Preparation method of high-strength catalyst carrier

Abstract

The invention belongs to the technical field of catalyst carriers, and particularly relates to a preparation method of a high-strength catalyst carrier, which comprises the following steps: S1, preparing a precursor; the preparation method comprises the following steps: dissolving ferric nitrate-zirconium nitrate composite salt, 2, 5-dihydroxy terephthalic acid and a monatomic Fe source in N-methyl pyrrolidone according to the ratio of the total molar weight of metal ions to the volume of N-methyl pyrrolidone of 1mmol: 5.6 mL, and reacting at 150 DEG C to form monatomic Fe-doped Fe-Zr-MOFs seed crystal; adding a reaction monomer and a protonic acid catalyst into the system, and heating to 170 DEG C for reaction; centrifuging after cooling, and carrying out gradient elution treatment and vacuum drying to obtain a precursor; s2, putting the precursor obtained in the step S1 into a mixed atmosphere tube furnace, introducing 12 vol% H2 / N, raising the temperature to 550 DEG C at 7 DEG C / min, and keeping the temperature for 3 hours; then introducing 9vol% SiH / Ar, raising the temperature to 1000 DEG C at the speed of 10 DEG C / min, and keeping the temperature for 6 hours; and cooling to obtain the low-magnetization carbon heterogeneous matrix.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalyst carrier, and particularly relates to a preparation method of a high-strength catalyst carrier. BACKGROUND

[0002] As the "skeleton" of catalytic reaction, the mechanical strength, thermal stability and pore structure of the catalyst carrier directly determine the service life and catalytic performance of the catalyst.

[0003] The catalyst carriers commonly used in the prior art mainly include gamma-Al2O3, SiO2, activated carbon and the like, but the existing catalyst carriers have some technical defects: for example, gamma-Al2O3 is prone to phase transition into alpha-Al2O3 when calcined at 600 DEG C or above, which causes the specific surface area to decrease from 200 m2 / g to below 50 m2 / g, and the mechanical strength is only 5-8 MPa, and the supported metal catalyst is prone to pulverization during the reaction process; The activated carbon carrier has a high specific surface area (up to 800-1000 m2 / g), but is prone to ablation at a temperature above 400 DEG C, and the interaction between the surface and the metal active sites is weak, which easily leads to the agglomeration of metal particles, and further causes the loss of catalytic activity; The traditional carbon carrier is prone to metal shedding after loading the metal catalyst due to the small number of surface functional groups, and cannot meet the use requirements of long-period catalytic reaction, therefore, developing a catalyst carrier with high strength, high-temperature stability and high loading capacity has become the key to breaking through the bottleneck of the existing technology. SUMMARY

[0004] In view of the above problems in the prior art, the application provides a preparation method of a high-strength catalyst carrier to solve the problems in the background art.

[0005] In order to solve the above technical problems, the application adopts the following technical scheme: A preparation method of a high-strength catalyst carrier, comprising the following steps: S1. Preparation of a precursor: a ferric-zirconium composite salt (Fe3+: Zr 4⁺molar ratio 1:4), 2,5-dihydroxyterephthalic acid, monatomic Fe source (dilute solution of Fe(NO3)3·9H2O, Fe monatomic loading 0.1-0.3 wt%), according to "total molar amount of metal ions: volume of N-methylpyrrolidone = 1 mmol: 5.6 mL", dissolved in N-methylpyrrolidone, pre-reacted at 150°C for 7 h to form monatomic Fe-doped Fe-Zr-MOFs seed crystals; 4,4'-diamino-diphenyl ether, 2,5-dihydroxyterephthalaldehyde, p-toluenesulfonic acid were added to the system, and the temperature was raised to 170°C for 30 h; after cooling, centrifugation was performed, and gradient elution was performed with N-methylpyrrolidone-acetone-deionized water, the amount of N-methylpyrrolidone, acetone, and deionized water was 3-5 times the volume of the precursor wet powder, the centrifugal speed was 8000-10000 rpm, and the centrifugal time was 5-8 min; after elution, the pH value of the supernatant after deionized water washing needed to be detected, until the pH value was stable in the neutral range of 6.5-7.5, to ensure that the water-soluble impurities were completely removed; vacuum drying at 90°C and 0.09 MPa for 18 h to obtain a single precursor; S2. Carbonization-doping treatment: the precursor obtained in step S1 was placed in a mixed gas atmosphere tube furnace, first passed through 12 vol% H2 / N2 (180 mL / min), and heated at 7°C / min to 550°C for 3 h; then passed through 9 vol% SiH4 / Ar, heated at 10°C / min to 1000°C for 6 h; cooled to obtain a Si-N-O co-doped, monatomic Fe-anchored low-magnetization carbon heterogeneous matrix; S3. ALD-MLD hybrid coating: the matrix obtained in step S2 was placed in a multifunctional deposition chamber (2×10⁻³ Torr), and three layers of cycles were sequentially performed: Bottom ALD: tetraisopropoxy titanium / O2-CO2 plasma (4:1), 300°C, 6 layers of TiO2 (12 nm) were deposited, 35 s / layer; Middle MLD: 1,6-hexanediol / 4,4'-diphenyl methane diisocyanate, 140°C, 3 layers of polyimide (8 nm) were deposited, 50 s / layer; Top intelligent response MLD: N-isopropyl acrylamide (NIPAM) / diisocyanate, 110°C, 2 layers of temperature-sensitive poly-N-isopropyl acrylamide (PNIPAM) (8 nm) were deposited, 45 s / layer; Forming a "TiO2-polyimide-PNIPAM" intelligent response hybrid coating (total thickness 28 nm), obtaining a coated carbon heterogeneous matrix; S4. Magnetization control: The substrate obtained in step (3) is placed in an atmospheric pressure plasma jet (APPJ) reaction device, and a N2 / B2H6 / SiH4 mixed gas (12:2:1.2, atmospheric pressure) is introduced. The APPJ power is 220W, the jet distance is 5mm, and the processing time is 50min. The substrate is cooled in Ar atmosphere at 5℃ / min to obtain a single-atom doped smart responsive low magnetization catalyst support.

[0006] Furthermore, in step S1, the single-atom Fe source is an N-methylpyrrolidone solution of 0.005 mol / L Fe(NO3)3·9H2O, and the amount added is 5-8% of the reaction system volume, to ensure that Fe is anchored to the N / O sites of the MOFs framework in single-atom form.

[0007] Furthermore, in step S3, the low critical dissolution temperature of the temperature-sensitive PNIPAM is 32-35℃. At the catalytic reaction temperature of 40-60℃, the hydrophobic pores are open, and after the reaction, when the temperature is lowered to below 25℃, the hydrophilic pores are closed.

[0008] Furthermore, in step S4, the discharge frequency of the APPJ device is 13.56MHz, the working gas flow rate (N2 / B2H6 / SiH4) is 200 / 30 / 15mL / min, and the plasma torch temperature is controlled at 80-120℃ to avoid the aggregation of single-atom Fe.

[0009] Furthermore, in step S1, the particle size of the single-atom Fe-doped Fe-Zr-MOFs seed crystal is 100-150 nm, and the coordination environment of the single-atom Fe is Fe-N4 / O2 (characterized by X-ray photoelectron spectroscopy (XPS)).

[0010] Furthermore, in step S3, the water contact angle of the smart response hybrid coating is 90-100° above 35°C (hydrophobic, open pores) and 30-40° below 25°C (hydrophilic, closed pores).

[0011] Furthermore, the obtained support has a compressive strength ≥23MPa, a specific surface area ≥1650m² / g, a calcination retention rate ≥94% at 950℃, and low magnetization parameters: saturation magnetization 4.2-4.5emu / g (fluctuation ±0.2emu / g), magnetic separation efficiency at 0.3T ≥90%, and agglomeration rate ≤7% at 24h. The single-atom Fe content of the obtained support is 0.08-0.25wt%, and the doping amounts of B, Si, and N are 1.6-1.9at%, 1.3-1.6at%, and 4.2-4.6at, respectively.

[0012] Further, the reaction monomers include aromatic amine monomers and aldehyde monomers, with a molar ratio of aromatic amine monomers to aldehyde monomers of 1:1.1-1.3; the aromatic amine monomer is 4,4'-diaminodiphenyl ether, and the aldehyde monomer is 2,5-dihydroxyterephthalaldehyde; the amount of protic acid catalyst added is 8%-18% of the total mass of the reaction system, and the protic acid catalyst is p-toluenesulfonic acid; wherein the total mass of the reaction system is calculated as the sum of the masses of all raw materials (metal salt, ligand, single-atom Fe source, solvent, reaction monomer, and catalyst).

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. Using Fe-Zr-MOFs as the crystal nucleus, its metal-organic coordination framework has high rigidity. The seed crystal size is controlled at 100-150nm to avoid agglomeration and pulverization caused by excessively small particle size. COFs shells are grown on the surface of MOFs crystal nuclei. The conjugated flexible chains of COFs can alleviate the thermal stress of the rigid MOFs framework during carbonization and coating processes, and prevent the framework from cracking. The hydroxyl groups (-OH) of OFs form coordination bonds with metal ions on the surface of MOFs, which enhances the interfacial bonding force of heterostructures. 2. By introducing a SiH4 / Ar mixed gas, Si atoms form Si-C covalent bonds with the carbon matrix, which inhibits the crystallization and agglomeration of the carbon skeleton at high temperatures, ensuring that the specific surface area retention rate is ≥94% after calcination at 950℃. First, the carbon is kept at 550℃ for 3 hours with 12 vol% H2 / N2 to remove organic impurities and oligomers from the precursor, avoiding the formation of "structural defect points" by residual impurities after carbonization, and ensuring that the carbon skeleton is dense and uniform. Attached Figure Description

[0014] Figure 1 This is a schematic flowchart of a method for preparing a high-strength catalyst support according to the present invention. Detailed Implementation

[0015] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0016] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual images. They should not be construed as limiting the scope of this application. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0017] Traditional carbon supports, due to their limited number of surface functional groups, are prone to metal detachment after loading metal catalysts, failing to meet the requirements of long-cycle catalytic reactions. Therefore, developing a catalyst support that combines high strength, high-temperature stability, and high loading capacity has become crucial to overcoming existing technological bottlenecks. This invention provides a method for preparing a high-strength catalyst support, specifically including... S1. Precursor preparation: Iron nitrate-zirconium nitrate composite salt, 2,5-dihydroxyterephthalic acid, and a single-atom Fe source were dissolved in N-methylpyrrolidone at 150℃ according to the ratio of "total molar amount of metal ions: volume of N-methylpyrrolidone = 1 mmol: 5.6 mL" to form single-atom Fe-doped Fe-Zr-MOFs seed crystals. The reactant monomer and protic acid catalyst were added to the system, and the temperature was raised to 170℃ for reaction. After cooling, the mixture was centrifuged, subjected to gradient elution, and vacuum dried to obtain a single-atom Fe-doped Fe-Zr-MOFs-4,4'-diaminodiphenyl ether-based COFs heterostructure powder (precursor). In this invention, Fe-Zr-MOFs are used as the crystal nucleus, and their metal-organic coordination framework (Fe³⁺ / Zr) 4 The high rigidity of the ⁺ (coordinated with 2,5-dihydroxyterephthalic acid) crystals, with the seed crystal size controlled at 100-150 nm, avoids agglomeration and pulverization caused by excessively small particle size. The COF shell (condensation of 4,4'-diaminodiphenyl ether and 2,5-dihydroxyterephthalaldehyde) is grown on the surface of the MOF crystal nucleus. The conjugated flexible chain of COFs can alleviate the thermal stress of the rigid MOF skeleton during carbonization and coating (such as the difference in expansion and contraction during carbonization heating), and prevent the skeleton from cracking. The hydroxyl groups (-OH) of OFs form coordination bonds with the metal ions on the surface of MOFs, which improves the interfacial bonding force of the heterostructure and avoids the decrease in strength caused by delamination.

[0018] S2. Carbonization-doping treatment; The powder obtained in step S1 is placed in a mixed atmosphere tube furnace. First, 12 vol% H2 / N2 is introduced, where "12 vol% H2 / N2" is a mixed gas composed of hydrogen and nitrogen, with hydrogen accounting for 12% by volume and nitrogen accounting for 88% by volume (vol% is the standard abbreviation for volume percentage, used to express the volume percentage of each component in the mixed gas); The temperature is increased to 550℃ at 7℃ / min and held for 3h; then 9 vol% SiH4 / Ar is introduced, which refers to a mixed gas composed of silane (SiH4) and argon (Ar), with silane accounting for 9% by volume and argon accounting for 91% by volume. The temperature is increased to 1000℃ at 10℃ / min and held for 6h; after cooling, a low-magnetization carbon heterostructure with Si-NO co-doped and single-atom Fe anchored is obtained; In this invention, a SiH4 / Ar mixed gas is introduced (held at 1000℃ for 6 hours), causing Si atoms to form Si-C covalent bonds with the carbon matrix (Si doping amount 1.3-1.6 at%). This inhibits the crystallization and agglomeration of the carbon skeleton at high temperatures, resulting in a specific surface area retention rate of ≥94% after calcination at 950℃ (compared to only 75% for the undoped carrier). First, 12 vol% H2 / N2 is used to hold the mixture at 550℃ for 3 hours to remove organic impurities and oligomers from the precursor, preventing residual impurities from forming "structural defect points" (such as micropore collapse and cracks) after carbonization, thus ensuring a dense and uniform carbon skeleton. The Fe-N4 / O2 single-atom structure can serve as "cross-linking nodes" for the carbon skeleton, enhancing the internal forces within the carbon matrix and preventing deformation of the skeleton under pressure. Low-magnetization carbon heterostructure refers to a precursor of MOFs-COFs heterostructure with single-atom Fe doping, a saturation magnetization of 4.2-4.5 emu / g (a core characteristic of low magnetization), and a magnetic separation efficiency of 89%-90.5% under a 0.3T magnetic field, which has the basic capability of "low-magnetic recycling".

[0019] S3. ALD-MLD Hybrid Coating: The low-magnetization carbon heterostructure obtained in step S2 is placed in a multifunctional deposition chamber and subjected to three-layer cycling sequentially. After deposition, a hybrid coating is formed, resulting in a coated low-magnetization carbon heterostructure. In this invention, in specific implementation, 6 layers of TiO2 (total thickness 12nm) are deposited at 300℃. The TiO2 hardness reaches 6-7GPa, which can resist particle collision and wear during catalytic packed bed operation, and at the same time act as a "physical barrier" to prevent strong acid / solvent from eroding the support skeleton. 3 layers of polyimide (total thickness 8nm) are deposited at 140℃. Its elastic modulus is about 2-3GPa, which can buffer TiO2 (thermal expansion coefficient 8×10⁻). 6 / ℃) and carbon matrix (thermal expansion coefficient 1×10⁻ 6 The thermal expansion difference (°C) prevents coating cracking during thermal cycling. The total thickness of the three-layer coating is only 28nm, avoiding the "excessive rigidity and increased brittleness" of the carrier caused by excessively thick coatings, thus balancing strength and toughness. The coated low-magnetization carbon heterostructure refers to a material formed by "forming a 'TiO2-polyimide-PNIPAM' three-layer coating on the surface of a low-magnetization carbon heterostructure through ALD-MLD hybrid coating", which still maintains the porosity and low magnetization characteristics (saturation magnetization 4.2-4.3 emu / g) of the low-magnetization carbon heterostructure.

[0020] S4. Magnetization control: The low-magnetization carbon heterostructure obtained in step S3 is placed in an atmospheric pressure plasma jet reactor, and a N2 / B2H6 / SiH4 mixed gas is introduced and cooled in an Ar atmosphere at 5℃ / min to obtain a catalyst support.

[0021] The APPJ treatment temperature is controlled at 80-120℃ (below the single-atom Fe migration temperature of 150℃). The surface of the carrier is "gently etched" by high-energy plasma, which generates nanopores (increasing the specific surface area) while avoiding high temperature damage to the internal framework structure. B (1.6-1.9at%) and N (4.2-4.6at%) atoms are doped into the surface of the carrier (depth 5-10nm) to form dense BC and NC bonds, which improves the surface density and impermeability, reduces the erosion of the framework by solvents / reactants, and indirectly ensures the overall strength. During APPJ treatment, airflow fluctuations are ≤±5mL / min to avoid surface ablation or structural inhomogeneity caused by excessively high local plasma energy, thus ensuring consistent carrier strength.

[0022] During the in-situ growth stage of the MOFs-COFs heterostructure precursor, a dilute N-methylpyrrolidone solution of 0.005 mol / L Fe(NO3)3·9H2O was introduced as a single-atom Fe source. Utilizing the strong coordination of Fe³⁺ with the N / O sites provided by 2,5-dihydroxyterephthalic acid in the MOFs framework, a stable Fe-N4 / O2 single-atom structure was formed. This single-atom Fe possesses dual functions as both a "micromagnetic center" and a "catalytically active site": as a micromagnetic center, it can help regulate the saturation magnetization of the support to 4.2-4.5 emu / g, ensuring low magnetic agglomeration; as an active site, it can synergistically interact with the supported Pd catalyst to improve catalytic selectivity.

[0023] A TiO2-polyimide-PNIPAM hybrid coating was constructed using ALD-MLD three-layer cyclic deposition, with the top PNIPAM layer exhibiting a defined low critical dissolution temperature (LCST 32-35℃). At catalytic reaction temperatures (40-60℃), PNIPAM exists in a hydrophobic contractile state, with open support pores, allowing reactants to efficiently contact active sites, increasing the specific surface area utilization rate to 90%. After the reaction, when the temperature is lowered to below 25℃, PNIPAM transforms into a hydrophilic swollen state, closing the pores and encapsulating the product. During magnetic separation, the product loss rate is reduced from 15% with traditional supports to below 5%, significantly improving product separation efficiency.

[0024] APPJ is an abbreviation for Atmospheric Pressure Plasma Jet. As a low-temperature plasma technology at ambient pressure, it generates a high-energy plasma torch in an open environment, replacing traditional high-vacuum plasma equipment, and is widely used in the industrial preparation of catalyst supports.

[0025] Atmospheric pressure plasma jets are used instead of traditional high-vacuum plasmas, and a N2 / B2H6 / SiH4 mixed gas is introduced under normal pressure to achieve B-Si-N ternary doping. The high-energy plasma torch (temperature 80-120℃) generated by APPJ can precisely act on the surface layer of the support (doping depth 5-10nm), avoiding damage to the deep carbon framework; The basic performance indicators of the obtained single-atom doped smart responsive low magnetization catalyst support are: compressive strength ≥23MPa, specific surface area ≥1650m² / g, specific surface area retention rate ≥94% after calcination in air at 950℃; and specific surface area retention rate ≥88% after soaking in 5wt%H2SO4 solution, 10wt%NaOH solution or DMF solvent for 24h.

[0026] The elemental content of the obtained single-atom doped smart-response low magnetization catalyst support is as follows: single-atom Fe content 0.08-0.25wt%, B doping amount 1.6-1.9at%, Si doping amount 1.3-1.6at%, and N doping amount 4.2-4.6at. The single-atom Fe content was detected by inductively coupled plasma atomic emission spectrometry, and the doping amounts of B, Si, and N elements were detected by X-ray photoelectron spectroscopy.

[0027] After the obtained support was used to support a 2wt% Pd catalyst, in the hydrogenation reaction of nitrobenzene (reaction conditions: 50℃, 0.3MPaH2, ethanol as solvent), the conversion rate of nitrobenzene was ≥99.5% and the selectivity of aniline was ≥99.2%; after 15 cycles, the catalytic activity retention rate was ≥92%; the product separation efficiency was 30% higher than that of the support without PNIPAM smart coating, and the residual amount of support in the solution after magnetic separation was <0.1mg / L.

[0028] Example 1 (1) Preparation of single-atom Fe-doped MOFs-COFs heterostructure precursor: Accurately weigh 0.81 g of ferric nitrate (corresponding to Fe³⁺ 2.5 mmol) and 3.33 g of zirconium nitrate (corresponding to Zr) 4 ⁺10 mmol), along with 2.42 g (12 mmol) of 2,5-dihydroxyterephthalic acid, were added to the reaction vessel. Then, 5 mL of a single-atom Fe source (0.005 mol / L Fe(NO3)3・9H2O N-methylpyrrolidone solution, accounting for 7.1% of the reaction system volume) was added, followed by the addition of N-methylpyrrolidone to a total volume of 70 mL, ensuring a 1 mmol:5.6 mL ratio between the total molar amount of metal ions (12.5 mmol) and the volume of N-methylpyrrolidone (70 mL). The reaction vessel was placed in an oil bath and pre-reacted at 150 °C for 7 h to form single-atom Fe-doped Fe-Zr-MOFs seed crystals (the seed crystal size was approximately 120 nm, as determined by dynamic light scattering). The following reactants and protic acid catalysts for COF framework construction were added to the above system: 1.98 g (10 mmol) of 4,4'-diaminodiphenyl ether and 1.52 g (10 mmol) of 2,5-dihydroxyterephthalaldehyde, in a molar ratio of 1:1 (falling within the range of 1:(1.1-1.3)), and 4 g of p-toluenesulfonic acid (accounting for 12% of the total mass of the reaction system, with a total mass of approximately 33.3 g). The reaction was heated to 170 °C and reacted for 30 h. After the reaction was completed, the mixture was cooled to room temperature, and the solid product was collected by centrifugation at 8000 rpm for 8 min.

[0029] The solid product was subjected to gradient elution: first, it was stirred at room temperature for 18 min with N-methylpyrrolidone (4 times the volume of the wet powder), centrifuged at 8000 rpm for 6 min, and the supernatant was discarded. This operation was repeated 4 times. Then, it was washed 4 times with acetone (the same amount as N-methylpyrrolidone) in the same manner. Finally, it was washed with deionized water until the pH of the supernatant stabilized at around 7.0, for a total of 4 washes. The eluted solid was placed in a vacuum drying oven and dried at 90℃ and 0.09 MPa for 18 h to obtain a single-atom Fe-doped Fe-Zr-MOFs-4,4'-diaminodiphenyl ether-based COFs heterostructure powder (i.e., the precursor for carbonization, characterized by X-ray photoelectron spectroscopy, showing that Fe is in a single-atom state and the coordination environment is Fe-N4 / O2). (2) The obtained carbonization precursor was placed in a quartz boat and placed in a mixed atmosphere tube furnace. First, a 12% volume fraction H2 / N2 mixed gas was introduced into the tube furnace, and the flow rate was controlled at 180 mL / min. The temperature was increased from room temperature to 550℃ at a rate of 7℃ / min. The temperature was held at this temperature for 3 hours to remove organic impurities in the precursor and perform preliminary carbonization. Then, the temperature was switched to a 9% volume fraction SiH4 / Ar mixed gas, and the flow rate was maintained at 180 mL / min. The temperature was increased to 1000℃ at a rate of 10℃ / min. The temperature was held for 6 hours to achieve Si-NO co-doping and single-atom Fe anchoring. After the holding period, the heating device was turned off and the mixture was allowed to cool naturally to room temperature. The low-magnetization carbon heterostructure with Si-NO co-doping and single-atom Fe anchoring was then obtained. (3) Place the low-magnetization carbon heterostructure obtained in step (2) into the multifunctional deposition chamber, close the chamber and evacuate to a basic vacuum level of 2×10⁻³ Torr. First, perform bottom layer ALD cyclic deposition: introduce tetraisopropoxy titanium vapor and O2-CO2 mixed plasma (O2:CO2 volume ratio 4:1), control the deposition temperature at 300℃, the single cycle time at 35s, and deposit a total of 6 layers to form a TiO2 coating with a thickness of 12nm. After the bottom layer deposition is completed, the middle layer MLD cyclic deposition is carried out: 1,6-hexanediol vapor and 4,4'-diphenylmethane diisocyanate vapor are introduced, the deposition temperature is adjusted to 140℃, the single cycle time is 50s, and a total of 3 layers are deposited to form a polyimide coating with a thickness of 8nm. After the middle layer deposition is completed, the top layer smart response MLD cyclic deposition is performed: N-isopropylacrylamide (NIPAM) vapor and diisocyanate vapor are introduced, the deposition temperature is reduced to 110℃, the single cycle time is 45s, and a total of 2 layers are deposited to form a PNIPAM coating with a thickness of 8nm. After the three-layer deposition was completed, a coated low-magnetization carbon heterostructure with a "TiO2-polyimide-PNIPAM" smart response hybrid coating (total thickness 28nm) was obtained. The water contact angle of the substrate was measured by a contact angle meter. The water contact angle of the substrate was 95° at 35℃ (hydrophobic state) and 35° at 25℃ (hydrophilic state), which met the smart response requirements. (4) Place the coated low-magnetization carbon heterostructure obtained in step (3) on the sample stage of the APPJ reaction apparatus, and adjust the distance between the jet nozzle and the sample surface to 5 mm. Introduce a N2 / B2H6 / SiH4 mixed gas into the reaction apparatus, controlling the N2 flow rate to 200 mL / min, the B2H6 flow rate to 30 mL / min, and the SiH4 flow rate to 15 mL / min, ensuring a volume ratio of 12:2:1.2. Turn on the APPJ apparatus, set the discharge frequency to 13.56 MHz and the power to 220 W, monitor the plasma torch temperature in real time using an infrared thermometer, and maintain it at around 100 °C for 50 min. After the treatment, close the APPJ apparatus and the gas valve, and cool it to room temperature at a rate of 5 °C / min in an Ar atmosphere, finally obtaining a single-atom doped smart responsive low-magnetization catalyst support.

[0030] Comparative Example 1 (without single-atom Fe doping): The preparation process was basically the same as in Example 1, except that the single-atom Fe source (0.005 mol / L Fe(NO3)3·9H2O N-methylpyrrolidone solution) was omitted in step (1). The remaining raw material amounts and process parameters were the same as in the example. Due to the lack of synergistic effect of single-atom Fe, the Pd catalyst dispersion of the support prepared in this comparative example was only 85%, and the aniline selectivity in the hydrogenation reaction of nitrobenzene was 96.3%, which was 3 percentage points lower than that in Example 1. At the same time, the fluctuation range of saturation magnetization intensity expanded to ±0.5 emu / g, and the magnetic stability decreased.

[0031] Comparative Example 2 (without PNIPAM smart coating): The preparation process was basically the same as in Example 1, except that the top-layer smart response MLD cyclic deposition was omitted in step (3), and the coating process was directly ended after the middle polyimide coating was deposited. The remaining steps and parameters remained unchanged. Because the carrier prepared in this comparative example did not have a PNIPAM smart coating, the pore structure was fixed, and the product could not be effectively encapsulated after the reaction. The product separation efficiency was only 68%, and the product loss rate reached 14.5%, which was 9.5 percentage points higher than that in Example 1. Moreover, because the total coating thickness was reduced by 8 nm, the corrosion resistance was slightly reduced, and the specific surface area retention rate after immersion in 5wt% H2SO4 was 3% lower than that in the example. Comparative Example 3 (Traditional vacuum plasma replacing APPJ): The preparation process was basically the same as in Example 1, except that in step (4), a conventional vacuum plasma device was used instead of the APPJ device, and the vacuum degree was controlled at 5 Torr. The other gas ratios and processing times were the same as in Example 1. Because this comparative example used a vacuum process, the equipment energy consumption reached 14.2 kWh / kg, which was 40% higher than that of Example 1. Moreover, the gas diffusion uniformity was poor in the vacuum environment, and the uniformity deviation of B, Si, and N element doping reached 12%, resulting in a large difference in magnetization intensity in different regions of the carrier, and the magnetic separation efficiency was 1.5 percentage points lower than that of Example 1.

[0032] Performance Testing and Analysis The Pd dispersion and hydrogenation selectivity of Example 1 were significantly higher than those of Comparative Example 1, demonstrating the "active site enhancement" effect of single-atom Fe; the product separation efficiency of Example 1 was 27.2% higher than that of Comparative Example 2, verifying the "dynamic channel control" value of the intelligent temperature-sensitive coating; the energy consumption of Example 1 was 40% lower than that of Comparative Example 3, highlighting the industrialization advantages of APPJ atmospheric pressure technology.

[0033] The above are merely embodiments of the present invention. The circuits, electronic components, and modules involved are all prior art, fully achievable by those skilled in the art, and require no further explanation. The scope of protection in this application does not involve improvements to the software and methods. Commonly known structures and characteristics in the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all prior art in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the application.

Claims

1. A method for preparing a high strength catalyst support, characterized by: Comprising the following steps: S1. Precursor preparation; Fe-Zr-MOFs seed doped with monatomic Fe was prepared by dissolving iron nitrate-zirconium nitrate composite salt, 2,5-dihydroxyterephthalic acid, monatomic Fe source in N-methyl pyrrolidone at a ratio of "total moles of metal ions:N-methyl pyrrolidone volume = 1 mmol:5.6 mL" and reacting at 150℃; Reaction monomer and protonic acid catalyst were added to the system, and the temperature was raised to 170℃ for reaction; After cooling, centrifugation, gradient elution treatment and vacuum drying, the precursor was obtained; S2. Carbonization-doping treatment; The precursor obtained in step S1 was placed in a mixed gas atmosphere tube furnace, first passed through 12vol% H2 / N2, 7℃ / min to 550℃ for 3h; Then pass 9vol% SiH4 / Ar, 10℃ / min to 1000℃ for 6h; Cooling to get low magnetization carbon heterogeneous matrix; S3. ALD-MLD hybrid coating: The low magnetization carbon heterogeneous matrix obtained in step S2 was placed in a multifunctional deposition chamber, and three layers of cyclic deposition were carried out in turn to form a hybrid coating, and a coated low magnetization carbon heterogeneous matrix was obtained; S4. Magnetization regulation: The coated low magnetization carbon heterogeneous matrix obtained in step S3 was placed in an atmospheric pressure plasma jet reaction device, and N2 / B2H6 / SiH4 mixed gas was introduced, and Ar gas was used as the atmosphere, 5℃ / min cooling, to obtain a catalyst carrier.

2. The method for preparing a high-strength catalyst support as described in claim 1, characterized in that: In step S1, the monatomic Fe source is a 0.005mol / L Fe(NO3)3·9H2O N-methyl pyrrolidone solution, and the addition amount is 5-8% of the volume of the reaction system.

3. The method for preparing a high-strength catalyst support as described in claim 1, characterized in that: In step S3, the three-layer cyclic deposition specifically includes; Bottom layer ALD cycle: using tetraisopropoxy titanium as metal organic source, O2, CO2 mixed plasma as oxidant, O2:CO2 volume ratio is 4:1, depositing 6 layers of TiO2 at 300℃, single layer thickness is about 2nm, total thickness is 12nm, single cycle time is 35s; Middle layer MLD cycle: using 1,6-hexanediol as dihydric alcohol monomer, 4,4'-diphenyl methane diisocyanate as diisocyanate monomer, depositing 3 layers of polyimide at 140℃, single layer thickness is about 2.7nm, total thickness is 8nm, single cycle time is 50s; Top layer MLD cycle: using N-isopropyl acrylamide as temperature-sensitive monomer, diisocyanate as crosslinking agent, depositing 2 layers of temperature-sensitive poly N-isopropyl acrylamide at 110℃, single layer thickness is about 4nm, total thickness is 8nm, single cycle time is 45s.

4. The method for preparing a high-strength catalyst support as described in claim 1, characterized in that: In step S4, the volume ratio of N2, B2H6 and SiH4 in the mixed gas is 12:2:1.2, the flow rate of N2 is 200mL / min, the flow rate of B2H6 is 30mL / min, and the flow rate of SiH4 is 15mL / min, and the plasma torch temperature is controlled at 80-120℃.

5. The method of claim 1, wherein: the high strength catalyst support has a density of at least 2.5 g / cm3. In step S1, the particle size of the monatomic Fe doped Fe-Zr-MOFs seed is 100-150nm.

6. The method for preparing a high-strength catalyst support as described in claim 3, characterized in that: The low critical solution temperature of the temperature-sensitive poly N-isopropyl acrylamide is 32-35℃, which is in a hydrophobic state at a catalytic reaction temperature of 40-60℃, and is in a hydrophilic state after reaction and cooling to below 25℃.

7. The method for preparing a high-strength catalyst support as described in claim 1, characterized in that: In step S1, the reaction monomers include aromatic amine monomers and aldehyde monomers, and the molar ratio of the aromatic amine monomers to the aldehyde monomers is 1:1.1-1.

3.

8. The method for preparing a high-strength catalyst support as described in claim 7, characterized in that: The aromatic amine monomers are 4,4'-diamino diphenyl ether, and the aldehyde monomers are 2,5-dihydroxy terephthaldehyde.

9. The method for preparing a high-strength catalyst support as described in claim 1, characterized in that: In step S1, the added amount of the protonic acid catalyst is 8%-18% of the total mass of the reaction system, and the protonic acid catalyst is p-toluenesulfonic acid.

10. The method for preparing a high-strength catalyst support as described in claim 1, characterized in that: The gradient elution treatment specifically includes washing with N-methyl pyrrolidone first, then washing with acetone, and finally washing with deionized water, and each step of washing is stirring at room temperature for 15-20 min and then centrifugation at 8000-10000 rpm for 5-8 min.

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