A method for recovering n-methylmorpholine from n-methylmorpholine-containing wastewater

Abstract

The present application relates to the technical field of chemical recovery, and discloses a method for recovering N-methylmorpholine from N-methylmorpholine-containing wastewater. The method comprises the following steps: adjusting the wastewater to be alkaline and distilling the wastewater to obtain N-methylmorpholine aqueous solution after distillation; adding solid alkali and water-carrying agent into the obtained N-methylmorpholine aqueous solution to carry out extraction and separation; and carrying out rectification on the organic phase obtained by extraction and separation to obtain N-methylmorpholine. The present application has the advantages of mild reaction condition, simple post-treatment step, high recovery rate of N-methylmorpholine, high purity of N-methylmorpholine, low water content, low production cost and suitability for industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the chemical recovery technical field, specifically relates to a kind of from N-methyl morpholine wastewater containing N-methyl morpholine recovery method. BACKGROUND

[0002] N-methyl morpholine is an organic compound, molecular formula is C5H 11 NO, colorless liquid, with ammonia smell, sensitive to air;It can be mixed with water, ethanol, benzene and diethyl ether.Solvent extraction is mostly used in the recovery of amine wastewater, but due to the good water solubility of amine, part of the residue is often left after extraction treatment, on the one hand, amine loss is more, on the other hand, the ammonia nitrogen in wastewater is high, it is difficult to handle, and more equipment is needed.N-methyl morpholine is often used as an acid binding agent in reactions (such as the synthesis of flonicamid), and the content of N-methyl morpholine hydrochloride in the wastewater obtained after treatment is about 32wt%, and the water content is about 68wt%.The wastewater must be recovered N-methyl morpholine, and then discharged.

[0003] At present, solvent extraction is mostly used in the recovery of amine wastewater, but due to the good water solubility of amine, part of the residue is often left after extraction treatment, on the one hand, amine loss is more, on the other hand, the ammonia nitrogen in wastewater is high, it is difficult to handle, and more equipment is needed.N-methyl morpholine is often used as an acid binding agent in reactions (such as the synthesis of flonicamid), and the content of N-methyl morpholine hydrochloride in the wastewater obtained after treatment is about 32wt%, and the water content is about 68wt%.The wastewater must be recovered N-methyl morpholine, and then discharged.

[0004] There are few reports on the method of recovering high content N-methyl morpholine from wastewater containing N-methyl morpholine, only CN102532060A, CN1339434A and CN109574958A involve the recovery of N-methyl morpholine and N-ethyl morpholine, but it is difficult to obtain high content N-methyl morpholine by using water carrying agent.

[0005] Therefore, it is urgent to develop a method for efficiently recovering high content N-methyl morpholine from wastewater containing N-methyl morpholine, and the water content needs to be controlled below 0.03% to facilitate subsequent application. SUMMARY

[0006] The present application provides a method for recovering high content N-methyl morpholine from wastewater containing N-methyl morpholine, which overcomes the defects of existing methods, such as complex operation, serious environmental pollution, low recovery of high content N-methyl morpholine, and difficulty in industrial production.The method provided by the present application can completely recover N-methyl morpholine from wastewater, has high recovery rate of N-methyl morpholine, and obtains high content N-methyl morpholine with low water content, which is suitable for industrial production.

[0007] In order to achieve the above purpose, the present application provides a method for recovering N-methyl morpholine from wastewater containing N-methyl morpholine, wherein the method comprises the following steps:

[0008] (1) adjusting the wastewater to be alkaline and distilling to obtain N-methyl morpholine aqueous solution after distillation;

[0009] (2) adding solid alkali and water-carrying agent to the N-methyl morpholine aqueous solution obtained in step (1) to perform extraction and separation;

[0010] (3) performing rectification on the organic phase obtained in step (2) to obtain N-methyl morpholine.

[0011] Through the technical scheme, the application has the following beneficial technical effects:

[0012] (1) The application directly distills the alkaline wastewater to obtain N-methyl morpholine aqueous solution with reduced water content, then adds solid alkali and water-carrying agent to the N-methyl morpholine aqueous solution to perform extraction and separation, so that the organic phase (with water content of about 1%) is obtained, the aqueous phase can be directly used for distillation of the next batch of wastewater, the organic phase after distillation contains water-carrying agent and N-methyl morpholine, the water-carrying agent is recovered and reused, and then rectification is performed to obtain qualified N-methyl morpholine.

[0013] (2) The application has mild reaction conditions, simple post-treatment steps, high recovery rate of N-methyl morpholine, high purity, low water content, low production cost and suitability for industrial production. DETAILED DESCRIPTION

[0014] The endpoints of the ranges and any values disclosed herein are not to be understood as being limited to the exact values recited as implicitly disclosed by the above notation are included in the ranges. Individual values are also disclosable by the disclosure of a range because the precise end points of the ranges and the individual values are not important unless context dictates otherwise. Ranges can be combined by their end points, by their end points and individual points, or by individual points, to produce new ranges that are disclosable according to the above.

[0015] The first aspect of the application provides a method for recovering N-methyl morpholine from N-methyl morpholine-containing wastewater, wherein the method comprises the following steps:

[0016] (1) adjusting the wastewater to be alkaline and distilling to obtain N-methyl morpholine aqueous solution after distillation;

[0017] (2) adding solid alkali and water-carrying agent to the N-methyl morpholine aqueous solution obtained in step (1) to perform extraction and separation;

[0018] (3) performing rectification on the organic phase obtained in step (2) to obtain N-methyl morpholine.

[0019] The present application can make the water content of the recovered N-methyl morpholine less than 0.03% (for example, 0.01%) by using the solid alkali and the water-carrying agent in combination, the solid alkali plays a role of drying, and can be reused. The present application is easy to operate, can process almost water-free N-methyl morpholine, has high recovery rate, is easy to be industrialized, and has wide application prospect.

[0020] By the method of the present application, N-methyl morpholine with high recovery rate, high purity and low water content can be obtained.

[0021] According to some embodiments of the present application, the pH of the wastewater is adjusted to 9-13 (for example, 9, 10, 11, 12, 13, and any value within the range of any two of the above) by using the alkaline adjusting agent in step (1), and preferably 9-11.

[0022] According to some embodiments of the present application, the alkaline adjusting agent is selected from sodium hydroxide and / or potassium hydroxide.

[0023] According to some embodiments of the present application, the distillation in step (1) is carried out at normal pressure until the internal temperature is 98-100°C.

[0024] According to some embodiments of the present application, the solid alkali in step (2) is sodium hydroxide and / or potassium hydroxide.

[0025] According to some embodiments of the present application, the amount of the solid alkali is 10-50wt% (for example, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, and any value within the range of any two of the above) of the wastewater, and preferably 12-22wt%. In the present application, too little amount of the solid alkali will result in too high water content in the recovered N-methyl morpholine, and too much amount of the solid alkali cannot further reduce the water content.

[0026] According to some embodiments of the present application, the water-carrying agent in step (2) is an alkane solvent, and is preferably at least one selected from n-hexane, cyclohexane and methylcyclopentane.

[0027] According to some embodiments of the present application, the amount of the water-carrying agent is 10-50wt% (for example, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, and any value within the range of any two of the above) of the wastewater, and preferably 20-50wt%. In the present application, too little amount of the water-carrying agent will result in too high water content in the recovered N-methyl morpholine, and too much amount of the water-carrying agent cannot further reduce the water content.

[0028] According to some embodiments of the present application, the water phase obtained from the extraction and separation in step (2) is recycled to step (1) to adjust the pH of the wastewater.

[0029] According to some embodiments of the present application, the operation of the rectification in step (3) comprises: warming the organic phase obtained from the extraction and separation in step (2) to perform normal pressure rectification to collect the water-carrying agent and N-methyl morpholine. The collected water-carrying agent can be recycled.

[0030] According to some embodiments of the present application, the N-methyl morpholine-containing wastewater mainly comprises at least one of N-methyl morpholine hydrochloride, N-methyl morpholine sulfate or N-methyl morpholine acetate, i.e. an aqueous solution containing at least one of N-methyl morpholine hydrochloride, N-methyl morpholine sulfate or N-methyl morpholine acetate.

[0031] The present application will be described in detail below through examples.

[0032] In the following examples and comparative examples, the specific conditions not specified are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be obtained through commercial channels.

[0033] In the following examples and comparative examples, the N-methyl morpholine content is detected by GC (gas chromatography); the water content is detected by Karl Fischer water titrator.

[0034] The N-methyl morpholine wastewater is: wastewater obtained from N-methyl morpholine as an acid-binding agent in the synthesis of flonicamid, and the main components are 32wt% N-methyl morpholine hydrochloride and 68wt% water.

[0035] Example 1

[0036] In a 1000mL four-necked flask, 600g of N-methyl morpholine wastewater and 250g of 30% sodium hydroxide solution or the separated water phase were mixed to adjust the pH to 10. Normal pressure distillation was started, and distilled to an internal temperature of 100°C, and 324g of N-methyl morpholine aqueous solution (with a water content of about 40%) was distilled out. 80g of sodium hydroxide solid (13.3wt% of the initial wastewater) and 150g of n-hexane (25wt% of the initial wastewater) were added, stirred for 0.5h, and the organic phase with a water content of 0.19% was obtained by extraction and separation, and the water phase was used to adjust the pH of the next batch of wastewater. The organic phase was warmed and normal pressure rectified, the n-hexane phase with a boiling point of 60-73°C was collected, and the temperature was continued to be raised to collect N-methyl morpholine with a boiling point of 114-116°C, and 137.8g of N-methyl morpholine was obtained. The calculated recovery rate was 97.7%, the N-methyl morpholine content detected by GC was 99.5%, and the water content was 0.01%.

[0037] Example 2

[0038] In a 1000ml four-necked flask, 600g of N-methylmorpholine waste water and 250g of 30% sodium hydroxide solution or the separated aqueous phase were mixed to adjust the pH to 10. Normal pressure distillation was started and the distillation was continued until the internal temperature reached 100°C, and 324g of N-methylmorpholine aqueous solution (containing about 40% water) was distilled out. 83g of solid potassium hydroxide (13.8% of the initial waste water) and 150g of cyclohexane (25% of the initial waste water) were added to the solution, and the mixture was stirred for 0.5h to obtain an organic phase containing 0.17% water and an aqueous phase. The aqueous phase was used to adjust the pH of the next batch of waste water. The organic phase was subjected to normal pressure distillation, and the distillate was collected at 74-82°C to obtain cyclohexane, and the temperature was increased to collect the distillate at 114-116°C to obtain 136.6g of N-methylmorpholine. The calculated recovery rate was 96.9%, and the N-methylmorpholine content was 99.7% and the water content was 0.01% as determined by GC.

[0039] Example 3

[0040] In a 1000ml four-necked flask, 600g of N-methylmorpholine waste water and 250g of 30% sodium hydroxide solution or the separated aqueous phase were mixed to adjust the pH to 10. Normal pressure distillation was started and the distillation was continued until the internal temperature reached 100°C, and 324g of N-methylmorpholine aqueous solution (containing about 40% water) was distilled out. 80g of solid sodium hydroxide (13.3% of the initial waste water) and 150g of methylcyclopentane (25% of the initial waste water) were added to the solution, and the mixture was stirred for 0.5h to obtain an organic phase containing 0.15% water and an aqueous phase. The aqueous phase was used to adjust the pH of the next batch of waste water. The organic phase was subjected to normal pressure distillation, and the distillate was collected at 62-71°C to obtain methylcyclopentane, and the temperature was increased to collect the distillate at 114-116°C to obtain 135.8g of N-methylmorpholine. The calculated recovery rate was 96.3%, and the N-methylmorpholine content was 99.6% and the water content was 0.01% as determined by GC.

[0041] Example 4

[0042] In a 1000ml four-necked flask, 600g of N-methylmorpholine waste water and 250g of 30% sodium hydroxide solution or the separated aqueous phase were mixed to adjust the pH to 10. Normal pressure distillation was started and the distillation was continued until the internal temperature reached 100°C, and 324g of N-methylmorpholine aqueous solution (containing about 40% water) was distilled out. 72g of solid sodium hydroxide (12% of the initial waste water) and 150g of n-hexane (25% of the initial waste water) were added to the solution, and the mixture was stirred for 0.5h to obtain an organic phase containing 0.29% water and an aqueous phase. The aqueous phase was used to adjust the pH of the next batch of waste water. The organic phase was subjected to normal pressure distillation, and the distillate was collected at 60-73°C to obtain n-hexane, and the temperature was increased to collect the distillate at 114-116°C to obtain 136.7g of N-methylmorpholine. The calculated recovery rate was 97%, and the N-methylmorpholine content was 99.5% and the water content was 0.03% as determined by GC.

[0043] Example 5

[0044] Into a 1000 mL four-necked flask, 600 g of N-methylmorpholine wastewater and 250 g of 30% sodium hydroxide solution or the separated aqueous phase were mixed to adjust the pH to 10. Normal pressure distillation was started, and the distillation was continued until the internal temperature reached 100°C, and 324 g of N-methylmorpholine aqueous solution (containing about 40% water) was distilled out. Then, 80 g of sodium hydroxide solid (13.3% of the initial wastewater) and 120 g of n-hexane (20% of the initial wastewater) were added, and the mixture was stirred for 0.5 h. The organic phase containing 0.29% water was obtained by extraction and separation, and the aqueous phase was used for the next batch of pH adjustment. The organic phase was subjected to normal pressure distillation at an elevated temperature, and n-hexane phase was collected at 60-73°C. The temperature was further increased, and N-methylmorpholine was collected at 114-116°C, and the amount was 135.9 g. The calculated recovery rate was 96.4%, the N-methylmorpholine content detected by GC was 99.4%, and the water content was 0.03%.

[0045] Example 6

[0046] Into a 1000 mL four-necked flask, 600 g of N-methylmorpholine wastewater and 250 g of 30% sodium hydroxide solution or the separated aqueous phase were mixed to adjust the pH to 10. Normal pressure distillation was started, and the distillation was continued until the internal temperature reached 100°C, and 324 g of N-methylmorpholine aqueous solution (containing about 40% water) was distilled out. Then, 80 g of sodium hydroxide solid (13.3% of the initial wastewater) and 120 g of n-hexane (20% of the initial wastewater) were added, and the mixture was stirred for 0.5 h. The organic phase containing 0.29% water was obtained by extraction and separation, and the aqueous phase was used for the next batch of pH adjustment. The organic phase was subjected to normal pressure distillation at an elevated temperature, and n-hexane phase was collected at 60-73°C. The temperature was further increased, and N-methylmorpholine was collected at 114-116°C, and the amount was 135.9 g. The calculated recovery rate was 96.4%, the N-methylmorpholine content detected by GC was 99.4%, and the water content was 0.03%.

[0047] Example 7

[0048] In a 1000 mL four-necked flask, 600 g of N-methylmorpholine wastewater and 250 g of 30% sodium hydroxide solution or layered aqueous phase were mixed to adjust the pH to 10. Start normal pressure distillation, evaporate to 100°C, evaporate 324 g of N-methylmorpholine aqueous solution (water content is about 40%), add 90 g of sodium hydroxide solid (15 wt% of the initial wastewater) and 150 g of n-hexane (25 wt% of the initial wastewater), stir for 0.5 h, extract and separate to obtain an organic phase with a water content of 0.29%, and the aqueous phase is used for the next batch of pH adjustment. The organic phase is warmed and normal pressure distilled, the n-hexane phase is collected at 60-73°C, and the N-methylmorpholine is collected at 114-116°C. The calculated recovery rate is 97.8%, the GC detection of N-methylmorpholine content is 99.5%, and the water content is 0.01%.

[0049] Example 8

[0050] In a 1000 mL four-necked flask, 600 g of N-methylmorpholine wastewater and 250 g of 30% sodium hydroxide solution or layered aqueous phase were mixed to adjust the pH to 10. Start normal pressure distillation, evaporate to 100°C, evaporate 324 g of N-methylmorpholine aqueous solution (water content is about 40%), add 90 g of sodium hydroxide solid (15 wt% of the initial wastewater) and 150 g of n-hexane (25 wt% of the initial wastewater), stir for 0.5 h, extract and separate to obtain an organic phase with a water content of 0.29%, and the aqueous phase is used for the next batch of pH adjustment. The organic phase is warmed and normal pressure distilled, the n-hexane phase is collected at 60-73°C, and the N-methylmorpholine is collected at 114-116°C. The calculated recovery rate is 97.8%, the GC detection of N-methylmorpholine content is 99.5%, and the water content is 0.01%.

[0051] Example 9

[0052] In a 1000 mL four-necked flask, 600 g of N-methylmorpholine wastewater and 250 g of 30% sodium hydroxide solution or layered aqueous phase were mixed to adjust the pH to 10. Start normal pressure distillation, evaporate to 100°C, evaporate 324 g of N-methylmorpholine aqueous solution (water content is about 40%), add 90 g of sodium hydroxide solid (15 wt% of the initial wastewater) and 150 g of n-hexane (25 wt% of the initial wastewater), stir for 0.5 h, extract and separate to obtain an organic phase with a water content of 0.29%, and the aqueous phase is used for the next batch of pH adjustment. The organic phase is warmed and normal pressure distilled, the n-hexane phase is collected at 60-73°C, and the N-methylmorpholine is collected at 114-116°C. The calculated recovery rate is 97.8%, the GC detection of N-methylmorpholine content is 99.5%, and the water content is 0.01%.

[0053] Comparative Example 1

[0054] Into a 1000 mL four-necked flask, 600 g of N-methylmorpholine wastewater and 250 g of 30% sodium hydroxide solution were mixed to adjust the pH to 10. Normal pressure distillation was started, and the distillation was continued until the internal temperature reached 100°C, and 324 g of N-methylmorpholine aqueous solution was distilled out. Then, 2 L of MTBE was added and extracted three times, and 40 g of anhydrous sodium sulfate was added and dried overnight. The MTBE was recovered by distillation, and then the fraction of 114-116°C was collected to obtain 73.4 g of N-methylmorpholine. The calculated recovery rate was 52%, and the N-methylmorpholine content was 97.5% and the water content was 1.5% as measured by GC.

[0055] Since the water content of the crude distillate was about 40%, and N-methylmorpholine was well soluble in water, it was difficult to extract it completely by a large amount of solvent, and thus the recovery rate was low.

[0056] Comparative Example 2

[0057] Into a 1000 mL four-necked flask, 600 g of N-methylmorpholine wastewater and 250 g of 30% potassium hydroxide solution were mixed to adjust the pH to 10. Normal pressure distillation was started, and the distillation was continued until the internal temperature reached 100°C, and 324 g of N-methylmorpholine aqueous solution was distilled out. Then, 600 g of cyclohexane was added, 40 g of anhydrous sodium sulfate was added and dried overnight, and then normal pressure distillation was performed at elevated temperature to collect the fraction of 74-82°C cyclohexane, and then the fraction of 114-116°C was collected to obtain 110 g of N-methylmorpholine. The calculated recovery rate was 78%, and the N-methylmorpholine content was 98% and the water content was 1.7% as measured by GC.

[0058] Comparative Example 3

[0059] Into a 1000 mL four-necked flask, 600 g of N-methylmorpholine wastewater and 250 g of 30% sodium hydroxide solution were mixed to adjust the pH to 10. Normal pressure distillation was started, and the distillation was continued until the internal temperature reached 100°C, and 324 g of N-methylmorpholine aqueous solution was distilled out. Then, 80 g of sodium hydroxide solid was added and stirred for 1 h to separate the liquid, and the water content was reduced to 5%. Then, 40 g of anhydrous sodium sulfate was added and dried overnight, and the water content was 1.8%. The fraction of 114-116°C was collected to obtain 120 g of N-methylmorpholine. The calculated recovery rate was 84%, and the N-methylmorpholine content was 98% and the water content was 1% as measured by GC.

[0060] Since the water content was too high, the drying effect of the solid base was limited, and even if anhydrous sodium sulfate was used for drying, it was difficult to reduce the water content to less than 1%.

[0061] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A method for recovering N-methylmorpholine from N-methylmorpholine-containing wastewater, characterized by, The method comprises the following steps: (1) adjusting the wastewater to be alkaline and distilling to obtain N-methyl morpholine aqueous solution after distillation; (2) adding solid alkali and water-carrying agent to the N-methyl morpholine aqueous solution obtained in step (1) to carry out extraction and separation; (3) rectifying the organic phase obtained in step (2) to obtain N-methyl morpholine; The solid alkali is sodium hydroxide and / or potassium hydroxide; the amount of the solid alkali is 10-50wt% of the wastewater; The water-carrying agent is selected from at least one of n-hexane, cyclohexane and methylcyclopentane; the amount of the water-carrying agent is 10-50wt% of the wastewater.

2. The method of claim 1, wherein, In step (1), the pH of the wastewater is adjusted to 9-13 by using an alkaline adjusting agent.

3. The method of claim 2, wherein, In step (1), the pH of the wastewater is adjusted to 9-11 by using an alkaline adjusting agent.

4. The method of claim 2, wherein, The alkaline adjusting agent is selected from sodium hydroxide and / or potassium hydroxide.

5. The method of any one of claims 1-4, wherein, The distillation in step (1) is carried out at normal pressure until the internal temperature is 98-100℃.

6. The method of any one of claims 1-4, wherein, The amount of the solid alkali in step (2) is 12-22wt% of the wastewater.

7. The method of any one of claims 1-4, wherein, The amount of the water-carrying agent is 20-50wt% of the wastewater.

8. The method of any one of claims 1-4, wherein, The aqueous phase obtained in step (2) is recycled to step (1) to adjust the pH of the wastewater.

9. The method of any one of claims 1-4, wherein, The rectification in step (3) comprises: warming the organic phase obtained in step (2) to carry out normal pressure rectification to collect the water-carrying agent and N-methyl morpholine.

10. The method of any one of claims 1-4, wherein, The N-methyl morpholine-containing wastewater is an aqueous solution containing at least one of N-methyl morpholine hydrochloride, N-methyl morpholine sulfate or N-methyl morpholine acetate.