Method for combined preparation of carbon nanotubes and hydrogen

Abstract

A method for combined preparation of carbon nanotubes and hydrogen. The method comprises: introducing a hydrocarbon carbon source gas and a carrier gas into a plasma generator, so that the hydrocarbon carbon source gas forms free carbon atoms and hydrogen atoms under the action of the generated plasma to obtain a reactive mixed gas flow; and introducing the reactive mixed gas flow, a catalyst precursor, and a growth promoter into a reactor for a floating catalyst chemical vapor deposition reaction to generate carbon nanotubes and hydrogen, wherein the catalyst precursor comprises a titanium-containing compound that can be carbonized to form titanium carbide, and in terms of molar percentage, the titanium-containing compound accounts for 55% or more of the total molar amount of the catalyst precursor. Hydrogen can be jointly prepared while carbon nanotubes are continuously prepared. The method can overcome defects existing in an existing floating catalyst chemical vapor deposition method, and the prepared carbon nanotubes have excellent electrical conductivity, good mechanical properties, and good crystallinity.

Description

A combined preparation method of carbon nanotubes and hydrogen Technical Field

[0001] The present invention relates to the field of chemical industry, in particular to a low-carbon production method for preparing carbon nanotubes and hydrogen using methane as a raw material, and specifically to a combined preparation method of carbon nanotubes and hydrogen. Background Art

[0002] Carbon nanotubes (CNTs), a new type of nanomaterial, possess excellent mechanical and electrical properties, as well as a large aspect ratio and high specific surface area. They have potential applications in electrochemical energy storage, catalysis, composites, and nanodevices. Currently, the main methods for preparing single-walled and multi-walled carbon nanotubes include arc deposition and floating catalytic chemical vapor deposition (FCCVD). FCCVD is a type of chemical vapor deposition method that injects reactants and a carrier gas into a high-temperature reactor to synthesize carbon nanotubes and assemble them into fibers in one step. Its characteristic is that the raw materials react freely in the carrier gas after injection, and no substrate is required for deposition.

[0003] In the prior art, when preparing carbon nanotubes using the floating catalyst method, a peristaltic pump or syringe is generally used to pass a liquid carbon source into a heating furnace through a pipe, so that the raw materials react in the heating furnace to grow carbon nanotubes. On the one hand, since the heating furnace is large and its internal temperature is very high, the raw materials react immediately after entering the tank, and the reaction products are often distributed in various positions in the heating furnace, making it difficult to collect the products later. Generally, a vacuum cleaner is required to assist in collecting the carbon nanotubes. On the other hand, since there are heating zones and non-heating zones in the heating furnace, the heating zone is the reaction temperature zone, and the non-heating zone has a lower temperature. When the reaction raw materials are passed into the heating furnace, some of the reaction raw materials and catalyst precursors will adhere to the furnace wall of the non-heating zone and cannot generate carbon nanotubes, while some of the reaction raw materials will adhere to the furnace wall between the boundary between the non-heating zone and the heating zone. The carbon nanotubes generated by the reaction of this part of the reaction raw materials are of different quality from those generated by the reaction in the heating zone. Therefore, the method of preparing carbon nanotubes using the prior art has the problem of uncontrollable carbon nanotube quality. Another typical floating catalytic method for producing metallic single-walled and multi-walled carbon nanotubes uses ferrocene as a catalyst, methane as a carbon source, and thiophene or carbon disulfide as a catalytic co-agent. While this floating catalytic method can produce single-walled and multi-walled carbon nanotubes, the synthesis process uses iron-containing catalysts such as ferrocene and gaseous carbon sources such as methane. Due to the low melting point of iron (1539°C), it forms a liquid phase during the high-temperature carbon nanotube synthesis reaction, making the catalyst difficult to control. This makes the production of single-walled and multi-walled carbon nanotubes very difficult and the quality is poor. Summary of the Invention

[0004] The purpose of the present invention is to overcome one or more deficiencies in the prior art and to provide a new method that can continuously produce carbon nanotubes while also jointly producing hydrogen. This method can overcome the defects of the existing FCCVD method, and the prepared carbon nanotubes have excellent electrical conductivity, good mechanical properties and crystallinity.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A combined preparation method of carbon nanotubes and hydrogen, comprising:

[0007] Passing a hydrocarbon source gas and a carrier gas into a plasma generator, so that the hydrocarbon source gas forms free carbon atoms and hydrogen atoms under the action of the generated plasma, thereby obtaining a reactive mixed gas flow;

[0008] The reactive mixed gas flow, catalyst precursor and growth promoter are introduced into a reaction furnace to carry out a floating catalytic chemical vapor deposition reaction to generate carbon nanotubes and hydrogen; wherein the catalyst precursor includes a titanium-containing compound that can be carbonized to form titanium carbide, and the titanium-containing compound accounts for more than 55% of the total molar amount of the catalyst precursor in terms of molar percentage.

[0009] In some embodiments of the present invention, the hydrocarbon source gas is a hydrocarbon compound that can be cracked. Further, the hydrocarbon compound that can be cracked includes methane, ethylene, or acetylene.

[0010] In some embodiments of the present invention, the methane is obtained by purifying one or more selected from biogas, natural gas, coalbed methane, shale gas and combustible ice.

[0011] In some embodiments of the present invention, the carrier gas is selected from nitrogen or an inert gas.

[0012] According to some preferred aspects of the present invention, the introduction amount of the hydrocarbon source gas is 10-400 sccm.

[0013] According to some preferred aspects of the present invention, the amount of the carrier gas introduced is 100-4000 sccm.

[0014] According to some preferred aspects of the present invention, the molar ratio of the catalyst precursor to the hydrocarbon source gas is 0.01-0.1:1.

[0015] According to some preferred aspects of the present invention, the molar ratio of the catalyst precursor to the growth promoter is 2-10:1.

[0016] In some embodiments of the present invention, the growth promoter is a combination of one or more selected from thiophene, sulfur powder, thiourea and carbon disulfide.

[0017] According to some preferred aspects of the present invention, the catalyst precursor further comprises a tungsten-containing compound that can be carburized to form tungsten carbide and / or a molybdenum-containing compound that can be carburized to form molybdenum carbide.

[0018] In some embodiments of the present invention, the molar amount of the titanium-containing compound in the catalyst precursor is 60%-80% by mole.

[0019] In some preferred embodiments of the present invention, the titanium-containing compound is titanocene dichloride, the tungsten-containing compound is tungsten hexachloride, and the molybdenum-containing compound is ammonium molybdate or a hydrate thereof.

[0020] According to some preferred aspects of the present invention, the combined preparation method further comprises: introducing carbon nanomaterials as growth seeds into the reactor, wherein the carbon nanomaterials are carbon nanotubes, and the molar ratio of the carbon nanomaterials to the hydrocarbon source gas is 0.05-0.1:1.

[0021] According to some preferred aspects of the present invention, the reaction is carried out at 1000-1800° C. and the reaction time is 1-30 min.

[0022] According to some preferred aspects of the present invention, the combined production method uses a combined production device to carry out the combined production of carbon nanotubes and hydrogen, and the combined production device comprises:

[0023] The plasma generator comprises an air flow inlet and an air flow outlet;

[0024] The reactor, auxiliary material feeding mechanism, carbon nanotube collecting mechanism and hydrogen collecting mechanism;

[0025] The reactor comprises a reactor body, the reactor body comprising a first feed port for introducing the reactive mixed gas flow, a second feed port for introducing auxiliary materials, and an outlet port, the auxiliary materials comprising the catalyst precursor and the growth promoter, the first feed port being in communication with the gas flow outlet, and the auxiliary material feeding mechanism being configured to add the auxiliary materials into the reactor body through the second feed port;

[0026] The carbon nanotube collecting mechanism includes a collecting chamber and a carbon nanotube collecting assembly arranged in the collecting chamber. The collecting chamber includes a chamber inlet and an airflow outlet. The chamber inlet is connected to the discharge port, and the airflow outlet is connected to the hydrogen collecting mechanism.

[0027] Furthermore, the carbon nanotube collecting mechanism can obtain nanotube bundles or nanotube films.

[0028] Furthermore, the combined production device also includes a heat exchanger, which includes a first pipeline and a second pipeline for exchanging heat with the first pipeline. The two ends of the first pipeline are respectively connected to the discharge port and the chamber inlet. One end of the second pipeline is used to introduce the hydrocarbon source gas, and the other end is connected to the air flow inlet.

[0029] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0030] The present invention realizes for the first time a process for the combined preparation of carbon nanotubes and hydrogen. Specifically, in the present invention, a hydrocarbon source gas and a carrier gas are first introduced into a plasma generator, where part of the gas is converted into high-energy plasma. Under the action of the generated plasma, the C-H chemical bonds of the hydrocarbon source gas are broken to form free carbon atoms and hydrogen atoms. In this state, when the hydrocarbon source gas is introduced into a reactor and encounters a titanium-containing compound capable of carbonizing to form titanium carbide, the titanium-containing compound carbonizes at high temperature to form titanium carbide (the melting point of titanium carbide is 3140°C). Under the action of the titanium and hydrogen atoms, carbon nanotubes and hydrogen are continuously and efficiently generated. In particular, the quality of the obtained carbon nanotubes is uniform and stable, avoiding the problems of large quality variations and difficult catalyst control that occur in existing floating catalyst preparation methods.

[0031] In particular, in the method of the present invention, since the energy source for the reaction temperature is primarily derived from the energy generated by gas cracking in the plasma generator, and the high-temperature cracked gas (including carbon atoms, hydrogen atoms, carrier gas, plasma, etc.) is introduced into the reactor, the high-temperature cracked gas can instantly and evenly fill the reactor, ensuring that the reaction process is always carried out at a uniform temperature. This solves the problem of existing heating reactors where the temperature difference between the heated and non-heated zones causes some of the reaction materials to adhere to the furnace walls in the non-heated zones, preventing carbon nanotubes from being generated. This greatly improves production efficiency and quality.

[0032] In addition, the present invention produces economic benefits while avoiding harmful gas emissions and wastewater generation while achieving clean production and realizing full utilization of hydrocarbon source gases with high atomic utilization rates. It can also provide technical support for the value-added utilization of methane-rich gas and the upgrading of carbon nanotube preparation technology in my country. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG1 is a schematic structural diagram of a combined production device according to an embodiment of the present invention;

[0034] FIG2 is a schematic structural diagram of a methane gas purification device according to an embodiment of the present invention;

[0035] In the accompanying drawings: 1, carrier gas storage tank; 2, plasma generator; 3, reactor; 4, auxiliary material feeding mechanism; 5, heat exchanger; 6, carbon nanotube collection mechanism; 61, collection chamber; 62, carbon nanotube collection assembly; 63, carbon nanotube fiber outlet; 7, hydrogen collection mechanism; 8, methane storage tank; 8a, biogas tank; 8b, drying system; 8c, desulfurization system; 8d, first decarbonization system; 8e, second decarbonization system; 8f, methane other source gas storage tank;

[0036] FIG3 is a scanning electron microscope image of carbon nanotubes prepared in Example 1 of the present invention (scale is 1 μm);

[0037] FIG4 is a transmission electron micrograph of carbon nanotubes prepared in Example 1 of the present invention (scale is 50 nm);

[0038] FIG5 is a scanning electron microscope image of carbon nanotubes prepared in Comparative Example 1 of the present invention (scale is 5 μm);

[0039] FIG6 is a scanning electron microscope image of the carbon nanotubes prepared in Comparative Example 2 of the present invention (the scale is 2 μm). DETAILED DESCRIPTION

[0040] The present invention innovatively combines plasma methods, utilizing direct or alternating current arc discharge from electrodes or electrodeless high-frequency discharges such as radio frequency and microwaves to generate plasma. The active substances in the plasma method are high-energy electrons and free radicals. Plasma is formed when the gas continuously absorbs energy from the outside to ionize and generate positive and negative ions and electrons. The decomposition of hydrocarbon source gases, such as methane, in plasma can occur in two ways: one is direct collision with free electrons for decomposition; the other is collision with excited active particles for decomposition. After being cracked into carbon atoms and hydrogen atoms, they are then introduced into a reactor containing a titanium-containing compound capable of carbonizing to form titanium carbide under the action of a carrier gas. The titanium-containing compound will carbonize at high temperatures to form titanium carbide. Under these conditions, the carbon atoms and hydrogen atoms can continuously and efficiently generate carbon nanotubes and hydrogen. Furthermore, the quality of the carbon nanotubes is uniform and stable, achieving the combined continuous production of carbon nanotubes and hydrogen.

[0041] Based on this, the present invention provides a method for the combined preparation of carbon nanotubes and hydrogen, the combined preparation method comprising:

[0042] Passing a hydrocarbon source gas and a carrier gas into a plasma generator, so that the hydrocarbon source gas forms free carbon atoms and hydrogen atoms under the action of the generated plasma, thereby obtaining a reactive mixed gas flow;

[0043] The reactive mixed gas flow, catalyst precursor and growth promoter are introduced into a reaction furnace to carry out a floating catalytic chemical vapor deposition reaction to generate carbon nanotubes and hydrogen; wherein the catalyst precursor includes a titanium-containing compound that can be carbonized to form titanium carbide, and the titanium-containing compound accounts for more than 55% of the total molar amount of the catalyst precursor in terms of molar percentage.

[0044] The method of the present invention will be further described below with reference to FIG1 and FIG2 .

[0045] 1 and 2 , the combined production method uses a combined production device to carry out the combined production of carbon nanotubes and hydrogen. The combined production device includes a carrier gas storage tank 1, a plasma generator 2, a reactor 3, an auxiliary material feeding mechanism 4, a heat exchanger 5, a carbon nanotube collecting mechanism 6, and a hydrogen collecting mechanism 7.

[0046] The plasma generator 2 includes an air flow inlet and an air flow outlet;

[0047] The reactor 3 includes a reactor body, which includes a first feed port for introducing a reactive mixed gas flow, a second feed port for introducing auxiliary materials, and a discharge port. The auxiliary materials include a catalyst precursor and a growth promoter. The first feed port is connected to the gas flow outlet, and the auxiliary material feeding mechanism is used to add the auxiliary materials into the reactor body through the second feed port.

[0048] The carbon nanotube collecting mechanism 6 includes a collecting chamber 61 and a carbon nanotube collecting assembly 62 disposed in the collecting chamber 61. The collecting chamber 61 includes a chamber inlet and an airflow outlet. The chamber inlet is connected to the discharge port, and the airflow outlet is connected to the hydrogen collecting mechanism 7.

[0049] The heat exchanger 5 includes a first pipeline and a second pipeline for exchanging heat with the first pipeline. The two ends of the first pipeline are respectively connected to the discharge port and the chamber inlet. One end of the second pipeline is used to introduce hydrocarbon source gas (for example, it can be connected to the methane storage tank 8), and the other end is connected to the air flow inlet.

[0050] One or more gas flow inlets can be designed and used to introduce hydrocarbon source gas and carrier gas.

[0051] The hydrocarbon source gas can preferably be methane. my country has abundant methane resources, which can be fully utilized. Methane can be obtained by purifying biogas, natural gas, coalbed methane, shale gas, and combustible ice. Of course, pure methane can also be directly selected for the process. Furthermore, when methane is prepared by purifying biogas, natural gas, coalbed methane, shale gas, and combustible ice, the methane gas purification device shown in Figure 2 can be used. The methane gas purification device includes: a methane storage tank 8, a biogas tank 8a, a drying system 8b, a desulfurization system 8c, a first decarbonization system 8d, a second decarbonization system 8e, and a methane other source gas storage tank 8f. Among them, the biogas tank 8a, the drying system 8b, the desulfurization system 8c, the first decarbonization system 8d and the methane storage tank 8 are connected in sequence, and the methane other source gas storage tank 8f, the second decarbonization system 8e and the methane storage tank 8 are connected in sequence. The methane other source gas storage tank 8f can store natural gas, combustible ice, coalbed methane or shale gas, etc.

[0052] For example, for biogas, it can be introduced into the drying system 8b through the biogas tank 8a. The drying process can use a drying tank filled with silica gel, activated alumina, molecular sieve or magnesium oxide as an adsorption desiccant. After drying, it is sequentially introduced into the desulfurization system 8c and the first decarbonization system 8d. The desulfurization process uses a desulfurization tank filled with activated carbon soaked in potassium iodide. The activated carbon can also be modified activated carbon. Commonly used modifiers are metal oxides and their salts, such as ZnO, CuO, CuSO4, Na2CO3, etc., and ionic liquids (for example, including but not limited to aminosulfonic acid lactic acid alkyl diamine complex ionic liquids) or complex amine liquids are used for desulfurization and decarbonization. After desulfurization and decarbonization, it is introduced into the methane storage tank 8 for buffering; for natural gas, combustible ice, coalbed methane or shale gas, it can be decarbonized through the second decarbonization system 8e and then introduced into the methane storage tank 8 for buffering.

[0053] The carrier gas may be nitrogen or an inert gas. The inert gas may be argon, helium, etc., preferably argon.

[0054] The carbon nanotube collection assembly 62 can be collected using a roller-shaped collection device or other collection methods, and mechanical force can be used to pull out carbon nanotube macro-aggregates, such as pulling out carbon nanotube fibers; in the actual preparation process, since the generated carbon nanotubes and hydrogen can flow out together with the carrier gas, they can be cooled onto a collection roller, pressed into a film, or twisted into carbon nanotube fibers.

[0055] Furthermore, after the generated carbon nanotubes and hydrogen can flow out together with the carrier gas and the carbon nanotubes are collected in the carbon nanotube collecting assembly 62, the remaining gas flow can be introduced into the hydrogen collecting mechanism 7. The hydrogen collecting mechanism 7 includes a hydrogen purifier. The principle of the hydrogen purifier is based on the metal palladium membrane hydrogen separation technology. The palladium membrane has good permeability to hydrogen. By utilizing the property that hydrogen atoms can pass through the crystal lattice, the only selection of hydrogen can be achieved. That is, under pressure drive, hydrogen can easily pass through the palladium membrane, while any other gas cannot pass through it, and it can intercept any gas impurities except hydrogen, so it can be used for hydrogen separation and purification.

[0056] Taking methane as the hydrocarbon source gas and argon as the carrier gas as an example, the implementation method of using the above-mentioned combined production device to jointly prepare carbon nanotubes and hydrogen includes:

[0057] Methane and argon are introduced into a plasma generator 2 through their respective air flow inlets (the plasma generator is not specifically limited, and can be any type of discharge method, whether it is a DC or AC arc discharge with electrodes or a high-frequency discharge method such as radio frequency or microwave, as long as it can produce a low-temperature plasma). The operating parameters of the plasma generator 2 are as follows: a power variation range of 30kW to 60kW, and a power supply that can be a thyristor rectifier power supply, which is a dedicated power supply for arc plasma generators. The operating parameters of the dedicated DC arc plasma generator power supply are as follows: operating voltage: continuously adjustable from 0 to 400V, Working current: 0~400A continuously adjustable. In the plasma generator 2, part of the gas is converted into high-energy active material plasma. Methane collides with free electrons or excited active materials to decompose, forming free carbon atoms and hydrogen atoms, which are then introduced into the reactor 3 as a reactive mixed gas flow along with the remaining argon. At the same time, the catalyst precursor and growth promoter are also introduced into the reactor 3. Specifically, the catalyst precursor and growth promoter have a molar ratio of 2:1 to 10:1. After the catalyst precursor and growth promoter are evenly mixed at room temperature, they are placed in a reactor. The auxiliary material feeding mechanism 4 is fed into the reaction furnace 3 by the electronic peristaltic pump in the auxiliary material feeding mechanism 4. The temperature in the reaction furnace 3 can be controlled at 1000-1800°C (the heat of this temperature actually comes from the decomposition of the plasma generator, that is, the temperature of the reactive mixed gas flow coming out of the plasma generator is basically at 1000-1800°C, and the reaction furnace does not need additional heating). The reaction time of the thermal reaction is 1-30 minutes, for example, 1 minute, 2 minutes, 3 minutes, 5 minutes, 10 minutes, 12 minutes, 15 minutes, etc. min, 20min, 25min, etc. When the reaction is completed, the generated carbon nanotubes, hydrogen and the remaining carrier gas flow out of the reactor 3. Since the overall temperature of the air flow is relatively high, this part of the waste heat can be utilized, for example, used to exchange heat with the introduced methane in the heat exchanger 5. This not only achieves the purpose of heat recycling, but also reduces the time consumption of heating to the temperature required for the system reaction. After that, it enters the carbon nanotube collecting mechanism 6 to collect the carbon nanotubes, and the remaining air flow enters the hydrogen collecting mechanism 7 to collect hydrogen, and the remaining carrier gas is recycled.

[0058] Furthermore, the amount of hydrocarbon source gas introduced is 10-400 sccm, and the amount of carrier gas introduced is 100-4000 sccm.

[0059] Furthermore, the molar ratio of the catalyst precursor to the hydrocarbon source gas is 0.01-0.1:1, and the molar ratio of the catalyst precursor to the growth promoter is 2-10:1.

[0060] Furthermore, the catalyst precursor also includes a tungsten-containing compound that can be carburized to form tungsten carbide and / or a molybdenum-containing compound that can be carburized to form molybdenum carbide; in some embodiments, the titanium-containing compound is dichlorotitanocene, the tungsten-containing compound is tungsten hexachloride, and the molybdenum-containing compound is ammonium molybdate or its hydrate.

[0061] Furthermore, the growth promoter is a combination of one or more selected from thiophene, sulfur powder, thiourea and carbon disulfide.

[0062] Furthermore, the combined preparation method also includes: introducing carbon nanomaterials as growth seeds into the reactor, wherein the carbon nanomaterials are carbon nanotubes, and the molar ratio of the carbon nanomaterials to the hydrocarbon source gas is 0.05-0.1:1.

[0063] The present invention can not only effectively avoid the disadvantages of the traditional plasma method that it can only produce agglomerated carbon black instead of carbon nanotubes; it can also avoid the problems of traditional catalytic cracking catalysts being deactivated due to carbon deposition, which will take away some catalysts that do not participate in catalysis when replaced, and the problem of catalyst melting and deactivation at high temperatures, thereby increasing the output, improving the efficiency of the catalyst, reducing the cost of catalyst replacement, and reducing the time consumption of heating to the temperature required for the system reaction.

[0064] The preparation process of the present invention is one-step, efficient, and easy to scale up; the gas phase flow uses inert gas, thereby reducing potential hazards.

[0065] The present invention prepares carbon nanotubes and hydrogen, generates economic benefits, avoids the emission of harmful gases, and does not generate wastewater, thus achieving clean production.

[0066] The present invention can provide technical support for the value-added utilization of methane-rich gas and the upgrading of nano-carbon preparation technology in my country.

[0067] At the same time, the method of the present invention is direct and simple, has good continuity, is controllable and easy to operate, and has good safety.

[0068] The above scheme is further described below in conjunction with specific examples; it should be understood that these examples are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following examples; the implementation conditions adopted in the examples can be further adjusted according to specific requirements, and the implementation conditions not specified are generally the conditions in routine experiments.

[0069] Unless otherwise specified in the following examples, all raw materials were purchased from commercial sources or prepared by conventional methods in the art.

[0070] Testing method for the purity of carbon nanotubes: Utilize TEM observation and image analysis to determine the type of carbon phase, calculate the proportion of carbon nanotubes in the carbon phase, and obtain the purity of carbon nanotubes. Example 1

[0071] The combined production apparatus and its operation process shown in FIG1 are used to jointly prepare carbon nanotubes and hydrogen. The process parameters include:

[0072] Turn on the power supply and turn on the plasma generator switch. Turn on the working gas, methane injection rate is 120 sccm, argon injection rate is 600 sccm, enter the plasma reactor, and purge for 2.0 minutes. Start the plasma generator. After starting, stabilize for 1.5 minutes. Start the auxiliary material feeding mechanism and record the time. Arc discharge generates plasma and releases heat. The cracked gas, that is, the reactive mixed gas, enters the reactor at high temperature. Adjust the working voltage to 300 V and the working current to 150 A. The temperature of the reactor was controlled at 1100±100°C. Simultaneously, titanocene dichloride, tungsten hexachloride, and sulfur powder were uniformly mixed at a molar ratio of 6:3:1 at room temperature, placed in an auxiliary material feeding mechanism, and fed into the reactor. The molar ratio of the total amount of titanocene dichloride and tungsten hexachloride added to the methane was controlled to be 0.05:1. After 2.0 minutes, the flue gas floating out of the discharge port of the reactor was collected to separate the carbon material and hydrogen. The scanning electron microscopy (SEM) image (Figure 3) and the transmission electron microscopy (TEM) image (Figure 4) of the obtained carbon nanomaterial show that the generated carbon material has the morphology of tubular carbon nanotubes with a purity of ≥ 99.9%, a tube diameter of 3-15 nm, and a small diameter with a relatively uniform distribution. Example 2

[0073] The combined production apparatus and its operation process shown in FIG1 are used to jointly prepare carbon nanotubes and hydrogen. The process parameters include:

[0074] Turn on the power supply and turn on the plasma generator switch. Turn on the working gas, methane injection rate is 360sccm, argon injection rate is 600sccm, enter the plasma reactor, and purge for 2.0 minutes. Start the plasma generator. After starting, stabilize for 1.5 minutes. Start the auxiliary material feeding mechanism and record the time. Arc discharge generates plasma and releases heat. The cracked gas, that is, the reactive mixed gas, enters the reactor at high temperature. Adjust the working voltage to 350 V and the working current to 170 A. The temperature of the reactor is controlled at 1400±100°C. Simultaneously, titanocene dichloride, tungsten hexachloride, and sulfur powder are uniformly mixed at a molar ratio of 6:3:1 at room temperature, placed in an auxiliary material feeding mechanism, and fed into the reactor. The molar ratio of the total amount of titanocene dichloride and tungsten hexachloride to the methane is controlled to be 0.05:1. After 2.0 minutes, the flue gas floating out of the discharge port of the reactor is collected to separate the carbon material and hydrogen. The collected carbon material has the morphology of tubular carbon nanotubes, with a purity of ≥ 98.4% and a tube diameter of 5-20 nm. Example 3

[0075] The combined production apparatus and its operation process shown in FIG1 are used to jointly prepare carbon nanotubes and hydrogen. The process parameters include:

[0076] Turn on the power supply and turn on the plasma generator switch. Turn on the working gas, methane injection rate is 360 sccm, argon injection rate is 600 sccm, enter the plasma reactor, and purge for 2.0 minutes. Start the plasma generator. After starting, stabilize for 1.5 minutes. Start the auxiliary material feeding mechanism and record the time. Arc discharge generates plasma and releases heat. The cracked gas, that is, the reactive mixed gas, enters the reactor at high temperature. Adjust the working voltage to 380 V and the working current to 200 A. The temperature of the reactor is controlled at 1700±100°C. At the same time, titanocene dichloride, tungsten hexachloride, and sulfur powder are uniformly mixed at a molar ratio of 6:3:1 at room temperature, placed in an auxiliary material feeding mechanism, and fed into the reactor. The molar ratio of the total amount of titanocene dichloride and tungsten hexachloride added to the methane is controlled to be 0.05:1. After 2.0 minutes, the flue gas floating out of the discharge port of the reactor is collected to separate the carbon material and hydrogen. The collected carbon material morphology is tubular carbon nanotubes with a purity of ≥96.2% and a tube diameter of 80~150nm. Example 4

[0077] The combined production apparatus and its operation process shown in FIG1 are used to jointly prepare carbon nanotubes and hydrogen. The process parameters include:

[0078] Turn on the power supply and turn on the plasma generator switch. Turn on the working gas, methane injection rate is 120 sccm, argon injection rate is 600 sccm, enter the plasma reactor, and purge for 2.0 minutes. Start the plasma generator. After starting, stabilize for 1.5 minutes. Start the auxiliary material feeding mechanism and record the time. Arc discharge generates plasma and releases heat. The cracked gas, that is, the reactive mixed gas, enters the reactor at high temperature. Adjust the working voltage to 300 V and the working current to 150 A. The temperature of the reactor is controlled at 1100±100°C. At the same time, titanocene dichloride, tungsten hexachloride, and sulfur powder are uniformly mixed at a molar ratio of 6:3:1 at room temperature, placed in an auxiliary material feeding mechanism, and fed into the reactor. The molar ratio of the total amount of titanocene dichloride and tungsten hexachloride added to the methane is controlled to be 0.1:1. After 2.0 minutes, the flue gas floating out of the discharge port of the reactor is collected to separate the carbon material and hydrogen. The collected carbon material morphology is tubular carbon nanotubes with a purity of ≥95% and a tube diameter of 50~200nm. Comparative Example 1

[0079] The method is basically the same as Example 1, except that titanocene dichloride is replaced by an equal molar amount of tungsten hexachloride, that is, the molar ratio of tungsten hexachloride to sulfur powder in Comparative Example 1 is 9:1.

[0080] The scanning electron microscope (SEM) image of the obtained carbon nanomaterial is shown in FIG5 . It can be seen that the generated carbon nanomaterial contains carbon nanotubes as well as a large amount of flaky and spherical carbon nanomaterials, and the purity of the carbon nanotubes is ≥68%. Comparative Example 2

[0081] The process is basically the same as Example 1, except that the molar ratio of titanocene dichloride, tungsten hexachloride and sulfur powder is controlled to be 3:6:1.

[0082] The scanning electron microscope (SEM) image of the obtained carbon nanomaterial is shown in FIG6 . It can be seen that the generated carbon nanomaterial is mainly carbon nanotubes, which are relatively concentrated in distribution, and a small amount of amorphous carbon nanomaterials with other morphologies are generated. The purity of the carbon nanotubes is ≥89%. Compared with Example 1, the diameter of the carbon nanotubes is larger, ranging from 30 to 80 nm.

[0083] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

[0084] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

Claims

1. A combined preparation method of carbon nanotubes and hydrogen, characterized in that The combined preparation method includes: Introducing a hydrocarbon carbon source gas and a carrier gas into a plasma generator, so that the hydrocarbon carbon source gas forms free carbon atoms and hydrogen atoms under the action of the generated plasma, and obtaining a reactive mixed gas stream; the flow rate of the hydrocarbon carbon source gas is 10-400 sccm, and the flow rate of the carrier gas is 100-4000 sccm; Introducing the reactive mixed gas stream, a catalyst precursor, carbon nanomaterials as growth seeds, and a growth promoter into a reaction furnace to carry out a floating catalyst chemical vapor deposition reaction to generate carbon nanotubes and hydrogen; Among them, the catalyst precursor includes a titanium-containing compound that can be carbonized to form titanium carbide, and in terms of molar percentage, the titanium-containing compound accounts for more than 55% of the total molar amount of the catalyst precursor; The feeding molar ratio of the catalyst precursor to the hydrocarbon carbon source gas is 0.01-0.1∶1; The feeding molar ratio of the catalyst precursor to the growth promoter is 2-10∶1; The catalyst precursor further includes a tungsten-containing compound that can be carbonized to form tungsten carbide and / or a molybdenum-containing compound that can be carbonized to form molybdenum carbide; The carbon nanomaterials are carbon nanotubes, and the molar ratio of the carbon nanomaterials to the hydrocarbon carbon source gas is 0.05-0.1:1; The reaction is carried out at 1000-1800 °C; This combined preparation method uses a combined production device to jointly prepare carbon nanotubes and hydrogen. The combined production device includes: The plasma generator, which includes a gas flow inlet and a gas flow outlet; The reaction furnace, an auxiliary material feeding mechanism, a carbon nanotube collection mechanism, and a hydrogen collection mechanism; The reaction furnace includes a reaction furnace body. The reaction furnace body includes a first feed port for introducing the reactive mixed gas stream, a second feed port for introducing auxiliary materials, and a discharge port. The auxiliary materials include the catalyst precursor and the growth promoter. The first feed port is communicated with the gas flow outlet, and the auxiliary material feeding mechanism is used to add the auxiliary materials into the reaction furnace body through the second feed port; The carbon nanotube collection mechanism includes a collection chamber and a carbon nanotube collection component arranged in the collection chamber. The collection chamber includes a chamber inlet and a gas flow discharge port. The chamber inlet is communicated with the discharge port, and the gas flow discharge port is communicated with the hydrogen collection mechanism. The carbon nanotube collection mechanism can obtain a nanotube bundle or a nanotube film; A heat exchanger, the heat exchanger includes a first pipeline and a second pipeline for heat exchange with the first pipeline. The two ends of the first pipeline are respectively communicated with the discharge port and the chamber inlet. One end of the second pipeline is used to introduce the hydrocarbon carbon source gas, and the other end is communicated with the gas flow inlet.

2. A combined preparation method of carbon nanotubes and hydrogen, characterized in that, The combined preparation method includes: Introducing a hydrocarbon carbon source gas and a carrier gas into a plasma generator, so that the hydrocarbon carbon source gas forms free carbon atoms and hydrogen atoms under the action of the generated plasma, and obtaining a reactive mixed gas stream; the flow rate of the hydrocarbon carbon source gas is 10-400 sccm, and the flow rate of the carrier gas is 100-4000 sccm; Introduce the reactive mixed gas stream, catalyst precursor, carbon nanomaterials as growth seeds, and growth promoter into a reaction furnace to carry out floating catalyst chemical vapor deposition reaction to produce carbon nanotubes and hydrogen gas; Among them, the catalyst precursor includes a titanium-containing compound capable of carbonizing to form titanium carbide, and in terms of molar percentage, the titanium-containing compound accounts for more than 55% of the total molar amount of the catalyst precursor; The molar ratio of the catalyst precursor to the hydrocarbon carbon source gas in the feed is 0.01 - 0.1∶1; The molar ratio of the catalyst precursor to the growth promoter in the feed is 2 - 10∶1; The catalyst precursor further includes a tungsten-containing compound capable of carbonizing to form tungsten carbide and / or a molybdenum-containing compound capable of carbonizing to form molybdenum carbide; The carbon nanomaterials are carbon nanotubes, and the molar ratio of the carbon nanomaterials to the hydrocarbon carbon source gas is 0.05 - 0.1:1; The reaction is carried out at 1000 - 1800 °C.

3. A method for the combined preparation of carbon nanotubes and hydrogen, characterized in that, This combined preparation method includes: Introduce the hydrocarbon carbon source gas and carrier gas into a plasma generator, and under the action of the generated plasma, the hydrocarbon carbon source gas forms free carbon atoms and hydrogen atoms to obtain a reactive mixed gas stream; Introduce the reactive mixed gas stream, catalyst precursor, and growth promoter into a reaction furnace to carry out floating catalyst chemical vapor deposition reaction to produce carbon nanotubes and hydrogen gas; among them, the catalyst precursor includes a titanium-containing compound capable of carbonizing to form titanium carbide, and in terms of molar percentage, the titanium-containing compound accounts for more than 55% of the total molar amount of the catalyst precursor.

4. The method for jointly preparing carbon nanotubes and hydrogen according to claim 1 or 2 or 3, characterized in that, The hydrocarbon carbon source gas is a hydrocarbon compound capable of being cracked.

5. The method for jointly preparing carbon nanotubes and hydrogen according to claim 4, wherein, The hydrocarbon compound capable of being cracked includes methane, ethylene, or acetylene.

6. The method for co-producing carbon nanotubes and hydrogen according to claim 5, wherein, The hydrocarbon compound capable of being cracked is methane, and the methane is obtained by purification from one or more of biogas, natural gas, coalbed methane, shale gas, and combustible ice.

7. The combined preparation method of carbon nanotubes and hydrogen according to claim 1 or 2 or 3, characterized in that, The carrier gas is selected from nitrogen or inert gas.

8. The method for jointly preparing carbon nanotubes and hydrogen according to claim 3, wherein The flow rate of the hydrocarbon carbon source gas is 10 - 400 sccm, and the flow rate of the carrier gas is 100 - 4000 sccm.

9. The method for co-preparing carbon nanotubes and hydrogen according to claim 3, characterized in that, The molar ratio of the catalyst precursor to the hydrocarbon carbon source gas in the feed is 0.01 - 0.1∶1.

10. The method for co-producing carbon nanotubes and hydrogen according to claim 3, characterized in that, The molar ratio of the catalyst precursor to the growth promoter in the feed is 2 - 10∶1.

11. The combined preparation method of carbon nanotubes and hydrogen according to claim 1 or 2 or 3 or 10, characterized in that, The growth promoter is a combination selected from one or more of thiophene, sulfur powder, thiourea, and carbon disulfide.

12. The method for co-preparing carbon nanotubes and hydrogen according to claim 3, characterized in that, The catalyst precursor further includes a tungsten-containing compound capable of carbonizing to form tungsten carbide and / or a molybdenum-containing compound capable of carbonizing to form molybdenum carbide.

13. The method for jointly preparing carbon nanotubes and hydrogen according to claim 12, wherein The titanium-containing compound is titanocene dichloride, the tungsten-containing compound is tungsten hexachloride, and the molybdenum-containing compound is ammonium molybdate or its hydrate.

14. The method for co-producing carbon nanotubes and hydrogen according to claim 3, wherein, This combined preparation method further includes: also introduce carbon nanomaterials as growth seeds into the reaction furnace. The carbon nanomaterials are carbon nanotubes, and the molar ratio of the carbon nanomaterials to the hydrocarbon carbon source gas is 0.05 - 0.1:

1.

15. The method for jointly preparing carbon nanotubes and hydrogen according to claim 3, wherein The reaction is carried out at 1000 - 1800 °C, and the reaction time is 1 - 30 min.

16. The method for jointly preparing carbon nanotubes and hydrogen according to claim 3, wherein, The combined preparation method uses a combined production device for the combined preparation of carbon nanotubes and hydrogen. The combined production device includes: The plasma generator, which includes an air flow inlet and an air flow outlet; The reaction furnace, the auxiliary material feeding mechanism, the carbon nanotube collection mechanism and the hydrogen collection mechanism; The reaction furnace includes a reaction furnace body. The reaction furnace body includes a first feed inlet for introducing the reactive mixed gas stream, a second feed inlet for introducing auxiliary materials, and a discharge outlet. The auxiliary materials include the catalyst precursor and the growth promoter. The first feed inlet is communicated with the air flow outlet. The auxiliary material feeding mechanism is used to add the auxiliary materials into the reaction furnace body through the second feed inlet; The carbon nanotube collection mechanism includes a collection chamber and a carbon nanotube collection assembly arranged in the collection chamber. The collection chamber includes a chamber inlet and an air flow discharge outlet. The chamber inlet is communicated with the discharge outlet. The air flow discharge outlet is communicated with the hydrogen collection mechanism. The carbon nanotube collection mechanism can obtain nanotube bundles or nanotube films.

17. The method for co-preparing carbon nanotubes and hydrogen according to claim 16, characterized in that, The combined production device further includes a heat exchanger. The heat exchanger includes a first pipeline and a second pipeline for exchanging heat with the first pipeline. The two ends of the first pipeline are respectively communicated with the discharge outlet and the chamber inlet. One end of the second pipeline is used to introduce the hydrocarbon source gas, and the other end is communicated with the air flow inlet.

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