A DMF synthesis device and method

Abstract

The present invention belongs to the technical field of chemical synthesis, and specifically relates to a DMF synthesis device and method. The DMF synthesis device includes at least one synthesis tube and at least one heat exchange tube. It is characterized in that the synthesis tube is arranged inside the heat exchange tube and both ends of the synthesis tube extend out of the heat exchange tube; cooling water is introduced into the heat exchange tube. The lower end of the synthesis tube is connected to a gas supply pipeline for introducing carbon monoxide gas, and the upper end of the synthesis tube is connected to a liquid supply pipeline for introducing a mixed liquid. An annular liquid supply tube is arranged inside the upper end of the synthesis tube, and the annular liquid supply tube is communicated with the liquid supply pipeline; liquid outlet holes are arranged on the annular liquid supply tube. The present invention avoids the crystallization product from adhering to the outer wall of the cooling device, reduces the workload of clearing the crystallization product. In addition, the heat exchange tube can timely discharge the heat generated by the reaction, avoiding the problem that the heat in the central area of the synthesis tube cannot be discharged in time, resulting in a decrease in the reaction rate.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical synthesis, and particularly relates to a DMF synthesis device and method. Background Art

[0002] DMF, whose full Chinese name is N,N-dimethylformamide, is a colorless and transparent liquid that can be miscible with water and most organic solvents. As an important chemical raw material and a solvent with excellent properties, DMF is mainly used in industries such as polyurethane, acrylic fiber, medicine, pesticide, dye, and electronics.

[0003] Currently, the commonly used method for synthesizing DMF industrially is to react dimethylamine with carbon monoxide in the presence of a catalyst in one step to synthesize DMF. Commonly used catalysts in the synthesis process include sodium methoxide, metal carbonyl compounds, quaternary ammonium salts, etc. Among them, sodium methoxide is a catalyst widely used in the one-step synthesis method of DMF due to its high catalytic rate, low cost, and suitability for large-scale production.

[0004] The reaction of synthesizing DMF using sodium methoxide as a catalyst is an exothermic reaction. As the reaction progresses, the temperature in the reaction kettle increases, which will cause the crystallization and precipitation of sodium methoxide, and thus is not conducive to the progress of the reaction. Therefore, the entire reaction process needs to be maintained within a constant temperature range, so it is necessary to timely take out the heat generated by the reaction from the reaction device during the reaction process. The usual practice is to set up a circulating cooling pipe in the space where carbon monoxide and dimethylamine react, and circulating cooling water is introduced into the cooling pipe to timely take out the heat released by the reaction from the reaction area. For example, a DMF synthesis and device disclosed in the prior art CN101337904B. The synthesis device includes a reactor, a cooling medium heat exchange device, and a cooling medium circulation pump provided between the reactor and the cooling medium heat exchange device. The reactor, the cooling medium circulation pump, and the cooling medium heat exchange device form a closed system, and a buffer tank is provided between the cooling medium outlet of the reactor and the cooling medium circulation pump; CO and dimethylamine are synthesized into DMF in one step in the reactor and the heat generated in the reactor is taken away by the cooling medium. Its characteristics are that the temperature of the cooling medium entering the reactor is controlled to be 90 - 94 °C, and the temperature of the cooling medium leaving the reactor is 94 - 98 °C; the cooling medium exchanges heat with the substances in the reactor through the U-shaped tube bundle provided in the reactor. Although this synthesis device takes away the heat generated by the reaction through the cooling medium, in actual use, there are still a large number of crystallization products on the outer wall of the U-shaped tube bundle and the inner wall of the reactor, and the improvement degree of the reaction efficiency is very limited.

[0005] This is because when sodium methoxide is used as a catalyst, sodium methoxide easily reacts with impurities in the reaction raw materials to form by-products such as sodium formate and sodium carbonate. These by-products crystallize on the inner wall of the reaction device and the outer wall of the cooling pipe in the reaction area. As the reaction time continues to extend, the crystallization accumulates continuously, affecting the gas-liquid two-phase contact of the reaction, resulting in a decrease in reaction efficiency, and it is necessary to stop the machine for cleaning regularly according to the production cycle.

[0006] Therefore, the prior art CN218872231U provides an N,N-dimethylformamide synthesis system, which includes a reactor, a CO purifier, and a circulating cooling system. The outer side of the inner wall of the reactor is connected to the circulating cooling system to adjust the inner cavity temperature; the inlet of the CO purifier is connected to the raw gas supply device, and the outlet is connected to the inner cavity of the reactor; several trays are staggered in the reactor. A dimethylamine feed port and a catalyst feed port are respectively arranged above the tray, and an inlet and an outlet for inputting raw gas are arranged at the lower part; the tray is provided with a liquid receiving tray with uniformly distributed guiding holes. An overflow weir is vertically arranged on the upper surface of the liquid receiving tray, and a downcomer is vertically arranged on the lower surface. A bubble promoter is arranged at the front part of the tray where the liquid enters the guiding hole.

[0007] The synthesis system sets a circulating cooling system on the outer wall of the reactor to prevent by-products from crystallizing and adhering to the outer wall of the cooling system. However, after the cooling system is set on the outer wall, it will cause uneven heat exchange between the cooling system and the reactor, resulting in uneven temperature distribution inside the reactor, and the heat in the central area of the reactor cannot be taken out in time, thereby affecting the reaction efficiency. Summary of the Invention

[0008] In order to solve the technical problem in the prior art that the heat inside the reactor cannot be taken out in time and the stable operation of the cooling system is not affected, the present invention provides a DMF synthesis device and method.

[0009] To achieve the above object, the technical solution of the present invention is as follows:

[0010] A DMF synthesis device includes: at least one synthesis tube and at least one heat exchange tube. The synthesis tube is arranged inside the heat exchange tube and both ends of the synthesis tube extend out of the heat exchange tube; cooling water is introduced into the heat exchange tube. The lower end of the synthesis tube is connected to a gas supply pipe for introducing carbon monoxide gas, and the upper end of the synthesis tube is connected to a liquid supply pipe for introducing a mixed liquid. An annular liquid supply pipe is arranged inside the upper end of the synthesis tube, and the annular liquid supply pipe is communicated with the liquid supply pipe; liquid outlet holes are arranged on the annular liquid supply pipe.

[0011] Further, the liquid outlet holes are arranged at the bottom of the annular liquid supply pipe, and the liquid outlet direction of the liquid outlet holes faces the inner wall of the synthesis tube.

[0012] Further, a plurality of liquid outlet holes are provided, and the plurality of liquid outlet holes are evenly spaced along the circumference of the annular liquid supply pipe.

[0013] Further, an annular gas supply pipe is arranged outside the lower end of the synthesis tube, a plurality of air inlet holes are arranged on the outer wall of the synthesis tube, and the annular gas supply pipe wraps the air inlet holes.

[0014] Further, the air inlet holes are evenly spaced along the circumference of the outer wall of the synthesis tube.

[0015] Further, a baffle is arranged on the inner wall of the synthesis tube. The upper end of the baffle is rotatably connected to the inner wall of the synthesis tube, the lower end of the baffle is a free end, and the air inlet holes can be closed when the baffle hangs down naturally.

[0016] Further, the maximum angle between the baffle and the inner wall of the synthesis tube is 5°.

[0017] Further, a preheating gas supply pipe is connected between the gas supply pipeline and the synthesis tube. The preheating gas supply pipe enters from the upper end of the heat exchange tube, extends downward to the lower end of the synthesis tube and is connected to the synthesis tube.

[0018] Further, a preheating liquid supply pipe is connected between the liquid supply pipeline and the synthesis tube. The preheating liquid supply pipe enters from the lower end of the heat exchange tube, extends upward to the upper end of the synthesis tube and is connected to the synthesis tube.

[0019] Further, a cooling water inlet is arranged at the lower end of the heat exchange tube, and a cooling water outlet is arranged at the upper end of the heat exchange tube.

[0020] Further, a scraping unit is further arranged at the upper end of the synthesis tube. The scraping unit includes a motor, an inner telescopic rod, and an outer telescopic rod. The inner telescopic rod is arranged inside the outer telescopic rod, and the motor drives the inner telescopic rod to extend and / or rotate; a connecting rod is hinged to the lower end of the inner telescopic rod, the connecting rod extends out of the outer telescopic rod, and a scraping blade is arranged at one end of the connecting rod extending out of the outer telescopic rod.

[0021] Further, the upper end of the synthesis tube is connected to a tail gas recovery pipeline, and a liquid discharge port is arranged at the bottom of the synthesis tube.

[0022] The present invention also provides a method for synthesizing DMF, adopting the above DMF synthesis device. The specific steps include:

[0023] S1. Introduce nitric oxide gas into the synthesis tube from the gas supply pipeline, and at the same time introduce a mixed solution of dimethylamine and a catalyst into the synthesis tube from the liquid supply pipeline, and introduce cooling water into the heat exchange tube from the cooling water inlet;

[0024] S2. Control the flow rate of the cooling water flowing into the heat pipe and the flow rate of the cooling water flowing out of the heat exchange tube, so that the temperature in the synthesis tube is controlled at 90°C - 110°C;

[0025] S3. After the synthesis reaction, discharge and collect the reacted liquid through the liquid discharge port, and discharge the gas generated by the reaction from the upper end of the synthesis tube to the tail gas recovery pipeline;

[0026] S4. Start the scraping unit to scrape the crystalline product on the inner wall of the synthesis tube from top to bottom, and the scraped crystalline product is discharged through the liquid discharge port at the bottom of the synthesis tube.

[0027] Further, after step S3, it further includes: re-introducing the reacted liquid discharged and collected from the liquid discharge port into the liquid supply pipeline for the synthesis reaction again.

[0028] Further, the temperature of the cooling water entering the heat exchange tube is 50°C - 60°C.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The DMF synthesis device provided by the present invention arranges the heat exchange tube outside the synthesis tube, thereby avoiding the attachment of crystalline products on the outer wall of the cooling device and preventing the influence on the stable operation of the cooling system; in addition, an annular liquid supply tube is arranged at the upper end of the synthesis tube, and the mixed liquid flows into the synthesis tube through the annular liquid supply tube, so that the mixed liquid can only flow along the inner wall of the synthesis tube, making the heat of the reaction concentrate on the inner wall of the synthesis tube, and then the heat exchange tube can timely discharge the heat generated by the reaction, avoiding the problem that the heat in the central area of the synthesis tube cannot be discharged in time, resulting in a decrease in the reaction rate.

[0031] The DMF synthesis device provided by the present invention first passes the reaction gas and the reaction mixture through the heat exchange tube and then into the synthesis tube, so that the temperatures of the reaction gas and the reaction mixture reach the required reaction temperature in advance, which can further improve the reaction rate.

[0032] The DMF synthesis device provided by the present invention timely scrapes the crystalline product on the inner wall of the synthesis tube through the scraping unit to ensure the rapid reuse of the synthesis tube. Description of the Drawings

[0033] Figure 1 It is a schematic structural diagram of the DMF synthesis device of the present invention.

[0034] Figure 2 It is a schematic structural diagram of the annular liquid supply tube described in the present invention.

[0035] Figure 3 It is a schematic cross-sectional structural diagram of the connection between the annular gas supply tube and the synthesis tube described in the present invention, and the baffle is hidden in the figure.

[0036] Figure 4 It is a schematic structural diagram of the state when gas is introduced into the synthesis tube.

[0037] Figure 5 It is a schematic structural diagram of the state when no gas is introduced into the synthesis tube.

[0038] Figure 6 It is a schematic structural diagram of the scraping unit in a non-scraping state.

[0039] Figure 7 It is a schematic structural diagram when the telescopic rod starts to extend outside the scraping state of the scraping unit.

[0040] Figure 8 It is a schematic structural diagram when the telescopic rod is fully extended outside the scraping state of the scraping unit.

[0041] Figure 9 It is a schematic structural diagram of the connection between the scraping blade and the connecting rod.

[0042] Figure 10 It is a schematic diagram of the position of the scraping blade and the inner wall of the synthesis tube when the scraping unit is scraping.

[0043] Explanation of reference numerals:

[0044] 11: Synthesis tube, 111: Reaction zone, 112: Condensation zone, 113: Collection zone, 114: Drain outlet, 12: Heat exchange tube, 121: Cold water inlet, 122: Hot water outlet, 13: Gas supply pipeline, 131: Preheating gas supply pipe, 132: Annular gas supply pipe, 14: Liquid supply pipeline, 141: Preheating liquid supply pipe, 142: Annular liquid supply pipe, 15: Motor, 16: Scraping unit, 61: Outer telescopic rod, 62: Inner telescopic rod, 161: Scraping blade, 162: Connecting rod, 163: Connecting shaft, 164: Spring, 165: Fixed shaft, 17: Tail gas recovery pipeline, 21: Liquid outlet hole, 31: Air inlet hole, 41: Baffle. Detailed implementation manners

[0045] Next, the technical solutions of the present invention will be clearly described in conjunction with the accompanying drawings. Obviously, the described embodiments are not all embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0046] It should be noted that unless otherwise specifically stated, the relative arrangements, numerical expressions and values of the components and steps described in these embodiments should not be construed as limiting the scope of the present invention. In addition, it should be understood that for the convenience of description, the sizes of the various components shown in the drawings are not necessarily drawn in actual proportional relationships. For example, the thickness, width, length or distance of some units may be enlarged relative to other structures.

[0047] The following description of the exemplary embodiments is merely illustrative and in no sense limits the present invention, its application, or its use. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail herein, but when applicable, these technologies, methods, and devices should be regarded as part of this specification.

[0048] This embodiment provides a DMF synthesis device, as Figure 1 shown, including: at least one synthesis tube 11 and at least one heat exchange tube 12. The synthesis tube 11 is disposed inside the heat exchange tube 12 and both ends of the synthesis tube 11 extend out of the heat exchange tube 12. The number of the synthesis tube 11 and the heat exchange tube 12 can be set as needed. For example Figure 1 shown in the DMF synthesis device, three heat exchange tubes 12 are provided, and one synthesis tube 11 is disposed in each of the three heat exchange tubes 12. A cooling water inlet is provided at the lower end of the heat exchange tube 12. In this embodiment, a total cooling water pipe is provided below the three heat exchange tubes 12, and the cooling water inlets at the lower ends of the three heat exchange tubes 12 are all connected to the cooling water pipe, and the cooling water pipe inputs cooling water from its cold water inlet 121. A cooling water outlet is provided at the upper end of the heat exchange tube 12. In this embodiment, a total water pipe is provided above the three heat exchange tubes 12. Since the temperature of the cooling water in the heat exchange tube rises after heat exchange, the water flowing out of the heat exchange tube is called hot water. The water pipe provided above is a hot water pipe, and the hot water pipe sends out water from its hot water outlet 122.

[0049] A gas supply line 13 is provided above the synthesis tube 11. The gas supply line 13 branches out into three branches to communicate with each synthesis tube 11. The branch is a preheating gas supply pipe 131. The preheating gas supply pipe 131 extends downward from the gas supply line 12, enters the heat exchange tube 12 from the upper end of the heat exchange tube 12, continues to extend downward to the lower end of the synthesis tube 11 and communicates with the synthesis tube 11. Before the reaction starts, carbon monoxide gas can be introduced into the synthesis tube 11 using a jet pump. After the reaction starts, the carbon monoxide gas exchanges heat with the cooling water in the heat exchange tube 12 before entering the synthesis tube 11, so that the temperature of the gas reaches the range of the synthesis reaction temperature, which is beneficial to the subsequent synthesis reaction; at the same time, carbon monoxide does not need to be heated and supplied using a jet pump. At this time, the jet pump can be stopped and normal temperature gas can be directly introduced, reducing energy waste and lowering costs.

[0050] Above the synthesis tube 11, a liquid supply pipeline 14 is provided. The liquid supply pipeline 14 branches into three branches to communicate with each synthesis tube 11. The three branches are preheating liquid supply pipes 141. The preheating liquid supply pipes 141 extend upward from the liquid supply pipeline 14, enter the heat exchange tube 12 from the lower end of the heat exchange tube 12, continue to extend upward to the upper end of the synthesis tube 11 and communicate with the synthesis tube 11. A mixed solution of dimethylamine and a catalyst is introduced into the liquid supply pipeline 14. After the reaction starts, the mixed solution exchanges heat with the water in the heat exchange tube 12 before entering the synthesis tube 11, so that the temperature of the mixed solution rises, which is beneficial to the subsequent synthesis reaction and improves the reaction rate.

[0051] Moreover, the preheating liquid supply pipes 141 and the preheating gas supply pipes 131 are arranged on both sides of the synthesis tube 11, which is beneficial to the pipeline arrangement and is also beneficial to the uniform temperature in the heat exchange tube 12, avoiding uneven temperature distribution inside the synthesis tube 11 caused by uneven heat exchange between the synthesis tube 11 and the heat exchange tube 12.

[0052] The part of the synthesis tube 11 wrapped by the heat exchange tube 12 is the reaction zone 111, the part of the synthesis tube 11 extending out of the lower end of the heat exchange tube 12 is the collection zone 113, and the part of the synthesis tube 11 extending out of the upper end of the heat exchange tube 12 is the condensation zone 112. Carbon monoxide gas and the mixed solution are introduced into the synthesis tube 11 for synthesis reaction. The heat generated by the synthesis reaction exchanges heat with the cooling water in the heat exchange tube 12. With the continuous inflow of low-temperature cooling water and the continuous output of high-temperature cooling water, the heat generated by the synthesis reaction is taken out in the first time, so that the temperature in the synthesis tube 11 is always stable within a preset range, avoiding the crystallization and precipitation of the catalyst sodium methoxide. At the same time, since the heat exchange tube 12 is arranged outside the synthesis tube 11, the reaction by-products only crystallize on the inner wall of the synthesis tube 11, greatly reducing the cleaning workload after crystallization, reducing costs and reducing the processing time.

[0053] An annular liquid supply pipe 142 is arranged inside the upper end of the reaction zone 111 of the synthesis tube 11, and the annular liquid supply pipe 142 communicates with the liquid supply pipeline 14; liquid outlet holes 21 are arranged on the annular liquid supply pipe 142. As Figure 2 shown, the outer edge of the annular liquid supply pipe 142 is arranged close to the inner wall of the synthesis tube 11. The liquid outlet holes 21 are arranged below the annular liquid supply pipe 142, and the liquid outlet direction of the liquid outlet holes 21 faces the inner wall of the synthesis tube 11. Ensure that the mixed solution ejected from the liquid outlet holes 21 can flow downward along the inner wall of the synthesis tube 11, so as to ensure that the synthesis reaction occurs on the inner wall of the synthesis tube 11, which is beneficial to the heat released after the reaction being taken out by the cooling water in time, and avoiding the problem that the heat in the central area of the synthesis tube 11 cannot be discharged in time, resulting in a decrease in the reaction rate.

[0054] Preferably, a plurality of liquid outlet holes 21 are provided. The plurality of liquid outlet holes 21 are evenly spaced along the circumference of the annular liquid supply pipe 142, so as to promote the mixed solution to flow out evenly along the inner wall of the synthesis pipe 11, increase the contact area between the mixed solution and the gas, and improve the reaction rate.

[0055] An annular gas supply pipe 132 is provided outside the lower end of the reaction zone of the synthesis pipe 11. A plurality of air inlet holes 31 are provided on the outer wall of the synthesis pipe 11, and the annular gas supply pipe 132 wraps the air inlet holes 31. As Figure 3 and Figure 4 shown, the air inlet holes 31 are evenly spaced along the circumference of the outer wall of the synthesis pipe 11. A baffle 41 is provided on the inner wall of the synthesis pipe 11. The upper end of the baffle 41 is rotatably connected to the inner wall of the synthesis pipe 11, and the lower end of the baffle 41 is a free end. When the baffle 41 hangs naturally, it can close the air inlet holes 31, as Figure 5 shown. The maximum angle between the baffle 41 and the inner wall of the synthesis pipe 11 is 5°. When the gas enters the reaction zone 111 from the annular gas supply pipe 132, the gas pushes the baffle 41 to open the air inlet holes 31. When gas supply is not required after the reaction ends, the baffle 41 closes the air inlet holes 31 under the action of gravity, preventing liquid from flowing reversely into the annular gas supply pipe 132 through the air inlet holes 31.

[0056] The condensation zone 112 at the upper end of the synthesis pipe 11 is connected to the tail gas recovery pipeline 17. The tail gas generated by the reaction is condensed in the condensation zone 112, and the condensed liquid falls back to the bottom of the synthesis pipe 11. The uncondensed gas is discharged to the tail gas recovery unit through the tail gas recovery pipeline 17. A liquid discharge port 114 is provided at the bottom of the collection area 113 of the synthesis pipe. The liquid after the reaction converges to the collection area 113, and the liquid in the collection area 113 is discharged through the liquid discharge port 114.

[0057] After the reaction ends, it is necessary to remove the crystals formed by the by-products on the inner wall of the reaction zone of the synthesis pipe. Therefore, a scraping unit 16 is also provided in the condensation zone 112 at the upper end of the synthesis pipe, as Figure 6As shown, the scraping unit 16 includes a motor 15, an inner telescopic rod 62, and an outer telescopic rod 61. The inner telescopic rod 62 is disposed inside the outer telescopic rod 61, and the motor 15 drives the inner telescopic rod 62 to extend and / or rotate. The inner telescopic rod 62 uses a multi-stage electric push rod, which is powered by the drive of the motor 15. The multi-stage electric push rod includes multiple sections of push rods sleeved in sequence. A lead screw is disposed at the central position inside the multi-stage electric push rod. The motor drives the lead screw to rotate, and the lead screw drives the adjacent push rod to linearly extend through the thread. After the push rod extends a certain distance, the outer push rods extend in sequence to form multi-stage telescoping. The multi-stage electric push rod is a prior art, so its specific structure will not be elaborated here. In addition, the outer telescopic rod 61 is also a multi-stage telescoping structure, which includes multiple rod sleeves threadedly connected in sequence. The uppermost rod sleeve is fixedly disposed, and a through hole is provided on the lowermost rod sleeve. The adjacent rod sleeves can extend a certain length by rotation.

[0058] The lower end of the inner telescopic rod 62 is hinged to a connecting rod 162. The connecting rod 162 extends out of the outer telescopic rod 61, and a scraping blade 161 is disposed at one end of the connecting rod 162 extending out of the outer telescopic rod 61. The connecting rod 162 can be provided with 1, 2 or multiple. The connecting rod 162 extends out through the through hole on the lowermost rod sleeve of the outer telescopic rod 61. The connecting rod 162 and the inner telescopic rod 62 are hinged by a connecting shaft 163, and a limiting block is disposed above the connecting rod 162 at the connecting shaft 163, so that the connecting rod 162 cannot continue to rotate upward after rotating to the horizontal state.

[0059] The initial state is as Figure 6 shown. There is a certain distance between the bottom of the inner telescopic rod 62 and the bottom of the outer telescopic rod 61, so that the connecting rod 162 and the scraping blade 161 droop under the action of gravity, and the scraping blade 161 does not contact the inner wall of the composite pipe 11. Start the motor 15, and the motor 15 drives the inner telescopic rod 62 to extend. During the extension of the inner telescopic rod 62, the connecting rod 162 rotates to the horizontal state, and then the scraping blade 161 contacts the inner wall of the composite pipe 11. The motor 15 continues to drive the inner telescopic rod 62. Since the inner telescopic rod 62 is restricted by the outer telescopic rod 61 and cannot extend, it turns into a rotational motion. The rotation of the inner telescopic rod 62 drives the connecting rod 162 to rotate, and the rotation of the connecting rod 162 drives the outer telescopic rod 61 to rotate. And since the outer telescopic rod 61 is a multi-stage telescoping structure, as Figure 7 and Figure 8 shown, therefore, during the rotation of the outer telescopic rod 61, it extends synchronously, and then drives the inner telescopic rod 62 to extend synchronously during the rotation, finally realizing the spiral descent of the scraping blade 161 and achieving the removal of large-area crystallization on the inner wall of the composite pipe 11.

[0060] After the cleaning is completed, the motor 15 rotates in the reverse direction, driving the inner telescopic rod 62 to rotate in the reverse direction, thereby driving the outer telescopic rod 61 to rotate in the reverse direction. Then, the outer telescopic rod 61 begins to shorten, driving the inner telescopic rod 62 to shorten as well. Finally, the connecting rod 162 and the wiper 161 rotate downward to return to the initial state, and then continue to rise to return to the initial position.

[0061] As Figure 9 shown is the connection structure of the connecting rod 162 and the wiper 161. Specifically: the end of the connecting rod 162 is hollow inside, and a spring 164 is arranged inside. A fixed shaft 165 is arranged on one side of the wiper 161. The fixed shaft 165 extends into the inside of the end of the connecting rod 162 and is fixedly connected to the spring 164. During the upward rotation of the wiper 161 and the rotation around the inner telescopic rod 62, the spring 164 can be used to achieve the close fit between the side wall of the wiper 161 and the synthesis tube 11, realizing high-efficiency cleaning. The shape of the wiper 161 is selected to be able to completely fit the inner side wall of the synthesis tube 11, which is beneficial for scraping the residues on the inner side wall. For example, the side of the wiper 161 where it fits the inner side wall of the synthesis tube 11 adopts an arc with the same radian as the inner side wall of the synthesis tube 11, and the end face of the wiper 161 adopts a wedge shape, as Figure 10 shown. The material of the wiper 161 is selected to be elastic and wear-resistant, such as polytetrafluoroethylene, etc.

[0062] The DMF synthesis method of the DMF synthesis device provided in this embodiment specifically includes the following steps:

[0063] S1. Pass nitric oxide gas into the synthesis tube 11 from the gas supply pipeline 13, and at the same time pass the mixed liquid of dimethylamine and catalyst into the synthesis tube 11 from the liquid supply pipeline 14. Pass cooling water into the heat exchange tube 12 from the cooling water inlet;

[0064] S2. Control the flow rate of the cooling water flowing into the heat exchange tube and the flow rate of the cooling water flowing out of the heat exchange tube, so that the temperature of the reaction zone of the synthesis tube 11 is controlled at 90°C - 110°C, and the pressure inside the synthesis tube 11 is maintained at about 2.1 MPa;

[0065] S3. After the synthesis reaction, discharge and collect the reacted liquid through the liquid discharge port 114, and discharge the gas generated by the reaction from the upper end of the synthesis tube 11 to the tail gas recovery pipeline 17; if the reaction is incomplete, the reacted liquid discharged and collected from the liquid discharge port can be re-passed into the liquid supply pipeline 13 for the synthesis reaction again.

[0066] S4. Start the scraping unit 16 to scrape the crystallization products on the inner wall of the synthesis tube 11 from top to bottom, and the scraped crystallization products are discharged through the liquid discharge port at the bottom of the synthesis tube.

[0067] Among them, the temperature of the cooling water entering the heat exchange tube 12 is 50°C - 60°C.

[0068] The above specific embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the scope of the technical solutions of the present invention, and all of them should be covered by the scope of the claims of the present invention.

Claims

1. A DMF synthesis device, comprising: At least one synthesis tube and at least one heat exchange tube, characterized in that the synthesis tube is arranged inside the heat exchange tube and both ends of the synthesis tube extend out of the heat exchange tube; cooling water is introduced into the heat exchange tube, the lower end of the synthesis tube is connected to a gas supply pipeline for introducing carbon monoxide gas, the upper end of the synthesis tube is connected to a liquid supply pipeline for introducing a mixed liquid, an annular liquid supply tube is arranged inside the upper end of the synthesis tube, and the annular liquid supply tube is communicated with the liquid supply pipeline; liquid outlet holes are arranged on the annular liquid supply tube; A preheating gas supply pipe is communicated between the gas supply pipeline and the synthesis tube. The preheating gas supply pipe enters from the upper end of the heat exchange tube, extends downward to the lower end of the synthesis tube and is communicated with the synthesis tube; A preheating liquid supply pipe is communicated between the liquid supply pipeline and the synthesis tube. The preheating liquid supply pipe enters from the lower end of the heat exchange tube, extends upward to the upper end of the synthesis tube and is communicated with the synthesis tube.

2. The DMF synthesis device according to claim 1, characterized in that, The liquid outlet holes are arranged at the bottom of the annular liquid supply tube, and the liquid outlet direction of the liquid outlet holes faces the inner wall of the synthesis tube.

3. The DMF synthesis device according to claim 1, characterized in that, An annular gas supply tube is arranged outside the lower end of the synthesis tube, and a plurality of air inlet holes are arranged on the outer wall of the synthesis tube, and the annular gas supply tube wraps the air inlet holes.

4. The DMF synthesis device according to claim 3, wherein A baffle is arranged on the inner wall of the synthesis tube. The upper end of the baffle is rotatably connected to the inner wall of the synthesis tube, the lower end of the baffle is a free end, and the air inlet holes can be closed when the baffle hangs down naturally.

5. The DMF synthesis device according to claim 4, wherein The maximum angle between the baffle and the inner wall of the synthesis tube is 5°.

6. The DMF synthesis device according to claim 1, characterized in that, A cooling water inlet is arranged at the lower end of the heat exchange tube, and a cooling water outlet is arranged at the upper end of the heat exchange tube.

7. The DMF synthesis device according to claim 1, characterized in that, A scraping unit is further arranged at the upper end of the synthesis tube. The scraping unit includes a motor, an inner telescopic rod and an outer telescopic rod. The inner telescopic rod is arranged inside the outer telescopic rod, and the motor drives the inner telescopic rod to extend and / or rotate; a connecting rod is hinged to the lower end of the inner telescopic rod, the connecting rod extends out of the outer telescopic rod, and a scraping blade is arranged at one end of the connecting rod extending out of the outer telescopic rod.

8. A method for synthesizing DMF, which uses the DMF synthesis device described in any one of claims 1-7, is characterized in that, Including: S1. Introduce nitrogen monoxide gas into the synthesis tube from the gas supply pipeline, at the same time introduce the mixed liquid of dimethylamine and catalyst into the synthesis tube from the liquid supply pipeline, and introduce cooling water into the heat exchange tube from the cooling water inlet; S2. Control the flow rate of the cooling water flowing into the heat pipe and the flow rate of the cooling water flowing out of the heat exchange tube to control the temperature inside the synthesis tube at 90°C - 110°C; S3. After the synthesis reaction, discharge and collect the reacted liquid through a drain port, and discharge the gas generated by the reaction from the upper end of the synthesis tube to a tail gas recovery pipeline; S4. Start the scraping unit to scrape the crystallization product on the inner wall of the synthesis tube from top to bottom, and the scraped crystallization product is discharged through the drain port at the bottom of the synthesis tube.

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