Methods for recovering byproduct salts of polyarylene ether nitrile

Abstract

This invention relates to a method for recovering polyarylene ether nitrile by-product salts, belonging to the field of salt recovery technology. The technical problem solved by this invention is to provide a method for recovering polyarylene ether nitrile by-product salts. The method includes: a) pulverizing the produced polyarylene ether nitrile solution to a particle size of 20 mesh or larger, and separating the solid and liquid to obtain an abrasive slurry; b) subjecting the abrasive slurry to multi-stage cross-flow limiting extraction to obtain an organic phase and a raffinate aqueous phase; c) neutralizing and evaporating the raffinate aqueous phase to recover the polyarylene ether nitrile by-product salts. This invention effectively separates the solvent and water in the abrasive slurry, and also separates the salts and organic impurities, achieving better separation of complex components. Through further neutralization and evaporation, the by-product salts are recovered, with a purity greater than 95% and a yield greater than 80%. The recovery process is simple and easy to control, avoiding the problem of salt precipitation and scaling clogging the tower bottom pump and pipelines. The recovery process is simple and easy to control, with high recovery efficiency and low energy consumption, enabling continuous, closed, and clean recovery of the equipment.

Description

Technical Field

[0001] This invention relates to a method for recovering salts from polyarylether nitrile byproducts, belonging to the field of salt recovery technology. Background Technology

[0002] The abrasive slurry produced after the production of polyaryletheronitrile contains a large amount of water, N-methylpyrrolidone solvent, potassium chloride and potassium carbonate, and a small amount of organic impurities. Failure to recycle the abrasive slurry will not only harm the environment but also waste resources and increase production costs. A common recycling method is to distill the abrasive slurry to separate the solvent and water, with salt precipitating at the bottom of the distillation column. However, this method is costly, discontinuous, difficult to collect salt, and prone to scaling and clogging of the equipment. Furthermore, the recovered salt contains many impurities, has a low yield, and is energy-intensive. Therefore, there is an urgent need to develop a salt recovery process to solve these problems.

[0003] Patent application CN201610597587.8 discloses a method for refining alkyl-terminated polyether by-product salts to prepare high-purity sodium chloride. The method involves dissolving the by-product salts in water at a specific ratio, adjusting the pH of the aqueous solution with acid, adding an organic solvent to extract the organic matter in the aqueous phase, allowing the layers to stand and separating the layers, removing the solvent from the organic phase to recover the end-terminated polyether, and then evaporating and crystallizing the aqueous phase to prepare high-purity sodium chloride. However, this method is not very effective when used to recover polyarylene ether nitrile by-product salts, resulting in low purity and low yield of the recovered salt. Summary of the Invention

[0004] To address the above deficiencies, the technical problem solved by this invention is to provide a method for recovering polyarylene ether nitrile byproduct salts.

[0005] The present invention provides a method for recovering polyarylene ether nitrile byproduct salts, comprising the following steps:

[0006] a. Crushing: The polyarylene ether nitrile solution after production is crushed to a particle size of 20 mesh or larger, and the solid and liquid are separated to obtain the abrasive slurry;

[0007] b. Extraction: The abrasive slurry is subjected to multi-stage cross-flow limit extraction to obtain an organic phase and a raffinate aqueous phase;

[0008] c. Raffinate aqueous phase treatment: After neutralizing the raffinate aqueous phase, evaporate it to recover the polyarylene ether nitrile by-product salt.

[0009] In one embodiment of the present invention, the polyarylene ether nitrile solution is generated by reacting diphenol and 2,6-dichlorobenzonitrile in an N-methylpyrrolidone solvent with excess potassium carbonate.

[0010] In one embodiment of the present invention, the pulverization is carried out using a colloid mill with a rotation speed of 4000-8000 r / min and a demineralized water medium.

[0011] In one embodiment of the present invention, the number of stages in the multi-stage cross-flow limiting extraction is 3 to 5.

[0012] In one embodiment of the present invention, each stage of the multi-stage cross-flow limiting extraction is performed as follows: extractant is added successively until the volume of the raffinate phase no longer decreases, then the mixture is allowed to stand and separate into layers, and the lower layer of the extracted organic phase is released.

[0013] In one embodiment of the present invention, the amount of extractant added each time is 10-30% of the total amount of abrasive liquid, and the extraction conditions are room temperature and pressure, with continuous stirring for 10-30 minutes.

[0014] In one embodiment of the present invention, the extractant is any one of chloroform, dichloromethane, and aniline.

[0015] In one embodiment of the present invention, step c, the neutralization, involves adding hydrochloric acid to adjust the pH value to neutral.

[0016] In one embodiment of the present invention, step c involves evaporation using a high-salt wastewater evaporator, which comprises a heater, a forced circulation pump, an evaporator separator, a crystallizer, a condenser, various material pumps, a condensate pump, a vacuum pump, and internal pipeline valves.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. This invention employs an extraction method to effectively separate the solvent and water in the abrasive slurry, and salts and organic impurities are also separated accordingly, enabling better separation of complex components. Further neutralization and evaporation recover the byproduct salt, with a purity greater than 95% and a yield exceeding 80%.

[0019] 2. The method of the present invention has a simple and easy-to-control recovery process, avoiding the problem of salt precipitation and scaling clogging the bottom pump and pipelines.

[0020] 3. The method of the present invention has high recovery efficiency and low energy consumption, and can realize continuous, closed and clean recovery of the device. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the process of recovering polyarylether nitrile byproduct salts in an embodiment of the present invention. Detailed Implementation

[0022] The present invention provides a method for recovering polyarylene ether nitrile byproduct salts, comprising the following steps:

[0023] a. Crushing: The polyarylene ether nitrile solution after production is crushed to a particle size of 20 mesh or larger, and the solid and liquid are separated to obtain the abrasive slurry;

[0024] b. Extraction: The abrasive slurry is subjected to multi-stage cross-flow limit extraction to obtain an organic phase and a raffinate aqueous phase;

[0025] c. Raffinate aqueous phase treatment: After neutralizing the raffinate aqueous phase, evaporate it to recover the polyarylene ether nitrile by-product salt.

[0026] This invention uses an extraction method to effectively separate complex components in the abrasive slurry, avoiding the problem of salt precipitation and scaling clogging the bottom pump and pipelines. Then, neutralization and evaporation are performed for recovery. The recovery process is simple and easy to control, highly efficient and energy-saving, and the purity of the recovered salt is greater than 95%, with a yield of more than 80%.

[0027] Extraction is a method that enriches the solvent in waste liquid into an extractant through extraction, and then further separates the components. After extraction, the grinding slurry is allowed to settle and separate into layers. The lower layer is the extracted organic phase, containing the extractant and solvent; the upper layer is the raffinate aqueous phase, containing water and salt. This process route, which separates the organic phase and salt solution in the grinding slurry before recovering the salt, is not only highly efficient and energy-saving, but also yields high purity and high recovery rate of the salt. It avoids clogging problems in the bottom pump and pipelines, enabling continuous, closed-loop, and clean recovery.

[0028] Step a involves pulverizing the produced polyarylether nitrile solution, separating the solid from the liquid. The resulting solid is the polyarylether nitrile product, and the resulting liquid is the abrasive slurry. This abrasive slurry contains N-methylpyrrolidone, water, potassium chloride, potassium carbonate, and organic impurities.

[0029] The polyarylene ether nitrile solution described in this invention is a solution obtained after the polymerization of polyarylene ether nitrile. In one embodiment of this invention, the polyarylene ether nitrile solution is generated by reacting diphenol and 2,6-dichlorobenzonitrile as raw materials in an N-methylpyrrolidone solvent with excess potassium carbonate.

[0030] In one embodiment of the present invention, the pulverization is carried out using a colloid mill with a rotation speed of 4000-8000 r / min and a demineralized water medium.

[0031] Step b is extraction, in which the abrasive slurry undergoes multi-stage cross-flow limiting extraction to obtain an organic phase and a raffinate aqueous phase. Extraction not only effectively separates the solvent and water in the abrasive slurry, but also separates salts and organic impurities.

[0032] In one embodiment of the present invention, the number of stages in the multi-stage cross-flow limiting extraction is 3 to 5.

[0033] In one embodiment of the present invention, each stage of the multi-stage cross-flow limiting extraction is performed as follows: extractant is added successively until the volume of the raffinate phase no longer decreases, then the mixture is allowed to stand and separate into layers, and the lower layer of the extracted organic phase is released.

[0034] In one embodiment of the present invention, the amount of extractant added each time is 10-30% of the total amount of abrasive liquid, and the extraction conditions are room temperature and pressure, with continuous stirring for 10-30 minutes.

[0035] The ambient temperature described in this invention is 20-25°C, and the ambient pressure is one atmosphere.

[0036] Commonly used extractants in the art are applicable to this invention. In one embodiment of this invention, the extractant is any one of chloroform, dichloromethane, and aniline.

[0037] Step c involves treating the raffinate aqueous phase; the raffinate aqueous phase is neutralized and then evaporated to recover the polyarylene ether nitrile byproduct salt.

[0038] In one embodiment of the present invention, step c, the neutralization, involves adding hydrochloric acid to adjust the pH value to neutral.

[0039] In one embodiment of the present invention, step c involves evaporation using a high-salt wastewater evaporator, which comprises a heater, a forced circulation pump, an evaporator separator, a crystallizer, a condenser, various material pumps, a condensate pump, a vacuum pump, and internal pipeline valves.

[0040] The specific embodiments of the present invention will be further described below with reference to examples, but the present invention is not limited to the scope of the embodiments described herein.

[0041] Example 1

[0042] This embodiment describes a method for recovering polyarylether nitrile byproduct salts, such as... Figure 1 As shown, the polyarylene ether nitrile solution after production is first pulverized using a colloid mill, and solid-liquid separation is performed to obtain an abrasive slurry. Then, the abrasive slurry is pumped into an extraction vessel for multi-stage cross-flow limiting extraction. Finally, the raffinate aqueous phase is treated by a high-salt wastewater evaporator and acid washing neutralization to recover the polyarylene ether nitrile byproduct salt. Specifically, the steps include:

[0043] Step 1: NMP solvent was added to the system for dilution, and the reaction was terminated by cooling to 120℃. A water circulation system was established in the colloid mill, and the polyarylene ether nitrile solution was pulverized at 6000 r / min. Solid-liquid separation was performed to obtain the grinding slurry. The NMP content in the grinding slurry was 6.01%, and the potassium ion concentration was 0.0085 g / mL.

[0044] Step 2: Pump the abrasive slurry into the extraction vessel for three-stage cross-flow limiting extraction. In the first stage, add 20% of the total volume of the extractant in chloroform each time, and continuously stir at high speed for 10 minutes at room temperature and pressure, then allow it to stand and separate into layers. If the volume of the raffinate phase no longer decreases, release the lower organic phase and repeat the operation for the next stage of extraction, finally obtaining the aqueous raffinate phase.

[0045] Step 3: Add hydrochloric acid to the raffinate aqueous phase to adjust the pH to neutral, and then pass it through a high-salt wastewater evaporator to recover the polyarylene ether nitrile byproduct salt.

[0046] Example 2

[0047] This embodiment describes a method for recovering polyarylene ether nitrile byproduct salts. First, the produced polyarylene ether nitrile solution is pulverized using a colloid mill, and solid-liquid separation is performed to obtain an abrasive slurry. Then, the abrasive slurry is pumped into an extraction vessel for multi-stage cross-flow limiting extraction. Finally, the raffinate aqueous phase is treated by a high-salt wastewater evaporator and acid washing neutralization to recover the polyarylene ether nitrile byproduct salts. Specifically, the method includes the following steps:

[0048] Step 1: NMP solvent was added to the system for dilution, and the reaction was terminated by cooling to 120℃. A water circulation system was established in the colloid mill, and the polyarylene ether nitrile solution was pulverized at 6000 r / min. Solid-liquid separation was performed to obtain the grinding slurry. The NMP content in the grinding slurry was measured to be 19.63%, and the potassium ion concentration was 0.0287 g / mL.

[0049] Step 2: Pump the abrasive slurry into the extraction vessel for three-stage cross-flow limiting extraction. In the first stage, add 20% of the total volume of the extractant in chloroform each time, and continuously stir at high speed for 10 minutes at room temperature and pressure, then allow it to stand and separate into layers. If the volume of the raffinate phase no longer decreases, release the lower organic phase and repeat the operation for the next stage of extraction, finally obtaining the aqueous raffinate phase.

[0050] Step 3: Add hydrochloric acid to the raffinate aqueous phase to adjust the pH to neutral, and then pass it through a high-salt wastewater evaporator to recover the polyarylene ether nitrile byproduct salt.

[0051] Comparative Example 1

[0052] This embodiment describes a method for recovering polyarylene ether nitrile byproduct salts. First, the produced polyarylene ether nitrile solution is pulverized using a colloid mill, and solid-liquid separation is performed to obtain an abrasive slurry. Then, the abrasive slurry is pumped into an extraction vessel for multi-stage cross-flow extraction. Finally, the raffinate aqueous phase is treated by a high-salt wastewater evaporator and acid washing neutralization to recover the polyarylene ether nitrile byproduct salts. Specifically, the method includes the following steps:

[0053] Step 1: NMP solvent was added to the system for dilution, and the reaction was terminated by cooling to 120℃. A water circulation system was established in the colloid mill, and the polyarylene ether nitrile solution was pulverized at 6000 r / min. Solid-liquid separation was performed to obtain the grinding slurry. The NMP content in the grinding slurry was 6.01%, and the potassium ion concentration was 0.0085 g / mL.

[0054] Step 2: Pump the abrasive slurry into the extraction vessel for three-stage cross-flow extraction. In the first stage, add chloroform at a 1:1 ratio with the extractant, and continuously stir at high speed for 10 minutes at room temperature and pressure. Then allow it to stand and separate into layers. Release the lower organic phase and repeat the operation for the next stage of extraction. Finally, obtain the raffinate aqueous phase.

[0055] Step 3: Add hydrochloric acid to the raffinate aqueous phase to adjust the pH to neutral, and then pass it through a high-salt wastewater evaporator to recover the polyarylene ether nitrile byproduct salt.

[0056] Comparative Example 2

[0057] This comparative method for recovering by-product salt first involves pulverizing the produced polyarylene ether nitrile solution using a colloid mill and separating the solid and liquid components to obtain a grinding slurry. Then, the grinding slurry is pumped into a distillation column for distillation recovery, separating the solvent and water. Finally, the salt slurry precipitated at the bottom of the distillation column is centrifuged to obtain the polyarylene ether nitrile by-product salt. The specific steps include:

[0058] Step 1: NMP solvent was added to the system for dilution, and the reaction was terminated by cooling to 120℃. A water circulation system was established in the colloid mill, and the polyarylene ether nitrile solution was pulverized at 6000 r / min. Solid-liquid separation was performed to obtain the grinding slurry. The NMP content in the grinding slurry was 6.01%, and the potassium ion concentration was 0.0085 g / mL.

[0059] Step 2: Pump the abrasive slurry into a distillation column for distillation recovery. The temperature at the top of the column is controlled at 99℃, and the temperature at the bottom of the column is controlled at 104±4℃ to separate water. The temperature at the top of the column is about 125℃, and the pressure is -89Kpa to separate the solvent.

[0060] Step 3: Centrifuge the salt slurry precipitated from the bottom of the distillation column to obtain polyarylene ether nitrile byproduct salt.

[0061] Comparative Example 3

[0062] This comparative example describes a method for recovering polyarylene ether nitrile byproduct salts. First, the produced polyarylene ether nitrile solution is pulverized using a colloid mill, and solid-liquid separation is performed to obtain a grinding slurry. Then, the grinding slurry is neutralized and pumped into an extraction vessel for multi-stage cross-flow limiting extraction. Finally, the raffinate aqueous phase is treated using a high-salt wastewater evaporator to recover the polyarylene ether nitrile byproduct salts. The specific steps include:

[0063] Step 1: NMP solvent was added to the system for dilution, and the reaction was terminated by cooling to 120℃. A water circulation system was established in the colloid mill, and the polyarylene ether nitrile solution was pulverized at 6000 r / min. Solid-liquid separation was performed to obtain the grinding slurry. The NMP content in the grinding slurry was measured to be 19.63%, and the potassium ion concentration was 0.0287 g / mL.

[0064] Step 2: After adjusting the pH to neutral by adding hydrochloric acid to the abrasive slurry, pump it into the extraction vessel for three-stage cross-flow limiting extraction. In the first stage, add 20% of the total volume of the extractant in chloroform each time, and continuously stir at high speed for 10 minutes at room temperature and pressure, then allow it to stand and separate into layers. If the volume of the raffinate phase no longer decreases, release the lower organic extract and repeat the operation for the next stage of extraction, finally obtaining the aqueous raffinate phase.

[0065] Step 3: The raffinate phase is passed through a high-salt wastewater evaporator to recover polyarylether nitrile byproduct salts.

[0066] The purity and yield of the recovered by-product salts from the examples and comparative examples were tested, and the results of the comparison of various test indicators are shown in Table 1 below.

[0067] Table 1. Various detection indicators

[0068]

[0069] As shown in the table above, the method for recovering polyarylether nitrile by-product salts according to an embodiment of the present invention employs extraction, which can effectively separate complex components and grinding slurries of different concentrations, and further recover by-products. The purity of the recovered salt is greater than 95%, and the yield is greater than 80%. In actual recovery, there are no problems with blockage of the bottom pump and pipelines. The operation is simple and easy to control, highly efficient, and energy-efficient. Furthermore, Examples 1 and Comparative Example 1 demonstrate that multi-stage cross-flow limiting extraction can significantly reduce the amount of extractant used without affecting the recovery effect of by-product salts.

Claims

1. A method for recovering polyarylene ether nitrile byproduct salts, characterized in that, Includes the following steps: a. Crushing: The produced polyarylene ether nitrile solution is crushed to a particle size of 20 mesh or larger, and the solid-liquid separation is performed to obtain the abrasive slurry; the polyarylene ether nitrile solution is produced by reacting diphenol and 2,6-dichlorobenzonitrile in an N-methylpyrrolidone solvent with excess potassium carbonate to generate b. Extraction: The abrasive slurry is subjected to multi-stage cross-flow limit extraction to obtain an organic phase and a raffinate aqueous phase; c. Raffinate aqueous phase treatment: After neutralizing the raffinate aqueous phase, evaporate it to recover the polyarylene ether nitrile by-product salt; Each stage of the multi-stage cross-flow limit extraction is operated as follows: extractant is added successively until the volume of the raffinate phase no longer decreases, then the mixture is allowed to stand and separate into layers, and the lower layer of the extracted organic phase is released. The amount of extractant added each time is 10-30% of the total amount of abrasive slurry. The extraction conditions are room temperature and pressure, and continuous stirring for 10-30 minutes. The extractant is any one of chloroform, dichloromethane, or aniline.

2. The method for recovering polyarylene ether nitrile by-product salts according to claim 1, characterized in that: The pulverization is performed using a colloid mill with a rotation speed of 4000–8000 r / min, and the circulating medium is demineralized water.

3. The method for recovering polyarylene ether nitrile by-product salts according to claim 1, characterized in that: The number of stages in the multi-stage cross-flow limiting extraction is 3 to 5.

4. The method for recovering polyarylene ether nitrile by-product salts according to claim 1, characterized in that: Step c, the neutralization is achieved by adding hydrochloric acid to adjust the pH value to neutral.

5. The method for recovering polyarylene ether nitrile by-product salts according to claim 1, characterized in that: Step c involves evaporation using a high-salt wastewater evaporator, which consists of a heater, a forced circulation pump, an evaporator separator, a crystallizer, a condenser, various material pumps, a condensate pump, a vacuum pump, and internal pipeline valves.

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