阅读说明：本技术 一种光热降解聚酯的方法 (Method for photo-thermal degradation of polyester ) 是由 刘钰 曹暮寒 陈金星 于 2021-08-16 设计创作，主要内容包括：本发明属于聚合物处理技术,具体涉及一种光热降解聚酯的方法。将聚酯、醇、催化剂和光热材料加入光反应器中,光照反应,完成光热降解聚酯,并进行酯交换反应得到酯单体,实现聚酯的化学回收。光热反应大幅提高了降解效率,光热效应与催化效应的结合,极大的缩短了反应时间,同时反应在常压下进行,利于工业应用。(The invention belongs to a polymer treatment technology, and particularly relates to a method for photo-thermal degradation of polyester. Polyester, alcohol, catalyst and photo-thermal material are added into a photo-reactor for photo-thermal reaction to finish photo-thermal degradation of polyester, and ester exchange reaction is carried out to obtain ester monomer, thus realizing chemical recovery of polyester. The photothermal reaction greatly improves the degradation efficiency, the combination of the photothermal effect and the catalytic effect greatly shortens the reaction time, and the reaction is carried out under normal pressure, thereby being beneficial to industrial application.)

1. A method for photo-thermal degradation of polyester is characterized by comprising the following steps of adding polyester, alcohol, a catalyst and a photo-thermal material into a photo-reactor, and carrying out a photo-thermal reaction to finish the photo-thermal degradation of polyester.

2. A method for preparing ester monomer by photo-thermal degradation of polyester is characterized by comprising the following steps of adding polyester, alcohol, a catalyst and a photo-thermal material into a photo-reactor, carrying out a light irradiation reaction, and then filtering a reaction solution to obtain a clear filtrate; and cooling and filtering the clear filtrate to obtain the ester monomer.

3. The method according to claim 1 or 2, wherein the reaction temperature is 80 to 190 ℃ and the reaction time is 30 to 90 min.

4. The method according to claim 1 or 2, wherein the photo-thermal material is one or more of a carbon nanomaterial, a sulfide, a plasmonic material.

5. A method as claimed in claim 1 or 2, characterised in that the photothermal material is used in an amount of 0.1-2% by mass of the polyester.

6. The process according to claim 1 or 2, characterized in that the catalyst is Zn (CH)₃COO)₂、Mn(CH₃COO)₂、Mg(CH₃COO)₂、Pb(CH₃COO)₂、ZnO、Fe₂O₃、Co₃O₄、MnO₂、SnO₂、Ni₂O₃、ZnCl₂、NaCl、MgCl₂、Na₂CO₃One or more of the above; the alcohol is one or more of ethylene glycol, glycerol, diethylene glycol, polyethylene glycol, triethylene glycol, butanediol and hexanediol.

7. The method according to claim 1 or 2, characterized in that the amount of catalyst is 0.5-10% of the mass of polyester; the amount of the alcohol is 2-6 times of the mass of the polyester.

8. The method of claim 2, wherein the clarified filtrate is cooled to obtain crystals, and then filtered to obtain the ester monomer.

9. The application of the photothermal material in the photothermal degradation of polyester.

10. Use according to claim 9, wherein the photothermal degradation is carried out at atmospheric pressure.

Technical Field

The invention belongs to a polymer treatment technology, and particularly relates to a method for photo-thermal degradation of polyester.

Background

Polyesters are conventional plastic products, with polyethylene terephthalate (PET) being used in a wide variety of amounts. PET is prepared by exchanging dimethyl terephthalate with ethylene glycol ester or synthesizing bis (2-hydroxyethyl) terephthalate by esterifying terephthalic acid and ethylene glycol, and then carrying out polycondensation reaction. PET is widely used in high strength fibers, packaging, films and plastic bottles as a thermoplastic having excellent physical and mechanical properties and chemical stability over a wide temperature range. PET is classified into fiber grade polyester chips and non-fiber grade polyester chips. Firstly, fiber-grade polyester is used for manufacturing polyester staple fibers and polyester filaments, and is a raw material for processing fibers and related products of polyester fiber enterprises. The terylene is used as the variety with the maximum yield in chemical fibers. Secondly, the non-fiber grade polyester also has the applications of bottles, films and the like, and is widely applied to the fields of packaging industry, electronic appliances, medical treatment and health, buildings, automobiles and the like, wherein the packaging is the largest non-fiber application market of the polyester, and the PET is the fastest growing field. At the same time, the huge PET consumption and production yields a large amount of PET waste, which makes the degradation and recovery of PET waste a great challenge, and furthermore, the production raw material of PET comes from a limited, non-renewable petroleum resource. Therefore, the recycling of the waste PET not only can reduce the damage to the environment, but also can prolong the resource utilization period, and bring huge social and economic benefits.

Currently, PET recycling processes include mechanical recycling processes and chemical recycling processes. The mechanical recycling method is to obtain new PET material by physically treating PET waste through separation, pulverization, washing, drying, melting and reforming. The mechanical recovery method has simple process, easy control and less equipment investment. Therefore, it is currently the predominant PET recycling process. However, chain scission reduces the molecular weight of PET, which degrades the performance of PET and prevents recycling. Chemical recovery is the process of degrading PET waste into monomers or other chemicals by various chemical means, and these monomers can be used to prepare PET by polycondensation. The method mainly comprises a hydrolysis method, a methanol alcoholysis method, an ethylene glycol alcoholysis method, a pyrolysis method, an ammonolysis method and the like, and compared with a mechanical recovery method, the chemical recovery method has the advantage that the quality of PET is not reduced, so that a permanent closed-loop cycle of PET recovery can be realized. Thus, chemical recovery provides a more efficient method for recovering PET, and at present, glycolysis and methanolysis are the two most mature methods for chemical recovery. Among them, the glycolysis method is the most potential method because glycol has a high boiling point and is not easy to volatilize; however, the prior art carries out glycolysis under the condition of oil bath or microwave heating, so that the glycolysis for recovering PET still needs to consume a large amount of energy (heat energy). Therefore, there is a need to develop new implementations to achieve more efficient degradation of PET.

Disclosure of Invention

The invention aims to provide a method for chemically recycling waste polyester by using a photo-thermal technology. Sunlight is a clean green energy, absorbed photon energy is converted into heat through the photothermal effect, and the energy is released in the form of heat.

A method for photo-thermal degradation of polyester comprises the following steps of adding polyester, alcohol, a catalyst and a photo-thermal material into a photo-reactor, and carrying out a light reaction for 30-90 min to complete the photo-thermal degradation of polyester.

The invention discloses a method for preparing an ester monomer by photo-thermal degradation of polyester, which comprises the following steps of adding polyester, alcohol, a catalyst and a photo-thermal material into a photoreactor, carrying out illumination reaction for 30-90 min, and then filtering reaction liquid to obtain clear filtrate; and cooling and filtering the clear filtrate to obtain the ester monomer.

The reaction temperature generated by illumination is 80-190 ℃, and ester exchange reaction is carried out when polyester is degraded to obtain ester monomers, so that chemical recovery of the polyester is realized, wherein the ester monomers comprise bis (2-hydroxyethyl) terephthalate, ethyl lactate, bisphenol A and the like. The polyester can be waste polyester or non-waste polyester. The waste polyester used in the present invention may be waste produced in the production process, or waste containing a large amount of impurities (oil, various inorganic fillers, pigments, and other polymers).

The photo-thermal material adopted by the invention is carbon nano material (carbon nano tube, graphene), sulfide (molybdenum sulfide, tungsten sulfide), plasmon material (gold nano rod, palladium nano sheet, Fe)₃O₄Nano meterCluster, Cu₉S₅Nanocrystals); preferably one of carbon nano-tube, molybdenum sulfide and palladium nano-cluster. The amount of the photo-thermal material is 0.1-2% of the polyester, and the preferable amount is 0.5-1% of the polyester.

The catalyst used in the invention is Zn (CH)₃COO)₂、Mn(CH₃COO)₂、Mg(CH₃COO)₂、Pb(CH₃COO)₂、ZnO、Fe₂O₃、Co₃O₄、MnO₂、SnO₂、Ni₂O₃、ZnCl₂、NaCl、MgCl₂、Na₂CO₃One or more of the above; preferably Zn (CH)₃COO)₂、Fe₂O₃、MgCl₂、Na₂CO₃One kind of (1). The amount of the catalyst is 0.5-10% of the mass of the polyester, and the preferable amount is 0.5-3% of the mass of the polyester.

The alcohol suitable for the invention is glycol, glycerol, diethylene glycol, polyethylene glycol, triethylene glycol, butanediol, hexanediol and the like. The amount of the alcohol is 2-6 times of the mass of the polyester, and preferably the amount of the glycol, the butanediol and the hexanediol is 2-4 times of the mass of the polyester.

The invention has the remarkable characteristic that the photo-thermal technology is adopted for heating and catalyzing a polyester degradation reaction system for the first time. The photothermal reaction greatly improves the degradation efficiency, the combination of the photothermal effect and the catalytic effect greatly shortens the reaction time, and the reaction can be carried out under normal pressure.

Drawings

FIG. 1 is a schematic diagram of an example photoreactor;

FIG. 2 is a nuclear magnetic spectrum of the ester monomer bis (2-hydroxyethyl) terephthalate, tested using a Bruker Avance DPX 600 MHz instrument with deuterated-dimethylsulfoxide as the solvent.

Detailed Description

The present invention will be further described by way of the following examples which are intended to illustrate the principal technical features and process advantages of the present invention, but the present invention is not limited to the following examples, and various changes and modifications can be made within the technical scope of the present invention without departing from the spirit of the invention described before and after. The raw materials of the invention are all the existing products, the specific reaction operation and the test method are the conventional methods in the field, wherein the photothermal reaction is carried out under normal pressure and conventional stirring in the air, a 300W xenon lamp is used for illumination, and an ATEST temperature detector is used for testing the temperature of the reaction system; the polyester chips are similar in size to the nail cover, the embodiment and the comparative example; the waste polyester was purchased from santa de force chemicals, ltd, kunshan, wherein examples 1-17, comparative example 1, and comparative example 2 were polyethylene terephthalate (PET).

Example 1

Taking 5g of waste PET fragments and 0.025 g of Zn (CH)₃COO)₂Adding a catalyst, 0.05 g of a carbon nano tube photo-thermal material and 20 g of ethylene glycol into a photoreactor, placing the reactor under a light source for illumination, and carrying out heat preservation reaction for 60 min when the system temperature is 190 ℃; after the reaction is finished, filtering and separating a filter cake containing the photo-thermal material and the catalyst while the reaction is hot, and drying the filter cake, wherein no polyester fragment is observed; naturally cooling the clear filtrate separated by filtering, and separating out white bis (2-hydroxyethyl) terephthalate crystals; then filtering, washing and drying to obtain the pure terephthalic acid bis (2-hydroxyethyl) ester monomer. Under the conditions, the degradation rate of PET is 100%, the yield of the monomer bis (2-hydroxyethyl) terephthalate is 95.39%, and the monomer yield is obtained according to the molar weight of the product ester monomer to the molar weight of polyester, wherein the molecular weight of the bis (2-hydroxyethyl) terephthalate is 254 g/mol, and the molecular weight of the polyester is 192 g/mol; FIG. 2 is a nuclear magnetic spectrum of monomeric bis (2-hydroxyethyl) terephthalate.

Example 2

Weighing 5g of waste PET fragments and 0.025 g of Zn (CH)₃COO)₂The method comprises the following steps of (1) weighing 20 g of ethylene glycol as a catalyst and 0.05 g of molybdenum sulfide photothermal material, adding the ethylene glycol into a photoreactor, placing the reactor under a light source for illumination, and carrying out heat preservation reaction for 60 min when the system temperature is 190 ℃; after the reaction was completed, the hot material was separated by filtration while it was hot and dried, and no polyester chips were observed. The filtrate is cooled down and the filtrate is cooled down,white bis (2-hydroxyethyl) terephthalate crystals precipitated. Then filtering, washing and drying to obtain the pure terephthalic acid bis (2-hydroxyethyl) ester monomer. Under these conditions, the degradation rate of PET was 100% and the yield of monomeric bis (2-hydroxyethyl) terephthalate was 94.24%.

Example 3

Weighing 5g of waste PET fragments and 0.025 g of Zn (CH)₃COO)₂Catalyst, 0.05 g palladium nano-sheet photo-thermal material, weighing 20 g ethylene glycol, adding into a photoreactor, placing the reactor under a light source for illumination, and keeping the temperature of the system at 190 ℃ for reaction for 60 min; after the reaction is finished, the hot material is filtered and separated while the material is hot, and then the material is dried. The filtrate was cooled and white bis (2-hydroxyethyl) terephthalate crystals precipitated. Then filtering, washing and drying to obtain the pure terephthalic acid bis (2-hydroxyethyl) ester monomer. Under these conditions, the degradation rate of PET was 100% and the yield of monomeric bis (2-hydroxyethyl) terephthalate was 93.77%.

Example 4

Weighing 5g of waste PET fragments and 0.025 g of Zn (CH)₃COO)₂The catalyst and 0.25 g of the carbon nano tube photo-thermal material are weighed, 20 g of ethylene glycol is added into a photo-reactor, then the reactor is placed under a light source for illumination, and the reaction is carried out for 60 min under the condition that the temperature of the system is 190 ℃; after the reaction is finished, the hot material is filtered and separated while the material is hot, and then the material is dried. The filtrate was cooled and white bis (2-hydroxyethyl) terephthalate crystals precipitated. Then filtering, washing and drying to obtain the pure terephthalic acid bis (2-hydroxyethyl) ester monomer. Under these conditions, the degradation rate of PET was 100% and the yield of monomeric bis (2-hydroxyethyl) terephthalate was 95.89%.

Weighing 5g of waste PET fragments and 0.025 g of Zn (CH)₃COO)₂The catalyst and 0.1 g of the carbon nano tube photo-thermal material are weighed, 20 g of ethylene glycol is added into a photo-reactor, then the reactor is placed under a light source for illumination, and the reaction is carried out for 60 min under the condition that the temperature of the system is 190 ℃; after the reaction is finished, the hot material is filtered and separated while the material is hot, and then the material is dried. The filtrate was cooled, and white BHET crystals precipitated. Then after filtration, water washing and dryingObtaining the pure terephthalic acid bis (2-hydroxyethyl) ester monomer. Under these conditions, the degradation rate of PET was 100% and the yield of monomeric bis (2-hydroxyethyl) terephthalate was 94.93%.

Weighing 5g of waste polyester chips and 0.025 g of Zn (CH)₃COO)₂The catalyst and 0.005 g of carbon nano tube photo-thermal material are weighed, 20 g of ethylene glycol is added into a photo-reactor, then the reactor is placed under a light source for illumination, and the reaction is carried out for 60 min under the condition that the temperature of the system is 190 ℃; after the reaction is finished, the hot material is filtered and separated while the material is hot, and then the material is dried. The filtrate was cooled and white bis (2-hydroxyethyl) terephthalate crystals precipitated. Then filtering, washing and drying to obtain the pure terephthalic acid bis (2-hydroxyethyl) ester monomer. Under these conditions, the degradation rate of PET was 100% and the yield of monomeric bis (2-hydroxyethyl) terephthalate was 89.32%.

Example 5

Weighing 5g of waste PET fragments and 0.025 g of Fe₂O₃The catalyst and 0.05 g of the carbon nano tube photo-thermal material are weighed, 20 g of ethylene glycol is added into a photo-reactor, then the reactor is placed under a light source for illumination, and the reaction is carried out for 60 min under the condition that the system temperature is 190 ℃; after the reaction is finished, the hot material is filtered and separated while the material is hot, and then the material is dried. The filtrate was cooled and white bis (2-hydroxyethyl) terephthalate crystals precipitated. Then filtering, washing and drying to obtain the pure terephthalic acid bis (2-hydroxyethyl) ester monomer. Under these conditions, the degradation rate of PET was 100% and the yield of monomeric bis (2-hydroxyethyl) terephthalate was 92.14%.

Example 6

Weighing 5g of waste PET chips and 0.025 g of MgCl₂The catalyst and 0.05 g of the carbon nano tube photo-thermal material are weighed, 20 g of ethylene glycol is added into a photo-reactor, then the reactor is placed under a light source for illumination, and the reaction is carried out for 60 min under the condition that the system temperature is 190 ℃; after the reaction is finished, the hot material is filtered and separated while the material is hot, and then the material is dried. The filtrate was cooled and white bis (2-hydroxyethyl) terephthalate crystals precipitated. Then filtering, washing and drying to obtain the pure terephthalic acid bis (2-hydroxyethyl) ester monomer. Under these conditions, of PETThe degradation rate was 100%, and the yield of monomeric bis (2-hydroxyethyl) terephthalate was 94.58%.

Example 7

Weighing 5g of waste PET fragments and 0.025 g of Na₂CO₃The catalyst and 0.05 g of the carbon nano tube photo-thermal material are weighed, 20 g of ethylene glycol is added into a photo-reactor, then the reactor is placed under a light source for illumination, and the reaction is carried out for 60 min under the condition that the system temperature is 190 ℃; after the reaction is finished, the hot material is filtered and separated while the material is hot, and then the material is dried. The filtrate was cooled and white bis (2-hydroxyethyl) terephthalate crystals precipitated. Then filtering, washing and drying to obtain the pure terephthalic acid bis (2-hydroxyethyl) ester monomer. Under the conditions, the degradation rate of PET is 100%, and the yield of the monomer terephthalic acid bis (2-hydroxyethyl) ester is 85.03%.

Example 8

Weighing 5g of waste PET fragments and 0.15 g of Zn (CH)₃COO)₂The catalyst and 0.05 g of the carbon nano tube photo-thermal material are weighed, 20 g of ethylene glycol is added into a photo-reactor, then the reactor is placed under a light source for illumination, and the reaction is carried out for 60 min under the condition that the system temperature is 190 ℃; after the reaction is finished, the hot material is filtered and separated while the material is hot, and then the material is dried. The filtrate was cooled and white bis (2-hydroxyethyl) terephthalate crystals precipitated. Then filtering, washing and drying to obtain the pure terephthalic acid bis (2-hydroxyethyl) ester monomer. Under these conditions, the degradation rate of PET was 100% and the yield of monomeric bis (2-hydroxyethyl) terephthalate was 95.73%.

Example 9

Weighing 5g of waste PET fragments and 0.025 g of Zn (CH)₃COO)₂The method comprises the following steps of (1) weighing 20 g of butanediol as a catalyst and 0.05 g of carbon nanotube photo-thermal material, adding the butanediol into a photoreactor, placing the reactor under a light source for illumination, and carrying out heat preservation reaction for 60 min when the system temperature is 190 ℃; after the reaction is finished, the hot material is filtered and separated while the material is hot, and then the material is dried. The filtrate was cooled and white bis (2-hydroxybutyl) terephthalate crystals precipitated. Then filtering, washing and drying to obtain the pure terephthalic acid bis (2-hydroxybutyl) ester monomer. Under the condition, the degradation rate of PET is 100 percent,the yield of monomeric bis (2-hydroxybutyl) terephthalate was 84.27%.

Example 10

Weighing 5g of waste PET fragments and 0.025 g of Zn (CH)₃COO)₂The catalyst and 0.05 g of carbon nano tube photo-thermal material are weighed, 20 g of hexanediol is added into a photo reactor, then the reactor is placed under a light source for illumination, and the reaction is carried out for 60 min under the condition that the system temperature is 190 ℃; after the reaction is finished, the hot material is filtered and separated while the material is hot, and then the material is dried. The filtrate was cooled and white bis (2-hydroxyhexyl) terephthalate crystals precipitated. Then filtering, washing and drying to obtain the pure terephthalic acid bis (2-hydroxyhexyl) ester monomer. Under these conditions, the degradation rate of PET was 100% and the yield of monomeric bis (2-hydroxyhexyl) terephthalate was 66.37%.

Example 11

Weighing 5g of waste PET fragments and 0.025 g of Zn (CH)₃COO)₂Catalyst, 0.05 g of carbon nano tube photo-thermal material, 10 g of ethylene glycol is weighed and added into a photo reactor, then the reactor is placed under a light source for illumination, and the reaction is carried out for 60 min under the condition that the system temperature is 190 ℃; after the reaction is finished, the hot material is filtered and separated while the material is hot, and then the material is dried. The filtrate was cooled and white bis (2-hydroxyethyl) terephthalate crystals precipitated. Then filtering, washing and drying to obtain the pure terephthalic acid bis (2-hydroxyethyl) ester monomer. Under these conditions, the degradation rate of PET was 100% and the yield of monomeric bis (2-hydroxyethyl) terephthalate was 90.27%.

Weighing 5g of waste PET fragments and 0.025 g of Zn (CH)₃COO)₂Catalyst, 0.05 g of carbon nano tube photo-thermal material, weighing 30 g of ethylene glycol, adding into a photo reactor, placing the reactor under a light source for illumination, and keeping the temperature of the system at 190 ℃ for reaction for 60 min; after the reaction is finished, the hot material is filtered and separated while the material is hot, and then the material is dried. The filtrate was cooled and white bis (2-hydroxyethyl) terephthalate crystals precipitated. Then filtering, washing and drying to obtain the pure terephthalic acid bis (2-hydroxyethyl) ester monomer. Under the condition, the degradation rate of PET is 100 percent, and the yield of the monomer terephthalic acid bis (2-hydroxyethyl) ester is94.48％。

Example 12

Weighing 5g of waste PET fragments and 0.025 g of Zn (CH)₃COO)₂The catalyst and 0.05 g of the carbon nano tube photo-thermal material are weighed, 20 g of ethylene glycol is added into a photo-reactor, then the reactor is placed under a light source for illumination, and the reaction is carried out for 60 min under the condition that the system temperature is 160 ℃; after the reaction was completed, the hot material was separated by filtration while it was hot and dried, and a small amount of polyester chips was observed. The filtrate was cooled and white bis (2-hydroxyethyl) terephthalate crystals precipitated. Then filtering, washing and drying to obtain the pure terephthalic acid bis (2-hydroxyethyl) ester monomer. Under these conditions, the yield of monomeric bis (2-hydroxyethyl) terephthalate was 83.93%, and the degradation rate of PET was 94.30%, as a small amount of polyester chips divided by 5 g.

Example 13

Weighing 5g of waste PET fragments and 0.025 g of Zn (CH)₃COO)₂The catalyst and 0.05 g of the carbon nano tube photo-thermal material are weighed, 20 g of ethylene glycol is added into a photo-reactor, then the reactor is placed under a light source for illumination, and the reaction is carried out for 60 min under the condition that the system temperature is 130 ℃; after the reaction was completed, the hot material was separated by filtration while it was hot and dried, and polyester chips were observed. The filtrate was cooled and white bis (2-hydroxyethyl) terephthalate crystals precipitated. Then filtering, washing and drying to obtain the pure terephthalic acid bis (2-hydroxyethyl) ester monomer. Under these conditions, the degradation rate of PET was 80.68%, and the yield of monomeric bis (2-hydroxyethyl) terephthalate was 71.27%.

Example 14

Weighing 5g of waste PET fragments and 0.025 g of Zn (CH)₃COO)₂Catalyst, 0.05 g of carbon nano tube photo-thermal material, weighing 30 g of ethylene glycol, adding into a photo-reactor, placing the reactor under a light source for illumination, and keeping the temperature of the system at 110 ℃ for reaction for 60 min; after the reaction was completed, the hot material was separated by filtration while it was hot and dried, and polyester chips were observed. The filtrate was cooled and white bis (2-hydroxyethyl) terephthalate crystals precipitated. Then filtering, washing and drying to obtain pure terephthalic acid bis (2-hydroxyethyl) ester monoAnd (3) a body. Under these conditions, the degradation rate of PET was 71.55%, and the yield of monomeric bis (2-hydroxyethyl) terephthalate was 59.82%.

Example 15

Weighing 5g of waste PET fragments and 0.025 g of Zn (CH)₃COO)₂Catalyst, 0.05 g of carbon nano tube photo-thermal material, weighing 30 g of ethylene glycol, adding into a photo-reactor, placing the reactor under a light source for illumination, and keeping the temperature of the system at 80 ℃ for reaction for 60 min; after the reaction was completed, the hot material was separated by filtration while it was hot and dried, and many polyester chips were observed. The filtrate was cooled and white bis (2-hydroxyethyl) terephthalate crystals precipitated. Then filtering, washing and drying to obtain the pure terephthalic acid bis (2-hydroxyethyl) ester monomer. Under these conditions, the degradation rate of PET was 65.39%, and the yield of monomeric bis (2-hydroxyethyl) terephthalate was 51.65%.

Comparative example 1

Weighing 5g of waste PET fragments and 0.025 g of Zn (CH)₃COO)₂Catalyst, 0.05 g of carbon nano tube photo-thermal material, 30 g of ethylene glycol is measured and added into a reactor, oil bath heating is carried out, and the system is kept at 80 ℃ for reaction for 60 min; after the reaction is finished, the hot material is filtered and separated while the hot material is hot, a large amount of polyester chips are observed, and the polyester chips are taken out and weighed to be still 5g, and the size of the polyester chips is not different from that of the original waste polyester chips, which indicates that the waste polyester chips are not degraded.

Weighing 5g of waste PET fragments and 0.025 g of Zn (CH)₃COO)₂Weighing 30 g of ethylene glycol as a catalyst, adding the ethylene glycol into a reactor, heating in an oil bath, and keeping the temperature of the system at 80 ℃ for reaction for 60 min; after the reaction is finished, filtering and separating out solids while the waste polyester chips are hot, drying the solids, observing a large amount of polyester chips, taking out the polyester chips, weighing the polyester chips to find that the polyester chips are still 5g, and the size of the polyester chips is not different from that of the original waste polyester chips, which indicates that the waste polyester chips are not degraded.

Example 16

Weighing 5g of waste PET fragments and 0.025 g of Zn (CH)₃COO)₂Catalyst, 0.05 g of carbon nano tube photo-thermal material, 20 g of ethylene glycol is weighed and added into a photo reactor, and then the reactor is placed under a light source for illuminationKeeping the temperature at 190 ℃ and reacting for 30 min; after the reaction is finished, the hot material is filtered and separated while the material is hot, and then the material is dried. The filtrate was cooled and white bis (2-hydroxyethyl) terephthalate crystals precipitated. Then filtering, washing and drying to obtain the pure terephthalic acid bis (2-hydroxyethyl) ester monomer. Under these conditions, the degradation rate of PET was 100% and the yield of monomeric bis (2-hydroxyethyl) terephthalate (BHET) was 90.39%.

Comparative example 2

Weighing 5g of waste PET fragments and 0.025 g of Zn (CH)₃COO)₂Weighing 20 g of ethylene glycol as a catalyst, adding the ethylene glycol into a reactor, heating in an oil bath, and carrying out heat preservation reaction for 30 min when the system temperature is 190 ℃; after the reaction was completed, the solid was separated by filtration while it was hot and dried, and slightly polyester chips were observed, and the degradation rate of PET was 37.83% and the yield of monomeric bis (2-hydroxyethyl) terephthalate was 20.39% by taking out and weighing.

The reaction time was adjusted to 90 min, the degradation rate of PET was 70.52%, and the yield of monomeric bis (2-hydroxyethyl) terephthalate was 60.18%.

Example 17

Weighing 5g of waste PET fragments and 0.025 g of Zn (CH)₃COO)₂The catalyst and 0.05 g of the carbon nano tube photo-thermal material are weighed, 20 g of ethylene glycol is added into a photo-reactor, then the reactor is placed under a light source for illumination, and the reaction is carried out for 90 min under the condition that the system temperature is 190 ℃; after the reaction is finished, the hot material is filtered and separated while the material is hot, and then the material is dried. The filtrate was cooled and white monomer bis (2-hydroxyethyl) terephthalate crystals precipitated. Then filtering, washing and drying to obtain the pure terephthalic acid bis (2-hydroxyethyl) ester monomer. Under these conditions, the degradation rate of PET was 100% and the yield of monomeric bis (2-hydroxyethyl) terephthalate was 95.94%.

Example 18

Weighing 5g of waste Polycarbonate (PC) chips and 0.025 g of Zn (CH)₃COO)₂Catalyst, 0.05 g of carbon nano tube photo-thermal material, 20 g of ethylene glycol is weighed and added into a photo reactor, then the reactor is placed under a light source for illumination, and the system temperature is kept at 100 DEG CReacting at a warm temperature for 30 min; after the reaction is finished, the hot material is filtered and separated while the material is hot, and then the material is dried. Adding ethyl acetate into the filtrate for extraction, and precipitating white monomer bisphenol A. Then filtering, washing and drying to obtain pure bisphenol A monomer. Under these conditions, the degradation rate of PC was 100% and the yield of monomeric bisphenol A monomer was 93.27%.

Weighing 5g of waste polylactic acid (PLA) fragments and 0.025 g of Zn (CH)₃COO)₂The catalyst and 0.05 g of the carbon nano tube photo-thermal material are weighed, 20 g of ethanol is added into a photo-reactor, then the reactor is placed under a light source for illumination, and the reaction is carried out for 30 min under the condition that the system temperature is 50 ℃; after the reaction is finished, the hot material is filtered and separated while the material is hot, and then the material is dried. The filtrate was distilled under reduced pressure to obtain ethyl lactate. Under the condition, the degradation rate of PLA is 100%, and the yield of monomer ethyl lactate is 89.11%.

The invention mainly applies the photo-thermal technology to heat the waste polyester and assist the catalytic degradation. Compared with the traditional heating mode, the photo-thermal technology is used for heating, so that the energy consumption in the polyester degradation process is reduced, and the degradation efficiency of the polyester is greatly improved. In particular, the invention can degrade polyester to prepare monomer under normal pressure and air, and is easy for industrialized popularization.