CN115650848A - Recovery method of waste PET - Google Patents

Recovery method of waste PET Download PDF

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Publication number
CN115650848A
CN115650848A CN202211333626.5A CN202211333626A CN115650848A CN 115650848 A CN115650848 A CN 115650848A CN 202211333626 A CN202211333626 A CN 202211333626A CN 115650848 A CN115650848 A CN 115650848A
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CN
China
Prior art keywords
bhet
product
antimony
reaction
filtrate
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Pending
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CN202211333626.5A
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Chinese (zh)
Inventor
周吉奎
刘牡丹
吕先谨
刘勇
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Institute of Resource Utilization and Rare Earth Development of Guangdong Academy of Sciences
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Institute of Resource Utilization and Rare Earth Development of Guangdong Academy of Sciences
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Priority to CN202211333626.5A priority Critical patent/CN115650848A/en
Publication of CN115650848A publication Critical patent/CN115650848A/en
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/62—Plastics recycling; Rubber recycling

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  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Polyesters Or Polycarbonates (AREA)
  • Separation, Recovery Or Treatment Of Waste Materials Containing Plastics (AREA)

Abstract

The invention belongs to the technical field of waste resource recycling, and particularly discloses a method for recycling waste polyester PET. The method comprises the steps of firstly carrying out glycolysis on the waste PET, then adding water, heating and hydrolyzing to remove heavy metal impurities such as antimony, and then removing impurities by using activated carbon and washing by using water to obtain the high-purity BHET product. The BHET monomer without antimony and other impurities can be used for producing high-quality regenerated PET polyester products, and high-valued utilization of waste PET polyester is really realized.

Description

Recovery method of waste PET
Technical Field
The invention relates to the technical field of waste resource recycling, in particular to a method for recycling waste polyester PET.
Background
Polyester PET (polyethylene terephthalate) is widely used in the fields of synthetic fibers, flexible packaging materials, beverage bottles, cosmetics, medicine packaging bottles, and the like because of its unique transparency, lightweight property, and chemical stability. At present, the global annual output of PET exceeds 8000 million tons, the consumption in 2021 year is more than 1 hundred million tons, and the demand is extremely large.
In recent years, various countries around the world are dedicated to the sustainable recycling of waste PET materials, wherein the most potential recycling method is an ethylene glycol method, the conditions of the method are mild, the selectivity of degradation products is high, PET can be directly degraded into BHET monomers, and the high-value utilization of the waste PET is realized. However, antimony in waste PET materials is not removed in the process of obtaining BHET monomer by degradation at present. Antimony catalysts, including antimony trioxide, antimony acetate, ethylene glycol antimony, and the like, are generally used in the synthesis of PET. The use of antimony based catalysts results in a small amount of heavy metal antimony remaining in the PET product. Antimony belongs to harmful heavy metals, and antimony poisoning can cause damage to the nervous system and cardiac muscle of a human body and has symptoms of luminal mucositis and the like. The content of residual antimony in the prior waste PET is generally 190-300mg -1 Meanwhile, if the metal antimony in the PET is not removed in the recovery process, the catalyst containing heavy metal is continuously adopted in the regeneration process of the PET, the content of antimony in the regenerated PET is likely to be too high, and the application range of the regenerated PET is greatly limited.
Therefore, it is desired to develop a method for recycling waste PET.
Disclosure of Invention
The invention mainly solves the technical problem of providing a method for recovering waste polyester PET, the BHET product obtained by the method has high purity and extremely low antimony content, and the high-quality PET material which can be used in the fields of food packaging, fiber for taking and the like can be obtained by regeneration.
In order to solve the technical problems, the invention adopts the technical scheme that: a method for recycling waste PET comprises the following steps:
s1: carrying out alcoholysis on the waste PET and ethylene glycol, reducing the temperature of a reaction solution after the alcoholysis to 100-120 ℃, and carrying out suction filtration while the reaction solution is hot to obtain a first filtrate;
s2: distilling the first filtrate under reduced pressure to remove ethylene glycol; adding water into the product after reduced pressure distillation, heating for reaction, and filtering to obtain a second filtrate;
s3: adding activated carbon into the second filtrate for adsorption and impurity removal, and filtering to obtain a third filtrate;
s4: washing the third filtrate with hot water until a clear and transparent BHET monomer solution is obtained;
s5: and crystallizing the BHET monomer solution at low temperature to obtain BHET crystals, and drying the BHET crystals to obtain a high-purity BHET product.
As an embodiment of the invention, in step S1, the alcoholysis reaction is carried out at 200-220 ℃ and 0.3-0.4 MPa in an inert environment for 2-4 h.
Wherein the mass ratio of the waste PET raw material to the ethylene glycol is 1: (0.5-2).
As an embodiment of the invention, zinc acetate is added as a catalyst during the alcoholysis reaction, and the dosage of the zinc acetate is 0.2-0.4% of the mass of the waste PET raw material.
In one embodiment of the present invention, in step S2, the temperature of the heating reaction by adding water is 80 to 100 ℃, and preferably, the mass ratio of the product after vacuum distillation to water is 1: (1-5). And after the heating reaction is finished, quickly filtering while the solution is hot to obtain a second filtrate.
Preferably, in the step S4, the hot water temperature is 70 to 90 ℃.
Preferably, in step S5, the drying conditions of the BHET crystals are: drying the mixture for 6 to 10 hours in a vacuum oven at the temperature of 60 ℃.
The invention also provides a BHET product obtained by the method.
Preferably, the content of antimony in the BHET product is less than or equal to 10mg.kg -1 。
The invention provides a novel method for recycling waste PET through alcoholysis, aiming at the problem that the residual antimony in the waste PET during recycling causes the antimony content in the recycled PET to be too high so that the application of the recycled PET is limited, the heavy metal antimony and the like are effectively removed in the recycling process, BHET products with low antimony content are prepared, and high-quality PET polyester materials can be further recycled.
Studies have found that antimony catalysts used in the synthesis of PET include antimony trioxide, antimony acetate and ethylene glycol antimony, and that the use of these antimony-containing catalysts results in a small amount of antimony remaining in the PET polyester. Wherein the antimony acetate and the ethylene glycol antimony are easy to hydrolyze and are converted into antimony trioxide, and the reaction formulas of the ethylene glycol antimony, the antimony acetate and water are as follows:
Sb 2 (OCH 2 CH 2 O) 3 +3H 2 O＝Sb 2 O 3 +3HOCH 2 CH 2 OH；
4Sb(CH 3 COO) 3 +5H 2 O＝2Sb 2 O 3 +12CH 3 COOH。
antimony trioxide has a solubility in water of only 2.7mg/L and is substantially insoluble in water, whereas BHET monomer, a degradation product of PET, has a relatively high solubility in water, and has a solubility of more than 30g/L when the water temperature is higher than 50 ℃. It was also surprisingly found during the study that the solubility of the degradation product BHET monomer in water increases dramatically when the water temperature is above 75 deg.C, and the solubility can reach more than 300 g/L. Therefore, the method effectively realizes the removal of the heavy metal antimony in the recovery process of the waste PET by utilizing the obvious solubility difference of the antimony trioxide and the BHET monomers in water and controlling the reaction conditions.
Firstly, carrying out alcoholysis on waste PET by using ethylene glycol, cooling after the reaction is finished, and taking out an alcoholysis product from a reaction kettle while the temperature of a reaction solution is reduced to 100-120 ℃; filtering the alcoholysis product by suction while the product is hot, and removing undegraded residual polyester in the alcoholysis product; carrying out reduced pressure distillation on the filtrate obtained by suction filtration at the temperature of 110-140 ℃, and distilling off glycol in the filtrate; adding deionized water into the product obtained after reduced pressure distillation, heating to 80-100 ℃, and then quickly filtering, wherein antimony acetate and ethylene glycol antimony are hydrolyzed to be converted into antimony trioxide in the heating process, the antimony trioxide has low solubility in water, and alcoholysis monomer BHET is extremely soluble in water, so that antimony-containing solids can be effectively separated by quickly filtering when the temperature is heated to 80-100 ℃, and insoluble oligomers can also be separated and removed; adding activated carbon into the filtrate obtained by rapid filtration to remove impurities by adsorption, and washing the obtained BHET monomer solution with deionized water to remove residual impurities in the product until clear and transparent BHET monomer solution is obtained; and (3) placing the clear and transparent BHET monomer liquid in a refrigerator with constant temperature of 0 ℃ for crystallization, filtering to obtain BHET crystals, and drying the BHET crystals in a vacuum oven to obtain the high-purity BHET product.
The invention adopts a glycol alcoholysis process to treat and recycle waste PET polyester, and PET degradation products are BHET monomers; the method effectively realizes the removal of impurity antimony in the material by using the obvious solubility difference of antimony trioxide and BHET monomers in water and adopting a clean and cheap hydrolysis method. The method does not introduce other impurity ions, does not increase other equipment, and has simple process, low energy consumption and low cost. The BHET monomer obtained after removing antimony and other impurities can be used for producing high-quality regenerated PET polyester products, and the high-valued utilization of the waste PET polyester is really realized.
Detailed Description
The technical solution of the present invention will be described in detail by specific examples.
Example 1
This example provides a method for recycling waste PET, which is to collect waste PET polyester with antimony content of 187.56mg.kg -1 The recovery treatment is carried out by the following steps:
(1) According to the mass ratio of 1: adding ethylene glycol and waste PET polyester raw materials into a high-pressure reaction kettle, adding zinc acetate as a catalyst, wherein the using amount of the zinc acetate is 0.3 percent of the mass of the waste PET polyester raw materials, sealing the reaction kettle, filling nitrogen, setting the reaction temperature to 210 ℃, keeping the pressure in the reaction kettle at 0.4MPa, reacting for 3 hours, and finishing the reaction; cooling with water, taking out the alcoholysis product from the reaction kettle when the temperature of the reaction liquid is reduced to 110 ℃, and carrying out suction filtration when the temperature is hot to remove residual non-alcoholysis polyester;
(2) Carrying out reduced pressure distillation on the filtrate obtained by suction filtration at 120 ℃, and distilling to remove ethylene glycol;
(3) Adding deionized water into the product after reduced pressure distillation, wherein the mass ratio of the product after reduced pressure distillation to water is 1:1, then heating to 90 ℃, quickly filtering, and separating and removing antimony-containing solids and other insoluble oligomers generated by hydrolysis;
(4) Adding active carbon into the filtrate obtained in the step (3), carrying out adsorption impurity removal and decoloration, and then filtering to remove the active carbon;
(5) Washing the liquid obtained by filtering in the step (4) with deionized water at 80 ℃ to remove residual impurities in the product until clear and transparent BHET monomer liquid is obtained;
(6) And (3) crystallizing the BHET monomer liquid in a refrigerator with constant temperature of 0 ℃, filtering to obtain BHET crystals, and drying the BHET crystals in a vacuum oven with the temperature of 60 ℃ for 8 hours to obtain the BHET product.
The detection shows that the obtained BHET product has the antimony content of 9.58mg.kg -1 And the antimony content is extremely low, which indicates that the antimony in the raw material PET is effectively removed.
Example 2
This example provides a method for recycling waste PET, which is to take waste PET polyester with an antimony content of 245.46mg.kg -1 The recovery treatment is carried out by the following steps:
(1) According to the mass ratio of 1.5: adding ethylene glycol and waste PET polyester raw materials into a high-pressure reaction kettle, adding zinc acetate as a catalyst, wherein the using amount of the zinc acetate is 0.4 percent of the mass of the waste PET polyester raw materials, sealing the reaction kettle, filling nitrogen, setting the reaction temperature to 210 ℃, keeping the pressure in the reaction kettle at 0.4MPa, reacting for 4 hours, and finishing the reaction; cooling with water, taking out the alcoholysis product from the reaction kettle when the temperature of the reaction liquid is reduced to 110 ℃, and carrying out suction filtration when the temperature is hot to remove residual non-alcoholysis polyester;
(2) Carrying out reduced pressure distillation on the filtrate obtained by suction filtration at 120 ℃, and distilling to remove ethylene glycol;
(3) Adding deionized water into the product after reduced pressure distillation, wherein the mass ratio of the product after reduced pressure distillation to water is 1:2, heating to 80 ℃, quickly filtering, and separating and removing antimony-containing solids and other insoluble oligomers generated by hydrolysis;
(4) Adding active carbon into the filtrate obtained in the step (3), carrying out adsorption impurity removal and decoloration, and then filtering to remove the active carbon;
(5) Washing the liquid obtained by filtering in the step (4) with deionized water at 80 ℃ to remove residual impurities in the product until clear and transparent BHET monomer liquid is obtained;
(6) And (3) crystallizing the BHET monomer liquid in a refrigerator with constant temperature of 0 ℃, filtering to obtain BHET crystals, and drying the BHET crystals in a vacuum oven with the temperature of 60 ℃ for 8 hours to obtain the BHET product.
Detection shows that the obtained BHET product has the antimony content of 8.27mg.kg -1 And the antimony content is extremely low, which indicates that the antimony in the raw material PET is effectively removed.
By adopting the BHET product obtained in the embodiment 2, a regeneration experiment for preparing PET is carried out by using the conventional method, and the obtained PET product meets the standard of a superior product in GB/T14189-93 through detection.
Although the invention has been described in detail hereinabove by way of general description, specific embodiments and experiments, it will be apparent to those skilled in the art that many modifications and improvements can be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims (8)

1. A method for recycling waste PET is characterized by comprising the following steps:
s1: carrying out alcoholysis on the waste PET and ethylene glycol, reducing the temperature of a reaction solution after the alcoholysis to 100-120 ℃, and carrying out suction filtration while the reaction solution is hot to obtain a first filtrate;
s2: distilling the first filtrate under reduced pressure to remove ethylene glycol; adding water into the product after reduced pressure distillation, heating for reaction, and filtering to obtain a second filtrate;
s3: adding activated carbon into the second filtrate for adsorption and impurity removal, and filtering to obtain a third filtrate;
s4: washing the third filtrate with hot water to obtain a clear and transparent BHET solution;
s5: crystallizing the BHET solution at low temperature to obtain BHET crystal, and drying the BHET crystal to obtain a high-purity BHET product.
2. The method according to claim 1, wherein in step S1, the alcoholysis reaction is carried out at a temperature of 200-220 ℃ and a pressure of 0.3-0.4 MPa for a reaction time of 2-4 h; the mass ratio of the waste PET raw material to the ethylene glycol is 1: (0.5-2).
3. The method according to claim 2, characterized in that zinc acetate is added as a catalyst during the alcoholysis reaction, and the amount of the zinc acetate is 0.2-0.4% of the mass of the waste PET raw material.
4. The method according to any one of claims 1 to 3, wherein in the step S2, the temperature for adding water to carry out heating reaction is 80-100 ℃, and/or the mass ratio of the product after reduced pressure distillation to water is 1: (1-5).
5. The method according to any one of claims 1 to 4, wherein the temperature of the hot water is 70 to 90 ℃ when the washing with hot water is performed in step S4.
6. The method according to any of claims 1 to 5, wherein in step S5, the BHET crystal drying conditions are: drying the mixture for 6 to 10 hours in a vacuum oven at the temperature of 60 ℃.
7. A BHET product obtained by the method of any of claims 1-6.
8. The BHET product of claim 7, wherein the antimony content is ≤ 10mg -1 。
CN202211333626.5A 2022-10-28 2022-10-28 Recovery method of waste PET Pending CN115650848A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202211333626.5A CN115650848A (en) 2022-10-28 2022-10-28 Recovery method of waste PET

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202211333626.5A CN115650848A (en) 2022-10-28 2022-10-28 Recovery method of waste PET

Publications (1)

Publication Number Publication Date
CN115650848A true CN115650848A (en) 2023-01-31

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Family Applications (1)

Application Number Title Priority Date Filing Date
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Country Status (1)

Country Link
CN (1) CN115650848A (en)

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