A vanadium pentoxide catalyst, a preparation method thereof and application thereof in preparation of photocatalytic nitrogen fixation products

Abstract

This invention discloses a vanadium pentoxide catalyst, its preparation method, and its application in the preparation of photocatalytic nitrogen fixation products, relating to the field of catalysts. The method includes the following steps: dissolving vanadium trichloride in a solvent and adding an organic ligand composed of trimesic acid and terephthalic acid; performing a hydrothermal reaction to obtain a vanadium-containing organometallic framework powder; and calcining to obtain vanadium pentoxide powder. This application prepares a vanadium-containing organometallic framework material with high specific surface area and strong adsorption capacity. The generated V₂O₅ material exhibits high responsiveness to visible light in sunlight. Simultaneously, by utilizing the organic ligand to regulate the morphology of vanadium pentoxide during the preparation process, the photocatalytic nitrogen fixation performance of the product is further effectively improved without altering the chemical structure of vanadium pentoxide. The preparation method is simple, and the production and labor costs are low.

Description

Technical Field

[0001] This invention relates to the field of catalysts, and more particularly to a vanadium pentoxide catalyst, its preparation method, and its application in the preparation of photocatalytic nitrogen fixation products. Background Technology

[0002] Ammonia (NH3), a crucial chemical substance, plays a vital role in various fields, including chemical production, food manufacturing, and fertilizer industry. Industrially, NH3 is typically produced via the Haber-Bosch process, but this method suffers from several drawbacks, including demanding reaction conditions, low conversion efficiency, and the release of large amounts of greenhouse gases. Therefore, developing a sustainable method to circumvent these problems and achieve efficient nitrogen fixation is urgently needed. Photocatalytic nitrogen reduction, utilizing the Earth's abundant solar energy, offers new opportunities for NH3 production under environmental conditions. Vanadium pentoxide (V2O5), a semiconductor photocatalyst, is responsive to visible light from sunlight and has already been applied in various photocatalytic fields.

[0003] To date, V2O5 materials have been successfully prepared by various methods, such as high-temperature synthesis, hydrothermal synthesis, and sol-gel synthesis. Metal-organic frameworks (MOFs) are organic-inorganic hybrid materials with intramolecular pores formed by the self-assembly of organic ligands and metal ions or clusters through coordination bonds. MOFs have a huge specific surface area, ordered pore structure, and tunable organic ligands and metal sites, giving them excellent photophysical / chemical properties, thus attracting great attention in the field of photocatalysis. MOFs have unique advantages in photocatalysis. First, MOFs have tunable structure-function, specifically in three aspects: (1) adjusting the light absorption range; (2) improving carrier separation efficiency; and (3) exposed unsaturated metal sites promote photocatalytic reactions. Meanwhile, MOFs materials have large pores and orderly arranged pore structures, as well as a huge specific surface area, which is conducive to the entry of guest molecules, enabling them to directly contact the active sites on MOFs. This shortens the electron transport distance, improves the carrier migration efficiency, and enhances photocatalytic activity, thus showing great application potential in the field of photocatalysis.

[0004] Meanwhile, since the morphology of the catalyst has a significant impact on the performance of photocatalysis, how to regulate the morphology of V2O5 during the preparation of V-MOF and ultimately improve the photocatalytic nitrogen fixation performance has become a problem that needs to be solved in the industry. Summary of the Invention

[0005] This invention provides a vanadium pentoxide catalyst, its preparation method, and its application in the preparation of photocatalytic nitrogen fixation products. By preparing a vanadium-containing organometallic framework material with high specific surface area and strong adsorption capacity, and by controlling the morphology of vanadium pentoxide, the photocatalytic nitrogen fixation performance is improved.

[0006] To address the aforementioned technical problems, one objective of this invention is to provide a method for preparing a vanadium pentoxide catalyst, comprising the following steps:

[0007] (1) Vanadium trichloride is dissolved in a solvent to form a solution, an organic ligand is added, and the mixture is stirred continuously. The organic ligand is composed of pyromellitic acid and terephthalic acid.

[0008] (2) The solution obtained in step (1) was subjected to a hydrothermal reaction, followed by washing, centrifugation, drying and grinding to obtain vanadium-containing organometallic framework powder;

[0009] (3) The vanadium-containing organometallic framework powder was calcined in air to obtain vanadium pentoxide powder.

[0010] By adopting the above technical solution, this application uses metal-organic frameworks (MOFs) as sacrificial templates. The vanadium-containing metal-organic framework (V-MOF) prepared by calcination can retain the original morphology of the MOF template, exhibiting high specific surface area and strong adsorption capacity. The generated V2O5 material is responsive to visible light in sunlight. At the same time, by controlling the organic ligands in the metal-organic framework preparation process, the morphology of vanadium pentoxide can be regulated. Without changing the chemical structure of vanadium pentoxide, the photocatalytic nitrogen fixation performance of the product is further effectively improved. The regulation method is simple and has low production and labor costs.

[0011] As a preferred embodiment, in step (1), the molar ratio of pyromellitic acid and terephthalic acid is (0.5-2):1.

[0012] As a preferred embodiment, in step (1), the molar ratio of vanadium trichloride to the organic ligand is (1-5):1.

[0013] As a preferred embodiment, in step (2), the temperature of the hydrothermal reaction is 160-200℃ and the time is 10-15h.

[0014] As a preferred embodiment, in step (3), the heating rate of calcination is 1-5℃ / min, the calcination temperature is 300-400℃, and the calcination time is 1-3h.

[0015] As a preferred embodiment, in step (1), the solvent is N,N-dimethylformamide.

[0016] As a preferred embodiment, in step (1), 10-20 mL of the solvent is added for every 1 mmol of vanadium trichloride.

[0017] To address the aforementioned technical problems, a second objective of this invention is to provide a method for preparing vanadium pentoxide catalysts.

[0018] As a preferred embodiment, the vanadium pentoxide catalyst has a porous nanoparticle morphology.

[0019] To address the aforementioned technical problems, a third objective of this invention is to provide an application of vanadium pentoxide catalyst in the preparation of photocatalytic nitrogen fixation products.

[0020] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0021] This application prepares vanadium-containing organometallic framework materials with high specific surface area and strong adsorption capacity. The generated V2O5 material has a high response to visible light in sunlight. At the same time, by controlling the organic ligands in the preparation process of the metal-organic framework, the morphology of vanadium pentoxide can be regulated. Without changing the chemical structure of vanadium pentoxide, the photocatalytic nitrogen fixation performance of the product is further effectively improved. The preparation method is simple and has low production and labor costs. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a method for preparing a vanadium pentoxide catalyst according to an embodiment of the present invention.

[0023] Figure 2 : XRD results of the photocatalysts in Example 1 and Comparative Examples 1-2 of this invention;

[0024] Figure 3 : These are the SEM images of the photocatalysts in Example 1 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1

[0027] A vanadium pentoxide catalyst, such as Figure 1 As shown, its preparation method includes the following steps:

[0028] (1) Dissolve 3.60 mmol of vanadium trichloride in 60 mL of anhydrous N,N-dimethylformamide and stir continuously to form a dark green solution;

[0029] (2) Add a mixture of 1.8 mmol terephthalic acid and 1.8 mmol trimellitic acid to the dark green solution in step (1), and stir continuously to obtain a mixed solution;

[0030] (3) The above mixed solution was transferred to a hydrothermal reactor for hydrothermal reaction at a temperature of 180°C for 12 hours. After the reaction was completed, the solution was washed, centrifuged, dried and ground to obtain a blue-green vanadium-containing organometallic framework material, denoted as V-MOF-3.

[0031] (4) The V-MOF-3 powder was calcined in air at a heating rate of 3℃ / min, a calcination temperature of 300℃, and a calcination time of 2h. After cooling to room temperature, yellowish-brown vanadium pentoxide powder was obtained, which was designated as photocatalyst 3.

[0032] Example 2

[0033] A vanadium pentoxide catalyst is prepared in the same way as in Example 1, with the same steps, reagents and process parameters. The difference is that the reaction temperature is 160°C in step (3).

[0034] Example 3

[0035] A vanadium pentoxide catalyst is prepared in the same way as in Example 1, with the same steps, reagents and process parameters. The difference is that the reaction temperature is 120°C in step (3).

[0036] Comparative Example 1

[0037] A vanadium pentoxide catalyst, the preparation method of which includes the following steps:

[0038] (1) Dissolve 3.60 mmol of vanadium trichloride in 60 mL of anhydrous N,N-dimethylformamide and stir continuously to form a dark green solution;

[0039] (2) Add 3.60 mmol of pyromellitic acid to the dark green solution in step (1) and stir continuously to obtain a mixed solution;

[0040] (3) The above mixed solution was transferred to a hydrothermal reactor for hydrothermal reaction at a temperature of 180°C for 12 hours. After the reaction was completed, the solution was washed, centrifuged, dried and ground to obtain a blue-green vanadium-containing organometallic framework material, denoted as V-MOF-1.

[0041] (4) The V-MOF-1 powder was calcined in air at a heating rate of 3℃ / min, a calcination temperature of 300℃, and a calcination time of 2h. After cooling to room temperature, yellowish-brown vanadium pentoxide powder was obtained, which was designated as photocatalyst 1.

[0042] Comparative Example 2

[0043] A vanadium pentoxide catalyst, the preparation method of which includes the following steps:

[0044] (1) Dissolve 3.60 mmol of vanadium trichloride in 60 mL of anhydrous N,N-dimethylformamide and stir continuously to form a dark green solution;

[0045] (2) Add 3.60 mmol of terephthalic acid to the dark green solution in step (1) and stir continuously to obtain a mixed solution;

[0046] (3) The above mixed solution was transferred to a hydrothermal reactor for hydrothermal reaction at a temperature of 180°C for 12 hours. After the reaction was completed, the solution was washed, centrifuged, dried and ground to obtain a blue-green vanadium-containing organometallic framework material, denoted as V-MOF-2.

[0047] (4) The V-MOF-2 powder was calcined in air at a heating rate of 3℃ / min, a calcination temperature of 300℃, and a calcination time of 2h. After cooling to room temperature, yellowish-brown vanadium pentoxide powder was obtained, which was designated as photocatalyst 2.

[0048] like Figure 2 As shown, the characteristic peaks of the XRD results of the photocatalysts in Example 1 and Comparative Examples 1-2 are consistent, indicating that the variation of ligands in the vanadium-containing organometallic framework does not change the basic structure of V2O5. Figure 3 As shown, the SEM images of the photocatalysts in Example 1 and Comparative Examples 1-2 show that the photocatalyst 3 in Example 1 has a porous nanoparticle morphology, the photocatalyst 1 in Comparative Example 1 has a block morphology, and the photocatalyst 2 in Comparative Example 2 has a nano-strip morphology. This indicates that the change in ligands in the vanadium-containing organometallic framework material only changes the final morphological characteristics of the photocatalyst.

[0049] Application examples

[0050] The application of a vanadium pentoxide catalyst in photocatalytic nitrogen fixation includes the following steps:

[0051] (1) Weigh 10 mg of the photocatalyst prepared in any of Examples 1-5 and Comparative Examples 1-2, disperse it in 100 mL of ultrapure water, without adding any sacrificial agent, and place it in a photocatalytic reaction bottle;

[0052] (2) Nitrogen gas was introduced for 30 minutes to remove oxygen. During the photocatalysis process, circulating nitrogen gas was continued to keep the entire reaction system in a nitrogen-saturated atmosphere. A 300W xenon lamp was used for continuous illumination.

[0053] (3) Take 4 mL of reaction solution every 15 min, centrifuge to remove the catalyst, and filter the catalyst with a 0.22 μm filter. Detect the generated ammonium ions in the supernatant with Nessler reagent (CAS No.: 7783-33-7) produced by McLean. The yield results are shown in Table 1 below.

[0054] Table 1 - Yields of ammonium ions in photocatalysts used in photocatalytic nitrogen fixation reactions in the examples and comparative examples of this application.

[0055] Testing items <![CDATA[Ammonium ion yield (μmol / g cat / h)]]> Example 1 85.96 Example 2 81.86 Example 3 75.10 Comparative Example 1 56.14 Comparative Example 2 29.83

[0056] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that 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 for those skilled in the art.

Claims

1. The application of a vanadium pentoxide catalyst in the preparation of photocatalytic nitrogen fixation products, characterized in that, The preparation method of the vanadium pentoxide catalyst includes the following steps: (1) Vanadium trichloride is dissolved in a solvent to form a solution, an organic ligand is added, and the mixture is stirred continuously. The organic ligand is composed of pyromellitic acid and terephthalic acid. (2) The solution obtained in step (1) is subjected to a hydrothermal reaction, followed by washing, centrifugation, drying and grinding to obtain vanadium-containing organometallic framework powder; (3) Calcining the vanadium-containing organometallic framework powder in air atmosphere to obtain vanadium pentoxide powder; In step (1), the molar ratio of pyromellitic acid and terephthalic acid is (0.5-2):1; In step (1), the molar ratio of vanadium trichloride to the organic ligand is (1-5):1; In step (2), the hydrothermal reaction temperature is 160-200℃ and the time is 10-15h; In step (3), the heating rate of calcination is 1-5℃ / min, the calcination temperature is 300-400℃, and the calcination time is 1-3h.

2. The application of the vanadium pentoxide catalyst as described in claim 1 in the preparation of photocatalytic nitrogen fixation products, characterized in that, In step (1), the solvent is N,N-dimethylformamide.

3. The application of the vanadium pentoxide catalyst as described in claim 1 in the preparation of photocatalytic nitrogen fixation products, characterized in that, In step (1), 10-20 mL of the solvent is added for every 1 mmol of vanadium trichloride.

4. The application of the vanadium pentoxide catalyst as described in claim 1 in the preparation of photocatalytic nitrogen fixation products, characterized in that, The vanadium pentoxide catalyst has a porous nanoparticle morphology.

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