A nitrogen-doped carbon-coated catalyst, a preparation method and application thereof

Abstract

The application discloses a nitrogen-doped carbon-coated catalyst and a preparation method and application thereof. The preparation method of the nitrogen-doped carbon-coated catalyst is carried out according to the following steps: step one: dissolving anhydrous zinc chloride in a solvent, and then adjusting the pH of the mixed solution to 9.5-11.5; adding 1H-1,2,3-triazole and stirring at room temperature to obtain a MET-Zn precursor; step two: dissolving the MET-Zn precursor and Fe, Co or Ni metal nitrate in solvents respectively, then mixing the two solutions, and carrying out ion exchange under nitrogen protection to obtain an ion-exchanged M-MET precursor; and step three: carbonizing the ion-exchanged M-MET precursor under an inert atmosphere to obtain the nitrogen-doped carbon-coated catalyst. The application provides application of the nitrogen-doped carbon-coated catalyst in a liquid-phase catalytic hydrogenation reaction of o-chloronitrobenzene, and the nitrogen-doped carbon-coated catalyst has the characteristics of high catalytic activity, selectivity and stability and can be magnetically recovered.

Description

Technical Field

[0001] This invention relates to a nitrogen-doped carbon-coated catalyst, its preparation method, and its application. Background Technology

[0002] In recent years, with the rapid development of my country's chemical industry, catalysis technology has become a core technology driving the chemical industry. Due to the scarcity and high cost of precious metal catalysts, they cannot meet the future needs of the chemical industry in the catalysis field. Non-precious metal catalysts, as good alternatives to precious metal catalysts, are widely used in catalytic degradation of organic pollutants and organic synthesis reactions due to their low cost and abundant resources. In particular, non-precious metal catalysts with Fe, Co, and Ni as active components can be magnetically recovered in heterogeneous reactions, greatly reducing recovery costs.

[0003] o-Chloroaniline (o-CAN) is an important chemical intermediate, a colorless to pale yellow oily liquid used in the manufacture of azo dyes, pharmaceutical intermediates, lithium batteries, and other chemical production fields. Due to its excellent performance and wide range of applications, it has high market demand and economic value. Currently, o-chloroaniline is mainly synthesized in industry using iron powder reduction and liquid-phase catalytic hydrogenation methods, as shown in Equations 1 and 2:

[0004]

[0005] Formula 1: Reaction equation for iron powder reduction

[0006]

[0007] Equation 2: Reaction formula for catalytic hydrogenation

[0008] While the iron powder reduction process is relatively mature in actual industrial production, it generates large amounts of iron sludge and acidic wastewater, severely polluting the environment and has been gradually phased out. Catalytic hydrogenation, due to its cleanliness, is currently a hot research topic. However, for the liquid-phase hydrogenation reaction of nitroaromatics containing halogen atoms (-Cl), dehalogenation easily occurs during the hydrogenation of nitro groups to form amino groups, leading to low selectivity for o-chloroaniline. Furthermore, catalysts with non-precious metals as active components typically suffer from poor hydrogenation activity, making it difficult to meet the demands of industrial production. Therefore, developing a highly selective, highly active, and economical non-precious metal liquid-phase hydrogenation catalyst has become an important research direction.

[0009] Metal-organic frameworks (MOFs) are crystalline porous materials with a periodic network structure formed by the self-assembly and interconnection of inorganic metal centers and organic ligands. In recent years, nitrogen-doped carbon-coated metal nanoparticle catalysts derived from MOF carbonization have attracted widespread attention in catalytic hydrogenation reactions. Among them, MET is a class of MOFs with extremely high nitrogen content, composed of divalent metal cations and 1H-1,2,3-triazole. Because this high-nitrogen-content MOF can form a high specific surface area nitrogen-doped carbon-coated structure in situ during carbonization, and possesses abundant nitrogen-doped active sites and highly dispersed metal active components, MET-Zn is considered a potentially excellent precursor for preparing nitrogen-doped carbon-coated metal nanoparticle catalysts. If the highly dispersed Zn in MET-Zn... 2+ Ion nodes replaced with Fe 2+ Co 2+ or Ni 2+ Nitrogen-doped carbon-coated metal nanoparticle catalysts, which have a large specific surface area, small and highly dispersed metal active components, and are magnetically recoverable, can be obtained by high-temperature carbonization under an inert gas atmosphere. This catalyst has the characteristics of high activity, high selectivity and easy recovery, and its application in the liquid-phase catalytic hydrogenation of o-chloronitrobenzene to o-chloroaniline is of great significance. Summary of the Invention

[0010] One objective of this invention is to provide a magnetically recoverable nitrogen-doped carbon-coated catalyst derived from MET-Zn ion exchange, its preparation method, and its applications. This catalyst utilizes MET-Zn ion exchange to replace Zn. 2+ After ion nodes are established, magnetic Fe, Co, or Ni can be used as the active metal component to achieve magnetic recovery of the catalyst, thereby reducing the catalyst recovery cost.

[0011] The second objective of this invention is to provide a nitrogen-doped carbon-coated catalyst that is magnetically recoverable and derived from MET-Zn ion exchange.

[0012] The third objective of this invention is to provide the application of the magnetically recoverable nitrogen-doped carbon-coated catalyst derived from MET-Zn ion exchange in the liquid-phase hydrogenation reaction of o-chloronitrobenzene, which exhibits excellent catalytic activity, stability, and selectivity.

[0013] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0014] In a first aspect, the present invention provides a method for preparing a magnetically recoverable nitrogen-doped carbon-coated catalyst derived from MET-Zn ion exchange, the preparation method comprising the following steps:

[0015] Step 1: Dissolve anhydrous zinc chloride in a mixed solvent of N,N-dimethylformamide, deionized water and anhydrous ethanol, and then add ammonia water dropwise to adjust the pH of the mixed solution to 9.5-11.5; add 1H-1,2,3-triazole, stir at room temperature for 8-14 hours, centrifuge to collect the white precipitate, and obtain the MET-Zn precursor after washing and drying.

[0016] Step 2: Dissolve the MET-Zn precursor obtained in Step 1 and Fe, Co or Ni metal nitrates in dimethyl sulfoxide solvent respectively. Then mix the two solutions, seal the reaction tube under nitrogen protection, and heat at 30-70℃ for 18-24h for ion exchange. After the ion exchange is completed, wash and dry to obtain the ion-exchanged M-MET (M = Fe, Co, Ni) precursor.

[0017] Step 3: The ion-exchanged M-MET precursor obtained in Step 2 is placed in an inert gas atmosphere and carbonized at 500-800℃ for 1-3h. The heating rate is 1-10℃ / min and the inert gas flow rate is 20-100mL / min to obtain nitrogen-doped carbon-coated catalyst M@NC (M = Fe, Co, Ni).

[0018] Preferably, in step one, the molar ratio of anhydrous zinc chloride to 1H-1,2,3-triazole is 1:3 to 4, and most preferably 1:3.0 to 3.5.

[0019] Preferably, in step one, the volume ratio of N,N-dimethylformamide:deionized water:anhydrous ethanol is 0.5-1.5:1-2:1, more preferably 1:1-2:1, and even more preferably 1:1.5:1.

[0020] Preferably, in step one, the pH of the mixed solution is adjusted to 11.

[0021] Preferably, in step one, the mixture is stirred at room temperature for 12 hours.

[0022] Preferably, in step one, the washing reagents are N,N-dimethylformamide and methanol solvent, respectively.

[0023] Preferably, in step one, the drying conditions are: drying at 50-80°C for 12-36 hours in a vacuum oven, more preferably drying at 60°C for 24 hours in a vacuum oven.

[0024] Preferably, in step two, the mass ratio of MET-Zn precursor to dimethyl sulfoxide is 1:50 to 150, more preferably 1:100; the mass ratio of Fe, Co, or Ni metal nitrate to dimethyl sulfoxide is 1:10 to 50, more preferably 1:20; and the mass ratio of MET-Zn precursor to Fe, Co, or Ni metal nitrate is 1:1 to 12, more preferably 1:5 to 7, and even more preferably 1:6.

[0025] Preferably, in step two, the ion exchange temperature is 50°C and the exchange time is 20 hours.

[0026] Preferably, in step two, the drying process involves drying in a vacuum oven at 100–180°C for 10–24 hours, and more preferably at 150°C for 18 hours.

[0027] Preferably, in step two, the selected metal precursor is nickel nitrate hexahydrate.

[0028] Preferably, in step two, the washing reagents are N,N-dimethylformamide, methanol, and dichloromethane.

[0029] Preferably, in step three, the selected inert gas is N2, the carbonization temperature is 600℃, the carbonization time is 2h, the heating rate is 2℃ / min, and the nitrogen flow rate is 30mL / min.

[0030] In a second aspect, the present invention provides a magnetically recoverable nitrogen-doped carbon-coated catalyst derived from MET-Zn ion exchange, prepared according to the preparation method described in the first aspect.

[0031] Thirdly, the present invention provides the application of the magnetically recoverable nitrogen-doped carbon-coated catalyst derived from MET-Zn ion exchange in the liquid-phase catalytic hydrogenation reaction of o-chloronitrobenzene.

[0032] The structural formulas of the o-chloronitrobenzene reactant and the o-chloroaniline product described in this invention are as follows:

[0033]

[0034] Preferably, the application involves adding o-chloronitrobenzene, solvent, and nitrogen-doped carbon-coated catalyst to a high-pressure reactor. After purging air with nitrogen, hydrogen is introduced to stir the reaction, producing o-chloroaniline. After the reaction is complete, the catalyst is magnetically recovered for reuse in the next cycle.

[0035] Preferably, the solvent is methanol.

[0036] Preferably, the mass amount of the nitrogen-doped carbon-coated catalyst is 2 to 10% of the mass of o-chloronitrobenzene, and most preferably 5%.

[0037] Preferably, in the reaction solution prepared from o-chloronitrobenzene and solvent, the mass fraction of o-chloronitrobenzene is 10-40 wt%.

[0038] Preferably, the hydrogen pressure is maintained at 1.0–1.6 MPa, more preferably at 1.2 MPa, and the reaction temperature is controlled at 60–100 °C, with 80 °C being optimal.

[0039] Preferably, the stirring speed is 500–1000 rpm.

[0040] Compared with existing technologies, this invention has the following advantages:

[0041] (1) The nitrogen-doped carbon-coated catalyst derived from MET-Zn ion exchange and magnetically recoverable provided by the present invention uses MET-Zn as a precursor in the preparation process. MET-Zn can be prepared by stirring at room temperature and pressure. Compared with other MOFs, the preparation process is simple and can be mass-produced.

[0042] (2) The nitrogen-doped carbon-coated catalyst derived from MET-Zn ion exchange provided by the present invention uses MET-Zn for ion exchange during the preparation process. The derived nitrogen-doped carbon-coated liquid-phase hydrogenation catalyst has a large specific surface area, small and highly dispersed metal nanoparticles, and can contact more reaction substrates and hydrogen, thereby improving the catalyst activity.

[0043] (3) The nitrogen-doped carbon-coated catalyst derived from MET-Zn ion exchange and capable of magnetic recovery provided by this invention has a large number of nitrogen atoms doped on the carbon layer, and the extra lone pair electrons of the nitrogen atoms are sp. 2 The hybrid carbon layer delocalized π system provides electrons, improving its electronic structure. In particular, the doping of pyridine nitrogen significantly reduces the band gap, thereby promoting the adsorption of reaction substrates and improving catalytic activity and selectivity.

[0044] (4) The nitrogen-doped carbon-coated catalyst based on MET-Zn ion exchange and which can be magnetically recovered is provided by the present invention. It is used as a probe reaction for the preparation of o-chloroaniline by liquid-phase hydrogenation of o-chloronitrobenzene. The product selectivity is high; the catalyst has good stability and can be reused multiple times; it has high safety during use; and it has high industrial application value.

[0045] (5) The nitrogen-doped carbon-coated catalyst derived from MET-Zn ion exchange and capable of magnetic recovery provided by this invention is used as a probe reaction in the liquid-phase hydrogenation of o-chloronitrobenzene to prepare o-chloroaniline. Because the catalyst contains nickel metal, it can be magnetically recovered using a magnet after the reaction, reducing the catalyst recovery cost. Attached Figure Description

[0046] Figure 1 (a) is a diagram showing the dispersion effect of the Ni@NC catalyst prepared in Example 1 in methanol solvent; (b) is a diagram showing the effect of the Ni / NC catalyst prepared in Example 1 being attracted by a magnet in methanol solvent.

[0047] Figure 2 This is the XRD pattern of the Ni@NC catalyst prepared in Example 1.

[0048] Figure 3 (a) is a SEM image of MET-Zn prepared in Comparative Example 2 without the addition of pH adjuster; (b)-(c) are SEM images of MET-Zn prepared in Example 1 with the addition of pH adjuster. Detailed Implementation

[0049] The technical solution of the present invention will be further illustrated below with specific embodiments. It should be noted that the embodiments are only used to further illustrate the present invention, but should not be construed as limiting the scope of protection of the present invention, which is not limited thereto in any way.

[0050] Unless otherwise specified in the embodiments of this invention, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained through conventional technical means or commercially available.

[0051] Comparative Example 1: Preparation method of Ni-MET precursor

[0052] 1.00 g of anhydrous zinc chloride was dissolved in a mixed solvent of 10 mL N,N-dimethylformamide, 15 mL deionized water, and 10 mL anhydrous ethanol, and stirred vigorously to ensure complete dissolution. A 28% ammonium hydroxide solution was added dropwise to adjust the pH of the solvent to 11. 1.62 g of 1H-1,2,3-triazole was added, and the mixture was stirred at room temperature for 12 h. The white precipitate was collected by centrifugation, washed with N,N-dimethylformamide and methanol, and the resulting solid product was dried in a vacuum oven at 60 °C for 24 h to obtain the precursor MET-Zn. 1.00 g of MET-Zn and 6.00 g of nickel nitrate hexahydrate were dissolved in 100 mL and 120 mL of dimethyl sulfoxide, respectively. The two solutions were then mixed and the reaction tube was sealed under nitrogen protection. The mixture was heated at 50 °C for 20 h for ion exchange. After the ion exchange was completed, the precipitate was washed with N,N-dimethylformamide, methanol, and dichloromethane. The precipitate was then dried in a vacuum oven at 150 °C for 18 h to obtain the ion-exchanged Ni-MET precursor.

[0053] Example 1

[0054] 1.00 g of anhydrous zinc chloride was dissolved in a mixed solvent of 10 mL N,N-dimethylformamide, 15 mL deionized water, and 10 mL anhydrous ethanol, and stirred vigorously to ensure complete dissolution. A 28% ammonium hydroxide solution was added dropwise to adjust the pH of the solvent to 11. 1.62 g of 1H-1,2,3-triazole was added, and the mixture was stirred at room temperature for 12 h. The white precipitate was collected by centrifugation, washed with N,N-dimethylformamide and methanol, and the resulting solid product was dried in a vacuum oven at 60 °C for 24 h to obtain the precursor MET-Zn. 1.00 g of MET-Zn and 6.00 g of nickel nitrate hexahydrate were dissolved in 100 mL and 120 mL of dimethyl sulfoxide, respectively. The two solutions were then mixed, and the reaction tube was sealed under nitrogen protection. Ion exchange was performed by heating at 50 °C for 20 h. After ion exchange, the precipitate was washed with N,N-dimethylformamide, methanol, and dichloromethane. The precipitate was then dried in a vacuum oven at 150 °C for 18 h to obtain the ion-exchanged Ni-MET precursor. The Ni-MET precursor was then carbonized at 600 °C for 2 h under a nitrogen atmosphere with a heating rate of 2 °C / min and a nitrogen flow rate of 30 mL / min. After cooling, the Ni@NC catalyst was obtained.

[0055] The dispersion effect and magnetic attraction effect of the Ni@NC catalyst prepared in Example 1 in methanol solvent are shown in the figure below. Figure 1 As shown, the solvent became clear again after being attracted by a magnet, indicating that the catalyst has excellent magnetic recovery performance. The XRD pattern of the Ni@NC catalyst is shown below. Figure 2 As shown, the intensity of the characteristic diffraction peaks of the (111), (200) and (220) crystal planes of Ni metal is relatively weak, indicating that the Ni metal nanoparticles are small in size and highly dispersed.

[0056] Comparative Example 2: No pH adjuster added

[0057] 1.00 g of anhydrous zinc chloride was dissolved in a mixed solvent of 10 mL N,N-dimethylformamide, 15 mL deionized water, and 10 mL anhydrous ethanol, and stirred vigorously until fully dissolved. 1.62 g of 1H-1,2,3-triazole was added, and the mixture was stirred at room temperature for 12 h. The white precipitate was collected by centrifugation and washed with N,N-dimethylformamide and methanol. The resulting solid product was dried in a vacuum oven at 60 °C for 24 h to obtain the precursor MET-Zn. 1.00 g of MET-Zn and 6.00 g of nickel nitrate hexahydrate were dissolved in 100 mL and 120 mL of dimethyl sulfoxide, respectively. The two solutions were then mixed, and the reaction tube was sealed under nitrogen protection. Ion exchange was performed by heating at 50 °C for 20 h. After ion exchange, the precipitate was washed with N,N-dimethylformamide, methanol, and dichloromethane. The precipitate was dried in a vacuum oven at 150 °C for 18 h to obtain the ion-exchanged Ni-MET precursor. The Ni-MET precursor was carbonized at 600℃ for 2 hours under a nitrogen atmosphere with a heating rate of 2℃ / min and a nitrogen flow rate of 30mL / min. After cooling, the Ni@NC-2 catalyst was obtained.

[0058] SEM images of MET-Zn prepared in Example 1 and MET-Zn prepared in Comparative Example 2 are shown below. Figure 3 As shown, the MET-Zn particles prepared without pH adjustment agent showed severe agglomeration, while the MET-Zn after pH adjustment exhibited a typical octahedral structure. This indicates that adjusting the solvent pH has a significant impact on the morphology and structure of MET-Zn, thereby affecting the catalytic performance of the catalyst.

[0059] Comparative Example 3: Ion exchange at room temperature

[0060] 1.00 g of anhydrous zinc chloride was dissolved in a mixed solvent of 10 mL N,N-dimethylformamide, 15 mL deionized water, and 10 mL anhydrous ethanol, and stirred vigorously until fully dissolved. 1.62 g of 1H-1,2,3-triazole was added, and the mixture was stirred at room temperature for 12 h. The white precipitate was collected by centrifugation and washed with N,N-dimethylformamide and methanol. The resulting solid product was dried in a vacuum oven at 60 °C for 24 h to obtain the precursor MET-Zn. 1.00 g of MET-Zn and 6.00 g of nickel nitrate hexahydrate were dissolved in 100 mL and 120 mL of dimethyl sulfoxide, respectively. The two solutions were then mixed, and the reaction tube was sealed under nitrogen protection. Ion exchange was carried out at room temperature for 20 h. After ion exchange, the precipitate was washed with N,N-dimethylformamide, methanol, and dichloromethane. The precipitate was dried in a vacuum oven at 150 °C for 18 h to obtain the ion-exchanged Ni-MET precursor. The Ni-MET precursor was carbonized at 600℃ for 2 hours under a nitrogen atmosphere with a heating rate of 2℃ / min and a nitrogen flow rate of 30mL / min. After cooling, the Ni@NC-3 catalyst was obtained.

[0061] Comparative Example 4: No ion exchange

[0062] 1.00 g of anhydrous zinc chloride was dissolved in a mixed solvent of 10 mL N,N-dimethylformamide, 15 mL deionized water, and 10 mL anhydrous ethanol, and stirred vigorously until fully dissolved. 1.62 g of 1H-1,2,3-triazole was added, and the mixture was stirred at room temperature for 12 h. The white precipitate was collected by centrifugation and washed with N,N-dimethylformamide and methanol. The resulting solid product was dried in a vacuum oven at 60 °C for 24 h to obtain the precursor MET-Zn. MET-Zn was carbonized at 600 °C for 2 h under a nitrogen atmosphere, with a heating rate of 2 °C / min and a nitrogen flow rate of 30 mL / min. After cooling, the Zn@NC-4 catalyst was obtained.

[0063] Comparative Example 5: Uncarbonized

[0064] 1.00 g of anhydrous zinc chloride was dissolved in a mixed solvent of 10 mL N,N-dimethylformamide, 15 mL deionized water, and 10 mL anhydrous ethanol, and stirred vigorously to ensure complete dissolution. 1.62 g of 1H-1,2,3-triazole was added, and the mixture was stirred at room temperature for 12 h. The white precipitate was collected by centrifugation, washed with N,N-dimethylformamide and methanol, and the resulting solid product was dried in a vacuum oven at 60 °C for 24 h to obtain the precursor MET-Zn. 1.00 g of MET-Zn and 6.00 g of nickel nitrate hexahydrate were dissolved in 100 mL and 120 mL of dimethyl sulfoxide, respectively. The two solutions were then mixed and the reaction tube was sealed under nitrogen protection. The reaction was carried out at room temperature for 20 h for ion exchange. After the ion exchange was completed, the precipitate was washed with N,N-dimethylformamide, methanol, and dichloromethane. The precipitate was then dried in a vacuum oven at 150 °C for 18 h to obtain the ion-exchanged Ni-MET precursor, which was designated as the Ni-MET catalyst.

[0065] Application Example 1

[0066] In a 250 mL high-pressure reactor, 0.5 g of the nitrogen-doped carbon-coated liquid-phase hydrogenation catalyst prepared in Example 1 based on MET-Zn ion exchange and capable of magnetic recovery, 10 g of o-chloronitrobenzene, and 80 mL of methanol were added sequentially. The reactor was then sealed. The air inside the reactor was first replaced with nitrogen three times, and then the nitrogen inside the reactor was repeatedly replaced with hydrogen three times. The hydrogen pressure inside the reactor was adjusted to 1.2 MPa, and then heated to 80 °C and stirred (stirring rate 750 rpm) for 3 h. After the reaction was completed, the catalyst was recovered by magnetic attraction and the organic layer was separated. The composition of the hydrogenation product in the filtrate was analyzed by high-performance gas chromatography. The separated solvent was washed with deionized water and methanol and dried to obtain the target product.

[0067] Application Example 2

[0068] In a 250 mL high-pressure reactor, 0.5 g of Ni@NC-2 catalyst prepared in Comparative Example 2, 10 g of o-chloronitrobenzene, and 80 mL of methanol were added sequentially. The reactor was then sealed. The air inside the reactor was first replaced with nitrogen three times, and then the nitrogen inside the reactor was repeatedly replaced with hydrogen three times. The hydrogen pressure inside the reactor was adjusted to 1.2 MPa, and then heated to 80 °C and stirred (stirring speed 750 rpm) for 3 h. After the reaction was completed, the catalyst was recovered by magnetic attraction and the organic layer was separated. The composition of the hydrogenation product in the filtrate was analyzed by high performance gas chromatography. The separated solvent was washed with deionized water and methanol and dried to obtain the target product.

[0069] Application Example 3

[0070] In a 250 mL high-pressure reactor, 0.5 g of Ni@NC-3 prepared in Comparative Example 3, 10 g of o-chloronitrobenzene, and 80 mL of methanol were added sequentially. The reactor was then sealed. The air inside the reactor was first replaced with nitrogen three times, and then the nitrogen inside the reactor was repeatedly replaced with hydrogen three times. The hydrogen pressure inside the reactor was adjusted to 1.2 MPa, and then heated to 80 °C and stirred (stirring speed 750 rpm) for 3 h. After the reaction was completed, the catalyst was recovered by magnetic attraction and the organic layer was separated. The composition of the hydrogenation product in the filtrate was analyzed by high performance gas chromatography. The separated solvent was washed with deionized water and methanol and dried to obtain the target product.

[0071] Application Example 4

[0072] In a 250 mL high-pressure reactor, 0.5 g of Zn@NC-4 prepared in Comparative Example 4, 10 g of o-chloronitrobenzene, and 80 mL of methanol were added sequentially. The reactor was then sealed. The air inside the reactor was first replaced with nitrogen three times, and then the nitrogen inside the reactor was repeatedly replaced with hydrogen three times. The hydrogen pressure inside the reactor was adjusted to 1.2 MPa, and then heated to 80 °C and stirred (stirring speed 750 rpm) for 3 h. After the reaction was completed, the catalyst was filtered and the organic layer was separated. The composition of the hydrogenation product in the filtrate was analyzed by high performance gas chromatography. The separated solvent was washed with deionized water and methanol and dried to obtain the target product.

[0073] Application Example 5

[0074] In a 250 mL high-pressure reactor, 0.5 g of Ni-MET prepared in Comparative Example 5, 10 g of o-chloronitrobenzene, and 80 mL of methanol were added sequentially. The reactor was then sealed. The air inside the reactor was first replaced with nitrogen three times, and then the nitrogen inside the reactor was repeatedly replaced with hydrogen three times. The hydrogen pressure inside the reactor was adjusted to 1.2 MPa, and then heated to 80 °C and stirred (stirring speed 750 rpm) for 3 h. After the reaction was completed, the catalyst was filtered and the organic layer was separated. The composition of the hydrogenation product in the filtrate was analyzed by high performance gas chromatography. The separated solvent was washed with deionized water and methanol and dried to obtain the target product.

[0075] Table 1. Comparison of catalyst performance in Examples 1-5

[0076] Application Examples catalyst Reaction time (mins) o-Chloronitrobenzene conversion rate (%) Product selectivity (%) 1 Ni@NC in Example 1 360 100.00 >99 2 Comparative Example 2 Ni@NC-2 360 90.00 >89 3 Comparative Example 3 Ni@NC-3 360 5.21 5.14 4 Comparative Example 4: Zn@NC-4 360 0 0 5 Comparative Example 5 Ni-MET 360 0 0

[0077] The comparison between Example 1 and Comparative Example 2 shows that adding ammonium hydroxide to adjust the solvent pH during the preparation of the MET-Zn precursor affects the morphology and structure of MET-Zn. A more regular MET-Zn structure results in a larger specific surface area and is beneficial for subsequent ion exchange. Therefore, the structure of MET-Zn affects the catalytic performance and stability of its carbonized derivative catalyst. The comparison between Example 1 and Comparative Example 3 shows that ion exchange at room temperature significantly reduces catalyst activity, indicating that ion exchange requires a certain reaction temperature; otherwise, the Zn in MET-Zn will remain untreated. 2+ Ion nodes cannot be completely replaced with Ni 2+ The presence of ions leads to a low content of Ni metal nanoparticles in the nitrogen-doped carbon-coated catalyst derived from its carbonization, resulting in poor catalytic activity. A comparison of Example 1 with Comparative Examples 4 and 5 shows that Zn metal has very weak catalytic activity as the active component in hydrogenation, and the MOF precursor cannot be directly used as a hydrogenation catalyst. Its catalytic activity often originates from the electron transfer between the metal active component after the MOF precursor carbonization and the conductive graphene carbon layer.

[0078] Application Example 6

[0079] The experimental conditions were the same as in Application Example 1, and the catalyst obtained by magnetic separation was reused in the next reaction. High-performance gas chromatography was used to analyze the composition of the hydrogenation products in the filtrate obtained from each reuse experiment, and the results are shown in Table 2.

[0080] Table 2 Results of application of catalyst in Example 1

[0081]

[0082]

[0083] *The reaction conditions are the same as in Application Example 1.

[0084] Application Example 7

[0085] The experimental conditions were the same as in Application Example 2, and the filtered catalyst was reused in the next reaction. High-performance gas chromatography (HPLC) was used to analyze the composition of the hydrogenation products in the filtrate obtained from each reuse experiment, and the results are shown in Table 3.

[0086] Number of times to apply Catalyst addition amount (g) Reaction time (mins) o-Chloronitrobenzene conversion rate (%) o-Chloroaniline yield (%) 1 0.5 360 91.00 90.15 2 0.5 360 84.10 79.45 3 0.5 360 64.29 60.57

[0087] *The reaction conditions are the same as in Application Example 2.

[0088] Application Example 8

[0089] The experimental conditions were the same as in Application Example 3, and the filtered catalyst was reused in the next reaction. High-performance gas chromatography was used to analyze the composition of the hydrogenation products in the filtrate obtained from each reuse experiment, and the results are shown in Table 4.

[0090] Number of times to apply Catalyst addition amount (g) Reaction time (mins) o-Chloronitrobenzene conversion rate (%) o-Chloroaniline yield (%) 1 0.5 360 5.21 5.14 2 0.5 360 4.20 4.12 3 0.5 360 2.49 2.32

[0091] *The reaction conditions are the same as in Application Example 3.

Claims

1. The application of a magnetically recoverable nitrogen-doped carbon-coated catalyst derived from MET-Zn ion exchange in the liquid-phase catalytic hydrogenation reaction of o-chloronitrobenzene, characterized in that: The preparation method of the magnetically recoverable nitrogen-doped carbon-coated catalyst derived from MET-Zn ion exchange is carried out according to the following steps: Step 1: Dissolve anhydrous zinc chloride in a mixed solvent of N,N-dimethylformamide, deionized water and anhydrous ethanol, and then add ammonia water dropwise to adjust the pH of the mixed solution to 9.5~11.5; add 1H-1,2,3-triazole, stir at room temperature for 8~14h, centrifuge to collect the white precipitate, and obtain the MET-Zn precursor after washing and drying; Step 2: Dissolve the MET-Zn precursor obtained in Step 1 and Fe, Co or Ni metal nitrate in dimethyl sulfoxide solvent respectively. Then mix the two solutions, seal the reaction tube under nitrogen protection, and heat at 30~70℃ for 18~24h for ion exchange. After the ion exchange is completed, wash and dry to obtain the ion-exchanged M-MET precursor. Step 3: The ion-exchanged M-MET precursor obtained in Step 2 is placed in an inert gas atmosphere and carbonized at 500~800℃ for 1~3h. The heating rate is 1~10℃ / min and the inert gas flow rate is 20~100mL / min. This yields a magnetically recoverable nitrogen-doped carbon-coated catalyst derived from MET-Zn ion exchange.

2. The application as described in claim 1, characterized in that: In step one, the molar ratio of anhydrous zinc chloride to 1H-1,2,3-triazole is 1:3~4.

3. The application as described in claim 2, characterized in that: In step one, the molar ratio of anhydrous zinc chloride to 1H-1,2,3-triazole is 1:3.0~3.

5.

4. The application as described in claim 1, characterized in that: In step one, the volume ratio of N,N-dimethylformamide:deionized water:anhydrous ethanol is 0.5~1.5:1~2:

1.

5. The application as described in claim 4, characterized in that: In step one, the volume ratio of N,N-dimethylformamide:deionized water:anhydrous ethanol is 1:1 to 2:

1.

6. The application as described in claim 5, characterized in that: In step one, the volume ratio of N,N-dimethylformamide:deionized water:anhydrous ethanol is 1:1.5:

1.

7. The application as described in claim 1, characterized in that: In step one, the pH of the mixed solution is adjusted to 11.

8. The application as described in claim 1, characterized in that: In step two, the mass ratio of MET-Zn precursor to dimethyl sulfoxide is 1:50~150, the mass ratio of Fe, Co or Ni metal nitrate to dimethyl sulfoxide is 1:10~50, and the mass ratio of MET-Zn precursor to Fe, Co or Ni metal nitrate is 1:1~12.

9. The application as described in claim 1, characterized in that: In step two, the ion exchange temperature is 50℃ and the exchange time is 20h.

10. The application as described in claim 1, characterized in that: In step two, the selected metal precursor is nickel nitrate hexahydrate.

11. The application as described in claim 1, characterized in that: In step three, the selected inert gas is N2, the carbonization temperature is 600℃, the carbonization time is 2h, the heating rate is 2℃ / min, and the nitrogen flow rate is 30mL / min.

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