A method for treating alpha-pyrrolidone distillation residue

Abstract

The present invention belongs to the field of waste resource utilization, and specifically relates to a method for treating α-pyrrolidone distillation residues, the residues including N-methyl-2-pyrrolidone, 3-methyl-2-pyrrolidone, 4-methyl-2-pyrrolidone, 4-pyrrolidone-based butanamide, oligomers and heavy components. The above method comprises the following steps: S1: separating and treating the distillation residues to obtain a first mixture including N-methyl-2-pyrrolidone, 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone, and a second mixture including 4-pyrrolidone-based butanamide, oligomers and heavy components. S2: hydroxylating or aminating the first mixture, and then reacting with boric acid to obtain a lubricating oil antiwear agent. S3: The second mixture is subjected to oxidation and saponification to obtain a saponified product. The present invention makes full use of the useful components in the distillation residues, can reduce resource waste and environmental pollution, and improve economic benefits.

Description

Technical Field

[0001] The invention relates to the technical field of waste resource utilization, and in particular to a method for treating alpha-pyrrolidone distillation residues. Background Art

[0002] α-Pyrrolidone, also known as pyrrolone, azepine, butyrolactam, is an important chemical raw material, widely used in medicine, textile, dye, coating, cosmetics and other industries. α-Pyrrolidone can be used to make nabendazole, nylon 4, polyvinyl pyrrolidone, artificial plasma, etc., and can also be used as a solvent in organic synthesis.

[0003] The industrial production of α-pyrrolidone is usually achieved by the reaction of γ-butyrolactone with liquid ammonia. After the reaction is completed, the reaction mixture is distilled to obtain a high-purity α-pyrrolidone product. However, during the distillation process, a certain amount of α-pyrrolidone distillation residue will be produced in the bottom of the tower. The α-pyrrolidone distillation residue mainly includes N-methyl-2-pyrrolidone, 3-methyl-2-pyrrolidone, 4-methyl-2-pyrrolidone, 4-pyrrolidone-based butyramide, oligomers and heavy components, which account for about 10-15% of the total product.

[0004] At present, the main method for treating the α-pyrrolidone distillation residue is to condense it into a viscous oily substance through a wiped film evaporator, and then spray the oily substance into small droplets for combustion to generate heat, and use the heat in the distillation process. Although this method can recover some energy, the combustion treatment cannot fully utilize the useful components in the residue, resulting in a waste of resources. In addition, the utilization efficiency of the heat generated by the combustion process is limited and it is not economically feasible. In addition, harmful gases may be generated during the combustion process, causing environmental pollution.

[0005] Therefore, there is an urgent need to provide a method for treating α-pyrrolidone distillation residues, which can fully utilize the useful components in the residues, reduce resource waste and environmental pollution, and improve economic benefits. Summary of the invention

[0006] 1. Technical issues to be resolved

[0007] In view of the above technical problems, the present invention provides a method for treating α-pyrrolidone distillation residues, so as to make full use of the useful components in the α-pyrrolidone distillation residues, reduce resource waste and environmental pollution, and improve economic benefits.

[0008] (II) Technical solution

[0009] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0010] The present invention provides a method for treating α-pyrrolidone distillation residue, wherein the α-pyrrolidone distillation residue comprises N-methyl-2-pyrrolidone, 3-methyl-2-pyrrolidone, 4-methyl-2-pyrrolidone, 4-pyrrolidone-based butyramide, oligomers and heavy components; the method comprises the following steps:

[0011] S1: separating and treating the α-pyrrolidone distillation residue to obtain a first mixture including N-methyl-2-pyrrolidone, 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone, and a second mixture including 4-pyrrolidone butyramide, oligomers and heavy components;

[0012] S2: subjecting the first mixture to a hydroxylation reaction, and then continuing to react with boric acid to obtain a borate ester compound for a lubricating oil anti-wear additive;

[0013] S3: subjecting the second mixture to oxidation reaction and saponification reaction in sequence to obtain a saponification product for industrial cleaning agent.

[0014] The method for treating the α-pyrrolidone distillation residue as described above, preferably, in step S1, the α-pyrrolidone distillation residue is added to a wiped film evaporator, N-methyl-2-pyrrolidone is collected at 205-210° C., and then the temperature is increased, and 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone are continuously collected at 240-250° C. to obtain a first mixture;

[0015] A second mixture comprising 4-pyrrolidonylbutanamide, oligomers and heavies was obtained at the bottom of the wiped film evaporator.

[0016] In the method for treating the α-pyrrolidone distillation residue as described above, preferably, in step S1, after obtaining the first mixture and the second mixture, the first mixture and the second mixture are decolorized by activated carbon respectively.

[0017] In the method for treating the α-pyrrolidone distillation residue as described above, preferably, in step S2, the first mixture is subjected to a hydroxylation reaction with formaldehyde at 60-70° C. for 3-5 hours under the action of a first catalyst to obtain a hydroxylated product;

[0018] The molar ratio of the first mixture to formaldehyde is 1:2-1:3;

[0019] The first catalyst is p-toluenesulfonic acid.

[0020] In the method for treating the α-pyrrolidone distillation residue as described above, preferably, in step S2, the hydroxylation product is reacted with boric acid at 80-90° C. for 6-8 hours under the action of a second catalyst to obtain a borate ester compound;

[0021] The second catalyst is sulfuric acid or trifluoromethanesulfonic acid.

[0022] In the method for treating the α-pyrrolidone distillation residue as described above, preferably, in step S2, the mass ratio of the hydroxylation product or the amination product to the boric acid is 1:1.2-1:1.5;

[0023] The mass of the first catalyst is 0.5-2% of the total mass of the first mixture and formaldehyde;

[0024] The mass of the second catalyst is 0.2-0.3% of the mass of the boric acid.

[0025] In the method for treating the α-pyrrolidone distillation residue as described above, preferably, in step S3, a third catalyst and a hydrogen peroxide solution are added to the second mixture, and the mixture is reacted at 60-80° C. for 3-5 hours to obtain an oxidation product; then sodium hydroxide is added to the oxidation product, and the mixture is reacted at 80-95° C. for 2-3 hours to obtain a saponification product;

[0026] The third catalyst is a soluble divalent iron salt, the mass of the third catalyst is 0.2-0.3% of the mass of the second mixture, the mass concentration of the hydrogen peroxide solution is 30-50%, the mass ratio of the second mixture to the hydrogen peroxide solution is 1:0.8-1:2, and the mass ratio of the oxidation product to sodium hydroxide is 1:1.1-1:1.2.

[0027] The method for treating the α-pyrrolidone distillation residue as described above, preferably, the preparation method of the industrial cleaning agent is as follows: adding a pH regulator to water, then adding a surfactant, mixing evenly, adding a saponification product to the system, stirring evenly to obtain an industrial cleaning agent;

[0028] The pH regulator is triethanolamine or sodium carbonate, and the surfactant is one or more of nonylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, sodium lauryl sulfate and cocamidopropyl betaine;

[0029] The pH regulator is used to adjust the pH of the industrial cleaning agent to 7-8.

[0030] In the method for treating α-pyrrolidone distillation residue as described above, preferably, in the industrial cleaning agent, the mass percentage of the saponification product is 5-8%, and the mass percentage of the surfactant is 0.1-5%.

[0031] The method for treating the α-pyrrolidone distillation residue as described above, preferably, the industrial cleaning agent further comprises, by mass percentage, 5-10% solubilizer, 0.2-0.3% chelating agent, 0.3-0.5% defoaming agent, 0.2-0.5% thickener and 0.01-0.03% antioxidant, and the balance is water;

[0032] The solubilizer is one or more of ethanol, isopropanol, propylene glycol and ethylene glycol, the chelating agent is ethylenediaminetetraacetic acid, the defoaming agent is silicone oil or polyether-modified silicone oil, the thickener is xanthan gum, carboxymethyl cellulose or polyvinyl alcohol, and the antioxidant is butylated hydroxyanisole or butylated hydroxytoluene.

[0033] (III) Beneficial effects

[0034] First, the present invention separates the α-pyrrolidone distillation residue to obtain a first mixture including N-methyl-2-pyrrolidone, 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone, and a second mixture including 4-pyrrolidone-based butyramide, oligomers and heavy components.

[0035] Secondly, the present invention performs hydroxylation on the first mixture, so that the nucleophilicity of N-methyl-2-pyrrolidone, 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone is enhanced, and it is easier to react with boric acid to generate borate ester compounds. The borate ester compounds prepared by the first mixture can be used as lubricating oil additives to form a stable protective film on the metal surface, reduce friction and wear, extend the service life of mechanical parts, and improve anti-wear performance. In addition, borate ester compounds have high chemical stability under high temperature and high pressure conditions, and therefore can also provide a lasting anti-wear effect.

[0036] Thirdly, the present invention further allows the second mixture to undergo oxidation reaction and saponification reaction, and uses the prepared saponification product in an industrial cleaning agent to effectively dissolve and clean oil stains, resins, etc. in industrial equipment. Therefore, the present invention can not only realize the resource utilization of α-pyrrolidone distillation residues, but also reduce resource waste and environmental pollution, and improve economic benefits. DETAILED DESCRIPTION

[0037] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below in conjunction with specific implementation methods.

[0038] The present invention provides a method for treating α-pyrrolidone distillation residue, wherein the α-pyrrolidone distillation residue includes N-methyl-2-pyrrolidone, 3-methyl-2-pyrrolidone, 4-methyl-2-pyrrolidone, 4-pyrrolidone butyramide, oligomers and heavy components. The above-mentioned method for treating α-pyrrolidone distillation residue specifically comprises the following steps:

[0039] S1: Separating the α-pyrrolidone distillation residue to obtain a first mixture including N-methyl-2-pyrrolidone, 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone, and a second mixture including 4-pyrrolidone-based butyramide, oligomers and heavy components.

[0040] S2: subjecting the first mixture to a hydroxylation reaction, and then further reacting it with boric acid to obtain a borate ester compound used as an anti-wear additive for lubricating oil.

[0041] S3: subjecting the second mixture to oxidation reaction and saponification reaction in sequence to obtain a saponification product for industrial cleaning agent.

[0042] Furthermore, in the α-pyrrolidone distillation residue, the content of N-methyl-2-pyrrolidone is ≥9%, the content of 3-methyl-2-pyrrolidone is ≥10%, the content of 4-methyl-2-pyrrolidone is ≥11%, the content of 4-pyrrolidone butanamide is ≥14%, the content of oligomers is ≥16%, and the remainder is heavy components.

[0043] The present invention performs hydroxylation on the first mixture, so that the nucleophilicity of N-methyl-2-pyrrolidone, 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone is enhanced, and it is easier to react with boric acid to generate borate ester compounds. The borate ester compounds prepared from the first mixture after hydroxylation and boric acid can be used as lubricating oil additives to form a stable protective film on the metal surface, reduce friction and wear, extend the service life of mechanical parts, and improve anti-wear performance. In addition, borate ester compounds have high chemical stability under high temperature and high pressure conditions, and therefore can also provide a lasting anti-wear effect.

[0044] Specifically, the polar groups in the borate ester molecules can be adsorbed on the metal surface to form an adsorption film. The adsorption film can reduce the friction coefficient between the metal surfaces and play a role in reducing friction. During the friction process, the borate ester molecules can also react chemically with the metal surface to form a chemical reaction film. The chemical reaction film usually has high hardness and wear resistance, which can effectively protect the metal surface and reduce wear. In addition, the borate ester molecules can also fill the tiny defects and pits on the metal surface, making the surface smoother and reducing the occurrence of wear. And borate ester compounds can also produce synergistic effects with other additives or lubricant components to further enhance their anti-wear properties.

[0045] The accumulation of lubricants, hydraulic oils, coolants, sealants, adhesives, and other chemicals used in mechanical equipment will form pollutants such as oil stains and resins on industrial equipment.

[0046] Contaminants such as oil stains increase friction between mechanical parts, causing increased wear and tear, and reducing equipment performance and efficiency. Oil stains and resins may clog key components such as pipes and valves, affecting the flow of fluids and causing equipment failures. In addition, accumulated oil stains and resins are flammable substances, especially in high temperature environments, which can easily cause fires. Therefore, the effective dissolution and cleaning of pollutants such as oil stains and resins is an important maintenance step for industrial equipment, which can ensure the normal operation of equipment and extend its service life.

[0047] Based on the above background, the present invention further performs oxidation and saponification treatment on the separated second mixture to obtain a saponification product, so that it can be made into an industrial cleaning agent to effectively dissolve and clean oil stains, resins, etc. in industrial equipment to ensure the normal operation of the equipment.

[0048] In summary, the present invention can not only realize the resource utilization of α-pyrrolidone distillation residues, but also reduce resource waste and environmental pollution, and improve economic benefits.

[0049] Preferably, in the above step S1, the α-pyrrolidone distillation residue is added to a wiped film evaporator, and N-methyl-2-pyrrolidone is collected at 205-210° C. After collecting N-methyl-2-pyrrolidone, the temperature is raised, and 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone are collected at 240-250° C. to obtain a first mixture. After the first mixture is collected, a second mixture including 4-pyrrolidone-based butanamide, oligomers and heavy components is obtained at the bottom of the wiped film evaporator.

[0050] The structures of N-methyl-2-pyrrolidone, 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone are similar. The boiling points of 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone are similar. The three components can be collected successively in the same time period. 4-pyrrolidone-based butanamide, oligomers and heavy components have high molecular weights and can be directly obtained at the bottom of the wiped film evaporator.

[0051] In addition, after the first mixture and the second mixture are separated in step S1, before steps S2 and S3, the first mixture and the second mixture can be decolorized by activated carbon to remove impurities and pigments therein to avoid affecting the appearance of subsequent lubricant anti-wear additives and industrial cleaning agents.

[0052] Preferably, in the above step S2, the hydroxylation reaction is as follows: under the action of the first catalyst, the first mixture is reacted with formaldehyde at 60-70° C. for 3-5 hours to obtain a hydroxylation product.

[0053] The principle of the hydroxylation reaction is: the lone pair of electrons on the nitrogen atom in N-methyl-2-pyrrolidone, 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone undergoes nucleophilic addition with the carbon-oxygen double bond in formaldehyde, and then generates hydroxylated products. The hydroxylation reaction of N-methyl-2-pyrrolidone, 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone with formaldehyde generates N-(hydroxymethyl)-N-methyl-2-pyrrolidone, 3-methyl-N-(hydroxymethyl)-2-pyrrolidone and 4-methyl-N-(hydroxymethyl)-2-pyrrolidone, respectively.

[0054] The molar ratio of the first mixture to formaldehyde is 1:2-1:3, and the first catalyst may be p-toluenesulfonic acid. It should be noted that the molar masses of N-methyl-2-pyrrolidone, 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone are exactly the same, so it can be equivalent to the first mixture having a clear amount of substance.

[0055] Further preferably, in the above step S2, the hydroxylation product is reacted with boric acid at 80-90° C. for 6-8 hours under the action of a second catalyst to obtain a borate ester compound. The second catalyst is preferably sulfuric acid or trifluoromethanesulfonic acid.

[0056] The hydroxylation products, including N-(hydroxymethyl)-N-methyl-2-pyrrolidone, 3-methyl-N-(hydroxymethyl)-2-pyrrolidone and 4-methyl-N-(hydroxymethyl)-2-pyrrolidone, all contain hydroxymethyl (-CH2OH) in their molecules. The hydroxyl (-OH) oxygen atom in the hydroxymethyl group has a lone pair of electrons. The lone pair of electrons of the oxygen atom of the hydroxymethyl group reacts with the boron atom in the boric acid molecule to form a borate ester bond.

[0057] In the molecules of N-(hydroxymethyl)-N-methyl-2-pyrrolidone, 3-methyl-N-(hydroxymethyl)-2-pyrrolidone and 4-methyl-N-(hydroxymethyl)-2-pyrrolidone, the oxygen atom of the hydroxymethyl group forms a borate ester bond with the boron atom of boric acid, and at the same time loses a molecule of water. The borate ester part of the product is -B(OH)2, which is connected to the original hydroxymethyl group.

[0058] The borate ester compounds obtained by the reaction of N-(hydroxymethyl)-N-methyl-2-pyrrolidone, 3-methyl-N-(hydroxymethyl)-2-pyrrolidone and 4-methyl-N-(hydroxymethyl)-2-pyrrolidone with boric acid can be named N-methyl-2-pyrrolidone-N-hydroxymethyl borate, 3-methyl-2-pyrrolidone-N-hydroxymethyl borate and 4-methyl-2-pyrrolidone-N-hydroxymethyl borate, respectively.

[0059] Further preferably, in the above step S2, the mass ratio of the hydroxylation product to the boric acid is 1:1.2-1:1.5, the mass of the first catalyst is 0.5-2% of the total mass of the first mixture and formaldehyde, and the mass of the second catalyst is 0.2-0.3% of the mass of the boric acid.

[0060] In the present invention, the purpose of subjecting the first mixture to hydroxylation is to introduce hydroxyl groups into the molecules of N-methyl-2-pyrrolidone, 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone so that the hydroxyl groups can react with boric acid to form borate ester compounds.

[0061] In addition, the introduced hydroxyl group still has a certain polarity after reacting with boric acid in step S2, and can be adsorbed on the metal surface through weak interaction forces such as hydrogen bonds, and can still form coordination bonds with the metal surface. This coordination bond is more stable than simple physical adsorption and can provide better anti-wear performance.

[0062] Further preferably, in step S3, a third catalyst and a hydrogen peroxide solution are added to the second mixture, the pH of the system is maintained between 4 and 8, and the reaction is carried out at 60-80° C. for 3-5 hours, so that the hydrogen peroxide partially oxidizes the organic compounds in the second mixture, reduces the content of macromolecular substances, and obtains oxidation products. The oxidation products include smaller fragment compounds, as well as small molecular compounds such as organic acids, aldehydes, and ketones.

[0063] After the oxidation reaction is completed, the reaction system is allowed to cool naturally, and then the pH of the system is adjusted to alkaline with a dilute alkali solution, such as a sodium hydroxide solution, to prepare for the subsequent saponification reaction. After the above preparations are completed, sodium hydroxide is slowly added to the oxidation product. The sodium hydroxide can be added in the form of a solid or a liquid with a higher concentration. It needs to be stirred continuously during the addition process, and then it is reacted at 80-95°C for 2-3 hours to obtain a saponification product.

[0064] The above-mentioned oxidation products include saponifiable compounds and non-saponifiable compounds. The saponifiable compounds generate compounds mainly composed of carboxylates after saponification reaction. Although the non-saponifiable compounds do not have sufficient active sites and cannot generate carboxylate compounds, these substances can still be added to industrial cleaning agents as auxiliary ingredients.

[0065] Thus, through the two-stage treatment of oxidation and saponification, the originally complex second mixture is transformed into a series of new compounds that can be used in industrial cleaning agents, reducing the harmful components in the original residue.

[0066] Further preferably, the third catalyst may be a soluble divalent iron salt, such as ferrous sulfite, ferrous chloride, etc., the mass of the third catalyst is 0.2-0.3% of the mass of the second mixture, the mass concentration of hydrogen peroxide in the hydrogen peroxide solution is 30-50%, the mass ratio of the second mixture to the hydrogen peroxide solution is 1:0.8-1:2, and the mass ratio of the oxidation product to sodium hydroxide is 1:1.1-1:1.2.

[0067] The preparation method of the industrial cleaning agent is as follows: add a pH adjusting agent to water, then add a surfactant, mix well, add a saponification product to the system, stir well to obtain the industrial cleaning agent. The pH adjusting agent can be triethanolamine or sodium carbonate, the surfactant can be one or more of nonylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, sodium lauryl sulfate and cocamidopropyl betaine, and the pH adjusting agent is used to adjust the pH of the industrial cleaning agent to 7-8.

[0068] In the industrial cleaning agent prepared in the present invention, the mass percentage of the saponification product is 5-8%, the mass percentage of the surfactant is 0.1-5%, and the balance is water.

[0069] In addition, further preferably, the industrial cleaning agent includes, by mass percentage, 5-8% of a saponification product, 0.1-5% of a surfactant, 5-10% of a solubilizer, 0.2-0.3% of a chelating agent, 0.3-0.5% of a defoaming agent, 0.2-0.5% of a thickener and 0.01-0.03% of an antioxidant, and the remainder is water.

[0070] The above-mentioned solubilizer is preferably one or more of ethanol, isopropanol, propylene glycol and ethylene glycol, the chelating agent is preferably ethylenediaminetetraacetic acid, the defoaming agent is preferably silicone oil or polyether-modified silicone oil, the thickener is preferably xanthan gum, carboxymethyl cellulose or polyvinyl alcohol, and the antioxidant is preferably butylated hydroxyanisole or butylated hydroxytoluene.

[0071] The industrial cleaning agent of the present invention uses triethanolamine or sodium carbonate as a pH regulator, and the pH value of the cleaning agent can be adjusted to 7-8, so that the industrial cleaning agent is in the range of neutral to weak alkaline, which is relatively mild to most surface materials and reduces the risk of corrosion to metals and other sensitive materials.

[0072] The present invention uses different types of surfactants such as nonylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, sodium lauryl sulfate and cocamidopropyl betaine, which can provide multiple functions such as decontamination, wetting, emulsification and dispersion, thereby enhancing the comprehensive performance of the industrial cleaning agent.

[0073] The present invention uses solubilizers such as ethanol, isopropanol, propylene glycol and ethylene glycol to improve the solubility of each component in the industrial cleaning agent, ensure that the various ingredients in the formula are evenly distributed, and improve the overall cleaning effect.

[0074] The present invention uses ethylenediaminetetraacetic acid as a chelating agent, which can effectively chelate calcium, magnesium and other ions in water, prevent the influence of hard water on the cleaning effect, and improve the applicability of industrial cleaning agents under different water quality conditions.

[0075] Silicone oil or polyether modified silicone oil as a defoaming agent can effectively reduce the generation of foam, reduce the foam during mechanical cleaning, and improve cleaning efficiency.

[0076] Thickeners such as xanthan gum, carboxymethyl cellulose or polyvinyl alcohol can adjust the viscosity of industrial cleaning agents, making them easier to adhere to the surface being cleaned, prolonging the contact time and improving the cleaning effect. And the appropriate viscosity also helps to maintain the stability of industrial cleaning agents during storage and transportation, preventing stratification or precipitation.

[0077] Butylated hydroxyanisole or butylated hydroxytoluene, as antioxidants, can protect other ingredients in industrial cleaning agents from oxidation and extend the shelf life of the product.

[0078] In order to further clarify the scheme of the present invention and its technical advancement, the following is a description in conjunction with specific embodiments and technical effects.

[0079] Example 1

[0080] This embodiment provides a method for treating α-pyrrolidone distillation residue, comprising the following steps:

[0081] S1: Add the α-pyrrolidone distillation residue to a wiped film evaporator, and collect N-methyl-2-pyrrolidone at 208°C. After collecting N-methyl-2-pyrrolidone, the temperature is raised, and 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone are collected at 245°C to obtain a first mixture. After the first mixture is collected, a second mixture including 4-pyrrolidone-based butyramide, oligomers and heavy components is obtained at the bottom of the wiped film evaporator. Then, the first mixture and the second mixture are decolorized by activated carbon.

[0082] S2: Under the action of p-toluenesulfonic acid, the first mixture is reacted with formaldehyde at 65° C. for 4 hours to obtain a hydroxylated product. Then, under the action of trifluoromethanesulfonic acid, the hydroxylated product is reacted with boric acid at 85° C. for 7 hours to obtain a borate ester compound.

[0083] In this step, the molar ratio of the first mixture to formaldehyde is 1:2.5, the mass of p-toluenesulfonic acid is 1% of the total mass of the first mixture and formaldehyde, the mass ratio of the hydroxylated product to boric acid is 1:1.4, and the mass of trifluoromethanesulfonic acid is 0.2% of the mass of boric acid.

[0084] S3: Add ferrous sulfate and a hydrogen peroxide solution with a mass concentration of 40% to the second mixture, and react at 70°C for 4 hours to obtain an oxidation product. After the oxidation reaction is completed, cool naturally, add sodium hydroxide solution to the oxidation product, adjust the pH of the system to 10, and then slowly add solid sodium hydroxide under stirring conditions, react at 85°C for 2.5 hours to obtain a saponification product. The mass of ferrous sulfate is 0.25% of the mass of the second mixture, the mass ratio of the second mixture to the hydrogen peroxide solution is 1:1, and the mass ratio of the oxidation product to the solid sodium hydroxide is 1:1.15.

[0085] Triethanolamine is added to water to adjust the pH to 7.4, and then cocamidopropyl betaine is added and mixed evenly. Ethanol, ethylenediaminetetraacetic acid, polyether-modified silicone oil, carboxymethyl cellulose and butylated hydroxyanisole are added to the system and mixed evenly. Finally, the saponification product is added and stirred evenly to obtain an industrial cleaning agent.

[0086] The industrial cleaning agent in this step includes, by mass percentage, 6% of saponification product, 0.1% of cocamidopropyl betaine, 8% of ethanol, 0.25% of ethylenediaminetetraacetic acid, 0.4% of polyether modified silicone oil, 0.3% of carboxymethyl cellulose, 0.02% of butylated hydroxyanisole and 84.93% of water.

[0087] After testing, the α-pyrrolidone distillation residue in this embodiment includes, by mass percentage, 9.1% of N-methyl-2-pyrrolidone, 10.3% of 3-methyl-2-pyrrolidone, 11.8% of 4-methyl-2-pyrrolidone, 15% of 4-pyrrolidone-based butyramide, 17.2% of oligomers, and the remainder is heavy components and unavoidable impurities.

[0088] Example 2

[0089] This embodiment provides a method for treating α-pyrrolidone distillation residue, comprising the following steps:

[0090] S1: Add the α-pyrrolidone distillation residue to a wiped film evaporator, and collect N-methyl-2-pyrrolidone at 205°C. After collecting N-methyl-2-pyrrolidone, the temperature is raised, and 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone are collected at 240°C to obtain a first mixture. After the first mixture is collected, a second mixture including 4-pyrrolidone-based butyramide, oligomers and heavy components is obtained at the bottom of the wiped film evaporator. Then, the first mixture and the second mixture are decolorized by activated carbon.

[0091] S2: Under the action of p-toluenesulfonic acid, the first mixture is reacted with formaldehyde at 62.5° C. for 4.2 hours to obtain a hydroxylated product. Then, under the action of trifluoromethanesulfonic acid, the hydroxylated product is reacted with boric acid at 85° C. for 7 hours to obtain a borate ester compound.

[0092] In this step, the molar ratio of the first mixture to formaldehyde is 1:2.6, the mass of p-toluenesulfonic acid is 0.5% of the total mass of the first mixture and formaldehyde, the mass ratio of the hydroxylated product to boric acid is 1:1.5, and the mass of trifluoromethanesulfonic acid is 0.3% of the mass of boric acid.

[0093] S3: Add ferrous chloride and a 30% mass concentration of hydrogen peroxide solution to the second mixture, react at 60°C for 5 hours to obtain an oxidation product. After the oxidation reaction is completed, cool naturally, add sodium hydroxide solution to the oxidation product, adjust the pH of the system to 10, and then slowly add solid sodium hydroxide under stirring conditions, react at 80°C for 3 hours to obtain a saponification product. The mass of ferrous chloride is 0.2% of the mass of the second mixture, the mass ratio of the second mixture to the hydrogen peroxide solution is 1:2, and the mass ratio of the oxidation product to the solid sodium hydroxide is 1:1.1.

[0094] Sodium carbonate is added to water to adjust the pH to 8.0, and then nonylphenol polyoxyethylene ether is added and mixed evenly. Isopropyl alcohol, ethylenediaminetetraacetic acid, silicone oil, xanthan gum and butylated hydroxytoluene are added to the system and mixed evenly. Finally, the saponification product is added and stirred evenly to obtain an industrial cleaning agent.

[0095] The industrial cleaning agent in this step includes, by mass percentage, 5% of saponification product, 2.5% of nonylphenol polyoxyethylene ether, 5% of isopropyl alcohol, 0.2% of ethylenediaminetetraacetic acid, 0.3% of silicone oil, 0.2% of xanthan gum, 0.01% of butylated hydroxytoluene and 86.79% of water.

[0096] The α-pyrrolidone distillation residue of this embodiment is the same as that of embodiment 1.

[0097] Example 3

[0098] This embodiment provides a method for treating α-pyrrolidone distillation residue, comprising the following steps:

[0099] S1: Add the α-pyrrolidone distillation residue to a wiped film evaporator, and collect N-methyl-2-pyrrolidone at 210°C. After collecting N-methyl-2-pyrrolidone, the temperature is raised, and 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone are collected at 250°C to obtain a first mixture. After the first mixture is collected, a second mixture including 4-pyrrolidone-based butanamide, oligomers and heavy components is obtained at the bottom of the wiped film evaporator. Then, the first mixture and the second mixture are decolorized by activated carbon.

[0100] S2: Under the action of p-toluenesulfonic acid, the first mixture is reacted with formaldehyde for hydroxylation at 60° C. for 5 h to obtain a hydroxylation product. Then, under the action of trifluoromethanesulfonic acid, the hydroxylation product is reacted with boric acid at 80° C. for 8 h to obtain a borate ester compound.

[0101] In this step, the molar ratio of the first mixture to formaldehyde is 1:2, the mass of p-toluenesulfonic acid is 1.5% of the total mass of the first mixture and formaldehyde, the mass ratio of the hydroxylated product to boric acid is 1:1.2, and the mass of trifluoromethanesulfonic acid is 0.25% of the mass of boric acid.

[0102] S3: Add ferrous sulfate and a hydrogen peroxide solution with a mass concentration of 50% to the second mixture, react at 80°C for 3 hours to obtain an oxidation product. After the oxidation reaction is completed, cool naturally, add sodium hydroxide solution to the oxidation product, adjust the pH of the system to 10, and then slowly add solid sodium hydroxide under stirring conditions, react at 95°C for 2 hours to obtain a saponification product. The mass of ferrous sulfate is 0.3% of the mass of the second mixture, the mass ratio of the second mixture to the hydrogen peroxide solution is 1:0.8, and the mass ratio of the oxidation product to the solid sodium hydroxide is 1:1.2.

[0103] Triethanolamine is added to water to adjust the pH to 7.2, and then fatty alcohol polyoxyethylene ether is added. After mixing evenly, propylene glycol, ethylenediaminetetraacetic acid, polyether modified silicone oil, polyvinyl alcohol and butylated hydroxyanisole are added to the system and mixed evenly. Finally, the saponification product is added and stirred evenly to obtain an industrial cleaning agent.

[0104] The industrial cleaning agent in this step includes, by mass percentage, 8% of saponification product, 5% of fatty alcohol polyoxyethylene ether, 10% of propylene glycol, 0.3% of ethylenediaminetetraacetic acid, 0.5% of polyether modified silicone oil, 0.5% of polyvinyl alcohol, 0.03% of butylated hydroxyanisole and 75.67% of water.

[0105] After testing, the α-pyrrolidone distillation residue in this embodiment includes, by mass percentage, 10.3% of N-methyl-2-pyrrolidone, 11.1% of 3-methyl-2-pyrrolidone, 11.4% of 4-methyl-2-pyrrolidone, 15.7% of 4-pyrrolidone-based butyramide, 16.1% of oligomers, and the remainder is heavy components and unavoidable impurities.

[0106] Example 4

[0107] This embodiment provides a method for treating α-pyrrolidone distillation residue, comprising the following steps:

[0108] S1: Add the α-pyrrolidone distillation residue to a wiped film evaporator, and collect N-methyl-2-pyrrolidone at 207°C. After collecting N-methyl-2-pyrrolidone, the temperature is raised, and 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone are collected at 244°C to obtain a first mixture. After the first mixture is collected, a second mixture including 4-pyrrolidone-based butanamide, oligomers and heavy components is obtained at the bottom of the wiped film evaporator. Then, the first mixture and the second mixture are decolorized by activated carbon.

[0109] S2: Under the action of p-toluenesulfonic acid, the first mixture is reacted with formaldehyde at 67.4° C. for 3.7 hours to obtain a hydroxylated product. Then, under the action of trifluoromethanesulfonic acid, the hydroxylated product is reacted with boric acid at 90° C. for 6 hours to obtain a borate ester compound.

[0110] In this step, the molar ratio of the first mixture to formaldehyde is 1:2.8, the mass of p-toluenesulfonic acid is 2% of the total mass of the first mixture and formaldehyde, the mass ratio of the hydroxylated product to boric acid is 1:1.3, and the mass of trifluoromethanesulfonic acid is 0.3% of the mass of boric acid.

[0111] S3: Add ferrous chloride and a 35% mass concentration of hydrogen peroxide solution to the second mixture, react at 75°C for 3 hours to obtain an oxidation product. After the oxidation reaction is completed, cool naturally, add sodium hydroxide solution to the oxidation product, adjust the pH of the system to 10, and then slowly add solid sodium hydroxide under stirring conditions, react at 90°C for 2 hours to obtain a saponification product. The mass of ferrous chloride is 0.24% of the mass of the second mixture, the mass ratio of the second mixture to the hydrogen peroxide solution is 1:0.9, and the mass ratio of the oxidation product to the solid sodium hydroxide is 1:1.1.

[0112] Triethanolamine is added to water to adjust the pH to 7.4, and then sodium dodecyl sulfate is added. After mixing evenly, ethanol, ethylenediaminetetraacetic acid, polyether-modified silicone oil, carboxymethyl cellulose and butylated hydroxyanisole are added to the system and mixed evenly. Finally, the saponification product is added and stirred evenly to obtain an industrial cleaning agent.

[0113] The industrial cleaning agent in this step includes, by mass percentage, 8% of saponification product, 2% of sodium lauryl sulfate, 7% of ethanol, 0.3% of ethylenediaminetetraacetic acid, 0.5% of polyether modified silicone oil, 0.4% of carboxymethyl cellulose, 0.02% of butylated hydroxyanisole and 81.78% of water.

[0114] The α-pyrrolidone distillation residue of this embodiment is the same as that of embodiment 3.

[0115] Example 5

[0116] This embodiment provides a method for treating α-pyrrolidone distillation residue, comprising the following steps:

[0117] S1: Add the α-pyrrolidone distillation residue to a wiped film evaporator, and collect N-methyl-2-pyrrolidone at 206°C. After collecting N-methyl-2-pyrrolidone, raise the temperature, and continue to collect 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone at 242°C to obtain a first mixture. After the first mixture is collected, a second mixture including 4-pyrrolidone-based butanamide, oligomers and heavy components is obtained at the bottom of the wiped film evaporator. Then, the first mixture and the second mixture are decolorized by activated carbon.

[0118] S2: Under the action of p-toluenesulfonic acid, the first mixture is reacted with formaldehyde at 70° C. for 3 h to obtain a hydroxylated product. Then, under the action of sulfuric acid, the hydroxylated product is reacted with boric acid at 80° C. for 8 h to obtain a borate ester compound.

[0119] In this step, the molar ratio of the first mixture to formaldehyde is 1:3, the mass of p-toluenesulfonic acid is 1.5% of the total mass of the first mixture and formaldehyde, the mass ratio of the hydroxylation product to boric acid is 1:1.4, and the mass of sulfuric acid is 0.3% of the mass of boric acid.

[0120] S3: Add ferrous sulfate and a hydrogen peroxide solution with a mass concentration of 42% to the second mixture, and react at 60°C for 3 hours to obtain an oxidation product. After the oxidation reaction is completed, cool naturally, add sodium hydroxide solution to the oxidation product, adjust the pH of the system to 10, and then slowly add solid sodium hydroxide under stirring conditions, react at 87°C for 3 hours to obtain a saponification product. The mass of ferrous sulfate is 0.26% of the mass of the second mixture, the mass ratio of the second mixture to the hydrogen peroxide solution is 1:1.5, and the mass ratio of the oxidation product to the solid sodium hydroxide is 1:1.13.

[0121] Add triethanolamine to water to adjust the pH to 7.4, then add fatty alcohol polyoxyethylene ether, mix well, add propylene glycol, ethylenediaminetetraacetic acid, silicone oil, xanthan gum and butylated hydroxytoluene to the system, mix well, finally add the saponification product, stir well to obtain the industrial cleaning agent.

[0122] The industrial cleaning agent in this step includes, by mass percentage, 7% of saponification product, 3% of fatty alcohol polyoxyethylene ether, 10% of propylene glycol, 0.25% of ethylenediaminetetraacetic acid, 0.5% of silicone oil, 0.5% of xanthan gum, 0.03% of butylated hydroxytoluene and 78.72% of water.

[0123] After testing, the α-pyrrolidone distillation residue in this embodiment includes, by mass percentage, 9.7% of N-methyl-2-pyrrolidone, 11.4% of 3-methyl-2-pyrrolidone, 12.3% of 4-methyl-2-pyrrolidone, 14.8% of 4-pyrrolidone-based butyramide, 16.9% of oligomers, and the remainder is heavy components and unavoidable impurities.

[0124] Example 6

[0125] This embodiment provides a method for treating α-pyrrolidone distillation residue, comprising the following steps:

[0126] S1: Add the α-pyrrolidone distillation residue to a wiped film evaporator, and collect N-methyl-2-pyrrolidone at 207°C. After collecting N-methyl-2-pyrrolidone, the temperature is raised, and 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone are collected at 244°C to obtain a first mixture. After the first mixture is collected, a second mixture including 4-pyrrolidone-based butanamide, oligomers and heavy components is obtained at the bottom of the wiped film evaporator. Then, the first mixture and the second mixture are decolorized by activated carbon.

[0127] S2: Under the action of p-toluenesulfonic acid, the first mixture is reacted with formaldehyde at 64.6° C. for 3.3 h to obtain a hydroxylated product. Then, under the action of trifluoromethanesulfonic acid, the hydroxylated product is reacted with boric acid at 61.3° C. for 4.7 h to obtain a borate ester compound.

[0128] In this step, the molar ratio of the first mixture to formaldehyde is 1:2.9, the mass of p-toluenesulfonic acid is 1% of the total mass of the first mixture and formaldehyde, the mass ratio of the hydroxylated product to boric acid is 1:1.4, and the mass of trifluoromethanesulfonic acid is 0.2% of the mass of boric acid.

[0129] S3: Add ferrous chloride and a hydrogen peroxide solution with a mass concentration of 37% to the second mixture, react at 71°C for 3.5 hours to obtain an oxidation product. After the oxidation reaction is completed, cool naturally, add sodium hydroxide solution to the oxidation product, adjust the pH of the system to 10, and then slowly add solid sodium hydroxide under stirring conditions, react at 82°C for 2.3 hours to obtain a saponification product. The mass of ferrous chloride is 0.27% of the mass of the second mixture, the mass ratio of the second mixture to the hydrogen peroxide solution is 1:1.6, and the mass ratio of the oxidation product to the solid sodium hydroxide is 1:1.14.

[0130] Sodium carbonate is added to water to adjust the pH to 7.8, and then sodium dodecyl sulfate is added. After mixing evenly, isopropyl alcohol, ethylenediaminetetraacetic acid, polyether-modified silicone oil, polyvinyl alcohol and butylated hydroxytoluene are added to the system and mixed evenly. Finally, the saponification product is added and stirred evenly to obtain an industrial cleaning agent.

[0131] The industrial cleaning agent in this step includes, by mass percentage, 8% of saponification product, 1.5% of sodium lauryl sulfate, 7% of isopropyl alcohol, 0.25% of ethylenediaminetetraacetic acid, 0.3% of polyether modified silicone oil, 0.5% of polyvinyl alcohol, 0.03% of butylated hydroxytoluene and 82.42% of water.

[0132] The α-pyrrolidone distillation residue of this embodiment is the same as that of Example 5.

[0133] Comparative Example 1

[0134] This comparative example provides a method for treating α-pyrrolidone distillation residue, which is different from Example 1 in that the hydroxylation product is reacted with boric acid at 60° C. for 4 hours, and the mass fraction of the saponification product in the industrial cleaning agent is 0%.

[0135] Comparative Example 2

[0136] This comparative example provides a method for treating α-pyrrolidone distillation residue, which is different from Example 2 in that the hydroxylation product is reacted with boric acid at 110° C. for 10 h, and then the saponification product in the industrial cleaning agent of Example 2 is replaced by the second mixture with the same mass fraction.

[0137] Test example ①:

[0138] The borate compounds prepared in Examples 1-6 and Comparative Examples 1-2 were added to lubricating oil as anti-wear agents to obtain different lubricating oils, which were respectively recorded as No. 1 lubricating oil, No. 2 lubricating oil, No. 3 lubricating oil, No. 4 lubricating oil, No. 5 lubricating oil, No. 6 lubricating oil, No. 7 lubricating oil and No. 8 lubricating oil. The compositions of the above-mentioned No. 1-8 lubricating oils are as follows:

[0139] 77wt% base oil, 10wt% viscosity index improver, 5wt% antioxidant, 2wt% anti-wear agent, 3wt% detergent dispersant, 2wt% corrosion inhibitor, 1wt% anti-foaming agent. The 77wt% base oil specifically includes 45wt% poly-alpha-olefin (PAO) and 32wt% mineral oil.

[0140] The friction and wear performance test of lubricating oil is an important means to evaluate its ability to protect mechanical parts from wear and reduce friction under actual working conditions. The performance of base oil and lubricating oils 1-8 were tested at the same temperature using a four-ball friction and wear tester.

[0141] Specifically, the test operation is as follows: three fixed balls are placed in the fixture at the bottom of the testing machine to ensure that the three fixed balls are in close contact to form a stable triangle. Then place a fourth ball above the three fixed balls as a rotating ball, add an appropriate amount of the lubricating oil to be tested to the test area, ensure that all spherical surfaces are fully covered, and rotate it through the spindle. The spindle speed is 1200r / min, the load is 360N, the test is 60min, and the oil pool is lubricated. The steel ball used in the test is a 12.7mm GCr15 standard steel ball. Before the test, the lubricating oil is ultrasonically treated in an ultrasonic machine for 30min to ensure that the lubricating oil is not modified. After the test, the test steel ball is cleaned several times with petroleum ether and then air-dried. The test results are shown in Table 1.

[0142] Table 1 Statistical table of friction and wear performance test results of lubricating oil No. 1-8

[0143]

[0144] As shown in Table 1, compared with the base oil, the friction coefficient of lubricating oil No. 1 to No. 6 lubricating oil can be reduced by about 30%, and the average wear spot diameter can be reduced by about 40-50% due to the addition of the boric acid ester compound prepared in Examples 1-6 as an anti-wear agent. The reaction temperature of the hydroxylated product and boric acid of lubricating oil No. 7 is too low, and the reaction time is too short. The reaction temperature of the hydroxylated product and boric acid of lubricating oil No. 8 is too high, and the reaction time is too long, which affects the anti-wear performance of the product, resulting in the improvement effect of the friction coefficient and the average wear spot diameter of the lubricating oil being significantly inferior to that of lubricating oil No. 1 to No. 6.

[0145] Test example ②:

[0146] The industrial cleaning agents prepared in Examples 1-6 and Comparative Examples 1-2 are respectively labeled as Industrial Cleaner No. 1, Industrial Cleaner No. 2, Industrial Cleaner No. 3, Industrial Cleaner No. 4, Industrial Cleaner No. 5, Industrial Cleaner No. 6, Industrial Cleaner No. 7, and Industrial Cleaner No. 8.

[0147] The above industrial cleaning agents No. 1-8 were sprayed in equal amounts on the oil stains on the surface of the machine, and wiped with a wiping cloth with the same strength and frequency. The above oil stains were made on the same mechanical equipment, and the composition of the oil stains on the surface of the mechanical equipment was the same, the residual time of the oil stains on the surface of the mechanical equipment was the same, and the initial thickness of the oil stains was also the same, all of which were 2.5 cm. The time required for the completion of cleaning and the cleaning effect of different industrial cleaning agents were recorded, as shown in Table 2.

[0148] Table 2 Statistical table of the cleaning effect of industrial cleaning agents No. 1-8 on oil stains on the surface of mechanical equipment

[0149]

[0150] As shown in Table 2, industrial cleaning agents No. 1-6 can completely clean the oil stains on the surface of mechanical equipment in a short time without oil residue. No. 7 industrial cleaning agent does not add saponification products, and the time required to complete the cleaning is significantly longer than that of industrial cleaning agents No. 1-6, and the cleaning effect is not good, and oil residues exist in the depressions. The second mixture is directly added to industrial cleaning agent No. 8, which makes the cleaning agent unusable, indicating that the appropriate addition of saponification products can improve the cleaning ability of industrial cleaning agents.

[0151] In the mold of the injection molding machine, resin may accumulate on the mold surface, nozzle and other parts, affecting the quality and production efficiency of the product. Remove the mold of the injection molding machine and place it in an ultrasonic treatment device filled with an equal amount of the above-mentioned industrial cleaning agents No. 1-8 for ultrasonic cleaning at 50°C. The above-mentioned resins exist in the same mold, and the type and composition of the resins are the same, the residual time of the resins on the mold is the same, and the initial thickness of the resins is also the same. Record the time required to complete the resin cleaning and the cleaning effect of different industrial cleaning agents, see Table 3 for details.

[0152] Table 3 Statistical table of the cleaning effect of industrial cleaning agents No. 1-8 on the residual resin in the injection molding machine mold

[0153]

[0154] As shown in Table 3, industrial cleaning agents No. 1-6 can completely remove the resin remaining on the mold surface in a short time. No. 7 industrial cleaning agent does not add saponification products, and the time required to remove the resin is significantly longer than that of No. 1-6 industrial cleaning agents, and the cleaning effect is not good, and some resin remains. Industrial cleaning agent No. 8 cannot be used due to the direct addition of the second mixture, indicating that the appropriate addition of saponification products can improve the cleaning ability of industrial cleaning agents on resins.

[0155] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for treating α-pyrrolidone distillation residue, wherein the α-pyrrolidone distillation residue comprises N-methyl-2-pyrrolidone, 3-methyl-2-pyrrolidone, 4-methyl-2-pyrrolidone, 4-pyrrolidone-based butyramide, oligomers and heavy components; characterized in that: The steps include: S1: separating and treating the α-pyrrolidone distillation residue to obtain a first mixture including N-methyl-2-pyrrolidone, 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone, and a second mixture including 4-pyrrolidone butyramide, oligomers and heavy components; S2: subjecting the first mixture to a hydroxylation reaction, and then continuing to react with boric acid at 80-90° C. for 6-8 hours to obtain a borate ester compound for a lubricating oil anti-wear additive; S3: subjecting the second mixture to oxidation reaction and saponification reaction in sequence to obtain a saponification product for industrial cleaning agent.

2. The method for treating α-pyrrolidone distillation residue according to claim 1, characterized in that: In step S1, the α-pyrrolidone distillation residue is added to a wiped film evaporator, N-methyl-2-pyrrolidone is collected at 205-210° C., and then the temperature is increased to continue to collect 3-methyl-2-pyrrolidone and 4-methyl-2-pyrrolidone at 240-250° C. to obtain a first mixture; A second mixture comprising 4-pyrrolidonylbutanamide, oligomers and heavies was obtained at the bottom of the wiped film evaporator.

3. The method for treating α-pyrrolidone distillation residue according to claim 1, characterized in that: In step S1, after obtaining the first mixture and the second mixture, the first mixture and the second mixture are decolorized by activated carbon.

4. The method for treating α-pyrrolidone distillation residue according to claim 1, characterized in that: In step S2, under the action of the first catalyst, the first mixture is subjected to a hydroxylation reaction with formaldehyde at 60-70° C. for 3-5 hours to obtain a hydroxylated product; The molar ratio of the first mixture to formaldehyde is 1:2-1:3; The first catalyst is p-toluenesulfonic acid.

5. The method for treating α-pyrrolidone distillation residue according to claim 4, characterized in that: In step S2, the hydroxylation product is reacted with boric acid under the action of a second catalyst to obtain a borate ester compound; The second catalyst is sulfuric acid or trifluoromethanesulfonic acid.

6. The method for treating α-pyrrolidone distillation residue according to claim 5, characterized in that: In step S2, the mass ratio of the hydroxylated product to the boric acid is 1:1.2-1:1.5; The mass of the first catalyst is 0.5-2% of the total mass of the first mixture and formaldehyde; The mass of the second catalyst is 0.2-0.3% of the mass of the boric acid.

7. The method for treating α-pyrrolidone distillation residue according to claim 1, characterized in that: In step S3, a third catalyst and a hydrogen peroxide solution are added to the second mixture, and the mixture is reacted at 60-80° C. for 3-5 hours to obtain an oxidation product; then sodium hydroxide is added to the oxidation product, and the mixture is reacted at 80-95° C. for 2-3 hours to obtain a saponification product; The third catalyst is a soluble divalent iron salt, the mass of the third catalyst is 0.2-0.3% of the mass of the second mixture, the mass concentration of the hydrogen peroxide solution is 30-50%, the mass ratio of the second mixture to the hydrogen peroxide solution is 1:0.8-1:2, and the mass ratio of the oxidation product to sodium hydroxide is 1:1.1-1:1.

2.

8. The method for treating α-pyrrolidone distillation residue according to claim 7, characterized in that: The preparation method of the industrial cleaning agent is as follows: adding a pH regulator to water, then adding a surfactant, mixing them evenly, adding a saponification product to the system, stirring them evenly to obtain the industrial cleaning agent; The pH regulator is triethanolamine or sodium carbonate, and the surfactant is one or more of nonylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, sodium lauryl sulfate and cocamidopropyl betaine; The pH regulator is used to adjust the pH of the industrial cleaning agent to 7-8.

9. The method for treating α-pyrrolidone distillation residue according to claim 8, characterized in that: In industrial cleaning agents, the mass percentage of saponification products is 5-8%, and the mass percentage of surfactants is 0.1-5%.

10. The method for treating α-pyrrolidone distillation residue according to claim 9, characterized in that: According to the percentage by mass, the industrial cleaning agent also includes 5-10% solubilizer, 0.2-0.3% chelating agent, 0.3-0.5% defoaming agent, 0.2-0.5% thickener and 0.01-0.03% antioxidant, and the balance is water; The solubilizer is one or more of ethanol, isopropanol, propylene glycol and ethylene glycol, the chelating agent is ethylenediaminetetraacetic acid, the defoaming agent is silicone oil or polyether-modified silicone oil, the thickener is xanthan gum, carboxymethyl cellulose or polyvinyl alcohol, and the antioxidant is butylated hydroxyanisole or butylated hydroxytoluene.

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