Method and device for recovering solvent generated in synthesis of polyphenyl ether

Abstract

The invention belongs to the technical field of polymer synthesis, and particularly relates to a method and a device for recovering a solvent generated in synthesis of polyphenyl ether. The solvent comprises a filtering solvent and a washing solvent which are generated by treating polyphenyl ether slurry, and the recovery method comprises the following steps: step 1, carrying out multi-stage extraction treatment on the filtering solvent and water, and separating an oil-phase solvent and a water-phase solvent; and 2, carrying out refining treatment on the oil-phase solvent to obtain toluene. And step 3, mixing the washing solvent with the water-phase solvent, then carrying out azeotropic removal treatment, separating out an azeotropic solvent and a mixed solution, and mixing the azeotropic solvent with the filtering solvent to repeat the step 1. And 4, separating methanol and water in the mixed solution, and repeating the step 1 by using the water in the step 4. It can be seen that the treatment capacity of the extraction procedure can be reduced by recycling the two solvents with different toluene and methanol contents respectively, water serves as the extraction agent, the extraction agent is non-toxic, harmless, cheap and easy to obtain and can be recycled, and by controlling the proportion of the extraction agent added into the system, on the basis that impurities are not introduced, the content of the toluene and the content of the methanol in the extraction procedure can be reduced. And a better extraction and separation effect is achieved with lower energy consumption. And the heat generated in the recovery process can be recycled in the system, so that the energy consumption of the whole process is further reduced.

Description

Technical Field

[0001] This application relates to the field of polymer synthesis technology, and in particular to a method and apparatus for recovering solvents generated during the synthesis of polyphenylene ether. Background Technology

[0002] With the rapid development of electronic information, copper-clad laminates (CCLs) have also flourished as substrates for printed circuit boards (PCBs). Polyphenylene ether (PPE), as a high-performance thermoplastic resin, possesses excellent mechanical properties, heat resistance, and dimensional stability, and exhibits low dielectric loss over a wide temperature and frequency range, making it an ideal material for CCL fabrication. The synthesis of low molecular weight PPE typically uses methanol and toluene as solvents. The large volume of solvent used significantly increases the difficulty of solvent recovery.

[0003] In related technologies, conventional distillation methods are insufficient for achieving efficient separation of methanol and toluene, and the high energy consumption of solvent evaporation significantly increases production costs. Furthermore, methanol and toluene form an azeotrope; introducing organic solvents for extraction and separation of methanol and toluene presents significant drawbacks for polyphenylene ether (PPE) production systems. Because PPE products are extremely sensitive to impurities, incomplete separation by the extractant, coupled with residual organic solvents reused in the production process, can interfere with the polymerization reaction, affecting key indicators such as mechanical strength, heat resistance, and dielectric properties, thereby reducing product quality. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems. This application provides a method and apparatus for recovering solvents generated during the synthesis of polyphenylene ether.

[0005] According to one aspect of this application, a method for recovering solvents generated during the synthesis of polyphenylene ethers is provided, the solvents including filtration solvents and washing solvents, the recovery method comprising:

[0006] Step 1: Perform multi-stage extraction on the filtered solvent and water to separate the oil phase solvent and the aqueous phase solvent;

[0007] Step two: The oil phase solvent is purified to obtain toluene;

[0008] Step 3: Mix the washing solvent with the aqueous solvent and perform a de-azeotropic treatment to separate the azeotropic solvent and the mixture. Then, mix the azeotropic solvent with the filtration solvent and repeat Step 1.

[0009] Step four: Separate the methanol and water from the mixture, and use the water from step four to repeat step one.

[0010] Compared with existing technologies, the solvent recovery method for the synthesis of polyphenylene ether provided in this application includes first performing multi-stage extraction treatment on the filtered solvent and water to separate the oil phase solvent and the aqueous phase solvent. This solvent, containing a high content of toluene and a low content of methanol, is partially miscible with water. Multi-stage extraction allows for multiple gas-liquid equilibrium partitioning, significantly improving the separation purity of the oil phase solvent and the aqueous phase solvent. Next, the oil phase solvent is purified to obtain toluene. Then, the washing solvent is mixed with the aqueous phase solvent and subjected to de-azeotropic treatment to separate the azeotropic solvent and the mixture. This azeotropic solvent is then mixed with the filtered solvent and repeatedly subjected to multi-stage extraction with water. Finally, methanol and water are separated from the mixture, and the water from step four is used for repeated extraction steps. In other words, the water used in this application includes both fresh water and recycled water. This method forms a closed loop of extraction-azeotropy-separation-reuse, reducing the amount of fresh water used and lowering energy consumption. Furthermore, the heat generated by separating water from the mixture can be exchanged with the feed heat during the azeotropic degassing process, allowing the heat to be recycled within the system and further reducing the overall energy consumption of the process. Water is both a natural byproduct of the polyphenylene ether reaction and a poor solvent, and when used as an extractant, it will not introduce new organic solvents or impurities into the system. Even if trace amounts remain in the subsequently recycled water, it will not negatively affect the polyphenylene ether polymerization reaction, product precipitation effect, or key indicators such as the mechanical strength, heat resistance, and dielectric properties of the final product, perfectly meeting the core requirement of the polyphenylene ether system for "no impurity interference."

[0011] Based on this, the filtration solvent in this embodiment has a high toluene content and a low methanol content. The washing solvent, on the other hand, has a low toluene content and a high methanol content. Compared to the traditional method of collecting and recycling all solvents from the polyphenylene ether production process, this application recovers the two solvents with different toluene and methanol contents separately, using water as the extractant. This extractant is non-toxic, harmless, inexpensive, readily available, and recyclable. By controlling its proportion in the system, a good extraction and separation effect can be achieved with low energy consumption without introducing impurities. Furthermore, the heat generated during the recovery of the washing solvent can be recycled within the system, further reducing the overall energy consumption of the process. Experiments show that the purity of toluene and methanol recovered by this method can reach up to 99.99%, and the recycling rate can reach over 99.5%, meeting the solvent recycling requirements of less than 0.01% catalyst content in toluene and at least 99.5% purity in methanol.

[0012] According to another aspect of this application, a solvent recovery apparatus for the synthesis of polyphenylene ether is provided. This apparatus is applied to the aforementioned method for recovering the solvent generated during the synthesis of polyphenylene ether, and includes:

[0013] The system includes a solvent filtration storage unit, a water storage unit, a multi-stage extraction and separation unit, an oil phase solvent buffer unit, an aqueous phase solvent buffer unit, an oil phase solvent refining unit, an aqueous phase solvent de-azeotropic unit, a washing solvent storage unit, a mixed liquid separation unit, a toluene storage unit, and a methanol storage unit. The outlets of the solvent filtration storage unit and the water storage unit are connected to the inlet of the multi-stage extraction and separation unit. The outlets of the multi-stage extraction and separation unit are connected to the inlets of the oil phase solvent buffer unit and the aqueous phase solvent buffer unit, respectively. The outlet of the oil phase solvent buffer unit is connected to the inlet of the oil phase solvent refining unit, and the outlet of the oil phase solvent refining unit is connected to the inlet of the toluene storage unit. The outlets of the washing solvent storage unit and the aqueous phase solvent buffer unit are connected to the inlet of the aqueous phase solvent de-azeotropic unit, respectively. The first outlet of the aqueous phase solvent de-azeotropic unit is connected to the inlet of the solvent filtration storage unit. The second outlet of the aqueous phase solvent de-azeotropic unit is connected to the inlet of the mixed liquid separation unit. The first outlet of the mixed liquid separation unit is connected to the inlet of the methanol storage unit, and the second outlet of the mixed liquid separation unit is connected to the inlet of the water storage unit.

[0014] Compared with the prior art, the beneficial effects of the solvent recovery device for synthesizing polyphenylene ether provided in this application are the same as the beneficial effects of the solvent recovery method for synthesizing polyphenylene ether described above, and will not be repeated here.

[0015] It should be understood that both the foregoing general description and the following detailed description are exemplary and intended to provide further illustration of the claimed technology. Attached Figure Description

[0016] The above and other objects, features, and advantages of this application will become more apparent from the more detailed description of the embodiments of this application in conjunction with the accompanying drawings. The accompanying drawings are used to provide a further understanding of the embodiments of this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof. In the accompanying drawings, the same reference numerals generally represent the same components or steps.

[0017] Figure 1 A flowchart illustrating a method for recovering solvents generated during the synthesis of polyphenylene ether according to an embodiment of this application is shown;

[0018] Figure 2 A schematic diagram of the structure of a solvent recovery device generated during the synthesis of polyphenylene ether according to an embodiment of this application is shown;

[0019] Figure 3 A schematic diagram of the solvent recovery device generated from the synthesis of polyphenylene ether in the comparative example of this application is shown.

[0020] Figure label:

[0021] 100 - Oil phase solvent refining unit; 101 - Toluene refining tower; 102 - First condenser-reflux assembly; 1021 - First condenser; 1022 - First reflux equipment; 1023 - First reflux pump; 1024 - First inlet line; 200 - Aqueous phase solvent de-azeotropic unit; 201 - Azeotropic tower; 202 - Second condenser-reflux assembly; 2021 - Second condenser; 2022 - Second reflux equipment; 2023 - Second reflux pump; 2024 - Second inlet line; 300 - Mixture separation unit; 301 - Methanol separation tower; 302 - Third condenser-reflux assembly; 3021 - Third condenser; 3022 - Third reflux equipment; 3023 - Third reflux pump; 3024 - Third inlet line; V101 - Filtration solvent storage equipment; V102 - Water storage equipment; V103 - Oil phase solvent buffer equipment; V104 - Water The following equipment is included: a solvent buffer unit; V105 - washing solvent storage unit; V106 - toluene storage unit; V107 - methanol storage unit; S101 - multi-stage extraction and separation unit; P101 - first transfer pump; P102 - second transfer pump; P103 - third transfer pump; P104 - fourth transfer pump; P105 - fifth transfer pump; P106 - sixth transfer pump; F101 - first solvent line; F102 - second solvent line; E101 - first reboiler unit; E102 - second reboiler unit; E103 - third reboiler unit; G101 - first bottom pump; G102 - second bottom pump; G103 - third bottom pump; M101 - first cooling unit; M102 - second cooling unit; M103 - third cooling unit; M104 - fourth cooling unit; and Y101 - preheating unit. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this application more apparent, exemplary embodiments according to this application will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments of this application. It should be understood that this application is not limited to the exemplary embodiments described herein.

[0023] With the rapid development of electronic information, copper-clad laminates (CCLs) have also flourished as substrates for printed circuit boards (PCBs). Polyphenylene ether (PPE), as a high-performance thermoplastic resin, possesses excellent mechanical properties, heat resistance, and dimensional stability, and exhibits low dielectric loss over a wide temperature and frequency range, making it an ideal material for CCL fabrication. The synthesis of low molecular weight PPE typically uses methanol and toluene as solvents. The large volume of solvent used significantly increases the difficulty of solvent recovery.

[0024] In related technologies, conventional distillation methods are insufficient for achieving efficient separation of methanol and toluene, and the high energy consumption of solvent evaporation significantly increases production costs. This is particularly true for the toluene-methanol system produced by polyphenylene ether (PPE), where the selection of the methanol-toluene separation method is crucial. Specifically, methanol and toluene form an azeotrope. If organic solvents are introduced to achieve extraction and separation of methanol and toluene, there are significant drawbacks for the PPE production system. Because PPE products are extremely sensitive to impurities, incomplete separation by the extractant, and the residual organic solvent reused in the production process, will interfere with the polymerization reaction of PPE, affecting key indicators such as the product's mechanical strength, heat resistance, and dielectric properties, thereby reducing product quality.

[0025] To address the aforementioned issues, this application provides a method for recovering solvents generated during the synthesis of polyphenylene ether. The solvents include filtration solvents and washing solvents, which can achieve good extraction and separation effects with low energy consumption without introducing impurities, ensuring that the recovered solvents meet the requirements for reuse. Figure 1 A flowchart illustrating a method for recovering solvents generated during the synthesis of polyphenylene ether according to embodiments of this application is shown. Figure 1 As shown, the recycling method includes:

[0026] Step 1: Perform multi-stage extraction on the filtered solvent and water to separate the oil phase solvent and the aqueous phase solvent.

[0027] For example, the filtration solvent in this application embodiment is only the filtrate produced by filtering the slurry after polyphenylene ether precipitation. It has a high content of toluene and a low content of methanol, and is partially miscible with water. Multi-stage extraction allows for multiple gas-liquid equilibrium distributions, significantly improving the separation purity of the oil phase solvent and the aqueous phase solvent. This application uses water as the extractant; by controlling its proportion in the system, a good extraction and separation effect can be achieved with low energy consumption without introducing impurities. Furthermore, this extractant is non-toxic, harmless, inexpensive, readily available, and recyclable. The mass ratio of the filtration solvent to water is 1:(1-3). Within this range, efficient transfer of methanol to the aqueous phase solvent is ensured, while excessive toluene entry into the aqueous phase solvent is avoided, reducing the difficulty and energy consumption of subsequent azeotropic de-extraction treatment. When the mass ratio of the filtration solvent to water is 1:2, it ensures the full dissolution of water-soluble components, reduces residual impurities in the oil phase solvent, provides purer materials for subsequent refining steps, and facilitates stratification of the oil and water phases, making extraction easier and improving the stability of the extraction operation, reducing entrainment losses, and ensuring efficient separation of the oil and water phase solvents. When the mass ratio of the filtration solvent to water is greater than 1:3, the proportion of water phase solvent is too high, and the oil phase solvent will be dispersed in fine droplets, which will increase the extraction time and the probability of emulsification in the system, thus adversely affecting the extraction effect and cost.

[0028] For example, the multi-stage extraction method in this application embodiment includes multi-stage countercurrent extraction or multi-stage cross-current extraction. Furthermore, the number of extraction stages in this application embodiment is two, three, or more, preferably two or three. Within this range, the extraction separation effect can be significantly improved, which is beneficial for obtaining high-purity toluene. Specifically, for the separation system of toluene and aqueous solvent, single-stage extraction is prone to insufficient mass transfer, resulting in a large amount of toluene and impurities remaining in the aqueous solvent, thereby affecting the azeotropic efficiency of the subsequent azeotropic step and increasing the difficulty of separating toluene and methanol. When the number of extraction stages is two or three, the residual oil solvent in the aqueous solvent can be further reduced, which is beneficial for reducing the purification difficulty and energy consumption in subsequent purification processes.

[0029] Meanwhile, the less residual filtration solvent in the aqueous solvent, the higher the purity of the azeotropic solvent separated during the subsequent de-azeotropic treatment, allowing for direct cyclic extraction.

[0030] Step 2: The oil phase solvent is purified to obtain toluene.

[0031] For example, in this embodiment, high-boiling-point impurities in the oil phase solvent are removed by distillation to obtain high-purity toluene, thus meeting the quality requirements of the solvent in the polyphenylene ether synthesis process. Specifically, the purification process in this embodiment is carried out at a pressure of 0.01–0.5 MPa. Within this pressure range, efficient separation of toluene and impurities can be achieved at a lower temperature, while avoiding the stringent requirements on equipment and control systems imposed by extreme pressures. The preferred purification pressure in this embodiment is 0.01–0.3 MPa, and most preferably 0.01–0.1 MPa.

[0032] Step three involves mixing the washing solvent with the aqueous solvent and then performing a de-azeotropic treatment to separate the azeotropic solvent and the mixture. The azeotropic solvent is then mixed with the filtration solvent, and step one is repeated. In this embodiment, the washing solvent is only the washing liquid generated during the washing of the polyphenylene ether product.

[0033] For example, after the washing solvent and the aqueous solvent are mixed, a preheating treatment is performed to obtain a preheated mixed solvent. Then, the preheated mixed solvent undergoes a de-azeotropic treatment. In this embodiment, the preheating temperature is 45–65°C, for example: 45°C, 50°C, 55°C, 60°C, 65°C, preferably 55°C. This reduces the heating energy consumption from room temperature to the boiling point during azeotropic distillation, and is particularly suitable for large-scale production using waste heat (such as condensate or waste gas heat) to recover heat, meeting energy-saving requirements. Furthermore, when the mixed solvent enters the azeotropic device after preheating, the gas and liquid phases reach equilibrium more quickly, which helps increase the throughput per unit time and improve azeotropic efficiency.

[0034] In practical applications, the washing solvent and the aqueous solvent can be mixed and preheated before being introduced into the de-azeotropic treatment equipment, or they can be introduced into the de-azeotropic treatment equipment at the same time in a certain proportion. This proportion can be adjusted according to the actual situation and is not limited here.

[0035] For example, the pressure of the de-azeotropic treatment in the embodiments of this application is 0.01 to 0.5 MPa, preferably 0.01 to 0.3 MPa, and most preferably 0.01 to 0.1 MPa.

[0036] Step four involves separating methanol and water from the mixture, and using the water from step four to repeat step one. In other words, the water used in this application includes both fresh water and recycled water. According to simulation calculations and process design, all recycled water should be reused as the extractant. A portion of the fresh water can then be used to compensate for the water loss during extraction. No other recycled water requires further treatment. Furthermore, the heat generated from separating the water from the mixture can be exchanged with the feed heat during the azeotropic de-extraction process, allowing heat to be recycled within the system and reducing the overall energy consumption of the process. The pressure for treating the mixture is 0.01–0.5 MPa.

[0037] Based on this, the filtration solvent in this embodiment has a high toluene content and a low methanol content. The washing solvent, on the other hand, has a low toluene content and a high methanol content. Compared to the traditional process of collecting and recycling all solvents from the polyphenylene ether production process, which results in higher energy consumption, this application recovers the two solvents with different toluene and methanol contents separately, using water as the extractant. This extractant is non-toxic, harmless, inexpensive, readily available, and recyclable. By controlling its proportion in the system, a good extraction and separation effect can be achieved with lower energy consumption without introducing impurities. Furthermore, the heat generated during the recovery of the washing solvent can be recycled within the system, further reducing the overall energy consumption of the process. Experiments show that the purity of toluene and methanol recovered by this method can reach up to 99.99%, with a catalyst content of less than 0.01% in the toluene, meeting the solvent reuse requirement of at least 99.5% purity for methanol.

[0038] Understandably, current solvent refining and recovery processes can vary in the number of equipment units required. For the oil phase in extraction separation, two towers can be used to separate light components, heavy components, and toluene. The first tower separates the light components, and the second separates toluene and heavy components. This method has relatively high equipment investment and energy consumption. For the alcohol removal tower in the aqueous phase of extraction separation, if higher purity methanol is required, a high- and low-pressure series tower can be used to separate methanol and water, reducing energy consumption. However, the equipment investment is relatively high, but the energy consumption is lower for a single tower separating methanol of the same purity.

[0039] If the recycled methanol in the polyphenylene ether (PPE) production process contains only a small amount of water as an impurity, it will not have a significant impact on the use of recycled methanol in PPE production.

[0040] This application also provides a solvent recovery device for the synthesis of polyphenylene ether, which is applied to the above-mentioned solvent recovery method for the synthesis of polyphenylene ether. It includes fewer devices and can separate the solvent into toluene and methanol that meet the requirements for reuse at a lower cost. Figure 2 A schematic diagram of the composition of a solvent recovery device generated from the synthesis of polyphenylene ether according to an embodiment of this application is shown. Figure 2 As shown, the apparatus includes: a filtration solvent storage unit V101, a water storage unit V102, a multi-stage extraction and separation unit S101, an oil phase solvent buffer unit V103, an aqueous phase solvent buffer unit V104, an oil phase solvent purification unit 100, an aqueous phase solvent de-azeotropic unit 200, a washing solvent storage unit V105, a mixed liquid separation unit 300, a toluene storage unit V106, and a methanol storage unit V107. The outlets of the filtration solvent storage unit V101 and the water storage unit V102 are both connected to the inlet of the multi-stage extraction and separation unit S101. The outlet of the multi-stage extraction and separation unit S101 is connected to the inlet of the oil phase solvent buffer unit V103 and the inlet of the aqueous phase solvent buffer unit V104, respectively. The outlet of the oil phase solvent buffer unit V103 is connected to the inlet of the oil phase solvent purification unit 100, and the outlet of the oil phase solvent purification unit 100 is connected to the inlet of the toluene storage unit V106. The washing solvent storage unit V105... The outlet of 05 is connected to the outlet of the aqueous solvent buffer device V104 and the inlet of the aqueous solvent de-azeotropic unit 200, respectively. The first outlet of the aqueous solvent de-azeotropic unit 200 is connected to the inlet of the filter solvent storage device V101. The second outlet of the aqueous solvent de-azeotropic unit 200 is connected to the inlet of the mixed liquid separation unit 300. The first outlet of the mixed liquid separation unit 300 is connected to the inlet of the methanol storage device V107. The second outlet of the mixed liquid separation unit 300 is connected to the inlet of the water storage device V102.

[0041] In practical applications, the recovery device also includes a first transfer pump P101, a second transfer pump P102, a third transfer pump P103, a fourth transfer pump P104, a fifth transfer pump P105, and a sixth transfer pump P106. Specifically, the first transfer pump P101 is located between the outlet of the filtration solvent storage device V101 and the inlet of the multi-stage extraction and separation device S101; the second transfer pump P102 is located between the outlet of the oil phase solvent buffer device V103 and the inlet of the oil phase solvent refining unit 100; the third transfer pump P103 is located between the outlet of the washing solvent storage device V105 and the outlet of the aqueous phase solvent buffer device V104; the fourth transfer pump P104 is located at the outlet of the toluene storage device V106; the fifth transfer pump P105 is located at the outlet of the methanol storage device V107; and the sixth transfer pump P106 is located between the outlet of the water storage device V102 and the inlet of the multi-stage extraction and separation device S101.

[0042] In practice, the filtration solvent from the precipitation stage of the polyphenylene ether (PPE) production process is collected in the filtration solvent storage device V101. Under the action of the first transfer pump P101, it enters the inlet of the multi-stage extraction and separation device S101 together with water flowing out from the outlet of the water storage device V102 in a certain proportion. Due to the difference in miscibility between toluene and water, the mixture is separated into oil phase solvent and aqueous phase solvent through multi-stage extraction. The oil phase solvent obtained from the extraction enters the inlet of the oil phase solvent buffer device V103 from the outlet of the multi-stage extraction and separation device S101 for temporary storage, while the aqueous phase solvent obtained from the extraction and separation enters the aqueous phase solvent buffer device V104 from the outlet of the multi-stage extraction and separation device S101 for temporary storage. This balances the fluctuations in the upstream and downstream material flow rates, ensuring the stable operation of the subsequent oil phase solvent refining unit 100 and the aqueous phase solvent de-azeotropic unit 200, and avoiding sudden changes in equipment load. Next, the oil phase solvent enters the inlet of the oil phase solvent refining unit 100 from the outlet of the oil phase solvent buffer device V103 via the second transfer pump P102 to refine the oil phase solvent and obtain high-purity toluene. This toluene can be recycled for the polyphenylene ether synthesis process under the action of the fourth transfer pump P104, reducing the cost of purchasing new solvents. Under the action of the third transfer pump P103, the aqueous phase solvent flows out from the outlet of the aqueous phase solvent buffer device V104 and enters the inlet of the aqueous phase solvent de-azeotropic unit 200 together with the washing solvent for de-azeotropic treatment. Among them, the azeotrope containing toluene and methanol can be used as an azeotropic solvent and returned from the first outlet of the aqueous phase solvent de-azeotropic unit 200 to the inlet of the filter solvent storage device V101 for recycling and participation in extraction. The remaining mixture enters the inlet of the mixture separation unit 300 from the second outlet of the aqueous phase solvent de-azeotropic unit 200 for further separation. After the mixture separation is completed, the separated methanol enters the inlet of methanol storage device V107 from the first outlet of the mixture separation unit 300. At this point, it can be reused in the polyphenylene ether synthesis process by the action of the fifth transfer pump P105, reducing the cost of purchasing new solvents. The separated water enters the water storage device V102 from the second outlet of the mixture separation unit 300. At this point, the water can be circulated to the multi-stage extraction separation device S101 for extraction by the sixth transfer pump P106.

[0043] As can be seen, the apparatus provided in this application involves relatively few devices and can separate solvents into toluene and methanol that meet the requirements for reuse at a low cost.

[0044] It should be understood that the ratio of the filtration solvent to water is as described above and will not be repeated here.

[0045] For example, the multi-stage extraction and separation device S101 in this application embodiment includes an extraction tower, a static extraction column / tank, and an extraction centrifuge, preferably an extraction centrifuge and an extraction tower.

[0046] In one optional embodiment, the oil phase solvent refining unit 100 of this application includes a toluene refining tower 101, a first condenser-reflux assembly 102, a first reboiler E101, a first product cooling device M101, and a first bottom product pump G101. The tower-side inlet of the toluene refining tower 101 is connected to the outlet of the oil phase solvent buffer device V103; the tower-side outlet of the toluene refining tower 101 is connected to the inlet of the toluene storage device V106 via the first product cooling device M101; the top outlet of the toluene refining tower 101 is connected to the top inlet of the toluene refining tower 101 via the first condenser-reflux assembly 102; and the bottom outlet of the toluene refining tower 101 is connected to the bottom inlet of the toluene refining tower 101 via the first reboiler E101. In this embodiment, the toluene refining tower 101 is a packed tower or a plate tower, preferably a packed tower.

[0047] It is understood that the oil phase solvent refining unit 100 in the embodiments of this application further includes a first solvent pipeline F101 and a second solvent pipeline F102. The inlet of the first solvent pipeline F101 is connected to the outlet of the first condensation reflux assembly 102, and the inlet of the second solvent pipeline F102 is connected to the bottom outlet of the toluene refining tower 101.

[0048] In practice, the oil phase solvent enters the toluene refining column 101 from the outlet of the oil phase solvent buffer device V103 via the second transfer pump P102. Under suitable pressure and top temperature of the toluene refining column 101, toluene can be efficiently separated from low-boiling-point impurities. After the low-boiling-point impurities in the gas phase flow out from the top outlet of the toluene refining column 101, under the action of the first reflux condenser 102, part of them are refluxed back to the toluene refining column 101 to maintain mass transfer balance, while the other part flows from the outlet of the first reflux condenser 102 to the first solvent pipeline F101 for further recovery. Then, toluene is directly collected from the tower side outlet of the toluene refining column 101, which is enriched with high-purity toluene. After being cooled by the first collection cooling device M101, it is stored in the toluene storage device V106 to avoid entrainment of low-boiling-point impurities at the top of the column or high-boiling-point impurities at the bottom of the column, thus meeting the requirements of polyphenylene ether synthesis for high-purity solvents. The liquid at the bottom of the column is enriched with heavy impurities that are difficult to vaporize (such as polymethylbenzene, tar-like substances, and high-boiling-point solvents). A portion of these heavy impurities is returned to the bottom of the toluene refining column 101 via the first reboiler E101, while the other portion flows into the second solvent pipeline F102 via the first bottom pump, serving as waste liquid for further recovery and treatment. It should be understood that after toluene is stored in the toluene storage device V106, it can either be sent to the polyphenylene ether preparation section for recycling or collected for later use; this can be adjusted according to actual conditions and is not limited here. Furthermore, the mass ratio of the portion of heavy impurities recycled to the toluene refining column 101 via the first reboiler E101 to the other portion of heavy impurities flowing out from the bottom outlet of the toluene refining column 101 can be adjusted according to actual conditions and is not limited here.

[0049] As can be seen, in this embodiment, the high-purity toluene is collected from the side outlet of the toluene refining column 101, which avoids contamination of the product by light components at the top of the column or heavy components at the bottom of the column, ensuring that the purity of the toluene meets the requirements of high-end applications (such as pharmaceutical and electronic grade solvents). The products flowing out from the bottom and top of the toluene refining column 101 are collected as waste liquid.

[0050] In practical applications, in order to achieve safe and stable delivery of produced fluid, such as Figure 2 As shown, the oil phase solvent refining unit 100 in this embodiment further includes a second extraction cooling device M102. The second extraction cooling device M102 is installed on the first solvent pipeline F101, and its outlet temperature is limited to 30–55°C, preferably 35–45°C, to ensure that the solvent in the pipeline remains in a liquid state and reduce the risk of component evaporation. The outlet temperature of the first extraction cooling device M101 can be set according to process requirements and is not limited here.

[0051] For example, such as Figure 2As shown, the first condensation reflux assembly 102 in this embodiment includes a first condensation device 1021, a first reflux device 1022, and a first reflux pump 1023; the first condensation device 1021 and the first reflux device 1022 are connected in series between the top outlet of the toluene refining tower 101 and the inlet of the first reflux pump 1023, and the outlet of the first reflux pump 1023 is connected to the top inlet of the toluene refining tower 101.

[0052] It is understood that this application also includes a first liquid inlet pipe 1024, one end of which is connected to the outlet of the first reflux pump 1023, and the other end of which is connected to the top inlet of the toluene refining tower 101.

[0053] In specific implementation, the gas phase flowing out from the top outlet of the toluene refining tower 101 is condensed to a preset temperature by the first condenser 1021, and then enters the first reflux pump 1023 through the first reflux device 1022. According to the preset reflux ratio, a portion flows out from the outlet of the first reflux pump 1023 and enters the top inlet of the toluene refining tower 101 along the first liquid inlet pipeline 1024. The other portion flows out from the outlet of the first reflux pump 1023 and is discharged into the first solvent pipeline F101 for further recovery. The first reflux device 1022 can act as a gas-liquid separation buffer. By adjusting the liquid level in the first reflux device 1022 in real time through the two streams at the outlet of the first reflux pump 1023 (refluxed back to the toluene refining tower 101 and discharged into the first solvent pipeline F101), it avoids sudden rises or falls in liquid level caused by fluctuations in the amount of gas phase at the top of the tower (such as changes in feed load), thereby stabilizing the pressure at the top of the tower. It should be understood that the first reflux device 1022 is a reflux tank.

[0054] For example, the top temperature of the toluene refining column in this embodiment is 80–120°C to achieve efficient separation of toluene from low-boiling-point impurities through fractionation. Within this temperature range, it can be ensured that low-boiling-point impurities, including methanol, are completely vaporized and exit the column with the overhead gas flow, while high-boiling-point impurities accumulate at the bottom of the toluene refining column. This also avoids the loss of light components from the top of the column due to toluene vaporization. Based on this, the top temperature of the toluene refining column in this embodiment is preferably 90–110°C, and most preferably 95–100°C.

[0055] This application embodiment also limits the outlet temperature of the first condenser to 45–70°C. Within this temperature range, it not only ensures the complete liquefaction of light component impurities in the overhead gas phase, providing a stable liquid phase for reflux and solvent extraction, and avoiding the accumulation of non-condensable gases and pressure fluctuations, but also maintains the gas-liquid balance within the column, ensuring the quality of the high-purity toluene extracted from the column-side outlet of the toluene refining column. Based on this, the preferred outlet temperature of the first condenser in this application embodiment is 55–65°C.

[0056] This application embodiment also limits the top reflux ratio of the toluene refining column to (30-40):1. Within this parameter range, not only can light component impurities be removed to the greatest extent, ensuring toluene purity and yield, but energy consumption can also be controlled within a reasonable range, thereby avoiding quality risks caused by too low a reflux ratio or energy waste caused by too high a reflux ratio. Based on this, the preferred top reflux ratio of the toluene refining column in this application embodiment is (33-37):1.

[0057] Furthermore, the embodiments of this application limit the temperature of the first reboiler to 99–150°C to avoid mass transfer stagnation within the column and to ensure that the heavy components are completely discharged in liquid form, preventing them from entering the column side of the toluene refining column with the rising gas phase. Based on this, the temperature of the first reboiler in the embodiments of this application is preferably 115–140°C, and most preferably 125–130°C.

[0058] In one alternative approach, such as Figure 2 As shown, the aqueous solvent de-azeotropic unit 200 in this embodiment includes an azeotropic tower 201, a second reflux condenser 202, a second reboiler E102, and a first bottom pump G101. The outlet of the aqueous solvent buffer device V104 and the outlet of the washing solvent storage device V105 are both connected to the tower-side inlet of the azeotropic tower 201; the top outlet of the azeotropic tower 201 is connected to the inlet of the second reflux condenser 202, and the outlet of the second reflux condenser 202 is connected to the top inlet of the azeotropic tower 201 and the inlet of the filtration solvent storage device V101, respectively; the bottom outlet of the azeotropic tower 201 is connected to the inlet of the second reboiler E102 and the inlet of the mixed liquid separation unit 300, respectively, and the outlet of the second reboiler E102 is connected to the bottom inlet of the azeotropic tower 201; the first bottom pump G101 is located between the bottom outlet of the azeotropic tower 201 and the inlet of the mixed liquid separation unit 300.

[0059] It is understood that the second condensation reflux assembly 202 also includes a second condensation device 2021, a second reflux device 2022, a second reflux pump 2023, and a second inlet pipe 2024. The second condensation device 2021 and the second reflux device 2022 are connected in series between the top outlet of the azeotropic tower 201 and the inlet of the second reflux pump 2023. One end of the second inlet pipe 2024 is connected to the outlet of the second reflux pump 2023, and the other end of the second inlet pipe 2024 is connected to the top inlet of the azeotropic tower 201. In addition, the solvent recovery device also includes a preheating device Y101. The inlet of the preheating device Y101 is connected to the outlet of the aqueous solvent buffer device V104 and the outlet of the washing solvent storage device V105, respectively, and the outlet of the preheating device Y101 is connected to the tower-side inlet of the azeotropic tower 201.

[0060] In practice, the washing solvent and aqueous solvent generated during the polyphenylene ether (PPE) production process flow out from the outlet of the washing solvent storage device V105 and the outlet of the aqueous solvent buffer device V104, respectively. After being preheated to a preset temperature by the preheating device Y101, they enter the azeotropic tower 201, ensuring that the feed temperature is close to the gas-liquid equilibrium temperature within the azeotropic tower 201. This avoids disturbances to the temperature field within the tower caused by low-temperature feed, ensuring stable gas-liquid mass transfer and improving separation efficiency. The gas phase flowing out from the top outlet of the azeotropic tower 201 is condensed to a preset temperature by the second condenser 2021 to prevent gas from entering the reflux pump and causing cavitation, while also facilitating subsequent storage and transportation. Next, the condensate enters the second reflux pump 2023 through the second reflux device 2022. According to a preset reflux ratio, a portion flows out from the outlet of the second reflux pump 2023 and enters the top inlet of the azeotropic tower 201 along the second inlet pipe 2024 to maintain the gas-liquid mass transfer balance within the tower. Another portion flows from the outlet of the second reflux pump 2023 to the inlet of the filter solvent storage device V101 for recycling. Part of the mixture at the bottom of the azeotropic tower 201 returns to the bottom of the azeotropic tower 201 via the second reboiler E102, while the other part flows through the first bottom pump G101 into the inlet of the mixture separation unit 300 for further separation.

[0061] It should be understood that the mass ratio of a portion of the mixture circulated to the bottom of the azeotropic tower 201 through the second reboiler E102 to another portion of the mixture flowing out from the bottom pump G101 of the first tower can be adjusted according to actual conditions, and is not limited here.

[0062] By way of example, the azeotropic tower in this application embodiment is a packed tower or a plate tower, preferably a packed tower. Its top temperature is 55–90°C, preferably 65–80°C, and most preferably 70–75°C. The bottom temperature of the azeotropic tower is 80–110°C, preferably 85–100°C, and most preferably 90–95°C, which is beneficial for improving separation efficiency.

[0063] In this embodiment, the outlet temperature of the second condenser in the second reflux assembly is 30–55°C to ensure that the gaseous material is cooled below its dew point temperature, allowing the condensable components (such as azeotropic agents, light component solvents, etc.) to completely liquefy and form a liquid reflux liquid. If the temperature is too high, some light components may not completely condense and enter the second reflux pump in gaseous form, causing pump cavitation and affecting reflux stability. If the temperature is too low, although complete condensation can be ensured, it will increase the energy consumption of the cooling medium, resulting in unnecessary energy waste. Therefore, in this embodiment, the outlet temperature of the second condenser is preferably 35–45°C. It should be understood that the azeotropic tower feed can exchange heat with the methanol separator bottom product, or it can be preheated by external heat supply. The methanol collected from the top of the methanol separator can be collected or recycled in the polyphenylene ether preparation section.

[0064] The azeotropic column in this embodiment has a reflux ratio of (1-5):1, which has high mass transfer efficiency and can achieve more precise azeotropic separation. If the reflux ratio is lower than 1:1, the loss of azeotropic agent in the top of the column increases, the concentration of azeotropic agent in the column decreases, leading to an azeotropic point shift and a deterioration in the separation effect. If the reflux ratio is higher than 5:1, it will lead to an increase in the residual azeotropic agent in the bottom material, increasing the load on the subsequent mixture separation unit. Based on this, the preferred reflux ratio of the azeotropic column in this embodiment is (2-4):1.

[0065] The temperature of the second reboiler in this embodiment is 80–110°C to balance separation efficiency and energy saving requirements. Based on this, the preferred temperature of the second reboiler in this embodiment is 85–100°C, and most preferably 90–95°C.

[0066] In one optional embodiment, the mixed liquid separation unit 300 of this application includes a methanol separation tower 301, a third condenser reflux assembly 302, a third reboiler device E103, and a second bottom pump G102; the bottom outlet of the azeotropic tower 201 is connected to the tower side inlet of the methanol separation tower 301 through the first bottom pump G101; the top outlet of the methanol separation tower 301 is connected to the inlet of the third condenser reflux assembly 302; the outlet of the third condenser reflux assembly 302 is connected to the top inlet of the methanol separation tower 301 and the inlet of the methanol storage device V107; the bottom outlet of the methanol separation tower 301 is connected to the inlet of the third reboiler device E103 and the inlet of the water storage device V102; the outlet of the third reboiler device E103 is connected to the bottom inlet of the methanol separation tower 301; and the second bottom pump G102 is located between the bottom outlet of the methanol separation tower 301 and the inlet of the water storage device V102.

[0067] In practice, the mixture flows out from the bottom outlet of the azeotropic tower 201 and enters the side inlet of the methanol separation tower 301 through the first bottom pump G101. Methanol-containing vapor flows out from the top outlet of the methanol separation tower 301, and under the action of the third reflux condenser 302, part of it flows back to the methanol separation tower 301 to maintain mass transfer balance, while the other part flows from the outlet of the third reflux condenser 302 to the methanol storage device V107. Part of the solvent at the bottom of the tower returns to the bottom of the methanol separation tower 301 through the third reboiler E103, while the other part flows into the water storage device V102 through the second bottom pump G102. At this time, fresh water can be injected into the water storage device V102 and returned to the multi-stage extraction separation device S101 as an extractant for recycling under the action of the sixth transfer pump P106. In other words, the separated recycled water is used for extraction, and fresh water replenishes the water lost during extraction.

[0068] It should be understood that after methanol is stored in methanol storage equipment V107, it can be either sent to the polyphenylene ether preparation section for recycling or collected for later use. This can be adjusted according to actual conditions and is not limited here. Furthermore, the mass ratio of a portion of the water circulated to methanol separation tower 301 through the third reboiler E103 to another portion of the water flowing out from the second bottom pump G102 can be adjusted according to actual conditions and is not limited here. In addition, this embodiment also includes a third bottom pump G103, which is installed on the second solvent pipeline F102. The third condensation reflux assembly 302 in this embodiment includes a third condensation device 3021, a third reflux device 3022, a third reflux pump 3023, and a third inlet pipeline 3024. Its working process is the same as that of the first and second condensation reflux assemblies and will not be described in detail here.

[0069] Exemplarily, the methanol separation tower in this application embodiment is a packed tower or a plate tower, preferably a packed tower. Furthermore, the outlet temperature of the third condenser included in the third reflux assembly in this application embodiment is 40–70°C to ensure complete condensation of the top vapor into a liquid phase. Based on this, the outlet temperature of the third condenser in this application embodiment is preferably 55–65°C.

[0070] The reflux ratio of the methanol separator in this embodiment is (1-2.5):1, which balances separation efficiency and low energy consumption. Based on this, the preferred reflux ratio of the methanol separator in this embodiment is (1.5-2):1.

[0071] The methanol separation tower in this embodiment has a top temperature of 55–90°C to achieve efficient separation of the light component water and methanol, and to ensure that water remains at the bottom of the tower, preventing it from being entrained to the top with methanol vapor. Based on this, the preferred top temperature of the methanol separation tower in this embodiment is 65–80°C, and most preferably 70–75°C. The pressure of the methanol separation tower is set to 0.01–0.5 MPa, preferably 0.01–0.3 MPa, and most preferably 0.01–0.1 MPa.

[0072] The methanol separation tower in this embodiment has a bottom temperature of 85–130°C, which ensures that the methanol and light components in the bottom liquid phase are fully vaporized, providing sufficient rising steam for the countercurrent contact of the gas and liquid phases inside the tower, and maintaining the mass and heat transfer dynamics of the distillation process. Based on this, the bottom temperature of the methanol separation tower in this embodiment is preferably 95–120°C, and most preferably 105–110°C.

[0073] The temperature of the third reboiler in this embodiment is 85–130°C, which effectively retains water and high-boiling-point impurities at the bottom of the column, while methanol rises with the steam to the top of the column and condenses, thereby obtaining high-purity methanol at the top of the column. The methanol content in the bottom residue can be controlled at an extremely low level required by the process. Based on this, the preferred temperature of the third reboiler in this embodiment is 95–120°C, and the most preferred temperature is 105–110°C.

[0074] In practical applications, to ensure safe and stable delivery of the produced fluid, the mixed liquid separation unit 300 in this embodiment further includes a third produced cooling device M103 and a fourth produced cooling device. The third produced cooling device M103 is located between the outlet of the third condensate reflux assembly 302 and the inlet of the methanol storage device V107, with an outlet temperature of 30–55°C, preferably 35–45°C. The fourth produced cooling device M104 is located between the outlet of the second bottom produced pump G102 and the inlet of the water storage device V102, with an outlet temperature of 30–55°C, preferably 35–45°C. Furthermore, the heat from the discharge from the bottom of the methanol separation tower 301 can exchange with the heat from the feed to the azeotropic tower 201, allowing heat to be recycled within the system and further reducing the overall energy consumption of the process.

[0075] To further demonstrate the effectiveness of the solvent recovery method for synthesized polyphenylene ether provided in the embodiments of this application, examples and comparative examples are used for illustration.

[0076] Example 1

[0077] Embodiment 1 of this application provides a method for recovering the solvent generated during the synthesis of polyphenylene ether, which includes the following steps.

[0078] Step 1: As Figure 2As shown, the solvent generated during the washing process of synthesizing polyphenylene ether is collected in the washing solvent storage device V105, and the solvent generated during the filtration process is collected in the filtration solvent storage device V101. The filtration solvent flows out from the outlet of the filtration solvent storage device V101 and enters the multi-stage extraction and separation device S101 with water at a mass ratio of 1:2 via the first transfer pump P101 for multi-stage extraction treatment, separating the oil phase solvent and the aqueous phase solvent. The oil phase solvent is fed from the outlet of the multi-stage extraction and separation device S101 into the oil phase solvent buffer device V103, and the aqueous phase solvent is fed from the outlet of the multi-stage extraction and separation device S101 into the aqueous phase solvent buffer device V104.

[0079] Step Two: Under the action of the second transfer pump P102, the oil phase solvent is transferred from the outlet of the oil phase solvent buffer device V103 to the tower-side inlet of the toluene refining tower 101 for refining. The top pressure of the toluene refining tower 101 is 0.03 MPa, and the top temperature is 98°C. The vapor overflowing from the top of the tower is condensed to 60°C by the first condenser 1021 and enters the first reflux device 1022. Under the action of the first reflux pump 1023, at a reflux ratio of 35:1, part of it is refluxed back to the toluene refining tower 101, and the other part flows into the first solvent pipeline F101. Under the action of the second outflow cooling device M102, it is cooled to 40°C and discharged as waste liquid. The toluene collected from the tower-side inlet of the toluene refining tower 101 is cooled by the first outflow cooling device M101 and then fed into the toluene storage device V106. Under the action of the fourth transfer pump P104, it is recycled as reused toluene in the polyphenylene ether synthesis process. The temperature of the first reboiler E101 at the bottom of the toluene refining tower 101 is 128°C. Part of the heavy component impurities at the bottom of the toluene refining tower 101 return to the bottom of the toluene refining tower 101 through the first reboiler E101, while the other part flows into the second solvent pipeline F102 through the first bottom pump G101 and is treated as waste liquid for further processing.

[0080] Step 3: Under the action of the third transfer pump P103, the aqueous solvent flows out from the outlet of the aqueous solvent buffer device V104 and mixes with the washing solvent flowing out from the outlet of the washing solvent storage device V105. After being preheated to 55°C by the preheating device Y101, it enters the azeotropic tower 201 for deazeotropic treatment. The pressure of the azeotropic tower 201 is 0.03 MPa and the temperature at the top of the azeotropic tower 201 is 72°C. The gas phase flowing out from the top of the azeotropic tower 201 is condensed and cooled to 40°C by the second condenser 2021 and enters the second reflux device 2022. According to the reflux ratio of 3:1, part of it flows out from the outlet of the second reflux pump 2023 and enters the top inlet of the azeotropic tower 201 along the second liquid inlet pipe 2024. The other part flows out from the outlet of the second reflux pump 2023 to the inlet of the filter solvent storage device V101 and is used as the azeotropic solvent for recycling extraction and separation. The temperature of the second reboiler E102 at the bottom of the azeotropic tower 201 is 92℃. Part of the mixture at the bottom of the azeotropic tower 201 returns to the bottom of the tower through the second reboiler E102, while part of it flows into the methanol separation tower 301 through the first bottom pump G101.

[0081] Step 4: The pressure at the top of methanol separation tower 301 is 0.03 MPa, and the temperature at the top is 72°C. The gas phase flowing out from the top of methanol separation tower 301 is condensed to 60°C by the third condenser 3021 and enters the third reflux device 3022. According to the reflux ratio of 1.76:1, part of it flows out from the outlet of the third reflux pump 3023 and enters the top inlet of methanol separation tower 301 along the third liquid inlet pipeline 3024. The other part flows out from the outlet of the third reflux pump 3023 and is cooled to 40°C by the third outflow cooling device M103. It is then collected in methanol storage device V107 and recycled in the polyphenylene ether preparation system by the action of the fifth transfer pump P105. The temperature of the third reboiler E103 at the bottom of the methanol separation tower is 107℃. Part of the solvent at the bottom of the tower returns to the bottom of the methanol separation tower 301 through the third reboiler E103, while the other part of the solvent is collected by the second bottom pump.

[0082] G102 first exchanges heat with the feed to azeotropic tower 201, then passes through the fourth outlet cooling device M104 to be cooled to 40°C. It is then mixed with fresh water and collected in water storage device V102. Under the action of the sixth transfer pump P106, it is used as an extractant to mix with the azeotropic solvent and circulate for extraction and separation. In other words, the separated recycled water is used for extraction, and fresh water replenishes the water lost during extraction.

[0083] Example 2

[0084] This application provides a method for recovering solvents generated during the synthesis of polyphenylene ether in Embodiment 2. The only difference between Embodiment 1 and Embodiment 2 is that the filtered solvent and water are introduced into the multi-stage extraction and separation equipment S101 at a ratio of 1:1, while the set conditions of the toluene refining tower 101, the azeotropic tower 201 and the methanol separation tower 301 remain unchanged.

[0085] Example 3

[0086] This application provides a method for recovering solvents generated during the synthesis of polyphenylene ether in Embodiment 3. The only difference between Embodiment 1 and Embodiment 3 is that the filtered solvent and water are introduced into the multi-stage extraction and separation equipment S101 at a ratio of 1:3, while the set conditions of the toluene refining tower 101, the azeotropic tower 201 and the methanol separation tower 301 remain unchanged.

[0087] Comparative Example 1

[0088] Figure 3 A schematic diagram of the solvent recovery apparatus generated during the synthesis of polyphenylene ether, as shown in the comparative example of this application, is illustrated. The apparatus for the solvent recovery method generated during the synthesis of polyphenylene ether provided in Comparative Example 1 of this application is as follows: Figure 3 As shown, the only difference from Example 1 is that the filtration solvent and washing solvent are mixed and then extracted together. The mixed solvent and water are fed into the multi-stage extraction and separation equipment S101 at a ratio of 1:2. The set conditions of the toluene refining tower 101, the azeotropic tower 201 and the methanol separation tower 301 remain unchanged.

[0089] Experimental Example 1

[0090] Test Examples 1 to 3 were conducted. The purity of the recovered methanol and toluene in Example 1 was measured to be 99.99%, and the purity of the recovered methanol in Example 2 was measured to be 99.30% and the purity of the recovered toluene was measured to be 99.00%.

[0091] Experimental Example 2

[0092] Test Examples 1 and 3 were conducted. The total heat exchange in Example 3 was 1.5 times higher than that in Example 1. Further increasing the amount of extractant would increase energy consumption.

[0093] Experimental Example 3

[0094] The test results were compared between Example 1 and Comparative Example 1. In Example 1, the purity of the recovered methanol was 99.99% and the purity of the recovered toluene was 99.99%. In Comparative Example 1, the purity of the recovered methanol was 99.92% and the purity of the recovered toluene was 99.98%. The total heat exchange of Comparative Example 1 was 2.3 times higher than that of Example 1.

[0095] In summary, (1) As shown in Experiment 1, a smaller amount of extractant water will reduce the purity of recycled toluene and methanol. (2) As shown in Experiment 2, a larger amount of extractant water will increase the energy consumption of the process. This invention can adjust the ratio of filtration solvent and extractant water to allow the solvent to be recycled in the system, thereby reducing the amount of solvent and energy consumption in the preparation of polyphenylene ether. (3) As shown in Experiment 3, in the method for recovering solvents generated during the synthesis of polyphenylene ether provided by this invention, the filtration solvent and washing solvent are collected and purified separately, and reasonable equipment and process parameters are set. Under their combined effect, the purity of methanol and toluene solvents in the recovery process is significantly improved, which can increase the economy of the entire process while saving energy and reducing emissions.

[0096] The above description is merely a specific embodiment of this application. Obviously, various modifications and combinations can be made without departing from the spirit and scope of this application. Accordingly, this specification and accompanying drawings are merely exemplary illustrations of this application as defined by the appended claims, and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and modifications of this application fall within the scope of the claims of this application and their equivalents, the intent of this application includes these modifications and modifications. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the protection scope of this application. Therefore, the protection scope of this application should be determined by the protection scope of the stated claims.

[0097] It should also be noted that in the apparatus and method of this application, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered as equivalent solutions of this application.

[0098] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of this application. Therefore, this application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0099] The above description has been given for illustrative and descriptive purposes. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although several exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations therein.

Claims

1. A method for recovering solvents generated during the synthesis of polyphenylene ether, wherein the solvent comprises a filtration solvent and a washing solvent, characterized in that, include: Step 1: Perform multi-stage extraction on the filtered solvent and water to separate the oil phase solvent and the aqueous phase solvent; Step two: The oil phase solvent is purified to obtain toluene; Step 3: Mix the washing solvent with the aqueous solvent and perform a de-azeotropic treatment to separate the azeotropic solvent and the mixture. Then, mix the azeotropic solvent with the filtration solvent and repeat Step 1. Step four: Separate the methanol and water from the mixture, and use the water from step four to repeat step one.

2. The method for recovering the solvent generated during the synthesis of polyphenylene ether as described in claim 1, characterized in that, In step one, the mass ratio of the filtration solvent to the water is 1:(1-3).

3. The method for recovering the solvent generated during the synthesis of polyphenylene ether as described in claim 1, characterized in that, In step two, the pressure of the refining process is 0.01 to 0.5 MPa.

4. The method for recovering the solvent generated during the synthesis of polyphenylene ether as described in claim 1, characterized in that, Step three includes: The washing solvent is mixed with the aqueous solvent and then preheated to obtain a preheated mixed solvent. The preheated mixed solvent is subjected to de-azeotropic treatment to separate the azeotropic solvent and the mixture. The azeotropic solvent is then mixed with the filtered solvent and step one is repeated.

5. The method for recovering the solvent generated during the synthesis of polyphenylene ether as described in claim 4, characterized in that, The preheating temperature is 45–65°C.

6. The method for recovering the solvent generated during the synthesis of polyphenylene ether as described in claim 1 or 4, characterized in that, In step three, the pressure for the de-azeotropic treatment is 0.01 to 0.5 MPa.

7. The method for recovering the solvent generated during the synthesis of polyphenylene ether as described in claim 1, characterized in that, In step four, the pressure for treating the mixture is 0.01 to 0.5 MPa.

8. A solvent recovery device generated during the synthesis of polyphenylene ether, characterized in that, A method for recovering solvents generated during the synthesis of polyphenylene ethers according to any one of claims 1 to 7, the apparatus comprising: The system includes a solvent filtration storage device, a water storage device, a multi-stage extraction and separation device, an oil phase solvent buffer device, an aqueous phase solvent buffer device, an oil phase solvent refining unit, an aqueous phase solvent de-azeotropic unit, a washing solvent storage device, a mixed liquid separation unit, a toluene storage device, and a methanol storage device. The outlets of the solvent filtration storage device and the water storage device are connected to the inlet of the multi-stage extraction and separation device. The outlets of the multi-stage extraction and separation device are connected to the inlets of the oil phase solvent buffer device and the aqueous phase solvent buffer device, respectively. The outlet of the oil phase solvent buffer device is connected to the inlet of the oil phase solvent refining unit, and the outlet of the oil phase solvent refining unit is connected to the inlet of the toluene storage device. The outlets of the washing solvent storage device and the aqueous phase solvent buffer device are connected to the inlets of the aqueous phase solvent de-azeotropic unit, respectively. The first outlet of the aqueous phase solvent de-azeotropic unit is connected to the inlet of the solvent filtration storage device, the second outlet of the aqueous phase solvent de-azeotropic unit is connected to the inlet of the mixed liquid separation unit, the first outlet of the mixed liquid separation unit is connected to the inlet of the methanol storage device, and the second outlet of the mixed liquid separation unit is connected to the inlet of the water storage device.

9. The solvent recovery device generated during the synthesis of polyphenylene ether as described in claim 8, characterized in that, The oil phase solvent refining unit includes a toluene refining column, a first condenser-reflux assembly, a first reboiler, and a first product cooling device. The column-side inlet of the toluene refining column is connected to the outlet of the oil phase solvent buffer device, and the column-side outlet of the toluene refining column is connected to the inlet of the toluene storage device through the first product cooling device. The top outlet of the toluene refining column is connected to the top inlet of the toluene refining column through the first condenser-reflux assembly, and the bottom outlet of the toluene refining column is connected to the bottom inlet of the toluene refining column through the first reboiler.

10. The solvent recovery device generated during the synthesis of polyphenylene ether as described in claim 9, characterized in that, The first condensation and reflux assembly includes a first condenser, a first reflux device, and a first reflux pump; the first condenser and the first reflux device are connected in series between the top outlet of the toluene refining column and the inlet of the first reflux pump, and the outlet of the first reflux pump is connected to the top inlet of the toluene refining column.

11. The solvent recovery device generated during the synthesis of polyphenylene ether as described in claim 10, characterized in that, The top temperature of the toluene refining column is 80-120°C, the outlet temperature of the first condenser is 45-70°C, the top reflux ratio of the toluene refining column is (30-40):1, and the temperature of the first reboiler is 99-150°C.

12. The solvent recovery device generated during the synthesis of polyphenylene ether as described in claim 8, characterized in that, The aqueous solvent de-azeotropic unit includes an azeotropic tower, a second reflux condenser, a second reboiler, and a first bottom pump. The outlet of the aqueous solvent buffer and the outlet of the washing solvent storage are both connected to the tower-side inlet of the azeotropic tower. The top outlet of the azeotropic tower is connected to the inlet of the second reflux condenser, and the outlet of the second reflux condenser is connected to the top inlet of the azeotropic tower and the inlet of the filtration solvent storage. The bottom outlet of the azeotropic tower is connected to the inlet of the second reboiler and the inlet of the mixed liquid separation unit, and the outlet of the second reboiler is connected to the bottom inlet of the azeotropic tower. The first bottom pump is located between the bottom outlet of the azeotropic tower and the inlet of the mixed liquid separation unit.

13. The solvent recovery device generated during the synthesis of polyphenylene ether as described in claim 12, characterized in that, The top temperature of the azeotropic tower is 55-90°C, the bottom temperature of the azeotropic tower is 80-110°C, the outlet temperature of the second condenser included in the second condensation reflux assembly is 30-55°C, the reflux ratio of the azeotropic tower is (1-5):1, and the temperature of the second reboiler is 80-110°C.

14. The solvent recovery device generated during the synthesis of polyphenylene ether as described in claim 12, characterized in that, The mixed liquid separation unit includes a methanol separation tower, a third condenser-reflux assembly, a third reboiler, and a second bottom pump. The bottom outlet of the azeotropic tower is connected to the tower-side inlet of the methanol separation tower via the first bottom pump. The top outlet of the methanol separation tower is connected to the inlet of the third condenser-reflux assembly. The outlet of the third condenser-reflux assembly is connected to both the top inlet of the methanol separation tower and the inlet of the methanol storage device. The bottom outlet of the methanol separation tower is connected to both the inlet of the third reboiler and the inlet of the water storage device. The outlet of the third reboiler is connected to the bottom inlet of the methanol separation tower. The second bottom pump is located between the bottom outlet of the methanol separation tower and the inlet of the water storage device.

15. The solvent recovery device generated during the synthesis of polyphenylene ether as described in claim 14, characterized in that, The outlet temperature of the third condenser reflux assembly is 40-70°C, the reflux ratio of the methanol separator is (1-2.5):1, the top temperature of the methanol separator is 55-90°C, the bottom temperature of the methanol separator is 85-130°C, and the temperature of the third reboiler is 85-130°C.

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