Method for promoting vaporization of volatile components in lactic acid oligomer depolymerization process by adding porous material

Abstract

The invention discloses a method for promoting vaporization of volatile components in a lactic acid oligomer depolymerization process by adding a porous material. The method is characterized in that a porous material is introduced in a lactic acid oligomer depolymerization process to provide a vapor nucleus, and vaporization of volatile components including low-molecular-weight lactic acid monomers, lactic acid dimers and lactic acid cyclic dimers is promoted. The used porous materials comprise zeolite, molecular sieves, carbon and ceramsite. Vaporization of volatile components generated in the lactic acid oligomer depolymerization process can be effectively promoted, and the method has the advantages of being simple in process, low in cost, environmentally friendly and the like.

Description

Technical Field

[0001] The invention relates to the technical field of organic matter decomposition, in particular to a method for promoting the vaporization of lactic acid oligomerization and depolymerization products. Background Art

[0002] Lactic acid is a natural organic compound that can be produced and degraded by living organisms. It is currently widely used in food, medicine, textiles, animal husbandry, and other fields. Its high-molecular-weight polymer, polylactic acid (PLA), is currently the most widely used, highest-volume, and most promising biodegradable plastic, and is considered a promising alternative to traditional petroleum-based plastics. According to incomplete statistics, my country will add at least 1.53 million tons of PLA production capacity over the next five years.

[0003] The industrial production and recycling of polylactic acid both involve the depolymerization of lactic acid oligomers. The depolymerization reaction of lactic acid oligomers can be considered a dynamic equilibrium reaction, with the main products being lactic acid monomers, lactic acid dimers, lactic acid cyclic dimers, and lactic acid polymers. Under high-temperature, negative-pressure reaction conditions, lactic acid monomers, dimers, and cyclic dimers with relatively low boiling points are relatively easily vaporized and released from the reaction system, while lactic acid polymers with higher boiling points undergo further depolymerization. Currently, research on the depolymerization of lactic acid oligomers focuses on the development of efficient catalysts, improvements in reaction equipment, and optimization of reaction parameters. Patent Publication No. CN116063271A discloses a method for promoting the depolymerization of lactic acid oligomers by adding a protonated solvent to a catalyst. Publications No. CN116041310A and CN116041313A both focus on equipment design and parameter optimization to achieve efficient depolymerization and vaporization of lactic acid oligomers. While all of the above methods can improve the vaporization of volatile components in the depolymerization products of lactic acid oligomers, they often suffer from drawbacks such as complex equipment, difficult processing, complex parameters, high filler costs, and the introduction of new impurities. Furthermore, these methods have largely reached a bottleneck in improving the vaporization capacity of volatile components during the depolymerization of lactic acid oligomers. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention provides a method for promoting the vaporization of volatile components during the depolymerization of lactic acid oligomers by adding a porous material. By adding the porous material during the reaction, the present invention provides vapor nuclei for the volatile components, reducing the ambient pressure when bubbles form, thereby promoting the rapid vaporization of the volatile components in the depolymerization product.

[0005] The object of the present invention is to provide a method for promoting the vaporization of volatile components in the depolymerization process of lactic acid oligomers by adding a porous material, comprising the following contents: Place the lactic acid oligomer mixed with a catalyst in a porous reaction vessel, then add a porous material thereto, heat up and reduce the pressure of the reaction device to cause the lactic acid oligomer to depolymerize, and allow its product to enter a low-temperature collection device through a port on the reaction vessel for condensation and collection.

[0006] In the above method, the molecular weight of the lactic acid oligomer ≥ 300, preferably the molecular weight is 600 - 3000. The lactic acid oligomer is generally prepared by dehydration and polycondensation using lactic acid as a raw material. The catalyst can be added before the polycondensation reaction or after the completion of the polycondensation reaction.

[0007] In the above method, the porous reactor has a plurality of openings, preferably 3 - 6 openings.

[0008] In the above method, the porous material mainly includes porous materials such as zeolite, molecular sieve, carbon, ceramsite, metal-organic framework (Metalorganic Framework, MOF), covalent organic framework (Covalent Organic Framework, COF), etc., and among them, zeolite, molecular sieve, carbon, and ceramsite with relatively low cost are preferred.

[0009] In the above method, the addition amount of the porous material is 0.1% - 40% of the lactic acid oligomer, preferably 0.5% - 5%.

[0010] In the above method, the heating up and pressure reduction means that the reaction temperature is 170 - 250 °C and the ambient pressure is 0 - 4 kPa, preferably the reaction temperature is 190 - 220 °C and the ambient pressure is 0 - 2 kPa.

[0011] In the above method, the temperature in the low-temperature collection device is -20 - 100 °C, preferably 10 - 40 °C.

[0012] The present invention applies a porous material to the depolymerization of lactic acid oligomers, and realizes the rapid vaporization of volatile components in the depolymerization product of lactic acid oligomers.

[0013] The following further describes the technical solution of the present invention through examples. Specific Embodiments

[0014] The following will further describe the present invention. It should be noted that this embodiment is based on the present technical solution, and gives detailed implementation manners and specific operation processes, but the present invention is not limited to this embodiment.

[0015] Example 1 Add 10 g of lactic acid oligomer with a molecular weight of 1000 to a 50 mL two-necked flask. Vacuum the reaction apparatus to a pressure of 1 kPa and react at 200 °C for 30 min. Collect the volatile components obtained by depolymerization through condensation. After analysis, the volatile components collected account for 57.8% of the raw material mass.

[0016] Example 2 Add 10 g of lactic acid oligomer with a molecular weight of 1000 and 0.1 g of zeolite to a 50 mL two-necked flask. Vacuum the reaction apparatus to a pressure of 1 kPa and react at 200 °C for 30 min. Collect the volatile components obtained by depolymerization through condensation. After analysis, the volatile components collected account for 73.8% of the raw material mass.

[0017] Example 3 Add 10 g of lactic acid oligomer with a molecular weight of 1000 and 0.5 g of porous carbon to a 50 mL two-necked flask. Vacuum the reaction apparatus to a pressure of 1 kPa and react at 200 °C for 30 min. Collect the volatile components obtained by depolymerization through condensation. After analysis, the volatile components collected account for 71.4% of the raw material mass.

[0018] Example 4 Add 10 g of lactic acid oligomer with a molecular weight of 1000 and 0.3 g of molecular sieve to a 50 mL two-necked flask. Vacuum the reaction apparatus to a pressure of 1 kPa and react at 200 °C for 30 min. Collect the volatile components obtained by depolymerization through condensation. After analysis, the volatile components collected account for 83.9% of the raw material mass.

[0019] Example 5 Add 10 g of lactic acid oligomer with a molecular weight of 1000 and 0.1 g of ceramsite to a 50 mL two-necked flask. Vacuum the reaction apparatus to a pressure of 1 kPa and react at 200 °C for 30 min. Collect the volatile components obtained by depolymerization through condensation. After analysis, the volatile components collected account for 74.9% of the raw material mass.

[0020] Example 6 Add 10 g of lactic acid oligomer with a molecular weight of 1000 and 0.1 g of molecular sieve to a 50 mL two-necked flask. Vacuum the reaction apparatus to a pressure of 1 kPa and react at 200 °C for 30 min. Collect the volatile components obtained by depolymerization through condensation. After analysis, the volatile components collected account for 82.5% of the raw material mass.

[0021] It can be seen from Examples 1-6 that the highest mass ratio of the volatile components collected can reach 83.9%, and the addition of a small amount of molecular sieve can produce a good promotion effect.

[0022] Therefore, a method for promoting the vaporization of volatile components during the depolymerization of lactic acid oligomers by adding porous materials proposed by the present invention can effectively promote the vaporization and collection of depolymerization products. A method for catalytically synthesizing diester-based cyclic esters using an ionic liquid analogue with the above structure, which combines a hydrogen bond acceptor with a high-purity hydroxy acid with a mass fraction higher than 90% and catalytically synthesizes diester-based cyclic esters through polymerization and depolymerization reactions under high temperature and low pressure conditions, has the advantages of simple process, low cost, environmental friendliness, etc.

[0023] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for promoting the vaporization of volatile components during the depolymerization of lactic acid oligomers by adding porous materials, characterized in that The porous materials include zeolite, molecular sieve, carbon, and ceramsite.

2. A method for promoting the vaporization of volatile components during the depolymerization of lactic acid oligomers by adding porous materials according to claim 1, characterized in that The addition amount of the porous material is 0.1%-40%.

3. The method of claim 1, wherein the method comprises: The molecular weight of the lactic acid oligomer is ≥300.

4. A method for promoting the vaporization of volatile components during the depolymerization of lactic acid oligomers by adding porous materials according to claim 1, characterized in that The volatile components are lactic acid monomer, lactic acid dimer, and lactic acid cyclic dimer.

5. A method for promoting the vaporization of volatile components during the depolymerization of lactic acid oligomers by adding porous materials according to claim 1, characterized in that A catalyst has been added during the depolymerization process.

6. A method for promoting the vaporization of volatile components during the depolymerization of lactic acid oligomers by adding porous materials according to claim 5, characterized in that The catalyst includes homogeneous catalyst and heterogeneous catalyst.

7. A method for promoting the vaporization of volatile components during the depolymerization of lactic acid oligomers by adding a porous material according to any one of claims 1-4, characterized in that It includes the following steps: (1) Oligomer depolymerization: Add the porous material to the lactic acid oligomer containing the catalyst and react it at an ambient pressure of 0-20 kPa and a temperature of 130-230 °C for 0.05-8 h; (2) Collection of depolymerization products: The gaseous product obtained by depolymerization is liquefied and collected through a condensation device at -10-40 °C.