Method for alcoholysis of waste PET polyester
By using supported metal oxide catalysts, the problem of difficult recycling of traditional catalysts has been solved, the alcoholysis efficiency and product purity of waste PET have been improved, and efficient PET conversion and BHET monomer yield have been achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DALIAN INSTITUTE OF CHEMICAL PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2024-12-09
- Publication Date
- 2026-06-09
AI Technical Summary
Traditional catalysts are difficult to recycle and have low efficiency in the alcoholysis of waste PET, resulting in low purity of alcoholysis products and low PET conversion rate.
A supported metal oxide catalyst is used, which combines a metal oxide support with an active metal oxide to form a catalyst for the alcoholysis reaction of waste PET.
This approach facilitates the separation and recovery of the catalyst, lowers the alcoholysis temperature, improves PET conversion and BHET monomer yield, and enhances the purity of the alcoholysis products.
Smart Images
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Figure BDA0005178742350000032
Abstract
Description
Technical Field
[0001] This application relates to a method for the alcoholysis of waste PET polyester, which belongs to the field of chemical engineering. Background Technology
[0002] Polyethylene terephthalate (PET) is a high-performance thermoplastic polymer widely used in packaging, textiles, electronics, automotive, healthcare, and construction due to its excellent transparency, chemical resistance, and thermal stability. Its diverse properties give PET high practical value and broad market demand. However, PET is difficult to degrade in nature, and large quantities of waste PET plastic exist in marine and terrestrial environments, posing a significant threat to the ecological environment. Traditional mechanical recycling methods result in a loss of plastic properties. In chemical recycling, long-chain polymers are degraded into monomers, which are then purified and repolymerized to obtain recycled PET, which can be used for new PET plastics, polyester fibers, etc., achieving efficient resource recycling.
[0003] Chemical recycling methods include alcoholysis, pyrolysis, ammonolysis, and liquefaction. Alcoholysis, with its mild reaction conditions and low volatility of the reagent ethylene glycol, is one of the most promising depolymerization methods. Developing efficient catalysts is key to promoting the depolymerization and recycling of waste PET. Most PET depolymerization catalysts are homogeneous, producing numerous reaction byproducts that are difficult to separate and recover (GreenChem. 2016, 18, 3997-4003). Heterogeneous catalysts, due to their lower porosity and specific surface area, exhibit lower catalytic efficiency. However, by utilizing supports with larger specific surface areas, heterogeneous catalysts possess sufficient active sites and adequate contact area, significantly improving degradation efficiency (Comput. Theor. Chem. 963, 403-411). Summary of the Invention
[0004] The method of using supported metal oxide catalysis to alcoholyze waste PET polyester overcomes the drawbacks of traditional catalysts that are difficult to recover. Moreover, this method has low raw material cost, high catalyst activity, low alcoholysis temperature, high PET conversion rate and BHET monomer yield, and high purity of alcoholysis products, and has broad application prospects.
[0005] According to one aspect of this application, a method for alcoholysis of waste PET polyester is provided, comprising the following steps:
[0006] Waste PET polyester is dissolved in ethylene glycol, contacted with a catalyst, and reacted to obtain bis(hydroxyethyl) terephthalate.
[0007] The waste PET polyester is selected from at least one of waste PET packaging bottles, waste PET film, and waste PET fiber.
[0008] The catalyst is composed of a metal oxide support and an active metal oxide supported on the surface of the metal oxide support;
[0009] The metal oxide support is selected from at least one of ZnO, γ-Al2O3, Fe3O4, SiO2, TiO2, CeO2, and MgO;
[0010] The active metal oxide is selected from at least one of MnO2, Co2O3, CeO2, PbO, CuO, NiO, and SnO2;
[0011] The mass of the active metal oxide is 5 to 60 wt% of the catalyst mass, wherein the mass of the active metal oxide is based on the mass of the metal element therein.
[0012] The catalyst is obtained through the following steps:
[0013] The metal oxide support was immersed in an aqueous solution containing an active metal oxide precursor, ammonia was added, the mixture was stirred, heated and allowed to stand, filtered, washed, dried and calcined to obtain the catalyst.
[0014] The active metal oxide precursor is selected from at least one of manganese nitrate, cobalt acetate, cerium acetate, lead acetate, copper nitrate, nickel nitrate, and tin dichloride.
[0015] The stirring time is 30–90 minutes;
[0016] The temperature for static setting is 20–100°C;
[0017] The settling time is 3 to 12 hours;
[0018] The drying temperature is 40–120°C.
[0019] The drying time is 6–24 hours.
[0020] The calcination temperature is 200–500°C;
[0021] The calcination time is 1 to 6 hours.
[0022] The mass ratio of the catalyst to waste PET polyester is 1:60 to 500.
[0023] Optionally, the mass ratio of the catalyst to waste PET polyester is 1:125 to 300.
[0024] The reaction temperature is 100–500°C;
[0025] Optionally, the reaction temperature is 160–380°C.
[0026] The reaction time is 1–24 hours;
[0027] Optionally, the reaction time is 5 to 18 hours.
[0028] The mass ratio of the waste PET polyester to ethylene glycol is 1:2.5 to 40;
[0029] Optionally, the mass ratio of the waste PET polyester to ethylene glycol is 1:5 to 25.
[0030] The beneficial effects that this application can produce include:
[0031] The method for alcoholysis of waste PET polyester catalyzed by supported metal oxides provided in this application overcomes the drawbacks of traditional catalysts being difficult to recover. Moreover, this method has a wide range of raw material sources and low cost, requires less catalyst and is easy to separate, has a low alcoholysis temperature, high PET conversion rate and BHET monomer yield, and high purity of alcoholysis products, and has broad application prospects. Detailed Implementation
[0032] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0033] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased commercially. Unless otherwise specified, all testing methods were conventional methods, and all instrument settings were as recommended by the manufacturers.
[0034] The analysis method in the embodiments of this application is as follows:
[0035] The conversion rate of PET was calculated using the following formula. The product was analyzed by high-performance liquid chromatography (HPLC), and the yield of BHET was calculated as follows:
[0036]
[0037]
[0038] Example 1:
[0039] A silica support was dispersed in an aqueous solution of copper nitrate (Cu(NO3)2·3H2O) (the Cu content in the solution was 8wt%, and the mass of water was the saturated water absorption of the support). Ammonia water with a volume ratio of 0.2 to the metal salt solution was added at 30°C. The mixture was stirred at 1000 rpm for 30 min, heated to 70°C and allowed to stand for 4 h. The resulting precipitate was filtered and washed, dried in an oven at 110°C for 12 h, and then calcined at 300°C in air for 5 h to obtain an 8wt% CuO / SiO2 catalyst.
[0040] In this embodiment, "8wt% CuO / SiO2 catalyst" means that the mass content of the metal element in the catalyst is 8wt%. Similar expressions in other embodiments of the catalyst are interpreted in a similar manner.
[0041] Waste PET bottle flakes, along with 8wt% CuO / SiO2 (at a mass ratio of 1:100) and ethylene glycol (at a mass ratio of 1:10), were added to a reactor. The mixture was heated to 180°C and reacted for 8 hours. After the reaction, the mixture was cooled to room temperature, and the product was separated from the unreacted PET by filtration. The unreacted PET was dried and weighed, and the PET conversion rate was calculated. An internal standard was added to the product, and samples were taken for liquid chromatography analysis to calculate the BHET yield. The PET conversion rate was 91%, and the BHET yield was 83%.
[0042] Example 2:
[0043] The iron oxide support was dispersed in an aqueous solution of manganese nitrate (Mn(NO3)2·4H2O) (the Mn content in the solution was 16wt%, and the mass of water was the saturated water absorption of the support). Ammonia water with a volume ratio of 0.15 to the metal salt solution was added at 20℃. The mixture was stirred at 1000rpm for 60min, heated to 50℃ and allowed to stand for 6h. The resulting precipitate was filtered and washed, dried in an oven at 110℃ for 12h, and then calcined at 250℃ in air for 6h to obtain a 16wt% MnO2 / Fe3O4 catalyst.
[0044] Waste PET film, along with 16wt% MnO2 / Fe3O4 at a mass ratio of 1:125 and ethylene glycol at a mass ratio of 1:40, were added to a reactor. The mixture was heated to 180°C and reacted for 16 hours. After the reaction, the mixture was cooled to room temperature, and the product was separated from the unreacted PET by filtration. The unreacted PET was dried and weighed, and the PET conversion rate was calculated. An internal standard was added to the product, and samples were taken for liquid chromatography analysis to calculate the BHET yield. The PET conversion rate was 99%, and the BHET yield was 89%.
[0045] Example 3:
[0046] Cerium dioxide support was dispersed in an aqueous solution of nickel nitrate (Ni(NO3)2·6H2O) (the Ni content in the solution was 58wt%, and the mass of water was the saturated water absorption of the support). Ammonia water with a volume ratio of 0.25 to the metal salt solution was added at 50℃. The mixture was stirred at 1000rpm for 30min, heated to 100℃ and allowed to stand for 7h. The resulting precipitate was filtered and washed, dried in an oven at 110℃ for 12h, and then calcined at 450℃ in air for 3h to obtain a 58wt% NiO / CeO2 catalyst.
[0047] PET fiber waste, along with 58wt% NiO / CeO2 (mass ratio 1:300) and ethylene glycol (mass ratio 1:30), were added to a reactor. The mixture was heated to 250°C and reacted for 1 hour. After the reaction, the mixture was cooled to room temperature, and the product was separated from the unreacted PET by filtration. The unreacted PET was dried and weighed, and the PET conversion rate was calculated. An internal standard was added to the product, and samples were taken for liquid chromatography analysis to calculate the BHET yield. The PET conversion rate was 82%, and the BHET yield was 70%.
[0048] Example 4:
[0049] Zinc oxide support was dispersed in an aqueous solution of cerium acetate (Ce(CH3COO)3) (Ce content in the solution was 40wt%, and the mass of water was the saturated water absorption of the support). Ammonia water with a volume ratio of 0.4 to the metal salt solution was added at 40℃. The mixture was stirred at 1000rpm for 80min, heated to 40℃ and allowed to stand for 8h. The resulting precipitate was filtered and washed, dried in an oven at 110℃ for 12h, and then calcined at 350℃ in air for 4h to obtain a 40wt% CeO2 / ZnO catalyst.
[0050] Waste PET bottle flakes, along with 40wt% CeO2 / ZnO (mass ratio 1:250) and ethylene glycol (mass ratio 1:20), were added to a reactor. The mixture was heated to 350℃ and reacted for 9 hours. After the reaction, the mixture was cooled to room temperature, and the product was separated from the unreacted PET by filtration. The unreacted PET was dried and weighed, and the PET conversion rate was calculated. An internal standard was added to the product, and samples were taken for liquid chromatography analysis to calculate the BHET yield. The PET conversion rate was 100%, and the BHET yield was 94%.
[0051] Example 5:
[0052] Zinc oxide support was dispersed in an aqueous solution of tin dichloride (SnCl2·2H2O) (the Sn content in the solution was 60wt%, and the mass of water was the saturated water absorption of the support). Ammonia water with a volume ratio of 0.5 to the metal salt solution was added at 10℃. The mixture was stirred at 1000rpm for 90min, heated to 30℃ and allowed to stand for 9h. The resulting precipitate was filtered and washed, dried in an oven at 110℃ for 12h, and then calcined at 400℃ in air for 2h to obtain a 60wt% SnO2 / ZnO catalyst.
[0053] Waste PET bottle flakes, along with 60wt% SnO2 / ZnO (mass ratio 1:60) and ethylene glycol (mass ratio 1:25), were added to a reactor. The mixture was heated to 100℃ and reacted for 24 hours. After the reaction, the mixture was cooled to room temperature, and the product was separated from the unreacted PET by filtration. The unreacted PET was dried and weighed, and the PET conversion rate was calculated. An internal standard was added to the product, and samples were taken for liquid chromatography analysis to calculate the BHET yield. The PET conversion rate was 86%, and the BHET yield was 74%.
[0054] Example 6:
[0055] An alumina support was dispersed in an aqueous solution of lead acetate (Pb(CH3COO)2·3H2O) (the Pb content in the solution was 32wt%, and the mass of water was the saturated water absorption of the support). Ammonia water with a volume ratio of 0.01 to the metal salt solution was added at 25°C. The mixture was stirred at 1000 rpm for 40 min, heated to 90°C, and allowed to stand for 3 h. The resulting precipitate was filtered, washed, dried in an oven at 110°C for 12 h, and then calcined at 200°C in air for 6 h to obtain a 32wt% PbO / γ-Al2O3 catalyst.
[0056] Waste PET bottle flakes, 32wt% PbO / γ-Al₂O₃ (mass ratio 1:400), and ethylene glycol (mass ratio 1:15) were added to a reactor. The mixture was heated to 500℃ and reacted for 1 hour. After the reaction, the mixture was cooled to room temperature, and the product was separated from the unreacted PET by filtration. The unreacted PET was dried and weighed, and the PET conversion rate was calculated. An internal standard was added to the product, and samples were taken for liquid chromatography analysis to calculate the BHET yield. The PET conversion rate was 81%, and the BHET yield was 72%.
[0057] Example 7:
[0058] Titanium dioxide support was dispersed in an aqueous solution of cobalt acetate (Co(NO3)2·6H2O) (the Co content in the solution was 5wt%, and the mass of water was the saturated water absorption of the support). Ammonia water with a volume ratio of 0.45 to the metal salt solution was added at 35℃. The mixture was stirred at 1000 rpm for 50 min, heated to 80℃ and allowed to stand for 12 h. The resulting precipitate was filtered and washed, dried in an oven at 110℃ for 12 h, and then calcined at 250℃ in air for 3 h to obtain a 5wt% Co2O3 / TiO2 catalyst.
[0059] Waste PET film, along with 5wt% Co₂O₃ / TiO₂ at a mass ratio of 1:125 and ethylene glycol at a mass ratio of 1:2.5, were added to a reactor. The mixture was heated to 210°C and reacted for 10 hours. After the reaction, the mixture was cooled to room temperature, and the product was separated from the unreacted PET by filtration. The unreacted PET was dried and weighed, and the PET conversion rate was calculated. An internal standard was added to the product, and samples were taken for liquid chromatography analysis to calculate the BHET yield. The PET conversion rate was 92%, and the BHET yield was 81%.
[0060] Example 8:
[0061] Magnesium oxide support was dispersed in an aqueous solution of nickel nitrate (Ni(NO3)2·6H2O) (the Ni content in the solution was 50wt%, and the mass of water was the saturated water absorption of the support). Ammonia water with a volume ratio of 0.35 to the metal salt solution was added at 45℃. The mixture was stirred at 1000rpm for 70min, heated to 80℃ and allowed to stand for 12h. The resulting precipitate was filtered and washed, dried in an oven at 110℃ for 12h, and then calcined at 500℃ in air for 1h to obtain a 50wt% NiO / MgO catalyst.
[0062] PET fiber waste, along with 50wt% NiO / MgO (mass ratio 1:500) and ethylene glycol (mass ratio 1:5), were added to a reactor. The mixture was heated to 450℃ and reacted for 20 hours. After the reaction, the mixture was cooled to room temperature, and the product was separated from the unreacted PET by filtration. The unreacted PET was dried and weighed, and the PET conversion rate was calculated. An internal standard was added to the product, and samples were taken for liquid chromatography analysis to calculate the BHET yield. The PET conversion rate was 94%, and the BHET yield was 87%.
[0063] Example 9:
[0064] Cerium dioxide support was dispersed in an aqueous solution of cobalt acetate (Co(NO3)2·6H2O) (the Co content in the solution was 58wt%, and the mass of water was the saturated water absorption of the support). Ammonia water with a volume ratio of 0.25 to the metal salt solution was added at 35°C. The mixture was stirred at 1000 rpm for 50 min, heated to 60°C and allowed to stand for 8 h. The resulting precipitate was filtered, washed, dried in an oven at 110°C for 12 h, and then calcined at 250°C in air for 6 h to obtain a 58wt% Co2O3 / CeO2 catalyst.
[0065] Waste PET film, along with 58 wt% Co₂O₃ / CeO₂ at a mass ratio of 1:450 and ethylene glycol at a mass ratio of 1:2.5, were added to a reactor. The mixture was heated to 350°C and reacted for 16 hours. After the reaction, the mixture was cooled to room temperature, and the product was separated from the unreacted PET by filtration. The unreacted PET was dried and weighed, and the PET conversion rate was calculated. An internal standard was added to the product, and samples were taken for liquid chromatography analysis to calculate the BHET yield. The PET conversion rate was 90%, and the BHET yield was 78%.
[0066] Example 10:
[0067] A silica support was dispersed in an aqueous solution of copper nitrate (Cu(NO3)2·3H2O) (the Cu content in the solution was 32wt%, and the mass of water was the saturated water absorption of the support). Ammonia water with a volume ratio of 0.4 to the metal salt solution was added at 50℃. The mixture was stirred at 1000 rpm for 30 min, heated to 70℃ and allowed to stand for 8 h. The resulting precipitate was filtered and washed, dried in an oven at 110℃ for 12 h, and then calcined at 450℃ in air for 3 h to obtain a 32wt% CuO / SiO2 catalyst.
[0068] Waste PET bottle flakes, along with 32wt% CuO / SiO2 at a mass ratio of 1:500 and ethylene glycol at a mass ratio of 1:30, were added to a reactor. The mixture was heated to 250°C and reacted for 10 hours. After the reaction, the mixture was cooled to room temperature, and the product was separated from the unreacted PET by filtration. The unreacted PET was dried and weighed, and the PET conversion rate was calculated. An internal standard was added to the product, and samples were taken for liquid chromatography analysis to calculate the BHET yield. The PET conversion rate was 87%, and the BHET yield was 74%.
[0069] Comparative Example 1:
[0070] Waste PET film, Fe3O4 (mass ratio 1:200), and ethylene glycol (mass ratio 1:20) were added to a reactor, and the mixture was heated to 180°C and reacted for 10 hours. After the reaction, the mixture was cooled to room temperature, and the product was separated from the unreacted PET by filtration. The unreacted PET was dried and weighed, and the PET conversion rate was calculated. An internal standard was added to the product, and samples were taken for liquid chromatography analysis to calculate the BHET yield. The PET conversion rate was 22%, and the BHET yield was 10%.
[0071] Comparative Example 2:
[0072] PET fiber waste, CeO2 (mass ratio 1:350), and ethylene glycol (mass ratio 1:30) were added to a reactor and heated to 250°C for 5 hours. After the reaction, the mixture was cooled to room temperature, and the product was separated from the unreacted PET by filtration. The unreacted PET was dried and weighed, and the PET conversion rate was calculated. An internal standard was added to the product, and samples were taken for liquid chromatography analysis to calculate the BHET yield. The PET conversion rate was 25%, and the BHET yield was 12%.
[0073] Comparative Example 3:
[0074] Waste PET bottle flakes, along with Co₂O₃ at a mass ratio of 1:400 and ethylene glycol at a mass ratio of 1:15, were added to a reaction vessel. The mixture was heated to 100°C and reacted for 16 hours. After the reaction, the mixture was cooled to room temperature, and the product was separated from the unreacted PET by filtration. The unreacted PET was dried and weighed, and the PET conversion rate was calculated. An internal standard was added to the product, and samples were taken for liquid chromatography analysis to calculate the BHET yield. The PET conversion rate was 54%, and the BHET yield was 43%.
[0075] Comparative Example 4:
[0076] Waste PET bottle flakes, SnO2 (mass ratio 1:200), and ethylene glycol (mass ratio 1:40) were added to a reactor and heated to 210°C, reacting for 8 hours. After the reaction, the mixture was cooled to room temperature, and the product was separated from the unreacted PET by filtration. The unreacted PET was dried and weighed, and the PET conversion rate was calculated. An internal standard was added to the product, and samples were taken for liquid chromatography analysis to calculate the BHET yield. The PET conversion rate was 48%, and the BHET yield was 36%.
[0077] Comparative Examples 1 and 2 show that the PET conversion rate and BHET yield are both low when the support is used alone. Comparative Examples 3 and 4 show that the PET conversion rate and BHET yield are higher when the active metal compound is used alone than when the support is used alone, but lower than when the active metal oxide is supported on the support. In comparison with the previous examples, the PET conversion rate and BHET yield are higher when the catalyst supported on the active metal oxide is used for degradation.
[0078] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A method for the alcoholysis of waste PET polyester, characterized in that, Includes the following steps: Waste PET polyester is dissolved in ethylene glycol, contacted with a catalyst, and reacted to obtain bis(hydroxyethyl) terephthalate. The waste PET polyester is selected from at least one of waste PET packaging bottles, waste PET film, and waste PET fiber. The catalyst is composed of a metal oxide support and an active metal oxide supported on the surface of the metal oxide support; The metal oxide support is selected from at least one of ZnO, γ-Al2O3, Fe3O4, SiO2, TiO2, CeO2, and MgO; The active metal oxide is selected from at least one of MnO2, Co2O3, CeO2, PbO, CuO, NiO, and SnO2; The mass of the active metal oxide is 5 to 60 wt% of the catalyst mass, wherein the mass of the active metal oxide is based on the mass of the metal element therein.
2. The method according to claim 1, characterized in that, The catalyst is obtained through the following steps: The metal oxide support was immersed in an aqueous solution containing an active metal oxide precursor, ammonia was added, the mixture was stirred, heated and allowed to stand, filtered, washed, dried and calcined to obtain the catalyst.
3. The method according to claim 2, characterized in that, The active metal oxide precursor is selected from at least one of manganese nitrate, cobalt acetate, cerium acetate, lead acetate, copper nitrate, nickel nitrate, and tin dichloride.
4. The method according to claim 2, characterized in that, The stirring time is 30–90 minutes; The temperature for static setting is 20–100°C; The settling time is 3 to 12 hours; The drying temperature is 40–120°C; The drying time is 6–24 hours; The calcination temperature is 200–500°C; The calcination time is 1 to 6 hours.
5. The method according to claim 1, characterized in that, The mass ratio of the catalyst to waste PET polyester is 1:60 to 500. Preferably, the mass ratio of the catalyst to waste PET polyester is 1:125 to 300.
6. The method according to claim 1, characterized in that, The reaction temperature is 100–500°C; Preferably, the reaction temperature is 160–380°C.
7. The method according to claim 1, characterized in that, The reaction time is 1–24 hours; Preferably, the reaction time is 5 to 18 hours.
8. The method according to claim 1, characterized in that, The mass ratio of the waste PET polyester to ethylene glycol is 1:2.5 to 40; Preferably, the mass ratio of the waste PET polyester to ethylene glycol is 1:5 to 25.