Coal-based porous carbon based on trace salt induction activation and preparation method thereof

Abstract

The invention belongs to the technical field of carbon materials, and discloses coal-based porous carbon based on trace salt induction activation and a preparation method thereof. The preparation method of the coal-based porous carbon based on trace salt induced activation comprises the following steps: uniformly mixing Zhundong coal and trace salt to obtain a mixed product, heating the mixed product in an inert atmosphere and then keeping the temperature constant to obtain a carbonized product, and cooling the carbonized product to room temperature in an active atmosphere to obtain activated carbon, sequentially carrying out acid pickling and drying treatment on activated carbon to obtain coal-based porous carbon; the catalytic action of positive ions in trace active salt and the induction action of negative ions can be combined, so that the action effect of the trace salt is further improved, the activation rate is increased, the distribution of a pore structure is regulated and controlled, the specific surface area of the coal-based porous carbon is increased, and the pore structure is also improved.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon materials, and particularly relates to a coal-based porous carbon based on trace salt-induced activation and a preparation method thereof. Background Art

[0002] With the continuous development of society and the increasing energy demand, the research on renewable energy and efficient energy conversion technologies has attracted increasing attention. In this context, coal-based porous carbon materials have received much attention due to their rich resources, sustainability, and extensive application potential in the energy field. However, the existing methods for preparing coal-based porous carbon materials often face a series of challenges, such as environmental pollution, equipment corrosion, high costs, etc., which limit their wide application. Therefore, seeking a more effective and greener method to prepare high-performance coal-based porous carbon materials has become one of the current research hotspots.

[0003] CN202310417499.5 proposes a coal-based porous carbon prepared by pyrolyzing a mixture of lignite, graphitic carbon nitride, and potassium salt. This method uses lignite as the precursor raw material, graphitic carbon nitride as the nitrogen dopant, and potassium salt as the chemical activation and thermal exfoliation agent. The prepared coal-based porous carbon can effectively regulate the pore structure of the specific surface area, and the obtained specific surface area is ≥ 300m 2 / g, and the pore size distribution is between 0.5 and 4 nm. CN110745824A discloses a method for regulating the pore matching of coal-based porous carbon based on trace potassium source catalytic activation. This method uses the catalytic effect of potassium metal salt on the physical activation process to strengthen the development of pore volume and specific surface area of porous carbon during the preparation process. By changing the type and addition ratio of potassium salt, the deep regulation of the average pore size and pore matching is realized, and the highest specific surface area can reach 1283.6m 2 / g, and the highest total pore volume can be 0.93cm 3 / g.

[0004] However, during the preparation of porous carbon, chemical activation often uses a large amount of alkalis (such as KOH, NaOH, etc.), salts (such as K2CO3, Na2CO3, ZnCl2, etc.) or acids (such as H3PO4) to activate the coal precursor. The proportion of the selected activator is relatively large (equal to or higher than the mass of the coal precursor), resulting in increased costs, a large amount of wastewater generated during washing, and serious corrosion of equipment. Secondly, the existing physical activation rate is slow, and the specific surface area of porous carbon is small. Summary of the Invention

[0005] The purpose of the present invention is to provide a coal-based porous carbon based on trace salt-induced activation and a preparation method thereof to overcome the problems existing in the prior art. The present invention can increase the specific surface area of coal-based porous carbon, improve the pore structure, help improve the adsorption performance, catalytic performance, and electrochemical performance of porous carbon, etc., so that it shows more excellent performance in different application fields.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a method for preparing coal-based porous carbon induced and activated by trace salts, which is characterized by comprising the following steps:

[0008] Uniformly mix Zhundong coal and trace salts to obtain a mixed product;

[0009] Heat up and then keep the temperature constant for the mixed product in an inert atmosphere to obtain a carbonized product;

[0010] Activate the carbonized product in an inert and active atmosphere or an active atmosphere, and then cool it to room temperature in an inert atmosphere to obtain activated carbon;

[0011] Successively carry out pickling and drying treatments on the activated carbon to obtain coal-based porous carbon;

[0012] Further, the trace salts include one or more of carbonates, bicarbonates, chlorides, and phosphates of sodium, potassium, calcium, and magnesium in any proportion;

[0013] Further, when the trace salts are one or more of carbonates and bicarbonates of sodium, potassium, calcium, and magnesium in any proportion, the inert gas includes one of nitrogen, argon, and neon; the active atmosphere includes CO2 or a mixture of CO2 and an inert gas;

[0014] Further, when the trace salts are one or more of chlorides and phosphates of sodium, potassium, calcium, and magnesium in any proportion, the inert gas includes one of nitrogen, argon, and neon; the active atmosphere includes H2O or a mixture of H2O and an inert gas;

[0015] Further, the mass ratio of Zhundong coal to trace salts is 1:(0.005 - 0.1);

[0016] Further, the uniform mixing includes mixing by liquid-phase impregnation and evaporation to dryness or mechanical ball milling;

[0017] Further, the temperature for heating up and then keeping the temperature constant is 700°C - 900°C; the time for keeping the temperature constant is 1.5 - 3h;

[0018] Further, the pickling specifically includes: mixing the activated carbon with a hydrochloric acid solution and then stirring, and then filtering, and washing the solid filter residue until the pH is neutral;

[0019] The hydrochloric acid solution is 6mol / L; the mass ratio of the hydrochloric acid solution to the activated carbon is (25 - 35):1; the stirring temperature is 50 - 70°C, and the stirring time is 2 - 4h;

[0020] Furthermore, the drying temperature is 100 - 110°C, and the drying time is 1 - 3 h.

[0021] In a second aspect, the present invention also provides a coal-based porous carbon activated by trace salt induction, which is obtained by the above-mentioned preparation method of a coal-based porous carbon activated by trace salt induction.

[0022] The above technical solution has the following advantages or beneficial effects:

[0023] In a first aspect, the present invention provides a preparation method of a coal-based porous carbon activated by trace salt induction. By combining the catalytic effect of cations and the induction effect of anions in trace active salts, the effect of trace salts is further enhanced; the combination of chemical activation and physical activation has many advantages of both. While increasing the activation rate, it regulates the distribution of pore structures, improves the specific surface area of the coal-based porous carbon and also optimizes the pore structure. The optimized pore structure helps to improve the adsorption performance, catalytic performance, and electrochemical performance of the porous carbon, etc., making it show more excellent performance in different application fields; the present invention only adds trace salts, with low cost and little pollution; at the same time, compared with the traditional complex porous carbon preparation process, it reduces the cumbersome intermediate links and operation steps, reduces the preparation difficulty, improves the preparation efficiency, and is conducive to large-scale industrial production.

[0024] Furthermore, by regulating various salts of sodium, potassium, calcium, and magnesium as activators, the pore structure of the coal-based porous carbon can be accurately regulated during the activation process. Different types of salts and their mixtures in any proportion can form a rich variety of pores with uniform sizes, effectively increasing the specific surface area, providing more active sites for mass transfer and reactions, and enhancing the adsorption, induction, and catalytic performance of the material.

[0025] Furthermore, when the trace salt is a specific mixture of carbonate and bicarbonate, one of nitrogen, argon, and neon is selected as the inert gas, which can be flexibly selected according to different process requirements and equipment conditions; for example, nitrogen is widely sourced and has a low cost, suitable for large-scale production; argon has more stable chemical properties and can play a better protective role in some fine preparation processes with extremely high requirements for the reaction atmosphere, ensuring the stability and repeatability of the reaction; using CO2 or a mixture of CO2 and an inert gas as the active atmosphere, CO2 can undergo specific chemical reactions with the coal-based material during the activation process, thereby effectively regulating the pore structure and specific surface area of the porous carbon; and mixing with an inert gas can further precisely control the activity and rate of the reaction, avoiding problems of over-activation or under-activation.

[0026] Furthermore, when chlorides and phosphates of sodium, potassium, calcium, and magnesium are selected as trace salts, a variety of inert gases such as nitrogen, argon, and neon are provided. Different inert gases have different physical and chemical properties. Operators can flexibly select the appropriate inert gas according to specific reaction conditions and equipment requirements to create a stable and suitable reaction atmosphere and ensure the smooth progress of the reaction. H2O or a mixture of H2O and inert gas is used as the active atmosphere. During the activation process, H2O can undergo unique hydrolysis, oxidation, and other reactions with the coal-based material and trace salts. The targeted design of the active atmosphere can precisely control the activity and direction of the reaction, making the formation process of porous carbon more controllable.

[0027] Furthermore, the mass ratio of Zhundong coal to trace salt is set within the range of 1:(0.005 - 0.1), which can ensure the uniform dispersion and full play of the trace salt in the coal-based system. An appropriate amount of trace salt can efficiently induce the activation reaction, making the coal molecular structure more easily etched and reorganized during the activation process, thereby improving the activation efficiency and shortening the reaction time.

[0028] Furthermore, to enable the trace salt to be fully dissolved in the liquid phase, during the impregnation process, Zhundong coal can come into contact with the salt solution in all directions. The salt ions can deeply penetrate into the internal pores and structures of the coal. As the evaporation process progresses, the salt adheres uniformly to the surface and inside of the coal particles, achieving a uniform mixture at the microscopic level, providing a good foundation for the subsequent activation reaction, ensuring the uniform distribution of the activator in the coal-based system, and facilitating the formation of a uniform porous structure. Through mechanical ball milling, with the impact, grinding, and shearing effects of the ball milling medium, Zhundong coal and the trace salt are fully mixed. During the ball milling process, the coal particles are continuously broken and refined, and at the same time, they come into full contact and fusion with the salt particles, enabling the salt to uniformly coat the surface of the coal particles, and some salt may be embedded in the lattice structure of the coal. This physical mixing method can also achieve a high degree of mixing uniformity, contributing to improving the uniformity and consistency of the activation reaction.

[0029] Furthermore, at a high temperature of 700°C to 900°C, the trace salt as an activator can induce the formation of a rich porous structure in the coal-based material. The pores include micropores, mesopores, and macropores, which helps to increase the specific surface area of the material. Through isothermal treatment, the organic substances in the coal-based material undergo pyrolysis and reorganization under the action of the trace salt to form a porous carbon material with a high specific surface area.

[0030] Furthermore, the hydrochloric acid solution can efficiently react with impurities such as metal ions and inorganic minerals in the activated carbon, dissolve and remove them, which helps to improve the purity of the activated carbon and reduce the influence of impurities on the subsequent application performance. During the pickling process, the hydrochloric acid reacts with some functional groups or impurities on the surface of the activated carbon, generating some gases or causing changes in some microstructures, thus helping to optimize the pore structure of the activated carbon. Pickling can remove some oxidizing functional groups on the surface of the activated carbon or introduce new surface groups, thereby changing its surface chemical properties.

[0031] Furthermore, drying at a temperature of 100 - 110 °C for 1 - 3 hours can efficiently remove the free water and bound water in the coal-based porous carbon material. The presence of water may affect the subsequent processing performance and application effect of the material, so this step is crucial for ensuring the material quality. Appropriate drying temperature and time can ensure that the coal-based porous carbon material does not undergo structural collapse or deformation during drying, helping to maintain the pore structure and specific surface area of the material, thereby maintaining its excellent adsorption performance and electrochemical performance.

[0032] In the second aspect, the present invention provides a coal-based porous carbon based on trace salt-induced activation. Through trace salt-induced activation, the coal-based porous carbon forms a rich microporous, mesoporous, and macroporous structure, significantly increasing the specific surface area of the material. The high specific surface area helps to increase the contact area between the material and reactants or adsorbates, thereby enhancing its adsorption performance and reaction activity. The presence of the hierarchical pore structure (micropores, mesopores, and macropores) not only increases the specific surface area but also optimizes the mass transfer performance of the material. Micropores provide a large number of adsorption sites, while mesopores and macropores help the rapid diffusion and transmission of reactants or adsorbates. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a process flow diagram of a preparation method of a coal-based porous carbon based on trace salt-induced activation according to the present invention;

[0034] Figure 2 is a scanning electron microscope image of Example 1 of the present invention;

[0035] Figure 3 is a high-resolution transmission electron microscope image of Example 1 of the present invention;

[0036] Figure 4 is a nitrogen adsorption / desorption isotherm diagram of Example 1 of the present invention;

[0037] Figure 5 is a scanning electron microscope image of Example 4 of the present invention;

[0038] Figure 6 is a high-resolution transmission electron microscope image of Example 4 of the present invention;

[0039] Figure 7It is the nitrogen adsorption / desorption isotherm diagram of Embodiment 4 of the present invention. Detailed implementation manners

[0040] The present invention will be further described in detail below in conjunction with specific embodiments, which are explanations of the present invention rather than limitations.

[0041] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0042] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0043] Embodiment 1:

[0044] Refer to Figure 1 , the present invention provides a preparation method of coal-based porous carbon based on trace salt-induced activation, including the following steps:

[0045] Step 1, mixing: Uniformly mix 30 g of Zhundong coal and 0.6 g of K2CO3 by mechanical ball milling, spread them in a crucible, and then place them in a horizontal tube furnace;

[0046] Step 2, carbonization: Under a N2 atmosphere of 480 mL / min, heat the mixture of Zhundong coal and K2CO3 at a heating rate of 10 °C / min to 800 °C, and keep it at a constant temperature of 800 °C for 2 h;

[0047] Step 3, activation: Switch N2 to 100% CO2, after activation at 800 °C, switch back to the N2 atmosphere and cool to room temperature to obtain activated carbon;

[0048] Step 4, pickling and drying: Mix a 6 mol / L hydrochloric acid solution with activated carbon in a mass ratio of 30:1, stir at 60 °C for 3 h, filter, and rinse the solid residue with deionized water until the pH is neutral. Then dry the solid residue in a hot air drying oven at 105 °C for 2 h to obtain coal-based porous carbon.

[0049] See Figures 2 to 4 , the specific surface area of the activated carbon prepared under the condition of 100% CO2 at a 50 wt.% combustion loss rate is the highest.

[0050] Example 2:

[0051] See Figure 1 , the present invention provides a method for preparing coal-based porous carbon based on micro-salt induced activation, including the following steps:

[0052] Step 1, mixing: Mix 10 g of Zhundong coal and 0.05 g of NaCl by liquid-phase impregnation and evaporation to dryness, spread them in a crucible, and then place them in a horizontal tube furnace;

[0053] Step 2, carbonization: Heat the mixture of Zhundong coal and NaCl in an argon atmosphere at 480 mL / min at a heating rate of 10 °C / min to 700 °C, and keep it at a constant temperature of 700 °C for 1.5 h;

[0054] Step 3, activation: Switch 40% argon to H2O, activate at 700 °C, and then switch back to an argon atmosphere and cool to room temperature to obtain activated carbon;

[0055] Step 4, pickling and drying: Mix a 6 mol / L hydrochloric acid solution with activated carbon in a mass ratio of 25:1, stir at 50 °C for 2 h, filter, and rinse the solid residue with deionized water until the pH is neutral. Then dry the solid residue in a hot air drying oven at 100 °C for 1 h to obtain coal-based porous carbon.

[0056] Example 3:

[0057] See Figure 1 , the present invention provides a method for preparing coal-based porous carbon based on micro-salt induced activation, including the following steps:

[0058] Step 1, mixing: Mix 10 g of Zhundong coal and 1 g of CaCO3 by mechanical ball milling evenly, spread them in a crucible, and then place them in a horizontal tube furnace;

[0059] Step 2, carbonization: Heat the mixture of Zhundong coal and CaCO3 in a neon atmosphere at 480 mL / min at a heating rate of 10 °C / min to 900 °C, and keep it at a constant temperature of 900 °C for 3 h;

[0060] Step 3, activation: Switch 60% neon to CO2, activate at 900 °C, then switch back to the neon atmosphere and cool to room temperature to obtain activated carbon;

[0061] Step 4, pickling and drying: Mix 6 mol / L hydrochloric acid solution with activated carbon in a mass ratio of 35:1, stir at 70 °C for 4 h, filter, and rinse the solid residue with deionized water until the pH is neutral. Then dry the solid residue in a hot air drying oven at 110 °C for 3 h to obtain coal-based porous carbon.

[0062] Example 4:

[0063] See Figure 1 、 Figures 5 to 7 , the present invention provides a preparation method of coal-based porous carbon based on trace salt-induced activation, including the following steps:

[0064] Step 1, mixing: Mix 30 g of Zhundong coal and 0.6 g of K2CO3, evaporate to dryness by liquid-phase impregnation, spread it in a crucible, and then put it into a horizontal tube furnace;

[0065] Step 2, carbonization: Under the N2 atmosphere of 480 mL / min, heat the mixture of Zhundong coal and K2CO3 at a heating rate of 10 °C / min to 800 °C, and keep it constant at 800 °C for 2 h;

[0066] Step 3, activation: Switch N2 to 80% CO2 - 40% H2O, activate at 800 °C, then switch back to the N2 atmosphere and cool to room temperature to obtain activated carbon;

[0067] Step 4, pickling and drying: Mix 6 mol / L hydrochloric acid solution with activated carbon in a mass ratio of 30:1, stir at 60 °C for 3 h, filter, and rinse the solid residue with deionized water until the pH is neutral. Then dry the solid residue in a hot air drying oven at 105 °C for 2 h to obtain coal-based porous carbon.

[0068] Example 5:

[0069] See Figure 1 , the present invention provides a preparation method of coal-based porous carbon based on trace salt-induced activation, including the following steps:

[0070] Step 1, mixing: Mix 30 g of Zhundong coal and 0.6 g of K2CO3, evaporate to dryness by liquid-phase impregnation, spread it in a crucible, and then put it into a horizontal tube furnace;

[0071] Step 2, carbonization: Under the argon atmosphere of 480 mL / min, heat the mixture of Zhundong coal and CaCl at a heating rate of 10 °C / min to 800 °C, and keep it constant at 800 °C for 2 h;

[0072] Step 3, Activation: Switch argon to 100% H2O, activate at 800 °C, then switch back to an argon atmosphere and cool to room temperature to obtain activated carbon;

[0073] Step 4, Pickling and Drying: Mix 6 mol / L hydrochloric acid solution with activated carbon in a mass ratio of 30:1, stir at 60 °C for 3 h, filter, and rinse the solid residue with deionized water until the pH is neutral. Then dry the solid residue in a hot air drying oven at 105 °C for 2 h to obtain coal-based porous carbon.

[0074] Example 6:

[0075] See Figure 1 , the present invention provides a method for preparing coal-based porous carbon based on micro-salt-induced activation, including the following steps:

[0076] Step 1, Mixing: Mix 10 g of Zhundong coal and 0.05 g of MgCO3, evaporate to dryness by liquid-phase impregnation, spread them in a crucible, and then place it in a horizontal tube furnace;

[0077] Step 2, Carbonization: Heat the mixture of Zhundong coal and MgCO3 at a heating rate of 10 °C / min to 750 °C in a neon atmosphere of 480 mL / min, and keep it at a constant temperature of 750 °C for 2 h;

[0078] Step 3, Activation: Switch 40% neon to CO2, activate at 750 °C, then switch back to a neon atmosphere and cool to room temperature to obtain activated carbon;

[0079] Step 4, Pickling and Drying: Mix 6 mol / L hydrochloric acid solution with activated carbon in a mass ratio of 30:1, stir at 60 °C for 3 h, filter, and rinse the solid residue with deionized water until the pH is neutral. Then dry the solid residue in a hot air drying oven at 100 °C for 1 h to obtain coal-based porous carbon.

[0080] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of coal-based porous carbon induced and activated by trace salts, characterized in that It includes the following steps: Uniformly mix Zhundong coal with trace salts to obtain a mixed product; Heat up and then keep the temperature constant for the mixed product under an inert atmosphere to obtain a carbonized product; Activate the carbonized product under an inert and active atmosphere or an active atmosphere, and then cool it to room temperature under an inert atmosphere to obtain activated carbon; Successively perform pickling and drying treatments on the activated carbon to obtain coal-based porous carbon.

2. The preparation method of coal-based porous carbon induced and activated by trace salts according to claim 1, characterized in that The trace salts include one or more mixtures in any proportion of carbonates, bicarbonates, chlorides, and phosphates of sodium, potassium, calcium, and magnesium.

3. The preparation method of coal-based porous carbon induced and activated by trace salt according to claim 2, wherein, When the trace salts are one or more mixtures in any proportion of carbonates and bicarbonates of sodium, potassium, calcium, and magnesium, the inert gas includes one of nitrogen, argon, and neon; the active atmosphere includes CO2 or a mixture of CO2 and an inert gas.

4. A method for preparing coal-based porous carbon induced and activated by trace salts according to claim 2, characterized in that, When the trace salts are one or more mixtures in any proportion of chlorides and phosphates of sodium, potassium, calcium, and magnesium, the inert gas includes one of nitrogen, argon, and neon; the active atmosphere includes H2O or a mixture of H2O and an inert gas.

5. A preparation method of coal-based porous carbon induced and activated by trace salts according to claim 1, characterized in that The mass ratio of Zhundong coal to trace salts is 1:(0.005 - 0.1).

6. A method for preparing a coal-based porous carbon induced and activated by trace salts according to claim 1, wherein, The uniform mixing includes mixing by liquid-phase impregnation and evaporation to dryness or mechanical ball milling.

7. A preparation method of coal-based porous carbon induced and activated by trace salts according to claim 1, characterized in that, The temperature for heating up and then keeping the temperature constant is 700°C - 900°C; the time for keeping the temperature constant is 1.5 - 3 h.

8. A preparation method of coal-based porous carbon induced and activated by trace salts according to claim 1, characterized in that, The pickling specifically includes: mixing the activated carbon with a hydrochloric acid solution and then stirring, and then filtering, and washing the solid filter residue until the pH is neutral; The hydrochloric acid solution is 6 mol / L; the mass ratio of the hydrochloric acid solution to the activated carbon is (25 - 35):1; the stirring temperature is 50 - 70°C, and the stirring time is 2 - 4 h.

9. A preparation method of coal-based porous carbon induced and activated by trace salts according to claim 1, characterized in that, The drying temperature is 100 - 110°C, and the drying time is 1 - 3 h.

10. A coal-based porous carbon activated by trace salt induction, characterized in that, Obtained by the preparation method of coal-based porous carbon induced by trace salts according to any one of claims 1 - 9 above.

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