A method for preparing bisphenol A dimethyl ether by one-step PC plastic polymerization

Abstract

The invention discloses a method for preparing bisphenol A dimethyl ether by one-step PC plastic polymerization, which involves comprehensive utilization of waste resources and cascade utilization of raw materials. The products of the method of the invention are bisphenol A dimethyl ether and dimethyl carbonate. Taking PC as an example, the method uses dimethyl carbonate as a methyl source, and multiple types of green ionic liquid catalysts catalyze the depolymerization of PC to achieve one-step preparation of bisphenol A dimethyl ether. The invention can be used for the depolymerization and upgrading of waste PC materials, and is also suitable for the methylation reaction of various compounds containing hydroxyl and amino functional groups, and the products are corresponding ethers, amines, bisphenol A dimethyl ether and other compounds.

Description

Technical Field

[0001] The present invention relates to a method for producing bisphenol A dimethyl ether by depolymerization and upgrading of PC with high selectivity, and relates to comprehensive utilization of waste resources and cascade utilization of raw materials. More specifically, the present invention relates to a direct methylation reaction of PC with the participation of dimethyl carbonate, and obtains bisphenol A dimethyl ether with high yield. Background Art

[0002] Polycarbonate (PC) is an important engineering plastic with excellent properties such as impact resistance, high temperature resistance and chemical resistance. It is widely used in electronic product housings, automotive parts, optical devices, medical devices, building materials and packaging materials. Due to the high hardness of PC plastics and the presence of different types of additives, the difficulty of recycling and reuse increases. Therefore, PC plastics are currently mainly recycled by physical methods. Waste PC plastics are collected, sorted, crushed, cleaned, melted and reprocessed to make new plastic products, but this method has high requirements on the mechanical strength of the equipment, the melting step requires high heating temperature and energy consumption, and the quality and performance of the recycled PC plastics are reduced. Therefore, there is an urgent need for more efficient and gentle technologies and methods to improve the recycling and treatment methods of PC plastics and achieve more efficient and sustainable high-value reuse of waste PC plastics.

[0003] At present, the chemical upgrading and recycling pathways of PC waste plastics mainly include pyrolysis, hydrocracking, liquefaction, alcoholysis, aminolysis, hydrolysis and glycolysis. Among them, pyrolysis, hydrocracking and liquefaction mainly decompose polymers into low molecular weight compounds through high temperature and high pressure, which can realize the conversion of waste PC plastics into liquid fuels or other aromatic compounds. However, the above strategies have poor reaction selectivity due to harsh reaction conditions, wide product distribution, and cannot achieve closed-loop recycling of PC plastics. PC solvent hydrolysis is a greener and milder approach, which uses nucleophilic reagents such as methanol, ethylene glycol, and water to attack carbonate bonds (-OC(=O)-O-) bonds to break CO bonds and obtain monomer bisphenol A (BPA) and other high value-added chemicals. BPA is the most important functional monomer after the depolymerization of PC waste, and it also plays an important role in the recycling of polymers. It can not only control the distribution of PC molecular structure and molecular weight, but also significantly improve the strength and wear resistance of PC. However, studies have shown that BPA may interfere with the endocrine system and pose potential risks to health. It has been included in the list of substances of high concern by the European Union in 2022. Although some industries have taken a series of measures to limit or replace the use of BPA in food packaging, baby products and other related fields, the production rate of PC is still increasing year by year, and the current PC production capacity has reached 6 million tons / year. Therefore, the development of PC waste directional conversion into low-toxic, structurally similar BPA substitutes has become a technical bottleneck that urgently needs to be broken through in the current waste PC treatment and closed-loop recycling field.

[0004] Bisphenol A dimethyl ether (BPAME) is a class of chemicals with similar structures to BPA. In addition to the function of BPA as a plastic monomer for the preparation of polymers such as polycarbonate and epoxy resin, BPAME can also be used in the preparation of semiconductor materials and pesticides and cancer research. In addition, studies have shown that BPAME's inhibitory effect on certain human enzymes is weaker than BPA, such as H3β-HSD2, which is mainly present in the renal tubular epithelial cells in the kidneys and plays an important role in renal metabolism. Currently, BPAME is mainly prepared by the methylation reaction of BPA with highly toxic methylating agents (dimethyl sulfate or methyl iodide), and the BPAME yield is usually less than 90%. Therefore, the development of an efficient and green synthesis pathway for BPAME is an industry problem that needs to be solved urgently.

[0005] Ionic liquids (IL), also known as low-temperature molten salts and room-temperature ionic liquids, refer to salts composed of weakly coordinated organic cations and inorganic / organic anions with a melting point generally below 100°C. ILs have the advantages of large electrochemical window, good solubility, good thermal stability, recyclability, designability of structure and properties, and controllability of functions, making them not only excellent solvents for many chemical reactions, but also catalysts for reactions. At present, the research on the use of ionic liquids to catalyze the depolymerization of PC mainly includes alcoholysis and hydrolysis, but there are generally problems such as large amount of ionic liquids, high reaction temperature and low product selectivity.

[0006] DMC is a relatively environmentally friendly methylation reagent with low toxicity and low volatility. It has little impact on the human body and the environment during use. It has been widely used in methylation reactions of functional groups such as hydroxyl, amino and carboxyl. Summary of the invention

[0007] The present invention aims at the needs of PC waste plastic depolymerization and product directional upgrading, as well as the shortcomings of the prior art, and provides a carbonate or carboxylate mediated method for depolymerization and upgrading of polycarbonate to bisphenol A dimethyl ether. Taking PC as a typical representative, the method uses green ionic liquid to catalyze the transesterification reaction of PC and DMC. In the reaction, DMC is used as a methyl source, and the conversion of PC to bisphenol A dimethyl ether can be achieved in one pot.

[0008] The specific technical solutions adopted by the present invention are as follows:

[0009]

[0010] In a first aspect, the present invention provides a method for preparing bisphenol A dimethyl ether by one-step PC plastic polymerization, which comprises:

[0011] S1, placing the raw material to be converted, the alkylation agent, the ionic liquid catalyst and the reaction solvent in a reaction kettle to form a reaction system;

[0012] The raw material to be converted is crushed polycarbonate (PC) material;

[0013] The alkylating agent is dimethyl carbonate or dimethyl pyrocarbonate;

[0014] The ionic liquid catalyst is an imidazole-type ionic liquid [Emim][Br] or [Bmim][Br], and the structural formula is as follows:

[0015]

[0016] The reaction solvent is one of N-methylpyrrolidone, N,N-dimethylformamide, γ-valerolactone, acetonitrile, toluene, 2-methyltetrahydrofuran and 1,4-dioxane;

[0017] S2, placing the reactor containing the reaction system at a depolymerization temperature of 140-160° C. to carry out a depolymerization reaction for 4-8 hours, and cooling the temperature to room temperature after the reaction is completed to obtain depolymerization products of bisphenol A dimethyl ether and dimethyl carbonate.

[0018] In a second aspect, the present invention provides a one-step method for preparing an ether compound, comprising:

[0019] S1, placing the raw material to be converted, the alkylation agent, the ionic liquid catalyst and the reaction solvent in a reaction kettle to form a reaction system;

[0020] The raw material to be converted comprises phenolic compounds, and the phenolic compounds include p-methylphenol, 4-isopropylphenol, 4-bromophenol, 4-nitrophenol or guaiacol;

[0021] The alkylating agent is dimethyl carbonate or dimethyl pyrocarbonate;

[0022] The ionic liquid catalyst is an imidazole-type ionic liquid [Emim][Br] or [Bmim][Br], and the structural formula is as follows:

[0023]

[0024] The reaction solvent is one of N-methylpyrrolidone, N,N-dimethylformamide, γ-valerolactone, acetonitrile, toluene, 2-methyltetrahydrofuran and 1,4-dioxane;

[0025] S2, placing the reactor containing the reaction system at a depolymerization temperature of 140-160° C. for 4-8 hours of depolymerization reaction, cooling to room temperature after the reaction is completed, and obtaining a depolymerization product which is the ether corresponding to the raw material to be converted.

[0026] In a third aspect, the present invention provides a one-step method for preparing an N-methylated compound, comprising:

[0027] S1, placing the raw material to be converted, the alkylation agent, the ionic liquid catalyst and the reaction solvent in a reaction kettle to form a reaction system;

[0028] The raw material to be converted comprises an amine compound or indole, and the amine compound comprises p-aniline, p-methylaniline, 4-isopropylaniline, 3-vinylaniline or 1-naphthylamine;

[0029] The alkylating agent is dimethyl carbonate or dimethyl pyrocarbonate;

[0030] The ionic liquid catalyst is an imidazole-type ionic liquid [Emim][Br] or [Bmim][Br], and the structural formula is as follows:

[0031]

[0032] The reaction solvent is one of N-methylpyrrolidone, N,N-dimethylformamide, γ-valerolactone, acetonitrile, toluene, 2-methyltetrahydrofuran and 1,4-dioxane;

[0033] S2, placing the reactor containing the reaction system at a depolymerization temperature of 140-160° C. for 4-8 hours of depolymerization reaction, cooling to room temperature after the reaction is completed, and obtaining a depolymerization product which is an N-methylated compound corresponding to the raw material to be converted.

[0034] As a preferred embodiment of the first, second and third aspects above, in the reaction system, the amount of the alkylating agent added is 4 to 6 times the amount of the raw material to be converted, calculated on a molar basis.

[0035] As a preferred embodiment of the first, second and third aspects above, in the reaction system, the amount of the ionic liquid catalyst added is 3 to 5 mol% of the raw material to be converted.

[0036] As a preferred embodiment of the first, second and third aspects above, in the reaction system, the reaction solvent is added in an amount of 1 to 5 mL / mmol of the raw material to be converted.

[0037] As a preferred embodiment of the first aspect, the polycarbonate material is waste of polycarbonate material.

[0038] As a preferred embodiment of the first aspect, the waste is in the form of discarded optical discs, barrels or films made of polycarbonate.

[0039] As a preferred embodiment of the first aspect, the waste needs to be pre-crushed into centimeter-sized flakes, particles or powders before being added into the reactor.

[0040] As a preference of the first aspect above, the alkylating agent is preferably dimethyl carbonate, and the reaction solvent is preferably N-methylpyrrolidone.

[0041] Preferably, the ionic liquid catalyst is [Emim][Br].

[0042] Preferably, the depolymerization temperature is 150°C.

[0043] Preferably, the depolymerization time is 6 hours.

[0044] Compared with the prior art, some embodiments of the present invention have the following beneficial effects:

[0045] (1) The ionic liquid catalyst used in the present invention has the advantages of high efficiency and greenness, and can promote the PC methylation reaction involving DMC and prepare high-purity bisphenol A dimethyl ether.

[0046] (2) The waste plastic PC methylation depolymerization strategy developed by the present invention has the advantages of mild conditions and high catalytic efficiency, and can achieve complete PC conversion under standard reaction conditions. This strategy has a wide range of applications, and the types of waste PC raw materials are varied. Various types of PC material waste, such as various types of PC waste CDs, PC waste buckets, and PC waste films, can all be efficiently upgraded and converted in a short period of time.

[0047] (3) The PET waste plastic matrix material of the present invention can also be replaced by various aromatic compounds containing hydroxyl and amino functional groups, and the products are high-value chemicals such as corresponding ethers and amines, which to a certain extent shows the high applicability of this strategy and further broadens the scope of waste plastic treatment and product appreciation. DETAILED DESCRIPTION

[0048] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, a detailed description is given below through specific embodiments. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below. The technical features in each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0049] The present invention provides a method for directional preparation of bisphenol A dimethyl ether by one-step plastic polymerization of polycarbonate (PC), which uses a green ionic liquid catalyst to catalyze the PC methylation reaction involving DMC to achieve directional preparation of PC to bisphenol A dimethyl ether. Dimethyl carbonate (DMC) is used as both a depolymerization agent and a methylation agent, and a high-value conversion of waste PC plastic to bisphenol A dimethyl ether (BPAME) is achieved through a "one-pot two-step method" under relatively mild conditions. The specific steps of the method for directional preparation of bisphenol A dimethyl ether by one-step plastic polymerization of polycarbonate (PC) are as follows:

[0050] S1, placing the raw material to be converted, i.e., crushed polycarbonate (PC) material, an alkylating agent, an ionic liquid catalyst and a reaction solvent in a reaction kettle to form a reaction system;

[0051] S2, placing the reactor containing the reaction system at a depolymerization temperature of 140-160° C. for 4-8 hours of depolymerization reaction, cooling to room temperature after the reaction is completed, and obtaining depolymerization products of bisphenol A dimethyl ether and dimethyl carbonate. Among the depolymerization products, bisphenol A dimethyl ether is the main target product of the present invention.

[0052] In the subsequent examples, the raw materials in the above reaction system are as follows: the polycarbonate material is the waste of crushed polycarbonate material; the alkylating agent is dimethyl carbonate and dimethyl pyrocarbonate; the reaction solvent is any one or more of N-methylpyrrolidone, N,N-dimethylformamide, γ-valerolactone, acetonitrile, toluene, 2-methyltetrahydrofuran and 1,4-dioxane; the ionic liquid catalyst is imidazole-type ionic liquid [Emim][Br], [Bmim][Br], and the structural formulas of the two and the structural formulas of other ionic liquids [Emim][Cl], [Emim][MeSO3], [EMIm][BF4], [Emim][OAc] used as comparison in the subsequent examples are as follows:

[0053]

[0054] In addition, if the polycarbonate material is PC, pure PC or PC waste can be used. If waste is used as raw material, the waste can be in the form of PC waste CDs, PC waste buckets and PC waste films, but the waste must be pre-crushed into centimeter-level flakes, particles or powders before adding to the reactor.

[0055] In the subsequent examples, the dosage ratio of each raw material in the above reaction system is as follows: in terms of molar amount, the amount of the alkylating agent added is 4 to 6 times the raw material to be converted; the amount of the ionic liquid catalyst added is 3 to 5 mol% of the raw material to be converted; the amount of the reaction solvent added is 1 to 5 mL / mmol of the raw material to be converted.

[0056] Of course, based on the same inventive concept, in addition to the crushed polycarbonate (PC) materials, the raw materials to be converted in the aforementioned steps S1 to S2 of the present invention can also be replaced by aromatic compounds containing hydroxyl and amino functional groups, such as phenolic compounds, amine compounds and indoles.

[0057] Therefore, in other embodiments, the present invention also provides a method for preparing ether compounds in a one-step process, which is basically the same as the method for preparing bisphenol A dimethyl ether in a one-step process by polycarbonate (PC) plastic polymerization shown in S1 to S2 above, with the only difference being that the raw material to be converted is replaced by a phenolic compound, such as p-methylphenol, 4-isopropylphenol, 4-bromophenol, 4-nitrophenol or guaiacol, and the corresponding depolymerization product is an ether compound corresponding to the raw material to be converted.

[0058] Therefore, in other embodiments, the present invention also provides a method for preparing N-methylated compounds in a one-step process, which is basically the same as the method for preparing bisphenol A dimethyl ether in a one-step process by polycarbonate (PC) plasticization shown in S1 to S2 above, with the only difference being that the raw material to be converted is replaced by an amine compound (such as aniline, p-methylaniline, 4-isopropylaniline, 3-vinylaniline or 1-naphthylamine) or indole, so that the corresponding depolymerization product is a methylated compound corresponding to the raw material to be converted.

[0059] The following examples are used to demonstrate the reaction results under different raw materials and parameters.

[0060] Example 1

[0061] In an autoclave reactor equipped with an electromagnetic stirrer, a thermocouple, and a programmable temperature controller, 0.254 g of CR-pure PC powder (1 mmol), 0.36 g of dimethyl carbonate (4 mmol), [Emim][Br] (5 mol%, the molar percentage is calculated based on the molar amount of PC powder) and N-methylpyrrolidone (2 mL) were added. After the autoclave reactor was placed, stirring and heating were turned on. The reaction system was heated to 150°C and reacted at this temperature for 6 hours. After the reaction was completed, the temperature was lowered to room temperature, and the resulting mixed solution was the product. The resulting mixed solution was diluted with dichloromethane, and the diluent was measured for yield by GC. The results showed that the PC decomposition rate of this embodiment was 100%, and the yield of bisphenol A dimethyl ether was 99%.

[0062] Example 2

[0063] 0.254 g of CR-pure PC powder (1 mmol), 0.36 g of dimethyl carbonate (4 mmol), [Bmim][Br] (20 mol%, the molar percentage is calculated based on the molar amount of PC powder) and N-methylpyrrolidone (2 mL) were added to an autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a programmable temperature controller. After placing the autoclave reactor, stirring and heating were turned on. The reaction system was heated to 150°C and reacted at this temperature for 6 hours. After the reaction was completed, the temperature was lowered to room temperature, and the resulting mixed solution was the product. The resulting mixed solution was diluted with dichloromethane, and the diluent was measured for yield by GC. The results showed that the PC decomposition rate of this embodiment was 100%, and the yield of bisphenol A dimethyl ether was 99%.

[0064] Example 3

[0065] 0.254 g of CR-pure PC powder (1 mmol), 0.36 g of dimethyl carbonate (4 mmol), [Bmim][Cl] (20 mol%, the molar percentage is calculated based on the molar amount of PC powder) and N-methylpyrrolidone (2 mL) were added to an autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a programmable temperature controller. After placing the autoclave reactor, stirring and heating were turned on. The reaction system was heated to 150°C and reacted at this temperature for 6 hours. After the reaction was completed, the temperature was lowered to room temperature, and the resulting mixed solution was the product. The resulting mixed solution was diluted with dichloromethane, and the diluent was measured for yield by GC. The results showed that the PC decomposition rate of this embodiment was 100%, and the yield of bisphenol A dimethyl ether was 42%.

[0066] Example 4

[0067] In an autoclave reactor equipped with an electromagnetic stirrer, a thermocouple, and a programmable temperature controller, 0.254 g of CR-pure PC powder (1 mmol), 0.36 g of dimethyl carbonate (4 mmol), ionic liquids ([Emim][OAc], [Mmim][Cl], [Emim][MeSO3], and [EMIm][BF4]) (5 mol%, the molar percentage is calculated based on the molar amount of PC powder) and N-methylpyrrolidone (2 mL) were added. After the autoclave reactor was placed, stirring and heating were turned on. The reaction system was heated to 150°C and reacted at this temperature for 6 hours. After the reaction was completed, the temperature was lowered to room temperature, and the resulting mixed solution was the product. The obtained mixed solution was diluted with dichloromethane, and the yield of the diluted solution was determined by GC. The results showed that when the ionic liquids in this embodiment were [Emim][OAc], [Mmim][Cl], [Emim][MeSO3] and [EMIm][BF4], the corresponding PC decomposition rates were all 100%, and the corresponding yields of bisphenol A dimethyl ether were 21%, 42%, 3% and 19%, respectively.

[0068] Example 5

[0069] In an autoclave reactor equipped with an electromagnetic stirrer, a thermocouple, and a programmable temperature controller, 0.254 g of CR-pure PC powder (1 mmol), 0.36 g of dimethyl carbonate (4 mmol), [Emim][Br] (5 mol%, the molar percentage is calculated based on the molar amount of PC powder) and solvent (N,N-dimethylformamide, γ-valerolactone, acetonitrile, toluene, 2-methyltetrahydrofuran and 1,4-dioxane) (2 mL) were added. After the autoclave reactor was placed, stirring and heating were turned on. The reaction system was heated to 140°C and reacted at this temperature for 6 hours. After the reaction was completed, the temperature was lowered to room temperature, and the resulting mixed solution was the product. The obtained mixed solution was diluted with dichloromethane, and the yield of the diluted solution was determined by GC. The results showed that when the solvent in this embodiment was N,N-dimethylformamide, γ-valerolactone, acetonitrile, toluene, 2-methyltetrahydrofuran and 1,4-dioxane, the corresponding PC decomposition rate was 100%, and the corresponding yield of bisphenol A dimethyl ether was 98%, 77%, 70%, 23%, 22% and 11%, respectively.

[0070] Example 6

[0071] The discarded PC plastic (three forms, namely, plastic barrel, film and optical disc) was crushed into centimeters in advance, and then 0.254 grams of PC plastic centimeters crushed material (1mmol), 0.36 grams of dimethyl carbonate (4mmol), [Emim][Br] (5mol%, the molar percentage is calculated based on the molar amount of PET material) and N-methylpyrrolidone (2mL) were added into an autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a programmable temperature controller. After the autoclave reactor was placed, stirring and heating were turned on. The reaction system was heated to 140°C and reacted at this temperature for 6h. After the reaction was completed, the temperature was lowered to room temperature, and the resulting mixed solution was the product. The diluent was measured for yield by GC, and the results showed that in this embodiment, the PC decomposition rate corresponding to the materials of the plastic barrel, film and optical disc was 100%, and the yields of bisphenol A dimethyl ether corresponding to each of them were 98%, 97% and 99%, respectively.

[0072] Example 7

[0073] 0.254 g PC (1 mmol) powder, alkylating agent (dimethyl pyrocarbonate) (4 mmol), [Emim] [Br] (5 mol%, the molar percentage is calculated based on the molar amount of PC powder) and N-methylpyrrolidone (2 mL) were added to an autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a programmable temperature controller. After placing the autoclave reactor, stirring and heating were turned on. The reaction system was heated to 140°C and reacted at this temperature for 6 hours. After the reaction was completed, the temperature was lowered to room temperature, and the resulting mixed solution was the product. The diluent was measured for yield by GC, and the results showed that the PC decomposition rate of this embodiment was 100%, and the yield of bisphenol A dimethyl ether was 96%.

[0074] Example 8

[0075] Aromatic phenol compounds (phenol, p-methylphenol, 4-isopropylphenol, 4-bromophenol, 4-nitrophenol and guaiacol) (1 mmol), 0.36 g of dimethyl carbonate (4 mmol), [Emim][Br] (5 mol%, the molar percentage is calculated based on the molar amount of aromatic phenol compounds) and N-methylpyrrolidone (2 mL) were added to an autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a programmable temperature controller. After placing the autoclave reactor, stirring and heating were turned on. The reaction system was heated to 150°C and reacted at this temperature for 6 hours. After the reaction was completed, the temperature was lowered to room temperature, and the resulting mixed solution was the product. The resulting mixed solution was passed through 1 The yield was determined by H NMR with mesitylene as the internal standard. The results showed that the products corresponding to the six aromatic phenol compounds of this example, phenol, p-methylphenol, 4-isopropylphenol, 4-bromophenol, 4-nitrophenol and guaiacol, were the corresponding ethers, namely anisole, p-methylanisole, 4-isopropylanisole, 4-bromoanisole, 4-nitrobenzene and 1,2-dimethoxybenzene, and the corresponding reaction conversion rates were all 100%, and the corresponding ether yields were 99%, 98%, 96%, 86%, 78% and 96%, respectively.

[0076] Example 9

[0077] Add aromatic amines (aniline, p-methylaniline, 4-isopropylaniline, 3-vinylaniline and 1-naphthylamine) or indole (1mmol), 0.36g of dimethyl carbonate (4mmol), [Emim][Br] (5mol%, the molar percentage is calculated based on the molar amount of aromatic amine) and N-methylpyrrolidone (2mL) into an autoclave reactor equipped with an electromagnetic stirrer, a thermocouple and a programmable temperature controller. After placing the autoclave reactor, start stirring and heating. The reaction system is heated to 180°C and reacted at this temperature for 6h. After the reaction is completed, cool to room temperature and the resulting mixed solution is the product. The resulting mixed solution is passed through 1The yield was determined by H NMR with mesitylene as the internal standard. The results showed that the products corresponding to the five aromatic amine compounds aniline, p-methylaniline, 4-isopropylaniline, 3-vinylaniline and 1-naphthylamine and indole in this example were the corresponding N-methylated compounds, namely N,N-dimethylaniline, N,N-dimethyl-p-toluidine, 4-isopropyl-N,N-dimethylaniline, N,N-dimethyl-3-vinylaniline, N,N-dimethylnaphthalene-1-amine and methylindole, and the corresponding reaction conversion rates were all 100%, and the corresponding N-methylated compound yields were 97%, 87%, 90%, 58%, 90% and 94%, respectively.

[0078] Example 10

[0079] In an autoclave reactor equipped with an electromagnetic stirrer, a thermocouple, and a programmable temperature controller, 0.192 g of CR-pure PC powder (1 mmol), a methylating agent (dimethyl pyrocarbonate) (4 mmol), [Emim][Br] (5 mol%, the molar percentage is calculated based on the molar amount of PC powder) and N-methylpyrrolidone (4 mL) were added. After the autoclave reactor was placed, stirring and heating were turned on. The reaction system was heated to 140°C and reacted at this temperature for 6 hours. After the reaction was completed, the temperature was cooled to room temperature, and the resulting mixed solution was the product. The resulting mixed solution was diluted with dichloromethane, and the diluent was measured for yield by GC, with n-dodecane as the internal standard. The results showed that the yield of bisphenol A dimethyl ether was 99%.

[0080] The above Examples 1 to 4 show that not all ionic liquids can be used to catalyze the above depolymerization reaction. Compared with other ionic liquid catalysts, the two ionic liquid catalysts [Emim][Br] and [Bmim][Br] have extremely high catalytic performance in catalyzing the depolymerization of polycarbonate materials to bisphenol A dimethyl ether.

[0081] The above-described embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A method for preparing bisphenol A dimethyl ether by one-step PC plastic polymerization, characterized in that: include: S1, placing the raw material to be converted, the alkylation agent, the ionic liquid catalyst and the reaction solvent in a reaction kettle to form a reaction system; The raw material to be converted is crushed polycarbonate material; The alkylating agent is dimethyl carbonate or dimethyl pyrocarbonate; The ionic liquid catalyst is an imidazole-type ionic liquid [Emim][Br] or [Bmim][Br], and the structural formula is as follows: The reaction solvent is one of N-methylpyrrolidone, N,N-dimethylformamide, γ-valerolactone and acetonitrile; S2, placing the reactor containing the reaction system at a depolymerization temperature of 140-160° C. to carry out a depolymerization reaction for 4-8 hours, and cooling the temperature to room temperature after the reaction is completed to obtain depolymerization products of bisphenol A dimethyl ether and dimethyl carbonate.

2. The method according to claim 1, characterized in that In the reaction system, the amount of the alkylating agent added is 4 to 6 times the amount of the raw material to be converted in terms of molar amount.

3. The method according to claim 1, characterized in that In the reaction system, the added amount of the ionic liquid catalyst is 3-5 mol% of the raw material to be converted.

4. The method according to claim 1, characterized in that In the reaction system, the reaction solvent is added in an amount of 1 to 5 mL / mmol of the raw material to be converted.

5. The method according to claim 1, characterized in that The polycarbonate material is waste of polycarbonate material.

6. The method according to claim 5, characterized in that The waste is in the form of discarded optical discs, barrels or films made of polycarbonate.

7. The method according to claim 6, characterized in that The waste must be crushed into centimeter-sized flakes, particles or powders before being added to the reactor.

8. The method according to claim 1, characterized in that The alkylating agent is dimethyl carbonate, and the reaction solvent is N-methylpyrrolidone.

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