A method for preparing m-xylylenediamine by hydrogenating isophthalonitrile

Abstract

This invention discloses a method for the hydrogenation of isophthalonitrile to prepare m-phenylenediamine, belonging to the field of organic chemical raw material synthesis technology. The catalyst utilizes ligand confinement to control the size of metal sites, and then employs a deposition-precipitation method to load noble metals onto the surface of a nano-support in the form of atomically dispersed single atoms and / or clusters, obtaining the atomically dispersed noble metal catalyst. The loading of the active metal in the catalyst is 0.1-1.5 wt%. The catalyst of this invention exhibits strong low-temperature hydrogenation activity and selectivity, making it highly suitable for applications in the catalytic hydrogenation of isophthalonitrile to prepare m-phenylenediamine under mild conditions (25-60 °C, 0.25-1.5 MPa). This catalyst features low raw material cost, simple preparation process, stable performance, and high catalytic activity, overcoming the stringent reaction conditions and the need for additional alkaline additives required by catalysts with non-noble metals such as Ni and Co as the main active components.

Description

Technical Field

[0001] This invention relates to the field of organic chemical raw material synthesis technology, specifically to an atomically dispersed noble metal catalyst for the hydrogenation reaction of isophthalonitrile, its preparation method, and its application. Background Technology

[0002] Primary amines are important compounds in organic chemistry, widely found in natural products and bioactive molecules. m-Phenylenediamine (MXDA), as an important class of amine compounds, has wide applications in epoxy resin curing agents and polyurethanes. Currently, MXDA is mainly prepared from isophthalonitrile (IPN) via liquid-phase hydrogenation. Because IPN contains two cyano groups, the reaction involves multiple hydrogenation steps. The conversion of the first cyano group to an amino group is relatively easy, but it reduces electronic defects in the ring, hindering further reduction of the second cyano group, making complete conversion to MXDA difficult. Furthermore, side reactions such as imine condensation and demethylation are often suppressed by adding liquid ammonia or alkali metals to the catalytic system, which incurs additional production costs. Industrially, the main selective hydrogenation catalysts used for IPN (Intracytoplasmic Phenomenon) production include Raney nickel catalysts and supported non-precious metal (Ni, Co) catalysts. However, these commercial catalysts require high temperature and high pressure conditions (≥100℃, ≥50 bar H2). Since cyano hydrogenation is an exothermic reaction, excessively high reaction temperatures can easily cause runaway reactions, affecting the selectivity of primary amines and catalyst lifetime. Furthermore, these catalytic reactions inevitably produce m-phenylenediamine dimers and trimers, requiring additional purification steps and increasing production costs. Noble metal catalysts for IPN hydrogenation to MXDA production have not been reported due to cost issues. Compared to non-precious metal catalysts, noble metal catalysts possess stronger H2 activation capabilities and are easier to use to achieve milder reaction conditions.

[0003] Patent CN120554233A reports a catalytic system for the hydrogenation of isophthalonitrile to prepare m-phenylenediamine. This system uses a nickel-cobalt alloy catalyst, which not only improves the conversion rate of IPN but also enhances the selectivity of MXDA, achieving complete conversion of IPN and 98% selectivity for MXDA. The catalyst performance is superior to ordinary skeletal nickel or cobalt catalysts. However, it requires a two-stage continuous flow reactor and harsh reaction conditions (≥80℃, >5 MPa), and the addition of liquid ammonia, posing challenges to production safety.

[0004] Heterogeneous catalytic reactions occur only on the surface of metal nanoparticles, while most of the metal atoms in the core do not exhibit any catalytic activity. In some catalytic reactions, supported metal nanoparticle catalysts exhibit low catalytic activity due to limited metal utilization, requiring stringent reaction conditions and increasing catalyst usage costs. Current research has found that when the size of the active metal on the support surface reaches the atomic level, its electronic state and structure change, potentially altering its activity in catalytic reactions and thus demonstrating superior catalytic performance. Doping the support surface can change the interaction between the support and the metal, thereby altering the catalyst's performance. Therefore, developing atomically dispersed metal catalysts can significantly improve metal utilization efficiency, especially reducing the cost of precious metal catalysts. Summary of the Invention

[0005] To address the problems of low active metal utilization, poor reactivity, and harsh reaction conditions in the current hydrogenation reaction of isophthalonitrile, requiring the addition of additional additives, this invention provides an atomically dispersed catalyst for the hydrogenation reaction of isophthalonitrile, its preparation method, and its application. In this catalyst, the active metal component is first combined with ligands at a fixed coordination ratio to determine its aggregate size. Then, it is uniformly loaded onto a modified nanosupport using a deposition-precipitation method, bonding with defects or functional groups on the support to form atomically dispersed metal single atoms and / or clusters, greatly improving the utilization rate of metal atoms. Utilizing the synergistic effect of multiple metal sites, the catalytic efficiency is improved, achieving highly efficient and selective hydrogenation of isophthalonitrile. This atomically dispersed supported noble metal catalyst for the catalytic reaction of isophthalonitrile exhibits high active metal atom utilization, high activity, and high selectivity, enabling the efficient synthesis of isophthalamide under mild reaction conditions.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing m-phenylenediamine by hydrogenation of isophthalonitrile, characterized in that: it employs an atomically dispersed noble metal catalyst for catalytic reaction; the reaction process uses isophthalonitrile and hydrogen as raw materials, and the reaction temperature is 20-60℃ (preferably 30-50℃, more preferably 40-45℃); the catalyst is composed of a modified nano-carbon support and an active metal component; the particle size of the modified nano-carbon material is 5-10 nm, wherein the active metal component is loaded on the modified nano-support to form atomically dispersed noble metal single atoms and / or clusters, the particle size of which is distributed in the range of 0.2-1.2 nm; the active metal component is one, two, or three of Pd, Ru, or Rh, and its loading is 0.1-1.5 wt% (preferably 0.2-1.2 wt%, more preferably 0.4-1.0 wt%), the metal being dispersed on the nano-support in an atomically dispersed cluster manner.

[0007] The atomically dispersed noble metal clusters are the active centers of the catalyst; the nano-carbon support is one or more of nanodiamond, nanographene, carbon nanotubes, nano-activated carbon, and carbon black.

[0008] The modified carbon nanomaterial has a shell structure with a graphene layer doped with boron atoms as the shell and the carbon nanomaterial itself as the core, forming a shell-encapsulated core structure. The surface has sp... 2 The structure comprises a defect-rich hybrid carbon / boron structure; the active metal component bonds with defects / vacancies on the support to form atomically dispersed noble metal single atoms or clusters; the boron doping source is one or more of ammonium borate, ammonium fluoroborate, and boric acid; the percentage of boron doping in the graphene layer is 1.0-5.0 wt% (preferably 2.5-4.0 wt%, more preferably 3.5-3.8 wt%); the thickness of the boron-doped graphene layer is 0.1-1.0 nm (preferably 0.2-0.75 nm, more preferably 0.3-0.5 nm).

[0009] The preparation process of modified carbon nanomaterials is as follows: 200 mg of carbon nanomaterial powder is placed in a container, and 15-75 wt% (preferably 40-60 wt%, more preferably 50-55 wt%) of boron source relative to the carbon nanomaterial and 30-50 ml (preferably 35-45 ml) of ethanol are added. The mixture is stirred at 60-100℃ (preferably 70-95℃, more preferably 80-90℃) for 1.5-3 h (preferably 2-2.5 h, more preferably 2-2.2 h). After filtration, the solid is dried and then calcined at 1100-1500℃ (preferably 1150-1350℃, more preferably 1180-1270℃) and a nitrogen and / or argon atmosphere at a flow rate of 60-100 mL / min (preferably 80-100 mL / min, more preferably 85-95 mL / min) for 2-4 h (preferably 2.5-3 h, more preferably 2.6-2.8 h). After annealing at 800-950℃ (preferably 840-900℃, more preferably 870-890℃) in an argon atmosphere for 0.5-1.5 h (preferably 0.8-1.2 h, more preferably 0.9-1.0 h), and then cooling to room temperature, the modified nano-carbon carrier material is obtained by washing and drying, denoted as NCB.

[0010] The preparation method of this catalyst includes the following steps: (1) Preparation of mother liquor containing active metal: Dissolve soluble active metal salt in water, and add the corresponding amount of ligand according to the molar ratio of metal to nitrogen-containing ligand 1:1-5:1 (preferably 1.5-3.0:1, more preferably 1.8-2.5:1) to obtain a metal precursor solution with a concentration of 10-20 g / L; (2) The active metal component is dispersed on the support by the deposition-precipitation method to obtain the atomically dispersed noble metal catalyst. The deposition-precipitation process is as follows: the modified nano carbon material and water are added to a container and dispersed to obtain a nano support dispersion. The modified nano carbon material aqueous dispersion is heated and stirred, and a precipitant solid powder is added to the dispersion. Then, the precursor solution containing active metal prepared in step (1) is added dropwise according to the required ratio. After stirring and reflux, it is allowed to stand for aging. After washing, filtration and drying, it is reduced in pure H2 or a mixed atmosphere of H2 and He to obtain the atomically dispersed noble metal catalyst.

[0011] The Pd metal salt is selected from any one or more of palladium chloride, palladium acetate, palladium acetylacetone, and palladium nitrate; the Ru metal salt is selected from any one or two of ruthenium chloride and ruthenium nitrate; the Rh metal salt is selected from any one or two of rhodium nitrate and rhodium chloride; and the nitrogen-containing ligand is selected from any one or more of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, and 2-aminopyridine.

[0012] In step (2), the deposition-precipitation method uses one or more of sodium carbonate, potassium carbonate, and sodium bicarbonate as the precipitant; the molar ratio of the precipitant to the active metal component is 2:1-20:1 (preferably 3:1-10:1); and the pH of the adjusted metal precursor solution is 8-11.

[0013] In step (2) of the deposition-precipitation method, The modified nano-carbon material aqueous dispersion uses 200 mg of modified nano-carbon material and 25-50 mL of water; after mixing, it is ultrasonically dispersed for 10-50 min; the oil bath temperature for heating the modified nano-carbon material aqueous dispersion is 90-105℃ (preferably 95-102℃, more preferably 98-100℃), the dispersion is stirred in the oil bath for 30-80 min, and the stirring and reflux time is 45-65 min (preferably 50-60 min). After stirring and reflux, it is cooled to room temperature and allowed to stand for 4- After 8 hours, the sample is washed with water and filtered. The drying is carried out in a vacuum drying oven at a temperature of 40-80℃ for 8-24 hours. The reduction is carried out in a pure H2 atmosphere or a mixture of H2 and He, with an H2 volume ratio of 5-100% (preferably 10-90%, more preferably 15-50%) and a volumetric flow rate of 50-100 ml / min. The reduction temperature is 120-300℃ (preferably 150-250℃, more preferably 180-220℃) and the reduction time is 1-3 hours (preferably 1.5-2 hours).

[0014] The reaction process is carried out in a batch reactor, using the catalyst to prepare m-phthalonitrile via selective hydrogenation. During the hydrogenation reaction of m-phthalonitrile, the solvent is any one or a mixture of two or more of methanol, ethanol, 2-methylimidazole and toluene, the molar concentration of m-phthalonitrile is 0.01-0.2 mol / L (preferably 0.05-0.1 mol / L), and the hydrogen pressure is 0.25-1.5 MPa (preferably 0.5-1.2 MPa, more preferably 0.8-1.0 MPa).

[0015] An atomically dispersed noble metal catalyst for the hydrogenation reaction of isophthalonitrile, the catalyst being composed of a nanosupport and an active metal component supported on the support; wherein the active metal component is uniformly supported on the nanosupport and bonds with defects / vacancies on the support to form atomically dispersed noble metal single atoms and / or clusters.

[0016] The active metal component is uniformly loaded on the nanocarrier in an atomically dispersed cluster manner; the Pd, Ru, or Rh atoms or clusters are the active centers of the noble metal catalyst.

[0017] The process for preparing m-phenylenediamine by hydrogenation of isophthalonitrile is as follows: Weigh out atomically dispersed Pd catalyst, solvent, and isophthalonitrile, and add them to the reactor. At room temperature, first fill with nitrogen and check for airtightness. After confirming good airtightness, purge the reactor five times with nitrogen and then five times with hydrogen. After purging, raise the temperature to the specified temperature at a rate of 5°C / min, and introduce hydrogen to the specified pressure. React under stirring conditions, continuously introducing hydrogen to maintain a constant pressure during the reaction.

[0018] The solvent is any one or a mixture of two of methanol, ethanol, 2-methylimidazole and toluene, preferably methanol, and the amount of solvent used is 10 mL.

[0019] The molar concentration of isophthalonitrile is 0.01-0.2 mol / L.

[0020] The reaction temperature is 25-60℃.

[0021] The pressure of the hydrogen gas is 0.25-1.5 MPa.

[0022] This invention enhances catalytic activity and effectively reduces catalyst costs by controlling the size of atomically dispersed noble metal catalysts and the adsorption of target products. The catalyst exhibits strong low-temperature hydrogenation activity and selectivity, making it highly suitable for applications involving the hydrogenation of isophthalonitrile to m-phenylenediamine under mild conditions (25-60 °C, 0.25-1.5 MPa). This catalyst boasts low raw material costs, a simple preparation process, stable performance, and high catalytic activity, overcoming the limitations of catalysts with non-noble metals such as Ni and Co as the main active components, which require stringent reaction conditions and the addition of alkaline promoters.

[0023] Compared with the prior art, the present invention has the following advantages: (1) This invention achieves a carrier-metal site-specific interaction by modifying the boron doping content on the carrier surface and regulating the coordination environment of precursor noble metal species. This allows noble metal species to be uniformly dispersed on the surface of the nanocarrier. The electronic defects / vacancies on the carrier surface provide anchoring sites for the active components, improving the dispersibility of active metal species on the carrier surface and effectively preventing the aggregation of metal nanoparticles. This results in a highly active catalyst with atomically dispersed structure, greatly improving the utilization rate of active metal atoms and catalyst performance.

[0024] (2) This invention forms noble metal atom clusters of different sizes by adjusting the mixing ratio of ligands and precursors, thereby leveraging their multi-site synergistic effect to regulate catalyst performance, effectively improving catalytic activity and reducing catalyst cost.

[0025] (3) The modified carbon material supported noble metal-based catalyst prepared in this invention was applied to the hydrogenation of isophthalonitrile to isophthalic dimethylamine, achieving high IPN conversion and high MXDA selectivity synthesis under mild conditions, with low energy consumption, high safety and good economic benefits.

[0026] The catalyst used in this invention has low raw material cost, is simple to prepare, and is environmentally friendly and efficient. Attached Figure Description

[0027] Figure 1 This is a scanning transmission electron microscope (STEM) image of the Pd atomic-level cluster catalyst in Example 1.

[0028] Figure 2 (a) and (b) represent the k and R spaces of the EXAFS of the Pd atomic-level cluster catalyst in Example 1.

[0029] Figure 3 The Raman spectra of the 05Pd / NDB catalyst and NDB support in Example 1 are shown.

[0030] Table 1 shows the EXAFS fitting results of the catalysts in Example 1 and Comparative Examples 1 and 2. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] In the following examples and comparative examples, the specific catalysts are represented by element symbols and English abbreviations, wherein Pd-palladium, Rh-Rhodium, Ru-Ruthenium, ND-Nanodiamond, NDB-Boron-modified nanodiamond material, NG-Nanographene, NGB-Boron-modified graphene, CNT-Carbon nanotube, CNTB-Boron-modified carbon nanotube, AC-Activated carbon, ACB-Boron-modified nano-activated carbon, CB-Carbon black, CBB-Boron-modified carbon black.

[0033] Example 1: (1) Catalyst preparation: A. Take a certain amount of Pd(NO3)2 mother liquor (an aqueous solution with Pd content of 0.5 wt%), add the corresponding amount of o-phenylenediamine according to the molar ratio of metal to nitrogen-containing ligand of 2.5:1, dilute with deionized water to 10 mL, and disperse by ultrasonication to obtain a metal precursor solution. Take 1.2 g of nanodiamond (ND) powder (particle size 5-10 nm) in a 100 mL flask, add ammonium borate (45 wt% relative to ND) and 30 mL of ethanol, stir at 80 °C for 2 h, filter, place the solid in a vacuum drying oven and dry at 80 °C for 12 h, then calcine at 1200 °C and 100 mL / min in an argon atmosphere for 2 h, followed by annealing at 800 °C in an argon atmosphere for 1 h, cool to room temperature, wash the solid with water and then vacuum dry to obtain the NDB modified support. STEM-EDX energy dispersive spectroscopy revealed a surface boron content of 3.6 wt%. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) showed a support particle size of 5.9-7.0 nm and a graphene layer thickness of 0.5 nm on the ND. Raman spectroscopy indicated that the support was located at approximately 1300-1500 cm⁻¹. -1 There is a sp 2 Characteristic vibrational peaks of hybrid boron / carbon materials. Nuclear magnetic resonance (¹¹B NMR) spectroscopy indicates chemical shifts in the range of 10–20 ppm, which is sp. 2 Hybridized B-characteristic signal. Figure 1 ) The modified carbon nanomaterial has a shell-and-core structure formed by a graphene layer doped with B atoms as the shell and the carbon nanomaterial itself as the core, and the surface has sp... 2 Defect-rich structures of hybrid carbon / boron; B. Mix 200 mg NDB powder with 30 mL deionized water in a flask and sonicate for 30 min. Place the resulting dispersion in an oil bath at 100 °C and stir for 30 min. Simultaneously, add sodium bicarbonate solid powder (total molar ratio of sodium bicarbonate to active metal is 10:1) to the dispersion to adjust the pH to approximately 9. Then, add the metal precursor solution dropwise, stir and reflux for 1 h, remove the flask, cool and let stand at room temperature for 4 h, filter the solid, and dry it in a vacuum drying oven at 60 °C for 12 h. Then, reduce it at 200 °C for 1.5 h under a mixed atmosphere of H2 / He (H2 accounting for 10 vol.%) to obtain the NDB-supported Pd catalyst, denoted as 05Pd / NDB. Figure 1 The image shown is a scanning transmission electron microscope (STEM) image of the catalyst with a Pd loading of 0.5 wt%. It can be seen that Pd is mainly dispersed on the carbon nanofiber support as atomically dispersed Pd species with a particle size of approximately 0.2-1.0 nm. The Pd-Pd coordination number obtained by R-space fitting of its synchrotron X-ray absorption fine structure spectrum Fourier transform (EXAFS-FT) is 2.8, while the Pd-C / O coordination number is 2.0, further confirming that it is an atomically dispersed Pd species and that there are Pd-C bond interactions between it and the support (see Appendix). Figure 2 ).

[0034] (2) Preparation of m-phenylenediamine by hydrogenation of isophthalonitrile: Weigh 20 mg of 0.5 Pd / NDB, 10 mL of methanol, and 1 mmol of isophthalonitrile and place them in a reaction vessel. At room temperature, first fill the vessel with nitrogen and check for airtightness. If airtightness is good, purge the vessel three times with nitrogen and then three times with hydrogen. After purging, introduce hydrogen to 1.0 MPa at 30 °C and react for 180 min with stirring at 700 rpm. Continuous hydrogen purging is maintained throughout the reaction to keep the pressure constant. The conversion rate of isophthalonitrile is 99.5%, and the selectivity is 98.9%.

[0035] Example 2 (1) Catalyst preparation: A. Take a certain amount of Rh(NO3)3 mother liquor (an aqueous solution with Rh content of 0.8 wt%), add the corresponding amount of o-phenylenediamine according to the molar ratio of metal to nitrogen-containing ligand of 2.5:1, dilute with deionized water to 10 mL, and sonicate to obtain a metal precursor solution. Take 1.2 g of nano-graphene (NG) powder (particle size 8-12 nm) in a 100 mL flask, add ammonium borate (45 wt% relative to NG) and 30 mL of ethanol, stir at 80 °C for 2 h, filter, place the solid in a vacuum drying oven and dry at 80 °C for 12 h, then calcine at 1200 °C and 100 mL / min in an argon atmosphere for 2 h, followed by annealing at 800 °C in an argon atmosphere for 1 h, cool, wash with water and then vacuum dry to obtain the NGB modified support. STEM-EDX spectroscopy revealed a surface boron content of 3.2 wt%. AC-HAADF-STEM observation showed a support particle size of 6.6-7.8 nm and a graphene layer thickness of 0.4 nm coated on the NG. Raman spectroscopy indicated that the support was located at approximately 1300-1500 cm⁻¹. -1 There is a sp 2 Characteristic vibrational peaks of hybrid boron / carbon materials; nuclear magnetic resonance (¹¹B NMR) spectroscopy indicates that the chemical shift is in the range of 10–20 ppm, which is sp. 2 Hybridized B characteristic signal.

[0036] B. 200 mg NGB powder was mixed with 40 mL of deionized water in a flask and ultrasonically dispersed for 30 min. The resulting dispersion was placed in an oil bath at 100 °C and stirred for 30 min. Simultaneously, potassium carbonate solid powder (total molar ratio of potassium carbonate to active metal was 6:1) was added to the dispersion to adjust the pH to approximately 10. Then, the metal precursor solution was added dropwise, stirred and refluxed for 1 h. The flask was then removed and allowed to cool and stand at room temperature for 4 h. The solid was filtered and dried in a vacuum drying oven at 60 °C for 12 h. Reduction was then carried out at 200 °C for 1.5 h under a mixed atmosphere of H2 / He (H2 accounting for 10 vol.%) to obtain the NGB-supported Rh catalyst, denoted as O8 Rh / NGB. Observation of the catalyst under AC-HAADF-STEM showed that Rh was mainly dispersed as atomically dispersed Rh species on the carbon nanofiber support, with particle sizes ranging from 0.3 to 0.75 nm. The Rh-Rh coordination number fitted to its EXAFS-FT spectrum in the R space is 2.4, which confirms that it is an atomically dispersed Rh species. The Rh-C / O coordination number is 2.6, which also confirms that it is an atomically dispersed Rh species and that there is an Rh-C bond interaction with the support.

[0037] (2) Preparation of m-phenylenediamine by hydrogenation of isophthalonitrile: Weigh 12.5 mg of 08Rh / NGB, 10 mL of methanol, and 1 mmol of isophthalonitrile and place them in a reaction vessel. At room temperature, first fill the vessel with nitrogen and check for airtightness. If airtightness is good, purge the reaction vessel three times with nitrogen and then three times with hydrogen. After purging, introduce hydrogen to 1.0 MPa at 30°C and react for 180 min with stirring at 700 rpm. Continuous hydrogen purging is maintained throughout the reaction to keep the pressure constant. The conversion rate of isophthalonitrile was 99.2%, and the selectivity was 97.6%.

[0038] Example 3 (1) Catalyst preparation: A. Take a certain amount of RuCl3 mother liquor (an aqueous solution with Ru content of 1.0 wt%), add the corresponding amount of o-phenylenediamine according to the molar ratio of metal to nitrogen-containing ligand of 2.5:1, dilute with deionized water to 10 mL, and disperse by ultrasonication to obtain a metal precursor solution. Take 1.2 g of carbon nanotube (CNT) powder (particle size 5-8 nm) in a 100 mL flask, add ammonium borate (45 wt% relative to CNT) and 30 mL of ethanol, stir at 100 °C for 2 h, filter, place the solid in a vacuum drying oven and dry at 80 °C for 12 h, then calcine at 1200 °C and 100 mL / min in an argon atmosphere for 2 h, followed by annealing at 800 °C in an argon atmosphere for 1 h, cool, wash with water, and then vacuum dry to obtain the CNTB modified support. STEM-EDX spectroscopy revealed a surface boron content of 3.3 wt%. AC-HAADF-STEM observation showed a support particle size of 4.5-6.0 nm and a graphene layer thickness of 0.2 nm coated on CNTs. Raman spectroscopy indicated that the support was located at approximately 1300-1500 cm⁻¹. -1 There is a sp 2 Characteristic vibrational peaks of hybrid boron / carbon materials; nuclear magnetic resonance (¹¹B NMR) spectroscopy indicates that the chemical shift is in the range of 10–20 ppm, which is sp. 2 Hybridized B characteristic signal.

[0039] B. 200 mg of CNTB powder was mixed with 40 mL of deionized water in a flask and ultrasonically dispersed for 30 min. The resulting dispersion was placed in an oil bath at 100 °C and stirred for 30 min. Simultaneously, sodium carbonate solid powder (total molar ratio of sodium carbonate to active metal was 6:1) was added to the dispersion to adjust the pH of the solution to approximately 10. Then, the metal precursor solution was added dropwise, and the mixture was stirred and refluxed for 1 h. After stirring, the flask was removed and allowed to cool and stand at room temperature for 4 h. The solid was filtered and dried in a vacuum drying oven at 60 °C for 12 h. Then, it was reduced at 200 °C for 1.5 h under a mixed atmosphere of H2 / He (H2 accounting for 10 vol.%) to obtain the CNTB-supported Ru catalyst, denoted as 10 Ru / CNTB. Observation of the catalyst under AC-HAADF-STEM showed that Ru was mainly dispersed in the form of atomically dispersed Ru species on the nano-carbon support, with a particle size of 0.2-0.8 nm. The Ru-Ru coordination number fitted to its EXAFS-FT spectrum in the R space is 3.1, which confirms that it is an atomically dispersed Ru species. The Ru-C / O coordination number is 2.0, which also confirms that it is an atomically dispersed Ru species and that there is a Ru-C bond interaction with the support.

[0040] (2) Preparation of m-phenylenediamine by hydrogenation of isophthalonitrile: Weigh 10 mg of 10Ru / CNTB, 10 mL of methanol, and 1 mmol of isophthalonitrile and place them in a reaction vessel. At room temperature, first fill the vessel with nitrogen and check for airtightness. If airtightness is good, purge the vessel three times with nitrogen and then three times with hydrogen. After purging, introduce hydrogen to 1.0 MPa at 40 °C and react for 180 min with stirring at 700 rpm. Continuous hydrogen purging is maintained throughout the reaction to keep the pressure constant. The conversion rate of isophthalonitrile is 97.2%, and the selectivity is 94.7%.

[0041] Example 4 (1) Catalyst preparation: A. Take a certain amount of Pd(NO3)2 mother liquor and RuCl3 mother liquor (aqueous solution with Pd and Ru content of 0.5 wt%), add the corresponding amount of m-phenylenediamine according to the molar ratio of the two metals to the nitrogen-containing ligand of 1:1:1, dilute with deionized water to 10 mL, and sonicate to obtain a metal precursor solution. Take 1.2 g of nano-activated carbon (AC) powder (particle size 8-15 nm) in a 100 mL flask, add boric acid of 35 wt% relative to AC and 30 mL of ethanol, stir at 100 °C for 2 h, filter, place the solid in a vacuum drying oven and dry at 80 °C for 12 h, then calcine at 1100 °C and 100 mL / min argon atmosphere for 1.5 h, then anneal at 800 °C in an argon atmosphere for 1 h, cool, wash with water and then vacuum dry to obtain the ACB modified support. STEM-EDX energy dispersive spectroscopy revealed a surface boron content of 4.9 wt%. AC-HAADF-STEM observation showed a support particle size of 9.6-11.7 nm and a graphene layer thickness of 1.0 nm coated on the activated carbon. Raman spectroscopy indicated that the support was located at approximately 1300-1500 cm⁻¹. -1 There is a sp 2 Characteristic vibrational peaks of hybrid boron / carbon materials; nuclear magnetic resonance (¹¹B NMR) spectroscopy indicates that the chemical shift is in the range of 10–20 ppm, which is sp. 2 Hybridized B characteristic signal.

[0042] B. 200 mg AC powder was mixed with 35 mL of deionized water in a flask and ultrasonically dispersed for 40 min. The resulting dispersion was placed in an oil bath at 95 °C and stirred for 30 min. Simultaneously, sodium bicarbonate solid powder (total molar ratio of sodium bicarbonate to active metal was 15:1) was added to the dispersion to adjust the pH of the solution to approximately 8.5. Then, the metal precursor solution was added dropwise, stirred and refluxed for 1 h, and the flask was removed and allowed to stand at room temperature for 4 h. The solid was filtered and dried in a vacuum drying oven at 60 °C for 12 h. Then, it was reduced at 250 °C for 2.0 h under a mixed atmosphere of H2 / He (H2 accounting for 10 vol.%) to obtain the AC-supported PdRu catalyst, denoted as 05Pd05Ru / ACB. Observation of the catalyst under AC-HAADF-STEM showed that Pd and Ru were mainly dispersed in the form of atomically dispersed species on the nano-carbon support, with most clusters having a particle size of 0.4-0.8 nm. The Pd-Pd coordination number fitted to the R space of its EXAFS-FT spectrum is 2.3; the Ru-Ru coordination number is 2.7; and the Pd-Ru coordination number is 0.8, which also confirms that it is an atomically dispersed Pd and Ru species.

[0043] (2) Preparation of m-phenylenediamine by hydrogenation of isophthalonitrile: Weigh 10 mg of 0.5Pd0.5Ru / ACB, 7.5 mL of methanol, 2.5 mL of ethanol, and 1 mmol of isophthalonitrile and place them in a reaction vessel. At room temperature, first fill the vessel with nitrogen and check for airtightness. If airtightness is good, purge the reaction vessel three times with nitrogen and then three times with hydrogen. After purging, introduce hydrogen to 0.9 MPa at 40°C and react for 180 min with stirring at 700 rpm. Continuous hydrogen purging is maintained throughout the reaction to keep the pressure constant. The conversion rate of isophthalonitrile is 98.9%, and the selectivity is 98.1%.

[0044] Example 5 (1) Catalyst preparation: A. Take a certain amount of PdCl2 mother liquor, RhCl3 mother liquor, and Ru(NO3)3 mother liquor (an aqueous solution with Pd, Rh, and Ru contents of 0.5 wt%), add the corresponding amount of 2-aminopyridine according to the molar ratio of the three metals to the nitrogen-containing ligand of 1:1:1:3, dilute with deionized water to 10 mL, and sonicate to obtain a metal precursor solution. Take 1.2 g of carbon black (CB) powder (particle size 10-15 nm) in a 100 mL flask, add 50 wt% ammonium fluoroborate relative to CB and 30 mL of ethanol, stir at 100 °C for 2 h, filter, place the solid in a vacuum drying oven and dry at 80 °C for 12 h, then calcine at 1270 °C and 100 mL / min in an argon atmosphere for 2.5 h, followed by annealing at 880 °C in an argon atmosphere for 1 h, cool, wash with water, and then vacuum dry to obtain the CBB modified support. STEM-EDX spectroscopy revealed a surface boron content of 4.1 wt%. AC-HAADF-STEM observation showed the support particle size to be 8.0-13.6 nm, with a graphene layer thickness of 0.5 nm coated on the CB. Raman spectroscopy indicated that the support was located at approximately 1300-1500 cm⁻¹. -1 There is a sp 2 Characteristic vibrational peaks of hybrid boron / carbon materials; nuclear magnetic resonance (¹¹B NMR) spectroscopy indicates that the chemical shift is in the range of 10–20 ppm, which is sp. 2 Hybridized B characteristic signal.

[0045] B. 200 mg of CBB powder was mixed with 40 mL of deionized water in a flask and ultrasonically dispersed for 30 min. The resulting dispersion was placed in an oil bath at 99 °C and stirred for 30 min. Simultaneously, potassium carbonate and sodium carbonate solid powders (potassium carbonate, sodium carbonate, and active metal molar ratio of 2.5:2.5:1) were added to the dispersion. The pH of the solution was adjusted to approximately 10. Then, the metal precursor solution was added dropwise, and the mixture was stirred and refluxed for 0.9 h. The flask was then removed, cooled to room temperature, and allowed to stand for 6 h. The solid was filtered and dried in a vacuum drying oven at 60 °C for 12 h. Finally, it was reduced at 250 °C for 3 h under a pure H2 atmosphere to obtain the CBB-supported ternary catalyst, denoted as O4PdO4RuO4Rh / CBB. Observation of the catalyst under AC-HAADF-STEM showed that the three metals were mainly dispersed in atomically dispersed clusters on the nano-carbon support, with particle sizes ranging from 0.4 to 0.9 nm. The R-space fitting of its EXAFS-FT spectra showed a coordination number of 2.9 for Rh-Rh, 2.0 for Pd-Pd, 2.5 for Ru-Ru, and 2.1 for Rh / Ru / Pd-C / O, confirming that it is an atomically dispersed noble metal species.

[0046] (2) Preparation of m-phenylenediamine by hydrogenation of isophthalonitrile: Weigh 10 mg of 0.4Pd0.4Ru0.4Rh / CBB, 10 mL of 2-methylimidazole, and 1 mmol of isophthalonitrile and place them in a reaction vessel. At room temperature, first fill the vessel with nitrogen and check for airtightness. If airtightness is good, purge the reaction vessel three times with nitrogen and then three times with hydrogen. After purging, introduce hydrogen to 0.8 MPa at 38°C and react for 60 min with stirring at 800 rpm. Continuous hydrogen purging is maintained throughout the reaction to keep the pressure constant. The conversion rate of isophthalonitrile is 99.9%, and the selectivity is 97.8%.

[0047] Example 6 (1) Catalyst preparation: A. A certain amount of Pd(OAc)₂ (palladium acetate) mother liquor and Pd(acac)₂ (palladium acetylacetone) mother liquor (Pd content 0.5wt%) were mixed. The corresponding amount of p-phenylenediamine was added according to a metal to nitrogen-containing ligand molar ratio of 2:1. The mixture was diluted with deionized water to 10mL and ultrasonically dispersed to obtain a metal precursor solution. 1.2 g of ND powder (particle size 5-10 nm) was placed in a 100mL flask. 15wt% ammonium borate and 25wt% boric acid (relative to ND) and 40mL ethanol were added. The mixture was stirred at 80℃ for 2h. After filtration, the solid was dried in a vacuum drying oven at 80℃ for 12h. Then, it was calcined at 1195℃ and 90mL / min in an argon atmosphere for 2.8h. Subsequently, it was annealed at 900℃ in an argon atmosphere for 1.5h. After cooling, it was washed with water and then vacuum dried to obtain the NDB modified support. STEM-EDX spectroscopy revealed a surface boron content of 3.5 wt%. AC-HAADF-STEM observation showed a support particle size of 6.1-8.9 nm and a graphene layer thickness of 0.2 nm coated on the ND. Raman spectroscopy indicated that the support was located at approximately 1300-1500 cm⁻¹. -1 There is a sp 2 Characteristic vibrational peaks of hybrid boron / carbon materials; nuclear magnetic resonance (¹¹B NMR) spectroscopy indicates that the chemical shift is in the range of 10–20 ppm, which is sp. 2 Hybridized B characteristic signal.

[0048] B. 200 mg NDB powder was mixed with 40 mL of deionized water in a flask and ultrasonically dispersed for 30 min. The resulting dispersion was placed in an oil bath at 102 °C and stirred for 30 min. Simultaneously, potassium carbonate solid powder (total molar ratio of potassium carbonate to active metal was 6:1) was added to the dispersion to adjust the pH to approximately 11. Then, the metal precursor solution was added dropwise, and the mixture was stirred and refluxed for 0.9 h. The flask was then removed and allowed to cool and stand at room temperature for 6 h. The solid was filtered and dried in a vacuum drying oven at 70 °C for 12 h. Finally, it was reduced at 250 °C for 2 h under a mixed atmosphere of H2 / He (H2 accounting for 20 vol.%) to obtain the NDB-supported Pd catalyst, denoted as O5Pd / NDB. Observation of the catalyst under AC-HAADF-STEM showed that metallic Pd was mainly dispersed in atomically dispersed clusters on the nano-carbon support, with particle sizes ranging from 0.3 to 0.8 nm. The Pd-Pd coordination number obtained by R-space fitting of its EXAFS-FT spectrum is 2.4; the Pd-O / C coordination number is 1.8, which also confirms that it is an atomically dispersed noble metal species.

[0049] (2) Preparation of m-phenylenediamine by hydrogenation of isophthalonitrile: 100 mg of 0.5 Pd / NDB, 10 mL of 2-methylimidazole, and 1 mmol of isophthalonitrile were weighed and placed in a reaction vessel. At room temperature, the vessel was first filled with nitrogen and the airtightness was checked. The airtightness was good. The reaction vessel was then purged three times with nitrogen and then three times with hydrogen. After purging, hydrogen was introduced at 50 °C to a pressure of 0.25 MPa, and the reaction was carried out at 800 rpm for 60 min with continuous hydrogen purging to maintain a constant pressure. The conversion rate of isophthalonitrile was 98.5%, and the selectivity was 96.6%.

[0050] Example 7 (1) Catalyst preparation: A. Take a certain amount of Pd(NO3)2 mother liquor (Pd content is 0.1wt%), add the corresponding amount of p-phenylenediamine according to the molar ratio of metal to nitrogen-containing ligand 1.5:1, dilute with deionized water to 10mL, and sonicate to obtain a metal precursor solution. Take 1.2g of ND powder (particle size 5-10 nm) in a 100ml flask, add ammonium borate (30wt% relative to ND) and 33ml of ethanol, stir at 80℃ for 2h, filter, place the solid in a vacuum drying oven and dry at 80℃ for 12h, then calcine at 1150℃ and 90 mL / min in an argon atmosphere for 2.0h, followed by annealing at 850℃ in an argon atmosphere for 1.2h, cool, wash with water and then vacuum dry to obtain the NDB modified support. STEM-EDX spectroscopy revealed a surface boron content of 2.8 wt%. AC-HAADF-STEM observation showed a support particle size of 5.7-7.9 nm and a graphene layer thickness of 0.3 nm coated on the ND. Raman spectroscopy indicated that the support was located at approximately 1300-1500 cm⁻¹. -1 There is a sp 2 Characteristic vibrational peaks of hybrid boron / carbon materials; nuclear magnetic resonance (¹¹B NMR) spectroscopy indicates that the chemical shift is in the range of 10–20 ppm, which is sp. 2 Hybridized B characteristic signal.

[0051] B. 200 mg of NDB powder was mixed with 40 mL of deionized water in a flask and ultrasonically dispersed for 30 min. The resulting dispersion was placed in an oil bath at 101 °C and stirred for 30 min. Simultaneously, sodium bicarbonate solid powder (total molar ratio of sodium bicarbonate to active metal was 20:1) was added to the dispersion to adjust the pH of the solution to approximately 9. Then, the metal precursor solution was added dropwise, and the mixture was stirred and refluxed for 0.9 h. The flask was then removed and allowed to cool and stand at room temperature for 6 h. The solid was filtered and dried in a vacuum drying oven at 60 °C for 12 h. Then, it was reduced at 150 °C for 2 h under a mixed atmosphere of H2 / He (H2 accounting for 10 vol.%) to obtain the NDB-supported Pd catalyst, denoted as O1Pd / NDB. Observation of the catalyst under AC-HAADF-STEM showed that metallic Pd was mainly dispersed as individual Pd atoms on the nano-carbon support, with a particle size of approximately 0.2-0.3 nm. The Pd-Pd coordination number fitted to its EXAFS-FT spectrum in R space was 0.2; the Pd-O / C coordination number was 3.5, which also confirmed that it is an atomically dispersed Pd species and is bonded to carbon defects.

[0052] (2) Preparation of m-phenylenediamine by hydrogenation of isophthalonitrile: Weigh 20 mg of 0.1Pd / NDB, 10 mL of methanol, and 1 mmol of isophthalonitrile and place them in a reaction vessel. At room temperature, first fill the vessel with nitrogen and check for airtightness. If airtightness is good, purge the reaction vessel three times with nitrogen and then three times with hydrogen. After purging, introduce hydrogen to 1.5 MPa at 50 °C and react for 240 min with stirring at 700 rpm. Continuous hydrogen purging is maintained throughout the reaction to keep the pressure constant. The conversion rate of isophthalonitrile is 98%, and the selectivity is 95.9%.

[0053] Example 8 (1) Catalyst preparation: A. Take a certain amount of Pd(NO3)2 mother liquor and Rh(NO3)3 mother liquor (aqueous solution with Pd and Rh content of 0.5 wt%), add the corresponding amount of p-phenylenediamine according to the molar ratio of the two metals to the nitrogen-containing ligand of 2.5:2.5:1, dilute with deionized water to 10 mL, and sonicate to obtain a metal precursor solution. Take 1.2 g of ND powder (particle size 5-10 nm) in a 100 mL flask, add ammonium borate (75 wt% relative to ND) and 50 mL of ethanol, stir at 80 °C for 3 h, filter, place the solid in a vacuum drying oven and dry at 80 °C for 12 h, then calcine at 1480 °C and 95 mL / min in an argon atmosphere for 4 h, followed by annealing at 850 °C in an argon atmosphere for 1.5 h, cool, wash with water and then vacuum dry to obtain the NDB modified support. STEM-EDX spectroscopy revealed a surface boron content of 4.9 wt%. AC-HAADF-STEM observation showed a support particle size of 5.7-6.5 nm and a graphene layer thickness of 0.9 nm coated on the ND. Raman spectroscopy indicated that the support was located at approximately 1300-1500 cm⁻¹. -1 There is a sp 2 Characteristic vibrational peaks of hybrid boron / carbon materials; nuclear magnetic resonance (¹¹B NMR) spectroscopy indicates that the chemical shift is in the range of 10–20 ppm, which is sp. 2 Hybridized B characteristic signal.

[0054] B. 200 mg NDB powder was mixed with 40 mL of deionized water in a flask and ultrasonically dispersed for 30 min. The resulting dispersion was placed in an oil bath at 98 °C and stirred for 75 min. Simultaneously, potassium carbonate solid powder (total molar ratio of potassium carbonate to active metal was 5:1) was added to the dispersion to adjust the pH to approximately 10. Then, the metal precursor solution was added dropwise, and the mixture was stirred and refluxed for 0.9 h. The flask was then removed, cooled to room temperature, and allowed to stand for 6 h. The solid was filtered and dried in a vacuum drying oven at 60 °C for 12 h. Finally, it was reduced at 300 °C for 1.5 h under a pure H2 atmosphere to obtain the NDB-supported PdRh catalyst, denoted as 05Pd05Rh / NDB. Observation of the catalyst under AC-HAADF-STEM showed that metal Pd and Rh were mainly supported on the nano-carbon support in an atomically dispersed manner, with cluster sizes ranging from 0.5 to 0.9 nm. The Pd-Pd coordination number fitted to its EXAFS-FT spectrum in the R space is 2.1; the Rh-Rh coordination number is 1.4; the Pd-Rh coordination number is 0.5; the Pd-O / C coordination number is 2.5; and the Rh-C / O coordination number is 1.9, which also confirms that it is an atomically dispersed metal species and is bonded to carbon defects.

[0055] (2) Preparation of m-phenylenediamine by hydrogenation of isophthalonitrile: Weigh 10 mg of 0.5Pd0.5Rh / NDB, 10 mL of methanol, and 1 mmol of isophthalonitrile and place them in a reaction vessel. At room temperature, first fill the vessel with nitrogen and check for airtightness. If airtightness is good, purge the reaction vessel three times with nitrogen and then three times with hydrogen. After purging, raise the temperature to 30°C at a rate of 5°C / min, and introduce hydrogen to a pressure of 1.2 MPa. React under stirring at 800 rpm for 150 min, continuously introducing hydrogen to maintain a constant pressure throughout the reaction. The conversion rate of isophthalonitrile is >99.9%, and the selectivity is 98.2%.

[0056] Example 9 (1) Catalyst preparation: The process and conditions were the same as those for catalyst preparation described in Example 1, except that the Pd content in the Pd(NO3)2 mother liquor was changed to 1.5 wt%, denoted as 15Pd / NDB.

[0057] (2) Preparation of m-phenylenediamine by hydrogenation of isophthalonitrile: 6.7 mg of 15Pd / NDB, 10 mL of methanol, and 1 mmol of isophthalonitrile were weighed and placed in a reaction vessel. At room temperature, the vessel was first filled with nitrogen and the airtightness was checked. The airtightness was good. The reaction vessel was then purged three times with nitrogen and then three times with hydrogen. After purging, hydrogen was introduced at 30°C to a pressure of 1.0 MPa, and the reaction was carried out at 700 rpm for 180 min with stirring. Hydrogen was continuously introduced during the reaction to maintain a constant pressure. The conversion rate of isophthalonitrile was 98.5%, and the selectivity was 98.6%.

[0058] Example 10 (1) Catalyst preparation: The process and conditions were the same as those for catalyst preparation described in Example 1, denoted as 05Pd / NDB. (Substrate expansion experiments were conducted using the catalyst preparation scheme of Example 1.) (2) Preparation of m-phenylenediamine by hydrogenation of isophthalonitrile: The substrates were phthalonitrile, terephthalonitrile, 1,6-adiponitrile, and 1,5-pentadionitrile. 20 mg of 0.5 Pd / NDB, 10 mL of methanol, and 1 mmol of substrate were weighed and placed in a reaction vessel. At room temperature, the vessel was first filled with nitrogen and the airtightness was checked. The airtightness was good. The reaction vessel was then purged three times with nitrogen and three times with hydrogen. After purging, the temperature was increased to 40 °C at a rate of 5 °C / min, and hydrogen was introduced to a pressure of 1.0 MPa. Hydrogen was continuously introduced during the reaction to maintain a constant pressure. Specific reaction times and results are shown in Table 1.

[0059]

[0060] Table 1

[0061] Example 11 (1) Catalyst preparation: The process and conditions are the same as those for catalyst preparation described in Example 1, except that the nano-carbon support is replaced by nano-graphene, carbon nanotubes, nano-activated carbon, and carbon black, while the modification treatment method remains the same. They are respectively denoted as 05Pd / NGB, 05Pd / CNTB, 05Pd / ACB, and 05Pd / CBB.

[0062] (2) Preparation of m-phenylenediamine by hydrogenation of isophthalonitrile: 20 mg of 0.5Pd / NGB, 0.5Pd / CNTB, 0.5Pd / ACB, and 0.5Pd / CBB were weighed out respectively, and 10 mL of methanol and 1 mmol of isophthalonitrile were added to each, placing them into a reaction vessel. At room temperature, the vessel was first filled with nitrogen and the airtightness was checked. The airtightness was good. The reaction vessel was then purged three times with nitrogen and hydrogen respectively. After purging, hydrogen was introduced at 30°C to a pressure of 1.0 MPa, and the reaction was carried out at 700 rpm for 180 min with stirring. Hydrogen was continuously introduced during the reaction to maintain a constant pressure. The 05Pd / NGB catalyst showed a 97.6% conversion rate and a 98.0% selectivity for isophthalonitrile; the 05Pd / CNTB catalyst showed a 97.9% conversion rate and a 97.8% selectivity; the 05Pd / ACB catalyst showed a 99.2% conversion rate and a 95.4% selectivity; and the 05Pd / CBB catalyst showed a 97.2% conversion rate and a 89.5% selectivity.

[0063] Comparative Example 1 (1) Catalyst preparation: The process and conditions were the same as those described in Example 1 for catalyst preparation, except that step (1) omitted step A, and the support in step B was replaced by undoped nanodiamond powder ND by mass instead of NDB. Other operations remained unchanged, and the resulting catalyst was denoted as 05Pd / ND. AC-HAADF-STEM observation showed that the support particle size was 7.8-9.3 nm. No characteristic signals corresponding to the B element were observed in the Raman and nuclear magnetic resonance (¹¹¹B NMR) spectra. The data from the EXAFS-FT spectrum R-space fitting are shown in Table 1. (2) Preparation of m-phenylenediamine by hydrogenation of isophthalonitrile: Weigh 20 mg of 0.5Pd / ND, 10 mL of methanol, and 2 mmol of isophthalonitrile and place them in a reaction vessel. At room temperature, first fill the vessel with nitrogen and check for airtightness. If airtightness is good, purge the vessel three times with nitrogen and then three times with hydrogen. After purging, introduce hydrogen to 1.0 MPa at 30°C and react for 180 min with stirring at 700 rpm. Hydrogen is continuously introduced during the reaction to maintain a constant pressure. The conversion rate of isophthalonitrile is 99.6%, and the selectivity is 71%.

[0064] Comparative Example 2 (1) Catalyst preparation: The process and conditions were the same as those described in Example 1 for catalyst preparation, except that in the process of preparing modified nanodiamond, after adding boron source and drying in step (1) A, the Ar treatment conditions were changed to 350℃ for 1h, and no subsequent annealing treatment was used. Other operations remained unchanged, and the catalyst was obtained, denoted as 05PdNL / NDB. The data of its EXAFS-FT spectrum R space fitting are shown in Table 1.

[0065] (2) Preparation of m-phenylenediamine by hydrogenation of isophthalonitrile: Weigh 20 mg of 0.5PdNL / NDB, 10 mL of methanol, and 2 mmol of isophthalonitrile and place them in a reaction vessel. At room temperature, first fill the vessel with nitrogen and check for airtightness. If airtightness is good, purge the reaction vessel three times with nitrogen and then three times with hydrogen. After purging, introduce hydrogen to 1.0 MPa at 30 °C and react for 180 min with stirring at 700 rpm. Continuous hydrogen purging is maintained throughout the reaction to keep the pressure constant. The conversion rate of isophthalonitrile was 78.6%, and the selectivity was 67.1%.

[0066]

[0067] Comparative Example 3 (1) Catalyst preparation: The process and conditions are the same as those described in Example 9 for catalyst preparation, except that: in step (1)B, no precipitant is added to adjust the pH of the metal precursor solution when preparing the catalyst by the deposition precipitation method, and other operations remain unchanged, and the catalyst is obtained and is recorded as 15PdNB / NDB.

[0068] (2) Preparation of m-phenylenediamine by hydrogenation of isophthalonitrile: Weigh 20 mg of 0.5PdNB / NDB, 10 mL of methanol, and 2 mmol of isophthalonitrile and place them in a reaction vessel. At room temperature, first fill the vessel with nitrogen and check for airtightness. If airtightness is good, purge the vessel three times with nitrogen and then with hydrogen. After purging, introduce hydrogen to 1.0 MPa at 30°C and react for 180 min with stirring at 700 rpm. Continuous hydrogen purging is maintained throughout the reaction to keep the pressure constant. The conversion rate of isophthalonitrile is 89.7%, and the selectivity is 18.9%.

[0069] Comparative Example 4 (1) Catalyst preparation: A. Take a certain amount of Pd(NO3)2 mother liquor (an aqueous solution with a Pd content of 2.0 wt%) and add it to a beaker with 2 ml of anhydrous ethanol. Stir for 5 min to obtain a metal precursor solution. Take 1.2 g of nanodiamond (ND) powder (particle size 5-10 nm) in a 100 ml flask, add ammonium borate (45 wt% relative to ND) and 30 ml of ethanol, stir at 80 °C for 2 h, filter, and place the solid in a vacuum drying oven to dry at 80 °C for 12 h. Then, calcine it at 1200 °C and 100 mL / min in an argon atmosphere for 2 h. After that, anneal it at 800 °C in an argon atmosphere for 1 h. After cooling to room temperature, wash the solid with water and then vacuum dry it to obtain the NDB modified support. STEM-EDX energy dispersive spectroscopy revealed a surface boron content of 3.6 wt%. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) showed a carrier particle size of 5.9-8.0 nm and a graphene layer thickness of 0.5 nm on the ND. Raman spectroscopy indicated that the carrier had a particle size of approximately 1300-1600 cm⁻¹. -1 There is a sp 2 Characteristic vibrational peaks of hybrid boron / carbon materials. Nuclear magnetic resonance (¹¹B NMR) spectroscopy indicates chemical shifts in the range of 10–20 ppm, at sp. 2 Hybridized B characteristic signal.

[0070] B. The metal precursor solution was added dropwise to a beaker containing 200 mg of NDB powder, stirred for 24 h, and then dried overnight in a vacuum drying oven at 60 °C to obtain the catalyst precursor. Reduction was carried out at 200 °C for 1.5 h under H2 atmosphere to obtain the NDB-supported Pd catalyst, denoted as 20PdW / NDB. AC-HAADF-STEM images show that Pd is mainly dispersed as nanoparticles on the carbon nanosupport, with a particle size of approximately 3-4 nm. The Pd-Pd coordination number fitted to the R space of its EXAFS-FT spectrum is 5.7, while the Pd-C / O coordination number is 1.2, further confirming that it is a nanoparticle Pd species.

[0071] (2) Preparation of m-phenylenediamine by hydrogenation of isophthalonitrile: Weigh 5 mg of 20PdW / NDB, 10 mL of methanol, and 2 mmol of isophthalonitrile and place them in a reaction vessel. At room temperature, first fill the vessel with nitrogen and check for airtightness. The airtightness was good. The reaction vessel was then purged three times with nitrogen and then three times with hydrogen. After purging, hydrogen was introduced at 30°C to a pressure of 1.0 MPa, and the reaction was carried out at 700 rpm for 180 min with continuous hydrogen purging to maintain a constant pressure. The conversion rate of isophthalonitrile was 9.5%, and no target product, m-phenylenediamine, was observed.

[0072] Comparative Example 5 (1) Catalyst preparation: The process and conditions are the same as those described in Example 1 for catalyst preparation, except that: in step (1)A, the amount of boron source added when preparing the modified nanodiamond support is changed to 100wt% relative to ND, the argon calcination treatment is changed to 4h at 1600℃, the annealing treatment is changed to 1h at 1000℃, and other operations remain unchanged. The resulting catalyst is denoted as 05Pd / NDB+. The surface B element content is 8.2wt% as determined by STEM-EDX energy dispersive spectroscopy. The support particle size is 6.6-9.2 nm as observed by aberration-corrected high-angle annular dark-field scanning transmission electron microscope (AC-HAADF-STEM). The thickness of the graphene layer coated on ND is 1.3 nm.

[0073] (2) Preparation of m-phenylenediamine by hydrogenation of isophthalonitrile: Weigh 20 mg of 0.5Pd / NDB+, 10 mL of methanol, and 2 mmol of isophthalonitrile and place them in a reaction vessel. At room temperature, first fill the vessel with nitrogen and check for airtightness. If airtightness is good, purge the vessel three times with nitrogen and then three times with hydrogen. After purging, introduce hydrogen to 1.0 MPa at 30 °C and react for 180 min with stirring at 700 rpm. Continuous hydrogen purging is maintained to keep the pressure constant throughout the reaction. The conversion rate of isophthalonitrile is 48.0%, and the selectivity for isophthalamide is 58.4%.

[0074] Comparative Example 6 (1) Catalyst preparation: The process and conditions were the same as those described in Example 1 for catalyst preparation, and the resulting catalyst was denoted as 05Pd / NDB.

[0075] (2) Preparation of m-phenylenediamine by hydrogenation of isophthalonitrile: 20 mg of 0.5 Pd / NDB, 10 mL of methanol, and 2 mmol of isophthalonitrile were weighed and placed in a reaction vessel. At room temperature, the vessel was first filled with nitrogen and the airtightness was checked. The airtightness was good. The reaction vessel was then purged three times with nitrogen and three times with hydrogen. After purging, hydrogen was introduced to 1.0 MPa at 80°C and 100°C, and the reaction was carried out for 180 min with stirring at 700 rpm. Hydrogen was continuously introduced during the reaction to maintain a constant pressure. At 80°C, the conversion rate of phthalonitrile was 100%, and the selectivity for m-phthalamide was 66.1%; at 100°C, the conversion rate of phthalonitrile was 100%, and the selectivity for m-phthalamide was 3.6%. Both reactions produced a large amount of the deamination byproduct 3-aminomethyltoluene.

[0076] Comparative Example 7 (1) Catalyst preparation: The process and conditions were the same as those described in Example 1 for catalyst preparation, and the resulting catalyst was denoted as 05Pd / NDB.

[0077] (2) Preparation of m-phenylenediamine by hydrogenation of isophthalonitrile: The reaction conditions differed from those in Example 1: isopropanol was used as the solvent, and the molar concentration of toluenedioxonium was changed to 0.5 mol / L, while other conditions remained unchanged. The conversion rate of isophthalonitrile was 45.3%, and the selectivity of isophthalamide was 47.9%.

[0078] Comparative Example 8 (1) Catalyst preparation: The process and conditions were the same as those described in Example 1 for catalyst preparation, and the resulting catalyst was denoted as 05Pd / NDB.

[0079] (2) Preparation of m-phenylenediamine by hydrogenation of isophthalonitrile: The reaction conditions differed from those in Example 1: the pressure of the hydrogen gas was changed to 2.0 MPa, while the other conditions remained the same. The conversion rate of isophthalonitrile was 100%, and the selectivity of m-phenylenediamine was 85.2%.

[0080] Table 1. Catalyst activity evaluation results in Example 10 The above examples are for reference only. Any technical solutions that are similar to or derived from the concept of this patent are within the scope of protection of this invention.

Claims

1. A method for preparing m-phenylenediamine by hydrogenation of isophthalonitrile, characterized in that: It employs an atomically dispersed noble metal catalyst for catalytic reaction; the reaction process uses isophthalonitrile and hydrogen as raw materials, and the reaction temperature is 20-60℃; the catalyst is composed of a modified nano-carbon support and an active metal component; the modified nano-carbon support has a particle size of 5-10 nm, wherein the active metal component is loaded on the modified nano-support to form atomically dispersed noble metal single atoms and / or clusters, with a species particle size distribution of 0.2-1.2 nm; the active metal component is one, two, or three of Pd, Ru, or Rh, with a loading of 0.1-1.5 wt%, and the metal is dispersed on the nano-support in an atomically dispersed cluster manner; the modified nano-carbon material has a shell structure with a graphene layer doped with B atoms as the shell and the nano-carbon material itself as the core, forming a shell-encapsulated core structure, and the surface has sp 2 The hybrid carbon / boron structure is defect-rich; the active metal component bonds with defects / vacancies on the support to form atomically dispersed noble metal single atoms or clusters; the doped boron source is one or more of ammonium borate, ammonium fluoroborate, and boric acid.

2. The method according to claim 1, characterized in that: The atomically dispersed noble metal clusters are the active centers of the catalyst; the nano-carbon support is one or more of nanodiamond, nanographene, carbon nanotubes, nano-activated carbon, and carbon black.

3. The method according to claim 1, characterized in that: The percentage of B atoms doped in the graphene layer is 1.0-5.0 wt%; the thickness of the B-doped graphene layer is 0.1-1.0 nm.

4. The method according to claim 1, 2 or 3, characterized in that: The preparation process of modified carbon nanomaterials is as follows: 200 mg of carbon nanomaterial powder is placed in a container, and 15-75 wt% boron source and 30-50 ml of ethanol are added relative to the carbon nanomaterial. The mixture is stirred at 60-100℃ for 1.5-3 h, filtered, and the solid is dried. Then, it is calcined at 1100-1500℃ in a nitrogen and / or argon atmosphere at 60-100 mL / min for 2-4 h. Subsequently, it is annealed at 800-950℃ in an argon atmosphere for 0.5-1.5 h. After cooling to room temperature, it is washed with water and dried to obtain the modified carbon nanomaterial carrier material, denoted as NCB.

5. The method according to claim 1, 2, 3 or 4, characterized in that: The preparation method of this catalyst includes the following steps: (1) Preparation of mother liquor containing active metal: Dissolve soluble active metal salt in water, add the corresponding amount of ligand according to the molar ratio of metal to nitrogen-containing ligand 1:1-5:1, and obtain a metal precursor solution with a concentration of 10-20 g / L. (2) The active metal component is dispersed on the support by the deposition-precipitation method to obtain the atomically dispersed noble metal catalyst. The deposition-precipitation process is as follows: the modified nano carbon material and water are added to a container and dispersed to obtain a nano support dispersion. The modified nano carbon material aqueous dispersion is heated and stirred, and a precipitant solid powder is added to the dispersion. Then, the precursor solution containing active metal prepared in step (1) is added dropwise according to the required ratio. After stirring and reflux, it is allowed to stand for aging. After washing, filtration and drying, it is reduced in pure H2 or a mixed atmosphere of H2 and He to obtain the atomically dispersed noble metal catalyst.

6. The method according to claim 5, characterized in that: The Pd metal salt is selected from any one or more of palladium chloride, palladium acetate, palladium acetylacetone, and palladium nitrate; the Ru metal salt is selected from any one or two of ruthenium chloride and ruthenium nitrate; the Rh metal salt is selected from any one or two of rhodium nitrate and rhodium chloride; and the nitrogen-containing ligand is selected from any one or more of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, and 2-aminopyridine.

7. The method according to claim 5, characterized in that: In step (2), the deposition-precipitation method uses one or more of sodium carbonate, potassium carbonate, and sodium bicarbonate as the precipitant; the molar ratio of the precipitant to the active metal component is 2:1-20:1; and the pH of the adjusted metal precursor solution is 8-11.

8. The method according to claim 5, characterized in that: In step (2) of the deposition-precipitation method, The modified nano-carbon material aqueous dispersion uses 200 mg of modified nano-carbon material and 25-50 mL of water. After mixing, it is ultrasonically dispersed for 10-50 min. The modified nano-carbon material aqueous dispersion is heated in an oil bath at 90-105℃, with stirring time of 30-80 min and reflux time of 45-65 min. After reflux, it is cooled to room temperature, allowed to stand for 4-8 h, washed with water, and filtered. Drying is carried out in a vacuum drying oven at 40-80℃ for 8-24 h. Reduction is performed in a pure H2 atmosphere or a mixture of H2 and He, with H2 volume ratio of 5-100% and a reducing atmosphere flow rate of 50-100 ml / min. The reduction temperature is 120-300℃, and the reduction time is 1-3 h.

9. The method according to claim 1, characterized in that: The reaction process is carried out in a batch reactor, using the catalyst to prepare m-phenylenediamine via selective hydrogenation; during the hydrogenation reaction of isophthalonitrile, the solvent is any one or a mixture of two or more of methanol, ethanol, 2-methylimidazole and toluene, the molar concentration of isophthalonitrile is 0.01-0.2 mol / L, and the hydrogen pressure is 0.25-1.5 MPa.

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