CN116041177A - Method for preparing R-3-hydroxybutyrate by degrading poly-3-hydroxybutyrate by recycling alcohol-trifluoroacetic acid solvent system - Google Patents

Method for preparing R-3-hydroxybutyrate by degrading poly-3-hydroxybutyrate by recycling alcohol-trifluoroacetic acid solvent system Download PDF

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CN116041177A
CN116041177A CN202211510662.4A CN202211510662A CN116041177A CN 116041177 A CN116041177 A CN 116041177A CN 202211510662 A CN202211510662 A CN 202211510662A CN 116041177 A CN116041177 A CN 116041177A
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hydroxybutyrate
trifluoroacetic acid
poly
alcohol
solvent system
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康世民
黄子稚
何伟鑫
袁皓俊
罗芷菁
徐勇军
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Dongguan New Energy Research Institute
Dongguan University of Technology
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Dongguan University of Technology
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    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C67/00—Preparation of carboxylic acid esters
    • C07C67/03—Preparation of carboxylic acid esters by reacting an ester group with a hydroxy group
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
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    • C07C67/52—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation
    • C07C67/54—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation by distillation
    • C—CHEMISTRY; METALLURGY
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    • C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
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    • C07B2200/07—Optical isomers
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Abstract

The invention belongs to the technical field of degradation and utilization of poly 3-hydroxybutyrate, and relates to a method for preparing R-3-hydroxybutyrate by degrading poly 3-hydroxybutyrate by recycling an alcohol-trifluoroacetic acid solvent system. The method comprises the following steps: and mixing poly 3-hydroxybutyrate, alcohol and trifluoroacetic acid solution, and then carrying out reaction, wherein after the reaction is finished, separation of a product and a solvent and solvent recovery are realized through a two-step distillation process. Solves the technical problems of more post-treatment process steps, more types of required chemicals, high energy consumption, difficult recycling of catalyst and high cost existing in the preparation of R-3-hydroxybutyrate by degrading poly-3-hydroxybutyrate in the prior art, realizes the preparation and separation of reaction products without introducing additional chemical reagents, obtains the R-3-hydroxybutyrate compound product by only two-step distillation process and realizes the efficient recycling of a catalytic solvent system, has the characteristics of simple process and convenient operation, and has potential industrialized application value.

Description

Method for preparing R-3-hydroxybutyrate by degrading poly-3-hydroxybutyrate by recycling alcohol-trifluoroacetic acid solvent system
Technical Field
The invention belongs to the technical field of degradation and utilization of poly 3-hydroxybutyrate, and relates to a method for preparing R-3-hydroxybutyrate by degrading poly 3-hydroxybutyrate by recycling an alcohol-trifluoroacetic acid solvent system.
Background
Poly (3-hydroxybutyrate) is a bio-polyester produced by microorganisms and is a green renewable resource. The degradation of poly-3-hydroxybutyrate to synthesize high value chiral chemicals based on the unique structure of poly-3-hydroxybutyrate (R-3-hydroxybutyrate as its structural monomer) has attracted considerable attention. Wherein, the poly 3-hydroxybutyrate can be degraded into R-3-hydroxybutyrate compounds (such as R-3-hydroxybutyrate methyl ester and R-3-hydroxybutyrate ethyl ester) with chiral functional groups in an alcohol solvent. The R-3-hydroxybutyrate compounds have important application value, such as R-3-hydroxybutyrate methyl ester is a raw material for synthesizing a glaucoma drug carbonic anhydrase inhibitor, and is also considered to have a certain therapeutic effect on neurodegenerative diseases (such as Alzheimer disease). In addition, methyl R-3-hydroxybutyrate is also a potentially renewable liquid oxy fuel.
The R-3-hydroxybutyrate compound can be obtained by heating and reacting poly-3-hydroxybutyrate in an alcohol solution system by using an acid catalyst. The acid catalyst is sulfuric acid, however, sulfuric acid has high boiling point and oxidizing property, which makes the separation and purification of the product after the reaction difficult. In general, sulfuric acid after reaction is difficult to separate and recycle, and a large amount of alkali solution is needed for neutralization treatment (a large amount of water is introduced and a large amount of sulfate is generated in the process), so that environmental problems are caused, and additional raw material cost and product separation process cost are caused. Hydrochloric acid is also a relatively common acid catalyst in poly-3-hydroxybutyrate alcoholysis. Poly (3-hydroxybutyrate) is dissolved in 1, 2-dichloroethane, methanol and hydrochloric acid solution system for reaction, for example, lee et al, the obtained product is washed with half saturated sodium chloride aqueous solution, saturated sodium bicarbonate aqueous solution and saturated sodium chloride aqueous solution in this order, the obtained aqueous phase is extracted twice with methylene chloride, and the combined extract is added to an organic layer to be dried over magnesium sulfate, and R-3-hydroxybutyrate (Lee et al preparation of alkyl (R) - (-) -3-hydroxybutyrate by acidic alcoholysis of poly- (R) - (-) -3-hydroxybutyrate) [ J ]. Enzyme and microbial technology,2000,27 (1-2): 33-36.) is prepared by rotary evaporation and vacuum distillation. The catalytic system used in this document, although capable of preparing R-3-hydroxybutyrate, has the following problems with this post-reaction treatment process: (1) The catalyst hydrochloric acid is difficult to recycle, and (2) alkaline substances are needed to be neutralized in the post-treatment process, so that the cost of chemical reagents is additionally increased; (3) The post-treatment process requires multiple water washes, which can lead to a large amount of wastewater; (4) The washed product is additionally added with an organic solvent dichloromethane for extraction, so that the solvent cost is increased; (5) The post-treatment process requires multiple washing, multiple extraction, drying and other separation and purification steps, so that the energy consumption and equipment investment of the process are increased.
For example, CN113416130A discloses a method for preparing R-3-methyl hydroxybutyrate, which takes polyhydroxyalkanoate as a raw material and takes a mixed solution of methanesulfonic acid/methyl methanesulfonate and methanol as a solvent, and the mixed solution reacts for 3-72 hours at 50-100 ℃ to prepare the R-3-methyl hydroxybutyrate. In a methyl methanesulfonate solvent system, the obtained reaction product is subjected to reduced pressure distillation at 45 ℃ to recover methanol, then is subjected to reduced pressure distillation at 70-110 ℃ to recover R-3-hydroxybutyrate, and finally the residual liquid is methyl methanesulfonate solvent which can be reused. However, although the patent realizes the recycling of the solvent, when the mixed solution of the methanesulfonic acid/the methanesulfonic acid methyl ester and the methanol is the solvent, the viscosity is larger, the stirring is not easy in the reaction process, the methanol is firstly recovered through reduced pressure distillation at 45 ℃ after the reaction is finished, then the product R-3-hydroxybutyric acid methyl ester is recovered through reduced pressure distillation at 70-110 ℃, finally the residual liquid is the methanesulfonic acid methyl ester solvent, impurities are easy to remain in the final solvent in the process, the solvent recovery is further troublesome, and the methanesulfonic acid methyl ester used in the process is a 2A type carcinogen, and the hazard is larger.
Therefore, the development process is simple, the operation is convenient, and the catalyst and the solvent can be recycled, so that the method has important significance in converting the poly-3-hydroxybutyrate into the R-3-hydroxybutyrate compound.
Disclosure of Invention
Aiming at the technical problems of more post-treatment process steps, more types of required chemicals, high energy consumption, difficult recycling of catalyst and high cost existing in the prior art when the poly-3-hydroxybutyrate is degraded to prepare the R-3-hydroxybutyrate, the invention provides a method for preparing the R-3-hydroxybutyrate by recycling an alcohol-trifluoroacetic acid solvent system. According to the invention, poly-3-hydroxybutyrate is converted into the R-3-hydroxybutyrate compound, so that the preparation and separation processes of reaction products are realized, the R-3-hydroxybutyrate compound product is obtained only through a two-step distillation process without introducing additional chemical reagents, the efficient recycling of a catalytic solvent system is realized, and the method has the characteristics of simple process and convenient operation, and represents potential industrial application value.
In order to achieve the above purpose, the technical scheme of the invention is realized as follows:
the method for preparing R-3-hydroxybutyrate by degrading poly-3-hydroxybutyrate by recycling alcohol-trifluoroacetic acid solvent system comprises the steps of adding poly-3-hydroxybutyrate, alcohol (methanol or ethanol) and trifluoroacetic acid solution into a reactor, and then reacting for 3-36 h at 80-120 ℃. Product separation is achieved by two-step distillation based on the difference in boiling points between the solvent system (mixed solution of alcohol and trifluoroacetic acid) and the target product (R-3-hydroxybutyrate). The solvent system (alcohol and trifluoroacetic acid mixed solution) is distilled and recovered at normal pressure at 60-90 ℃ and then decompressed (1X 10) at 50-100 DEG C 4 ～1×10 3 Pa) distilling to recover the R-3-hydroxybutyrate compound.
The mass volume ratio of the poly 3-hydroxybutyrate to the alcohol to the trifluoroacetic acid is 1g (4-5) mL (4-6) mL.
The alcohol and trifluoroacetic acid mixed solution obtained by atmospheric distillation can be continuously used as a solvent system to develop poly-3-hydroxybutyrate to prepare the R-3-hydroxybutyrate compound.
The solvent system used in the invention is a mixed solution of alcohol (methanol or ethanol) and trifluoroacetic acid, the solvent system can be recovered by simple distillation, and other strong acid catalysts (such as sulfuric acid, hydrochloric acid and the like) are not needed to be specially added in the reaction process. In this reaction system, trifluoroacetic acid is both a low boiling point solvent (boiling point 72.4 ℃) and a strong carboxylic acid catalyst (pka=0.23). Under the condition of heating, the presence of trifluoroacetic acid accelerates the dissolution of poly-3-hydroxybutyrate, and meanwhile, the strong acid property of the trifluoroacetic acid catalyzes the alcoholysis reaction of poly-3-hydroxybutyrate and alcohol (methanol or ethanol), so that the corresponding R-3-hydroxybutyrate compound is generated. After the reaction was completed, the reaction solution included a low boiling point solvent (trifluoroacetic acid having a boiling point of 72.4 ℃, methanol having a boiling point of 64.8 ℃ or ethanol having a boiling point of 78.3 ℃) and a relatively high boiling point of R-3-hydroxybutyrate (methyl R-3-hydroxybutyrate having a boiling point of 161.9 ℃ and ethyl R-3-hydroxybutyrate having a boiling point of 175 ℃). Because the boiling points of the solvent and the product are greatly different, the solvent system and the R-3-hydroxybutyrate compound can be orderly recovered in sequence by a simple fractional distillation mode.
The invention has the following beneficial effects:
1. the trifluoroacetic acid used in the invention is used as a reaction solvent and a catalyst, and any other acid catalyst is not needed to be added in the reaction process. And the solvent system in the invention is low-boiling trifluoroacetic acid and alcohol, and recovery and recycling can be realized through simple distillation.
2. Compared with the prior art, the invention does not need to add an alkaline neutralizer, water washing, drying agent to dry the product, extraction separation by introducing other solvents and the like in the post-treatment process of the reaction. In the invention, only poly 3-hydroxybutyrate (raw material) and solvent system (alcohol and trifluoroacetic acid) are needed as chemicals from reaction to separation to obtain the R-3-hydroxybutyrate product, and the raw material types of the needed chemicals are greatly reduced, and meanwhile, the process steps are greatly simplified and the energy consumption is reduced.
3. The invention solves the problems that the traditional acid catalyst cannot be recycled, the post-treatment process has multiple steps, high energy consumption and the post-treatment requires various additional chemicals, establishes a scheme system which has simple process, convenient operation, recoverable and reusable solvent and has good technical application prospect, and other additional chemicals are not required to be introduced in the separation process. In addition, the yield of the R-3-hydroxybutyric acid methyl ester produced after the reaction of the poly-3-hydroxybutyric acid ester of the present invention can reach 113wt% based on the mass of the raw material poly-3-hydroxybutyric acid ester.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 shows a reaction scheme of poly (3-hydroxybutyrate) in a methanol-trifluoroacetic acid solution in accordance with the present invention.
FIG. 2 is a sample of the colorless transparent solution obtained in example 1 of the present invention.
FIG. 3 is a GC-MS qualitative analysis chart of the reaction solution of example 1 of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without any inventive effort, are intended to be within the scope of the invention.
Example 1
The method for preparing R-3-hydroxybutyrate by degrading poly-3-hydroxybutyrate by recycling alcohol-trifluoroacetic acid solvent system (the reaction flow of poly-3-hydroxybutyrate in methanol-trifluoroacetic acid solution is shown in figure 1) comprises the following steps:
(1) 1g of poly 3-hydroxybutyrate, 5mL of methanol and 5mL of trifluoroacetic acid were added to 15mL of a glass-digested tube with a sealing stopper, and the glass-digested tube was sealed. The glass digestion tube was heated to 100℃and reacted at 100℃for 7 hours to obtain a colorless transparent solution (see FIG. 2), and after the treatment of the obtained solution (neutralization of trifluoroacetic acid), GC-MS qualitative analysis (see FIG. 3) and GC-FID quantitative analysis were performed to detect that methyl R-3-hydroxybutyrate was produced and its yield was as high as 113% by weight (based on the mass of the starting poly-3-hydroxybutyrate).
(2) Gradually heating and distilling the reaction solution obtained in the step (1) at 60-85 ℃ under normal pressure (firstly, evaporating most of the solvent at 60 ℃ and slowly heating to 85 ℃ to evaporate the solvent), and then recovering to obtain reaction solvent (trifluoroacetic acid and methanol); the remaining liquid was then subjected to reduced pressure (1X 10) 4 ～1×10 3 Pa) and gradually heating to distill (firstly, steaming at 50 ℃ and then slowly heating to 90 ℃ to distill), thus obtaining the R-3-hydroxybutyric acid methyl ester.
(3) And recycling the obtained reaction solvent. Adding the reaction solvent obtained in the step (2) and 0.5g of poly (3-hydroxybutyrate) into a 10mL glass digestion tube with a sealing plug, repeating the step (1) and the step (2), and reacting to obtain R-3-hydroxybutyrate methyl ester; and the separation of the methyl R-3-hydroxybutyrate and the reaction solvent (trifluoroacetic acid and methanol) was achieved by two-step distillation. Also, the reaction solvent (trifluoroacetic acid and methanol) recovered for the second time can be reused for the poly 3-hydroxybutyrate catalytic degradation reaction again.
Example 2
The method for preparing the R-3-hydroxybutyrate by degrading the poly-3-hydroxybutyrate by recycling the alcohol-trifluoroacetic acid solvent system comprises the following steps:
(1) 1g of poly 3-hydroxybutyrate, 4mL of methanol and 4mL of trifluoroacetic acid were added to 15mL of a glass-digested tube with a sealing stopper, and the glass-digested tube was sealed. The glass digestion tube was heated to 120℃and reacted at 120℃for 3 hours to obtain a colorless transparent homogeneous solution, and the obtained homogeneous solution was treated and subjected to GC-MS qualitative analysis and GC-FID quantitative analysis to detect that methyl R-3-hydroxybutyrate was produced and that the yield was 95% by weight (based on the mass of the raw material poly-3-hydroxybutyrate).
(2) Gradually heating and distilling the reaction solution obtained in the step (1) at 60-85 ℃ under normal pressure (firstly, evaporating most of the solvent at 60 ℃ and slowly heating to 85 ℃ to evaporate the solvent), and then recovering to obtain reaction solvent (trifluoroacetic acid and methanol); the remaining liquid was then subjected to reduced pressure (1X 10) 4 ～1×10 3 Pa) and gradually heating to distill (firstly, steaming at 50 ℃ and then slowly heating to 90 ℃ to distill), thus obtaining the R-3-hydroxybutyric acid methyl ester.
Example 3
The method for preparing the R-3-hydroxybutyrate by degrading the poly-3-hydroxybutyrate by recycling the alcohol-trifluoroacetic acid solvent system comprises the following steps:
(1) 1g of poly 3-hydroxybutyrate, 4mL methanol and 6mL trifluoroacetic acid were added to a 15mL glass digestion tube with a sealing stopper, and the glass digestion tube was sealed. The glass digestion tube was heated to 80℃and reacted at 80℃for 36 hours to obtain a colorless transparent homogeneous solution, and the obtained homogeneous solution was treated and subjected to GC-MS qualitative analysis and GC-FID quantitative analysis to detect that methyl R-3-hydroxybutyrate was produced and that the yield was 101% by weight (based on the mass of the raw material poly-3-hydroxybutyrate).
(2) Gradually heating and distilling the reaction solution obtained in the step (1) at 60-85 ℃ under normal pressure (firstly, evaporating most of the solvent at 60 ℃ and slowly heating to 85 ℃ to evaporate the solvent), and then recovering to obtain reaction solvent (trifluoroacetic acid and methanol); the remaining liquid was then subjected to reduced pressure (1X 10) 4 ～1×10 3 Pa) and gradually heating to distill (firstly, steaming at 50 ℃ and then slowly heating to 90 ℃ to distill), thus obtaining the R-3-hydroxybutyric acid methyl ester.
Example 4
The method for preparing the R-3-hydroxybutyrate by degrading the poly-3-hydroxybutyrate by recycling the alcohol-trifluoroacetic acid solvent system comprises the following steps:
(1) 1g of poly 3-hydroxybutyrate, 5mL ethanol and 5mL trifluoroacetic acid were added to 15mL glass-digested tube with a sealing stopper, and the glass-digested tube was sealed. The glass digestion tube was heated to 100℃and reacted at 100℃for 12 hours to obtain a colorless transparent homogeneous solution, and the obtained homogeneous solution was treated and subjected to GC-MS qualitative analysis and GC-FID quantitative analysis, and the reaction was detected to produce ethyl R-3-hydroxybutyrate in a yield of 112% by weight (calculated based on the mass of the starting poly-3-hydroxybutyrate).
(2) Gradually heating and distilling the reaction solution obtained in the step (1) at 60-90 ℃ under normal pressure (firstly, evaporating most of the solvent at 60 ℃ and slowly heating to 90 ℃ to evaporate the solvent), and then recovering to obtain reaction solvent (trifluoroacetic acid and ethanol); the remaining liquid was then subjected to reduced pressure (1X 10) 4 ～1×10 3 Pa) and gradually heating and distilling (firstly, starting to evaporate at 55 ℃ and then slowly heating to 100 ℃ to evaporate) to obtain the R-3-ethyl hydroxybutyrate.
Example 5
The method for preparing the R-3-hydroxybutyrate by degrading the poly-3-hydroxybutyrate by recycling the alcohol-trifluoroacetic acid solvent system comprises the following steps:
(1) 1g of poly 3-hydroxybutyrate, 4mL ethanol and 4mL trifluoroacetic acid were added to 15mL glass-digested tube with a sealing stopper, and the glass-digested tube was sealed. The glass digestion tube was heated to 100℃and reacted at 120℃for 6 hours to obtain a colorless transparent homogeneous solution, and the obtained homogeneous solution was treated and subjected to GC-MS qualitative analysis and GC-FID quantitative analysis, and the reaction was detected to produce ethyl R-3-hydroxybutyrate in a yield of 106% by weight (calculated based on the mass of the starting poly-3-hydroxybutyrate).
(2) Gradually heating and distilling the reaction solution obtained in the step (1) at 60-90 ℃ under normal pressure (firstly, evaporating most of the solvent at 60 ℃ and slowly heating to 90 ℃ to evaporate the solvent), and then recovering to obtain reaction solvent (trifluoroacetic acid and ethanol); the remaining liquid was then subjected to reduced pressure (1X 10) 4 ～1×10 3 Pa) and gradually heating and distilling (firstly, starting to evaporate at 55 ℃ and then slowly heating to 100 ℃ to evaporate) to obtain the R-3-ethyl hydroxybutyrate.
Example 6
The method for preparing the R-3-hydroxybutyrate by degrading the poly-3-hydroxybutyrate by recycling the alcohol-trifluoroacetic acid solvent system comprises the following steps:
(1) 1g of poly 3-hydroxybutyrate, 4mL ethanol and 4mL trifluoroacetic acid were added to 15mL glass-digested tube with a sealing stopper, and the glass-digested tube was sealed. The glass digestion tube was heated to 90℃and reacted at 90℃for 36 hours to obtain a colorless transparent homogeneous solution, and the obtained homogeneous solution was treated and subjected to GC-MS qualitative analysis and GC-FID quantitative analysis, and the reaction was detected to produce ethyl R-3-hydroxybutyrate in a yield of 96% by weight (calculated based on the mass of the starting poly-3-hydroxybutyrate).
(2) Gradually heating and distilling the reaction solution obtained in the step (1) at 60-90 ℃ under normal pressure (firstly, evaporating most of the solvent at 60 ℃ and slowly heating to 90 ℃ to evaporate the solvent), and then recovering to obtain reaction solvent (trifluoroacetic acid and methanol); the remaining liquid was then subjected to reduced pressure (1X 10) 4 ～1×10 3 Pa) and gradually heating and distilling (firstly, starting to evaporate at 55 ℃ and then slowly heating to 100 ℃ to evaporate) to obtain the R-3-ethyl hydroxybutyrate.
Comparative example 1
The procedure of example 1 was repeated except that formic acid was used instead of trifluoroacetic acid, and that methyl R-3-hydroxybutyrate was not produced after detection.
Comparative example 2
The trifluoroacetic acid in example 2 was replaced with acetic acid, and the other steps were exactly the same as in example 2, and no formation of methyl R-3-hydroxybutyrate was found.
Comparative example 3
The trifluoroacetic acid in example 3 was replaced with chloroacetic acid, and the other steps were exactly the same as in example 3, and no formation of methyl R-3-hydroxybutyrate was found to occur.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.

Claims (10)

1. The method for preparing R-3-hydroxybutyrate by degrading poly-3-hydroxybutyrate by recycling alcohol-trifluoroacetic acid solvent system is characterized by comprising the following steps: and mixing poly 3-hydroxybutyrate, alcohol and trifluoroacetic acid, and then carrying out reaction, wherein after the reaction is finished, separation of a product and a solvent and solvent recovery are realized through a two-step distillation process.
2. The method for preparing R-3-hydroxybutyrate by degrading poly-3-hydroxybutyrate using alcohol-trifluoroacetic acid solvent system according to claim 1, wherein the method comprises the steps of: the alcohol is methanol or ethanol.
3. The process for preparing R-3-hydroxybutyrate by degrading poly-3-hydroxybutyrate using a cyclic utilization alcohol-trifluoroacetic acid solvent system according to claim 1 or 2, wherein: the mass volume ratio of the poly 3-hydroxybutyrate to the alcohol to the trifluoroacetic acid is 1g (4-5) mL (4-6) mL.
4. The process for preparing R-3-hydroxybutyrate by degrading poly-3-hydroxybutyrate using a cyclic utilization alcohol-trifluoroacetic acid solvent system according to claim 1 or 2, wherein: the temperature of the reaction is 80-120 ℃.
5. The method for preparing R-3-hydroxybutyrate by degrading poly-3-hydroxybutyrate using an alcohol-trifluoroacetic acid solvent system according to claim 4, wherein the method comprises the steps of: the reaction time is 3-36 h.
6. The method for preparing R-3-hydroxybutyrate by degrading poly-3-hydroxybutyrate using alcohol-trifluoroacetic acid solvent system according to claim 1,2 or 5, wherein the first distillation process of the two-step distillation process is: and (3) carrying out normal pressure distillation at 60-90 ℃ to recover a solvent system, wherein the solvent system is a mixed solution of trifluoroacetic acid and alcohol.
7. The method for preparing R-3-hydroxybutyrate by degrading poly-3-hydroxybutyrate using alcohol-trifluoroacetic acid solvent system according to claim 6, wherein the second distillation process of the two-step distillation process is: and (3) carrying out reduced pressure distillation at 50-100 ℃ to obtain the product.
8. The method for preparing R-3-hydroxybutyrate by degrading poly-3-hydroxybutyrate using an alcohol-trifluoroacetic acid solvent system according to claim 7, wherein the method comprises the steps of: the pressure of the reduced pressure distillation is 1×10 4 ～1×10 3 Pa。
9. The process for preparing R-3-hydroxybutyrate from poly-3-hydroxybutyrate using the cyclic utilization of an alcohol-trifluoroacetic acid solvent system according to any one of claims 1,2, 5, 7 or 8, wherein: the product is R-3-hydroxybutyrate, including R-3-hydroxybutyrate methyl or R-3-hydroxybutyrate ethyl.
10. The method for preparing R-3-hydroxybutyrate by degrading poly-3-hydroxybutyrate using an alcohol-trifluoroacetic acid solvent system according to claim 9, wherein the method comprises the steps of: the yield of the product R-3-hydroxybutyrate is 96 to 113wt% based on the mass of the poly-3-hydroxybutyrate.
CN202211510662.4A 2022-11-29 2022-11-29 Method for preparing R-3-hydroxybutyrate by degrading poly-3-hydroxybutyrate by recycling alcohol-trifluoroacetic acid solvent system Pending CN116041177A (en)

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