A system and method for the synthesis of high purity n,n-dimethylformamide

Abstract

The application relates to the field of N,N-dimethylformamide, and specifically provides a high-purity N,N-dimethylformamide synthesis system and method, which comprises a fixed bed reactor; a cooling pipe is fixedly connected in the fixed bed reactor; a connecting pipe is communicated in the cooling pipe; and a gas pump is fixedly connected to one end of the connecting pipe away from the cooling pipe; when the fixed bed reactor is working, the temperature inside the fixed bed reactor continuously rises; when the temperature rises to more than 400 DEG, a first control valve on a water inlet pipe is opened; then cold water is injected into the cooling pipe from the water inlet pipe; and then the first control valve is closed; at this time, the cooling pipe absorbs the heat inside the fixed bed reactor due to the cold water, so that the temperature inside the fixed bed reactor is reduced, and the problems of catalyst coking due to local overheating, increased side reactions and reduced catalyst utilization rate when the temperature inside the reactor is too high are reduced.

Description

Technical Field

[0001] This invention relates to the field of N,N-dimethylformamide synthesis technology, and to a synthesis system and method for high-purity N,N-dimethylformamide. Background Technology

[0002] Existing N,N-dimethylformamide synthesis systems consist of a combination of multiple instruments, the most important of which is a fixed-bed reactor, which needs to operate in a high-temperature environment.

[0003] A Chinese patent with publication number CN112898174A discloses a method for preparing N,N-dimethylformamide. This method uses dimethylamine and carbon monoxide (CO) as reactants, and DMF is prepared via a carbonylation reaction involving CO insertion under catalysis. The reaction conditions are as follows: the reaction is carried out in a fixed-bed reactor at a pressure of 1.0–8.0 MPa.

[0004] When N,N-dimethylformamide is synthesized in a fixed-bed reactor, multiple reactors need to be connected in parallel within the fixed-bed reactor. The catalyst is loaded into the tubes for the reaction, and the temperature inside the reactor needs to be controlled in a timely manner. When the temperature inside the reactor is too high, problems such as catalyst coking due to local overheating, increased side reactions, and decreased catalyst utilization will occur. Summary of the Invention

[0005] In view of the above-mentioned technical problems existing in the prior art, the purpose of this invention is to provide a synthesis system and method for high-purity N,N-dimethylformamide, which can rapidly cool down a fixed-bed reactor.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A synthesis system for high-purity N,N-dimethylformamide includes a fixed-bed reactor; a cooling pipe is connected inside the fixed-bed reactor, the cooling pipe is connected to an air pump, a piston is slidably connected inside the cooling pipe, and a first outlet pipe and an inlet pipe are connected inside the fixed-bed reactor, with a first control valve fixedly installed on both the first outlet pipe and the inlet pipe.

[0008] Furthermore, the cooling pipe provided by the present invention is connected to a U-shaped pipe, and the cooling pipe is connected to an air outlet pipe. A first solenoid valve is fixedly installed on the air outlet pipe. An elastic rope is connected to the side of the piston near the air pump, and the end of the elastic rope away from the piston is fixedly connected to the inner wall of the cooling pipe.

[0009] During operation, water is injected into the cooling pipe, flowing into the U-shaped tube. The U-shaped tube increases the rate of heat absorption within the fixed-bed reactor. Simultaneously, the cooling pipe is not fully filled. Then, an air pump continuously injects gas into the cooling pipe, pushing a piston. This piston then forces the water in the cooling pipe and U-shaped tube to flow. When the piston can no longer be pushed, the first solenoid valve on the outlet pipe automatically opens, allowing air to escape. The elastic rope then pulls the piston back to its original position. Once the piston moves behind the outlet pipe, the first solenoid valve closes, and the gas continues to push the piston. This causes the piston to move the water back and forth within the cooling pipe and U-shaped tube, effectively increasing the water's heat absorption within the fixed-bed reactor.

[0010] Furthermore, the U-shaped tube provided by the present invention has a second water outlet pipe connected to the bend, and a second solenoid valve is fixedly connected to the second water outlet pipe.

[0011] Furthermore, the cooling pipe provided by the present invention is connected to the conduit inside, and a fixing plate is fixedly connected to the inner wall of the cooling pipe. A rotating shaft is rotatably connected to the side of the fixing plate near the piston, and a plurality of stirring blades are fixedly connected to the rotating shaft.

[0012] Furthermore, the cooling pipe provided by the present invention has a connecting pipe inside, an air pump is fixedly connected to the end of the connecting pipe away from the cooling pipe, a second control valve is fixedly installed on the connecting pipe, and a conduit is connected to the connecting pipe.

[0013] During operation, when the air pump injects gas into the piston, the pressure pushing the piston causes some of the gas to enter the conduit. At this time, the gas in the conduit enters the water in the cooling pipe, causing the water flow to impact the agitator blade. The agitator blade then stirs the water in the cooling pipe. This water flow agitation can improve the heat absorption in the fixed bed reactor and improve the water temperature uniformity. At the same time, the gas ejected from the conduit will exert a force on the liquid at the end of the U-shaped tube near the agitator blade, promoting the water flow in the U-shaped tube.

[0014] Furthermore, the present invention provides that each of the several stirring blades is fixedly connected with a connecting line, and a ball made of rubber is fixedly connected to the end of the connecting line away from the stirring blade. During operation, when the stirring blade rotates, the connecting line will drive the ball to rotate, and the ball will stir the water, thereby further improving the stirring effect on the water.

[0015] Furthermore, the cooling pipe provided by the present invention has a first magnet fixedly connected to the inner wall of the corresponding stirring blade, and a second magnet is fixedly connected to each of the stirring blades. When the second magnet moves to the position of the first magnet, the end of the second magnet closer to the first magnet attracts it, and the end of the second magnet farther from the first magnet repels it. The present invention can increase the rotation speed of the stirring blade by utilizing the repulsive and attractive forces of the first and second magnets, thereby improving the stirring effect on the water.

[0016] Furthermore, the end of the first outlet pipe away from the cooling pipe provided by the present invention is connected to a recovery box. One side of the recovery box is fixedly connected to the fixed bed reactor. A drawer is slidably connected inside the recovery box. A sleeve is fitted on the surface of the cooling pipe. A heat-conducting pipe is connected inside the sleeve. The other end of the heat-conducting pipe is connected to the recovery box.

[0017] This invention also provides a method for synthesizing high-purity N,N-dimethylformamide, which utilizes the aforementioned high-purity N,N-dimethylformamide synthesis system and includes the following steps:

[0018] (1) Select dimethylamine and CO as raw materials, then pass CO into a fixed bed reactor and put dimethylamine into the fixed bed reactor (1) for reaction;

[0019] (2) A composite catalyst is added to the reaction tube of the fixed bed reactor (1) to react with the raw materials. The reaction pressure is 1.2-8.4 MPa. When the temperature inside the fixed bed reactor (1) is too high, water is added to the cooling tube (5) to cool down the fixed bed reactor (1).

[0020] (3) Wait for the raw materials to be synthesized into N,N-dimethylformamide in the fixed bed reactor (1) under high temperature and catalyst reaction.

[0021] Specifically, the present invention utilizes the above-described high-purity N,N-dimethylformamide synthesis system for cooling. The specific steps for cooling the fixed-bed reactor by adding water into the cooling pipe are as follows:

[0022] (1) Open the first control valve on the water inlet pipe, and cold water is injected into the cooling pipe from the water inlet pipe. Then close the first control valve on the water inlet pipe.

[0023] (2) When the water temperature is constant, open the first control valve on the first outlet pipe so that the water is discharged from the first outlet pipe. Start the air pump so that the air pump injects gas into the connecting pipe. The gas enters the cooling pipe and pushes the piston so that the piston pushes all the water in the cooling pipe out of the first outlet pipe.

[0024] When water is injected into the cooling pipe, the water flows into the connected U-shaped pipe. The air pump continuously injects gas into the cooling pipe, and the gas pushes the piston. The piston pushes the water in the cooling pipe and the U-shaped pipe to flow. When the piston can no longer be pushed, the first solenoid valve on the vent pipe opens automatically, and the air is discharged from the vent pipe. The elastic rope pulls the piston to reset. When the piston moves to the rear of the vent pipe, the first solenoid valve closes, and the gas continues to push the piston. At this time, the piston pushes the water back and forth to flow in the cooling pipe and the U-shaped pipe.

[0025] When the air pump injects gas into the piston, some of the gas enters the duct, and the gas in the duct enters the water in the cooling pipe (5). The water flow impacts the agitator, and the agitator stirs the water in the cooling pipe. At the same time, the gas ejected from the duct will exert a force on the liquid at the end of the U-shaped tube near the agitator, promoting the flow of water in the U-shaped tube.

[0026] When the agitator blade rotates, the connecting line drives the ball to rotate, the ball agitates the water, and the agitator blade rotates counterclockwise under the impact of the water flow. At this time, when the second magnet has not passed the first magnet, the first magnet and the second magnet attract each other, and when the second magnet passes the first magnet, they repel each other. The rotation speed of the agitator blade is increased by using the repulsive and attractive forces of the first magnet and the second magnet.

[0027] When the water in the U-shaped tube is discharged, the sealing plug on the second outlet pipe is removed. At this time, the water will be discharged from the second outlet pipe. The heat of the fixed bed reactor is absorbed through the sleeve, and the heat enters the recovery box through the heat conduction pipe. At this time, other things can be dried in the recovery box, which plays a role in heat recovery. When the water in the cooling pipe is discharged, the water enters the drawer from the first outlet pipe and is recovered by the drawer.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. When the fixed-bed reactor is in operation, the internal temperature of the fixed-bed reactor will continue to rise. When the temperature rises to more than 400 degrees, the first control valve on the inlet pipe is opened, and then cold water is injected into the cooling pipe from the inlet pipe. Then the first control valve is closed. At this time, the cooling pipe will absorb the heat inside the fixed-bed reactor due to the cold water, thereby achieving the effect of cooling the inside of the fixed-bed reactor. This reduces the problems of catalyst coking due to local overheating, increased side reactions, and decreased catalyst utilization rate that may occur when the temperature inside the reactor is too high.

[0030] 2. Water is injected into the cooling pipe, flowing into the U-shaped tube. The U-shaped tube increases the rate of heat absorption in the fixed-bed reactor. Simultaneously, the cooling pipe is not fully filled. An air pump continuously injects gas into the cooling pipe, pushing a piston. This piston then forces the water to flow through the cooling pipe and U-shaped tube. When the piston can no longer be pushed, the first solenoid valve on the outlet pipe automatically opens, allowing air to escape. The elastic rope then pulls the piston back to its original position. Once the piston moves behind the outlet pipe, the first solenoid valve closes, and the gas continues to push the piston. This causes the piston to move the water back and forth within the cooling pipe and U-shaped tube, effectively increasing the water's heat absorption within the fixed-bed reactor.

[0031] 3. When the air pump pushes the piston, some gas enters the conduit. At this time, the gas in the conduit enters the water in the cooling pipe, causing the water flow to impact the agitator blade. The agitator blade then stirs the water in the cooling pipe. This water flow agitation can improve the heat absorption in the fixed bed reactor and improve the water temperature uniformity. At the same time, the gas ejected from the conduit will exert a force on the liquid at the end of the U-shaped tube near the agitator blade, promoting the water flow in the U-shaped tube. When the agitator blade rotates, the connecting line will drive the sphere to rotate. At this time, the sphere will stir the water, thereby further improving the water stirring effect.

[0032] 4. By using the repulsive and attractive forces between the first and second magnets, the rotation speed of the stirring blade can be increased, thereby improving the stirring effect on the water. Attached Figure Description

[0033] Figure 1 This is a partial cross-sectional view of the fixed-bed reactor of the present invention;

[0034] Figure 2 This is a three-dimensional structural diagram of the cooling pipe in this invention;

[0035] Figure 3 In this invention Figure 2 Enlarged view of point A;

[0036] Figure 4 In this invention Figure 1 Enlarged view of point B;

[0037] Figure 5 This is a flowchart of the synthesis method of the present invention.

[0038] In the diagram: 1. Fixed-bed reactor; 2. Air pump; 3. Connecting pipe; 4. First control valve; 5. Cooling pipe; 6. Piston; 7. Water inlet pipe; 8. Second control valve; 9. First water outlet pipe; 10. Guide tube; 11. Fixing plate; 12. Rotating shaft; 13. Stirring blade; 14. Connecting line; 15. Ball; 16. First magnet; 17. Second magnet; 18. U-tube; 19. Air outlet pipe; 20. Elastic rope; 21. Second water outlet pipe; 22. Sleeve; 23. Heat conduction pipe; 24. Recovery box; 25. Drawer; 26. Second solenoid valve. Detailed Implementation

[0039] The present invention will be further described below with reference to specific implementation examples. However, the description of the following embodiments is only for the purpose of helping to understand the principles and core ideas of the present invention, and is not intended to limit the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements made to the present invention without departing from the principles of the present invention also fall within the scope of protection of the claims of the present invention.

[0040] The following is in conjunction with the appendix Figure 1-5 The present invention provides a detailed description of the specific implementation of a synthesis system and method for high-purity N,N-dimethylformamide.

[0041] Example 1

[0042] This embodiment provides a synthesis system for high-purity N,N-dimethylformamide, combined with the attached... Figure 1-5 This section will explain its specific structure and working principle.

[0043] like Figure 1-4As shown in the embodiment of the present invention, a synthesis system for high-purity N,N-dimethylformamide includes a fixed-bed reactor 1. A cooling pipe 5 is fixedly connected inside the fixed-bed reactor 1, and a connecting pipe 3 is connected inside the cooling pipe 5. An air pump 2 is fixedly connected to the end of the connecting pipe 3 away from the cooling pipe 5. A piston 6 is slidably connected inside the cooling pipe 5. A first outlet pipe 9 and an inlet pipe 7 are connected inside the fixed-bed reactor 1. A sealing plug is sealed inside the inlet pipe 7. A first control valve 4 is fixedly installed on both the first outlet pipe 9 and the inlet pipe 7. During operation, when the fixed-bed reactor 1 is working, the temperature inside the fixed-bed reactor 1 will continuously rise. When the temperature rises to over 400 degrees Celsius, the valve on the inlet pipe 7 is opened. First control valve 4 is used. Then, cold water is injected into cooling pipe 5 from water inlet pipe 7. Then, first control valve 4 is closed. At this time, cooling pipe 5 will absorb heat from the inside of fixed bed reactor 1 due to the cold water, thereby achieving the effect of cooling the inside of fixed bed reactor 1. This reduces the problems of catalyst coking due to local overheating, increased side reactions, and decreased catalyst utilization when the temperature inside the reactor is too high. After the water temperature is constant, first control valve 4 on first water outlet pipe 9 is opened, allowing water to be discharged from first water outlet pipe 9. Then, air pump 2 is started, allowing air pump 2 to inject gas into connecting pipe 3. At this time, the gas will enter cooling pipe 5 and push piston 6, causing piston 6 to push all the water in cooling pipe 5 out of first water outlet pipe 9. Piston 6 is made of steel.

[0044] In a preferred embodiment, the cooling pipe 5 provided by the present invention is connected to a U-shaped pipe 18, and an air outlet pipe 19 is also connected to the cooling pipe 5. A first solenoid valve is fixedly installed on the air outlet pipe 19. An elastic rope 20 is fixedly connected to the side of the piston 6 near the air pump 2, and the end of the elastic rope 20 away from the piston 6 is fixedly connected to the inner wall of the cooling pipe 5. During operation, water is injected into the cooling pipe 5, which then flows into the U-shaped pipe 18. The U-shaped pipe 18 can increase the heat absorption rate in the fixed bed reactor 1. At the same time, the water in the cooling pipe 5 is not full. Then, the air pump 2 is used to circulate the water in the cooling pipe 5. Gas is continuously injected, causing the gas to push piston 6. At this time, piston 6 will push the water in cooling pipe 5 and U-shaped tube 18 to flow. When piston 6 can no longer be pushed, the first solenoid valve on the exhaust pipe 19 will automatically open, and air will be discharged from the exhaust pipe 19. Then, elastic rope 20 will pull piston 6 to reset. After piston 6 moves behind exhaust pipe 19, the first solenoid valve will close, and gas will continue to push piston 6. At this time, piston 6 will push the water back and forth in cooling pipe 5 and U-shaped tube 18, which will make the water flow and thus enhance the heat absorption effect of water in fixed bed reactor 1.

[0045] In a preferred embodiment, a second control valve 8 is fixedly installed on the connecting pipe 3 provided by the present invention. A conduit 10 is connected to the connecting pipe 3. The conduit 10 is internally connected to the cooling pipe 5, and the section of the conduit 10 connected to the cooling pipe 5 is inclined. A fixing plate 11 is fixedly connected to the inner wall of the cooling pipe 5. An inclined rotating shaft 12 is rotatably connected to the side of the fixing plate 11 near the piston 6. An agitator 13 is fixedly connected to the surface of the rotating shaft 12. During operation, when the air pump 2 injects gas into the piston 6, the pressure pushing the piston 6 causes some gas to enter the conduit 10. At this time, the gas in the conduit 10 will enter the water in the cooling pipe 5, causing the water flow to impact the agitator 13. The agitator 13 will then agitate the water in the cooling pipe 5. The agitation of the water flow can improve the heat absorption effect in the fixed bed reactor 1 and improve the water temperature uniformity. At the same time, the gas ejected from the conduit 10 will exert a force on the liquid at the end of the U-shaped tube 18 near the agitator 13, promoting the water flow in the U-shaped tube 18.

[0046] In a preferred embodiment, the stirring blade 13 provided by the present invention is uniformly and fixedly connected with a connecting line 14, and a ball 15 is fixedly connected to one end of the connecting line 14 away from the stirring blade 13. The ball 15 is made of rubber material. When the stirring blade 13 rotates, the connecting line 14 will drive the ball 15 to rotate. At this time, the ball 15 will stir the water, thereby further improving the stirring effect of the water.

[0047] In a preferred embodiment, the cooling pipe 5 provided by the present invention is fixedly connected to the inner wall of the stirring blade with a first magnet 16. The stirring blade is uniformly fixedly connected with a second magnet 17. When the second magnet 17 moves to the position of the first magnet 16, the end of the second magnet 17 close to the first magnet 16 attracts it, and the end of the second magnet 17 away from the first magnet 16 repels it. During operation, the stirring blade 13 rotates counterclockwise under the impact of the water flow. At this time, when a second magnet 17 has not passed the first magnet 16, the first magnet 16 will attract the second magnet 17. When a second magnet 17 passes the first magnet 16, they will repel each other. By using the repulsive and attractive forces of the first magnet 16 and the second magnet 17, the rotation speed of the stirring blade 13 can be increased, thereby improving the stirring effect on the water.

[0048] In a preferred embodiment, the bend of the U-shaped tube 18 provided by the present invention is connected to a second water outlet pipe 21, and the water outlet end of the second water outlet pipe 21 is connected to a sealing plug. During operation, when it is necessary to drain the water in the U-shaped tube 18, the second solenoid valve 26 is opened, and the water will be drained from the second water outlet pipe 21 to avoid water remaining in the U-shaped tube 18. After the water is drained, the second solenoid valve 26 is closed.

[0049] In a preferred embodiment, the end of the first water outlet pipe 9 away from the cooling pipe 5 is connected to a recovery box 24. One side of the recovery box 24 is fixedly connected to the fixed bed reactor 1. A drawer 25 is slidably connected inside the recovery box 24. A sleeve 22 is fitted on the surface of the cooling pipe 5. A heat-conducting pipe 23 is connected inside the sleeve 22. The other end of the heat-conducting pipe 23 is connected to the recovery box 24. During operation, the sleeve 22 can absorb the heat from the fixed bed reactor 1, allowing the heat to enter the recovery box 24 through the heat-conducting pipe 23. At this time, other items can be dried inside the recovery box 24, thus recovering the heat. When the water in the cooling pipe 5 is discharged, the water will enter the drawer 25 from the first water outlet pipe 9 and be recovered by the drawer 25. The sleeve 22 is a hollow copper sleeve.

[0050] Example 2

[0051] like Figure 5 As shown, this embodiment provides a method for synthesizing high-purity N,N-dimethylformamide. This method is applicable to the above-mentioned synthesis system for high-purity N,N-dimethylformamide and includes the following steps:

[0052] S1: Dimethylamine and CO are selected as raw materials, and then the raw material dimethylamine is put into fixed bed reactor 1 for reaction;

[0053] S2: A copper-based composite catalyst is added to the reaction tube of the fixed-bed reactor 1 to react with the raw materials. The reaction pressure is 1.2-8.4 MPa. When the temperature inside the fixed-bed reactor 1 is too high, water is added to the cooling pipe 5 to cool the fixed-bed reactor.

[0054] S3: Wait for the raw materials to be synthesized into N,N-dimethylformamide under high temperature and catalyst reaction in fixed bed reactor 1.

[0055] By reacting the raw materials at a pressure of 1.2-8.4 MPa, the purity of the final synthesized N,N-dimethylformamide can be improved.

[0056] When the temperature inside the fixed-bed reactor 1 is too high, water is added to the cooling pipe 5 to cool the reactor. The specific cooling steps are as follows:

[0057] like Figure 1-4As shown, when the fixed-bed reactor 1 is working, the internal temperature of the fixed-bed reactor 1 will continuously rise. When the temperature exceeds 400 degrees Celsius, the first control valve 4 on the inlet pipe 7 is opened, and cold water is injected into the cooling pipe 5 from the inlet pipe 7. Then, the first control valve 4 is closed. At this time, the cooling pipe 5 absorbs heat from the fixed-bed reactor 1 due to the cold water, thereby cooling the internal temperature of the fixed-bed reactor 1. This reduces the problems of catalyst coking due to local overheating, increased side reactions, and decreased catalyst utilization caused by excessively high temperatures inside the reactor. After the water temperature stabilizes, the first control valve 4 on the first outlet pipe 9 is opened, allowing water to be discharged from the first outlet pipe 9. Then, the air pump 2 is started, allowing... Gas is injected into the connecting pipe 3 by air pump 2. This gas enters the cooling pipe 5 and pushes piston 6, causing piston 6 to push all the water in the cooling pipe 5 out through the first water outlet pipe 9. Piston 6 is made of steel. Water is injected into the cooling pipe 5, flowing into the U-shaped tube 18. The U-shaped tube 18 increases the heat absorption rate in the fixed-bed reactor 1. Simultaneously, the water in the cooling pipe 5 and U-shaped tube 18 is not completely filled. Air pump 2 then continuously injects gas into the cooling pipe 5, causing the gas to push piston 6. Piston 6 then pushes the water in the cooling pipe 5 and U-shaped tube 18 to flow. When piston 6 can no longer be pushed, the first solenoid valve on the air outlet pipe 19 automatically opens, allowing air to escape from the air outlet pipe 19. The sex rope 20 pulls the piston 6 to reset. Then, when the piston 6 moves behind the outlet pipe 19, the first solenoid valve closes, and the gas continues to push the piston 6. At this time, the piston 6 pushes the water back and forth within the cooling pipe 5 and the U-shaped pipe 18, thus enhancing the water's heat absorption effect within the fixed-bed reactor 1. When the air pump 2 injects gas into the piston 6, the pressure pushing the piston 6 causes some gas to enter the conduit 10. This gas then enters the water in the cooling pipe 5, causing the water flow to impact the agitator 13. The agitator 13 then stirs the water in the cooling pipe 5. This water agitation enhances the heat absorption within the fixed-bed reactor 1, improves the water's temperature uniformity, and simultaneously... The gas ejected from tube 10 exerts a force on the liquid at the end of U-shaped tube 18 near the stirring blade 13, promoting the flow of water within U-shaped tube 18. When the stirring blade 13 rotates, the connecting line 14 drives the ball 15 to rotate, which in turn agitates the water, further enhancing the agitation effect. Under the impact of the water flow, the stirring blade 13 rotates counterclockwise. When a second magnet 17 has not passed the first magnet 16, the first magnet 16 attracts the second magnet 17. When the second magnet 17 passes the first magnet 16, they repel each other. By utilizing the repulsive and attractive forces of the first magnet 16 and the second magnet 17, the rotation speed of the stirring blade 13 can be increased, thereby enhancing the agitation effect on the water.When it is necessary to drain the water from the U-tube 18, remove the sealing plug on the second outlet pipe 21. The water will then drain from the second outlet pipe 21, preventing water residue from remaining in the U-tube 18. The hollow copper sleeve 22 absorbs heat from the fixed-bed reactor 1, allowing the heat to enter the recovery box 24 through the heat pipe 23. This allows other items to be dried within the recovery box 24, thus recovering heat. When the water in the cooling pipe 5 is drained, it will enter the drawer 25 from the first outlet pipe 9 and be recovered by the drawer 25.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A synthesis system for high-purity N,N-dimethylformamide, characterized in that: The reactor includes a fixed bed reactor (1); a cooling pipe (5) is connected inside the fixed bed reactor (1), the cooling pipe (5) is connected to an air pump (2), a piston (6) is slidably connected inside the cooling pipe (5), a first outlet pipe (9) and an inlet pipe (7) are connected inside the fixed bed reactor (1), and a first control valve (4) is fixedly installed on both the first outlet pipe (9) and the inlet pipe (7); The cooling pipe (5) is connected to a U-shaped pipe (18), and the cooling pipe (5) is connected to an air outlet pipe (19). A first solenoid valve is fixedly installed on the air outlet pipe (19). The piston (6) is connected to an elastic rope (20) on the side near the air pump (2). The end of the elastic rope (20) away from the piston (6) is fixedly connected to the inner wall of the cooling pipe (5). The cooling pipe (5) is connected to the conduit (10). A fixing plate (11) is fixedly connected to the inner wall of the cooling pipe (5). A rotating shaft (12) is rotatably connected to the side of the fixing plate (11) near the piston (6). Several stirring blades (13) are fixedly connected to the rotating shaft (12). The cooling pipe (5) is connected to a connecting pipe (3), and an air pump (2) is fixedly connected to one end of the connecting pipe (3) away from the cooling pipe (5). A second control valve (8) is fixedly installed on the connecting pipe (3), and a conduit (10) is connected to the connecting pipe (3).

2. The synthesis system for high-purity N,N-dimethylformamide according to claim 1, characterized in that: The bend of the U-shaped pipe (18) is connected to a second water outlet pipe (21), and a second solenoid valve (26) is fixedly connected to the second water outlet pipe (21).

3. The synthesis system for high-purity N,N-dimethylformamide according to claim 1, characterized in that: A connecting line (14) is fixedly connected to each of the agitating blades (13), and a ball (15) is fixedly connected to one end of the connecting line (14) away from the agitating blade (13).

4. The synthesis system for high-purity N,N-dimethylformamide according to claim 1, characterized in that: The cooling pipe (5) is fixedly connected to the inner wall of the agitator (13) with a first magnet (16). Several agitators are fixedly connected with second magnets (17). When the second magnet (17) moves to the position of the first magnet (16), the end of the second magnet (17) close to the first magnet (16) attracts it, and the end of the second magnet (17) away from the first magnet (16) repels it.

5. The synthesis system for high-purity N,N-dimethylformamide according to claim 1, characterized in that: The end of the first water outlet pipe (9) away from the cooling pipe (5) is connected to a recovery box (24). One side of the recovery box (24) is fixedly connected to the fixed bed reactor (1). A drawer (25) is slidably connected inside the recovery box (24). A sleeve (22) is fitted on the surface of the cooling pipe (5). A heat-conducting pipe (23) is connected inside the sleeve (22). The other end of the heat-conducting pipe (23) is connected to the recovery box (24).

6. A method for synthesizing high-purity N,N-dimethylformamide, the method being applicable to the synthesis system of high-purity N,N-dimethylformamide according to any one of claims 1-5, characterized in that: Includes the following steps: (1) Select dimethylamine and CO as raw materials, then pass CO into a fixed bed reactor and put dimethylamine into the fixed bed reactor (1) for reaction; (2) A composite catalyst is added to the reaction tube of the fixed bed reactor (1) to react with the raw materials. The reaction pressure is 1.2-8.4 MPa. When the temperature inside the fixed bed reactor (1) is too high, water is added to the cooling tube (5) to cool down the fixed bed reactor (1). (3) Wait for the raw materials to be synthesized into N,N-dimethylformamide in the fixed bed reactor (1) under high temperature and catalyst reaction.

7. The method for synthesizing high-purity N,N-dimethylformamide as described in claim 6, characterized in that: The specific steps for cooling the fixed-bed reactor (1) by adding water into the cooling pipe (5) are as follows: (1) Open the first control valve (4) on the water inlet pipe (7), cold water is injected into the cooling pipe from the water inlet pipe (7), and then close the first control valve (4) on the water inlet pipe (7). (2) When the water temperature is constant, open the first control valve (4) on the first outlet pipe (9) so that the water is discharged from the first outlet pipe (9). Start the air pump (2) so that the air pump (2) injects gas into the connecting pipe (3). The gas enters the cooling pipe (5) and pushes the piston (6) so that the piston (6) pushes all the water in the cooling pipe (5) out of the first outlet pipe (9). When water is injected into the cooling pipe, the water flows into the connected U-shaped pipe (18). The air pump (2) continuously injects gas into the cooling pipe (5). The gas pushes the piston (6), and the piston (6) pushes the water in the cooling pipe (5) and the U-shaped pipe (18) to flow. When the piston (6) can no longer be pushed, the first solenoid valve on the air outlet pipe (19) opens automatically, and the air is discharged from the air outlet pipe (19). The elastic rope (20) pulls the piston (6) to reset. When the piston (6) moves to the back of the air outlet pipe (19), the first solenoid valve closes, and the gas continues to push the piston (6). At this time, the piston (6) pushes the water back and forth to flow in the cooling pipe (5) and the U-shaped pipe (18). When the air pump (2) injects gas into the piston (6), some of the gas enters the conduit (10), and the gas in the conduit (10) enters the water in the cooling pipe (5). The water flow impacts the agitator (13), and the agitator (13) agitates the water in the cooling pipe (5). At the same time, the gas ejected from the conduit (10) will exert a force on the liquid at the end of the U-shaped tube (18) near the agitator (13), promoting the flow of water in the U-shaped tube (18). When the agitator (13) rotates, the connecting line (14) drives the ball (15) to rotate. The ball (15) agitates the water. The agitator (13) rotates counterclockwise under the impact of the water flow. At this time, when the second magnet (17) has not passed the first magnet (16), the first magnet (16) and the second magnet (17) attract each other. When the second magnet (17) passes the first magnet (16), they repel each other. The rotation speed of the agitator (13) is increased by the force of repulsion and attraction between the first magnet (16) and the second magnet (17). When the water in the U-shaped tube (18) is discharged, the sealing plug on the second outlet pipe (21) is removed. At this time, the water will be discharged from the second outlet pipe (21) and absorb the heat of the fixed bed reactor (1) through the sleeve (22). The heat will enter the recovery box (24) through the heat conduction pipe (23). At this time, other things are dried in the recovery box (24), which plays the role of heat recovery. When the water in the cooling pipe (5) is discharged, the water enters the drawer (25) from the first outlet pipe (9) and is recovered by the drawer (25).

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