Hierarchical porous activated carbon and application thereof, and method for preparing hierarchical porous activated carbon from Bassa wood

Abstract

The invention belongs to the technical field of waste gas adsorption, and particularly relates to hierarchical porous activated carbon, application of the hierarchical porous activated carbon and a method for preparing the hierarchical porous activated carbon from balsa wood. The pore size of micropores in the activated carbon disclosed by the invention comprises two intervals of 0.5-0.85 nm and 1-2 nm. And the interval is respectively matched with the molecular dynamic diameter of styrene and the size of a pore channel through which a single molecule passes. Wherein the size of the pore structure ranges from 0.5 nm to 0.85 nm, styrene adsorbed in the pore structure is subjected to single-molecule adsorption, the styrene adsorbed in the pore structure is separated from one another by a pore wall material, aggregation of the gathered styrene under the thermal effect condition is prevented, and the problem that activated carbon saturated in adsorption is difficult to regenerate is avoided; the size of the pore structure ranges from 1 nm to 2 nm, styrene passes in the form of a single molecule, the possibility that the styrene is aggregated and polymerized when moving and transmitting in a pore channel is reduced, and efficient desorption and regeneration of the styrene are promoted.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of waste gas adsorption, and particularly relates to a hierarchical porous activated carbon and application thereof, and a method for preparing the hierarchical porous activated carbon from Balsa wood. BACKGROUND

[0002] Styrene is a common chemical raw material, which can be polymerized by itself or with other material monomers, and is widely used in the fields of synthetic resin, synthetic fiber, styrene-butadiene rubber, plastic industry and glass steel industry. The saturated vapor pressure of styrene at 20 DEG C ambient temperature is about 700 Pa, which belongs to volatile organic compounds (VOCs). Styrene spilled in the environment can enter the human body through inhalation, skin contact and other ways, and cause serious harm to the human body's red blood cells, central nervous system, lungs, liver and kidney system, and even cause cancer. Therefore, international and domestic environmental protection organizations have strict requirements on the content of styrene in the environment. Therefore, the removal and treatment of styrene in the human living and production environment, especially in the glass steel, plastic and resin production plant, become necessary work to protect the environment and maintain normal production.

[0003] At present, researchers have developed various methods for treating styrene waste gas in the environment, such as combustion method, catalytic method, washing method and adsorption method. Among them, the activated carbon adsorption method has the characteristics of low raw material price, simple operation, strong environmental protection equipment applicability, etc., and is the most economical and applicable styrene waste gas treatment method with the widest industrial application range. However, the current commercial activated carbon still has a low adsorption capacity for styrene, generally 300 mg / g-500 mg / g. Therefore, it is necessary to further improve the styrene adsorption capacity of activated carbon. SUMMARY

[0004] The application aims to provide a hierarchical porous activated carbon and application thereof, and a method for preparing the hierarchical porous activated carbon from Balsa wood, and the hierarchical porous activated carbon prepared by the preparation method provided by the application has a high adsorption capacity for styrene.

[0005] In order to achieve the above-mentioned purpose, the application provides the following technical scheme:

[0006] The application provides a method for preparing a hierarchical porous activated carbon from Balsa wood, which comprises the following steps:

[0007] After the Balsa wood is pre-carbonized, the Balsa wood is mixed with a pore forming agent and water, and is allowed to stand to obtain a precursor material; the pore forming agent comprises potassium salt, ammonium bicarbonate and melamine; the potassium salt comprises at least one of potassium carbonate and potassium bicarbonate;

[0008] Carbonize the precursor material to obtain the hierarchical porous activated carbon.

[0009] Preferably, the particle size of the Bashan wood is not more than 80 mesh; the pre-carbonization temperature is 190-210℃, and the time is 8-16h.

[0010] Preferably, the mass ratio of the potassium salt, ammonium bicarbonate and melamine is 0.5-1.5:0.2-1:0.2-1.

[0011] Preferably, the mass ratio of the Bashan wood and the pore-forming agent is 1:0.9-3.5;

[0012] The mass ratio of the Bashan wood and water is 1:4-10.

[0013] Preferably, the standing is carried out under sealed conditions, and the standing time is 12-24h.

[0014] Preferably, the carbonization comprises sequentially carrying out first carbonization and second carbonization;

[0015] The temperature of the first carbonization is 70-90℃, the temperature rising rate for rising to the temperature of the first carbonization is 5-10℃ / min, and the holding time is 6-12h;

[0016] The temperature of the second carbonization is 700-800℃, the temperature rising rate for rising to the temperature of the second carbonization is 1-4℃ / min, and the holding time is 2-4h.

[0017] Preferably, after the carbonization, further comprising carrying out post-treatment on the obtained carbonized material, and the post-treatment comprises: cooling the carbonized material to below 60℃, water washing the cooled material to neutral, acid immersion of the material after the acid immersion, and drying the material after the water washing to neutral again;

[0018] The solvent used in the acid immersion is a hydrochloric acid solution, the concentration of the hydrochloric acid solution is 1.5mol / L, and the acid immersion time is 6-36h.

[0019] The present application also provides a hierarchical porous activated carbon prepared by the method.

[0020] The microporous structure comprises first microporous structure and second microporous structure.

[0021] The pore size of the first microporous structure is 0.5-0.85nm, and the pore size of the second microporous structure is 1-2nm, and 2nm is not included.

[0022] Preferably, the pore size of the mesoporous structure is 2-10nm.

[0023] The ratio of the pore volume of the first microporous structure, the second microporous structure and the mesoporous structure to the total pore volume is 18-25%, 30-41%, and 16-26%, respectively;

[0024] The total pore volume of the hierarchical porous structure is 0.9-1.2 cm 3 / g in the range of 0.5-190 nm.

[0025] The specific surface area of the hierarchical porous activated carbon is 1800-2300 m 2 / g.

[0026] The application further provides the use of the hierarchical porous activated carbon in adsorbing styrene.

[0027] The application provides a method for preparing hierarchical porous activated carbon from Bashan wood, comprising the following steps: after pre-carbonization of Bashan wood, mixing the Bashan wood with a pore-forming agent and water, and standing to obtain a precursor material; the pore-forming agent comprises potassium salt, ammonium bicarbonate and melamine; the potassium salt comprises at least one of potassium carbonate and potassium bicarbonate; and carbonizing the precursor material to obtain the hierarchical porous activated carbon.

[0028] The application utilizes the multi-scale micrometer-level pore structure and carbon element network of Bashan wood itself, and the pore-forming effect of the pore-forming agent on Bashan wood powder, so that the micropore size of the prepared activated carbon material is mainly distributed in two intervals of 0.5-0.85 nm and 1-2 nm. The two intervals are matched with the molecular dynamics diameter (0.6 nm) of styrene molecules and the pore size (1.1 nm-1.6 nm) through which the styrene molecules can pass in a single molecule form. In the micropore range, first, the pore structure size in the interval of 0.5 nm-0.85 nm can enable the styrene molecules adsorbed in the pore structure to be single molecule adsorption, in which case, the styrene molecules adsorbed in the pore structure are separated from each other by the pore wall material, preventing the styrene molecules from aggregating together under the condition of thermal effect, and avoiding the problem that the saturated activated carbon material is difficult to regenerate. Second, the pore structure size in the interval of 1 nm-2 nm can enable the styrene molecules to pass in a single molecule form, and this pore structure reduces the possibility of aggregation and polymerization of the styrene molecules when moving and transporting in the pore, and promotes the efficient desorption and regeneration of the styrene molecules.

[0029] In addition, Bashan wood itself has several micrometer-scale channels and channel walls with micrometer and sub-micrometer channels arranged along the growth direction of the wood material, which can provide corresponding multi-scale micrometer-level pore structures in the carbon material after carbonization. This multi-scale micrometer-sub-micrometer macroporous structure is beneficial to the rapid transmission of styrene molecules to the adsorption sites in the activated carbon material and the rapid desorption process. Attached Figure Description

[0030] Figure 1 SEM image of balsa wood sawdust material obtained in Example 1;

[0031] Figure 2 Here is a SEM image of the hierarchical porous activated carbon obtained in Example 1;

[0032] Figure 3 The image shows the pore size distribution of the hierarchical porous activated carbon obtained in Example 1.

[0033] Figure 4 The curve shows the change in the amount of styrene adsorbed by the hierarchical porous activated carbon obtained in Example 1. Detailed Implementation

[0034] This invention provides a method for preparing hierarchical porous activated carbon using balsa wood, comprising the following steps:

[0035] Balsa wood is pre-carbonized, mixed with a pore-forming agent and water, and allowed to stand to obtain a precursor material; the pore-forming agent includes potassium salt, ammonium bicarbonate and melamine; the potassium salt includes at least one of potassium carbonate and potassium bicarbonate;

[0036] The precursor material is carbonized to obtain the hierarchical porous activated carbon.

[0037] In this invention, balsa wood is pre-carbonized, mixed with a pore-forming agent and water, and left to stand to obtain a precursor material.

[0038] In this invention, the particle size of the balsa wood is preferably no more than 80 mesh, and more preferably 40-80 mesh. In this invention, the balsa wood is preferably sawdust generated during the cutting and processing of balsa wood material for wind turbine blade cores, and the undersize material obtained by sieving through a 40-80 mesh sieve. Using balsa wood sawdust from the core material processing as raw material in this invention has the following three advantages: First, it eliminates the wood crushing process, reducing process steps and saving energy and equipment; second, balsa wood sawdust is a waste material from wind turbine blade core material processing plants, and its low price helps reduce the price of the prepared activated carbon, improving the product's market competitiveness; third, the use of balsa wood sawdust waste material also solves the waste disposal problem of wind turbine blade core material processing plants, which is conducive to the construction of a zero-waste factory.

[0039] In the present application, the temperature of the pre-carbonization is preferably 190-210℃, and can be specifically 190℃, 200℃, or 210℃; the time is preferably 8-16h, and can be specifically 8h, 10h, 12h, 14h, or 16h. In the present application, the pre-carbonization is preferably electric heating baking. In the present application, the pre-carbonization can remove the water and part of the water-repellent oily substances in the wood powder material, so that the wood powder can fully absorb the pore-forming agent aqueous solution after processing, and the dispersibility of the pore-forming agent material in the processed wood powder is improved.

[0040] In the present application, the potassium salt includes at least one of potassium carbonate and potassium bicarbonate; the mass ratio of the potassium salt, the ammonium bicarbonate, and the melamine is preferably 0.5-1.5:0.2-1:0.2-1. In the present application, the mass ratio of the basswood and the pore-forming agent is preferably 1:0.9-3.5; the mass ratio of the basswood and the water is preferably 1:4-10.

[0041] In the present application, the mixing is preferably performed under stirring, and the stirring time is preferably 30min. In the present application, the standing is preferably performed under sealing, and the standing time is preferably 12-24h. In the present application, during the standing, the potassium ions (K + ) in the potassium salt can be adsorbed into the wood powder, and the theoretical radius of the K + ions is 0.36nm, which is conducive to the construction of the micropore structure of 0.5-0.85nm during the carbonization of the wood powder. The potassium ions in the potassium salt react with NH3·H2O generated after the ammonium bicarbonate is dissolved in water to generate potassium amide (KNH2·NH3), and the potassium ions in the potassium salt can also react with the melamine molecules dissolved in water to generate potassium melamine (K(C3N6H5)). The dimension of the long axis direction of the molecular cell in the potassium amide crystal is about 1.1nm, and this kind of molecular structure is conducive to the construction of the micropore structure of 1-2nm; the dimension of the long axis direction of the molecular cell in the potassium melamine crystal is about 1.9nm, and this kind of molecular structure is conducive to the construction of the mesopore structure of >2nm; in addition, the potassium amide molecules can release ammonia gas during heating, and the potassium melamine molecules can release hydrogen gas during heating, and these gas molecules generated during heating are conducive to the construction of the mesopore and macropore structures.

[0042] After the standing, the present application preferably does not perform any post-processing process, and directly performs the subsequent carbonization.

[0043] After obtaining the precursor material, the present application carbonizes the precursor material to obtain the multi-level pore activated carbon.

[0044] In the present application, the carbonization is preferably carried out under a protective atmosphere, which is preferably high-purity nitrogen or high-purity argon. In the present application, the carbonization preferably comprises sequentially performing first carbonization and second carbonization; the temperature of the first carbonization is preferably 70-90℃, and can be specifically 70℃, 80℃, or 90℃; the temperature rising rate for rising to the temperature of the first carbonization is preferably 5-10℃ / min, and can be specifically 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, or 10℃ / min; the holding time is preferably 6-12h, and can be specifically 6h, 8h, 10h, or 12h; during the first carbonization, on one hand, the water in the raw material slurry is discharged, and on the other hand, the derived pore-forming agent of the pore-forming agent is converted from a free state to a molecular state and combined in the wood powder-based raw material, so as to facilitate the pore-forming effect in the second carbonization process.

[0045] In the present application, the temperature of the second carbonization is preferably 700-800℃, and can be specifically 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃, or 800℃; the temperature rising rate for rising to the temperature of the second carbonization is preferably 1-4℃ / min, and can be specifically 1℃ / min, 2℃ / min, 3℃ / min, or 4℃ / min; the holding time is preferably 2-4h, and can be specifically 2h, 3h, or 4h; during the second carbonization, the carbon-containing wood components (mainly including cellulose, hemicellulose, and lignin) in the Bashan wood powder are carbonized to generate carbon materials through dehydrogenation, deoxidation, and other reactions in the process of high-temperature heating; at the same time, the pore-forming agent materials (such as potassium ions, KNH2·NH3, and K(C3N6H5)) generate thermal decomposition reactions in the process of heating and carbonization, to generate solid compounds of potassium elements and gas molecules such as NH3 and H2, so as to generate a pore-forming effect and generate a porous carbon material with multiple pore size structures.

[0046] In the present application, the carbonization is preferably carried out in an atmosphere-protected furnace.

[0047] In the present application, after the carbonization, the obtained carbonized material is preferably further subjected to post-treatment, which preferably comprises: cooling the carbonized material to below 60℃, water-washing the cooled material to neutral, then acid immersion, water-washing the acid-immersed material to neutral again, and then drying; the solvent used in the acid immersion is preferably a hydrochloric acid solution, the concentration of the hydrochloric acid solution is preferably 1.5mol / L, and the acid immersion time is preferably 6-36h.

[0048] In the specific embodiment of the present application, the carbonization process is as follows: the precursor material is loaded into a corundum crucible with a cover, the loading volume is 60-80% of the volume of the crucible; after the crucible cover is closed, the crucible containing the material is placed in a protective atmosphere furnace, and the first carbonization and the second carbonization are sequentially performed under a protective atmosphere; then the carbonized material after cooling is washed with water to neutral, and then subjected to acid immersion; then it is washed with water again to neutral; finally, the obtained product is placed in a drying box for drying to obtain a hierarchical pore activated carbon.

[0049] The present application also provides a hierarchical pore activated carbon prepared by the method described in the above technical solution, which comprises a macropore structure, a mesopore structure and a micropore structure; the micropore structure comprises a first micropore structure and a second micropore structure.

[0050] The pore diameter of the first micropore structure is 0.5-0.85 nm, and the pore diameter of the second micropore structure is 1-2 nm, but not including 2 nm.

[0051] In the present application, the pore diameter of the mesopore structure is preferably 2-10 nm; the pore volume of the first micropore structure, the second micropore structure and the mesopore structure accounts for 18-25%, 30-41% and 16-26% of the total pore volume, respectively. In the present application, the total pore volume of the hierarchical pore structure is 0.9-1.2 cm 3 / g in the range of 0.5-190 nm. 2 / g in the present application.

[0052] The present application also provides the application of the hierarchical pore activated carbon described in the above technical solution in adsorbing styrene. The present application does not have special limitations on the implementation mode of the application, and the application of the present application can be used by those skilled in the art. In the present application, the first adsorption amount of the hierarchical pore activated carbon for styrene is 900-1200 mg / g, and it can be used repeatedly, and the adsorption amount of styrene is 700-1000 mg / g after 5 times of regeneration.

[0053] Unless otherwise specified, the materials and equipment used in the present application are commercially available in the art.

[0054] The technical solutions in the present application will be described clearly and completely in combination with the embodiments in the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0055] Example 1

[0056] The sawdust in the process of processing and preparing the wind power blade core material by Jiangxi Oureison New Energy Technology Co., Ltd. using the balsa wood material as raw material (the production place is Papua New Guinea) is sieved by using a 60-mesh screen, and the undersize is recorded as the balsa wood sawdust material;

[0057] The obtained balsa wood sawdust material is pre-carbonized by electric heating at 200℃ for 8h, then the pre-carbonized balsa wood, potassium bicarbonate, ammonium bicarbonate and melamine are added into water, and mechanically stirred and mixed for 30min, wherein the weight ratio of the balsa wood sawdust material, potassium bicarbonate, ammonium bicarbonate, melamine and water is 1:1:0.5:0.5:8; the mixed material is placed in a plastic sealed barrel and sealed for 20h, and then dried to obtain a precursor material;

[0058] The precursor material is loaded into a corundum crucible with a cover, and the loading volume is 80% of the volume of the crucible; after covering the crucible cover, the crucible containing the material is placed in an atmosphere protection furnace, and under the protection of high-purity argon atmosphere, it is first heated to 80℃ at a rate of 5℃ / min, and kept for 10h; then, it is heated to 780℃ at a rate of 3℃ / min, and kept for 3h; then cooled to 40℃, and the cooled carbonized material is washed to neutral with water, and placed in a 1.5mol / L hydrochloric acid aqueous solution for acid immersion for 24h; then washed to neutral again; finally, the obtained product is placed in a drying box for drying to obtain a multi-level pore activated carbon.

[0059] Example 2

[0060] The sawdust in the process of processing and preparing the wind power blade core material by Jiangxi Oureison New Energy Technology Co., Ltd. using the balsa wood material as raw material (the production place is Papua New Guinea) is sieved by using a 60-mesh screen, and the undersize is recorded as the balsa wood sawdust material;

[0061] The obtained balsa wood sawdust material is pre-carbonized by electric heating at 200℃ for 8h, then the pre-carbonized balsa wood, potassium bicarbonate, ammonium bicarbonate and melamine are added into water, and mechanically stirred and mixed for 30min, wherein the weight ratio of the balsa wood sawdust material, potassium bicarbonate, ammonium bicarbonate, melamine and water is 1:1:0.5:0.5:8; the mixed material is placed in a plastic sealed barrel and sealed for 20h, and then dried to obtain a precursor material;

[0062] The precursor material is loaded into a corundum crucible with a cover, and the loading volume is 80% of the volume of the crucible; after covering the crucible cover, the crucible containing the material is placed in an atmosphere protection furnace, and under the protection of high-purity argon atmosphere, it is first heated to 90℃ at a rate of 8℃ / min, and kept for 12h; then, it is heated to 750℃ at a rate of 2℃ / min, and kept for 4h; then it is cooled to room temperature, and the cooled carbonized material is washed with water to neutral, and then placed in a 1.2mol / L hydrochloric acid aqueous solution for acid leaching for 20h; then it is washed with water again to neutral; finally, the obtained product is placed in a drying box for drying, and a multi-level pore activated carbon is obtained.

[0063] Example 3

[0064] The sawdust in the process of processing and preparing wind power blade core material by Jiangxi Oureison New Energy Technology Co., Ltd. using balsa wood as raw material (produced in Papua New Guinea) is sieved using a 40-mesh sieve, and the undersize material is recorded as balsa sawdust material;

[0065] The obtained balsa sawdust material is pre-carbonized by electric heating at 190℃ for 15h, and then the pre-carbonized balsa, potassium bicarbonate, ammonium bicarbonate and melamine are added to water and mechanically stirred for 30min, wherein the weight ratio of balsa sawdust material, potassium bicarbonate, ammonium bicarbonate, melamine and water is 1:0.5:0.2:0.2:4; the stirred material is placed in a plastic sealed barrel and sealed for 12h, and then dried to obtain a precursor material;

[0066] The precursor material is loaded into a corundum crucible with a cover, and the loading volume is 80% of the volume of the crucible; after covering the crucible cover, the crucible containing the material is placed in an atmosphere protection furnace, and under the protection of high-purity argon atmosphere, it is first heated to 90℃ at a rate of 8℃ / min, and kept for 12h; then, it is heated to 750℃ at a rate of 2℃ / min, and kept for 4h; then it is cooled to room temperature, and the cooled carbonized material is washed with water to neutral, and then placed in a 1.2mol / L hydrochloric acid aqueous solution for acid leaching for 20h; then it is washed with water again to neutral; finally, the obtained product is placed in a drying box for drying, and a multi-level pore activated carbon is obtained.

[0067] Example 4

[0068] The sawdust in the process of processing and preparing wind power blade core material by Jiangxi Oureison New Energy Technology Co., Ltd. using balsa wood as raw material (produced in Papua New Guinea) is sieved using a 40-mesh sieve, and the undersize material is recorded as balsa sawdust material;

[0069] The obtained sawdust material of balsa wood is pre-carbonized by electric heating at 200℃ for 12h, then the pre-carbonized balsa wood, potassium bicarbonate, ammonium bicarbonate and melamine are added into water and mechanically stirred and mixed for 20min, wherein the weight ratio of the sawdust material of balsa wood, potassium bicarbonate, ammonium bicarbonate, melamine and water is 1:1:0.7:0.3:6; the mixed material is placed in a plastic sealed barrel and stored for 24h, and then dried to obtain a precursor material;

[0070] The precursor material is loaded into a corundum crucible with a lid, and the loading volume is 60% of the volume of the crucible; after covering the lid of the crucible, the crucible containing the material is placed in an atmosphere protection furnace, and under the protection of high-purity argon atmosphere, it is first heated to 85℃ at a rate of 6℃ / min and kept for 8h; then it is heated to 800℃ at a rate of 4℃ / min and kept for 2.5h; then it is cooled to 30℃, and the cooled carbonized material is washed to neutral with water, placed in a 2.0mol / L hydrochloric acid aqueous solution, and acid soaked for 16h; then it is washed to neutral again; finally, the obtained product is placed in a drying box for drying to obtain a multi-level pore activated carbon.

[0071] Example 5

[0072] The sawdust in the process of processing and preparing wind power blade core material by Jiangxi Oureison New Energy Technology Co., Ltd. using balsa wood as raw material (produced in Papua New Guinea) is sieved using a 60 mesh sieve, and the undersize material is recorded as balsa wood sawdust material;

[0073] The obtained balsa wood sawdust material is pre-carbonized by electric heating at 200℃ for 8h, then the pre-carbonized balsa wood, potassium carbonate, ammonium bicarbonate and melamine are added into water and mechanically stirred and mixed for 30min, wherein the weight ratio of the balsa wood sawdust material, potassium carbonate, ammonium bicarbonate, melamine and water is 1:1:0.5:0.5:8; the mixed material is placed in a plastic sealed barrel and stored for 20h, and then dried to obtain a precursor material;

[0074] The precursor material is loaded into a corundum crucible with a lid, and the loading volume is 80% of the volume of the crucible; after covering the lid of the crucible, the crucible containing the material is placed in an atmosphere protection furnace, and under the protection of high-purity argon atmosphere, it is first heated to 80℃ at a rate of 5℃ / min and kept for 10h; then it is heated to 780℃ at a rate of 3℃ / min and kept for 3h; then it is cooled to 40℃, and the cooled carbonized material is washed to neutral with water, placed in a 1.5mol / L hydrochloric acid aqueous solution, and acid soaked for 24h; then it is washed to neutral again; finally, the obtained product is placed in a drying box for drying to obtain a multi-level pore activated carbon.

[0075] Comparative Example 1

[0076] The sawdust in the process of processing and preparing a wind power blade core material by Jiangxi Oureison New Energy Technology Co., Ltd. using balsa wood material as raw material (originating from Papua New Guinea) is sieved using a 60-mesh sieve, and the undersize is recorded as balsa sawdust material;

[0077] The obtained balsa sawdust material is pre-carbonized by electric heating at 200 ℃ for 8 h, and then the pre-carbonized balsa wood, potassium bicarbonate and melamine are added to water and mechanically stirred and mixed for 30 min, wherein the weight ratio of the balsa sawdust material, potassium bicarbonate, melamine and water is 1:1:0.5:8. After stirring and mixing, the material is placed in a plastic sealed barrel and sealed for 20 h, and then dried to obtain a precursor material;

[0078] The precursor material is loaded into a corundum crucible with a lid, and the loading volume is 80% of the volume of the crucible. After covering the lid of the crucible, the crucible containing the material is placed in an atmosphere protection furnace under the protection of high-purity argon atmosphere. First, the temperature is raised to 80 ℃ at a rate of 6 ℃ / min and kept for 10 h. Then, the temperature is raised to 780 ℃ at a rate of 3 ℃ / min and kept for 3 h. After cooling to room temperature, the carbonized material is washed with water to neutral, placed in a 2.0 mol / L hydrochloric acid aqueous solution, and acid soaked for 18 h. Then, it is washed with water to neutral again. Finally, the obtained product is placed in a drying box to dry, and a hierarchical pore activated carbon is obtained.

[0079] Performance test

[0080] Test Example 1

[0081] The apparent morphology of the balsa sawdust material obtained in the example and the final obtained activated carbon is characterized by using a scanning electron microscope, and the element composition analysis of the obtained activated carbon is performed by using an energy spectrum analyzer;

[0082] Figure 1 The SEM image of the balsa sawdust material obtained in Example 1 is shown in FIG. 1; Figure 2 The SEM image of the hierarchical pore activated carbon obtained in Example 1 is shown in FIG. 2; Figure 1 As can be seen from FIG. 1, the balsa sawdust material sieved by 60 mesh contains nearly parallel arranged pores with a diameter of about tens of microns, and the pore walls contain micron and sub-micron sized pore structures. As can be seen from FIG. 2, the obtained hierarchical pore activated carbon has micron-sized pore structure and pit structure on the surface, and the pore walls and pits also contain a large amount of sub-micron-based pore structure. Figure 2

[0083] The element spectrum analysis data of the activated carbon obtained in Example 1 is shown in Table 1;

[0084] Table 1 Element spectrum analysis data of the activated carbon obtained in Example 1​

[0085]

[0086] As can be seen from Table 1, the main component of the obtained activated carbon is carbon (C), and the weight percentage of carbon element in the material is 95.89%, and a small amount of oxygen, nitrogen and other elements are also contained.

[0087] Test Example 2

[0088] The specific surface area and pore size distribution of the activated carbon obtained in the examples and comparative examples were tested by using a specific surface area and pore size analyzer;

[0089] As can be seen from Table 2, the micropore size of the prepared multi-stage pore activated carbon is mainly distributed in the two intervals of 0.5nm-0.85nm and 1nm-2nm; and also contains part of mesoporous structure, and the pore size of the mesoporous structure is mainly distributed in the 2-10nm interval with smaller size. Figure 3

[0090] The specific surface area and pore volume data of the obtained activated carbon in different pore ranges are shown in Table 2;

[0091] Table 2 Specific surface area and pore volume of the activated carbon obtained in the examples and comparative examples

[0092]

[0093] As can be seen from Table 2, the specific surface area of the activated carbon material obtained in Example 1 is 2159m 2 / g, the pore volume in the 0.5nm-0.85nm pore size interval is 0.207cm 3 / g, the pore volume in the 1nm-2nm pore size interval is 0.450cm 3 / g, and the pore volume in the 2nm-10nm pore size interval is 0.267cm 3 / g.

[0094] The specific surface area of the activated carbon obtained in Example 2 is 2297m 2 / g, and the ratio of the pore volume distributed in the 0.5nm-0.85nm, 1nm-2nm and 2nm-10nm pore size intervals is about 1:2.1:1.2.

[0095] The specific surface area of the activated carbon obtained in Example 3 is 1843m 2 / g, the pore volume in the 0.5nm-0.85nm pore size interval is 0.198cm 3 / g, the pore volume in the 1nm-2nm pore size interval is 0.361cm 3 / g, and the pore volume in the 2nm-10nm pore size interval is 0.162cm 3 / g.

[0096] ​The specific surface area of the activated carbon obtained in Example 4 was 2013 m2 / g, the ratio of the micropore volume distributed in the pore size interval of 0.5 nm-0.85 nm, 1 nm-2 nm and 2 nm-10 nm was about 1:2.1:1.2. 2 The specific surface area of the activated carbon obtained in Example 4 was 2013 m2 / g, the ratio of the micropore volume distributed in the pore size interval of 0.5 nm-0.85 nm, 1 nm-2 nm and 2 nm-10 nm was about 1:2.1:1.2.

[0097] The specific surface area of the activated carbon obtained in Example 5 was 2084 m2 / g, the micropore volume distributed in the pore size interval of 0.5 nm-0.85 nm and 1 nm-2 nm was 0.268 cm3 / g and 0.346 cm3 / g respectively, and the mesopore volume distributed in the pore size interval of 2 nm-10 nm was 0.286 cm3 / g. 2 The specific surface area of the activated carbon obtained in Example 4 was 2013 m2 / g, the ratio of the micropore volume distributed in the pore size interval of 0.5 nm-0.85 nm, 1 nm-2 nm and 2 nm-10 nm was about 1:2.1:1.2. 3 The specific surface area of the activated carbon obtained in Example 4 was 2013 m2 / g, the ratio of the micropore volume distributed in the pore size interval of 0.5 nm-0.85 nm, 1 nm-2 nm and 2 nm-10 nm was about 1:2.1:1.2. 3 The specific surface area of the activated carbon obtained in Example 4 was 2013 m2 / g, the ratio of the micropore volume distributed in the pore size interval of 0.5 nm-0.85 nm, 1 nm-2 nm and 2 nm-10 nm was about 1:2.1:1.2. 3 The specific surface area of the activated carbon obtained in Example 4 was 2013 m2 / g, the ratio of the micropore volume distributed in the pore size interval of 0.5 nm-0.85 nm, 1 nm-2 nm and 2 nm-10 nm was about 1:2.1:1.2.

[0098] The specific surface area of the activated carbon obtained in Example 4 was 2013 m2 / g, the ratio of the micropore volume distributed in the pore size interval of 0.5 nm-0.85 nm, 1 nm-2 nm and 2 nm-10 nm was about 1:2.1:1.2. 2 The specific surface area of the activated carbon obtained in Example 4 was 2013 m2 / g, the ratio of the micropore volume distributed in the pore size interval of 0.5 nm-0.85 nm, 1 nm-2 nm and 2 nm-10 nm was about 1:2.1:1.2. 3 The specific surface area of the activated carbon obtained in Example 4 was 2013 m2 / g, the ratio of the micropore volume distributed in the pore size interval of 0.5 nm-0.85 nm, 1 nm-2 nm and 2 nm-10 nm was about 1:2.1:1.2.

[0099] Test Example 3

[0100] The multi-stage pore activated carbon obtained in the examples and comparative examples was subjected to static styrene gas adsorption test. After adsorption saturation, the styrene gas adsorption saturated activated carbon material was placed in a 160℃ air drying oven for 12h desorption. After desorption, the activated carbon was subjected to static styrene gas adsorption test again. The adsorption test was repeated for 5 times, and the obtained styrene gas adsorption data is shown in Table 3.

[0101] Table 3 Adsorption test results of the activated carbon obtained in the examples and comparative examples

[0102]

[0103] Figure 4 The adsorption amount change curve of the activated carbon obtained in Example 1 for adsorbing styrene; from Figure 4 It can be seen that the first adsorption amount of the obtained activated carbon for styrene gas can reach 1150mg / g, and the reduction trend of the styrene adsorption amount gradually slows down in the adsorption-desorption cycle use process, and the fifth styrene adsorption amount is about 930mg / g, indicating that the obtained activated carbon material can be regenerated and used.

[0104] It can be seen from Table 3 that the first adsorption amount of the activated carbon obtained in Example 2 for styrene gas can reach 1203mg / g, and the fifth styrene adsorption amount is 992mg / g in the adsorption-desorption cycle use process, indicating that the obtained activated carbon material can be regenerated and used.

[0105] The first adsorption amount of styrene of the activated carbon obtained in Example 3 is 918 mg / g, and the fifth adsorption amount of styrene is 746 mg / g during the adsorption-desorption cycle, and the obtained activated carbon material can be regenerated and used.

[0106] The first adsorption amount of styrene of the activated carbon obtained in Example 4 is 1086 mg / g, and the fifth adsorption amount of styrene is 894 mg / g during the adsorption-desorption cycle, and the obtained activated carbon material can be regenerated and used.

[0107] The first adsorption amount of styrene of the activated carbon obtained in Example 5 is 971 mg / g, and the fifth adsorption amount of styrene is 785 mg / g during the adsorption-desorption cycle, and the obtained activated carbon material can be regenerated and used.

[0108] The first adsorption amount of styrene of the activated carbon obtained in Comparative Example 1 is 583 mg / g, and the fifth adsorption amount of styrene is 277 mg / g during the adsorption-desorption cycle.

[0109] It can be seen from Tables 2 and 3 that the adsorption amount of styrene of the activated carbon material is positively correlated with the sum of the pore volumes of the micropores with pore diameters of 0.5-0.85 nm and 1-2 nm of the corresponding activated carbon, that is, the larger the sum of the pore volumes, the larger the corresponding adsorption amount of styrene.

[0110] Although the above examples have made a detailed description of the present application, it is only a part of the embodiments of the present application, but not all the embodiments, and other embodiments can be obtained according to the present embodiments without creativity, and these embodiments all belong to the protection scope of the present application.

Claims

1. A method for preparing a hierarchically porous activated carbon using Bashan wood, characterized by, The method comprises the following steps: After pre-carbonization of the balsa wood, the balsa wood is mixed with a pore-forming agent and water to obtain a precursor material; the pore-forming agent comprises a potassium salt, ammonium bicarbonate and melamine; the potassium salt comprises at least one of potassium carbonate and potassium bicarbonate; The precursor material is carbonized to obtain the multi-level pore activated carbon.

2. The method of claim 1, wherein, The particle size of the balsa wood is not more than 80 mesh; the pre-carbonization temperature is 190-210℃, and the pre-carbonization time is 8-16h.

3. The method of claim 1, wherein, The mass ratio of the potassium salt, ammonium bicarbonate and melamine is 0.5-1.5:0.2-1:0.2-1.

4. The method according to claim 1 or 3, characterized in that, The mass ratio of the balsa wood and the pore-forming agent is 1:0.9-3.5; The mass ratio of the balsa wood and water is 1:4-10.

5. The method of claim 1, wherein, The standing is carried out in a sealed condition, and the standing time is 12-24h.

6. The method of claim 1, wherein, The carbonization comprises sequentially carrying out first carbonization and second carbonization; The first carbonization temperature is 70-90℃, the temperature rising rate for rising to the first carbonization temperature is 5-10℃ / min, and the holding time is 6-12h; The second carbonization temperature is 700-800℃, the temperature rising rate for rising to the second carbonization temperature is 1-4℃ / min, and the holding time is 2-4h.

7. The method according to claim 1 or 6, characterized in that, After the carbonization, the obtained carbonized material is further subjected to post-treatment, and the post-treatment comprises: cooling the carbonized material to below 60℃, water washing the cooled material to neutral, acid immersion of the water washed material, and drying the acid immersed material; The acid immersion solvent is a hydrochloric acid solution, the concentration of the hydrochloric acid solution is 1.5mol / L, and the acid immersion time is 6-36h.

8. The hierarchically porous activated carbon produced by the process of any one of claims 1 to 7, characterized by, The multi-level pore activated carbon comprises a macropore structure, a mesopore structure and a micropore structure; The micropore structure comprises a first micropore structure and a second micropore structure; The first micropore structure has a pore size of 0.5-0.85nm, and the second micropore structure has a pore size of 1-2nm, but 2nm is not included.

9. The hierarchical pore activated carbon of claim 8, wherein, The mesopore structure has a pore size of 2-10nm; The pore volume proportions of the first micropore structure, the second micropore structure and the mesopore structure to the total pore volume are 18-25%, 30-41% and 16-26%, respectively; The total pore volume of the hierarchical porous structure is 0.9-1.2 cm3 / g in the range of 0.5-190 nm. 3 / g; The specific surface area of the multi-level porous activated carbon is 1800-2300 m 2 / g.

10. The multi-level pore activated carbon of claim 8 or 9 is used for adsorbing styrene.

Images