CN113387355A - Method for preparing porous carbon spheres from biomass raw material - Google Patents
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Abstract
The invention relates to a method for preparing porous carbon spheres by using biomass raw materials, which comprises the following steps of crushing biomass, and uniformly mixing the crushed biomass with a phosphorus-containing acidic solution in proportion; carrying out hydrothermal reaction on the mixed solution obtained in the step to complete hydrolysis and precarbonization of the biomass to obtain a carbon sphere precursor; dehydrating and drying the obtained carbon sphere precursor, then putting the carbon sphere precursor into a pyrolysis furnace, and carrying out fast pyrolysis under the protection of inert atmosphere to obtain porous carbon spheres; the invention forms carbon spheres in the process of fast pyrolysis, and the carbon spheres are generated at high heating rate; the time for forming carbon spheres by subsequent high-temperature activation is greatly shortened by pre-carbonizing in a hydrothermal process.
Description
Technical Field
The invention belongs to the field of carbon sphere preparation, and particularly relates to the field of porous carbon spheres prepared from biomass.
Background
The carbon sphere is a zero-dimensional carbon material and is a new material, and the carbon sphere material draws great attention of the scientific community by virtue of high specific surface area, good conductivity, adjustable porosity, surface functionalization, ordered porous structure, controllable particle size and form distribution, excellent active sites, and mechanical and thermal stability; the application potential of the porous carbon spheres in the directions of supercapacitors, electrocatalysts, electrode materials, heavy metal ion adsorption and the like is because some properties of the porous carbon spheres are very attractive, such as high specific surface area, regular shape, stable structure and the like; the carbon spheres are prepared by using biomass with low price and wide source, particularly porous carbon spheres with high specific surface area are used as electrode materials or catalyst carriers with high stability and the like, so that the high added value and high efficiency utilization of the biomass can be realized; the preparation method of the carbon spheres comprises a chemical vapor deposition method, a template method, a microemulsion polymerization method and a hydrothermal method, wherein the hydrothermal method has mild operation conditions, the size of the obtained carbon spheres is controllable, and the hydrothermal method has a good treatment effect, the hydrothermal process is a thermochemical conversion process carried out in a subcritical water medium under mild operation conditions, but the specific surface area of the carbon spheres obtained by the hydrothermal method is usually low (less than 20m2/g) under the condition of no special treatment, and in order to enrich the pore structure of the prepared carbon spheres, a chemical activating agent is usually required to be introduced, or extra thermal treatment is carried out to regulate and control the pores; the strong corrosion of the chemical activator to the surface of the carbon material and the violent reaction in the heat treatment process make the maintenance of the well-defined spherical shape very difficult; in the prior art, carbohydrate, lignin and derivatives thereof or various resins are mainly used as raw materials, so that the cost is high, and compared with common raw materials such as glucose and lignin, the original biomass has a complex structure and various components, and is not favorable for forming carbon spheres with regular shapes and uniform sizes, so that the application of the biomass raw materials in the preparation of the carbon spheres is greatly limited.
Disclosure of Invention
In order to solve the problems, the invention achieves the purposes through the following technical scheme:
a method for preparing porous carbon spheres by using biomass raw materials comprises the following steps:
crushing biomass and uniformly mixing the crushed biomass with a phosphorus-containing acidic solution in proportion;
step two, carrying out hydrothermal reaction on the mixed solution obtained in the step to complete hydrolysis and pre-carbonization of the biomass to obtain a carbon sphere precursor;
and step three, dehydrating and drying the obtained carbon sphere precursor, then putting the carbon sphere precursor into a pyrolysis furnace, and performing fast pyrolysis under the protection of inert atmosphere to obtain the porous carbon sphere.
As a further optimization scheme of the invention, the hydrothermal reaction is carried out in a subcritical water medium environment with high temperature and high pressure.
As a further optimization scheme of the invention, the biomass comprises any one or a combination of more than two of xylitol, xylose, xylan, glucose, cellobiose, cellulose, starch, hemicellulose, chitosan, chitin, sucrose, fructose, wood, bagasse, corn straw, waste paper, rapeseed cake, jatropha curcas cake, cake meal, vinasse, waste protein, microalgae, plastic waste, recycled plastic and other agricultural and urban solid wastes, food wastes, carbohydrates or lignocellulosic materials.
As a further optimized scheme of the invention, the phosphorus-containing acidic solution is a phosphoric acid aqueous solution or an acidic phosphate solution; the acid phosphate solution is any one of a solution formed by acid phosphate and inorganic acid, a solution formed by acid phosphate and organic acid, a solution formed by non-acid phosphate and inorganic acid and a solution formed by non-acid phosphate and organic acid; the acidic phosphate comprises dipotassium hydrogen phosphate, sodium dihydrogen phosphate and ammonium dihydrogen phosphate, the non-acidic phosphate comprises disodium hydrogen phosphate, sodium phosphate, potassium phosphate, calcium phosphate and ammonium polyphosphate, the inorganic acid comprises hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid, and the organic acid comprises formic acid, acetic acid, citric acid and oxalic acid.
As a further optimization scheme of the invention, the mixing ratio of the phosphorus-containing acidic solution and the biomass particles is controlled between 0.1:1 and 4:1 according to the phosphorus/carbon mass ratio.
As a further optimization scheme of the invention, the temperature of the hydrothermal reaction in the second step is 70-300 ℃.
As a further optimization scheme of the invention, the time of hydrothermal reaction in the second step is 1-24 h.
As a further optimization scheme of the invention, the temperature of the fast pyrolysis in the third step is 350-600 ℃.
As a further optimization scheme of the invention, the time of the fast pyrolysis is 1min-120 min.
The invention has the beneficial effects that:
1) according to the invention, hydrothermal pretreatment is carried out through a phosphorus-containing acidic solution, the processes of biomass hydrolysis, carbonization and recombination are coupled, and then carbon spheres are produced in a fast pyrolysis stage, so that the time required for preparing high-quality carbon spheres is shortened, and the defects are mutually compensated through hydrothermal and fast pyrolysis steps, so that the quality of the porous carbon spheres is improved;
2) forming carbon spheres in the fast pyrolysis process, and generating the carbon spheres at a high heating rate; the time for forming carbon spheres by subsequent high-temperature activation is greatly shortened by pre-carbonizing in a hydrothermal process;
3) the acid hydrothermal process does not need a high-requirement working environment, the requirement on preparation equipment is low, the process operation is simple, and the energy loss is small; the fast pyrolysis process is shorter in time and can repeatedly pyrolyze the acid hydrothermal precursor at the pyrolysis temperature; the preparation efficiency of the carbon spheres is improved, and the method is suitable for mass production.
Drawings
FIG. 1 is an SEM image of porous carbon spheres prepared by acid hydrothermal and fast pyrolysis of biomass;
FIG. 2 is an SEM image of acid hydrothermal products of biomass;
FIG. 3 is a BET detection report of porous carbon spheres prepared by acid hydrothermal and fast pyrolysis of biomass;
FIG. 4 is an isothermal adsorption curve of porous carbon spheres prepared by acid hydrothermal and fast pyrolysis of biomass;
Detailed Description
The present application will now be described in further detail with reference to the drawings, it should be noted that the following detailed description is given for illustrative purposes only and is not to be construed as limiting the scope of the present application, as those skilled in the art will be able to make numerous insubstantial modifications and adaptations to the present application based on the above disclosure.
As shown in fig. 1 to 4, a method for preparing porous carbon spheres from biomass raw material comprises the following steps: the method comprises the following steps:
crushing biomass and uniformly mixing the crushed biomass with a phosphorus-containing acidic solution in proportion;
specifically, firstly, biomass is crushed into particles of 40-80 meshes, and then 4g of the crushed biomass particles are weighed and mixed with a phosphoric acid solution according to a phosphorus/carbon mass ratio of 0.1:1 to 4:1, preferably according to a phosphorus/carbon mass ratio of 3:1 to form a mixture;
wherein the biomass comprises any one or the combination of more than two of agricultural and urban solid wastes, food wastes, carbohydrates or wood fiber materials, such as xylitol, xylose, xylan, glucose, cellobiose, cellulose, starch, hemicellulose, chitosan, chitin, sucrose, fructose, wood, bagasse, corn straws, waste paper, rapeseed cakes, jatropha curcas cakes, vinasse, waste proteins, microalgae, plastic wastes, regenerated plastics and the like;
the phosphorus-containing acidic solution is a phosphoric acid aqueous solution or an acidic phosphate solution, and the acidic phosphate solution is any one of a solution formed by acidic phosphate and inorganic acid, a solution formed by acidic phosphate and organic acid, a solution formed by non-acidic phosphate and inorganic acid and a solution formed by non-acidic phosphate and organic acid; specifically, the acidic phosphate includes dipotassium hydrogen phosphate, sodium dihydrogen phosphate, and ammonium dihydrogen phosphate; the non-acidic phosphate comprises disodium hydrogen phosphate, sodium phosphate, potassium phosphate, calcium phosphate, and ammonium polyphosphate; the inorganic acid comprises hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid; the organic acid includes formic acid, acetic acid, citric acid, oxalic acid;
step two, carrying out hydrothermal reaction on the mixed solution in the step two under the environment of high-temperature and high-pressure subcritical water medium to complete hydrolysis and precarbonization of the biomass to obtain a carbon sphere precursor;
specifically, the mixed solution of the biomass and the phosphorus-containing acidic solution is put into a hydrothermal reaction kettle with the volume of 50ml, heated at the temperature of 200 ℃ for 12 hours and then taken out; after the reaction kettle is cooled to room temperature, pouring the hydrothermal product into a beaker, and dehydrating and drying in a drying oven at 105 ℃ to obtain a carbon sphere precursor;
wherein, the subcritical water medium means that water is heated to a temperature higher than a boiling point and lower than a critical point, and system pressure is controlled to keep the water in a liquid state, and the water in such a state is called subcritical water; under normal conditions, water is a polar compound; under the pressure of 505kPa, the dielectric constant is reduced from 70 to 1 along with the temperature rise (50-300 ℃), namely the property of the solution is gradually changed from strong polarity to non-polarity, and the solute can be extracted from low polarity to high polarity; under the conditions of higher temperature and pressure and lower polarity of water, nonpolar compounds can be extracted;
in the hydrothermal process, the phosphorus-containing acidic solution catalyzes the biomass to carry out hydrolysis, dehydration, decarboxylation, aromatization and repolymerization synergistically, so as to change the original structure of the biomass, and the chemical reactions are carried out under the liquid phase conditions of temperature (180-250 ℃) and holding pressure (10-40 bar); specifically, cellulose, hemicellulose and lignin are hydrolyzed to produce corresponding monosaccharides (mainly glucose) and aromatic compounds, and this process is accelerated by the relatively high hydrogen ion concentration in the acid hydrothermal environment. The monosaccharides thereafter undergo dehydration and cleavage (i.e. ring opening and C-C bond cleavage) processes to yield different soluble products, such as furfural-like compounds, alcohols associated with hydroxymethylfurfural, acids and aldehydes; with the increase of the concentration of soluble products in the solution, the decomposition products and phosphoric acid have polymerization reaction or condensation reaction, including intermolecular dehydration, aldol condensation and the like, to form aromatic clusters and other soluble polymers;
under certain critical conditions (100-; when the carbon spheres reach the nano level, the carbon spheres become a sol system, if the sol system is not uniform, such as the concentration is too high or the reaction time is too long, the carbon spheres are crosslinked and agglomerated, even irregular hydrothermal coke is grown, and the carbon spheres with uniform size can be prepared only by selecting reasonable reaction conditions;
the nucleation is carried out explosively, and the growth is very rapid in the initial time after the nucleation, so that the carbon spheres have large volume and form pores with each other, the pores can increase the surface area of the spheres and are beneficial to the infiltration of phosphoric acid molecules, under the internal environment of a reaction kettle, the raw materials and the phosphoric acid are crosslinked and carbonized to a certain degree to obtain spherical carbon materials with different sizes, and the hydrothermal carbon spheres with required particle size and morphology are obtained by controlling the experimental parameters such as the proportion of reactants, the reaction time, the temperature and the like;
the above description is the process of weakening and reconstructing the original biomass structure by the acid hydrothermal method to obtain the precursor generated by the porous carbon spheres, and at this time, through the operations of the first step and the second step, a small amount of carbon spheres appear on the surface of the product, but the pores are poor, and the specific surface area is low; the specific structure can be seen in figure 2;
in addition, the acid hydrothermal carbonization process usually occurs at a temperature lower than 300 ℃, a series of reactions such as dehydration, polymerization, hydrolysis and the like usually occur, hydrolysis and pre-carbonization of biomass are efficiently completed in the biological hyaluronic acid hydrothermal carbonization process, and the acid hydrothermal carbonization process is a spontaneous adiabatic process, so most of biomass carbon is finally converted into carbon in a carbon material, extra loss is little, the carbon atom efficiency is high, and meanwhile, the acid hydrothermal method has a good ash removal effect compared with common hydrothermal method, is particularly suitable for secondary utilization of waste biomass, and realizes ash removal while mixing and pre-carbonization;
step three, dehydrating and drying the obtained carbon sphere precursor, then putting the carbon sphere precursor into a pyrolysis furnace, and performing fast pyrolysis under the protection of inert atmosphere to obtain porous carbon spheres;
specifically, the carbon sphere precursor is placed into a pyrolysis furnace, fast pyrolysis is carried out under the protection of inert atmosphere, the temperature of the fast pyrolysis furnace is controlled at 450 ℃, the time of the fast pyrolysis is controlled at 5min, and after the fast pyrolysis is carried out, washing, drying and collecting are carried out to obtain the porous carbon spheres.
In the prior art, because the traditional method for preparing the carbon spheres is to modify the formed carbon spheres and needs mild heat treatment conditions, the heat treatment method used for preparing the porous carbon spheres at present is generally slow pyrolysis and has low efficiency; the fast pyrolysis usually adopts high-temperature gas to rapidly treat biomass, has the characteristics of fast temperature rise, short reaction time and the like, but has poor treatment effect on massive or granular materials, so the main target product of the fast pyrolysis technology is bio-oil, the yield of the treated carbon is low, the reaction is violent, the regular spherical structure is difficult to obtain, and the fast pyrolysis technology is not suitable for preparing porous carbon spheres;
in the application, the rapid pyrolysis process is a pretreatment process of acid-water heating, so that the defects of pre-carbonization and structural recombination are well compensated, the biomass structure is more stable in the pre-carbonization process, the transfer of carbon elements to gas-phase and liquid-phase products in the rapid pyrolysis process is reduced, acid hydrolysis products are rapidly dehydrated and polymerized in the rapid pyrolysis process, phosphoric acid and the biomass hydrolysis products are combined in a cross-linking manner, the intermolecular spacing is reduced, the macro expression is that the surface of a carbon material shrinks to form ravines, and the ravines are mutually connected and form a spherical structure along with the development of the ravines;
in addition, the traditional method for preparing the carbon spheres is to form spheres by a hydrothermal method, introduce an activating agent and perform pore regulation and control through heat treatment, and a milder regulation and control strategy is needed to stabilize the structure of the carbon spheres; in the method, the acid hydrothermal reaction is used for weakening the biomass structure to generate a polymer cluster and other biomass hydrolysis products, and in the rapid pyrolysis process, the acid hydrothermal products are further subjected to dehydration polymerization to develop and form regular carbon spheres on the basis of the polymer cluster; in the whole process, phosphoric acid serves as an acid catalyst, promotes bond cracking and crosslinking through cyclization and condensation reaction, and is combined with organic matters to form phosphate and polyphosphate bridges so as to connect and crosslink biopolymer fragments and play a role in activating pore-forming; the short activation time ensures that the carbon spheres are not collapsed due to excessive activation after being generated, and the final effect is achieved.
Example 1
In the embodiment, six different types of biomass raw materials are selected and crushed into particles of 40-80 meshes, 4g of the biomass particles are respectively weighed for standby application, and porous carbon spheres are respectively prepared according to the following steps;
a method for preparing porous carbon spheres by using biomass raw materials comprises the following steps:
crushing biomass into particles of 40-80 meshes;
step two, weighing 4g of crushed biomass particles for standby, then weighing a certain amount of phosphoric acid solution to dilute to 30ml, and controlling the mass ratio of phosphorus to carbon of the biomass in the phosphoric acid solution box to be 3:1 to form a mixture;
step three, putting the mixture into a hydrothermal reaction kettle with the volume of 50ml, heating at the temperature of 200 ℃ for 12 hours, and taking out;
step four, after the reaction kettle is cooled to room temperature, pouring the hydrothermal product into a beaker, and dehydrating and drying in a drying oven at 105 ℃ to obtain a carbon sphere precursor;
and fifthly, putting the carbon spheres into a pyrolysis furnace, performing fast pyrolysis under the protection of inert atmosphere, controlling the temperature of the fast pyrolysis furnace at 450 ℃, controlling the time of the fast pyrolysis at 5min, and after performing fast cooling, washing, drying and collecting to obtain the porous carbon spheres.
Different rapidly pyrolyzed hierarchical-pore phosphorus-doped carbon materials are respectively collected and detected, and the specific surface areas of the phosphorus-doped carbon materials prepared from six different types of biomass are shown in table 1:
TABLE 1 specific surface area and pore volume for preparing porous carbon spheres from different kinds of biomass raw materials
Example 2
In the embodiment, wood chips are used as biomass raw materials, and the influence of different phosphorus sources and acid sources on the properties of the porous carbon spheres is tested, wherein the hydrothermal temperature is 200 ℃, the hydrothermal time is 12 hours, the pyrolysis temperature is 450 ℃, and the pyrolysis time is 5 min; the specific operation steps are similar to the example 1, only the types of the phosphorus source and the acid source are changed, and the PH of the solution is controlled to be less than 3 by controlling the amount of the added acid source;
TABLE 2 specific surface area and elemental composition for preparation of porous carbon spheres from different phosphorus and acid sources
Example 3
In this example, wood chips were used as biomass raw material, and the influence of 4 different phosphorus-carbon ratios on the properties of porous carbon spheres was tested, where the hydrothermal temperature in this experiment was 200 ℃, the hydrothermal time was 12h, the pyrolysis temperature was 450 ℃, and the pyrolysis time was 5min. The specific procedure was similar to example 1, with only the phosphorus to carbon ratio being varied.
TABLE 3 specific surface area and pore volume for preparing porous carbon spheres with different phosphorus to carbon ratios
Example 4
In this example, wood chips were used as biomass raw material, and the influence of 4 different hydrothermal temperatures on the properties of porous carbon spheres was tested, where the phosphorus-carbon ratio in this experiment was 3:1, the hydrothermal time was 12h, the pyrolysis temperature was 450 ℃, and the pyrolysis time was 5min. The specific procedure was similar to example 1, with only the hydrothermal temperature being varied.
TABLE 4 specific surface area and pore volume for preparing porous carbon spheres with different hydrothermal reaction times
Example 5
In this example, wood chips were used as biomass raw material, and the influence of 4 different hydrothermal times on the properties of porous carbon spheres was tested, and the phosphorus-carbon ratio in this experiment was 3:1, hydrothermal temperature of 200 ℃, pyrolysis temperature of 450 ℃ and pyrolysis time of 5min, the specific operation steps were similar to those of example 1, only the hydrothermal time was changed.
TABLE 5 specific surface area and pore volume for preparation of porous carbon spheres at different hydrothermal times
Example 6
In this embodiment, with the saw dust as biomass raw material, test 7 different pyrolysis temperatures to the influence of porous carbon sphere nature, this experiment phosphorus-carbon ratio is 3:1, the hydrothermal temperature is 200 ℃, the hydrothermal time is 12 hours, and the pyrolysis time is 5min. The specific procedure was similar to example 1, with only the pyrolysis temperature being varied.
TABLE 6 specific surface area and pore volume for preparation of porous carbon spheres at different pyrolysis temperatures
Example 7
In this example, the wood chips are used as biomass raw materials, the influence of 6 different pyrolysis times on the properties of the porous carbon spheres is tested, and the phosphorus-carbon ratio in this experiment is 3:1, the hydrothermal temperature is 200 ℃, the hydrothermal time is 12h, and the pyrolysis temperature is 450 ℃. The specific procedure was similar to example 1, with only the pyrolysis time being varied.
TABLE 7 specific surface area and pore volume for preparation of porous carbon spheres with different pyrolysis times
The shape, the particle size and the surface pore structure of the carbon sphere can be changed by different hydrothermal doping amounts of phosphoric acid, hydrothermal time and temperature, and the hydrothermal carbon with the required particle size can be obtained by different reaction conditions of acid hydrothermal pretreatment in the early stage; the spherical carbon spheres formed in the precursor have uniform particle size and are regular spheres, so that reliable guarantee is provided for the continuous optimization of the formation of the carbon spheres by the later-stage fast pyrolysis;
the specific surface area of the carbon spheres decreases as the hydrothermal temperature increases, and the average pore diameter of the carbon spheres increases as the hydrothermal temperature increases. Dispersing carbon spheres and gradually roughening the surface; the change of the temperature can obviously influence the balling degree and the dispersity of the carbon spheres;
when the hydrothermal temperature is 80 ℃, the biomass is not subjected to complete dehydration condensation, so that no carbon spheres are formed; when the hydrothermal temperature is increased to 140 ℃, spherical morphology begins to be formed, but the decomposition and carbon sphere growth processes are slow; when the hydrothermal temperature reaches 200 ℃, monodisperse carbon spheres with uniform size can be obtained, because the proper temperature has more balanced processes of dehydration, condensation, nucleation and growth, thereby avoiding agglomeration caused by adhesion; with the further increase of the hydrothermal temperature (more than 200 ℃), the carbon spheres are crosslinked, the sphericity is deteriorated, and irregular hydrothermal coke appears, because the biomass is rapidly decomposed due to the overhigh temperature, small molecules rapidly move and form crystal nuclei rapidly, and the crystal nuclei continuously absorb the surrounding small molecules and collide with each other and are entangled and crosslinked together, so that a large amount of irregular hydrothermal coke is formed;
therefore, the optimal hydrothermal temperature for preparing the carbon spheres is 200 ℃, when the hydrothermal temperature reaches 200 ℃, the surface wrinkles of the carbon spheres are obvious, and the carbon spheres are extruded and deformed, which shows that the stability of the carbon spheres is deteriorated due to the excessively high hydrothermal temperature;
meanwhile, too short hydrothermal time causes that small molecules cannot complete the nucleation and growth processes, so that the yield of carbon spheres is extremely low; when the hydrothermal time is increased to 12h, the carbon spheres with uniform size can be obtained due to sufficient nucleation and growth processes of the carbon spheres, the formed carbon spheres are continuously changed along with the further increase of the hydrothermal time, the crosslinking phenomenon is generated among the carbon spheres, the crosslinking phenomenon is more serious along with the increase of the hydrothermal time, and the spherical appearance is seriously damaged; therefore, the selection of the proper hydrothermal time is the key to obtain the carbon spheres with uniform size, and the optimal hydrothermal time is 12 h.
Comparative example 1
In this comparative example, the effect on the properties of a phosphorus-doped biomass carbon material was tested using only a hydrothermal reaction of biomass with a phosphorus-containing acidic solution, i.e., without a fast pyrolysis process, using wood chips as the biomass feedstock, with a phosphorus-to-carbon ratio of 3:1, the hydrothermal temperature is 200 ℃, the pyrolysis temperature is 450 ℃, and the pyrolysis time is 5min, the specific operation steps are similar to those of example 1;
a method for preparing porous carbon spheres by using biomass raw materials comprises the following steps:
crushing biomass into particles of 40-80 meshes;
step two, weighing 4g of crushed biomass particles for standby, then weighing a certain amount of phosphoric acid solution to dilute to 30ml, and controlling the mass ratio of phosphorus to carbon of the biomass in the phosphoric acid solution box to be 3:1 to form a mixture;
step three, putting the mixture into a hydrothermal reaction kettle with the volume of 50ml, heating at the temperature of 200 ℃ for 12 hours, and taking out;
step four, after the reaction kettle is cooled to room temperature, pouring the hydrothermal product into a beaker, and dehydrating and drying in a drying oven at 105 ℃ to obtain a carbon sphere precursor;
collecting the carbon sphere precursor and detecting;
comparing the SEM images of fig. 1 and 2, it can be seen from the SEM images that the specific surface area and the total pore volume of the carbon spheres obtained after hydrothermal treatment are small, and the pore structure is mostly microporous, while the nitrogen adsorption and desorption curve of the carbon spheres prepared by acid-water thermal combination of the carbon spheres obtained by fast pyrolysis is an iv-type adsorption curve, the pore structure is changed from microporous to mesoporous, and the specific surface area and the mesoporous pore volume of the carbon spheres are increased.
The carbon microspheres prepared by the acid hydrothermal method have low graphitization degree, almost are in an amorphous state, and the yield of the carbon microspheres is low, so that the graphitization degree of the carbon microspheres needs to be improved by combining high-temperature heat treatment, the hydrothermal carbon spheres are subjected to graphitization treatment in a nitrogen environment in a quick pyrolysis process, the carbon nanospheres subjected to high-temperature treatment are subjected to sphere contraction, the graphitization degree is improved, and the carbon spheres are convenient to form.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.
Claims (9)
1. A method for preparing porous carbon spheres by using biomass raw materials is characterized by comprising the following steps: the method comprises the following steps:
crushing biomass and uniformly mixing the crushed biomass with a phosphorus-containing acidic solution in proportion;
step two, carrying out hydrothermal reaction on the mixed solution obtained in the step to complete hydrolysis and pre-carbonization of the biomass to obtain a carbon sphere precursor;
and step three, dehydrating and drying the obtained carbon sphere precursor, then putting the carbon sphere precursor into a pyrolysis furnace, and performing fast pyrolysis under the protection of inert atmosphere to obtain the porous carbon sphere.
2. The method for preparing the porous carbon spheres from the biomass raw material as claimed in claim 1, wherein the method comprises the following steps: the hydrothermal reaction is carried out in a subcritical water medium environment with high temperature and high pressure.
3. The method for preparing the porous carbon spheres from the biomass raw material as claimed in claim 1, wherein the method comprises the following steps: the biomass comprises any one or the combination of more than two of agricultural and urban solid wastes, food wastes, carbohydrates or wood fiber materials, such as xylitol, xylose, xylan, glucose, cellobiose, cellulose, starch, hemicellulose, chitosan, chitin, sucrose, fructose, wood, bagasse, corn straws, waste paper, rapeseed cakes, jatropha curcas cakes, vinasse, waste proteins, microalgae, plastic wastes, regenerated plastics and the like.
4. The method for preparing the porous carbon spheres from the biomass raw material as claimed in claim 1, wherein the method comprises the following steps: the phosphoric acid-containing solution is phosphoric acid aqueous solution or acid phosphate solution; the acid phosphate solution is any one of a solution formed by acid phosphate and inorganic acid, a solution formed by acid phosphate and organic acid, a solution formed by non-acid phosphate and inorganic acid and a solution formed by non-acid phosphate and organic acid; the acidic phosphate comprises dipotassium hydrogen phosphate, sodium dihydrogen phosphate and ammonium dihydrogen phosphate, the non-acidic phosphate comprises disodium hydrogen phosphate, sodium phosphate, potassium phosphate, calcium phosphate and ammonium polyphosphate, the inorganic acid comprises hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid, and the organic acid comprises formic acid, acetic acid, citric acid and oxalic acid.
5. The method for preparing the porous carbon spheres from the biomass raw material as claimed in claim 1, wherein the method comprises the following steps: the mixing ratio of the phosphorus-containing acidic solution and the biomass particles is controlled to be between 0.1:1 and 4:1 according to the phosphorus/carbon mass ratio.
6. The method for preparing the porous carbon spheres from the biomass raw material as claimed in claim 1, wherein the method comprises the following steps: the temperature of the hydrothermal reaction in the second step is 70-300 ℃.
7. The method for preparing the porous carbon spheres from the biomass raw material as claimed in claim 1, wherein the method comprises the following steps: the time of hydrothermal reaction in the second step is 1-24 h.
8. The method for preparing the porous carbon spheres from the biomass raw material as claimed in claim 1, wherein the method comprises the following steps: the temperature of the fast pyrolysis in the third step is 350-600 ℃.
9. The method for preparing the porous carbon spheres from the biomass raw material as claimed in claim 1, wherein the method comprises the following steps: the time of the fast pyrolysis in the third step is 1min-120 min.
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| CN113816359A (en) * | 2021-10-20 | 2021-12-21 | 长春工业大学 | Method for preparing porous carbon material by biomass low-temperature hydrothermal and low-temperature carbonization |
| CN115181574A (en) * | 2022-08-15 | 2022-10-14 | 施可丰化工股份有限公司 | Saline-alkali soil conditioner and preparation method thereof |
| CN115240987A (en) * | 2022-05-17 | 2022-10-25 | 中国计量大学 | Woven mesh-shaped composite structure carbon and preparation method and application thereof |
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| CN116425149A (en) * | 2023-04-03 | 2023-07-14 | 哈尔滨工程大学 | Preparation method of graphene-like micro-nanospheres serving as lithium ion battery anode material |
| CN117285027A (en) * | 2023-11-24 | 2023-12-26 | 成都锂能科技有限公司 | Crosslinked starch derived carbon sphere and preparation method and application thereof |
| CN117285027B (en) * | 2023-11-24 | 2024-02-02 | 成都锂能科技有限公司 | Crosslinked starch derived carbon sphere and preparation method and application thereof |
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