A supercritical decolorization and degradation coupling system and method for waste dyed PET foam.

Abstract

The present invention discloses a supercritical decolorization and degradation coupling system and method for waste dyed PET foam. In order to solve the problem that the two functions of decolorization and degradation could not be achieved in the same system at one time in the past, the present invention first introduces carbon dioxide and a co-solvent into a reactor containing PET foam under a supercritical state for decolorization, and the PET foam can be completely decolorized under appropriate conditions. After the decolorization is completed, methanol is introduced into the reactor for circulation, and the decolorized PET foam is subjected to alcoholysis reaction under a sub- / supercritical state, and a high-purity degradation product can be obtained after post-processing. The system and method complete the two-step decolorization and alcoholysis reactions in one system at one time, and have the advantages of simple process, small equipment investment, high reaction efficiency, high product quality, low operating cost, and continuous production. It provides a new way to purify, recycle and high-quality utilization of waste dyed PET foam, which is in line with the concept of sustainable development.

Description

Technical Field

[0001] This invention relates to the field of waste plastic resource utilization and recycling technology, and in particular to a supercritical decolorization and degradation coupling system and method for waste dyed PET foam. Background Art

[0002] Polyethylene terephthalate (PET) is a semi-crystalline thermoplastic polymer that plays a vital role in thermoplastic polyesters. It is widely used in the plastics industry due to its stable chemical structure, good flexibility and processability, and low cost. Currently, domestic and international research on waste PET recycling focuses primarily on PET bottles, emphasizing improved recycling processes, increased recovery rates, and expanded application areas. Dyed PET, as a significant component of waste polyester, is widely used; however, due to its high separation and purification costs, it is typically disposed of through landfill or incineration. This limits the scope and lifespan of the degradation products. Therefore, decolorization is crucial for achieving its resource recovery and upgraded reuse.

[0003] Chemical recycling utilizes chemical methods to depolymerize waste polyester into monomers, which can then be polymerized back into virgin materials, retaining the properties of the materials or the economic value of the polymers. This allows for the upgraded recycling of waste PET polyester. Hydrolysis, alcoholysis, and ammonolysis are currently the main methods of chemical recycling. Among them, alcoholysis is the most widely used method in industry, primarily using methanol, ethylene glycol, and polyols to yield ethylene glycol (EG), dimethyl terephthalate (DMT), ethylene glycol terephthalate (BHET), dioctyl terephthalate (DOTP), etc. Studies have successfully applied alcoholysis to the degradation of polyester, yielding high yields of monomers.

[0004] Decolorizing waste PET dyeing can reduce the adverse effects of impurities such as dyeing agents and ensure product quality. Currently, direct decolorization of dyed polyester is mostly done by sodium hypochlorite oxidation or by using Na2S2O4 / caustic soda as a reducing agent, but its decolorization performance is poor, especially when the demand for dyed polyester is high, the decolorization efficiency is difficult to meet market requirements. Dimethyl sulfoxide (DMSO) has good swelling properties because of its small molecular weight, which allows it to enter the amorphous region of polyester more easily. N,N-dimethylformamide (DMF) and acetone have strong solubility for organic compounds, good chemical stability and can be recycled, making them suitable as decolorizing agents for foam materials. However, these are all chemical decolorization methods, which inevitably generate a large amount of organic waste liquid, making subsequent treatment difficult and increasing recycling costs. Supercritical CO2 is widely used in extraction, foaming, polymerization reactions and cleaning because it is easy to reach critical conditions, non-toxic, highly soluble and has excellent diffusion ability. Supercritical CO2 possesses the ability to swell polymers and readily penetrates the interior of polyester. Combined with its dye-dissolving ability, it extracts dyes from polyester, significantly improving decolorization efficiency compared to traditional methods. The CO2 used in the decolorization process is non-toxic, inexpensive, and recyclable, meeting the dual-carbon target requirements. Supercritical fluids have also attracted attention due to their relatively mild reaction conditions and excellent properties such as strong diffusivity and solubility. Supercritical / subcritical methanol possesses physicochemical properties not found in other organic solvents; it can be used as both a reaction medium and a reactant, exhibiting excellent transport, solubility, and reactivity characteristics. Its application in plastic degradation offers advantages such as rapid reaction speed, mildness, and the absence of gases and byproducts, making it suitable as a recyclable solvent. Chinese patent CN115198509A discloses a supercritical carbon dioxide decolorization system and method, achieving a process route that allows for multiple recycling of carbon dioxide and decolorizing agents, with a decolorization rate of over 90% for textiles. However, this system is complex to operate and can only perform a single decolorization operation. Chinese patent CN118185123A invented a method for methanol alcoholysis of waste PET polyester catalyzed by a non-metallic eutectic solvent, which successfully degraded PET and obtained a certain yield of DMT monomer. However, this method uses a catalyst, which results in high cost.

[0005] Existing technologies have extensively reported processes for simple polyester decolorization and degradation, with some even applied industrially. However, significant problems include high equipment investment, long production cycles, high operating costs, large plant and land area requirements, and cumbersome upstream and downstream process connections, which greatly increases the cost of polyester recycling and severely hinders the large-scale industrialization of the technology. Therefore, inventing an integrated decolorization-degradation system and method is key to solving these problems.

[0006] Currently, the decolorization and degradation of dyed PET has been a major obstacle in the industrial recycling of waste PET polyester. There is an urgent need for a highly efficient, environmentally friendly, low-cost, and high-yield coupled solution for PET decolorization and degradation to integrate the decolorization and degradation processes, shorten the recycling process of waste polyester, improve economic efficiency, and alleviate the environmental pollution and energy consumption problems caused by waste polyester. Summary of the Invention

[0007] To address the technical challenges of integrating decolorization and degradation of dyed PET foam, this invention proposes a supercritical decolorization and degradation coupling system and method for waste dyed PET foam.

[0008] The technical solution of this invention:

[0009] A supercritical decolorization and degradation coupling system for waste dyed PET foam includes a first filter, a second filter, a carbon dioxide storage tank, a co-solvent storage tank, a methanol storage tank, a condenser, a first plunger pump, a second plunger pump, a constant flow pump, a heater, a circulation pump, a dye collection tank, a degradation product storage tank, multiple reactors, and a separator.

[0010] The outlet of the carbon dioxide storage tank is connected in sequence via pipeline to a first filter, a condenser, a regulating valve, and a first plunger pump for conveying liquid carbon dioxide. The co-solvent storage tank is connected via pipeline to a constant flow pump for conveying the co-solvent stream. The mixed fluid resulting from the convergence of the carbon dioxide and co-solvent streams is connected via pipeline to the inlet of a heater. The outlet pipeline of the heater is connected in parallel to multiple reactors. These reactors are interconnected, and the mixed fluid flowing out of the reactors after decolorization is connected to the inlet of a separator. The separator separates the gas and liquid. The gas outlet of the separator is connected to the inlet of the carbon dioxide storage tank via pipeline and a second filter, and the liquid outlet of the separator is connected to a dye collection tank.

[0011] The methanol storage tank is connected to a second plunger pump via pipeline, and then to the methanol inlets of multiple reactors in parallel. The outlets of the multiple reactors are connected to their respective methanol inlets via pipelines and circulation pumps, forming a circulation loop. The product outlets of the multiple reactors are all connected to a degradation product storage tank.

[0012] The reactor and separator are used for continuous decolorization and degradation reactions. Both the reactor and separator are equipped with heating jackets to control the temperature. A pressure reducing valve needs to be installed on the carbon dioxide storage tank. The entire system needs to be equipped with a vent valve for shutdown and maintenance. Valves need to be installed at both ends of the reactor and separator to ensure stable operation of the system.

[0013] A supercritical decolorization and degradation coupling method for waste dyed PET foam includes the following steps:

[0014] (1) The PET foam is crushed using a crusher;

[0015] (2) After sieving the crushed PET foam, fill the reactor to form a packed bed, and set the reactor temperature at 60℃~80℃;

[0016] (3) Carbon dioxide carrying the co-solvent is mixed and preheated by a heater and then introduced into the reactor for decolorization. The pressure of carbon dioxide is maintained at 15-18 MPa, the flow rate of carbon dioxide is 2 cm / s-10 cm / s, and the flow rate of the co-solvent is set to 0.02 cm / s-0.1 cm / s.

[0017] (4) Carbon dioxide entrained co-solvent flows through the first reactor and comes into full contact with the PET foam in the packed bed to decolorize it. The decolorization time is 2h to 4h.

[0018] (5) After decolorization is complete, stop feeding carbon dioxide and co-solvent into the first reactor, open the valve for supplying the medium from the first reactor to the second reactor, and discharge the carbon dioxide medium containing the co-solvent remaining in the first reactor into the second reactor so that it can be fully utilized. After the pressure of the two reactors is balanced, close the valve for supplying the medium from the first reactor to the second reactor, and input the remaining carbon dioxide in the first reactor into the separator until the pressure of the first reactor is 1MPa to 2MPa. Then start feeding carbon dioxide and co-solvent into the second reactor to complete the switching between the first and second reactors. At this time, the second reactor performs the decolorization operation under the same conditions as the first reactor. The carbon dioxide remaining in the first reactor can be used as an enhancing medium for alcoholysis reaction. After the carbon dioxide and co-solvent fluid that has extracted the dye are transported to the separator, gas-liquid separation is performed. The vaporized carbon dioxide is filtered through the second filter and returned to the carbon dioxide storage tank. The co-solvent and dye are stored in liquid state in the dye collection tank for further processing.

[0019] (6) Change the temperature of the first reactor to 200-240℃, and introduce methanol into the reactor at a mass ratio of 6-8:1 to PET foam. The initial pressure of the reactor is 1-2 MPa, which is the residual carbon dioxide pressure when the pressure is released. After heating, the final reaction pressure is 8-15 MPa. After the temperature and pressure stabilize, turn off the methanol feed pump and turn on the methanol circulation pump to circulate methanol so that it can undergo alcoholysis reaction with the decolorized PET foam. The initial reaction pressure is 1-2 MPa, the reaction temperature is 220℃-240℃, and the reaction time is 1-2 hours.

[0020] (7) After the alcoholysis reaction is completed, the product in the first reactor is introduced into the degradation product storage tank, the first reactor is cleaned and refilled with dyed PET foam, and the decolorization step is repeated. The decolorization-alcoholysis coupling reaction is carried out in sequence to achieve the purpose of recovering the dye and PET degradation products of dyed PET foam in one system.

[0021] The solid phase product of the alcoholysis reaction is mainly dimethyl terephthalate (DMT), and the liquid phase product is mainly ethylene glycol (EG). The products are separated into solid and liquid phases. The solid phase product is dried, and the liquid phase product is separated from the liquid phase by rotary evaporation. The cosolvent and methanol can be recycled after separation and purification.

[0022] HPLC (High Performance Liquid Chromatography) analysis of the main product, DMT, revealed a 100% depolymerization rate for PET foam, a DMT yield of 64%–80%, high reaction purity, and no significant side reactions. Figure 3 This refers to the product form after decolorization and alcoholysis.

[0023] Furthermore, the co-solvent is dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), ethylene glycol (EG), or acetone.

[0024] Furthermore, the mass ratio of the pulverized PET foam to the co-solvent is 1:8 to 10.

[0025] The advantages of this invention are: it completes the two-step reaction of decolorization and alcoholysis in one system, realizing the coupling of decolorization and alcoholysis. It has the advantages of simple process, low equipment investment, high reaction efficiency, green and environmentally friendly, good reaction selectivity, high product quality, low operating cost, and continuous production. It provides a new way to purify, recycle and utilize waste dyed PET foam, which is in line with the concept of sustainable development. Attached Figure Description

[0026] Figure 1 This invention proposes a supercritical decolorization and degradation coupling system for waste dyed PET foam.

[0027] Figure 2 The images shown are of the morphology of PET foam material before and after crushing during a specific implementation of this invention; the left image is before crushing; the right image is after crushing.

[0028] Figure 3 These are morphological diagrams of the products after decolorization and degradation during a specific implementation of the present invention; the left image shows the product after decolorization; the right image shows the product after degradation.

[0029] Figure 4 This is a liquid chromatogram of DMT after decolorization and degradation in an embodiment of the present invention. Detailed Implementation

[0030] The process flow in the embodiments of the present invention will be described in detail below with reference to the accompanying drawings and specific implementation methods. However, these specific implementation methods are not intended to limit the present invention.

[0031] The system structure diagram of this invention embodiment is as follows: Figure 1As shown, three reactors and one separator are connected in parallel. Preheated carbon dioxide, carrying the co-solvent, enters the decolorization process from the bottom of the first reactor, and then flows into the separator from the top of the reactor through a pipeline. The carbon dioxide is separated in the separator and then passes through a second filter to a carbon dioxide storage tank for continuous recycling. The co-solvent and dye are collected in a dye collection tank, and the co-solvent can be separated and recycled to a co-solvent storage tank for reuse.

[0032] After the first reactor has completed continuous decolorization, the supply of co-solvent and carbon dioxide is stopped. Methanol is then introduced using a second plunger pump to carry out the degradation reaction. A circulation pump allows the methanol to circulate in the first reactor to improve reaction efficiency.

[0033] While the first reactor is undergoing degradation, co-solvent and carbon dioxide are continuously introduced into the second reactor to decolorize the foamed material. Then, the foamed material in the second reactor is degraded according to the previous steps. While the foamed material in the second reactor is undergoing degradation, the foamed material in the third reactor can also be decolorized. At the same time, the product from the first reactor that has completed the degradation reaction can be collected, and the reactor can be reloaded to continue the previous decolorization and degradation operation. By adjusting the valves in the system, continuous operation of decolorization and degradation can be achieved.

[0034] Example 1

[0035] PET foam is pulverized using a pulverizer, then sieved and filled into a reactor to form a packed bed. The reactor temperature is set at 60℃. Carbon dioxide, carrying DMSO, is mixed and preheated by a heater before being introduced into the reactor for decolorization. The carbon dioxide pressure is maintained at 15MPa, the carbon dioxide flow rate is 2cm / s, and the co-solvent flow rate is set at 0.02cm / s. The mass ratio of the co-solvent (DMSO) to the pulverized PET foam is controlled at 10:1. The carbon dioxide carrying the co-solvent flows through the first reactor and fully contacts the PET foam in the packed bed, decolorizing it for 2 hours. After decolorization, the flow of carbon dioxide and co-solvent into the first reactor is stopped. The valve supplying the medium from the first reactor to the second reactor is opened, discharging the carbon dioxide medium carrying the co-solvent from the first reactor into the second reactor for full utilization. Once the pressures of the two reactors are balanced, the valve supplying the medium from the first reactor to the second reactor is closed. The remaining carbon dioxide in the first reactor is fed into a separator until the pressure in the first reactor reaches 1MPa. Then, carbon dioxide and co-solvent are introduced into the second reactor, completing the switch between the first and second reactors. At this point, the second reactor performs the decolorization operation under the same conditions as the first reactor. The residual carbon dioxide in the first reactor can be used as an enhancing medium for the alcoholysis reaction. The carbon dioxide and co-solvent fluid, after extracting the dye, are transported to a separator for gas-liquid separation. The vaporized carbon dioxide is filtered through a second filter and returned to the carbon dioxide storage tank. The co-solvent and dye are stored in liquid form in a dye collection tank for later processing. The temperature of the first reactor is changed to 220℃, and methanol is introduced into the reactor at a mass ratio of 6:1 to the foam material. The initial pressure of the reactor is 1 MPa, the pressure of the residual carbon dioxide at the time of depressurization. After the temperature and pressure stabilize, the methanol feed pump is turned off, and the methanol circulation pump is turned on to circulate methanol, allowing it to undergo an alcoholysis reaction with the decolorized PET foam material for 2 hours. After the alcoholysis reaction is completed, the product is collected. HPLC (high performance liquid chromatography) analysis of the main product, DMT, shows that the depolymerization rate of the PET foam material is 100%, and the DMT yield is 64%.

[0036] Example 2

[0037] PET foam is pulverized using a pulverizer, then sieved and filled into a reactor to form a packed bed. The reactor temperature is set at 70℃. Carbon dioxide, entrained with DMF, is mixed and preheated by a heater before being introduced into the reactor for decolorization. The carbon dioxide pressure is maintained at 16 MPa, the carbon dioxide flow rate is 6 cm / s, and the co-solvent flow rate is set at 0.06 cm / s. The mass ratio of the co-solvent (DMF) to the pulverized PET foam is controlled at 9:1. The carbon dioxide entrained with the co-solvent flows through the first reactor, making full contact with the PET foam in the packed bed and decolorizing it for 3 hours. After decolorization, the flow of carbon dioxide and co-solvent into the first reactor is stopped. The valve supplying the medium from the first reactor to the second reactor is opened, discharging the carbon dioxide medium carrying the co-solvent from the first reactor into the second reactor for full utilization. Once the pressures of the two reactors are balanced, the valve supplying the medium from the first reactor to the second reactor is closed. The remaining carbon dioxide in the first reactor is fed into a separator until the pressure in the first reactor reaches 1.5 MPa. Then, carbon dioxide and co-solvent are introduced into the second reactor, completing the switch between the first and second reactors. At this point, the second reactor performs the decolorization operation under the same conditions as the first reactor. The residual carbon dioxide in the first reactor can be used as an enhancing medium for the alcoholysis reaction. The carbon dioxide and co-solvent fluid, after extracting the dye, are transported to a separator for gas-liquid separation. The vaporized carbon dioxide is filtered through a second filter and returned to the carbon dioxide storage tank. The co-solvent and dye are stored in liquid form in a dye collection tank for further processing. The temperature of the first reactor is changed to 230℃, and methanol is introduced into the reactor at a mass ratio of 7:1 to the foam material. The initial pressure of the reactor is 1.5 MPa, the pressure of the residual carbon dioxide at depressurization. After the temperature and pressure stabilize, the methanol feed pump is turned off, and the methanol circulation pump is turned on to circulate methanol, allowing it to undergo an alcoholysis reaction with the decolorized PET foam material for 1.5 hours. After the alcoholysis reaction is complete, the product is collected. HPLC (High Performance Liquid Chromatography) analysis of the main product, DMT, shows that the depolymerization rate of the PET foam material is 100%, and the DMT yield is 71%.

[0038] Example 3

[0039] PET foam is pulverized using a pulverizer, then sieved and filled into a reactor to form a packed bed. The reactor temperature is set at 80℃. Carbon dioxide, carrying acetone, is mixed and preheated by a heater before being introduced into the reactor for decolorization. The carbon dioxide pressure is maintained at 18MPa, the carbon dioxide flow rate is 10cm / s, and the co-solvent flow rate is set at 0.1cm / s. The mass ratio of the co-solvent (acetone) to the pulverized PET foam is controlled at 8:1. The carbon dioxide carrying the co-solvent flows through the first reactor and fully contacts the PET foam in the packed bed to decolorize it for 4 hours. After decolorization, the flow of carbon dioxide and co-solvent into the first reactor is stopped. The valve for supplying the medium from the first reactor to the second reactor is opened, and the carbon dioxide medium carrying the co-solvent remaining in the first reactor is discharged into the second reactor to ensure its full utilization. After the pressures of the two reactors are balanced, the valve for supplying the medium from the first reactor to the second reactor is closed. The remaining carbon dioxide in the first reactor is fed into a separator until the pressure in the first reactor reaches 2MPa. Then, carbon dioxide and co-solvent are introduced into the second reactor, completing the switch between the first and second reactors. At this point, the second reactor performs the decolorization operation under the same conditions as the first reactor. The residual carbon dioxide in the first reactor can be used as an enhancing medium for the alcoholysis reaction. The carbon dioxide and co-solvent fluid, after extracting the dye, are transported to a separator for gas-liquid separation. The vaporized carbon dioxide is filtered through a second filter and returned to the carbon dioxide storage tank. The co-solvent and dye are stored in liquid form in a dye collection tank for later processing. The temperature of the first reactor is changed to 240℃, and methanol is introduced into the reactor at a mass ratio of 8:1 to the foam material. The initial pressure of the reactor is 2 MPa, the pressure of the residual carbon dioxide during depressurization. After the temperature and pressure stabilize, the methanol feed pump is turned off, and the methanol circulation pump is turned on to circulate methanol, allowing it to undergo an alcoholysis reaction with the decolorized PET foam material for 1 hour. After the alcoholysis reaction is complete, the product is collected. HPLC (High Performance Liquid Chromatography) analysis of the main product, DMT, shows that the depolymerization rate of the PET foam material is 100%, and the DMT yield is 80%.

Claims

1. A supercritical decolorization and degradation coupling system for waste dyed PET foam, characterized in that, It includes a first filter, a second filter, a carbon dioxide storage tank, a co-solvent storage tank, a methanol storage tank, a condenser, a first plunger pump, a second plunger pump, a constant flow pump, a heater, a circulation pump, a dye collection tank, a degradation product storage tank, multiple reactors, and a separator; The outlet of the carbon dioxide storage tank is connected in sequence to a first filter, a condenser, a regulating valve, and a first plunger pump via pipelines for transporting liquid carbon dioxide. The cosolvent storage tank is connected to a constant flow pump via pipelines for transporting the cosolvent. The mixed fluid after the pipelines transporting carbon dioxide and the cosolvent merge is connected to the inlet of a heater via a pipeline. The outlet pipeline of the heater is connected in parallel to multiple reactors. The multiple reactors can be interconnected, and the mixed fluid flowing out of the reactors after decolorization is connected to the inlet of a separator. The separator is used to separate gas and liquid. The gas outlet of the separator is connected to the inlet of the carbon dioxide storage tank via pipelines and a second filter. The liquid outlet of the separator is connected to the dye collection tank. The methanol storage tank is connected to a second plunger pump via a pipeline, and then connected in parallel to the methanol inlets of multiple reactors; the outlets of multiple reactors are connected to the methanol inlets of their respective reactors via pipelines and circulation pumps to form a circulation loop; the product outlets of multiple reactors are all connected to a degradation product storage tank. The reactor and separator are used for continuous decolorization and degradation reactions. Both the reactor and separator are equipped with heating jackets to control the temperature. A pressure reducing valve needs to be installed on the carbon dioxide storage tank. The entire system needs to be equipped with a vent valve for shutdown and maintenance. Valves need to be installed at both the inlet and outlet of the reactor and separator to ensure stable operation of the system.

2. A supercritical decolorization and degradation coupling method for waste dyed PET foam using the supercritical decolorization and degradation coupling system of claim 1, characterized in that, The steps include: (1) The PET foam is crushed using a crusher; (2) After sieving the crushed PET foam, fill the reactor to form a packed bed, and set the reactor temperature at 60℃~80℃; (3) Carbon dioxide carrying the co-solvent is mixed and preheated by a heater and then introduced into the reactor for decolorization. The pressure of carbon dioxide is maintained at 15-18 MPa, the flow rate of carbon dioxide is 2 cm / s-10 cm / s, and the flow rate of the co-solvent is set to 0.02 cm / s-0.1 cm / s. (4) Carbon dioxide entrained co-solvent flows through the first reactor and comes into full contact with the PET foam in the packed bed to decolorize it. The decolorization time is 2h to 4h. (5) After decolorization is completed, stop feeding carbon dioxide and co-solvent into the first reactor, open the valve for supplying the medium from the first reactor to the second reactor, and discharge the carbon dioxide medium containing the co-solvent remaining in the first reactor to the second reactor so that it can be fully utilized. After the pressure of the two reactors is balanced, close the valve for supplying the medium from the first reactor to the second reactor, and input the remaining carbon dioxide in the first reactor into the separator until the pressure of the first reactor is 1MPa to 2MPa. Start feeding carbon dioxide and co-solvent into the second reactor to complete the switching of the first and second reactors. At this time, the second reactor performs the decolorization operation under the same conditions as the first reactor. The carbon dioxide remaining in the first reactor can be used as an enhancing medium for alcoholysis. After the carbon dioxide and co-solvent fluid that have extracted the dye are transported to the separator, gas-liquid separation is performed. The vaporized carbon dioxide is filtered through the second filter and returned to the carbon dioxide storage tank. The co-solvent and dye are stored in the dye collection tank in liquid state for post-processing. (6) Change the temperature of the first reactor to 200-240℃, and introduce methanol into the reactor at a mass ratio of 6-8:1 to PET foam. The initial pressure of the reactor is 1-2 MPa, which is the residual carbon dioxide pressure when the pressure is released. After heating, the final reaction pressure is 8-15 MPa. After the temperature and pressure stabilize, turn off the methanol feed pump and turn on the methanol circulation pump to circulate methanol so that it can undergo alcoholysis reaction with the decolorized PET foam. The reaction time is 1-2 hours. (7) After the alcoholysis reaction is completed, the product in the first reactor is introduced into the degradation product storage tank, the first reactor is cleaned and refilled with dyed PET foam, and the decolorization step is repeated. The decolorization-alcoholysis coupling reaction is carried out in sequence to achieve the purpose of recovering the dye and PET degradation products of dyed PET foam in one system.

3. The supercritical decolorization and degradation coupling method for waste dyed PET foam according to claim 2, characterized in that, The co-solvent is dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), ethylene glycol (EG), or acetone.

4. The supercritical decolorization and degradation coupling method for waste dyed PET foam according to claim 2, characterized in that, The mass ratio of the pulverized PET foam to the co-solvent is 1:8 to 10.

5. The supercritical decolorization and degradation coupling method for waste dyed PET foam according to claim 2, characterized in that, The decolorization-alcoholization coupling reaction was successfully carried out sequentially within a single system.

Images