Combined preparation method of carbon nano tube and hydrogen

Abstract

The invention discloses a carbon nanotube and hydrogen combined preparation method, which comprises the following steps: 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 a reactive mixed gas flow is obtained; introducing the reactive mixed gas flow, a catalyst precursor and a growth promoter into a reaction furnace, and carrying out a floating catalytic chemical vapor deposition reaction to generate carbon nanotubes and hydrogen; the catalyst precursor comprises a titanium-containing compound capable of being carbonized to form titanium carbide, and the titanium-containing compound accounts for more than 55% of the total molar weight of the catalyst precursor according to the molar percentage content; according to the method, hydrogen can be jointly prepared while the carbon nanotubes are continuously prepared and produced, the defects existing in an existing floating catalytic chemical vapor deposition method can be overcome, and the prepared carbon nanotubes have excellent conductivity and good mechanical property and crystallinity.

Description

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) are a new type of nanomaterial with excellent mechanical and electrical properties, as well as a huge aspect ratio and high specific surface area. They have potential application prospects in electrochemical energy storage, catalysis, composites and nanodevices. At present, the methods for preparing single-walled and multi-walled carbon nanotubes mainly include arc method and floating catalytic chemical vapor deposition (FCCVD). Among them, FCCVD is a type of chemical vapor deposition method. It is a technology that injects reactants and carrier gases into a high-temperature reactor to synthesize carbon nanotubes and assemble them into fibers in one step. The 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 a syringe is generally used to pass a liquid carbon source into a heating furnace through a pipeline, so that the raw materials react in the heating furnace to grow carbon nanotubes. On the one hand, since the heating furnace is large in size and its internal temperature is very high, the raw materials react immediately after entering the tank, and the products after the reaction are often distributed in various positions in the heating furnace, making it difficult to collect the products in the later stage. 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 a reaction temperature zone, and the temperature of the non-heating zone is relatively low. When the reaction raw materials are passed into the heating furnace, part 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 part of the reaction raw materials will adhere to the furnace wall between the boundary of 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 method for preparing metallic single-walled and multi-walled carbon nanotubes using the floating catalytic method is to use ferrocene as a catalyst, methane as a carbon source, and thiophene or carbon disulfide as a catalytic aid. Although the floating catalytic method can prepare 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 (melting point is 1539°C), a liquid phase is formed in the high-temperature reaction of synthesizing carbon nanotubes, making it difficult to control the catalyst, making it very difficult to prepare single-walled and multi-walled carbon nanotubes 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 and simultaneously produce 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, the combined preparation method 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 in terms of molar percentage, the titanium-containing compound accounts for more than 55% of the total molar amount of the catalyst precursor.

[0009] In some embodiments of the present invention, the hydrocarbon source gas is a hydrocarbon that can be cracked. Further, the hydrocarbon 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 feed 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 capable of being carburized to form tungsten carbide and / or a molybdenum-containing compound capable of being 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 percentage.

[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 its hydrate.

[0020] According to some preferred aspects of the present invention, the combined preparation method further comprises: introducing carbon nanomaterials as growth seeds into the reaction furnace, 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 airflow inlet and an airflow outlet;

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

[0025] The reactor comprises a reactor body, the reactor body comprises a first feed inlet for introducing the reactive mixed gas flow, a second feed inlet for introducing auxiliary materials, and a discharge port, the auxiliary materials comprising the catalyst precursor and the growth promoter, the first feed inlet 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 inlet;

[0026] The carbon nanotube collecting mechanism comprises a collecting chamber and a carbon nanotube collecting assembly arranged in the collecting chamber. The collecting chamber comprises 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 airflow 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 the process of jointly preparing carbon nanotubes and hydrogen for the first time. Specifically, in the present invention, firstly, hydrocarbon source gas and carrier gas are introduced into a plasma generator, part of the gas is converted into high-energy plasma in the plasma generator, and the hydrocarbon source gas will have its CH chemical bonds broken by the generated plasma to form free carbon atoms and hydrogen atoms. In this state, when introduced into a reaction furnace and meets a titanium-containing compound that can be carbonized to form titanium carbide, the titanium-containing compound will be carbonized at high temperature to form titanium carbide (the melting point of titanium carbide is 3140° C.), and carbon atoms and hydrogen atoms can continuously and efficiently generate carbon nanotubes and hydrogen under their action. In particular, the quality of the obtained carbon nanotubes is uniform and stable, avoiding the problems of large quality differences and difficult catalyst control in the existing floating catalyst method.

[0031] In particular, in the method of the present invention, since the energy source of the reaction temperature basically comes from the energy generated by the cracking of the gas in the plasma generator, and the high-temperature cracking gas (including carbon atoms, hydrogen atoms, carrier gas, plasma, etc.) is introduced into the reactor, it can instantly and evenly fill the reactor, so that the reaction process is always carried out at a uniform temperature, which solves the problem that part of the reaction raw materials caused by the temperature difference between the heating zone and the non-heating zone of the existing heating reactor will adhere to the furnace wall of the non-heating zone and cannot generate carbon nanotubes, thereby greatly improving the production efficiency and production quality.

[0032] In addition, the present invention prepares carbon nanotubes and hydrogen to generate economic benefits while avoiding harmful gas emissions and no wastewater generation, thereby achieving clean production and 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] Figure 1 It is a structural schematic diagram of a combined production device in an embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the structure of a methane gas purification device in 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] Figure 3 This is a scanning electron microscope image of the carbon nanotubes prepared in Example 1 of the present invention (scale is 1 μm);

[0037] Figure 4 This is a transmission electron microscope image of the carbon nanotubes prepared in Example 1 of the present invention (scale is 50 nm);

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

[0039] Figure 6 This is a scanning electron microscope image of the carbon nanotubes prepared in Comparative Example 2 of the present invention (scale is 2 μm). DETAILED DESCRIPTION

[0040] The present invention innovatively combines the plasma method, using the DC or AC arc discharge of the electrode or the electrodeless high-frequency discharge such as radio frequency and microwave to obtain plasma. The active substances of the plasma method are high-energy electrons and free radicals. When the gas continuously absorbs energy from the outside to ionize and generate positive and negative ions and electrons, plasma is formed. The decomposition of hydrocarbon carbon source gas such as methane in plasma can be carried out in two ways: one is to decompose by direct collision with free electrons; the other is to decompose by collision with excited active particles; after being cracked into carbon atoms and hydrogen atoms, they are allowed to enter the reactor containing titanium-containing compounds that can be carbonized to form titanium carbide under the action of carrier gas. The titanium-containing compounds will be carbonized at high temperature to form titanium carbide. Carbon atoms and hydrogen atoms can continuously and efficiently generate carbon nanotubes and hydrogen under their action, and the quality of carbon nanotubes is uniform and stable, realizing the joint continuous preparation of carbon nanotubes and hydrogen.

[0041] Based on this, the present invention provides a method for jointly preparing carbon nanotubes and hydrogen, the 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 in terms of molar percentage, the titanium-containing compound accounts for more than 55% of the total molar amount of the catalyst precursor.

[0044] Combine the following Figure 1 and Figure 2 The method of the present invention is further introduced.

[0045] See also Figure 1 to Figure 2 As shown, the combined preparation method adopts a combined production device to carry out the combined preparation of carbon nanotubes and hydrogen, and the combined production device includes a carrier gas storage tank 1, a plasma generator 2, a reaction furnace 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 airflow inlet and an airflow outlet;

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

[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 to be used to introduce hydrocarbon source gas and carrier gas.

[0051] The hydrocarbon source gas can preferably be methane. my country has abundant methane resources and 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. Further, when methane is prepared by purifying biogas, natural gas, coalbed methane, shale gas, and combustible ice, it can be used. Figure 2The methane gas purification device shown is carried out, and 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, wherein 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, and 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 successively 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 component 62 can be collected by 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, when the generated carbon nanotubes and hydrogen can flow out together with the carrier gas and after the carbon nanotubes are collected by 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 any gas impurities except hydrogen can be intercepted, 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 gas flow inlets (the plasma generator is not specifically limited, and can be any type of plasma as long as it can produce low-temperature plasma, whether it is a DC or AC arc discharge with electrodes or a high-frequency discharge without electrodes such as radio frequency or microwave). The operating parameters of the plasma generator 2 are as follows: a power variation range of 30kW to 60kW, and the power supply can be a thyristor rectifier power supply, which is a special power supply for arc plasma generators. The operating parameters of the DC arc plasma generator special power supply are as follows: operating voltage: 0 to 400V continuously adjustable, 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 the growth promoter are also introduced into the reactor 3. Specifically, the catalyst precursor and the growth promoter have a molar ratio of 2:1 to 10:1. After the catalyst precursor and the growth promoter are evenly mixed at room temperature, they are placed in a reactor. The auxiliary material feeding mechanism 4 is injected 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 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 finished, the generated carbon nanotubes, hydrogen and the remaining carrier gas flow out of the reactor 3. Since the overall temperature of the gas 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 for heating to the temperature required for the system reaction. After that, the carbon nanotubes are collected in the carbon nanotube collecting mechanism 6, and the remaining gas 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 titanocene dichloride, 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 reaction furnace, 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 drawbacks of the traditional plasma method that it can only produce agglomerated carbon black instead of carbon nanotubes; it can also avoid the problem that the traditional catalytic cracking catalyst is deactivated due to carbon deposition, part of the catalyst that does not participate in catalysis is taken away during replacement, and the problem of catalyst melting and deactivation at high temperature, thereby increasing the output, increasing the efficiency of the catalyst, reducing the cost of catalyst replacement, and reducing the time consumption for heating to the temperature required for the system reaction.

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

[0065] The present invention prepares carbon nanotubes and hydrogen, generates economic benefits, avoids the emission of harmful gases, and does not generate waste water, 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 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 embodiments; it should be understood that these embodiments 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 embodiments; the implementation conditions adopted in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0069] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

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

[0071] Example 1

[0072] Using the above Figure 1 The combined production device and its operation process are used to prepare carbon nanotubes and hydrogen, and the process parameters include:

[0073] The power supply was turned on, and the switch of the plasma generator was turned on. The working gas was turned on. The methane injection rate was 120 sccm, and the argon injection rate was 600 sccm. The plasma reactor was entered and purged for 2.0 minutes. The plasma generator was started. After starting, it was stabilized for 1.5 minutes. The auxiliary material feeding mechanism was started, and the time was recorded at the same time. The arc discharge generated plasma and released heat. The cracking gas, i.e., the reactive mixed gas flow, entered the reactor at high temperature. The working voltage was adjusted to 300V, the working current was adjusted to 150A, and the temperature of the reactor was controlled to be 1100±100°C. At the same time, dichlorobis(pentylene)titanium chloride, tungsten hexachloride and sulfur powder were mixed uniformly at a molar ratio of 6:3:1 at room temperature, placed in the auxiliary material feeding mechanism, and sent to the reactor. The total addition amount of dichlorobis(pentylene)titanium chloride and tungsten hexachloride was controlled to be 0.05:1 with respect to the feeding molar ratio of methane. 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 microscope (SEM) image of the obtained carbon nanomaterial is as follows: Figure 3 As shown in the transmission electron microscope (TEM) Figure 4 As shown, it can be seen that the morphology of the generated carbon material is tubular carbon nanotubes, the purity of the carbon nanotubes is ≥99.9%, the tube diameter is 3-15nm, and the diameter of the carbon nanotubes is small and the distribution is relatively uniform.

[0074] Example 2

[0075] Using the above Figure 1 The combined production device and its operation process are used to prepare carbon nanotubes and hydrogen, and the process parameters include:

[0076] Turn on the power, turn on the plasma generator switch, turn on the working gas, the methane injection rate is 360sccm, the argon injection rate is 600sccm, enter the plasma reactor, and purge for 2.0 minutes, start the plasma generator, stabilize for 1.5 minutes after startup, start the auxiliary material feeding mechanism, and record the time at the same time. The arc discharge generates plasma and releases heat. The cracking gas, that is, the reactive mixed gas flow, enters the reactor at high temperature. Adjust the working voltage to 350V and the working current to 170A. Control the temperature of the reactor to 1400±100℃; at the same time, titanocene dichloride, tungsten hexachloride and sulfur powder are mixed evenly at a molar ratio of 6:3:1 at room temperature, placed in an auxiliary material feeding mechanism, and fed into a reactor, wherein the molar ratio of the total addition amount of titanocene dichloride and tungsten hexachloride to the feeding amount of 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, the purity of the carbon nanotubes is ≥98.4%, and the tube diameter is 5-20nm.

[0077] Example 3

[0078] Using the above Figure 1 The combined production device and its operation process are used to prepare carbon nanotubes and hydrogen, and the process parameters include:

[0079] Turn on the power, 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, stabilize for 1.5 minutes after startup, start the auxiliary material feeding mechanism, and record the time at the same time. The arc discharge generates plasma and releases heat. The cracking gas, that is, the reactive mixed gas, enters the reactor at high temperature. Adjust the working voltage to 380V and the working current to 200A. Control the temperature of the reactor to 1 700±100℃; at the same time, titanocene dichloride, tungsten hexachloride and sulfur powder are mixed evenly at a molar ratio of 6:3:1 at room temperature, placed in an auxiliary material feeding mechanism, and fed into a reactor, wherein the molar ratio of the total addition amount of titanocene dichloride and tungsten hexachloride to the feeding amount of 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, the purity of the carbon nanotubes is ≥96.2%, and the tube diameter is 80-150nm.

[0080] Example 4

[0081] Using the above Figure 1 The combined production device and its operation process are used to prepare carbon nanotubes and hydrogen, and the process parameters include:

[0082] Turn on the power, turn on the plasma generator switch, turn on the working gas, the methane injection rate is 120sccm, the argon injection rate is 600sccm, enter the plasma reactor, and purge for 2.0 minutes, start the plasma generator, stabilize for 1.5 minutes after startup, start the auxiliary material feeding mechanism, and record the time at the same time. The arc discharge generates plasma and releases heat. The cracking gas, that is, the reactive mixed gas flow, enters the reactor at high temperature. Adjust the working voltage to 300V and the working current to 150A to control the temperature of the reactor. is 1100±100℃; at the same time, dichlorotitacenene, tungsten hexachloride and sulfur powder are mixed evenly at a molar ratio of 6:3:1 at room temperature, placed in an auxiliary material feeding mechanism, and fed into a reactor, wherein the total added amount of dichlorotitacenene and tungsten hexachloride and the feeding molar ratio of methane are 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, and the collected carbon material has the morphology of tubular carbon nanotubes, the purity of the carbon nanotubes is ≥95%, and the tube diameter is 50-200nm.

[0083] Comparative Example 1

[0084] 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.

[0085] The scanning electron microscope (SEM) image of the obtained carbon nanomaterial is as follows: Figure 5 As shown, it can be seen that the generated carbon nanomaterials contain carbon nanotubes as well as a large amount of flake-shaped and spherical carbon nanomaterials, wherein the purity of the carbon nanotubes is ≥68%.

[0086] Comparative Example 2

[0087] 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.

[0088] The scanning electron microscope (SEM) image of the obtained carbon nanomaterial is as follows: Figure 6 As shown, it can be seen that the generated carbon nanomaterials are mainly carbon nanotubes, which are distributed more concentratedly, 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, and the tube diameter is 30-80nm.

[0089] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

[0090] The endpoints and any values ​​of the ranges disclosed in this article 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 endpoint values ​​of each range, the endpoint values ​​of each range and the 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 as specifically disclosed in this article.

Claims

1. A method for the combined preparation of carbon nanotubes and hydrogen, characterized in that: The combined preparation method comprises: 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; 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 in terms of molar percentage, the titanium-containing compound accounts for more than 55% of the total molar amount of the catalyst precursor.

2. The method for jointly preparing carbon nanotubes and hydrogen according to claim 1, characterized in that: The hydrocarbon source gas is a hydrocarbon that can be cracked, and the hydrocarbon that can be cracked includes methane, ethylene or acetylene.

3. The method for jointly preparing carbon nanotubes and hydrogen according to claim 2, characterized in that: The methane is obtained by purifying one or more selected from biogas, natural gas, coal-bed methane, shale gas and combustible ice.

4. The method for jointly preparing carbon nanotubes and hydrogen according to claim 1, characterized in that: The carrier gas is selected from nitrogen or an inert gas.

5. The method for jointly preparing carbon nanotubes and hydrogen according to claim 1 or 4, characterized in that: The amount of hydrocarbon source gas introduced is 10-400 sccm, and the amount of carrier gas introduced is 100-4000 sccm.

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

1.

7. The method for jointly preparing carbon nanotubes and hydrogen according to claim 1, characterized in that: The feed molar ratio of the catalyst precursor to the growth promoter is 2-10:

1.

8. The method for jointly preparing carbon nanotubes and hydrogen according to claim 1 or 7, characterized in that: The growth promoter is a combination of one or more selected from thiophene, sulfur powder, thiourea and carbon disulfide.

9. The method for jointly preparing carbon nanotubes and hydrogen according to claim 1, characterized in that: The catalyst precursor further includes a tungsten-containing compound capable of being carburized to form tungsten carbide and / or a molybdenum-containing compound capable of being carburized to form molybdenum carbide.

10. The method for jointly preparing carbon nanotubes and hydrogen according to claim 9, characterized in that: 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.

11. The method for jointly preparing carbon nanotubes and hydrogen according to claim 1, characterized in that: The combined preparation method further comprises: introducing carbon nanomaterials as growth seeds into the reaction furnace, 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.

12. The method for jointly preparing carbon nanotubes and hydrogen according to claim 1, characterized in that: The reaction is carried out at 1000-1800° C. and the reaction time is 1-30 min.

13. The method for jointly preparing carbon nanotubes and hydrogen according to claim 1, characterized in that: The combined preparation method adopts a combined production device to carry out the combined preparation of carbon nanotubes and hydrogen, and the combined production device comprises: The plasma generator comprises an airflow inlet and an airflow outlet; The reaction furnace, auxiliary material feeding mechanism, carbon nanotube collecting mechanism and hydrogen collecting mechanism; The reactor comprises a reactor body, the reactor body comprises a first feed inlet for introducing the reactive mixed gas flow, a second feed inlet for introducing auxiliary materials, and a discharge port, the auxiliary materials comprising the catalyst precursor and the growth promoter, the first feed inlet 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 inlet; 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 an airflow outlet. The chamber inlet is connected to the discharge port, and the airflow outlet is connected to the hydrogen collection mechanism. The carbon nanotube collection mechanism can obtain nanotube bundles or nanotube films.

14. The method for jointly preparing carbon nanotubes and hydrogen according to claim 13, characterized in that: 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 airflow inlet.

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