A method for directional high-value polycarbonate under the action of polyionic liquid catalyst

Abstract

The invention discloses a method for directional high-value conversion of polycarbonate under the action of a polyionic liquid catalyst, belonging to the technical field of depolymerization and recovery of polymer materials. The polyionic liquid catalyst uses an ionic liquid and an acrylate as comonomers, adds a crosslinking agent and an initiator, and undergoes a heating copolymerization reaction in an organic solvent system under an inert gas atmosphere, and is obtained by post-processing. A reaction system comprising polycarbonate, the polyionic liquid catalyst, an epoxy compound, and a polar solvent is further constructed, and the reaction system is placed at a temperature of 130 to 150° C. in an air atmosphere for a reaction of 6 hours or more, thereby achieving directional high-value conversion of the polycarbonate into bisphenol A and cyclic carbonate. The method of the invention has broad application prospects in the field of waste plastics treatment.

Description

Technical Field

[0001] The invention relates to the technical field of depolymerization and recovery of polymer materials, and in particular to a method for directional high-value conversion of polycarbonate under the action of a polyionic liquid catalyst. Background Art

[0002] Ionic liquids are liquid organic salts composed of cations and anions. They possess advantages such as low volatility, non-flammability, high conductivity, and excellent thermal stability. They are now widely used in catalysis, separation, organic synthesis, and medical materials. Polyionic liquids are derived from ionic liquid monomers, where the cations, anions, or both of these monomers are incorporated into a polymer backbone. Compared to ionic liquids, polyionic liquids have more adjustable ionic moieties, resulting in improved processability, designability, and recyclability. A variety of polyionic liquids have been developed. For example, Chinese Patent Publication No. CN116574214A discloses a polyionic liquid catalyst, its preparation method, and application. This invention involves polymerizing 1-vinyl-3-butylimidazolium hydrogen sulfate monomer and a hydrogen sulfate crosslinker in the presence of an initiator to produce a polyionic liquid catalyst that combines the advantages of solid acids, ionic liquids, and polymers. This catalyst is used in the esterification reaction of acids and alcohols. Chinese Patent Publication No. CN108689838A discloses a swellable acidic polyionic liquid. This polyionic liquid, using 1-vinyl-3-alkylimidazolium bromide ionic liquid and sodium acrylate as comonomers, is obtained through free radical polymerization and acidification with an equimolar amount of acid. This polyionic liquid can be used to catalyze the esterification of formic acid with olefins to produce formic esters.

[0003] Plastic products provide immense convenience for modern life. However, with the increasing use of plastics, increasing the reuse rate of discarded plastics has become a pressing issue. Traditional plastic recycling technologies struggle to fully utilize carbon resources and pose environmental and biosafety concerns. Chemical recycling technologies can transform waste plastics into basic chemical raw materials or other high-value-added chemicals, achieving resource appreciation. This conversion of waste plastics into chemical monomers is crucial for promoting the sustainable development of the plastics economy. However, there are currently no reports of polyionic liquids being used to enhance the value of waste plastics.

[0004] Polycarbonate (PC) plastic is a non-crystalline thermoplastic with excellent physical, chemical, and processing properties, occupying a key position in the engineering plastics market. Although studies have reported that ionic liquid catalysts can be used for the depolymerization of PC (such as in Chinese patent documents with publication numbers CN117603044A and CN101429100A), the ionic liquid catalyst is difficult to separate from the product, which increases the difficulty of subsequent purification steps and may also lead to product contamination and ionic liquid loss. Summary of the Invention

[0005] In order to address the deficiencies in the above-mentioned prior art, the present invention provides the use of polyionic liquid catalysts in the depolymerization and recovery of polycarbonate, as well as a method for the targeted high-value conversion of polycarbonate under the action of corresponding polyionic liquid catalysts, which has broad application prospects in the field of waste plastics processing.

[0006] The specific technical solutions adopted are as follows:

[0007] The invention relates to an application of a polyionic liquid catalyst in the depolymerization and recovery of polycarbonate. The polyionic liquid catalyst is prepared by the following method: using an ionic liquid and an acrylate as comonomers, adding a crosslinking agent and an initiator, heating and copolymerizing in an organic solvent system under an inert gas atmosphere, and obtaining the polyionic liquid catalyst through post-treatment.

[0008] The ionic liquid is selected from at least one of 1-vinyl-3-ethylimidazolium bromide ([VEIm][Br]), 1-vinyl-3-butylimidazolium bromide ([VBIm][Br]), 1-vinyl-3-ethylimidazolium tetrafluoroborate ([VEIm][BF4]), and 1-vinyl-3-ethylimidazolium hexafluorophosphate ([VEIm][PF6]);

[0009] The molar ratio of the ionic liquid to the acrylate is 0.5-2:1;

[0010] The temperature of the heating copolymerization reaction is 60-110°C and the time is 8-24 hours.

[0011] Specifically, the polycarbonate is bisphenol A polycarbonate; and the acrylate is selected from zinc acrylate, sodium acrylate or magnesium acrylate.

[0012] The initiator includes azobisisobutyronitrile, and the cross-linking agent includes divinylbenzene.

[0013] More preferably, the amount of the initiator added is 20-50 wt% of the total mass of the comonomers, and the amount of the cross-linking agent added is 20-60 wt% of the total mass of the comonomers.

[0014] Preferably, the organic solvent includes acetonitrile, methanol or ethanol.

[0015] Preferably, the inert gas atmosphere is a nitrogen atmosphere, and the post-treatment method is: cooling the reaction liquid, further filtering it, washing it with water and ethanol, and vacuum drying it to obtain the polyionic liquid catalyst.

[0016] The present invention also provides a method for directional high-value polycarbonate under the action of a polyionic liquid catalyst, the method comprising:

[0017] Constructing a reaction system comprising polycarbonate, the polyionic liquid catalyst, an epoxy compound, and a polar solvent, and reacting the reaction system at a temperature of 130 to 150° C. under an air atmosphere for 6 hours or longer to obtain bisphenol A and a cyclic carbonate;

[0018] The polar solvent is selected from N -Methylpyrrolidone, N , N -dimethylformamide, or N -Methylpyrrolidone, N , N The polar solvent significantly enhances the contact efficiency between the polyionic liquid catalyst and the polymer substrate by promoting the swelling and dissolution of the polycarbonate.

[0019] The epoxy compound is at least one of styrene oxide, 1,2-propylene oxide or 1,2-butylene oxide.

[0020] Preferably, the molar ratio of polycarbonate to epoxy compound is 1:0.5-3; and the amount of the polyionic liquid catalyst added is 1-30 wt% of the mass of the polycarbonate.

[0021] More preferably, the molar ratio of polycarbonate to epoxy compound is 1:1-2, and the amount of polyionic liquid catalyst added is 15-30 wt% based on 100 mol% of polycarbonate. This raw material ratio promotes sufficient depolymerization of polycarbonate and the efficient production of bisphenol A and cyclic carbonate, while avoiding unnecessary increases in raw material costs and balancing reaction efficiency and cost-effectiveness.

[0022] Preferably, the ratio of polycarbonate to polar solvent is 1 g:5-15 mL.

[0023] Further preferably, the polar solvent is selected from N -Methylpyrrolidone, N , N A mixture of at least one organic solvent and water in dimethylformamide, wherein the volume ratio of water to organic solvent is 0.3-2:100. The organic solvent promotes the swelling of the polymer, and water acts as a nucleophile to attack PC and cause hydrolysis.

[0024] More preferably, in order to take into account both reaction efficiency and product yield, the reaction system is placed at a temperature of 130-150° C. under air atmosphere for 6 h to 10 h.

[0025] The present invention also provides the application of the method for directional high-value conversion of polycarbonate under the action of polyionic liquid catalyst in the treatment of waste plastics.

[0026] Specifically, the waste plastic is waste made of bisphenol A polycarbonate, including waste CDs, waste buckets, waste films, waste bottles, waste plates, waste sheets, etc. The method of the present invention is applicable to various forms of waste polycarbonate samples.

[0027] When upgrading and converting waste plastics, they need to be pre-crushed into centimeter-sized flakes, granules or powders to ensure their resource utilization effect, so as to obtain bisphenol A and cyclic carbonates in a targeted and high-yield manner.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The present invention provides an efficient dual upgrading and conversion method for bisphenol A polycarbonate, which realizes the selective cleavage and reconstruction of carbonate bonds and bisphenol A units in polycarbonate molecules.

[0030] (2) The method for directional high-value-added polycarbonate under the action of polyionic liquid catalyst in the present invention has a wide range of substrate applicability, not only limited to styrene oxide, but also applicable to 1,2-propylene oxide and 1,2-butylene oxide. The reaction conditions are mild, and it has higher environmental friendliness, resource utilization efficiency and operational safety, high chemical monomer yield and high application value.

[0031] (3) The polyionic liquid catalyst used in the present invention has good mechanical strength and chemical stability. After the reaction is completed, the catalyst can be quickly recovered by simple centrifugal separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 FT-IR spectra of polyionic liquid VB-Br-Zn-MeCN and ionic liquid monomer [VBIm][Br].

[0033] Figure 2 is the reaction scheme equation in representative Example 1. DETAILED DESCRIPTION

[0034] The present invention will be further illustrated below in conjunction with the examples. It should be understood that these examples are intended to illustrate the present invention only and are not intended to limit the scope of the invention. The operating methods in the following examples where specific conditions are not specified are generally based on conventional conditions or the conditions recommended by the manufacturer. Contents not described in detail in this specification sheet belong to the prior art known to those skilled in the art. The experimental materials used in the following examples, unless otherwise specified, can be purchased from conventional biochemical reagent companies.

[0035] To a 25 mL Schlenk tube, 1-vinyl-3-butylimidazolium bromide [VBIm][Br] (2 mmol), zinc acrylate (1 mmol), 2,2'-azobisisobutyronitrile (AIBN, 1.1 mmol, as a free radical initiator), divinylbenzene (DVB, 2 mmol, as a cross-linker), and acetonitrile (6 mL, as a reaction solvent) were added in sequence. The reaction mixture was placed in an oil bath at 70 °C and polymerized under an inert atmosphere for 12 hours. After completion of the reaction, the system was cooled to room temperature, and the product was isolated by filtration and washed three times with distilled water and three times with ethanol to remove unreacted monomers and impurities. Finally, the crude product was dried in vacuo at 60 °C for 12 hours to obtain the desired product, VB-Br-Zn-MeCN.

[0036] Under the same conditions, [VBIm][Br] was replaced by [VEIm][Br], [VEIm][BF4] or [VEIm][PF6] to obtain VE-Br-Zn-MeCN, VE-BF4-Zn-MeCN and VE-PF6-Zn-MeCN, respectively.

[0037] Under the same conditions, zinc acrylate was replaced by magnesium acrylate or sodium acrylate to obtain VB-Br-Mg-MeCN or VB-Br-Na-MeCN.

[0038] Under the same conditions, acetonitrile was replaced with methanol or ethanol to obtain VB-Br-Zn-MeOH or VB-Br-Zn-EtOH.

[0039] The FT-IR spectra of VB-Br-Zn-MeCN and [VBIm][Br] are as follows Figure 1 As shown in Figure 2, infrared spectroscopy confirmed the presence of IL monomers in the polyionic liquid: 2885~3006 cm - ¹ is the CH stretching vibration of the imidazole ring, 1445 and 1390 cm - ¹ is the vibration of the imidazole ring skeleton, 1152 cm - ¹ is the stretching vibration of the imidazole ring. Compared with pure [VBIm][Br], 1654 cm - The disappearance of the C=C stretching vibration peak at ¹ further supports this conclusion. - C=O stretching vibration at ¹ and 660 cm - The Zn-O stretching vibration at ¹ indicates that zinc acrylate participates in the polymerization reaction.

[0040] The reaction processes of the following examples and comparative examples were all carried out under normal pressure without applying additional pressure. The polycarbonate PC powders used were all bisphenol A polycarbonate. The reaction scheme is shown in FIG. Figure 2shown.

[0041] Example 1

[0042] PC powder (0.508 g, 2 mmol), styrene oxide (SO, 3 mmol), and polyionic liquid catalyst VB-Br-Zn-MeCN (20 wt%, relative to PC mass) were added in sequence to a 10 mL Schlenk tube. N N-methylpyrrolidone (NMP, 5 mL) was used as the reaction solvent. The reaction system was placed in an oil bath preheated to 140 °C under air atmosphere and reacted for 10 hours with continuous stirring. After the reaction was completed, the reaction mixture was quickly transferred to an ice-water bath and cooled to room temperature. Trioxane was used as the internal standard and the results were analyzed by H NMR spectroscopy ( 1 The reaction products were quantitatively analyzed by H NMR to determine the yields of bisphenol A and cyclic carbonate. The results showed that the yield of bisphenol A in this example was 71%, and the yield of styrene carbonate was 77%.

[0043] Example 2

[0044] PC powder (0.508 g, 2 mmol), styrene oxide (SO, 3 mmol), and different polyionic liquid catalysts (VE-Br-Zn-MeCN, VE-BF4-Zn-MeCN, VE-PF6-Zn-MeCN, 20 wt%, relative to the mass of PC) were added to multiple 10 mL Schlenk tubes. N N-methylpyrrolidone (NMP, 5 mL) was used as the reaction solvent. The reaction system was placed in an oil bath preheated to 140 °C under air atmosphere and reacted for 10 hours with continuous stirring. After the reaction was completed, the reaction mixture was quickly transferred to an ice-water bath and cooled to room temperature. Trioxane was used as the internal standard and the results were analyzed by H NMR spectroscopy ( 1 The reaction products were quantitatively analyzed by H NMR to determine the yields of bisphenol A and cyclic carbonate. The results showed that the yields of bisphenol A in this example were 63%, 52%, and 56%, respectively, and the yields of styrene carbonate were 47%, 17%, and 0%, respectively.

[0045] Example 3

[0046] PC powder (0.508 g, 2 mmol), styrene oxide (SO, 3 mmol), and polyionic liquid catalyst VB-Br-Zn-MeCN (20 wt%, relative to PC mass) were added to multiple 10 mL Schlenk tubes, respectively. N -The volume of methyl pyrrolidone is 1, and the amount of deionized water added is N-methylpyrrolidone 0.36%, 0.54%, 0.72%, 0.9%) and N N-methylpyrrolidone (NMP, 5 mL) was used as the reaction solvent. The reaction system was placed in an oil bath preheated to 140 °C under air atmosphere and reacted for 10 hours with continuous stirring. After the reaction was completed, the reaction mixture was quickly transferred to an ice-water bath and cooled to room temperature. Trioxane was used as the internal standard and the results were analyzed by H NMR spectroscopy ( 1 The reaction products were quantitatively analyzed using H NMR to determine the yields of bisphenol A and cyclic carbonate. The results showed that the yields of bisphenol A in this example were 74%, 83%, 99%, and 99%, respectively, and the yields of styrene carbonate were 80%, 86%, 98%, and 99%, respectively.

[0047] The amount of deionized water added is N Under the experimental parameters of 0.72% methylpyrrolidone, the polyionic liquid catalyst was separated by centrifugation after the reaction. The separated polyionic liquid catalyst was transferred to a 10 mL Schlenk tube. No additional polyionic liquid catalyst was added. All other reaction conditions and parameters remained the same. After four cycles, the yield of bisphenol A was 99% and the yield of styrene carbonate was 94%.

[0048] Example 4

[0049] PC powder (2 mmol), different molar numbers of styrene oxide (the molar ratio of PC powder to styrene oxide was 1:1.3, 1:1.8, and 1:2, respectively), and polyionic liquid catalyst VB-Br-Zn-MeCN (20 wt%, relative to the mass of PC) were added to multiple 10 mL Schlenk tubes. N -The volume of methyl pyrrolidone is 1, and the amount of deionized water added is N 0.72% of methylpyrrolidone (0.036 g) and N-methylpyrrolidone (NMP, 5 mL) were used as the reaction solvent. The reaction system was placed in an oil bath preheated to 140 °C under air atmosphere and reacted for 10 hours with continuous stirring. After the reaction, the reaction mixture was quickly transferred to an ice-water bath and cooled to room temperature. Trioxane was used as the internal standard and the results were analyzed by nuclear magnetic resonance spectroscopy ( 1 The reaction products were quantitatively analyzed by H NMR to determine the yields of bisphenol A and cyclic carbonate. The results showed that the yields of bisphenol A in this example were 94%, 99%, and 99%, respectively, and the yields of styrene carbonate were 95%, 99%, and 99%, respectively.

[0050] Example 5

[0051] PC powder (2 mmol), styrene oxide (SO, 3 mmol), and different weights of polyionic liquid catalyst VB-Br-Zn-MeCN (15 wt%, 30 wt%, relative to the weight of PC) were added to multiple 10 mL Schlenk tubes, and deionized water ( N -The volume of methyl pyrrolidone is 1, and the amount of deionized water added is N -methylpyrrolidone (0.72%, 0.036 g) and N N-methylpyrrolidone (NMP, 5 mL) was used as the reaction solvent. The reaction system was placed in an oil bath preheated to 140 °C under air atmosphere and reacted for 10 hours with continuous stirring. After the reaction was completed, the reaction mixture was quickly transferred to an ice-water bath and cooled to room temperature. Trioxane was used as the internal standard and the results were analyzed by H NMR spectroscopy ( 1 The reaction products were quantitatively analyzed using H NMR to determine the yields of bisphenol A and cyclic carbonate. The results showed that the yields of bisphenol A in this example were 95% and 99%, respectively, and the yields of styrene carbonate were 92% and 99%, respectively.

[0052] Example 6

[0053] PC powder (2 mmol), styrene oxide (SO, 3 mmol), polyionic liquid catalyst VB-Br-Zn-MeCN (20 wt%, relative to PC mass), and deionized water (100 mL) were added to a 10 mL Schlenk tube. N -The volume of methyl pyrrolidone is 1, and the amount of deionized water added is N -methylpyrrolidone (0.72%, 0.036 g) and N -Methylpyrrolidone (NMP, 5 mL) was used as the reaction solvent. The reaction system was placed in an oil bath preheated to 130 and 150°C under air atmosphere and reacted for 10 hours with continuous stirring. After the reaction, the reaction mixture was quickly transferred to an ice-water bath and cooled to room temperature. Trioxane was used as the internal standard and the results were analyzed by nuclear magnetic resonance spectroscopy ( 1 The reaction products were quantitatively analyzed by H NMR to determine the yields of bisphenol A and cyclic carbonate. The results showed that the yields of bisphenol A in this example were 93% and 99%, respectively, and the yields of styrene carbonate were 81% and 99%, respectively.

[0054] Example 7

[0055] In several 10 mL Schlenk tubes, 0.254 g cm-scale PC waste fragments (buckets, CDs, transparent plates, about 2 mmol), styrene oxide (SO, 3 mmol), polyionic liquid catalyst VB-Br-Zn-MeCN (20 wt%, relative to the mass of PC) and deionized water (about 100 mL) were added. N -The volume of methyl pyrrolidone is 1, and the amount of deionized water added is N -methylpyrrolidone (0.72%, 0.036 g) and N N-methylpyrrolidone (NMP, 5 mL) was used as the reaction solvent. The reaction system was placed in an oil bath preheated to 140 °C under air atmosphere and reacted for 10 hours with continuous stirring. After the reaction was completed, the reaction mixture was quickly transferred to an ice-water bath and cooled to room temperature. Trioxane was used as the internal standard and the results were analyzed by H NMR spectroscopy ( 1 The reaction products were quantitatively analyzed by H NMR to determine the yields of bisphenol A and cyclic carbonate. The results showed that the yields of bisphenol A in this example were 95%, 97%, and 98%, respectively, and the yields of styrene carbonate were 94%, 96%, and 95%, respectively.

[0056] Example 8

[0057] PC powder (2 mmol), different epoxy compounds (1,2-propylene oxide, 1,2-butylene oxide, 3 mmol), and polyionic liquid catalyst VB-Br-Zn-MeCN (20 wt%, relative to the mass of PC) were added to multiple 10 mL Schlenk tubes, and deionized water (100 mL) was added. N -The volume of methyl pyrrolidone is 1, and the amount of deionized water added is N -methylpyrrolidone (0.72%, 0.036 g) and N N-methylpyrrolidone (NMP, 5 mL) was used as the reaction solvent. The reaction system was placed in an oil bath preheated to 140 °C under air atmosphere and reacted for 10 hours with continuous stirring. After the reaction was completed, the reaction mixture was quickly transferred to an ice-water bath and cooled to room temperature. Trioxane was used as the internal standard and the results were analyzed by H NMR spectroscopy ( 1 The reaction products were quantitatively analyzed using H NMR to determine the yields of bisphenol A and cyclic carbonate. The results showed that the yields of bisphenol A in this example were 98% and 96%, respectively, and the yields of cyclic carbonate were 97% and 98%, respectively. The corresponding cyclic carbonate structure is shown below:

[0058] .

[0059] Example 9

[0060] PC powder (2 mmol), styrene oxide (SO, 3 mmol), and polyionic liquid catalyst VB-Br-Zn-MeCN (20 wt%, relative to PC mass) were added to several 10 mL Schlenk tubes, and deionized water ( N -The volume of methyl pyrrolidone is 1, and the amount of deionized water added is N -methylpyrrolidone (0.72%, 0.036 g) and N N-methylpyrrolidone (NMP, 5 mL) was used as the reaction solvent. The reaction system was placed in an oil bath preheated to 140 °C under air atmosphere and reacted for 8 h, 9 h, 11 h, and 12 h under continuous stirring. After the reaction, the reaction mixture was quickly transferred to an ice-water bath and cooled to room temperature. Trioxane was used as the internal standard and the results were analyzed by H NMR spectroscopy ( 1 The reaction products were quantitatively analyzed by H NMR to determine the yields of bisphenol A and cyclic carbonate. The results showed that the yields of bisphenol A in this example were 85%, 92%, 99%, and 99%, respectively, and the yields of styrene carbonate were 83%, 87%, 99%, and 99%, respectively.

[0061] Comparative Example 1

[0062] The method for directional high value of polycarbonate under the action of polyionic liquid catalyst in this comparative example and Example 3 (the amount of deionized water added is N -methyl pyrrolidone 0.72%) is that the polyionic liquid catalyst and deionized water are not added, and the other reaction conditions and parameters are the same. After the reaction is completed, a mixed solution is obtained, and the obtained mixed solution is passed through 1 The yield was determined by H NMR with trioxane as the internal standard. The results showed that the yield of bisphenol A in this comparative example was 18.3%, and the yield of styrene carbonate was 7.4%.

[0063] Comparative Example 2

[0064] The method for directional high value of polycarbonate under the action of polyionic liquid catalyst in this comparative example and Example 3 (the amount of deionized water added is N -methylpyrrolidone 0.72%), without adding polyionic liquid catalyst and deionized water, adding 20 wt% [VBIm][Br], the other reaction conditions and parameters are the same, after the reaction is completed, a mixed solution is obtained, and the obtained mixed solution is passed through 1 The yield was determined by H NMR with trioxane as the internal standard. The results showed that the yield of bisphenol A in this comparative example was 32.7%, and the yield of styrene carbonate was 10%.

[0065] Comparative Example 3

[0066] The method for directional high value of polycarbonate under the action of polyionic liquid catalyst in this comparative example and Example 3 (the amount of deionized water added is N -methylpyrrolidone 0.72%), without adding NMP, adding 5mL water, the other reaction conditions and parameters are the same, after the reaction is completed, a mixed solution is obtained, and the obtained mixed solution is passed through 1 The yield was determined by H NMR with trioxane as the internal standard. The results showed that the yield of bisphenol A in this comparative example was 0%, and the yield of styrene carbonate was 0%.

[0067] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. Application of polyionic liquid catalyst in depolymerization and recovery of polycarbonate, characterized in that: The polyionic liquid catalyst is prepared by the following method: using ionic liquid and acrylate as comonomers, adding a crosslinking agent and an initiator, heating and copolymerizing in an organic solvent system under an inert gas atmosphere, and obtaining the polyionic liquid catalyst through post-treatment; The ionic liquid is selected from at least one of 1-vinyl-3-ethylimidazolium bromide, 1-vinyl-3-butylimidazolium bromide, 1-vinyl-3-ethylimidazolium tetrafluoroborate, and 1-vinyl-3-ethylimidazolium hexafluorophosphate; The molar ratio of the ionic liquid to the acrylate is 0.5-2:1; The temperature of the heating copolymerization reaction is 60-110°C and the time is 8-24 hours; When depolymerizing and recovering polycarbonate, a reaction system comprising polycarbonate, a polyionic liquid catalyst, an epoxy compound, and a polar solvent is constructed, and the reaction system is placed at a temperature of 130 to 150° C. under an air atmosphere for a reaction of 6 hours or more; The polar solvent is selected from N -Methylpyrrolidone, N , N -dimethylformamide, or N -Methylpyrrolidone, N , N - a mixture of at least one of dimethylformamide and water.

2. The use of the polyionic liquid catalyst according to claim 1 in depolymerization and recovery of polycarbonate, characterized in that: The acrylate salt is selected from zinc acrylate, sodium acrylate or magnesium acrylate.

3. The use of the polyionic liquid catalyst according to claim 1 in depolymerization and recovery of polycarbonate, characterized in that: The initiator includes azobisisobutyronitrile, and the cross-linking agent includes divinylbenzene.

4. A method for directional high-value polycarbonate under the action of a polyionic liquid catalyst, characterized in that: Methods include: A reaction system comprising polycarbonate, a polyionic liquid catalyst, an epoxy compound, and a polar solvent is constructed, and the reaction system is placed at a temperature of 130 to 150°C under an air atmosphere for 6 hours or longer to obtain bisphenol A and a cyclic carbonate. The polar solvent is selected from N -Methylpyrrolidone, N , N -dimethylformamide, or N -Methylpyrrolidone, N , N - a mixture of at least one of dimethylformamide and water; The polyionic liquid catalyst is prepared by the following method: using ionic liquid and acrylate as comonomers, adding a crosslinking agent and an initiator, heating and copolymerizing in an organic solvent system under an inert gas atmosphere, and obtaining the polyionic liquid catalyst through post-treatment; The ionic liquid is selected from at least one of 1-vinyl-3-ethylimidazolium bromide, 1-vinyl-3-butylimidazolium bromide, 1-vinyl-3-ethylimidazolium tetrafluoroborate, and 1-vinyl-3-ethylimidazolium hexafluorophosphate; Acrylate is selected from zinc acrylate, sodium acrylate or magnesium acrylate; The molar ratio of the ionic liquid to the acrylate is 0.5-2:1; The temperature of the heating copolymerization reaction is 60-110°C and the time is 8-24 hours.

5. The method for directional high-value polycarbonate under the action of a polyionic liquid catalyst according to claim 4, characterized in that: The epoxy compound is at least one of styrene oxide, 1,2-propylene oxide or 1,2-butylene oxide.

6. The method for directional high-value conversion of polycarbonate under the action of a polyionic liquid catalyst according to claim 4, characterized in that: The molar ratio of polycarbonate to epoxy compound is 1:0.5-3; and the added amount of polyionic liquid catalyst is 1-30wt% of the mass of polycarbonate.

7. The method for directional high value-added polycarbonate under the action of a polyionic liquid catalyst according to claim 4, characterized in that: The ratio of polycarbonate to polar solvent is 1 g:5-15 mL.

8. The method for directional high-value conversion of polycarbonate under the action of a polyionic liquid catalyst according to claim 4, characterized in that: Polar solvents are selected from N -Methylpyrrolidone, N , N - a mixture of at least one organic solvent and water in dimethylformamide.

9. The method for directional high value-added polycarbonate under the action of a polyionic liquid catalyst according to claim 4, characterized in that: The reaction system is placed at 130-150° C. under air atmosphere for 6-12 h.

10. Use of the method for directional high-value conversion of polycarbonate under the action of a polyionic liquid catalyst according to any one of claims 4 to 9 in the treatment of waste plastics.

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