A natural clay mineral encapsulated noble metal catalyst and a method for its preparation

Abstract

The application belongs to the technical field of noble metal catalysts, and particularly relates to a natural clay mineral encapsulated noble metal catalyst and a preparation method thereof. The chemical expression of the catalyst is A@MMT-S; wherein A is one or a combination of Rh, Ru, Ni, Pt and Ir, MMT-S is a delaminated montmorillonite subjected to acid treatment, and the average size of the metal A nanoparticles is less than 2 nm. The preparation method of the application successfully removes the cations between the layers of the montmorillonite through a simple acid treatment method, opens the clay mineral layers, forms ideal empty interlayer spaces, and is very suitable for encapsulating metal particles. Meanwhile, the rich interlayer silanol nests formed by the acid treatment can effectively fix the metal nanoparticles, prevent the aggregation of the metal nanoparticles, and improve the dispersity and stability of the metal. The natural clay mineral montmorillonite is used as a carrier, the cost is low, and the resource is rich, so that the preparation cost is greatly reduced, and the application has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of precious metal catalyst technology, specifically relating to a precious metal catalyst encapsulated in natural clay minerals and its preparation method. Background Technology

[0002] Heterogeneous metal catalysts play a crucial role in chemical reactions, particularly in energy conversion and storage. Due to their high catalytic efficiency, these catalysts are widely used in various reactions, including hydrogen production, pollutant degradation, and fuel cells. Noble metal catalysts (such as platinum, palladium, and rhodium) have attracted considerable attention due to their excellent catalytic activity; however, their high cost and limited resources severely restrict their large-scale application. To reduce costs and improve catalyst utilization, researchers have developed catalysts based on non-noble metals (such as iron, nickel, and cobalt) and metal alloys. By optimizing the combination and structure of the metals, synergistic effects have been achieved, significantly improving catalytic performance and stability.

[0003] Metal-based heterogeneous catalysts have been extensively studied and proven to be highly efficient in hydrogen production via the hydrolysis of ammonia borane. These catalysts include noble metal catalysts (such as rhodium, ruthenium, platinum, palladium, and gold), non-noble metal catalysts (such as iron, cobalt, nickel, and copper), and metal phosphide catalysts (such as nickel phosphide and cobalt phosphide). Among these catalysts, noble metal nanocatalysts exhibit the highest hydrogen production activity. However, the scarcity and high cost of noble metals limit their widespread use in practical applications. To address this issue, researchers have developed alloy catalysts, particularly alloys combining noble and non-noble metals. This not only improves the utilization rate of noble metals but also significantly enhances catalytic activity through synergistic effects, especially in promoting the cleavage of the -OH bonds in water molecules, which is the rate-determining step of the entire reaction.

[0004] Currently, much research focuses on developing metal alloy nanoparticles for the hydrolysis of ammonia borane. These alloys include bimetallic systems such as rhodium-nickel, rhodium-cobalt, ruthenium-nickel, ruthenium-cobalt, and palladium-nickel, as well as trimetallic systems such as palladium-cobalt-silver, platinum-gold-cobalt, platinum-gold-nickel, and platinum-cobalt-nickel. Due to their high surface energy, these nanocatalysts often exhibit severe aggregation, leading to larger metal particle sizes (typically exceeding 3 nm), thereby reducing catalytic efficiency and stability. Therefore, preparing ultrafine metal nanoparticle catalysts with high dispersibility and high stability remains a significant challenge. Furthermore, the complex structure-function relationships within multimetallic alloys in ammonia borane hydrolysis systems have been rarely investigated in depth.

[0005] Currently, sheet-like materials used for preparing highly dispersed metal catalysts, such as nitrogen-doped and aniline-functionalized graphene, graphitic carbon nitride (g-C3N4), and two-dimensional zeolites, are considered ideal materials. These materials possess high surface area and abundant surface anchoring groups, enabling effective immobilization of metal nanoparticles. However, the high production cost of these sheet-like materials limits their widespread application. Many metal nanocatalysts tend to aggregate during preparation due to their high surface energy, leading to increased metal particle size (typically exceeding 3 nanometers). This aggregation not only reduces catalyst activity but also severely affects its stability. Effectively preventing the aggregation of metal nanoparticles and maintaining their high dispersibility is a significant challenge. Many metal nanocatalysts exhibit poor stability at high temperatures and in redox atmospheres, limiting their long-term use in practical applications. Improving the thermal and chemical stability of catalysts is essential for their practical application. The structure-function relationship within multi-metal alloys is complex, and the specific mechanism in the hydrolysis reaction of ammonia borane has not been fully investigated. A deeper understanding of these relationships will contribute to the design of more efficient catalysts, but current research in this area remains insufficient.

[0006] Therefore, although current research has made significant progress in developing efficient ammonia borane hydrolysis catalysts, it still faces challenges such as high material costs, metal nanoparticle aggregation, and insufficient catalyst stability. Summary of the Invention

[0007] The technical problem to be solved by this invention is to provide a natural clay mineral-encapsulated precious metal catalyst and its preparation method. By using montmorillonite (MMT), a low-cost and naturally abundant clay mineral, as a carrier, and through acid treatment, ultrafine metal nanoparticles are successfully immobilized and encapsulated. This significantly improves the dispersibility and stability of the catalyst and significantly reduces production costs, thus providing a new, economical, and efficient route for hydrogen production from ammonia borane hydrolysis. The technical solution adopted is as follows:

[0008] A natural clay mineral-encapsulated noble metal catalyst, with the chemical formula A@MMT-S, wherein A is one or more of Rh, Ru, Ni, Pt, and Ir, and MMT-S is acid-treated, layer-exfoliated montmorillonite. The average size of the nanoparticles of metal A is less than 2 nm. If multiple metals are used, the average size of the metal alloy nanoparticles is also less than 2 nm.

[0009] Preferably, the chemical formula is Rh x Ru 1-x Ni y@MMT-S; where x and y are the molar ratios of Rh, Ru, and Ni, 0 ≤ x ≤ 1, 0 ≤ y ≤ 0.5; the acid is any one of nitric acid, hydrochloric acid, and sulfuric acid. The chemical expression can also be Rh x Ru 1-x @MMT-S, at this time y is 0, 0≤x≤1.

[0010] A method for preparing a precious metal catalyst encapsulated in natural clay minerals includes the following steps:

[0011] (1) Montmorillonite (MMT) was added to a nitric acid aqueous solution and continuously stirred in a water bath to obtain layer-exfoliated montmorillonite MMT-S;

[0012] (2) Dry the prepared MMT-S to remove the adsorbed water; add the dehydrated MMT-S to the aqueous solution of metal salt A under vigorous stirring and continue stirring;

[0013] (3) After stirring, the catalyst is dried overnight in a vacuum freeze dryer and then reduced in a hydrogen atmosphere to obtain the A@MMT-S catalyst.

[0014] Preferably, in step (1), the concentration of the nitric acid aqueous solution is 5-7 M; the temperature of the water bath is 60-90 °C; and the stirring time in the water bath is 1-10 h.

[0015] Preferably, in step (1), the concentration of the nitric acid aqueous solution is 7M; the temperature of the water bath is 80℃; and the stirring time in the water bath is 5h.

[0016] Preferably, in step (2), the ratio of the mole of A to the mass of MMT-S ranges from 0.030 to 0.080 mmol / g, with a further preferred ratio of 0.045 mmol / g. If multiple metals are included, the ratio is the total mole of all metals.

[0017] Preferably, in step (2), the aqueous solution of the metal salt of A is RuCl. 3、 RhCl 3、 Ni(NO3) 2、 H2PtCl 6、 One or more combinations of IrCl3 aqueous solutions.

[0018] Preferably, in step (2), MMT-S is dried in a drying oven at 100°C for 1-2 hours; the aqueous solution of metal salt A is added to the dehydrated MMT-S under vigorous stirring and then stirred for 2-3 hours.

[0019] Preferably, in step (3), the vacuum freeze-drying time is 12 to 24 hours.

[0020] Preferably, in step (3), the temperature of hydrogen atmosphere reduction is 200-600℃, such as 300℃ or 400℃, and the reduction time is 1-2h.

[0021] The catalyst prepared by this invention can be applied to the hydrolysis of ammonia borane to produce hydrogen.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] This invention uses montmorillonite, a natural clay mineral, as a carrier. It is inexpensive and abundant, which greatly reduces the preparation cost. It is superior to existing technologies in terms of economy, simplicity, and catalytic performance, and has broad application prospects.

[0024] The preparation method of this invention successfully removes cations between montmorillonite layers through a simple acid treatment, opening up the clay mineral layers and forming ideal empty interlayer spaces, which are very suitable for encapsulating metal particles. Simultaneously, the abundant interlayer silanol nests formed by acid treatment can effectively immobilize metal nanoparticles, preventing their aggregation and improving the dispersibility and stability of the metal.

[0025] The catalyst prepared in this invention exhibits excellent catalytic performance in the hydrolysis of ammonia borane to produce hydrogen. For example, at 298 K, the optimized Rh... 0.8 Ru 0.2 Ni 0.25 @MMT-S catalyst achieved up to 1960 min -1 Its extremely high TOF (transformation frequency) value is significantly higher than that of most existing advanced catalysts. Attached Figure Description

[0026] Figure 1 This is a flowchart of the preparation method in Example 1 of the present invention.

[0027] Figure 2 The images show a comparison of SEM images of acid-treated MMT-S and untreated MMT at different sizes. (a) and (b) are SEM images of MMT-S samples of 1µm and 100nm, respectively, and (c) and (d) are SEM images of MMT samples of 1µm and 100nm, respectively.

[0028] Figure 3 High-resolution STEM comparison images and size distribution maps of different catalysts prepared in this invention; where (ac) represents Rh 0.8 Ru 0.2 Ni 0.25 @MMT-S different high-resolution STEM images and size distribution maps, (df) for Rh 0.8 Ru 0.2Different high-resolution STEM images and size distribution maps of @MMT-S, (gi)Rh@MMT-S, and (jl)Rh / MMT.

[0029] Figure 4 High-resolution STEM images and size distribution maps of catalysts prepared by untreated MMT and other noble metals supported on MMT-S supports are shown. Among them, (ab) is the STEM image and size distribution of Ru@MMT-S, (cd) is the STEM image and size distribution of Ru / MMT, (ef) is the STEM image and size distribution of Pt@MMT-S, (gh) is the STEM image and size distribution of Pt / MMT, (ij) is the STEM image and size distribution of Ir@MMT-S, and (kl) is the STEM image and size distribution of Ir / MMT.

[0030] Figure 5 The graph shows the relationship between the volume of hydrogen produced by the catalyst at room temperature and the hydrolysis time of ammonia borane; where (a) the graph shows the relationship between the reaction time (in minutes) and volume of hydrogen production by Ru@MMT and Ru@MMT-S(ah) catalysts; (b) the graph shows the relationship between the reaction time (in minutes) and volume of Ru@MMT-S and Rh catalysts. x Ru 1-x @MMT-S hydrogen production reaction time (in minutes) versus volume; (c) Figure shows Rh 0.8 Ru 0.2 @MMT-S and Rh x Ru 1-x Ni y @MMT-S hydrogen production stripping time (in minutes) versus volume; (d) Figure shows a comparison of TOF values ​​for hydrogen production by hydrolysis of ammonia borane with different catalysts.

[0031] Figure 6 XRD patterns of Ru@MMT-S catalysts prepared from montmorillonite treated with different acids.

[0032] Figure 7 High-resolution STEM images and size distribution of the Ru@MMT-S-10h sample.

[0033] Figure 8 The TOF value is the result of hydrolysis of ammonia borane by Ru / MMT and Ru@MMT-S(ah) catalysts at room temperature.

[0034] Figure 9 A comparison of the volume of H2 produced by the hydrolysis of ammonia borane using Rh / MMT and Rh@MMT-S (5 hours) catalysts versus time.

[0035] Figure 10 The TOF values ​​for hydrolysis and dehydrogenation on RhxRu1-x@MMT-S catalyst with different Rh / Ru molar ratios are given.

[0036] Figure 11 Rh with different Ni contents 0.8 Ru 0.2 Ni y TOF value of @MMT-S catalyst in hydrodehydrogenation of ammonia borane. Detailed Implementation

[0037] The specific implementation schemes of the present invention will be clearly and completely described below with reference to the embodiments. The described embodiments are only a part of all the implementation cases and do not represent all the embodiments of the present invention. Unless otherwise specified, the raw materials and chemical reagents used in the embodiments can be obtained through conventional commercial means.

[0038] Example 1

[0039] like Figure 1 As shown, a method for preparing a precious metal catalyst encapsulated in natural clay minerals includes the following steps:

[0040] First, commercially available montmorillonite was treated in nitric acid solution to remove interlayer calcium ions. 2.0 g of montmorillonite was added to 50 mL of 7M nitric acid (HNO3) aqueous solution, and the solution was continuously stirred in an 80°C water bath for several hours. The delaminated montmorillonite was named MMT-S(ah), where 'a' represents the acid treatment time, which ranges from 1 to 10 hours. Alternatively, it can be denoted as MMT-S-ah.

[0041] like Figure 2 It can be seen that the MMT-S treated with nitric acid has clear stratification, opening up the clay mineral layers and forming ideal empty interlayer spaces. In contrast, the MMT stratification is unclear.

[0042] Metal clusters encapsulated in MMT-S were prepared by an initial wet impregnation method. Specifically, 0.2 g of MMT-S was pre-dried at 100 °C for 1 hour to remove adsorbed moisture. Then, an aqueous solution of RhCl3, RuCl3, and Ni(NO3)2 in a molar ratio of 0.8:0.2:0.25 was added to the dehydrated MMT-S under vigorous stirring for 2 hours. After drying the sample overnight in a vacuum freeze dryer, it was reduced at 300 °C for 2 hours under a hydrogen atmosphere and named RhCl3. 0.8 Ru 0.2 Ni 0.25 @MMT-S.

[0043] Ultrafine ternary rhodium-ruthenium-nickel alloy nanoparticles encapsulated within sheet-like montmorillonite layers were prepared using the method described above. High-resolution scanning transmission electron microscopy images revealed that the average size of the metal alloy nanoparticles was less than 2 nanometers, and they were encapsulated within the montmorillonite by interlayer silanol. Due to the confinement effect of montmorillonite, the trimetallic catalyst exhibited excellent thermal stability in oxidizing and reducing atmospheres and at temperatures up to 600°C.

[0044] Example 2

[0045] 0.2 g of MMT-S was pre-dried at 100 °C for 1 hour to remove adsorbed moisture. Then, 0.045 mL of 0.2 M ruthenium chloride (RuCl3) aqueous solution was added to the dehydrated MMT-S under vigorous stirring for 2 hours. After drying the sample overnight in a vacuum freeze dryer, it was reduced at 300 °C for 2 hours under a hydrogen atmosphere and named Ru@MMT-S.

[0046] Other areas not mentioned are the same as in Example 1.

[0047] Example 3

[0048] 0.2 g of MMT-S was pre-dried at 100 °C for 1 hour to remove adsorbed moisture. Then, 0.045 mL of 0.2 M RhCl3 aqueous solution was added to the dehydrated MMT-S under vigorous stirring for 2 hours. After drying the sample overnight in a vacuum freeze dryer, it was reduced at 300 °C for 2 hours under a hydrogen atmosphere and named Rh@MMT-S.

[0049] Other areas not mentioned are the same as in Example 1.

[0050] Example 4

[0051] 0.2 g of MMT-S was pre-dried at 100 °C for 1 hour to remove adsorbed moisture. Then, RhCl was added in a molar ratio of 0.8:0.2. 3、 A RuCl3 aqueous solution was added to dehydrated MMT-S under vigorous stirring, and the mixture was stirred for 2 hours. After drying the sample overnight in a vacuum freeze dryer, it was reduced at 300°C for 2 hours under a hydrogen atmosphere and named Rh. 0.8 Ru 0.2 @MMT-S.

[0052] Other areas not mentioned are the same as in Example 1.

[0053] Example 5

[0054] 0.2 g of MMT-S was pre-dried at 100 °C for 1 hour to remove adsorbed moisture. Then, 0.045 mL of 0.2 M H₂PtCl₆ aqueous solution was added to the dehydrated MMT-S under vigorous stirring for 2 hours. After drying the sample overnight in a vacuum freeze dryer, it was reduced at 300 °C for 2 hours under a hydrogen atmosphere and named Pt@MMT-S.

[0055] Other areas not mentioned are the same as in Example 1.

[0056] Example 6

[0057] 0.2 g of MMT-S was pre-dried at 100 °C for 1 hour to remove adsorbed moisture. Then, 0.045 mL of 0.2 M IrCl3 aqueous solution was added to the dehydrated MMT-S under vigorous stirring for 2 hours. After drying the sample overnight in a vacuum freeze dryer, it was reduced at 300 °C for 2 hours under a hydrogen atmosphere and named Ir@MMT-S.

[0058] Example 7

[0059] Following the method in Example 1, commercially available montmorillonite was treated in nitric acid solution to remove interlayer calcium ions. The stirring times in a water bath were 3 h, 5 h, and 10 h, respectively, yielding MMT-S (3 h), MMT-S (5 h), and MMT-S (10 h). Ru catalysts were then prepared from these three acid-treated montmorillonite samples, yielding Ru@MMT-S (3 h), Ru@MMT-S (5 h), and Ru@MMT-S (10 h).

[0060] Example 8

[0061] Commercially available montmorillonite was treated in nitric acid solution to remove interlayer calcium ions, and the mixture was continuously stirred in a water bath for 5 h to obtain MMT-S(5h). 0.2 g of MMT-S(5h) was pre-dried at 100 °C for 1 h to remove adsorbed moisture. Then, the catalyst Rh was prepared. x Ru 1-x @MMT-S, with x values ​​of 0, 0.2, 0.4, 0.6, 0.8, and 1.0, different catalysts were obtained: Ru@MMT-S(5h) and Rh. 0.2 Ru 0.8 @MMT-S(5h), Rh 0.4 Ru 0.6 @MMT-S(5h), Rh 0.6 Ru 0.4 @MMT-S(5h), Rh 0.8 Ru 0.2 @MMT-S(5h), Rh@MMT-S(5h).

[0062] Comparative Example 1

[0063] Metal clusters encapsulated in montmorillonite (MMT) without acid treatment were prepared by initial wet impregnation. Ru / MMT, Rh / MMT, Pt / MMT, and Ir / MMT samples were prepared according to the method in Example 1.

[0064] like Figure 3 As shown, Rh 0.8 Ru 0.2 Ni 0.25 @MMT-S、Rh 0.8 Ru 0.2 The average diameters of @MMT-S and Rh@MMT-S are 1.4 nm, 1.5 nm, and 1.1 nm, respectively, which are significantly smaller than those of the Rh / MMT sample (~2.8 nm). Acid-treated MMT-S can better encapsulate metal atoms, exhibiting a small average particle size and good dispersion of metal nanoparticles or metal alloy nanoparticles.

[0065] like Figure 4 As shown, the encapsulation method of this invention can also use MMT-S as a carrier for the synthesis of platinum and iridium nanoparticles. For the Pt@MMT-S and Ir@MMT-S samples, highly dispersed metal nanoparticles were encapsulated in MMT-S, with average sizes of 1.8 nm and 1.4 nm, respectively. In contrast, on the untreated montmorillonite carrier, the platinum nanoparticles were unevenly distributed, and the particle size significantly increased to 4.1 nm, further demonstrating that MMT-S is a stable carrier for anchoring highly dispersed metal particles. No reflection peaks corresponding to metal particles were detected in these metal@MMT-S samples, indicating that the highly dispersed metal nanoparticles were successfully encapsulated.

[0066] Application Examples

[0067] An experiment was conducted on equipment including a reaction unit and a gas collection device to release hydrogen from the AB hydrolysis reaction. Specifically, 50 mg of Rh was used. 0.8 Ru 0.2 Ni 0.25 The @MMT-S catalyst and 0.5 mL of deionized water were mixed in a 25 mL two-necked flask and stirred in a water bath at a preset temperature (273–298 K). The volume of gas released was recorded when 0.5 mL of a 2 M ammonia borane aqueous solution was added to the flask. The molar ratio of the noble metal to ammonia borane (based on ICP-OES results) was kept constant at 0.002. The composition of the released gas was determined by gas chromatography equipped with a thermal conductivity detector. The composition of the liquid product was determined by 1H and 11B nuclear magnetic resonance measurements. After the initial run, the catalyst was separated from the solution by centrifugation and washed with water until the supernatant became neutral. The catalyst was then dried in an oven at 80 °C and reused in the ammonia borane hydrolysis reaction.

[0068] Hydrogen production from ammonia borane via hydrolysis was tested on an MMT-S encapsulated metal catalyst at 298 K without any basic additives. Figure 5 As shown in (a), the hydrogen generation rate from the hydrolysis of ammonia borane increased with increasing montmorillonite-supported acid treatment time from 0 h to 5 h. However, further extending the acid treatment to 10 h led to a decrease in the TOF value of the Ru@MMT-S catalyst, which may be attributed to a decrease in the crystallinity of the montmorillonite sheets and a slight increase in the metal size, such as... Figure 6 XRD images and Figure 7 STEM images were used to determine the optimal acid treatment time for montmorillonite as 5 h, and this was applied to the preparation of all MMT-S supported metal catalysts.

[0069] On Ru@MMT-S(5h) catalyst, such as Figure 5 As shown in (a), ammoniaborane can be hydrolyzed to produce 73.5 mL of hydrogen gas within 5 minutes, with a TOF value of 541 mol. H2 ·mol -1 Ru min -1 ( Figure 8 As shown), it is higher than that of the untreated Ru@MMT catalyst (330 mol). H2 ·mol -1 Ru min -1 Similarly, such as Figure 9 As shown, the TOF of the Rh@MMT-S (5h) catalyst is 1309 mol. H2 ·mol -1 Rh min -1 ) compared to Rh / MMT catalyst (665mol) H2 ·mol -1 Rh min -1 The results indicate that, due to the small size of the metal nanoparticles encapsulated within the montmorillonite layer, acid treatment of the montmorillonite material plays a crucial role in enhancing its catalytic activity, and that rhodium metal exhibits higher catalytic activity than ruthenium in the hydrolysis of ammonia borane.

[0070] To determine Rh x Ru 1-x The optimal alloying ratio of rhodium to ruthenium using the MMT-S catalyst was used to synthesize several Rh-containing compounds with different molar ratios. x Ru 1-x @MMT-S catalyst for the hydrolysis of ammonia boronane. For example... Figure 5 (b) and Figure 10 As shown, Rh x Ru1-x The hydrogen production rate of the @MMT-S catalyst exhibits a volcanic change with increasing rhodium / ruthenium ratio. Among all RhRu@MMT-S catalysts, the optimized Rh... 0.8 Ru 0.2 The @MMT-S catalyst exhibits the highest TOF value, at 1596 mol. H2 ·mol -1 (Rh+Ru) min -1 This surpasses the single-metal Ru@MMT-S and Rh@MMT-S catalysts. Introducing nickel to create a trimetallic rhodium-ruthenium-nickel alloy can further improve the hydrogen production rate, see [link to relevant documentation]. Figure 5 (c), (d) and Figure 11 As shown, this is because the rhodium-ruthenium-nickel ternary alloy nanoparticles are encapsulated within the montmorillonite intermediate layer, forming a stable structure. This encapsulation method ensures high dispersibility and anti-aggregation ability of the metal nanoparticles. The synergistic effect of the ternary alloy significantly enhances the activation ability of water molecules, promotes the hydrolysis reaction of ammonia borane, and improves catalytic efficiency. The unique structure and composition distribution of the trimetallic alloy optimize the reaction conditions and enhance the performance of the catalyst.

[0071] It is worth noting that at 298K, in optimized Rh 0.8 Ru 0.2 Ni 0.25 On the MMT-S catalyst, the hydrolysis of ammonia borane can produce 73.5 mL of hydrogen gas within 1 minute, reaching 1960 mol. H2 ·mol -1 (Rh+Ru) min -1 The extremely high TOF value surpasses most of the state-of-the-art catalysts previously reported, such as Rh(0) / nanoCeO2 (TOF = 144 min). -1 , Appl.Catal.B-Environ.2018,237,1012), Rh / AC (TOF=188min -1 , J. Colloid Interface Sci. 2019, 546, 324), Rh / P(triaz)-free (TOF=260min -1 , J.Am.Chem.Soc.2017,139,8971), Rh / OPNC (TOF=433min -1 , J. Colloid Interface Sci. 2021, 594, 131), Rh@S-1-H (TOF=699min -1, Angew.Chem.Int.Ed.2019,58,18570), Rh / CNTs (TOF=706min -1 , Int.J.Hydrog.Energy2015,40,2207), Rh / WO3 (TOF=749min -1 , Int.J.Hydrog.Energy 2021,46,14259), Rh2P@HMC (TOF=939min -1 , Chem.Commun.2021,57,12345), RhCo / TiO2 (TOF=1000min -1 , J.Am.Chem.Soc.2023,145(9),5486), RhNi@HMC (TOF=1294min -1 , Inorg.Chem.2021,60,6820), Rh / IPP-SiO2 (TOF=1295min -1 , Fuel 2023,333,126366),.

[0072] The English abbreviation for catalyst and its corresponding Chinese translation are as follows:

[0073] Rh(0) / nanoCeO2: Zero-valent rhodium supported on nano-cerium oxide;

[0074] Rh / AC: Rhodium supported on activated carbon;

[0075] Rh / P(triaz)-free: Rhodium supported on a polyionic liquid;

[0076] Rh / OPNC: Nitrogen-doped graphene loaded with rhodium;

[0077] Rh@S-1-H: Pure silica molecular sieve-1 supported with rhodium;

[0078] Rh / CNTs: Rhodium supported on carbon nanotubes;

[0079] Rh / WO3: Tungsten oxide supported on rhodium;

[0080] Rh2P@HMC: Hollow mesoporous carbon nanoreactor encapsulated with rhodium phosphide;

[0081] RhCo / TiO2: Rhodium-cobalt bimetallic nanocatalyst supported on titanium dioxide;

[0082] RhNi@HMC: Rhodium-nickel encapsulated in nitrogen-doped hollow mesoporous carbon nanoreactors;

[0083] Rh / IPP-SiO2: Rhodium nanoparticle catalyst supported on a silica-modified grapefruit peel inner layer-derived carbonaceous material.

[0084] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing a precious metal catalyst encapsulated in natural clay minerals, characterized in that, The chemical formula of the noble metal catalyst encapsulated in natural clay ore is Rh x Ru 1-x Ni y @MMT-S; where x and y are the molar ratios of Rh, Ru, and Ni, 0 < x < 1, 0 < y < 0.5; MMT-S is the acid-treated layer-stripped montmorillonite, and the acid is nitric acid; the average size of the metal nanoparticles is less than 2 nm; The preparation method includes the following steps: (1) Montmorillonite was added to a nitric acid aqueous solution and continuously stirred in a water bath to obtain layered montmorillonite MMT-S; the concentration of the nitric acid aqueous solution was 7M; the temperature of the water bath was 80℃; and the stirring time in the water bath was 5 h. (2) Dry the prepared MMT-S to remove the adsorbed water; add the dehydrated MMT-S to the aqueous solution of Rh, Ru and Ni metal salts under vigorous stirring, and continue stirring; (3) After stirring, dry overnight in a vacuum freeze dryer, and then reduce in a hydrogen atmosphere to obtain Rh. x Ru 1-x Ni y @MMT-S catalyst.

2. The method for preparing a precious metal catalyst encapsulated in natural clay minerals according to claim 1, characterized in that, In step (2), the aqueous solution of the metal salts of Rh, Ru, and Ni is RuCl. 3、 RhCl 3、 Ni(NO3)2 aqueous solution.

3. The method for preparing a precious metal catalyst encapsulated in natural clay minerals according to claim 1, characterized in that, In step (2), the ratio of the sum of the moles of Rh, Ru, and Ni to the mass of MMT-S ranges from 0.030 to 0.080 mmol / g.

4. The method for preparing a precious metal catalyst encapsulated in natural clay minerals according to claim 1, characterized in that, In step (2), MMT-S is dried in a drying oven at 100°C for 1-2 hours; the aqueous solution of Rh, Ru, and Ni metal salts is added to the dehydrated MMT-S under vigorous stirring and then stirred for 2-3 hours.

5. The method for preparing a precious metal catalyst encapsulated in natural clay minerals according to claim 1, characterized in that, In step (3), the vacuum freeze-drying time is 12 to 24 hours.

6. The method for preparing a precious metal catalyst encapsulated in natural clay minerals according to claim 1, characterized in that, In step (3), the temperature for hydrogen atmosphere reduction is 200-300℃, and the reduction time is 1-2h.

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