Preparation method of carbon nanomaterial

Abstract

The invention belongs to the technical field of micro-nano synthesis, and particularly discloses a preparation method of a carbon nanomaterial, and the preparation method comprises the following steps: S1, inert gas is introduced into a plasma generation area, the temperature of the center of the plasma generation area is greater than or equal to 5000 DEG C, and high-energy carrier gas is obtained; and S2, mixing the high-energy carrier gas with the reaction mixed gas, and reacting at 1000-1600 DEG C to prepare the carbon nanomaterial, the reaction mixed gas comprises a carbon source, a catalyst precursor and a carrier gas. Compared with the technical scheme that both the reaction mixed gas and the inert gas are introduced into the plasma reaction zone, the preparation method provided by the invention only introduces the inert gas into the plasma reaction zone, so that the continuous production time is longer, the yield is higher, the graphitization degree of the obtained carbon nanomaterial is higher, the ash content is obviously reduced, the pipe diameter is smaller, and the pipe length is larger.

Description

Technical Field

[0001] The invention belongs to the technical field of micro-nano synthesis, and particularly relates to a method for preparing carbon nanomaterials. Background Art

[0002] Carbon nanomaterials are carbon materials with dispersed phases less than 100 nm in at least one dimension. The special structure of the carbon nanomaterials gives them highly specialized properties. For example, single-walled carbon nanotubes (SWCNTs) are single-layer carbon atoms connected by sp 2 The cylindrical nanostructured carbon formed by hybridization has unique physical, chemical and mechanical properties. Compared with multi-walled carbon nanotubes, single-walled carbon nanotubes have a better aspect ratio and a higher degree of graphitization (I G / I D These properties give single-walled carbon nanotubes excellent electrical conductivity and mechanical properties. Therefore, single-walled carbon nanotubes are an excellent conductive additive for electrode materials. They can build a highly efficient conductive network in the positive and negative electrode materials of batteries at extremely low addition ratios (as low as 0.05%), significantly improving the cycle stability and rapid charge and discharge capabilities of lithium batteries. They have broad application prospects in future new energy secondary batteries.

[0003] In the prior art, the preparation method of carbon nanomaterials based on chemical vapor deposition (CVD) has the advantages of high product purity, strong controllability, and scalability, and is currently the mainstream method for producing carbon nanomaterials. However, due to the high complexity of the CVD process in actual production, which is affected by multiple factors such as temperature, pressure, flow rate, and the selection of reactants and catalysts, the particle size distribution of the obtained carbon nanomaterials is relatively wide, making it difficult to achieve stable control of the purity, tube diameter and tube wall structure of the generated carbon nanomaterials. At the same time, achieving efficient unification of output and quality in the preparation of carbon nanomaterials still faces great difficulties. There is an urgent need for an industrial large-scale production method that can efficiently and continuously prepare carbon nanomaterials with a high degree of graphitization, especially single-walled carbon nanotubes. Summary of the Invention

[0004] In order to overcome at least one technical problem existing in the above-mentioned prior art, one of the objects of the present invention is to provide a method for preparing carbon nanomaterials, which can achieve continuous and stable production for more than 30 hours and can realize large-scale continuous preparation of carbon nanomaterials with a high degree of graphitization.

[0005] A second object of the present invention is to provide an application of the carbon nanomaterial obtained by the above preparation method in the field of batteries.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A first aspect of the present invention provides a method for preparing a carbon nanomaterial, comprising the following steps:

[0008] S1: introducing an inert gas into a plasma generating region, wherein the temperature at the center of the plasma generating region is ≥5000° C., to obtain a high-energy carrier gas;

[0009] S2: mixing the high-energy carrier gas and the reaction mixture and reacting them at 1000-1600° C. to produce the carbon nanomaterial;

[0010] The reaction mixed gas includes a carbon source, a catalyst precursor and a carrier gas.

[0011] By controlling the reaction temperature between 1000°C and 1600°C, the present invention allows the reaction mixture to contact a high-energy carrier gas, generating highly graphitized carbon nanomaterials. The reaction mixture rapidly exchanges energy with the high-energy carrier gas, transforming the catalyst precursor into highly active catalyst nanoparticles (1-3 nm in diameter), forming a highly concentrated aerosol catalyst. During the catalyst cracking and reconstruction process, the carbon source simultaneously cracks and deposits on the catalyst surface, forming the carbon nanomaterial.

[0012] During the research and development process, the inventors discovered that if the growth of high-quality carbon nanomaterials is to be achieved, it is necessary to effectively control the size of the reactive catalyst particles so that the size of the catalyst particles is ≤3nm. However, the pyrolysis temperature of the catalyst precursors in the prior art is usually low, about 1000°C, resulting in a low energy density, which is insufficient to fully decompose a large amount of catalyst precursors into single atoms, and it is difficult to avoid the agglomeration and deactivation of highly active catalyst molecules, thereby limiting the growth of carbon nanomaterials. The present invention uses a high-energy carrier gas and a reaction mixture to perform rapid energy exchange to achieve rapid decomposition of the catalyst precursor and the carbon source, forming a high-concentration catalyst aerosol (≤3nm), and completing the deposition and coating of carbon atoms on the highly active catalyst particles under conditions suitable for the growth of carbon nanomaterials (i.e., a reaction temperature of 1000-1600°C), which can effectively avoid further agglomeration and deactivation of the active catalyst particles.

[0013] The present invention passes an inert gas through the plasma generating zone to generate a high-energy carrier gas. This high-energy carrier gas is used as the primary energy source, and then heating is used to control the reaction temperature between 1000°C and 1600°C as an energy supplement. This avoids the energy supply uniformity issues associated with traditional CVD methods, allowing for a narrower catalyst size distribution and further optimization of the carbon nanomaterial diameter distribution and graphitization degree. Furthermore, this method effectively prevents the reaction mixture containing the carbon source and catalyst precursor used for growth from passing directly through the plasma generating zone, significantly improving the continuity and stability of the plasma reactor.

[0014] In some embodiments of the present invention, the temperature at the center of the plasma generating region is 5000°C to 9000°C; in some embodiments of the present invention, the temperature at the center of the plasma generating region is selected from 5000°C, 5100°C, 5200°C, 5300°C, 5400°C, 5500°C, 5600°C, 5700°C, 5800°C, 5900°C, 6000°C, 6100°C, 6200°C, 6300°C, 6400°C, 6500°C. , 6600°C, 6700°C, 6800°C, 6900°C, 7000°C, 7100°C, 7200°C, 7300°C, 7400°C, 7500°C, 7600°C, 7700°C, 7800°C, 7900°C, 8000°C, 8100°C, 8200°C, 8300°C, 8400°C, 8500°C, 8600°C, 8700°C, 8800°C, 8900°C, and 9000°C, or a range formed by any two of them. The plasma generating area uses electromagnetic waves to excite the inert gas to form a plasma flame.

[0015] In some embodiments of the present invention, the reaction temperature is 1000-1600°C; in some embodiments of the present invention, the reaction temperature can be selected from any value among 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, 1450°C, 1500°C, 1550°C, 1600°C or a range formed by any two of them.

[0016] In some embodiments of the present invention, the carbon source includes at least one of alkanes, alkenes, alkynes, and carbon powder.

[0017] In some embodiments of the present invention, the alkane includes at least one of methane and ethane.

[0018] In some embodiments of the present invention, the carrier gas and the inert gas are each selected from at least one of nitrogen, argon, and helium.

[0019] In some embodiments of the present invention, the catalyst precursor includes a metal organic compound and a sulfur-containing promoter. The metal organic compound includes at least one of ferrocene, nickelocene, cobaltocene, carbonyl iron, and cobalt carbonyl. The sulfur-containing promoter includes at least one of elemental sulfur and a sulfur-containing organic small molecule. The sulfur-containing promoter can promote the growth of the carbon nanomaterial.

[0020] In some embodiments of the present invention, the weight average molecular weight of the sulfur-containing organic small molecule is ≤500.

[0021] In some embodiments of the present invention, the sulfur-containing organic small molecule is selected from thiophene.

[0022] In some embodiments of the present invention, the metal organic compound includes at least one of ferrocene and carbonyl iron; in some embodiments of the present invention, the metal organic compound is ferrocene.

[0023] In some embodiments of the present invention, the molar ratio of iron atoms to sulfur atoms in the catalyst precursor is (1 to 80):1; in some embodiments of the present invention, the molar ratio of iron atoms to sulfur atoms in the catalyst precursor is selected from any value of 1:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, 55:1, 60:1, 65:1, 70:1, 75:1, 80:1, or a range formed by any two of the values, for example: (2 to 50):1.

[0024] In some embodiments of the present invention, the catalyst precursor is added in gaseous or solid form.

[0025] In some embodiments of the present invention, the reaction time is 1 to 60 s; in some embodiments of the present invention, the reaction time is any value among 1s, 5s, 10s, 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s, 60s, or a range formed by any two of them.

[0026] In some embodiments of the present invention, the flow rate of the inert gas is 1500-2500 L / min; in some embodiments of the present invention, the flow rate of the inert gas is 1500 L / min, 1520 L / min, 1540 L / min, 1560 L / min, 1580 L / min, 1600 L / min, 1650 L / min, 1700 L / min, 1750 L / min, 1800 L / min, 1850 L / min, 1900 L / min, 1950 L / min, 2000 L / min, 2050 L / min, 2100 L / min, 2150 L / min, 2200 L / min, 2250 L / min, 2300 L / min, 2350 L / min, 2400 L / min, 2450 L / min, 2500 L / min, any one of the values ​​or a range formed by any two of them.

[0027] In some embodiments of the present invention, the ratio of the flow rate of the high-energy carrier gas to the total flow rate of the reaction mixture and the high-energy carrier gas is ≥0.5; in some embodiments of the present invention, the ratio of the flow rate of the high-energy carrier gas to the total flow rate of the reaction mixture and the high-energy carrier gas is any one of 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95 or a range value formed by any two of them.

[0028] In some embodiments of the present invention, the inlet temperature of the plasma generating zone is 0-200°C; in some embodiments of the present invention, the inlet temperature of the plasma generating zone is any one of 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, and 200°C, or a range formed by any two of the values.

[0029] In some embodiments of the present invention, the temperature of the reaction mixture is 150° C. to 800° C.; in some embodiments of the present invention, the temperature of the reaction mixture is any one of 150° C., 200° C., 250° C., 300° C., 350° C., 400° C., 450° C., 500° C., 550° C., 600° C., 650° C., 700° C., 750° C., and 800° C., or a range formed by any two of these values. The reaction mixture can be quickly and fully mixed during the preheating process, which is beneficial to the smooth progress of the subsequent reaction.

[0030] In some embodiments of the present invention, step S2 is: passing the high-energy carrier gas through a transition zone with a median temperature of 2800-3200°C, and then mixing with the reaction mixed gas to react in a growth zone with a temperature of 1000-1600°C.

[0031] In some embodiments of the present invention, the time required from the inert gas entering the plasma generating zone to the inert gas and the reaction mixed gas is ≤0.4s, that is, the total residence time of the inert gas in the plasma generating zone and the transition zone is ≤0.4s; in some embodiments of the present invention, the time required from the inert gas entering the plasma generating zone to the inert gas and the reaction mixed gas is 0.01s, 0.02s, 0.03s, 0.04s, 0.05s, 0.06s, 0.07s, 0.08s, 0.09s, 0.10s, 0.11s, 0.12s, 0.13s, 0.14s, 0.15s, 0.16s, 0.17s, 0.18s, 0.19s, 0.20s, 0.21s, 0.22s, 0.23s, 0.24s, 0.25s, 0.26s, 0.27s, 0.28s, 0.29s, 0.30s, 0.31s, 0.32s, 0.33s, 0.34s, 0.35s, 0.36s, 0.37s, 0.38s, 0.39s, 0.40s, 0.41s, 0.42s, 0.43s, 0.44s, 0.45s, 0.46s, 0.47s, 0.48s, 0.49s, 0.50s, 0.51s, 0.52s, 0.53s, 0.54s, 0.55s, 0.56s, 0.57s, 0.58s, 0.59 0.11s, 0.12s, 0.13s, 0.14s, 0.15s, 0.16s, 0.17s, 0.18s, 0.19s, 0.20s, 0.21s, 0.22s, 0.23s, 0.24s, 0.25s, 0.26s, 0.27s, 0.28s, 0.29s, 0.30s, 0.31s, 0.32s, 0.33s, 0.34s, 0.35s, 0.36s, 0.37s, 0.38s, 0.39s, and 0.40s, or a range formed by any two of the values.

[0032] In some embodiments of the present invention, the inner wall material of the growth zone is selected from at least one of graphite and silicon carbide.

[0033] In some embodiments of the present invention, the heating method of the growth zone is selected from at least one of furnace wire heating, silicon carbon rod heating, silicon molybdenum rod heating, and electromagnetic induction heating.

[0034] In some embodiments of the present invention, the median temperature of the transition zone is 2800-3200°C; in some embodiments of the present invention, the median temperature of the transition zone can be selected from any value of 2800°C, 2850°C, 2900°C, 2950°C, 3000°C, 3050°C, 3100°C, 3150°C, 3200°C, or a range formed by any two of them.

[0035] In some embodiments of the present invention, the flow rate ratio of the carbon source and the carrier gas in the reaction mixture is 1:(1-20); in some embodiments of the present invention, the flow rate ratio of the carbon source and the carrier gas in the reaction mixture is any one of 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, and 1:20, or a range formed by any two of the values.

[0036] In some embodiments of the present invention, the carbon nanomaterial Raman spectrum has an I G / I DValue ≥ 100; In some embodiments of the present invention, the I in the Raman spectrum of the carbon nanomaterial G / I D The value is 110 to 130; In some embodiments of the present invention, the I G / I D The value is 112 to 128.

[0037] In some embodiments of the present invention, based on the mass percentage of the carbon nanomaterial being 100%, the mass percentage of ash in the carbon nanomaterial is ≤15%.

[0038] In some embodiments of the present invention, the diameter of the carbon nanomaterial is 1 to 3 nm.

[0039] In some embodiments of the present invention, the preparation method is implemented in a plasma reactor; the plasma reactor includes a plasma generating zone, a transition zone and a growth zone arranged in sequence, and a plasma generator inlet is provided at the end of the plasma generating zone; a reaction mixture inlet is provided at the connection position between the transition zone and the growth zone.

[0040] The second aspect of the present invention provides the application of the carbon nanomaterial prepared by the preparation method described in the first aspect of the present invention in the field of batteries.

[0041] The beneficial effects of the present invention are as follows: compared with the technical solution of introducing both the reaction mixture and the inert gas into the plasma reaction zone, the preparation method of the present invention introduces only the inert gas into the plasma reaction zone, which has a longer continuous production time and can work continuously for more than 30 hours, a higher output, and a yield of 130.7 to 151.2 g / h. The degree of graphitization of the obtained carbon nanomaterial is higher, and its I G / I D When the value exceeds 112, the ash content is significantly reduced, and its value is less than 14%, the tube diameter is smaller, and the tube length is longer.

[0042] In addition, the preparation method of the present invention can better achieve the control of the size of the catalyst precursor and the narrowing of its distribution, so that the catalyst precursor is cracked into an aerosol with a particle size of ≤3nm, thereby achieving the control of the diameter of the carbon nanomaterial and the optimization of the degree of graphitization. By controlling the airflow field formed by various gases, controlling the proportion of each component, controlling the temperature and residence time, etc., the purity and yield of the obtained carbon nanomaterial are improved and optimized. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the structure of the reactor used in the preparation method in Examples 1 to 3 and Comparative Example 1.

[0044] Figure 2Schematic diagram of the structure of the reactor used in the preparation method in Comparative Example 2.

[0045] Figure 3 This is the Raman test spectrum of the carbon nanomaterial prepared in Example 1.

[0046] Figure 4 This is a transmission electron microscope image of the carbon nanomaterial obtained in Example 1.

[0047] Figure 5 This is a scanning electron microscope image of the carbon nanomaterial obtained in Example 1.

[0048] Figure 6 This is a scanning electron microscope image of the carbon nanomaterial obtained in Example 2.

[0049] Figure 7 This is a scanning electron microscope image of the carbon nanomaterial obtained in Example 3.

[0050] Figure 8 This is a scanning electron microscope image of the carbon nanomaterial obtained in Comparative Example 1.

[0051] Figure 9 This is a scanning electron microscope image of the carbon nanomaterial obtained in Comparative Example 2.

[0052] Reference numerals:

[0053] Plasma generator inlet 100, plasma generation zone 200, transition zone A300, reaction mixture inlet 310, growth zone A400;

[0054] Plasma reactor inlet 500, plasma flame zone 600, center of plasma flame zone 610, transition zone B700, growth zone B800. DETAILED DESCRIPTION

[0055] The specific implementation of the present invention will be further described in detail below in conjunction with the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that if there are any processes that are not particularly described in detail below, they can be implemented or understood by those skilled in the art with reference to the prior art. The reagents or instruments used that do not indicate the manufacturer are all conventional products that can be purchased commercially.

[0056] The inner wall material of the growth zone A400 and the growth zone B800 used in the following examples and comparative examples is graphite, and the heating method of the growth zone A400 is silicon carbon rod heating.

[0057] Example 1

[0058] This example provides a method for preparing carbon nanomaterials. The preparation method is Figure 1The plasma reactor shown is implemented in the plasma reactor, which includes a plasma generator inlet 100, a plasma generating zone 200, a transition zone A300, a reaction mixture inlet 310, and a growth zone A400.

[0059] The preparation method comprises the following steps:

[0060] (1) Argon gas is introduced into the reaction chamber from the plasma generator inlet 100 as a carrier gas at a flow rate of 2000 L / min. The argon gas passes through the plasma generating region 200 and is converted into a high-energy carrier gas. The center temperature of the plasma generating region 200 is 6000°C.

[0061] (2) The high-energy carrier gas passes through the transition zone A300 and reaches the mixture inlet 310, where the residence time t2 = 0.071 s, the movement path L2 = 0.1 m, and the average cross-sectional area of ​​the transition zone is S2 = 0.283 m 2 , median temperature T2 = 3000℃.

[0062] (3) Ferrocene and thiophene were used as catalyst precursors (the amount of catalyst precursor added was 100 g / h, and the molar ratio of iron atoms to sulfur atoms was 5:1), natural gas was used as a carbon source (the main component was methane, with a flow rate of 15 L / min), and argon was used as a carrier gas (with a flow rate of 100 L / min). After the three were fully mixed, they were preheated to 600°C and added to the reaction chamber through the reaction mixture inlet 310.

[0063] (4) The reaction mixture in step (3) is fully contacted and mixed with the high-energy carrier gas, and then passed through the growth zone A400 to generate carbon nanomaterials, which are then collected and weighed. The temperature T3 of the growth zone A400 is set to 1200°C, the length L3 of the growth zone A400 is 2m, and the average cross-sectional area S2 is 0.283m. 2 The residence time of the reaction mixture in the growth zone was t3 = 2.973s, and the product was collected for a total of 34 hours. The product weighed 5141g and the average yield was 151.2g / h.

[0064] Example 2

[0065] This example provides a method for preparing carbon nanomaterials. The preparation method is Figure 1 The plasma reactor shown is implemented in the plasma reactor, which includes a plasma generator inlet 100, a plasma generating zone 200, a transition zone A300, a reaction mixture inlet 310, and a growth zone A400.

[0066] The preparation method comprises the following steps:

[0067] (1) Argon gas is introduced into the reaction chamber from the plasma generator inlet 100 as a carrier gas at a flow rate of 1500 L / min. The argon gas passes through the plasma generating region 200 and is converted into a high-energy carrier gas. The center temperature of the plasma generating region 200 is 6000°C.

[0068] (2) The high-energy carrier gas passes through the transition zone A300 and reaches the mixture inlet 310, where the residence time t2 = 0.095 s, the movement path L2 = 0.1 m, and the average cross-sectional area of ​​the transition zone is S2 = 0.283 m 2 , median temperature T2 = 3000℃.

[0069] (3) Ferrocene and thiophene were used as catalyst precursors (the amount of catalyst precursor added was 100 g / h, and the molar ratio of iron atoms to sulfur atoms was 5:1), natural gas was used as a carbon source (the main component was methane, with a flow rate of 15 L / min), and argon was used as a carrier gas (with a flow rate of 100 L / min). After the three were fully mixed, they were preheated to 600°C and added to the reaction chamber through the reaction mixture inlet 310.

[0070] (4) The reaction mixture in step (3) is fully contacted and mixed with the high-energy carrier gas, and then passed through the growth zone A400 to generate carbon nanomaterials, which are then collected and weighed. The temperature T3 of the growth zone A400 is set to 1200°C, the length L3 of the growth zone A400 is 2m, and the average cross-sectional area S2 is 0.283m. 2 The residence time of the mixture in the growth zone was t3 = 3.874s, and the total collection time was 35h. The product weighed 4575g, and the average yield was 130.7g / h.

[0071] Example 3

[0072] This example provides a method for preparing carbon nanomaterials. The preparation method is Figure 1 The plasma reactor shown is implemented in the plasma reactor, which includes a plasma generator inlet 100, a plasma generating zone 200, a transition zone A300, a reaction mixture inlet 310, and a growth zone A400.

[0073] The preparation method comprises the following steps:

[0074] (1) Argon gas is introduced into the reaction chamber from the plasma generator inlet 100 as a carrier gas at a flow rate of 1500 L / min. The argon gas passes through the plasma generating region 200 and is converted into a high-energy carrier gas. The center temperature of the plasma generating region 200 is 6000°C.

[0075] (2) The high-energy carrier gas passes through the transition zone A300 and reaches the reaction mixture inlet 310, where the residence time t2 = 0.095 s, the movement path L2 = 0.1 m, and the average cross-sectional area of ​​the transition zone is S2 = 0.283 m 2 , median temperature T2 = 3000℃.

[0076] (3) Ferrocene and elemental sulfur were used as catalyst precursors (the amount of catalyst precursor added was 100 g / h, and the molar ratio of iron atoms to sulfur atoms was 5:1), natural gas was used as a carbon source (the main component was methane, with a flow rate of 15 L / min), and argon was used as a carrier gas (with a flow rate of 100 L / min). After the three were fully mixed, they were preheated to 600°C and added to the reaction chamber through the reaction mixture inlet 310.

[0077] (4) The reaction mixture in step (3) is fully contacted and mixed with the high-energy carrier gas, and then passed through the growth zone A400 to generate carbon nanomaterials, which are then collected and weighed. The temperature T3 of the growth zone A400 is set to 1400°C, the length L3 of the growth zone A400 is 2m, and the average cross-sectional area S2 is 0.283m. 2 The residence time of the mixture in the growth zone was t3 = 3.411s, and the total collection time was 31h. The product weighed 4396g, and the average yield was 141.8g / h.

[0078] Comparative Example 1

[0079] The only difference between the preparation method of carbon nanomaterials in this example and Example 1 is that: in step (1) of this example, argon is used as the carrier gas. After the argon is preheated to 1200°C, it is introduced into the reaction chamber from the plasma generator inlet 100. The argon flow rate is 2000 L / min. The plasma generator is not turned on in the plasma generating area 200. The temperature of the generating area is close to the inlet preheating temperature, so the argon is not converted into a high-energy carrier gas.

[0080] In this case, the product was collected for 3 hours and weighed 41 g.

[0081] Comparative Example 2

[0082] This example provides a method for preparing carbon nanomaterials. The preparation method is Figure 2 The plasma reactor shown is implemented in the plasma reactor, which includes a plasma reactor inlet 500, a plasma flame zone 600, a center 610 of the plasma flame zone, a transition zone B700, and a growth zone B800.

[0083] The preparation method comprises the following steps:

[0084] (1) Electromagnetic waves are used to excite argon gas to form a plasma flame zone 600 (the flow rate of the inert argon gas is 150 L / min), and the temperature of the center 610 of the plasma flame zone is 6000°C;

[0085] (2) using ferrocene and thiophene as catalyst precursors (the amount of catalyst precursor added is 110 g / h, and the molar ratio of iron atoms to sulfur atoms is 60:1), natural gas as a carbon source (the main component is methane, the flow rate is 15 L / min), and argon as a carrier gas (the flow rate is 9 L / min). After the three are fully mixed, they enter the plasma flame zone 600 through the plasma reactor inlet 500;

[0086] The residence time of the reaction mixture from the inlet 500 of the plasma reactor at a temperature of 200° C. to the center 610 of the plasma flame zone is t4 = 0.0065 s; the movement path length is L4 = 0.1 m, and the plasma flame zone 600 is cylindrical with an average cross-sectional area S4 = 0.000314 m 2 , the median temperature of T4 is about 3000℃;

[0087] (3) When the reaction mixture of step (2) passes through the plasma flame zone 600, it is mixed with the inert gas argon used to provide the plasma high temperature in step (1) to obtain a new mixture;

[0088] The new mixture moves from the center 610 of the plasma flame zone, through the remaining part of the plasma flame zone 600 and the transition zone B700, into the growth zone B800. The movement duration is t5 = 0.0676 s. The movement path length is L5 = 0.3 m. The average cross-sectional area of ​​the plasma reactor within the L5 path distance is S5 = 0.00784 m 2 , the median temperature of T5 is about 3000℃;

[0089] (4) The temperature of the growth zone B800 close to the transition zone B700 is about 2000°C, and the temperature away from the transition zone B700 is about 1200°C;

[0090] The mixture obtained in step (3) stays in the growth zone B800 for t6 = 1.26 s. The growth zone B800 is cylindrical with an axial length L6 = 0.8 m and a cross-sectional area S6 = 0.0314 m. 2 , T6 median temperature is about 1600℃;

[0091] (5) The product produced in step (4) was collected for a total of 11 hours, and the product weighed 1326.3 g.

[0092] In the above embodiments and comparative examples, the residence time t in each step is n The calculation method is:

[0093]

[0094] Where: S n : The average cross-sectional area of ​​the plasma reactor perpendicular to the axial direction in the calculation area, in m 2 ; If the calculation area is irregular in shape, the average cross-sectional area is the ratio of the volume of the calculation area to the axial length.

[0095] V n : Total gas flow, in m 3 / s;

[0096] T n : Temperature, in °C; if the temperature is uneven, use the median thermometer, i.e. the temperature at the midpoint of the axial length;

[0097] L n : The axial length of the calculation area, in meters.

[0098] The formula for calculating the average yield is: average yield = product mass / collection time;

[0099] Performance testing:

[0100] The Raman spectra of the carbon nanomaterials prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were tested respectively. During the test, the laser power density irradiated on the sample was less than 1 mW / μm. 2 , the integration time is 10 to 60 seconds. Figure 3 As shown, and read the I in the Raman spectrum G Value and I D value, and then calculate I G / I D The test results are shown in Table 1 below. G The Raman spectrum of the obtained carbon nanomaterial is between 1500 and 1620 cm -1 Peak intensity within the range, I D The Raman spectrum is at 1350 cm -1 The peak intensity of I G / I D The value is positively correlated with the degree of graphitization of the obtained carbon nanomaterials.

[0101] The ash content of the carbon nanomaterials prepared in Examples 1 to 3 and Comparative Examples 1 to 2 was tested by a calcination method. The specific method is as follows: about 1 g (accurate to 0.1 mg) of the carbon nanomaterial sample was weighed in a muffle furnace and calcined at 900°C in an air atmosphere for 4 h. The ash content after calcination was weighed using a 1 / 10,000 balance, and the mass percentage of the ash content in the product before calcination was calculated. The test results are shown in Table 1 below.

[0102] The morphologies of the carbon nanomaterials obtained in Examples 1 to 3 and Comparative Examples 1 to 2 were tested using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM), respectively. Figure 4 As shown, the scanning electron microscope images of the carbon nanomaterials obtained in Examples 1 to 3 and Comparative Examples 1 to 2 are shown as follows: Figures 5 to 9 As shown, combined with the RMB peak wave number range of Raman, the diameters and lengths of 100 carbon nanomaterials were counted and averaged by high-resolution transmission electron microscopy to obtain the diameter and length data of the carbon nanomaterials prepared in Examples 1 to 3 and Comparative Examples 1 to 2, respectively, as shown in Table 1 below.

[0103] The powder resistivity of the carbon nanomaterial samples prepared in Examples 1 to 3 and Comparative Examples 1 to 2 was tested using a four-probe resistivity tester to evaluate their conductive properties. The specific test results are shown in Table 1 below.

[0104] Table 1 Performance test results of carbon nanomaterials of Examples 1 to 3 and Comparative Examples 1 to 2

[0105]

[0106]

[0107] As shown in Table 1, compared with Comparative Examples 1 to 2, the preparation methods in Examples 1 to 3 of the present invention have longer continuous production time (can work continuously for more than 30 hours), higher output (output reaches 130.7 to 151.2 g / h), and the degree of graphitization of the obtained carbon nanomaterials is higher (I G / I D The ash content is significantly reduced (less than 14%), the tube diameter is smaller, and the tube length is larger. Examples 1 to 3 of the present invention can stably achieve the preparation of highly graphitized carbon nanomaterials over a long time scale based on different high-energy argon gas injection rates and different temperature conditions in the growth zone. However, the high-energy argon gas loading has a direct impact on the cracking of the catalyst precursor and the carbon source, thereby regulating the product properties of the carbon nanomaterial.

[0108] Combined with the scanning electron microscope image, it can be seen that the low-energy carrier gas used in Comparative Example 1 results in the catalyst not being able to achieve rapid decomposition. There are more catalyst particles on the surface of the obtained carbon nanomaterial compared to Examples 1 to 3, and its charge transfer properties are also significantly different from those of Examples 1 to 3. A comprehensive analysis of Comparative Example 1 and Examples 1 to 3 shows that the preparation scheme of Examples 1 to 3 of the present invention using a high-energy carrier gas and a raw material mixture for rapid energy exchange is very critical for the rapid generation of highly active carbon atoms and their arrangement to form highly graphitized carbon nanomaterials. Low-energy carrier gas will significantly reduce the yield of carbon nanomaterials and the degree of graphitization of the product, which is reflected in I G / ID a significant decline.

[0109] A comprehensive analysis of Comparative Example 2 and Examples 1 to 3 shows that the yields of Examples 1 to 3 are significantly improved under the conditions of the same carbon source concentration, and since the reactants are prevented from passing through the plasma generating zone, the stability of production can be improved and the production time can be extended. At the same time, the carbon nanomaterials obtained in Examples 1 to 3 of the preparation method of the present invention are further optimized in properties compared with Comparative Example 2. The significant reduction in ash content indicates that the quality purity of the product has been greatly improved, while reducing the difficulty and cost of product post-processing. The diameter of the carbon nanomaterials obtained in Examples 1 to 3 is further reduced compared to Comparative Example 2, and the tube length is also increased, which is beneficial to the application of carbon nanomaterials in charge transport in secondary batteries. The product morphology and resistivity of Comparative Example 2 are similar to those of Examples 1 to 3, but relatively more large catalyst clusters can be observed from the scanning electron microscope photos.

[0110] In summary, the carbon nanomaterial prepared in the present invention has a high degree of graphitization, a better aspect ratio and a lower ash content, which can give full play to the charge transport properties of the carbon nanomaterial and make it have extremely high application potential in the application of secondary batteries.

[0111] While the embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A method for preparing a carbon nanomaterial, characterized in that: The following steps are involved: S1: introducing an inert gas into a plasma generating region, wherein the temperature at the center of the plasma generating region is ≥5000° C., to obtain a high-energy carrier gas; S2: mixing the high-energy carrier gas and the reaction mixture and reacting them at 1000-1600° C. to produce the carbon nanomaterial; The reaction mixed gas includes a carbon source, a catalyst precursor and a carrier gas.

2. The method for preparing carbon nanomaterials according to claim 1, wherein: The carbon source includes at least one of alkanes, alkenes, alkynes, and carbon powder; And / or, the carrier gas and the inert gas are each selected from at least one of nitrogen, argon, and helium.

3. The method for preparing carbon nanomaterials according to claim 1, wherein: The catalyst precursor includes a metal organic compound and a sulfur-containing auxiliary agent, wherein the metal organic compound includes at least one of ferrocene, nickelocene, cobaltocene, carbonyl iron, and cobalt carbonyl; and the sulfur-containing auxiliary agent includes at least one of elemental sulfur and sulfur-containing organic small molecules.

4. The method for preparing carbon nanomaterials according to claim 3, wherein: The metal organic compound includes at least one of ferrocene and carbonyl iron; the molar ratio of iron atoms to sulfur atoms in the catalyst precursor is (1-80):

1.

5. The method for preparing carbon nanomaterials according to claim 1, wherein: The reaction time is 1 to 60 seconds; and / or, the time from the time the inert gas is introduced into the plasma generating zone to the time the inert gas is mixed with the reaction mixed gas is ≤ 0.4 seconds.

6. The method for preparing carbon nanomaterials according to claim 1, wherein: The flow rate of the inert gas is 1500-2500 L / min; And / or, the ratio of the flow rate of the high-energy carrier gas to the total flow rate of the reaction mixed gas and the high-energy carrier gas is ≥0.

5.

7. The method for preparing carbon nanomaterials according to claim 1, wherein: The inlet temperature of the plasma generating zone is 0-200°C; And / or, the temperature of the reaction mixture is 150-800°C.

8. The method for preparing carbon nanomaterials according to claim 1, wherein: The step S2 is: passing the high-energy carrier gas through a transition zone with a median temperature of 2800-3200° C., and then mixing with the reaction mixed gas to react in a growth zone with a temperature of 1000-1600° C.

9. The method for preparing carbon nanomaterials according to claim 1, wherein: The flow rate ratio of the carbon source to the carrier gas in the reaction mixed gas is 1:(1-20).

10. Use of the carbon nanomaterial prepared by the preparation method according to any one of claims 1 to 9 in the field of batteries.

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