Method for catalyzing and depolymerizing polylactic acid and analogue thereof by magnesium catalysis system
阅读说明：本技术 一种镁催化体系催化解聚聚乳酸及其类似物的方法 (Method for catalyzing and depolymerizing polylactic acid and analogue thereof by magnesium catalysis system ) 是由 王庆刚 徐广强 周先悦 于 2021-09-08 设计创作，主要内容包括：本发明公开了一种镁催化体系催化解聚聚乳酸及其类似物的方法,属于聚酯解聚技术领域。本发明是在双(六甲基二硅基氮烷)镁或二丁基镁催化剂催化下,在醇类化合物参与下实现聚乳酸及其类似物的醇解获得有机小分子,从而实现废弃聚乳酸及其类似物的有效利用。本发明采用结构简单绿色环保的镁催化剂催化,工艺绿色环保,在温和条件下即可高效进行反应,且该催化剂具有很好的普适性,对于各种不同结构的聚乳酸及其类似物材料均具有很好的解聚效果。(The invention discloses a method for catalyzing and depolymerizing polylactic acid and an analogue thereof by a magnesium catalysis system, belonging to the technical field of polyester depolymerization. The invention realizes alcoholysis of polylactic acid and analogues thereof under the catalysis of bis (hexamethyldisilazane) magnesium or dibutyl magnesium catalyst and the participation of alcohol compounds to obtain organic micromolecules, thereby realizing effective utilization of the waste polylactic acid and analogues thereof. The catalyst has good universality, and has good depolymerization effect on polylactic acid and similar materials with various different structures.)
1. A method for catalytic depolymerization of polylactic acid and its analogues by magnesium catalytic system features that under normal pressure and protection of inertial gas and at a certain temp, the polylactic acid or its analogues is used as polymerizing unit, and under the condition of organic solvent or no solvent, magnesium Mg [ N (SiMe) is added3)2]2Or dibutyl magnesium MgBu2The polymerization unit is catalyzed and depolymerized in alcohol compounds under the catalysis of a catalyst.
2. The method of claim 1, wherein the polymerization unit is one or more of the following structures:
wherein R is1、R2Is hydrogen, alkyl, alkoxy, aryl or halogen atom, and n is 1 or more.
3. The method of claim 1, wherein the number average molecular weight of the polymeric unit is 102～107g/mol。
4. The method of claim 1, wherein the alcohol compound is one or more than two of C1-C50 alcohols mixed at any ratio.
5. The method of claim 4, wherein the alcohol compound is one or more of methanol, ethanol, isopropanol, butanol, tert-butanol, benzyl alcohol, and phenylpropanol, and is mixed at any ratio.
6. The method of claim 1 or 4, wherein the alcohol compound is methanol.
7. The method of claim 1, wherein the organic solvent is one or more of benzene, toluene, xylene, dichloromethane and tetrahydrofuran, and is mixed at any ratio.
8. The method for controllably depolymerizing polylactic acid and analogues thereof by using the magnesium catalyst system according to claim 1, wherein the amount of the catalyst is 0.1-10 wt% of the polymerization unit.
9. The method of claim 1, wherein the temperature is 20-200 ℃.
10. The method of claim 1, wherein the inert gas is argon or nitrogen.
Technical Field
The invention relates to a method for catalyzing and depolymerizing polylactic acid and an analogue thereof by a magnesium catalysis system, belonging to the technical field of polyester depolymerization.
Background
Aliphatic polyester-based biomass materials, which are perfect substitutes for petroleum-derived materials, can be produced by biological photosynthesis from carbon dioxide, water and sunlight available in the atmosphere, have been used for the production of fuels and fine chemicals with the goal of achieving zero net carbon emissions. Polyester materials are widely used in packaging materials and pharmaceutical industry due to their biocompatibility and degradability, particularly polylactic acid materials. And therefore has received increasing attention worldwide. However, mass production of polylactic acid materials also raises concerns about post-treatment of waste polyester. Although polylactic acid, as a degradable polymer, is capable of degrading into carbon dioxide and water, this usually requires certain harsh environmental conditions and is time consuming. The method for efficiently and conveniently realizing the post-treatment of the polylactic acid material is an environmental problem which needs to be solved at present.
At present, the methods for recycling the polymer mainly comprise high-temperature pyrolysis, hydrolysis, an enzymolysis method and the like. However, pyrolysis and hydrolysis usually require high temperature, so that more energy is consumed, and the operation cost is increased; the enzymolysis method has specificity, can only depolymerize certain specific polyester materials, and has certain limitation. Another chemical recycling method is to alcoholyze the polyester into small organic molecules by transesterification with alcohol. The method can realize depolymerization of the polymer and complete post-treatment of the waste polymer, and simultaneously, the generated alcoholysis product is effectively utilized as a useful chemical so as to change the waste polymer into valuables, and the method conforms to the principle of sustainable development, thereby having important research significance.
There are only few reports on transesterification and alcoholysis of polylactic acid. Enthaler et al reported a method of depolymerisation of polylactide using stannous octoate catalysis (Polymer. chem., 2020, 11, 2625-2629) by microwave heating to 160 ℃ in the presence of methanol to depolymerise the polylactide to methyl lactate. However, metallic tin has some toxicity, and the high temperature condition causes the production cost to be increased.
Therefore, for the post-treatment of the waste polyester material, the cyclic utilization of the polymer through alcoholysis has a plurality of advantages, but a simple, efficient, green and environment-friendly catalytic system is urgently needed, so that the depolymerization of the polyester material can be rapidly realized under mild conditions. This is of great significance for environmental protection and sustainable development.
Disclosure of Invention
The invention provides a method for catalyzing and depolymerizing polylactic acid and analogues thereof by using a magnesium catalytic system, aiming at solving the technical problems in the prior art.
The technical scheme of the invention is as follows:
a process for preparing the polylactic acid or its analog by catalytic depolymerizing in Mg-catalyst system includes such steps as polymerizing under the protection of inertial gas and at a certain temp and under the condition of organic solvent or no solvent in bis (hexamethyldisilazane) Mg [ N (SiMe)3)2]2Or dibutyl magnesium MgBu2The polymerization unit is catalyzed and depolymerized in alcohol compounds under the catalysis of a catalyst.
Further defined, the polymerized units are one or more of the following structures:
wherein R is1、R2Is hydrogen, alkyl, alkoxy, aryl or halogen atom, and n is 1 or more.
Further defined, the number average molecular weight of the polymerized units is 102～107g/mol。
Further, the alcohol compound is one or more of C1-C50 alcohol and is mixed in any proportion.
Further, the alcohol compound is one or more of methanol, ethanol, isopropanol, butanol, tert-butanol, benzyl alcohol, and phenylpropanol, and is mixed at any ratio.
More particularly, the alcohol compound is methanol.
Further limit, the organic solvent is one or more than two of benzene, toluene, xylene, dichloromethane and tetrahydrofuran which are mixed in any proportion.
Further, the amount of the catalyst added is 0.1 to 10 wt% based on the polymerization unit.
Further limiting, the temperature is 20-200 ℃.
Further defined, the inert gas is argon or nitrogen.
The invention has the following beneficial effects:
(1) the catalyst adopted by the invention is a bis (hexamethyldisilazane) magnesium or dibutyl magnesium catalyst with simple and green structure, and can depolymerize polylactic acid and analogues thereof into small organic molecules under mild conditions through ester exchange reaction catalyzed by the catalyst in the presence of alcohol compounds, thereby realizing reutilization of the waste polylactic acid and conforming to the principle of sustainable development.
(2) The invention adopts the magnesium catalyst with simple structure to catalyze the depolymerization of polylactic acid and the like, and the magnesium metal is nontoxic, colorless, cheap and easy to obtain, has good biocompatibility, and ensures that the production process is more green and environment-friendly; and the catalyst has a simple structure and few synthesis steps, so that the production cost is more economic.
(3) The catalytic system adopted by the invention has good universality and good depolymerization effect on polylactic acid and analogues thereof with various structures.
Drawings
FIG. 1 is a nuclear magnetic spectrum of a depolymerization product of polylactic acid of example 2;
FIG. 2 shows the states of the respective stages in the depolymerization process of polylactic acid in example 2.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The experimental procedures used in the following examples are conventional unless otherwise specified. The materials, reagents, methods and apparatus used, unless otherwise specified, are conventional in the art and are commercially available to those skilled in the art.
Example 1:
depolymerization of polylactic acid
The experimental process comprises the following steps:
a5 mL Schlenk flask was charged, vacuum-baked, and purged with argon, and then 288mg of polylactic acid (M) was added to the flaskn26000g/mol, PDI 1.09), then 3.8Mg of Mg [ N (SiMe) is added3)2]2The catalyst was added to 2mL of methanol and 2mL of methylene chloride outside the glove box, and the mixture was stirred at room temperature to react. After the reaction is carried out for 1.5h, nuclear magnetic detection is carried out on the reaction system, the conversion rate of the polymer is 99%, and the obtained alcoholysis product is methyl lactate.
Example 2:
depolymerization of polylactic acid
The experimental process comprises the following steps:
a500 mL three-necked flask was taken, vacuum-baked and purged with argon, and then 16.32g of a commercial polylactic acid product (manufacturer: Nigaku, Shuangtong Daiki Co., Ltd.; diameter: 12mm) was put into a glove box, followed by 1.15g of Mg [ N (SiMe)3)2]2113mL of methanol and 113mL of methylene chloride were added to the outside of the glove box as a catalyst, and the reaction was stirred at room temperature. After reacting for 2 hours, nuclear magnetic detection is carried out on the reaction system, the conversion rate of the polymer is 99%, and the obtained alcoholysis product is methyl lactate. The remaining methanol was removed by distillation to obtain 20.84g of methyl lactate in 80% yield.
Example 3:
depolymerization of polylactic acid
The experimental process comprises the following steps:
a5 mL Schlenk flask was charged with 144mg of polylactic acid (M) in a glove box after evacuating and replacing argon gasn11300g/mol, PDI 1.17), then 7.0Mg of Mg [ N (SiMe) was added3)2]2The catalyst is arranged outside the glove box,1mL of methanol was added, and the reaction was stirred at room temperature. After reacting for 2h, nuclear magnetic detection is carried out on the reaction system, the conversion rate of the polymer is 99%, and the obtained alcoholysis product is methyl lactate.
Example 4:
depolymerization of polylactic acid
The experimental process comprises the following steps:
a50 mL Schlenk flask was taken, vacuum-baked and purged with argon, and then 11.0g of polylactic acid (M) was added to the flaskn49900g/mol, PDI 1.13), and then 492Mg of Mg [ N (SiMe)3)2]2And adding 30mL of methanol outside the glove box, and stirring at normal temperature for reaction. After reacting for 40 minutes, nuclear magnetic detection is carried out on the reaction system, the conversion rate of the polymer is 99%, and the obtained alcoholysis product is methyl lactate. The remaining methanol was removed by distillation to obtain 14.2g of methyl lactate in 92% yield.
Example 5:
depolymerization of polyethylglycolide
The experimental process comprises the following steps:
a5 mL Schlenk flask was charged, vacuum-baked, and purged with argon, and 86mg of polyethylglycolide (M) was added to the flaskn10337g/mol, PDI 1.26) and then 3.5Mg of Mg [ N (SiMe) was added3)2]2Catalyst, add 1mL methanol outside the glove box, stir reaction at room temperature. After reacting for 2h, nuclear magnetic detection is carried out on the reaction system, the conversion rate of the polymer is 99%, and the obtained alcoholysis product is 2-hydroxy methyl butyrate.
Example 6:
depolymerization of polyisopropylglycolide
The experimental process comprises the following steps:
a5 mL Schlenk flask was taken, vacuum-baked and purged with argon, and then 100mg of poly (isopropyl glycolide) (M) was added to the flaskn10700g/mol, PDI 1.22), then 3.5Mg of Mg [ N (SiMe) was added3)2]2Catalyst, add 1mL methanol outside the glove box, stir reaction at room temperature. After reacting for 2h, nuclear magnetic detection is carried out on the reaction system, the conversion rate of the polymer is 99%, and the obtained alcoholysis product is 2-hydroxy-3-methyl butyric acid methyl ester.
Example 7:
depolymerization of poly (propylglycolide)
The experimental process comprises the following steps:
a5 mL Schlenk flask was taken, vacuum-baked and purged with argon, and then 100mg of poly (propylglycolide) (M) was added to the flaskn10780g/mol, PDI 1.17), then 3.5Mg of Mg [ N (SiMe) was added3)2]2Catalyst, add 1mL methanol outside the glove box, stir reaction at room temperature. After reacting for 2h, nuclear magnetic detection is carried out on the reaction system, the conversion rate of the polymer is 99%, and the obtained alcoholysis product is 2-hydroxy methyl valerate.
Example 8:
depolymerization of polybutyl glycolide
The experimental process comprises the following steps:
a5 mL Schlenk flask was taken, vacuum-baked and purged with argon, and then 100mg of polybutylglycolide (M) was added to the flaskn11400g/mol, PDI 1.32), then 3.5Mg of Mg [ N (SiMe) was added3)2]2Catalyst, add 1mL methanol outside the glove box, stir reaction at room temperature. Reaction 2After h, nuclear magnetic detection is carried out on the reaction system, the conversion rate of the polymer is 99%, and the obtained alcoholysis product is 2-hydroxy methyl caproate.
Example 9:
depolymerization of polyisobutylglycolide
The experimental process comprises the following steps:
a5 mL Schlenk flask was taken, vacuum-baked and purged with argon, and then 100mg of polyisobutylglycolide (M) was added into the glove boxn12000g/mol, PDI 1.21), then 3.5Mg of Mg [ N (SiMe) was added3)2]2Catalyst, add 1mL methanol outside the glove box, stir reaction at room temperature. After 4 hours of reaction, nuclear magnetic detection is carried out on the reaction system, the conversion rate of the polymer is 99%, and the obtained alcoholysis product is 2-hydroxy-4-methyl pentanoic acid methyl ester.
Example 10:
depolymerization of poly-sec-butyl glycolide
The experimental process comprises the following steps:
a5 mL Schlenk flask was taken, vacuum-baked and purged with argon, and then 100mg of poly-sec-butylglycolide (M) was added to the flaskn13200g/mol, PDI 1.28), then 3.5Mg of Mg [ N (SiMe) is added3)2]2Catalyst, add 1mL methanol outside the glove box, stir reaction at room temperature. After 5h of reaction, nuclear magnetic detection is carried out on the reaction system, the conversion rate of the polymer is 99%, and the obtained alcoholysis product is 2-hydroxy-3-methyl pentanoic acid methyl ester.
Example 11:
depolymerization of poly (benzyl glycolide)
The experimental process comprises the following steps:
a5 mL Schlenk flask was charged with 148mg of poly (benzylglycolide) (M) in a glove box after evacuating and replacing argon gasn9200g/mol, PDI 1.22), then 3.5Mg of Mg [ N (SiMe) is added3)2]2Catalyst, add 1mL methanol outside the glove box, stir reaction at room temperature. After reacting for 2h, nuclear magnetic detection is carried out on the reaction system, the conversion rate of the polymer is 99%, and the obtained alcoholysis product is benzyl methyl lactate.
Example 12:
depolymerization of poly (benzylethyl glycolide)
The experimental process comprises the following steps:
a5 mL Schlenk flask was charged, vacuum-baked, and purged with argon, and then 160mg of poly (benzylethyl glycolide) (M) was added to the flaskn9500g/mol, PDI 1.21), then 3.5Mg of Mg [ N (SiMe) was added3)2]2Catalyst, add 1mL methanol outside the glove box, stir reaction at room temperature. After reacting for 2h, nuclear magnetic detection is carried out on the reaction system, the conversion rate of the polymer is 99%, and the obtained alcoholysis product is benzyl ethyl methyl lactate.
Example 13:
depolymerization of polylactic acid
The experimental process comprises the following steps:
a5 mL Schlenk flask was charged, vacuum-baked, and purged with argon, and then 288mg of polylactic acid (M) was added to the flaskn26.0kg/mol, PDI 1.09), then 3.8Mg of Mg [ N (SiMe) was added3)2]2The catalyst was added to 2mL of ethanol and 2mL of methylene chloride outside the glove box, and the mixture was stirred at room temperature to react. After reacting for 2h, detecting the reaction system by nuclear magnetism, wherein the conversion rate of the polymer is 98 percent, and obtainingThe alcoholysis product is ethyl lactate.
Example 14:
depolymerization of polylactic acid
The experimental process comprises the following steps:
a500 mL three-neck flask was taken, vacuum-baked and replaced with argon, and then 15g of a commercial polylactic acid product (manufacturer: Henxin environmental protection technologies, Inc.; model: BG73) was added to the flask, followed by 1.15g of Mg [ N (SiMe)3)2]2113mL of ethanol and 113mL of methylene chloride were added to the outside of the glove box as a catalyst, and the reaction was stirred at room temperature. After reacting for 2 hours, detecting the reaction system by nuclear magnetism, wherein the conversion rate of the polymer is 99 percent, and the obtained alcoholysis product is ethyl lactate. The remaining ethanol was removed by distillation to obtain 18.3g of ethyl lactate with a yield of 85%.
Example 15:
depolymerization of polylactic acid
The experimental process comprises the following steps:
a5 mL Schlenk flask was charged, vacuum-baked, and purged with argon, and then 144mg of polylactide (M) was added into the glove boxn11300g/mol, PDI 1.17), then 7.0Mg of Mg [ N (SiMe) was added3)2]2And adding 1mL of ethanol outside the glove box, and stirring at normal temperature for reaction. After reacting for 2h, nuclear magnetic detection is carried out on the reaction system, the conversion rate of the polymer is 99%, and the obtained alcoholysis product is ethyl lactate.
Example 16:
depolymerization of polylactic acid
The experimental process comprises the following steps:
a50 mL Schlenk flask was evacuated and purged with argon, and then 12.0g of polylactide (M) was added to the flaskn49900g/mol, PDI 1.13), followed by 495Mg of Mg [ N (SiMe) added3)2]2And adding 30mL of ethanol outside the glove box as a catalyst, and stirring at normal temperature for reaction. After reacting for 1h, nuclear magnetic detection is carried out on the reaction system, the conversion rate of the polymer is 99%, and the obtained alcoholysis product is ethyl lactate. The remaining ethanol was removed by distillation to obtain 15.3g of ethyl lactate with a yield of 88%.
Example 17:
depolymerization of polyethylglycolide
The experimental process comprises the following steps:
a5 mL Schlenk flask was taken, vacuum-baked and purged with argon, and then 100mg of polyethylglycolide (M) was added to the flaskn10337g/mol, PDI 1.26) and then 3.5Mg of Mg [ N (SiMe) was added3)2]2And adding 1mL of ethanol outside the glove box, and stirring at normal temperature for reaction. After reacting for 2h, nuclear magnetic detection is carried out on the reaction system, the conversion rate of the polymer is 99%, and the obtained alcoholysis product is ethyl 2-hydroxybutyrate.
Example 18:
depolymerization of poly (benzyl glycolide)
The experimental process comprises the following steps:
a5 mL Schlenk flask was charged, vacuum-baked, and purged with argon, and 150mg of poly (benzylglycolide) (M) was added to the flaskn9200g/mol, PDI 1.22), then 3.5Mg of Mg [ N (SiMe) is added3)2]2And adding 1mL of ethanol outside the glove box, and stirring at normal temperature for reaction. After 5h reaction, the reaction was checked by nuclear magnetic resonanceIn the system, the conversion rate of the polymer is 99 percent, and the obtained alcoholysis product is ethyl phenyl lactate.
Example 19:
depolymerization of polylactic acid
The experimental process comprises the following steps:
a50 mL Schlenk flask was taken, vacuum-baked and purged with argon, and then 11.0g of polylactic acid (M) was added to the flaskn49900g/mol, PDI 1.13), and then 220mg of MgBu is added2And adding 30mL of methanol outside the glove box, and stirring at normal temperature for reaction. After reacting for 50 minutes, nuclear magnetic detection is carried out on the reaction system, the conversion rate of the polymer is 99%, and the obtained alcoholysis product is methyl lactate. The remaining methanol was removed by distillation to obtain 13.2g of methyl lactate with a yield of 86%.
Example 20:
depolymerization of poly (benzyl glycolide)
The experimental process comprises the following steps:
a5 mL Schlenk flask was charged, vacuum-baked, and purged with argon, and 150mg of poly (benzylglycolide) (M) was added to the flaskn9700g/mol, PDI 1.12), then 1.4mg of MgBu is added2Catalyst, add 1mL methanol outside the glove box, stir reaction at room temperature. After reacting for 3h, nuclear magnetic detection is carried out on the reaction system, the conversion rate of the polymer is 99%, and the obtained alcoholysis product is benzyl methyl lactate.
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
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