Method for in-situ CO2 conversion and activation of Fe-K modified porous activated carbon and application of Fe-K modified porous activated carbon

Abstract

The invention discloses a method for in-situ CO2 conversion and activation of Fe-K modified porous activated carbon and application of the Fe-K modified porous activated carbon. The method comprises the following steps: (1) dipping and drying: adding ferric citrate, potassium carbonate and a carbon material into water, fully dissolving and dispersing, heating at 50-90 DEG C to evaporate moisture to obtain a Fe-K loaded carbon material, and drying in a drying oven at 80-120 DEG C for later use; (2) high-temperature pyrolysis: carrying out high-temperature pyrolysis on the Fe-K loaded carbon material at 500-700 DEG C for 2-6 hours to obtain a Fe-K modified carbon material; and (3) blending pyrolysis: uniformly mixing the Fe-K modified carbon material and limestone in a mass ratio of (0.1-3): 1, carrying out high-temperature co-pyrolysis for 2-8 hours, and reacting at a constant temperature of 600-900 DEG C to obtain the Fe-K modified porous activated carbon. According to the method, carbon material activation and CO2 generated by limestone decomposition are linked, carbonate decomposition and charcoal activation are integrated, the carbon reaction activity is increased by introducing iron and potassium elements, in-situ reduction of CO2 generated in the carbonate decomposition process in the cement industry is achieved, and meanwhile the selectivity of in-situ CO2 conversion can be improved.

Description

Technical Field

[0001] This invention relates to the field of carbon neutralization catalysis in the cement industry, specifically to a method for in-situ CO2 conversion and activation of Fe-K modified porous activated carbon and its application. Background Technology

[0002] The cement industry is the second largest industrial source of carbon emissions globally, accounting for 5-7% of total global carbon emissions. Its carbon emissions mainly come from the combustion of fossil fuels during energy supply and the decomposition of carbonate feedstocks during clinker production. For the former, emission reductions can be achieved through energy structure optimization and the introduction of renewable energy or alternative fuels. For the latter, the decomposition of carbonates is essentially a stable pathway for carbon dioxide release. If targeted capture and utilization mechanisms can be embedded at this stage, it is hoped that carbon emission sources can be transformed into carbon resources, thereby creating an economically feasible and emission-reduction-friendly closed-loop path for the cement industry.

[0003] To enhance pore structure and optimize material properties, carbon materials typically require activation treatment, with high-temperature CO2 etching being a common method. However, this process presents several key challenges: 1. Catalytic performance: Insufficient and unevenly distributed active sites lead to low CO2 adsorption activation efficiency; poor product selectivity hinders the targeted preparation of high-value-added products; and slow reaction kinetics fail to meet industrial efficiency requirements. 2. Activation process: High-temperature CO2 etching is energy-intensive and costly, and the activation level is difficult to control precisely, potentially leading to carbon material framework collapse or insufficient porosity; the surface chemistry is unstable after activation, and beneficial functional groups are easily lost. 3. Stable recycling: Structural degradation can occur during the reaction due to pore blockage and framework breakage; regeneration and cleaning damage active sites, resulting in significant performance degradation after repeated recycling. Summary of the Invention To address the aforementioned problems, the purpose of this invention is to provide a method for in-situ CO2 conversion and activation of Fe-K modified porous activated carbon. This method links the activation of carbon materials with the CO2 generated from limestone decomposition, establishing a synergistic production process that integrates carbonate decomposition with biochar activation. By introducing iron and potassium elements to increase the reactivity of carbon, in-situ reduction of CO2 generated during carbonate decomposition in the cement industry can be achieved, while also improving the selectivity of in-situ CO2 conversion.

[0004] The purpose of this invention is to provide a method for in-situ CO2 conversion and activation of Fe-K modified porous activated carbon, the method comprising the following steps: (1) Impregnation and drying: Select a certain proportion of ferric citrate and potassium carbonate as Fe and K precursors, add ferric citrate, potassium carbonate and carbon material to a mass excess of distilled water, evaporate the water under stirring in an 80°C water bath to obtain Fe-K loaded carbon material, and dry it for later use. (2) High-temperature pyrolysis: The Fe-K-loaded carbon material was pyrolyzed at 500-700 ℃ for 4 h to obtain Fe-K modified carbon material; (3) Blending pyrolysis: Fe-K modified carbon material and limestone are then uniformly mixed at a mass ratio of 0.1-3:1 and co-pyrolyzed at high temperature. The reaction is set to a constant temperature of 600-900 ℃ to obtain Fe-K modified porous activated carbon.

[0005] Furthermore, in step (1), the carbon material is a non-metallic material with carbon as the main component, including one or more of biomass carbon, coal, graphite products, and carbon fiber.

[0006] Furthermore, in step (1), the Fe and K precursors are soluble and easily pyrolyzable metal salts with Fe and K as the main components, including one or more of citrate, acetate, and nitrate.

[0007] Further, in step (1), the mass ratio of ferric citrate, potassium carbonate and carbon material is 5-20: 2-15: 10-50.

[0008] Further, in step (3), before the blending pyrolysis, the Fe-K modified carbon material is ground to 20-30 micrometers and blended with limestone with particles of 60-80 micrometers.

[0009] Further, in step (3), after blending and pyrolysis, in-situ CO2 conversion is carried out to obtain CO syngas, quicklime, and the Fe-K modified porous activated carbon.

[0010] Further, in step (4), the Fe-K modified porous activated carbon removes impurities by sieving and acid washing.

[0011] Furthermore, pickling is performed using water-soluble acids, including citric acid and hydrochloric acid.

[0012] The second objective of this method is to provide applications for the Fe-K modified porous carbon materials prepared by the method, including applications in carbon electrode materials, storage materials, and adsorption materials.

[0013] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: The beneficial effects of this invention are as follows: 1. This invention links the activation of carbon materials with the CO2 generated from limestone decomposition, establishing a synergistic production process that integrates carbonate decomposition with biochar activation. This enables in-situ reduction of CO2 generated during carbonate decomposition in the cement industry, thereby reducing raw material costs. This solution not only effectively reduces carbon emissions but also allows for the joint production of high-purity quicklime as a cement raw material and high-value-added activated carbon materials, thus providing a potential new pathway for the cement industry, which emphasizes resource utilization and emission reduction.

[0014] 2. Gas-solid reaction systems are often limited by slow reaction kinetics and frequently require the participation of metal catalysts. Considering the permissible range of elements introduced into cement raw materials (Ni and Cu are restricted), Fe-based catalysts show good application potential. Fe itself can be used as a component of cement raw materials or supported on the surface of carbon materials to enhance their catalytic performance. However, compared with nickel-based catalysts, Fe-based catalysts still have lower activity, requiring adjustment of their electronic structure or modification of the carbon support to improve their performance. This invention increases carbon reactivity by introducing potassium, and a certain concentration of potassium can be accepted in cement raw materials. CO2 generated from limestone decomposition is converted in situ into CO syngas, achieving "emission-as-conversion," and promoting carbon neutrality and technology pathways in the cement industry. 3. The carbon material is activated simultaneously during the limestone decomposition process, avoiding the use of traditional CO2 or chemical activators, reducing secondary pollution and energy consumption. The material has a specific surface area >1000 m² after acid washing. 2 / g, possessing excellent adsorption and catalytic activity, is suitable for various catalytic, adsorption and energy storage scenarios.

[0015] 4. Carbon emission reduction is achieved in the limestone decomposition process during cement production through reaction. Solid co-pyrolysis achieves more than 99% carbonate decomposition, and the CO selectivity in the converted gas is greater than 90%. When the obtained activated carbon is used as a carbon electrode, it exhibits a specific capacitance of 245 mAh / g in an aqueous zinc-manganese battery, which is higher than commercial performance. The obtained quicklime can be used to further blend with other cement raw materials to produce cement.

[0016] 5. Biochar (such as bamboo charcoal) can be used as a carbon source, which is renewable and in line with the development trend of green materials. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1This is a schematic flowchart of a method for in-situ CO2 conversion and activation of Fe-K modified porous activated carbon provided in Embodiment 1 of the present invention; Figure 2 SEM image of activated carbon obtained by blending and pyrolyzing unloaded bamboo charcoal using the method of Example 1, showing that the basic pore structure of biomass is maintained. Figure 3 The image shows a SEM image of the Fe-K modified porous activated carbon prepared in Example 1 of this invention. It shows that the Fe-K modified porous activated carbon maintains the basic pore structure of biomass while developing many pore structures on its surface, demonstrating better activation and pore formation. Figure 4 The graph shows the in-situ CO2 conversion reaction curve during the co-pyrolysis of ordinary bamboo charcoal and limestone. It can be seen from the graph that the CO gas selectivity is 61.5% at 800℃. Figure 5 The figure shows the in-situ CO2 conversion reaction curve during the co-pyrolysis of Fe-K modified porous activated carbon and limestone according to the present invention. It can be seen from the figure that the CO gas selectivity is 90.2% at 800 °C. Figure 6 Bamboo charcoal (C 100 ) and Fe-K modified porous activated carbon (K 10 Fe 10 C 80 The capacitance of bamboo charcoal electrode used as carbon electrode material in aqueous zinc-manganese batteries was 140 mAh / g, and that of Fe-K modified porous activated carbon electrode was 245 mAh / g. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1 This embodiment discloses a method for in-situ CO2 conversion and activation of Fe-K modified porous activated carbon. For example... Figure 1 As shown in the flowchart, the specific steps of the method are as follows: 8 g of ferric citrate and 6 g of potassium carbonate were dissolved in excess distilled water. 10 g of bamboo charcoal powder was added to the solution, and the mixture was heated and stirred in an 80 °C water bath until the water evaporated, yielding a solid sample. The solid sample was then placed in a 100 °C oven for 24 h to further remove moisture. The dried sample was then pyrolyzed at 550 °C for 4 h to obtain Fe-K modified porous activated carbon. The Fe-K modified porous activated carbon was then ground to 20-30 micrometers and blended with limestone particles of 60-80 micrometers (2 g each). The high-temperature pyrolysis conversion reaction was set at a constant temperature of 800 °C for 4 h. The solid was then sieved through a 40-micrometer sieve to obtain quicklime and Fe-K modified porous activated carbon. The Fe-K modified porous activated carbon after the reaction was washed with citric acid solution to remove metal ions from the porous carbon material. It was then washed with distilled water and anhydrous ethanol 3-5 times, and dried in an 80°C oven. The resulting Fe-K modified porous activated carbon had a specific surface area greater than 1000 m². 2 / g.

[0021] Figure 4 The graph shows the in-situ CO2 conversion reaction curve during the co-pyrolysis of ordinary bamboo charcoal and limestone according to the present invention. It can be seen from the graph that the CO gas selectivity is 61.5% at 800 °C. Figure 5 The graph shows the in-situ CO2 conversion reaction curve during the co-pyrolysis of Fe-K modified porous activated carbon and limestone. The graph indicates that the CO selectivity in the gas produced by the solid co-pyrolysis conversion is greater than 90%. Figure 6 The results show that the capacitance of the aqueous zinc-manganese battery when the obtained activated carbon is used as a carbon electrode is 245 mAh / g, which is higher than that of commercially available batteries. In contrast, the capacitance of the aqueous zinc-manganese battery when unloaded bamboo charcoal is used as a carbon electrode is 140 mAh / g. Therefore, the Fe-K modified porous carbon material for in-situ CO2 conversion described in this invention can effectively convert CO2 generated from limestone decomposition and activate its own material properties. It can be applied to other fields to achieve carbon emission reduction in the production process and reduce product manufacturing costs.

[0022] Example 2: Preparation of Fe-K modified porous activated carbon using straw charcoal as a carbon source This embodiment discloses a method for in-situ CO2 conversion activation of Fe-K modified porous activated carbon. The aim is to illustrate that carbon materials are not limited to bamboo charcoal, and that the Fe-K loading ratio has a significant impact on performance.

[0023] Specific steps: 10g of straw biochar (obtained from agricultural waste straw through anaerobic pyrolysis at 500°C) was used as the carbon base. 4g of ferric citrate and 8g of potassium carbonate were dissolved in excess distilled water. The straw biochar was added to the above solution and stirred in an 80°C water bath until the water evaporated, then dried in a 100°C oven for 24 hours. The dried sample was pyrolyzed at 600°C for 4 hours to obtain Fe-K modified straw carbon. This material was ground to 20-30 micrometers and uniformly mixed with 2g each of 60-80 micrometer limestone. A co-pyrolysis reaction was carried out at 750°C for 4 hours. After the reaction, the mixture was sieved and acid-washed with citric acid solution, then washed with distilled water and ethanol, and dried to obtain Fe-K modified porous straw carbon material.

[0024] Under these conditions, the selectivity for in-situ CO2 conversion to CO reaches 85%. The specific surface area of ​​the obtained porous carbon material is approximately 950 m². 2 / g. When used as an electrode material in zinc-manganese batteries, its capacitance reaches 210 mAh / g. Benefits of this embodiment: It demonstrates that agricultural waste can serve as a high-quality carbon precursor, broadening raw material sources, reducing costs, and exhibiting good reactivity in the mid-temperature range.

[0025] Example 3: High Fe loading and high reaction temperature can enhance catalytic performance. This embodiment provides a method for in-situ CO2 conversion activation of Fe-K modified porous activated carbon. The aim is to explore the further enhancement of catalytic performance by high Fe loading.

[0026] Specific steps: Using 10g of bamboo charcoal as a base, add it, along with 12g of ferric citrate and 3g of potassium carbonate, to excess distilled water. Subsequent impregnation, drying, and initial pyrolysis (600°C) steps are the same as in Example 1. The obtained Fe-K modified carbon is mixed with limestone at a mass ratio of 1:1 (1g carbon material, 1g limestone). A co-pyrolysis reaction is carried out at a high temperature of 800°C for 4 hours. Post-reaction treatment steps are the same as in Example 1.

[0027] Results: Under high Fe loading, CO selectivity was further improved to 94%, indicating that high Fe content can provide more active sites at high temperatures, thus enhancing CO2 reduction. The resulting carbon material has a specific surface area of ​​approximately 1000 m². 2 / g. Its electrode capacitance is 230 mAh / g.

[0028] Example 4: Energy-saving application at low co-pyrolysis temperature This embodiment provides a method for in-situ CO2 conversion activation of Fe-K modified porous activated carbon. The aim of this embodiment is to explore how this method can produce Fe-K modified porous activated carbon that retains activity even at relatively low temperatures, thus adapting to milder process conditions.

[0029] Specific steps: The preparation steps of Fe-K modified bamboo charcoal are exactly the same as in Example 1. The obtained modified carbon is mixed with limestone at a mass ratio of 1:1 (1g carbon material, 1g limestone). The co-pyrolysis reaction is carried out at 650°C, and the reaction time is extended to 6 hours. The post-reaction treatment steps are the same as in Example 1.

[0030] Results: At lower temperatures, the CO selectivity was 78%, which, although lower than at high temperatures, was still significantly better than that of the unmodified material.

[0031] Due to the mild reaction and minimal erosion of the carbon skeleton, the resulting material has a specific surface area of ​​approximately 800 m². 2 Although the carbon structure is more complete, its mechanical properties may be superior. The electrode capacitance is 180 mAh / g.

[0032] This embodiment demonstrates the applicability of the technology under medium and low temperature conditions, providing a feasible path for energy-sensitive or equipment-limited industrial applications, while also obtaining high-performance activated carbon products.

[0033] It should be noted that the above examples are merely preferred embodiments of the present invention, and the present invention can also substitute specific operational steps and various reactants in the above methods. Therefore, all equivalent changes made based on the description and illustrations of the present invention, whether directly or indirectly applied to other related technical fields, are included within the scope of the present invention.

Claims

1. A method for in-situ CO2 conversion and activation of Fe-K modified porous activated carbon, characterized in that, The method includes the following steps: (1) Impregnation and drying: Ferric citrate and potassium carbonate are selected as precursors. Ferric citrate, potassium carbonate and carbon materials are added to water and fully dissolved and dispersed. The water is evaporated by heating at 50-90℃ to obtain Fe-K loaded carbon materials. The materials are dried in an oven at 80-120℃ for 24-48 hours and then dried for later use. (2) High-temperature pyrolysis: The Fe-K-loaded carbon material is pyrolyzed at 500-700 ℃ for 2-6 h to obtain Fe-K modified carbon material; (3) Blending pyrolysis: Fe-K modified carbon material and limestone are then uniformly mixed at a mass ratio of 0.1-3:1 and co-pyrolyzed at high temperature for 2-8 h. The reaction is set at a constant temperature of 600-900℃ to obtain Fe-K modified porous activated carbon.

2. The method for in-situ CO2 conversion and activation of Fe-K modified porous activated carbon as described in claim 1, characterized in that, In step (1), the carbon material is a non-metallic material with carbon as the main component, including one or more of biomass carbon, coal, graphite products, and carbon fiber.

3. The method for in-situ CO2 conversion and activation of Fe-K modified porous activated carbon as described in claim 1, characterized in that, In step (1), the Fe and K precursors are soluble and easily pyrolyzable metal salts with Fe and K as the main components, including one or more of citrate, acetate, and nitrate.

4. The method for in-situ CO2 conversion and activation of Fe-K modified porous activated carbon as described in claim 1, characterized in that, In step (1), the mass ratio of ferric citrate, potassium carbonate and carbon material is 5-20:2-15:10-50.

5. The method for in-situ CO2 conversion and activation of Fe-K modified porous activated carbon as described in claim 1, characterized in that, In step (3), before the blending pyrolysis, the Fe-K modified carbon material is ground to 20-30 micrometers and blended with limestone with particles of 60-80 micrometers.

6. The method for in-situ CO2 conversion and activation of Fe-K modified porous activated carbon as described in claim 1, characterized in that, In step (3), after blending and pyrolysis, in-situ CO2 conversion is carried out to obtain CO syngas, quicklime, and the Fe-K modified porous activated carbon.

7. The method for in-situ CO2 conversion and activation of Fe-K modified porous activated carbon as described in claim 1, characterized in that, In step (4), the Fe-K modified porous activated carbon is subjected to sieving and acid washing to remove impurities.

8. The method for in-situ CO2 conversion and activation of Fe-K modified porous activated carbon as described in claim 7, characterized in that, Pickling is performed using water-soluble acids, including citric acid and hydrochloric acid.

9. The application of the Fe-K modified porous carbon material prepared by the method of claim 1, characterized in that, The Fe-K modified porous activated carbon has applications in carbon electrode materials, storage materials, and adsorption materials.

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