A vanadium-molybdenum disulfide / aluminum oxide composite material, a preparation method thereof, and an application thereof in catalytic thermal cracking of hydrogen sulfide to prepare sulfur and hydrogen

Abstract

The present invention discloses a vanadium-molybdenum disulfide / aluminum oxide composite material, a preparation method thereof, and an application thereof in catalytic thermal cracking of hydrogen sulfide to prepare sulfur and hydrogen, belonging to the technical field of resource utilization of gaseous pollutants. The vanadium-molybdenum disulfide / aluminum oxide composite material is composed of molybdenum disulfide nanoparticles doped with amorphous vanadium supported on a porous aluminum oxide carrier. The composite material exhibits excellent catalytic stability and catalytic activity in the process of catalytic thermal cracking of hydrogen sulfide to prepare hydrogen and sulfur. Moreover, the preparation process of the composite material is simple and efficient, the process flow is short, the reaction conditions are mild, and it has the potential for large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to a catalytic material, in particular to a vanadium-molybdenum disulfide / aluminum oxide composite material, and also relates to a preparation method of the vanadium-molybdenum disulfide / aluminum oxide composite material, and further relates to the application of the vanadium-molybdenum disulfide / aluminum oxide composite material in the catalytic thermal cracking of hydrogen sulfide to prepare hydrogen and sulfur, belonging to the technical field of resource utilization of gaseous pollutants. Background Art

[0002] Hydrogen sulfide is an acidic gas with strong toxicity and corrosiveness, which widely exists in industrial processes such as petrochemical industry, natural gas purification, and coal processing. It not only causes serious corrosion to industrial equipment, but also pollutes the ecological environment and poses a major threat to human health. Even at extremely low concentrations, hydrogen sulfide can damage the respiratory system and can cause poisoning or even death in severe cases. Therefore, the effective and harmless treatment of hydrogen sulfide has become an important topic in the fields of chemical engineering and environmental protection. Traditional hydrogen sulfide treatment methods, such as the Claus process, although can effectively convert hydrogen sulfide, not only cause waste of hydrogen resources, but also are accompanied by the emission of harmful gases such as sulfur dioxide, and cannot achieve efficient resource recovery and green treatment.

[0003] In recent years, the thermal catalytic cracking technology is considered to be a promising solution for treating hydrogen sulfide, especially having significant advantages in utilizing industrial waste heat and mature equipment. However, the catalysts of existing thermal catalytic cracking methods often have problems such as insufficient activity, poor stability, and limited sulfur poisoning resistance, which severely restrict the industrial application of this technology. Therefore, developing a long-lasting catalyst with high catalytic activity, thermal stability, and sulfur poisoning resistance has become an important task at present.

[0004] Due to its unique layered structure and abundant edge active sites, molybdenum disulfide is far superior to many traditional transition metal oxides and sulfides and has been widely used in the catalytic cracking reaction of hydrogen sulfide. However, the catalytic performance of pure molybdenum disulfide is easily affected by particle agglomeration at high temperatures, resulting in a rapid decline in its activity. The literature ("Constrained Growth of MoS2 Nanosheets within a Mesoporous Silica Shell and Its Effects on Defect Sites and Catalyst Stability for H2S Decomposition, Kelvin Mingyao Kwok, et al., ACS Catalysis 2018 8 (1), 714-724.") discloses the catalytic cracking of hydrogen sulfide by pure molybdenum disulfide nanoparticles, but its catalytic stability is poor, and the cracking efficiency decreases by 19% within 4 hours, with obvious performance decline. Chinese Patent (Publication No. CN104524934B) discloses a method for catalytically decomposing hydrogen sulfide into hydrogen and sulfur by microwave, and its composite catalyst includes an active component (such as transition metal sulfide), an optional carrier (such as γ-Al2O3), and a promoter component (such as perovskite-type catalyst). While removing the toxic and harmful gas hydrogen sulfide, it produces sulfur and hydrogen, and can make the most efficient use of hydrogen sulfide in the waste gas. However, its catalyst composition is complex, a promoter is required, the cost is high, and its degradation efficiency of hydrogen sulfide is low. In addition, the high-temperature stability of the transition metal sulfide catalyst is poor, and it does not solve this technical problem. Summary of the Invention

[0005] Aiming at the technical problems existing in the prior art, the first object of the present invention is to provide a vanadium-molybdenum disulfide / aluminum oxide composite material composed of amorphous vanadium-doped molybdenum disulfide nanoparticles supported on a porous aluminum oxide carrier. This composite material has good thermal stability, and its catalytic active sites are abundant and evenly distributed, showing high catalytic activity, enabling it to maintain high catalytic performance for a long time under high-temperature conditions.

[0006] The second object of the present invention is to provide a preparation method of the vanadium-molybdenum disulfide / aluminum oxide composite material. This method is simple to operate, has mild conditions, low cost, and has good industrial applicability.

[0007] The third object of the present invention is to provide an application of the vanadium-molybdenum disulfide / aluminum oxide composite material in the catalytic thermal cracking of hydrogen sulfide to prepare hydrogen and sulfur. This catalytic material shows high catalytic cracking efficiency and stable performance for hydrogen sulfide gas, and is particularly suitable for the industrial process of catalytically cracking hydrogen sulfide at high temperatures to prepare hydrogen and sulfur.

[0008] To achieve the above technical objectives, the present invention provides a vanadium-molybdenum disulfide / aluminum oxide composite material, which is composed of molybdenum disulfide nanoparticles doped with amorphous vanadium supported on a porous aluminum oxide carrier; the molar amounts of vanadium and molybdenum elements in the amorphous vanadium-doped molybdenum disulfide nanoparticles are 1-50% of the molar amount of aluminum oxide in the porous aluminum oxide carrier; the molar amount of vanadium element in the amorphous vanadium-doped molybdenum disulfide nanoparticles is 1-50% of the molar amount of molybdenum element.

[0009] The active component of the vanadium-molybdenum disulfide / aluminum oxide composite material of the present invention is vanadium-doped molybdenum disulfide, and the carrier is porous aluminum oxide. The porous aluminum oxide not only has strong thermal stability and corrosion resistance, can withstand the high-temperature environment during thermal cracking and the strong corrosion environment of hydrogen sulfide gas, but also has a high specific surface area and a developed pore structure, and there is a strong interaction between aluminum oxide and molybdenum disulfide, which can achieve the highly dispersed and stable loading of the vanadium-doped molybdenum disulfide active component, expose more catalytic active sites, effectively prevent the particle aggregation of molybdenum disulfide under high-temperature conditions, and thus exhibit long-term stable high catalytic activity. At the same time, its porous structure and high specific surface area are also conducive to the adsorption of hydrogen sulfide gas and promote its pyrolysis process. In the vanadium-doped molybdenum disulfide, vanadium is doped in the lattice of molybdenum disulfide in an amorphous form, which can significantly improve the catalytic performance by enhancing the sulfur vacancy density and optimizing the generation of unsaturated molybdenum sites. Moreover, the synergistic effect between vanadium and molybdenum disulfide can optimize the distribution of catalytic active sites of molybdenum disulfide, making it show higher efficiency and stability in the hydrogen sulfide cracking reaction.

[0010] The molar amounts of vanadium and molybdenum elements in the amorphous vanadium-doped molybdenum disulfide nanoparticles of the present invention are 1-50% of the molar amount of aluminum oxide in the aluminum oxide carrier. A lower vanadium-molybdenum loading will result in fewer catalytic active components and lower efficiency in treating high-concentration hydrogen sulfide. An excessive loading will reduce the specific surface area of the catalyst and reduce the exposure of active components. Secondly, an excessive vanadium-molybdenum loading will also lead to waste of the catalyst and an increase in the production cost of the catalyst. The molar amounts of vanadium and molybdenum elements in the amorphous vanadium-doped molybdenum disulfide nanoparticles are further preferably 10-30% of the molar amount of aluminum oxide in the aluminum oxide carrier.

[0011] The molar amount of vanadium element in the amorphous vanadium-doped molybdenum disulfide nanoparticles of the present invention is 1-50% of the molar amount of molybdenum element. With the increase in the doping amount of amorphous vanadium in molybdenum disulfide, the concentration of unsaturated molybdenum sites and sulfur vacancies in the catalyst will increase, which is beneficial to improving the catalytic performance of the catalyst. However, if the doping amount of amorphous vanadium is further increased, there will be no further obvious increase in the improvement of the catalytic performance of the catalyst. The molar amount of vanadium element in the amorphous vanadium-doped molybdenum disulfide nanoparticles is further preferably 5-25% of the molar amount of molybdenum element.

[0012] The present invention also provides a method for preparing a vanadium-molybdenum disulfide / aluminum oxide composite material, which comprises the following steps:

[0013] (1) Mixing a porous aluminum oxide support and a sulfur source with a molybdenum-vanadium mixed metal salt solution to form a sulfidation reaction solution;

[0014] (2) Transferring the sulfidation reaction solution into a high-pressure reactor for hydrothermal reaction to obtain a precursor material;

[0015] (3) Drying and calcining the precursor material under an oxygen-free condition to obtain the product.

[0016] In the process of preparing the vanadium-molybdenum disulfide / aluminum oxide composite material of the present invention, the key lies in realizing the step-by-step, orderly and efficient sulfidation process of the metal through three-step heat treatment of "hydrothermal-drying-calcining". This process not only ensures the in-situ loading of molybdenum disulfide on the surface of the porous aluminum oxide, realizes stable binding and uniform dispersion, but also uses vanadium elements to regulate the structural defects and active sites of molybdenum disulfide, and finally forms highly active nano vanadium-molybdenum disulfide particles.

[0017] As a preferred embodiment, the concentration of molybdenum ions in the molybdenum-vanadium mixed metal salt solution is 0.001 - 1 mol / L.

[0018] As a preferred embodiment, the molar ratio of vanadium ions to molybdenum ions in the molybdenum-vanadium mixed metal salt solution is 1 - 50:100.

[0019] As a preferred embodiment, the molar amount ratio of aluminum oxide in the porous aluminum oxide support to the total molar amount of vanadium ions and molybdenum ions in the molybdenum-vanadium mixed metal salt solution is 100:1 - 50.

[0020] As a preferred embodiment, the molar amount ratio of sulfur element in the sulfur source to the total molar amount of vanadium ions and molybdenum ions in the molybdenum-vanadium mixed metal salt solution is 2 - 6:1. By using an appropriately excessive sulfur source, metal ions can be fully converted into metal sulfides, and the excessive sulfur can prevent material oxidation and sulfur volatilization loss at high temperature in subsequent heat treatment reactions.

[0021] As a preferred embodiment, the porous aluminum oxide support includes at least one of spherical porous aluminum oxide, fibrous porous aluminum oxide, and amorphous porous aluminum oxide. The preferred porous aluminum oxide material has a high specific surface area and a rich pore structure, which can improve the dispersibility and loading stability of vanadium-molybdenum disulfide. At the same time, it is beneficial to the adsorption and enrichment of hydrogen sulfide gas and promotes the pyrolysis process of hydrogen sulfide gas.

[0022] As a preferred embodiment, the molybdenum-vanadium mixed metal salt solution contains at least one molybdenum salt of ammonium dimolybdate, ammonium tetramolybdate, ammonium heptamolybdate, ammonium tetrathiomolybdate. The preferred molybdenum salts are all common molybdenum salts with good water solubility.

[0023] As a preferred embodiment, the molybdenum-vanadium mixed metal salt solution contains at least one vanadium salt such as ammonium metavanadate and ammonium polyvanadate. The preferred vanadium salts are all common vanadium salts with good water solubility.

[0024] As a preferred embodiment, the sulfur source includes at least one of sodium sulfide, thiourea, sodium thiosulfate, and thioacetamide. The preferred sulfur source is a common water-soluble sulfur-containing compound.

[0025] As a preferred embodiment, the conditions for the hydrothermal reaction are: the temperature is 60~200 °C, and the time is 1~24 h. Under the preferred hydrothermal reaction conditions, it is beneficial to the in-situ generation of molybdenum disulfide on the porous alumina support, and the bonding strength between molybdenum disulfide and the porous alumina support is improved.

[0026] As a preferred embodiment, the conditions for drying are: the temperature is 30~120 °C, and the time is 1~48 h.

[0027] As a preferred embodiment, the conditions for calcination are: the temperature is 400~1000 °C, and the time is 1~24 h.

[0028] Through heat treatment processes such as drying and calcination, not only can the further complete sulfidation of molybdenum be realized, but also the crystal structure of molybdenum disulfide can be effectively regulated, so that low-crystallinity molybdenum disulfide is transformed into highly crystalline and ordered nano-molybdenum disulfide crystals. And under high-temperature conditions, it is beneficial for excessive sulfur to sublime to expose more active sites, and at the same time, it is beneficial for the doping of vanadium to increase the formation of unsaturated molybdenum sites, further improving the catalytic performance of the catalytic material.

[0029] The oxygen-free environment of the present invention is under a protective atmosphere (such as nitrogen, argon, helium) or vacuum.

[0030] The present invention also provides an application of a vanadium-molybdenum disulfide / aluminum oxide composite material, which is used for catalytically cracking hydrogen sulfide to prepare sulfur and hydrogen. The vanadium-molybdenum disulfide / aluminum oxide composite material provided by the present invention also has an efficient catalytic cracking effect on hydrogen sulfide under high-temperature conditions, especially under common industrial high-temperature conditions (such as above 600 °C), showing excellent hydrogen sulfide catalytic cracking efficiency, which benefits from the active sites of the molybdenum disulfide structure regulated by vanadium doping and the enhanced thermal stability of the aluminum oxide support.

[0031] As a preferred embodiment, the mass-volume ratio of the vanadium-molybdenum disulfide / aluminum oxide composite material to the hydrogen sulfide gas is 0.1~10 mg / mL.

[0032] As a preferred embodiment, the volume concentration of the hydrogen sulfide gas is 0.01~100%.

[0033] As a preferred solution, the temperature range of the thermal cracking is 400~1500 °C. As the temperature increases, the thermal cracking efficiency of hydrogen sulfide by the vanadium-molybdenum disulfide / aluminum oxide composite material first increases and then tends to be stable. Therefore, the further preferred temperature range of the thermal cracking is 800~1000 °C.

[0034] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0035] The active ingredient of the vanadium-molybdenum disulfide / aluminum oxide composite material of the present invention, the amorphous vanadium-doped molybdenum disulfide nanoparticles, have excellent dispersion and stable combination on the surface of the porous aluminum oxide carrier, have strong thermal stability and hydrogen sulfide corrosion resistance, and have high activity in catalyzing the thermal decomposition of hydrogen sulfide.

[0036] The preparation method of the vanadium-molybdenum disulfide / aluminum oxide composite material of the present invention is simple to operate, mild in conditions, and low in cost, and is suitable for large-scale industrial production.

[0037] Compared with the existing catalytic materials, the vanadium-molybdenum disulfide / aluminum oxide composite material of the present invention realizes the optimization of the crystal structure of molybdenum disulfide by amorphous vanadium doping, forms more active sites, and the constraint effect of the porous aluminum oxide carrier effectively prevents the high-temperature agglomeration behavior of molybdenum disulfide, thereby improving the overall catalytic efficiency.

[0038] The vanadium-molybdenum disulfide / aluminum oxide composite material catalyst of the present invention is applicable to various hydrogen sulfide treatment processes. Especially in the context of the rapid development of the hydrogen production industry, it has great market prospects. Its economy and environmental protection enable it to replace the traditional desulfurization process and be expanded into a multifunctional catalytic material, providing a new path for efficient hydrogen production and comprehensive resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic process flow diagram for preparing the vanadium-molybdenum disulfide / aluminum oxide composite material of the present invention.

[0040] Figure 2 It is a schematic diagram of the hydrogen sulfide cracking efficiency of the vanadium-molybdenum disulfide / aluminum oxide composite materials prepared in Example 1, Example 2, and Example 3 of the present invention.

[0041] Figure 3 It is a schematic diagram of the long-term hydrogen sulfide cracking test of the vanadium-molybdenum disulfide / aluminum oxide composite material prepared in Example 2 of the present invention.

[0042] Figure 4 It is a schematic diagram of the hydrogen sulfide cracking efficiency at different temperatures of the vanadium-molybdenum disulfide / aluminum oxide composite material prepared in Example 2 of the present invention.

[0043] Figure 5Schematic diagram of the hydrogen sulfide cracking efficiency of the materials prepared in Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention.

[0044] Figure 6 XRD patterns of the vanadium-molybdenum disulfide / aluminum oxide composites prepared in Example 1, Example 2, and Example 3 of the present invention.

[0045] Figure 7 Scanning electron micrograph of the vanadium-molybdenum disulfide / aluminum oxide composite prepared in Example 2 of the present example.

[0046] Figure 8 R-space fitting curve of the vanadium element Fourier transform extended X-ray absorption fine structure (EXAFS) of the vanadium-molybdenum disulfide / aluminum oxide composite prepared in Example 2 of the present invention. Detailed description of the specific implementation

[0047] The technical solutions in the embodiments of the present invention will be described in detail in conjunction with the accompanying drawings. The described embodiments are only partial embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention. The technical solutions between the embodiments can be combined with each other, but it must be ensured that it can be realized by those of ordinary skill in the art. If there are contradictions or impossibilities in the combination of technical solutions, it should be considered that the combination is not established and is not within the protection scope of the present invention. For the numerical range in the embodiments, unless otherwise specified, any value between each endpoint and including the endpoints can be selected. The technical and scientific terms used in the present invention are consistent with the understanding of those of ordinary skill in the art of the prior art, and the prior art methods, devices, and materials similar or equivalent to those described in the embodiments can also be adopted. The following specific embodiments are preferred embodiments, and those of ordinary skill in the art can make improvements and refinements without departing from the principle, and these improvements also fall within the protection scope of the present invention. The specific embodiments do not limit the protection scope of the present invention, and changing the embodiments does not affect the protection scope of the main claims.

[0048] The following cases are all carried out in a high-temperature fluidized bed reaction device. During the experiment, 20 mg of the catalyst was weighed and placed in a quartz filling column with an inner diameter of 3 mm, and the hydrogen sulfide cracking performance was tested in the temperature range of 600 °C to 1000 °C. The experimental conditions were as follows: the flow rate of the flue gas containing hydrogen sulfide was set at 20 mL / min, the hydrogen sulfide concentration was 1%, and the balance gas was nitrogen. The change in hydrogen sulfide concentration was monitored in real time by an on-line hydrogen sulfide gas analyzer to evaluate the cracking performance and stability of the catalyst.

[0049] Example 1

[0050] Ammonium molybdate tetrahydrate (0.260 g) and ammonium metavanadate (0.009 g) were dissolved in 40 mL of deionized water. Subsequently, 1 g of amorphous porous alumina was weighed, 20 mL of ethanol was added as a dispersant, and it was thoroughly mixed with the above mixed solution. Then, 0.5 g of thioacetamide was added to form a sulfidation reaction solution. The mixed solution was transferred to a high-pressure reactor and hydrothermally treated at 180 °C for 24 hours. After the reaction, it was naturally cooled to room temperature, the black precipitate was collected by filtration, and it was alternately washed with ethanol and deionized water to obtain a precursor material. The precursor material was placed in a vacuum environment and dried at 60 °C for 10 hours, then transferred to a tubular furnace, heated to 800 °C at a heating rate of 5 °C / min under nitrogen protection, and held for 2 hours. Finally, it was naturally cooled to obtain a vanadium-molybdenum disulfide / alumina composite material.

[0051] For the vanadium-molybdenum disulfide / alumina composite material obtained in Example 1, the theoretical molar ratio of vanadium / molybdenum ions was 5:95, denoted as AMV1. The hydrogen sulfide cracking performance of AMV1 was tested at 800 °C. After stabilization, the cracking efficiency reached 65%, showing excellent catalytic activity and stability, which proved its application potential in high-temperature hydrogen sulfide treatment.

[0052] Example 2

[0053] Ammonium molybdate tetrahydrate (0.248 g) and ammonium metavanadate (0.018 g) were dissolved in 40 mL of deionized water. Subsequently, 1 g of amorphous porous alumina was weighed, 20 mL of ethanol was added as a dispersant, and it was thoroughly mixed with the above mixed solution. Then, 0.5 g of thioacetamide was added to form a sulfidation reaction solution. The mixed solution was transferred to a high-pressure reactor and hydrothermally treated at 180 °C for 24 hours. After the reaction, it was naturally cooled to room temperature, the black precipitate was collected by filtration, and it was alternately washed with ethanol and deionized water to obtain a precursor material. The precursor material was placed in a vacuum environment and dried at 60 °C for 10 hours, then transferred to a tubular furnace, heated to 800 °C at a heating rate of 5 °C / min under nitrogen protection, and held for 2 hours. Finally, it was naturally cooled to obtain a vanadium-molybdenum disulfide / alumina composite material.

[0054] For the vanadium-molybdenum disulfide / alumina composite material obtained in Example 2, the theoretical molar ratio of vanadium / molybdenum ions was 10:90, denoted as AMV2. The hydrogen sulfide cracking performance of the AMV2 sample was tested at 800 °C. After stabilization, the cracking efficiency reached 72%, which was further improved compared to the cracking efficiency of AMV1.

[0055] Example 3

[0056] Ammonium molybdate tetrahydrate (0.220 g) and ammonium metavanadate (0.036 g) were dissolved in 40 mL of deionized water. Subsequently, 1 g of amorphous porous alumina was weighed, 20 mL of ethanol was added as a dispersant, and it was thoroughly mixed with the above mixed solution. Then, 0.5 g of thioacetamide was added to form a sulfidation reaction solution. The mixed solution was transferred to a high-pressure reactor and hydrothermally treated at 180 °C for 24 hours. After the reaction ended, it was naturally cooled to room temperature. The black precipitate was collected by filtration and washed alternately with ethanol and deionized water to obtain a precursor material. The precursor material was placed in a vacuum environment and dried at 60 °C for 10 hours. Then it was transferred to a tubular furnace and heated to 800 °C at a heating rate of 5 °C / min under nitrogen protection and held for 2 hours. Finally, it was naturally cooled to obtain a vanadium-molybdenum disulfide / alumina composite material.

[0057] For the vanadium-molybdenum disulfide / alumina composite material obtained in Example 3, the theoretical molar ratio of vanadium / molybdenum ions was 20:80, denoted as AMV3. The AMV3 sample was tested for hydrogen sulfide cracking performance at 800 °C. After stabilization, the cracking efficiency reached 69%, showing a slight decrease compared to the cracking efficiency of AMV2.

[0058] Example 4

[0059] Ammonium molybdate tetrahydrate (0.248 g) and ammonium metavanadate (0.018 g) were dissolved in 40 mL of deionized water. Subsequently, 1 g of amorphous porous alumina was weighed, 20 mL of ethanol was added as a dispersant, and it was thoroughly mixed with the above mixed solution. Then, 0.5 g of thioacetamide was added to form a sulfidation reaction solution. The mixed solution was transferred to a high-pressure reactor and hydrothermally treated at 200 °C for 24 hours. After the reaction ended, it was naturally cooled to room temperature. The black precipitate was collected by filtration and washed alternately with ethanol and deionized water to obtain a precursor material. The precursor material was placed in a vacuum environment and dried at 60 °C for 10 hours. Then it was transferred to a tubular furnace and heated to 900 °C at a heating rate of 5 °C / min under nitrogen protection and held for 2 hours. Finally, it was naturally cooled to obtain a vanadium-molybdenum disulfide / alumina composite material.

[0060] For the vanadium-molybdenum disulfide / alumina composite material obtained in Example 4, the theoretical molar ratio of vanadium / molybdenum ions was 10:90, denoted as AMV4. The AMV4 sample was tested for hydrogen sulfide cracking performance at 800 °C. After stabilization, the cracking efficiency reached 72%, showing the same catalytic performance as AMV2.

[0061] Example 5

[0062] The long-term cracking performance test of the vanadium-molybdenum disulfide / alumina composite material of Example 2 was carried out at 800 °C, and the results are as Figure 3As shown, the hydrogen sulfide cracking efficiency remains at 72% within 10 h, demonstrating its good long-term cracking stability. In addition, the hydrogen sulfide cracking efficiency of AMV2 was evaluated at different temperatures, and the results are as Figure 4 shown. At 600 °C, the cracking efficiency is 50%; at 1000 °C, the cracking efficiency increases to 75%, showing high catalytic performance over a wide operating temperature range.

[0063] Comparative Example 1

[0064] 2.0 g of polyether P123 was dissolved in 40 mL of ethanol, and 3.0 mL of 67% nitric acid and 4.0 g of aluminum isopropoxide were added under vigorous stirring. The mixture was covered with a polyethylene film and continuously stirred at room temperature for about 12 h to ensure thorough mixing. Then, the mixture was placed in an oven at 60 °C and heated for 48 h to allow the solvent to evaporate completely. The dried solid precursor was calcined at 800 °C for 2 h with a heating rate of 2 °C / min, and finally an amorphous porous alumina material was prepared.

[0065] The alumina material prepared in Comparative Example 1 was tested for hydrogen sulfide cracking performance at 800 °C. The test showed that the hydrogen sulfide cracking efficiency was only 50%. Compared with the vanadium-molybdenum disulfide / alumina composite material prepared in Example 2, this comparative example showed lower catalytic performance, indicating that using only the carrier alumina as a catalyst could not effectively improve the hydrogen sulfide cracking efficiency.

[0066] Comparative Example 2

[0067] Ammonium molybdate tetrahydrate (0.278 g) was dissolved in 40 mL of deionized water, and 20 mL of ethanol was added as a dispersant. It was thoroughly mixed with the above mixed solution, and then 0.5 g of thioacetamide was added to form a sulfidation reaction solution. The mixed solution was transferred to a high-pressure reaction kettle and hydrothermally treated at 200 °C for 24 h. After the reaction, it was naturally cooled to room temperature, and the black precipitate was collected by filtration and washed alternately with ethanol and deionized water to obtain a precursor material. The precursor material was placed in a vacuum environment and dried at 60 °C for 10 h, then transferred to a tube furnace, heated to 800 °C at a heating rate of 5 °C / min under nitrogen protection, and held for 2 h, and finally naturally cooled to obtain a molybdenum disulfide material.

[0068] The molybdenum disulfide material obtained in Comparative Example 2 was tested for hydrogen sulfide cracking performance at 800 °C. The initial cracking efficiency was relatively high, but the cracking efficiency gradually decreased to 57%, showing an obvious trend of catalytic deactivation. The performance degradation was related to the thermal stability of molybdenum disulfide itself and the reduction of active sites during the hydrogen sulfide cracking process. In addition, without introducing vanadium or alumina as co-components, its catalytic performance was significantly lower than that of the composite material in Example 2. This further illustrates the important role of vanadium element and alumina matrix in enhancing the thermal stability and catalytic activity of the composite catalytic material.

[0069] Comparative Example 3

[0070] Ammonium molybdate tetrahydrate (0.278 g) was dissolved in 40 mL of deionized water. Subsequently, 1 g of amorphous porous alumina was weighed, 20 mL of ethanol was added as a dispersant, and it was thoroughly mixed with the above mixed solution. Then, 0.5 g of thioacetamide was added to form a sulfidation reaction solution. The mixed solution was transferred to a high-pressure reaction kettle and hydrothermally treated at 200 °C for 24 hours. After the reaction, it was naturally cooled to room temperature, the black precipitate was collected by filtration, and washed alternately with ethanol and deionized water to obtain a precursor material. The precursor material was placed in a vacuum environment, dried at 60 °C for 10 hours, then transferred to a tube furnace, heated to 800 °C at a heating rate of 5 °C / min under nitrogen protection, and held for 2 hours, and finally naturally cooled to obtain a molybdenum disulfide / alumina composite material.

[0071] For the molybdenum disulfide / alumina composite material obtained in Comparative Example 3, the loading amount of molybdenum disulfide was 20 wt%. The hydrogen sulfide cracking performance was tested at 800 °C, and the cracking efficiency was only 62%, which was significantly lower than that of the vanadium-molybdenum disulfide / alumina composite material in Example 2. Although this sample showed certain catalytic activity, due to the lack of introduction of vanadium element as an auxiliary active component, the catalytic performance was limited. This indicates that the introduction of vanadium element can significantly improve the synergy and overall performance of the catalytic material.

[0072] The crystal structures of the materials prepared in Example 1, Example 2, and Example 3 were analyzed by XRD, as Figure 6 shown. The diffraction peaks at 37.7 ° , 45.9 ° , 94.7 ° were for the carrier alumina, and the diffraction peaks at 14.4 ° , 32.7 ° , 39.6 ° , 58.4 °The diffraction peaks at [specific location] are consistent with the (002), (100), (103), and (110) crystal planes of molybdenum disulfide. No peaks of polymeric molybdenum disulfide were observed in the catalyst, indicating that alumina effectively restricts the agglomeration behavior of molybdenum disulfide nanosheets and prevents their combination into polymeric molybdenum disulfide during the high-temperature process. The addition of vanadium to molybdenum disulfide did not affect the crystal structure of molybdenum disulfide. The presence of vanadium sulfide-related crystal phases was not detected in AM1, AM2, and AMV3, indicating that vanadium exists in the molybdenum disulfide lattice in an amorphous form, which is conducive to the formation of more sulfur vacancies and thus improves the hydrogen sulfide cracking performance of the catalyst.

[0073] SEM analysis was performed on the vanadium-molybdenum disulfide / alumina composite material prepared in Example 2, and the results are as Figure 7 shown. Molybdenum disulfide is stacked on the surface of alumina in a three-dimensional sheet-like morphology, and this loading morphology exposes more active components, effectively enhancing the catalytic performance.

[0074] The Fourier transform extended X-ray absorption fine structure (EXAFS) R-space fitting curve of the vanadium element in the vanadium-molybdenum disulfide / alumina composite material prepared in Example 2 is as Figure 8 shown. Based on the Fourier transform extended X-ray absorption fine structure (EXAFS) R-space fitting, there is only a single significant main scattering peak in the local coordination environment of vanadium. The fitting results show that this peak completely belongs to the interaction between vanadium and sulfur atoms in the first coordination shell (V-S bond), and the corresponding average coordination number is 3.5 ± 0.4. It was further verified by full-spectrum fitting and multi-shell structure models, and no scattering signals related to V-V, V-O, or V-Mo were found. The above indicates that the coordination environment of vanadium is dominated by sulfur atoms, excluding the possibility of an oxidation state (V-O bond) or a vanadium-molybdenum hybrid structure. Vanadium atoms are highly dispersed and embedded in the material matrix in a completely isolated single-atom form, without forming vanadium metal clusters or vanadium metal sulfides.

[0075] The content disclosed above is only the preferred embodiment of the present invention, aiming to better illustrate the technical solution of the present invention, rather than limiting the protection scope of the claims of the present invention. Those of ordinary skill in the art can understand and implement all or part of the above processes, and make equivalent transformations or improvements within the technical concept and scope of the claims of the present invention. These transformations or improvements still fall within the protection scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention, or the direct or indirect application of the solutions to other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A vanadium-molybdenum disulfide / aluminum oxide composite material for catalytically cracking hydrogen sulfide to prepare sulfur and hydrogen, characterized in that: It is composed of amorphous vanadium-doped molybdenum disulfide nanoparticles supported on a porous alumina carrier; In the amorphous vanadium-doped molybdenum disulfide nanoparticles, the molar amounts of vanadium and molybdenum elements are 1-50% of the molar amount of alumina in the porous alumina carrier; In the amorphous vanadium-doped molybdenum disulfide nanoparticles, the molar amount of vanadium element is 1-50% of the molar amount of molybdenum element; The vanadium-molybdenum disulfide / alumina composite material is prepared by the following method, including the following steps: (1) Mix the porous alumina carrier, sulfur source and molybdenum-vanadium mixed metal salt solution to form a sulfidation reaction solution; (2) Transfer the sulfidation reaction solution to an autoclave for hydrothermal reaction to obtain a precursor material; (3) Dry and calcine the precursor material under an oxygen-free condition to obtain the product.

2. The preparation method of a vanadium-molybdenum disulfide / aluminum oxide composite material according to claim 1, characterized in that: It includes the following steps: (1) Mix the porous alumina carrier, sulfur source and molybdenum-vanadium mixed metal salt solution to form a sulfidation reaction solution; (2) Transfer the sulfidation reaction solution to an autoclave for hydrothermal reaction to obtain a precursor material; (3) Dry and calcine the precursor material under an oxygen-free condition to obtain the product.

3. According to the preparation method of a vanadium-molybdenum disulfide / alumina composite material described in claim 2, wherein: The concentration of molybdenum ions in the molybdenum-vanadium mixed metal salt solution is 0.001-1 mol / L; The molar ratio of vanadium ions to molybdenum ions in the molybdenum-vanadium mixed metal salt solution is 1-50:100; The ratio of the molar amount of alumina in the porous alumina carrier to the total molar amount of vanadium ions and molybdenum ions in the molybdenum-vanadium mixed metal salt solution is 100:1-50; The ratio of the molar amount of sulfur element in the sulfur source to the total molar amount of vanadium ions and molybdenum ions in the molybdenum-vanadium mixed metal salt solution is 2-6:

1.

4. According to the preparation method of a vanadium-molybdenum disulfide / alumina composite material described in claim 2, wherein: The porous alumina carrier includes at least one of spherical porous alumina, fibrous porous alumina, and amorphous porous alumina; The molybdenum-vanadium mixed metal salt solution contains at least one molybdenum salt such as ammonium dimolybdate, ammonium tetramolybdate, ammonium heptamolybdate, ammonium tetrathiomolybdate; The molybdenum-vanadium mixed metal salt solution contains at least one vanadium salt such as ammonium metavanadate, ammonium polyvanadate; The sulfur source includes at least one of sodium sulfide, thiourea, sodium thiosulfate, thioacetamide.

5. A method for preparing a vanadium-molybdenum disulfide / aluminum oxide composite material according to any one of claims 3 to 4, characterized in that: The conditions of the hydrothermal reaction are: temperature is 60-200 °C, and time is 1-24 h.

6. A method for preparing a vanadium-molybdenum disulfide / aluminum oxide composite material according to any one of claims 2 to 4, characterized in that: The conditions of the drying are: temperature is 30-120 °C, and time is 1-48 h.

7. A method for preparing a vanadium-molybdenum disulfide / aluminum oxide composite material according to any one of claims 2 to 4, characterized in that: The conditions of the calcination are: temperature is 400-1000 °C, and time is 1-24 h.

8. Use of a vanadium-molybdenum disulfide / aluminum oxide composite material according to claim 1, characterized in that: It is used for catalytically cracking hydrogen sulfide to prepare sulfur and hydrogen.

9. According to the application of a vanadium-molybdenum disulfide / alumina composite material described in claim 8, wherein: The mass-volume ratio of the vanadium-molybdenum disulfide / alumina composite material to hydrogen sulfide gas is 0.1-10 mg / mL; The volume concentration of the hydrogen sulfide gas is 0.01-100%; The temperature range of the thermal cracking is 400-1500 °C.

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