CN115571880A - Preparation method of biomass-based hierarchical porous carbon - Google Patents
Preparation method of biomass-based hierarchical porous carbon Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title claims abstract description 29
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Images
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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
-
- 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
- C01B32/348—Metallic compounds
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Carbon And Carbon Compounds (AREA)
Abstract
The invention relates to the technical field of porous material preparation, and provides a preparation method of biomass-based hierarchical porous carbon. According to the invention, biomass is adopted as a carbon material precursor to be carbonized under different conditions, an activating agent is adopted to activate the biomass, a template agent is adopted to make holes in the biomass, and graphene oxide is also adopted to pretreat the biomass. The preparation method provided by the invention is simple and feasible, and the prepared biomass-based hierarchical porous carbon has a large specific surface area and a hierarchical pore composite structure. The biomass-based hierarchical porous carbon prepared by the method is widely applied to the fields of chemical production, medical carriers, environmental protection, electrode materials, soil improvement and the like, for example, the biomass-based hierarchical porous carbon can be used as a catalyst or a carrier of the catalyst to participate in catalytic reaction, and can be used as an electrode material in an electrochemical device, a purifying agent for water purification and the like.
Description
Technical Field
The invention relates to the technical field of porous material preparation, in particular to a preparation method of biomass-based hierarchical porous carbon.
Background
Activated Carbon (AC) is a carbonaceous porous solid particulate material prepared by pyrolysis of precursors under oxygen-free or anoxic conditions. Activated carbon is classified into three types according to its pore structure: micropores (pore size less than 2 nm), mesopores (pore size between 2nm and 50 nm) and macropores (pore size greater than 50 nm). The biomass-based carbon is one of activated carbon, and is characterized in that biomass is used as a precursor of the carbon material to be carbonized under different conditions. The biomass used as the precursor of the carbon material has wide sources, high carbon forming rate, low cost, reproducibility and diversified structures, and is an ideal raw material for designing and synthesizing high-quality carbon materials. However, the method for preparing the activated carbon, the porous carbon and the like by adopting the pure biomass has the problems of single pore channel and small specific surface area of the obtained material.
Disclosure of Invention
Aiming at the problems, the invention aims to provide a preparation method of biomass-based hierarchical porous carbon, the preparation method provided by the invention is simple and feasible, and the prepared biomass-based hierarchical porous carbon has a large specific surface area and a hierarchical porous composite structure.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of biomass-based hierarchical porous carbon, which comprises the following steps:
(1) Carrying out pre-carbonization treatment on the biomass to obtain pre-carbonized porous carbon;
(2) Mixing the pre-carbonized porous carbon with an activating agent for carbonization treatment to obtain biomass-based hierarchical porous carbon;
the biomass-based hierarchical porous carbon comprises micropores, mesopores and macropores.
Preferably, the activating agent comprises one or more of phosphoric acid, potassium hydroxide and zinc chloride.
Preferably, when the activating agent is phosphoric acid, the mixing is drying after the pre-carbonized porous carbon is immersed in phosphoric acid water solution;
when the activator is zinc chloride, the mixing is drying after mixing the pre-carbonized porous carbon with zinc chloride and water.
The invention also provides a preparation method of the biomass-based hierarchical porous carbon, which comprises the following steps:
mixing biomass and a template agent for carbonization treatment to obtain a carbonized product, wherein the template agent is a magnesium salt or magnesium oxide;
and removing the template agent in the carbonized product by adopting an acid leaching method to obtain the biomass-based hierarchical porous carbon.
Preferably, the magnesium salt comprises MgCl 2 、Mg(CH 3 COO) 2 And Mg 3 (C 6 H 5 O 7 ) 2 One or more of them.
Preferably, when the templating agent is MgCl 2 And Mg (CH) 3 COO) 2 In one or both cases, the mixing is performed by immersing the biomass in an aqueous templating agent solution and then drying the biomass.
Preferably, the temperature of the carbonization treatment is 600-800 ℃, the heating rate is 2-5 ℃/min, and the time of the carbonization treatment is 1-2 h.
The invention also provides a preparation method of the biomass-based hierarchical porous carbon, which comprises the following steps:
(1) Mixing biomass, water and a graphene oxide solution, and drying to obtain a biomass powder precursor;
(2) Performing first carbonization treatment on the biomass powder precursor to obtain first biomass-based porous carbon;
(3) And mixing the first biomass-based porous carbon with potassium hydroxide for second carbonization treatment to obtain the biomass-based hierarchical porous carbon.
Preferably, the temperature of the first carbonization treatment is 400-450 ℃, the temperature rise rate is 2-10 ℃/min, and the time of the first carbonization treatment is 2-6 h;
the temperature of the second carbonization treatment is 800-900 ℃, the heating rate is 2-5 ℃/min, and the time of the second carbonization treatment is 0.5-5 h.
Preferably, the ratio of the mass of the biomass to the volume of the graphene oxide solution is 1g:5 to 25mL.
The invention provides a preparation method of biomass-based hierarchical porous carbon, which comprises the following steps: (1) Carrying out pre-carbonization treatment on the biomass to obtain pre-carbonized porous carbon; (2) Mixing the pre-carbonized porous carbon with an activating agentMixing and carbonizing to obtain biomass-based hierarchical porous carbon; the biomass-based hierarchical porous carbon comprises micropores, mesopores and macropores. According to the invention, biomass is used as a precursor, the basic skeleton of the carbon material is obtained by pre-carbonization, then an activating agent is added to carry out carbonization together with the pre-carbonized porous carbon, and the pre-carbonized porous carbon is subjected to chemical reaction or chemical action, so that the porous carbon material with a large specific surface area and a multi-level pore composite structure is prepared. The results of the examples show that the specific surface area of the biomass-based hierarchical porous carbon prepared by the method is as high as 1859.68m 2 g -1 。
The invention also provides a preparation method of the biomass-based hierarchical porous carbon, which comprises the following steps: mixing biomass with a template agent for carbonization treatment to obtain a carbonized product, wherein the template agent is a magnesium salt or magnesium oxide; and removing the template agent in the carbonized product by adopting an acid leaching method to obtain the biomass-based hierarchical porous carbon. The invention utilizes the micro-pores generated by the heating escape of the moisture, other small molecules, impurities and the like contained in the biomass during the carbonization process. Meanwhile, the template agent and C are subjected to redox reaction at a certain temperature, magnesium oxide is reduced into a magnesium simple substance, C is oxidized into carbon dioxide gas to escape, the carbon dioxide gas escapes to form a hole, the metal simple substance obtained by reduction is removed in the later pickling step, an occupied vacancy is left to become another hole, and the two holes are different in size. The collapse and reconstruction of the skeleton in the carbonization process of the whole biomass form a macroporous structure, so that the porous carbon material with a large specific surface area and a hierarchical porous composite structure is prepared. The specific surface area of the biomass-based hierarchical porous carbon prepared by the method is up to 1133.49m 2 g -1 。
The invention also provides a preparation method of the biomass-based hierarchical porous carbon, which comprises the following steps: (1) Mixing biomass, water and a graphene oxide solution, and drying to obtain a biomass powder precursor; (2) Performing first carbonization treatment on the biomass powder precursor to obtain first biomass-based porous carbon; (3) Mixing the first biomass-based porous carbon with potassium hydroxide for second carbonization treatment to obtain biomassA base-graded porous carbon. The graphene oxide has a specific lamellar structure, occupies space, induces and catalyzes the graphitization of biomass carbon, simultaneously generates carbon dioxide, carbon monoxide and carbon by redox reaction with the biomass at high temperature, and the original skeleton structure and lamellar space occupation are damaged in the complex reaction, so that a porous structure with hierarchical pores is reconstructed, finally, the first biomass porous carbon is continuously subjected to pore-forming, KOH can be decomposed in the carbonization process, metal K can etch the carbon skeleton at high temperature to form pores, and meanwhile, the complex chemical reaction is generated at high temperature to generate K 2 CO 3 、K 2 O and CO 2 And the like, play a role in pore forming in the carbonization process of the porous carbon. Since the substances generated in the carbonization process have different molecular sizes, the escape of the substances at high temperature is caused by the mutual overlapping of pores with different sizes, thereby generating a hierarchical structure with different pore sizes and forming a larger specific surface area. The specific surface area of the biomass-based hierarchical porous carbon prepared by the method is as high as 2194.42m 2 g -1 。
The biomass-based hierarchical porous carbon prepared by the method has rich pore structure types, and comprises micropores, mesopores and macropores. The catalyst can be widely applied to the fields of chemical production, medical carriers, environmental protection, electrode materials, soil improvement and the like, and can be used as a catalyst or a carrier of the catalyst to participate in catalytic reaction, and can be used as an electrode material in an electrochemical device, a purifying agent for water purification and the like.
Drawings
Fig. 1 is an SEM image of biomass-based hierarchical porous carbon prepared in example 9 of the present invention;
fig. 2 is a TEM image of biomass-based hierarchical porous carbon prepared in example 9 of the present invention;
FIG. 3 is a pore distribution diagram of biomass-based hierarchical porous carbon prepared in examples 8 to 9 of the present invention;
fig. 4 is an SEM image of biomass-based hierarchical porous carbon prepared in example 35 of the present invention;
FIG. 5 is a pore distribution map of biomass-based hierarchical porous carbon prepared in example 35 of the present invention;
fig. 6 is an SEM image of the biomass porous carbon prepared in comparative example 1 of the present invention.
Detailed Description
The invention provides a preparation method (marked as method one) of biomass-based hierarchical porous carbon, which comprises the following steps:
(1) Carrying out pre-carbonization treatment on the biomass to obtain pre-carbonized porous carbon;
(2) Mixing the pre-carbonized porous carbon with an activating agent for carbonization treatment to obtain biomass-based hierarchical porous carbon;
the biomass-based hierarchical porous carbon comprises micropores, mesopores and macropores.
In the present invention, unless otherwise specified, each of the substances is a commercially available product well known to those skilled in the art.
According to the invention, the biomass is subjected to pre-carbonization treatment to obtain the pre-carbonized porous carbon. In the invention, the biomass preferably comprises one or more of passion fruit peel, shaddock peel, mangosteen peel, lignin and bean dregs, and more preferably comprises one or two of passion fruit peel and lignin; before the pre-carbonization treatment, the biomass is preferably cleaned, diced and dried; the cleaning solution is preferably distilled water; the length and the width of the cutting block are independent and preferably 0.1-0.5 cm; the drying temperature is preferably 80-100 ℃, and the drying equipment is preferably a blast oven; the pre-carbonization treatment is preferably performed under nitrogen; the temperature of the pre-carbonization treatment is preferably 400-800 ℃, the heating rate is preferably 2-10 ℃/min, and the time is preferably 2-6 h; the pre-carbonization device is preferably a tube furnace.
After the pre-carbonized porous carbon is obtained, mixing the pre-carbonized porous carbon with an activating agent for carbonization treatment to obtain biomass-based hierarchical porous carbon; the biomass-based hierarchical porous carbon comprises micropores, mesopores and macropores. In the invention, the activating agent preferably comprises one or more of phosphoric acid, potassium hydroxide and zinc chloride; when the activator is phosphoric acid, the mixing is preferably carried out by dipping the pre-carbonized porous carbon in an aqueous phosphoric acid solution and then drying; the mass concentration of the phosphoric acid aqueous solution is preferably 85 to 95 percent, and more preferably 85 to 88 percent; the ratio of the mass of the pre-carbonized porous carbon to the volume of the phosphoric acid aqueous solution is preferably 1g: 1-5 mL; the time for soaking is preferably 6-10 h; the drying temperature is preferably 80-100 ℃; the drying is preferably air drying. The invention uses phosphoric acid as an activator to promote hydrolysis of cellulose and hemicellulose sugars in the biomass and form a 'phosphoric acid-polymer' complex with the biomass. During the carbonization treatment, phosphoric acid and biomass generate obvious crosslinking reaction and promote aromatization of the pre-carbonized porous carbon, so that a porous structure of loose biomass activated carbon is formed, wherein graphite-like crystals are main structural units and are derived from aromatization of precursor carbon atoms and condensation of aromatic rings.
In the present invention, when the activator is potassium hydroxide, the mass ratio of the pre-carbonized porous carbon to the potassium hydroxide is preferably 1; the mixing mode has no special requirements, and the mixture is uniform. The potassium hydroxide has the function of etching the pre-carbonized porous carbon in the temperature raising process of carbonization treatment, so that a large number of micropores are generated, and the specific surface area of the product is increased.
In the present invention, when the activating agent is zinc chloride, the mixing is preferably performed by mixing the pre-carbonized porous carbon with zinc chloride and water and then drying; the mixing is preferably carried out under stirring conditions; the stirring time is preferably 0.5 to 10 hours, and more preferably 5 to 10 hours; the drying temperature is preferably 80-100 ℃; the drying mode is preferably air-blast drying; the ratio of the mass of the pre-carbonized porous carbon to the mass of the zinc chloride to the volume of water is preferably 1g: 20 to 100mL, more preferably 1g: 30 to 50mL. According to the invention, zinc chloride and the pre-carbonized porous carbon are mixed by a wet method, wherein the zinc chloride particles can generate an occupying effect in the pre-carbonized porous carbon, and the zinc chloride particles expand in situ along with the rise of temperature to cause the breakage of lateral bonds of cellulose molecules, so that the internal micelle void is increased. Meanwhile, as zinc chloride has certain vapor pressure, zinc chloride particles are gasified and escaped along with the rise of the carbonization treatment temperature, so that vacancy pores are generated in the carbon material, and the specific surface area of a product is increased.
In the invention, the temperature of the carbonization treatment is preferably 400-900 ℃, more preferably 450-800 ℃, and the time is preferably 1-7 h, more preferably 2-6 h; the carbonization treatment is preferably performed under nitrogen; the heating rate of the carbonization treatment is preferably 2-5 ℃/min; after the carbonization treatment, the invention also preferably comprises washing and drying the obtained carbonized product in sequence; the washing solution is preferably distilled water and/or hydrochloric acid aqueous solution; the concentration of the hydrochloric acid aqueous solution is preferably 0.5-2 mol/L; the method has no special requirements on the washing mode, and the obtained carbonized product is washed to be neutral; the drying temperature is preferably 80-90 ℃, and the drying time is 24 hours; the drying is preferably air-blast drying.
The invention also provides a preparation method of the biomass-based hierarchical porous carbon (marked as method II), which comprises the following steps:
mixing biomass with a template agent for carbonization treatment to obtain a carbonized product, wherein the template agent is a magnesium salt or magnesium oxide; and removing the template agent in the carbonized product by adopting an acid leaching method to obtain the biomass-based hierarchical porous carbon.
In the invention, the biomass preferably comprises one or more of passion fruit peel, shaddock peel, mangosteen peel, lignin and bean dregs, and more preferably comprises one or two of passion fruit peel and lignin; before the carbonization treatment, the biomass is preferably cleaned, cut into pieces, dried and ground; the cleaning solution is preferably distilled water; the particle size of the cut blocks is preferably 0.5 multiplied by 0.5cm; the drying temperature is preferably 80-100 ℃, and the drying equipment is preferably a blast oven; the grinding has no special requirements, and the grinding is carried out by conventional grinding and uniform mixing; the magnesium salt preferably comprises MgCl 2 、Mg(CH 3 COO) 2 And Mg 3 (C 6 H 5 O 7 ) 2 One or more of the above; when the template agent is MgCl 2 And Mg (CH) 3 COO) 2 In one or both cases, the mixing is preferably performed by immersing the biomass in an aqueous templating agent solution and then drying; the concentration of the template agent aqueous solution is preferably 0.01 to 0.333g/mL, more preferablyPreferably 0.1 to 0.2g/mL; the ratio of the mass of the biomass to the volume of the template aqueous solution is preferably 1g:8 to 20mL, more preferably 1g: 10-14 mL; the time for soaking is preferably 8-10 h; the drying temperature is preferably 80-100 ℃, and the drying equipment is preferably a blast oven.
In the present invention, when the template agent is MgO and Mg 3 (C 6 H 5 O 7 ) 2 In one or two of (a), the mass ratio of the biomass to the template is 1; the mixing mode has no special requirements, and the mixture is uniform. Because the magnesium oxide and the magnesium citrate are insoluble in water, the invention adopts a dry mixing mode for mixing.
In the invention, the temperature of the carbonization treatment is preferably 600-800 ℃, the heating rate is preferably 2-5 ℃/min, and the time of the carbonization treatment is preferably 1-2 h; the carbonization treatment is preferably performed under nitrogen. The template agent adopted by the invention has oxidation-reduction reaction with biomass in the carbonization and temperature rise process, and CO is released by decomposition 2 And waiting for the micromolecular gas to realize the pore-forming of the biomass.
After a carbonized product is obtained, the invention adopts an acid leaching method to remove the template agent in the carbonized product, so as to obtain the biomass-based hierarchical porous carbon. In the present invention, the acid leaching method is specifically preferably: soaking the carbonized product in an acid solution; the acidic solution is preferably an aqueous hydrochloric acid solution; the concentration of the hydrochloric acid aqueous solution is preferably 0.1-1 mol/L; the soaking time is preferably 24-48 h; after soaking, the obtained wet biomass-based hierarchical porous carbon is preferably washed and dried in sequence; the washing solution is preferably deionized water; the method has no special requirement on the washing mode, and the wet biomass-based hierarchical porous carbon is washed to be neutral; the drying temperature is preferably 50-80 ℃, and the drying time is 10-20 h; the drying is preferably air-blast drying.
The invention also provides a preparation method of the biomass-based hierarchical porous carbon (marked as method III), which comprises the following steps:
(1) Mixing biomass, water and a graphene oxide solution, and drying to obtain a biomass powder precursor;
(2) Performing first carbonization treatment on a biomass powder precursor to obtain first biomass-based porous carbon;
(3) And mixing the first biomass-based porous carbon with potassium hydroxide for second carbonization treatment to obtain the biomass-based hierarchical porous carbon.
According to the invention, the biomass is mixed with the graphene oxide solution and then dried to obtain the biomass powder precursor. In the invention, the biomass comprises one or more of passion fruit peel, shaddock peel, mangosteen peel, lignin and bean dregs, and more preferably one or two of passion fruit peel and lignin; the lignin is preferably lignin carbon powder; before the carbonization treatment, the biomass is preferably cleaned, cut into pieces and dried; the cleaning solution is preferably distilled water; the particle size of the cut blocks is preferably 0.5 multiplied by 0.5cm; the drying temperature is preferably 80-100 ℃, and the drying equipment is preferably a blast oven; the concentration of the graphene oxide solution is preferably 1 mg/mL-10 mg/mL, and more preferably 3 mg/mL-6 mg/mL; the ratio of the mass of the biomass, the volume of water and the volume of the graphene oxide solution is preferably 1g:10mL of: 5 to 25mL, more preferably 1g:10mL of: 5-15 mL; the mixing mode is preferably that the biomass is mixed with water and graphene oxide solution and then ultrasonic treatment is carried out; the ultrasonic time is preferably 10-60 min; the power of the ultrasonic wave is preferably 10-40W; the drying temperature is preferably 80-100 ℃, and the drying equipment is preferably an electric heating air blast drying box.
After the biomass powder precursor is obtained, the biomass powder precursor is subjected to first carbonization treatment to obtain first biomass-based porous carbon. In the present invention, the temperature of the first carbonization treatment is preferably 400 to 450 ℃, and the rate of temperature rise is preferably 2 to 10 ℃/min, and more preferably 2 to 5 ℃/min; the time of the first carbonization treatment is preferably 2 to 6 hours; the first carbonization treatment is preferably performed under nitrogen.
After the first biomass-based porous carbon is obtained, the first biomass-based porous carbon and potassium hydroxide are mixed for second carbonization treatment, and the biomass-based hierarchical porous carbon is obtained. In the present invention, the mass ratio of the first biomass-based porous carbon to potassium hydroxide is preferably 1:1 to 5, more preferably 1:2 to 4; the mixing mode is preferably that the pre-carbonized biomass-based hierarchical porous carbon and potassium hydroxide are ground together; the grinding time is preferably 30-60 min; the temperature of the second carbonization treatment is preferably 800-900 ℃, the heating rate is preferably 2-5 ℃/min, and the time of the second carbonization treatment is preferably 0.5-5 h, and more preferably 0.5-1 h; the second carbonization treatment is preferably performed under nitrogen; after the second carbonization treatment, the invention preferably further comprises washing and drying the obtained second carbonized product in sequence; the washing solution is preferably deionized water; the washing mode has no special requirement, and the obtained second carbonized product is washed to be neutral; the drying temperature is preferably 50-100 ℃, and the drying time is 12-24 hours; the drying is preferably air-blast drying.
In order to further illustrate the present invention, the following examples are provided to describe the preparation method of the biomass-based hierarchical porous carbon provided by the present invention in detail, but they should not be construed as limiting the scope of the present invention.
The passion fruit used in the embodiment of the invention is from a local supermarket in Harbin city, and the production place is Guangxi.
The graphene oxide solution used in the embodiment of the invention is prepared by the following steps:
weighing 3g of natural graphite flake, and adding into a container containing 360mLH 2 SO 4 And 40mLH 3 PO 4 To the mixed acid solution of (1), 18g of KMnO was slowly added with continuous stirring 4 At this point the solution was slightly exothermic. The mixture was heated to 50 ℃ and stirred for 12 hours, and the reaction mixture was cooled to room temperature and then poured into 400mL of 30% H solution containing 3mL of H 2 O 2 To obtain a golden yellow sticky substance; and (4) centrifuging the golden yellow sticky matter, and drying the obtained solid at the temperature of 50 ℃ to obtain the graphene oxide. 1g of graphene oxide was dispersed in 1000mL of water by ultrasonic waves to obtain a graphene oxide solution.
Example 1
(1) Washing passion fruit peel with distilled water to remove impurities, cutting into 0.2cm multiplied by 0.2cm squares, and drying in a forced air oven at 95 ℃ for 24 hours to obtain pretreated passion fruit peel;
(2) Putting the quartz boat with the pretreated passion fruit peel into a tube furnace, introducing nitrogen, heating to 400 ℃ at a heating rate of 5 ℃/min for 2.5 hours for pre-carbonization, and naturally cooling the obtained product to room temperature to obtain pre-carbonized porous carbon;
(3) Dipping the pre-carbonized porous carbon in a phosphoric acid aqueous solution with the mass fraction of 85% for 6h to obtain the pre-carbonized porous carbon containing phosphoric acid, and performing forced air drying on the pre-carbonized porous carbon containing phosphoric acid at 80 ℃ for 24h to obtain a pre-carbonized porous carbon precursor, wherein the volume ratio of the mass of the pre-carbonized porous carbon to the phosphoric acid aqueous solution is 1g:3mL;
(4) And (2) putting the quartz boat filled with the pre-carbonized porous carbon precursor into a tubular furnace, introducing nitrogen, heating to 500 ℃ at the heating rate of 5 ℃/min, carrying out carbonization treatment for 2 hours, naturally cooling the product subjected to carbonization treatment to room temperature, washing the product subjected to carbonization with distilled water to be neutral, filtering, and carrying out forced air drying at 80 ℃ for 24 hours to obtain the biomass-based hierarchical porous carbon.
Example 2
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 1, except that:
the temperature of the pre-carbonization treatment in the step (2) is changed from 400 ℃ to 600 ℃.
Example 3
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 1, except that:
and (3) setting the volume ratio of the mass of the pre-carbonized porous carbon in the step (3) to the phosphoric acid aqueous solution to be 1g:3mL was changed to 1g:1mL;
the temperature of the pre-carbonization treatment in the step (2) was changed from 400 ℃ to 550 ℃.
Example 4
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 1, except that:
and (4) setting the volume ratio of the mass of the pre-carbonized porous carbon in the step (3) to the phosphoric acid aqueous solution to be 1g:3mL was changed to 1g:2mL.
Example 5
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 1, except that:
the temperature of the carbonization treatment in the step (4) was changed from 500 ℃ to 550 ℃.
Example 6
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 1, except that:
the carbonization temperature in the step (4) was changed from 500 ℃ to 650 ℃.
TABLE 1 Performance results, such as specific surface area, of the products corresponding to the different steps in examples 1, 3-6
Remarking: s BET (m 2 g -1 ) Is the specific surface area of the product; s micro (m 2 g -1 ) Is the micropore area of the product; s micro /S BET Is the micropore ratio of the product; d aver (nm) is the average pore size of the product; v p (cm 3 g -1 ) Is the pore volume of the product; the explanations of the English labels in tables 2-10 are not repeated and are consistent with Table 1.
From table 1, it can be seen that: when biomass passion fruit peel and H 3 PO 4 When the amount of (a) is changed, the specific surface area and other parameters of the biomass-based hierarchical porous carbon are correspondingly changed. Due to H in the activation process 3 PO 4 Can be combined with organic matters in biomass such as cellulose and hemicellulose to form a phosphate ester bond, and polymer fragments are promoted to be crosslinked to generate interaction. This reaction occurs during carbonization and as the temperature increases, the crosslinked biomass carbon material decomposes and releases small gaseous molecules (CO) 2 And H 2 O, etc.) to promote the formation of a pore structure, and H is expressed 3 PO 4 Activating pore-forming action. In the method, when the volume ratio of the mass of the pre-carbonized porous carbon to the phosphoric acid aqueous solution is1g:3mL, the pore-forming effect is optimal when the carbonization temperature is 500 ℃, and the specific surface area of the prepared porous carbon material is 432.34m 2 g -1 The contribution of micropores to all pores is 20.34%, the rest is the contribution of mesopore and macropore, and the combination of the data of average pore diameter of 1.0nm can conjecture that the contribution of mesopore and micropore is more, and part of macropore is generated by the recombination of skeleton in carbonization.
In example 6, the carbonization temperature is increased to 650 ℃, the carbonization temperature is higher, the structure of the biomass is excessively ablated, part of the microporous structure is damaged, the gasification degree of the solid material is increased, the carbon skeleton is collapsed, the microporous and mesoporous structures cannot be effectively maintained, the contribution of micropores to all pores is reduced (5.24%), and the specific surface area of the prepared material is correspondingly reduced (74.95 m) 2 g -1 )。
Example 7
(1) Washing passion fruit peel with distilled water to remove impurities, cutting into 0.2cm multiplied by 0.2cm squares, and drying in a forced air oven at 95 ℃ for 24 hours to obtain pretreated passion fruit peel;
(2) Putting the quartz boat with the pretreated passion fruit peel into a tube furnace, introducing nitrogen, heating to 400 ℃ at a heating rate of 5 ℃/min for carrying out pre-carbonization treatment for 3 hours, and naturally cooling the obtained product to room temperature to obtain pre-carbonized porous carbon;
(3) Fully mixing the pre-carbonized porous carbon and potassium hydroxide at room temperature to obtain a pre-carbonized porous carbon mixed dry material, wherein the mass ratio of the pre-carbonized porous carbon to the potassium hydroxide is 1:2;
(4) Putting the quartz boat filled with the pre-carbonized porous carbon mixed dry material into a tube furnace, introducing nitrogen, heating to 800 ℃ at a heating rate of 5 ℃/min for carbonization for 2 hours, naturally cooling the product after carbonization to room temperature, and alternately washing the product after carbonization to be neutral by using distilled water and hydrochloric acid aqueous solution, wherein the concentration of the hydrochloric acid aqueous solution is 1mol/L; and filtering and drying for 24h to obtain the biomass-based hierarchical porous carbon.
Example 8
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 7, except that:
and (3) setting the mass ratio of the pre-carbonized porous carbon to the potassium hydroxide in the step (3) as 1:2 is changed into 1:1.
example 9
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 7, except that:
and (4) mixing the precarbonized porous carbon and the potassium hydroxide in the step (3) in a mass ratio of 1:2 is changed into 1:3.
fig. 1 is an SEM image of the biomass-based hierarchical porous carbon prepared in example 9 of the present invention, and it can be seen from fig. 1 that the surface of the biomass-based hierarchical porous carbon has a porous lamellar structure, the diameter of the pores on the surface of the material is about 10 to 20 micrometers, the surface morphology of the material shows typical macroporous characteristics, and the data in table 2 are combined to obtain the material S prepared in example 9 BET The maximum value is 1859.68m 2 The volume of micropores in the sample was 44.13% of the total pore volume, indicating that the surface of the material prepared in this example had a macroporous structure and more micropores were present therein. Referring to fig. 2, fig. 2 is a TEM image of the biomass-based hierarchical porous carbon prepared in example 9 of the present invention, and it can be seen from fig. 2 that the inner pores of the biomass-based hierarchical porous carbon are not uniform in diameter, and the pores with different diameters are overlapped with each other to form a hierarchical pore structure.
Fig. 3 is a pore distribution diagram of the biomass-based hierarchical porous carbon prepared in examples 8 to 9 of the present invention, and it can be seen from fig. 3 that a large number of micropores exist in the vicinity of less than 2nm and 2nm, and partial mesopores exist in the vicinity of 9nm and 13 nm. Referring to the SEM image of fig. 1, it is understood that the biomass-based hierarchical porous carbon prepared in example 9 of the present invention has a hierarchical pore structure of micropores, mesopores, and macropores.
Example 10
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 7, except that:
and (4) mixing the precarbonized porous carbon and the potassium hydroxide in the step (3) in a mass ratio of 1:2 is changed into 1:4.
example 11
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 7, except that:
and (3) setting the mass ratio of the pre-carbonized porous carbon to the potassium hydroxide in the step (3) as 1:2 is changed into 1:5.
table 2 performance results, such as specific surface area, of biomass-based hierarchical porous carbons prepared in examples 7 to 11
| Examples | S BET (m 2 g -1 ) | S micro (m 2 g -1 ) | S micro /S BET | d aver (nm) | V p (cm 3 g -1 ) |
| Example 7 | 1327.66 | 728.49 | 54.87 | 1.54 | 0.3451 |
| Example 8 | 1288.30 | 539.52 | 41.88 | 1.44 | 0.4091 |
| Example 9 | 1859.68 | 820.71 | 44.13 | 1.41 | 0.5745 |
| Example 10 | 1342.39 | 748.98 | 55.79 | 1.41 | 0.3520 |
| Example 11 | 865.07 | 461.63 | 53.36 | 1.41 | 0.2754 |
From table 2, it can be seen that: specific surface area S of porous carbon Material obtained in example 9 BET Up to 1859.68m 2 g -1 . Analytical examples 7 to 11, the biomass porous carbon material produced more porous channels and larger S BET The reasons for this are: KOH can be etched when formed in pores, KOH is decomposed under a high-temperature environment, and decomposition products and a carbon matrix generate a series of oxidation-reduction actions to generate gas and etch the carbon matrix framework, so that micropores are generated on the surface. The generation and the quantity of the pore channels are changed along with the change of the proportion of the activating agent KOH, and the S of the porous carbon prepared by the invention BET The size of the adsorbent pores is mainly distributed between 1.8 and 2.5nm along with the increase and decrease of the KOH amount. From the above data, it can be seen that too high KOH concentration may cause the micropores to penetrate, form mesopores, and reduce the specific surface area. Examples of whichS in 9 BET The maximum value is 1859.68m 2 In terms of/g, micropores accounted for 44.13% of the total pore volume. The pore volume is 0.5745cm 3 The average pore diameter is 1.41nm, and the specific surface area is maximized as the material becomes more microporous after KOH activation.
Example 12
(1) Washing passion fruit peel with distilled water to remove impurities, cutting into 0.5cm multiplied by 0.5cm squares, and drying in a forced air oven at 85 ℃ for 30 hours to obtain pretreated passion fruit peel;
(2) Putting the quartz boat with the pretreated passion fruit peel into a tube furnace, introducing nitrogen, heating to 400 ℃ at a heating rate of 2 ℃/min for 2 hours for pre-carbonization, and naturally cooling the obtained product to room temperature to obtain pre-carbonized porous carbon;
(3) Uniformly mixing the pre-carbonized porous carbon and zinc chloride, adding distilled water, stirring for 10 hours to obtain the zinc chloride-containing pre-carbonized porous carbon, and drying the zinc chloride-containing pre-carbonized porous carbon in an oven at 80 ℃ for 24 hours to obtain a pre-carbonized porous carbon precursor, wherein the ratio of the mass of the pre-carbonized porous carbon to the mass of the zinc chloride to the volume of the distilled water is 1g:1g:40mL;
(4) Putting the quartz boat with the pre-carbonized porous carbon precursor into a tubular furnace, introducing nitrogen, heating to 500 ℃ at the heating rate of 5 ℃/min, carrying out carbonization for 3 hours, naturally cooling the product after carbonization to room temperature, and alternately washing the product after carbonization to be neutral by using distilled water and hydrochloric acid aqueous solution, wherein the concentration of the hydrochloric acid aqueous solution is 1mol/L; and filtering and carrying out forced air drying at 80 ℃ for 24 hours to obtain the biomass-based hierarchical porous carbon.
Example 13
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 12, except that:
and (4) enabling the ratio of the mass of the pre-carbonized porous carbon in the step (3) to the mass of zinc chloride to be 1:1 is changed into 1:2.
example 14
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 12, except that:
and (4) enabling the ratio of the mass of the pre-carbonized porous carbon in the step (3) to the mass of zinc chloride to be 1:1 is changed into 1:3.
example 15
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 12, except that:
and (4) enabling the ratio of the mass of the pre-carbonized porous carbon in the step (3) to the mass of zinc chloride to be 1:1 is changed into 1:4.
example 16
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 12, except that:
and (3) enabling the mass ratio of the mass of the pre-carbonized porous carbon in the step (3) to the mass of the zinc chloride to be 1:1 is changed into 1:3;
the carbonization temperature of 500 ℃ in the step (4) is changed into 600 ℃.
Table 3 performance results, such as specific surface area, of biomass-based hierarchical porous carbons prepared in examples 12 to 16
| Examples | S BET (m 2 g -1 ) | S micro (m 2 g -1 ) | S micro /S BET | d aver (nm) | V p (cm 3 g -1 ) |
| Example 12 | 453.48 | 278.54 | 26.80 | 1.52 | 0.1175 |
| Example 13 | 1037.57 | 278.60 | 26.85 | 1.25 | 0.9125 |
| Example 14 | 1227.78 | 153.69 | 12.52 | 1.1 | 1.1587 |
| Example 15 | 1094.39 | 71.98 | 6.57 | 1.05 | 1.2738 |
| Example 16 | 1179.63 | 164.53 | 13.95 | 1.13 | 1.2672 |
ZnCl 2 The preparation method can play the roles of a dehydrating agent and an activating agent in the preparation process of the biomass porous carbon. As can be seen from table 3, the preparation temperature was 500 c,the ratio of the mass of the pre-carbonized porous carbon to the mass of zinc chloride is from 1:1 to 1:3, the specific surface area of the obtained porous carbon material is gradually increased; the optimal proportion of the preparation temperature is 1:3 (example 14) and a specific surface area of 1227.80m 2 In terms of volume/g, micropores account for 12.52% of the total pore volume, the average pore diameter is 1.16nm, and the proportion of mesopores is large, and the pores of the porous carbon material prepared in the embodiment are a hierarchical structure in which micropores, mesopores and macropores coexist. When the mass of the pre-carbonized porous carbon and the mass of the zinc chloride are 1:4 (example 15), the ratio of the activating component is high, and the matrix skeleton of the biomass carbon is destroyed in the temperature rising process, resulting in the reduction of the specific surface area. The increase of the carbonization temperature is favorable for promoting the condensation reaction of the biomass matrix, the cracking of cellulose and the melting and gasification of zinc chloride at 600 ℃ play a role in pore forming, and the higher S of the porous carbon material is caused BET And high porosity due to sintering effects, high temperatures of 600 degrees celsius may cause some carbon shrinkage, realignment causes pore aggregation, and destruction of some micropores to promote formation of some macropores. From this, it is understood that the pores of the biomass-based hierarchical porous carbon prepared in the present invention are a hierarchical structure in which micropores, mesopores, and macropores coexist.
Example 17
(1) Washing passion fruit peel with distilled water to remove impurities, cutting into 0.5cm multiplied by 0.5cm squares, drying in a forced air oven at 85 ℃ for 30h, and grinding to obtain pretreated passion fruit peel powder;
(2) Dry-mixing 1g of pretreated passion fruit peel powder and 0.25g of MgO, placing the mixture in a tubular furnace, raising the temperature to 600 ℃ at a heating rate of 5 ℃/min in a nitrogen atmosphere for carbonization for 1h, and then naturally cooling to room temperature to obtain biomass-based hierarchical porous carbon containing a template agent;
(3) Soaking the biomass-based hierarchical porous carbon containing the template agent in 0.1mol/L hydrochloric acid water solution for 24 hours to remove MgO, so as to obtain wet biomass-based hierarchical porous carbon, washing the wet biomass-based hierarchical porous carbon with deionized water to be neutral, and drying in a 50 ℃ oven for 10 hours to obtain the biomass-based hierarchical porous carbon.
Example 18
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 17, except that:
changing the carbonization temperature in the step (2) from 600 ℃ to 700 ℃.
Example 19
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 17, except that:
changing the carbonization temperature in the step (2) from 600 ℃ to 800 ℃.
Example 20
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 17, except that:
changing the carbonization temperature in the step (2) from 600 ℃ to 800 ℃;
changing the MgO of 0.25g in the step (2) into the MgO of 0.125 g.
Example 21
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 17, except that:
changing the carbonization temperature in the step (2) from 600 ℃ to 800 ℃;
the amount of MgO used in step (2) was changed from 0.25g to 0.375 g.
Example 22
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 17, except that:
changing the carbonization temperature in the step (2) from 600 ℃ to 800 ℃;
changing the MgO of 0.25g in the step (2) to MgO of 0.5 g.
Example 23
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 17, except that:
changing the carbonization temperature in the step (2) from 600 ℃ to 800 ℃;
the amount of MgO used in the step (2) was changed from 0.25g to 0.625 g.
Table 4 performance results such as specific surface area of biomass-based hierarchical porous carbon prepared in examples 17 to 23
| Examples | S BET (m 2 g -1 ) | S micro (m 2 g -1 ) | S micro /S BET | d aver (nm) | V p (cm 3 g -1 ) |
| Example 17 | 194.24 | 138.44 | 71.27 | 7.70 | 0.08 |
| Example 18 | 291.43 | 238.33 | 81.78 | 5.02 | 0.13 |
| Example 19 | 329.78 | 241.39 | 73.20 | 7.85 | 0.14 |
| Example 20 | 688.65 | 298.74 | 43.38 | 2.73 | 0.24 |
| Example 21 | 892.57 | 314.99 | 35.29 | 4.05 | 0.30 |
| Example 22 | 844.64 | 349.47 | 41.38 | 4.44 | 0.30 |
| Example 23 | 1133.49 | 207.30 | 0.1839 | 3.74 | 0.34 |
From table 4, it can be seen that: the specific surface area of the sample increased with the increase in temperature, indicating that the temperature contributed to the increase in the specific surface area of the sample. As the amount of the MgO template agent is increased, the specific surface area of the sample tends to increase, and the pore volume also increases, reaching the maximum value of 1133.49m in example 23 2 The ratio of micropores is smaller, the average pore diameter is 3.73nm, and the mesoporous structure belongs to the mesoporous category, which indicates that macropores and mesoporesThe contribution of pores is large, and the structure of the integral pores of the biomass-based hierarchical porous carbon belongs to a hierarchical structure with micro-meso-macro pores coexisting.
Example 24
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 17, except that:
changing 0.25gMgO to 1.52gMg 3 (C 6 H 5 O 7 ) 2 。
Example 25
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 17, except that:
the MgO of 0.25g is changed into the Mg of 0.76g 3 (C 6 H 5 O 7 ) 2 ；
The carbonization temperature of 600 ℃ is changed into 700 ℃.
Example 26
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 17, except that:
the MgO of 0.25g is changed into the Mg of 2.28g 3 (C 6 H 5 O 7 ) 2 ；
The carbonization temperature is changed from 600 ℃ to 700 ℃.
Example 27
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 17, except that:
the MgO of 0.25g is changed into the Mg of 3.04g 3 (C 6 H 5 O 7 ) 2 ；
The carbonization temperature of 600 ℃ is changed into 700 ℃.
Example 28
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 17, except that:
changing 0.25gMgO to 1.52gMg 3 (C 6 H 5 O 7 ) 2 ；
The carbonization temperature of 600 ℃ is changed into 700 ℃.
Table 5 performance results such as specific surface area of biomass-based hierarchical porous carbon prepared in examples 24 to 28
| Examples | S BET (m 2 g -1 ) | S micro (m 2 g -1 ) | S micro /S BET | d aver (nm) | V p (cm 3 g -1 ) |
| Example 24 | 417.36 | 201.79 | 48.35 | 4.58 | 0.16 |
| Example 25 | 329.72 | 177.51 | 53.84 | 4.72 | 0.13 |
| Example 26 | 523.32 | 82.76 | 15.81 | 4.13 | 0.15 |
| Example 27 | 566.76 | 59.64 | 10.52 | 3.95 | 0.16 |
| Example 28 | 623.24 | 81.41 | 13.06 | 3.63 | 0.18 |
Table 5 shows the specific surface area and pore structure parameters of the biomass-based porous carbon materials prepared in examples 24 to 28. In examples 24 to 28, the template underwent a complicated decomposition reaction at the carbonization temperature during the carbonization process to produce magnesium carbonate and magnesium oxide, which further underwent a redox reaction with the matrix C to produce CO 2 The small molecules escape to realize pore-forming; the generated metal Mg compound is removed by acid washing, occupied holes are left, and the finally obtained biomass-based hierarchical porous carbon can form an interpenetrating hole structure. The test data in table 5 shows that the average pore size of the biomass-based porous carbon is between 3 and 6nm, indicating the contribution of macropores and mesopores.
Example 29
Washing passion fruit peel with distilled water to remove impurities, cutting into 0.5cm multiplied by 0.5cm squares, drying in a forced air oven at 85 ℃ for 30h, and grinding to obtain pretreated passion fruit peel powder;
1g of pretreated passion fruit peel powder is added to 10ml0.133g/ml MG (CH) 3 COO) 2 Soaking the biomass in the aqueous solution for 8 hours, and drying the solution in an oven at 80 ℃ for 10 hours to obtain a biomass baseGrading a porous carbon precursor;
placing the biomass-based hierarchical porous carbon precursor into a tubular furnace, heating to 600 ℃ at a heating rate of 5 ℃/min under a nitrogen atmosphere for carbonization for 1h, and naturally cooling to room temperature to obtain the biomass-based hierarchical porous carbon containing the template agent;
the biomass-based hierarchical porous carbon containing the template agent is placed into 0.1mol/L hydrochloric acid water solution to be soaked for 24 hours to remove metal magnesium and compounds of the metal magnesium, so that wet biomass-based hierarchical porous carbon is obtained, the wet biomass-based hierarchical porous carbon is washed to be neutral by deionized water, and is placed into a 50 ℃ drying oven to be dried for 10 hours, so that the biomass-based hierarchical porous carbon is obtained.
Example 30
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 29, except that:
the carbonization temperature of 600 ℃ is changed into 700 ℃.
Example 31
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 29, except that:
the carbonization temperature of 600 ℃ is changed to 800 ℃.
Example 32
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 29, except that:
0.133g/mLMg (CH) 3 COO) 2 The aqueous solution of (2) was changed to 0.067g/mLMg (CH) 3 COO) 2 An aqueous solution of (a);
the carbonization temperature of 600 ℃ is changed into 700 ℃.
Example 33
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 29, except that:
0.133g/mLMg (CH) 3 COO) 2 The aqueous solution of (2) was changed to 0.200g/mLMg (CH) 3 COO) 2 An aqueous solution of (a);
the carbonization temperature of 600 ℃ is changed into 700 ℃.
Example 34
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 29, except that:
0.133g/mLMg (CH) 3 COO) 2 The aqueous solution of (A) was changed to 0.266g/mLMg (CH) 3 COO) 2 An aqueous solution of (a);
the carbonization temperature of 600 ℃ is changed into 700 ℃.
Example 35
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 29, except that:
0.133g/mLMg (CH) 3 COO) 2 The aqueous solution of (2) was changed to 0.333g/mLMg (CH) 3 COO) 2 The aqueous solution of (a);
the carbonization temperature of 600 ℃ is changed into 700 ℃.
Fig. 4 is an SEM image of the biomass-based hierarchical porous carbon prepared in example 35 of the present invention, and it can be seen from fig. 4 that the introduction of magnesium acetate can cause the biomass to generate a large number of pores in the carbonization process, the pore diameter is large, the range of macropores is included, and the layering of the bulk material is more distinct.
Fig. 5 is a pore distribution diagram of the biomass-based hierarchical porous carbon prepared in example 35 of the present invention, and it can be seen from fig. 5 that the biomass-based hierarchical porous carbon provided by the present invention has pore distribution in both the micropore and mesopore scale domains, and it can be seen from the SEM image of fig. 4 that the biomass-based hierarchical porous carbon prepared in this example has a hierarchical pore structure with distinct micropores, mesopores, and macropores.
Table 6 performance results, such as specific surface area, of biomass-based hierarchical porous carbons prepared in examples 29 to 35
From table 6, it can be seen that: the average pore diameter of the biomass-based porous carbon prepared by using magnesium acetate as a template agent is between 5nm and 9nm, which is greater than that of the biomass-based porous carbon material prepared by using magnesium citrate as a template agent, and thus it is known that contribution of the mesoporous and macroporous portions in the biomass-based porous carbons prepared in examples 29 to 35 is greater. The formation of the pore channels is related to the escape of a series of small molecular substances generated by the decomposition of the template agent at high temperature and the reaction with the matrix C material. However, due to the difference of the template agents, the reaction complexity degree generated in the heat treatment process is different, so that a porous structure with different pore channel parameters is obtained, and the method has the advantage that the graded porous material can be prepared.
Example 36
Washing passion fruit peel with distilled water to remove impurities, cutting into 0.5cm multiplied by 0.5cm squares, drying in a forced air oven at 85 ℃ for 30h, and grinding to obtain pretreated passion fruit peel powder;
1g of pretreated passion fruit peel powder is added to 10mL of 0.127 g.ml -1 MgCl 2 Soaking the biomass-based hierarchical porous carbon precursor in the aqueous solution for 8 hours, and drying the aqueous solution in an oven at 80 ℃ for 10 hours to obtain a biomass-based hierarchical porous carbon precursor;
placing the biomass-based hierarchical porous carbon precursor into a tubular furnace, heating to 600 ℃ at a heating rate of 5 ℃/min under a nitrogen atmosphere for carbonization for 1h, and naturally cooling to room temperature to obtain the biomass-based hierarchical porous carbon containing the template agent;
the biomass-based hierarchical porous carbon containing the template agent is placed into 0.1mol/L hydrochloric acid aqueous solution to be soaked for 24 hours to remove metal magnesium and compounds thereof, so that wet biomass-based hierarchical porous carbon is obtained, the wet biomass-based hierarchical porous carbon is washed to be neutral by deionized water and is placed into a 50 ℃ drying oven to be dried for 10 hours, and the biomass-based hierarchical porous carbon is obtained.
Example 37
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 36, except that:
the carbonization temperature of 600 ℃ is changed into 700 ℃.
Example 38
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 36, except that:
the carbonization temperature of 600 ℃ is changed into 800 ℃.
Example 39
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 36, except that:
0.127 g/mL of MgCl 2 The aqueous solution of (a) was changed to 0.064g/mLMgCl 2 An aqueous solution of (a).
Example 40
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 36, except that:
adding 0.127 g/mL MgCl 2 The aqueous solution of (a) was changed to 0.191g/mLMgCl 2 An aqueous solution of (a).
Example 41
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 36, except that: 0.127 g/mL MgCl was added 2 The aqueous solution of (a) was changed to 0.254g/mLMgCl 2 An aqueous solution of (a).
Example 42
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 36, except that: 0.127 g.mL of MgCl 2 The aqueous solution of (a) was changed to 0.318g/mLMgCl 2 An aqueous solution of (a).
Table 7 performance results, such as specific surface area, of biomass-based hierarchical porous carbons prepared in examples 36 to 42
| Examples | S BET (m 2 g -1 ) | S micro (m 2 g -1 ) | S micro /S BET | d aver (nm) | V p (cm 3 g -1 ) |
| Example 36 | 262.45 | 159.08 | 60.61 | 6.83 | 0.10 |
| Example 37 | 160.31 | 96.44 | 60.16 | 8.76 | 0.06 |
| Example 38 | 56.56 | 8.00 | 14.14 | 11.95 | 0.01 |
| Example 39 | 141.68 | 108.31 | 76.45 | 7.14 | 0.06 |
| Example 40 | 271.72 | 168.55 | 62.03 | 9.35 | 0.11 |
| EXAMPLE 41 | 306.12 | 206.19 | 67.36 | 10.36 | 0.13 |
| Example 42 | 322.94 | 196.22 | 60.76 | 9.04 | 0.13 |
From table 7, it can be seen that: with MgCl 2 Specific surface area S of biomass-based porous carbon material prepared for template BET Smaller, but larger average pore size data can be obtained, for example, the average pore size of the material in example 38 is 11.95nm and the average pore size of the material in example 41 is 10.36nm. Due to the template MgCl 2 The carbonization decomposition process is not as complicated as magnesium acetate and magnesium citrate, and the generated small molecular products are less, so that the S of the obtained material is less BET The value is smaller, but the whole material has the possibility of skeleton recombination in the carbonization process, so the material particles are stacked to cause the contribution of a large-pore part to be more, and therefore, the biomass-based porous carbon material with larger average pore diameter is obtained.
Example 43
Washing passion fruit peel with distilled water to remove impurities, cutting into 0.5cm × 0.5cm squares, drying in a forced air oven at 85 ℃ for 30 hours, and grinding to obtain pretreated passion fruit peel powder;
mixing 1g of pretreated passion fruit peel powder with 10mL of water, adding 10mL of graphene oxide solution, carrying out ultrasonic mixing for 30min, wherein the ultrasonic power is preferably 35W to obtain a mixed solution, and drying the mixed solution in an electrothermal blowing drying oven at 80 ℃ for 10h to obtain a passion fruit powder precursor;
placing the passion fruit powder precursor into a tubular furnace, heating to 450 ℃ at a heating rate of 2 ℃/min under the nitrogen atmosphere, carrying out first carbonization treatment for 2h, and naturally cooling to obtain first biomass-based porous carbon;
co-grinding a first biomass-based porous carbon and potassium hydroxide solids for 30min, wherein the mass ratio of the first biomass-based porous carbon to potassium hydroxide is 1: and 3, putting the porous carbon into the tubular furnace again, introducing nitrogen, exhausting air, raising the temperature to 800 ℃ at the speed of 5 ℃/min, carrying out second carbonization treatment for 1h, naturally cooling the obtained product subjected to the second carbonization treatment to room temperature, washing the product subjected to the second carbonization treatment to be neutral by deionized water, and carrying out forced air drying for 24h at the temperature of 50 ℃ to obtain the biomass-based hierarchical porous carbon.
Example 44
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 43, except that:
mixing a first biomass-based porous carbon and potassium hydroxide in a mass ratio of 1: changing 3 into 1:4.
example 45
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 43, except that:
mixing a first biomass-based porous carbon and potassium hydroxide in a mass ratio of 1: changing 3 into 1:2.
example 46
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 43, except that:
10mL of the graphene oxide solution was changed to 5mL.
Example 47
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 43, except that:
the volume of the graphene oxide solution was changed from 10mL to 15mL.
Table 8 performance results such as specific surface area of biomass-based hierarchical porous carbon prepared in examples 43 to 47
| Examples | S BET (m 2 g -1 ) | S micro (m 2 g -1 ) | S micro /S BET | d aver (nm) | V p (cm 3 g -1 ) |
| Example 43 | 1286.99 | 442.56 | 34.39 | 2.62 | 0.44 |
| Example 44 | 91.00 | -- | -- | 2.62 | 0.38 |
| Example 45 | 1300.32 | -- | -- | 2.53 | 0.46 |
| Example 46 | 1336.28 | 336.55 | 25.19 | 2.62 | 0.42 |
| Example 47 | 1460.43 | 364.50 | 24.96 | 2.70 | 0.48 |
Table 8 gives the relevant parameters of the pores of the biomass-based hierarchical porous carbon prepared in examples 43 to 47. The influence of the amount of KOH on the pore structure of the material in the preparation of the biomass-based hierarchical porous carbon is great, and when the mass ratio of the first biomass-based porous carbon to the potassium hydroxide is 1:4 (example 44), a large amount of KOH reacts with the matrix carbon atoms of the first biomass-based porous carbon at high temperature, and K atoms have a strong etching effect on the skeleton of the first biomass porous carbon, so that the skeleton of the first biomass porous carbon material collapses, and the re-stacked and constructed porous carbon material blocks or opens the original microporous structure, so that the specific surface area of the material is reduced. The average pore diameter of the materials prepared in examples 43 to 47 was between 2 and 3nm, and the specific surface area S of the bond BET Data, the pore structures of examples 43, 46 and 47 can be analyzed to be a microporous-mesoporous-macroporous composite hierarchical structure, wherein the average pore diameter is between 2 and 3 nm; the pore structures of examples 44 to 45 are mesoporous-macroporous hierarchical structures, with the contribution of mesopores being more than that of macropores.
Example 48
Mixing 1g of lignin carbon powder with 10mL of water, adding 10mL of graphene oxide solution, carrying out ultrasonic mixing for 30min, wherein the ultrasonic power is preferably 35W to obtain a mixed solution, and drying the mixed solution in an electrothermal blowing dry box at 80 ℃ for 10h to obtain a lignin carbon powder precursor;
putting the lignin carbon powder precursor into a tubular furnace, heating to 450 ℃ at a heating rate of 2 ℃/min under a nitrogen atmosphere for 2h to perform first carbonization treatment, and naturally cooling to obtain first biomass-based porous carbon;
grinding the first biomass-based porous carbon and the potassium hydroxide solid together for 30min, wherein the mass ratio of the first biomass-based porous carbon to the potassium hydroxide is 1: and 3, putting the porous carbon into the tubular furnace again, introducing nitrogen, exhausting air, raising the temperature to 800 ℃ at the speed of 5 ℃/min, carrying out second carbonization treatment for 1h, naturally cooling the obtained product subjected to the second carbonization treatment to room temperature, washing the product subjected to the second carbonization treatment to be neutral by deionized water, and carrying out forced air drying for 24h at the temperature of 50 ℃ to obtain the biomass-based hierarchical porous carbon.
Example 49
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 48, except that:
mixing a first biomass-based porous carbon and potassium hydroxide in a mass ratio of 1: changing 3 into 1:2.
example 50
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 48, except that:
mixing a first biomass-based porous carbon and potassium hydroxide in a mass ratio of 1: changing 3 into 1:4.
example 51
Biomass-based hierarchical porous carbon was prepared with reference to the procedure of example 48, except that:
changing 10mL of graphene oxide solution into 15mL;
mixing a first biomass-based porous carbon and potassium hydroxide in a mass ratio of 1: changing 3 into 1:4.
table 9 performance results, such as specific surface area, of biomass-based hierarchical porous carbons prepared in examples 48 to 51
| Examples | S BET (m 2 g -1 ) | S micr o(m 2 g -1 ) | S micr o/S BET | d aver (nm) | V p (cm 3 g -1 ) |
| Example 48 | 2029.04 | 183.93 | 9.06 | 2.64 | 0.57 |
| Example 49 | 1875.39 | 554.42 | 29.56 | 3.17 | 0.59 |
| Example 50 | 2194.42 | 206.21 | 9.40 | 2.45 | 0.62 |
| Example 51 | 1774.27 | 447.23 | 25.21 | 2.47 | 0.55 |
From table 9 it can be seen that: the biomass-based hierarchical porous carbons provided by the embodiments 48 to 51 of the invention have large specific surface areas and average pore diameters of 2 to 3nm, and belong to micro-mesoporous composite pore structures. In example 50, compared with example 44, the amount of KOH was consistent, and the type of biomass was changed, and the result of comparing the specific surface area was obtained, which shows that in the present invention, the type of biomass, the type of activating agent, the amount of biomass used, and other factors all have great influence on the preparation result of the material, and the ideal biomass porous carbon material with larger specific surface area and controllable pore structure can be obtained by adjusting the type of biomass, the type of activating agent, template agent, and other agents, and the carbonization temperature and the temperature raising rate according to the actual needs.
Comparative example 1
Washing passion fruit peel with distilled water to remove impurities, cutting into 0.2 x 0.2cm squares, and drying in a forced air oven at 95 ℃ for 24 hours; putting the quartz boat filled with the dried passion fruit biomass into a tube furnace, introducing nitrogen, heating to 400 ℃ at the heating rate of 2 ℃/min, carbonizing for 2.5 hours, naturally cooling the carbonized product to room temperature, repeatedly washing the carbonized product with distilled water to be neutral, filtering, and drying for 24 hours at 80 ℃ to obtain the biomass porous carbon.
Fig. 6 is an SEM image of the biomass porous carbon prepared in comparative example 1 of the present invention, and it can be seen from fig. 6 that the material has a bulk layered structure, but the surface has no significant pores.
Comparative example 2
The biomass porous carbon was prepared with reference to the procedure of comparative example 1, except that:
the heating rate of 2 ℃/min is changed into the heating rate of 5 ℃/min;
the carbonization temperature of 400 ℃ is changed to 500 ℃.
Comparative example 3
The biomass porous carbon was prepared with reference to the procedure of comparative example 1, except that:
the carbonization temperature of 400 ℃ is changed to 600 ℃.
Table 10 performance results such as specific surface area of biomass porous carbon prepared in comparative examples 1 to 3
| Comparative example | S BET (m 2 g -1 ) | S micr o(m 2 g -1 ) | S micr o/S BET | d aver (nm) | V p (cm 3 g -1 ) |
| Comparative example 1 | 1.04 | 0.24 | 23.07 | 0.95 | 0.0039 |
| Comparative example 2 | 2.24 | 0.28 | 11.57 | 0.34 | 0.0011 |
| Comparative example 3 | 2.88 | 0.72 | 25.04 | 0.27 | 0.0016 |
As can be seen from table 10: the carbon material prepared by direct carbonization without any treatment has a specific surface area of less than 10m through a BET test 2 The pore volume is virtually zero per gram.
The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be construed as the protection scope of the present invention.
Claims (10)
1. The preparation method of the biomass-based hierarchical porous carbon is characterized by comprising the following steps:
(1) Carrying out pre-carbonization treatment on the biomass to obtain pre-carbonized porous carbon;
(2) Mixing the pre-carbonized porous carbon with an activating agent for carbonization treatment to obtain biomass-based hierarchical porous carbon;
the biomass-based hierarchical porous carbon comprises micropores, mesopores and macropores.
2. The preparation method of claim 1, wherein the activator comprises one or more of phosphoric acid, potassium hydroxide and zinc chloride.
3. The production method according to claim 1 or 2, characterized in that, when the activator is phosphoric acid, the mixing is drying after impregnating the pre-carbonized porous carbon in an aqueous phosphoric acid solution;
when the activator is zinc chloride, the mixing is drying after mixing the pre-carbonized porous carbon with zinc chloride and water.
4. The preparation method of the biomass-based hierarchical porous carbon is characterized by comprising the following steps:
mixing biomass and a template agent for carbonization treatment to obtain a carbonized product, wherein the template agent is a magnesium salt or magnesium oxide;
and removing the template agent in the carbonized product by adopting an acid leaching method to obtain the biomass-based hierarchical porous carbon.
5. The process according to claim 4, wherein the magnesium salt comprises MgCl 2 、Mg(CH 3 COO) 2 And Mg 3 (C 6 H 5 O 7 ) 2 One or more of them.
6. The method of claim 5, wherein the template is MgCl 2 And Mg (CH) 3 COO) 2 In one or both of the above, the mixing is performed by immersing the biomass in an aqueous template solution and then drying the immersed biomass.
7. The method according to claim 4, wherein the temperature of the carbonization treatment is 600 to 800 ℃, the temperature increase rate is 2 to 5 ℃/min, and the time of the carbonization treatment is 1 to 2 hours.
8. The preparation method of the biomass-based hierarchical porous carbon is characterized by comprising the following steps:
(1) Mixing biomass, water and a graphene oxide solution, and drying to obtain a biomass powder precursor;
(2) Performing first carbonization treatment on the biomass powder precursor to obtain first biomass-based porous carbon;
(3) And mixing the first biomass-based porous carbon with potassium hydroxide for second carbonization treatment to obtain the biomass-based hierarchical porous carbon.
9. The method according to claim 8, wherein the temperature of the first carbonization treatment is 400 to 450 ℃, the temperature increase rate is 2 to 10 ℃/min, and the time of the first carbonization treatment is 2 to 6 hours;
the temperature of the second carbonization treatment is 800-900 ℃, the heating rate is 2-5 ℃/min, and the time of the second carbonization treatment is 0.5-5 h.
10. The method according to claim 8, wherein the ratio of the mass of the biomass to the volume of the graphene oxide solution is 1g: 5-25 mL.
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