CN113716562A - Method for preparing porous carbon material by treating tobacco waste with molten salt - Google Patents
Method for preparing porous carbon material by treating tobacco waste with molten salt Download PDFInfo
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- 150000003839 salts Chemical class 0.000 title claims abstract description 93
- 241000208125 Nicotiana Species 0.000 title claims abstract description 76
- 235000002637 Nicotiana tabacum Nutrition 0.000 title claims abstract description 76
- 239000003575 carbonaceous material Substances 0.000 title claims abstract description 69
- 238000000034 method Methods 0.000 title claims abstract description 51
- 239000002699 waste material Substances 0.000 title claims abstract description 26
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 77
- 239000002994 raw material Substances 0.000 claims abstract description 54
- 238000003763 carbonization Methods 0.000 claims abstract description 34
- 239000002245 particle Substances 0.000 claims abstract description 32
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 27
- 238000001035 drying Methods 0.000 claims abstract description 26
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 25
- 229910017053 inorganic salt Inorganic materials 0.000 claims abstract description 19
- 239000012298 atmosphere Substances 0.000 claims abstract description 18
- 238000010438 heat treatment Methods 0.000 claims abstract description 15
- 239000008367 deionised water Substances 0.000 claims abstract description 8
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 8
- 238000004140 cleaning Methods 0.000 claims abstract description 6
- 238000001816 cooling Methods 0.000 claims abstract description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 60
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 52
- 229910052799 carbon Inorganic materials 0.000 claims description 26
- 229910052759 nickel Inorganic materials 0.000 claims description 26
- 235000019441 ethanol Nutrition 0.000 claims description 24
- 238000002791 soaking Methods 0.000 claims description 24
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- 239000000203 mixture Substances 0.000 claims description 17
- 238000005406 washing Methods 0.000 claims description 17
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- 239000006230 acetylene black Substances 0.000 claims description 9
- 238000002360 preparation method Methods 0.000 claims description 9
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- 239000000919 ceramic Substances 0.000 claims description 6
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 5
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- 150000001340 alkali metals Chemical class 0.000 claims description 2
- 229910052784 alkaline earth metal Inorganic materials 0.000 claims description 2
- 150000001342 alkaline earth metals Chemical class 0.000 claims description 2
- 150000004649 carbonic acid derivatives Chemical class 0.000 claims description 2
- 150000004820 halides Chemical class 0.000 claims description 2
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- 238000010626 work up procedure Methods 0.000 claims description 2
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- 239000000126 substance Substances 0.000 description 15
- 239000003990 capacitor Substances 0.000 description 13
- 239000006260 foam Substances 0.000 description 13
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical group [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 11
- 239000007864 aqueous solution Substances 0.000 description 11
- 238000004146 energy storage Methods 0.000 description 11
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 10
- 230000004913 activation Effects 0.000 description 10
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- 229910001220 stainless steel Inorganic materials 0.000 description 10
- 239000010935 stainless steel Substances 0.000 description 10
- 239000011148 porous material Substances 0.000 description 9
- 239000010936 titanium Substances 0.000 description 8
- 229910052719 titanium Inorganic materials 0.000 description 8
- 239000013543 active substance Substances 0.000 description 7
- 239000003610 charcoal Substances 0.000 description 7
- 239000001301 oxygen Substances 0.000 description 7
- 229910052760 oxygen Inorganic materials 0.000 description 7
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 6
- 229910052757 nitrogen Inorganic materials 0.000 description 6
- 238000001514 detection method Methods 0.000 description 5
- ZOMNIUBKTOKEHS-UHFFFAOYSA-L dimercury dichloride Chemical class Cl[Hg][Hg]Cl ZOMNIUBKTOKEHS-UHFFFAOYSA-L 0.000 description 5
- 239000003792 electrolyte Substances 0.000 description 5
- 238000000227 grinding Methods 0.000 description 5
- 229910052697 platinum Inorganic materials 0.000 description 5
- 238000000197 pyrolysis Methods 0.000 description 5
- 239000000725 suspension Substances 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 4
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 4
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- 239000001110 calcium chloride Substances 0.000 description 4
- 229910001628 calcium chloride Inorganic materials 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
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- 229910052700 potassium Inorganic materials 0.000 description 4
- 239000011591 potassium Substances 0.000 description 4
- 229910052708 sodium Inorganic materials 0.000 description 4
- 239000011734 sodium Substances 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000001913 cellulose Substances 0.000 description 3
- 229920002678 cellulose Polymers 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 239000007772 electrode material Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- AKEKKCGPLHMFCI-UHFFFAOYSA-L potassium sodium hydrogen carbonate Chemical compound [Na+].[K+].OC([O-])=O.OC([O-])=O AKEKKCGPLHMFCI-UHFFFAOYSA-L 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- 229920002488 Hemicellulose Polymers 0.000 description 2
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 229910052681 coesite Inorganic materials 0.000 description 2
- 239000000498 cooling water Substances 0.000 description 2
- 229910052906 cristobalite Inorganic materials 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- -1 ferrous metals Chemical class 0.000 description 2
- 125000000524 functional group Chemical group 0.000 description 2
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- 229920005610 lignin Polymers 0.000 description 2
- 239000007800 oxidant agent Substances 0.000 description 2
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Chemical compound [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 230000005855 radiation Effects 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 229910052682 stishovite Inorganic materials 0.000 description 2
- 229910052905 tridymite Inorganic materials 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- 229910021586 Nickel(II) chloride Inorganic materials 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- 238000002159 adsorption--desorption isotherm Methods 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910001413 alkali metal ion Inorganic materials 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
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- 230000000911 decarboxylating effect Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
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- 239000003344 environmental pollutant Substances 0.000 description 1
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- 239000000395 magnesium oxide Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 229910052863 mullite Inorganic materials 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 231100000956 nontoxicity Toxicity 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000007146 photocatalysis Methods 0.000 description 1
- 230000001699 photocatalysis Effects 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
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- 229910000027 potassium carbonate Inorganic materials 0.000 description 1
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- 230000008646 thermal stress Effects 0.000 description 1
- 210000003462 vein Anatomy 0.000 description 1
- 239000011592 zinc chloride Substances 0.000 description 1
Images
Classifications
-
- 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
- C01B32/318—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
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-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
- H01G11/26—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-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
Abstract
The invention belongs to the field of biomass resource utilization and materials, and particularly relates to a method for preparing a capacitive porous carbon material by treating tobacco waste with molten salt, which comprises the following steps: (1) cleaning tobacco waste, drying, and crushing; (2) drying inorganic salt and heating to a certain carbonization temperature under the protection of inert gas; (3) immersing the raw material particles in molten salt, and carbonizing for a certain time; then cooling the product in an inert atmosphere; (4) and cleaning and removing impurities from the product by using dilute hydrochloric acid, deionized water and ethanol in sequence, and drying in vacuum to obtain the porous carbon material, wherein the specific capacitance of the porous carbon material under the current density of 1A/g by using a three-electrode testing system and a two-electrode testing system is 142-178F/g and 78-137F/g respectively. The method can prepare the carbon material with high added value, not only can reduce environmental pollution, but also can increase economic benefit, and realizes the resource utilization of the tobacco waste to achieve the purpose of changing waste into valuable.
Description
Technical Field
The invention relates to a method for preparing a porous carbon material by treating tobacco waste with molten salt, belonging to the field of materials.
Background
The porous carbon material has rich porous structure, large specific surface area, stable property, low cost and easy obtaining, and is widely applied to the fields of adsorption, catalyst carriers (photocatalysis and electrocatalysis), electrode materials of super capacitors and the like. The super capacitor has the characteristics of high charging and discharging rate, high power density, good stability, long cycle life and the like, is concerned, and has wide application in the fields of electronics, electrical equipment, new energy automobiles and the like.
The raw materials for preparing the porous carbon material comprise organic matters, high polymers, coal tar and biomass. The biomass is renewable, has wide sources and unique three-dimensional structure, so that the biomass-based porous carbon material can be prepared by using a self-template method of the biomass. Tobacco straw (tobacco stalk), tobacco stem (leaf vein), tobacco powder and the like in the tobacco waste are rich in cellulose, lignin, hemicellulose and other components. The content of cellulose in the tobacco stalk reaches 38-45%, and the proportion of the cellulose, the lignin and the hemicellulose is about 4:3: 3. The porous carbon material with high added value can be prepared after the tobacco waste is carbonized, so that the environmental pollution can be reduced, the economic benefit can be increased, and the aim of changing waste into valuable by recycling the tobacco waste is fulfilled.
Generally, methods for producing a carbon material from biomass include a high-temperature pyrolysis method and a hydrothermal carbonization method. The high-temperature pyrolysis refers to a process of heating the biomass to 350-700 ℃ at a certain heating rate under an inert atmosphere (or under an oxygen-deficient condition) so that molecules in the biomass are decomposed to generate coke. The hydrothermal carbonization method is an accelerated coalification process of dehydrating and decarboxylating biomass in a 150-350 ℃ aqueous solution. In order to obtain higher specific surface area and performance, the carbon materials prepared by the two methods also need to be further activated (including physical activation and chemical activation), and the physical activation method is to activate the carbon materials at 600-1000 ℃ by using carbon dioxide, water vapor and the like as oxidants; the chemical activation method is to use HNO3、H2SO4、H3PO4、KOH、NaOH、NiCl2And ZnCl2Activating the oxidant at 400-900 deg.c. Physical activation in contrast to chemical activationThe activator reacts with carbon during the reaction, which reduces the yield of the product. In addition, since the chemical activation method has complicated treatment steps, the activator is expensive, the amount of consumption is large, the recovery is difficult, and the like, it is a direction of development to find a process for recovering the activator and easily separating the activator from the product.
Although the surface of the biomass charcoal subjected to high-temperature pyrolysis and hydrothermal carbonization has rich oxygen-containing functional groups, the wettability of the carbon material and a solution medium is improved, and the adsorption performance of the biomass charcoal on polar pollutants is improved, the ordered structure in the carbon material is greatly reduced due to the excessive functional groups, and the biomass charcoal is generally in a random structure, so that the cycle performance of the biomass charcoal serving as the electrode material of the supercapacitor is adversely affected. In addition, the activated material has the characteristics of rich specific surface area, developed pore structure, narrow pore size distribution and the like, is beneficial to improving the adsorption performance of the material, but also causes the reduction of the conductivity of the material, so that the direct application of the carbon material to the fields of catalysis, batteries, capacitors and energy storage is limited to a certain extent.
At present, most of processes for preparing carbon materials with developed pore structures by using tobacco stalks as raw materials are a process of high-temperature pyrolysis and then activation, and microwave radiation pyrolysis (summer laugh et al, chemical bulletin, 2011,69:2627, Penjinhui et al, forest chemical and industry, 2002,22:85, Zhang Lebo et al, chemical engineering, 2007,35:67, Zhang Lebo et al, chemical development, 2006,25:415, Zhang Lebo et al, safety and environmental bulletin, 2004,4:51.) is also used. Compared with the traditional heating process, although the microwave radiation process has higher efficiency, convenient operation, short activation time and low energy consumption, the manufacture of large-scale production high-power microwave equipment has certain difficulty and high cost, and the microwave process is in a laboratory stage at present.
The ash content of the biomass charcoal is more and reaches 10-58%, the content of the biomass charcoal is related to the types of raw materials, and the ash content is increased along with the increase of the carbonization temperature (Wangchinchen and the like, the chemical industry progresses 2012,31: 907.). How to remove excessive ash by a simple method to increase the pore structure of the biomass charcoal is a question to be discussed. The molten salt has low steam pressure, high heat capacity and good performanceThe biomass carbonization catalyst has the characteristics of heat conductivity, dissolving capacity, catalytic performance, activation performance and the like, can dissolve some inert components in biomass to improve a gap structure, and can accelerate a carbonization process. For example, SiO2Solubility in NaCl-KCl-NaF at 850 deg.C is about 1.2% (He Xiaofeng et al, Chinese non-ferrous metals, 2008,18:929.), SiO2The carbon dioxide has high solubility in the carbonate molten salt; ni in molten salts2+、Zn2+、Fe2+And alkali metal ions have certain catalytic cracking properties due to their ability to accelerate the breaking of Chemical bonds (Yang H.et al, Chinese Chemical Letters,2002,13: 787; Yang H.et al, Electrochemical and solid-state Letters,2002,5: A141; Yin H.Y.et al, Environmental science&technology,2014,48: 8101.). In addition, because the solubility of oxygen in the molten salt is very low, the carbonization atmosphere can be conveniently controlled to an oxygen-poor or even oxygen-free environment.
Disclosure of Invention
In order to fill the blank in the prior art, the invention provides a method for preparing a porous carbon material by treating tobacco waste with molten salt, which comprises the following operation steps:
(1) pretreatment of raw materials
The raw material tobacco waste is cleaned and dried by reverse osmosis water (RO water) and then crushed to a proper particle size.
(2) Pretreatment of inorganic salts
And (2) putting a proper amount of inorganic salt into the ceramic crucible, putting the ceramic crucible and the inorganic salt into the graphite crucible, putting the graphite crucible into the reactor, and putting the reactor into a tubular electric furnace to dry the inorganic salt.
(3) Carbonizing, wherein the carbonizing process is carried out in an inert atmosphere and sequentially comprises the following steps:
firstly, putting dried inorganic salt into a reactor, and heating to a carbonization temperature to form molten salt;
secondly, wrapping the pretreated raw material particles obtained in the step (1) with foamed nickel or putting the pretreated raw material particles into a carbonization basket and immersing the raw material particles into molten salt for carbonization for 0.5-8 hours;
thirdly, after charring, the product is removed from the molten salt, then cooled to a temperature below 500 ℃ in an inert atmosphere, and then removed from the reactor.
(4) Work-up of the product
And (3) cleaning the product with RO water to remove residual salt, soaking with dilute hydrochloric acid, washing with deionized water to neutrality, soaking with ethanol, leaching, and vacuum drying to obtain the porous carbon material.
Further, the tobacco waste in the step (1) comprises tobacco stalks, tobacco stems and/or tobacco powder.
Further, the raw material in the step (1) is washed with RO water for 3-5 times to remove impurities such as silt and dust in the raw material.
Furthermore, the raw material drying in the step (1) is drying for 10-24 hours at 105-110 ℃ to remove residual moisture in the raw material as much as possible.
Further, the particle size of the raw material in the step (1) is 10-100 meshes, and if the particle size is too fine, the carbonized product is difficult to collect.
Further, the inorganic salt in the step (2) is a simple substance inorganic salt or a mixed salt prepared by more than two simple substance inorganic salts according to a certain proportion, and the simple substance inorganic salt comprises hydroxides, halides, carbonates and sulfates of alkali metals, alkaline earth metals and transition metals.
Furthermore, the inorganic salt is anhydrous calcium chloride or a mixed salt of sodium carbonate and potassium carbonate, and the molar ratio of sodium to potassium in the mixed salt is 59: 41.
Further, the drying temperature of the inorganic salt in the step (2) is 200-250 ℃, and the time is 5-24 hours, so as to remove residual moisture in the inorganic salt.
Further, the step (3) of immersing in the molten salt means that the liquid level of the molten salt exceeds 0.5-10 cm of the raw material.
The ceramic crucible in the step (2) is made of corundum (alumina), magnesia, mullite or zirconia, and a proper crucible is selected according to the corrosivity (solubility) of the molten salt.
The graphite crucible in the step (2) can be used as a protective crucible, and the graphite can also consume oxygen in the reactor so as to maintain the low-oxygen environment of the system.
And (3) the upper part of the reactor in the step (2) is provided with a circulating cooling water cooling system to facilitate operation.
Further, the heating rate in the heating step (3) is 3-10 ℃/min, so that the leakage of the molten salt caused by the cracking of the ceramic crucible due to thermal stress is prevented.
Further, the carbonization temperature in the step (3) is 450-1000 ℃, the carbonization time is 0.5-8 h, and the carbonization temperature is determined by factors such as a molten salt system, the performance of the porous carbon material, the yield and the like; furthermore, the carbonization temperature is 850 ℃, and the carbonization time is 1-3 h.
Further, the carbonization basket in the step (3) is made of foamed nickel or stainless steel mesh.
Further, the step (3) of immersing the raw material particles in the molten salt is completed by a lifting device which is provided with a lifting rod and a molten salt liquid level positioning system so as to determine the depth of the molten salt and the depth of the raw material immersion.
Further, the cooling time in the inert atmosphere in the step (3) is 10-30 min.
Further, the inert gas in the step (3) is Ar or N with low purity2(concentration of about 99.9%) because oxygen solubility in molten salt is very low, and a low oxygen environment can be conveniently maintained.
The concentration of the dilute hydrochloric acid in the step (4) is 0.1-2 mol/L.
And (4) soaking the dilute hydrochloric acid for 1-24 hours, and repeating for 1-3 times to remove impurities such as residual solidified salts, oxides and the like.
And (4) soaking the ethanol in the step (4) for 1-24 hours in absolute ethanol or 95 wt.% ethanol, and repeating for 1-3 times to remove liquid oily substances and other organic substances adsorbed in the product.
And (4) drying the product in the step (4) in vacuum at the temperature of 80-90 ℃ for 6-12 h.
The invention also provides application of the porous carbon material prepared by the method in preparation of a supercapacitor electrode.
The application comprises the following steps:
firstly, adding a proper amount of conductive agent, adhesive and dispersant into a porous carbon material, and uniformly mixing to obtain a mixture;
secondly, removing a proper amount of dispersant from the mixture, rolling the mixture into a carbon film with uniform thickness, drying the carbon film in vacuum, cutting the dried carbon film into a proper size, and pressing the carbon film on a current collector to obtain a single-chip supercapacitor electrode;
thirdly, assembling the two-electrode supercapacitor assembly: and (3) placing the diaphragm between the two monolithic supercapacitor electrodes to obtain the two-electrode supercapacitor assembly.
In the preparation of the supercapacitor electrode in the step (4), the porous carbon material product needs to be ground into carbon powder with uniform particle size by an agate mortar so as to be used as an active substance of the electrode.
Further, the conductive agent is acetylene black, the adhesive is PTFE (polytetrafluoroethylene), the dispersing agent is absolute ethyl alcohol or isopropanol, and the mass ratio of the porous carbon material to the acetylene black to the PTFE is 8:1: 1.
Further, the thickness of the carbon film in the step (II) is 0.01-0.1 mm.
Further, the temperature of vacuum drying of the carbon film in the step (II) is 60-85 ℃, and the time is 5-10 hours.
Further, pressing the cut carbon film on a current collector made of materials such as foamed nickel, a titanium mesh or a stainless steel mesh in the step (II), keeping the pressure at 4-9 MPa for 1-2 min, and obtaining the single-chip supercapacitor electrode.
Further, the diaphragm used in the step (III) is a water-based acid and alkali resistant diaphragm.
Compared with the prior art, the invention has the following innovations:
(1) the raw material adopts tobacco waste with wide sources.
(2) Because the molten salt is a heat storage medium and contains metal ions and anions, carbonization and activation can be simultaneously carried out in the molten salt, and in addition, the molten salt has certain dissolving capacity, so that impurities in a product can be dissolved out, the pore structure is increased, and the subsequent product treatment process is reduced.
(3) The raw materials are fully contacted with the molten salt, the product is easily separated from the molten salt, the molten salt can be repeatedly used, the lost molten salt can be supplemented by adding simple substance salt or prepared mixed salt, the whole preparation process is simple, and the method is suitable for large-scale production.
(4) The structure and the performance of the porous carbon material product can be effectively regulated and controlled through parameters such as molten salt composition, temperature, time and the like, the specific capacitance is high, and the porous carbon material product can be used as a super capacitor electrode material.
(5) In the method, the process for preparing the porous carbon material by treating the tobacco waste with the molten salt has the characteristics of simple operation flow, low price of inorganic salt, no toxicity, various varieties, strong selectivity, wide operation temperature range, controllable structure and performance of the product, easy separation of the molten salt and the product, repeated utilization of the molten salt, cost saving and the like. If the focused solar heat energy is fully utilized to heat the molten salt, the clean production of preparing the porous carbon material by carbonizing the tobacco waste with the molten salt can be realized.
Drawings
FIG. 1 shows the CaCl of the tobacco stems of example 1 at 850 deg.C2The porous carbon material prepared by the medium carbonization for 3h is respectively tested by a three-electrode system, namely a GCD curve (a), a CV curve (c) and a Nyquist diagram (e), and is tested by a two-electrode system, namely a GCD curve (b), a CV curve (d) and a Nyquist diagram (f). CV diagram is a rectangle with a rule of comparison, GCD is a symmetrical triangle with a rule of comparison, the high frequency band of the Nyquist diagram is an approximate circular arc, the low frequency band is a straight line with an angle of approximately 90 degrees, and the curve reflects the charge transfer resistance RctThe diameter of the arc of (2) is smaller. The above data indicate that the carbon material has better electric double layer capacitance.
FIG. 2 shows the CaCl of the tobacco stems of example 4 at 850 deg.C2SEM image of porous carbon material prepared by medium carbonization for 1 h. The carbon material is shown to have a rich pore structure.
FIG. 3 shows the CaCl temperature of 850 ℃ of the tobacco stems in example 42N of porous carbon material prepared by medium carbonization for 1h2Adsorption-desorption curve (a) and pore size distribution curve (b). N of the carbon material2The adsorption-desorption isotherms are of type I and type II and have the form H4The hysteresis loop is known by combining a pore size distribution curve, the carbon material has a large number of micropores and mesopores, belongs to a porous carbon material, and has a BET specific surface area of 752m2Per g, total pore volume of 0.51cm3/g。
Detailed Description
The applicant will further describe the relevant contents of the present invention in detail with reference to the following specific examples, but the embodiments of the present invention are not limited to these examples. The process conditions and parameters not specifically specified in the examples can be carried out with reference to the general operating conditions and techniques.
Embodiment 1a method for preparing a porous carbon material by treating tobacco waste with molten salt sequentially comprises the following steps:
(1) washing tobacco stems with proper amount of RO water for 4 times, removing silt and dust in the tobacco stems, drying the tobacco stems at 105 ℃ for 12 hours, crushing the dried tobacco stems by using a universal crusher, and separating raw material particles with proper particle size by using a sieve.
(2) Weighing 500g of anhydrous calcium chloride in a corundum crucible, placing the corundum crucible and the calcium chloride in a graphite crucible, then placing the corundum crucible and the calcium chloride in an open stainless steel reactor with a circulating cooling water cooling system, heating the corundum crucible and the calcium chloride to 250 ℃ in a tubular electric furnace, and drying the corundum crucible and the calcium chloride for 12 hours at 250 ℃.
(3) Then under the protection of nitrogen, the temperature of the tubular electric furnace is increased to 850 ℃ according to the heating rate of 6 ℃/min (at the moment, a molten salt system with the depth of about 6cm is formed); weighing about 5g of tobacco stem raw material with the particle size of 10-20 meshes (materials which can penetrate through a 10-mesh sieve but not a 20-mesh sieve, the same below), prepared in the step (1), wrapping the tobacco stem raw material with nickel foam (the wrapping with nickel foam is convenient for collecting products, and the carbonized solid products are still in the nickel foam, and if the products are not wrapped, the products are dispersed in molten salt and are not easy to collect), and fixing the tobacco stem raw material on a lifting rod (the lifting rod can be arranged on a reactor, and can also be designed on a cross beam, and the lifting rod is arranged above the reactor and the same below the reactor in the description); then, the lifting rod is adjusted through a molten salt liquid level positioning system to enable the tobacco stem raw material to be immersed in the molten salt (the immersion requirement is that the raw material is completely immersed in the molten salt, the liquid level of the molten salt exceeds 0.5-10 cm of the raw material, the same is carried out below), and then the tobacco stem raw material is carbonized for 3 hours at 850 ℃; after carbonization, the product is moved out of the liquid surface of the molten salt through a lifting rod and is cooled in an inert atmosphere for 15min so that the temperature of the product is cooled to be below 500 ℃ to prevent the high-temperature product from being oxidized in the air, and then the product is moved out of the reactor.
In both the temperature rise and carbonization processes of the above operations, 99.9% purity Ar was used to maintain the inert atmosphere of the system.
The molten salt after the product is separated can be reused.
(4) Firstly, washing with RO water to remove residual solidified salt in the product; then, after the washed product was soaked in 1mol/L hydrochloric acid for 6 hours, the product was taken out, and then soaked in 1mol/L hydrochloric acid for 6 hours, followed by washing the product with deionized water to neutrality (the washing solution pH was 7, the same applies below); finally, soaking the mixture for 8 hours by using 95 wt.% of ethanol, repeating the ethanol soaking process for 1 time, and then leaching the mixture by using ethanol; and (4) drying the washed product at 80 ℃ for 8h in vacuum to obtain the porous carbon material. The product yield under these conditions was 18.2%.
(5) The preparation method of the supercapacitor electrode comprises the following steps:
grinding the porous carbon material in the step (4) to carbon powder with uniform particle size, then weighing a proper amount of carbon powder, acetylene black and PTFE suspension (measured by PTFE, the same below) according to a mass ratio of 8:1:1, simultaneously adding absolute ethyl alcohol as a dispersing agent for full mixing, rolling a sticky material formed after removing the proper amount of ethyl alcohol into a uniform carbon film with the thickness of 0.05mm, performing vacuum drying for 5 hours at 65 ℃, cutting the dried carbon film into a plurality of phi 1cm circular sheets, weighing to determine the mass of an active substance (weighing the mass of the circular sheets by an electronic balance, multiplying by 80% to obtain the mass of the active substance, the same below), then pressing on a foam nickel and a titanium mesh at 6MPa respectively to obtain a supercapacitor electrode-foam nickel electrode and a titanium mesh electrode, and performing the following detection respectively:
wherein, the titanium mesh electrode is arranged at 1mol/L H2SO4And (2) testing the energy storage performance of the carbon material in the aqueous solution by adopting a three-electrode system (in the three-electrode system, a platinum sheet electrode and a saturated calomel electrode are respectively adopted as a counter electrode and a reference electrode).
The foamed nickel electrodes with the same size and the approximately same mass are separated by an alkali-resistant diaphragm to form a two-electrode super capacitor assembly, 6mol/LKOH aqueous solution is used as electrolyte, and a two-electrode system is adopted to test the energy storage performance of the carbon material.
Relevant electrochemical testing of the carbon material performance is shown in figure 1. The porous carbon material is prepared into a supercapacitor electrode, and the specific capacitance calculated by GCD discharge curves of a three-electrode and two-electrode test system under the current density of 1A/g is 148.24F/g and 100.97F/g respectively.
Embodiment 2 a method for preparing a porous carbon material by treating tobacco waste with molten salt includes the following steps:
(1) washing tobacco stems with proper amount of RO water for 4 times, removing silt and dust in the tobacco stems, drying the tobacco stems for 8 hours at 110 ℃, crushing the dried tobacco stems by using a universal crusher, and separating raw material particles with proper particle size by using a sieve.
(2) 500g of sodium carbonate-potassium carbonate mixed salt (sodium/potassium molar ratio 59/41) is weighed into a corundum crucible, the corundum crucible together with the mixed salt is placed into a graphite crucible, then the graphite crucible is placed into an open stainless steel reactor, the stainless steel crucible is heated to 250 ℃ in a tubular electric furnace, and the corundum crucible is dried for 14 hours at 250 ℃.
(3) Then under the protection of nitrogen, the temperature of the tubular electric furnace is increased to 850 ℃ at the heating rate of 5 ℃/min (at the moment, a molten salt system with the depth of about 6cm is formed); accurately weighing about 10g of the tobacco stem raw material with the particle size of 10-20 meshes, prepared in the step (1), wrapping the tobacco stem raw material with foamed nickel, and fixing the tobacco stem raw material on a lifting rod; then adjusting the lifting rod to immerse the tobacco stalk raw material in the molten salt, and carbonizing for 2h at 850 ℃; and finally, after carbonization is finished, the product is moved out of the liquid level of the molten salt through a lifting rod and is cooled in an inert atmosphere for 20min so that the temperature of the product is cooled to be below 500 ℃ to prevent the high-temperature product from being oxidized in the air, and then the product is moved out of the reactor.
Ar with the purity of 99.9 percent is used in the process of temperature rise and carbonization to maintain the inert atmosphere of the system. The molten salt after the product is separated can be reused.
(4) Firstly, washing with RO water to remove residual solidified salt in the product; then, soaking the cleaned product for 12 hours by using 2mol/L hydrochloric acid, taking out, soaking for 12 hours by using 2mol/L hydrochloric acid, and then washing the product to be neutral by using deionized water; finally, soaking the mixture for 4 hours by using 95 wt.% of ethanol, repeating the ethanol soaking process for 2 times, and leaching the mixture by using ethanol; and (4) drying the washed product at 85 ℃ for 6 hours in vacuum to obtain the porous carbon material. The product yield under these conditions was 12.1%.
(5) The preparation method of the supercapacitor electrode comprises the following steps:
grinding the porous carbon material in the step (4) to carbon powder with uniform particle size, then weighing a proper amount of carbon powder, acetylene black and PTFE suspension according to a mass ratio of 8:1:1, simultaneously adding absolute ethyl alcohol as a dispersing agent for full mixing, rolling a sticky matter formed by removing the proper amount of ethyl alcohol into a uniform carbon film with the thickness of 0.04mm, drying the uniform carbon film in vacuum at 75 ℃ for 3 hours, cutting the dried carbon film into a plurality of phi 1cm circular sheets, simultaneously weighing to determine the mass of an active substance, and then respectively pressing the circular sheets on a foam nickel net and a titanium net under 7MPa to respectively obtain a super capacitor electrode-a foam nickel electrode and a titanium net electrode, wherein the following detection is respectively carried out:
wherein, the titanium mesh electrode is arranged at 1mol/L H2SO4And (2) testing the energy storage performance of the carbon material in the aqueous solution by adopting a three-electrode system (in the three-electrode system, a platinum sheet electrode and a saturated calomel electrode are respectively adopted as a counter electrode and a reference electrode).
The foamed nickel electrodes with the same size and the approximately same mass are separated by an alkali-resistant diaphragm to form a two-electrode super capacitor assembly, and a two-electrode system is adopted to test the energy storage performance of the carbon material by taking a 6mol/LKOH aqueous solution as an electrolyte.
The specific capacitance calculated by GCD discharge curves of the three-electrode and two-electrode test systems under the current density of 1A/g is 178.13F/g and 137.72F/g respectively.
Embodiment 3 a method for preparing a porous carbon material by treating tobacco waste with molten salt, comprising the following steps:
(1) cleaning tobacco stalks with proper amount of RO water for 4 times, removing silt and dust in the tobacco stalks, drying the tobacco stalks for 6 hours at 110 ℃, crushing the dried tobacco stalks by using a universal crusher, and separating raw material particles with proper particle size by using a sieve.
(2) 500g of sodium carbonate-potassium carbonate mixed salt (sodium/potassium molar ratio 59/41) are weighed into a corundum crucible, the corundum crucible together with the mixed salt is placed into a graphite crucible, then the graphite crucible is placed into an open stainless steel reactor, the stainless steel crucible is heated to 230 ℃ in a tubular electric furnace, and the corundum crucible is dried for 16 hours at 230 ℃.
(3) Then under the protection of nitrogen, the temperature of the tubular electric furnace is increased to 850 ℃ at the heating rate of 5 ℃/min (at the moment, a molten salt system with the depth of about 6cm is formed); accurately weighing about 10g of the tobacco stalk raw material with the grain size of 10-20 meshes prepared in the step (1), wrapping the tobacco stalk raw material with foamed nickel, and fixing the tobacco stalk raw material on a lifting rod; then adjusting the lifting rod to immerse the tobacco stalk raw material in the molten salt, and carbonizing for 3h at 850 ℃; and finally, after carbonization is finished, the product is moved out of the liquid level of the molten salt through a lifting rod and is cooled in an inert atmosphere for 15min so that the temperature of the product is cooled to be below 500 ℃ to prevent the high-temperature product from being oxidized in the air, and then the product is moved out of the reactor. 99.9% pure Ar was used during the temperature ramp and charring to maintain an inert atmosphere. The molten salt after the product is separated can be reused.
(4) Firstly, washing with RO water to remove residual solidified salt in the product; then, soaking the cleaned product for 10 hours by using 1mol/L hydrochloric acid, taking out, soaking for 10 hours by using 1mol/L hydrochloric acid, and then washing the product to be neutral by using deionized water; finally, soaking the mixture for 4 hours by using 95 wt.% of ethanol, repeating the ethanol soaking process for 1 time, and leaching the mixture by using ethanol; and (4) drying the washed product at 80 ℃ for 7 hours in vacuum to obtain the porous carbon material. The product yield under these conditions was 9.6%.
(5) The preparation method of the supercapacitor electrode comprises the following steps:
grinding the porous carbon material in the step (4) to carbon powder with uniform particle size, then weighing a proper amount of carbon powder, acetylene black and PTFE suspension according to a mass ratio of 8:1:1, simultaneously adding absolute ethyl alcohol as a dispersing agent for full mixing, rolling a sticky matter formed by removing the proper amount of ethyl alcohol into a uniform carbon film with the thickness of 0.04mm, drying the uniform carbon film in vacuum at 70 ℃ for 6 hours, cutting the dried carbon film into a plurality of phi 1cm circular sheets, simultaneously weighing to determine the mass of an active substance, and then respectively pressing the circular sheets on a foam nickel net and a titanium net under 8MPa to respectively obtain a super capacitor electrode-a foam nickel electrode and a titanium net electrode, wherein the following detection is respectively carried out:
wherein, the titanium mesh electrode is arranged at 1mol/L H2SO4And (2) testing the energy storage performance of the carbon material in the aqueous solution by adopting a three-electrode system (in the three-electrode system, a platinum sheet electrode and a saturated calomel electrode are respectively adopted as a counter electrode and a reference electrode).
The foamed nickel electrodes with the same size and the approximately same mass are separated by an alkali-resistant diaphragm to form a two-electrode super capacitor assembly, 6mol/LKOH aqueous solution is used as electrolyte, and a two-electrode system is adopted to test the energy storage performance of the carbon material.
The specific capacitance calculated by GCD discharge curves of the three-electrode and two-electrode test systems under the current density of 1A/g is 176.42F/g and 137.43F/g respectively.
Embodiment 4 a method for preparing a porous carbon material by treating tobacco waste with molten salt, comprising the following steps:
(1) washing tobacco stems with proper amount of RO water for 5 times, removing silt and dust, drying at 110 deg.C for 10h, crushing with universal pulverizer, and sieving to obtain raw material particles with proper particle size.
(2) Weighing 500g of anhydrous calcium chloride in a corundum crucible, placing the corundum crucible and the anhydrous calcium chloride in a graphite crucible, then placing the corundum crucible and the anhydrous calcium chloride in an open stainless steel reactor, heating the corundum crucible and the anhydrous calcium chloride to 250 ℃ in a tubular electric furnace, and drying the corundum crucible and the anhydrous calcium chloride for 14 hours at the temperature of 250 ℃.
(3) Then under the protection of nitrogen, the temperature of the tubular electric furnace is increased to 850 ℃ according to the heating rate of 8 ℃/min (at the moment, a molten salt system with the depth of about 6cm is formed); accurately weighing about 5g of the tobacco stem raw material with the particle size of 10-20 meshes, prepared in the step (1), wrapping the tobacco stem raw material with foamed nickel, and fixing the tobacco stem raw material on a lifting rod; then adjusting the lifting rod to immerse the tobacco stalk raw material in the molten salt, and carbonizing for 1h at 850 ℃; and finally, after carbonization is finished, the product is moved out of the liquid level of the molten salt through a lifting rod and is cooled in an inert atmosphere for 20min so that the temperature of the product is cooled to be below 500 ℃ to prevent the high-temperature product from being oxidized in the air, and then the product is moved out of the reactor. 99.9% pure Ar was used during the temperature ramp and charring to maintain an inert atmosphere. The molten salt after the product is separated can be reused.
(4) Firstly, washing with RO water to remove residual solidified salt in the product; then, soaking the cleaned product for 12 hours by using 0.5mol/L hydrochloric acid, taking out, soaking for 12 hours by using 0.5mol/L hydrochloric acid, and then washing the product to be neutral by using deionized water; finally, soaking the mixture for 6 hours by using 95 wt.% of ethanol, repeating the ethanol soaking process for 1 time, and leaching the mixture by using ethanol; and (4) drying the washed product at 85 ℃ for 6 hours in vacuum to obtain the porous carbon material. The product yield under these conditions was 18.9%.
(5) The preparation method of the supercapacitor electrode comprises the following steps:
grinding the porous carbon material in the step (4) to carbon powder with uniform particle size, then weighing a proper amount of carbon powder, acetylene black and PTFE suspension according to a mass ratio of 8:1:1, simultaneously adding absolute ethyl alcohol as a dispersing agent for full mixing, rolling a sticky matter formed by removing the proper amount of ethyl alcohol into a uniform carbon film with the thickness of 0.05mm, drying the uniform carbon film in vacuum at 60 ℃ for 8 hours, cutting the dried carbon film into a plurality of phi 1cm circular sheets, simultaneously weighing to determine the mass of an active substance, and then respectively pressing the circular sheets on a foam nickel net and a titanium net at 9MPa to respectively obtain a super capacitor electrode-a foam nickel electrode and a titanium net electrode, wherein the following detection is respectively carried out:
wherein, the titanium mesh electrode is arranged at 1mol/L H2SO4And (2) testing the energy storage performance of the carbon material in the aqueous solution by adopting a three-electrode system (in the three-electrode system, a platinum sheet electrode and a saturated calomel electrode are respectively adopted as a counter electrode and a reference electrode).
The foamed nickel electrodes with the same size and the approximately same mass are separated by an alkali-resistant diaphragm to form a two-electrode super capacitor assembly, 6mol/L KOH aqueous solution is used as electrolyte, and a two-electrode system is adopted to test the energy storage performance of the carbon material. The specific capacitance calculated by GCD discharge curves of the three-electrode and two-electrode test systems under the current density of 1A/g is 142.27F/g and 78.97F/g respectively.
Embodiment 5 a method for preparing a porous carbon material by treating tobacco waste with molten salt, comprising the following steps:
(1) washing tobacco stems for 3 times by using proper amount of RO water, drying the tobacco stems for 8 hours at 110 ℃ after removing silt and dust, crushing the dried tobacco stems by using a universal crusher, and separating raw material particles with proper particle size by using a sieve.
(2) 500g of sodium carbonate-potassium carbonate mixed salt (sodium/potassium molar ratio 59/41) are weighed into a corundum crucible, the corundum crucible together with the mixed salt is placed into a graphite crucible, then the graphite crucible is placed into an open stainless steel reactor, the stainless steel crucible is heated to 235 ℃ in a tubular electric furnace, and the corundum crucible is dried for 15 hours at 235 ℃.
(3) Then under the protection of nitrogen, the temperature of the tubular electric furnace is increased to 850 ℃ according to the heating rate of 6 ℃/min (at the moment, a molten salt system with the depth of about 6cm is formed); accurately weighing about 10g of the tobacco stem raw material with the particle size of 10-20 meshes, prepared in the step (1), wrapping the tobacco stem raw material with foamed nickel, and fixing the tobacco stem raw material on a lifting rod; then adjusting the lifting rod to immerse the tobacco stalk raw material in the molten salt, and carbonizing for 1h at 850 ℃; and finally, after carbonization is finished, the product is moved out of the liquid level of the molten salt through a lifting rod and is cooled in an inert atmosphere for 15min so that the temperature of the product is cooled to be below 500 ℃ to prevent the high-temperature product from being oxidized in the air, and then the product is moved out of the reactor. 99.9% pure Ar was used during the temperature ramp and charring to maintain an inert atmosphere. The molten salt after the product is separated can be reused.
(4) Firstly, washing with RO water to remove residual solidified salt in the product; then, soaking the cleaned product for 11 hours by using 1.5mol/L hydrochloric acid, taking out, soaking for 11 hours by using 1.5mol/L hydrochloric acid, and then washing the product to be neutral by using deionized water; finally, soaking the mixture for 12 hours by using 95 wt.% of ethanol, repeating the ethanol soaking process for 1 time, and then leaching the mixture by using ethanol; and (4) drying the washed product at 80 ℃ for 5 hours in vacuum to obtain the porous carbon material. The product yield under these conditions was 14.9%.
(5) The preparation method of the supercapacitor electrode comprises the following steps:
grinding the porous carbon material in the step (4) to carbon powder with uniform particle size, then weighing a proper amount of carbon powder, acetylene black and PTFE suspension according to a mass ratio of 8:1:1, simultaneously adding absolute ethyl alcohol as a dispersing agent for full mixing, rolling a sticky matter formed by removing the proper amount of ethyl alcohol into a uniform carbon film with the thickness of 0.06mm, drying the uniform carbon film in vacuum at 80 ℃ for 9 hours, cutting the dried carbon film into a plurality of phi 1cm circular sheets, simultaneously weighing to determine the mass of an active substance, and then respectively pressing the circular sheets on a foam nickel net and a titanium net under 4MPa to respectively obtain a super capacitor electrode-a foam nickel electrode and a titanium net electrode, wherein the following detection is respectively carried out:
wherein, the titanium mesh electrode is arranged at 1mol/L H2SO4A three-electrode system is adopted in the aqueous solution to test the energy storage performance of the carbon material (in the three-electrode system, a platinum sheet electrode and a saturated calomel electrode are respectively adopted as a counter electrode and a reference electrode.
The foamed nickel electrodes with the same size and the approximately same mass are separated by an alkali-resistant diaphragm to form a two-electrode super capacitor assembly, 6mol/L KOH aqueous solution is used as electrolyte, and a two-electrode system is adopted to test the energy storage performance of the carbon material. The specific capacitance calculated by GCD discharge curves of the three-electrode and two-electrode test systems under the current density of 1A/g is 176.71F/g and 112.22F/g respectively.
Claims (10)
1. A method for preparing a porous carbon material by treating tobacco waste with molten salt comprises the following steps:
(1) pretreatment of raw materials
Cleaning and drying the tobacco waste raw material by reverse osmosis water, and then crushing the tobacco waste raw material to a proper particle size;
(2) pretreatment of inorganic salts
Putting a proper amount of inorganic salt into a ceramic crucible, putting the ceramic crucible and the inorganic salt into a graphite crucible, putting the graphite crucible into a reactor, and putting the reactor into a tubular electric furnace to dry the inorganic salt;
(3) charring
The carbonization process is carried out in inert atmosphere, and comprises the following steps in sequence:
firstly, putting dried inorganic salt into a reactor, and heating to a carbonization temperature to form molten salt;
secondly, wrapping the pretreated raw material particles obtained in the step (1) with foamed nickel or putting the pretreated raw material particles into a carbonization basket and immersing the raw material particles into molten salt for carbonization for 0.5-8 hours;
thirdly, after carbonization, taking out the product from the molten salt, then cooling the product to a temperature lower than 500 ℃ in an inert atmosphere, and then removing the product out of the reactor;
(4) work-up of the product
And (3) cleaning the product with reverse osmosis water to remove residual salt, soaking with dilute hydrochloric acid, washing with deionized water to neutrality, soaking with ethanol, leaching, and vacuum drying to obtain the porous carbon material.
2. The method of claim 1, wherein the tobacco waste of step (1) comprises tobacco stems, tobacco stems and/or tobacco dust.
3. The method according to claim 1, wherein the inorganic salt in step (2) is an elemental inorganic salt or a mixed salt prepared from two or more elemental inorganic salts according to a certain ratio, and the elemental inorganic salt comprises at least one of hydroxides, halides, carbonates, and sulfates of alkali metals, alkaline earth metals, and transition metals.
4. The method according to claim 3, wherein the step (3) of immersing in the molten salt means that the liquid level of the molten salt exceeds the raw material by 0.5-10 cm.
5. The method according to claim 4, wherein the carbonization temperature in the step (3) is 450-1000 ℃.
6. The method according to claim 1, wherein the product obtained in the step (4) is dried under vacuum at 80-90 ℃ for 6-12 hours.
7. Use of a porous carbon material prepared by the method of any one of claims 1 to 6 in the preparation of an electrode for a supercapacitor.
8. The application according to claim 7, characterized in that it comprises the following steps:
firstly, adding a proper amount of conductive agent, adhesive and dispersant into a porous carbon material, and uniformly mixing to obtain a mixture;
secondly, removing a proper amount of dispersant from the mixture, rolling the mixture into a carbon film with uniform thickness, drying the carbon film in vacuum, cutting the dried carbon film into a proper size, and pressing the carbon film on a current collector to obtain a single-chip supercapacitor electrode;
thirdly, assembling the two-electrode supercapacitor assembly: and (3) placing the diaphragm between the two monolithic supercapacitor electrodes to obtain the two-electrode supercapacitor assembly.
9. The use according to claim 8, wherein the conductive agent is acetylene black, the binder is PTFE, the dispersant is absolute ethyl alcohol or isopropyl alcohol, and the mass ratio of the porous carbon material to the acetylene black to the PTFE is 8:1: 1.
10. The use according to claim 8, wherein the membrane used in step (three) is a water-based acid and alkali resistant membrane.
Priority Applications (1)
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114149023A (en) * | 2021-12-02 | 2022-03-08 | 南京工程学院 | High-value conversion and reuse method for tobacco waste |
| CN114931232A (en) * | 2022-06-13 | 2022-08-23 | 湖北中烟工业有限责任公司 | Heating cigarette cartridge and preparation method thereof |
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| CN104071789A (en) * | 2014-07-14 | 2014-10-01 | 武汉大学 | Method for preparing capacitive active carbon powder through biomaterial treated by fused salt |
| CN108117073A (en) * | 2017-12-29 | 2018-06-05 | 中南民族大学 | A kind of method and application that porous carbon materials are prepared using water hyacinth |
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| CN104071789A (en) * | 2014-07-14 | 2014-10-01 | 武汉大学 | Method for preparing capacitive active carbon powder through biomaterial treated by fused salt |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114149023A (en) * | 2021-12-02 | 2022-03-08 | 南京工程学院 | High-value conversion and reuse method for tobacco waste |
| CN114149023B (en) * | 2021-12-02 | 2024-01-26 | 南京工程学院 | Method for high-value conversion and reutilization of tobacco waste |
| CN114931232A (en) * | 2022-06-13 | 2022-08-23 | 湖北中烟工业有限责任公司 | Heating cigarette cartridge and preparation method thereof |
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