CN108726517B - Method for improving volume specific capacitance of rice hull-based capacitance carbon - Google Patents
Method for improving volume specific capacitance of rice hull-based capacitance carbon Download PDFInfo
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- CN108726517B CN108726517B CN201810807326.3A CN201810807326A CN108726517B CN 108726517 B CN108726517 B CN 108726517B CN 201810807326 A CN201810807326 A CN 201810807326A CN 108726517 B CN108726517 B CN 108726517B
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 85
- 235000007164 Oryza sativa Nutrition 0.000 title claims abstract description 80
- 235000009566 rice Nutrition 0.000 title claims abstract description 80
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 76
- 238000000034 method Methods 0.000 title claims abstract description 27
- 240000007594 Oryza sativa Species 0.000 title 1
- 241000209094 Oryza Species 0.000 claims abstract description 79
- 239000010426 asphalt Substances 0.000 claims abstract description 55
- 239000002296 pyrolytic carbon Substances 0.000 claims abstract description 34
- 239000003054 catalyst Substances 0.000 claims abstract description 19
- 238000007598 dipping method Methods 0.000 claims abstract description 6
- 238000010438 heat treatment Methods 0.000 claims description 67
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 24
- 238000001816 cooling Methods 0.000 claims description 21
- 238000001035 drying Methods 0.000 claims description 20
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 16
- 239000000203 mixture Substances 0.000 claims description 16
- 230000003197 catalytic effect Effects 0.000 claims description 15
- 238000002156 mixing Methods 0.000 claims description 15
- 239000007788 liquid Substances 0.000 claims description 13
- 238000006243 chemical reaction Methods 0.000 claims description 12
- 239000000843 powder Substances 0.000 claims description 12
- 238000005470 impregnation Methods 0.000 claims description 10
- 230000007935 neutral effect Effects 0.000 claims description 10
- 238000005406 washing Methods 0.000 claims description 10
- 239000012065 filter cake Substances 0.000 claims description 9
- 239000007787 solid Substances 0.000 claims description 9
- 239000002904 solvent Substances 0.000 claims description 9
- 229910052757 nitrogen Inorganic materials 0.000 claims description 8
- 230000008569 process Effects 0.000 claims description 7
- 238000000967 suction filtration Methods 0.000 claims description 7
- 239000000725 suspension Substances 0.000 claims description 7
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 6
- 239000003513 alkali Substances 0.000 claims description 6
- 239000012535 impurity Substances 0.000 claims description 6
- 239000011812 mixed powder Substances 0.000 claims description 6
- 238000012216 screening Methods 0.000 claims description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 5
- 238000010992 reflux Methods 0.000 claims description 5
- 238000003756 stirring Methods 0.000 claims description 5
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 claims description 4
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 claims description 4
- 239000002243 precursor Substances 0.000 claims description 4
- 238000002360 preparation method Methods 0.000 claims description 4
- 238000007789 sealing Methods 0.000 claims description 4
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 claims description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 2
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 claims description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 2
- 238000010000 carbonizing Methods 0.000 claims description 2
- HPXRVTGHNJAIIH-UHFFFAOYSA-N cyclohexanol Chemical compound OC1CCCCC1 HPXRVTGHNJAIIH-UHFFFAOYSA-N 0.000 claims description 2
- 239000008367 deionised water Substances 0.000 claims description 2
- 229910021641 deionized water Inorganic materials 0.000 claims description 2
- 238000001914 filtration Methods 0.000 claims description 2
- 238000002791 soaking Methods 0.000 claims description 2
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 claims description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 2
- 230000018044 dehydration Effects 0.000 abstract description 8
- 238000006297 dehydration reaction Methods 0.000 abstract description 8
- 239000002028 Biomass Substances 0.000 abstract description 7
- 238000000197 pyrolysis Methods 0.000 abstract description 7
- 230000004048 modification Effects 0.000 abstract description 3
- 238000012986 modification Methods 0.000 abstract description 3
- 230000001351 cycling effect Effects 0.000 abstract description 2
- 238000002309 gasification Methods 0.000 abstract description 2
- 239000000126 substance Substances 0.000 abstract description 2
- 239000000463 material Substances 0.000 description 8
- 239000002245 particle Substances 0.000 description 8
- 239000003990 capacitor Substances 0.000 description 7
- 239000002994 raw material Substances 0.000 description 6
- 239000010903 husk Substances 0.000 description 5
- 230000007613 environmental effect Effects 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 238000001994 activation Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000007772 electrode material Substances 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 239000000706 filtrate Substances 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 230000004913 activation Effects 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 238000007233 catalytic pyrolysis Methods 0.000 description 1
- 238000010277 constant-current charging Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 235000019441 ethanol Nutrition 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/30—Active carbon
- C01B32/312—Preparation
- C01B32/318—Preparation characterised by the starting materials
- C01B32/324—Preparation characterised by the starting materials from waste materials, e.g. tyres or spent sulfite pulp liquor
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/30—Active carbon
- C01B32/312—Preparation
- C01B32/342—Preparation characterised by non-gaseous activating agents
- C01B32/348—Metallic compounds
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
- H01G11/32—Carbon-based
- H01G11/34—Carbon-based characterised by carbonisation or activation of carbon
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
- H01G11/32—Carbon-based
- H01G11/44—Raw materials therefor, e.g. resins or coal
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
- H01G11/86—Processes for the manufacture of hybrid or EDL capacitors, or components thereof specially adapted for electrodes
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Abstract
The invention discloses a method for improving the volume specific capacitance of rice hull-based capacitance carbon, which belongs to the field of biomass energy chemical industry, and adopts three methods to improve tap density and volume specific capacitance; in particular to: (1) the dehydration fixed carbon catalyst is adopted for dipping treatment, and the fixed carbon content is increased by temperature-controlled pyrolysis; (2) after the pyrolytic carbon is subjected to hydrothermal desiliconization, the template carbon is treated by using impregnated asphalt to fill micropores caused by gasification, so that the tap density is improved; (3) the electrode asphalt is used for modifying the surface of the capacitance carbon, so that the conductivity and the tap density are improved. Compared with the prior art, the rice hull-based capacitance carbon is prepared by different modification treatment methods, so that the tap density, the volume specific capacitance, the cycling stability and the capacitance carbon yield of the capacitance carbon are improved.
Description
Technical Field
The invention belongs to the field of biomass energy chemical industry, discloses a method for improving the volume specific capacitance of rice hull-based capacitance carbon, and particularly relates to a method for improving the volume specific capacitance of rice hull carbon by impregnating rice hulls with a dehydration solid carbon catalyst, treating template carbon by impregnating pitch, and modifying the capacitance carbon by electrode pitch.
Background
The biomass material has the characteristics of wide source, environmental friendliness and the like. In recent years, the preparation of capacitance carbon by using biomass as a raw material has attracted much attention. The rice hulls are renewable biomass resources with low price and huge yield, and the capacitance carbon prepared by taking the rice hulls as a raw material has a multi-stage pore canal structure and a larger specific surface area, but the rice hull-based capacitance carbon serving as the electrode material of the super capacitor has the main problems that the rice hull fixed carbon content is low, the volume ratio capacitance of the super capacitor is small, and the volume of the super capacitor is larger when the capacitance of unit mass is stored, so that the commerciality of the super capacitor is lower, and the super capacitor is not beneficial to practical application.
In order to improve the volume specific capacitance of the rice hull-based capacitance carbon, the rice hull is treated by a dehydration solid carbon catalyst and then pyrolyzed, desiliconized pyrolytic carbon is modified by using impregnated asphalt, and the rice hull-based capacitance carbon is treated by using electrode asphalt after being activated. Asphalt is a material with high fixed carbon content and good conductivity, and the desiliconized pyrolytic carbon and activated carbon are modified by the asphalt, so that the tap density of the material can be improved, the volume specific capacitance is improved, and the conductivity of the material is also increased, so that the electrochemical performance is improved. The dehydration solid carbon catalyst catalyzes the dehydration of the rice husk in the pyrolysis process, controls the temperature, increases the dehydration time of the rice husk in the pyrolysis process, and reduces the generation of gas phase and liquid phase, thereby increasing the content of solid phase, further improving the yield of the rice husk carbon and improving the volume ratio capacitance of capacitance carbon.
The problems of the existing rice hull-based capacitance carbon are as follows:
1. a large amount of carbon of the rice hulls is lost in a gas state and a liquid state in the pyrolysis process, and the fixed carbon content is low;
2. the rice hull capacitance carbon has poor conductivity, so that electrolyte ions are difficult to transport;
3. the tap density is low, and the volume specific capacitance is influenced.
There is therefore a need in the art for a new solution to this problem.
Disclosure of Invention
In the rice hull pyrolysis process, volatile components escape to form a large number of micropores, the tap density of pyrolytic carbon is low, after desiliconization and activation, the tap density of capacitance carbon is lower, so that the volume specific capacitance is low, and the storage capacity of a capacitor with the same volume is low, so that the application of rice hull carbon (or biomass carbon) in the fields of energy storage batteries and supercapacitors is limited. The prepared material has the characteristics of good electrochemical stability, high volume specific capacitance and high capacity of the electrode material of the super capacitor, and has the advantages of low cost, small pollution, environmental friendliness and large-scale production.
In order to achieve the purpose, the invention adopts the following technical scheme: the method for improving the volume specific capacitance of the rice hull-based capacitance carbon is characterized by comprising the following steps of:
screening rice hulls to remove impurities, crushing to obtain rice hull powder, mixing the rice hull powder with a catalyst solution, then carrying out impregnation treatment, cooling to room temperature after the impregnation treatment is finished, carrying out suction filtration, and drying a filter cake at 80-100 ℃ to obtain pretreated rice hulls;
step two, placing the pretreated rice hulls prepared in the step one in a tubular furnace, firstly heating to 200-300 ℃, pyrolyzing for 0.5h, then heating to 500-600 ℃, pyrolyzing for 1h under the protection of nitrogen, and cooling to room temperature to obtain pyrolytic carbon;
step three, according to the solid-liquid ratio of 1Kg: adding the pyrolytic carbon obtained in the step two and a NaOH solution with the concentration of 5 wt% into a reaction kettle according to the proportion of 10L, heating and refluxing for 2h, cooling, filtering and separating, washing a filter cake to be neutral, and drying to obtain desiliconized pyrolytic carbon;
step four, uniformly mixing the desiliconized pyrolytic carbon obtained in the step three with impregnated asphalt, placing the mixture in a reaction kettle, heating to 150-250 ℃, impregnating for 2-5 h under the pressure of 0.1-0.6 MPa, and cooling to obtain an asphalt impregnated precursor;
transferring the pitch impregnation precursor obtained in the step four into a tubular furnace, heating to 600-1000 ℃, and carbonizing for 1-2 h to prepare pitch impregnation pyrolytic carbon;
step six, treating the pitch impregnated pyrolytic carbon prepared in the step five to obtain carbon powder, uniformly mixing the carbon powder and alkali according to a carbon-alkali ratio of 1 (2.0-2.5), placing the mixture in a tubular furnace, heating to 450 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 0.5h, continuing heating to 700 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 1h, cooling to room temperature, taking out the mixture, washing the mixture to be neutral by using hot deionized water, and drying at 120 ℃ to prepare the catalytic rice hull/pitch-based capacitive carbon.
The method for improving the volume specific capacitance of the rice hull-based capacitance carbon is characterized by further comprising the following steps:
step seven, preparing asphalt modified capacitance carbon:
(1) adding the catalytic rice hull/asphalt-based capacitance carbon prepared in the sixth step into an asphalt suspension, stirring and dispersing for 0.5-2 h, heating to recover the solvent, placing the solid in a drying box, and drying at 85 ℃ for 5-12 h to prepare asphalt/capacitance carbon mixed powder;
(2) and (2) transferring the asphalt/capacitance carbon mixed powder prepared in the step (1) to a tubular furnace, heating to 150-250 ℃ under the protection of nitrogen, carrying out constant-temperature heat treatment for 1-2 h, heating to 600-1000 ℃ again, carrying out constant-temperature heat treatment for 1-2 h, cooling, and scattering to prepare the asphalt modified capacitance carbon.
The impregnation treatment process in the first step is as follows: adding the rice hull powder and the catalyst solution into a reaction kettle, sealing, heating by using steam at the temperature of 120-130 ℃, and pressurizing and dipping for 1 h; or the temperature of the heating system is 30-50 ℃, and the soaking is carried out for 24h at constant temperature.
The catalyst in the first step is NH4Cl、NH4OH、HCl、H2SO4、H3PO4One or a mixture of more than two of the above.
The mass concentration of the catalyst solution in the first step is 0-20%.
The solid-to-liquid ratio of the rice hull powder and the catalyst solution in the first step is 1Kg (5-20) L.
The preparation method of the asphalt suspension in the seventh step comprises the following steps: and adding asphalt powder into the solvent, and stirring and dispersing for 0.5-2 h to obtain an asphalt suspension.
In the seventh step, the solid content ratio of the asphalt to the catalytic rice hull/asphalt-based capacitance carbon is (10-30): 100.
and the solvent in the seventh step is one or a mixture of two of cyclohexanol, absolute ethyl alcohol, acetone, tetrahydrofuran, cyclohexane and n-hexane.
The solid-liquid ratio of the asphalt to the solvent is 5 Kg-15 Kg to 100L.
Through the design scheme, the invention can bring the following beneficial effects:
1. the used rice hull is a renewable biomass resource, and the preparation process is pollution-free and low in price; the asphalt material has wide source, low cost and environmental protection, and can be produced in large scale.
2. The solid carbon catalyst is used for treating the rice hulls to promote dehydration, reduce the loss of gas phase and liquid phase of the rice hulls in the carbonization process and increase the content of the fixed carbon.
3. The asphalt can form a flowing state when reaching the softening point temperature, and the flowing asphalt can modify the modified pyrolytic carbon in the activation process, so that the electrochemical performance of the material is effectively improved.
4. The fixed carbon content of the asphalt is high, and the asphalt and the rice hull pyrolytic carbon are co-activated to improve the tap density of the activated carbon, so that the volume specific capacitance of the material is improved.
5. The template carbon is treated by using the dipping pitch, fine carbon powder is coated on the surface of the particles to be uniform in particle size, micropores caused by gasification are filled, and the tap density is improved.
Drawings
FIG. 1 is a schematic diagram of the specific capacitance and cycle number of 20000 constant current charging/discharging times when the current density is 1A/g in examples 1 and 2 of the present invention.
Detailed Description
In order to more clearly illustrate the invention, the invention is further described below in connection with preferred embodiments. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention. Well-known methods and procedures have not been described in detail so as not to obscure the present invention.
Example 1
(1) Screening raw material rice hulls to remove impurities, and crushing to obtain rice hull powder with the particle size of 10-20 mm for later use;
(2) placing the rice hull powder obtained in the step (1) in a tubular furnace, heating to 200 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, carrying out pyrolysis dehydration for 0.5h, heating to 500 ℃ at a heating rate of 5 ℃/min, and carrying out pyrolysis for 1h to obtain pyrolytic carbon;
(3) mixing the pyrolytic carbon obtained in the step (2) with a NaOH solution with the concentration of 5 wt% according to the solid-to-liquid ratio of 1Kg to 10L, heating and refluxing for 2h, cooling to room temperature, performing suction filtration, washing a filter cake to be neutral, and drying to obtain desiliconized rice hull pyrolytic carbon;
(4) adding the desiliconized rice hull pyrolytic carbon obtained in the step (3) and sodium hydroxide into a high-speed mixer according to the mass ratio of 1:2.5, uniformly mixing, transferring into a nitrogen-protected tube furnace, heating to 450 ℃ at the heating rate of 5 ℃/min, keeping for 0.5h, heating to 700 ℃ at the heating rate of 5 ℃/min, keeping for 1h, cooling to room temperature, washing to be neutral, and drying at 120 ℃ to obtain the rice hull-based capacitance carbon AC 1.
Example 2
(1) Screening raw material rice hull to remove impurities, crushing to 10-20 mm particle size and 5 wt% NH41Kg of OH solution according to the solid-to-liquid ratio: adding 10L of the rice husk into a reaction kettle, sealing and heating to 120 ℃, pressurizing and dipping for 1h, reducing the temperature to room temperature, then carrying out suction filtration, adjusting the concentration of filtrate, recycling, and drying a filter cake at 100 ℃ to obtain a catalyst for treating the rice husk for later use;
(2) putting the rice hulls treated by the catalyst obtained in the step (1) into a tubular furnace, heating to 200 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, pyrolyzing for 0.5h, heating to 500 ℃ at a heating rate of 5 ℃/min, and pyrolyzing for 1h to obtain pyrolytic carbon;
(3) mixing the pyrolytic carbon obtained in the step (2) with a NaOH solution with the concentration of 5 wt% according to the solid-to-liquid ratio of 1Kg to 10L, heating and refluxing for 2h, cooling to room temperature, performing suction filtration, washing a filter cake to be neutral, and drying to obtain desiliconized pyrolytic carbon;
(4) adding the desiliconized pyrolytic carbon obtained in the step (3) and sodium hydroxide into a nitrogen-protected tubular furnace according to the carbon-alkali mass ratio of 1:2.5, heating to 450 ℃ at the heating rate of 5 ℃/min, keeping for 0.5h, heating to 700 ℃ at the heating rate of 5 ℃/min, keeping for 1h, cooling to room temperature, washing to be neutral, and drying at 120 ℃ to obtain the catalytic rice hull-based capacitance carbon AC 2.
Example 3
(1) Screening raw material rice hull to remove impurities, crushing to 10-20 mm particle size and 5 wt% NH4Adding an OH solution into a reaction kettle according to the solid-to-liquid ratio of 1Kg to 10L, sealing and heating to 120 ℃, pressurizing and dipping for 1h, cooling to room temperature, carrying out suction filtration, adjusting the concentration of filtrate, recycling, and drying a filter cake at 100 ℃ to obtain a catalyst for treating rice hulls for later use;
(2) putting the rice hulls treated by the catalyst obtained in the step (1) into a tubular furnace, heating to 200 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, pyrolyzing for 0.5h, heating to 500 ℃ at the heating rate, and pyrolyzing for 1h to obtain catalytic pyrolysis carbon;
(3) mixing the catalytic pyrolytic carbon obtained in the step (2) with a NaOH solution with the concentration of 5 wt% according to the solid-to-liquid ratio of 1Kg to 10L, heating and refluxing for 2h, cooling to room temperature, performing suction filtration, washing a filter cake to be neutral, and drying to obtain desiliconized pyrolytic carbon;
(4) uniformly mixing the desiliconized pyrolytic carbon obtained in the step (3) with impregnated asphalt according to the mass ratio of 4:1, placing the mixture in a reaction kettle, heating to 200 ℃, impregnating for 2 hours under the pressure of 0.5MPa, and cooling to obtain asphalt impregnated pyrolytic carbon;
(5) and (3) adding the asphalt-impregnated pyrolytic carbon obtained in the step (4) and sodium hydroxide into a nitrogen-protected tubular furnace according to the mass ratio of carbon to alkali of 1:2.5, heating to 450 ℃ at the heating rate of 5 ℃/min, keeping for 0.5h, heating to 700 ℃ at the heating rate of 5 ℃/min, keeping for 1h, cooling to room temperature, washing to be neutral, and drying at 120 ℃ to obtain the catalytic rice hull/asphalt-based capacitive carbon AC 3.
Example 4
Uniformly mixing the desiliconized pyrolytic carbon obtained in the step (3) with the impregnated asphalt according to the mass ratio of 6:1, placing the mixture in a reaction kettle, and obtaining catalytic rice hull/asphalt-based capacitive carbon AC4 under the same conditions as in the example 3.
Example 5
Uniformly mixing the desiliconized pyrolytic carbon obtained in the step (3) with the impregnated asphalt according to the mass ratio of 8:1, placing the mixture in a reaction kettle, and obtaining catalytic rice hull/asphalt-based capacitive carbon AC5 under the same conditions as in the example 3.
Example 6
Uniformly mixing the desiliconized pyrolytic carbon obtained in the step (3) with the impregnated asphalt according to the mass ratio of 10:1, placing the mixture in a reaction kettle, and obtaining the catalytic rice hull/asphalt-based capacitive carbon AC6 under the same conditions as in the example 3.
Example 7
Screening and removing impurities from raw material rice hulls, crushing the rice hulls into particles with the particle size of 10-20 mm, mixing the particles with HCl solution with the mass concentration of 2% according to the solid-liquid ratio of 1Kg to 10L, and obtaining the catalytic rice hull/asphalt-based capacitance carbon AC7 under the other conditions consistent with the embodiment 3.
Example 8
(1) Adding the catalytic rice hull/asphalt-based capacitance carbon prepared in example 3 into an electrode asphalt ethanol suspension according to a dry-basis mass ratio of 4:1, stirring and dispersing for 1h, heating to recover a solvent, placing the solid in a drying oven, and drying at 85 ℃ for 5 h-12 h to prepare asphalt/capacitance carbon mixed powder;
(2) and transferring the asphalt/capacitance carbon mixed powder into a tube furnace, heating to 200 ℃ under the protection of nitrogen, carrying out constant-temperature heat treatment for 1h, heating to 800 ℃ again, carrying out constant-temperature heat treatment for 1h, cooling, and scattering to prepare the asphalt modified capacitance carbon AC 8.
TABLE 1 Cyclic stability vs. specific capacitance for the examples
Note: the volumetric capacitance and the cycling stability were both tested in 6moL/L KOH electrolyte.
It can be seen from table 1 that the volume specific capacitance of the catalytic rice hull/asphalt-based capacitance carbon is greatly improved compared with that of the rice hull-based capacitance carbon, and the electrochemical cycle stability is also excellent.
It should be apparent that the above description of the embodiments is only for the purpose of helping understanding the method of the present invention and the core idea thereof, but it should be apparent to those skilled in the art that various changes, modifications and substitutions can be made to the embodiments without departing from the spirit and principle of the present invention described in the claims, and those improvements and modifications also fall within the protection scope of the claims of the present invention.
Claims (8)
1. The method for improving the volume specific capacitance of the rice hull-based capacitance carbon is characterized by comprising the following steps of:
screening rice hulls to remove impurities, crushing to obtain rice hull powder, mixing the rice hull powder with a catalyst solution, then carrying out impregnation treatment, cooling to room temperature after the impregnation treatment is finished, carrying out suction filtration, and drying a filter cake at 80-100 ℃ to obtain pretreated rice hulls; the impregnation treatment process is as follows: adding the rice hull powder and the catalyst solution into a reaction kettle, sealing, heating by using steam at the temperature of 120-130 ℃, and pressurizing and dipping for 1 h; or the temperature of the heating system is 30-50 ℃, and the soaking is carried out for 24h at constant temperature;
step two, placing the pretreated rice hulls prepared in the step one in a tubular furnace, firstly heating to 200-300 ℃, pyrolyzing for 0.5h, then heating to 500-600 ℃, pyrolyzing for 1h under the protection of nitrogen, and cooling to room temperature to obtain pyrolytic carbon;
step three, according to the solid-liquid ratio of 1kg: adding the pyrolytic carbon obtained in the step two and a NaOH solution with the concentration of 5 wt% into a reaction kettle according to the proportion of 10L, heating and refluxing for 2h, cooling, filtering and separating, washing a filter cake to be neutral, and drying to obtain desiliconized pyrolytic carbon;
step four, uniformly mixing the desiliconized pyrolytic carbon obtained in the step three with impregnated asphalt, placing the mixture in a reaction kettle, heating to 150-250 ℃, impregnating for 2-5 h under the pressure of 0.1-0.6 MPa, and cooling to obtain an asphalt impregnated precursor;
transferring the pitch impregnation precursor obtained in the step four into a tubular furnace, heating to 600-1000 ℃, and carbonizing for 1-2 h to prepare pitch impregnation pyrolytic carbon;
step six, treating the pitch-impregnated pyrolytic carbon prepared in the step five to obtain carbon powder, uniformly mixing the carbon powder and alkali according to a carbon-alkali ratio of 1 (2.0-2.5), placing the mixture in a tubular furnace, heating to 450 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 0.5h, continuing heating to 700 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 1h, cooling to room temperature, taking out the mixture, washing the mixture to be neutral by using hot deionized water, and drying at 120 ℃ to prepare the catalytic rice hull/pitch-based capacitive carbon;
step seven, preparing asphalt modified capacitance carbon:
(1) adding the catalytic rice hull/asphalt-based capacitance carbon prepared in the sixth step into an asphalt suspension, stirring and dispersing for 0.5-2 h, heating to recover the solvent, placing the solid in a drying box, and drying at 85 ℃ for 5-12 h to prepare asphalt/capacitance carbon mixed powder;
(2) and (2) transferring the asphalt/capacitance carbon mixed powder prepared in the step (1) to a tubular furnace, heating to 150-250 ℃ under the protection of nitrogen, carrying out constant-temperature heat treatment for 1-2 h, heating to 600-1000 ℃ again, carrying out constant-temperature heat treatment for 1-2 h, cooling, and scattering to prepare the asphalt modified capacitance carbon.
2. The method for improving the volume specific capacitance of rice hull-based capacitance carbon as claimed in claim 1, wherein: the catalyst in the first step is NH4Cl、NH4OH、HCl、H2SO4、H3PO4One or a mixture of more than two of the above.
3. The method for improving the volume specific capacitance of rice hull-based capacitance carbon as claimed in claim 1, wherein: the mass concentration of the catalyst solution in the first step is 0-20%.
4. The method for improving the volume specific capacitance of rice hull-based capacitance carbon as claimed in claim 1, wherein: the solid-to-liquid ratio of the rice hull powder and the catalyst solution in the first step is 1kg (5-20) L.
5. The method for improving the volume specific capacitance of rice hull-based capacitance carbon as claimed in claim 1, wherein: the preparation method of the asphalt suspension in the seventh step comprises the following steps: and adding asphalt powder into the solvent, and stirring and dispersing for 0.5-2 h to obtain an asphalt suspension.
6. The method for improving the volume specific capacitance of rice hull-based capacitance carbon as claimed in claim 1, wherein: in the seventh step, the solid content ratio of the asphalt to the catalytic rice hull/asphalt-based capacitance carbon is (10-30): 100.
7. the method for improving the volume specific capacitance of rice hull-based capacitance carbon as claimed in claim 1, wherein: and the solvent in the seventh step is one or a mixture of two of cyclohexanol, absolute ethyl alcohol, acetone, tetrahydrofuran, cyclohexane and n-hexane.
8. The method for improving the volume specific capacitance of rice hull-based capacitance carbon as claimed in claim 1, wherein: the solid-liquid ratio of the asphalt to the solvent is (5 kg-15 kg) to 100L.
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