A method for recovering methylamine in a catalyst during polyphenylene ether production

Abstract

The present application relates to the field of chemical material recycling, in particular to a method for recycling methylamine in a polyphenyl ether production process. The method comprises adding 0.1% to 15% of a quaternary ammonium salt to a mixed amine containing methylamine, performing a polyphenyl ether synthesis reaction, separating oil and water after the reaction, adjusting the pH of the separated wastewater, adding a good solvent for polyphenyl ether, and recycling the methylamine. The quaternary ammonium salt comprises one or more of trimethyloctylammonium chloride, benzyltrimethylammonium chloride, trioctylmethylammonium chloride, cetyltrimethylammonium bromide, and tetramethylammonium chloride. The present application changes the polyphenyl ether catalyst system, recycles methylamine that is easily soluble in a poor solvent for polyphenyl ether into a good solvent for polyphenyl ether, and can be well used in the reaction without affecting the quality of the finished product, and is low in cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical material recycling, and particularly relates to a method for recycling methylamine in a catalyst in a polyphenyl ether production process. BACKGROUND

[0002] Polyphenyl ether is one of the five engineering plastics, and is widely applied due to good chemical, physical and electrochemical properties. The modified polyphenyl ether resin has good chemical resistance, high temperature resistance, high strength, low shrinkage and high flowability, and is widely applied to the electrical, automobile and other industrial material fields.

[0003] The synthesis of polyphenyl ether is to use cuprous salt and mixed amine as catalysts to oxidize and couple 2,6-dimethylphenol in a good solvent of polyphenyl ether under oxygen to obtain polyphenyl ether solution. The waste water and the polyphenyl ether solution are separated by centrifugal separation, and a poor solvent of polyphenyl ether is added to the polyphenyl ether solution to precipitate polyphenyl ether particles. After filtration and drying, the polyphenyl ether product is obtained. The good solvent and the poor solvent of polyphenyl ether will enter the solvent recovery unit for purification and recycling. The polyphenyl ether catalyst cuprous salt and mixed amine cannot be recycled and treated after the reaction, and can only be used as hazardous waste. The cuprous salt will be deactivated when it comes into contact with water, and has no recycling value. The methylamine in the mixed amine is a kind of amine with high price and large amount, and it is necessary and economically beneficial to recycle the methylamine alone.

[0004] The currently used recycling technology is to adjust the pH value to alkaline by adding alkali to the waste water, so that the alkali reacts with the copper salt-methylamine complex to generate copper hydroxide and methylamine. The good solvent of polyphenyl ether is added to extract the methylamine. The polyphenyl ether good solvent with methylamine enters the solvent recovery unit for purification. The solvent recovery unit also contains the poor solvent of polyphenyl ether. The mixed solvent of the good solvent and the poor solvent will change the solubility parameter of the methylamine. The solubility parameter of the methylamine in the new mixed solvent is 30 times larger than that in the original single solvent. The methylamine dissolved in the good solvent of polyphenyl ether precipitates into the poor solvent of polyphenyl ether, so that the methylamine accumulated in the poor solvent increases. However, the poor solvent of polyphenyl ether cannot be used for polymerization, and needs to be intermittently discharged to waste the methylamine and ultimately affect the quality of the finished product, resulting in increased production cost and insufficient competitiveness. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a method for recycling methylamine in a catalyst in a polyphenyl ether production process.

[0006] The application provides a method for recovering methylamine in a catalyst in a polyphenyl ether production process, comprising the following steps: adding 0.1-15% of quaternary ammonium salt into mixed amine containing methylamine, performing a polyphenyl ether synthesis reaction, performing oil-water separation on the product after the reaction, adjusting the pH of the separated wastewater, adding a good solvent of polyphenyl ether, and recovering the methylamine; the quaternary ammonium salt comprises one or more of trimethyloctylammonium chloride, benzyltrimethylammonium chloride, trioctylmethylammonium chloride, hexadecyltrimethylammonium bromide and tetramethylammonium chloride. The application can change the polyphenyl ether catalyst system by adding a specific type and amount of quaternary ammonium salt into the original mixed amine system, recover the methylamine which is easily dissolved in a poor solvent of polyphenyl ether into a good solvent of polyphenyl ether, and the recovered methylamine does not affect the performance of the finished product, the added quaternary ammonium salt can be well mixed with the organic amine and does not affect the reaction and the quality of the finished product, and the used quaternary ammonium salt does not have a great impact on the cost.

[0007] Preferably, the amount of the quaternary ammonium salt added is 0.2-15%, preferably 0.2-10%; the quaternary ammonium salt is trimethyloctylammonium chloride, benzyltrimethylammonium chloride or trioctylmethylammonium chloride. In the application, the quaternary ammonium salt and the amount can be optimized, especially the specific quaternary ammonium salt at the preferred amount, to better play the synergistic effect of the quaternary ammonium salt and the methylamine and improve the recovery effect of the methylamine.

[0008] Further preferably, lye is added to the wastewater, the lye is a 20-40% sodium hydroxide solution, and preferably, the pH of the wastewater is adjusted to 9-13. The application finds that when the pH of the wastewater is adjusted to 9-13 in the above manner, the recovery effect of the methylamine can be significantly improved.

[0009] Preferably, the good solvent of the polyphenyl ether is aromatic hydrocarbon or halogenated hydrocarbon; the aromatic hydrocarbon comprises one or more selected from benzene, toluene and xylene, and the halogenated hydrocarbon comprises chloroform; preferably, the good solvent of the polyphenyl ether is toluene or xylene. The good solvent used in the application, especially toluene and xylene, can better integrate with the quaternary ammonium salt, better play a role in the system, and further improve the recovery effect of the methylamine.

[0010] Further preferably, the volume ratio of the good solvent of the polyphenyl ether to the wastewater is 0.5-1.5:1. The extraction effect of the good solvent of the polyphenyl ether and the wastewater is better when the above ratio is adopted.

[0011] Further preferably, the methylamine is methyl ethylamine, dimethylbutylamine, hexamethylenetetramine, methyl dicyclohexylamine or dimethylformamide.

[0012] As preferred, the method further comprises mixing the good solvent of polyphenylene ether with the wastewater under alkaline condition, and performing liquid-liquid separation, wherein the upper liquid of the separation comprises the good solvent of polyphenylene ether, methylamine and quaternary ammonium salt, and the separation temperature is 15-40℃. In the application, by adding alkali liquor to the wastewater, the methylamine and quaternary ammonium salt dissolved in the wastewater can form a complex, and can more easily melt into the good solvent of polyphenylene ether, so that the methylamine can be better recovered.

[0013] Further preferably, the method further comprises mixing the upper liquid with the poor solvent of polyphenylene ether, and performing purification, wherein the temperature of the bottom of the purification tower is 90-110℃, and the temperature of the top of the purification tower is 60-70℃, so as to obtain a mixture comprising the good solvent of polyphenylene ether, the poor solvent of polyphenylene ether and methylamine, and then adding water to separate, so as to obtain the good solvent of polyphenylene ether containing methylamine, which is re-injected into the synthesis reaction of polyphenylene ether. In the application, by using the rectifying tower to rectify, the methylamine is separated from other high-boiling amine, so that the methylamine can be better recovered in the subsequent process.

[0014] Further preferably, the method further comprises concentrating, precipitating, filtering and drying the oil phase of the oil-water separation, so as to obtain polyphenylene ether; and the filtrate obtained by filtering is subjected to solvent recovery, wherein the filtrate comprises the poor solvent of polyphenylene ether. In the application, by using the poor solvent of polyphenylene ether to wash, the good solvent of polyphenylene ether containing methylamine can be better recovered, and the waste of methylamine can be reduced.

[0015] Further preferably, the poor solvent of polyphenylene ether is at least one of methanol, ethanol, isopropyl alcohol, n-butyl alcohol, acetone, methyl ethyl ketone and water, and preferably is methanol or ethanol.

[0016] According to a preferred embodiment of the present invention, 0.2% to 10% of a quaternary ammonium salt is added to a mixed amine, and the reaction is carried out according to the polymerization reaction procedure. After the reaction is completed, the mixture is transferred to a curing tank, where a capping agent is added for end-capping. Oil-water separation is performed using a centrifuge. The separated wastewater contains complexes such as cuprous salt, mixed amine, and capping agent. A strong alkaline sodium hydroxide solution is added to a wastewater collection tank to adjust the pH of the wastewater to 9-13. A good solvent of polyphenylene ether is added and mixed with the alkaline wastewater, which is then transferred to a liquid-liquid separation tank. The temperature is controlled between 15-40°C. The upper layer contains the good solvent and organic amines such as methylamine and quaternary ammonium salt, while the lower layer contains wastewater, copper salt, and capping agent. The solvent-to-wastewater ratio is controlled... The oil phase is concentrated, precipitated, filtered, and dried to obtain the polyphenylene ether product. The filtrate containing undesirable solvents of polyphenylene ether enters the solvent recovery process. The upper layer of good solvents of polyphenylene ether and methylamine enter the solvent recovery process and are mixed with the undesirable solvents of polyphenylene ether. The mixture is then purified by a purification tower, with the bottom temperature controlled at 90-110℃ and the top temperature controlled at 60-70℃. A mixture of good solvents of polyphenylene ether, undesirable solvents, and methylamine is obtained. Water is added to the mixture for liquid-liquid separation, with the ratio of water to undesirable solvents of polyphenylene ether being 0.5-1.5. The top layer contains a large amount of good solvents of polyphenylene ether containing methylamine, which is returned to the solvent collection tank for later use. Finally, the mixture is reintroduced into the polymerization reaction.

[0017] According to the present invention, a method for recovering methylamine from a catalyst during the production of polyphenylene ether (PPE) is provided. The method involves preparing the catalyst methylamine from PPE using a solution recovery method. The PPE solution method uses cuprous salt and mixed amines as catalysts and acidic inorganic salts as end-capping agents to terminate the chain reaction. Initially, the catalyst and inorganic salts need to be separated; otherwise, they will enter the finished product during subsequent precipitation, leading to increased copper content and impurities. The inorganic salts, cuprous salts, and mixed organic amines form a complex dissolved in water. Centrifugation is then used to separate the water phase containing the organic amines, cuprous salts, and inorganic salts from the oil phase. The aqueous phase is acidic; sodium hydroxide solution is added to it to dissociate the complex, generating copper hydroxide precipitate, which precipitates the methylamine bound to the complex. This precipitate is then extracted using a good solvent for PPE. The extracted good solvent for polyphenylene ether (PPE) and methylamine are recycled to a solvent recovery unit for further purification. The oil phase is concentrated, precipitated, filtered, and dried to obtain the finished PPE product. During the filtration stage, the filtrate containing both good and bad solvents of PPE enters the solvent recovery unit. In the solvent recovery process, the good and bad solvents of PPE mix, altering the solubility of methylamine and making it more soluble in the bad solvent of PPE. Therefore, a quaternary ammonium salt is added to the catalyst as a phase transfer agent. The quaternary ammonium salt enters the solvent recovery unit along with the organic solvent, inhibiting the formation of extracts between the bad solvent of PPE and methylamine, thereby preventing methylamine from entering the bad solvent of PPE. This yields methylamine soluble in the good solvent of PPE, which is then purified and separated to improve the purity of the good solvent of PPE and methylamine.

[0018] The present application changes the adjustment of the polyphenyl ether catalyst mixed amine system, adds a quaternary ammonium salt which does not affect the polymerization effect, and recycles the methylamine which is easily dissolved in the poor solvent of the polyphenyl ether into the good solvent of the polyphenyl ether. The method can reduce the accumulation of methylamine in the poor solvent of the polyphenyl ether, the recycled methylamine is pure, and the methylamine dissolved in the good solvent of the polyphenyl ether is re-injected into the polymerization reaction, which has no effect on the reaction process, and the performance of the finished polyphenyl ether product has small fluctuations, meeting the market application requirements.

[0019] The present application has at least the following beneficial effects: the present application optimizes the adjustment of the polyphenyl ether catalyst mixed amine system, adds a small amount of quaternary ammonium salt, changes the mixed amine catalyst system, which has no effect on the reaction compared with the original system, and the performance of the finished product has no obvious change, the cost does not need to increase much, the quaternary ammonium salt does not cause environmental pollution, but can increase the content of methylamine in the good solvent of the polyphenyl ether, reduce the unit consumption of methylamine, reduce the cost, and improve the product competitiveness; the good solvent of the polyphenyl ether containing a large amount of methylamine is re-injected into the reaction, the reaction process is the same as adding pure methylamine, and the performance has no obvious change; the recycling of methylamine greatly reduces the COD content in the wastewater, reduces the difficulty of wastewater treatment, ensures the long-period stable and clean operation of the system, and is a major innovation in the field of polyphenyl ether solution method. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0021] Figure 1 The flowchart for recycling methylamine in the catalyst in the production process of polyphenyl ether provided by the embodiments of the present application. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. The following embodiments are used to illustrate the present application, but not to limit the scope of the present application. If the specific technology or condition is not specified in the embodiments, it is implemented according to the technology or condition described in the literature in the art, or according to the product manual. The implementation conditions in the embodiments can be further adjusted according to the specific experimental conditions or factory conditions. If the implementation conditions are not specified, they are usually the conditions in the conventional experiments. The materials, reagents and the like used in the following embodiments are commercially available unless otherwise specified.

[0023] The following examples are intended to illustrate the present application but not to limit the scope of the present application.

[0024] The polyphenyl ether synthesis method used in the following examples and comparative examples of the present application is as follows:

[0025] First, 22t of toluene is added as a good solvent for polyphenyl ether. In the presence of a cuprous salt and a mixed amine, 800Kg of 2,6-dimethylphenol is added as a PPE seed. Then, the remaining 5000Kg of 2,6-dimethylphenol is added while oxygen is being introduced. The 2,6-dimethylphenol is added within 40 minutes, and then oxygen is continuously introduced for reaction. After 50 minutes of continuous reaction, oxygen supply is stopped, and the reaction is completed. Then, an aqueous solution of ethylenediaminetetraacetic acid is added to cap the ends, and the temperature is maintained at 60°C. Then, the water phase containing the catalyst and capping agent is separated out by separation to obtain a polyphenyl ether solution.

[0026] When toluene in the above method is replaced by xylene, a polyphenyl ether solution containing xylene is obtained.

[0027] Example 1

[0028] The present example provides a method for recovering methylamine in the catalyst in the production process of polyphenyl ether, as shown in Figure 1 The method comprises the following steps:

[0029] According to the amount of 5% of trimethyl octyl ammonium chloride in the original mixed amine, the mixed amine is configured, and is put into the reaction kettle for reaction. The specific reaction maturation steps are carried out according to the above-mentioned reaction maturation steps. The water phase separated out by centrifugal separation is put into the water phase tank. 30% sodium hydroxide solution is added thereto to adjust the solution PH to 11, and the temperature is controlled at 35°C. Then, toluene is added according to toluene: wastewater = 0.7:1, and is put into the liquid-liquid separation tank. The liquid at the top of the separation tank is returned to the solvent recovery, and the liquid at the bottom is discharged to the wastewater pretreatment. The oil phase separated out by centrifugal separation is put into the oil phase collection tank, and is put into the flash tank for concentration. The toluene concentrated out is recovered into the solvent recovery, and the oil phase is put into the precipitation kettle, and is precipitated using methanol. Then, filtration is carried out, and the filtrate is put into the solvent recovery. The solvent recovery is taken out to the purification column for purification. The column kettle temperature is controlled at 95°C, and the column top temperature is controlled at 67°C. The toluene, methanol, and methylamine mixture is put into the reflux tank. Water is added according to the water: methanol ratio = 1:1, and is put into the liquid-liquid separation tank. The toluene at the top of the separation tank is collected into the toluene collection tank, and the methanol at the bottom is separated into the methanol separation column. The toluene in the toluene tank is put into the polymerization kettle for reaction again.

[0030] Example 2

[0031] The present example provides a method for recovering methylamine in the catalyst in the production process of polyphenyl ether, which comprises the following steps:

[0032] According to the amount of 8% of trimethyl octyl ammonium chloride in the original mixed amine, configure into mixed amine, put into the reaction kettle for reaction, specific according to the above reaction curing step, centrifugal separation of water phase into water phase tank, add 30% sodium hydroxide solution to it, adjust the solution PH to 11, temperature control at 38℃, then add toluene: waste water = 0.9:1, go to liquid-liquid separation tank, the top liquid of separation tank returns to solvent recovery, the bottom liquid goes to waste water pretreatment; The oil phase separated by centrifugation enters the oil phase collection tank, enters the flash tank for concentration, and the concentrated toluene is recovered into the solvent recovery, and the oil phase enters the precipitation kettle, uses methanol for precipitation, then filters, and the filtrate enters the solvent recovery; The solvent recovery is taken to the purification column for purification, the column temperature is controlled at 95℃, the top temperature is controlled at 67℃, toluene, methanol, methylamine mixture and the like enter the reflux tank, water is added according to the ratio of water:methanol = 1.02:1, goes to liquid-liquid separation tank, the top of separation tank goes to toluene collection tank, the bottom goes to methanol separation column to separate methanol, and the toluene in toluene tank is put into the polymerization kettle for reaction again.

[0033] Example 3

[0034] The embodiment provides a method for recovering methylamine in a catalyst in a polyphenyl ether production process, comprising the following steps:

[0035] According to the amount of 8% of trimethyl octyl ammonium chloride in the original mixed amine, configure into mixed amine, put into the reaction kettle for reaction, specific according to the above reaction curing step, centrifugal separation of water phase into water phase tank, add 30% sodium hydroxide solution to it, adjust the solution PH to 11, temperature control at 38℃, then add toluene: waste water = 0.9:1, go to liquid-liquid separation tank, the top liquid of separation tank returns to solvent recovery, the bottom liquid goes to waste water pretreatment; The oil phase separated by centrifugation enters the oil phase collection tank, enters the flash tank for concentration, and the concentrated toluene is recovered into the solvent recovery, and the oil phase enters the precipitation kettle, uses methanol for precipitation, then filters, and the filtrate enters the solvent recovery; The solvent recovery is taken to the purification column for purification, the column temperature is controlled at 95℃, the top temperature is controlled at 67℃, toluene, methanol, methylamine mixture and the like enter the reflux tank, water is added according to the ratio of water:methanol = 1.02:1, goes to liquid-liquid separation tank, the top of separation tank goes to toluene collection tank, the bottom goes to methanol separation column to separate methanol, and the toluene in toluene tank is put into the polymerization kettle for reaction again.

[0036] Example 4

[0037] The embodiment provides a method for recovering methylamine in a catalyst in a polyphenyl ether production process, comprising the following steps:

[0038] According to the proportion of benzyl trimethyl ammonium chloride in the original mixed amine, 10% is added, configured into mixed amine, put into the reaction kettle for reaction, according to the above reaction maturation step, the centrifugal separation of the water phase into the water phase tank, add 30% sodium hydroxide solution to the solution, adjust the PH to 11, control the temperature at 38℃, then add xylene according to xylene: waste water = 0.8:1, go to liquid-liquid separation tank, the top liquid of the separation tank returns to the solvent recovery, and the bottom liquid goes to the wastewater pretreatment; The centrifugally separated oil phase enters the oil phase collection tank, enters the flash tank for concentration, the concentrated xylene is recovered into the solvent recovery, and the oil phase enters the precipitation kettle, uses methanol for precipitation, then filters, and the filtrate enters the solvent recovery; The solvent recovery is taken to the purification column for purification, the column temperature is controlled at 95℃, the top temperature is controlled at 67℃, the xylene, methanol, methylamine mixture and the like enter the reflux tank, water is added according to the water: methanol ratio = 1.1:1, goes to the liquid-liquid separation tank, the top of the separation tank goes to the xylene collection tank, the bottom goes to the methanol separation column to separate methanol, and the xylene in the xylene tank is put into the polymerization kettle for reaction again.

[0039] Example 5

[0040] The embodiment provides a method for recovering methylamine in a catalyst in a polyphenyl ether production process, comprising the following steps:

[0041] According to the proportion of benzyl trimethyl ammonium chloride in the original mixed amine, 10% is added, configured into mixed amine, put into the reaction kettle for reaction, according to the above reaction maturation step, the centrifugal separation of the water phase into the water phase tank, add 30% sodium hydroxide solution to the solution, adjust the PH to 11, control the temperature at 38℃, then add xylene according to xylene: waste water = 0.8:1, go to liquid-liquid separation tank, the top liquid of the separation tank returns to the solvent recovery, and the bottom liquid goes to the wastewater pretreatment; The centrifugally separated oil phase enters the oil phase collection tank, enters the flash tank for concentration, the concentrated xylene is recovered into the solvent recovery, and the oil phase enters the precipitation kettle, uses methanol for precipitation, then filters, and the filtrate enters the solvent recovery; The solvent recovery is taken to the purification column for purification, the column temperature is controlled at 95℃, the top temperature is controlled at 67℃, the xylene, methanol, methylamine mixture and the like enter the reflux tank, water is added according to the water: methanol ratio = 1.1:1, goes to the liquid-liquid separation tank, the top of the separation tank goes to the xylene collection tank, the bottom goes to the methanol separation column to separate methanol, and the xylene in the xylene tank is put into the polymerization kettle for reaction again.

[0042] Comparative Example 1

[0043] The same as the implementation step of example 3, the difference is only that no benzyl trimethyl ammonium chloride is added, that is, no quaternary ammonium salt is added to configure the mixed amine, and then it is put into the reaction kettle for reaction. The specific operation is carried out according to the above reaction maturation step. The separated water phase is centrifuged into the water phase tank. 30% sodium hydroxide solution is added to the water phase tank. The solution PH is adjusted to 12. The temperature is controlled at 38℃. Then xylene is added according to xylene: waste water = 1:1. The liquid is separated into the liquid-liquid separation tank. The top liquid of the separation tank is returned to the solvent recovery. The bottom liquid is discharged to the waste water pretreatment. The centrifuged oil phase is collected into the oil phase collection tank and then concentrated in the flash tank. The concentrated xylene is recovered into the solvent recovery. The oil phase is put into the precipitation kettle and precipitated with methanol. Then it is filtered. The filtrate is put into the solvent recovery. The solvent recovery is purified in the purification column. The column kettle temperature is controlled at 95℃. The column top temperature is controlled at 67℃. The xylene, methanol, methyl amine mixture and the like are put into the reflux tank. Water is added according to the water: methanol ratio = 1.05:1. The liquid is separated into the liquid-liquid separation tank. The top liquid of the separation tank is collected into the xylene collection tank. The bottom liquid is separated into the methanol separation column to separate the methanol. The xylene in the xylene tank is put into the polymerization kettle for reaction.

[0044] Comparative example 2

[0045] The same as example 4, the difference is only that the PH is only 6. The benzyl trimethyl ammonium chloride is added according to the proportion of 10% in the original mixed amine. The mixed amine is configured. It is put into the reaction kettle for reaction. The specific operation is carried out according to the above reaction maturation step. The separated water phase is centrifuged into the water phase tank. 30% sodium hydroxide solution is added to the water phase tank. The solution PH is adjusted to 6. The temperature is controlled at 38℃. Then xylene is added according to xylene: waste water = 0.8:1. The liquid is separated into the liquid-liquid separation tank. The top liquid of the separation tank is returned to the solvent recovery. The bottom liquid is discharged to the waste water pretreatment. The centrifuged oil phase is collected into the oil phase collection tank and then concentrated in the flash tank. The concentrated xylene is recovered into the solvent recovery. The oil phase is put into the precipitation kettle and precipitated with methanol. Then it is filtered. The filtrate is put into the solvent recovery. The solvent recovery is purified in the purification column. The column kettle temperature is controlled at 95℃. The column top temperature is controlled at 67℃. The xylene, methanol, methyl amine mixture and the like are put into the reflux tank. Water is added according to the water: methanol ratio = 1.1:1. The liquid is separated into the liquid-liquid separation tank. The top liquid of the separation tank is collected into the xylene collection tank. The bottom liquid is separated into the methanol separation column to separate the methanol. The xylene in the xylene tank is put into the polymerization kettle for reaction.

[0046] The products obtained in Examples 1-5 and Comparative Examples 1 and 2 were detected, separated according to the difference of the retention time of different compounds in the same chromatographic column, and the response signals of different compounds were recorded after the detector, and the area percentage method was used for quantification. The instrument was a gas chromatograph: TRACE1310, equipped with a TCD detector, and the chromatographic parameters were as follows: injection port: 240°C, detector: 250°C, chromatographic column: DB-130m x 0.45mm x 2.55μm, column temperature: constant temperature 70°C, running time 10min, carrier gas: He(≥99.999%), mode: constant pressure 5.000Psi, split flow 100mL / min, injection volume: 1.0μL, after the chromatograph was stabilized, the area percentage was used for quantification. The content test results are shown in Table 1.

[0047] Table 1 Content of methylamine in toluene / xylene (%)

[0048]

[0049]

[0050] Although the present application has been described in detail with general description and specific embodiments above, some modifications or improvements can be made on the basis of the present application, which is obvious to those skilled in the art. Therefore, these modifications or improvements made on the basis of not deviating from the spirit of the present application, all belong to the scope of the present application claimed.

Claims

1. A method for recovering methylamine from a catalyst during the production of polyphenylene ether, characterized in that, include: A quaternary ammonium salt (3%–10%) is added to a mixed amine containing methylamine to synthesize polyphenylene ether (PPE). The reaction product is subjected to oil-water separation, and the pH of the separated wastewater is adjusted to 9–13 to obtain alkaline wastewater. A good solvent for PPE is mixed with the alkaline wastewater, and liquid-liquid separation is performed. The separated upper liquid is mixed with a poor solvent for PPE and purified to obtain a mixture containing a good solvent for PPE, a poor solvent for PPE, and methylamine. Water is then added for separation to obtain PPE containing methylamine. A good solvent; the quaternary ammonium salt is selected from one or more of trimethyloctylammonium chloride, benzyltrimethylammonium chloride, trioctylmethylammonium chloride, hexadecyltrimethylammonium bromide, and tetramethylammonium chloride; the good solvent for the polyphenylene ether is an aromatic hydrocarbon or a halogenated hydrocarbon; the aromatic hydrocarbon is selected from one or more of benzene, toluene, and xylene, and the halogenated hydrocarbon is chloroform; the volume ratio of the good solvent for the polyphenylene ether to the wastewater is 0.5 to 1.5:1; the poor solvent for the polyphenylene ether is at least one of methanol, ethanol, isopropanol, n-butanol, acetone, methyl ethyl ketone, and water.

2. The method for recovering methylamine from the catalyst during the production of polyphenylene ether according to claim 1, characterized in that, An alkaline solution, which is a 20-40% sodium hydroxide solution, is added to the wastewater.

3. The method for recovering methylamine from a catalyst during the production of polyphenylene ether according to claim 1 or 2, characterized in that, The methylamine is methyl ethylamine, dimethyl butylamine, hexamethylenetetramine, methyl dicyclohexylamine, or dimethylformamide.

4. The method for recovering methylamine from a catalyst during the production of polyphenylene ether according to claim 1 or 2, characterized in that, The separated upper liquid comprises a good solvent for polyphenylene ether, methylamine, and quaternary ammonium salt, and the separation temperature is 15–40°C.

5. The method for recovering methylamine from the catalyst during the production of polyphenylene ether according to claim 3, characterized in that, The separated upper liquid comprises a good solvent for polyphenylene ether, methylamine, and quaternary ammonium salt, and the separation temperature is 15–40°C.

6. The method for recovering methylamine from a catalyst during the production of polyphenylene ether according to claim 4, characterized in that, The temperature of the bottom of the purification tower is 90-110℃, and the temperature of the top of the purification tower is 60-70℃. The good solvent containing methylamine polyphenylene ether obtained by separation is added back into the synthesis reaction of polyphenylene ether.

7. The method for recovering methylamine from a catalyst during the production of polyphenylene ether according to claim 5, characterized in that, The temperature of the bottom of the purification tower is 90-110℃, and the temperature of the top of the purification tower is 60-70℃. The good solvent containing methylamine polyphenylene ether obtained by separation is added back into the synthesis reaction of polyphenylene ether.

8. The method for recovering methylamine from a catalyst during the production of polyphenylene ether according to claim 1 or 2, characterized in that, It also includes concentrating, precipitating, filtering and drying the oil phase after oil-water separation to obtain polyphenylene ether; the filtrate obtained by filtration is then subjected to solvent recovery, wherein the filtrate contains undesirable solvents for polyphenylene ether.

9. The method for recovering methylamine from a catalyst during the production of polyphenylene ether according to claim 3, characterized in that, It also includes concentrating, precipitating, filtering and drying the oil phase after oil-water separation to obtain polyphenylene ether; the filtrate obtained by filtration is then subjected to solvent recovery, wherein the filtrate contains undesirable solvents for polyphenylene ether.

10. The method for recovering methylamine from a catalyst during the production of polyphenylene ether according to claim 4, characterized in that, It also includes concentrating, precipitating, filtering and drying the oil phase after oil-water separation to obtain polyphenylene ether; the filtrate obtained by filtration is then subjected to solvent recovery, wherein the filtrate contains undesirable solvents for polyphenylene ether.

11. The method for recovering methylamine from a catalyst during the production of polyphenylene ether according to claim 5, characterized in that, It also includes concentrating, precipitating, filtering and drying the oil phase after oil-water separation to obtain polyphenylene ether; the filtrate obtained by filtration is then subjected to solvent recovery, wherein the filtrate contains undesirable solvents for polyphenylene ether.

12. The method for recovering methylamine from a catalyst during the production of polyphenylene ether according to claim 6, characterized in that, It also includes concentrating, precipitating, filtering and drying the oil phase after oil-water separation to obtain polyphenylene ether; the filtrate obtained by filtration is then subjected to solvent recovery, wherein the filtrate contains undesirable solvents for polyphenylene ether.

13. The method for recovering methylamine from a catalyst during the production of polyphenylene ether according to claim 7, characterized in that, It also includes concentrating, precipitating, filtering and drying the oil phase after oil-water separation to obtain polyphenylene ether; the filtrate obtained by filtration is then subjected to solvent recovery, wherein the filtrate contains undesirable solvents for polyphenylene ether.

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