Method for freezing and storing CO2 by using functional carbon with Janus structure

Abstract

The invention discloses a method for freezing and storing CO2 by using functional carbon with a Janus structure, which comprises the following steps of: 1, doping, mixing and drying pickled straws, inert metal salt and a high-performance activating agent, and activating in a high-temperature inert atmosphere to prepare a functional carbon material with a mesoporous-microporous tandem hydrophobic functional carbon structure; 2, carrying out hydrothermal carbonization reaction on the functional carbon material and a substance containing nitrogen and oxygen elements to obtain internal hydrophobic-external hydrophilic functional carbon powder with a Janus structure; and 3, placing the carbon powder in a high-pressure CO2 environment for saturated adsorption, placing the carbon powder in an aqueous solution, and freezing and sealing. According to the invention, a directional freezing system based on internal hydrophobic-external hydrophilic mesoporous-microporous hole series connection type functional carbon with high CO2 adsorption capacity is constructed, so that low-temperature long-time high-capacity stable storage of CO2 is realized, and the problem of a carbon source in a novel adsorption compression carbon dioxide supercritical / transcritical energy storage system is fundamentally solved.

Description

Technical Field

[0001] The present invention belongs to the field of CCUS (Carbon Capture, Utilization and Storage), and relates to a method for CO2 storage, specifically to a method for stably storing post-combustion captured CO2 and transporting it to an adsorption-compressed carbon dioxide super / transcritical energy storage system. Background Art

[0002] In 2019, coal accounted for as high as 58% of China's energy consumption. By 2050, fossil energy will still play an important role, accounting for 10 - 15% of China's energy consumption. CCUS will be the only technical option to achieve near-zero emissions of this part of fossil energy.

[0003] Energy storage is an important support for the high-quality development of the new energy industry. By breaking through the energy time and space allocation ability that breaks through time and space constraints, a new power system architecture with a dynamic balance of "source - grid - load" is constructed, effectively solving the structural contradiction between the intermittency of wind and solar power generation and the persistence of grid demand.

[0004] The new adsorption-compressed carbon dioxide super / transcritical energy storage system is a type of compressed gas energy storage. Compared with air, compressed CO2 has advantages such as high cycle efficiency and large energy storage density. At the same time, the post-combustion CO2 capture technology provides an abundant carbon source for it. However, gas leakage occurs during the transportation of the captured biochar material, reducing the CO2 transportation efficiency. Summary of the Invention

[0005] To solve the above problems, based on the biochar CO2 capture technology, the present invention provides a method for storing CO2 with a Janus-structured functional carbon ice. This method realizes the directional etching of biomass by systematically analyzing molten metal salts assisted pyrolysis gas and activators, promotes the directional deep pore etching of the activator, realizes the construction of a series-connected "meso - micro" pore structure, and constructs defect sites on the surface with inert molten metal salts to realize the construction of a Janus structure with internal hydrophobic - external hydrophilic properties. After placing the adsorbed carbon material in liquid water, it is frozen and blocked, fundamentally solving the carbon source problem in the new adsorption-compressed carbon dioxide super / transcritical energy storage system.

[0006] The object of the present invention is achieved through the following technical solutions:

[0007] A method for storing CO2 with a Janus-structured functional carbon ice includes the following steps:

[0008] Step 1: Mix pickled straw with inert metal salts and a high-performance activator, dry them, and then activate them under high-temperature inert atmosphere conditions to prepare a functional carbon material with a series-connected "meso - micro" pore hydrophobic functional carbon structure. The specific steps are as follows:

[0009] Step 1.1: Place the straw powder in a sulfuric acid solution, stir, perform acid washing, and filter by suction until neutral. Among them: the concentration of the sulfuric acid solution is 0.1 - 0.5 mol / L, and the solid-liquid ratio is 1:5 - 15;

[0010] Step 1.2: Place the acid-washed straw obtained in Step 1.1, the mixture of a high-performance activator, and an inert metal salt aqueous solution in a water bath and stir magnetically to obtain the loaded straw powder. Subsequently, place it in a blast drying oven for drying to remove the remaining moisture. Among them: the inert metal salt includes one of salts with relatively weak activation performance such as KCl, NaCl, CuCl₂, etc.; the high-performance activator includes one of KOH, ZnCl₂, K₂CO₃; the mass ratio of the acid-washed straw to the high-performance activator is 1:0.5 - 3, and the ratio of the high-performance activator to the inert metal salt is 1:1 - 3; the drying time is 8 - 14 h;

[0011] Step 1.3: Place the dried straw powder obtained in Step 1.2 in a horizontal tube furnace and activate it under a protective atmosphere. Among them: the protective atmosphere is N₂. In order to sufficiently reduce the content of hydrophilic groups in the carbon material, the N₂ flow rate is 0.5 - 3 L / min; the activation temperature is 700 - 900 °C, the heating rate is 5 - 10 °C / min, and the activation holding time is 1 - 2 h;

[0012] Step 1.4: Place the activated functional carbon powder in Step 1.3 in a sulfuric acid solution, stir, filter by suction with deionized water until neutral, and dry to obtain a functional carbon material with a tandem type "meso-micro" pore structure and a large number of surface defect sites. Among them: the concentration of the sulfuric acid solution is 0.1 - 0.5 mol / L, and the solid-liquid ratio is 1:5 - 15;

[0013] Step 2: Perform hydrothermal carbonization reaction on the functional carbon material obtained in Step 1 and a nitrogen and oxygen-containing substance in a reaction kettle, wash with deionized water, and then perform drying treatment to obtain a functional carbon powder with a Janus structure of internal hydrophobic - external hydrophilic. Among them: the mass ratio of the functional carbon material to the nitrogen and oxygen-containing substance is 1:0.5 - 3; the nitrogen and oxygen-containing substance is one of acetic acid, urea, etc.; the temperature of the hydrothermal carbonization is 180 - 220 °C, the time is 20 - 30 h; the drying time is 8 - 14 h;

[0014] Step 3: Place the functional carbon powder with a Janus structure of internal hydrophobic - external hydrophilic obtained in Step 2 in a high-pressure CO₂ environment for saturated adsorption, and then place it in an aqueous solution for cryopreservation. Among them: the CO₂ pressure is 20 - 50 bar, the adsorption temperature is -16 °C to 0 °C (the higher the gas pressure, the lower the freezing point of water), the mass ratio of the functional carbon powder with a Janus structure of internal hydrophobic - external hydrophilic to water is 1:0.5 - 4, and the preservation temperature is -30 °C to -16 °C.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. By deeply exploring the multi-scale elementary ordering strategy of functional carbon, the mechanism of high-capacity CO2 adsorption, and the mechanism of ice sequestration on the surface of functional carbon, the present invention constructs an oriented ice-sealing system based on an internal hydrophobic-external hydrophilic "meso-micro" pore series-connected type functional carbon with high CO2 adsorption capacity, so as to achieve stable sequestration of CO2 with high capacity at low temperature for a long time, and fundamentally solve the carbon source problem in the new adsorption compression carbon dioxide super / cross-critical energy storage system.

[0017] 2. The present invention develops functional carbon with high adsorption capacity and high stability for CO2 sequestration and the corresponding technology. The pore structure of the functional carbon is distributed in a "meso-micro" pore series-connected type, achieving the superimposition of the advantages of meso-pores and micro-pores (rapid migration of meso-pores - stable adsorption of micro-pores) under low temperature and high pressure. Its hydrophilic functional groups are distributed in a surface-oriented manner, which is conducive to the oriented nucleation of ice crystals on the surface of the functional carbon, realizing stable sequestration of high-capacity CO2.

[0018] 3. The present invention uses an inert metal molten salt to assist a high-performance activator to construct a functional carbon with a series-connected "meso-micro" pore structure, giving full play to the advantages of various pore sizes during the adsorption / desorption process, and achieving the effect of 1 + 1 > 2.

[0019] 4. The present invention uses the defect sites constructed by passivating the surface of the functional carbon with an inert metal molten salt to provide hydrophilic group loading sites, and realizes directional repair only on the surface and in the meso- and macropores of the functional carbon by adjusting the content of the oxygen source substance. The construction of hydrophilic groups effectively enhances the stability of ice-sequestered gas.

[0020] 5. The present invention stably and efficiently transports the CO2 captured after combustion to the new adsorption compression carbon dioxide super / cross-critical energy storage system, providing a carbon source for the super / cross-critical compressed carbon dioxide energy storage system. Description of the Drawings

[0021] Figure 1 It is a conceptual diagram of a functional carbon material with a "meso-micro" pore series-connected type hydrophobic functional carbon structure. Detailed Embodiments

[0022] The technical solutions of the present invention will be further described below in conjunction with the embodiments, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention shall be covered by the protection scope of the present invention.

[0023] Example 1:

[0024] 3.0 g of pickled straw, 2.0 g of KOH, and 2.0 g of NaCl were added to 80 ml of aqueous solution. The resulting mixture was magnetically stirred at 50 °C for 6 h to obtain a homogeneous viscous solution, which was then transferred to a forced-air drying oven and dried at 105 °C for 12 h. Then, the straw powder was transferred to a horizontal tube furnace and heated to 750 °C at a heating rate of 5 °C / min and held for 1 h. When it cooled to room temperature, the black powder was taken out, mixed with an excessive amount of sulfuric acid solution, placed in a water bath, and magnetically stirred at room temperature for 12 h to wash away the residual alkali and salt. After suction filtration until neutral, it was dried to obtain a functional carbon material with a "meso-micro" pore series-connected hydrophobic functional carbon structure.

[0025] The obtained carbon powder and 1 g of urea were simultaneously placed in 80 ml of deionized water, magnetically stirred for 5 min, and then transferred to a reaction kettle. Hydrothermal treatment was carried out at 200 °C for 24 h. Then, the reaction kettle was taken out, cooled to room temperature, opened, and the upper-layer brown turbid liquid was poured out. Subsequently, it was washed with deionized water until neutral. The obtained carbon powder was placed in a forced-air drying oven and dried at 105 °C for 12 h to obtain a functional carbon powder with an internal hydrophobic-external hydrophilic functional carbon structure with a Janus structure. Subsequently, it was placed in an environment of 0 °C and 20 bar to fully adsorb CO2. The carbon material after adsorption saturation was mixed with an aqueous solution at a mass ratio of 1:1 and subjected to freeze-sealing at -15 °C.

[0026] Example 2:

[0027] 3.0 g of pickled straw, 2.0 g of K2CO3, and 2.0 g of NaCl were added to 80 ml of aqueous solution. The resulting mixture was magnetically stirred at 60 °C for 8 h to obtain a homogeneous viscous solution, which was then transferred to a forced-air drying oven and dried at 105 °C for 12 h. Then, the straw powder was transferred to a horizontal tube furnace and heated to 700 °C at a heating rate of 5 °C / min and held for 1 h. When it cooled to room temperature, the black powder was taken out, mixed with an excessive amount of sulfuric acid solution, placed in a water bath, and magnetically stirred at room temperature for 12 h to wash away the residual alkali and salt. After suction filtration until neutral, it was dried to obtain a functional carbon material with a "meso-micro" pore series-connected hydrophobic functional carbon structure.

[0028] The obtained carbon powder and 1 g of methanol were simultaneously placed in 80 ml of deionized water, magnetically stirred for 5 min, and then transferred to a reaction kettle. Hydrothermal treatment was carried out at 200 °C for 24 h. Then, the reaction kettle was taken out, cooled to room temperature, opened, and then washed with deionized water until neutral. The obtained carbon powder was placed in a forced-air drying oven and dried at 105 °C for 12 h to obtain a functional carbon powder with an internal hydrophobic-external hydrophilic functional carbon structure with a Janus structure. Subsequently, it was placed in an environment of 0 °C and 20 bar to fully adsorb CO2. The carbon material after adsorption saturation was mixed with an aqueous solution at a mass ratio of 1:0.5 and subjected to freeze-sealing at -15 °C.

[0029] Example 3:

[0030] Add 3.0 g of pickled straw, 2.0 g of ZnCl2, and 1.0 g of NaCl into 80 ml of aqueous solution. Magnetically stir the obtained mixture at 45 °C for 8 h to obtain a uniform viscous solution, and then transfer it to a forced-air drying oven to dry at a temperature of 105 °C for 12 h. Then transfer the straw powder to a horizontal tube furnace and heat it to 700 °C at a heating rate of 5 °C / min, and hold for 1 h. When it cools to room temperature, take out the black powder, mix it with an excessive amount of sulfuric acid solution, place it in a water bath, and magnetically stir it at room temperature for 12 h to wash away the residual alkali and salt. After suction filtration until neutral, dry it to obtain a functional carbon material with a "meso-micro" pore series-connected hydrophobic functional carbon structure.

[0031] Place the obtained carbon powder and 1 g of acetic acid in 80 ml of deionized water and magnetically stir for 5 min, then transfer it to a reaction kettle, hydrothermally treat it at 190 °C for 24 h, then take out the reaction kettle, cool it to room temperature and open it, and then wash it with deionized water until neutral. Place the obtained carbon powder in a forced-air drying oven and dry it at 105 °C for 12 h to obtain a functional carbon powder with an internal hydrophobic-external hydrophilic function with a Janus structure. Then place it in an environment of 0 °C and 20 bar to fully adsorb CO2. Mix the carbon material saturated with adsorption and the aqueous solution at a mass ratio of 1:0.5 and perform freeze-sealing at -15 °C.

Claims

1. A method for storing CO2 by functional carbon ice with Janus structure, characterized in that The method includes the following steps: Step 1: Mix pickled straw with an inert metal salt and a high-performance activator, dry the mixture, and then activate it under a high-temperature inert atmosphere to prepare a functional carbon material with a "meso-micro" pore series-connected hydrophobic functional carbon structure, where: the mass ratio of the pickled straw to the high-performance activator is 1:0.5 - 3, and the ratio of the high-performance activator to the inert metal salt is 1:1 - 3; Step 2: Hydrothermally carbonize the functional carbon material obtained in Step 1 with a nitrogen- and oxygen-containing substance in a reaction kettle, wash it with deionized water, and then dry it to obtain a Janus-structured internal hydrophobic-external hydrophilic functional carbon powder, where: the mass ratio of the functional carbon material to the nitrogen- and oxygen-containing substance is 1:0.5 - 3; Step 3: Place the Janus-structured internal hydrophobic-external hydrophilic functional carbon powder obtained in Step 2 in a high-pressure CO2 environment for saturated adsorption, and then place it in an aqueous solution for freeze storage.

2. The method for storing CO2 by the functional carbon ice with Janus structure according to claim 1, wherein The specific steps of Step 1 are as follows: Step 1-1: Place the straw powder in a sulfuric acid solution, stir, pickle, and filter it until neutral; Step 1-2: Magnetically stir the mixture of the pickled straw obtained in Step 1-1, the high-performance activator, and the inert metal salt aqueous solution in a water bath to obtain the loaded straw powder, and then place it in a blast drying oven for drying to remove the remaining moisture; Step 1-3: Place the dried straw powder obtained in Step 1-2 in a horizontal tube furnace and activate it under a protective atmosphere; Step 1-4: Place the activated functional carbon powder in Step 1-3 in a sulfuric acid solution, stir it, filter it with deionized water until neutral, and dry it to obtain a functional carbon material with a series-connected "meso-micro" pore structure and a large number of surface defect sites.

3. The method for storing CO2 by the functional carbon ice with a Janus structure according to claim 2, wherein In Step 1-1, the concentration of the sulfuric acid solution is 0.1 - 0.5 mol / L, and the solid-liquid ratio is 1:5 - 15.

4. The method for storing CO2 by the functional carbon ice with Janus structure according to claim 1 or 2, characterized in that The inert metal salt includes one of KCl, NaCl, and CuCl2, and the high-performance activator includes one of KOH, ZnCl2, and K2CO3.

5. The method for storing CO2 by the functional carbon ice with Janus structure according to claim 2, wherein In Step 1-3, the protective atmosphere is N2, the N2 flow rate is 0.5 - 3 L / min; the activation temperature is 700 - 900 °C, the heating rate is 5 - 10 °C / min, and the activation holding time is 1 - 2 h.

6. The method for storing CO2 by the functional carbon ice with Janus structure according to claim 2, wherein In Step 1-4, the concentration of the sulfuric acid solution is 0.1 - 0.5 mol / L, and the solid-liquid ratio is 1:5 - 15.

7. The method for storing CO2 by the functional carbon ice with a Janus structure according to claim 1, characterized in that In Step 2, the nitrogen- and oxygen-containing substance is one of acetic acid and urea.

8. The method for storing CO2 by the functional carbon ice with Janus structure according to claim 1, characterized in that In Step 2, the temperature of the hydrothermal carbonization is 180 - 220 °C, the time is 20 - 30 h; the drying time is 8 - 14 h.

9. The method for storing CO2 by the functional carbon ice with Janus structure according to claim 1, wherein In Step 3, the CO2 pressure is 20 - 50 bar, and the adsorption temperature is -16 °C to 0 °C.

10. The method for storing CO2 in a functional carbon ice with a Janus structure according to claim 1, characterized in that In Step 3, the mass ratio of the Janus-structured internal hydrophobic-external hydrophilic functional carbon powder to water is 1:0.5 - 4, and the storage temperature is -30 °C to -16 °C.

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