CN114195663A - Preparation method of 6-aminocaproic acid - Google Patents
Preparation method of 6-aminocaproic acid Download PDFInfo
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- CN114195663A CN114195663A CN202111567043.4A CN202111567043A CN114195663A CN 114195663 A CN114195663 A CN 114195663A CN 202111567043 A CN202111567043 A CN 202111567043A CN 114195663 A CN114195663 A CN 114195663A
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C227/00—Preparation of compounds containing amino and carboxyl groups bound to the same carbon skeleton
- C07C227/14—Preparation of compounds containing amino and carboxyl groups bound to the same carbon skeleton from compounds containing already amino and carboxyl groups or derivatives thereof
- C07C227/18—Preparation of compounds containing amino and carboxyl groups bound to the same carbon skeleton from compounds containing already amino and carboxyl groups or derivatives thereof by reactions involving amino or carboxyl groups, e.g. hydrolysis of esters or amides, by formation of halides, salts or esters
- C07C227/20—Preparation of compounds containing amino and carboxyl groups bound to the same carbon skeleton from compounds containing already amino and carboxyl groups or derivatives thereof by reactions involving amino or carboxyl groups, e.g. hydrolysis of esters or amides, by formation of halides, salts or esters by hydrolysis of N-acylated amino-acids or derivatives thereof, e.g. hydrolysis of carbamates
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G69/00—Macromolecular compounds obtained by reactions forming a carboxylic amide link in the main chain of the macromolecule
- C08G69/02—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids
- C08G69/08—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids derived from amino-carboxylic acids
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G69/00—Macromolecular compounds obtained by reactions forming a carboxylic amide link in the main chain of the macromolecule
- C08G69/02—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids
- C08G69/08—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids derived from amino-carboxylic acids
- C08G69/14—Lactams
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Abstract
The present disclosure relates to a method for preparing 6-aminocaproic acid, the method comprising: s1, dehydrating the caprolactam waste liquid for the first time, and polymerizing at high temperature to obtain a polymer; adding an acidic solution into the polymer, and carrying out reflux depolymerization to obtain a first product; s2, adding the first product into an alcohol solvent for dissolving after the first product is subjected to reduced pressure dehydration to obtain a second product; performing first filtration on the second product to obtain a first filtrate; and S3, adding organic amine or introducing ammonia gas into the first filtrate, adjusting the pH of the first filtrate to 7-8, and then carrying out second filtration to obtain crude 6-aminocaproic acid. The method disclosed by the invention saves the cost of directly treating the caprolactam waste liquid as the wastewater, and can extract effective substances in the caprolactam waste liquid to synthesize the aminocaproic acid.
Description
Technical Field
The disclosure relates to the technical field of chemical industry, in particular to a method for separating and preparing 6-aminocaproic acid by taking waste liquid obtained by a rearrangement method for preparing caprolactam as a raw material.
Background
Currently, the following two common treatment methods for caprolactam waste liquid are commercially available: firstly, the mass fraction of organic matters and salt in the waste liquid is increased to 40-70%, and then spray combustion is carried out at 900 ℃; secondly, the content of organic matters in the wastewater is reduced by adopting a biochemical system. However, the two traditional treatment methods have the defects of high energy consumption, high operation cost, high ammonia content in the discharged wastewater, no recycling of valuable components in the wastewater and the like.
Aminocaproic acid is applied to the medical field as a hemostatic agent, has obvious effect on certain severe bleeding caused by increased hemolytic activity of cellulose protein, and is suitable for acute diseases such as oozing or local bleeding during various surgical operations, gynecological bleeding, gastrointestinal bleeding and the like.
In the document "comparison of direct recycling process of several concentrated solutions in nylon 6 polymerization" (volume 26, phase 3 of the synthetic fiber industry, month 6 in 2003, face allergy, bang, and euro-jin hua), it is disclosed that the nylon 6 slices must be extracted with hot water to remove caprolactam and oligomers, and a concentrated solution containing 80% of extractables is obtained, and the concentrated solution is directly recycled to the polymerization process, which is a fundamental way to reduce the unit consumption of caprolactam in nylon 6. However, the concentrated solution is generated in the caprolactam polymerization process, and the technical problem that the waste liquid generated after the waste liquid such as benzene extraction waste liquid, ion exchange waste liquid and the like generated in the caprolactam production process is concentrated is difficult to treat is not solved.
Chinese patent document CN101857550A discloses a method for producing 6-aminocaproate and 6-aminocaproic acid by depolymerizing nylon-6 waste, but the method is directed to the formed nylon-6 waste, and no corresponding treatment method is proposed for the mixed waste liquid containing caprolactam monomer and its oligomer.
Disclosure of Invention
The invention aims to provide a method for recycling caprolactam waste liquid and an aminocaproic acid extraction and preparation method.
In order to achieve the above object, the present disclosure provides a method for preparing 6-aminocaproic acid, the method comprising:
s1, dehydrating the waste liquid of the caprolactam preparation by the rearrangement method for the first time, and polymerizing at high temperature to obtain a polymer; adding an inorganic acid solution into the polymer, and performing reflux depolymerization to obtain a first product;
s2, adding the first product into an alcohol solvent for dissolving after the first product is subjected to reduced pressure dehydration to obtain a second product; performing first filtration on the second product to obtain a first filtrate;
s3, adding organic amine or introducing ammonia gas into the first filtrate, adjusting the pH of the first filtrate to 7-8, and then carrying out second filtration to obtain crude 6-aminocaproic acid;
wherein the waste liquid from the rearrangement process for preparing caprolactam is at least one of the waste liquid from the sulfuric acid liquid phase rearrangement process for preparing caprolactam and the waste liquid from the sulfuric acid gas phase rearrangement process for preparing caprolactam.
Optionally, the rearrangement process caprolactam waste stream comprises water, 6-aminocaproic acid, caprolactam and polymers of caprolactam; the waste liquid of the rearrangement method for preparing caprolactam contains not more than 90 weight percent of water and not less than 5 weight percent of polymers of 6-aminocaproic acid, caprolactam and caprolactam by the total weight based on the weight of the waste liquid of the rearrangement method for preparing caprolactam; preferably, the waste liquid from the rearrangement process for producing caprolactam contains not more than 65% by weight of water and not less than 18% by weight of polymers of 6-aminocaproic acid, caprolactam and caprolactam; further preferably, the waste liquid from the rearrangement process for producing caprolactam contains not more than 50% by weight of water and not less than 35% by weight of polymers of 6-aminocaproic acid, caprolactam and caprolactam in total.
Optionally, the waste liquid from the rearrangement process for preparing caprolactam is a concentrated waste liquid obtained by solid-liquid separation, and the concentration of caprolactam in the waste liquid from the rearrangement process for preparing caprolactam is 30-50 wt%.
Optionally, the caprolactam rearrangement process waste stream comprises 8-12 wt% caprolactam, 5-10 wt% 6-aminocaproic acid, 1-5 wt% caprolactam oligomer, 6-10 wt% ammonium sulfate and 2-13 wt% of the remaining impurities, based on the weight of the caprolactam rearrangement process waste stream.
Optionally, the water content of the caprolactam waste liquid after the first dehydration is 1 to 10 wt%, preferably 1 to 3 wt%; the water content of the first product after dehydration under reduced pressure is 1 to 8% by weight, preferably 1 to 2% by weight.
Optionally, the mass ratio of the acidic solution to the polymer is (1.1-1.8): 1; preferably (1.2-1.5): 1; optionally, the inorganic acid solution is selected from at least one of a hydrochloric acid solution, a sulfuric acid solution and a phosphotungstic acid solution; the organic acid solution is at least one selected from acetic acid solution, p-toluenesulfonic acid, methanesulfonic acid, citric acid and tartaric acid; preferably, the inorganic acid is a hydrochloric acid solution.
Optionally, the amount of the alcohol solvent is 0.5-5mL/g, preferably 1-3mL/g, based on the total weight of caprolactam and caprolactam polymer contained in the waste liquid from the rearrangement process for preparing caprolactam; the alcoholic solvent is selected from monohydric alcohol, dihydric alcohol or a mixture thereof; preferably, the alcoholic solvent is selected from at least one of methanol, ethanol, isopropanol, ethylene glycol and propylene glycol; more preferably, the alcoholic solvent is ethanol.
Optionally, the organic amine is triethylamine and/or ethylenediamine.
Optionally, in step S1, the dehydration condition includes: the temperature is 100-; the conditions of the high temperature polymerization include: the temperature is 180 ℃ and 300 ℃, and the time is 2-10 h; the conditions for the reflux depolymerization include: the temperature is 90-130 ℃, and the time is 6-18 h; in step S2, the conditions for dehydration under reduced pressure include: the pressure is-0.08 to-0.3 MPa, the temperature is 50 to 80 ℃, and the time is 2 to 8 hours.
Optionally, the method further comprises: washing the crude 6-aminocaproic acid to obtain a pure 6-aminocaproic acid product. Optionally, the washed solvent is selected from at least one of ethanol, methanol, acetone, and diethyl ether; the washing conditions include: the washing temperature is 30-60 ℃, the washing time is 0.5-4h, and the washing times are 1-3.
Optionally, the purity of the pure 6-aminocaproic acid prepared by the present disclosure is greater than 99%.
Through the technical scheme, the method saves the cost of directly treating the caprolactam waste liquid as the wastewater, can extract effective substances in the caprolactam waste liquid to synthesize the 6-aminocaproic acid, and the purity of the pure 6-aminocaproic acid prepared by the method is high and can be more than 99%.
Additional features and advantages of the disclosure will be set forth in the detailed description which follows.
Detailed Description
The following describes in detail specific embodiments of the present disclosure. It should be understood that the detailed description and specific examples, while indicating the present invention, are intended for purposes of illustration and explanation only and are not intended to limit the present disclosure.
The present disclosure provides a method for preparing 6-aminocaproic acid, the method comprising:
s1, dehydrating the waste liquid of the caprolactam preparation by the rearrangement method for the first time, and polymerizing at high temperature to obtain a polymer; adding an acidic solution into the polymer, and carrying out reflux depolymerization to obtain a first product;
s2, adding the first product into an alcohol solvent for dissolving after the first product is subjected to reduced pressure dehydration to obtain a second product; performing first filtration on the second product to obtain a first filtrate;
s3, adding organic amine or introducing ammonia gas into the first filtrate, adjusting the pH of the first filtrate to 7-8, and then carrying out second filtration to obtain crude 6-aminocaproic acid;
wherein the waste liquid from the rearrangement process for preparing caprolactam is at least one of the waste liquid from the sulfuric acid liquid phase rearrangement process for preparing caprolactam and the waste liquid from the sulfuric acid gas phase rearrangement process for preparing caprolactam.
The preparation method of 6-aminocaproic acid in the disclosure can extract effective substances in the waste liquid from the rearrangement process for preparing caprolactam, and synthesize the substances into 6-aminocaproic acid. Specifically, the caprolactam waste liquid generated by concentrating waste liquids such as benzene extraction waste liquid and ion exchange waste liquid generated in the caprolactam production process is used as a production raw material, and the caprolactam waste liquid is subjected to high-temperature polymerization after being dehydrated for the first time to obtain a polymer, wherein the polymer is a mixture of caprolactam oligomer formed by copolymerizing organic matters and inorganic matters in the waste liquid and ammonium sulfate; adding an acidic solution into the polymer to carry out reflux depolymerization to obtain amino caproic acid salt; the first product is decompressed and dehydrated, then is added into an alcohol solvent for dissolving and is filtered to obtain a first filtrate, and the first filtrate is mainly an alcoholic solution of amino caproic acid salt; adding organic amine into the first filtrate or introducing ammonia gas, adjusting the pH to 7-8, and filtering to obtain crude 6-aminocaproic acid. The disclosed method saves the cost of direct wastewater treatment and extracts the effective substances in the caprolactam waste liquid.
In accordance with the present disclosure, the waste stream from the rearrangement process to produce caprolactam may comprise water, 6-aminocaproic acid, caprolactam, and polymers of caprolactam; the waste liquid from the rearrangement process for producing caprolactam may contain not more than 90% by weight of water and not less than 5% by weight of polymers of 6-aminocaproic acid, caprolactam and caprolactam, based on the weight of the waste liquid from the rearrangement process for producing caprolactam; preferably, the waste liquid from the rearrangement process for producing caprolactam may contain not more than 65% by weight of water and not less than 18% by weight of polymers of 6-aminocaproic acid, caprolactam and caprolactam; further preferably, the waste liquid from the rearrangement process for producing caprolactam contains not more than 50% by weight of water and not less than 35% by weight of polymers of 6-aminocaproic acid, caprolactam and caprolactam in total.
The waste liquid from the rearrangement process for producing caprolactam in the present disclosure may be a concentrated waste liquid from solid-liquid separation, and the concentration of caprolactam in the waste liquid from the rearrangement process for producing caprolactam may be 30 to 50 wt%.
According to the present disclosure, the caprolactam rearrangement process waste stream may comprise 8 to 12 wt% caprolactam, 5 to 10 wt% aminocaproic acid, 1 to 5 wt% polymers of caprolactam, 6 to 10 wt% ammonium sulfate and 2 to 13 wt% of the remaining impurities, based on the weight of the caprolactam rearrangement process waste stream.
According to the disclosure, the water content of the caprolactam waste liquid after the first dehydration may be 1 to 10 wt.%, preferably 1 to 3 wt.%; the water content of the first product after dehydration under reduced pressure is 1 to 8% by weight, preferably 1 to 2% by weight.
According to the present disclosure, the mass ratio of the acidic solution to the polymer may be (1.1-1.8): 1; preferably (1.2-1.5): 1; the inorganic acid solution may be at least one selected from a hydrochloric acid solution, a sulfuric acid solution, and a phosphotungstic acid solution; the organic acid solution may be selected from at least one of acetic acid solution, p-toluenesulfonic acid, methanesulfonic acid, citric acid, and tartaric acid; preferably, the acidic solution is a hydrochloric acid solution.
According to the disclosure, the alcohol solvent can be used in an amount of 0.5-5mL/g, preferably 1-3mL/g, based on the total weight of caprolactam and caprolactam polymer contained in the waste liquid from the rearrangement process for preparing caprolactam; the alcoholic solvent may be selected from monohydric alcohols, dihydric alcohols or mixtures thereof; preferably, the alcohol solvent may be selected from at least one of methanol, ethanol, isopropanol, ethylene glycol and propylene glycol; more preferably, the alcoholic solvent is ethanol.
According to the present disclosure, the organic amine may be triethylamine and/or ethylenediamine.
According to the present disclosure, in step S1, the dehydration condition may include: the temperature is 100-; the conditions of the high temperature polymerization may include: the temperature is 180 ℃ and 300 ℃, and the time is 2-10 h; the conditions for the reflux depolymerization may include: the temperature is 90-130 ℃, and the time is 6-18 h; in step S2, the conditions for reduced pressure dehydration may include: the pressure is-0.08 to-0.3 MPa, the temperature is 50 to 80 ℃, and the time is 2 to 8 hours.
According to the present disclosure, the method may further include: washing the crude 6-aminocaproic acid to obtain a pure aminocaproic acid product.
According to the present disclosure, the washed solvent may be selected from at least one of ethanol, methanol, acetone, and diethyl ether; the washing conditions may include: the washing temperature is 30-60 ℃, the washing time is 0.5-4h, and the washing times are 1-3.
As a preferred embodiment of the present disclosure, the purity of the pure aminocaproic acid is more than 99%.
The present disclosure is further illustrated by the following examples, but is not to be construed as being limited thereby.
The materials, reagents, instruments and equipment used in the examples of the present disclosure are commercially available, unless otherwise specified.
Wherein, the caprolactam waste liquid that this disclosed embodiment used is got from the hills petrochemical industry, and its nature is: the relative density is 1.18g/cm3The solids content was 40% by weight, the pH 4.7, the caprolactam content 12% by weight, the aminocaproic acid content 10% by weight, the caprolactam oligomer content 3% by weight and the ammonium sulphate content 10% by weight, 5% other impurities.
Example 1
200g of caprolactam waste liquid is dehydrated, the total weight of the dehydrated caprolactam waste liquid is 82g, and the water content is 2.4 percent by weight; and (3) carrying out high-temperature polymerization on the dehydrated caprolactam waste liquid to obtain a high polymer, wherein the high-temperature polymerization conditions are as follows: the mixture was polymerized for 2 hours after being heated to 240 ℃ at a heating rate of 5 ℃/s. To the resulting polymer were added 82g of water and 49.2g of concentrated sulfuric acid, and depolymerization was performed at 110 ℃ under reflux for 8 hours to obtain a first product.
And (3) dehydrating the first product under reduced pressure, adding the dehydrated first product into 240mL of ethanol for dissolving to obtain a second product, and performing first filtration on the second product to obtain a first filtrate. Wherein, the conditions of the reduced pressure dehydration are as follows: the pressure is-0.1 MPa, the temperature is 50 ℃, and the time is 5 h. The water content in the first product after dehydration under reduced pressure was 6% by weight.
And adding 20g of triethylamine into the first filtrate, adjusting the pH value of the first filtrate to 7, and then carrying out second filtration to obtain crude aminocaproic acid.
Example 2
100g of caprolactam waste liquid is taken for dehydration treatment, the total weight of the dehydrated caprolactam waste liquid is 42g, and the water content is 4.8 percent by weight; and (3) carrying out high-temperature polymerization on the dehydrated caprolactam waste liquid to obtain a high polymer, wherein the high-temperature polymerization conditions are as follows: the temperature is raised to 230 ℃ at the temperature raising rate of 8 ℃/s, and then the polymerization is carried out for 6 h. 42g of water and 20g of acetic acid were added to the obtained polymer, and depolymerization was performed at 110 ℃ under reflux for 6 hours to obtain a first product.
And (3) dehydrating the first product under reduced pressure, adding the dehydrated first product into 120mL of acetone for dissolving to obtain a second product, and performing first filtration on the second product to obtain a first filtrate. Wherein, the conditions of the reduced pressure dehydration are as follows: the pressure is-0.2 MPa, the temperature is 40 ℃, and the time is 4 h. The water content in the first product after dehydration under reduced pressure was 5% by weight.
And adding 13g of triethylamine into the first filtrate, adjusting the pH value of the first filtrate to 7, and then carrying out second filtration to obtain crude aminocaproic acid.
Example 3
200g of caprolactam waste liquid is dehydrated, the total weight of the dehydrated caprolactam waste liquid is 83g, and the water content is 3.6 percent by weight; and (3) carrying out high-temperature polymerization on the dehydrated caprolactam waste liquid to obtain a high polymer, wherein the high-temperature polymerization conditions are as follows: the temperature is raised to 200 ℃ at the heating rate of 8 ℃/s, and then the polymerization is carried out for 8 h. 83g of water and 40g of methanesulfonic acid were added to the obtained polymer, and depolymerization was performed at 130 ℃ under reflux for 5 hours to obtain a first product.
And (3) dehydrating the first product under reduced pressure, adding the dehydrated first product into 300mL of ethanol for dissolving to obtain a second product, and performing first filtration on the second product to obtain a first filtrate. Wherein, the conditions of the reduced pressure dehydration are as follows: the pressure is-0.09 MPa, the temperature is 55 ℃, and the time is 5 h. The water content in the first product after dehydration under reduced pressure was 3% by weight.
And introducing ammonia gas into the first filtrate, adjusting the pH of the first filtrate to 7.5, and then performing second filtration to obtain crude aminocaproic acid, wherein the flow rate of the ammonia gas is 30mL/min, and the introduction time is 600 s.
Example 4
200g of caprolactam waste liquid is dehydrated, the total weight of the dehydrated caprolactam waste liquid is 83g, and the water content is 3.6 percent by weight; and (3) carrying out high-temperature polymerization on the dehydrated caprolactam waste liquid to obtain a high polymer, wherein the high-temperature polymerization conditions are as follows: the polymerization was carried out for 9 hours after the temperature was raised to 260 ℃ at a rate of 5 ℃/s. 83g of water and 44g of concentrated hydrochloric acid were added to the obtained polymer, and depolymerization was performed at 100 ℃ under reflux for 12 hours to obtain a first product.
And (3) dehydrating the first product under reduced pressure, adding the dehydrated first product into 200mL of ethanol for dissolving to obtain a second product, and performing first filtration on the second product to obtain a first filtrate. Wherein, the conditions of the reduced pressure dehydration are as follows: the pressure is-0.2 MPa, the temperature is 40 ℃, and the time is 4 h. The water content in the first product after dehydration under reduced pressure was 3% by weight.
And adding 25g of triethylamine into the first filtrate, adjusting the pH value of the first filtrate to 8, and then carrying out second filtration to obtain crude aminocaproic acid.
Example 5
200g of caprolactam waste liquid is dehydrated, the total weight of the dehydrated caprolactam waste liquid is 81g, and the water content is 1.2 percent by weight; and (3) carrying out high-temperature polymerization on the dehydrated caprolactam waste liquid to obtain a high polymer, wherein the high-temperature polymerization conditions are as follows: the temperature is raised to 210 ℃ at the temperature raising rate of 6 ℃/s, and then the polymerization is carried out for 10 h. To the resulting polymer, 81g of water and 50g of citric acid were added, and depolymerization was performed at 100 ℃ under reflux for 5 hours to obtain a first product.
And (3) dehydrating the first product under reduced pressure, adding the dehydrated first product into 260mL of ethanol for dissolving to obtain a second product, and performing first filtration on the second product to obtain a first filtrate. Wherein, the conditions of the reduced pressure dehydration are as follows: the pressure is-0.1 MPa, the temperature is 50 ℃, and the time is 5 h. The water content in the first product after dehydration under reduced pressure was 2% by weight.
And adding 30g of triethylamine into the first filtrate, adjusting the pH value of the first filtrate to 7, and then carrying out second filtration to obtain crude aminocaproic acid.
Example 6
The comparative example was prepared as in example 1, except that the present disclosure replaced the reflux depolymerization for 8h with 3 h.
Example 7
The comparative example was prepared as in example 1, except that the present disclosure replaced the 6% water content of the first product after dehydration under reduced pressure with 15%.
Test example
The products prepared in examples 1-7 were washed to obtain final products, each of which was weighed and tested for purity, and the specific results are shown in table 1. The specific washing method comprises the following steps: washing with ethanol as lotion at 40 deg.C for 3 times (2 hr each time). The purity test method comprises the following steps: taking 0.2g of product, adding 5mL of formaldehyde solution for dissolution, adding 20mL of ethanol and 2 drops of phenolphthalein indicator solution, titrating to the solution with sodium hydroxide titration solution (0.l mol/L) until the solution is reddish, taking 15mL of newly boiled cold water, and adding 5mL of formaldehyde solution and 20mL of ethanol for blank test correction. Each L mL of sodium hydroxide titration solution (0.L mol/L) corresponds to 13.12mg of aminocaproic acid.
TABLE 1
| Group of | Quality of crude product | Quality of final product | Purity of final product |
| Example 1 | 27g | 23g | 99.6％ |
| Example 2 | 30g | 27g | 99.9％ |
| Example 3 | 26g | 22g | 99.1％ |
| Example 4 | 29g | 27g | 99.8％ |
| Example 5 | 20g | 18g | 99.2％ |
| Example 6 | 5g | 2g | 93.5％ |
| Example 7 | 8g | 3g | 98.2％ |
As can be seen from table 1: the pure product of 6-aminocaproic acid prepared by the method has good purity and high yield; a comparison of example 1 with examples 6 to 7 shows that the yield and purity of the product are affected when the depolymerization time is too short or the degree of dehydration is insufficient.
The preferred embodiments of the present disclosure have been described in detail above, however, the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present disclosure within the technical idea of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.
It should be noted that, in the foregoing embodiments, various features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, various combinations that are possible in the present disclosure are not described again.
In addition, any combination of various embodiments of the present disclosure may be made, and the same should be considered as the disclosure of the present disclosure, as long as it does not depart from the spirit of the present disclosure.
Claims (10)
1. A method for preparing 6-aminocaproic acid, comprising:
s1, dehydrating the waste liquid of the caprolactam preparation by the rearrangement method for the first time, and polymerizing at high temperature to obtain a polymer; adding an acidic solution into the polymer, and carrying out reflux depolymerization to obtain a first product;
s2, adding the first product into an alcohol solvent for dissolving after the first product is subjected to reduced pressure dehydration to obtain a second product; performing first filtration on the second product to obtain a first filtrate;
s3, adding organic amine or introducing ammonia gas into the first filtrate, adjusting the pH of the first filtrate to 7-8, and then carrying out second filtration to obtain crude 6-aminocaproic acid;
wherein the waste liquid from the rearrangement process for preparing caprolactam is at least one of the waste liquid from the sulfuric acid liquid phase rearrangement process for preparing caprolactam and the waste liquid from the sulfuric acid gas phase rearrangement process for preparing caprolactam.
2. The method of claim 1, wherein,
the waste liquid from the rearrangement process for preparing caprolactam contains water, 6-aminocaproic acid, caprolactam and polymers of caprolactam;
the waste liquid of the rearrangement method for preparing caprolactam contains not more than 90 weight percent of water and not less than 5 weight percent of polymers of 6-aminocaproic acid, caprolactam and caprolactam;
preferably, the waste liquid from the rearrangement process for preparing caprolactam contains not more than 65 wt% of water, and not less than 18 wt% of polymers of 6-aminocaproic acid, caprolactam and caprolactam;
further preferably, the waste liquid from the rearrangement process for producing caprolactam contains not more than 50% by weight of water and not less than 35% by weight of polymers of 6-aminocaproic acid, caprolactam and caprolactam in total.
3. The method of claim 1 or 2,
the waste liquid of the rearrangement method for preparing caprolactam is the waste liquid of solid-liquid separation after concentration, and the concentration of caprolactam in the waste liquid of the rearrangement method for preparing caprolactam is 30-50 wt%.
4. The process according to claim 1, wherein the caprolactam rearrangement process waste stream comprises 8 to 12% by weight of caprolactam, 5 to 10% by weight of 6-aminocaproic acid, 1 to 5% by weight of polymers of caprolactam, 6 to 10% by weight of ammonium sulfate and 2 to 13% by weight of the remaining impurities, based on the weight of the caprolactam rearrangement process waste stream.
5. The process according to claim 1, wherein the water content of the caprolactam waste liquid after the first dehydration is 1 to 10% by weight, preferably 1 to 3% by weight;
the water content of the first product after dehydration under reduced pressure is 1 to 8% by weight, preferably 1 to 2% by weight.
6. The production method according to claim 1,
the mass ratio of the acidic solution to the polymer is (1.1-1.8): 1; preferably (1.2-1.5): 1;
the acid solution is an inorganic acid solution or an organic acid solution;
optionally, the inorganic acid solution is selected from at least one of a hydrochloric acid solution, a sulfuric acid solution and a phosphotungstic acid solution; the organic acid solution is at least one selected from acetic acid solution, p-toluenesulfonic acid, methanesulfonic acid, citric acid and tartaric acid;
preferably, the acidic solution is a hydrochloric acid solution.
7. The process according to claim 1, wherein the alcohol solvent is used in an amount of 0.5 to 5mL/g, preferably 1 to 3mL/g, based on the total weight of caprolactam and caprolactam polymer contained in the waste liquid from the rearrangement process for producing caprolactam;
the alcoholic solvent is selected from monohydric alcohol, dihydric alcohol or a mixture thereof; preferably, the alcoholic solvent is selected from at least one of methanol, ethanol, isopropanol, ethylene glycol and propylene glycol; more preferably, the alcoholic solvent is ethanol.
8. The production method according to claim 1, wherein the organic amine is triethylamine and/or ethylenediamine.
9. The production method according to claim 1,
in step S1, the dehydration conditions include: the temperature is 100-; the conditions of the high temperature polymerization include: the temperature is 180 ℃ and 300 ℃, and the time is 2-10 h; the conditions for the reflux depolymerization include: the temperature is 90-130 ℃, and the time is 6-18 h;
in step S2, the conditions for dehydration under reduced pressure include: the pressure is-0.08 to-0.3 MPa, the temperature is 50 to 80 ℃, and the time is 2 to 8 hours.
10. The method of making of claim 1, the method further comprising: washing the crude 6-aminocaproic acid to obtain a pure 6-aminocaproic acid product;
optionally, the washed solvent is selected from at least one of ethanol, methanol, acetone, and diethyl ether; the washing conditions include: the washing temperature is 30-60 ℃, the washing time is 0.5-4h, and the washing times are 1-3.
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