Modified needle coke catalyst, its preparation method and application

Abstract

The application discloses a modified needle coke catalyst and a preparation method and application thereof, and the preparation method comprises the following steps: S1, obtaining needle coke and pretreating the needle coke to obtain pretreated needle coke; S2, performing ball milling treatment on the pretreated needle coke to obtain needle coke nanoparticles; and S3, performing nitric acid etching treatment on the needle coke nanoparticles, centrifuging, washing and drying to obtain the modified needle coke catalyst. ‑ ORR generates H2O2, and can maintain high selectivity and high energy utilization efficiency in a wide potential range, and can be used for electro-synthesis of H2O2 in alkaline and neutral media.

Description

Technical Field

[0001] This invention relates to the field of electrocatalysis technology, and in particular to a modified needle-shaped coke catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen peroxide (H2O2), as an important green oxidant, is widely used in chemical synthesis and pollutant treatment, and is a cornerstone of modern chemical industry. Currently, over 95% of H2O2 is produced via the anthraquinone process, which suffers from high energy consumption, heavy reliance on large-scale industrial infrastructure, and the generation of numerous harmful byproducts. Electrocatalytic two-electron oxygen reduction (2e...) - ORR (Organic Renewable Energy) is a green alternative that allows for the economical, on-site production of H2O2 using only air, water, and renewable electricity.

[0003] The key to the electrochemical synthesis of H₂O₂ lies in designing highly efficient and stable catalytic materials to drive the oxygen reduction reaction via a two-electron pathway, thereby achieving maximum reaction efficiency. Currently, noble metals and their compounds (such as Pt-Hg, Pd-Hg, and Au-Pd) exhibit high 2e electron density. - While ORR exhibits high activity and selectivity, its high cost and resource scarcity severely limit its large-scale commercial application. Furthermore, single-atom dispersed transition metal catalysts (such as Co-NC) and transition metal compound catalysts (such as CoSe2) have also been used in the electrosynthesis of H2O2, although they can achieve higher 2e... - While ORR exhibits high selectivity, its preparation processes typically require high-temperature heat treatment at hundreds of degrees Celsius and complex separation and purification, making large-scale, rapid industrial production difficult. Therefore, developing catalytic materials that can be easily and extensively prepared, and achieving high 2e⁻ content, is crucial. - ORR selectivity and activity are crucial for improving the efficiency of electrochemical H2O2 production.

[0004] Among existing catalytic materials, carbon materials have initially gained popularity due to their low cost, high conductivity, and tunable structure, particularly in the 2e-phase. - The field of ORR (Organic Oxygen Reduction) has attracted much attention. The main carbon materials used include carbon black, carbon nanotubes, graphene, and carbon quantum dots. However, pure carbon materials exhibit low 2e content due to their weak adsorption capacity for oxygen reduction reaction intermediates. -ORR selectivity and activity. While some existing technologies can improve the selectivity and catalytic activity of hydrogen peroxide electrosynthesis by optimizing the electronic structure and surface properties of carbon materials, the production of high-quality carbon nanomaterials (such as carbon nanotubes and graphene) relies on energy-intensive processes and expensive equipment, driving up catalyst costs. Furthermore, existing preparation processes face significant challenges during industrial scale-up; methods such as high-temperature carbonization and chemical vapor deposition are not only energy-intensive but also involve cumbersome post-processing steps, making it difficult to guarantee consistent product quality. Simultaneously, the reliance on precision equipment in some processes leads to high upfront investment, long production cycles, and low yields. In summary, limited by high preparation costs, complex processes, and low production efficiency, existing high-performance carbon-based catalysts cannot meet the return on investment requirements of industrial applications, severely hindering the industrialization and promotion of H2O2 electrosynthesis technology. Summary of the Invention

[0005] The purpose of this invention is to provide a modified needle coke catalyst, its preparation method and application, which utilizes a low-cost carbon source and an efficient and controllable method to prepare carbon-based catalysts in large quantities, overcoming the shortcomings of existing carbon materials in terms of raw materials, processes, environmental protection and performance, thereby reducing energy consumption and equipment investment, and promoting the industrial application of H2O2 electrosynthesis.

[0006] The technical solution of the present invention is as follows: On the one hand, a method for preparing a modified needle-shaped coke catalyst is provided, comprising the following steps: S1: Obtain needle coke and preprocess it to obtain preprocessed needle coke; S2: The pretreated needle coke is ball-milled to obtain needle coke nanoparticles; S3: The needle-shaped coke nanoparticles are etched with nitric acid, centrifuged, washed, and dried to obtain the modified needle-shaped coke catalyst.

[0007] Preferably, in step S1, the pretreatment includes crushing and cleaning, wherein the cleaning is used to remove surface oil and impurities from the needle coke.

[0008] Preferably, acetone and ethanol are used for cleaning.

[0009] Preferably, in step S2, during ball milling, the pretreated needle coke is mixed with a grinding aid, and then grinding media is added for grinding.

[0010] Preferably, the grinding aid is an alkali metal chloride or an alkaline earth metal chloride.

[0011] Preferably, the mass ratio of the pretreated needle coke to the grinding aid is 1:2.

[0012] Preferably, in step S2, the particle size of the needle-shaped coke nanoparticles is 100-500 nm.

[0013] Preferably, in step S3, when performing nitric acid etching, the needle-shaped coke nanoparticles are placed in a 30% nitric acid solution and then stirred at 60-80°C for 3-7 hours.

[0014] On the other hand, a modified needle coke catalyst prepared by any one of the above-described methods is also provided, and its application in the electrosynthesis of hydrogen peroxide is also provided.

[0015] The beneficial effects of this invention are: 1. The catalyst prepared by the method of the present invention can be synthesized at low cost and in a simple manner, and the catalyst synthesis stage does not require a high-temperature treatment process above 100°C. 2. In alkaline or neutral electrolytes, the modified needle coke catalyst of this invention exhibits a higher 2e content than most modified carbon materials. - ORR selectivity maintains high two-electron pathway selectivity over a wide potential range (0-0.4 V), with H2O2 selectivity reaching 85% and electron transfer number between 2.2 and 2.3; 3. The modified needle coke catalyst of this invention exhibits high energy conversion efficiency over a wide voltage range. Under alkaline media conditions, using an H-type electrolytic cell at 0.4V (vs RHE), the H2O2 production rate can reach 365 mmol gcat. -1 h -1 With a Faraday efficiency (FE) as high as 90%, the catalyst demonstrates excellent oxygen reduction ability and is one of the best performing catalysts for the electrosynthesis of H2O2. 4. In long-term durability tests, the modified needle coke catalyst of this invention can maintain its performance for more than 12 hours at a high current density without degradation, and its stability far exceeds that of most catalysts of the same type, which can meet the actual needs of various application scenarios. 5. Given the excellent oxygen reduction performance and low cost of the modified needle coke catalyst of this invention, this invention will provide a very promising alternative method for the dispersed synthesis of H2O2, and promote the development of green chemical industry. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic flowchart of the preparation method of the modified needle coke catalyst of the present invention; Figure 2 Here is a scanning electron microscope image of the modified needle coke catalyst from Example 1; Figure 3 The Raman spectra of needle coke and modified needle coke catalyst in Example 1 are shown below. Figure 4 X-ray diffraction patterns of needle coke and modified needle coke catalyst in Example 1; Figure 5 Example 1: needle coke and modified needle coke catalyst; Comparative Example 1: modified commercial carbon black catalyst, under alkaline medium 2e - Schematic diagram of ORR electrochemical performance test results; where (a) is the linear voltammetric scan polarization curve test result, (b) is the hydrogen peroxide selectivity calculation result, and (c) is the number of transferred electrons calculation result. Figure 6 For Example 1, needle coke and modified needle coke catalyst, and Comparative Example 1, modified commercial carbon black catalyst were tested in a neutral medium at 2°C. - Schematic diagram of ORR electrochemical performance test results; where (a) is the linear voltammetric scan polarization curve test result, (b) is the hydrogen peroxide selectivity calculation result, and (c) is the number of transferred electrons calculation result. Figure 7 The samples from Examples 1-3, after being etched with nitric acid for different times, were subjected to 2e etching in an alkaline medium. - Schematic diagram of ORR electrochemical performance test results; where (a) is the linear voltammetric scan polarization curve test result, (b) is the hydrogen peroxide selectivity calculation result, and (c) is the number of transferred electrons calculation result. Figure 8 The diagram shows the Faraday efficiency test results of the modified needle coke catalyst in Example 1 at various potentials in media with different pH levels; where (a) is a schematic diagram of the test results in alkaline medium (pH=13) and (b) is a schematic diagram of the test results in neutral medium (pH=7). Figure 9 This is a schematic diagram showing the stability test results of the modified needle coke catalyst in Example 1. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and technical features described in this application can be combined with each other. It should also be pointed out that, unless otherwise indicated, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terms "comprising" or "including" and similar words used in this invention refer to elements or objects preceding the word that encompass the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0019] On one hand, the present invention provides a method for preparing a modified needle-shaped coke catalyst, comprising the following steps: S1: Obtain needle coke and preprocess it to obtain preprocessed needle coke.

[0020] In this invention, needle coke is used to prepare the catalyst. Needle coke is a high-quality carbon-containing material with a mature production route, high capacity, and competitive low cost for large-scale applications. Furthermore, needle coke is characterized by low sulfur, low ash, and low metallic impurities, making it an ideal electrocatalytic material to replace high-cost carbon materials such as carbon nanotubes and graphene. Compared to other petroleum coke, needle coke exhibits high crystallinity, high graphitization, and low sulfur content, demonstrating excellent conductivity and making it suitable as a precursor for high-performance carbon materials. Sponge coke in petroleum coke exhibits a porous, sponge-like structure with high porosity but low conductivity; pellet coke is composed of tightly packed fine spherical particles, has high sulfur content, and its conductivity is also inferior to needle coke. This invention selects needle coke as a catalyst precursor, leveraging its high conductivity and ease of forming a conductive framework to provide a good electron transport basis for subsequent modification.

[0021] In one specific embodiment, the pretreatment includes a crushing process and a cleaning process, wherein the cleaning process is used to remove surface oil and impurities from the needle coke. Optionally, acetone and ethanol are used for the cleaning process.

[0022] In the above embodiments, needle-shaped coke powder can be obtained through pulverization, which facilitates the ball milling process in step S2 to obtain needle-shaped coke nanoparticles. Cleaning removes surface oil and impurities from the needle-shaped coke, preventing these impurities from affecting the subsequent nitric acid etching in step S3 and the performance of the final modified needle-shaped coke catalyst.

[0023] In the above embodiments, acetone and ethanol are used for cleaning. Acetone has stronger cleaning power and can handle more stubborn oil stains and organic residues; ethanol has relatively mild cleaning power and is suitable for removing light stains and as a rinsing agent to help remove residual cleaning agents or impurities.

[0024] S2: The pretreated needle coke is ball-milled to obtain needle coke nanoparticles.

[0025] In one specific embodiment, during ball milling, the pretreated needle coke is mixed with a grinding aid, and then grinding media are added for grinding. Optionally, the mass ratio of the pretreated needle coke to the grinding aid is 1:2.

[0026] In the above embodiments, by adding a grinding aid during ball milling, the grinding aid can insert between needle-shaped coke particles during the ball milling process, break up the agglomeration between particles, and make the material easier to grind and refine, thereby improving ball milling efficiency and shortening grinding time.

[0027] In one specific embodiment, the grinding aid is an alkali metal chloride or an alkaline earth metal chloride. Optionally, the grinding aid is sodium chloride or potassium chloride. It should be noted that the grinding aid in this embodiment is only a preferred grinding aid of the present invention, and other grinding aids in the prior art that can improve ball milling efficiency and shorten grinding time can also be applied to the present invention.

[0028] In one specific embodiment, the ball milling process includes the following sub-steps: adding pretreated needle coke to a ball mill jar, adding a small amount of anhydrous ethanol as a dispersant; then adding two types of agate balls of different sizes (the mass ratio of small balls to large balls is 2:1), and ball milling at 350-500 rpm for 20-30 hours to obtain the needle coke nanoparticles. Optionally, the small balls have a diameter of 3 mm, and the large balls have a diameter of 5 mm.

[0029] It should be noted that if a grinding aid is added during ball milling, the ball milling product needs to be cleaned to remove the grinding aid, and then heated and dried to obtain the needle-shaped coke nanoparticles.

[0030] In one specific embodiment, the needle-shaped coke nanoparticles have a particle size of 100-500 nm. In this embodiment, using needle-shaped coke nanoparticles of this particle size helps to increase the specific surface area of ​​the catalyst, thereby exposing more active sites, allowing more reactant molecules to contact the catalyst surface, and improving the rate and efficiency of the electrocatalytic reaction.

[0031] S3: The needle-shaped coke nanoparticles are etched with nitric acid, centrifuged, washed, and dried to obtain the modified needle-shaped coke catalyst.

[0032] In this invention, nitric acid etching is used to oxidize the surface of needle coke. Compared with some other oxidation methods, the nitric acid oxidation method has relatively mild reaction conditions (such as room temperature or lower temperatures), does not require complex equipment or high-energy-consuming processes, and can reduce catalyst preparation costs and safety risks in the preparation process. Other existing methods for introducing oxygen atoms, such as sulfuric acid oxidation, require the use of 98% concentrated sulfuric acid as an oxidant, which has high safety risks and costs; potassium permanganate oxidation may leave manganese oxides and other impurities after the reaction, which need to be removed through complex washing and purification steps, increasing process complexity and cost; air oxidation relies on oxygen in the air to react with carbon materials, and the reaction rate and degree of oxidation are greatly affected by factors such as temperature, time, and air flow rate, which may lead to uneven oxidation on the surface or inside of the carbon materials, affecting the consistency of material properties.

[0033] In one specific embodiment, during the nitric acid etching process, the needle-shaped coke nanoparticles are placed in a 30% nitric acid solution and then stirred at 60-80°C for 3-7 hours.

[0034] In this invention, a ball milling-assisted surface oxidation process is used to modify needle coke, enabling the large-scale, low-cost synthesis of modified needle coke catalysts. The modified needle coke undergoes alterations in its electronic structure and surface properties, resulting in a modified needle coke catalyst that differs from other modified carbon materials and can efficiently catalyze 2e⁻. - ORR generates H2O2 while maintaining high selectivity and high energy utilization efficiency over a wide potential range.

[0035] On the other hand, the present invention also provides a modified needle coke catalyst prepared by any one of the above-described methods, and its application in the electrosynthesis of hydrogen peroxide. Optionally, H2O2 is electrosynthesized in an alkaline or neutral medium.

[0036] Example 1 A modified needle-shaped coke catalyst, such as Figure 1 As shown, it is prepared through the following steps: (1) Obtain needle coke, crush the needle coke with a pulverizer, wash it with ethanol and acetone in sequence, and dry it in an oven at 60 °C for 12 h; (2) Weigh 0.5 kg of dried needle coke and mix it with 1.0 kg of sodium chloride, and add it to a ball mill jar with a total capacity of 100 L; add 5 kg of agate balls and 100 mL of anhydrous ethanol as a dispersant to the jar, and ball mill at 400 rpm for 24 h; after ball milling, separate the grinding balls and the material by sieving, wash the ball milling product thoroughly with deionized water, and dry it at 60 ℃ to obtain needle coke nanoparticles (particle size of 100-500 nm). (3) The needle-shaped coke nanoparticles were placed in a 30% nitric acid solution and acid-treated at 80 °C for 5 h. After treatment, the particles were centrifuged and washed with deionized water until the filtrate was neutral. Finally, the particles were dried in a 60 °C oven to obtain the modified needle-shaped coke catalyst (yield of 92%).

[0037] Example 2 Unlike Example 1, the acid treatment time in step (3) of this example is 3 hours.

[0038] Example 3 Unlike Example 1, the acid treatment time in step (3) of this example is 7 hours.

[0039] Comparative Example 1 A modified commercial carbon black catalyst is prepared by the following steps: (1) Weigh 0.5 kg of commercial carbon black and 1.0 kg of sodium chloride and mix them together, then add them to a ball mill jar with a total capacity of 100 L. Add 5 kg of agate balls and 100 mL of anhydrous ethanol as a dispersant to the jar, and ball mill at 400 rpm for 24 h. After ball milling, separate the grinding balls and the material by sieving, wash the ball milling product thoroughly with deionized water, and dry it at 60 ℃ to obtain commercial carbon black nanoparticles (particle size of 100-500 nm). (2) The commercial carbon black nanoparticles were placed in a 30% nitric acid solution and acid-treated at 80 °C for 5 h. After treatment, the particles were centrifuged and washed with deionized water until the precipitate was neutral. Finally, the particles were dried in a 60 °C oven to obtain the modified commercial carbon black catalyst (yield of 85%).

[0040] Test Example 1 The morphology of the modified needle-shaped coke catalysts in each embodiment was observed using scanning electron microscopy, with the results for Example 1 as follows: Figure 2 As shown. From Figure 2 As can be seen, the modified needle-shaped coke catalyst of the present invention exhibits an irregular sheet-like morphology and has a high specific surface area.

[0041] Test Example 2 Raman spectroscopy analysis was performed on the modified needle coke catalysts of each embodiment. The Raman spectra of the raw material needle coke and the finished modified needle coke catalyst of Example 1 are shown below. Figure 3 As shown. From Figure 3 It can be seen that, compared with needle coke, the modified needle coke catalyst has an increased degree of defect, which is related to the destruction of the ordered structure of carbon materials caused by the generation of oxygen-containing functional groups.

[0042] Test Example 3 X-ray diffraction analysis was performed on the modified needle coke catalysts of each embodiment. The X-ray diffraction patterns of the raw material needle coke and the finished modified needle coke catalyst of Example 1 are shown below. Figure 4 As shown. From Figure 4 It can be seen that both needle coke and modified needle coke catalysts are composed of carbon. Compared with needle coke, modified needle coke has a lower degree of graphitization and an increased interlayer distance between carbon layers, which is related to the generation of defects and the insertion of oxygen-containing functional groups into the graphite interlayer.

[0043] Test Example 4 The 2e content of each catalyst was tested under alkaline medium. - The ORR electrochemical performance, including the test results of the raw material needle coke of Example 1, the finished modified needle coke catalyst of Example 1, and the modified commercial carbon black catalyst of Comparative Example 1, are as follows: Figure 5 As shown. From Figure 5 It can be seen that after modification, the disk current and ring current density of the modified needle coke are significantly improved, and the H2O2 selectivity reaches a maximum of 86% in alkaline medium. In contrast, commercial carbon black, after being modified using the same method, only achieves a maximum H2O2 selectivity of 70%. This fully demonstrates that using needle coke as a precursor material for the preparation of 2e - ORR catalysts have significant advantages.

[0044] Test Example 5 The 2e⁻ content of each catalyst was tested under neutral medium. - The ORR electrochemical performance, including the test results of the raw material needle coke of Example 1, the finished modified needle coke catalyst of Example 1, and the modified commercial carbon black catalyst of Comparative Example 1, are as follows: Figure 6 As shown, the comparative test results of Examples 1-3 are as follows: Figure 7 As shown. From Figure 6 and Figure 7 As can be seen, after modification, the modified needle coke catalyst of this invention exhibits H2O2 selectivity exceeding 80% in neutral medium, which is far higher than that of modified commercial carbon black catalysts.

[0045] Test Example 6 The Faraday efficiency of the catalysts in each embodiment was tested at various potentials in media with different pH levels. The test results for the modified needle coke catalyst in Example 1 are as follows: Figure 8 As shown. From Figure 8 It can be seen that the modified needle coke catalyst of this invention has a Faraday efficiency of over 80% at various potentials in media with different acidity and alkalinity, indicating that the modified needle coke catalyst of this invention has a high efficiency for 2e- ... - ORR exhibits strong selectivity, demonstrating the efficient conversion of electrical energy into chemical energy.

[0046] Test Example 6 Stability tests were conducted on the modified needle coke catalysts of each embodiment, with the test results for the modified needle coke catalyst of Example 1 as follows: Figure 9 As shown. From Figure 9 As can be seen, at a constant potential, the current density of the modified needle-shaped coke catalyst of this invention reaches 15 mA cm⁻¹. -2 The above results show that the current remained stable over 12 hours, indicating that the modified needle coke catalyst of this invention did not experience significant loss of active sites, structural degradation, or poisoning. It can continuously and efficiently promote electrochemical reactions and maintain stable catalytic activity.

[0047] It should be noted that the above test examples are only test data of some embodiments of the present invention. Other embodiments of the present invention have similar performance to Example 1, and all have high catalytic activity, high selectivity and high stability.

[0048] The above description is merely a representative embodiment of the present invention and is not intended to limit the present invention in any way. Any embodiment made by those skilled in the art without departing from the scope of the present invention and utilizing the disclosed technical content is an equivalent embodiment of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a modified needle-shaped coke catalyst, characterized in that, Includes the following steps: S1: Obtain needle coke and preprocess it to obtain preprocessed needle coke; S2: The pretreated needle coke is ball-milled to obtain needle coke nanoparticles; S3: The needle-shaped coke nanoparticles are etched with nitric acid, centrifuged, washed, and dried to obtain the modified needle-shaped coke catalyst.

2. The method for preparing the modified needle-shaped coke catalyst according to claim 1, characterized in that, In step S1, the pretreatment includes crushing and cleaning, wherein the cleaning is used to remove surface oil and impurities from the needle coke.

3. The method for preparing the modified needle-shaped coke catalyst according to claim 2, characterized in that, Acetone and ethanol are used for cleaning.

4. The method for preparing the modified needle-shaped coke catalyst according to claim 1, characterized in that, In step S2, during ball milling, the pretreated needle coke is mixed with a grinding aid, and then grinding media are added for grinding.

5. The method for preparing the modified needle-shaped coke catalyst according to claim 4, characterized in that, The grinding aid is an alkali metal chloride or an alkaline earth metal chloride.

6. The method for preparing the modified needle-shaped coke catalyst according to claim 4, characterized in that, The mass ratio of the pretreated needle coke to the grinding aid is 1:

2.

7. The method for preparing the modified needle-shaped coke catalyst according to any one of claims 1-6, characterized in that, In step S2, the particle size of the needle-shaped coke nanoparticles is 100-500 nm.

8. The method for preparing the modified needle-shaped coke catalyst according to any one of claims 1-6, characterized in that, In step S3, during the nitric acid etching process, the needle-shaped coke nanoparticles are placed in a 30% nitric acid solution and then stirred at 60-80°C for 3-7 hours.

9. A modified needle-shaped coke catalyst, characterized in that, It is prepared by the method described in any one of claims 1-8 for the preparation of modified needle coke catalyst.

10. The application of the modified needle coke catalyst as described in claim 9 in the electrosynthesis of hydrogen peroxide.

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