A supported palladium-nickel alloy catalyst, its preparation method and application

Abstract

This invention relates to the field of catalyst technology, specifically a supported palladium-nickel alloy catalyst, its preparation method, and its application. The catalyst comprises a palladium-nickel alloy with a total loading of 1%-20% and a nitrogen-doped carbon support with a nitrogen doping content of 10-20 at%, wherein the mass ratio of palladium to nickel is 1:0.1-10. The supported palladium-nickel alloy catalyst provided by this invention uses the palladium-nickel alloy as the active component and the nitrogen-doped carbon support as the support. Through the interaction between the active component and the support, the active metal Ni forms C=O and C-O functional groups on the nitrogen-doped carbon support, which is beneficial for the adsorption of nitro compounds. In the catalytic hydrogenation of fluorinated nitrobenzene to fluorinated aniline, the nitrogen-doped carbon material facilitates the dispersion of Ni and Pd active components. The presence of N element improves the dispersion of the active metal, resulting in a catalyst with fast reaction rate, high conversion rate, and good product selectivity. It effectively controls the degree of hydrogenation and prevents excessive hydrogenation and dehalogenation.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a supported palladium-nickel alloy catalyst, its preparation method, and its application. Background Technology

[0002] Fluorinated aniline is a novel fine chemical intermediate that has emerged in recent years due to the demand for fluorinated pesticides, pharmaceuticals, and dyes. Its downstream derivatives market is in a growth phase, with strong global demand, and future market demand is expected to maintain rapid growth. Therefore, fluorinated aniline has high research and commercial value in the agricultural and pharmaceutical fields.

[0003] Currently, aniline is typically prepared by the hydrogenation reduction of nitrobenzene due to its low cost and easy availability. Existing methods utilize Raney Ni or Pd / C catalysts (noble metal catalysts) for catalytic hydrogenation. However, for advanced functionalized nitrobenzene compounds containing special groups such as C=C, halogen atoms, carboxylic acid derivatives, or heterocyclic compounds, standard catalytic systems like Raney Ni do not achieve good selectivity. Noble metal catalysts are widely used in the nitrobenzene reduction reaction due to their long lifespan, high catalytic activity, and mild reaction conditions. However, the high price of noble metals necessitates the development of noble metal-non-noble metal alloy catalysts with good catalytic performance to reduce catalyst costs, a problem that urgently needs to be solved for industrial production.

[0004] Existing technologies, such as Chinese patent document CN 115301277 A (application number 202211082335.3), disclose a bimetallic nitrogen-hexacarbon catalyst, its preparation method, and its application. This catalyst includes an activated carbon support and a loading material, where the loading material comprises a nitrogen-hexacarbon compound, a non-precious metal element, and a precious metal element. It utilizes the interaction between nitrogen atoms and precious metal atoms to suppress the dechlorination reaction during hydrogenation and improve product selectivity. However, the non-precious metal used in this patent is one of iron, copper, or zinc, which does not achieve good catalytic performance in the catalytic conversion of fluorinated nitrobenzene to fluorinated aniline. Furthermore, copper and zinc are non-magnetic, making catalyst recovery relatively difficult. Additionally, the catalyst preparation method requires the use of strong acid nitric acid, and nitrogen doping and metal loading are performed in two steps, reducing the catalyst preparation efficiency. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a supported palladium-nickel alloy catalyst, its preparation method and application, which uses a nitrogen-containing carbon material as a support and a palladium-nickel alloy as an active component to effectively catalytically hydrogenate fluorinated nitrobenzene to produce fluorinated aniline.

[0006] To achieve the above-mentioned technical effects, the present invention adopts the following technical solution:

[0007] A supported palladium-nickel alloy catalyst comprises a total loading of 1%-20% palladium-nickel alloy and a nitrogen-doped carbon support with a nitrogen doping amount of 10-20 at%, wherein the mass ratio of palladium to nickel is 1:0.1-10.

[0008] Preferably, in the supported palladium-nickel alloy catalyst, the total loading of palladium-nickel alloy is 1%-15%.

[0009] Preferably, in the supported palladium-nickel alloy catalyst, the mass ratio of palladium to nickel is 1:5-10.

[0010] Preferably, the supported palladium-nickel alloy catalyst has a specific surface area of ​​500-800 m². 2 / g.

[0011] This application also provides a method for preparing the above-mentioned supported palladium-nickel alloy catalyst, comprising the following steps:

[0012] S1. Carrier pretreatment: The carbon material is calcined to obtain a carbon carrier material;

[0013] S2. Preparation of catalyst intermediate: Dissolve the palladium precursor, nickel precursor and nitrogen source in water and mix well to obtain a mixed solution. Impregnate the carbon support material obtained in step S1 with the mixed solution and dry to obtain the catalyst intermediate.

[0014] S3. Calcination: The catalyst intermediate obtained in step S2 is calcined in an inert gas atmosphere to obtain the supported palladium-nickel alloy catalyst.

[0015] Preferably, in step S1, the calcination temperature is 300℃-1000℃ and the calcination time is 1h-10h.

[0016] Preferably, in step S2, the palladium precursor is selected from at least one of palladium nitrate, palladium acetate, sodium chloropalladium, or ammonium chloropalladium; the nickel precursor is selected from nickel nitrate or nickel acetate.

[0017] More preferably, in step S2, palladium nitrate is used as the precursor for palladium, and nickel nitrate is used as the precursor for nickel. The oxygen surface clusters generated on the carbon support surface during impregnation and high-temperature calcination synergistically dope nitrogen elements, resulting in better metal dispersion.

[0018] Preferably, in step S2, the mass ratio of nitrogen source to carbon material is 1:5-10.

[0019] Preferably, in step S2, the impregnation time of the carbon carrier material is 30 min to 300 min, and the temperature is maintained at 0℃ to 80℃ during impregnation.

[0020] Preferably, in step S2, the drying conditions are vacuum drying at 0℃-120℃ for 1h-24h.

[0021] Preferably, in step S3, during calcination in an inert gas atmosphere, the heating rate is 1-15℃ / min, the calcination temperature is 100℃-800℃, and the calcination time is 1h-10h.

[0022] This invention also provides the application of the above-mentioned supported palladium-nickel alloy catalyst or the supported palladium-nickel alloy catalyst prepared by the preparation method, for the preparation of fluoroaniline, wherein the preparation method is as follows:

[0023] Fluorinated nitrobenzene is contacted with a supported palladium-nickel alloy catalyst in a saturated alcohol under a hydrogen atmosphere, and a hydrogenation reaction is carried out under stirring to obtain fluorinated aniline.

[0024] Preferably, in the method for preparing fluoroaniline, the pressure of the hydrogen atmosphere is 0.1 MPa-2 MPa; the reaction temperature is 80℃-100℃; the reaction time is 1h-3h; the stirring speed is 800 r / min; the mass ratio of fluoronitrobenzene to saturated alcohol is 1:1-50; and the mass ratio of supported palladium-nickel alloy catalyst to fluoronitrobenzene is 1:20-100.

[0025] The beneficial effects of this invention are:

[0026] 1. The supported palladium-nickel alloy catalyst provided by this invention uses palladium-nickel alloy as the active component and nitrogen-containing carbon as the support. Through the interaction between the active component and the support, the active metal Ni forms C=O and CO functional groups on the nitrogen-containing carbon support, which is beneficial to the adsorption of nitro compounds. In the catalytic hydrogenation of fluorinated nitrobenzene to prepare fluorinated aniline, the nitrogen-containing carbon material is beneficial to the dispersion of Ni and Pd active components. The presence of N element can make the active metal more dispersed, so that the catalyst has the effects of fast reaction rate, high conversion rate and good product selectivity, effectively controlling the degree of hydrogenation and preventing excessive hydrogenation and dehalogenation.

[0027] 2. The preparation method of the supported palladium-nickel alloy catalyst provided by this invention completes nitrogen doping and metal loading in one step, simplifying the preparation process. Simultaneously, the nitrogen source and metal precursor react together with the carbon support, providing not only a nitrogen source for nitrogen doping but also effectively controlling the particle size during metal loading, preventing excessive metal aggregation on the support surface, and effectively increasing the specific surface area of ​​the active component. Nitrate ions interact with the carbon support during impregnation and calcination, generating oxygen surface groups on the carbon support surface. These oxygen surface groups play a crucial role in stabilizing Ni particles and preferentially adsorbing nitro groups. Furthermore, the preparation process does not use environmentally polluting substances such as strong acids and alkalis, making it green and environmentally friendly. It also features simple operation and convenient recycling, greatly improving reaction stability and the economic efficiency of the preparation process. Detailed Implementation

[0028] The present invention will be further described below with reference to embodiments.

[0029] In the examples, comparative examples, and experimental cases, all apparatus and reagents used were readily available and commercially available. For instance, the reaction vessel was a YT-SFP-100 100mL stainless steel high-pressure reactor manufactured by Shanghai Yantu Experimental Instrument Co., Ltd., and the gas chromatograph used was a GC-8890 gas chromatograph manufactured by Agilent Technologies, Inc. The specific surface area of ​​the catalyst was measured according to GB / T 5816 - Determination of Surface Area of ​​Catalysts and Adsorbents.

[0030] Example 1:

[0031] A supported palladium-nickel alloy catalyst comprises a palladium-nickel alloy with a total loading of 11% and a nitrogen-doped carbon support with a nitrogen doping content of 20 at%, wherein the mass ratio of palladium to nickel is 1:10. The preparation method of the catalyst is as follows:

[0032] S1. Carrier pretreatment: 1g of activated carbon was calcined at 900℃ for 1h to obtain carbon carrier material;

[0033] S2. Preparation of catalyst intermediate: Dissolve 25 mg palladium nitrate, 495 mg nickel nitrate and 0.425 g urea in 20 mL of water and mix well to obtain a mixed solution. Impregnate the carbon support material obtained in step S1 with the mixed solution at a temperature of 25 °C for 40 min. After impregnation, vacuum dry at 105 °C for 2 h to obtain the catalyst intermediate.

[0034] S3. Calcination: The catalyst intermediate obtained in step S2 is calcined at 800°C for 2 hours under a nitrogen atmosphere at a heating rate of 4°C / min to obtain the above-mentioned supported palladium-nickel alloy catalyst.

[0035] Fluorinated aniline was prepared using the supported palladium-nickel alloy catalyst obtained in Example 1. The specific preparation steps are as follows:

[0036] In a 100 mL stainless steel reactor, 0.5 g of the supported palladium-nickel alloy catalyst prepared in Example 1, 2 g of 2,4-dinitrofluorobenzene, and 50 g of methanol were added. The hydrogen pressure was maintained at 0.8 MPa. The reaction was carried out at 100 °C with stirring at 800 r / min for 2 h. Heating and stirring were then stopped, and the reactor was cooled rapidly with cold water. The air was purged, and the sample was taken out for gas chromatography analysis. The data showed that the conversion rate of fluoronitrobenzene was 98.2%, and the selectivity for producing fluoroaniline was 97.5%. The specific surface area of ​​the supported palladium-nickel alloy catalyst was determined to be 800 m² / g by the BET method. 2 / g.

[0037] Example 2:

[0038] A supported palladium-nickel alloy catalyst comprises a total loading of 11% palladium-nickel alloy and a nitrogen-doped carbon support with a nitrogen doping content of 20 at%, wherein the mass ratio of palladium to nickel is 1:10. The preparation method of this catalyst differs from the preparation method provided in Example 1 in that 21 mg of palladium acetate is used instead of palladium nitrate as the palladium precursor.

[0039] Example 3:

[0040] A supported palladium-nickel alloy catalyst comprises a total loading of 11% palladium-nickel alloy and a nitrogen-doped carbon support with a nitrogen doping content of 20 at%, wherein the mass ratio of palladium to nickel is 1:10. The preparation method of this catalyst differs from the preparation method provided in Example 1 in that 27.6 mg of sodium chloropalladate is used instead of palladium nitrate as the palladium precursor.

[0041] Example 4:

[0042] A supported palladium-nickel alloy catalyst comprises a palladium-nickel alloy with a total loading of 11% and a nitrogen-doped carbon support with a nitrogen doping amount of 20 at% and a mass ratio of palladium to nickel of 1:10. The preparation method of this catalyst differs from the preparation method provided in Example 1 in that 26.7 mg of ammonium chloropalladate is used instead of palladium nitrate as the palladium precursor.

[0043] Example 5:

[0044] A supported palladium-nickel alloy catalyst comprises a total loading of 11% palladium-nickel alloy and a nitrogen-doped carbon support with a nitrogen doping amount of 20 at%, wherein the mass ratio of palladium to nickel is 1:10. The preparation method of this catalyst differs from the preparation method provided in Example 1 in that 423 mg of nickel acetate is used instead of nickel nitrate as the nickel precursor.

[0045] Example 6:

[0046] A supported palladium-nickel alloy catalyst comprises a total loading of 11% palladium-nickel alloy and a nitrogen-doped carbon support with a nitrogen doping content of 20 at%, wherein the mass ratio of palladium to nickel is 1:10. The preparation method of this catalyst differs from the preparation method provided in Example 1 in that 12.5 mg palladium nitrate and 10.5 mg palladium acetate are used instead of palladium nitrate as the palladium precursor.

[0047] Example 7:

[0048] A supported palladium-nickel alloy catalyst comprises a palladium-nickel alloy with a total loading of 11% and a nitrogen-doped carbon support with a nitrogen doping amount of 20 at%, wherein the mass ratio of palladium to nickel is 1:10. The preparation method of this catalyst differs from the preparation method provided in Example 1 in that 8.3 mg palladium nitrate, 7 mg palladium acetate and 9.2 mg sodium chloropalladate are used instead of palladium nitrate as the palladium precursor.

[0049] Example 8:

[0050] A supported palladium-nickel alloy catalyst comprises a total loading of 11% palladium-nickel alloy and a nitrogen-doped carbon support with a nitrogen doping amount of 20 at% wherein the mass ratio of palladium to nickel is 1:10. The preparation method of this catalyst differs from the preparation method provided in Example 1 in that 0.425 g of ethylenediamine is used as the nitrogen source.

[0051] Example 9:

[0052] A supported palladium-nickel alloy catalyst comprises a total loading of 11% palladium-nickel alloy and a nitrogen-doped carbon support with a nitrogen doping amount of 20 at% wherein the mass ratio of palladium to nickel is 1:10. The preparation method of this catalyst differs from the preparation method provided in Example 1 in that 0.5 g of ammonia water is used as the nitrogen source.

[0053] Example 10:

[0054] A supported palladium-nickel alloy catalyst comprises a total loading of 1.1% palladium-nickel alloy and a nitrogen-doped carbon support with a nitrogen doping content of 20 at%, wherein the mass ratio of palladium to nickel is 1:0.1. The preparation method of this catalyst differs from the preparation method provided in Example 1 in that the mass of nickel nitrate added is 4.95 mg.

[0055] Example 11:

[0056] A supported palladium-nickel alloy catalyst comprises a palladium-nickel alloy with a total loading of 11% and a nitrogen-doped carbon support with a nitrogen doping amount of 10 at%, wherein the mass ratio of palladium to nickel is 1:10. The preparation method of this catalyst differs from the preparation method provided in Example 1 in that the mass of urea added is 0.213 g.

[0057] Example 12:

[0058] A supported palladium-nickel alloy catalyst comprises a palladium-nickel alloy with a total loading of 11% and a nitrogen-doped carbon support with a nitrogen doping content of 20 at%, wherein the mass ratio of palladium to nickel is 1:10. The preparation method of this catalyst differs from the method provided in Example 1 in that, in step S1, the activated carbon is calcined at 350°C for 8.5 h. The specific surface area of ​​the supported palladium-nickel alloy catalyst, measured by the BET method, is 672 m².2 / g.

[0059] Example 13:

[0060] A supported palladium-nickel alloy catalyst comprises a palladium-nickel alloy with a total loading of 11% and a nitrogen-doped carbon support with a nitrogen doping amount of 20 at% and a mass ratio of palladium to nickel of 1:10. The preparation method of this catalyst differs from the preparation method provided in Example 1 in that, in step S2, the impregnation temperature is 80°C and the impregnation time is 300 min.

[0061] Example 14:

[0062] A supported palladium-nickel alloy catalyst comprises a palladium-nickel alloy with a total loading of 11% and a nitrogen-doped carbon support with a nitrogen doping amount of 20 at%, wherein the mass ratio of palladium to nickel is 1:10. The preparation method of this catalyst differs from the preparation method provided in Example 1 in that, in step S2, the drying temperature is 120°C and the drying time is 22 h.

[0063] Example 15:

[0064] A supported palladium-nickel alloy catalyst comprises a palladium-nickel alloy with a total loading of 11% and a nitrogen-doped carbon support with a nitrogen doping content of 20 at%, wherein the mass ratio of palladium to nickel is 1:10. The preparation method of this catalyst differs from the preparation method provided in Example 1 in that, in step S3, the heating rate is 12°C / min, the calcination temperature is 150°C, and the drying time is 10 h. The specific surface area of ​​the supported palladium-nickel alloy catalyst, measured by the BET method, is 500 m². 2 / g.

[0065] Comparative Example 1:

[0066] A supported palladium-on-carbon catalyst comprises a total palladium loading of 1% and a nitrogen-doped carbon support with a nitrogen doping amount of 20 at%. The preparation method of this catalyst differs from the preparation method provided in Example 1 in that nickel nitrate is not added in step S2.

[0067] Comparative Example 2:

[0068] A supported palladium-on-carbon catalyst comprises a total loading of 10% nickel and a nitrogen-doped carbon support with a nitrogen doping amount of 20 at%. The preparation method of this catalyst differs from the preparation method provided in Example 1 in that palladium nitrate is not added in step S2.

[0069] Comparative Example 3:

[0070] A supported palladium-nickel-carbon catalyst comprises a palladium-nickel alloy with a total loading of 11% and a carbon support. The preparation method of this catalyst differs from that provided in Example 1 in that urea is not added in step S2. The specific surface area of ​​the supported palladium-nickel alloy catalyst, measured by the BET method, is 232 m². 2 / g

[0071] Comparative Example 4:

[0072] A supported palladium-iron alloy catalyst comprises a total loading of 11% palladium-iron alloy and a nitrogen-doped carbon support with a nitrogen doping amount of 20 at%. The preparation method of this catalyst differs from the preparation method provided in Example 1 in that, in step S2, nickel nitrate is no longer added but 723 mg of ferric nitrate is added instead.

[0073] Comparative Example 5:

[0074] A supported palladium-cobalt alloy catalyst comprises a total loading of 11% palladium-cobalt alloy and a nitrogen-doped carbon support with a nitrogen doping content of 20 at%. The preparation method of this catalyst differs from the preparation method provided in Example 1 in that, in step S2, instead of adding nickel nitrate, 494 mg of cobalt nitrate is added.

[0075] Comparative Example 6:

[0076] A supported palladium-zinc alloy catalyst comprises a palladium-cobalt alloy with a total loading of 11% and a nitrogen-doped carbon support with a nitrogen doping amount of 20 at%. The preparation method of this catalyst differs from the preparation method provided in Example 1 in that, in step S2, instead of adding nickel nitrate, 380 mg of copper nitrate is added.

[0077] Comparative Example 7:

[0078] A supported palladium-zinc alloy catalyst comprises a palladium-cobalt alloy with a total loading of 11% and a nitrogen-doped carbon support with a nitrogen doping amount of 20 at%. The preparation method of this catalyst differs from the preparation method provided in Example 1 in that, in step S2, instead of adding nickel nitrate, 455 mg of zinc nitrate is added.

[0079] Comparative Example 8:

[0080] A supported palladium-nickel alloy catalyst comprises a palladium-nickel alloy with a total loading of 11% and a nitrogen-doped carbon support with a nitrogen doping content of 20 at%, wherein the mass ratio of palladium to nickel is 1:10. The preparation method of the catalyst is as follows:

[0081] S1. Carrier pretreatment: 1g of activated carbon was calcined at 900℃ for 1h to obtain carbon carrier material;

[0082] S2. Preparation of nitrogen-doped support: Dissolve 0.425g of urea in 1mL of water, and impregnate the carbon support material obtained in step S1 to obtain nitrogen-doped support;

[0083] S3. Metal support: Dissolve 25 mg palladium nitrate and 495 mg nickel nitrate in 20 mL of water and mix well to obtain a mixed solution. Impregnate the nitrogen-carbon support material obtained in step S2 with the mixed solution at a temperature of 25 °C for 40 min. After impregnation, vacuum dry at 105 °C for 2 h to obtain the catalyst intermediate.

[0084] S4. Calcination: The catalyst intermediate obtained in step S3 is calcined at 800°C for 2 hours under a nitrogen atmosphere at a heating rate of 4°C / min to obtain the above-mentioned supported palladium-nickel alloy catalyst.

[0085] Experimental Example 1:

[0086] Fluorinated aniline was prepared using a catalyst, and the method for preparing fluorinated aniline provided in Example 1 was used. The catalyst obtained in Example 1 was replaced in equal amounts with the catalysts prepared in different examples and comparative examples. The specific experimental results are shown in Table 1.

[0087] Table 1. Catalytic experimental results with different catalysts

[0088]

[0089]

[0090] The conversion rate is calculated as follows in the table: The selective calculation method is as follows In the formula, m NB This represents the peak area of ​​2,4-dinitrofluorobenzene, expressed in pA·s; m AN This represents the peak area of ​​2,4-diaminofluorobenzene, expressed in pA·s; m by-product This represents the peak area of ​​the byproduct, expressed in pA·s.

[0091] As shown in Table 1, compared with Examples 2-4 and 6-7, Example 1 exhibits better catalytic efficiency and selectivity. This is because when palladium nitrate is used as a precursor, nitrate ions can provide a certain amount of nitrogen for doping during the preparation process. The interaction between nitrate ions and carbon support generates oxygen surface clusters, resulting in better metal dispersion. Therefore, the catalyst prepared in Example 1 has better catalytic performance.

[0092] Compared to Example 5, Example 1 exhibits better catalytic efficiency and selectivity. This is because when nickel nitrate is used as a precursor, nitrate ions can provide nitrogen for doping during the preparation process. The interaction between nitrate ions and the carbon support generates oxygen surface clusters, resulting in better metal dispersion. Therefore, the catalyst prepared in Example 1 has better catalytic performance.

[0093] Compared with Examples 8-9, Example 1 showed better catalytic efficiency and selectivity. This is because when urea is used as a nitrogen source, the H2 generated during high-temperature pyrolysis will catalyze the Ni... 2+ It is reduced to metallic Ni.

[0094] Compared with Example 10, Example 1 showed better catalytic rate and selectivity. This is because a higher loading of active metal Ni leads to better catalyst performance. Therefore, the catalyst prepared in Example 1 exhibits better catalytic effect.

[0095] Compared to Example 11, Example 1 exhibits better catalytic efficiency and selectivity. This is because a higher nitrogen doping concentration leads to a stronger interaction between N and the activated carbon support. Therefore, the catalyst prepared in Example 1 demonstrates superior catalytic performance.

[0096] Compared to Examples 12-15, Example 1 exhibits better catalytic rate and selectivity. This is because the conditions during catalyst preparation are crucial for the interaction between the active metal and the support in the catalyst, and Example 1 represents the optimal conditions. Therefore, the catalyst prepared in Example 1 demonstrates superior catalytic performance.

[0097] Compared with Comparative Examples 1-2, Example 1 showed better catalytic efficiency and selectivity. This is because the performance of catalysts with a single active metal loading is relatively poor compared to metal alloy catalysts. Therefore, the catalyst prepared in Example 1 has better catalytic effect.

[0098] Compared with Comparative Example 3, Example 1 showed better catalytic efficiency and selectivity. This is because the nitrogen-doped support can better bind with the active metal Ni, avoiding excessive metal aggregation on the support surface. The specific surface area of ​​the prepared supported palladium-nickel alloy catalyst increased from 232 m² / g. 2 / g increased to 800m 2 / g. Therefore, the catalyst prepared in Example 1 has better catalytic performance.

[0099] Compared with Comparative Examples 4-7, Example 1 showed better catalytic efficiency and selectivity. This is because the interaction between Ni and Pd is better than that between other metals. Therefore, the catalyst prepared in Example 1 has better catalytic performance.

[0100] Compared with Comparative Example 8, Example 1 showed better catalytic efficiency and selectivity. This is because the one-step reaction conditions are not only simple and easy to operate, but also facilitate better interaction between the active metal and the carbon support. Therefore, the catalyst prepared in Example 1 has better catalytic performance.

[0101] Experimental Example 2:

[0102] Fluorinated aniline was prepared using a supported palladium-nickel alloy catalyst. The catalyst prepared in Example 1 was used for catalysis, but the reaction conditions were different for each group. The specific reaction conditions and experimental results are shown in Table 2.

[0103] Table 2. Catalytic experimental results under different reaction conditions

[0104]

[0105]

[0106] In the table, the conversion rate and selectivity are calculated using the same method as in Experiment Example 1.

[0107] As shown in Table 2, under the reaction conditions of Experimental Group 1, the conversion rate and selectivity were optimal. When the reaction conditions were different, such as comparing Experimental Group 1 with Experimental Group 2, the reaction temperature affected the selectivity of the catalyst because the reduction reaction of the reactants was not complete at lower temperatures; compared with Experimental Group 3, the reaction pressure affected the conversion rate of the catalyst because the hydrogenation degree was insufficient at lower pressures; compared with Experimental Group 4, the reaction time affected both the conversion rate and selectivity of the catalyst because the reaction was not complete at shorter times; compared with Experimental Groups 1 and 5, and Experimental Group 8, both the reaction temperature and the feed ratio affected the conversion rate and selectivity of the catalyst. When the amount of catalyst added was insufficient, the conversion rate and selectivity were negatively impacted. The selectivity is relatively low. Increasing the reaction temperature to 150℃ affects the selectivity of the catalyst, and the defluorination of the reactants leads to a decrease in selectivity. Compared with experimental group 6, increasing the reaction temperature to 120℃ has little effect on the conversion rate and selectivity of the catalyst, and can be ignored. Compared with experimental group 7, the reaction time affects the conversion rate and selectivity of the catalyst. As shown in experimental group 1, after 120 min of reaction, both the conversion rate and selectivity are above 97%. After extending the reaction time to 360 min, both the conversion rate and selectivity reach above 99%. This is because the reaction is more complete after extending the reaction time. However, after 120 min, the change in conversion rate and selectivity with time is smaller. Therefore, the most economical reaction time should be 120 min.

Claims

1. A method for preparing fluoroaniline, characterized in that, Fluorinated nitrobenzene is contacted with a supported palladium-nickel alloy catalyst in a saturated alcohol under a hydrogen atmosphere, and a hydrogenation reaction is carried out under stirring to obtain fluorinated aniline; the supported palladium-nickel alloy catalyst comprises a total loading of 1%-20% palladium-nickel alloy and a nitrogen-doped carbon support with a nitrogen doping amount of 10-20 at%, and the mass ratio of palladium to nickel is 1:0.1-10. The preparation method of the supported palladium-nickel alloy catalyst includes the following steps: S1. Carrier pretreatment: The carbon material is calcined to obtain a carbon carrier material; S2. Preparation of catalyst intermediate: Dissolve the palladium precursor, nickel precursor and nitrogen source in water and mix well to obtain a mixed solution. Impregnate the carbon support material obtained in step S1 with the mixed solution and dry to obtain the catalyst intermediate. The palladium precursor is palladium nitrate and the nickel precursor is nickel nitrate. S3. Calcination: The catalyst intermediate obtained in step S2 is calcined in an inert gas atmosphere to obtain the supported palladium-nickel alloy catalyst.

2. The method for preparing fluoroaniline according to claim 1, characterized in that, In the preparation method of the fluoroaniline, the pressure of the hydrogen atmosphere is 0.1MPa-2MPa; the reaction temperature is 80℃-100℃; the reaction time is 1h-3h; the stirring speed is 800r / min; the mass ratio of fluoronitrobenzene to saturated alcohol is 1:1-50; and the mass ratio of supported palladium-nickel alloy catalyst to fluoronitrobenzene is 1:20-100.

3. The method for preparing fluoroaniline according to claim 1, characterized in that, The total loading of palladium-nickel alloy is 1%-15%.

4. The method for preparing fluoroaniline according to claim 1, characterized in that, The mass ratio of palladium to nickel is 1:5-10.

5. The method for preparing fluoroaniline according to claim 1, characterized in that, The supported palladium-nickel alloy catalyst has a specific surface area of ​​500-800 m². 2 / g.

6. The method for preparing fluoroaniline according to claim 1, characterized in that, In step S1, the calcination temperature is 300℃-1000℃ and the calcination time is 1h-10h.

7. The method for preparing fluoroaniline according to claim 1, characterized in that, In step S2, the mass ratio of nitrogen source to carbon material is 1:5-10, the impregnation time of carbon carrier material is 30min-300min, the temperature is maintained at 0℃-80℃ during impregnation, and the drying conditions are vacuum drying at 0℃-120℃ for 1h-24h. In step S3, during calcination in an inert gas atmosphere, the heating rate is 1-15℃ / min, the calcination temperature is 150℃-800℃, and the calcination time is 1h-10h.

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