CN115650947A - Refining method of glycolide - Google Patents
Refining method of glycolide Download PDFInfo
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- CN115650947A CN115650947A CN202211069832.XA CN202211069832A CN115650947A CN 115650947 A CN115650947 A CN 115650947A CN 202211069832 A CN202211069832 A CN 202211069832A CN 115650947 A CN115650947 A CN 115650947A
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Abstract
The invention belongs to the technical field of chemical product refining, and particularly relates to a method for refining glycolide by coupling membrane separation and recrystallization. The method of the invention comprises the following steps: (1) Dissolving crude glycolide product with polar solvent I, and dissolving with N 2 Pressing the totally dissolved glycolide into a reactor I through a membrane device, concentrating and drying to obtain a refined product I; (2) Adding the refined product I into a reactor II, adding a recrystallization solvent in two steps, stirring and cooling until crystallization is complete, centrifuging, filtering, and drying in vacuum to constant weight to obtain a refined product II; wherein, the recrystallization solvent is a polar solvent II: alcohols: the volume ratio of the ethers is 0.5 to 1.2:0.1 to 2:0.5 to 2.2. The invention can realize the refining of glycolide at low temperature or normal temperature by introducing a membrane treatment technology, has no phase change in the membrane separation process, does not generate secondary pollution, reduces the recrystallization times, and is easy to recycle the related organic solvent.
Description
Technical Field
The invention belongs to the technical field of chemical product refining, and particularly relates to a method for refining glycolide by coupling membrane separation and recrystallization.
Background
Polyglycolic acid (PGA), also known as polyglycolic acid, is a kind of aliphatic polyester-based polymer material with a minimum number of carbon units, a high biodegradation rate, good biocompatibility and a completely degradable ester structure. PGA with high molecular weight is widely applied in the biomedical material field of operation suture lines, artificial tissues, drug controlled release systems and the like.
Glycolide is an important intermediate for the preparation of high molecular weight polyglycolic acid. At present, polyglycolic acid, which is required to meet the requirements of surgical sutures and other applications, is required to meet the requirements of intrinsic viscosity number of 1 or more and mass average molecular weight of more than one hundred thousand, and the purity of glycolide seriously restricts the increase of molecular weight of polyglycolic acid high polymer, which puts higher requirements on the purification of glycolide.
The main method for preparing glycolide at present is to prepare the glycolide by the polycondensation of glycolic acid or methyl glycolate and the depolymerization reaction of oligomer thereof, the crude glycolide (purity is more than or equal to 85.0 percent and maximum single impurity is less than or equal to 8.0 percent) prepared by the method usually contains water, glycolic acid oligomer or high-boiling point cracking impurity and other impurities, and the existence of the impurities can greatly influence the molecular weight of the obtained polymer in the ring-opening polymerization process of the glycolide, so that how to remove the impurities and prepare the high-purity glycolide becomes an important problem to be solved in the refining process of the glycolide.
The purification method of glycolide reported in the current patent comprises a recrystallization method, a solvent extraction method, a gas-assisted evaporation method, a rectification method, a melt crystallization method and the like. Among them, recrystallization is frequently used, and the more common method is repeated recrystallization of crude glycolide by using organic solvents such as ethyl acetate, and the recrystallization purification methods of glycolide are reported in patents US5223630, CN100999516, CN101054371, and the like.
In fact, although the recrystallization method has the advantage of high purification purity, the method has no obvious effect on removing some impurities with large relative molecular mass, such as glycolic acid oligomers and mechanical impurities.
In addition, the increase of the recrystallization times can also cause the yield of the product to be sharply reduced, and the operation process is complex and tedious because multiple times of filtration and washing are needed in the operation process, so that the single operation process has certain limitation in the face of complex industrial production conditions.
The membrane separation technology is a method for separating a mixture by utilizing a membrane, in particular to a pressure-driven membrane separation technology, namely, the membrane is used as the selective permeability between two phases by utilizing the fluid pressure difference as the driving force, so that one or more components of the two phases permeate the membrane and other components are intercepted, thereby realizing the separation between different components and achieving the purposes of separation, concentration and purification.
The membrane separation technology has the advantages of reducing energy consumption, improving the quality and yield of products, reducing environmental pollution, reducing production cost, improving income and the like, but the single membrane separation technology has the limitation of limited impurity removal capability and almost no obvious removal effect on small molecular impurities.
Disclosure of Invention
In order to solve the technical problems, the invention provides an efficient and economic glycolide refining method, namely a method for coupling membrane separation and recrystallization, which can well remove main impurities, namely glycolic acid, oligomers thereof, mechanical impurities and the like after crude glycolide is purified, and can ensure higher yield and purity of the refined glycolide at the same time.
In order to achieve the purpose, the invention adopts the technical scheme that:
s1, placing crude glycolide into a reactor I at room temperature, adding a polar solvent I, stirring for 1-2 h, and performing membrane treatment after complete dissolution;
then, carrying out rotary evaporation and concentration on the obtained product filtrate, carrying out centrifugal filtration, and drying in vacuum to constant weight to obtain a refined product I, and meanwhile, recovering the solvent I;
s2, adding the refined product I into a reactor II, adding a recrystallization solvent in two steps, namely adding a polar solvent II, heating to 60-70 ℃, mechanically stirring to completely dissolve the refined product I, maintaining for 15-60 min after dissolution, gradually cooling until the product is separated out, adding a mixed solvent of a low-boiling point alcohol reagent and a low-boiling point ether reagent, stirring for 0.5-1.5 h, continuously cooling to 5-10 ℃, crystallizing for 6-8 h, centrifuging and filtering after complete crystallization, and drying in vacuum to constant weight to obtain the refined product II.
In the above step, the polar solvent I is any one of acetone, ethyl acetate, dichloromethane, chloroform, ethanol, dimethyl sulfoxide, N-dimethylformamide and N, N-dimethylacetamide solvents;
preferably, the polar solvent I is any one of acetone, ethyl acetate, dichloromethane and N, N-dimethylformamide;
preferably, the polar solvent I is any one of acetone, ethyl acetate and dichloromethane;
the mass of the polar solvent I is 5-50 times of that of the crude glycolide;
preferably, the mass of the polar solvent I is 6 to 45 times of the mass of the crude glycolide
Preferably, the mass of the polar solvent I is 8-30 times of that of the crude glycolide;
the membrane for processing and filtering is any one of a microporous filter membrane, an ultrafiltration membrane, a nanofiltration membrane, an osmosis membrane, a reverse osmosis membrane and a metal or ceramic composite membrane;
preferably, the membrane is any one of a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane and a metal or ceramic composite membrane;
the membrane material is any one of cellulose acetate, mixed cellulose ester, polyamide, nylon, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, polyether sulfone, polypropylene, polyacrylonitrile and metal and ceramic materials;
preferably, the material of the selective membrane is any one of nylon, polypropylene, polyvinyl chloride, polytetrafluoroethylene, polyamide, polyvinylidene fluoride and polyacrylonitrile;
the pore diameter range of the microporous filter membrane is 0.01-10 mu m;
preferably, the pore diameter of the microporous filter membrane is in the range of 0.01-0.5 μm;
the polar solvent II is one and/or more of acetone, ethyl acetate, dichloromethane, chloroform, ethanol and dimethyl sulfoxide;
preferably, the polar solvent II is any one of acetone, ethyl acetate and dichloromethane;
the low-boiling point alcohol reagent is any one of methanol, ethanol, n-propanol, isopropanol, n-butanol and tert-butanol;
preferably, the low-boiling point alcohol reagent is any one of methanol, ethanol, n-propanol and isopropanol;
the low-boiling-point ether reagent is any one of diethyl ether, petroleum ether, isopropyl ether, n-butyl ether, tetrahydrofuran, tert-butyl ether and methyl tert-butyl ether;
preferably, the low-boiling point ether reagent is any one of diethyl ether, isopropyl ether, n-butyl ether, tert-butyl ether and methyl tert-butyl ether;
the amount of the recrystallization solvent is 1.5 to 5.3 times of the mass of the refined product I;
preferably, the amount of the recrystallization solvent is 2.0 to 3.3 times the mass of the purified product I;
the recrystallization solvent contains a polar solvent II: low boiling point alcohol reagent: the volume ratio of the low boiling point ether reagent is 0.5-1.2: 0.1 to 2:0.5 to 2.2;
preferably, the volume ratio of the three solvents is 0.8-1.2: 0.1 to 1.0:0.8 to 2.2;
the vacuum drying conditions are as follows: -0.07 to-0.1MPa, 30 to 50 ℃;
preferably, the vacuum drying conditions are as follows: -0.09MPa,40 ℃.
The invention has the beneficial effects that:
(1) The whole coupling process for purifying and refining glycolide is relatively simple, the operation is simple and convenient, the equipment is simple, the investment is low, the cost is low, and the purity of the obtained glycolide is high;
(2) Adopting a membrane separation technology; the membrane separation process is operated at low temperature or normal temperature, the whole process has no phase change, no secondary pollution is generated, and the organic solvent is easy to recycle; the adoption of the membrane separation technology replaces the technical processes of natural sedimentation, plate-and-frame filtration, vacuum drum rotation, centrifugal separation, solvent extraction, resin purification, activated carbon decoloration and the like in the traditional process;
(3) Three recrystallization solvents with different proportions are adopted, so that the purification effect is obvious, the recrystallization times can be reduced, the recrystallization times are controlled to be 1-2 times, the treatment procedure is greatly simplified, the yield is increased, and the yield after mother liquor recovery can reach 85% -95%; in addition, the added organic solvent is easy to recycle and has little influence on the environment.
Description attached drawings FIG. 1 is a gas chromatogram of a sample of example 2 (note: the peak of the solvent dissolving the sample at 0.73min, the following chromatogram is also true);
FIG. 2 is a gas chromatogram of a sample of example 3;
FIG. 3 is a gas chromatogram of a sample from example 5.
Detailed Description
The present invention will now be described in further detail with reference to specific embodiments thereof for the purpose of enabling those skilled in the art to better understand the invention.
Example 1
At room temperature, 680g of crude glycolide and 6.8L of ethyl acetate are added into a reactor I, and then stirred for 1 hour to be completely dissolved; after completion of the dissolution, N is used 2 Blowing and pressing the crude glycolide solution in the reactor I into a reactor II through a polytetrafluoroethylene microporous filter membrane with the pore diameter of 0.1 mu m, then carrying out rotary evaporation and concentration on the filtrate in the reactor II, and recycling the ethyl acetate solvent;
after the concentration is finished, the residue in the reactor II is centrifugally filtered, the filtered mother liquor is used for the next crude product treatment, and the filter cake is dried to constant weight under the vacuum condition of-0.09MPa and 40 ℃ to obtain 600g of refined product I, wherein the yield is 88.2%.
Adding 597g of the refined product I into a reactor II, adding 520mL of ethyl acetate, heating from room temperature to 65 ℃, mechanically stirring, and keeping for 45min after complete dissolution;
then gradually cooling to separate out a solid product, adding 165mL of isopropanol and 515mL of methyl tert-butyl ether, stirring for 1h, continuously cooling to 5 ℃ and crystallizing for 6-8 h, after the crystallization is finished, centrifuging and filtering, recovering a filtering mother liquor for refining the refined product I next time, and drying a filter cake to constant weight under vacuum of-0.09 MPa and 40 ℃ to obtain a white solid, namely a refined product II, wherein the yield is 544g, and the purity is 99.85%.
Example 2
The processing technique and the operating conditions are the same as those of the example 1, except that:
dissolving 800g of crude glycolide in 8L of ethyl acetate, filtering by a polyvinyl chloride ultrafiltration membrane, concentrating, filtering, and drying to obtain a refined product I;
and recrystallizing the refined product I, wherein 1.84L of recrystallization solvent is prepared from polar solvent ethyl acetate: n-propanol: isopropyl ether =1:0.3:1, obtaining a refined product II;
through detection and analysis, the purity of the glycolide is 99.93%, and the yield is 92.1%.
Example 3
The processing technique and the operating conditions are the same as those of the example 1, except that:
dissolving crude glycolide 476g in acetone 4.8L, filtering with nylon microporous membrane with pore diameter of 0.22 μm, concentrating, and filtering to obtain refined product I;
and recrystallizing the refined product I, wherein the recrystallization solvent is 1.19L, and the volume ratio of the solvents is acetone: isopropyl alcohol: methyl tert-butyl ether =0.8:1:1.1, obtaining a refined product II;
through detection and analysis, the purity of the glycolide is 99.95%, and the yield is 89.6%.
Example 4
The processing technique and the operating conditions are the same as those of the example 1, except that:
dissolving 530g of crude glycolide in a mixed solvent of 2.8L of acetone and 2.5L of ethyl acetate, filtering with a polytetrafluoroethylene microporous membrane with the pore diameter of 0.45 mu m, concentrating, filtering, and drying to obtain a refined product I;
and recrystallizing the refined product I, and recrystallizing with 1.27L of a recrystallization solvent, wherein the volume ratio of the solvents is (acetone + ethyl acetate): isopropyl alcohol: tert-butyl ether = (0.5 + 0.5): 1.1:1.2, obtaining 485g of a refined product II; through detection and analysis, the purity of the glycolide is 99.88 percent, and the yield is 91.5 percent.
Example 5
The processing technique and the operating conditions are the same as those in embodiment 1, but the differences are that:
dissolving 573g of crude glycolide in 12L of ethyl acetate, filtering by a polyamide nanofiltration membrane, concentrating, filtering, and drying to obtain a refined product I;
and recrystallizing the refined product I, wherein 1.26L of recrystallization solvent is prepared, and the volume ratio of the solvents is ethyl acetate: n-propanol: methyl tert-butyl ether =0.9:1.2:1.2, obtaining a finished product II of a final product;
through detection and analysis, the purity of the glycolide is 99.97%, and the yield is 87.7%.
Example 6
The processing technique and the operating conditions are the same as those of embodiment 1, except that:
dissolving crude glycolide 670g in acetone 10L, filtering with polypropylene microporous membrane with pore diameter of 0.22 μm, concentrating, filtering, and drying to obtain refined product I;
and recrystallizing the refined product I, wherein the recrystallization solvent is 1.26L, and the volume ratio of the solvents is acetone: n-butanol: tertiary butyl ether =0.8:1:1.2, obtaining a refined product II;
through detection and analysis, the purity of the glycolide is 99.84%, and the yield is 93.3%.
Comparative example 1 (No Membrane separation treatment)
Adding 425g of crude glycolide and 3.4L of ethyl acetate into the reactor 1 at room temperature, heating to 65 ℃ from room temperature, mechanically stirring, and keeping for 45min after complete dissolution;
then gradually cooling to separate out a solid product, continuously cooling to 5 ℃ for crystallization for 6-8 h, centrifuging and filtering after crystallization is finished, using the filtered mother liquor for next crude product treatment, and heating the filter cake to be dried to constant weight in vacuum at 40 ℃ to obtain 388g of refined product I with the yield of 91.3%.
Adding 386g of the refined product I into a reactor, adding 400mL of ethyl acetate, heating the temperature from room temperature to 65 ℃, mechanically stirring, and keeping for 45min after complete dissolution;
then gradually cooling to separate out a solid product, adding 160mL of n-propanol and 420mL of isopropyl ether, stirring for 1h, continuously cooling to 5 ℃ for crystallization for 6-8 h, after complete crystallization, centrifuging, throwing and filtering, and drying a filter cake to constant weight under the conditions of-0.09MPa and 40 ℃ to obtain a white solid, namely a refined product II;
the detection shows that the yield of the refined product II is 359g, the yield is 93.0 percent, and the purity is 98.63 percent.
Note: when detecting a sample, the solution is in a slightly turbid state when dissolved, and the organic membrane is filtered for detection;
comparative example 2 (No secondary recrystallization step)
The treatment process and the operating conditions were the same as in example 1, except that:
dissolving 615g of crude glycolide in 8L of ethyl acetate, filtering by a polyacrylonitrile ultrafiltration membrane, concentrating, filtering, and drying to obtain a refined product I;
the purity of the glycolide is 95.08% and the yield is 94.9% through detection.
Comparative example 3 (Single recrystallization solvent)
The processing technique and the operating conditions are the same as those of the example 1, except that:
dissolving 378g of crude glycolide in 4L of ethyl acetate, filtering by a polypropylene membrane of 0.22 mu m, concentrating, filtering, and drying to obtain a refined product I;
recrystallizing the refined product I for 5 times, wherein the dosage of ethyl acetate is 350ml each time, and obtaining a refined product II;
through detection and analysis, the purity of the glycolide is 99.90%, and the yield is 57.7%.
Comparative example 4 (two recrystallization solvents)
The processing technique and the operating conditions are the same as those of the example 1, except that:
dissolving 403g of crude glycolide in 4.2L of ethyl acetate, filtering with a polyvinylidene fluoride membrane of 0.45 μm, concentrating, filtering, and drying to obtain refined product I;
and recrystallizing the refined product I for 4 times, wherein each time, the volume ratio of a recrystallization solvent is 500mL, and the volume ratio of the recrystallization solvent is ethyl acetate: isopropanol =1:0.8, obtaining a refined product II;
through detection and analysis, the purity of the glycolide is 99.95%, and the yield is 55.6%.
To more intuitively show our examples and comparative examples, we tabulate the data in the following table:
note: the processes of concentration, centrifugal filtration and drying of the refined product I obtained after membrane separation and filtration are called primary recrystallization;
as can be seen from comparative example 1, the purity was not 99.5% without membrane separation treatment; it can also be seen from comparative example 2 that it is difficult to achieve higher glycolide purity with a single membrane treatment, and neither can meet the polymerization requirements. As can be seen from comparative examples 3 and 4, although the purity of the obtained glycolide meets the polymerization requirement, the recrystallization times of the single or two recrystallization solvents are more, the yield is lower, the operation procedures are increased, and the production cost is undoubtedly increased.
The above embodiments are merely exemplary to illustrate the operation and efficacy of the present invention, and are not intended to limit the present invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes be covered by the claims without departing from the spirit and technical concept of the present invention.
Claims (10)
1. A method for refining glycolide, which is characterized by comprising the following steps:
s1: placing the crude glycolide into a reactor I at room temperature, adding a polar solvent I, stirring for 1 to 2h, and performing membrane treatment after complete dissolution to obtain a filtrate;
then, carrying out rotary evaporation and concentration on the filtrate, carrying out centrifugal filtration, and drying in vacuum to constant weight to obtain a refined product I;
s2: adding the refined product I into a reactor II, and adding a recrystallization solvent by two steps: adding a polar solvent II, heating to 60-70 ℃, stirring to completely dissolve the refined product I, maintaining for 15-60min after dissolution, and gradually cooling until the product is separated out; then adding a low-boiling point alcohol and a low-boiling point ether reagent, stirring for 0.5 to 1.5 hours, continuously cooling to 5 to 10 ℃, crystallizing for 6 to 8 hours, centrifuging and filtering after complete crystallization, and drying in vacuum to constant weight to obtain a refined product II.
2. The glycolide purification process according to claim 1 wherein the membrane treatment operation in step S1 is a process using N 2 Blowing and pressing the crude glycolide solution in the reactor I into a reactor II through a membrane device.
3. The method for purifying glycolide according to claim 1, wherein in step S1, the vacuum drying conditions are as follows: -0.07 to-0.1MPa, 30 to 50 ℃.
4. The method for purifying glycolide according to claim 1, wherein in step S1, the polar solvent I is at least one solvent selected from the group consisting of acetone, ethyl acetate, methylene chloride, chloroform, ethanol, dimethyl sulfoxide, N-dimethylformamide and N, N-dimethylacetamide.
5. The method for purifying glycolide according to claim 1, wherein in step S1, the mass of the polar solvent I is 5 to 50 times the mass of the crude glycolide.
6. The method for purifying glycolide according to claim 1, wherein the membrane used in the membrane treatment in step S1 is any one of a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, a permeation membrane, a reverse osmosis membrane, a metal or ceramic composite membrane;
the membrane material is any one of cellulose acetate, mixed cellulose ester, polyamide, nylon, polytetrafluoroethylene, polyvinyl chloride, polyvinylidene fluoride, polyacrylonitrile, polyether sulfone, polypropylene and metal and ceramic materials;
the aperture of the microporous filter membrane is 0.01 to 10 mu m.
7. The method for purifying glycolide as claimed in claim 1, wherein in the recrystallization solvent in step S2, the polar solvent ii is at least one of acetone, ethyl acetate, methylene chloride, chloroform, ethanol, and dimethyl sulfoxide.
8. The method for purifying glycolide as claimed in claim 1, wherein in the recrystallization solvent in step S2, the low-boiling alcohol reagent is at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, and t-butanol.
9. The method of purifying glycolide according to claim 1, wherein the low-boiling-point ether reagent in the recrystallization solvent in step S2 is at least one of diethyl ether, petroleum ether, isopropyl ether, n-butyl ether, tetrahydrofuran, t-butyl ether, and methyl t-butyl ether.
10. The method for purifying glycolide according to claim 1, wherein the amount of the recrystallization solvent is 1.5 to 5.3 times the mass of the purified product I;
and (3) a polar solvent II in the recrystallization solvent: alcohol reagents: the volume ratio of the ether reagent is 0.5 to 1.2:0.1 to 2:0.5 to 2.2.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100999516A (en) * | 2006-01-12 | 2007-07-18 | 中南大学 | Purifying process of glycolide |
| CN101054371A (en) * | 2007-05-24 | 2007-10-17 | 复旦大学 | Preparation method for glycolide |
| CN113135889A (en) * | 2021-03-29 | 2021-07-20 | 中国神华煤制油化工有限公司 | Process for purifying crude cyclic esters |
| CN114014836A (en) * | 2021-12-16 | 2022-02-08 | 内蒙古久泰新材料有限公司 | Method for purifying cyclic lactide |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100999516A (en) * | 2006-01-12 | 2007-07-18 | 中南大学 | Purifying process of glycolide |
| CN101054371A (en) * | 2007-05-24 | 2007-10-17 | 复旦大学 | Preparation method for glycolide |
| CN113135889A (en) * | 2021-03-29 | 2021-07-20 | 中国神华煤制油化工有限公司 | Process for purifying crude cyclic esters |
| CN114014836A (en) * | 2021-12-16 | 2022-02-08 | 内蒙古久泰新材料有限公司 | Method for purifying cyclic lactide |
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