A method for preparing 2,2′-bipyridine

Abstract

The present invention discloses a preparation method of 2,2'-bipyridine, which comprises the following steps: in the presence of a solvent, using 2-cyanopyridine and acetylene as raw materials, and catalytically cyclizing to form 2,2'-bipyridine in a microchannel reactor; the cyclization reaction temperature is 180-270 °C, and the cyclization reaction pressure is 0.2-0.7 Mpa. This preparation method is safe, environmentally friendly, and low in cost. The reaction materials are easy to handle, continuous production can be carried out, and high-purity products are easily obtained.

Description

Technical Field

[0001] The present invention relates to the field of pharmaceutical technology, and in particular to a preparation method of 2,2'-bipyridine. Background Art

[0002] 2,2'-Bipyridine is an important intermediate of diquat, especially. In recent years, with the decline of the paraquat and glyphosate markets, the diquat market has increasingly attracted the widespread attention of countries around the world. 2,2'-Bipyridine also has a wide range of applications in pesticides, pharmaceuticals, dyes, spices, etc. Therefore, the research on its industrial production process has important significance.

[0003] At present, there are mainly the following three industrial production processes of 2,2'-bipyridine:

[0004] (1) Pyridine undergoes self-coupling under the action of catalysts such as FeCl3 or Raney Ni to produce 2,2'-bipyridine; in this reaction route, it is relatively easy to generate an impurity that is difficult to purify - terpyridine, which is a highly carcinogenic substance and has high requirements for production safety and production processes.

[0005] (2) 2-Halopyridine undergoes coupling with its Grignard reagent or zinc reagent under the action of a catalyst to produce 2,2'-bipyridine; 2-halopyridine is relatively expensive, and a large amount of metal is used in the preparation of the Grignard reagent or zinc reagent, resulting in a large amount of three wastes and high costs.

[0006] (3) 2-Cyanopyridine and acetylene are catalytically cyclized by cobaltocene to produce 2,2'-bipyridine (such as patent application CN108658848A); in this route, long-term high-temperature and high-pressure reaction conditions are required, the reaction time is long, acetylene is very easy to undergo self-polymerization reaction and explosion, and impurities such as benzene will be generated due to the self-polymerization of acetylene, greatly increasing the toxic waste liquid and purification steps, and the cost of the cobaltocene catalyst is high.

[0007] Therefore, it is very necessary to develop a production process of 2,2'-bipyridine that is safe, environmentally friendly, low-cost, and has a small risk of using acetylene. Summary of the Invention

[0008] Purpose of the Invention

[0009] To overcome the above deficiencies, the purpose of the present invention is to provide a preparation method of 2,2'-bipyridine, which is safe, environmentally friendly, low-cost, the reaction materials are easy to handle, can be continuously produced, and it is easy to obtain high-purity products.

[0010] Solution

[0011] To achieve the purpose of the present invention, the technical solution adopted by the present invention is as follows:

[0012] In a first aspect, the present invention provides a method for preparing 2,2'-bipyridine, comprising the following steps: in the presence of a solvent, using 2-cyanopyridine and acetylene as raw materials, and catalytically cyclizing them into 2,2'-bipyridine in a microchannel reactor; the cyclization reaction temperature is 180-270 °C, and the cyclization reaction pressure is 0.2-0.7 Mpa.

[0013] Further, the reaction temperature is 190-250 °C, optionally 200-250 °C, optionally 200-240 °C; optionally 200-230 °C;

[0014] and / or, the cyclization reaction pressure is 0.2-0.6 Mpa, optionally 0.3-0.6 Mpa, optionally 0.3-0.5 Mpa;

[0015] and / or, the reaction residence time (referring to the total residence time in the reaction module, that is, the time from entering the reaction module to exiting the reaction module) is 0.1-1 h, optionally 0.2-0.9 h, optionally 0.3-0.9 h, optionally 0.3-0.8 h, optionally 0.4-0.8 h, optionally 0.4-0.7 h.

[0016] and / or, the cyclization reaction is carried out in a solvent. Optionally, the solvent includes one or more of toluene, xylene, and pseudocumene; preferably, the solvent is selected from toluene; optionally, when the solvent is toluene, the rectification reflux ratio is 1:3; optionally, when the solvent is pseudocumene, the rectification reflux ratio is 1:5;

[0017] and / or, the catalyst is ferrocene and / or cobaltocene; optionally, the catalyst is ferrocene.

[0018] Further, before the cyclization reaction, the mixed solution of 2-cyanopyridine, catalyst, and solvent is preheated and then reacted with acetylene in the microchannel reactor; the preheating temperature is 180-270 °C, optionally 190-250 °C, optionally 200-250 °C, optionally 200-240 °C; optionally 200-230 °C;

[0019] and / or, the mass ratio of 2-cyanopyridine to the catalyst is 300-500:1, optionally 350-450:1, optionally 380-440:1;

[0020] and / or, the mass ratio of 2-cyanopyridine to the solvent is 1:2-8, optionally 1:3-6, optionally 1:3.4-4.5;

[0021] The mass ratio of the feed amounts of 2-cyanopyridine and acetylene is 2:0.6 - 1.5, optionally 2:0.7 - 1.3, optionally 2:0.9 - 1.1, optionally 2:0.95 - 1.15, and optionally 2:1.

[0022] Furthermore, the mass transfer coefficient of the microchannel reactor is 1 - 30 Ka, and the heat exchange capacity is above 1700 KW / m 2 ·K;

[0023] And / or, the microchannel reactor is a microporous array microchannel reactor, a finned microchannel reactor, a capillary microchannel reactor, or a multi-stream parallel microreactor.

[0024] Furthermore, the microchannel reactor includes: a preheating module, several microchannel reaction modules, and a quenching module;

[0025] Optionally, the microchannel structure in the microchannel reaction module of the microchannel reactor is selected from a direct flow channel structure and / or an enhanced mixing channel structure,

[0026] Optionally, the direct flow channel structure is a tubular structure;

[0027] Optionally, the enhanced mixing channel structure is a T-shaped structure, a spherical structure, a spherical structure with baffles, a water droplet-shaped structure, or a heart-shaped structure;

[0028] Optionally, the number of microchannel reaction modules of the microchannel reactor is 3 - 8, optionally 4 - 8, optionally 5 - 8, and optionally 6;

[0029] Optionally, the channel diameter is 0.5 mm - 10 mm;

[0030] Optionally, the material of the microchannel reaction module is selected from Hastelloy C alloy and / or Monel alloy.

[0031] Furthermore, 2-cyanopyridine, the catalyst, and the solvent enter the microchannel reaction module after being preheated in the preheating module through the preheating module;

[0032] Optionally, the mixed solution of preheated 2-cyanopyridine, the catalyst, and the solvent and acetylene enter the microchannel reaction module for reaction; optionally, the mixed solution of 2-cyanopyridine, the catalyst, and the solvent and acetylene enter several microchannel reaction modules for reaction in sequence;

[0033] Optionally, the feeding rate of the mixed solution of 2-cyanopyridine, the catalyst, and the solvent is 1 - 10 kg / min;

[0034] Optionally, the feeding rate of acetylene is 0.1 - 1 kg / min;

[0035] Optionally, the quenching module is a Corning straight channel, and the reaction is stopped by cooling down in the quenching module.

[0036] Furthermore, each material is dehydrated and dried before the reaction;

[0037] And / or, temperature measurement points are respectively arranged at the feed inlet and the discharge outlet of the microchannel reactor.

[0038] Furthermore, the reaction materials are distilled to obtain the product.

[0039] Advantageous Effects

[0040] (1) The preparation method of 2,2′-bipyridine and the microchannel reactor of the present invention, through continuous research, it is found that at a certain temperature, a smaller reaction pressure can be used to enable acetylene to participate in the reaction, with high safety, greatly reducing the risk of explosion. This preparation method is safe, environmentally friendly, low-cost, the reaction materials are easy to handle, continuous production can be carried out, and high-purity products are easily obtained. Description of the Drawings

[0041] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplary illustrations do not constitute a limitation on the embodiments. The special word "exemplary" here means "serving as an example, an embodiment or an illustration". Any embodiment illustrated as "exemplary" here does not have to be interpreted as being superior to or better than other embodiments.

[0042] Figure 1 It is the microchannel type of the microchannel reactor of the present invention, where (a) is a T-shaped channel structure, (b) is a spherical channel structure, (c) is a spherical channel structure with baffles, (d) is a water droplet-shaped channel structure, and (e) is a Corning microchannel mixing structure.

[0043] Figure 2 It is the reaction channel of the microchannel reactor used in the embodiment of the present invention, where (a) is a Corning straight channel module, and (b) is a Corning "heart-shaped" microchannel reaction module.

[0044] Figure 3 It is the microchannel reactor used in the embodiment of the present invention, where 1 is a liquid-phase pump, 2 is a gas-phase pump, 3 is a premixing and preheating module, 4-9 are "heart-shaped" microchannel reaction modules, and 10 is a quenching module. Detailed Embodiments

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0046] In addition, to better illustrate the present invention, numerous specific details are given in the following specific embodiments. Those skilled in the art should understand that the present invention can be implemented without some specific details. In some embodiments, raw materials, schemes, methods, means, etc. well-known to those skilled in the art are not described in detail to highlight the gist of the present invention.

[0047] Unless otherwise clearly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "having" etc. will be understood to include the stated elements or components, without excluding other elements or other components.

[0048] The product content in the following examples was quantitatively detected by gas chromatography with internal standard method.

[0049] In the following examples, the yield of the product is the ratio of the actual production output of the product obtained from the raw materials participating in the reaction to the theoretically calculated production output of the product.

[0050] For example, if 400 kg of 2-cyanopyridine (content 99.5%) is weighed and put in, the actual input amount of 2-cyanopyridine = 400 × 0.995 = 398 kg. After the reaction, 4.78 kg of 2-cyanopyridine remains (this remaining amount is the mass converted after detecting the purity by the internal standard method). Then the conversion rate of 2-cyanopyridine = (1 - 4.78 / 398) × 100% = 98.8%. Based on the 393.22 kg (= 398 - 4.78 kg) of 2-cyanopyridine actually participating in the reaction, the theoretically calculated output of 2,2'-bipyridine is 598.83 kg (the molecular weight of 2,2'-bipyridine is 156, and the molecular weight of 2-cyanopyridine is 104). The actual output of 2,2'-bipyridine is 584.46 kg (this actual output is the mass converted after detecting the purity by the internal standard method). Then the yield of 2,2'-bipyridine = (584.46 / 598.83) * 100% = 97.6%.

[0051] 2-cyanopyridine, ferrocene, cobaltocene, toluene, xylene, pseudocumene, and acetylene in the following examples are commercially available.

[0052] Example 1

[0053] Microchannel reaction system: Select and attachFigure 2 A Corning straight channel module (as an accessory Figure 3 Premixing and preheating module 3 in the microchannel reactor), Corning "heart-shaped" microchannel reaction module (as an additional Figure 3 Six "heart-shaped" microchannel reaction modules 4-9) of the microchannel reactor and one Corning straight channel module (as an auxiliary Figure 3 The quenching module 10 of the microchannel reactor is as follows Figure 3 The reaction flow diagram depicts a continuous-flow microchannel reaction system. Thermal oil was used as the heat exchange medium. Based on the principle of forced heat transfer in the microchannel reactor, only two temperature measurement points were set up at the reactor's inlet and outlet. Before the reaction, the microchannel reaction system and connecting piping were dehydrated and dried, and then tested for airtightness at 2.0 MPa.

[0054] 400kg of 2-cyanopyridine (content 99.5%), 1kg of ferrocene (content 99%) and 1600kg of toluene (content 99.5%) were mixed evenly to form a mixture. The mixture was stored in a storage tank and stored by adding Figure 3 The liquid phase pump 1 (such as a diaphragm metering pump) in the microchannel reaction system continuously and stably adds the mixture to the microchannel reaction system. The feed rate of the liquid phase pump 1 is: 6.67kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (content 98%) is stored in a cylinder and is added by the attached Figure 3 A gas phase pump 2 (e.g., a diaphragm metering pump) continuously and quantitatively feeds acetylene into the microchannel reaction system, directly into the "heart-shaped" microchannel reaction module 4. The feed rate of gas phase pump 2 is 0.667 kg / min. In the "heart-shaped" microchannel reaction modules 4-9, the heat exchanger temperature is set at 200°C (i.e., the reaction temperature), the reaction pressure is set at 0.3 MPa, and the total residence time of the reaction in the "heart-shaped" microchannel reaction modules 4-9 is 30 minutes.

[0055] In the heart-shaped microchannel reaction module 4-9, the 2-cyanopyridine in the mixture reacts with acetylene. The crude reaction product is collected after passing through the quenching module 10 to obtain a product mixture, which is then sliced and distilled to obtain a solid.

[0056] The results of 2,2′-bipyridine gas phase internal standard method detection showed that the conversion rate of 2-cyanopyridine was 98.8% and the yield of 2,2′-bipyridine was 97.6%.

[0057] Example 2

[0058] Microchannel reaction system: select the attached Figure 2One Corning straight channel module (as the premixing and preheating module 3), six Corning "heart-shaped" microchannel reaction modules, and one Corning straight channel module (as the quenching module 10). According to the reaction process shown in the appendix Figure 3 A continuous flow microchannel reaction system is composed. The reaction heat exchange medium is heat-conducting oil. According to the principle of forced heat transfer of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively dehydrated and dried, and a 2.0 MPa airtightness inspection is carried out.

[0059] 380 kg of 2-cyanopyridine (content 99.5%), 1 kg of ferrocene (content 99%), and 1700 kg of toluene (content 99.5%). The three materials are mixed evenly to form a mixture. The mixture is stored in a storage tank and is continuously and stably added to the microchannel reaction system through the liquid-phase pump 1 (such as a diaphragm metering pump) in the appendix Figure 3 . The feeding speed of the liquid-phase pump 1 is: 6.94 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (content 98%) is stored in a steel cylinder and is continuously and quantitatively added to the microchannel reaction system through the gas-phase pump 2 (such as a diaphragm metering pump) in the appendix Figure 3 . It directly enters the "heart-shaped" microchannel reaction module 4. The feeding speed of the gas-phase pump 2 is: 0.634 kg / min. In the "heart-shaped" microchannel reaction modules 4-9, the heat exchanger temperature is set at 220 °C (i.e., the reaction temperature), the reaction pressure is set at 0.4 MPa, and the total residence time of the reaction in the "heart-shaped" microchannel reaction modules 4-9 is 28 min.

[0060] In the "heart-shaped" microchannel reaction modules 4-9, 2-cyanopyridine in the mixture reacts with acetylene. The reaction crude product is collected after passing through the quenching module 10, and the product mixture is obtained, and then a solid is obtained by distillation and slicing.

[0061] Detected by the 2,2'-bipyridine gas-phase internal standard method, the results show that the conversion rate of 2-cyanopyridine is 99.0%, and the yield of 2,2'-bipyridine is 97.7%.

[0062] Example 3

[0063] Microchannel reaction system: Select one Corning straight channel module (as the premixing and preheating module 3), six Corning "heart-shaped" microchannel reaction modules, and one Corning straight channel module (as the quenching module 10) in the appendix Figure 2 . According to the appendix Figure 3The reaction process shown constitutes a continuous flow microchannel reaction system. The reaction heat exchange medium is heat transfer oil. According to the principle of forced heat transfer in the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a airtightness inspection is carried out at 2.0 MPa.

[0064] 440 kg of 2-cyanopyridine (content 99.5%), 1 kg of ferrocene (content 99%), and 1500 kg of toluene (content 99.5%). The three materials are mixed evenly to form a mixture, and the mixture is stored in a storage tank. Through the Figure 3 liquid pump 1 (such as a diaphragm metering pump) in the attachment, the mixture is continuously and stably added to the microchannel reaction system. The feeding speed of the liquid pump 1 is: 6.47 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (content 98%) is stored in a steel cylinder. Through the Figure 3 gas pump 2 (such as a diaphragm metering pump) in the attachment, acetylene is continuously and quantitatively added to the microchannel reaction system and directly enters the "heart-shaped" microchannel reaction module 4. The feeding speed of the gas pump 2 is: 0.733 kg / min. In the "heart-shaped" microchannel reaction modules 4 - 9, the heat exchanger temperature is set at 230 °C (i.e., the reaction temperature), the reaction pressure is set at 0.5 MPa, and the total residence time of the reaction in the "heart-shaped" microchannel reaction modules 4 - 9 is 40 min.

[0065] In the "heart-shaped" microchannel reaction modules 4 - 9, 2-cyanopyridine in the mixture reacts with acetylene. The reaction crude product is collected after passing through the quenching module 10, and the subsequent product is obtained by distillation and slicing to get a solid.

[0066] Detection by the 2,2'-bipyridine gas phase internal standard method shows that the conversion rate of 2-cyanopyridine is 99.3%, and the yield of 2,2'-bipyridine is 98.3%.

[0067] Example 4

[0068] Microchannel reaction system: Select one Corning straight channel module (as the premixing and preheating module 3), three Corning "heart-shaped" microchannel reaction modules, and one Corning straight channel module (as the quenching module 10) from the attachment. Figure 2 According to the reaction process shown in the attachment, a continuous flow microchannel reaction system is constituted. The reaction heat exchange medium is heat transfer oil. According to the principle of forced heat transfer in the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a airtightness inspection is carried out at 2.0 MPa. Figure 3

[0069] ​2-Cyanopyridine (content 99.5%) 440 kg, ferrocene (content 99%) 1 kg, and toluene (content 99.5%) 1500 kg. The three materials are mixed evenly to form a mixture, which is stored in a storage tank. Through the Figure 3 liquid-phase pump 1 (such as a diaphragm metering pump) in the attachment, the mixture is continuously and stably added to the microchannel reaction system. The feeding speed of the liquid-phase pump 1 is: 3.235 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (content 98%) is stored in a steel cylinder. Through the Figure 3 gas-phase pump 2 (such as a diaphragm metering pump) in the attachment, acetylene is continuously and quantitatively added to the microchannel reaction system and directly enters the "heart-shaped" microchannel reaction module 4. The feeding speed of the gas-phase pump 2 is: 0.367 kg / min. In the "heart-shaped" microchannel reaction modules 4-7, the heat exchanger temperature is set at 230 °C (i.e., the reaction temperature), and the reaction pressure is set at 0.5 MPa. The total residence time of the reaction in the "heart-shaped" microchannel reaction modules 4-7 is 40 min.

[0070] In the "heart-shaped" microchannel reaction modules 4-7, 2-cyanopyridine in the mixture reacts with acetylene. The reaction crude product is collected after passing through the quenching module 10 to obtain a product mixture, and then a solid is obtained by distillation and slicing.

[0071] Detected by the 2,2'-bipyridine gas-phase internal standard method, the results show that the conversion rate of 2-cyanopyridine is 99.2%, and the yield of 2,2'-bipyridine is 98.4%.

[0072] The six reaction modules are changed to three, and the feeding amount is halved, which can meet the reaction requirements, but the production capacity is halved.

[0073] Example 5

[0074] Microchannel reaction system: Select one Corning straight-channel module (as the premixing and preheating module 3), six Corning "heart-shaped" microchannel reaction modules, and one Corning straight-channel module (as the quenching module 10) in the attachment. A continuous-flow microchannel reaction system is composed according to the reaction process shown in the attachment. The reaction heat transfer medium is heat-conducting oil. According to the forced heat transfer principle of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively dehydrated and dried, and a 2.0 MPa airtightness inspection is carried out. Figure 2 Figure 3

[0075] Figure 3 2-Cyanopyridine (content 99.5%) 440 kg, cobaltocene (content 99%) 1 kg, and toluene (content 99.5%) 1500 kg. The three materials are mixed evenly to form a mixture, which is stored in a storage tank. Through the Figure 3 ​The liquid-phase pump 1 (such as a diaphragm metering pump) in it continuously and stably adds the mixture to the microchannel reaction system. The feeding speed of the liquid-phase pump 1 is: 6.47 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (with a content of 98%) is stored in a steel cylinder and is attached through Figure 3 The gas-phase pump 2 (such as a diaphragm metering pump) in it continuously and quantitatively adds acetylene to the microchannel reaction system and directly enters the "heart-shaped" microchannel reaction module 4. The feeding speed of the gas-phase pump 2 is: 0.733 kg / min. In the "heart-shaped" microchannel reaction modules 4 to 9, the heat exchanger temperature is set at 230 °C (i.e., the reaction temperature), the reaction pressure is set at 0.5 MPa, and the total residence time for the reaction in the "heart-shaped" microchannel reaction modules 4 to 9 is 40 min.

[0076] In the "heart-shaped" microchannel reaction modules 4 - 9, 2-cyanopyridine in the mixture reacts with acetylene. The crude reaction product is collected after passing through the quenching module 10 to obtain a product mixture, and then a solid is obtained by distillation and slicing.

[0077] Detection by the 2,2′-bipyridine gas-phase internal standard method shows that the conversion rate of 2-cyanopyridine is 99.1% and the yield of 2,2′-bipyridine is 98.2%.

[0078] In this example, cobaltocene is used for the reaction, which can meet the reaction requirements. However, cobaltocene has a high price, high activity, and is extremely prone to sublimation. When used or stored, air must be isolated, and the storage conditions are difficult.

[0079] Example 6

[0080] Microchannel reaction system: Select one Corning straight-channel module (as the premixing and preheating module 3), six Corning "heart-shaped" microchannel reaction modules, and one Corning straight-channel module (as the quenching module 10). A continuous-flow microchannel reaction system is composed according to the reaction process shown in Figure 2 The reaction heat transfer medium uses heat-conducting oil. According to the forced heat transfer principle of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a 2.0 MPa airtightness inspection is carried out. Figure 3 440 kg of 2-cyanopyridine (with a content of 99.5%), 1 kg of ferrocene (with a content of 99%), and 1500 kg of xylene (with a content of 99.5%) are mixed evenly to form a mixture. The mixture is stored in a storage tank and is attached through

[0081] Figure 3 Figure 3The liquid-phase pump 1 (such as a diaphragm metering pump) in it continuously and stably adds the mixture to the microchannel reaction system. The feeding speed of the liquid-phase pump 1 is: 6.47 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (with a content of 98%) is stored in a steel cylinder and is attached through Figure 3 the gas-phase pump 2 (such as a diaphragm metering pump) in it continuously and quantitatively adds acetylene to the microchannel reaction system and directly enters the "heart-shaped" microchannel reaction module 4. The feeding speed of the gas-phase pump 2 is: 0.733 kg / min. In the "heart-shaped" microchannel reaction modules 4-9, the heat exchanger temperature is set at 230 °C (i.e., the reaction temperature), the reaction pressure is set at 0.5 MPa, and the total residence time of the reaction in the "heart-shaped" microchannel reaction modules 4-9 is 40 min.

[0082] In the "heart-shaped" microchannel reaction modules 4-9, 2-cyanopyridine in the mixture reacts with acetylene. The crude reaction product is collected after passing through the quenching module 10, and the subsequent product mixture is obtained by distillation and slicing to get a solid.

[0083] Detected by the 2,2'-bipyridine gas-phase internal standard method, the results show that the conversion rate of 2-cyanopyridine is 99.2%, and the yield of 2,2'-bipyridine is 98.2%.

[0084] The solvent used in this example is xylene. Xylene has a higher boiling point than toluene. Xylene itself has three isomers, ortho, meta, and para, and is a mixture. When separating, it increases the separation difficulty and also consumes more energy during purification.

[0085] Example 7

[0086] Microchannel reaction system: Select one Corning straight-channel module (as the premixing and preheating module 3), six Corning "heart-shaped" microchannel reaction modules, and one Corning straight-channel module (as the quenching module 10). According to the reaction process shown in Figure 2 a continuous-flow microchannel reaction system is composed. The reaction heat transfer medium uses heat-conducting oil. According to the forced heat transfer principle of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a 2.0 MPa airtightness inspection is carried out. Figure 3 440 kg of 2-cyanopyridine (with a content of 99.5%), 1 kg of ferrocene (with a content of 99%), and 1500 kg of pseudocumene (with a content of 99.5%) are mixed evenly to form a mixture. This mixture is stored in a storage tank and is attached through

[0087] Figure 3 ​The liquid-phase pump 1 (such as a diaphragm metering pump) in it continuously and stably adds the mixture to the microchannel reaction system. The feeding speed of the liquid-phase pump 1 is: 6.47 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (with a content of 98%) is stored in a steel cylinder and is attached through Figure 3 The gas-phase pump 2 (such as a diaphragm metering pump) in it continuously and quantitatively adds acetylene to the microchannel reaction system and directly enters the "heart-shaped" microchannel reaction module 4. The feeding speed of the gas-phase pump 2 is: 0.733 kg / min. In the "heart-shaped" microchannel reaction modules 4 to 9, the heat exchanger temperature is set at 230 °C (i.e., the reaction temperature), the reaction pressure is set at 0.5 MPa, and the total residence time of the reaction in the "heart-shaped" microchannel reaction modules 4 to 9 is 40 min.

[0088] In the "heart-shaped" microchannel reaction modules 4 - 9, 2-cyanopyridine in the mixture reacts with acetylene. The crude reaction product is collected after passing through the quenching module 10, and the subsequent product mixture is obtained by distillation and slicing to get a solid.

[0089] Detection by 2,2'-bipyridine gas-phase internal standard method shows that the conversion rate of 2-cyanopyridine is 99.0% and the yield of 2,2'-bipyridine is 98.3%.

[0090] The boiling point of pseudocumene in this example is 168 °C, which is higher than that of toluene. During separation, the separation difficulty increases, and the energy consumption during purification is also higher.

[0091] Comparative Example 1

[0092] Microchannel reaction system: Select one Corning straight-channel module in Figure 2 (as the premixing and preheating module 3), six Corning "heart-shaped" microchannel reaction modules, and one Corning straight-channel module (as the quenching module 10). A continuous-flow microchannel reaction system is composed according to the reaction process shown in Figure 3 . The reaction heat transfer medium uses heat-conducting oil. According to the forced heat transfer principle of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a 2.0 MPa airtightness inspection is carried out.

[0093] 440 kg of 2-cyanopyridine (with a content of 99.5%), 1 kg of ferrocene (with a content of 99%), and 440 kg of toluene (with a content of 99.5%) are mixed evenly to form a mixture. The mixture is stored in a storage tank and is attached through Figure 3The liquid-phase pump 1 (such as a diaphragm metering pump) in it continuously and stably adds a mixture to the microchannel reaction system. The feeding speed of the liquid-phase pump 1 is: 2.94 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (with a content of 98%) is stored in a steel cylinder and is attached through Figure 3 The gas-phase pump 2 (such as a diaphragm metering pump) in it continuously and quantitatively adds acetylene to the microchannel reaction system and directly enters the "heart-shaped" microchannel reaction module 4. The feeding speed of the gas-phase pump 2 is: 0.733 kg / min. In the "heart-shaped" microchannel reaction modules 4 to 9, the heat exchanger temperature is set at 230 °C (i.e., the reaction temperature), the reaction pressure is set at 0.5 MPa, and the total residence time for the reaction in the "heart-shaped" microchannel reaction modules 4 to 9 is 40 min.

[0094] In the "heart-shaped" microchannel reaction modules 4 - 9, 2-cyanopyridine in the mixture reacts with acetylene. The crude reaction product is collected after passing through the quenching module 10, and the subsequent product mixture is obtained by distillation and slicing to get a solid.

[0095] Detection by the 2,2′-bipyridine gas-phase internal standard method shows that the conversion rate of 2-cyanopyridine is 88.5%, and the yield of 2,2′-bipyridine is 98.4%.

[0096] In this example, the mass ratio of 2-cyanopyridine to toluene is 1:1, the amount of solvent is insufficient, the concentration of 2-cyanopyridine is too high, and 11.5% remains unreacted.

[0097] Comparative Example 2

[0098] Microchannel reaction system: Select one Corning straight-channel module (as the premixing and preheating module 3), six Corning "heart-shaped" microchannel reaction modules, and one Corning straight-channel module (as the quenching module 10). A continuous-flow microchannel reaction system is formed according to the reaction process shown in Figure 2 The reaction heat transfer medium uses heat-conducting oil. According to the forced heat transfer principle of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a 2.0 MPa airtightness inspection is carried out. Figure 3 440 kg of 2-cyanopyridine (with a content of 99.5%), 1 kg of ferrocene (with a content of 99%), and 4400 kg of toluene (with a content of 99.5%) are mixed evenly to form a mixture. The mixture is stored in a storage tank and is attached through

[0099] Figure 3 ​The liquid-phase pump 1 (such as a diaphragm metering pump) in it continuously and stably adds the mixture to the microchannel reaction system. The feeding speed of the liquid-phase pump 1 is: 16.14 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (with a content of 98%) is stored in a steel cylinder and enters through the attached Figure 3 The gas-phase pump 2 (such as a diaphragm metering pump) in it continuously and quantitatively adds acetylene to the microchannel reaction system and directly enters the "heart-shaped" microchannel reaction module 4. The feeding speed of the gas-phase pump 2 is: 0.733 kg / min. In the "heart-shaped" microchannel reaction modules 4-9, the heat exchanger temperature is set at 230 °C (i.e., the reaction temperature), the reaction pressure is set at 0.5 MPa, and the total residence time for the reaction in the "heart-shaped" microchannel reaction modules 4-9 is 40 min.

[0100] In this embodiment, the mass ratio of 2-cyanopyridine to toluene is 1:10. The concentration of 2-cyanopyridine is too low, and 6.5% remains unreacted; there is a large amount of solvent, which is not conducive to recovery and causes energy consumption waste.

[0101] Comparative Example 3

[0102] Microchannel reaction system: Select one Corning straight-channel module in the attached Figure 2 as the premixing and preheating module 3, three Corning "heart-shaped" microchannel reaction modules, and one Corning straight-channel module as the quenching module 10. A continuous-flow microchannel reaction system is composed according to the reaction flow shown in the attached Figure 3 The reaction heat transfer medium is thermal oil. According to the forced heat transfer principle of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a airtightness inspection is carried out at 2.0 MPa.

[0103] 440 kg of 2-cyanopyridine (with a content of 99.5%), 1 kg of ferrocene (with a content of 99%), and 1500 kg of toluene (with a content of 99.5%) are mixed evenly to form a mixture. The mixture is stored in a storage tank and enters through the attached Figure 3 The liquid-phase pump 1 (such as a diaphragm metering pump) in it continuously and stably adds the mixture to the microchannel reaction system. The feeding speed of the liquid-phase pump 1 is: 6.47 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (with a content of 98%) is stored in a steel cylinder and enters through the attached Figure 3The gas-phase pump 2 (such as a diaphragm metering pump) in it continuously and quantitatively adds acetylene to the microchannel reaction system and directly enters the "heart-shaped" microchannel reaction module 4. The feeding speed of the gas-phase pump 2 is: 0.733 kg / min. In the "heart-shaped" microchannel reaction modules 4 to 7, the heat exchanger temperature is set at 230 °C (i.e., the reaction temperature), the reaction pressure is set at 0.5 MPa, and the total residence time for the reaction in the "heart-shaped" microchannel reaction modules 4 to 7 is 40 min.

[0104] In the "heart-shaped" microchannel reaction modules 4 - 7, 2-cyanopyridine in the mixture reacts with acetylene. The crude reaction product is collected after passing through the quenching module 10 to obtain a product mixture, and then a solid is obtained by distillation slicing.

[0105] Detection by the 2,2′-bipyridine gas-phase internal standard method shows that the conversion rate of 2-cyanopyridine is 49.65%, and the yield of 2,2′-bipyridine is 98.3%.

[0106] When the "heart-shaped" microchannel reaction module changes from six pieces to three pieces, with the same feeding amount, half of the 2-cyanopyridine will remain, and half of the acetylene will leave in the form of waste gas, and the reaction residence time is insufficient; the boiling point of 2-cyanopyridine is 211 - 215 °C, and that of bipyridine is 273 °C. The remaining 2-cyanopyridine increases the separation difficulty and energy consumption.

[0107] Comparative Example 4

[0108] Microchannel reaction system: Select one Corning straight-channel module (as the premixing and preheating module 3), six Corning "heart-shaped" microchannel reaction modules, and one Corning straight-channel module (as the quenching module 10). A continuous-flow microchannel reaction system is formed according to the reaction process shown in the appendix. The reaction heat transfer medium uses heat-conducting oil. According to the forced heat transfer principle of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a airtightness check is carried out at 2.0 MPa. Figure 2 In the appendix, one Corning straight-channel module (as the premixing and preheating module 3), six Corning "heart-shaped" microchannel reaction modules, and one Corning straight-channel module (as the quenching module 10). A continuous-flow microchannel reaction system is formed according to the reaction process shown in the appendix. The reaction heat transfer medium uses heat-conducting oil. According to the forced heat transfer principle of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a airtightness check is carried out at 2.0 MPa. Figure 3 According to the reaction process shown, a continuous-flow microchannel reaction system is formed. The reaction heat transfer medium uses heat-conducting oil. According to the forced heat transfer principle of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a airtightness check is carried out at 2.0 MPa.

[0109] 440 kg of 2-cyanopyridine (content 99.5%), 1 kg of ferrocene (content 99%), and 1500 kg of toluene (content 99.5%) are mixed evenly to form a mixture, and the mixture is stored in a storage tank. Through the liquid-phase pump 1 (such as a diaphragm metering pump) in the appendix, the mixture is continuously and stably added to the microchannel reaction system. The feeding speed of the liquid-phase pump 1 is: 6.47 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (content 98%) is stored in a steel cylinder and passes through the appendix Figure 3 In the appendix, the liquid-phase pump 1 (such as a diaphragm metering pump) continuously and stably adds the mixture to the microchannel reaction system. The feeding speed of the liquid-phase pump 1 is: 6.47 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (content 98%) is stored in a steel cylinder and passes through the appendix Figure 3The gas-phase pump 2 (such as a diaphragm metering pump) in it continuously and quantitatively adds acetylene to the microchannel reaction system and directly enters the "heart-shaped" microchannel reaction module 4. The feeding speed of the gas-phase pump 2 is: 0.733 kg / min. In the "heart-shaped" microchannel reaction modules 4 to 9, the heat exchanger temperature is set at 230 °C (i.e., the reaction temperature), the reaction pressure is set at 0.1 MPa, and the total residence time for the reaction in the "heart-shaped" microchannel reaction modules 4 to 9 is 40 min.

[0110] In the "heart-shaped" microchannel reaction modules 4 - 9, 2-cyanopyridine in the mixture reacts with acetylene. The crude reaction product is collected after passing through the quenching module 10 to obtain a product mixture, and then a solid is obtained by distillation slicing.

[0111] Detection by the 2,2'-bipyridine gas-phase internal standard method shows that the conversion rate of 2-cyanopyridine is 69.3%, and the yield of 2,2'-bipyridine is 98.3%.

[0112] This example shows that when the reaction pressure is too low, the reaction is incomplete, and 30% of 2-cyanopyridine remains. The boiling point of 2-cyanopyridine is 211 - 215 °C, and that of bipyridine is 273 °C. The remaining 2-cyanopyridine increases the separation difficulty and energy consumption.

[0113] Comparative Example 5

[0114] Microchannel reaction system: Select one Corning straight-channel module (as the premixing and preheating module 3), six Corning "heart-shaped" microchannel reaction modules, and one Corning straight-channel module (as the quenching module 10). A continuous-flow microchannel reaction system is composed according to the reaction process shown in the appendix. The reaction heat exchange medium uses heat-conducting oil. According to the principle of forced heat transfer of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a airtightness inspection is carried out at 2.0 MPa. Figure 2 one in the appendix. Figure 3 As shown, a continuous-flow microchannel reaction system is formed. The reaction heat exchange medium uses heat-conducting oil. According to the principle of forced heat transfer of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a airtightness inspection is carried out at 2.0 MPa.

[0115] 440 kg of 2-cyanopyridine (content 99.5%), 1 kg of ferrocene (content 99%), and 1500 kg of toluene (content 99.5%) are mixed evenly to form a mixture. The mixture is stored in a storage tank and continuously and stably added to the microchannel reaction system through the liquid-phase pump 1 (such as a diaphragm metering pump) in the appendix. The feeding speed of the liquid-phase pump 1 is: 6.47 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (content 98%) is stored in a steel cylinder and passes through the appendix Figure 3 the liquid-phase pump 1 in it (such as a diaphragm metering pump), continuously and stably adds the mixture to the microchannel reaction system. The feeding speed of the liquid-phase pump 1 is: 6.47 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (content 98%) is stored in a steel cylinder and passes through the appendix Figure 3In the gas-phase pump 2 (such as a diaphragm metering pump), acetylene is continuously and quantitatively added to the microchannel reaction system and directly enters the "heart-shaped" microchannel reaction module 4. The feeding rate of the gas-phase pump 2 is: 0.733 kg / min. In the "heart-shaped" microchannel reaction modules 4 to 9, the heat exchanger temperature is set at 230 °C (i.e., the reaction temperature), the reaction pressure is set at 1.2 MPa, and the total residence time for the reaction in the "heart-shaped" microchannel reaction modules 4 to 9 is 40 min.

[0116] In the "heart-shaped" microchannel reaction modules 4 - 9, 2-cyanopyridine in the mixture reacts with acetylene. The crude reaction product is collected after passing through the quenching module 10 to obtain a product mixture, and then a solid is obtained by subsequent distillation and slicing.

[0117] Detection by the 2,2'-bipyridine gas-phase internal standard method shows that the conversion rate of 2-cyanopyridine is 89.1%, and the yield of 2,2'-bipyridine is 98.2%.

[0118] This example shows that when the reaction pressure is high, the pressure of acetylene used is high, and benzene is produced by the self-polymerization of acetylene. As a result, with the same amount of acetylene, it is not sufficient to react with 2-cyanopyridine, and 10.9% of 2-cyanopyridine remains. Moreover, the higher the reaction pressure, the higher the risk, the more dangerous it is, and the greater the risk of acetylene explosion. The by-product benzene produced by the reaction is a Class I carcinogen, which increases the toxic waste liquid and purification steps and requires higher reaction requirements.

[0119] Comparative Example 6

[0120] Microchannel reaction system: Select one Corning straight-channel module (as the premixing and preheating module 3), six Corning "heart-shaped" microchannel reaction modules, and one Corning straight-channel module (as the quenching module 10). A continuous-flow microchannel reaction system is composed according to the reaction process shown in the appendix. The reaction heat exchange medium uses heat-conducting oil. According to the forced heat transfer principle of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a 2.0 MPa airtightness inspection is carried out. Figure 2 A continuous-flow microchannel reaction system is composed according to the reaction process shown in the appendix. The reaction heat exchange medium uses heat-conducting oil. According to the forced heat transfer principle of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a 2.0 MPa airtightness inspection is carried out. Figure 3 A continuous-flow microchannel reaction system is composed according to the reaction process shown in the appendix. The reaction heat exchange medium uses heat-conducting oil. According to the forced heat transfer principle of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a 2.0 MPa airtightness inspection is carried out.

[0121] 440 kg of 2-cyanopyridine (content 99.5%), 1 kg of ferrocene (content 99%), and 1500 kg of toluene (content 99.5%) are mixed evenly to form a mixture. The mixture is stored in a storage tank and continuously and stably added to the microchannel reaction system through the liquid-phase pump 1 (such as a diaphragm metering pump) in the appendix. The feeding rate of the liquid-phase pump 1 is: 6.47 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (content 98%) is stored in a steel cylinder and passes through the appendix Figure 3 440 kg of 2-cyanopyridine (content 99.5%), 1 kg of ferrocene (content 99%), and 1500 kg of toluene (content 99.5%) are mixed evenly to form a mixture. The mixture is stored in a storage tank and continuously and stably added to the microchannel reaction system through the liquid-phase pump 1 (such as a diaphragm metering pump) in the appendix. The feeding rate of the liquid-phase pump 1 is: 6.47 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (content 98%) is stored in a steel cylinder and passes through the appendix Figure 3The gas-phase pump 2 (such as a diaphragm metering pump) in it continuously and quantitatively adds acetylene to the microchannel reaction system and directly enters the "heart-shaped" microchannel reaction module 4. The feeding speed of the gas-phase pump 2 is: 0.733 kg / min. In the "heart-shaped" microchannel reaction modules 4-9, the heat exchanger temperature is set at 100 °C (i.e., the reaction temperature), the reaction pressure is set at 0.5 MPa, and the total residence time of the reaction in the "heart-shaped" microchannel reaction modules 4-9 is 40 min.

[0122] In the "heart-shaped" microchannel reaction modules 4-9, 2-cyanopyridine in the mixture reacts with acetylene. The crude reaction product is collected after passing through the quenching module 10 to obtain a product mixture, and then a solid is obtained by distillation slicing.

[0123] Detection by the 2,2'-bipyridine gas-phase internal standard method shows that the conversion rate of 2-cyanopyridine is 27.8%, and the yield of 2,2'-bipyridine is 99.3%.

[0124] In this example, the reaction temperature is 100 °C, and 72.2% of 2-cyanopyridine remains. The reaction temperature is too low and the reaction is too poor.

[0125] Comparative Example 7

[0126] Microchannel reaction system: Select one Corning straight-channel module (as the premixing and preheating module 3), six Corning "heart-shaped" microchannel reaction modules, and one Corning straight-channel module (as the quenching module 10). A continuous-flow microchannel reaction system is composed according to the reaction process shown in the appendix. The reaction heat exchange medium uses heat-conducting oil. According to the forced heat transfer principle of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a airtightness inspection is carried out at 2.0 MPa. Figure 2 One Corning straight-channel module (as the premixing and preheating module 3), six Corning "heart-shaped" microchannel reaction modules, and one Corning straight-channel module (as the quenching module 10). According to the appendix Figure 3 The reaction process shown is used to form a continuous-flow microchannel reaction system. The reaction heat exchange medium uses heat-conducting oil. According to the forced heat transfer principle of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a airtightness inspection is carried out at 2.0 MPa.

[0127] 440 kg of 2-cyanopyridine (content 99.5%), 1 kg of ferrocene (content 99%), and 1500 kg of toluene (content 99.5%). The three materials are mixed evenly to form a mixture, and the mixture is stored in a storage tank. Through the liquid-phase pump 1 (such as a diaphragm metering pump) in the appendix Figure 3 The mixture is continuously and stably added to the microchannel reaction system. The feeding speed of the liquid-phase pump 1 is: 6.47 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (content 98%) is stored in a steel cylinder. Through the appendix Figure 3The gas-phase pump 2 (such as a diaphragm metering pump) in it continuously and quantitatively adds acetylene to the microchannel reaction system and directly enters the "heart-shaped" microchannel reaction module 4. The feeding speed of the gas-phase pump 2 is: 0.733 kg / min. In the "heart-shaped" microchannel reaction modules 4-9, the heat exchanger temperature is set at 130 °C (i.e., the reaction temperature), the reaction pressure is set at 0.5 MPa, and the total residence time for the reaction in the "heart-shaped" microchannel reaction modules 4-9 is 40 min.

[0128] In the "heart-shaped" microchannel reaction modules 4-9, 2-cyanopyridine in the mixture reacts with acetylene. The crude reaction product is collected after passing through the quenching module 10 to obtain a product mixture, and then a solid is obtained by distillation and slicing.

[0129] Detection by the 2,2'-bipyridine gas-phase internal standard method shows that the conversion rate of 2-cyanopyridine is 41.4%, and the yield of 2,2'-bipyridine is 99.5%.

[0130] In this example, the reaction temperature is 130 °C, and 58.6% of 2-cyanopyridine remains, indicating that the reaction temperature is too low and the reaction is too poor.

[0131] Comparative Example 8

[0132] Microchannel reaction system: Select one Corning straight-channel module (as the premixing and preheating module 3), six Corning "heart-shaped" microchannel reaction modules, and one Corning straight-channel module (as the quenching module 10). A continuous-flow microchannel reaction system is composed according to the reaction process shown in the appendix. The reaction heat exchange medium uses heat-conducting oil. According to the forced heat transfer principle of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a airtightness inspection is carried out at 2.0 MPa. Figure 2 One Corning straight-channel module (as the premixing and preheating module 3), six Corning "heart-shaped" microchannel reaction modules, and one Corning straight-channel module (as the quenching module 10). A continuous-flow microchannel reaction system is composed according to the reaction process shown in the appendix. The reaction heat exchange medium uses heat-conducting oil. According to the forced heat transfer principle of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a airtightness inspection is carried out at 2.0 MPa. Figure 3 The reaction heat exchange medium uses heat-conducting oil. According to the forced heat transfer principle of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a airtightness inspection is carried out at 2.0 MPa.

[0133] 440 kg of 2-cyanopyridine (content 99.5%), 1 kg of ferrocene (content 99%), and 1500 kg of toluene (content 99.5%) are mixed evenly to form a mixture. The mixture is stored in a storage tank and continuously and stably added to the microchannel reaction system through the liquid-phase pump 1 (such as a diaphragm metering pump) in the appendix. The feeding speed of the liquid-phase pump 1 is: 6.47 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (content 98%) is stored in a steel cylinder and passes through the appendix Figure 3 The liquid-phase pump 1 (such as a diaphragm metering pump) in it continuously and stably adds the mixture to the microchannel reaction system. The feeding speed of the liquid-phase pump 1 is: 6.47 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (content 98%) is stored in a steel cylinder and passes through the appendix Figure 3The gas-phase pump 2 (such as a diaphragm metering pump) in it continuously and quantitatively adds acetylene to the microchannel reaction system and directly enters the "heart-shaped" microchannel reaction module 4. The feeding speed of the gas-phase pump 2 is: 0.733 kg / min. In the "heart-shaped" microchannel reaction modules 4 to 9, the heat exchanger temperature is set at 330 °C (i.e., the reaction temperature), the reaction pressure is set at 0.5 MPa, and the total residence time for the reaction in the "heart-shaped" microchannel reaction modules 4 to 9 is 40 min.

[0134] In the "heart-shaped" microchannel reaction modules 4 - 9, 2-cyanopyridine in the mixture reacts with acetylene. The crude reaction product is collected after passing through the quenching module 10 to obtain a product mixture, and then a solid is obtained by distillation and slicing.

[0135] Detection by the 2,2'-bipyridine gas-phase internal standard method shows that the conversion rate of 2-cyanopyridine is 99.9%, and the yield of 2,2'-bipyridine is 90.3%.

[0136] In this example, the reaction temperature is 330 °C, and 0.1% of 2-cyanopyridine remains, indicating that the reaction is complete, but the yield is low, indicating that there are side reactions in the materials; it shows that the temperature is too high and the side reactions are aggravated.

[0137] Comparative Example 9

[0138] Microchannel reaction system: Select one Corning straight-channel module (as the premixing and preheating module 3), six Corning "heart-shaped" microchannel reaction modules, and one Corning straight-channel module (as the quenching module 10). A continuous-flow microchannel reaction system is composed according to the reaction process shown in the appendix. The reaction heat exchange medium uses heat-conducting oil. According to the principle of forced heat transfer of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a airtightness inspection is carried out at 2.0 MPa. Figure 2 One Corning straight-channel module (as the premixing and preheating module 3), six Corning "heart-shaped" microchannel reaction modules, and one Corning straight-channel module (as the quenching module 10). A continuous-flow microchannel reaction system is composed according to the reaction process shown in the appendix. The reaction heat exchange medium uses heat-conducting oil. According to the principle of forced heat transfer of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a airtightness inspection is carried out at 2.0 MPa. Figure 3 The reaction heat exchange medium uses heat-conducting oil. According to the principle of forced heat transfer of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a airtightness inspection is carried out at 2.0 MPa.

[0139] 440 kg of 2-cyanopyridine (content 99.5%), 1 kg of ferrocene (content 99%), and 1500 kg of toluene (content 99.5%) are mixed evenly to form a mixture, and the mixture is stored in a storage tank. Through the liquid-phase pump 1 (such as a diaphragm metering pump) in the appendix, the mixture is continuously and stably added to the microchannel reaction system. The feeding speed of the liquid-phase pump 1 is: 6.47 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (content 98%) is stored in a steel cylinder. Through the appendix Figure 3 The liquid-phase pump 1 (such as a diaphragm metering pump) in it continuously and stably adds the mixture to the microchannel reaction system. The feeding speed of the liquid-phase pump 1 is: 6.47 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (content 98%) is stored in a steel cylinder. Through the appendix Figure 3The gas-phase pump 2 (such as a diaphragm metering pump) in it continuously and quantitatively adds acetylene to the microchannel reaction system and directly enters the "heart-shaped" microchannel reaction module 4. The feeding speed of the gas-phase pump 2 is: 0.733 kg / min. In the "heart-shaped" microchannel reaction modules 4-9, the heat exchanger temperature is set at 150 °C (i.e., the reaction temperature), the reaction pressure is set at 0.5 MPa, and the total residence time for the reaction in the "heart-shaped" microchannel reaction modules 4-9 is 40 min.

[0140] In the "heart-shaped" microchannel reaction modules 4-9, 2-cyanopyridine in the mixture reacts with acetylene. The crude reaction product is collected after passing through the quenching module 10 to obtain a product mixture, and then a solid is obtained by distillation and slicing.

[0141] Detection by the 2,2'-bipyridine gas-phase internal standard method shows that the conversion rate of 2-cyanopyridine is 61.5%, and the yield of 2,2'-bipyridine is 99.4%.

[0142] In this example, the reaction temperature is 150 °C, and 38.5% of 2-cyanopyridine remains, indicating that the reaction temperature is too low and the reaction is too poor. The boiling point of 2-cyanopyridine is 215 °C, and the boiling point of 2,2'-bipyridine is 272.5 °C, with a boiling point difference of 57.5 °C. Under high vacuum conditions, the boiling point difference becomes even smaller, which brings difficulties to separation, resulting in 2-cyanopyridine being carried in 2,2'-bipyridine, not only affecting the purity but also causing waste of raw materials and increasing costs. During the reaction process, 2-cyanopyridine should be reacted completely as much as possible.

[0143] Comparative Example 10

[0144] Microchannel reaction system: Select one Corning straight-channel module (as the premixing and preheating module 3), six Corning "heart-shaped" microchannel reaction modules, and one Corning straight-channel module (as the quenching module 10). A continuous-flow microchannel reaction system is composed according to the reaction flow shown. The reaction heat transfer medium is thermal oil. According to the forced heat transfer principle of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a 2.0 MPa airtightness inspection is carried out. Figure 2 in it Figure 3 As shown. The reaction heat transfer medium is thermal oil. According to the forced heat transfer principle of the microchannel reactor, only two temperature measurement points are set at the inlet and outlet of the reactor. Before the reaction, the microchannel reaction system and the connecting pipelines are respectively subjected to water removal and drying treatment, and a 2.0 MPa airtightness inspection is carried out.

[0145] 440 kg of 2-cyanopyridine (content 99.5%), 1 kg of ferrocene (content 99%), and 1500 kg of toluene (content 99.5%). The three materials are mixed evenly to form a mixture, and the mixture is stored in a storage tank and passed through Figure 3The liquid-phase pump 1 (such as a diaphragm metering pump) therein continuously and stably adds a mixture to the microchannel reaction system. The feeding speed of the liquid-phase pump 1 is: 6.47 kg / min. After passing through the microchannel premixing and preheating module 3, it enters the "heart-shaped" microchannel reaction module 4. Acetylene (with a content of 98%) is stored in a steel cylinder and is attached through Figure 3 the gas-phase pump 2 (such as a diaphragm metering pump) therein continuously and quantitatively adds acetylene to the microchannel reaction system and directly enters the "heart-shaped" microchannel reaction module 4. The feeding speed of the gas-phase pump 2 is: 0.733 kg / min. In the "heart-shaped" microchannel reaction modules 4 to 9, the heat exchanger temperature is set at 170 °C (i.e., the reaction temperature), the reaction pressure is set at 0.5 MPa, and the residence time for the reaction in the "heart-shaped" microchannel reaction modules 4 to 9 is 40 min.

[0146] In the "heart-shaped" microchannel reaction modules 4 - 9, 2-cyanopyridine in the mixture reacts with acetylene. The crude reaction product is collected after passing through the quenching module 10 to obtain a product mixture, and then a solid is obtained by distillation and slicing.

[0147] Detection by the 2,2'-bipyridine gas-phase internal standard method shows that the conversion rate of 2-cyanopyridine is 78.7% and the yield of 2,2'-bipyridine is 99.3%.

[0148] In this embodiment, the reaction temperature is 150 °C, and 21.3% of 2-cyanopyridine remains, indicating that the reaction temperature is too low and the reaction is too poor. The boiling point of 2-cyanopyridine is 215 °C, and the boiling point of 2,2'-bipyridine is 272.5 °C, with a boiling point difference of 57.5 °C. Under high vacuum conditions, the boiling point difference becomes even smaller, which brings difficulties to separation, resulting in 2-cyanopyridine being carried in 2,2'-bipyridine, not only affecting the purity but also causing waste of raw materials and increasing costs. During the reaction process, 2-cyanopyridine should be reacted completely as much as possible;

[0149] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A preparation method of 2,2'-bipyridine, characterized in that, It includes the following steps: In the presence of a solvent, using 2-cyanopyridine and acetylene as raw materials, catalytically cyclize to synthesize 2,2'-bipyridine in a microchannel reactor; the cyclization reaction temperature is 190 - 250 °C, and the cyclization reaction pressure is 0.2 - 0.6 Mpa; The catalyst is ferrocene and / or cobaltocene; the mass ratio of 2-cyanopyridine to the catalyst is 300 - 500:1; The mass ratio of 2-cyanopyridine to the solvent is 1:2 - 8; The mass ratio of the feed amounts of 2-cyanopyridine and acetylene is 2:0.6 - 1.5; Before the cyclization reaction, the mixed solution of 2-cyanopyridine, the catalyst and the solvent is preheated and then reacts with acetylene in the microchannel reactor; the preheating temperature is 180 - 270 °C; The feeding rate of the mixed solution of 2-cyanopyridine, the catalyst and the solvent is 1 - 10 kg / min; The feeding rate of acetylene is 0.1 - 1 kg / min; The microchannel reactor includes: a preheating module, several microchannel reaction modules and a quenching module; The microchannel structure in the microchannel reaction module of the microchannel reactor is selected from a straight-through channel structure and / or an enhanced mixing channel structure; The number of microchannel reaction modules of the microchannel reactor is 4 - 8; The reaction residence time is 0.4 - 1 h.

2. The preparation method according to claim 1, wherein The reaction temperature is 200 - 250 °C.

3. The preparation method according to claim 1, wherein, The reaction temperature is 200 - 240 °C.

4. The preparation method according to claim 1, characterized in that, The reaction temperature is 200 - 230 °C.

5. The preparation method according to claim 1, characterized in that, The cyclization reaction pressure is 0.3 - 0.6 Mpa.

6. The preparation method according to claim 1, characterized in that, The cyclization reaction pressure is 0.3 - 0.5 Mpa.

7. According to the preparation method described in any one of claims 1 to 6, characterized in that, The reaction residence time is 0.4 - 0.9 h.

8. The preparation method according to any one of claims 1 to 6, characterized in that, The reaction residence time is 0.4 - 0.8 h.

9. The preparation method according to any one of claims 1 to 6, characterized in that, The reaction residence time is 0.4 - 0.7 h.

10. The preparation method according to any one of claims 1 to 6, characterized in that, The cyclization reaction is carried out in a solvent.

11. The preparation method according to any one of claims 1 to 6, characterized in that, The solvent includes one or more of toluene, xylene, and pseudocumene.

12. The preparation method according to any one of claims 1 to 6, characterized in that, The solvent is selected from toluene.

13. The preparation method according to claim 12, characterized in that, When the solvent is toluene, the rectification reflux ratio is 1:

3.

14. The preparation method according to claim 12, characterized in that, When the solvent is pseudocumene, the rectification reflux ratio is 1:

5.

15. The preparation method according to any one of claims 1 to 6, characterized in that, The catalyst is ferrocene.

16. The preparation method according to any one of claims 1 to 6, characterized in that, Before the cyclization reaction, the preheating temperature is 190 - 250 °C.

17. The preparation method according to claim 16, wherein Before the cyclization reaction, the preheating temperature is 200 - 250 °C.

18. The preparation method according to claim 16, characterized in that, Before the cyclization reaction, the preheating temperature is 200 - 240 °C.

19. The preparation method according to claim 16, characterized in that, Before the cyclization reaction, the preheating temperature is 200 - 230 °C.

20. The preparation method according to any one of claims 1 to 6, characterized in that, The mass ratio of 2-cyanopyridine to the catalyst is 350 - 450:

1.

21. The preparation method according to any one of claims 1 to 6, characterized in that, The mass ratio of 2-cyanopyridine to the catalyst is 380 - 440:

1.

22. The preparation method according to any one of claims 1 to 6, characterized in that, The mass ratio of 2-cyanopyridine to the solvent is 1:3 - 6.

23. The preparation method according to any one of claims 1 to 6, characterized in that, The mass ratio of 2-cyanopyridine to the solvent is 1:3.4 - 4.

5.

24. The preparation method according to any one of claims 1 to 6, characterized in that, The mass ratio of the feed amounts of 2-cyanopyridine and acetylene is 2:0.7 - 1.

3.

25. The preparation method according to any one of claims 1 to 6, characterized in that, The mass ratio of the feed amounts of 2-cyanopyridine and acetylene is 2:0.9 - 1.

1.

26. The preparation method according to any one of claims 1 to 6, characterized in that, The mass ratio of the feed amounts of 2-cyanopyridine and acetylene is 2:0.95 - 1.

15.

27. The preparation method according to any one of claims 1 to 6, characterized in that, The mass ratio of the feed amounts of 2-cyanopyridine and acetylene is 2:

1.

28. The preparation method according to any one of claims 1 to 6, characterized in that, The mass transfer coefficient of the microchannel reactor is 1 to 30 Ka, and the heat exchange capacity is above 1700 KW / m 2 ·K.

29. The preparation method according to any one of claims 1 to 6, characterized in that, The microchannel reactor is a microporous array type microchannel reactor, a finned microchannel reactor, a capillary microchannel reactor or a multi-stream parallel flow microreactor.

30. The preparation method according to any one of claims 1 to 6, characterized in that, The straight-through channel structure is a tubular structure.

31. The preparation method according to any one of claims 1 to 6, characterized in that, The enhanced hybrid channel structure is a T-shaped structure, a spherical structure, a spherical structure with baffles, a water droplet-shaped structure or a heart-shaped structure.

32. The preparation method according to any one of claims 1 to 6, characterized in that, The number of microchannel reaction modules of the microchannel reactor is 5 to 8.

33. The preparation method according to any one of claims 1 to 6, characterized in that, The number of microchannel reaction modules of the microchannel reactor is 6.

34. The preparation method according to any one of claims 1 to 6, characterized in that, The channel diameter is 0.5 mm to 10 mm.

35. The preparation method according to any one of claims 1 to 6, characterized in that, The material of the microchannel reaction module is selected from Hastelloy C alloy and / or Monel alloy.

36. The preparation method according to any one of claims 1 to 6, characterized in that, 2-cyanopyridine, a catalyst and a solvent enter the microchannel reaction module after being preheated in the preheating module.

37. The preparation method according to any one of claims 1 to 6, characterized in that, The preheated mixed solution of 2-cyanopyridine, a catalyst and a solvent and acetylene enter the microchannel reaction module for reaction.

38. The preparation method according to claim 37, characterized in that, The mixed solution of 2-cyanopyridine, a catalyst and a solvent and acetylene enter several microchannel reaction modules for reaction in sequence.

39. The preparation method according to any one of claims 1 to 6, characterized in that, The quenching module is a Corning straight channel, and the reaction is stopped by cooling in the quenching module.

40. The preparation method according to any one of claims 1 to 6, characterized in that, Each material is dehydrated and dried before the reaction.

41. The preparation method according to any one of claims 1 to 6, characterized in that, Temperature measuring points are respectively arranged at the feed inlet and the discharge outlet of the microchannel reactor.

42. The preparation method according to any one of claims 1 to 6, characterized in that, The reaction materials are distilled to obtain the product.

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