A method for purifying single-walled carbon nanotubes
By using non-oxidizing acids and bubbles to synergistically purify single-walled carbon nanotubes, the problems of incomplete impurity removal and structural damage in existing technologies are solved, achieving efficient and non-destructive purification results.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHENZHEN XINKAI CARBON ENERGY TECHNOLOGY CO LTD
- Filing Date
- 2026-03-17
- Publication Date
- 2026-06-09
AI Technical Summary
Existing purification methods are difficult to efficiently remove metallic impurities and amorphous carbon from single-walled carbon nanotubes, and they are prone to damaging the carbon nanotube structure.
A non-oxidizing acid and bubble synergistic purification method is adopted. The non-oxidizing acid solution in the heated reaction vessel is mixed with gas to generate a gentle microturbulence, which breaks up the carbon nanotube aggregates, ensuring that each carbon nanotube is in uniform contact with the acid solution, removing impurities, and protecting the carbon nanotube structure at the same time.
It achieves efficient removal of metallic impurities and amorphous carbon, maintains the structural integrity of carbon nanotubes, and avoids excessive oxidative damage.
Smart Images
Figure CN122166766A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of single-walled carbon nanotube technology, and in particular to a method for purifying single-walled carbon nanotubes. Background Technology
[0002] Currently, single-walled carbon nanotubes (SUVs) are mainly prepared via arc discharge, laser evaporation, and catalytic thermal decomposition. In their production, besides large-scale preparation processes, purification is also a crucial step affecting applications. The prepared samples often contain a large number of impurities, primarily carbon impurities (such as graphite particles, carbon nanoparticles, and amorphous carbon) and metallic impurities derived from transition metal catalysts. These impurities severely restrict the performance and applications of SUVs. Therefore, developing efficient purification methods to obtain high-purity SUV products is of great significance.
[0003] Existing purification methods, such as strong acid oxidation and density gradient centrifugation, either have problems with low impurity removal rates or easily damage the single-walled carbon nanotube structure.
[0004] Therefore, there is an urgent need to develop a purification method for single-walled carbon nanotubes that can achieve efficient impurity removal while effectively maintaining the integrity of the carbon nanotube structure. Summary of the Invention
[0005] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the first aspect of the present invention proposes a method for purifying single-walled carbon nanotubes, which can achieve efficient impurity removal while effectively maintaining the structural integrity of the carbon nanotubes.
[0006] A method for purifying single-walled carbon nanotubes according to a first aspect of the present invention includes the following steps: Crude single-walled carbon nanotubes and a non-oxidizing acid solution are mixed in a reaction vessel; gas is introduced into the reaction vessel; the reaction is heated, and solid-liquid separation is achieved.
[0007] According to a preferred embodiment of the present invention, the non-oxidizing acid in the non-oxidizing acid solution includes acetic acid and / or hydrochloric acid.
[0008] According to a preferred embodiment of the present invention, if the non-oxidizing acid in the non-oxidizing acid solution is acetic acid, the concentration of the non-oxidizing acid solution is 8 mol / L to 16 mol / L.
[0009] According to a preferred embodiment of the present invention, if the non-oxidizing acid in the non-oxidizing acid solution is hydrochloric acid, the concentration of the non-oxidizing acid solution is 1 mol / L to 3 mol / L.
[0010] According to a preferred embodiment of the present invention, the volume-to-mass ratio of the non-oxidizing acid solution to the crude single-walled carbon nanotubes is 1 mL: (1~10) g.
[0011] According to a preferred embodiment of the present invention, the gas includes at least one of carbon dioxide, oxygen, or air.
[0012] According to a preferred embodiment of the present invention, the flow rate of the gas is 0.1~1 Nm³. 3 / h.
[0013] According to a preferred embodiment of the present invention, the temperature of the heating reaction is 80°C to 250°C.
[0014] According to a preferred embodiment of the present invention, the heating reaction time is 1h to 12h.
[0015] According to a preferred embodiment of the present invention, the solid-liquid separation step includes filtration, washing, and freeze drying.
[0016] According to a preferred embodiment of the present invention, the crude single-walled carbon nanotubes are prepared by conventional methods, such as arc discharge, laser evaporation, and catalytic thermal decomposition.
[0017] The method for purifying single-walled carbon nanotubes according to embodiments of the present invention has at least the following beneficial effects: This invention uses non-oxidizing acids and bubbles to synergistically purify single-walled carbon nanotubes, which can ensure the effective removal of metallic impurities and amorphous carbon while protecting the single-walled carbon nanotubes from structural damage.
[0018] This is because non-oxidizing acids provide a mild acidic environment to dissolve metal catalysts while causing almost no damage to the bulk structure of single-walled carbon nanotubes. The continuously outputting bubbles generate mild and persistent microturbulence in the liquid. This turbulence effectively breaks up carbon nanotube aggregates, constantly renewing the solid-liquid interface and ensuring that each carbon nanotube is in full contact with the acid, thus achieving uniform mass transfer. The microturbulence generated by the bubbles ensures the uniformity and high efficiency of the reaction, exhibiting excellent removal effects on tightly coated amorphous carbon and metal catalysts.
[0019] Furthermore, when oxygen or air is introduced, under heating or ambient temperature conditions, dissolved oxygen can work with glacial acetic acid to gently oxidize amorphous carbon, converting it into carbon dioxide or soluble oxygen-containing groups, thereby removing it. Carbon dioxide bubbles create an acidic environment and help maintain the inert atmosphere of the system, preventing excessive oxidation.
[0020] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description
[0021] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a SEM image of the crude single-walled carbon nanotubes of the present invention; Figure 2 This is a SEM image of the purified single-walled carbon nanotubes from Example 1 of this invention.
[0022] Figure 3 This is a Tg curve of the crude single-walled carbon nanotubes of the present invention; Figure 4 This is a Tg curve of the purified single-walled carbon nanotubes from Example 1 of the present invention; Figure 5 This is the Raman spectrum of the purified single-walled carbon nanotubes from Example 1 of this invention; Figure 6 This is the Raman spectrum of the purified single-walled carbon nanotubes of Comparative Example 2 of this invention. Detailed Implementation
[0023] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.
[0024] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in this technical field.
[0025] In some embodiments of the present invention, a method for purifying single-walled carbon nanotubes is provided, comprising the following steps: Crude single-walled carbon nanotubes and a non-oxidizing acid solution are mixed in a reaction vessel; gas is introduced into the reaction vessel; the reaction is heated, and solid-liquid separation is achieved.
[0026] It is understood that the present invention uses non-oxidizing acid and bubbles to synergistically purify single-walled carbon nanotubes, which can ensure the effective removal of metallic impurities and amorphous carbon, while protecting the single-walled carbon nanotubes from structural damage.
[0027] This is because non-oxidizing acids provide a mild acidic environment to dissolve metal catalysts while causing almost no damage to the bulk structure of single-walled carbon nanotubes. The continuously outputting bubbles generate mild and persistent microturbulence in the liquid. This turbulence effectively breaks up carbon nanotube aggregates, constantly renewing the solid-liquid interface and ensuring that each carbon nanotube is in full contact with the acid, thus achieving uniform mass transfer. The microturbulence generated by the bubbles ensures the uniformity and high efficiency of the reaction, exhibiting excellent removal effects on tightly coated amorphous carbon and metal catalysts.
[0028] Furthermore, when oxygen or air is introduced, under heating or ambient temperature conditions, dissolved oxygen can work with glacial acetic acid to gently oxidize amorphous carbon, converting it into carbon dioxide or soluble oxygen-containing groups, thereby removing it. Carbon dioxide bubbles create an acidic environment and help maintain the inert atmosphere of the system, preventing excessive oxidation.
[0029] According to a preferred embodiment of the present invention, the non-oxidizing acid in the non-oxidizing acid solution includes acetic acid and / or hydrochloric acid.
[0030] According to a preferred embodiment of the present invention, if the non-oxidizing acid in the non-oxidizing acid solution is acetic acid, the concentration of the non-oxidizing acid solution is 8 mol / L to 16 mol / L. For example, it includes 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L, 12 mol / L, 13 mol / L, 14 mol / L, 15 mol / L, 16 mol / L, or any sub-range consisting of two of the above values.
[0031] Therefore, using acetic acid in this range results in a mild and gentle reaction with metal catalysts, providing a wide process window that does not cause additional damage to carbon nanotubes even with extended soaking times.
[0032] According to a preferred embodiment of the present invention, if the non-oxidizing acid in the non-oxidizing acid solution is hydrochloric acid, the concentration of the non-oxidizing acid solution is 1 mol / L to 3 mol / L. For example, it includes 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, or any sub-range consisting of two of the above values.
[0033] Therefore, it can not only weaken Cl - The intercalation effect is achieved, and 1~3 mol / L dilute hydrochloric acid still has sufficient acidity to effectively dissolve the metal catalyst.
[0034] According to a preferred embodiment of the present invention, the volume-to-mass ratio of the non-oxidizing acid solution to the crude single-walled carbon nanotubes is 1 mL: (1~10) g. For example, this includes sub-ranges of volume-to-mass ratios of 1 mL: 1 g, 1 mL: 2 g, 1 mL: 3 g, 1 mL: 4 g, 1 mL: 5 g, 1 mL: 6 g, 1 mL: 7 g, 1 mL: 8 g, 1 mL: 9 g, 1 mL: 10 g, or any two of the above ratios.
[0035] According to a preferred embodiment of the present invention, the gas includes at least one of carbon dioxide, oxygen, or air.
[0036] According to a preferred embodiment of the present invention, the flow rate of the gas is 0.1~1 Nm³. 3 / h. For example, including 0.1 Nm 3 / h, 0.2 Nm 3 / h, 0.3 Nm 3 / h, 0.4 Nm 3 / h, 0.5 Nm 3 / h, 0.6 Nm 3 / h, 0.7 Nm 3 / h, 0.8 Nm 3 / h, 0.9 Nm 3 / h、1 Nm 3 / h or a subrange consisting of any two of the above values.
[0037] According to a preferred embodiment of the present invention, the flow rate of the gas is 0.5~1 Nm³. 3 / h. For example, including 0.5 Nm 3 / h, 0.6 Nm 3 / h, 0.7 Nm 3 / h, 0.8 Nm 3 / h, 0.9 Nm 3 / h、1 Nm 3 / h or a subrange consisting of any two of the above values.
[0038] According to a preferred embodiment of the present invention, the temperature of the heating reaction is 80°C to 250°C. For example, it includes 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, or any sub-range composed of two of the above values.
[0039] According to a preferred embodiment of the present invention, the heating reaction time is 1h to 12h. For example, it includes 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h or any subrange composed of two of the above values.
[0040] According to a preferred embodiment of the present invention, the solid-liquid separation step includes filtration, washing, and freeze drying.
[0041] According to a preferred embodiment of the present invention, the crude single-walled carbon nanotubes are prepared by conventional methods, such as arc discharge, laser evaporation, and catalytic thermal decomposition.
[0042] In the embodiments and comparative examples of this invention, crude single-walled carbon nanotubes with different metal catalysts can be prepared according to the examples in CN120039867A.
[0043] In the examples and comparative examples, the metal element content was obtained by ICP testing.
[0044] Examples 1-45 Examples 1-45 provide a series of methods for purifying single-walled carbon nanotubes, comprising the following steps: 50.0 g of crude single-walled carbon nanotubes were placed in an acid-resistant reactor, and 5000 mL of 80% glacial acetic acid solution was added. Gas was continuously introduced through a one-way valve from the side of the reactor, and the acid-resistant reactor was heated to 130 °C. During the reaction, bubbles were observed to rise uniformly, and the system remained in a uniform suspension. After the reaction, the mixture was filtered, washed repeatedly with deionized water until the filtrate was neutral, and the filter cake was placed in a freeze-drying oven and dried for 20 hours to obtain the purified sample. The different purification conditions are shown in Table 1.
[0045] Comparative Example 1 Comparative Example 1 provides a method for purifying single-walled carbon nanotubes, comprising the following steps: 50.0 g of crude single-walled carbon nanotubes were placed in an acid-resistant reactor, and 5000 mL of 80% glacial acetic acid solution was added. The reactor was heated to 130 °C. After the reaction was complete, the mixture was filtered and repeatedly washed with deionized water until the filtrate was neutral. The filter cake was then dried in a freeze-drying oven for 20 hours to obtain the purified sample. The different purification conditions are shown in Table 1.
[0046] Comparative Example 2 Comparative Example 1 provides a method for purifying single-walled carbon nanotubes, comprising the following steps: 50.0 g of crude single-walled carbon nanotubes were placed in an acid-resistant reactor, and 5000 mL of 50% dilute nitric acid solution was added. Gas was continuously introduced through a one-way valve from the side of the reactor, and the acid-resistant reactor was heated to 130°C. During the reaction, bubbles were observed to rise uniformly, and the system remained in a uniform suspension. After the reaction, the mixture was filtered, washed repeatedly with deionized water until the filtrate was neutral, and the filter cake was placed in a freeze-drying oven and dried for 20 hours to obtain the purified sample. The different purification conditions are shown in Table 1.
[0047] Table 1
[0048] As can be seen from Examples 1 to 45, the purification method of the present invention can effectively remove different types of metal catalysts.
[0049] Furthermore, the SEM images of the crude single-walled carbon nanotubes prepared in this invention and the SEM images of the purified single-walled carbon nanotube samples from Example 1 are shown below. Figure 1 and Figure 2 As shown, Figure 1 As can be seen, the carbon nanotubes contain many bright and dark speckled metallic catalysts and amorphous carbon. After purification... Figure 2 Carbon nanotubes are clearly visible, and the metal catalyst and amorphous carbon are removed.
[0050] Furthermore, the SEM images of the crude single-walled carbon nanotubes prepared in this invention and the Tg curves of the purified single-walled carbon nanotube sample from Example 1 are shown below. Figure 3 and Figure 4 As shown, Figure 3 As can be seen, weight loss begins as early as 300℃, which is the weight loss temperature of amorphous carbon. After purification... Figure 4 The weight loss temperature starts at 500℃, indicating that amorphous carbon has been effectively removed.
[0051] Furthermore, the purified single-walled carbon nanotubes from Example 1 of this invention were subjected to Raman spectroscopy, and the results are as follows: Figure 5 As shown, the Raman data after purification shows an extremely low D peak, indicating that the carbon nanotubes are intact and have not been damaged during purification.
[0052] Furthermore, Raman spectroscopy was performed on the purified single-walled carbon nanotubes of Example 2, and the results are as follows: Figure 6 As shown, the D peak in the purified Raman data increased, indicating that the purification process was damaged.
[0053] The present invention has been described in detail above with reference to the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.
Claims
1. A method for purifying single-walled carbon nanotubes, characterized in that, Includes the following steps: Crude single-walled carbon nanotubes and a non-oxidizing acid solution are mixed in a reaction vessel; gas is introduced into the reaction vessel; the reaction is heated, and solid-liquid separation is achieved.
2. The method for purifying single-walled carbon nanotubes according to claim 1, characterized in that, The non-oxidizing acids in the non-oxidizing acid solution include acetic acid and / or hydrochloric acid.
3. The method for purifying single-walled carbon nanotubes according to claim 1, characterized in that, If the non-oxidizing acid in the non-oxidizing acid solution is acetic acid, the concentration of the non-oxidizing acid solution is 8 mol / L to 16 mol / L.
4. The method for purifying single-walled carbon nanotubes according to claim 1, characterized in that, If the non-oxidizing acid in the non-oxidizing acid solution is hydrochloric acid, the concentration of the non-oxidizing acid solution is 1 mol / L to 3 mol / L.
5. The method for purifying single-walled carbon nanotubes according to claim 1, characterized in that, The volume-to-mass ratio of the non-oxidizing acid solution to the crude single-walled carbon nanotubes is 1 mL: (1~10) g.
6. The method for purifying single-walled carbon nanotubes according to claim 1, characterized in that, The gas includes at least one of carbon dioxide, oxygen, or air.
7. The method for purifying single-walled carbon nanotubes according to claim 1, characterized in that, The flow rate of the gas is 0.1~1 Nm³. 3 / h.
8. The method for purifying single-walled carbon nanotubes according to claim 1, characterized in that, The temperature of the heating reaction is 80℃~250℃.
9. The method for purifying single-walled carbon nanotubes according to claim 1, characterized in that, The heating reaction time is 1h to 12h.
10. The method for purifying single-walled carbon nanotubes according to claim 1, characterized in that, The solid-liquid separation steps include filtration, washing, and freeze drying.