CN114570380A - Catalyst for growing ultrahigh specific surface area and few-wall carbon nano-tube and application thereof - Google Patents

Catalyst for growing ultrahigh specific surface area and few-wall carbon nano-tube and application thereof Download PDF

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CN114570380A
CN114570380A CN202210189995.5A CN202210189995A CN114570380A CN 114570380 A CN114570380 A CN 114570380A CN 202210189995 A CN202210189995 A CN 202210189995A CN 114570380 A CN114570380 A CN 114570380A
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carbon
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CN114570380B (en
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李卫力
张新杰
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Nori Shenzhen New Technology Co ltd
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/84—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/85—Chromium, molybdenum or tungsten
    • B01J23/88—Molybdenum
    • B01J23/887—Molybdenum containing in addition other metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/8872—Alkali or alkaline earth metals
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    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61—Surface area
    • 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61—Surface area
    • B01J35/615—100-500 m2/g
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61—Surface area
    • B01J35/617—500-1000 m2/g
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    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/16—Preparation
    • C01B32/162—Preparation characterised by catalysts
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Abstract

The invention discloses a catalyst for growing a carbon nano tube with ultrahigh specific surface area and few walls and application thereof, and provides a preparation method of the catalyst for growing the carbon nano tube, which comprises the following steps: preparing an active metal precursor, a non-active metal precursor and a carrier precursor into a precursor solution; preparing a precipitant solution from a precipitant and a carboxylic acid polymer; and mixing the precursor solution and the precipitant solution to perform precipitation reaction, and collecting the precipitate to obtain the carbon nanotube growth catalyst. According to the scheme, the medium active metal precursor and the non-active metal precursor are rapidly complexed at the moment of contact with the carboxylic acid polymer and rapidly precipitated under the action of the precipitant, so that a small-size and uniform dispersion state is formed, the final catalyst has a smaller size, more uniform distribution and higher stability, and the carbon source can be catalyzed to deposit and form the low-wall carbon nanotube with a higher specific surface area.

Description

Catalyst for growing ultrahigh specific surface area and few-wall carbon nano-tube and application thereof
Technical Field
The application relates to the technical field of carbon nanotubes, in particular to a catalyst for growing ultrahigh specific surface area and few-wall carbon nanotubes and application thereof.
Background
Carbon Nanotubes (CNTs) are one-dimensional nanocarbon materials with a hollow tubular structure, consisting of carbon atoms arranged in a hexagonal lattice, having a diameter of about 1 to 100nm and a high aspect ratio. Theoretically, carbon nanotubes have superior tensile strength, excellent thermal conductivity, excellent electrical conductivity, and chemical stability. Due to its excellent physical and chemical properties, CNTs exhibit potential applications in the fields of composite materials, new energy, aerospace, biotechnology, electronics, semiconductors, and the like, and have been widely and deeply studied. Over the years of development, CNTs have achieved commercial applications in conductive plastics and battery conductive additives.
The synthesis method of the CNT mainly includes an arc discharge method, a laser evaporation method, and a chemical vapor deposition method. In contrast to the arc discharge method and the laser evaporation method, which are not suitable for mass production of CNTs due to cost and equipment limitations, the chemical vapor deposition method becomes a major process for producing large-tonnage carbon nanotubes, and the process of the chemical vapor deposition method is specifically as follows: organic small molecules (such as ethylene, propylene, ethanol and the like) are catalyzed by a transition metal catalyst under the high-temperature condition to crack and deposit solid carbon nanotubes, hydrogen and the like.
CNTs can be classified into three types according to the number of tube walls: single-walled CNTs having a diameter of about 1 nm; double-walled CNTs having a diameter of about 1.4-3 nm; and multi-walled CNTs having a diameter of about 5 to 100 nm. In the process of multi-walled CNT synthesis, the problem is that as the number of walls of the multi-walled carbon nanotubes increases, the proportion of disordered graphite also increases, resulting in a decrease in the quality of the multi-walled carbon nanotubes. For this reason, the industry has been striving to reduce the number of walls of multi-walled CNTs and increase their specific surface area. Therefore, the low-wall CNT is more and more favored by the industry, and the gap of the low-wall carbon nanotube product with high specific surface area in the market is larger. The reason is that the low-wall CNTs have higher requirements for catalysts, and the catalysts have important effects on growth and structural control of CNTs in terms of the preparation process of chemical vapor deposition, and thus, there is a need for providing a catalyst capable of growing ultra-high specific surface area low-wall carbon nanotubes.
Disclosure of Invention
The present application is directed to solving at least one of the problems in the prior art. Therefore, the application provides a catalyst for growing ultrahigh specific surface area and few-wall carbon nanotubes and application thereof.
In a first aspect of the present application, there is provided a method for preparing a carbon nanotube growth catalyst, the method comprising the steps of:
preparing an active metal precursor, a non-active metal precursor and a carrier precursor into a precursor solution;
simultaneously contacting the precursor solution with a precipitator and a carboxylic acid polymer to perform precipitation reaction, and collecting the precipitate to obtain a carbon nano tube growth catalyst;
wherein, the active metal element of the active metal precursor is selected from at least one of Fe, Co and Ni;
the inactive metal element of the inactive metal precursor is selected from at least one of Mo, V, W and Cr;
the carrier element of the carrier precursor is selected from at least one of Al and Mg.
According to the preparation method of the embodiment of the application, at least the following beneficial effects are achieved:
according to the scheme, the carboxylic acid polymer and the metal precursor for complexing are separated, and concurrent instantaneous coprecipitation is carried out while mixing, namely, the active metal precursor and the inactive metal precursor are quickly complexed at the moment of contact with the carboxylic acid polymer and quickly precipitated under the action of a precipitating agent, so that a small-size and uniform dispersion state is formed, the final catalyst has a smaller size, more uniform distribution and higher stability, and a carbon source can be catalyzed to deposit and form the carbon nanotube with less wall and higher specific surface area.
The precursor solution is contacted with the precipitant and the carboxylic acid polymer simultaneously, which means that the contact of the carboxylic acid polymer and the precipitant with the precursor system in the precursor solution does not form a specific sequence macroscopically, for example, the carboxylic acid polymer and the precipitant can be prepared into a reaction solution first and then mixed with the precursor solution; and the three can be simultaneously mixed, so that the concurrent instantaneous co-precipitation can be ensured to occur while mixing.
It can be understood that, in order to enable the active metal precursor, the inactive metal precursor and the precipitating agent to complex and precipitate more rapidly, slow dripping and vigorous stirring can be adopted during mixing so that rapid complex precipitation can be realized at the moment when the two solutions meet to form uniform small particles.
The precipitating agent in the above reaction may be any precipitating agent known in the art that is capable of causing a precipitation reaction of the metal cations in the precursor solution, such as an alkaline solution. It will be appreciated that the precipitant solution preferably does not contain any metal ions in order not to affect the composition of the catalyst formed by the precipitation reaction.
The active metal precursor, the inactive metal precursor, and the carrier precursor refer to soluble components containing an active metal element, an inactive metal element, and a carrier element, respectively, such as soluble salts, specifically including but not limited to fluorine salts, chlorine salts, nitrate salts, sulfate salts, and the like.
In some embodiments of the present application, the active metal elements of the active metal precursor include Fe and Co.
In some embodiments of the present application, the inactive metal element of the inactive metal precursor includes at least one of Mo, V, and W.
In some embodiments of the present application, the support element of the support precursor is at least one of Al and Mg, and the support component formed is Al2O3And at least one of MgO.
In some embodiments of the present application, during the mixing reaction, the mixing (dropping) speed of the precursor solution and other reaction raw materials and the concentrations of the active metal precursor, the inactive metal precursor, the precipitant and the complexing agent in the solution are controlled such that the pH of the system during the mixing reaction is about 8.
In some embodiments herein, the carboxylic acid polymer is an optional complexing agent that can be used to complex with the active metal precursor. The carboxylic acid polymer is used as a complexing agent, and the special chain structure of the carboxylic acid polymer is utilized to promote the dispersion of active metal and inactive metal in the reaction process, so that the specific surface area of the carbon nano tube catalytically grown by the catalyst is finally improved.
In some embodiments herein, the monomer of the carboxylic acid polymer is selected from at least one of acrylic acid, maleic acid, itaconic acid. When the carboxylic acid polymer containing the monomer is complexed with metal cations in the precursor, the active metal can be dispersed more uniformly by the complexation effect.
In some embodiments herein, the carboxylic acid polymer is a homopolymer, copolymer, or mixture. Mixtures include, but are not limited to, mixtures of at least two homopolymers, mixtures of at least two copolymers, mixtures of at least one homopolymer and at least one copolymer. Such as a homopolymer formed from monomers such as acrylic acid, maleic acid, itaconic acid, or the like, or a copolymer comprising at least one of the monomers, or a mixture comprising the foregoing homopolymers and/or copolymers.
In some embodiments herein, the carboxylic acid polymer is at least one of polyacrylic acid, polymaleic acid, acrylic acid maleic acid copolymer.
In some embodiments of the present application, the precipitating agent is selected from at least one of ammonium carbonate, ammonium bicarbonate, aqueous ammonia, urea.
In some embodiments of the present application, the molar ratio of active metal element to carrier element is (0.5 to 0.65): 1. too low content of active metal elements can result in poor activity of the prepared catalyst, and the growth rate of the carbon nanotubes grown by catalysis is low. If the content of the active metal element is too high, the active metal particles are large, and carbon nanotubes with large wall number and large tube diameter are grown.
In some embodiments of the present application, the molar ratio of active metal element to inactive metal element is (10-20): 1. the inactive metal in the precursor plays a role of physical barrier, prevents active metal particles from agglomerating and growing up under the high-temperature condition of catalytic or pre-catalytic roasting reduction, and hinders the growth of the ultrahigh specific surface area and few-wall carbon nanotube.
In some embodiments of the present application, the active metal elements of the active metal precursor include Fe and Co, the inactive metal elements of the inactive metal precursor include at least one of Mo, V and W, the carrier elements of the carrier precursor are at least one of Al and Mg, and the molar ratio of the active metal elements to the carrier elements is (0.5-0.65): 1, the molar ratio of active metal elements to inactive metal elements is (10-20): 1.
in some embodiments of the present application, the molar ratio of Fe to Co is 1: (1 to 100), preferably 1: (1-10), 1: (1-5).
It can be understood that the precursor, the complexing agent and the precipitating agent are subjected to a precipitation reaction, and the hydroxide is directly formed, and considering the chemical vapor deposition process for preparing the carbon nanotube, the metal hydroxide can be roasted and reduced under the high-temperature condition of the chemical vapor deposition to form a mixture or an alloy of simple substances of metal to participate in the catalytic reaction. Therefore, the step of calcination reduction may be omitted or retained during the preparation of the catalyst. If the step of roasting reduction needs to be reserved, roasting can be carried out at 400-800 ℃, and further roasting is carried out at 400-700 ℃, 500-700 ℃ and 600-700 ℃.
In some embodiments of the present application, the precipitate is collected by filtering and drying the precipitate, wherein the drying temperature is preferably 80 to 200 ℃, and further 120 to 180 ℃; the drying time is 6-24 h.
In some embodiments of the present application, the precursor solution and the precipitant solution are dropped into the reaction vessel separately and simultaneously at a constant speed, and the high-speed stirring is maintained, so that the precursor solution and the precipitant solution are mixed uniformly and rapidly, and a precipitation reaction occurs.
In some embodiments of the present application, the stirring speed of the high-speed stirring is 300rpm or more, preferably 600rpm or more, and further 1000rpm or more and 1500rpm or more.
In a second aspect of the present application, a carbon nanotube growth catalyst is provided, which is prepared by the preparation method described above.
In a third aspect of the present application, there is provided a method for preparing a carbon nanotube, the method comprising the steps of: and (2) carrying out chemical vapor deposition on a carbon source under the action of a catalyst under a protective atmosphere to obtain the carbon nano tube, wherein the catalyst is the carbon nano tube growth catalyst or the carbon nano tube growth catalyst prepared by the preparation method.
In some embodiments of the present application, the carbon source is an optional carbon source material capable of participating in the reaction in the form of a reaction gas, including but not limited to hydrocarbons in a gas phase at normal temperature, such as at least one of methane, ethane, ethylene, propane, propylene, acetylene, and the like. In some preferred embodiments, the carbon source is ethylene or propylene. It is understood that other commonly used carbon sources such as ethanol, acetone, dimethyl ether, etc. may also be used as the carbon source required in the preparation process.
In some embodiments of the present application, the reaction temperature of the chemical vapor deposition is 600 to 700 ℃, preferably 600 to 660 ℃, more preferably 610 to 650 ℃, and 620 to 640 ℃; the reaction time of the chemical vapor deposition is 10 to 30 minutes, and more preferably 15 to 20 minutes.
In some embodiments of the present application, the protective atmosphere refers to protection from air, oxygen, and the like by inert gas, nitrogen, and the like, so as to avoid affecting the growth of the carbon nanotubes.
In a fourth aspect of the present application, there is provided a carbon nanotube produced by the foregoing production method. The carbon nanotubes prepared by the method have a diameter of at least 430m2The specific surface area/g shows that the carbon nanotubes are entangled when observed under a mirror, and the carbon nanotubes have excellent properties in various aspects due to their high specific surface area. Furthermore, the specific surface area of the prepared carbon nano tube can reach 450m by adjusting the process parameters2500m above/g2550m above/g2More than g.
In a fifth aspect of the present application, there is provided a composition comprising the aforementioned carbon nanotubes. The composition is formed by using the carbon nano tube as a main raw material or an additive component, and comprises but is not limited to a polymer conductive additive, a lithium battery positive electrode conductive agent, a conductive slurry, other additives or lubricants and the like.
The application aims to provide a growth catalyst of a few-wall carbon nanotube, which comprises an active component, an inactive component and a carrier component. Make itThe catalyst can be matched with optimized process conditions to produce ultrahigh specific surface area (for example, more than 550 m) at higher rate2The winding type few-wall carbon nano tube has excellent catalytic growth effect and has larger application prospect in the preparation of the carbon nano tube.
Additional aspects and advantages of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present application.
Drawings
FIG. 1 shows the reaction conditions in example 1 of the present application under nitrogen: ethylene 2: 1, and a scanning electron micrograph of the carbon nanotube grown at 640 ℃ for 10 minutes.
Fig. 2 and 3 show the results of the present application in example 1 under nitrogen: ethylene 2: 1, grown at 640 ℃ for 10 minutes, and a transmission electron micrograph of the resulting carbon nanotubes.
Detailed Description
The conception and the resulting technical effects of the present application will be clearly and completely described in conjunction with the embodiments below, so that the objects, features and effects of the present application can be fully understood. Obviously, the described embodiments are only a part of the embodiments of the present application, and not all embodiments, and other embodiments obtained by those skilled in the art without inventive efforts based on the embodiments of the present application belong to the protection scope of the present application.
The following detailed description of embodiments of the present application is provided for the purpose of illustration only and is not intended to be construed as a limitation of the application.
In the description of the present application, the meaning of a plurality is one or more, the meaning of a plurality is two or more, and the above, below, exceeding, etc. are understood as excluding the present number, and the above, below, within, etc. are understood as including the present number. If the first and second are described for the purpose of distinguishing technical features, they are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated. About is understood to mean floating up and down within the range of + -20%, + -15%, + -10%, + -8%, + -5%, + -3%, + -2%, + -1%, + -0.5%, + -0.2%, + -0.1% of the point values.
In the description of the present application, reference to the description of the terms "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
In the following examples, the "entangled carbon nanotube" refers to a secondary aggregation form of the carbon nanotube, and can be confirmed by Scanning Electron Microscopy (SEM).
The yields of catalyst and growth process are expressed in "rate of draw".
Multiplying factor (total weight of CNT after reaction-weight of pre-reaction catalyst)/weight of pre-reaction catalyst
Example 1
The embodiment provides a carbon nanotube growth catalyst, and a preparation method thereof comprises the following steps:
taking Fe (NO)3)3·9H2O、Co(NO3)2·6H2O and Al (NO)3)3·9H2And dissolving the O in deionized water respectively to prepare a solution with the concentration of the corresponding metal element of 1.5mol/Kg for later use. To obtain (NH)4)6Mo7O24·4H2Dissolving O in deionized water to prepare a solution with the Mo element concentration of 0.15mol/Kg for later use. To obtain (NH)4)2CO3Dissolving in deionized water to prepare 3mol/Kg solution for later use.
According to the element mole ratio of Fe: co: mo: 1-Al: 1: 0.1: and 3.2, respectively measuring 25g, 25g and 80g of precursor solutions of Fe, Co, Mo and Al according to the metering ratio, and mixing to obtain the precursor solutions.
Take 190g(NH4)2CO3And adding 14g of acrylic acid-maleic acid copolymer with the mass content of 49% into the solution, and uniformly mixing to obtain a precipitant solution.
200mL of deionized water was added to a 2L three-necked flask, and the precursor solution and the precipitant solution were added dropwise simultaneously while maintaining vigorous stirring. And (3) continuing stirring for half an hour after the dropwise adding is finished, and measuring the final pH to be 8-8.5 by using a pH test paper.
Filtering to obtain a precipitate (note that after filtering, washing with a large amount of deionized water is not needed), drying in a drying oven at 150 ℃ for 12 hours, and grinding the dried product into fine powder to obtain the carbon nanotube growth catalyst with few walls.
The embodiment also provides a carbon nanotube, and the preparation method of the carbon nanotube comprises the following steps:
carbon nanotube growth experiments were performed in a horizontal fixed bed quartz reactor. And (3) uniformly placing the prepared low-wall carbon nanotube growth catalyst in a quartz boat, and then pushing the quartz boat into a constant-temperature area of the tube furnace. The temperature was raised to the reaction temperature under nitrogen atmosphere, and then ethylene was introduced as a carbon source. After reacting for a certain time, turning off ethylene, cooling to room temperature in the nitrogen atmosphere, taking out the carbon nano tube, weighing, calculating the multiplying power, and measuring the specific surface area by a BET method.
The results are shown in tables 1 and 2, which are nitrogen gas during the reaction: ethylene-1: 1. nitrogen gas: ethylene 2: test result at 1.
Table 1. nitrogen: ethylene-1: 1 carbon nanotube growth results with different experimental parameters
Figure BDA0003524199190000061
Figure BDA0003524199190000071
Table 2. nitrogen: ethylene 2: 1 carbon nanotube growth results with different experimental parameters
Experimental number Reaction temperature/. degree.C Reaction time/min Production multiplying power CNT specific surface area/(m)2/g)
1 600 10 3.5 496
2 620 10 6.5 546
3 640 10 10 565
4 660 10 18 523
As can be seen from the measurement results in tables 1 and 2, the specific surface area of the carbon nanotubes prepared in the examples of the present application is 430m2More than g, and can further reach 500m by adjusting reaction parameters2More than g. And in the presence of nitrogen: ethylene 2: 1, when the reaction temperature is about 640 ℃, the specific surface area is more than 550m2Low wall CNT per g. On the other hand, comparing the growth rates, it was found that the growth rate of CNTs gradually increased with increasing temperature.
Referring to fig. 1, which is a scanning electron microscope image of the carbon nanotubes grown at 640 ℃ for 10 minutes in table 2, it can be seen that the carbon nanotubes prepared in the examples of the present application have a significant "winding type" secondary aggregation morphology. Referring to fig. 2 and 3, which are transmission electron micrographs of carbon nanotubes grown at 640 c for 10 minutes in table 2, it can be seen that the diameter of the carbon nanotubes prepared by this method is approximately 3nm or less, which is typical of the few-walled carbon nanotubes.
Further analysis is shown below, the specific surface area of the CNTs and their number of walls has a direct relationship to the tube diameter, with fewer walls and larger specific surface. The number of walls and the diameter of the tube are influenced by factors such as the particle size of the active component particles in the growth catalyst, and generally speaking, the smaller the particle size of the active component particles, the smaller the number of walls of the obtained CNT, the smaller the tube diameter, and the larger the specific surface area of the carbon nanotube. The initial particle size of the active component particles of the growing catalyst is determined by the preparation method of the catalyst, but the particle size of the active component particles can grow gradually along with the reaction temperature at a higher reaction temperature, so that the wall number is increased, and the tube diameter is enlarged until the catalyst is inactivated. Lowering the reaction temperature can slow down the growth of catalyst particles, but the contradiction is that the lowering of the reaction temperature causes the CNT growth rate to be slow and the production efficiency to be lowered.
In the embodiment of the application, the specific surface area of more than 550m is successfully prepared by optimizing the catalyst preparation method and combining the more appropriate carbon nanotube growth conditions2Low wall CNT of/g。
Comparative example 1
The present comparative example provides a carbon nanotube growth catalyst, the preparation method of which comprises the steps of:
taking Fe (NO)3)3·9H2O、Co(NO3)2·6H2O and Al (NO)3)3·9H2O is respectively dissolved in deionized water to prepare 1.5mol/Kg solution for later use. To obtain (NH)4)6Mo7O24·4H2Dissolving O in deionized water to prepare 0.15mol/Kg solution for later use. To obtain (NH)4)2CO3Dissolving in deionized water to prepare 3mol/Kg solution for later use.
According to the element mole ratio of Fe: co: mo: 1-Al: 1: 0.1: and 3.2, respectively weighing 25g, 25g and 80g of Fe, Co, Mo and Al precursor solutions, mixing, adding 14g of acrylic acid-maleic acid copolymer with the mass content of 49%, and uniformly mixing to obtain the precursor solution.
190g of (NH) are taken4)2CO3The solution is used as a precipitant solution.
200mL of deionized water was added to a 2L three-necked flask, and the precursor solution and the precipitant solution were added dropwise simultaneously while maintaining vigorous stirring. And (3) continuing stirring for half an hour after the dropwise adding is finished, and measuring the final pH to be 8-8.5 by using a pH test paper.
And (3) filtering to obtain a precipitate, drying the precipitate in a drying oven at 150 ℃ for 12 hours, and grinding the dried product into fine powder to obtain the low-wall carbon nanotube growth catalyst.
The present comparative example also provides a carbon nanotube, which is prepared by the following method:
carbon nanotube growth experiments were performed in a horizontal fixed bed quartz reactor. The catalyst for growing the carbon nanotube with less wall prepared in the comparative example is taken and evenly placed in a quartz boat, and then the quartz boat is pushed into a constant temperature area of the tube furnace. The temperature was raised to the reaction temperature under nitrogen atmosphere, and then ethylene was introduced as a carbon source. After reacting for a certain time, turning off ethylene, cooling to room temperature in the nitrogen atmosphere, taking out the carbon nano tube, weighing, calculating the multiplying power, and measuring the specific surface area by a BET method.
The results are shown in table 3, for nitrogen during the reaction: ethylene 2: test result at 1.
TABLE 3 growth results of carbon nanotubes according to different experimental parameters of comparative example 1
Experimental number Reaction temperature/. degree.C Reaction time/min Production multiplying power CNT specific surface area/(m)2/g)
1 600 10 4.1 416
2 620 10 7 423
3 640 10 15 424
4 660 10 19 429
Comparing the results in table 3 of comparative example 1 with the results in table 2 of example 1, in the preparation process of the catalyst of comparative example 1, the acrylic maleic acid copolymer as the complexing agent is directly added into the metal precursor solution, the precursor and the complexing agent are firstly complexed in the reaction, then the precipitation is carried out by the precipitator, and the specific surface area of the finally obtained CNT is lower than 450m2In contrast, example 1 is much greater than 450m under equivalent conditions2(g) up to 565m2Is a very great improvement over comparative example 1.
Example 2
This example provides a method for preparing a carbon nanotube growth catalyst, which is different from example 1 in that aluminum nitrate is replaced with magnesium nitrate in an equimolar amount.
Example 3
This example provides a method for preparing a carbon nanotube growth catalyst, which is different from example 1 in that ammonium molybdate is replaced with equimolar ammonium tungstate.
Example 4
This example provides a method for preparing a carbon nanotube growth catalyst, which is different from example 1 in that the ratio of Fe: co: mo: the molar ratio of Al is 1: 1: 0.2: 4.
the carbon nanotube catalysts prepared in examples 2 to 4 can achieve the effect of growing ultrahigh specific surface area and few-wall carbon nanotubes similar to that of example 1, and are not repeated herein.
The present application has been described in detail with reference to the embodiments, but the present application is not limited to the embodiments described above, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present application. Furthermore, the embodiments and features of the embodiments of the present application may be combined with each other without conflict.

Claims (10)

1. The preparation method of the carbon nano tube growth catalyst is characterized by comprising the following steps:
preparing an active metal precursor, a non-active metal precursor and a carrier precursor into a precursor solution;
simultaneously contacting the precursor solution with a precipitator and a carboxylic acid polymer to generate a precipitation reaction, and collecting the precipitate to obtain the carbon nano tube growth catalyst;
wherein the active metal element of the active metal precursor is selected from at least one of Fe, Co and Ni;
the inactive metal element of the inactive metal precursor is selected from at least one of Mo, V, W and Cr;
the carrier element of the carrier precursor is selected from at least one of Al, Mg and Ti.
2. The method according to claim 1, wherein the monomer of the carboxylic acid polymer is at least one selected from acrylic acid, maleic acid, and itaconic acid.
3. The method of claim 1, wherein the carboxylic acid polymer is a homopolymer, a copolymer, or a mixture;
preferably, the carboxylic acid polymer is at least one of polyacrylic acid, polymaleic acid and acrylic acid-maleic acid copolymer.
4. The method according to any one of claims 1 to 3, wherein the precipitant is at least one selected from ammonium carbonate, ammonium bicarbonate, aqueous ammonia, and urea.
5. The production method according to any one of claims 1 to 3, characterized in that the molar ratio of the active metal element to the carrier element is (0.5 to 0.65): 1.
6. the production method according to any one of claims 1 to 3, wherein the molar ratio of the active metal element to the inactive metal element is (10 to 20): 1.
7. a carbon nanotube growth catalyst produced by the production method according to any one of claims 1 to 6.
8. The preparation method of the carbon nano tube is characterized by comprising the following steps: performing chemical vapor deposition on a carbon source under the action of a catalyst under a protective atmosphere to obtain the carbon nanotube, wherein the catalyst is the carbon nanotube growth catalyst in claim 7 or the carbon nanotube growth catalyst prepared by the preparation method in any one of claims 1 to 6;
preferably, the reaction temperature of the chemical vapor deposition is 600-700 ℃, and the reaction time is 10-30 minutes;
preferably, the reaction temperature of the chemical vapor deposition is 610-650 ℃;
preferably, the reaction temperature of the chemical vapor deposition is 620-640 ℃.
9. A carbon nanotube produced by the production method according to claim 8.
10. A composition comprising the carbon nanotubes of claim 9.
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