A carbon material, its preparation method and application

Abstract

This invention provides a carbon material, its preparation method, and its applications. The preparation method includes: mixing citric acid, magnesium salt, and an organic solvent, then adding ammonia water, followed by sequential water bath heating and carbonization to obtain the carbon material. The preparation method of the carbon material of this invention is simple and inexpensive. The prepared carbon material exhibits excellent hydrogen sulfide adsorption performance and can be widely used in the efficient purification of hydrogen sulfide from various gas sources.

Description

Technical Field

[0001] This invention belongs to the field of catalytic environmental technology, and relates to a carbon material, its preparation method, and its application. Background Technology

[0002] Hydrogen sulfide is a toxic gas with a strong, foul odor and is widely present in both indoor and outdoor environments. The emission and pollution of hydrogen sulfide seriously impacts the quality of life and the ecological environment, posing a threat to human health. Therefore, removing hydrogen sulfide has become an important task.

[0003] Currently, room temperature oxidation based on carbon materials is a widely studied method for removing hydrogen sulfide. The principle of this method is that under certain humidity conditions, a water film forms on the surface of the carbon material, which absorbs and dissociates hydrogen sulfide to form HS-. Subsequently, these HS- are oxidized to elemental sulfur by reactive oxygen species. This method is characterized by high efficiency and low cost, and has a wide range of applications.

[0004] To further improve the removal of hydrogen sulfide from carbon materials, researchers have introduced alkaline earth metal oxides and nitrogen-containing functional groups. These substances can significantly increase the alkalinity of the carbon material surface, thereby promoting the adsorption and dissociation of hydrogen sulfide. In general, researchers are continuously exploring and researching new methods and technologies to more effectively remove hydrogen sulfide, improve the quality of life for residents, and protect the ecological environment.

[0005] CN111992237A discloses a nitrogen-rich carbon material catalyst, its preparation method, and its application in the selective oxidation of hydrogen sulfide. The functionalized nitrogen-rich carbon material catalyst is obtained by heat-treating polyaniline in air. This catalyst effectively oxidizes hydrogen sulfide gas to elemental sulfur, exhibiting high conversion efficiency and selectivity. The prepared catalyst can effectively oxidize hydrogen sulfide gas to elemental sulfur.

[0006] CN110694659A discloses a layered porous nitrogen-doped carbon material, its preparation method, and its application. It discloses the preparation of layered nitrogen-doped carbon materials using pyromellitic dianhydride and ethylenediamine as raw materials via a mild solvothermal method, and their application in the selective catalytic oxidation of hydrogen sulfide.

[0007] However, the above-mentioned disclosures all focus on improving the conversion efficiency of hydrogen sulfide above 90°C. How to prepare a carbon material that can be applied to the purification of hydrogen sulfide at room temperature simply and at low cost is an important research direction in this field. Summary of the Invention

[0008] The purpose of this invention is to provide a simple and low-cost method for preparing a carbon material applicable to the purification of hydrogen sulfide at room temperature, as well as its preparation method and application.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] One objective of this invention is to provide a method for preparing carbon materials, the method comprising:

[0011] Citric acid, magnesium salt, and organic solvent are mixed and then ammonia is added. The mixture is then subjected to water bath heating and carbonization in sequence to obtain the carbon material.

[0012] This invention involves adding ammonia to a mixed solution of citric acid and magnesium salts to alter the state of the gel formed by the citric acid complexation method. The resulting carbon material has a more regular pore structure, and the ammonia contains nitrogen-containing functional groups. By introducing ammonia, nitrogen-containing functional groups are introduced, thereby improving the room-temperature hydrogen sulfide oxidation performance of the carbon material.

[0013] The carbon material preparation method of this invention is simple and inexpensive. The prepared carbon material has excellent hydrogen sulfide adsorption performance and can be widely used in the field of efficient purification of hydrogen sulfide in various gas sources.

[0014] As a preferred embodiment of the present invention, the magnesium salt includes any one or a combination of at least two of magnesium nitrate, magnesium chloride, or magnesium acetate.

[0015] Preferably, the organic solvent includes an alcohol.

[0016] Preferably, the alcohol liquid includes any one or a combination of at least two of ethanol, ethylene glycol, or polyethylene glycol, wherein typical but non-limiting examples of the combination include combinations of ethanol and ethylene glycol, combinations of ethylene glycol and polyethylene glycol, or combinations of ethanol and polyethylene glycol, etc.

[0017] As a preferred technical solution of the present invention, the molar ratio of citric acid and magnesium salt is 1:3 to 3:1, wherein the molar ratio can be 1:3, 1:2, 1:1, 2:1 or 3:1, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0018] Preferably, the ratio of citric acid to organic solvent is 1g:(20-50)ml, wherein the ratio can be 1g:20ml, 1g:25ml, 1g:30ml, 1g:35ml, 1g:40ml, 1g:45ml or 1g:50ml, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0019] As a preferred technical solution of the present invention, the molar ratio of the magnesium salt and ammonia is 1:(1-5), wherein the molar ratio can be 1:1, 1:2, 1:3, 1:4 or 1:5, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] In this invention, adding too much or too little ammonia water will affect the formation of magnesium complex in the raw material solution.

[0021] As a preferred technical solution of the present invention, the water bath heating temperature is 50-90℃, wherein the temperature can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃ or 90℃, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0022] If the water bath heating temperature is too high or too low, the solvent will evaporate too quickly or too slowly, thus affecting the gel formation state.

[0023] Preferably, the water bath heating time is 8 to 12 hours, wherein the time can be 8 hours, 8.5 hours, 9 hours, 9.5 hours, 10 hours, 10.5 hours, 11 hours, 11.5 hours or 12 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] As a preferred technical solution of the present invention, the carbonization is carried out after the water bath heating and drying.

[0025] Preferably, the drying temperature is 80-120°C, wherein the temperature can be 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0026] Preferably, the drying time is 8 to 12 hours, wherein the time can be 8 hours, 8.5 hours, 9 hours, 9.5 hours, 10 hours, 10.5 hours, 11 hours, 11.5 hours or 12 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] As a preferred technical solution of the present invention, the carbonization temperature is 600-900℃, wherein the temperature can be 600℃, 650℃, 700℃, 750℃, 800℃, 850℃ or 900℃, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0028] If the carbonization temperature is too high, the structure of the carbon material formed will be destroyed; if the carbonization temperature is too low, the precursor cannot be fully decomposed and a well-developed porous structure cannot be formed.

[0029] Preferably, the carbonization time is 1 to 3 hours, wherein the time can be 1 hour, 2 hours or 3 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0030] Preferably, the heating rate of the carbonization is 1 to 5 °C / min, wherein the heating rate can be 1 °C / min, 2 °C / min, 3 °C / min, 4 °C / min or 5 °C / min, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0031] Preferably, the carbonization atmosphere is a nitrogen atmosphere.

[0032] Preferably, the gas flow rate for carbonization is 50–200 mL / min, wherein the gas flow rate can be 50 mL / min, 80 mL / min, 100 mL / min, 120 mL / min, 140 mL / min, 160 mL / min, 180 mL / min or 200 mL / min, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0033] As a preferred technical solution of the present invention, the preparation method includes:

[0034] Citric acid, magnesium salt, and organic solvent are mixed and then ammonia is added. The mixture is then subjected to sequential water bath heating at 50–90°C for 8–12 hours and carbonization at 600–900°C for 1–3 hours with a heating rate of 1–5°C / min to obtain the carbon material.

[0035] A second objective of this invention is to provide a carbon material prepared by the preparation method described in one objective.

[0036] A third objective of this invention is to provide an application of the carbon material as described in objective two, wherein the carbon material is applied in the field of hydrogen sulfide gas purification.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) The carbon material prepared by this invention exhibits excellent adsorption performance for hydrogen sulfide at room temperature, with an adsorption breakthrough time of up to 54 hours and an H2S adsorption capacity as high as 2.41 g / g. cat. ;

[0039] (2) The method for preparing carbon materials in this invention is simple, low-cost, and can be used for large-scale production. Attached Figure Description

[0040] Figure 1 These are the hydrogen sulfide adsorption curves and adsorption capacity diagrams of the carbon material prepared in Example 1 of this invention. Detailed Implementation

[0041] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0042] Example 1

[0043] This embodiment provides a method for preparing a carbon material, the method comprising the following steps:

[0044] (1) After mixing citric acid, magnesium nitrate and ethanol, ammonia water is added to obtain the precursor. The molar ratio of citric acid to magnesium nitrate is 1:1, the ratio of citric acid to ethanol is 1g:35ml, and the molar ratio of magnesium nitrate to ammonia water is 1:3.

[0045] (2) The precursor described in step (1) is subjected to water bath heating, drying and carbonization in sequence to obtain the carbon material. The parameters for water bath heating are: water bath heating temperature is 80℃ and time is 10h; the parameters for drying are: drying temperature is 100℃ and time is 10h; the parameters for carbonization are: carbonization temperature is 800℃, time is 2h, heating rate is 2℃ / min, atmosphere is nitrogen atmosphere, and nitrogen gas flow rate is 150mL / min.

[0046] Example 2

[0047] This embodiment provides a method for preparing a carbon material, the method comprising the following steps:

[0048] (1) After mixing citric acid, magnesium chloride and ethylene glycol, ammonia water is added to obtain the precursor. The molar ratio of citric acid to magnesium chloride is 1:3, the ratio of citric acid to ethylene glycol is 1g:20ml, and the molar ratio of magnesium chloride to ammonia water is 1:1.

[0049] (2) The precursor described in step (1) is subjected to water bath heating, drying and carbonization in sequence to obtain the carbon material. The parameters for water bath heating are: water bath heating temperature is 50℃ and time is 12h; the parameters for drying are: drying temperature is 80℃ and time is 12h; the parameters for carbonization are: carbonization temperature is 600℃, time is 3h, heating rate is 1℃ / min, atmosphere is nitrogen atmosphere, and nitrogen gas flow rate is 50mL / min.

[0050] Example 3

[0051] This embodiment provides a method for preparing a carbon material, the method comprising the following steps:

[0052] (1) After mixing citric acid, magnesium acetate and polyethylene glycol, ammonia water is added to obtain the precursor. The molar ratio of citric acid to magnesium acetate is 3:1, the addition ratio of citric acid to polyethylene glycol is 1g:50ml, and the molar ratio of magnesium acetate to ammonia water is 1:5.

[0053] (2) The precursor described in step (1) is subjected to water bath heating, drying and carbonization in sequence to obtain the carbon material. The parameters for water bath heating are: water bath heating temperature is 90℃ and time is 8h; the parameters for drying are: drying temperature is 120℃ and time is 8h; the parameters for carbonization are: carbonization temperature is 900℃, time is 1h, heating rate is 5℃ / min, atmosphere is nitrogen atmosphere, and nitrogen gas flow rate is 200mL / min.

[0054] Example 4

[0055] In this embodiment, the only difference is that the molar ratio of magnesium nitrate and ammonia in step (1) is replaced with 1:8. All other conditions are the same as in Example 1.

[0056] Example 5

[0057] In this embodiment, the only difference is that the molar ratio of magnesium nitrate and ammonia in step (1) is replaced with 2:1. All other conditions are the same as in Example 1.

[0058] Example 6

[0059] In this embodiment, the only difference is that the water bath heating temperature in step (2) is replaced with 40°C, and all other conditions are the same as in embodiment 1.

[0060] Example 7

[0061] In this embodiment, the only difference is that the water bath heating temperature in step (2) is replaced with 100°C. All other conditions are the same as in embodiment 1.

[0062] Example 8

[0063] In this embodiment, the carbonization temperature in step (2) is replaced with 500°C, but all other conditions are the same as in Example 1.

[0064] Example 9

[0065] In this embodiment, the carbonization temperature in step (2) is replaced with 1000℃, and all other conditions are the same as in Example 1.

[0066] Comparative Example 1

[0067] Except for step (1) where ammonia was not added, all other conditions in this comparative example were the same as in Example 1.

[0068] Comparative Example 2

[0069] Except for step (2), which does not involve water bath heating, the conditions in this comparative example are the same as those in Example 1.

[0070] The adsorption performance of hydrogen sulfide on the carbon materials prepared in Examples 1-9 and Comparative Examples 1-2 at room temperature was tested. The test results are shown in Table 1. The adsorption curve and adsorption capacity of the carbon material prepared in Example 1 for hydrogen sulfide at room temperature are shown in the figure. Figure 1 As shown.

[0071] The testing method for hydrogen sulfide adsorption performance included: activity evaluation was conducted in a plug flow reactor (6 mm in diameter), with the reaction gas passing through a carbon material in a single pass (100 mg of carbon material). The initial atmosphere composition was (500 ppm hydrogen sulfide, 70% relative humidity, 20% oxygen, nitrogen balance, gas flow rate of 100 mL / min), the test temperature was 25 °C, and the test pressure was one atmosphere. Breakthrough was considered to have occurred when the hydrogen sulfide concentration in the outlet gas reached 50 ppm. The hydrogen sulfide adsorption capacity was calculated by integrating the adsorption curve based on the breakthrough time.

[0072] Table 1

[0073] Example 1 2.41 Example 2 1.97 Example 3 2.12 Example 4 0.88 Example 5 0.21 Example 6 1.02 Example 7 0.98 Example 8 0.31 Example 9 0.52 Comparative Example 1 0.10 Comparative Example 2 0.18

[0074] As can be seen from the table above: Examples 1-3 show that the carbon material prepared by the present invention has excellent hydrogen sulfide adsorption performance;

[0075] Examples 4-5: An excessively high or low molar ratio of magnesium nitrate to ammonia will affect the formation of magnesium complexes in the raw material solution, thereby affecting the hydrogen sulfide adsorption capacity of its carbonization products.

[0076] In Examples 6-7, excessively high or low water bath heating temperatures can cause solvent evaporation to occur too quickly or too slowly, thus affecting the gel formation state and consequently the structure of the carbonized products and their hydrogen sulfide adsorption capacity.

[0077] In Examples 8-9, excessively high carbonization temperatures will damage the structure of the formed carbon material, while excessively low carbonization temperatures will prevent the precursor from being fully decomposed and thus prevent the formation of a well-developed porous structure. Both excessively high and excessively low carbonization temperatures are detrimental to hydrogen sulfide adsorption.

[0078] In Comparative Example 1, without the addition of ammonia, a stable citric acid complex gel could not be formed, which affected the physicochemical properties of the carbonization products and was not conducive to the adsorption of hydrogen sulfide.

[0079] Comparative Example 2 also failed to obtain a stable gel without water bath heating, thus affecting the hydrogen sulfide adsorption capacity.

[0080] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a carbon material, characterized in that, The preparation method includes: Citric acid, magnesium salt, and organic solvent are mixed and then ammonia is added. The mixture is then subjected to water bath heating at 50-90°C for 8-12 hours and carbonization at 600-900°C for 1-3 hours with a heating rate of 1-5°C / min to obtain the carbon material. The molar ratio of magnesium salt to ammonia is 1:(1-5). The carbon material is used in the field of hydrogen sulfide gas purification.

2. The preparation method according to claim 1, characterized in that, The magnesium salt includes any one or a combination of at least two of magnesium nitrate, magnesium chloride, or magnesium acetate.

3. The preparation method according to claim 1, characterized in that, The organic solvent includes alcohols.

4. The preparation method according to claim 3, characterized in that, The alcoholic liquid includes any one or a combination of at least two of ethanol, ethylene glycol, or polyethylene glycol.

5. The preparation method according to claim 1, characterized in that, The molar ratio of citric acid to magnesium salt is 1:3 to 3:

1.

6. The preparation method according to claim 1, characterized in that, The ratio of citric acid to organic solvent is 1g:(20~50)ml.

7. The preparation method according to claim 1, characterized in that, After being heated in a water bath, the product is dried before carbonization.

8. The preparation method according to claim 7, characterized in that, The drying temperature is 80~120℃.

9. The preparation method according to claim 7, characterized in that, The drying time is 8-12 hours.

10. The preparation method according to claim 1, characterized in that, The carbonization atmosphere is a nitrogen atmosphere.

11. The preparation method according to claim 1, characterized in that, The carbonization gas flow rate is 50~200mL / min.

12. A carbon material, characterized in that, The carbon material is prepared by the preparation method according to any one of claims 1-11; the carbon material is applied in the field of hydrogen sulfide gas purification.

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