Preparation method of o-phenylenediamine

Abstract

The invention discloses a preparation method of o-phenylenediamine, and belongs to the technical field of organic synthesis. The invention relates to a preparation method of o-phenylenediamine, which comprises the following steps: pressurizing hydrogen to reduce o-nitroaniline in the presence of a solvent and a modified catalyst to obtain o-phenylenediamine, wherein the modified catalyst is a palladium-based catalyst loaded by a modified nitrogen and boron doped carbon nanotube, and the modified nitrogen and boron doped carbon nanotube is a nitrogen and boron doped carbon nanotube treated by (11-mercaptoundecyl)-N, N, N-trimethyl ammonium bromide. In the process of preparing o-phenylenediamine through catalytic reduction of o-nitroaniline, the modified catalyst and the modified nitrogen-boron-doped carbon nanotubes are used, palladium can be firmly fixed to the carbon nanotubes, agglomeration or loss of palladium in the reaction process is prevented, the cycle performance of the catalyst is improved, and the catalytic capacity of the palladium-based catalyst can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic synthesis, and particularly relates to a method for preparing o-phenylenediamine. Background Art

[0002] O-phenylenediamine, also known as 1,2-diaminobenzene, is a traditional fine chemical intermediate and an important intermediate for dyes, pesticides, auxiliaries, photosensitive materials, etc. It can be used to manufacture polyamides, carbendazim, thiophanate-methyl, Vat Red GG, leveling agents and antioxidant MB, and can also be used to prepare developers and surfactants, etc.

[0003] Patent CN109232271 B provides a method for catalytically reducing o-nitroaniline to prepare o-phenylenediamine. This patent uses graphene oxide loaded with bimetals as a catalyst and conducts hydrogenation reduction in a reaction kettle with a polytetrafluoroethylene inner lining. The solution solves the problems of difficult industrial production in the existing process and difficult long-term maintenance of stable activity of the catalyst, and has broad industrial application prospects. However, the preparation of the bimetallic catalyst requires precise control of factors such as the ratio, distribution, and morphology of the metals to ensure the activity and selectivity of the catalyst, increasing the technical difficulty of the production process. Summary of the Invention

[0004] In order to solve the problem that the preparation of the bimetallic catalyst in the background art requires precise control of factors such as the ratio, distribution, and morphology of the metals to ensure the activity and selectivity of the catalyst, increasing the technical difficulty of the production process, the purpose of the present invention is to provide a method for preparing o-phenylenediamine.

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

[0006] A method for preparing o-phenylenediamine, comprising the following steps:

[0007] Under the presence of a solvent and a modified catalyst, o-nitroaniline is reduced by pressurized hydrogen to obtain o-phenylenediamine; wherein, the modified catalyst is a palladium-based catalyst supported on modified nitrogen and boron doped carbon nanotubes, and the modified nitrogen and boron doped carbon nanotubes are nitrogen and boron doped carbon nanotubes treated with (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide.

[0008] Further, the dosage ratio of the solvent, o-nitroaniline, and the modified catalyst is 20 mL: 2 g: 0.05 - 0.08 g.

[0009] Further, the solvent is any one of water, methanol, ethanol, and ether.

[0010] Further, the specific parameters of the pressurized hydrogen reduction are: the hydrogen pressure is 0.5 - 1 MPa, and the reaction temperature is 80 - 90 °C.

[0011] Furthermore, the preparation method of the modified catalyst is as follows:

[0012] S1: Add nitrogen-boron doped carbon nanotubes into water, then add (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide, and ultrasonicate for 20 - 30 min to obtain a mixed solution; put the obtained mixed solution into a microwave oven and heat it to boiling, maintain the boiling state for 10 - 30 min, then rinse and filter with distilled water to make the pH value of the effluent neutral, and finally filter. The obtained filter cake is dried and ground to obtain modified nitrogen-boron doped carbon nanotubes;

[0013] Among them, the dosage ratio of nitrogen-boron doped carbon nanotubes, water, and (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide is 1 g : 20 - 30 mL : 0.5 - 1.5 mL.

[0014] S2: Add 0.02 mol / L of PdCl 2 and modified nitrogen-boron doped carbon nanotubes into deionized water, ultrasonically mix at room temperature, then add hydrazine hydrate, ultrasonicate at 60 °C, after completion, centrifuge, wash with deionized water 3 - 4 times, and dry in vacuum to obtain the modified catalyst.

[0015] Among them, the dosage ratio of deionized water, 0.02 mol / L of PdCl 2 , modified nitrogen-boron doped carbon nanotubes, and hydrazine hydrate is 50 mL : 0.5 mL : 0.4 - 0.6 g : 2 mL.

[0016] Carbon nanotubes have received extensive attention in recent years due to their good thermal stability, mechanical stability, and electron conduction performance. These pores may provide a special confinement environment for metal catalysts and catalytic reactions, which can prevent metal particle agglomeration, thereby promoting the dispersion of active species and the improvement of the anti-agglomeration ability. Moreover, due to the unique electronic structure of the curved graphene wall, the performance of metal catalysts may also be modified, which is conducive to improving the catalytic performance.

[0017] Introducing nitrogen atoms into carbon nanotubes can adjust the electronic structure of carbon nanotubes, enhance the electron conductivity of carbon nanotubes, thereby improving the catalytic efficiency of the modified catalyst. And the lone pair electrons contained in nitrogen atoms can form coordination bonds with palladium, which is beneficial to the fixation and dispersion of palladium, improving the catalytic efficiency while also enhancing the recycling ability of the catalyst. Boron atoms are electron-deficient elements. By forming B - C bonds and introducing them into carbon nanotubes, the concentration of P-type carriers can be increased, significantly improving the conductivity, and further improving the catalytic performance of the modified catalyst. In the present invention, nitrogen and boron elements are uniformly doped in carbon nanotubes, and the two can jointly improve the conductivity of carbon nanotubes through synergistic effects, thereby improving the catalytic performance of the modified catalyst.

[0018] In order to further improve the dispersibility of nitrogen and boron doped carbon nanotubes and prevent the re - aggregation of doped carbon nanotubes due to van der Waals forces or π - π stacking during drying or storage. The present invention also adds (11 - mercaptoundecyl)-N,N,N - trimethylammonium bromide on the basis of nitrogen and boron doped carbon nanotubes. (11 - mercaptoundecyl)-N,N,N - trimethylammonium bromide can be used as a dispersant to improve the dispersibility of nitrogen and boron doped carbon nanotubes, so that the palladium - based catalyst is more uniformly dispersed in the nitrogen and boron doped carbon nanotubes, increasing the exposure of active sites, improving the catalytic efficiency and reusability of the catalyst, and preventing the loss of the catalyst. And (11 - mercaptoundecyl)-N,N,N - trimethylammonium bromide is a bifunctional molecule with mercapto and quaternary ammonium salt groups. The sulfur atom in the mercapto contains lone pair electrons, which can form strong coordination bonds with palladium, firmly fixing palladium in the carbon nanotubes and preventing palladium from aggregating or losing during the reaction.

[0019] Further, the preparation method of nitrogen and boron doped carbon nanotubes is as follows:

[0020] A1: Add multi - walled carbon nanotubes to the mixed acid, reflux at 80 - 100 °C for 2 - 4 h, wash with distilled water until neutral, and dry at 60 - 80 °C to obtain pretreated multi - walled carbon nanotubes;

[0021] Among them, the dosage ratio of multi - walled carbon nanotubes to the mixed acid is 1 g: 60 - 80 mL; the mixed acid is composed of concentrated nitric acid and concentrated sulfuric acid according to a volume ratio of 3:1.

[0022] The above steps remove some impurities on the surface of multi - walled carbon nanotubes and increase the active sites on the surface of multi - walled carbon nanotubes, which is beneficial to the subsequent loading of the catalyst.

[0023] A2: Mix the pretreated multi - walled carbon nanotubes with (1H - benzo[d]imidazol - 2 - yl)boronic acid, grind evenly with a mortar, calcine in nitrogen, wash, and dry at 80 °C to obtain nitrogen and boron doped carbon nanotubes.

[0024] Among them, the mass ratio of the pretreated multi - walled carbon nanotubes to (1H - benzo[d]imidazol - 2 - yl)boronic acid is 1:(1 - 3).

[0025] In the above reaction steps, (1H - benzo[d]imidazol - 2 - yl)boronic acid contains nitrogen and boron elements. After calcination, nitrogen, fluorine, and boron co - doped carbon nanotubes can be obtained. By mixing the pretreated multi - walled carbon nanotubes with (1H - benzo[d]imidazol - 2 - yl)boronic acid, the uniform doping of nitrogen and boron elements on the surface of carbon nanotubes can be realized, which is beneficial to improving the activity of the subsequent catalyst. This method avoids the problem of uneven doping that may occur when adding nitrogen source and boron source separately, thereby improving the doping efficiency and doping quality and simplifying the process flow.

[0026] Further, in step A1, the multi-walled carbon nanotubes have a diameter of 30 - 50 nm and a length of 100 - 500 μm.

[0027] Further, in step A2, the calcination temperature is 600 - 800 °C and the time is 2 - 4 h.

[0028] Advantages of the present invention:

[0029] 1. In the process of catalytic reduction of o-nitroaniline to prepare o-phenylenediamine, the present invention uses a modified catalyst. The modified catalyst of the present invention is a palladium-based catalyst supported on modified nitrogen and boron co-doped carbon nanotubes. The modified nitrogen and boron co-doped carbon nanotubes are nitrogen and boron co-doped carbon nanotubes treated with (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide. The modified nitrogen and boron co-doped carbon nanotubes can firmly fix palladium on the carbon nanotubes, prevent palladium from agglomerating or leaking during the reaction, improve the recycling performance of the catalyst, and can improve the catalytic ability of the palladium-based catalyst.

[0030] 2. By precisely controlling the addition amount of the modified catalyst, the present invention obtains a catalyst dosage with a relatively high catalytic efficiency. When the addition amount of the modified catalyst is too much, the excessive catalyst will occupy the space in the reaction kettle, affect the diffusion rate of the reactants in the catalyst, and thus reduce the reaction rate. When the addition amount of the modified catalyst is too little, the number of reactive sites decreases, which will reduce the reaction rate and prolong the reaction time. Specific embodiments

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] Example 1

[0033] A method for preparing o-phenylenediamine includes the following steps:

[0034] In a reaction kettle with a polytetrafluoroethylene liner, add 20 mL of methanol, 0.05 g of the modified catalyst, and 2 g of o-nitroaniline, and reduce o-nitroaniline by pressurized hydrogen to obtain o-phenylenediamine; wherein, the specific parameters of the pressurized hydrogen reduction are: the hydrogen pressure is 0.5 MPa and the reaction temperature is 80 - 90 °C.

[0035] The preparation method of the modified catalyst is:

[0036] S1: Add 1 g of nitrogen and boron co-doped carbon nanotubes to 30 mL of water, then add 0.5 mL of (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide, and ultrasonicate for 20 min to obtain a mixed solution. Place the obtained mixed solution in a microwave oven and heat it to boiling, maintain the boiling state for 10 min, then rinse and filter with distilled water until the pH value of the effluent is neutral. Finally, filter, dry the obtained filter cake, and grind it to obtain modified nitrogen and boron co-doped carbon nanotubes;

[0037] S2: Add 0.5 mL of 0.02 mol / L PdCl 2 and 0.4 g of modified nitrogen and boron co-doped carbon nanotubes to 50 mL of deionized water, ultrasonically mix at room temperature, then add 2 mL of hydrazine hydrate, ultrasonicate at 60 °C, centrifuge after completion, wash 4 times with deionized water, and dry in vacuo to obtain a modified catalyst.

[0038] The preparation method of the nitrogen and boron co-doped carbon nanotubes is as follows:

[0039] A1: Add 1 g of multi-walled carbon nanotubes to 60 mL of a mixed acid (the mixed acid is composed of concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:1), reflux at 80 °C for 2 h, wash with distilled water until neutral, and dry at 60 °C to obtain pretreated multi-walled carbon nanotubes;

[0040] A2: Mix 1 g of pretreated multi-walled carbon nanotubes with 1 g of (1H-benzo[d]imidazol-2-yl)boronic acid and grind them evenly with a mortar. Calcine in nitrogen, the calcination temperature is 600 °C, the time is 2 h, wash, and dry at 80 °C to obtain nitrogen and boron co-doped carbon nanotubes.

[0041] Example 2

[0042] A preparation method of o-phenylenediamine, comprising the following steps:

[0043] In a reaction kettle with a polytetrafluoroethylene inner lining, add 20 mL of methanol, 0.065 g of the modified catalyst, and 2 g of o-nitroaniline, and reduce o-nitroaniline by pressurized hydrogen to obtain o-phenylenediamine; wherein, the specific parameters of the pressurized hydrogen reduction are: the hydrogen pressure is 0.8 MPa, and the reaction temperature is 85 °C.

[0044] The preparation method of the modified catalyst is as follows:

[0045] S1: Add 1 g of nitrogen and boron co-doped carbon nanotubes to 30 mL of water, then add 1 mL of (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide, and ultrasonicate for 30 min to obtain a mixed solution. Place the obtained mixed solution in a microwave oven and heat it to boiling, maintain the boiling state for 30 min, then rinse and filter with distilled water until the pH value of the effluent is neutral. Finally, filter, dry the obtained filter cake, and grind it to obtain modified nitrogen and boron co-doped carbon nanotubes;

[0046] S2: Add 0.5 mL of 0.02 mol / L PdCl 2 and 0.5 g of modified nitrogen and boron co-doped carbon nanotubes to 50 mL of deionized water, ultrasonically mix at room temperature, then add 2 mL of hydrazine hydrate, ultrasonically treat at 60 °C, after completion, centrifuge, wash 4 times with deionized water, and dry in vacuum to obtain the modified catalyst.

[0047] The preparation method of the nitrogen and boron co-doped carbon nanotubes is as follows:

[0048] A1: Add 1 g of multi-walled carbon nanotubes to 70 mL of mixed acid (the mixed acid is composed of concentrated nitric acid and concentrated sulfuric acid according to a volume ratio of 3:1), reflux at 100 °C for 4 h, wash with distilled water until neutral, and dry at 80 °C to obtain pretreated multi-walled carbon nanotubes;

[0049] A2: Mix 1 g of pretreated multi-walled carbon nanotubes with 2 g of (1H-benzo[d]imidazol-2-yl)boronic acid and grind evenly with a mortar, calcine in nitrogen, the calcination temperature is 800 °C, the time is 4 h, wash, and dry at 80 °C to obtain the nitrogen and boron co-doped carbon nanotubes.

[0050] Example 3

[0051] A preparation method of o-phenylenediamine, comprising the following steps:

[0052] In a reaction kettle with a polytetrafluoroethylene inner liner, add 20 mL of methanol, 0.08 g of modified catalyst and 2 g of o-nitroaniline, and reduce o-nitroaniline by pressurized hydrogen to obtain o-phenylenediamine; wherein, the specific parameters of the pressurized hydrogen reduction are: the hydrogen pressure is 0.8 MPa and the reaction temperature is 90 °C.

[0053] The preparation method of the modified catalyst is as follows:

[0054] S1: Add 1 g of nitrogen and boron co-doped carbon nanotubes to 30 mL of water, then add 1.5 mL of (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide, ultrasonically treat for 30 min to obtain a mixed solution; put the obtained mixed solution into a microwave oven and heat to boiling, maintain the boiling state for 30 min, then rinse and filter with distilled water to make the pH value of the effluent neutral, and finally filter, dry the obtained filter cake, and grind to obtain the modified nitrogen and boron co-doped carbon nanotubes;

[0055] S2: Add 0.5 mL of 0.02 mol / L PdCl 2 and 0.6 g of modified nitrogen and boron co-doped carbon nanotubes to 50 mL of deionized water, ultrasonically mix at room temperature, then add 2 mL of hydrazine hydrate, ultrasonically treat at 60 °C, after completion, centrifuge, wash 4 times with deionized water, and dry in vacuum to obtain the modified catalyst.

[0056] The preparation method of nitrogen and boron co-doped carbon nanotubes is as follows:

[0057] A1: Add 1 g of multi-walled carbon nanotubes to 80 mL of a mixed acid (the mixed acid is composed of concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:1), reflux at 100 °C for 4 h, wash with distilled water until neutral, and dry at 80 °C to obtain pretreated multi-walled carbon nanotubes;

[0058] A2: Mix 1 g of pretreated multi-walled carbon nanotubes with 3 g of (1H-benzo[d]imidazol-2-yl)boronic acid and grind them evenly with a mortar, calcine in nitrogen, the calcination temperature is 700 °C, the time is 3 h, wash, and dry at 80 °C to obtain nitrogen and boron co-doped carbon nanotubes.

[0059] Example 4

[0060] The difference between this example and Example 1 is that:

[0061] Replace "0.05 g of modified catalyst" in Example 1 with "0.04 g of modified catalyst", and the other raw materials and steps are the same as in Example 1.

[0062] Example 5

[0063] The difference between this example and Example 1 is that:

[0064] Replace "0.08 g of modified catalyst" in Example 3 with "0.09 g of modified catalyst", and the other raw materials and steps are the same as in Example 3.

[0065] Comparative Example 1

[0066] The difference between this comparative example and Example 1 is that:

[0067] Replace "1 g of (1H-benzo[d]imidazol-2-yl)boronic acid" in step A2 with "0.5 g of melamine and 0.5 g of boron trioxide", and the other raw materials and steps are the same as in Example 1.

[0068] Comparative Example 2

[0069] The difference between this comparative example and Example 1 is that:

[0070] Replace "1 g of (1H-benzo[d]imidazol-2-yl)boronic acid" in step A2 with "1 g of melamine", and the other raw materials and steps are the same as in Example 1.

[0071] Comparative Example 3

[0072] The difference between this comparative example and Example 1 is that:

[0073] The preparation method of carbon nanotubes is as follows:

[0074] 1 g of multi-walled carbon nanotubes was added to 60 mL of a mixed acid (the mixed acid was composed of concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:1), refluxed at 80 °C for 2 h, washed with distilled water until neutral, and dried at 60 °C to obtain pretreated multi-walled carbon nanotubes. The remaining raw materials and steps were the same as in Example 1.

[0075] Comparative Example 4

[0076] The difference between this comparative example and Example 1 was that:

[0077] The preparation method of the modified catalyst was as follows:

[0078] 0.5 mL of 0.02 mol / L PdCl was added to 50 mL of deionized water 2 and 0.4 g of nitrogen and boron-doped carbon nanotubes, ultrasonically mixed at room temperature, then 2 mL of hydrazine hydrate was added, ultrasonically treated at 60 °C, centrifuged after completion, washed 4 times with deionized water, and dried in vacuo to obtain the modified catalyst. The remaining raw materials and steps were the same as in Example 1.

[0079] The catalytic activity results of the catalysts in Examples 1 - 5 and Comparative Examples 1 - 4 were analyzed and tested, and the test results are shown in Table 1.

[0080] Table 1

[0081]

[0082]

[0083] As can be seen from Table 1, the catalytic activities of the catalysts in Examples 1 - 5 were higher than those in Comparative Examples 1 - 4. In the present invention, even by adding only one metal, the catalyst still had a conversion rate of 98.2% after 9 cycles.

[0084] Compared with Examples 1 and 3, in Example 4 and Example 5, the catalyst dosage in Example 1 was too small, and the dosage in Example 5 was too large. The catalytic activities of both were lower than those in Example 1 and Example 3 respectively, indicating that too much or too little catalyst would affect the catalytic activity, and the catalyst addition amount in the present invention was the optimal amount.

[0085] Compared with Example 1, in Comparative Example 1, the boron source and nitrogen source were added separately, and its catalytic activity was lower than that in Example 1, indicating that by mixing the pretreated multi-walled carbon nanotubes with (1H-benzo[d]imidazol-2-yl)boronic acid, uniform doping of nitrogen and boron elements on the surface of the carbon nanotubes could be achieved, which was beneficial to improving the activity of the subsequent catalyst.

[0086] Comparative Example 2 and Example 1 are compared. Comparative Example 2 does not contain boron element, and its catalyst activity is lower than that of Example 1, indicating that boron atom is an electron-deficient element. By forming B-C bonds and introducing them into carbon nanotubes, the concentration of P-type carriers can be increased, the conductivity can be significantly improved, and thus the catalytic performance of the modified catalyst can be improved.

[0087] Comparative Example 3 and Example 1 are compared. It does not contain boron element and nitrogen element, and its catalytic performance is lower than that of Example 1, indicating that introducing nitrogen atoms into carbon nanotubes can adjust the electronic structure of carbon nanotubes, enhance the electron conductivity of carbon nanotubes, and thus improve the catalytic efficiency of the modified catalyst. Moreover, the lone pair electrons contained in nitrogen atoms can form coordination bonds with palladium, which is beneficial to the fixation and dispersion of palladium, improving the catalytic efficiency and also enhancing the reusability of the catalyst. Boron atom is an electron-deficient element. By forming B-C bonds and introducing them into carbon nanotubes, the concentration of P-type carriers can be increased, the conductivity can be significantly improved, and thus the catalytic performance of the modified catalyst can be improved.

[0088] Comparative Example 4 and Example 1 are compared. (11-Mercaptoundecyl)-N,N,N-trimethylammonium bromide is not added, and its catalyst activity is lower than that of Example 1, indicating that (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide can be used as a dispersant to improve the dispersion of nitrogen and boron doped carbon nanotubes, and then make the palladium-based catalyst more uniformly dispersed in the nitrogen and boron doped carbon nanotubes, increasing the exposure of active sites, improving the catalytic efficiency and reusability of the catalyst, and preventing the loss of the catalyst. Moreover, (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide is a bifunctional molecule with mercapto and quaternary ammonium salt groups. The sulfur atom in the mercapto contains lone pair electrons, which can form strong coordination bonds with palladium, firmly fixing palladium in the carbon nanotubes and preventing palladium from agglomerating or losing during the reaction.

[0089] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent in such process, method, article or device.

[0090] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing o-phenylenediamine, characterized in that: The following steps are involved: In the presence of a solvent and a modified catalyst, pressurized hydrogen is used to reduce o-nitroaniline to obtain o-phenylenediamine; wherein the modified catalyst is a palladium-based catalyst supported by modified nitrogen-boron-doped carbon nanotubes, and the modified nitrogen-boron-doped carbon nanotubes are nitrogen-boron-doped carbon nanotubes treated with (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide.

2. The method for preparing o-phenylenediamine according to claim 1, characterized in that: The usage ratio of the solvent, o-nitroaniline and the modified catalyst is 20 mL: 2 g: 0.05-0.08 g.

3. The method for preparing o-phenylenediamine according to claim 1, characterized in that: The solvent is any one of water, methanol, ethanol and ether.

4. The method for preparing o-phenylenediamine according to claim 1, characterized in that: The specific parameters of pressurized hydrogen reduction are: hydrogen pressure of 0.5-1MPa and reaction temperature of 80-90°C.

5. The method for preparing o-phenylenediamine according to claim 1, characterized in that: The preparation method of the modified catalyst is: S1: adding nitrogen-boron-doped carbon nanotubes to water, then adding (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide, and ultrasonicating for 20-30 minutes to obtain a mixed solution; heating the obtained mixed solution to boiling, maintaining the boiling state for 10-30 minutes, and then washing and filtering with distilled water to make the pH value of the effluent neutral, and finally filtering, drying the obtained filter cake, grinding, and obtaining modified nitrogen-boron-doped carbon nanotubes; S2: Add 0.02 mol / L PdCl2 and modified nitrogen-boron-doped carbon nanotubes into deionized water, mix them by ultrasonication at room temperature, then add hydrazine hydrate, ultrasonicate at 60°C, centrifuge, wash, and vacuum dry to obtain a modified catalyst.

6. The method for preparing o-phenylenediamine according to claim 5, characterized in that: In step S1, the amount ratio of nitrogen-boron-doped carbon nanotubes, water, and (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide is 1 g: 20-30 mL: 0.5-1.5 mL; in step S2, the amount ratio of deionized water, 0.02 mol / L PdCl2, modified nitrogen-boron-doped carbon nanotubes, and hydrazine hydrate is 50 mL: 0.5 mL: 0.4-0.6 g: 2 mL.

7. The method for preparing o-phenylenediamine according to claim 5, characterized in that: The preparation method of nitrogen-boron doped carbon nanotubes is as follows: A1: adding multi-walled carbon nanotubes to mixed acid, reflux at 80-100°C for 2-4h, washing with distilled water until neutral, and drying at 60-80°C to obtain pretreated multi-walled carbon nanotubes; A2: The pretreated multi-walled carbon nanotubes were mixed with (1H-benzo[D]imidazol-2-yl)boric acid, ground in a mortar, calcined in nitrogen, washed, and dried at 80° C. to obtain nitrogen-boron doped carbon nanotubes.

8. The method for preparing o-phenylenediamine according to claim 7, characterized in that: In step A1, the ratio of multi-walled carbon nanotubes to mixed acid is 1g:60-80mL; the mixed acid is composed of concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:1; the specifications of the multi-walled carbon nanotubes are a diameter of 30-50nm and a length of 100-500μm.

9. The method for preparing o-phenylenediamine according to claim 7, characterized in that: In step A2, the mass ratio of the pretreated multi-walled carbon nanotubes to (1H-benzo[D]imidazol-2-yl)boric acid is 1:(1-3).

10. The method for preparing o-phenylenediamine according to claim 7, characterized in that: In step A2, the calcination temperature is 600-800° C. and the calcination time is 2-4 hours.

Images