CN111574394B - Method for treating carboxylic acid-containing DMF (dimethyl formamide) in sucralose production - Google Patents
Method for treating carboxylic acid-containing DMF (dimethyl formamide) in sucralose production Download PDFInfo
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- CN111574394B CN111574394B CN202010439444.0A CN202010439444A CN111574394B CN 111574394 B CN111574394 B CN 111574394B CN 202010439444 A CN202010439444 A CN 202010439444A CN 111574394 B CN111574394 B CN 111574394B
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C231/00—Preparation of carboxylic acid amides
- C07C231/22—Separation; Purification; Stabilisation; Use of additives
- C07C231/24—Separation; Purification
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
- C07C51/43—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
- C07C51/43—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation
- C07C51/44—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation by distillation
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
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Abstract
The invention relates to a method for treating carboxylic acid-containing DMF in sucralose production, which comprises the following steps: a. adding a small amount of sodium hydroxide into DMF containing carboxylic acid recovered from sucralose production for reaction, evaporating and condensing to obtain a mixture containing carboxylic acid, DMF, DMA and DMAC; b. adding sodium hydroxide with equal molar ratio into the mixture for neutralization reaction, evaporating and concentrating the reaction liquid to obtain a white sodium acetate finished product, and condensing the evaporated gas to obtain a DMF solution without carboxylic acid; c. conveying the DMF solution without carboxylic acid to a first rectifying tower for distillation, condensing the gas phase at the tower top to obtain a mixture containing water DMF, and obtaining a mixture of DMAC, tetramethylurea and impurities at the tower bottom; d. dehydrating the aqueous DMF mixture, and rectifying for the second time to obtain high-purity DMF; e. and rectifying the mixture at the bottom of the first rectifying tower again to obtain DMAC and raffinate containing DMAC and tetramethylurea. The method has the advantages of simple process and high DMF (dimethyl formamide) recovery efficiency, avoids the generation of solid salt slag in the traditional process, reduces the production cost and reduces the pollution.
Description
Technical Field
The invention belongs to the field of food additives in chemical technology, and particularly relates to a method for treating carboxylic acid-containing DMF in production of converted sucralose.
Background
Sucralose is a fresh sweetener, the sweetness of which is 800 times of 600-fold of sucrose, and the sweetness of which is pure and similar to sucrose, and which is not absorbed by human body, has no bioaccumulation and high safety, so that the sucralose industry is rapidly developed in this year, the production enterprises are gradually increased, and the yield is continuously improved. In the esterification chlorination process in the production process of sucralose, a large amount of DMF is used as a solvent, and because the recovered DMF contains certain moisture and acetic acid, the DMF needs to be rectified, dehydrated and deacidified in a rectification mode and then returned to esterification chlorination for reuse, and in the dehydration deacidification process of the recovered DMF, the acetic acid and the DMF are subjected to azeotropy, and DMF containing 15-20% of carboxylic acid can be generated at the bottom of the deacidification tower. The prior art mainly treats an acidic DMF solution by a method of directly adding alkali for neutralization, and has the defects that DMF can be decomposed under strong alkaline conditions, DMF loss is caused, complicated operation processes such as distillation, crystallization and filtration are carried out after neutralization, and simultaneously, a large amount of solid salt residues which are difficult to treat are generated.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a method for treating carboxylic acid-containing DMF in sucralose production, which has the advantages of simple operation, high efficiency, high recovery rate and low cost.
In order to achieve the purpose of the invention, the invention adopts the following technical scheme:
a method for processing carboxylic acid-containing DMF in sucralose production is characterized by comprising the following steps:
a. conveying carboxylic acid-containing DMF recovered in sucralose production to a primary evaporator, adding sodium hydroxide with the amount of 3-5% of the feeding amount of the carboxylic acid-containing DMF (about 3-5% of the feeding amount of the carboxylic acid-containing DMF, mainly reacting with a small amount of carboxylic acid, fixing some high-boiling organic impurities, facilitating discharge of a bottom concentrated solution, and keeping a distilled solution colorless and transparent), stirring for complete reaction, and then evaporating and condensing the carboxylic acid-containing DMF at-0.098 MPa and 60-80 ℃ to obtain a colorless and transparent mixture containing carboxylic acid, DMF, DMA and DMAC and free of solid-phase impurities;
b. adding the mixture into a neutralization evaporator, adding sodium hydroxide in equimolar amount according to the content of carboxylic acid (by central control analysis) to perform neutralization reaction until the temperature is completely not increased, then opening steam to perform evaporation concentration on reaction liquid under the conditions of-0.098 MPa and 60-110 ℃, directly evaporating to dryness, obtaining a white sodium acetate finished product in the neutralization evaporator, and condensing DMF gas which is obtained by evaporation and does not contain carboxylic acid to obtain a DMF solution which does not contain carboxylic acid;
c. conveying the DMF solution without carboxylic acid into a first rectifying tower for distillation under the conditions of-0.098 MPa and 60-110 ℃, condensing a gas phase obtained at the top of the first rectifying tower to obtain a water-containing DMF mixture, and obtaining a tower bottom mixture containing DMAC, tetramethylurea and a small amount of impurities at the bottom of the tower;
d. dehydrating the water-containing DMF mixture through a dehydrating tower, and carrying out secondary rectification on the dehydrated DMF in a second rectifying tower under the conditions of-0.098 MPa and 60-110 ℃ to recover and obtain high-purity DMF;
e. the mixture at the bottom of the first rectifying tower is rectified and separated again under the conditions of-0.098 MPa and 100-130 ℃ to obtain DMAC and residual liquid containing DMAC and tetramethylurea.
The further technical scheme is that in the DMF containing carboxylic acid recovered in the production of the sucralose, the mass fraction of the carboxylic acid is 15-20%.
In a further embodiment, the carboxylic acid comprises at least one of formic acid and acetic acid.
The further technical scheme is that in the neutralization evaporator, the pH value after neutralization reaction is 6.5-7.5.
The further technical scheme is that the colorless and transparent mixture which does not contain solid-phase impurities and contains carboxylic acid, DMF, DMA and DMAC and sodium hydroxide in a molar ratio of 1: 1-1.2 according to the acid calculation.
The further technical scheme is that the mixture obtained from the top of the first rectifying tower comprises DMF, dimethylamine and water.
The further technical scheme is that the mixture at the bottom of the first rectifying tower comprises at least one of DMF, DMAC and tetramethylurea.
The further technical scheme is that the mass percent of DMF in the high-purity DMF obtained by the secondary rectification of the second rectifying tower is more than or equal to 99.5 percent, the water content is less than 500ppm, and the acid content is less than 500 ppm.
Compared with the prior art, the method has the advantages that a small amount of sodium hydroxide is added in one-time evaporation to react with a small amount of carboxylic acid mainly under the action of strong base, so that some high-boiling organic impurities are fixed, the discharge of a concentrated solution at the bottom is facilitated, the discharged distillate can be kept colorless and transparent, colorless and transparent DMF containing acetic acid is obtained through distillation and condensation, then three functions of neutralization, distillation and concentration and stirring discharge are realized in a neutralization reaction evaporator, a high-purity byproduct sodium acetate is directly obtained, and the DMF containing no acid is recovered; vacuum decompression operation is adopted in the rectification separation operation process, so that the operation temperature of the system is reduced to a great extent, and the decomposition of DMF (dimethyl formamide) at high temperature is avoided; compared with the prior art that the direct neutralization of acid-containing DMF requires complex steps such as neutralization, condensation, filter pressing and the like, the salt obtained by filter pressing is hazardous waste containing impurities, and the process can obtain a high-purity sodium acetate byproduct. The method provided by the invention has simple process, the product purity meets the requirement, and the method is a carboxylic acid-containing DMF recycling process method with better application prospect.
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FIG. 1 is a process flow diagram of the present invention.
Detailed Description
To explain technical contents, structural features, achieved objects and effects of the technical solutions in detail, the following detailed description is given with reference to the accompanying drawings in combination with the specific embodiments.
Example 1
As shown in figure 1, the acetic acid contained in the acid discharged from the bottom of the deacidification tower in the DMF recovery section of sucralose is: 20wt%, DMF: adding 80wt% of acidic DMF into a primary evaporator, simultaneously adding 3% of sodium hydroxide, and distilling and condensing (-0.098 MPa, 60-100 ℃) to obtain colorless transparent DMF containing acetic acid.
Adding the acetic acid-containing DMF into a neutralization evaporator (the neutralization evaporator is a device with stirring and automatic discharging, and can realize three functions of neutralization, evaporation concentration and solid discharging), adding sodium hydroxide with equal molar ratio to ensure that the pH value of a mixture after reaction is 7.0, neutralizing reactants to obtain water, DMF and sodium acetate, then carrying out evaporation concentration (-0.098 MPa, 60-100 ℃), condensing gas phase (circulating water is condensed to 30-50 ℃) to obtain acid-free DMF, and obtaining high-purity sodium acetate in the neutralization evaporator.
Then, the DMF which does not contain acid is sent into a rectifying tower for rectification (the operating conditions of the rectifying tower are that the number of theoretical plates is 20, the reflux ratio is 1, the pressure is 30kPa, and the temperature is 110 ℃), a tower top mixture comprising water, DMF and dimethylamine is obtained at the tower top of the rectifying tower, and a tower bottom mixture comprising DMF, DMAC and tetramethylurea is obtained at the tower bottom of the rectifying tower.
The bottom mixture was again rectified under reduced pressure (theoretical plate number 20, reflux ratio 1, pressure 30kPa, temperature 118 ℃) to separate DMAC.
The water-containing DMF at the tower top is dehydrated by a dehydration tower (-0.098 MPa, 60-100 ℃), the heavy component containing DMF at the tower bottom is rectified under reduced pressure (the theoretical plate number is 25, the reflux ratio is 1, the pressure is 30kPa, the temperature is 115 ℃) to obtain DMF with the mass fraction of more than or equal to 99.5 percent, the water content is less than 500ppm, the acid content is less than 500ppm, and the DMF recovery rate is more than or equal to 98 percent.
The obtained high-purity sodium acetate and DMAC were sold separately as commercial products.
Example 2
Acetic acid contained in the acid-removing tower bottom discharged from the trichlorosucrose DMF recovery section: 15wt%, DMF: adding 85wt% of acidic DMF into a neutralization evaporator, simultaneously adding 5wt% of sodium hydroxide, adding colorless transparent DMF containing acetic acid obtained by distillation and condensation into the neutralization reaction evaporator, adding sodium hydroxide with equal molar ratio to ensure that the pH value of the mixture after reaction is 7.0, neutralizing reactants, namely water, DMF and sodium acetate, then carrying out evaporation and concentration, condensing a gas phase to obtain DMF free of acid, and obtaining high-purity sodium acetate in the evaporator; then, feeding acid-free DMF obtained by gas phase condensation into a rectifying tower, obtaining a tower top mixture comprising water, DMF and dimethylamine from the tower top of the rectifying tower, obtaining a tower bottom mixture comprising DMF, DMAC and tetramethylurea from the tower bottom of the rectifying tower, and carrying out the operating conditions of the rectifying tower: the theoretical plate number is 20, the reflux ratio is 1, the pressure is 30kPa, and the temperature is 110 ℃.
And (3) carrying out reduced pressure rectification on the mixture at the bottom of the tower (the number of theoretical plates is 20, the reflux ratio is 1, the pressure is 30kPa, and the temperature is 118 ℃) to operate and separate DMAC, dehydrating the DMF containing water at the top of the tower through a dehydrating tower, and refining the heavy component containing DMF at the bottom of the tower through reduced pressure rectification (the number of theoretical plates is 25, the reflux ratio is 1, the pressure is 30kPa, and the temperature is 115 ℃) to obtain DMF with the mass fraction of more than or equal to 99.5%, the moisture content of less than 500ppm, the acid content of less than 500ppm, and the DMF recovery rate of more than or equal to 98%.
Example 3
Acetic acid contained in the acid-removing tower bottom discharged from the sucralose DMF recovery section: 18wt%, DMF: adding 82wt% of acidic DMF into a neutralization evaporator, simultaneously adding 4 wt% of sodium hydroxide, adding colorless and transparent DMF containing acetic acid obtained by distillation and condensation into the neutralization reaction evaporator, adding sodium hydroxide with equal molar ratio to ensure that the pH value of the mixture after reaction is 7.0, neutralizing reactants, namely water, DMF and sodium acetate, then carrying out evaporation and concentration, condensing a gas phase to obtain DMF free of acid, and adding high-purity sodium acetate into the evaporator; then, feeding acid-free DMF obtained by gas phase condensation into a rectifying tower, obtaining a tower top mixture comprising water, DMF and dimethylamine from the tower top of the rectifying tower, obtaining a tower bottom mixture comprising DMF, DMAC and tetramethylurea from the tower bottom of the rectifying tower, and carrying out the operating conditions of the rectifying tower: the theoretical plate number is 20, the reflux ratio is 1, the pressure is 30kPa, and the temperature is 110 ℃.
And performing reduced pressure rectification on the mixture at the bottom of the tower (the number of theoretical plates is 20, the reflux ratio is 1, the pressure is 30kPa, the temperature is 118 ℃) to separate DMAC, dehydrating the DMF containing water at the top of the tower through a dehydrating tower, and refining the heavy component containing DMF at the bottom of the tower through reduced pressure rectification (the number of theoretical plates is 25, the reflux ratio is 1, the pressure is 30kPa, the temperature is 115 ℃) to obtain DMF with the mass fraction of more than or equal to 99.5%, the water content of less than 500ppm, the acid content of less than 500ppm and the DMF recovery rate of more than or equal to 98%.
It should be noted that, although the above embodiments have been described herein, the invention is not limited thereto. Therefore, based on the innovative concepts of the present invention, the technical solutions of the present invention can be directly or indirectly applied to other related technical fields by making changes and modifications to the embodiments described herein, or by using equivalent structures or equivalent processes performed in the content of the present specification and the attached drawings, which are included in the scope of the present invention.
Claims (4)
1. A method for processing carboxylic acid-containing DMF in sucralose production is characterized by comprising the following steps: a, conveying DMF containing carboxylic acid recovered in sucralose production to a primary evaporator, adding sodium hydroxide which is 3-5% of the feeding amount of the DMF containing carboxylic acid, stirring and reacting completely, and then evaporating and condensing the DMF containing carboxylic acid at-0.098 MPa and 60-80 ℃ to obtain a colorless and transparent mixture containing carboxylic acid, DMF, DMA and DMAC and not containing solid-phase impurities;
b. adding the mixture into a neutralization evaporator, adding sodium hydroxide with equimolar amount according to the content of carboxylic acid for neutralization reaction, completely reacting until the temperature does not rise any more, then opening steam to evaporate and concentrate reaction liquid under the conditions of-0.098 MPa and 60-110 ℃, directly evaporating to dryness, obtaining a white sodium acetate finished product in the neutralization evaporator, and condensing DMF gas which is obtained by evaporation and does not contain carboxylic acid to obtain a DMF solution which does not contain carboxylic acid;
c. conveying the DMF solution without carboxylic acid into a first rectifying tower for distillation under the conditions of-0.098 MPa and 60-110 ℃, condensing a gas phase obtained at the top of the first rectifying tower to obtain a water-containing DMF mixture, and obtaining a tower bottom mixture containing DMAC, tetramethylurea and a small amount of impurities at the bottom of the tower;
d. dehydrating the water-containing DMF mixture through a dehydrating tower, and carrying out secondary rectification on the dehydrated DMF in a second rectifying tower under the conditions of-0.098 MPa and 60-110 ℃ to recover and obtain high-purity DMF;
e. the mixture at the bottom of the first rectifying tower is rectified and separated again under the conditions of-0.098 MPa and 100-130 ℃ to obtain DMAC and residual liquid containing DMAC and tetramethylurea;
in the DMF containing carboxylic acid recovered in the production of the sucralose, the mass fraction of the carboxylic acid is 15-20%;
the carboxylic acid comprises at least one of formic acid and acetic acid;
in the neutralization evaporator, the pH value after neutralization reaction is 6.5-7.5;
the mass percent of DMF in the high-purity DMF obtained by secondary rectification of the second rectifying tower is more than or equal to 99.5 percent, the water content is less than 500ppm, and the acid content is less than 500 ppm.
2. The method for treating carboxylic acid-containing DMF in sucralose production according to claim 1, wherein the colorless and transparent mixture containing carboxylic acid, DMF, DMA and DMAC without solid-phase impurities in step b is 1: 1-1.2 by acid molar ratio.
3. The method of claim 1, wherein the mixture obtained from the top of the first distillation column comprises DMF, dimethylamine and water.
4. The method of claim 1, wherein the first distillation column bottom mixture comprises at least one of DMF, DMAC, and tetramethylurea.
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| EP4227290A4 (en) * | 2020-10-23 | 2023-12-27 | Anhui Jinhe Industrial Co., Ltd. | Dmf recycling method |
| CN112574052A (en) * | 2020-11-30 | 2021-03-30 | 安徽金禾实业股份有限公司 | Distillation treatment method of DMAC reaction solution |
| CN113698291B (en) * | 2021-08-17 | 2022-08-19 | 安徽金禾实业股份有限公司 | Method and device for treating acetic acid in acidic DMF and co-producing magnesium acetate |
| CN113636951B (en) * | 2021-09-22 | 2023-06-27 | 安徽金禾实业股份有限公司 | Treatment method of waste DMF in sucralose production |
| CN113666838A (en) * | 2021-09-22 | 2021-11-19 | 安徽金禾实业股份有限公司 | Method for recovering low-concentration DMF (dimethyl formamide) through double-tower coupling in sucralose production |
| CN114957032A (en) * | 2022-05-24 | 2022-08-30 | 翁源广业清怡食品科技有限公司 | Method for recovering DMF finished product and acetate byproduct from acid-containing DMF in sucralose production process |
| CN115677527A (en) * | 2022-11-17 | 2023-02-03 | 安徽金禾实业股份有限公司 | Method for purifying acidic DMF in sucralose production |
| CN116496172B (en) * | 2023-06-27 | 2023-09-15 | 苏州巨联环保有限公司 | Treatment method of high-acidity DMF (dimethyl formamide) rectification liquid and treatment method of DMF waste liquid |
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| JPS52151113A (en) * | 1976-06-07 | 1977-12-15 | Nippon Kagaku Kikai Seizo | Method of removing formic acid formed by decomposition of dimetyl formamide in dehydrator of dimethyle * |
| US5498709A (en) * | 1994-10-17 | 1996-03-12 | Mcneil-Ppc, Inc. | Production of sucralose without intermediate isolation of crystalline sucralose-6-ester |
| CN102030672B (en) * | 2010-12-09 | 2013-10-09 | 南京大学 | Process for reclaiming super-high-purity N,N-dimethyl acetamide solvent in polyurethane fibre production process |
| CN108358807B (en) * | 2018-01-13 | 2020-07-17 | 安徽金禾实业股份有限公司 | Method and device for recycling and treating acidic DMF (dimethyl formamide) and waste residue sodium acetate |
| CN110423192A (en) * | 2019-08-14 | 2019-11-08 | 郑州中科新兴产业技术研究院 | A kind of recovery method of spandex DMAC/ acetic acid organic liquid waste |
| CN110759832A (en) * | 2019-11-16 | 2020-02-07 | 安徽金禾实业股份有限公司 | DMAC (dimethylacetamide) residual liquid recycling device and method |
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