Polycarbonate recovery method based on composite catalytic system

Abstract

The invention belongs to the technical field of chemical recovery of high polymer materials, and relates to a polycarbonate recovery method based on a composite catalytic system, which comprises the following steps: constructing a reaction system comprising bisphenol A polycarbonate, phenol, organic alkali, inorganic alkali and ionic liquid, and carrying out constant-temperature and constant-pressure reaction on the reaction system for 2.5-5 hours at 130-170 DEG C and 0.4-0.9 MPa in a nitrogen atmosphere to obtain bisphenol A. Through targeted activation and solvation effects of the ionic liquid with a special structure, stereo regulation and selective enhancement effects of the organic base and efficient bond breaking effects of the inorganic base, a trinity synergistic mechanism is formed, side reactions are reduced, the product yield and purity are improved, meanwhile, efficient recovery and reuse of the catalyst are achieved, and the method is suitable for industrial production. The goal of efficient, directional and green degradation of PC under laboratory conditions is achieved.

Description

Technical Field

[0001] This invention belongs to the field of polymer chemical recycling technology, and relates to a polycarbonate recycling method based on a composite catalytic system. Background Technology

[0002] Polycarbonate (PC), a transparent and impact-resistant engineering plastic, has a global annual production exceeding 7 million tons and is widely used in electronics, automobiles, construction, and other fields. As PC products reach their end-of-life (typically 3-8 years), over 2 million tons of waste PC are generated annually. If incinerated or landfilled, this not only wastes bisphenol A (PC monomer, with a market price of approximately 12,000 yuan / ton) resources but also releases toxic gases (such as dioxins) or occupies land resources.

[0003] Chemical recycling is an important approach to achieving efficient recycling of waste polycarbonate, among which alcoholysis recycling has attracted much attention because it can depolymerize polycarbonate into high-value monomers (such as bisphenol A and BPA). However, alcoholysis faces the following core problems in its industrial application: 1) Low depolymerization efficiency of single catalysts: When using only a single inorganic base (such as NaOH), although it can quickly break ester bonds, the strong alkalinity easily leads to carbonization of bisphenol A (product purity ≤90%), and the catalyst and product are difficult to separate after the reaction (requiring multiple water washings, increasing wastewater discharge); when using only a single organic base (such as triethylamine), the nucleophilic activity is insufficient, PC depolymerization takes more than 10 hours (long production cycle), and the depolymerization rate is ≤80% (a large amount of oligomers remain); when using only ionic liquids (such as [BMIM]BF4), although the solubility is good, it cannot effectively break ester bonds when used alone, and the depolymerization rate is only 65-70%.

[0004] 2) Poor solvent compatibility: Existing processes mostly use methanol and ethanol as solvents, but PC has low solubility in methanol (solubility ≤ 5 g / 100mL at 25℃), and it needs to be heated to above 200℃ to dissolve, which leads to increased energy consumption; in addition, methanol is highly volatile (boiling point 64.7℃), and the solvent loss rate in the reaction is ≥ 15%, which pollutes the environment and increases costs.

[0005] 3) Side reactions are difficult to control: The intermediate diphenyl carbonate (DPC) generated during alcoholysis is prone to hydrolysis (generating phenol and CO2) or transesterification side reactions (generating low-boiling substances), resulting in a bisphenol A yield of ≤85%, making it difficult to obtain high-purity bisphenol A products. Subsequent purification requires distillation (high energy consumption) or column chromatography (difficult to industrialize).

[0006] Therefore, developing a low-energy-consumption, highly selective, and recyclable catalyst-solvent system is the core requirement for solving the bottleneck of industrialization of PC alcoholysis recovery. Summary of the Invention

[0007] This invention addresses the technical problems of low depolymerization efficiency, numerous side reactions, and poor solvent compatibility in single catalytic systems for PC degradation. It provides a polycarbonate recovery method based on a composite catalytic system, employing a composite catalytic system of "specially substituted imidazole ionic liquid - sterically hindered tertiary amine / alkanolamine organic base - high ionic strength alkali metal hydroxide." Through the targeted activation and solvation of the specially structured ionic liquid, the stereoregulation and selectivity enhancement of the organic base, and the efficient bond-breaking effect of the inorganic base, a "three-in-one" synergistic mechanism is formed. This reduces side reactions, improves product yield and purity, and simultaneously achieves efficient catalyst recovery and reuse, thus achieving the goal of efficient, targeted, and green degradation of PC under laboratory conditions.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for recovering polycarbonate based on a composite catalytic system, comprising the following steps: A reaction system comprising bisphenol A type polycarbonate, phenol, organic base, inorganic base and ionic liquid was constructed. The reaction system was subjected to isothermal and isobaric reaction at 130-170 °C and 0.4-0.9 MPa for 2.5-5 h under nitrogen atmosphere to obtain bisphenol A. The structural formula of the ionic liquid is as follows: Where R1 is selected from C 8~12 Branched alkyl groups, C 6~10 Aromatic alkyl or adamantyl alkyl; R2 and R3 are selected from C 1~6 alkyl or cyclohexyl; R4 is selected from hydrogen or C 1~3 The alkyl group; A is selected from any one of hexafluorophosphate anion, bis(trifluoromethanesulfonylimide) anion, and trifluoromethanesulfonate anion; The organic base is a sterically hindered tertiary amine or alcohol amine compound; the inorganic base is a high ionic strength alkali metal hydroxide.

[0009] In the above technical solution, the organic base is selected from any one or more of N-methyldicyclohexylamine, 1-adamantaneamine, N-ethyl-N-phenylethanolamine, N-cyclohexyl-N-benzylmethylamine or 2,2,6,6-tetramethylpiperidinamine.

[0010] In the above technical solution, the amount of organic base added is 0.8~2.5% of the mass of bisphenol A polycarbonate.

[0011] This invention selects organic bases with steric hindrance, such as N-methyldicyclohexylamine and 1-adamantaneamine. The large cyclic or adamantyl groups in their molecular structures offer the following advantages: First, their basicity is mild and controllable, avoiding the carbonization of bisphenol A caused by strong alkalinity. The pH of the reaction solution can be monitored in the laboratory using a pH meter (maintained at 8-10 during the reaction). Second, the steric hindrance effect can shield the active site of the intermediate DPC, inhibiting side reactions. The content of byproducts can be detected by HPLC in the laboratory at ≤1.2%. Third, they can form hydrogen bonds with ionic liquid anions, synergistically enhancing the nucleophilicity of phenol and accelerating ester bond cleavage. Compared with conventional organic bases, these less common organic bases can achieve high selectivity in small amounts (0.8%-2.5%) in the laboratory and are easily separated from the product.

[0012] In the above technical solution, the inorganic base is selected from one or two of rubidium hydroxide and cesium hydroxide.

[0013] In the above technical solution, the amount of inorganic alkali added is 0.3~1.5% of the mass of bisphenol A polycarbonate.

[0014] This invention selects rubidium hydroxide (RbOH), cesium hydroxide (CsOH), or a composite system thereof. The ionic radii of Rb⁺ and Cs⁺ are larger than those of Na⁺ and K⁺, and their ionic strength is higher. They can efficiently break ester bonds at low dosages (0.3~1.5%) in the laboratory, ensuring complete depolymerization of PC. At the same time, the synergistic effect of ionic liquid and organic base can reduce the amount of inorganic base used, reducing the difficulty of metal residue detection in the laboratory (metal residue ≤0.01 mg / g as detected by ICP-MS).

[0015] In the above technical solution, the ionic liquid is selected from 1-benzyl-3-cyclohexylimidazolium hexafluorophosphate ([BzCyMIM][PF6], R1=benzyl, R3=cyclohexyl, anion=PF6⁻), 1-adamantyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([AdMIM][Tf2N], R1=adamantyl, R3=methyl, anion=Tf2N⁻), and 1-isooctyl-3-ethylimidazolium trifluoromethanesulfonate ([i-OcEMIM)). [CF3SO3], R1=isooctyl, R3=ethyl, anion=CF3SO3⁻), 1-phenylethyl-3-isopropylimidazolium hexafluorophosphate ([PhEMIM][PF6], R1=phenylethyl, R3=isopropyl, anion=PF6⁻) or 1-adamantyl-2-methylimidazolium bis(trifluoromethanesulfonyl)imide ([AdMMIM][Tf2N], R1=adamantyl, R2=R3=methyl, anion=Tf2N⁻).

[0016] In the above technical solution, the amount of ionic liquid added is 1.5 to 4.5% of the mass of bisphenol A polycarbonate.

[0017] This invention selects imidazole ionic liquids with bulky substituents (benzyl, adamantyl, isooctyl). Laboratory-grade reagents must have a moisture content ≤0.1% (to avoid moisture-induced side reactions). The bulky substituents in the cation restrict the hydrolysis pathway of the intermediate DPC through steric hindrance, while the aromatic substituents enhance the interaction with the PC molecular chain through π-π stacking. The anions are selected from hexafluorophosphates and bis(trifluoromethanesulfonyl)imide salts with moderate nucleophilicity, which can synergistically enhance the nucleophilic attack ability of phenol with the organic base, while avoiding side reactions caused by excessive nucleophilicity. Compared with conventional ionic liquids, this type of specially structured ionic liquid can achieve efficient activation at laboratory dosages (1.5%-4.5%) and is easily recovered by vacuum distillation, reducing experimental costs.

[0018] In the above technical solution, the mass ratio of bisphenol A polycarbonate to phenol is 1:7~13, preferably 1:9~11. When the mass ratio of PC to phenol is less than 1:7, PC dissolves insufficiently (dissolution rate ≤85%); when it is greater than 1:13, the energy consumption for phenol recovery increases (energy consumption increases by 15% for every doubling of phenol usage).

[0019] In the above technical solution, the heating rate of the reaction system is 5.5~7 ℃ / min. The reaction temperature is 130-170 ℃, preferably 140-160 ℃, more preferably 145~155 ℃. Below 145 ℃, the nucleophilic activity of PhO⁻ is insufficient (depolymerization rate ≤90%); above 155 ℃, phenol is easily oxidized to benzoquinone (benzoquinone peak area ≥0.5% as detected by HPLC), affecting the purity of bisphenol A. The reaction pressure is 0.4~0.9 MPa, preferably 0.6~0.7 MPa. Below 0.6 MPa, the volatile amount of phenol increases (loss rate ≥8%); above 0.7 MPa, the risk of sealing the reaction vessel increases, safety decreases, and equipment cost increases. The reaction time is 2.5 to 5 hours, preferably 3 to 4 hours. Within this time range, the PC depolymerization reaction is complete (depolymerization rate ≥ 97.5%) and there are few side reactions (byproduct content ≤ 1.2%). In the laboratory, the optimal reaction endpoint can be determined by HPLC detection through timed sampling.

[0020] The composite catalyst system of this invention forms a unique "targeted activation-stereotropic regulation-efficient bond breaking" mechanism through the synergistic effect of special structural components: 1) In the targeted activation stage: the cation of the special structure imidazole ionic liquid activates the PC molecular chain through π-π stacking (characteristic absorption peaks of PC-ionic liquid interaction detected by UV-Vis spectrophotometer in the laboratory) and coordination (chemical shift change of carbonyl oxygen in PC ester bond monitored by ¹H NMR), increasing the electrophilicity of the carbonyl carbon; the anion forms hydrogen bonds with the phenol hydroxyl group (shift of phenol hydroxyl stretching vibration peak monitored by FT-IR), enhancing its nucleophilic attack capability. 2) In the stereotropic regulation stage: the sterically hindered organic base molecule occupies the space sites around the PC ester bond through large-volume substituents (stereotropic effect verified by molecular simulation calculations in the laboratory), shielding the hydrolysis active sites of intermediate DPC and inhibiting side reactions; at the same time, it forms a synergistic effect with the ionic liquid anion, further enhancing the nucleophilicity of phenol (ester bond breaking rate monitored by HPLC). 3) In the efficient bond-breaking stage: The cations (Rb⁺, Cs⁺) of the high-ionic-strength inorganic base form an electrostatic interaction with the oxygen atom of the PC ester bond (detected by X-ray photoelectron spectroscopy (XPS), polarizing the ester bond). Hydroxide ions (OH⁻) then attack the activated carbonyl carbon, achieving efficient ester bond cleavage. In the laboratory, by controlling the amount of inorganic base (0.3%-1.5%), bisphenol A carbonization caused by strong alkalinity can be avoided (product color is detected by a colorimeter; L value ≥ 95, no obvious carbonization phenomenon).

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs a composite catalytic system consisting of a specially substituted imidazole ionic liquid, a sterically hindered tertiary amine / alkanolamine organic base, and a high-ionic-strength alkali metal hydroxide. Through the targeted activation and solvation of the specially structured ionic liquid, the stereoregulation and selectivity enhancement of the organic base, and the efficient bond-breaking effect of the inorganic base, a synergistic "three-in-one" mechanism is formed. The structural characteristics of the rare component compensate for the defects of the traditional component, reduce side reactions, and improve product yield and purity. At the same time, it achieves efficient catalyst recovery and reuse, thus achieving the goal of efficient, targeted, and green degradation of PC under laboratory conditions. Detailed Implementation

[0022] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the test methods in the following embodiments are conventional methods.

[0023] The PC raw materials used in this example are: waste bisphenol A type PC, such as electronic casings and building panels. A single type of PC is selected for pretreatment: impurities such as metal and rubber are removed; the material is crushed and screened through a standard sieve (20 mesh, 0.85 mm aperture) to obtain particles with a diameter of 4-6 mm; it is then ultrasonically cleaned with deionized water (120 W power, 40 kHz frequency) for 12-18 min (to remove oil / dust); dried in a vacuum drying oven at 65-75 ℃ (0.08 MPa vacuum) for 2.5 h; and stored in a desiccator for later use (moisture content ≤0.05%, Karl Fischer method). Phenol, 99.5%, Sinopharm Group; [BzCyMIM][PF6], 98%, Shanghai Chengjie Chemical; N-methyldicyclohexylamine, 99%, Alfa Aesar; RbOH, 98%, Sigma-Aldrich. Product detection was performed using an Agilent 1260 HPLC system. Detection conditions: C18 column, 4.6 mm × 250 mm, 5 μm; mobile phase: methanol:water = 80:20 (v / v); flow rate: 1.0 mL / min; detection wavelength: 275 nm; column temperature: 30 ℃. Data processing and quantification were performed using the external standard method. The PC depolymerization rate was calculated by weighing the undegraded PC.

[0024] Example 1 Take 5 g of pretreated waste PC electronic casing (single material, metal excluded), add 50 g of phenol, along with 0.15 g of [BzCyMIM][PF6], 0.075 g of N-methyldicyclohexylamine, and 0.04 g of RbOH in a nitrogen glove box, transfer to a polytetrafluoroethylene-lined high-pressure reactor, and stir at 400 r / min for 15 min until the PC particles are completely dispersed. Seal the high-pressure reactor, purge the air inside the reactor three times with nitrogen (each purge pressure 0.3 MPa, held for 30 s), raise the temperature to 150 ℃ at 6.2 ℃ / min and adjust the nitrogen pressure to 0.65 MPa, and react at a constant temperature and pressure for 3.5 h with stirring at 400 r / min.

[0025] After the reaction was completed, the temperature was lowered to room temperature at 4 °C / min, and the pressure was slowly released (pressure release rate ≤ 0.05 MPa / min). The reaction solution was transferred to a rotary evaporator, and unreacted phenol (48.15 g, recovery rate 96.3%) was recovered by vacuum distillation at 0.09 MPa and 90 °C. The remaining product was added to 30 mL of deionized water, stirred at 350 r / min for 35 min, transferred to a refrigerator, and crystallized at 2 °C for 3 h. After centrifugation at 3500 r / min for 12 min, crude bisphenol A was obtained. The crude product was recrystallized once with 30 mL of anhydrous ethanol (reflux temperature 78 °C, filtered while hot), and then dried under vacuum at 65 °C and 0.09 MPa for 2.5 h to obtain the finished bisphenol A. The supernatant after centrifugation (containing the composite catalytic component) was transferred to a rotary evaporator and dehydrated at 60 °C and 0.09 MPa for 3 h to obtain the recovered catalyst, which was sealed and placed in a desiccator for later use.

[0026] The test results showed that the PC depolymerization rate was 97.8%, the bisphenol A yield was 94.8%, and the purity was 99.5%.

[0027] Example 2 Take 6 g of pretreated waste PC optical disc substrate (moisture content 0.04%), add 66 g of phenol, 0.21 g of [AdMIM][Tf2N], 0.12 g of 1-adamantaneamine, and 0.06 g of CsOH in a nitrogen glove box, transfer to a polytetrafluoroethylene-lined high-pressure reactor, and stir at 400 r / min for 15 min until the PC particles are completely dispersed. Seal the high-pressure reactor, replace the air in the reactor with nitrogen three times (each replacement pressure 0.3 MPa, pressure held for 30 s), raise the temperature to 152 ℃ at 6.2 ℃ / min and adjust the nitrogen pressure to 0.68 MPa, and react at a constant temperature and pressure for 3.2 h with stirring at 400 r / min.

[0028] After the reaction was complete, the temperature was lowered to room temperature at 4 °C / min, and the pressure was slowly released (pressure release rate ≤ 0.05 MPa / min). The reaction solution was transferred to a rotary evaporator, and unreacted phenol (48.15 g, recovery rate 96.3%) was recovered by vacuum distillation at 0.09 MPa and 90 °C. The remaining product was added to 30 mL of deionized water, stirred at 350 r / min for 35 min, transferred to a refrigerator, and crystallized at 2 °C for 3 h. After centrifugation at 3500 r / min for 12 min, crude bisphenol A was obtained. The crude product was recrystallized once with 30 mL of anhydrous ethanol (reflux temperature 78 °C, filtered while hot), and then dried under vacuum at 65 °C and 0.09 MPa for 2.5 h to obtain the finished bisphenol A. The supernatant (containing catalyst components) after centrifugation was transferred to a rotary evaporator and dehydrated at 60 °C and 0.09 MPa for 3 h to obtain the recovered catalyst, which was sealed and placed in a desiccator for later use.

[0029] The test results showed that the PC depolymerization rate was 98.1%, the bisphenol A yield was 95.2%, and the purity was 99.4%, which verified the compatibility of the catalyst components.

[0030] Example 3 Take 4 g of pretreated waste PC building material (moisture content 0.03%), add 36 g of phenol, 0.112 g of [i-OcEMIM][CF3SO3], 0.048 g of N-ethyl-N-phenylethanolamine, and 0.0280 g of RbOH-CsOH composite system (RbOH:CsOH=1.5:1) in a nitrogen glove box, transfer to a polytetrafluoroethylene-lined high-pressure reactor, and stir at 400 r / min for 15 min until the PC particles are completely dispersed. Seal the high-pressure reactor, replace the air in the reactor with nitrogen three times (each replacement pressure 0.3 MPa, pressure held for 30 s), raise the temperature to 148℃ at 6.2 ℃ / min and adjust the nitrogen pressure to 0.62 MPa, and react at a constant temperature and pressure for 3.8 h with stirring at 400 r / min.

[0031] After the reaction was complete, the temperature was lowered to room temperature at 4 °C / min, and the pressure was slowly released (pressure release rate ≤ 0.05 MPa / min). The reaction solution was transferred to a rotary evaporator, and unreacted phenol (48.15 g, recovery rate 96.3%) was recovered by vacuum distillation at 0.09 MPa and 90 °C. The remaining product was added to 30 mL of deionized water, stirred at 350 r / min for 35 min, transferred to a refrigerator, and crystallized at 2 °C for 3 h. After centrifugation at 3500 r / min for 12 min, crude bisphenol A was obtained. The crude product was recrystallized once with 30 mL of anhydrous ethanol (reflux temperature 78 °C, filtered while hot), and then dried under vacuum at 65 °C and 0.09 MPa for 2.5 h to obtain the finished bisphenol A. The supernatant (containing catalyst components) after centrifugation was transferred to a rotary evaporator and dehydrated at 60 °C and 0.09 MPa for 3 h to obtain the recovered catalyst, which was sealed and placed in a desiccator for later use.

[0032] The test results showed that the PC depolymerization rate was 97.6%, the bisphenol A yield was 94.5%, the purity was 99.3%, and the by-product content of the composite inorganic alkali system (0.8%) was lower than that of the single inorganic alkali system (1.2%), which verified the synergistic advantage.

[0033] Example 4 The composite catalytic component recovered in Example 1 was reused 5 times, with the same experimental parameters as in Example 1 each time. After each cycle, the catalyst structure was characterized by FT-IR (characteristic peaks showed no significant shift), and the residual Rb⁺ content was detected by ICP-MS to be ≤0.008 mg / g.

[0034] The test results showed that after 5 cycles, the PC depolymerization rate was 95.2%±0.5%, the bisphenol A yield was 92.1%±0.6%, the purity was 98.9%±0.3%, and the catalyst loss rate was 2.8%, which verified its cycle stability.

[0035] Comparative Example 1 This comparative example is basically the same as Example 1, except that N-methyldicyclohexylamine is replaced with triethylamine and RbOH is replaced with NaOH.

[0036] The test results showed that the PC depolymerization rate was 88.0%, the bisphenol A yield was 86.0%, and the purity was 97.2%, proving that the specially substituted ionic liquid selected in this invention needs to be combined with an inorganic base with high ionic strength and an organic base with steric hindrance to exhibit a high depolymerization efficiency.

[0037] Comparative Example 2 This comparative example is basically the same as Example 1, except that only 0.1500 g of [BzCyMIM][PF6] is added.

[0038] The test results showed that the PC depolymerization rate was 78.0%, the bisphenol A yield was 75.0%, and the purity was 89.0%, proving that a single ionic liquid cannot achieve efficient depolymerization and requires synergistic action with organic and inorganic bases.

[0039] Comparative Example 3 This comparative example is basically the same as Example 1, except that N-methyldicyclohexylamine is removed.

[0040] The test results showed that the PC depolymerization rate was 90.6%, the bisphenol A yield was 88.2%, and the purity was 96.8%, proving that the depolymerization efficiency of the binary composite catalytic system of ionic liquid + inorganic base was lower than that of the ternary composite catalytic system of ionic liquid + inorganic base + organic base of this invention.

[0041] Comparative Example 4 This comparative example is basically the same as Example 1, except that RbOH is removed.

[0042] The test results showed that the PC depolymerization rate was 85.3%, the bisphenol A yield was 83.1%, and the purity was 95.5%, proving that the depolymerization efficiency of the binary composite catalytic system of ionic liquid + organic is lower than that of the ternary composite catalytic system of ionic liquid + inorganic base + organic base of this invention.

[0043] Comparative Example 5 This comparative example is basically the same as Example 1, except that phenol is replaced with methanol.

[0044] The test results showed that the PC depolymerization rate was 82.4%, the bisphenol A yield was 79.7%, and the purity was 94.1%, proving that the depolymerization efficiency of the ternary composite catalytic system of ionic liquid + inorganic base + organic base in the present invention is higher than that of conventional alcoholysis in methanol solvent.

[0045] Comparative Example 6 This comparative example is basically the same as Example 1, except that [BzCyMIM][PF6] is replaced with 1-ethyl-3-methylimidazolium acetate ([EMIM]Ac).

[0046] The test results showed that the PC depolymerization rate was 86.7%, the bisphenol A yield was 84.3%, and the purity was 96.4%, proving that the depolymerization efficiency of the ternary composite catalytic system composed of conventional ionic liquid + organic base + inorganic base would be reduced.

[0047] The embodiments described above are merely preferred embodiments of the present invention and are only used to explain the present invention. They are not intended to limit the scope of the present invention. For those skilled in the art, other implementation methods can be easily made by substitution or modification based on the technical content disclosed in this specification. Therefore, all changes and improvements made on the principle of the present invention should be included within the scope of the patent application of the present invention.

Claims

1. A method for recovering polycarbonate based on a composite catalytic system, characterized in that, Includes the following steps: A reaction system comprising bisphenol A type polycarbonate, phenol, organic base, inorganic base and ionic liquid was constructed. The reaction system was subjected to isothermal and isobaric reaction at 130-170 °C and 0.4-0.9 MPa for 2.5-5 h under nitrogen atmosphere to obtain bisphenol A. The structural formula of the ionic liquid is as follows: Where R1 is selected from C 8~12 Branched alkyl groups, C 6~10 Aromatic alkyl or adamantyl alkyl; R2 and R3 are selected from C 1~6 alkyl or cyclohexyl; R4 is selected from hydrogen or C 1~3 The alkyl group; A is selected from any one of hexafluorophosphate anion, bis(trifluoromethanesulfonylimide) anion, and trifluoromethanesulfonate anion; The organic base is a sterically hindered tertiary amine or alcohol amine compound; the inorganic base is a high ionic strength alkali metal hydroxide.

2. The polycarbonate recycling method according to claim 1, characterized in that, The organic base is selected from one or more of N-methyldicyclohexylamine, 1-adamantaneamine, N-ethyl-N-phenylethanolamine, N-cyclohexyl-N-benzylmethylamine, or 2,2,6,6-tetramethylpiperidinamine.

3. The polycarbonate recycling method according to claim 1, characterized in that, The amount of organic base added is 0.8 to 2.5% of the mass of bisphenol A polycarbonate.

4. The polycarbonate recycling method according to claim 1, characterized in that, The inorganic base is selected from one or both of rubidium hydroxide and cesium hydroxide.

5. The polycarbonate recycling method according to claim 1, characterized in that, The amount of inorganic alkali added is 0.3~1.5% of the mass of bisphenol A polycarbonate.

6. The polycarbonate recycling method according to claim 1, characterized in that, The ionic liquid is selected from any one of 1-benzyl-3-cyclohexylimidazolium hexafluorophosphate, 1-adamantyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-isooctyl-3-ethylimidazolium trifluoromethanesulfonate, 1-phenylethyl-3-isopropylimidazolium hexafluorophosphate, or 1-adamantyl-2-methylimidazolium bis(trifluoromethanesulfonyl)imide.

7. The polycarbonate recycling method according to claim 1, characterized in that, The amount of the ionic liquid added is 1.5 to 4.5% of the mass of bisphenol A polycarbonate.

8. The polycarbonate recycling method according to claim 1, characterized in that, The mass ratio of bisphenol A polycarbonate to phenol is 1:7~13.

9. The polycarbonate recycling method according to claim 1, characterized in that, The heating rate of the reaction system is 5.5~7 °C / min.