A graphite oxide and manganese oxide, their preparation method and uses

Abstract

This disclosure relates to a method for preparing graphite oxide and manganese oxide, comprising the following steps: 1. Mixing graphite with concentrated acid, then adding potassium permanganate in batches to obtain a mixture; 2. Heating the mixture to react, adding water and stirring, then separating the liquid and solid phases to obtain a liquid phase and a solid phase, the liquid phase being the separation stock solution, and the solid phase being recovered to obtain graphite oxide; 3. Mixing the separation stock solution with an auxiliary agent, performing a hydrothermal reaction, and recovering the solid phase material. The preparation method of this invention achieves the simultaneous preparation of graphite oxide and manganese oxide, with a high amount of potassium permanganate used in the preparation of graphite oxide, resulting in a fast oxidation rate and good oxidation effect. Furthermore, no additional manganese source is required when preparing manganese oxide, reducing the preparation cost of manganese oxide. The process of preparing graphite oxide and manganese oxide using this invention can significantly reduce the content of manganese ions in wastewater, solving the problem of environmental pollution caused by wastewater discharge.

Description

Technical Field

[0001] This disclosure pertains to the field of graphite oxide, specifically relating to a graphite oxide and manganese oxide, their preparation methods, and uses. Background Technology

[0002] Graphite oxide is an important type of graphite product, used to prepare popular downstream products such as expanded graphite and graphene. Currently, the main method for producing graphite oxide is to oxidize graphite using strong oxidants such as potassium permanganate. However, existing methods result in high manganese ion content in the wastewater, making environmental treatment difficult and placing significant pressure on environmental protection.

[0003] Hydrogen sulfide and carbonyl sulfide are the main forms of sulfide impurities commonly found in gases, especially in hydrogen. Current international standards impose strict requirements on the sulfide content of hydrogen used in fuel cells. Ensuring the sulfide content of hydrogen for fuel cells is a key technological challenge. Existing desulfurization technologies rarely address mixed sulfides or utilize manganese oxides for this purpose. Summary of the Invention

[0004] The purpose of this invention is to provide graphite oxide and manganese oxide, their preparation method, and applications. The preparation method of this invention achieves the simultaneous production of manganese oxide and graphite oxide, with a high dosage of potassium permanganate used in the graphite oxide preparation process, resulting in rapid oxidation and good oxidation effect. Furthermore, no additional manganese source is required when preparing manganese oxide, reducing the preparation cost. This invention simultaneously produces manganese oxide and graphite oxide, and can significantly reduce the content of manganese ions and other pollutants in wastewater, solving the environmental pollution problems caused by wastewater discharge during the graphite oxide process.

[0005] To achieve the above objectives, a first aspect of the present invention provides a method for preparing graphite oxide and manganese oxide, the method comprising:

[0006] S1 mixes graphite with concentrated acid and then adds potassium permanganate in batches to obtain a mixture.

[0007] S2 involves heating and reacting the mixture, adding water and stirring, and then separating the liquid and solid phases to obtain the liquid phase and solid phase respectively. The liquid phase is the original separation solution, and the solid phase is recovered to obtain graphite oxide.

[0008] S3 mixes the separation stock solution with the auxiliary agent, carries out a hydrothermal reaction, and recovers the solid phase material;

[0009] The additive is one or more of ammonium persulfate, sodium persulfate, potassium persulfate and sodium hypochlorite, and the mass ratio of the additive to the graphite is (0.2-10):1.

[0010] The conditions for the hydrothermal reaction include: a temperature of 100–200°C and a time of 1–72 h.

[0011] Optionally, the mass ratio of the additive to the graphite is (0.5-5):1;

[0012] The conditions for the hydrothermal reaction include: a temperature of 100–150°C and a time of 2–24 hours.

[0013] Optionally, the oxygen content of the graphite oxide is 15-40% by weight, and the carbon content is 60-85% by weight.

[0014] Optionally, the graphite is one or more of natural flake graphite, natural cryptocrystalline graphite, and artificial graphite;

[0015] The graphite has a carbon content of 98% or more by weight, an ash content of less than 2%, and a mesh size of 20 to 2000 mesh.

[0016] Optionally, the concentrated acid is selected from one or more of sulfuric acid, nitric acid, and perchloric acid;

[0017] C0 is any concentration between N-10% and N+10%, preferably any concentration between N-5% and N+5%, where C0 is the concentration of the concentrated acid and N is the highest concentration of the concentrated acid in analytical grade reagent.

[0018] Optionally, the mass ratio of the concentrated acid to the graphite is (20-150):1, preferably (30-100):1;

[0019] The mass ratio of potassium permanganate to graphite is (2-8):1, preferably (3-6):1;

[0020] The mass ratio of potassium permanganate to graphite in each batch is (0.05-1):1, preferably (0.1-0.5):1;

[0021] The mass ratio of water to graphite is (50-2000):1, preferably (80-250):1.

[0022] Optionally, the method further includes:

[0023] In step S1, after adding potassium permanganate in batches and mixing, the temperature is controlled to below 40°C, preferably below 30°C, more preferably below 20°C, and the mixture is stirred for 0.2 to 12 hours; no sodium nitrate or hydrogen peroxide is added during the reaction.

[0024] In step S2, the conditions for the heating reaction include: a temperature of 30–60°C and a time of 0.2–6 h; and a stirring time of 0.1–5 h for adding water.

[0025] A second aspect of the present invention provides a manganese oxide prepared using the method provided in the first aspect of the present invention.

[0026] Optionally, the XRD pattern of the manganese oxide has characteristic peaks at 2θ positions of 28.6±0.5°, 37.4±0.3°, 41.0±0.3°, 42.8±0.3°, 56.6±0.3°, 59.4±0.3°, 64.9±0.3°, and 72.4±0.3°, respectively; and the half-width at 28.6±0.5° is greater than 0.1°.

[0027] Based on the mass of the manganese oxide, the manganese oxide contains 30-55% Mn, 0.8-10% S, and 1-10% K.

[0028] The specific surface area of ​​the manganese oxide is 10 to 100 m². 2 / g, preferably 30-60m 2 / g, pore volume is 0.05-0.5ml / g, preferably 0.1-0.3ml / g, pore size is 12-36nm, preferably 15-30nm.

[0029] The third aspect of the present invention provides the use of the manganese oxide provided in the second aspect of the present invention for the removal of sulfides in a gas.

[0030] Through the above technical solution, the preparation method of the present invention involves mixing graphite with concentrated acid and potassium permanganate, and then mixing it with additives for a hydrothermal reaction, thereby simultaneously preparing manganese oxide and graphite oxide. Since a high amount of potassium permanganate is used in the preparation of graphite oxide, no additional manganese source is required, and no sodium nitrate or hydrogen peroxide is added during the reaction, reducing the preparation cost of manganese oxide. The present invention simultaneously produces manganese oxide and graphite oxide, and the prepared graphite oxide and manganese oxide exhibit excellent performance in treating wastewater from the graphite oxide preparation process, significantly reducing the content of manganese ions and other pollutants in the wastewater, thus solving the environmental pollution problems caused by wastewater discharge during the graphite oxide preparation process.

[0031] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0032] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0033] Figure 1 The image shows the XRD pattern of the manganese oxide prepared in Example 1 of this invention. Detailed Implementation

[0034] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0035] The first aspect of this invention provides a method for preparing graphite oxide and manganese oxide, the method comprising:

[0036] S1 mixes graphite with concentrated acid and then adds potassium permanganate in batches to obtain a mixture.

[0037] S2 involves heating and reacting the mixture, adding water and stirring, and then separating the liquid and solid phases to obtain the liquid phase and solid phase respectively. The liquid phase is the original separation solution, and the solid phase is recovered to obtain graphite oxide.

[0038] S3 mixes the separation stock solution with the auxiliary agent, carries out a hydrothermal reaction, and recovers the solid phase material;

[0039] The additive is one or more of ammonium persulfate, sodium persulfate, potassium persulfate and sodium hypochlorite, preferably ammonium persulfate and potassium persulfate, and the mass ratio of the additive to the graphite is (0.2-10):1, preferably (0.5-5):1, more preferably (1-3):1;

[0040] The conditions for the hydrothermal reaction include: a temperature of 100–200°C, preferably 100–150°C, and a time of 1–72 h, preferably 2–24 h.

[0041] The preparation method of this invention involves first reacting graphite with concentrated acid and potassium permanganate to obtain graphite oxide, then mixing the separated stock solution with an auxiliary agent for a hydrothermal reaction, thereby simultaneously preparing manganese oxide and graphite oxide. Because a high amount of potassium permanganate is used in the preparation of graphite oxide, no additional manganese source is required, and no sodium nitrate or hydrogen peroxide is added during the reaction, significantly improving process safety and reducing the preparation cost of manganese oxide.

[0042] In the above embodiments, by controlling the mass ratio of the additive to graphite and the hydrothermal reaction conditions within a preferred range, it is beneficial to improve the various properties of manganese oxide and graphite oxide.

[0043] In one specific embodiment of the present invention, the oxygen content of the graphite oxide is 15-40% by weight, preferably 20-35% by weight, and the carbon content is 60-85% by weight, preferably 65-80% by weight.

[0044] In one specific embodiment of the present invention, the graphite is one or more of natural flake graphite, natural cryptocrystalline graphite and artificial graphite, preferably natural flake graphite.

[0045] The graphite has a carbon content of 98% by weight or more, preferably 99% by weight or more, more preferably 99.9% by weight or more, an ash content of 2% or less, preferably 1% or less, more preferably 0.1% or less, and a mesh size of 20 to 2000 mesh, preferably 50 to 500 mesh.

[0046] In one specific embodiment of the present invention, the concentrated acid is selected from one or more of sulfuric acid, nitric acid and perchloric acid, preferably sulfuric acid;

[0047] C0 is any concentration between N-10% and N+10%, preferably any concentration between N-5% and N+5%, where C0 is the concentration of the concentrated acid and N is the highest concentration of the concentrated acid in analytical grade reagent.

[0048] In one specific embodiment of the present invention, the mass ratio of the concentrated acid to the graphite is (20-150):1, preferably (30-100):1;

[0049] The mass ratio of potassium permanganate to graphite is (2-8):1, preferably (3-6):1;

[0050] The mass ratio of potassium permanganate to graphite in each batch is (0.05-1):1, preferably (0.1-0.5):1;

[0051] The mass ratio of water to graphite is (50-2000):1, preferably (80-250):1.

[0052] In one specific embodiment of the present invention, the method further includes:

[0053] In step S1, after mixing with potassium permanganate, the temperature is controlled to below 40°C, preferably below 30°C, more preferably below 20°C, and stirring is performed for 0.2 to 12 hours, preferably 0.5 to 6 hours; no sodium nitrate or hydrogen peroxide is added during the reaction.

[0054] In step S2, the conditions for the heating reaction include: a temperature of 30–60°C, preferably 40–50°C, and a time of 0.2–6 h, preferably 0.5–4 h; the time for adding water and stirring is 0.1–5 h, preferably 0.5–2 h.

[0055] A second aspect of the present invention provides a manganese oxide prepared using the method provided in the first aspect of the present invention.

[0056] In one specific embodiment of the present invention, the XRD pattern of the manganese oxide has characteristic peaks at 2θ positions of 28.6±0.5°, 37.4±0.3°, 41.0±0.3°, 42.8±0.3°, 56.6±0.3°, 59.4±0.3°, 64.9±0.3°, and 72.4±0.3°, respectively; and the half-width at half-maximum (WHM) of the diffraction peak at 28.6±0.5° is greater than 0.1°.

[0057] Based on the mass of the manganese oxide, the manganese oxide contains 30-55% by weight of Mn, preferably 35-50% by weight; 0.8-10% by weight of S, preferably 1.2-6% by weight; 1-10% by weight of K, preferably 3-8% by weight; and the balance is mainly O.

[0058] The specific surface area of ​​the manganese oxide is 10 to 100 m². 2 / g, preferably 30-60m 2 / g, pore volume is 0.05-0.5ml / g, preferably 0.1-0.3ml / g, pore size is 12-36nm, preferably 15-30nm.

[0059] This invention produces manganese oxide crystalline powder while preparing graphite oxide. Furthermore, the method of this invention can significantly reduce the content of manganese ions in wastewater. Generally, the manganese ion content is less than 50 ppm, which can be directly discharged, thus solving the problem of environmental pollution caused by wastewater discharge during the preparation of graphite oxide.

[0060] The third aspect of the present invention provides the use of the manganese oxide provided in the second aspect of the present invention for the removal of sulfides in a gas.

[0061] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto.

[0062] All reagents used in this invention are commercially available analytical grade reagents.

[0063] Example 1

[0064] a) Add 150 ml of concentrated sulfuric acid (mass concentration greater than 98%) and 5 g of graphite to a beaker and mix to obtain a mixture;

[0065] b. Add 25g of potassium permanganate in 5 equal batches to the mixture obtained in step a, and stir and mix at 10℃ for 1 hour to obtain the mixture.

[0066] c. Stir the mixture obtained in step b under autogenous pressure at 35°C for 2 hours.

[0067] d. Add 150 ml of water to the mixture in step c, continue stirring and reacting at 90 °C for 1 h, and then filter to obtain solid graphite oxide and separation solution;

[0068] e. At 120℃ and autogenous pressure, the original solution from step d is mixed with 5g of potassium persulfate and hydrothermally treated for 24h to separate the solid phase manganese oxide.

[0069] The XRD pattern of the prepared manganese oxide is shown in the figure. Figure 1 As shown.

[0070] Example 2

[0071] The preparation method in Example 1 is used, except that in step e, the separation solution in step d is mixed with 1g of potassium persulfate.

[0072] Example 3

[0073] The preparation method in Example 1 was used, except that in step e, the reaction temperature was 160°C and the hydrothermal treatment time was 2 hours.

[0074] Example 4

[0075] The preparation method in Example 1 is used, except that in step e, 5g of potassium persulfate is replaced with 5g of ammonium persulfate.

[0076] Example 5

[0077] The preparation method in Example 1 was used, except that in step a, 100 ml of concentrated sulfuric acid was added.

[0078] Example 6

[0079] The preparation method in Example 1 was used, except that 15g of potassium permanganate was added in step b.

[0080] Example 7

[0081] The preparation method in Example 1 was used, except that the reaction temperature in step c was 30°C.

[0082] Example 8

[0083] The preparation method in Example 1 was used, except that 450 ml of water was added in step d.

[0084] Example 9

[0085] The preparation method in Example 1 is used, except that in step b, the mass ratio of potassium permanganate to graphite added in each batch is 5:3, that is, potassium permanganate is added in 3 batches.

[0086] Example 10

[0087] The preparation method in Example 1 was used, except that in step a, 150 ml of concentrated nitric acid was added instead of concentrated sulfuric acid.

[0088] Comparative Example 1

[0089] The preparation method in Example 1 is used, except that in step b, 25g of potassium permanganate is added to the mixture obtained in step a all at once.

[0090] Comparative Example 2

[0091] The preparation method in Example 1 was used, except that in step e, the reaction temperature was 250°C and the hydrothermal treatment time was 96 h.

[0092] Comparative Example 3

[0093] The preparation method in Example 1 is used, except that in step e, the separation stock solution in step d is mixed with 30g of potassium persulfate.

[0094] Test case

[0095] The XRD patterns of the samples were obtained using a Rigaku D / MaxA-ⅢA X-ray diffractometer (Japan). Test conditions: Cu target Kα radiation, voltage 30 kV, current 20 mA, step scan, scan range 5°–80°.

[0096] The elemental content of the samples was determined by XPS on a VGESCA-LABS X-ray photoelectron spectrometer, using Mg Kα X-rays as the laser source. The binding energy of each element in the species on the surface of the desulfurizer was calibrated by the C1s binding energy (284.6 eV) of the carbon contaminants on the surface.

[0097] The temperature nitrogen adsorption-desorption (BET) test was performed using a JW-BK200C specific surface area and pore size analyzer from Beijing Jingwei Gaobo Co., Ltd. Specific surface area and pore volume were calculated using the two-parameter BET equation, and pore distribution was calculated using the BJH method.

[0098] 500 mg of the sample prepared according to the present invention and the comparative example were used as a removal agent and loaded into the isothermal section of a passivated fixed-bed microreactor with an inner diameter of 12 mm and a length of 500 mm. The reactor was filled with quartz sand on both the top and bottom. The sulfide content in the sulfur-containing raw material was 5000 ppm (carrier gas was hydrogen, and the sulfide was a complex of hydrogen sulfide and carbonyl sulfide in a molar ratio of 1:1). The sulfide removal reaction was carried out at 60 °C and 2 MPa at a flow rate of 100 ml / min. The sulfide content in the material after the removal reaction was analyzed online, and the sulfide removal rate was calculated. The sulfide removal rate after 1 h is shown in Table 1, and other characterization results of the prepared samples are shown in Table 2. The XRD pattern of the manganese oxide prepared in Example 1 of the present invention is shown in Table 2. Figure 1 As shown.

[0099] Table 1

[0100]

[0101]

[0102] Table 2

[0103]

[0104] As can be seen from the test results in Tables 1 and 2, the manganese oxide prepared by the method provided by this invention has a larger specific surface area and pore volume, and a moderate pore size compared with the comparative example. It exhibits excellent sulfur removal performance in the process of removing sulfides from gases, with a sulfur removal rate of over 90% in the material. At the same time, no sodium nitrate and hydrogen peroxide need to be added during the reaction, reducing the cost of the prepared materials. The manganese oxide produced can also significantly reduce the content of manganese ions and other substances in wastewater.

[0105] The test results of Examples 1-10 show that when the preparation method, type and amount of additives, and reaction conditions are within the limits of this invention, the effect and performance of the product prepared by this invention can be improved. A comparison of Examples 1 and Examples 2-10 shows that when the type and amount of additives, hydrothermal reaction conditions, type and amount of concentrated acid, amount and batch of potassium permanganate, heating temperature, stirring time, and the mass ratio of water to graphite are all within the preferred limits of this invention, the performance of the manganese oxide prepared by this invention in removing sulfides can be further improved, and the manganese ion content in the wastewater from preparation can be significantly reduced.

[0106] The test results of Comparative Examples 1-3 show that in Comparative Example 1, potassium permanganate was added to graphite in one step, and the reaction temperature rapidly rose to over 80℃. Some material splashed, resulting in uneven adsorption of potassium permanganate on the graphite. This led to excessively large pore volumes and diameters in the prepared manganese oxides, resulting in poor adsorption of sulfides in the gas, low removal rates, and excessively high manganese ion content in the wastewater. In Comparative Example 2, the hydrothermal treatment temperature was too high and the treatment time was too long. Excessively high temperatures can cause the thermal decomposition of oxygen-containing groups, thus affecting the product structure. The structure of the prepared manganese oxide resulted in a small specific surface area, pore volume, and pore size, which led to its inability to effectively remove sulfides from the gas, resulting in a low removal rate. Furthermore, the manganese ion content in the wastewater was higher compared to Examples 1-10. In Comparative Example 3, the excessive amount of potassium persulfate and the excessive degree of oxidation were not conducive to the formation of manganese oxides, resulting in a small specific surface area, small pore volume, and small pore size of the prepared manganese oxides. This resulted in poor product performance, which led to its inability to effectively remove sulfides from the gas, resulting in a low removal rate. Additionally, the manganese ion content in the wastewater was too high.

[0107] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0108] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0109] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing manganese oxide and graphite oxide, wherein, The method includes: S1 After mixing graphite with concentrated acid, potassium permanganate is added in batches to obtain a mixture. S2 After heating and reacting the mixture, water is added and stirred. After solid-liquid separation, liquid phase and solid phase are obtained respectively. The liquid phase is the original separation solution, and the solid phase is recovered to obtain graphite oxide. S3 The separation solution is mixed with the additives, subjected to a hydrothermal reaction, and the solid material is recovered; The additive is one or more of ammonium persulfate, sodium persulfate, potassium persulfate and sodium hypochlorite, and the mass ratio of the additive to the graphite is (0.2~10):1; The conditions for the hydrothermal reaction include: a temperature of 100~200℃ and a time of 1~72h; The mass ratio of potassium permanganate to graphite is (2~8):

1.

2. The method according to claim 1, wherein, The mass ratio of the additive to the graphite is (0.5~5):1; The conditions for the hydrothermal reaction include: a temperature of 100~150℃ and a time of 2~24h.

3. The method according to claim 1, wherein, The oxygen content of the graphite oxide is 15-40% by weight, and the carbon content is 60-85% by weight.

4. The method according to claim 1, wherein, The graphite is one or more of natural flake graphite, natural cryptocrystalline graphite, and artificial graphite. The graphite has a carbon content of 98% or more, an ash content of less than 2% by weight, and a mesh size of 20 to 2000 mesh.

5. The method according to claim 1, wherein, The concentrated acid is selected from one or more of sulfuric acid, nitric acid, and perchloric acid; C0 is any concentration between N-10% and N+10%, where C0 is the concentration of the concentrated acid and N is the highest concentration of the concentrated acid in analytical grade reagent.

6. The method according to claim 5, wherein, C0 can be any concentration between N-5% and N+5%.

7. The method according to claim 1, wherein, The mass ratio of the concentrated acid to the graphite is (20~150):1; The mass ratio of potassium permanganate to graphite is (3~6):1; The mass ratio of potassium permanganate to graphite in each batch is (0.05~1):1; The mass ratio of water to graphite is (50~2000):

1.

8. The method according to claim 7, wherein, The mass ratio of the concentrated acid to the graphite is (30~100):

1.

9. The method according to claim 7, wherein, The mass ratio of potassium permanganate to graphite in each batch is (0.1~0.5):

1.

10. The method according to claim 7, wherein, The mass ratio of water to graphite is (80~250):

1.

11. The method according to claim 1, wherein, The method also includes: In step S1, after mixing with potassium permanganate, the temperature is controlled below 40°C and stirred for 0.2 to 12 hours; no sodium nitrate or hydrogen peroxide is added during the reaction. In step S2, the conditions for the heating reaction include: a temperature of 30~60℃ and a time of 0.2~6h; the time for adding water and stirring is 0.1~5h.

12. The method according to claim 11, wherein, In step S1, after mixing with potassium permanganate, the temperature is controlled to be below 30°C.

13. The method according to claim 12, wherein, In step S1, after mixing with potassium permanganate, the temperature is controlled to be below 20°C.

14. Manganese oxide prepared by the method according to any one of claims 1 to 13.

15. The manganese oxide according to claim 14, wherein, The XRD pattern of the manganese oxide shows characteristic peaks at 2θ positions of 28.6±0.5°, 37.4±0.3°, 41.0±0.3°, 42.8±0.3°, 56.6±0.3°, 59.4±0.3°, 64.9±0.3°, and 72.4±0.3°, respectively; and the half-width at 28.6±0.5° is greater than 0.1°. Based on the mass of the manganese oxide, the manganese oxide contains 30-55% Mn by weight; 0.8-10% S by weight; and 1-10% K by weight. The specific surface area of ​​the manganese oxide is 10~100m². 2 / g, pore volume is 0.05~0.5ml / g, pore size is 12~36nm.

16. The manganese oxide according to claim 15, wherein, The specific surface area of ​​the manganese oxide is 30~60m². 2 / g, pore volume is 0.1~0.3ml / g, pore size is 15~30nm.

17. Use of manganese oxides for sulfide removal in gas according to any one of claims 14 to 16.

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