Continuous evaporation desublimation purification process of ODA

Abstract

The invention relates to the technical field of separation and purification of fine chemicals, and discloses a continuous evaporation desublimation purification process of ODA, which comprises the following steps: step 1, melting; step 2, primary sublimation crystallization: conveying the molten ODA into a primary sublimator for light component removal treatment, enabling a gas-phase component to enter a primary desublimation device for crystallization, and enabling a liquid-phase component to enter a secondary sublimator; step 3, secondary sublimation crystallization: heating and evaporating the light component removed ODA in a secondary sublimator, enabling a gas-phase component to enter a product desublimation device for crystallization, enabling a small amount of undesublimated ODA and impurities in the product desublimation device to enter a tail gas desublimation device, and enabling residual liquid to enter a tertiary sublimator; and 4, third-stage sublimation crystallization: heating and evaporating the ODA residual liquid subjected to the second-stage sublimation treatment in a third-stage sublimator, crystallizing a gas-phase component in the third-stage sublimator, collecting crystals, returning to a melting stage for recycling, and discharging heavy-component residual liquid. The problems of solvent residue, low yield, low efficiency and high labor intensity in the prior art are solved.

Description

Technical Field

[0001] The invention relates to the technical field of separation and purification of fine chemicals, and in particular to a continuous evaporation and desublimation purification process of ODA. Background Art

[0002] 4,4-Diaminodiphenylether (4,4-Diaminodiphenyle-ther or 4,4-Oxydianiline), referred to as DADPE or ODA, is a high value-added fine chemical intermediate. It is the main monomer for synthesizing heat-resistant plastics such as polyimide and polymaleimide. Among them, polyimide (PI) has the advantages of high temperature resistance, radiation resistance and high mechanical strength, and is used in films, coatings, fibers, foam plastics and photoresists. The continuous use temperature of PI film reaches 250℃, and even 450℃ in a short term. It is widely used in aviation, navigation, atomic energy, electronic and electrical industries, etc. ODA is also a curing agent for synthesizing epoxy resins, an intermediate for dyes and a synthetic raw material for spices.

[0003] At present, the ODA products on the market mainly include sublimation products and crystallization products. The particles of sublimation products on the market are relatively large (5-10cm in diameter), which is not convenient for the subsequent dissolution of materials. It takes a long time to stir and dissolve after feeding, which affects the production efficiency. If the material is not fully dissolved, it will also result in a low product yield. It is understood that the sublimation technology of this product is not yet mature. Most manufacturers still use the crystallization method to produce crystallization products.

[0004] The ODA crystallization process mainly includes cooling crystallization and dissolution crystallization. The cooling crystallization method mainly uses anhydrous dimethylformamide or anhydrous methanol as solvent, and forms a supersaturated solution by cooling to achieve the purpose of ODA crystal precipitation. The dissolution crystallization method mainly uses anhydrous dimethylformamide as solvent and water as dissolution agent. Water is added dropwise in the system to rapidly reduce the solubility of ODA in the dimethylformamide-water mixed solvent, forming a supersaturated solution to precipitate crystals. The yield of ODA product obtained by the dissolution crystallization method is high, but the mother liquor of the dissolution crystallization method is a mixture of water and dimethylformamide, and it is difficult to recover dimethylformamide by ordinary distillation. At present, the main problems of the cooling crystallization method are: low yield, deep product chromaticity, small product crystal particle size, wide particle size distribution, difficult to filter, wash and dry, inconvenient for subsequent processing and use, and the crystallization process is prone to wall adhesion, which makes the crystallization process difficult to control and easy to aggregate during long-term storage. Therefore, it is of great significance to seek a method for refining ODA with moderate particle size and uniform distribution, easy to dissolve and high storage stability. Summary of the invention

[0005] The present invention aims to provide a continuous evaporation-desublimation purification process for ODA to solve the problems of solvent residue, low yield, dark product chromaticity, small product grain size, wide particle size distribution, difficulty in filtering, washing and drying, long sublimation cycle, manual scraping, low efficiency and high labor intensity in the prior art.

[0006] To achieve the above object, the present invention adopts the following technical scheme: a continuous evaporation and desublimation purification process of ODA, comprising the following steps:

[0007] Step 1, melting: heating and melting the crude ODA;

[0008] Step 2, primary sublimation crystallization: the molten ODA is transported to the primary sublimator for light removal, the gaseous component enters the primary condenser for crystallization, and the liquid component enters the secondary sublimator;

[0009] Step 3, secondary sublimation crystallization: the ODA after light removal treatment is heated and evaporated in the secondary sublimator, the gas phase components enter the product condenser for crystallization, the small amount of ODA and impurities that are not condensed in the product condenser enter the tail gas condenser, and the residual liquid enters the tertiary sublimator;

[0010] Step 4, three-stage sublimation crystallization: The ODA residual liquid after the secondary sublimation treatment is heated and evaporated in the three-stage sublimator, and the gas phase component enters the three-stage condenser for crystallization. After the crystals are collected, they are returned to the melting stage for recycling, and the heavy component residual liquid is discharged.

[0011] Preferably, as an improvement, in step 1, the heating and melting is carried out under stirring conditions, and the heating temperature is 190°C.

[0012] Preferably, as an improvement, in step 2, the temperature in the primary sublimator is 160-200° C., and the absolute pressure is 10-100 Pa.

[0013] Preferably, as an improvement, in step 2, the cooling temperature of the primary desublimator is 40-80°C.

[0014] Preferably, as an improvement, in step 3, the temperature in the secondary sublimator is 190-230° C., and the absolute pressure is 10-100 Pa.

[0015] Preferably, as an improvement, in step 3, the cooling temperature of the product desublimator is 130-180°C, and the cooling temperature of the tail gas desublimator is 40-50°C.

[0016] Preferably, as an improvement, in step 4, the temperature in the three-stage sublimator is 200-240° C., and the absolute pressure is 10-100 Pa.

[0017] Preferably, as an improvement, in step 4, the cooling temperature of the three-stage desublimator is 40-50°C.

[0018] The principle and advantage of this scheme are as follows: in practical application, in this technical scheme, in view of the problems existing in the prior art in purifying ODA, such as residual solvent, low yield, dark product chromaticity, small product crystal particle size, wide particle size distribution, difficulty in filtering, washing and drying, long sublimation cycle, manual scraping, low efficiency and high labor intensity, the purification process is comprehensively optimized, and a three-stage evaporation and sublimation method is adopted (evaporation and sublimation / sublimation crystallization includes two main processes: solid sublimation and gas sublimation. When there is a significant difference in the partial pressure of each component in the solid system to be separated in the gas phase, and each component is relatively stable to heat, the solid system to be separated is heated, and the easily sublimated component becomes gaseous and evaporates from the solid, and the cooling evaporates The gas emitted is condensed to obtain purified crystals of easily sublimable components. ), after the crude ODA is melted, it is de-lightened in the primary sublimator. In the primary sublimator, the low-boiling impurities in the molten ODA evaporate at 160-200°C and an absolute pressure of 10-100Pa. The evaporated impurity steam carries part of the ODA into the primary desublimator and is cooled to 40-80°C for crystallization; the de-lightened ODA enters the secondary sublimator, where the ODA is heated and evaporated at 190-230°C and an absolute pressure of 10-100Pa. The evaporated ODA steam enters the secondary desublimator unit, where the ODA is cooled to 130-180°C for desublimation and crystallization in the front-end product desublimator. The small amount of ODA and impurities that are not condensed are cooled and condensed at 40-50°C in the tail gas desublimator. The condensed products are collected in the tail gas desublimation product tank and returned to the front-end melting kettle for recycling. In the three-stage sublimator, the residual ODA and a small amount of heavy impurities are heated and evaporated at 200-240°C and an absolute pressure of 10-100Pa. The evaporated ODA and heavy impurity vapors are mixed and enter the three-stage desublimator, where they are cooled to 40-50°C for desublimation and crystallization. The crystals are collected and returned to the front-end melting kettle for recycling; the residual liquid is discharged to the waste liquid treatment process.

[0019] The beneficial effects of this technical solution are:

[0020] 1. This technical solution adopts a three-stage sublimation and desublimation treatment process, and optimizes the process conditions such as sublimation temperature, desublimation temperature and desublimation time. In particular, the desublimation temperature at the product extraction stage has a key influence on the product color. If the desublimation temperature is too low, the product is yellow. At the same time, this technical solution can also change the appearance of the product by adjusting the desublimation temperature and desublimation time, such as: it can be adjusted into a sheet, a block (adjustable thickness), or a powder to meet the needs of different downstream products.

[0021] 2. High product purity: Compared with most separation processes, the product purity obtained by sublimation crystallization in this technical solution is higher. The mass yield of ODA content above 99.9% is 87.4%, and the percentage yield is 88.5%, which is higher than the implementation standard. At the same time, it can reach 99.99% by coupling with melt crystallization and other technologies to synthesize ultra-high purity products.

[0022] 3. Simple and efficient process: Compared with high-purity product purification processes such as melt crystallization and recrystallization, this technical solution has a simpler process flow and higher production efficiency.

[0023] 4. No introduction of solvent: The sublimation crystallization purification process does not require the addition of solvent, which not only avoids the contamination of the product by the solvent, but also reduces the solvent recovery process and solves the problem of solvent residue in the product.

[0024] 5. Low energy consumption: Compared with traditional sublimation equipment, this process and equipment reduces energy consumption by about 60%, while greatly reducing manual operations and significantly reducing operating costs.

[0025] 6. High degree of automation: The production process and supporting equipment can realize continuous production with a high degree of automation, get rid of labor-intensive processes, and realize the vision of green environmental protection, energy saving, high efficiency and intelligent manufacturing.

[0026] 7. This technical solution adopts high vacuum evaporation and desublimation purification, covering three processes: removal of light components, product evaporation and desublimation, and product recovery; the product purity can reach 99.9%, the yield can reach more than 90%, the production cost is only 1 / 3 of the old process, and the number of operators is reduced by more than 3 / 4, which has very high economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of crude ODA raw material in an embodiment of the present invention.

[0028] Figure 2 This is a picture of the bulk ODA product after purification in an embodiment of the present invention.

[0029] Figure 3 This is a picture of the purified flaky ODA product in an example of the present invention.

[0030] Figure 4 This is a liquid chromatogram of the evaporation-desublimation product ODA in an embodiment of the present invention.

[0031] Figure 5 This is a picture of the black ODA product obtained by melt crystallization in Comparative Example 1 of the present invention.

[0032] Figure 6 This is a process flow chart of continuous evaporation and desublimation purification in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The following is further described in detail through specific implementations, but the implementation of the present invention is not limited thereto. Unless otherwise specified, the technical means used in the following implementations are conventional means well known to those skilled in the art; the experimental methods used are all conventional methods; the materials, reagents, etc. used can all be obtained from commercial channels.

[0034] Program Overview:

[0035] like Figure 6 As shown: A continuous evaporation and desublimation purification process of ODA, comprising the following steps:

[0036] Step 1: Put the ODA dried products and the unqualified products in the later stage into a melting kettle, stir and heat to 190°C, and after they are completely melted, transport them to the primary sublimator at a constant flow rate (3-6.7 kg / h, which can be adjusted according to needs in actual application) for light removal treatment.

[0037] Step 2: In the primary sublimator, the low boiling point impurities in the molten ODA evaporate at 160-200°C and an absolute pressure of 10-100 Pa. The evaporated impurity vapor carries part of the ODA into the primary sublimator and is cooled to 40-80°C for crystallization. The crystals are continuously scraped off at the scraper of the primary sublimator into the storage tank. After a certain amount is collected, they are concentrated for sublimation and recovery. The molten ODA that has been light-removed in the primary sublimator is transported to the secondary sublimator.

[0038] Step 3, the ODA after light removal enters the secondary sublimator, and is heated and evaporated at 190-230°C and an absolute pressure of 10-100Pa. The evaporated ODA vapor enters the product condenser, and the ODA is cooled to 130-180°C in the front-stage product condenser for condensation and crystallization. The crystals are continuously scraped off to the storage tank at the condenser scraper, and collected and packaged. The small amount of ODA and impurities that have not been condensed are cooled and condensed at 40-50°C in the tail gas condenser, and the condensed products are collected in the tail gas condensation product tank and returned to the front melting kettle for recycling. The ODA residual liquid treated in the secondary sublimator is transported to the tertiary sublimator.

[0039] Step 4: In the three-stage sublimator, the residual ODA and a small amount of heavy impurities are heated and evaporated at 200-240°C and an absolute pressure of 10-100 Pa. The evaporated ODA and heavy impurity vapors are mixed and enter the three-stage desublimator, where they are cooled to 40-50°C for desublimation and crystallization. The crystals are collected and returned to the front melting kettle for recycling. The residual liquid is discharged to the waste liquid treatment process.

[0040] Example 1

[0041] A continuous evaporation and desublimation purification process of ODA comprises the following steps:

[0042] S1. Put the ODA crude product ( Figure 1 ) is added to the silo of the melting kettle, stirred and heated to 190°C, and after it is completely melted (usually 1 to 2 hours), it is transported to the primary sublimator at a flow rate of 6.7kg / h.

[0043] S2: primary sublimator + primary condenser: the heating temperature of the primary sublimator is 190°C, the cooling temperature of the primary condenser is 20°C, and the impurity removal is started under the condition of absolute pressure of 100Pa to obtain samples 1 and 2.

[0044] S3, secondary sublimator + secondary desublimator: the liquid ODA after delightening in S2 is transported to the secondary sublimator at a flow rate of 6.5 kg / h. The heating temperature of the secondary sublimator is 210°C, the cooling temperature of the secondary desublimator is 160°C, and the finished product is started to be collected under an absolute pressure of 50 Pa (samples 3 to 9 are obtained, and samples are taken every 20 minutes, and their content is detected by LC).

[0045] S4, three-stage sublimator + three-stage desublimator: The residual liquid in S3 is transported to the three-stage sublimator at a flow rate of 0.5kg / h. The heating temperature of the three-stage sublimator is 240°C, the cooling temperature of the three-stage desublimator is 40°C, and the product containing heavy impurities in the latter stage is started to be extracted under an absolute pressure of 20Pa (sample 10 is obtained).

[0046] Note: In this embodiment, both the heating medium and the cooling medium are thermal oil.

[0047] Experimental Example 1 Sample Content Determination

[0048] 1. Experimental method: The ODA content of the above-obtained samples 1 to 10 was determined by liquid chromatography. The detection method was carried out in accordance with the provisions of GB / T617-2006: After the obtained samples were dissolved in a solvent, 4,4-diaminodiphenyl ether and other components were separated in a chromatographic column by a liquid chromatograph, and the chromatogram was recorded by a chromatographic workstation to obtain the content of 4,4-diaminodiphenyl ether and other components.

[0049] 2. Reagents and Materials

[0050] The preparation of the reagents used shall be carried out according to the scheme of GB / T601. The reagents and raw materials shall meet the following requirements:

[0051] a) Acetonitrile: purity greater than 99.99%;

[0052] b) Phosphate buffer: pH 6.86;

[0053] c) Buffer A: PH value 6.86 phosphate standard buffer mixed with water 1:4

[0054] d) Mobile phase: buffer A: acetonitrile = 55:45.

[0055] 3. Instruments and equipment

[0056] Instruments and equipment should meet the following requirements:

[0057] a) Detector: UV-visible light detector;

[0058] b) Recorder: chromatography workstation;

[0059] c) Injector: 100 μL micro syringe;

[0060] d) Chromatographic column: C18 (4.6*150mm, 5um).

[0061] 4. Chromatographic conditions

[0062] (1) Setting conditions

[0063] Flow rate: 1mL / min

[0064] Temperature: 40℃

[0065] Injection volume: 10 μL

[0066] Mobile phase: Buffer A: Acetonitrile = 55:45

[0067] Running time: 20 minutes

[0068] (2) Operating conditions

[0069] Peak width: 5

[0070] Slope: 70

[0071] Minimum peak area: 100

[0072] Stop time: 25min

[0073] 5. Specific measurement steps

[0074] (1) Preparation of sample solution

[0075] Weigh about 17 mg of sample, accurately weigh it, place it in a 25 ml volumetric flask, dissolve it with an appropriate amount of acetonitrile, ultrasonically cool it, and make up to volume with acetonitrile.

[0076] (2) Start the chromatograph and inject the sample after all the indicators of the instrument are stable. First, inject a blank sample and then inject the sample solution. Measure the peak area of ​​each component and calculate the content of 4,4'-diaminodiphenyl ether in the sample by the area normalization method.

[0077] (3) Display of results

[0078] For the same sample, the analysis results are expressed as the arithmetic mean of two measurement results.

[0079] The test results are shown in Table 1 and Figure 4 As shown: after purification, the ODA content in each sample of this technical solution is greater than 98%, the mass yield of ODA content above 99.9% is 87.4%, and the percentage yield is 88.5%. Figure 2-3 This is a physical picture of evaporation condensation crystallization ODA, where Figure 2 Pure white block. Figure 3 It is in the form of finer pure white flakes with metallic luster. In actual application, the product's appearance can be changed by adjusting the sublimation temperature and time, such as small flakes, blocks (the thickness of the blocks can be adjusted), or powder to meet the needs of different downstream products.

[0080] Table 1

[0081]

[0082] Comparative Example 1

[0083] This comparative example adopts the method of melt crystallization for purification, and the specific operation is as follows:

[0084] First-stage crystallization operation steps:

[0085] ① Chemical process: Add the crude 4,4-diaminodiphenyl ether into the chemical process kettle, set the circulating liquid temperature of the chemical process kettle to 220℃, and introduce nitrogen for protection during the chemical process. When all the materials are melted, use a pump to pump the materials into the crystallizer.

[0086] ②Crystallization: Set the circulating liquid temperature to 190℃ and slowly cool it down. When the internal temperature drops to 193℃, crystals begin to precipitate in the crystallizer. Control the circulating liquid temperature at 188-190℃ and the internal temperature of the crystallizer at 190℃. Discharge the mother liquor after 4 hours of crystallization.

[0087] ③ Sweating: Raise the circulating liquid temperature to 190-192°C and the temperature inside the crystallizer to 188°C for sweating for 5 hours.

[0088] ④Chemicalization: Raise the temperature of the circulating liquid to 200°C for chemical synthesis to obtain a crystalline product.

[0089] Secondary crystallization operation steps:

[0090] ①Chemical: Add the first-level crystal products collected in multiple batches into the chemical kettle, set the circulating liquid temperature of the chemical kettle to 220℃, and introduce nitrogen for protection during the chemical process. When all the materials are melted, use a pump to pump the materials into the crystallizer.

[0091] ②Crystallization: Set the circulating liquid temperature to 191℃ and slowly cool it down. When the internal temperature drops to 194.1℃, crystals begin to precipitate in the crystallizer. Control the circulating liquid temperature at 190-192℃ and the internal temperature at 194℃. Discharge the mother liquor after 6 hours of crystallization.

[0092] ③ Sweating: Raise the circulating liquid temperature to 190-195℃ and the temperature inside the crystallizer to 190℃ for sweating for 4 hours.

[0093] ④Chemicalization: Raise the temperature of the circulating liquid to 200°C for chemical synthesis to obtain a crystalline product.

[0094] Experimental Example 2

[0095] The raw materials, mother liquor, sweating liquid and products of the primary crystallization and secondary crystallization in Comparative Example 1 were tested for content by liquid chromatography. The specific test results are shown in Table 2: Compared with evaporation sublimation crystallization, melt crystallization can obtain 99.95% high-purity products, but the yield is lower. The total yield of the two-stage crystallization product is only 39.85%. At the same time, the melt crystallization product is in the form of black crystals ( Figure 5 ), subsequent decolorization treatment is required, otherwise it will be difficult to proceed to the next application.

[0096] Table 2

[0097]

[0098] Comparative Example 2: Melt Crystallization + Sublimation Crystallization Coupling

[0099] The melt crystallization operation steps are the same as those in comparative example 1. The product after melt crystallization is put into a sublimator. The operation steps are the same as those in S2 in embodiment 1. Only secondary sublimation crystallization and decolorization are performed, and the removal of the impurities after the removal of the front impurities is not performed. The crystallization product, sublimation product and kettle residue in comparative example 2 are tested for content, and the results are shown in Table 3: The results show that by adopting the operation of two-stage melt crystallization combined with sublimation crystallization, the purity of the melt crystallization product can reach 99.99%, and the product can be white flakes. The single-pass yield of the melt crystallization step is 39.85% (the recycling yield of the mother liquor and the sweating liquid after application is ≥80%), and the mass yield of the decolorization step is 95.2%, so the total yield of crystallization + decolorization is ≥76.16%. By adopting the coupling method of melt crystallization + sublimation crystallization, a product with a content of ≥99.99% and qualified chromaticity can be obtained. This method can be used as a research direction for preparing high-purity products in the future, and the total yield can be improved by further optimization.

[0100] Table 3

[0101]

[0102] Comparative Example 3 Solvent Crystallization

[0103] In this comparative example, the specific operating steps of solvent crystallization are as follows: the crude ODA product is dispersed in a mixed solvent of ethyl acetate and ethanol in a mass ratio of 1:1, the mass ratio of ODA to the mixed solvent is 1:3, and then heated to 40-50°C and n-heptane is added dropwise at a temperature of 30 minutes after the addition is completed. After cooling to 10-20°C, the mixture is stirred for 1 hour, filtered, the filter cake is rinsed with a solvent, and vacuum dried to obtain the finished ODA product.

[0104] The results show that the product yield is less than 80% and the product purity is only about 90%.

[0105] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A continuous evaporation and desublimation purification process of ODA, characterized in that: The steps include: Step 1, melting: heating and melting the crude ODA; Step 2, primary sublimation crystallization: the molten ODA is transported to the primary sublimator for light removal, the gaseous component enters the primary condenser for crystallization, and the liquid component enters the secondary sublimator; Step 3, secondary sublimation crystallization: the ODA after light removal treatment is heated and evaporated in the secondary sublimator, the gas phase components enter the product condenser for crystallization, the small amount of ODA and impurities that are not condensed in the product condenser enter the tail gas condenser, and the residual liquid enters the tertiary sublimator; Step 4, three-stage sublimation crystallization: The ODA residual liquid after the secondary sublimation treatment is heated and evaporated in the three-stage sublimator, and the gas phase component enters the three-stage condenser for crystallization. After the crystals are collected, they are returned to the melting stage for recycling, and the heavy component residual liquid is discharged.

2. The continuous evaporation-desublimation purification process of ODA according to claim 1, characterized in that: In step 1, heating and melting are carried out under stirring conditions, and the heating temperature is 190°C.

3. The continuous evaporation-desublimation purification process of ODA according to claim 2, characterized in that: In step 2, the temperature in the primary sublimator is 160-200° C., and the absolute pressure is 10-100 Pa.

4. The continuous evaporation-desublimation purification process of ODA according to claim 3, characterized in that: In step 2, the cooling temperature of the first-stage desublimator is 40-80°C.

5. The continuous evaporation-desublimation purification process of ODA according to claim 4, characterized in that: In step 3, the temperature in the secondary sublimator is 190-230° C., and the absolute pressure is 10-100 Pa.

6. The continuous evaporation-desublimation purification process of ODA according to claim 5, characterized in that: In step 3, the cooling temperature of the product desublimator is 130-180°C, and the cooling temperature of the tail gas desublimator is 40-50°C.

7. The continuous evaporation-desublimation purification process of ODA according to claim 6, characterized in that: In step 4, the temperature in the three-stage sublimator is 200-240° C., and the absolute pressure is 10-100 Pa.

8. The continuous evaporation-desublimation purification process of ODA according to claim 7, characterized in that: In step 4, the cooling temperature of the three-stage desublimator is 40-50°C.

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