CN116262232A - Catalyst for synthesizing discrete distribution carbon nano tube and preparation method and application thereof - Google Patents
Catalyst for synthesizing discrete distribution carbon nano tube and preparation method and application thereof Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 107
- 239000002041 carbon nanotube Substances 0.000 title claims abstract description 105
- 229910021393 carbon nanotube Inorganic materials 0.000 title claims abstract description 105
- 239000003054 catalyst Substances 0.000 title claims abstract description 91
- 238000002360 preparation method Methods 0.000 title claims abstract description 28
- 230000002194 synthesizing effect Effects 0.000 title claims abstract description 19
- 238000009826 distribution Methods 0.000 title description 18
- 229910052751 metal Inorganic materials 0.000 claims abstract description 38
- 239000002184 metal Substances 0.000 claims abstract description 35
- 239000011148 porous material Substances 0.000 claims abstract description 19
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 48
- 229910021645 metal ion Inorganic materials 0.000 claims description 18
- 239000008139 complexing agent Substances 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 15
- 239000002245 particle Substances 0.000 claims description 13
- 239000000843 powder Substances 0.000 claims description 11
- 150000003839 salts Chemical class 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- APUPEJJSWDHEBO-UHFFFAOYSA-P ammonium molybdate Chemical compound [NH4+].[NH4+].[O-][Mo]([O-])(=O)=O APUPEJJSWDHEBO-UHFFFAOYSA-P 0.000 claims description 9
- 229940010552 ammonium molybdate Drugs 0.000 claims description 9
- 235000018660 ammonium molybdate Nutrition 0.000 claims description 9
- 239000011609 ammonium molybdate Substances 0.000 claims description 9
- 238000001816 cooling Methods 0.000 claims description 9
- 238000005187 foaming Methods 0.000 claims description 9
- 238000000227 grinding Methods 0.000 claims description 9
- 238000003756 stirring Methods 0.000 claims description 9
- WEVYAHXRMPXWCK-UHFFFAOYSA-N Acetonitrile Chemical compound CC#N WEVYAHXRMPXWCK-UHFFFAOYSA-N 0.000 claims description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 6
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 6
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 6
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 4
- 239000002904 solvent Substances 0.000 claims description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 2
- FEWJPZIEWOKRBE-JCYAYHJZSA-N Dextrotartaric acid Chemical compound OC(=O)[C@H](O)[C@@H](O)C(O)=O FEWJPZIEWOKRBE-JCYAYHJZSA-N 0.000 claims description 2
- 229910002651 NO3 Inorganic materials 0.000 claims description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 2
- FEWJPZIEWOKRBE-UHFFFAOYSA-N Tartaric acid Natural products [H+].[H+].[O-]C(=O)C(O)C(O)C([O-])=O FEWJPZIEWOKRBE-UHFFFAOYSA-N 0.000 claims description 2
- QGAVSDVURUSLQK-UHFFFAOYSA-N ammonium heptamolybdate Chemical compound N.N.N.N.N.N.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.[Mo].[Mo].[Mo].[Mo].[Mo].[Mo].[Mo] QGAVSDVURUSLQK-UHFFFAOYSA-N 0.000 claims description 2
- 229910052786 argon Inorganic materials 0.000 claims description 2
- 235000015165 citric acid Nutrition 0.000 claims description 2
- 239000001307 helium Substances 0.000 claims description 2
- 229910052734 helium Inorganic materials 0.000 claims description 2
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 2
- 229910052757 nitrogen Inorganic materials 0.000 claims description 2
- 235000006408 oxalic acid Nutrition 0.000 claims description 2
- 239000011975 tartaric acid Substances 0.000 claims description 2
- 235000002906 tartaric acid Nutrition 0.000 claims description 2
- 238000010304 firing Methods 0.000 claims 2
- 239000000463 material Substances 0.000 abstract description 3
- 238000003980 solgel method Methods 0.000 abstract description 2
- 239000007952 growth promoter Substances 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 9
- 238000005229 chemical vapour deposition Methods 0.000 description 8
- 229910002554 Fe(NO3)3·9H2O Inorganic materials 0.000 description 7
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- 238000005303 weighing Methods 0.000 description 7
- 238000000465 moulding Methods 0.000 description 5
- 230000008569 process Effects 0.000 description 5
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- 230000003197 catalytic effect Effects 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
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- 238000005516 engineering process Methods 0.000 description 3
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- 239000002923 metal particle Substances 0.000 description 3
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 241000282326 Felis catus Species 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 229910003481 amorphous carbon Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 238000010891 electric arc Methods 0.000 description 1
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- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000000386 microscopy Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- 239000010453 quartz Substances 0.000 description 1
- 239000012495 reaction gas Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
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- 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
- 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
-
- B01J35/40—
-
- 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
- C01B32/162—Preparation characterised by catalysts
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B2202/00—Structure or properties of carbon nanotubes
- C01B2202/20—Nanotubes characterized by their properties
- C01B2202/36—Diameter
Abstract
The invention discloses a catalyst for synthesizing discrete distributed carbon nanotubes, a preparation method and application thereof, and belongs to the technical field of catalysts. The catalyst consists of active component, carbon nanotube promoter and carrier, the carrier is MgO, the metal active component is Fe, co, ni, cr and other metal elements, the growth promoter of carbon nanotube is Mo, the metal active component/Mo molar ratio is 1-5, the content of active metal and promoter is 5-30 wt% of the carrier mass, the active metal and the carrier are made into gel through sol-gel process, the gel is foamed into porous material in a baking oven, the material is baked in inert atmosphere at 700-900 deg.c and then baked in air at 400-600 deg.c to obtain the catalyst for synthesizing carbon nanotube.
Description
Technical Field
The invention belongs to the technical field of catalysts, and particularly relates to a catalyst for synthesizing discrete distributed carbon nanotubes, and a preparation method and application thereof.
Background
The carbon nano tube is a super material with great potential and is an ideal core base material for constructing a future super-strong structure and a carbon-based semiconductor device. The assembly of carbon nanotubes into macroscopic bodies (such as fibers, films, foams, etc.) is one of the important ways to realize the macroscopic applications of carbon nanotubes. The carbon nanotube is a nano-sized tubular carbon material having graphite crystals found in a high-resolution transmission microscope by electron technology microscopy expert Iijima of NEC corporation of Japan in 1991. The carbon nanotubes have been found to be prepared by arc discharge, laser evaporation and Chemical Vapor Deposition (CVD), which are tens of methods for preparing carbon nanotubes, wherein the CVD method is widely used because of low reaction temperature, easily controlled parameters, and capability of preparing a large number of discrete and high-quality carbon nanotubes. The key point of the CVD method for preparing the carbon nanotubes is that the catalyst is prepared, and the preparation of the metal catalyst with controllable particle size is the key point for preparing the carbon nanotubes with discrete distribution and high quality, so that the catalyst for growing the carbon nanotubes needs to be optimally selected, and the combination of the present catalytic method and the CVD method is currently considered as the preparation method with the most industrial prospect of the carbon nanotubes.
The catalytic method for preparing the carbon nano tube has the advantages of high yield, low cost, easy control of technological parameters and the like. However, the composition, preparation conditions and activation conditions of the catalyst in the catalytic method are important factors influencing the morphology and yield of the carbon nanotubes, and one or more of the metal elements such as Fe, co, ni, cr are commonly used for growing the carbon nanotubes, so that the composition elements and preparation conditions of the grown carbon nanotubes are optimally obtained, and therefore, the catalyst preparation components and conditions are required to be researched, so that the industrialized popularization of the carbon nanotubes is promoted. Along with the development of carbon nanotube preparation technology, various methods are applied to the preparation of catalysts for growing carbon nanotubes, and as the growth of the carbon nanotubes is harsh to the physicochemical properties of the catalysts, the diameter of the prepared carbon nanotubes and the width of the distribution range of the prepared carbon nanotubes are directly related to the composition and the particle size of the metal catalysts, such as the particle size, the bulk density and the particle size distribution of the metal catalysts, and the particle uniformity has an influence on the growth of the carbon nanotubes; the catalyst prepared in the production or experimental process is low in primary yield and needs to be crushed and sieved for two or more times, so that the prepared metal catalyst is complex in process and difficult to control, and waste of the catalyst is caused, for example, a large number of large-mesh catalysts after crushing do not meet production conditions, and the problems of catalyst waste, high cost and the like exist; how to prepare the metal catalyst with uniform particle size, narrow distribution range and high mechanical strength is a difficult problem for preparing the metal catalyst, and is also a technical key for preparing the carbon nano tube with high crystallinity and uniform tube diameter by using a fluidized bed.
Disclosure of Invention
In order to solve the technical problems in the background technology, the invention provides the catalyst for synthesizing the discrete distribution carbon nano tube, which has the advantages of simple manufacturing process, good thermal stability and uniform particle size, and the preparation method and the application thereof.
In order to solve the technical problems, the invention adopts the following technical scheme:
the preparation process of catalyst for synthesizing discrete distributed carbon nanotube includes the following steps:
(1) Dissolving salt of active metal A and salt of carbon nanotube accelerator B into solvent, wherein the molar ratio of active metal A to metal ion of carbon nanotube accelerator B is (1-5) 1;
(2) Adding salt of carrier metal C, wherein the total mass of the active metal A and the carbon nano tube accelerator B is 5-30wt% of the total mass of the carrier;
(3) Adding a metal ion complexing agent D, stirring in a water bath to prepare a uniform solution until sol is formed, and finally forming gel;
(4) Placing the gel obtained in the step (3) at 50-150 ℃ for foaming and forming to prepare a porous material;
(5) Grinding the porous material obtained in the step (4) into powder, and placing the powder into an inert atmosphere at 700-1000 ℃ for roasting for 1-10h;
(6) And cooling to room temperature after roasting, and then heating to 300-600 ℃ in air to roast for 1-10h to obtain the catalyst for synthesizing the discrete distributed carbon nano tubes.
Further, the active metal A in the step (1) is one or more than two of Fe, co, ni, cr; the carbon nano tube accelerator B is Mo; the solvent is one or more of water, methanol, ethanol and acetonitrile.
Further, the salt of the active metal A in the step (1) is one or more than two of sulfate, nitrate and chloride of the active metal A; the salt of the carbon nanotube accelerator B is one or a combination of two of ammonium molybdate and ammonium heptamolybdate.
Further, in the step (2), the carrier metal C is one or a combination of more than two of Mg, al and Si.
Further, in the step (3), the metal ion complexing agent D is one or a combination of more than two of citric acid, oxalic acid and tartaric acid.
Further, the molar quantity of the metal ion complexing agent D in the step (3) is more than or equal to the total molar quantity of the active metal A, the carbon nanotube accelerator B and the carrier metal C, and the quantity of the complexing agent added is required to meet the effect of completely dispersing metal ions.
Further, in the step (5), the roasting temperature is 700-900 ℃ and the roasting time is 1-4 hours, and the inert atmosphere is one or the combination of more than two of argon, helium, nitrogen and the like.
Further, in the step (6), the roasting temperature is 400-600 ℃, the roasting time is 2-6 hours, and the roasting at different temperatures can influence the particle size of the metal active component in the catalyst and the specific surface area of the carrier.
The invention also provides a catalyst for synthesizing the discrete distribution carbon nano tube prepared by the preparation method.
Further, the particle size of the catalyst is 5-100 nm.
Further, the carrier of the catalyst is MgO and Al 2 O 3 、SiO 2 One or a combination of two or more of them.
The invention also provides application of the catalyst in preparation of the carbon nano tube.
Further, the carbon nanotubes are prepared by chemical vapor deposition.
Compared with the prior art, the invention has the following beneficial effects:
1. the metal active component, the carbon nano tube accelerator and the carrier synthesized by the sol-gel method are used as the catalyst, and can be used for synthesizing the carbon nano tubes by a Chemical Vapor Deposition (CVD) method.
2. According to the invention, the complexing agent is added into the metal salt solution as the metal ion dispersing agent, so that metal ions can be well dispersed on the carrier, the phenomenon of non-uniform active metal particles caused by agglomeration of active metals can be prevented, the problems of messy carbon nanotube samples, intertwining and difficult dispersion caused by subsequent growth of carbon nanotubes by using the catalyst are avoided, and a large amount of amorphous carbon and other impurities exist in the catalyst; meanwhile, the complexing agent can also keep uniformity of metal particles, is loaded on a carrier, can reduce surface tension, promotes more uniform distribution of metal elements, prevents the metal particles from being precipitated on the surface of the carrier, and can be easily removed without damaging surface properties on a catalyst carrier in the process of growing the carbon nano tube, and can still keep a dispersion state.
3. The preparation method of the catalyst is simple, the roasting process is simple, the process flow for preparing the carbon nano tube is simplified, the carbon nano tube with uniform tube diameter is obtained, the tube diameter of the carbon nano tube is mainly distributed at 7-9 nm, the tube diameter is long, and the yield is also obviously improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention, the drawings to which the embodiments relate will be briefly described.
Fig. 1 is an XRD pattern of the catalyst of example 4 of the present invention.
FIG. 2 shows TEM image (a) and particle size distribution (b) of the catalyst of example 4 of the present invention.
Fig. 3 is a graph (a) and a graph (c) of SEM of carbon nanotubes prepared by the catalyst of example 1 and a graph (b) and a graph (d) of SEM of carbon nanotubes prepared by the catalyst of comparative example 1.
Fig. 4 is SEM image (a) and TEM image (b, c) of the carbon nanotubes prepared by the catalyst of example 4 of the present invention.
Detailed Description
The following detailed description of the invention is provided in connection with examples, but the implementation of the invention is not limited thereto, and it is obvious that the examples described below are only some examples of the invention, and that it is within the scope of protection of the invention to those skilled in the art to obtain other similar examples without inventive faculty.
Example 1:
the preparation method of the catalyst for synthesizing the discretely distributed carbon nano tube comprises the following steps of:
step one: according to the total mass of Fe and Mo being 20wt% of the total mass of the carrier, the molar ratio of Fe/Mo being 5:1, 1.0746g of Fe (NO 3 ) 3 ·9H 2 O and 0.0939g ammonium molybdate;
step two: adding immobilized carrier metal salt Mg (NO) 3 ) 2 ·6H 2 O, mass 6.4100g;
step three: adding metal ion complexing agent citric acid, weighing the mass of the citric acid as 22.7357g, stirring in a water bath to prepare a uniform solution, forming sol, and finally forming gel;
step four: placing the gel obtained in the step three into a baking oven at 100 ℃, and foaming and forming to prepare a porous material;
step five: grinding the porous material in the fourth step into powder, and roasting for 2 hours in an inert atmosphere at 800 ℃;
step six: and cooling to room temperature after roasting, and then roasting in air at the temperature of 500 ℃ for 4 hours to obtain the catalyst for growing the carbon nanotubes in discrete distribution.
Step seven: and step six, the obtained catalyst is used for testing the yield of the grown carbon nano tube:
the catalyst is used for growing the carbon nano tube in a reaction tube with the inner diameter of 48mm, 0.5g of the catalyst is weighed and placed in a quartz boat to be evenly spread, and the catalyst is placed in Ar for 80mL min -1 Purging for 0.5h at a flow rate of 5 ℃ for 5 min after exhausting the air in the reaction tube -1 Heating to 500 ℃ with the flow rate of 80mL min -1 Reducing the catalyst by pure hydrogen for 2 hours; then heating to 800 ℃, and the reaction gas is CH 4 And H 2 Is a mixed gas (V) CH4 :V H2 =40:80), total flow rate 120mL min -1 And reacting for 2 hours to grow the carbon nano tube. Then naturally cooling to room temperature in Ar atmosphere, calculating the yield of the carbon nano tube in the reaction, wherein the yield is g.g cat -1 ·h -1 To calculate. The calculation formula is as follows:
m before for the catalyst mass before growing the carbon nano-tube, m after For the total mass of the catalyst and the carbon nanotubes after growing the carbon nanotubes, t is the reaction time for the growth of the carbon nanotubes, and the yield of the carbon nanotubes synthesized by the catalyst prepared in example 1 is shown in table 1.
Example 2:
the preparation method of the catalyst for synthesizing the discretely distributed carbon nano tube comprises the following steps of:
step one: according to the total mass of Fe and Mo, 20 of the total mass of the carrierwt%, fe/Mo molar ratio 3:1, dissolving 0.9187g Fe (NO 3 ) 3 ·9H 2 O and 0.1338g ammonium molybdate;
step two: the same as in example 1;
step three: adding metal ion complexing agent citric acid, weighing the mass of the citric acid as 22.3876g, stirring in a water bath to prepare a uniform solution, forming sol, and finally forming gel;
step four: placing the gel obtained in the step three into a baking oven at 100 ℃, and foaming and forming to prepare a porous material;
step five: grinding the porous material in the fourth step into powder, and roasting for 2 hours in an inert atmosphere at 800 ℃;
step six: and cooling to room temperature after roasting, and then roasting in air at the temperature of 500 ℃ for 4 hours to obtain the catalyst for growing the carbon nanotubes in discrete distribution.
Step seven: catalyst used for growing carbon nanotubes yield test the same as in example 1, the yield of the catalyst grown carbon nanotubes is shown in table 1.
Example 3:
the preparation method of the catalyst for synthesizing the discretely distributed carbon nano tube comprises the following steps of:
step one: according to the total mass of Fe and Mo being 20wt% of the total mass of the carrier, the molar ratio of Fe/Mo being 1:1, 0.5333g of Fe (NO 3 ) 3 ·9H 2 O and 0.2330g ammonium molybdate;
step two: the same as in example 1;
step three: adding metal ion complexing agent citric acid, weighing the mass of the citric acid as 21.5290g, stirring in a water bath to prepare a uniform solution, forming sol, and finally forming gel;
step four: placing the gel obtained in the step three into a baking oven at 100 ℃, and foaming and molding to prepare a porous material;
step five: grinding the porous material into powder, and roasting in an inert atmosphere at 800 ℃ for 2 hours;
step six: and cooling to room temperature after roasting, and then roasting in air at the temperature of 500 ℃ for 4 hours to obtain the catalyst for growing the carbon nanotubes in discrete distribution.
Step seven: catalyst used for growing carbon nanotubes yield test the same as in example 1, the yield of the catalyst grown carbon nanotubes is shown in table 1.
Example 4:
the preparation method of the catalyst for synthesizing the discretely distributed carbon nano tube comprises the following steps of:
step one: according to the total mass of Fe and Mo being 5wt% of the total mass of the carrier, the molar ratio of Fe/Mo being 5:1, 0.2687g of Fe (NO 3 ) 3 ·9H 2 O with 0.0235g of ammonium molybdate;
step two: the same as in example 1;
step three: adding metal ion complexing agent citric acid, weighing the mass of the citric acid as 20.1065g, stirring in a water bath to prepare a uniform solution, forming sol, and finally forming gel;
step four: placing the gel obtained in the step three into a baking oven at 100 ℃, and foaming and molding to prepare a porous material;
step five: grinding the porous material in the fourth step into powder, and roasting for 2 hours in an inert atmosphere at 800 ℃;
step six: and cooling to room temperature after roasting, and then roasting in air at the temperature of 500 ℃ for 4 hours to obtain the catalyst for growing the carbon nanotubes in discrete distribution.
Step seven: catalyst used for growing carbon nanotubes yield test the same as in example 1, the yield of the catalyst grown carbon nanotubes is shown in table 1.
The catalyst prepared in example 4 was a fe—mo/MgO catalyst (as shown in fig. 1), and the TEM image and the particle size distribution of the catalyst were as shown in fig. 2, so that it can be seen that the particle size distribution of the obtained catalyst was relatively uniform, and it was used for growth of carbon nanotubes at 800 ℃, and the SEM image and the TEM image of the obtained carbon nanotubes were as shown in fig. 4, so that it can be seen that the high-quality discrete-distribution carbon nanotubes were obtained.
Example 5:
the preparation method of the catalyst for synthesizing the discretely distributed carbon nano tube comprises the following steps of:
step one: according to the total mass of Fe and Mo being 10wt% of the total mass of the carrier, the molar ratio of Fe/Mo being 5:1, 0.5373g of Fe (NO 3 ) 3 ·9H 2 O with 0.047g of ammonium molybdate;
step two: the same as in example 1;
step three: adding metal ion complexing agent citric acid, weighing the mass of the citric acid as 20.9829g, stirring in a water bath to prepare a uniform solution, forming sol, and finally forming gel;
step four: placing the gel obtained in the step three into a baking oven at 100 ℃, and foaming and molding to prepare a porous material;
step five: grinding the porous material into powder, and roasting in an inert atmosphere at 800 ℃ for 2 hours;
step six: and cooling to room temperature after roasting, and then roasting in air at the temperature of 500 ℃ for 4 hours to obtain the catalyst for growing the carbon nanotubes in discrete distribution.
Step seven: catalyst used for growing carbon nanotubes yield test the same as in example 1, the yield of the catalyst grown carbon nanotubes is shown in table 1.
Example 6:
the preparation method of the catalyst for synthesizing the discretely distributed carbon nano tube comprises the following steps of:
step one: according to the total mass of Fe and Mo being 30wt% of the total mass of the carrier, the molar ratio of Fe/Mo being 5:1, 1.6119g of Fe (NO 3 ) 3 ·9H 2 O and 0.1409g ammonium molybdate;
step two: the same as in example 1;
step three: adding metal ion complexing agent citric acid, weighing the mass of the citric acid as 24.4886g, stirring in a water bath to prepare a uniform solution, forming sol, and finally forming gel;
step four: placing the gel obtained in the step three into a baking oven at 100 ℃, and foaming and molding to prepare a porous material;
step five: grinding the porous material into powder, and roasting in an inert atmosphere at 800 ℃ for 2 hours;
step six: and cooling to room temperature after roasting, and then roasting in air at the temperature of 500 ℃ for 4 hours to obtain the catalyst for growing the carbon nanotubes in discrete distribution.
Step seven: catalyst used for growing carbon nanotubes yield test the same as in example 1, the yield of the catalyst grown carbon nanotubes is shown in table 1.
Comparative example 1:
the preparation method of the catalyst for synthesizing the carbon nano tube comprises the following steps of:
step one: according to the total mass of Fe and Mo being 20wt% of the total mass of the carrier, the molar ratio of Fe/Mo being 5:1, 1.0746g of Fe (NO 3 ) 3 ·9H 2 O and 0.0939g ammonium molybdate;
step two: the same as in example 1;
step three: adding metal ion complexing agent citric acid, weighing the mass of the citric acid as 22.7357g, stirring in a water bath to prepare a uniform solution, forming sol, and finally forming gel;
step four: placing the gel obtained in the step three into a baking oven at 100 ℃, and foaming and molding to prepare a porous material;
step five: and step four, grinding the porous material into powder, and placing the powder into an air atmosphere at 500 ℃ for roasting for 4 hours to obtain the catalyst for growing the carbon nano tubes.
Step six: catalyst used for growing carbon nanotubes yield test the same as in example 1, the yield of the catalyst grown carbon nanotubes is shown in table 1.
Table 1: comparison of the yields of carbon nanotubes synthesized by the catalysts of examples 1 to 6 and comparative example 1
As can be seen from Table 1, the catalyst calcined by the inert gas has higher carbon nanotube growth activity, and the catalysts of examples 1 to 6 all show better carbon nanotube growth activity, wherein the catalyst of example 6 has the highest yield of carbon nanotubes grown, 0.5g of the catalyst is reacted for 2 hours at 800 ℃ by introducing methane gas with a content of 33.33%, and the yield of carbon nanotubes is 4.68 g.g cat -1 ·h -1 。
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
Claims (10)
1. The preparation method of the catalyst for synthesizing the discrete distributed carbon nano tubes is characterized by mainly comprising the following steps:
(1) Dissolving salt of active metal A and salt of carbon nanotube accelerator B into solvent, wherein the molar ratio of active metal A to metal ion of carbon nanotube accelerator B is (1-5) 1;
(2) Adding salt of carrier metal C, wherein the total mass of the active metal A and the carbon nano tube accelerator B is 5-30wt% of the total mass of the carrier;
(3) Adding a metal ion complexing agent D, stirring in a water bath to prepare a uniform solution until sol is formed, and finally forming gel;
(4) Placing the gel obtained in the step (3) at 50-150 ℃ for foaming and forming to prepare a porous material;
(5) Grinding the porous material obtained in the step (4) into powder, and roasting for 1-10h in an inert atmosphere at 700-1000 ℃;
(6) And cooling to room temperature after roasting, and then heating to 300-600 ℃ in air to roast for 1-10h to obtain the catalyst for synthesizing the discrete distributed carbon nano tubes.
2. The method according to claim 1, wherein the active metal a in step (1) is one or a combination of two or more of Fe, co, ni, cr; the carbon nano tube accelerator B is Mo; the solvent is one or more of water, methanol, ethanol and acetonitrile.
3. The preparation method according to claim 1, wherein the salt of the active metal a in the step (1) is one or a combination of two or more of sulfate, nitrate and chloride of the active metal a; the salt of the carbon nanotube accelerator B is one or a combination of two of ammonium molybdate and ammonium heptamolybdate.
4. The method according to claim 1, wherein the carrier metal C in the step (2) is one or a combination of two or more of Mg, al, si.
5. The preparation method according to claim 1, wherein the metal ion complexing agent D in the step (3) is one or a combination of more than two of citric acid, oxalic acid and tartaric acid; the molar quantity of the metal ion complexing agent D is more than or equal to the total molar quantity of the active metal A, the carbon nano tube accelerator B and the carrier metal C.
6. The method according to claim 1, wherein the baking temperature in the step (5) is 700-900 ℃ and the baking time is 1-4 hours, and the inert atmosphere is one or a combination of more than two of argon, helium and nitrogen.
7. The method according to claim 1, wherein the firing temperature in step (6) is 400 to 600 ℃ and the firing time is 2 to 6 hours.
8. A catalyst prepared by the preparation method of any one of claims 1 to 7.
9. The catalyst of claim 8, wherein the catalyst has a particle size of 5 to 100nm.
10. Use of the catalyst of claim 8 or 9 in the preparation of carbon nanotubes.
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