A low-sulfur activated carbon and its preparation method

Abstract

This invention provides a low-sulfur activated carbon and its preparation method. The low-sulfur activated carbon meets the following conditions: sulfur content ≤230ppm, mesopore ratio 50-70%, and specific surface area 500-800m². 2 / g, total pore volume is 0.4–0.6 cm³. 3 / g, with a mesopore volume of 0.2–0.4 cm³. 3 / g. This invention uses activated carbon with high sulfur content as raw material and employs a synergistic catalytic and activation method using hydrogen and water vapor to synergistically reduce the residual sulfur content in activated carbon or improve the removal rate of sulfur impurities in activated carbon. At the same time, it reduces the amount of hydrogen used compared to existing technologies, resulting in lower production costs.

Description

Technical Field

[0001] This invention belongs to the field of activated carbon preparation, specifically relating to a low-sulfur activated carbon and its preparation method. Background Technology

[0002] Activated carbon is a common carbon material widely used in adsorption, separation, energy storage, and catalysis, especially as a support for noble metal catalysts in various catalytic reactions. Commercially available activated carbon, due to its diverse origins, has a relatively small specific surface area and is predominantly microporous (pore size <2nm), containing only a small amount of mesoporous structure, which cannot meet the requirements of different catalytic reactions. Precisely controlling the pore structure of activated carbon is a key technical issue in expanding the applications of carbon materials. CN115520863A discloses a method for preparing coal-based activated carbon, mainly by mixing coal powder, metal salt, and solvent, followed by hydrothermal or solvothermal reaction, and activation to obtain activated carbon with a specific surface area of ​​800-1300 m². 2 / g, mesopore volume 0.1-0.55cm³ 3 / g of coal-based activated carbon. Although this method improves the specific surface area and mesoporosity of the sample, it introduces transition metal salts such as iron, cobalt, or nickel salts into the system, which not only increases the cost of raw materials but also complicates subsequent processing procedures.

[0003] Furthermore, most activated carbon carbonization materials contain sulfur impurities, which, without special treatment, make them difficult to use as supports for supported precious metal catalysts. The presence of sulfur impurities can lead to poisoning and deactivation of precious metal catalysts (An investigation on Pd / C industrial catalysts for the purification of terephthalic acid. Catalysis Today, 44(1998), 129-135.). Taking wood-based activated carbon as an example, it can be selected from high-quality sawdust, wood blocks, coconut shells, fruit shells, etc. Due to the different sources and origins of the raw materials, the content of sulfur impurities is greatly affected by the activation process during the subsequent carbonization and activation of activated carbon. Patent CN102190297B discloses a method for preparing low-sulfur activated carbon, which mainly uses hydrogen as a desulfurizing agent and plant or mineral activated carbon as raw material. The activated carbon is desulfurized for 1-20 hours at a temperature of 700-1000℃, atmospheric pressure, and a molar ratio of hydrogen to activated carbon of 1:50-250. The sulfur content in the activated carbon can be as low as ≤50ppm. This technology uses a large amount of hydrogen, resulting in a waste of resources, and the high temperature required for sulfur removal leads to low desulfurization accuracy. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a low-sulfur activated carbon and its preparation method, which overcomes the problems of high sulfur content and small mesopore volume in activated carbon. At the same time, the preparation method is simple and low in cost.

[0005] In a first aspect, the present invention provides a low-sulfur activated carbon, wherein the low-sulfur activated carbon satisfies the following conditions:

[0006] Sulfur content ≤230ppm, mesoporous ratio 50-70%, specific surface area 500-800m² 2 / g, total pore volume is 0.4–0.6 cm³. 3 / g, with a mesopore volume of 0.2–0.4 cm³. 3 / g.

[0007] In a second aspect, the present invention provides a method for preparing low-sulfur activated carbon, comprising the following steps:

[0008] S1. The activated carbon raw material is pretreated under a hydrogen atmosphere to obtain the pretreated activated carbon raw material.

[0009] S2. The pretreated activated carbon raw material is treated in a mixed atmosphere of hydrogen and water vapor.

[0010] In some embodiments, the sulfur content of the activated carbon raw material is greater than 100 ppm, for example, 100-500 ppm, preferably greater than 300 ppm, for example, preferably 300-500 ppm. For example, the sulfur content of the activated carbon raw material can be 110 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 330 ppm, 360 ppm, 380 ppm, 410 ppm, 440 ppm, 470 ppm, or 500 ppm. This invention is applicable to the desulfurization of activated carbon raw materials with high sulfur content.

[0011] In some embodiments, the activated carbon raw material is wood or fruit shell carbonized material; preferably, the activated carbon raw material is fruit shell carbonized material. This invention does not impose any particular limitation on the activated carbon required for desulfurization; currently, both wood and fruit shell activated carbon materials are suitable and can achieve good technical results.

[0012] In some embodiments, the activated carbon raw material is coconut shell-based activated carbon.

[0013] In some embodiments, the pretreatment temperature is 350 to 550°C, for example, 350°C, 380°C, 410°C, 450°C, 470°C, 500°C, 530°C, or 550°C.

[0014] In some implementations, the pretreatment time is 0.5 to 3 hours, for example, 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours.

[0015] In some embodiments, the pretreatment temperature is 400–500°C, for example 400°C, 420°C, 440°C, 460°C, 480°C, or 500°C.

[0016] In some implementations, the pretreatment time is 1 to 2 hours, for example, 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, or 2 hours.

[0017] In some embodiments, the processing temperature in step S2 is 700 to 900°C, for example, 700°C, 730°C, 780°C, 820°C, 850°C, 880°C or 900°C.

[0018] In some implementations, the processing time is 0.5 to 6 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours.

[0019] In some embodiments, the processing temperature in step S2 is 750 to 850°C, for example, 750°C, 780°C, 800°C, 820°C or 850°C.

[0020] In some implementations, the processing time is 1 to 3 hours.

[0021] In some embodiments, the sulfur content in the low-sulfur activated carbon is ≤230ppm, preferably 50 to 230ppm, for example 50ppm, 80ppm, 130ppm, 150ppm, 180ppm, 200ppm or 230ppm.

[0022] In some embodiments, the specific surface area of ​​the low-sulfur activated carbon is 500–800 m². 2 / g, for example 500m 2 / g、530m 2 / g、550m 2 / g、570m 2 / g、590m 2 / g、610m 2 / g、640m 2 / g、680m 2 / g、720m 2 / g、760m 2 / g or 800m 2 / g.

[0023] In some embodiments, the total pore volume of the low-sulfur activated carbon is 0.4–0.6 cm³. 3 / g, for example 0.415cm 3 / g, 0.455cm 3 / g, 0.489cm 3 / g, 0.518cm 3 / g, 0.559cm 3 / g or 0.592cm 3 / g.

[0024] In some embodiments, the mesopore volume of the low-sulfur activated carbon is 0.2–0.4 cm³. 3 / g, for example 0.211cm 3 / g, 0.256cm 3 / g, 0.351cm 3 / g or 0.389cm 3 / g.

[0025] In some embodiments, the mesopore content of the low-sulfur activated carbon is 50-70%, for example 51%, 53%, 57%, 61%, 64% or 68%.

[0026] In some embodiments, the volume hourly space velocity (VHSV) of hydrogen is 10–30 h⁻¹ during the pretreatment process. -1 For example, 10h -1 15h -1 20h -1 25h -1 or 30h -1 .

[0027] In some embodiments, the volume hourly space velocity of the water vapor is 5–20 h⁻¹. -1 For example, 5h -1 8h -1 13h -1 16h -1 or 20h -1 .

[0028] This invention uses high-sulfur activated carbon as raw material and employs a synergistic catalytic and activation method using hydrogen and water vapor to synergistically reduce the residual sulfur content in the activated carbon or improve the removal rate of sulfur impurities. Simultaneously, it reduces the amount of hydrogen used compared to existing technologies, resulting in lower production costs. Specifically, pretreatment is first performed in a hydrogen environment at a suitable temperature, followed by the introduction of water vapor to achieve sulfur removal at a lower temperature, effectively increasing the sample's surface area, total pore volume, and mesoporosity. Compared to existing technologies, the activated carbon treatment process described in this invention is simple, requiring only reducing gas hydrogen and green solvent water, without the need for other chemical reagents, resulting in low production costs and facilitating large-scale processing of activated carbon. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention in any way. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and techniques have also been described in many publications.

[0030] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0031] The present invention will be described in detail below through embodiments.

[0032] The specific surface area and pore structure of activated carbon were measured by nitrogen physical adsorption.

[0033] The sulfur content of activated carbon was determined by ICP-AES.

[0034] In this invention, the radius of the pore structure in the activated carbon is 2–50 nm.

[0035] Example 1

[0036] Weigh 30 grams of coconut shell-based activated carbon and place it in a tube furnace for pretreatment under a hydrogen atmosphere. The pretreatment conditions are a hydrogen atmosphere and a volume hourly space velocity (VHSV) of 20 h⁻¹. -1 The temperature was kept constant at 450℃ for 1 hour; then, steam treatment was performed simultaneously under the condition that the volume hourly space velocity was 10 h⁻¹. -1 The activated carbon was heated to 700℃ for 2 hours and then naturally cooled to room temperature to obtain low-sulfur activated carbon. The structural parameters of the obtained low-sulfur activated carbon are shown in Table 1.

[0037] Example 2

[0038] Weigh 30 grams of coconut shell-based activated carbon and place it in a tube furnace for pretreatment under a hydrogen atmosphere. The pretreatment conditions are a hydrogen volume hourly space velocity (HHSV) of 20 h⁻¹. -1 The temperature was kept constant at 450℃ for 1 hour; then, steam treatment was carried out simultaneously at a flow rate of 10 h⁻¹. -1 The activated carbon was heated to 750℃ for 2 hours and then naturally cooled to room temperature to obtain low-sulfur activated carbon. The structural parameters of the obtained low-sulfur activated carbon are shown in Table 1.

[0039] Example 3

[0040] Weigh 30 grams of coconut shell-based activated carbon and place it in a tube furnace for pretreatment under a hydrogen atmosphere. The pretreatment conditions are a hydrogen volume hourly space velocity (HHSV) of 20 h⁻¹. -1 The temperature was kept constant at 450℃ for 1 hour; then, steam treatment was performed simultaneously under the condition that the volume hourly space velocity was 10 h⁻¹. -1 The activated carbon was heated to 800℃ for 2 hours and then naturally cooled to room temperature to obtain low-sulfur activated carbon. The structural parameters of the obtained low-sulfur activated carbon are shown in Table 1.

[0041] Example 4

[0042] Weigh 30 grams of coconut shell-based activated carbon and place it in a tube furnace for pretreatment under a hydrogen atmosphere. The pretreatment conditions are a hydrogen volume hourly space velocity (HHSV) of 20 h⁻¹. -1 The temperature was kept constant at 450℃ for 1 hour; then, steam treatment was performed simultaneously under the condition that the volume hourly space velocity was 10 h⁻¹. -1 The activated carbon was heated to 850℃ for 2 hours and then naturally cooled to room temperature to obtain low-sulfur activated carbon. The structural parameters of the obtained low-sulfur activated carbon are shown in Table 1.

[0043] Example 5

[0044] Weigh 30 grams of coconut shell-based activated carbon and place it in a tube furnace for pretreatment under a hydrogen atmosphere. The pretreatment conditions are a hydrogen volume hourly space velocity (HHSV) of 20 h⁻¹. -1 The temperature was kept constant at 450℃ for 1 hour; then, steam treatment was performed simultaneously under the condition that the volume hourly space velocity was 10 h⁻¹. -1 The activated carbon was heated to 900℃ for 2 hours and then naturally cooled to room temperature to obtain low-sulfur activated carbon. The structural parameters of the obtained low-sulfur activated carbon are shown in Table 1.

[0045] Example 6

[0046] Weigh 30 grams of coconut shell-based activated carbon and place it in a tube furnace for pretreatment under a hydrogen atmosphere. The pretreatment conditions are a hydrogen volume hourly space velocity (HHSV) of 20 h⁻¹. -1 The temperature was kept constant at 450℃ for 1 hour; then, steam treatment was performed simultaneously under the condition that the volume hourly space velocity was 10 h⁻¹. -1 The activated carbon was heated to 700℃ for 1 hour and then naturally cooled to room temperature to obtain low-sulfur activated carbon. The structural parameters of the obtained low-sulfur activated carbon are shown in Table 1.

[0047] Example 7

[0048] Weigh 30 grams of coconut shell-based activated carbon and place it in a tube furnace for pretreatment under a hydrogen atmosphere. The pretreatment conditions are a hydrogen volume hourly space velocity (HHSV) of 20 h⁻¹. -1 The temperature was kept constant at 450℃ for 1 hour; then, steam treatment was performed simultaneously under the condition that the volume hourly space velocity was 10 h⁻¹. -1 The activated carbon was heated to 800℃ for 1 hour and then naturally cooled to room temperature to obtain low-sulfur activated carbon. The structural parameters of the obtained low-sulfur activated carbon are shown in Table 1.

[0049] Example 8

[0050] Weigh 30 grams of coconut shell-based activated carbon and place it in a tube furnace for pretreatment under a hydrogen atmosphere. The pretreatment conditions are a hydrogen volume hourly space velocity (HHSV) of 20 h⁻¹. -1 The temperature was kept constant at 450℃ for 1 hour; then, steam treatment was performed simultaneously under the condition that the volume hourly space velocity was 10 h⁻¹. -1 The activated carbon was heated to 900℃ for 1 hour and then naturally cooled to room temperature to obtain low-sulfur activated carbon. The structural parameters of the obtained low-sulfur activated carbon are shown in Table 1.

[0051] Example 9

[0052] Weigh 30 grams of coconut shell-based activated carbon and place it in a tube furnace for pretreatment under a hydrogen atmosphere. The pretreatment conditions are a hydrogen volume hourly space velocity (HHSV) of 20 h⁻¹. -1 The temperature was kept constant at 450℃ for 1 hour; then, steam treatment was performed simultaneously under the condition that the volume hourly space velocity was 10 h⁻¹. -1 The activated carbon was heated to 900℃ for 5 hours and then naturally cooled to room temperature to obtain low-sulfur activated carbon. The structural parameters of the obtained low-sulfur activated carbon are shown in Table 1.

[0053] Example 10

[0054] Weigh 30 grams of coconut shell-based activated carbon and place it in a tube furnace for pretreatment under a hydrogen atmosphere. The pretreatment conditions are a hydrogen volume hourly space velocity (HHSV) of 20 h⁻¹. -1 The temperature was kept constant at 850℃ for 1 hour; then, steam treatment was performed simultaneously under the condition that the volume hourly space velocity was 10 h⁻¹. -1 The activated carbon was heated to 850℃ for 1 hour and then naturally cooled to room temperature to obtain low-sulfur activated carbon. The structural parameters of the obtained low-sulfur activated carbon are shown in Table 1.

[0055] Comparative Example 1

[0056] The activated carbon treatment process is the same as the preparation process in Example 10, except that hydrogen pretreatment is performed and steam treatment is not carried out. Specifically, 30 grams of coconut shell-based activated carbon are weighed and placed in a tube furnace for treatment under a hydrogen atmosphere with a hydrogen volume hourly space velocity of 20 h⁻¹. -1 The carbon was heated to 850℃ for 2 hours and then naturally cooled to room temperature to obtain low-sulfur activated carbon. The structural parameters of the obtained low-sulfur activated carbon are shown in Table 1.

[0057] Comparative Example 2

[0058] The activated carbon treatment process is the same as the preparation process in Example 10, except that there is no hydrogen pretreatment in the system, only steam treatment. Specifically, 30 grams of coconut shell-based activated carbon are weighed and placed in a tube furnace for steam treatment at a steam volume hourly space velocity (HHSV) of 10 h⁻¹. -1 The carbon was heated to 850℃ for 2 hours and then naturally cooled to room temperature to obtain low-sulfur activated carbon. The structural parameters of the obtained low-sulfur activated carbon are shown in Table 1.

[0059] Comparative Example 3

[0060] The activated carbon treatment process is the same as the preparation process in Example 10, except that hydrogen and water vapor are used simultaneously to treat the activated carbon in the pretreatment stage. Specifically, 30 grams of coconut shell-based activated carbon are weighed and placed in a tube furnace. The furnace is then heated in a hydrogen and water vapor atmosphere with a hydrogen volume hourly space velocity (HHSV) of 20 h⁻¹. -1 Water vapor volume hourly space velocity 10 h⁻¹ -1 The carbon was heated to 850℃ for 2 hours and then naturally cooled to room temperature to obtain low-sulfur activated carbon. The structural parameters of the obtained low-sulfur activated carbon are shown in Table 1.

[0061] Comparative Example 4

[0062] The activated carbon treatment process is the same as the preparation process in Example 10, except that the order of hydrogen and steam treatment is reversed. Specifically, 30 grams of coconut shell-based activated carbon are weighed and placed in a tube furnace for initial steam treatment with a steam volume hourly space velocity (HHSV) of 10 h⁻¹. -1 The sample was kept at 850℃ for 1 hour, followed by hydrogen treatment with a hydrogen volume hourly space velocity (HHSV) of 20 h⁻¹. -1 The mixture was kept at 850℃ for 1 hour and then naturally cooled to room temperature to obtain low-sulfur activated carbon. The structural parameters of the obtained low-sulfur activated carbon are shown in Table 1.

[0063] Table 1

[0064]

[0065] Examples 1-5 further verified the effect of treatment temperature on desulfurization rate by varying the treatment temperature of coconut shell-based activated carbon in a mixed atmosphere of hydrogen and water vapor. Table 1 shows that the desulfurization rate gradually increases with increasing treatment temperature, but the mesopore ratio decreases when the treatment temperature exceeds 850℃. Examples 6-9 demonstrate that the longer the treatment time, the higher the desulfurization rate. Example 10, compared to Example 1, shows that excessively high pretreatment temperatures reduce the desulfurization rate.

[0066] In Comparative Example 1, only hydrogen pretreatment was performed without water vapor treatment. When the hydrogen volume hourly space velocity in Comparative Example 1 was the same as that in Example 4, the desulfurization rate was significantly reduced. This further illustrates that the present application uses hydrogen and water vapor for synergistic catalysis and activation, which can reduce the amount of hydrogen used, increase the desulfurization rate, and reduce costs.

[0067] In summary, compared with the above embodiments and comparative examples, it can be seen that the present invention uses activated carbon with high sulfur content as raw material and employs a synergistic catalytic and activation method using hydrogen and water vapor to synergistically reduce the residual sulfur content in activated carbon or improve the removal rate of sulfur impurities in activated carbon. At the same time, it reduces the amount of hydrogen used compared to existing technologies, resulting in lower production costs. Specifically, pretreatment is first performed in a hydrogen environment at a suitable temperature, followed by the introduction of water vapor at a higher temperature to achieve sulfur removal, while effectively increasing the surface area, total pore volume, and mesoporosity of the sample. Compared with existing technologies, the activated carbon treatment process of the present invention is simple, requiring only reducing gas hydrogen and green solvent water, without the need to introduce other chemical reagents, resulting in low production costs and facilitating large-scale processing of activated carbon.

[0068] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing low-sulfur activated carbon, comprising the following steps: S1. The activated carbon raw material is pretreated under a hydrogen atmosphere to obtain pretreated activated carbon raw material; the pretreatment temperature is 350-550℃; during the pretreatment process, the hydrogen volume hourly space velocity is 10-30 h⁻¹. -1 ; S2. The pretreated activated carbon raw material is treated in a mixed atmosphere of hydrogen and water vapor; the treatment temperature is 700–900°C; and the volume hourly space velocity of the water vapor is 5–20 h⁻¹. -1 .

2. The preparation method according to claim 1, characterized in that, The sulfur content of the activated carbon raw material is greater than 100 ppm.

3. The preparation method according to claim 1, characterized in that, The sulfur content of the activated carbon raw material is 100-500 ppm.

4. The preparation method according to claim 1, characterized in that, The sulfur content of the activated carbon raw material is greater than 300 ppm.

5. The preparation method according to claim 1, characterized in that, The sulfur content of the activated carbon raw material is 300-500 ppm.

6. The preparation method according to claim 1, characterized in that, The activated carbon raw material is wood or fruit shell carbonized material.

7. The preparation method according to claim 1, characterized in that, The activated carbon raw material is a carbonized material made from fruit shells.

8. The preparation method according to claim 1, characterized in that, The activated carbon raw material is coconut shell-based activated carbon.

9. The preparation method according to claim 1, characterized in that, The pretreatment time is 0.5 to 3 hours.

10. The preparation method according to claim 1, characterized in that, The pretreatment temperature is 400–500°C, and the pretreatment time is 1–2 hours.

11. The preparation method according to claim 1, characterized in that, The processing time is 0.5 to 6 hours.

12. The preparation method according to claim 1, characterized in that, In step S2, the processing temperature is 750–850°C, and the processing time is 1–3 hours.

13. The preparation method according to claim 1, characterized in that, The sulfur content in the low-sulfur activated carbon is ≤230ppm.

14. The preparation method according to claim 1, characterized in that, The sulfur content in the low-sulfur activated carbon is 50–230 ppm.

15. The preparation method according to claim 1, characterized in that, The specific surface area of ​​the low-sulfur activated carbon is 500-800 m². 2 / g, the total pore volume of the low-sulfur activated carbon is 0.4–0.6 cm³. 3 / g, the mesopore volume of the low-sulfur activated carbon is 0.2-0.4cm. 3 / g, wherein the mesopore ratio of the low-sulfur activated carbon is 50-70%.

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