Process for the preparation of o-chloroaniline by hydrogenation of o-chloronitrobenzene

Abstract

This invention belongs to the field of fine chemical technology, specifically relating to a process for the hydrogenation of o-chloronitrobenzene to o-chloroaniline. The process includes the following steps: o-chloronitrobenzene reacts with hydrogen in the presence of a Pd / N,B-C catalyst to obtain o-chloroaniline; the Pd / N,B-C catalyst comprises an N,B co-doped carbon support and a Pd active component supported on the support. This invention utilizes a Pd / N,B-C catalyst combined with a solvent-free preparation process to achieve a highly efficient and selective conversion of o-chloronitrobenzene to o-chloroaniline.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical technology, specifically relating to a process for preparing o-chloroaniline by hydrogenation of o-chloronitrobenzene. Background Technology

[0002] o-Chloroaniline is an important fine chemical intermediate used in industries such as pesticides, pharmaceuticals, dyes, and polyurethanes. Currently, its synthesis methods mainly include electrolytic reduction, chemical reduction, and catalytic hydrogenation reduction. Among these, catalytic hydrogenation has become a focus of research and application in this field due to its advantages such as mild reaction conditions, easy product separation, and minimal and easily treatable waste.

[0003] However, the dechlorination side reaction accompanying the reduction of the target nitro group during catalytic hydrogenation is a core challenge leading to decreased product selectivity. Traditional skeletal nickel catalysts are prone to initiating dechlorination side reactions during hydrogenation, resulting in poor selectivity and environmental pollution. Therefore, developing novel hydrogenation catalysts with high selectivity and environmental friendliness is crucial for achieving efficient synthesis of o-chloroaniline.

[0004] Chinese patent application CN1660774A discloses a method for preparing o-chloroaniline. The method uses o-nitrochlorobenzene as a raw material and reacts it at 150℃-250℃ in the presence of ethanol solvent and catalyst. After the reaction is complete, o-chloroaniline is obtained by post-treatment. The catalyst is selected from one of the following: Ru / C, amorphous NiB, Ni-Fe-B, Ni-Co-B. This technical solution has low hydrogen transfer efficiency, poor atom economy, and it is difficult to balance conversion rate and selectivity. In addition, this solution has the problem of alcohol solvent recovery.

[0005] Chinese patent application CN106732733A discloses the preparation of a nitrogen-doped carbon-coated core-shell nickel-iron alloy nanocatalyst and its application in catalyzing the hydrogenation reaction of o-chloronitrobenzene. The catalyst has a complex core-shell structure, which requires the synthesis of an LDH precursor (involving steps such as colloid milling, crystallization, and freeze-drying) before mixing and pyrolyzing it with a nitrogen source. The process is cumbersome, energy-intensive, difficult to scale up industrially, and costly. Summary of the Invention

[0006] Existing processes for preparing o-chloroaniline suffer from poor catalyst selectivity and the problem of alcohol solvent recovery. To address this issue, this invention provides a process for preparing o-chloroaniline by hydrogenation of o-chloronitrobenzene.

[0007] To achieve the objectives of this invention, the following technical solution is adopted:

[0008] This invention provides a process for preparing o-chloroaniline by hydrogenation of o-chloronitrobenzene, comprising the following steps: o-Chloronitrobenzene reacts with hydrogen in the presence of a Pd / N,BC catalyst to yield o-chloroaniline.

[0009] The Pd / N,BC catalyst comprises an N,B co-doped carbon support and a Pd active component supported on the support.

[0010] By adopting the above technical solution, the N,B co-doped carbon support has excellent pore structure and chemical stability, which can play a good anchoring role for the Pd active component, effectively avoiding the aggregation of Pd particles during the reaction process, and giving the catalyst excellent long-term stability. This process uses hydrogen as a reducing agent, and no toxic or harmful pollutants are generated. At the same time, no solvent needs to be added to the reaction system, and the subsequent product separation is simple.

[0011] In the Pd / N,BC catalyst, the Pd loading is 0.2%-0.5%.

[0012] By adopting the above technical solution, at this loading level, the N,B co-doped carbon support has excellent dispersion and anchoring effects on the Pd active component, ensuring that the catalyst has high-efficiency catalytic hydrogenation performance.

[0013] The reaction is carried out at a temperature of 60-100℃, a pressure of 0.1-1 MPa, and a mass hourly space velocity of 0.5-2 h⁻¹. -1 The hydrogen-to-oil ratio is (1-10):1.

[0014] By adopting the above technical solution, the reaction conditions are mild, which can effectively suppress the hydrogenolysis side reaction of the C-Cl bond in the o-chloronitrobenzene molecule and reduce the generation of dechlorination impurities.

[0015] The reaction was carried out under solvent-free conditions.

[0016] Preferably, the preparation method of the Pd / N,BC catalyst includes the following steps: (1) Mix carbon materials, boric acid and urea, and pyrolyze them at high temperature under an inert atmosphere to obtain N,B co-doped carbon support; (2) Mix the N,B co-doped carbon support, H2PdCl4 solution and water, stir thoroughly, separate, wash and dry to obtain Pd precursor / N,BC; (3) The Pd precursor / N,BC is heated to 300-350℃ in Ar atmosphere and then switched to 5% H2 / Ar mixture. The mixture is reduced at 300-350℃ for 1.5-2h and then cooled to obtain Pd / N,BC catalyst.

[0017] By adopting the above technical solution, the catalyst preparation process is simple and convenient to operate; high-temperature pyrolysis is used to achieve co-doping of N and B elements in the carbon support, thereby regulating the electronic structure and surface chemical properties of the carbon support, enhancing the interaction between the support and the Pd active component, and improving the catalytic activity and stability of the catalyst; the subsequent reduction step has a moderate temperature, avoiding the growth of Pd particles caused by high-temperature reduction, and ensuring that the catalyst has a high specific surface area and a high number of active sites.

[0018] Preferably, in step (1), the mass ratio of the carbon material, boric acid and urea is 1:(0.5-2):(0.4-1.2).

[0019] By adopting the above technical solution, within this mass ratio range, it can be ensured that N and B elements are uniformly distributed in the carbon support. If the amount of boric acid or urea is low, there will be too few N and B elements, making it impossible to form an effective N,B co-doped structure and thus difficult to exert the synergistic effect of modifying the support. If the amount is too high, it is easy to agglomerate, destroy the pore structure of the carbon support, and reduce the specific surface area of ​​the support. The N,B co-doped carbon support prepared under this ratio can provide a good structural basis for efficient catalytic hydrogenation reaction to the greatest extent.

[0020] Preferably, in step (1), the carbon material is selected from activated carbon, carbon nanotubes, and graphene.

[0021] By adopting the above technical solutions, activated carbon and other carbon materials have high specific surface area, well-developed pore structure and excellent conductivity, which can provide sufficient sites for the doping of N and B elements, and at the same time create favorable conditions for the loading of Pd active components and the transport of reactants and products. In addition, activated carbon and other carbon materials have strong chemical stability and are not prone to structural damage during high-temperature pyrolysis and hydrogenation reactions, which can ensure the long-term stability of the catalyst.

[0022] Preferably, in step (1), the pyrolysis temperature is 750-900℃ and the pyrolysis time is 2-4h.

[0023] By adopting the above technical solution, at this pyrolysis temperature, it is possible to ensure that urea is fully carbonized and N element is doped, while promoting the decomposition of boric acid to introduce B element into the carbon support structure, forming a stable N,B co-doped structure. If the temperature is too low, the doping will be insufficient and the support modification effect will be poor. If the temperature is too high, the carbon support is prone to excessive graphitization, resulting in a decrease in specific surface area. A pyrolysis time of 2-4 hours can ensure that heteroatoms diffuse and dop in the carbon support uniformly, avoiding the problem of uneven doping caused by insufficient time and improving the quality of the support.

[0024] Preferably, in step (2), the ratio of the amount of N,B co-doped carbon support to water is 1g:(100-150)mL.

[0025] By adopting the above technical solution, water at this dosage can fully disperse the N,B co-doped carbon support in the system, avoiding support aggregation.

[0026] Preferably, in step (2), the stirring temperature is 30-50℃ and the stirring time is 12-20h.

[0027] By adopting the above technical solution, a stirring temperature of 30-50℃ can accelerate the diffusion rate of Pd ions in H2PdCl4 solution, promote the interaction between Pd ions and the active sites on the surface of N,B co-doped carbon support, and improve the loading efficiency of Pd precursor; a stirring time of 12-20h can ensure that Pd ions are fully adsorbed on the support surface, avoiding problems such as insufficient Pd loading or uneven distribution due to insufficient adsorption.

[0028] In summary, the beneficial effects of this invention are: 1. In the Pd / N,BC catalyst prepared by this invention, there is a synergistic effect between the N,B co-doped carbon support and the Pd active component. It can not only significantly improve the dispersion of the Pd active component, but also regulate the electronic structure of Pd, enhance its adsorption and activation ability for nitro groups in o-chloronitrobenzene, and effectively suppress the hydrogenolysis side reaction of C-Cl bond, greatly reduce the generation of dechlorination impurities, and make the target product o-chloroaniline highly selective and highly pure. 2. This invention uses a Pd catalyst supported on an N,B co-doped carbon support and combines it with a solvent-free preparation process to achieve a highly efficient and selective conversion of o-chloronitrobenzene to o-chloroaniline. The target product has high purity and few by-products. The catalyst has low preparation cost, good stability and can be recycled, reducing production energy consumption and cost. The entire process is mild, simple to operate and highly safe, making it easy to promote and apply in industrial applications. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments.

[0030] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples and comparative examples are commercially available.

[0031] Preparation Example 1: Preparation of Pd / N,BC Catalyst (1) Grind 100g of activated carbon and pass it through a 100-200 mesh sieve. Stir it with 100mL of 1mol / L nitric acid solution at 80°C for 6h. After cooling, wash the filtrate until the pH=7. Dry it in a forced-air drying oven at 120°C for 12h to obtain dried activated carbon.

[0032] Add 5g of dry activated carbon to 150mL of a mixed aqueous solution containing 8g of boric acid and 2g of urea, stir at room temperature for 6h to fully impregnate, place the beaker in an 80°C water bath to slowly evaporate most of the water to form a viscous slurry, and dry in a forced-air drying oven at 80°C for 12h to obtain the precursor powder. The precursor powder was evenly spread in a quartz boat, placed in a tube furnace, purged with argon gas for 30 min, heated to 900 °C at a heating rate of 5 °C / min, held for 2 h, cooled to room temperature, washed 3 times with hot water, and dried in a forced-air drying oven at 80 °C for 12 h to obtain N,B co-doped carbon support. (2) Mix 1g of N,B co-doped carbon support with 150mL of water, stir for 30min, slowly add 5mL of H2PdCl4 solution with a concentration of 1.0mg Pd / mL, stir at 35℃ for 18h; centrifuge the slurry, wash with deionized water until there are no chloride ions in the supernatant, transfer to a vacuum drying oven and dry at 60℃ for 12h to obtain Pd precursor / N,BC; (3) The Pd precursor / N,BC was heated to 350°C in an Ar atmosphere and then switched to a 5% H2 / Ar mixture. The mixture was reduced at 350°C for 2 hours and then cooled to obtain the Pd / N,BC catalyst.

[0033] Preparation Example 2: Preparation of Pd / N,BC Catalyst (1) Grind 100g of activated carbon and pass it through a 100-200 mesh sieve. Stir it with 100mL of 1mol / L nitric acid solution at 80°C for 6h. After cooling, wash the filtrate until the pH=7. Dry it in a forced-air drying oven at 120°C for 12h to obtain dried activated carbon.

[0034] Add 5g of dry activated carbon to 150mL of a mixed aqueous solution containing 4g of boric acid and 4g of urea, stir at room temperature for 6h to fully impregnate, place the beaker in an 80°C water bath to slowly evaporate most of the water to form a viscous slurry, and dry in a forced-air drying oven at 80°C for 12h to obtain the precursor powder. The precursor powder was evenly spread in a quartz boat, placed in a tube furnace, purged with argon gas for 30 min, heated to 750 °C at a heating rate of 5 °C / min, held for 3 h, cooled to room temperature, washed 3 times with hot water, and dried in a forced-air drying oven at 80 °C for 12 h to obtain N,B co-doped carbon support. (2) Mix 1g of N,B co-doped carbon support with 100mL of water, stir for 30min, slowly add 4mL of H2PdCl4 solution with a concentration of 1.0mg Pd / mL, stir at 50℃ for 12h; centrifuge the slurry, wash with deionized water until there are no chloride ions in the supernatant, transfer to a vacuum drying oven and dry at 60℃ for 12h to obtain Pd precursor / N,BC; (3) The Pd precursor / N,BC was heated to 350°C in an Ar atmosphere and then switched to a 5% H2 / Ar mixture. The mixture was reduced at 350°C for 2 hours and then cooled to obtain the Pd / N,BC catalyst.

[0035] Preparation Example 3: Preparation of Pd / N,BC Catalyst (1) Grind 100g of activated carbon and pass it through a 100-200 mesh sieve. Stir it with 100mL of 1mol / L nitric acid solution at 80°C for 6h. After cooling, wash the filtrate until the pH=7. Dry it in a forced-air drying oven at 120°C for 12h to obtain dried activated carbon.

[0036] Add 5g of dry activated carbon to 150mL of a mixed aqueous solution containing 7.5g of boric acid and 5g of urea, stir at room temperature for 6h to fully impregnate, place the beaker in an 80°C water bath to slowly evaporate most of the water to form a viscous slurry, and dry in a forced-air drying oven at 80°C for 12h to obtain the precursor powder. The precursor powder was evenly spread in a quartz boat, placed in a tube furnace, purged with argon gas for 30 min, heated to 800 °C at a heating rate of 5 °C / min, held for 4 h, cooled to room temperature, washed 3 times with hot water, and dried in a forced-air drying oven at 80 °C for 12 h to obtain N,B co-doped carbon support. (2) Mix 1g of N,B co-doped carbon support with 100mL of water, stir for 30min, slowly add 2mL of H2PdCl4 solution with a concentration of 1.0mg Pd / mL, stir at 40℃ for 20h; centrifuge the slurry, wash with deionized water until there are no chloride ions in the supernatant, transfer to a vacuum drying oven and dry at 60℃ for 12h to obtain Pd precursor / N,BC; (3) The Pd precursor / N,BC was heated to 300°C in an Ar atmosphere and then switched to a 5% H2 / Ar mixture. The mixture was reduced at 300°C for 2 hours and then cooled to obtain the Pd / N,BC catalyst.

[0037] Preparation Example 4: Preparation of Pd / N,BC Catalyst (1) Grind 100g of carbon nanotubes and pass them through a 100-200 mesh sieve. Stir them with 100mL of 1mol / L nitric acid solution at 80°C for 6h. After cooling, wash the filtrate until the pH=7. Dry it in a forced-air drying oven at 120°C for 12h to obtain dried carbon nanotubes.

[0038] Add 5g of dried carbon nanotubes to 150mL of a mixed aqueous solution containing 2.5g of boric acid and 6g of urea, stir at room temperature for 6h to fully impregnate, place the beaker in an 80°C water bath to slowly evaporate most of the water to form a viscous slurry, and dry in a forced-air drying oven at 80°C for 12h to obtain the precursor powder. The precursor powder was evenly spread in a quartz boat, placed in a tube furnace, purged with argon gas for 30 min, heated to 800 °C at a heating rate of 5 °C / min, held for 3 h, cooled to room temperature, washed 3 times with hot water, and dried in a forced-air drying oven at 80 °C for 12 h to obtain N,B co-doped carbon support. (2) Mix 1g of N,B co-doped carbon support with 120mL of water, stir for 30min, slowly add 3mL of H2PdCl4 solution with a concentration of 1.0mg Pd / mL, stir at 30℃ for 20h; centrifuge the slurry, wash with deionized water until there are no chloride ions in the supernatant, transfer to a vacuum drying oven and dry at 60℃ for 12h to obtain Pd precursor / N,BC; (3) The Pd precursor / N,BC was heated to 300°C in an Ar atmosphere and then switched to a 5% H2 / Ar mixture. The mixture was reduced at 300°C for 1.5 h and then cooled to obtain the Pd / N,BC catalyst.

[0039] Preparation Example 5: Preparation of Pd / N,BC Catalyst (1) Grind 100g of graphene, pass it through a 100-200 mesh sieve, stir it with 100mL of 1mol / L nitric acid solution at 80°C for 6h, cool it, wash it until the filtrate reaches pH=7, and dry it in a forced-air drying oven at 120°C for 12h to obtain dried graphene.

[0040] Add 5g of dry graphene to 150mL of a mixed aqueous solution containing 5g of boric acid and 5g of urea, stir at room temperature for 6h to fully impregnate, place the beaker in an 80°C water bath to slowly evaporate most of the water to form a viscous slurry, and dry in a forced-air drying oven at 80°C for 12h to obtain the precursor powder. The precursor powder was evenly spread in a quartz boat, placed in a tube furnace, purged with argon gas for 30 min, heated to 850 °C at a heating rate of 5 °C / min, held for 4 h, cooled to room temperature, washed 3 times with hot water, and dried in a forced-air drying oven at 80 °C for 12 h to obtain N,B co-doped carbon support. (2) Mix 1g of N,B co-doped carbon support with 150mL of water, stir for 30min, slowly add 5mL of H2PdCl4 solution with a concentration of 1.0mg Pd / mL, stir at 35℃ for 15h; centrifuge the slurry, wash with deionized water until there are no chloride ions in the supernatant, transfer to a vacuum drying oven and dry at 60℃ for 12h to obtain Pd precursor / N,BC; (3) The Pd precursor / N,BC was heated to 350°C in an Ar atmosphere and then switched to a 5% H2 / Ar mixture. The mixture was reduced at 350°C for 2 hours and then cooled to obtain the Pd / N,BC catalyst.

[0041] Preparation Example 6: Preparation of Pd / N,BC Catalyst (1) Grind 100g of graphene, pass it through a 100-200 mesh sieve, stir it with 100mL of 1mol / L nitric acid solution at 80°C for 6h, cool it, wash it until the filtrate reaches pH=7, and dry it in a forced-air drying oven at 120°C for 12h to obtain dried graphene.

[0042] Add 5g of dry graphene to 150mL of a mixed aqueous solution containing 9g of boric acid and 6g of urea, stir at room temperature for 6h to fully impregnate, place the beaker in an 80°C water bath to slowly evaporate most of the water to form a viscous slurry, and dry in a forced-air drying oven at 80°C for 12h to obtain the precursor powder. The precursor powder was evenly spread in a quartz boat, placed in a tube furnace, purged with argon gas for 30 min, heated to 850 °C at a heating rate of 5 °C / min, held for 4 h, cooled to room temperature, washed 3 times with hot water, and dried in a forced-air drying oven at 80 °C for 12 h to obtain N,B co-doped carbon support. (2) Mix 1g of N,B co-doped carbon support with 150mL of water, stir for 30min, slowly add 2mL of H2PdCl4 solution with a concentration of 1.0mg Pd / mL, stir at 40℃ for 16h; centrifuge the slurry, wash with deionized water until there are no chloride ions in the supernatant, transfer to a vacuum drying oven and dry at 60℃ for 12h to obtain Pd precursor / N,BC; (3) The Pd precursor / N,BC was heated to 300°C in an Ar atmosphere and then switched to a 5% H2 / Ar mixture. The mixture was reduced at 300°C for 2 hours and then cooled to obtain the Pd / N,BC catalyst.

[0043] Preparation Example 7: Preparation of Pd / N,BC Catalyst (1) Grind 100g of activated carbon and pass it through a 100-200 mesh sieve. Stir it with 100mL of 1mol / L nitric acid solution at 80°C for 6h. After cooling, wash the filtrate until the pH=7. Dry it in a forced-air drying oven at 120°C for 12h to obtain dried activated carbon.

[0044] Add 5g of dry activated carbon to 150mL of a mixed aqueous solution containing 10g of boric acid and 5g of urea, stir at room temperature for 6h to fully impregnate, place the beaker in an 80°C water bath to slowly evaporate most of the water to form a viscous slurry, and dry in a forced-air drying oven at 80°C for 12h to obtain the precursor powder. The precursor powder was evenly spread in a quartz boat, placed in a tube furnace, purged with argon gas for 30 min, heated to 800 °C at a heating rate of 5 °C / min, held for 3 h, cooled to room temperature, washed 3 times with hot water, and dried in a forced-air drying oven at 80 °C for 12 h to obtain N,B co-doped carbon support. (2) Mix 1g of N,B co-doped carbon support with 150mL of water, stir for 30min, slowly add 3mL of H2PdCl4 solution with a concentration of 1.0mg Pd / mL, stir at 30℃ for 20h; centrifuge the slurry, wash with deionized water until there are no chloride ions in the supernatant, transfer to a vacuum drying oven and dry at 60℃ for 12h to obtain Pd precursor / N,BC; (3) The Pd precursor / N,BC was heated to 320°C in an Ar atmosphere and then switched to a 5% H2 / Ar mixture. The mixture was reduced at 320°C for 1.5 h and then cooled to obtain the Pd / N,BC catalyst.

[0045] Example 1 Using o-chloronitrobenzene as a raw material, o-chloronitrobenzene was thoroughly mixed with hydrogen gas measured by a mass flow meter in a static mixer using a metering pump. The mixture was then fed from the top into an isothermal bed reactor containing the Pd / N,BC catalyst prepared in Preparation Example 1. The reaction was carried out at a controlled temperature of 80°C, a reaction pressure of 1 MPa, and a mass hourly space velocity of 0.8 h⁻¹. -1 The hydrogen-to-oil ratio (molar ratio of hydrogen gas intake to o-chloronitrobenzene) was 5:1. The reacted material flowed out from the bottom of the reactor and entered a high-pressure gas-liquid separator. The liquid product was collected, sampled, and analyzed by gas chromatography to determine the conversion rate of o-chloronitrobenzene and the selectivity of o-chloroaniline.

[0046] Example 2 Using 1 kg of o-chloronitrobenzene as raw material, o-chloronitrobenzene was thoroughly mixed with hydrogen gas measured by a mass flow meter in a static mixer using a metering pump. The mixture was then fed from the top into an isothermal bed reactor containing the Pd / N,BC catalyst prepared in Preparation Example 3. The reaction was carried out at a controlled temperature of 100 °C, a reaction pressure of 0.5 MPa, and a mass hourly space velocity of 1.2 h⁻¹. -1 The hydrogen-to-oil ratio was 8:1. The reacted material flowed out from the bottom of the reactor and entered a high-pressure gas-liquid separator. The liquid product was collected, sampled, and analyzed by gas chromatography to determine the conversion rate of o-chloronitrobenzene and the selectivity of o-chloroaniline.

[0047] Example 3 Using 1 kg of o-chloronitrobenzene as raw material, o-chloronitrobenzene was thoroughly mixed with hydrogen gas measured by a mass flow meter in a static mixer using a metering pump. The mixture was then fed from the top into an isothermal bed reactor containing the Pd / N,BC catalyst prepared in Preparation Example 2. The reaction was carried out at a controlled temperature of 60°C, a reaction pressure of 0.2 MPa, and a mass hourly space velocity of 0.5 h⁻¹. -1 The hydrogen-to-oil ratio was 2:1. The reacted material flowed out from the bottom of the reactor and entered a high-pressure gas-liquid separator. The liquid product was collected, sampled, and analyzed by gas chromatography to determine the conversion rate of o-chloronitrobenzene and the selectivity of o-chloroaniline.

[0048] Example 4 Using 1 kg of o-chloronitrobenzene as raw material, o-chloronitrobenzene was thoroughly mixed with hydrogen gas measured by a mass flow meter in a static mixer using a metering pump. The mixture was then fed from the top into an isothermal bed reactor containing the Pd / N,BC catalyst prepared in Preparation Example 3. The reaction was carried out at a controlled temperature of 90 °C, a reaction pressure of 1 MPa, and a mass hourly space velocity of 1.5 h⁻¹. -1 The hydrogen-to-oil ratio was 4:1. The reacted material flowed out from the bottom of the reactor and entered a high-pressure gas-liquid separator. The liquid product was collected, sampled, and analyzed by gas chromatography to determine the conversion rate of o-chloronitrobenzene and the selectivity of o-chloroaniline.

[0049] Example 5 Using 1 kg of o-chloronitrobenzene as raw material, o-chloronitrobenzene was thoroughly mixed with hydrogen gas measured by a mass flow meter in a static mixer using a metering pump. The mixture was then fed from the top into an isothermal bed reactor containing the Pd / N,BC catalyst prepared in Preparation Example 1. The reaction was carried out at a controlled temperature of 90 °C, a reaction pressure of 0.2 MPa, and a mass hourly space velocity of 2 h⁻¹. -1 The hydrogen-to-oil ratio was 1:1. The reacted material flowed out from the bottom of the reactor and entered a high-pressure gas-liquid separator. The liquid product was collected, sampled, and analyzed by gas chromatography to determine the conversion rate of o-chloronitrobenzene and the selectivity of o-chloroaniline.

[0050] Example 6 Using 1 kg of o-chloronitrobenzene as raw material, o-chloronitrobenzene was thoroughly mixed with hydrogen gas measured by a mass flow meter in a static mixer using a metering pump. The mixture was then fed from the top into an isothermal bed reactor containing the Pd / N,BC catalyst prepared in Preparation Example 5. The reaction was carried out at a controlled temperature of 60 °C, a reaction pressure of 1 MPa, and a mass hourly space velocity of 1.8 h⁻¹. -1 The hydrogen-to-oil ratio was 10:1. The reacted material flowed out from the bottom of the reactor and entered a high-pressure gas-liquid separator. The liquid product was collected, sampled, and analyzed by gas chromatography to determine the conversion rate of o-chloronitrobenzene and the selectivity of o-chloroaniline.

[0051] Example 7 Using 1 kg of o-chloronitrobenzene as raw material, o-chloronitrobenzene was thoroughly mixed with hydrogen gas measured by a mass flow meter in a static mixer using a metering pump. The mixture was then fed from the top into an isothermal bed reactor containing the Pd / N,BC catalyst prepared in Preparation Example 5. The reaction was carried out at a controlled temperature of 70 °C, a reaction pressure of 0.3 MPa, and a mass hourly space velocity of 1 h⁻¹. -1 The hydrogen-to-oil ratio was 5:1. The reacted material flowed out from the bottom of the reactor and entered a high-pressure gas-liquid separator. The liquid product was collected, sampled, and analyzed by gas chromatography to determine the conversion rate of o-chloronitrobenzene and the selectivity of o-chloroaniline.

[0052] Example 8 Using 1 kg of o-chloronitrobenzene as raw material, o-chloronitrobenzene was thoroughly mixed with hydrogen gas measured by a mass flow meter in a static mixer using a metering pump. The mixture was then fed from the top into an isothermal bed reactor containing the Pd / N,BC catalyst prepared in Preparation Example 4. The reaction was carried out at a controlled temperature of 80 °C, a reaction pressure of 0.8 MPa, and a mass hourly space velocity (HHSV) of 1.6 h⁻¹. -1 The hydrogen-to-oil ratio was 8:1. The reacted material flowed out from the bottom of the reactor and entered a high-pressure gas-liquid separator. The liquid product was collected, sampled, and analyzed by gas chromatography to determine the conversion rate of o-chloronitrobenzene and the selectivity of o-chloroaniline.

[0053] Example 9 Using 1 kg of o-chloronitrobenzene as raw material, o-chloronitrobenzene was thoroughly mixed with hydrogen gas measured by a mass flow meter in a static mixer using a metering pump. The mixture was then fed from the top into an isothermal bed reactor containing the Pd / N,BC catalyst prepared in Preparation Example 3. The reaction was carried out at a controlled temperature of 95°C, a reaction pressure of 1 MPa, and a mass hourly space velocity of 1.5 h⁻¹. -1 The hydrogen-to-oil ratio was 6:1. The reacted material flowed out from the bottom of the reactor and entered a high-pressure gas-liquid separator. The liquid product was collected, sampled, and analyzed by gas chromatography to determine the conversion rate of o-chloronitrobenzene and the selectivity of o-chloroaniline.

[0054] Example 10 Using 1 kg of o-chloronitrobenzene as raw material, o-chloronitrobenzene was thoroughly mixed with hydrogen gas measured by a mass flow meter in a static mixer using a metering pump. The mixture was then fed from the top into an isothermal bed reactor containing the Pd / N,BC catalyst prepared in Preparation Example 3. The reaction was carried out at a controlled temperature of 100 °C, a reaction pressure of 0.4 MPa, and a mass hourly space velocity of 0.8 h⁻¹. -1 The hydrogen-to-oil ratio was 5:1. The reacted material flowed out from the bottom of the reactor and entered a high-pressure gas-liquid separator. The liquid product was collected, sampled, and analyzed by gas chromatography to determine the conversion rate of o-chloronitrobenzene and the selectivity of o-chloroaniline.

[0055] Comparative Example 1 The difference from Example 1 is that this comparative example uses an equal amount of Pd / C catalyst (without N or B doping) instead of Pd / N,BC catalyst, while the other reactants, amounts, and reaction conditions are the same as in Example 1.

[0056] Comparative Example 2 The difference from Example 1 is that this comparative example uses an equal amount of Pd / NC catalyst (N doped only) instead of Pd / N,BC catalyst, while the other reactants, amounts, and reaction conditions are the same as in Example 1.

[0057] Comparative Example 3 The difference from Example 1 is that this comparative example uses an equal amount of Pd / BC catalyst (B doped only) instead of Pd / N,BC catalyst, while the other reactants, amounts, and reaction conditions are the same as in Example 1.

[0058] The conversion rates of o-chloronitrobenzene and the selectivity of o-chloroaniline in Examples 1-10 and Comparative Examples 1-3 are shown in Table 1 below.

[0059] Table 1 Test Results

[0060] As shown in Table 1, the conversion rate of o-chloronitrobenzene in Examples 1-10 was ≥99.9%, and the selectivity of o-chloroaniline was ≥99.80%, with small data fluctuations and stable product performance.

[0061] Comparative Example 1: The conversion rate of o-chloronitrobenzene and the selectivity of o-chloroaniline were significantly lower, which proved the modification and enhancement effect of N and B elements co-doping on carbon support. The dual doping can significantly improve the dispersibility and catalytic selectivity of Pd active components and suppress dechlorination side reactions.

[0062] Comparative Examples 2 and 3: The conversion rate of o-chloronitrobenzene and the selectivity of o-chloroaniline were better than those of Comparative Example 1, but still lower than those of the present invention, indicating that the co-doping of N and B produced a synergistic effect, which can achieve multiple effects such as increased active sites and enhanced Pd anchoring effect.

[0063] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A process for preparing o-chloroaniline by hydrogenation of o-chloronitrobenzene, characterized in that, Includes the following steps: o-Chloronitrobenzene reacts with hydrogen in the presence of Pd / N,BC catalysts to give o-chloroaniline; The Pd / N,BC catalyst comprises an N,B co-doped carbon support and a Pd active component supported on the support.

2. The process for preparing o-chloroaniline by hydrogenation of o-chloronitrobenzene according to claim 1, characterized in that, In the Pd / N,BC catalyst, the Pd loading is 0.2%-0.5%.

3. The process for preparing o-chloroaniline by hydrogenation of o-chloronitrobenzene according to claim 1, characterized in that, The reaction is carried out at a temperature of 60-100℃, a pressure of 0.1-1 MPa, and a mass hourly space velocity of 0.5-2 h⁻¹. -1 The hydrogen-to-oil ratio is (1-10):

1.

4. The process for preparing o-chloroaniline by hydrogenation of o-chloronitrobenzene according to any one of claims 1-3, characterized in that, The reaction was carried out under solvent-free conditions.

5. The process for preparing o-chloroaniline by hydrogenation of o-chloronitrobenzene according to claim 1, characterized in that, The preparation method of the Pd / N,BC catalyst includes the following steps: (1) Mix carbon materials, boric acid and urea, and pyrolyze them at high temperature under an inert atmosphere to obtain N,B co-doped carbon support; (2) Mix the N,B co-doped carbon support, H2PdCl4 solution and water, stir thoroughly, separate, wash and dry to obtain Pd precursor / N,BC; (3) The Pd precursor / N,BC is heated to 300-350℃ in Ar atmosphere and then switched to 5% H2 / Ar mixture. The mixture is reduced at 300-350℃ for 1.5-2h and then cooled to obtain Pd / N,BC catalyst.

6. The process for preparing o-chloroaniline by hydrogenation of o-chloronitrobenzene according to claim 5, characterized in that, In step (1), the mass ratio of the carbon material, boric acid and urea is 1:(0.5-2):(0.4-1.2).

7. The process for preparing o-chloroaniline by hydrogenation of o-chloronitrobenzene according to claim 5, characterized in that, In step (1), the carbon material is selected from one of activated carbon, carbon nanotubes, and graphene.

8. The process for preparing o-chloroaniline by hydrogenation of o-chloronitrobenzene according to claim 5, characterized in that, In step (1), the pyrolysis temperature is 750-900℃ and the pyrolysis time is 2-4h.

9. The process for preparing o-chloroaniline by hydrogenation of o-chloronitrobenzene according to claim 5, characterized in that, In step (2), the ratio of N,B co-doped carbon support to water is 1g:(100-150)mL.

10. The process for preparing o-chloroaniline by hydrogenation of o-chloronitrobenzene according to claim 5, characterized in that, In step (2), the stirring temperature is 30-50℃ and the stirring time is 12-20h.

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