℃ for 5 hours.

[0053] 18g of activated SO4 was filled into the pipes of the fixed-bed reactor. 2- For the TiO2 catalyst, weigh 259 g of 2-methylpyridine and 477.2 g of formaldehyde aqueous solution (mass fraction 35%), mix them to obtain a mixed solution; heat the fixed-bed reactor to 350 °C, and run the mixture at a flow rate of 0.30 mL / min (mass space velocity 1 h⁻¹). -1 The mixed solution was pumped from the bottom of the reactor into a fixed-bed reactor for reaction. The reaction liquid was collected from the top outlet of the fixed-bed reactor. The reaction process was monitored by gas chromatography. After 2 hours of reaction, the conversion rate of 2-methylpyridine was 83.1% and the selectivity of 2-vinylpyridine was 88.6%. After a single continuous reaction of 24 hours, the conversion rate of 2-methylpyridine dropped to 10.9% and the selectivity of 2-vinylpyridine dropped to 86%.

[0054] For SO4 2- / TiO2 catalyst activation and regeneration: Stop the reaction, wait for the temperature to drop to room temperature, drain the reaction solution, and pump in methanol to remove SO4. 2- The TiO2 catalyst was washed until the washing solution became clear and transparent, and then activated and regenerated by high-temperature air purging at 450℃ for 4-5 hours. After each activation and regeneration, the same ratio of 2-methylpyridine to formaldehyde aqueous solution, the same flow rate, and the same single continuous reaction time were used. SO4 2-The TiO2 catalyst was activated and regenerated three times. During the fourth catalytic reaction to prepare 2-vinylpyridine, the reaction time was 2 hours, the conversion rate of 2-methylpyridine was 65%, and the selectivity of 2-vinylpyridine was 78.1%.

[0055] After a single continuous reaction is completed, the reaction liquid is collected and distilled at atmospheric pressure at a temperature of about 95℃ for 4 hours. The fraction at about 65-80℃ is collected to obtain pure 2-vinylpyridine.

[0056] While the embodiments of the present invention have been specifically described in the above examples, those skilled in the art should understand that these are merely illustrative examples. Various modifications or improvements to the technical solutions and implementation methods of the present invention without departing from the spirit and scope of the invention fall within the scope of the invention. The scope of protection of the present invention can be defined by the claims.

Claims

1. A method for the synthesis of 2-vinylpyridine via solid acid catalysis, characterized in that: include: In a fixed-bed reactor, 2-methylpyridine and an aqueous formaldehyde solution are reacted to produce 2-vinylpyridine under the action of a solid acid catalyst.

2. The method for synthesizing 2-vinylpyridine by solid acid catalysis according to claim 1, characterized in that: The formaldehyde aqueous solution has a mass fraction of 35% to 40%.

3. The method for the solid acid-catalyzed synthesis of 2-vinylpyridine according to claim 1, characterized in that: The molar ratio of 2-methylpyridine to formaldehyde is 1:1 to 1:

12.

4. The method for the solid acid-catalyzed synthesis of 2-vinylpyridine according to claim 1 or 4, characterized in that: The molar ratio of 2-methylpyridine to formaldehyde is 1:2 to 1:2.

5.

5. The method for synthesizing 2-vinylpyridine by solid acid catalysis according to claim 1, characterized in that: The solid acid catalyst is selected from H-ZSM-5 molecular sieve, HY molecular sieve, WO3 / ZrO2, and SO4. 2- / ZrO2、SO4 2- One or more of / TiO2 and γ-Al2O3.

6. The method for the solid acid-catalyzed synthesis of 2-vinylpyridine according to claim 1 or 5, characterized in that: The solid acid catalyst is γ-Al2O3.

7. The method for the solid acid-catalyzed synthesis of 2-vinylpyridine according to claim 1, characterized in that: The solid acid catalyst has a mass hourly space velocity (HHSV) of 0.1 h⁻¹. -1 ~2h -1 Preferably 0.8h -1 ~1h -1 .

8. The method for the solid acid-catalyzed synthesis of 2-vinylpyridine according to claim 1, characterized in that: The reaction temperature is 180–380°C, preferably 220–360°C.

9. The method for the solid acid-catalyzed synthesis of 2-vinylpyridine according to claim 1, characterized in that: After the reaction was completed, the reaction solution was subjected to atmospheric distillation at 95°C, and the fraction at 65-80°C was collected to obtain pure 2-vinylpyridine.

10. The method for synthesizing 2-vinylpyridine by solid acid catalysis according to claim 1, characterized in that: When the conversion rate of 2-methylpyridine decreases to 10-15%, the solid acid catalyst is activated and regenerated. The activation and regeneration process involves first washing the solid acid catalyst with methanol until the washing liquid is clear and transparent, and then purging it with high-temperature air at 450°C for 4-5 hours.