阅读说明：本技术 一种3-甲基吡啶的合成方法 (Synthetic method of 3-methylpyridine ) 是由 张少鹏 陈启明 潘炎烽 周中平 于 2020-12-31 设计创作，主要内容包括：本发明涉及一种3-甲基吡啶的合成方法,属于化学合成技术领域。一种3-甲基吡啶的合成方法,该方法以乙醛或其多聚物、甲醛或其多聚物为原料,在催化剂的作用下,在180-300℃和4-10MPa的工艺条件下在管道反应器或固定床反应器中反应,反应完毕后的物料经冷却后得到3-甲基吡啶反应液,经过萃取、浓缩、精馏后,得到3-甲基吡啶产品和可循环套用的催化剂。本发明的合成方法采用酸性催化剂+连续化生产,实现了低成本、高收率和高选择性的3-甲基吡啶合成。本发明通过改变催化剂,实现了催化剂的套用、反应器的变化,保证产品收率稳步提高,成本降低。(The invention relates to a synthetic method of 3-methylpyridine, belonging to the technical field of chemical synthesis. A process for synthesizing 3-methylpyridine uses acetaldehyde or its polymer, formaldehyde or its polymer as raw materials, and reacts in a pipeline reactor or fixed-bed reactor under the action of catalyst and under the technological conditions of 180-300 deg.C and 4-10MPa, the reacted materials are cooled to obtain 3-methylpyridine reaction liquid, and the 3-methylpyridine product and catalyst which can be used repeatedly are obtained after extraction, concentration and rectification. The synthesis method adopts the acid catalyst and continuous production, and realizes the synthesis of the 3-methylpyridine with low cost, high yield and high selectivity. The invention realizes the application of the catalyst and the change of the reactor by changing the catalyst, ensures the stable improvement of the product yield and reduces the cost.)

1. A synthetic method of 3-methylpyridine is characterized in that: the method takes acetaldehyde or a polymer thereof, formaldehyde or a polymer thereof as raw materials, and reacts in a pipeline reactor or a fixed bed reactor under the process conditions of 180 ℃ and 300 ℃ and 4-10MPa under the action of a catalyst, the materials after the reaction are cooled to obtain 3-methylpyridine reaction liquid, and the 3-methylpyridine product and the catalyst which can be recycled are obtained after extraction, concentration and rectification.

2. The method for synthesizing 3-methylpyridine according to claim 1, wherein the catalyst is one or more of dilute sulfuric acid, methanesulfonic acid, sodium sulfate and sulfonic solid acid.

3. The method for synthesizing 3-methylpyridine according to claim 2, wherein the dilute sulfuric acid is an aqueous solution of sulfuric acid having a mass fraction of 0.1-10%.

4. The method for synthesizing 3-methylpyridine according to claim 1, wherein the acetaldehyde and its polymer is paraldehyde, and the formaldehyde and its polymer are selected from one or more of formalin, paraformaldehyde, and urotropin.

5. A process for the synthesis of 3-methylpyridine according to claim 1, characterized in that the molar ratio of formaldehyde to acetaldehyde in the starting material is in the range of 0.1:1 to 10:1, and the weight ratio of the total material to the catalyst is between 0.1:1 and 10: 1.

6. The process for synthesizing 3-methylpyridine according to claim 5, wherein the molar ratio of formaldehyde to acetaldehyde in the starting material is in the range of 1.1: 1 to 2.9:1, and the weight ratio of the total feed to the catalyst is between 0.2:1 and 2: 1.

7. The method for synthesizing 3-methylpyridine according to claim 1, wherein the reaction temperature is 200 ℃ and the reaction pressure is controlled to be 4-8 MPa.

8. The process for synthesizing 3-methylpyridine according to claim 1, wherein the pipeline reactor or the fixed bed reactor is used for continuous operation, and the residence time of the reaction materials in the pipeline is controlled to be 5-60 minutes.

9. The process according to claim 8, wherein the process is carried out continuously in a pipeline reactor or a fixed bed reactor, and the residence time of the reaction mixture in the pipeline is controlled to 10 to 30 minutes.

Technical Field

The invention relates to a synthetic method of 3-methylpyridine, belonging to the technical field of chemical synthesis.

Background

3-methylpyridine, also known as beta-methylpyridine and 3-picoline, is an organic synthetic intermediate and solvent, is a colorless oily liquid, and has unpleasant odor. Mixing with water, ethanol, and diethyl ether. It is inflammable to open fire and high temperature and produces toxic nitrogen oxide gas when heated. The product is used as intermediate of imidacloprid and acetamiprid in pesticide, and can be used for synthesizing 3-methylpyridine-N-oxide as next step intermediate, or used as medicine intermediate, dye intermediate, resin intermediate, etc.

The existing 3-methylpyridine production process includes a gas-solid phase contact catalytic method using propylene aldehyde and ammonia, ethanol, formaldehyde and ammonia, acetaldehyde or paraldehyde, formaldehyde, hexamethylenetetramine, acrolein, propionaldehyde, triallylamine and 2-methylglutaronitrile as raw materials and a gas-liquid phase catalytic method using 2-methylglutaronitrile as raw materials.

Wherein, the synthesis process using formaldehyde, acetaldehyde and ammonia as raw materials adopts a fixed bed reactor to obtain a pyridine mixture including 3-methylpyridine, and 3-methylpyridine is obtained after a series of separation means, and the yield of the 3-methylpyridine is about 30 percent generally. II. 3-methylpyridine is quickly obtained by taking 3-methylpiperidine as a raw material through dehydrogenation, and the method is limited by raw materials and processes and cannot be popularized. III, synthesizing a pyridine mixture with high content of 3-methylpyridine by using acrolein, propionaldehyde and ammonia as raw materials through a fluidized bed reactor, but the raw material supply is limited; IV, under the action of a diammonium hydrogen phosphate saline solution, performing high-temperature and high-pressure reaction on the raw materials of paraldehyde and urotropine to obtain the 3-methylpyridine. The above-mentioned several routes have the problems of low yield, more by-products, especially more pyridine, and the main reason for these problems is that the reactivity of formaldehyde and acetaldehyde is high, and if the reaction is carried out by one-pot method, the conversion to other by-products is easy.

In view of the fact that the salt water solution adopted by the 3-methylpyridine synthesis catalyst is unstable and has high concentration, solid salt is easy to be generated and precipitated; although the ionic liquid can solve the problem of instability of the saline solution, the ionic liquid has high cost and is not beneficial to industrialization.

Disclosure of Invention

Aiming at the defects of low yield, more byproducts and high cost of 3-methylpyridine in the prior art, the invention provides the synthesis method of the 3-methylpyridine, and the method realizes the synthesis of the 3-methylpyridine with high yield and high selectivity.

The technical scheme adopted by the invention for solving the technical problems is as follows:

a process for synthesizing 3-methylpyridine uses acetaldehyde or its polymer, formaldehyde or its polymer as raw materials, and reacts in a pipeline reactor or fixed-bed reactor under the action of catalyst and under the technological conditions of 180-300 deg.C and 4-10MPa, the reacted materials are cooled to obtain 3-methylpyridine reaction liquid, and the 3-methylpyridine product and catalyst which can be used repeatedly are obtained after extraction, concentration and rectification. The synthesis method adopts the acid catalyst and continuous production, and realizes the synthesis of the 3-methylpyridine with low cost, high yield and high selectivity. In the prior art, paraldehyde and urotropine are mainly used as raw materials, and the 3-methylpyridine is prepared under the catalysis of a diammonium hydrogen phosphate saline solution. The invention realizes the application of the catalyst and the change of the reactor by changing the catalyst, ensures the stable improvement of the product yield and reduces the cost.

The invention takes acetaldehyde or polymers thereof, formaldehyde or polymers thereof as raw materials, does not have solvents such as ethanol and the like, adopts one or more of dilute sulfuric acid, methanesulfonic acid, sodium sulfate and sulfonic acid-based solid acid catalysts as catalysts, and carries out reaction in a pipeline or fixed bed reactor, on one hand, the catalysts are easy to obtain and have low price, and the solvents such as ethanol and the like are not needed, so that the production cost is effectively reduced, meanwhile, the yield of 3-methylpyridine is further improved, and the generation of byproducts is reduced; on the other hand, the catalyst can be continuously applied, and the continuous production is realized.

Preferably, the catalyst is one or more of dilute sulfuric acid, methanesulfonic acid, sodium sulfate and sulfonic acid-based solid acid. Dilute sulfuric acid is preferred. Preferably, the dilute sulfuric acid is an aqueous solution of 0.1-10% by mass of sulfuric acid.

Preferably, the acetaldehyde and its polymer are selected from one or more of acetaldehyde, paraldehyde or paraldehyde, and the formaldehyde and its polymer are selected from one or more of formalin, paraformaldehyde and urotropin.

Preferably, the molar ratio of formaldehyde to acetaldehyde in the feed is in the range of 0.1:1 to 10:1, and the weight ratio of the total material to the catalyst is between 0.1:1 and 10: 1. Preferably, the molar ratio of formaldehyde to acetaldehyde in the feed is in the range of 1.1: 1 to 2.9:1, and the weight ratio of the total feed to the catalyst is between 0.2:1 and 2: 1.

Preferably, the reaction temperature is 200 ℃ and 300 ℃, and the reaction pressure is controlled to be 4-8 MPa.

Preferably, a pipeline reactor or a fixed bed reactor is adopted for continuous operation, and the residence time of reaction materials in the pipeline is controlled to be 5-60 minutes. Further, the residence time is preferably controlled to 10 to 30 minutes.

The invention has the beneficial effects that:

1. the invention controls the reaction speed of acetaldehyde and formaldehyde under the condition of one or more of dilute sulfuric acid, methanesulfonic acid, sodium sulfate and sulfonic acid base solid acid catalysts at different temperatures, thereby being most beneficial to synthesizing 3-methylpyridine.

2. The invention adopts dilute sulphuric acid, methanesulfonic acid, sodium sulfate and sulfonic acid base solid acid as catalysts, avoids salt precipitation, reduces production cost, has little harm to the environment and is beneficial to large-scale production.

3. The invention adopts dilute sulphuric acid, methanesulfonic acid, sodium sulfate and sulfonic acid group solid acid as catalysts, can be recycled after extraction, concentration or filtration, and has simple and convenient post-treatment process.

4. The method adopts a pipeline reactor or a fixed bed reactor, greatly reduces the production cost under the condition of adopting low-cost catalyst and no solvents such as ethanol and the like, further improves the high selectivity and the high yield of the 3-methylpyridine, has simple operation, can realize continuous production and is suitable for large-scale production.

5. Compared with the prior art, the synthesis method of the method has the advantages that the yield of the 3-methylpyridine is below 65%, and the proportion of the 3-methylpyridine to other pyridine byproducts in the product is 5/1-6/1. The yield of the 3-methylpyridine can reach over 74 percent, and the proportion of the 3-methylpyridine product to other pyridine by-products can be controlled between 7/1 and 9/1.

Detailed Description

The technical solution of the present invention will be further specifically described below by way of specific examples. It is to be understood that the practice of the invention is not limited to the following examples, and that any variations and/or modifications may be made thereto without departing from the scope of the invention.

In the present invention, all parts and percentages are by weight, unless otherwise specified, and the equipment and materials used are commercially available or commonly used in the art. The methods in the following examples are conventional in the art unless otherwise specified.

The sulfonic acid group solid acid catalyst is a sulfonic acid type SBA-15 solid acid catalyst.

Example 1

A synthetic method of 3-methylpyridine is carried out in a 2L high-pressure reaction kettle. The material is conveyed by a high-pressure metering pump.

750g of 8% dilute sulfuric acid is prepared and is ready for use.

Weighing 186g of urotropin and 300g of water, and uniformly mixing for later use.

306g of paraldehyde is weighed out for use.

And (3) vacuumizing the high-pressure kettle by using a vacuum pump, then inserting one feed inlet of the high-pressure kettle into dilute sulfuric acid, opening a feed valve, sucking the weighed dilute sulfuric acid catalyst into the high-pressure kettle, closing a feed inlet valve and an exhaust valve of the high-pressure kettle after the material suction is finished, and closing the vacuum pump.

Starting the autoclave for stirring, setting the stirring speed to be 1000r/min, setting the heating temperature to be 250 ℃, and starting heating.

When the temperature reaches 250 ℃, the flow rates of the high-pressure metering pumps of the urotropine material and the paraldehyde material are respectively set to be 8.1g/min and 5.1g/min, 792g is fed after 1 hour, and the pressure in the autoclave is increased from 0.1MPa to 4MPa during the heating period.

Keeping the temperature for 1h after the feeding is finished, introducing cooling water into a coil pipe in a high-pressure kettle, cooling to 40 ℃, introducing nitrogen into the high-pressure kettle to press out reaction liquid, extracting the reaction liquid for multiple times by using dichloromethane, recovering dichloromethane from an organic phase by simple distillation, wherein the recovery temperature is not more than 105 ℃, starting to perform reduced pressure rectification after the dichloromethane is recovered, the vacuum degree is-0.01 MPa, the recovery temperature is not more than 160 ℃, recovering to obtain 309.5g of crude product, the content of mixed pyridine in the crude product is 87%, the yield of mixed pyridine (calculated by paraldehyde) is 88%, and the proportion of 3-methylpyridine in the crude product is 78.3%. The concentrated solution after the water phase is concentrated is used as a catalyst for application.

The results of 10 consecutive batches of catalyst application are shown in Table 1.

TABLE 1

Batch for use (time)	Content of mixed pyridine in crude product (%)	Content of 3-methylpyridine in crude product (%)	Yield (% of mixed pyridine) based on paraldehyde
				1	87.3	78.6	88.6
2	87.1	78.4	88.3
				3	87	78.3	88
4	86.9	77.8	87.8
				5	87.1	78.5	88.4
6	86.6	77.3	87.4
				7	86.8	78	88
8	87	78.2	87.9
				9	86.4	77.9	87.1
10	87.5	78.9	89

Example 2

A process for the synthesis of 3-methylpyridine, the synthesis being carried out continuously in a high mixing degree tubular reactor having a length of 20m and an internal diameter of the tube of 4 mm. The materials and catalyst were transported by high pressure pump with residence time of 15 min.

1500g of 3% dilute sulfuric acid is prepared for standby.

930g of urotropin, 1500g of water and 1530g of paraldehyde are weighed and mixed uniformly for later use.

Opening a catalyst high-pressure metering pump, adjusting the feeding flow to be 4.5g/min, opening an electric heating system of the pipeline reactor, and setting the heating temperature to be 250 ℃. When the pressure in the reaction tube reaches 3.6MPa, opening an outlet valve of the pipeline reactor, and controlling the pressure in the reactor to be about 3.6 MPa.

Opening a material high-pressure metering pump to pump a mixed solution of urotropine and paraldehyde, adjusting the feeding flow to be 14g/min, adjusting the opening of an outlet valve of the pipeline reactor, and continuously controlling the pressure in the reactor to be about 3.6 MPa.

And cooling the reacted feed liquid by using a cooler, recovering the reaction liquid by adopting the method in the example 1 to obtain a crude product, and recovering 1582g of the crude product, wherein the content of mixed pyridine in the crude product is 89%, the yield of the mixed pyridine (calculated by paraldehyde) is 92%, and the proportion of 3-methylpyridine in the crude product is 80%.

Example 3

A process for the synthesis of 3-methylpyridine, which is carried out continuously in a 2.5L fixed-bed reactor with high degree of mixing. The materials are conveyed by a high-pressure pump.

900g of a sulfonic acid type SBA-15 solid acid catalyst was added to the fixed bed.

930g of urotropin and 1500g of water are weighed and mixed evenly for standby.

1530g of paraldehyde are weighed out for use.

The electric heating system of the fixed bed reactor is turned on, and the heating temperature is set to be 250 ℃. When the bed temperature reached 250 c,

respectively opening a urotropine material high-pressure metering pump and a paraldehyde high-pressure metering pump, adjusting the feeding flow to be 5g/min, adjusting the opening of an outlet valve of the fixed bed reactor, and continuously controlling the pressure in the reactor to be about 3.6 MPa.

After the reaction, the feed liquid was cooled by a cooler, and 1581g of crude pyridine was recovered in the manner described in example 1, wherein the content of mixed pyridine in the crude pyridine was 90%, the yield of mixed pyridine (calculated as paraldehyde) was 93%, and the ratio of 3-methylpyridine in the mixed pyridine was 82%.

After the catalyst is continuously used for 3 days, the content of the mixed pyridine in the crude product is stabilized at 90%, the yield of the mixed pyridine (calculated by paraldehyde) is stabilized at 92.3%, and the proportion of the 3-methylpyridine in the crude product is stabilized at 81.5%.

The embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same or similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.

The synthesis method of 3-methylpyridine provided by the invention is described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.