CN115477300A - Carbon nano tube, fluidized bed preparation process thereof and conductive agent - Google Patents
Carbon nano tube, fluidized bed preparation process thereof and conductive agent Download PDFInfo
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- CN115477300A CN115477300A CN202210926489.XA CN202210926489A CN115477300A CN 115477300 A CN115477300 A CN 115477300A CN 202210926489 A CN202210926489 A CN 202210926489A CN 115477300 A CN115477300 A CN 115477300A
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- 239000002041 carbon nanotube Substances 0.000 title claims abstract description 151
- 229910021393 carbon nanotube Inorganic materials 0.000 title claims abstract description 151
- 238000002360 preparation method Methods 0.000 title claims abstract description 41
- 239000006258 conductive agent Substances 0.000 title abstract description 24
- 239000003054 catalyst Substances 0.000 claims abstract description 112
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims abstract description 72
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- UFMZWBIQTDUYBN-UHFFFAOYSA-N cobalt dinitrate Chemical compound [Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O UFMZWBIQTDUYBN-UHFFFAOYSA-N 0.000 description 5
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- KBJMLQFLOWQJNF-UHFFFAOYSA-N nickel(ii) nitrate Chemical compound [Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O KBJMLQFLOWQJNF-UHFFFAOYSA-N 0.000 description 4
- 229910017052 cobalt Inorganic materials 0.000 description 3
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Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/15—Nano-sized carbon materials
- C01B32/158—Carbon nanotubes
- C01B32/16—Preparation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
- B01J8/1809—Controlling processes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
- B01J8/24—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The application belongs to the technical field of materials, and particularly relates to a carbon nanotube, a fluidized bed preparation process thereof and a conductive agent. The preparation process of the carbon nano tube fluidized bed comprises the following steps: flowing an alkaline precipitator, oxalic acid and a metal salt solution into a base solution in parallel, carrying out coprecipitation reaction, and separating to obtain a catalyst; in the volume ratio of hydrogen to inert atmosphere of 1: (20-40) carrying out reduction treatment on the catalyst under the condition to obtain a reduced catalyst; and conveying the reduction catalyst into a fluidized bed reactor, introducing mixed atmosphere containing carbon source gas, water vapor and carrier gas, introducing pulse gas at intervals, carrying out fluidized growth of the carbon nano tube, and separating to obtain the carbon nano tube. According to the method, the process for preparing the carbon nano tube by the fluidized bed is optimized, so that the carbon nano tube powder which is thin-walled, high in length-diameter ratio, large in tube diameter, low in specific surface and good in dispersing performance is obtained.
Description
Technical Field
The application belongs to the technical field of materials, and particularly relates to a carbon nano tube, a fluidized bed preparation process thereof and a conductive agent.
Background
The conductive agent is an important raw material for manufacturing the conductive paste, the carbon nano tube has excellent electrical property, the conductive paste manufactured by using the carbon nano tube conductive agent has a conductive effect obviously superior to that of the traditional carbon black, can reduce the addition of the positive and negative electrode conductive agents of the battery, has obvious advantages in the aspects of improving the energy density of the battery and prolonging the cycle service life, and is suitable for being used as an electrode material of a lithium ion battery.
The existing mass production method for preparing the carbon nano tube on a large scale is a fluidized bed preparation process. The yield of the carbon nano tube prepared by the fluidized bed process is high, but because the carbon nano tube stays in the reaction furnace for a long time, the generated carbon nano tube is mostly multi-wall carbon nano tube which is disorderly gathered together, and the carbon nano tube is difficult to disperse in the conductive slurry and has poor conductivity.
In order to improve the conductivity of the carbon nanotubes in the conductive paste and form a good conductive path, thin-walled carbon nanotubes with a high aspect ratio are required, and a low specific surface area is required to improve the dispersibility of the carbon nanotubes in the conductive paste.
Disclosure of Invention
The application aims to provide a carbon nanotube, a fluidized bed preparation process thereof and a conductive agent, and aims to solve the problems of poor dispersibility and poor conductivity of the carbon nanotube prepared by the conventional fluidized bed to a certain extent.
In order to achieve the purpose of the application, the technical scheme adopted by the application is as follows:
in a first aspect, the present application provides a process for preparing a fluidized bed of carbon nanotubes, comprising the steps of:
flowing an alkaline precipitator, oxalic acid and a metal salt solution into a base solution in parallel, carrying out coprecipitation reaction, and separating to obtain a catalyst;
under the condition that the volume ratio of hydrogen to inert atmosphere is 1: (20-40) carrying out reduction treatment on the catalyst under the condition to obtain a reduced catalyst;
and conveying the reduction catalyst into a fluidized bed reactor, introducing mixed atmosphere containing carbon source gas, water vapor and carrier gas, introducing pulse gas at intervals, carrying out fluidized growth of the carbon nano tube, and separating to obtain the carbon nano tube.
In a second aspect, the present application provides a carbon nanotube prepared by the above method.
In a third aspect, the present application provides a conductive agent, which contains the carbon nanotubes.
According to the preparation process of the carbon nanotube fluidized bed, oxalic acid is added during preparation of the catalyst, the acidity of the oxalic acid is weak, the oxalic acid can be complexed with an alkaline precipitator and metal salt, the coprecipitation reaction process is well controlled, the precipitation of the generated catalyst is accelerated, the particle size of precipitates is reduced, and the catalyst with small particle size is ensured to be prepared. The structure and the pipe diameter of the carbon nano tube which grows subsequently can be regulated and controlled, thereby improving the electrochemical performance of the carbon nano tube. In the volume ratio of hydrogen to inert atmosphere of 1: (20-40) reducing the catalyst to activate the metal in the catalyst, improving the catalytic activity, reducing the catalyst under the condition of low hydrogen content, effectively reducing the catalyst agglomeration, balancing the activity and agglomeration of the catalyst, and being beneficial to improving the growth efficiency of the thin-walled carbon nanotube. And then, conveying the reduction catalyst into a fluidized bed reactor, and introducing mixed atmosphere containing carbon source gas, water vapor and carrier gas, wherein the carbon source gas provides a carbon source for the growth of the carbon nanotubes, the water vapor can react with more active carbon at high temperature, amorphous carbon is removed or the generation efficiency of the multi-walled carbon nanotubes is inhibited, and the generation content of the single-walled or thin-walled carbon nanotubes is improved. In addition, pulse gas is introduced into the carbon nano tube at intervals in the process of fluidized growth, so that material agglomeration in the fluidized bed can be effectively avoided, the material is uniformly dispersed in the fluidized bed, the generation of multi-walled carbon nano tubes caused by agglomeration is prevented, and the purity of the thin-walled carbon nano tubes is improved. According to the method, the process for preparing the carbon nano tube by the fluidized bed is optimized, so that the carbon nano tube powder which is thin-walled, high in length-diameter ratio, large in tube diameter, low in specific surface and good in dispersing performance is obtained.
The carbon nanotube provided by the second aspect of the present application is prepared by the above method, and has a thin wall, a high aspect ratio, a large tube diameter, a low specific surface, good dispersibility, and excellent conductivity. The application prospect of the carbon nano tube in the conductive agent is improved.
In the technical field, the thin-walled carbon nanotube specifically refers to a carbon nanotube mixture with the wall number of 1-4.
The conductive agent provided by the third aspect of the application has the advantages that the conductive agent contains the carbon nano tube, the carbon nano tube is thin-walled, high in length-diameter ratio, large in tube diameter, low in specific surface area, good in dispersion performance, low in resistivity, excellent in conductivity and good in mechanical property, and the dispersion stability of the conductive agent and the conductivity of the conductive agent are ensured by using the conductive agent as the conductive agent.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a schematic flow chart of a fluidized bed preparation process of carbon nanotubes provided in the examples of the present application;
FIG. 2 is a transmission electron microscope image of a carbon nanotube provided in example 1 of the present application;
fig. 3 is a micro-topography of the carbon nanotubes provided in example 1 of the present application after being made into a conductive paste.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application more clearly apparent, the present application is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
In this application, the term "and/or" describes an association relationship of associated objects, which means that there may be three relationships, for example, a and/or B, which may mean: a is present alone, A and B are present simultaneously, and B is present alone. Wherein A and B can be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship.
In the present application, "at least one" means one or more, "a plurality" means two or more. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of the singular or plural items. For example, "at least one (one) of a, b, or c," or "at least one (one) of a, b, and c," may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, and c may be single or plural, respectively.
It should be understood that, in various embodiments of the present application, the sequence numbers of the foregoing processes do not imply an execution sequence, some or all of the steps may be executed in parallel or executed sequentially, and the execution sequence of each process should be determined by its function and inherent logic, and should not limit the implementation process of the embodiments of the present application.
The terminology used in the embodiments of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the examples of this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
The weight of the related components mentioned in the examples of the present application may not only refer to the specific content of each component, but also represent the proportional relationship of the weight among the components, and therefore, the content of the related components according to the examples of the present application is scaled up or down within the scope disclosed in the examples of the present application. Specifically, the mass in the examples of the present application may be in units of mass known in the chemical industry, such as μ g, mg, g, and kg.
The terms "first" and "second" are used for descriptive purposes only and are used for distinguishing purposes such as substances from one another, and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. For example, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX, without departing from the scope of embodiments of the present application. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.
As shown in fig. 1, a first aspect of the embodiments of the present application provides a fluidized bed preparation process of carbon nanotubes, including the following steps:
s10, enabling an alkaline precipitator, oxalic acid and a metal salt solution to flow into a base solution in a parallel mode, carrying out coprecipitation reaction, and separating to obtain a catalyst;
s20, in the volume ratio of hydrogen to inert atmosphere of 1: (20-40) carrying out reduction treatment on the catalyst under the condition to obtain a reduced catalyst;
and S30, conveying the reduction catalyst into a fluidized bed reactor, introducing mixed atmosphere containing carbon source gas, water vapor and carrier gas, introducing pulse gas at intervals, performing fluidized growth of the carbon nano tube, and separating to obtain the carbon nano tube.
According to the preparation process of the carbon nanotube fluidized bed, oxalic acid is added during preparation of the catalyst, the oxalic acid is weak in acidity, and can be complexed with an alkaline precipitator and a metal salt, so that the coprecipitation reaction process is well controlled, the precipitation of the generated catalyst is accelerated, the particle size of precipitates is reduced, and the catalyst with small particle size is ensured to be prepared. The structure and the pipe diameter of the carbon nano tube which grows subsequently can be regulated and controlled, thereby improving the electrochemical performance of the carbon nano tube. In the volume ratio of hydrogen to inert atmosphere of 1: (20-40) reducing the catalyst to activate the metal in the catalyst, improving the catalytic activity, reducing the catalyst under the condition of low hydrogen content, effectively reducing the catalyst agglomeration, balancing the activity and agglomeration of the catalyst, and being beneficial to improving the growth efficiency of the thin-walled carbon nanotube. And then, conveying the reduction catalyst into a fluidized bed reactor, and introducing mixed atmosphere containing carbon source gas, water vapor and carrier gas, wherein the carbon source gas provides a carbon source for the growth of the carbon nanotubes, the water vapor can react with more active carbon at high temperature, amorphous carbon is removed or the generation efficiency of the multi-walled carbon nanotubes is inhibited, and the generation content of the single-walled or thin-walled carbon nanotubes is improved. In addition, pulse gas is introduced into the carbon nano tube at intervals in the process of fluidized growth, so that material agglomeration in the fluidized bed can be effectively avoided, the material is uniformly dispersed in the fluidized bed, the generation of multi-walled carbon nano tubes caused by agglomeration is prevented, and the purity of the thin-walled carbon nano tubes is improved. According to the embodiment of the application, the carbon nanotube powder with thin wall, high length-diameter ratio, large pipe diameter, low specific surface and good dispersion performance is obtained by optimizing the process for preparing the carbon nanotube by the fluidized bed.
In some embodiments, in the step S10, the basic precipitant, the oxalic acid, and the metal salt solution are co-flowed into the base solution to perform the co-precipitation reaction. In some embodiments, after preparing a metal salt into a metal salt solution, under a stirring state, allowing an alkaline precipitator, oxalic acid and the metal salt solution to flow into a base solution in parallel, performing a coprecipitation reaction, filtering and separating the generated catalyst precipitate, putting the catalyst precipitate into an oven for drying overnight, wherein the drying temperature is preferably 150-200 ℃, further grinding the dried catalyst, and refining and homogenizing the particle size of the catalyst to obtain catalyst fine powder.
In some embodiments, the molar ratio of the alkaline precipitant, oxalic acid, and metal salt is (1.05 to 1.2): (1.05-1.2): 1. the oxalic acid added in the embodiment of the application can be complexed with the alkaline precipitator and the metal salt, so that the reaction process is well controlled, and the particle size of precipitated particles separated out in the coprecipitation process is reduced. The molar dosage of the alkaline precipitator and the oxalic acid is slightly higher than that of the metal salt, which is beneficial to regulating and controlling the formed particle size of the catalyst, so that the prepared catalyst has small particle size and high uniformity, and is beneficial to subsequently regulating and controlling the tube diameter and the structure of the grown carbon nano tube.
In some embodiments, the conditions of the co-precipitation reaction include: reacting for 2-3 hours at the temperature of 60-70 ℃ to ensure that the metal salt in the reaction system fully reacts with the alkaline precipitator and the oxalic acid to form metal catalyst precipitate.
In some embodiments, the alkaline precipitating agent comprises at least one of ammonium carbonate, ammonium bicarbonate, urea, aqueous ammonia; these alkaline precipitants are capable of combining with metal ions in the metal salt solution to form a metal catalyst precipitate.
In some embodiments, the metal salts include iron, cobalt, nickel, and magnesium salts; the iron salt and the cobalt salt provide main catalyst active components for the catalyst, the nickel salt provides secondary catalyst active components for the catalyst, the iron-cobalt metal catalyst can be assisted to provide catalytic activity, and the magnesium salt serves as a carrier of the catalyst to provide an attached carrier for the growth of the catalyst. Specifically, metal elements in iron salt, cobalt salt and nickel salt in the metal salt form Fe-Co-Ni alloy catalyst active particles which are attached to the surfaces of magnesium metal salt particles.
In some embodiments, the molar ratio of iron, cobalt, nickel, and magnesium salts is 1: (0.8-1.2): (0.5-0.7): (3-4). Wherein, magnesium salt mainly provides a carrier for the catalyst, so the molar content is relatively high, iron salt and cobalt salt provide main catalytic active components for the catalyst, and nickel salt provides auxiliary active components for the catalyst, so the molar ratio of the main catalytic active metal is higher than that of the auxiliary catalytic active metal. The catalyst prepared by the iron salt, the cobalt salt, the nickel salt and the magnesium salt according to the proportion has better catalytic activity, small particle size and high uniformity.
In some embodiments, the form of the metal salt includes at least one of a nitrate, a chloride, a sulfate. In some embodiments, the iron salt comprises at least one of ferric nitrate, ferric chloride, ferric sulfate; the cobalt salt comprises at least one of cobalt nitrate, cobalt chloride and cobalt sulfate; the magnesium salt comprises at least one of magnesium nitrate, magnesium chloride and magnesium sulfate.
In some embodiments, the catalyst has a particle size of 10 to 15nm; the catalyst prepared by the embodiment of the application has small particle size and high uniformity, and the particle size of the catalyst not only controls the carbon free radical directly needed by the growth of the carbon nano tube, but also more importantly directly serves as a template to control the structure of the carbon nano tube. The most intuitive embodiment of determining the carbon nanotube structure by the particle size of the catalyst is to influence the tube diameter of the obtained carbon nanotube. The catalyst with the grain diameter of 10-15 nm ensures that the grown carbon nano tube has more uniform tube diameter, and improves the purity of the carbon nano tube.
In some embodiments, the base liquid is selected from water. Specifically, flowing an alkaline precipitator, oxalic acid and a metal salt solution into base solution water in parallel, carrying out coprecipitation reaction, filtering and separating, and putting into an oven for drying overnight to obtain the catalyst.
In some embodiments, in the step S20, the step of performing a reduction treatment on the catalyst includes: at the temperature of 300-400 ℃, the volume ratio of hydrogen to inert atmosphere is 1: (20-40) reducing for 60-100 min. The catalyst is pre-reduced and activated in a high-temperature hydrogen atmosphere. The metal oxide in the catalyst is reduced into active metal by utilizing the strong reducibility of hydrogen, but the transition metal element is easy to generate the phenomenon of sintering and agglomeration by using the hydrogen reduction, so that the activity of the catalyst is reduced, the yield is reduced, and the pipe diameter consistency of the produced carbon nano tube is also poor. Therefore, the balance of catalyst activation and agglomeration is regulated and controlled by controlling the hydrogen proportion in the reaction atmosphere, and the preparation of the thin-wall carbon nanotubes with different wall numbers is facilitated. In some embodiments, the inert atmosphere comprises nitrogen, argon, helium, and the like.
In some embodiments, in step S30, the reducing catalyst is conveyed to the fluidized bed reactor by using an inert atmosphere such as nitrogen, helium, argon, and the like, a mixed atmosphere containing a carbon source gas, water vapor, and a carrier gas is introduced, and a pulse gas is introduced at intervals to perform fluidized growth of the carbon nanotubes, and the carbon nanotubes are separated.
In some embodiments, the volume ratio of the carbon source gas, the water vapor and the carrier gas in the mixed atmosphere is (1-1.4): (0.01-0.03): 1. In this case, when the carbon-containing feedstock gas is catalytically decomposed into carbon products, the trace amount of water prevents the formation of amorphous carbon or multi-walled carbon nanotubes, and increases the purity of the thin-walled carbon nanotubes. Specifically, the water vapor can react with the more active C, and can be used for removing impurities and amorphous carbon. Therefore, the outer carbon tube part of the multi-wall carbon nano tube can react with water vapor to be removed, and the multi-wall carbon nano tube can react with the single-wall carbon nano tube more easily than the single-wall carbon nano tube, so that the content of the single-wall carbon nano tube is increased to a certain extent. But the addition amount needs to be very small, otherwise the cracking growth of the carbon source into the carbon nano tube is influenced.
In some embodiments, the carbon source gas comprises at least one of propylene, ethylene, hexane, acetylene, methane, butane, carbon monoxide, benzene, ethanol. At least one carbon source gas selected from acetylene, ethylene, hexane, methane, propylene, butane, carbon monoxide, benzene and ethanol adopted in the embodiment of the application can be rapidly and stably cracked into carbon atoms under the condition that the temperature is 600-700 ℃, so that a material basis is provided for rapid, efficient and stable growth of subsequent carbon nanotubes. Propylene is preferably used as the carbon source gas, and the reaction is easy to control.
In some embodiments, the carrier gas comprises at least one of nitrogen, argon, helium; these carrier gases have good stability.
In some embodiments, the flow rate of the mixing atmosphere is 1000 to 1400L/min, which facilitates uniform and stable growth of the carbon nanotubes in the fluidized reactor.
In some embodiments, the temperature condition of the fluidized growth is 600-700 ℃ and the time is 40-60 min, under which the carbon source is promoted to crack and the carbon nanotube growth is catalyzed.
In some embodiments, the pulsed gas comprises at least one of nitrogen, argon, helium.
In some embodiments, the flow rate of the pulse gas is 50 to 100L/min. In some embodiments, the interval between pulses of gas is between 2 and 5min. In the embodiment of the application, the pulse gas is introduced at intervals in the fluidized growth process of the carbon nano tube, and the pulse gas is mainly used for scattering and agglomerating the dense part of the material, so that the material is dispersed, and the generation of the multi-wall carbon nano tube caused by agglomeration is prevented. The interval time and the flow velocity of the carbon nano tube can not hinder the fluidized growth of the carbon nano tube in the fluidized bed reactor, can effectively prevent the agglomeration phenomenon of the carbon nano tube, and improves the purity of the thin-wall carbon nano tube. In some embodiments, the pulsed gas is introduced at a fluidized material accumulation site of the fluidized bed reactor, for example, a gas distributor disposed at the material accumulation site inside the fluidized bed reactor participates in the fluidized growth process of the carbon nanotubes.
In some embodiments, after the fluidized growth is finished, the introduction of carbon source gas and water vapor is stopped, the flow velocity of inert atmosphere in the fluidized bed reactor is controlled to be 0.5-1.0m/s, the generated carbon nano tube is separated from the carrier, and the carbon nano tube is obtained after cooling.
In some embodiments, a fluidized bed carbon nanotube production process comprises the steps of:
s11, mixing the raw materials in a molar ratio of (1.05-1.2): (1.05-1.2): 1, enabling the alkaline precipitator, the oxalic acid and the metal salt solution to flow into base solution water, carrying out coprecipitation reaction for 2-3 hours at the temperature of 60-70 ℃, and separating to obtain a catalyst; wherein the metal salt comprises the following components in a molar ratio of 1: (0.8-1.2): (0.5-0.7): (3-4) iron, cobalt, nickel and magnesium salts; the alkaline precipitant comprises at least one of ammonium carbonate, ammonium bicarbonate, urea and ammonia water; the particle size of the catalyst is 10-15 nm;
s21, at the temperature of 300-400 ℃, the volume ratio of hydrogen to inert atmosphere is 1: (20-40) reducing the catalyst for 60-100 min to obtain a reduced catalyst;
s31, conveying the reduction catalyst into a fluidized bed reactor, and introducing the reduction catalyst into the fluidized bed reactor at a flow rate of 1000-1400L/min according to a volume ratio of (1-1.4): (0.01-0.03) introducing at least one pulse gas of nitrogen, argon and helium at a flow rate of 50-100L/min at an interval of 2-5 min in a mixed atmosphere of 1 carbon source gas, water vapor and carrier gas to carry out fluidized growth of the carbon nano tube, and separating to obtain the carbon nano tube; wherein the carbon source gas comprises at least one of propylene, ethylene, hexane, acetylene, methane, butane, carbon monoxide, benzene and ethanol; the carrier gas comprises at least one of nitrogen, argon, helium.
In a second aspect, the present embodiments provide a carbon nanotube, which is prepared by the above method.
The carbon nanotube provided by the second aspect of the embodiment of the present application is made by the above method, and has a thin wall, a high aspect ratio, a large tube diameter, a low specific surface, a good dispersibility, and an excellent conductivity. The application prospect of the carbon nano tube in the conductive agent is improved.
In some embodiments, the carbon nanotubes comprise a mixture of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes, wherein the mass percentage of the single-walled carbon nanotubes is 10 to 20wt%. The single-walled carbon nanotube has more excellent conductivity and mechanical properties, and the carbon nanotube in the embodiment of the application contains 10-20 wt% of the single-walled carbon nanotube, so that the conductivity and the mechanical properties of the whole carbon nanotube can be effectively improved.
In some embodiments, the carbon nanotubes have an average length of not less than 150 μm, an average tube diameter of 5 to 10nm, and an average specific surface area of 200 to 260m 2 (ii)/g, powder resistivity 10 to 15 m.OMEGA.. Cm. The carbon nano tube has the advantages of long average length, large tube diameter and low specific area, the dispersibility of the carbon nano tube is improved, and meanwhile, the carbon nano tube also has low resistivity and good conductivity.
In a third aspect of the embodiments of the present application, a conductive agent is provided, and the conductive agent includes the carbon nanotube.
The conductive agent provided by the third aspect of the embodiment of the present application includes the carbon nanotube, and the carbon nanotube has a thin wall, a high aspect ratio, a large tube diameter, a low specific surface, good dispersibility, a low resistivity, excellent conductivity, and good mechanical properties, and when the carbon nanotube is used as a conductive agent, the dispersion stability of the conductive agent is ensured, and the conductivity of the conductive agent is also ensured.
In order to make the above implementation details and operations of the present application clearly understood by those skilled in the art and to make the progress of the carbon nanotubes and the fluidized bed preparation process thereof, and the conductive agent in the examples of the present application obviously manifest, the above technical solutions are illustrated by a plurality of examples below.
Example 1
A fluidized bed preparation process of carbon nanotubes comprises the following steps:
1. preparation of the catalyst
Preparing hydrated ferric nitrate, hydrated cobalt nitrate, hydrated nickel nitrate and hydrated magnesium nitrate into a metal salt solution, wherein the molar ratio of Fe: co: ni: mg =1:1:0.6:3.5. under stirring, mixing the mixture in a molar ratio of 1.05:1.05:1, adding ammonia water, oxalic acid and a metal salt solution into the base solution water in a concurrent flow manner, and reacting for 2 hours at the temperature of 60 ℃; filtering, placing in a drying oven for drying overnight at 150 ℃, and further grinding into fine powder to obtain the catalyst with the particle size of 10-15 nanometers.
2. Catalyst reduction
Introducing a mixture with the volume ratio of 1:30 of hydrogen and nitrogen mixed gas, and reducing the catalyst for 60min at the temperature of 400 ℃ to obtain the reduced catalyst.
3. Carbon nanotube preparation
Continuously conveying the reduction catalyst into the fluidized bed reactor by using nitrogen, wherein the gas velocity ratio is 1.2: 0.02. Reacting at 660 ℃ for 40min; in the reaction process, nitrogen pulse gas is introduced at intervals of 100L/min every 5min; after the reaction is finished, the gas is changed into pure nitrogen, the gas speed in the fluidized bed is controlled to be 0.5-1.0m/s, so that the generated carbon nano tube is separated from the inert carrier particles, and the temperature is naturally reduced, so that the carbon nano tube is obtained.
Example 2
A fluidized bed preparation process of carbon nanotubes comprises the following steps:
1. preparation of the catalyst
Preparing hydrated ferric sulfate, hydrated cobalt sulfate, hydrated nickel sulfate and hydrated magnesium sulfate into a metal salt solution, wherein the molar ratio of Fe: co: ni: mg =1:1:0.5:3.0. under stirring, mixing the mixture in a molar ratio of 1.1:1.2:1, adding ammonia water, oxalic acid and a metal salt solution into the base solution water in a concurrent flow manner, and reacting for 3 hours at the temperature of 70 ℃; filtering, placing in an oven for drying overnight at the drying temperature of 200 ℃, and further grinding into fine powder to obtain the catalyst with the particle size of 10-15 nanometers.
2. Catalyst reduction
Introducing a mixture with the volume ratio of 1:35 for 60min at the temperature of 350 ℃, and obtaining the reduced catalyst.
3. Carbon nanotube preparation
Continuously conveying the reduction catalyst into the fluidized bed reactor by using nitrogen, wherein the gas velocity ratio is 1.1: 0.02. Reacting at 680 deg.C for 40min; in the reaction process, nitrogen pulse gas is introduced at intervals of 100L/min at a gas speed of 4 min; after the reaction is finished, the gas is changed into pure nitrogen, the gas speed in the fluidized bed is controlled to be 0.5-1.0m/s, so that the generated carbon nano tube is separated from the inert carrier particles, and the temperature is naturally reduced, so that the carbon nano tube is obtained.
Example 3
A fluidized bed preparation process of carbon nanotubes comprises the following steps:
1. preparation of the catalyst
Preparing hydrated ferric chloride, hydrated cobalt chloride, hydrated nickel chloride and hydrated magnesium chloride into a metal salt solution, wherein the molar ratio of Fe: co: ni: mg =1:1:0.4:3.2. under stirring, mixing the mixture in a molar ratio of 1.1:1.1:1, adding ammonia water, oxalic acid and a metal salt solution into the base solution water in a concurrent flow manner, and reacting for 3 hours at the temperature of 65 ℃; filtering, placing in an oven for drying overnight at 180 ℃, and further grinding into fine powder to obtain the catalyst with the particle size of 10-15 nanometers.
2. Catalyst reduction
Introducing a mixture with the volume ratio of 1:40 of hydrogen and nitrogen mixed gas, and reducing the catalyst for 90min at the temperature of 350 ℃ to obtain the reduced catalyst.
3. Carbon nanotube preparation
Continuously conveying the reduction catalyst into the fluidized bed reactor by using nitrogen, wherein the gas velocity ratio is 1.1: 0.02. Reacting at 680 deg.C for 40min; in the reaction process, nitrogen pulse gas is introduced at intervals of 100L/min at a gas speed of 4 min; after the reaction is finished, the gas is changed into pure nitrogen, the gas speed in the fluidized bed is controlled to be 0.5-1.0m/s, so that the generated carbon nano tube is separated from the inert carrier particles, and the temperature is naturally reduced, so that the carbon nano tube is obtained.
Comparative example 1
A fluidized bed preparation process of carbon nanotubes comprises the following steps:
1. preparation of the catalyst
Preparing hydrated ferric nitrate, hydrated cobalt nitrate, hydrated nickel nitrate and hydrated magnesium nitrate into a metal salt solution, wherein the molar ratio of Fe: co: ni: mg =1:1:0.4:3.2. under stirring, mixing the mixture in a molar ratio of 1.1:1.1:1, adding ammonia water, oxalic acid and a metal salt solution into the base solution water in a concurrent flow manner, and reacting for 3 hours at the temperature of 65 ℃; filtering, placing in an oven for drying overnight at 180 ℃, and further grinding into fine powder to obtain the catalyst with the particle size of 10-15 nanometers.
2. Catalyst reduction
Introducing a mixture with the volume ratio of 1:1, and reducing the catalyst for 30min at the temperature of 350 ℃ to obtain the reduced catalyst.
3. Carbon nanotube preparation
Continuously conveying the reduction catalyst into the fluidized bed reactor by using nitrogen, wherein the gas velocity ratio is 1.1: 0.02. Reacting at 680 deg.C for 40min; in the reaction process, nitrogen pulse gas is introduced at intervals of 100L/min at a gas speed of 4 min; after the reaction is finished, the gas is changed into pure nitrogen, the gas speed in the fluidized bed is controlled to be 0.5-1.0m/s, so that the generated carbon nano tube is separated from the inert carrier particles, and the temperature is naturally reduced, so that the carbon nano tube is obtained.
Comparative example 2
A fluidized bed preparation process of carbon nanotubes comprises the following steps:
1. preparation of the catalyst
Preparing hydrated ferric nitrate, hydrated cobalt nitrate, hydrated nickel nitrate and hydrated magnesium nitrate into a metal salt solution, wherein the molar ratio of Fe: co: ni: mg =1:1:0.6:3.5. under stirring, mixing the mixture in a molar ratio of 1.05:1.05:1, adding ammonia water, oxalic acid and a metal salt solution into the base solution water in a concurrent flow manner, and reacting for 2 hours at the temperature of 60 ℃; filtering, placing in a drying oven for drying overnight at 150 ℃, and further grinding into fine powder to obtain the catalyst with the particle size of 10-15 nanometers.
2. Catalyst reduction
Introducing a mixture with the volume ratio of 1:30 of hydrogen and nitrogen mixed gas, and reducing the catalyst for 60min at the temperature of 400 ℃ to obtain the reduced catalyst.
3. Carbon nanotube preparation
The reduced catalyst was continuously fed into the fluidized bed reactor with nitrogen at a gas velocity ratio of 1.2:1 Nitrogen and propylene were fed in at a total flow rate of 1200L/min. Reacting at 660 ℃ for 40min; in the reaction process, nitrogen pulse gas is introduced at intervals of 100L/min at a gas speed of 5min; after the reaction is finished, the gas is changed into pure nitrogen, the gas speed in the fluidized bed is controlled to be 0.5-1.0m/s, so that the generated carbon nano tube is separated from the inert carrier particles, and the temperature is naturally reduced, so that the carbon nano tube is obtained.
Comparative example 3
1. Preparation of the catalyst
Preparing hydrated ferric nitrate, hydrated cobalt nitrate, hydrated nickel nitrate and hydrated magnesium nitrate into a metal salt solution, wherein the molar ratio of Fe: co: ni: mg =1:1:0.6:3.5. under stirring, mixing the mixture in a molar ratio of 1.05:1.05:1, adding ammonia water, oxalic acid and a metal salt solution into the base solution water in a concurrent flow manner, and reacting for 2 hours at the temperature of 60 ℃; filtering, placing in a drying oven for drying overnight at 150 ℃, and further grinding into fine powder to obtain the catalyst with the particle size of 10-15 nanometers.
2. Catalyst reduction
Introducing a mixture with the volume ratio of 1:30 of hydrogen and nitrogen mixed gas, and reducing the catalyst for 60min at the temperature of 400 ℃ to obtain the reduced catalyst.
3. Carbon nanotube preparation
Continuously conveying the reduction catalyst into the fluidized bed reactor by using nitrogen, wherein the gas velocity ratio is 1.2: 0.02. Reacting at 660 ℃ for 40min; after the reaction is finished, the gas is changed into pure nitrogen, the gas speed in the fluidized bed is controlled to be 0.5-1.0m/s, so that the generated carbon nano tube is separated from the inert carrier particles, and the temperature is naturally reduced, so that the carbon nano tube is obtained.
Further, to verify the advancement of the embodiments of the present application, the following performance tests were performed:
1. the carbon nanotube powder prepared in examples 1 to 3 was subjected to structural characterization, and its length and tube diameter were characterized by an electron microscope and a scanning electron microscope, wherein the transmission electron microscope image of the carbon nanotube prepared in example 1 is shown in fig. 2.
2. Using a specific surface and aperture analyzer (model 3H-2000PS4, model Bei Shide Instrument science and technology (Beijing) Ltd.) by N 2 Characterization of the specific surface area (m) of the carbon nanotubes 2 /g)。
3. And testing the resistivity of the carbon nano tube powder by using a semiconductor powder resistivity tester.
4. The carbon nanotubes prepared in examples 1 to 3 and comparative examples 1 to 3 were prepared into a conductive paste according to a conventional method in the art, wherein the CNT was added in an amount of 0.6%; the control group adopts commercial Tiannai scientific and technical LB1G3-54NMP series conductive paste, wherein the content of the graphene is 5.00 +/-0.15%. And (3) testing the conductivity of the conductive paste, wherein the testing method comprises the following steps: and adjusting the gap of a scraper to 400 micrometers, coating the prepared carbon nanotube conductive slurry on a carbon fiber paper substrate, drying at 80 ℃, and testing the sheet resistance under the pressure of 2 MPa. The control group was tested using the same method. Wherein, the microscopic topography of the conductive paste prepared by the carbon nano tube in the embodiment 1 after being coated on the substrate and dried is shown in the attached figure 3.
The test results are shown in table 1 below:
TABLE 1
According to the test results, the carbon nano tube prepared by the fluidized bed process has better length, tube diameter and specific surface area, and the resistivity is lower. And after the carbon nano tube is prepared into conductive slurry to be coated on the substrate and dried, the formed film has lower resistivity and shows better conductive performance. However, the physical and chemical properties of the carbon nanotubes prepared according to comparative example 1, in which the hydrogen content in the catalyst reduction operation was excessively high during the preparation of the carbon nanotubes according to comparative example 1, no water vapor was added during the preparation of the carbon nanotubes according to comparative example 2, and no pulse gas was added at intervals during the preparation of the carbon nanotube catalyst according to comparative example 3, were lower than those of examples 1 to 3 of the present application.
The above description is only a preferred embodiment of the present application and should not be taken as limiting the present application, and any modifications, equivalents, improvements, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (10)
1. A preparation process of a carbon nano tube fluidized bed is characterized by comprising the following steps:
flowing an alkaline precipitator, oxalic acid and a metal salt solution into a base solution in parallel, carrying out coprecipitation reaction, and separating to obtain a catalyst;
in the volume ratio of hydrogen to inert atmosphere of 1: (20-40) carrying out reduction treatment on the catalyst under the condition to obtain a reduced catalyst;
and conveying the reduction catalyst into a fluidized bed reactor, introducing mixed atmosphere containing carbon source gas, water vapor and carrier gas, introducing pulse gas at intervals, carrying out fluidized growth of the carbon nano tube, and separating to obtain the carbon nano tube.
2. The fluidized bed preparation process of carbon nanotubes according to claim 1, wherein the molar ratio of the alkaline precipitant, the oxalic acid and the metal salt is (1.05-1.2): (1.05-1.2): 1;
and/or the alkaline precipitant comprises at least one of ammonium carbonate, ammonium bicarbonate, urea and ammonia water;
and/or the metal salt comprises iron salt, cobalt salt, nickel salt and magnesium salt;
and/or the form of the metal salt comprises at least one of nitrate, chloride and sulfate;
and/or the particle size of the catalyst is 10-15 nm;
and/or, the base fluid is selected from water.
3. The fluidized bed preparation process of carbon nanotubes according to claim 2, wherein the molar ratio of the iron salt, the cobalt salt, the nickel salt and the magnesium salt is 1: (0.8-1.2): (0.5 to 0.7): (3-4).
4. The fluidized bed preparation process of carbon nanotubes according to any one of claims 1 to 3, wherein the step of subjecting the catalyst to a reduction treatment comprises: at the temperature of 300-400 ℃, the volume ratio of hydrogen to inert atmosphere is 1: (20-40) reducing for 60-100 min;
and/or, the conditions of the coprecipitation reaction include: reacting for 2-3 hours at the temperature of 60-70 ℃.
5. The fluidized bed preparation process of carbon nanotubes according to claim 4, wherein the volume ratio of the carbon source gas, the water vapor and the carrier gas in the mixed atmosphere is (1-1.4): (0.01-0.03) 1;
and/or the carbon source gas comprises at least one of propylene, ethylene, hexane, acetylene, methane, butane, carbon monoxide, benzene and ethanol;
and/or the carrier gas comprises at least one of nitrogen, argon and helium;
and/or the flow rate of the mixed atmosphere is 1000-1400L/min.
6. The fluidized bed carbon nanotube production process of claim 5, wherein the pulse gas comprises at least one of nitrogen, argon, helium;
and/or the flow rate of the pulse gas is 50-100L/min;
and/or the interval introduction time of the pulse gas is 2-5 min;
and/or the pulse gas is introduced at the fluidized material accumulation part of the fluidized bed reactor.
7. The carbon nanotube fluidized bed preparation process according to claim 1 or 6, wherein after the fluidized growth is finished, the introduction of the carbon source gas and the steam is stopped, and the inert atmosphere flow rate in the fluidized bed reactor is controlled to be 0.5 to 1.0m/s, so that the generated carbon nanotubes are separated from the carrier to obtain the carbon nanotubes;
and/or the temperature condition of the fluidized growth is 600-700 ℃, and the time is 40-60 min.
8. A carbon nanotube produced by the method according to any one of claims 1 to 7.
9. The carbon nanotube of claim 8, wherein the carbon nanotube comprises 10 to 20wt% of single-walled carbon nanotube;
and/or the average length of the carbon nano tube is not less than 150 mu m, the average tube diameter is 5-10 nm, and the average specific surface area is 200-260 m 2 And/g, the powder resistivity is 10-15 m Ω & cm.
10. An electroconductive agent comprising the carbon nanotube according to any one of claims 8 to 9.
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