Precious metal-based catalyst as well as preparation method and application thereof

Abstract

The invention discloses a noble metal-based catalyst as well as a preparation method and application thereof, and belongs to the technical field of methanol steam reforming hydrogen production and catalysts. The noble metal-based catalyst comprises a carrier, an auxiliary agent metal and an active metal, the carrier comprises CeO2, and the shape of the carrier is in a rod shape; the active metal comprises Pt; the auxiliary agent metal comprises In2O3; the active sites of the noble metal-based catalyst comprise Pt < 2 + > and Pt < delta + >, the Pt < 2 + > is higher than 85%, and the Pt < delta + > is lower than 15%. 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 steam reforming of methanol and catalysts, and particularly relates to a noble metal-based catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] As an effective means of hydrogen production, the technology of steam reforming of methanol has attracted much attention due to the flexibility of its distributed application. However, with the continuous increase in hydrogen demand, the requirements for the hydrogen production process and hydrogen purity are also constantly improving. Although the copper-based catalysts used in traditional industrialization have high catalytic activity, their pyrophoricity and stability problems limit their application scope. Noble metal-based catalysts, especially platinum-based catalysts, have become potential catalytic systems due to their excellent stability and reactivity.

[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. 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-based 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 purpose, an embodiment of the present application provides a noble metal-based catalyst, including: a carrier, a promoter metal, and an active metal;

[0006] The carrier includes CeO2, and the morphology of the carrier is rod-shaped;

[0007] The active metal includes Pt;

[0008] The promoter metal includes In2O3;

[0009] The active sites of the noble metal-based catalyst include: Pt 2+ and Pt δ+ , where, Pt 2+ is higher than 85%, and Pt δ+ is lower than 15%.

[0010] In one embodiment, the specific surface area of the carrier is 70-160 m 2 g -1 ;

[0011] and / or, the pore volume of the carrier is 0.35-0.97 m 3 g -1 .

[0012] In one embodiment, the noble metal-based catalyst comprises: 3-7 wt.% promoter metal and 0.01-1.5 wt.% active metal.

[0013] In one embodiment, the average diameter of the support is 3-20 nm and the length is 30-150 nm.

[0014] In one embodiment, the main exposed crystal planes of the support are (110) and (111);

[0015] and / or, the oxygen vacancies O of the noble metal-based catalyst v are 32-55%.

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

[0017] Prepare the support by a hydrothermal method, wherein the support comprises CeO2 and the morphology of the support is rod-shaped;

[0018] Load the active metal and the promoter metal on the support to obtain the noble metal-based catalyst, wherein the promoter metal comprises In2O3, the active metal comprises Pt, and the active sites of the noble metal-based catalyst comprise: Pt 2+ and Pt δ+ , wherein, Pt 2+ is higher than 85%, and Pt δ+ is lower than 15%.

[0019] In one embodiment, the step of preparing the support 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 support.

[0022] In one embodiment, the heating temperature when heating the solid-liquid mixture is 90-110 °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 support to obtain the noble metal-based 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 support in the mixed solution, take out the support loaded with the active metal and the promoter metal and calcine to obtain the noble metal-based catalyst.

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

[0028] One or more technical solutions proposed by the present application have at least the following technical effects: providing a noble metal-based catalyst, including: a carrier, a promoter metal, and an active metal; the carrier includes CeO2, and the morphology of the carrier is rod-shaped; the active metal includes Pt; the promoter metal includes In2O3; the active sites of the noble metal-based catalyst include: Pt 2+ and Pt δ+ , where, Pt 2+ is higher than 85%, and Pt δ+ is lower than 15%. Since the used CeO2 carrier has a rod-shaped morphology, it has a strong dispersion effect on the promoter metal and is prone to strong interaction, so that In2O3 mainly exists as highly dispersed nano-small particles, and Pt can also be better dispersed. When the dispersion of Pt is better, the interaction among the active metal - promoter metal and the carrier is enhanced, the Pt 0 nanoparticles disappear, and the active sites of Pt are mainly atomically dispersed Pt 2+ and cluster Pt δ+ , and a Pt 2+ -In2O3-CeO2 structural interface is formed as the main reaction path, and there are also a small number of Pt δ+ paths. Furthermore, when the noble metal-based catalyst is applied to methanol steam reforming (MSR), the Pt metal sites (Pt 2+ ) 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 Pt 2+ -In2O3-CeO2 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. Description of the Drawings

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

[0030] Figure 2 It is a schematic flow diagram of the preparation method of the noble metal-based catalyst involved in the embodiment of the present application;

[0031] Figure 3 It is a schematic diagram of the TEM result involved in the embodiment of the present application;

[0032] Figure 4 It is a schematic diagram of the XPS result involved in the embodiment of the present application;

[0033] Figure 5 This is a schematic diagram of the infrared results related to the solution of the embodiment of this application.

[0034] The realization of the purpose of this application, functional features and advantages will be further described with reference to the embodiments and the accompanying drawings. Specific Embodiments

[0035] To make the purpose, technical solutions and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this 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 all be obtained as conventional products through commercial purchase.

[0036] Hereinafter, embodiments of a noble metal-based catalyst, its preparation method and application disclosed in this application will be specifically described in detail with reference to the accompanying drawings as appropriate. However, there will 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 descriptions from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following descriptions are provided for those skilled in the art to fully understand this application, and are not intended to limit the subject matter recited in the claims.

[0037] The "range" disclosed in this application is 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 boundary of a specific range. The range defined in this way can include 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 60-120 and 80-110 are listed for a specific parameter, ranges of 60-110 and 80-120 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, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise stated, the numerical range "a~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 "0~5" means that all real numbers between "0~5" have been fully listed in this article, and "0~5" 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 integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0038] If there is no special description, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0039] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions.

[0040] Unless otherwise specified, all steps of this application can be carried out in sequence or randomly, preferably in sequence. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out in sequence, or may also include steps (b) and (a) carried out in sequence. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or may also include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0041] Unless otherwise specified, the terms "comprising" and "including" mentioned in this application mean open-ended, and can also be closed-ended. For example, the "comprising" and "including" may mean that other components not listed may also be included or comprised, or may only include or comprise the listed components.

[0042] Unless otherwise specified, in this application, the term "or" is inclusive. 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).

[0043] 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.

[0044] 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 manner of this application. The appearances of "in one embodiment" in different places in this specification do not all refer to the same embodiment, nor are they separate or alternative embodiments that are mutually exclusive with other embodiments.

[0045] 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.

[0046] 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.

[0047] In the embodiments of the present application, since the used CeO2 carrier has a rod-like morphology, it has a strong dispersion effect on the promoter metal and is prone to strong interaction, making In2O3 mainly in the form of highly dispersed nano-small particles, and Pt can also be better dispersed. When the dispersion of Pt is good, the interaction among the active metal-promoter metal and the carrier is enhanced, and the Pt 0 nanoparticles disappear, and the active sites of Pt are mainly atomically dispersed Pt 2+ and cluster Pt δ+ , and a Pt 2+ -In2O3-CeO2 structural interface is formed as the main reaction path, and there are also a small number of Pt δ+ paths. Furthermore, when the noble metal-based catalyst is applied to methanol steam reforming (MSR), the Pt metal sites (Pt 2+ ) 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 Pt 2+ -In2O3-CeO2 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 the by-products.

[0048] The first aspect of the embodiments of the present application provides a noble metal-based catalyst, including: a carrier, a promoter metal, and an active metal;

[0049] The carrier includes CeO2, and the morphology of the carrier is rod-like;

[0050] The active metal includes Pt;

[0051] The promoter metal includes In2O3;

[0052] The active sites of the noble metal-based catalyst include: Pt 2+ and Pt δ+ , where Pt 2+ is higher than 85%, and Pt δ+ is lower than 15%.

[0053] In a feasible embodiment, Pt (platinum) is a highly 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 support surface, preventing its sintering or aggregation, thereby maintaining a high specific surface area and the number of active sites, ensuring that the catalyst maintains high efficiency throughout the reaction process.

[0054] In a feasible embodiment, the introduction of In2O3 can enhance the interaction between the support and the active metal, especially through the strong metal-support interaction (SMSI); this interaction helps to stabilize the Pt particles, preventing them from sintering and aggregating during high-temperature or long-term reaction processes, thereby maintaining the high dispersion and large specific surface area of the catalyst, ensuring continuous high catalytic activity. Secondly, In2O3, as a good electron donor, can promote the formation of oxygen vacancies on the catalyst surface. These oxygen vacancies not only act as active sites directly participating in the adsorption and conversion of reactants but also provide additional oxygen storage capacity, helping to maintain the oxygen supply required for the reaction and reducing the generation of CO in the products.

[0055] 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 that the catalyst does not deactivate during long-term operation, thereby reducing the replacement frequency of the catalyst during actual application, lowering the maintenance cost, and improving the production efficiency. The support used in the embodiment of the present application has a rod-like structure and a large mesopore volume, and is prone to generating a large number of oxygen vacancies. These oxygen vacancies are not only active sites directly participating in the adsorption and activation of reactant molecules (such as methanol and water) but also act as oxygen storage centers, providing or accepting oxygen atoms during the reaction process, thereby promoting the formation and conversion of key intermediates. For example, during the MSR process, the oxygen vacancies in CeO2 can help decompose methanol into CO and H2, and further convert CO into CO2 and additional H2 through the water-gas shift reaction (WGS). This not only increases the hydrogen production but also reduces the generation of the by-product CO and improves the hydrogen purity.

[0056] In a feasible embodiment, the specific surface area of the support is 70 - 160 m 2 g -1 ; for example, 70 m 2 g -1 、75 m 2 g -1, 80 m 2 g -1 , 85 m 2 g -1 , 90 m 2 g -1 , 95 m 2 g -1 , 100 m 2 g -1 , 105 m 2 g -1 , 110 m 2 g -1 , 115 m 2 g -1 , 120 m 2 g -1 , 125 m 2 g -1 , 130 m 2 g -1 , 135 m 2 g -1 , 140 m 2 g -1 , 145 m 2 g -1 , 150 m 2 g -1 , 155 m 2 g -1 , 160 m 2 g -1 etc.

[0057] In a feasible embodiment, the pore volume of the carrier is 0.35 - 0.97 m 3 g -1 ; 0.35 m 3 g -1 , 0.36 m 3 g -1 , 0.38 m 3 g -1 , 0.4 m 3 g -1 , 0.42 m 3 g -1 , 0.44 m 3 g -1 , 0.46 m 3 g -1 , 0.48 m 3 g -1 , 0.5 m 3 g -1 , 0.52 m 3 g -1 , 0.54 m 3 g -1 , 0.56 m3 g -1 、 0.58 m 3 g -1 、 0.6 m 3 g -1 、 0.62 m 3 g -1 、 0.64 m 3 g -1 、 0.66 m 3 g -1 、 0.68 m 3 g -1 、 0.7 m 3 g -1 、 0.72 m 3 g -1 、 0.74 m 3 g -1 、 0.76 m 3 g -1 、 0.78 m 3 g -1 、 0.8 m 3 g -1 、 0.82 m 3 g -1 、 0.84 m 3 g -1 、 0.86 m 3 g -1 、 0.88 m 3 g -1 、 0.9 m 3 g -1 etc.

[0058] In a feasible embodiment, the morphology of the CeO2 support in the embodiments of the present application is rod-shaped, and the exposed crystal planes are mainly (110) and (111). Among them, the atomic arrangement on the (110) crystal plane is sparse, and it is easier for O to precipitate, and it is easier to form a large number of defect sites and oxygen vacancies. It has a strong dispersion effect on the promoter metal and is prone to strong interaction, so that In2O3 mainly exists as highly dispersed nano-small particles, and Pt can also be better dispersed. When the dispersion of Pt is better, the interaction between the active metal-promoter metal and the support is enhanced, and the Pt 0 nano-particles disappear, and the active sites of Pt are mainly atomically dispersed Pt 2+ and cluster Pt δ+ , and form a Pt 2+ -In2O3-CeO2 structural interface as the main reaction path, and there are also a small number of Pt δ+ paths. Furthermore, when the noble metal-based catalyst is applied to the steam reforming of methanol to produce hydrogen, it will use Pt metal sites (Pt 2+)As an efficient active center, it can effectively promote methanol dissociation and water molecule activation, and accelerate the methanol steam reforming reaction. And the synergy of Pt 2+ -In2O3-CeO2 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.

[0059] In a feasible embodiment, the main exposed crystal planes of the carrier are (110) and (111).

[0060] In a feasible embodiment, the oxygen vacancies O of the noble metal-based catalyst v are 32-55%.

[0061] In a feasible example, since the morphology of CeO2 is rod-shaped, its main exposed crystal planes are (110) and (111). The (110) crystal plane has a higher oxygen vacancy concentration, while the (111) crystal plane provides a moderate oxygen vacancy concentration and good oxygen migration ability, which helps to maintain the catalytic activity while ensuring the structural stability. Furthermore, the abundant oxygen vacancies and unsaturated coordinated cerium ions on the (110) crystal plane can effectively adsorb and activate oxygen molecules, while the (111) crystal plane helps with subsequent reaction steps, such as the stabilization and conversion of intermediate products.

[0062] In a feasible example, the oxygen vacancies O of the noble metal-based catalyst in the embodiments of the present application v are 32-55%. A higher proportion of oxygen vacancies means more active sites, thus improving the activation efficiency of water molecules. At the same time, it helps to guide the reaction along the expected path, reduce the occurrence of side reactions, optimize the selectivity of H2, and increase the hydrogen production.

[0063] Optionally, in the noble metal-based catalyst of the embodiments of the present application, the Pt 2+ -In2O3-CeO2 structural interface is mainly dominant. This structure makes it easy to generate oxygen vacancies on In2O3, and the generated hydroxyl groups can directly react with formaldehyde to produce monodentate-bonded formate intermediates (m-*HCOO), forming a direct path. However, for the small amount of Pt that fails to be evenly dispersed on In2O3, the Pt δ+ -CeO□ structure formed with CeO2 may lead to a more complex reaction path, that is, depending on the distance of the oxygen vacancies, it may follow a direct path or a cooperative path. The existence of these two paths reflects the diversity of the internal structure of the catalyst and the complexity of the reaction mechanism, and also demonstrates the possibility of optimizing the reaction path by regulating the catalyst structure.

[0064] Exemplarily, referring to Figure 1 , Figure 1 (1) is Pt 2+The direct path, in which methanol and water are adsorbed on Pt respectively 2+ and Pt 2+ -At the oxygen vacancies at the In2O3-CeO2 interface of Pt, methanol is gradually dehydrogenated to form formaldehyde (HCHO), while H2O decomposes in the oxygen vacancies to form H and OH. The adsorbed formaldehyde (CH2O) can directly react with OH to form monodentate m-*HCOO, and then decompose to form CO2 and H2. The conversion rate of this process is relatively fast. Figure 1 (2) is the cooperative reaction path of Pt δ+ with the oxygen vacancies at the In2O3-CeO2 interface. In this path, methanol and water are adsorbed on Pt δ+ and the oxygen vacancies at the In2O3-CeO2 interface respectively. Methanol is gradually dehydrogenated to form formaldehyde (HCHO), while H2O decomposes in the oxygen vacancies to form H and OH. However, since the oxygen vacancies and Pt δ+ are not adjacent, the OH formed in the oxygen vacancies needs to migrate to Pt δ+ before it can react with CH2O to form bidentate bi-*HCOO and decompose to form CO2 and H2. The migration of OH is involved in this process, so the conversion rate is relatively slow.

[0065] In a feasible embodiment, the noble metal-based catalyst includes: 3-7 wt.% promoter metal and 0.01-1.5 wt.% active metal. For example, the loading amount of the promoter metal is 3 wt.%, 3.5 wt.%, 4 wt.%, 4.5 wt.%, 5 wt.%, 5.5 wt.%, 6 wt.%, 6.5 wt.%, 7 wt.%, etc. The loading amount of the active metal is 0.01 wt.%, 0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, 1 wt.%, 1.1 wt.%, 1.2 wt.%, 1.3 wt.%, 1.4 wt.%, 1.5 wt.%, etc.

[0066] In a feasible embodiment, when the loading amount of the active metal is too high, it may lead to the agglomeration 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, thereby weakening the catalytic efficiency. Secondly, a high loading amount may cause too high a coverage on the surface of the support, hindering the reactant molecules from contacting important active centers such as promoters or oxygen vacancies on the support, and thus affecting the synergistic effect. On the contrary, when the loading amount of the active metal is too low, although the cost can be saved and the above-mentioned agglomeration problem can be avoided, 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, in the embodiments of the present application, the loading amount of the active metal in the noble metal-based catalyst is determined to be 0.01-1.5 wt.%.

[0067] In a feasible embodiment, when the loading amount of the promoter metal is too high, it may lead to partial shielding of the active sites on the catalyst surface. Since the promoter metal particles are relatively large, too much promoter metal will cover the surface of the active metal, reducing the exposed effective active sites, thereby reducing 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, and thus weakening the synergistic effect between the two, 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 that the provided oxygen vacancies and additional active centers are insufficient, which is not conducive to promoting the adsorption, activation of reactant molecules, and the formation of intermediate products. For example, in the MSR process, an appropriate amount of promoter metal helps to stabilize the hydroxyl species and promote their migration to the Pt active center to generate a bidentate-bonded formate intermediate. 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, in the embodiments of the present application, the loading amount of the promoter metal in the noble metal-based catalyst is determined to be 3-7 wt.%.

[0068] In a feasible embodiment, the average diameter of the support is 3-20 nm and the length is 30-150 nm; for example, the average diameter of the support is 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, etc. The length of the support is 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, etc.

[0069] Optionally, the noble metal-based catalyst of the embodiments of the present application can be used for the methanol steam reforming reaction to produce hydrogen.

[0070] In this embodiment, the noble metal catalyst has a high dispersion of Pt and a larger number of active sites. Therefore, it has excellent performance in activating and decomposing methanol and water molecules. At the same time, the highly dispersed promoter particles and the mainly exposed (110) crystal plane of the rod shape result in a high oxygen vacancy content in the catalyst. The atomic arrangement on the (110) crystal plane is loose, making it easier to occur the O precipitation - filling cycle. Thus, the two effects are superimposed, and the oxygen vacancy of this catalyst is relatively high (32 - 55%), enabling the decomposition of Pt to methanol and the promoter support to water to be promoted simultaneously. Therefore, the catalyst has a higher methanol conversion rate and maintains a low selectivity to CO. In addition, the more defect sites of the rod shape have a stronger anchoring effect on the promoter In2O3, which can inhibit the agglomeration and over - reduction of In2O3 during the reaction, increasing the stability of the catalyst.

[0071] Further, referring to Figure 2 , the embodiment of the present application also provides a preparation method of a noble metal - based catalyst. The preparation method of the noble metal - based catalyst includes the following steps:

[0072] Step S10, preparing a support by a hydrothermal method, where the support includes CeO2 and the morphology of the support is rod - shaped;

[0073] In a feasible embodiment, a rod - shaped CeO2 support is obtained by the hydrothermal method.

[0074] In a feasible implementation manner, step S10, the step of preparing a support by a hydrothermal method includes:

[0075] Step S11, mixing a NaOH solution and a cerium nitrate solution to obtain a solid - liquid mixture;

[0076] Step S12, heating the solid - liquid mixture and centrifuging and washing to obtain the support.

[0077] In a feasible embodiment, a 6 - 9M NaOH solution and a 0.2 - 0.6M cerium nitrate solution are provided. The NaOH solution and the cerium nitrate solution are mixed to generate a precipitate, obtaining a solid - liquid mixture. The solid - liquid mixture is heated at a temperature of 90 - 110°C for 5 - 35 h to carry out a hydrothermal reaction, and then a rod - shaped CeO2 support is obtained through centrifuging, washing, and drying. The average diameter of the support is 3 - 20 nm, the length is 30 - 150 nm, the specific surface area is 70 - 160 m 2 g -1 , and the pore volume is 0.35 - 0.97 m 3 g -1 .

[0078] Optionally, the concentration of NaOH can be 6M, 7M, 8M, 9M, etc.

[0079] Optionally, the cerium nitrate concentration can be 0.2M, 0.3M, 0.4M, 0.5M, 0.6M, etc.

[0080] Optionally, the heating temperature of the solid-liquid mixture is 90°C, 95°C, 100°C, 105°C, 110°C, etc.

[0081] Optionally, the heating duration of the solid-liquid mixture is 5h, 10h, 15h, 20h, 25h, 30h, 35h, etc.

[0082] In this embodiment, by controlling the hydrothermal reaction conditions, a rod-shaped CeO2 support is prepared. Among them, the average diameter of the support is 3 - 20 nm, the length is 30 - 150 nm, the specific surface area is 70 - 160 m 2 g -1 , and the pore volume is 0.35 - 0.97 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-based catalyst, thereby promoting methanol dissociation and water molecule activation, accelerating the methanol steam reforming reaction, and reducing the generation of CO in the products.

[0083] Step S20, load the active metal and the promoter metal on the support to obtain a noble metal-based catalyst. Among them, the promoter metal includes In2O3, the active metal includes Pt, and the active sites of the noble metal-based catalyst include: Pt 2+ and Pt δ+ , where, Pt 2+ is higher than 85%, and Pt δ+ is lower than 15%.

[0084] In a feasible embodiment, provide an active metal including Pt, and provide a promoter metal including In2O3; load the active metal and the promoter metal on the support to obtain a noble metal-based catalyst. Among them, the active sites of the noble metal-based catalyst include: Pt 2+ and Pt δ+ , where, Pt 2+ is higher than 85%, and Pt δ+ is lower than 15%.

[0085] In a feasible embodiment, step S20, the steps of loading the active metal and the promoter metal on the support to obtain a noble metal-based catalyst include:

[0086] Step S21, prepare an active metal solution and a promoter metal solution;

[0087] Step S22, mix the active metal solution and the promoter metal solution to obtain a mixed solution;

[0088] Step S23: 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-based catalyst.

[0089] In a feasible embodiment, prepare an active metal solution and a promoter metal solution, and mix them to obtain a mixed solution; place the carrier in the mixed solution, subject it to ultrasonic treatment, then place it for impregnation, and dry and calcine to obtain a Pt-In2O3 / CeO2-r noble metal-based catalyst.

[0090] Optionally, the calcination temperature is 300 - 550 °C, and the calcination duration is 2 - 10 h.

[0091] Optionally, the noble metal-based catalyst prepared in the embodiments of the present application can be used in the methanol steam reforming reaction for hydrogen production.

[0092] In this embodiment, since the CeO2 carrier used has a rod-like morphology, it has a strong dispersion effect on the promoter metal and is prone to strong interactions, so that In2O3 mainly exists as highly dispersed nano-small particles, and Pt can also be better dispersed. When the dispersion of Pt is better, the interaction among the active metal - promoter metal and the carrier is enhanced, and the Pt 0 nanoparticles disappear, and the active sites of Pt are mainly atomically dispersed Pt 2+ and cluster Pt δ+ , and a Pt 2+ -In2O3-CeO2 structural interface is formed as the main reaction path, and there are also a small number of Pt δ+ paths. Furthermore, when the noble metal-based catalyst is applied to methanol steam reforming for hydrogen production, Pt metal sites (Pt 2+ ) 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 Pt 2+ -In2O3-CeO2 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.

[0093] 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 reflect the advanced performance of the embodiments of the present application, the following uses multiple embodiments to illustrate the above technical solutions.

[0094] Example 1

[0095] (1) Weigh cerium nitrate and dissolve it in deionized water to prepare a 0.2 M cerium nitrate solution; weigh NaOH and dissolve it in deionized water to prepare a 7 M NaOH solution; mix the NaOH solution and the cerium nitrate solution to obtain a solid-liquid mixture;

[0096] (2) Transfer the solid-liquid mixture into a polytetrafluoroethylene liner, place it in a stainless steel hydrothermal autoclave and tighten the seal; place the hydrothermal autoclave in an oven at 100 °C and heat for 24 h to obtain rod-shaped CeO2 support (CeO2-r).

[0097] (3) Prepare chloroplatinic acid solution, where the concentration of Pt 4+ is 0.21 M; prepare In(NO3)3 solution, and the concentration of In 3+ is 0.56 M.

[0098] (4) Pipette an appropriate amount of chloroplatinic acid solution and In(NO3)3 solution, and weigh the CeO2-r 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 Pt-In2O3 / CeO2-r catalyst, where the theoretical loading of Pt is 1 wt.%, and the theoretical loading of In2O3 is 7 wt.%.

[0099] Example 2

[0100] The experimental steps are the same as those in Example 1, except that:

[0101] In step (2), place the hydrothermal autoclave in an oven at 90 °C and heat for 12 h to obtain rod-shaped CeO2 support (CeO2-r1).

[0102] Example 3

[0103] The experimental steps are the same as those in Example 1, except that:

[0104] In step (2), place the hydrothermal autoclave in an oven at 105 °C and heat for 24 h to obtain rod-shaped CeO2 support (CeO2-r2).

[0105] Comparative Example 1

[0106] The experimental steps are the same as those in Example 1, except that:

[0107] In step (2), place the hydrothermal autoclave in an oven at 130 °C and heat for 24 h to obtain a CeO2 support (CeO2-h) mixed with rods and cubes.

[0108] Comparative Example 2

[0109] The experimental steps are the same as those in Example 1, except that:

[0110] Select CTAB surfactant, and prepare CeO2 with nanoparticles stacked by sol-gel method. Among them, control the heating rate at 1 °C / min, heat up to 450 °C, and maintain calcination for 4 h to obtain CeO2 with particles stacked (CTAB-1 °C / min).

[0111] Comparative Example 3

[0112] The experimental procedure was the same as that of Example 1, except that:

[0113] CTAB surfactant was selected, and CeO2 with nanoparticle accumulation was prepared by sol-gel method. The heating rate was controlled at 4 °C / min, heated to 450 °C, and calcined for 4 h. CeO2 with particle accumulation (CTAB-4 °C / min) was obtained.

[0114] Comparative Example 4

[0115] The experimental procedure was the same as that of Example 1, except that: only the active metal Pt was loaded, and the promoter metal In2O3 was not loaded.

[0116] The specific surface area, pore volume and loading amount of the catalysts in Examples 1 to 3 and Comparative Examples 1 to 4 were tested, and the experimental results are shown in Table 1 below; according to Table 1, it can be seen that for the carrier CeO2-r 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 loading amount and actual loading amount of Pt and In2O3 were close.

[0117] Table 1

[0118]

[0119]

[0120] TEM test was carried out on Example 1, and the results are referred to Figure 3 , among which, Figure 3 a to c are characterization diagrams at different magnification factors. It can be seen that the prepared carrier has a rod-like morphology, the particles are uniform, the average diameter is 10 nm, and the length is about 100 nm. Referring to Figure 3 atomically dispersed Pt can be observed 2+ , there is Pt 2+ -In2O3-CeO2 structural interface, and Pt δ+ -CeO2 structure is also observed; while In2O3 mainly exists as nanoscale small particles and has a strong interaction with Pt and CeO2.

[0121] XPS characterization was carried out on Example 1 and Comparative Examples 2 and 3, and the results are referred to Figure 4 and Table 2 below, among which, Figure 4 is the schematic diagram of the XPS characterization results of Example 1; it can be seen that in Example 1, Pt is mainly in the form of Pt 2+ , and there is a small amount of Pt δ+ ; there are a large number of oxygen vacancies in O, and there are many Pt 2+ -In2O3-CeO2 in In2O3, while Pt2+ and Pt δ+ The ratios are 95% and 5% respectively, with oxygen vacancies mainly accounting for 43%, while Pt in In2O3 2+ -In2O3-CeO2 has 40%.

[0122] Table 2

[0123]

[0124] The catalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were applied to hydrogen production by steam reforming of methanol; through a micro fixed-bed quartz tube reactor, the performance evaluation of the catalysts for hydrogen production by steam reforming of methanol was carried out. The reaction was carried out under 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 an on-line chromatograph for detection. The experimental results are shown in Table 3 below:

[0125] Table 3

[0126]

[0127]

[0128] According to the above experimental results, it can be seen that the noble metal-based catalysts prepared in Examples 1 to 3 of the present application have good methanol conversion rate and CO selectivity, and at the same time have outstanding stability. The methanol conversion rate can reach up to 97% at 340 °C, and the CO selectivity is relatively low (1.9%); the stability of each catalyst was characterized by testing the duration during which the methanol conversion rate of each catalyst remained above 85%. Furthermore, it was found that Examples 1 to 3 could still maintain a methanol conversion rate of 85% after 200 - 240 h, with outstanding stability. And according to the experimental results of Comparative Example 4, after adding In2O3, due to its easy agglomeration, the methanol conversion rate and stability will decrease to some extent. However, if In2O3 is not added, the CO content in the product will be too high.

[0129] The in-situ infrared MSR reaction was carried out on the catalyst of Example 1 to detect the generation of intermediate products during the MSR reaction. The results are referred to Figure 5 , among which, Figure 5 Figure a shows the vibration peak wavelength range of carbonate and formate, Figure 5 Figure b is the vibration peak wavelength range of CO2 and CO; according to Figure 5It can be seen that the intermediate products in the MSR reaction process in Example 1 include monodentate m-*HCOO, bidentate bi-*HCOO, CO, and CO2. During the low-temperature reaction process, the peak of CO2 can always be found, indicating that a large number of active surface oxygen, lattice oxygen, and oxygen vacancies on the porous rods can adsorb and activate the decomposition of water at a lower temperature, promote the competitive reaction of MSR, and reduce the MD reaction. Therefore, both the conversion rate and the CO2 selectivity are the highest. For the adsorption peak of CO, the peak of CO-Pt 0 was not observed, indicating that Pt is highly dispersed at the atomic level on CeO2-r and has a strong interaction with the carrier. At 2078 cm -1 , there is a peak of CO adsorbed on single-atom Pt (CO-Pt1), verifying that Pt can be atomically dispersed on the porous rods. As the temperature increases, the CO-Pt δ+ is also clearly observed. The m-*HCOO increases greatly, indicating that the reaction rate in this system is faster, that is, the direct path is the main one. The bi-*HCOO is also observed and increases with the increase in temperature, indicating that the synergistic path of a small amount of Pt δ+ +-CeO2 also reacts rapidly. The peak of -OH is found in the rods, probably because water decomposes on a large number of oxygen vacancies on In2O3 and CeO2 and then -OH is adsorbed. It shows that the Pt-In2O3 / CeO2-r catalyst mainly undergoes the direct reaction path, and the synergistic path also occurs. The peak of HCHO was not observed for both catalysts, indicating that the presence of In2O3 and water inhibits the side reaction of the desorption and decomposition of HCHO to produce CO. Therefore, the surface defect characteristics of CeO2 not only affect the dispersion and valence state of the active metal Pt, but also affect the dispersion of In2O3, form a large number of oxygen vacancies, adsorb a large amount of -OH, and promote the reaction.

[0130] 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-based catalyst, characterized in that The noble metal-based catalyst comprises: a carrier, a promoter metal and an active metal; The carrier includes CeO2, and the carrier has a rod-like morphology; The active metal includes Pt; The auxiliary metal includes In2O3; The active sites of the noble metal-based catalyst include: Pt 2+ and Pt δ+ , where Pt 2+ Above 85%, Pt δ+ Less than 15%.

2. The noble metal-based catalyst according to claim 1, characterized in that The specific surface area of ​​the carrier is 70 to 160 m 2 g -1 ; And / or, the pore volume of the carrier is 0.35 to 0.97 m 3 g -1 .

3. The noble metal-based catalyst according to claim 1, characterized in that The noble metal-based catalyst comprises: 3-7 wt.% of promoter metal and 0.01-1.5 wt.% of active metal.

4. The noble metal-based catalyst according to claim 1, characterized in that The average diameter of the carrier is 3-20 nm, and the length is 30-150 nm.

5. The noble metal-based catalyst according to claim 1, characterized in that The main exposed crystal faces of the carrier are (110) and (111); And / or, the oxygen vacancies O of the noble metal-based catalyst v It is 32 to 55%.

6. A method for preparing a noble metal-based catalyst, characterized in that: The method is used to prepare the noble metal-based 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 has a rod-like morphology; Active metal and auxiliary metal are loaded on the carrier to prepare a noble metal-based catalyst, wherein the auxiliary metal includes In2O3, the active metal includes Pt, and the active sites of the noble metal-based catalyst include: Pt 2+ and Pt δ+ , where Pt 2+ Above 85%, Pt δ+ Less than 15%.

7. The method for preparing a noble metal-based 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 centrifuged for washing to obtain the carrier.

8. The method for preparing a noble metal-based catalyst according to claim 7, characterized in that: The solid-liquid mixture is heated at a temperature of 90 to 110° C. and a heating time of 5 to 35 hours.

9. The method for preparing a noble metal-based catalyst according to claim 6, characterized in that: The step of loading active metal and promoter metal on the carrier to prepare a noble metal-based 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-based catalyst.

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

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