CN114275781B - Method for preparing porous carbon material by regenerating alkali activated biomass raw material - Google Patents
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- 239000002028 Biomass Substances 0.000 title claims abstract description 55
- 239000003575 carbonaceous material Substances 0.000 title claims abstract description 53
- 238000000034 method Methods 0.000 title claims abstract description 42
- 239000002994 raw material Substances 0.000 title claims abstract description 30
- 239000003513 alkali Substances 0.000 title claims abstract description 18
- 230000001172 regenerating effect Effects 0.000 title claims abstract description 8
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 64
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 62
- 239000000706 filtrate Substances 0.000 claims abstract description 38
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims abstract description 33
- 238000000197 pyrolysis Methods 0.000 claims abstract description 32
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 21
- 230000004913 activation Effects 0.000 claims abstract description 19
- 239000012190 activator Substances 0.000 claims abstract description 16
- 238000001914 filtration Methods 0.000 claims abstract description 16
- 230000003213 activating effect Effects 0.000 claims abstract description 13
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- 239000000047 product Substances 0.000 claims abstract description 10
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- 238000010521 absorption reaction Methods 0.000 claims abstract description 5
- 102000004169 proteins and genes Human genes 0.000 claims abstract description 5
- 108090000623 proteins and genes Proteins 0.000 claims abstract description 5
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 51
- 239000000463 material Substances 0.000 claims description 31
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 28
- 238000006243 chemical reaction Methods 0.000 claims description 21
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 16
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims description 15
- 239000001569 carbon dioxide Substances 0.000 claims description 14
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 14
- 229910001415 sodium ion Inorganic materials 0.000 claims description 10
- 229910001414 potassium ion Inorganic materials 0.000 claims description 9
- 239000011343 solid material Substances 0.000 claims description 8
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- 238000010438 heat treatment Methods 0.000 claims description 4
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- 235000011149 sulphuric acid Nutrition 0.000 claims 1
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 229940090663 penicillin v potassium Drugs 0.000 description 6
- HCTVWSOKIJULET-LQDWTQKMSA-M phenoxymethylpenicillin potassium Chemical group [K+].N([C@H]1[C@H]2SC([C@@H](N2C1=O)C([O-])=O)(C)C)C(=O)COC1=CC=CC=C1 HCTVWSOKIJULET-LQDWTQKMSA-M 0.000 description 6
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Abstract
The application discloses a method for preparing a porous carbon material by regenerating a strong alkali activated biomass raw material. Adding organic biomass raw materials rich in proteins such as sludge, kitchen waste, biological fermentation residues, algae and the like into carbon material preparation equipment, etching biomass by taking strong alkali as an activating agent, and introducing CO 2 And (3) performing post-filtration, performing pyrolysis pore-forming on filter residues, adding dilute sulfuric acid or oxalic acid or a mixture of the dilute sulfuric acid and the oxalic acid into raw carbon 1 generated by pyrolysis, filtering, washing the filter residues which are raw carbon 2 to neutrality, and drying to obtain a porous carbon material finished product. CaO or Ca (OH) was added to filtrate 1 and filtrate 2 2 Or the mixture of the two is filtered, the filtrate is mixed and thickened, and a small amount of fresh activator is added to perform a new round of biomass activation. The filtered substances 1 and 2 are configured into suspension for pyrolysis waste gas absorption and purification. The application has the advantages of low cost, good pore-forming effect, less waste production, etc.
Description
Technical Field
The application relates to a method for preparing a porous carbon material by biomass, in particular to a method for preparing a porous carbon material by regenerating a strong alkali activated biomass raw material; in particular to a method for preparing a porous carbon material by activating sludge, kitchen waste, biological fermentation residues, algae and the like by using strong alkali, which belongs to the sub-field of recycling organic solid wastes in the technical field of environmental protection.
Background
With the development of society and urbanization in China, the demand of the porous carbon material is continuously increasing, and the market demand of the porous carbon material in China is estimated to reach about 93 ten thousand tons in 2025. As main raw materials for manufacturing porous carbon materials, coconut shells, fruit shells, wood and coal, a situation of providing shortage has now occurred, and there is an urgent need to solve alternative raw materials.
Because of the organic biomass such as sludge, kitchen waste, biological fermentation residues, algae and the like which are rich in proteins, the organic carbon content is higher, the porous carbon material has a certain similarity with the traditional porous carbon material preparation, and the porous carbon material prepared by taking the sludge, the fungus residues and the like as raw materials is widely paid attention as a novel recycling disposal mode. The porous carbon material is prepared by using organic solid wastes such as sludge, kitchen waste, biological fermentation residues, algae and the like to replace coal, wood and shells, so that the raw material cost is reduced, a feasible recycling treatment mode is provided for the high-protein organic solid wastes, and the raw material source of the porous carbon material is expanded.
In the research of the existing activation mode, chemical activation proves that the porous carbon material with high specific surface area is easier to prepare than physical activation, but the problems of high cost, secondary pollution and the like caused by chemical activation are still to be researched and solved by students. Existing physical treatment methods mainly use pyrolysis to form holes, but direct pyrolysis can cause structural collapse, and effective holes are difficult to form.
Disclosure of Invention
An object of the present application is to provide a porous carbon material prepared by activating biomass using strong alkali, which has a larger porosity and a relatively uniform pore size.
Another object of the present application is to provide a porous carbon material prepared by activating biomass using strong alkali, which has excellent hydrothermal stability.
Still another object of the present application is that an activator used in the preparation of porous carbon materials from biomass activated by strong alkali can be efficiently recycled, saving energy and reducing cost.
The application relates to a method for preparing a porous carbon material by regenerating a strong alkali activated biomass raw material, which comprises the following steps:
(1) Carrying out activation treatment on the suspension of the biomass raw material to obtain a material 1, wherein an activating agent comprises alkali metal hydroxide;
(2) Introducing carbon dioxide gas into the material 1 to obtain a material 2, filtering the material 2, and separating filtrate 1 and a solid material 3;
(3) And carrying out pyrolysis reaction and subsequent acid washing, filtering and drying treatment on the solid material 3 to obtain filtrate 2 and a porous carbon material finished product.
In the application, after the biomass raw material is subjected to alkali metal hydroxide activation treatment, organic components are corroded by strong alkali, and a pore structure is etched in biomass. And then introducing carbon dioxide gas, and reacting the carbon dioxide with alkali metal ions to form alkali metal carbonate, wherein the alkali metal carbonate is decomposed into alkali metal oxide, carbon monoxide, carbon dioxide, water vapor and the like in the pyrolysis process. The oxide of alkali metal and biomass carbon undergo oxidation-reduction reaction to generate carbon monoxide, and the biomass is activated in a chemical activation mode; the decomposition to produce carbon dioxide and water vapor further develops the pore structure of the porous carbon in a physical activation mode. When the alkali metal is K, na, the carbonate K thereof 2 CO 3 、Na 2 CO 3 The oxide formed by decomposition is K 2 O、Na 2 O，K 2 O、Na 2 The K, na ions generated by the reduction of O by carbon can be inserted into a carbon lattice, so that the carbon lattice expands, and a carbon lattice structure is formed after water washing.
The porous carbon material prepared after pyrolysis has high porosity, not only has pores on the surface, but also forms pores in the deep layer structure of the porous carbon material, thereby forming a three-dimensional honeycomb, sheet and foam pore structure. To achieve the final object of the present application, ca (OH) is added to the filtrate separated in the above steps (2) and (3) 2 And/or CaO, obtaining a precipitate after reaction, and filtering to obtain a filtrate serving as an activator solution.
In the method provided by the application, ca (OH) is further added into the waste liquid in the preparation of the porous carbon material 2 And/or CaO can be recycled to the method for preparing the porous carbon material by biomass. Not only purifying the waste liquid generated in the process of preparing the porous carbon material from biomass, but also further changing the waste liquid into a usable activating agent.
The porous carbon material prepared by the method can be used as an adsorption material, an electrode material, a carrier material, a biological fermentation compost substrate and the like, and has wide application range and huge application prospect.
Drawings
Fig. 1 is a schematic diagram of a method and a system for preparing a porous carbon material by regenerating a strong alkali activated biomass raw material according to the present application.
FIG. 2 is a scanning electron microscope image of porous carbon prepared in example 1 of the present application;
FIG. 3 is a scanning electron microscope image of the porous carbon prepared in comparative example 2.
Detailed Description
The method of preparing porous carbon materials from the regenerated strong base activated biomass feedstock of the present application is described in further detail below. And do not limit the scope of the application, which is defined by the claims. Certain disclosed specific details provide a thorough understanding of the various disclosed embodiments. However, one skilled in the relevant art will recognize that embodiments can be practiced without one or more of the specific details, with other materials, etc.
In the description and in the claims, the terms "comprising," including, "and" containing "are to be construed as open-ended, meaning" including, but not limited to, unless the context requires otherwise.
Reference in the specification to "an embodiment," "one embodiment," "another embodiment," or "certain embodiments," etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, it is not necessary for an "embodiment," "one embodiment," "another embodiment," or "certain embodiments" to refer to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. The various features disclosed in the specification may be replaced by alternative features serving the same, equivalent or similar purpose. Thus, unless expressly stated otherwise, the disclosed features are merely general examples of equivalent or similar features.
The experimental procedures, which do not address the specific conditions in the examples below, are generally carried out under conventional conditions or under conditions recommended by the manufacturer. All percentages, ratios, proportions, or parts are by weight unless otherwise indicated.
Definition:
"biomass feedstock" includes, but is not limited to, protein-rich organic biomass feedstock such as sludge, kitchen waste, biological fermentation residues, or algae.
Biomass in a broad sense includes all plants, microorganisms, animals fed by plants, microorganisms and waste products produced thereby. The biomass feedstock is herein the part of biomass that is described but not limited to such high protein content biomass.
Preferably, the biomass raw material in the application is organic biomass with the protein content more than or equal to 20%.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, any methods and materials similar or equivalent to those described herein can be used in the methods of the present application. The preferred methods and materials described herein are presented for illustrative purposes only.
The application relates to a method for preparing a porous carbon material by regenerating a strong alkali activated biomass raw material, which comprises the following steps:
(1) Carrying out activation treatment on the suspension of the biomass raw material to obtain a material 1, wherein an activating agent comprises alkali metal hydroxide;
(2) Introducing carbon dioxide gas into the material 1 to obtain a material 2, filtering the material 1, and separating filtrate 1 and a solid material 3;
(3) And carrying out pyrolysis reaction and subsequent treatment on the solid material 3 to obtain a porous carbon material finished product.
The alkali metal hydroxide includes, but is not limited to, sodium hydroxide, potassium hydroxide. After the biomass raw material is subjected to alkali metal hydroxide activation treatment, organic components are corroded by strong alkali, and a pore structure is etched in the biomass. In the pyrolysis process, when the alkali metal is K, na, the carbonate K thereof 2 CO 3 、Na 2 CO 3 The oxide formed by decomposition is K 2 O、Na 2 O，K 2 O、Na 2 K, na, which is formed by reduction of O by carbon, is inserted into the carbon lattice in an ionic form, resulting in swelling of the carbon latticeExpanding and washing with water to form a carbon grid structure.
In certain embodiments, in step (1), the mass ratio of biomass feedstock to sodium hydroxide or potassium hydroxide is from 1:0.1 to 1:2.
The mass ratio of the biomass raw material to the alkali metal hydroxide herein refers to the mass ratio of the dry basis mass of the biomass raw material to the mass of the alkali metal hydroxide.
After the alkali metal hydroxide is added, the pH of the biomass raw material suspension is more than or equal to 13. The biomass feedstock is treated under such conditions.
In certain embodiments, in step (2), carbon dioxide gas is introduced in an amount of 0.002 to 0.06mol CO per gram of biomass 2 The pH value of the material 1 is less than or equal to 11.
Carbon dioxide reacts with alkali metal ions to form alkali metal carbonates, which decompose to alkali metal oxides, carbon monoxide, carbon dioxide, water vapor, etc. during pyrolysis. The oxide of alkali metal and biomass carbon undergo oxidation-reduction reaction to generate carbon monoxide, and the biomass is activated in a chemical activation mode; the decomposition to produce carbon dioxide and water vapor further develops the pore structure of the porous carbon in a physical activation mode.
In certain embodiments, the alkali metal hydroxide is potassium hydroxide. The porous carbon obtained by the potassium hydroxide treatment has a larger pore volume and more micropores than those obtained by the alkali metal hydroxide treatment in the other two cases.
In certain embodiments, the conditions of the pyrolysis reaction in step (3) are: the pyrolysis temperature is 300-800 ℃, and the temperature is controlled by adopting temperature programming, and the temperature rising rate is 5-20 ℃/min.
The high temperature during pyrolysis can enhance the carbonization degree of the biomass-based porous carbon material, degrade and release organic matters in the biomass-based porous carbon material, and promote the formation of the porous structure of the porous carbon material. Especially, the proportion of micropores in the porous carbon is higher within the temperature rising rate of 5-20 ℃/min.
The solid material 3 is pyrolyzed to obtain carbon 1, and the carbon 1 is filtered after being treated by dilute sulfuric acid and/or oxalic acid to obtain filtrate 2 and carbon 2; the raw carbon 2 is washed to be neutral, and then dried to obtain a finished product of the porous carbon material.
In certain embodiments, the conditions for drying raw carbon 2: drying in an oven at 80-105 ℃ to constant weight. The purpose of the drying is to sufficiently evaporate the moisture in the porous carbon material.
The dilute sulfuric acid and the oxalic acid can be selected or mixed for use, and the molar ratio of the dilute sulfuric acid and/or the oxalic acid to potassium ions and/or sodium ions in the original carbon 1 is 1:2-1.1:2.
On the other hand, ca (OH) was added to filtrate 1 and/or filtrate 2 2 And/or CaO, obtaining a precipitate after reaction, and filtering to obtain a filtrate serving as an activator solution.
Ca(OH) 2 And/or the addition amount of CaO depends on the amount of alkali metal ions, ca (OH), in the filtrate 2 And/or the molar ratio of CaO to potassium ions and/or sodium ions in the filtrate 1 is 1:2-1.2:2. Ca (OH) 2 And/or the mol ratio of CaO to potassium ions and/or sodium ions in the filtrate 2 is 1:2-1.3:2 until the pH value of the solution is more than or equal to 13.
The activator recovered from the filtrate is mixed together and then blended with fresh activator to a concentration suitable for preparing porous carbon material, and the mixture is recycled.
In certain embodiments, filtrate 1 and/or filtrate 2 is added with Ca (OH) 2 And/or the precipitate obtained by CaO reaction is prepared into suspension which can be used for absorbing the pyrolysis gas in the step (3).
In the method for preparing the porous carbon material by using the biomass, the porous carbon material has good performance, and the generated byproducts can be reused in the reaction, for example, the solution after the reaction of the filtrate can be recovered to obtain the alkali hydroxide of the activating agent, and the generated precipitate can be used for absorbing and purifying pyrolysis gas. The production cost is greatly reduced, and the pollution to the environment is greatly reduced.
In the method for preparing the porous carbon material by the substance, CO is introduced into the material 1 in the step (2) 2 The reactions that occur are mainly (if the activator is potassium hydroxide):
CO 2 +H 2 O→H 2 CO 3 ，KOH+H 2 CO 3 →K 2 CO 3 +H 2 O。
in the step (3), the material 3 is pyrolyzed to obtain raw carbon 1 and pyrolysis gas, and the reaction mainly comprises: k (K) 2 CO 3 →K 2 O+CO 2 ↑，K 2 CO 3 +2C→2K+3CO，C+K 2 O2 K+CO, and K is reversely generated at a lower pyrolysis temperature 2 CO 3 ，CO 2 +K 2 O→K 2 CO 3 。
In the technical scheme, dilute sulfuric acid and/or oxalic acid is added into the raw carbon 1, and the reaction mainly comprises the following steps:
K 2 O+H 2 SO 4 →K 2 SO 4 +H 2 O，K 2 O+H 2 C 2 O 4 →K 2 C 2 O 4 +H 2 O
in the technical proposal, ca (OH) is added after the filtrate 1 is filtered 2 And CaO, the reactions taking place are mainly: k (K) 2 CO 3 +Ca(OH) 2 →KOH+CaCO 3 ↓
In the technical proposal, ca (OH) is added after the filtrate 2 is filtered 2 And CaO, the reactions taking place are mainly:
K 2 SO 4 +Ca(OH) 2 →KOH+CaSO 4 ↓，K 2 SO 4 +H 2 C 2 O 4 →KOH+CaC 2 O 4 ↓
in the above technical scheme, the filtered substance 1 and the filtered substance 2 are configured into suspension, and are used for pyrolysis waste gas absorption and purification, and the reactions mainly include:
SO 2 +H 2 O→H 2 SO 3
SO 2 +O 2 →SO 3
SO 3 +H 2 O→H 2 SO 4
CaCO 3 +H 2 SO 3 →CaSO 3 ↓+H 2 O+CO 2 ↑
CaCO 3 +H 2 SO 4 →CaSO 4 ↓+H 2 O+CO 2 ↑
CaC 2 O 4 +H 2 SO 4 →CaSO 4 ↓+H 2 C 2 O 4
in addition, other acid/alkali gases, soluble gases, macromolecular organic components such as H 2 S、HCN、NH 3 Neutralization, absorption reactions of oils, etc.
The method for preparing the porous carbon material by using the biomass of the application and the technical effects obtained are further described below by using specific examples of antibiotic residues (penicillin V potassium residues).
Antibiotic bacterial residues (penicillin V potassium bacterial residues) are composed of the following components:
example 1
As shown in fig. 1, the raw material of the protein-rich antibiotic residues (penicillin V potassium residues) of the residues of the bio-fermentation industry was added to the porous carbon material preparing apparatus, naOH and KOH were added according to 1: and 1, mixing and then using the mixture as an activating agent, and etching the antibiotic residues by using the activating agent to obtain a material 1, wherein the mass ratio of the antibiotic residues to the activating agent is 1:0.8, and the pH value in the suspension is 13.5.
CO is introduced into the material 1 2 And obtaining a material 2, wherein the carbon dioxide gas is added into the penicillin V potassium bacteria residue by 0.036mol per gram until the pH value of the material 1 is less than or equal to 11. Filtering the material 2 to obtain filtrate 1 and material 3; and (3) pyrolyzing the material 3 at 600 ℃, wherein the heating rate is 5 ℃/min, and the material is kept for 60min after the material reaches 600 ℃ to obtain the raw carbon 1 and pyrolysis gas. Adding dilute sulfuric acid and oxalic acid into the carbon 1 to wash out impurities, and filtering to obtain carbon 2 and filtrate 2, wherein the molar ratio of the dilute sulfuric acid and oxalic acid to potassium ions and sodium ions in the carbon 1 is 1:2. Washing the raw carbon 2 to be neutral and drying at 105 ℃ to obtain a finished product of the porous carbon material.
Ca (OH) was added to filtrate 1 2 And CaO, ca (OH) 2 And the mol ratio of CaO to potassium ions and/or sodium ions in the filtrate 1 is 1.1:2, and the activator solution 1 and the filtered substance 1 are obtained after precipitation and filtration; ca (OH) was added to filtrate 2 2 And CaO, ca (OH) 2 And the mol ratio of CaO to potassium ions and/or sodium ions in the filtrate 1 is 1:2, and the activator solution 2 and the filtered substance 2 are obtained after precipitation and filtration. Mixing the activator solution 1 and the activator solution 2, thickening, adding a small amount of fresh activator, and returning to an activator dispensing pool; the filtered substances 1 and 2 are configured into suspension for pyrolysis waste gas absorption and purification, and the generated CaSO 4 And CaSO 3 And collecting and disposing.
The specific surface area and the pore diameter structure of the prepared porous carbon are tested and analyzed, and the specific surface area of the porous carbon material prepared by the method reaches 1675.42m 2 Per gram, higher than the specific surface area of the commercially available activated carbon, and the total pore volume of the porous carbon is 0.847m 3 And/g, wherein the micropore ratio reaches 89.21%. The surface morphology of the porous carbon was observed using a scanning electron microscope SEM (fig. 1), the porous carbon surface was distributed with rich, coarse cellular and lamellar pore structures, and there were some less sharp small protrusions at the outer edges of the openings of the pores. The developed porous structure of the porous carbon is obtained by the combined actions of chemical activation, physical activation, K atom etching and the like in the reaction process. The pore structure exists on the solid surface, the activation action enters the internal structure of the porous carbon material, and the three-dimensional porous carbon material is formed, so that the specific surface area is further increased.
Example 2
The procedure and process parameters for preparing porous carbon in this example refer to example 1, and differ from those in example in that potassium hydroxide is used as the alkali metal hydroxide, and the mass ratio of antibiotic residues to potassium hydroxide is 1:1.5. In addition, the material 3 is pyrolyzed at 400 ℃, the heating rate is 10 ℃/min, and the material is kept for 70min after reaching 400 ℃, so as to obtain the raw carbon 1 and pyrolysis gas. The subsequent treatment of the raw carbon 1 was the same as in example 1, to obtain a porous carbon finished product. The prepared porous carbon is subjected to test analysis on specific surface area and pore size structure, and the result shows that the porous carbon has larger pore volume and more micropores.
Comparative example 1
Using antibiotic residues (penicillin V potassium residues) as raw materials, KOH and NaOH were added at 1:1, wherein the mass ratio of the antibiotic residues to the activator is 1:0.8. Not introducing CO 2 Preparing porous carbon by direct pyrolysis and activation, wherein the pyrolysis temperature is 600 ℃, the heating rate is 5 ℃/min, and the raw carbon 1 and pyrolysis gas are obtained after the temperature reaches 600 ℃ and the temperature is kept for 60 min; adding dilute sulfuric acid and oxalic acid into the raw carbon 1 to wash out impurities, and filtering to obtain raw carbon 2 and filtrate 2; washing the raw carbon 2 to be neutral and drying at 105 ℃ to obtain a finished product of the porous carbon material. The specific surface area of the porous carbon is 1146.10m 2 Per g, total pore volume of 0.515m 3 And/g, wherein the micropore accounts for 66.80%. The porous carbon material is prepared using the method. In comparison with the method of the present application (e.g., example 1), the method of the present application provides only etching of strong base during the preparation of porous carbon, and lacks the alkali and CO of the present application 2 The activating effect under the synergistic effect can generate a certain amount of carbon dioxide in the pyrolysis process of biomass raw materials, but belongs to ineffective CO 2 The necessary reaction with the base does not occur as in the application, eventually resulting in a relatively low specific surface area and pore volume.
Comparative example 2
Using antibiotic residues (penicillin V potassium residues) as raw materials, firstly using KOH for impregnation treatment, wherein the impregnation ratio is 1:0.8, after uniformly mixing for 30min, adding a molar ratio of KOH to the mixed suspension of 1:1, filtering, drying the solid, and pyrolyzing at 650 ℃ for 120min. And (3) washing the generated porous carbon to be neutral by using ethanol and deionized water, and then drying in an oven at 105 ℃ to finally obtain the porous carbon. The specific surface area of the porous carbon is only 646.20m 2 Per gram, total pore volume 0.298m 3 /g, and of which there are mainly macropores (23.2%) and mesopores (63.8%). When the surface morphology is observed (fig. 3), the phenomena of fracture and collapse of part of the parts are found, and a plurality of lamellar structures are formed to form larger pores. In addition, a plurality of granular protruding structures are formed in partial areas, and the grains are approximately round and spherical and mutually connectedThe phase is unordered to bond, increasing the specific surface area of the carbon material. In fact, the pore structure produced is far less than that of the porous carbon produced by the method of the present application, due to two points: (1) After mixing by using dilute acid, the obtained alkali metal salt is not easy to decompose in the pyrolysis activation process, and is difficult to react with carbon in biomass in a chemical corrosion manner; (2) Due to no CO 2 The pyrolysis process lacks the decomposition of strong alkali weak acid salt, the physical activation step can not be carried out, and no way is provided for further expanding the pore structure.
In the examples of the present application, the specific surface area, pore volume, pore size distribution and the like of the porous carbon were measured by the BET method.
Claims (10)
1. A method for preparing a porous carbon material by regenerating a strong alkali activated biomass raw material, comprising the following steps:
(1) Carrying out activation treatment on the suspension of the biomass raw material to obtain a material 1, wherein an activating agent comprises alkali metal hydroxide, and after the alkali metal hydroxide is added, the pH value of the suspension of the biomass raw material is more than or equal to 13;
(2) Introducing carbon dioxide gas into the material 1 to obtain a material 2, filtering the material 2, and separating filtrate 1 and a solid material 3, wherein the introduced amount of the carbon dioxide gas is 0.002~0.06 mol CO per gram of biomass 2 The pH value of the material 1 is less than or equal to 11;
(3) Carrying out pyrolysis reaction and subsequent treatment on the solid material 3 to obtain a porous carbon material finished product;
the alkali metal hydroxide comprises sodium hydroxide and potassium hydroxide,
the pyrolysis reaction conditions in the step (3) are as follows: the pyrolysis temperature is 400-600 ℃, and the heating rate is 5-20 ℃/min;
the biomass raw material is organic biomass with the mass content of protein being more than or equal to 20 percent.
2. The method of claim 1, wherein in step (1), the biomass raw material and sodium hydroxide or potassium hydroxide are used in a mass ratio of 1:0.1 to 1:2.
3. The method according to claim 1, characterized in that the solid material 3 is pyrolyzed to obtain raw carbon 1, and the raw carbon 1 is filtered after being treated with dilute sulfuric acid and/or oxalic acid to obtain filtrate 2 and raw carbon 2; the raw carbon 2 is washed to be neutral, and then dried to obtain a finished product of the porous carbon material.
4. A method according to claim 3, wherein the molar ratio of dilute sulphuric acid and/or oxalic acid to potassium ions and/or sodium ions in the raw carbon 1 is 1:2 to 1.1:2.
5. A method according to claim 3, wherein the raw carbon 2 is dried in an oven at a temperature of 80-105 ℃ to a constant weight.
6. The method according to any one of claims 1 to 5, wherein Ca (OH) is added to the filtrate 1 2 And/or CaO, obtaining a precipitate after reaction, and filtering to obtain a filtrate serving as an activator solution.
7. The method according to claim 6, wherein Ca (OH) 2 And/or the molar ratio of CaO to potassium ions and/or sodium ions in the filtrate 1 is 1:2-1.2:2.
8. A method according to claim 3, characterized in that Ca (OH) is added to filtrate 2 2 And/or CaO, obtaining a precipitate after reaction, and filtering to obtain a filtrate serving as an activator solution.
9. The method according to claim 8, wherein Ca (OH) 2 And/or the molar ratio of CaO to potassium ions and/or sodium ions in the filtrate 2 is 1:2-1.3:2.
10. The method according to claim 8, wherein Ca (OH) is added to filtrate 1 and/or filtrate 2 2 And/or the precipitate obtained by CaO reaction is prepared into a suspension for the absorption step (3)Is a pyrolysis gas of (a).
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| CN104649265A (en) * | 2015-02-04 | 2015-05-27 | 昆明理工大学 | Method for preparing active carbon with high specific surface area from walnut shell |
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