Method for catalyzing degradation of polyester into high value-added chemicals by using basic ionic liquid
By using a strongly nucleophilic organic nitrogen heterocyclic alkaline ionic liquid catalyst to catalyze the degradation of polyester into high-value-added chemicals at low temperature and low pressure, the problem of high-temperature and high-pressure corrosion of equipment in existing technologies has been solved, achieving efficient and environmentally friendly polyester conversion.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DONGHUA UNIV
- Filing Date
- 2026-02-10
- Publication Date
- 2026-05-15
AI Technical Summary
Existing technologies require high temperature and pressure or strong acid and alkali catalysis in the polyester degradation process, which causes severe equipment corrosion and poor catalyst stability, making it difficult to achieve low-energy consumption and high-efficiency conversion into high-value-added chemicals.
Using a strongly nucleophilic organic nitrogen heterocyclic basic ionic liquid as a catalyst, combined with alcohols or amines as reactants, polyester is catalyzed to degrade into high-value-added chemicals within a time range of 0℃ to 90℃ and 0.1h to 24h.
It enables the rapid and efficient conversion of polyester into high-value-added chemicals under low temperature and low pressure conditions. The catalyst is recyclable, has a high degradation rate, and is suitable for industrial applications.
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Figure CN122036498A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of green catalysis and chemical recycling degradation technology, and relates to a method for polyester degradation, specifically a method for rapidly converting polyester into high-value-added chemicals under low-energy conditions using alkaline ionic liquid catalysis. Background Technology
[0002] Polyester is a general term for polymers obtained by the condensation polymerization of polyols and polyacids, mainly referring to polyethylene terephthalate (PET), and also conventionally including linear thermoplastic resins such as polybutylene terephthalate (PBT) and polyarylates. It is a class of high-performance, widely used engineering plastics, extensively applied in fiber materials, textile fabrics, clothing, and the manufacture of beverage bottles, food containers, films, and sheets. With the increase in polyester production, the amount of waste polyester materials is also increasing; however, waste PET is difficult to degrade in the natural environment. Recycling polyester (PET, etc.) can protect the environment, promote the development of a circular economy, and is of great significance for building a low-carbon energy and sustainable development society.
[0003] Currently, the main methods for recycling PET are physical recycling and chemical recycling. Physical recycling refers to the process of washing, crushing, remelting, and regranulating or flake-making waste PET. While the physical recycling process is simple and the equipment is easy to operate, the performance of PET after physical recycling is significantly reduced, leading to a downgrade in product quality and making it difficult to meet the needs of the food and fiber industries, thus limiting its application. Chemical recycling is not limited by the source of PET raw materials; PET composite materials or low-quality PET waste can be recycled multiple times, resulting in high-quality recycled products with wide applications. Chemical recycling can transform waste PET into useful small molecules, monomers, intermediate raw materials, or other industrial raw materials through chemical reactions, thereby achieving the recycling and transformation of waste PET into high-value-added chemicals. Therefore, chemical recycling is undoubtedly the preferred method for waste PET recycling.
[0004] Chemical recycling methods primarily degrade polyester materials into monomers or chemical raw materials through alcoholysis, hydrolysis, and ammonolysis. The degradation of waste PET typically requires high temperature, high pressure, or strong acid / base catalysts. For example, Chinese invention patent CN 113149825A discloses a method for the catalytic degradation of polyethylene terephthalate (PET): PET fragments and a catalyst are mixed and heated, and a degradation reaction occurs under the combined action of steam and the catalyst; wherein the catalyst is a zinc compound. This method degrades waste PET into terephthalic acid and ethylene glycol, with the reaction temperature controlled below 300℃, and the yields of terephthalic acid and ethylene glycol can reach 90-99 wt% and 91-99 wt%, respectively. This method requires high-temperature conditions for PET degradation, and the catalyst used is prone to corroding equipment, placing high demands on the equipment and making large-scale application difficult.
[0005] Chinese invention patent CN 118955281A discloses a method for catalytic degradation of polyester using an alkaline ionic liquid. The method uses an alkaline ionic liquid as a catalyst and an alcohol or amine as a reactant to catalytically degrade the polyester. The alkaline ionic liquid is a mixture of one or more of the following structural formulas: X + Y - In the formula, X + Y is an organic base cation. - It is a phenolic anion. However, phenolic anions are easily oxidized, resulting in insufficient stability; moreover, when the catalytic reaction temperature drops to around 50°C, the catalytic degradation rate decreases to only about 52%, and the reliability deteriorates.
[0006] Therefore, there is an urgent need for a green, environmentally friendly, low-cost, short-reaction-time, low-reaction-temperature, high-yield, recyclable, and universally applicable catalyst to convert polyester into high-value-added chemical monomers, thereby realizing the high-value-added chemical conversion and recycling of waste polyethylene terephthalate under low-energy conditions. Summary of the Invention
[0007] To address the aforementioned technical problems, the present invention aims to provide a method for catalytically degrading polyester into high-value-added chemicals using alkaline ionic liquids, thereby achieving rapid degradation of polyester under low energy consumption conditions.
[0008] To achieve the above-mentioned technical objectives, the present invention provides a method for catalytic degradation of polyester into high-value-added chemicals using alkaline ionic liquids, comprising the following steps: Alkaline ionic liquids are used as catalysts, and alcohols and / or amines are used as reactants to catalyze polyester degradation. The alkaline ionic liquid is a mixture of one or more components selected from the following general structural formulas: X+ Y - , In the formula, X + It is a basic cation, Y - It is a strongly nucleophilic organic nitrogen heterocyclic anion.
[0009] Optimally, the Y - It is a combination of one or more of the following organic nitrogen heterocyclic anions: , In the formula, R5 is selected from C1~C4 alkyl, alkoxy, cycloalkyl, alkenyl, phenyl and benzyl.
[0010] Furthermore, the X + It is a combination of one or more of the following structures: , In the formula, R1, R2, R3 and R4 are independently selected from C1 to C8 alkyl, alkoxy, cycloalkyl, alkenyl, phenyl and benzyl.
[0011] Furthermore, the reaction temperature for catalytic polyester degradation is 0℃~90℃, the reaction time is 0.1h~24h, and the reaction pressure is atmospheric pressure or auto-pressure.
[0012] Furthermore, the reaction temperature for catalytic polyester degradation is 0℃~40℃.
[0013] Preferably, the alcohol is a mixture selected from one or more of methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, and butanediol.
[0014] Preferably, the amine is a mixture selected from one or more of primary amines, secondary amines, mono-secondary amines, and secondary amines.
[0015] Further, the amine is a mixture of one or more selected from methylamine, ethylamine, propylamine, butylamine, ethylenediamine, propylenediamine, and butylenediamine.
[0016] Optimally, the molar ratio of the reactant to the polyester is 10 to 80, and the molar ratio of the catalyst to the polyester is 0.1 to 5.
[0017] Optimally, the polyester is a mixture selected from one or more of polyethylene terephthalate, propylene terephthalate, polybutylene terephthalate and polyarylate.
[0018] This invention utilizes an alkaline ionic liquid-catalyzed method for degrading polyester into high-value-added chemicals. By using an alkaline ionic liquid with strongly nucleophilic organic nitrogen heterocyclic anions as a catalyst, a mild and rapid degradation of polyester (especially PET) into high-value-added chemicals is achieved (reaction temperature 0℃~90℃ (temperature can be as low as 0℃~40℃), reaction time 0.1h~24h). This is because the alkaline ionic liquid can accelerate polyester degradation and its conversion into high-value-added chemical monomers through the interaction of cations with the ester bonds of polyester and the nucleophilic interaction of anions with alcohols and amines via the ester bonds. Compared with other reported alkaline catalysts, this method offers cleaner and more efficient catalyst synthesis, enabling the degradation of polyester into high-value-added chemical monomers under low reaction temperature and short reaction time conditions, with low energy consumption, demonstrating promising prospects for industrial application. Attached Figure Description
[0019] Figure 1 This is a chemical schematic diagram illustrating the chemical principle of the present invention, which utilizes alkaline ionic liquids to catalyze the degradation of polyester.
[0020] Figure 2 These are the 1H NMR spectrum and infrared spectrum of dimethyl terephthalate prepared in Example 2. Detailed Implementation
[0021] This invention utilizes a method for catalytic degradation of polyester into high-value-added chemicals using alkaline ionic liquids. The alkaline ionic liquid is used as a catalyst, and alcohols and / or amines are used as reactants to catalyze the degradation of polyester (the degradation principle is described in [reference needed]). Figure 1 The alkaline ionic liquid is a mixture of one or more components selected from the following general structural formulas: X + Y - In the formula, X + It is a basic cation, Y - It is a strongly nucleophilic organic nitrogen heterocyclic anion. Compared with other reported basic catalysts, the catalyst synthesis is cleaner and more efficient, and it can degrade polyester into high-value-added chemical monomers under conditions of low reaction temperature and short reaction time, significantly reducing depolymerization energy consumption and showing good prospects for industrial application.
[0022] The Y - It is a combination of one or more of the following organic nitrogen heterocyclic anions: , In the formula, R5 is selected from C1~C4 alkyl, alkoxy, cycloalkyl, alkenyl, phenyl and benzyl.
[0023] The X + It is a combination of one or more of the following structures: , In the formula, R1, R2, R3, and R4 are independently selected from C1 to C8 alkyl, alkoxy, cycloalkyl, alkenyl, phenyl, and benzyl. R1 and R2 are preferably independently selected from phenyl, benzyl, C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, and C8 alkyl, more preferably C1 alkyl-C4 alkyl or phenyl.
[0024] The reaction temperature for catalyzing polyester degradation is 0℃~90℃, the reaction time is 0.1h~24h, and the reaction pressure is atmospheric pressure or auto-pressure (e.g., the reaction temperature can be 0℃, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃ or 90℃; the reaction time can be 0.1h, 1h, 2h, 4h, 8h, 12h, 16h, 18h, 20h or 24h); but preferably 0℃~40℃, because the alkaline ionic liquid containing the above-mentioned strongly nucleophilic organic nitrogen heterocyclic anion still has good performance in catalyzing polyester degradation within this temperature range.
[0025] The alcohol is a mixture selected from one or more of methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, and butylene glycol. The amine is a mixture selected from one or more of monoprimary amines, bisprimary amines, monosecondary amines, and bissecondary amines, preferably a mixture selected from one or more of methylamine, ethylamine, propylamine, butylamine, ethylenediamine, propylenediamine, and butylenediamine. The molar ratio of the reactant to the polyester is 10 to 80 (e.g., 10, 20, 30, 40, 50, 60, 70, or 80 times), and the molar ratio of the catalyst to the polyester is 0.1 to 5 (e.g., 0.1, 0.2, 0.5, 1, 2, 3, 4, or 5 times). The polyester is a mixture selected from one or more of polyethylene terephthalate, polyethylene terephthalate, polybutylene terephthalate, and polyarylates.
[0026] After the reaction is complete, the degradation rate of the polyester (using polyethylene terephthalate as an example, i.e., PET) and the selectivity of the product are calculated using the following formulas: , Where A represents the initial mass of added PET, and B represents the mass of undegraded PET.
[0027] The preferred embodiments of the present invention will now be described in detail. Example 1
[0028] This embodiment provides a series of methods for preparing alkaline ionic liquids, including the following steps: Taking 1,8-diazabicyclo[5.4.0]undec-7-ene succinimide ([HDBU][Suc]) as an example: 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and succinimide (Suc) were dissolved in anhydrous ethanol (100 mL) at a molar ratio of 1:1 (1 mmol of each was used in this example). The mixture was heated and stirred at 60 °C for 4 h under nitrogen. The solvent was removed using a vacuum rotary evaporator, and then dried in a vacuum oven at 60 °C for 24 h to obtain the target ionic liquid [HDBU][Suc].
[0029] By changing the appropriate raw materials and using the same preparation method, other alkaline ionic liquids involved in this invention can be obtained (see the aforementioned general chemical formula). Example 2
[0030] This embodiment provides a method for catalytically degrading polyester into high-value-added chemicals using alkaline ionic liquids, as detailed below: The alkaline ionic liquid ([HDBU][Suc], used as a catalyst), methanol (as a reactant), and polyethylene terephthalate (powder) prepared in Example 1 were sequentially added to a 15 mL pressure-resistant bottle (containing 0.576 g (3 mmol) of polyethylene terephthalate, 4.8 g (0.15 mol) of methanol, and 3 mmol of catalyst [HDBU][Suc]). After sealing, the reaction temperature was controlled at 40 °C and the reaction was carried out for 6 h. After cooling to room temperature, 50 mL of acetonitrile was added to dissolve the precipitate, and the mixture was filtered. The filter cake was unreacted polyethylene terephthalate, and the solvent in the filtrate was removed by vacuum rotary evaporation. Water was then added to obtain a white solid precipitate, which was dimethyl terephthalate. Its 1H NMR spectrum and infrared spectrum are shown below. Figure 2 As shown, the aqueous phase was subjected to vacuum distillation to remove water and ethylene glycol, and then dried in a vacuum oven to recover the catalyst. Under these conditions, the degradation rate of polyethylene terephthalate was 92.3%, and the yield of dimethyl terephthalate monomer was 90.4%, calculated according to the aforementioned formula. Example 3
[0031] This embodiment provides a method for catalytic degradation of polyester into high-value-added chemicals using an alkaline ionic liquid, which is basically the same as that in Example 2, except that the catalyst is changed to 1,5,7-triazabicyclo[4.4.0]dec-5-ene succinimide ([HTBD][Suc]). Under these conditions, the calculated degradation rate of polyethylene terephthalate is 98.5%, and the yield of dimethyl terephthalate monomer is 95.1%. Example 4
[0032] This embodiment provides a method for catalytic degradation of polyester into high-value-added chemicals using an alkaline ionic liquid, which is basically the same as that in Example 2, except that the catalyst is changed to 1,1,3,3-tetramethylguanidine succinimide ([HTMG][Suc]). Under these conditions, the calculated degradation rate of polyethylene terephthalate is 82.0%, and the yield of dimethyl terephthalate monomer is 80.2%. Example 5
[0033] This embodiment provides a method for catalytic degradation of polyester into high-value-added chemicals using an alkaline ionic liquid. It is essentially the same as that in Example 2, except that the catalyst is replaced with tetrabutylphosphine succinimide ([P... 4444 [Suc]). Under these conditions, the degradation rate of polyethylene terephthalate was calculated to be 78.5%, and the yield of dimethyl terephthalate monomer was 75.6%. Example 6
[0034] This embodiment provides a method for catalytic degradation of polyester into high-value-added chemicals using an alkaline ionic liquid. It is essentially the same as that in Example 2, except that the catalyst is replaced with tetrabutylamine succinimide ([N... 4444 [Suc]). Under these conditions, the degradation rate of polyethylene terephthalate was calculated to be 76.8%, and the yield of dimethyl terephthalate monomer was 73.9%. Example 7
[0035] This embodiment provides a method for catalytic degradation of polyester into high-value-added chemicals using alkaline ionic liquids. It is essentially the same as that in Example 2, except that the reaction temperature is controlled at 60°C. Under these conditions, the calculated degradation rate of polyethylene terephthalate is 100%, and the yield of dimethyl terephthalate monomer is 93.6%. Example 8
[0036] This embodiment provides a method for catalytic degradation of polyester into high-value-added chemicals using alkaline ionic liquids. It is essentially the same as that in Example 2, except that the reaction temperature is controlled at 50°C. Under these conditions, the calculated degradation rate of polyethylene terephthalate is 96.8%, and the yield of dimethyl terephthalate monomer is 92.2%. Example 9
[0037] This embodiment provides a method for catalytic degradation of polyester into high-value-added chemicals using alkaline ionic liquids. It is essentially the same as that in Example 2, except that the reaction temperature is controlled at 0°C. Under these conditions, the calculated degradation rate of polyethylene terephthalate is 53.5%, and the yield of dimethyl terephthalate monomer is 50.1%. Example 10
[0038] This embodiment provides a method for catalytic degradation of polyester into high-value-added chemicals using alkaline ionic liquids. It is essentially the same as that in Example 3, except that polyethylene terephthalate is replaced with polypropylene terephthalate. Under these conditions, the calculated degradation rate of polyethylene terephthalate is 100%, and the yield of dimethyl terephthalate monomer is 92.2%. Example 11
[0039] This embodiment provides a method for catalytic degradation of polyester into high-value-added chemicals using alkaline ionic liquids. It is essentially the same as that in Example 3, except that polyethylene terephthalate is replaced with polybutylene terephthalate. Under these conditions, the calculated degradation rate of polyethylene terephthalate is 100%, and the yield of dimethyl terephthalate monomer is 91.3%.
[0040] Examples 12-16 Examples 12-16 provide a method for catalyzing the degradation of polyester into high-value-added chemicals using alkaline ionic liquids. It is basically the same as that in Example 3, except that the catalyst is replaced with the ionic liquid catalyst recovered in Example 3 (the catalysts in Examples 12-16 are recycled 1 to 5 times respectively). The final results are shown in Table 1.
[0041] Table 1 Results of polyester degradation experiments in Examples 12-16
[0042] Comparative Example 1 This example provides a method for catalytic degradation of polyester into high-value-added chemicals using an alkaline ionic liquid, which is essentially the same as that in Example 2, except that the catalyst is replaced with the alkaline ionic liquid 1,8-diazabicyclo[5.4.0]undec-7-enephenol ([HDBU][PhO]). Under these conditions, the calculated degradation rate of polyethylene terephthalate is 32.1%, and the yield of dimethyl terephthalate monomer is 30.1%.
[0043] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A method for catalytically degrading polyester into high-value-added chemicals using alkaline ionic liquids, characterized in that, Includes the following steps: Alkaline ionic liquids are used as catalysts, and alcohols and / or amines are used as reactants to catalyze polyester degradation. The alkaline ionic liquid is a mixture of one or more components selected from the following general structural formulas: X + Y - , In the formula, X + It is a basic cation, Y - It is a strongly nucleophilic organic nitrogen heterocyclic anion.
2. The method for catalytic degradation of polyester into high-value-added chemicals using alkaline ionic liquids according to claim 1, characterized in that, The Y - It is a combination of one or more of the following organic nitrogen heterocyclic anions: .
3. The method for catalytic degradation of polyester into high-value-added chemicals using alkaline ionic liquids according to claim 1 or 2, characterized in that, The X + It is a combination of one or more of the following structures: ， In the formula, R1, R2, R3 and R4 are independently selected from C1 to C8 alkyl, alkoxy, cycloalkyl, alkenyl, phenyl and benzyl.
4. The method for catalytic degradation of polyester into high-value-added chemicals using alkaline ionic liquids according to claim 1 or 2, characterized in that: The reaction temperature for catalytic polyester degradation is 0℃~90℃, the reaction time is 0.1h~24h, and the reaction pressure is atmospheric pressure or auto-pressure.
5. The method for catalytic degradation of polyester into high-value-added chemicals using alkaline ionic liquids according to claim 4, characterized in that: The reaction temperature for the catalytic degradation of polyester is 0℃~40℃.
6. The method for catalytic degradation of polyester into high-value-added chemicals using alkaline ionic liquids according to claim 1, characterized in that: The alcohol is a mixture selected from one or more of methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, and butanediol.
7. The method for catalytic degradation of polyester into high-value-added chemicals using alkaline ionic liquids according to claim 1, characterized in that: The amine is a mixture of one or more selected from primary amines, secondary amines, and bisamines.
8. The method for catalytic degradation of polyester into high-value-added chemicals using alkaline ionic liquids according to claim 7, characterized in that: The amine is a mixture of one or more selected from methylamine, ethylamine, propylamine, butylamine, ethylenediamine, propylenediamine, and butyldiamine.
9. The method for catalytic degradation of polyester into high-value-added chemicals using alkaline ionic liquids according to claim 1, characterized in that: The molar ratio of the reactant to the polyester is 10 to 80, and the molar ratio of the catalyst to the polyester is 0.1 to 5.
10. The method for catalytic degradation of polyester into high-value-added chemicals using alkaline ionic liquids according to claim 1, characterized in that: The polyester is a mixture selected from one or more of polyethylene terephthalate, propylene terephthalate, polybutylene terephthalate and polyarylate.