Method for producing hydrogen by catalyzing methanol steam reforming at low temperature

Abstract

The invention relates to the technical field of hydrogen production, in particular to a method for producing hydrogen by catalyzing methanol steam reforming at a low temperature. The method comprises the steps of raw material preparation, vaporization and preheating, reforming reaction, product post-treatment and the like, the used Pt-Co / N-C catalyst is prepared by taking graphene oxide, aniline, ferric nitrate and the like as raw materials through polymerization, pyrolysis, hydrochloric acid treatment and metal load reduction, a nitrogen-doped carbon carrier and Pt-Co alloy active components are contained, and wrapped Fe3C is retained. The low-temperature high-efficiency hydrogen production is realized, CO generation is inhibited, the catalyst stability is high, the process energy consumption is low, the integration degree is high, and the device is suitable for a distributed hydrogen energy supply scene.

Description

Technical Field

[0001] This invention relates to the field of hydrogen production technology, and in particular to a method for producing hydrogen through catalytic methanol steam reforming at low temperatures. Background Technology

[0002] Methanol steam reforming for hydrogen production has become a core technology for distributed hydrogen energy supply (such as proton exchange membrane fuel cells) due to the wide availability of methanol as a raw material, convenient storage and transportation, and high hydrogen production efficiency. However, existing industrial hydrogen production processes generally rely on Cu / ZnO / Al2O3 series catalysts, and their optimal reaction temperature needs to be controlled between 220-300℃. This technical route has significant drawbacks:

[0003] On the one hand, high-temperature operation leads to high energy consumption, and the reactor needs continuous external heating to maintain the reaction temperature, which not only reduces energy utilization efficiency, but also increases the equipment's high-temperature resistance requirements and operating costs; moreover, high temperature easily causes Cu particles to sinter and agglomerate, and trace sulfur and chlorine impurities in the raw materials will quickly poison the Cu active sites, resulting in short catalyst life and frequent replacement, which further increases process costs.

[0004] On the other hand, high-temperature thermodynamic conditions are more likely to induce methanol decomposition side reactions, resulting in CO volume concentration in the product gas often exceeding 1%. Proton exchange membrane fuel cells are extremely sensitive to CO, and even trace amounts of CO can poison the battery electrodes. Therefore, an additional complex CO removal device is required, which increases system complexity and investment costs, limiting the application of this technology in miniaturized, mobile hydrogen production scenarios.

[0005] Although existing research attempts to develop low-temperature methanol steam reforming catalysts, most of these solutions suffer from problems such as insufficient low-temperature activity, poor CO selectivity control, or poor catalyst stability. They are unable to meet the industrial requirements of "low-temperature operation, high hydrogen purity, and long lifespan," and breakthroughs in novel catalysts and supporting processes are urgently needed to address these bottlenecks. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the existing technology and to propose a method for producing hydrogen by catalytic steam reforming of methanol at low temperature.

[0007] To achieve the above objectives, the present invention provides a method for producing hydrogen through catalytic steam reforming of methanol at low temperature, comprising the following steps:

[0008] S1. Raw material preparation: Mix methanol and deionized water to obtain raw material solution;

[0009] S2. Vaporization and preheating: The raw material liquid is fed into the vaporizer via a metering pump. After vaporization at 120-180℃, a mixed gas is obtained, which is then mixed with circulating hydrogen and preheated to the reaction temperature to obtain a mixed gas.

[0010] S3. Reforming reaction: The mixed gas is passed through a fixed-bed reactor packed with Pt-Co / NC catalyst. The reaction conditions are: temperature 120-180℃, pressure 0.3-0.7MPa, and weight hourly space velocity 2500-3500mL·g. -1 ·h -1 The contact time is 0.5-1s, resulting in high-temperature reformed gas;

[0011] S4. Product post-processing: After heat exchange between the high-temperature reformed gas and the feed liquid, the gas is cooled to room temperature by circulating water. After gas-liquid separation, the liquid phase is returned to the feed system, and the gas phase is purified by the PSA system to obtain hydrogen.

[0012] The preparation method of the Pt-Co / NC catalyst is as follows:

[0013] (1) Graphene oxide was added to deionized water and ultrasonically dispersed for 10-20 min to obtain a dispersion. Aniline and ferric nitrate were then added, and ammonium persulfate was added while stirring at 0-5℃. After reacting for 8-12 h, the mixture was filtered. The resulting solid was washed and dried to obtain Fe-PANI / GO. Fe-PANI / GO was placed in a tube furnace under nitrogen protection and heated to 600-700℃ at a heating rate of 3-7℃ / min. The temperature was maintained for 1-3 h. After cooling to room temperature, the mixture was ground through a 10-20 mesh sieve to obtain the pyrolysis product. During the process, the amino groups of aniline molecules formed hydrogen bonds with the oxygen-containing groups on the surface of graphene oxide (GO), causing aniline to be uniformly adsorbed on the surface of GO sheets. The Fe groups dissociated from ferric nitrate formed hydrogen bonds. 3+ It undergoes coordination with the amino group of aniline, transferring Fe... 3+ When uniformly immobilized in an aniline / GO system, ammonium persulfate (APS) slowly decomposes at 0-5°C to generate sulfate radicals, which initiate the oxidative polymerization of aniline molecules.

[0014] Aniline + SO4 - →Aniline free radicals →polymerize to form polyaniline (PANI) chains;

[0015] Low-temperature control is used to slow down the polymerization rate and prevent disordered growth of PANI chains; the molar ratio of APS to aniline is 1-1.2:1 to ensure complete polymerization of aniline; ultimately forming a structure with GO sheets as the substrate, PANI chains encapsulating GO, and Fe... 3+ Fe-PANI / GO with embedded PANI chains is then processed in a tube furnace. In the low-temperature stage (200-400℃), non-carbon elements (H and some N as H2O and NH3) in the PANI chains are removed, and PANI gradually transforms into amorphous carbon. The oxygen-containing groups on the GO surface decompose into CO2 and H2O, reducing GO to reduced graphene oxide (rGO). In the medium-temperature stage (400-600℃), the amorphous carbon acts as a reducing agent, reducing Fe... 3+ Reduced to Fe-based active species (Fe 0Fe3O4, Fe3C), high temperature stage (600-700℃): Fe-based active species (Fe 0 (Fe3O4, Fe3C) act as "catalytic graphitization reagents" to guide amorphous carbon to recombine into an ordered graphene-like structure; at the same time, the N atoms remaining in aniline are embedded in the carbon skeleton to form pyridine nitrogen and graphitic nitrogen.

[0016] (2) Under ultrasound, the pyrolysis product was added to dilute hydrochloric acid for 8-12 hours, filtered, washed with deionized water until neutral, and dried to obtain a nitrogen-doped carbon support. During the process, dilute hydrochloric acid can selectively remove "free Fe-based active species not wrapped by the carbon layer" and retain "Fe3C tightly wrapped by the graphene-like carbon layer". At the same time, it can regulate the pore structure of the support to avoid free Fe catalyzing side reactions in subsequent reactions. The chemical reaction equation is as follows:

[0017] Fe 0 +2HCl→FeCl2+H2↑(Fe 0 (dissolve);

[0018] Fe3O4 + 8HCl → 2FeCl3 + FeCl2 + 4H2O (Fe3O4 dissolves);

[0019] During pyrolysis, some Fe3C is tightly wrapped by the graphene-like carbon layer, preventing hydrochloric acid from penetrating and thus not reacting. It remains in the carbon support. This part of Fe3C can enhance the conductivity of the support and promote electron transfer, and does not directly participate in the catalytic reaction, thus avoiding interference with the activity of Pt-Co.

[0020] (3) Chloroplatinic acid and cobalt nitrate were added to deionized water and stirred for 20-40 min to obtain a mixed salt solution. Nitrogen-doped carbon support was added to the mixed salt solution, stirred and sonicated for 20-40 min, filtered, dried, and then reduced in a hydrogen / argon mixed gas at a heating rate of 1-3 °C / min to 300-400 °C for 1-3 h. After cooling to room temperature, Pt-Co / NC catalyst was obtained. During the process, chloroplatinic acid H2PtCl6 dissociated into PtCl6 in water. 2- Cobalt nitrate Co(NO3)2 dissociates into Co 2+ Meanwhile, the pyridine nitrogen and graphitic nitrogen on the nitrogen-doped carbon support surface contain lone pairs of electrons, which can react with PtCl6. 2- Co 2+ Coordinate bonds are formed (N→Pt / Co), achieving uniform adsorption of metal ions on the support surface; in the hydrogen / argon gas mixture, argon acts as a protective gas (to prevent metal oxidation), and hydrogen acts as a reducing agent; the heating rate of 1-3℃ / min avoids sudden temperature rise that could lead to sintering of metal particles; at 300-400℃, hydrogen reduces the metal ions to elemental form.

[0021] PtCl62- +2H2→Pt 0 +6Cl - +4H + (Pt 0 generate);

[0022] Co 2+ +H2→Co 0 +2H + (Co 0 generate);

[0023] Restored Pt 0 Co 0 Pt-Co alloy particles with similar atomic radii easily form a face-centered cubic structure. The alloy particles are anchored by coordination with the nitrogen doping sites of the support, avoiding migration and sintering. Pt is responsible for activating the CH bond of methanol, and Co promotes the dissociation of H2O to generate OH*, thus achieving synergistic catalysis of methanol steam reforming at low temperature.

[0024] Preferably, the molar ratio of methanol to deionized water in S1 is 1:2-3.

[0025] Preferably, the volume ratio of the mixed gas and the circulating hydrogen gas in S2 is 1:0.03-0.07.

[0026] Preferably, the circulating hydrogen in S2 refers to a portion of the crude hydrogen that is diverted and drawn out before purification by the PSA system after gas-liquid separation in the product post-processing.

[0027] Preferably, the PSA system in S4 is filled with activated alumina, activated carbon, and molecular sieves. When the gas phase enters the PSA system, due to the differences in adsorption characteristics of the gas components, different components form adsorption enrichment zones at different positions in the PSA system. The strongest adsorbed component, CO2, is enriched at the inlet end of the PSA system, and the weakest adsorbed component, H2, is enriched at the outlet end of the PSA system. The enrichment zones of the remaining components are distributed in the middle of the PSA system according to the differences in adsorption strength, thereby realizing the separation and purification of hydrogen.

[0028] Preferably, in (1), the weight ratio of graphene oxide, deionized water and aniline is 1:400-600:8-12.

[0029] Preferably, the molar ratio of aniline, ferric nitrate and ammonium persulfate in (1) is 1:0.1-0.3:0.03-0.05.

[0030] Preferably, in step (2), the pyrolysis product and dilute hydrochloric acid are in a weight ratio of 1:8-12.

[0031] Preferably, the concentration of dilute hydrochloric acid in (2) is 1 mol / L.

[0032] Preferably, in (3), the molar ratio of chloroplatinic acid to cobalt nitrate is 1:1.8-2.2.

[0033] Preferably, the concentration of metal ions in the mixed salt solution in (3) is 3-7 wt%.

[0034] Preferably, in step (3), the nitrogen-doped carbon support and the mixed salt solution are in a weight ratio of 1:15-25.

[0035] Preferably, the hydrogen / argon mixed gas in (3) refers to the mixture of hydrogen and argon in a volume ratio of 5:95.

[0036] Preferably, the mechanism of low-temperature catalytic methanol steam reforming for hydrogen production in the method is as follows:

[0037] Nitrogen doping is the core of achieving high-efficiency catalysis at low temperatures: On the one hand, the difference in electronegativity between nitrogen atoms and carbon causes local charge distribution on the carbon support, enhancing its anchoring ability for Pt-Co alloy particles. Through the coordination of the lone pair electrons of N atoms with the d orbitals of Pt and Co, stable metal-nitrogen bonds are formed, inhibiting the migration and aggregation of active particles and maintaining high dispersibility at low temperatures. On the other hand, nitrogen doping increases the number of defect sites on the surface of the carbon support, improving its adsorption capacity for methanol and water molecules, increasing the concentration of reactants on the catalyst surface, and lowering the reaction energy barrier at low temperatures.

[0038] Pyridine nitrogen, as the main reactive nitrogen species, optimizes the Pt-Co activity through electronic effects: after forming a coordinate bond with Pt, it shifts the d-band center of Pt upward, enhancing its activation ability for methanol CH bonds. Simultaneously, it enhances the redox activity of Co through electron transfer, promoting the dissociation of water molecules to generate OH-. - Species; furthermore, the weak adsorption of pyridine nitrogen on CO molecules can capture trace amounts of generated CO, preventing it from occupying Pt active sites, while simultaneously facilitating the reaction of CO and OH. - The secondary reaction (generating CO2) provides space, significantly inhibiting CO overflow;

[0039] Graphite nitrogen enhances the effect through its structure and electronic conduction: its six-membered ring structure is conjugated with the carbon skeleton, improving the conductivity of the support and accelerating the transfer of electrons between Pt and Co sites, enabling efficient coupling of methanol activation and water splitting steps; at the same time, graphite nitrogen enhances the rigidity of the carbon support, and together with the supporting effect of Fe3C, maintains the mesoporous structure and specific surface area of ​​the support, ensuring the rapid diffusion of reactants and products and avoiding mass transfer limitation at low temperatures.

[0040] Pt is primarily responsible for the initial activation of methanol molecules. Under nitrogen doping, the adsorption energy of methanol on its surface decreases, and the activation energy for CH bond breaking drops significantly, generating intermediates such as CH3O. Co, on the other hand, specializes in the dissociation of water molecules. With the enhanced electron transport of graphite nitrogen, Co...3+ / Co 2+ Redox improves cycle efficiency and generates a large amount of OH-. - The species further reacts with CH3O to generate intermediates such as CH2O and HCOO*; finally, at the Pt-Co interface, the intermediates decompose into CO2 and H2, completing the entire reforming process.

[0041] Nitrogen doping, through a triple effect of electronic regulation (optimizing the electronic state of active sites), structural stabilization (anchoring active particles and maintaining the support structure), and adsorption optimization (enhancing reactant adsorption and inhibiting CO), forms a coupling mechanism with the activity synergy of Pt-Co alloy and the structural support of Fe3C. This enables the reforming reaction, which originally required temperatures above 220℃ to proceed efficiently, to achieve high conversion rates and low CO generation at temperatures of 120-180℃, breaking through the low-temperature activity bottleneck of traditional catalysts.

[0042] Beneficial effects of the invention:

[0043] 1. This invention, through the innovative design of a Pt-Co / NC catalyst, lowers the reaction temperature for methanol steam reforming to hydrogen production to 120-180℃, significantly reducing energy consumption compared to the traditional high-temperature range of 220-300℃. Low-temperature operation not only reduces the external heating demand of the reactor and lowers energy loss, but also relaxes the high-temperature resistance requirements for equipment materials, allowing the use of conventional corrosion-resistant materials to meet process needs, significantly reducing equipment manufacturing and maintenance costs. Simultaneously, the low-temperature environment avoids the problems of easy sintering of catalyst active components and easy poisoning of impurities in traditional high-temperature processes, extending catalyst lifespan and reducing downtime losses and material costs caused by frequent catalyst replacements. It is more suitable for the low-energy consumption and low-cost requirements of miniaturized, mobile hydrogen production scenarios.

[0044] 2. This invention utilizes the dual effects of Pt-Co bimetallic synergy and nitrogen-doped carbon support to construct a reaction system that efficiently suppresses CO formation. In the Pt-Co alloy, Co can efficiently dissociate water molecules to generate sufficient OH-. - The species promptly oxidizes the CH2O intermediate generated during methanol activation into CO2, reducing CO formation at the source; the pyridine nitrogen and graphitic nitrogen in the support can also weakly adsorb small amounts of generated CO, allowing it to further react with OH-. - The reaction converts to CO2. This design maintains the CO volume concentration in the product at an extremely low level, eliminating the need for additional complex deep CO removal devices. High-purity hydrogen can be obtained using only a conventional PSA system, simplifying the process, reducing system complexity and investment costs, while avoiding hydrogen loss due to the CO removal step and improving overall hydrogen production efficiency.

[0045] 3. The Pt-Co / NC catalyst prepared in this invention exhibits excellent structural stability. The nitrogen-doped carbon support firmly anchors the Pt-Co alloy particles through coordination, preventing their migration and aggregation during long-term reactions. The encapsulated Fe3C within the support further enhances the graphene-like structural stability of the carbon support, preventing support collapse. Simultaneously, the introduction of circulating hydrogen stabilizes the reaction system, reducing active site blockage and carbon deposition. Furthermore, the heat exchange design between the feed liquid and the high-temperature reforming gas not only achieves energy recycling but also stabilizes the reaction temperature, avoiding the impact of localized temperature fluctuations on the catalyst and process. These design features collectively ensure that the catalyst maintains high efficiency and activity during 100 hours of continuous operation, with stable and reliable process operation, meeting the requirements for industrial continuous hydrogen production.

[0046] 4. This invention optimizes the ratio of methanol to deionized water to 1:2-3. This ratio ensures complete methanol conversion while avoiding water waste. The raw materials are readily available and inexpensive, requiring no special pretreatment before use. The process flow is highly integrated, from raw material preparation, vaporization preheating, reforming reaction to product post-processing, with each step closely linked: the vaporized raw material liquid is precisely mixed with circulating hydrogen; the waste heat from the high-temperature reforming gas is used to preheat the raw material; and the liquid phase after gas-liquid separation can be returned to the raw material system for recycling, achieving efficient utilization of resources and energy. This highly integrated process design results in a small system footprint and fast start-up speed, meeting the large-scale needs of industrial hydrogen production scenarios as well as adapting to distributed and portable hydrogen energy supply scenarios, thus having a wide range of applications. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0048] Preparation Example 1: The specific preparation method of Pt-Co / NC catalyst is as follows:

[0049] (1) 10g of graphene oxide was added to 4kg of deionized water and ultrasonically dispersed for 10min to obtain a dispersion. Then, 80g of aniline and 20.77g of ferric nitrate were added. The mixture was cooled to 0-5℃ and 5.88g of ammonium persulfate was added under stirring. After reacting for 8h, the mixture was filtered. The obtained solid was washed and dried to obtain Fe-PANI / GO. Fe-PANI / GO was placed in a tube furnace and heated to 600℃ at a heating rate of 3℃ / min under nitrogen protection. The temperature was held for 1h. After cooling to room temperature, the mixture was ground through a 10-20 mesh sieve to obtain the pyrolysis product.

[0050] (2) Under ultrasound, 10g of pyrolysis product was added to 80g of 1mol / L dilute hydrochloric acid for 8h. After filtration, it was washed with deionized water until neutral and dried to obtain nitrogen-doped carbon support.

[0051] (3) Add 10g of chloroplatinic acid and 8.04g of cobalt nitrate to deionized water and stir for 20 min to obtain a mixed salt solution with a metal ion concentration of 3wt%. Add 10g of nitrogen-doped carbon support to 150g of mixed salt solution, stir and sonicate for 20 min, filter, dry, and then reduce in a hydrogen / argon mixed gas (hydrogen and argon are mixed in a volume ratio of 5:95) at a heating rate of 1℃ / min to 300℃ for 1 h. After cooling to room temperature, Pt-Co / NC catalyst is obtained.

[0052] Preparation Example 2: The specific preparation method of the Pt-Co / NC catalyst is as follows:

[0053] (1) 10g of graphene oxide was added to 5kg of deionized water and ultrasonically dispersed for 15min to obtain a dispersion. Then, 100g of aniline and 51.94g of ferric nitrate were added. The mixture was cooled to 0-5℃ and 9.80g of ammonium persulfate was added under stirring. After reacting for 10h, the mixture was filtered. The obtained solid was washed and dried to obtain Fe-PANI / GO. Fe-PANI / GO was placed in a tube furnace and heated to 650℃ at a heating rate of 5℃ / min under nitrogen protection. The temperature was maintained for 2h. After cooling to room temperature, the mixture was ground through a 10-20 mesh sieve to obtain the pyrolysis product.

[0054] (2) Under ultrasound, 10g of pyrolysis product was added to 100g of 1mol / L dilute hydrochloric acid for 10h. After filtration, it was washed with deionized water until neutral and dried to obtain nitrogen-doped carbon support.

[0055] (3) Add 10g of chloroplatinic acid and 8.93g of cobalt nitrate to deionized water and stir for 30 min to obtain a mixed salt solution with a metal ion concentration of 5wt%. Add 10g of nitrogen-doped carbon support to 200g of mixed salt solution, stir and sonicate for 30 min, filter, dry, and then reduce in a hydrogen / argon mixed gas (hydrogen and argon are mixed in a volume ratio of 5:95) at a heating rate of 2℃ / min to 350℃ for 2 h. After cooling to room temperature, Pt-Co / NC catalyst is obtained.

[0056] Preparation Example 3: The specific preparation method of the Pt-Co / NC catalyst is as follows:

[0057] (1) 10g of graphene oxide was added to 6kg of deionized water and ultrasonically dispersed for 20min to obtain a dispersion. Then, 120g of aniline and 93.49g of ferric nitrate were added. The mixture was cooled to 0-5℃ and 14.70g of ammonium persulfate was added under stirring. After reacting for 12h, the mixture was filtered. The obtained solid was washed and dried to obtain Fe-PANI / GO. Fe-PANI / GO was placed in a tube furnace and heated to 700℃ under nitrogen protection at a heating rate of 7℃ / min. The temperature was held for 3h. After cooling to room temperature, the mixture was ground through a 10-20 mesh sieve to obtain the pyrolysis product.

[0058] (2) Under ultrasound, 10g of pyrolysis product was added to 120g of dilute hydrochloric acid with a concentration of 1mol / L for 12h. After filtration, it was washed with deionized water until neutral and dried to obtain nitrogen-doped carbon support.

[0059] (3) Add 10g of chloroplatinic acid and 9.82g of cobalt nitrate to deionized water and stir for 40 min to obtain a mixed salt solution with a metal ion concentration of 7wt%. Add 10g of nitrogen-doped carbon support to 250g of mixed salt solution, stir and sonicate for 40 min, filter, dry, and then reduce in a hydrogen / argon mixed gas (hydrogen and argon are mixed in a volume ratio of 5:95) at a heating rate of 3℃ / min to 400℃ for 3 h. After cooling to room temperature, Pt-Co / NC catalyst is obtained.

[0060] Comparative Preparation Example 1: The difference between Comparative Preparation Example 1 and Preparation Example 2 is that ferric nitrate is not added in step (1).

[0061] Comparative Preparation Example 2: The difference between Comparative Preparation Example 2 and Preparation Example 2 is that in step (1), Fe-PANI / GO was placed in a tube furnace and heated to 500°C for 2 hours under nitrogen protection at a heating rate of 5°C / min.

[0062] Comparative Preparation Example 3: The difference between Comparative Preparation Example 3 and Preparation Example 2 is that in step (3), 10g of chloroplatinic acid and 4.46g of cobalt nitrate were added to deionized water and stirred for 30min to obtain a mixed salt solution with a metal ion concentration of 5wt%.

[0063] Comparative Preparation Example 4: The difference between Comparative Preparation Example 4 and Preparation Example 2 is that the Pt-Co / NC catalyst is replaced with a Pt-Co / C catalyst. The specific preparation method is as follows: The specific preparation method of the Pt-Co / C catalyst includes the following steps:

[0064] 10g of chloroplatinic acid and 8.93g of cobalt nitrate were added to deionized water and stirred for 30min to obtain a mixed salt solution with a metal ion concentration of 5wt%. 10g of graphene oxide was added to 200g of the mixed salt solution, stirred and sonicated for 30min, filtered, dried, and then reduced in a hydrogen / argon mixed gas (hydrogen and argon were mixed in a volume ratio of 5:95) at a heating rate of 2℃ / min to 350℃ for 2h. After cooling to room temperature, the Pt-Co / C catalyst was obtained.

[0065] Comparative preparation example 5: The difference between comparative preparation example 5 and preparation example 2 is that step (2) is omitted, and the remaining steps are the same as in preparation example 2.

[0066] Example 1: A method for producing hydrogen by catalytic steam reforming of methanol at low temperature, comprising the following steps:

[0067] S1. Raw material preparation: Mix methanol and deionized water at a molar ratio of 1:2 to obtain the raw material solution;

[0068] S2. Vaporization and preheating: The raw material liquid is fed into the vaporizer via a metering pump. After vaporization at 120°C, a mixed gas is obtained and then mixed with circulating hydrogen at a volume ratio of 1:0.03. The mixture is then preheated to the reaction temperature to obtain a mixed gas.

[0069] S3. Reforming reaction: The mixed gas was passed through a fixed-bed reactor packed with the Pt-Co / NC catalyst prepared according to Preparation Example 1. The reaction conditions were: temperature 120℃, pressure 0.3MPa, and weight hourly space velocity 2500 mL·g. -1 ·h -1 The contact time is 0.5s, resulting in high-temperature reformed gas;

[0070] S4. Product post-processing: After heat exchange between the high-temperature reformed gas and the feed liquid, the gas is cooled to room temperature by circulating water. After gas-liquid separation, the liquid phase is returned to the feed system, and the gas phase is purified by the PSA system, which contains activated alumina, activated carbon and molecular sieves, to obtain hydrogen.

[0071] Example 2: A method for producing hydrogen by catalytic steam reforming of methanol at low temperature, comprising the following steps:

[0072] S1. Raw material preparation: Mix methanol and deionized water at a molar ratio of 1:2.5 to obtain the raw material solution;

[0073] S2. Vaporization and preheating: The raw material liquid enters the vaporizer through a metering pump. After vaporization at 150°C, the resulting mixed gas is mixed with circulating hydrogen at a volume ratio of 1:0.05 and preheated to the reaction temperature to obtain the mixed gas.

[0074] S3. Reforming reaction: The mixed gas was passed through a fixed-bed reactor packed with the Pt-Co / NC catalyst prepared according to Preparation Example 2. The reaction conditions were: temperature 150℃, pressure 0.5MPa, and weight hourly space velocity 3000 mL·g. -1 ·h -1 The contact time was 0.75s, resulting in high-temperature reformed gas.

[0075] S4. Product post-processing: After heat exchange between the high-temperature reformed gas and the feed liquid, the gas is cooled to room temperature by circulating water. After gas-liquid separation, the liquid phase is returned to the feed system, and the gas phase is purified by the PSA system, which contains activated alumina, activated carbon and molecular sieves, to obtain hydrogen.

[0076] Example 3: A method for producing hydrogen by catalytic steam reforming of methanol at low temperature, comprising the following steps:

[0077] S1. Raw material preparation: Mix methanol and deionized water at a molar ratio of 1:3 to obtain the raw material solution;

[0078] S2. Vaporization and preheating: The raw material liquid enters the vaporizer through a metering pump, vaporizes at 1180℃, and then the mixed gas is mixed with circulating hydrogen at a volume ratio of 1:0.07. The mixture is then preheated to the reaction temperature to obtain the mixed gas.

[0079] S3. Reforming reaction: The mixed gas was passed through a fixed-bed reactor packed with the Pt-Co / NC catalyst prepared according to Preparation Example 3. The reaction conditions were: temperature 180℃, pressure 0.7MPa, and weight hourly space velocity 3500 mL·g. -1 ·h -1 The contact time is 1 second, and high-temperature reformed gas is obtained;

[0080] S4. Product post-processing: After heat exchange between the high-temperature reformed gas and the feed liquid, the gas is cooled to room temperature by circulating water. After gas-liquid separation, the liquid phase is returned to the feed system, and the gas phase is purified by the PSA system, which contains activated alumina, activated carbon and molecular sieves, to obtain hydrogen.

[0081] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that the Pt-Co / NC catalyst prepared according to Preparation Example 2 is replaced with the Pt-Co / NC catalyst prepared according to Comparative Preparation Example 1.

[0082] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that the Pt-Co / NC catalyst prepared according to Preparation Example 2 is replaced with the Pt-Co / NC catalyst prepared according to Comparative Preparation Example 2.

[0083] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that the Pt-Co / NC catalyst prepared according to Preparation Example 2 is replaced with the Pt-Co / NC catalyst prepared according to Comparative Preparation Example 3.

[0084] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that the Pt-Co / NC catalyst prepared according to Preparation Example 2 is replaced with the Pt-Co / C catalyst prepared according to Comparative Preparation Example 4.

[0085] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that the Pt-Co / NC catalyst prepared according to Preparation Example 2 is replaced with the Pt-Co / NC catalyst prepared according to Comparative Preparation Example 5.

[0086] Comparative Example 6: The difference between Comparative Example 6 and Example 2 is that the mixed gas is not mixed with the circulating hydrogen in step S2.

[0087] Performance testing:

[0088] 1. Methanol conversion rate: Gas chromatography (GC-2014, equipped with TDX-01 column) was used to detect the concentration of methanol in the feed gas before and after the reforming reaction in Examples 1-3 and Comparative Examples 1-6, respectively. The conversion rate was calculated according to the formula "conversion rate = (methanol concentration before reaction - methanol concentration after reaction) / methanol concentration before reaction × 100%". The experimental results are shown in Table 1.

[0089] 2. CO volume concentration in the product: The volume concentration of CO in the reformed gas of Examples 1-3 and Comparative Examples 1-6 was directly detected using the same gas chromatography (equipped with an FID detector) used in the methanol conversion test described above. The experimental results are shown in Table 1.

[0090] 3. Catalyst stability: Under the reaction conditions of Examples 1-3 and Comparative Examples 1-6, the catalyst was continuously run for 100 hours. The methanol conversion rate was measured at the initial 1 hour and 100 hours. The conversion rate was calculated according to the formula "attenuation rate = (initial conversion rate - 100-hour conversion rate) / initial conversion rate × 100%". The experimental results are shown in Table 1.

[0091] 4. Catalyst coking amount: The catalysts of Examples 1-3 and Comparative Examples 1-6 after continuous operation for 100h were heated to 800℃ at 10℃ / min in an air atmosphere (flow rate 50mL / min). The weight loss of the catalyst was recorded by thermogravimetric analysis. The weight loss rate is the amount of coking. The experimental results are shown in Table 1.

[0092] Table 1 Performance Test Results

[0093] Methanol conversion rate / % CO volume concentration / % Attenuation rate / % Carbon deposits / % Example 1 99.71 0.0064 1.03 0.34 Example 2 99.93 0.0056 0.89 0.22 Example 3 99.96 0.0061 0.97 0.40 Comparative Example 1 92.43 0.11 9.05 1.79 Comparative Example 2 90.65 0.18 13.8 2.32 Comparative Example 3 93.72 0.070 6.23 0.91 Comparative Example 4 86.84 0.43 18.50 2.82 Comparative Example 5 94.88 0.34 7.54 1.11 Comparative Example 6 93.75 0.028 8.05 1.23

[0094] Performance Analysis:

[0095] As can be seen from the experimental data in Table 1, the method of the present invention used in Examples 1-3 for hydrogen production by low-temperature methanol steam reforming exhibits better overall performance than Comparative Examples 1-6. Specifically, the methanol conversion rate is significantly higher, the CO volume concentration in the product is significantly lower, the catalyst stability is stronger, and the amount of carbon deposit is less. Among them, Example 2 has the best overall performance, achieving the best balance in terms of the completeness of methanol conversion, the inhibition effect of CO byproducts, the stability of long-term catalyst operation, and the ability to resist carbon deposits. This is due to the high synergy between the raw material ratio, reaction process parameters, and Pt-Co / NC catalyst structure in Example 2, which perfectly matches the core requirements of low-temperature reforming for hydrogen production.

[0096] The core mechanism behind the excellent methanol conversion rate in Example 2 lies in the fact that all key parameters are within their optimal matching range, and the catalyst active sites achieve efficient exposure and synergistic effect. From the raw material perspective, the methanol to deionized water molar ratio used in Example 2 provides sufficient steam for methanol reforming to promote complete methanol conversion without excessive dilution of methanol concentration or a decrease in reaction rate due to excess water. From the reaction process perspective, the set reaction temperature maximizes the catalytic ability of the Pt-Co alloy active sites. At this temperature, the breaking efficiency of the CH bond in methanol by Pt and the dissociation efficiency of water molecules by Co reach equilibrium. Simultaneously, the pressure parameter increases the adsorption concentration of reactants on the catalyst surface. Combined with appropriate weight hourly space velocity and contact time, this ensures the reaction... The catalyst and active sites are in full contact and react completely. From the catalyst structure perspective, the Fe3C species introduced by ferric nitrate in the catalyst used in Example 2 significantly enhances the conductivity of the nitrogen-doped carbon support, accelerating electron transfer between active sites. Simultaneously, the pyridine nitrogen and graphitic nitrogen on the surface of the nitrogen-doped carbon support firmly anchor the Pt-Co alloy particles, preventing aggregation at active sites. Furthermore, the molar ratio of Pt to Co precisely optimizes their electronic structures. After adjustment of the electron cloud density of Pt by Co, the activation barrier for the CH bond of methanol is significantly reduced, while Co efficiently dissociates water molecules to generate OH-. - The species provide sufficient oxide species for subsequent steps in methanol reforming, and the three work synergistically to promote efficient methanol conversion. In contrast, the comparative example showed a methanol conversion rate far lower than that of Example 2, possibly due to insufficient conductivity of the support and unstable anchoring of active sites caused by the lack of Fe source in catalyst preparation, insufficient activation of active sites caused by the reaction temperature deviating from the optimal range, or incomplete reaction caused by improper feed ratio.

[0097] The CO volume concentration in the product of Example 2 was significantly lower than that in other groups. The key lies in its construction of a multi-pathway synergistic mechanism involving "rapid oxidation of intermediates - CO adsorption inhibition - free Fe removal," which kinetically blocks CO generation and accumulation. Firstly, the Co content in the catalyst used in Example 2 was within the optimal range, enabling efficient dissociation of water molecules to generate a large amount of OH-.- Species, these OH - The species can rapidly capture the CH2O intermediate generated during methanol activation (CH2O is a key precursor for CO formation), oxidizing it to a performic acid intermediate. This intermediate further decomposes into CO2 and H2, reducing CO formation at the source. Secondly, the pyridine nitrogen and graphitic nitrogen sites in the catalyst support have a weak adsorption effect on CO molecules. Even if a very small amount of CO is generated, it will be adsorbed onto the support surface by these nitrogen sites, preventing it from remaining on the Pt-Co active sites or being discharged with the products. At the same time, the adsorbed CO can also react with adjacent OH groups. - The species further react to generate CO2, achieving secondary CO elimination; in addition, the dilute hydrochloric acid treatment step in the catalyst preparation process can selectively remove free Fe species (such as Fe) that are not encapsulated by the carbon layer. 0 Free Fe species (Fe3O4, etc.) readily catalyze the decomposition of methanol into CO under low-temperature conditions; their removal can significantly reduce the CO source in this pathway. In contrast, insufficient Co content may lead to OH... - The low amount of CO generated, the inability to oxidize CH2O in time, the retention of a large amount of free Fe due to the lack of dilute hydrochloric acid treatment, or the lack of CO adsorption inhibition due to the absence of nitrogen doping on the carrier all resulted in a CO volume concentration much higher than in Example 2.

[0098] In Example 2, the catalyst exhibited a significantly lower conversion rate decline after 100 hours of continuous operation compared to other groups. This is primarily due to the dual guarantee provided by both catalyst structural stability and reaction process stability. From a structural perspective, a strong interaction exists between the nitrogen-doped carbon support and the Pt-Co alloy particles. The pyridine nitrogen and graphitic nitrogen on the support surface form coordination bonds with Pt and Co atoms through lone pairs of electrons. This coordination firmly anchors the Pt-Co alloy particles, preventing migration and aggregation due to temperature fluctuations or reactant erosion during long-term operation, thus ensuring a stable number of active sites. Simultaneously, the encapsulated Fe3C species retained in the support enhance the graphene-like structural stability of the carbon support, preventing structural collapse due to prolonged exposure to the reaction atmosphere and further maintaining the exposed state of the active sites. From the perspective of the reaction process, the introduction of circulating hydrogen can effectively stabilize the reaction system. As a dilution gas, circulating hydrogen can reduce the local concentration of methanol on the catalyst surface, preventing the active sites from being blocked by excessively adsorbed methanol or intermediates. Simultaneously, circulating hydrogen can maintain a certain hydrogen partial pressure within the reaction system, inhibiting carbon deposition on the catalyst surface and oxidation of active metals, thus reducing non-selective deactivation of active sites. In contrast, the catalyst in the control example showed significant activity degradation after long-term operation, with a degradation rate far exceeding that of Example 2, due to factors such as the lack of nitrogen doping in catalyst preparation leading to unstable active site anchoring and easy agglomeration, the absence of circulating hydrogen resulting in large fluctuations in the reaction system and easy blockage of active sites, or insufficient pyrolysis temperature leading to a loose support structure and easy collapse.

[0099] In Example 2, the amount of coke deposited on the catalyst after 100 hours of operation was significantly lower than that in other groups, mainly due to the precise control of the raw material ratio and the anti-coke properties of the catalyst structure. Regarding the raw material ratio, the water-to-alcohol ratio used in Example 2 effectively inhibits coke formation. Sufficient water vapor not only provides the necessary oxide species for the reaction but also reacts with carbon species that may form on the catalyst surface (e.g., C + H₂O → CO + H₂), converting the carbon species into gaseous products and preventing their deposition on the catalyst surface to form coke. Simultaneously, this water-to-alcohol ratio prevents excessive water from causing an excessively low reaction rate, thus avoiding prolonged residence time of reactants on the catalyst surface and the resulting deep decomposition and coke formation. From the perspective of catalyst structure, on the one hand, the high conductivity of the catalyst reduces the formation of local hot spots, which easily lead to excessive decomposition of methanol and the generation of carbon species. The Fe3C-enhanced conductivity in the catalyst of Example 2 allows for uniform heat transfer during the reaction, preventing excessively high local temperatures. On the other hand, the mesoporous structure of the nitrogen-doped carbon support optimizes mass transfer efficiency, allowing reactants and products to pass quickly through the support pores, reducing the retention and deposition of carbon species within the pores. Simultaneously, the uniform dispersion of Pt-Co alloy particles prevents local concentration of active sites, preventing carbon deposition due to excessive local reactions. In contrast, the comparative example, either due to an insufficient water-to-methanol ratio leading to inadequate water vapor and inability to promptly eliminate carbon species, or due to poor catalyst conductivity resulting in local hot spots, or due to disordered support pore structure leading to poor mass transfer, all resulted in a significantly higher carbon deposition rate than Example 2.

[0100] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for catalytic hydrogen production from methanol steam reforming at low temperature, characterized in that, The method comprises the following steps: S1. Raw material preparation: mixing methanol and deionized water to obtain a raw material solution; S2. Vaporization and preheating: the raw material solution is fed into a vaporizer by a metering pump, and after vaporization at 120-180 DEG C, a mixed gas is obtained, which is mixed with circulating hydrogen gas and preheated to the reaction temperature to obtain a mixed gas; S3. Reformation reaction: the mixed gas is passed through a fixed bed reactor filled with Pt-Co / N-C catalyst, the reaction conditions are: temperature 120-180℃, pressure 0.3-0.7 MPa, weight space velocity 2500-3500 mL·g -1 ·h -1 -1, contact time 0.5-1 s, to obtain a high-temperature reformed gas; S4. Product post-treatment: after heat exchange with the raw material solution, the high-temperature reforming gas is cooled to room temperature by circulating water, and after gas-liquid separation, the liquid phase is returned to the raw material system, and the gas phase is purified by a PSA system to obtain hydrogen gas.

2. The method for producing hydrogen from methanol by steam reforming at low temperature according to claim 1, characterized in that, The preparation method of the Pt-Co / N-C catalyst is as follows: (1) graphene oxide is added to deionized water, ultrasonic dispersion is performed for 10-20 min to obtain a dispersion liquid, aniline and ferric nitrate are added, and ammonium persulfate is added under stirring at a temperature of 0-5 DEG C, reaction is performed for 8-12 h, the obtained solid is filtered, washed and dried to obtain Fe-PANI / GO; Fe-PANI / GO is placed in a tube furnace, heated to 600-700 DEG C at a heating rate of 3-7 DEG C / min under nitrogen protection, cooled to room temperature, ground through a 10-20 mesh sieve to obtain a pyrolysis product; (2) the pyrolysis product is added to dilute hydrochloric acid under ultrasonic for 8-12 h, filtered, washed with deionized water until neutral, and dried to obtain a nitrogen-doped carbon carrier; (3) chloroplatinic acid and cobalt nitrate are added to deionized water, stirred for 20-40 min to obtain a mixed salt solution, the nitrogen-doped carbon carrier is added to the mixed salt solution, stirred and ultrasonic is performed for 20-40 min, filtered, dried, and reduced in a hydrogen / argon mixed gas at a heating rate of 1-3 DEG C / min to 300-400 DEG C for 1-3 h, cooled to room temperature to obtain a Pt-Co / N-C catalyst.

3. The method for producing hydrogen from methanol by steam reforming at low temperature according to claim 1, characterized in that, The molar ratio of methanol to deionized water in S1 is 1:2-3.

4. The method for producing hydrogen from methanol by steam reforming at low temperature according to claim 1, characterized in that, The volume ratio of the mixed gas to the circulating hydrogen gas in S2 is 1:0.03-0.07, and the circulating hydrogen gas refers to a part of the crude hydrogen gas introduced before the gas phase after gas-liquid separation in the product post-treatment is purified by the PSA system.

5. The method for producing hydrogen from methanol by steam reforming at low temperature according to claim 1, characterized in that, In the PSA system in S4, active alumina, activated carbon and molecular sieves are filled, and due to the difference in adsorption characteristics of the gas components, different components form adsorption enrichment zones at different positions in the PSA system, the strongest adsorption component CO2 is enriched at the inlet end of the PSA system, the weakest adsorption component H2 is enriched at the outlet end of the PSA system, and the remaining components are distributed in the middle part of the PSA system according to the difference in adsorption strength, thereby realizing the separation and purification of hydrogen gas.

6. The method for producing hydrogen from methanol by steam reforming at low temperature according to claim 2, characterized in that, In (1), the weight ratio of graphene oxide, deionized water and aniline is 1:400-600:8-12, and the molar ratio of aniline, ferric nitrate and ammonium persulfate is 1:0.1-0.3:0.03-0.

05.

7. The method for producing hydrogen from methanol by steam reforming at low temperature according to claim 2, characterized in that, In (2), the weight ratio of the pyrolysis product to dilute hydrochloric acid is 1:8-12, and the concentration of dilute hydrochloric acid is 1 mol / L.

8. The method for producing hydrogen from methanol by steam reforming at low temperature according to claim 2, characterized in that, In (3), the molar ratio of chloroplatinic acid to cobalt nitrate is 1:1.8-2.

2.

9. The method for producing hydrogen from methanol by steam reforming at low temperature according to claim 2, characterized in that, The concentration of metal ions in the mixed salt solution in (3) is 3-7 wt%.

10. The method for producing hydrogen from methanol by steam reforming at low temperature according to claim 2, characterized in that, The nitrogen-doped carbon carrier in the (3) and the mixed salt solution are in a weight ratio of 1:15-25, and the hydrogen / argon mixed gas refers to hydrogen and argon mixed in a volume ratio of 5:95.