A method for producing graphene from needle coke

Abstract

The application provides a method for preparing graphene from needle coke, and belongs to the technical field of graphene preparation. The method comprises the following steps: 1) mixing needle coke, a strong oxidizing agent and a solvent, and performing ultrasonic treatment on the mixture to obtain an ultrasonic material; 2) performing high-temperature and high-pressure treatment on the ultrasonic material, and instantaneously releasing pressure after the high-temperature and high-pressure treatment is completed to obtain exfoliated needle coke; and 3) performing vacuum microwave treatment on the exfoliated needle coke to obtain graphene. The method provided by the application is simple in process, suitable for industrial production, and can prepare graphene with a high single-layer rate and good quality.

Description

Technical Field

[0001] This invention belongs to the field of graphene preparation technology, and particularly relates to a method for preparing graphene using needle coke. Background Technology

[0002] Graphene is generally prepared from flake graphite using methods such as mechanical exfoliation, chemical vapor deposition, epitaxial crystal growth, or redox methods.

[0003] Mechanical exfoliation obtains pure graphene sheets by mechanically exfoliating graphite, but its low yield prevents large-scale production. Chemical vapor deposition (CVD) or epitaxial growth uses thermally decomposed hydrocarbon gases deposited on nickel or copper sheets to prepare graphene. This method can produce large-area single-layer or multi-layer graphene, but its uniformity and thickness are difficult to control. Additionally, growing graphene on insulating substrates, such as silicon carbide, can produce extremely thin sheets, but this method is expensive and difficult to produce in large areas.

[0004] Traditional redox methods utilize graphite powder or graphite fibers to chemically exfoliate functionalized graphite oxides using strong oxidizing agents such as sulfuric acid and nitric acid, or other oxidizing agents. These oxides are then rapidly expanded and exfoliated in a high-temperature furnace at 1100°C to 1250°C. However, if the exfoliated graphene is not collected quickly, it is prone to deformation and warping, resulting in inconsistent graphene quality. Furthermore, the exfoliated graphene is easily combustible in high-temperature air, posing a potential fire hazard and posing a safety threat to the industrial application of graphene production. Summary of the Invention

[0005] This invention provides a method for preparing graphene using needle coke. The method is simple, suitable for industrial production, and produces graphene with high monolayer ratio and good quality.

[0006] To achieve the above objectives, the present invention provides a method for preparing graphene using needle-shaped coke, comprising the following steps:

[0007] 1) Mix needle coke, strong oxidant and solvent, and sonicate the mixture to obtain ultrasonic material;

[0008] 2) The ultrasonic material is subjected to high temperature and high pressure treatment. After the high temperature and high pressure treatment is completed, the pressure is released instantaneously to obtain the stripped needle coke.

[0009] 3) The stripped needle-like coke is subjected to vacuum microwave treatment to obtain graphene.

[0010] Preferably, the strong oxidant in step 1) is one or more of sulfuric acid, potassium permanganate and nitric acid.

[0011] Preferably, the sulfur content in the needle coke in step 1) is >2% by weight, and the particle size of the needle coke is <1mm.

[0012] Preferably, the solvent in step 1) includes one or more of ethanol, N-methylpyrrolidone, tetrahydrofuran, and pyrrole.

[0013] Preferably, the mass ratio of needle coke, strong oxidant and solvent in step 1) is 1-1.5:2-3:4-6.

[0014] Preferably, in step 1), stirring is also performed during the ultrasonic treatment.

[0015] Preferably, in step 2), the high-temperature and high-pressure treatment is performed at a pressure of 1–15 MPa, a temperature of 150–200 °C, and a time of 60–300 min.

[0016] Preferably, the high-pressure device used for high-temperature and high-pressure treatment in step 2) is provided with a number of micro-hole outlets, the diameter of which is 1 to 1.1 mm.

[0017] Preferably, the process further includes drying the stripped needle coke before vacuum microwave treatment.

[0018] Preferably, the microwave power during the vacuum microwave treatment in step 3) is 10-20 kW and the time is 30-120 min.

[0019] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0020] This invention uses needle coke as a raw material to prepare graphene, which is less expensive than flake graphite, thus reducing production costs. By combining ultrasonic, high-temperature and high-pressure, and vacuum microwave graphitization processes, thin-sheet graphene is obtained. Furthermore, the production process of this invention is simple, has a short reaction cycle, and high production efficiency. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This invention provides a method for preparing graphene from needle coke, comprising the following steps:

[0023] 1) Mix needle coke, strong oxidant and solvent, and sonicate the mixture to obtain ultrasonic material;

[0024] 2) The ultrasonic material is subjected to high temperature and high pressure treatment. After the high temperature and high pressure treatment is completed, the pressure is released instantaneously to obtain the stripped needle coke.

[0025] 3) The stripped needle-like coke is subjected to vacuum microwave treatment to obtain graphene.

[0026] This invention involves mixing needle coke, a strong oxidant, and a solvent, and then ultrasonicating the mixture to obtain an ultrasonic material. In this invention, the sulfur content of the needle coke in step 1) is preferably >2% by weight, and the particle size of the needle coke is preferably <1 mm. In this invention, the strong oxidant is preferably one or more of sulfuric acid, potassium permanganate, and nitric acid. The solvent preferably includes one or more of ethanol, N-methylpyrrolidone, tetrahydrofuran, and pyrrole. In this invention, the mass ratio of needle coke, strong oxidant, and solvent is 1–1.5:2–3:4–6. In this invention, the ultrasonic frequency is preferably 20–30 kHz, and the ultrasonic time is preferably 60–120 min. In this invention, ultrasonication allows the needle coke to be more uniformly dispersed in the solvent, and the intercalating agent dissolves in the solvent, making it easier for the intercalating agent to enter the gaps in the needle coke and thus insert into the interlayer of the needle coke. By mixing needle coke, a hydroxide, and a solvent and then ultrasonicating, the needle coke is fully dispersed in the organic solvent of the strong oxidant, preparing for the next step of stripping. In this invention, to further ensure uniform mixing of the materials, stirring is preferably also performed during the ultrasonic treatment.

[0027] This invention uses needle coke as raw material. Compared with graphite, needle coke has a larger interlayer spacing, more impurities, and a lower price. The larger interlayer spacing makes it easier for intercalating agents to enter the interlayer spacing, and the more impurities can be vaporized in the subsequent vacuum microwave treatment process, thereby achieving the purpose of stripping the needle coke.

[0028] After obtaining the ultrasonic material, this invention subjectes it to high-temperature and high-pressure treatment. The pressure is then released instantaneously after the high-temperature and high-pressure treatment to obtain peeled needle coke. In this invention, the pressure of the high-pressure treatment is preferably 1–15 MPa, the temperature is preferably 150–200°C, and the time is preferably 60–300 min. In this invention, the needle coke and a strong oxidant are heated by high-temperature treatment. Under high-temperature and high-pressure conditions, the strong oxidant inserts between the needle coke layers, peeling off the needle coke. In this invention, the high-pressure device for high-temperature and high-pressure treatment is preferably equipped with several micro-hole outlets, the diameter of which is preferably 1–1.1 mm. In this invention, by providing micro-hole outlets, the peeled needle coke can be ejected from the micro-hole outlets under strong pressure when the pressure is released instantaneously, thereby further peeling off the needle coke, achieving a better peeling effect and reducing the sheet thickness. This invention does not have a special limitation on the source of the high-pressure device; conventional equipment in the art can be used.

[0029] After obtaining the stripped needle-like coke, the present invention performs vacuum microwave treatment on the stripped needle-like coke to obtain graphene. In the present invention, to facilitate microwave treatment, after stripping the needle-like coke, a drying process is preferably performed, specifically by solid-liquid separation followed by vacuum drying. In the present invention, the microwave power during the vacuum microwave treatment is preferably 10-20 kW, and the time is preferably 30-120 min. In the present invention, by performing vacuum microwave treatment on the stripped needle-like coke, the needle-like coke is graphitized to obtain graphene. In the present invention, microwave treatment under vacuum conditions can avoid the fire hazard caused by graphene combustion. At the same time, using microwaves for graphitization treatment can quickly obtain energy, allowing the needle-like coke to quickly remove functional groups and impurities such as sulfur, reducing the deformation and warping of graphene, thereby obtaining graphene with high morphological uniformity.

[0030] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0031] The needle coke used in the following examples has a sulfur content of 4% and a particle size of <1mm. The flake graphite has a particle size of 325 mesh.

[0032] Example 1

[0033] Needle coke, sulfuric acid, and ethanol were mixed in a mass ratio of 1:2:6. The mixture was then ultrasonicated (30 kHz, 60 min) while simultaneously stirring at 500 rpm to obtain an ultrasonically processed material. This material was then treated at 150°C and 10 MPa for 300 min, followed by instantaneous pressure release. The needle coke was ejected from the micro-orifice of a high-pressure device (1 mm aperture). The ejected material was subjected to solid-liquid separation to obtain exfoliated needle coke. This exfoliated needle coke was then subjected to vacuum microwave treatment (20 kW, 60 min) to obtain graphene.

[0034] Example 2

[0035] Needle coke, nitric acid, and tetrahydrofuran were mixed in a mass ratio of 1:3:5. The mixture was then ultrasonicated (frequency 25 kHz, time 90 min) while simultaneously stirring at 400 r / min to obtain an ultrasonically processed material. This material was then treated at 180℃ and 15 MPa for 240 min, followed by instantaneous pressure release. The needle coke was ejected from the micro-orifice of the high-pressure device (orifice diameter 1 mm). The ejected material was subjected to solid-liquid separation to obtain exfoliated needle coke. This exfoliated needle coke was then subjected to vacuum microwave treatment (power 15 kW, time 90 min) to obtain graphene.

[0036] Example 3

[0037] Needle coke, potassium permanganate, and N-methylpyrrolidone were mixed in a mass ratio of 1.5:3:6. The mixture was then ultrasonicated (frequency 20 kHz, time 120 min) while simultaneously stirring at 500 r / min to obtain ultrasonic material. The ultrasonic material was then treated at 200℃ and 1 MPa for 180 min, followed by instantaneous pressure release. The needle coke was ejected from the micro-orifice outlet of the high-pressure device (orifice diameter 1.1 mm). The ejected material was subjected to solid-liquid separation to obtain exfoliated needle coke. The exfoliated needle coke was then subjected to vacuum microwave treatment (power 10 kW, time 120 min) to obtain graphene.

[0038] Comparative Example 1

[0039] Needle coke, sulfuric acid, and ethanol were mixed in a mass ratio of 1:2:6. The mixture was then ultrasonicated (30 kHz, 60 min) while simultaneously stirring at 500 rpm to obtain an ultrasonically processed material. This material was then treated at 150°C and 10 MPa for 300 min, followed by instantaneous pressure release. The needle coke was ejected from the micro-orifice of a high-pressure device (1 mm aperture). The ejected material was subjected to solid-liquid separation to obtain exfoliated needle coke. This exfoliated needle coke was then subjected to vacuum microwave treatment (5 W, 30 min) to obtain graphene.

[0040] Comparative Example 2

[0041] The difference from Example 1 is that no ultrasonic treatment was performed.

[0042] Needle coke, sulfuric acid, and ethanol were mixed in a mass ratio of 1:2:6 and stirred at 500 rpm for 120 min to obtain a mixture. The mixture was then treated at 150°C and 10 MPa for 300 min, followed by instantaneous pressure release. The needle coke was ejected from the micro-orifice of the high-pressure device (1 mm aperture). The ejected material was subjected to solid-liquid separation to obtain exfoliated needle coke. The exfoliated needle coke was then subjected to vacuum microwave treatment (20 kW, 60 min), followed by drying to obtain graphene.

[0043] Comparative Example 3

[0044] The difference from Example 1 is that graphitization is performed by sintering, and the specific operation is as follows:

[0045] Needle coke, sulfuric acid, and ethanol were mixed in a mass ratio of 1:2:6. The mixture was then ultrasonicated (30 kHz, 60 min) while simultaneously stirring at 500 rpm to obtain an ultrasonically processed material. This material was then treated at 150°C and 10 MPa for 300 min, followed by instantaneous pressure release. The needle coke was ejected from the micro-orifice of the high-pressure device (1 mm aperture). The ejected material was subjected to solid-liquid separation to obtain exfoliated needle coke. This exfoliated needle coke was then calcined under vacuum at 2800°C for 5 h to obtain graphene.

[0046] Performance testing

[0047] The properties of the graphene prepared in Examples 1-3 and Comparative Examples 1-3 were tested.

[0048] Table 1 Properties of Graphene

[0049]

[0050] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing graphene from needle coke, characterized in that, Includes the following steps: 1) Mix needle coke, strong oxidant and solvent, and sonicate the mixture to obtain ultrasonic material; 2) The ultrasonic material is subjected to high temperature and high pressure treatment. After the high temperature and high pressure treatment is completed, the pressure is released instantaneously to obtain the stripped needle coke. 3) The stripped needle-like coke is subjected to vacuum microwave treatment to obtain graphene; In step 2), the high-temperature and high-pressure treatment is carried out at a pressure of 1~15 MPa, a temperature of 150~200℃, and a time of 60~300 min.

2. The method according to claim 1, characterized in that, The strong oxidizing agent mentioned in step 1) is one or more of sulfuric acid, potassium permanganate and nitric acid.

3. The method according to claim 1, characterized in that, By weight percentage, the sulfur content in the needle coke in step 1) is >2%, and the particle size of the needle coke is <1mm.

4. The method according to claim 1, characterized in that, The solvent mentioned in step 1) includes one or more of ethanol, N-methylpyrrolidone, tetrahydrofuran, and pyrrole.

5. The method according to claim 1, characterized in that, The mass ratio of needle coke, strong oxidant and solvent in step 1) is 1~1.5:2~3:4~6.

6. The method according to claim 1, characterized in that, In step 1), stirring is also performed during the ultrasonic treatment process.

7. The method according to claim 1, characterized in that, The high-pressure device used for high-temperature and high-pressure treatment in step 2) is equipped with several micro-hole outlets, the diameter of which is 1~1.1mm.

8. The method according to claim 1, characterized in that, The process also includes drying the stripped needle coke before vacuum microwave treatment.

9. The method according to claim 1, characterized in that, The microwave power during vacuum microwave processing described in step 3) is 10~20kw, and the time is 30~120min.

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