A device for preparing embedded magnetic metal carbon nanotubes and a preparation method thereof

Abstract

The present invention provides a device for preparing embedded magnetic metal carbon nanotubes, comprising a gas mixer, a preheater, a fluidized bed reaction device, a cooler and a water washing tank connected in sequence, wherein the input end of the gas mixer is connected to a raw material conveying channel; the output end of the water washing tank is connected to the outside; the fluidized bed reaction device comprises a fluidized bed reactor and a magnetic metal oxide particle layer arranged in the fluidized bed reactor, the fluidized bed reactor is provided with an air inlet at the bottom and an air outlet at the top, the air inlet is connected to the output end of the preheater, and the air outlet is connected to the cooler, and the catalyst particle layer moves in the fluidized bed reactor with the air flow from the air outlet; in addition, the present invention also provides a method for preparing embedded magnetic metal carbon nanotubes. Through the above technical scheme, many problems in the prior art of preparing embedded magnetic metal carbon nanotubes, such as high cost, complex preparation process, high energy consumption, low degree of graphitization, and environmental unfriendliness, are solved.

Description

Technical Field

[0001] The present invention relates to the field of carbon nanotubes, and in particular to a device for preparing carbon nanotubes embedded with magnetic metals and a preparation method thereof. Background Art

[0002] Carbon nanotubes (CNTs), including multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs), are ideal reinforcements for structural composite materials, and therefore possess strong mechanical properties. CNTs also possess excellent electrical properties, and by controlling their diameter and helicity, they can be used in the construction of molecular or nanodevices. Their tubular hollow cavities enable their use in nanostructured reactors. Furthermore, due to their high specific surface area, low resistivity, and good chemical stability, CNTs hold great potential for applications in catalysts, battery materials, and the biological field. Most applications rely on the functionalized surface of CNTs.

[0003] In recent years, the application of magnetic materials has focused on filling carbon nanotubes with nanoparticles or coating them with a magnetic shell. Common synthesis methods include liquid phase synthesis, chemical vapor deposition, arc discharge, and laser evaporation.

[0004] Prior art CN105499561B discloses a method for preparing magnetic carbon nanotubes by immersing carbon nanotubes in an iron salt solution and then calcining the resulting magnetic carbon nanotubes. Prior art CN110102255B discloses a method for preparing a molecular sieve-doped magnetic carbon nanotube composite material by loading magnetic iron oxide and calcium carbonate onto carbon nanotubes to obtain magnetic carbon nanotubes, which are then doped with molecular sieves. Prior art CN105056887A discloses a method for preparing a negative-Ca magnetic carbon nanotube composite material by uniformly depositing magnetic ferroferric oxide and calcium carbonate nanoparticles on the surface of carbon nanotubes to obtain magnetic carbon nanotubes. Although these methods can successfully produce magnetic carbon nanotubes, the resulting magnetic carbon nanotubes have large diameters, are complex and difficult to prepare, and are often environmentally unfriendly, energy-intensive, and uneconomical.

[0005] In summary, the existing technology has many problems in preparing embedded magnetic metal carbon nanotubes, such as high cost, complex preparation process, high energy consumption, low degree of graphitization, and environmental friendliness. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a device for preparing embedded magnetic metal carbon nanotubes, which is used to solve many problems in the prior art such as high cost, complex preparation process, high energy consumption, low degree of graphitization, and environmental friendliness in preparing embedded magnetic metal carbon nanotubes. At the same time, the present invention will also provide a method for preparing embedded magnetic metal carbon nanotubes.

[0007] To achieve the above purposes and other related purposes,

[0008] In a first aspect, the present invention provides an apparatus for preparing carbon nanotubes embedded with magnetic metals, comprising a gas mixer, a preheater, a fluidized bed reaction device, a cooler, and a water washing tank connected in sequence, wherein the input end of the gas mixer is connected to a raw material conveying channel; the output end of the water washing tank is connected to the outside world;

[0009] The fluidized bed reaction device includes a fluidized bed reactor and a magnetic metal oxide particle layer arranged in the fluidized bed reactor. The fluidized bed reactor is provided with an air inlet at the bottom and an air outlet at the top. The air inlet is connected to the output end of the preheater, and the air outlet is connected to the cooler. The catalyst particle layer moves in the fluidized bed reactor along with the air flow from the air outlet.

[0010] Through the above technical solution, methane feed gas enters the fluidized bed reactor through the feed delivery channel and the gas mixer, and undergoes a catalytic cracking reaction with the magnetic metal oxide in the fluidized bed reactor, thereby producing hydrogen and embedded magnetic metal carbon nanotubes. After the reaction is completed, the mixture of hydrogen and embedded magnetic metal carbon nanotubes first passes through a cooler and is cooled to room temperature in the cooler, thereby liquefying part of the gas, and then passes through a water washing tank for further gas cleaning, gas-solid separation, and interception of solid products.

[0011] In one embodiment of the present invention, the raw material delivery channel includes a methane delivery channel and a nitrogen delivery channel that are independent of each other.

[0012] Through the above technical solution, the methane delivery channel is used to transport methane raw gas, and the nitrogen delivery pipe is used to transport nitrogen into the fluidized bed reactor as a protector to prevent the air in the fluidized bed reactor from interfering with the catalytic cracking reaction or other safety hazards.

[0013] In one embodiment of the present invention, the inner diameter of the fluidized bed reactor is 0.5-1 cm.

[0014] In one embodiment of the present invention, the particle size of the magnetic metal oxide particle layer is 20-40 nm.

[0015] In one embodiment of the present invention, the magnetic metal oxide particle layer is iron oxide, nickel oxide, or a mixture of the two.

[0016] A second aspect of the present invention provides a method for preparing carbon nanotubes embedded with magnetic metals, comprising the following steps:

[0017] S1. Methane gas is transported as a raw material gas to a fluidized bed reactor, and a catalytic cracking reaction is carried out under the catalytic action of a magnetic metal oxide. The reaction temperature is 600° C., the pressure is normal pressure, and the reaction time is 2 to 10 hours to obtain a raw material matrix;

[0018] S2, cooling the raw material matrix after the catalytic cracking reaction in step S1 to room temperature under a nitrogen environment, placing it in dilute acid, and stirring it at room temperature for 3 to 10 hours to obtain a crude product of embedded metal carbon nanotubes;

[0019] S3. Place the crude embedded metal carbon nanotubes in mixed acid and stir for 12 to 24 hours, let it stand for 8 to 10 hours, then wash it with distilled water 2 to 3 times, and dry it at 60 to 80° C. for 4 to 6 hours to obtain embedded magnetic metal carbon nanotubes.

[0020] In one embodiment of the present invention, a pretreatment step is provided before step S1, and the pretreatment step comprises: introducing nitrogen into the reactor, wherein the volume of the introduced nitrogen is greater than or equal to the volume of air in the reactor.

[0021] In one embodiment of the present invention, the dilute acid in step S2 is any one of hydrochloric acid, nitric acid or sulfuric acid, or a combination thereof, and the concentration of the dilute acid is 0.2-0.5 mol / L.

[0022] In one embodiment of the present invention, the mixed acid in step S3 comprises a mixture of sulfuric acid and nitric acid in a volume ratio of 1:(2-3), wherein the concentration of sulfuric acid is 1-3 mol / L and the concentration of nitric acid is 2-4 mol / L.

[0023] In one embodiment of the present invention, in step S2, the raw material matrix is cooled to room temperature, washed with water, filtered, and then placed in dilute acid.

[0024] As described above, the device and method for preparing embedded magnetic metal carbon nanotubes of the present invention have the following beneficial effects:

[0025] The implementation steps of the present invention are simple and controllable, the reaction conditions are relatively mild, the solid waste resource utilization rate is high, the product quality is stable, and the particle size is uniform; the present invention effectively controls the emission of greenhouse gas carbon dioxide. In addition, in addition to producing magnetic carbon nanotube materials and high-value-added hydrogen, the present invention also realizes resource-based zero-emission technology, which is very environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1It shows a schematic structural diagram of a device for preparing embedded magnetic metal carbon nanotubes disclosed in Example 1 of the present invention.

[0027] Component number description

[0028] 1. Methane delivery channel; 2. Nitrogen delivery channel; 3. Preheater; 4. Fluidized bed reactor; 5. Magnetic metal oxide particle layer; 6. Air inlet; 7. Air outlet; 8. Cooler; 9. Water washing tank; 10. Gas mixer. DETAILED DESCRIPTION

[0029] The following describes the implementation of the present invention through specific embodiments. People skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0030] Example 1

[0031] A device for preparing embedded magnetic metal carbon nanotubes, such as Figure 1 As shown, it includes a gas mixer 10, a preheater 3, a fluidized bed reaction device, a cooler 8 and a water washing tank 9 which are connected in sequence. The input end of the gas mixer 10 is connected to the raw material conveying channel; the output end of the water washing tank 9 is connected to the outside.

[0032] The raw material delivery channel includes a methane delivery channel 1 and a nitrogen delivery channel 2 which are independent of each other; the methane delivery channel 1 is used to deliver methane raw gas, and the nitrogen delivery pipe is used to deliver nitrogen to the fluidized bed reactor 4 as a protector to prevent the air in the fluidized bed reaction device from interfering with the catalytic cracking reaction or other safety hazards.

[0033] The fluidized bed reaction device includes a fluidized bed reactor 4 and a magnetic metal oxide particle layer 5 arranged in the fluidized bed reactor 4. The fluidized bed reactor 4 is provided with an air inlet 6 at the bottom and an air outlet 7 at the top. The air inlet 6 is connected to the output end of the preheater 3, and the air outlet 7 is connected to the cooler 8. The catalyst particle layer moves in the fluidized bed reactor 4 along with the air flow from the air outlet 7.

[0034] During use, the methane raw gas enters the fluidized bed reactor 4 through the raw material delivery channel and the gas mixer 10, and undergoes a catalytic cracking reaction with the magnetic metal oxide in the fluidized bed reactor 4, thereby producing hydrogen and embedded magnetic metal carbon nanotubes. After the reaction is completed, the mixture of hydrogen and embedded magnetic metal carbon nanotubes first passes through the cooler 8 and is cooled to room temperature in the cooler 8, thereby liquefying part of the gas, and then passes through the water washing tank 9 to further clean the gas, separate the gas and solid, and retain the solid product.

[0035] Furthermore, the inner diameter of the fluidized bed reactor 4 is 0.5-1 cm.

[0036] Furthermore, the particle size of the magnetic metal oxide particle layer 5 is 20-40 nm, and the magnetic metal oxide particle layer 5 is iron oxide, nickel oxide, or a mixture of the two.

[0037] Example 2

[0038] A method for preparing embedded magnetic metal nanotubes comprises the following steps:

[0039] S1. Place 0.5 g of nickel oxide catalyst with a particle size of 20 nm in a fluidized bed reactor, and introduce nitrogen to exhaust the air in the reactor;

[0040] S2. Methane gas was introduced as a raw material into a fluidized bed reactor at a temperature of 600° C. and a flow rate of 200 mL / min under normal pressure for a catalytic cracking reaction for 6 h to obtain a raw material matrix;

[0041] S3, the raw material matrix after the catalytic cracking reaction in step S2 is cooled to room temperature under a nitrogen environment, the product and the remaining catalyst are collected, and then placed in a dilute acid (i.e., a mixed solution of hydrochloric acid, nitric acid, and sulfuric acid) and stirred at room temperature for 10 hours to obtain a crude product of embedded nickel-carbon onion; wherein the concentration of the mixed solution is 0.5 mol / L;

[0042] S4. Place the crude nickel-embedded carbon nanotubes in a mixed acid (i.e., a mixed solution of 1 mol / L sulfuric acid and 3 mol / L nitric acid), stir for 24 hours, let it stand and wash, then wash it three times with a large amount of distilled water, let it stand and wash again, then vacuum filter it, and dry it at 60°C for 6 hours, wherein the volume mixing ratio of sulfuric acid and nitric acid is 1:3.

[0043] In the above step S1, the delivery volume of the nitrogen is greater than or equal to the volume of air in the fluidized bed reactor.

[0044] In this embodiment, the reaction with the dilute acid or mixed acid in steps S3 and S4 is carried out by transferring the separated solids filtered in the water washing tank in Example 1 to an independent container for reaction.

[0045] In addition, the source of the methane raw gas used in this embodiment is the fermentation and purification of organic matter in urban solid waste and industrial solid waste.

[0046] Example 3

[0047] A method for preparing embedded magnetic metal nanotubes comprises the following steps:

[0048] S1. Place 0.5 g of an iron oxide catalyst with a particle size of 25 nm in a fluidized bed reactor, and introduce nitrogen to expel the air in the reactor;

[0049] S2. Methane gas was introduced as a raw material into a fluidized bed reactor at a flow rate of 300 mL / min at 800° C. and normal pressure for 6 h to perform a catalytic cracking reaction to obtain a raw material matrix;

[0050] S3, the raw material matrix after the catalytic cracking reaction in step S2 is cooled to room temperature under a nitrogen environment, the product and the remaining catalyst are collected, and then placed in a dilute acid (i.e., a mixed solution of hydrochloric acid, nitric acid, and sulfuric acid) and stirred at room temperature for 10 hours to obtain a crude product of embedded nickel-carbon onion; wherein the concentration of the mixed solution is 0.5 mol / L;

[0051] S4. Place the crude nickel-embedded carbon nanotubes in a mixed acid (i.e., a mixed solution of 1 mol / L sulfuric acid and 3 mol / L nitric acid), stir for 24 hours, let it stand for cleaning, then wash it three times with a large amount of distilled water, let it stand for cleaning again, and then vacuum filter it, and dry it at 80°C for 6 hours to obtain embedded magnetic metal carbon nanotubes, wherein the volume mixing ratio of sulfuric acid and nitric acid is 1:2.

[0052] In the above step S1, the delivery volume of the nitrogen is greater than or equal to the volume of air in the fluidized bed reactor.

[0053] In this embodiment, the reaction with the dilute acid or mixed acid in steps S3 and S4 is carried out by transferring the separated solids filtered in the water washing tank in Example 1 to an independent container for reaction.

[0054] In addition, the source of the methane raw gas used in this embodiment is the fermentation and purification of organic matter in urban solid waste and industrial solid waste.

[0055] Performance testing

[0056] The embedded magnetic metal nanotubes prepared in Example 2 and Example 3 were subjected to characterization tests and methane conversion rate tests. The test results are shown in Table 1.

[0057] Table 1

[0058]

[0059] As shown in Table 1, the effect of iron oxide catalyst on methane conversion rate is better than that of nickel oxide, and the embedded magnetic metal nanotubes prepared by nickel oxide have a larger specific surface area and a higher carbon tube yield.

[0060] In summary, the present invention features simple and controllable steps, relatively mild reaction conditions, high solid waste resource utilization, stable product quality, and uniform particle size. It also effectively controls greenhouse gas carbon dioxide emissions. Furthermore, in addition to producing magnetic carbon nanotube materials and high-value-added hydrogen, it also achieves zero-emission resource-based technology, making it highly environmentally friendly. Therefore, the present invention effectively overcomes the shortcomings of existing technologies and possesses high industrial value.

[0061] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for preparing carbon nanotubes embedded with magnetic metals, characterized in that: The method is based on a device for preparing embedded magnetic metal carbon nanotubes, which includes a gas mixer, a preheater, a fluidized bed reaction device, a cooler, and a water washing tank connected in sequence. The input end of the gas mixer is connected to a raw material conveying channel; the output end of the water washing tank is connected to the outside world. The raw material delivery channel includes a methane delivery channel and a nitrogen delivery channel which are independent of each other; the methane delivery channel is used to deliver methane raw gas, and the nitrogen delivery pipe is used to deliver nitrogen as a protective gas to the fluidized bed reactor; The fluidized bed reaction device includes a fluidized bed reactor and a magnetic metal oxide particle layer disposed in the fluidized bed reactor. The fluidized bed reactor is provided with an air inlet at the bottom and an air outlet at the top. The air inlet is connected to the output end of the preheater, and the air outlet is connected to the cooler. The catalyst particle layer moves in the fluidized bed reactor along with the air flow from the air outlet. The inner diameter of the fluidized bed reactor is 0.5 to 1 cm. The magnetic metal oxide particle layer is a nickel oxide catalyst. The method comprises the following steps: S1. Place 0.5 g of a nickel oxide catalyst with a particle size of 20 nm in a fluidized bed reactor and introduce nitrogen to expel the air in the reactor; wherein the nitrogen delivery volume is greater than or equal to the air volume in the fluidized bed reactor; S2. Methane gas was introduced as a raw material into a fluidized bed reactor at a temperature of 600° C. and a flow rate of 200 mL / min under normal pressure for a catalytic cracking reaction for 6 h to obtain a raw material matrix; S3. Cooling the raw material matrix after the catalytic cracking reaction in step S2 to room temperature under a nitrogen environment, collecting the product and the residual catalyst, and then placing it in dilute acid and stirring it at room temperature for 10 hours to obtain a crude product of nickel-embedded carbon nanotubes; wherein the dilute acid is a mixed solution of hydrochloric acid, nitric acid and sulfuric acid, and the concentration of the dilute acid is 0.5 mol / L; S4. Place the crude nickel-embedded carbon nanotubes in mixed acid, stir for 24 hours, let it stand and wash, then wash with distilled water three times, let it stand and wash again, vacuum filter, and dry at 60°C for 6 hours to obtain nickel-embedded carbon nanotubes; wherein the mixed acid is a mixed solution of sulfuric acid with a concentration of 1 mol / L and nitric acid with a concentration of 3 mol / L in a volume ratio of 1:

3.

2. The method according to claim 1, characterized in that The carbon nanotube yield of the nickel-embedded carbon nanotubes is 134.6 g / gcat, and the specific surface area is 126.43 m 2 / g, and magnetic property is 67emu / g.

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