Carbon nanocage, preparation method and application thereof

Abstract

The present application relates to a kind of carbon nanocage and its preparation method and application, the preparation method includes the following steps: (1) magnesium salt and carbonate are mixed to be reacted, obtain basic magnesium carbonate;(2) the basic magnesium carbonate of step (1) and polyaniline are mixed pyrolysis, then acid treatment is carried out, obtain the carbon nanocage.The carbon nanocage prepared by the present application has high specific surface area, rich defect surface and hierarchical pore structure, and can be used in cigarette filter, and high reduction rate to phenol is realized at very low addition amount (1.2 mg / branch).

Description

Technical Field

[0001] This invention relates to the field of carbon materials and cigarette harm reduction technology, and in particular to a carbon nanocage, its preparation method and application. Background Technology

[0002] Smoking poses a serious threat to human health. Besides nicotine, the main components of cigarette smoke contain thousands of compounds. Among them, phenol, benzo[a]pyrene (B[a]P), and aldehydes and ketones are highly toxic and carcinogenic. Reducing the phenol content in cigarettes is of great significance to the health of smokers.

[0003] Adding adsorbents to cigarette filters is an effective and convenient way to reduce harmful substances in mainstream cigarette smoke. Commonly used adsorbents include activated carbon, zeolite, carbon nanotubes, and graphene, but each has its own limitations: activated carbon has insufficient macropores, which is not conducive to the rapid passage of smoke; carbon nanotubes have limited specific surface area and low adsorption capacity; graphene sheets tend to stack, leading to a decrease in effective adsorption area, etc.

[0004] Therefore, developing a carbon-based adsorbent material with high specific surface area, multi-level porous structure, and nitrogen doping to specifically reduce the content of harmful substances such as phenol in mainstream cigarette smoke has significant social and application value. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a carbon nanocage, its preparation method, and its applications. The carbon nanocage prepared by this invention possesses a high specific surface area, a surface rich in defects, and a hierarchical pore structure, and can be used in cigarette filter rods to achieve a high reduction rate of p-phenol at extremely low addition levels (1.2 mg / cigarette).

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing carbon nanocages, the method comprising the following steps: (1) Mix magnesium salt and carbonate to react and obtain basic magnesium carbonate; (2) The basic magnesium carbonate and polyaniline from step (1) are mixed and pyrolyzed, and then acid-treated to obtain the carbon nanocage.

[0007] This invention first prepares basic magnesium carbonate as a template material, then uses polyaniline as a carbon source for pyrolysis. The nitrogen-doped carbon generated from the pyrolysis of polyaniline coats the surface of the in-situ generated magnesium oxide particles. Acid treatment is then performed to remove the template, yielding nitrogen-doped carbon nanocages. The resulting carbon nanocages possess a mesoscopic structure, high specific surface area, and a surface rich in nitrogen heteroatoms, facilitating the rapid passage of flue gas. They are particularly suitable for the adsorption of phenol in flue gas, and the phenol component interacts well with the surface of the carbon nanocages. - They have strong interactions, effectively avoiding secondary poisoning caused by desorption.

[0008] Preferably, the nitrogen content of the carbon nanocage is 3-8 at% (for example, it can be 3 at%, 4 at%, 5 at%, 6 at%, 7 at%, 8 at%, etc.).

[0009] Preferably, the magnesium salt in step (1) includes any one or a combination of at least two of magnesium sulfate, magnesium nitrate, magnesium citrate or magnesium chloride.

[0010] Preferably, the carbonate in step (1) includes any one or a combination of at least two of sodium carbonate, sodium bicarbonate, potassium carbonate, or potassium bicarbonate.

[0011] Preferably, the reaction in step (1) is carried out in a reaction tube.

[0012] Preferably, the diameter of the reaction tube is 2-20 mm (e.g., 2 mm, 5 mm, 10 mm, 15 mm, 20 mm, etc.).

[0013] Preferably, the reaction in step (1) specifically includes: mixing an aqueous solution of magnesium salt and an aqueous solution of carbonate in a reaction tube, and obtaining basic magnesium carbonate after the reaction.

[0014] In this invention, a peristaltic pump can be used to deliver aqueous solutions of magnesium salts and carbonates. The reaction time can be controlled by changing the peristaltic pump rate and the reaction tube length. The reaction in the reaction tube yields a porous, micron-sized spherical basic magnesium carbonate template assembled from nanosheets. This method allows for continuous preparation with good product morphology consistency. Carbon nanocages prepared using this template exhibit better adsorption performance for phenol.

[0015] Preferably, the concentrations of the aqueous solutions of the magnesium salt and the carbonate are each independently 0.05-0.3M (e.g., 0.05M, 0.1M, 0.15M, 0.2M, 0.3M, etc.).

[0016] Preferably, the reaction temperature is 60-90℃ (e.g., 60℃, 65℃, 70℃, 80℃, 85℃, 90℃, etc.), and the time is 0.5-4h (e.g., 0.5h, 1h, 2h, 3h, 4h, etc.).

[0017] In this invention, by controlling a higher reaction temperature, compared to a reaction at room temperature (25°C), a hierarchical porous structure with a complete structure can be obtained, which is more conducive to the contact between carbon nanocages and flue gas and the full adsorption of phenol.

[0018] Preferably, the mass ratio of basic magnesium carbonate and polyaniline in step (2) is 1:0.5-5.0 (for example, it can be 1:0.5, 1:2, 1:4, 1:5, etc.).

[0019] In this invention, the specific surface area (400-1200 m²) of the obtained carbon nanocages can be controlled by changing the amount of polyaniline used. 2 If the amount of polyaniline is too low, the yield of carbon nanocages will be low and the nanocage structure will be incomplete; if the amount is too high, the specific surface area of ​​the carbon nanocages will be small, which is not conducive to the full adsorption of phenol.

[0020] Preferably, the weight-average molecular weight of the polyaniline in step (2) is 10,000-100,000 (e.g., 10,000, 20,000, 50,000, 80,000, 100,000, etc.).

[0021] Preferably, the mixing in step (2) specifically includes: dispersing basic magnesium carbonate and polyaniline in a solvent, and then removing the solvent by stirring and evaporation to obtain a mixture of basic magnesium carbonate and polyaniline.

[0022] Preferably, the solvent includes any one or a combination of at least two of water, ethanol, acetone or isopropanol.

[0023] Preferably, the pyrolysis in step (2) includes: heating to 600-800℃ (e.g., 600℃, 650℃, 700℃, 750℃, 800℃, etc.) at a rate of 1-10℃ / min (e.g., 1℃ / min, 5℃ / min, 8℃ / min, 10℃ / min, etc.) and holding at that temperature for 2-4h (e.g., 2h, 2.5h, 3h, 3.5h, 4h, etc.).

[0024] In this invention, when the pyrolysis temperature is too low, the polyaniline is not completely pyrolyzed, which affects the adsorption effect; when the temperature is too high, the pyrolysis of polyaniline leads to low carbon deposition and incomplete nanocage morphology. Within the above specific range, the adsorption effect of the obtained carbon nanocage can be improved.

[0025] Preferably, the pyrolysis in step (2) is carried out under a protective atmosphere, preferably any one or a combination of nitrogen or argon.

[0026] In a second aspect, the present invention provides a carbon nanocage, which is prepared according to the carbon nanocage preparation method described in the first aspect.

[0027] Thirdly, the present invention provides an application of the carbon nanocage described in the second aspect in reducing phenol in mainstream cigarette smoke.

[0028] Fourthly, the present invention provides a filter rod for adsorbing phenol in mainstream cigarette smoke, wherein the filter rod contains the carbon nanocage described in the second aspect.

[0029] Preferably, the amount of carbon nanocages added to the filter rod is 0.2-5 mg / rod (e.g., 0.2 mg / rod, 0.5 mg / rod, 1 mg / rod, 1.5 mg / rod, 2 mg / rod, 5 mg / rod, etc.), and more preferably 0.6-2 mg / rod.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects: The nitrogen-doped carbon nanocage material provided by this invention has a high specific surface area, a defect-rich surface, and a hierarchical porous structure. It has excellent permeability to smoke and abundant adsorption sites. It can be used in cigarette filter rods to achieve a high reduction rate of phenol at an extremely low addition amount (1.2 mg / cigarette), and its performance is superior to that of traditional adsorbents. Attached Figure Description

[0031] Figure 1 This is a diagram of the reaction apparatus for step (1) of Example 1.

[0032] Figure 2 This is a SEM image (magnification 5,000) of the carbon nanocages obtained in Example 1.

[0033] Figure 3 This is a SEM image (magnification 20,000) of the carbon nanocage obtained in Example 1.

[0034] Figure 4 This is a TEM image of the carbon nanocage obtained in Example 1.

[0035] Figure 5 This is the N2 adsorption-desorption isotherm diagram of the carbon nanocage obtained in Example 1.

[0036] Figure 6 This is the XPS spectrum of the carbon nanocage obtained in Example 1.

[0037] Figure 7 This is a schematic diagram of the filter rod filled with carbon nanocages in Test Example 2. Detailed Implementation

[0038] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0039] The polyaniline used in the following examples and comparative examples was purchased from Aladdin, with a weight-average molecular weight of 80,000; polydopamine was purchased from Xi'an Ruixi Biotechnology, with a weight-average molecular weight of 7,000; and polypyrrole was purchased from Maclean, with a weight-average molecular weight of 15,000.

[0040] The diameter of the reaction tube is 10 mm.

[0041] Example 1 This embodiment provides a method for preparing carbon nanocages, the method comprising the following steps: (1) Prepare 2000 mL of 0.2 M MgSO4 aqueous solution and 2000 mL of 0.2 M Na2CO3 aqueous solution respectively. Pump them out separately using a peristaltic pump and mix them at a three-way valve before flowing into the reaction tube. Place the reaction tube in a 75℃ water bath. After the two solutions are mixed in the reaction tube, a white precipitate is formed. The reaction time is controlled to 1 hour by adjusting the pumping speed of the peristaltic pump. The reaction solution flows out from the end of the reaction tube. After filtration, washing with water, and drying, basic magnesium carbonate is obtained. The reaction apparatus is as follows: Figure 1 As shown; (2) The basic magnesium carbonate and polyaniline from step (1) are mixed in a mass ratio of 1:3 and dispersed in an ethanol solvent. The solvent is removed by evaporation under stirring. The resulting powder mixture is placed in a tube furnace and heated to 700°C at a rate of 5°C / min in a N2 atmosphere. After holding at this temperature for 3 hours, it is cooled and then placed in a hydrochloric acid aqueous solution (1.0M) to remove the basic magnesium carbonate. After filtration, washing with water and drying, carbon nanocages are obtained.

[0042] Example 2 This embodiment provides a method for preparing carbon nanocages, the method comprising the following steps: (1) Prepare 2000 mL of 0.05 M Mg(NO3)2 aqueous solution and 2000 mL of 0.05 M K2CO3 aqueous solution respectively. Draw them out with a peristaltic pump and mix them at the three-way valve into the reaction tube. Place the reaction tube in a 60℃ water bath. After the two solutions are mixed in the reaction tube, they react to form a white precipitate. The reaction time is controlled to be 3 hours by adjusting the pumping speed of the peristaltic pump. The reaction solution flows out from the end of the reaction tube. After filtration, washing with water and drying, basic magnesium carbonate is obtained. (2) The basic magnesium carbonate and polyaniline from step (1) are mixed at a mass ratio of 1:5 and dispersed in acetone solvent. The solvent is removed by evaporation under stirring. The resulting powder mixture is placed in a tube furnace and heated to 600°C at a rate of 10°C / min in N2 atmosphere. After holding at this temperature for 4 hours, it is cooled and then placed in hydrochloric acid aqueous solution (0.5M) to remove the basic magnesium carbonate. After filtration, washing with water and drying, carbon nanocages are obtained.

[0043] Example 3 This embodiment provides a method for preparing carbon nanocages, the method comprising the following steps: (1) Prepare 2000 mL of 0.3 M MgCl2 aqueous solution and 2000 mL of 0.3 M Na2CO3 aqueous solution respectively. Draw them out with a peristaltic pump and mix them at the three-way valve into the reaction tube. Place the reaction tube in a 90℃ water bath. After the two solutions are mixed in the reaction tube, they react to form a white precipitate. The reaction time is controlled to be 0.5 hours by adjusting the pumping speed of the peristaltic pump. The reaction solution flows out from the end of the reaction tube. After filtration, washing with water and drying, basic magnesium carbonate is obtained. (2) The basic magnesium carbonate and polyaniline from step (1) are mixed in a mass ratio of 1:1 and dispersed in an aqueous solvent. The solvent is removed by evaporation under stirring. The resulting powder mixture is placed in a tube furnace and heated to 800°C at a rate of 4°C / min in a N2 atmosphere. After holding at this temperature for 2 hours, the mixture is cooled and then placed in a hydrochloric acid aqueous solution (2M) to remove the basic magnesium carbonate. After filtration, washing with water and drying, carbon nanocages are obtained.

[0044] Example 4 This embodiment provides a method for preparing carbon nanocages. The difference between the preparation method and that in Example 1 is that in step (1), 4000 mL of water is placed in a flask and heated to 75°C. MgSO4 and Na2CO3 are added at a concentration of 0.1 M respectively. The mixture is reacted in the flask for 1 hour. After filtration, washing with water and drying, basic magnesium carbonate is obtained. The operation in step (2) remains unchanged.

[0045] Example 5 This embodiment provides a method for preparing carbon nanocages. The only difference between this method and Example 1 is that the mass ratio of basic magnesium carbonate and polyaniline in step (2) is changed to 1:8, while other operations remain unchanged.

[0046] Example 6 This embodiment provides a method for preparing carbon nanocages. The only difference between this method and Example 1 is that the mass ratio of basic magnesium carbonate and polyaniline in step (2) is changed to 1:0.2, while other operations remain unchanged.

[0047] Example 7 This embodiment provides a method for preparing carbon nanocages. The only difference between this method and that in Example 1 is that in step (2), the temperature is raised to 500°C and held for 3 hours, while other operations remain unchanged.

[0048] Example 8 This embodiment provides a method for preparing carbon nanocages. The only difference between this method and that in Example 1 is that in step (2), the temperature is raised to 900°C and held for 3 hours, while other operations remain unchanged.

[0049] Comparative Example 1 This comparative example provides a method for preparing carbon nanocages. The difference between the preparation method and Example 1 is that step (1) prepares MgO nanoparticles as templates for step (2) preparing carbon nanocages. MgO nanoparticles were purchased from Maclean, M824207-100g, 99%; Step (2) remains unchanged.

[0050] Comparative Example 2 This comparative example provides a method for preparing carbon nanocages. The only difference between this method and Example 1 is that in step (2), polyaniline is replaced with polydopamine in equal amounts, while other operations remain unchanged.

[0051] Comparative Example 3 This comparative example provides a method for preparing carbon nanocages. The only difference between this method and Example 1 is that in step (2), polyaniline is replaced with polypyrrole in equal amounts, while other operations remain unchanged.

[0052] Test Example 1 Structural testing SEM tests were performed on the carbon nanocages obtained in Example 1 ( Figures 2-3 ) and TEM test ( Figure 4 Test results show that the product has a hierarchical porous structure in which hollow carbon nanocages are interconnected to form carbon nanosheets, and then the nanosheets are assembled into microspheres.

[0053] The carbon nanocages obtained in Example 1 were subjected to N2 adsorption-desorption tests, such as... Figure 5 As shown, the test results indicate that the product has a hierarchical pore structure in which micropores, mesopores, and macropores coexist.

[0054] XPS spectroscopy was performed on the carbon nanocages obtained in Example 1, as follows: Figure 6 As shown, the test results indicate that the product contains C, N, and O elements.

[0055] Test Example 2 The carbon nanocages provided in each embodiment and comparative example were added to the cigarette filter rod at an addition rate of 1.2 mg / cigarette. Figure 7 With zero addition as the control group, the phenol content in mainstream flue gas was tested according to the YC / T 255-2008 industry standard, and the results are shown in Table 1.

[0056] Table 1 Test results: (1) As can be seen from Examples 1 to 8, the present invention uses basic magnesium carbonate as a template and polyaniline as a carbon source to obtain carbon nanocages with high specific surface area, rich defect surface and hierarchical porous structure, which are particularly suitable for the adsorption of phenol. Adding it to the filter rod can achieve a phenol reduction rate of 36.68-64.76%.

[0057] (2) By comparing Example 1 and Example 4, it can be seen that by placing the reaction of basic magnesium carbonate in a reaction tube, the present invention can obtain basic magnesium carbonate with better morphology and structure, thereby further improving the adsorption effect of the prepared carbon nanocage on phenol.

[0058] A comparison of Examples 1 and 5-8 shows that the present invention can improve the phenol adsorption rate by adjusting the amount of polyaniline and the pyrolysis temperature.

[0059] The comparison between Example 1 and Comparative Example 1 shows that when MgO nanoparticles are used as templates, the resulting product has no mesoporous structure, and the lack of hierarchical porous structure leads to a decrease in its adsorption performance for phenol.

[0060] The comparison between Example 1 and Comparative Examples 2-3 shows that the carbon nanocages prepared with polyaniline have a relatively larger specific surface area and more defects. When polydopamine or polypyrrole is used as the carbon source material, the adsorption effect of the prepared carbon nanocages on phenol decreases.

[0061] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing carbon nanocages, characterized in that, The preparation method includes the following steps: (1) Mix magnesium salt and carbonate to react and obtain basic magnesium carbonate; (2) The basic magnesium carbonate and polyaniline from step (1) are mixed and pyrolyzed, and then acid-treated to obtain the carbon nanocage.

2. The preparation method according to claim 1, characterized in that, The magnesium salt in step (1) includes any one or a combination of at least two of magnesium sulfate, magnesium nitrate, magnesium citrate, or magnesium chloride; Preferably, the carbonate in step (1) includes any one or a combination of at least two of sodium carbonate, sodium bicarbonate, potassium carbonate, or potassium bicarbonate.

3. The preparation method according to claim 1 or 2, characterized in that, The reaction described in step (1) is carried out in a reaction tube; Preferably, the reaction in step (1) specifically includes: mixing an aqueous solution of magnesium salt and an aqueous solution of carbonate in a reaction tube, and obtaining basic magnesium carbonate after the reaction.

4. The preparation method according to claim 3, characterized in that, The concentrations of the aqueous solutions of the magnesium salt and carbonate are each independently 0.05-0.3 M; Preferably, the reaction temperature is 60-90℃ and the time is 0.5-4h.

5. The preparation method according to any one of claims 1-4, characterized in that, The mass ratio of basic magnesium carbonate to polyaniline in step (2) is 1:0.5-5.0; Preferably, the polyaniline in step (2) has a weight-average molecular weight of 10,000-100,000.

6. The preparation method according to any one of claims 1-5, characterized in that, The mixing in step (2) specifically includes: dispersing basic magnesium carbonate and polyaniline in a solvent, and then removing the solvent by stirring and evaporation to obtain a mixture of basic magnesium carbonate and polyaniline; Preferably, the solvent includes any one or a combination of at least two of water, ethanol, acetone or isopropanol; Preferably, the pyrolysis in step (2) includes: heating to 600-800℃ at a rate of 1-10℃ / min and holding at that temperature for 2-4 hours.

7. A carbon nanocage, characterized in that, The carbon nanocage is prepared by the method of any one of claims 1-6.

8. The application of the carbon nanocage according to claim 7 in reducing phenol in mainstream cigarette smoke.

9. A filter rod for adsorbing phenol in mainstream cigarette smoke, characterized in that, The filter rod contains the carbon nanocage as described in claim 7.

10. The filter rod according to claim 9, characterized in that, The amount of carbon nanocages added to the filter rod is 0.2-5 mg / rod.

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