Catalyst and Preparation Method Thereof, Carbon Nanotube and Preparation Method Thereof

Abstract

The present invention discloses a catalyst, which is used for synthesizing carbon nanotubes. The catalyst includes: a main body, the main body includes a plurality of catalytic metal particles; a carrier, the carrier includes a plurality of carrier particles, wherein the carrier particles have a porous structure, the specific surface area of the carrier particles is larger than the specific surface area of the catalytic metal particles, the catalytic metal particles are loaded by the carrier particles, the material of the carrier particles includes blast furnace slag; a modifier, the modifier includes a plurality of metal oxide particles. The present invention also discloses a preparation method of the catalyst, carbon nanotubes and a preparation method thereof.

Description

Technical Field

[0001] The present invention relates to the field of carbon nanotubes, and specifically, to a catalyst and its preparation method, and a carbon nanotube and its preparation method. Background Art

[0002] In the prior art, supported catalysts are mainly used for the synthesis of carbon nanotubes. The catalyst consists of an active metal, a promoter, and a support. The choice of the support material is the main source of the preparation cost. However, currently, the support raw materials usually select oxides such as Al2O3, MgO, SiO2, and CaO and their salt compounds. Although the above choices show good stability, the raw material cost is relatively high. In addition, the single nature of these support materials limits their application potential in catalytic cracking reactions. To achieve the best catalytic effect, it is often necessary to mix multiple salts through complex ratios and adjustments to find the optimal combination, which undoubtedly increases the complexity and cost of the preparation.

[0003] Therefore, finding a support material with low cost and excellent performance plays a decisive role in reducing the overall cost of the catalyst. And how to economically and efficiently adjust the catalyst formula to significantly improve the yield and performance while reducing the cost has become an urgent problem to be solved. Summary of the Invention

[0004] The present invention aims to solve one of the technical problems in the related art to a certain extent. For this purpose, the present invention provides a catalyst and its preparation method, and a carbon nanotube and its preparation method.

[0005] To achieve the above object, as the first aspect of the present invention, a catalyst is disclosed. The catalyst is used for synthesizing carbon nanotubes, and the catalyst includes:

[0006] A main body, the main body includes a plurality of catalytic metal particles;

[0007] A support, the support includes a plurality of support particles. Among them, the specific surface area of the support particles is greater than the specific surface area of the catalytic metal particles. The catalytic metal particles are supported by the support particles, and the material of the support particles includes blast furnace slag;

[0008] A modifier, the modifier includes a plurality of metal oxide particles, and the modifier is used to modify the support particles.

[0009] Further, inside and / or on the surface of the support particles, a plurality of the metal oxide particles are distributed, and the plurality of metal oxide particles are combined with the support particles.

[0010] Further, the modifier includes basic metal oxides.

[0011] Further, the modifier includes at least one of magnesium oxide, zinc oxide, zirconium oxide, and titanium oxide.

[0012] Further, in the catalyst, the modifier accounts for 0.5% to 15% of the weight of the carrier.

[0013] Further, in the catalyst, the mass of the metal element in the main body is 10% to 30% of the weight of the carrier.

[0014] Further, the metal element of the catalytic metal particles includes at least one of iron, cobalt, and nickel.

[0015] As the second aspect of the present invention, a method for preparing a catalyst is provided. The preparation method includes:

[0016] Providing initial blast furnace slag;

[0017] Enriching catalytic metal and modified metal in the initial blast furnace slag to obtain an initial catalyst;

[0018] Calcining the initial catalyst to prepare the above-mentioned catalyst, which is used for synthesizing carbon nanotubes.

[0019] Further, enriching catalytic metal and modified metal in the initial blast furnace slag to obtain an initial catalyst includes:

[0020] Mixing a first metal salt, a second metal salt, and water to form a mixed solution, wherein the metal in the first metal salt corresponds to the catalytic metal, and the metal in the second metal salt corresponds to the modified metal;

[0021] Using an impregnation method or a coprecipitation method to mix the mixed solution with the initial blast furnace slag to obtain a first mixed solution;

[0022] Performing a drying and pulverizing treatment on the first mixed solution to obtain the initial catalyst.

[0023] Further, in the step of calcining the initial catalyst, the calcination temperature is between 300°C and 700°C, and the calcination time is between 0.5 hour and 3 hours.

[0024] Further, providing initial blast furnace slag includes:

[0025] Pulverizing the blast furnace slag to obtain a first blast furnace slag;

[0026] Performing an acid modification treatment on the first blast furnace slag with an acidic solution, wherein the acidic solution corrodes the first blast furnace slag to form a surface microporous structure to obtain the initial blast furnace slag.

[0027] As a third aspect of the present invention, a method for preparing carbon nanotubes is disclosed. The preparation method includes heating a catalyst to a temperature between 680°C and 800°C, introducing a carbon source gas for reaction to obtain initial carbon nanotubes, and the catalyst is the above-mentioned catalyst;

[0028] Cooling the initial carbon nanotubes to room temperature to obtain the carbon nanotubes.

[0029] As a fourth aspect of the present invention, a carbon nanotube is disclosed, and the carbon nanotube is obtained by using the above-mentioned preparation method.

[0030] In view of the unique by-product of blast furnace slag in China, its large accumulation not only becomes an environmental burden but also causes great waste of resources. Given that blast furnace slag is rich in key components such as CaO, SiO 2 、Al 2 O 3 、MgO, etc., it can be regarded as a multi-component composite carrier. Its stable chemical composition and appropriate component ratio make it an ideal choice for a catalyst carrier. By applying blast furnace slag to the field of carbon nanotube preparation, not only the raw material cost of the catalyst is significantly reduced, but also the resource utilization of blast furnace slag is realized, which strongly promotes the development of the resource recycling economy.

[0031] Compared with traditional catalyst carriers for carbon nanotubes, blast furnace slag has similar physical and chemical properties, including excellent adsorption performance, outstanding thermal stability and chemical stability. However, as a multi-component composite carrier, blast furnace slag has higher adsorption performance and reaction activity. At the same time, the multi-component composite carrier can broaden the reaction activity temperature window, and there are crystalline phases with various crystal structures formed inside the multi-component composite carrier. There are lattice distortions between these polycrystalline phases, which hinder the further growth of active metals during high-temperature catalysis, thus effectively suppressing the increase in the diameter of carbon nanotubes, and also making it difficult for active components to migrate and aggregate to improve the activity of the catalyst and increase the yield. These characteristics make the catalyst with blast furnace slag as the carrier show stronger stability when preparing carbon nanotubes, which in turn helps to produce high-quality carbon nanotubes with consistent diameters and higher yields.

[0032] In view of the problems that may exist when blast furnace slag is used as a catalyst support, such as insufficient pores, limited specific surface area, and the influence on the loading and dispersion of active components, the present invention particularly uses metal oxide particles as a modifier to modify the blast furnace slag. On the one hand, the metal oxide can improve the inherent acidity of the blast furnace slag, reduce the carbon deposition on the surface of the active metal particles by the subsequent carbon source, or reduce the formation of carbon deposition by providing basic sites; on the other hand, the metal oxide can interact with the slag support, destroying the original crystal phase structure of the blast furnace slag, generating micropores on the surface of the support and opening the internal channels, providing active sites for the active metal particles and reaction gases, and the lattice distortion generated by the destruction can also inhibit the growth and migration of the active metal particles. At the same time, the metal oxide modifier not only enhances the adsorption capacity of the blast furnace slag support, but also has a certain adsorption capacity itself. The two cooperate to adsorb the active metal particles, so that the active metal particles are fixed on the support, further reducing the detachment and desorption of the active metal particles.

[0033] These effective modification methods significantly optimize the performance of blast furnace slag as a catalyst support, providing a solid guarantee for the preparation of carbon nanotubes with more excellent performance.

[0034] These features and advantages of the present invention will be disclosed in detail in the following specific embodiments and the accompanying drawings. The best embodiments or means of the present invention will be shown in detail in combination with the accompanying drawings, but it is not a limitation to the technical solution of the present invention. In addition, these features, elements, and components appear in multiple in each of the following texts and drawings, and different symbols or numbers are marked for convenience of representation, but they all represent components with the same or similar structures or functions. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described below with reference to the accompanying drawings:

[0036] Figure 1 It is a schematic structural diagram of an embodiment of the catalyst provided by the present invention;

[0037] Figure 2 It is a flowchart of an embodiment of the catalyst preparation method provided by the present invention;

[0038] Figure 3 It is a scanning electron microscope photograph of the carbon nanotubes prepared by the catalyst of Example 1;

[0039] Figure 4 It is a scanning electron microscope photograph of the carbon nanotubes prepared by the catalyst of Example 3;

[0040] Figure 5 It is a scanning electron microscope photograph of the carbon nanotubes prepared by the catalyst of Comparative Example 1;

[0041] Figure 6 Scanning electron microscope photograph of carbon nanotubes prepared with the catalyst of Comparative Example 3.

[0042] Explanation of reference numerals

[0043] 1: catalyst; 1a: catalytic metal particles; 1b: support particles; 1c: metal oxide particles Detailed implementation manners

[0044] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. Based on the embodiments in the implementation manners, it is intended to explain the present invention and should not be construed as a limitation of the present invention.

[0045] As used herein, the phrase "in one embodiment" or "instance" or "example" means that a particular feature, structure, or characteristic described in connection with the embodiment itself can be included in at least one embodiment of the present disclosure. The appearances of the phrase "in one embodiment" in various places in the specification do not necessarily refer to the same embodiment.

[0046] The shapes, sizes, proportions, angles, quantities, etc. disclosed in the accompanying drawings for explaining the catalyst and carbon nanotubes of the present invention are exemplary, and the present invention is not limited to what is shown. For example, although the support particles are represented by circular particles in the figures, it does not mean that the actual support particles are a combination of circular particles, and the parameters such as the sizes, positions, and structures of the different circular particles shown in the accompanying drawings are intended to explain the present invention, and the present invention is not necessarily limited to the above parameters shown.

[0047] Carbon nanotubes, as a unique one-dimensional nanomaterial, exhibit broad application potential in many fields due to their excellent mechanical properties, electrical properties, thermal properties, chemical stability, and light weight. It is widely used to improve the performance of lithium-ion batteries, enhance the performance of conductive plastics, as a reinforcing agent for high-performance composite materials, and plays an important role in biomedical research, environmental protection, and sensor technology. Among them, the lithium-ion battery field is the main market for the large-scale commercial application of carbon nanotubes. With technological progress and the broadening of application fields, the application prospects of carbon nanotubes will continue to expand.

[0048] The cost issue is one of the key factors restricting the widespread application of carbon nanotubes. By developing new catalysts, reducing the raw material cost of the catalysts, and simultaneously improving the product performance, the production cost can be reduced and the market competitiveness of the products can be enhanced. The catalyst consists of an active metal, a promoter, and a carrier. Among them, the carrier often accounts for more than half of the total mass of the catalyst. Therefore, finding a carrier material with low cost and excellent performance is decisive for reducing the overall cost of the catalyst. Currently, oxides such as Al2O3, MgO, SiO2, and CaO are usually selected as the carrier, and widely used carrier raw materials, such as high-purity aluminum salts, magnesium salts, and their oxides, although showing good stability, have relatively high raw material costs. And to achieve the best catalytic effect, it is often necessary to mix multiple salts through complex proportioning and adjustment to find the optimal combination, which undoubtedly increases the complexity and cost of preparation.

[0049] Through the research of the inventors of this application, it is found that blast furnace slag, as a by-product in the iron and steel smelting process, its large accumulation not only becomes an environmental burden but also causes great waste of resources. The composition of the slag comes from the following aspects: (1) gangue in the ore; (2) coke ash; (3) flux oxides; the main components of gangue and ash are acidic oxides of SiO2 and Al2O3; the flux oxides are mainly basic oxides of CaO and MgO, and the proportion of these components is as high as 95% of the total mass. These components usually have excellent adsorption properties provided by the porous structure, as well as excellent chemical stability and thermal stability, and have similar physical and chemical characteristics to the catalyst carriers of traditional carbon nanotubes. It is an ideal material choice as a carrier. Using blast furnace slag as a carrier greatly reduces the raw material cost of the catalyst and more importantly realizes the resource utilization of blast furnace slag, which strongly promotes the development of the resource recycling economy.

[0050] At the same time, blast furnace slag can be regarded as a multi-component composite carrier composed of components such as CaO - SiO2 - MgO - Al2O3. The synergistic effect of its multi-components can promote the more uniform dispersion of the active components on the surface of the carrier, and the multi-components can broaden the reaction activity temperature range. This makes the catalyst with blast furnace slag as the carrier show stronger stability when preparing carbon nanotubes, and further helps to produce high-quality carbon nanotubes with consistent tube diameters and higher yields.

[0051] However, when blast furnace slag is used as a catalyst carrier, there may be problems such as insufficient pores, limited specific surface area, and affecting the loading and dispersion of active components. Based on the above problems, as the first aspect of the present invention, a catalyst is disclosed, as Figure 1 shown, Catalyst 1 is used for synthesizing carbon nanotubes, and Catalyst 1 includes:

[0052] a main body, the main body includes a plurality of catalytic metal particles 1a;

[0053] A carrier, the carrier includes a plurality of carrier particles 1b, wherein the specific surface area of the carrier particles is greater than that of the catalytic metal particles, the catalytic metal particles are supported by the carrier particles, and the material of the carrier particles includes blast furnace slag;

[0054] A modifier, the modifier includes a plurality of metal oxide particles 1c.

[0055] Compared with the traditional carbon nanotube catalyst support, blast furnace slag is a multi-component composite support, which has higher adsorption performance and reaction activity. At the same time, the multi-component composite support can broaden the reaction activity temperature window, and there are crystalline phases with various crystal structures formed inside the multi-component composite support. There is lattice distortion between these polycrystalline phases, which hinders the further growth of the active metal during the high-temperature catalysis process, thus effectively inhibiting the increase in the carbon nanotube diameter. Moreover, it also makes it difficult for the active components to migrate and aggregate to improve the activity of the catalyst and increase the yield. These characteristics make the catalyst with blast furnace slag as the support show stronger stability when preparing carbon nanotubes, and further contribute to the production of high-quality carbon nanotubes with consistent diameter and higher yield.

[0056] In the present invention, there is no special limitation on the way to obtain blast furnace slag, which can be obtained by purchasing or by preparation.

[0057] In the present invention, the modifier is used to modify the carrier particles 1b of blast furnace slag. Using metal oxide particles 1c as the modifier, on the one hand, the metal oxide particles 1c can improve the inherent acidity of blast furnace slag, reduce the carbon deposition on the surface of the catalytic metal particles 1a by the subsequent carbon source, or reduce the formation of carbon deposition by providing basic sites; on the other hand, after the blast furnace slag is treated at high temperature, its structure becomes more dense, and the specific surface area and pore volume are relatively small. However, the metal oxide particles 1c can interact with the slag carrier or form a solid solution, so that the original crystal phase structure of the blast furnace slag is destroyed, micropores are generated on the carrier surface and the internal channels are opened, providing active sites for the catalytic metal particles 1a and the reaction gas. And the lattice distortion generated by the destruction can also inhibit the growth and migration of the catalytic metal particles 1a. At the same time, the metal oxide particles 1c not only enhance the adsorption capacity of the blast furnace slag carrier, but also have a certain adsorption capacity themselves. The two cooperate to adsorb the catalytic metal particles 1a, so that the catalytic metal particles 1a are fixed on the carrier particles 1b, further reducing the detachment and desorption of the catalytic metal particles 1a.

[0058] The modifier of the present invention significantly optimizes the performance of blast furnace slag as a catalyst support by modifying the blast furnace slag, providing a solid guarantee for the preparation of carbon nanotubes with more excellent performance.

[0059] The present invention does not make special limitations on the distribution of the modifier in the catalyst. In order to improve the modification effect and make the interaction between the metal oxide particles 1c and the carrier particles 1b stronger, thereby obtaining higher adsorption performance and reaction activity, preferably, a plurality of metal oxide particles 1c are distributed inside and / or on the surface of the carrier particles 1b. This distribution method enables the individual carrier particles 1b to be simultaneously affected by the interaction of the metal oxide particles 1c at multiple positions, and lattice distortion or changes in the crystal phase can occur at multiple positions, thereby effectively dispersing and inhibiting the growth of more catalytic metal particles 1a. In some embodiments, the metal oxide particles 1c can be adsorbed into the porous structure of the carrier particles 1b. During subsequent high-temperature processes, the adsorbed multiple metal oxide particles 1c combine with the carrier particles 1b through physical or chemical reactions. For example, when the modifier is Al2O3, it is adsorbed in the pores of the blast furnace slag carrier particles in the form of Al2O3 particles. Al2O3 belongs to a weakly acidic oxide in the slag and acts as a network former in the slag, and is easily combined with substances such as TiO2, MgO, and SiO2 in the blast furnace slag to form a composite crystal structure. The lattice distortion generated by this crystal structure change will hinder the growth, migration, and aggregation of the catalytic metal particles, thereby improving the dispersibility of the carrier. In addition, alumina itself also has a porous adsorption effect, which further increases the adsorption capacity of the carrier for the catalytic metal particles. In addition, by adding different metal oxide particles, the phase transition nodes of multiple components can be adjusted to obtain an ideal phase structure composition and improve the comprehensive performance of the carrier.

[0060] The present invention does not make special limitations on the composition of the modifier, as long as it satisfies that the metal oxide particles can modify the blast furnace slag. For example, the modifier is at least one of MgO, Al2O3, ZnO, ZrO2, and TiO2. Preferably, the modifier is an alkaline metal oxide. The advantages are that, on the one hand, it can neutralize the acidity of the blast furnace slag carrier to avoid the carbon deposition effect, and on the other hand, the alkaline metal oxide particles can provide electrons to the catalytic metal particles, thereby shifting the d-band center of the catalytic metal atoms upward, gradually approaching the Fermi level, increasing the bonding stability, improving the adsorption strength of the catalytic metal atoms, promoting the absorption and dissociation of the carbon source on the surface of the catalytic metal atoms, and providing more activity for the catalytic metal atoms. Preferably, the modifier includes at least one of magnesium oxide, zinc oxide, zirconium oxide, and titanium oxide. The above-mentioned alkaline metal oxides react with the acidic blast furnace slag carrier to form channels on the surface and inside of the carrier particles, which can provide a larger adsorption area for the active substances.

[0061] The present invention does not impose any special limitation on the proportion of the modifier in the carrier by weight. A lower proportion will lead to a significant reduction in the modification effect and cannot effectively improve the various properties of the blast furnace slag carrier. While an excessive proportion will result in a decrease in the quality of the produced carbon nanotubes. After the proportion of the modifier exceeds 50%, the diameter of the produced carbon nanotubes becomes thicker and the carbon yield decreases. In addition, too much modifier will coat the surface of the blast furnace slag, which may block the microporous structure and affect the entry of catalytic metal particles into the interior of the carrier. At the same time, it will make the properties of the blast furnace slag carrier tend to be a single carrier, unable to generate lattice distortion, and thus unable to inhibit the growth or migration of catalytic metal particles. Preferably, in the catalyst, the modifier accounts for 0.5% to 15% of the weight of the carrier.

[0062] The present invention does not impose any special limitation on the weight proportion of the catalytic metal particles in the carrier. The lower the proportion of the catalytic metal particles in the carrier by weight, that is, the lower the loading amount, the more uniformly the catalytic metal particles are dispersed on the carrier, the smaller the catalytic metal particles, the thinner the diameter of the prepared carbon nanotubes, and the larger the specific surface area of the carbon nanotubes. However, an excessive loading amount may introduce more impurities. Preferably, in the catalyst, the mass of the metal element in the main body is 10% to 30% of the weight of the carrier.

[0063] The present invention does not impose any special limitation on the catalytic metal particles. Preferably, the catalytic metal particles include at least one of iron, cobalt, nickel, and molybdenum elements. Iron, cobalt, and nickel can react with the carbon source to form metastable carbides, making the catalysts prepared therefrom have the highest efficiency in growing carbon nanotubes, and they are relatively ideal choices among the catalysts for synthesizing carbon nanotubes.

[0064] As the second aspect of the present invention, a preparation method of a catalyst is provided. As Figure 2 shown, the preparation method includes:

[0065] Step S100: Provide the initial blast furnace slag;

[0066] Step S110: Enrich the catalytic metal and the modifying metal in the initial blast furnace slag to obtain an initial catalyst, wherein the modifier includes metal oxides;

[0067] Step S120: Calcinate the initial catalyst to prepare the above-mentioned catalyst, and the catalyst is used for synthesizing carbon nanotubes.

[0068] In step S100, the initial blast furnace slag includes components such as CaO, SiO2, Al2O3, and MgO. In order to improve the surface area, pore volume, adsorption property, etc. of the initial blast furnace slag as a carrier, some physical modifications and chemical modifications are carried out on the initial blast furnace slag, specifically including:

[0069] The blast furnace slag is crushed to obtain the first blast furnace slag. As an alternative implementation, high-speed shear crushing technology is used to crush the blast furnace slag, and the first blast furnace slag with a mesh size below 100 is obtained through screening. Crushing the blast furnace slag can promote the subsequent full mixing of the catalytic metal and the modifier with it, increasing the reaction area.

[0070] The first blast furnace slag is acid-modified with an acidic solution. Here, the acidic solution corrodes the first blast furnace slag to form a surface microporous structure, obtaining the initial blast furnace slag. Preferably, the acid used to modify the blast furnace slag can be at least one of nitric acid, hydrochloric acid, and citric acid.

[0071] In step S110, the catalytic metal and the modifying metal are enriched in the initial blast furnace slag to obtain the initial catalyst, including:

[0072] The first metal salt, the second metal salt, and water are mixed to form a mixed solution. Here, the metal in the first metal salt corresponds to the catalytic metal, and the metal in the second metal salt corresponds to the modifying metal. Specifically, the first metal salt includes any one or more of iron salts, cobalt salts, nickel salts, and molybdenum salts. The salts include at least one of nitrates, hydrochlorides, acetates, and sulfates. The molybdenum salt is ammonium heptamolybdate. The second metal salt includes at least one of magnesium salts, aluminum salts, zinc salts, zirconium salts, and titanium salts. Weigh a set amount of the first metal salt and the second metal salt and dissolve them in deionized water. Preferably, the concentration of the above mixed salts is between 0.5 mol / L and 5 mol / L.

[0073] The mixed solution and the initial blast furnace slag are mixed using the impregnation method or the co-precipitation method to obtain the first mixed solution. In some embodiments, the steps of using the impregnation method include: adding the initial blast furnace slag to the above mixed solution, stirring at high speed at room temperature for 6 h, then heating to 80 °C and continuing to stir until the water is completely evaporated. In other embodiments, the steps of using the co-precipitation method include: adding the initial blast furnace slag to the above mixed solution, stirring at high speed at room temperature for 30 min to form a suspension. While continuously stirring at high speed, a precipitating agent is slowly added dropwise to the suspension until the pH value of the mixed solution reaches within the range of 9 - 11. Then, let it stand for 3 h and wash it to neutral with a centrifuge. Preferably, the precipitating agent is selected from at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, and ammonia water. The concentration of the precipitating agent is between 0.5 mol / L and 5 mol / L, and the dropping rate of the precipitating agent is between 1 mL / min and 10 mL / min to obtain a better precipitation effect.

[0074] The first mixed solution is dried and pulverized to obtain an initial catalyst. To fully remove moisture and reduce the particle size of the catalyst, preferably, the drying temperature is in the range of 60 °C to 120 °C, and a high-speed shearing pulverization method is used to pulverize the dried solid material to a particle average diameter less than or equal to 5 microns.

[0075] In step S120, preferably, the calcination temperature is between 300 °C and 700 °C, the calcination time is between 0.5 hour and 3 hours, and the calcination atmosphere is air.

[0076] As the third aspect of the present invention, a method for preparing carbon nanotubes is disclosed. The preparation method includes: heating the above catalyst to between 680 °C and 800 °C, introducing a carbon source gas for reaction to obtain initial carbon nanotubes. In some embodiments, in a horizontal fixed-bed reactor, the catalyst powder is evenly spread on a quartz boat, and under nitrogen protection, it is gradually heated to between 680 °C and 800 °C, and at least one of methane, ethylene, and propylene gases is introduced as a carbon source. After reacting for a set time, the gas supply is turned off;

[0077] The initial carbon nanotubes are cooled to room temperature to obtain carbon nanotubes, and the cooling atmosphere is nitrogen.

[0078] As the fourth aspect of the present invention, a carbon nanotube is disclosed, which is obtained by using the above preparation method.

[0079] The present invention will be further described below in conjunction with preparation examples and implementation examples.

[0080] Preparation Example

[0081] Preparation Example 1

[0082] A method for preparing a catalyst includes:

[0083] S1. Provide initial blast furnace slag. Among them, the blast furnace slag is pulverized by using a high-speed shearing pulverization technique and sieved to obtain particles below 100 mesh;

[0084] S2. Enrich the catalytic metal and the modified metal in the initial blast furnace slag. Specifically, 7.2 g of iron nitrate and 4.9 g of cobalt nitrate are weighed and dissolved in 35 mL of deionized water to form a mixed solution with a concentration of 1 mol / L. 10 g of the initial blast furnace slag is weighed and mixed with the mixed solution, and high-speed stirring is carried out at room temperature for 6 h. Subsequently, the temperature is raised to 80 °C and stirring is continued until the water is completely evaporated. The obtained solid material is transferred to an oven at 100 °C for drying for 12 h. After drying is completed, it is pulverized to obtain an initial catalyst;

[0085] S3. Calcinate the initial catalyst. Specifically, place the initial catalyst in a muffle furnace and calcine it in an air atmosphere at 600 °C for 0.5 h to obtain the Fe-Co / BFS catalyst (denote blast furnace slag as BFS).

[0086] Preparation Example 2

[0087] Prepare the catalyst using the same preparation method as in Preparation Example 1, except that in step S1, after pulverizing the blast furnace slag, obtain the first blast furnace slag, weigh 20 g of the first blast furnace slag and mix it with 30 mL of nitric acid (concentration 1 mol / L), soak for 3 h, then filter and wash with deionized water until the pH value of the mixture reaches 7. Then, place the filter cake in an oven at 120 °C and dry for about 12 hours. Finally, conduct a calcination treatment in air at 450 °C for 1 hour. Finally, prepare the Fe-Co / hn-BFS catalyst (denote nitric acid-modified blast furnace slag as hn-BFS).

[0088] Preparation Example 3

[0089] Prepare the catalyst using the same preparation method as in Preparation Example 1, except that in step S2, weigh 7.2 g of iron nitrate, 4.9 g of cobalt nitrate, and 3.2 g of magnesium nitrate and dissolve them in 47 mL of deionized water to form a mixed solution with a concentration of 1 mol / L. Weigh 10 g of the initial blast furnace slag and mix it with the mixed solution, and stir at high speed at room temperature for 30 min to form a suspension. While continuously stirring at high speed, dropwise add a sodium hydroxide solution with a concentration of 2 mol / L to the suspension, and control the dropping speed at 1 mL / min until the pH value of the mixed solution reaches within the range of 9 - 11. Then, let it stand for 3 h and wash it to neutral with a centrifuge. Transfer the above precipitate to an oven at 80 °C and dry for 12 h. After drying, pulverize it to obtain the initial catalyst;

[0090] In step S3, calcine it in an air atmosphere at 550 °C for 1 h to obtain the Fe-Co / BFS-MgO catalyst.

[0091] Preparation Example 4

[0092] Prepare the catalyst using the same preparation method as in Preparation Example 3, except that in step S1, after pulverizing the blast furnace slag, obtain the first blast furnace slag, weigh 20 g of the first blast furnace slag and mix it with 30 mL of nitric acid (concentration 1 mol / L), soak for 3 h, then filter and wash with deionized water until the pH value of the mixture reaches 7. Then, place the filter cake in an oven at 120 °C and dry for about 12 hours. Finally, conduct a calcination treatment in air at 450 °C for 1 hour. Finally, prepare the Fe-Co / hn-BFS-MgO catalyst.

[0093] Preparation Example 5

[0094] A method for preparing a catalyst, comprising:

[0095] S1. Provide initial blast furnace slag. Among them, the blast furnace slag is pulverized by high-speed shear pulverization technology, and the slag with a particle size below 100 mesh is obtained by screening to obtain the first blast furnace slag. Weigh 20 g of the first blast furnace slag and mix it with 30 mL of nitrocitric acid solution (concentration: 2 mol / L), soak for 3 h, and then filter and wash with deionized water until the pH value of the mixture reaches 7. Then, place the filter cake in an oven at 120 °C and dry for about 12 hours. Finally, perform a roasting treatment in air at 450 °C for 1 hour to obtain the initial blast furnace slag;

[0096] S2. Enrich catalytic metals and modified metals in the initial blast furnace slag. Specifically, weigh 9.9 g of cobalt nitrate, 1.2 g of ammonium heptamolybdate, and 3.2 g of magnesium nitrate, dissolve them in 53 mL of deionized water to form a mixed solution with a concentration of 1 mol / L. Weigh 10 g of the initial blast furnace slag and mix it with the mixed solution, and stir at high speed at room temperature for 30 min to form a suspension. Under continuous high-speed stirring, dropwise add a sodium carbonate solution with a concentration of 3 mol / L to the suspension, and control the dropping rate at 2 mL / min until the pH value of the mixed solution reaches within the range of 9-11. Then, let it stand for 3 h and wash it to neutral with a centrifuge. Transfer the above precipitate to an oven at 110 °C and dry for 12 h. After drying, pulverize it to obtain the initial catalyst;

[0097] S3. Perform a calcination treatment on the initial catalyst. Specifically, place the initial catalyst in a muffle furnace and calcine it in an air atmosphere at 500 °C for 1 h to obtain a Co-Mo / ca-BFS-MgO catalyst (denote the citric acid-modified blast furnace slag as ca-BFS).

[0098] Preparation Example 6

[0099] The catalyst is prepared by the same preparation method as in Preparation Example 5, except that in step S2, 9.9 g of cobalt nitrate, 1.2 g of ammonium heptamolybdate, and 2.3 g of zinc nitrate are weighed and dissolved in 48 mL of deionized water to form a mixed solution with a concentration of 1 mol / L. Finally, a Co-Mo / ca-BFS-ZnO catalyst is prepared.

[0100] Preparation Example 7

[0101] A method for preparing a catalyst, comprising:

[0102] S1. Weigh 7.2 g of iron nitrate and 4.9 g of cobalt nitrate, and dissolve them in 35 mL of deionized water to form a mixed solution with a concentration of 1 mol / L. Weigh 10 g of γ-Al2O3 and add it to the mixed solution. Stir at high speed at room temperature for 6 h, then heat up to 80 °C and continue stirring until the water is completely evaporated to obtain a solid substance. Transfer the solid substance to an oven at 100 °C and dry it for 12 h. After drying, pulverize it to obtain the initial catalyst;

[0103] S2. Place the above initial catalyst in a muffle furnace and calcine it in an air atmosphere at 600 °C for 0.5 h to obtain the Fe-Co / γ-Al2O3 catalyst.

[0104] Preparation Example 8

[0105] The catalyst was prepared using the same preparation method as in Preparation Example 7, except that γ-Al2O3 was replaced with MgO. Finally, the Fe-Co / MgO catalyst was prepared.

[0106] Preparation Example 9

[0107] A method for preparing a catalyst, comprising:

[0108] S1. Weigh 7.2 g of iron nitrate and 4.9 g of cobalt nitrate, and dissolve them in 35 mL of deionized water to form a mixed solution with a concentration of 1 mol / L. Weigh 10 g of CaO and add it to the mixed solution. Stir the resulting mixed solution at high speed at room temperature for 30 min to form a suspension. While continuously stirring at high speed, add a sodium hydroxide solution with a concentration of 2 mol / L to the suspension at a dropping rate controlled at 1 mL / min until the pH value of the mixed solution reaches within the range of 9 to 11. Then, let it stand for 3 h and wash it to neutral with a centrifuge. Transfer the precipitate to an oven at 80 °C and dry it for 12 h. After drying, pulverize it to obtain the initial catalyst;

[0109] S2. Place the above initial catalyst in a muffle furnace and calcine it in an air atmosphere at 550 °C for 1 h to finally obtain the Fe-Co / CaO catalyst.

[0110] Preparation Example 10

[0111] A method for preparing a catalyst, comprising:

[0112] S1. Weigh 9.9 g of cobalt nitrate and 1.2 g of ammonium heptamolybdate, and dissolve them in 40 mL of deionized water to form a mixed solution with a concentration of 1 mol / L. Add 10 g of SiO2 to the mixed solution and stir at high speed for 30 min at room temperature to form a suspension. While continuously stirring at high speed, dropwise add a sodium carbonate solution with a concentration of 3 mol / L to the suspension at a dropping rate controlled at 2 mL / min until the pH value of the mixed solution reaches within the range of 9 - 11. Then, let it stand for 3 h and wash it with a centrifuge until it is neutral. Transfer the precipitate to an oven at 110 °C and dry it for 12 h. After drying is completed, pulverize it to obtain the initial catalyst;

[0113] S2. Place the above-mentioned initial catalyst in a muffle furnace and calcine it in an air atmosphere at 500 °C for 1 h to obtain the Co-Mo / SiO2 catalyst.

[0114] Preparation Example 11

[0115] The catalyst was prepared using the same preparation method as in Preparation Example 10, except that SiO2 was replaced with γ-Al2O3, and finally the Co-Mo / γ-Al2O3 catalyst was prepared.

[0116] Preparation Example 12

[0117] The catalyst was prepared using the same preparation method as in Preparation Example 10, except that in step S1, 4.14 g of zirconium nitrate was also added to the mixed solution. Finally, the Co-Mo / SiO2-ZrO2 catalyst was prepared.

[0118] The specific parameters of the components in the above preparation examples are shown in Table 1, and the preparation parameters are shown in Table 2.

[0119] Table 1

[0120]

[0121] Table 2

[0122]

[0123] Examples

[0124] Example 1

[0125] A method for preparing carbon nanotubes, comprising:

[0126] In a horizontal fixed-bed reactor, 1 g of Fe-Co / BFS catalyst powder was evenly spread in a quartz boat. Subsequently, under the protection of 300 sccm of nitrogen, it was heated to the set temperature of 680 °C, and 300 sccm of propylene gas was introduced. During this process, the flow rate of nitrogen remained constant. After reacting for 1 h, the supply of propylene gas was turned off, and it was naturally cooled to room temperature in a nitrogen atmosphere to obtain Sample 1.

[0127] Example 2

[0128] Carbon nanotubes were prepared using the same preparation method as in Example 1, except that it was heated to the set temperature of 750 °C to obtain Sample 2.

[0129] Example 3

[0130] Carbon nanotubes were prepared using the same preparation method as in Example 1, except that 1 g of Fe-Co / hn-BFS catalyst was used, and finally Sample 3 was prepared.

[0131] Example 4

[0132] Carbon nanotubes were prepared using the same preparation method as in Example 1, except that 1 g of Fe-Co / BFS-MgO catalyst was used, and finally Sample 4 was prepared.

[0133] Example 5

[0134] Carbon nanotubes were prepared using the same preparation method as in Example 1, except that 1 g of Fe-Co / hn-BFS-MgO catalyst was used, and finally Sample 5 was prepared.

[0135] Example 6

[0136] Carbon nanotubes were prepared using the same preparation method as in Example 1, except that 1 g of Co-Mo / ca-BFS-MgO catalyst was used, and finally Sample 6 was prepared.

[0137] Example 7

[0138] Carbon nanotubes were prepared using the same preparation method as in Example 1, except that 1 g of Co-Mo / ca-BFS-MgO catalyst was used and it was heated to the set temperature of 750 °C, and finally Sample 7 was prepared.

[0139] Example 8

[0140] Carbon nanotubes were prepared using the same preparation method as in Example 1, except that 1 g of Co-Mo / ca-BFS-ZnO catalyst was used, and finally Sample 8 was prepared.

[0141] Comparative Example 1

[0142] The carbon nanotubes were prepared using the same preparation method as in Example 1, except that 1 g of Fe-Co / γ-Al 2 O 3 catalyst was used, and finally Sample 9 was prepared.

[0143] Comparative Example 2

[0144] The carbon nanotubes were prepared using the same preparation method as in Example 1, except that 1 g of Fe-Co / γ-Al 2 O 3 catalyst was used, heated to the set temperature of 750 °C, and finally Sample 10 was prepared.

[0145] Comparative Example 3

[0146] The carbon nanotubes were prepared using the same preparation method as in Example 1, except that 1 g of Fe-Co / MgO catalyst was used, and finally Sample 11 was prepared.

[0147] Comparative Example 4

[0148] The carbon nanotubes were prepared using the same preparation method as in Example 1, except that 1 g of Fe-Co / CaO catalyst was used, and finally Sample 12 was prepared.

[0149] Comparative Example 5

[0150] The carbon nanotubes were prepared using the same preparation method as in Example 1, except that 1 g of Co-Mo / SiO 2 catalyst was used, and finally Sample 13 was prepared.

[0151] Comparative Example 6

[0152] The carbon nanotubes were prepared using the same preparation method as in Example 1, except that 1 g of Co-Mo / γ-Al 2 O 3 catalyst was used, and finally Sample 14 was prepared.

[0153] Comparative Example 7

[0154] The carbon nanotubes were prepared using the same preparation method as in Example 1, except that 1 g of Co-Mo / SiO 2 -ZrO 2 catalyst was used, and finally Sample 15 was prepared.

[0155] Comparative Example 8

[0156] The carbon nanotubes were prepared using the same preparation method as in Example 1, except that 1 g of Co-Mo / SiO2 -ZrO 2 The catalyst was heated to the set temperature of 750 °C, and finally sample 16 was prepared.

[0157] The specific preparation parameters of the examples are shown in Table 3.

[0158] Table 3

[0159]

[0160] Test Example

[0161] The composition of the blast furnace slag in the preparation examples was analyzed by X-ray fluorescence spectrometer (XRF), and the results are shown in Table 4. The specific surface area, pore volume and pore diameter of the blast furnace slag in the preparation examples were tested, and the results are shown in Table 5. An electronic balance was used to measure the mass of the carbon nanotubes prepared in the examples and comparative examples, and the corresponding mass data of the carbon nanotubes were obtained, as shown in Table 6. The diameter and specific surface area of the carbon nanotubes were measured and statistically analyzed, and the statistical results are shown in Table 6. The scanning electron microscope of the FEI InspectF50 model was used to observe the microstructure of the carbon nanotubes in Example 1, Example 3, Comparative Example 1 and Comparative Example 3 respectively, and the microscopic morphology photos of the carbon nanotubes corresponded to Figure 3 , Figure 4 , Figure 5 and Figure 6 shown. It can be seen from the figure that the morphology characteristics of the carbon nanotubes prepared by using blast furnace slag as the carrier and the conventional carrier catalyst are the same. There are multiple carbon nanotubes, the pore size is the same, and an oriented structure is shown, maintaining the microscopic morphological characteristics. It can be shown that the introduction of the blast furnace slag carrier does not cause pollution to the growth of carbon nanotubes, nor does it affect the morphology and structure of the finally produced carbon nanotube product.

[0162] Table 4

[0163]

[0164] Table 5

[0165]

[0166] As can be seen from Table 4, when blast furnace slag is used as the carrier, the content of the key components meets the purity requirements, and no extra impurities are introduced, so as not to pollute the catalyst and the final product.

[0167] As can be seen from Table 5, in view of the problems that may exist when blast furnace slag is used as a catalyst support, such as insufficient pores, limited specific surface area, and the influence on the loading and dispersion of active components, strategies such as acid modification or inert component modification were adopted for blast furnace slag. These effective modification methods significantly optimized the performance of blast furnace slag as a catalyst support, significantly increased the specific surface area and pore volume, and provided a solid guarantee for the preparation of carbon nanotubes with more excellent performance.

[0168] Table 6

[0169]

[0170] It can be seen from the above experimental data that compared with the blast furnace slag multi-component composite support catalysts used in Examples 1 to 8, the carbon nanotubes prepared from the catalysts based on single supports in Comparative Examples 1 to 8 showed lower carbon yields, smaller specific surface areas, and coarser tube diameters. From the microscopic structure, the carbon nanotubes prepared in Examples 1 and 3 showed an ordered bundle arrangement, and the tube diameter distribution was relatively uniform. In contrast, the carbon nanotubes prepared in Comparative Examples 1 and 3 were randomly arranged and had coarser tube diameters. These comparisons show that the multi-component composite support catalysts in the examples have obvious advantages in improving catalytic activity and the dispersion ability of active metals compared with the single support catalysts in the comparative examples.

[0171] Compared with Examples 1 and 3, in Examples 4 to 8, metal oxide particles were used as modifiers to modify the blast furnace slag support. As a result, it can be seen that the carbon nanotube yield and the specific surface area of the carbon nanotubes of the blast furnace slag support catalyst modified by the modifier are higher.

[0172] The SiO in Comparative Example 7 2 -ZrO 2 The two-component composite support catalyst, although its activity and metal dispersion ability are improved compared with the single support catalysts in Comparative Examples 1 to 6, still does not perform as well as the multi-component composite support catalysts in Examples 1 to 8.

[0173] In addition, comparing Example 1 with Example 2, and comparing Example 6 with Example 7, the multi-component composite support catalyst proposed in this application can still maintain high catalytic activity at a high temperature of 750 °C. This characteristic is not reflected in the data of Comparative Examples 1 and 2 and Comparative Examples 7 and 8, and the activity of the latter is significantly reduced under the same high temperature conditions. This result fully proves that the multi-component composite support catalyst developed in this application not only has a wider active temperature window, but also can effectively resist temperature fluctuations during the production process, thus ensuring the stability and reliability of the catalytic process.

[0174] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes but is not limited to the content described in the drawings and the above specific embodiments. Any modification that does not deviate from the functional and structural principles of the present invention will be included in the scope of the claims.

Claims

1. A method for preparing carbon nanotubes, characterized in that: The preparation method comprises: The catalyst is heated to between 680°C and 750°C, and a carbon source gas is introduced to react to obtain initial carbon nanotubes; Cooling the initial carbon nanotubes to room temperature to obtain the carbon nanotubes; The preparation method of the catalyst comprises: Providing initial blast furnace slag, wherein the blast furnace slag is crushed to obtain first blast furnace slag, and the first blast furnace slag is acid-modified using an acidic solution, wherein the acidic solution corrodes the first blast furnace slag to form a surface microporous structure to obtain the initial blast furnace slag; The catalytic metal and the modified metal are enriched in the initial blast furnace slag to obtain an initial catalyst, wherein a first metal salt, a second metal salt and water are mixed to form a mixed solution, the metal in the first metal salt corresponds to the catalytic metal, the metal in the second metal salt corresponds to the modified metal, and the modified metal has no catalytic activity, the mixed solution is mixed with the initial blast furnace slag by an impregnation method or a coprecipitation method to obtain a first mixed solution, and the first mixed solution is dried and crushed to obtain the initial catalyst; The initial catalyst is calcined to prepare the catalyst, which includes: a main body, a carrier and a modifier, the mass of the metal element in the main body is 10% to 30% of the weight of the carrier, the modifier accounts for 0.5% to 15% of the weight of the carrier, the main body includes a plurality of catalytic metal particles, the metal elements of the catalytic metal particles include at least one of iron, cobalt and nickel, and the modifier includes at least one of magnesium oxide, zinc oxide, zirconium oxide and titanium oxide.

2. The preparation method according to claim 1, characterized in that: The carrier includes a plurality of carrier particles, the carrier particles have a porous structure, the specific surface area of ​​the carrier particles is greater than the specific surface area of ​​the catalytic metal particles, and the catalytic metal particles are supported by the carrier particles.

3. The preparation method according to claim 2, characterized in that: A plurality of the metal oxide particles are distributed inside and / or on the surface of the carrier particles, and the plurality of the metal oxide particles are combined with the carrier particles.

4. The preparation method according to any one of claims 1 to 3, characterized in that In the step of calcining the initial catalyst, the calcination temperature is between 300° C. and 700° C., and the calcination time is between 0.5 hour and 3 hours.

5. A carbon nanotube, characterized in that: The carbon nanotubes are prepared by the preparation method described in any one of claims 1 to 4.

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