Method for catalyzing styrene epoxidation with silicon carbide quantum dots

Abstract

The application belongs to the field of catalyst preparation and provides a method for catalyzing styrene epoxidation by silicon carbide quantum dots. The method for catalyzing styrene epoxidation by silicon carbide quantum dots comprises the following steps: uniformly mixing styrene or its derivative, an organic solvent and silicon carbide quantum dots to form a suspension, transferring the suspension to a reaction kettle, sealing the reaction kettle, purging with oxygen, pressurizing, heating and stirring to react. The method for catalyzing styrene epoxidation by silicon carbide quantum dots provided by the application can reach a styrene conversion rate of 100% and a styrene oxide selectivity of 90%. The reaction process is green and environmentally friendly, the reaction conditions are mild, the time period is short, the operation is simple, the product yield is high, and the cost is low. Therefore, the method is an efficient and environmentally friendly styrene epoxidation process.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation and relates to a method for catalyzing the epoxidation of styrene using silicon carbide quantum dots. Background Technology

[0002] Epoxidized phenylene oxide, an important organic intermediate, is colorless, odorless, and water-soluble, widely used in the production of fragrances, pharmaceuticals, and organic synthesis, such as in the hydrogenation process to produce phenylethanol. Traditional methods for preparing epoxidized phenylene oxide include the bromoethanol method, the chloroethanol method, and the Halcon method. These methods have certain drawbacks, such as expensive raw materials, high production costs, numerous side reactions, complex products, and the generation of large amounts of corrosive and hazardous waste, causing environmental pollution. Although traditional catalysts have been gradually replaced by transition metal catalysts and oxidants, most of these transition metal catalysts are toxic to humans and expensive. Therefore, there is an urgent need to develop a higher-quality, more environmentally friendly method to optimize the epoxidation process of epoxidized phenylene oxide. Summary of the Invention

[0003] This invention provides a method for epoxidation of styrene using silicon carbide quantum dots as a catalyst. This method uses silicon carbide quantum dots as a catalyst, and the production process of epoxidation of styrene oxide is more environmentally friendly and has a high conversion rate.

[0004] The method for catalyzing the epoxidation of styrene using silicon carbide quantum dots includes the following steps:

[0005] Styrene or its derivatives, an organic solvent, and silicon carbide quantum dots are mixed evenly to form a suspension. The suspension is then transferred to a reaction vessel, sealed, purged with oxygen, pressurized, heated, and stirred before the reaction proceeds.

[0006] Furthermore, the ratio of styrene or its derivatives, organic solvent, and silicon carbide quantum dots is (5-20) mg:(10-50) ml:1 nmol;

[0007] The organic solvent is selected from one or more of cyclohexanone, acetonitrile, and N,N-dimethylformamide;

[0008] The reaction pressure is 0.1–2 MPa, the reaction temperature is 30–110 °C, and the reaction time is 6 h.

[0009] The oxygen purging is performed 3-6 times.

[0010] Furthermore, the ratio of styrene or its derivatives, organic solvent, and silicon carbide quantum dots is 20 mg: 20 ml: 1 nmol;

[0011] The organic solvent is selected from cyclohexanone;

[0012] The reaction pressure was 0.1 MPa, the reaction temperature was 70°C, and the reaction time was 6 hours.

[0013] Furthermore, the silicon carbide quantum dots are prepared by the following method:

[0014] Silicon carbide was dispersed in a mixed aqueous solution of hydrofluoric acid and nitric acid, heated to 100°C in a hydrothermal reactor and maintained for 1-6 hours. After being removed and cooled to room temperature, the solution was diluted with deionized water and ultrasonically vibrated. Large particles were then removed by centrifugation, and the acidity of the solution was removed by solvent evaporation and quantum dot redispersement. After dialysis, the solution was freeze-dried to obtain the silicon carbide quantum dots.

[0015] Furthermore, the ratio of the silicon carbide to the hydrofluoric acid-nitric acid mixed aqueous solution is 1g:2ml-20ml;

[0016] The hydrofluoric acid-nitric acid mixed aqueous solution contains hydrofluoric acid (40 wt%) and nitric acid (65 wt%) in a volume ratio of 0.5-3:1.

[0017] Furthermore, the ratio of the silicon carbide to the hydrofluoric acid-nitric acid mixed aqueous solution is 1g:10ml;

[0018] The hydrofluoric acid-nitric acid mixed aqueous solution has a volume ratio of 3:1 for hydrofluoric acid and nitric acid.

[0019] Further, dilute with 10-50 ml of deionized water and sonicate for 30-120 min.

[0020] Centrifugation speed is 8000-10000 rpm, duration is 5-15 min;

[0021] The solvent evaporates at a temperature of 90-150℃ for 12-24 hours.

[0022] The volume of deionized water added during redispersion is 10-50 ml, the molecular weight cutoff of the dialysis membrane is 8000-14000, and the dialysis time is 12-36 h.

[0023] The freeze-drying temperature is -60℃, and the freeze-drying time is 1-24h;

[0024] The particle size of silicon carbide quantum dots is 1-6 nm.

[0025] Further, the volume of deionized water added was 30 ml, and the sonication time was 60 min;

[0026] The volume of deionized water added during redispersion was 30 ml.

[0027] Furthermore, the heating method is water bath heating;

[0028] The freeze-drying method involves quick-freezing with liquid nitrogen and then placing the product into a freeze dryer.

[0029] Beneficial effects:

[0030] The styrene epoxidation method using silicon carbide quantum dots catalyzed by this invention can achieve a styrene conversion rate of up to 100% and an epoxy phenylene oxide selectivity of up to 90%. The reaction process generates no harmful gases, is environmentally friendly, operates under mild conditions, has a short reaction time, and is simple to operate. Furthermore, it offers high product yield and low cost, making it a highly efficient and environmentally friendly styrene epoxidation process. Attached Figure Description

[0031] Figure 1 The flowchart illustrates the method for epoxidation of styrene using silicon carbide quantum dots as a catalyst, as provided by this invention. Detailed Implementation

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but this should not be construed as limiting the scope of the present invention.

[0033] See Figure 1 This invention provides a method for catalyzing the epoxidation of styrene using silicon carbide quantum dots, comprising the following steps:

[0034] Styrene or its derivatives, an organic solvent, and silicon carbide quantum dots are mixed evenly to form a suspension. The suspension is then transferred to a reaction vessel, sealed, purged with oxygen, pressurized, heated, and stirred before the reaction proceeds.

[0035] Silicon carbide quantum dots are prepared by the following method:

[0036] Silicon carbide was dispersed in a mixed aqueous solution of hydrofluoric acid and nitric acid, heated to 100°C in a hydrothermal reactor and maintained for 1-6 hours. After being removed and cooled to room temperature, the solution was diluted with deionized water and ultrasonically vibrated. Large particles were then removed by centrifugation, and the acidity of the solution was removed by solvent evaporation and quantum dot redispersement. After dialysis, the solution was freeze-dried to obtain the silicon carbide quantum dots.

[0037] Carbon-based catalysts often exhibit high catalytic activity and renewability, but they are flammable and lack good stability at high temperatures. Silicon carbide quantum dots (SiC QDs), as an emerging nanomaterial, possess the honeycomb structure of graphene and the excellent electrical and thermal conductivity and good thermal stability of SiC. The silicon carbide quantum dots prepared by the method provided in this invention have a surface rich in hydroxyl and carboxyl groups, which are highly beneficial for catalyzing oxidation reactions and can serve as ideal catalysts in epoxidation reactions.

[0038] Example 1

[0039] 1.00 g of SiC was weighed and dispersed in a mixed aqueous solution of 7.5 ml hydrofluoric acid and 2.5 ml nitric acid. The solution was transferred to a hydrothermal reactor, sealed, and heated at 100 °C for 1 h. After removal, the solution was cooled to room temperature. 30 ml of deionized water was added, and the mixture was ultrasonically vibrated for 1 h. After centrifugation, the supernatant was evaporated to dryness, and 30 ml of deionized water was added again for redispersing. After dialyzing, the solution was freeze-dried to obtain the SiC QDs catalyst.

[0040] 5 mg of the SiC QDs catalyst prepared by the above method was weighed and placed in a high-temperature and high-pressure reactor. 20 ml of cyclohexanone and 1 mmol of styrene were added to the reactor. After sealing and purging with oxygen four times, the oxygen pressure was maintained at 0.1 MPa. Under stirring, the reaction system was heated to 70°C for 6 hours. The conversion rate of styrene was 35%, and the selectivity for epoxide was 70%.

[0041] Example 2

[0042] 1.00 g of SiC was weighed and dispersed in a mixed aqueous solution of 7.5 ml hydrofluoric acid and 2.5 ml nitric acid. The solution was transferred to a hydrothermal reactor, sealed, and heated at 100 °C for 1 h. After removal, the solution was cooled to room temperature. 30 ml of deionized water was added, and the mixture was ultrasonically vibrated for 1 h. After centrifugation, the supernatant was evaporated to dryness, and 30 ml of deionized water was added again for redispersing. After dialyzing, the solution was freeze-dried to obtain the SiC QDs catalyst.

[0043] 20 mg of the SiC QDs catalyst prepared by the above method was weighed and placed in a high-temperature and high-pressure reactor. 20 ml of cyclohexanone and 1 mmol of styrene were added to the reactor. After sealing and purging with oxygen four times, the oxygen pressure was maintained at 0.1 MPa. Under stirring, the reaction system was heated to 70°C for 6 hours. The conversion rate of styrene was 87%, and the selectivity for epoxide was 90%.

[0044] Compared with Example 1, increasing the amount of SiC QDs catalyst can significantly improve the conversion rate of styrene and the selectivity of epoxide phenylene oxide.

[0045] Example 3

[0046] 1.00 g of SiC was weighed and dispersed in a mixed aqueous solution of 7.5 ml hydrofluoric acid and 2.5 ml nitric acid. The solution was transferred to a hydrothermal reactor, sealed, and heated at 100 °C for 1 h. After removal, the solution was cooled to room temperature. 30 ml of deionized water was added, and the mixture was ultrasonically vibrated for 1 h. After centrifugation, the supernatant was evaporated to dryness, and 30 ml of deionized water was added again for redispersing. After dialyzing, the solution was freeze-dried to obtain the SiC QDs catalyst.

[0047] 20 mg of the SiC QDs catalyst prepared by the above method was weighed and placed in a high-temperature and high-pressure reactor. 20 ml of acetonitrile and 1 mmol of styrene were added to the reactor. After sealing and purging with oxygen four times, the oxygen pressure was maintained at 0.1 MPa. Under stirring, the reaction system was heated to 70°C for 6 hours. The conversion rate of styrene was 30%, and the selectivity for epoxide was 60%.

[0048] Example 4

[0049] 1.00 g of SiC was weighed and dispersed in a mixed aqueous solution of 7.5 ml hydrofluoric acid and 2.5 ml nitric acid. The solution was transferred to a hydrothermal reactor, sealed, and heated at 100 °C for 1 h. After removal, the solution was cooled to room temperature. 30 ml of deionized water was added, and the mixture was ultrasonically vibrated for 1 h. After centrifugation, the supernatant was evaporated to dryness, and 30 ml of deionized water was added again for redispersing. After dialyzing, the solution was freeze-dried to obtain the SiC QDs catalyst.

[0050] 20 mg of the SiC QDs catalyst prepared by the above method was weighed and placed in a high-temperature and high-pressure reactor. 20 ml of ethanol and 1 mmol of styrene were added to the reactor. After sealing and purging with oxygen four times, the oxygen pressure was maintained at 0.1 MPa. Under stirring, the reaction system was heated to 70 °C for 6 hours. The conversion rate of styrene was 37%, and the selectivity of epoxide was 48%.

[0051] Example 5

[0052] 1.00 g of SiC was weighed and dispersed in a mixed aqueous solution of 7.5 ml hydrofluoric acid and 2.5 ml nitric acid. The solution was transferred to a hydrothermal reactor, sealed, and heated at 100 °C for 1 h. After removal, the solution was cooled to room temperature. 30 ml of deionized water was added, and the mixture was ultrasonically vibrated for 1 h. After centrifugation, the supernatant was evaporated to dryness, and 30 ml of deionized water was added again for redispersing. After dialyzing, the solution was freeze-dried to obtain the SiC QDs catalyst.

[0053] 20 mg of the SiC QDs catalyst prepared by the above method was weighed and placed in a high-temperature and high-pressure reactor. 20 ml of N,N-dimethylformamide and 1 mmol of styrene were added to the reactor. The reactor was sealed and purged with oxygen four times. The oxygen pressure was maintained at 0.1 MPa. Under stirring, the reaction system was heated to 70°C for 6 hours. The conversion rate of styrene was 35%, and the selectivity for epoxide was 77%.

[0054] Compared to Example 2, the solvents used in Examples 3 to 5 are different. The mechanism of a conventional epoxidation reaction can be broadly divided into two stages: (1) activation of molecular oxygen on the catalyst surface; and (2) selective epoxidation of C=C bonds. According to Examples 2 to 5, solvents with ketone structures, especially cyclic ketone structures, play a crucial role in the reaction mechanism and oxygen activation. The conversion rate of cyclohexanone, the solvent used in Example 2, is significantly higher than in other cases. Furthermore, cyclohexanone can interact with oxygen atoms adsorbed on the SiC QDs surface to form free radicals, and styrene is activated on the SiC QDs surface to form free radicals. The peroxide formed by the interaction of these two components spontaneously dissociates, thereby promoting the increased selectivity of epoxide phenylene oxide. Therefore, the use of cyclohexanone plays a crucial role in the reaction mechanism and oxidation activation process, thus offering a more significant advantage in choosing cyclohexanone as a solvent.

[0055] Example 6

[0056] 1.00 g of SiC was weighed and dispersed in a mixed aqueous solution of 7.5 ml hydrofluoric acid and 2.5 ml nitric acid. The solution was transferred to a hydrothermal reactor, sealed, and heated at 100 °C for 1 h. After removal, the solution was cooled to room temperature. 30 ml of deionized water was added, and the mixture was ultrasonically vibrated for 1 h. After centrifugation, the supernatant was evaporated to dryness, and 30 ml of deionized water was added again for redispersing. After dialyzing, the solution was freeze-dried to obtain the SiC QDs catalyst.

[0057] 20 mg of the SiC QDs catalyst prepared by the above method was weighed and placed in a high-temperature and high-pressure reactor. 20 ml of cyclohexanone and 1 mmol of styrene were added to the reactor. After sealing and purging with oxygen four times, the oxygen pressure was maintained at 0.5 MPa. Under stirring, the reaction system was heated to 70°C for 6 hours. The conversion rate of styrene was 100%, and the selectivity for epoxide was 78%.

[0058] Compared to Example 2, Example 6 introduced excessive oxygen, causing styrene to be over-oxidized to form benzaldehyde, thereby reducing the selectivity of epoxide phenylene oxide.

[0059] Example 7

[0060] 1.00 g of SiC was weighed and dispersed in a mixed aqueous solution of 7.5 ml hydrofluoric acid and 2.5 ml nitric acid. The solution was transferred to a hydrothermal reactor, sealed, and heated at 100 °C for 1 h. After removal, the solution was cooled to room temperature. 30 ml of deionized water was added, and the mixture was ultrasonically vibrated for 1 h. After centrifugation, the supernatant was evaporated to dryness, and 30 ml of deionized water was added again for redispersing. After dialyzing, the solution was freeze-dried to obtain the SiC QDs catalyst.

[0061] 20 mg of the SiC QDs catalyst prepared by the above method was weighed and placed in a high-temperature and high-pressure reactor. 20 ml of cyclohexanone and 1 mmol of styrene were added to the reactor. After sealing and purging with oxygen four times, the oxygen pressure was maintained at 0.1 MPa. Under stirring, the reaction system was heated to 100°C for 6 hours. The conversion rate of styrene was 100%, and the selectivity for epoxide was 82%.

[0062] Compared with Example 2, increasing the reaction temperature in Example 6 can accelerate the reaction rate of styrene, but it also causes styrene to be over-oxidized to form benzaldehyde, thereby reducing the selectivity of epoxide phenyl ethane.

[0063] Example 8

[0064] 1.00 g of SiC was weighed and dispersed in a mixed aqueous solution of 7.5 ml hydrofluoric acid and 2.5 ml nitric acid. The solution was transferred to a hydrothermal reactor, sealed, and heated at 100 °C for 1 h. After removal, the solution was cooled to room temperature. 30 ml of deionized water was added, and the mixture was ultrasonically vibrated for 1 h. After centrifugation, the supernatant was evaporated to dryness, and 30 ml of deionized water was added again for redispersing. After dialyzing, the solution was freeze-dried to obtain the SiC QDs catalyst.

[0065] 20 mg of the SiC QDs catalyst prepared by the above method was weighed and placed in a high-temperature and high-pressure reactor. 20 ml of cyclohexanone and 1 mmol of 4-methylstyrene were added to the reactor. After sealing and purging with oxygen four times, the oxygen pressure was maintained at 0.1 MPa. Under stirring, the reaction system was heated to 70°C for 6 hours. The conversion rate of styrene was 74%, and the selectivity for epoxide was 78%.

[0066] Example 9

[0067] 1.00 g of SiC was weighed and dispersed in a mixed aqueous solution of 7.5 ml hydrofluoric acid and 2.5 ml nitric acid. The solution was transferred to a hydrothermal reactor, sealed, and heated at 100 °C for 1 h. After removal, the solution was cooled to room temperature. 30 ml of deionized water was added, and the mixture was ultrasonically vibrated for 1 h. After centrifugation, the supernatant was evaporated to dryness, and 30 ml of deionized water was added again for redispersing. After dialyzing, the solution was freeze-dried to obtain the SiC QDs catalyst.

[0068] 20 mg of the SiC QDs catalyst prepared by the above method was weighed and placed in a high-temperature and high-pressure reactor. 20 ml of cyclohexanone and 1 mmol of 3-methylstyrene were added to the reactor. The reactor was sealed and purged with oxygen four times. The oxygen pressure was maintained at 0.1 MPa. Under stirring, the reaction system was heated to 70 °C for 6 hours. The conversion rate of styrene was 65%, and the selectivity for epoxide was 70%.

[0069] Example 10

[0070] 1.00 g of SiC was weighed and dispersed in a mixed aqueous solution of 7.5 ml hydrofluoric acid and 2.5 ml nitric acid. The solution was transferred to a hydrothermal reactor, sealed, and heated at 100 °C for 1 h. After removal, the solution was cooled to room temperature. 30 ml of deionized water was added, and the mixture was ultrasonically vibrated for 1 h. After centrifugation, the supernatant was evaporated to dryness, and 30 ml of deionized water was added again for redispersing. After dialyzing, the solution was freeze-dried to obtain the SiC QDs catalyst.

[0071] 20 mg of the SiC QDs catalyst prepared by the above method was weighed and placed in a high-temperature and high-pressure reactor. 20 ml of cyclohexanone and 1 mmol of 2-methylstyrene were added to the reactor. The reactor was sealed and purged with oxygen four times. The oxygen pressure was maintained at 0.1 MPa. Under stirring, the reaction system was heated to 70 °C for 6 hours. The conversion rate of styrene was 60%, and the selectivity for epoxide was 62%.

[0072] Compared with Example 2, styrene with different substituents in Examples 8, 9 and 10 can all undergo epoxidation, but the selectivity is slightly reduced.

[0073] Comparative Example 1

[0074] 1.00 g of Co(NO3)2 was weighed into a crucible and calcined at 550 °C for 8 h. After grinding, CoO was obtained. x catalyst.

[0075] Weigh 20 mg of the CoO prepared by the above method x The catalyst was placed in a high-temperature, high-pressure reactor. 20 ml of cyclohexanone and 1 mmol of styrene were added to the reactor. After sealing and purging with oxygen four times, the oxygen pressure was maintained at 0.5 MPa. Under stirring, the reaction system was heated to 70°C for 6 hours. The conversion rate of styrene was 55%, and the selectivity for epoxide was 72%.

[0076] Comparative Example 2

[0077] 1.00 g of AgNO3 was weighed into a crucible and calcined at 550 °C for 8 h. After grinding, AgO catalyst was obtained.

[0078] 20 mg of the Ag / SiC catalyst prepared by the above method was weighed and placed in a high-temperature and high-pressure reactor. 20 ml of cyclohexanone and 1 mmol of styrene were added to the reactor. After sealing and purging with oxygen three times, the oxygen pressure was maintained at 0.1 MPa. Under stirring, the reaction system was heated to 70°C for 6 hours. The conversion rate of styrene was 63%, and the selectivity for epoxide was 75%.

[0079] Comparative Examples 1 and 2 used metal oxides commonly used in epoxidation reactions as catalysts. The catalyst described in this invention, compared to those in Comparative Examples 1 and 2 which did not contain any metal as a catalyst, exhibits performance comparable to metal-based catalysts.

[0080] In summary, this invention represents the first application of non-metallic catalysts, SiC QDs, in the epoxidation reaction of styrene, achieving a styrene conversion rate of up to 57% and a selectivity for epoxides of phenylene oxide up to 82%. This experiment provides an environmentally friendly, efficient, and metal-free catalyst for the epoxidation of styrene and styrene containing other substituents on the benzene ring. Its reaction mechanism differs from traditional metal-based catalysts, while its performance is similar to metal-based catalysts, offering a new approach for developing high-performance non-metallic catalysts.

[0081] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for epoxidizing styrene using silicon carbide quantum dots as catalysts, characterized in that, Includes the following steps: Styrene or its derivatives, organic solvents and silicon carbide quantum dots are mixed evenly to form a suspension. The suspension is transferred to a reaction vessel and sealed. After being purged with oxygen, the mixture is pressurized, heated and stirred to react. The ratio of styrene or its derivatives, organic solvent and silicon carbide quantum dots is (5-20) mg: (10-50) ml: 1 nmol; The organic solvent is selected from one or more of cyclohexanone, acetonitrile, and N,N-dimethylformamide; The silicon carbide quantum dots are prepared by the following method: silicon carbide is dispersed in a mixed aqueous solution of hydrofluoric acid and nitric acid, heated to 100°C in a hydrothermal reactor and maintained for 1-6 hours, then removed and cooled to room temperature, diluted with deionized water and ultrasonically vibrated, then large particles are removed by centrifugation, the acidity of the solution is removed by solvent evaporation and quantum dot redispersion, dialyzed and then freeze-dried to obtain the silicon carbide quantum dots. The reaction pressure is 0.1–2 MPa, the reaction temperature is 30–110 °C, and the reaction time is 6 h.

2. The method for epoxidation of styrene using silicon carbide quantum dots as described in claim 1, characterized in that, The oxygen purging is performed 3-6 times.

3. The method for epoxidation of styrene using silicon carbide quantum dots as described in claim 1, characterized in that, The ratio of styrene or its derivatives, organic solvent and silicon carbide quantum dots is 20 mg: 20 ml: 1 nmol; The organic solvent is selected from cyclohexanone; The reaction pressure was 0.1 MPa, the reaction temperature was 70°C, and the reaction time was 6 hours.

4. The method for epoxidation of styrene using silicon carbide quantum dots as described in claim 1, characterized in that, The ratio of silicon carbide to the hydrofluoric acid-nitric acid mixed aqueous solution is 1g: 2ml-20ml; The hydrofluoric acid-nitric acid mixed aqueous solution has a volume ratio of hydrofluoric acid to nitric acid of 0.5-3:

1.

5. The method for epoxidation of styrene using silicon carbide quantum dots as described in claim 4, characterized in that, The ratio of silicon carbide to the hydrofluoric acid-nitric acid mixed aqueous solution is 1g:10ml; The hydrofluoric acid-nitric acid mixed aqueous solution has a volume ratio of 3:1 for hydrofluoric acid and nitric acid.

6. The method for epoxidation of styrene using silicon carbide quantum dots as described in claim 1, characterized in that, The volume of deionized water added for dilution is 10-50 ml, and the sonication time is 30-120 min. Centrifugation speed is 8000-10000 rpm, duration is 5-15 min; The solvent evaporates at a temperature of 90-150℃ for 12-24 hours. The volume of deionized water added during redispersion is 10-50 ml, the molecular weight cutoff of the dialysis membrane is 8000-14000, and the dialysis time is 12-36 h. The freeze-drying temperature is -60℃, and the freeze-drying time is 1-24h; The particle size of silicon carbide quantum dots is 1-6 nm.

7. The method for epoxidation of styrene using silicon carbide quantum dots as described in claim 6, characterized in that, The volume of deionized water added for dilution is 30 ml, and the sonication time is 60 min. The volume of deionized water added during redispersion was 30 ml.

8. The method for epoxidation of styrene using silicon carbide quantum dots as described in claim 1, characterized in that, The heating method is water bath heating; The freeze-drying method involves quick-freezing with liquid nitrogen and then placing the product into a freeze dryer.

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