An ultramicroporous carbon material for capturing carbon tetrafluoride and a preparation method and application thereof

Abstract

This invention discloses an ultramicroporous carbon material for capturing carbon tetrafluoride. The material has a nitrogen content of 2–25 wt%, an average pore size of 0.5–2.0 nm, an ultramicropore size <0.7 nm accounting for 30%–95%, an extremely micropore size of 0.7–2.0 nm accounting for 5%–70%, and a surface area of ​​600–1200 m². 2 / g. The above-mentioned microporous carbon material has a microporous structure and nitrogen-doped polar surface that match the molecular size of carbon tetrafluoride, and has excellent adsorption performance for the greenhouse gas carbon tetrafluoride, which can meet the needs of adsorption and capture of the greenhouse gas carbon tetrafluoride in industrial application scenarios.

Description

Technical Field

[0001] This invention relates to the field of greenhouse gas emission reduction materials technology, and in particular to the preparation and application of an ultramicroporous carbon material for capturing carbon tetrafluoride. Background Technology

[0002] Carbon tetrafluoride (CTF) is a greenhouse gas that needs to be controlled under the Kyoto Protocol. Compared to carbon dioxide, CTF has an extremely high global warming potential (GWP). 100 =6500), which has a long-lasting impact on global warming.

[0003] Currently, carbon tetrafluoride (CTF) emissions mainly originate from aluminum smelting and semiconductor manufacturing processes. Specifically, during aluminum electrolysis, due to the anode effect, fluorides used as fluxes react with carbon anodes to form CTF. In semiconductor manufacturing, CTF is primarily used as a dry etching agent and cleaning agent; unused CTF becomes a greenhouse gas emission. Besides being a greenhouse gas, CTF is also a chemical with extremely high economic value. Therefore, recycling emitted CTF can not only reduce greenhouse gas emissions but also generate economic value.

[0004] To achieve the recycling and utilization of carbon tetrafluoride, efficient capture of its emissions is a necessary prerequisite. Adsorption technology is a low-energy, high-efficiency gas capture technology with great application prospects in the capture of carbon tetrafluoride, a fluorinated greenhouse gas. The core of adsorption technology lies in developing highly efficient adsorption materials for target molecules to achieve specific capture.

[0005] Patent CN106241800B discloses a method for preparing activated carbon specifically for adsorbing carbon tetrafluoride using anthracite powder and bituminous coal-based activated carbon as raw materials. The prepared activated carbon exhibits good carbon tetrafluoride adsorption performance. However, the preparation process of this activated carbon is complex and has a long cycle, requiring a total of eight steps, including powder mixing, kneading, extrusion molding, curing, shaping, secondary oxygen-free dry distillation, activation, and sieving. Furthermore, the activation step involves high activation temperature and high energy consumption, which is not conducive to industrial application.

[0006] Patent CN112915966A discloses a method for preparing activated carbon by activating polyaniline with potassium carbonate. The prepared polyaniline-based activated carbon exhibits good carbon tetrafluoride adsorption performance. However, the preparation process of this polyaniline-based activated carbon requires secondary calcination with potassium carbonate, and additional washing and drying steps are needed to remove the calcination products of the activating agent potassium carbonate. The preparation process is complex, energy-intensive, and the use of large amounts of solvents will also cause significant environmental pollution.

[0007] Patent CN114288812A discloses a method for adsorption and separation using microporous carbon material in contact with fluorinated electron gas. The microporous carbon material is obtained by pyrolysis of polyvinylidene chloride resin. This microporous carbon material exhibits excellent adsorption capacity for sulfur hexafluoride, but poor adsorption performance for carbon tetrafluoride.

[0008] Patent CN114789045A discloses a fluorinated organic porous framework material with a nanoporous structure and strong hydrophobic properties, exhibiting good carbon tetrafluoride adsorption capacity. However, the synthesis of this fluorinated organic porous framework material requires the use of expensive organic monomers, resulting in high preparation costs and hindering its industrial application.

[0009] In summary, existing carbon tetrafluoride (CT) trapping materials suffer from a series of problems, including high energy consumption and environmental unfriendliness in their preparation methods, the need for large amounts of solvents during the reaction process leading to environmental pollution, and high material cost making industrial application difficult. Therefore, finding a trapping material with stable structure, large adsorption capacity, ultraporous structure matching the molecular size of CT, and suitability for industrial applications is of paramount importance. Summary of the Invention

[0010] To address the aforementioned technical problems, this invention proposes an ultramicroporous carbon material with stable structure, large adsorption capacity, ultramicroporous structure matching the molecular size of carbon tetrafluoride, and suitable for industrial applications.

[0011] The objective of this invention is achieved through the following technical solution:

[0012] A microporous carbon material for capturing carbon tetrafluoride has a nitrogen content of 2–25 wt%, an average pore size of 0.5–2.0 nm, a micropore size <0.7 nm accounting for 30%–95%, an ultramicropore size of 0.7–2.0 nm accounting for 5%–70%, and a specific surface area of ​​600–1200 m². 2 / g.

[0013] Preferably, the ultramicroporous carbon material used to capture carbon tetrafluoride has a nitrogen content of 2-10 wt%, an average pore size of 0.5-1.0 nm, an ultramicropore size of <0.7 nm accounting for 60%-95%, an extremely micropore size of 0.7-2.0 nm accounting for 5%-40%, and a specific surface area of ​​900-1200 m². 2 / g.

[0014] The CF bond in the carbon tetrafluoride molecule is chemically very stable and does not easily undergo electron transfer with the adsorbent surface to form chemical adsorption. Therefore, constructing a pore structure and polar surface that matches the size of the carbon tetrafluoride molecule to enhance the physical adsorption of the adsorbent surface and the carbon tetrafluoride molecule is an effective means to improve the adsorption capacity of carbon tetrafluoride.

[0015] This invention reveals that certain halogen-containing polymers undergo in-situ dehalogenation reactions under high-temperature conditions. The removal of halogens leads to the formation of carbon-carbon double bonds within the polymer, resulting in polymer-derived ultraporous carbon materials with high specific surface areas. Furthermore, it generates ultraporous structures in the carbon material with sizes similar to carbon tetrafluoride molecules (approximately 0.47 nanometers), which enhances the carbon tetrafluoride adsorption performance. Besides controlling pore size, the surface polarity of the carbon material is also a key factor affecting its adsorption performance. Since nitrogen atoms are similar in size to carbon atoms, they can migrate in-situ into the carbon material framework under high-temperature carbonization conditions, forming nitrogen-doped carbon materials. Moreover, due to the different electronegativity of nitrogen and carbon atoms, nitrogen doping forms polar CN bonds within the carbon material, enhancing its surface polarity. Therefore, the more polar carbon material surface in the ultramicroporous carbon material for capturing carbon tetrafluoride described in this invention can undergo stronger molecular polarization with carbon tetrafluoride molecules, thereby enhancing the interaction between carbon tetrafluoride molecules and the carbon material surface and improving the carbon tetrafluoride adsorption performance of the material.

[0016] The present invention provides a method for preparing any of the aforementioned ultraporous carbon materials for capturing carbon tetrafluoride, the method comprising: carbonizing a mixture of a halogen-containing polymer and a nitrogen-containing compound for 1 to 8 hours, and obtaining the ultraporous carbon material after cooling.

[0017] The halogenated polymer is selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, or ethylene-tetrafluoroethylene copolymer.

[0018] The nitrogen-containing compound is selected from at least one of urea, melamine, dicyandiamide, aminocyanide, or polyaniline.

[0019] Furthermore, the halogenated polymer and nitrogen-containing compound can be mixed evenly in a mixer before carbonization to form a mixture of the halogenated polymer and nitrogen-containing compound.

[0020] Further, the mixture of halogen-containing polymer and nitrogen-containing compound is carbonized in a tubular calcination furnace. Preferably, the calcination atmosphere is selected from at least one of nitrogen, helium, or carbon dioxide, with a gas flow rate of 50–1000 mL / min, a calcination heating rate of 1–10 °C / min, a calcination temperature of 500–1000 °C, and a calcination time of 1–8 h. More preferably, the calcination atmosphere is selected from at least one of nitrogen or helium, with a gas flow rate of 300–800 mL / min, a calcination heating rate of 2–5 °C / min, a calcination temperature of 600–800 °C, and a calcination time of 3–5 h.

[0021] This invention introduces nitrogen atoms into the framework of an ultraporous carbon material by adding a nitrogen-containing compound. Under high-temperature carbonization conditions, the nitrogen-containing compound can undergo a dehalogenation crosslinking reaction with the halogen-containing polymer, achieving nitrogen doping. Nitrogen doping makes the carbon material surface more polarized, which is beneficial for improving adsorption performance. Secondly, by adjusting the ratio of the halogen-containing polymer to the nitrogen-containing compound, the pore size of the prepared ultraporous carbon material for capturing carbon tetrafluoride can be changed. During carbonization, the added nitrogen-containing compound undergoes a dehalogenation crosslinking reaction with the halogen-containing polymer, thereby reducing the formation of carbon-carbon double bonds and self-polymerization of the halogen-containing polymer during heating due to dehalogenation. Since the pores formed by the crosslinking of the halogen-containing polymer and the nitrogen-containing compound are larger than those formed by the self-polymerization of the halogen-containing polymer, the addition of the nitrogen-containing compound will form a larger pore structure in the microporous carbon material. However, the addition of excessive nitrogen-containing compound will inhibit the in-situ dehalogenation reaction of the halogen-containing polymer under carbonization conditions, resulting in a decrease in the specific surface area of ​​the prepared carbon material and reducing its adsorption performance. Therefore, appropriate nitrogen doping can enable ultraporous carbon materials to have better carbon tetrafluoride capture ability.

[0022] Preferably, in the mixture of the halogen-containing polymer and the nitrogen-containing compound, the mass ratio of the nitrogen-containing compound to the halogen-containing polymer is 1:20 to 1:2. Under this ratio, the ultramicroporous carbon material for capturing carbon tetrafluoride has a nitrogen content of 2-25 wt%, an average pore size of 0.5-2.0 nm, a proportion of 30%-95% of ultramicropores with a pore size <0.7 nm, a proportion of 5%-70% of micropores with a pore size of 0.7-2.0 nm, and a specific surface area of ​​600-1200 m². 2 / g.

[0023] More preferably, in the mixture of the halogen-containing polymer and the nitrogen-containing compound, the mass ratio of the nitrogen-containing compound to the halogen-containing polymer is 1:20 to 1:5. Under this ratio, the ultramicroporous carbon material for capturing carbon tetrafluoride has a nitrogen content of 2-10 wt%, an average pore size of 0.5-1.0 nm, a proportion of 60%-95% of ultramicropores with a pore size <0.7 nm, a proportion of 5%-40% of micropores with a pore size of 0.7-2.0 nm, and a specific surface area of ​​900-1200 m². 2 / g.

[0024] The present invention also provides a method for applying any of the above-mentioned microporous carbon materials for capturing carbon tetrafluoride, for capturing carbon tetrafluoride in industrial production exhaust gas.

[0025] The pore size of the ultramicroporous carbon material used to capture carbon tetrafluoride is matched with the size of carbon tetrafluoride molecules, which helps to enhance the physical adsorption of carbon tetrafluoride. Furthermore, the doping of nitrogen into the ultramicroporous carbon material enhances the polarity of the adsorbent surface, which is beneficial for inducing the polarization of carbon tetrafluoride molecules, thereby further enhancing the physical adsorption of carbon tetrafluoride. Therefore, the ultramicroporous carbon material for capturing carbon tetrafluoride described in this invention can efficiently adsorb and capture the fluorine-containing greenhouse gas carbon tetrafluoride, especially carbon tetrafluoride in industrial production exhaust gases.

[0026] The application method of the ultramicroporous carbon material for capturing carbon tetrafluoride according to the present invention specifically includes the following steps:

[0027] 100-800h -1 A carbon tetrafluoride gas with a concentration of 0.5% to 10% is introduced at space velocity into a trap containing any of the aforementioned microporous carbon materials. The carbon tetrafluoride in the inflow gas stream is captured using the microporous carbon material at a temperature of 20 to 50°C. The concentration of carbon tetrafluoride in the outflow gas stream is monitored. When the concentration of carbon tetrafluoride rises to the concentration in the inflow gas stream, the capture is stopped.

[0028] Specifically, online mass spectrometry is used to detect the concentration of carbon tetrafluoride in the outflow gas stream in real time. When the concentration of carbon tetrafluoride rises to the concentration in the inflow gas stream, the capture is stopped, and the adsorption breakthrough curve of carbon tetrafluoride is obtained. Then, the adsorption capacity of carbon tetrafluoride in the ultramicroporous carbon material is calculated.

[0029] The carbon tetrafluoride gas with a concentration of 0.5-10% is a carbon tetrafluoride / inert gas mixture diluted with an inert gas, wherein the inert gas is selected from nitrogen or helium.

[0030] Preferably, any of the above-mentioned ultramicroporous carbon materials for capturing carbon tetrafluoride are used, and the mixture is subjected to treatment at 20–35°C for 200–600 hours. -1 A carbon tetrafluoride gas with a concentration of 1-3% diluted with nitrogen is introduced at space velocity.

[0031] The ultramicroporous carbon material for capturing carbon tetrafluoride described in this invention can be activated before use to further improve its adsorption performance for carbon tetrafluoride. Specifically, the activation treatment includes the following steps: the activation temperature is 200–400°C, the activation pressure is 0.01–2 bar, the activation heating rate is 2–10°C / min, the activation time is 1–5 h, the activation atmosphere is nitrogen or helium, and the gas flow rate is 10–50 mL / min.

[0032] Preferably, the activation treatment includes the following steps: the activation temperature is 250-350℃, the activation pressure is 0.01-1 bar, the activation heating rate is 3-5℃ / min, the activation time is 2-4 h, the activation atmosphere is nitrogen, and the gas flow rate is 20-30 mL / min.

[0033] The microporous carbon material for capturing carbon tetrafluoride described in this invention can be regenerated after desorption treatment.

[0034] Compared with the prior art, the beneficial effects of the present invention include:

[0035] 1. The ultramicroporous carbon material of the present invention has an ultramicroporous structure that matches the size of carbon tetrafluoride molecules, a high nitrogen doping content, and a high specific surface area, exhibiting excellent carbon tetrafluoride adsorption performance.

[0036] 2. The preparation process of the ultra-microporous carbon material described in this invention is simple, does not require the use of activators, detergents or other environmentally polluting processes, is low in cost, environmentally friendly, green and environmentally friendly, and suitable for industrial production;

[0037] 3. The ultra-microporous carbon material described in this invention can efficiently adsorb carbon tetrafluoride and can be widely used for the capture and recovery of carbon tetrafluoride, a greenhouse gas, in industrial exhaust gases. Attached Figure Description

[0038] Figure 1 Transmission electron microscopy (TEM) image of Ads 1, an ultraporous carbon material prepared in Example 1;

[0039] Figure 2 The nitrogen isotherm adsorption-desorption curve of the ultramicroporous carbon material Ads 1 prepared in Example 1 at liquid nitrogen temperature is the material characterization result.

[0040] Figure 3 The results of the carbon tetrafluoride adsorption breakthrough curve of Ads 1, an ultramicroporous carbon material prepared in Example 1. Detailed Implementation

[0041] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.

[0042] Example 1

[0043] A. Preparation of ultraporous carbon material: First, 10g of polyvinylidene chloride and 1g of melamine were mixed in a mixer. The resulting mixture was placed in a calcining quartz boat. Then, the calcining quartz boat was placed in a tubular calcining furnace to carbonize the mixture of halogen-containing polymer and nitrogen-containing compound. The carbonization atmosphere was nitrogen, the gas flow rate was 500mL / min, the heating rate was 5℃ / min, the carbonization temperature was 700℃, and the carbonization time was 3h. After the calcining furnace cooled down, the ultraporous carbon material for capturing carbon tetrafluoride was obtained, denoted as Ads 1.

[0044] B. Activation treatment of ultraporous carbon materials: 4g of the above Ads 1 was loaded into a fixed bed trap with an inner diameter of 6mm, an activation temperature of 300℃, an activation pressure of 1bar, an activation heating rate of 5℃ / min, an activation time of 3h, an activation atmosphere of nitrogen, and a gas flow rate of 30mL / min.

[0045] C. Application of ultraporous carbon materials: The capture temperature was set to 30℃, and 1% carbon tetrafluoride gas diluted with nitrogen at a flow rate of 30mL / min was introduced into the Ads 1 fixed bed trap after activation treatment in step B above. The composition of the gas flowing out of the trap was detected by online mass spectrometry to obtain the adsorption breakthrough curve of carbon tetrafluoride.

[0046] D. Calculation of the adsorption capacity of the ultraporous carbon material: The adsorption capacity of the ultraporous carbon material Ads1 can be calculated using the following formula:

[0047]

[0048] Where V is the adsorption capacity (mL / g), F is the gas flow rate (mL / min), t is the adsorption saturation time (min), c is the concentration of carbon tetrafluoride (%), and m is the mass of adsorbent used (g).

[0049] The obtained ultraporous carbon material Ads 1 was characterized by transmission electron microscopy, and the results are as follows: Figure 1 As shown in the figure, the prepared material has a rich sub-nanometer slit pore structure.

[0050] Figure 2 The nitrogen isotherm adsorption-desorption curves of Ads 1 are the material characterization results. The data show that the material exhibits the characteristics of a type I adsorption curve and there is no hysteresis loop in the adsorption-desorption curve. This phenomenon indicates that the prepared carbon material is a typical microporous material.

[0051] Figure 3The results of the adsorption breakthrough curve of Ads 1 for carbon tetrafluoride show that initially C / C0 is 0, indicating that carbon tetrafluoride is completely adsorbed. As the adsorption process proceeds, C / C0 gradually increases until it becomes 1, at which point the adsorption reaches saturation. The corresponding adsorption saturation time is t.

[0052] The calculation and analysis methods used in this invention mainly include:

[0053] 1. Calculation method of average pore size and proportion of ultramicropores: The average pore size and proportion of ultramicropores can be obtained by simulation calculation using the Horvath-Kawazoe (HK) model based on the nitrogen isothermal adsorption curve characterization results of ultramicroporous carbon materials.

[0054] 2. Calculation method of specific surface area: Based on the characterization results of nitrogen isothermal adsorption curves of ultramicroporous carbon materials, the specific surface area can be obtained by simulation calculation using the multi-point Brunauer-Emmett-Teller (BET) model.

[0055] 3. Nitrogen content analysis method: Elemental analysis was performed using an X-ray fluorescence spectrometer (PANalytical Axios).

[0056] Based on the above calculations and analysis, the average pore size of Ads 1 is 0.5–1.0 nm, with 93% being micropores with a pore size <0.7 nm, and a specific surface area of ​​1183 m². 2 / g, with a nitrogen content of 8.7wt%.

[0057] Example 2

[0058] The operation of Example 2 is the same as that of Example 1, except that the mass ratio of nitrogen-containing compound and halogen-containing polymer is 1:20, and other operations remain unchanged. The resulting microporous carbon material is denoted as Ads 2.

[0059] According to the calculation and analysis methods described in Example 1, the average pore size of Ads 2 is 0.5–1.0 nm, the proportion of micropores with a pore size <0.7 nm is 82%, and the specific surface area is 1195 m². 2 / g, with a nitrogen content of 3.1wt%.

[0060] Example 3

[0061] The operation of Example 3 is the same as that of Example 1, except that the carbonization temperature is 800℃, and other operations remain unchanged. The resulting microporous carbon material is denoted as Ads 3.

[0062] According to the calculation and analysis methods described in Example 1, the average pore size of Ads 3 is 0.5–1.0 nm, the proportion of micropores with a pore size <0.7 nm is 78%, and the specific surface area is 1105 m². 2 / g, with a nitrogen content of 8.9wt%.

[0063] Example 4

[0064] The operation of Example 4 is the same as that of Example 1, except that the carbonization atmosphere is helium, and other operations remain unchanged. The resulting microporous carbon material is denoted as Ads 4.

[0065] According to the calculation and analysis methods described in Example 1, the average pore size of Ads 4 is 0.5–1.0 nm, the proportion of micropores with a pore size <0.7 nm is 84%, and the specific surface area is 1156 m². 2 / g, with a nitrogen content of 8.7wt%.

[0066] Example 5

[0067] The operation of Example 5 is the same as that of Example 1, except that the nitrogen-containing compound is urea. All other operations remain the same, and the resulting microporous carbon material is denoted as Ads 5.

[0068] According to the calculation and analysis methods described in Example 1, the average pore size of Ads 5 is 0.5–1.0 nm, the proportion of micropores with a pore size <0.7 nm is 83%, and the specific surface area is 983 m². 2 / g, with a nitrogen content of 8.3wt%.

[0069] Example 6

[0070] The operation of Example 6 is the same as that of Example 1, except that the nitrogen-containing compound is polyaniline, and the other operations remain unchanged. The resulting microporous carbon material is denoted as Ads 6.

[0071] According to the calculation and analysis methods described in Example 1, the average pore size of Ads 6 is 0.5–1.0 nm, the proportion of micropores with a pore size <0.7 nm is 81%, and the specific surface area is 1050 m². 2 / g, with a nitrogen content of 8.1wt%.

[0072] Example 7

[0073] The operation of Example 7 is the same as that of Example 1, except that the halogen-containing polymer is polyvinylidene fluoride, and the other operations remain unchanged. The resulting microporous carbon material is denoted as Ads 7.

[0074] According to the calculation and analysis methods described in Example 1, the average pore size of Ads 7 is 0.5–1.0 nm, the proportion of micropores with a pore size <0.7 nm is 90%, and the specific surface area is 1075 m². 2 / g, with a nitrogen content of 9.2wt%.

[0075] Example 8

[0076] The operation of Example 8 is the same as that of Example 1, except that the halogenated polymer is polyvinyl chloride, and the other operations remain unchanged. The resulting microporous carbon material is denoted as Ads 8.

[0077] According to the calculation and analysis methods described in Example 1, the average pore size of Ads 8 is 0.5–1.0 nm, the proportion of micropores with a pore size <0.7 nm is 82%, and the specific surface area is 1043 m². 2 / g, nitrogen content is 7.5wt%.

[0078] Example 9

[0079] The operation of Example 9 is the same as that of Example 1, except that the halogen-containing polymer is polyvinyl fluoride, and the other operations remain unchanged. The resulting microporous carbon material is denoted as Ads 9.

[0080] According to the calculation and analysis methods described in Example 1, the average pore size of Ads 9 is 0.5–1.0 nm, the proportion of micropores with a pore size <0.7 nm is 78%, and the specific surface area is 1047 m². 2 / g, with a nitrogen content of 8.1wt%.

[0081] Example 10

[0082] The operation of Example 10 is the same as that of Example 1, except that the mass ratio of nitrogen-containing compound and halogen-containing polymer is 1:2, and other operations remain unchanged. The resulting microporous carbon material is denoted as Ads 10.

[0083] According to the calculation and analysis methods described in Example 1, the average pore size of Ads 10 is 1.0–2.0 nm, the proportion of micropores with a pore size <0.7 nm is 42%, and the specific surface area is 753 m². 2 / g, with a nitrogen content of 21.3wt%.

[0084] Example 11

[0085] The operation of Example 11 is the same as that of Example 1, except that: the halogenated polymer is polyvinylidene fluoride, the mass ratio of nitrogen-containing compound to halogenated polymer is changed to 1:2, and other operations remain unchanged. The resulting microporous carbon material is denoted as Ads11.

[0086] According to the calculation and analysis methods described in Example 1, the average pore size of Ads 11 is 1.0–2.0 nm, the proportion of micropores with a pore size <0.7 nm is 33%, and the specific surface area is 826 m². 2 / g, nitrogen content is 23.5wt%.

[0087] Comparative Example 1

[0088] The operation of Comparative Example 1 is the same as that of Example 1, except that no nitrogen-containing compound is added and all other operations remain unchanged. The resulting ultraporous carbon material is denoted as Ads D1.

[0089] According to the analytical method described in Example 1, Ads D1 has an average pore size of 0.5–1.0 nm, with 90% being micropores with a pore size <0.7 nm, and a specific surface area of ​​1080 m². 2 / g.

[0090] Comparative Example 2

[0091] The operation of Comparative Example 2 is the same as that of Example 1, except that the mass ratio of nitrogen-containing compound and halogen-containing polymer is 1:1, and other operations remain unchanged. The resulting ultraporous carbon material is denoted as Ads D2.

[0092] According to the calculation and analysis methods described in Example 1, the average pore size of Ads D2 is 2.0–4.0 nm, the proportion of micropores with a pore size <0.7 nm is 2%, and the specific surface area is 537 m². 2 / g, with a nitrogen content of 33.2wt%.

[0093] Comparative Example 3

[0094] The operation of Comparative Example 3 is the same as that of Example 1, except that the halogen-containing polymer is polyvinylidene fluoride, no nitrogen-containing compound is added, and other operations remain unchanged. The resulting ultraporous carbon material is denoted as Ads D3.

[0095] According to the calculation and analysis methods described in Example 1, the average pore size of Ads D3 is 0.5–1.0 nm, the proportion of micropores with a pore size <0.7 nm is 91%, and the specific surface area is 1165 m². 2 / g.

[0096] Comparative Example 4

[0097] The operation of Comparative Example 4 is the same as that of Example 1, except that: the halogenated polymer is polyvinylidene fluoride, the mass ratio of nitrogen-containing compound to halogenated polymer is 1:1, and other operations remain unchanged. The resulting ultraporous carbon material is denoted as Ads D4.

[0098] According to the calculation and analysis methods described in Example 1, the average pore size of Ads D4 is 2.0–4.0 nm, the proportion of micropores with a pore size <0.7 nm is 3%, and the specific surface area is 442 m². 2 / g, with a nitrogen content of 34.9wt%.

[0099] Comparative Example 5

[0100] The adsorbent used in Comparative Example 5 was commercial activated carbon, denoted as Ads D5.

[0101] According to the calculation and analysis methods described in Example 1, the average pore size of Ads D5 is 1.0–2.0 nm, the proportion of micropores with a pore size <0.7 nm is 23%, and the specific surface area is 1064 m². 2 / g.

[0102] Table 1 summarizes the evaluation results of the carbon tetrafluoride adsorption performance of Ads 1 to Ads 11 prepared in the examples and Ads D1 to Ads D5 prepared in the comparative examples under the above test conditions.

[0103] As shown in Table 1, the adsorption capacity of carbon tetrafluoride in carbon materials prepared without nitrogen-containing compounds (such as Comparative Examples 1 and 3) is significantly lower than that of the ultraporous carbon materials prepared using nitrogen-containing compounds in other examples, even though the prepared materials have abundant ultraporous structures with pore sizes <0.7 nm and high specific surface area. When the mass ratio of nitrogen-containing compound to halogen-containing polymer is 1:1 (such as Comparative Examples 2 and 4), the nitrogen content of the generated carbon material increases to 25–35 wt%, the average pore size increases to 2.0–4.0 nm, the proportion of ultraporous structures with pore sizes <0.7 nm decreases to 1%–5%, and the specific surface area decreases to 400–600 m². 2 / g, and its carbon tetrafluoride adsorption capacity is also significantly lower than that of the ultraporous carbon materials prepared in other examples.

[0104] The above experimental results indicate that the nitrogen content is 2–25 wt%, the average pore size is 0.5–2.0 nm, the proportion of micropores with a pore size <0.7 nm is 30–95%, and the specific surface area is 600–1200 m². 2 The ultraporous carbon material with a density of / g exhibits excellent carbon tetrafluoride adsorption performance. This is because the addition of an appropriate amount of nitrogen-containing compounds can, on the one hand, increase the surface polarity of the carbon material, and on the other hand, maintain the ultraporous and high specific surface area characteristics of the carbon material, achieving a coupling effect between surface polarity and pore structure, thereby effectively improving the CF4 adsorption performance of the material.

[0105] In addition, the present invention also tested the carbon tetrafluoride adsorption performance of a commercial activated carbon sample (Comparative Example 5) under the conditions of Example 12. The results showed that the carbon tetrafluoride adsorption performance of the commercial activated carbon was significantly lower than that of the ultraporous carbon material prepared in the examples of the present invention.

[0106] Table 1 Summary of carbon tetrafluoride adsorption evaluation results for each example and comparative example

[0107]

Claims

1. A method for applying an ultraporous carbon material, characterized in that: The aforementioned microporous carbon material is used to capture carbon tetrafluoride in industrial exhaust gases. The microporous carbon material has a nitrogen content of 2–25 wt%, an average pore size of 0.5–2.0 nm, a micropore size <0.7 nm accounting for 30%–95%, an ultramicropore size of 0.7–2.0 nm accounting for 5%–70%, and a specific surface area of ​​600–1200 m². 2 / g; The method for preparing the ultraporous carbon material includes: carbonizing a mixture of a halogen-containing polymer and a nitrogen-containing compound at a mass ratio of 1:20 to 1:2 at 500 to 1000°C for 1 to 8 hours, and obtaining the ultraporous carbon material after cooling. The halogen-containing polymer is selected from at least one of polytetrafluoroethylene, polyvinyl fluoride, polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, or ethylene-tetrafluoroethylene copolymer. The nitrogen-containing compound is selected from at least one of urea, melamine, dicyandiamide, aminocyanide, or polyaniline.

2. The method for applying the ultraporous carbon material according to claim 1, characterized in that: The ultraporous carbon material has a nitrogen content of 2–10 wt%, an average pore size of 0.5–1.0 nm, an ultramicropore size of <0.7 nm accounting for 60%–95%, an extremely micropore size of 0.7–2.0 nm accounting for 5%–40%, and a specific surface area of ​​900–1200 m². 2 / g.

3. The method of applying the ultraporous carbon material according to claim 1, characterized in that: In the mixture of halogen-containing polymer and nitrogen-containing compound, the mass ratio of nitrogen-containing compound to halogen-containing polymer is 1:20 to 1:

5.

4. The method of applying the ultraporous carbon material according to claim 1, characterized in that: In the mixture of halogen-containing polymer and nitrogen-containing compound, the mass ratio of nitrogen-containing compound to halogen-containing polymer is 1:20 to 1:

5.

5. The method of applying the ultraporous carbon material according to claim 1, characterized in that: 100–800 h -1 A carbon tetrafluoride gas with a concentration of 0.5-10% is introduced at space velocity into a trap containing the ultramicroporous carbon material. At 20-50 °C, the ultramicroporous carbon material traps the carbon tetrafluoride in the gas stream.

6. The method of applying the ultraporous carbon material according to claim 1, characterized in that: The ultraporous carbon material is activated before application, including the following steps: the activation temperature is 200-400℃, the activation pressure is 0.01-2 bar, the activation heating rate is 2-10℃ / min, the activation time is 1-5 h, the activation atmosphere is nitrogen or helium, and the gas flow rate is 10-50 mL / min.

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