Method and equipment for preparing carbon nanotubes

Abstract

The invention discloses a method and equipment for rapidly and continuously preparing carbon nano tubes with adjustable tube diameters, which are used for continuously and rapidly preparing carbon nano tubes with different tube diameters and at least comprise a catalyst precursor atomizing chamber, a plasma device, a carbon nano tube preparation reactor, a collector and a tail gas treatment device. A catalyst precursor solution enters the atomizing chamber through the injection pump to be atomized, atomized mist enters the plasma treatment device and then enters a reaction from a sample inlet in the upper portion of the reactor, after the reaction in the reactor is completed for a short time, the carbon nanotubes are collected from a collecting device on the lower portion of the reactor, and tail gas can be returned to the reactor after being filtered by the filter. The tail gas can be repeatedly used; and the continuous preparation of the carbon nano tubes with different tube diameters can be realized.

Description

Technical Field

[0001] The invention relates to the technical field of carbon nanotubes, and in particular to a method and equipment for rapidly, continuously and controllably preparing carbon nanotubes with different diameters. Background Art

[0002] Carbon nanotubes have excellent physical and chemical properties, such as good mechanical properties, thermal stability, special electrical properties, thermal conductivity, hydrogen storage, adsorption and catalytic properties, etc. Therefore, they have attracted the attention of researchers at home and abroad since their introduction. Carbon nanotubes have broad application prospects in many fields such as nanoelectronic devices, catalyst carriers, electrochemical materials, composite materials, etc.

[0003] Carbon nanotubes are tubes formed by the curling of graphene structures composed of six-membered carbon rings. The tubes are generally composed of single or multiple layers, closed at both ends, with diameters ranging from a few nanometers to hundreds of nanometers, and lengths of up to several centimeters. Carbon nanotubes, with their special structure, show extremely strong quantum effects and unique physical and chemical properties, and have great potential for application in many fields such as catalysis, composite materials, energy storage materials, and microelectronic devices.

[0004] The preparation methods of carbon nanotubes include: graphite arc method, chemical vapor deposition method, laser evaporation graphite method, template method, organic plasma spray method, etc. Among them, chemical vapor deposition method is the most widely used preparation method at present, mainly because of its simple equipment, low reaction temperature, easy control of reaction process and high yield. However, there are many problems in the preparation of carbon nanotubes by this method: 1. It is necessary to prepare the catalyst first, and the catalyst preparation cycle is long and there are many control factors; 2. The catalyst preparation process will produce wastewater containing acid, alkali, metal and non-metal ions. The cost of subsequent water treatment process is high and does not meet the requirements of low-carbon environmental protection; 3. The active centers of catalysts prepared by traditional methods often exist in the form of large particle aggregation. When nanotubes grow on the surface of the active center, they generally experience the fragmentation of the catalyst active center, and then grow carbon nanotubes on the catalyst sites exposed by the fragmentation. This will result in a longer growth cycle of the carbon nanotubes and affect the preparation efficiency of the carbon nanotubes; 4. When carbon nanotubes grow in the aggregated state of the catalyst active center, they are easily affected by steric hindrance and bend, which affects the quality of the prepared carbon nanotubes; 5. When single-walled carbon nanotubes are prepared by chemical vapor deposition, the metal size of the catalyst active center should be controlled below 3nm, which is extremely difficult for traditional catalysts.

[0005] Therefore, it is very valuable to achieve environmentally friendly, efficient, continuous and controllable preparation of carbon nanotubes with different diameters. Summary of the invention

[0006] In view of the problems of high equipment requirements and difficulty in industrial production in the prior art, the present invention provides a method and equipment for the rapid and continuous preparation of carbon nanotubes with controllable speed. Conventional equipment can be directly used to achieve industrial continuous production of carbon nanotubes with different diameters. The equipment requirements are low and there is no need to design high-temperature preparation equipment. The obtained carbon nanotube products have high purity and adjustable diameter distribution.

[0007] In a first aspect, the present invention provides a method and apparatus for rapidly, continuously and controllably preparing carbon nanotubes, comprising the following steps:

[0008] S1, preparing a precursor solution by mixing active metal organic matter, carrier organic matter, sulfur-containing auxiliary substance and carbon source organic solvent;

[0009] S2, the precursor solution is pumped to the nozzle on the atomizing chamber to be atomized, and the argon carrier gas is introduced into the atomizing chamber. After being atomized, it is heated and vaporized in the atomizing chamber in the form of an aerosol, and enters the central channel of the plasma. In the high temperature of 6000-10000K and inert atmosphere of the plasma torch, evaporation, dissociation, atomization and excitation occur, and catalyst active particles are formed, which react with the treated carbon source to produce carbon nanotubes, and at the same time continue to react with the added gaseous carbon source and auxiliary gas in the reaction zone. The two carbon sources promote each other and the addition of auxiliary gas increases the yield of carbon nanotubes;

[0010] S3. After the short-term reaction in the reactor is completed, the carbon nanotubes are collected from the lower collecting device of the reactor, and the tail gas is filtered by the filter and returned to the reactor.

[0011] Furthermore, the active metal organic matter is an iron salt, a cobalt salt, or a nickel salt, the iron salt comprises a mixture of one or more of ferrocene, pentacarbonyl iron, and ferric acetate, the cobalt salt comprises an organic cobalt salt such as cobalt acetate, and the nickel salt comprises an organic nickel salt such as nickel acetate; the carrier is an aluminum organic matter or a magnesium organic matter or a mixture of two of them; the sulfur-containing auxiliary substance comprises a mixture of one or more of thiophene, sulfur monohydrate, carbon disulfide, methyl mercaptan, thiophenol, and diphenyl disulfide; the carbon source solvent is a combination of one or more of toluene, methanol, ethanol, propanol, isopropanol, tetrahydrofuran, xylene, and ethyl acetate.

[0012] Further, the gaseous carbon source is one or more combinations of organic olefin chemicals such as methane, ethylene, propylene, etc.; the auxiliary gas is one or more combinations of water vapor, carbon monoxide or hydrogen;

[0013] Further, the injection speed of the mixed catalyst precursor is 0.02-5000 μL / min; the carrier gas is argon, the flow rate of Ar carrier gas is 1-100 L / min, the flow rate of H2 is 0.1-30 L / min, and the water vapor is generated by pumping liquid input to gasify in the reaction zone, and the flow rate is 10 μL-10 ml / min;

[0014] Furthermore, the mass ratio of active metal element, auxiliary metal element, sulfur element and carrier element is 1:(0.07-0.5):(0.001-0.05):(0-10).

[0015] Further, the heating temperature of the atomization chamber is controlled at 50-500°C, preferably 100-300°C;

[0016] Further, the reaction temperature of chemical vapor deposition is 600-1400°C, the preferred reaction temperature of multi-walled carbon nanotubes is 650-900°C, and the preferred temperature of single-walled carbon nanotubes is 900-1300°C;

[0017] Further, the reaction time is 1 to 180 s;

[0018] Furthermore, the plasma equipment is a device that can generate high-temperature plasma or low-temperature plasma.

[0019] The carbon nanotubes prepared by the method and the device can be single-walled carbon nanotubes or multi-walled carbon nanotubes. By controlling the preparation process conditions, single-walled carbon nanotubes with a diameter of 1-3nm or multi-walled carbon nanotubes with a diameter of 3-100nm can be prepared.

[0020] The method and device for continuously and rapidly preparing carbon nanotubes with different diameters as claimed in claim 1 is characterized in that the beneficial effects of the present invention are:

[0021] The present invention controls the ratio of active metal elements, auxiliary metal elements, sulfur elements, and carrier elements to adjust the diameter of carbon nanotubes;

[0022] (2) The present invention controls the flow rate of the catalyst precursor solution, can precisely and quantitatively control the amount of carbon source and active metal source entering, and regulate the ratio of carbon source to catalyst, so that the product pipe diameter can be adjusted;

[0023] (3) The present invention can make the temperature of the plasma cloud reaction uniform by controlling the flow rate of argon gas, increase the reaction active area, and facilitate the continuous preparation of carbon nanotubes with different diameters;

[0024] (4) The present invention increases the length and density of carbon nanotubes and improves the growth rate of the catalyst by adding a gaseous carbon source in the reaction zone;

[0025] (5) The present invention is directed to the continuous preparation of carbon nanotubes. The preparation system is connected in series, which can improve production efficiency, reduce energy and material waste, reduce manual operation and management costs, and improve product quality and consistency. The control process and monitoring of the production process are reduced, problems can be discovered and solved in a timely manner, and the quality and stability of the product are improved. The entire process is simple and easy to repeat and scale up. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is a SEM scanning electron microscope image of the multi-walled carbon nanotubes prepared in Example 1 of the present invention;

[0028] Figure 2 This is a SEM scanning electron microscope image of the single-walled carbon nanotube mixture obtained in Experiment No. 2 in Table 1 of the embodiment of the present invention;

[0029] Figure 3 This is a TEM transmission electron microscope image of single-walled carbon nanotubes obtained after acid washing of the single-walled carbon nanotube mixture of Experiment No. 2 in Table 1 of the embodiment of the present invention;

[0030] Figure 4 This is the Raman spectrum of the single-walled carbon nanotubes obtained after acid washing of the single-walled carbon nanotube mixture of Experiment No. 2 in Table 1 of the embodiment of the present invention;

[0031] Figure 5 A diagram of a device for rapidly, continuously and controllably preparing carbon nanotubes with different diameters according to an embodiment of the present invention; DETAILED DESCRIPTION

[0032] The present invention provides a method for preparing carbon nanotubes, which can realize a method for rapidly, continuously and controllably preparing carbon nanotubes with different diameters, comprising the following steps:

[0033] (1) Preparation of catalyst

[0034] The steps include:

[0035] 1. Mix toluene (carbon source solvent), ferrocene (active metal organic matter) and thiophene (sulfur-containing additive) in a mass ratio of 95%, ferrocene 4%, and thiophene 1%. The mass ratio can be extended to (92-96): (3-7): (0.1-6), stir evenly, and prepare a catalyst precursor solution.

[0036] 2. Place the catalyst precursor solution prepared in step 1 in multiple 50 ml syringes, and use a micro-injection pump to atomize the catalyst precursor solution in the syringe through an atomizer in sequence. In other embodiments, a vaporization chamber may also be included. After the catalyst precursor solution is atomized, it vaporizes in the range of 80-450 ° C, preferably at a temperature of 300 ° C. The raw material is gasified in the vaporization chamber, mixed with carrier gas nitrogen and hydrogen, and transported to the plasma device for treatment. The plasma device can also be a composite device to prepare a carbon nanotube catalyst. The reaction conditions in the plasma device are shown in the patent applied for (23-1-7236jTR--2024100399157 A composite high-temperature heat source generator, the content of the patent, including equipment and reaction conditions, can be introduced into the new patent. Of course, the carbon nanotube preparation device of this patent can also not use a composite generator, but only use a plasma generator, the purpose of which is to bombard the metal elements in the active metal organic matter to make it a metal atom in the active center of the catalyst).

[0037] 3. Controlling the concentration of metal atoms in the plasma device can effectively control the diameter of the metal particles, thereby affecting the diameter and number of layers of the subsequently generated carbon nanotubes.

[0038] The atomic diameters of Fe, Co, and Ni are 0.115-0.117nm, or about 0.12nm, and the atomic diameters of the three are approximately the same.

[0039] (2) Preparation of carbon nanotubes:

[0040] The influence of active metal types and active metal concentrations,

[0041] Further, the injection speed of the mixed catalyst precursor is 0.02-5000 μL / min; the carrier gas is argon, N2, the flow rate of Ar carrier gas is 1-100 L / min, the flow rate of H2 is 0.1-30 L / min, and the water vapor is generated by pumping liquid input to the reaction zone for gasification, and the flow rate is 10 μL-10 ml / min;

[0042] Further, the heating temperature of the vaporization chamber is controlled at 50-500°C, preferably 100-300°C;

[0043] Further, the reaction temperature of chemical vapor deposition is 600-1400°C, the preferred reaction temperature of multi-walled carbon nanotubes is 650-900°C, and the preferred temperature of single-walled carbon nanotubes is 900-1300°C;

[0044] Furthermore, the reaction time is 1 to 180 seconds.

[0045] The carrier is one or a mixture of organic aluminum compounds and magnesium organic compounds, such as triethylaluminum, triisobutylaluminum, dimethylmagnesium, bis(cyclopentadienyl)magnesium bromide;

[0046] The carbon source solvent is a combination of one or more of toluene, methanol, ethanol, propanol, isopropanol, tetrahydrofuran, xylene and ethyl acetate.

[0047] Further, the injection speed of the mixed catalyst precursor is 0.1-1000 μL / min; the carrier gas is argon, N2, the flow rate of Ar carrier gas is 1-100 L / min, the flow rate of H2 is 0.1-30 L / min, and the water vapor is generated by pumping liquid input to the reaction zone for gasification, and the flow rate is 10 μL-10 ml / min;

[0048] The sulfur content affects the catalyst particle size, prevents iron aggregation, and increases the size of iron particles, which ultimately affects the diameter of carbon tubes.

[0049] Preparation of single-walled carbon nanotubes

[0050] M(Fe:S)≥10:1, single-walled carbon nanotubes with a diameter of 1-3nm can be continuously prepared;

[0051] After purification, the specific surface area of ​​the single-walled tube is more than 900. G / I D ≥50;

[0052] Table 1 Single-walled carbon nanotube growth data under different process parameters

[0053]

[0054]

[0055] Preparation of multi-walled carbon nanotubes

[0056] By adjusting the process conditions, the preparation of multi-walled carbon nanotubes with a diameter of 3-100nm can be controlled, and the specific surface area after purification is less than 800.

[0057] Table 2 Growth data of multi-walled carbon nanotubes under different process parameters

[0058]

[0059] Example 1 Preparation of multi-walled carbon nanotubes

[0060] The temperature was raised to the reaction temperature under an argon atmosphere, and the multi-walled carbon nanotube growth catalyst prepared in Example A in Table 2 was taken, and a carrier gas nitrogen was used to continuously deliver it at the bottom of the reactor under a slight positive pressure, and then hydrogen and methane were introduced. After a certain period of continuous reaction, the methane and hydrogen were turned off, and the temperature was lowered to room temperature under a nitrogen atmosphere, and the multi-walled carbon nanotube mixture was taken out, and the SEM and specific surface area were tested. The SEM image showed that the prepared carbon nanotube array had a better morphology and fewer defects.

[0061] Example 2 Preparation of single-walled carbon nanotubes

[0062] The temperature was raised to the reaction temperature under an argon atmosphere, and the gas treated with the single-walled carbon nanotube growth catalyst prepared in Example A in Table 1 was transported to the reactor. The temperature in the furnace was 1100°C. During the downward transportation, carbon nanotubes were generated by reaction. The reaction products were output from the lower end of the fluidized bed reactor and entered the material collection tank. The tail gas passed through the filter and entered the tail gas treatment device. The prepared carbon nanotubes are single-walled carbon nanotubes, such as Figure 2 SEM image.

[0063] Example 3 Preparation of single-walled carbon nanotubes

[0064] The temperature was raised to the reaction temperature under an argon atmosphere, and the single-walled carbon nanotube growth catalyst prepared in Implementation Table 1 was taken, and a carrier gas argon was continuously delivered at the bottom of the reactor under a slight positive pressure, and then hydrogen and methane were introduced. After a certain period of continuous reaction, the methane and hydrogen were turned off. The reaction temperature was 1300°C, and the reaction time was 60 minutes. When the temperature dropped to room temperature under an argon atmosphere, the single-walled carbon nanotube mixture was taken out, the weight was weighed, and the SEM and Raman tests were performed.

[0065] 10g of the single-walled carbon nanotube mixture was placed in a fluidized bed at 400℃ and 80mm in diameter, and 100L / h of nitrogen and 80ml / min of carbon dioxide were introduced for pretreatment to remove impurities and open defects to make the acid easier to purify; then the pretreated single-walled carbon nanotube mixture was placed in 100g of 36% concentrated hydrochloric acid, acidified in a water bath at 90-100℃ for 10h, washed with purified water until the pH was 6-7, and dried at 120℃ to constant weight, finally obtaining single-walled carbon nanotubes with a purity of more than 99% and a specific surface area of ​​1187m 2 / g,I G / D =95.

[0066] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method and device for continuously and rapidly preparing carbon nanotubes with different diameters, wherein the preparation method is characterized in that: The steps include: S1, preparing a precursor solution by mixing active metal organic matter, carrier organic matter, sulfur-containing auxiliary substance and carbon source organic solvent; S2, the precursor solution is pumped to the nozzle on the atomizing chamber to be atomized, and the argon carrier gas is introduced into the atomizing chamber. After being atomized, it is heated and vaporized in the atomizing chamber in the form of an aerosol, and enters the central channel of the plasma. In the high temperature of 6000-10000K and inert atmosphere of the plasma torch, evaporation, dissociation, atomization and excitation occur, and catalyst active particles are formed, which react with the treated carbon source to produce carbon nanotubes, and at the same time continue to react with the added gaseous carbon source and auxiliary gas in the reaction zone. The two carbon sources promote each other and the addition of auxiliary gas increases the yield of carbon nanotubes; S3. After the short-term reaction in the reactor is completed, the carbon nanotubes are collected from the lower collecting device of the reactor, and the tail gas is filtered by the filter and returned to the reactor. In the step S1, the active metal organic matter is an iron salt, a cobalt salt, or a nickel salt, the iron salt comprises a mixture of one or more of ferrocene, pentacarbonyl iron, and ferric acetate, the cobalt salt comprises an organic cobalt salt such as cobalt acetate, and the nickel salt comprises an organic nickel salt such as nickel acetate; the carrier is an aluminum organic matter or a magnesium organic matter or a mixture of two of them; the sulfur-containing auxiliary substance comprises a mixture of one or more of thiophene, sulfur monohydrate, carbon disulfide, methyl mercaptan, thiophenol, and diphenyl disulfide; and the carbon source solvent is a combination of one or more of toluene, methanol, ethanol, propanol, isopropanol, tetrahydrofuran, xylene, and ethyl acetate. In step S2, the gaseous carbon source is one or more combinations of organic olefin chemicals such as methane, ethylene, propylene, etc.; the auxiliary gas is one or more combinations of water vapor, carbon monoxide or hydrogen; In the step S2, the injection speed of the mixed catalyst precursor is 0.02-5000 μL / min; the carrier gas is argon, the flow rate of Ar carrier gas is 1-100 L / min, the flow rate of H2 is 0.1-30 L / min, and the water vapor is generated by pumping liquid input to the reaction zone for gasification, and the flow rate is 10 μL-10 ml / min; In step S2, the heating temperature of the atomization chamber is controlled at 50-500°C; The carbon nanotubes prepared by the method and the device can be single-walled carbon nanotubes or multi-walled carbon nanotubes. By controlling the preparation process conditions, single-walled carbon nanotubes with a diameter of 0.5-3nm or multi-walled carbon nanotubes with a diameter of 3-150nm can be prepared. A method and apparatus for continuously and rapidly preparing carbon nanotubes of different diameters as claimed in claim 1, characterized in that the mass ratio of the catalyst active metal element, the sulfur element, and the carrier element is 1:(0.07-0.5):(0.001-0.05):(0-10).

2. The method for preparing single-walled carbon nanotubes according to claim 1, characterized in that: The reaction temperature of chemical vapor deposition is 600-1400° C., and the reaction time is 3-180 seconds.

3. A method and apparatus for continuously and rapidly preparing carbon nanotubes with different diameters according to any one of claims 1 to 3, characterized in that: The device for preparing carbon nanotubes by floating method comprises the following steps: a catalyst precursor solvent tank (1) enters a gas-liquid two-phase atomizing nozzle (3) through a pump (2); the gas phase is argon gas, which is introduced into a heatable atomizer (4) as a carrier gas and an excitation gas; after the solvent carbon source and the catalyst precursor are heated, they enter a plasma device (5) along with the argon gas; the catalyst active particles and carbon source that are dissociated, atomized and excited enter a reactor (6) through the undissociated argon gas; after the carbon tubes are prepared, they enter a material collecting device (7) and an exhaust gas emission and recovery device (8).

4. The atomizing nozzle can be a gas-liquid two-phase flow nozzle, including an ultrasonic atomizing nozzle. The penetration distance after atomization cannot be greater than the diameter or width of the atomizer, and the size of the liquid after atomization is <100μm.

5. Liquid delivery pumps can be selected from horizontal flow pumps, micro-injection pumps, plunger pumps, etc. according to the range of injection volume.

6. Plasma can be selected from microwave plasma equipment and inductively coupled plasma equipment.

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