A bimetallic catalyst for hydrogen production via methanol steam reforming over a wide temperature range and its preparation method.

Abstract

This invention discloses a bimetallic catalyst for wide-temperature-range methanol steam reforming to produce hydrogen and its preparation method, belonging to the field of catalytic materials technology. The catalyst uses CuSiO3 as a support, Cu as the core non-precious metal catalytic component, and Pt as a low-proportion doped precious metal component, forming a bi-cluster structure. The preparation method includes steps such as copper ammonia solution preparation, CuSiO3 support synthesis, Pt loading, and calcination reduction. Uniform dispersion of Cu on SiO2 is achieved through copper ammonia complexation, followed by isothermal evaporation and stepwise pyrolysis reduction to form a Pt-Cu bi-cluster structure. This catalyst combines the cost advantages of non-precious metals with the high catalytic efficiency and CO poisoning resistance of precious metals, solving the technical pain points of traditional single-copper-based catalysts such as narrow temperature range adaptability, easy high-temperature deactivation, high CO selectivity, and high cost of pure platinum-based catalysts. It is perfectly suited for wide-temperature-range methanol steam reforming to produce hydrogen-fuel cell co-processing systems and has significant industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of catalytic materials technology, specifically relating to a bimetallic catalyst for wide-temperature-range methanol steam reforming hydrogen production and its preparation method, which is particularly suitable for wide-temperature-range hydrogen production scenarios in methanol steam reforming hydrogen production-fuel cell co-processing systems. Background Technology

[0002] Hydrogen energy, as a clean and efficient secondary energy source, has become a core industry demand due to its efficient and low-cost production. Methanol steam reforming for hydrogen production has become the mainstream technology for distributed hydrogen production and in-situ hydrogen supply from fuel cells due to its convenient raw material storage and transportation and mild reaction conditions, showing broad application prospects.

[0003] In existing methanol steam reforming hydrogen production technologies, the mainstream catalyst is the Cu-SiO2 single copper-based catalyst. However, this type of catalyst has significant limitations: poor adaptability over a wide temperature range, low catalytic activity at low temperatures, and easy sintering and deactivation of copper grains at high temperatures. Furthermore, its high selectivity for carbon monoxide (CO) makes it highly susceptible to electrode poisoning in fuel cells, failing to meet the hydrogen supply requirements of fuel cells. To address these issues, the industry has developed precious metal catalysts such as platinum-ruthenium alloys, which exhibit excellent resistance to CO poisoning and high catalytic activity. However, platinum and ruthenium are rare and precious metals, resulting in extremely high raw material costs and hindering large-scale industrial application.

[0004] Some studies have attempted to use a bimetallic modification route combining non-precious metals and platinum to optimize catalyst performance through synergistic effects. However, due to limitations in preparation processes, existing bimetallic catalysts generally suffer from uneven dispersion of active components and weak bimetallic synergistic effects, failing to simultaneously achieve hydrogen production efficiency, operational stability, and low CO selectivity, thus making it difficult to meet the practical operating requirements of methanol reforming-fuel cell co-processing. Therefore, developing a cost-effective methanol steam reforming hydrogen production catalyst with good wide temperature range adaptability, high activity, and low CO selectivity has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] To address the aforementioned deficiencies in existing technologies, the present invention aims to provide a bimetallic catalyst for wide-temperature-range methanol steam reforming hydrogen production and its preparation method. This invention solves the technical pain points of traditional single copper-based catalysts, such as narrow temperature range adaptability, easy deactivation at high temperatures, high CO selectivity, and high cost and industrialization difficulty of pure platinum-based / platinum-ruthenium alloy catalysts. It achieves a balance between controllable cost, high activity over a wide temperature range, low CO selectivity, and long-term stability, thus meeting the practical application requirements of methanol steam reforming hydrogen production-fuel cell co-processing systems.

[0006] To achieve the above objectives, the present invention provides a bimetallic catalyst for hydrogen production by methanol steam reforming in a wide temperature range. The catalyst is a Pt-Cu bimetallic supported catalyst with CuSiO3 as the support. The active components include metallic Cu and metallic Pt, wherein the molar ratio of Cu to Pt is 20:1 to 40:1.

[0007] Furthermore, the molar ratio of Cu to Pt is 30:1.

[0008] The present invention also provides a method for preparing the bimetallic catalyst as described above, comprising the following steps: (1) Dissolve the copper source in deionized water, add concentrated ammonia and stir to obtain a copper ammonia solution; (2) Add SiO2 to the copper ammonia solution obtained in step (1), stir to disperse, and then let it stand for aging to obtain a suspension; (3) Heat the suspension obtained in step (2) and adjust the pH to alkaline to obtain the suspension after reaction; (4) Wash and filter the suspension obtained in step (3), and dry the resulting filter cake to obtain CuSiO3 support; (5) Dissolve the CuSiO3 support obtained in step (4) and the platinum source in deionized water, heat and evaporate to dryness to obtain a solid; (6) The solid obtained in step (5) is subjected to a first heat treatment in an air atmosphere and a second heat treatment in a reducing atmosphere to obtain the bimetallic catalyst.

[0009] Furthermore, the copper source mentioned in step (1) is copper nitrate; the stirring time is 4 to 6 hours, and the stirring speed is 300 to 600 rpm.

[0010] Furthermore, in step (2), the stirring time is 2 to 4 hours, the stirring speed is 300 to 600 rpm, and the aging time is 6 to 12 hours.

[0011] Furthermore, in step (3), the heating temperature is 70~90℃, the stirring time is 2~3 hours, and the stirring speed is 300~600 rpm; the pH is adjusted to 9~11.

[0012] Furthermore, in step (4), the drying temperature is 90~110℃ and the drying time is 10~14 hours.

[0013] Furthermore, the platinum source mentioned in step (5) is platinum tetrachloride; the heating temperature is 60~70℃, and the heating time is 1~2 hours.

[0014] Furthermore, the process conditions for the first heat treatment in step (6) are: 5℃·min -1The temperature is increased to 300-500℃ at a heating rate, and pyrolysis is performed for 2-4 hours; the process conditions for the second heat treatment are: under a 10% H2 / Ar atmosphere, at a heating rate of 5℃·min -1 The heating rate is increased to 300~500℃, and pyrolysis is carried out for 3~5 hours.

[0015] The present invention also provides the application of the bimetallic catalyst prepared according to the above-described method or the bimetallic catalyst prepared according to the above-described method in the production of hydrogen by methanol steam reforming.

[0016] The beneficial effects of this invention are: This invention uses non-precious metal Cu as the core catalytic component, with precious metal Pt only as a low-proportion doping, significantly reducing the amount of precious metal used and effectively retaining the cost advantage of non-precious metal-based catalysts, meeting the economic needs of large-scale industrial production. In the dual-cluster structure formed by Cu and Pt, the Pt clusters can activate the low-temperature catalytic activity of the Cu unit cell while effectively inhibiting the high-temperature sintering deactivation of Cu grains. This allows the catalyst to maintain high activity across a wide temperature range from 170℃ to 350℃, achieving high methanol conversion at 260℃ and above, making it the only existing catalyst system to achieve full conversion across a wide temperature range. The Pt clusters possess a collective resistance to CO poisoning, effectively blocking the CO generation pathway during methanol reforming, and this effect remains stable across a wide temperature range. The catalyst of this invention has an initial CO selectivity of only 0.23%, which only rises to 0.74% after a 100-hour long-cycle reaction, far below the CO tolerance threshold of fuel cell electrodes, completely solving the fuel cell poisoning problem caused by the high CO selectivity of traditional Cu-based catalysts. This invention leverages the stable structure of the CuSiO3 support and the synergistic effect of the Pt-Cu bi-clusters. The catalyst undergoes a 100-hour long-cycle reaction at a core reaction temperature of 260℃, exhibiting no sudden drop in methanol conversion or increase in CO selectivity. Its performance is significantly superior to pure Cu-based and other bimetallic catalysts, making it perfectly suited for continuous operation in methanol steam reforming for hydrogen production in fuel cells. The invention employs a preparation process involving copper-ammonia complexation, isothermal evaporation, and stepwise calcination reduction. This process is simple and easy to operate, with highly controllable process parameters, uniform dispersion of the active components, and good product repeatability, facilitating industrial-scale production. Attached Figure Description

[0017] Figure 1 The graphs show the methanol conversion rates at different reaction temperatures for Examples 1-3 and Comparative Examples 1-4. Figure 2 The graphs show the CO selectivity performance at different reaction temperatures for Examples 1-3 and Comparative Examples 1-4. Figure 3 This is a graph showing the long-term conversion rate and CO selectivity of Example 1 of the present invention at a reaction temperature of 260°C. Detailed Implementation

[0018] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. These embodiments are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0019] Example 1: A Pt-Cu bimetallic methanol reforming hydrogen production catalyst, the preparation method of which includes the following steps: 1) Dissolve 1.343 g of anhydrous copper nitrate in 30 ml of deionized water and stir. Add concentrated ammonia dropwise until the pH is about 10. After stirring for 4 hours, the solution turns into a deep blue transparent copper ammonia solution. 2) Add 0.43 g of commercial SiO2 to the dark blue transparent copper ammonia solution in 1), stir for 4 hours, and let stand for 12 hours to age; 3) Heat the suspension obtained in step 2) in an 80°C constant temperature oil bath for 2 hours; 4) The suspension obtained in 3) was washed three times with deionized water and anhydrous ethanol to remove nitrate. The resulting filter cake was dried at 100°C for 12 hours to finally obtain CuSiO3 support. 5) Dissolve 1 gram of the CuSiO3 support obtained in 4) and 0.081 grams of platinum tetrachloride in 10 ml of deionized water, and heat at a constant temperature of 65°C for 2 hours until no liquid remains; 6) The solid obtained in step 5) is heated in a muffle furnace at 5 °C·min. -1 The temperature was increased from room temperature to 400℃ for pyrolysis over 4 hours. After cooling, the mixture was transferred to a tube furnace and pyrolyzed at 5℃·min under 10% H2 / Ar gas conditions. -1 The temperature was increased from room temperature to 400℃ for 4 hours for pyrolysis, and finally a Pt-CuSiO3 catalyst with a Cu:Pt molar ratio of 30:1 was obtained.

[0020] Example 2: Compared with Example 1, the amount of platinum tetrachloride added in step 5 was adjusted to obtain a Cu:Pt molar ratio of 20:1 in the catalyst, while other conditions remained unchanged.

[0021] Example 3: Compared with Example 1, the amount of platinum tetrachloride added in step 5 was adjusted to obtain a Cu:Pt molar ratio of 40:1 in the catalyst, while other conditions remained unchanged.

[0022] Comparative Example 1 Compared with Example 1, the amount of platinum tetrachloride added in step 5 was adjusted to obtain a Cu:Pt molar ratio of 10:1 in the catalyst, while other conditions remained unchanged.

[0023] Comparative Example 2 Compared with Example 1, the amount of platinum tetrachloride added in step 5 was adjusted to obtain a Cu:Pt molar ratio of 50:1 in the catalyst, while other conditions remained unchanged.

[0024] Comparative Example 3 Compared to Example 1, the mass of platinum tetrachloride was changed to 0g, while other conditions remained unchanged.

[0025] Comparative Example 4 Compared with Example 1, anhydrous copper nitrate was replaced with nickel nitrate hexahydrate, and the Ni:Pt molar ratio in the prepared catalyst was 30:1, while other conditions remained unchanged.

[0026] Performance testing methods: 1g of catalyst (50 mesh particle size) was loaded into the isothermal zone of a fixed-bed quartz tube reactor, and fixed at both ends with quartz wool. 11g of quartz sand was added to the lower end of the reactor, and 6g of quartz sand was added to the upper end. Before the reaction, the catalyst needed to be pretreated in a reducing atmosphere. It was reduced to 400℃ for 4 hours in a 10% H₂ / Ar atmosphere at a heating rate of 5℃ / min before being added to the reactor. Before the reaction started, Ar gas was introduced to purge the air in the reactor. After the reaction temperature was reached, a methanol-water solution (water-to-ethanol ratio of 2) was introduced into the reactor at a rate of 0.07ml / min using a constant flow pump. Finally, the gas from the methanol-water vapor reforming was passed into a GC (gas chromatograph) to analyze its composition.

[0027] Table 1 shows the methanol conversion and CO selectivity of the catalysts in Examples 1-3 and Comparative Examples 1-4 at different temperatures. Long-term performance test results are shown in [Table 1]. Figure 3 .

[0028] Table 1. Results of methanol conversion and CO selectivity tests for different catalysts.

[0029] Combination Figure 1 and Figure 2Example 1 achieved a 93% conversion rate at a low temperature of 170℃, high methanol conversion at 260℃ and above, and maintained no degradation at a high temperature of 350℃, making it the only catalyst among all samples to achieve full conversion over a wide temperature range. The Pt clusters in a 30:1 ratio form a highly efficient bi-cluster synergistic structure with Cu. The Pt clusters activate the low-temperature catalytic activity of the Cu moiety while inhibiting high-temperature sintering of Cu grains, allowing the catalyst to maintain high activity at both low and high temperatures, perfectly leveraging the bimetallic synergistic effect. Furthermore, the Pt clusters possess a collective anti-CO poisoning effect, effectively blocking the CO generation pathway during methanol reforming. This effect remains stable over a wide temperature range and does not significantly weaken even with increased temperature, providing a core guarantee for low CO selectivity. Comparative Example 3, a pure Cu system without Pt, exhibits extremely high CO selectivity, more than 15 times that of Example 1, directly demonstrating that Pt clusters are the only effective means to solve the problem of high CO selectivity in traditional Cu-based catalysts. In Example 3, the Cu:Pt ratio was increased to 40:1. Pt began to tend to be dispersed into single atoms, and no complete Pt clusters were formed. Single Pt atoms could not form a collective synergistic effect, and the activation and sintering inhibition effects on Cu units were weakened. Therefore, its overall conversion rate was lower than that of Example 1, showing that Pt clusters can improve methanol conversion efficiency more than single Pt atoms.

[0030] In Comparative Example 1, the Pt ratio was too high, resulting in disordered cluster structure and disrupting the Cu-Pt synergistic equilibrium. In Comparative Example 2, the Pt ratio was too low, failing to form effective Pt clusters; Pt was almost a single atom in quantity and insufficient. Neither example exhibited a complete dual-cluster synergistic effect, demonstrating that the formation of Pt clusters requires a strict ratio range; deviation from this range leads to the failure of the synergistic effect. Without Pt doping, there was no catalytic enhancement effect from Pt; the Cu-based unit exhibited low low-temperature activity and was prone to sintering at high temperatures. Ni, after replacing Cu, could not form a cluster synergistic structure with Pt.

[0031] Traditional Cu-based catalysts suffer from poor wide-temperature adaptability and high CO selectivity, essentially due to the lack of precious metals in their high-efficiency modification; pure Pt-based catalysts are costly, primarily due to excessive Pt dosage. This invention, through a design that controls the proportion of Pt clusters, achieves both low-proportion Pt doping and maximizes the synergistic effect of these clusters, fundamentally resolving the industry's core technical challenge of balancing cost and performance at the phase level. The catalyst formed by Pt clusters at a 30:1 ratio achieves high methanol conversion and extremely low CO selectivity over a wide temperature range, with controllable cost, making it perfectly suited for methanol steam reforming to hydrogen production-fuel cell co-processing systems.

[0032] Example 1, as the optimal Pt-CuSiO3 bimetallic catalyst of this patent (Cu:Pt=30:1), demonstrates its 100-hour long-term performance in a methanol steam reforming hydrogen production reaction at 260℃. This represents a comprehensive implementation and direct verification of the core invention of the patent. The catalyst utilizes the precisely designed 30:1 optimal ratio to form a complete Pt-Cu bi-cluster structure. Combined with a CuSiO3 support prepared by copper-ammonia complexation and high-temperature drying, and a stepwise preparation process of muffle furnace pyrolysis + tube furnace H2 / Ar reduction, the Pt clusters synergistically activate the catalytic activity of Cu elementary elements and inhibit the high-temperature sintering of Cu grains. Furthermore, the collective resistance of the Pt clusters... The CO poisoning effect continuously blocks the CO generation pathway, achieving excellent performance over a long period: initially, a high methanol conversion rate and an extremely low CO selectivity of 0.23% are achieved. During the 100-hour long-cycle reaction, the conversion rate only slowly and smoothly declines to 94%, and the CO selectivity increases slightly to 0.74%. At the 60-hour node, the conversion rate and CO selectivity stabilize at 97% and 0.45%, respectively. There is no sudden drop in activity or sudden increase in CO selectivity throughout the process, which is far superior to pure Cu-based catalysts and other comparative catalysts. This long-cycle performance not only solves the industry pain points of traditional single Cu-based catalysts, such as poor wide-temperature adaptability, easy sintering and deactivation at high temperatures, and high CO selectivity, but also significantly reduces the amount of precious metals used by low proportion of Pt doping, taking into account the cost requirements of industrialization. At the same time, the consistently low CO selectivity over a long period is far below the CO tolerance threshold of fuel cell electrodes, perfectly adapting to the actual working conditions of methanol steam reforming hydrogen production-fuel cell co-processing. This fully demonstrates the core technical advantages of the patented dual-cluster structure design in terms of high activity, low CO selectivity and long-cycle stability over a wide temperature range.

[0033] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A bimetallic catalyst for hydrogen production via methanol steam reforming over a wide temperature range, characterized in that, The catalyst is a Pt-Cu bimetallic supported catalyst with CuSiO3 as the support. The active components include metallic Cu and metallic Pt, wherein the molar ratio of Cu to Pt is 20:1 to 40:

1.

2. The bimetallic catalyst according to claim 1, characterized in that, The molar ratio of Cu to Pt is 30:

1.

3. A method for preparing a bimetallic catalyst as described in claim 1 or 2, characterized in that, Includes the following steps: (1) Dissolve the copper source in deionized water, add concentrated ammonia and stir to obtain a copper ammonia solution; (2) Add SiO2 to the copper ammonia solution obtained in step (1), stir to disperse, and then let it stand for aging to obtain a suspension; (3) Heat the suspension obtained in step (2) and adjust the pH to alkaline to obtain the suspension after reaction; (4) Wash and filter the suspension obtained in step (3), and dry the resulting filter cake to obtain CuSiO3 support; (5) Dissolve the CuSiO3 support obtained in step (4) and the platinum source in deionized water, heat and evaporate to dryness to obtain a solid; (6) The solid obtained in step (5) is subjected to a first heat treatment in an air atmosphere and a second heat treatment in a reducing atmosphere to obtain the bimetallic catalyst.

4. The preparation method according to claim 3, characterized in that, The copper source mentioned in step (1) is copper nitrate; the stirring time is 4 to 6 hours and the stirring speed is 300 to 600 rpm.

5. The preparation method according to claim 3, characterized in that, In step (2), the stirring time is 2 to 4 hours, the stirring speed is 300 to 600 rpm, and the aging time is 6 to 12 hours.

6. The preparation method according to claim 3, characterized in that, In step (3), the heating temperature is 70~90℃, the stirring time is 2~3 hours, and the stirring speed is 300~600 rpm; the pH is adjusted to 9~11.

7. The preparation method according to claim 3, characterized in that, In step (4), the drying temperature is 90~110℃ and the drying time is 10~14 hours.

8. The preparation method according to claim 3, characterized in that, The platinum source mentioned in step (5) is platinum tetrachloride; the heating temperature is 60~70℃ and the heating time is 1~2 hours.

9. The preparation method according to claim 3, characterized in that, The process conditions for the first heat treatment in step (6) are: 5℃·min -1 The temperature is increased to 300-500℃ at a heating rate, and pyrolysis is performed for 2-4 hours; the process conditions for the second heat treatment are: under a 10% H2 / Ar atmosphere, at a heating rate of 5℃·min -1 The heating rate is increased to 300~500℃, and pyrolysis is carried out for 3~5 hours.

10. The application of the bimetallic catalyst according to claim 1 or 2, or the bimetallic catalyst prepared by any one of claims 3-9, in methanol steam reforming for hydrogen production.

Images