Carbon nanotube preparation device and method

Abstract

The invention provides a carbon nanotube preparation device and method, the device is a transparent reactor, a light-transmitting wall is arranged in the reactor, the interior of the reactor is divided into a reaction zone and an illumination zone by the light-transmitting wall, and a heater is arranged on the outer wall of the reactor. The preparation method comprises the following steps: introducing a carbon source gas from one end of a reactor under illumination and heating conditions, carrying out conversion on a catalyst, and discharging the generated carbon-containing mixed material and gas from the other end. Due to the excitation effect of light, the light-off temperature of the catalyst can be reduced by 150-250 DEG C compared with that of the prior art, and high-temperature sintering of the catalyst can be inhibited, so that the few-wall (1-3-layer) carbon nanotubes can be prepared at low temperature, and the method has the advantages of low cost and continuous operation.

Description

Technical Field

[0001] The present application relates to the technical field of heterogeneous catalysis and nanomaterial manufacturing, and in particular, to a device and method for preparing carbon nanotubes. Background Art

[0002] Carbon nanotubes are one-dimensional materials with excellent electrical conductivity, thermal conductivity and mechanical properties, and are widely used in many fields such as composite conductive enhancement and catalyst carrier. The performance of carbon nanotubes is related to their structure. As the number of walls decreases, the weight-based electrical conductivity increases significantly.

[0003] Traditional methods for preparing carbon nanotubes include chemical vapor deposition. During the preparation, the diameter of few-walled carbon nanotubes is always related to the catalyst grain size. The supercooling condensation and precipitation of the carbon source and the maintenance of crystallinity are related to high reaction temperatures. However, based on the Ostward ripening model, the catalyst grain size always increases significantly with increasing temperature, and the catalyst grain size directly affects the diameter of carbon nanotubes. At the same time, the controlled cracking of the carbon source will affect the precipitation of few-walled tubes. The chemically inert carbon source controls the carbon precipitation rate due to its low conversion rate, which is also related to reducing the number of amorphous carbon and carbon nanotube layers.

[0004] For the above reasons, the preparation of few-walled carbon nanotubes generally suffers from low yield and high cost during high-temperature vapor deposition, which limits the expansion of its application areas. Summary of the invention

[0005] To solve the above problems, the present application provides a device using photothermal synergistic catalysis, which activates the catalyst by light and heat at the same time, effectively reducing the temperature range of its cracking carbon source, making the catalyst grains more controllable. Also, due to the light absorption effect of carbon materials, the carbon precipitation rate at the carbon-metal interface is promoted, thereby effectively improving the yield of few-walled carbon nanotubes and reducing the preparation cost.

[0006] In a first aspect, the present application provides a carbon nanotube preparation device, comprising a reactor; The interior of the reactor is divided into a reaction zone and an illumination zone, and the reaction zone and the illumination zone are separated by a light-transmitting wall; The reaction zone is provided with a feed inlet at one end and a discharge outlet at the other end; An illuminator is arranged in the illuminator area, and light emitted by the illuminator passes through the light-transmitting wall to reach the reaction area; A heater is arranged outside the reactor, and the heater is wrapped around the circumferential outer wall of the reactor.

[0007] Optionally, the illumination area is provided with an opening; The opening allows the illuminator to enter the irradiation area along the length direction of the reactor.

[0008] Optionally, the reactor is made of any one of quartz, high-temperature glass and transparent ceramics, and the light-transmitting wall is made of quartz glass or fluoride glass.

[0009] Optionally, the thickness of the light-transmitting wall is 1 mm-20 mm.

[0010] Optionally, the reactor is a cylindrical reactor; The light-transmitting wall is an annular structure, and the reaction zone is located between the outer wall of the cylindrical reactor and the outer wall of the light-transmitting wall; The illumination area is located in a hollow area enclosed by the inner wall of the light-transmitting wall.

[0011] In a second aspect, the present application provides a method for preparing the carbon nanotubes, which is applicable to the device for preparing the carbon nanotubes in the first aspect, and comprises: Step S1: Adjust the illumination of the illuminator in the illumination area of ​​the reactor to 10 5 LX-10 7 LX; Step S2: Turn on the heater to raise the temperature of the reaction zone to 500°C-750°C; Step S3: feeding a carbon source gas and a catalyst having a volume concentration ratio of (90-99)%:(1-10)% into a reaction zone through a feed port, and under the action of light and heat, the carbon source gas is cracked to generate few-walled carbon nanotubes having 1-3 wall layers, and the carbon-containing mixed material obtained by the reaction is discharged from the reaction zone through a discharge port; Step S4: when the carbon-containing mixed material covers the light-transmitting wall, the introduction of the carbon source gas and the catalyst is stopped, and air is introduced into the reaction zone through the feed inlet to oxidize and remove the carbon-containing mixed material on the light-transmitting wall; Step S5: repeating steps S3-S4 until all cracking reactions are completed, and the carbon-containing mixed material is ground to remove the catalyst to obtain the carbon nanotubes; Wherein, the carbon source gas includes organic matter with a carbon atom number of 1-20; The catalyst is composed of a catalytic metal and a carrier, wherein the catalytic metal includes at least one of iron, cobalt, nickel, chromium, silver, gold, platinum, copper, zinc, palladium, molybdenum, tungsten, manganese and titanium, and the carrier includes at least one of magnesium oxide, silicon oxide, aluminum oxide, hydrotalcite and molecular sieve.

[0012] Optionally, in step S1, the illumination of the illuminator is adjusted to 2×10 6 LX-8×10 6 LX.

[0013] Optionally, the total content of sulfur, nitrogen, phosphorus, arsenic and halogen elements contained in the organic matter is 0 PPm-20 PPm; The carbon source gas includes any one of hydrocarbons and alcohols with carbon atoms of 5-8, polycyclic aromatic hydrocarbons with carbon atoms of 15-20, hydrocarbons in the diesel boiling range, methane, cyclohexane, and hydrocarbons and ketones in the diesel boiling range; The oxygen content of the carbon source gas is less than 30%.

[0014] Optionally, the grain size of the catalytic metal is 0.5 nm-1.5 nm, and the mass fraction of the catalytic metal in the catalyst is 0.1%-10%.

[0015] In a third aspect, the present application provides a carbon nanotube obtained by the method for preparing the carbon nanotube according to the second aspect.

[0016] In summary, the present application includes at least one of the following beneficial technical effects: 1. The present application provides a carbon nanotube preparation device. By setting an illuminator, a photothermal synergistic catalytic system is formed in the reactor, so that when the device is used, it is more convenient to provide a light source and a heat source at the same time, thereby promoting the reaction.

[0017] 2. The present application provides a method for preparing carbon nanotubes, which effectively reduces the activation temperature of the catalyst by 150°C-250°C. The improvement of the catalyst activity and the reduction of the activation temperature broaden the types of carbon sources that can grow few-walled tubes by 60%-65%, and reduce the carbon source cost by 30%-60%. After the temperature is reduced, the growth of the catalyst particle size can be hindered, and the retention of small catalyst grains can be increased by 50%-65%. Based on the above method, the content of carbon nanotubes in the few-walled tubes in the final product can be increased by 30%-35%. Moreover, in step S5, the carbon nanotubes are separated from the catalyst in time by grinding, and the catalyst structure is not destroyed. The separated catalyst can still be recycled many times, which reduces the preparation cost by 80%-95%. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0019] Figure 1 A structural diagram of a carbon nanotube preparation device proposed in an embodiment of the present application is shown; Figure 2 A structural diagram of another carbon nanotube preparation device proposed in an embodiment of the present application is shown; Figure 3 A flow chart of a method for preparing carbon nanotubes proposed in an application example is shown.

[0020] Description of reference numerals: 1. Reactor; 11. reaction zone; 111. feed port; 112. discharge port; 12. illumination area; 121. illumination device; 122. opening; 13. Translucent wall; 14. Heater. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0022] In the drawings, the size of the constituent elements, the thickness of the layer or the area may be exaggerated for the sake of clarity. Therefore, any implementation of the present disclosure is not necessarily limited to the size shown in the drawings, and the shapes and sizes of the components in the drawings do not reflect the true proportions. In addition, the drawings schematically show ideal examples, and any implementation of the present disclosure is not limited to the shapes or values ​​shown in the drawings.

[0023] In the related art, the conventional chemical vapor deposition method for preparing carbon nanotubes mainly has the following problems, including: 1. In the process of preparing carbon nanotubes by chemical vapor deposition, the catalyst grains serve as the "seeds" for the growth of carbon nanotubes, and their size directly affects the diameter of carbon nanotubes. According to the Ostward ripening model, as the reaction temperature increases, the solubility difference between catalyst grains increases, causing small grains to dissolve and re-precipitate on large grains, thereby increasing the average size of catalyst grains. In other words, high reaction temperatures help the carbon source molecules to supercool and condense and arrange in order on the catalyst surface, but too high a temperature will also lead to a significant increase in the catalyst grains, thereby affecting the diameter and morphology of carbon nanotubes; 2. The chemically inert carbon source used has a low conversion rate and a slow cracking rate. Although this helps to control the carbon precipitation rate and deposit carbon atoms or carbon fragments on the catalyst grains in an orderly manner to form few-walled carbon nanotubes, it also results in a low yield of the converted few-walled carbon nanotubes.

[0024] Based on the above problems, the embodiments of the present application provide a device and method for preparing carbon nanotubes, which can reduce the temperature of cracking carbon sources, make the particle size of the catalyst more controllable, and thus make the diameter of the generated carbon nanotubes more controllable, while accelerating the cracking reaction and increasing the yield of few-walled carbon nanotubes.

[0025] See also Figure 1 , Figure 1 A carbon nanotube preparation device provided in an embodiment of the present application is shown, which specifically includes a reactor 1; The reactor 1 is internally divided into a reaction zone 11 and an illumination zone 12, and the reaction zone 11 and the illumination zone 12 are separated by a light-transmitting wall 13; The reaction zone 11 is provided with a feed port 111 at one end and a discharge port 112 at the other end; An illuminator 121 is disposed in the illuminator area 12, and light emitted by the illuminator 121 passes through the light-transmitting wall 13 to reach the reaction area 11; A heater 14 is disposed outside the reactor 1 , and the heater 14 is wrapped around the circumferential outer wall of the reactor 1 .

[0026] In the device provided in the embodiment of the present application, by providing the illuminator 121, a photothermal synergistic catalytic system is formed inside the reactor 1, and the preparation efficiency can be improved when the device is used to prepare carbon nanotubes. In particular, the yield of the output of few-walled carbon nanotubes is greatly improved, meeting the urgent demand of the industry for high-performance few-walled carbon nanotubes.

[0027] The present application reduces energy consumption and raw material waste, improves resource utilization, and reduces the preparation cost of carbon nanotubes by optimizing the internal structure of the device and applying the photothermal synergistic catalytic mechanism, making the production of carbon nanotubes more economical and efficient.

[0028] In some embodiments, the feed port 111 of the reaction zone 11 is opened at the bottom and the discharge port 112 is opened at the top. When used, the reactants enter the reaction zone 11 from bottom to top along the feed port 111, and the obtained products are discharged from the discharge port 112 at the top.

[0029] In some embodiments, the heater 14 may be an electric heater (system), a shell and tube external heating reactor, a shell and tube internal heating reactor, etc. The type of the heater 14 is not specifically limited in the embodiments of the present application.

[0030] See also Figure 2 , Figure 2Another carbon nanotube preparation device provided in an embodiment of the present application is shown, in which a feed port 111 on the reaction zone 11 is opened at the top, and a discharge port 112 is opened at the bottom. When used, the reactants enter the reaction zone 11 from top to bottom along the feed port 111, and the obtained product is discharged from the discharge port 112 at the bottom.

[0031] In some embodiments, the illumination area 12 is provided with an opening 122; The opening 122 allows the illuminator 121 to enter the irradiation area 12 along the length direction of the reactor 1 .

[0032] In specific implementation, by providing the opening 122, the illuminator 121 is more convenient to install and remove. When the illumination provided by the illuminator 121 is insufficient, a new illuminator 121 can be replaced to improve the convenience of the device application. The illuminator 121 is fixed in the illumination area 12 in a manner including but not limited to: bolt fixing, bracket fixing, hanging fixing, adsorption fixing, etc.

[0033] In some embodiments, the reactor 1 is made of any one of quartz, high-temperature glass and transparent ceramics, and the light-transmitting wall 13 is made of quartz glass or fluoride glass.

[0034] In the process of preparing carbon nanotubes, the material selection of the reactor 1 needs to meet the requirements of high temperature resistance, high pressure resistance and chemical corrosion resistance, and also meet the requirements of high light transmittance, so that the light emitted by the illuminator 121 can pass through the light-transmitting wall 13 to reach the reaction area 11. It is also convenient to observe the reaction process in the reaction area 11 from outside the reactor 1. The above materials all have these functions and can be well applied to the device provided in the embodiment of the present application.

[0035] In some embodiments, the thickness of the light-transmitting wall 13 is 1 mm-20 mm.

[0036] Since the device provided in the present application is used to prepare carbon nanotubes, the reaction process has high temperature and is corrosive. It is necessary to reasonably set the thickness of the light-transmitting wall 13 to ensure high light transmittance while being resistant to high temperature and corrosion so that the reaction process can proceed stably.

[0037] In a specific implementation, the thickness of the light-transmitting wall 13 is 5 mm-15 mm.

[0038] In some embodiments, the reactor 1 is a cylindrical reactor; The light-transmitting wall 13 is an annular structure, and the reaction zone 11 is located between the outer wall of the cylindrical reactor and the outer wall of the light-transmitting wall 13; The illumination area 12 is located in a hollow area enclosed by the inner wall of the light-transmitting wall 13 .

[0039] By setting up a cylindrical reactor, the reaction zone 11 can be evenly distributed around the illumination zone 12 , and combined with the annular structure of the light-transmitting wall 13 , light can be evenly irradiated into the reaction zone 11 , forming a synergistic catalytic effect with the heat generated by the heater 14 .

[0040] The cylindrical reactor has a compact structure and high space utilization. The reaction zone 11 and the illumination zone 12 are separated by a light-transmitting wall 13, which not only ensures the uniformity of illumination, but also fully utilizes the internal space of the reactor 1, making the entire preparation process more efficient and energy-saving.

[0041] See also Figure 3 , Figure 3 The method for preparing carbon nanotubes provided in the embodiment of the present application is shown, and the specific operations include: S1: Adjust the illumination of the illuminator in the illumination area of ​​the reactor to 10 5 LX-10 7 LX; S2: Turn on the heater to raise the temperature of the reaction zone to 500°C-750°C; S3: feeding a carbon source gas and a catalyst having a volume concentration ratio of (90-99)%:(1-10)% into a reaction zone through a feed port, and under the action of light and heat, the carbon source gas is cracked to generate few-walled carbon nanotubes having 1-3 wall layers, and the carbon-containing mixed material obtained by the reaction is discharged from the reaction zone through a discharge port; S4: when the carbon-containing mixed material covers the light-transmitting wall, stop introducing the carbon source gas and the catalyst, and introduce air into the reaction zone through the feed inlet to oxidize and remove the carbon-containing mixed material on the light-transmitting wall; S5: repeating steps S3-S4 until all cracking reactions are completed, and the carbon-containing mixed material is ground to remove the catalyst to obtain the carbon nanotubes; Wherein, the carbon source gas includes organic matter with a carbon atom number of 1-20; The catalyst is composed of a catalytic metal and a carrier, wherein the catalytic metal includes at least one of iron, cobalt, nickel, chromium, silver, gold, platinum, copper, zinc, palladium, molybdenum, tungsten, manganese and titanium, and the carrier includes at least one of magnesium oxide, silicon oxide, aluminum oxide, hydrotalcite and molecular sieve.

[0042] The method for preparing carbon nanotubes provided in the embodiment of the present application effectively reduces the temperature of the cracked carbon source by precisely adjusting the illumination of the illuminator and the temperature of the reaction zone, and optimizing the ratio of the carbon source gas and the catalyst, so as to limit the growth of the catalyst particles and keep the catalyst with a small particle size longer, which helps to efficiently prepare the few-walled carbon nanotubes with 1-3 tube wall layers, and solves the problem of low yield and high cost of few-walled carbon nanotubes in the traditional preparation method. The present application adopts the method of photothermal synergistic catalysis, combined with the light absorption effect of the carbon source, so that the carbon precipitation rate at the carbon-metal interface is accelerated, thereby reducing the generation of amorphous carbon, making the number of carbon nanotube generation layers more controllable, so as to accurately produce more carbon nanotubes with 1-3 tube wall layers.

[0043] The method provided in the embodiment of the present application fully utilizes light energy and heat energy in the preparation process, reducing energy consumption. The method has clear steps, is easy to operate, and is easy to implement industrial production.

[0044] In step S4, due to the fast reaction rate in the reaction zone, a large amount of carbon-containing mixed materials will be produced, some of which will cover the light-transmitting wall, affecting the illumination effect. Therefore, it is necessary to stop the introduction of carbon source gas and catalyst, and introduce air into the reaction zone to oxidize and remove the carbon-containing mixed materials on the light-transmitting wall, so as to maintain a stable illumination effect and allow the reaction to proceed smoothly.

[0045] In some embodiments, the temperature of the reaction zone affects the cracking of the carbon source gas and the generation of carbon nanotubes. Controlling the temperature at 500°C-750°C can ensure that the catalyst has high activity, inhibit the excessive growth of carbon nanotubes, make the cracking of the carbon source gas more complete, and accelerate the generation of carbon nanotubes.

[0046] Preferably, the temperature of the reaction zone is raised to 550°C-700°C.

[0047] In some embodiments, the volume concentration ratio of the carbon source gas to the catalyst is (95-98)%:(2-5)%. By limiting the ratio of the carbon source gas to the catalyst, it is more conducive to forming carbon nanotubes with a stable structural morphology.

[0048] In some embodiments, the catalyst residence time in the reaction zone is 1 to 6 minutes.

[0049] In some embodiments, in step S1, the illumination of the illuminator is adjusted to 2×10 6 LX-8×10 6 LX. Illumination has an important influence on the effect of photothermal synergistic catalysis. Appropriate illumination helps to improve the activity of the catalyst and accelerate the cracking of the carbon source.

[0050] In some embodiments, the total content of sulfur, nitrogen, phosphorus, arsenic and halogen elements contained in the organic matter is 0 PPm-20 PPm; The carbon source gas includes any one of hydrocarbons and alcohols with carbon atoms of 5-8, polycyclic aromatic hydrocarbons with carbon atoms of 15-20, hydrocarbons in the diesel boiling range, methane, cyclohexane, and hydrocarbons and ketones in the diesel boiling range; The oxygen content of the carbon source gas is less than 30%.

[0051] By setting the content of sulfur, nitrogen, phosphorus, arsenic and halogen elements contained in the organic matter to be low, it is helpful to improve the purity of the carbon nanotubes finally obtained. The reduction of impurity elements is also conducive to reducing the interference factors in the growth process of carbon nanotubes, making the cracking of carbon source gas on the catalyst surface more controllable, and more conducive to the generation of few-walled carbon nanotubes with 1-3 tube wall layers. Among them, impurity elements such as sulfur and nitrogen are easy to react with the catalyst, reducing their content, so that the catalyst can maintain a high stability and activity, thereby extending the service life of the catalyst, allowing the catalyst to be recycled and reducing production costs.

[0052] In a specific implementation, preferably, the oxygen content of the carbon source gas is less than 20%. More preferably, the oxygen content of the carbon source gas is less than 5%.

[0053] In some embodiments, the catalytic metal has a grain size of 0.5 nm-1.5 nm, and the mass fraction of the catalytic metal in the catalyst is 0.1%-10%.

[0054] By adjusting the crystal size of the catalytic metal to 0.5 nm-1.5 nm, the catalyst particles can maintain a uniform size during the cracking reaction. Catalysts with smaller particle sizes are more conducive to guiding the carbon source gas to crack efficiently and controllably on its surface, thereby generating more few-walled carbon nanotubes with 1-3 wall layers.

[0055] Since the catalyst is composed of catalytic metal and carrier, the mass fraction of catalytic metal in the catalyst is in the range of 0.1%-10%, which can ensure that the catalyst has sufficient active sites while avoiding excessive metal particles causing catalyst agglomeration or deactivation.

[0056] Preferably, the crystal size of the catalytic metal is 0.6 nm-1.3 nm.

[0057] The mass fraction of the catalytic metal in the catalyst is 1%-8%.

[0058] The present application provides a carbon nanotube obtained by the above-mentioned carbon nanotube preparation method. In the carbon nanotube, the carbon nanotube with 1-3 tube wall layers accounts for 85%-96% of the total number of carbon nanotubes.

[0059] The method of the embodiment of the present application greatly improves the yield of carbon nanotubes with 1-3 wall layers by designing a preparation device and optimizing reaction conditions. The high proportion of few-walled carbon nanotubes obtained makes the prepared carbon nanotube materials have application potential in more fields. For example, in the biomedical field, few-walled carbon nanotubes have attracted much attention due to their good biocompatibility and cell permeability; in the field of sensors, the high sensitivity and rapid response characteristics of few-walled carbon nanotubes make them ideal sensing materials, and so on.

[0060] Example The following examples 1-4 all adopt Figure 1 The carbon nanotube preparation device shown is specifically: Example 1 Step 1: Place the illuminator along the opening in the illumination area of ​​the reactor and adjust its illumination to 1×10 5 LX; Step 2: Start the outermost electric heating system (heater) of the reactor to raise the temperature in the reaction zone and the illumination zone to 700°C-750°C; Step 3: A carbon source gas (wherein the carbon source gas is an organic matter with a carbon atom number of 1-3, an oxygen content of less than 5%, and does not contain sulfur, nitrogen, phosphorus, arsenic, halogen and other elements) and a catalyst (a metal-supported catalyst, wherein the metal is 1% iron + 2% molybdenum, and the crystal size is 0.5 nm-0.6 nm; the carrier is magnesium aluminum hydrotalcite) are introduced into the reaction zone from the bottom feed port, and the carbon source gas is cracked on the catalyst under the action of light and heat to generate few-walled carbon nanotubes, and the volume concentration of the catalyst in the carbon source gas is controlled to be 3%, and the residence time of the catalyst in the reaction zone is controlled to be 3 minutes, and the carbon-containing mixed material obtained by the reaction is discharged from the reaction zone from the top discharge port; Step 4: When the light-transmitting wall of the reaction zone is covered by the carbon-containing mixed material and the light is insufficient, the carbon source gas and the catalyst are stopped, and air is introduced from the feed port to oxidize and remove the carbon-containing mixed material on the light-transmitting wall at 550°C; Step 5: Repeat the above steps to make the process continuous until all cracking reactions are completed. The carbonaceous mixed material is ground and the catalyst is removed to obtain carbon nanotubes, which are used as products. The proportion of small-walled (1-3 layers) carbon nanotubes in the product is 92%; the catalyst continues to participate in the next cycle.

[0061] Example 2 Step 1: Place the illuminator along the opening in the illumination area of ​​the reactor and adjust its illumination to 2×10 6 LX; Step 2: Start the outermost electric heating system of the reactor to raise the temperature in the reaction zone and the illumination zone to 700°C-750°C; Step 3: A carbon source gas (wherein the carbon source gas is a hydrocarbon and alcohol with a carbon number of 5-8, an oxygen content of less than 20%, and does not contain sulfur, nitrogen, phosphorus, arsenic, halogen and other elements) and a catalyst (a metal-supported catalyst, wherein the metal is 2% nickel + 3% copper, and the crystal size is 0.5 nm-0.9 nm; the carrier is a molecular sieve) are introduced into the reaction zone from the bottom feed port. The carbon source gas is cracked on the catalyst under the action of light and heat to generate few-walled carbon nanotubes. The volume concentration of the catalyst in the carbon source gas is controlled to be 10%, and the residence time of the catalyst in the reaction zone is controlled to be 3 minutes. The carbon-containing mixed material obtained by the reaction is discharged from the reaction zone from the top discharge port; Step 4: When the light-transmitting wall of the reaction zone is covered by the carbon-containing mixed material and the light is insufficient, the carbon source gas and the catalyst are stopped, and air is introduced from the feed inlet to oxidize and remove the carbon-containing mixed material on the light-transmitting wall at 650°C; Step 5: Repeat the above steps to make the process continuous until all cracking reactions are completed, and the carbonaceous mixed material is ground to remove the catalyst to obtain carbon nanotubes, which are used as products. The proportion of small-walled (1-3 layers) carbon nanotubes in the product is 85%; the catalyst continues to participate in the next cycle.

[0062] Example 3 Step 1: Place the illuminator along the opening in the illumination area of ​​the reactor and adjust its illumination to 8×10 6 LX; Step 2: Start the outermost electric heating system of the reactor to raise the temperature in the reaction zone and the illumination zone to 750°C; Step 3: A carbon source gas (the carbon source gas is methane) and a catalyst (a metal-supported catalyst, wherein the metal is 1% palladium + 4% copper + 5% zinc, and the crystal size is 0.8 nm-1.5 nm; the carrier is 70% alumina + 20% silicon oxide) are introduced into the reaction zone from the bottom feed port. The carbon source gas is cracked on the catalyst under the action of light and heat to generate few-walled carbon nanotubes. The volume concentration of the catalyst in the carbon source gas is controlled to be 1%-5%, and the residence time of the catalyst in the reaction zone is controlled to be 6 minutes. The carbon-containing mixed material obtained by the reaction is discharged from the reaction zone from the top discharge port; Step 4: When the light-transmitting wall of the reaction zone is covered by the carbon-containing mixed material and the light is insufficient, the carbon source gas and the catalyst are stopped, and air is introduced from the feed port to oxidize and remove the carbon-containing mixed material on the light-transmitting wall at 700°C; Step 5: Repeat the above steps to make the process continuous until all cracking reactions are completed, and the carbonaceous mixed material is ground to remove the catalyst to obtain carbon nanotubes, which are used as products. The proportion of small-walled (1-2 layer) carbon nanotubes in the product is 96%; the catalyst continues to participate in the next cycle.

[0063] Example 4 Step 1: Place the illuminator along the opening in the illumination area of ​​the reactor and adjust its illumination to 4×10 6 LX; Step 2: Start the outermost electric heating system of the reactor to raise the temperature in the reaction zone and the illumination zone to 680°C-710°C; Step 3: introducing a carbon source gas (the carbon source gas is a diesel boiling range hydrocarbon and ketone, ether, sulfur, nitrogen, phosphorus, arsenic, halogen and other elements with a total content of 10 PPm) and a catalyst (a metal-supported catalyst, wherein the metal is 0.05% gold + 0.05% silver, and the crystal size is 0.5nm-1.25 nm; the carrier is 90% alumina + 9.9% molecular sieve) into the reaction zone from the bottom feed port, and the carbon source gas is cracked on the catalyst under the action of light and heat to generate few-walled carbon nanotubes, and the volume concentration of the catalyst in the carbon source gas is controlled to be 2%, and the residence time of the catalyst in the reaction zone is controlled to be 2.5 minutes, and the carbon-containing mixed material obtained by the reaction is discharged from the reaction zone from the top discharge port; Step 4: When the light-transmitting wall of the reaction zone is covered by the carbon-containing mixed material and the light is insufficient, the carbon source gas and the catalyst are stopped, and air is introduced from the feed port to oxidize and remove the carbon-containing mixed material on the light-transmitting wall at 500°C; Step 5: Repeat the above steps to make the process continuous until all cracking reactions are completed, and the carbonaceous mixed material is ground to remove the catalyst to obtain carbon nanotubes, which are used as products. The proportion of small-walled (1-2 layer) carbon nanotubes in the product is 96%; the catalyst continues to participate in the next cycle.

[0064] The following examples 5-7 all adopt Figure 2 The carbon nanotube preparation device shown is specifically: Example 5 Step 1: Place the illuminator along the opening in the illumination area of ​​the reactor and adjust the illumination to 6×10 6 LX; Step 2: Start the outermost electric heating system of the reactor to raise the temperature in the reaction zone and the illumination zone to 550°C-650°C; Step 3: A carbon source gas (the carbon source gas is a polycyclic aromatic hydrocarbon with a carbon atom number of 15-20) and a catalyst (a metal-supported catalyst, wherein the metal is 6.6% cobalt + 1.4% tungsten, and the crystal size is 0.5 nm-0.7 nm; the carrier is 50% hydrotalcite + 42% molecular sieve) are introduced into the reaction zone from the top feed port. The carbon source gas is cracked on the catalyst under the action of light and heat to generate few-walled carbon nanotubes. The volume concentration of the catalyst in the carbon source gas is controlled to be 2.5%, and the residence time of the catalyst in the reaction zone is controlled to be 3 minutes. The carbon-containing mixed material obtained by the reaction is discharged from the reaction zone from the discharge port at the bottom; Step 4: When the light-transmitting wall of the reaction zone is covered by the carbon-containing mixed material and the light is insufficient, the carbon source gas and the catalyst are stopped, and air is introduced from the feed port to oxidize and remove the carbon-containing mixed material on the light-transmitting wall at 600°C; Step 5: Repeat the above steps to make the process continuous until all cracking reactions are completed, and the carbon-containing mixed material is ground to remove the catalyst to obtain carbon nanotubes, which are used as products. The proportion of small-walled (1-2 layer) carbon nanotubes in the product is 94%; the catalyst continues to participate in the next cycle.

[0065] Example 6 Step 1: Place the illuminator along the opening in the illumination area of ​​the reactor and adjust its illumination to 1×10 7 LX; Step 2: Start the outermost electric heating system of the reactor to raise the temperature in the reaction zone and the illumination zone to 650°C-710°C; Step 3: A carbon source gas (the carbon source gas is a diesel boiling range hydrocarbon, with a total content of 20 PPm of sulfur, nitrogen, phosphorus, arsenic, halogen and other elements) and a catalyst (a metal-supported catalyst, wherein the metal is 5% nickel + 5% tungsten, and the crystal size is 1.0 nm-1.3 nm; the carrier is 90% magnesium oxide) are introduced into the reaction zone from the top feed port. The carbon source gas is cracked on the catalyst under the action of light and heat to generate few-walled carbon nanotubes. The volume concentration of the catalyst in the carbon source gas is controlled to be 1%, and the residence time of the catalyst in the reaction zone is controlled to be 1-6 minutes. The carbon-containing mixed material obtained by the reaction is discharged from the reaction zone from the discharge port at the bottom; Step 4: When the light-transmitting wall of the reaction zone is covered by the carbon-containing mixed material and the light is insufficient, the carbon source gas and the catalyst are stopped, and air is introduced from the feed port to oxidize and remove the carbon-containing mixed material on the light-transmitting wall at 500°C; Step 5: Repeat the above steps to make the process continuous until all cracking reactions are completed, and the carbonaceous mixed material is ground to remove the catalyst to obtain carbon nanotubes, which are used as products. The proportion of small-walled (1-3 layers) carbon nanotubes in the product is 85%-96%; the catalyst continues to participate in the next cycle.

[0066] Example 7 Step 1: Place the illuminator along the opening in the illumination area of ​​the reactor and adjust the illumination to 7×10 6 LX; Step 2: Start the outermost electric heating system of the reactor to raise the temperature in the reaction zone and the illumination zone to 750°C; Step 3: A carbon source gas (the carbon source gas is cyclohexane) and a catalyst (a metal-supported catalyst, wherein the metal is 0.1% platinum + 0.9% titanium, and the crystal size is 0.5 nm-0.8 nm; the carrier is 60% alumina + 39% magnesium oxide) are introduced into the reaction zone from the top feed port. The carbon source gas is cracked on the catalyst under the action of light and heat to generate few-walled carbon nanotubes. The volume concentration of the catalyst in the carbon source gas is controlled to be 4%-5%, and the residence time of the catalyst in the reaction zone is controlled to be 4 minutes. The carbon-containing mixed material obtained by the reaction is discharged from the reaction zone from the discharge port at the bottom; Step 4: When the light-transmitting wall of the reaction zone is covered by the carbon-containing mixed material and the light is insufficient, the carbon source gas and the catalyst are stopped, and air is introduced from the feed inlet to oxidize and remove the carbon-containing mixed material on the light-transmitting wall at 650°C; Step 5: Repeat the above steps to make the process continuous until all cracking reactions are completed, and the carbonaceous mixed material is ground to remove the catalyst to obtain carbon nanotubes, which are used as products. The proportion of small-walled (1-2 layers) carbon nanotubes in the product is 90%; the catalyst continues to participate in the next cycle.

[0067] In summary, the present application provides a carbon nanotube preparation device and method, which activates the catalyst simultaneously by using light and heat by setting an illuminator, effectively reducing the activation temperature of the catalyst by 150°C-250°C, increasing the catalyst small grain retention by 50%-65%, and increasing the content of few-walled carbon nanotubes in the product by 30%-35%. Due to the increase in catalyst activity and the decrease in activation temperature, the types of carbon sources that can grow few-walled tubes are expanded by 60%-65%, and the cost of carbon sources is reduced by 30%-60%. Finally, the grinding technology is used to separate the carbon nanotubes from the catalyst in time, and the catalyst structure is not destroyed. The separated catalyst can be recycled many times, reducing the cost by 80%-95%.

[0068] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0069] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present application.

[0070] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or terminal device including the elements.

[0071] The above is a detailed introduction to the carbon nanotube preparation device and method provided by the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for general technicians in this field, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A device for preparing carbon nanotubes, characterized in that: including a reactor; The interior of the reactor is divided into a reaction zone and an illumination zone, and the reaction zone and the illumination zone are separated by a light-transmitting wall; The reaction zone is provided with a feed inlet at one end and a discharge outlet at the other end; An illuminator is arranged in the illuminator area, and light emitted by the illuminator passes through the light-transmitting wall to reach the reaction area; A heater is arranged outside the reactor, and the heater is wrapped around the circumferential outer wall of the reactor.

2. The carbon nanotube preparation device according to claim 1, characterized in that: The illumination area is provided with an opening; The opening allows the illuminator to enter the irradiation area along the length direction of the reactor.

3. The carbon nanotube preparation device according to claim 1, characterized in that: The reactor is made of any one of quartz, high temperature glass and transparent ceramics; The light-transmitting wall is made of quartz glass or fluoride glass.

4. The carbon nanotube preparation device according to claim 1, characterized in that: The thickness of the light-transmitting wall is 1 mm-20 mm.

5. The device for preparing carbon nanotubes according to claim 1, characterized in that: The reactor is a cylindrical reactor; The light-transmitting wall is an annular structure, and the reaction zone is located between the outer wall of the cylindrical reactor and the outer wall of the light-transmitting wall; The illumination area is located in a hollow area enclosed by the inner wall of the light-transmitting wall.

6. A method for preparing the carbon nanotubes, characterized in that: The method is applicable to the carbon nanotube preparation device according to any one of claims 1 to 5, and the method comprises: S1, adjust the illumination of the illuminator in the illumination area of ​​the reactor to 10 5 LX-10 7 LX; S2, turn on the heater to raise the temperature of the reaction zone to 500°C-750°C; S3, feeding a carbon source gas and a catalyst having a volume concentration ratio of (90-99)%:(1-10)% into a reaction zone through a feed port, and under the action of light and heat, the carbon source gas is cracked to generate few-walled carbon nanotubes having 1-3 wall layers, and the carbon-containing mixed material obtained by the reaction is discharged from the reaction zone through a discharge port; S4, when the carbon-containing mixed material covers the light-transmitting wall, stop introducing the carbon source gas and the catalyst, and introduce air into the reaction zone through the feed inlet to oxidize and remove the carbon-containing mixed material on the light-transmitting wall; S5, repeating steps S3-S4 until all cracking reactions are completed, and the carbon-containing mixed material is ground to remove the catalyst to obtain the carbon nanotubes; Wherein, the carbon source gas includes organic matter with a carbon atom number of 1-20; The catalyst is composed of a catalytic metal and a carrier, wherein the catalytic metal includes at least one of iron, cobalt, nickel, chromium, silver, gold, platinum, copper, zinc, palladium, molybdenum, tungsten, manganese and titanium, and the carrier includes at least one of magnesium oxide, silicon oxide, aluminum oxide, hydrotalcite and molecular sieve.

7. The method for preparing carbon nanotubes according to claim 6, characterized in that: In step S1, the illumination of the illuminator is adjusted to 2×10 6 LX-8×10 6 LX.

8. The method for preparing carbon nanotubes according to claim 6, characterized in that: The total content of sulfur, nitrogen, phosphorus, arsenic and halogen elements contained in the organic matter is 0 PPm-20 PPm; The carbon source gas includes at least one of hydrocarbons and alcohols with carbon atoms of 5-8, polycyclic aromatic hydrocarbons with carbon atoms of 15-20, hydrocarbons in the diesel boiling range, methane, cyclohexane, and hydrocarbons and ketones in the diesel boiling range; The oxygen content of the carbon source gas is less than 30%.

9. The method for preparing carbon nanotubes according to claim 6, characterized in that: The crystal grain size of the catalytic metal is 0.5 nm-1.5 nm, and the mass fraction of the catalytic metal in the catalyst is 0.1%-10%.

10. A carbon nanotube obtained by the method for preparing carbon nanotubes according to any one of claims 6 to 9.

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