CN115784227A - Method for preparing porous carbon from agriculture and forestry biomass - Google Patents
Method for preparing porous carbon from agriculture and forestry biomass Download PDFInfo
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- 239000002028 Biomass Substances 0.000 title claims abstract description 103
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 86
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 78
- 238000000034 method Methods 0.000 title claims abstract description 45
- 239000003513 alkali Substances 0.000 claims abstract description 66
- 238000005245 sintering Methods 0.000 claims abstract description 56
- 238000002791 soaking Methods 0.000 claims abstract description 42
- 238000001035 drying Methods 0.000 claims abstract description 35
- 229920005610 lignin Polymers 0.000 claims abstract description 32
- 239000002253 acid Substances 0.000 claims abstract description 31
- 238000004140 cleaning Methods 0.000 claims abstract description 31
- 239000002994 raw material Substances 0.000 claims abstract description 31
- 238000002156 mixing Methods 0.000 claims abstract description 12
- 239000000243 solution Substances 0.000 claims description 122
- KWYUFKZDYYNOTN-UHFFFAOYSA-M potassium hydroxide Substances [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 28
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- 244000105624 Arachis hypogaea Species 0.000 claims description 11
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- 235000018262 Arachis monticola Nutrition 0.000 claims description 11
- 235000020232 peanut Nutrition 0.000 claims description 11
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 9
- 239000010902 straw Substances 0.000 claims description 7
- 239000012670 alkaline solution Substances 0.000 claims description 5
- 241000609240 Ambelania acida Species 0.000 claims description 3
- 240000008042 Zea mays Species 0.000 claims description 3
- 235000005824 Zea mays ssp. parviglumis Nutrition 0.000 claims description 3
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- 238000005516 engineering process Methods 0.000 abstract description 5
- 239000000047 product Substances 0.000 description 37
- 230000000052 comparative effect Effects 0.000 description 18
- 239000011148 porous material Substances 0.000 description 18
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- 238000006243 chemical reaction Methods 0.000 description 9
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 8
- 239000013078 crystal Substances 0.000 description 8
- 230000007935 neutral effect Effects 0.000 description 7
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- XAEFZNCEHLXOMS-UHFFFAOYSA-M potassium benzoate Chemical compound [K+].[O-]C(=O)C1=CC=CC=C1 XAEFZNCEHLXOMS-UHFFFAOYSA-M 0.000 description 2
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- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/30—Active carbon
- C01B32/312—Preparation
- C01B32/318—Preparation characterised by the starting materials
- C01B32/324—Preparation characterised by the starting materials from waste materials, e.g. tyres or spent sulfite pulp liquor
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/30—Active carbon
- C01B32/312—Preparation
- C01B32/342—Preparation characterised by non-gaseous activating agents
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- Engineering & Computer Science (AREA)
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Abstract
The invention provides a method for preparing porous carbon by using agricultural and forestry biomass. The method for preparing the porous carbon by the agricultural and forestry biomass comprises the steps of mixing and soaking the agricultural and forestry biomass raw material with an alkali solution to obtain the alkali solution of lignin, drying the alkali solution of the lignin, sintering a product, soaking the product obtained in the previous step in an acid solution, and finally cleaning and drying the product obtained in the previous step to obtain the porous carbon. The method of the invention adopts agriculture and forestry biomass as raw material, makes full use of biomass resources, and belongs to green cleaning technology.
Description
Technical Field
The invention belongs to the technical field of biomass resource utilization, and particularly relates to a method for preparing porous carbon from agriculture and forestry biomass.
Background
The biomass porous carbon is a product obtained by taking organic matters (such as wood, manure or leaves and other biomass) existing in nature as a precursor and thermally cracking the organic matters under the conditions of limited oxygen supply and relatively low temperature. The material has wide, various and rich sources, and belongs to renewable resources in natural environment, so the material can meet the requirements of green, economic and chemical industry. Compared with other carbon products, the biomass-derived carbon material can be prepared from biomass in one step, and the final product can also contain other trace elements contained in a biomass precursor, so that more and more research and development are focused on the preparation and practical application of the biomass carbon material.
At present, methods for preparing porous carbon by biomass mainly comprise a template method, a pyrolysis activation method, a hydrothermal carbonization method, a molten salt carbonization method, a spray pyrolysis method, a chemical vapor deposition method and the like, and although a precursor of the porous carbon by biomass has the advantages of wide source, rich species, low preparation cost, capability of recycling, diversification, rich natural structure and the like, the specific surface area of the existing porous carbon by biomass is not ideal.
Therefore, there is still a need to develop a new method for preparing porous carbon from agricultural and forestry biomass.
Disclosure of Invention
The present invention is directed to solving at least one of the above problems in the prior art. Therefore, the invention provides a method for preparing porous carbon by using agricultural and forestry biomass, and the porous carbon prepared by the method has the specific surface area of more than 2600m 2 ·g -1 。
The invention also provides the porous carbon.
The first aspect of the invention provides a method for preparing porous carbon by using agricultural and forestry biomass, which comprises the following steps:
s1: mixing and soaking an agriculture and forestry biomass raw material and an alkali solution to obtain an alkali solution of lignin;
s2: drying the alkali solution of the lignin, and sintering the product;
s3: soaking the product obtained in the step S2 in an acid solution;
s4: and (5) cleaning and drying the product obtained in the step (S3) to obtain the porous carbon.
The invention relates to a technical scheme of a method for preparing porous carbon by using agricultural and forestry biomass, which at least has the following beneficial effects:
the method for preparing the porous carbon by the agricultural and forestry biomass comprises the steps of mixing and soaking an agricultural and forestry biomass raw material and an alkali solution to obtain an alkali solution of lignin, drying the alkali solution of the lignin, sintering a product, soaking the product obtained in the previous step in an acid solution, and finally cleaning and drying the product to obtain the porous carbon. The method of the invention adopts agriculture and forestry biomass as raw material, makes full use of biomass resources, and belongs to green cleaning technology.
The method for preparing the porous carbon by the agricultural and forestry biomass is simple to operate, can be realized without expensive equipment and complex process control, has wide raw material sources, and is suitable for large-scale popularization.
The biomass is composed of cellulose, hemicellulose and lignin, and the activation mechanism of biomass carbon after high-temperature carbonization is mainly as follows: firstly, biological carbon as a reducing agent and an activator alkali solution and generated salt generate oxidation-reduction reaction to etch a carbon skeleton to form a porous network structure, and then a chemical activation process is formed, and secondly, the generation of pores is further promoted by the diffusion process of water, carbon dioxide and the like generated in the reaction from the inside of the carbon skeleton, and a physical activation process is formed. Meanwhile, the generated metal is intercalated into the carbon crystal lattice, so that the defect and expansion of the carbon crystal lattice can be promoted, more pores are formed, and a porous structure is formed.
Agroforestry biomass refers to biomass from agriculture and forestry. Among various renewable energy sources, nuclear energy and large hydropower have potential ecological environment risks, regional resource restriction exists in wind energy, geothermal energy and the like, rapid development is limited and questioned, and biomass energy is approved by people due to the characteristics of universality, richness, renewability and the like. The uniqueness of biomass lies in that the biomass can store solar energy and also is a renewable carbon source which can be converted into conventional solid, liquid and gaseous fuels, and energy sources such as coal, petroleum, natural gas and the like are also converted from biomass energy. In general, biomass refers to various organisms produced by photosynthesis using the atmosphere, water, land, and the like, and all living organic substances capable of growing are generally referred to as biomass. The agricultural and forestry biomass has the characteristics of renewability, low pollution and wide distribution.
Biomass includes plants, animals and microorganisms. In a broad sense, biomass includes all plants, microorganisms, and animals that feed on plants, microorganisms, and waste from their production. Representative biomass materials include crops, crop wastes, wood wastes, and animal wastes. In a narrow sense, biomass mainly refers to lignocellulose (lignin for short) such as straws and trees except grains and fruits in the production process of agriculture and forestry, leftovers in the processing industry of agricultural products, wastes in agriculture and forestry, and livestock and poultry manure and wastes in the production process of animal husbandry.
According to some embodiments of the invention, in step S1, the agriculture and forestry biomass feedstock includes at least one of straw, cogongrass grass, corn cobs, peanut shells, and sugar cane bagasse.
According to some embodiments of the invention, the alkali solution comprises at least one of a NaOH solution and a KOH solution.
According to some embodiments of the invention, the alkali solution is a KOH solution.
The biomass is composed of cellulose, hemicellulose and lignin, and the activation mechanism of biomass carbon after high-temperature carbonization is mainly as follows: first, a redox reaction between biochar as a reducing agent and an activator KOH solution and generated potassium salt etches a carbon skeleton to form a porous network structure, which is called a chemical activation process, as shown in equations (1), (2) and (4). Next, the process of outward diffusion of water, carbon dioxide, and the like generated in the reaction from the inside of the carbon skeleton further promotes the generation of pores, which is called a physical activation process, as shown in reaction formulas (3), (5) to (8). Meanwhile, the generated metal K is intercalated into the carbon crystal lattice, so that the defect and expansion of the carbon crystal lattice can be promoted, more pores are formed, and a porous structure is formed, such as the reaction formulas (1), (2) and (4).
6KOH+2C→2K+3H 2 +2K 2 CO 3 (1)，
K 2 CO 3 +2C→2K+3CO(2)，
K 2 CO 3 →K 2 O+CO 2 (3)，
C+K 2 O→2K+CO(4)，
2KOH→K 2 O+H 2 O(5)，
CO+H 2 O→CO 2 +H2(6)，
C+H 2 O→CO+H 2 (7)，
CO 2 +C→2CO(8)。
According to some embodiments of the invention, the alkali solution has a mass concentration of 10% to 30%.
According to some embodiments of the invention, the alkali solution has a mass concentration of 20% to 30%.
According to some embodiments of the invention, the alkali solution has a mass concentration of 20%.
According to some embodiments of the invention, in step S1, 15g to 25g of the agricultural and forestry biomass raw material is added per liter of the alkali solution.
According to some embodiments of the invention, in step S1, 20g to 25g of the agricultural and forestry biomass raw material is added per liter of the alkali solution.
According to some embodiments of the invention, in step S1, 20g of the agroforestry biomass feedstock is added per liter of the alkali solution.
According to some embodiments of the invention, in step S1, the soaking time is 1h to 3h.
According to some embodiments of the invention, the soaking time in step S1 is 2 to 3 hours.
According to some embodiments of the invention, in step S1, the soaking time is 2h.
According to some embodiments of the invention, the temperature of the soaking in step S1 is room temperature.
According to some embodiments of the invention, in the step S2, the temperature of the drying is 30 ℃ to 50 ℃.
According to some embodiments of the invention, the temperature of the drying in step S2 is 40 ℃ to 50 ℃.
According to some embodiments of the invention, the temperature of the drying is 40 ℃ in step S2.
According to some embodiments of the invention, the sintering temperature in step S2 is 600 ℃ to 900 ℃.
According to some embodiments of the invention, the sintering temperature in step S2 is 700 ℃ to 900 ℃.
According to some embodiments of the invention, the sintering temperature in step S2 is 800 to 900 ℃.
According to some embodiments of the invention, in step S2, the sintering time is 1.5h to 2.5h.
According to some embodiments of the invention, in step S2, the sintering time is 2h to 2.5h.
According to some embodiments of the invention, in step S2, the sintering time is 2h.
According to some embodiments of the invention, in step S2, the sintering is performed under nitrogen.
According to some embodiments of the invention, in step S2, the temperature increase rate of the sintering is 5 ℃/min to 15 ℃/min.
According to some embodiments of the invention, in step S2, the temperature increase rate of the sintering is 10 ℃/min to 15 ℃/min.
According to some embodiments of the invention, the concentration of the acid solution in step S3 is 8wt% to 12wt%.
According to some embodiments of the invention, the acid solution has a concentration of 10wt% in step S3.
According to some embodiments of the invention, in step S3, the acid solution is a hydrochloric acid solution.
According to some embodiments of the invention, in step S4, the cleaning may be performed with hot water until the cleaning solution is neutral.
In a second aspect of the invention, there is provided a porous carbon prepared by the method.
The invention relates to one of the technical schemes of porous carbon, which at least has the following beneficial effects:
when the porous carbon is prepared, firstly, agriculture and forestry biomass raw materials are mixed with an alkaline solution and then soaked to obtain the alkaline solution of lignin, then, after the alkaline solution of lignin is dried, products are sintered, then, the products obtained in the previous step are soaked in an acid solution, and finally, the products obtained in the previous step are cleaned and dried to obtain the porous carbon. The method of the invention adopts agriculture and forestry biomass as raw material, makes full use of biomass resources, and belongs to green cleaning technology. The specific surface area of the finally prepared porous carbon is superior to that of the existing biomass porous carbon.
According to some embodiments of the invention, the porous carbon has a specific surface area greater than 2600m 2 ·g -1 。
Drawings
Fig. 1 is a microscopic topography of the porous carbon prepared in example 2.
Fig. 2 is a microscopic morphology view of the porous carbon prepared in comparative example 1.
Detailed Description
The following are specific examples of the present invention, and the technical solutions of the present invention will be further described with reference to the examples, but the present invention is not limited to the examples.
In some embodiments of the invention, the invention provides a method for preparing porous carbon from agricultural and forestry biomass, comprising the steps of:
s1: mixing and soaking an agriculture and forestry biomass raw material and an alkali solution to obtain an alkali solution of lignin;
s2: drying the alkali solution of lignin, and sintering the product;
s3: soaking the product obtained in the step S2 in an acid solution;
s4: and (5) cleaning and drying the product obtained in the step (S3) to obtain the porous carbon.
The method for preparing the porous carbon by the agricultural and forestry biomass comprises the steps of mixing the agricultural and forestry biomass raw material with an alkali solution, soaking to obtain the alkali solution of lignin, drying the alkali solution of lignin, sintering the product, soaking the product obtained in the previous step in an acid solution, and finally cleaning and drying the product to obtain the porous carbon. The method of the invention adopts agriculture and forestry biomass as raw material, makes full use of biomass resources, and belongs to green cleaning technology.
The method for preparing the porous carbon by the agricultural and forestry biomass is simple to operate, can be realized without expensive equipment and complex process control, has wide raw material sources, and is suitable for large-scale popularization.
It should be noted that, as long as the biomass is composed of cellulose, hemicellulose and lignin, the carbon activation mechanism of the biomass after high-temperature carbonization mainly is as follows: firstly, biological carbon as a reducing agent and an activator alkali solution and generated salt generate oxidation-reduction reaction to etch a carbon skeleton to form a porous network structure, so that a chemical activation process is formed, and secondly, the process that water, carbon dioxide and the like generated in the reaction diffuse outwards from the interior of the carbon skeleton further promotes the generation of pores, so that a physical activation process is formed. Meanwhile, the generated metal is intercalated into the carbon crystal lattice, so that the defect and expansion of the carbon crystal lattice can be promoted, more pores are formed, and a porous structure is formed.
Further, agricultural and forestry biomass refers to biomass from agriculture and forestry. Among various renewable energy sources, nuclear energy and large hydropower have potential ecological environment risks, regional resource restriction exists in wind energy, geothermal energy and the like, rapid development is limited and questioned, and biomass energy is approved by people due to the characteristics of universality, richness, renewability and the like. The uniqueness of biomass lies in that the biomass can store solar energy and also can be converted into conventional solid, liquid and gaseous fuels by using a renewable carbon source, and energy sources such as coal, petroleum, natural gas and the like are substantially converted from biomass energy. In general, biomass refers to various organisms produced by photosynthesis using the atmosphere, water, land, and the like, and all living organic substances capable of growing are generally referred to as biomass. The agriculture and forestry biomass has the characteristics of renewability, low pollution and wide distribution.
In particular, biomass includes plants, animals and microorganisms. In a broad sense, biomass includes all plants, microorganisms, and animals that feed on plants, microorganisms, and waste from their production. Representative biomass materials include crops, crop wastes, wood wastes, and animal wastes. In a narrow sense, biomass mainly refers to lignocellulose (lignin for short) such as straws and trees except grains and fruits in the production process of agriculture and forestry, leftovers in the processing industry of agricultural products, wastes of agriculture and forestry, and feces and wastes of livestock and poultry in the production process of animal husbandry.
In some embodiments of the invention, in step S1, the agricultural and forestry biomass feedstock includes at least one of straw, cogongrass, corn cobs, peanut hulls, and bagasse.
In some embodiments of the invention, the alkali solution comprises at least one of a NaOH solution and a KOH solution.
In some embodiments of the invention, the base solution is a KOH solution.
The biomass is composed of cellulose, hemicellulose and lignin, and the activation mechanism of biomass carbon after high-temperature carbonization is mainly as follows: first, a redox reaction between biochar as a reducing agent and an activator KOH solution and a generated potassium salt etches a carbon skeleton to form a porous network structure, which is called a chemical activation process, such as reaction formulas (1), (2), and (4). Next, the process of outward diffusion of water, carbon dioxide, and the like generated in the reaction from the inside of the carbon skeleton further promotes the generation of pores, which is called a physical activation process, as shown in reaction formulas (3), (5) to (8). Meanwhile, the generated metal K is intercalated into the carbon crystal lattice, so that the defect and expansion of the carbon crystal lattice can be promoted, more pores are formed, and a porous structure is formed, such as the reaction formulas (1), (2) and (4).
6KOH+2C→2K+3H 2 +2K 2 CO 3 (1)，
K 2 CO 3 +2C→2K+3CO(2)，
K 2 CO 3 →K 2 O+CO 2 (3)，
C+K 2 O→2K+CO(4)，
2KOH→K 2 O+H 2 O(5)，
CO+H 2 O→CO 2 +H2(6)，
C+H 2 O→CO+H 2 (7)，
CO 2 +C→2CO(8)。
In some embodiments of the invention, the mass concentration of the alkali solution may be 10% to 30%.
In some embodiments of the present invention, the mass concentration of the alkali solution may also be 20% to 30%.
In some embodiments of the invention, the alkali solution has a mass concentration of about 20%.
In some embodiments of the invention, in step S1:
15-25 g of agriculture and forestry biomass raw materials are added into each liter of alkali solution.
20-25 g of agriculture and forestry biomass raw materials are added into each liter of alkali solution.
20g of agriculture and forestry biomass raw materials are added into each liter of alkali solution.
The soaking time can be 1-3 h.
The soaking time can be 2-3 h.
The soaking time is about 2 hours.
The temperature of soaking was room temperature.
In some embodiments of the invention, in step S2:
the drying temperature can be 30-50 ℃.
The drying temperature can also be 40-50 ℃.
The drying temperature is about 40 ℃.
The sintering temperature can be 600-900 ℃.
The sintering temperature can also be 700-900 ℃.
The sintering temperature can also be 800-900 ℃.
The sintering time can be 1.5-2.5 h.
The sintering time can also be 2-2.5 h.
The sintering time is about 2h.
Sintering was performed under nitrogen.
The temperature rise rate of sintering is 5 ℃/min to 15 ℃/min.
The temperature rise rate of sintering can also be 10-15 ℃/min.
In some embodiments of the invention, in step S3:
the concentration of the acid solution may be 8wt% to 12wt%.
The concentration of the acid solution is about 10wt%.
In some embodiments of the invention, in step S3:
the acid solution is hydrochloric acid solution.
In some embodiments of the invention, in step S4:
the cleaning can be carried out by using hot water until the cleaning solution is neutral.
In other embodiments of the present invention, the present invention also provides a porous carbon prepared by the method of the present invention.
The porous carbon is prepared by mixing and soaking the agricultural and forestry biomass raw materials and an alkali solution to obtain an alkali solution of lignin, drying the alkali solution of the lignin, sintering a product, soaking the product obtained in the previous step in an acid solution, and finally cleaning and drying the product to obtain the porous carbon. The method of the invention adopts agriculture and forestry biomass as raw material, makes full use of biomass resources, and belongs to green cleaning technology. The specific surface area of the finally prepared porous carbon is superior to that of the existing biomass porous carbon.
In some embodiments of the invention, the specific surface area of the porous carbon is greater than 2600m 2 ·g -1 。
The technical solution of the present invention will be better understood by referring to the following specific examples.
In the following examples and comparative examples, the solute of the alkaline solution used was potassium hydroxide, analytically pure. The acid solution was 36.5% hydrochloric acid solution. The equipment used for sintering is a muffle furnace.
Example 1
This example uses agriculture and forestry living beings to prepare a porous carbon, includes the following step:
s1: mixing and soaking an agriculture and forestry biomass raw material and an alkali solution to obtain an alkali solution of lignin;
s2: drying the alkali solution of the lignin, and sintering the product;
s3: soaking the product obtained in the step S2 in an acid solution;
s4: and (5) cleaning and drying the product obtained in the step (S3) to obtain the porous carbon.
The mass concentration of the alkali solution is 20%.
In the step S1, the agriculture and forestry biomass raw material is peanut shells, and 20g of peanut shells are added into each liter of alkali solution.
In the step S1, the soaking time is 2 hours, and the soaking temperature is room temperature.
In step S2, the drying temperature is 40 ℃.
The sintering temperature was 600 ℃.
The sintering time is 2h, and the sintering is carried out under the nitrogen condition.
The heating rate of sintering is 10 ℃/min.
In step S3, the concentration of the acid solution is 10wt%, and the acid solution is hydrochloric acid solution.
In step S4, the cleaning is carried out by using hot water until the cleaning solution is neutral.
Example 2
In this embodiment, the porous carbon is prepared from agricultural and forestry biomass, and the method includes the following steps:
s1: mixing and soaking an agriculture and forestry biomass raw material and an alkali solution to obtain an alkali solution of lignin;
s2: drying the alkali solution of lignin, and sintering the product;
s3: soaking the product obtained in the step S2 in an acid solution;
s4: and (4) cleaning and drying the product obtained in the step (S3) to obtain the porous carbon.
The mass concentration of the alkali solution is 30 percent.
In the step S1, the agricultural and forestry biomass raw material is peanut shells, and 20g of peanut shells are added into each liter of alkali solution.
In the step S1, the soaking time is 2 hours, and the soaking temperature is room temperature.
In step S2, the drying temperature is 40 ℃.
The sintering temperature was 700 ℃.
The sintering time is 2h, and the sintering is carried out under the nitrogen condition.
The heating rate of sintering is 10 ℃/min.
In step S3, the concentration of the acid solution is 10wt%, and the acid solution is hydrochloric acid solution.
In step S4, the cleaning is carried out by using hot water until the cleaning solution is neutral.
Comparative example 1
The porous carbon prepared by the agriculture and forestry biomass used in the comparative example comprises the following steps:
s1: mixing and soaking an agriculture and forestry biomass raw material and an alkali solution to obtain an alkali solution of lignin;
s2: drying the alkali solution of the lignin, and sintering the product;
s3: soaking the product obtained in the step S2 in an acid solution;
s4: and (5) cleaning and drying the product obtained in the step (S3) to obtain the porous carbon.
The mass concentration of the alkali solution is 40%.
In the step S1, the agriculture and forestry biomass raw material is peanut shells, and 20g of peanut shells are added into each liter of alkali solution.
In the step S1, the soaking time is 2 hours, and the soaking temperature is room temperature.
In step S2, the drying temperature is 40 ℃.
The sintering temperature was 900 ℃.
The sintering time is 2h, and the sintering is carried out under the nitrogen condition.
The heating rate of sintering is 10 ℃/min.
In step S3, the concentration of the acid solution is 10wt%, and the acid solution is hydrochloric acid solution.
In step S4, the cleaning is carried out by using hot water until the cleaning solution is neutral.
Comparative example 2
The porous carbon is prepared from agricultural and forestry biomass in the comparative example, and the method comprises the following steps:
s1: mixing and soaking an agriculture and forestry biomass raw material and an alkali solution to obtain an alkali solution of lignin;
s2: drying the alkali solution of the lignin, and sintering the product;
s3: soaking the product obtained in the step S2 in an acid solution;
s4: and (4) cleaning and drying the product obtained in the step (S3) to obtain the porous carbon.
The mass concentration of the alkali solution is 20%.
In the step S1, the agricultural and forestry biomass raw material is peanut shells, and 20g of cogongrass peanut shells are added into each liter of alkali solution.
In the step S1, the soaking time is 2 hours, and the soaking temperature is room temperature.
In step S2, the drying temperature is 40 ℃.
The sintering temperature was 950 ℃.
The sintering time is 2h, and the sintering is carried out under the nitrogen condition.
The heating rate of sintering is 10 ℃/min.
In step S3, the concentration of the acid solution is 10wt%, and the acid solution is hydrochloric acid solution.
In step S4, the cleaning is carried out by using hot water until the cleaning solution is neutral.
Comparative example 3
The porous carbon is prepared from agricultural and forestry biomass in the comparative example, and the method comprises the following steps:
s1: mixing and soaking an agriculture and forestry biomass raw material and an alkali solution to obtain an alkali solution of lignin;
s2: drying the alkali solution of the lignin, and sintering the product;
s3: soaking the product obtained in the step S2 in an acid solution;
s4: and (5) cleaning and drying the product obtained in the step (S3) to obtain the porous carbon.
The mass concentration of the alkali solution is 20%.
In the step S1, the agricultural and forestry biomass raw material is straw, and 20g of straw is added into each liter of alkali solution.
In the step S1, the soaking time is 2 hours, and the soaking temperature is room temperature.
In step S2, the drying temperature is 40 ℃.
The sintering temperature was 900 ℃.
The sintering time is 2h, and the sintering is carried out under the nitrogen condition.
The heating rate of sintering is 10 ℃/min.
In step S3, the concentration of the acid solution is 10wt%, and the acid solution is hydrochloric acid solution.
In step S4, the cleaning is carried out by using hot water until the cleaning solution is neutral.
Test example
The porous carbons prepared in example 2 and comparative example 1 were observed by a scanning microscope as shown in fig. 1 and fig. 2, respectively.
As can be seen by comparing fig. 1 and fig. 2, the porous carbons prepared in example 2 and comparative example 1 have more pore structures, however, the porous carbon prepared in comparative example 1 has less dense pores than the porous carbon prepared in example 2, and it is presumed that an excessively high sintering temperature causes collapse of part of the pore structures.
In addition, specific surface areas of the porous carbons prepared in examples 1, 2 and comparative examples 1 to 3 were also tested, and the specific surface area of the porous carbon prepared in example 1 was 2610m 2 ·g -1 . The specific surface area of the porous carbon prepared in example 2 was 2638m 2 ·g -1 . The specific surface area of the porous carbon prepared in comparative example 1 was 2450m 2 ·g -1 . The specific surface area of the porous carbon prepared in comparative example 2 was 2280m 2 ·g -1 . Specific surface area of porous carbon prepared in comparative example 3Is 2580m 2 ·g -1 。
In examples 1 and 2, the mass concentration of the alkali solution was 20% and 30%, respectively, and in comparative example 1, the mass concentration of the alkali solution was 40%. The specific surface area of the porous carbons prepared in examples 1 and 2 and comparative example 1 was increased and then decreased, because the pore formation process was divided into three stages of pore formation, pore enlargement and pore collapse in the porous carbon preparation process. When the KOH amount is appropriate, appropriate CO can be generated 2 And H 2 O, so that a part of the pores becomes large while new pores are formed, so that the specific surface area is sharply increased. However, when KOH is excessive, a portion of the macropores may collapse due to the transition of etching, resulting in a reduction in specific surface area.
In comparative example 2, the sintering temperature was too high, which negatively affected the formation of pores, and thus, the specific surface area was reduced.
The present invention has been described in detail with reference to the embodiments, but the present invention is not limited to the embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.
Claims (10)
1. The method for preparing the porous carbon by the agricultural and forestry biomass is characterized by comprising the following steps:
s1: mixing and soaking an agriculture and forestry biomass raw material and an alkali solution to obtain an alkali solution of lignin;
s2: drying the alkali solution of the lignin, and sintering the product;
s3: soaking the product obtained in the step S2 in an acid solution;
s4: and (5) cleaning and drying the product obtained in the step (S3) to obtain the porous carbon.
2. The method of claim 1, wherein the agricultural biomass feedstock comprises at least one of straw, cogongrass, corn cobs, peanut hulls, and bagasse.
3. The method of claim 1, wherein the base solution comprises at least one of a NaOH solution and a KOH solution.
4. The method according to claim 3, wherein the mass concentration of the alkali solution is 10-30%.
5. The method according to any one of claims 1 to 4, wherein in step S1, 15g to 25g of the agricultural or forestry biomass raw material is added per liter of the alkaline solution.
6. The method according to any one of claims 1 to 4, wherein the sintering temperature in step S2 is 600 ℃ to 900 ℃.
7. The method according to any one of claims 1 to 4, wherein in step S2, the sintering time is 1.5h to 2.5h.
8. The method according to any one of claims 1 to 4, wherein the concentration of the acid solution in step S3 is 8 to 12 wt.%.
9. The method according to any one of claims 1 to 4, wherein the temperature increase rate of the sintering is 5 ℃/min to 15 ℃/min.
10. The method according to any one of claims 1 to 4, characterized in that the specific surface area of the porous carbon is greater than 2600m 2 ·g -1 。
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