A noble metal-based catalyst, a preparation method and application thereof

Abstract

The application discloses a noble metal-based catalyst and a preparation method and application thereof, and the noble metal-based catalyst comprises a carrier, an auxiliary metal and an active metal, wherein the carrier is CeO2, the active metal is a noble metal of Group VIII, and the auxiliary metal comprises one or more of In, Mo, Cu and Mg; the active metal loading is 0.05% to 4% and the auxiliary metal oxide loading is 0.5% to 15% based on the total mass of the noble metal-based catalyst; the particle size of the CeO2 carrier is 4nm to 50mu, the specific surface area is 35.51 to 222.2m 2 g ‑1 2, and the pore volume is 0.04 to 0.34. The application improves the specific surface area and the pore volume of CeO2 by regulating the type of a template agent in a carrier preparation process and the heating rate in a calcination process, realizes high dispersion of Pt metal particles and auxiliary metals, and thus improves the conversion rate of methanol steam reforming for hydrogen production and the stability of the catalyst and reduces the CO selectivity.

Description

Technical Field

[0001] This invention relates to the fields of methanol vapor reforming for hydrogen production and catalyst technology, specifically to a noble metal-based catalyst, its preparation method, and its application. Background Technology

[0002] Methanol vapor reforming for hydrogen production is an efficient method for obtaining hydrogen and can be adapted to distributed applications in various settings. Therefore, it places higher demands on the hydrogen production process and the purity of the hydrogen. While traditional industrial copper-based catalysts exhibit high activity and selectivity, they also suffer from high self-ignition and low stability. In contrast, noble metal-based catalysts offer higher stability and reactivity, making them promising catalytic systems. Platinum-based catalysts are commonly used among these.

[0003] Traditional Pt-based catalysts primarily facilitate methanol cracking. Due to the lack of active sites for water dissociation on the support, water is difficult to decompose, resulting in the production of mainly CO and H2. Converting CO to CO2 is challenging, even though high conversion rates and stability are observed at medium to low temperatures. High CO concentrations significantly hinder subsequent hydrogen purification processes and poison fuel cell electrodes, causing rapid deactivation and severely impacting lifespan; this process is irreversible. Therefore, improving water decomposition and suppressing CO generation in Pt-based catalysts is a major challenge.

[0004] Mesoporous materials such as CeO2 or ZrO2 possess a certain specific surface area, a regular and ordered pore structure, and a narrow pore size distribution, and are commonly used as catalyst supports. CeO2 contains Ce... 3+ and Ce 4+ The conversion between valence states enables redox cycles, exhibiting excellent oxygen storage / release capabilities and rapid oxygen vacancy diffusion. As a catalyst support, it enhances water adsorption and promotes water decomposition, thus frequently used as a support in methanol steam reforming catalysts for hydrogen production. Currently, the oxygen vacancies in CeO2 within Pt / CeO2 catalysts are insufficient for complete water dissociation, resulting in high CO selectivity when used in methanol steam reforming for hydrogen production. Furthermore, a dilemma exists between improving conversion / stability and reducing CO selectivity. Increasing catalytic activity solely to improve conversion / stability leads to higher CO selectivity, which significantly hinders subsequent hydrogen purification. Conversely, reducing CO selectivity results in lower conversion / stability.

[0005] Therefore, for Pt / CeO2 catalysts used in methanol steam reforming to produce hydrogen, the problem that people hope to solve is how to simultaneously improve methanol conversion and catalyst stability, as well as reduce CO selectivity.

[0006] To address the above problems, this invention is proposed. Summary of the Invention

[0007] This invention aims to overcome the shortcomings of existing technologies. Addressing the dilemma of balancing improved conversion / stability with reduced CO concentration in Pt / CeO2 catalysts used for methanol vapor reforming to produce hydrogen, this invention improves the specific surface area and pore volume of the support by adjusting the template agent in the support preparation process and the heating rate during support calcination. This enhances the dispersibility of the active metal and additives, thereby reducing CO selectivity while maintaining excellent methanol conversion and catalytic stability, resulting in hydrogen-rich gas with low CO concentration.

[0008] The technical solution adopted in this invention is as follows:

[0009] The first aspect of this invention provides a noble metal-based catalyst, comprising a support, a promoter metal, and an active metal, wherein the support is CeO2, the active metal is a Group VIII noble metal, and the promoter metal includes one or more of In, Mo, Cu, and Mg; based on the total mass of the noble metal-based catalyst, the active metal loading is 0.05%–4%, and the promoter metal oxide loading is 0.5%–15%; the CeO2 support has a particle size of 4 nm–50 μm and a specific surface area of ​​35.51–222.20 m². 2 g -1 The pore volume is 0.04-0.34.

[0010] Preferably, the CeO2 support is composed of 50-150nm nanoparticles formed by stacking 4-10nm nanoparticles.

[0011] Preferably, the active metal includes one or more of Pt, Pd, Ru, and Rh, and the valence state of the active metal is 0-2; based on the total mass of the noble metal-based catalyst, the active metal loading is 1%, and the auxiliary metal oxide loading is 7%.

[0012] A second aspect of the present invention provides a method for preparing the noble metal-based catalyst described in the first aspect of the present invention, comprising the following steps:

[0013] (1) Preparation of the carrier;

[0014] (2) Loaded with active metals and auxiliary metals;

[0015] In step (1), the CeO2 support is prepared using the sol-gel method, which includes the following steps:

[0016] (11) The ethanol solution for preparing the template agent is solution A; the aqueous solution for preparing the complexing agent is solution B; and the aqueous solution for preparing the cerium salt is solution C.

[0017] (12) Mix solution B and solution C to obtain a mixed solution, then add solution A dropwise to the mixed solution to obtain a suspension, stir the suspension, and then let it stand to obtain a sol;

[0018] (13) The sol obtained in step (2) is dried and calcined to obtain the carrier.

[0019] Preferably, in step (11), the concentration of solution A is 0.01–2 M; the concentration of solution B is 0.05–5 M; the concentration of solution C is 0.1–10 M; the cerium salt includes inorganic salts or organic salts, wherein the inorganic salts include nitrates and chlorates, and the organic salts include acetates; the template agent is selected from hexadecyltrimethylammonium bromide, diethylamine, and ethylenediaminetetraacetic acid; the complexing agent is selected from citric acid, ascorbic acid, ammonia, or urea.

[0020] In step (12), the stirring temperature is room temperature, the stirring time is 1-10h, and the standing time is 0.5h-5h.

[0021] In step (13), the drying conditions are: drying temperature is 40-200℃, drying time is 1-7 days; the calcination conditions are: heating rate is 0.1-100℃ / min, calcination temperature is 350-800℃, and calcination time is 2-24h.

[0022] Preferably, in step (2), the active metal and additives are loaded using a co-impregnation method, which includes the following steps:

[0023] (21) Prepare a soluble active metal salt solution; prepare a soluble auxiliary agent salt solution;

[0024] (21) The support is poured into a mixed solution of active metal solution and auxiliary agent solution, and the mixture is shaken while pouring. After sonication, it is placed for impregnation, and then dried and calcined to obtain a noble metal-based catalyst.

[0025] Preferably, in step (21), the concentration of the active metal in the active metal salt solution is 0.05–4 M; and the concentration of the auxiliary metal in the auxiliary salt solution is 0.1–10 M.

[0026] In step (22), the ultrasonic time is 5-120 min, the immersion temperature is room temperature, and the immersion time is 1-24 h;

[0027] The drying conditions are as follows: drying temperature is 40-70℃, drying time is 4-24h; the calcination conditions are as follows: calcination environment is air, calcination temperature is 300-800℃, calcination time is 2-12h.

[0028] The third aspect of the present invention provides an application of the noble metal-based catalyst described in the first aspect of the present invention in the methanol vapor reforming hydrogen production reaction.

[0029] Preferably, the precious metal-based catalyst is shaped and crushed, and sieved to obtain particles of 20-100 mesh. Then, it is mixed with quartz sand of the same particle size. Subsequently, the mixture of precious metal-based catalyst and quartz sand is loaded into a fixed bed for in-situ reduction. The reduction temperature is 250-500℃, the reduction time is 1-8h, and the reduction atmosphere is a mixture of hydrogen and nitrogen. The volume percentage of hydrogen in the mixture is 5%-50% of the total volume of hydrogen and nitrogen. After in-situ reduction, methanol vapor reforming is carried out to produce hydrogen.

[0030] The mass ratio of the precious metal-based catalyst to the quartz sand is 1:X (X = 1-10);

[0031] The methanol vapor reforming reaction for hydrogen production is carried out at atmospheric pressure, with a reaction temperature of 200℃ to 420℃, a water-to-carbon ratio of 1 to 5, and a methanol mass hourly space velocity of 1 to 20 h⁻¹. -1 The preferred temperature is 340℃, the preferred water-to-carbon ratio is 1, and the preferred mass hourly space velocity is 3 h⁻¹. -1 .

[0032] Preferably, the noble metal-based catalyst described in the first aspect of the present invention is used to improve methanol conversion and reduce CO selectivity.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. This invention successfully prepared a noble metal-based catalyst with highly dispersed active metal and auxiliary metal. The noble metal-based catalyst comprises a support, an auxiliary metal, and an active metal, wherein the support is CeO2, the CeO2 support has a particle size of 4 nm-50 μm, and a specific surface area of ​​35.51-222.20 m². 2 g -1 The pore volume is 0.04-0.34. This invention provides a noble metal-based catalyst for methanol steam reforming to produce hydrogen. It can reduce CO selectivity while ensuring excellent methanol conversion and catalytic stability, thereby obtaining hydrogen-rich gas with low CO concentration.

[0035] 2. This invention discovers that the particle size, specific surface area, and pore volume of a carrier can be significantly altered simply by controlling the calcination rate during carrier preparation. This invention, by changing the calcination rate, yields nanoparticles of 50-150 nm (222.20 nm) stacked from 4-10 nm nanoparticles. 2 g -1 Specific surface area and 0.34 cm² 3 CeO2 (CTAB-0.1℃ / min) mesoporous nanomaterials with a pore volume of / g, while the specific surface area of ​​currently commercial CeO2 supports is only 20m². 2Using the CeO2 support prepared in this invention as a catalyst at approximately / g can achieve high dispersion of Pt metal particles and auxiliary metals. The highly dispersed auxiliary can promote the dissociation of water, thereby improving the conversion rate of methanol steam reforming to produce hydrogen, the stability of the catalyst, and reducing CO selectivity.

[0036] 3. The sol-gel method is used to prepare the support. The choice of template agent in the preparation process has an important impact on the particle size, specific surface area and pore volume of the support. The present invention uses CTAB as a template, which is more conducive to improving the specific surface area and pore volume of the support, thereby improving the dispersibility of active metals and additives and improving the performance of the catalyst.

[0037] 4. This invention improves the dispersibility of Pt by introducing an auxiliary metal. The In₂O₃ surface is readily reduced to form oxygen vacancies, which greatly promotes water decomposition and further enhances the dispersion of the active metal Pt, causing Pt to exhibit a +2 valence, meaning the Pt surface is more electron-deficient. This allows the reaction to primarily follow the methanol vapor reforming hydrogen production pathway, i.e., the CO₂ generation pathway, significantly suppressing CO formation and maintaining a low CO concentration over a wide range of medium and high temperatures. Furthermore, due to the larger specific surface area of ​​the carrier in this invention, Pt and In₂O₃ can form a highly dispersed load, suppressing clustering and sintering, increasing hydrothermal stability, and altering the surface charge state of Pt, causing Pt to exhibit a positive valence. δ+ or Pt 2+ . Attached Figure Description

[0038] Figure 1 The images show X-ray diffraction characteristics of the catalysts and supports used in Examples 1 and 2.

[0039] Figure 2 The catalyst and support of Example 1 are shown by SEM characterization. Where a represents the support and be represents the catalyst.

[0040] Figure 3 The catalyst and support of Example 2 are characterized by SEM and TEM. Here, ab represents the support, and cd represents the catalyst.

[0041] Figure 4 XPS characterization of the catalysts in Examples 1 and 2.

[0042] Figure 5 The performance of methanol vapor reforming for hydrogen production was tested for the catalysts of Comparative Example 1 and Comparative Example 2.

[0043] Figure 6 The methanol vapor reforming hydrogen production performance of the catalysts in Examples 1 and 2 was tested.

[0044] Figure 7Catalyst lifetime tests for Examples 1 and 2. Detailed Implementation

[0045] The present invention will be further described below through embodiments, but is not limited to these embodiments. Experimental methods not specifically described in the embodiments generally use conventional conditions and conditions described in manuals, or conditions recommended by the manufacturer. The general equipment, materials, reagents, etc., used are all commercially available unless otherwise specified.

[0046] The purpose of this invention is to provide a preparation method that allows for the control of the specific surface area of ​​the support, resulting in high specific surface area CeO2 nanoparticle supports. This improves the dispersion of the auxiliary agent In2O3 and the active metal Pt, enhances the interaction among the three, facilitates charge transfer, increases water dissociation sites, improves competition in the CO2 reaction pathway, and reduces competition in the CO formation pathway. This method also provides a method for preparing highly dispersed catalysts of noble metals such as Pt. The catalyst uses CTAB (hexadecyl trimethyl ammonium bromide), diethylamine, and EDTA (ethylenediaminetetraacetic acid) as templates at a concentration of 0.2-0.8 M, with CeO2 as the catalyst carrier. 3+ Inorganic salts such as nitrates and chlorates, and organic salts such as acetates, are used as cerium sources. Citric acid, ascorbic acid, ammonia, or urea (concentration 0.5-1.5M) are added and stirred to form a sol. After drying, a gel is formed, poured into a borosilicate petri dish, and transferred to a muffle furnace. The calcination temperature is varied (10℃ / min, 5℃ / min, 0.5℃ / min, 0.1℃ / min, etc.) and calcined at 350-1000℃ for 2-8 hours to change the carrier size. The formation of pores and mesopores yielded CeO2 macroporous bulk materials and mesoporous CeO2 nanoparticles with large specific surface area. At least one of Group VIII noble metals, such as Pt, Pd, Ru, and Rh, was loaded as the active metal via co-impregnation, achieving high dispersion at low loading levels (0.05%–4%). In, Mo, Cu, and Mg were loaded as additives to assist in the dispersion of the noble metals and promote water dissociation; the addition amounts ranged from 0.5% to 15%. After calcination, in-situ reduction was performed, and the resulting catalyst was packed into a fixed bed for methanol steam reforming to produce hydrogen. The catalyst was characterized by XRD, BET, SEM, TEM, XPS, and H2-TPR, verifying that the support possessed a microstructure of 35.51–222.2 μm. 2 g -1 The high specific surface area of ​​the material results in high dispersion of the additive In2O3 and the active metal Pt.

[0047] Commercial CeO2 typically has a specific surface area of ​​20 m². 2 g -1The surface area of ​​the CeO2 carrier obtained by the method of this invention is approximately 222.20 m². 2 g -1 Pt metal particles are highly dispersed and exhibit positive valence. In2O3 achieves high dispersion of nanoparticles and disperses and immobilizes the active component noble metal, thus achieving high performance, high stability, and low CO selectivity in high-temperature methanol-to-hydrogen production.

[0048] The specific steps of the method described in this invention are as follows:

[0049] Example 1:

[0050] Preparation of CeO2 support:

[0051] First, prepare CTAB ethanol solution (solution A) with a concentration of 0.35M; prepare citric acid monohydrate aqueous solution (solution B) with a concentration of 0.97M; prepare Ce... 3+ The salt solution was prepared as solution C, with a concentration of 1.67 M. Solutions B and C were mixed, and solution A was added dropwise to the mixture to obtain a suspension. The suspension was stirred at room temperature for 2 hours and then poured into a 90 cm diameter borosilicate glass petri dish resistant to high-temperature calcination. After standing for 1 hour, a sol was formed. The synthesized sol was dried in an oven at 60 °C for 3 days to obtain a gel. This gel was then transferred to a muffle furnace for programmed temperature-controlled calcination, with a heating rate controlled at 5 °C / min, reaching 450 °C and maintaining the temperature for 4 hours. Particles with a diameter of 20 μm-40 μm and a particle size of 58.17 μm were obtained. 2 g -1 CeO2 (CTAB-5℃ / min) mesoporous material with specific surface area.

[0052] Using the prepared CeO2 as a support, active metal Pt and In2O3 additives were loaded using a co-impregnation method:

[0053] Prepare chloroplatinic acid solution, Pt 4+ The concentration is 0.21M; prepare an In(NO3)3 solution, In 3+ The concentration is 0.56M; transfer an appropriate amount of Pt 4+ Solution and In 3+The CeO2 support obtained in step one was weighed and added to the solution while being slowly added and shaken, and then sonicated for 30 min. After 12 h at room temperature, it was dried at 60 °C under vacuum for 12 h, and then calcined in air at 450 °C for 4 h to obtain the Pt-In2O3 / CeO2 (CTAB-5 °C / min) catalyst. The obtained powder was shaped and crushed, and sieved to obtain particles of 40-60 mesh for later use. Before use, the sieved catalyst particles were mixed with quartz sand of the same particle size at a ratio of 1:2, and then loaded into a fixed bed for in-situ reduction at 350 °C for 2 h in a 50% H2 / N2 mixed atmosphere.

[0054] Example 2

[0055] Compared with Example 1, the difference is that the heating rate during calcination is 0.5℃ / min.

[0056] The gel was obtained using the same method as described above and transferred to a muffle furnace for programmed temperature-controlled calcination. The heating rate was controlled at 0.5℃ / min, reaching 450℃ and maintaining the temperature for 4 hours. This yielded nanoparticles of 50-150nm size and 218.36 μm in diameter, formed by the aggregation of 4-10nm nanoparticles. 2 g -1 CeO2 (CTAB-0.5℃ / min) mesoporous nanomaterials with high specific surface area and Pt-In2O3 / CeO2 (CTAB-0.5℃ / min).

[0057] Example 3:

[0058] Compared with Example 1, the difference is that the heating rate during calcination is 0.1℃ / min.

[0059] The gel was obtained using the same method as described above and transferred to a muffle furnace for programmed temperature-controlled calcination. The heating rate was controlled at 0.1℃ / min, and the temperature was increased to 450℃ and maintained for 4 hours. This yielded nanoparticles of 50-150nm size and 222.20nm in diameter, formed by the aggregation of 4-10nm nanoparticles. 2 g -1 CeO2 (CTAB-0.1℃ / min) mesoporous nanomaterials with high specific surface area and Pt-In2O3 / CeO2 (CTAB-0.1℃ / min).

[0060] Example 4:

[0061] Compared with Example 1, the difference is that the heating rate during calcination is 10°C / min.

[0062] The gel was obtained using the same method as described above and transferred to a muffle furnace for programmed temperature-controlled calcination. The heating rate was controlled at 10 °C / min, and the temperature was increased to 450 °C and maintained for 4 hours. Particles with a diameter of 30 μm-50 μm and a particle size of 42.79 μm were obtained. 2 g -1 Mesoporous materials with specific surface area of ​​CeO2 (CTAB-10℃ / min) and Pt-In2O3 / CeO2 (CTAB-10℃ / min).

[0063] Example 5:

[0064] Compared with Example 1, the difference is that the template agent is EDTA.

[0065] First, prepare EDTA ethanol solution (solution A) with a concentration of 0.5M; prepare citric acid monohydrate aqueous solution (solution B) with a concentration of 0.97M; prepare Ce... 3+ The salt solution was prepared as solution B, with a concentration of 1.67 M. Solutions B and C were mixed, and solution A was added dropwise to the mixture to obtain a suspension. The suspension was stirred at room temperature for 2 hours, then poured into a high-temperature resistant calcining petri dish and allowed to stand for 3 hours to form a sol. The synthesized sol was dried in an oven at 50 °C for 2 days to obtain a gel. This gel was then transferred to a muffle furnace for programmed temperature-controlled calcination, with a heating rate controlled at 5 °C / min, reaching 500 °C and maintaining the temperature for 6 hours. A 35.51 M solution was obtained. 2 g -1 Mesoporous materials with specific surface area of ​​CeO2 (EDTA-5℃ / min) and Pt-In2O3 / CeO2 (EDTA-5℃ / min).

[0066] Example 6:

[0067] Compared with Example 1, the difference is that the template agent is diethylamine.

[0068] First, prepare an ethanolic solution of diethylamine (solution A) with a concentration of 0.45 M; prepare an aqueous solution of citric acid monohydrate (solution B) with a concentration of 0.91 M; prepare Ce... 3+ The salt solution was prepared as solution B, with a concentration of 1.67 M. Solutions B and C were mixed, and solution A was added dropwise to the mixture to obtain a suspension. This suspension was stirred at room temperature for 2 hours, then poured into a high-temperature resistant calcining petri dish and allowed to stand for 3 hours to form a sol. The synthesized sol was dried in an oven at 50 °C for 2 days to obtain a gel. This gel was then transferred to a muffle furnace for programmed temperature-controlled calcination, with a heating rate controlled at 5 °C / min, reaching 500 °C and maintaining this temperature for 6 hours. A 47.6 M solution was obtained. 2 g -1Mesoporous materials with specific surface area of ​​CeO2 (diethylamine -5℃ / min) and Pt-In2O3 / CeO2 (diethylamine -5℃ / min).

[0069] Comparative Example 1

[0070] The difference from Example 1 is that only the active metal Pt is loaded, and no In2O3 additive is added.

[0071] Pt was loaded using the impregnation method. A chloroplatinic acid solution was prepared, containing Pt. 4+ The concentration is 0.21M; transfer an appropriate amount of Pt 4+ The CeO2 support obtained in step one was weighed and added to the solution while being slowly added and shaken, and then sonicated for 30 min. After 12 h at room temperature, it was dried at 60 °C under vacuum for 12 h, and then calcined in air at 450 °C for 4 h to obtain the Pt / CeO2 (CTAB-5 °C / min) catalyst. The obtained powder was shaped and crushed, and sieved to obtain particles of 40-60 mesh for later use. Before use, the sieved catalyst particles were mixed with quartz sand of the same particle size at a ratio of 1:2, and then loaded into a fixed bed for in-situ reduction at 350 °C for 2 h in a 50% H2 / N2 mixed atmosphere.

[0072] Comparative Example 2

[0073] The difference from Example 2 is that only the active metal Pt is loaded, without the addition of In2O3 promoter. Pt is loaded by impregnation method, the same as in Comparative Example 1, to obtain a Pt / CeO2 (CTAB-0.5℃ / min) catalyst.

[0074] Comparative Example 3

[0075] The difference from Comparative Example 1 is that the supported active metal is Pd, and the catalyst also does not contain In2O3 promoter, resulting in Pd / CeO2 (CTAB-5℃ / min).

[0076] Comparative Example 4

[0077] The difference from Example 1 is that the active metal Pd is supported to obtain a Pd-In2O3 / CeO2 (CTAB-5℃ / min) catalyst supported on 1% Pt and 7% In2O3.

[0078] Comparative Example 5

[0079] The difference compared to Comparative Example 1 is that the carrier is commercial CeO2.

[0080] Using commercial cerium oxide as a carrier, ascorbic acid was added and stirred for 3 hours to modify and pretreat the commercial carrier. 1% Pt was loaded by the same impregnation method as in Comparative Example 1, and then dried and calcined in the same way as above to obtain Pt / CeO2 (commercial).

[0081] Comparative Example 6

[0082] The difference from Example 1 is that the carrier is commercial CeO2.

[0083] Using commercial cerium oxide as a carrier, ascorbic acid was added and stirred for 3 hours to modify and pretreat the commercial carrier. 1% Pt and 7% In2O3 were loaded by the same co-impregnation method as above, and after drying and calcination in the same manner as in Example 1, Pt-In2O3 / CeO2 (commercial) was obtained.

[0084] The specific surface area and pore volume data of different carrier samples are shown in Table 1.

[0085] XRD, SEM and TEM showed that a slower calcination rate resulted in smaller CeO2 particles, a larger specific surface area, and a larger mesopore volume, thus successfully obtaining CeO2 mesoporous materials.

[0086] Furthermore, successful loading of precious metals and additives can be observed by XRD, XPS and TEM, with precious metal loading at 1% and additive loading at 7%.

[0087] Figure 1 X-ray diffraction (XRD) images of the catalysts and supports from Examples 1 and 2. Figure 1 It can be seen that the main peaks are characteristic peaks of CeO2. The peak of CeO2 (CTAB-5℃ / min) is sharper than that of CeO2 (CTAB-0.5℃ / min), indicating that the former has a larger particle size and the latter has a smaller particle size. No Pt peaks were observed in Examples 1 and 2, indicating that Pt is highly dispersed. Figure 1 (ii) The In2O3 peaks observed in Example 1 but not in Example 2 indicate that In2O3 was highly dispersed in Example 2, while in Example 1, the small specific surface area and pore volume caused In2O3 agglomeration. This result can also be verified by... Figure 2 and Figure 3 This has been confirmed.

[0088] Figure 2 The images show SEM images of the catalyst and support from Example 1, where a represents the support and be represents the catalyst. It can be observed that the support consists of irregularly shaped large particles with honeycomb-like macropores. Figure 2 a), while the overall morphology of the catalyst did not change after In2O3 loading. Figure 2b) Aggregates of In2O3 were observed through mapping, with aggregated particles ranging from 50 to 500 nm. Figure 2 cd), and Figure 1 The conclusions are consistent. And... Figure 3 The SEM and TEM images from Example 2 show that the 50-150 nm nanoparticles are composed of smaller 4-10 nm nanoparticles stacked together. Figure 3 ab), while surface scans of Pt and In2O3 revealed that Pt and In2O3 were highly dispersed and did not aggregate. Pt was dispersed at the single-atom level or into particles smaller than 2 nm, while In2O3 was dispersed at the nanoscale. Figure 3 cd).

[0089] Figure 4 XPS characterization of Examples 1 and 2 mainly observed the changes in the valence states of Pt, O, and In₂O₃. In Example 1, Pt was in a near-zero valence state. δ+ The primary component is Pt, with a small amount of divalent Pt; while in Example 2, Pt is mainly composed of Pt. 2+ The majority is Pt, with a small portion being Pt. δ+ The divalent Pt indicates a strong interaction between Pt and In₂O₃ and CeO₂, which is the main reason for its high activity.

[0090] Table 1. Specific surface area and pore volume data of samples with different carriers.

[0091]

[0092]

[0093] As can be seen from the data in Table 1, under the same template agent, the slower the heating rate, the larger the specific surface area and pore volume of the CeO2 support. Under the same heating rate, the CeO2 support obtained with the template agent CTAB has a larger specific surface area and pore volume.

[0094] Application example:

[0095] The methanol vapor reforming hydrogen production catalysts prepared in Examples 1-6 and Comparative Examples 1-6 were used to evaluate the performance of the catalysts in methanol vapor reforming hydrogen production in a micro fixed-bed reactor with a transparent quartz tube. The reaction was carried out at atmospheric pressure, at a reaction temperature of 260-340℃, with a methanol to water ratio of 1:1 (mol / mol) in the feedstock, and a WHSV of 3 h⁻¹. -1 Nitrogen gas is used as the carrier gas during the reaction. The exhaust gas is condensed and then analyzed by an online gas chromatograph.

[0096] The key preparation conditions of the catalysts in Examples 1-6 and Comparative Examples 1-6, and the methanol conversion rate and CO selectivity of the prepared catalyst samples in the methanol steam reforming reaction for hydrogen production are shown in Table 2.

[0097] Table 2 Key preparation conditions and catalytic performance of different catalysts

[0098]

[0099]

[0100] The reaction products in Examples 1-2 and Comparative Examples 1-2 were characterized and analyzed, and the results are as Figure 5 and Figure 6 shown, mainly including the conversion rate of methanol (MeOH) and the selectivity of carbon monoxide (CO). The catalyst life test results of Example 2 and Example 1 are as Figure 7 shown. It can be seen from Figure 7 that the Pt-In2O3 / CeO2 (CTAB-0.5℃ / min) catalyst prepared by the present invention can still maintain a methanol conversion rate of 90% after being used for 130 hours. It can be seen that the Pt-In2O3 / CeO2 (CTAB-0.5℃ / min) catalyst prepared by the present invention has good stability in the methanol steam reforming reaction for hydrogen production.

[0101] The CeO2 support prepared by this invention can regulate the particle size and specific surface area, thereby changing and improving the activity of the support itself, making the catalyst have good activity and hydrothermal stability for methanol steam reforming to produce hydrogen. The results show that under the same reaction conditions, the slower the heating rate of the support, the larger the specific surface area, the better the dispersion of Pt and In2O3, and the better the catalyst performance.

[0102] It can be seen from the comparison of Comparative Example 1, Comparative Example 2 and Comparative Example 5 that when only Pt is loaded, the methanol conversion rate is ranked as Pt / CeO2 (CTAB-0.5℃ / min) > Pt / CeO2 (CTAB-5℃ / min) > Pt / CeO2 (commercial), and the CO concentration is just the opposite, Pt / CeO2 (CTAB-0.5℃ / min) < Pt / CeO2 (CTAB-5℃ / min) ≈ Pt / CeO2 (commercial).

[0103] It can be seen from the comparison of Comparative Example 1 and Comparative Example 3 that the catalytic performance of the catalyst loaded with the active metal Pd is similar to that loaded with Pt, and the methanol conversion rates of the two are close, only the CO concentration of Pd / CeO2 (CTAB-5℃ / min) is slightly higher.

[0104] Comparisons of Examples 1-6, Comparative Examples 4 and 6 show that the methanol conversion rate decreased after adding In2O3, but the CO conversion rate decreased significantly. Specifically, the methanol conversion rates were: Pt-In2O3 / CeO2 (CTAB -0.1℃ / min) > Pt-In2O3 / CeO2 (CTAB -0.5℃ / min) > Pt-In2O3 / CeO2 (CTAB -5℃ / min) > Pt-In2O3 / CeO2 (EDTA -5℃ / min) > Pt-In2O3 / CeO2 (diethylamine -5℃ / min) > Pt-In2O3 / CeO2 (CTAB -10℃ / min) > Pt-In2O3 / CeO2 (quotient). With the same template agent, a slower heating rate resulted in a higher methanol conversion rate. However, with the same heating rate, the catalyst obtained using the template agent CTAB had a higher methanol conversion rate and lower CO selectivity. However, overall, Pt-In2O3 / CeO2 (CTAB-0.1℃ / min) can significantly reduce CO selectivity while ensuring a high methanol conversion rate, thus solving the dilemma of improving conversion / stability and reducing CO concentration.

[0105] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a noble metal-based catalyst, characterized in that, The noble metal-based catalyst comprises a support, a promoter metal, and an active metal, wherein the support is CeO2, the active metal is the noble metal Pt, and the promoter metal includes In; based on the total mass of the noble metal-based catalyst, the active metal loading is 0.05%~4%, and the promoter metal oxide loading is 0.5%~15%; the CeO2 support consists of 50-150 nm nanoparticles formed by stacking 4-10 nm nanoparticles, with a specific surface area of ​​218.36-222.20 m². 2 g -1 The pore volume is 0.32-0.34 cm³. 3 / g; Pt is dispersed at the single-atom level or in particles smaller than 2nm, while In₂O₃ is dispersed at the nanoscale; the valence state of the active metal Pt is Pt 2+ The majority is Pt, with a small portion being Pt. δ+ ; The preparation method of the noble metal-based catalyst includes the following steps: (1) Preparation of the carrier; (2) Loaded with active metals and auxiliary metals; In step (1), the CeO2 support is prepared using the sol-gel method, which includes the following steps: (11) The ethanol solution for preparing the template agent is solution A; the aqueous solution for preparing the complexing agent is solution B; and the aqueous solution for preparing the cerium salt is solution C. (12) Mix solution B and solution C to obtain a mixed solution, then add solution A dropwise to the mixed solution to obtain a suspension, stir the suspension, and then let it stand to obtain a sol; (13) The sol obtained in step (12) is dried and calcined to obtain the carrier; In step (13), the calcination conditions are: the heating rate is 0.1-0.5℃ / min.

2. The preparation method according to claim 1, characterized in that, Based on the total mass of the noble metal-based catalyst, the active metal loading is 1% and the auxiliary metal oxide loading is 7%.

3. The preparation method according to claim 1, characterized in that, In step (11), the concentration of solution A is 0.01~2 M; the concentration of solution B is 0.05~5 M; the concentration of solution C is 0.1~10 M; the cerium salt includes inorganic salts or organic salts, wherein the inorganic salts include nitrates and chlorates, and the organic salts include acetates; the template agent is selected from hexadecyltrimethylammonium bromide, diethylamine, and ethylenediaminetetraacetic acid; the complexing agent is selected from citric acid, ascorbic acid, ammonia, or urea; In step (12), the stirring temperature is room temperature, the stirring time is 1-10h, and the standing time is 0.5h-5h; In step (13), the drying conditions are: drying temperature of 40-200℃ and drying time of 1-7 days; the calcination conditions are: calcination temperature of 350-800℃ and calcination time of 2-24h.

4. The preparation method according to claim 1, characterized in that, In step (2), active metals and additives are loaded using a co-impregnation method, which includes the following steps: (21) Prepare a soluble active metal salt solution; prepare a soluble auxiliary agent salt solution; (22) The carrier is poured into a mixed solution of active metal solution and auxiliary agent solution, and shaken while pouring. After sonication, it is placed for impregnation, and then dried and calcined to obtain a noble metal-based catalyst.

5. The preparation method according to claim 4, characterized in that, In step (21), the concentration of the active metal in the active metal salt solution is 0.05~4 M; the concentration of the auxiliary metal in the auxiliary salt solution is 0.1~10 M; In step (22), the ultrasonic time is 5-120 min, the immersion temperature is room temperature, and the immersion time is 1-24 h; The drying conditions are: drying temperature 40-70℃, drying time 4-24h; The roasting conditions are as follows: the roasting environment is air, the roasting temperature is 300-800℃, and the roasting time is 2-12h.

6. The application of a noble metal-based catalyst prepared by the preparation method according to any one of claims 1-5 in the methanol steam reforming hydrogen production reaction.

7. The application according to claim 6, characterized in that, The precious metal-based catalyst is shaped and crushed, and sieved to obtain particles of 20-100 mesh. Then it is mixed with quartz sand. Subsequently, the mixture of precious metal-based catalyst and quartz sand is loaded into a fixed bed for in-situ reduction. The reduction temperature is 250-500℃, the reduction time is 1-8h, and the reduction atmosphere is a mixture of hydrogen and nitrogen. The volume percentage of hydrogen in the mixture is 5%-50% of the total volume of hydrogen and nitrogen. After in-situ reduction, methanol vapor reforming is carried out to produce hydrogen. The mass ratio of the precious metal-based catalyst to the quartz sand is 1:(1-10). The methanol vapor reforming reaction for hydrogen production is carried out at atmospheric pressure, with a reaction temperature of 200℃ to 420℃, a water-to-carbon ratio of 1 to 5, and a methanol mass hourly space velocity of 1 to 20 h⁻¹. -1 .

8. The application according to claim 6, characterized in that, The noble metal-based catalyst described above is used to improve methanol conversion and reduce CO selectivity.

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