CN119039136B - Method for degrading and upgrading polyester material by using aromatic ester solvent - Google Patents

Abstract

The invention discloses a method for upgrading polyester materials by degradation of aromatic ester solvents, comprising the following steps: placing polyester materials, aromatic ester solvents, and solid base catalysts in a reaction kettle, heating for depolymerization reaction, and obtaining dicarboxylic acid esters and diphenyl esters, wherein the aromatic ester solvents are at least one of methyl benzoate, p-methyl benzoate, methyl phenylacetate, ethyl benzoate, m-methyl benzoate, etc., and the solid base catalyst is at least one of zinc oxide, magnesium oxide, cadmium oxide, zinc hydroxide, or cadmium hydroxide. The aromatic ester and solid base catalytic system used in the invention has good solubility for textile waste, can realize the upgrading and recycling of color textile waste that is difficult to handle, without complicated pre-decolorization and pre-separation, and the reaction conditions are mild, the catalytic efficiency is high, and the method of the invention can also be applied to waste containing other similar polyesters, and has a wide range of applications.

Description

Method for degrading and upgrading polyester material by using aromatic ester solvent

Technical Field

The invention relates to an innovative cyclic utilization of waste resources and a refined cascade utilization strategy of raw materials, in particular to a method for degrading and upgrading polyester materials by using an aromatic ester solvent.

Background

In the clothing and food residence, the clothing is arranged at the first position, and the clothing has the function of shielding and keeping warm, and reflects the identity and aesthetic change. With the rising rapid fashion trend, the demand for textiles is also increasing. The 2023 global fiber production was statistically increased to 1.13 hundred million tons, almost doubled in the last 20 years, and it was expected that 2030 would be increased to 1.49 hundred million tons.

Fast and fashionable consumption further shortens the life of the textile. According to National Institute of Standards and Technology (NIST) statistics, over 500 million garments are discarded each year during production. The annual production of textile waste worldwide is estimated to be 9200 ten thousand tons, of which less than 1% is recycled and about three quarters is landfilled or incinerated, resulting in huge waste of resources and serious environmental pollution. The greenhouse gas emissions produced by textiles account for 5-10% of the global greenhouse gas emissions, about one third or more of the microplastic entering the ocean comes from clothing waste. Therefore, development of sustainable and environmentally friendly textile recycling technology is imperative.

At present, textiles are mainly divided into two main categories, natural textiles and synthetic textiles. Although the production of plant and animal materials (such as cotton and wool) is relatively stable, the yield of synthetic textiles is rapidly increasing, with the most widely used synthetic fiber being PET, and by 2021 its market share in global fiber production will reach 54%. The most straightforward method to recycle waste PET is to use it as a fuel energy source, however, plastic combustion releases large amounts of toxic gases and produces large amounts of carbon emissions, which is contrary to the sustainable development concept of low carbon emissions.

In addition, mechanical recycling is also the most common method for recycling colored textiles, but for multi-fiber textiles, improper treatment of additives and colorants often results in shortened fiber length, impaired toughness, strength and creep resistance, and can only be recycled as low value products such as wipes, fillers and insulation materials.

Chemical recovery techniques have attracted considerable attention and have been widely studied. However, polyester fibers in textiles are often tightly interwoven with other fibers (including cotton, nylon, and spandex) and with various dyes. Thus, chemical recovery of mixed textile waste prior to reprocessing typically requires expensive sorting and separation to avoid unwanted product mixing. For example, zuo et al have established a new closed loop strategy to recycle waste polyester textiles by developing a variety of techniques including the decolorization of waste textiles, glycolysis of the decolorized polyester textiles, and purification of BHET products, while the remaining unreacted other waste textiles are not treated (Green chem.,2023, 25 (11), 4429-4437). On this basis Vlachos et al utilized microwave-assisted glycolysis to recover polyester, cotton, nylon and spandex from the mixed textile waste. Although pre-decolorization and pre-classification are not required, polyester and spandex are completely degraded within 15 minutes, while cotton and nylon are completely retained, polyester is only degraded into monomers, and no upgraded product is obtained (sci.adv., 2024, 10 (27), eado 6827).

Therefore, a sustainable recovery technology of complex mixed textile waste (especially terylene cotton, i.e. interweaved mixture of terylene and cotton) is developed, the problems of expensive and complex pre-bleaching, pre-sorting and separation at present are solved, and meanwhile, the textile waste is effectively upgraded into high-value chemicals, so that the method is a new direction and a new challenge for realizing comprehensive green transformation of the textile industry.

Disclosure of Invention

Aiming at the problems of expensive and complex pre-bleaching, pre-sorting and separating in textile waste degradation, single product upgrading and the like, the invention provides a method for degrading and upgrading polyester materials by using an aromatic ester solvent.

A method for degrading and upgrading polyester materials by using aromatic ester solvents comprises the following steps:

Placing polyester materials, aromatic ester solvents and solid base catalysts in a reaction kettle, and heating to perform depolymerization reaction to obtain dicarboxylic acid ester and diphenyl ester, wherein the aromatic ester solvents are at least one of methyl benzoate, p-methyl benzoate, methyl phenylacetate, ethyl benzoate, m-methyl benzoate, o-methyl benzoate, methyl phenylpropionate, allyl benzoate, ethyl p-methylbenzoate, ethyl o-methylbenzoate or ethyl m-methylbenzoate, and the solid base catalysts are at least one of zinc oxide, magnesium oxide, cadmium oxide, zinc hydroxide or cadmium hydroxide.

Preferably, the polyester-based material is a textile waste material comprising polyethylene terephthalate (PET).

Polyester fibers made from PET are typically tightly interwoven with other fibers (synthetic or natural polymers) of cotton, nylon, spandex, dyes, etc., requiring expensive sorting and separation (e.g., high temperature and long-time decolorization) prior to reprocessing. According to the principle of similar compatibility, the invention adopts the aromatic ester solvent with good solubility to the textile waste containing polyester fibers, can directly dissolve and strip PET from the closely interwoven complex textiles, and depolymerizes the polyester fibers into dicarboxylic acid esters through transesterification; in addition, the invention can effectively reduce the activation energy of the reaction by introducing the solid base catalyst, so that the reaction is carried out at a lower temperature, the reaction condition is milder and controllable, and the selectivity and the yield of the target product are higher.

Preferably, the polyethylene terephthalate-containing textile waste comprises at least one of polyester cloth, cotton blended cloth, polyester fiber, PU blended cloth, rayon blended cloth and the like. For example, the polyester fabric, polyester-cotton blended fabric, polyester fiber-PU blended fabric and polyester fiber-rayon blended fabric can be used. Further preferably, the polyethylene terephthalate-containing textile waste is polyethylene terephthalate-containing waste color textile waste. The invention utilizes the solubility of the aromatic ester solvent to PET, and can strip the PET tightly interwoven with impurities with high efficiency, thereby avoiding expensive sorting and separation in the earlier stage and further improving the purity of the product.

Preferably, the mass ratio of the polyethylene terephthalate in the polyethylene terephthalate-containing textile waste is 40-100%. The proportion of polyester in most of the waste materials from polyester-containing textiles on the market is within this range.

The process of the invention is also applicable to waste materials containing other similar polyesters. For example, the polyester material is waste material containing polybutylene terephthalate, including cloth containing the material, computer key caps, fuse boxes, switches, sockets or electronic element supports, and the like.

Preferably, the polyester material is required to be crushed into cm-level flakes, particles or powder before being added into the reaction kettle, so that the recycling effect of the polyester material is ensured, and the dicarboxylic ester monomer is obtained in a directional upgrading and high yield.

Preferably, 2-8 mL of aromatic ester solvent is added to each mmol of polyester material. Further preferably, 4-6 mL of aromatic ester solvent is added to each mmol of polyester material. More preferably, 5mL of aromatic ester solvent is added per mmol of polyester-based material. Within this control range, the yield of the reaction product is highest and the amount of aromatic ester solvent used is smallest.

Preferably, the addition amount of the solid base catalyst is 20-80 mol% of the polyester material. Further preferably, the addition amount of the solid base catalyst is 20-50mol% of the polyester material. Within this range, the reaction time can be shortened and the product yield maximized.

Preferably, the reaction temperature of the depolymerization reaction is 160-240 ℃ and the reaction time is 5-16 h. Further preferably, the reaction temperature of the depolymerization reaction is 180-220 ℃. More preferably, the depolymerization reaction is carried out at a reaction temperature of 200 ℃.

Preferably, the aromatic ester solvent is methyl benzoate, and the polyester material is textile waste containing polyethylene terephthalate. Methyl benzoate is a natural aromatic ester compound, and can be extracted from natural essential oil such as oleum Caryophylli. The solid base catalyst is adopted to catalyze the transesterification reaction of methyl benzoate and the blended product containing PET, the PET is degraded into dimethyl terephthalate (DMT), and the methyl benzoate is upgraded into high-value diethylene glycol dibenzoate (EGD) after capturing glycol units in the PET.

In the invention, methyl benzoate can be used for improving the solubility of PET in a solvent and leaving waste residues except PET in textile waste, and can be used as a capturing agent of EGD generated by PET depolymerization, so that the product DMT is obtained through transesterification, and meanwhile, high-value Ethylene Glycol Dibenzoate (EGD) is co-produced, thereby improving the economy of atom utilization.

DMT is an important bulk chemical product and has wide application prospect in the industries of building, packaging, electronics and the like. EGD is widely used as an important synthetic intermediate for preparing paint, perfume, plastic additive and the like. The brand new strategy for degrading the PET-containing waste textiles is helpful for improving the recycling economy of the textiles and promoting the comprehensive green transformation of the textile industry.

Preferably, the aromatic ester solvent is methyl benzoate, the polyester material is textile waste containing polyethylene terephthalate, the solid base catalyst is zinc oxide, the reaction temperature is 180-220 ℃, and the reaction time is 10-15 h. More preferably, the reaction temperature is 200 ℃ and the reaction time is 12 hours. Under the condition, the yield of the target product dimethyl phthalate can reach 99 percent, and the yield of the diethylene glycol dibenzoate can reach 85 percent.

The invention can also use other aromatic esters with similar structures as solvents, such as methyl p-methylbenzoate, ethyl benzoate, allyl benzoate and the like, and the products are corresponding dimethyl terephthalate, diethyl terephthalate, diallyl terephthalate, diphenyl terephthalate and the like.

Compared with the prior art, the invention has at least the following beneficial effects:

(1) The aromatic ester and solid base catalytic system adopted by the invention has better solubility to polyester materials, and can realize the upgrading recovery of color textile waste which is difficult to treat without complex pre-decolorization and pre-separation;

(2) The strategy for degrading and upgrading the textile waste by using the aromatic ester has the advantages of mild reaction conditions and high catalytic efficiency, can realize complete conversion of PET under standard reaction conditions, does not need a high-pressure environment, can finish depolymerization under normal pressure, has the yield of the prepared dicarboxylic ester as high as 99%, has the yield of the diphenyl ester as high as 85%, is beneficial to improving the economic recoverability of textiles, and promotes the comprehensive green transformation of textile industry;

(3) The invention can adopt various aromatic ester solvents such as p-methyl benzoate, methyl phenylacetate, ethyl benzoate, allyl benzoate and the like, and can also use other similar aromatic ester solvents to degrade polyester-containing materials so as to obtain different transesterification products, thereby widening the range of the products;

(4) The method has a high applicability range, for example, the textile waste containing PET can be replaced by other materials containing similar polyesters such as polybutylene terephthalate and the like, and the field range of the treated polyester materials is further widened.

Detailed Description

The present invention will be described in more detail with reference to the following embodiments. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the invention, whereby the invention is not limited to the specific embodiments disclosed below. The technical features of the embodiments of the invention can be combined correspondingly on the premise of no mutual conflict.

The invention provides a method for degrading and upgrading textile waste by using an aromatic ester solvent, which uses aromatic ester and PET to carry out transesterification under the catalysis of solid alkali, wherein the PET is degraded into a monomer DMT, and the aromatic ester is dehydrated and condensed into diphenyl ester after capturing glycol. The method comprises the following specific steps:

s1, placing crushed textile waste, aromatic ester raw materials and a solid base catalyst into a reaction kettle to form a reaction system;

And S2, placing the reaction kettle containing the reaction system at a depolymerization temperature of 160-240 ℃ for a depolymerization reaction of 5-16 hours, and cooling to room temperature after the reaction is completed to obtain a depolymerization product containing dicarboxylic acid ester and diphenyl ester.

In the following examples, the raw materials in the above reaction system are as follows:

The polyester material is a material containing polyethylene glycol terephthalate and polybutylene terephthalate, the aromatic ester raw materials are methyl benzoate, methyl p-methylbenzoate, ethyl benzoate and allyl benzoate, and the solid base catalyst is zinc oxide, magnesium oxide and cadmium oxide.

If the polyester material is PET, pure PET or PET waste can be used. The waste is in the form of complex waste color PET, such as polyester cloth, polyester-cotton blended cloth, polyester fiber-PU blended cloth and polyester fiber-rayon blended cloth, and if the polyester material is polybutylene terephthalate, the polyester material can be selected as the cloth, computer key cap, fuse box, switch, socket or electronic element bracket. However, the waste is crushed into cm-sized flakes, granules or powder before being added into the reaction kettle.

The reaction results under the different starting materials and parameters are shown below by way of example.

Example 1

An autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a program temperature controller was charged with 0.192 g cm-sized crushed materials (1 mmol) of pure polyester material, methyl benzoate (2, 5, 8 mL/mmol polyester material) and ZnO (35 mol%), and after the autoclave reactor was set, stirring and heating were started. The reaction system was warmed to 200 ℃ and reacted at that temperature 12 h. After the reaction is completed, the temperature is reduced to room temperature, and the obtained mixed solution is the product. The obtained mixed solution was diluted with methylene chloride, and the yield of the diluted solution was measured by GC, and the result showed that the PET degradation rate of this example was 100%, the yields of dimethyl terephthalate were 92%, 99%, 95%, and the yields of diethylene glycol dibenzoate were 82%, 85%, 83%, respectively.

Example 2

An autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a program temperature controller was charged with 0.192 g cm-sized crushed polyester material (1 mmol), 5mL methyl benzoate (5 mL/mmol polyester material) and ZnO (20 mol%, 35 mol% and 50 mol%), and after the autoclave reactor was set, stirring and heating were started. The reaction system was warmed to 200 ℃ and reacted at that temperature 12 h. After the reaction is completed, the temperature is reduced to room temperature, and the obtained mixed solution is the product. The obtained mixed solution was diluted with methylene chloride, and the yield of the diluted solution was measured by GC, and the result showed that the PET degradation rate of this example was 100%, the yields of dimethyl terephthalate were 92%, 99%, 97%, and diethylene glycol dibenzoate were 82%, 85%, respectively.

Example 3

An autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a program temperature controller was charged with 0.192 g cm-sized crushed materials (1 mmol) of pure polyester material, 5 mL methyl benzoate (5 mL/mmol polyester material) and ZnO (35 mol%), and after the autoclave reactor was set, stirring and heating were started. The reaction system was warmed to 180, 200, 220 ℃ respectively and reacted at that temperature 12 h. After the reaction is completed, the temperature is reduced to room temperature, and the obtained mixed solution is the product. The obtained mixed solution was diluted with methylene chloride, and the yield of the diluted solution was measured by GC, and the result showed that the PET degradation rate of this example was 100%, the yields of dimethyl terephthalate were 91%, 99%, 96%, and the yields of diethylene glycol dibenzoate were 81%, 85%, 83%, respectively.

Example 4

An autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a program temperature controller was charged with 0.192 g cm-sized crushed materials (1 mmol) of pure polyester material, 5mL of methyl benzoate (5 mL/mmol of polyester material) and ZnO (35 mol%), and after the autoclave reactor was set, stirring and heating were started. The reaction system was warmed to 200 ℃ and reacted at that temperature to 8, 12, 16 h, respectively. After the reaction is completed, the temperature is reduced to room temperature, and the obtained mixed solution is the product. The obtained mixed solution was diluted with methylene chloride, and the yield of the diluted solution was measured by GC, and the result showed that the PET degradation rate of this example was 100%, the yields of dimethyl terephthalate were 90%, 99%, 97%, and the yields of diethylene glycol dibenzoate were 77%, 85%, 83%, respectively.

Example 5

An autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a program temperature controller was charged with 0.192 g cm-sized crushed materials (1 mmol) of pure polyester material and 5 mL methyl benzoate (5 mL/mmol polyester material), and after the autoclave reactor was placed with ZnO, mgO, cdO (35 mol%) as a catalyst, stirring and heating were started. The reaction system was warmed to 200 ℃ and reacted at that temperature 12 h. After the reaction is completed, the temperature is reduced to room temperature, and the obtained mixed solution is the product. The obtained mixed solution was diluted with methylene chloride, and the yield of the diluted solution was measured by GC, and mesitylene was used as an internal standard, and the results showed that the PET degradation rate of this example was 100%, the yields of dimethyl terephthalate were 99%, and the yields of diethylene glycol dibenzoate were 85%, 84%, and 85%, respectively.

Example 6

An autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a program temperature controller was charged with 0.192 g of 80% polyester-20% cotton blend cloth cm-sized crushed material (1 mmol), 5mL methyl benzoate (5 mL/mmol polyester-based material) and ZnO (35 mol%), and after the autoclave reactor was set, stirring and heating were started. The reaction system was warmed to 200 ℃ and reacted at that temperature 12 h. After the reaction is completed, the temperature is reduced to room temperature, and the obtained mixed solution is the product. The resulting mixture was diluted with methylene chloride, and the yield of the diluted solution was measured by GC, and mesitylene was used as an internal standard, which indicated that the PET degradation rate of this example was 100%, the yield of dimethyl terephthalate was 99%, and the yield of diethylene glycol dibenzoate was 85%.

Example 7

An autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a program temperature controller was charged with 0.192 g of a crushed material (1 mmol) of cm-grade 95% polyester fiber-3% PU blended fabric, 5mL methyl benzoate (5 mL/mmol polyester material) and ZnO (35 mol%), and after the autoclave reactor was set, stirring and heating were started. The reaction system was warmed to 200 ℃ and reacted at that temperature 12 h. After the reaction is completed, the temperature is reduced to room temperature, and the obtained mixed solution is the product. The resulting mixture was diluted with methylene chloride, and the yield of the diluted solution was measured by GC, and mesitylene was used as an internal standard, which indicated that the PET degradation rate of this example was 100%, the yield of dimethyl terephthalate was 99%, and the yield of diethylene glycol dibenzoate was 84%.

Example 8

An autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a program temperature controller was charged with 0.192 g of 40% polyester fiber-60% rayon blend cloth cm-sized crushed material (1 mmol), 5mL methyl benzoate (5 mL/mmol polyester material) and ZnO (35 mol%), and after the autoclave reactor was set, stirring and heating were started. The reaction system was warmed to 200 ℃ and reacted at that temperature 12 h. After the reaction is completed, the temperature is reduced to room temperature, and the obtained mixed solution is the product. The resulting mixture was diluted with methylene chloride, and the yield of the diluted solution was measured by GC, and mesitylene was used as an internal standard, which indicated that the PET degradation rate of this example was 100%, the yield of dimethyl terephthalate was 99%, and the yield of diethylene glycol dibenzoate was 85%.

Example 9

An autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a program temperature controller was charged with 0.192 g cm-sized crushed polyester material (1 mmol), 5mL ethyl benzoate (5 mL/mmol polyester material) and ZnO (35 mol%), and after the autoclave reactor was set, stirring and heating were started. The reaction system was warmed to 200 ℃ and reacted at that temperature 12 h. After the reaction is completed, the temperature is reduced to room temperature, and the obtained mixed solution is the product. The resulting mixture was diluted with methylene chloride, and the yield of the diluted solution was measured by GC, and mesitylene was used as an internal standard, which indicated that the PET degradation rate of this example was 100%, the diethyl terephthalate yield was 97%, and the diethylene glycol dibenzoate yield was 84%.

Example 10

An autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a program temperature controller was charged with 0.192 g cm-sized crushed materials (1 mmol) of pure polyester material, 5mL of methyl phenylpropionate (5 mL/mmol of polyester material) and ZnO (35 mol%), and after the autoclave reactor was set, stirring and heating were started. The reaction system was warmed to 200 ℃ and reacted at that temperature 12 h. After the reaction is completed, the temperature is reduced to room temperature, and the obtained mixed solution is the product. The resulting mixture was diluted with methylene chloride, and the yield of the diluted solution was measured by GC, and mesitylene was used as an internal standard, which indicated that the PET degradation rate of this example was 100%, the yield of dimethyl terephthalate was 98%, and the yield of diethylene glycol diphenyl propionate was 83%.

Example 11

A computer key cap cm-level crushed material (1 mmol) of 0.256 g polybutylene terephthalate material, 5mL methyl benzoate (5 mL/mmol polyester material) and CdO (35 mol%) were added into an autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a program temperature controller, and after the autoclave reactor was placed, stirring and heating were started. The reaction system was warmed to 200 ℃ and reacted at that temperature 12 h. After the reaction is completed, the temperature is reduced to room temperature, and the obtained mixed solution is the product. The resulting mixture was diluted with methylene chloride, and the yield of the diluted solution was measured by GC, and mesitylene was used as an internal standard, which indicated that the PET degradation rate of this example was 100%, the dibutyl terephthalate yield was 95%, and the diethylene glycol dibenzoate yield was 84%.

Comparative example 1

An autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a program temperature controller was charged with 0.192 g cm-sized crushed materials (1 mmol) of pure polyester material, 5mL methyl benzoate (5 mL/mmol polyester material) and Cu (OH) ₂ (35 mol%), and after the autoclave reactor was set up, stirring and heating were started. The reaction system was warmed to 200 ℃ and reacted at that temperature 12 h. After the reaction is completed, the temperature is reduced to room temperature, and the obtained mixed solution is the product. The resulting mixture was diluted with methylene chloride, and the yield of the diluted solution was measured by GC, and mesitylene was used as an internal standard, which indicated that the yield of dimethyl terephthalate was 0% and the yield of diethylene glycol dibenzoate was 0% in this example.

Comparative example 2

An autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a program temperature controller was charged with 0.192 g cm-sized crushed materials of pure polyester (1 mmol), 5 mL methyl benzoate (5 mL/mmol polyester-based material) and K ₂CO₃ (35 mol%), and after the autoclave reactor was set up, stirring and heating were started. The reaction system was warmed to 200 ℃ and reacted at that temperature 12 h. After the reaction is completed, the temperature is reduced to room temperature, and the obtained mixed solution is the product. The resulting mixture was diluted with methylene chloride, and the yield of the diluted solution was measured by GC, and mesitylene was used as an internal standard, which indicated that the yield of dimethyl terephthalate was 0% and the yield of diethylene glycol dibenzoate was 0% in this example.

Comparative example 3

An autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a program temperature controller was charged with 0.192 g cm-sized crushed materials of polyester (1 mmol), 5mL methyl benzoate (5 mL/mmol polyester-based material) and Ca (OH) ₂ (35 mol%), and after the autoclave reactor was set up, stirring and heating were started. The reaction system was warmed to 200 ℃ and reacted at that temperature 12 h. After the reaction is completed, the temperature is reduced to room temperature, and the obtained mixed solution is the product. The resulting mixture was diluted with methylene chloride, and the yield of the diluted solution was measured by GC, and mesitylene was used as an internal standard, which indicated that the yield of dimethyl terephthalate was 3% and the yield of diethylene glycol dibenzoate was 0% in this example.

Comparative example 4

An autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a program temperature controller was charged with 0.192 g cm-sized crushed materials of pure polyester (1 mmol), 5mL methyl benzoate (5 mL/mmol polyester-based material) and H-ZSM-5 molecular sieve (35 mol%), and after the autoclave reactor was set, stirring and heating were started. The reaction system was warmed to 200 ℃ and reacted at that temperature 12 h. After the reaction is completed, the temperature is reduced to room temperature, and the obtained mixed solution is the product. The resulting mixture was diluted with methylene chloride, and the yield of the diluted solution was measured by GC, and mesitylene was used as an internal standard, which indicated that the yield of dimethyl terephthalate was 0% and the yield of diethylene glycol dibenzoate was 0% in this example.

Comparative example 5

An autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a program temperature controller was charged with 0.192 g cm-sized crushed materials of pure polyester (1 mmol), 5 mL methyl benzoate (5 mL/mmol polyester-based material) and Amberlyst 15 (35 mol%), and after the autoclave reactor was set, stirring and heating were started. The reaction system was warmed to 200 ℃ and reacted at that temperature 12h. After the reaction is completed, the temperature is reduced to room temperature, and the obtained mixed solution is the product. The resulting mixture was diluted with methylene chloride, and the yield of the diluted solution was measured by GC, and mesitylene was used as an internal standard, which indicated that the yield of dimethyl terephthalate was 0% and the yield of diethylene glycol dibenzoate was 0% in this example.

Examples 1-11 and comparative examples 1-5 show that not all catalysts can be used for catalyzing the depolymerization reaction, and ZnO, mgO, cdO has extremely high catalytic performance in catalyzing the reaction of aromatic esters and colored textile waste materials to carboxylic esters and diphenyl esters compared with other catalysts.

The above embodiment is only a preferred embodiment of the present invention, but it is not intended to limit the present invention. Various changes and modifications may be made by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present invention. Therefore, all the technical schemes obtained by adopting the equivalent substitution or equivalent transformation are within the protection scope of the invention.

Claims (10)

1. The method for degrading and upgrading the polyester material by using the aromatic ester solvent is characterized by comprising the following steps of:

Placing polyester materials, an aromatic ester solvent and a solid base catalyst into a reaction kettle, and heating to perform depolymerization reaction to obtain dicarboxylic acid ester and diphenyl ester, wherein the aromatic ester solvent is at least one of methyl benzoate, p-methyl benzoate, methyl phenylacetate, ethyl benzoate, m-methyl benzoate, o-methyl benzoate, methyl phenylpropionate or allyl benzoate, and the solid base catalyst is at least one of zinc oxide, magnesium oxide, cadmium oxide, zinc hydroxide or cadmium hydroxide.

2. The method of claim 1, wherein the polyester-based material is polyethylene terephthalate-containing textile waste or polybutylene terephthalate-containing waste.

3. The method of claim 2, wherein the polyethylene terephthalate-containing textile waste comprises at least one of polyester cloth, cotton blend cloth, polyester fiber, PU blend cloth, rayon blend cloth.

4. A method according to claim 3, wherein the mass ratio of polyethylene terephthalate in the polyethylene terephthalate-containing textile waste is 40-100%.

5. The method according to claim 1, wherein 2-8 ml of the aromatic ester solvent is added per mmol of the polyester-based material.

6. The method according to claim 1, wherein the solid base catalyst is added in an amount of 20 to 80mol% of the polyester-based material.

7. The method of claim 1, wherein the depolymerization reaction is carried out at a reaction temperature of 160-240 ℃ for a reaction time of 5-16 hours.

8. The method according to any one of claims 1 to 7, wherein 4 to 6ml of the aromatic ester solvent is added per mmol of the polyester material, the addition amount of the solid base catalyst is 20 to 50 mol% of the polyester material, and the reaction temperature of the depolymerization reaction is 180 to 220 ℃.

9. The method of any one of claims 1-7, wherein the aromatic ester solvent is methyl benzoate, the polyester material is polyethylene terephthalate-containing textile waste, the dicarboxylic acid ester is dimethyl terephthalate, and the diphenyl ester is diethylene glycol dibenzoate.

10. The method of claim 9, wherein the solid base catalyst is zinc oxide, the reaction temperature is 180-220 ℃, and the reaction time is 10-15 hours.