Method for manufacturing bisphenol a

Abstract

To provide a method for manufacturing bisphenol A.SOLUTION: The method includes subjecting a polycarbonate and an aliphatic monohydric alcohol to a depolymerization reaction in the presence of sodium aluminate and a solvent, to obtain a first crude product containing bisphenol A.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for recovering or processing polymers, and in particular to a method for depolymerizing polycarbonate to obtain bisphenol A. [Background technology]

[0002] In recent years, many countries have placed great emphasis on recycling and reuse of polycarbonate waste. Currently, the mainstream method for recycling polycarbonate waste is chemical recycling, which has low requirements for the purity of polycarbonate waste, and the bisphenol A obtained through chemical recycling can be reused. Chemical recycling methods involve depolymerizing polycarbonate to obtain bisphenol A through processes such as pyrolysis, hydrolysis, alcoholysis, ammonolysis, or hydrogenolysis.

[0003] Among the chemical recycling methods mentioned above, alcoholysis is the most promising due to its high yield of bisphenol A. In alcoholysis, bisphenol A is obtained by depolymerizing polycarbonate in the presence of a catalyst. The catalyst can be, for example, a homogeneous catalyst or a heterogeneous catalyst. Heterogeneous catalysts have the advantage of being easily separated and reused. An example of a homogeneous catalyst is an alkali metal alkoxide, such as sodium methoxide.

[0004] An example of a conventional technique for depolymerizing polycarbonate using a heterogeneous catalyst is Patent Document 1, which discloses a supported catalyst composite catalyst. The composite catalyst uses a basic metal oxide as a carrier, a transition metal salt as an active component, and an alkali metal alkoxide as a catalytic aid. Among these, the basic metal oxides are one or more of MgO, CaO, CuO, MnO2, Fe2O3, FeO, CoO, and Co3O4 mixed in any ratio; the transition metal salts are one or more of chlorides, nitrates, acetates, sulfates, and acetylacetonates of iron, cobalt, nickel, copper, zinc, and manganese mixed in any ratio; and the alkali metal alkoxides are one or more of potassium methoxide, sodium methoxide, potassium ethoxide, sodium ethoxide, potassium isopropoxide, sodium 1-propanolate, sodium isopropoxide, potassium tert-butoxide, sodium n-butoxide, sodium tert-butoxide, potassium tert-pentoxide, and sodium tert-pentoxide mixed in any ratio.

[0005] The method for depolymerizing polycarbonate plastic using such a composite catalyst involves depolymerizing the polycarbonate plastic with an aliphatic monohydric alcohol in the presence of the composite catalyst at a temperature of 80°C to 100°C, either in a state where the polycarbonate plastic is dissolved in an organic solvent or in a state where no solvent is added, for a period of time ranging from 2 hours to 10 hours, to obtain bisphenol A. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Chinese Patent Application Publication No. 114904542 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a new method for producing bisphenol A. [Means for solving the problem]

[0008] The present invention provides a method for producing bisphenol A, comprising the step of obtaining a first crude product containing bisphenol A by depolymerizing a polycarbonate and an aliphatic monohydric alcohol in the presence of sodium aluminate and a solvent. [Effects of the Invention]

[0009] The present invention provides a new method for producing bisphenol A by using sodium aluminate as a catalyst to promote the depolymerization reaction between polycarbonate and aliphatic monohydric alcohol, thereby ensuring the production of bisphenol A. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an X-ray diffraction pattern of bisphenol A of Example 1 and commercially available bisphenol A. [Figure 2] FIG. 1 is a diagram showing the Fourier transform infrared spectra of bisphenol A in Example 1 and commercially available bisphenol A. [Figure 3] 1A and 1B are diagrams of differential scanning calorimetry and thermogravimetric analysis of bisphenol A in Example 1. [Figure 4] 1 is a diagram of proton nuclear magnetic resonance 1H-NMR of bisphenol A in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] In describing the present invention, the terms "first", "second", etc. are used for distinction purposes only and do not teach or imply any relative importance. The present invention will now be described in detail.

[0012] The method for producing bisphenol A of the present invention includes the steps of: depolymerizing polycarbonate and an aliphatic monohydric alcohol in the presence of sodium aluminate and a solvent to obtain a first crude product containing bisphenol A, sodium aluminate, the solvent, and unreacted aliphatic monohydric alcohol; The method includes a step of obtaining sodium aluminate and a second crude product by solid-liquid separation of the first crude product, the second crude product containing bisphenol A, a solvent, and an unreacted aliphatic monohydric alcohol, and purifying bisphenol A by removing the solvent and the unreacted aliphatic monohydric alcohol from the second crude product to obtain purified bisphenol A.

[0013] The following describes sodium aluminate, polycarbonate, aliphatic monohydric alcohol, solvent, and depolymerization reaction conditions.

[0014] In some embodiments, the polycarbonate is, for example but not limited to, polycarbonate waste, where the material is polycarbonate.

[0015] Because sodium aluminate is a heterogeneous catalyst, it can be separated from the first crude product by solid-liquid separation, and the separated sodium aluminate can be recovered and reused.

[0016] In some embodiments, the amount of sodium aluminate used is, but is not limited to, in the range of 0.01 to 0.2 parts by weight when the amount of polycarbonate used is 1 part by weight.In some embodiments, the amount of sodium aluminate used is, but is not limited to, in the range of 0.01 to 0.06 parts by weight when the amount of polycarbonate used is 1 part by weight.

[0017] In some embodiments, the aliphatic monohydric alcohol includes, but is not limited to, methanol, ethanol, etc. In some embodiments, the aliphatic monohydric alcohol is selected from the group consisting of methanol, ethanol, and combinations thereof. In some embodiments, the aliphatic monohydric alcohol is methanol.

[0018] In some embodiments, for example, when the amount of polycarbonate used is 1 part by weight, the amount of aliphatic monohydric alcohol used is, but is not limited to, in the range of 0.3 parts by weight to 2.4 parts by weight. In some embodiments, for example, when the amount of polycarbonate used is 1 part by weight, the amount of aliphatic monohydric alcohol used is, but is not limited to, in the range of 0.3 parts by weight to 2 parts by weight.

[0019] The solvent can dissolve the polycarbonate, improve mass transfer, and deliver the aliphatic monohydric alcohol and sodium aluminate to the polycarbonate molecular chains to promote the depolymerization reaction. In some embodiments, a substance with a polarity similar to that of polycarbonate according to the Hanson solubility parameter is used as the solvent.

[0020] Examples of solvents include, but are not limited to, tetrahydrofuran (THF), chloroform, dimethyl carbonate (DMC), dichloromethane (DCM), acetone, acetonitrile, n-heptane, or cyclohexane. In some embodiments, the solvent is selected from the group consisting of tetrahydrofuran, chloroform, dimethyl carbonate, dichloromethane, acetone, acetonitrile, n-heptane, cyclohexane, and combinations thereof. In some embodiments, the solvent is tetrahydrofuran. In some embodiments, the solvent is chloroform. In some embodiments, the solvent is dimethyl carbonate. In some embodiments, the solvent is dichloromethane. In some embodiments, the solvent is acetone. In some embodiments, the solvent is acetonitrile. In some embodiments, the solvent is n-heptane. In some embodiments, the solvent is cyclohexane.

[0021] In some embodiments, for example, when the amount of polycarbonate used is 1 part by weight, the amount of solvent used is, but is not limited to, in the range of 0.6 parts by weight to 2.7 parts by weight. In some embodiments, for example, when the amount of polycarbonate used is 1 part by weight, the amount of solvent used is, but is not limited to, in the range of 1 part by weight to 2.7 parts by weight.

[0022] In some embodiments, for example, when the amount of polycarbonate used is 1 part by weight, the amount of sodium aluminate used is in the range of 0.01 parts by weight to 0.06 parts by weight, the amount of aliphatic monohydric alcohol used is in the range of 0.3 parts by weight to 2 parts by weight, and the amount of solvent used is in the range of 1 part by weight to 2.7 parts by weight, but is not limited to these.

[0023] In some embodiments, the depolymerization reaction is carried out at a reaction temperature within a range of, for example, but not limited to, 25°C to 64.7°C. In some embodiments, the depolymerization reaction is carried out at a reaction temperature within a range of, for example, but not limited to, 25°C to 60°C. When the depolymerization reaction temperature is within a range of 25°C to 64.7°C and the aliphatic monohydric alcohol is methanol or ethanol, the reaction temperature is lower than the boiling point of methanol or ethanol, so the depolymerization reaction can be operated at atmospheric pressure (1 atm), eliminating the need for a high-pressure reactor, thereby reducing the operational difficulty of the depolymerization reaction and improving safety. In some embodiments, the depolymerization reaction is carried out at a reaction pressure of 1 atm, eliminating the need for a high-pressure reactor, thereby reducing the operational difficulty of the depolymerization reaction and improving safety. In some embodiments, the depolymerization reaction is carried out for a reaction time within a range of, for example, but not limited to, 0.25 hours to 9 hours. In some embodiments, the depolymerization reaction is carried out at a reaction temperature in the range of 25° C. to 60° C., a reaction pressure of 1 atm, and a reaction time in the range of 0.25 hours to 9 hours, but is not limited thereto.

[0024] In some embodiments, the specific method for solid-liquid separation is, for example, but not limited to, suction filtration. In some embodiments, the specific method for removing the solvent and unreacted aliphatic monohydric alcohol is, for example, but not limited to, rotary evaporation. [Example]

[0025] The method for producing bisphenol A of the present invention will be specifically described below using Examples 1 to 35.

[0026] Example 1 In Example 1, 5 parts by weight of polycarbonate (manufacturer: Wanhua Chemical Group Co., Ltd., China, model number: A1107), 5 parts by weight of methanol, 10 parts by weight of tetrahydrofuran, and 0.05 parts by weight of sodium aluminate were mixed, and then the polycarbonate and methanol were stirred in the presence of tetrahydrofuran and sodium aluminate to cause a depolymerization reaction between the polycarbonate and methanol at 25°C and atmospheric pressure (1 atm) for 9 hours, thereby obtaining a first crude product containing bisphenol A, the sodium aluminate, the tetrahydrofuran, and unreacted methanol.

[0027] The first crude product was then subjected to suction filtration to obtain a second crude product containing the sodium aluminate, bisphenol A, tetrahydrofuran, and unreacted methanol. The tetrahydrofuran and unreacted methanol in the second crude product were then removed using a rotary evaporator to purify bisphenol A, thereby obtaining purified bisphenol A.

[0028] According to Equation 1, which is the formula for the yield of bisphenol A, the yield of bisphenol A in Example 1 was calculated to be 38%.

[0029]

number

[0030] An X-ray diffraction analysis was carried out using an X-ray diffractometer (manufacturer: Rigaku Corporation, model number: SmartLab SE) on the bisphenol A of Example 1. The obtained X-ray diffraction pattern is shown in FIG.

[0031] A Fourier-transform infrared spectroscopy (FTIR) analysis was performed on the bisphenol A of Example 1 using a Fourier-transform infrared spectrometer (manufacturer: PerkinElmer Inc., USA, model number: Spectrum 100). The obtained FTIR diagram is shown in FIG.

[0032] A differential scanning calorimetry (DSC) analysis was performed on the bisphenol A of Example 1 using a differential scanning calorimeter (manufacturer: TA Instruments, USA, model number: SDT 650). The resulting DSC diagram is shown in FIG.

[0033] Thermogravimetric analysis (TGA) was performed on the bisphenol A of Example 1 using a thermogravimetric analyzer (manufacturer: TA Instruments, USA, model number: SDT 650). The resulting TGA diagram is shown in FIG.

[0034] Nuclear magnetic resonance spectroscopy (NMR) was performed on the bisphenol A of Example 1 using a nuclear magnetic resonance spectrometer (manufacturer: Bruker, USA, model number: AVIII-500). 1 The H-NMR diagram is shown in FIG.

[0035] <Examples 2 to 35> The differences between Examples 2 to 35 and Example 1 are that the amount of sodium aluminate used, the amount of solvent used, the type of solvent, and the reaction conditions for the depolymerization reaction were changed, as shown in Table 1. In addition, the yield of bisphenol A for each of Examples 2 to 35 was calculated according to the above formula 1. The results are also shown in Table 1.

[0036] [Table 1]

[0037] The X-ray diffraction pattern in Figure 1 shows that the bisphenol A of Example 1 has the same crystal structure as commercially available bisphenol A (manufacturer: Thermo Fisher Scientific, USA, purity: 97%). The FTIR pattern in Figure 2 shows that the bisphenol A of Example 1 has the same functional group structure as commercially available bisphenol A. The DSC and TGA patterns in Figure 3 show that the bisphenol A of Example 1 has a melting point of 156°C and a decomposition temperature of 260°C. 1 The H-NMR diagram shows that the bisphenol A of Example 1 has the characteristic peaks of bisphenol A. The above analysis results prove that the method for producing bisphenol A of the present invention can reliably produce bisphenol A.

[0038] According to the above, the present invention provides a new method for producing bisphenol A by using sodium aluminate as a catalyst to promote the depolymerization reaction of polycarbonate with aliphatic monohydric alcohol to obtain bisphenol A, and the yield of bisphenol A produced by the method for producing bisphenol A of the present invention reaches up to 97.6%. In addition, sodium aluminate is an inexpensive heterogeneous catalyst that can be easily separated and reused, and the depolymerization reaction can be carried out at room temperature and atmospheric pressure, which not only reduces production costs and operational complexity but also improves safety.

[0039] The above-described embodiments are illustrative for explaining the principles and effects of the present invention, and are not intended to limit the present invention. Those skilled in the art may make slight changes or modifications to the above-described embodiments without departing from the spirit and scope of the present invention. Therefore, all changes and modifications made by those skilled in the art without departing from the gist of the present invention should be considered to fall within the scope of protection of the present invention. [Industrial Applicability]

[0040] The method for producing bisphenol A of the present invention is suitable for recycling polycarbonate.

Claims

1. A method for producing bisphenol A, comprising the step of obtaining a first crude product containing bisphenol A by depolymerizing a polycarbonate and an aliphatic monohydric alcohol in the presence of sodium aluminate and a solvent.

2. the first crude product further comprises the sodium aluminate, the solvent, and unreacted aliphatic monohydric alcohol; 2. The method for producing bisphenol A according to claim 1, further comprising the steps of: subjecting the first crude product to solid-liquid separation to obtain the sodium aluminate and a second crude product, the second crude product containing the bisphenol A, the solvent, and the unreacted aliphatic monohydric alcohol; and purifying the bisphenol A by removing the solvent and the unreacted aliphatic monohydric alcohol from the second crude product to obtain purified bisphenol A.

3. 2. The method for producing bisphenol A according to claim 1, wherein the solvent is selected from the group consisting of tetrahydrofuran, chloroform, dimethyl carbonate, dichloromethane, acetone, acetonitrile, n-heptane, cyclohexane, and combinations thereof.

4. 2. The method for producing bisphenol A according to claim 1, wherein the aliphatic monohydric alcohol is selected from the group consisting of methanol, ethanol, and combinations thereof.

5. 2. The method for producing bisphenol A according to claim 1, wherein the amount of sodium aluminate used is in the range of 0.01 to 0.2 parts by weight, based on 1 part by weight of the polycarbonate used.

6. 2. The method for producing bisphenol A according to claim 1, wherein the amount of the solvent used is in the range of 0.6 to 2.7 parts by weight, based on 1 part by weight of the polycarbonate used.

7. 2. The method for producing bisphenol A according to claim 1, wherein the amount of the aliphatic monohydric alcohol used is in the range of 0.3 to 2.4 parts by weight, based on 1 part by weight of the polycarbonate used.

8. The method for producing bisphenol A according to claim 1, wherein the depolymerization reaction is carried out at a reaction temperature in the range of 25°C to 64.7°C.

9. 2. The method for producing bisphenol A according to claim 1, wherein the depolymerization reaction is carried out at a reaction pressure of 1 atm.

10. The method for producing bisphenol A according to claim 1, wherein the depolymerization reaction is carried out for a reaction time ranging from 0.25 hours to 9 hours.

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