A redox graphene-based composite material, a method for preparing the same and use thereof

Abstract

This disclosure relates to a graphene oxide-based composite material, its preparation method, and its uses. The method includes: S1, mixing graphite, potassium permanganate, and a strong oxidizing acid to obtain a mixture; S2, heating the mixture, and then subjecting the heated material to microwave calcination. The preparation method of this disclosure uses a microwave calcination process to reduce graphene oxide. No water is added during the entire preparation process, thus avoiding wastewater discharge and NO emissions. x To address a range of issues, including emissions, the resulting redox graphene-based composite material exhibits excellent desulfurization performance.

Description

Technical Field

[0001] This disclosure pertains to the field of graphene-based materials, specifically relating to a redox graphene-based composite material, its preparation method, and its applications. Background Technology

[0002] Reduced graphene is an important downstream product of graphite. Currently, the main method for producing reduced graphene is to oxidize graphite with strong oxidants such as potassium permanganate, then exfoliate and reduce it. However, existing methods suffer from problems such as high manganese ion content in wastewater, difficulty in environmental treatment, and significant environmental pressure. Summary of the Invention

[0003] The purpose of this disclosure is to provide a redox graphene-based composite material, its preparation method, and its applications. The method disclosed uses a microwave calcination process to reduce graphene oxide. No water is added during the entire preparation process, thus avoiding wastewater discharge and NO emissions. x A series of issues, including emissions.

[0004] To achieve the above objectives, the first aspect of this disclosure provides a method for preparing a redox graphene-based composite material, the method comprising: S1. Mix graphite, potassium permanganate, and a strong oxidizing acid to obtain a mixture. S2. The mixture is heated, and the resulting heated material is then microwave roasted.

[0005] Optionally, the graphite is natural graphite and / or artificial graphite; the carbon content of the graphite is 95% by weight or more, the ash content is less than 2%, and the mesh size is 20 to 2000 mesh; wherein the strong oxidizing acid includes one or more of concentrated sulfuric acid, concentrated nitric acid, and concentrated perchloric acid, preferably concentrated sulfuric acid; the mass concentration of the concentrated sulfuric acid is 70% or more.

[0006] Optionally, the mass ratio of potassium permanganate to graphite is (1~10):1, preferably (1~8):1; the mass ratio of the strong oxidizing acid to graphite is (20~80):1, preferably (30~60):1.

[0007] Optionally, the method further includes: in step S1, adding graphite and potassium permanganate to a strong oxidizing acid and mixing, and controlling the temperature of the mixture to be below 35°C, preferably below 30°C, for stirring, with a stirring time of 0.5~12h, preferably 1~6h.

[0008] Optionally, in step S2, the heating conditions include: stirring the mixture at a temperature of 40~90℃, preferably 40~70℃, for 0.5~24h, preferably 2~12h.

[0009] Optionally, the microwave roasting conditions include: microwave roasting the heated material using a microwave processing device under an inert atmosphere, wherein the microwave roasting temperature is 300~800℃, preferably 400~600℃; and the time is 2~600s, preferably 10~200s. The absolute pressure of the inert atmosphere is 1~150kPa, and the power of the microwave processing device is 300~1500W, preferably 600~1200W; the inert atmosphere includes one or more of nitrogen, helium, argon and krypton.

[0010] The second aspect of this disclosure provides a redox graphene-based composite material prepared using the method described in the first aspect of this disclosure.

[0011] Optionally, the redox graphene-based composite material includes carbon, manganese, potassium, sulfur, and oxygen. Based on the total mass of the redox graphene-based composite material, the carbon content is 10-25% by weight, the manganese content (calculated as manganese oxide) is 25-50% by weight, the potassium content (calculated as potassium oxide) is 10-25% by weight, and the sulfur content (calculated as sulfur dioxide) is 2-20% by weight. The bulk density of the redox graphene-based composite material is 0.1-0.8 g / ml.

[0012] This third aspect of the disclosure provides the use of the redox graphene-based composite material described in the second aspect of the disclosure for the removal of sulfides from gases.

[0013] Optionally, the use includes: contacting the hydrogen to be purified with the redox graphene-based composite material described in the second aspect of this disclosure to carry out a purification reaction; wherein the mass content of sulfides in the hydrogen to be purified is less than 2000 ppm, and the content of sulfides in the hydrogen to be purified is calculated as hydrogen sulfide. Optionally, the purification reaction conditions include: a temperature of 80~200℃, a pressure of 0.5~3.0MPa, and a space velocity of 10~2000h⁻¹. -1 .

[0014] Through the above technical solution, this disclosure provides a redox graphene-based composite material, its preparation method, and its applications. The method uses a microwave calcination process to directly reduce graphene oxide. No water is added during the entire preparation process, thus avoiding wastewater discharge and NO emissions. x A series of issues such as emissions. The prepared redox graphene-based composite material not only contains carbon, but also contains appropriate amounts of manganese, potassium, sulfur and other elements. Compared with conventional manganese oxides, the redox graphene-based composite material disclosed in this paper is more porous, which is conducive to the diffusion and contact of gas molecules. It exhibits excellent performance when used in adsorption desulfurization and other reaction processes, and has a good adsorption desulfurization effect.

[0015] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Detailed Implementation

[0016] The specific embodiments of this disclosure are described in detail below with reference to examples. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0017] The first aspect of this disclosure provides a method for preparing a redox graphene-based composite material, the method comprising: S1. Mix graphite, potassium permanganate, and a strong oxidizing acid to obtain a mixture. S2. The mixture is heated, and the resulting heated material is then microwave roasted.

[0018] The method disclosed herein uses a microwave calcination process to directly reduce graphene oxide. No water is added during the entire preparation process, thus avoiding wastewater discharge and NO emissions. x A series of issues, including emissions.

[0019] In one specific embodiment of this disclosure, the graphite is natural graphite and / or artificial graphite; the carbon content of the graphite is 95% by weight or more, the ash content is less than 2%, and the mesh size is 20 to 2000 mesh; wherein, the strong oxidizing acid includes one or more of concentrated sulfuric acid, concentrated nitric acid, and concentrated perchloric acid, preferably concentrated sulfuric acid; the mass concentration of the concentrated sulfuric acid is 70% or more.

[0020] In one specific embodiment of this disclosure, the mass ratio of potassium permanganate to graphite is (1~10):1, preferably (1~8):1; the mass ratio of the strong oxidizing acid to graphite is (20~80):1, preferably (30~60):1.

[0021] In one specific embodiment of this disclosure, the method further includes: in step S1, graphite and potassium permanganate are added to a strong oxidizing acid and mixed, and the temperature of the mixture is controlled to be below 35°C, preferably below 30°C, more preferably 5~20°C, and the mixture is stirred for 0.5~12h, preferably 1~6h.

[0022] In one specific embodiment of this disclosure, step S2 includes heating the mixture at a temperature of 40-90°C, preferably 40-70°C, for 0.5-24 hours, preferably 2-12 hours. In the above embodiment, the preferred heating conditions facilitate further oxidation of graphite, which in turn facilitates further exfoliation and reduction of the oxidized graphite during subsequent microwave calcination, resulting in a more porous graphene-based composite material with a more suitable elemental content. This, in turn, is more conducive to the diffusion and contact of gas molecules.

[0023] In one specific embodiment of this disclosure, the microwave calcination conditions include: microwave calcining the heated material using a microwave processing device under an inert atmosphere; the microwave calcination temperature is 300~800℃, preferably 400~600℃; the time is 2~600s, preferably 10~200s; the absolute pressure of the inert atmosphere is 1~150kPa, preferably 5~100kPa; the power of the microwave processing device is 300~1500W, preferably 600~1200W; the inert atmosphere includes one or more of nitrogen, helium, argon, and krypton. In the above embodiment, selecting the preferred microwave calcination conditions is beneficial for further reducing the graphene oxide in the heated material, and the explosive heating effect of microwaves facilitates the stripping of the graphene oxide component from the material, resulting in a more porous shape of the obtained reduced-oxidation graphene-based composite material, which is more conducive to the diffusion and contact of gas molecules.

[0024] The second aspect of this disclosure provides a redox graphene-based composite material prepared using the method described in the first aspect of this disclosure.

[0025] In one specific embodiment of this disclosure, the redox graphene-based composite material comprises carbon, manganese, potassium, sulfur, and oxygen. Based on the total mass of the redox graphene-based composite material, the carbon content is 10-25% by weight, preferably 12-20% by weight; the manganese content (calculated as manganese oxide) is 25-50% by weight, preferably 30-45% by weight; the potassium content (calculated as potassium oxide) is 10-25% by weight, preferably 12-20% by weight; the sulfur content (calculated as sulfur dioxide) is 2-20% by weight, preferably 5-15% by weight; and the balance is oxygen. The bulk density of the redox graphene-based composite material is 0.1-0.8 g / ml, preferably 0.2-0.5 g / ml.

[0026] The redox graphene-based composite material prepared in this disclosure is a composition of redox graphene, manganese oxide, and manganese salt, etc. The redox graphene refers to the material obtained by oxidizing graphite with potassium permanganate in a strongly oxidizing acid system, followed by microwave calcination, exfoliation, and reduction under an inert atmosphere. This redox graphene-based composite material not only contains carbon but also appropriate amounts of manganese, potassium, sulfur, and other elements. Furthermore, it is more porous than conventional manganese oxides, which facilitates the diffusion and contact of gas molecules, allowing it to react with sulfides. When used in adsorption and desulfurization processes, it exhibits excellent performance and good adsorption and desulfurization effects.

[0027] This third aspect of the disclosure provides the use of the redox graphene-based composite material described in the second aspect of the disclosure for the removal of sulfides from gases.

[0028] In one specific embodiment of this disclosure, the use includes: contacting the hydrogen to be purified with the redox graphene-based composite material described in the second aspect of this disclosure to carry out a purification reaction; wherein the mass content of sulfides in the hydrogen to be purified is below 2000 ppm, and the sulfide content in the hydrogen to be purified is calculated as hydrogen sulfide; optionally, the conditions for the purification reaction include: a temperature of 80~200℃, preferably 100~160℃; a pressure of 0.5~3.0 MPa, preferably 1~2.5 MPa; and a space velocity of 10~2000 h⁻¹. -1 Preferably 50~1000h -1 .

[0029] The redox graphene-based composite material disclosed herein can effectively remove sulfides from the hydrogen to be purified during the hydrogen purification reaction process, and the sulfide content in the purified hydrogen can meet the standard requirements for sulfide content in hydrogen used in fuel cells.

[0030] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited thereto.

[0031] All reagents used in this disclosure are commercially available analytical grade reagents.

[0032] Example 1 S1. In a three-necked flask containing 150 ml of concentrated sulfuric acid (98% by mass), flake graphite and potassium permanganate are added simultaneously, and the mixture is stirred at 10°C for 1 h to obtain a mixture; wherein the mass ratio of potassium permanganate to graphite is 3.6:1, and the mass ratio of concentrated sulfuric acid to graphite is 30:1. S2. The mixture obtained in step S1 is heated and stirred at 60°C for 3 hours. Then, the heated material is sent to a microwave processing device and microwave calcined in a nitrogen atmosphere with a power of 1200W and an absolute pressure of 30kPa. The microwave calcination temperature is 600°C and the time is 50s to obtain the redox graphene-based composite material.

[0033] Example 2 The preparation method in Example 1 was used, except that in step S2, the reaction was carried out at 75°C for 0.5 h.

[0034] Example 3 The preparation method in Example 1 was used, except that in step S2, the microwave calcination temperature was 350°C and the time was 6 seconds.

[0035] Comparative Example 1 The preparation method in Example 1 is used, except that microwave roasting is not used in step S2. Instead, the heated material is sent into a muffle furnace and roasted in a nitrogen atmosphere.

[0036] Comparative Example 2 The preparation method in Example 1 is used, except that the mixture obtained in step S1 is not heated, but directly microwave roasted.

[0037] Test case The materials prepared in the examples and comparative examples were tested as follows: The elemental composition of the samples was determined by XPS on a VGESCA-LABS X-ray photoelectron spectrometer, with Mg as the prime mover. Kα Using X-rays as a laser source, the binding energy of each element in the species on the surface of the desulfurizer is calibrated by the C1s binding energy (284.6 eV) of the carbon contaminants on the surface.

[0038] The bulk density was determined using the RIPP31-90 method (edited by Yang Cuiding et al., Petrochemical Analysis Methods, Science Press, 1990).

[0039] The sulfide content in hydrogen gas after adsorption by the adsorbent was analyzed by online chromatography (Shimadzu Nexis-2030, Japan) and SCD fluorescence detector (SCD-2030).

[0040] 500 mg of the material prepared in this embodiment and the comparative example were used as adsorbents and loaded into the isothermal section of the reactor of a passivated fixed-bed microreactor with an inner diameter of 10 mm and a length of 600 mm. Quartz sand was filled both above and below the reactor. Hydrogen gas with a hydrogen sulfide content of 1000 ppm was used as the feedstock standard gas, and the reaction was carried out at 120 °C, 2.2 MPa, and a space velocity of 200 h⁻¹. -1The hydrogen gas was purged to carry out a sulfide removal reaction, and the hydrogen sulfide content in the hydrogen gas after the reaction was analyzed online to calculate the sulfide removal rate. The test results of the sulfide removal rate after 2 hours are shown in Table 1, and other characterization results of the prepared product are shown in Table 2.

[0041] Table 1

[0042] Table 2

[0043] As can be seen from the test results in Tables 1 and 2, compared with Comparative Examples 1-2, the redox graphene-based composite materials prepared by Examples 1-3 using the method provided in this disclosure have a smaller bulk density and more suitable elemental content, effectively removing sulfides from the materials. When used in the hydrogen purification reaction process containing sulfides, they exhibit excellent sulfide removal performance, achieving a sulfide removal rate of over 90%. Furthermore, no water is added during the entire preparation process, avoiding wastewater discharge and NO emissions. x Addressing a range of issues, including emissions, and reducing production costs.

[0044] Comparative Example 1 did not use microwave calcination, resulting in a less fluffy composite material with a larger bulk density, which reduced the removal rate of sulfides from hydrogen. Comparative Example 2 did not heat the mixture, resulting in the graphite in the composite material not being oxidized. During the microwave stage, the graphite sheets could not be peeled into graphene structures, and the sulfide removal rate was significantly lower than that of Example 1.

[0045] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0046] 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, this disclosure will not describe the various possible combinations separately.

[0047] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for preparing redox graphene-based composite materials, characterized in that, The method includes: S1. Mix graphite, potassium permanganate, and a strong oxidizing acid to obtain a mixture. S2. The mixture is heated, and the resulting heated material is then microwave roasted.

2. The method according to claim 1, wherein, The graphite is natural graphite and / or artificial graphite; the carbon content of the graphite is more than 95% by weight, the ash content is less than 2%, and the mesh size is 20 to 2000 mesh. The strong oxidizing acid includes one or more of concentrated sulfuric acid, concentrated nitric acid, and concentrated perchloric acid, preferably concentrated sulfuric acid; the mass concentration of the concentrated sulfuric acid is 70% or more.

3. The method according to claim 1, wherein, The mass ratio of potassium permanganate to graphite is (1~10):1, preferably (1~8):1; the mass ratio of strong oxidizing acid to graphite is (20~80):1, preferably (30~60):

1.

4. The method according to claim 1, wherein, The method further includes: in step S1, graphite and potassium permanganate are added to a strong oxidizing acid and mixed, and the temperature of the mixture is controlled to be below 35°C, preferably below 30°C, for stirring, and the stirring time is 0.5~12h, preferably 1~6h.

5. The method according to claim 1, wherein, In step S2, the heating conditions include: stirring the mixture at a temperature of 40~90℃, preferably 40~70℃, for 0.5~24h, preferably 2~12h.

6. The method according to claim 1, wherein, The conditions for microwave roasting include: microwave roasting the heated material in an inert atmosphere using a microwave processing device, wherein the microwave roasting temperature is 300~800℃, preferably 400~600℃; and the time is 2~600s, preferably 10~200s. The absolute pressure of the inert atmosphere is 1~150kPa, and the power of the microwave processing device is 300~1500W, preferably 600~1200W; the inert atmosphere includes one or more of nitrogen, helium, argon and krypton.

7. The redox graphene-based composite material prepared by the method according to any one of claims 1 to 6.

8. The redox graphene-based composite material according to claim 7, characterized in that, The redox graphene-based composite material comprises carbon, manganese, potassium, sulfur, and oxygen. Based on the total mass of the redox graphene-based composite material, the carbon content is 10-25% by weight, the manganese content (calculated as manganese oxide) is 25-50% by weight, the potassium content (calculated as potassium oxide) is 10-25% by weight, and the sulfur content (calculated as sulfur dioxide) is 2-20% by weight. The bulk density of the redox graphene-based composite material is 0.1~0.8 g / ml.

9. Use of the redox graphene-based composite material according to claim 7 or 8 in the removal of sulfides from gases.

10. The use according to claim 9, characterized in that, The application includes: contacting the hydrogen to be purified with the redox graphene-based composite material according to any one of claims 7 to 8 to carry out a purification reaction; wherein the mass content of sulfides in the hydrogen to be purified is less than 2000 ppm, and the content of sulfides in the hydrogen to be purified is calculated as hydrogen sulfide; Optionally, the purification reaction conditions include: a temperature of 80~200℃, a pressure of 0.5~3.0MPa, and a space velocity of 10~2000h⁻¹. -1 .

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