Preparation method of high-purity multi-walled carbon nanotube

Abstract

The invention discloses a preparation method of a high-purity multi-walled carbon nanotube, and relates to the technical field of carbon nanomaterials. The preparation method comprises the following steps: adding a self-made catalyst into a carbon source solvent to obtain a mixed solution; adding a cocatalyst into the prepared mixed solution to obtain an organic mixed solution; a carrier gas is introduced into microwave plasma cloud equipment, then the prepared organic mixed solution is injected into the microwave plasma cloud equipment, the multi-walled carbon nanotube is prepared in the plasma cloud equipment, and the high-purity multi-walled carbon nanotube is obtained. According to the preparation method, the yield and the purity of the multi-walled carbon nanotube are further improved by self-preparing the catalyst.

Description

Technical Field

[0001] The invention relates to the technical field of carbon nanomaterials, and in particular to a method for preparing high-purity multi-walled carbon nanotubes. Background Art

[0002] The main methods for preparing multi-walled carbon nanotubes are arc discharge, laser evaporation and chemical vapor deposition (CVD). In addition to these three commonly used methods, there are also electron radiation, electrolysis and thermal polymerization.

[0003] There are many factors that affect the CVD reaction of synthesizing multi-walled carbon nanotubes, especially the choice of catalyst, which has an important influence on the conversion rate, electrochemical properties, tube diameter and distribution of multi-walled carbon nanotubes. For example, after sintering, the active components of the catalyst will agglomerate into particles, resulting in low conversion rate and uneven distribution of multi-walled carbon nanotube diameter.

[0004] Common methods for preparing multi-walled carbon nanotube catalysts include impregnation and precipitation. The catalyst carriers commonly used in the impregnation method are natural minerals such as vermiculite and montmorillonite. The catalysts obtained using these minerals have a unit catalyst yield of only about 10 times the synthesis of multi-walled carbon nanotubes, and the metal elements and silicon content are relatively high, and the subsequent acid washing and purification process is complicated; the catalyst obtained by the precipitation method, the multi-walled carbon nanotubes synthesized by vapor deposition are mostly entangled, and the unit catalyst yield of multi-walled carbon nanotubes can reach about 30 times, but the tube diameter is about 20nm. In addition, in the commonly used precipitation method, the factors that can be used to regulate the catalyst structure and performance are relatively single, and it is difficult to improve the reaction efficiency of the catalyst. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing high-purity multi-walled carbon nanotubes to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing high-purity multi-walled carbon nanotubes, the preparation steps of the high-purity multi-walled carbon nanotubes are:

[0008] (1) Adding the self-made catalyst into the carbon source solvent to obtain a mixed solution;

[0009] (2) adding a co-catalyst to the mixed solution obtained in step (1) to obtain an organic mixed solution;

[0010] (3) introducing a carrier gas into the microwave plasma cloud device, and then injecting the organic mixed solution obtained in step (2) into the microwave plasma cloud device, so that multi-walled carbon nanotubes are obtained in the plasma cloud device, that is, high-purity multi-walled carbon nanotubes are obtained.

[0011] The preparation process of the homemade catalyst in step (1) is as follows:

[0012] a. Take 3-5 parts of cobalt nitrate hexahydrate, 3-5 parts of yttrium nitrate hexahydrate and 50-80 parts of deionized water by weight, add cobalt nitrate hexahydrate and yttrium nitrate hexahydrate into deionized water, stir and dissolve for 30-40 minutes at a speed of 600-800 r / min to obtain a precursor solution;

[0013] b. Adding a magnesium oxide carrier of 5-8 times the mass of cobalt nitrate hexahydrate to the precursor solution, stirring and mixing at a rotation speed of 600-800 r / min for 30-50 min to obtain an impregnation precursor mixture;

[0014] c. Transfer the impregnation precursor mixture to a rotary evaporator, evaporate the water under a vacuum degree of 0.1-0.3MPa and a temperature of 45-55°C, dry at 80-90°C for 12-18h, and calcine the catalyst in a muffle furnace at 600-750°C for 2-3h to obtain a homemade catalyst.

[0015] In step b, the magnesium oxide carrier is prepared by pyrolyzing basic magnesium carbonate at 500-560° C. for 1-2 hours.

[0016] The carbon source solvent in step (1) is any one of methanol, ethanol, tetrahydrofuran or butyl acetate.

[0017] The co-catalyst in step (2) is any one of methyl mercaptan or thiophenol.

[0018] The mass ratio of the self-made catalyst to the co-catalyst in step (2) is 160:-300:1.

[0019] The injection speed of the organic mixed solution in step (3) is 10-20 mL / min.

[0020] The carrier gas in step (3) is a mixed carrier gas of hydrogen, methane and nitrogen.

[0021] In step (3), the hydrogen flow rate is 2-30 L / min, the methane flow rate is 5-20 L / min, and the nitrogen flow rate is 10-70 L / min.

[0022] In summary, due to the adoption of the above technology, the beneficial effects of the present invention are:

[0023] (1) The present invention utilizes a self-made catalyst, and active metal particles are fixed on a carrier. The strong metal-carrier interaction causes the multi-walled carbon nanotubes to grow according to a bottom growth mode. In this growth mechanism, methane decomposition occurs on the lower surface of the catalyst, and dissolved carbon diffuses upward. Through the coupling effect of the dispersed anchoring of the high-melting-point metal and the supporting effect of the magnesium oxide carrier, catalyst particles with uniform size distribution can be obtained, which are rich in active sites and are not prone to agglomeration after calcination, fully meeting the prerequisite for preparing multi-walled carbon nanotubes with high yield, and the multi-walled carbon nanotubes have high purity.

[0024] (2) The process of producing multi-walled carbon nanotube arrays by CVD method using the catalyst prepared by the present invention is simple and easy to operate, and has high conversion rate and uniform distribution of multi-walled carbon nanotube diameters. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0026] Example 1

[0027] A method for preparing high-purity multi-walled carbon nanotubes, the preparation steps of the high-purity multi-walled carbon nanotubes are:

[0028] (1) Adding the self-made catalyst into the carbon source solvent to obtain a mixed solution;

[0029] (2) adding a co-catalyst to the mixed solution obtained in step (1) to obtain an organic mixed solution;

[0030] (3) introducing a carrier gas into the microwave plasma cloud device, and then injecting the organic mixed solution obtained in step (2) into the microwave plasma cloud device, so that multi-walled carbon nanotubes are obtained in the plasma cloud device, that is, high-purity multi-walled carbon nanotubes are obtained.

[0031] The preparation process of the homemade catalyst in step (1) is as follows:

[0032] a. Take 5 parts of cobalt nitrate hexahydrate, 3 parts of yttrium nitrate hexahydrate and 80 parts of deionized water by weight, add cobalt nitrate hexahydrate and yttrium nitrate hexahydrate into deionized water, stir and dissolve for 30 minutes at a speed of 600 r / min to obtain a precursor solution;

[0033] b. Adding a magnesium oxide carrier having a mass 8 times that of cobalt nitrate hexahydrate to the precursor solution, stirring and mixing for 50 minutes at a rotation speed of 600 r / min to obtain an impregnation precursor mixture;

[0034] c. The impregnation precursor mixture was transferred to a rotary evaporator, and the water was evaporated under a vacuum degree of 0.1 MPa and 55°C. After drying at 90°C for 12 h, the catalyst was calcined in a muffle furnace at 750°C for 2 h to obtain a homemade catalyst.

[0035] The magnesium oxide carrier in step b is prepared by pyrolyzing basic magnesium carbonate at 560° C. for 2 h.

[0036] The carbon source solvent in step (1) is methanol.

[0037] The co-catalyst in step (2) is thiophenol.

[0038] The mass ratio of the self-made catalyst to the co-catalyst in step (2) is 300:1.

[0039] The injection rate of the organic mixed solution in step (3) is 20 mL / min in the morning.

[0040] The carrier gas in step (3) is a mixed carrier gas of hydrogen, methane and nitrogen.

[0041] In step (3), the hydrogen flow rate is 30 L / min, the methane flow rate is 5 L / min, and the nitrogen flow rate is 70 L / min.

[0042] Example 2

[0043] A method for preparing high-purity multi-walled carbon nanotubes, the preparation steps of the high-purity multi-walled carbon nanotubes are:

[0044] (1) Adding the self-made catalyst into the carbon source solvent to obtain a mixed solution;

[0045] (2) adding a co-catalyst to the mixed solution obtained in step (1) to obtain an organic mixed solution;

[0046] (3) introducing a carrier gas into the microwave plasma cloud device, and then injecting the organic mixed solution obtained in step (2) into the microwave plasma cloud device, so that multi-walled carbon nanotubes are obtained in the plasma cloud device, that is, high-purity multi-walled carbon nanotubes are obtained.

[0047] The preparation process of the homemade catalyst in step (1) is as follows:

[0048] a. Take 3 parts of cobalt nitrate hexahydrate, 5 parts of yttrium nitrate hexahydrate and 50 parts of deionized water by weight, add cobalt nitrate hexahydrate and yttrium nitrate hexahydrate into deionized water, stir and dissolve for 30 minutes at a speed of 800 r / min to obtain a precursor solution;

[0049] b. Adding a magnesium oxide carrier having a mass 8 times that of cobalt nitrate hexahydrate to the precursor solution, stirring and mixing for 50 minutes at a rotation speed of 600 r / min to obtain an impregnation precursor mixture;

[0050] c. The impregnation precursor mixture was transferred to a rotary evaporator, and the water was evaporated under a vacuum degree of 0.1 MPa and 55°C. After drying at 90°C for 12 h, the catalyst was calcined in a muffle furnace at 750°C for 2 h to obtain a homemade catalyst.

[0051] In step b, the magnesium oxide carrier is prepared by pyrolyzing basic magnesium carbonate at 560° C. for 1-2 hours.

[0052] The carbon source solvent in step (1) is methanol

[0053] The co-catalyst in step (2) is methyl mercaptan.

[0054] The mass ratio of the self-made catalyst to the co-catalyst in step (2) is 300:1.

[0055] The injection rate of the organic mixed solution in step (3) is 20 mL / min in the morning.

[0056] The carrier gas in step (3) is a mixed carrier gas of hydrogen, methane and nitrogen.

[0057] In step (3), the hydrogen flow rate is 15 L / min, the methane flow rate is 10 L / min, and the nitrogen flow rate is 30 L / min.

[0058] Example 3

[0059] A method for preparing high-purity multi-walled carbon nanotubes, the preparation steps of the high-purity multi-walled carbon nanotubes are:

[0060] (1) Adding the self-made catalyst into the carbon source solvent to obtain a mixed solution;

[0061] (2) adding a co-catalyst to the mixed solution obtained in step (1) to obtain an organic mixed solution;

[0062] (3) introducing a carrier gas into the microwave plasma cloud device, and then injecting the organic mixed solution obtained in step (2) into the microwave plasma cloud device, so that multi-walled carbon nanotubes are obtained in the plasma cloud device, that is, high-purity multi-walled carbon nanotubes are obtained.

[0063] The preparation process of the homemade catalyst in step (1) is as follows:

[0064] a. Take 5 parts of cobalt nitrate hexahydrate, 3 parts of yttrium nitrate hexahydrate and 80 parts of deionized water by weight, add cobalt nitrate hexahydrate and yttrium nitrate hexahydrate into deionized water, stir and dissolve for 40 minutes at a speed of 600 r / min to obtain a precursor solution;

[0065] b. Adding a magnesium oxide carrier having a mass 8 times that of cobalt nitrate hexahydrate to the precursor solution, stirring and mixing for 50 minutes at a rotation speed of 700 r / min to obtain an impregnation precursor mixture;

[0066] c. The impregnation precursor mixture was transferred to a rotary evaporator, and the water was evaporated under a vacuum degree of 0.1 MPa and 55°C. After drying at 80°C for 18 h, the catalyst was calcined at 600°C in a muffle furnace for 3 h to obtain a homemade catalyst.

[0067] The magnesium oxide carrier in step b is prepared by pyrolysis of basic magnesium carbonate at 500° C. for 1 h.

[0068] The carbon source solvent in step (1) is methanol

[0069] The co-catalyst in step (2) is thiophenol.

[0070] The mass ratio of the self-made catalyst to the co-catalyst in step (2) is 160:1.

[0071] The injection rate of the organic mixed solution in step (3) is 15 mL / min in the morning.

[0072] The carrier gas in step (3) is a mixed carrier gas of hydrogen, methane and nitrogen.

[0073] In step (3), the hydrogen flow rate is 30 L / min, the methane flow rate is 10 L / min, and the nitrogen flow rate is 60 L / min.

[0074] Comparative Example 1

[0075] A method for preparing high-purity multi-walled carbon nanotubes, the preparation steps of the high-purity multi-walled carbon nanotubes are:

[0076] (1) adding ferrocene to a carbon source solvent to obtain a mixed solution;

[0077] (2) adding a co-catalyst to the mixed solution obtained in step (1) to obtain an organic mixed solution;

[0078] (3) introducing a carrier gas into the microwave plasma cloud device, and then injecting the organic mixed solution obtained in step (2) into the microwave plasma cloud device, so that multi-walled carbon nanotubes are obtained in the plasma cloud device, that is, high-purity multi-walled carbon nanotubes are obtained.

[0079] The co-catalyst in step (2) is thiophenol.

[0080] The mass ratio of the self-made catalyst to the co-catalyst in step (2) is 160:1.

[0081] The injection rate of the organic mixed solution in step (3) is 15 mL / min in the morning.

[0082] The carrier gas in step (3) is a mixed carrier gas of hydrogen, methane and nitrogen.

[0083] In step (3), the hydrogen flow rate is 30 L / min, the methane flow rate is 10 L / min, and the nitrogen flow rate is 60 L / min.

[0084] Detection: Multi-walled carbon nanotube data test table

[0085]

[0086] By comparing Examples 1-3 with Comparative Example 1, it can be seen that the present invention utilizes a self-made catalyst, active metal particles are fixed on a carrier, and a strong metal-carrier interaction will cause the multi-walled carbon nanotubes to grow according to a bottom growth mode. In this growth mechanism, methane decomposition occurs on the lower surface of the catalyst, and dissolved carbon diffuses upward. Through the coupling effect of the dispersed anchoring of the high-melting-point metal and the supporting effect of the magnesium oxide carrier, catalyst particles with uniform size distribution can be obtained, and the active sites are rich and not prone to agglomeration after calcination, which fully meets the prerequisite for preparing multi-walled carbon nanotubes with high yield, and the purity of the multi-walled carbon nanotubes is relatively high. The process of producing multi-walled carbon nanotube arrays by CVD method using the catalyst prepared by the present invention is simple and easy to operate, and at the same time, the conversion rate is high and the diameter distribution of the multi-walled carbon nanotubes is uniform.

[0087] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0088] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

Claims

1. A method for preparing high-purity multi-walled carbon nanotubes, characterized in that: The preparation steps of the high-purity multi-walled carbon nanotubes are: (1) Adding the self-made catalyst into the carbon source solvent to obtain a mixed solution; (2) adding a co-catalyst to the mixed solution obtained in step (1) to obtain an organic mixed solution; (3) introducing a carrier gas into the microwave plasma cloud device, and then injecting the organic mixed solution obtained in step (2) into the microwave plasma cloud device, so that multi-walled carbon nanotubes are obtained in the plasma cloud device, that is, high-purity multi-walled carbon nanotubes are obtained.

2. The method for preparing high-purity multi-walled carbon nanotubes according to claim 1, characterized in that: The preparation process of the homemade catalyst in step (1) is as follows: a. Take 3-5 parts of cobalt nitrate hexahydrate, 3-5 parts of yttrium nitrate hexahydrate and 50-80 parts of deionized water by weight, add cobalt nitrate hexahydrate and yttrium nitrate hexahydrate into deionized water, stir and dissolve for 30-40 minutes at a speed of 600-800 r / min to obtain a precursor solution; b. Adding a magnesium oxide carrier of 5-8 times the mass of cobalt nitrate hexahydrate to the precursor solution, stirring and mixing at a rotation speed of 600-800 r / min for 30-50 min to obtain an impregnation precursor mixture; c. Transfer the impregnation precursor mixture to a rotary evaporator, evaporate the water under a vacuum degree of 0.1-0.3 MPa and 45-55°C, dry at 80-90°C for 12-18 hours, and calcine the catalyst at 600-750°C in a muffle furnace for 2-3 hours to obtain a homemade catalyst.

3. The method for preparing high-purity multi-walled carbon nanotubes according to claim 2, characterized in that: In step b, the magnesium oxide carrier is prepared by pyrolyzing basic magnesium carbonate at 500-560° C. for 1-2 hours.

4. The method for preparing high-purity multi-walled carbon nanotubes according to claim 1, characterized in that: The carbon source solvent in step (1) is any one of methanol, ethanol, tetrahydrofuran or butyl acetate.

5. The method for preparing high-purity multi-walled carbon nanotubes according to claim 1, characterized in that: The co-catalyst in step (2) is any one of methyl mercaptan or thiophenol.

6. The method for preparing high-purity multi-walled carbon nanotubes according to claim 1, characterized in that: The mass ratio of the self-made catalyst to the co-catalyst in step (2) is 160:-300:

1.

7. The method for preparing high-purity multi-walled carbon nanotubes according to claim 1, characterized in that: The injection speed of the organic mixed solution in step (3) is 10-20 mL / min.

8. The method for preparing high-purity multi-walled carbon nanotubes according to claim 1, characterized in that: The carrier gas in step (3) is a mixed carrier gas of hydrogen, methane and nitrogen.

9. The method for preparing high-purity multi-walled carbon nanotubes according to claim 8, characterized in that: In step (3), the hydrogen flow rate is 2-30 L / min, the methane flow rate is 5-20 L / min, and the nitrogen flow rate is 10-70 L / min.

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