Preparation method of graphite oxide

Abstract

A method for preparing graphite oxide includes: mixing graphite, an intercalating agent and a solvent to obtain a mixed solution; heating the mixed solution, and adding the same oxidant to the mixed solution in multiple stages, so that the graphite in the mixed solution undergoes oxidation reactions successively, and a reaction solution is obtained after all the graphite reacts; water is added to the reaction solution to undergo a hydrolysis reaction to obtain graphite oxide; wherein the ratio of the mass of the oxidant added in each stage to the oxidation reaction time of the current stage is defined as the oxidant feeding rate, and the oxidant feeding rate of the latter stage of two adjacent stages is less than the oxidant feeding rate of the previous stage. By adding the oxidant in a preset feeding method, the oxidant can be continuously replenished in the mixed solution, which is beneficial to reducing the consumption caused by the self-decomposition of the oxidant, and is beneficial to maintaining a suitable oxidant concentration in the mixed solution to meet the oxidant concentration required for oxidation of different regions of the graphite, so that the oxidation of the graphite is more complete.

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 uses graphite as a raw material and oxidizes the graphite under the action of an oxidant. However, the existing method usually has the problem that the inside of the graphite is difficult to oxidize, which affects the quality of the graphite oxide. 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 graphite, an intercalating agent and a solvent to obtain a mixed solution; heating the mixed solution, and adding the same oxidant to the mixed solution in multiple stages, so that the graphite in the mixed solution undergoes oxidation reactions one after another, and a reaction solution is obtained after all the graphites react; adding water to the reaction solution to cause a hydrolysis reaction to obtain the graphite oxide; wherein the ratio of the mass of the oxidant added in each stage to the oxidation reaction time of the current stage is defined as the oxidant feeding rate, and the oxidant feeding rate of the latter stage of two adjacent stages is less than the oxidant feeding rate of the previous stage.

[0005] In some possible implementations, the ratio of the oxidant feeding rate in the first stage to the oxidant feeding rate in the last stage is 2:1 to 10:1.

[0006] In some possible implementations, the mass ratio of the total input mass of the oxidant to the mass of the graphite is 2:1 to 8:1.

[0007] In some possible implementations, the total duration of the oxidation reaction is 2 h to 20 h.

[0008] In some possible implementations, the oxidant includes at least one of potassium permanganate, potassium perchlorate, and potassium ferrate.

[0009] In some possible implementations, the graphite includes at least one of block graphite, earthy graphite, flake graphite, expanded graphite, and intercalated graphite.

[0010] In some possible implementations, the graphite has a particle size of 10 μm to 1000 μm.

[0011] In some possible implementations, the intercalant and the solvent are both sulfuric acid, and the concentration of the sulfuric acid is 82 wt % to 98.3 wt %.

[0012] In some possible implementations, the intercalant and the solvent are both sulfuric acid, and the ratio of the sulfuric acid to the graphite is 15 mL:1 g to 200 mL:1 g.

[0013] In some possible implementations, the intercalant and the solvent are both sulfuric acid, and the volume ratio of the water to the sulfuric acid is 0.5:1 to 3:1.

[0014] In some possible implementations, the temperature of the heated mixed solution is 15° C. to 60° C.

[0015] In some possible implementations, the hydrolysis temperature is 70°C to 98°C.

[0016] In some possible implementations, the hydrolysis time is 10 min to 80 min.

[0017] In some possible implementations, after the hydrolysis reaction, the method further includes: adding 30% by mass of hydrogen peroxide to the reaction solution after the hydrolysis reaction, wherein the ratio of the hydrogen peroxide to the graphite is 2 mL:1 g to 10 mL:1 g.

[0018] The present application adds the oxidant by feeding it multiple times in stages. By feeding the oxidant multiple times, the oxidant can be continuously supplemented in the mixed solution, which is conducive to reducing the consumption caused by the self-decomposition of the oxidant and improving the utilization rate of the oxidant. In addition, the present application also finds that the oxidation reaction of graphite occurs at the solid-liquid interface, from the edge of the graphite to the center, and the reaction speed is fast at first and then slow. Therefore, it is speculated that the consumption rate of the oxidant is also fast at first and then slow. Based on this, the present application sets the relationship between the two oxidant feeding speeds, that is, controls the oxidant feeding speed to be slower and slower, which is conducive to maintaining a suitable oxidant concentration in the mixed solution, meeting the oxidant concentration requirements required for oxidation of different regions of graphite from the edge to the center, making the oxidation of graphite more sufficient, and solving the problem that some regions of graphite are difficult to oxidize. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is an optical microscope image of the aqueous dispersion of graphite oxide provided in Example 1 of the present application.

[0020] Figure 2 This is the X-ray diffraction pattern of graphite oxide provided in Example 1 of the present application.

[0021] Figure 3 This is an optical microscope image of the aqueous dispersion of graphite oxide provided in Example 2 of the present application. DETAILED DESCRIPTION

[0022] 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.

[0023] Based on this, an embodiment of the present application provides a method for preparing graphite oxide, comprising: mixing graphite, an intercalating agent and a solvent to obtain a mixed liquid; heating the mixed liquid, and adding the same oxidant to the mixed liquid in multiple stages, so that the graphite in the mixed liquid undergoes oxidation reaction successively, and a reaction liquid is obtained after all the graphites react; water is added to the reaction liquid to cause a hydrolysis reaction to obtain the graphite oxide; wherein the ratio of the mass of the oxidant added in each stage to the oxidation reaction time of the current stage is defined as the oxidant feeding rate, and the oxidant feeding rate of the latter stage of two adjacent stages is less than the oxidant feeding rate of the previous stage.

[0024] The current Hummers method usually feeds the oxidant once and then heats it for oxidation reaction. The present application found that when the oxidant is dissolved in a solvent (such as sulfuric acid), it begins to self-decompose, which is a waste of the oxidant. Moreover, when the oxidation reaction of graphite begins, the concentration of the oxidant drops rapidly, and it is easy to happen that when the oxidant is lower than the threshold concentration, some areas of the graphite (such as the part close to the center of the graphite) have not been fully oxidized.

[0025] Based on this, the application puts in the oxidant by feeding it multiple times in stages. By feeding the oxidant multiple times, the oxidant can be continuously supplemented in the mixed solution, which is conducive to reducing the consumption caused by the self-decomposition of the oxidant and improving the utilization rate of the oxidant. In addition, the application also finds that the oxidation reaction of graphite occurs at the solid-liquid interface, from the edge of the graphite to the center. According to the theory of chemical kinetics and experimental experience, this type of reaction speed is fast at first and then slow. Therefore, it is speculated that the consumption rate of the oxidant is also fast at first and then slow. Based on this, the application sets the relationship between the two oxidant feeding speeds, that is, controls the oxidant feeding speed to be slower and slower, which is conducive to maintaining a suitable oxidant concentration in the mixed solution, meeting the oxidant concentration requirements required for oxidation of different regions of graphite from the edge to the center, making the oxidation of graphite more sufficient, and solving the problem that some areas of graphite are difficult to oxidize.

[0026] It can be understood that when the oxidant feeding rate in each stage is basically the same, it can be regarded as the oxidant being added to the mixed liquid at a uniform speed. When the oxidant feeding rate in the latter stage of two adjacent stages is greater than the oxidant feeding rate in the previous stage, it means that the oxidant feeding rate is getting faster and faster, that is, the oxidant is added to the mixed liquid at an accelerated speed. Since the consumption rate of the oxidant is presumed to be fast at first and then slow, when the total amount of graphite input is constant, the uniform or accelerated oxidant addition may lead to insufficient oxidant concentration in the mixed liquid during the early stage of graphite oxidation, resulting in restricted graphite oxidation. In the late stage of graphite oxidation, the oxidant concentration in the mixed liquid is too high, the self-decomposition behavior of the oxidant is aggravated, and the oxidant is wasted.

[0027] In some embodiments, the ratio of the oxidant feeding speed in the first stage to the oxidant feeding speed in the last stage is 2:1 to 10:1. For example, the ratio of the oxidant feeding speed in the first stage to the oxidant feeding speed in the last stage can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1 or any value within the range formed by any two of the above values. Setting the above speed ratio relationship is conducive to further maintaining the appropriate oxidant concentration in the mixed solution to meet the oxidant concentration requirements required for oxidation of different regions of graphite from the edge to the center.

[0028] In some embodiments, the mass ratio of the total input mass of the oxidant to the mass of the graphite is 2:1 to 8:1. For example, the mass ratio of the total input mass of the oxidant to the graphite can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1 or any value within the range formed by any two of the above values. It can be understood that the total input mass of the oxidant is the sum of the masses of the oxidant added in all stages. Setting the relationship between the total input mass of the oxidant and the mass of the graphite is conducive to further maintaining the appropriate oxidant concentration in the mixed solution, further promoting the full oxidation of the graphite, and solving the problem that some areas of the graphite are difficult to oxidize.

[0029] In some embodiments, the total duration of the oxidation reaction is 2 h to 20 h. For example, the total duration of the oxidation reaction can be 2 h, 4 h, 6 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h or any value within the range formed by any two of the above values. It can be understood that after each addition of the oxidant, the mixed solution reacts for a period of time, and the total duration for all graphite in the mixed solution to react is the total duration of the oxidation reaction. Controlling the total duration of the oxidation reaction within the above range is conducive to better controlling the progress of the mixed solution reaction and promoting the full oxidation of graphite.

[0030] In some embodiments, the oxidant includes at least one of potassium permanganate, potassium perchlorate and potassium ferrate. Under the preset oxidant feeding method of the present application, the oxidant is selected from the above substances to promote full oxidation of graphite each time the feeding is performed.

[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 10 μm to 1000 μm. For example, the particle size of the graphite can be 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 suitable for preparing the above-mentioned graphite in various states or graphite of the above-mentioned particle size. Through the oxidant feeding method preset in the present application, the graphite raw material selection can obtain good oxidation effect by the above selection.

[0032] In some embodiments, the intercalant and the solvent are both sulfuric acid, and the concentration of the sulfuric acid is 82wt% to 98.3wt%. For example, the concentration of sulfuric acid can be 82wt%, 83wt%, 84.5wt%, 86wt%, 87.5wt%, 89wt%, 90.5wt%, 92wt%, 93.5wt%, 95wt%, 96.5wt%, 98wt%, 98.3wt%, or any value within the range formed by any two of the above values. The concentration of the sulfuric acid used is controlled within the above range, which is conducive to the insertion of sulfuric acid molecules into the graphite layers to form sulfuric acid intercalation compounds.

[0033] In some embodiments, the intercalant and the solvent are both sulfuric acid, and the ratio of the sulfuric acid to the graphite is 15 mL: 1 g to 200 mL: 1 g. For example, the ratio of sulfuric acid to graphite can be 15 mL: 1 g, 20 mL: 1 g, 30 mL: 1 g, 50 mL: 1 g, 70 mL: 1 g, 100 mL: 1 g, 120 mL: 1 g, 150 mL: 1 g, 180 mL: 1 g, 200 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 mixed solution, so that the graphite can maintain good contact or react with other substances.

[0034] In some embodiments, the intercalant and the solvent are both sulfuric acid, and the volume ratio of water to sulfuric acid is 0.5:1 to 3:1. For example, the volume ratio may be 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, or any value within the range formed by any two of the above values. It can be understood that controlling the volume relationship of water and sulfuric acid is conducive to the full hydrolysis of the reaction solution and the full discharge of the intercalant in the graphite structure.

[0035] In some embodiments, the temperature of the heated mixed solution is 15° C. to 60° C. For example, the heated temperature can be 15° C., 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 heating to the above temperature is conducive to the oxidation reaction of the mixed solution.

[0036] In some embodiments, the hydrolysis temperature is 70°C to 98°C, which is conducive to promoting the hydrolysis reaction. For example, the hydrolysis temperature can be 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 98°C or any value within the range of any two of the above values.

[0037] In some embodiments, the hydrolysis time is 10 min to 80 min, which is conducive to sufficient hydrolysis. For example, the hydrolysis time can be 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min or any value within the range of any two of the above values.

[0038] In some embodiments, after the hydrolysis reaction, the method further comprises: adding 30% hydrogen peroxide by mass to the reaction solution after the hydrolysis reaction, wherein 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, and 10 mL:1 g. It can be understood that controlling the dosage relationship between hydrogen peroxide and graphite is conducive to timely termination of the reaction, thereby helping to control the oxygen content of the resulting oxidized graphite.

[0039] 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.

[0040] Embodiment 1: A method for preparing graphite oxide, comprising the steps of: Step 1: Take 325 mesh natural graphite as raw material, 97wt% sulfuric acid as solvent and intercalation agent, and potassium permanganate as oxidant. The total amount of the three is 10 g, 300 mL, and 40 g respectively.

[0041] Step 2: Start stirring to mix graphite and sulfuric acid evenly, raise the temperature to 30 °C, and start adding potassium permanganate in 4 times: the first time is 10 g within a time interval of 40 minutes, the second time is 10 g within a time interval of 60 minutes, the third time is 10 g within a time interval of 90 minutes, and the fourth time is 10 g within a time interval of 130 minutes. After the addition of potassium permanganate is completed, continue the reaction for 60 minutes, maintain the temperature at 30±5 °C during the process, and the total feeding and oxidation time is 320 minutes.

[0042] Step 3: Slowly add 600 mL of deionized water at a rate of 2 mL / min. During the process, control the temperature of the mixed solution not to exceed 60 °C. After the water is added, raise the temperature of the mixed solution to 90 °C, maintain it for 20 min, and then cool it naturally. Add 30 mL of 30wt% hydrogen peroxide to stop the reaction.

[0043] Step 4: Filter, wash and dry to obtain graphite oxide.

[0044] Embodiment 2: A method for preparing graphite oxide, comprising the steps of: Step 1: Take 100 mesh intercalated graphite as raw material, 94wt% sulfuric acid as solvent, and potassium permanganate as oxidant. The total amount of the three is 5 g, 200 mL, and 15 g respectively.

[0045] Step 2: Start stirring to mix graphite and sulfuric acid evenly, raise the temperature to 25 °C, and start adding potassium permanganate in 3 times: the first time is 5 g within a time interval of 60 minutes, the second time is 5 g within a time interval of 80 minutes, and the third time is 5 g within a time interval of 150 minutes. After the addition of potassium permanganate is completed, continue the reaction for 120 minutes. The total feeding and oxidation time is 290 minutes.

[0046] Step 3: Slowly add 400 mL of deionized water at a rate of 2 mL / min. During the process, control the temperature of the mixed solution not to exceed 60 °C. After the water is added, raise the temperature of the mixed solution to 90 °C, maintain it for 30 min, and then cool it naturally. Add 20 mL of 30wt% hydrogen peroxide to stop the reaction.

[0047] Step 4: Filter, wash and dry to obtain graphite oxide.

[0048] Embodiment 3: A method for preparing graphite oxide, comprising the steps of: Step 1: Take 325 mesh natural graphite as raw material, 98.3wt% sulfuric acid as solvent and intercalation agent, and potassium permanganate as oxidant. The total amount of the three is 1 g, 30 mL, and 3 g respectively.

[0049] Step 2: Start stirring to mix graphite and sulfuric acid evenly, raise the temperature to 35 °C, and start adding potassium permanganate in 4 batches: the first time, add 0.75 g and let stand for 10 min, the second time, add 0.75 g and let stand for 20 min, the third time, add 0.75 g and let stand for 30 min, the fourth time, add 0.75 g and let stand for 60 min. The total feeding and oxidation time is 120 min.

[0050] Step 3: Slowly add 60 mL of deionized water. After the water is added, raise the temperature of the mixture to 90 °C, maintain for 20 minutes, and then cool naturally. Add 30 wt% hydrogen peroxide to stop the reaction.

[0051] Step 4: Filter, wash and dry to obtain graphite oxide.

[0052] Comparative Example 1: The difference from Example 3 is that, in the second step, potassium permanganate is added in one go.

[0053] Comparative Example 2: The difference from Example 3 is that in the second step, potassium permanganate is added in 4 times, 0.75 g is added in the first time and allowed to stand for 30 min, 0.75 g is added in the second time and allowed to stand for 30 min, 0.75 g is added in the third time and allowed to stand for 30 min, and 0.75 g is added in the fourth time and allowed to stand for 30 min. The total feeding and oxidation time is 120 min.

[0054] The present application has carried out optical microscope morphology test and XRD analysis on the graphite oxide of Example 1-2. Figure 1 In the aqueous dispersion of graphite oxide in Example 1, the graphite oxide is in the form of transparent flakes, and no unevenly oxidized black particles are found in the center of the graphite flakes, indicating that the graphite is fully oxidized. Figure 2 In the XRD spectrum of graphite oxide in Example 1, there is a characteristic peak of graphite oxide near 11.4°, and no other miscellaneous peaks are seen, indicating that the graphite is fully oxidized.

[0055] See also Figure 3In the aqueous dispersion of graphite oxide in Experimental Example 2, the graphite oxide is in the form of transparent flakes, and no unevenly oxidized black particles are observed in the center of the graphite flakes, indicating that the graphite is fully oxidized.

[0056] The present application analyzes the oxygen content of the graphite oxide of Example 3 and Comparative Examples 1-2, and the test method includes: using a combustion method and an element analyzer to determine the mass fraction of the oxygen element in the washed and dried graphite oxide. Please refer to Table 1 for the test results.

[0057] Table 1. Test results of oxygen content of graphite oxide in Example 3 of the present application and Comparative Examples 1-2 Embodiments 1-3 of the present application add the oxidant through a preset feeding method, which can continuously replenish the oxidant in the mixed liquid, thereby helping to reduce the consumption caused by the self-decomposition of the oxidant, improve the utilization rate of the oxidant, and help the mixed liquid maintain a suitable oxidant concentration to meet the oxidant concentration required for oxidation of different regions of the graphite, thereby making the oxidation of the graphite more complete.

[0058] Compared with Example 3, the oxidant in Comparative Example 1 is added at one time, the oxidant in the mixed solution is self-decomposed, the utilization rate is low, and after the oxidation reaction starts, the oxidant is rapidly consumed, and the concentration of the oxidant in the mixed solution decreases rapidly, resulting in the unoxidized part of the graphite being difficult to continue to react well, so that the oxygen content of the oxidized graphite is significantly lower.

[0059] Compared with Example 3, the oxidant in Comparative Example 2 is added in multiple times. Although the oxidant is continuously added to the mixed liquid, which reduces the consumption caused by the self-decomposition of the oxidant to a certain extent, the oxidant is added to the mixed liquid in a uniform feeding manner. Since the consumption rate of the oxidant is fast at first and then slows down, when the total amount of graphite input is constant, the uniform rate of oxidant addition may lead to insufficient oxidant concentration in the mixed liquid during the early stage of graphite oxidation, resulting in restricted graphite oxidation. In the late stage of graphite oxidation, the oxidant concentration in the mixed liquid is too high, the self-decomposition behavior of the oxidant is aggravated, and the oxidant is wasted.

[0060] 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 graphite, an intercalating agent and a solvent to obtain a mixed solution; The mixed solution is heated, and the same oxidant is added to the mixed solution in multiple stages, so that the graphite in the mixed solution undergoes oxidation reaction successively, and a reaction solution is obtained after all the graphite reacts; Adding water to the reaction solution to cause a hydrolysis reaction to obtain the graphite oxide; The ratio of the mass of the oxidant added in each stage to the oxidation reaction time in the current stage is defined as the oxidant feeding rate, and the oxidant feeding rate in the latter stage of two adjacent stages is smaller than the oxidant feeding rate in the previous stage.

2. The preparation method according to claim 1, characterized in that In the multiple stages, a ratio of the oxidant feeding rate in the first stage to the oxidant feeding rate in the last stage is 2:1 to 10:

1.

3. The preparation method according to claim 1, characterized in that: The mass ratio of the total input mass of the oxidant to the mass of the graphite is 2:1 to 8:

1.

4. The preparation method according to claim 1, characterized in that The total duration of the oxidation reaction is 2 h to 20 h.

5. The preparation method according to claim 1, characterized in that: 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 10 μm to 1000 μm.

7. The preparation method according to claim 1, characterized in that: The intercalant and the solvent are both sulfuric acid, and the sulfuric acid satisfies at least one of the following conditions: (1) The concentration of the sulfuric acid is 82wt% to 98.3wt%; (2) The ratio of the sulfuric acid to the graphite is 15 mL:1 g to 200 mL:1 g; (3) The volume ratio of the water to the sulfuric acid is 0.5:1 to 3:

1.

8. The preparation method according to claim 1, characterized in that The temperature of the heated mixed solution is 15°C to 60°C.

9. The preparation method according to claim 1, characterized in that: The hydrolysis reaction satisfies at least one of the following conditions: (1) The hydrolysis temperature is 70°C to 98°C; (2) The hydrolysis time is 10 min to 80 min.

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

Images