Method for preparing graphene-like material using metallurgical coke fines

Abstract

The present application relates to a kind of methods for preparing graphene-like using metallurgical coke powder, comprising crushing, high pressure extraction, chemical oxidation, solid phase reduction and solvent stripping etc.;The present application solves the problem of high value-added utilization of coke powder in coking enterprises, the shape and size distribution of the obtained graphene-like are uniform, and the impurity content is extremely low, which develops a cheap and easy-to-obtain production raw material for graphene manufacturing, can reduce production cost, and shorten production process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of graphene material preparation, and particularly relates to a method for preparing graphene-like material by using metallurgical coke powder. BACKGROUND

[0002] Carbon-based nanomaterials have attracted extensive scientific attention in recent years due to their unique physical, chemical, electronic and mechanical properties, which are used as key components of fuel cells, biosensors, catalysts, batteries and electronic devices. The most original synthesis of nanomaterials uses expensive carbon precursors such as high-purity graphite, while the reserves of natural graphite are extremely low and the production cost of synthetic graphite is high. At present, technologies for synthesizing carbon-based nanomaterials using relatively cheap coal and abundant biomass resources have been developed, but when coal or biomass is used as raw material, the degree of ordering of the matrix carbon structure is poor, and further high-temperature treatment is needed to meet the use requirements.

[0003] The main methods for producing graphene using coal as raw material include chemical vapor deposition (CVD), arc discharge, oxidation-extraction (OCE), chemical leaching, templating, heat treatment or dielectric barrier discharge (DBD) plasma, and hydrazine chemical oxidation-reduction. Among them, the chemical route (oxidation and subsequent reduction) and the physical route (solvent stripping) with simple operation are the most commonly used methods.

[0004] Metallurgical coke powder (particle size <5mm) is one of the by-products of the coking process, which is mostly produced during the coke crushing process, accounting for 4% of the coke products in the metallurgical industry. The characteristics of the coke matrix are simple hexagonal crystal stacking of about 1nm, presenting a turbine layer structure, containing a small amount of dispersed minerals. Before blast furnace ironmaking, during the coking carbonization process at 900-1100℃, carbon of different sizes is reoriented in local parallel arrangement, which is also called graphitization. Although the coke powder has been applied to blast furnace injection, sintering coal blending, waste gas treatment materials and other industrial production, the overall research on the comprehensive utilization of coke powder is still in the low value-added stage. Therefore, it is of great significance to use coke powder to provide low-cost new carbon materials, lithium battery anode materials and nanomaterials for large-scale production.

[0005] The Chinese patent application with the application number CN201911071952.1 discloses "a method for preparing a graphene-like material based on biomass waste and its application". The biomass waste is heated and calcined at 600-1500℃ for 1-5h under the protection of a protective gas to obtain carbonized biomass material. The carbonized biomass material is mixed with an activating agent and then dried, and calcined at 400-1500℃ for 1-5h under the protection of a protective gas to obtain an activated mixture. The activated mixture is placed in a hydrothermal reaction kettle containing acid solution and reacted at 120-220℃ for 6-12h to obtain a hydrothermal oxidation mixture. The hydrothermal oxidation mixture is cleaned and then ultrasonically peeled to obtain a dispersion of biomass-based graphene-like material. The dispersion of biomass-based graphene-like material is freeze-dried to obtain biomass-based graphene-like material. This method mainly uses biomass as raw material, but has the following problems: 1. The fixed carbon content of biomass is very low, and the content of volatile matter and ash is high, so the influence of impurities during processing is large; 2. The carbon structure of biomass has a high degree of disorder, and multiple high-temperature calcination is required to obtain ideal graphene structure, so the process is complex and the processing cost is greatly increased.

[0006] The Chinese patent application with the application number CN202110175216.1 discloses "a preparation method of lignite-based graphene and its application". Lignite is extracted by a strong alkali weak acid salt, and the liquid phase product after extraction is subjected to hydrothermal treatment, activation, acid washing and drying to obtain lignite-based graphene. By adjusting the type, concentration, hydrothermal temperature and time, activation temperature and time, etc. of the mixed solution, the morphology of lignite-based graphene is controlled. This method uses inorganic salt solution to remove impurities in lignite, but it will interfere with the efficiency of later oxidation and activation. At the same time, to achieve the best effect, multiple repeated water washing steps are required in the extraction and acid washing processes, greatly increasing the processing time and cost.

[0007] The article "Coal-based new materials-coal-based graphene preparation and research progress of graphene application in heat conduction field" (Coal Geology, Vol. 45, No. 1, January 2020) records that "coal-based graphene is graphene converted from coal as raw material. After high-temperature heat treatment, coal-based graphene is obtained by using conventional graphene preparation methods". The heat treatment process of raw coal requires a high temperature of 2000℃ and a good sealing environment. The treatment of raw coal also has the disadvantages of incomplete impurity removal and low quality of coal-based graphene, and the feasibility of the scheme is poor. SUMMARY

[0008] The application provides a method for preparing graphene-like substance by using metallurgical coke powder, solves the problem of high value-added utilization of coke powder in a coking enterprise, and obtains graphene-like substance with uniform shape and size distribution and extremely low impurity content, which is a cheap and easily-obtained production raw material for graphene manufacturing, and can reduce production cost and shorten production process.

[0009] In order to achieve the above-mentioned purpose, the application adopts the following technical scheme:

[0010] A method for preparing graphene-like substance by using metallurgical coke powder comprises the following steps:

[0011] 1) crushing and screening: after being ground and screened, the metallurgical coke powder becomes ultrafine coke powder with a particle size of less than 20 microns;

[0012] 2) high-pressure extraction: the ultrafine coke powder and an extraction agent are added into a high-pressure reaction kettle, and high-pressure extraction is carried out under a protective atmosphere; then, the ultra-pure carbon is obtained through centrifugation, rotary evaporation and drying;

[0013] 3) chemical oxidation: the ultra-pure carbon is reacted with a strong oxidizing agent to obtain an oxidized carbon material;

[0014] 4) solid-phase reduction: the oxidized carbon material is reduced at high temperature to obtain an activated graphene-like precursor material;

[0015] 5) solvent stripping: the graphene-like precursor material is stripped in an organic solvent to obtain graphene-like substance.

[0016] Further, in the step 1), the particle size of the metallurgical coke powder is less than 5 mm, and a planetary high-energy ball mill is used for grinding; the ball milling time is 6-12 hours, the ball milling speed is 50-200 r / min in revolution and 200-400 r / min in rotation; the material of the ball milling tank is stainless steel, and the material of the grinding ball is zirconium oxide.

[0017] Further, in the step 2), the solid-liquid ratio of the ultrafine coke powder and the extraction agent is 1:20-1:50; the extraction agent is one of the following three kinds:

[0018] (1) N-methyl pyrrolidone pure solvent;

[0019] (2) mixed solvent of n-hexane and N-methyl pyrrolidone, and the volume ratio of the two is 1:1-5:1;

[0020] (3) mixed solvent of tetrahydrofuran and N-methyl pyrrolidone, and the volume ratio of the two is 1:1-5:1.

[0021] Further, in the step 2), the high-pressure extraction process is as follows: the extraction temperature is 200-400 DEG C, the constant temperature is 1-6h; the pressure is kept at 0.4-5.0 MPa during the extraction process; the mixture of the superfine coke powder and the extractant is stirred during the extraction process, and the stirring speed is 200-600 r / min; the protective atmosphere is high-purity N2 or high-purity Ar.

[0022] Further, in the step 2), the centrifugation, rotary evaporation and drying mode is as follows: the solid-liquid separation is carried out by using the centrifugal method, the separated liquid phase is subjected to the rotary evaporation to remove the solvent, and the obtained solid is washed and then dried in a vacuum drying box at a temperature of 55-75 DEG C for 12-24h.

[0023] Further, in the step 3), the mixing ratio of the ultrapure carbon and the strong oxidant is as follows: ultrapure carbon: sodium nitrate: potassium permanganate = 1:1:5-1:1:9.

[0024] Further, the operation process of the step 3) is as follows: the ultrapure carbon and the strong oxidant are mixed under ice-bath, the reaction temperature is controlled to be not more than 20 DEG C, the stirring reaction is carried out for 10-30 min, then the temperature is increased to 30-40 DEG C, and the stirring is continuously carried out for 25-60 min; then deionized water is slowly added according to the volume ratio of 1:1, hydrogen peroxide is added after 15-25 min to reduce the residual oxidant, so that the solution becomes bright yellow; hot filtration is carried out, and the filter cake is washed with a 5% HCl solution and deionized water until no sulfate radical is detected in the filtrate; finally, the filter cake is dried in a vacuum drying box at 50-80 DEG C to obtain the oxidized carbon material.

[0025] Further, in the step 4), the solid-phase reduction is carried out under a protective atmosphere at a temperature of 1000 DEG C-1200 DEG C for 1-3h; the protective gas is high-purity N2 or high-purity Ar.

[0026] Further, in the step 5), the solvent stripping is specifically as follows: the graphene-like precursor material is dispersed in a 1mg / mL N-methyl pyrrolidone solution, and ultrasonic treatment is carried out at a temperature of 50-70 DEG C for 3-6h; then the obtained solution is subjected to rotary evaporation, and finally the graphene-like material is obtained.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] 1) The problem of high-value utilization of coke powder in coking enterprises is solved;

[0029] 2) A cheap and easily available production raw material for the manufacture of graphene is developed, which can reduce the production cost and shorten the production process;

[0030] 3) The graphenes obtained by the method have uniform size and shape distribution and extremely low impurity content, and will not affect the local structure of the graphene material. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a process flow chart of the method for preparing graphenes from metallurgical coke powder according to the application.

[0032] Figure 2 is a comparison chart of X-ray photoelectron spectroscopy (XPS) of the ultrafine coke powder before and after treatment in Example 1.

[0033] Figure 3 is a comparison chart of Raman spectroscopy of the ultrafine coke powder before and after treatment in Example 1.

[0034] Figure 4 is a comparison chart of X-ray diffraction (XRD) spectroscopy of the ultrafine coke powder before and after treatment in Example 1.

[0035] Figure 5 is a comparison chart of transmission electron microscopy (TEM) images of the ultrafine coke powder before and after treatment in Example 1. DETAILED DESCRIPTION

[0036] The specific embodiments of the application will be further described below in conjunction with the accompanying drawings:

[0037] As shown in Figure 1 , the method for preparing graphenes from metallurgical coke powder according to the application comprises the following steps:

[0038] 1) Crushing and sieving: after grinding and sieving, the metallurgical coke powder is obtained as ultrafine coke powder with a particle size of 20 μm or less;

[0039] 2) High-pressure extraction: the ultrafine coke powder and an extractant are added to a high-pressure reaction kettle, and high-pressure extraction is carried out under a protective atmosphere; then, the ultra-pure carbon is obtained by centrifugation, rotary evaporation and drying;

[0040] 3) Chemical oxidation: the ultra-pure carbon is reacted with a strong oxidizing agent to obtain an oxidized carbon material;

[0041] 4) Solid-phase reduction: the oxidized carbon material is reduced at high temperature to obtain an activated graphene precursor material;

[0042] 5) Solvent exfoliation: the graphene precursor material is exfoliated in an organic solvent to obtain graphenes.

[0043] Further, in the step 1), the particle size of the metallurgical coke powder is <5mm, and the grinding is performed by using a planetary high-energy ball mill; the ball milling time is 6-12h, the ball milling speed is: 50-200r / min for revolution speed and 200-400r / min for rotation speed; the material of the ball milling tank is stainless steel, and the material of the grinding ball is zirconium oxide.

[0044] Further, in the step 2), the solid-liquid ratio of the ultra-fine coke powder to the extractant is 1:20-1:50; the extractant is one of the following three:

[0045] (1) N-methyl pyrrolidone pure solvent;

[0046] (2) mixed solvent of n-hexane and N-methyl pyrrolidone, the volume ratio of the two is 1:1-5:1;

[0047] (3) mixed solvent of tetrahydrofuran and N-methyl pyrrolidone, the volume ratio of the two is 1:1-5:1.

[0048] Further, in the step 2), the process of high-pressure extraction is: the extraction temperature is 200-400℃, and the constant temperature is 1-6h; the pressure is kept at 0.4-5.0MPa during the extraction process; the mixture of the ultra-fine coke powder and the extractant is stirred during the extraction process, and the stirring speed is 200-600r / min; the protective atmosphere is high-purity N2 or high-purity Ar.

[0049] Further, in the step 2), the centrifugation, rotary evaporation and drying method is: the solid-liquid separation is performed by using the centrifugation method, the solvent in the separated liquid phase is removed by using the rotary evaporation method, and the obtained solid is washed and then dried in a vacuum drying box at a temperature of 55-75℃ for 12-24h.

[0050] Further, in the step 3), the mixing ratio of the ultra-pure carbon and the strong oxidant is: ultra-pure carbon: sodium nitrate: potassium permanganate = 1:1:5-1:1:9.

[0051] Further, the operation process of the step 3 is: the ultra-pure carbon and the strong oxidant are mixed under ice bath, the reaction temperature is controlled to be not more than 20℃, the stirring reaction is performed for 10-30min, then the temperature is increased to 30-40℃, and the stirring is continuously performed for 25-60min; then deionized water is slowly added according to the volume ratio of 1:1, and after 15-25min, hydrogen peroxide is added to reduce the residual oxidant, so that the solution becomes bright yellow; hot filtration is performed, and the filter cake is washed with a 5% HCl solution and deionized water until no sulfate radical is detected in the filtrate; finally, the filter cake is dried in a vacuum drying box at 50-80℃ to obtain the oxidized carbon material.

[0052] Further, in the step 4), the solid phase reduction is carried out at 1000-1200℃ for 1-3h under a protective atmosphere; the protective gas is high-purity N2 or high-purity Ar.

[0053] Further, in the step 5), the solvent stripping is specifically as follows: the graphene-like precursor material is dispersed in an N-methyl pyrrolidone solution with a concentration of 1mg / mL, and is ultrasonically treated at 50-70℃ for 3-6h; then the obtained solution is spin-evaporated, and finally the graphene-like material is obtained.

[0054] The method for preparing graphene-like material from metallurgical coke powder provided by the application comprises the steps of crushing and screening, high-pressure extraction, chemical oxidation, solid phase reduction and solvent stripping, and the specific process is as follows:

[0055] 1. Crushing and screening: the metallurgical coke powder is ball milled by a planetary high-energy ball mill, the material of the ball mill tank is stainless steel, the material of the milling ball is zirconia, the ball milling time is 6-12h, the revolution speed is 50-200r / min, and the rotation speed is 200-400r / min; after screening, the ultrafine coke powder with a particle size of less than 20μm is obtained. The purpose of preparing the ultrafine coke powder is to increase the contact area in the subsequent physical and chemical treatment processes, so as to improve the treatment efficiency.

[0056] 2. High-pressure extraction: the above ultrafine coke powder is mixed with an extractant; the extractant can be selected from one of the following three kinds:

[0057] (1) N-methyl pyrrolidone (NMP) pure solvent with a solid-liquid ratio of 1:20-1:50;

[0058] (2) mixed solvent of n-hexane (HXN) and N-methyl pyrrolidone with a volume ratio of 1:1-5:1;

[0059] (3) mixed solvent of tetrahydrofuran (THF) and N-methyl pyrrolidone with a volume ratio of 1:1-5:1.

[0060] The ultrafine coke powder and the extractant are added into a high-pressure reaction kettle in a proportion of solid-liquid ratio 1:30-1:50, heated to a target temperature of 200-400℃ under a protective atmosphere, and then kept at the constant temperature for 1-6h; during the heating process, the pressure is always kept at 0.4-5.0MPa, and a stirring device is used for stirring at a stirring speed of 200-600r / min. After the heated mixture is naturally cooled to room temperature, it is taken out, and subjected to solid-liquid separation by a centrifugal separator; the separated liquid phase is subjected to solvent removal by spin evaporation, and the solvent is recycled. The solid obtained by spin evaporation is repeatedly washed with fresh solvent and deionized water, and then is placed into a vacuum drying box and dried at 55-75℃ for 12-24h to obtain ultra-pure carbon. In this process, the impurities in the ultrafine coke powder are separated from the carbon by high-temperature and high-pressure extraction of the ultrafine coke powder by the organic solvent.

[0061] 3. Chemical oxidation: Add ultrapure carbon, sodium nitrate (NaNO3), and potassium permanganate (KMNO4) into a reaction bottle in a ratio of 1:1:5 to 1:1:9, mix under ice bath, control the reaction temperature to be no more than 20°C, stir for 10 to 30 min, then increase the temperature to 30 to 40°C, continue to stir for 25 to 60 min, then slowly add deionized water in a volume ratio of 1:1. After 15 to 25 min, add hydrogen peroxide to reduce the residual oxidant, so that the solution turns bright yellow. Filter while hot, and wash with a 5% HCl solution and deionized water until no sulfate is detected in the filtrate. Finally, dry the filter cake in a vacuum drying oven at 50 to 80°C to obtain the oxidized carbon material. This process oxidizes graphite by introducing a strong acidic medium, destroying its II conjugated structure, introducing oxygen-containing functional groups (such as hydroxyl, ketone, ether bond, etc.) between the layers, thereby weakening the van der Waals force between the layers, and obtaining oxidized graphite with a relatively regular structure.

[0062] 4. Solid phase reduction: Activate the obtained oxidized carbon material at 1000 to 1200°C in a high-temperature atmosphere furnace filled with high-purity N2 or high-purity Ar for 1 to 3 h to obtain an activated graphene-like precursor material. Remove the oxygen-containing functional groups between the layers of graphite by high-temperature reduction to obtain pure graphite layers.

[0063] 5. Solvent exfoliation: Disperse the graphene-like precursor material in a 1 mg / mL N-methyl pyrrolidone (NMP) solution at a temperature of 50 to 70°C and ultrasonically treat for 3 to 6 h; the graphene-like precursor material can be better dispersed in organic solvents. Perform rotary evaporation on the obtained solution to finally obtain graphene.

[0064] The following examples are implemented on the premise of the technical solutions of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following examples.

[0065]

Example 1

[0066] In this embodiment, graphene is prepared from metallurgical coke powder from a coking enterprise, and the specific operation steps are as follows:

[0067] 1. Crushing and sieving: Use a planetary high-energy ball mill to ball mill the metallurgical coke powder, with a ball milling time of 6 h and a ball milling speed of 100 r / min for revolution and 200 r / min for rotation. After sieving, obtain ultrafine coke powder with a particle size of 10 μm or less.

[0068] 2. High pressure extraction: Using N-methyl pyrrolidone (NMP) pure solvent as the extractant, the above ultra-fine coke powder and the extractant were added into a high-pressure reaction kettle at a solid-liquid ratio of 1:40, heated to a target temperature of 350°C under an atmosphere of high-purity argon, and then kept at the constant temperature for 3 hours. During the heating process, the pressure was kept at 3.0 MPa, and the stirring speed was 300 r / min. After natural cooling to room temperature, the solid-liquid separation was performed by using a centrifugal separator. The separated liquid phase was subjected to solvent removal by rotary evaporation, and the solvent was recycled. The solid obtained by rotary evaporation was repeatedly washed with deionized water, and then placed in a vacuum drying oven for vacuum drying at 70°C for 24 hours to obtain ultra-pure carbon.

[0069] 3. Chemical oxidation: The ultra-pure carbon, sodium nitrate (NaNO3), and potassium permanganate (KMnO4) were added into a 500 ml reaction bottle at a ratio of 1:1:7, mixed under ice bath, and the reaction temperature was controlled at 18°C. Stirring was performed for 25 min, then the temperature was increased to 35°C, and stirring was continued for 30 min. Deionized water was slowly added at a volume ratio of 1:1. After 20 min, hydrogen peroxide was added to reduce the residual oxidant, and the solution turned bright yellow. Hot filtration was performed, and repeated washing was performed with 5% HCl solution and deionized water until no sulfate was detected in the filtrate. Finally, the filter cake was dried in a vacuum drying oven at 60°C to obtain an oxidized carbon material.

[0070] 4. Solid-phase reduction: The obtained oxidized carbon material was activated in a high-temperature atmosphere furnace filled with protective gas at 1100°C for 1.5 hours to obtain an activated graphene-like precursor material.

[0071] 5. Solvent stripping: The graphene-like precursor material was dispersed in a 1 mg / mL N-methyl pyrrolidone (NMP) solution, and ultrasonic treatment was performed at 60°C for 6 hours. The obtained solution was subjected to rotary evaporation to finally obtain graphene.

[0072] The graphene obtained in this example has extremely low impurity content. The ash content of the carbon powder obtained by high-pressure leaching and rotary evaporation of organic solvent is less than 1%, which does not affect the local structure of the graphene material. Meanwhile, the structure of the graphene obtained in this example was analyzed by means of Raman spectroscopy, transmission electron microscopy, XPS, XRD, etc. Figure 2 is the X-ray photoelectron spectroscopy (XPS) comparison before and after the treatment of ultra-fine coke powder, which shows that the number of acidic functional groups in the treated ultra-fine coke powder increases significantly, which is due to the oxidation of NaNO3 and KMnO4. Due to the presence of many oxygen-containing functional groups, the C / O ratio of the ultra-fine carbon powder decreases from about 4.2 before treatment to about 1.9 after treatment. By using peak separation, it is found that the sp 2The hybrid carbon atom reached 81.76%, higher than 60.66% before treatment.

[0073] Figure 3 is the Raman spectrum comparison of the ultra-fine coke powder before and after treatment. The Raman spectra of the coke ultra-fine powder before and after treatment both show a relatively wide D band (maximum 1350 cm -1 ) and G band (maximum 1580 cm -1 ), representing sp 3 defects and sp 2 highly graphitized structure in graphite, respectively. After treatment, the D band of the coke powder is weaker, the G band is stronger, and the symmetry peak at 2700 cm -1 is more obvious, indicating that the product is composed of multi-layer graphene sheets with fewer defects. The maximum bandwidth is relatively narrow (40 cm -1 ), but is obviously wider than 14 cm -1 , which is commonly used as quasi-perfect high-orientation pyrolytic graphite. Using the deconvolution method developed by A.C. Ferrari et al. to characterize the structural information hidden in the overlapping area of the G band and the D band, it is found that after chemical and physical comprehensive treatment, the ID / IG of the sample decreases from 1.074 to 0.607, which indicates that the graphitization level of graphene has been improved. IV / IG decreases from 0.975 to 0.423, indicating the transformation of various non-graphitic structures to graphitic structures.

[0074] Figure 4 is the X-ray diffraction (XRD) spectrum comparison of the ultra-fine coke powder before and after treatment. The XRD spectrum of the coke before treatment shows a relatively wide range around 26° in the 002 wave band with medium intensity, and the d 002 calculated by Bragg's law is about 0.48 nm, showing a lower-order crystal structure. After chemical and physical treatment, the 002 wave band becomes more sharp, indicating that the size of the microcrystalline graphite increases in the Lc direction. The calculation results also show that Lc increases from 2.683 nm to 8.224 nm, and La increases from 4.91 nm to 5.911 nm. The main preparation method of this embodiment includes chemical method and physical method, i.e. changing the carbon structure ordering degree of carbon base and changing its regular structure to high-order structure.

[0075] Figure 5 is the transmission electron microscope (TEM) image comparison of the ultra-fine coke powder before and after treatment. It is observed that there is no obvious nanostructure change in the coke sample before treatment, the carbon structure is highly disordered, and there is no multi-aromatic layer. After oxidation, thermal peeling and solvent peeling, there is a nanostructure with a wrinkle appearance characteristic of graphene materials. The treated sample has uniform shape and uniform size distribution, with a diameter of 3.61±0.25 nm and no orientation. The crystal hexagonal pattern in the TEM image and the evidence of the increase in the size of the multi-aromatic layer shown by the Raman spectrum confirm the presence of graphene in the product.

[0076] The performance of the carbon material of Example 1 before and after treatment is compared as shown in Table 1.

[0077] Table 1 Performance comparison of carbon material of Example 1 before and after treatment

[0078] Detection method Indicator Before treatment After treatment XPS sp 2 ]] 60.66％ 81.76％ Raman spectroscopy I D / I G ]]> 1.074 0.607 Raman spectroscopy I V / xG ]]> 0.975 0.423 Transmission electron microscopy Structural size - 3.61±0.25 XRD [[ L c ]]> 2.683 8.224 XRD La 4.911 5.911

[0079] [Example 2]

[0080] In this embodiment, graphene-like is prepared from metallurgical coke powder from a steel plant, and the specific operation steps are as follows:

[0081] 1. Crushing and screening: the metallurgical coke powder is ball milled using a planetary high-energy ball mill, the ball milling time is 6h, the ball milling speed is: 50r / min for revolution speed and 300r / min for rotation speed, and after screening, ultra-fine coke powder with particle size of 5μm or less is obtained.

[0082] 2. High-pressure extraction: using a mixture of tetrahydrofuran (THF) and N-methyl pyrrolidone as an extractant, the above ultra-fine coke powder and the extractant are added into a high-pressure reaction kettle at a solid-liquid ratio of 1:40, heated to a target temperature of 380℃ under an atmosphere of high-purity argon, then kept at a constant temperature for 5h, the pressure is kept at 4.0MPa during the heating process, and the stirring speed is 600r / min. After natural cooling to room temperature, solid-liquid separation is carried out using a centrifugal separator, the separated liquid phase is subjected to solvent removal by rotary evaporation, and the solvent is recycled. The solid obtained by rotary evaporation is repeatedly washed with deionized water and then placed in a vacuum drying oven at 70℃ for 12h to obtain ultra-pure carbon.

[0083] 3. Chemical oxidation: the ultra-pure carbon, sodium nitrate (NaNO3), and potassium permanganate (KMNO4) are added into a 500ml reaction bottle at a ratio of 1:1:7, mixed under ice bath, the reaction temperature is controlled at 16℃, stirred for 18min, then heated to 30℃, continue to stir for 60min, then slowly add deionized water at a volume ratio of 1:1. After 25min, add hydrogen peroxide to reduce the residual oxidant, so that the solution turns bright yellow. Hot filtration is carried out, and repeatedly washed with 5% HCl solution and deionized water until no sulfate is detected in the filtrate. Finally, the filter cake is dried in a vacuum drying oven at 80℃ to obtain an oxidized carbon material.

[0084] 4. Solid-phase reduction: the obtained oxidized carbon material is activated in a high-temperature atmosphere furnace filled with protective gas at 1150℃ for 3h to obtain an activated graphene-like precursor material.

[0085] 5. Solvent stripping: disperse the graphene-like precursor material in N-methyl pyrrolidone (NMP) solution with a concentration of 1 mg / mL, and ultrasonic treatment at 70°C for 6 hours; then spin the obtained solution to obtain graphene.

[0086] The graphene-like material obtained in this example has very low impurity content (less than 0.02%), which does not affect the local structure of the graphene-like material. Meanwhile, the structure of the graphene-like material obtained in this example is analyzed by means of Raman spectroscopy, transmission electron microscopy, XPS, XRD and other means, and the results of Raman spectroscopy are as follows: I D / I G = 0.483, I V / I G = 0.392. The results of transmission electron microscopy show that the graphene-like material prepared in this example has uniform shape and size distribution, with a diameter of 3.86 ± 0.05 nm. The results of XPS show that the sp 2 hybridization mode of carbon atoms accounts for about 85.93%.

[0087]

Example 3

[0088] In this example, graphene-like material is prepared from metallurgical coke powder from a steel plant, and the specific operation steps are as follows:

[0089] 1. Crushing and screening: use a planetary high-energy ball mill to ball mill the metallurgical coke powder, with a ball milling time of 8 hours, a revolution speed of 50 r / min, and a rotation speed of 300 r / min. After screening, ultra-fine coke powder with a particle size of 1 μm or less is obtained.

[0090] 2. High-pressure extraction: use a mixture of tetrahydrofuran (THF) and N-methyl pyrrolidone as an extractant, and add the ultra-fine coke powder and the extractant to a high-pressure reaction kettle at a solid-liquid ratio of 1:50. Under an atmosphere of high-purity Ar, heat to a target temperature of 350°C, and then maintain the temperature for 3 hours. The pressure is maintained at 2.0 MPa during the heating process, and the stirring speed is 600 r / min. After natural cooling to room temperature, remove and separate the solid and liquid phases using a centrifugal separator. The separated liquid phase is spin-evaporated to remove the solvent, which is recycled. The solid obtained by spin-evaporation is repeatedly washed with deionized water, and then placed in a vacuum drying oven at 60°C for 16 hours to obtain ultra-pure carbon.

[0091] 3. Chemical oxidation: add ultrapure carbon, sodium nitrate (NaNO3), potassium permanganate (KMNO4) in a ratio of 1:1:7 into a 500ml reaction bottle, mix under ice bath, control the reaction temperature at 15℃, stir for 20min, then warm up to 30℃, continue to stir for 40min, then slowly add deionized water in a volume ratio of 1:1. Add hydrogen peroxide to reduce the residual oxidant after 20min, and the solution turns bright yellow. Filter while hot, and wash repeatedly with 5% HCl solution and deionized water until no sulfate is detected in the filtrate. Finally, dry the filter cake in a vacuum drying oven at 70℃ to obtain the oxidized carbon material.

[0092] 4. Solid phase reduction: activate the obtained oxidized carbon material at 1200℃ in a high-temperature atmosphere furnace filled with protective gas for 2h to obtain an activated graphene-like precursor material.

[0093] 5. Solvent stripping: disperse the graphene-like precursor material in a 1mg / mL N-methyl pyrrolidone (NMP) solution, and ultrasonically treat at 70℃ for 6h; then spin the obtained solution to obtain graphene.

[0094] The graphene obtained in this embodiment has very low impurity content (less than 0.03%), which does not affect the local structure of the graphene material. At the same time, the structure of the graphene obtained in this embodiment is analyzed by means of Raman spectroscopy, transmission electron microscopy, XPS, XRD and the like, and it is found that the Raman spectroscopy result is I D / I G =0.475, I V / I G =0.373, and the transmission electron microscopy result shows that the graphene material prepared in this embodiment is uniform in shape and size distribution, with a diameter of 4.23±0.05nm. The XPS result shows that the sp 2 hybridization mode of carbon atoms accounts for about 87.48%.

[0095] The above merely describes the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can make equivalent replacements or changes to the technical solutions and inventive concepts of the present application within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for preparing graphene-like substances using metallurgical coke powder, characterized in that, Includes the following steps: 1) Crushing and screening: Metallurgical coke powder is ground and screened to obtain ultrafine coke powder with a particle size of less than 20μm; 2) High-pressure extraction: Ultrafine coke powder and extractant are added to a high-pressure reactor and high-pressure extraction is carried out under a protective atmosphere; then ultrapure carbon is obtained by centrifugation, rotary evaporation and drying. The solid-liquid ratio of ultrafine coke powder to extractant is 1:20 to 1:50; the extractant is one of the following three: (1) N-methylpyrrolidone pure solvent; (2) A mixed solvent of n-hexane and N-methylpyrrolidone, with a volume ratio of 1:1 to 5:1; (3) A mixed solvent of tetrahydrofuran and N-methylpyrrolidone, with a volume ratio of 1:1 to 5:1; The high-pressure extraction process is as follows: the extraction temperature is 200-400℃, and the temperature is kept constant for 1-6 hours; the pressure is maintained at 0.4-5.0 MPa during the extraction process; the mixture of ultrafine coke powder and extractant is stirred during the extraction process at a stirring speed of 200-600 r / min; the protective atmosphere is high-purity N2 or high-purity Ar. 3) Chemical oxidation: reacting ultrapure carbon with a strong oxidizing agent to obtain carbon oxide materials; 4) Solid-phase reduction: Carbon oxide materials are reduced at high temperature to obtain activated graphene-like precursor materials; 5) Solvent exfoliation: The graphene-like precursor material is exfoliated in an organic solvent to obtain graphene-like material.

2. The method for preparing graphene-like substances using metallurgical coke powder according to claim 1, characterized in that, In step 1), the particle size of the metallurgical coke powder is <5mm, and it is ground using a planetary high-energy ball mill; the ball milling time is 6 to 12 hours, and the ball milling speed is: revolution speed 50 to 200 r / min, rotation speed 200 to 400 r / min; the ball mill jar is made of stainless steel, and the grinding balls are made of zirconium oxide.

3. The method for preparing graphene-like substances using metallurgical coke powder according to claim 1, characterized in that, In step 2), the centrifugation, rotary evaporation, and drying are performed as follows: centrifugation is used for solid-liquid separation, the separated liquid phase is removed by rotary evaporation to remove the solvent, and the solid obtained by rotary evaporation is washed and dried in a vacuum drying oven at 55-75°C for 12-24 hours.

4. The method for preparing graphene-like substances using metallurgical coke powder according to claim 1, characterized in that, In step 3), the mixing ratio of ultrapure carbon to strong oxidant is: ultrapure carbon: sodium nitrate: potassium permanganate = 1:1:5 to 1:1:

9.

5. The method for preparing graphene-like substances using metallurgical coke powder according to claim 1, characterized in that, The operation process of step 3 is as follows: ultrapure carbon and a strong oxidant are mixed in an ice bath, the reaction temperature is controlled not to exceed 20°C, and the reaction is stirred for 10-30 minutes. Then the temperature is raised to 30-40°C and stirring is continued for 25-60 minutes. Deionized water is then slowly added at a volume ratio of 1:

1. After 15-25 minutes, hydrogen peroxide is added to reduce the residual oxidant, making the solution bright yellow. The solution is filtered while hot and washed with 5% HCl solution and deionized water until no sulfate ions are detected in the filtrate. Finally, the filter cake is dried in a vacuum drying oven at 50-80°C to obtain carbon oxide material.

6. The method for preparing graphene-like substances using metallurgical coke powder according to claim 1, characterized in that, In step 4), the solid-phase reduction is carried out under a protective atmosphere at a temperature of 1000℃~1200℃ for 1~3h; the protective gas is high-purity N2 or high-purity Ar.

7. The method for preparing graphene-like substances using metallurgical coke powder according to claim 1, characterized in that, In step 5), solvent exfoliation specifically involves: dispersing the graphene-like precursor material in an N-methylpyrrolidone solution with a concentration of 1 mg / mL, and ultrasonically treating it at a temperature of 50–70 °C for 3–6 h; then rotary evaporating the resulting solution to finally obtain the graphene-like material.

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