A method for producing carbon by cracking methane based on molten medium regulation

Abstract

The present application relates to the technical field of methane cracking and carbon production, and in particular to a method for methane cracking and carbon production based on molten medium regulation. The method comprises the following steps: placing a molten medium catalyst in a tubular furnace, heating the temperature to a reaction temperature at a heating rate of 7-10°C / min, introducing argon gas during the heating process, introducing methane when the temperature reaches the reaction temperature, and cooling the argon atmosphere to room temperature after the reaction is completed, and collecting the produced carbon product. The reaction temperature is 850-1000°C; the molten medium catalyst comprises a modified metal-based material and a chloride salt; and the modified metal-based material comprises a modified metal and a foamed metal.

Description

Technical Field

[0001] The present application relates to the technical field of methane cracking and carbon production, and in particular to a methane cracking and carbon production method based on molten medium regulation. Background Art

[0002] As one of the cleanest fossil fuels, natural gas's high-value, clean utilization has garnered widespread attention, as it's considered a key technology with broad development prospects in the energy transition. Natural gas is often directly burned for energy, generating significant amounts of carbon dioxide. Currently, in addition to direct combustion, steam methane reforming (SMR) is another industrial-scale method of utilization. In this process, methane and steam react under catalysis to produce carbon dioxide and hydrogen, which still results in carbon dioxide emissions. However, methane cracking to produce hydrogen and carbon products not only eliminates carbon dioxide emissions but also produces value-added carbon products.

[0003] Molten metal catalysis catalyzes methane cracking. Due to the effects of bubbles and density, carbon can float on the surface of the melt, enabling a long-term continuous reaction. Molten metal catalysis suffers from high reaction temperatures (greater than 1000°C), resulting in a large amount of residual metal impurities in the carbon product. Molten salt catalysis can remove a large amount of impurities through simple water washing, but its activity is relatively low. Therefore, it is particularly important to find a method that can achieve high methane cracking activity at lower temperatures, thereby producing a carbon product with a low impurity content, and to find a way to directly apply the carbon product containing small amounts of metals. Summary of the Invention

[0004] To achieve the purpose mentioned in the background technology, the present application provides a method for producing carbon by cracking methane based on molten medium regulation, characterized in that it includes the following steps:

[0005] The molten medium catalyst is placed in a tubular furnace and heated to the reaction temperature at a heating rate of 7-10 ° C / min, and argon is introduced during the heating process. When the temperature reaches the reaction temperature, methane is introduced. After the reaction is completed, the argon atmosphere is cooled to room temperature and the prepared carbon product is collected. The reaction temperature is 850-1000 ° C.

[0006] The molten medium catalyst includes a modified metal-based material and a chloride salt;

[0007] The modified metal-based material includes modified metal and foam metal, and the preparation method of the modified metal includes:

[0008] After dispersing metal particles in ethanol, adding nano-boron nitride dispersion, stirring for 2 hours, drying at 80°C, and calcining at 600°C in an argon atmosphere for 1 hour to form a boron nitride adsorption layer to obtain metal-boron nitride, the mass volume ratio of the metal particles to ethanol is 1 g: 20 mL, the volume of the nano-boron nitride dispersion is 40-60% of the ethanol, and the concentration of the nano-boron nitride dispersion is 0.1 mg / mL;

[0009] A 0.1 mol / L NH4VO3 solution was prepared and adjusted to a pH of 3. The metal-boron nitride was added thereto, reacted at 80°C for 2 h, filtered, and calcined in a nitrogen atmosphere at 500°C for 3 h to obtain precursor particles. The mass volume ratio of the metal-boron nitride to the NH4VO3 solution was 1 g: 20 mL.

[0010] The precursor particles were immersed in an acetic acid solution of 2 wt% chitosan oligosaccharide, stirred at room temperature for 6 h, filtered and dried, and then calcined in an argon atmosphere at 700°C for 2 h to obtain a modified metal. The mass volume ratio of the precursor particles to the acetic acid solution of 2 wt% chitosan oligosaccharide was 1 g: (15~25) mL.

[0011] Preferably, the preparation method of the modified metal-based material comprises the following steps:

[0012] The modified metal and metal foam were immersed in acetone, deionized water, and ethanol in sequence and ultrasonically treated for 30–40 min;

[0013] The modified metal and foam metal are then immersed in a 0.5-1 mol / L hydrochloric acid solution for ultrasonic treatment for 30-50 min.

[0014] The modified metal and foam metal are further immersed in deionized water for ultrasonic treatment for 40 to 50 minutes, and then transferred to a vacuum drying oven for drying. The modified metal is formed into a spherical or foil shape, and then the modified metal and foam metal are positioned in the tubular furnace reaction tube as follows: along the length direction of the tubular furnace reaction tube, methane gas enters from the bottom end of the tubular furnace reaction tube, passes through the foam metal and the modified metal in sequence, and the diameter of the foam metal is equal to the inner diameter of the tubular furnace reaction tube.

[0015] Preferably, the foam metal has a thickness of 5 mm and a pore size of 60 ppi.

[0016] Preferably, the chloride salt is one or more of KCl, NaCl, NiCl2, and MnCl2.

[0017] Preferably, the metal particles are one or more of copper, nickel, and iron;

[0018] The foam metal is one or more of copper, nickel and iron.

[0019] Preferably, when argon is introduced during the heating process, the reaction is carried out under normal pressure, with an argon flow rate of 20-80 mL / min and a methane flow rate of 20-60 mL / min.

[0020] Preferably, after collecting the prepared carbon product, the following steps are further included:

[0021] The carbon product was filtered and washed 5 to 7 times with deionized water, and dried to obtain a carbon product;

[0022] Alternatively, the carbon product is filtered and washed 5 to 7 times with deionized water, transferred to 200 to 300 mL of a 10 to 20% hydrochloric acid solution with a magnetic stirrer, and stirred at 500 to 700 rpm for 5 to 6 hours, followed by filtration 3 to 5 times with 200 to 300 mL of deionized water, and dried to obtain a carbon product.

[0023] The beneficial effects of the technical solution provided by this application include:

[0024] The present application provides a method for producing carbon by cracking methane based on the regulation of a molten medium. The interfacial interaction between the modified metal and the molten chloride salt can adjust the electron cloud density of the metal, reduce the C-H bond dissociation energy barrier, and promote methane cracking. The fluidity of the molten salt can flush carbon deposits on the metal surface. At the same time, the high thermal conductivity of the metal can accelerate heat transfer and avoid carbon deposition caused by local overheating. The pore structure of the foam metal pre-disperses the methane gas flow, changes the number and size of bubbles, and increases the gas-liquid contact area. The chemical inertness of boron nitride and VO2 synergize to promote methane cracking while protecting the metal, extending the service life of the molten medium catalyst, and at the same time achieving the production of a variety of carbon products with low metal content at a lower temperature (≤1000°C), and the carbon products containing cleaning and etching and untreated carbon products are put into practical application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0026] Figure 1 The SEM images of the carbon products prepared in Examples 1 to 4, Comparative Example 1, and Comparative Example 2 provided in this application are shown in FIG. Figure 1 (a)~ Figure 1 (f) SEM images of Examples 1 to 4, Comparative Example 1, and Comparative Example 2 are shown in order. DETAILED DESCRIPTION

[0027] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0028] See also Figure 1 As shown, the present application provides a methane cracking carbon production method based on molten medium regulation (hereinafter referred to as methane cracking carbon production method).

[0029] Example 1

[0030] The methane cracking method provided in this embodiment comprises the following steps:

[0031] A modified Cu metal foil with dimensions of 0.25 mm * 60 mm * 200 mm (thickness * width * length) was used, along with a copper foam with a diameter equal to the inner diameter of the tubular furnace reaction tube (15 mm), a thickness of 5.0 mm, and a 60 ppi. Chloride salt, a mixture of KCl and NiCl2 (mass ratio 3:1) was used to cover the top of the modified Cu metal foil.

[0032] The modified Cu metal foil and copper foam were immersed in acetone, deionized water, and ethanol in sequence and ultrasonically treated for 30 min;

[0033] The modified Cu metal foil and copper foam were then immersed in 1 mol / L hydrochloric acid solution and ultrasonically treated for 30 min.

[0034] The modified Cu metal foil and copper foam were immersed in deionized water and ultrasonically treated for 40 minutes. The modified Cu metal foil was then transferred to a vacuum drying oven for drying. The modified Cu metal foil was rolled with a spacing of 2 mm along the width direction. The copper foam was then placed under the modified Cu metal foil to obtain a modified metal-based material.

[0035] The modified metal-based material and the above-mentioned chloride salt as a molten medium catalyst were placed in a tubular furnace and heated to a reaction temperature of 1000°C at a heating rate of 7°C / min. 70 mL / min of argon was introduced during the heating process. After reaching the reaction temperature, the argon flow rate was reduced to 45.5 mL / min, and 24.5 mL / min of methane was introduced for 8 hours. After the reaction was completed, the argon atmosphere was cooled to room temperature, and the prepared carbon product was collected. The collected carbon product was filtered and washed with deionized water five times and dried to obtain a carbon product. The washed carbon product can be used as a working electrode for the electrocatalytic oxygen evolution reaction.

[0036] Specifically, the modified metal-based material in this embodiment includes a modified Cu metal foil and foamed copper, wherein the preparation method of the modified Cu metal foil includes:

[0037] After dispersing 40 g of copper particles (100 nm) in 800 mL of ethanol, 400 mL of 0.1 mg / mL nano-boron nitride dispersion was added. After stirring for 2 h, the mixture was dried at 80°C and calcined in an argon atmosphere at 600°C for 1 h to form a boron nitride adsorption layer to obtain metal-boron nitride.

[0038] Prepare 800 mL of 0.1 mol / L NH4VO3 solution, adjust the pH to 3, add 40 g of metal-boron nitride, react at 80°C for 2 h, filter, and calcine in a nitrogen atmosphere at 500°C for 3 h to obtain precursor particles;

[0039] 40 g of the precursor particles were immersed in an acetic acid solution of 2 wt% chitosan oligosaccharide, stirred at room temperature for 6 h, filtered and dried, and then calcined at 700 °C in an argon atmosphere for 2 h to obtain a modified Cu metal foil with a thickness of 0.25 mm; the composition of the acetic acid solution of 2 wt% chitosan oligosaccharide was 16 g chitosan oligosaccharide, 80 mL acetic acid and 720 mL deionized water.

[0040] Example 2

[0041] The methane cracking method provided in this embodiment comprises the following steps:

[0042] A modified Fe metal foil with dimensions of 0.25 mm * 10 mm * 200 mm (thickness * width * length) and a foamed iron with a diameter equal to the inner diameter of the tubular furnace reaction tube (15 mm), a thickness of 5.0 mm, and a 60 ppi, and a chloride salt covering the top of the modified Fe metal foil, wherein the chloride salt is NaCl;

[0043] The modified Fe metal foil and iron foam were immersed in acetone, deionized water, and ethanol in sequence and ultrasonically treated for 40 min;

[0044] The modified Fe metal foil and foamed iron were then immersed in a 0.5 mol / L hydrochloric acid solution and ultrasonically treated for 50 min.

[0045] The modified Fe metal foil and the iron foam were immersed in deionized water and ultrasonically treated for 50 minutes, and then transferred to a vacuum drying oven for drying. The modified Fe metal foil was formed into a tube with its width as the circumference, and the iron foam was placed under the modified Fe metal foil to obtain a modified metal-based material.

[0046] The modified metal-based material and chloride salt as a molten medium catalyst were placed in a tubular furnace and heated to a reaction temperature of 1000°C at a heating rate of 7°C / min. 80 mL / min of argon was introduced during the heating process. After reaching the reaction temperature, the argon flow rate was reduced to 56 mL / min, and 24 mL / min of methane was introduced for 8 hours. After the reaction was completed, the argon atmosphere was cooled to room temperature, and the prepared carbon product was collected. The collected carbon product was filtered and washed 7 times with deionized water, transferred to 300 mL of 20% hydrochloric acid solution with a magnetic stirrer, and stirred at 500 rpm for 6 hours. Subsequently, it was filtered 5 times with 300 mL of deionized water and dried to obtain the carbon product. The washed carbon product can be used as an electrode material for supercapacitors.

[0047] Specifically, the modified metal-based material in this embodiment includes a modified Fe metal foil and foamed iron, wherein the preparation method of the modified Fe metal foil includes:

[0048] After dispersing 30 g of iron particles (100 nm) in 600 mL of ethanol, 300 mL of 0.1 mg / mL nano-boron nitride dispersion was added. After stirring for 2 h, the mixture was dried at 80°C and calcined in an argon atmosphere at 600°C for 1 h to form a boron nitride adsorption layer to obtain metal-boron nitride.

[0049] Prepare 600 mL of 0.1 mol / L NH4VO3 solution, adjust the pH to 3, add 30 g of metal-boron nitride, react at 80°C for 2 h, filter, and calcine in a nitrogen atmosphere at 500°C for 3 h to obtain precursor particles;

[0050] 30 g of the precursor particles were immersed in an acetic acid solution of 2 wt% chitosan oligosaccharide, stirred at room temperature for 6 h, filtered and dried, and then calcined in an argon atmosphere at 700 °C for 2 h to obtain a modified Fe metal foil with a thickness of 0.25 mm; the composition of the acetic acid solution of 2 wt% chitosan oligosaccharide was 12 g chitosan oligosaccharide, 60 mL acetic acid and 540 mL deionized water.

[0051] Example 3

[0052] The methane cracking method provided in this embodiment comprises the following steps:

[0053] A modified nickel metal foil with dimensions of 0.25 mm * 60 mm * 200 mm (thickness * width * length) was used, along with nickel foam with a diameter equal to the inner diameter of the tubular furnace reaction tube (15 mm), a thickness of 5.0 mm, and a 60 ppi. Chloride salt, a mixture of NaCl and MnCl2 (mass ratio 3:1) was used to cover the top of the modified nickel metal foil.

[0054] The modified Ni metal foil and nickel foam were immersed in acetone, deionized water, and ethanol in sequence and ultrasonically treated for 30 min;

[0055] The modified Ni metal foil and nickel foam were then immersed in 1 mol / L hydrochloric acid solution and ultrasonically treated for 30 min;

[0056] The modified Ni metal foil and nickel foam were immersed in deionized water and ultrasonically treated for 40 minutes. The modified Ni metal foil was then transferred to a vacuum drying oven for drying. The modified Ni metal foil was rolled with a spacing of 2 mm along the width direction. The nickel foam was then placed under the modified Ni metal foil to obtain a modified metal-based material.

[0057] The modified metal-based material and chloride salt as a molten medium catalyst were placed in a tubular furnace and heated to a reaction temperature of 900°C at a heating rate of 10°C / min. During the heating process, 70 mL / min of argon was introduced. After reaching the reaction temperature, the argon flow rate was reduced to 45.5 mL / min, and 24.5 mL / min of methane was introduced for 8 hours. After the reaction was completed, the argon atmosphere was cooled to room temperature, and the prepared carbon product was collected. The collected carbon product was filtered and washed with deionized water for 7 times, transferred to 300 mL of 10% hydrochloric acid solution with a magnetic stirrer, and stirred at 500 rpm for 5 hours. Subsequently, it was filtered with 200 mL of deionized water for 3 times and dried to obtain the carbon product. The washed carbon product can be used for industrial coatings.

[0058] Specifically, the modified metal-based material in this embodiment includes a modified Ni metal foil and nickel foam, wherein the preparation method of the modified Ni metal foil includes:

[0059] After dispersing 30 g of nickel particles (100 nm) in 600 mL of ethanol, 300 mL of 0.1 mg / mL nano-boron nitride dispersion was added. After stirring for 2 h, the mixture was dried at 80°C and calcined in an argon atmosphere at 600°C for 1 h to form a boron nitride adsorption layer to obtain metal-boron nitride.

[0060] Prepare 600 mL of 0.1 mol / L NH4VO3 solution, adjust the pH to 3, add 30 g of metal-boron nitride, react at 80°C for 2 h, filter, and calcine in a nitrogen atmosphere at 500°C for 3 h to obtain precursor particles;

[0061] 30 g of the precursor particles were immersed in a 2 wt% chitosan oligosaccharide acetic acid solution, stirred at room temperature for 6 h, filtered and dried, and then calcined at 700 °C in an argon atmosphere for 2 h to obtain a modified Ni metal foil with a thickness of 0.25 mm; the composition of the 2 wt% chitosan oligosaccharide acetic acid solution was 15 g chitosan oligosaccharide, 30 mL acetic acid and 675 mL deionized water.

[0062] Example 4

[0063] The methane cracking method provided in this embodiment comprises the following steps:

[0064] The modified Cu balls, each 3 mm in diameter, were used to fill a 20 cm height. A nickel foam with a diameter equal to the inner diameter of the tubular furnace reactor (15 mm), a thickness of 5.0 mm, and a 60 ppi was used. Chloride salt, a mixture of KCl and NiCl2 (mass ratio 3:1), was used to cover the top of the modified Cu balls.

[0065] The modified Cu balls and nickel foam were immersed in acetone, deionized water, and ethanol in sequence and ultrasonically treated for 30 min;

[0066] The modified Cu balls and nickel foam were then immersed in 1 mol / L hydrochloric acid solution and ultrasonically treated for 30 min.

[0067] The modified Cu balls and nickel foam were immersed in deionized water for ultrasonic treatment for 40 min, and then transferred to a vacuum drying oven for drying. The nickel foam was placed under the modified Cu balls to obtain a modified metal-based material.

[0068] The modified metal-based material and chloride salt as a molten medium catalyst were placed in a tubular furnace and heated to a reaction temperature of 1000°C at a heating rate of 7°C / min. During the heating process, 70 mL / min of argon was introduced. After reaching the reaction temperature, the argon flow rate was reduced to 45.5 mL / min, and 24.5 mL / min of methane was introduced for 8 hours. After the reaction was completed, the argon atmosphere was cooled to room temperature, and the prepared carbon product was collected. The collected carbon product was filtered and washed with deionized water for 6 times, transferred to 300 mL of 10% hydrochloric acid solution with a magnetic stirrer, and stirred at 500 rpm for 5 hours. Subsequently, it was filtered three times with 200 mL of deionized water and dried to obtain the carbon product. The washed carbon product can be used for industrial coatings.

[0069] Specifically, the modified metal-based material in this embodiment includes modified Cu balls and nickel foam, wherein the preparation method of the modified Cu balls includes:

[0070] After dispersing 200 g of copper particles (100 nm) in 4 L of ethanol, 1.6 L of a 0.1 mg / mL nano-boron nitride dispersion was added. After stirring for 2 h, the mixture was dried at 80 °C and calcined in an argon atmosphere at 600 °C for 1 h to form a boron nitride adsorption layer to obtain metal-boron nitride.

[0071] Prepare 4 L of 0.1 mol / L NH4VO3 solution, adjust the pH to 3, add 200 g of metal-boron nitride, react at 80°C for 2 h, filter, and calcine in a nitrogen atmosphere at 500°C for 3 h to obtain precursor particles;

[0072] 200 g of precursor particles were immersed in a 2 wt% chitosan oligosaccharide acetic acid solution, stirred at room temperature for 6 h, filtered and dried, and then calcined at 700 °C in an argon atmosphere for 2 h to obtain modified Cu spheres; the composition of the 2 wt% chitosan oligosaccharide acetic acid solution was 80 g chitosan oligosaccharide, 400 mL acetic acid, and 3.6 L deionized water.

[0073] Comparative Example 1

[0074] The difference from Example 1 is that modified Cu metal foil is not added to the modified metal-based material in the molten medium catalyst, but is replaced by an equal amount of Cu metal foil.

[0075] Comparative Example 2

[0076] The difference from Example 1 is that the modified Cu metal foil in the modified metal-based material is replaced by an unmodified Cu metal foil, and no foam copper is added.

[0077] Comparative Example 3

[0078] The difference from Example 1 is that after the reaction temperature is raised, the argon gas is turned off, 55 mL / min of methane is introduced, and the reaction is carried out for 8 hours; the collected carbon product is also filtered and washed 5 times with deionized water, and dried to obtain a carbon product; the washed carbon product can be used as an anode material for fuel cells.

[0079] It should be noted that in the above embodiments and comparative examples, the size of the tubular furnace reaction tube used is 15 mm × 600 mm, and the positional relationship between the modified metal and the foam metal is as follows: along the length direction of the tubular furnace reaction tube, methane gas enters from the bottom end of the tubular furnace reaction tube, passes through the foam metal and the modified metal in sequence.

[0080] The types of carbon products and conversion rates obtained by the preparation methods provided in Examples 1 to 4 and Comparative Examples 1 to 2 are shown in Table 1.

[0081] Table 1

[0082]

[0083] It should be noted that the conversion rate in Table 1 is the peak conversion rate during the reaction process of the preparation method. In Examples 1 to 4, after the carbon product is prepared, the present application provides two methods for washing the carbon product. The carbon product obtained by washing by the method of "filtering and washing with deionized water 5 to 7 times, and drying to obtain a carbon product" can be used for electrocatalytic oxygen evolution reaction (OER); the carbon product obtained by washing by the method of "filtering and washing the carbon product with deionized water 5 to 7 times, transferring it to 200 to 300 mL of hydrochloric acid solution with a concentration of 10 to 20% with a magnetic stirrer, and stirring at a speed of 500 to 700 rpm for 5 to 6 hours, and then filtering with 200 to 300 mL of deionized water 3 to 5 times, and drying to obtain a carbon product" can be used for electronic devices and batteries, as well as for coatings and lubricants. The more obvious difference is whether the carbon product after washing contains metal impurities. One of the carbon applications is selected in Table 1.

[0084] The carbon products prepared in Examples 1 to 4, Comparative Examples 1 and 2 were characterized by scanning electron microscopy (SEM). The characterization results are shown in FIG. Figure 1 As shown, Figure 1 (a)~ Figure 1 (f) SEM images of Examples 1 to 4, Comparative Example 1, and Comparative Example 2 are shown in order.

[0085] In Example 2, the modified Fe metal foil is made into a tubular shape, and the conversion rate does not decrease much compared to Example 1 in which the modified Cu metal foil is made into a roll. In Example 3, modified Ni metal foil and nickel foam are used as part of the molten medium catalyst, and its conversion rate is greatly improved compared to Example 1 and Example 4, indicating that nickel as a modified metal has a good coordination effect with chitosan oligosaccharide. At the same time, a comparative result is obtained through Example 3 and Example 4 - Example 4 reduces the dosage ratio of chitosan oligosaccharide compared to Example 3, indicating that the reduction in the proportion of chitosan oligosaccharide will weaken its chelating effect.

[0086] In Example 1 and Example 4, the ratio of metal to chitosan oligosaccharide is the same. The difference is that the modified metal in Example 1 is a modified Cu metal foil and the foam metal is foam copper, while the modified metal in Example 4 is a modified Cu ball and the foam metal is foam nickel. This shows that the modified Cu metal made into a spherical shape has a higher conversion rate in catalyzing methane cracking than the modified Cu metal made into a foil. The reason is that the bubbles are deformed in the spherical Cu metal, which increases the contact area between the bubbles and the molten medium catalyst and the reaction is more complete.

[0087] Compared with Comparative Example 1, Example 1 has a relatively higher methane conversion rate because Comparative Example 1 only uses Cu foil and foam copper, which have lower thermal conductivity, which on the one hand reduces the reaction rate and on the other hand reduces the catalytic activity.

[0088] Compared with Comparative Example 2, Example 1 has a relatively high methane conversion rate because the addition of copper foam disperses the bubbles and promotes sufficient contact between the bubbles and the molten medium catalyst. At the same time, in Comparative Example 2, unmodified Cu is used, and its C-H bond dissociation energy barrier is 420 kJ / mol, which requires a temperature above 1100°C to achieve efficient cracking. In the absence of copper foam and the Cu metal foil surface is not modified with boron nitride and chitosan oligosaccharide, the carbon deposition rate increases, the side reactions increase, and the methane conversion rate decreases significantly.

[0089] Compared with Comparative Example 2, the methane conversion rate in Comparative Example 1 is relatively higher because the addition of foamed copper disperses the bubbles and promotes sufficient contact between the bubbles and the molten medium catalyst.

[0090] Compared with Example 1 and Comparative Example 3, the total air intake flow rate of Comparative Example 3 is reduced and the gas introduced is pure methane, which increases the contact time between the bubbles and the molten medium catalyst and promotes sufficient contact between the bubbles and the molten medium catalyst, thereby improving the peak methane conversion rate. However, due to the high cracking rate under pure methane conditions, the surface of the thin film carbon cannot relax evenly, which will lead to carbon growth and stacking. Therefore, in the second half of the reaction, the conversion rate will show a downward trend.

[0091] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for producing carbon by cracking methane based on molten medium regulation, characterized in that: It includes the following steps: The molten medium catalyst is placed in a tubular furnace and heated to the reaction temperature at a heating rate of 7-10 ° C / min, and argon is introduced during the heating process. When the temperature reaches the reaction temperature, methane is introduced. After the reaction is completed, the argon atmosphere is cooled to room temperature and the prepared carbon product is collected. The reaction temperature is 850-1000 ° C. Wherein, the molten medium catalyst comprises a modified metal-based material and a chloride salt; The modified metal-based material includes modified metal and foam metal, and the preparation method of the modified metal includes: After dispersing metal particles in ethanol, adding nano-boron nitride dispersion, stirring for 2 hours, drying at 80°C, and calcining at 600°C in an argon atmosphere for 1 hour to form a boron nitride adsorption layer to obtain metal-boron nitride, the mass volume ratio of the metal particles to ethanol is 1 g: 20 mL, the volume of the nano-boron nitride dispersion is 40-60% of the ethanol, and the concentration of the nano-boron nitride dispersion is 0.1 mg / mL; A 0.1 mol / L NH4VO3 solution was prepared and adjusted to a pH of 3. The metal-boron nitride was added thereto, reacted at 80°C for 2 h, filtered, and calcined in a nitrogen atmosphere at 500°C for 3 h to obtain precursor particles. The mass volume ratio of the metal-boron nitride to the NH4VO3 solution was 1 g: 20 mL. The precursor particles were immersed in an acetic acid solution of 2 wt% chitosan oligosaccharide, stirred at room temperature for 6 h, filtered and dried, and then calcined in an argon atmosphere at 700°C for 2 h to obtain a modified metal. The mass volume ratio of the precursor particles to the acetic acid solution of 2 wt% chitosan oligosaccharide was 1 g: (15~25) mL.

2. The method for producing carbon by cracking methane based on molten medium control according to claim 1, characterized in that: The preparation method of the modified metal-based material comprises the following steps: The modified metal and metal foam were immersed in acetone, deionized water, and ethanol in sequence and ultrasonically treated for 30–40 min; The modified metal and foamed metal were then immersed in a 0.5-1 mol / L hydrochloric acid solution for ultrasonic treatment for 30-50 min. The modified metal and foamed metal are further immersed in deionized water for ultrasonic treatment for 40 to 50 minutes, and then transferred to a vacuum drying oven for drying. The modified metal is formed into a sphere, a roll, or a tube. The modified metal and the foamed metal are then positioned in a tubular furnace reaction tube as follows: along the length direction of the tubular furnace reaction tube, methane gas enters from the bottom end of the tubular furnace reaction tube, passes through the foamed metal and the modified metal in sequence, and the diameter of the foamed metal is equal to the inner diameter of the tubular furnace reaction tube.

3. The method for producing carbon by cracking methane based on molten medium control according to claim 2, characterized in that: The foam metal has a thickness of 5 mm and a pore size of 60 ppi.

4. The method for producing carbon by cracking methane based on molten medium control according to claim 1, characterized in that: The chloride salt is one or more of KCl, NaCl, NiCl2, and MnCl2.

5. The method for producing carbon by cracking methane based on molten medium control according to claim 1, characterized in that: The metal particles are one or more of copper, nickel, and iron; The foam metal is one or more of copper, nickel and iron.

6. The method for producing carbon by cracking methane based on molten medium control according to claim 1, characterized in that: When argon was introduced during the heating process, the reaction was carried out under normal pressure, with an argon flow rate of 20-80 mL / min and a methane flow rate of 20-60 mL / min.

7. The method for producing carbon by cracking methane based on molten medium control according to claim 1, characterized in that: After collecting the carbon product, the following steps are also included: The carbon product was filtered and washed 5 to 7 times with deionized water, and dried to obtain a carbon product; Alternatively, the carbon product is filtered and washed 5 to 7 times with deionized water, transferred to 200 to 300 mL of a 10 to 20% hydrochloric acid solution with a magnetic stirrer, and stirred at 500 to 700 rpm for 5 to 6 hours, followed by filtration 3 to 5 times with 200 to 300 mL of deionized water, and dried to obtain a carbon product.

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