The invention discloses a method for preparing N, Napos through melt crystallization. Method for preparing 2-bis-(2, 2, 6, 6-tetramethyl-4-piperidinyl) 1, 6-hexamethylenediamine
By using the melt crystallization method in the process of purifying N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine, the heat exchange system and crystallization device are used to control heating and cooling, the problems of high energy consumption and environmental pollution in the prior art are solved, and a low-energy-consuming and efficient purification effect is achieved.
Patent Information
- Application Number
- CN202311494240.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-10
- Publication Date
- 2025-05-13
AI Technical Summary
In the prior art, the evaporation crystallization method has problems such as high energy consumption, high pollution and unenvironmental protection when purifying N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine, and the solvent recrystallization method is harmful to the environment.
The purification of N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine is carried out by melt crystallization. By setting up a first and a second heat exchange system, a melt crystallization device, a raw material tank and a receiving tank in the purification system, the heating and cooling process is controlled to achieve low energy consumption purification.
It reduces the energy consumption of the purification process, improves the purity of the product, simplifies the operating process, reduces the harm to the environment, and does not require the introduction of new solvents.
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Figure CN119977872A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of chemical purification, and particularly relates to a method for preparing N,N′-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine by melt crystallization. Background Art
[0002] Evaporation and crystallization technology is one of the most common unit operations in chemical production. This method evaporates the solvent in the solution by heating, thereby crystallizing the solvent to achieve the purpose of purifying chemical substances and chemical products. However, with the global energy shortage and the increasing demand for environmentally friendly production technology, the evaporation and crystallization technology used in industry has high energy consumption and high pollution, which is contrary to the purpose of green industrial development at this stage.
[0003] N,N′-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine (hexanediamine piperidine) is an important raw material used in the preparation of hindered amine light stabilizers. Hexanediamine piperidine will generate a variety of impurities during the preparation process, and the impurities mainly include 2,2,6,6-tetramethylpiperidinol, 2,2,6,6-tetramethylpiperidone, 1,6-hexanediamine, 2,2,6,6-tetramethylpiperidone and 1,6-hexanediamine monosubstituted products and asymmetric products. In the past, the solvent recrystallization method was often used to purify hexanediamine piperidine. Because new solvents need to be introduced during the crystallization process and it is harmful to the environment, this method is not recommended for use in industry.
[0004] CN114949901 adopts a continuous distillation method to purify N,N′-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine, which has high energy consumption. The purity of the obtained hexanediaminepiperidine is 95.6%, and the equipment investment cost is high. Therefore, it is urgent to find a low-energy consumption and high-efficiency method to purify hexanediaminepiperidine.
[0005] As a new method of chemical separation, melt crystallization has low energy consumption, high purity of separated chemical substances, and is environmentally friendly. It has gradually become an emerging method of separation in the chemical industry. Summary of the invention
[0006] The invention overcomes the defects in the prior art and provides a method for preparing N,N′-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine by melt crystallization. The method reduces energy consumption, has low requirements on the purity of crude N,N′-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine, does not require the introduction of new solvents, has no obvious harm to the environment, simplifies the operation process, and improves production efficiency.
[0007] The present invention provides a method for purifying N,N′-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine, wherein the method is carried out in a purification system. The system comprises a first heat exchange system, a second heat exchange system, a melt crystallization device, a primary raw material tank, a first receiving tank and a second receiving tank, the melt crystallization device comprises a feed port, a crystallization plate, a heating jacket and a sealing cover, the sealing cover is used to seal the heating jacket, the sealing cover is a flat plate with holes, the aperture of the holes matches the crystallization plate, the crystallization plate penetrates the holes and is arranged in the melt crystallization device, the feed port and the sealing cover are connected by a pipeline, the crystallization plate is connected by a pipeline to the first heat exchange system, the heating jacket is connected by a pipeline to the second heat exchange system, the primary raw material tank is connected to the feed port of the melt crystallization device, and the first receiving tank and the second receiving tank are respectively connected to the first discharge port and the second discharge port of the melt crystallization device.
[0008] Furthermore, the crystallization plate is a hollow structure filled with a heat-conducting medium, and the temperature of the crystallization plate is controlled by the first heat exchange system and the heat-conducting medium.
[0009] Furthermore, the heating jacket is a hollow structure filled with a heat-conducting medium, and the temperature of the heating jacket is controlled by the second heat exchange system and the heat-conducting medium.
[0010] Furthermore, the primary raw material tank also includes a crude product feed port, and the crude product feed port is arranged at the upper end of the primary raw material tank.
[0011] Furthermore, the first receiving tank further comprises a first discharge valve, and the first discharge valve is arranged at the lower end of the first receiving tank.
[0012] Furthermore, the second receiving tank also includes a second discharge valve, and the second discharge valve is arranged at the lower end of the second receiving tank.
[0013] The method comprises the following steps: step 1): adding crude N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine to a melt crystallization device, heating the melt crystallization device to a first heating temperature through a heat exchange system until low melting point impurities melt, discharging the impurities, and continuing to heat the remaining material to a second heating temperature until all the crude N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine is melted;
[0014] Step 2): Cooling down the heat exchange system;
[0015] Step 3): When crystallization occurs on the crystallization plate, the heat exchange system described in step 2) is continuously cooled down. When the thickness of the crystallization layer is 2 to 20 cm, the cooling is stopped.
[0016] Step 4): The remaining uncrystallized material in the melt crystallization device is used as the next batch of raw materials, and the crystallization layer material (pure product) of step 3) is heated to melt through a heat exchange system, and the pure product is collected.
[0017] Furthermore, the heat exchange system includes a first heat exchange system and a second heat exchange system.
[0018] In one embodiment of the present invention, the method comprises the following steps:
[0019] Step 1): adding crude N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine to a melt crystallization device, and simultaneously heating the melt crystallization device to a first heating temperature by a first heat exchange system and a second heat exchange system until low-melting-point impurities melt, and discharge the impurities, and continuing to heat the remaining material to a second heating temperature until all the crude N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine melts;
[0020] Step 2): performing a cooling treatment on the first heat exchange system and the second heat exchange system simultaneously;
[0021] Step 3): When crystallization occurs on the crystallization plate, the first heat exchange system and the second heat exchange system described in step 2) are continuously cooled down, and when the thickness of the crystal layer is 2 to 20 cm, the cooling is stopped;
[0022] Step 4): The remaining uncrystallized material in the melt crystallization device of step 3) is used as the next batch of raw materials, and the crystallization layer material (pure product) of step 3) is heated to melt through the first heat exchange system, and the pure product is collected.
[0023] Further, in step 1), the first heating temperature is 45-65°C (such as 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C, 65°C), preferably, 50-65°C, more preferably, 50-60°C.
[0024] Further, in step 1), the second heating temperature is 65-85°C (such as 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 82°C, 83°C, 84°C, 85°C), preferably, 70-85°C, more preferably, 70-80°C.
[0025] Furthermore, the heating temperatures of the first heat exchange system and the second heat exchange system in step 1) may be the same or different.
[0026] Further, the heating temperatures of the first heat exchange system and the second heat exchange system in step 1) can be 50-85°C (such as 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 82°C, 83°C, 84°C, 85°C).
[0027] In one embodiment of the present invention, step 1) heats the melt crystallization device to a first heating temperature through the first heat exchange system and the second heat exchange system at the same time until the low melting point impurities melt, which specifically includes the following steps: setting the heating temperatures of the first heat exchange system and the second heat exchange system to 50-65°C, and heating the melt crystallization device to the first heating temperature until the low melting point impurities melt.
[0028] In one embodiment of the present invention, step 1) further heating the remaining material to a second heating temperature until the crude N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine product is completely melted, which specifically comprises the following steps: setting the heating temperatures of the first heat exchange system and the second heat exchange system to 70-80°C, and further heating the remaining material to the second heating temperature until the crude N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine product is completely melted.
[0029] Furthermore, the purity of the crude N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine in step 1) is 75-95% (e.g., 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%), preferably, 70-90%.
[0030] Furthermore, in step 2), the cooling rate of the first heat exchange system is higher than the cooling rate of the second heat exchange system.
[0031] Furthermore, in step 2), the cooling rate of the second heat exchange system is 1 to 8°C / h (such as 1°C / h, 2°C / h, 3°C / h, 4°C / h, 5°C / h, 6°C / h, 7°C / h, 8°C / h), preferably 2 to 7°C / h, and more preferably 2 to 5°C / h.
[0032] Furthermore, in step 2), the cooling rate of the first heat exchange system is 2 to 10°C / h (such as 2°C / h, 3°C / h, 4°C / h, 5°C / h, 6°C / h, 7°C / h, 8°C / h, 9°C / h, 10°C / h), preferably 3 to 10°C / h, and more preferably 3 to 6°C / h.
[0033] Furthermore, in step 3), the temperature after the first heat exchange system is cooled down is lower than the temperature after the second heat exchange system is cooled down.
[0034] Further, in step 3), the temperature of the second heat exchange system after cooling is 55-70°C (such as 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, 70°C), preferably, 55-65°C, and more preferably, 60-65°C.
[0035] Further, in step 3), the temperature of the first heat exchange system after cooling is 40-60°C (such as 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C), preferably, 50-60°C, more preferably, 53-58°C.
[0036] Furthermore, the purity of the uncrystallized remaining material in the step 3) melt crystallization device is 50-70% (mass fraction), for example, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%.
[0037] In one embodiment of the present invention, when the purity of the uncrystallized residual material in the melt crystallization device in step 3) is 50-70% (mass fraction), it is used as a primary raw material and mixed with a higher purity crude N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine, and the purity of the mixed crude N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine is controlled between 80% and 90% (mass fraction).
[0038] In one embodiment of the present invention, if the purity of the uncrystallized remaining material in the melt crystallization device in step 3) is lower than 50 (mass fraction), it is discharged and no longer used.
[0039] Furthermore, in step 3), the thickness of the crystal layer is 2 to 20 cm (such as 2 cm, 3 cm, 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm, 11 cm, 12 cm, 13 cm, 14 cm, 15 cm, 16 cm, 17 cm, 18 cm, 19 cm, 20 cm), preferably 5 to 15 cm, and more preferably 5 to 10 cm.
[0040] The preparation process of the present invention is suitable for the purification of low-purity N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine. Except for the N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine entering the separation process, the crude N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine obtained in each step can be used as a primary raw material. The N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine in the whole system can be recovered, and the purity of the N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine reaches more than 99%. The preparation process of the invention adopts a continuous solvent-free method to purify the N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine, does not need to treat the solvent, simplifies the process flow, and improves the production efficiency. Compared with the recrystallization process or other purification processes, the energy consumption of the process is effectively reduced, and the purity of the N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine prepared by the process can reach a higher level. BRIEF DESCRIPTION OF THE DRAWINGS
[0041] Figure 1 The present invention is a schematic diagram of the process flow of continuous melt crystallization production of N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine using the method of the present invention.
[0042] Figure 2 This is a schematic diagram of the process flow for continuous melt crystallization production of N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine using the method of Comparative Example 4.
[0043] 1-first heat exchange system, 2-second heat exchange system, 3-second receiving tank, 4-melting crystallization device, 5-first receiving tank, 6-primary raw material tank, 31-second discharge valve, 41-feed port, 42-crystallization plate, 43-heating jacket, 51-first discharge valve, 61-crude product feed port, 44-sealing plate. DETAILED DESCRIPTION
[0044] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the best implementation case.
[0045] The present invention is further described in detail below in conjunction with the accompanying drawings.
[0046] In the description of the present invention, it should be understood that the orientations or positional relationships indicated by the terms "up", "down", "left", "right", "front", "back", "middle", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not specifically indicate that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.
[0047] Example 1
[0048] A method for purifying N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine through melt crystallization, wherein the method is carried out in a purification system.
[0049] The system comprises a first heat exchange system-1, a second heat exchange system-2, a melt crystallization device-4, a primary raw material tank-6, a first receiving tank-5 and a second receiving tank-3, the melt crystallization device-4 comprises a feed port-41, a crystallization plate-42, a heating jacket-43 and a sealing cover-44, the sealing cover-44 is used to seal the heating jacket-43, the sealing cover-44 is a flat plate with holes, the aperture of the holes matches the crystallization plate-42, the crystallization plate-42 passes through the holes and is arranged in the melt crystallization device-4, the feed port-41 and the sealing cover-44 are connected by a pipeline, the crystallization plate-42 is connected to the first heat exchange system-1 by a pipeline, the heating jacket-43 is connected to the second heat exchange system-2 by a pipeline, the primary raw material tank-6 is connected to the feed port-41 of the melt crystallization device, the first receiving The tank-5 and the second receiving tank-3 are respectively connected to the first discharge port and the second discharge port of the melt crystallization device-4; the crystallization plate-42 is a hollow structure filled with a heat-conducting medium, and the temperature of the crystallization plate-42 is controlled by the first heat exchange system-1 and the heat-conducting medium; the heating jacket-43 is a hollow structure filled with a heat-conducting medium, and the temperature of the heating jacket-43 is controlled by the second heat exchange system-2 and the heat-conducting medium; the primary raw material tank-6 also includes a crude product feed port-61, and the crude product feed port-61 is arranged at the upper end of the primary raw material tank-6; the first receiving tank-5 also includes a first discharge valve-51, and the first discharge valve-51 is arranged at the lower end of the first receiving tank-5; the second receiving tank-3 also includes a second discharge valve-31, and the second discharge valve-31 is arranged at the lower end of the second receiving tank-3.
[0050] The method comprises the following steps:
[0051] like Figure 1 As shown, the process flow of continuous melt crystallization production of N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine is as follows: open the feed port, add the crude N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine into the melt crystallization device, open the first heat exchange system and the second heat exchange system to heat up to 50-65°C until the low melting point impurities melt, discharge the impurities into the first receiving tank, and discharge them from the first discharge valve, continue to heat the remaining materials to the second heating temperature of 70-80°C, and start cooling; the second heat exchange system is cooled at a cooling rate of 2-5°C / h, and the first heat exchange system is cooled at a rate of 3-6°C / h. When the second heat exchange system is cooled to (60-65)°C and the first heat exchange system is cooled to (53-58)°C, crystallization begins. When the crystal layer reaches a thickness of 5-10 cm, crystallization is stopped, and the remaining uncrystallized material in the melt crystallization device is placed in the first receiving tank, and the first heat exchange system is started to heat the material on the crystallization plate to melt, and then placed in the second receiving tank to collect the pure product. The crude product in the first receiving tank is returned to the melt crystallization device to continue the next step of melt crystallization. When the purity of the crude N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl) 1,6-hexanediamine in the first receiving tank is lower than 50% (mass fraction), it is no longer used as a primary raw material.
[0052] The platinum-cobalt color number in the present invention is tested by GB / T 3143-1982 Liquid Chemical Product Color Determination Method (Hazen Unit - Platinum-Cobalt Color Number);
[0053] Heat resistance test steps: put the sample into a thermal oxygen aging box (Shanghai Jinghong Testing Equipment Factory), set the temperature to 195°C, oxidize for 2 hours, and take out the sample to cool.
[0054] Example 2
[0055] Open the feed pipe, add the crude N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine to the melt crystallization device, heat the first heat exchange system and the second heat exchange system to 55°C until the low melting point impurities melt, discharge the impurities to the first receiving tank, and discharge from the first discharge valve, continue to heat the remaining materials (80°C for the first heat exchange system and the second heat exchange system) until the materials are completely melted and then start to cool down; the second heat exchange system cools down at a cooling rate of 5°C / h, and the first heat exchange system cools down at a rate of 6°C / h. When the second heat exchange system cools down to 65°C and the first heat exchange system cools down to 58°C, crystals appear on the crystallization plate, and crystallization stops when the crystal layer thickness is 10cm. Put the remaining uncrystallized materials in the melt crystallization device into the first receiving tank, heat the first heat exchange system until the materials on the crystallization plate melt, put the materials into the second receiving tank, and collect the pure products. The crude product in the first receiving tank is returned to the melt crystallization device to continue the next step of melt crystallization.
[0056] The contents of various substances before and after crystallization are shown in Table 1.
[0057] Table 1 Material content before and after crystallization
[0058]
[0059]
[0060] Table 2 Platinum-Cobalt Color Number
[0061] Normal temperature (20℃) After heat treatment Before crystallization 55 89 After crystallization 15 45
[0062] The comprehensive energy consumption is calculated to be 0.138 tce / t (ton of standard coal / ton of product). There are many types of impurities before crystallization, but the types of impurities are significantly reduced after crystallization. By adopting the preparation process of the present invention, the purity of the target product - hexamethylenediaminepiperidine can be as high as 99.5%.
[0063] Example 3
[0064] The crude hexamethylenediamine piperidine (mass fraction 80.23%) in the first receiving tank is pumped into the melt crystallization device through the primary raw material tank. The first heat exchange system and the second heat exchange system are heated to 60°C until the low melting point impurities melt, and the impurities are discharged into the first receiving tank and discharged from the first discharge valve. The remaining materials continue to be heated (70°C for the first heat exchange system and the second heat exchange system) until the materials are completely melted and then begin to cool down; the second heat exchange system is cooled at a cooling rate of 4°C / h, and the first heat exchange system is cooled at a rate of 5°C / h. When the second heat exchange system is cooled to 62°C and the first heat exchange system is cooled to 56°C, crystals appear on the crystallization plate, and crystallization stops when the crystal layer thickness is 5cm. The remaining uncrystallized materials in the melt crystallization device are placed in the first receiving tank, and the first heat exchange system is started to heat until the materials on the crystallization plate melt, and the materials are placed in the second receiving tank to collect the pure products. The crude product of the first receiving tank is returned to the melt crystallization device to continue the next step of melt crystallization.
[0065] The contents of various substances before and after crystallization are shown in Table 3.
[0066] Table 3 Material content before and after crystallization
[0067]
[0068] Table 4 Platinum-Cobalt Color Number
[0069] Normal temperature (20℃) After heat treatment Before crystallization 61 98 After crystallization 26 47
[0070] The comprehensive energy consumption is calculated to be 0.142 tce / t (ton of standard coal / ton of product). There are many types of impurities before crystallization, but the types of impurities are significantly reduced after crystallization. By adopting the preparation process of the present invention, the purity of the target product - hexamethylenediaminepiperidine can be as high as 99.1%.
[0071] Example 4
[0072] The crude N,N′-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine is added to the melt crystallization device from the primary raw material tank. The first heat exchange system and the second heat exchange system are heated to 50°C until the low melting point impurities melt, and the impurities are discharged to the first receiving tank and discharged from the first discharge valve. The remaining materials continue to be heated (75°C for the first heat exchange system and the second heat exchange system) until the materials are completely melted and then start to cool down; the second heat exchange system is cooled at a cooling rate of 2°C / h, and the first heat exchange system is cooled at a rate of 4°C / h. When the second heat exchange system is cooled to 60°C and the first heat exchange system is cooled to 53°C, crystals appear on the crystallization plate, and crystallization stops when the crystal layer thickness is 8cm. The remaining uncrystallized materials in the melt crystallization device are placed in the first receiving tank, and the first heat exchange system is started to heat until the materials on the crystallization plate melt, and the materials are placed in the second receiving tank to collect the pure products. The crude product in the first receiving tank is returned to the melt crystallization device to continue the next step of melt crystallization.
[0073] The contents of various substances before and after crystallization are shown in Table 5.
[0074] Table 5 Material content before and after crystallization
[0075]
[0076] Table 6 Platinum-Cobalt Color Number
[0077] Normal temperature (20℃) After heat treatment Before crystallization 29 75 After crystallization 18 43
[0078] The comprehensive energy consumption is calculated to be 0.140 tce / t (ton of standard coal / ton of product). There are many types of impurities before crystallization, but the types of impurities are significantly reduced after crystallization. By adopting the preparation process of the present invention, the purity of the target product - hexamethylenediaminepiperidine can be as high as 99.2%.
[0079] Comparative Example 1
[0080] The crude N,N′-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine (purity, 90% by mass or more) and acetone are uniformly mixed in a mass ratio of 5:2 and stirred for 0.5h, cooled to below 10°C, centrifuged, and the lower layer solid is retained; the lower layer solid material is mixed with acetone in a mass ratio of 5:2, the temperature is increased (below the boiling point of acetone) until the material is completely dissolved, filtered, cooled to below 10°C, centrifuged, and a solid precipitate is obtained; the solid precipitate is heated, and the solvent is removed by means of reduced pressure distillation to obtain a refined crude N,N′-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine.
[0081] The contents of various substances before and after recrystallization are shown in Table 7.
[0082] Table 7 Material content before and after recrystallization
[0083]
[0084] Table 8 Platinum-Cobalt Color Number
[0085] Normal temperature (20℃) After heat treatment Before crystallization 53 88 After crystallization 23 51
[0086] The comprehensive energy consumption is calculated to be 0.205tce / t (ton of standard coal / ton of product), which is relatively high. There are many types of impurities before crystallization, but fewer types of impurities after crystallization.
[0087] Comparative Example 2
[0088] Open the feed pipe and add the crude N,N′-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine to the melt crystallization device. The first heat exchange system and the second heat exchange system heat up (80°C for the first heat exchange system and the second heat exchange system) until the materials are completely melted and then start cooling; the second heat exchange system cools down at a cooling rate of 5°C / h, and the first heat exchange system cools down at a rate of 6°C / h. When the second heat exchange system cools down to 65°C and the first heat exchange system cools down to 58°C, crystals appear on the crystallization plate, and crystallization stops when the crystal layer thickness is 10cm. Put the remaining materials in the melt crystallization device into the first receiving tank, heat the second heat exchange system until the materials on the crystallization plate are melted, put the materials into the second receiving tank, and collect the pure products. The crude products in the first receiving tank are returned to the melt crystallization device to continue the next step of melt crystallization.
[0089] The contents of various substances before and after crystallization are shown in Table 9.
[0090] Table 9 Material content before and after crystallization
[0091]
[0092] Table 10 Platinum-Cobalt Color Number
[0093] Normal temperature (20℃) After heat treatment Before crystallization 52 95 After crystallization 26 56
[0094] The comprehensive energy consumption is calculated to be 0.154tce / t (ton of standard coal / ton of product), which is relatively high. There are many types of impurities before crystallization, but the types of impurities are reduced after crystallization. The purity of the target product, hexamethylenediaminepiperidine, is 95%, which is relatively low.
[0095] Comparative Example 3
[0096] Open the feed pipe and add the crude N,N′-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine to the melt crystallization device. The first heat exchange system and the second heat exchange system heat up (85°C for the first heat exchange system and the second heat exchange system) until the materials are completely melted and then start cooling; the second heat exchange system cools down at a cooling rate of 10°C / h, and the first heat exchange system cools down at a rate of 8°C / h. When the second heat exchange system cools down to 58°C and the first heat exchange system cools down to 65°C, crystals appear on the heating jacket, and crystallization stops when the crystal layer thickness is 10cm. Put the remaining materials in the melt crystallization device into the first receiving tank, heat the first heat exchange system and the second heat exchange system until the materials on the heating jacket are melted, put the materials into the second receiving tank, and collect the pure products. The crude products in the first receiving tank are returned to the melt crystallization device to continue the next step of melt crystallization.
[0097] The contents of various substances before and after crystallization are shown in Table 11.
[0098] Table 11 Material content before and after crystallization
[0099]
[0100]
[0101] Table 12 Platinum-Cobalt Color Number
[0102] Normal temperature (20℃) After heat treatment Before crystallization 47 89 After crystallization 30 65
[0103] The comprehensive energy consumption is calculated to be 0.153tce / t (ton of standard coal / ton of product), which is relatively high. There are many types of impurities before crystallization, but the types of impurities are reduced after crystallization. The purity of the target product, hexamethylenediaminepiperidine, is 94%, which is relatively low.
[0104] Comparative Example 4
[0105] Open the feed pipe, add the crude N,N′-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine to the melt crystallization device, heat the first heat exchange system to 55°C, discharge the impurities to the first discharge tank, and start cooling after the temperature rises until the material is completely melted; the first heat exchange system cools down at a cooling rate of 5°C / h; when the first heat exchange system cools down to 58°C, crystals appear on the crystallization plate / heating jacket, and crystallization stops when the crystal layer thickness reaches 10cm. Put the remaining material in the melt crystallization device into the first receiving tank, heat the first heat exchange system until the crystallized material melts, put the material into the second receiving tank, and collect the pure product. The crude product in the first receiving tank is returned to the melt crystallization device to continue the next step of melt crystallization.
[0106] The contents of various substances before and after crystallization are shown in Table 13.
[0107] Table 13 Material content before and after crystallization
[0108]
[0109] Table 14 Platinum-Cobalt Color Number
[0110] Normal temperature (20℃) After heat treatment Before crystallization 65 99 After crystallization 28 65
[0111] The comprehensive energy consumption is calculated to be 0.152tce / t (ton of standard coal / ton of product), which is relatively high. There are many types of impurities before crystallization, but the types of impurities are reduced after crystallization. The purity of the target product, hexamethylenediaminepiperidine, is 95%, which is relatively low.
[0112] Comparative Example 5
[0113] The crude N,N′-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine is added to the melt crystallization device from the primary raw material tank. The first heat exchange system and the second heat exchange system are heated to 50°C until the low melting point impurities melt, and the impurities are discharged to the first receiving tank and discharged from the first discharge valve. The remaining materials continue to be heated (75°C for the first heat exchange system and the second heat exchange system) until the materials are completely melted and then start to cool down; the second heat exchange system is cooled at a cooling rate of 2°C / h, and the first heat exchange system is cooled at a rate of 4°C / h. When the second heat exchange system is cooled to 60°C and the first heat exchange system is cooled to 53°C, crystals appear on the crystallization plate, and crystallization stops when the crystal layer thickness is 20cm. The remaining uncrystallized materials in the melt crystallization device are placed in the first receiving tank, and the first heat exchange system is started to heat until the materials on the crystallization plate melt, and the materials are placed in the second receiving tank to collect the pure products. The crude product in the first receiving tank is returned to the melt crystallization device to continue the next step of melt crystallization.
[0114] The contents of various substances before and after crystallization are shown in Table 5.
[0115] Table 15 Material content before and after crystallization
[0116]
[0117] Table 16 Platinum-Cobalt Color Number
[0118] Normal temperature (20℃) After heat treatment Before crystallization 27 79 After crystallization 21 46
[0119] The comprehensive energy consumption is calculated to be 0.161tce / t (ton of standard coal / ton of product), which is relatively high. There are many types of impurities before crystallization, but the types of impurities are reduced after crystallization. The purity of the target product, hexamethylenediaminepiperidine, is 98%, which is relatively low.
Claims
1. A method for purifying N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)1,6-hexanediamine, wherein the method is carried out in a purification system, wherein the system comprises a first heat exchange system, a second heat exchange system, a melt crystallization device, a primary raw material tank, a first receiving tank and a second receiving tank, wherein the melt crystallization device comprises a feed port, a crystallization plate, a heating jacket and a sealing cover, wherein the sealing cover is used to seal the heating jacket, wherein the sealing cover is a flat plate with holes, wherein the aperture of the holes matches the crystallization plate, wherein the crystallization plate penetrates the holes and is arranged in the melt crystallization device, wherein the feed port and the sealing cover are connected via a pipeline, wherein the crystallization plate is connected via a pipeline to the first heat exchange system, wherein the heating jacket is connected via a pipeline to the second heat exchange system, wherein the primary raw material tank is connected to the feed port of the melt crystallization device, wherein the first receiving tank and the second receiving tank are respectively connected to the first discharge port and the second discharge port of the melt crystallization device; The method comprises the following steps: Step 1): adding crude N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine to a melt crystallization device, heating the melt crystallization device to a first heating temperature through a heat exchange system until low-melting-point impurities melt, discharging the impurities, and continuing to heat the remaining material to a second heating temperature until all the crude N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine is melted; Step 2): Cooling down the heat exchange system; Step 3): When crystallization occurs on the crystallization plate, the heat exchange system described in step 2) is continuously cooled down. When the thickness of the crystallization layer is 2 to 20 cm, the cooling is stopped. Step 4): the remaining uncrystallized material in the melt crystallization device is used as the next batch of raw materials, the crystallization layer material in step 3) is heated to melt through a heat exchange system, and the pure product is collected; The heat exchange system comprises a first heat exchange system and a second heat exchange system; In step 2), the cooling rate of the first heat exchange system is higher than the cooling rate of the second heat exchange system.
2. The method according to claim 1, characterized in that The heating temperatures of the first heat exchange system and the second heat exchange system in step 1) are the same or different.
3. The method according to claim 1, characterized in that In step 2), the cooling rate of the first heat exchange system is 2 to 10°C / h; Preferably, in step 2), the cooling rate of the second heat exchange system is 1-8°C / h.
4. The method according to claim 2, characterized in that The heating temperatures of the first heat exchange system and the second heat exchange system in step 1) are 50-85°C respectively.
5. The method according to claim 4, characterized in that Step 1) The melt crystallization device is heated to a first heating temperature by the first heat exchange system and the second heat exchange system at the same time to melt the low-melting-point impurities, which specifically includes the following steps: the heating temperatures of the first heat exchange system and the second heat exchange system are set to 50-65°C, and the melt crystallization device is heated to the first heating temperature to melt the low-melting-point impurities.
6. The method according to claim 1, characterized in that Step 1) further heating the remaining material to a second heating temperature until the crude N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine product is completely melted, which specifically comprises the following steps: setting the heating temperatures of the first heat exchange system and the second heat exchange system to 70-80° C., and further heating the remaining material to a second heating temperature until the crude N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine product is completely melted.
7. The method according to claim 1, characterized in that In step 1), the purity of the crude N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine is 75-95%, preferably 70-90%.
8. The method according to claim 1, characterized in that In step 3), the temperature of the first heat exchange system after cooling is 40-60°C, preferably 50-60°C.
9. The method according to claim 1, characterized in that In step 3), the temperature of the second heat exchange system after cooling is 55-70°C, preferably 55-65°C.
10. The method according to claim 1, characterized in that Step 3) The thickness of the crystal layer is 5 to 15 cm, preferably 5 to 10 cm.