CN115285983B - Method for recycling negative electrode retired graphite and method for modifying manganese oxide by using negative electrode retired graphite - Google Patents
Method for recycling negative electrode retired graphite and method for modifying manganese oxide by using negative electrode retired graphite Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 148
- 229910002804 graphite Inorganic materials 0.000 title claims abstract description 64
- 239000010439 graphite Substances 0.000 title claims abstract description 64
- 238000000034 method Methods 0.000 title claims abstract description 45
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 title abstract description 10
- 238000004064 recycling Methods 0.000 title abstract description 10
- 229910021389 graphene Inorganic materials 0.000 claims abstract description 66
- 239000003054 catalyst Substances 0.000 claims abstract description 30
- 241000533950 Leucojum Species 0.000 claims abstract description 27
- 239000000243 solution Substances 0.000 claims description 28
- 238000003756 stirring Methods 0.000 claims description 26
- 239000000725 suspension Substances 0.000 claims description 19
- 239000007787 solid Substances 0.000 claims description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 18
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 15
- 238000006243 chemical reaction Methods 0.000 claims description 13
- 238000002360 preparation method Methods 0.000 claims description 11
- 239000008367 deionised water Substances 0.000 claims description 10
- 229910021641 deionized water Inorganic materials 0.000 claims description 10
- 238000001035 drying Methods 0.000 claims description 8
- 238000005406 washing Methods 0.000 claims description 8
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 6
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 6
- 230000008569 process Effects 0.000 claims description 5
- 239000007788 liquid Substances 0.000 claims description 4
- 239000010453 quartz Substances 0.000 claims description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 4
- 239000010926 waste battery Substances 0.000 claims description 4
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 3
- 238000010335 hydrothermal treatment Methods 0.000 claims description 3
- 239000011259 mixed solution Substances 0.000 claims description 3
- 238000010899 nucleation Methods 0.000 claims description 3
- 239000002244 precipitate Substances 0.000 claims description 3
- 238000001914 filtration Methods 0.000 claims description 2
- 230000006911 nucleation Effects 0.000 claims description 2
- 238000002156 mixing Methods 0.000 claims 1
- 238000011069 regeneration method Methods 0.000 abstract description 9
- 230000008929 regeneration Effects 0.000 abstract description 8
- 230000003197 catalytic effect Effects 0.000 abstract description 7
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 abstract description 6
- 229910052744 lithium Inorganic materials 0.000 abstract description 6
- 230000015572 biosynthetic process Effects 0.000 abstract description 4
- 230000007547 defect Effects 0.000 abstract description 4
- 238000005054 agglomeration Methods 0.000 abstract description 3
- 230000002776 aggregation Effects 0.000 abstract description 3
- 238000003786 synthesis reaction Methods 0.000 abstract description 3
- 229910000314 transition metal oxide Inorganic materials 0.000 abstract description 3
- 239000003607 modifier Substances 0.000 abstract description 2
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 36
- 239000011229 interlayer Substances 0.000 description 10
- 239000010410 layer Substances 0.000 description 7
- 239000012535 impurity Substances 0.000 description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 5
- 229910052760 oxygen Inorganic materials 0.000 description 5
- 239000001301 oxygen Substances 0.000 description 5
- 230000027756 respiratory electron transport chain Effects 0.000 description 5
- 239000002245 particle Substances 0.000 description 4
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- 239000002086 nanomaterial Substances 0.000 description 3
- 239000012855 volatile organic compound Substances 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- 238000005411 Van der Waals force Methods 0.000 description 2
- 241000276425 Xiphophorus maculatus Species 0.000 description 2
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- 238000009830 intercalation Methods 0.000 description 2
- 230000002687 intercalation Effects 0.000 description 2
- 238000002386 leaching Methods 0.000 description 2
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
- 238000013021 overheating Methods 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 230000001007 puffing effect Effects 0.000 description 2
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- 238000012360 testing method Methods 0.000 description 2
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- 239000012494 Quartz wool Substances 0.000 description 1
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- 239000011572 manganese Substances 0.000 description 1
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- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
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Classifications
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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
- C01B32/15—Nano-sized carbon materials
- C01B32/182—Graphene
- C01B32/184—Preparation
- C01B32/19—Preparation by exfoliation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8668—Removing organic compounds not provided for in B01D53/8603 - B01D53/8665
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8678—Removing components of undefined structure
- B01D53/8687—Organic components
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
- B01J23/32—Manganese, technetium or rhenium
- B01J23/34—Manganese
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/08—Heat treatment
- B01J37/10—Heat treatment in the presence of water, e.g. steam
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
- B01D2257/708—Volatile organic compounds V.O.C.'s
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/84—Recycling of batteries or fuel cells
Abstract
The application relates to a method for recycling negative electrode retired graphite and a method for modifying manganese oxide by using the same. On one hand, the application solves the problem of recycling a large amount of lithium battery negative electrode graphite resources in the current industrial application, and the prepared snowflake graphene has special morphology and excellent performance. On the other hand, the graphene after improved regeneration is an excellent modifier, and the prepared rGO@alpha-MnO 2 The catalyst overcomes the defects of low catalytic performance, synthesis agglomeration and difficult regeneration of transition metal oxide, and compared with common alpha-MnO 2 The performance is greatly improved.
Description
Technical Field
The application belongs to the technical field of catalyst preparation, and relates to a method for recycling negative electrode retired graphite and a method for modifying manganese oxide by using the same.
Background
The disclosure of this background section is only intended to increase the understanding of the general background of the application and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art already known to those of ordinary skill in the art.
Retired graphite typically contains contaminants originating from electrolytes, binders, solid electrolyte interface films (SEI) and copper foil so that it is difficult to directly utilize. How to reuse a large amount of lithium battery negative electrode graphite resources in industrial application is a technical problem to be solved urgently. In general, intercalation and deintercalation of lithium ions during charge and discharge of a lithium battery can lead to expansion of interlayer spacing of graphite, weakening of interlayer van der waals force, and compared with common graphite, the lithium battery is easier to form a platy carbon nanomaterial and is a high-quality carbon source for synthesizing graphene. The problems of impurity removal and recycling of the retired graphite cathode can be perfectly solved by means of high-energy microwaves. On one hand, the interlayer pollutants generate overheating effect to quickly heat and gasify, so that retired graphite impurity removal is realized; on the other hand, the gasification products are released instantly, the spacing between graphite layers is enlarged, and then a puffing effect is generated, so that the generation of high-quality graphene is facilitated. The graphene synthesized by the method has larger interlayer spacing and more defects in theory, and can greatly improve the electron transfer rate and reduce the particle size of the nano material by compounding with the transition metal oxide, so that the graphene has wide application prospect. Further, high-quality graphene and alpha-MnO are utilized 2 The defects of low performance, synthesis agglomeration and difficult regeneration of the current VOCs catalyst can be effectively solved by compounding, the treatment of waste with waste is truly realized, and the reasonable utilization of resources is realized.
Disclosure of Invention
In order to solve the problems in the prior art, the application provides a method for recycling negative electrode retired graphite and a method for modifying manganese oxide by using the same. Firstly, the application solves the problem of recycling a large amount of resources of lithium battery negative electrode graphite in the current industrial application, and provides a high-energy microwave thermal shock-improved Hummers method for preparing snowflake graphene, so that the prepared graphene has special morphology and excellent performance, and is an excellent modifier. Then, rGO@alpha is prepared by an anchor-nucleation growth process-MnO 2 A catalyst. In one aspect, graphene oxide oxygen-containing functionality is taken as Mn 2+ The anchoring site of the catalyst can promote the dispersibility of the catalyst, effectively inhibit the agglomeration of particles and reduce the particle size. On the other hand, snowflake graphene is used as an electron transmission channel, so that the electron transfer characteristic of a catalyst can be effectively improved, the regeneration of oxygen vacancies is promoted, and the synthesized rGO@alpha-MnO 2 The catalyst can realize the efficient degradation of VOCs at low temperature.
Specifically, the technical scheme of the application is as follows:
in a first aspect of the application, a method for recycling negative electrode retired graphite is provided, a regeneration method of a high-energy microwave repeated impact-improved Hummers method is created, and finally snowflake graphene oxide suspension is prepared.
Specifically, the method comprises the following steps:
firstly, placing negative graphite obtained by disassembling a completely discharged waste battery into NaOH solution for stirring; then filtering, washing and drying; placing graphite powder into a quartz reactor for microwave impact, introducing Ar under a closed condition, and adjusting the power and the temperature of a solid microwave source; after the microwave impact is circulated for a plurality of times, the graphite powder is treated by adopting a modified Hummers method to obtain graphene oxide suspension.
Further, the concentration of the NaOH solution is 2-4mol/L.
Further, the flow rate of Ar introduced into each 1g of retired graphite is 300-1000mL/min.
Further, the solid state microwave source power is 1000W and the upper temperature limit is 1200 ℃.
Further, the impact mode is to cool for 30s after reaching the upper limit temperature once, and then continue to heat up for a total of 5-20 cycles; and then taking out the graphite sample, and placing the graphite sample in a drying oven for standby.
Further, the graphene oxide suspension is obtained by treating graphite powder by adopting a modified Hummers method. Firstly, placing expanded graphite treated by microwave in a beaker, adding concentrated H into the beaker 2 SO 4 (98%) and stirring continuously for 30min under ice bath, the solid-to-liquid ratio of the expanded graphite to the concentrated sulfuric acid is 1: (20-40), in g: and (3) mL. Stirring while stirringIn the process, H is added dropwise to the solution 3 PO 4 The volume ratio of the concentrated sulfuric acid to the phosphoric acid is (6-8): 1. then KMnO is carried out 4 Adding the solid into the mixed solution ten times at intervals of 5-7min, KMnO 4 The mass ratio of the graphite to the expanded graphite is 6:1. then, stirring for 2h respectively at 35 ℃ under ice bath, adding a proper amount of deionized water after stirring, heating to 80 ℃ and continuing stirring for 1h. Finally, H is added dropwise after stirring is completed 2 O 2 (30%) desired concentration of H 2 SO 4 And H is 2 O 2 The volume ratio of (1-3): and 1, washing with water for 5-7 times to obtain graphene oxide suspension.
According to the second aspect of the application, snowflake graphene solid is obtained by freeze-drying snowflake graphene suspension prepared by the method.
In a third aspect of the application, a snowflake graphene modified alpha-MnO is provided 2 A method for preparing the catalyst. By virtue of the excellent properties of graphene, with MnO 2 The performance of the prepared catalyst is compared with that of common MnO 2 The catalyst has greatly improved catalytic performance.
The method specifically comprises the following steps:
placing the graphene oxide suspension in a container, adding deionized water, and adding MnSO into the solution 4 ·H 2 O, stirring until the solid is dissolved; KMnO 4 Dripping the solution into the solution, and continuously stirring for 1-2h to complete the primary reaction; after the solution reaction is stopped, heating the solution at 150 ℃ for 12 hours to complete the nucleation process; taking out the precipitate after hydrothermal treatment, washing and drying to obtain snowflake graphene modified alpha-MnO 2 A catalyst.
Further, the concentration of the graphene oxide suspension is 1-3mg/mL.
Further, graphene oxide and MnSO 4 ·H 2 The mass ratio of O is (1-5): 53.
further, the volume of deionized water filled should be such that the total volume of solution reaches 50% of the liner volume of the reactor.
Further, the reaction is carried out in the presence of KMnO 4 With MnSO 4 ·H 2 The molar ratio of O should be kept at (8-9): 3.
in a fourth aspect of the application, snowflake graphene modified alpha-MnO prepared by the method is provided 2 A catalyst.
Depending on the operating principle and structural composition of the lithium battery negative electrode, retired graphite typically contains contaminants originating from electrolytes, binders, solid electrolyte interface films (SEI) and copper foil, making it difficult to directly utilize. However, compared to natural crystalline flake graphite, intercalation and deintercalation of lithium ions during charge and discharge of a battery causes expansion of graphite interlayer spacing, weakening of interlayer van der waals force, and easier formation of platy and sp2 hybridized carbon nanomaterial. At the same time, the attached oxygen-containing groups may prevent interlayer polymerization from occurring. Therefore, the intrinsic structure with expanded decommissioning graphite interlayer spacing makes the intrinsic structure easier to be intercalated, and the intrinsic structure used as a raw material for preparing graphene or graphene oxide has an inherent advantage condition.
According to the application, the retired graphite cathode is selected as a grapheme carbon source, the retired graphite is repeatedly impacted by high-energy microwaves to complete graphite puffing, and snowflake graphene oxide is synthesized by an improved Hummers method. Simultaneously, adopting a hydrothermal method to generate alpha-MnO on graphene oxide in situ 2 A nano catalyst. By means of improved graphene and alpha-MnO 2 An electron transfer channel is formed, so that the electron transfer capability is improved, the regeneration of oxygen vacancies is accelerated, and the performance of the catalyst is further improved.
One or more of the technical schemes in the application has the following beneficial effects:
(1) The application realizes the regeneration preparation of the high-performance graphene material by the negative electrode retired graphite. The microwave is acted on the retired graphite to induce rapid heating through unique high-energy microwave repeated impact, and meanwhile, local hot spots and overheating effects in the form of arc plasma are generated to enable interlayer impurities to be rapidly gasified, so that impurity removal and stripping of the retired negative graphite are realized. And meanwhile, by improving the Hummers method, the expanded graphite is oxidized and reused, so that a new idea is provided for the recycling of the graphite.
(2) The application provides a graphene improvement method. By improving the carbon source, the high-quality snowflake graphene with excellent performance and special morphology is synthesized. Compared with common graphene, the prepared snowflake graphene has more edge defects and larger interlayer spacing, and can improve the electron transfer capability and the oxygen vacancy regeneration capability of the catalyst after being compounded with transition metal oxide.
(3) The application provides a rGO@MnO 2 Methods of using the composite materials in the catalytic field. The prepared catalyst is compared with common MnO 2 The structure is optimized, the electron transmission performance is improved, and the toluene degradation performance is greatly improved. Meanwhile, through modification of graphene, the catalytic performance of the graphene is greatly improved under high humidity, and toluene is efficiently degraded under high humidity atmosphere.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application.
FIG. 1 is a process flow diagram of the present application;
FIG. 2 is a scanning electron microscope image of retired graphite as is;
FIG. 3 is a scanning electron microscope image of exfoliated expanded graphite after repeated impact of high energy microwaves;
FIG. 4 is a scanning electron micrograph of snowflake graphene prepared by a modified Hummers method;
FIG. 5 is an enlarged view of a snowflake graphene solid scanning electron microscope prepared by a modified Hummers method;
FIG. 6 is a graph showing the performance of each catalyst in the dry state for the catalytic oxidation of toluene;
FIG. 7 is a graph showing the performance of each catalyst in catalyzing the oxidation of toluene in a wet environment.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
Example 1
A method for preparing snowflake graphene by regenerating retired negative electrode graphite comprises the following steps:
firstly, placing negative graphite obtained by disassembling the discharged waste batteries in 2L of NaOH solution (2 mol/L) and stirring for 1h to remove part of DMF impurities. Subsequently, the graphite in the solution was filtered, washed to a solution ph=7 and dried at 90 ℃ for 12h. Next, 0.5g of the graphite powder after alkaline leaching was weighed, placed in a quartz reactor, and Ar (300 mL/min) was introduced under airtight conditions after an infrared thermocouple was installed. Subsequently, the solid state microwave source power was adjusted to 1000W with an upper temperature limit of 1200 ℃. The impact mode is to cool for 30s after reaching the upper limit temperature once, and then to continue to heat up for a total of 5-20 cycles. Taking out the graphite sample after each impact, and placing the graphite sample in a drying oven for standby. And (3) placing a proper amount of pretreated expanded graphite into a beaker, and treating by adopting a modified Hummers method to obtain graphene oxide suspension. The operation is as follows, firstly, the expanded graphite treated by microwave is placed in a beaker, and concentrated H is added into the beaker 2 SO 4 (98%) and stirring continuously for 30min under ice bath, the solid-to-liquid ratio of the expanded graphite to the concentrated sulfuric acid is 1:30, in g: and (3) mL. During stirring, H was added dropwise to the solution 3 PO 4 The volume ratio of phosphoric acid to concentrated sulfuric acid is 1:7.5. then KMnO is carried out 4 Adding the solid into the mixed solution ten times at intervals of 6min KMnO 4 The mass ratio of the graphite to the expanded graphite is 6:1. then, stirring for 2h respectively at 35 ℃ under ice bath, adding a proper amount of deionized water after stirring, heating to 80 ℃ and continuing stirring for 1h. Finally, dropwise adding H after stirring 2 O 2 (30%) desired concentration of H 2 SO 4 And H is 2 O 2 The volume ratio is 1: and 3, washing with water for 5-7 times to obtain graphene oxide suspension. The concentration of the graphene oxide suspension is set to 2mg/mL for standby. And freeze-drying the graphene oxide suspension liquid to obtain snowflake graphene solid.
Example 2
Retired negative electrode graphite regeneration preparation rGO@alpha-MnO 2 A method of preparing a highly effective VOCs catalyst comprising:
the preparation process diagram is shown in figure 1. Firstly, when the volume of a hydrothermal kettle is selected to be 100ml, 5ml and 10ml of graphene suspension prepared in example 1 are measured respectively, the graphene suspension is placed in a beaker, different amounts of deionized water are added, and the volume of the solution is set to be 50ml. Then, mnSO is added to the solution 4 ·H 2 O solid is stirred until the solid is dissolved, and graphene oxide and MnSO are oxidized 4 ·H 2 The mass ratio of O is 1:53 and 2:53. subsequently, KMnO was weighed 4 Preparing solid into solution, slowly dripping into the solution, and stirring for 30min to react KMnO 4 With MnSO 4 ·H 2 The molar ratio of O should be kept at 8:3. after the reaction of the solutions had ceased, the solutions were placed in respective 100ml polytetrafluoroethylene tanks and heated at 150℃for 12h. Taking out the precipitate after hydrothermal treatment, washing with deionized water for three times, drying at 110deg.C for 12 hr, and marking the solids as 1% rGO @ α -MnO respectively 2 、2％rGO@α-MnO 2 . For comparative experiments, 50ml of deionized water was measured and the above procedure was repeated to obtain a sample labeled as α -MnO 2 . The dosage of the medicines required by the preparation process is proportionally increased according to the increase of the volume of the reaction vessel.
Scanning electron microscope test analysis for snowflake graphene preparation process
As shown in fig. 2, the graphite powder after the alkaline leaching treatment is as it is, and has rough surface and particles of different sizes attached, and the analysis is considered to be waste battery electrolyte or untreated clean KOH residues. The graphite powder is compact in shape and is typical of the multi-layer stacking phenomenon of graphite layers.
As shown in fig. 3, in example 1, the characteristics of graphite powder changed greatly after ten impacts with microwaves. First, the dense graphite structure is exfoliated into a plurality of graphite sheets, the graphite layers have different intervals, and the surfaces of the graphite layers have wrinkles. Next, the graphite layer had a smooth surface and remained intact. According to analysis, graphite powder solid is peeled off after ten times of repeated microwave impact, a graphite layer is thinned, and impurities on the surface of graphite are removed through multiple times of impact, so that the preparation of graphene is facilitated.
As shown in fig. 4, snowflake graphene prepared by the modified Hummers method exhibits a monolayer thin snowflake morphology. As shown in fig. 5, by magnification, it was observed that there were many wrinkles on the snowflake graphene surface, which is typical of graphene morphology.
Catalyst performance test:
catalyst test preparation: the catalyst powder obtained in example 2, 0.2-0.4g, was tableted and sieved to 40-60 mesh, and packed in a quartz reactor, and fixed using double-layered quartz wool. The synthesis air of 250-500mL/min was used to carry vaporized toluene into the reactor for reaction, with toluene concentration set at 300ppm. Simultaneously, the water vapor generating device is connected in parallel, and the atmosphere humidity value is synchronously controlled. The reactor is placed in a vertical tube furnace, and the tube furnace is set to be programmed to heat up the catalyst. At the reactor outlet, a gas chromatograph was equipped for tail gas detection and toluene conversion was calculated by the following formula:
wherein [ tolutene ]] in and[Toluene] out Representing the inlet toluene concentration and the outlet toluene concentration, respectively.
A schematic of toluene conversion at 25% relative humidity and 80000 ml/(gh) space velocity is shown in FIG. 6. First, 2% rGO-alpha-MnO 2 Exhibits optimal catalytic performance, T90 is about 166.8 ℃,1% rGO-alpha-MnO 2 The performance is relatively poor due to the smaller doping amount of graphene. Second, compared to 1% flake rGO@α -MnO 2 、α-MnO 2 The catalyst performance of the composite snowflake graphene is greatly improved, which proves that the composite snowflake graphene effectively improves the electron transmission performance, and further improves the catalyst performance.
The toluene conversion at wet conditions (rh=80-85%) and at a space velocity of 80000 ml/(gh) is schematically shown in fig. 7. On the one hand, the performance of the improved catalyst in a wet environment is maintained, which proves that rGO@alpha-MnO 2 Has higher hydrophobic property and can adapt to severe catalytic atmosphere. On the other hand, the catalyst performance of snowflake graphene with the doping amount of 2 percent is better than 1 percentWhich demonstrates that snowflake graphene plays an important role in combating high humidity environments.
The above description is only of the preferred embodiments of the present application and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (8)
1. Snowflake graphene modified alpha-MnO 2 The preparation method of the catalyst is characterized by comprising the following steps:
placing graphene oxide suspension in a container, adding deionized water, and adding MnSO into the solution 4 ·H 2 O, stirring until the solid is dissolved; KMnO 4 Dripping the solution into the solution, and continuously stirring for 1-2h to complete the primary reaction; after the reaction of the solution is stopped, heating the solution at 150 ℃ for 12 hours to complete the nucleation process; taking out the precipitate after hydrothermal treatment, washing and drying to obtain snowflake graphene modified alpha-MnO 2 A catalyst;
the graphene oxide suspension is prepared by a method for reutilizing negative electrode retired graphite;
the method for reutilizing the negative electrode retired graphite comprises the following steps:
firstly, placing negative graphite obtained by disassembling a completely discharged waste battery into NaOH solution for stirring; then filtering, washing and drying; placing the obtained graphite powder into a quartz reactor for microwave impact, introducing Ar under a closed condition, and adjusting the power and the temperature of a solid microwave source; after microwave impact, treating the graphite powder by adopting an improved Hummers method to obtain graphene oxide suspension;
the power of the solid microwave source is 1000W, and the upper limit of the temperature is 1200 ℃; the impact mode is that after reaching the upper limit temperature once, the temperature is cooled for 30 seconds, and then the temperature is continuously raised for a total of 5-20 times; and taking out the expanded graphite powder after each impact, and placing the expanded graphite powder in a drying oven for standby.
2. The method according to claim 1, wherein the concentration of the NaOH solution is 2-4mol/L.
3. The process of claim 1, wherein a flow rate of 300-1000mL/min of Ar is required per 1g of retired graphite.
4. The method according to claim 1, wherein,
the specific steps of the improved Hummers method are as follows: mixing and stirring the expanded graphite treated by the microwaves with concentrated sulfuric acid, wherein the solid-to-liquid ratio is 1: (20-40), in g: mL; during stirring, H was added dropwise to the solution 3 PO 4 The volume ratio of the concentrated sulfuric acid to the phosphoric acid is (6-8): 1, a step of; then KMnO is carried out 4 Adding the solid into the mixed solution ten times at intervals of 5-7min, KMnO 4 The mass ratio of the graphite to the expanded graphite is 6:1, a step of; then, respectively stirring for 2 hours at 35 ℃ under ice bath, adding a proper amount of deionized water after stirring, heating to 80 ℃ and continuing stirring for 1 hour; finally, H is added dropwise after stirring is completed 2 O 2 (30%) desired concentration of H 2 SO 4 And H is 2 O 2 The volume ratio of (1-3): 1, and then washing for 5-7 times to obtain graphene oxide suspension, wherein the concentration of the suspension is 1-3mg/mL.
5. The preparation method according to claim 1, wherein the graphene oxide suspension is used in an amount corresponding to the amounts of graphene oxide and MnSO 4 ·H 2 The mass ratio of O is (1-5): 53.
6. the method according to claim 1, wherein the deionized water is used in an amount such that the total volume of the reaction solution is 50% of the volume of the reaction vessel.
7. The preparation method according to claim 6, wherein KMnO is used for reacting the desired KMnO 4 With MnSO 4 ·H 2 Moles of OThe ratio should be kept at (8-9): 3.
8. snowflake graphene modified alpha-MnO prepared by the method according to any one of claims 1-7 2 A catalyst.
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