Coating type catalyst for synthesizing carbon nano tube, preparation method of coating type catalyst and carbon nano tube synthesis method
By modifying the metal precursor and forming oil-phase nanodispersions, the problems of complex preparation process and poor catalytic performance of the existing catalyst are solved, and the yield and quality of carbon nanotubes are significantly improved.
Patent Information
- Application Number
- CN202311583950.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-24
- Publication Date
- 2025-05-27
AI Technical Summary
The preparation process of existing catalysts for carbon nanotube synthesis is complicated, and the morphology, size and dispersion of catalyst particles are difficult to control, which affects the catalytic performance and the controllable synthesis of carbon nanotubes.
By contacting the metal precursor with the modifier in an oily solvent, the modified metal nanoparticles were prepared and dispersed in the oily solvent to form an oily nanodispersion and coated on the substrate, which significantly improved the uniformity and controllability of the catalyst.
The activity and catalytic performance of the coated catalysts of synthetic carbon nanotubes have been significantly improved, the yield and quality of carbon nanotubes have been improved, and the problems of complex catalyst preparation process and poor catalytic performance have been solved.
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Figure BDA0004569338730000141 
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Abstract
Description
Technical Field
[0001] The present invention relates to the field of carbon nanotube synthesis, and particularly relates to a coated catalyst for synthesizing carbon nanotubes, a preparation method thereof, and a carbon nanotube synthesis method. Background Art
[0002] Carbon nanotubes have attracted extensive attention from many researchers in various fields such as materials, chemistry, medicine, microelectronics, energy, and catalysis due to their unique structure, excellent mechanical properties, and unique physical and chemical properties.
[0003] The synthesis methods of carbon nanotubes mainly include arc discharge method, laser evaporation method, chemical vapor deposition method, flame method, electrolysis method, template method, hydrothermal method, ion radiation method, ion bombardment growth method, and solar energy method, etc. Among them, the chemical vapor deposition method, also known as the catalytic cracking method, is widely used in the preparation of carbon nanotubes because of its advantages such as simple operation, low cost, high yield, and suitability for large-scale production. When preparing carbon nanotubes by the chemical vapor deposition method, the catalyst for carbon nanotube synthesis assists the cracking of the carbon source gas at high temperature. When the carbon content reaches the saturation state, it precipitates on the surface of the catalyst for carbon nanotube synthesis to form carbon nanotubes.
[0004] At present, the conventional coated catalyst for carbon nanotube synthesis is to coat a metal salt solution on the surface of a substrate, and then reduce it to metal particles through processes such as calcination, reduction, and cooling, and then use it for the synthesis of carbon nanotubes. The above catalyst preparation process is complex, and it is difficult to control the morphology, size, dispersion degree, etc. of the catalyst particles. Therefore, it seriously affects the catalytic performance, is not conducive to the controllable synthesis of carbon nanotubes, and limits the synthesis of carbon nanotubes.
[0005] Therefore, there is an urgent need to develop a catalyst for carbon nanotube synthesis that can improve the synthesis effect of carbon nanotubes. Summary of the Invention
[0006] The purpose of the present invention is to overcome the problems such as the limitation of carbon nanotube synthesis existing in the prior art, and provide a coated catalyst for synthesizing carbon nanotubes, a preparation method thereof, and a carbon nanotube synthesis method. The preparation method of the coated catalyst for synthesizing carbon nanotubes provided by the present invention completely changes the preparation method of the catalyst for carbon nanotube synthesis in the prior art that directly coats an active metal salt solution on a substrate. The modified metal nanoparticles are dispersed in an oily solvent to form a uniform dispersion, so that the active metal is controllably and uniformly distributed on the substrate, thereby significantly improving the activity and catalytic performance of the obtained coated catalyst for synthesizing carbon nanotubes, and thus greatly improving the yield and quality of carbon nanotubes.
[0007] To achieve the above object, a first aspect of the present invention provides a method for preparing a coated catalyst for synthesizing carbon nanotubes, wherein the method comprises the following steps:
[0008] 1) In the presence of a first solvent, contacting a metal precursor with a modifier to obtain modified metal nanoparticles;
[0009] 2) Dispersing the modified metal nanoparticles in an oily solvent to obtain an oil-phase nano-dispersion;
[0010] 3) Coating the oil-phase nano-dispersion on a substrate and performing a drying treatment.
[0011] Preferably, in step 1), the modifier is one or more of oleic acid, linoleic acid, caprylic acid, capric acid, lauric acid, myristic acid, stearic acid, behenic acid, oleylamine, stearylamine, and silane coupling agent, preferably one or more of oleylamine, oleic acid, and silane coupling agent.
[0012] Preferably, the first solvent is one or more of dioctyl ether, benzene, toluene, cyclohexane, n-hexane, ethyl acetate, acetone, benzyl alcohol, and tetrahydrofuran, more preferably dioctyl ether and / or benzyl alcohol.
[0013] Preferably, the metal precursor is a salt and / or complex of one or more selected from Fe, Co, Mo, Ni, Cu, Ag, Au, Ru, Rh, Pd, and Pt, more preferably a complex of one or more of Fe, Co, Mo, Ni, Cu, Ag, Au, Ru, Rh, Pd, and Pt; further preferably a complex of Co and Mo.
[0014] Preferably, in step 1), the weight ratio of the metal precursor to the first solvent is 1:100 - 1000; more preferably 1:200 - 500.
[0015] Preferably, the molar ratio of the metal precursor to the modifier is 1:0.1 - 10; more preferably 1:0.5 - 5.
[0016] Preferably, the conditions of the contact include: temperature is 120 - 300 °C, and time is 0.2 - 3 h.
[0017] Preferably, the contact is carried out under stirring.
[0018] Preferably, the modified metal nanoparticles are one or more of Fe, Co, Mo, Ni, Cu, Ag, Au, Ru, Rh, Pd, and Pt; more preferably, the modified metal nanoparticles are a combination of Co and Mo.
[0019] Preferably, the molar ratio of Co to Mo is 1:0.05 - 2, more preferably 1:0.1 - 0.3.
[0020] Preferably, the particle size of the modified metal nanoparticles is 1 - 50 nm, more preferably 1 - 10 nm.
[0021] Preferably, in step 2), the oily solvent is one or more of dioctyl ether, benzene, toluene, cyclohexane, n - hexane, ethyl acetate, acetone, and tetrahydrofuran.
[0022] Preferably, relative to 1 g of the modified metal nanoparticles, the amount of the oily solvent used is 100 - 10000 mL, more preferably 500 - 3000 mL.
[0023] Preferably, in step 2), a dispersant and / or a film - forming agent is further added to the oil - phase nanodispersion.
[0024] Preferably, the dispersant is one or more of oleic acid, linoleic acid, caprylic acid, capric acid, lauric acid, myristic acid, stearic acid, behenic acid, oleylamine, stearylamine, and silane coupling agent.
[0025] Preferably, the film - forming agent is one or more of polyvinyl formal, polyvinyl acetal, polyvinyl butyral, polyvinyl alcohol, collodion, zein, sodium carboxymethyl cellulose, and polyvinyl pyrrolidone.
[0026] Preferably, the weight ratio of the modified metal nanoparticles to the dispersant is 1:0.01 - 10.
[0027] Preferably, the weight ratio of the modified metal nanoparticles to the film - forming agent is 1:0.01 - 10.
[0028] Preferably, in step 3), the material of the substrate is selected from one or more of single - crystal silicon, silicon dioxide, diamond, zirconia, alumina, magnesia, titanium dioxide, quartz, glass, silicon carbide, silicon nitride, iron, stainless steel, titanium, and molybdenum; more preferably, the material of the substrate is selected from one or more of single - crystal silicon, silicon dioxide, and alumina.
[0029] Preferably, based on the metal nanoparticles, the coating amount of the coating is 0.01 - 10 mg / cm 2 , more preferably 0.01 - 20 mg / cm 2 .
[0030] Preferably, the conditions of the drying treatment include: the drying temperature is 30 - 90 °C, and the drying time is 6 - 24 h.
[0031] In the second aspect of the present invention, a coated catalyst for synthesizing carbon nanotubes prepared by the method described in the first aspect of the present invention is provided.
[0032] In the third aspect of the present invention, a method for synthesizing carbon nanotubes is provided, wherein the method is carried out using the coated catalyst for synthesizing carbon nanotubes described in the second aspect of the present invention.
[0033] Preferably, the method includes: in the presence of an inert gas, catalytic reaction of a carbon source gas with the coated catalyst for synthesizing carbon nanotubes.
[0034] Preferably, the conditions of the catalytic reaction include: temperature is 500 - 900 °C, and time is 0.5 - 3 h.
[0035] Preferably, the carbon source gas is selected from one or more of methane, ethylene, acetylene, ethanol, and propylene.
[0036] Preferably, relative to 0.01 g of the coated catalyst for synthesizing carbon nanotubes in terms of metal nanoparticles, the feeding amount of the carbon source gas is 100 - 1000 mL / min.
[0037] Through the above technical solution, the inherent method of directly coating an active metal salt solution on a substrate and performing reduction treatment in the prior art is broken. By first subjecting the active metal to modification treatment to prepare metal nanoparticles, the modified metal particles can be uniformly dispersed in an oily solvent without sedimentation, forming the oil-phase nano-dispersion. Such an oil-phase nano-dispersion belongs to a colloidal system, and the dispersion state of the metal nanoparticles is stable and can exist stably for a long time.
[0038] Compared with the metal salt solution, the particle morphology, size, and physical and chemical properties of the oil-phase nano-dispersion are easier to control, so that the conditions of the coating operation are easier to control, thereby controlling the properties of the coated catalyst. Thus, the uniformity and controllability of the obtained catalyst can be significantly improved during coating, and a coated catalyst for synthesizing carbon nanotubes with uniformly dispersed active components and controllable size and structure can be obtained.
[0039] The active components in the coated catalyst for synthesizing carbon nanotubes provided by the present invention are not only uniformly distributed but also have good adhesion, can be stacked into various three-dimensional structures for use as needed, can significantly increase the contact area with the carbon source gas, and thus can greatly increase the yield and quality of carbon nanotubes during the preparation of carbon nanotubes, providing a new idea for the preparation of carbon nanotubes. Detailed Embodiments
[0040] The endpoints and any values within the ranges disclosed in this document are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this document.
[0041] The first aspect of the present invention provides a method for preparing a coated catalyst for synthesizing carbon nanotubes, wherein the method comprises the following steps:
[0042] 1) In the presence of a first solvent, contacting a metal precursor with a modifier to obtain modified metal nanoparticles;
[0043] 2) Dispersing the modified metal nanoparticles in an oily solvent to obtain an oil-phase nano-dispersion;
[0044] 3) Coating the oil-phase nano-dispersion on a substrate and performing a drying treatment.
[0045] The inventors of the present invention found in a large number of experiments and production practices that when preparing a coated catalyst for synthesizing carbon nanotubes by the existing method, there are problems such as uneven dispersion of active metal salts in the solution, difficulty in controlling the distribution of active metals by coating, and poor quality of the coated catalyst for synthesizing carbon nanotubes obtained after reduction treatment, which seriously affect the preparation of carbon nanotubes.
[0046] Based on this, the inventors of the present invention found through a large number of studies that by first modifying the metal precursor of the coated catalyst for synthesizing carbon nanotubes to obtain modified metal nanoparticles, an oil-phase nano-dispersion with uniform dispersion, no sedimentation, and stable existence can be obtained when it is dispersed in an oily solvent, and then using the oil-phase nano-dispersion as a coating solution to coat on a substrate, the uniformity of distribution and catalytic activity of the prepared coated catalyst for synthesizing carbon nanotubes can be significantly improved, and thus the yield of carbon nanotubes can be significantly increased.
[0047] Hereinafter, the method for preparing a coated catalyst for synthesizing carbon nanotubes will be described in detail first.
[0048] In step 1), in the presence of a first solvent, contacting a metal precursor with a modifier to obtain modified metal nanoparticles.
[0049] As described above, different from directly using a salt solution of an active metal for coating in the prior art, in the present invention, the metal precursor is first modified through the above step 1).
[0050] The purpose of the modification treatment here is twofold. One is to control the nucleation and growth of nanoparticles; the other is to cause the active metal to form metal nanoparticles through modification. The modified metal nanoparticles can be dispersed in an oily solvent to obtain an oil-phase nano-dispersion, enabling the metal nanoparticles to be uniformly dispersed and stably present in the oily solvent without aggregation and sedimentation.
[0051] In the present invention, the metal nanoparticles refer to nanoparticles composed of metal atoms or metal ions.
[0052] In the present invention, the oil-phase nano-dispersion refers to a dispersion system in which nanoparticles or aggregates are uniformly and stably dispersed in an oily solvent.
[0053] In the present invention, after the oil-phase nano-dispersion is allowed to stand for 24 hours and observed through a transmission electron microscope (TEM), no precipitation and aggregates are found, and it is confirmed to be a monodisperse nano-metal particle.
[0054] In addition, the inventors found through experiments that the oil-phase nano-dispersion provided by the present invention remains monodisperse metal nanoparticles after being placed for one month.
[0055] In the present invention, the metal precursor refers to the precursor of the active metal used in the coated catalyst for synthesizing carbon nanotubes. It can be salts and / or complexes of active metals commonly used in the art as coated catalysts for synthesizing carbon nanotubes, without particular limitation.
[0056] For example, the metal precursor can be selected from salts and / or complexes of one or more of Fe, Co, Mo, Ni, Cu, Ag, Au, Ru, Rh, Pd, and Pt.
[0057] Preferably, the metal precursor is a complex of one or more of Fe, Co, Mo, Ni, Cu, Ag, Au, Ru, Rh, Pd, and Pt.
[0058] The inventors of the present invention unexpectedly found during the research process that when preparing the coated catalyst for synthesizing carbon nanotubes by the method of the present invention, among the above metal precursors, the combination of Co and Mo can achieve significantly better catalytic performance compared with other metal precursors, and can significantly increase the yield of the prepared carbon nanotubes within the range of unit time and unit catalyst dosage.
[0059] Therefore, in a preferred embodiment of the present invention, the metal precursor is a complex of Co and Mo. And, more preferably, in the metal precursor, the molar ratio of Co to Mo is 1:0.05 - 2, further preferably 1:0.1 - 0.3, whereby the catalytic performance of the resulting coated catalyst for synthesizing carbon nanotubes can be further significantly improved, thus significantly increasing the yield of carbon nanotubes prepared subsequently.
[0060] According to the present invention, in step 1), the modifier is used for surface modification treatment of the nanoparticles, so that the size and dispersibility of the nanoparticles are controlled.
[0061] In the present invention, the modifier in step 1) can be various modifiers capable of achieving the above purposes.
[0062] For example, the modifier can be one or more of oleic acid, linoleic acid, caprylic acid, capric acid, lauric acid, myristic acid, stearic acid, behenic acid, oleylamine, stearylamine, and silane coupling agent, preferably one or more of oleylamine, oleic acid, and silane coupling agent.
[0063] According to the present invention, the amount of the modifier can be determined according to the amount of the metal precursor. For example, the molar ratio of the metal precursor to the modifier can be 1:1 - 10; preferably 1:2 - 5. By using the modifier within the above dosage range, the modification effect can be further improved, the dispersion degree of the modified metal nanoparticles in the oily solvent can be increased, and thus the catalytic performance of the resulting coated catalyst for synthesizing carbon nanotubes can be improved.
[0064] In the present invention, there is no particular limitation on the first solvent, and it is preferably various oily solvents commonly used in the art. For example, the first solvent can be one or more of dioctyl ether, benzene, toluene, cyclohexane, n - hexane, ethyl acetate, acetone, benzyl alcohol, and tetrahydrofuran, more preferably dioctyl ether and / or benzyl alcohol.
[0065] In addition, in the present invention, the amount of the first solvent is not particularly limited and can be appropriately selected according to the amount of the metal precursor. For example, the weight ratio of the metal precursor to the first solvent can be 1:100 - 1000, preferably 1:200 - 500. By limiting the amount of the first solvent within the above range, the modification effect can be further improved.
[0066] According to the first aspect of the present invention, by contacting the metal precursor with the modifier and controlling the conditions of the contact reaction, on the one hand, the metal precursor decomposes to obtain metal nanoparticles, and on the other hand, the obtained metal is modified to obtain metal nanoparticles that can be uniformly and stably dispersed in the subsequent oily solvent.
[0067] Therefore, in the present invention, the conditions of the contact are crucial, which need to be able to achieve the purpose of modifying and decomposing the metal precursor. In the present invention, the conditions of the contact may include: the temperature is 120 - 300 °C, and the time is 0.2 - 3 h; preferably, the conditions of the contact include: the temperature is 200 - 290 °C, and the time is 0.5 - 3 h; more preferably, the conditions of the contact include: the temperature is 260 - 280 °C, and the time is 1 - 3 h.
[0068] In addition, in order to improve the modification efficiency and reduction effect, preferably, the contact is carried out under stirring.
[0069] On the other hand, in the present invention, by controlling the temperature, time (i.e., contact time), modifier / metal ratio, and solvent properties of the modification treatment, etc., the size of the obtained metal nanoparticles can be controlled.
[0070] Specifically, generally, the particle size of the obtained metal nanoparticles can be reduced by increasing the temperature of the modification treatment and increasing the modification treatment time. In addition, generally, the particle size of the obtained metal nanoparticles can also be reduced by increasing the dosage of the modifier, etc.
[0071] In the present invention, preferably, through the modification treatment in step 1), the particle size of the modified metal nanoparticles is 1 - 50 nm, more preferably 1 - 10 nm, and further preferably 3 - 5 nm. By limiting the particle size of the metal nanoparticles subjected to the modification treatment within the above range, it is more beneficial to improve the catalytic activity of the coated catalyst of the synthesized carbon nanotubes prepared and significantly improve the preparation efficiency of the carbon nanotubes.
[0072] Next, in step 2), the modified metal nanoparticles are dispersed in an oily solvent to obtain an oil-phase nano-dispersion.
[0073] The metal nanoparticles obtained through the modification treatment in step 1) already have the property of stable dispersion. Therefore, even if they are dispersed in an oily solvent, the metal nanoparticles will not aggregate or settle, but can form an oil-phase nano-dispersion with uniform distribution and stable existence.
[0074] According to the present invention, the metal nanoparticles in step 2) correspond to the metal precursor used in step 1). For example, the modified metal nanoparticles can be one or more of Fe, Co, Mo, Ni, Cu, Ag, Au, Ru, Rh, Pd, Pt.
[0075] For example, when the metal precursor used in step 1) is an iron complex, the modified metal nanoparticles in step 2) are iron nanoparticles.
[0076] In addition, preferably, the modified metal nanoparticles are a combination of Co and Mo; more preferably, the molar ratio of Co to Mo is 1:0.05 - 2, and further preferably 1:0.1 - 0.3. The inventors of the present invention have found that by using a combination of Co and Mo and further limiting the molar ratio of the two within the above range, the catalytic performance of the coated catalyst of the obtained synthesized carbon nanotubes can be further significantly improved.
[0077] In addition, in step 2), there is no particular limitation on the oily solvent, and it can be various low-polarity solvents with an oily nature commonly used in the art. For example, the oily solvent can be one or more of benzene, toluene, cyclohexane, n-hexane, ethyl acetate, acetone, and tetrahydrofuran, and preferably cyclohexane and / or ethyl acetate.
[0078] According to the present invention, there is no particular limitation on the amount of the oily solvent, as long as it can disperse the metal nanoparticles and obtain the oily-phase nano-dispersion. For example, the amount of the oily solvent can be selected according to the amount of the metal nanoparticles. For example, relative to 1 g of the modified metal nanoparticles, the amount of the oily solvent can be 100 - 10,000 mL, and preferably 500 - 3,000 mL. By using the above amount, not only can the metal nanoparticles be uniformly dispersed, but also the metal nanoparticles can be ensured to be at a suitable dispersion concentration, ensuring the catalytic performance of the catalyst of the synthesized carbon nanotubes obtained after coating.
[0079] In step 2), the dispersion can be carried out by various conventional means for dispersion in the art. For example, after mixing the modified metal nanoparticles with the oily solvent, stirring can be carried out, etc. This is a well-known method and will not be elaborated here.
[0080] Furthermore, in step 2), in order to further enhance the dispersion effect and make the metal nanoparticles more uniformly and stably dispersed in the oily solvent, preferably, other additives are further added to the oily-phase nano-dispersion.
[0081] The additives can be, for example, dispersants, film-forming agents, stabilizers, and adhesion agents, etc.
[0082] The dispersant can further improve the dispersion performance of the metal nanoparticles in the oily solvent.
[0083] As the dispersant, for example, it can be one or more of oleic acid, linoleic acid, caprylic acid, capric acid, lauric acid, myristic acid, stearic acid, behenic acid, oleylamine, stearylamine, and silane coupling agent, and preferably one or more of oleic acid and silane coupling agent.
[0084] In addition, the dosage of the dispersant can be appropriately selected according to the amount of the modified metal nanoparticles. For example, the weight ratio of the modified metal nanoparticles to the dispersant can be 1:0.01 - 10.
[0085] The film-forming agent can further enhance the adhesion of the oil-phase nano-dispersion and the hardness of the coated catalyst layer, and improve the stability of the nanoparticles and the dispersibility after coating.
[0086] As the film-forming agent, for example, it can be one or more of polyvinyl formal, polyvinyl acetal, polyvinyl butyral, polyvinyl alcohol, collodion, zein, sodium carboxymethyl cellulose, and polyvinylpyrrolidone, and preferably polyvinyl alcohol.
[0087] In addition, the dosage of the film-forming agent can be appropriately selected according to the amount of the modified metal nanoparticles. For example, the weight ratio of the modified metal nanoparticles to the film-forming agent can be 1:0.01 - 10.
[0088] Next, in step 3), the oil-phase nano-dispersion is coated on the substrate and dried.
[0089] According to the present invention, the oil-phase nano-dispersion obtained in step 2) can be used as a coating liquid for coating, that is, the oil-phase nano-dispersion is coated on the substrate and dried.
[0090] Here, the material of the substrate is not particularly limited and can be various materials of the substrate commonly used in the preparation of coated catalysts for synthesizing carbon nanotubes in the art. For example, the material of the substrate can be selected from one or more of single-crystalline silicon, silicon dioxide, diamond, zirconia, alumina, magnesia, titanium dioxide, quartz, glass, silicon carbide, silicon nitride, iron, stainless steel, titanium, and molybdenum; preferably, the substrate is selected from one or more of single-crystalline silicon, silicon dioxide, and alumina.
[0091] In addition, in the present invention, the shape and size of the substrate are not particularly limited and can be the size of a conventional substrate in the art.
[0092] For example, the shape of the substrate can be sheet-like, the length can be 20 - 80 mm, the width can be 5 - 40 mm, and the thickness can be 0.1 - 10 mm.
[0093] In the present invention, the substrate can be pretreated before use. For example, it can be polished, acid-etched, hydrophilized, and ultrasonically treated, etc., to increase the adhesion between the substrate and the metal nanoparticles and improve the performance of the prepared coated catalyst for synthesizing carbon nanotubes.
[0094] The above processing method can be carried out by using the well-known methods in the art and will not be elaborated here.
[0095] On the other hand, in the present invention, the coating method is not particularly limited either, and various coating methods in the art can be adopted. For example, the coating method can be spraying, roll coating, spin coating, knife coating, dip coating, slot coating, inkjet printing, screen printing, 3D printing, intaglio printing, etc., as long as the coating can be uniform.
[0096] In the present invention, preferably, the coating is carried out by spin coating.
[0097] In the present invention, there is no particular limitation on the coating amount of the coating either. For example, in terms of metal nanoparticles, it can be 0.01 - 10 mg / cm 2 , preferably 0.01 - 20 mg / cm 2 . The above coating amount can improve the catalytic performance of the catalyst for preparing the synthesized carbon nanotubes, and thus improve the yield of the obtained carbon nanotubes.
[0098] Then, in step 3), the coated product is dried. The conditions for the drying treatment are not particularly limited as long as the drying purpose can be achieved. For example, the conditions for the drying treatment include: the drying temperature is 30 - 90 °C, and the drying time is 6 - 24 h.
[0099] In addition, preferably, the drying is carried out under vacuum.
[0100] The preparation method of the coated catalyst for synthesizing carbon nanotubes provided in the first aspect of the present invention is very simple. It abandons the processes such as coating and calcining of metal salt solutions that are difficult to control in the prior art. By first modifying the metal precursor to obtain metal nanoparticles with controllable sizes and capable of being uniformly dispersed in the oily solvent, and then using the obtained oil-phase nano-dispersion for coating, the dispersion degree of the active metal can be significantly improved and the coating amount can be controlled.
[0101] Moreover, in the present invention, by first performing the reduction treatment on the metal precursor as described in step 1), the reduction treatment effect can be ensured, and the performance of the catalyst is significantly improved compared with the methods of salt solution coating, calcining and reducing in the prior art.
[0102] The second aspect of the present invention provides a coated catalyst for synthesizing carbon nanotubes prepared by the method described in the first aspect above.
[0103] According to the second aspect of the present invention, in the coated catalyst of the obtained synthesized carbon nanotubes, the active components on the substrate are uniformly distributed, and the active components have all undergone sufficient and consistent modification treatments, so that the catalytic activity of the coated catalyst of the obtained synthesized carbon nanotubes is stable and uniform, the morphology is controllable during the preparation process, and the size of the active metal particles can also be artificially controlled in the modification treatment step of step 1). Moreover, the coating structure can also be adjusted through the coating treatment of step 3). Therefore, compared with the existing coated catalysts for synthesizing carbon nanotubes, its stability and activity are both significantly improved, which is very conducive to the efficient and high-yield synthesis of carbon nanotubes.
[0104] The third aspect of the present invention provides a method for synthesizing carbon nanotubes, wherein the method uses the coated catalyst for synthesizing carbon nanotubes described in the second aspect of the present invention.
[0105] As described above, the coated catalyst for synthesizing carbon nanotubes provided in the second aspect of the present invention has a uniform and controllable morphology and strong adhesion of the active metal particles on the substrate. Therefore, when the catalyst is used for synthesizing carbon nanotubes, it can be designed into various three-dimensional structures for use, thereby improving the synthesis efficiency of carbon nanotubes in the unit reactor space.
[0106] In the present invention, the method for synthesizing carbon nanotubes can be carried out by various conventional methods in the art. Except that the coated catalyst for synthesizing carbon nanotubes is the coated catalyst for synthesizing carbon nanotubes provided in the second aspect of the present invention, other steps can adopt the well-known methods in the art.
[0107] According to a preferred embodiment of the present invention, the method for synthesizing carbon nanotubes includes: carrying out a catalytic reaction between a carbon source gas and the coated catalyst for synthesizing carbon nanotubes in the presence of an inert gas.
[0108] In addition, preferably, the conditions of the catalytic reaction include: the temperature is 500 - 900 °C, and the time is 0.5 - 3 h.
[0109] Furthermore, the carbon source gas is not particularly limited. For example, it can be one or more of methane, ethylene, acetylene, ethanol, and propylene; preferably ethylene and / or propylene.
[0110] The inert gas can be, for example, nitrogen.
[0111] In the present invention, the flow rate of the carbon source gas can be determined according to the usage amount of the coated catalyst for synthesizing carbon nanotubes. Preferably, with respect to 0.01 g of the coated catalyst for synthesizing carbon nanotubes in terms of metal nanoparticles, the flow rate of the carbon source gas is 100 - 1000 mL / min. By carrying out the reaction within the above catalyst usage range, the synthesis efficiency of carbon nanotubes can be further improved, the waste of the carbon source gas can be reduced, and the energy consumption can be lowered.
[0112] By using the coated catalyst for synthesizing carbon nanotubes provided by the present invention and adopting the method provided by the third aspect of the present invention to prepare carbon nanotubes, the yield and quality of the prepared carbon nanotubes can be significantly improved.
[0113] The present invention will be described in detail below through preparation examples and implementation examples.
[0114] In the following preparation examples, the size of the substrate silicon wafer used is 20 mm × 40 mm, and the thickness is 1 mm.
[0115] After the oil-phase nano-dispersion prepared in the following preparation examples is allowed to stand for 24 h and observed by transmission electron microscopy (TEM), it is confirmed to be monodisperse metal nanoparticles.
[0116] Preparation Examples 1 - 3
[0117] 1) Modification treatment:
[0118] The modifier and the metal precursor are added to 100 mL of dioctyl ether, and the reaction is carried out under nitrogen protection. After that, centrifugation is carried out to obtain a solid phase, and the obtained solid phase is washed 5 times with distilled water to obtain modified metal nanoparticles;
[0119] 2) Dispersion treatment:
[0120] The modified metal nanoparticles obtained in step 1) are mixed with toluene and stirred evenly. Among them, with respect to 1 g of the modified metal nanoparticles, the usage amount of toluene used is 1000 mL to obtain an oil-phase nano-dispersion;
[0121] 3) Coating and drying:
[0122] The oil-phase nano-dispersion prepared by the method described in step 2) is coated on the washed silicon wafer by spin coating. Among them, in terms of metal nanoparticles, the coating amount is 0.1 mg / cm 2 , and the coated silicon wafer is vacuum dried at 60 °C for 10 hours to obtain the coated catalysts C1 - C3 for synthesizing carbon nanotubes.
[0123] The specific parameters of Preparation Examples 1 - 3 are shown in Table 1 below:
[0124] Table 1
[0125]
[0126]
[0127] Preparation Example 4
[0128] The method of Preparation Example 1 was followed, except that
[0129] in step 1), the precursor was replaced with Co in the same molar amount 2 (CO) 8 and Mo(CO) 6 (i.e., the total molar amount of (Co 2 (CO) 8 and Mo(CO) 6 used in Preparation Example 4 was the same as the molar amount of Co 2 (CO) 8 in Preparation Example 1), with a Co:Mo molar ratio of 1:0.15, and the particle size of the obtained nano metal particles was 3.6 nm.
[0130] Catalyst C4 was obtained.
[0131] Preparation Example 5
[0132] The method of Preparation Example 1 was followed, except that
[0133] in step 2), oleylamine was further added to the oil-phase nano dispersion, and the addition amount of oleylamine was 200 mg relative to 1 L of the oil-phase nano dispersion.
[0134] Catalyst C5 was obtained.
[0135] Preparation Example 6
[0136] The method of Example 1 was followed, except that
[0137] in step 1), the contact conditions included: the contact temperature was 210 °C and the contact time was 2 h.
[0138] The particle size of the obtained nano metal particles was 5.8 nm.
[0139] Catalyst C6 was obtained.
[0140] Comparative Preparation Example 1
[0141] 1) 20 mmol of Co 2 (CO) 8 was dissolved in 100 mL of dioctyl ether to obtain a coating solution, where, relative to 100 mL of dioctyl ether, Co 2 (CO) 8The dosage of
[0142] 2) The coating solution prepared by the method described in step 1) was spin-coated on the washed silicon wafer by the spin-coating method described in step 3) of Example 1, so that the coating amount was 0.1 mg / cm 2 , and the coated silicon wafer was vacuum dried at 60 °C for 10 hours;
[0143] 3) The coated catalyst supported on the silicon wafer was reduced in a gas stream of 600 standard cubic centimeters per minute of argon and 400 standard cubic centimeters per minute of hydrogen at 800 °C for 5 minutes, and then naturally cooled to 25 °C.
[0144] Catalyst D1 was obtained.
[0145] Example
[0146] 1) The porcelain boat containing the coated catalyst for synthesizing carbon nanotubes was transferred into a CVD tube furnace, the temperature in the furnace was set to 700 °C, the heating rate was 20 °C / min, and at the same time, nitrogen was purged with a nitrogen flow rate of 700 mL / min;
[0147] 2) After the temperature was raised to 700 °C, the nitrogen flow rate was reduced to 300 mL / min, and ethylene gas was introduced. The flow rate of the ethylene gas was 300 mL / min, and the reaction was carried out for 0.5 h;
[0148] 3) After the reaction was completed, the ethylene gas was turned off, and nitrogen was continuously introduced for cooling with a flow rate of 700 mL / min. After the temperature was cooled to 25 °C, all gases were turned off, the carbon nanotubes were collected, and the mass of the obtained carbon nanotubes was weighed.
[0149] According to the above method, catalysts C1-C6 and D1 prepared by Preparation Examples 1-6 and Comparative Preparation Example 1 were respectively used for carbon nanotube synthesis.
[0150] The yield of the carbon nanotubes prepared by each catalyst (that is, the mass of the obtained carbon nanotubes relative to 1 g of the catalyst (calculated based on the metal therein)) was calculated, and the results are shown in Table 2 below:
[0151] Table 2
[0152] Catalyst C1 C2 C3 C4 C5 C6 D1 Yield of carbon nanotubes 14.2 11.8 12.5 18.4 18.1 9.2 6.2
[0153] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.
Claims
1. A method for preparing a coated catalyst for synthesizing carbon nanotubes, It is characterized in that The method comprises the following steps: 1) contacting a metal precursor with a modifier in the presence of a first solvent to obtain modified metal nanoparticles; 2) dispersing the modified metal nanoparticles in an oily solvent to obtain an oil phase nanodispersion; 3) coating the oil phase nanodispersion on a substrate and performing a drying process.
2. The preparation method according to claim 1, in, In step 1), the modifier is one or more of oleic acid, linoleic acid, caprylic acid, capric acid, lauric acid, myristic acid, stearic acid, oleylamine behenate, stearylamine and a silane coupling agent, preferably one or more of oleylamine, oleic acid and a silane coupling agent; Preferably, the first solvent is one or more of dioctyl ether, benzene, toluene, cyclohexane, n-hexane, ethyl acetate, acetone, benzyl alcohol and tetrahydrofuran, more preferably dioctyl ether and / or benzyl alcohol; Preferably, the metal precursor is a salt and / or complex selected from one or more of Fe, Co, Mo, Ni, Cu, Ag, Au, Ru, Rh, Pd and Pt, more preferably a complex of one or more of Fe, Co, Mo, Ni, Cu, Ag, Au, Ru, Rh, Pd and Pt; More preferred is a complex of Co and Mo.
3. The preparation method according to claim 1 or 2, in, In step 1), preferably, the weight ratio of the metal precursor to the first solvent is 1:100-1000; preferably 1:200-500; Preferably, the molar ratio of the metal precursor to the modifier is 1:0.1-10; preferably 1:0.5-5; Preferably, the contacting conditions include: temperature of 120-300°C and time of 0.2-3h; Preferably, the contacting is carried out under stirring.
4. The preparation method according to any one of claims 1 to 3, in, The modified metal nanoparticles are one or more of Fe, Co, Mo, Ni, Cu, Ag, Au, Ru, Rh, Pd and Pt; Preferably, the modified metal nanoparticles are a combination of Co and Mo; more preferably, the molar ratio of Co to Mo is 1:0.05-2, and further preferably 1:0.1-0.3; Preferably, the particle size of the modified metal nanoparticles is 1-50 nm, more preferably 1-10 nm.
5. The preparation method according to any one of claims 1 to 3, in, In step 2), the oily solvent is one or more of dioctyl ether, benzene, toluene, cyclohexane, n-hexane, ethyl acetate, acetone and tetrahydrofuran; Preferably, relative to 1 g of the modified metal nanoparticles, the amount of the oily solvent used is 100-10000 mL, more preferably 500-3000 mL.
6. The preparation method according to any one of claims 1 to 3, in, In step 2), a dispersant and / or a film-forming agent is further added to the oil phase nanodispersion; Preferably, the dispersant is one or more of oleic acid, linoleic acid, caprylic acid, capric acid, lauric acid, myristic acid, stearic acid, oleyl behenate, stearylamine and a silane coupling agent; Preferably, the film-forming agent is one or more of polyvinyl formal, polyvinyl acetal, polyvinyl butyral, polyvinyl alcohol, collodion, zein, sodium carboxymethyl cellulose and polyvinyl pyrrolidone; Preferably, the weight ratio of the modified metal nanoparticles to the dispersant is 1:0.01-10; Preferably, the weight ratio of the modified metal nanoparticles to the film-forming agent is 1:0.01-10.
7. The preparation method according to any one of claims 1 to 3, in, In step 3), the material of the substrate is selected from one or more of single crystal silicon, silicon dioxide, diamond, zirconium oxide, aluminum oxide, magnesium oxide, titanium dioxide, quartz, glass, silicon carbide, silicon nitride, iron, stainless steel, titanium and molybdenum; Preferably, the material of the substrate is selected from one or more of single crystal silicon, silicon dioxide and aluminum oxide; Preferably, the coating amount is 0.01-10 mg / cm 2 , more preferably 0.01-20 mg / cm 2 ; Preferably, the drying conditions include: drying temperature of 30-90° C., and drying time of 6-24 h.
8. A coated catalyst for synthesizing carbon nanotubes prepared by the method according to any one of claims 1 to 7.
9. A method for synthesizing carbon nanotubes, It is characterized in that The method is carried out using the coated catalyst for synthesizing carbon nanotubes as claimed in claim 8.
10. The method for synthesizing carbon nanotubes according to claim 9, in, The method comprises: In the presence of an inert gas, catalytically reacting a carbon source gas with the coated catalyst for synthesizing carbon nanotubes; Preferably, the conditions of the catalytic reaction include: temperature of 500-900°C and time of 0.5-3h; Preferably, the carbon source gas is selected from one or more of methane, ethylene, acetylene, ethanol and propylene; Preferably, the amount of the carbon source gas introduced is 100-1000 mL / min relative to 0.01 g of the coated catalyst for synthesizing carbon nanotubes in terms of metal nanoparticles.