A method for preparing porous materials

Abstract

This invention discloses a method for preparing a porous material, comprising the following steps: (1) mixing water, a pore-forming agent, a carbon source, and an extrusion aid, kneading to form a plastic body; (2) sealing and storing the plastic body for a certain period of time, kneading the plastic body again, extruding it into shape, and then hydrothermally treating the shaped particles under sealed conditions; (3) drying the product after hydrothermal treatment in step (2), and then subjecting it to low-temperature calcination and high-temperature calcination under an inert atmosphere; (4) activating the product from step (3) with water vapor, drying it, and obtaining a porous material. The porous material of this invention has carbon particles of a certain shape, with large-sized through channels inside the particles, high crushing strength, and strong wear resistance, and has good application prospects in catalysis, adsorption separation, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of non-metallic functional materials and relates to a method for preparing porous materials. Background Technology

[0002] Porous carbon materials are widely used in adsorption separation, catalysis, and new energy fields due to their large specific surface area, controllable pore structure, high physicochemical stability, and low preparation cost. Current applications of carbon materials are mainly focused on adsorption, separation, and catalysis; therefore, specific surface area and pore structure are extremely important physicochemical properties of carbon materials, largely determining their performance in applications.

[0003] CN2012101945199 describes a process where phenolic resin, epoxy resin, and other materials are thoroughly mixed with a curing agent and then heated for curing. The cured material is then pulverized, and polyvinyl alcohol is added as a pore-forming agent, along with graphite powder and other materials as a support. After thorough mixing, the mixture is pressed into a preform and carbonized at high temperature under gas protection to obtain a pore size of 0.05-10 μm and a specific surface area of ​​100-1000 m². 2 / g of mesoporous and macroporous carbon. The preparation requires high-cost raw materials such as phenolic resin, epoxy resin, and polyvinyl alcohol, as well as hard particulate raw materials such as graphite powder, activated carbon powder, activated carbon fiber, and carbon nanotubes. The resulting mesoporous and macroporous carbon is diffusely distributed and has poor three-dimensional connectivity.

[0004] Existing activated carbon is generally obtained by carbonization and activation of hard raw materials such as carbon powder and biomass. The pore size of the product belongs to the micro-mesoporous category. In contrast, the macroporous activated carbon obtained by the decomposition method using pore-forming agents has a dispersed pore distribution and poor three-dimensional connectivity. In terms of molding, it is mainly obtained by mixing hard activated carbon with a binder and then extruding it. Since the binder can only interact with the surface of the hard particles, the compatibility between the two is limited, thus affecting the strength and wear resistance of the activated carbon particles. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing porous materials. The porous material of this invention comprises carbon particles of a specific shape, with large-sized interconnected channels within the particles. It exhibits high crushing strength and strong wear resistance, and shows promising application prospects in catalysis, adsorption separation, and other fields.

[0006] The method for preparing the porous material of the present invention includes the following:

[0007] (1) Mix water, pore-forming agent, carbon source and extrusion aid, knead to form a plastic body;

[0008] (2) After sealing and storing the plastic body for a certain period of time, knead the plastic body again and extrude it into shape. Then, treat the shaped particles with hydrothermal treatment under sealed conditions.

[0009] (3) Dry the product after hydrothermal treatment in step (2), and then calcine it under low temperature and high temperature under an inert atmosphere;

[0010] (4) Activate the product of step (3) with water vapor and dry it to obtain a porous material.

[0011] In the method of the present invention, the carbon source in step (1) is a mixture of glutinous rice flour and wheat flour, and the amount of glutinous rice flour accounts for 10%-25% of the mass of the carbon source by weight.

[0012] In the method of the present invention, the amount of water used in step (1) is 15%-35% of the total amount of flour by mass.

[0013] In the method of the present invention, the pore-forming agent used in step (1) is baking powder, which can be a commercially available product. The amount of pore-forming agent used is 1%-5% of the mass of the carbon source.

[0014] In the method of the present invention, the extrusion aid in step (1) is one or more of guar gum powder, methylcellulose, and polyethylene glycol, and the extrusion aid is 0.5-5% of the carbon source mass by weight.

[0015] In the method of the present invention, there are no special requirements for the order of adding materials in step (1). It is preferable to gelatinize the glutinous rice flour first. The gelatinization conditions are: add the glutinous rice flour to water with a weight of 1-3 times its own weight, heat it to 58-100℃ under stirring, and keep it for 5-30 minutes.

[0016] In the method of the present invention, the temperature for sealing and storing the plastic body in step (1) is 25-45℃, and the storage time is 0.5-3 hours.

[0017] In the method of the present invention, the time for re-kneading in step (2) is 60-120 minutes, and the ambient temperature is room temperature.

[0018] In the method of the present invention, the extruded granules in step (2) are cylindrical, clover-shaped, four-leaf clover-shaped, or other shapes suitable for extrusion by a molding machine.

[0019] In the method of this invention, the hydrothermal treatment in step (2) involves no direct contact between the water and the molded object. The hydrothermal temperature is 100-200℃, the time is 0.5-5 hours, and the pressure is the self-generated pressure under sealed conditions.

[0020] In the method of the present invention, the drying in step (3) is performed at 60-200℃ for 1-48 hours, preferably at 100-150℃ for 3-24 hours.

[0021] In the method of this invention, the low-temperature calcination conditions in step (3) are: calcination temperature of 200-350℃ and calcination time of 2-5 hours; the high-temperature calcination conditions are: calcination temperature of 750-1000℃ and calcination time of 1-5 hours. The inert atmosphere is nitrogen and / or an inert gas.

[0022] In the method of the present invention, the steam activation in step (4) involves heating the product of step (3) under the condition of passing steam through it. The activation conditions are: temperature 500-1000℃, time 0.5-3 hours, and steam flow rate required per gram of product is 1-10 grams / hour.

[0023] In the method of the present invention, the drying in step (4) is conventional drying, and the conditions are drying at 100-200℃ for 1-48 hours.

[0024] In the method of the present invention, the shaped body described in step (4) is cylindrical, clover-shaped, four-leaf clover-shaped, or other shapes that can be extruded by an extruder.

[0025] The porous material of this invention has the following properties: it has a dual-channel structure of micropores and macropores, the three-dimensional interconnected channels of the macropores have a size of 5-50 μm, and a specific surface area of ​​800-1800 m². 2 / g, the crushing strength of the particles is 10-25N / mm, and the mass abrasion rate is less than 0.5%.

[0026] The carbon source used in this invention is flour, which can absorb water and swell. The raw material has a self-adhesive effect, eliminating the need for additional binders. Because it lacks hard carbon particles, the raw material has good plasticity and, after conversion into activated carbon, exhibits high crushing strength and low abrasion rate. Baking powder generates gas during kneading, forming three-dimensional interconnected macropores within the particles. Wheat flour particles absorb water and swell under the influence of water, forming a three-dimensional interwoven structure with proteins. Through two kneading processes, this three-dimensional structure becomes more stable and dense. Hydrothermal steaming hardens the starch and protein, fixing the shape of the plastic body. The incorporated glutinous rice flour generally has a high proportion of branched starch; after gelatinization, it acts as a binder, further enhancing the strength of the molded body, and also converts into carbon during carbonization. Through steam activation, the three-dimensional macroporous carbon material is rich in micro- and mesoporous channels, thus possessing a high specific surface area. The porous shaped carbon material prepared by the method of this invention has both micropores and macropores, exhibiting excellent catalytic and adsorption separation effects in various application scenarios. Attached Figure Description

[0027] Figure 1 An optical camera photograph of the porous material prepared in Example 1.

[0028] Figure 2 Scanning electron microscope (SEM) image of the porous material prepared in Example 1. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the embodiments. The particle size was measured by vernier calipers, the mechanical strength was tested by a DL3 type strength tester, the microstructure and macropore morphology were observed and measured by scanning electron microscopy, the specific surface area was tested by the BET method, and the wear rate was tested according to the method described in HG / T 3927-2007.

[0030] Example 1

[0031] Mix 60g glutinous rice flour, 6g baking powder, 5g guar gum powder, and 500g wheat flour evenly, then add 90g water and stir and knead into a plastic body. Seal the plastic body at 35℃ for 2 hours, knead again for 60 minutes, then extrude it into cylindrical strips. Steam the cylindrical strips at 120℃ for 1.5 hours, cool, and dry at 120℃ for 12 hours. Place them in a tube furnace under nitrogen protection, heat to 300℃ and hold for 5 hours, then heat to 850℃ and hold for 3 hours. After cooling, introduce steam and heat to 750℃ and hold for 3 hours. The steam flow rate is 7g / hour per gram of sample. After activation, remove and dry at 120℃ for 12 hours to obtain the high specific surface area activated carbon granules described in this invention.

[0032] The resulting cylindrical carbon particles had a diameter of 1.5 mm. BET testing showed that the material had a specific surface area of ​​924 m². 2 The particles, with a density of 1.5-3.1 nm, exhibit micro- and mesoporous channels, a crushing strength of 12 N / mm, and an abrasion rate of 0.45. Scanning electron microscopy revealed that the formed particles possess three-dimensional channels of 7-49 μm.

[0033] Example 2

[0034] Disperse 70g of glutinous rice flour in 150g of water and stir at 95℃ for 30 minutes to gelatinize. Mix 4g of baking powder, 7g of guar gum powder, and 500g of wheat flour evenly, then add the gelatinized glutinous rice flour and knead into a plastic body. Seal the plastic body at 35℃ for 3 hours, knead again for 80 minutes, and then extrude it into clover strips. Steam the clover strips at 150℃ for 2 hours, cool them, and dry them at 150℃ for 12 hours. Place them in a tube furnace under nitrogen protection, raise the temperature to 300℃ and hold for 5 hours, then raise the temperature to 950℃ and hold for 3 hours. After cooling, introduce steam and raise the temperature to 850℃ and hold for 3 hours. The steam flow rate is 10g / hour per gram of sample. After activation, remove the activated carbon and dry it at 120℃ for 12 hours to obtain activated carbon granules.

[0035] The resulting strip-shaped carbon particles had a diameter of 1.5 mm. BET testing showed that the material had a specific surface area of ​​1231 m². 2The particles, with a density of 1.1–3.2 nm, exhibit micro- and mesoporous channels, a crushing strength of 15.6 N / mm, and an abrasion rate of 0.37. Scanning electron microscopy reveals that the formed particles possess three-dimensional channels of 5–47 μm.

[0036] Example 3

[0037] Disperse 80g of glutinous rice flour in 180g of water and stir until gelatinized at 90℃. Mix 5g of baking powder, 5g of guar gum powder, and 500g of wheat flour evenly, then add the gelatinized glutinous rice flour and knead into a plastic body. Seal and store the plastic body at 30℃ for 5 hours, then knead again for 100 minutes. Extrude it into cylindrical strips and steam them at 150℃ for 3 hours. After cooling, remove them and dry them at 120℃ for 12 hours. Place them in a tube furnace under nitrogen protection, raise the temperature to 300℃ and hold for 5 hours, then raise the temperature to 1000℃ and hold for 3 hours. After cooling, introduce steam and raise the temperature to 950℃ and hold for 3 hours. The steam flow rate is 5g / hour per gram of sample. After activation, remove them and dry them at 120℃ for 12 hours as usual to obtain activated carbon granules.

[0038] The resulting strip-shaped carbon particles had a diameter of 2 mm. BET testing showed that the material had a specific surface area of ​​1494 m². 2 / g, with micro-mesopores of 1.1-4.5 nm, crushing strength of 22.4 N / mm, and abrasion rate of 0.27. Scanning electron microscopy revealed that the formed particles had three-dimensional channels of 15-21 μm.

[0039] Example 4

[0040] Disperse 120g of glutinous rice flour in 200g of water and stir until gelatinized at 80℃. Mix 5g of baking powder, 5g of guar gum powder, and 500g of wheat flour evenly, then add the gelatinized glutinous rice flour and knead into a plastic body. Seal and store the plastic body at 30℃ for 5 hours, then knead again for 120 minutes. Extrude it into cylindrical strips and steam them at 150℃ for 3 hours. After cooling, remove them and dry them at 120℃ for 12 hours. Place them in a tube furnace under argon protection, raise the temperature to 300℃ and hold for 5 hours, then raise the temperature to 1000℃ and hold for 3 hours. After cooling, introduce steam and raise the temperature to 950℃ and hold for 3 hours. The steam flow rate is 6g / hour per gram of sample. After activation, remove them and dry them at 120℃ for 12 hours as usual to obtain activated carbon granules.

[0041] The resulting strip-shaped carbon particles had a diameter of 2 mm. BET testing showed that the material had a specific surface area of ​​1757 m². 2 The particles, with a density of 0.9-6.7 nm, exhibit micro- and mesoporous channels, a crushing strength of 24.5 N / mm, and an abrasion rate of 0.22. Scanning electron microscopy reveals that the formed particles possess three-dimensional channels of 8-39 μm.

[0042] Comparative Example 1

[0043] Similar to Example 1, except that wheat flour is not added, the hardening effect is not good, and the final granules are difficult to form relatively regular columnar granules.

[0044] Comparative Example 2

[0045] Similar to Example 1, except that hydrothermal treatment is not performed, the final molded particles are difficult to form relatively regular columnar particles.

[0046] Comparative Example 3

[0047] Similar to Example 1, except that it was directly extruded after being sealed and stored. The final molded particles were relatively loose and difficult to form regular columnar particles.

[0048] Comparative Example 4

[0049] Similar to Example 1, except that the calcination process involves a single-stage calcination, where the temperature is directly raised to 850°C and held for 3 hours. This material has a lower carbon conversion rate, still contains polymeric organic matter, and the final granules are relatively loose.

Claims

1. A method for preparing a porous material, characterized in that... The process includes the following steps: (1) mixing water, pore-forming agent, carbon source, and extrusion aid, kneading to form a plastic body; (2) sealing and storing the plastic body for a certain period of time, kneading the plastic body again, extruding it into shape, and then hydrothermally treating the shaped particles under sealed conditions; (3) drying the product after hydrothermal treatment in step (2), and then calcining it at low temperature and high temperature under an inert atmosphere; (4) activating the product of step (3) with water vapor, drying it, and obtaining a porous material. The carbon source mentioned in step (1) is a mixture of glutinous rice flour and wheat flour, with the amount of glutinous rice flour accounting for 10%-25% of the carbon source by mass. The low-temperature roasting conditions mentioned in step (3) are: roasting temperature of 200-350℃ and roasting time of 2-5 hours; the high-temperature roasting conditions are: roasting temperature of 750-1000℃. The steam activation conditions described in step (4) are: temperature 500-1000℃, time 0.5-3 hours, and steam flow rate of 1-10 g / hour required per gram of product; The porous material has a dual-channel structure of micropores and macropores, with the three-dimensional interconnected channels of the macropores having a size of 5-50 μm and a specific surface area of ​​800-1800 m². 2 / g, the crushing strength of the particles is 10-25N / mm, and the mass abrasion rate is less than 0.5%.

2. The method according to claim 1, characterized in that: The amount of water used in step (1) is 15%-35% of the total amount of flour by mass.

3. The method according to claim 1, characterized in that: The pore-forming agent used in step (1) is baking powder. The amount of pore-forming agent used is 1%-5% of the mass of the carbon source.

4. The method according to claim 1, characterized in that: The extrusion aid mentioned in step (1) is one or more of guar gum powder, methylcellulose, and polyethylene glycol, and the extrusion aid is 0.5-5% of the carbon source mass by weight.

5. The method according to claim 1, characterized in that: First, gelatinize the glutinous rice flour. The gelatinization conditions are as follows: add the glutinous rice flour to water with a weight of 1-3 times its own weight, heat to 58-100℃ while stirring, and keep it for 5-30 minutes.

6. The method according to claim 1, characterized in that: In step (1), the temperature for sealing and storing the plastic body is 25-45℃, and the storage time is 0.5-3 hours.

7. The method according to claim 1, characterized in that: The re-mixing time in step (2) is 60-120 minutes.

8. The method according to claim 1, characterized in that: In step (2), the hydrothermal treatment does not involve direct contact between water and the molded object. The hydrothermal temperature is 100-200℃, the time is 0.5-5 hours, and the pressure is the self-generated pressure under closed conditions.

9. The method according to claim 1, characterized in that: The drying conditions described in step (3) are 60-200℃ for 1-48 hours.

10. The method according to claim 1, characterized in that: The inert atmosphere mentioned in step (3) is an inert gas.

11. The method according to claim 10, characterized in that: The inert atmosphere mentioned in step (3) is nitrogen.

12. The method according to claim 1, characterized in that: The drying conditions described in step (4) are: drying at 100-200℃ for 1-48 hours.

13. A porous material prepared by the method of any one of claims 1 to 12.

14. The application of the porous material according to claim 13 in the fields of catalysis and adsorption.

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