Gradient pore channel base charged adsorbent, preparation method thereof and application of gradient pore channel base charged adsorbent in air carbon capture
By designing gradient channel structures in adsorbents, combined with 3D printing and activation technology, the problems of low adsorption efficiency and poor stability of existing adsorbents at low CO2 concentrations are solved, and efficient CO2 capture and long-life adsorbent performance are achieved, which is suitable for large-scale applications of direct air capture technology.
Patent Information
- Application Number
- CN202510313887.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-17
- Publication Date
- 2025-05-09
AI Technical Summary
The adsorption efficiency of existing adsorbents at low CO2 concentrations is limited and their stability is poor, limiting the large-scale application of direct air capture (DAC) technology.
Gradient pore base charged adsorbent is used to design the macrostructure through 3D printing technology, and the activation method is used to achieve mesophase formation, forming a cross-scale throughput network of macropores, mesopores and micropores, improving specific surface area and CO2 capture capability.
The CO2 adsorption amount at low CO2 concentration is significantly improved to reach 0.5 mmol/g, which is better than conventional activated carbon and charged adsorbents, and the capacity retention rate is ≥95% after 100 adsorption-desorption cycles, making it suitable for large-scale DAC applications.
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Figure CN119951479A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of adsorbents, and in particular relates to a gradient pore base charged adsorbent and a preparation method thereof, and application thereof in air carbon capture. Background Art
[0002] In order to achieve the net zero emission target and effectively curb climate change, humans need to take a dual path of "emission reduction" and "carbon removal" in parallel. As an important solution for carbon removal, the core bottleneck of direct air capture (DAC) technology lies in the performance breakthrough of adsorbents. Existing DAC systems mainly rely on two types of adsorption materials, namely chemical adsorbents based on strong alkaline solutions (such as potassium hydroxide) and solid alkaline adsorbents (such as calcium hydroxide). Although these materials have the ability to capture CO2, their regeneration process requires high-temperature treatment of more than 900°C, resulting in huge energy consumption and operating costs. Although the emerging metal organic framework materials (MOFs) reduce the regeneration temperature to about 100°C, they face new problems such as insufficient material stability and high preparation costs.
[0003] The high regeneration energy consumption and complex process of existing adsorbents limit the large-scale application of DAC. Therefore, it is necessary to develop new adsorbents with low cost, low temperature regeneration and strong stability to break through the bottleneck of existing DAC technology. Inspired by the battery electrode charging process, researchers introduced active hydroxide ions (OH-) into porous carbon materials through electrochemical means to form a new type of "charged adsorbent". Its advantages are that it uses the conductivity of the material to achieve rapid regeneration (90-100°C) through resistive heating without external energy or complex equipment; it can be prepared using cheap activated carbon as raw material through a battery charging process, which is simple and the materials are easily available; OH- can form carbonates / bicarbonates with CO2, significantly improving the CO2 capture capacity at low pressure (close to atmospheric concentration).
[0004] However, the above-mentioned charged adsorbents still have some problems, such as being extremely sensitive to humidity. In a high humidity environment, water molecules occupy the hydrophilic pores, thereby weakening the CO2 adsorption capacity; and their capacity is limited under the current DAC system conditions, which is only 0.14-0.2mmol / g, lower than some metal-organic framework materials and requires further optimization, thus limiting the large-scale application of charged adsorbents. Summary of the invention
[0005] In view of the above-mentioned prior art, the present invention provides a gradient pore base charged adsorbent and a preparation method thereof and application in air carbon capture, which solves the problems of limited adsorption efficiency and poor stability at low CO2 concentrations in the prior art.
[0006] In order to achieve the above object, the technical solution adopted by the present invention is: to provide a method for preparing a gradient pore base charged adsorbent, comprising the following steps:
[0007] S1: dispersing the activated carbon precursor, pore former and binder in water to obtain composite slurry 1;
[0008] S2: Printing the composite slurry 1 by using 3D printing technology to obtain a preform;
[0009] S3: pre-oxidizing the preform in an air atmosphere;
[0010] S4: carbonizing the preform after pre-oxidation under an inert atmosphere to obtain fractal channel activated carbon powder;
[0011] S5: The fractal channel activated carbon powder is kept at 950°C in a CO2 atmosphere for 1 to 2 hours, and then mixed with KOH at a mass ratio of 1:2 at 850°C in a nitrogen atmosphere for 1 to 2 hours to obtain a crude product;
[0012] S6: The mixture of the crude product and polytetrafluoroethylene was mixed with ethanol at a solid-liquid ratio of 1 g:3 mL to obtain composite slurry 2, and then the composite slurry 2 was molded into a film of 0.2 to 0.3 mm, and the film was vacuum dried at 100° C. for 24 hours, and then cut to obtain an activated carbon electrode sheet;
[0013] S7: In KOH electrolyte, the activated carbon electrode sheet is used as the positive electrode, and a potential of +0.565 V relative to the standard hydrogen electrode is applied for 4 hours to obtain a gradient pore base charged adsorbent.
[0014] The beneficial effects of the present invention are as follows: the method provided by the present invention innovatively integrates the macroscopic structural design of 3D printing and the meso-microscopic pore-forming mechanism of the activation method, realizes the cross-scale coordinated regulation of pores, and successfully realizes the cross-scale interconnected network of macropores (>50nm), mesopores (2~50nm) and micropores (<2nm), wherein the macropores are directly formed by precise path design, the mesopores are generated by the dual effects of pore-forming agent decomposition and KOH etching, and the micropores are derived from the selective etching of the carbon matrix during the activation process. The cross-scale interconnected network of the three makes the specific surface area exceed 2500m 2 / g, and then anchoring of OH- is achieved through electrochemical polarization, so that the adsorption capacity of the prepared gradient pore base charged adsorbent is increased by more than 200% compared with the traditional charged adsorbent.
[0015] Based on the above technical solution, the present invention can also be improved as follows.
[0016] Furthermore, the activated carbon precursor is obtained by mixing lignin and polyacrylonitrile in a mass ratio of 6:4, the pore-forming agent is obtained by compounding NH4HCO3 and polyethylene glycol in a mass ratio of 3:1, the adhesive is polyvinyl alcohol, and the mass ratio of the activated carbon precursor, the pore-forming agent and the adhesive is 60-80:10-15:3-8.
[0017] Furthermore, the solid content of the composite slurry is 30-50wt%.
[0018] The technical effect of adopting the further technical scheme is as follows: the aromatic ring structure of lignin provides a precursor unit for the formation of micropores, the high carbon yield of polyacrylonitrile ensures the skeleton strength, NH4HCO3 is thermally decomposed at 200°C to generate CO2 / NH3 bubbles to construct mesopores, and the decomposition residue of polyethylene glycol forms 2-5nm pores, and the hydrogen bond network generated by polyvinyl alcohol makes the slurry exhibit shear thinning characteristics at 10-50Pa·s (25°C), which meets the requirements of 3D printing.
[0019] Furthermore, the process parameters of the 3D printing technology are: nozzle diameter 300 μm, layer height 70-90% of the nozzle diameter, printing path is a cross grid structure, and the grid spacing is 120-180% of the nozzle diameter.
[0020] The technical effect of adopting the further technical solution is that the configuration can ensure a porosity of 70% while achieving a compressive strength of 8 to 12 MPa, and obtain a macroporous structure of >50 nm.
[0021] Furthermore, the pre-oxidation is performed by increasing the temperature to 200-300° C. at a heating rate of 2° C. / min and keeping the temperature for 3 h.
[0022] Furthermore, the carbonization step was performed by increasing the temperature to 800-900° C. at a heating rate of 5° C. / min and maintaining the temperature for 2 h.
[0023] Furthermore, the mass ratio of the crude product to the polytetrafluoroethylene in the mixture of the crude product and the polytetrafluoroethylene is 95:5.
[0024] The technical effect of adopting further technical solutions is: the gradient pores in the fractal structure achieved through the double activation process can greatly increase the density of active sites, and then the anchoring of OH- is achieved through electrochemical polarization, so that the amount of OH- charged is greatly increased, so that the performance of the final gradient pore base charged adsorbent is greatly improved.
[0025] The invention also provides a gradient pore base charged adsorbent prepared by a preparation method of the gradient pore base charged adsorbent.
[0026] The present invention also provides application of gradient pore base charged adsorbent in air carbon capture.
[0027] The beneficial effects of the present invention are as follows: the gradient pore base charged adsorbent provided by the present invention successfully realizes a cross-scale interconnected network of macropores (>50nm), mesopores (2~50nm) and micropores (<2nm), and the CO2 adsorption capacity (20℃ / 400ppm) reaches 0.5mmol / g at low CO2 concentration, which is significantly better than the adsorption performance of conventional activated carbon (about 0.05mmol / g) and conventional charged adsorbents (less than 0.3mmol / g), and the capacity retention rate is ≥95% after 100 adsorption-desorption cycles. Its excellent performance allows it to be used on a large scale on DAC, so the gradient pore base charged adsorbent has excellent industrial prospects. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 This is a micropore field emission scanning electron microscope image of the gradient pore base charged adsorbent prepared in Example 1;
[0029] Figure 2 This is a mesoporous field emission scanning electron microscope image of the gradient pore base charged adsorbent prepared in Example 1;
[0030] Figure 3 This is a macroporous field emission scanning electron microscope image of the gradient pore base charged adsorbent prepared in Example 1;
[0031] Figure 4 This is a specific surface area analysis diagram of the gradient pore base charged adsorbent prepared in Example 1;
[0032] Figure 5 The CO2 adsorption performance diagram of Example 1 and Comparative Examples 1-2;
[0033] Figure 6 This is the CO2 cyclic adsorption and desorption performance diagram of Example 1;
[0034] Figure 7 This is a performance diagram of CO2 adsorption under different humidity conditions of Example 1. DETAILED DESCRIPTION
[0035] The specific implementation modes of the present invention are described in detail below with reference to the embodiments.
[0036] Example 1
[0037] A method for preparing a gradient pore base charged adsorbent comprises the following steps:
[0038] S1: 6 g of lignin and 4 g of polyacrylonitrile were mixed, 1.5 g of NH4HCO3 and 0.5 g of polyethylene glycol were added, and then 1 g of polyvinyl alcohol was added, and then the mixture was dispersed in 20 mL of deionized water to obtain composite slurry 1;
[0039] S2: The process parameters of the 3D printing technology are set to a nozzle diameter of 300 μm, a Koch fractal curve generated by an L-system algorithm for the printing path, a printing layer height of 240 μm, a printing speed of 8 mm / s, a path interval of 450 μm, and composite slurry 1 is printed to obtain a preform with a porosity of 72±3%;
[0040] S3: placing the preform in an air atmosphere, raising the temperature to 240°C at a heating rate of 2°C / min and keeping the temperature for 3 hours to obtain a pre-oxidized preform;
[0041] S4: placing the pre-oxidized preform in a nitrogen atmosphere, raising the temperature to 850°C at a heating rate of 5°C / min and keeping the temperature for 2 hours to obtain fractal channel activated carbon powder;
[0042] S5: The fractal channel activated carbon powder was kept at 950°C in a CO2 atmosphere (flow rate 100 mL / min) for 1.5 h, then mixed with KOH at a mass ratio of 1:2, and kept at 850°C in a nitrogen atmosphere for 1.5 h to obtain a crude product;
[0043] S6: A mixture of the crude product (95 wt%) and polytetrafluoroethylene (5 wt%) was mixed with ethanol at a solid-liquid ratio of 1 g:3 mL to obtain a composite slurry 2, and then the composite slurry 2 was kneaded and rolled into a 0.25 mm film, and the film was vacuum dried at 100° C. for 24 h, and then cut into circular sheets with a diameter of 1 cm to obtain an activated carbon electrode sheet;
[0044] S7: In a 6M KOH electrolyte, an activated carbon electrode was used as the positive electrode, and a potential of +0.565 V relative to the standard hydrogen electrode was applied for 4 h to obtain a gradient pore base charged adsorbent.
[0045] Example 2
[0046] A method for preparing a gradient pore base charged adsorbent comprises the following steps:
[0047] S1: 6 g of lignin and 4 g of polyacrylonitrile were mixed, 1.875 g of NH4HCO3 and 0.625 g of polyethylene glycol were added, and then 0.5 g of polyvinyl alcohol was added, and then dispersed in 33 mL of deionized water to obtain composite slurry 1;
[0048] S2: The process parameters of the 3D printing technology are set to a nozzle diameter of 300 μm, a Koch fractal curve generated by an L-system algorithm for the printing path, a printing layer height of 210 μm, a printing speed of 8 mm / s, a path interval of 360 μm, and composite slurry 1 is printed to obtain a preform with a porosity of 72±3%;
[0049] S3: placing the preform in an air atmosphere, raising the temperature to 200°C at a heating rate of 2°C / min and keeping the temperature for 3 hours to obtain a pre-oxidized preform;
[0050] S4: placing the pre-oxidized preform in a nitrogen atmosphere, raising the temperature to 800°C at a heating rate of 5°C / min and keeping the temperature for 2 hours to obtain fractal channel activated carbon powder;
[0051] S5: The fractal channel activated carbon powder was kept at 950°C in a CO2 atmosphere (flow rate 100 mL / min) for 1 h, then mixed with KOH at a mass ratio of 1:2, and kept at 850°C in a nitrogen atmosphere for 1 h to obtain a crude product;
[0052] S6: A mixture of the crude product (95 wt%) and polytetrafluoroethylene (5 wt%) was mixed with ethanol at a solid-liquid ratio of 1 g:3 mL to obtain a composite slurry 2, and then the composite slurry 2 was kneaded and rolled into a 0.2 mm film, and the film was vacuum dried at 100° C. for 24 h, and then cut into circular sheets with a diameter of 1 cm to obtain an activated carbon electrode sheet;
[0053] S7: In a 6M KOH electrolyte, an activated carbon electrode was used as the positive electrode, and a potential of +0.565 V relative to the standard hydrogen electrode was applied for 4 h to obtain a gradient pore base charged adsorbent.
[0054] Example 3
[0055] A method for preparing a gradient pore base charged adsorbent comprises the following steps:
[0056] S1: 6 g of lignin and 4 g of polyacrylonitrile were mixed, 0.94 g of NH4HCO3 and 0.31 g of polyethylene glycol were added, and then 1 g of polyvinyl alcohol was added, and then dispersed in 12.5 mL of deionized water to obtain composite slurry 1;
[0057] S2: The process parameters of the 3D printing technology are set to a nozzle diameter of 300 μm, a Koch fractal curve generated by an L-system algorithm for the printing path, a printing layer height of 270 μm, a printing speed of 8 mm / s, a path interval of 540 μm, and composite slurry 1 is printed to obtain a preform with a porosity of 72±3%;
[0058] S3: placing the preform in an air atmosphere, raising the temperature to 300°C at a heating rate of 2°C / min and keeping the temperature for 3 hours to obtain a pre-oxidized preform;
[0059] S4: placing the pre-oxidized preform in a nitrogen atmosphere, raising the temperature to 900°C at a heating rate of 5°C / min and keeping the temperature for 2 hours to obtain fractal channel activated carbon powder;
[0060] S5: The fractal channel activated carbon powder was kept at 950°C in a CO2 atmosphere (flow rate 100 mL / min) for 2 h, then mixed with KOH at a mass ratio of 1:2, and kept at 850°C in a nitrogen atmosphere for 2 h to obtain a crude product;
[0061] S6: A mixture of the crude product (95 wt%) and polytetrafluoroethylene (5 wt%) was mixed with ethanol at a solid-liquid ratio of 1 g:3 mL to obtain a composite slurry 2, and then the composite slurry 2 was kneaded and rolled into a 0.3 mm film, and the film was vacuum dried at 100° C. for 24 h, and then cut into circular sheets with a diameter of 1 cm to obtain an activated carbon electrode sheet;
[0062] S7: In a 6M KOH electrolyte, an activated carbon electrode was used as the positive electrode, and a potential of +0.565 V relative to the standard hydrogen electrode was applied for 4 h to obtain a gradient pore base charged adsorbent.
[0063] Comparative Example 1
[0064] This comparative example is activated carbon.
[0065] Comparative Example 2
[0066] A method for preparing a charged adsorbent comprises the following steps:
[0067] S1: The activated carbon was immersed in 6M HNO3, refluxed at 80°C for 12h, then washed with deionized water until neutral, and vacuum dried at 60°C for 24h to obtain pretreated activated carbon;
[0068] S2: A mixture of pretreated activated carbon (95 wt%) and polytetrafluoroethylene (5 wt%) was mixed with ethanol at a solid-liquid ratio of 1 g:3 mL, kneaded and rolled into a 0.25 mm film, and the film was vacuum dried at 100 ° C for 24 h, and then cut into circular slices with a diameter of 1 cm to obtain an activated carbon electrode sheet;
[0069] S3: In a 6M KOH electrolyte, the activated carbon electrode sheet is used as the positive electrode, and a potential of +0.565 V relative to the standard hydrogen electrode is applied for 4 hours to obtain a charged adsorbent.
[0070] The performance effects of the gradient pore base charged adsorbents prepared in Examples 1 to 3 are similar, and the gradient pore base charged adsorbent prepared in Example 1 is used in subsequent experiments.
[0071] Experimental Example 1
[0072] Microscopic analysis experiment: The gradient pore base charged adsorbent prepared in Example 1 was analyzed using a scanning electron microscope. The experimental results are shown in the figure. Figure 1 This is a micropore field emission scanning electron microscope image of a gradient pore base charged adsorbent. Figure 2This is a mesoporous field emission scanning electron microscopy image of a gradient pore base charged adsorbent. Figure 3 This is a macropore field emission scanning electron micrograph of the gradient pore base charged adsorbent. Pore sizes of different sizes correspond to micropores, mesopores and macropores, which are clearly visible in the figure, indicating the successful preparation of the gradient pore base charged adsorbent.
[0073] Experimental Example 2
[0074] Specific surface area analysis experiment: The specific surface area of the gradient pore base charged adsorbent prepared in Example 1 was analyzed by gas adsorption method. The experimental results are as follows: Figure 4 As shown in Figure 2, the specific surface area of the gradient pore base charged adsorbent reaches 2850 m 2 / g, indicating that the adsorbent can provide more adsorption sites.
[0075] Experimental Example 3
[0076] Air carbon capture experiment 1: The gradient pore base charged adsorbent prepared in Example 1, the activated carbon of Comparative Example 1 and the charged adsorbent prepared in Comparative Example 2 were degassed at 100°C for 15 hours in vacuum to remove residual moisture and impurities, and then 400ppm CO2 was introduced at 30°C to simulate dry air adsorption, and 100% N2 and 100°C were used for desorption to test the CO2 adsorption performance of the adsorbent at ultra-low concentrations. The experimental results are shown in FIG. Figure 5 As shown, the adsorption capacity of the gradient pore base charged adsorbent prepared in Example 1 is stable at about 0.45 mmol / g, which is much better than that of Comparative Examples 1-2.
[0077] Experimental Example 4
[0078] Cycle experiment: The gradient pore base charged adsorbent prepared in Example 1 was degassed at 100°C for 15 hours in vacuum to remove residual moisture and impurities, and then CO2 was adsorbed at 25°C for 20 minutes and CO2 was desorbed at 100°C for 20 minutes. The cycle was repeated 100 times. The results are as follows: Figure 6 As shown, after 100 cycles, the gradient pore base charged adsorbent still maintained 95% of its capacity, showing excellent stability.
[0079] Experimental Example 5
[0080] Air carbon capture experiment 2: The gradient pore base charged adsorbent prepared in Example 1 was degassed at 100°C for 15 hours in vacuum to remove residual moisture and impurities. The air carbon capture experiment was carried out under the same adsorption conditions as in Experiment 3, but at 10% and 40% humidity respectively. The experimental results are shown in FIG. Figure 7As shown, the CO2 adsorption capacity of the gradient pore base charged adsorbent prepared in Example 1 under a humidity environment of 40% is stable at 0.42 mmol / g, which is not much different from that under a humidity environment of 10%, indicating that after physical and chemical modification, the gradient pore base charged adsorbent still maintains excellent adsorption performance under high humidity conditions.
[0081] Although the specific implementation of the present invention is described in detail in conjunction with the embodiments, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.
Claims
1. A method for preparing a gradient pore base charged adsorbent, characterized in that: The following steps are involved: S1: dispersing the activated carbon precursor, pore former and binder in water to obtain composite slurry 1; S2: Printing the composite slurry 1 by using 3D printing technology to obtain a preform; S3: pre-oxidizing the preform in an air atmosphere; S4: carbonizing the preform after pre-oxidation under an inert atmosphere to obtain fractal channel activated carbon powder; S5: The fractal channel activated carbon powder is kept at 950°C in a CO2 atmosphere for 1 to 2 hours, then mixed with KOH at a mass ratio of 1:2, and kept at 850°C in a nitrogen atmosphere for 1 to 2 hours to obtain a crude product; S6: The mixture of the crude product and polytetrafluoroethylene was mixed with ethanol at a solid-liquid ratio of 1 g:3 mL to obtain composite slurry 2, and then the composite slurry 2 was molded into a film of 0.2 to 0.3 mm, and the film was vacuum dried at 100° C. for 24 hours, and then cut to obtain an activated carbon electrode sheet; S7: In KOH electrolyte, the activated carbon electrode sheet is used as the positive electrode, and a potential of +0.565 V relative to the standard hydrogen electrode is applied for 4 hours to obtain a gradient pore base charged adsorbent.
2. The method for preparing the gradient pore base charged adsorbent according to claim 1, characterized in that: The activated carbon precursor is obtained by mixing lignin and polyacrylonitrile in a mass ratio of 6:4, the pore-forming agent is obtained by compounding NH4HCO3 and polyethylene glycol in a mass ratio of 3:1, the adhesive is polyvinyl alcohol, and the mass ratio of the activated carbon precursor, the pore-forming agent and the adhesive is 60-80:10-15:3-8.
3. The method for preparing the gradient pore base charged adsorbent according to claim 1, characterized in that: The solid content of the composite slurry 1 is 30-50wt%.
4. The method for preparing the gradient pore base charged adsorbent according to claim 1, characterized in that: The process parameters of the 3D printing technology are: a nozzle diameter of 300 μm, a layer height of 70 to 90% of the nozzle diameter, a cross-grid structure for the printing path, and a grid spacing of 120 to 180% of the nozzle diameter.
5. The method for preparing the gradient pore base charged adsorbent according to claim 1, characterized in that: The pre-oxidation is to increase the temperature to 200-300° C. at a heating rate of 2° C. / min and keep the temperature for 3 hours.
6. The method for preparing the gradient pore base charged adsorbent according to claim 1, characterized in that: The carbonization is carried out by raising the temperature to 800-900° C. at a heating rate of 5° C. / min and keeping the temperature for 2 hours.
7. The method for preparing the gradient pore base charged adsorbent according to claim 1, characterized in that: The mass ratio of the crude product to the polytetrafluoroethylene in the mixture of the crude product and the polytetrafluoroethylene is 95:
5.
8. The gradient pore base charged adsorbent prepared by the preparation method of the gradient pore base charged adsorbent according to any one of claims 1 to 7.
9. Use of the gradient pore base charged adsorbent according to claim 8 in air carbon capture.