CN107051382A - A kind of carbon dioxide adsorption porous carbon nanofiber material and preparation method thereof - Google Patents

Abstract

The present invention discloses a kind of carbon dioxide（CO₂）Absorption porous carbon nanofiber material and preparation method thereof, belongs to nano material and field of environmental improvement.Preparation method includes：DTG screens carbon matrix precursor and organic pore-forming agents；Prepare spinning solution；Method of electrostatic spinning obtains composite nano-fiber membrane；By low temperature pre-oxidation, high temperature cabonization processing, superhigh specific surface area porous carbon nanofiber material is obtained.The method can exempt activation step prepared by traditional carbon material, and cost is low, and preparation technology is simple, alternative to regulate and control its pore structure.The present invention provides a kind of effective carbon-dioxide adsorbent, with superhigh specific surface area, superelevation porosity；With substantial amounts of micropore and ultramicropore, be highly advantageous to carbon dioxide adsorption, makes its carbon dioxide adsorption capacity big；The material has desorption conditions gentle simultaneously, and material repeats the advantages of utilizing, and it is had a good application prospect in collecting carbonic anhydride field and environmental improvement benefit.

Description

A kind of porous carbon nanofiber material for carbon dioxide adsorption and preparation method thereof

technical field

The invention discloses a porous carbon nanofiber material for carbon dioxide adsorption and a preparation method thereof, belonging to the field of nanomaterials and environmental treatment.

Background technique

In recent years, the greenhouse effect has been a hot issue in the environmental field, mainly caused by the enrichment of greenhouse gases in the atmosphere. Carbon dioxide is an important component of greenhouse gases. With the increasing frequency of human economic activities and the massive consumption of fossil fuels, the concentration of carbon dioxide in the atmosphere is increasing year by year; the impact of the greenhouse effect on the global climate is becoming more and more serious, resulting in global warming, extreme Climate anomalies such as occur from time to time; therefore, the reduction of carbon dioxide emissions and the capture of carbon dioxide are extremely important.

As a commonly used solid adsorbent, carbon materials have the characteristics of high specific surface area, high porosity, good thermal stability and chemical stability, etc., and have great application prospects in the field of carbon dioxide adsorption; a large number of scholars at home and abroad have engaged in related research and reported A variety of carbon materials, including activated carbon, carbon nanofibers, carbon nanotubes, graphene, etc., have been applied in the field of carbon dioxide adsorption, and have achieved good adsorption effects, such as: James M. Tour et al. (ACS Appl. Mater. Interfaces, 2015 ,7, 1376−1382), Zhenan Bao et al. (J. Am. Chem. Soc. 2016, 138, 1001−1009) and patent CN105664850A "Preparation method and application of a high-performance carbon-based carbon dioxide adsorbent material", Preparation of activated carbon materials by activating carbon precursors to adsorb carbon dioxide, and Ki Bong Lee et al. (Carbon, 99, 2016, 354-360) and Jun Liu et al. Preparation of carbon nanofibers to adsorb carbon dioxide; although these materials have a significant adsorption effect on _CO2 , most of the carbon dioxide adsorbents developed at this stage need to be prepared by physical activation or chemical activation methods. The activation process involved in the preparation method is complex and difficult to control; the activation reagent is highly corrosive, and the equipment maintenance cost is high; and secondary pollution is easily generated after activation, causing new environmental management problems.

The hybrid electrospinning method is a method that uses two or more immiscible polymers for hybrid electrospinning to prepare composite nanofiber membranes; this method mainly stretches the polymer solution into filaments through high-voltage electrostatic force, Form nanofiber membranes; the prepared nanofibers are uniform in size, with diameters ranging from tens of nanometers to several microns; as we all know, electrospun nanofiber membranes can be prepared by low-temperature pre-oxidation, high-temperature carbonization, and high-temperature activation. High specific surface area Carbon nanofiber material; for the preparation of carbon nanofiber material by composite electrospinning nanofiber membrane, due to the different physical properties of two or more polymers mixed, one or more of them can be processed in the subsequent heat treatment process (pre-oxidation and carbonization) are easily removed by thermal decomposition, thereby forming a large number of pores in the generated carbon nanofiber skeleton, which will greatly increase the specific surface area and porosity of the material. Therefore, carbon nanofiber materials with high specific surface area and high porosity can be obtained without activation treatment.

The method of preparing porous carbon nanofiber materials by hybrid electrospinning and heat treatment has attracted widespread attention, and has become a research hotspot in academia and industry; many researchers at home and abroad have published related research results, such as Jae-Wook Lee et al. (Small, 2007, 91-95), Young Hee Lee et al. (Chem. Commun., 2010, 1320-1322), Yuegang Zhang et al. (Energy Environ. Sci., 2011, 4, 5053) and patents CN102074683A "a porous carbon nanofiber negative electrode material for lithium ion batteries and its preparation method", CN105098160A "a hollow porous carbon/silicon nanofiber lithium battery negative electrode material doped with graphene and its preparation method" and CN104674382A "a Preparation method of porous carbon nanofibers for ionization and deionization”; usually, this method has problems such as incomplete decomposition of thermally unstable polymers after heat treatment, resulting in mass residues, structure collapse to form closed pores, etc., resulting in the specific surface area of carbon nanofibers At the same time, the composite electrospun carbon nanofiber material is mainly used in electrode materials, and is usually prepared by coaxial electrospinning or adding doped materials to increase its mesopore content and increase its electrochemical activity. However, the content of micropores and ultramicropores plays a key role in the carbon dioxide adsorption performance, so in the past, the composite electrospun carbon nanofiber materials containing a large number of mesopores have low carbon dioxide adsorption capacity; therefore, in the absence of activation treatment At the same time, how to prepare porous carbon nanofiber materials with high specific surface area, high micropore and ultramicropore content, and good carbon dioxide adsorption performance by hybrid electrospinning method and heat treatment method is a hot and difficult point of current research.

Contents of the invention

The purpose of the present invention is to solve the above-mentioned composite electrospun carbon nanofiber material as a carbon dioxide adsorbent, the specific surface area is low, the porosity is low, the content of micropores and ultramicropores is small, and the carbon dioxide adsorption capacity is small, etc., to provide a carbon dioxide adsorption. The carbon nanofiber material and its preparation method, while exempting from activation treatment, prepare a porous carbon nanofiber material with high specific surface area, high porosity, high micropore and ultramicropore content, improve its carbon dioxide adsorption capacity, and obtain Efficient carbon dioxide adsorbent.

The present invention provides a high-efficiency carbon dioxide adsorbent, which has the characteristics of ultra-high specific surface area, ultra-high porosity, and controllable pore structure; in particular, the material has a porous structure, and the mesopores are conducive to the _CO2 gas in the material. Transmission, so that it has fast adsorption kinetics; a large number of micropores and ultramicropores are extremely conducive to carbon dioxide adsorption, making it a large carbon dioxide adsorption capacity; at the same time, the adsorption force of the material is an electrostatic force between molecules, which is a typical physical adsorption It has the advantages of mild desorption conditions and reusable materials, so it has good application prospects and environmental governance benefits in the field of carbon dioxide capture.

The technical scheme of the present invention is: reasonably screen out appropriate polymers as carbon precursors and organic pore-forming agents by thermogravimetric analysis, and prepare composite electrospun nanofibers by hybrid electrospinning technology. According to the thermogravimetric analysis data, reasonable The parameters of pre-oxidation and carbonization can be adjusted to completely remove thermally unstable polymers, and a high-efficiency carbon dioxide adsorbent with high specific surface area, high porosity, high micropore and ultramicropore content can be prepared; this method can avoid activation The cost is low, the preparation process is simple, and the secondary pollution problem in the activation process is avoided; at the same time, the pore structure of the prepared material can be reasonably regulated to form a large number of micropores and ultramicropores, which is conducive to the adsorption of carbon dioxide; specifically including The following steps.

(1) Take a small amount of polymer and analyze the thermal stability of the target polymer at a certain temperature through a thermogravimetric analyzer in an analytical gas atmosphere; polymers with good thermal stability (mass remaining after thermogravimetric analysis) are used as carbon precursors , polymers with poor thermal stability (no mass remaining after thermogravimetric analysis) are used as organic pore formers.

(2) Mix and dissolve the carbon precursor and the organic pore-forming agent in a certain proportion in an organic solvent to prepare a mixed spinning solution with a certain mass fraction.

(3) Transfer the mixed spinning solution in step (2) to a syringe, and prepare a composite electrospun nanofiber membrane by electrospinning technology.

(4) The composite electrospun nanofiber membrane obtained in step (3) is placed in a blast oven, and pre-oxidized at a low temperature in an air atmosphere to obtain pre-oxidized porous nanofibers.

(5) The pre-oxidized porous nanofiber membrane obtained in step (4) is placed in a carbonization furnace, and carbonized at a high temperature to obtain porous carbon nanofibers.

The analytical gas atmosphere in the step (1) is N ₂ , O ₂ or a mixture of the two in a ratio of 9:1-1:9; the certain temperature in the step (1) is 200-1000°C.

The carbon precursor in the step (2) is one or more of polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), phenolic resin, and pitch.

The organic pore-forming agent in the step (2) is polymethyl methacrylate (PMMA), cellulose acetate (CA), polypropylene pyrrolidone (PVP), polyethylene oxide (PEO), polyvinyl alcohol (PVA) , polyvinyl butyral (PVB), nylon 6 in one or more.

The organic solvent in the step (2) is one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), tetrahydrofuran (THF), and ethanol .

The mass fraction of the mixed spinning solution in the step (2) is 10-30%, wherein the ratio of the carbon precursor to the organic pore former is 9:1-1:9.

The electrospinning process conditions in the step (3) are as follows: the static spinning voltage is 10-25 kv, the receiving distance is 10-30 cm, the spinning liquid flow rate is 0.5-2 ml/min, and the spinning time is 10-30 h .

The pre-oxidation process conditions in the step (4) are as follows: the temperature is 200-300°C, the heating rate is 1-10°C/min, and the treatment time is 1-6 h, wherein the pre-oxidation temperature and treatment time are determined by the carbon precursor and Determined by thermogravimetric analysis data of organic pore formers.

The carbonization process conditions in the step (5) are: the temperature is 600-1000 °C, the heating rate is 1-10 °C, and the treatment time is 1-6 h, wherein the carbonization temperature and treatment time are determined by the carbon precursor and the organic pore-forming agent determined by thermogravimetric analysis data.

Compared with the existing carbon dioxide adsorbents, the beneficial effects obtained by the present invention are: (1) The carbon nanofibers prepared by the present invention are ultrafine nanofibers (with an outer diameter of 100 nm-2 µm), which have ultra-high Specific surface area (specific surface area is 200-1600 m ² /g), pore structure is developed (pore diameter is 0.1-100nm, pore volume is 0.2-2cm ³ /g), micropores are more (micropore volume is 0.1-1.5cm ³ /g); (2) The material of the present invention has a very good adsorption effect on carbon dioxide, and a developed porous structure is formed in the pre-oxidation process and carbonization process, which is not only conducive to the diffusion of external carbon dioxide gas inside the material, but also a large number of micro The pores show an excellent adsorption effect on carbon dioxide, and show good adsorption performance under low pressure (1 bar), and the adsorption capacity of carbon dioxide is 1.5-10 mmol/g; (3) The carbon dioxide adsorption process of the material of the present invention is physical adsorption, The adsorption rate is fast, and the material has a small adsorption heat for carbon dioxide, and can be desorbed at room temperature, which is beneficial to the recycling of the material.

Compared with the existing preparation method of carbon dioxide adsorbent of carbon material, the effective effect obtained by the preparation method of the present invention is: the pore-forming performance is remarkable, the complicated activation step in the preparation of traditional carbon material can be exempted, the cost is low, the preparation process is simple, and The secondary pollution problem in the activation process is avoided; according to the thermogravimetric analysis data, the pre-oxidation and carbonization treatment parameters can be reasonably adjusted, and the pore structure of the prepared material can be selectively adjusted to form a large number of micropores and ultra-micropores, which is beneficial to carbon dioxide adsorption; the method of the invention has simple process, low energy consumption, little damage to equipment, is beneficial to expand production, and is a high-efficiency, energy-saving and environment-friendly preparation method.

Description of drawings

FIG. 1 is a thermogravimetric curve diagram of PAN and PMMA in Example 1.

2-4 are SEM images of PAN/PMMA porous carbon nanofibers in Example 1.

Fig. 5 is the N adsorption _- desorption curve diagram of PAN/PMMA porous carbon nanofiber in embodiment 1.

6 is a pore size distribution diagram of PAN/PMMA porous carbon nanofibers in Example 1.

FIG. 7 is a CO ₂ adsorption curve of PAN/PMMA porous carbon nanofibers in Example 1.

detailed description

A carbon dioxide adsorption porous carbon nanofiber material and preparation method thereof of the present invention are described below through some specific embodiments. It should be understood that the following specific embodiments are illustrative and do not limit the scope of the present invention. The essence of the present invention The scope and scope are limited by the claims; for researchers in this field, without departing from the essence and scope of the invention, it is also within the scope of this invention to make various changes to the selection of materials and the control parameters of preparation in these embodiments. protection scope of the invention.

Example 1.

Porous carbon nanofiber material for carbon dioxide prepared from PAN and PMMA.

(1) Weigh ~20mg of PAN and PMMA polymer powders respectively, put them into crucibles, place them in a thermogravimetric analyzer, feed _N2 gas at a flow rate of 60ml/min, and heat at a heating rate of 5°C/min Up to 1000°C, the thermogravimetric analyzer automatically records the weight loss of the two polymers. Its thermogravimetric curve is shown in Figure 1; therefore, PAN is used as a carbon precursor, and PMMA is an organic pore-forming agent.

(2) Weigh PAN and PMMA with a mass ratio of 1:1 and add them to DMF. Stir continuously at room temperature until the polymer is completely dissolved to form a uniform and transparent solution. The mass fraction of the spinning solution is 15%.

(3) Transfer the spinning solution prepared in step (2) into the syringe and connect it to the autosampler, connect the needle to a high-voltage power supply for electrospinning, and use the receiving device to receive PAN/PMMA composite electrospinning Nanofiber membrane; the flow rate is 1ml/min, the spinning voltage is 17kv, and the distance between the needle and the receiver is 15cm.

(4) The electrospun composite nanofiber membrane obtained in step (3) was placed in a vacuum drying oven, and dried in vacuum at 90° C. for 12 hours to remove residual organic solvents.

(5) Place the nanofiber membrane dried in step (4) in a blast drying oven for pre-oxidation, place the nanofiber membrane vertically, and fix both ends with iron clips to prevent it from shrinking due to heat. , adjusting the temperature to 280° C., the heating rate to 10° C./min, and pre-oxidizing treatment for 1 hour to obtain a PAN/PMMA pre-oxidized nanofiber membrane.

(6) Place the pre-oxidized nanofiber membrane obtained in step (5) in a vacuum tube furnace for carbonization treatment; vacuumize the tube furnace for 3 times to remove the original residual air in the tube, and then introduce N ₂ at a flow rate of The carbonization temperature is set to 200ml/min, the carbonization temperature is set to 1000°C, the heating rate is 5°C/min, and the carbonization time is 1h to obtain a PAN/PMMA porous carbon nanofiber material; the SEM of the obtained sample is shown in Figure 2-4, and the carbon nanofiber The outer diameter of the material is 450nm; through the N ₂ adsorption and desorption test, the results are shown in Figure 5. The specific surface area of the material is 1100.74m ² /g analyzed by the BET method, and the pore volume of the material is 0.577cm ³ analyzed by the DFT method /g, the micropore volume is 0.376 cm ³ /g, and the pore size distribution diagram is shown in Figure 6.

(7) Weigh ~100mg of the porous carbon nanofiber material prepared in Example 1, transfer it to an adsorption tube, and activate it in high-purity _N2 at 200°C for 6 hours; after activation, transfer the adsorption tube to carbon dioxide high-pressure adsorption In the instrument, at 0°C and 25°C, the adsorption effect of carbon dioxide within the pressure range of 1 bar was measured, and the carbon dioxide adsorption curve of the porous carbon nanofiber material at 0°C and 1 bar pressure is shown in Figure 7; in Example 1 The prepared material has a carbon dioxide adsorption capacity of 4.21 mmol/g at 0° C. and 1 bar pressure; the carbon dioxide adsorption capacity of the material prepared in Example 1 is 3.02 mmol/g at 25° C. and 1 bar pressure.

Example 2.

Porous carbon nanofiber material for carbon dioxide prepared from PAN and PMMA.

(1) Weigh PAN and PMMA with a mass ratio of 1:1 and add them to DMF. At room temperature, stir continuously until the polymer is completely dissolved to form a uniform and transparent solution. The mass fraction of the spinning solution is 15%.

(2) Transfer the spinning liquid prepared in step (1) into the syringe and connect it to the autosampler, connect the needle to a high-voltage power supply for electrospinning, and use the receiving device to receive PAN/PMMA composite electrospinning Nanofiber membrane; the flow rate is 1ml/min, the spinning voltage is 17kv, and the distance between the needle and the receiver is 15cm.

(3) The electrospun composite nanofiber membrane obtained in step (2) was placed in a vacuum drying oven, and dried in vacuum at 90° C. for 12 hours to remove residual organic solvents.

(4) Place the nanofiber membrane dried in step (3) in a blast drying oven for pre-oxidation. The nanofiber membrane is placed vertically, and both ends are fixed with iron clips to prevent it from shrinking due to heat. , adjusting the temperature to 280° C., the heating rate to 10° C./min, and pre-oxidizing treatment for 1 hour to obtain a PAN/PMMA pre-oxidized nanofiber membrane.

(5) Place the pre-oxidized nanofiber membrane obtained in step (4) in a vacuum tube furnace for carbonization treatment; vacuumize the tube furnace for 3 times to remove the original residual air in the tube, and then introduce N ₂ at a flow rate of The carbonization temperature is 200ml/min, the carbonization temperature is set to be 800°C, the heating rate is ₅ °C/min, and the carbonization time is 1h to obtain a PAN/PMMA carbon nanofiber material; the outer diameter of the obtained carbon nanofiber is 450nm; According to the test, the specific surface area of the material is 711.39m ² /g by BET analysis, and the pore volume is 0.401cm ³ /g and the micropore volume is 0.206 cm ³ /g by DFT analysis.

(6) Weigh ~100mg of the porous carbon nanofiber material prepared in Example 2, transfer it to an adsorption tube, and activate it in high-purity _N2 at 200°C for 6 hours; after activation, transfer the adsorption tube to carbon dioxide high-pressure adsorption In the instrument, the adsorption effect of carbon dioxide in the pressure range of 1 bar was measured at 0 ° C and 25 ° C respectively; the carbon dioxide adsorption capacity of the material prepared in Example 2 was 3.41 mmol/g at 0 ° C and 1 bar pressure; Example 2 The carbon dioxide adsorption capacity of the material prepared in is 2.47 mmol/g at 25 °C and 1 bar pressure.

Example 3.

Porous carbon nanofiber material for carbon dioxide prepared from PAN and PMMA.

(1) Weigh PAN and PMMA with a mass ratio of 1:1 and add them to DMF. At room temperature, stir continuously until the polymer is completely dissolved to form a uniform and transparent solution. The mass fraction of the spinning solution is 15%.

(2) Transfer the spinning liquid prepared in step (1) into the syringe and connect it to the autosampler, connect the needle to a high-voltage power supply for electrospinning, and use the receiving device to receive PAN/PMMA composite electrospinning Nanofiber membrane; the flow rate is 1ml/min, the spinning voltage is 17kv, and the distance between the needle and the receiver is 15cm.

(3) The electrospun composite nanofiber membrane obtained in step (2) was placed in a vacuum drying oven, and dried in vacuum at 90° C. for 12 hours to remove residual organic solvents.

(4) Place the nanofiber membrane dried in step (3) in a blast drying oven for pre-oxidation. The nanofiber membrane is placed vertically, and both ends are fixed with iron clips to prevent it from shrinking due to heat. , adjusting the temperature to 280° C., the heating rate to 10° C./min, and pre-oxidizing treatment for 1 hour to obtain a PAN/PMMA pre-oxidized nanofiber membrane.

(5) Place the pre-oxidized nanofiber membrane obtained in step (4) in a vacuum tube furnace for carbonization treatment; vacuumize the tube furnace for 3 times to remove the original residual air in the tube, and then introduce N ₂ at a flow rate of The carbonization temperature is 200ml/min, the carbonization temperature is set at 600°C, the heating rate is ₅ °C/min, and the carbonization time is 1h to obtain a PAN/PMMA carbon nanofiber material; the outer diameter of the obtained carbon nanofiber is 400nm; According to the test, the specific surface area of the material is 417.55m ² /g measured by BET method, and the pore volume is 0.266cm ³ /g and the micropore volume is 0.138 cm ³ /g by DFT analysis.

(6) Weigh ~100mg of the porous carbon nanofiber material prepared in Example 3, transfer it to an adsorption tube, and activate it in high-purity _N2 at 200°C for 6 hours; after activation, transfer the adsorption tube to carbon dioxide high-pressure adsorption In the instrument, under 0 ℃ and 25 ℃, the adsorption effect of carbon dioxide in the pressure range of 1 bar is measured respectively; The material prepared in embodiment 3 is 2.64 mmol/g to the carbon dioxide adsorption capacity under 0 ℃, 1 bar pressure condition; embodiment 3 The carbon dioxide adsorption capacity of the material prepared in is 2.17 mmol/g at 25 °C and 1 bar pressure.

Example 4.

Porous carbon nanofiber material for carbon dioxide prepared from PAN and PMMA.

(1) Weigh PAN and PMMA with a mass ratio of 1:1 and add them to DMF. At room temperature, stir continuously until the polymer is completely dissolved to form a uniform and transparent solution. The mass fraction of the spinning solution is 15%.

(2) Transfer the spinning liquid prepared in step (1) into the syringe and connect it to the autosampler, connect the needle to a high-voltage power supply for electrospinning, and use the receiving device to receive PAN/PMMA composite electrospinning Nanofiber membrane; the flow rate is 1ml/min, the spinning voltage is 17kv, and the distance between the needle and the receiver is 15cm.

(3) The electrospun composite nanofiber membrane obtained in step (2) was placed in a vacuum drying oven, and dried in vacuum at 90° C. for 12 hours to remove residual organic solvents.

(4) Place the nanofiber membrane dried in step (3) in a blast drying oven for pre-oxidation. The nanofiber membrane is placed vertically, and both ends are fixed with iron clips to prevent it from shrinking due to heat. , the temperature was adjusted to 240°C, the heating rate was 10°C/min, and the pre-oxidation treatment was performed for 1 hour to obtain a PAN/PMMA pre-oxidized nanofiber membrane.

(5) Place the pre-oxidized nanofiber membrane obtained in step (4) in a vacuum tube furnace for carbonization treatment; vacuumize the tube furnace for 3 times to remove the original residual air in the tube, and then introduce N ₂ at a flow rate of The carbonization temperature is 200ml/min, the carbonization temperature is set to be 1000°C, the heating rate is ₅ °C/min, and the carbonization time is 1h to obtain a PAN/PMMA carbon nanofiber material; the outer diameter of the obtained carbon nanofiber is 450nm; According to the test, the specific surface area of the material is 395.12m ² /g measured by BET method, and the pore volume is 0.203cm ³ /g and the micropore volume is 0.156 cm ³ /g by DFT analysis.

(6) Weigh ~100mg of the porous carbon nanofiber material prepared in Example 4, transfer it to an adsorption tube, and activate it in high-purity _N2 at 200°C for 6 hours; after activation, transfer the adsorption tube to carbon dioxide high-pressure adsorption In the instrument, under 0 ℃ and 25 ℃, the adsorption effect of carbon dioxide in the pressure range of 1 bar is measured respectively; The material prepared in embodiment 4 is 3.14 mmol/g to the carbon dioxide adsorption capacity under 0 ℃, 1 bar pressure condition; embodiment 4 The carbon dioxide adsorption capacity of the material prepared in is 2.30 mmol/g at 25 °C and 1 bar pressure.

Example 5.

Porous carbon nanofiber material for carbon dioxide prepared from PAN and PMMA.

(1) Weigh PAN and PMMA with a mass ratio of 1:1 and add them to DMF. At room temperature, stir continuously until the polymer is completely dissolved to form a uniform and transparent solution. The mass fraction of the spinning solution is 15%.

(2) Transfer the spinning liquid prepared in step (1) into the syringe and connect it to the autosampler, connect the needle to a high-voltage power supply for electrospinning, and use the receiving device to receive PAN/PMMA composite electrospinning Nanofiber membrane; the flow rate is 1ml/min, the spinning voltage is 17kv, and the distance between the needle and the receiver is 15cm.

(3) The electrospun composite nanofiber membrane obtained in step (2) was placed in a vacuum drying oven, and dried in vacuum at 90° C. for 12 hours to remove residual organic solvents.

(4) Place the nanofiber membrane dried in step (3) in a blast drying oven for pre-oxidation. The nanofiber membrane is placed vertically, and both ends are fixed with iron clips to prevent it from shrinking due to heat. , the temperature was adjusted to 300°C, the heating rate was 10°C/min, and the pre-oxidation treatment was performed for 1 hour to obtain a PAN/PMMA pre-oxidized nanofiber membrane.

(5) Place the pre-oxidized nanofiber membrane obtained in step (4) in a vacuum tube furnace for carbonization treatment; vacuumize the tube furnace for 3 times to remove the original residual air in the tube, and then introduce N ₂ at a flow rate of The carbonization temperature is 200ml/min, the carbonization temperature is set to be 1000°C, the heating rate is ₅ °C/min, and the carbonization time is 1h to obtain a PAN/PMMA carbon nanofiber material; the outer diameter of the obtained carbon nanofiber is 450nm; According to the test, the specific surface area of the material is 853.17m ² /g measured by BET method, and the pore volume of the material is 0.596cm ³ /g and the micropore volume is 0.279cm ³ /g by DFT analysis.

(6) Weigh ~100mg of the porous carbon nanofiber material prepared in Example 5, transfer it to an adsorption tube, and activate it in high-purity _N2 at 200°C for 6 hours; after activation, transfer the adsorption tube to carbon dioxide high-pressure adsorption In the instrument, at 0°C and 25°C, the adsorption effect of carbon dioxide in the pressure range of 1 bar was measured respectively; the material prepared in Example 5 had a carbon dioxide adsorption capacity of 3.74mmol/g at 0°C and 1 bar pressure; Example 5 The carbon dioxide adsorption capacity of the material prepared in 25°C and 1 bar pressure is 2.57mmol/g.

Example 6.

A porous carbon nanofiber material for carbon dioxide prepared from PAN and PVP.

(1) Weigh ~20mg of PAN and PVP polymer powders respectively, put them into crucibles, place them in a thermogravimetric analyzer, feed _N2 gas at a flow rate of 60ml/min, and heat at a heating rate of 5°C/min Up to 1000°C, the thermogravimetric analyzer automatically records the weight loss of the two polymers. PAN has mass residues, and PVP has no mass residues; therefore, PAN acts as a carbon precursor and PVP is an organic pore-forming agent.

(2) Weigh PAN and PVP with a mass ratio of 1:1 and add them to DMF. Stir continuously at room temperature until the polymer is completely dissolved to form a uniform and transparent solution. The mass fraction of the spinning solution is 15%.

(3) Transfer the spinning solution prepared in step (2) into the syringe and connect it to the autosampler, connect the needle to a high-voltage power supply for electrospinning, and use the receiving device to receive PAN/PVP composite electrospinning Nanofiber membrane; the flow rate is 1ml/min, the spinning voltage is 17kv, and the distance between the needle and the receiver is 15cm.

(4) The electrospun composite nanofiber membrane obtained in step (3) was placed in a vacuum drying oven, and dried in vacuum at 90° C. for 12 hours to remove residual organic solvents.

(5) Place the nanofiber membrane dried in step (4) in a blast drying oven for pre-oxidation, place the nanofiber membrane vertically, and fix both ends with iron clips to prevent it from shrinking due to heat. , the temperature was adjusted to 280°C, the heating rate was 10°C/min, and the pre-oxidation treatment was performed for 1 hour to obtain a PAN/PVP pre-oxidized nanofiber membrane.

(6) Place the pre-oxidized nanofiber membrane obtained in step (5) in a vacuum tube furnace for carbonization treatment; vacuumize the tube furnace for 3 times to remove the original residual air in the tube, and then introduce N ₂ at a flow rate of The carbonization temperature is 200ml/min, the carbonization temperature is set at 1000°C, the heating rate is 5°C/min, and the carbonization time is 1h to obtain the PAN/PVP carbon nanofiber material; through the _N2 adsorption and desorption test, the material is measured by the BET method The specific surface area is 354.67m ² /g, and the pore volume of the material is 0.176cm ³ /g and the micropore volume is 0.143cm ³ /g through DFT analysis.

(7) Weigh ~100mg of the porous carbon nanofiber material prepared in Example 6, transfer it to an adsorption tube, and activate it in high-purity _N2 at 200°C for 6 hours; after activation, transfer the adsorption tube to carbon dioxide high-pressure adsorption In the instrument, at 0°C and 25°C, the adsorption effect of carbon dioxide in the pressure range of 1 bar was measured respectively; the material prepared in Example 6 had an adsorption capacity of 3.21mmol/g for carbon dioxide at 0°C and 1 bar pressure; Example 6 The carbon dioxide adsorption capacity of the material prepared in is 2.45 mmol/g at 25 °C and 1 bar pressure.

Example 7.

A porous carbon nanofiber material for carbon dioxide prepared from PAN and PVP.

(1) Weigh PAN and PVP with a mass ratio of 1:1 and add them to DMF. At room temperature, stir continuously until the polymer is completely dissolved to form a uniform and transparent solution. The mass fraction of the spinning solution is 15%.

(2) Transfer the spinning solution prepared in step (1) into the syringe and connect it to the autosampler, connect the needle to a high-voltage power supply for electrospinning, and use the receiving device to receive PAN/PVP composite electrospinning Nanofiber membrane; the flow rate is 1ml/min, the spinning voltage is 17kv, and the distance between the needle and the receiver is 15cm.

(3) The electrospun composite nanofiber membrane obtained in step (2) was placed in a vacuum drying oven, and dried in vacuum at 90° C. for 12 hours to remove residual organic solvents.

(4) Place the nanofiber membrane dried in step (3) in a blast drying oven for pre-oxidation. The nanofiber membrane is placed vertically, and both ends are fixed with iron clips to prevent it from shrinking due to heat. , the temperature was adjusted to 280°C, the heating rate was 10°C/min, and the pre-oxidation treatment was performed for 1 hour to obtain a PAN/PVP pre-oxidized nanofiber membrane.

(5) Place the pre-oxidized nanofiber membrane obtained in step (4) in a vacuum tube furnace for carbonization treatment; vacuumize the tube furnace for 3 times to remove the original residual air in the tube, and then introduce N ₂ at a flow rate of The carbonization temperature is 200ml/min, the carbonization temperature is set at 800°C, the heating rate is 5°C/min, and the carbonization time is 1h to obtain a PAN/PVP carbon nanofiber material; through the _N2 adsorption and desorption test, the material is measured by the BET method The specific surface area is 267.22m ² /g, and the pore volume of the material is 0.135cm ³ /g and the micropore volume is 0.107cm ³ /g through DFT analysis.

(6) Weigh ~100mg of the porous carbon nanofiber material prepared in Example 7, transfer it to an adsorption tube, and activate it in high-purity _N2 at 200°C for 6 hours; after activation, transfer the adsorption tube to carbon dioxide high-pressure adsorption In the instrument, under 0 ℃ and 25 ℃, the adsorption effect to carbon dioxide in the pressure range of 1 bar is measured respectively; The material prepared in embodiment 7 is 2.54 mmol/g to the carbon dioxide adsorption capacity under 0 ℃, 1 bar pressure condition; Embodiment 7 The carbon dioxide adsorption capacity of the material prepared in is 2.10 mmol/g at 25 °C and 1 bar pressure.

Example 8.

A porous carbon nanofiber material for carbon dioxide prepared from PAN and PVP.

(1) Weigh PAN and PVP with a mass ratio of 1:1 and add them to DMF. At room temperature, stir continuously until the polymer is completely dissolved to form a uniform and transparent solution. The mass fraction of the spinning solution is 15%.

(2) Transfer the spinning solution prepared in step (1) into the syringe and connect it to the autosampler, connect the needle to a high-voltage power supply for electrospinning, and use the receiving device to receive PAN/PVP composite electrospinning Nanofiber membrane; the flow rate is 1ml/min, the spinning voltage is 17kv, and the distance between the needle and the receiver is 15cm.

(3) The electrospun composite nanofiber membrane obtained in step (2) was placed in a vacuum drying oven, and dried in vacuum at 90° C. for 12 hours to remove residual organic solvents.

(4) Place the nanofiber membrane dried in step (3) in a blast drying oven for pre-oxidation. The nanofiber membrane is placed vertically, and both ends are fixed with iron clips to prevent it from shrinking due to heat. , the temperature was adjusted to 280°C, the heating rate was 10°C/min, and the pre-oxidation treatment was performed for 1 hour to obtain a PAN/PVP pre-oxidized nanofiber membrane.

(5) Place the pre-oxidized nanofiber membrane obtained in step (4) in a vacuum tube furnace for carbonization treatment; vacuumize the tube furnace for 3 times to remove the original residual air in the tube, and then introduce N ₂ at a flow rate of The carbonization temperature is 200ml/min, the carbonization temperature is set at 600°C, the heating rate is 5°C/min, and the carbonization time is 1h to obtain a PAN/PVP carbon nanofiber material; through the _N2 adsorption and desorption test, the material is measured by the BET method The specific surface area is 157.44m ² /g, and the pore volume of the material is 0.0788cm ³ /g and the micropore volume is 0.064cm ³ /g through DFT analysis.

(6) Weigh ~100mg of the porous carbon nanofiber material prepared in Example 8, transfer it to an adsorption tube, and activate it in high-purity _N2 at 200°C for 6 hours; after activation, transfer the adsorption tube to carbon dioxide high-pressure adsorption In the instrument, under 0 ℃ and 25 ℃, the adsorption effect of carbon dioxide in the pressure range of 1 bar is measured respectively; The material prepared in embodiment 8 is 2.34mmol/g to the carbon dioxide adsorption capacity under 0 ℃, 1 bar pressure condition; embodiment 8 The carbon dioxide adsorption capacity of the material prepared in is 2.05 mmol/g at 25 °C and 1 bar pressure.

Example 9.

Porous carbon nanofiber materials for carbon dioxide prepared from PAN and CA.

(1) Weigh ~20mg of PAN and CA polymer powders respectively, put them into crucibles, place them in a thermogravimetric analyzer, feed _N2 gas at a flow rate of 60ml/min, and heat at a heating rate of 5°C/min Up to 1000°C, the thermogravimetric analyzer automatically records the weight loss of the two polymers. PAN has mass residues, while CA has no mass residues; therefore, PAN acts as a carbon precursor and CA acts as an organic pore-forming agent.

(2) Weigh PAN and CA with a mass ratio of 1:1 and add them to DMF. Stir continuously at room temperature until the polymer is completely dissolved to form a uniform and transparent solution. The mass fraction of the spinning solution is 30%.

(3) Transfer the spinning solution prepared in step (2) into the syringe and connect it to the autosampler, connect the needle to a high-voltage power supply for electrospinning, and use the receiving device to receive PAN/CA composite electrospinning Nanofiber membrane; the flow rate is 1ml/min, the spinning voltage is 17kv, and the distance between the needle and the receiver is 15cm.

(4) The electrospun composite nanofiber membrane obtained in step (3) was placed in a vacuum drying oven, and dried in vacuum at 90° C. for 12 hours to remove residual organic solvents.

(5) Place the nanofiber membrane dried in step (4) in a blast drying oven for pre-oxidation, place the nanofiber membrane vertically, and fix both ends with iron clips to prevent it from shrinking due to heat. , the temperature was adjusted to 280°C, the heating rate was 10°C/min, and the pre-oxidation treatment was performed for 1 hour to obtain the PAN/CA pre-oxidized nanofiber membrane.

(6) Place the pre-oxidized nanofiber membrane obtained in step (5) in a vacuum tube furnace for carbonization treatment; vacuumize the tube furnace for 3 times to remove the original residual air in the tube, and then introduce N ₂ at a flow rate of The carbonization temperature is 200ml/min, the carbonization temperature is set at 800°C, the heating rate is 5°C/min, and the carbonization time is 1h to obtain a PAN/CA carbon nanofiber material; through the _N2 adsorption and desorption test, the material is measured by the BET method The specific surface area is 380.34m ² /g, and the pore volume of the material is 0.258cm ³ /g and the micropore volume is 0.146cm ³ /g through DFT analysis.

(7) Weigh ~100mg of the porous carbon nanofiber material prepared in Example 9, transfer it to an adsorption tube, and activate it in high-purity _N2 at 200°C for 6 hours; after activation, transfer the adsorption tube to carbon dioxide high-pressure adsorption In the instrument, the adsorption effect of carbon dioxide in the pressure range of 1 bar was measured at 0 ° C and 25 ° C respectively; the carbon dioxide adsorption capacity of the material prepared in Example 9 was 3.59 mmol/g at 0 ° C and 1 bar pressure; Example 9 The carbon dioxide adsorption capacity of the material prepared in is 2.57 mmol/g at 25 °C and 1 bar pressure.

Claims (10)

1. A porous carbon nanofiber material for carbon dioxide adsorption and a preparation method thereof, characterized in that the preparation method: use a thermogravimetric analyzer to reasonably screen out a polymer as a suitable carbon precursor and an organic pore-forming agent, and mix the electrostatic Spinning technology and one-step high-temperature carbonization treatment to prepare porous carbon nanofiber membrane; this method has remarkable pore-forming performance, can avoid the complicated activation steps in the traditional carbon material preparation, has low cost, simple preparation process, and avoids secondary pollution in the activation process Problem; According to the thermogravimetric analysis data, the pre-oxidation and carbonization treatment parameters can be reasonably adjusted, and the pore structure of the prepared material can be selectively adjusted to form a large number of micropores and ultra-micropores, which is conducive to the adsorption of carbon dioxide. It is an efficient, An energy-saving and environment-friendly preparation method; specifically comprising the following steps: (1) Take a small amount of polymer and analyze the thermal stability of the target polymer at a certain temperature through a thermogravimetric analyzer in an analytical gas atmosphere; polymers with good thermal stability (mass remaining after thermogravimetric analysis) are used as carbon precursors , polymers with poor thermal stability (no mass remaining after thermogravimetric analysis) are used as organic pore-forming agents; (2) Mix and dissolve the carbon precursor and the organic pore-forming agent in an organic solvent in a certain proportion, and prepare a mixed spinning solution with a certain mass fraction; (3) Transfer the mixed spinning solution in step (2) to a syringe, and prepare a composite electrospinning nanofiber membrane by electrospinning technology; (4) placing the composite electrospun nanofiber membrane obtained in step (3) in a blast oven, and pre-oxidizing at a low temperature in an air atmosphere to obtain pre-oxidized porous nanofibers; (5) The pre-oxidized porous nanofiber membrane obtained in step (4) is placed in a carbonization furnace, and carbonized at a high temperature to obtain porous carbon nanofibers. 2. A carbon dioxide adsorption porous carbon nanofiber material and preparation method thereof, characterized in that the material: has an ultra-high specific surface area, ultra-high porosity; has an obvious porous structure, a large number of mesopores and micropores coexist; has Fast adsorption kinetics and large adsorption capacity for carbon dioxide; at the same time, the adsorption force of the material is intermolecular electrostatic force, the desorption conditions are mild, and the material can be reused. It has good application prospects and environmental governance benefits in the field of carbon dioxide capture. 3. A porous carbon nanofiber material for carbon dioxide adsorption and its preparation method according to claim 1, characterized in that the gas atmosphere for analysis in the step (1) is N ₂ , O ₂ or both according to 9: 1-1:9 ratio of mixed gas; the certain temperature in the step (1) is 200-1000°C. 4. The porous carbon nanofiber material for carbon dioxide adsorption and its preparation method according to claim 1, characterized in that the carbon precursor in the step (1) is polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), phenolic resin, pitch (pitch) in one or more. 5. The porous carbon nanofiber material for carbon dioxide adsorption and its preparation method according to claim 1, characterized in that the organic pore-forming agent in the step (1) is polymethyl methacrylate (PMMA), One or more of cellulose acetate (CA), polypropylene pyrrolidone (PVP), polyethylene oxide (PEO), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), and nylon 6. 6. The porous carbon nanofiber material for carbon dioxide adsorption and its preparation method according to claim 1, characterized in that the organic solvent in the step (2) is N,N-dimethylformamide (DMF) One or more of , N,N-dimethylacetamide (DMAC), tetrahydrofuran (THF), and ethanol. 7. The porous carbon nanofiber material for carbon dioxide adsorption and its preparation method according to claim 1, characterized in that the mass fraction of the mixed spinning solution in the step (2) is 10-30%, wherein carbon The ratio of precursor to organic pore former is 9:1-1:9. 8. A porous carbon nanofiber material for carbon dioxide adsorption and its preparation method according to claim 1, characterized in that the electrospinning process conditions in the step (3) are: the static spinning voltage is 10-25 kv, The receiving distance is 10-30cm, the flow rate of spinning liquid is 0.5-2 ml/min, and the spinning time is 10-30 h. 9. A porous carbon nanofiber material for carbon dioxide adsorption and its preparation method according to claim 1, characterized in that the pre-oxidation process conditions in the step (4) are: the temperature is 200-300°C, and the heating rate is 1-10°C/min, and the treatment time is 1-6 h, wherein the pre-oxidation temperature and treatment time are determined by the thermogravimetric analysis data of the carbon precursor and the organic pore-forming agent. 10. A porous carbon nanofiber material for carbon dioxide adsorption and its preparation method according to claim 1, characterized in that the carbonization process conditions in the step (5) are as follows: the temperature is 600-1000 °C, and the heating rate is 1 -10 ℃, the treatment time is 1-6 h, and the carbonization temperature and treatment time are determined by the thermogravimetric analysis data of the carbon precursor and the organic pore former.