Aramid resin ball supported catalyst, its preparation method and application

Abstract

This invention belongs to the field of catalyst preparation and chemical catalytic hydrogenation technology, specifically relating to an aramid resin ball supported catalyst, its preparation method, and its application. The aramid resin ball supported catalyst provided by this invention comprises hollow aramid resin balls and noble metal nanoparticles anchored on the surface and internal pores of the hollow aramid resin balls through coordination complexation with amide groups in the aramid. During high-temperature calcination at 300-400℃, the aramid skeleton maintains its three-dimensional porous structure without collapse due to its excellent high-temperature resistance, thus obtaining a highly uniformly dispersed supported catalyst. This catalyst exhibits mild reaction conditions, extremely high conversion rates, and excellent cycle stability in nitro reduction, olefin double bond reduction, and deep reduction of benzene rings, showing great promise for industrial applications.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation and chemical catalytic hydrogenation technology, specifically relating to an aramid resin ball-supported catalyst, its preparation method, and its application. Background Technology

[0002] Supported noble metal catalysts (such as Pd / C, Ru / Al2O3, etc.) are widely used in the chemical industry for various catalytic hydrogenation reactions, such as nitro reduction, olefin double bond reduction, and deep reduction of benzene rings. However, the interaction between traditional supports and noble metals is often weak. During high-temperature preparation or long-term reaction, noble metals are prone to migration and aggregation, leading to a sharp reduction in active sites and a decrease in catalytic efficiency.

[0003] To address the problem of metal agglomeration, introducing support materials with strong coordination capabilities is a current research hotspot. Aramid (aromatic polyamide), as a special high-performance polymer, possesses excellent high-temperature resistance and chemical corrosion resistance in its molecular backbone, and its main chain contains a large number of electron-rich amide groups, theoretically making it an ideal material for complexing and coordinating noble metal ions. However, due to the extreme difficulty in processing aramid, preparing it into porous microsphere structures suitable as catalyst supports presents significant technological challenges, greatly limiting its application in the field of catalysis.

[0004] Currently, although there are reports on the preparation of porous microsphere catalysts using polymers / resins (such as polystyrene and epoxy resins), conventional resins often only serve as sacrificial templates and are completely decomposed and burned off during the high-temperature calcination (typically >500℃) required for the actual preparation of noble metal catalysts. While this sacrificial template method can form pores, it loses the chemical anchoring effect of polymer functional groups on noble metal nanoparticles, leading to the continued agglomeration of noble metals at high temperatures. Therefore, developing a catalyst support that can be processed into porous microspheres while retaining the polymer framework during high-temperature calcination, thereby continuously utilizing its functional groups for metal coordination and complexation, is a pressing technical challenge in this field. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an aramid resin ball-supported catalyst, its preparation method and application. The aramid resin in the aramid resin ball-supported catalyst provided by the present invention is not only resistant to high temperature, but its dense amide groups have a strong complexing effect on noble metal ions, which can achieve extreme dispersion of noble metals, so that the catalyst has ultra-high activity and stability and can be applied to a variety of catalytic hydrogenation reactions.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides an aramid resin ball supported catalyst, comprising hollow aramid resin balls and noble metal nanoparticles supported on the surface and internal pores of the hollow aramid resin balls.

[0007] Preferably, the noble metal nanoparticles are ruthenium nanoparticles or palladium nanoparticles; the mass of the noble metal nanoparticles accounts for 1 to 10 wt% of the total mass of the aramid resin ball supported catalyst.

[0008] Preferably, the hollow aramid resin spheres have a particle size distribution of 0.4~0.8mm and a specific surface area of ​​50~600m². 2 / g.

[0009] This invention also provides a method for preparing the aramid resin ball-supported catalyst described in the above technical solution, comprising the following steps: An aromatic diamine monomer, a lithium metal salt, and a p-aromatic diacyl chloride are subjected to an in-situ polycondensation reaction in a polar aprotic solvent to obtain a polymer solution. The polymer solution and deprotonated solvent are reacted with a continuous flow microchannel, or droplet precipitation or spray drying is used to form droplets, which are then collected in a precipitation system and subsequently frozen and freeze-dried to obtain hollow aramid resin microspheres. The hollow aramid resin microspheres were mixed with a precursor solution containing noble metal salts, loaded and dried, and the resulting solid material was sintered in an oxygen-containing atmosphere and reduced in a hydrogen atmosphere to obtain the aramid resin microsphere supported catalyst.

[0010] Preferably, the aromatic diamine monomer is one or more selected from p-phenylenediamine, m-phenylenediamine, 2-(4-aminophenyl)-5-aminobenzimidazole, 4,4'-diaminodiphenyl ether, 2-chloro-1,4-phenylenediamine, and 2,5-dichloro-1,4-phenylenediamine; the aromatic diacyl chloride is one or more selected from terephthaloyl chloride, isophthaloyl chloride, and 4,4'-biphenyldicarboxylate chloride; and the lithium metal salt is lithium chloride and / or lithium bromide.

[0011] Preferably, the sintering temperature is below 530°C, and the holding time is 1~12h.

[0012] Preferably, the reduction treatment is performed at a temperature of 200-500°C for 1-10 hours.

[0013] The present invention also provides the application of the aramid resin ball supported catalyst described in the above technical solution or the aramid resin ball supported catalyst prepared by the preparation method described in the above technical solution in catalytic hydrogenation reaction.

[0014] Preferably, the catalytic hydrogenation reaction includes one or more of the following: reduction of nitro compounds to amine compounds, reduction of carbon-carbon double bonds to single bonds, and deep reduction of benzene rings to cyclohexyl structures.

[0015] The present invention also provides a method for catalytic hydrogenation reaction, comprising the following steps: The reaction substrate, catalyst, and hydrogen are subjected to a catalytic hydrogenation reaction in a solvent to obtain the product; The catalyst is the aramid resin ball supported catalyst described in the above technical solution or the aramid resin ball supported catalyst prepared by the preparation method described in the above technical solution.

[0016] This invention provides an aramid resin ball supported catalyst, comprising hollow aramid resin balls and noble metal nanoparticles supported on the surface and internal pores of the hollow aramid resin balls.

[0017] Beneficial effects: 1) The numerous amide groups in the aramid polymer segments effectively complex noble metal Ru or Pd ions during impregnation, preparing highly uniformly dispersed ultrafine noble metal nanoparticles (or sub-nanoclusters) precursors. More importantly, existing porous polymer microspheres (such as polystyrene and epoxy resins) often serve only as sacrificial templates when preparing catalysts, being completely decomposed and burned off during high-temperature sintering (e.g., above 500°C), forming inorganic pores and failing to provide chemical anchoring for the metal. In contrast, the aramid resin used in this invention has a thermal decomposition temperature exceeding 530°C, and its polymer backbone is perfectly preserved during high-temperature sintering and reduction processes at 300-400°C. This not only maintains the mechanical strength of the microspheres but also allows the high-temperature resistant amide groups on the backbone to form strong interfacial coordination complexes with the noble metal at high temperatures, fundamentally preventing the high-temperature aggregation of the noble metal—something traditional resin carriers cannot achieve. Infrared spectroscopy confirmed that the C=O stretching vibration of the amide bond in the aramid resin underwent a significant red shift after loading with noble metals, which conclusively proved that the nitrogen and oxygen atoms of the amide group formed a strong interfacial coordination complex with the noble metals at high temperatures, preventing the high-temperature aggregation of the noble metals.

[0018] 2) Based on its extremely high metal dispersion and effective active sites, this catalyst can achieve efficient hydrogenation at lower reaction temperatures and hydrogen pressures, resulting in a significant increase in conversion rate.

[0019] 3) This catalyst can not only efficiently catalyze the reduction of nitro compounds under mild conditions, but its extremely high intrinsic activity is even sufficient to drive the deep hydrogenation reduction of benzene rings with extremely high reaction energy barriers. At the same time, it also exhibits excellent selectivity in the reduction of olefin double bonds. Attached Figure Description

[0020] Figure 1SEM cross-sectional morphology of the hollow aramid resin spheres prepared in Example 1-A; Figure 2 Infrared spectra of hollow aramid resin spheres prepared in Example 1-A before and after complexing with noble metal Ru; Figure 3 Thermogravimetric analysis diagram of the aramid resin ball supported catalyst (5wt% Ru / aramid) prepared in Example 2; Figure 4 Scanning electron microscope (SEM) image and elemental distribution map of the aramid resin ball-supported catalyst prepared in Example 2. Detailed Implementation

[0021] This invention provides an aramid resin ball supported catalyst, comprising hollow aramid resin balls and noble metal nanoparticles supported on the surface and internal pores of the hollow aramid resin balls.

[0022] Unless otherwise specified, the present invention does not have special requirements on the source of raw materials used, and commercially available products well known to those skilled in the art can be used.

[0023] In one embodiment, the hollow aramid resin ball is a high-temperature resistant resin carrier that maintains its three-dimensional porous skeleton without collapsing after being treated at a high temperature of 300~400℃.

[0024] In one embodiment, the noble metal nanoparticles are ruthenium (Ru) nanoparticles or palladium (Pd) nanoparticles; the mass of the noble metal nanoparticles accounts for 1 to 10 wt% of the total mass of the aramid resin ball supported catalyst, and is 5 wt% in a specific embodiment.

[0025] In one embodiment, the hollow aramid resin balls are prepared by continuous flow microchannel reaction combined with freeze-drying technology; the particle size distribution of the hollow aramid resin balls is 0.4~0.8mm, specifically 0.5mm in this embodiment, and the specific surface area is 50~600m². 2 / g, specifically 250m in the embodiment. 2 / g; The hollow aramid resin spheres are microparticles with a hollow porous structure inside and a spherical shape.

[0026] The polymer backbone of the hollow aramid resin ball contains dense amide groups. The noble metal nanoparticles are anchored to the surface and internal channels of the hollow aramid resin ball by coordinating and complexing with the nitrogen and oxygen atoms in the amide groups.

[0027] This invention reveals that the molecular framework of aramid (aromatic polyamide) possesses excellent high-temperature resistance and chemical corrosion resistance. In particular, its main chain contains a large number of electron-rich amide groups, which can form extremely strong coordination and complexation with noble metal ions. During subsequent high-temperature calcination and reduction processes at 300–400°C, the aramid retains its framework without collapse due to its high-temperature resistance. Simultaneously, the dual effects of physical confinement and chemical bonding completely prevent the migration and aggregation of noble metal nanoparticles, thus yielding a highly uniformly dispersed supported catalyst. This catalyst exhibits mild reaction conditions, extremely high conversion rates, and excellent cycle stability in nitro reduction, olefin double bond reduction, and deep reduction of benzene rings, demonstrating significant potential for industrial applications.

[0028] This invention also provides a method for preparing the aramid resin ball-supported catalyst described in the above technical solution, comprising the following steps: An aromatic diamine monomer, a lithium metal salt, and a p-aromatic diacyl chloride are subjected to an in-situ polycondensation reaction in a polar aprotic solvent to obtain a polymer solution. The polymer solution and deprotonated solvent are reacted with a continuous flow microchannel, or droplet precipitation or spray drying is used to form droplets, which are then collected in a precipitation system and subsequently frozen and freeze-dried to obtain hollow aramid resin microspheres. The hollow aramid resin microspheres were mixed with a precursor solution containing noble metal salts, loaded and dried, and the resulting solid material was sintered in an oxygen-containing atmosphere and reduced in a hydrogen atmosphere to obtain the aramid resin microsphere supported catalyst.

[0029] This invention involves in-situ polycondensation of an aromatic diamine monomer, a lithium metal salt, and a p-aromatic diacyl chloride in a polar aprotic solvent to obtain a polymer solution.

[0030] In one embodiment, the aromatic diamine monomer is one or more selected from p-phenylenediamine, m-phenylenediamine, 2-(4-aminophenyl)-5-aminobenzimidazole (APBIA / DAPBI), 4,4'-diaminodiphenyl ether (ODA), 2-chloro-1,4-phenylenediamine (Cl-PPD), and 2,5-dichloro-1,4-phenylenediamine, with p-phenylenediamine being a specific example; the aromatic diacyl chloride is one or more selected from terephthaloyl chloride (TPC), isophthaloyl chloride (IPC), and 4,4'-biphenyldicarboxylate, with terephthaloyl chloride being a specific example; the lithium metal salt is lithium chloride and / or lithium bromide, with LiCl being a specific example; the polar aprotic solvent is N,N The aromatic diamine monomer is selected from one or more of dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO), with N,N-dimethylacetamide (DMAc) being the most specific example. The molar ratio of the aromatic diamine monomer to the lithium metal salt is 1:1 to 10, with 1:5 being the most specific example. The molar ratio of the aromatic diamine monomer to the p-aromatic diacyl chloride is 1:0.95 to 1.05, with 1:1 being the most specific example. The ratio of the amount of the aromatic diamine monomer to the volume of the polar aprotic solvent is (0.005 to 0.05) mol:100 mL, with 0.01 mol:100 mL being the most specific example.

[0031] In one embodiment, the temperature of the in-situ polycondensation reaction is -10~20℃, specifically 0℃ in this embodiment, and the time is 0.5~6h, specifically 1h in this embodiment; the in-situ polycondensation reaction is carried out under nitrogen protection.

[0032] As one embodiment, the step of in-situ polycondensation reaction of aromatic diamine monomer, lithium metal salt, and p-aromatic diacyl chloride in a polar aprotic solvent is as follows: the polar aprotic solvent is mechanically stirred under nitrogen protection, followed by the addition of aromatic diamine monomer and lithium metal salt. After dissolution, aromatic diacyl chloride is added and mechanical stirring continues. The resulting viscous liquid is dialyzed to obtain a polymer solution. The mechanical stirring rate is 200~2000 r / min, specifically 500~1000 r / min in this embodiment, and the time is 0.1~2 h, specifically 30 min in this embodiment. The continued mechanical stirring rate is 200~2000 r / min, specifically 1000 r / min in this embodiment, and the time is 0.5~6 h, specifically 1 h in this embodiment. The dialyzation is carried out in N,N-dimethylacetamide (DMAc) solution. The dialyzation time is 5~48 h, specifically 24 h in this embodiment.

[0033] After obtaining the polymer solution, the present invention reacts the polymer solution with a deprotonated solvent through a continuous flow microchannel reaction, direct drop precipitation, or spray drying to form droplets, which are then collected in a precipitation system and subsequently frozen and freeze-dried to obtain hollow aramid resin microspheres.

[0034] In one embodiment, the deprotonating solvent is one or more of isopropanol, anhydrous ethanol, methanol, tert-butanol, and anhydrous acetonitrile, with isopropanol being used in a specific embodiment; the precipitation system is a mixed precipitation system of water and ethanol; the volume fraction of ethanol in the mixed precipitation system of water and ethanol is 10-75%, with 50% being used in a specific embodiment.

[0035] In one embodiment, the process of droplet formation in the continuous flow microchannel reaction is as follows: a polymer solution is transferred into a syringe, a deprotonated solvent is placed in another syringe, and a glass microchannel reactor is connected. The reactor outlet is placed in a mechanically stirred precipitation system, and the two phases merge inside the channel to continuously generate droplets. The inner diameter of the glass microchannel reactor is 0.2 mm. The flow rates of the two phases are independently between 0.01 and 1 mL / min. In a specific embodiment, the flow rates of the two phases are 0.5 mL / min for the polymer solution and 2.0 mL / min for the deprotonated solvent.

[0036] In one embodiment, the process of forming droplets by the direct droplet precipitation method is as follows: the polymer solution is placed in a constant pressure dropping funnel or a high-pressure injection pump, and droplets are formed through a needle at room temperature and directly added drop by drop into a mechanically stirred precipitation system; the speed of the needle is 0.1~10mL / min, specifically 1mL / min in this embodiment; the diameter of the needle is 0.1~2.0mm, specifically 0.5mm in this embodiment; the mechanical stirring speed is 200~2000r / min, specifically 1000r / min in this embodiment.

[0037] In one embodiment, before freezing, the process further includes: washing; the washing reagent is deionized water; the freezing temperature is -50~-10℃, specifically -20℃ in this embodiment, and the time is 6~48h, specifically 24h in this embodiment; the freeze-drying temperature is -60~-30℃, specifically -45℃ in this embodiment, and the time is 12~72h, specifically 36h in this embodiment.

[0038] After obtaining the hollow aramid resin microspheres, the present invention mixes the hollow aramid resin microspheres with a precursor liquid containing noble metal salts, loads them, and dries them. The resulting solid material is then sintered in an oxygen-containing atmosphere and reduced in a hydrogen atmosphere to obtain the aramid resin microsphere supported catalyst.

[0039] In one embodiment, the noble metal salt includes ruthenium nitrate or palladium nitrate, specifically ruthenium nitrate; the precursor solution containing the noble metal salt is an aqueous solution; the concentration of noble metal ions in the precursor solution is 0.1~50 mg / mL, specifically 6.0~10 mg / mL (ruthenium) or 12.25 mg / mL (palladium); the loading is performed by a saturated impregnation method; the saturated impregnation method involves isothermal shaking at room temperature to allow the noble metal ions to be fully complexed by the amide groups in the resin; the room temperature is 25°C; the isothermal shaking rate is 50~300 r / min, specifically 150 r / min, and the time is 2~48 h, specifically 24 h.

[0040] In one embodiment, the drying is rotary drying; the temperature of the rotary drying is 40~80℃, specifically 60℃ in this embodiment, and the time is 0.5~4h, specifically 1h in this embodiment.

[0041] In one embodiment, the oxygen-containing atmosphere is an air atmosphere; the sintering temperature is below 530°C, specifically 300°C in this embodiment, and the holding time is 1~12h, or 4~10h in another embodiment, specifically 5h in this embodiment. Sintering converts noble metal ions into oxides. The sintering temperature is below the thermal decomposition temperature of aramid resin, 530°C, so that noble metal ions are converted into oxides while retaining the aramid resin skeleton.

[0042] In one implementation, the reduction treatment temperature is 200~500℃, specifically 400℃ in this embodiment, and the holding time is 1~10h. In another implementation, it is 2~6h, specifically 5h in this embodiment.

[0043] This invention provides the application of the aramid resin ball supported catalyst described in the above technical solution or the aramid resin ball supported catalyst prepared by the preparation method described in the above technical solution in catalytic hydrogenation reaction.

[0044] In one embodiment, the catalytic hydrogenation reaction includes one or more of the following: reduction of nitro compounds to amine compounds, reduction of carbon-carbon double bonds to single bonds, and deep reduction of benzene rings to cyclohexyl structures; the reduction of nitro compounds is the nitro reduction during the preparation of aramid monomers; the deep reduction of benzene rings is the hydrogenation of phenolic compounds to cyclohexanol, or the hydrogenation of benzene to cyclohexane.

[0045] The present invention also provides a method for catalytic hydrogenation reaction, comprising the following steps: The reaction substrate, catalyst, and hydrogen are subjected to a catalytic hydrogenation reaction in a solvent to obtain the product; The catalyst is the aramid resin ball supported catalyst described in the above technical solution or the aramid resin ball supported catalyst prepared by the preparation method described in the above technical solution.

[0046] In one embodiment, the reaction substrate is 2-(4-nitrophenyl)-5-nitrobenzimidazole, styrene, or phenol; the solvent is water or an organic solvent; the organic solvent is methanol or ethanol; the molar ratio of the reaction substrate to the catalyst is 10~1000:1 (based on the active metal in the catalyst, i.e., based on the noble metal in the aramid resin ball supported catalyst), and in a specific embodiment it is 100:1; the concentration of the reaction substrate in the solvent is 0.01~1.0 mol / L, and in a specific embodiment it is 0.1 mol / L.

[0047] In one embodiment, the temperature of the catalytic hydrogenation reaction is 20~150℃, specifically 40℃, 60℃ or 100℃ in the embodiment, the hydrogen pressure is 0.1~5MPa, specifically 0.5MPa, 1.0MPa or 3.0MPa in the embodiment, and the time is 0.5~12h, specifically 1h, 2h or 3h in the embodiment.

[0048] In one embodiment, when the reaction substrate is 2-(4-nitrophenyl)-5-nitrobenzimidazole, the product obtained is a heterocyclic aramid diamine monomer M3, and the catalytic hydrogenation reaction is carried out at a temperature of 60°C, a hydrogen pressure of 1.0 MPa, and a time of 2 h.

[0049] As one implementation method, after the catalytic hydrogenation reaction, the aramid resin ball-supported catalyst is recovered and recycled; the number of recycling times is >10 times, and in a specific embodiment, it is 15 times.

[0050] As one implementation method, before recycling, the process further includes: activating the recycled aramid resin ball-supported catalyst; the activation process is as follows: after washing the recycled aramid resin ball-supported catalyst, it is vacuum dried, and then in-situ reduction activation is performed in hydrogen; the washing is performed by continuously rinsing three times with anhydrous methanol and / or acetone; the vacuum drying temperature is 60°C and the time is 2 hours; the device used for the in-situ reduction activation is a hydrogenation reactor; the in-situ reduction activation temperature is 250°C and the time is 2 hours; the hydrogen is performed by introducing high-purity hydrogen at atmospheric pressure or 0.5 MPa. This invention removes residual adsorbed substrates and products from the recycled aramid resin ball-supported catalyst through washing, and the in-situ reduction activation in hydrogen restores some of the metal species oxidized on the micro-surface to an active metallic state.

[0051] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0052] Example 1-A This embodiment provides a continuous flow preparation method for aramid resin microspheres, the steps of which are as follows: Preparation of polymer precursor solution by low-temperature polymerization: At 0℃, 100 mL of DMAc was added to a 250 mL jacketed beaker, and mechanically stirred at 500 r / min for 30 min under nitrogen protection. Subsequently, 1.08 g of p-phenylenediamine (0.01 mol) and 2.12 g of LiCl (0.05 mol) were added, dissolved, and then 2.03 g of terephthaloyl chloride (TPC) (0.01 mol) was added. The mixture was mechanically stirred at 1000 r / min for 1 h to obtain a viscous liquid. The reaction solution was dialyzed in a large amount of DMAc solution for 24 h to obtain the polymer solution. Continuous flow preparation of microspheres: The polymer solution was transferred to a 10 mL syringe, and isopropanol (the deprotonating solvent) was placed in another 10 mL syringe. A glass microchannel reactor with an inner diameter of 0.2 mm was connected, and the reactor outlet was placed in a mechanically stirred 50% water / ethanol mixture. The flow rates of the two phases were controlled at 0.5 mL / min for the polymer solution and 2.0 mL / min for the deprotonating solvent isopropanol, allowing droplets to continuously form inside the channel. The precipitate was collected and frozen at -20°C for 24 h, followed by freeze-drying at -45°C for 36 h, yielding a particle size distribution of 0.5 mm and a specific surface area of ​​250 m². 2 / g hollow aramid resin balls.

[0053] Scanning electron microscopy cross-sectional analysis showed that the resin particles had a good porous structure. Figure 1 ).

[0054] Example 1-B This embodiment provides a dropwise precipitation method for preparing aramid resin microspheres, the steps of which are as follows: The polymer solution obtained in Example 1-A was placed in a high-pressure injection pump and, at room temperature, dripped directly into a 50% water / isopropanol mixed precipitation and coagulation bath under mechanical stirring at 1000 rpm through a 0.5 mm diameter needle. The generated resin microspheres were collected, washed with deionized water, and then frozen at -20°C for 24 h, followed by freeze-drying at -45°C for 36 h, to obtain hollow aramid resin spheres with regular morphology.

[0055] Example 2 This embodiment provides a method for preparing a 5wt% Ru / aramid catalyst, the steps of which are as follows: After drying the blank hollow aramid resin balls prepared in Example 1-A, weigh 9.5g and place them in a 50mL beaker. Add a ruthenium nitrate aqueous solution with a concentration of 10mg / mL (0.5g calculated as Ru element). Using the saturated impregnation method, place the beaker in a shaker and shake it at a constant temperature of 150r / min and 25℃ for 24h to allow the amide groups to fully complex Ru ions.

[0056] After complexing with Ru ions, the infrared spectrum of the aramid resin shows that the C=O stretching vibration (amide I band) on its amide bond shifts to a lower wavenumber (red shift), while its CN stretching vibration (amide II band) shifts to a higher wavenumber (blue shift). Figure 2 ).

[0057] Subsequently, it was dried by rotary evaporation at 60°C for 1 hour, and then sintered in a muffle furnace at 300°C for 5 hours in air atmosphere to convert Ru ions into RuO2. It was then transferred to a tube furnace and sintered and reduced at 400°C for 5 hours under hydrogen atmosphere to finally obtain an aramid resin ball supported catalyst - 5wt% Ru / aramid.

[0058] Thermogravimetric analysis showed that the aramid resin support did not undergo structural decomposition at 300℃, and the prepared 5wt% Ru / aramid catalyst also exhibited good thermal stability. Figure 3 ).

[0059] Scanning electron microscopy analysis showed that uniformly sized Ru nanoparticles were uniformly dispersed on the surface of the aramid resin carrier. Figure 4 ).

[0060] Example 3 This embodiment provides a method for preparing a 5wt% Pd / aramid catalyst, the steps of which are as follows: Using the same steps as in Example 2, except that ruthenium nitrate was replaced with an equal molar amount of palladium nitrate solution, and subjected to the same impregnation, air sintering at 300°C and hydrogen reduction at 400°C, a 5% Pd / aramid catalyst was prepared.

[0061] Example 4 This embodiment provides an application of a 5wt% Ru / aramid catalyst in the reduction of nitro compounds, and the steps are as follows: The precursor of the key heterocyclic aramid monomer M3 (2-(4-nitrophenyl)-5-nitrobenzimidazole) was used as the substrate. The substrate, methanol solvent, and 5 wt% Ru / aramid catalyst prepared in Example 2 were added to a reactor. The molar ratio of substrate to catalyst was 100:1 (based on active metal Ru), and the molar ratio of substrate to methanol solvent was 0.1 mol / L. The reaction was carried out under extremely mild conditions of only 60 °C and 1.0 MPa hydrogen pressure for 2 h to obtain the heterocyclic aramid diamine monomer M3.

[0062] Results: Nitro compound conversion >99.9%, target product (M3 monomer) selectivity >99%. Compared with traditional Pd / C catalysts that require higher temperatures and pressures, the catalyst of this invention significantly reduces energy consumption and exhibits excellent nitro reduction activity.

[0063] Example 5 This embodiment provides an application of a 5wt% Pd / aramid catalyst in the reduction of carbon-carbon double bonds, and the steps are as follows: Using styrene as a substrate, the hydrogenation reduction ability of the catalyst for carbon-carbon double bonds (C=C) was tested. Styrene, ethanol solvent, and the 5% Pd / aramid catalyst prepared in Example 3 were added to a reactor. The molar ratio of styrene to catalyst was 100:1 (based on the active metal Pd), and the molar ratio of styrene to ethanol solvent was 0.1 mol / L. The reaction was carried out at 40 °C and 0.5 MPa hydrogen pressure for 1 h to obtain ethylbenzene.

[0064] Results: The C=C double bond of styrene was completely reduced with a conversion rate of 100%, and the selectivity of the product ethylbenzene was 100%. No side reactions of excessive reduction of the benzene ring occurred, demonstrating excellent double bond hydrogenation activity and specificity and selectivity.

[0065] Example 6 This embodiment provides an application of a 5wt% Ru / aramid catalyst in the deep reduction of benzene rings, and the steps are as follows: Due to its aromatic conjugated structure, the benzene ring has an extremely high hydrogenation barrier, and traditional catalysts typically require extremely harsh conditions. This example uses phenol as a substrate to test the benzene ring reduction capability of a catalyst. Phenol, an aqueous solvent, and the 5 wt% Ru / aramid catalyst prepared in Example 2 were added to a reactor. The molar ratio of phenol to catalyst was 100:1 (based on the active metal Ru), and the molar ratio of phenol to aqueous solvent was 0.1 mol / L. The reaction was carried out at 100°C and 3.0 MPa hydrogen pressure for 3 h to obtain cyclohexanol.

[0066] Test results show that the conversion rate of phenol to cyclohexanol reaches 98.5%, with a selectivity >99%. This result demonstrates that due to the anchoring effect of the amide groups on Ru nanoparticles in the aramid resin substrate, the catalyst exposes a large number of highly efficient active sites, enabling the originally extremely difficult deep hydrogenation reaction of aromatic rings to be completed efficiently under relatively mild temperature and pressure conditions.

[0067] Comparative Example 1 This comparative example provides the preparation of a 5wt% Ru / Al2O3 catalyst supported on a conventional commercial alumina support, and the steps are as follows: To highlight the structural advantages of the aramid resin ball carrier of this invention, this comparative example is provided. 9.5 g of a commercially available γ-Al₂O₃ carrier (microspheres with a particle size similar to that of Example 1) was used, and impregnated with a ruthenium nitrate solution containing 0.5 g of Ru using the same saturated impregnation method as in Example 2. Subsequently, it was sintered at 300°C in air for 5 h, and then reduced at 400°C under hydrogen conditions for 5 h to obtain a conventional 5 wt% Ru / Al₂O₃ catalyst.

[0068] Due to the lack of complexing and anchoring effects of amide groups, Ru metal exhibited significant agglomeration on the surface of conventional alumina.

[0069] Comparative Example 2 This comparative example provides a method for preparing a 5wt% Ru catalyst based on conventional polystyrene resin (sacrificial template), and the steps are as follows: Conventional polystyrene microspheres (0.5 mm in diameter) were weighed to replace the aramid resin spheres, and ruthenium nitrate solution was added using the same impregnation method as in Example 2. During sintering in air at 300°C, the polystyrene skeleton underwent severe carbonization and partial decomposition; subsequently, it was reduced with hydrogen at 400°C. Due to the inability of conventional resins to maintain their skeleton at high temperatures and the lack of strong complexation by amide groups, metallic Ru exhibited severe agglomeration.

[0070] Comparative Example 3 This comparative example provides a method for preparing an aramid resin-supported 5wt% Ru catalyst exceeding the safe calcination temperature, with the following steps: The same aramid resin microspheres as in Example 2 were used for impregnation. However, in the high-temperature sintering and reduction steps, the temperature was increased to 600°C (higher than the thermal decomposition temperature of aramid, 530°C). The high temperature caused the aramid polymer backbone to completely break and the skeleton to collapse, the amide groups to decompose and disappear, and the confining anchoring effect on Ru was lost, resulting in a severely agglomerated deactivated catalyst.

[0071] Example 7 This embodiment provides catalyst performance evaluation and comparative data analysis. To verify the superior performance of the catalysts of the present invention (5wt% Ru / aramid in Example 2 and 5wt% Pd / aramid in Example 3) compared with conventional catalysts (Comparative Examples 1-3) in catalytic hydrogenation, they were applied to nitro reduction, double bond reduction, and benzene ring reduction reactions, respectively. All reactions were carried out in high-pressure reactors of the same specifications, and the specific comparative data are shown in Table 1: Table 1 Performance of different catalysts

[0072] Example 8 This embodiment provides a catalyst cycle stability test, the steps of which are as follows: The 5wt% Ru / aramid catalyst of Example 2 and the conventional catalyst of Comparative Example 1 were used in batches in a nitro reduction system. The results showed that the aramid resin-based catalyst of the present invention maintained a conversion rate of over 99% for the M3 monomer after 15 consecutive cycles, with no significant metal leaching; while the conventional catalyst of Comparative Example 1 showed a conversion rate of less than 60% after the fourth cycle.

[0073] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. An aramid resin ball-supported catalyst, characterized in that, It includes hollow aramid resin spheres and noble metal nanoparticles loaded on the surface and internal pores of the hollow aramid resin spheres.

2. The aramid resin ball-supported catalyst according to claim 1, characterized in that, The noble metal nanoparticles are ruthenium nanoparticles or palladium nanoparticles; the mass of the noble metal nanoparticles accounts for 1 to 10 wt% of the total mass of the aramid resin ball supported catalyst.

3. The aramid resin ball-supported catalyst according to claim 1, characterized in that, The hollow aramid resin spheres have a particle size distribution of 0.4~0.8mm and a specific surface area of ​​50~600m². 2 / g.

4. The method for preparing the aramid resin ball-supported catalyst according to any one of claims 1 to 3, characterized in that, Includes the following steps: An aromatic diamine monomer, a lithium metal salt, and a p-aromatic diacyl chloride are subjected to an in-situ polycondensation reaction in a polar aprotic solvent to obtain a polymer solution. The polymer solution and deprotonated solvent are reacted with a continuous flow microchannel, or droplet precipitation or spray drying is used to form droplets, which are then collected in a precipitation system and subsequently frozen and freeze-dried to obtain hollow aramid resin microspheres. The hollow aramid resin microspheres were mixed with a precursor solution containing noble metal salts, loaded and dried, and the resulting solid material was sintered in an oxygen-containing atmosphere and reduced in a hydrogen atmosphere to obtain the aramid resin microsphere supported catalyst.

5. The preparation method according to claim 4, characterized in that, The aromatic diamine monomer is one or more selected from p-phenylenediamine, m-phenylenediamine, 2-(4-aminophenyl)-5-aminobenzimidazole, 4,4'-diaminodiphenyl ether, 2-chloro-1,4-phenylenediamine, and 2,5-dichloro-1,4-phenylenediamine; the aromatic diacyl chloride is one or more selected from terephthaloyl chloride, isophthaloyl chloride, and 4,4'-biphenyldicarboxylate chloride; and the lithium metal salt is lithium chloride and / or lithium bromide.

6. The preparation method according to claim 4, characterized in that, The sintering temperature is below 530℃, and the holding time is 1~12h.

7. The preparation method according to claim 4, characterized in that, The reduction treatment is carried out at a temperature of 200~500℃ for 1~10h.

8. The application of the aramid resin ball supported catalyst according to any one of claims 1 to 3 or the aramid resin ball supported catalyst prepared by the preparation method according to any one of claims 4 to 7 in catalytic hydrogenation reaction.

9. The application according to claim 8, characterized in that, The catalytic hydrogenation reaction includes one or more of the following: reduction of nitro compounds to amine compounds, reduction of carbon-carbon double bonds to single bonds, and deep reduction of benzene rings to cyclohexyl structures.

10. A method for catalytic hydrogenation reaction, characterized in that, Includes the following steps: The reaction substrate, catalyst, and hydrogen are subjected to a catalytic hydrogenation reaction in a solvent to obtain the product; The catalyst is the aramid resin ball supported catalyst according to any one of claims 1 to 3 or the aramid resin ball supported catalyst prepared by the preparation method according to any one of claims 4 to 7.

Images