A method for preparing bisphenol A dialkyl ether from waste PC using phosphate ester

Abstract

The invention discloses a method for preparing bisphenol A dialkyl ether from waste PC using phosphate ester, belonging to the technical field of solid waste recycling. The method comprises: placing crushed waste PC, phosphate ester as an alkylating agent, an alkaline catalyst and a solvent in a reaction kettle to form a reaction system; placing the reaction system at a temperature of 60 to 160° C. under air conditions to carry out a depolymerization reaction for 5 minutes or longer; and cooling the reaction system to room temperature after the reaction is completed to obtain the product bisphenol A dialkyl ether; the phosphate ester as the alkylating agent is selected from trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, triallyl phosphate, ethyl dimethylphosphonate, tetramethylmethylenebis(phosphonate) or benzyl dimethylphosphonate. The method has milder reaction conditions and faster reaction speed, and can prepare a variety of products including bisphenol A dimethyl ether, bisphenol A diethyl ether, bisphenol A dipropyl ether, bisphenol A dibutyl ether and bisphenol A diallyl ether.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste recycling and utilization, and particularly relates to a method for preparing bisphenol A dialkyl ether from waste PC with the participation of phosphate ester. Background Art

[0002] Polycarbonate (PC) is an engineering plastic with excellent chemical resistance, widely used in electronic product housings, automotive components, optical devices, medical equipment, and building materials. Currently, waste PC is primarily processed through mechanical recycling, but as the number of recycling cycles increases, product quality and performance gradually decline, resulting in this method becoming a downgraded recycling process. In contrast, chemical upcycling of waste PC can convert it into high-value-added chemical monomers, offering greater economic benefits. Existing methods include pyrolysis, hydrocracking, liquefaction, alcoholysis, aminolysis, hydrolysis, and glycolysis.

[0003] Chinese patent publication CN118164826A discloses a method for recovering bisphenol A from waste PC. The method comprises the following steps: 1) crushing the waste PC and dissolving it in a solvent; adding a bimetallic-modified solid base catalyst and a C1-C4 alcohol; and conducting an alcoholysis reaction under an inert atmosphere to generate a reaction solution containing BPA; 2) filtering the reaction solution and then distilling it to remove the solvent and the C1-C4 alcohol to obtain crude BPA; 3) dissolving the crude BPA in an alkaline solution, filtering out impurities, and then adding acid to adjust the pH to ≤7 to precipitate BPA solids. The BPA solids are washed, dried, and recrystallized by adding phenol. The precipitated solids are then vacuum desorbed to obtain bisphenol A (BPA).

[0004] Chinese patent document CN115368627A discloses a method for recovering flame-retardant polyester. The method determines the flame-retardant polyester as polyester A or polyester B according to the type of flame retardant. The polyester A is a polyester whose flame retardant is one or more of decabromodiphenyl ethane, decabromodiphenyl ether, hexabromocyclododecane, and brominated epoxy; and the polyester B is a polyester whose flame retardant is one or more of phosphate flame retardant, tetrabromobisphenol A, tetrabromobisphenol S, and brominated polycarbonate. The polyester A is first subjected to microwave alcoholysis and then to extraction treatment to recover the flame retardant; while the polyester B is first subjected to extraction treatment to recover the flame retardant and then to microwave alcoholysis to recover the polyester.

[0005] Solvolysis methods, including the aforementioned ones, are green and mild. They attack the carbonate bond (-OC(=O)-O-) via nucleophiles such as methanol, ethylene glycol, and water, cleaving the CO bond and yielding bisphenol A (BPA) and other high-value-added chemicals. However, current chemical solvolysis methods primarily focus on capturing the side-chain carbonate bonds, while neglecting the high-value-added upgrading of main-chain bisphenol A. Summary of the Invention

[0006] In response to the needs for the treatment and utilization of phosphate compounds and the targeted upgrading of PC waste plastics, as well as the shortcomings of the existing technology, the present invention provides a method for preparing bisphenol A dialkyl ether from waste PC with the participation of phosphate esters. The method uses phosphate esters as alkylating agents and can achieve high-value conversion of waste PC plastics into bisphenol A dialkyl ethers.

[0007] The specific technical solutions adopted are as follows:

[0008] A method for preparing bisphenol A dialkyl ether from waste PC with the participation of phosphate ester comprises the following steps:

[0009] The crushed waste PC, alkylating agent phosphate, alkaline catalyst and solvent are placed in a reactor to form a reaction system. The reaction system is placed at a temperature of 60 to 160° C. under air conditions for a depolymerization reaction of 5 minutes or more. After the reaction is completed, the temperature is cooled to room temperature to obtain the product bisphenol A dialkyl ether.

[0010] The alkylating agent phosphate ester is selected from trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, triallyl phosphate, dimethylphosphonoethyl ethyl ester, tetramethylmethylenebis(phosphonate) or dimethylphosphonoacetic acid benzyl ester;

[0011] The base catalyst is an inorganic base or an organic base;

[0012] The product bisphenol A dialkyl ether includes bisphenol A dimethyl ether, bisphenol A diethyl ether, bisphenol A dipropyl ether, bisphenol A dibutyl ether or bisphenol A diallyl ether.

[0013] Polycarbonate PC depolymerizes under the action of an alkaline catalyst to produce bisphenol A. The alkali removes the hydrogen protons of bisphenol A, thereby increasing the nucleophilicity of the oxygen anion of bisphenol A, thereby inducing bisphenol A to attack the alkoxy bond of the phosphate ester, thereby breaking the CO bond and obtaining bisphenol A dialkyl ether.

[0014] Optionally, the solvent is N -Methylpyrrolidone, N , N -dimethylformamide, N , N - one of dimethylacetamide, dimethyl sulfoxide, acetonitrile, and tetrahydrofuran.

[0015] Preferably, the depolymerization reaction time is 10 min to 12 h.

[0016] Preferably, the mass ratio of the alkylating agent phosphate to the waste PC is 0.2-6:1, further 1.5-5:1.

[0017] Preferably, the alkaline catalyst includes potassium carbonate, sodium carbonate, potassium methoxide, sodium bicarbonate, sodium acetate, cesium carbonate or sodium hydroxide, and the mass ratio of the added amount of the alkaline catalyst to the waste PC is 1-10:1, further 2.5-8:1.

[0018] Preferably, the ratio of solvent to waste PC is 2-20 mL:1 g.

[0019] Specifically, under standard reaction conditions, 0.254 g PC (1 mmol), 0.42 g trimethyl phosphate (3 mmol), 0.977 g cesium carbonate (3 mmol) and 2 mL N,N -dimethylformamide was reacted at 100°C for 30 minutes to obtain bisphenol A dimethyl ether with a selectivity of 99% and a yield of 99%.

[0020] Waste PC can be pure PC or PC material waste, including PC waste discs, PC waste buckets or PC waste films.

[0021] Preferably, the base catalyst is cesium carbonate and the solvent is N , N -dimethylformamide. Under the corresponding catalyst and solvent conditions, the yield of the product bisphenol A dialkyl ether is higher.

[0022] Preferably, the temperature of the depolymerization reaction is 100 to 160° C., and the reaction time is 30 minutes to 12 hours.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) Compared with other methods for upgrading PC to bisphenol A dimethyl ether, the present invention has milder reaction conditions and faster reaction speed. The representative methods for upgrading PC to bisphenol A dimethyl ether in the prior art require 150°C and 6-8 hours to achieve a yield of 99%, while the method of the present invention only takes 30 minutes at 100°C to achieve a 99% yield of bisphenol A dialkyl ether.

[0025] (2) The method of the present invention can further expand the reaction products, not only limited to bisphenol A dimethyl ether, but also can prepare a variety of products including bisphenol A diethyl ether, bisphenol A dipropyl ether, bisphenol A dibutyl ether and bisphenol A diallyl ether. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the depolymerization reaction route in Example 1.

[0027] Figure 2 This is the H NMR spectrum of bisphenol A dimethyl ether (deuterated chloroform).

[0028] Figure 3This is the carbon NMR spectrum of bisphenol A dimethyl ether (deuterated chloroform).

[0029] Figure 4 This is the H NMR spectrum (deuterated chloroform) of bisphenol A diethyl ether synthesized in Example 9.

[0030] Figure 5 This is the C-NMR spectrum (deuterated chloroform) of bisphenol A diethyl ether synthesized in Example 9.

[0031] Figure 6 This is the H NMR spectrum (deuterated chloroform) of bisphenol A diallyl ether synthesized in Example 9.

[0032] Figure 7 This is the H NMR spectrum (deuterated chloroform) of bisphenol A diallyl ether synthesized in Example 9. DETAILED DESCRIPTION

[0033] The present invention will be further illustrated below in conjunction with the examples and accompanying drawings. 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.

[0034] Comparative Example 1

[0035] In a pressure-resistant tube reactor equipped with an electromagnetic stirrer, thermocouple, and programmable temperature controller, 0.254 g of CR-purity PC powder (1 mmol), 0.36 g of dimethyl carbonate (4 mmol), [EMIm][Br] (0.05 mmol), and NMP (2 mL) were added. After the pressure-resistant tube reactor was placed, stirring and heating were initiated. The reaction system was heated to 100°C and allowed to react at this temperature for 6 hours. After completion of the reaction, the temperature was cooled to room temperature, and the resulting mixed solution was the product. The resulting mixed solution was diluted with ethyl acetate, and the dilution was analyzed by GC for yield. The results showed that the yield of bisphenol A dimethyl ether was <5%.

[0036] Comparative Example 2

[0037] In a pressure-resistant tube reactor equipped with an electromagnetic stirrer, thermocouple, and programmable temperature controller, 0.254 g of CR-purity PC powder (1 mmol), 0.72 g of dimethyl carbonate (8 mmol), n-butyl bromide (0.02 mmol), and NMP (2 mL) were added. After the pressure-resistant tube reactor was placed, stirring and heating were initiated. The reaction system was heated to 100°C and maintained at this temperature for 6 hours. After completion of the reaction, the temperature was cooled to room temperature, and the resulting mixed solution was the product. The resulting mixed solution was diluted with ethyl acetate, and the dilution was analyzed by GC for yield. The results showed that the yield of the product, bisphenol A dimethyl ether, was <1%.

[0038] Example 1

[0039] In a pressure tube reactor equipped with an electromagnetic stirrer, a thermocouple, and a programmable temperature controller, 0.254 g of CR-purity PC powder (1 mmol), 0.42 g of trimethyl phosphate (3 mmol), 0.977 g of cesium carbonate (3 mmol) and N,N -dimethylformamide (2 mL), place the pressure tube reactor, start stirring and heating. The reaction system is heated to 100°C and reacted at this temperature for 30 minutes. After the reaction is completed, the temperature is cooled to room temperature, and the resulting mixed solution is the product. The resulting mixed solution is diluted with ethyl acetate, and the dilution is measured by GC for yield. The results show that the PC decomposition rate of this example is 100%, and the yield of bisphenol A dimethyl ether is 99%.

[0040] The depolymerization reaction scheme in this embodiment is as follows Figure 1 As shown, the nuclear magnetic hydrogen spectrum and nuclear magnetic carbon spectrum of the synthesized bisphenol A dimethyl ether are as follows Figure 2 and Figure 3 shown.

[0041] Example 2

[0042] In a pressure tube reactor equipped with an electromagnetic stirrer, a thermocouple and a programmable temperature controller, 0.254 g of CR purity PC powder (1 mmol), different masses of trimethyl phosphate (0.5, 1, 2, 3, 4, 5 and 6 mmol), cesium carbonate (3 mmol) and N , N -dimethylformamide (3 mL), after placing the pressure tube reactor, start stirring and heating. The reaction system was heated to 100 ° C and reacted at this temperature for 30 minutes. 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 ethyl acetate, and the dilution was measured for yield by GC. The results showed that the yields of bisphenol A dimethyl ether in this example were 11%, 34%, 97%, 99%, 99%, 99%, and 99%, respectively.

[0043] Example 3

[0044] In a pressure tube reactor equipped with an electromagnetic stirrer, a thermocouple and a programmable temperature controller, 0.254 g of CR-purity PC powder (1 mmol), 0.42 g of trimethyl phosphate (3 mmol), different masses of cesium carbonate (1, 2, 3, 4, 5 and 6 mmol) and N , N -dimethylformamide (3 mL), after placing the pressure tube reactor, start stirring and heating. The reaction system was heated to 100°C and reacted at this temperature for 30 minutes. 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 ethyl acetate, and the dilution was measured for yield by GC. The results showed that the PC decomposition rate of this example was 100%, and the yields of bisphenol A dimethyl ether were 53%, 92%, 99%, 99%, 99%, and 99%, respectively.

[0045] Example 4

[0046] In a pressure tube reactor equipped with an electromagnetic stirrer, a thermocouple and a programmable temperature controller, 0.254 g of CR-pure PC powder (1 mmol), 0.42 g of trimethyl phosphate (3 mmol), different base catalysts (NaOH, NaOAc, NaHCO3, KOMe, Na2CO3 and K2CO3) (3 mmol) and N , N -dimethylformamide (3 mL), after placing the pressure tube reactor, start stirring and heating. The reaction system was heated to 100°C and reacted at this temperature for 30 minutes. 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 ethyl acetate, and the dilution was measured for yield by GC. The results showed that the PC decomposition rate of this example was 100%, and the yields of bisphenol A dimethyl ether were 58%, 60%, 31%, 6%, 37% and 6%, respectively.

[0047] Example 5

[0048] In a pressure tube reactor equipped with an electromagnetic stirrer, a thermocouple and a programmable temperature controller, 0.254 g of CR-purity PC powder (1 mmol), 0.42 g of trimethyl phosphate (3 mmol), 0.977 g of Cs2CO3 (3 mmol) and N , N-dimethylformamide (3 mL), after placing the pressure tube reactor, start stirring and heating. The reaction system was heated to different temperatures (60°C, 80°C, 100°C, 120°C, 140°C, 160°C) and reacted at the corresponding temperature for 30 minutes. 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 ethyl acetate, and the dilution was measured for yield by GC. The results showed that the PC decomposition rate of this example was 100%, and the yields of bisphenol A dimethyl ether were 58%, 60%, 99%, 99%, 99%, and 99%, respectively.

[0049] Example 6

[0050] The discarded PC plastics (plastic barrels, films and CDs) were crushed into centimeter-level pieces in advance. Then, 0.254 g of the centimeter-level crushed PC plastics (about 1 mmol), 0.42 g of trimethyl phosphate (3 mmol), 0.977 g of cesium carbonate (3 mmol) and 0.1 g of iodine were added into a pressure tube reactor equipped with an electromagnetic stirrer, a thermocouple and a programmable temperature controller. N , N -dimethylformamide (3 mL), place the pressure tube reactor, start stirring and heating. The reaction system was heated to 100 ° C and reacted at this temperature for 30 minutes. After the reaction was completed, the temperature was cooled to room temperature, and the resulting mixed solution was the product. The dilution was diluted with ethyl acetate, and the dilution was measured by GC for yield. The results showed that the PC decomposition rate of this example was 100%, and the yields of bisphenol A dimethyl ether were 97%, 98% and 99%, respectively.

[0051] Example 7

[0052] In a pressure tube reactor equipped with an electromagnetic stirrer, a thermocouple and a programmable temperature controller, 0.254 g of CR-purity PC powder (1 mmol), 0.42 g of trimethyl phosphate (3 mmol), 0.977 g of Cs2CO3 (3 mmol) and N , N -dimethylformamide (3 mL) was added to the pressure-resistant tube reactor and stirred and heated. The reaction system was heated to 100°C and allowed to react at this temperature for different times (3 minutes, 5 minutes, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 6 hours, and 12 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 ethyl acetate, and the dilution was measured for yield by GC. The results showed that the PC decomposition rate in this example was 100%, and the yields of bisphenol A dimethyl ether were 7%, 22%, 91%, 98%, 99%, 99%, 99%, 99%, 99%, and 99%, respectively.

[0053] Example 8

[0054] In a pressure tube reactor equipped with an electromagnetic stirrer, a thermocouple and a programmable temperature controller, 0.254 g of PC (1 mmol), different alkylating agents (phosphonates (ethyl dimethylphosphonoacetate, tetramethylmethylenebis(phosphonate) and benzyl dimethylphosphonate)) (3 mmol), 0.977 g of cesium carbonate (3 mmol) and N , N -dimethylformamide (3 mL), place the pressure tube reactor, start stirring and heating. The reaction system was heated to 100°C and reacted at this temperature for 30 minutes. After the reaction was completed, the temperature was cooled to room temperature, and the resulting mixed solution was the product. The dilution solution was measured for yield by GC. The results showed that the PC decomposition rate of this example was 100%, and the yields of bisphenol A dimethyl ether were 96%, 99%, and 81%, respectively.

[0055] Example 9

[0056] In a pressure tube reactor equipped with an electromagnetic stirrer, a thermocouple and a programmable temperature controller, 0.254 g of PC (1 mmol), different alkylating agents (triethyl phosphate, tripropyl phosphate, tributyl phosphate and triallyl phosphate), 0.977 g of cesium carbonate (3 mmol) and N , N -dimethylformamide (3 mL), after placing the pressure tube reactor, start stirring and heating. The reaction system was heated to 100 ° C and reacted at this temperature for 30 minutes. After the reaction was completed, it was cooled to room temperature, and the resulting mixed solution was the product. The dilution was measured for yield by GC. The results showed that the PC decomposition rate of this example was 100%, and the products were bisphenol A diethyl ether (99%), bisphenol A dipropyl ether (66%), bisphenol A dibutyl ether (77%) and bisphenol A diallyl ether (64%).

[0057] The nuclear magnetic hydrogen spectrum and nuclear magnetic carbon spectrum of the representative bisphenol A diethyl ether synthesized in this embodiment are as follows: Figure 4 and Figure 5 As shown, the nuclear magnetic hydrogen spectrum and nuclear magnetic carbon spectrum of bisphenol A diallyl ether are as follows: Figure 6 and Figure 7 shown.

[0058] Example 10

[0059] In a pressure tube reactor equipped with an electromagnetic stirrer, a thermocouple and a programmable temperature controller, 0.254 g of PC (1 mmol), different alkylating agents (triethyl phosphate, tripropyl phosphate, tributyl phosphate and triallyl phosphate), 0.977 g of cesium carbonate (3 mmol) and N , N-dimethylformamide (3 mL), after placing the pressure tube reactor, start stirring and heating. The reaction system was heated to 140 ° C and reacted at this temperature for 30 minutes. After the reaction was completed, the temperature was cooled to room temperature, and the resulting mixed solution was the product. The dilution was measured for yield by GC. The results showed that the PC decomposition rate of this example was 100%, and the products were bisphenol A diethyl ether (97%), bisphenol A dipropyl ether (66%), bisphenol A dibutyl ether (96%) and bisphenol A diallyl ether (99%).

[0060] 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. A method for preparing bisphenol A dialkyl ether from waste PC with the participation of phosphate ester, characterized in that: The following steps are involved: The crushed waste PC, alkylating agent phosphate, alkaline catalyst and solvent are placed in a reaction kettle to form a reaction system. The reaction system is placed at a temperature of 100 to 140° C. under air conditions to carry out a depolymerization reaction for 30 minutes to 6 hours. After the reaction is completed, the temperature is cooled to room temperature to obtain the product bisphenol A dialkyl ether. The alkylating agent phosphate ester is selected from trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, triallyl phosphate, dimethylphosphonoethyl ethyl ester, tetramethylmethylenebis(phosphonate) or dimethylphosphonoacetic acid benzyl ester; The base catalyst is cesium carbonate; The solvent is N , N -dimethylformamide; The product bisphenol A dialkyl ether includes bisphenol A dimethyl ether, bisphenol A diethyl ether, bisphenol A dipropyl ether, bisphenol A dibutyl ether or bisphenol A diallyl ether; The mass ratio of the added amount of the alkali catalyst to the waste PC is 1-10:

1.

2. The method for preparing bisphenol A dialkyl ether from waste PC with the participation of phosphate ester according to claim 1, characterized in that: The mass ratio of the alkylating agent phosphate to the waste PC is 0.2-6:

1.

3. The method for preparing bisphenol A dialkyl ether from waste PC with the participation of phosphate ester according to claim 1, characterized in that: The ratio of solvent to waste PC is 2-20 mL:1g.

4. The method for preparing bisphenol A dialkyl ether from waste PC with the participation of phosphate ester according to claim 1, characterized in that: Waste PCs include waste PC discs, waste PC buckets or waste PC films.

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