A catalyst for online hydrogen production by methanol reforming and a preparation method thereof

Abstract

This invention discloses a catalyst for online methanol reforming to produce hydrogen and its preparation method, belonging to the field of catalytic chemistry and energy materials. The catalyst for online methanol reforming to produce hydrogen is composed of supported core-shell composite particles and has the following components and structural characteristics: the catalytically active core is metallic copper nanoparticles with a particle size controlled at 10-15 nm, prepared by liquid-phase reduction, with copper nitrate as the copper source, and coated with a polyhydroxy organic stabilizer to prevent agglomeration; the metallic copper nanoparticles are coated with a dense silica inorganic shell layer with a thickness of 2-3 nm, formed by a sol-gel method; this invention effectively prevents the migration and sintering of copper particles under high-temperature reaction conditions by coating the metallic copper nanoparticles with a dense silica shell layer.

Description

Technical Field

[0001] This invention relates to the field of catalytic chemistry and energy materials, and more specifically, to a catalyst for online methanol reforming to produce hydrogen and a method for preparing the same. Background Technology

[0002] Methanol steam reforming for hydrogen production has become an important technology for fuel cells and on-board hydrogen supply due to its low-temperature operation, high hydrogen purity, and good carbon efficiency. While traditional Cu / ZnO / Al2O3 catalysts exhibit some activity at lower temperatures, they generally suffer from problems such as easy sintering of copper particles, insufficient thermal stability, severe carbon buildup during the reaction, and high CO content in the byproduct, limiting long-term application and system integration. Furthermore, some improved solutions use zirconium oxide or cerium oxide as protective layers or additives, which, while improving anti-sintering performance and water-gas shift reaction activity to some extent, pose toxicity risks and dust hazards in industrial applications for cerium oxide and its salts. Zirconia, under long-term high-concentration exposure, may also cause respiratory health risks. These safety concerns hinder the sustainability requirements of catalysts in distributed energy, on-board applications, and large-scale deployment. In recent years, research has begun to focus on non-toxic, harmless, and environmentally friendly alternative materials to maintain or improve catalytic performance while reducing environmental and health risks, thereby driving the development of methanol reforming for hydrogen production technology towards a safer and greener direction. Summary of the Invention

[0003] The purpose of this invention is to provide a catalyst and its preparation method for online methanol reforming to produce hydrogen, thereby addressing the problems mentioned in the background: cerium oxide and its salts pose toxicity risks and dust hazards in industrial applications, and zirconium oxide may also cause respiratory health risks under long-term high-concentration exposure. These safety deficiencies hinder the sustainability requirements of catalysts in distributed energy, vehicle applications, and large-scale deployment.

[0004] A catalyst for online methanol reforming to produce hydrogen, the catalyst being composed of supported core-shell composite particles, having the following composition and structural characteristics: The catalytic active core is a copper nanoparticle with a particle size controlled at 10-15 nanometers. It is prepared by liquid-phase reduction and the copper source is copper nitrate. The surface is coated with a polyhydroxy organic stabilizer to prevent agglomeration. The copper nanoparticles are coated with a dense silica inorganic shell with a thickness of 2-3 nanometers, which is formed by the sol-gel method. The silicon source is tetraethoxysilane (TEOS), and the shell has an amorphous dense structure. The dense silica inorganic shell is further coated with an iron oxide auxiliary active layer with a thickness of 0.5–1.5 nm. The iron oxide content accounts for 2–4 wt% of the total mass of the catalyst. The iron oxide shell is formed by co-precipitation-heat treatment. The iron oxide possesses Fe under the reaction conditions. 3+ / Fe 2+ Reversible properties; The polyhydroxy organic stabilizer, the dense silica inorganic shell, and the iron oxide-assisted active layer core-shell nanostructured particles are uniformly distributed at a loading of 0.5–1.5 wt% in a core-shell nanostructure with a particle size of 150–220 μm. 2 The specific surface area and pore size distribution are concentrated in the γ-Al2O3 support between 5 and 10 nanometers. The γ-Al2O3 support is pretreated by dehydroxylation to enhance the interfacial fixation strength.

[0005] When the catalyst is used in the methanol steam reforming reaction, the conditions are 200–300 °C, methanol / water molar ratio of 1:1.2–1:1.5, and space velocity of 3000 h⁻¹. -1 Under these conditions, the CO volume fraction in the reaction outlet gas is less than 0.5%, and the sintering rate of copper particles is less than 5% within 80 hours.

[0006] Preferably, the thickness of the dense silica inorganic shell is controlled at 2.0 ± 0.3 nm. The silica inorganic shell is formed by a sol-gel reaction in isopropanol solvent using tetraethoxysilane (TEOS) as a precursor under acidic conditions (pH 4.5–5.5), followed by calcination at 500 °C in air to obtain a dense and continuous amorphous SiO2 layer. The shell can uniformly cover the entire surface of the copper nanoparticles, avoiding direct contact between particles and inhibiting the migration and sintering of copper nanoparticles under reaction conditions of 200–300 °C.

[0007] Preferably, the thickness of the iron oxide auxiliary active layer is controlled at 1.0 ± 0.2 nm. The iron oxide auxiliary active layer uses ferric nitrate (Fe(NO3)3) as the iron source, which is precipitated in an aqueous solution by ammonia titration to pH 9.0 ± 0.2 to form a Fe(OH)3 precursor. Subsequently, it is calcined in air at 350–450 °C for 1 hour to form an ultrathin iron oxide shell with hematite (α-Fe2O3) as the main crystalline phase. Under a reducing atmosphere, the iron oxide can be partially converted to the Fe3O4 phase, thereby providing reversible Fe during the reaction process. 3+ / Fe 2+ Redox pairs.

[0008] Preferably, the iron oxide-assisted active layer can be pre-reduced under a hydrogen atmosphere before the methanol vapor reforming reaction to form an Fe... 3+ / Fe 2+The composite phase with oxygen reservoir characteristics, the interface structure formed by the iron oxide active layer and the silica shell can promote the activation of H2O molecules and the dissociation of OH bonds, thereby strengthening the water-gas shift (WGS) reaction channel, stably maintaining the CO volume fraction below 0.5% in the reaction gas, and improving the catalyst's resistance to thermal cycling degradation.

[0009] A method for preparing a catalyst for online methanol reforming to produce hydrogen includes the following steps: S1. Dissolve Cu(NO3)2 in deionized water to form a 0.05-0.2 mol / L solution, add 0.5%-1.5% PVA stabilizer by mass, and slowly add 0.15-0.25 mol / L NaBH4 reducing solution dropwise at 0-5℃ for 10-30 minutes; the total stirring time from the start of the dropwise addition to the end of the reduction is 20-50 minutes, to obtain a copper nanoparticle sol with a particle size controlled at 10-15 nm. S2. The copper nanoparticle sol is added to a tetraethoxysilane (TEOS) system with isopropanol as solvent. The pH value is adjusted between 4.5 and 5.5. The precursor of silica shell is formed by temperature-controlled hydrolysis. After drying, it is calcined in air at 500°C for 2 hours to form a dense silica inorganic shell. S3. The particles after forming a dense silica shell are immersed in an aqueous solution of Fe(NO3)3, the pH is adjusted to 9.0±0.2, ammonia is added dropwise to precipitate and form a Fe(OH)3 layer, then dried and calcined in air to generate an iron oxide auxiliary active layer; S4. The three-layer core-shell composite particles containing the copper nanoparticles, the dense silica inorganic shell, and the iron oxide auxiliary active layer are loaded onto a γ-Al2O3 support that has undergone dehydroxylation pretreatment by impregnation. After drying, the temperature is increased to 500°C at 2°C / min under a high-purity argon atmosphere and held at the temperature for 2 hours to obtain a catalyst for online methanol reforming to produce hydrogen.

[0010] Preferably, the 0.15-0.25 mol / L NaBH4 reducing solution in step S1 can be replaced with a 0.1%-0.3% hydrazine hydrate solution or a 0.05-0.15 mol / L ascorbic acid solution, and the reaction temperature is controlled within the range of 0-10°C, and the stirring time is controlled within 20-40 minutes.

[0011] Preferably, in step S2, the solvent in the tetraethoxysilane (TEOS) system is isopropanol, with a volume fraction of not less than 90%, the pH value is adjusted by diluting acetic acid or ammonia, the drying temperature is 80-120°C, and the heating rate during calcination is 1-3°C / min.

[0012] Preferably, in step S3, the concentration of the Fe(NO3)3 aqueous solution is 0.05mol / L to 0.15mol / L, the rate of ammonia addition is controlled at 0.5mL / min to 1.5mL / min, the precipitation temperature is maintained at 25 to 35℃, and the resulting precipitate is dried at 100 to 120℃ and then calcined in air at 400 to 650℃ for 1 to 2 hours.

[0013] Preferably, the specific surface area of ​​the γ-Al₂O₃ support in step S4 is 150–220 m². 2 / g, pore size distribution controlled at 5-10 nm, dehydroxylation pretreatment is performed by heating at 400-600℃ in air atmosphere for 2-3 hours, and the final loading is controlled at 0.5-1.5 wt%.

[0014] Compared with the prior art, the advantages of this invention are: (1) The present invention effectively prevents copper particles from migrating and sintering under high temperature reaction conditions by coating the copper nanoparticles with a dense silica shell.

[0015] (2) The catalyst design ensures that the size of the copper nanoparticles is 10–15 nm, the active sites are fully exposed, and the interface between the iron oxide auxiliary layer and the silica shell maintains the high conversion rate of methanol. At the same time, it can still stably output high H2 production under short time and thermal cycling conditions.

[0016] (3) The synergistic effect of the core-shell composite structure and the γ-Al2O3 support improves the catalyst’s resistance to decay in thermal cycling and water vapor environments. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall process for preparing a catalyst for online methanol reforming to produce hydrogen according to the present invention. Detailed Implementation

[0018] Examples 1-4 Example 1 A method for preparing a catalyst for online methanol reforming to produce hydrogen includes the following steps: S1. Weigh 2.42 g of Cu(NO3)2·3H2O and dissolve it in deionized water to prepare a 0.100 mol / L solution. Add 1.0 wt% polyvinyl alcohol (PVA, molecular weight approximately 30,000) as a stabilizer relative to the mass of copper nitrate, and stir to dissolve in an ice-water bath (0–5℃). Then, slowly add 100 mL of 0.200 mol / L NaBH4 solution, controlling the addition time at 20 minutes. Continue stirring the reaction for another 30 minutes to obtain a sol of metallic copper nanoparticles with a particle size controlled at approximately 12 nm.

[0019] S2. The above-mentioned copper nanoparticle sol was added to 200 mL of isopropanol-TEOS system, wherein the volume fraction of isopropanol was 95% and the amount of TEOS added was 3 mL. The pH was adjusted to 5.0 ± 0.1 with diluted acetic acid, and the reaction was stirred at room temperature for 4 hours to obtain a silica shell precursor. The obtained product was dried in an oven at 100 °C for 12 hours, and then heated to 500 °C in air at a heating rate of 2 °C / min and held at that temperature for 2 hours to form a dense silica inorganic shell with an average thickness of approximately 2.0 nm.

[0020] S3. The above-mentioned silica-coated copper nanoparticles were dispersed in 100 mL of 0.100 mol / L Fe(NO3)3 solution. After stirring evenly, concentrated ammonia (25%) was added dropwise at a rate of 1.0 mL / min until the pH of the solution was adjusted to 9.0 ± 0.1, and the precipitation temperature was maintained at 30 °C. The precipitate was dried at 110 °C for 12 hours, and then heated to 650 °C at 3 °C / min in air and held at that temperature for 1 hour to generate an iron oxide auxiliary active layer with a thickness of about 1.0 nm, the main crystalline phase of which was α-Fe2O3.

[0021] S4. A three-layer core-shell composite particle containing copper nanoparticles, a silica shell, and an iron oxide active layer is dispersed in anhydrous ethanol and loaded onto a γ-Al₂O₃ support that has undergone dehydroxylation pretreatment by impregnation. The γ-Al₂O₃ support has a specific surface area of ​​200 m². 2 The pore size distribution is concentrated at 7.5 nm. The dehydroxylation pretreatment method is heating at 500 °C for 2 hours in air atmosphere. After loading, the product is vacuum dried at 80 °C for 10 hours, and finally heated to 500 °C at 2 °C / min in high-purity argon atmosphere and held at the temperature for 2 hours to obtain the final catalyst. The composite particle loading is controlled at 1.0 wt%.

[0022] Example 2 S1. Weigh 2.42 g of Cu(NO3)2·3H2O and dissolve it in deionized water to prepare a 0.100 mol / L solution; add 1.0 wt% polyvinyl alcohol (PVA, molecular weight approximately 30,000) as a stabilizer relative to the mass of copper nitrate. Stir and dissolve in an ice-water bath (0–5℃). Then slowly add 200 mL of 0.10 mol / L ascorbic acid solution, controlling the addition time at 25 minutes, and continue stirring the reaction for 20 minutes to obtain a sol of metallic copper nanoparticles with an average particle size of approximately 13 nm.

[0023] S2. The above copper nanoparticle sol was added to 250 mL of isopropanol-TEOS system, with isopropanol volume fraction of 92% and TEOS added in 4 mL. The pH was adjusted to 4.8 ± 0.1 using diluted acetic acid, and the reaction was stirred at room temperature for 5 hours. The resulting product was dried at 120 °C for 10 hours, and then heated to 500 °C at 3 °C / min in air and held at that temperature for 2 hours to form a dense silica inorganic shell with a thickness of approximately 2.3 nm.

[0024] S3. Disperse silica-coated copper nanoparticles in 120 mL of 0.080 mol / L Fe(NO3)3 solution, stir until homogeneous, and then add ammonia dropwise at a rate of 0.8 mL / min until the pH of the solution is adjusted to 9.0 ± 0.2. Maintain the precipitation temperature at 28 °C. The resulting precipitate is dried at 100 °C for 12 hours, and then heated to 600 °C at a rate of 2 °C / min in air and held at that temperature for 1.5 hours to form an iron oxide-assisted active layer with a thickness of approximately 0.9 nm.

[0025] S4. The three-layer core-shell composite particles were loaded onto a γ-Al₂O₃ support using an impregnation method. The support had a specific surface area of ​​180 m². 2 The pore size distribution was concentrated at 6.5 nm. The product was pretreated by dehydroxylation by heating at 450℃ in air for 2.5 hours. After loading, the product was dried under vacuum at 90℃ for 8 hours, and finally heated to 500℃ at 2℃ / min under high-purity argon atmosphere and held at that temperature for 2 hours. The loading of composite particles was controlled at 1.2 wt%.

[0026] Example 3 S1. Weigh 4.84 g of Cu(NO3)2·3H2O and dissolve it in deionized water to prepare a 0.200 mol / L solution; add 1.5 wt% PVA relative to the mass of copper nitrate, and stir to dissolve at 5 °C. Then slowly add 150 mL of 0.2 wt% hydrazine hydrate solution, controlling the addition time at 30 minutes, and continue stirring the reaction for 40 minutes to obtain a copper nanoparticle sol with a particle size controlled at 11 nm.

[0027] S2. Copper nanoparticle sol was added to 180 mL of isopropanol-TEOS system, with isopropanol volume fraction of 96% and TEOS added at 2.5 mL. The pH was adjusted to 5.3 ± 0.1 using ammonia, and the reaction was carried out at room temperature for 3.5 hours. The resulting product was dried at 80 °C for 14 hours, and then heated to 500 °C at a rate of 1 °C / min and held at that temperature for 2 hours to form a dense silica inorganic shell with a thickness of approximately 1.8 nm.

[0028] S3. Disperse silica-coated copper particles in 150 mL of 0.050 mol / L Fe(NO3)3 solution, and add ammonia dropwise at a rate of 0.5 mL / min until the pH reaches 9.1 ± 0.1. The precipitation temperature is 25 °C. The resulting precipitate is dried at 120 °C for 10 hours, and then heated to 700 °C at a rate of 3 °C / min under air atmosphere and held at that temperature for 1 hour to obtain an iron oxide-assisted active layer with a thickness of approximately 1.1 nm.

[0029] S4. The composite particles were loaded onto a γ-Al₂O₃ support by impregnation, with a specific surface area of ​​220 m². 2 / g, with a pore size distribution concentrated at 9.0 nm, was dehydroxylated by heating at 600 °C in air for 2 hours. The loaded product was dried at 100 °C for 8 hours, and finally heated to 500 °C at 3 °C / min under high-purity argon atmosphere and held at that temperature for 2 hours, with a loading of 0.8 wt%.

[0030] Example 4 S1. Weigh 1.21 g of Cu(NO3)2·3H2O and dissolve it in deionized water to prepare a 0.050 mol / L solution; add 1.0 wt% PVA and stir to dissolve under 0℃ ice bath conditions. Then slowly add 80 mL of 0.150 mol / L NaBH4 solution over 15 minutes, and continue stirring for 25 minutes to obtain a copper nanoparticle sol with an average particle size of 14 nm.

[0031] S2. Copper nanoparticle sol was added to 220 mL of isopropanol-TEOS system, with isopropanol volume fraction of 90% and TEOS added at 3.5 mL. The pH was adjusted to 4.6 ± 0.1 using diluted acetic acid, and the reaction was stirred at room temperature for 6 hours. The product was dried at 100 °C for 10 hours, and then heated to 500 °C in air at a rate of 1.5 °C / min and held at that temperature for 3 hours to form a silica shell with a thickness of approximately 2.5 nm.

[0032] S3. Disperse silica-coated copper particles in 80 mL of 0.150 mol / L Fe(NO3)3 solution, and add ammonia dropwise at a rate of 1.5 mL / min until the pH reaches 9.0 ± 0.2, maintaining the precipitation temperature at 35 °C. The precipitate is dried at 100 °C for 12 hours, then heated to 400 °C at a rate of 2 °C / min under air atmosphere and held at this temperature for 2 hours to form an iron oxide-assisted active layer with a thickness of approximately 0.7 nm.

[0033] S4. Impregnate and load the three-layer core-shell structured composite particles onto a γ-Al₂O₃ support with a specific surface area of ​​150 m². 2The sample, with a pore size distribution concentrated at 5.5 nm, underwent dehydroxylation pretreatment by heating at 400℃ in air for 3 hours. After loading, the sample was vacuum dried at 85℃ for 12 hours, and finally heated to 500℃ at a rate of 2℃ / min under a high-purity argon atmosphere and held at that temperature for 2 hours. The loading amount was 1.5 wt%.

[0034] Comparative Example 1 Preparation steps S1. Preparation of copper nanoparticle sol Exactly the same as Example 1: Weigh 2.42 g of Cu(NO3)2·3H2O and dissolve it in deionized water to prepare a 0.100 mol / L solution; add 1.0 wt% PVA stabilizer and stir to dissolve in an ice-water bath (0–5℃); slowly add 100 mL of 0.200 mol / L NaBH4 solution over 20 minutes, and continue stirring for 30 minutes to obtain a copper nanoparticle sol with a particle size of about 12 nm.

[0035] S2. Coated iron oxide auxiliary active layer Copper nanoparticles were directly dispersed in 100 mL of 0.100 mol / L Fe(NO3)3 solution. After stirring evenly, concentrated ammonia was added dropwise to bring the pH to 9.0 ± 0.1. The precipitation temperature was 30 °C. The precipitate was dried at 110 °C for 12 hours and then calcined in air at 650 °C for 1 hour to generate an iron oxide-assisted active layer with a thickness of about 1.0 nm.

[0036] S3. Loading onto γ-γ-Al2O3 support Same as in Example 1: Impregnated with a γ-Al2O3 support (specific surface area 200 m²) that has undergone dehydroxylation pretreatment. 2 / g, pore size 7.5nm, pretreated at 500℃ for 2 hours), dried for 10 hours, and finally heated to 500℃ in high-purity argon and held at that temperature for 2 hours, with a loading of 1.0wt%, to obtain the catalyst of Comparative Example 1.

[0037] Comparative Example 2 Preparation steps S1. Preparation of copper nanoparticle sol Same as in Example 1 (2.42 g Cu(NO3)2·3H2O → 0.1 mol / L solution, 1.0 wt% PVA, NaBH4 reduction at 0–5 °C).

[0038] S2. Silica-coated shell Same as in Example 1: The pH was adjusted to 5.0±0.1 in the isopropanol-TEOS system, stirred at room temperature for 4 hours, dried at 100°C for 12 hours, and calcined in air at 500°C for 2 hours to form a dense silica shell with a thickness of about 2.0 nm.

[0039] S3. Loading onto γ-Al2O3 support Same as in Example 1: Impregnated with γ-Al2O3 (200m) that has undergone dehydroxylation pretreatment. 2 / g, pore size 7.5nm, 500℃ for 2h), dried for 10 hours, heated to 500℃ under high-purity argon, held at that temperature for 2 hours, with a loading of 1.0wt%, to obtain the catalyst of Comparative Example 2.

[0040] Experiment: Performance Comparison of Catalysts for Online Methanol Steam Reforming to Hydrogen 1. Experimental Procedure Experimental conditions: Reactor: Fixed-bed microreactor, inner diameter 6mm, length 300mm; Catalyst loading: 0.5g, each catalyst is mixed with 40-60 mesh quartz sand; Reactant gas: methanol / water = 1:1.3 molar ratio, space velocity 3000 h⁻¹ -1 ; Reaction temperatures: 200℃, 250℃, 300℃, 2 hours per temperature point; Thermal cycling test: 200℃ to 300℃ for 10 cycles, 1 hour per temperature; step: S1. Catalyst loading: Mix each catalyst powder with quartz sand and load it into the reactor; purge with nitrogen, heat to 200°C, and maintain for 30 minutes.

[0041] S2. Methanol steam reforming reaction: The methanol / water mixture is controlled to be introduced into the reactor at a space velocity of 3000 h⁻¹. -1 The samples were maintained at 200℃, 250℃, and 300℃ for 2 hours, respectively, and gas samples were collected every 30 minutes. The concentrations of H2, CO, CO2, and CH3OH were analyzed using a gas chromatograph (GC).

[0042] S3. Thermal cycling experiment: The reaction temperature was cycled 10 times between 200℃ and 300℃, with each temperature lasting 1 hour. After the cycle, the outlet gas was collected, and the changes in CO volume fraction and H2 yield were analyzed.

[0043] S4. Sintering detection: After the thermal cycling experiment, catalyst samples were taken for TEM characterization; the average diameter of copper particles and sintering rate were measured.

[0044] The experimental results are shown in Table 1: Table 1 In Comparative Example 1, which lacked a silica shell, the sintering rate of copper particles increased significantly (12.5%), the H2 yield decreased, and CO emissions increased. This indicates that the silica shell can effectively inhibit the migration and sintering of copper nanoparticles and ensure the stability of the catalyst.

[0045] Comparative Example 2 lacked an iron oxide-assisted active layer, resulting in a CO volume fraction increase to 0.9% and moderate thermal cycling stability. This indicates that the iron oxide layer helps to enhance the water-gas reaction channel and reduce CO emissions.

[0046] Examples 1–4 all have a silica shell and an iron oxide-assisted active layer, with high H2 yield (90–92%), low CO (<0.5%), low sintering rate (<5%), and high thermal cycling stability, demonstrating the excellent performance of the catalyst in online methanol reforming for hydrogen production.

[0047] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and modifications can be made to the present invention without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a catalyst for online methanol reforming to produce hydrogen, characterized in that, Includes the following steps: S1. Dissolve Cu(NO3)2·3H2O in deionized water to form a 0.05-0.2 mol / L solution. Add 0.5%-1.5% polyvinyl alcohol stabilizer relative to the mass of copper nitrate. Slowly add 0.15-0.25 mol / L NaBH4 reducing solution at 0-5℃ for 10-30 minutes. The total stirring time from the start of the addition to the end of the reduction is 20-50 minutes to obtain a copper nanoparticle sol with a particle size controlled at 10-15 nm. S2. The copper nanoparticle sol is added to a tetraethoxysilane system with isopropanol as solvent, the pH value is adjusted between 4.5 and 5.5, and a silica shell precursor is formed by temperature-controlled hydrolysis. After drying, it is calcined in air at 500°C for 2 hours to form a dense silica inorganic shell. S3. The particles after forming a dense silica shell are immersed in an aqueous solution of Fe(NO3)3, ammonia is added dropwise, the pH is adjusted to 9.0±0.2, and a Fe(OH)3 layer is precipitated. Then the precipitate is dried and calcined in air to generate an iron oxide auxiliary active layer. S4. A three-layer core-shell composite particle containing copper nanoparticles, a dense silica inorganic shell, and an iron oxide auxiliary active layer was loaded onto a γ-Al2O3 support that had undergone dehydroxylation pretreatment by impregnation. After drying, the temperature was increased to 500℃ at 2℃ / min under a high-purity argon atmosphere and held at the temperature for 2 hours to obtain a catalyst for online methanol reforming to produce hydrogen.

2. The method for preparing a catalyst for online methanol reforming to hydrogen production according to claim 1, characterized in that, In step S1, the 0.15–0.25 mol / L NaBH4 reducing solution is replaced with a 0.1%–0.3% hydrazine hydrate solution or a 0.05 mol / L–0.15 mol / L ascorbic acid solution, and the reaction temperature is controlled within the range of 0–10°C, and the stirring time is controlled within the range of 20–40 minutes.

3. The method for preparing a catalyst for online methanol reforming to hydrogen production according to claim 1, characterized in that, In step S2, the solvent in the tetraethoxysilane system is isopropanol, with a volume fraction of not less than 90%. The pH value is adjusted by diluting acetic acid or ammonia. The drying temperature is 80–120°C, and the heating rate during calcination is 1–3°C / min.

4. The method for preparing a catalyst for online methanol reforming to hydrogen production according to claim 1, characterized in that, In step S3, the concentration of the Fe(NO3)3 aqueous solution is 0.05 mol / L to 0.15 mol / L, the rate of ammonia addition is controlled at 0.5 mL / min to 1.5 mL / min, the precipitation temperature is maintained at 25 to 35 °C, and the resulting precipitate is dried at 100 to 120 °C and then calcined in air at 400 to 650 °C for 1 to 2 hours.

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