Catalyst, method for preparing few-walled carbon nanotubes by adopting catalyst and application of few-walled carbon nanotubes

Abstract

The invention provides a catalyst, a method for preparing a few-walled carbon nanotube by adopting the catalyst and application of the few-walled carbon nanotube, and the catalyst for preparing the few-walled carbon nanotube comprises the following steps: adding inorganic salt containing a metal active component, ammonium molybdate and water into a reactor, and uniformly stirring to obtain a solution A; weighing a carrier and adding the carrier into the solution A to obtain a mixture B; pouring the mixture B into a reaction kettle, stirring and heating, and completely reacting to obtain turbid liquid; roasting the turbid liquid, and grinding and sieving the roasted solid to obtain a catalyst; wherein the active component is iron and / or cobalt, and the inorganic salt is at least one of acetate and nitrate; the carrier is any one of hydrotalcite, aluminum oxide or magnesium oxide. According to the present invention, by controlling the amounts of the metal active component and the cocatalyst, the prepared catalyst can produce the few-walled carbon nanotube, and the preparation method of the catalyst is simple, and the production cost is low.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon nanotubes, and in particular relates to a catalyst, a method for preparing oligo-walled carbon nanotubes by using the catalyst, and applications of the oligo-walled carbon nanotubes. Background Art

[0002] Few-walled Carbon Nanotubes (FWNTs) are an important member of the carbon nanotube family, which is between single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). Few-walled carbon nanotubes are composed of a few layers (usually 2-5 layers) of graphene sheets coaxially wrapped. Compared with single-walled carbon nanotubes, they have more layers, but still maintain a smaller diameter and a higher aspect ratio. Due to their moderate number of layers and properties, Few-walled carbon nanotubes can be used as a bridge connecting SWCNTs and MWCNTs, and play a role in applications that require a balance between conductivity and mechanical strength. They have broad application prospects in electronic devices, composite material reinforcement, sensors and other fields. Few-walled carbon nanotubes have the characteristics of high purity, high crystallinity, good flexibility and strong stability. They have excellent performance in conductivity, aspect ratio and flexibility, and are suitable for improving the conductivity of electrodes in lithium-ion batteries, and have potential application value in smart wearable fabrics and related devices.

[0003] At present, the preparation methods of oligo-walled carbon nanotubes include chemical vapor deposition, arc discharge method, laser ablation method, etc. In the open literature, the reactor is heated, a catalyst is added, and then a carbon source and hydrogen are introduced to react, and the proportion of hydrogen in the growth atmosphere is adjusted to obtain oligo-walled carbon nanotubes with an average wall number of 3 to 6, or oligo-walled carbon nanotubes are prepared using a fluidized bed reactor device. Summary of the invention

[0004] In view of this, the present invention aims to provide a catalyst, a method for preparing oligo-walled carbon nanotubes using the catalyst, and an application of oligo-walled carbon nanotubes, which can prepare oligo-walled carbon nanotubes with an average wall number of 3 to 5.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] A catalyst for preparing oligo-walled carbon nanotubes, comprising the following steps:

[0007] (1) adding an inorganic salt containing a metal active component, ammonium molybdate and water into a reactor and stirring to obtain a solution A;

[0008] (2) Weigh the carrier and add it to solution A to obtain mixture B;

[0009] (3) Pour mixture B into a reaction kettle, stir and heat, and obtain a suspension after the reaction is complete;

[0010] (4) calcining the suspension, and grinding and sieving the calcined solid to obtain a catalyst;

[0011] The active component in step (1) is iron and / or cobalt, and the inorganic salt is at least one of acetate and nitrate; the carrier in step (2) is any one of hydrotalcite, aluminum oxide or magnesium oxide.

[0012] Furthermore, the molar ratio of iron and / or cobalt to molybdenum in the active component is 1:1 to 1:10.

[0013] Furthermore, in step (2), the mass fraction of the carrier in the mixture B is 22-56%.

[0014] Furthermore, in step (3), the heating temperature is 85-120° C., and the reaction time is 3-5 hours.

[0015] Furthermore, in step (4), the calcination temperature is 450-650° C., and the calcination time is 1-6 hours.

[0016] A method for preparing oligo-walled carbon nanotubes comprises placing a catalyst in a reactor, heating the reactor to 500-800°C under a nitrogen atmosphere, introducing hydrogen for reduction for 10 min, and then introducing propylene for reaction for 60 min. The total flow rate is 450 m 3 / h.

[0017] Furthermore, the reactor is a fixed bed, a moving bed or a fluidized bed.

[0018] A few-walled carbon nanotube is prepared by the above preparation method.

[0019] The application of the above-mentioned oligo-walled carbon nanotubes in the preparation of silicon-based positive electrode materials.

[0020] Catalyst action mechanism:

[0021] In the present invention, the content of the metal active component is low, and the content of the co-catalyst is significantly higher than the content of the metal active component. Due to the high content of the co-catalyst, the metal active component is evenly isolated by a large amount of the co-catalyst component. During the calcination process, the metal active component and the co-catalyst both generate metal oxides. As the calcination temperature increases, the metal active component oxide particles are separated by the co-catalyst particles and cannot agglomerate with the adjacent metal active component particles. The formed metal active component oxide particles are relatively small, and the grown carbon nanotubes are oligo-walled carbon nanotubes with 3 to 5 walls.

[0022] Compared with the prior art, the catalyst, the method for preparing oligo-walled carbon nanotubes using the catalyst and the application of oligo-walled carbon nanotubes described in the present invention have the following advantages:

[0023] The catalyst prepared by the present invention can generate oligo-walled carbon nanotubes by controlling the amounts of metal active components and co-catalysts, and the preparation method of the catalyst is simple and the production cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a scanning electron microscope image of the carbon nanotubes grown in Example 4;

[0025] Figure 2 This is a transmission electron microscope of the carbon nanotubes grown in Example 4;

[0026] Figure 3 This is the transmission electron microscopy of the carbon nanotubes grown in Comparative Example 1. DETAILED DESCRIPTION

[0027] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods, unless otherwise specified, are all conventional methods.

[0028] The present invention will be described in detail below with reference to the embodiments and the accompanying drawings.

[0029] Embodiment 1:

[0030] Weigh 2.0 kg of ferric nitrate nonahydrate, 1.0 kg of ammonium molybdate heptahydrate and 5 kg of pure water respectively, mix and pour into the reactor, and stir evenly at room temperature. Add 2.8 kg of hydrotalcite to the above mixture B, stir and heat to the reaction temperature of 100°C, and the reaction time is 5 hours. The solid obtained by roasting at 550°C for 3 hours is ground through a 100-mesh sieve to obtain a catalyst.

[0031] Embodiment 2:

[0032] Weigh 1.0 kg of cobalt acetate, 3.0 kg of ammonium molybdate heptahydrate and 12 kg of pure water respectively, mix and pour into the reactor, and stir evenly at room temperature. Add 6.8 kg of magnesium oxide to the above mixture B, stir and heat to the reaction temperature of 110°C, and the reaction time is 3 hours. The solid obtained by roasting at 500°C for 4 hours is ground through a 100-mesh sieve to obtain a catalyst.

[0033] Embodiment 3:

[0034] Weigh 1.5 kg of ferric nitrate nonahydrate, 0.5 kg of cobalt acetate, 5.0 kg of ammonium molybdate heptahydrate and 30 kg of pure water, mix and pour into a reactor, and stir evenly at room temperature. Add 8.0 kg of alumina to the above mixture B, stir and heat to a reaction temperature of 90°C, and the reaction time is 5 hours. The solid obtained by calcining at 650°C for 4 hours is ground through a 100-mesh sieve to obtain a catalyst.

[0035] Embodiment 4:

[0036] 1 kg of the catalyst prepared in Example 2 was placed in a moving bed reactor, with nitrogen as the carrier gas and propylene as the reaction gas. The temperature was raised to 700°C under a nitrogen atmosphere, and hydrogen was introduced for reduction for 10 min, and then propylene was introduced for reaction for 60 min, with a total flow rate of 450 m 3 / h. Figure 1 The scanning electron microscope photograph of the carbon nanotubes grown in Example 4 shows that the carbon nanotubes are in bundle shape. Figure 2 The transmission electron microscope photograph of the carbon nanotubes grown in Example 4 shows that the diameter of the carbon nanotubes is uniform and less than 10 nm, and the number of walls is 3 to 5.

[0037] Comparative Example 1:

[0038] Weigh 1.0 kg of cobalt acetate, 0.15 kg of ammonium molybdate heptahydrate and 12 kg of pure water respectively, mix and pour into the reactor, and stir evenly at room temperature. Add 6.8 kg of magnesium oxide to the above mixed solution, stir and heat to the reaction temperature of 110°C, and the reaction time is 3 hours. The solid obtained by roasting at 500°C for 4 hours is ground and sieved to obtain the catalyst.

[0039] Comparative Example 2:

[0040] Weigh 1.0 kg of cobalt acetate and 12 kg of pure water, mix and pour into the reactor, and stir evenly at room temperature. Add 6.8 kg of magnesium oxide to the mixed solution, stir and heat to the reaction temperature of 110 ° C, and the reaction time is 3 hours. The solid obtained by roasting at 500 ° C for 4 hours is ground and sieved to obtain a catalyst.

[0041] Comparative Example 3:

[0042] 1 kg of the catalyst prepared in Comparative Example 1 was placed in a moving bed reactor, with nitrogen as the carrier gas and propylene as the reaction gas. The temperature was raised to 700°C under a nitrogen atmosphere, hydrogen was introduced for reduction for 10 min, and propylene was introduced for reaction for 60 min, with a total flow rate of 450 m 3 / h. Figure 3The transmission electron microscope photograph of the carbon nanotubes grown in Comparative Example 3 is shown. Through the transmission electron microscope, it can be observed that the diameter of the carbon nanotubes is relatively large, greater than 10 nm, and the number of walls is greater than 5 layers.

[0043] The positive electrode material, carbon nanotubes and N-methylpyrrolidone (NMP) were mixed and stirred at room temperature for 4 hours. The evenly mixed positive electrode slurry was coated on a PET film and dried in a vacuum drying oven. The resistivity of the electrode was tested using a four-probe test method. The results are shown in Table 1.

[0044] Cathode Materials Carbon Nanotubes Addition amount (%) Electrode sheet resistivity (Ω·cm) Lithium Iron Phosphate Example 4 Growth of carbon nanotubes 0.2 0.4-0.5 Lithium Iron Phosphate Comparative Example 3 Growth of carbon nanotubes 1.3 0.8-1.0

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A catalyst for preparing oligo-walled carbon nanotubes, characterized in that: The following steps are included: (1) adding an inorganic salt containing a metal active component, ammonium molybdate and water into a reactor and stirring to obtain a solution A; (2) Weigh the carrier and add it to solution A to obtain mixture B; (3) Pour mixture B into a reaction kettle, stir and heat, and obtain a suspension after the reaction is complete; (4) calcining the suspension, and grinding and sieving the calcined solid to obtain a catalyst; The active component in step (1) is iron and / or cobalt, and the inorganic salt is at least one of acetate and nitrate; the carrier in step (2) is any one of hydrotalcite, aluminum oxide or magnesium oxide.

2. The catalyst for preparing oligo-walled carbon nanotubes according to claim 1, characterized in that: The molar ratio of iron and / or cobalt to molybdenum in the active component is 1:1 to 1:

10.

3. The catalyst for preparing oligo-walled carbon nanotubes according to claim 1, characterized in that: In the step (2), the mass fraction of the carrier in the mixture B is 22-56%.

4. The catalyst for preparing oligo-walled carbon nanotubes according to claim 1, characterized in that: In the step (3), the heating temperature is 85-120° C. and the reaction time is 3-5 hours.

5. The catalyst for preparing oligo-walled carbon nanotubes according to claim 1, characterized in that: In the step (4), the calcination temperature is 450-650° C. and the calcination time is 1-6 hours.

6. A method for preparing oligo-walled carbon nanotubes, characterized in that: The catalyst according to any one of claims 1 to 5 is placed in a reactor, heated to 500-800°C under a nitrogen atmosphere, introduced with hydrogen for reduction for 10 min, and then introduced with propylene for reaction for 60 min, with a total flow rate of 450 m 3 / h.

7. The method for preparing oligo-walled carbon nanotubes according to claim 6, characterized in that: The reactor is a fixed bed, a moving bed or a fluidized bed.

8. An oligo-walled carbon nanotube, characterized in that: The method is prepared according to claim 6 or 7.

9. Use of the oligo-walled carbon nanotubes according to claim 8 in the preparation of silicon-based positive electrode materials.

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