Amino acid-zinc complex catalyst, preparation thereof and application of amino acid-zinc complex catalyst in PET degradation
By using a nitrogen-terminated amino acid-zinc complex catalyst to catalyze PET degradation, the problems of residue and environmental impact associated with existing catalysts in high-value fields have been solved, achieving efficient and environmentally friendly PET degradation and high-purity product production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-06
- Publication Date
- 2026-04-21
AI Technical Summary
Existing PET degradation catalysts have limitations in high-value applications due to residue limitations and environmental burdens, and their catalytic efficiency needs to be improved.
An amino acid-zinc complex catalyst, formed by complexing nitrogen-terminated amino acids with zinc oxide or zinc hydroxide, is used for the alcoholysis reaction of PET. The catalyst is simple to prepare and has good biocompatibility.
It achieves efficient and environmentally friendly PET degradation, with high product purity, suitable for high-value fields, and the catalyst is easy to scale up.
Smart Images
Figure CN121895183A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of chemical technology, and specifically relates to a catalyst for catalyzing the chemical degradation of polyethylene terephthalate (PET), specifically a biocompatible catalyst based on an amino acid-zinc complex, its preparation method, and its application. Background Technology
[0002] Polyethylene terephthalate (PET) is widely used in packaging, fibers, and other fields due to its excellent properties, but its huge consumption has also brought serious environmental problems. Chemical recycling methods, especially alcoholysis, can degrade PET into its monomer diethyl terephthalate (BHET), thereby achieving a closed-loop resource cycle, and is currently a research hotspot.
[0003] Traditional PET degradation catalysts are mostly metal salts (such as zinc acetate and manganese acetate) or metal oxides (such as titanium dioxide and zinc oxide). Although these catalysts have a certain catalytic efficiency, they have inherent drawbacks: first, the catalyst may remain in the product, limiting its recyclable application in high-value fields (such as medical and food packaging); second, some catalysts are non-renewable, and their production process itself may impose a burden on the environment.
[0004] In recent years, the development of green, mild, and efficient catalysts has become a trend. Amino acids are the basic building blocks of living organisms and possess excellent biocompatibility and biodegradability. Zinc amino acids can be used as food additives and zinc supplements, and are expected to be developed into a new type of catalyst with both catalytic activity and biosafety. Currently, there are no reports on the preparation of catalysts using nitrogen-terminated amino acids complexed with zinc and their application in PET degradation. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a novel amino acid-zinc complex catalyst, its preparation, and its application in PET degradation. The catalyst of this invention has widely available raw materials, good biocompatibility, is environmentally friendly, and has a simple preparation method with high catalytic efficiency. To achieve the above objectives, this invention adopts the following technical solution: One aspect of this invention relates to an amino acid-zinc complex catalyst, which is formed by the complexation of a nitrogen-terminated amino acid with zinc oxide or zinc hydroxide.
[0006] In a preferred embodiment of the present invention, the nitrogen-terminated amino acid is one or more of Ac-glutamic acid (Boc-Gly), Ac-histidine (Ac-His), Boc-valine (Boc-Val), and Fmoc-glycine (Fmoc-Gly).
[0007] In a preferred embodiment of the present invention, the amino acid-zinc complex catalyst is an N-acetyl-glutamic acid-zinc complex or a 9-fluorenylmethoxycarbonyl-glycine-zinc complex.
[0008] Another aspect of the present invention relates to a method for preparing the above-mentioned catalyst, comprising the following steps: (1) Dissolve the nitrogen-terminated amino acid in water or an organic solvent to prepare a solution with a concentration of 0.1-0.5 g / mL; (2) Add zinc oxide or zinc hydroxide to the solution obtained in step (1) and stir the reaction at 20-100 °C for 6-0.1 hours; (3) After the reaction is completed, the reaction solution is cooled to room temperature, concentrated and dried to obtain the amino acid-zinc complex catalyst.
[0009] Another aspect of the present invention relates to the application of the above-mentioned catalyst in the catalytic degradation of PET.
[0010] The present invention also relates to a method for catalytic degradation of PET, wherein the method uses ethylene glycol (EG) as a depolymerization solvent and the above-mentioned amino acid-zinc complex as a catalyst to carry out an alcoholysis reaction on PET.
[0011] In a preferred embodiment of the present invention, the amount of the amino acid-zinc complex is 0.5%-2.0% of the mass of PET, the degradation reaction temperature is 150-200 °C, and the reaction time is 6-0.5 hours.
[0012] In a preferred embodiment of the invention, the method further includes recovering bis(hydroxyethyl) terephthalate from the degradation products.
[0013] In a preferred embodiment of the present invention, the recovery of diethyl terephthalate is achieved by hot filtration of the degradation liquid, collecting unreacted PET, adding boiling water to the cooled filtrate, allowing it to cool naturally to crystallize, collecting white crystals by vacuum filtration, washing with cold water, and drying to obtain high-purity diethyl terephthalate.
[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Green and environmentally friendly with biocompatibility: The core component of the catalyst, amino acids, has excellent biocompatibility and biodegradability. Furthermore, the degradation product, BHET, has high purity and is suitable for high-value applications.
[0015] 2. High catalytic efficiency: The complex structure formed by amino acids and zinc can effectively activate the carbonyl group in PET molecules, promote the breaking of CO bonds, and achieve efficient degradation under relatively mild conditions.
[0016] 3. Simple preparation: The catalyst preparation process does not require complex equipment or high-energy-consuming steps, the reaction conditions are mild, and it is easy to scale up production.
[0017] 4. Wide range of sources: Amino acid raw materials can be derived from biomass, which is in line with the concept of sustainable development. Attached Figure Description
[0018] Figure 1 This is a chemical structure diagram of the Zn(Ac-Glu)2 complex prepared in Example 1 of the present invention.
[0019] Figure 2 The infrared spectrum of the Zn(Ac-Glu)2 complex prepared in Example 1 of this invention is shown.
[0020] Figure 3 This is the mass spectrum of the Zn(Ac-Glu)2 complex prepared in Example 1 of the present invention.
[0021] Figure 4 This is a chemical structure diagram of the Zn(Fmoc-Gly)2 complex prepared in Example 2 of the present invention.
[0022] Figure 5 The infrared spectrum of the Zn(Fmoc-Gly)2 complex prepared in Example 2 of this invention.
[0023] Figure 6 This describes the degradation process of the PET bottle in Example 5 of the present invention. Detailed Implementation
[0024] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. All technologies implemented based on the above description of the present invention fall within the scope of the present invention.
[0025] Example 1: Preparation of N-acetyl-glutamic acid-zinc complex (Zn(Ac-Glu)2) (1) Weigh 3.78 g of N-acetyl-glutamic acid (Ac-Glu) into a 500 mL beaker, add 100 mL of water, and stir for 5 min.
[0026] (2) Add 0.81 g of zinc oxide (ZnO) to the above solution and react at 100 °C for 0.5 h with stirring until clear and transparent.
[0027] (3) The catalyst was dried in a vacuum drying oven at 60 °C for 5 hours to obtain a transparent blocky Zn(Ac-Glu)2 catalyst. The chemical structure of the catalyst is shown in the attached figure. Figure 1 As shown, its infrared spectrum is attached. Figure 2 As shown, the mass spectrometry is as follows Figure 3 As shown.
[0028] Example 2: Preparation of 9-fluorenylmethoxycarbonyl-glycine-zinc complex (Zn(Fmoc-Gly)2) The preparation method is the same as in Example 1, except that the raw materials are replaced with 5.94 g Fmoc-glycine and 0.99 g zinc hydroxide, and the solvent is replaced with methanol, to obtain a white powdered Zn(Fmoc-Gly)2 catalyst.
[0029] (1) Weigh 5.94 g of 9-fluorenylmethoxycarbonyl-glycine (Fmoc-Gly) into a 500 mL beaker, add 100 mL of methanol, and stir for 5 min.
[0030] (2) Add 0.99 g of zinc hydroxide (Zn(OH)2) to the above solution, then add acetic acid dropwise until the solution is completely clear and transparent, and react at 60 °C for 0.5 h with stirring.
[0031] (3) Add 100 mL of water to the above solution. A large amount of precipitate will precipitate in the solution. After filtering the precipitate, dry it in a vacuum drying oven at 60 °C for 5 hours to obtain powdered Zn(Fmoc-Gly)2 catalyst. The chemical structure of the catalyst is shown in the attached figure. Figure 4 As shown, the infrared spectrum is as follows Figure 5 As shown.
[0032] Example 3: Degradation of PET powder (using Zn(Ac-Glu)2 catalyst) (1) 10 g of PET powder, 40 mL of ethylene glycol (EG) and 0.1 g (1.0% of the mass of PET) of Zn(Ac-Glu)2 catalyst prepared in Example 1 were added to a 100 mL three-necked flask containing a stir bar, a condenser and a thermometer.
[0033] (2) Place the reaction system in an oil bath at 190°C and reflux for 1 hour under magnetic stirring.
[0034] (3) After the reaction is complete, filter while hot and collect the unreacted PET. After the filtrate is cooled, add 50 mL of boiling water and allow it to cool naturally to crystallize. Collect the white crystals by suction filtration, wash twice with cold water, dry and weigh, and calculate the yield of the product diethyl terephthalate (BHET).
[0035] Results: The PET degradation rate was 99%, and the BHET yield was 98%. Among these: Degradation rate = BFET yield = = The coefficient 1.323 in the formula comes from the molar mass ratio of the repeating units of BHET and PET (254.24 / 192.17). Example 4: Degradation of PET powder (using Zn(Fmoc-Gly)2 catalyst) The method was the same as in Example 3, except that the catalyst was replaced with the Zn(Fmoc-Gly)2 catalyst prepared in Example 2, the reaction temperature was 190 °C, and the reaction time was 1 hour.
[0036] Results: The degradation rate of PET was 93%, and the yield of BHET was 91%.
[0037] Example 5: Degradation of commercial PET bottles (using Zn(Ac-Glu)2 catalyst) The method is the same as in Example 3, except that the PET powder is replaced with a commercial PET mineral water bottle with a mass of 15 g, the catalyst mass is still 1% (0.15 g) of the reactant mass, the reaction temperature is 190 ℃, and the reaction time is 2 hours.
[0038] Results: The PET degradation rate was 98%, and the BHET yield was 95%. The degradation process of the PET bottle is shown in the attached figure. Figure 5 As shown.
[0039] Comparative Example 1: No catalyst The method is the same as in Example 3, but without adding any catalyst.
[0040] Results: PET showed almost no degradation and no BHET crystals were precipitated.
[0041] Comparative Example 2: Using pure zinc oxide catalyst The method is the same as in Example 3, except that the catalyst is replaced with an equal amount of pure zinc oxide (0.1 g).
[0042] Results: The degradation rate of PET was 65%, and the yield of BHET was 55%.
[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. An amino acid-zinc complex catalyst, which is formed by the complexation of a nitrogen-terminated amino acid with zinc oxide or zinc hydroxide.
2. The catalyst according to claim 1, wherein the nitrogen-terminated protected amino acid is one or more of Ac-glutamic acid (Boc-Gly), Ac-histidine (Boc-Ala), Boc-valine (Boc-Val), and Fmoc-glycine (Fmoc-Gly).
3. The catalyst according to claim 1, wherein the amino acid-zinc complex catalyst is an N-acetyl-glutamic acid-zinc complex or a 9-fluorenylmethoxycarbonyl-glycine-zinc complex.
4. A method for preparing the catalyst according to any one of claims 1-3, comprising the following steps: (1) Dissolve the nitrogen-terminated amino acid in water or an organic solvent to prepare a solution with a concentration of 0.1-0.5 g / mL; (2) Add zinc oxide or zinc hydroxide to the solution obtained in step (1) and stir the reaction at 20-100 °C for 6-0.1 hours; (3) After the reaction is completed, the reaction solution is cooled to room temperature, concentrated and dried to obtain the amino acid-zinc complex catalyst.
5. The application of the catalyst according to any one of claims 1-3 in the catalytic degradation of PET.
6. A method for catalytic degradation of PET, wherein the method comprises using ethylene glycol (EG) as a depolymerization solvent and the amino acid-zinc complex according to any one of claims 1-3 as a catalyst to carry out an alcoholysis reaction on PET.
7. The method according to claim 6, wherein the amount of the amino acid-zinc complex is 0.5%-2.0% of the mass of PET, the degradation reaction temperature is 150-200 °C, and the reaction time is 6-0.5 hours.
8. The method of claim 7, further comprising recovering diethyl terephthalate from the degradation products.
9. The method according to claim 8, wherein the recovery of diethyl terephthalate is achieved by hot filtration of the degradation liquid, collecting unreacted PET, adding boiling water to the cooled filtrate, allowing it to cool naturally to crystallize, collecting white crystals by vacuum filtration, washing with cold water, and drying to obtain high-purity diethyl terephthalate.