High-entropy metal alkene catalyst for ammoxidation as well as preparation method and application of high-entropy metal alkene catalyst

Abstract

The invention belongs to the technical field of catalytic materials, and particularly relates to a high-entropy metal alkene catalyst for ammoxidation, a preparation method and application. The high-entropy metal alkene catalyst is a PdCoNiPtZn high-entropy alloy, and is of a two-dimensional alkene structure; the preparation method of the high-entropy metal alkene catalyst comprises the following steps: S1, uniformly mixing palladium acetylacetonate, nickel acetylacetonate, platinum acetylacetonate, cobalt acetylacetonate, zinc acetylacetonate, ascorbic acid and tungsten hexacarbonyl to obtain a mixture I; s2, adding the mixture I obtained in the step S1 into a mixed solution of N, N-dimethylformamide and glacial acetic acid to obtain a mixed solution; s3, carrying out ultrasonic oscillation treatment on the mixed solution to obtain a uniform solution, and then putting the uniform solution into a sealed container to react to obtain a mixed solution II; and S4, adding an ethanol solution into the mixed solution II, and then performing centrifugation, cleaning and drying treatment to obtain the high-entropy metal alkene catalyst.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic materials, and in particular relates to a high entropy metal olefin catalyst for ammonia oxidation, a preparation method and an application thereof. Background Art

[0002] In recent years, ammonia has been proposed as a promising candidate fuel for anion exchange membrane fuel cell technology. Direct ammonia is a carbon-free technology that combines the high energy density of ammonia with the high efficiency of fuel cells. However, the technology faces two major challenges: ammonia crossover (due to the high solubility of ammonia in water) and the slow ammonia oxidation reaction.

[0003] Platinum is considered to be the most effective catalyst for ammonia oxidation reactions because of its moderate binding strength to nitrogen adsorbents. However, its performance in actual ammonia oxidation reactions is far from satisfactory. Since platinum metal is prone to agglomeration, its atomic utilization is too low. Metalloene is mainly composed of an atomic thin layer of insufficiently coordinated metal atoms. This structure can provide an ultra-high specific surface area, improve atomic utilization and expose highly active surface metal atoms. Therefore, it can greatly improve the catalyst activity. In addition, pure platinum catalysts are prone to catalyst poisoning, resulting in a sharp decline in catalytic performance, while PdCoNiPtZn high entropy metalloene catalysts have extremely strong anti-toxicity, allowing the catalyst to remain active. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a high entropy metal olefin catalyst for ammonia oxidation, a preparation method and an application thereof.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A high entropy metal olefin catalyst for ammonia oxidation, wherein the high entropy metal olefin catalyst is a PdCoNiPtZn high entropy alloy having a two-dimensional olefin structure.

[0007] Furthermore, the two-dimensional olefin-like structure is a curved sheet-like structure.

[0008] Furthermore, the single layer thickness of the high entropy metal olefin catalyst is 0.1-0.3 nm.

[0009] Furthermore, the atomic proportion of a single metal element contained in the high entropy metal olefin catalyst is 5-50%.

[0010] A method for preparing a high entropy metal olefin catalyst for ammoxidation, the preparation method comprising the following steps:

[0011] S1, mixing palladium acetylacetonate, nickel acetylacetonate, platinum acetylacetonate, cobalt acetylacetonate, zinc acetylacetonate, ascorbic acid and tungsten hexacarbonyl uniformly to obtain a mixture 1;

[0012] S2, adding the mixture obtained in step S1 to a mixed solution of N,N-dimethylformamide and glacial acetic acid to obtain a mixed solution;

[0013] S3, subjecting the mixed solution to ultrasonic oscillation to obtain a uniform solution, and then placing the uniform solution into a sealed container for reaction to obtain a second mixed solution;

[0014] S4. Add ethanol solution to the mixed solution 2, and then obtain a high entropy metal olefin catalyst after centrifugation, washing and drying.

[0015] Furthermore, the mass ratio of palladium acetylacetonate, nickel acetylacetonate, platinum acetylacetonate, cobalt acetylacetonate, zinc acetylacetonate, ascorbic acid and tungsten hexacarbonyl is: (0.1-1.5): (0.1-1.5): (0.1-1.5): (0.1-1.5): (0.1-1.5): (4-8): (3-6).

[0016] Furthermore, when preparing the mixed solution, the molar ratio of N,N-dimethylformamide:glacial acetic acid is 4:1.

[0017] Furthermore, in step S3, the temperature during ultrasonic oscillation is 20-35° C., and the oscillation time is 1-4 hours; the reaction temperature in the sealed container is 60-90° C., and the reaction time is 6-18 hours.

[0018] Furthermore, in step S4, the rotation speed of the centrifugal treatment is 6000-10000 rpm, and the centrifugal treatment time is 1-2 hours; the cleaning liquid used for cleaning is an ethanol solution; and the temperature during drying is 50-80°C.

[0019] The high entropy metal olefin catalyst for ammonia oxidation described above is used to prepare ammonia in an ammonia oxidation reaction.

[0020] Beneficial effects of the present invention:

[0021] 1. Compared with conventional commercial platinum-iridium-carbon catalysts, the high entropy metal olefin catalyst for ammonia oxidation provided in the present application has significantly improved ammonia oxidation activity, can prevent catalyst poisoning, and has good stability.

[0022] 2. The preparation method of the high entropy metal olefin catalyst provided in this application requires raw materials that are all bulk commercial products and have low cost.

[0023] 3. The preparation method of the high entropy metal olefin catalyst for ammonia oxidation provided in the present application has the advantages of simple and safe preparation process and is easy to achieve large-scale preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 is a scanning electron microscope image of the PdCoNiPtZn catalyst in Example 1.

[0026] Figure 2 The X-ray diffraction patterns of Example 1 and Comparative Examples 1-4 are shown.

[0027] Figure 3 It is a performance comparison chart of Example 1 and Comparative Examples 1-4.

[0028] Figure 4 It is a stability comparison chart of Example 1 and Comparative Examples 1-4. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] As mentioned above, the present application relates to a method for preparing a high entropy metal olefin catalyst for ammoxidation. The metal olefin catalyst described in the present application is prepared by a wet chemical method. Compared with the existing commercial platinum-iridium-carbon catalyst, the high entropy metal olefin catalyst prepared in the present application has higher activity and good application prospects.

[0031] Unless otherwise specified, all numbers appearing in the specification and claims of this application, such as temperature and time, should not be understood as absolutely precise values. Due to the standard deviation of the measurement technology, the measured values ​​inevitably have certain experimental errors.

[0032] The present application is described in detail below with reference to embodiments, but is not limited to these embodiments.

[0033] Unless otherwise specified, the raw materials and reagents in the examples of the present application can be purchased through commercial channels. The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0034] Preparation of high entropy metal olefin catalyst: Add acetylacetonate palladium, acetylacetonate cobalt, acetylacetonate nickel, acetylacetonate platinum, acetylacetonate zinc, ascorbic acid and hexacarbonyl tungsten to a mixed solution of N,N-dimethylformamide and glacial acetic acid, ultrasonicate for 1 to 4 hours, then react at 80°C for 1 hour, cool to room temperature, collect by centrifugation, and wash to obtain a high entropy metal olefin catalyst.

[0035] Example 1

[0036] This embodiment provides a method for preparing a high entropy metal olefin catalyst for ammoxidation, specifically:

[0037] S1. 10 mg of palladium acetylacetonate, 10 mg of cobalt acetylacetonate, 8 mg of nickel acetylacetonate, 10 mg of platinum acetylacetonate, 6 mg of zinc acetylacetonate, 80 mg of ascorbic acid and 60 mg of tungsten hexacarbonyl are uniformly mixed to obtain a mixture 1;

[0038] S2, adding the mixture obtained in step S1 to a mixed solution of 16 mL of N,N-dimethylformamide and 4 mL of glacial acetic acid to obtain a mixed solution;

[0039] S3, subjecting the mixed solution to ultrasonic oscillation to obtain a uniform solution, the ultrasonic treatment temperature is 25°C, the ultrasonic oscillation time is 1h, and then the uniform solution is placed in a sealed container for reaction to obtain a mixed solution 2, the reaction temperature is 80°C, and the reaction time is 12h;

[0040] S4. Cooling the mixed solution 2 to room temperature, then adding ethanol solution to the mixed solution 2, washing with ethanol for 6 times, and then centrifuging, washing, and drying to obtain a high entropy metal olefin catalyst.

[0041] Comparative Example 1

[0042] Compared with Example 1, in the preparation of Comparative Example 1, cobalt acetylacetonate is missing from the preparation raw materials, and other preparation raw materials are the same as those in Example 1, to prepare a high entropy metal olefin catalyst.

[0043] Comparative Example 2

[0044] Compared with Example 1, in the preparation of Comparative Example 2, nickel acetylacetonate is missing from the preparation raw materials, and other preparation raw materials are the same as those in Example 1, to prepare a high entropy metal olefin catalyst.

[0045] Comparative Example 3

[0046] Compared with Example 1, in the preparation of Comparative Example 3, acetylacetonate platinum is missing from the preparation raw materials, and other preparation raw materials are the same as those in Example 1, to prepare a high entropy metal olefin catalyst.

[0047] Comparative Example 4

[0048] Compared with Example 1, in Comparative Example 4, zinc acetylacetonate is missing from the raw materials for preparation, and other raw materials for preparation are the same as those in Example 1, thereby obtaining a high entropy metal olefin catalyst.

[0049] Performance Test:

[0050] The test of the catalyst for ammonia oxidation prepared in Example 1 and Comparative Examples 1 to 4 was carried out in the following specific steps:

[0051] (1) Typically, 2 mg of catalyst, 0.5 mg of acetylene black, and 10 μL of Nafion solution (5 wt%) were dispersed in 190 μL of ethanol and ultrasonicated for at least 1 hour to form a uniform ink. 15 μL of catalyst ink was loaded on a 0.196 cm -2 The electrode was dried at room temperature for 30 minutes;

[0052] (2) In 1 M potassium hydroxide solution (argon atmosphere), the voltammetry was performed at 50 mV s -1 Scan rate, activation was performed in the voltage range of 0.22-1.12 V (vs. RHE) until the CV curves completely overlapped;

[0053] (3) The activated catalyst was placed in a 1M potassium hydroxide + 0.1M ammonia solution (argon atmosphere) and the voltammetry was performed at 5mV s -1 Scan rate, take the overlapping curve to get the catalyst performance.

[0054] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

[0055] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0056] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A high entropy metal olefin catalyst for ammoxidation, characterized in that: The high entropy metal olefin catalyst is a PdCoNiPtZn high entropy alloy, which is a two-dimensional olefin structure.

2. A high entropy metal olefin catalyst for ammoxidation according to claim 1, characterized in that: The two-dimensional olefin-like structure is a bent sheet-like structure.

3. A high entropy metal olefin catalyst for ammoxidation according to claim 1, characterized in that: The single layer thickness of the high entropy metal olefin catalyst is 0.1-0.3 nm.

4. A high entropy metal olefin catalyst for ammoxidation according to claim 1, characterized in that: The atomic proportion of a single metal element contained in the high entropy metal olefin catalyst is 5-50%.

5. A method for preparing a high entropy metal olefin catalyst for ammoxidation, characterized in that: The preparation method comprises the following steps: S1, mixing palladium acetylacetonate, nickel acetylacetonate, platinum acetylacetonate, cobalt acetylacetonate, zinc acetylacetonate, ascorbic acid and tungsten hexacarbonyl uniformly to obtain a mixture 1; S2, adding the mixture obtained in step S1 to a mixed solution of N,N-dimethylformamide and glacial acetic acid to obtain a mixed solution; S3, subjecting the mixed solution to ultrasonic oscillation to obtain a uniform solution, and then placing the uniform solution into a sealed container for reaction to obtain a second mixed solution; S4. Add ethanol solution to the mixed solution 2, and then obtain a high entropy metal olefin catalyst after centrifugation, washing and drying.

6. The method for preparing a high entropy metal olefin catalyst for ammoxidation according to claim 5, characterized in that: The mass ratios of palladium acetylacetonate, nickel acetylacetonate, platinum acetylacetonate, cobalt acetylacetonate, zinc acetylacetonate, ascorbic acid and tungsten hexacarbonyl are: (0.1-1.5): (0.1-1.5): (0.1-1.5): (0.1-1.5): (0.1-1.5): (4-8): (3-6).

7. The method for preparing a high entropy metal olefin catalyst for ammoxidation according to claim 5, characterized in that: When preparing the mixed solution, the molar ratio of N,N-dimethylformamide to glacial acetic acid is 4:

1.

8. The method for preparing a high entropy metal olefin catalyst for ammoxidation according to claim 5, characterized in that: The temperature during ultrasonic oscillation in step S3 is 20-35° C., and the oscillation time is 1-4 hours; the reaction temperature in the sealed container is 60-90° C., and the reaction time is 6-18 hours.

9. The method for preparing a high entropy metal olefin catalyst for ammoxidation according to claim 5, characterized in that: In step S4, the rotation speed of the centrifugal treatment is 6000-10000 rpm, and the centrifugal treatment time is 1-2 hours; the cleaning liquid used for cleaning is an ethanol solution; and the temperature during drying is 50-80°C.

10. A high entropy metal olefin catalyst for ammoxidation as claimed in any one of claims 1 to 4, used for preparing ammonia in an ammoxidation reaction.

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