Catalyst preparation method, catalyst, and carbon dioxide trapping method

Abstract

The invention relates to the technical field of carbon capture, in particular to a preparation method of a catalyst, the catalyst and a carbon dioxide capture method. The preparation method of the catalyst comprises the following steps: mixing a porous biomass material with an oxygen-containing functional group with a solution containing a metal salt and a nitrogen source, and drying to prepare a loaded biomass material; and carrying out pyrolysis treatment on the loaded biomass material to prepare the metal-nitrogen-biomass-based carbon catalyst. According to the preparation method of the catalyst provided by the embodiment of the invention, the interaction force between the active sites in the metal-nitrogen-biomass-based carbon (M-N-C) catalyst and the biomass-based carbon carrier is enhanced, the structural stability of the catalyst is improved, the structural change in CO2 absorption-desorption circulation is inhibited, the agglomeration and migration phenomena of metal elements are reduced, and the CO2 absorption-desorption efficiency is improved. Further, the service life of the catalyst is prolonged, and the catalytic performance is guaranteed.

Description

Technical Field

[0001] This application relates to the field of carbon capture technology, and in particular to methods for preparing catalysts, catalysts, and methods for capturing carbon dioxide. Background Technology

[0002] Carbon capture technology is an effective way to reduce carbon emissions and achieve net-zero emissions. Among carbon capture technologies, chemical absorption is widely used in industrial carbon capture due to its mature technology and high absorption efficiency.

[0003] The amine solution absorption method utilizes an amine solution to capture CO2 from flue gas in an absorption tower, generating a rich solution. This rich solution is then pumped to a desorption tower, where high-purity CO2 is released through high-temperature heating, regenerating the lean solution for reuse. However, the CO2 desorption and regeneration process requires heating to 110°C–130°C to decompose stable absorption products, resulting in significant energy consumption, high steam costs, amine solution volatilization losses, and equipment corrosion.

[0004] To improve regeneration efficiency, researchers are using catalysts to catalyze CO2 desorption, thereby lowering the decomposition temperature. Among these, metal-nitrogen-carbon (MNC) materials, due to their unique electronic structure and high atom utilization, have shown great potential in the field of catalysis and are being explored for application in CO2 desorption processes.

[0005] The CO2 desorption process takes place in a high-temperature, strongly alkaline aqueous environment, which places extremely stringent requirements on the structural stability of the catalyst. However, MNC catalysts prepared by traditional methods have weak interactions between the active sites and the support, making them prone to structural changes during repeated CO2 absorption and desorption cycles, affecting the catalyst's durability. At the same time, metal elements are prone to agglomeration or migration during long-term use, leading to a reduction in active sites and a decline in catalytic performance. Summary of the Invention

[0006] Therefore, it is necessary to provide a method for preparing the catalyst, the catalyst itself, and a method for capturing carbon dioxide, in order to improve the structural stability of the MNC catalyst used for CO2 desorption in organic amine solutions, thereby increasing the catalyst's lifespan and ensuring its catalytic performance.

[0007] A first aspect of this application provides a method for preparing a catalyst, the method comprising the following steps: mixing a porous biomass material having oxygen-containing functional groups with a solution containing a metal salt and a nitrogen source, drying the mixture to prepare a supported biomass material; and subjecting the supported biomass material to pyrolysis treatment to prepare a metal-nitrogen-biomass-based carbon catalyst.

[0008] In some embodiments, the pyrolysis treatment specifically includes the following steps: sequentially subjecting the loaded biomass material to a first-stage pyrolysis treatment and a second-stage pyrolysis treatment, wherein the temperature of the first-stage pyrolysis treatment is lower than the temperature of the second-stage pyrolysis treatment.

[0009] In some embodiments, the pyrolysis treatment satisfies at least one of the following conditions: (1) the temperature of the first stage pyrolysis treatment is 300°C to 400°C; (2) the temperature of the second stage pyrolysis treatment is 700°C to 900°C.

[0010] In some embodiments, after pyrolyzing the supported biomass material, the preparation method further includes the following step: activating the metal-nitrogen-biomass-based carbon catalyst.

[0011] In some embodiments, the activation treatment satisfies at least one of the following conditions: (1) The activation treatment specifically includes: physical activation by introducing an activation gas; (2) The activation treatment specifically includes: secondary pyrolysis treatment after mixing the metal-nitrogen-biomass-based carbon catalyst with the activator solution.

[0012] In some embodiments, the activation treatment satisfies at least one of the following conditions: (1) the activation gas is selected from at least one of carbon dioxide and water vapor; (2) the flow rate of the activation gas is 50 mL / min to 100 mL / min; (3) the activator solution is selected from at least one of potassium hydroxide aqueous solution and phosphoric acid aqueous solution; (4) the temperature of the secondary pyrolysis treatment is 600℃ to 800℃.

[0013] In some embodiments, the preparation method satisfies at least one of the following conditions: (1) the oxygen-containing functional groups of the porous biomass material include at least one of hydroxyl and carboxyl groups; (2) the porous biomass material is selected from at least one of coconut shell, walnut shell, pine nut shell, fruit shell, chestnut shell, peanut shell, rice shell, wood, sawdust, straw, and sugarcane bagasse; (3) the particle size of the porous biomass material is 50 μm to 150 μm; (4) the specific surface area of ​​the porous biomass material is 50 m². 2 / g~1000 m 2 / g; (5) The mass ratio of porous biomass material to solution is 1:(5~10); (6) The metal salt is selected from at least one of iron salt, copper salt, manganese salt, nickel salt and cobalt salt; (7) The metal salt is selected from at least one of nitrate, acetate, sulfate and hydrochloride; (8) The concentration of metal salt in solution is 0.1 mol / L~0.5 mol / L; (9) The nitrogen source is selected from at least one of urea and melamine; (10) The mass of nitrogen source is 10%~30% of the mass of biomass material.

[0014] A second aspect of this application provides a catalyst comprising a catalyst prepared using the method described in the first aspect.

[0015] In some embodiments, the metal-nitrogen-biomass-based carbon catalyst satisfies at least one of the following conditions: (1) the loading of metal elements in the metal-nitrogen-biomass-based carbon catalyst is 5wt% to 15wt%; (2) the size of graphite crystallites in the metal-nitrogen-biomass-based carbon catalyst is 2 nm to 5 nm.

[0016] A third aspect of this application provides a method for capturing carbon dioxide, the method comprising the following steps: adsorbing carbon dioxide with an organic amine solution; adding the catalyst described in the second aspect to the organic amine solution containing adsorbed carbon dioxide for desorption, and collecting the carbon dioxide.

[0017] Compared with traditional technologies, this application has at least the following beneficial effects:

[0018] The catalyst preparation method provided in this application involves using porous biomass material with oxygen-containing functional groups as a carbon source during the solution mixing stage. The abundant oxygen-containing functional groups within the biomass material serve as anchor points, allowing metal ions to bind through coordination. Simultaneously, metal salts and nitrogen sources are loaded onto the biomass material, achieving molecular-level dispersion of the metal salts and nitrogen sources within the pores of the porous biomass material. Subsequently, during the pyrolysis stage, the coordination between metal ions and oxygen-containing functional groups hinders the migration and aggregation of metal elements, enabling them to effectively bind with nitrogen-containing fragments generated during pyrolysis, forming MNC sites. Furthermore, it delays the loss of oxygen-containing components, contributing to the formation of a more stable biomass-based carbon framework. This enhances the interaction between the active sites and the biomass-based carbon support in the metal-nitrogen-biomass-based carbon (MNC) catalyst, improving the catalyst's structural stability, suppressing structural changes during the CO2 absorption-desorption cycle, reducing metal element aggregation and migration, thereby extending the catalyst's lifespan and ensuring optimal catalytic performance. Attached Figure Description

[0019] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0020] Figure 1 This is a schematic flowchart of a catalyst preparation method according to one embodiment of this application. Detailed Implementation

[0021] Reference will now be made to detailed embodiments of this application, one or more of which are described below. Each example is provided for explanation and not for limitation of this application. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to this application without departing from its scope or spirit. For example, features described or illustrated as part of one embodiment may be used in another embodiment to produce further embodiments.

[0022] Therefore, this application is intended to cover such modifications and variations falling within the scope of the appended claims and their equivalents. Other objects, features, and aspects of this application are disclosed in or will be apparent from the following detailed description. It will be understood by those skilled in the art that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of this application.

[0023] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0024] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0025] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0026] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0027] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0028] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0029] Carbon capture technology is an effective way to reduce carbon emissions and achieve net-zero emissions. Among carbon capture technologies, chemical absorption is widely used in industrial carbon capture due to its mature technology and high absorption efficiency.

[0030] The amine solution absorption method utilizes an amine solution to capture CO2 from flue gas in an absorption tower, generating a rich solution. This rich solution is then pumped to a desorption tower, where high-purity CO2 is released through high-temperature heating, regenerating the lean solution for reuse. However, the CO2 desorption and regeneration step requires heating to 110°C–130°C to decompose stable absorption products (such as carbamates). - ) and protonated amines (MEAH) + The energy consumption is huge, resulting in high steam costs, amine solution volatilization losses, and equipment corrosion.

[0031] To improve regeneration efficiency, researchers are using catalysts to catalyze CO2 desorption, thereby lowering the decomposition temperature. Among these, metal-nitrogen-carbon (MNC) materials, due to their unique electronic structure and high atom utilization, have shown great potential in the field of catalysis and are being explored for application in CO2 desorption processes.

[0032] The CO2 desorption process takes place in a high-temperature, strongly alkaline aqueous environment, which places extremely stringent requirements on the structural stability of the catalyst. However, MNC catalysts prepared by traditional methods have weak interactions between the active sites and the support, making them prone to structural changes during repeated CO2 absorption and desorption cycles, affecting the catalyst's durability. At the same time, metal elements are prone to agglomeration or migration during long-term use, leading to a reduction in active sites and a decline in catalytic performance.

[0033] Therefore, in a first aspect, this application provides a method for preparing a catalyst, such as... Figure 1 As shown, the preparation method includes the following steps:

[0034] S1. A porous biomass material with oxygen-containing functional groups is mixed with a solution containing a metal salt and a nitrogen source, and then dried to prepare a loaded biomass material.

[0035] S2. Pyrolysis treatment of supported biomass materials to prepare metal-nitrogen-biomass-based carbon catalysts.

[0036] The catalyst preparation method provided in this application embodiment, in the solution mixing stage (step S1), uses porous biomass material with oxygen-containing functional groups as a carbon source. Utilizing the abundant oxygen-containing functional groups of the biomass material itself as anchor points, metal ions are bound through coordination. Simultaneously, metal salts and nitrogen sources are loaded onto the biomass material, achieving molecular-level dispersion of the metal salts and nitrogen sources within the pores of the porous biomass material. Subsequently, in the pyrolysis treatment stage (step S2), due to the coordination between metal ions and oxygen-containing functional groups, on the one hand, the metal elements are difficult to migrate and aggregate, and can effectively bind with the nitrogen-containing fragments generated by pyrolysis, forming MNC sites; on the other hand, it delays the loss of oxygen-containing components, helping to form a more stable biomass-based carbon framework, enhancing the interaction force between the active sites and the biomass-based carbon support in the metal-nitrogen-biomass-based carbon (MNC) catalyst, improving the structural stability of the catalyst, suppressing structural changes in the CO2 absorption-desorption cycle, reducing the aggregation and migration of metal elements, thereby improving the catalyst's lifespan and ensuring its catalytic performance.

[0037] In some embodiments, prior to step S1, the preparation method further includes:

[0038] S01. The porous biomass material is subjected to crushing and ball milling processes in sequence.

[0039] Thus, by sequentially crushing and ball milling porous biomass materials, the particle size is significantly reduced and the specific surface area is increased. At the same time, more oxygen-containing functional groups are exposed, thereby providing more sites for coordination with metal ions, improving the loading efficiency of metal and nitrogen sources, promoting the full generation of MNC active sites during subsequent pyrolysis, and improving the structural stability of metal-nitrogen-biomass-based carbon catalysts.

[0040] In some embodiments, the mixing process in step S1 includes ultrasonic treatment. Thus, by employing ultrasonic treatment in the mixing step, the impregnation efficiency and loading uniformity of the metal salt and nitrogen source within the biomass material are improved, metal agglomeration during subsequent pyrolysis is suppressed, and uniformly distributed MNC active sites are formed.

[0041] In some embodiments, in step S1, the oxygen-containing functional groups of the porous biomass material include at least one of hydroxyl and carboxyl groups. Thus, by selecting porous biomass raw materials containing hydroxyl or carboxyl groups, the hydroxyl and carboxyl groups can coordinate with metal ions, increasing the bonding strength between the metal element and the biomass material, thereby reducing the migration of metal elements during pyrolysis and improving the structural stability of the MNC catalyst.

[0042] In some embodiments, in step S1, the porous biomass material is selected from at least one of coconut shells, walnut shells, pine nut shells, fruit shells, chestnut shells, peanut shells, rice husks, wood, sawdust, straw, and sugarcane bagasse. Specifically, the sawdust can be oak sawdust, maple sawdust, acacia sawdust, pine sawdust, etc.; the straw can be corn straw, soybean straw, peanut straw, wheat straw, etc.

[0043] In some embodiments, in step S1, the particle size of the porous biomass material is 50 μm to 150 μm. Exemplarily, the particle size of the biomass material can be, but is not limited to, 50 μm, 75 μm, 100 μm, 125 μm, and 150 μm. Thus, the moderate particle size range of the biomass material provides a high specific surface area while preventing agglomeration, thereby improving the uniformity of metal loading and solution homogeneity.

[0044] In some embodiments, in step S1, the specific surface area of ​​the porous biomass material is 50 m². 2 / g~1000 m 2 / g. For example, the specific surface area of ​​porous biomass materials can be, but is not limited to, 50 m². 2 / g、200 m 2 / g、400 m 2 / g、600m 2 / g、800 m 2 / g, 1000 m 2 / g. Thus, by selecting biomass materials with large adsorption capacity, more metal is ultimately reduced inside the catalyst, resulting in superior performance.

[0045] In some embodiments, in step S1, the mass ratio of porous biomass material to solution is 1:(5~10). Exemplarily, the mass ratio of biomass material to solution can be, but is not limited to, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10.

[0046] In some embodiments, in step S1, the metal salt is selected from at least one of iron, copper, manganese, nickel, and cobalt salts. Thus, selecting iron, copper, manganese, nickel, or cobalt salts as the active metal source can effectively form MNC sites during pyrolysis, increasing the number of catalytic active centers and thereby improving CO2 desorption efficiency.

[0047] In some embodiments, in step S1, the metal salt is selected from at least one of nitrates, acetates, sulfates, and hydrochlorides. Thus, by selecting readily soluble metal salts such as nitrates, acetates, sulfates, or chlorides, the metal ions are fully dissolved and uniformly distributed in the solution system, improving the coordination efficiency of the metal ions and reducing the possibility of metal agglomeration during pyrolysis.

[0048] Further, in step S1, the metal salt is selected from at least one of nitrate and acetate.

[0049] In some embodiments, in step S1, the concentration of the metal salt in the solution is 0.1 mol / L to 0.5 mol / L. Exemplarily, the concentration of the metal salt in the solution can be, but is not limited to, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, or 0.5 mol / L. Thus, by selecting an appropriate metal salt concentration, the uniformity of metal distribution is improved while ensuring the subsequent generation of sufficient MNC active centers.

[0050] In some embodiments, in step S1, the nitrogen source is selected from at least one of urea and melamine. Thus, using urea or melamine as the nitrogen source results in a high nitrogen content, which releases more nitrogen-containing fragments during pyrolysis, facilitating the formation of MNC sites with metals and enhancing the catalytic activity for CO2 desorption.

[0051] In some embodiments, in step S1, the mass of the nitrogen source is 10% to 30% of the mass of the biomass material. For example, the mass of the nitrogen source can be, but is not limited to, 10%, 15%, 20%, 25%, or 30% of the mass of the biomass material. In this way, an appropriate amount of nitrogen source can ensure sufficient nitrogen doping while ensuring the structural stability of the biomass-based carbon framework.

[0052] In some embodiments, the pyrolysis process in step S2 is carried out under an inert atmosphere. Specifically, the inert atmosphere can be nitrogen or argon.

[0053] In some implementations, step S2 specifically includes the following steps:

[0054] S21. The loaded biomass material is subjected to a first-stage pyrolysis treatment and a second-stage pyrolysis treatment in sequence. The temperature of the first-stage pyrolysis treatment is lower than the temperature of the second-stage pyrolysis treatment.

[0055] Thus, the loaded biomass material is first subjected to a first-stage pyrolysis treatment (i.e., pre-carbonization treatment) at a lower temperature to effectively remove volatile components and form a stable anchoring structure under the interaction of oxygen-containing functional groups and metal elements; during the second-stage pyrolysis treatment, metal atoms in the anchoring structure can effectively combine with the nitrogen-containing fragments generated by pyrolysis to form MNC active sites, thereby improving the loading uniformity of active sites.

[0056] In some embodiments, in step S21, the temperature of the first-stage pyrolysis treatment is 300°C to 400°C. Exemplarily, the temperature of the first-stage pyrolysis treatment can be, but is not limited to, 300°C, 320°C, 340°C, 360°C, 380°C, or 400°C.

[0057] In some embodiments, in step S21, the temperature of the second-stage pyrolysis treatment is 700°C to 900°C. Exemplarily, the temperature of the second-stage pyrolysis treatment can be, but is not limited to, 700°C, 750°C, 800°C, 850°C, or 900°C.

[0058] In some embodiments, in step S21, the second-stage pyrolysis treatment employs a gradient heating process, with the heating gradients being 700℃, 800℃, and 900℃ respectively. This achieves hierarchical activation and ordered pore formation. At 700℃, the disordered carbon and partially cross-linked structures in the carbon skeleton begin to rearrange, generating preliminary micropores and mesopores. Simultaneously, residual nitrogen- and oxygen-containing groups continue to decompose, generating gases. These gases act as in-situ activators, gently etching the carbon layer and beginning to form a rich porous structure. At 800℃, the temperature increases, enhancing the mobility of carbon atoms and initiating the growth of graphite crystallites. Simultaneously, the gas activation effect intensifies, further expanding and connecting pores to form a well-developed hierarchical pore system. At 900℃, deep graphitization is achieved, repairing defects in the carbon skeleton and moderately increasing the size of the graphite crystallites (controlled within 2 nm to 5 nm). The electrical conductivity and chemical stability of the carbon material are significantly enhanced. This protects the internal MNC active sites from erosion by the high-temperature hydrothermal environment.

[0059] In some embodiments, step S2 of the preparation method further includes the following steps:

[0060] S3. Activate the metal-nitrogen-biomass-based carbon catalyst.

[0061] Thus, by activating the pyrolysis catalyst, the specific surface area is increased, thereby improving the catalytic activity of the CO2 desorption reaction.

[0062] In some embodiments, step S3, the activation process, specifically includes:

[0063] S31. Physical activation is performed by introducing an activation gas.

[0064] Further, in step S31, the physical activation temperature is 500℃~1000℃, and the time is 0.5h~3h. For example, the physical activation temperature can be, but is not limited to, 500℃, 600℃, 700℃, 800℃, 900℃, or 1000℃; and the physical activation time can be, but is not limited to, 0.5h, 1h, 1.5h, 2h, 2.5h, or 3h.

[0065] In this way, by introducing an activation gas, the catalyst material is physically activated at high temperature, increasing the specific surface area of ​​the catalyst and providing more active sites for the CO2 desorption reaction, thereby improving the catalytic efficiency.

[0066] In some embodiments, in step S31, the activating gas is selected from at least one of carbon dioxide and water vapor.

[0067] In some embodiments, in step S31, the flow rate of the activation gas is 50 mL / min to 100 mL / min. Exemplarily, the flow rate of the activation gas can be, but is not limited to, 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, 90 mL / min, and 100 mL / min. Thus, by controlling the flow rate range of the activation gas, the specific surface area of ​​the catalyst can be effectively increased while maintaining the structural strength of the catalyst framework.

[0068] In some embodiments, step S3, the activation process, specifically includes:

[0069] S32. The metal-nitrogen-biomass-based carbon catalyst is mixed with the activator solution and then subjected to secondary pyrolysis treatment.

[0070] In some embodiments, in step S32, the activator solution is selected from at least one of an aqueous solution of potassium hydroxide and an aqueous solution of phosphoric acid.

[0071] In some embodiments, the temperature of the secondary pyrolysis treatment in step S32 is 600°C to 800°C. Exemplarily, the temperature of the secondary pyrolysis treatment can be, but is not limited to, 600°C, 650°C, 700°C, 750°C, or 800°C.

[0072] A second aspect of this application provides a catalyst comprising a catalyst prepared using the method described in the first aspect.

[0073] It is understandable that the catalyst prepared by the catalyst preparation method provided in the first aspect above has a dual-functional site synergistic mechanism. The metal center acts as a Lewis acid to promote the polarization of C=O bonds, and the nitrogen-doped biomass-based carbon acts as a Lewis base to stabilize intermediates. The synergy between the two can optimize the electron transfer process in the reaction pathway, reduce the desorption activation energy of organic amine solutions adsorbed with carbon dioxide, improve CO2 desorption efficiency, and lower the desorption temperature threshold.

[0074] In some embodiments, the loading of metal elements in the metal-nitrogen-biomass-based carbon catalyst is 5 wt% to 15 wt%. Exemplarily, the loading of metal elements in the metal-nitrogen-biomass-based carbon catalyst can be, but is not limited to, 5 wt%, 7.5 wt%, 10 wt%, 12.5 wt%, and 15 wt%. By controlling the metal loading within this range, sufficient MNC active centers can be formed in the catalyst, improving catalytic efficiency, while avoiding agglomeration caused by excessive metal content, thus improving structural stability.

[0075] In this paper, the loading of metal elements in the metal-nitrogen-biomass-based carbon catalyst can be measured using either inductively coupled plasma atomic emission spectrometry (ICP-AES) or atomic absorption spectrometry (AAS). In some embodiments, the graphite crystallite size in the metal-nitrogen-biomass-based carbon catalyst is 2 nm to 5 nm. Exemplarily, the graphite crystallite size in the metal-nitrogen-biomass-based carbon catalyst can be, but is not limited to, 2 nm, 3 nm, 4 nm, and 5 nm. Within the above-mentioned graphite crystallite size range, the chemical and electrochemical stability of the material can be guaranteed while ensuring catalytic activity. It is understood that if the graphite crystallite size is too small, the carbon material tends to be highly disordered (mainly amorphous carbon). Although more defect sites are exposed for loading active centers, the chemical and electrochemical stability of the material will be severely reduced. If the graphite crystallite size is too large, the material tends to be highly graphitized (similar to graphite sheets), with high stability, but the specific surface area will decrease sharply, the number of active sites that can be loaded will be drastically reduced, and the carbon surface will tend to be inert, which is not conducive to the interaction with active components or reactants, resulting in insufficient catalytic activity.

[0076] In this paper, the size of graphite crystallites can be obtained by X-ray diffraction (XRD). Specifically, the average thickness of the graphene sheets along the stacking direction can be calculated from the XRD diffraction peaks using the Scherrer formula.

[0077] A third aspect of this application provides a method for capturing carbon dioxide, the method comprising the following steps:

[0078] S01. Adsorb carbon dioxide using organic amine solution.

[0079] S02. Add the catalyst from the second aspect above to the organic amine solution that has adsorbed carbon dioxide to desorb the carbon dioxide and collect the carbon dioxide.

[0080] Furthermore, the organic amine solution includes ethanolamine.

[0081] The present application will be further described below with reference to specific embodiments and comparative examples.

[0082] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0083] Example 1

[0084] This embodiment provides a catalyst and its preparation method.

[0085] (1) The coconut shells were crushed, then ball-milled and sieved to select particles with a diameter range of 60 μm to 100 μm and a specific surface area range of 50 m².2 / g~200 m 2 Prepare / g of coconut shell powder for later use.

[0086] (2) Prepare 200 mL of 0.3 mol / L nickel nitrate solution and dissolve 2 g of urea in it to obtain a mixed solution.

[0087] (3) Add 10g of coconut shell powder to the above mixed solution, sonicate at room temperature for 30 min, let stand for 12 h, stir and evaporate the solvent at 80℃ to obtain the loaded biomass material. Among them, urea is equivalent to 20% of the mass of coconut shell powder.

[0088] (4) Under a nitrogen atmosphere, the temperature is first increased to 350℃ at a rate of 5℃ / min for the first stage of pyrolysis treatment and held for 1h; the temperature is increased in the order of 700℃, 800℃ and 900℃, and held for 1h at 700℃ and 800℃ respectively, and then held for 2h at 900℃ to form MNC active sites and obtain nickel-nitrogen-coconut shell based carbon catalyst.

[0089] (5) Introduce CO2 at a flow rate of 80 mL / min and physically activate at 800℃ for 1 h.

[0090] The parameters of the prepared nickel-nitrogen-coconut shell-based carbon catalyst are as follows: ICP and XRD analysis showed that the nickel loading was 8.5 wt% and the graphite crystallite size was 3.2 nm.

[0091] Example 2

[0092] The preparation method of the catalyst in this embodiment is basically the same as that in Example 1, except that:

[0093] Replace the coconut shells in step (1) with pine wood chips. The pine wood chips have a particle size range of 60 μm to 100 μm and a specific surface area of ​​600 m². 2 / g~1000 m 2 / g.

[0094] The parameters of the prepared nickel-nitrogen-pine wood-based carbon catalyst are as follows: ICP and XRD analysis showed that the nickel loading was 7.8 wt% and the graphite crystallite size was 2.9 nm.

[0095] Example 3

[0096] The preparation method of the catalyst in this embodiment is basically the same as that in Example 1, except that:

[0097] Replace the urea in step (2) with melamine.

[0098] The parameters of the prepared nickel-nitrogen-coconut shell-based carbon catalyst are as follows: ICP and XRD analysis showed that the nickel loading was 9.1 wt% and the graphite crystallite size was 3.5 nm.

[0099] Example 4

[0100] The preparation method of the catalyst in this embodiment is basically the same as that in Example 1, except that:

[0101] In step (2), 0.3 mol / L nickel nitrate is replaced with 0.1 mol / L ferric nitrate.

[0102] The parameters of the prepared iron-nitrogen-coconut shell-based carbon catalyst are as follows: ICP and XRD analysis showed that the iron loading was 5.5 wt% and the graphite crystallite size was 3.0 nm.

[0103] Example 5

[0104] The preparation method of the catalyst in this embodiment is basically the same as that in Example 1, except that:

[0105] In step (5), the nickel-nitrogen-coconut shell-based carbon catalyst is impregnated with a KOH solution of 2 mol / L and then subjected to a secondary pyrolysis treatment at 750℃ for 2 h.

[0106] The parameters of the prepared nickel-nitrogen-coconut shell-based carbon catalyst are as follows: ICP and XRD analysis showed that the nickel loading was 8.3 wt% and the graphite crystallite size was 3.8 nm.

[0107] Example 6

[0108] The preparation method of the catalyst in this embodiment is basically the same as that in Example 1, except that:

[0109] Step (5) is omitted, and no activation treatment is performed.

[0110] The parameters of the prepared nickel-nitrogen-coconut shell-based carbon catalyst are as follows: ICP and XRD analysis showed that the nickel loading was 8.7 wt% and the graphite crystallite size was 3.0 nm.

[0111] Comparative Example 1

[0112] The preparation method of the catalyst in this comparative example is basically the same as that in Example 1, except that:

[0113] Replace the coconut shell in step (1) with 8 mm coal-based columnar activated carbon (Qizhong Chemical (Zhengzhou) Co., Ltd.). This product has no significant oxygen-containing functional groups and a specific surface area >800 m². 2 / g.

[0114] The parameters of the prepared nickel-nitrogen-coal-based carbon catalyst are as follows: ICP and XRD analysis showed that the nickel loading was 6.2 wt%, and no obvious graphite microcrystal peaks were detected.

[0115] Comparative Example 2

[0116] This comparative example provides a catalyst and its preparation method.

[0117] (1) Dissolve 20g of dimethylimidazole in 50mL of methanol to obtain the first solution; dissolve 5g of zinc nitrate in 50mL of methanol to obtain the second solution; pour the first solution into the second solution, stir thoroughly, then centrifuge and dry under vacuum at 60℃ for 24h to obtain zinc-based metal-organic framework material ZIF-8.

[0118] (2) Place ZIF-8 in a tube furnace and heat it from room temperature to 900°C in a nitrogen atmosphere at a heating rate of 5°C / min. Hold the temperature for 2 hours to obtain nitrogen-doped carbon material.

[0119] (3) Prepare 100 mL of 0.3 mol / L nickel nitrate solution, add 5 g of nitrogen-doped carbon material to the nickel nitrate solution, stir thoroughly, then centrifuge and dry at 100℃ for 6 h to obtain the metal-based carbon material precursor, namely the composite of nickel and nitrogen-doped carbon material.

[0120] (4) Under a nitrogen atmosphere, the metal-based carbon material precursor was heated to 900°C for 2 hours at a heating rate of 5°C / min to obtain black Ni-NC catalyst powder.

[0121] The parameters of the prepared Ni-NC catalyst are as follows: ICP and XRD analysis showed that the nickel loading was 5.2 wt% and the graphite crystallite size was 4.1 nm.

[0122] Performance testing

[0123] (1) Catalytic efficiency test

[0124] A 30 wt% ethanolamine (MEA) solution rich in CO2 was used as the test object. Under constant temperature of 90℃, 0.1 g of catalyst was added to 100 mL of the rich solution (CO2 loading: 0.5 mol CO2 / mol MEA). The CO2 desorption rate was recorded using an online gas mass flow meter, and the average desorption rate (unit: mmol CO2·g) was calculated. -1 ·min -1 ).

[0125] (2) Catalyst lifetime test

[0126] The catalyst was subjected to continuous adsorption-desorption cycle tests in a MEA-rich solution at 90 °C. Each cycle consisted of adsorption to saturation at 40 °C, followed by catalytic desorption at 90 °C. The number of cycles at which the initial CO2 desorption rate decreased to 80% was recorded and defined as the catalyst lifetime.

[0127] The test results are shown in Table 1.

[0128] Table 1

[0129]

[0130] As shown in Table 1, comparing Examples 1-6 and Comparative Examples 1-2, it can be seen that the catalyst preparation method provided in this application enhances the structural stability of the catalyst, inhibits structural changes in the CO2 absorption-desorption cycle, improves the service life of the catalyst, and ensures the catalytic performance.

[0131] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0132] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for preparing a catalyst, characterized in that, Includes the following steps: Porous biomass materials with oxygen-containing functional groups are mixed with a solution containing metal salts and nitrogen sources, and then dried to prepare loaded biomass materials. The supported biomass material was subjected to pyrolysis to prepare a metal-nitrogen-biomass-based carbon catalyst.

2. The method for preparing the catalyst according to claim 1, characterized in that, The pyrolysis process specifically includes the following steps: The loaded biomass material is subjected to a first-stage pyrolysis treatment and a second-stage pyrolysis treatment in sequence, wherein the temperature of the first-stage pyrolysis treatment is lower than the temperature of the second-stage pyrolysis treatment.

3. The method for preparing the catalyst according to claim 2, characterized in that, The pyrolysis treatment satisfies at least one of the following conditions: (1) The temperature of the first stage of pyrolysis treatment is 300℃~400℃; (2) The temperature of the second stage pyrolysis treatment is 700℃~900℃.

4. The method for preparing the catalyst according to claim 1, characterized in that, After pyrolysis treatment of the loaded biomass material, the process further includes the following steps: The metal-nitrogen-biomass-based carbon catalyst was activated.

5. The method for preparing the catalyst according to claim 4, characterized in that, The activation process satisfies at least one of the following conditions: (1) The activation process specifically includes: physical activation by introducing an activation gas; (2) The activation treatment specifically includes: mixing the metal-nitrogen-biomass-based carbon catalyst with the activator solution and then performing a secondary pyrolysis treatment.

6. The method for preparing the catalyst according to claim 5, characterized in that, The activation process satisfies at least one of the following conditions: (1) The activating gas is selected from at least one of carbon dioxide and water vapor; (2) The flow rate of the activating gas is 50 mL / min to 100 mL / min; (3) The activator solution is selected from at least one of potassium hydroxide aqueous solution and phosphoric acid aqueous solution; (4) The temperature of the secondary pyrolysis treatment is 600℃~800℃.

7. The method for preparing the catalyst according to any one of claims 1 to 6, characterized in that, At least one of the following conditions must be met: (1) The oxygen-containing functional groups of the porous biomass material include at least one of hydroxyl and carboxyl groups; (2) The porous biomass material is selected from at least one of coconut shell, walnut shell, pine nut shell, fruit shell, chestnut shell, peanut shell, rice shell, wood, sawdust, straw and sugarcane bagasse; (3) The particle size of the porous biomass material is 50 μm to 150 μm; (4) The specific surface area of ​​the porous biomass material is 50 m². 2 / g~1000 m 2 / g; (5) The mass ratio of the porous biomass material to the solution is 1:(5~10); (6) The metal salt is selected from at least one of iron salts, copper salts, manganese salts, nickel salts and cobalt salts; (7) The metal salt is selected from at least one of nitrates, acetates, sulfates and hydrochlorides; (8) The concentration of the metal salt in the solution is 0.1 mol / L to 0.5 mol / L; (9) The nitrogen source is selected from at least one of urea and melamine; (10) The mass of the nitrogen source is 10% to 30% of the mass of the biomass material.

8. A catalyst, characterized in that, This includes catalysts prepared using the catalyst preparation method described in any one of claims 1 to 7.

9. The catalyst according to claim 8, characterized in that, The metal-nitrogen-biomass-based carbon catalyst satisfies at least one of the following conditions: (1) The loading of metal elements in the metal-nitrogen-biomass-based carbon catalyst is 5wt%~15wt%; (2) The graphite crystallite size in the metal-nitrogen-biomass-based carbon catalyst is 2 nm to 5 nm.

10. A method for capturing carbon dioxide, characterized in that, Includes the following steps: Carbon dioxide is adsorbed using an organic amine solution; The catalyst described in claim 8 or 9 is added to the organic amine solution containing adsorbed carbon dioxide to desorb the carbon dioxide and collect the carbon dioxide.

Images