Trimer cobalt cluster catalyst supported on nitrogen-carbon material and application thereof

Abstract

The present application relates to a kind of trimer cobalt cluster catalyst supported on nitrogen carbon material and its application, wherein the trimer cobalt cluster catalyst supported on nitrogen carbon material is composed of carrier and active component supported on carrier, and the active component is trimer cobalt cluster, and the carrier is nitrogen carbon material;The trimer cobalt cluster catalyst supported on nitrogen carbon material is prepared using salt template method, and metal cobalt is supported on nitrogen carbon material in the form of low nuclear cluster.The present application selects glucose and urea as carbon source and nitrogen source respectively, uses sodium chloride as template to construct high specific surface area and porous structure carbon carrier, and prepares trimer cobalt cluster catalyst supported on nitrogen carbon material by high-temperature calcination, realizes atomic dispersion of cobalt cluster, so as to expose more active sites, improve atomic utilization rate of active site, and low cost.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, specifically to a triatomic cobalt cluster catalyst supported on nitrogen and carbon materials and its application. Background Technology

[0002] Aniline is an important organic chemical raw material and fine chemical intermediate, with over 300 derivative products. It is widely used in dyes, pharmaceuticals, agrochemicals, fragrances, rubber, and synthetic materials. In recent years, with the rapid development and growth of the global polyurethane industry, the demand for its core raw material, 4,4'-diphenylmethane diisocyanate, has continued to rise, thereby driving the vigorous development of the market and industry for aniline—an irreplaceable upstream basic raw material.

[0003] Currently, there are three main methods for preparing aniline: iron powder reduction, phenol amination, and nitrobenzene catalytic hydrogenation. The iron powder reduction method is a traditional production method that reduces nitrobenzene to aniline and iron oxide using iron powder in a hydrochloric acid medium at approximately 100ºC. This method is gradually being phased out by manufacturers due to its complex equipment, difficulty in recovering reaction heat, high iron powder consumption, and severe environmental pollution. The application of the phenol amination method in large-scale aniline production is limited by multiple economic and technological challenges. Although this method has the advantages of simple process and low waste, its high infrastructure investment and energy consumption, production costs affected by raw material price fluctuations, and separation and purification problems caused by the co-production of diphenylamine severely weaken its market competitiveness. Currently, 85% of the world's total aniline production is produced by nitrobenzene catalytic hydrogenation, mainly including fixed-bed gas-phase catalytic hydrogenation, fluidized-bed gas-phase catalytic hydrogenation, and nitrobenzene liquid-phase catalytic hydrogenation processes. These processes have the advantages of being able to be carried out in the gas or liquid phase, producing high-quality products, being environmentally friendly, and having simple operation. The liquid-phase catalytic hydrogenation process for nitrobenzene involves the hydrogenation of nitrobenzene to aniline under anhydrous conditions at 150–250°C and 0.15–1.0 MPa using a noble metal catalyst. The product is then obtained through distillation, achieving a yield of up to 99%. Noble metal catalysts primarily consist of metals such as Pt, Pd, and Rh supported on alumina, activated carbon, etc. These catalysts offer advantages such as high catalytic activity and long lifespan, but their production cost is relatively high. Therefore, developing catalysts that combine low cost and high activity has become a current research hotspot.

[0004] Transition metal catalysts (Co, Fe, Ni, Mn) are inexpensive and exhibit high activity in the catalytic hydrogenation of nitrobenzene. Traditional catalysts are typically nanoscale metal particles, which, while offering good catalytic performance, suffer from low atom utilization and poor atom economy. Therefore, it is of great significance to develop a non-precious metal catalyst with a simple synthesis method, high atom utilization, and low cost for the selective hydrogenation of nitrobenzene to aniline under mild conditions. Summary of the Invention

[0005] One objective of this invention is to provide a triatomic cobalt cluster catalyst supported on nitrogen-carbon materials, which solves the technical problems of low atom utilization and harsh reaction conditions of traditional nanocatalysts; another objective of this invention is to provide the application of this triatomic cobalt cluster catalyst supported on nitrogen-carbon materials.

[0006] The technical solution adopted by this invention to solve its technical problem is as follows: This triatomic cobalt cluster catalyst supported on a nitrogen-carbon material consists of a support and an active component supported on the support. The active component is a triatomic cobalt cluster, and the support is a nitrogen-carbon material. The triatomic cobalt cluster catalyst supported on a nitrogen-carbon material is prepared by a salt template method, in which metallic cobalt is supported on the nitrogen-carbon material in the form of low-nuclear clusters. The specific preparation method includes the following steps: Step 1: Dissolve cobalt salt, zinc salt, glucose, urea, amino acids, and salt template in deionized water and stir at room temperature to form a mixed solution; the molar ratio of cobalt ions to zinc ions is 1:4~80, the mass ratio of cobalt salt to glucose is 1:1~100, the mass ratio of cobalt salt to urea is 1:1~100, the mass ratio of cobalt salt to amino acids is 1:1~100, and the mass ratio of cobalt salt to salt template is 1:5~1000. Step 2: The obtained mixed solution is rapidly cooled in liquid nitrogen and then freeze-dried, and then ground to obtain a solid powder; Step 3: Calcine the solid powder under an inert atmosphere, disperse the resulting black powder in deionized water to remove the salt template, then centrifuge and vacuum dry to obtain a black solid product; Step 4: The black solid product obtained in Step 3 is activated in an ammonia atmosphere to obtain a three-atom cobalt cluster catalyst supported on a nitrogen-carbon material. The three-atom cobalt cluster catalyst is a porous three-dimensional structure composed of interconnected nanosheets.

[0007] In the above scheme, the mass percentage content of cobalt in the triatomic cobalt cluster catalyst supported on nitrogen and carbon materials is 0.1~10wt%.

[0008] In step one of the above scheme, the cobalt salt is cobalt nitrate hexahydrate, and the zinc salt is zinc nitrate hexahydrate; the salt template is one of sodium chloride, potassium chloride, lithium chloride, sodium fluoride, potassium fluoride, sodium sulfate, potassium sulfate, sodium nitrate, and potassium nitrate.

[0009] In step one of the above scheme, the amino acid is one of glycine, glutamic acid, lysine, histidine, L-aspartic acid, and L-leucine; the stirring time is 0.5 to 12 hours.

[0010] In step two of the above scheme, the freeze-drying process lasts for 12 to 96 hours.

[0011] In step three of the above scheme, the calcination temperature is 500~1400 ºC, the calcination time is 1~4 hours, the heating rate during calcination is 2~20 ºC / min, and the inert gas used is 99.999% Ar or N2.

[0012] In step three of the above scheme, the vacuum drying temperature is 60~90 ºC and the drying time is 24~72 hours.

[0013] In step four of the above scheme, the activation temperature is 300~1200 ºC, the activation time is 0.5~4 hours, and the heating rate is 2~20ºC / min.

[0014] The aforementioned triatomic cobalt cluster catalyst supported on nitrogen and carbon materials is used for the selective hydrogenation of nitrobenzene to aniline. Beneficial effects

[0015] (1) In this invention, glucose and urea are selected as carbon source and nitrogen source, respectively. Sodium chloride is used as template to construct a carbon support with high specific surface area and porous structure. The three-atom cobalt cluster catalyst loaded on nitrogen and carbon materials is prepared by high temperature calcination, which realizes the atomic-level dispersion of cobalt clusters, thereby exposing more active sites and improving the atomic utilization rate of active sites.

[0016] (2) The three-atom cobalt cluster catalyst supported on nitrogen and carbon materials disclosed in this invention exhibits excellent catalytic activity in the catalytic hydrogenation of nitrobenzene to aniline reaction, with a selectivity of up to 99% under mild reaction conditions (20ºC, 1 atm).

[0017] (3) The preparation method of this invention is simple and inexpensive, and the catalyst has the characteristics of high activity, long life and low cost. The cluster composed of three cobalt atoms can synergistically catalyze the hydrogenation reaction of nitrobenzene, breaking through the technical difficulties of low atom utilization and harsh reaction conditions of traditional nanocatalysts.

[0018] (4) The present invention is composed of three cobalt atoms and a nitrogen-carbon support, and has unique geometric and electronic properties, which can efficiently catalyze the conversion of nitrobenzene into aniline under mild conditions. Attached Figure Description

[0019] Figure 1 This is a SEM image of the triatomic cobalt cluster catalyst supported on nitrogen-carbon materials obtained in Example 1; Figure 2 This is a TEM image of the triatomic cobalt cluster catalyst supported on nitrogen-carbon materials obtained in Example 1; Figure 3 This is an AC HAADF-STEM image of the triatomic cobalt cluster catalyst supported on nitrogen-carbon materials obtained in Example 1; Figure 4 This is the XRD pattern of the triatomic cobalt cluster catalyst supported on nitrogen and carbon materials obtained in Example 1; Figure 5 This is a comparison chart of the conversion frequencies of the triatomic cobalt cluster catalyst supported on nitrogen-carbon materials obtained in Example 1 and the comparative catalyst. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings: Example 1:

[0021] This triatomic cobalt cluster catalyst supported on nitrogen-carbon material consists of low-nuclear cobalt clusters (composed of three cobalt atoms) and the nitrogen-carbon material it supports. It consists of a support and an active component supported on the support. The active component is the triatomic cobalt cluster, and the support is the nitrogen-carbon material. The triatomic cobalt cluster catalyst supported on nitrogen-carbon material is prepared by the salt template method, in which metallic cobalt is supported on the nitrogen-carbon material in the form of low-nuclear clusters.

[0022] The preparation method of this triatomic cobalt cluster catalyst supported on nitrogen and carbon materials is as follows: 1. Dissolve 0.024 g cobalt nitrate hexahydrate, 0.4 g zinc nitrate hexahydrate, 1.8 g glucose, 0.9 g urea, 0.6 g glycine and 10 g sodium chloride in 30 mL of deionized water and stir at room temperature for 1 hour to form a mixed solution. 2. The obtained mixed solution was rapidly cooled in liquid nitrogen and then freeze-dried for 24 hours, and then ground to obtain a solid powder; 3. The above solid powder was placed in a tube furnace and calcined under an argon atmosphere. It was treated at 950ºC for 3 hours with a heating rate of 2ºC / min. The resulting black powder was dispersed in deionized water to remove sodium chloride, then centrifuged and vacuum dried at 80ºC for 24 hours. IV. The black solid product obtained in the above steps is activated in an ammonia atmosphere at an activation temperature of 900ºC, a heating rate of 5ºC / min, and an activation time of 1 hour to obtain a triatomic cobalt cluster catalyst supported on nitrogen and carbon materials.

[0023] The three-atom cobalt cluster catalyst supported on nitrogen and carbon materials obtained in Example 1 was subjected to structural characterization and performance testing.

[0024] like Figure 1 and Figure 2 The images shown are SEM and TEM images of the three-atom cobalt cluster catalyst supported on nitrogen-carbon materials obtained in Example 1. The images show that the catalyst obtained in Example 1 has a porous three-dimensional structure composed of interconnected nanosheets, and no obvious cobalt nanoparticles were observed in the images.

[0025] like Figure 3 The image shown is an AC HAADF-STEM image of the triatomic cobalt cluster catalyst supported on nitrogen-carbon material obtained in Example 1, indicating that cobalt is supported on the nitrogen-carbon material in the form of small clusters on the surface of the catalyst obtained in Example 1.

[0026] like Figure 4 The image shows the XRD pattern of the triatomic cobalt cluster catalyst supported on nitrogen-carbon material obtained in Example 1. In the figure, 24º and 43º correspond to the (002) crystal plane and (101) crystal plane of graphite carbon, respectively, and there are no metal characteristic diffraction peaks. Example 2:

[0027] The only difference between this embodiment and Embodiment 1 is that the amino acid in step one is L-leucine. Example 3:

[0028] The only difference between this embodiment and Embodiment 1 is that the stirring time in step one is 2 hours. Example 4:

[0029] The only difference between this embodiment and Embodiment 1 is that the freeze-drying time in step two is 48 hours. Example 5:

[0030] The only difference between this embodiment and Embodiment 1 is that the calcination temperature in step three is 900 ºC. Example 6:

[0031] The only difference between this embodiment and Embodiment 1 is that the calcination time in step three is 72 hours. Example 7:

[0032] The only difference between this embodiment and Embodiment 1 is that the heating rate in step three is 3 ºC / min. Example 8:

[0033] The only difference between this embodiment and Embodiment 1 is that the calcination temperature in step four is 950 ºC. Example 9:

[0034] The only difference between this embodiment and Embodiment 1 is that the calcination time in step four is 2 hours. Example 10:

[0035] The only difference between this embodiment and Embodiment 1 is that the heating rate in step four is 3 ºC / min.

[0036] Comparative Example 1:

[0037] The difference between this comparative example and Example 1 is that sodium chloride was not added in step one.

[0038] Comparative Example 2:

[0039] The only difference between this comparative example and Example 1 is that an acid washing step is added after step four, and the sample is treated with 2 M sulfuric acid at 90ºC for 48 hours.

[0040] Comparative Example 3:

[0041] The only difference between this comparative example and Example 1 is that the amount of cobalt nitrate hexahydrate added in step one is 0.12 g.

[0042] Comparative Example 4:

[0043] The only difference between this comparative example and Example 1 is that cobalt nitrate hexahydrate was not added in step one.

[0044] Catalytic performance testing of the triatomic cobalt cluster catalyst supported on nitrogen and carbon materials according to this invention: The catalytic performance of the catalyst was evaluated in a 25 mL Schlenk glass container under a 1 atm argon atmosphere. 0.3 mmol nitrobenzene, 0.6 mmol sodium borohydride aqueous solution, and 5 mg of catalyst were dispersed in 3 mL methanol / water (v / v = 1 / 1) and reacted at 20ºC. During the reaction, the liquid products were separated and analyzed by gas chromatography.

[0045] Figure 5 This is a comparison of the conversion frequencies of the cobalt-3 atom cluster catalyst supported on nitrogen-carbon material obtained in Example 1 with other catalysts. As shown in the figure, the cobalt-3 atom cluster catalyst supported on nitrogen-carbon material exhibits a conversion frequency as high as 7327 h⁻¹ for the hydrogenation of nitrobenzene to aniline. -1 This indicates that the catalyst has excellent catalytic efficiency.

[0046] This invention prepares a three-atom cobalt cluster catalyst supported on nitrogen and carbon materials. The method is simple, environmentally friendly, and the reaction conditions are mild. The catalyst exhibits good catalytic activity in the hydrogenation of nitrobenzene to aniline.

Claims

1. A three-atom cobalt cluster catalyst supported on a nitrogen-carbon material, characterized in that: This triatomic cobalt cluster catalyst supported on a nitrogen-carbon material consists of a support and an active component supported on the support. The active component is a triatomic cobalt cluster, and the support is a nitrogen-carbon material. The triatomic cobalt cluster catalyst supported on a nitrogen-carbon material is prepared using a salt template method, in which metallic cobalt is supported on the nitrogen-carbon material in the form of low-nuclear clusters. The specific preparation method includes the following steps: Step 1: Dissolve cobalt salt, zinc salt, glucose, urea, amino acids, and salt template in deionized water and stir at room temperature to form a mixed solution. The molar ratio of cobalt ions to zinc ions is 1:16.3, the mass ratio of cobalt salt to glucose is 1:75, the mass ratio of cobalt salt to urea is 1:37.5, the mass ratio of cobalt salt to amino acids is 1:25, and the mass ratio of cobalt salt to salt template is 1:416.

67. The salt template is one of sodium chloride, potassium chloride, lithium chloride, sodium fluoride, potassium fluoride, sodium sulfate, and potassium sulfate. Step 2: The obtained mixed solution is rapidly cooled in liquid nitrogen and then freeze-dried, and then ground to obtain a solid powder; Step 3: Calcine the solid powder under an inert atmosphere at a temperature of 950~1400 ºC. Disperse the resulting black powder in deionized water to remove the salt template, then centrifuge and vacuum dry to obtain a black solid product. Step 4: Activate the black solid product obtained in Step 3 in an ammonia atmosphere at an activation temperature of 900~1200ºC for 4 hours to obtain a three-atom cobalt cluster catalyst supported on a nitrogen-carbon material. The three-atom cobalt cluster catalyst is a porous three-dimensional structure composed of interconnected nanosheets.

2. The triatomic cobalt cluster catalyst supported on nitrogen and carbon materials according to claim 1, characterized in that: The mass percentage content of cobalt in the triatomic cobalt cluster catalyst supported on nitrogen and carbon materials is 0.1~10wt%.

3. The triatomic cobalt cluster catalyst supported on nitrogen and carbon materials according to claim 2, characterized in that: In step one, the cobalt salt is cobalt nitrate hexahydrate, and the zinc salt is zinc nitrate hexahydrate.

4. The triatomic cobalt cluster catalyst supported on nitrogen and carbon materials according to claim 3, characterized in that: In step one, the amino acid is one of glycine, glutamic acid, lysine, histidine, L-aspartic acid, and L-leucine; the stirring time is 0.5 to 12 hours.

5. The triatomic cobalt cluster catalyst supported on nitrogen and carbon materials according to claim 4, characterized in that: In step two, the freeze-drying process lasts for 12 to 96 hours.

6. The triatomic cobalt cluster catalyst supported on nitrogen and carbon materials according to claim 5, characterized in that: In step three, the calcination time is 1 to 4 hours, the heating rate during calcination is 2 to 20 ºC / min, and the inert gas used is 99.999% Ar or N2.

7. The triatomic cobalt cluster catalyst supported on nitrogen and carbon materials according to claim 6, characterized in that: In step three, the vacuum drying temperature is 60~90 ºC and the drying time is 24~72 hours.

8. The triatomic cobalt cluster catalyst supported on nitrogen and carbon materials according to claim 7, characterized in that: The heating rate during the activation treatment in step four is 2~20ºC / min.

9. The application of the triatomic cobalt cluster catalyst supported on nitrogen-carbon materials as described in claim 8, characterized in that: The triatomic cobalt cluster catalyst supported on nitrogen and carbon materials is used for the selective hydrogenation of nitrobenzene to aniline.

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