A glucose-modified activated carbon composite material, its preparation method and application

Abstract

This invention relates to the field of methane catalytic cracking for hydrogen production, and particularly to a glucose-modified activated carbon composite material, its preparation method, and its application. In this invention, activated carbon and glucose are used as the main raw materials, and a glucose-modified activated carbon catalyst is prepared through an impregnation-carbonization process. During carbonization, glucose gradually melts, dehydrates, and cracks to form carbonaceous intermediates. Simultaneously, gases such as H2O, CO, and CO2 are released. These gases activate the pore structure of the activated carbon, promoting the development of micropores and mesopores. Furthermore, the intermediates interact with the activated carbon surface, increasing the content of oxygen-containing functional groups, especially C=O-related functional groups. The resulting fluffy carbon black after glucose carbonization further enhances the initial activity during the methane catalytic cracking reaction and extends the catalytic life.

Description

Technical Field

[0001] This invention relates to the field of methane catalytic cracking for hydrogen production, and particularly to a glucose-modified activated carbon composite material, its preparation method, and its application. Background Technology

[0002] Hydrogen is a crucial component of future clean energy, with wide applications in fuel cells, energy storage, and industrial production. In recent years, hydrogen production has primarily involved methods such as water electrolysis, biomass-based hydrogen production, methane-based hydrogen production, and hydrocarbon reforming. Among these, catalytic cracking of methane can simultaneously yield hydrogen free of carbon oxides and carbon nanotubes, avoiding the significant carbon dioxide emissions associated with traditional methane steam reforming and partial oxidative reforming processes.

[0003] Currently, catalysts for methane catalytic cracking to hydrogen production mainly use noble metals (Pt, Ru, or Pd) and a small amount of non-noble metals (Ni, Fe, or Co) as active sites. Noble metal catalysts exhibit good catalytic activity, but their high cost prevents large-scale industrial production. Non-noble metal catalysts are prone to particle sintering, loss of active sites, and severe carbon deposition and deactivation during high-temperature reactions, thus affecting their long-term stable operation. In contrast, carbon-based catalysts have advantages such as lower cost, wider availability, strong resistance to sintering, and adaptability to carbon deposition environments, thus attracting increasing attention.

[0004] Activated carbon is a typical porous carbon material, typically possessing a large specific surface area, well-developed pore structure, and abundant oxygen-containing functional groups on its surface, providing favorable conditions for the adsorption and activation of methane molecules. However, existing activated carbon catalysts still suffer from problems such as low initial activity and significant activity decay after prolonged operation during the catalytic cracking reaction of methane. Summary of the Invention

[0005] To overcome the above problems, the present invention provides a glucose-modified activated carbon composite material, its preparation method, and its application.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a glucose-modified activated carbon composite material, which uses activated carbon as a matrix and is loaded with fluffy carbon black after glucose carbonization. The total pore volume of the glucose-modified activated carbon composite material is 0.43~0.45 cm³. 3 / g, with a micropore volume ratio of 80~88%, a mesopore volume ratio of 12~20%, and an average pore size of 1.5~1.8 nm.

[0007] In one or more embodiments, the temperature for glucose carbonization is 450~850°C, preferably 650°C.

[0008] A second aspect of the present invention provides a method for preparing the glucose-modified activated carbon composite material described in the first aspect, comprising the following steps: Activated carbon was impregnated with a glucose solution, and the solid was collected and dried to obtain the precursor material. Glucose-modified activated carbon composite material was obtained by carbonizing the precursor material in an anaerobic environment.

[0009] In one or more embodiments, the activated carbon has a particle size of 125-180 μm.

[0010] In one or more embodiments, the glucose is anhydrous glucose.

[0011] In one or more embodiments, the concentration of the glucose solution is 18-22 g / L, preferably 20 g / L.

[0012] In one or more embodiments, the mass ratio of activated carbon to glucose is (5~10):1, preferably 7:1.

[0013] In one or more embodiments, the immersion time is 55 to 70 minutes, preferably 60 minutes.

[0014] In one or more embodiments, the oxygen-free environment includes nitrogen and an inert gas.

[0015] In one or more embodiments, the carbonization temperature is 450~850℃, preferably 650℃; the carbonization temperature is 3~5 h; Preferably, the carbonization process includes: first heating to 430~450℃ and holding at that temperature for 30~35 min, and then holding at 450~850℃ for 150~200 min.

[0016] A third aspect of the present invention provides the application of the glucose-modified activated carbon composite material described in the first aspect or the glucose-modified activated carbon composite material prepared by the preparation method described in the second aspect as a catalyst, said application including catalytic cracking of methane to produce hydrogen.

[0017] In one or more embodiments, the temperature for catalytic methane cracking to produce hydrogen is 850~950℃, preferably 900℃.

[0018] The beneficial effects of this invention are as follows: The glucose-modified activated carbon composite material in this invention not only improves the initial activity of the methane catalytic cracking reaction but also extends the catalytic lifetime. This is because: during the carbonization process, the gases released by glucose, such as H2O, CO, and CO2, can activate the pore structure of activated carbon, promoting the development of micropores and mesopores; this provides more active sites for the methane cracking reaction and more space for carbon deposition; the intermediates formed during glucose carbonization can interact with the activated carbon surface, increasing the content of oxygen-containing functional groups on the surface, especially C=O-related functional groups; this provides more potential active sites for the methane cracking reaction, improving the initial reaction activity and sustained catalytic performance of the catalyst. The fluffy carbon black formed after glucose carbonization provides more adsorption space for CH4 molecules and also provides attachment sites for the carbon deposits generated during the reaction, thus helping to delay the complete coverage of the catalyst's active sites by carbon deposits and improving the catalyst's sustained reaction performance. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0020] Figure 1 The preparation process of glucose-modified activated carbon composite material; Figure 2 The images are scanning electron microscope (SEM) images of the glucose-modified activated carbon composite material prepared in Example 1 and the unmodified activated carbon in Comparative Example 1. (a) and (b) are SEM images of the unmodified activated carbon at different magnifications, and (c) and (d) are SEM images of the glucose-modified activated carbon composite material at different magnifications. Figure 3 The pore structure characterization results are shown for the glucose-modified activated carbon composite material prepared in Example 1 and the unmodified activated carbon in Comparative Example 1. Among them, (a) is the N2 adsorption-desorption isotherm diagram and (b) is the pore size distribution diagram. Figure 4 Fourier transform infrared spectra of unmodified activated carbon and glucose-modified activated carbon composites; Figure 5 The image shows a comparison of X-ray photoelectron spectroscopy (XPS) C1s fitting of the glucose-modified activated carbon composite material prepared in Example 1 and the unmodified activated carbon in Comparative Example 1, where (a) is the unmodified activated carbon and (b) is the glucose-modified activated carbon composite material. Figure 6 The process of testing the performance of methane catalytic cracking for hydrogen production; Figure 7The graphs show the CH4 conversion rates of glucose-modified activated carbon composites obtained under different carbonization temperatures; where (a) is the instantaneous CH4 conversion rate graph and (b) is the average CH4 conversion rate graph. Figure 8 The graph shows the CH4 conversion results of catalysts with different mass ratios of activated carbon and glucose under carbonization conditions at 650℃; where (a) is the instantaneous CH4 conversion graph and (b) is the average CH4 conversion graph. Detailed Implementation

[0021] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] Currently, catalysts for methane catalytic cracking to hydrogen production mainly use noble metals (Pt, Ru, or Pd) and a small amount of non-noble metals (Ni, Fe, or Co) as active sites. Noble metal catalysts exhibit good catalytic activity, but their high cost prevents large-scale industrial production. Non-noble metal catalysts are prone to particle sintering, loss of active sites, and severe carbon deposition and deactivation during high-temperature reactions, thus affecting their long-term stable operation. In contrast, carbon-based catalysts have advantages such as lower cost, wider availability, strong resistance to sintering, and adaptability to carbon deposition environments, thus attracting increasing attention.

[0024] Activated carbon is a typical porous carbon material, typically possessing a large specific surface area, well-developed pore structure, and abundant oxygen-containing functional groups on its surface, providing favorable conditions for the adsorption and activation of methane molecules. However, existing activated carbon catalysts still suffer from problems such as low initial activity and significant activity decay after prolonged operation during the catalytic cracking reaction of methane.

[0025] This invention uses activated carbon and glucose as the main raw materials to prepare a glucose-modified activated carbon catalyst through impregnation-carbonization. During carbonization, glucose gradually melts, dehydrates, and cracks to form carbonaceous intermediates, while gases such as H2O, CO, and CO2 are released. These intermediates and gases can all react with the activated carbon. The gases H2O, CO, and CO2 activate the pore structure of the activated carbon, promoting the development of micropores and mesopores. Simultaneously, the intermediates interact with the activated carbon surface, increasing the content of oxygen-containing functional groups, particularly C=O-related functional groups. The development of micropores and mesopores not only provides more active sites for the methane cracking reaction but also provides more space for carbon deposition. The increased content of C=O-related functional groups provides more potential active sites for the methane cracking reaction, improving the initial reaction activity and sustained catalytic performance of the catalyst. Furthermore, the fluffy carbon black formed after glucose carbonization can provide more adsorption space for CH4 molecules, and also provide attachment sites for the carbon deposits generated during the reaction, thereby helping to delay the complete coverage of the catalyst's active sites by carbon deposits and improving the catalyst's sustained reaction performance.

[0026] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0027] The principle and evaluation formula of methane catalytic cracking reaction: The catalytic cracking reaction of methane is shown in equation (1): (1); The instantaneous CH4 conversion rate during the catalytic cracking of methane is calculated according to equation (2): (2); In the formula, XCH4 is the conversion rate of methane, %; φvol, H2 is the volume fraction of H2 in the product gas, vol%; φvol,CH4 is the volume fraction of CH4 in the product gas, vol%.

[0028] The average conversion rate of methane during the catalytic cracking process is calculated according to formula (3): (3); In the formula X Ave, CH4 represents the average CH4 conversion rate during the catalytic cracking of methane, in %. t is the reaction time for the catalytic cracking of methane, in min.

[0029] Example 1 Figure 1 For the preparation process of glucose-modified activated carbon composite materials, refer to Figure 1 A glucose-modified activated carbon composite material was synthesized.

[0030] Coconut shell activated carbon was washed with deionized water until the washing solution was clear and free of impurities, and then dried in an oven at 80℃. The dried activated carbon was then pulverized and sieved, and activated carbon with a particle size of 125~180 μm was collected for later use. Anhydrous glucose with a purity of 99% was used.

[0031] (1) Weigh 1 g of glucose into a beaker and add 50 mL of deionized water to dissolve it completely; then add 7 g of activated carbon to form a suspension. Place the beaker in a 20℃ constant temperature water bath stirrer and stir for 60 min to allow the glucose to fully impregnate into the pores of the activated carbon. After impregnation, filter and dry the sample to obtain the precursor material.

[0032] (2) The precursor material was placed in a tube furnace and carbonized under a N2 atmosphere by programmed heating. The heating program was as follows: from room temperature to 450°C and held for 30 min, then continued to 650°C and held for 180 min. After cooling, glucose-modified activated carbon composite material was obtained.

[0033] Example 2 Compared with Example 1, the carbonization temperature in step (2) was adjusted to 450°C, that is, the heating procedure was to raise the temperature from room temperature to 450°C and hold it for 210 min.

[0034] The remaining process is the same as in Example 1.

[0035] Example 3 Compared with Example 1, the carbonization temperature in step (2) was adjusted to 850°C. That is, the heating program was: from room temperature to 450°C and held for 30 min, then continued to rise to 850°C and held for 180 min, and after cooling, glucose modified activated carbon composite material was obtained.

[0036] The remaining process is the same as in Example 1.

[0037] Example 4 Compared with Example 1, the ratio of glucose to activated carbon in step (1) was adjusted.

[0038] Weigh 1 g of glucose into a beaker and add 50 mL of deionized water to dissolve it completely; then add 5 g of activated carbon to form a suspension. The remaining process is the same as in Example 1.

[0039] Example 5 Compared with Example 1, the ratio of glucose to activated carbon in step (1) was adjusted.

[0040] Weigh 1 g of glucose into a beaker and add 50 mL of deionized water to dissolve it completely; then add 10 g of activated carbon to form a suspension. The remaining process is the same as in Example 1.

[0041] Comparative Example 1 Compared to Example 1, no modification was made to the activated carbon.

[0042] Figure 2 Scanning electron microscope images of the glucose-modified activated carbon composite material prepared in Example 1 and the unmodified activated carbon in Comparative Example 1.

[0043] from Figure 2 As can be seen, the surface of unmodified activated carbon is relatively smooth, with a regular pore structure and smooth pore edges. However, after glucose modification, the sample surface is no longer smooth, exhibiting a distinct fluffy carbon black structure, and the pore edges become irregular. These phenomena indicate that glucose was successfully loaded onto the surface and pores of activated carbon after carbonization, significantly affecting the microstructure of the activated carbon surface. The fluffy carbonaceous structure formed during glucose carbonization provides more adsorption space for CH4 molecules and also provides attachment sites for the carbon deposits generated during the reaction, thus helping to delay the complete coverage of the catalyst's active sites by carbon deposits and improving the catalyst's sustained reaction performance.

[0044] Figure 3 The pore structure characterization results are shown for the glucose-modified activated carbon composite material prepared in Example 1 and the unmodified activated carbon in Comparative Example 1. Figure 3 In the middle (a), the N2 adsorption-desorption isotherm diagram is shown. Figure 3 (b) is the aperture distribution diagram.

[0045] Depend on Figure 3 As shown in (a), both the unmodified activated carbon and the glucose-modified activated carbon composite exhibit typical type I isotherms, indicating that both are predominantly microporous. Compared to the unmodified activated carbon, the glucose-modified activated carbon composite shows a higher N2 adsorption capacity across the entire pressure range, indicating that glucose modification improves the adsorption performance of the activated carbon.

[0046] Depend on Figure 3 As shown in (b), the pore structure of the glucose-modified activated carbon composite material exhibits a significant increase in the pore size range of 2–10 nm, indicating that glucose modification promotes the development of the mesoporous structure. Furthermore, combined with the specific surface area and pore volume test results, the specific surface area of ​​the unmodified activated carbon is 1005.23 m². 2 / g, total pore volume is 0.41 cm³ 3 / g, micropore volume is 0.35cm³ 3 / g; The specific surface area of ​​the glucose-modified activated carbon composite material increased to 1043.19 m². 2 / g, total pore volume increased to 0.44cm³. 3 / g, micropore volume increased to 0.37 cm³. 3 / g. The results showed that glucose modification could simultaneously promote the development of micropores and mesopores in activated carbon, thereby providing more active sites for methane cracking and more space for carbon deposition.

[0047] The surface chemical structures of the glucose-modified activated carbon composite material prepared in Example 1 and the unmodified activated carbon in Comparative Example 1 were characterized using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results are as follows: Figure 4 and Figure 5 As shown. Among them, Figure 4 This is a Fourier transform infrared spectrum; Figure 5 This is a comparison of X-ray photoelectron spectroscopy (XPS) C 1s fitting images. Figure 5 In the middle (a), the XPS C 1s fitting plot of unmodified activated carbon is shown. Figure 5 (b) is the XPS C1s fitting plot of glucose-modified activated carbon composite material.

[0048] Depend on Figure 4 It can be seen that the positions of the main characteristic absorption peaks of the samples before and after glucose modification are basically the same, indicating that glucose modification did not introduce new types of oxygen-containing functional groups, but the relative contents of various functional groups changed, indicating that the intermediates formed during glucose carbonization can interact with the surface of activated carbon, thereby regulating its surface chemical structure.

[0049] XPS C 1s peak fitting analysis was performed on the sample, and the results are as follows: Figure 5 As shown in Table 1. From Figure 5 (a) and Figure 5 As shown in Table 1 (b), under carbonization conditions of 650℃, there are significant differences in the surface functional group composition between the unmodified activated carbon and the glucose-modified activated carbon composite material. Compared with unmodified activated carbon, the total amount of oxygen-containing functional groups on the surface of glucose-modified activated carbon increased from 20.40% to 24.83%, an increase of 4.43%; among them, the content of C=O-related functional groups increased from 4.35% to 10.11%, showing the most significant increase. These results indicate that glucose modification is beneficial for increasing the oxygen-containing functional groups on the surface of activated carbon, especially C=O-related functional groups, thereby providing more potential active sites for methane cracking reactions and improving the initial reaction activity and sustained catalytic performance of the catalyst. Table 1 XPS C1s fitting results of unmodified activated carbon and glucose-modified activated carbon composite materials.

[0050] Note: The total amount of oxygen-containing functional groups is the sum of the peak areas of the three types of oxygen-containing functional groups: CO, C=O, and C(O)O.

[0051] Experimental Example 1 (1) Performance test of methane catalytic cracking for hydrogen production Figure 6 The reaction was carried out in a fixed-bed reactor as shown. The catalyst samples obtained in the examples and comparative examples were respectively packed into quartz reaction tubes with a packing amount of 3 g. A mixture of 20% CH4 and 80% N2 by volume was introduced at 900°C, and the single reaction time was 180 min. The composition of the outlet gas was detected in real time using an MRU VARIO gas analyzer, and the instantaneous CH4 conversion rate and the average CH4 conversion rate were calculated according to equations (2) and (3).

[0052] The test results showed that the initial CH4 conversion rate of the unmodified activated carbon was 67.55%, which decreased to 46.92% at 20 min and to 25.18% at 180 min, with an average CH4 conversion rate of 35.58%.

[0053] (2) The CH4 conversion results of glucose-modified activated carbon composite materials obtained under different carbonization temperatures are as follows: Figure 7 As shown, where Figure 7 (a) shows the instantaneous CH4 conversion rate. Figure 5 (b) shows the average CH4 conversion rate.

[0054] Depend on Figure 7 As shown in (a), both the unmodified activated carbon and the glucose-modified activated carbon composites exhibited a gradual decrease in CH4 conversion rate over time during the reaction, indicating that carbon deposition leads to a gradual decline in catalyst activity. The unmodified activated carbon's CH4 conversion rate rapidly decreased from 67.55% to 46.92% within 0–20 min, then continued to decrease slowly within 20–180 min, eventually reaching 25.18%. In contrast, the glucose-modified activated carbon composites carbonized at 450℃, 650℃, and 850℃ showed a decrease in CH4 conversion rate from 71.82%, 86.14%, and 62.08% to 48.87%, 56.04%, and 37.26% within 0–30 min, respectively, before the decrease leveled off, reaching 29.74%, 35.30%, and 25.45% at 180 min. These results indicate that glucose modification can delay the catalyst deactivation process and improve the catalyst's sustained reaction performance.

[0055] Depend on Figure 7 As shown in Figure (b), the average CH4 conversion rate of unmodified activated carbon within 0–180 min was 35.58%, while the average CH4 conversion rates of glucose-modified activated carbon obtained by carbonization at 450℃, 650℃, and 850℃ were 40.12%, 47.48%, and 32.77%, respectively. Among them, the sample carbonized at 650℃ showed the highest instantaneous CH4 conversion rate and average CH4 conversion rate, indicating that 650℃ is the optimal carbonization temperature.

[0056] (3) Effect of different activated carbon to glucose mass ratios on the performance of methane catalytic cracking for hydrogen production The CH4 conversion rates of catalysts with different activated carbon to glucose mass ratios obtained under carbonization conditions at 650℃ are shown below. Figure 8 As shown, where Figure 8 (a) shows the instantaneous CH4 conversion rate. Figure 8 (b) shows the average CH4 conversion rate.

[0057] Depend on Figure 8 As shown in (a), the initial CH4 conversion rate of the catalyst was relatively high when the activated carbon to glucose mass ratios were 5:1, 7:1, and 10:1, indicating that the initial reaction activity was mainly affected by the carbonization temperature, while the different mass ratios had a relatively small impact on the initial activity. However, as the reaction proceeded, the deactivation rates of the samples with different mass ratios varied. Within 0–30 min, the CH4 conversion rates of the three catalysts decreased to 50.48%, 56.04%, and 53.98%, respectively; at 180 min, they decreased to 30.76%, 35.30%, and 32.30%, respectively. Among them, the sample with a mass ratio of 7:1 showed a higher instantaneous CH4 conversion rate throughout the entire reaction process.

[0058] Depend on Figure 8 As shown in Figure (b), the average CH4 conversion rate of unmodified activated carbon was 35.58%, while the average CH4 conversion rates of glucose-modified activated carbon with mass ratios of 5:1, 7:1, and 10:1 were 45.37%, 47.48%, and 42.33%, respectively. The results indicate that the catalyst exhibits the best overall catalytic performance when the mass ratio of activated carbon to glucose is 7:1. Excessive glucose addition can lead to the generation of more carbon black and blockage of some pores; insufficient glucose addition is insufficient to fully activate the pore structure of the activated carbon and regulate the surface functional groups, thus hindering further improvement in catalytic performance.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A glucose-modified activated carbon composite material, characterized in that, It uses activated carbon as a matrix and is loaded with fluffy carbon black after glucose carbonization; The total pore volume of the glucose-modified activated carbon composite material is 0.43~0.45 cm³. 3 / g, with a micropore volume ratio of 80~88%, a mesopore volume ratio of 12~20%, and an average pore size of 1.5~1.8 nm.

2. The glucose-modified activated carbon composite material as described in claim 1, characterized in that, The temperature for glucose carbonization is 450~850℃, preferably 650℃.

3. The method for preparing the glucose-modified activated carbon composite material according to claim 1 or 2, characterized in that, Includes the following steps: Activated carbon was impregnated with a glucose solution, and the solid was collected and dried to obtain the precursor material. Glucose-modified activated carbon composite material was obtained by carbonizing the precursor material in an anaerobic environment.

4. The preparation method according to claim 3, characterized in that, The particle size of activated carbon is 125~180 μm.

5. The preparation method according to claim 3, characterized in that, The concentration of the glucose solution is 18-22 g / L, preferably 20 g / L; Alternatively, the mass ratio of activated charcoal to glucose is (5~10):1, preferably 7:

1.

6. The preparation method according to claim 3, characterized in that, The soaking time is 55-70 minutes, preferably 60 minutes.

7. The preparation method according to claim 3, characterized in that, An anaerobic environment includes nitrogen and inert gases.

8. The preparation method according to claim 3, characterized in that, The carbonization temperature is 450~850℃, preferably 650℃; the carbonization time is 3~5 h; Preferably, the carbonization process includes: first heating to 430~450℃ and holding at that temperature for 30~35 min, and then holding at 450~850℃ for 150~200 min.

9. The application of the glucose-modified activated carbon composite material according to claim 1 or 2 or the glucose-modified activated carbon composite material prepared by the preparation method according to any one of claims 3 to 8 as a catalyst, said application including catalytic cracking of methane to produce hydrogen.

10. The application as described in claim 9, characterized in that, The temperature for catalytic methane cracking to produce hydrogen is 850~950℃, preferably 900℃.

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