Method for preparing multi-walled carbon nanotubes from carbon monoxide
By using carbon monoxide as the carbon source under the action of metal composite catalyst, the reaction temperature is reduced, and the multi-wall carbon nanotubes are prepared by chemical vapor deposition method, which solves the problems of high equipment requirements, large energy consumption and insufficient yield in the prior art, and achieves high yield and low cost multi-wall carbon nanotube preparation.
Patent Information
- Application Number
- CN202311442436.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-01
- Publication Date
- 2025-05-06
AI Technical Summary
In the prior art, when preparing multi-wall carbon nanotubes, the equipment requirements are high, the energy consumption is high, the cost is high, and the yield is not enough to meet industrial needs.
Carbon monoxide is used as the carbon source, and under the action of metal composite catalysts (such as Co and Mo), the reaction temperature is reduced to below 800°C, and multi-walled carbon nanotubes are prepared by chemical vapor deposition.
It effectively reduces equipment requirements and energy consumption, significantly improves the yield of multi-wall carbon nanotubes, up to 500%, reduces production costs, and meets the needs of industrial production.
Smart Images
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of carbon nanotube preparation, and in particular relates to a method for preparing multi-walled carbon nanotubes by using carbon monoxide. Background Art
[0002] Carbon nanotubes are one-dimensional nanomaterials with a hollow tubular structure. They can be divided into single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) according to the number of curled tube wall layers. Single-walled carbon nanotubes are composed of a single graphite sheet seamlessly wrapped in a cylindrical tube, while multi-walled carbon nanotubes are formed by concentric nesting of multiple single-walled carbon nanotubes. Among them, multi-walled carbon nanotubes have electrical conductivity, thermal conductivity, strength, toughness, stiffness and other properties far exceeding those of ordinary materials. Therefore, they are widely studied in the fields of conductive and high-strength composite materials, energy storage and conversion devices, sensors, field emission displays and radiation sources, hydrogen storage media, etc. In particular, there is a large gap in the demand for multi-walled carbon nanotubes in the field of lithium-ion battery positive electrode materials and high-strength composite materials, and it is urgent to develop a process that can prepare multi-walled carbon nanotubes in large quantities and at low cost.
[0003] At present, the methods for preparing multi-walled carbon nanotubes mainly include chemical vapor deposition, laser ablation and arc discharge. Among them, chemical vapor deposition has become the most widely used method because of its simple operation, simple equipment, easy scale-up, continuous production and low cost. Chemical vapor deposition is usually carried out in a high-temperature tube furnace. At a certain temperature, the carbon source is cracked on the catalyst surface to generate carbon nanotubes. Therefore, the quality (degree of graphitization), output, wall number and tube diameter of the carbon nanotube product are jointly determined by the catalyst, carbon source and growth conditions.
[0004] Usually, the reaction temperature needs to be above 800°C when using carbon sources such as methane and ethanol, which has high requirements for equipment and large energy consumption. In addition, the reaction temperature of carbon sources such as ethylene and acetylene is relatively low but the cost is high. Carbon monoxide is a common carbon source for growing carbon nanotubes. Due to its inherent reducibility, the reduction of the catalyst and the growth of carbon tubes can be a continuous process, and there is no need to introduce a reducing gas separately to activate the catalyst. In addition, the bond energy of the carbon-oxygen bond in carbon monoxide is about 1070kJ / mol, and the bond energy of a carbon-hydrogen bond in methane is about 413kJ / mol. The energy consumption required for the cracking of carbon monoxide is less than the energy consumption required for the complete cracking of methane. Therefore, using carbon monoxide as a carbon source is more suitable for preparing large quantities of carbon nanotubes at a lower temperature. However, the preparation temperature of the current production process needs to be further reduced to increase the yield of carbon nanotubes to meet industrial needs. Summary of the invention
[0005] To solve the above problems, the present invention provides a method for preparing multi-walled carbon nanotubes from carbon monoxide. Under the action of a metal composite catalyst, CO is used as a carbon source to prepare multi-walled carbon nanotubes with high yield. The reaction temperature and equipment requirements are effectively reduced, energy is saved, and production costs are reduced. The yield can be as high as 500%, meeting the requirements for expanding production.
[0006] The present invention aims to provide a method for preparing multi-walled carbon nanotubes with carbon monoxide. The method uses carbon monoxide as a carbon source and prepares multi-walled carbon nanotubes in the presence of a catalyst.
[0007] The catalyst is a metal composite catalyst, wherein the metal is selected from one or more of Fe, Co, Ni, Cu, Cr, Mn, Ti, V, Mo, Ru, Pt and Au, preferably selected from one or more of CoNi, CoCu, CoMo and NiCu, and more preferably Co and Mo.
[0008] The preparation temperature of the method is below 800°C, preferably 450-750°C, more preferably 500-700°C, such as 600-700°C.
[0009] The object of the present invention is to provide multi-walled carbon nanotubes prepared by the method for preparing multi-walled carbon nanotubes with carbon monoxide.
[0010] The present invention has the following beneficial effects:
[0011] (1) The method provided in the present invention uses a metal composite catalyst to catalyze the preparation of multi-walled carbon nanotubes, which greatly improves the yield of carbon nanotubes, up to 500%. The increase in yield makes this method promising for promotion and application in actual production.
[0012] (2) The method of preparing multi-walled carbon nanotubes with carbon monoxide in the present invention is carried out at a relatively low growth temperature, such as 500° C., which reduces the equipment requirements, saves energy, and realizes the low-temperature growth preparation of multi-walled carbon nanotubes.
[0013] (3) The present invention achieves high-yield preparation of high-quality multi-walled carbon nanotubes through the development and selection of catalysts under low-flow carbon monoxide, below 800°C, and normal pressure conditions, making the process conditions milder, reducing control requirements and equipment requirements, and being more conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 The scanning electron microscope image, transmission electron microscope image, Raman spectrum and tube wall number distribution diagram of the carbon nanotube I in Example 1 of the present invention are shown;
[0015] Figure 2 The scanning electron microscope image of carbon nanotube II in Example 2 of the present invention is shown;
[0016] Figure 3 The scanning electron microscope image of carbon nanotube III in Example 3 of the present invention is shown;
[0017] Figure 4 The scanning electron microscope image of carbon nanotube IV in comparative example 1 of the present invention is shown;
[0018] Figure 5 The scanning electron microscope image of the carbon nanotube V in Comparative Example 2 of the present invention is shown;
[0019] Figure 6 , Figure 7 , Figure 8 The scanning electron microscope images and transmission electron microscope images of carbon nanotubes VI, carbon nanotubes VII, and carbon nanotubes VIII in Example 4 of the present invention are shown respectively;
[0020] Fig. 9 shows a scanning electron microscope image of carbon nanotube IX in Example 5 of the present invention;
[0021] Fig.10 A scanning electron microscope image of carbon nanotube X in Example 6 of the present invention is shown. DETAILED DESCRIPTION
[0022] The present invention is described in detail below through specific implementation modes, and the characteristics and advantages of the present invention will become clearer and more specific with these descriptions.
[0023] The invention provides a method for preparing multi-walled carbon nanotubes by using carbon monoxide. The method uses carbon monoxide as a carbon source and prepares multi-walled carbon nanotubes in the presence of a catalyst.
[0024] In the method, air in the reactor is first removed by protective gas, the temperature is raised, and then carbon monoxide is introduced to prepare multi-walled carbon nanotubes. The protective gas is selected from gases that do not react with carbon monoxide, carbon nanotubes and catalysts, preferably argon and / or nitrogen, more preferably argon.
[0025] The catalyst is a metal composite catalyst, wherein the metal is selected from one or more of Fe, Co, Ni, Cu, Cr, Mn, Ti, V, Mo, Ru, Pt and Au, preferably selected from one or more of Co and Ni, Co and Mo and Ni and Cu, more preferably Co and Ni, Co and Mo, such as Co and Mo. Multi-walled carbon nanotubes can be prepared using the above catalyst to improve the yield. By using Co and Ni, Co and Mo, especially Co and Mo, and coordinating the process conditions, the yield of multi-walled carbon nanotubes can be greatly improved to obtain high-quality products.
[0026] In the metal composite catalyst, the molar ratio of Co to Mo is 1:0.01 to 1:5, preferably 1:0.1 to 1:2, and more preferably 1:0.1 to 1:0.2. The present invention has been found through a large number of experiments that the molar ratio of Co to Mo has a great influence on the yield of carbon nanotubes. Within the above-mentioned molar ratio range of Co to Mo, the yield can be increased to more than 140%, especially within the range of 1:0.1 to 1:0.2, the yield is increased to more than 300%, and can even reach 500%.
[0027] Preferably, the metal composite catalyst is supported on a metal oxide carrier, and the metal oxide carrier is selected from one or more of the oxides of Mg, Al, Si, Ti, Mn, Ce, La and Zr, preferably one or more of MgO, Al2O3, TiO2 and ZrO2, and more preferably MgO and / or Al2O3.
[0028] More preferably, the metal composite catalyst is supported on a metal oxide support, that is, Co and Mo are supported on MgO and Al2O3 (denoted as CoMo / MgO-Al2O3).
[0029] The molar ratio of the metal component to the metal oxide support is 0.01 to 0.5, preferably 0.1 to 0.3, and more preferably 0.13 to 0.16.
[0030] The preparation temperature of the method is below 800°C, preferably 450-750°C, more preferably 500-700°C, such as 600-700°C. In the present invention, under the action of the metal composite catalyst, the temperature of preparing carbon nanotubes with carbon monoxide as the carbon source is effectively reduced, and high-yield growth can be achieved below 800°C. Under the condition that other conditions remain unchanged, the method of the present invention can obtain a higher yield at 500°C. When the preparation temperature is increased, the yield of carbon nanotubes is first greatly increased and then slightly reduced. Compared with the existing process, the preparation temperature of carbon nanotubes is effectively reduced.
[0031] The carbon monoxide flow rate is 20-1000sccm, preferably 50-400sccm, more preferably 50-200sccm, such as 50-100sccm. By controlling the carbon monoxide flow rate, the carbon nanotube yield can be adjusted and the carbon source gas utilization rate can be improved. Within the above range, the yield can reach more than 300%.
[0032] The carbon monoxide introduction time is 15-65 min, preferably 10-55 min, more preferably 15-30 min.
[0033] Preferably, the method is carried out under normal pressure.
[0034] The present invention also provides multi-walled carbon nanotubes prepared by the method for preparing multi-walled carbon nanotubes with carbon monoxide. The number of walls of the multi-walled carbon nanotubes is 2-14.
[0035] The present invention adopts a chemical vapor deposition method under normal pressure conditions, uses carbon monoxide as a carbon source, and under the action of a metal composite catalyst, especially a CoMo / MgO-Al2O3 catalyst, effectively lowers the growth temperature of carbon nanotubes compared to 800-1100°C in the prior art, reduces equipment requirements, greatly improves the yield, and produces high-quality multi-walled carbon nanotubes, meeting the needs of expanding production, and is expected to be applied in the field of industrial production.
[0036] Example
[0037] Example 1
[0038] Catalyst preparation: The salts of the metal components are dissolved to form a mixed solution, including cobalt nitrate, ammonium molybdate, magnesium nitrate, and aluminum nitrate. The molar ratio of each component is 1:0.2:5:2.5, based on the molar amount of the metal element in the compound. Urea is then added as a precipitant, and the total molar ratio of urea to metal ions is 1:1. The mixed solution is heated at 100°C to precipitate to form a hydroxide. The obtained mixed hydroxide is washed and dried, and then heated at 30°C / min for 10 minutes in an air atmosphere to complete calcination to obtain a catalyst precursor.
[0039] Growth of carbon nanotubes: 20 mg of catalyst precursor powder was placed in a quartz boat, and the quartz boat was placed in the center of a tube furnace. After introducing argon gas to remove the air in the tube, the temperature was raised to 600°C. Under normal pressure, the inert gas was cut into carbon monoxide, and the flow rate was 200 sccm for 30 minutes. Under the action of carbon monoxide, the catalyst precursor was reduced and converted into a catalyst, which was calculated as CoMo / MgO-Al2O3. The introduction of carbon monoxide was stopped, and the quartz boat was taken out after cooling to room temperature to obtain carbon nanotubes I. The yield of carbon nanotubes was measured to be 370% (yield = weight of carbon nanotubes (excluding catalyst) / weight of catalyst). Figure 1 The scanning electron microscope image, transmission electron microscope image, Raman spectrum and tube wall number distribution diagram of carbon nanotube I are shown in Figure 1. Figure 1 It can be seen that the number of carbon nanotube walls is mostly distributed between 3 and 10. In its Raman spectrum, the relative intensities of the G peak and the D peak are relatively high, and the carbon nanotubes are of good quality and high purity.
[0040] Example 2
[0041] Carbon nanotubes II were prepared according to the method for preparing carbon nanotubes I in Example 1, except that the flow rate of carbon monoxide was 50 sccm. The yield of carbon nanotubes was measured to be 500%. Figure 2 This is a scanning electron microscope image of carbon nanotube II.
[0042] Example 3
[0043] Carbon nanotubes III were prepared according to the method for preparing carbon nanotubes I in Example 1, except that during the catalyst preparation process, the molar ratio of cobalt nitrate, ammonium molybdate, magnesium nitrate and aluminum nitrate was 1:0.1:5:2.5, based on the molar amount of the metal elements in the compound. The yield of carbon nanotubes was measured to be 325%. Figure 3 This is a scanning electron microscope image of carbon nanotube III.
[0044] Example 4
[0045] According to the method for preparing carbon nanotube I in Example 1, carbon nanotube VI, carbon nanotube VII and carbon nanotube VIII were grown at 500°C, 550°C and 700°C respectively. The yields after reaction at 500°C, 550°C and 700°C were measured to be 68%, 260% and 350% respectively. Figure 6 , Figure 7 , Figure 8 They are scanning electron microscope images and transmission electron microscope images of carbon nanotube VI, carbon nanotube VII, and carbon nanotube VIII respectively.
[0046] Example 5
[0047] Carbon nanotubes IX were prepared according to the method for preparing carbon nanotubes II in Example 2, except that the flow rate of carbon monoxide was 400 sccm. The yield of carbon nanotubes was measured to be 325%. Fig. 9 This is a scanning electron microscope image of carbon nanotube IX.
[0048] Example 6
[0049] Carbon nanotubes X were prepared according to the method for preparing carbon nanotubes III in Example 3, except that during the catalyst preparation process, the molar ratio of cobalt nitrate, ammonium molybdate, magnesium nitrate and aluminum nitrate was 1:3:5:2.5. The yield of carbon nanotubes was measured to be 146%. Fig.10 This is a scanning electron microscope image of carbon nanotube X.
[0050] Comparative Example
[0051] Comparative Example 1
[0052] The catalyst Ni / MgO-Al2O3 was prepared according to the method in Example 1, except that the metal components used were nickel nitrate, magnesium nitrate and aluminum nitrate, and the molar ratio of the components was 1:5:2.5, calculated based on the molar amount of the metal element in the compound.
[0053] Carbon nanotubes IV were prepared according to the method for preparing carbon nanotubes I in Example 1, except that Ni / MgO-Al2O3 was used as a catalyst. The yield of carbon nanotubes was measured to be 112%. Figure 4 This is a scanning electron microscope image of carbon nanotube IV.
[0054] Comparative Example 2
[0055] The catalyst CoCu / MgO-Al2O3 was prepared according to the method in Example 1, except that the metal components used were cobalt nitrate, copper nitrate, magnesium nitrate and aluminum nitrate, and the molar ratio of the components was 1:1:5:2.5, calculated based on the molar amount of the metal element in the compound.
[0056] Carbon nanotubes V were prepared according to the method for preparing carbon nanotubes I in Example 1, except that CoCu / MgO-Al2O3 was used as a catalyst. The yield of carbon nanotubes was measured to be 15%. Figure 5 This is a scanning electron microscope image of carbon nanotube V.
[0057] The present invention is described in detail above in conjunction with specific embodiments and / or exemplary examples and drawings, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.
Claims
1. A method for preparing multi-walled carbon nanotubes using carbon monoxide, wherein the method uses carbon monoxide as a carbon source and prepares multi-walled carbon nanotubes in the presence of a catalyst at a preparation temperature below 800°C.
2. The method according to claim 1, characterized in that The catalyst is a metal composite catalyst, wherein the metal is selected from one or more of Fe, Co, Ni, Cu, Cr, Mn, Ti, V, Mo, Ru, Pt and Au, preferably selected from one or more of Co and Ni, Co and Mo, and Ni and Cu.
3. The method according to claim 2, characterized in that The metal is selected from Co and Ni or Co and Mo.
4. The method according to claim 2, characterized in that: In the metal composite catalyst, the metals are Co and Mo, and the molar ratio of Co to Mo is 1:0.01 to 1:5, preferably 1:0.1 to 1:
3.
5. The method according to claim 1, characterized in that The metal composite catalyst is supported on a metal oxide carrier, and the metal oxide carrier is selected from one or more of the oxides of Mg, Al, Si, Ti, Mn, Ce, La and Zr, preferably one or more of MgO, Al2O3, TiO2 and ZrO2.
6. The method according to claim 1, characterized in that The preparation temperature of the method is 450-750°C, preferably 500-700°C.
7. The method according to claim 1, characterized in that The carbon monoxide flow rate is 20-1000 sccm, preferably 50-400 sccm.
8. The method according to claim 1, characterized in that The method is carried out under normal pressure.
9. The method according to claim 1, characterized in that: In the method, air in a reactor is firstly removed by using protective gas, the temperature is increased, and then carbon monoxide is introduced to prepare multi-walled carbon nanotubes.
10. The multi-walled carbon nanotubes prepared by the method for preparing multi-walled carbon nanotubes with carbon monoxide according to any one of claims 1 to 9, characterized in that: The number of walls of the multi-walled carbon nanotubes is 2-14.