A method of degrading a polymer

Abstract

The application provides a polymer degradation method, comprising the following steps: under visible light conditions, a polymer and an oxidant generate an oxidation product through an oxidation reaction under the action of a catalyst; wherein the catalyst is selected from a compound or a mixture capable of generating chlorine or bromine radicals in situ; the oxidant is selected from oxygen or air, the pressure of the oxidant gas is 1 atm-100 atm; the reaction temperature of the oxidation reaction is 0 DEG C-100 DEG C, and the reaction time is 8h-48h. The degradation method has low reaction cost, can convert the polymer into a high-value chemical product, and has simple operation, good safety, and is a mild and environment-friendly degradation method. The degradation method can solve the problems of increased reaction cost and environmental pollution in the polymer degradation process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic intermediate synthesis, and particularly relates to a degradation method of a polymer. BACKGROUND

[0002] At present, the total amount of global waste plastics reaches 63 billion tons, and only about 10% of the waste plastics is recycled, and about 90% of the waste plastics is directly filled or accumulated in the natural environment, which seriously pollutes the environment ecology, and the microplastics ions existing in the natural environment can also become carriers of toxic substances, which can cause damage to human health through the food chain and drinking water.

[0003] The existing technology mainly recycles the plastics through mechanical recycling, biodegradation or non-biodegradation. The non-biodegradation mainly converts the waste plastics into monomers, oligomers or high-value chemical raw materials such as high carbon hydrocarbons by means of oxidation, pyrolysis or hydrogenation cracking. However, in these reaction processes, expensive metal catalysts such as ruthenium, iridium and palladium are often used or high-temperature pyrolysis is adopted, which has certain defects in economy and environmental protection, and can increase the reaction cost and pollute the environment. SUMMARY

[0004] The present application aims to provide a degradation method of a polymer, so as to solve the problems of increased reaction cost and environmental pollution caused by the degradation of the polymer. The specific technical scheme is as follows:

[0005] The present application provides a degradation method of a polymer, which comprises the following steps: under the condition of visible light, the polymer and an oxidizing agent generate an oxidation product under the action of a catalyst; wherein the catalyst is selected from a compound or a mixture which can generate chlorine or bromine radicals in situ; the polymer is selected from any one of polystyrene, polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, styrene-butadiene rubber, acrylonitrile-styrene resin and styrene-maleic anhydride copolymer; the oxidizing agent is selected from oxygen or air, and the pressure of the oxidizing agent gas is 1 atm-100 atm; the reaction temperature of the oxidation reaction is 0℃-100℃, and the reaction time is 8h-48h.

[0006] In some embodiments of the present application, the molar ratio of the monomer constituting the polymer to the catalyst is (1:(0.001-0.5). In the present application, the number of moles of the monomer constituting the polymer=(the ratio of the mass of the polymer to the molecular weight of the repeating unit) x N, and N is the number of structural units of the repeating unit. For a homopolymer, N=1; for a binary copolymer, N=2.

[0007] In some embodiments of the application, the catalyst is selected from at least one of a halogen-containing organic solvent selected from the group consisting of dichloromethane, 1,1-dichloroethane, 1,2-dichloroethane, trichloroethane, tetrachloroethane, dibromomethane, 1,1-dibromoethane, 1,2-dibromoethane, trichloromethane, tribromomethane, tetrachloromethane, tetrabromomethane, chlorobenzene, bromobenzene, dichlorobenzene, dibromobenzene, trichlorobenzene, and tribromobenzene.

[0008] In some embodiments of the application, the catalyst is selected from at least one of tert-butyl hypochlorite, hydrochloric acid, or hydrobromic acid.

[0009] In some embodiments of the application, the catalyst is a mixture consisting of a halogen-containing organic solvent selected from at least one of dichloromethane, 1,1-dichloroethane, 1,2-dichloroethane, trichloroethane, tetrachloroethane, dibromomethane, 1,1-dibromoethane, 1,2-dibromoethane, trichloromethane, tribromomethane, tetrachloromethane, tetrabromomethane, chlorobenzene, bromobenzene, dichlorobenzene, dibromobenzene, trichlorobenzene, and tribromobenzene, and a halogenated acid selected from at least one of hydrochloric acid or hydrobromic acid.

[0010] In some embodiments of the application, the catalyst is a mixture consisting of a halogen-containing organic solvent selected from at least one of dichloromethane, 1,1-dichloroethane, 1,2-dichloroethane, trichloroethane, tetrachloroethane, dibromomethane, 1,1-dibromoethane, 1,2-dibromoethane, trichloromethane, tribromomethane, tetrachloromethane, tetrabromomethane, chlorobenzene, bromobenzene, dichlorobenzene, dibromobenzene, trichlorobenzene, and tribromobenzene, and a mixture that generates a halogenated acid in situ selected from at least one of a mixture of lithium chloride and acetic acid, a mixture of sodium chloride and acetic acid, or a mixture of sodium bromide and acetic acid.

[0011] In some embodiments of the application, the wavelength of the visible light is between 300 nm and 800 nm.

[0012] In some embodiments of the application, the oxidation reaction is further added with a solvent selected from at least one of acetonitrile, acetone, tetrahydrofuran, dichloromethane, 1,1-dichloroethane, 1,2-dichloroethane, trichloroethane, tetrachloroethane, dibromomethane, 1,1-dibromoethane, 1,2-dibromoethane, trichloromethane, tribromomethane, tetrachloromethane, tetrabromomethane, chlorobenzene, bromobenzene, dichlorobenzene, dibromobenzene, trichlorobenzene, tribromobenzene, and N,N-dimethylformamide.

[0013] Advantages of embodiments of the application:

[0014] The application provides a polymer degradation method, in which a polymer and an oxidant are subjected to an oxidation reaction under the action of a catalyst under visible light conditions at 0-100 DEG C to generate an oxidation product, thereby realizing efficient and green degradation of the polymer. The degradation method has low reaction cost, can convert the polymer into a high-value chemical product at a high reaction rate, and is simple to operate and safe, and is a mild and environmentally friendly degradation method. The degradation method can solve the problems of increased reaction cost and environmental pollution in the polymer degradation process. Of course, implementing any product or method of the application does not necessarily achieve all the advantages described above. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the present application and the prior art, the following briefly introduces the drawings needed to be used in the examples and the prior art. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other embodiments can also be obtained from these drawings.

[0016] Figure 1 NMR hydrogen spectrum of the product benzoic acid in example 1 of the present application;

[0017] Figure 2 NMR carbon spectrum of the product benzoic acid in example 1 of the present application;

[0018] Figure 3 NMR hydrogen spectrum of the product acetophenone in example 1 of the present application;

[0019] Figure 4 NMR carbon spectrum of the product acetophenone in example 1 of the present application;

[0020] Figure 5 NMR hydrogen spectrum of the product terephthalic acid in example 17 of the present application;

[0021] Figure 6 NMR carbon spectrum of the product terephthalic acid in example 17 of the present application. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions, and advantages of the present application more clear and obvious, the following further describes the present application in detail with reference to the drawings and examples. Obviously, the described examples are only some of the embodiments of the present application, but not all. Based on the examples in the present application, all other technical solutions obtained by those skilled in the art belong to the scope of protection of the present application.

[0023] Therefore, the application provides a polymer degradation method, which comprises the following steps: under visible light, a polymer and an oxidant generate an oxidation product under the action of a catalyst; wherein the catalyst is selected from a compound or mixture capable of generating chlorine or bromine radicals in situ; the polymer is selected from any one of polystyrene, polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, styrene-butadiene rubber, acrylonitrile-styrene resin and styrene-maleic anhydride copolymer; the oxidant is selected from oxygen or oxygen, and the pressure of the oxidant gas is 1 atm-100 atm; the reaction temperature of the oxidation reaction is 0-100 ℃, and the reaction time is 8-48 h.

[0024] In some embodiments of the application, the molar ratio of the monomer constituting the polymer to the catalyst is 1:(0.001-0.5). In the application, the number of moles of the monomer constituting the polymer=(the ratio of the mass of the polymer to the molecular weight of the repeating unit)×N, and N is the number of structural units constituting the repeating unit. For a homopolymer, N=1; for a binary copolymer, N=2. For example, for polyethylene terephthalate, acrylonitrile-styrene resin and styrene-maleic anhydride copolymer, the number of structural units N constituting the repeating unit is 2.

[0025] In the application, the weight average molecular weight (Mw) of the polymer is 3000-360000. The weight average molecular weight of the polymer in the above range can be degraded by the degradation method provided by the application.

[0026] In some embodiments of the application, the catalyst is selected from at least one of halogen-containing organic solvents selected from dichloromethane, 1,1-dichloroethane, 1,2-dichloroethane, trichloroethane, tetrachloroethane, dibromomethane, 1,1-dibromoethane, 1,2-dibromoethane, trichloromethane, tribromomethane, tetrachloromethane, tetrabromomethane, chlorobenzene, bromobenzene, dichlorobenzene, dibromobenzene, trichlorobenzene and tribromobenzene.

[0027] In some embodiments of the application, the catalyst is selected from any one of tert-butyl hypochlorite, hydrochloric acid or hydrobromic acid.

[0028] In some embodiments of the application, the catalyst is a mixture composed of a halogen-containing organic solvent and a halogenated acid, the halogen-containing organic solvent is selected from at least one of dichloromethane, 1,1-dichloroethane, 1,2-dichloroethane, trichloroethane, tetrachloroethane, dibromomethane, 1,1-dibromoethane, 1,2-dibromoethane, trichloromethane, tribromomethane, tetrachloromethane, tetrabromomethane, chlorobenzene, bromobenzene, dichlorobenzene, dibromobenzene, trichlorobenzene and tribromobenzene, and the halogenated acid is selected from at least one of hydrochloric acid or hydrobromic acid.

[0029] In some embodiments of the present application, the catalyst is a mixture consisting of a halogen-containing organic solvent and a mixture of halogenated acid generated in situ, and the mixture of halogenated acid generated in situ is selected from any one of a mixture of lithium chloride and acetic acid, a mixture of sodium chloride and acetic acid, or a mixture of sodium bromide and acetic acid.

[0030] In some embodiments of the present application, the wavelength of visible light is 300 nm to 800 nm.

[0031] In some embodiments of the present application, a solvent is further added to the oxidation reaction, and the solvent is selected from at least one of acetonitrile, acetone, tetrahydrofuran, dichloromethane, 1,1-dichloroethane, 1,2-dichloroethane, trichloroethane, tetrachloroethane, dibromomethane, 1,1-dibromoethane, 1,2-dibromoethane, trichloromethane, tribromomethane, tetrachloromethane, tetrabromomethane, chlorobenzene, bromobenzene, dichlorobenzene, dibromobenzene, trichlorobenzene, tribromobenzene, and N,N-dimethylformamide.

[0032] In the present application, the reaction vessel used must be capable of achieving the oxidation reaction promoted by light in a certain atmosphere, and the reaction vessel used includes, but is not limited to, a photoreactor or a quartz tube, as long as the reaction vessel used can achieve the purpose of the present application.

[0033] In the present application, the method for separating the target product after the light-promoted reaction is stopped is a separation method commonly used in the art, such as filtration, distillation under reduced pressure, extraction, etc., and the separation method is not limited in the present application, as long as the separation method can achieve the purpose of the present application.

[0034] In the present application, the light source used is not particularly limited, as long as the light source can achieve the purpose of the present application. In the present application, the power of the light source used ranges from 1 W to 100 W. Exemplarily, a 10 W light-emitting diode (LED) lamp is used as the light source.

[0035] In the present application, the term "yield" means the molar percentage of the actual yield of a certain product to the theoretical yield; in the present application, the calculation formula of the yield is: target product yield = actual generated moles of target product / theoretical generated moles of target product x 100%.

[0036] Hereinafter, embodiments of the present application will be described more specifically by citing examples and comparative examples. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are mass-based.

[0037] Test methods and equipment

[0038] The product was analyzed by nuclear magnetic resonance spectrometer for nuclear magnetic hydrogen spectrum and nuclear magnetic carbon spectrum, to confirm the molecular structure of the target product and quantitatively determine the yield of the target product.

[0039] For liquid products with low boiling points (e.g. formic acid, acetone, etc.), nuclear magnetic resonance spectroscopy was performed by adding dibromomethane (CH2Br2) as an internal standard to the solution after the reaction. The number of moles of the target product generated was calculated from the ratio of the peak areas in the hydrogen nuclear magnetic resonance spectrum, i.e. the actual number of moles of the target product generated = (peak area of the target product / peak area of the internal standard) x the number of moles of the internal standard. The yield was then calculated as the percentage of the actual number of moles of the target product generated and the theoretical number of moles of the target product.

[0040] Example 1

[0041] Polystyrene degradation:

[0042]

[0043] In a 25 mL reaction tube, polystyrene (Mw = 260000, 20.8 mg), hydrochloric acid (0.02 mmol), dichloromethane (CH2Cl2, 2.0 mL) were added. After the reaction tube was sealed, it was cooled using liquid nitrogen, followed by replacing the air in the reaction tube with oxygen (1.0 atm) on a double manifold. Then it was irradiated on a 400 nm LED lamp (10 W) device at 35 °C for 24 hours (h). After the reaction was completed, it was cooled to room temperature, the solvent was removed under reduced pressure, and silica gel flash chromatography was performed to obtain benzoic acid (9.2 mg, yield 38%) and acetophenone (7.7 mg, yield 32%). The hydrogen nuclear magnetic resonance spectrum of benzoic acid is shown in Figure 1 , and the carbon nuclear magnetic resonance spectrum is shown in Figure 2 ; the hydrogen nuclear magnetic resonance spectrum of acetophenone is shown in Figure 3 , and the carbon nuclear magnetic resonance spectrum is shown in Figure 4 .

[0044] Hydrogen and carbon nuclear magnetic resonance spectra of benzoic acid: 1 H NMR (400 MHz, DMSO-d6) δ 12.95 (br s, 1H), 7.96-7.93 (m, 2H), 7.64-7.60 (m, 1H), 7.50 (t, J = 7.6 Hz, 2H). 13 C NMR (100 MHz, DMSO-d6) δ 167.7, 133.2, 131.1, 129.6, 128.9.

[0045] Hydrogen and carbon nuclear magnetic resonance spectra of acetophenone: 1 H NMR (400 MHz, CDCl3) δ 7.96 (d, J = 7.2 Hz, 2H), 7.56 (t, J = 8.4 Hz, 1H), 7.46 (t, J = 7.7 Hz, 2H), 2.60 (s, 3H). 13C NMR (100 MHz, CDC13) δ 198.2, 137.1, 133.1, 128.5, 128.3, 26.6.

[0046] Example 2

[0047] Polystyrene degradation:

[0048]

[0049] Compared to Example 1, the difference is that the solvent is changed to 1,2- dichloroethane (DCE), as follows:

[0050] In a 25 mL reaction tube was added polystyrene (Mw= 260000, 20.8 mg), hydrochloric acid (0.02 mmol), DCE (2.0 mL). The reaction tube was sealed and cooled using liquid nitrogen, then the air in the reaction tube was replaced with oxygen (1.0 atm) on a double manifold. After that, it was illuminated on a 400 nm LED lamp (10 W) device, 35 °C for 24 hours. After the reaction was completed, it was cooled to room temperature, the solvent was removed under reduced pressure, and silica gel flash chromatography was used for purification to obtain benzoic acid (8.5 mg, yield 35%) and acetophenone (7.7 mg, yield 32%).

[0051] Example 3

[0052] Polystyrene degradation:

[0053]

[0054] Compared to Example 1, the difference is that the solvent is changed to 1,2- dichloroethane (DCE), as follows:

[0055] In a 25 mL reaction tube was added polystyrene (Mw= 260000, 20.8 mg), hydrochloric acid (0.02 mmol), DCE (2.0 mL). The reaction tube was sealed and cooled using liquid nitrogen, then the air in the reaction tube was replaced with oxygen (1.0 atm) on a double manifold. After that, it was illuminated on a 400 nm LED lamp (10 W) device, 35 °C for 24 hours. After the reaction was completed, it was cooled to room temperature, the solvent was removed under reduced pressure, and silica gel flash chromatography was used for purification to obtain benzoic acid (8.5 mg, yield 35%) and acetophenone (7.7 mg, yield 32%).

[0056] Example 4

[0057] Polystyrene degradation:

[0058]

[0059] The difference compared to Example 1 is that the solvent is changed to chloroform (CHCl3) and the reaction time is extended to 48 hours, as follows:

[0060] In a 25 mL reaction tube was added polystyrene (Mw = 260000, 20.8 mg), hydrochloric acid (0.02 mmol), CHCl3(2.0 mL). After the reaction tube was sealed it was cooled using liquid nitrogen, then the air in the reaction tube was replaced with oxygen (1.0 atm) on a double manifold. It was then illuminated on a 400 nm LED lamp (10 W) setup at 35 °C for 48 hours. After the reaction was complete it was cooled to room temperature, the solvent was removed under reduced pressure, and flash chromatography on silica gel gave benzoic acid (1.2 mg, 5% yield) and acetophenone (1.9 mg, 8% yield).

[0061] Example 5

[0062] Polystyrene degradation:

[0063]

[0064] The difference compared to Example 1 is that the solvent is changed to a mixture of dichloromethane and acetonitrile, as follows:

[0065] In a 25 mL reaction tube was added polystyrene (Mw = 260000, 20.8 mg), hydrochloric acid (0.02 mmol), a mixture of dichloromethane and acetonitrile (1:1 by volume) (2.0 mL). After the reaction tube was sealed it was cooled using liquid nitrogen, then the air in the reaction tube was replaced with oxygen (1.0 atm) on a double manifold. It was then illuminated on a 400 nm LED lamp (10 W) setup at 35 °C for 24 hours. After the reaction was complete it was cooled to room temperature, the solvent was removed under reduced pressure, and flash chromatography on silica gel gave benzoic acid (5.4 mg, 22% yield) and acetophenone (5.6 mg, 23% yield).

[0066] Example 6

[0067] Polystyrene degradation:

[0068]

[0069] The difference compared to Example 1 is that the light source is changed to 420 nm, as follows:

[0070] A 25 mL reaction tube was charged with polystyrene (Mw = 260000, 20.8 mg), hydrochloric acid (0.02 mmol), CH2Cl2(2.0 mL). The reaction tube was sealed and cooled using liquid nitrogen, then the air in the reaction tube was replaced with oxygen (1.0 atm) on a double manifold. After that, the reaction was illuminated on a 420 nm LED lamp (10 W) device, 35 °C for 24 hours. After the reaction was completed, it was cooled to room temperature, the solvent was removed under reduced pressure, and silica gel flash chromatography was used for purification to obtain benzoic acid (5.1 mg, yield 21%) and acetophenone (4.3 mg, yield 18%).

[0071] Example 7

[0072] Polystyrene degradation:

[0073]

[0074] Compared with Example 1, the difference is that the light source is changed to mixed blue light, as follows:

[0075] A 25 mL reaction tube was charged with polystyrene (Mw = 260000, 20.8 mg), hydrochloric acid (0.02 mmol), CH2Cl2(2.0 mL). The reaction tube was sealed and cooled using liquid nitrogen, then the air in the reaction tube was replaced with oxygen (1.0 atm) on a double manifold. After that, the reaction was illuminated on a 420 nm LED lamp (10 W) device, 35 °C for 24 hours. After the reaction was completed, it was cooled to room temperature, the solvent was removed under reduced pressure, and silica gel flash chromatography was used for purification to obtain benzoic acid (5.1 mg, yield 21%) and acetophenone (4.3 mg, yield 18%).

[0076] Example 8

[0077] Polystyrene degradation:

[0078]

[0079] Compared with Example 1, the difference is that the reaction temperature is changed to 60 °C, as follows:

[0080] A 25 mL reaction tube was charged with polystyrene (Mw = 260000, 20.8 mg), hydrochloric acid (0.02 mmol), CH2Cl2(2.0 mL). The reaction tube was sealed and cooled using liquid nitrogen, then the air in the reaction tube was replaced with oxygen (1.0 atm) on a double manifold. After that, the reaction was illuminated on a 420 nm LED lamp (10 W) device, 35 °C for 24 hours. After the reaction was completed, it was cooled to room temperature, the solvent was removed under reduced pressure, and silica gel flash chromatography was used for purification to obtain benzoic acid (5.1 mg, yield 21%) and acetophenone (4.3 mg, yield 18%).

[0081] Example 9

[0082] Polystyrene degradation:

[0083]

[0084] Compared to Example 1, the difference is that the solvent is changed to DCE and the catalyst is changed to HBr.

[0085] In a 25 mL reaction tube was added polystyrene (Mw = 260000, 20.8 mg), HBr (0.02 mmol), DCE (2.0 mL). The reaction tube was sealed and cooled using liquid nitrogen, then the air in the reaction tube was replaced with oxygen (1.0 atm) on a double manifold. After that, the reaction was illuminated on a 400 nm LED lamp (10 W) device, 35 °C for 24 hours. After the reaction was completed, it was cooled to room temperature, the solvent was removed under reduced pressure, and silica gel flash chromatography was used for purification to obtain benzoic acid (6.8 mg, yield 28%) and acetophenone (5.3 mg, yield 22%).

[0086] Example 10

[0087] Polystyrene degradation:

[0088]

[0089] Compared to Example 1, the difference is that the solvent is changed to DCE and the catalyst is changed to HBr.

[0090] In a 25 mL reaction tube was added polystyrene (Mw = 260000, 20.8 mg), HBr (0.02 mmol), DCE (2.0 mL). The reaction tube was sealed and cooled using liquid nitrogen, then the air in the reaction tube was replaced with oxygen (1.0 atm) on a double manifold. After that, the reaction was illuminated on a 400 nm LED lamp (10 W) device, 35 °C for 24 hours. After the reaction was completed, it was cooled to room temperature, the solvent was removed under reduced pressure, and silica gel flash chromatography was used for purification to obtain benzoic acid (6.8 mg, yield 28%) and acetophenone (5.3 mg, yield 22%).

[0091] Example 11

[0092] Polystyrene degradation:

[0093]

[0094] Compared to Example 1, the difference is that the solvent is changed to DCE and the catalyst is changed to HBr.

[0095] A 25 mL reaction tube was charged with polystyrene (Mw = 260000, 20.8 mg), lithium chloride and acetic acid mixture (LiCl + AcOH, molar ratio of lithium chloride: acetic acid = 1 : 1, 20 pL, 1 M, 0.02 mmol), DCE (2.0 mL). The reaction tube was sealed and cooled using liquid nitrogen, then the air in the reaction tube was replaced with oxygen (1.0 atm) on a double manifold. After that, it was illuminated on a 400 nm LED lamp (10 W) device at 35 °C for 24 hours. After the reaction was completed, it was cooled to room temperature, the solvent was removed under reduced pressure, and silica gel flash chromatography was used for purification to obtain benzoic acid (5.6 mg, yield 23%) and acetophenone (4.5 mg, yield 19%).

[0096] Example 12

[0097] Polystyrene degradation:

[0098]

[0099] Compared with Example 1, the difference is that the solvent is changed to DCE, and the catalyst is tert-butyl hypochlorite.

[0100] A 25 mL reaction tube was charged with polystyrene (Mw = 260000, 20.8 mg), tert-butyl hypochlorite (t-BuOCl, 2.2 mg, 0.02 mmol), DCE (2.0 mL). The reaction tube was sealed and cooled using liquid nitrogen, then the air in the reaction tube was replaced with oxygen (1.0 atm) on a double manifold. After that, it was illuminated on a 400 nm LED lamp (10 W) device at 35 °C for 24 hours. After the reaction was completed, it was cooled to room temperature, the solvent was removed under reduced pressure, and silica gel flash chromatography was used for purification to obtain benzoic acid (4.9 mg, yield 20%) and acetophenone (3.5 mg, yield 15%).

[0101] Example 13

[0102] Polystyrene degradation:

[0103]

[0104] A 25 mL reaction tube was charged with polystyrene (Mw = 260000, 20.8 mg), CH2Cl2(2.0 mL). The reaction tube was sealed and cooled using liquid nitrogen, then the air in the reaction tube was replaced with oxygen (1.0 atm) on a double manifold. After that, it was illuminated on a 400 nm LED lamp (10 W) device at 35 °C for 24 hours. After the reaction was completed, it was cooled to room temperature, the solvent was removed under reduced pressure, and silica gel flash chromatography was used for purification to obtain benzoic acid (4.9 mg, yield 20%) and acetophenone (2.3 mg, yield 10%).

[0105] Example 14

[0106] Polyvinyl chloride degradation:

[0107]

[0108] In a 25 mL reaction tube, polyvinyl chloride (Mw= 200000, 12.4 mg), CH2Cl2(2.0 mL) were added. After the reaction tube was sealed, it was cooled using liquid nitrogen, followed by replacing the air in the reaction tube with oxygen (1.0 atm) on a double manifold. It was then illuminated in front of a 400 nm LED lamp (10 W) device at 35 °C for 24 h. After the reaction was completed, CH2Br2was added as an internal standard, and the amount of formic acid was calculated by 1H NMR analysis, which gave a yield of 4%.

[0109] 1H NMR of formic acid: 1 H NMR (400 MHz, CDC13) δ 8.03 (s, 1H).

[0110] Example 15

[0111] Polyethylene degradation:

[0112]

[0113] In a 25 mL reaction tube, polyethylene (Mw= 4000, 5.6 mg), hydrochloric acid (0.02 mmol), chlorobenzene (CB, 2.0 mL) were added. After the reaction tube was sealed, it was cooled using liquid nitrogen, followed by replacing the air in the reaction tube with oxygen (1.0 atm) on a double manifold. It was then illuminated in front of a 400 nm LED lamp (10 W) device at 100 °C for 24 h. After the reaction was completed, CH2Br2was added as an internal standard, and the amount of formic acid was calculated by 1H NMR analysis, which gave a yield of 6%.

[0114] Example 16

[0115] Polypropylene degradation:

[0116]

[0117] In a 25 mL reaction tube, polypropylene (Mw= 4000, 8.4 mg), hydrochloric acid (0.02 mmol), chlorobenzene (CB, 2.0 mL) were added. After the reaction tube was sealed, it was cooled using liquid nitrogen, followed by replacing the air in the reaction tube with oxygen (1.0 atm) on a double manifold. It was then illuminated in front of a 400 nm LED lamp (10 W) device at 100 °C for 24 h. After the reaction was completed, CH2Br2was added as an internal standard, and the amount of formic acid was calculated by 1H NMR analysis, which gave a yield of 6%.

[0118] 1H NMR of acetone: 1H NMR (400 MHz, CDC13) δ 2.12 (s, 6H).

[0119] The NMR hydrogen spectrum of formic acid is: 1 H NMR (400 MHz, CDC13) δ 8.03 (s, 1H).

[0120] Example 17:

[0121] Polyethylene terephthalate degradation:

[0122]

[0123] In a 25 mL reaction tube, polyethylene terephthalate (Mw= 30000, 45.6 mg), hydrochloric acid (0.02 mmol), chlorobenzene (CB, 2.0 mL) were added. After sealing the reaction tube, it was cooled using liquid nitrogen, followed by replacing the air in the reaction tube with oxygen (1.0 atm) on a double manifold. Then it was irradiated in front of a 400 nm LED lamp (10 W) device at 100 °C for 24 h. After the reaction was completed, it was cooled to room temperature, CH2Br2was added as an internal standard, and formic acid (yield 82%) was obtained by NMR hydrogen spectrum analysis. Then the solvent was removed under reduced pressure, and silica gel flash chromatography was used to purify to obtain terephthalic acid (17.3 mg, yield 52%). The NMR hydrogen spectrum of terephthalic acid is shown in Figure 5 , and the NMR carbon spectrum is shown in Figure 6 .

[0124] The NMR hydrogen and carbon spectra of terephthalic acid are: 1 H NMR (400 MHz, DMSO) δ 13.25 (s, 2H), 8.04 (s, 4H). 13 C NMR (100 MHz, DMSO) δ 167.2, 135.0, 129.9.

[0125] Example 18:

[0126] Butyl rubber degradation:

[0127]

[0128] A 25 mL reaction tube was charged with butadiene-styrene rubber (Mw = 140000, 31.6 mg), hydrochloric acid (0.02 mmol), CH2Cl2(2.0 mL). After the reaction tube was sealed, it was cooled using liquid nitrogen, followed by replacing the air in the reaction tube with oxygen (1.0 atm) on a double manifold. It was then illuminated in front of a 400 nm LED lamp (10 W) setup at 35 °C for 24 h. After the reaction was complete, it was cooled to room temperature, CH2Br2was added as an internal standard, and the formic acid was analyzed by nuclear magnetic hydrogen and carbon spectroscopy (yield 50%). The solvent was then removed under reduced pressure, and the benzoic acid was purified by flash chromatography on silica gel (4.4 mg, 18% yield).

[0129] Example 19:

[0130] Degradation of acrylonitrile-styrene resin:

[0131]

[0132] A 25 mL reaction tube was charged with acrylonitrile-styrene resin (Mw = 165000, 31.4 mg), hydrochloric acid (0.02 mmol), CH2Cl2(2.0 mL). After the reaction tube was sealed, it was cooled using liquid nitrogen, followed by replacing the air in the reaction tube with oxygen (1.0 atm) on a double manifold. It was then illuminated in front of a 400 nm LED lamp (10 W) setup at 35 °C for 24 h. After the reaction was complete, it was cooled to room temperature, CH2Br2was added as an internal standard, and the formic acid was analyzed by nuclear magnetic hydrogen and carbon spectroscopy (yield 62%). The solvent was then removed under reduced pressure, and the benzoic acid was purified by flash chromatography on silica gel (5.4 mg, 22% yield).

[0133] Example 20:

[0134] Degradation of styrene-maleic anhydride copolymer:

[0135]

[0136] A 25 mL reaction tube was charged with styrene-maleic anhydride copolymer (Mw = 60000, 40.4 mg), hydrochloric acid (0.02 mmol), CH2Cl2(2.0 mL). After the reaction tube was sealed, it was cooled using liquid nitrogen, followed by replacing the air in the reaction tube with oxygen (1.0 atm) on a double manifold. It was then illuminated in front of a 400 nm LED lamp (10 W) setup at 35 °C for 24 h. After the reaction was complete, it was cooled to room temperature, CH2Br2was added as an internal standard, and the formic acid was analyzed by nuclear magnetic hydrogen and carbon spectroscopy (yield 35%). The solvent was then removed under reduced pressure, and the benzoic acid was purified by flash chromatography on silica gel (3.7 mg, 15% yield).

[0137] Example 21

[0138] Polystyrene degradation:

[0139]

[0140] In a 25 mL reaction tube, polystyrene (Mw = 260000, 20.8 mg), hydrochloric acid (0.02 mmol), acetonitrile (CH3CN, 2.0 mL) were added. After the reaction tube was sealed, it was cooled using liquid nitrogen, followed by replacing the air in the reaction tube with oxygen (1.0 atm) on a double-tube. Then it was illuminated on a 400 nm LED lamp (10 W) device at 35 °C for 24 hours. After the reaction was completed, it was cooled to room temperature, the solvent was removed under reduced pressure, and silica gel flash chromatography was used for purification to obtain benzoic acid (5.3 mg, yield 22%) and acetophenone (4.3 mg, yield 18%).

[0141] According to the polymer degradation method provided in the embodiments of the present application, under visible light conditions, the polymer and the oxidizing agent undergo an oxidation reaction under the action of the catalyst at a temperature of 0-100 °C to generate an oxidation product, thereby realizing efficient and green degradation of the polymer. The degradation method has low reaction cost, can convert the polymer into high-value chemical products at a high reaction rate, and is simple to operate and safe, and is a mild and environmentally friendly degradation method. Using the degradation method of the present application to degrade the polymer can solve the problems of increased reaction cost and environmental pollution in the degradation process of the polymer.

[0142] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for degrading a polymer, comprising the following steps: under visible light conditions, the polymer and an oxidant undergo an oxidation reaction in the presence of a catalyst to generate oxidation products; wherein, The polymer is selected from any one of polystyrene, polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, styrene-butadiene rubber, acrylonitrile-styrene resin, and styrene-maleic anhydride copolymer. The oxidant is selected from oxygen or air, and the pressure of the oxidant gas is 1 atm-100 atm; The oxidation reaction occurs at a temperature of 0℃-100℃ and a reaction time of 8h-48h. The molar ratio of the monomers constituting the polymer to the catalyst is 1:(0.001-0.5); The catalyst is selected from: 1) A halogenated organic solvent, wherein the halogenated organic solvent is selected from at least one of dichloromethane, 1,1-dichloroethane, 1,2-dichloroethane, trichloroethane, tetrachloroethane, dibromomethane, 1,1-dibromoethane, 1,2-dibromoethane, trichloromethane, tribromomethane, tetrachloromethane, tetrabromomethane, chlorobenzene, bromobenzene, dichlorobenzene, dibromobenzene, trichlorobenzene and tribromobenzene; 2) Any one of tert-butyl hypochlorite, hydrochloric acid, or hydrobromic acid; 3) A mixture consisting of a halogenated organic solvent and a haloacid; The halogen-containing organic solvent is selected from at least one of dichloromethane, 1,1-dichloroethane, 1,2-dichloroethane, trichloroethane, tetrachloroethane, dibromomethane, 1,1-dibromoethane, 1,2-dibromoethane, trichloromethane, tribromomethane, tetrachloromethane, tetrabromomethane, chlorobenzene, bromobenzene, dichlorobenzene, dibromobenzene, trichlorobenzene, and tribromobenzene; The haloacid is selected from at least one of hydrochloric acid or hydrobromic acid; 4) A mixture consisting of a halogenated organic solvent and a mixture of in-situ generated haloacids, wherein the mixture of in-situ generated haloacids is selected from any one of a mixture of lithium chloride and acetic acid, a mixture of sodium chloride and acetic acid, or a mixture of sodium bromide and acetic acid.

2. The degradation method according to claim 1, wherein, The wavelength of the visible light is 300nm-800nm.

3. The degradation method according to claim 1, wherein, The oxidation reaction further includes the addition of a solvent selected from at least one of acetonitrile, acetone, tetrahydrofuran, dichloromethane, 1,1-dichloroethane, 1,2-dichloroethane, trichloroethane, tetrachloroethane, dibromomethane, 1,1-dibromoethane, 1,2-dibromoethane, trichloromethane, tribromomethane, tetrachloromethane, tetrabromomethane, chlorobenzene, bromobenzene, dichlorobenzene, dibromobenzene, trichlorobenzene, tribromobenzene, and N,N-dimethylformamide.

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