Preparation method and preparation device of adipic acid dihydrazide

Abstract

The application belongs to the technical field of chemical production, and particularly relates to a preparation method and a preparation device of adipic acid dihydrazide. The preparation method of the adipic acid dihydrazide comprises the following steps: S1, treating raw materials; S2, adding the raw materials into a reaction tank for reaction; S3, cooling and crystallizing; S4, washing the crystals and purifying; and S5, drying and packaging the purified crystals. In the process of the reaction of the raw materials in the reaction tank, the raw materials are fully mixed by a mixing mechanism arranged in the reaction tank. The mixing mechanism pushes the mixed solution in the upper layer downward and pushes the mixed solution in the lower layer upward, so that the mixed solution flows in the axial direction, the mixed solution in the middle layer is subjected to turbulent flow, the mixed solution is more uniformly mixed, and the mixing effect is improved.

Description

Technical Field

[0001] This invention relates to the field of chemical production technology, specifically to a method and apparatus for preparing adipic acid dihydrazide. Background Technology

[0002] Adipic acid dihydrazide is a white crystalline solid that is readily soluble in water. It is mainly used as a curing agent for epoxy powder coatings and as a coating additive, as well as as a metal deactivator and other polymeric additives and water treatment agents. The industrial preparation of adipic acid dihydrazide often uses the direct reaction method of dimethyl adipic acid and hydrazine hydrate.

[0003] Chinese Patent CN116371342A discloses an apparatus for preparing adipic acid dihydrazide. By increasing the contact area with the mixed solution through the first and second helical blades, the cooling and crystallization rate is accelerated. The relative rotation of the first and second helical blades increases the degree of mixing of the mixed solution, making the cooled and crystallized adipic acid dihydrazide more uniform.

[0004] However, the first and second helical blades of the above-mentioned preparation device drive the mixed liquid to circulate in the lower cavity of the reaction shell. The mixed liquid circulates along this path, resulting in a single mixing path, which affects the mixing efficiency and the mixing effect. Summary of the Invention

[0005] The purpose of this invention is to provide an apparatus for preparing adipic acid dihydrazide to solve the problems mentioned in the background art.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: The present invention provides a method for preparing adipic acid dihydrazide, comprising the following steps: S1: Dimethyl adipic acid is pulverized to 150-250 mesh, and hydrazine hydrate is dehydrated through molecular sieve to a water content of ≤5%. The molar ratio of dimethyl adipic acid to hydrazine hydrate is 1:(2.05-2.10). S2: Close all valves of the reaction vessel, replace the air in the reaction vessel with nitrogen three times, and put the crushed dimethyl adipate powder and 99.8% industrial methanol at a mass ratio of 1:(3~5) into the sealed reaction vessel. Stir the inside of the reaction vessel with the mixing mechanism, and use the jacket cooling water to control the temperature inside the reaction vessel at 20~30℃. Then add hydrazine hydrate dropwise into the reaction vessel at a rate of 1.0~2.0L / h, and then raise the temperature to total reflux for 0.5~1h. Keep the temperature inside the reaction vessel at 60-75℃ to allow the dimethyl adipate powder to fully dissolve and react. After the dropwise addition is completed, keep the reaction at this temperature for 4-6 hours. During the reaction, a white solid will gradually precipitate. Stop adding hydrazine hydrate when the residual amount of dimethyl adipate is ≤0.5%. S3: Continue heating, and control the temperature inside the reaction vessel at 70~80℃ to evaporate industrial methanol, water and excess hydrazine hydrate. Then, use jacket cooling water to cool the inside of the reaction vessel to 10~15℃ at a rate of 5-10℃ / h, and keep it at this temperature while stirring slowly for 1 hour to allow the adipic acid dihydrazine crystals to fully separate and grow. Then, perform solid-liquid separation to obtain adipic acid dihydrazine crystals containing water, and recover the mother liquor. S4: The separated adipic acid dihydrazide crystals containing water are washed 2-3 times with industrial methanol with a concentration of 99.8% to remove residual industrial methanol, excess hydrazine hydrate and by-products. The washed adipic acid dihydrazide crystals containing water are then purified in the recrystallization unit. S5: The purified adipic acid dihydrazide crystals containing moisture are dried at 40-80℃ and 40-53KPa until the moisture content is ≤0.5%. After drying, the crystals are crushed and sieved to 200-300 mesh, and finally sealed and packaged to obtain the finished adipic acid dihydrazide product.

[0007] An apparatus for preparing adipic acid dihydrazide includes a reaction vessel. A dissolving component for dissolving dimethyl adipic acid is fixedly connected to the upper end of the reaction vessel. A mixing mechanism is rotatably connected to the bottom of the inner wall of the reaction vessel. A switching mechanism is fixedly connected to the side of the mixing mechanism near the bottom of the reaction vessel. The switching mechanism is used to switch the stirring effect of the mixing mechanism on the mixed solution. A feed inlet is fixedly connected to the upper end of the dissolving component via a valve. The dissolving component is connected to the reaction vessel via a valve. A discharge outlet is fixedly connected to the bottom of the reaction vessel via a valve.

[0008] Furthermore, the mixing mechanism includes a central tube rotatably connected to the inner wall of the reaction vessel. An array of stirring rods is fixedly connected to the central tube. Each stirring rod has a first mounting groove and an array of rotating rods fixedly connected to it. Each rotating rod has a second mounting groove connected to the first mounting groove. An array of rotating shafts is rotatably connected to the rotating rods. Each rotating shaft has a stirring blade fixedly connected to one end outside the rotating rod. A first pushing blade is fixedly connected to the upper end of the central tube. A scraper is fixedly connected to the outer wall of the central tube near the bottom of the reaction vessel, with one side of the scraper inclined. A second pushing blade is fixedly connected to the outer wall of the central tube above the scraper. A driven gear is fixedly connected to one end of the central tube that extends through and outside the reaction vessel. A drive motor is fixedly connected to the bottom of the reaction vessel. A drive gear is fixedly connected to the output end of the drive motor, and the drive gear meshes with the driven gear.

[0009] Furthermore, the switching mechanism includes a bevel gear fixedly connected to one end of the rotating shaft located in the second mounting groove. A first connecting rod is slidably connected inside the rotating rod. A rack is fixedly connected to the end of the first connecting rod near the bevel gear. A second connecting rod is hinged to the end of the first connecting rod away from the rack. A sliding rod is slidably connected inside the first mounting groove. The second connecting rod is rotatably connected to the sliding rod. A sliding seat is hinged to the end of the sliding rod located inside the central tube. The sliding seat is slidably connected to the central tube. A push rod is fixedly connected through the sliding seat. An electric push rod is fixedly connected to one end of the push rod. The electric push rod is fixedly connected to the central tube. A fixing component is fixedly connected to the end of the rotating rod near the stirring rod.

[0010] Furthermore, the fixing component includes an array of limiting grooves formed on the end of the rotating rod near the stirring rod. A limiting block is slidably connected to the inner wall of the stirring rod near the limiting groove. A connecting rod is hinged to the end of the limiting block away from the limiting groove. A connecting rod is hinged to the end of the connecting rod away from the limiting block. The end of the connecting rod away from the connecting rod is hinged to the sliding rod.

[0011] Furthermore, the end of the limiting block near the limiting groove is tapered, and the width of the limiting block is greater than the width of the limiting groove.

[0012] Furthermore, the number of racks and bevel gears is equal, the sidewalls of each rack are fixed to each other, and the racks mesh with the bevel gears.

[0013] Furthermore, the second propulsion blade is located above the scraper, and the scraper and the second propulsion blade are offset from each other.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The apparatus for preparing adipic acid dihydrazide of the present invention, by setting up a mixing mechanism, thoroughly mixes the mixed solution. The mixing mechanism pushes the upper layer of mixed solution downward and the lower layer of mixed solution upward, causing the mixed solution to flow axially, which improves the mixing efficiency and promotes turbulence in the middle layer of mixed solution, making the mixed solution more uniform and improving the mixing effect. The switching mechanism adjusts the stirring effect of the mixing mechanism on the mixed solution. During the mixing reaction stage, it increases the contact area between the mixing mechanism and the mixed solution to improve the mixing effect. During the cooling and crystallization stage, it reduces the contact area between the mixing mechanism and the mixed solution to reduce the disturbance to the mixed solution, accelerate the crystallization speed, and make the crystals more evenly distributed in the mixed solution. At the same time, it avoids the generation of more small crystal nuclei by violent stirring and the easier adsorption of impurities on the crystal surface.

[0015] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0016] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0017] Figure 1 This is a schematic diagram of the overall structure of the apparatus for preparing adipic acid dihydrazide according to the present invention; Figure 2 This is a bottom-view three-dimensional structural diagram of the apparatus for preparing adipic acid dihydrazide according to the present invention; Figure 3 yes Figure 2 Enlarged view of point A in the middle; Figure 4 This is a schematic diagram of the internal structure of the apparatus for preparing adipic acid dihydrazide according to the present invention; Figure 5 This is a cross-sectional schematic diagram of the apparatus for preparing adipic acid dihydrazide according to the present invention; Figure 6 This is a partial cross-sectional schematic diagram of the mixing mechanism of the preparation apparatus for adipic acid dihydrazide of the present invention; Figure 7 This is a schematic diagram of the connection structure between the rotating rod and the stirring blade in the preparation apparatus of adipic dihydrazide of the present invention; Figure 8 This is a schematic diagram of the connection structure between the fixed component and the rotating rod in the preparation apparatus for adipic acid dihydrazide of the present invention.

[0018] In the diagram: 1. Reaction vessel; 2. Mixing mechanism; 3. Switching mechanism; 4. Inlet; 5. Outlet; 6. Central tube; 7. Stirring rod; 8. First mounting slot; 9. Rotating rod; 10. Second mounting slot; 11. Rotating shaft; 12. Stirring blade; 13. First pusher blade; 14. Scraper; 15. Second pusher blade; 16. Driven gear; 17. Drive motor; 18. Drive gear; 19. Bevel gear; 21. First connecting rod; 22. Rack; 23. Second connecting rod; 24. Sliding rod; 25. Sliding seat; 26. Push rod; 27. Electric push rod; 31. Limiting slot; 32. Limiting block; 33. Connecting rod; 34. Connecting rod. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0020] A method for preparing adipic acid dihydrazide includes the following steps: S1: Dimethyl adipic acid is pulverized to 150~250 mesh, and hydrazine hydrate is dehydrated through molecular sieve to a water content of ≤5%. The molar ratio of dimethyl adipic acid to hydrazine hydrate is 1:(2.05~2.10). S2: Close all valves of reaction vessel 1, replace the air in reaction vessel 1 with nitrogen three times, add the crushed dimethyl adipate powder and 99.8% industrial methanol at a mass ratio of 1:(3~5) into the sealed reaction vessel 1, stir the inside of reaction vessel 1 with mixing mechanism 2, control the temperature inside reaction vessel 1 at 20~30℃ with jacket cooling water, then add hydrazine hydrate dropwise into reaction vessel 1 at a rate of 1.0~2.0L / h, then raise the temperature to total reflux for 0.5~1h, and keep the temperature inside reaction vessel 1 at 60-75℃ to fully dissolve and react the dimethyl adipate powder. After the dropwise addition is completed, keep the reaction at this temperature for 4-6 hours. During the reaction, a white solid will gradually precipitate out. Stop adding hydrazine hydrate when the residual amount of dimethyl adipate is ≤0.5%. S3: Continue heating, and control the temperature inside the reaction vessel 1 at 70~80℃ to distill off industrial methanol, water and excess hydrazine hydrate. Then, use jacket cooling water to cool the inside of the reaction vessel 1 to 10~15℃ at a rate of 5-10℃ / h, and keep it at the temperature while stirring slowly for 1 hour to allow the adipic acid dihydrazine crystals to fully separate and grow. Then, perform solid-liquid separation to obtain adipic acid dihydrazine crystals containing water, and recover the mother liquor. S4: The separated adipic acid dihydrazide crystals containing water are washed 2-3 times with industrial methanol with a concentration of 99.8% to remove residual industrial methanol, excess hydrazine hydrate and by-products. The washed adipic acid dihydrazide crystals containing water are then purified in the recrystallization unit. S5: The purified adipic acid dihydrazide crystals containing moisture are dried at 40-80℃ and 40-53KPa until the moisture content is ≤0.5%. After drying, the crystals are crushed and sieved to 200-300 mesh, and finally sealed and packaged to obtain the finished adipic acid dihydrazide product.

[0021] Example 1 S1: Dimethyl adipic acid is pulverized to 200 mesh, and hydrazine hydrate is dehydrated through a molecular sieve to a moisture content of 3.5%. The molar ratio of dimethyl adipic acid to hydrazine hydrate is 1:2.08. S2: Close all valves of reaction vessel 1, replace the air in reaction vessel 1 with nitrogen three times, add the crushed dimethyl adipate powder and 99.8% industrial methanol at a mass ratio of 1:4 into the sealed reaction vessel 1, stir the inside of reaction vessel 1 with mixing mechanism 2, control the temperature inside reaction vessel 1 at 25℃ with jacket cooling water, then add hydrazine hydrate dropwise into reaction vessel 1 at a rate of 1.5L / h, then raise the temperature to total reflux for 0.8h, maintain the temperature inside reaction vessel 1 at 70℃, keep the reaction at this temperature for 5h after the dropwise addition is complete, and stop adding hydrazine hydrate when the residual mass ratio of dimethyl adipate is 0.32%; S3: Continue heating, and control the temperature inside the reaction vessel 1 at 75°C to distill off industrial methanol, water and excess hydrazine hydrate. Then, use jacket cooling water to cool the inside of the reaction vessel 1 to 12°C at a rate of 8°C / h, and keep it at this temperature while stirring slowly for 1 hour to allow the adipic acid dihydrazine crystals to fully separate and grow. Then, perform solid-liquid separation to obtain adipic acid dihydrazine crystals containing water, and recover the mother liquor. S4: The separated adipic acid dihydrazide crystals containing water were washed three times with industrial methanol with a concentration of 99.8% to remove residual industrial methanol, excess hydrazine hydrate and by-products. The washed adipic acid dihydrazide crystals containing water were then purified in the recrystallization unit. S5: The purified adipic acid dihydrazide crystals containing water are dried at 60℃ and 48KPa until the water content is 0.38%. After drying, they are crushed and sieved to 250 mesh, and finally sealed and packaged to obtain the finished adipic acid dihydrazide product.

[0022] Example 2 S1: Dimethyl adipic acid is pulverized to 150 mesh, and hydrazine hydrate is dehydrated through a molecular sieve to a moisture content of 4.8%. The molar ratio of dimethyl adipic acid to hydrazine hydrate is 1:2.05. S2: Close all valves of reaction vessel 1, replace the air in reaction vessel 1 with nitrogen three times, add the crushed dimethyl adipate powder and 99.8% industrial methanol at a mass ratio of 1:3 into the sealed reaction vessel 1, stir the inside of reaction vessel 1 with mixing mechanism 2, control the temperature inside reaction vessel 1 at 20℃ with jacket cooling water, then add hydrazine hydrate dropwise into reaction vessel 1 at a rate of 1.0L / h, then raise the temperature to total reflux for 0.5h, maintain the temperature inside reaction vessel 1 at 60℃, keep the reaction at the temperature for 4h after the dropwise addition is completed, and stop adding hydrazine hydrate when the residual mass ratio of dimethyl adipate is 0.45%; S3: Continue heating, and control the temperature inside the reaction vessel 1 at 70°C to distill off industrial methanol, water, and excess hydrazine hydrate. Then, use jacket cooling water to cool the inside of the reaction vessel 1 to 10°C at a rate of 5°C / h, and keep it at this temperature while stirring slowly for 1 hour to allow the adipic acid dihydrazine crystals to fully separate and grow. Then, perform solid-liquid separation to obtain adipic acid dihydrazine crystals containing water, and recover the mother liquor. S4: The separated adipic acid dihydrazide crystals containing water were washed twice with industrial methanol with a concentration of 99.8% to remove residual industrial methanol, excess hydrazine hydrate and by-products. The washed adipic acid dihydrazide crystals containing water were then purified in the recrystallization unit. S5: The purified adipic acid dihydrazide crystals containing water are dried at 40℃ and 40KPa until the water content is 0.42%. After drying, they are crushed and sieved to 200 mesh, and finally sealed and packaged to obtain the finished adipic acid dihydrazide product.

[0023] Example 3 S1: Dimethyl adipic acid is pulverized to 150 mesh, and hydrazine hydrate is dehydrated through a molecular sieve to a water content of 4.8%. The molar ratio of dimethyl adipic acid to hydrazine hydrate is 1:2.10. S2: Close all valves of reaction vessel 1, replace the air in the reaction vessel with nitrogen three times, add the crushed dimethyl adipate powder and 99.8% industrial methanol at a mass ratio of 1:4 into the sealed reaction vessel 1, stir the inside of the reaction vessel 1 with mixing mechanism 2, control the temperature inside the reaction vessel 1 at 30℃ with jacket cooling water, then add hydrazine hydrate dropwise into the reaction vessel 1 at a rate of 2.0L / h, then raise the temperature to total reflux for 1h, keep the temperature inside the reaction vessel 1 at 75℃, and keep the reaction at this temperature for 6h after the dropwise addition is complete. Stop adding hydrazine hydrate when the residual mass ratio of dimethyl adipate is 0.28%. S3: Continue heating, and control the temperature inside the reaction vessel 1 at 80°C to distill off industrial methanol, water and excess hydrazine hydrate. Then, use jacket cooling water to cool the inside of the reaction vessel 1 to 15°C at a rate of 10°C / h, and keep it at this temperature while stirring slowly for 1 hour to allow the adipic acid dihydrazine crystals to fully separate and grow. Then, perform solid-liquid separation to obtain adipic acid dihydrazine crystals containing water, and recover the mother liquor. S4: The separated adipic acid dihydrazide crystals containing water were washed three times with industrial methanol with a concentration of 99.8% to remove residual industrial methanol, excess hydrazine hydrate and by-products. The washed adipic acid dihydrazide crystals containing water were then purified in the recrystallization unit. S5: The purified adipic acid dihydrazide crystals containing water are dried at 80℃ and 53KPa until the water content is 0.31%. After drying, they are crushed and sieved to 300 mesh, and finally sealed and packaged to obtain the finished adipic acid dihydrazide product.

[0024]

[0025] The following comparative examples all deviate from the parameter range of the basic steps, but the remaining operations are consistent with Example 1. The specific parameters and results are as follows: Comparative Example 1 The difference from Example 1 is that the molar ratio of dimethyl adipic acid to hydrazine hydrate in S1 is 1:1.95, while the other parameters remain unchanged.

[0026] Reaction results: After 6 hours of incubation, the residual mass of dimethyl adipate was 1.82%, which did not meet the reaction cessation standard; after extending the reaction for another 2 hours, the residual mass was still 0.97%, and the purity of the final product was low.

[0027] Comparative Example 2 The difference from Example 1 is that the heat preservation reaction temperature in S2 is controlled at 55°C, while the other parameters remain unchanged.

[0028] Reaction results: Dimethyl adipic acid dissolves slowly, and only a small amount of white solid precipitates after 4 hours of reaction; after 8 hours of incubation, the residual mass of dimethyl adipic acid is 1.23%, the product yield decreases significantly, and the crystal particles are small and prone to agglomeration.

[0029] Comparative Example 3 The difference from Example 1 is that the cooling rate in S3 is controlled at 15℃ / h, while the other parameters remain unchanged.

[0030] Reaction results: Crystals precipitated too quickly, the particles were uneven, and a large number of impurities were trapped inside; after washing and recrystallization, the purity of the product still did not meet the requirements, and the water content was 0.89%.

[0031] Comparative Example 4 The difference from Example 1 is that in S5, the vacuum drying temperature is 35°C, the pressure is 35 kPa, and the drying time is 4 hours, while the other parameters remain unchanged.

[0032] Reaction results: The crystals were not dried sufficiently, and the moisture content was 0.92%, which did not meet the requirements of the finished product; moreover, the dried crystals were prone to absorbing moisture, and clumping occurred after crushing, making them difficult to sieve.

[0033] Comparative Example 5 The difference from Example 1 is that nitrogen replacement was not performed in S2; the raw materials were directly added and hydrazine hydrate was added dropwise, while the other parameters remained unchanged.

[0034] Reaction results: Yellow impurities appeared during the reaction, and the product color was yellowish instead of pure white; after testing, the purity of the product decreased by 8.3%, and the content of by-products increased, making subsequent purification more difficult.

[0035]

[0036] The deviation of the molar ratio of dimethyl adipic acid to hydrazine hydrate in Comparative Example 1 resulted in incomplete reaction, excessive residue of dimethyl adipic acid, and a significant decrease in product purity and yield. This demonstrates that a molar ratio of 1:2.05 to 1:2.10 is crucial for ensuring a complete reaction, and that excess hydrazine hydrate can promote the complete reaction of dimethyl adipic acid and reduce residue.

[0037] The deviation of the holding temperature in Comparative Example 2 resulted in a slow dissolution rate of dimethyl adipic acid, a decrease in the reaction rate, a small amount of crystal precipitation, and a significant reduction in yield. This indicates that a holding temperature of 60-75℃ can ensure the full dissolution of reactants and efficient reaction, and is one of the core parameters for improving product yield.

[0038] The comparative example showed that the cooling rate deviated from the standard, resulting in crystal precipitation that was too fast, which prevented the crystals from growing sufficiently and caused them to encapsulate impurities. These impurities were difficult to remove during subsequent purification, and the water content exceeded the standard. This demonstrates that a slow cooling rate of 5~10℃ / h can allow the crystals to precipitate fully and grow uniformly, reduce impurity encapsulation, and ensure that the crystal purity and water content meet the standards.

[0039] The deviation of the vacuum drying parameters in Comparative Example 4 resulted in insufficient drying of the crystals, excessive moisture content, and easy absorption of moisture and clumping. This indicates that drying conditions of 40-80℃ and 40-53KPa can ensure rapid dehydration of the crystals, achieving a moisture content of ≤0.5%, while preventing the crystals from absorbing moisture and deteriorating.

[0040] Comparative Example 5 did not undergo nitrogen purging. The air in the reaction vessel reacted with the reactants and products, resulting in yellowing of the products, an increase in by-products, and a significant decrease in purity. This demonstrates that the nitrogen purging step can effectively isolate air, prevent side reactions, and ensure the purity and appearance quality of the products.

[0041] In summary, the various process parameters (dimethyl adipic acid powder mesh size, hydrazine hydrate moisture content and molar ratio, reaction temperature, cooling rate, drying parameters, and nitrogen replacement) of the preparation method of the present invention are all in harmony and indispensable. Only by strictly controlling them within the set range can high-purity, high-yield, and moisture-content-compliant finished products of adipic acid dihydrazine be prepared. Moreover, the process is stable and can be industrialized.

[0042] Please see Figures 1 to 8 An apparatus for preparing adipic acid dihydrazide includes a reaction vessel 1. A dissolving component for dissolving dimethyl adipic acid is fixedly connected to the upper end of the reaction vessel 1. A mixing mechanism 2 is rotatably connected to the bottom of the inner wall of the reaction vessel 1. A switching mechanism 3 is fixedly connected to the side of the mixing mechanism 2 near the bottom of the reaction vessel 1. The switching mechanism 3 is used to switch the stirring effect of the mixing mechanism 2 on the mixed solution. A feed inlet 4 is fixedly connected to the upper end of the dissolving component through a valve. The dissolving component is connected to the reaction vessel 1 through a valve. A discharge outlet 5 is fixedly connected to the bottom end of the reaction vessel 1 through a valve.

[0043] The solid oxalic acid particles are dissolved using a melting assembly (a conventional electric heating plate is used to heat the solid oxalic acid particles to melt them; the temperature can be set to 50°C to ensure that the oxalic acid remains in a liquid state and does not decompose). Then, hydrazine hydrate and the dissolved dimethyl oxalic acid are added to reaction vessel 1. A mixing mechanism 2 mixes the hydrazine hydrate and the dissolved dimethyl oxalic acid to obtain a mixed solution. The mixing mechanism 2 thoroughly mixes the solution, pushing the upper layer of the mixed solution downwards while simultaneously pushing the lower layer upwards, enhancing the axial flow of the mixed solution, improving the mixing efficiency, and pushing the middle layer... The turbulent flow of the mixed solution makes the mixture more uniform and improves the mixing effect. The switching mechanism 3 is used to adjust the stirring effect of the mixing mechanism 2 on the mixed solution. During the mixing reaction stage, the contact area between the mixing mechanism 2 and the mixed solution is increased to improve the mixing effect. During the cooling and crystallization stage, the contact area between the mixing mechanism 2 and the mixed solution is reduced to reduce the disturbance to the mixed solution. Stirring can promote the diffusion of solute molecules adipic acid dihydrazide to the crystal surface, accelerate the crystallization speed, and make the crystals more uniformly distributed in the mixed solution. At the same time, it avoids the generation of more small crystal nuclei by violent stirring and prevents impurities from being adsorbed on the crystal surface, which would affect the purity of the finished product.

[0044] Please see Figures 1 to 5 The mixing mechanism 2 includes a central tube 6 rotatably connected to the inner wall of the reaction vessel 1. A stirring rod 7 is fixedly connected in an array on the central tube 6. A first mounting groove 8 is provided on the stirring rod 7. A rotating rod 9 is fixedly connected in an array on the stirring rod 7. A second mounting groove 10 is provided on the rotating rod 9. The second mounting groove 10 is connected to the first mounting groove 8. A rotating shaft 11 is rotatably connected in an array on the rotating rod 9. A stirring blade 12 is fixedly connected to one end of each rotating shaft 11 located outside the rotating rod 9. A first pushing blade 13 is fixedly connected to the upper end of the central tube 6. A scraper 14 is fixedly connected to the outer wall of the central tube 6 near the bottom of the reaction vessel 1. One side of the scraper 14 is inclined. A second pushing blade 15 is fixedly connected to the outer wall of the central tube 6 above the scraper 14. A driven gear 16 is fixedly connected to one end of the central tube 6 that passes through and extends outside the reaction vessel 1. A drive motor 17 is fixedly connected to the bottom of the reaction vessel 1. A drive gear 18 is fixedly connected to the output end of the drive motor 17. The drive gear 18 meshes with the driven gear 16.

[0045] When mixing the mixed solution, the drive motor 17 is started, which drives the drive gear 18 to rotate. The drive gear 18 rotates, which in turn drives the driven gear 16 to rotate. The rotating gear drives the central tube 6 to rotate, which in turn drives the first pusher blade 13 to rotate. The first pusher blade 13 continuously pushes the solution downward. At the same time, the rotation of the central tube 6 drives the second pusher blade 15 to rotate, which continuously pushes the solution upward, causing the mixed solution to flow axially. The rotation of the central tube 6 drives the stirring rod 7 to rotate, which in turn drives the rotating rod 9 to rotate around the central tube 6. The rotation of the rotating rod 9 drives the rotating shaft 11 to rotate, which in turn drives the stirring blade 12 to rotate around the central tube 6. While rotating around the central tube 6, the stirring blade 12 is initially in an inclined state and is in contact with the mixed solution. The mixed solution causes the stirring blade 12 to rotate around the rotating shaft 11, causing turbulence in the mixed solution at the stirring blade 12, thereby making the mixed solution more uniform. During cooling and crystallization, the drive motor 17 rotates slowly, thereby slowly stirring the mixed solution and reducing disturbance to the mixed solution. Stirring can promote the diffusion of solute molecules to the crystal surface and accelerate the crystallization speed. The scraper 14 can scrape the bottom of the reaction vessel 1 to prevent crystal accumulation.

[0046] Please see Figure 6 and Figure 8 The switching mechanism 3 includes a bevel gear 19 fixedly connected to one end of the rotating shaft 11 located in the second mounting groove 10. A first connecting rod 21 is slidably connected in the rotating rod 9. A rack 22 is fixedly connected to the end of the first connecting rod 21 near the bevel gear 19. A second connecting rod 23 is hinged to the end of the first connecting rod 21 away from the rack 22. A sliding rod 24 is slidably connected in the first mounting groove 8. The second connecting rod 23 is rotatably connected to the sliding rod 24. A sliding seat 25 is hinged to the end of the sliding rod 24 located in the central tube 6. The sliding seat 25 is slidably connected to the central tube 6. A push rod 26 is fixedly connected through the sliding seat 25. An electric push rod 27 is fixedly connected to one end of the push rod 26. The electric push rod 27 is fixedly connected to the central tube 6. A fixing component is fixedly connected to the end of the rotating rod 9 near the stirring rod 7.

[0047] During cooling and crystallization, the electric push rod 27 is activated, which drives the push rod 26 to move. The push rod 26 moves, which drives the sliding seat 25 to move. The sliding seat 25 moves, which drives the second connecting rod 23 to move. The second connecting rod 23 moves, which drives the first connecting rod 21 to move. The first connecting rod 21 moves, which drives the rack 22 to move. The rack 22 moves, which drives the bevel gear 19 to rotate. The bevel gear 19 rotates, which drives the rotating shaft 11 to rotate. The rotating shaft 11 rotates, which drives the stirring blade 12 to rotate, making the stirring blade 12 flush with the axis of the stirring rod 7. This reduces the contact area between the stirring blade 12 and the mixed solution when the stirring rod 7 drives the stirring blade 12 to rotate, reduces the disturbance to the mixed solution, accelerates the crystallization speed, and makes the crystals more evenly distributed in the solution. At the same time, it avoids the generation of more small crystal nuclei by violent stirring and the easier adsorption of impurities on the crystal surface. During mixing, the electric push rod 27 drives the push rod 26 to reset. The movement process is the opposite of the above process. The stirring blade 12 and the stirring rod 7 form a certain angle, which increases the contact area between the stirring blade 12 and the mixed solution, strengthens the stirring of the mixed solution, and makes the mixed solution more uniform.

[0048] Please see Figure 7 The fixing component includes a limiting groove 31 arrayed on the rotating rod 9 near the agitating rod 7. A limiting block 32 is slidably connected to the inner wall of the agitating rod 7 near the limiting groove 31. A connecting rod 33 is hinged to the end of the limiting block 32 away from the limiting groove 31. A connecting rod 34 is hinged to the end of the connecting rod 33 away from the limiting block 32. The end of the connecting rod 34 away from the connecting rod 33 is hinged to the sliding rod 24.

[0049] During cooling and crystallization, the sliding rod 24 moves while driving the connecting rod 34 to move. The connecting rod 34 moves while driving the connecting rod 33 to move. The connecting rod 33 moves while driving the limiting block 32 to move. The limiting block 32 engages with the limiting groove 31, thereby restricting the rotating rod 9 and preventing it from rotating, thus reducing disturbance to the mixed solution. During mixing, the process is reversed. The limiting block 32 disengages from the limiting groove 31, and the rotating rod 9 can rotate freely, causing the stirring blade 12 to rotate as well. This causes turbulence in the mixed solution at the stirring blade 12, resulting in a more uniform mixing of the mixed solution.

[0050] Please see Figure 8 The end of the limiting block 32 near the limiting groove 31 is tapered. The width of the limiting block 32 is greater than the width of the limiting groove 31. The tapered shape of one end of the limiting block 32 facilitates insertion into the limiting groove 31. Furthermore, the greater width of the limiting block 32 than the limiting groove 31 prevents the rotating rod 9 from rotating.

[0051] Please see Figure 7 The number of racks 22 and bevel gears 19 is equal, the sidewalls of each rack 22 are fixed to each other, and the racks 22 and bevel gears 19 mesh with each other.

[0052] Please see Figure 4 and Figure 5 The second propulsion blade 15 is located above the scraper 14, and the scraper 14 and the second propulsion blade 15 are offset.

[0053] The first propeller blade 13 pushes the solution downward, and the second propeller blade 15 pushes the solution upward.

[0054] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing adipic acid dihydrazide, characterized in that, Includes the following steps: S1: Dimethyl adipic acid is pulverized to 150-250 mesh, and hydrazine hydrate is dehydrated through molecular sieve to a water content of ≤5%. The molar ratio of dimethyl adipic acid to hydrazine hydrate is 1:(2.05-2.10). S2: Close all valves of the reaction vessel (1), replace the air in the reaction vessel (1) with nitrogen three times, and put the crushed dimethyl adipate powder and industrial methanol with a concentration of 99.8% into the sealed reaction vessel (1) at a mass ratio of 1: (3~5). The mixing mechanism (2) stirs the inside of the reaction vessel (1). The temperature inside the reaction vessel (1) is controlled at 20~30℃ by the jacket cooling water. Then, hydrazine hydrate is added to the reaction vessel (1) at a rate of 1.0~2.0L / h. The temperature is then raised to total reflux for 0.5~1h. The temperature inside the reaction vessel (1) is kept at 60-75℃ so that the dimethyl adipate powder can be fully dissolved and reacted. After the addition is completed, the reaction is kept at this temperature for 4-6 hours. During the reaction, white solids will gradually precipitate. When the residual amount of dimethyl adipate is ≤0.5%, the addition of hydrazine hydrate is stopped. S3: Continue heating, and control the temperature inside the reaction vessel (1) at 70~80℃ to distill off industrial methanol, water and excess hydrazine hydrate. Then, use jacket cooling water to cool the inside of the reaction vessel (1) to 10~15℃ at a rate of 5-10℃ / h, keep it warm and stir slowly for 1h to allow the adipic acid dihydrazine crystals to fully separate and grow. Then, perform solid-liquid separation to obtain adipic acid dihydrazine crystals containing water, and recover the mother liquor. S4: The separated adipic acid dihydrazide crystals containing water are washed 2-3 times with industrial methanol with a concentration of 99.8% to remove residual industrial methanol, excess hydrazine hydrate and by-products. The washed adipic acid dihydrazide crystals containing water are then purified in the recrystallization unit. S5: The purified adipic acid dihydrazide crystals containing moisture are dried at 40-80℃ and 40-53KPa until the moisture content is ≤0.5%. After drying, the crystals are crushed and sieved to 200-300 mesh, and finally sealed and packaged to obtain the finished adipic acid dihydrazide product.

2. An apparatus for preparing adipic acid dihydrazide, used for preparing the adipic acid dihydrazide according to claim 1, characterized in that, The reaction vessel includes a reaction vessel (1), a dissolving component for dissolving dimethyl adipate is fixedly connected to the upper end of the reaction vessel (1), a mixing mechanism (2) is rotatably connected to the bottom of the inner wall of the reaction vessel (1), a switching mechanism (3) is fixedly connected to the side of the mixing mechanism (2) near the bottom of the reaction vessel (1), the switching mechanism (3) is used to switch the stirring effect of the mixing mechanism (2) on the mixed solution, a feed port (4) is fixedly connected to the upper end of the dissolving component through a valve, the dissolving component is connected to the reaction vessel (1) through a valve, and a discharge port (5) is fixedly connected to the bottom of the reaction vessel (1) through a valve.

3. The apparatus for preparing adipic acid dihydrazide according to claim 2, characterized in that, The mixing mechanism (2) includes a central tube (6) rotatably connected to the inner wall of the reaction vessel (1). An array of stirring rods (7) are fixedly connected to the central tube (6). A first mounting groove (8) is provided on the stirring rods (7). An array of rotating rods (9) is fixedly connected to the stirring rods (7). A second mounting groove (10) is provided on the rotating rods (9), and the second mounting groove (10) communicates with the first mounting groove (8). An array of rotating shafts (11) are rotatably connected to the rotating rods (9). An agitator (12) is fixedly connected to one end of each rotating shaft (11) outside the rotating rod (9). The upper end of the central tube (6)... A first pusher blade (13) is fixedly connected. A scraper (14) is fixedly connected to the outer wall of the central tube (6) near the bottom of the reaction tank (1). One side of the scraper (14) is inclined. A second pusher blade (15) is fixedly connected to the outer wall of the central tube (6) above the scraper (14). A passive gear (16) is fixedly connected to one end of the central tube (6) that passes through and extends to the outside of the reaction tank (1). A drive motor (17) is fixedly connected to the bottom of the reaction tank (1). A drive gear (18) is fixedly connected to the output end of the drive motor (17). The drive gear (18) meshes with the passive gear (16).

4. The apparatus for preparing adipic acid dihydrazide according to claim 3, characterized in that, The switching mechanism (3) includes a bevel gear (19) fixedly connected to one end of the rotating shaft (11) located in the second mounting groove (10). A first connecting rod (21) is slidably connected in the rotating rod (9). A rack (22) is fixedly connected to one end of the first connecting rod (21) near the bevel gear (19). A second connecting rod (23) is hinged to one end of the first connecting rod (21) away from the rack (22). A sliding rod (24) is slidably connected in the first mounting groove (8). (23) Rotary connection with sliding rod (24), one end of sliding rod (24) located inside central tube (6) is hinged to sliding seat (25), sliding seat (25) is slidably connected to central tube (6), push rod (26) is fixedly connected through sliding seat (25), one end of push rod (26) is fixedly connected to electric push rod (27), electric push rod (27) is fixedly connected to central tube (6), and a fixing component is fixedly connected to one end of rotating rod (9) near stirring rod (7).

5. The apparatus for preparing adipic acid dihydrazide according to claim 4, characterized in that, The fixing component includes a limiting groove (31) arrayed on the rotating rod (9) near the stirring rod (7). A limiting block (32) is slidably connected to the inner wall of the stirring rod (7) near the limiting groove (31). A connecting rod (33) is hinged to the end of the limiting block (32) away from the limiting groove (31). A connecting rod (34) is hinged to the end of the connecting rod (33) away from the limiting block (32). The end of the connecting rod (34) away from the connecting rod (33) is hinged to the sliding rod (24).

6. The apparatus for preparing adipic acid dihydrazide according to claim 5, characterized in that, The end of the limiting block (32) near the limiting groove (31) is tapered, and the width of the limiting block (32) is greater than the width of the limiting groove (31).

7. The apparatus for preparing adipic acid dihydrazide according to claim 4, characterized in that, The number of racks (22) and bevel gears (19) is equal, the sidewalls of each rack (22) are fixed to each other, and the racks (22) mesh with the bevel gears (19).

8. The apparatus for preparing adipic acid dihydrazide according to claim 3, characterized in that, The second pusher blade (15) is located above the scraper (14), and the scraper (14) and the second pusher blade (15) are offset from each other.

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