A method for preparing high-purity phenoxazone based on a low-energy consumption melt crystallization-distillation coupling process

Abstract

The present application relates to fine chemical, pesticide intermediate separation and purification technical field, disclose a kind of based on low energy consumption melt crystallization-distillation coupling process preparation high-purity benzene ether ketone method, comprising the following steps: S1, primary static crystallization: benzene ether ketone crude product is melted and crystallized after temperature reduction, gradient sweating, gravity is discharged mother liquor, obtain primary product;S2, secondary static crystallization: primary product is crystallized again, depth sweating, obtain the finished product benzene ether ketone with purity ≥99.5%;S3, tertiary mother liquor crystallization: the mother liquor discharged with low-purity sweating liquid is collected to tertiary crystallization recovery;S4, the mother liquor of quaternary mother liquor crystallization: the mother liquor discharged with tertiary crystallization is carried out quaternary crystallization again;S5, the lowest eutectic distillation of residual liquid: the lowest eutectic residual liquid generated with quaternary crystallization is carried out vacuum distillation recovery effective component;S6, rectification recovery liquid returns quaternary crystallization.The present application solves the problems of organic solvent risk and ideal purity in the existing technology of benzene ether ketone refining method.

Description

Technical Field

[0001] This invention relates to the field of fine chemical and pesticide intermediate separation and purification technology, specifically to a method for preparing high-purity phenyl ether ketone based on a low-energy-consumption melt crystallization-distillation coupled process. Background Technology

[0002] Phenylacetone (2-chloro-4-(4-chlorophenoxy)acetophenone, CAS: 119851-28-4) is a core intermediate in the synthesis of the highly efficient, broad-spectrum, and low-toxicity fungicide difenoconazole. Its purity, isomer content, color, and volatile matter directly determine the product quality, yield, and impurity levels of difenoconazole. With increasingly stringent domestic environmental policies and the rapid development of the high-end pesticide market, downstream enterprises are imposing stringent requirements on phenylacetone: purity ≥99.5%, isomers ≤0.5%, color ≤10 APHA, and no solvent residue. Industrial phenylacetone is mainly prepared through etherification and condensation reactions. The reaction system is complex, and the product contains a large number of structurally similar positional isomers, polychlorinated derivatives, unreacted raw materials, light components, and high-boiling substances. The isomers have highly similar boiling points and polarities to the product phenylacetone, making deep removal difficult using conventional separation methods.

[0003] Currently, the industry commonly uses the following two purification routes: 1. Recrystallization from organic solvents Using toluene, xylene, methanol, ethanol, etc. as solvents, crude phenyl ether ketone is heated to dissolve, hot filtered, cooled to crystallize, centrifuged, and vacuum dried to obtain the finished product. This process has obvious defects: (1) It uses a large amount of organic solvents, resulting in high VOC emissions, high safety risks, and high environmental protection costs; (2) Solvent recovery is energy-intensive and it is difficult to completely remove solvent residues; (3) Centrifugation and drying equipment require large investments, have high operating costs, and are complex to operate; (4) The phenyl ether ketone content in the mother liquor is high and cannot be efficiently recovered, resulting in a comprehensive yield of only 80%; (5) It is difficult to stably control the isomers below ≤0.5%.

[0004] 2. Reduced pressure distillation Because phenyl ether ketone and its isomers have very similar boiling points, conventional vacuum distillation is insufficient for efficient separation, making it difficult to obtain high-purity products and meet the high-end requirement of 99.5%. Furthermore, phenyl ether ketone is unstable at high temperatures and is prone to discoloration and decomposition over prolonged periods at high temperatures. Additionally, distillation is energy-intensive, requires expensive equipment, has low single-tower throughput, and is unsuitable for large-scale production.

[0005] Therefore, developing a novel process for recovering eutectic compounds by static melting and crystallization coupled with distillation has become an urgent need for the high-end, green, and large-scale production of phenyl ether ketone. Summary of the Invention

[0006] The present invention aims to provide a method for preparing high-purity phenyl ether ketone based on a low-energy-consumption melt crystallization-distillation coupled process, so as to solve the problems of organic solvent risk and unsatisfactory purification purity in the existing phenyl ether ketone purification methods.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing high-purity phenyl ether ketone based on a low-energy-consumption melt crystallization-distillation coupled process, comprising the following steps: S1. Primary static crystallization: After melting the crude phenyl ether ketone, the product is cooled to crystallize, subjected to gradient sweating, and discharged by gravity to obtain the primary product. S2, Secondary Static Crystallization: The primary product is recrystallized and deeply volatilized to obtain a finished product of phenyl ether ketone with a purity ≥99.5%; S3, Third-stage mother liquor crystallization: Collect the mother liquor discharged from the first-stage crystallization and the low-purity sweating liquid for third-stage crystallization recovery; S4. Crystallization of mother liquor in the fourth stage: The mother liquor discharged from the third stage crystallization is crystallized again in the fourth stage. S5. Minimum Eutectic Residue Distillation: The minimum eutectic residue produced by the fourth-stage crystallization is subjected to vacuum distillation to recover the effective components. S6. The distillation recovery liquid is returned to the fourth-stage crystallization.

[0008] Preferably, as an improvement, in step S1, the melting temperature of the crude phenyl ether ketone is 65~70℃.

[0009] Preferably, as an improvement, in step S1, the final crystallization temperature of primary crystallization is 36~41℃, the cooling rate is 0.5~3℃ / h, the crystallization time is 4.0~5.5h, the sweating temperature is 41~59℃, and the sweating time is 7.5~10.0h.

[0010] Preferably, as an improvement, in step S2, the purity of the secondary crystallization raw material is 98.9%~99.1%, the crystallization endpoint temperature of the secondary crystallization is 49~53℃, the sweating endpoint temperature is 58~60℃, and the sweating time is 5.0~7.5 h.

[0011] Preferably, as an improvement, in step S3, the purity of the raw material for tertiary crystallization is 82%~86%, and the crystallization endpoint temperature is 33~37℃.

[0012] Preferably, as an improvement, in step S3, the tertiary crystallizer is purified by sweating to a purity of ≥92% and then reused as feed for the primary crystallizer.

[0013] Preferably, as an improvement, in step S4, the purity of the fourth-stage crystallization raw material is 78%~82%, and the crystallization endpoint temperature is 30~33℃.

[0014] Preferably, as an improvement, in step S4, the evaporation purification of the fourth-stage crystallizer to a purity of ≥85% is reused as feed for the third-stage crystallizer.

[0015] Preferably, as an improvement, in step S5, the distillation conditions are: vacuum 600~1200Pa, kettle temperature 120~180℃, and column top temperature 155~175℃.

[0016] Preferably, as an improvement, in step S5, the purity of the distillation recovery liquid is 78%~82%, and it is reused for fourth-stage crystallization.

[0017] The principle and advantages of this solution are as follows: In practical applications, this technical solution addresses the problems existing in the separation and purification of phenyl ether ketones by analyzing the characteristics of the raw materials and products: the pure phenyl ether ketone has a melting point of 54-56℃, while the isomers have significantly lower melting points than the main product. The mixture of the two products exhibits a fixed eutectic equilibrium point with a minimum content of 67%. This invention abandons the industry-standard solvent medium and directly relies on temperature gradient control of solid-liquid equilibrium to achieve separation. This approach is highly specific for phenyl ether ketone systems with multiple impurities. 1) High-temperature melting (65~70℃) achieves complete homogeneous liquefaction of crude product, eliminates the interference of solvent and solute co-solution, and avoids the formation of a ternary co-solution system between solvent and isomers and phenyl ether ketone, which increases the difficulty of separation; 2) The primary / secondary main crystallization adopts low-speed temperature control and long-time crystallization (4.0~5.5h for primary crystallization and a dedicated temperature window for secondary crystallization). The extremely slow cooling rate of 0.5~3℃ / h induces the regular growth of large and complete crystals of phenyl ether ketone on the heat exchange wall, avoiding the common problems in the industry of rapid cooling crystallization producing fine crystals and encapsulating isomer-rich mother liquor. 3) Gradient temperature rise sweating (1℃ / h programmed temperature rise) utilizes the solubility difference between the crystal surface and internal impurities to peel off the isomer-rich mother liquor wrapped in the interstices of the crystal layer by layer; and innovatively classifies and separates sweating liquid and mother liquor of different purities for storage, abandoning the industry's extensive model of mixing and recycling materials, and eliminating the dilution of high-purity intermediate products by low-purity impurities from the material flow direction.

[0018] Furthermore, conventional melt crystallization in the industry only involves a single-stage mother liquor reuse. This invention, however, sets up three- and four-stage recovery crystallization units based on the purity gradient of the material, forming a purity-tiered recycling chain: the first-stage crystallization produces 82%~86% low-purity mother liquor, which is purified to ≥92% by the third-stage crystallization and returned to the first-stage feed; the third-stage crystallization produces 78%~82% mother liquor, which is purified to ≥85% by the fourth-stage crystallization and returned to the third-stage feed. This graded recovery logic is a specific and creative optimization and matching based on the purity decay law of continuous crystallization of phenyl ether ketone. Through step-by-step purification, the vast majority of the effective components of the mother liquor circulate within the crystallization unit, significantly reducing the amount of material requiring distillation. When the mother liquor circulates to 67% of the minimum eutectic component, the solid-liquid balance of conventional melt crystallization fails, making further purification impossible, and the industry generally discards the residual liquor directly. This invention unconventionally sends the extreme residual liquid separately into vacuum distillation, treating only a small amount of eutectic waste liquid, rather than distilling all the crude product: using a high vacuum of 600~1200Pa and a low temperature of 120~180℃, the boiling point of phenyl ether ketone is significantly reduced, avoiding high-temperature decomposition and discoloration; the 78%~82% recovery liquid obtained by distillation precisely matches the purity requirements of the fourth-stage crystallization feed, and is directly refluxed to the fourth-stage crystallization, constructing a closed loop with zero waste liquid discharge throughout the process, solving the problem of the inability to recover the lowest eutectic material.

[0019] The beneficial effects of this technical solution are as follows: 1. This technical solution completely eliminates the addition of organic solvents, thereby eliminating solvent loss, solvent recovery energy consumption, and the cost of organic waste liquid and hazardous waste disposal from the source. The device relies solely on heat transfer oil / ethylene glycol water medium for temperature control. Only a small amount of distillation residue is generated at the level of waste. The device is equipped with a sealed intermediate tank to buffer all mother liquor and saturation liquid. There is no process waste liquid discharged throughout the entire process, resulting in significant environmental advantages.

[0020] 2. This technical solution significantly improves the separation yield. The overall yield of traditional solvent crystallization is only about 60-80%, while the overall yield of this coupled process is 86.88%, and the yield per 100% is increased to 91.90%. The mother liquor fractional crystallization enables the internal recycling and reuse of most low-grade materials, greatly reducing raw material loss and meeting the economic benefit requirements of an industrial production scale of 3,500 tons per year.

[0021] 3. This technical solution significantly reduces process energy consumption. Melting and crystallization do not require high-energy-consuming operations such as solvent evaporation and condensation. The distillation unit only processes a small amount of mother liquor that has reached the limit of the eutectic equilibrium point, which greatly reduces the distillation feed load. At the same time, the mother liquor crystallization optimizes the crystal structure, improves the sweating separation efficiency, shortens the single batch cycle, and reduces the energy consumption of temperature control medium circulation.

[0022] 4. This technical solution offers greater control over product purity. It obtains 98.8%~99.0% intermediate product through primary purification and crystallization, and then produces a compliant finished product with ≥99.5% phenyl ether ketone and ≤0.5% isomer impurities through secondary gradient sweating refining. The segmented sweating process allows for graded reuse of materials to avoid dilution of high-quality products by low-purity materials, ensuring that the purity indicators meet the standards for high-end products. Attached Figure Description

[0023] Figure 1 This is a process flow diagram for the low-energy-consumption melt crystallization-distillation coupling process of preparing high-purity phenyl ether ketone according to the present invention.

[0024] Figure 2 This is a DSC thermal analysis curve of crude phenyl ether ketone raw material.

[0025] Figure 3 This is a DSC thermal analysis curve of the refined high-purity phenyl ether ketone product.

[0026] Figure 4 This is the gas chromatographic FID spectrum of crude phenyl ether ketone raw material.

[0027] Figure 5 This is a real photo of the first-stage static melting and crystallization process.

[0028] Figure 6 This is a real photo of the secondary static melting and crystallization process.

[0029] Figure 7 This is the gas chromatogram of the secondary crystallized product.

[0030] Figure 8 These are real photos of the entire process of three-stage mother liquor crystallization.

[0031] Figure 9 The gas chromatogram is used to verify the lowest eutectic component of phenyl ether ketone. Detailed Implementation

[0032] The following detailed description provides further details on specific embodiments, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following embodiments are conventional means well known to those skilled in the art; the experimental methods used are all conventional methods; and the materials and reagents used are all commercially available.

[0033] Example 1 like Figure 1 As shown, a method for preparing high-purity phenyl ether ketone (CAS No.: 119851-28-4) based on a low-energy-consumption melt crystallization-distillation coupled process includes the following steps: S1. Primary static crystallization: After the crude phenyl ether ketone is melted at 65~70℃, it is cooled to crystallize, subjected to gradient sweating (1℃ / h programmed temperature increase), and the mother liquor is discharged by gravity to obtain the primary product; the final crystallization temperature is 36~41℃, the cooling rate is 0.5~3℃ / h, the crystallization time is 4.0~5.5h, the sweating temperature is 41~59℃, and the sweating time is 7.5~10.0h; S2, Secondary Static Crystallization: The purity of the primary product is 98.9%~99.1%. The primary product is recrystallized and subjected to deep perspiration to obtain a finished phenyl ether ketone with a purity ≥99.5%. The crystallization endpoint temperature is 49~53℃, the perspiration endpoint temperature is 58~60℃, the perspiration time is 5.0~7.5 h, and the purity of the finished phenyl ether ketone is ≥99.5%, with isomers ≤0.5%. S3, Tertiary Mother Liquor Crystallization: The mother liquor discharged from the primary crystallization and the low-purity sweating liquid (the purity of the low-purity sweating liquid is basically equivalent to that of the mother liquor, but lower than the content of the raw materials) are collected and recycled through tertiary crystallization; the purity of the raw materials for tertiary crystallization is 82%~86%, the crystallization endpoint temperature is 33~37℃, and the sweating is purified to a purity ≥92%, which is then reused as feed for primary crystallization. S4. Crystallization of mother liquor in the fourth stage: The mother liquor discharged from the third stage crystallization is crystallized again in the fourth stage; the purity of the raw material for the fourth stage crystallization is 78%~82%, the crystallization endpoint temperature is 30~33℃, and it is purified by sweating to a purity of ≥85% and then reused as feed for the third stage crystallization. S5. Minimum Eutectic Residue Distillation: The minimum eutectic residue generated by the fourth-stage crystallization is sent to vacuum distillation to recover the effective components; the distillation conditions are: vacuum 600~1200Pa, kettle temperature 120~180℃, column top temperature 155~175℃, and the purity of the distillation recovery liquid is 78%~82%, which is reused in the fourth-stage crystallization. S6. The distillation recovery liquid is returned to the fourth-stage crystallization to achieve a closed loop for the entire system.

[0034] The final product obtained by the refining process in this embodiment has a purity of ≥99.5%, isomers ≤0.5%, a yield of ≥91% (100% purity), and no organic solvents, wastewater, or hazardous waste discharge.

[0035] The thermal analysis DSC charts of the phenoxy ketone raw material and the final product in this embodiment are as follows: Figure 2 and Figure 3 As shown: The results show that the phenyl ether ketone raw material begins to melt at 53℃, completely melts at 59℃, begins to evaporate at 245℃, and completely evaporates at 293℃; the phenyl ether ketone product begins to melt at 57℃, completely melts at 63℃, begins to evaporate at 249℃, and completely evaporates at 285℃.

[0036] In this embodiment, the GC detection method and conditions are as follows: Table 1

[0037] The main experimental data for each batch are summarized in the table below: Primary crystallization: The experimental raw material (94.1184%) underwent primary crystallization at a medium temperature of 41-48℃ and an internal temperature of 42.8-49.78℃. Crystallization took 4.5 hours, resulting in a crystallization rate of 82.86%. During the sweating process, the internal temperature was controlled at 43.5-57.9℃, and the medium temperature at 46-57.5℃. The internal temperature rose slowly during the sweating process. The sweating period was 10.0 hours, followed by 1.0 hour of material processing, for a single cycle of 15.50 hours. The gas chromatogram of the phenyl ether ketone raw material is shown below. Figure 4 As shown in the diagram, the primary crystallization process is as follows: Figure 5 As shown.

[0038] The experimental results are shown in Table 2: Table 2 Material Name weight / g Percentage % Cumulative percentage Test results (%) raw material 2160.0 100 100 94.1184 Mother liquor 370.3 17.14 17.14 86.2569 sweating liquid 1 235.0 10.88 28.02 79.9878 sweating liquid 2 208.2 9.64 37.66 91.7525 product 1327.9 61.48 99.14 98.9464 Secondary crystallization: Using the primary crystallized sweating liquid and chemical products as raw materials, purification is achieved through melt crystallization. The secondary crystallization medium temperature is 50.5~52.1℃, and the internal temperature is 49.8~52.1℃. Crystallization takes 2.5 hours, with a crystallization rate of 83.37%. During the sweating process, the internal temperature is controlled at 53.7~58.4℃, and the medium temperature is 56.7~59.8℃. The internal temperature rises slowly during the sweating process. The sweating process takes 6.0 hours, and the chemical process takes 1.0 hour, with a single cycle of 9.5 hours. A 99.78% qualified product is obtained. The secondary crystallization process diagram is shown below. Figure 6 As shown, the gas chromatogram of the secondary crystallized product is as follows: Figure 7 As shown.

[0039] The experimental results are shown in Table 3: Table 3 Material Name weight / g Percentage % Cumulative percentage Test results (%) raw material 1321.7 100 100 98.9464 Mother liquor 151.1 11.43 11.43 96.4956 sweat 175.6 13.29 24.72 97.7754 product 986.2 74.62 99.33 99.7802 Three-stage crystallization (mother liquor crystallization): The mother liquor crystallization medium temperature is 46~28℃, the internal temperature is 46.9~30.1℃, crystallization time is 6.5h, and the crystallization rate is 96.5% (there is some material trapped, not completely drained). During the sweating process, the medium temperature is controlled at 37~51℃, the internal temperature is 36.8~50.5℃, and the internal temperature rises slowly with the sweating process. The sweating time is 3.5h, the material melting time is 1.0h, and the single-cycle time is 13.0h. The mother liquor crystallization process diagram is shown below. Figure 8 As shown.

[0040] The experimental results are shown in Table 4: the product purity is 94.0275% (initial raw material 94.1184%), and the yield is 43.28%.

[0041] Table 4 Material Name weight / g Percentage % Cumulative percentage Test results (%) raw material 805 100 100 85.9262 Mother liquor 24.9 3.09 3.09 79.4633 sweating liquid 1 190.1 23.61 26.71 79.4328 sweating liquid 2 154.6 19.20 45.91 78.9679 sweating liquid 3 73.8 9.17 55.08 81.4538 product 348.4 43.28 98.36 94.0275 Fourth-order crystallization (mother liquor crystallization): The experimental results are shown in Table 5: After crystallization, the experimental raw material (78.6723%) can be purified to 85.7220%, with a single-pass yield of 61.51% and a single-pass cycle of 4.0h.

[0042] After two crystallizations using raw material with a purity of 67.4053%, the mother liquor content stabilized at around 67%, and the minimum eutectic content of this phenyl ether ketone sample was 67%.

[0043] Table 5 Material Name weight / g Percentage % Cumulative percentage Test results (%) raw material 122.1 100 100 78.6723 Mother liquor 46.7 38.25 38.25 67.4053 product 75.1 61.51 99.76 85.7220 The detection results of eutectic distillation are shown in Table 6: Table 6 Material Name weight / g Percentage % Cumulative percentage Test results (%) raw material 301.5 100.00 100.00 67.4053 Fraction 1 43.4 14.39 14.39 57.7980 Fraction 2 41.6 13.80 28.19 55.9543 product 174.3 57.8 85.99 81.5723 The remains of the cauldron 42.2 14.00 99.99 0.1439 The above test results show that: Primary crystallization of the product of this invention: purified from 94.1184% to 98.9464%, single-pass yield 61.48%, single-pass cycle 11.0 h. Secondary crystallization of the product: purified from 98.9464% to 99.5478%, single-pass yield 74.62%, single-pass cycle 7.0 h. Mother liquor crystallization: purified from 85.9262% to 94.0275%, single-pass yield 43.28%, single-pass cycle 7.5 h. Mother liquor crystallization: purified from 78.6723% to 85.7220%, single-pass yield 61.51%, single-pass cycle 4.0 h.

[0044] Low eutectic content exploration experiment: Using 67.4054% purity raw material as the raw material, two crystallizations were performed, and the content of the mother liquor was stabilized at around 67%. It is speculated that the lowest eutectic content of this phenyl ether ketone sample is 67%. Figure 9 The eutectic temperature is 24℃. Distillation process: The product purity is reduced from 67.4053% to 81.5723%, with a mass yield of 57.8% and a 100% yield of 66.8%.

[0045] Based on the above experimental data, the circulating mass yield of the molten crystallization step after the sweating liquid was applied was 80%, and the circulating yield was 85%; after coupled distillation treatment of the mother liquor with low eutectic content, the circulating mass yield was 86.88%, and the circulating yield was 91.90%.

[0046] Comparative Example 1 The difference between this comparative example and Example 1 is as follows: In this comparative example, the secondary crystallization medium temperature of the experimental raw material (98.8982%) was 50.5~52.1℃, the internal temperature was 49.8~52.1℃, crystallization time was 2.5h, and the crystallization rate was 83.37%. During the sweating process, the internal temperature was controlled at 53.7~58.4℃, the medium temperature was 56.7~59.8℃, and the internal temperature rose slowly with the sweating process. The sweating time was 6.0h, the chemical treatment time was 1.0h, and the single-cycle time was 9.5h. The product purity was 99.5984%, and the yield was 42.91%. The mixed sweating process (2+3+chemical treatment) yielded 67.79%, the purity was 99.5183%, and the single-cycle time was 5.5h. The results in Table 7 show that: this comparative example did not use precise segmented gradient sweating, and the single-pass product yield of secondary crystallization was only 42.91%, which is far lower than the single-pass yield of 74.62% of secondary crystallization in Example 1; although the purity met the standard after mixing multiple sweating liquids, the material diversion control was poor, and a large amount of high-quality products were mixed into the sweating liquid, which increased the back-end circulation load and lengthened the overall production cycle.

[0047] Table 7 Material Name weight / g Percentage % Cumulative percentage Test results / % raw material 2281.4 100 100 98.8982 Mother liquor 379.3 16.63 16.63 97.7647 sweating liquid 1 345.6 15.15 31.77 96.6594 sweating liquid 2 338.4 14.83 46.61 99.2816 sweating liquid 3 229.2 10.05 56.65 99.5253 Chemicals 979.0 42.91 99.57 99.5984 Comparative Example 2 The difference between this comparative example and Example 1 is as follows: In this comparative example, the temperature of the tertiary crystallization (mother liquor crystallization) medium was 27~38℃, the internal temperature was 29.8~40.2℃, crystallization time was 5.5h, and the crystallization rate was 98.01%. During the sweating process, the internal temperature was controlled at 39.2~53.7℃, the medium temperature was 38~53℃, and the internal temperature rose slowly with the sweating process. The sweating time was 10.5h, the material was processed for 0.5h, and the single-cycle time was 16.5h. The product purity was 92.1675%, and the yield was 17.84%. Purification to the raw material level was not achieved.

[0048] Poor separation may be due to incomplete drainage of the mother liquor. The separation effect after coagulation and sweating is not good. The crystallization temperature and time can be optimized, and sweating can be performed after the mother liquor is completely drained.

[0049] Comparative Example 3 The difference between this comparative example and Example 1 is that in this comparative example, the mother liquor crystallization medium temperature is 28~38℃, the internal temperature is 31.4~40.8℃, crystallization time is 5.0h, and the crystallization rate is 89.44%. During the sweating process, the internal temperature is controlled at 40.1~50.7℃, and the medium temperature is 40~51.5℃. The internal temperature rises slowly during the sweating process, which lasts 7.5h, followed by 0.5h of material processing, for a single cycle of 13.0h. The product purity is 90.4115%, and the yield is 32.52%. The three-stage crystallization temperature range setting in this comparative example is unreasonable, resulting in the product purity failing to reach the raw material level.

[0050] Comparative Example 4 The difference between this comparative example and Example 1 is as follows: In this comparative example, the temperature of the primary crystallization medium for the experimental raw material (94.3416%) was 40.1~46.3℃, the internal temperature was 39.4~45.6℃, crystallization time was 3.0h, and the crystallization rate was 92.34%. During the sweating process, the internal temperature was controlled at 43.6~57.6℃, the medium temperature was 46.2~59.7℃, and the internal temperature rose slowly with the sweating process. The sweating time was 7.5h, the chemical treatment time was 1.0h, and the single-cycle time was 11.5h. The product purity was 99.2711%, and the yield was 38.80%. The mixed sweating liquid 3+4+chemical was used as the secondary crystallization raw material. After mixing, the purity was 98.8982%, the yield was 58.65%, and the single-cycle time was 9.5h.

[0051] Table 8 Material Name weight / g Percentage % Cumulative percentage Test results / % raw material 3969.9 100 100 94.3416 Mother liquor 304.2 7.66 7.66 82.2105 sweating liquid 1 694.5 17.49 25.16 83.3126 sweating liquid 2 586.4 14.77 39.93 93.0576 sweating liquid 3 434.2 10.94 50.87 97.6448 sweating liquid 4 353.7 8.91 59.77 98.7617 Chemicals 1540.4 38.80 98.58 99.2711 The data in Table 8 show that the cooling rate and crystallization time of the primary crystallization in this comparative example are unreasonable: crystallization took only 3.0 hours, resulting in incomplete crystal growth and a large amount of impurities entrained in the fine crystals. Furthermore, the single-pass yield of the primary crystallization in this comparative example is extremely low: only 38.80%, compared to 61.48% in Example 1. A large amount of product from this comparative example enters each stage of the sweating liquid, leading to a significant increase in the feed pressure for the secondary crystallization stage. Because Comparative Example 4 did not employ a gradient slow heating and sweating process, impurity removal was insufficient, requiring mixing multiple stages of sweating liquid to meet the purity requirements of the secondary raw materials, thus lengthening the process and increasing energy consumption.

[0052] Comparative Example 5 This comparative example, Chinese patent CN 104876811 A, discloses a purification method for 3,4′-dichlorophenyl ether ketone, which uses solvent crystallization for purification. The crystallization solvent system is petroleum ether and cyclohexane, a single aliphatic hydrocarbon solvent. The crystallization yield is 72-78%, and the product purity is ≥99.2%. This method cannot achieve the product yield and purity of the embodiments of this invention.

[0053] Comparative Example 6 This comparative example is disclosed in Chinese patent CN113861004A, which discloses a catalytic synthesis method for phenyl ether ketone, an intermediate of phenyl ether methyl ether azole. The method uses a cooling crystallization process with a single crystallization yield of 75%~82% and a single impurity of ≤0.3%. However, phenyl ether ketone still has considerable solubility at the crystallization endpoint of 15~20℃, resulting in low raw material utilization rate in single batch production and limited single batch output.

[0054] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing high-purity phenyl ether ketone based on a low-energy-consumption melt crystallization-distillation coupled process, characterized in that, Includes the following steps: S1. Primary static crystallization: After melting the crude phenyl ether ketone, the product is cooled to crystallize, subjected to gradient sweating, and discharged by gravity to obtain the primary product. S2, Secondary Static Crystallization: The primary product is recrystallized and deeply volatilized to obtain a finished product of phenyl ether ketone with a purity ≥99.5%; S3, Third-stage mother liquor crystallization: Collect the mother liquor discharged from the first-stage crystallization and the low-purity sweating liquid for third-stage crystallization recovery; S4. Crystallization of mother liquor in the fourth stage: The mother liquor discharged from the third stage crystallization is crystallized again in the fourth stage. S5. Minimum Eutectic Residue Distillation: The minimum eutectic residue produced by the fourth-stage crystallization is subjected to vacuum distillation to recover the effective components. S6. The distillation recovery liquid is returned to the fourth-stage crystallization.

2. The method for preparing high-purity phenyl ether ketone based on a low-energy-consumption melt crystallization-distillation coupled process according to claim 1, characterized in that: In step S1, the melting temperature of the crude phenyl ether ketone is 65~70℃.

3. The method for preparing high-purity phenyl ether ketone based on a low-energy-consumption melt crystallization-distillation coupled process according to claim 2, characterized in that: In step S1, the final crystallization temperature of primary crystallization is 36~41℃, the cooling rate is 0.5~3℃ / h, the crystallization time is 4.0~5.5h, the sweating temperature is 41~59℃, and the sweating time is 7.5~10.0h.

4. A method for preparing high-purity phenyl ether ketone based on a low-energy-consumption melt crystallization-distillation coupled process according to claim 3, characterized in that: In step S2, the purity of the secondary crystallization raw material is 98.9%~99.1%, the crystallization endpoint temperature of the secondary crystallization is 49~53℃, the sweating endpoint temperature is 58~60℃, and the sweating time is 5.0~7.5 h.

5. The method for preparing high-purity phenyl ether ketone based on a low-energy-consumption melt crystallization-distillation coupled process according to claim 4, characterized in that: In step S3, the purity of the raw material for tertiary crystallization is 82%~86%, and the crystallization endpoint temperature is 33~37℃.

6. The method for preparing high-purity phenyl ether ketone based on a low-energy-consumption melt crystallization-distillation coupled process according to claim 5, characterized in that: In step S3, the tertiary crystallizer is purified by sweating to a purity of ≥92% and then reused as feed for the primary crystallizer.

7. The method for preparing high-purity phenyl ether ketone based on a low-energy-consumption melt crystallization-distillation coupled process according to claim 6, characterized in that: In step S4, the purity of the fourth-stage crystallization raw material is 78%~82%, and the crystallization endpoint temperature is 30~33℃.

8. The method for preparing high-purity phenyl ether ketone based on a low-energy-consumption melt crystallization-distillation coupled process according to claim 7, characterized in that: In step S4, the quaternary crystallizer is purified by sweating to a purity of ≥85% and then reused as feed for the tertiary crystallizer.

9. The method for preparing high-purity phenyl ether ketone based on a low-energy-consumption melt crystallization-distillation coupled process according to claim 8, characterized in that: In step S5, the distillation conditions are: vacuum 600~1200Pa, kettle temperature 120~180℃, and column top temperature 155~175℃.

10. The method for preparing high-purity phenyl ether ketone based on a low-energy-consumption melt crystallization-distillation coupled process according to claim 9, characterized in that: In step S5, the distillation recovery liquid has a purity of 78%~82% and is reused for fourth-stage crystallization.

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