CuNiSn-based molten catalyst for preparing graphene and preparation method of CuNiSn-based molten catalyst

Abstract

The invention relates to the technical field of preparation of catalysts, in particular to a CuNiSn-based molten catalyst for preparing graphene and a preparation method of the CuNiSn-based molten catalyst for preparing the graphene. The preparation method comprises the steps that S1, NiO-SnO2 precursor powder is prepared; s2, NiO-SnO2 powder and copper particles are mixed, mixed gas with the volume ratio of nitrogen to hydrogen being 1: 2 is injected into a reactor, then the temperature is increased to 800 DEG C, heat preservation is conducted for 3-4 h, and CuNi-Sn alloy blocks are obtained after the temperature is decreased to the room temperature; and S3, a smelting furnace is preheated in advance and pumped to a high-vacuum state, the CuNi-Sn alloy block and the alloy modifier are put into a crucible and put into the smelting furnace, it is ensured that the CuNi-Sn alloy block and the alloy modifier are fully mixed with the CuNi-Sn alloy block, then heat preservation is conducted for 10-15 h, and the CuNiSn-based fusion catalyst for preparing the graphene is obtained after the CuNi-Sn alloy block is cooled to the room temperature. The low solubility and high diffusivity characteristics of Ga and the ability of In to reduce the viscosity of the Ga-Sn liquid alloy, improve the carbon diffusion kinetics and enhance the electron transfer efficiency in cooperation with a conductive network of boron-doped graphdiyne jointly act on the waste plastic cracking process, the number of carbon layers of graphene can be effectively controlled, and the specific surface area and quality of graphene can be improved.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, specifically to a CuNiSn-based molten catalyst for preparing graphene and its preparation method. Background Technology

[0002] Waste plastic disposal is one of the most pressing environmental problems facing the world. With the widespread use and rapid increase in consumption of plastic products, the accumulation of waste plastics has reached alarming levels. Traditional methods for waste plastic disposal mainly include landfill, incineration, and recycling. However, these methods all have significant limitations and environmental problems. While landfilling is simple and easy, waste plastics are difficult to degrade in soil, occupying land resources for a long time and potentially polluting soil and groundwater. Incineration produces large amounts of harmful gases and particulate matter, posing a serious threat to air quality. Although recycling is a more environmentally friendly method, its practical application is not ideal due to the diversity of plastic types, the complexity of recycling technologies, and the uncertainty of the quality of recycled plastics.

[0003] In recent years, researchers have been dedicated to developing efficient and environmentally friendly technologies for the degradation of waste plastics. Among these, the application of catalysts has become a hot research topic. Applying high-entropy alloy catalysts to waste plastic treatment holds promise for accelerating the degradation rate of waste plastics, reducing reaction conditions, and thus saving energy and costs. By controlling the composition and structure of high-entropy alloys, efficient degradation of specific types of waste plastics can be achieved, reducing the generation of byproducts and improving the quality and value of degradation products. The environmental impact generated during their preparation and use is relatively small, aligning with the principles of green chemistry and sustainable development. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a CuNiSn-based molten catalyst and its preparation method for graphene. Molten CuNiSn alloys are often used as catalysts in methane cracking for carbon production, exhibiting high conversion rates and considerable carbon yields. The introduction of molten Ga and In aims to: the low solubility and high diffusivity of carbon in liquid Ga create an environment conducive to uniform graphene formation; the smooth surface provided by the liquid metal and its surface electrons promote uniform graphene growth at the substrate-liquid metal interface; and the addition of metallic In reduces the viscosity of the Ga-Sn liquid alloy, enhances carbon diffusion kinetics, and synergistically strengthens the electron transfer efficiency through the conductive network of boron-doped graphynylene. By controlling the content of the metal elements Ga and In, a high-entropy alloy catalyst is prepared to control the number of carbon layers in graphene from waste plastic degradation products. This innovation not only solves the problem of waste plastic treatment but also reduces production costs and increases the economic value of products through efficient preparation of high-quality graphene, while simultaneously reducing environmental pollution, achieving a win-win situation for both environmental and economic benefits. To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a CuNiSn-based melt catalyst for graphene preparation includes the following preparation steps: S1. Preparation of NiO-SnO2 precursor powder: According to the mass fraction, 30-40 parts of nickel salt solution were annealed in argon at a temperature range of 500-750℃ for 3-5h and then dispersed in water. 10-20 parts of tin salt solution and 10-15 parts of acidic modification liquid were added. After ultrasonic dispersion for 30-50min, vacuum drying was carried out at a temperature of 120-150℃ for 4-6h. After annealing at 1850-1900℃ for 2-3h, NiO-SnO2 powder was obtained. S2. Mix NiO-SnO2 powder with 32-48 parts of copper particles, put it into a reactor, inject a mixed gas of nitrogen and hydrogen in a volume ratio of 1:2 into the reactor at room temperature, raise the temperature to 1900-2000℃ and keep it at that temperature for 3-4 hours to obtain CuNiSn liquid alloy, and then lower it to room temperature to obtain CuNiSn alloy block. S3. Preheat the melting furnace to 1000-1500℃ and evacuate it to a high vacuum state. Place the CuNiSn alloy block obtained in step S2 and 10-15 parts of alloy modifier into a crucible and place it in the melting furnace. Ensure that it is fully mixed with the CuNiSn alloy block and keep it at 1000-1500℃ for 10-15 hours. After cooling to room temperature, a CuNiSn-based molten catalyst for preparing graphene is obtained. The preparation of alloy modifiers includes the following steps: S21. Mix 0.5-2 parts of boron-doped graphynylene with 18-20 parts of N-methylpyrrolidone and ultrasonically disperse at a frequency of 40 kHz for 2-4 h to obtain a uniform dispersion. S22. Place 4-6 parts of liquid Ga and 1-3 parts of In powder in an argon-protected ball mill jar, add 8-10 parts of N-methylpyrrolidone, and ball mill at 250-300 r / min for 1-2 h to obtain a suspension; S23. Mix the uniform dispersion and suspension obtained in steps S21 and S22 and stir at 400-500 r / min for 2-4 h at 60℃ to obtain the alloy modifier.

[0005] Preferably, the preparation of the acid-modified solution includes the following steps: S11. Phosphotungstic acid and 1-ethyl-3-methylimidazolium dicyandiamide salt are mixed at a mass ratio of 1:3 to obtain an acidic mixture; S12. Add acetonitrile as a solvent to the acidic mixture obtained in step S1, and ultrasonically disperse at a frequency of 40 kHz for 2-4 hours to obtain an acid-modified solution.

[0006] Preferably, the preparation of boron-doped graphynylene includes the following steps: S211. Mix 1-3 parts of hexachlorocyclotriphosphazene and 3-5 parts of phenylacetylene, and add 0.05-0.1 parts of bis(triphenylphosphine)palladium dichloride, 0.1-0.2 parts of cuprous iodide and 45-50 parts of anhydrous tetrahydrofuran. Stir at 450-500 r / min for 15-20 min to obtain a primary mixture. S212. Add 3-5 parts of triethylamine and 0.5-0.8 parts of triethylborane to the mixture obtained in step S211, raise the temperature to 80℃, and stir at a speed of 350-400 r / min for 18-20 h to obtain a secondary mixture; S213. Cool the secondary mixture to room temperature and filter it. Wash the obtained solid with anhydrous tetrahydrofuran 3-4 times, dry it under vacuum and then crush it to obtain boron-doped graphyne.

[0007] Preferably, the nickel salt solution is selected from two or more of nickel sulfamate, nickel hypophosphite, nickel acetate, nickel nitrate, and nickel phosphate.

[0008] Preferably, the tin-containing salt solution is selected from two or more of sodium stannous acid, tin sulfate, tin tetrachloride, tin acetate, and tin fluoride.

[0009] Preferably, the frequency of ultrasonic dispersion in step S1 is 40 kHz.

[0010] Preferably, the gas flow rate in the reactor in step S2 is controlled within the range of 20-50 sccm.

[0011] A CuNiSn-based melt catalyst for preparing graphene, prepared according to the above preparation method.

[0012] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention introduces two key elements, Ga and In, through an alloy modifier, which optimizes the catalytic performance of CuNiSn-based high-entropy alloys. The boron-doped graphdiyne nanosheets synthesized through the Sonogashira coupling reaction work synergistically with the alloy modifier to form an interpenetrating conductive network during smelting. This reduces the activation energy for waste plastic degradation by 35%, significantly improves the degradation efficiency of waste plastics, reduces reaction conditions, and reduces energy consumption.

[0013] 2. This invention utilizes the low solubility and high diffusivity of Ga, and the ability of In to reduce the viscosity of Ga-Sn liquid alloys, thereby enhancing carbon diffusion kinetics and synergistically improving electron transfer efficiency through the conductive network of boron-doped graphynylene, to jointly act on the waste plastic pyrolysis process. This can effectively control the number of carbon layers in graphene and improve the specific surface area and quality of graphene.

[0014] 3. The acidic modified liquid of this invention increases the specific surface area and surface activity of NiO-SnO2 powder, providing more active sites for subsequent catalytic reactions. At the same time, it introduces acidic sites and electronic defects on the catalyst surface, which work synergistically with the alloy modifier to enhance the adsorption capacity of intermediate products of waste plastic pyrolysis and accelerate the degradation reaction. Attached Figure Description

[0015] Figure 1 This is a process flow diagram of the preparation of the CuNiSn-based molten catalyst for preparing graphene according to the present invention; Figure 2 This is a process flow diagram for preparing the alloy modifier of the present invention; Figure 3 This is a flow chart of the preparation process of the acid-modified liquid of the present invention; Figure 4 This is a flowchart of the preparation process of boron-doped graphdiyne according to the present invention. Figure 5 The image shows the XRD pattern of the CuNiSn-based molten catalyst for preparing graphene obtained in Example 1 of this invention. Figure 6 The graphene prepared by cracking waste plastic using the CuNiSn-based melt catalyst obtained in Example 1 of this invention is shown in the SEM image at the 10-micrometer scale. Figure 7 The image shows a 5-micrometer SEM image of graphene prepared by cracking waste plastics using the CuNiSn-based melt catalyst obtained in Example 1 of this invention. Detailed Implementation

[0016] The present invention will now be clearly and completely described in conjunction with embodiments thereof. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0017] Please see Figure 1-7 The present invention provides a technical solution: Using CuNiSn alloy as the matrix, combined with Ga and In as key elements in the alloy modifier, a high-entropy alloy system with excellent catalytic activity is formed. The combination of Cu, Ni, and Sn elements provides a stable catalytic platform for waste plastic pyrolysis, while the addition of Ga and In further optimizes the catalytic performance. Ga has low solubility and high diffusivity for carbon in the liquid state, which makes the distribution of carbon in liquid Ga more uniform, thus creating favorable conditions for the uniform growth of graphene. The addition of Ga can effectively reduce the aggregation of graphene and control the number of carbon layers in graphene, thereby improving the quality of graphene. The addition of In reduces the viscosity of Ga-Sn liquid alloy, improves carbon diffusion kinetics, and enhances electron transfer efficiency in conjunction with the conductive network of boron-doped graphynylene. At the same time, through the synergistic effect with boron-doped graphynylene, the redox properties of the alloy modifier can regulate the oxygen content in the reaction environment, reduce the formation of by-products, and improve the carbon conversion rate and graphene yield. Through a multi-step synthesis process, including the preparation of NiO-SnO2 precursor powder, the reduction of CuNi-Sn alloy, and the smelting of high-entropy alloy, the composition and structure of the alloy can be precisely controlled. This invention ensures that the metal and its oxides are in a molten state by controlling the temperature, and utilizes a mixed gas of nitrogen and hydrogen to ensure better mixing of the metal and its oxides in a high-temperature molten state, effectively reducing the metal oxides to elemental metals. This process optimization not only ensures uniform mixing of the alloy, but also further improves the alloy's stability and catalytic performance through quenching and tempering treatments.

[0018] Example 1 A method for preparing a CuNiSn-based melt catalyst for graphene preparation: Before preparing the CuNiSn-based molten catalyst for graphene preparation, an acidic modification solution, an alloy modifier, and boron-doped graphynylene are first prepared: The preparation of the acid-modified solution includes the following steps: S11. Phosphotungstic acid and 1-ethyl-3-methylimidazolium dicyandiamide salt are mixed at a mass ratio of 1:3 to obtain an acidic mixture; S12. Add acetonitrile as a solvent to the acidic mixture obtained in step S1, and ultrasonically disperse at a frequency of 40 kHz for 2-4 hours to obtain an acid-modified solution; The preparation of alloy modifiers includes the following steps: S21. Mix 0.5g of boron-doped graphyne with 18g of N-methylpyrrolidone and ultrasonically disperse at a frequency of 40kHz for 2h to obtain a uniform dispersion. S22. Place 4g of liquid Ga and 1g of In powder in an argon-protected ball mill jar, add 8g of N-methylpyrrolidone, and ball mill at 250r / min for 1h to obtain a suspension; S23. Mix the uniform dispersion and suspension obtained in steps S21 and S22 and stir at 400 r / min for 2 h at 60 °C to obtain the alloy modifier; The preparation of boron-doped graphdiyne includes the following steps: S211. Mix 1g of hexachlorocyclotriphosphazene and 3g of phenylacetylene, and add 0.05g of bis(triphenylphosphine)palladium dichloride, 0.1g of cuprous iodide and 45g of anhydrous tetrahydrofuran. Stir at 450r / min for 15min to obtain a primary mixture. S212. Add 3g of triethylamine and 0.5g of triethylborane to the mixture obtained in step S211, raise the temperature to 80℃, and stir at 350r / min for 18h to obtain a secondary mixture; S213. Cool the secondary mixture to room temperature and filter it. Wash the obtained solid three times with anhydrous tetrahydrofuran, dry it under vacuum and then crush it to obtain boron-doped graphyne. Preparation of NiO-SnO2 precursor powder: 15g of nickel aminosulfonate and 15g of nickel hypophosphite were annealed in argon at 500℃ for 3h and then dispersed in water. 5g of sodium stannous acid, 5g of tin sulfate and 10g of acidic modification solution were added. After ultrasonic dispersion for 30min, the mixture was vacuum dried at 120℃ for 4h, annealed at 1850℃ for 2h and cooled to room temperature to obtain NiO-SnO2 powder. S2. Mix NiO-SnO2 powder with 32g of copper particles and place it in a reactor. Under room temperature conditions, control the flow rate within the range of 20sccm and inject a mixed gas with a nitrogen and hydrogen volume ratio of 1:2 into the reactor. Then raise the temperature to 1900℃ and keep it at that temperature for 3h to obtain CuNiSn liquid alloy. After cooling to room temperature, obtain CuNiSn alloy block. S3. Preheat the melting furnace to 1000℃ and evacuate it to a high vacuum state. Place the CuNiSn alloy block obtained in step S2 and 10g of alloy modifier into a crucible and place it in the melting furnace. Ensure that it is fully mixed with the CuNiSn alloy block and keep it at 1000℃ for 10h. After cooling to room temperature, a CuNiSn-based molten catalyst for preparing graphene is obtained.

[0019] Example 2 A method for preparing a CuNiSn-based melt catalyst for graphene preparation: Before preparing the CuNiSn-based molten catalyst for graphene preparation, an acidic modification solution, an alloy modifier, and boron-doped graphynylene are first prepared: The preparation of the acid-modified solution includes the following steps: S11. Phosphotungstic acid and 1-ethyl-3-methylimidazolium dicyandiamide salt are mixed at a mass ratio of 1:3 to obtain an acidic mixture; S12. Acetonitrile is added as a solvent to the acidic mixture obtained in step S1, and the mixture is ultrasonically dispersed at a frequency of 40 kHz for 4 h to obtain an acid-modified solution; The preparation of alloy modifiers includes the following steps: S21. Mix 2g of boron-doped graphyne with 20g of N-methylpyrrolidone and ultrasonically disperse at a frequency of 40kHz for 4h to obtain a uniform dispersion. S22. Place 6g of liquid Ga and 3g of In powder in an argon-protected ball mill jar, add 10g of N-methylpyrrolidone, and ball mill at 300r / min for 2h to obtain a suspension; S23. Mix the uniform dispersion and suspension obtained in steps S21 and S22 and stir at 500 r / min for 4 h at 60 °C to obtain the alloy modifier; The preparation of boron-doped graphdiyne includes the following steps: S211. Mix 3g of hexachlorocyclotriphosphazene and 5g of phenylacetylene, and add 0.1g of bis(triphenylphosphine)palladium dichloride, 0.2g of cuprous iodide and 50g of anhydrous tetrahydrofuran. Stir at 500r / min for 20min to obtain a primary mixture. S212. Add 5g of triethylamine and 0.8g of triethylborane to the mixture obtained in step S211, raise the temperature to 80℃, and stir at 400r / min for 20h to obtain a secondary mixture; S213. Cool the secondary mixture to room temperature and filter it. Wash the obtained solid four times with anhydrous tetrahydrofuran, dry it under vacuum and then crush it to obtain boron-doped graphyne. Preparation of NiO-SnO2 precursor powder: 20g of nickel acetate and 20g of nickel nitrate were annealed in argon at 750℃ for 5h and then dispersed in water. 10g of tin tetrachloride, 10g of tin acetate and 15g of acidic modification solution were added. After ultrasonic dispersion for 50min, the mixture was vacuum dried at 150℃ for 6h, annealed at 1900℃ for 3h and cooled to room temperature to obtain NiO-SnO2 powder. S2. Mix NiO-SnO2 powder with 48g of copper particles and place it in a reactor. Under room temperature conditions, control the flow rate within the range of 50sccm and inject a mixed gas with a nitrogen and hydrogen volume ratio of 1:2 into the reactor. Then raise the temperature to 2000℃ and keep it at that temperature for 4h to obtain CuNiSn liquid alloy. After cooling to room temperature, obtain CuNiSn alloy block. S3. Preheat the melting furnace to 1500℃ and evacuate it to a high vacuum state. Place the CuNiSn alloy block obtained in step S2 and 15g of alloy modifier into a crucible and place it in the melting furnace. Ensure that it is fully mixed with the CuNiSn alloy block and keep it at 1500℃ for 15h. After cooling to room temperature, a CuNiSn-based molten catalyst for preparing graphene is obtained.

[0020] Example 3 A method for preparing a CuNiSn-based melt catalyst for graphene preparation: Before preparing the CuNiSn-based molten catalyst for graphene preparation, an acidic modification solution, an alloy modifier, and boron-doped graphynylene are first prepared: The preparation of the acid-modified solution includes the following steps: S11. Phosphotungstic acid and 1-ethyl-3-methylimidazolium dicyandiamide salt are mixed at a mass ratio of 1:3 to obtain an acidic mixture; S12. Acetonitrile is added as a solvent to the acidic mixture obtained in step S1, and the mixture is ultrasonically dispersed at a frequency of 40 kHz for 3 h to obtain an acid-modified solution; The preparation of alloy modifiers includes the following steps: S21. Mix 1g of boron-doped graphyne with 19g of N-methylpyrrolidone and ultrasonically disperse at a frequency of 40kHz for 3h to obtain a uniform dispersion. S22. Place 5g of liquid Ga and 2g of In powder in an argon-protected ball mill jar, add 9g of N-methylpyrrolidone, and ball mill at 270r / min for 1.5h to obtain a suspension; S23. Mix the uniform dispersion and suspension obtained in steps S21 and S22 and stir at 450 r / min for 3 h at 60 °C to obtain the alloy modifier; The preparation of boron-doped graphdiyne includes the following steps: S211. Mix 2g of hexachlorocyclotriphosphazene and 4g of phenylacetylene, and add 0.07g of bis(triphenylphosphine)palladium dichloride, 0.15g of cuprous iodide and 47g of anhydrous tetrahydrofuran. Stir at 470r / min for 16min to obtain a primary mixture. S212. Add 4g of triethylamine and 0.6g of triethylborane to the mixture obtained in step S211, raise the temperature to 80℃, and stir at 360r / min for 19h to obtain a secondary mixture; S213. Cool the secondary mixture to room temperature and filter it. Wash the obtained solid three times with anhydrous tetrahydrofuran, dry it under vacuum and then crush it to obtain boron-doped graphyne. Preparation of NiO-SnO2 precursor powder: 13g of nickel nitrate and 20g of nickel phosphate were annealed in argon at 600℃ for 4h to form nickel oxide, which was then dispersed in water. 7g of tin sulfate, 7g of tin acetate and 11g of acidic modification solution were added, and the mixture was ultrasonically dispersed for 40min. After vacuum drying at 130℃ for 5h, it was annealed at 1855℃ for 2.5h and cooled to room temperature to obtain NiO-SnO2 powder. S2. Mix NiO-SnO2 powder with 40g of copper granules and place it in a reactor. Under room temperature conditions, control the flow rate within the range of 30sccm and inject a mixed gas with a nitrogen and hydrogen volume ratio of 1:2 into the reactor. Then raise the temperature to 1950℃ and hold for 3.5h to obtain CuNiSn liquid alloy. After cooling to room temperature, obtain CuNiSn alloy block. S3. Preheat the melting furnace to 1100℃ and evacuate it to a high vacuum state. Place the CuNiSn alloy block obtained in step S2 and 11g of alloy modifier into a crucible and place it in the melting furnace. Ensure that it is fully mixed with the CuNiSn alloy block and keep it at 1100℃ for 11h. After cooling to room temperature, a CuNiSn-based molten catalyst for preparing graphene is obtained.

[0021] Example 4 A method for preparing a CuNiSn-based melt catalyst for graphene preparation: Before preparing the CuNiSn-based molten catalyst for graphene preparation, an acidic modification solution, an alloy modifier, and boron-doped graphynylene are first prepared: The preparation of the acid-modified solution includes the following steps: S11. Phosphotungstic acid and 1-ethyl-3-methylimidazolium dicyandiamide salt are mixed at a mass ratio of 1:3 to obtain an acidic mixture; S12. Acetonitrile is added as a solvent to the acidic mixture obtained in step S1, and the mixture is ultrasonically dispersed at a frequency of 40 kHz for 3.5 h to obtain an acid-modified solution; The preparation of alloy modifiers includes the following steps: S21. Mix 1.5g of boron-doped graphyne with 19g of N-methylpyrrolidone and ultrasonically disperse at a frequency of 40kHz for 3.5h to obtain a uniform dispersion. S22. Place 5g of liquid Ga and 2g of In powder in an argon-protected ball mill jar, add 9g of N-methylpyrrolidone, and ball mill at 290r / min for 1.5h to obtain a suspension; S23. Mix the uniform dispersion and suspension obtained in steps S21 and S22 and stir at 480 r / min for 3.5 h at 60 °C to obtain the alloy modifier; The preparation of boron-doped graphdiyne includes the following steps: S211. Mix 2g of hexachlorocyclotriphosphazene and 4g of phenylacetylene, and add 0.08g of bis(triphenylphosphine)palladium dichloride, 0.16g of cuprous iodide and 48g of anhydrous tetrahydrofuran. Stir at 480r / min for 18min to obtain a primary mixture. S212. Add 4g of triethylamine and 0.7g of triethylborane to the mixture obtained in step S211, raise the temperature to 80℃, and stir at 380r / min for 19h to obtain a secondary mixture; S213. Cool the secondary mixture to room temperature and filter it. Wash the obtained solid four times with anhydrous tetrahydrofuran, dry it under vacuum and then crush it to obtain boron-doped graphyne. Preparation of NiO-SnO2 precursor powder: 17g of nickel hypophosphite and 20g of nickel nitrate were annealed in argon at 700℃ for 4.5h and then dispersed in water. 10g of tin tetrachloride, 8g of tin fluoride and 14g of acidic modification solution were added. After ultrasonic dispersion for 45min, the mixture was vacuum dried at 140℃ for 5.5h, annealed at 1880℃ for 2.5h and cooled to room temperature to obtain NiO-SnO2 powder. S2. Mix NiO-SnO2 powder with 45g of copper granules and place it in a reactor. Under room temperature conditions, control the flow rate within the range of 40sccm and inject a mixed gas with a nitrogen and hydrogen volume ratio of 1:2 into the reactor. Then raise the temperature to 1970℃ and hold for 3.5h to obtain CuNiSn liquid alloy. After cooling to room temperature, obtain CuNiSn alloy block. S3. Preheat the melting furnace to 1400℃ and evacuate it to a high vacuum state. Place the CuNiSn alloy block obtained in step S2 and 14g of alloy modifier into a crucible and place it in the melting furnace. Ensure that it is fully mixed with the CuNiSn alloy block and keep it at 1400℃ for 14h. After cooling to room temperature, a CuNiSn-based molten catalyst for preparing graphene is obtained.

[0022] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that no acidic modifying solution was added; the other steps are exactly the same in Comparative Example 1 and Example 1.

[0023] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the alloy modifier added in Comparative Example 2 lacks liquid Ga; the other steps are exactly the same in Comparative Example 2 and Example 1.

[0024] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the alloy modifier added in Comparative Example 3 lacks In powder; the other steps are exactly the same in Comparative Example 3 and Example 1.

[0025] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that no alloy modifier was added; the other steps are exactly the same in Comparative Example 4 and Example 1.

[0026] Performance testing: The specific surface area of ​​the CuNiSn-based molten catalysts for graphene preparation obtained in Examples 1-4 and Comparative Examples 1-4 was determined by nitrogen adsorption-desorption isotherms (Micromeritics ASAP 2460) under the conditions of a pretreatment temperature of 200℃, a degassing time of 6h, and an adsorption temperature of -196℃ using the BET (Brunauer-Emmett-Teller) method, with a pretreatment temperature of 200℃, a degassing time of 6h, and an adsorption temperature of -196℃.

[0027] The CuNiSn-based molten catalysts for graphene preparation obtained in Examples 1-4 and Comparative Examples 1-4 were mixed with polyethylene (waste plastic model) at a mass ratio of 1:10 and pyrolyzed in a tube furnace at 800°C under a nitrogen atmosphere for 2 hours. The solid product was collected, washed with hydrochloric acid to remove metal residues, dried, and the mass of graphene was weighed. The carbon yield (%) = (mass of graphene / mass of initial plastic) × 100%.

[0028] The CO2 concentration in the pyrolysis tail gas was analyzed using online gas chromatography (Agilent 7890B). The difference in CO2 generation between the catalyst-free and catalyst-added conditions was compared. The CO2 removal rate (%) was calculated as (1 - CO2 concentration with catalyst / CO2 concentration without catalyst) × 100%. The final test results are shown in Table 1 below. Table 1

[0029] The specific surface area of ​​Examples 1-4 was significantly higher than that of Comparative Examples 1-3, indicating that the acidic modified liquid and boron-doped graphynylene significantly increased the active sites of the catalyst by optimizing the precursor dispersion and surface defects. The carbon yield and CO2 removal rate of Examples 1-4 were much higher than those of Comparative Examples 1-4, indicating that the alloy modifier and boron-doped graphynylene worked synergistically to significantly reduce the activation energy of waste plastic pyrolysis and improve carbon conversion efficiency.

[0030] The number of graphene layers in Examples 1-4 was significantly lower than that in Comparative Examples 1-4, indicating that the low-carbon solubility characteristics of the alloy modifier prepared from liquid Ga, In powder, and boron-doped graphdiyne effectively suppressed graphene stacking. Combined with the oxygen regulation capability of In, efficient preparation of thin-layer graphene was achieved. Comparative Example 4 (without alloy modifier) ​​had as many as 19 graphene layers, further verifying the necessity of Ga and In in regulating the graphene structure.

[0031] Appendix Figure 5The image shows the XRD pattern of the CuNiSn-based molten catalyst for preparing graphene obtained in Example 1. Except for Ga, which has a relatively high matching degree, the matching degree of other elements is low. The presence of N may be due to air that was not completely removed during the synthesis process.

[0032] Appendix Figure 6 and attached Figure 7 The attached image shows the latest SEM image of graphene prepared by pyrolyzing waste plastics using the CuNiSn-based melt catalyst obtained in Example 1 of this invention. Figure 6 Images captured at a scale of 10 micrometers, with attached Figure 7 The image was taken at a scale of 5 micrometers. The gray, transparent, flocculent material in the image is graphene prepared by cracking waste plastics using the CuNiSn-based melt catalyst obtained in Example 1 of this invention.

[0033] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a CuNiSn-based molten catalyst for graphene preparation, characterized in that, The preparation steps include the following: S1. Preparation of NiO-SnO2 precursor powder: According to the mass fraction, 30-40 parts of nickel salt solution were annealed in argon at a temperature range of 500-750℃ for 3-5h and then dispersed in water. 10-20 parts of tin salt solution and 10-15 parts of acidic modification liquid were added. After ultrasonic dispersion for 30-50min, vacuum drying was carried out at a temperature of 120-150℃ for 4-6h. After annealing at 1850-1900℃ for 2-3h, NiO-SnO2 powder was obtained. S2. Mix NiO-SnO2 powder with 32-48 parts of copper particles, put it into a reactor, inject a mixed gas of nitrogen and hydrogen in a volume ratio of 1:2 into the reactor at room temperature, raise the temperature to 1900-2000℃ and keep it at that temperature for 3-4 hours to obtain CuNiSn liquid alloy, and then lower it to room temperature to obtain CuNiSn alloy block. S3. Preheat the melting furnace to 1000-1500℃ and evacuate it to a high vacuum state. Place the CuNiSn alloy block obtained in step S2 and 10-15 parts of alloy modifier into a crucible and place it in the melting furnace. Ensure that it is fully mixed with the CuNiSn alloy block and keep it at 1000-1500℃ for 10-15 hours. After cooling to room temperature, a CuNiSn-based molten catalyst for preparing graphene is obtained. The preparation of the alloy modifier includes the following steps: S21. Mix 0.5-2 parts of boron-doped graphynylene with 18-20 parts of N-methylpyrrolidone and ultrasonically disperse at a frequency of 40 kHz for 2-4 h to obtain a uniform dispersion. S22. Place 4-6 parts of liquid Ga and 1-3 parts of In powder in an argon-protected ball mill jar, add 8-10 parts of N-methylpyrrolidone, and ball mill at 250-300 r / min for 1-2 h to obtain a suspension; S23. Mix the uniform dispersion and suspension obtained in steps S21 and S22 and stir at 400-500 r / min for 2-4 h at 60℃ to obtain the alloy modifier; The preparation of the acid-modified solution includes the following steps: S11. Phosphotungstic acid is mixed with 1-ethyl-3-methylimidazolium dicyandiamide salt to obtain an acidic mixture; S12. Add acetonitrile as a solvent to the acidic mixture obtained in step S1, and ultrasonically disperse at a frequency of 40 kHz for 2-4 hours to obtain an acid-modified solution.

2. The method for preparing a CuNiSn-based molten catalyst for graphene according to claim 1, characterized in that, The preparation of the boron-doped graphdiyne includes the following steps: S211. Mix 1-3 parts of hexachlorocyclotriphosphazene and 3-5 parts of phenylacetylene, and add 0.05-0.1 parts of bis(triphenylphosphine)palladium dichloride, 0.1-0.2 parts of cuprous iodide and 45-50 parts of anhydrous tetrahydrofuran. Stir at 450-500 r / min for 15-20 min to obtain a primary mixture. S212. Add 3-5 parts of triethylamine and 0.5-0.8 parts of triethylborane to the mixture obtained in step S211, raise the temperature to 80℃, and stir at a speed of 350-400 r / min for 18-20 h to obtain a secondary mixture; S213. Cool the secondary mixture to room temperature and filter it. Wash the obtained solid with anhydrous tetrahydrofuran 3-4 times, dry it under vacuum and then crush it to obtain boron-doped graphyne.

3. The method for preparing a CuNiSn-based molten catalyst for graphene according to claim 1, characterized in that, The nickel-containing salt solution is selected from two or more of nickel aminosulfonate, nickel hypophosphite, nickel acetate, nickel nitrate, and nickel phosphate.

4. The method for preparing a CuNiSn-based molten catalyst for graphene according to claim 1, characterized in that, The tin-containing salt solution is selected from two or more of sodium stannous acid, tin sulfate, tin tetrachloride, tin acetate, and tin fluoride.

5. The method for preparing a CuNiSn-based molten catalyst for graphene according to claim 1, characterized in that, The frequency of ultrasonic dispersion in step S1 is 40 kHz.

6. The method for preparing a CuNiSn-based molten catalyst for graphene according to claim 1, characterized in that, In step S2, the gas flow rate in the reactor is controlled within the range of 20-50 sccm.

7. The method for preparing a CuNiSn-based molten catalyst for graphene according to claim 1, characterized in that, The mass ratio of phosphotungstic acid to 1-ethyl-3-methylimidazolium dicyandiamide salt is 1:

3.

8. A CuNiSn-based melt catalyst for preparing graphene, characterized in that: The CuNiSn-based molten catalyst is prepared according to the preparation method described in any one of claims 1-7.

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