Precious metal catalyst as well as preparation method and application thereof

Abstract

The invention discloses a noble metal catalyst and a preparation method and application thereof, and belongs to the technical field of methanol steam reforming hydrogen production and catalysts. The noble metal catalyst comprises a carrier, an auxiliary agent metal and an active metal, the carrier comprises CeO2, the morphology of the carrier is cubic, and particles are regular; the active metal comprises Pt; the auxiliary agent metal comprises In2O3; the active sites of the noble metal catalyst comprise Pt0 and Pt delta +, the content of Pt0 is higher than 50%, and the content of Pt delta + is 10-35%. According to the invention, the ratio of CO in the product is effectively reduced.

Description

Technical Field

[0001] The present application relates to the technical fields of hydrogen production by methanol steam reforming and catalysts, and particularly relates to a noble metal catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] The methanol steam reforming hydrogen production technology, as an efficient hydrogen production method, has extensive application potential and can meet the hydrogen demands of various distributed scenarios. Therefore, higher requirements are put forward for the hydrogen production process and hydrogen purity. The traditional copper-based catalysts used in industrialization, although showing high catalytic activity and selectivity, have problems such as high pyrophoricity and insufficient stability, which limit their wide application. In contrast, noble metal-based catalysts, especially platinum-based catalysts, exhibit higher stability and reactivity, becoming a catalytic system that has attracted much attention.

[0003] However, traditional Pt-based catalysts mainly promote the cracking reaction of methanol. Due to the lack of water dissociation active sites on the carrier, it is difficult to decompose water, and the main products are CO and H2, and it is difficult to further convert CO into CO2, resulting in a relatively high proportion of CO in the products. Summary of the Invention

[0004] The main purpose of the present application is to provide a noble metal catalyst, a preparation method thereof, and an application thereof, aiming to effectively reduce the proportion of CO in the products.

[0005] To achieve the above object, an embodiment of the present application provides a noble metal catalyst, including: a carrier, a promoter metal, and an active metal;

[0006] The carrier includes CeO2, and the morphology of the carrier is a cube with regular particles;

[0007] The active metal includes Pt;

[0008] The promoter metal includes In2O3;

[0009] The active sites of the noble metal catalyst include: Pt 0 and Pt δ+ wherein, Pt 0 is higher than 50%, and Pt δ+ is 10 - 35%.

[0010] In one embodiment, the specific surface area of the carrier is 5 - 30 m 2 g -1 ;

[0011] and / or, the pore volume of the carrier is 0.01 - 0.1 m 3 g -1 .

[0012] In one embodiment, the noble metal catalyst comprises: 3-35 wt.% of a promoter metal and 1-30 wt.% of an active metal.

[0013] In one embodiment, the particle size of the carrier is 10-500 nm.

[0014] In one embodiment, the main exposed crystal plane of the carrier is (100);

[0015] and / or, the oxygen vacancies O of the noble metal catalyst v is less than 15%.

[0016] The embodiment of the present application further provides a preparation method of a noble metal catalyst, which is applied to prepare the noble metal catalyst as described above, and comprises the following steps:

[0017] Prepare the carrier by a hydrothermal method, wherein the carrier comprises CeO2, and the morphology of the carrier is a cube with regular particles;

[0018] Load the active metal and the promoter metal on the carrier to obtain the noble metal catalyst, wherein the promoter metal comprises In2O3, the active metal comprises Pt, and the active sites of the noble metal catalyst comprise: Pt 0 and Pt δ+ , wherein, Pt 0 is higher than 50%, and Pt δ+ is 10-35%.

[0019] In one embodiment, the step of preparing the carrier by a hydrothermal method comprises:

[0020] Mix the NaOH solution and the cerium nitrate solution to obtain a solid-liquid mixture;

[0021] Heat the solid-liquid mixture, and centrifuge and wash to obtain the carrier.

[0022] In one embodiment, the heating temperature when heating the solid-liquid mixture is 160-185 °C, and the heating duration is 5-35 h.

[0023] In one embodiment, the step of loading the active metal and the promoter metal on the carrier to obtain the noble metal catalyst comprises:

[0024] Prepare the active metal solution and the promoter metal solution;

[0025] Mix the active metal solution and the promoter metal solution to obtain a mixed solution;

[0026] Place the carrier in the mixed solution, take out the carrier loaded with the active metal and the promoter metal and calcine to obtain the noble metal catalyst.

[0027] The embodiments of the present application also provide an application of the above-mentioned noble metal catalyst in the hydrogen production reaction by methanol steam reforming.

[0028] One or more technical solutions proposed in the present application have at least the following technical effects: providing a noble metal catalyst, including: a carrier, a promoter metal, and an active metal; the carrier includes CeO2, and the morphology of the carrier is a cube with regular particles; the active metal includes Pt; the promoter metal includes In2O3; the active sites of the noble metal catalyst include: Pt 0 and Pt δ+ , where Pt 0 is higher than 50%, and Pt δ+ is 10-35%. By using CeO2 with a cubic morphology as the carrier and adding In2O3 as the promoter metal, the proper dispersion of Pt is promoted, so as to regulate the valence state of the active sites of Pt to: Pt 0 and Pt δ+ , while the proportion of Pt 0 is higher than 50%, and the proportion of Pt δ+ is 10-35%; furthermore, it promotes the reaction paths of Pt in the noble metal catalyst to include: the direct path of Pt 0 , the Pt 0 -In2O3 synergistic path, the Pt δ+ -In2O3 synergistic path, and the Pt 0 -Pt δ+ synergistic path, and the direct path of Pt 0 and the Pt 0 -In2O3 synergistic path are the main reaction paths. Furthermore, when the noble metal catalyst is applied to methanol steam reforming (MSR), the Pt metal sites (Pt 0 ) will be used as efficient active centers, thus effectively promoting methanol dissociation and water molecule activation, and accelerating the methanol steam reforming reaction. The synergistic effect of the Pt 0 -In2O3 synergistic path can further improve the selectivity and efficiency of the reaction, especially by enhancing the adsorption and conversion of intermediates and reducing the generation of CO in by-products; at the same time, the Pt 0 -In2O3 synergistic path also helps to maintain the structural integrity of the catalyst at high temperatures and ensure its long-term high performance during the MSR process. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic diagram of the reaction path of the noble metal catalyst involved in the embodiment solution of the present application Figure 1 ;

[0030] Figure 2Schematic diagram of the reaction path of the noble metal catalyst involved in the solution of the embodiment of the present application Figure 2 ;

[0031] Figure 3 Schematic diagram of the reaction path of the noble metal catalyst involved in the solution of the embodiment of the present application Figure 3 ;

[0032] Figure 4 Schematic flow chart of the preparation method of the noble metal catalyst involved in the solution of the embodiment of the present application;

[0033] Figure 5 Schematic diagram of the TEM result involved in the solution of the embodiment of the present application;

[0034] Figure 6 Schematic diagram of the XPS result involved in the solution of the embodiment of the present application;

[0035] Figure 7 Schematic diagram of the infrared result involved in the solution of the embodiment of the present application.

[0036] The realization, functional characteristics and advantages of the purpose of the present application will be further described with reference to the accompanying drawings in conjunction with the embodiments. Detailed implementation manners

[0037] To make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0038] Hereinafter, the embodiments of the noble metal catalyst, its preparation method and application of the present application are specifically disclosed in detail with reference to the accompanying drawings as appropriate. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0039] The "ranges" disclosed in this application are defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations. In addition, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0040] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0041] If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0042] If there is no special instruction, all steps of this application can be carried out sequentially or randomly, and preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0043] If there is no special instruction, the "including" and "comprising" mentioned in this application mean open-ended, and can also be closed-ended. For example, the "including" and "comprising" can mean that other components not listed can also be included or comprised, or can only include or comprise the listed components.

[0044] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) while B is true (or exists); or both A and B are true (or exist).

[0045] To make the above objects, features, and advantages of this application more obvious and understandable, the technical solutions of this application will be further described below in conjunction with the accompanying drawings and embodiments. However, this application is not limited to the listed embodiments, and should also include any other well-known changes within the scope of the rights required by this application.

[0046] As used herein, the term "one embodiment" or "embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of this application. The phrase "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it an individual or alternative embodiment that is mutually exclusive with other embodiments.

[0047] To better understand the technical solutions of this application, the following will be described in detail in conjunction with the accompanying drawings of the specification and specific implementation manners.

[0048] In conventional technologies, traditional Pt-based catalysts mainly promote the cracking reaction of methanol. Due to the lack of water dissociation active sites on the carrier, it is difficult to decompose water, and the main products are CO and H2. It is difficult to further convert CO into CO2, resulting in a relatively high proportion of CO in the products.

[0049] In the embodiments of this application, by using cubic-shaped CeO2 as the carrier and adding In2O3 as the promoter metal, the proper dispersion of Pt is promoted, thereby regulating the valence state of the active sites of Pt to be: Pt 0 and Pt δ+ , and at the same time, the proportion of Pt 0 is higher than 50%, and the proportion of Pt δ+ is 10 - 35%; furthermore, the reaction paths of Pt in the noble metal catalyst are promoted to include: the direct path of Pt 0 , the Pt 0 -In2O3 synergy path, the Pt δ+ -In2O3 synergy path, and the Pt 0 -Pt δ+ synergy path, and the direct path of Pt 0 and the Pt 0 -In2O3 synergy path are the main reaction paths. Furthermore, when the noble metal catalyst is applied to methanol steam reforming (MSR), it will use Pt metal sites (Pt0 ) As an efficient active center, it can effectively promote methanol dissociation and water molecule activation, accelerating the methanol steam reforming reaction. And Pt 0 -In2O3 synergistic pathway can further improve the selectivity and efficiency of the reaction, especially by enhancing the adsorption and conversion of intermediates and reducing the formation of CO in by-products; meanwhile, Pt 0 -In2O3 synergistic pathway also helps to maintain the structural integrity of the catalyst at high temperatures, ensuring its high-efficiency performance during the MSR process for a long time.

[0050] The first aspect of the embodiment of the present application provides a noble metal catalyst, including: a carrier, a promoter metal, and an active metal;

[0051] The carrier includes CeO2, and the morphology of the carrier is a cube;

[0052] The active metal includes Pt;

[0053] The promoter metal includes In2O3;

[0054] The active sites of the noble metal catalyst include: Pt 0 and Pt δ+ , where Pt 0 is higher than 50%, and Pt δ+ is 10-35%.

[0055] In a feasible embodiment, Pt (platinum) is an efficient catalytic active center, showing extremely high catalytic activity for key steps such as methanol dissociation and water molecule activation. It can effectively reduce the reaction activation energy, enabling the MSR reaction to proceed smoothly at a relatively low temperature. This not only improves the energy utilization efficiency but also reduces the demand for high-temperature equipment and lowers the operating cost. In addition, there is a strong metal-support interaction (SMSI) between Pt and the support material, and this interaction is particularly obvious under MSR conditions. Through this interaction, Pt can be stably dispersed on the surface of the support, preventing its sintering or aggregation, thus maintaining a high specific surface area and the number of active sites, ensuring the catalyst maintains high-efficiency performance throughout the reaction process.

[0056] In a feasible embodiment, the introduction of In2O3 can enhance the interaction between the support and the active metal, especially through strong metal-support interaction (SMSI); this interaction helps to stabilize Pt particles, preventing them from sintering and aggregating during high-temperature or long-term reactions, thus maintaining the high dispersion and large specific surface area of the catalyst, ensuring continuous and efficient catalytic activity. In addition, the presence of In2O3 can also regulate the electronic properties of the Pt surface, changing its adsorption ability and activation efficiency for reactant molecules, further improving the selectivity and rate of the MSR reaction. Moreover, the introduction of In2O3 helps to enhance the thermal stability and anti-poisoning ability of the catalyst. In practical applications, the MSR reaction may face challenges in high-temperature environments and various impurity gases (such as sulfides, chlorides, etc.), which are likely to cause the inactivation of ordinary catalysts. However, In2O3 can effectively resist the above adverse effects by changing the chemical composition and structural characteristics of the catalyst surface, maintaining long-term stable catalytic performance.

[0057] In a feasible embodiment, CeO2, as an excellent support material, has excellent thermal stability and mechanical strength, and can maintain its structural integrity under high-temperature and high-pressure conditions, ensuring the long-term operation of the catalyst without inactivation, thereby reducing the replacement frequency of the catalyst during actual application, lowering the maintenance cost, and improving production efficiency. In addition, there is a strong metal-support interaction between CeO2 and noble metals (e.g., Pt), and this interaction is crucial for optimizing the catalyst performance. It helps to stabilize metal nanoparticles, preventing them from sintering or aggregating at high temperatures, thus maintaining a high dispersion and specific surface area. At the same time, SMSI can also change the electronic structure of the metal surface, making the catalyst more selective for specific reaction paths and further improving the catalytic efficiency. Exemplarily, in a system containing CeO2, Pt nanoparticles can obtain better reducibility and higher catalytic activity through the interaction with CeO2, which is particularly beneficial for the MSR reaction.

[0058] In a feasible embodiment, the specific surface area of the support is 5 - 30 m 2 g -1 ; for example, 5 m 2 g -1 、6 m 2 g -1 、7 m 2 g -1 、8 m 2 g -1 、9 m 2 g -1 、10 m 2 g -1 、11 m 2 g -1 、12 m 2 g-1 、 13 m 2 g -1 、 14 m 2 g -1 、 15 m 2 g -1 、 16 m 2 g -1 、 17 m 2 g -1 、 18 m 2 g -1 、 19 m 2 g -1 、 20 m 2 g -1 、 21 m 2 g -1 、 22 m 2 g -1 、 23 m 2 g -1 、 24 m 2 g -1 、 25 m 2 g -1 、 26 m 2 g -1 、 27 m 2 g -1 、 28 m 2 g -1 、 29 m 2 g -1 、 30 m 2 g -1 etc.

[0059] In a feasible embodiment, the pore volume of the carrier is 0.01 - 0.1 m 3 g -1 ; 0.01 m 3 g -1 、 0.02 m 3 g -1 、 0.03 m 3 g -1 、 0.04 m 3 g -1 、 0.05 m 3 g -1 、 0.06 m 3 g -1 、 0.07 m 3 g -1 、 0.08 m 3 g -1 、 0.09 m 3 g -1 、 0.1 m 3 g -1 etc.

[0060] In a feasible embodiment, the morphology of the CeO2 support in the embodiments of the present application is a cube, and thus the support has a relatively small specific surface area and pore volume; the relatively small specific surface area helps to improve the stability of Pt nanoparticles, reduce the dispersion density, thereby reducing the interaction between particles, reducing the possibility of their aggregation or sintering, and thus maintaining the high efficiency of Pt during high-temperature or long-term operation. In addition, the limited specific surface area can also promote a stronger metal-support interaction, making the metal nanoparticles more firmly anchored on the support, enhancing their thermal stability and anti-poisoning ability. Secondly, the relatively small specific surface area and mesopore volume can regulate the valence state of the active sites of Pt to: Pt 0 and Pt δ+ , where the proportion of Pt 0 is higher than 50%, and the proportion of Pt δ+ is 10-35%; thus optimizing the reaction path, and promoting the reaction path of Pt in the noble metal catalyst to include: the direct path of Pt 0 , the Pt 0 -In2O3 synergy path, the Pt δ+ -In2O3 synergy path, and the Pt 0 -Pt δ+ synergy path, and taking the direct path of Pt 0 and the Pt 0 -In2O3 synergy path as the main reaction paths. Thus, when the noble metal catalyst is applied to MSR, it will use the Pt metal site (Pt 0 ) as an efficient active center, thereby effectively promoting methanol dissociation and water molecule activation, and accelerating the methanol steam reforming reaction. The synergy of the Pt 0 -In2O3 synergy path can further improve the selectivity and efficiency of the reaction, especially by enhancing the adsorption and conversion of intermediates and reducing the generation of CO in by-products; at the same time, the Pt 0 -In2O3 synergy path also helps to maintain the structural integrity of the catalyst at high temperatures, ensuring its long-term high efficiency during the MSR process.

[0061] In a feasible embodiment, the main exposed crystal plane of the support is (100).

[0062] In a feasible embodiment, the oxygen vacancies O v of the noble metal catalyst are less than 15%.

[0063] In a feasible embodiment, since cubic-shaped CeO2 is selected as the carrier, the main exposed crystal plane of the carrier is (100). The (100) crystal plane has higher symmetry and a more compact atomic arrangement. Compared with other crystal planes, such as (110) or (111), it is thermodynamically more stable. Therefore, under the same conditions, the energy barrier for forming oxygen vacancies on the (100) crystal plane is higher, resulting in a lower spontaneous generation rate of oxygen vacancies; and the surface atomic arrangement of the (100) crystal plane is regular and there are fewer dangling bonds (i.e., unpaired electrons), which means that more energy is required to break these stable chemical bonds to form oxygen vacancies. Therefore, the oxygen vacancies O of the noble metal catalyst in the embodiments of the present application v is less than 15%. Further, due to the high stability of the (100) crystal plane, it can provide a more uniform and firm support environment for noble metal nanoparticles (such as Pt). In such an environment, the metal nanoparticles are not prone to aggregation or sintering, which helps to maintain the high performance of the catalyst, especially under high-temperature or long-term operating conditions. In addition, although the (100) crystal plane has fewer oxygen vacancies, it can selectively adsorb certain types of reactant molecules. For example, in the MSR process, this selective adsorption can help to guide the reaction along a more favorable path, reduce the generation of by-product CO, and improve the purity of hydrogen; and the relatively simple pore structure is usually accompanied by a lower oxygen vacancy density, which can reduce the diffusion resistance of reactants and products inside the carrier, making the reaction more uniform and efficient. For fast reactions, such a design can significantly reduce the rate decline problem caused by diffusion limitations.

[0064] Optionally, the active sites of the noble metal catalyst include: Pt 0 and Pt δ+ , where, Pt 0 is higher than 50%, Pt δ+ is 10 - 35%, there is no Pt 2+ , but there may still be a small amount of unreduced PtO2. Based on the valence states and proportions of the above activities, the reaction paths of the noble metal catalyst in the embodiments of the present application include: the direct path of Pt 0 , the Pt 0 -In2O3 cooperative path, the Pt δ+ -In2O3 cooperative path, and the Pt 0 -Pt δ+ cooperative path, and the direct path of Pt 0 and the Pt 0 -In2O3 cooperative path are the main reaction paths.

[0065] Exemplarily, referring to Figure 1 , for Pt 0For the MSR reaction path, when the support lacks oxygen vacancies, it is difficult to adsorb and decompose water, and methanol is mainly adsorbed on Pt 0 for decomposition to produce formaldehyde (HCHO). Lack of OH generated from water decomposition results in easy desorption of formaldehyde from Pt 0 and cleavage to produce a large amount of CO.

[0066] Exemplarily, referring to Figure 2 , for the MSR reaction path of Pt 0 -, the addition of the promoter In2O3 promotes the dispersion of Pt, and a small amount of Pt can be formed δ+ (refer to Figure 3 ), while In2O3 mainly exists as large particles or bulk particles, and some small In2O3 particles are more likely to generate oxygen vacancies. Therefore, the 0 Pt-In2O3 synergistic path enables water to decompose more easily, reduces the CO concentration, eases the subsequent difficulty of CO removal, and thus reduces the poisoning of the fuel cell platinum electrode by CO.

[0067] Exemplarily, referring to Figure 3 , for the 0 Pt- δ+ Pt- 0 In2O3 synergistic path. Due to the different surface electron charges of Pt δ+ and Pt δ+ , methanol is more likely to be adsorbed on Pt 0 , but is more likely to decompose on Pt 0 . Therefore, a small part of the adjacent Pt δ+ and Pt 0 can undergo a synergistic reaction. Methanol is adsorbed and decomposed on Pt δ+ to form formaldehyde, and the desorbed formaldehyde migrates and adsorbs onto Pt δ+ ; while the OH generated from the adsorption and decomposition of water in the oxygen vacancy also migrates onto Pt δ+ , and can form formate on Pt

[0068] to decompose into CO2 and H2. 0 In this system, it is mainly dominated by Pt δ+ , with less Pt 0 . Therefore, the δ+ Pt-In2O3 synergistic path is the main reaction path, while the 0 Pt-In2O3 and δ+ Pt-Pt-In2O3 synergistic paths account for a relatively small proportion.

[0069] Optionally, since In2O3 mainly exists in the form of large particles or bulk, the formation of oxygen vacancies is relatively difficult and the proportion of oxygen vacancies is low. These characteristics make the hydroxyl groups generated by the decomposition of water molecules at the oxygen vacancies need to go through a relatively long migration path to contact the Pt active center and participate in the reaction. However, this spatial separation promotes the formation of bidentate-bound formate (bi-*HCOO) as an intermediate product, reflecting the synergistic effect between Pt and In2O3. The reaction path of formate has a lower formation of CO than the formaldehyde path, and the participation of water can inhibit the direct cleavage of HCHO into CO and H2. If the formaldehyde and methoxy groups in the system undergo a chain growth reaction to form methyl formate, the reaction conversion rate will be reduced. Therefore, the formate reaction path can promote the methanol-water conversion rate and reduce the formation of CO.

[0070] In a feasible embodiment, the noble metal catalyst includes: 3 to 35 wt.% of promoter metal and 1 to 30 wt.% of active metal. For example, the loading amount of the promoter metal is 3 wt.%, 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, etc. The loading amount of the active metal is 1 wt.%, 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, etc.

[0071] In a feasible example, when the loading amount of the active metal is too high, it may lead to the aggregation of active metals, forming larger particles. This not only reduces the effective surface area of the active metal but also decreases the number of active sites provided by the active metal per unit mass, thus weakening the catalytic efficiency. Secondly, a high loading amount may cause an overly high coverage on the surface of the carrier, hindering the reactant molecules from contacting important active centers such as the promoter or oxygen vacancies on the carrier, and thus affecting the synergistic effect. On the contrary, when the loading amount of the active metal is too low, although it can save costs and avoid the above-mentioned aggregation problem, it also means that there are insufficient active sites on the catalyst surface, which is not enough to fully activate the reactant molecules, resulting in a decrease in the catalytic reaction rate. Therefore, the embodiment of the present application determines that the loading amount of the active metal in the noble metal catalyst is 1 to 30 wt.%.

[0072] In a feasible embodiment, when the loading amount of the promoter metal is too high, it may cause partial shielding of the active sites on the catalyst surface. Since the promoter metal particles are relatively large, excessive promoter metal will cover the surface of the active metal, reducing the exposed effective active sites and thus lowering the overall activity of the catalyst. In addition, too high a loading of the promoter metal may change the electronic properties of the catalyst, affecting the strong metal-support interaction between the active metal and the promoter metal, thereby weakening their synergistic effect and ultimately affecting the catalytic efficiency and selectivity. On the contrary, when the loading amount of the promoter metal is too low, although the above problems can be avoided, a lower content of the promoter metal means insufficient oxygen vacancies and additional active centers provided, which is disadvantageous for promoting the adsorption, activation of reactant molecules, and the formation of intermediate products. For example, in the MSR process, an appropriate amount of the promoter metal helps to stabilize the hydroxyl species and promote their migration to the Pt active centers to generate bidentate-bound formate intermediates. If the content of the promoter metal is too low, this process will be inhibited, resulting in a decrease in the efficiency of the catalytic path. Therefore, the embodiment of the present application determines that the loading amount of the promoter metal in the noble metal catalyst is 3-35 wt.%.

[0073] In a feasible embodiment, the particle size of the carrier is 10-500 nm; for example, the particle size of the carrier is 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, etc. Larger particles have greater internal mass transfer resistance, and the diffusion paths of reactant molecules and product molecules inside the particles become longer, which may lead to a decrease in the reaction rate. On the contrary, if the particle size of the carrier is too low, it may increase the tendency of agglomeration between the carrier particles, affecting its stability and utilization rate. Therefore, the embodiment of the present application determines that the particle size of the carrier in the noble metal catalyst is 10-500 nm.

[0074] Optionally, the noble metal catalyst of the embodiment of the present application can be used for the hydrogen production reaction by steam reforming of methanol.

[0075] In this embodiment, by using cubic-shaped CeO2 as the carrier and adding In2O3 as the promoter metal, the proper dispersion of Pt is promoted, thereby regulating the valence states of the active sites of Pt to be: Pt 0 and Pt δ+ , while the proportion of Pt 0 is higher than 50%, and the proportion of Pt δ+ is 10-35%; furthermore, it promotes the reaction paths of Pt in the noble metal catalyst to include: the direct path of Pt 0 , the Pt 0 -In2O3 synergistic path, the Pt δ+ -In2O3 synergistic path, and the Pt 0 -Pt δ+The co - operative path, with the direct path of Pt 0 and the Pt 0 -In2O3 co - operative path as the main reaction paths. Furthermore, when applying noble metal catalysts to methanol steam reforming (MSR), the Pt metal sites (Pt 0 ) act as efficient active centers, thus effectively promoting methanol dissociation and water molecule activation, and accelerating the methanol steam reforming reaction. The synergistic effect of the Pt 0 -In2O3 co - operative path can further improve the selectivity and efficiency of the reaction, especially by enhancing the adsorption and conversion of intermediates and reducing the generation of CO in by - products; meanwhile, the Pt 0 -In2O3 co - operative path also helps to maintain the structural integrity of the catalyst at high temperatures, ensuring its high - efficiency performance during the MSR process for a long time.

[0076] Furthermore, referring to Figure 4 , the embodiments of the present application also provide a preparation method of a noble metal catalyst. The preparation method of the noble metal catalyst includes the following steps:

[0077] Step S10, preparing a support by a hydrothermal method, wherein the support includes CeO2, and the morphology of the support is cubic, with regular particles;

[0078] In a feasible embodiment, a CeO2 support with a cubic morphology is obtained by a hydrothermal method.

[0079] In a feasible embodiment, step S10, the step of preparing a support by a hydrothermal method includes:

[0080] Step S11, mixing a NaOH solution and a cerium nitrate solution to obtain a solid - liquid mixture;

[0081] Step S12, heating the solid - liquid mixture and centrifuging and washing to obtain the support.

[0082] In a feasible embodiment, a 6 - 9M NaOH solution and a 0.2 - 0.6M cerium nitrate solution are provided. Mixing the NaOH solution and the cerium nitrate solution to produce a precipitate, and obtaining a solid - liquid mixture. Heating the solid - liquid mixture at a temperature of 160 - 185°C for 5 - 35 h to carry out a hydrothermal reaction, and then through centrifuging and washing, a CeO2 support with a cubic morphology is obtained after drying. Among them, the particle size of the support is 10 - 500 nm, the specific surface area is 5 - 30 m 2 g -1 , and the pore volume is 0.01 - 0.1 m 3 g -1 .

[0083] Optionally, the concentration of NaOH can be 6M, 7M, 8M, 9M, etc.

[0084] Optionally, the concentration of cerium nitrate can be 0.2M, 0.3M, 0.4M, 0.5M, 0.6M, etc.

[0085] Optionally, the heating temperature of the solid-liquid mixture is 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, etc.

[0086] Optionally, the heating duration of the solid-liquid mixture is 5h, 10h, 15h, 20h, 25h, 30h, 35h, etc.

[0087] In this embodiment, by controlling the hydrothermal reaction conditions, a CeO2 support with a cubic morphology is prepared. Among them, the particle size of the support is 10 - 500 nm, the specific surface area is 5 - 30 m 2 g -1 , and the pore volume is 0.01 - 0.1 m 3 g -1 . This support helps to regulate the valence state and proportion of the active sites of the active metal in the noble metal catalyst, thereby promoting methanol dissociation and water molecule activation, accelerating the methanol steam reforming reaction, and reducing the generation of CO in the products.

[0088] Step S20: Load an active metal and a promoter metal on the support to obtain a noble metal catalyst. Among them, the promoter metal includes In2O3, the active metal includes Pt, and the active sites of the noble metal catalyst include: Pt 0 and Pt δ+ , where, Pt 0 is higher than 50%, and Pt δ+ is 10 - 35%.

[0089] In a feasible embodiment, an active metal including Pt is provided, and a promoter metal including In2O3 is provided; an active metal and a promoter metal are loaded on the support to obtain a noble metal catalyst. Among them, the active sites of the noble metal catalyst include: Pt 0 and Pt δ+ , where, Pt 0 is higher than 50%, and Pt δ+ is 10 - 35%.

[0090] In a feasible implementation manner, step S20: The step of loading an active metal and a promoter metal on the support to obtain a noble metal catalyst includes:

[0091] Step S21: Prepare an active metal solution and a promoter metal solution;

[0092] Step S22: Mix the active metal solution and the promoter metal solution to obtain a mixed solution;

[0093] Step S23: Place the carrier in the mixed solution, take out the carrier loaded with the active metal and the promoter metal, and calcine it to obtain the noble metal catalyst.

[0094] In a feasible embodiment, an active metal solution and a promoter metal solution are prepared and mixed to obtain a mixed solution; the carrier is placed in the mixed solution, ultrasonicated, then left for impregnation, and dried and calcined to obtain a Pt-In2O3 / CeO2-c noble metal catalyst.

[0095] Optionally, the calcination temperature is 300-550 °C, and the calcination duration is 2-10 h.

[0096] Optionally, the noble metal catalyst prepared in the embodiments of the present application can be used in the methanol steam reforming reaction for hydrogen production.

[0097] In this embodiment, by using cubic-shaped CeO2 as the carrier and adding In2O3 as the promoter metal, the proper dispersion of Pt is promoted, so as to regulate the valence state of the active sites of Pt to: Pt 0 and Pt δ+ , and at the same time, the proportion of Pt 0 is higher than 50%, and the proportion of Pt δ+ is 10-35%; furthermore, the reaction path of Pt in the noble metal catalyst is promoted to include: the direct path of Pt 0 , the Pt 0 -In2O3 synergy path, the Pt δ+ -In2O3 synergy path, and the Pt 0 -Pt δ+ synergy path, and the direct path of Pt 0 and the Pt 0 -In2O3 synergy path are the main reaction paths. Furthermore, when the noble metal catalyst is applied to methanol steam reforming for hydrogen production (methanolsteam reforming, MSR), the Pt metal sites (Pt 0 ) will be used as efficient active centers, so as to effectively promote methanol dissociation and water molecule activation and accelerate the methanol steam reforming reaction. The synergy of the Pt 0 -In2O3 synergy path can further improve the selectivity and efficiency of the reaction, especially by enhancing the adsorption and conversion of intermediates and reducing the generation of CO in by-products; at the same time, the Pt 0 -In2O3 synergy path also helps to maintain the structural integrity of the catalyst at high temperatures and ensure its long-term high performance during the MSR process.

[0098] To enable those skilled in the art to clearly understand the details and operations of the above embodiments of the present application, and to significantly demonstrate the progressive performance of the embodiments of the present application, the above technical solutions will be illustrated by multiple embodiments as follows.

[0099] Example 1

[0100] (1) Weigh cerium nitrate and dissolve it in deionized water to prepare a 0.2M cerium nitrate solution; weigh NaOH and dissolve it in deionized water to prepare a 6M NaOH solution; mix the NaOH solution and the cerium nitrate solution to obtain a solid-liquid mixture.

[0101] (2) Transfer the solid-liquid mixture to a polytetrafluoroethylene inner liner, place it in a stainless-steel hydrothermal autoclave, and tighten the seal; place the hydrothermal autoclave in an oven at 180 °C and heat for 24 h to obtain a cubic CeO2 support (CeO2-c).

[0102] (3) Prepare a chloroplatinic acid solution, where the concentration of Pt 4+ is 0.21M; prepare an In(NO3)3 solution, and the concentration of In 3+ is 0.56M.

[0103] (4) Pipette an appropriate amount of the chloroplatinic acid solution and the In(NO3)3 solution, and weigh the CeO2-c support obtained in step (2), add them to the solution, shake well while slowly adding, and ultrasonicate for 30 min; then impregnate at room temperature for 12 h, dry, and calcine in air at 450 °C for 4 h to obtain a Pt-In2O3 / CeO2-c catalyst, where the theoretical loading of Pt is 1 wt.%, and the theoretical loading of In2O3 is 7 wt.%.

[0104] Example 2

[0105] The experimental steps are the same as those in Example 1, except that:

[0106] In step (2), place the hydrothermal autoclave in an oven at 185 °C and heat for 12 h to obtain a cubic CeO2 support (CeO2-c1).

[0107] Example 3

[0108] The experimental steps are the same as those in Example 1, except that:

[0109] In step (2), place the hydrothermal autoclave in an oven at 160 °C and heat for 12 h to obtain a cubic CeO2 support (CeO2-c1).

[0110] Comparative Example 1

[0111] The experimental steps are the same as those in Example 1, except that the preparation steps of the CeO2 support include:

[0112] (1) Weigh 4.4 g of cerium nitrate and dissolve it in 70 mL of deionized water. Stir at 50 °C and add ammonia water dropwise. A precipitate gradually appears. Stop adding when the precipitate no longer increases and continue stirring.

[0113] (2) Centrifuge, wash, and dry to obtain a CeO2 support composed of irregular large particles and nanometer particle aggregates.

[0114] Comparative Example 2

[0115] The experimental steps are the same as those in Example 1, except that the CeO2 support is commercial CeO2 powder.

[0116] Comparative Example 3

[0117] The experimental steps are the same as those in Example 1, except that only the active metal Pt is loaded, and the promoter metal In2O3 is not loaded.

[0118] The specific surface area, pore volume, and loading amount of the catalysts in Examples 1 to 3 and Comparative Examples 1 to 3 were tested. The experimental results are shown in Table 1 below; according to Table 1, it can be seen that for the support CeO2-c prepared in the examples of the present application, after loading Pt and In2O3, the specific surface area and pore volume changed little, and the theoretical and actual loading amounts of Pt and In2O3 were close.

[0119] Table 1

[0120]

[0121] Perform TEM testing on Example 1, and the results are referred to Figure 5 , where Figure 5 a to d are characterization diagrams at different magnification factors. It can be seen that the prepared support has a cubic morphology, regular particles, and non-uniform particle sizes. However, large particles and larger bulk particles were observed after adding In2O3, indicating that the cubic support has a weak ability to disperse Pt and In2O3.

[0122] Perform XPS characterization on Example 1 and Comparative Example 3, and the results are referred to Figure 6 and Table 2 below. Among them, Figure 6 is the schematic diagram of the XPS characterization results of Example 1. It can be seen that the valence state of Pt in Example 1 is mainly Pt 0 , and the presence of In2O3 further promotes the dispersion and interaction of Pt. Therefore, a small amount of Pt δ+ is formed. In Comparative Example 3, it is mainly Pt 0 , but there is a small amount of unreduced PtO2 in both.

[0123] Table 2

[0124]

[0125] The catalysts prepared in Example 1 and Comparative Example 3 were subjected to in-situ infrared MSR reaction to detect the generation of intermediate products during the MSR reaction, and the results are referred to Figure 7 ; According to Figure 7 It can be seen that bidentate bi-*HCOO, CO, and CO2 were mainly observed in Example 1. In Comparative Example 3, the CO vibration peak was very high, indicating that the methanol cracking (MD) reaction was mainly carried out. After adding In2O3, the CO vibration peak in Example 1 had only a slight intensity, and the vibration peak of CO2 increased, indicating that even when the dispersion of In2O3 was poor, the generation of CO could be inhibited. The intermediate products in both Example 1 and Comparative Example 3 were bidentate bi-*HCOO. Therefore, in Example 1, the Pt 0 -In2O3 path was mainly carried out, and there was also a small amount of Pt δ+ +-CeO2 synergistic path, as well as Pt 0 -Pt δ+ synergistic path. This was mainly because in the cubic catalyst system, it was difficult to generate oxygen vacancies, and the generated amount was small. Therefore, it was difficult to form adjacent oxygen vacancies, mainly non-adjacent oxygen vacancies. Therefore, -OH needed to migrate to the Pt 0 or Pt δ+ sites for the next reaction.

[0126] The catalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were applied to the production of hydrogen by steam reforming of methanol; through a micro fixed-bed quartz tube reactor, the performance evaluation of the catalysts for the production of hydrogen by steam reforming of methanol was carried out. The reaction was carried out at atmospheric pressure. When the reaction temperature was 260-340 °C, the ratio of methanol to water in the raw material was 1:1 (mol / mol), the WHSV was 3 h-1, and nitrogen was used as the carrier gas during the reaction. After the tail gas was condensed, the gas phase entered the on-line chromatograph for detection. The experimental results are shown in Table 3 below:

[0127] Table 3

[0128]

[0129]

[0130] According to the above experimental results, it can be seen that the noble metal catalysts prepared in Examples 1 to 3 of the present application have good methanol conversion rate and CO selectivity performance, and the CO selectivity is relatively excellent. The stability of each catalyst was characterized by testing the duration for which the methanol conversion rate of each catalyst remained above 85%. It was further found that in Example 1 at 340 °C, a stability of 70 h could be achieved; although the conversion rate of the catalyst with additives was lower than that without additives, the addition of additives greatly reduced the concentration of CO, that is, it promoted the MSR reaction path and reduced the MD reaction path. This was mainly attributed to Pt 0-Synergistic effect of oxygen vacancies in In2O3. In addition, a small amount of dispersed Pt clusters Pt δ+ can improve the activity of Pt. Compared with Pt 0 sites, it is more conducive to the formation of the synergistic path and effectively inhibits the production of CO from formaldehyde cracking. Although the catalyst stability is better without adding promoters, the MD reaction mainly occurs without adding promoters, so the CO selectivity is very high. In this method, during the catalyst preparation process, the carrier characteristics and the dispersion of the promoters can be further optimized to improve the catalyst performance.

[0131] The above are only the preferred embodiments of the present application, and do not limit the patent scope of the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the patent protection scope of the present application.

Claims

1. A noble metal catalyst, characterized in that The noble metal catalyst comprises: a carrier, a promoter metal and an active metal; The carrier includes CeO2, and the carrier has a cubic morphology and regular particles; The active metal includes Pt; The auxiliary metal includes In2O3; The active sites of the noble metal catalyst include: Pt 0 and Pt δ+ , where Pt 0 Above 50%, Pt δ+ It is 10 to 35%.

2. The noble metal catalyst according to claim 1, characterized in that The specific surface area of ​​the carrier is 5 to 30 m 2 g -1 ; And / or, the pore volume of the carrier is 0.01 to 0.1 m 3 g -1 .

3. The noble metal catalyst according to claim 1, characterized in that The noble metal catalyst comprises: 3-35 wt.% of promoter metal and 1-30 wt.% of active metal.

4. The noble metal catalyst according to claim 1, characterized in that The particle size of the carrier is 10 to 500 nm.

5. The noble metal catalyst according to claim 1, characterized in that The main exposed crystal face of the carrier is (100); And / or, the oxygen vacancies O of the noble metal catalyst v Less than 15%.

6. A method for preparing a noble metal catalyst, characterized in that: The method is used to prepare the precious metal catalyst according to any one of claims 1 to 5, and the method comprises the following steps: The carrier is prepared by a hydrothermal method, wherein the carrier comprises CeO2, and the morphology of the carrier is cubic and the particles are regular; Active metal and auxiliary metal are loaded on the carrier to prepare a noble metal catalyst, wherein the auxiliary metal includes In2O3, the active metal includes Pt, and the active sites of the noble metal catalyst include: Pt 0 and Pt δ+ , where Pt 0 Above 50%, Pt δ+ It is 10 to 35%.

7. The method for preparing a noble metal catalyst according to claim 6, characterized in that: The step of preparing the carrier by hydrothermal method comprises: mixing the NaOH solution and the cerium nitrate solution to prepare a solid-liquid mixture; The solid-liquid mixture is heated and washed by centrifugation to obtain the carrier.

8. The method for preparing a noble metal catalyst according to claim 7, characterized in that: The solid-liquid mixture is heated at a temperature of 160 to 185° C. and for a heating time of 5 to 35 hours.

9. The method for preparing a noble metal catalyst according to claim 6, characterized in that: The step of loading the active metal and the auxiliary metal on the carrier to prepare the noble metal catalyst comprises: Prepare active metal solution and auxiliary metal solution; Mixing the active metal solution and the auxiliary metal solution to obtain a mixed solution; The carrier is placed in the mixed solution, and the carrier loaded with active metal and auxiliary metal is taken out and calcined to obtain the noble metal catalyst.

10. Use of the noble metal catalyst according to any one of claims 1 to 5 in hydrogen production by methanol steam reforming.

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