Porous carbon material preparation method based on fluidized bed steam step-by-step activation method

Abstract

The invention discloses a porous carbon material preparation method based on a fluidized bed steam step-by-step activation method, and belongs to the field of porous carbon material preparation, the method comprises the following steps: carbonizing a biomass carbon-based raw material to prepare first carbonized particles; the first carbonized particles are subjected to acid pickling, and second carbonized particles with the ash content being smaller than 0.3% and the pH value being 6-8 are obtained; placing the second carbonized particles in a fluidized bed reactor, and carrying out first activation treatment; and stopping heating after the first activation treatment is completed, keeping the temperature when the temperature of the fluidized bed reactor is reduced to 850 DEG C, carrying out second activation treatment, and cooling to room temperature after the second activation treatment is completed. The method is simple in process operation, green and environment-friendly, and has a wide large-scale production prospect.

Description

Technical Field

[0001] The present invention relates to the field of preparation of porous carbon materials, and particularly to a method for preparing porous carbon materials based on a stepwise activation method of steam in a fluidized bed. Background Art

[0002] With the rapid development of gas-phase silicon-carbon anode materials, porous carbon-based materials, as the framework materials for preparing gas-phase silicon-carbon by silane deposition, have also generated a huge market demand. How to prepare porous carbon materials with physical and chemical performance indicators meeting the requirements of the silane gas-phase deposition process and ensure energy conservation, environmental protection, economy and other requirements is of great significance.

[0003] At present, the academic and industrial circles have proposed to prepare porous carbon materials by means of alkali activation, steam activation or carbon dioxide (CO2) activation. Alkali activation mainly mixes KOH (potassium hydroxide) with a carbon-based material in a certain stoichiometric ratio and then calcines at a high temperature. However, the alkali activation preparation process has high corrosion to high-temperature calcination equipment, the pore structure of the prepared porous carbon materials is difficult to control, is extremely prone to collapse, and the amount of alkaline materials used is large and the price is expensive, resulting in high material costs. The carbon dioxide activation method has a slow reaction rate and lower activation ability than steam. Higher temperatures and longer times will be used during the etching process, making the carbon dioxide activation process energy-consuming and with low production efficiency. Therefore, the batch preparation of porous carbon materials mainly focuses on the steam activation process. The steam activation method is a green and environmentally friendly way to prepare porous carbon materials because it is not corrosive to equipment.

[0004] Although the early prepared porous carbon materials used a rotary kiln for steam activation and pore etching, due to the uneven turnover of the materials inside the rotary kiln, the pore structure distribution of the materials was unreasonable and the uniformity was poor. The principle of a fluidized bed device is to use gas to blow a powder solid particle, and the material boils during this process. The blowing gas and the solid powder belong to the gas-solid phase mixing and contacting method. Therefore, the contact area is wider and more sufficient. How to use a fluidized bed device to prepare porous carbon materials with a uniform pore structure distribution and stable performance is of great significance.

[0005] Waste biomass materials have natural advantages in preparing porous carbon materials due to their rich internal pore structure and abundant and easily available raw materials. How to select a suitable carbon-based material for purification, carbonization and other pretreatment processes, and use the stepwise activation method of steam in a fluidized bed to prepare a porous carbon skeleton with a reasonable pore size distribution, appropriate pore volume and specific surface area meeting the requirements of silane deposition for preparing a silicon-carbon anode material is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0006] One of the objectives of the present invention is to provide a method for preparing porous carbon materials based on a stepwise activation method with fluidized bed water vapor, so as to solve the problems of slow reaction rate and low activation ability in the prior art carbon dioxide activation method.

[0007] The present invention is realized through the following technical solutions. A method for preparing porous carbon materials based on a stepwise activation method with fluidized bed water vapor includes the following steps: S100. Carbonize the biomass carbon-based raw material to obtain the first carbonized particles; S200. Pickle the first carbonized particles to obtain the second carbonized particles with an ash content <0.3% and a pH value of 6-8; S300. Place the second carbonized particles in a fluidized bed reactor. Heat the second carbonized particles from room temperature to 1000°C at a rate of 5°C / min, keep the temperature constant for 0.5 h. After the temperature and the state of the second carbonized particles are stable, perform the first activation treatment through a water vapor generator; S400. After the first activation treatment is completed, stop heating. Keep the temperature of the fluidized bed reactor at 850°C and perform the second activation treatment. After the second activation treatment is completed, adjust the flow rate of the protective gas to 5 L / min until the temperature drops to room temperature.

[0008] Further, the carbonization treatment is as follows: Place the biomass carbon-based raw material in a high-temperature tubular furnace. Use nitrogen as the protective gas and heat it to 500-1000°C at a heating rate of 3-10°C / min, keep the temperature constant for 0-12 h, perform pyrolytic carbonization to remove organic substances to form biomass carbon, and crush it into particles with a size of 20-100 μm.

[0009] Further, the biomass carbon-based raw material is one or a combination of more of the following: coconut shell, betel nut shell, straw, nut shell, fruit peel, bamboo, wood, charcoal, starch.

[0010] Further, the pickling is carried out by soaking the first carbonized particles in a pickling solution at a temperature of 60-100°C for 0-12 h.

[0011] Further, the pickling solution is a mixed solution with a concentration of 1 mol / L prepared by mixing hydrochloric acid, nitric acid, and hydrofluoric acid in a ratio of 1:1:1.

[0012] Further, the activation treatment includes: Adjust the water vapor flow rate to 1-100 L / min and the protective gas flow rate to 1-20 L / min. After continuous activation for 4 h, turn off the water vapor and adjust the protective gas flow rate to 1-10 L / min.

[0013] On the other hand, the present invention provides a porous carbon material based on a stepwise activation method with fluidized bed water vapor, and the porous carbon material is prepared according to the preparation method described above.

[0014] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0015] The present invention selects organic biomass raw material waste for secondary utilization, turning waste into treasure with low cost. The porous carbon material prepared by the stepwise activation method of high-temperature water vapor in a fluidized bed reactor has a uniform pore structure distribution, high material quality uniformity, simple process operation, is green and environmentally friendly, and has broad prospects for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not constitute a limitation to the embodiments of the present invention. In the drawings:

[0017] Figure 1 It is a scanning electron microscope image of the porous carbon material provided in Embodiment 2 of the present invention.

[0018] Figure 2 It is a nitrogen isothermal adsorption-desorption curve graph of the porous carbon material provided in Embodiment 2 of the present invention.

[0019] Figure 3 It is a pore volume-pore size distribution graph of the porous carbon material provided in Embodiment 2 of the present invention.

[0020] Figure 4 It is an XRD graph of the porous carbon material provided in Embodiment 2 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0022] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the said documents. In case of conflict with any incorporated document, the content of this specification shall prevail. Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to. Unless the context clearly indicates otherwise, the expressions "a" and "an" used herein include plural references. It should be noted that "first", "second", "type A", "type B", etc. are only for convenience of description and easy distinction, and should not be construed as indicating or implying relative importance. The term "about" used herein represents a range of ±20% of the value following it. In some embodiments, the term "about" represents a range of ±10% of the value following it. In some embodiments, the term "about" represents a range of ±5% of the value following it.

[0023] Example 1

[0024] This example discloses a method for preparing a porous carbon material based on a stepwise activation method with fluidized bed water vapor, which includes the following steps:

[0025] Step 1: Carbonize the biomass carbon-based raw material to prepare first carbonized particles.

[0026] Specifically, the carbonization treatment is carried out by placing the biomass carbon-based raw material in a high-temperature tubular furnace, using nitrogen as the protective gas, with a heating rate of 3 - 10 °C / min, heating to 500 - 1000 °C, holding at a constant temperature for 0 - 12 h, performing pyrolytic carbonization to remove organic substances to form biomass carbon, and crushing it into particles with a size of 20 - 100 μm.

[0027] The biomass carbon-based raw material in this example can be selected from one or a combination of coconut shells, betel nut shells, straw, nut shells, fruit peels, bamboo, wood, charcoal, starch, etc. as the raw material.

[0028] Step 2: Pickle the first carbonized particles to obtain second carbonized particles with an ash content < 0.3% and a pH value of 6 - 8.

[0029] Specifically, the pickling is carried out by soaking the first carbonized particles in a pickling solution at a temperature of 60 - 100 °C for 0 - 12 h for pickling.

[0030] In this embodiment, the pickling solution can be a single acidic solution such as hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, etc. as the pickling solution, or a mixed solution prepared by mixing multiple acidic solutions as the pickling solution.

[0031] Step 3: Place the second carbonized particles in a fluidized bed reactor. Heat the second carbonized particles from room temperature to 1000 °C at a rate of 5 °C / min, keep the temperature constant for 0.5 h. After the temperature and the state of the second carbonized particles are stable, perform the first activation treatment through a steam generator.

[0032] Specifically, the activation treatment includes: adjusting the steam flow rate to 1 - 100 L / min and the protective gas flow rate to 1 - 20 L / min. After continuous activation for 4 h, shut down the steam, and adjust the protective gas flow rate to 1 - 10 L / min.

[0033] The protective gas in the activation treatment can be one or a combination of helium, neon, argon, krypton, xenon, nitrogen.

[0034] Step 4: After the first activation treatment is completed, stop heating. When the temperature of the fluidized bed reactor drops to 850 °C, maintain this temperature and perform the second activation treatment.

[0035] After the second activation treatment is completed, adjust the protective gas flow rate to 5 L / min until the temperature drops to room temperature. A porous carbon material is prepared.

[0036] Example 2

[0037] In this embodiment, a method for preparing a porous carbon material based on a fluidized bed steam stepwise activation method is disclosed, including the following steps:

[0038] Step 1: Select washed and dried coconut shells as raw materials for carbonization treatment. Under a nitrogen protective gas, in a high-temperature tubular furnace, raise the temperature to 600 °C at a heating rate of 5 °C / min, and keep the temperature constant for 6 h for carbonization. The material obtained after carbonization is marked as Sample A.

[0039] Step 2: Crush Sample A into fine particles of 20 - 100 μm and mark it as Sample B.

[0040] Step 3: Mix Sample B with a mixed solution of hydrochloric acid, nitric acid, and hydrofluoric acid in a ratio of 1:1:1 to prepare a mixed solution with a concentration of 1 mol / L. Soak it in the solution at 80 °C for 4 h for pickling. The ash content after pickling is <0.3%, and the pH value is 6 - 8. Mark it as Sample C.

[0041] Step 4: Select sample C and place it in the fluidized bed reactor. Using nitrogen as the inert protective gas, heat the material from room temperature to 1000 °C at a rate of 5 °C / min, hold the temperature constant for 0.5 h. After the temperature and the state of the material are stable, use deionized water as the steam raw material, process it through a steam generator, adjust the steam flow rate to 15 L / min, and the inert protective gas flow rate to 5 L / min. After continuous activation for about 4 h, shut down the steam and adjust the nitrogen flow rate to 10 L / min.

[0042] Step 5: Stop heating. After the temperature of the fluidized bed reactor drops to 850 °C, hold the temperature constant, adjust the flow rate of the inert protective gas to 3 L / min, then introduce steam and adjust the steam flow rate to 9 L / min to precisely control the macroporous structure. Adjust the steam activation time to 8 h. After the steam activation is completed, adjust the nitrogen flow rate to 5 L / min until the temperature drops, and then the biomass-based porous carbon material prepared by the stepwise steam activation in the fluidized bed can be obtained. Its specific surface area is 1555.09 m2 / g, the pore volume is 0.83 cm3 / g, and the pore size is 2.14 nm.

[0043] Figure 1 The scanning electron microscope image of the porous carbon material prepared by the method in this example is shown.

[0044] Figure 2 The scanning electron microscope image prepared by the method in this example is shown.

[0045] Figure 3 The pore volume - pore size distribution diagram of the porous carbon material prepared by the method in this example is shown.

[0046] Figure 4 The XRD pattern of the porous carbon material prepared by the method in this example is shown.

[0047] Example 3

[0048] The difference between the preparation method in this example and that in Example 2 lies in that different biomass carbon-based raw materials are selected. In this example, charcoal is selected as the raw material and crushed into powder with a particle size of about D50 50 μm. The remaining steps are the same as those in Example 2. The finally obtained porous carbon material has a specific surface area of 1623.18 m2 / g, a pore volume of 0.85 cm3 / g, and a pore size of 2.33 nm.

[0049] Example 4

[0050] The difference between the preparation method in this embodiment and that in Embodiment 2 lies in the different biomass carbon-based raw materials selected. Bamboo is selected as the raw material in this embodiment, and the remaining steps are the same as those in Embodiment 2. The finally obtained porous carbon material has a specific surface area of 1582.48 m2 / g, a pore volume of 0.82 cm3 / g, and a pore size of 2.21 nm.

[0051] Example 5

[0052] The difference between the preparation method in this embodiment and that in Embodiment 2 lies in the different biomass carbon-based raw materials selected. Betel nut shells are selected as the raw material in this embodiment, and the remaining steps are the same as those in Embodiment 2. The finally obtained porous carbon material has a specific surface area of 1489.31 m2 / g, a pore volume of 0.79 cm3 / g, and a pore size of 2.03 nm.

[0053] The test data of the porous carbon materials prepared in Examples 2 to 5 are summarized to obtain the test data table of the porous carbon materials as shown in Table 1.

[0054] Table 1. Test data table of porous carbon materials

[0055]

[0056] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a porous carbon material based on a stepwise activation method with water vapor in a fluidized bed, characterized in that, The preparation method includes: S100. Carbonizing the biomass carbon-based raw material to obtain first carbonized particles; S200. Pickling the first carbonized particles to obtain second carbonized particles with an ash content <0.3% and a pH value of 6 - 8; S300. Placing the second carbonized particles in a fluidized bed reactor, heating the second carbonized particles from room temperature to 1000°C at a rate of 5°C / min, maintaining the temperature at a constant value for 0.5 h, and after the temperature and the state of the second carbonized particles are stable, performing a first activation treatment through a steam generator; S400. After the first activation treatment is completed, stop heating, and when the temperature of the fluidized bed reactor drops to 850°C, maintain this temperature and perform a second activation treatment; After the second activation treatment is completed, adjust the flow rate of the protective gas to 5 L / min until the temperature drops to room temperature.

2. The preparation method of the porous carbon material based on the stepwise activation method of water vapor in a fluidized bed according to claim 1, characterized in that, The carbonization treatment is as follows: Place the biomass carbon-based raw material in a high-temperature tube furnace, use nitrogen as the protective gas, heat it to 500 - 1000°C at a heating rate of 3 - 10°C / min, keep the temperature constant for 0 - 12 h, perform pyrolytic carbonization to remove organic substances to form biomass carbon, and crush it into particles with a size of 20 - 100 μm.

3. The method for preparing a porous carbon material based on a stepwise activation method with fluidized bed water vapor according to claim 1 or 2, characterized in that, The biomass carbon-based raw material is one or a combination of more than one of the following: coconut shell, betel nut shell, straw, nut shell, fruit peel, bamboo, wood, charcoal, starch.

4. The preparation method of the porous carbon material based on the stepwise activation method of water vapor in a fluidized bed according to claim 1, characterized in that, The pickling is carried out by soaking the first carbonized particles in a pickling solution at a temperature of 60 - 100°C for 0 - 12 h for pickling.

5. The method for preparing a porous carbon material based on the stepwise activation method of water vapor in a fluidized bed according to claim 1, wherein The activation treatment includes: adjusting the steam flow rate to 1 - 100 L / min and the protective gas flow rate to 1 - 20 L / min; After continuously activating for 4 h, shut down the steam and adjust the protective gas flow rate to 1 - 10 L / min.

6. The method for preparing a porous carbon material based on the stepwise activation method with fluidized bed water vapor according to claim 1, characterized in that, The protective gas is one or a combination of more than one of the following: helium, neon, argon, krypton, xenon, nitrogen.

7. A porous carbon material based on a stepwise activation method of water vapor in a fluidized bed, characterized in that, The porous carbon material is prepared according to the preparation method described in any one of claims 1 - 6.

Images