A device and method for preparing oligo-walled carbon nanotubes by scalable arc discharge

Abstract

The present invention belongs to the technical field of nanomaterial preparation, and relates to an apparatus and method for preparing oligo-walled carbon nanotubes by scalable arc discharge. The apparatus comprises: at least one synthesis unit, at least one scraping unit, at least one barrier unit, at least one collection unit, a catalyst melt, and a drive unit. The present invention uses a rotating catalyst melt connected to a dual-electrode DC arc to continuously prepare uniform catalyst nanoparticles. The rotating melt and the scraping unit cooperate to remove coke attached to the surface of the catalyst melt, keeping the catalyst surface clean, which is conducive to the sustainable preparation of uniform catalyst nanoparticles for the growth of oligo-walled carbon nanotubes and maintaining the equipment's long-term stable growth of oligo-walled carbon nanotubes. This is particularly important for achieving both high-yield and high-quality oligo-walled carbon nanotubes, and has significant commercial value.

Description

Technical Field

[0001] The invention belongs to the technical field of nano material preparation, and relates to a device and method for preparing oligo-walled carbon nanotubes by scalable arc discharge. Background Art

[0002] Single-walled carbon nanotubes (SWCNTs), as a typical one-dimensional nanomaterial, have excellent mechanical, thermal and optical properties, as well as huge aspect ratio, high specific surface area and lightweight characteristics. Their light weight, high strength, high electrical conductivity and high thermal conductivity have potential application prospects in key application research and product development in the fields of wearable electric heating, electromagnetic shielding, lithium-ion battery electrode materials, water filtration and purification.

[0003] Currently, the most commonly used methods for producing oligo-walled carbon nanotubes are floating chemical vapor deposition (FCCVD) and novel plasma chemistry. FCCVD is an economical method, and despite nearly 20 years of continuous optimization of the FCCVD process, while the initial product produced is of high purity and a high degree of graphitization, it has not yet overcome the technical challenges of producing 100 grams of single-walled carbon nanotubes per day. The continuous collection of the product is uncontrollable, and mass production on a ton-scale is even more difficult, limiting its application. References: Nanoscale, 2019, 11, 18483–1849. Chinese invention patent publication numbers are CN109437157B, CN111348642B, and CN108408716B.

[0004] Over the past decade, advances in plasma chemistry have led to the widespread adoption of plasma vapor deposition (PVA) for the production of single-walled carbon nanotubes (SWCNTs) in both research and industry. The advantage of PVA is that it can produce high-quality SWCNTs at high temperatures, opening up a new path for the industrial production of high-quality SWCNTs. For example, Chinese invention patents CN113860287B, CN113929084B, and CN110217777A all utilize a single-electrode DC arc furnace with a cathode at the top and a graphite crucible anode at the bottom. Discharge between the cathodes creates a high-temperature plasma to prepare the catalyst for growing SWCNTs. While single-walled carbon nanotubes with a G / D ratio exceeding 70 can be produced, these furnaces suffer from a bottom anode effect, making sustained and stable operation difficult.

[0005] Another major challenge is the generation of large amounts of coke. As the reaction proceeds, coke accumulates in the reaction chamber and accumulates on the crucible's upper surface. This coke accumulation not only easily leads to arc interruption and reduces arc stability, but also gradually dissolves into the melt, affecting its compositional uniformity. Excessive incorporation of highly crystalline carbon significantly reduces the activity of the melt-prepared catalyst, hindering catalytic cracking and product formation. This results in a decreasing SWCNT content in the subsequent product, making product growth unsustainable and seriously impacting the continuous and stable production of the product. On the one hand, the yield gradually decreases as the reaction proceeds, necessitating the suspension of the experiment, cooling to room temperature, cleaning out the coke, and then resuming the experiment, which is time-consuming and labor-intensive. On the other hand, the gradual increase in carbon-coated iron and coke rich in iron particles in the initial product reduces the purity of the carbon nanotubes and poses significant challenges to subsequent purification, posing a significant challenge to the industrial production of oligo-walled carbon nanotubes. Summary of the Invention

[0006] The present invention discloses an apparatus and method for preparing oligo-walled carbon nanotubes by scalable arc discharge, so as to solve any of the above-mentioned and other potential problems in the prior art.

[0007] In order to solve the problems existing in the prior art, the technical solution adopted by the present invention is: a device for preparing oligo-walled carbon nanotubes by scalable arc discharge, the device comprising: a furnace body, a preheater, a conveyor and a collection unit, characterized in that the device also comprises: at least one synthesis unit, at least one scraping unit, at least one barrier unit, a catalyst melt and a driving unit;

[0008] The barrier unit is arranged inside the furnace body to separate the furnace body into two left and right chambers, the scraping unit is arranged at the upper end of the left chamber, and the synthesis unit is arranged at the upper end of the right chamber. The catalyst melt is arranged horizontally inside the furnace body and is located below the scraping unit and the synthesis unit.

[0009] The driving unit is arranged outside one side of the furnace body and is fixedly connected to one end of the catalyst melt arranged in the furnace body through a connecting shaft, driving the catalyst melt to rotate and telescopically move;

[0010] The catalyst aid conveyor and the preheater are arranged on the top of the outer side of the furnace body and are both connected to the synthesis unit;

[0011] A collecting unit is respectively provided below the synthesis unit and the scraping unit, and the collecting units are both connected to the bottom of the furnace body.

[0012] Furthermore, the synthesis unit comprises: a hollow cathode electrode gun, a hollow anode electrode gun, a hollow graphite electrode and a carbon source mixed gas injection pipe;

[0013] The collection unit is divided into a first collection chamber, which is mainly used to recover oligo-walled carbon nanotube products, and a second collection chamber, which is mainly used to recover coke. The first collection chamber is located directly below the synthesis unit, and the second collection chamber is located directly below the scraping unit. Both collection chambers are equipped with a transition chamber. When the collection chamber collects a large amount of product, the transition chamber can be used to transfer the product out of the collection chamber without stopping the experiment, so as to continuously collect the product and extend the reaction time.

[0014] One end of the hollow cathode electrode gun and the hollow anode electrode gun are inserted into the interior of the furnace body from the top of the furnace body, and a certain distance is separated between the hollow cathode electrode gun and the hollow anode electrode gun; the other ends of the hollow cathode electrode gun and the hollow anode electrode gun are connected to the preheater and the conveyor respectively;

[0015] Furthermore, the carbon source mixed gas injection pipe is arranged between the hollow cathode electrode gun and the hollow anode electrode gun, and is connected to the preheater.

[0016] Furthermore, the scraping unit includes: a first curved scraper, a second curved scraper, a first drive motor, a second drive motor and a controller;

[0017] The first drive motor and the second drive motor are arranged on the top of the furnace body and are connected to the first arc scraper and the second arc scraper respectively through connecting shafts, and the controller is connected to the first drive motor and the second drive motor respectively.

[0018] Furthermore, the barrier unit is a plate with a circular hole in the middle, the center of the circular hole is concentric with the catalyst melt, one end of the plate is fixed to the top of the furnace body, and the distance d between the end of the other end and the surface of the catalyst melt is 10-100 mm;

[0019] The material of the middle circular hole plate is refractory metal tungsten, tantalum, tantalum-iron alloy, magnesium-carbon material, corundum material or graphite.

[0020] Furthermore, the material of the middle circular hole plate is refractory metal tungsten, tantalum, tantalum-iron alloy, magnesium-carbon material, corundum material or graphite.

[0021] Furthermore, the catalyst melt is a hollow metal cylinder with a diameter of not less than 30 cm, and a cooling unit is provided inside the hollow metal cylinder;

[0022] Furthermore, the center distance D between the hollow cathode and anode electrodes is between 50-350 mm.

[0023] Furthermore, the catalyst melt is an iron-containing compound or mixture, which is used to conduct parallel hollow cathode electrodes and hollow anode electrodes to form a plasma arc. It is pressed into a cylindrical shape and contains at least one of nickel, cobalt, iron carbide, carboxyl iron, carbonyl iron, cobalt, nickel alloy, tungsten, tantalum, rhenium, molybdenum, yttrium, lanthanum, and dysprosium.

[0024] Another object of the present invention is to provide a method for preparing single-walled carbon nanotubes using the above-mentioned device, the method specifically comprising the following steps:

[0025] S1) placing the co-catalyst in a conveyor and introducing an inert gas to evacuate the furnace body;

[0026] S2) starting a plasma arc to pass through the catalyst melt, starting a drive unit to rotate and expand the catalyst melt, and starting a preheater to preheat the mixed gas and carbon source mixed gas;

[0027] S3) a catalyst promoter is quantitatively conveyed into the furnace body through the hollow cathode and anode electrodes via a conveyor, the catalyst promoter encounters the locally molten catalyst melt in the arc region, and the catalyst promoter further restricts the growth of nanocatalyst evaporated from the catalyst melt, thereby preparing catalyst particles of 0.5-6 nanometers, and a carbon source mixed gas is introduced into the furnace body, where it is catalytically cracked under the action of the arc to produce oligo-walled carbon nanotubes that fall into the first collecting chamber;

[0028] S4) As the reaction proceeds, when the catalyst melt rotates and contracts in a direction away from the cathode and anode, lift the first curved scraper and press down the second curved scraper to scrape off the coke attached to the surface of the melt and drop it into the second collection chamber. When the catalyst melt rotates and contracts in a direction close to the cathode and anode, press down the first curved scraper and lift the second curved scraper to allow the coke attached to the surface of the rotating melt to fall into the second collection chamber, so that the catalyst melt always remains clean, which is conducive to the continuous generation of catalyst nanoparticles for continuous growth.

[0029] Furthermore, the catalyst promoter S1) is thiophene, dimethyl sulfoxide, carbon disulfide, sulfur powder, hydrogen sulfide, sulfur dioxide, ferrous sulfide, methanesulfonic acid, ferrous sulfate, tungsten sulfide, manganese sulfide, molybdenum sulfide or other sulfur-containing compounds or mixtures;

[0030] Furthermore, the catalyst melt in said S1) rotates at a rate of 6-360 revolutions per minute, is extended and retracted no more than 100 times per minute, and has an extension distance of no less than 100 mm.

[0031] Furthermore, the carbon source mixed gas preheating temperature in S2) is 200-550°C; the synthesis unit is heated to 600-1600°C;

[0032] Furthermore, the mixed gas in S2) is a mixture of inert gas, reducing gas and water vapor, wherein the volume of inert gas accounts for 20-65%, the volume of reducing gas accounts for 30-65%, and the rest is water vapor; the carbon source mixed gas contains carbon source gas, reducing gas and a trace amount of oxygen, the volume of carbon source gas accounts for 15-55%; the volume of reducing gas accounts for 30-84%, and the rest is oxygen.

[0033] For this method, the inert gas is selected from at least one of argon, nitrogen, and helium, preferably argon; the reducing gas is at least one of hydrogen, carbon monoxide, and ammonia.

[0034] The carbon source gas is preferably natural gas, methane, ethane, propane, butane, pentane, hexane, ethylene, propylene, aliphatic hydrocarbons, hydrocarbons having 1 to 10 carbon atoms, monocyclic or bicyclic aromatic hydrocarbons having condensed or isolated rings, and olefins C x H 2x , wherein x is 2, 3 or 4, other gaseous hydrocarbons having a high saturated vapor pressure, ethanol, at least one of anthracene or anthracene oil vapor.

[0035] Beneficial effects of the present invention: Due to the adoption of the above technical solution, the device of the present invention adopts a rotating catalyst melt with double scrapers connected to a double-electrode DC arc, which can sustainably prepare catalyst nanoparticles of uniform size for the preparation of oligo-walled carbon nanotubes. The double scrapers in the low-temperature zone cooperate to remove the coke enriched on the surface of the catalyst melt, keep the surface of the catalyst melt clean, prevent coking from deactivating the catalyst, and facilitate the sustainable preparation of uniform catalyst nanoparticles for the growth of oligo-walled carbon nanotubes. The scraping unit allows the coke to fall into the coke collection chamber at the lower end as much as possible, and the lighter carbon nanomaterials float into the product collection chamber with the air flow, thereby achieving preliminary separation of the products, avoiding the contamination of the products by coke rich in a large number of iron particles, and improving the purity of the initial product.

[0036] A cooling device is provided inside the catalyst melt to ensure that the rotating catalyst melt always remains partially melted and does not form large droplets. Maintaining the relatively stable shape of the cylindrical melt is conducive to the preparation of uniform nano-catalyst particles. The rotating melt will compensate for the 2-fold temperature difference between the cathode and anode of the dual DC electrodes, causing the temperature uniformity of the reaction melt.

[0037] The dual electrodes can provide more high-temperature reaction zones for growth, and the bottomless anode effect can extend the reaction time, improve preparation efficiency, and increase production capacity, with an output of up to 1kg per hour.

[0038] The introduction of trace amounts of water vapor and oxygen can play a certain role in etching coke. It reduces the impact of coke accumulation on the air flow field, thermal field and the preparation of uniform catalysts, so as to achieve the purpose of continuous and stable growth. The average Raman ion of the prepared product is G / ID The carbon nanotubes have a high crystallinity of 45 or more and a continuous stability time of more than 100 hours.

[0039] Multiple synthesis units, scraping units, collection units, and barrier units can be added to the furnace, which contains a long, rotating, movable catalyst melt, to achieve scalable production. Each production unit grows 1kg per hour, yielding 10kg per day. Three production units can produce 30kg per day. Theoretically, production capacity can reach ton-level production in 34 days, making it possible to produce oligo-arm carbon nanotubes at a breakthrough ton-level production.

[0040] The gaseous carbon source of the device of the present invention passes through the high-temperature zone of the plasma arc core. Due to the presence of catalyst particles of different sizes, a portion of the gaseous carbon source is prematurely cracked under the action of the large-particle catalyst to form solid highly crystalline carbon and highly crystalline carbon-coated iron structures, which coke at the lower end of the hollow electrode gun and slowly cover the surface of the melt. This will affect the continuous preparation of nano-sized catalysts, further affecting the entire airflow field and arc stability, making product generation difficult to sustain. The coked carbon will slowly melt into the melt, affecting the uniformity of the melt composition. The incorporation of excessive highly crystalline carbon will greatly reduce the activity of the melt-prepared catalyst, affecting the catalytic cracking product generation. As a result, the content of SWCNTs in the subsequent products becomes less and less, and product growth cannot be sustained. This seriously affects the continuous and stable preparation of the product.

[0041] In each synthesis unit, the cathode electrode gun and the anode electrode gun follow the principle of minimum resistance, and discharge occurs between the cathode and anode with the lowest resistance. Therefore, the present invention limits the distance between each group of cathodes and anodes. At the same time, a scraping unit and a barrier unit are also present between the two synthesis units in the scalable production unit, which is relatively far apart. Therefore, the cathodes and anodes of multiple synthesis units will not discharge each other and affect the preparation of catalyst nanoparticles. The production units are independent of each other and will not affect each other. Few-walled carbon nanotubes refer to carbon nanotubes with three or fewer walls, including single-walled carbon nanotubes, double-walled carbon nanotubes, and triple-walled carbon nanotubes.

[0042] The synthesis unit and scraping unit are separated by a barrier unit. This prevents the high-temperature arc from posing high temperature requirements on the scraping unit, maintaining a relatively low temperature environment in the scraping unit. Furthermore, it ensures the relatively stable airflow and temperature fields required by the synthesis unit while preventing oligo-walled products from drifting into the scraping unit. The nanostructures obtained using the described methods and apparatuses are relevant to materials science, nanotechnology, plasma physics, applied chemistry, and many other promising areas, particularly in lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic diagram of the structure of a device for preparing oligo-walled carbon nanotubes by scalable arc discharge according to the present invention.

[0044] Figure 2 Schematic diagram of the structure of the expanded multi-synthesis unit of the device of the present invention.

[0045] Figure 3 It is a side view of the barrier unit and catalyst melt of the device of the present invention.

[0046] Figure 4 This is a schematic diagram of a scanning electron microscope of the oligo-walled carbon nanotubes prepared in Example 3 of the present invention.

[0047] Figure 5 This is a schematic diagram of thermogravimetric characterization of walled carbon nanotubes prepared using the apparatus of the present invention in Example 4 of the present invention.

[0048] Figure 6 Schematic diagram of the Raman spectrum of the oligo-walled carbon nanotubes prepared in Example 3 of the present invention.

[0049] Figure 7 This is a transmission electron microscope diagram of the oligo-walled carbon nanotubes prepared in Example 3 of the present invention.

[0050] Figure 8 This is a transmission electron microscope diagram of the coking product prepared in Example 3 of the present invention.

[0051] In the picture:

[0052] 100. Furnace body; 110. Synthesis unit; 111. Hollow cathode electrode gun; 112. Hollow anode electrode gun; 113. Hollow graphite electrode; 115. Carbon source mixture gas injection pipe; 130. Preheater; 150. Conveyor; 170. Barrier unit; 190. Drive unit; 210. Catalyst melt; 211. Cooling unit; 220. Scraping unit; 221. First curved scraper; 222. Second curved scraper; 223. First drive motor; 224. Second drive motor; 225. Controller; 330. Collection unit; 331. First collection chamber; 332. Second collection chamber; 333. Transition chamber. DETAILED DESCRIPTION

[0053] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0054] In order to solve the problems existing in the prior art, the technical solution adopted by the present invention is: a device capable of preparing oligo-walled carbon nanotubes by scalable arc discharge.

[0055] like Figure 1As shown, the present invention provides an arc discharge device for preparing oligo-walled carbon nanotubes, the device comprising: a furnace body 100, a preheater 130, a conveyor 150, a collecting unit 330, a synthesis unit 110, a scraping unit 220, a barrier unit 170, a catalyst melt 210 and a driving unit 190;

[0056] The scraping unit 220 and the synthesis unit 110 are arranged at the upper end of the furnace body 100 at a certain distance, the barrier unit 170 is arranged between the scraping unit 220 and the synthesis unit 110, and the catalyst melt 210 is arranged inside the furnace body 100 and below the scraping unit 220 and the synthesis unit 110; the barrier unit and the catalyst melt are shown in the side view. Figure 3 shown.

[0057] The driving unit 190 is disposed outside one side of the furnace body 100 and is fixedly connected to one end of the catalyst melt via a connecting shaft to drive the catalyst melt 210 to rotate and telescopically move;

[0058] The catalyst additive conveyor 150 and the preheater 130 are both connected to the synthesis unit 110 .

[0059] The synthesis unit includes: a hollow cathode electrode gun 111, a hollow anode electrode gun 112, a hollow graphite electrode 113 and a carbon source mixed gas injection pipe 115;

[0060] The collecting unit 330 is divided into a first collecting chamber 331, which is mainly used to recover oligo-walled carbon nanotube products, and a second collecting chamber 332, which is mainly used to recover coke. The first collecting chamber is located directly below the synthesis unit, and the second collecting chamber is located directly below the scraping unit. Both collecting chambers are equipped with a transition chamber 333. When the collecting chamber collects a large amount of products, the transition chamber 333 can be used to transfer the products out of the collecting chamber without stopping the experiment, so as to continuously collect the products and extend the reaction time.

[0061] One end of the hollow cathode electrode gun 111 and the hollow anode electrode gun 112 are inserted into the interior of the furnace body from the top of the furnace body 100, and a certain distance is separated between the hollow cathode electrode gun 111 and the hollow anode electrode gun 112; the other ends of the hollow cathode electrode gun and the hollow anode electrode gun are connected to the preheater 130 and the conveyor 150 respectively;

[0062] The carbon source mixed gas injection pipe 115 is disposed between the hollow cathode electrode gun 111 and the hollow anode electrode gun 112 and is connected to the preheater 130 .

[0063] The scraping unit 220 includes: a first curved scraper 221, a second curved scraper 222, a first driving motor 223, a second driving motor 224 and a controller 225;

[0064] The first drive motor 223 and the second drive motor 224 are arranged on the top of the furnace body 100 and are connected to the first arc scraper 221 and the second arc scraper 222 respectively through connecting shafts. The controller 225 is connected to the first drive motor and the second drive motor respectively.

[0065] The barrier unit 170 is a central circular hole plate, the center of which is concentric with the catalyst melt 210, and one end of the central circular hole plate is fixed to the top of the furnace body, and the distance d between the end of the other end and the surface of the catalyst melt 210 is 10-100 mm;

[0066] The material of the middle circular hole plate is refractory metal tungsten, tantalum, tantalum-iron alloy, magnesium-carbon material, corundum material or graphite. Figure 3 shown.

[0067] The catalyst melt 210 is a hollow metal cylinder with a diameter of not less than 30 cm, and a cooling unit 211 is provided inside the hollow metal cylinder; the center distance D between the hollow cathode and anode electrodes is between 50-350 mm.

[0068] The catalyst melt 210 is an iron-containing compound or mixture, which is used to conduct two parallel sets of electrodes to form a plasma arc. It is pressed into a cylindrical shape and contains at least one of nickel, cobalt, iron carbide, carboxyl iron, carbonyl iron, cobalt, nickel alloy, tungsten, tantalum, rhenium, molybdenum, yttrium, lanthanum, and dysprosium.

[0069] like Figure 2 As shown, a schematic structural diagram of the multiple synthesis units after the device of the present invention is expanded, the device adopts three synthesis units 110 and three scraping units 220 arranged in sequence and equidistantly, and a barrier unit 170 is provided between each synthesis unit 110 and the scraping unit 220, and the three synthesis units 110 share a catalyst melt 210, and a collection unit 330 is provided below each synthesis unit 110 and the scraping unit 220, and a transition chamber 333 is provided at the bottom of each collection unit 330.

[0070] Another object of the present invention is to provide a method for preparing single-walled carbon nanotubes using the above-mentioned device, the method specifically comprising the following steps:

[0071] S1) placing the catalyst promoter in the conveyor 150 and introducing an inert gas to evacuate the furnace body 100;

[0072] S2) starting a plasma arc to conduct through the catalyst melt 210, starting the drive unit 190 to rotate and expand the catalyst melt, and starting the preheater 130 to preheat the mixed gas and the carbon source mixed gas;

[0073] S3) A catalyst promoter is quantitatively fed into the furnace body via the conveyor 150 through the hollow cathode electrode gun 111 and the hollow anode electrode 112. The catalyst promoter passes through the arc region and meets the partially molten catalyst melt 210. The catalyst promoter further restricts the growth of nanocatalysts evaporated from the catalyst melt, thereby preparing catalyst particles of 0.5-6 nanometers. A carbon source gas mixture is introduced into the furnace, where it is catalytically cracked by the arc to produce oligo-walled carbon nanotubes that fall into the first collection chamber 331.

[0074] S4) As the reaction proceeds, when the catalyst melt 210 rotates and contracts in a direction away from the cathode and anode, the first arc-shaped scraper 221 is lifted and the second arc-shaped scraper 222 is pressed down to allow the coke attached to the surface of the melt to fall into the second collection chamber 332. When the catalyst melt rotates and contracts in a direction close to the cathode and anode, the first arc-shaped scraper 221 is pressed down and the second arc-shaped scraper 222 is lifted to allow the coke attached to the surface of the rotating melt to fall into the second collection chamber, so that the catalyst melt can always remain in a clean state, which is conducive to the continuous generation of catalyst nanoparticles for continuous growth.

[0075] The catalyst promoter S1) is thiophene, dimethyl sulfoxide, carbon disulfide, sulfur powder, hydrogen sulfide, sulfur dioxide, ferrous sulfide, methanesulfonic acid, ferrous sulfate, tungsten sulfide, manganese sulfide, molybdenum sulfide or other sulfur-containing compounds or mixtures;

[0076] The catalyst melt 210 in S1) rotates at a rate of 6-360 revolutions per minute, and is extended and retracted no more than 100 times per minute, with a distance of no less than 100 mm.

[0077] The carbon source mixed gas preheating temperature in S2) is 200-550°C; the synthesis unit 110 is heated to 600-1600°C;

[0078] The mixed gas in S2) is a mixture of inert gas, reducing gas and water vapor, wherein the inert gas accounts for 20-65% by volume, the reducing gas accounts for 30-65% by volume, and the rest is water vapor; the carbon source mixed gas contains carbon source gas, reducing gas and a trace amount of oxygen, wherein the volume of the carbon source gas accounts for 15-55%; the reducing gas accounts for 30-84%, and the rest is oxygen.

[0079] For this method, the inert gas is selected from at least one of argon, nitrogen, and helium, preferably argon; the reducing gas is at least one of hydrogen, carbon monoxide, and ammonia.

[0080] The carbon source gas is preferably natural gas, methane, ethane, propane, butane, pentane, hexane, ethylene, propylene, aliphatic hydrocarbons, hydrocarbons having 1 to 10 carbon atoms, monocyclic or bicyclic aromatic hydrocarbons having condensed or isolated rings, and olefins C x H 2x , wherein x is 2, 3 or 4, other gaseous hydrocarbons having a high saturated vapor pressure, ethanol, at least one of anthracene or anthracene oil vapor.

[0081] Example 1

[0082] The catalyst promoter, thiophene, is placed in a conveyor, and the furnace is evacuated by introducing inert argon. A plasma arc is then initiated through the catalyst melt, heating it to 960°C. The distance D between the hollow cathode and anode electrodes is 120 mm. The catalyst melt is a 20 cm diameter hollow metal cylinder containing iron and dysprosium, with a cooling unit inside. The catalyst melt rotates at 60 revolutions per minute and expands and contracts 10 times per minute over a distance of 280 mm.

[0083] The preheater is activated to preheat the mixed gas and carbon source gas mixture to 350°C. The mixed gas is a mixture of inert gas, reducing gas, and water vapor. The inert gas is argon, accounting for 65% by volume, the reducing gas is hydrogen, accounting for 33% by volume, and the remainder is water vapor. The carbon source gas mixture contains carbon source gas, reducing gas, and a trace amount of oxygen. The carbon source gas is natural gas, accounting for 55.5% by volume, the reducing gas is carbon monoxide, accounting for 44% by volume, and the remainder is oxygen.

[0084] The barrier unit is a middle circular hole plate made of tungsten material, the center of which is concentric with the catalyst melt and the distance d from the surface of the catalyst melt is 60mm. Catalyst particles of 0.5-6 nanometers are prepared, and a carbon source mixed gas and the prepared catalyst nanoparticles are introduced. Under the action of the electric arc, catalytic cracking is carried out to generate oligo-walled carbon nanotubes that fall into the first collection chamber. As the reaction proceeds, when the catalyst melt rotates and contracts away from the cathode and anode, the first arc-shaped scraper is lifted and the second arc-shaped scraper is pressed down to allow the coke attached to the surface of the melt to fall into the second collection chamber. When the catalyst melt rotates and contracts close to the cathode and anode, the first arc-shaped scraper is pressed down and the second arc-shaped scraper is lifted to allow the coke attached to the surface of the rotating melt to fall into the second collection chamber, so that the catalyst melt can always remain in a clean state, which is conducive to the continuous generation of catalyst nanoparticles for continuous growth.

[0085] From Table 2, we can see that the average I of the primary product obtained in Example 1 G / I D The ratio is 35, the product TG residue is 47.6%, the initial product output of oligo-walled carbon nanotubes is 0.73 kg / h, and the continuous reaction time can reach 198 hours.

[0086] The device and method of the present invention can facilitate the continuous and effective production of large quantities of oligo-walled carbon nanotubes over a long period of time, and can also achieve similar effects to other similar reactors, thus having certain versatility.

[0087] High-quality oligo-walled carbon nanotube samples were characterized by Raman spectroscopy, thermogravimetric analysis, scanning electron microscopy and energy-dispersive X-ray spectroscopy, transmission electron microscopy, and ultraviolet-visible-near-infrared absorption spectroscopy according to GB / T 32871-2016, GB / T 24490-2009, GB / T 32869-2016, GB / T 30534-2014, and GB / T 39114-2020. The test protocol is described in Table 1.

[0088] Table 1 Test plan

[0089] Technical Specifications unit Evaluation Method Carbon tube content wt% TEM, EDX, TGA Number of carbon nanotube walls / TEM, EDX, TGA Carbon nanotube diameter nm Raman, TEM, NIR-Vis <![CDATA[I G / I D ratio]]> / Raman Specific surface area <![CDATA[m 2 / g]]> BET

[0090] Example 2

[0091] The difference between the device and process method of Example 1 is that the co-catalyst is manganese sulfide, the furnace body is heated to 1160°C, and the distance D between the hollow cathode and anode electrodes is 280mm. The catalyst melt comprises a hollow metal cylinder of iron and molybdenum with a diameter of 30cm. The catalyst melt rotates at 120 revolutions per minute, and expands and contracts 30 times per minute, with a telescopic distance of 360mm. The preheating temperature of the carbon source mixture is 450°C, and the mixed gas is an inert gas, argon, which accounts for 35% by volume, hydrogen, which accounts for 43% by volume, and the rest is water vapor. In the carbon source mixture, the carbon source gas is methane, which accounts for 45% by volume, the reducing gas is carbon monoxide, which accounts for 54% by volume, and the rest is oxygen. The barrier unit is a middle circular hole plate made of tantalum, and the distance d from the surface of the catalyst melt is 50mm.

[0092] From Table 2, it can be seen that the average I of the primary product obtained in Example 2 G / I D The ratio is 48, the product TG residue is 35.3%, the initial product output of oligo-walled carbon nanotubes is 0.89 kg / h, and the continuous reaction time can reach 268 hours, which exceeds 10 days.

[0093] Example 3

[0094] The apparatus and process of Example 2 differ in that the co-catalyst is methanesulfonic acid, the furnace is heated to 1550° C., the catalyst melt comprises a hollow metal cylinder of iron, nickel, and yttrium, with an outer diameter of 60 cm, and the catalyst melt rotates at 180 rpm.

[0095] The carbon source gas mixture is preheated to 550°C. The mixture consists of argon (40% by volume), hydrogen (55% by volume), and water vapor (the remainder). The carbon source gas mixture contains a carbon source gas, a reducing gas, and a trace amount of oxygen. Propylene (35.5% by volume) and carbon monoxide (64% by volume) are the reducing gas. The barrier element is a corundum plate with a central circular hole, and the distance d from the catalyst melt surface is 30 mm.

[0096] Figure 6 The Raman spectrum of the sample prepared in Example 3 has an obvious and sharp RBM characteristic absorption peak at 180 cm-1, that is, the product contains single-walled carbon nanotubes. Under the test conditions of an excitation wavelength of 532 nm, the product I is calculated. G / I D The ratio is 62, that is, the prepared product contains high-quality single-walled carbon nanotubes. From Table 2, we know that the TG residue of the initial product is 21.8%. Figure 4 Scanning electron microscopy shows that the sample of Example 3 has fewer impurities on the surface, which is consistent with the TG residue characterization results. Figure 7 Transmission electron microscopy of the product prepared in Example 3 showed that the product also contained obvious double-walled carbon nanotubes. Figure 8 Transmission electron microscopy of the coke product collected in Example 3 shows that the coke product is mainly carbon spheres with a diameter of 50-300 nm. The yield of the primary product of oligo-walled carbon nanotubes is 1.1 kg / h, and the continuous reaction time can reach 267 hours, which is more than 10 days.

[0097] Example 4

[0098] The apparatus and process of Example 3 differ in that the co-catalyst is methanesulfonic acid, the furnace is heated to 1350°C, the catalyst melt comprises a hollow metal cylinder of iron and lanthanum with an outer diameter of 40 cm, and the catalyst melt rotates at 240 rpm. The melt retracts and retracts six times per minute over a distance of 500 mm. The barrier element is a magnesium-carbon plate with a central circular hole, and the distance d from the catalyst melt surface is 15 mm.

[0099] from Figure 5 The TG characterization of the product in Example 4 shows that the residue is 19.5%. From Table 2, we can see that the average I G / I D The ratio is 65, the output of the primary product of oligo-walled carbon nanotubes is 1.2 kg / h, and the continuous reaction time can reach 245 hours, which exceeds 10 days.

[0100] Example 5

[0101] The process of Example 3 is adopted, except that a furnace body containing a long rotating movable catalyst melt is equipped with three combined units, a scraping unit, a collecting unit and a blocking unit to achieve the purpose of expanding the production unit. Figure 2 As shown in Table 2, the average I of the primary product obtained in Example 5 is G / I D The ratio is 56, the product TG residue is 17.8%, and the output of the primary product of oligo-walled carbon nanotubes is 3.2kg / h. Based on 10 hours of work per day, 3 production units can produce more than 30kg per day. Theoretically, the production capacity can reach ton-level preparation in 32 days, making it possible to break through the ton-level production of oligo-walled carbon nanotubes, and the future is promising.

[0102] Table 2 Product indicators in the examples

[0103]

[0104] The description of the above embodiments is only used to help understand the method of this application and its core idea; at the same time, for those skilled in the art, according to the idea of this 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 limiting the present application.

[0105] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different nouns to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. For example, "including" and "comprising" mentioned throughout the specification and claims are open-ended terms, so they should be interpreted as "including / including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problems within the preset error range and basically achieve the technical effects. The subsequent description in the specification is a preferred embodiment of the present application, but the description is for the purpose of illustrating the general principles of the present application, and is not used to limit the scope of the present application. The scope of protection of the present application shall be as defined in the attached claims.

[0106] It should also be noted that the terms "include," "comprises," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or system comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or system. In the absence of further limitations, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the product or system comprising the element.

[0107] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0108] The above description shows and describes several preferred embodiments of the present application. However, as previously mentioned, it should be understood that the present application is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Instead, the present application can be used in various other combinations, modifications, and environments and can be modified within the scope of the application concept described herein through the above teachings or technology or knowledge in the relevant field. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present application should be protected by the claims appended hereto.

Claims

1. A device for preparing oligo-walled carbon nanotubes by scalable arc discharge, comprising: A furnace, a preheater, a conveyor and a collecting unit, characterized in that the device further comprises: at least one synthesis unit, at least one scraping unit, at least one barrier unit, a catalyst melt and a driving unit; The barrier unit is arranged inside the furnace body to separate the furnace body into two left and right chambers, the scraping unit is arranged at the upper end of the left chamber, and the synthesis unit is arranged at the upper end of the right chamber. The catalyst melt is arranged horizontally inside the furnace body and is located below the scraping unit and the synthesis unit. The driving unit is arranged outside one side of the furnace body and is fixedly connected to one end of the catalyst melt arranged in the furnace body through a connecting shaft, driving the catalyst melt to rotate and telescopically move; The catalyst aid conveyor and the preheater are arranged on the top of the outer side of the furnace body and are both connected to the synthesis unit; A collecting unit is provided below the synthesis unit and the scraping unit, and both collecting units are connected to the bottom of the furnace body; The synthesis unit comprises: a hollow cathode electrode gun, a hollow anode electrode gun, a hollow graphite electrode and a carbon source mixed gas injection pipe; One end of the hollow cathode electrode gun and the hollow anode electrode gun are inserted into the interior of the furnace body from the top of the furnace body, and a certain distance is separated between the hollow cathode electrode gun and the hollow anode electrode gun; the other ends of the hollow cathode electrode gun and the hollow anode electrode gun are connected to the preheater and the conveyor respectively; The carbon source mixed gas injection pipe is arranged between the hollow cathode electrode gun and the hollow anode electrode gun, and is connected to the preheater; The pole center distance D between the hollow cathode electrode gun and the hollow anode electrode gun is 50-350 mm.

2. The device according to claim 1, characterized in that The scraping unit includes: a first curved scraper, a second curved scraper, a first drive motor, a second drive motor and a controller; The first drive motor and the second drive motor are arranged on the top of the furnace body and are connected to the first arc scraper and the second arc scraper respectively through connecting shafts, and the controller is connected to the first drive motor and the second drive motor respectively.

3. The device according to claim 1, characterized in that The barrier unit is a plate with a circular hole in the middle, the center of the circular hole is concentric with the catalyst melt, one end of the plate is fixed to the top of the furnace body, and the distance d between the end of the other end and the surface of the catalyst melt is 10-100 mm; The material of the middle circular hole plate is refractory metal tungsten, tantalum, tantalum-iron alloy, magnesium-carbon material, corundum material or graphite. The catalyst melt is a hollow metal cylinder with a diameter of not less than 30 cm, and a cooling unit is provided inside the hollow metal cylinder; The catalyst melt is an iron-containing compound or mixture.

4. A method for preparing oligo-walled carbon nanotubes using the apparatus according to any one of claims 1 to 3, characterized in that: The method specifically comprises the following steps: S1) placing the co-catalyst in a conveyor and introducing an inert gas to evacuate the furnace body; S2) starting a plasma arc to pass through the catalyst melt, starting a drive unit to rotate and expand the catalyst melt, and starting a preheater to preheat the mixed gas and carbon source mixed gas; S3) a certain amount of catalyst promoter is introduced into the furnace body through the hollow cathode and anode electrodes, and the preheated carbon source mixed gas is simultaneously introduced into the furnace body; The catalyst promoter passes through the arc area and meets the catalyst melt. Under the action of the arc, it evaporates to obtain catalyst particles of 0.5-6 nanometers, which then react with the carbon source mixed gas after catalytic cracking to produce oligo-walled carbon nanotube products. S4) starting a scraping unit to scrape off the coke attached to the surface of the catalyst melt.

5. The method according to claim 4, characterized in that The catalyst promoter S1) is thiophene, dimethyl sulfoxide, carbon disulfide, sulfur powder, hydrogen sulfide, sulfur dioxide, ferrous sulfide, methanesulfonic acid, ferrous sulfate, tungsten sulfide, manganese sulfide, molybdenum sulfide or a mixture thereof.

6. The method according to claim 4, characterized in that The catalyst melt in said S2) rotates at a rate of 6-360 revolutions per minute, is extended and retracted no more than 100 times per minute, and has a retracted distance of no less than 100 mm.

7. The method according to claim 4, characterized in that The carbon source mixed gas preheating temperature in S2) is 200-550°C; the synthesis unit is heated to 600-1600°C.

8. The method according to claim 4, characterized in that The mixed gas in S2) comprises a mixed gas of inert gas, reducing gas and water vapor, wherein the inert gas accounts for 20-65% by volume, the reducing gas accounts for 30-65% by volume, and the rest is water vapor; The carbon source mixed gas comprises carbon source gas, reducing gas and oxygen, wherein the volume proportion of the carbon source gas is 15-55%, the reducing gas is 30-84%, and the rest is oxygen.

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