A method for producing a hollow-fiber-shaped carbon molecular sieve

Abstract

This invention discloses a method for preparing hollow fibrous carbon molecular sieves, comprising the following steps: (1) using a mixture of polyimide, polyvinylpyrrolidone and N-methylpyrrolidone as spinning solution, and an aqueous solution or an ethanol solution of N-methylpyrrolidone as core solution, wet spinning is performed using a dual-channel spinneret to obtain a fiber structure with hollow channels; (2) first, the fibers obtained in step (1) are subjected to solvent exchange and drying treatment, and then soaked in a silane coupling agent, and after soaking, they are transferred to an oxygen-free, high-humidity environment to undergo a crosslinking reaction with water vapor; after the reaction, they are vacuum dried; (3) under an inert atmosphere, the fibers obtained in step (2) are subjected to multi-stage heating pyrolysis treatment, first rapidly heating to 250~300℃, and then slowly heating to (T 终温 -15℃, and finally slowly raise the temperature to 700~900℃ (T). 终温 The carbon molecular sieve prepared by the method of this invention exhibits selective adsorption capacity and good conductivity when used in gas separation applications. It not only achieves high adsorption capacity and efficiency but also enables rapid regeneration via Joule heating, thereby effectively reducing regeneration energy consumption.

Description

Technical Field

[0001] This invention relates to a method for preparing hollow fibrous carbon molecular sieves. Background Technology

[0002] In recent years, hollow fiber adsorption materials have attracted widespread attention in the separation field due to their high specific surface area and efficient mass transfer characteristics. However, about 50% of the process energy consumption in the chemical industry is concentrated in the chemical separation process. Among them, traditional adsorption separation technology relies on heat-driven regeneration (such as temperature swing adsorption) or high-pressure operation (such as pressure swing adsorption), which has problems such as high energy consumption and complex operation.

[0003] Carbon molecular sieves (CMS) materials have shown promise in gas separation due to their tunable microporous structure and chemical stability. Furthermore, the intrinsic conductivity of CMS materials enables Joule heating-based temperature-dependent adsorption. Compared to traditional thermal regeneration methods that rely on external heat sources, Joule heating technology achieves rapid temperature rise through the material's intrinsic resistance, offering significant advantages such as fast response, low energy consumption, and short regeneration cycles. However, existing CMS materials are mostly in granular or bulk form, resulting in drawbacks such as small effective area, low mass transfer efficiency, inconvenient loading operations, and large bed pressure drops during gas adsorption. Simultaneously, during regeneration, issues such as high mass transfer resistance and discontinuous conductive networks further lead to slow Joule heating desorption rates, high energy consumption, and poor regeneration uniformity, severely limiting their practical applications. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a method for preparing hollow fibrous carbon molecular sieves. The carbon molecular sieves prepared by this method have selective adsorption capacity and good conductivity when used for gas separation applications. They can not only achieve high adsorption capacity and adsorption efficiency, but also achieve rapid regeneration through Joule heating technology, thereby effectively reducing regeneration energy consumption.

[0005] Technical solution: The preparation method of hollow fibrous carbon molecular sieve of the present invention includes the following steps:

[0006] (1) Using a mixture of polyimide (PI), polyvinylpyrrolidone (PVP) and N-methylpyrrolidone (NMP) as the spinning solution, and NMP / H2O or NMP / CH3CH2OH solution as the core solution, wet spinning is performed using a dual-channel spinneret to obtain a fiber structure with regular hollow channels.

[0007] (2) First, the fiber obtained in step (1) is subjected to solvent exchange and drying treatment, and then it is soaked in silane coupling agent. After soaking, it is transferred to an oxygen-free and high-humidity environment to undergo cross-linking reaction with water vapor. After the cross-linking reaction, it is vacuum dried.

[0008] (3) Under an inert atmosphere, the fibers obtained in step (2) are subjected to multi-stage heating pyrolysis treatment. First, the temperature is rapidly increased to 250~300℃, and then slowly increased to (T). 终温 -15℃, and finally slowly raise the temperature to 700~900℃ (T 终温 (Preferably 850℃), and keep warm at this temperature for 2~3 hours.

[0009] In step (1), polyimide (PI), as a carbon material precursor, is dissolved together with the pore-forming agent polyvinylpyrrolidone (PVP) in N-methylpyrrolidone (NMP) to form a homogeneous spinning solution. PI provides the carbon skeleton structure, PVP generates a porous structure through non-solvent-induced phase separation during the subsequent wet spinning process, and NMP serves as both a solvent and a solution viscosity adjuster. In the spinning solution, the mass percentages of PI, PVP, and NMP are 18-20%, 5-6%, and 74-77%, respectively. When wet spinning is performed using a dual-channel spinneret, the core solution is an NMP / H2O or NMP / CH3CH2OH solution (NMP mass percentage is 80-90%). By controlling the extrusion speed of the spinning solution and the core solution (spinning solution extrusion speed: 0.5-10 mL / min; core solution extrusion speed: 0.2-10 mL / min), the take-up roller traction speed (0.1-100 m / min), and the height of the air gap (0-20 cm), the fiber structure with regular hollow channels is formed by utilizing the difference in diffusion kinetics between the aqueous phase and the non-solvent system.

[0010] In step (2), the fibers obtained in step (1) are first soaked in deionized water for 3-5 days to remove the remaining NMP and PVP; then, they are successively immersed in alcohol solvents and alkane solvents for solvent exchange to reduce surface tension and prevent the collapse of the pores after drying; the fibers after solvent exchange are placed in a vacuum oven and dried at 60-80℃ for 3-6 hours to obtain hollow fiber precursors. The hollow fiber precursors are then soaked in silane coupling agent, and after soaking, they are transferred to a closed oxygen-free, high-humidity environment to undergo cross-linking reaction with water vapor. This process can significantly improve the thermal stability of the fibers and avoid structural collapse during the subsequent high-temperature carbonization process; wherein, the silane coupling agent is vinyltrimethoxysilane (CAS No. 2768-02-7); the mass concentration of the silane coupling agent in the solution is 10-30%; after the cross-linking reaction, the fibers are vacuum dried at 130-150℃ for 10-12 hours.

[0011] In step (3), the heating rate is 13.3~15℃ / min during the first heating stage; 2~5℃ / min during the second heating stage; and 0.25~1℃ / min during the third heating stage. The initial rapid heating to 250℃ is followed by a slow heating at 2~5℃ / min to (T...终温 -15)℃, and then slowly raised to the final temperature, causing PI molecules to undergo directional carbonization to form graphite microcrystals. The CMS hollow fiber of this invention achieves highly efficient selective adsorption of gases through ultra-micropores and microporous structures, and utilizes the intrinsic conductivity of the material to achieve rapid gas desorption by applying voltage and directly Joule heating.

[0012] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The carbon molecular sieve prepared by the method of the present invention has both a high specific surface area and a three-dimensional interconnected pore structure. Its unique mass transfer path can significantly improve the adsorption capacity and adsorption rate of the material in the specific adsorption process. At the same time, since the material also has good electrical conductivity, it can effectively reduce the energy consumption of the adsorbent desorption process and shorten the regeneration cycle. Attached Figure Description

[0013] Figure 1 This is a process flow diagram of the method of the present invention;

[0014] Figure 2 This is a schematic diagram illustrating the specific adsorption and desorption process of CO2 by the CMS prepared in Example 1 and Comparative Examples 1-5.

[0015] Figure 3 The image shows the morphology of the CMS-850 obtained in Example 1.

[0016] Figure 4 The image shows the morphology of the CMS-700 obtained in Comparative Example 1.

[0017] Figure 5 The image shows the morphology of the CMS-800 obtained in Comparative Example 2.

[0018] Figure 6 The image shows the morphology of CMS-900 obtained in Comparative Example 3.

[0019] Figure 7 The image shows the morphology of CMS-P-850 prepared in Comparative Example 4.

[0020] Figure 8 This is a pore size distribution diagram for Example 1;

[0021] Figure 9 The adsorption capacity diagrams for CO2 and N2 are shown for Example 1 and Comparative Examples 1-5.

[0022] Figure 10 The adsorption kinetics of CO2 in Example 1 and Comparative Examples 1-5 are shown.

[0023] Figure 11 The cyclic stability diagram of CMS-850 obtained in Example 1;

[0024] Figure 12The resistance data graphs for Example 1 and Comparative Examples 1-5 are shown below;

[0025] Figure 13 Infrared thermal image of CMS-850 obtained in Example 1;

[0026] Figure 14 The infrared thermal image of the CMS-700 prepared in Comparative Example 1 is shown.

[0027] Figure 15 The infrared thermal image of the CMS-800 prepared in Comparative Example 2 is shown.

[0028] Figure 16 The infrared thermal image of the CMS-900 prepared in Comparative Example 3 is shown.

[0029] Figure 17 The infrared thermal image of the CMS-P-850 prepared in Comparative Example 4 is shown.

[0030] Figure 18 Infrared thermal image of CMS-V-850 prepared in Comparative Example 5;

[0031] Figure 19 The graphs show the temperature change over time during Joule thermal desorption in Examples 1 and Comparative Examples 2-5. Detailed Implementation

[0032] Example 1

[0033] The present invention discloses a method for preparing hollow fibrous carbon molecular sieves, comprising the following steps:

[0034] (1) Mix 18% polyimide (commercial model: Evonik P84®), 6% PVP and 76% NMP evenly by mass percentage to form a homogeneous spinning solution; and mix 90wt% NMP and 10wt% H2O evenly to form a core solution.

[0035] (2) Pass the spinning solution and core solution through Figure 1 The wet spinning equipment shown is used to prepare hollow fiber matrix. The specific process parameters during wet spinning are as follows: spinning pressure: 0.6 MPa; spinning solution temperature: 60℃; dual-channel spinneret inner diameter: 2.3 mm / 0.25 mm (outer channel / inner channel); spinning solution extrusion speed: 0.5 mL / min; core solution extrusion speed: 0.2 mL / min; take-up roller traction speed: 0.8 m / min; air gap: 5 cm.

[0036] (3) The fiber with regular hollow channels obtained in step (2) was soaked in deionized water for 3 days, and then soaked in methanol and n-hexane for 1 hour each for solvent exchange; after solvent exchange, the fiber was placed in a vacuum oven and dried at 60°C for 3 hours to obtain hollow fiber precursor.

[0037] (4) The hollow fiber precursor was soaked in hexane containing 20wt% silane coupling agent for 24h, and then transferred to a closed, high-humidity N2 environment to react for 24h (with water vapor). After the reaction, it was placed in a vacuum drying oven at 130℃ for 12h to dry.

[0038] (5) The hollow fibers processed in step (4) are placed in a tube furnace and argon gas is introduced at a rate of 200 mL / min for three-stage heating pyrolysis (the oxygen content in the reaction system is kept below 20 ppm by continuously introducing inert gas); the specific heating parameters are as follows: in the first stage of heating, the temperature is rapidly increased from room temperature (25℃) to 250℃ at a rate of 13.3℃ / min; in the second stage of heating, the temperature is slowly increased from 250℃ to 835℃ at a rate of 3.85℃ / min; in the third stage of heating, the temperature is slowly increased from 835℃ to 850℃ at a rate of 0.25℃ / min; and the temperature is held at 850℃ for 2 hours to obtain hollow fibrous carbon molecular sieve, named CMS-850.

[0039] like Figure 3 As shown, CMS-850 possesses a porous structure, which facilitates adsorbate diffusion and enables it to exhibit highly efficient mass transfer adsorption capabilities. At 25 °C and 1 bar, the adsorption capacities of CMS-850 for CO2 and N2 are 2.00 mmol·g⁻¹, respectively. -1 and 0.26 mmol·g -1 The corresponding results are as follows Figure 9 As shown in the figure. Comparative analysis with CMS-700, CMS-800 and CMS-900 revealed that the adsorption capacity of the material decreases with increasing pyrolysis temperature.

[0040] The hollow fiber wall thickness of CMS-850 prepared in Example 1 is 40 μm and the inner diameter is 0.3 mm.

[0041] The carbon material obtained in Example 1 is a CMS material, and its CMS characteristics were confirmed by pore size distribution characterization: the pore size distribution data measured by CO2 adsorption-desorption test at 0℃ showed that the pore size distribution of this CMS material exhibits a typical bimodal structure. Figure 8 The two characteristic pore size ranges are 4~7Å (ultramicropores) and 7~10Å (micropores), which are consistent with the molecular sieve pore structure unique to carbon molecular sieve materials.

[0042] like Figure 2As shown, Example 1 was applied to gas separation. The specific application process was as follows: 0.1g of material was packed into an adsorption column. A mixture of simulated low-concentration industrial CO2 tail gas (CO2 / N2=10:90, vol%) was introduced under the conditions of 25℃ and 1 bar. The CO2 concentration at the outlet of the adsorption column was monitored in real time by online gas chromatography, and the time to reach adsorption equilibrium was recorded.

[0043] like Figure 10 As shown, the CMS-850 prepared in Example 1 can reach 90% of its equilibrium adsorption capacity for CO2 within 2 minutes in a mixed gas with a volume ratio of CO2 / N2=10:90, which confirms that the CMS-850 prepared in this invention can achieve rapid adsorption and has high adsorption efficiency.

[0044] After adsorption, CMS-850 was energized at 30V. After 30 seconds, the entire material was uniformly heated and remained stable at over 130℃. Figure 13 This allows for rapid desorption (generally, all CO2 adsorbed by the material will be desorbed at 80~90℃).

[0045] After desorption, CMS-850 was used again for the gas separation described above. After repeating this process 10 times, its adsorption capacity remained at 1.9 mmol·g. -1 Above this, its adsorption capacity remains above 90% of the initial adsorption capacity. Figure 11 Since the adsorption of CO2 by CMS is mainly physical adsorption without the formation of chemical bonds, the adsorption process has good reversibility, thus exhibiting good cycle stability.

[0046] Comparative Example 1

[0047] A method for preparing hollow fibrous carbon molecular sieves includes the following steps:

[0048] (1) Mix 18% polyimide (commercial model: Evonik P84®), 6% PVP and 76% NMP evenly by mass percentage to form a homogeneous spinning solution; and mix 90wt% NMP and 10wt% H2O evenly to form a core solution.

[0049] (2) Hollow fiber matrix was prepared by wet spinning of spinning solution and core solution; the specific process parameters during wet spinning are as follows: spinning pressure: 0.6MPa; spinning solution temperature: 60℃; inner diameter of dual-channel spinneret: 2.3mm / 0.25mm (outer channel / inner channel); spinning solution extrusion speed: 0.5mL / min; core solution extrusion speed: 0.2mL / min; take-up roller traction speed: 0.8m / min; air gap: 5cm;

[0050] (3) The fiber with regular hollow channels obtained in step (2) was soaked in deionized water for 3 days, and then soaked in methanol and n-hexane for 1 hour each for solvent exchange; after solvent exchange, the fiber was placed in a vacuum oven and dried at 60°C for 3 hours to obtain hollow fiber precursor.

[0051] (4) The hollow fiber precursor was soaked in hexane containing 20wt% silane coupling agent for 24h, and then transferred to a closed, high-humidity N2 environment to react for 24h (with water vapor). After the reaction, it was placed in a vacuum drying oven at 130℃ for 12h to dry.

[0052] (5) The hollow fibers processed in step (4) are placed in a tube furnace and argon gas is introduced at a rate of 200 mL / min for three-stage heating pyrolysis. The specific heating parameters are as follows: In the first stage of heating, the temperature is rapidly increased from room temperature (25℃) to 250℃ at a rate of 13.3℃ / min; In the second stage of heating, the temperature is slowly increased from 250℃ to 685℃ at a rate of 3.85℃ / min; In the third stage of heating, the temperature is slowly increased from 685℃ to 700℃ at a rate of 0.25℃ / min; and the temperature is maintained at 700℃ for 2 hours to obtain hollow fibrous carbon molecular sieve, named CMS-700.

[0053] like Figure 4 As shown, CMS-700 has a porous structure, and at 25 °C and 1 bar, the adsorption capacities of CMS-700 for CO2 and N2 are 2.50 mmol·g, respectively. -1 and 0.40 mmol·g -1 The corresponding results are as follows Figure 9 As shown.

[0054] like Figure 2 As shown, Comparative Example 1 is applied to gas separation. The specific application process is as follows: 0.1g of material is packed into an adsorption column. Under the conditions of 25℃ and 1 bar, a mixed gas simulating low-concentration industrial CO2 tail gas (CO2 / N2=10:90, vol%) is introduced. The CO2 concentration at the outlet of the adsorption column is monitored in real time by online gas chromatography, and the time to reach adsorption equilibrium is recorded.

[0055] like Figure 10 As shown, the CMS-700 prepared in Comparative Example 1 also reached 90% of its equilibrium adsorption capacity for CO2 within 2 minutes in a mixed gas with a volume ratio of CO2 / N2 = 10:90.

[0056] Comparative Example 2

[0057] A method for preparing hollow fibrous carbon molecular sieves includes the following steps:

[0058] (1) Mix 18% polyimide (commercial model: Evonik P84®), 6% PVP and 76% NMP evenly by mass percentage to form a homogeneous spinning solution; and mix 90wt% NMP and 10wt% H2O evenly to form a core solution.

[0059] (2) Hollow fiber matrix was prepared by wet spinning of spinning solution and core solution; the specific process parameters during wet spinning are as follows: spinning pressure: 0.6MPa; spinning solution temperature: 60℃; inner diameter of dual-channel spinneret: 2.3mm / 0.25mm (outer channel / inner channel); spinning solution extrusion speed: 0.5mL / min; core solution extrusion speed: 0.2mL / min; take-up roller traction speed: 0.8m / min; air gap: 5cm;

[0060] (3) The fiber with regular hollow channels obtained in step (2) was soaked in deionized water for 3 days, and then soaked in methanol and n-hexane for 1 hour each for solvent exchange; after solvent exchange, the fiber was placed in a vacuum oven and dried at 60°C for 3 hours to obtain hollow fiber precursor.

[0061] (4) The hollow fiber precursor was soaked in hexane containing 20wt% silane coupling agent for 24h, and then transferred to a closed, high-humidity N2 environment to react for 24h (with water vapor). After the reaction, it was placed in a vacuum drying oven at 130℃ for 12h to dry.

[0062] (5) The hollow fibers processed in step (4) are placed in a tube furnace and argon gas is introduced at a rate of 200 mL / min for three-stage heating pyrolysis. The specific heating parameters are as follows: In the first stage of heating, the temperature is rapidly increased from room temperature (25℃) to 250℃ at a rate of 13.3℃ / min; In the second stage of heating, the temperature is slowly increased from 250℃ to 785℃ at a rate of 3.85℃ / min; In the third stage of heating, the temperature is slowly increased from 785℃ to 800℃ at a rate of 0.25℃ / min; and the temperature is maintained at 800℃ for 2 hours to obtain hollow fibrous carbon molecular sieve, named CMS-800.

[0063] like Figure 5 As shown, CMS-800 has a porous structure, and at 25 °C and 1 bar, the adsorption capacities of CMS-800 for CO2 and N2 are 2.38 mmol·g, respectively. -1 and 0.28 mmol·g -1 The corresponding results are as follows Figure 9 As shown.

[0064] like Figure 2As shown, Comparative Example 2 is applied to gas separation. The specific application process is as follows: 0.1g of material is packed into an adsorption column. Under the conditions of 25℃ and 1 bar, a mixed gas simulating low-concentration industrial CO2 tail gas (CO2 / N2=10:90, vol%) is introduced. The CO2 concentration at the outlet of the adsorption column is monitored in real time by online gas chromatography, and the time to reach adsorption equilibrium is recorded.

[0065] like Figure 10 As shown, the CMS-800 prepared in Comparative Example 2 also reached 90% of its equilibrium adsorption capacity for CO2 within 2 minutes in a mixed gas with a volume ratio of CO2 / N2 = 10:90.

[0066] Comparative Example 3

[0067] A method for preparing hollow fibrous carbon molecular sieves includes the following steps:

[0068] (1) Mix 18% polyimide (commercial model: Evonik P84®), 6% PVP and 76% NMP evenly by mass percentage to form a homogeneous spinning solution; and mix 90wt% NMP and 10wt% H2O evenly to form a core solution.

[0069] (2) Hollow fiber matrix was prepared by wet spinning of spinning solution and core solution; the specific process parameters during wet spinning are as follows: spinning pressure: 0.6MPa; spinning solution temperature: 60℃; inner diameter of dual-channel spinneret: 2.3mm / 0.25mm (outer channel / inner channel); spinning solution extrusion speed: 0.5mL / min; core solution extrusion speed: 0.2mL / min; take-up roller traction speed: 0.8m / min; air gap: 5cm;

[0070] (3) The fiber with regular hollow channels obtained in step (2) was soaked in deionized water for 3 days, and then soaked in methanol and n-hexane for 1 hour each for solvent exchange; after solvent exchange, the fiber was placed in a vacuum oven and dried at 60°C for 3 hours to obtain hollow fiber precursor.

[0071] (4) The hollow fiber precursor was soaked in hexane containing 20wt% silane coupling agent for 24h, and then transferred to a closed, high-humidity N2 environment to react for 24h (with water vapor). After the reaction, it was placed in a vacuum drying oven at 130℃ for 12h to dry.

[0072] (5) The hollow fibers processed in step (4) are placed in a tube furnace and argon gas is introduced at a rate of 200 mL / min for three-stage heating pyrolysis. The specific heating parameters are as follows: In the first stage of heating, the temperature is rapidly increased from room temperature (25℃) to 250℃ at a rate of 13.3℃ / min; In the second stage of heating, the temperature is slowly increased from 250℃ to 885℃ at a rate of 3.85℃ / min; In the third stage of heating, the temperature is slowly increased from 885℃ to 900℃ at a rate of 0.25℃ / min; and the temperature is maintained at 900℃ for 2 hours to obtain hollow fibrous carbon molecular sieve, named CMS-900.

[0073] like Figure 6 As shown, CMS-900 has a porous structure. Under conditions of 25 °C and 1 bar, the adsorption capacities of CMS-900 for CO2 and N2 are 1.61 mmol·g, respectively. -1 and 0.24 mmol·g -1 The corresponding results are as follows Figure 9 As shown.

[0074] like Figure 2 As shown, Comparative Example 3 is applied to gas separation. The specific application process is as follows: 0.1g of material is packed into an adsorption column. Under the conditions of 25℃ and 1 bar, a mixed gas simulating low-concentration industrial CO2 tail gas (CO2 / N2=10:90, vol%) is introduced. The CO2 concentration at the outlet of the adsorption column is monitored in real time by online gas chromatography, and the time to reach adsorption equilibrium is recorded.

[0075] like Figure 10 As shown, the CMS-900 prepared in Comparative Example 3 also reached 90% of its equilibrium adsorption capacity for CO2 within 2 minutes in a mixed gas with a volume ratio of CO2 / N2=10:90.

[0076] Comparative Example 4

[0077] A method for preparing hollow fibrous carbon molecular sieves includes the following steps:

[0078] (1) Mix 18% polyimide (commercial model: Evonik P84®), 6% PVP and 76% NMP evenly by mass percentage to form a homogeneous spinning solution; and mix 90wt% NMP and 10wt% H2O evenly to form a core solution.

[0079] (2) Hollow fiber matrix was prepared by wet spinning of spinning solution and core solution; the specific process parameters during wet spinning are as follows: spinning pressure: 0.6MPa; spinning solution temperature: 60℃; inner diameter of dual-channel spinneret: 2.3mm / 0.25mm (outer channel / inner channel); spinning solution extrusion speed: 0.5mL / min; core solution extrusion speed: 0.2mL / min; take-up roller traction speed: 0.8m / min; air gap: 5cm;

[0080] (3) The fiber with regular hollow channels obtained in step (2) was soaked in deionized water for 3 days, and then soaked in methanol and n-hexane for 1 hour each for solvent exchange; after solvent exchange, the fiber was placed in a vacuum oven and dried at 60°C for 3 hours to obtain hollow fiber precursor.

[0081] (4) The hollow fibers processed in step (3) are placed in a tube furnace and argon gas is introduced at a rate of 200 mL / min for three-stage heating pyrolysis. The specific heating parameters are as follows: In the first stage of heating, the temperature is rapidly increased from room temperature (25℃) to 250℃ at a rate of 13.3℃ / min; In the second stage of heating, the temperature is slowly increased from 250℃ to 835℃ at a rate of 3.85℃ / min; In the third stage of heating, the temperature is slowly increased from 835℃ to 850℃ at a rate of 0.25℃ / min; and the temperature is maintained at 850℃ for 2 hours to obtain hollow fibrous carbon molecular sieve, named CMS-P-850.

[0082] like Figure 7 As shown, CMS-P-850 has a dense structure, which is unfavorable for adsorbate diffusion. At 25 °C and 1 bar, the adsorption capacities of CMS-P-850 for CO2 and N2 are 0.52 mmol·g⁻¹, respectively. -1 and 0.11 mmol·g -1 The corresponding results are as follows Figure 9 As shown.

[0083] like Figure 2 As shown, Comparative Example 4 is applied to gas separation. The specific application process is as follows: 0.1g of material is packed into an adsorption column. Under the conditions of 25℃ and 1 bar, a mixed gas simulating low-concentration industrial CO2 tail gas (CO2 / N2=10:90, vol%) is introduced. The CO2 concentration at the outlet of the adsorption column is monitored in real time by online gas chromatography, and the time to reach adsorption equilibrium is recorded.

[0084] like Figure 10As shown, in a mixed gas with a volume ratio of CO2 / N2 = 10:90, the CMS-P-850 prepared in Comparative Example 4 took about 3 minutes to reach 90% of its equilibrium adsorption capacity for CO2. Compared to CMS-850, the time to reach the equilibrium adsorption capacity was extended by more than 50%.

[0085] Comparative Example 5

[0086] A method for preparing hollow fibrous carbon molecular sieves includes the following steps:

[0087] (1) Mix 18% polyimide (commercial model: Evonik P84®), 6% PVP and 76% NMP evenly by mass percentage to form a homogeneous spinning solution; and mix 90wt% NMP and 10wt% H2O evenly to form a core solution.

[0088] (2) Hollow fiber matrix was prepared by wet spinning of spinning solution and core solution; the specific process parameters during wet spinning are as follows: spinning pressure: 0.6MPa; spinning solution temperature: 60℃; inner diameter of dual-channel spinneret: 2.3mm / 0.25mm (outer channel / inner channel); spinning solution extrusion speed: 0.5mL / min; core solution extrusion speed: 0.2mL / min; take-up roller traction speed: 0.8m / min; air gap: 5cm;

[0089] (3) The fiber with regular hollow channels obtained in step (2) was soaked in deionized water for 3 days, and then soaked in methanol and n-hexane for 1 hour each for solvent exchange; after solvent exchange, the fiber was placed in a vacuum oven and dried at 60°C for 3 hours to obtain hollow fiber precursor.

[0090] (4) The hollow fiber precursor was soaked in hexane containing 50wt% silane coupling agent for 24h, and then transferred to a closed, high-humidity N2 environment to react for 24h (with water vapor). After the reaction, it was placed in a vacuum drying oven at 130℃ for 12h to dry.

[0091] (5) The hollow fibers processed in step (4) are placed in a tube furnace and argon gas is introduced at a rate of 200 mL / min for three-stage heating pyrolysis. The specific heating parameters are as follows: In the first stage of heating, the temperature is rapidly increased from room temperature (25℃) to 250℃ at a rate of 13.3℃ / min; In the second stage of heating, the temperature is slowly increased from 250℃ to 835℃ at a rate of 3.85℃ / min; In the third stage of heating, the temperature is slowly increased from 835℃ to 850℃ at a rate of 0.25℃ / min; and the temperature is maintained at 850℃ for 2 hours to obtain hollow fibrous carbon molecular sieve, named CMS-V-850.

[0092] At 25 °C and 1 bar, the adsorption capacities of CMS-V-850 for CO2 and N2 were 1.51 mmol·g, respectively. -1 and 0.22 mmol·g -1 The corresponding results are as follows Figure 9 As shown, the gas adsorption capacity of CMS-V-850 is lower than that of CMS-850. This is because CMS is the core component for gas adsorption, while the silane coupling agent does not have adsorption properties. When the amount of silane coupling agent increases from 20wt% to 50wt%, the relative proportion of CMS in the material decreases, the number of effective adsorption sites decreases, and thus the CO2 and N2 adsorption capacity of CMS-V-850 is lower than that of CMS-850.

[0093] like Figure 2 As shown, Comparative Example 5 is applied to gas separation. The specific application process is as follows: 0.1g of material is packed into an adsorption column. Under the conditions of 25℃ and 1 bar, a mixed gas simulating low-concentration industrial CO2 tail gas (CO2 / N2=10:90, vol%) is introduced. The CO2 concentration at the outlet of the adsorption column is monitored in real time by online gas chromatography, and the time to reach adsorption equilibrium is recorded.

[0094] like Figure 10 As shown, the CMS-V-850 prepared in Comparative Example 5 also reached 90% of its equilibrium adsorption capacity for CO2 within 2 minutes in a mixed gas with a volume ratio of CO2 / N2=10:90.

[0095] The specific procedure for testing the conductivity of CMS-850 is as follows:

[0096] 1. Sample preparation: Take 10 CMS-850 hollow fibers (20cm in length), arrange them in parallel and fix them, ensuring that both ends and the middle are exposed.

[0097] 2. Circuit setup: Connect the middle end of 10 CMS-850 hollow fiber optic cables to the positive terminal of the power supply and the two ends to the negative terminal to form a symmetrical circuit.

[0098] 3. Voltage setting: Apply a constant voltage of 30V, record the current value, and calculate the resistivity of CMS-850.

[0099] 4. Temperature monitoring: The temperature distribution of CMS-850 is observed in real time using an infrared thermal imager, and the temperature change curve is recorded within 5 minutes of power-on.

[0100] The resistors of CMS-850 are as follows Figure 12 As shown, and compared with CMS-700, CMS-800, and CMS-900, it was found that the resistivity of the material decreases with increasing pyrolysis temperature. Figure 13As shown, under a constant voltage of 30V, CMS-850 exhibits significant Joule thermal response characteristics: the temperature in a local area can exceed 120℃ after 10s of power-on, and after 30s, the entire material is uniformly heated and remains stable above 130℃.

[0101] The specific procedure for testing the conductivity of CMS-700 is as follows:

[0102] 1. Sample preparation: Take 10 CMS-700 hollow fibers (20cm in length), arrange them in parallel and fix them, ensuring that both ends and the middle are exposed.

[0103] 2. Circuit setup: Connect the middle end of 10 CMS-700 hollow fiber optic cables to the positive terminal of the power supply and the two ends to the negative terminal to form a symmetrical circuit.

[0104] 3. Voltage setting: Apply a constant voltage of 30V, record the current value, and calculate the resistivity of CMS-700.

[0105] 4. Temperature monitoring: The temperature distribution of CMS-700 is observed in real time using an infrared thermal imager, and the temperature change curve is recorded within 5 minutes of power-on.

[0106] The resistors of CMS-700 are as follows Figure 12 As shown. Figure 14 As shown, under a constant voltage of 30V, the temperature of the CMS-700 remains basically unchanged, mainly due to its high resistance.

[0107] The specific procedure for testing the conductivity of CMS-800 is as follows:

[0108] 1. Sample preparation: Take 10 CMS-800 hollow fibers (20cm in length), arrange them in parallel and fix them, ensuring that both ends and the middle are exposed.

[0109] 2. Circuit setup: Connect the middle end of 10 CMS-800 hollow fiber optic cables to the positive terminal of the power supply and the two ends to the negative terminal to form a symmetrical circuit.

[0110] 3. Voltage setting: Apply a constant voltage of 30V, record the current value, and calculate the resistivity of CMS-800.

[0111] 4. Temperature monitoring: The temperature distribution of CMS-800 is observed in real time using an infrared thermal imager, and the temperature change curve is recorded within 5 minutes of power-on.

[0112] The resistors of CMS-800 are as follows Figure 12 As shown. Figure 15As shown, under a constant voltage of 30V, CMS-800 exhibits significant Joule thermal response characteristics: the temperature in a local area can exceed 70℃ after 10s of power-on, and after 30s, the entire material is uniformly heated and remains stable above 80℃.

[0113] The specific procedure for testing the conductivity of CMS-900 is as follows:

[0114] 1. Sample preparation: Take 10 CMS-900 hollow fibers (20cm in length), arrange them in parallel and fix them, ensuring that both ends and the middle are exposed.

[0115] 2. Circuit setup: Connect the middle end of 10 CMS-900 hollow fiber optic cables to the positive terminal of the power supply and the two ends to the negative terminal to form a symmetrical circuit.

[0116] 3. Voltage setting: Apply a constant voltage of 30V, record the current value, and calculate the resistivity of CMS-900.

[0117] 4. Temperature monitoring: The temperature distribution of CMS-900 is observed in real time using an infrared thermal imager, and the temperature change curve is recorded within 5 minutes of power-on.

[0118] The resistors of CMS-900 are as follows Figure 12 As shown. Figure 16 As shown, under a constant voltage of 30V, CMS-900 exhibits significant Joule thermal response characteristics: the temperature in a local area can exceed 130℃ after 10s of power-on, and after 30s, the entire material is uniformly heated and remains stable above 160℃.

[0119] The specific procedure for testing the conductivity of CMS-P-850 is as follows:

[0120] 1. Sample preparation: Take 10 CMS-P-850 hollow fibers (20cm in length), arrange them in parallel and fix them, ensuring that both ends and the middle are exposed.

[0121] 2. Circuit setup: Connect the middle end of 10 CMS-P-850 hollow fiber optic cables to the positive terminal of the power supply and the two ends to the negative terminal to form a symmetrical circuit.

[0122] 3. Voltage setting: Apply a constant voltage of 30V, record the current value, and calculate the resistivity of CMS-P-850.

[0123] 4. Temperature monitoring: The temperature distribution of CMS-P-850 is observed in real time using an infrared thermal imager, and the temperature change curve is recorded within 5 minutes of power-on.

[0124] The resistors of CMS-P-850 are as follows Figure 12 As shown. Figure 17As shown, under a constant voltage of 30V, CMS-P-850 exhibits significant Joule thermal response characteristics: the temperature in a local area can exceed 130℃ after 10s of power-on, and after 30s, the entire material is uniformly heated and remains stable above 140℃.

[0125] The specific procedure for testing the conductivity of CMS-V-850 is as follows:

[0126] 1. Sample preparation: Take 10 CMS-V-850 hollow fibers (20cm in length), arrange them in parallel and fix them, ensuring that both ends and the middle are exposed.

[0127] 2. Circuit setup: Connect the middle end of 10 CMS-V-850 hollow fiber optic cables to the positive terminal of the power supply and the two ends to the negative terminal to form a symmetrical circuit.

[0128] 3. Voltage setting: Apply a constant voltage of 30V, record the current value, and calculate the resistivity of CMS-V-850.

[0129] 4. Temperature monitoring: The temperature distribution of CMS-V-850 is observed in real time using an infrared thermal imager, and the temperature change curve is recorded within 5 minutes of power-on.

[0130] The resistors of CMS-V-850 are as follows Figure 12 As shown. Figure 18 As shown, under a constant voltage of 30V, CMS-V-850 exhibits significant Joule thermal response characteristics: the temperature in a local area can exceed 90℃ after 10s of power-on, and after 30s, the entire material is uniformly heated and remains stable above 100℃.

[0131] Figure 19 The temperature-time curves for CMS-800, CMS-850, CMS-900, CMS-P-850, and CMS-V-850 are shown. These curves record in detail the dynamic temperature changes throughout the entire process, from power-on startup and temperature stabilization to subsequent power-off cooling, reflecting the instantaneous temperature values, heating rate trends, and final stable temperature range at different time points. Infrared thermal imaging data indicates that the Joule heating generated by the intrinsic conductivity of this material exhibits rapid response (<10s) and low energy consumption. This in-situ heating mechanism not only achieves rapid desorption of the adsorbate but also ensures the integrity of the material structure. Therefore, the method of this invention can prepare conductive carbon molecular sieves with hollow fiber structures, overcoming the high energy consumption problem of traditional adsorbent thermal desorption. Utilizing the electrically driven Joule heating effect, instantaneous desorption with rapid temperature rise within 30s can be achieved.

Claims

1. A method for preparing hollow fibrous carbon molecular sieves, characterized in that, Includes the following steps: (1) Using a mixture of polyimide, polyvinylpyrrolidone and N-methylpyrrolidone as the spinning solution, and an aqueous solution of N-methylpyrrolidone or an ethanol solution of N-methylpyrrolidone as the core solution, wet spinning is performed using a dual-channel spinneret to obtain a fiber structure with hollow channels. (2) First, the fiber obtained in step (1) is subjected to solvent exchange and drying treatment, and then it is soaked in silane coupling agent. After soaking, it is transferred to an oxygen-free and high-humidity environment to undergo cross-linking reaction with water vapor; after the reaction, it is vacuum dried. (3) Under an inert atmosphere, the fibers obtained in step (2) are subjected to multi-stage heating pyrolysis treatment. First, the temperature is rapidly increased to 250~300℃, and then slowly increased to (T). 终温 -15℃, then slowly raise the temperature to 700~900℃ and keep it at that temperature for 2~3 hours.

2. The method for preparing hollow fibrous carbon molecular sieves according to claim 1, characterized in that: In step (1), the spinning solution contains, by mass percentage, 18-20% polyimide, 5-6% polyvinylpyrrolidone, and 74-77% N-methylpyrrolidone.

3. The method for preparing hollow fibrous carbon molecular sieves according to claim 1, characterized in that: In step (1), the mass percentage of N-methylpyrrolidone in the core fluid is 80-90%.

4. The method for preparing hollow fibrous carbon molecular sieves according to claim 1, characterized in that: In step (1), the specific parameters in the wet spinning process are: spinning solution extrusion speed: 0.5~10mL / min; core solution extrusion speed: 0.2~10mL / min; take-up wheel traction speed: 0.1~100m / min; air gap height: 0~20cm.

5. The method for preparing hollow fibrous carbon molecular sieves according to claim 1, characterized in that: In step (2), the solvent exchange specifically involves immersing the fiber obtained in step (1) in deionized water for 3-5 days; and then sequentially immersing it in alcohol solvent and alkane solvent for solvent exchange.

6. The method for preparing hollow fibrous carbon molecular sieves according to claim 1, characterized in that: In step (2), the drying process after solvent exchange is carried out at a temperature of 60~80℃ and a drying time of 3~6h to obtain the hollow fiber precursor.

7. The method for preparing hollow fibrous carbon molecular sieves according to claim 1, characterized in that: In step (2), the hollow fiber precursor is immersed in a solution containing a silane coupling agent, wherein the silane coupling agent is vinyltrimethoxysilane; the mass concentration of the silane coupling agent in the solution is 10~30%.

8. The method for preparing hollow fibrous carbon molecular sieves according to claim 1, characterized in that: In step (2), the soaking time is 22-24h and the cross-linking reaction time is 22-24h.

9. The method for preparing hollow fibrous carbon molecular sieves according to claim 1, characterized in that: In step (2), the temperature for drying after the crosslinking reaction is 130~150℃ and the drying time is 10~12h.

10. The method for preparing hollow fibrous carbon molecular sieves according to claim 1, characterized in that: In step (3), the heating rate is 13.3~15℃ / min during the first heating stage; the heating rate is 2~5℃ / min during the second heating stage; and the heating rate is 0.25~1℃ / min during the third heating stage.

Images