A method and device for recovering 3-hydroxypropionitrile from wastewater

Abstract

The present invention proposes a method and a device for recovering 3-hydroxypropionitrile in wastewater, and belongs to the technical field of wastewater recovery. The method for recovering 3-hydroxypropionitrile in wastewater comprises the following steps: 1) mixing wastewater, alkaline solution and electrolyte, decomposing the obtained mixed material to obtain decomposed wastewater; 2) extracting or adsorbing and regenerating the decomposed wastewater to obtain an extract containing 3-hydroxypropionitrile or a regenerated liquid containing 3-hydroxypropionitrile; 3) molecularly distilling the extract containing 3-hydroxypropionitrile or the regenerated liquid containing 3-hydroxypropionitrile to obtain 3-hydroxypropionitrile. The method provided by the present invention can effectively recover 3-hydroxypropionitrile in wastewater and reduce production costs.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater recovery, and in particular relates to a method for recovering 3-hydroxypropionitrile in wastewater and a device used therein. Background Art

[0002] Phosphate compounds and nitrile compounds are commonly used additives for lithium-ion electrolytes, and have a significant effect on improving the high voltage performance, high temperature performance and cycle performance of lithium-ion batteries. Studies have found that tris(2-cyanoethyl)phosphate and tris(2-cyanoethyl)phosphite can be used as additives for high-voltage lithium-ion battery electrolytes to improve the high temperature performance and cycle performance of batteries.

[0003] In the production and synthesis process of tris(2-cyanoethyl)phosphate and tris(2-cyanoethyl)phosphite, 3-hydroxypropionitrile is the main raw material, which is expensive and accounts for a very high proportion of the raw material cost, about 80%. Through testing, it was found that the main destination of 3-hydroxypropionitrile in the reaction process is the synthesis of participating products and by-products, and the other is 3-hydroxypropionitrile that does not participate in the reaction. In the production process, some products, by-products (di(2-cyanoethyl)phosphite, di(2-cyanoethyl)phosphate, (2-cyanoethyl)phosphite, (2-cyanoethyl)phosphate), and 3-hydroxypropionitrile that does not participate in the reaction eventually enter the wastewater. In view of the extremely high material cost of 3-hydroxypropionitrile, the recycling of 3-hydroxypropionitrile in wastewater has extremely high economic value. Summary of the invention

[0004] The invention provides a method for recovering 3-hydroxypropionitrile in wastewater and a device used therefor. The method provided by the invention can effectively recover 3-hydroxypropionitrile in wastewater and reduce production costs.

[0005] In order to achieve the above object, the present invention provides a method for recovering 3-hydroxypropionitrile in wastewater, comprising the following steps:

[0006] 1) Mixing wastewater, alkaline solution and electrolyte, decomposing the obtained mixture to obtain decomposed wastewater;

[0007] 2) extracting or adsorbing the decomposed wastewater to obtain an extract containing 3-hydroxypropionitrile or a regenerated liquid containing 3-hydroxypropionitrile;

[0008] 3) The extract containing 3-hydroxypropionitrile or the regeneration liquid containing 3-hydroxypropionitrile is molecularly distilled to obtain 3-hydroxypropionitrile.

[0009] Preferably, the wastewater in step 1) is wastewater generated by the preparation of tris(2-cyanoethyl)phosphate or tris(2-cyanoethyl)phosphite; the alkaline solution includes one or more of sodium hydroxide aqueous solution, potassium hydroxide solution, ammonia water, sodium carbonate solution, potassium carbonate solution, sodium bicarbonate solution and potassium bicarbonate solution.

[0010] Preferably, the electrolyte in step 1) includes one or more of sodium chloride, potassium nitrate, sodium nitrate, potassium sulfate and sodium sulfate.

[0011] Preferably, in step 1), the amount of alkali added to the alkaline solution is 1 to 10 times the content of 3-hydroxypropionitrile in the wastewater; and the amount of the electrolyte added is 1% to 50% of the mass of the wastewater.

[0012] Preferably, during the decomposition in step 1), the pH is ≥ 10, the temperature is 30-100° C., and the time is 0.5-20 h.

[0013] Preferably, the extraction agent used for extraction in step 2) includes one or more of butanone, methyl isobutyl ketone, toluene, cyclohexane and dichloromethane.

[0014] Preferably, the temperature during extraction in step 2) is 0-100° C., and the mass ratio of wastewater to extractant is 1:0.4-100.

[0015] Preferably, in step 2), a resin is used for adsorption, and after obtaining the resin that adsorbs 3-hydroxypropionitrile, a regeneration liquid is used for regeneration; the regeneration liquid includes one or more of acetonitrile, acetone, cyclohexane, toluene and N-methylpyrrolidone; the volume ratio of the regeneration liquid to the resin is 0.5~100:1.

[0016] Preferably, the pressure during molecular distillation in step 3) is 3Pa~1000Pa, and the temperature is 10~228°C.

[0017] Preferably, the molecular distillation in step 3) further comprises removing water using a molecular sieve.

[0018] The present invention provides a device for recovering 3-hydroxypropionitrile in the wastewater described in any one of the above, comprising:

[0019] Reactors, extraction units and molecular distillation units;

[0020] The discharge port of the reactor is connected to the material feed port of the extraction device; the extractant discharge port of the molecular distillation device is connected to the extractant feed port of the extraction device; the extractant discharge port of the extraction device is connected to the feed port of the molecular distillation device.

[0021] Preferably, the extraction device comprises a first extraction device, a second extraction device and a third extraction device;

[0022] The discharge port of the reactor is connected to the material feed port of the first extraction device; the wastewater discharge port of the first extraction device is connected to the material feed port of the second extraction device; the wastewater discharge port of the second extraction device is connected to the material feed port of the third extraction device; the extractant discharge port of the molecular distillation device is connected to the extractant feed port of the third extraction device; the extract liquid discharge port of the third extraction device is connected to the extractant feed port of the second extraction device; the extract liquid discharge port of the second extraction device is connected to the extractant feed port of the first extraction device; the extract liquid discharge port of the first extraction device is connected to the feed port of the molecular distillation device.

[0023] The present invention provides a device for recovering 3-hydroxypropionitrile in the wastewater described in any one of the above items, comprising:

[0024] A reactor, a first adsorption regeneration device, a second adsorption regeneration device and a molecular distillation device;

[0025] The discharge port of the reactor is connected to the feed ports of the first adsorption regeneration device and the second adsorption regeneration device respectively; the upper material discharge ports of the first adsorption regeneration device and the second adsorption regeneration device 7 are connected to the feed port of the molecular distillation device respectively; the regeneration liquid discharge port of the molecular distillation device is connected to the regeneration liquid feed port of the first adsorption regeneration device and the second adsorption regeneration device respectively.

[0026] Compared with the prior art, the advantages and positive effects of the present invention are:

[0027] The method for recovering 3-hydroxypropionitrile in wastewater provided by the present invention comprises the following steps: partially tris(2-cyanoethyl)phosphate or tris(2-cyanoethyl)phosphite, and byproducts generated by preparing tris(2-cyanoethyl)phosphate or tris(2-cyanoethyl)phosphite are decomposed and converted into 3-hydroxypropionitrile; 3-hydroxypropionitrile is recovered by extraction or adsorption, the recovery amount is greatly increased, and the 3-hydroxypropionitrile is reused for production, thereby greatly reducing the cost of raw materials.

[0028] The method provided by the invention has mild reaction conditions, simple operation process and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A diagram of a production unit for recovering 3-hydroxypropionitrile by extraction;

[0030] Figure 2 A diagram of a production unit for recovering 3-hydroxypropionitrile by adsorption;

[0031] Among them, 1 is a reactor, 2 is a first extraction device, 3 is a second extraction device, 4 is a third extraction device, 5 is a molecular distillation device, 6 is a first adsorption regeneration device, and 7 is a second adsorption regeneration device. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] The present invention provides a method for recovering 3-hydroxypropionitrile in wastewater, comprising the following steps:

[0034] 1) Mixing wastewater, alkaline solution and electrolyte, decomposing the obtained mixture to obtain decomposed wastewater;

[0035] 2) extracting or adsorbing the decomposed wastewater to obtain an extract containing 3-hydroxypropionitrile or a regenerated liquid containing 3-hydroxypropionitrile;

[0036] 3) The extract containing 3-hydroxypropionitrile or the regeneration liquid containing 3-hydroxypropionitrile is molecularly distilled to obtain 3-hydroxypropionitrile.

[0037] The present invention mixes wastewater, alkaline solution and electrolyte, decomposes the obtained mixture, and obtains decomposed wastewater. In the present invention, the wastewater is preferably wastewater produced by preparing tris(2-cyanoethyl)phosphate or tris(2-cyanoethyl)phosphite; the alkaline solution preferably includes one or more of sodium hydroxide aqueous solution, potassium hydroxide solution, ammonia water, sodium carbonate solution, potassium carbonate solution, sodium bicarbonate solution and potassium bicarbonate solution. In the present invention, the electrolyte preferably includes one or more of sodium chloride, potassium nitrate, sodium nitrate, potassium sulfate and sodium sulfate. In the present invention, the amount of alkali added in the alkaline solution is preferably 1 to 10 times the content of 3-hydroxypropionitrile in the wastewater; the amount of electrolyte added is preferably 1% to 50% of the mass of the wastewater, more preferably 5% to 20%. In the present invention, an alkaline solution is added, and the byproducts tris(2-cyanoethyl)phosphite, tris(2-cyanoethyl)phosphate, di(2-cyanoethyl)phosphite, di(2-cyanoethyl)phosphate, (2-cyanoethyl)phosphite, and (2-cyanoethyl)phosphate in the wastewater can be decomposed into corresponding phosphates or phosphites and 3-hydroxypropionitrile under alkaline conditions. At the same time, some products tris(2-cyanoethyl)phosphite and tris(2-cyanoethyl)phosphate can be decomposed into corresponding phosphates or phosphites and 3-hydroxypropionitrile under alkaline conditions. In the present invention, adding electrolytes to the wastewater before decomposition can reduce the solubility of 3-hydroxypropionitrile and the extractant, and improve the subsequent extraction efficiency of 3-hydroxypropionitrile. In the present invention, adding an excess of alkali is conducive to accelerating the decomposition rate of the byproducts.

[0038] Taking sodium hydroxide solution as an alkaline solution as an example, the reaction equation is as follows:

[0039] PO(OCH2CH2CN)3+3NaOH===Na3PO4+3HOCH2CH2CN

[0040] PO(OH)(OCH2CH2CN)2+3NaOH===Na3PO4+2HOCH2CH2CN+H2O

[0041] PO(OH)2(OCH2CH2CN)+3NaOH===Na3PO4+HOCH2CH2CN+2H2O

[0042] P(OCH2CH2CN)3+3NaOH===Na3PO4+3HOCH2CH2CN

[0043] P(OH)(OCH2CH2CN)2+3NaOH===Na3PO4+2HOCH2CH2CN+H2O

[0044] P(OH)2(OCH2CH2CN)+3NaOH===Na3PO4+HOCH2CH2CN+2H2O

[0045] In the present invention, when decomposing, pH is preferably ≥ 10; temperature is preferably 30-100°C, more preferably 35-60°C; time is preferably 0.5-20h, more preferably 3-10h. In the present invention, the decomposition conditions will directly affect the recovery of 3-hydroxypropionitrile. The higher the temperature and the higher the pH, the faster the decomposition conversion rate, but too high a temperature may cause the decomposition or conversion of 3-hydroxypropionitrile. It is understandable that the decomposition conditions defined in the present invention are the optimal range.

[0046] After obtaining the decomposed wastewater, the present invention extracts or regenerates the decomposed wastewater by adsorption to obtain an extract containing 3-hydroxypropionitrile or a regenerated liquid containing 3-hydroxypropionitrile. In the present invention, the extractant for extraction preferably includes one or more of butanone, methyl isobutyl ketone, toluene, cyclohexane and dichloromethane. The temperature during extraction is preferably 0-100°C, more preferably 20-40°C; the mass ratio of wastewater to extractant is preferably 1:0.4-100, more preferably 1:4-10. In the present invention, it is preferred to use resin for adsorption, and then regenerate the resin after obtaining the resin that adsorbs 3-hydroxypropionitrile; the regenerated liquid preferably includes one or more of acetonitrile, acetone, cyclohexane, toluene and N-methylpyrrolidone; the volume ratio of the regenerated liquid to the resin is preferably 0.5-100:1, more preferably 2-8:1.

[0047] After obtaining the extract containing 3-hydroxypropionitrile or the regeneration liquid containing 3-hydroxypropionitrile, the present invention performs molecular distillation on the extract containing 3-hydroxypropionitrile or the regeneration liquid containing 3-hydroxypropionitrile to obtain 3-hydroxypropionitrile. In the present invention, the pressure during molecular distillation is preferably 3Pa~1000Pa, more preferably 5Pa~145Pa; the temperature is preferably 10~228°C, more preferably 15~50°C.

[0048] In the present invention, the molecular distillation is preferably followed by removing water using a molecular sieve. In the present invention, the molecular sieve is preferably a 3A molecular sieve, a 4A molecular sieve, or a 5A molecular sieve.

[0049] The method for recovering 3-hydroxypropionitrile in wastewater provided by the present invention comprises the following steps: partially tris(2-cyanoethyl)phosphate or tris(2-cyanoethyl)phosphite, and byproducts generated by preparing tris(2-cyanoethyl)phosphate or tris(2-cyanoethyl)phosphite are decomposed and converted into 3-hydroxypropionitrile; 3-hydroxypropionitrile is recovered by extraction or adsorption, the recovery amount is greatly increased, and the 3-hydroxypropionitrile is reused for production, thereby greatly reducing the cost of raw materials.

[0050] like Figure 1As shown, the present invention provides a device for recovering 3-hydroxypropionitrile in the wastewater described in any one of the above, comprising:

[0051] Reactor 1, extraction device and molecular distillation device 5;

[0052] The discharge port of the reactor 1 is connected to the material feed port of the extraction device; the extractant discharge port of the molecular distillation device 5 is connected to the extractant feed port of the extraction device; the extractant discharge port of the extraction device is connected to the feed port of the molecular distillation device 5.

[0053] In the present invention, in order to fully extract, it is preferred to use a multi-stage extraction method for extraction. In the present invention, the extraction device preferably includes a first extraction device 2, a second extraction device 3, a third extraction device 4 and a molecular distillation device 5;

[0054] The discharge port of the reactor 1 is connected to the material feed port of the first extraction device 2; the wastewater discharge port of the first extraction device 2 is connected to the material feed port of the second extraction device 3; the wastewater discharge port of the second extraction device 3 is connected to the material feed port of the third extraction device 4; the extractant discharge port of the molecular distillation device 5 is connected to the extractant feed port of the third extraction device 4; the extractant discharge port of the third extraction device 4 is connected to the extractant feed port of the second extraction device 3; the extractant discharge port of the second extraction device 3 is connected to the extractant feed port of the first extraction device 2; the extractant discharge port of the first extraction device 2 is connected to the feed port of the molecular distillation device 5.

[0055] In the present invention, a multi-stage extraction device is used for extraction. During operation, the mixed material and the extractant enter the multi-stage extraction device in a reverse contact manner, that is, the decomposed wastewater enters from the first extraction device, and the extractant enters from the third extraction device.

[0056] like Figure 2 As shown, the present invention provides a device for recovering 3-hydroxypropionitrile in the wastewater described in any one of the above items, comprising:

[0057] A reactor 1, a first adsorption regeneration device 6, a second adsorption regeneration device 7 and a molecular distillation device 5; the discharge port of the reactor 1 is connected to the feed ports of the first adsorption regeneration device 6 and the second adsorption regeneration device 7 respectively; the upper material discharge ports of the first adsorption regeneration device 6 and the second adsorption regeneration device 7 are connected to the feed port of the molecular distillation device 5 respectively; the regeneration liquid discharge port of the molecular distillation device 5 is connected to the regeneration liquid feed ports of the first adsorption regeneration device 6 and the second adsorption regeneration device 7 respectively.

[0058] The device for recovering 3-hydroxypropionitrile in wastewater provided by the present invention is provided with a first adsorption regeneration device 6 and a second adsorption regeneration device 7. When the first adsorption regeneration device 6 is regenerated, the second adsorption regeneration device 7 is adsorbed, so that continuous production can be carried out.

[0059] When working (normal continuous operation), the connecting pipeline between the reactor 1 and the first adsorption regeneration device 6, and the connecting pipeline between the molecular distillation device 5 and the second adsorption regeneration device 7. Close the connecting pipeline between the reactor 1 and the second adsorption regeneration device 7, and the connecting pipeline between the molecular distillation device 5 and the first adsorption regeneration device 6. The decomposed wastewater transferred from the reactor 1 is transferred to the first adsorption regeneration device 6 to contact with the resin for adsorption, and at the same time, the regeneration liquid separated in the molecular distillation device 5 is transferred to the second adsorption regeneration device 7. The 3-hydroxypropionitrile adsorbed in the resin is separated from the resin and dissolved in the regeneration liquid. The regeneration liquid dissolved with 3-hydroxypropionitrile is transferred to the molecular distillation device 5 again for molecular distillation, and 3-hydroxypropionitrile and the regeneration liquid are separated to obtain the product 3-hydroxypropionitrile. When the resin in the first adsorption regeneration device 6 is mixed with the regeneration liquid for regeneration, the connecting pipeline between the reactor 1 and the first adsorption regeneration device 6 is closed, and the connecting pipeline between the reactor 1 and the second adsorption regeneration device 7 is opened, and the decomposed wastewater transferred from the reactor 1 is transferred to the second adsorption regeneration device 7 for adsorption and regeneration.

[0060] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0061] The production equipment in Examples 1 to 4 and Comparative Examples 1 to 2 is as follows Figure 1 shown.

[0062] The production equipment in Example 5 is as follows Figure 2 shown.

[0063] The wastewater used in the embodiments and comparative examples is the wastewater generated when producing tris(2-cyanoethyl)phosphate, wherein tris(2-cyanoethyl)phosphate is produced by the method disclosed in CN117164619A. The mass concentration of 3-hydroxypropionitrile in the wastewater is 1.8%, and the mass concentrations of tris(2-cyanoethyl)phosphate, di(2-cyanoethyl)phosphate, and (2-cyanoethyl)phosphate are 1.6%, 2.2%, and 2.6%, respectively.

[0064] Example 1

[0065] The reactor was preheated to 40°C, wastewater was introduced into the reactor at a rate of 100 g / min, sodium hydroxide solution with a mass concentration of 32% was introduced into the reactor at a rate of 15.6 g / min, and sodium nitrate was introduced into the reactor at a rate of 10 g / min. The pH value of the obtained mixture was 13.2, the total residence time was 6 h, and the 3-hydroxypropionitrile content in the wastewater after decomposition at the reactor outlet was 4.64%, and the effective alkaline hydrolysis rate was 90.9%.

[0066] The decomposed wastewater enters from the material feed port of the first extraction device, and the extractant methyl isobutyl ketone enters from the extractant feed port of the third extraction device. The mass ratio of wastewater to methyl isobutyl ketone is 1:10, the extraction temperature is controlled at 20°C, and the extraction is performed for 2 hours. The content of 3-hydroxypropionitrile in the wastewater after extraction is 0.07%, and the content of 3-hydroxypropionitrile in methyl isobutyl ketone is 0.457%.

[0067] After extraction, methyl isobutyl ketone enters molecular distillation, the material entry temperature is 30°C, the reaction pressure is 145 Pa, and 5.84 g of 3-hydroxypropionitrile with a purity of 98.3% is obtained at the bottom of the molecular distillation per minute.

[0068] Example 2

[0069] The reactor was preheated to 50°C, wastewater entered the reactor at a rate of 100 g / min, 32% sodium hydroxide solution entered the reactor at a rate of 23.4 g / min, and sodium chloride entered the reactor at a rate of 15 g / min. The pH value of the obtained mixture was 13.5, the total residence time was 5 h, and the 3-hydroxypropionitrile content in the wastewater after decomposition at the reactor outlet was 4.36%, and the effective alkaline hydrolysis rate was 95.6%.

[0070] The decomposed wastewater enters from the material feed port of the first extraction device, and the extractant butanone enters from the extractant feed port of the third extraction device. The mass ratio of wastewater to butanone is 1:5, the extraction temperature is controlled at 50°C, and the extraction is performed for 2 hours. The content of 3-hydroxypropionitrile in the wastewater after extraction is 0.02%, and the content of 3-hydroxypropionitrile in butanone is 0.868%.

[0071] After extraction, butanone enters molecular distillation, the material entry temperature is 15°C, the reaction pressure is 7 Pa, and 6.03 g of 3-hydroxypropionitrile with a purity of 99.6% is obtained per minute at the bottom of the molecular distillation.

[0072] Example 3

[0073] The reactor was preheated to 90°C, wastewater entered the reactor at a rate of 100 g / min, a solution of sodium hydroxide with a mass concentration of 32% entered the reactor at a rate of 23.4 g / min, and sodium chloride entered the reactor at a rate of 15 g / min. The pH value of the obtained mixture was 13.5, the total residence time was 9 h, and the 3-hydroxypropionitrile content in the wastewater after decomposition at the reactor outlet was 1.65%, and the effective alkaline hydrolysis rate was 42.2%.

[0074] The decomposed wastewater enters from the material feed port of the first extraction device, and the extractant butanone enters from the extractant feed port of the third extraction device. The mass ratio of wastewater to butanone is 1:5, the extraction temperature is controlled at 30°C, and the extraction is performed for 2 hours. The content of 3-hydroxypropionitrile in the wastewater after extraction is 0.013%, and the content of 3-hydroxypropionitrile in butanone is 0.527%.

[0075] After extraction, butanone enters molecular distillation, the material entry temperature is 35°C, the reaction pressure is 100 Pa, and 4.18 g of 3-hydroxypropionitrile with a purity of 87.4% is obtained at the bottom of the molecular distillation per minute.

[0076] Example 4

[0077] The reactor was preheated to 30°C, wastewater entered the reactor at a rate of 100 g / min, 10% sodium carbonate solution entered the reactor at a rate of 7.8 g / min, and potassium sulfate entered the reactor at a rate of 5 g / min. The pH value of the obtained mixture was 10.7, the total residence time was 5 h, and the 3-hydroxypropionitrile content in the wastewater after decomposition at the reactor outlet was 3.89%, and the effective alkaline hydrolysis rate was 58.4%.

[0078] The decomposed wastewater is fed from the material feed port of the first extraction device, and the extractant butanone is fed from the extractant feed port of the third extraction device. The mass ratio of wastewater to butanone is 1:3, the extraction temperature is controlled at 40°C, and the extraction is performed for 2 hours. The content of 3-hydroxypropionitrile in the wastewater after extraction is 0.26%, and the content of 3-hydroxypropionitrile in butanone is 1.21%;

[0079] After extraction, butanone enters molecular distillation, the material entry temperature is 90°C, the reaction pressure is 1000 Pa, and 4.15 g of 3-hydroxypropionitrile with a purity of 96.1% is obtained at the bottom of the molecular distillation per minute.

[0080] Example 5

[0081] The reactor was preheated to 40°C, wastewater entered the reactor at a rate of 100 g / min, 10% sodium carbonate solution entered the reactor at a rate of 7.8 g / min, and potassium sulfate entered the reactor at a rate of 5 g / min. The pH value of the obtained mixture was 10.7, the total residence time was 5 h, and the 3-hydroxypropionitrile content in the wastewater after decomposition at the reactor outlet was 4.02%, and the effective alkaline hydrolysis rate was 61.7%.

[0082] The decomposed wastewater and resin are mixed for adsorption. The volume ratio of the decomposed wastewater to the resin is 1:2. After the adsorption is completed, the content of 3-hydroxypropionitrile in the wastewater is 0.27%; the resin adsorbed with 3-hydroxypropionitrile is mixed with acetonitrile to regenerate the resin. The volume ratio of the resin to acetonitrile is 1:3, and 3-hydroxypropionitrile is separated and dissolved from the resin into the regeneration liquid. The content of 3-hydroxypropionitrile in the regeneration liquid is 0.54%.

[0083] The regenerated liquid enters the molecular distillation, the material entry temperature is 90°C, the reaction pressure is 1000 Pa, and 3.74 g of 3-hydroxypropionitrile with a purity of 95.2% is obtained at the bottom of the molecular distillation per minute.

[0084] Comparative Example 1

[0085] The difference from Example 1 is that no electrolyte is added, and other operations are exactly the same as Example 1. The specific operations are as follows:

[0086] The reactor was preheated to 40°C, wastewater was introduced into the reactor at a rate of 100 g / min, and a sodium hydroxide solution with a mass concentration of 32% was introduced into the reactor at a rate of 15.6 g / min. The pH value of the obtained mixture was 13.2, and the total residence time was 6 h. The content of 3-hydroxypropionitrile in the wastewater after decomposition at the reactor outlet was 4.64%, and the effective alkaline hydrolysis rate was 90.9%.

[0087] The decomposed wastewater enters from the material feed port of the first extraction device, and the extractant methyl isobutyl ketone enters from the extractant feed port of the third extraction device. The mass ratio of wastewater to methyl isobutyl ketone is 1:10, the extraction temperature is controlled at 20°C, and the extraction is performed for 2 hours. The content of 3-hydroxypropionitrile in the wastewater after extraction is 0.61%, the content of 3-hydroxypropionitrile in methyl isobutyl ketone is 0.4%, and the extraction rate is 86.9%.

[0088] After extraction, methyl isobutyl ketone enters molecular distillation, the material entry temperature is 30°C, the reaction pressure is 145 Pa, and 6.08 g of 3-hydroxypropionitrile with a purity of 83.2% is obtained at the bottom of the molecular distillation per minute.

[0089] Comparative Example 2

[0090] The difference from Example 1 is that a sodium hydroxide solution with a mass concentration of 32% enters the reactor at a rate of 0.5 g / min, and other operations are exactly the same as those in Example 1. The specific operations are as follows:

[0091] The reactor was preheated to 40°C, wastewater was introduced into the reactor at a rate of 100 g / min, sodium hydroxide solution with a mass concentration of 32% was introduced into the reactor at a rate of 0.5 g / min, and sodium nitrate was introduced into the reactor at a rate of 10 g / min. The pH value of the obtained mixture was 7.6, and the total residence time was 6 h. The content of 3-hydroxypropionitrile in the wastewater after decomposition at the reactor outlet was 1.91%, and the effective alkaline hydrolysis rate was 8%.

[0092] The decomposed wastewater enters from the material feed port of the first extraction device, and the extractant methyl isobutyl ketone enters from the extractant feed port of the third extraction device. The mass ratio of wastewater to methyl isobutyl ketone is 1:10, the extraction temperature is controlled at 20°C, and the extraction is performed for 2 hours. The content of 3-hydroxypropionitrile in the wastewater after extraction is 0.003%, the content of 3-hydroxypropionitrile in methyl isobutyl ketone is 0.19%, and the extraction rate is 99.8%.

[0093] After extraction, methyl isobutyl ketone enters molecular distillation, the material entry temperature is 30°C, the reaction pressure is 145 Pa, and 2.74 g of 3-hydroxypropionitrile with a purity of 83.5% is obtained at the bottom of the molecular distillation per minute.

[0094] Comparative Example 3

[0095] The wastewater enters from the material feed port of the first extraction device, and the extractant methyl isobutyl ketone enters from the extractant feed port of the third extraction device. The mass ratio of wastewater to methyl isobutyl ketone is 1:10, the extraction temperature is controlled at 20°C, and the extraction is performed for 2 hours. After the extraction, the content of 3-hydroxypropionitrile in the wastewater is 0.027%, the content of 3-hydroxypropionitrile in methyl isobutyl ketone is 0.18%, and the extraction rate is 98.5%.

[0096] After extraction, methyl isobutyl ketone enters molecular distillation, the material entry temperature is 30°C, the reaction pressure is 145 Pa, and 2.13 g of 3-hydroxypropionitrile with a purity of 83.3% is obtained at the bottom of the molecular distillation per minute.

[0097] Comparative Example 4

[0098] The difference from Example 4 is that the reactor is preheated to 10°C, and the other operations are exactly the same as those in Example 4. The specific operations are as follows:

[0099] The reactor was preheated to 10°C, wastewater entered the reactor at a rate of 100 g / min, 10% sodium carbonate solution entered the reactor at a rate of 7.8 g / min, and potassium sulfate entered the reactor at a rate of 5 g / min. The pH value of the obtained mixture was 10.7, the total residence time was 5 h, and the 3-hydroxypropionitrile content in the wastewater after decomposition at the reactor outlet was 2.79%, and the effective alkaline hydrolysis rate was 30.4%.

[0100] The decomposed wastewater enters from the material feed port of the first extraction device, and the extractant butanone enters from the extractant feed port of the third extraction device. The mass ratio of wastewater to butanone is 1:3, the extraction temperature is controlled at 40°C, and the extraction is performed for 2 hours. The content of 3-hydroxypropionitrile in the wastewater after extraction is 0.20%, and the content of 3-hydroxypropionitrile in butanone is 0.863%;

[0101] After extraction, butanone enters molecular distillation, the material entry temperature is 90°C, the reaction pressure is 1000 Pa, and 4.48 g of 3-hydroxypropionitrile with a purity of 63.6% is obtained at the bottom of the molecular distillation per minute.

[0102] Among them: the effective alkaline hydrolysis rate refers to the ratio of tris(2-cyanoethyl)phosphate, di(2-cyanoethyl)phosphate, and (2-cyanoethyl)phosphate that can be alkaline hydrolyzed into 3-hydroxypropionitrile, which is calculated as the ratio of the 3-hydroxypropionitrile actually obtained by alkaline hydrolysis to the 3-hydroxypropionitrile that should be obtained theoretically. For example, 100g of tris(2-cyanoethyl)phosphate wastewater was tested for tris(2-cyanoethyl)phosphate, di(2-cyanoethyl)phosphate, and (2-cyanoethyl)phosphate, which were 1.6%, 2.2%, and 2.6%, respectively. After being mixed with 5g of alkali and 5g of electrolyte for a certain period of time, tris(2-cyanoethyl)phosphate, di(2-cyanoethyl)phosphate, and (2-cyanoethyl)phosphate were completely decomposed to form 3-hydroxypropionitrile. The maximum theoretical amount of 3-hydroxypropionitrile in 110g of aqueous solution was 4.43g, and the actual content of 3-hydroxypropionitrile in water was 4.23g. The effective alkaline hydrolysis rate = 4.23 / 4.43*100% = 95.5%.

[0103] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for recovering 3-hydroxypropionitrile in wastewater, characterized in that: The steps include: 1) Mixing wastewater, alkaline solution and electrolyte, decomposing the obtained mixture to obtain decomposed wastewater; 2) extracting or adsorbing the decomposed wastewater to obtain an extract containing 3-hydroxypropionitrile or a regenerated liquid containing 3-hydroxypropionitrile; 3) molecularly distilling the extract containing 3-hydroxypropionitrile or the regenerated liquid containing 3-hydroxypropionitrile to obtain 3-hydroxypropionitrile; The wastewater in step 1) is wastewater produced by the preparation of tris(2-cyanoethyl)phosphate or tris(2-cyanoethyl)phosphite; the alkaline solution is selected from one or more of sodium hydroxide aqueous solution, potassium hydroxide solution, ammonia water, sodium carbonate solution, potassium carbonate solution, sodium bicarbonate solution and potassium bicarbonate solution; The electrolyte in step 1) is selected from one or more of sodium chloride, potassium nitrate, sodium nitrate, potassium sulfate and sodium sulfate; In step 1), the amount of alkali added to the alkaline solution is 1 to 10 times the content of 3-hydroxypropionitrile in the wastewater; and the amount of the electrolyte added is 1% to 50% of the mass of the wastewater.

2. The method for recovering 3-hydroxypropionitrile in waste water according to claim 1, characterized in that When decomposing in step 1), pH ≥ 10, temperature is 30-100°C, and time is 0.5-20h.

3. The method for recovering 3-hydroxypropionitrile in waste water according to claim 1, characterized in that The extraction agent used for extraction in step 2) is selected from one or more of butanone, methyl isobutyl ketone, toluene, cyclohexane and dichloromethane.

4. The method for recovering 3-hydroxypropionitrile in waste water according to claim 1, characterized in that The temperature during extraction in step 2) is 0-100°C, and the mass ratio of wastewater to extractant is 1:0.4-100.

5. The method for recovering 3-hydroxypropionitrile in waste water according to claim 1, characterized in that In step 2), resin is used for adsorption to obtain a resin that adsorbs 3-hydroxypropionitrile, and then a regeneration liquid is used for regeneration; the regeneration liquid is selected from one or more of acetonitrile, acetone, cyclohexane, toluene and N-methylpyrrolidone; the volume ratio of the regeneration liquid to the resin is 0.5~100:

1.

6. The method for recovering 3-hydroxypropionitrile in waste water according to claim 1, characterized in that The pressure during molecular distillation in step 3) is 3Pa~1000Pa, and the temperature is 10~228°C.

7. The method for recovering 3-hydroxypropionitrile in waste water according to claim 1, characterized in that: After the molecular distillation in step 3), the method further comprises removing water by using a molecular sieve.

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