Preparation method of graphite oxide

Abstract

The invention relates to a graphite oxide preparation method, which comprises: mixing sulfuric acid and an oxidizing agent at a temperature of 3-7 DEG C so as to completely dissolve the oxidizing agent in the sulfuric acid to obtain a solution; mixing the solution with graphite at the temperature of 3-7 DEG C to obtain slurry; heating and stirring the slurry, and carrying out oxidation reaction on graphite in the slurry under the condition of isolating air and water vapor; and mixing the slurry after the oxidation reaction with water, and hydrolyzing to obtain the graphite oxide. According to the preparation method of the graphite oxide, the materials are added according to the preset sequence, the oxidizing agent can be better dissolved in the system, mixing and reaction are carried out under the preset condition, and the graphite oxide with high oxidation degree and yield can be obtained under the condition that the input amount of sulfuric acid is reduced.

Description

Technical Field

[0001] The present application relates to the field of material preparation, and in particular to a method for preparing graphite oxide. Background Art

[0002] Graphite oxide can be produced by a modified Hummers method, which requires a large amount of sulfuric acid. The cost of sulfuric acid usually accounts for about 40% of the total preparation cost. In addition, a large amount of water is consumed and a large amount of waste dilute acid is produced during the product washing process. As a result, the current method has the problems of high raw material costs and difficulty in waste liquid treatment, which brings serious environmental pressure. Summary of the invention

[0003] In view of this, the present application provides a method for preparing graphite oxide to solve at least one of the above problems.

[0004] To achieve the above-mentioned purpose, the present application provides a method for preparing graphite oxide, comprising: mixing sulfuric acid and an oxidant at a temperature of 3°C to 7°C, so that the oxidant is completely dissolved in the sulfuric acid to obtain a solution; mixing the solution with graphite at a temperature of 3°C to 7°C to obtain a slurry; heating and stirring the slurry, and causing an oxidation reaction of the graphite in the slurry under the condition of isolating air and water vapor; mixing the slurry after the oxidation reaction with water and hydrolyzing it to obtain the graphite oxide.

[0005] In some possible implementations, the ratio of the sulfuric acid to the graphite is 10 mL:1 g to 35 mL:1 g.

[0006] In some possible implementations, the sulfuric acid and the oxidant are mixed for 1 h to 10 h.

[0007] In some possible implementations, the temperature of the slurry after the heating is 20° C. to 60° C.

[0008] In some possible implementations, the concentration of the sulfuric acid is 77.5 wt % to 98.5 wt %.

[0009] In some possible implementations, the oxidant includes at least one of potassium permanganate, potassium perchlorate, and potassium ferrate.

[0010] In some possible implementations, the graphite includes at least one of block graphite, earthy graphite, flake graphite, expanded graphite, and intercalated graphite.

[0011] In some possible implementations, the graphite has a particle size of 5 μm to 1000 μm.

[0012] In some possible implementations, the oxidation reaction time is 12 h to 120 h.

[0013] In some possible implementations, the mass ratio of the water to the graphite is 20 to 60.

[0014] In some possible implementations, the hydrolysis temperature is 50° C. to 95° C., and the time is 5 min to 60 min.

[0015] In some possible implementations, the preparation method further includes: adding hydrogen peroxide with a mass fraction of 30% to the hydrolyzed slurry, and the ratio of the hydrogen peroxide to the graphite is 2 mL:1 g to 10 mL:1 g.

[0016] The method for preparing graphite oxide of the present application adds materials in a preset order, and performs mixing and reaction under preset conditions, so that graphite oxide with a high oxidation degree and yield can be obtained with a reduced amount of sulfuric acid input.

[0017] Among them, the present application is charged and mixed at a lower temperature, which can reduce the spontaneous reaction after the reactants are mixed, which is beneficial to control the progress of the graphite oxidation reaction and reduce the unnecessary consumption of the reactants. In addition, after sulfuric acid is first mixed with an oxidant to obtain a solution, graphite is added, which is beneficial for the oxidant to be better dissolved in the system, and the whole system can maintain good fluidity and stirrability under relatively less sulfuric acid volume conditions, so that the added graphite can smoothly contact with sulfuric acid or oxidant. In addition, the control system isolates air and water vapor for reaction, which is beneficial to promote the graphite in the slurry to react under relatively less sulfuric acid volume conditions, and completes the conversion to graphite oxide.

[0018] Therefore, compared with the existing process, the graphite oxide preparation method of the present application can reduce the input amount of sulfuric acid when preparing graphite oxide of the same output and quality, and save the cost of subsequent treatment of waste acid. In addition, since the entire system can maintain good fluidity and stirrability after adding graphite, the resources required for stirring (such as stirring time, stirring equipment and stirring energy consumption) invested to ensure material transfer are reduced, which is also conducive to controlling production costs. In addition, since the input amount of sulfuric acid is lower, the exothermic behavior of mixing with water is reduced, which is more conducive to controlling the reaction temperature, thereby helping to improve the quality of graphite oxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic flow chart of a method for preparing graphite oxide provided in one embodiment of the present application. DETAILED DESCRIPTION

[0020] The embodiments of the present application are described in detail below. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application; it should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by technicians in the technical field of the present application; in the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other; many specific details are elaborated in the following description to facilitate a full understanding of the present application, and the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0021] In view of the problem that the current Hummers method for preparing graphite oxide requires a large amount of sulfuric acid, this application analyzes the input and conversion of sulfuric acid in such methods. In this method, a large amount of sulfuric acid is usually stirred and mixed with graphite, and with the participation of a small amount of sulfuric acid, the graphite is converted into a sulfuric acid-graphite mixture (specifically, a sulfuric acid intercalation compound); then, an oxidant is added to the sulfuric acid-graphite mixture and the remaining large amount of sulfuric acid solvent, and preliminary oxidation is carried out under long-term stirring; finally, the system containing a large amount of sulfuric acid solvent is dispersed in water and finally converted into graphite oxide; it can be seen that this method needs to be completed in a large amount of concentrated sulfuric acid, and a small amount (approximately less than 5%) of sulfuric acid participates in the chemical reaction as a reactant, and the remaining large amount of sulfuric acid is used as a solvent, and the excess solvent is used to assist material transfer (to ensure the fluidity and stirrability of the reaction mixture).

[0022] The inventors of the present application have found that the related art usually adds a solid-liquid separation process after the intercalation oxidation step to separate part of the concentrated sulfuric acid from the reaction solution. Although the separated sulfuric acid can be used for a new round of graphite oxide preparation to alleviate the problem of sulfuric acid input cost, the residual oxidant and moisture in the separated sulfuric acid may affect the oxidation reaction process when it is used again, and the residual solid particles may also affect the viscosity of the reaction mixture when it is used again, which may lead to problems such as unstable oxygen content of the product and uneven oxidation degree. Therefore, there is still a need to improve the existing method to achieve the purpose of reducing the amount of sulfuric acid input.

[0023] Based on this, an embodiment of the present application provides a method for preparing graphite oxide, please refer to Figure 1 ,include: Step 1: Mix sulfuric acid and an oxidant at a temperature of 3°C to 7°C, so that the oxidant is completely dissolved in the sulfuric acid to obtain a solution.

[0024] Step 2: Mixing the solution with graphite at a temperature of 3°C to 7°C to obtain a slurry.

[0025] For example, the specific temperature in the above conditions can be 3°C, 3.5°C, 4°C, 4.5°C, 5°C, 5.5°C, 6°C, 6.5°C, 7°C or any value within the range formed by any two of the above values.

[0026] Steps 1 and 2 are charged and mixed at the above-mentioned lower temperature, which can reduce the spontaneous reaction after the reactants are mixed, which is beneficial to controlling the progress of the graphite oxidation reaction and reducing unnecessary consumption of the reactants. At the same time, in step 1 and step 2, sulfuric acid and the oxidant are first mixed to obtain a solution, and then graphite is added, which is beneficial for the oxidant to be better dissolved in the system, and the whole system can maintain good fluidity and stirrability under relatively less sulfuric acid volume conditions, so that the added graphite can smoothly contact with sulfuric acid or the oxidant, and promote the subsequent conversion process.

[0027] In some embodiments, the time for mixing the sulfuric acid and the oxidant is 1 h to 10 h. For example, the time for mixing the sulfuric acid and the oxidant can be 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, or any value within the range formed by any two of the above values. Controlling the mixing time within the above range is conducive to the solid oxidant being fully dissolved in the sulfuric acid to form a solution.

[0028] In some embodiments, the ratio of sulfuric acid to graphite is 10 mL: 1 g to 35 mL: 1 g. For example, the ratio of sulfuric acid to graphite can be 10 mL: 1 g, 15 mL: 1 g, 20 mL: 1 g, 25 mL: 1 g, 30 mL: 1 g, 35 mL: 1 g, or any value within the range formed by any two of the above values. Controlling the ratio of sulfuric acid to graphite within the above range is conducive to maintaining good fluidity and stirrability of the system, so that the added graphite can smoothly contact or react with sulfuric acid or oxidant.

[0029] In some embodiments, the concentration of the sulfuric acid is 77.5wt% to 98.5wt%. For example, the concentration of sulfuric acid can be 77.5wt%, 79wt%, 80.5wt%, 83wt%, 84.5wt%, 86wt%, 87.5wt%, 89wt%, 90.5wt%, 92wt%, 93.5wt%, 95wt%, 96.5wt%, 98wt%, 98.5wt% or any value within the range of any two of the above values. It is understandable that when the concentration of the sulfuric acid used is controlled within the above range, it is beneficial for sulfuric acid molecules to be inserted into the graphite interlayer to form a sulfuric acid intercalation compound.

[0030] In some embodiments, the oxidant includes at least one of potassium permanganate, potassium perchlorate and potassium ferrate. It is understandable that the oxidant selected from the above substances has a strong oxidizing effect and can promote the oxidation of the reactants.

[0031] In some embodiments, the graphite includes at least one of block graphite, earthy graphite, flake graphite, expanded graphite and intercalated graphite. In some embodiments, the particle size of the graphite is 5 μm to 1000 μm. For example, the particle size of the graphite can be 5 μm, 10 μm, 20 μm, 50 μm, 100 μm, 300 μm, 500 μm, 800 μm, 1000 μm or any value within the range composed of any two of the above values. The preparation method of the present application is applicable to the preparation of the above-mentioned graphite in various states or graphite of the above-mentioned particle size. When the above-mentioned graphite is used as a raw material for preparation, the input amount of sulfuric acid can be reduced.

[0032] Step 3: heating and stirring the slurry, and allowing the graphite in the slurry to undergo an oxidation reaction under the condition of isolating from air and water vapor.

[0033] In the above process, under preset conditions, the graphite in the system contacts sulfuric acid to form a sulfate-graphite mixture (including a sulfate intercalation compound). The sulfate intercalation compound is transformed into an amorphous structure and converted into graphite hydrogen sulfate under the action of the oxidant, completing the oxidation reaction involving the oxidant.

[0034] By isolating the air and water vapor through the control system for reaction, it is beneficial to promote the slurry to react under relatively less sulfuric acid volume conditions and complete the conversion to graphite oxide. The condition of isolating air and water vapor can be achieved by placing the slurry in a storage container, the material of the storage container can include but is not limited to stainless steel, polyethylene, polytetrafluoroethylene or glass, and the storage container can include but is not limited to cylinder, cube or cone.

[0035] In some embodiments, the temperature of the slurry after the heating is 20° C. to 60° C. For example, the temperature of the slurry after the heating can be 20° C., 25° C., 30° C., 35° C., 40° C., 45° C., 50° C., 55° C., 60° C., or any value within the range formed by any two of the above values. It can be understood that the slurry at the above temperature is conducive to the oxidation reaction.

[0036] In some embodiments, the oxidation reaction time is 12 h to 120 h. For example, the oxidation reaction time can be 12 h, 24 h, 36 h, 48 h, 60 h, 72 h, 84 h, 96 h, 108 h, 120 h, or any value within the range formed by any two of the above values. It can be understood that controlling the oxidation reaction time within the above range is conducive to the sufficient reaction and conversion of graphite in the slurry.

[0037] Step 4: mixing the slurry after the oxidation reaction with water and hydrolyzing it to obtain the graphite oxide.

[0038] The intercalated and oxidized graphite obtained in the above steps can generate graphite oxide after hydrolysis.

[0039] In some embodiments, the mass ratio of water to graphite is 20 to 60. For example, the mass ratio of water to graphite can be 20, 25, 30, 35, 40, 45, 50, 55, 60, or any value within the range formed by any two of the above values. It can be understood that controlling the mass ratio of water to graphite is conducive to the full hydrolysis of the intercalated and oxidized graphite and the full discharge of sulfuric acid in the graphite structure.

[0040] In some embodiments, the hydrolysis temperature is 50°C to 95°C, and the time is 5 min to 60 min. For example, the hydrolysis temperature can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, or any value within the range formed by any two of the above values, and the hydrolysis time can be 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, or any value within the range formed by any two of the above values.

[0041] In some embodiments, the preparation method further comprises: adding hydrogen peroxide with a mass fraction of 30% to the hydrolyzed slurry, and the ratio of hydrogen peroxide to graphite is 2 mL: 1 g to 10 mL: 1 g. For example, the ratio of hydrogen peroxide to graphite can be 2 mL: 1 g, 3 mL: 1 g, 4 mL: 1 g, 5 mL: 1 g, 6 mL: 1 g, 7 mL: 1 g, 8 mL: 1 g, 9 mL: 1 g, 10 mL: 1 g. It can be understood that controlling the dosage relationship of hydrogen peroxide and graphite is conducive to timely termination of the reaction, thereby helping to control the oxygen content of the resulting oxidized graphite.

[0042] The scheme of the present application will be explained below in conjunction with the embodiments. Those skilled in the art will understand that the following examples are only used to explain the present application and cannot be construed as limiting the present application. Unless otherwise stated, the reagents, software and instruments not specifically stated in the following embodiments are all conventional commercial products or open source.

[0043] Embodiment 1: A method for preparing graphite oxide, comprising the steps of: Step 1: At low temperature (controlled temperature of 5°C ± 2°C), add potassium permanganate to 14 mL of 98.3wt% concentrated sulfuric acid in a container. The addition process takes 30 minutes, and then stir for 30 minutes until it is completely dissolved to obtain a solution. Step 2: Keep the temperature low (control the temperature at 5 ℃ ± 2 ℃), pour in graphite (1 g graphite, 325 mesh, natural graphite), stir for 30 min until uniform, obtain slurry, heat to 35 ℃, stir for 5 min, the slurry becomes viscous, stop stirring, cover the container to form a relatively closed space.

[0044] Step 3: Transfer the covered container to a constant temperature box at 35 °C and let it stand for 5 hours for reaction. After the reaction, the mixture will be in a semi-solid state.

[0045] Step 4: Disperse the semi-solid mixture into 60 mL of water, heat to 90 °C for 30 min, add 2 mL of hydrogen peroxide after cooling, filter, wash once with dilute hydrochloric acid, wash twice with water, and freeze-dry to obtain graphite oxide.

[0046] Comparative Example 1: The current Hummers method is used to prepare graphite oxide, and the steps include: Step 1: Mix graphite (1 g graphite, 325 mesh, natural graphite) with 30 mL of 98.3wt% concentrated sulfuric acid at low temperature (about 5°C) for 30 min to form a uniform slurry, slowly add potassium permanganate within 1 hour, then heat to 35°C and continue stirring. After 12 hours, the reaction is completed.

[0047] Step 2: Add 60 mL of water, heat to 90 °C and maintain for 30 min. After cooling, add 2 mL of hydrogen peroxide, filter, wash once with dilute hydrochloric acid, wash twice with water, and freeze-dry to obtain graphite oxide.

[0048] Comparative Example 2: Graphite (1 g of graphite, 325 mesh, natural graphite) was mixed with 22 mL of 98.3 wt% concentrated sulfuric acid at low temperature (about 5 °C) for 30 min to form a uniform slurry, potassium permanganate was slowly added within 1 h, and then the temperature was raised to 35 °C and stirred continuously. After 3 h, the mixture became viscous and dry, with poor fluidity, and mechanical stirring was hindered.

[0049] The mixture was dispersed in 44 mL of water, heated to 90 °C for 30 min, and then cooled and added with 2 mL of hydrogen peroxide. The mixture was filtered, washed once with dilute hydrochloric acid, washed twice with water, and freeze-dried to obtain graphite oxide.

[0050] The difference from Comparative Example 1 is that the volume of 98.3 wt % concentrated sulfuric acid in the first step is 22 mL.

[0051] Comparative Example 3: Graphite (1 g of graphite, 325 mesh, natural graphite) was mixed with 14 mL of 98.3 wt% concentrated sulfuric acid at low temperature (about 5 °C) for 30 min to form a uniform slurry, and potassium permanganate was slowly added. After about 40 minutes, the mixture became viscous and dry, with almost no fluidity, and it was difficult to stir mechanically. At this time, the oxidant was not completely dissolved, and it was difficult for the oxidant to continue to dissolve due to insufficient concentrated sulfuric acid.

[0052] The mixture was dispersed in 28 mL of water, heated to 90 °C for 30 min, and then cooled and added with 2 mL of hydrogen peroxide. The mixture was filtered, washed once with dilute hydrochloric acid, washed twice with water, and freeze-dried to obtain graphite oxide.

[0053] The difference from Comparative Example 1 is that the volume of 98.3 wt % concentrated sulfuric acid in the first step is 14 mL.

[0054] The present application conducted a yield analysis on the graphite oxide of Example 1 and Comparative Examples 1-3, and determined the mass fraction of oxygen element by using a combustion method on the washed and dried graphite oxide. Please refer to Table 1 for the analysis results.

[0055] Table 1. Analysis results of the yield and oxygen content of graphite oxide in Example 1 and Comparative Examples 1-3 of the present application In Example 1 of the present application, the materials are added in a preset order, which is conducive to better dissolution of the oxidant in the system, and mixing and reaction are performed under preset conditions, so that graphite oxide with a high oxidation degree and yield can be obtained with a reduced amount of sulfuric acid input.

[0056] Compared with Example 1, it can be seen from Comparative Examples 1-3 that, under the same sulfuric acid dosage level (such as Comparative Example 3), when the current preparation method is used for preparation, the reaction raw material mixture is viscous and dry, almost without fluidity, and difficult to be mechanically stirred, resulting in the oxidant in the mixture not being completely dissolved, and due to insufficient concentrated sulfuric acid, the oxidant is also difficult to continue to dissolve, resulting in the obtained graphite oxide yield and oxygen content being far inferior to the examples of the present application; gradually increasing the amount of sulfuric acid input (such as Comparative Example 2), although the amount of solvent is increased during preparation, the reaction raw material mixture is still viscous and dry, with poor fluidity, mechanical stirring is hindered, and the oxidation effect of graphite is still poor; when the amount of sulfuric acid input continues to increase (such as Comparative Example 1), under the condition of ensuring that the reaction raw material mixture has sufficient fluidity, it is necessary to perform mechanical stirring for a longer time, and the obtained graphite oxide yield and oxygen content are comparable to those of the examples of the present application, indicating that the preparation method of the present application can reduce the amount of sulfuric acid input in the graphite oxide preparation process, while saving the cost of subsequent treatment of waste acid.

[0057] In addition, since the preparation method of the present application can maintain good fluidity and stirrability of the entire system after adding graphite, it reduces the resources required for stirring to ensure material transfer (such as stirring time, stirring equipment and stirring energy consumption), which is also conducive to controlling production costs.

[0058] The above implementation modes are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the above preferred implementation modes, a person skilled in the art should understand that the technical solutions of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for preparing graphite oxide, characterized in that: The preparation method comprises: Mixing sulfuric acid and an oxidant at a temperature of 3°C to 7°C so that the oxidant is completely dissolved in the sulfuric acid to obtain a solution; mixing the solution with graphite at a temperature of 3°C to 7°C to obtain a slurry; Heating and stirring the slurry, and causing the graphite in the slurry to undergo an oxidation reaction under the condition of isolating from air and water vapor; The slurry after the oxidation reaction is mixed with water and hydrolyzed to obtain the graphite oxide.

2. The preparation method according to claim 1, characterized in that The ratio of the sulfuric acid to the graphite is 10 mL:1 g to 35 mL:1 g.

3. The preparation method according to claim 1, characterized in that The sulfuric acid and the oxidant are mixed for 1 to 10 hours.

4. The preparation method according to claim 1, characterized in that The temperature of the slurry after the heating is 20°C to 60°C.

5. The preparation method according to claim 1, characterized in that: The preparation method satisfies at least one of the following conditions: (1) The concentration of the sulfuric acid is 77.5wt% to 98.5wt%; (2) The oxidant includes at least one of potassium permanganate, potassium perchlorate and potassium ferrate.

6. The preparation method according to claim 1, characterized in that: The graphite satisfies at least one of the following conditions: (1) The graphite includes at least one of block graphite, earthy graphite, flake graphite, expanded graphite and intercalated graphite; (2) The particle size of the graphite is 5 μm to 1000 μm.

7. The preparation method according to claim 1, characterized in that The oxidation reaction time is 12 h to 120 h.

8. The preparation method according to claim 1, characterized in that: The mass ratio of the water to the graphite is 20 to 60.

9. The preparation method according to claim 1, characterized in that: The hydrolysis temperature is 50°C to 95°C, and the time is 5 min to 60 min.

10. The preparation method according to claim 1, characterized in that: The preparation method further comprises: Add 30% by mass of hydrogen peroxide to the hydrolyzed slurry, and the ratio of the hydrogen peroxide to the graphite is 2 mL:1 g to 10 mL:1 g.

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