Amorphous oxide confined type metal catalyst, preparation and use thereof

Abstract

This invention relates to the field of metal catalytic materials, and more particularly to amorphous oxide-confined metal catalysts, their preparation, and their applications. The catalyst includes amorphous XO. y Nanolayers, and discretely distributed on amorphous XO y The nanolayer contains Tm nanoparticles; wherein Tm is a transition metal with CO2 reduction activity; the amorphous XO y X in the nanolayer is a p-block element that readily forms amorphous oxides; the amorphous XO y In the nanolayer, 0 < y ≤ 2. This amorphous oxide-confined metal catalyst can serve as a self-heating methanation catalyst. This amorphous oxide-confined metal catalyst (Tm@XO) y It has extremely low effective thermal conductivity, ranging from 0.05 to 1.5 W / m². ‑1 K ‑1 Between these elements, the catalyst is kept warm and the reaction process is driven by self-heating.

Description

Technical Field

[0001] This invention relates to the field of metal catalytic materials, and more particularly to amorphous oxide confined metal catalysts, their preparation, and their applications. Background Technology

[0002] The drive for global carbon neutrality is accelerating a profound paradigm shift in the energy landscape, moving from fossil fuel dependence to a renewable energy-dominated system. However, the continuous surge in installed capacity of renewable energy sources such as wind and solar power presents significant challenges to long-term energy storage and spatiotemporal absorption due to their inherent intermittency, volatility, and seasonal fluctuations. These issues remain the primary bottlenecks limiting the grid connection of high-penetration renewable energy sources. Among emerging technologies coupling energy storage with the carbon cycle, power-to-gas (PtG) stands out. It utilizes renewable energy electricity to produce green hydrogen through water electrolysis and converts captured CO2 (from industrial or atmospheric sources) into synthetic natural gas. This approach enables long-term storage of surplus renewable energy and facilitates the resource utilization of CO2, becoming a cornerstone technological pathway connecting energy transition and achieving carbon neutrality.

[0003] CO2 methanation (Sabatier reaction) is a strongly exothermic reaction. Thermodynamically, lower temperatures favor complete CO2 conversion and higher methane selectivity. However, the CO2 molecule is chemically stable and exhibits a large kinetic barrier at low temperatures. Therefore, traditional thermocatalytic systems must operate at relatively high temperatures (300–400 °C) and rely on external heating to continuously heat the catalyst bed.

[0004] To address these challenges, global efforts are focused on catalyst optimization and process engineering. In catalyst development, noble metals such as Ru and Rh have become mainstream systems due to their excellent intrinsic low-temperature activity and methane selectivity, further enhanced through active metal size control and ion doping. For non-noble metal Ni-based catalysts, modification using promoters, bimetallic alloying, and support optimization has partially alleviated problems such as insufficient low-temperature activity, high-temperature sintering, and coking. At the forefront of process technology, more complex reactor structures—such as catalytic membranes and fluidized bed reactors—are designed to optimize mass and heat transfer, significantly improving overall performance.

[0005] However, most existing highly active catalysts still rely on traditional supports (such as TiO2 and CeO2), which not only have insufficient catalytic activity at low temperatures and poor thermal stability, but also rapidly dissipate the heat of reaction into the external environment. Once external heating is removed, the bed temperature drops sharply below the ignition threshold, causing the catalytic process to quench rapidly.

[0006] Therefore, existing technologies need to be improved. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of the present invention is to provide an amorphous oxide confined metal catalyst, its preparation and application, in order to solve at least one of the following problems: the low-temperature activity of traditional catalysts is insufficient, the thermal stability is poor and the heat dissipation is too fast.

[0008] The technical solution of the present invention is as follows: In a first aspect, the present invention provides an amorphous oxide confined metal catalyst, comprising: Including amorphous XO y Nanolayers, and discretely distributed on amorphous XO y Tm nanoparticles in the nanolayer; Wherein, Tm is a transition metal with CO2 reduction activity; The amorphous XO y X in the nanolayer is a p-block element that readily forms amorphous oxides; The amorphous XO y In the nanolayer, 0 < y ≤ 2.

[0009] It should be noted that the amorphous oxide confined metal catalyst in this embodiment is amorphous XO. y Nano-confined Tm catalysts are denoted as Tm@XO y .

[0010] Optionally, the Tm nanoparticles are spherical, ellipsoidal, or rod-shaped, with a size of 2-100 nm. Preferably, they are 10-20 nm.

[0011] Optionally, the amorphous XO y The thickness of the nanolayer is 1-10 nm, Tm@XO y There is no particular limitation on the macroscopic particle size, which is usually 5nm-1μm.

[0012] Optionally, the amorphous oxide confined metal catalyst Tm@XO y The specific surface area is 10-300m² 2 / g, the amorphous oxide confined metal catalyst has pores, wherein the specific surface area outside the pores accounts for between 20% and 95%.

[0013] Optionally, the Tm nanoparticles and amorphous XO y Between the nanolayers, there is also a sub-nanometer-thick amorphous Tm-X intermetallic compound. The elemental ratio of Tm to X in the Tm-X intermetallic compound is not limited.

[0014] Optionally, Tm is Ru, Pd, Rh, Pt, Ni, Co, Fe, Cu, or Mn. Preferably, Tm is Ru, Rh, Ni, or Co. More preferably, Tm is Ru or Ni (because Ru and Ni have better catalytic activity and selectivity for CO2 methanation). Specifically, Tm is Ru (because Ru has low-temperature catalytic activity).

[0015] Optionally, the amorphous XO y X in the nanolayer is Si, Ge, B, or Al. Si and Al are preferred, and Si is further preferred based on the thermal stability and thermal conductivity of amorphous oxides.

[0016] Optionally, the Tm nanoparticles and amorphous XO y The molar ratio of Tm to X in the nanolayer is between 0.2 and 3, preferably between 0.2 and 1.5. From the perspective of catalytic activity and selectivity for autothermal CO2 methanation, a ratio of 1 is most preferred.

[0017] Secondly, the present invention provides a method for preparing an amorphous oxide confined metal catalyst, comprising the following steps: S1. Prepare intermetallic compound A-Tm-X, and then grind it into powder form. S2. Etch the powdered intermetallic compound A-Tm-X with acid to remove A, obtaining self-assembled Tm-XO. y Two-dimensional superlattice materials; S3, the obtained self-assembled Tm-XO y Two-dimensional superlattice materials are heat-treated in an inert or reducing atmosphere to obtain the amorphous oxide confined metal catalyst. S4. The product obtained by heat treatment is placed in an exothermic reaction, and the heat released during the reaction drives the product obtained by heat treatment to undergo structural reconstruction in situ, forming the amorphous oxide confined metal catalyst. Wherein, Tm is a transition metal with CO2 reduction activity; the amorphous XO y X in the nanolayer is a p-block element that readily forms amorphous oxides; the amorphous XO y In the nanolayer, 0 < y ≤ 2; A is an active metal.

[0018] Optionally, in preparing the intermetallic compound A-Tm-X, A, Tm, and X are mixed in stoichiometric ratio, and then melted using electric arc melting, induction furnace melting, or solid-state melting. There are no limitations on the material preparation conditions; commonly used conditions are appropriately selected.

[0019] Optionally, A is an alkali metal, alkaline earth metal, or rare earth metal. It is readily and selectively removed by an etchant. Specifically, it can be Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu. From the perspective of self-assembly of the nanoconfined structure, La and Ce are preferred; from the perspective of catalytic activity and subsequent catalyst optimization, La is particularly preferred.

[0020] Optionally, acid etching specifically includes immersing the powdered intermetallic compound A-Tm-X in concentrated acid and then stirring for 6-24 hours.

[0021] Of course, after soaking, it still needs to be centrifuged, washed, and dried.

[0022] Optionally, the inert or reducing atmosphere is Ar, H2, He, or N2. Considering the self-assembly efficiency of the metal particles, H2 is particularly preferred.

[0023] Optionally, the heat treatment temperature is 200-800℃, and the time is 6-16 hours. Considering subsequent catalytic performance, 300-400℃ is preferred, and 8-12 hours is particularly preferred. The gas purity is preferably 99.9999%, and the flow rate is not particularly limited, but 40 mL / min is preferred. -1 There is no specific limit to the gas pressure, which is usually between 1 bar and 10 bar.

[0024] Optionally, the exothermic power density of the exothermic reaction is 0.5–50 W·g. -1 Preferably 5–30 W·g -1 The optimal value is 24 W·g -1 .

[0025] Thirdly, the present invention provides the application of the aforementioned amorphous oxide confined metal catalyst in the catalytic production of methane, ethane, and ethylene from CO2 and H2.

[0026] Beneficial Effects: This invention provides an amorphous oxide confined metal catalyst, its preparation, and its application. This invention utilizes acid etching of the intermetallic compound A-Tm-X (where A is an alkali metal, alkaline earth metal, or rare earth metal; Tm is a transition metal; and X is a p-block element forming the amorphous oxide), combined with heat treatment and exothermic reaction structural reconstruction to form a pudding-like amorphous oxide confined metal catalyst, which includes amorphous XO. y Nanolayers, and discretely distributed on amorphous XO y Tm nanoparticles in the nanolayer. Experiments showed that this amorphous oxide-confined metal catalyst can serve as a self-heating methanation catalyst. This amorphous oxide-confined metal catalyst (Tm@XO) yIt has extremely low effective thermal conductivity, ranging from 0.05 to 1.5 W / m. -1 K -1 This allows for the preservation of the catalyst and the self-heating-driven reaction process. Furthermore, the amorphous oxide confined metal catalyst (Tm@XO) obtained in this embodiment... y It possesses extremely strong activation capabilities for CO2 and H2, and can reversibly adsorb / desorb CO2 and H2 below 100 °C. It can efficiently adsorb CO2 and H2 and produce CH4 at room temperature and atmospheric pressure, thus it can be selected as a CO2 methanation catalyst. Attached Figure Description

[0027] Figure 1 The diagram shows the combined structural characterization of the confined metal catalyst obtained in Example 1 of this invention, where a is the XRD pattern and b is the TEM and EDS elemental distribution diagram.

[0028] Figure 2 The images show the temperature-programmed desorption characterization curves of the confined metal catalyst obtained in Example 1 of this invention, where a is the temperature-programmed desorption curve of hydrogen and b is the temperature-programmed desorption curve of carbon dioxide.

[0029] Figure 3 The graph shows the catalytic performance and thermal management characteristics of the confined metal catalyst obtained in Example 1 of this invention. In the graph, a is the stability and temperature evolution curve of the fixed-bed CO2 methanation reaction, and b is a comparison graph of the CH4 space-time yield (STY) of the catalyst with the performance of previously reported work.

[0030] Figure 4 The test diagram shows the self-heating maintenance characteristics of the confined metal catalyst obtained in Example 1 of the present invention under different low-energy-consumption triggering methods. Detailed Implementation

[0031] This invention provides an amorphous oxide-confined metal catalyst, its preparation, and its application. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0032] Despite extensive research on catalyst composition optimization and reactor engineering surrounding CO2 methanation, a core contradiction stemming from the intrinsic characteristics of the reaction remains unresolved: the strongly exothermic nature of the Sabatier reaction (ΔH = -165 kJ·mol⁻¹). -1 Thermodynamic-kinetic paradox between CO2 molecule activation difficulties at low temperatures and the difficulty of CO2 molecule activation at low temperatures. Thermodynamically, low temperatures (<250℃) are extremely favorable, achieving near 100% equilibrium conversion and methane selectivity; however, the C=O bond dissociation energy of CO2 is as high as approximately 804 kJ·mol⁻¹. -1Its chemical inertness results in an extremely high kinetic barrier at low temperatures, causing the reaction rate to almost stagnate. As a result, traditional thermocatalytic systems have to push the reaction window to 300–400°C in exchange for acceptable kinetic performance—essentially a compromise operation far from the thermodynamically optimal range, which fundamentally limits energy efficiency and carbon conversion rate.

[0033] Currently, most mainstream highly active catalysts use crystalline oxides (such as TiO2, CeO2, and Al2O3) as supports, relying on their surface defects or metal-support interactions to anchor active metals such as Ru, Rh, or Ni. However, these crystalline supports expose two related inherent defects in the reaction environment: firstly, their thermal conductivity is either too high or too moderate (e.g., about 30 W·m for Al2O3). -1 ·K -1 TiO2 is lower but still within 10 W·m -1 ·K -1 While the above methods can transfer heat to a certain extent, they are insufficient to quickly dissipate the instantaneous heat of reaction, leading to localized hot spots (exceeding 600°C) within the bed, directly inducing thermal sintering and carrier phase transformation. Secondly, if an attempt is made to "lock in" heat by reducing thermal conductivity to maintain low-temperature self-heating operation, the rigid heat transfer path of the crystalline carrier due to its ordered lattice structure prevents it from achieving isotropic low thermal conductivity—that is, the thermal conductivity of crystalline materials is strongly correlated with their crystal structure, making it difficult to independently reduce it to the ideal range. This contradiction puts the existing catalytic system in a dilemma between "heat dissipation to prevent sintering" and "heat preservation to maintain self-heating."

[0034] Therefore, developing a catalyst with high low-temperature activity, resistance to sintering, low thermal conductivity, and the ability to achieve self-driving (self-heating) through its own reaction exothermic reaction has significant engineering application value and importance.

[0035] Based on this, this embodiment provides an amorphous oxide confined metal catalyst, comprising: Amorphous XO y Nanolayers, and discretely distributed on amorphous XO y Tm nanoparticles in the nanolayer; wherein, Tm is a transition metal with CO2 reduction activity; The amorphous XO y X in the nanolayer is a p-block element that readily forms amorphous oxides; The amorphous XO y In the nanolayer, 0 < y ≤ 2.

[0036] It should be noted that the amorphous oxide confined metal catalyst in this embodiment is amorphous XO. y Nano-confined Tm catalysts are denoted as Tm@XO y The amorphous XO in this embodiment yThe nanolayer exhibits an amorphous nanoconfinement effect, which activates the low-temperature catalytic performance of the Tm metal in the Tm nanoparticles while providing a thermal insulation effect, thus enabling efficient long-term methane production without an external heat source. It not only improves low-temperature catalytic performance but also possesses strong anti-sintering ability and extremely low thermal conductivity due to its nanoconfinement characteristics. It can be entirely driven by its own exothermic reaction, using only CO2 and H2 as raw materials, and can be cold-started by a simple trigger (such as a lighter or focused sunlight), eliminating the need for continuous external heating in traditional methanation processes. This embodiment enhances catalytic performance and anti-sintering ability through the nanoconfinement effect, while utilizing the amorphous encapsulation effect to reduce heat loss, thereby achieving a synergistic improvement in activity, stability, and self-heating catalytic performance. Experiments have shown that the amorphous oxide confined metal catalyst (Tm@XO) obtained in this embodiment... y It has extremely low effective thermal conductivity, ranging from 0.05 to 1.5 W / m². -1 K -1 This allows for the preservation of the catalyst and the self-heating-driven reaction process. Furthermore, the amorphous oxide confined metal catalyst (Tm@XO) obtained in this embodiment... y It possesses extremely strong CO2 and H2 activation capabilities, and can reversibly adsorb / desorb CO2 and H2 below 100℃. Specifically, when X is Si or Ge, y≤2; when X is B or Al, y≤1.5.

[0037] In some embodiments, the Tm nanoparticles are spherical, ellipsoidal, or rod-shaped, with a size of 2-100 nm, which can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm. Preferably, the size is 10-20 nm, such as 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, or 20 nm.

[0038] In some embodiments, the amorphous oxide-confined metal catalyst has a pudding-like shape. Macroscopically, it consists of Tm nanoparticles discretely distributed within the amorphous XO₂. y Within the nanolayer, at the microscopic level, each Tm nanoparticle is coated with amorphous XO. y Nanolayer encapsulation.

[0039] In some embodiments, the amorphous oxide confined metal catalyst (Tm@XO) y The macroscopic particle size of ) is not particularly limited, and is usually 5nm-1μm.

[0040] In some embodiments, the amorphous XO yThe thickness of the nanolayer is 1-10nm, for example, 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm.

[0041] In some embodiments, the amorphous oxide confined metal catalyst Tm@XO y The specific surface area is 10-300m² 2 / g, for example: 10m 2 / g, 50m 2 / g, 100m 2 / g, 150m 2 / g、200m 2 / g、250m 2 / g、300m 2 / g. The amorphous oxide confined metal catalyst has pores, wherein the specific surface area outside the pores accounts for 20% to 95%, for example, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 95%.

[0042] In some embodiments, the Tm nanoparticles and amorphous XO y Between the nanolayers, there is also a sub-nanometer-thick amorphous Tm-X intermetallic compound. The elemental ratio of Tm to X in the Tm-X intermetallic compound is not limited.

[0043] In some embodiments, Tm is Ru, Pd, Rh, Pt, Ni, Co, Fe, Cu, or Mn. Preferably, Tm is Ru, Rh, Ni, or Co. More preferably, Tm is Ru or Ni (because Ru and Ni have better catalytic activity and selectivity for CO2 methanation). Specifically, Tm is Ru (because Ru has low-temperature catalytic activity).

[0044] In some embodiments, the amorphous XO y X in the nanolayer is Si, Ge, B, or Al. Si and Al are preferred, and Si is further preferred based on the thermal stability and thermal conductivity of amorphous oxides.

[0045] In some embodiments, the Tm nanoparticles and amorphous XO yThe molar ratio of Tm to X in the nanolayer is between 0.2 and 3, for example, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.8:1, and 3.0:1. Preferably, it is between 0.2 and 1.5. From the perspective of catalytic activity and selectivity for autothermal CO2 methanation, the optimal ratio is 1.

[0046] This embodiment also provides a method for preparing an amorphous oxide confined metal catalyst, comprising the following steps: S1. Prepare intermetallic compound A-Tm-X, and then grind it into powder form. S2. Etch the powdered intermetallic compound A-Tm-X with acid to remove A, obtaining self-assembled Tm-XO. y Two-dimensional superlattice materials; S3, the obtained self-assembled Tm-XO y Two-dimensional superlattice materials are heat-treated in an inert or reducing atmosphere to obtain the amorphous oxide confined metal catalyst. S4. The product obtained by heat treatment is placed in an exothermic reaction, and the heat released during the reaction drives the product obtained by heat treatment to undergo structural reconstruction in situ, forming the amorphous oxide confined metal catalyst. Wherein, Tm is a transition metal with CO2 reduction activity; the amorphous XO y X in the nanolayer is a p-block element that readily forms amorphous oxides; the amorphous XO y In the nanolayer, 0 < y ≤ 2; A is an active metal.

[0047] It should be noted that the amorphous oxide confined metal catalyst in this embodiment uses the intermetallic compound A-Tm-X as a precursor. Through selective acid etching combined with heat treatment self-assembly, the heat-treated product is placed in an exothermic reaction. The heat released during the exothermic reaction drives the structural reconstruction of the heat-treated product in situ, forming the amorphous oxide confined metal catalyst. (For example, when a mixed reaction gas of CO2 and H2 is introduced into the heat-treated product, a high local heat is generated inside the material. The intense thermal shock drives the fracture of the Tm (e.g., Ru) layered structure, while simultaneously promoting the fracture of the surrounding amorphous XO.) y (SiO) yLocal migration occurs under thermal drive, transforming the original two-dimensional superlattice structure into an amorphous XO. y The coated nano-Tm structure). The amorphous oxide confined metal catalyst (Tm@XO) obtained in this embodiment y The amorphous oxide-confined metal catalyst (Tm@XO) obtained primarily through acid etching, heat treatment, and exothermic reaction structure reconstruction exhibits good chemical and thermal stability. Furthermore, its nano-confined structure endows the core Tm active metal with strong resistance to sintering, which is advantageous for catalytic applications. Experiments have shown that the amorphous oxide-confined metal catalyst (Tm@XO) obtained in this example demonstrates good chemical and thermal stability. y It has extremely low effective thermal conductivity, ranging from 0.05 to 1.5 W / m. -1 K -1 This allows for the preservation of the catalyst and the self-heating-driven reaction process. Furthermore, the amorphous oxide confined metal catalyst (Tm@XO) obtained in this embodiment... y It possesses extremely strong activation capabilities for CO2 and H2, and can reversibly adsorb / desorb CO2 and H2 below 100℃. It can efficiently adsorb CO2 and H2 and produce CH4 at room temperature and atmospheric pressure, and is therefore selected as a CO2 methanation catalyst.

[0048] In some embodiments, when preparing the intermetallic compound A-Tm-X, A, Tm, and X are mixed in stoichiometric ratios, and then melted using arc melting, induction furnace melting, or solid-state melting. The material preparation conditions are not limited; commonly used conditions are appropriately selected. Of course, to eliminate impurity phases, the intermetallic compound A-Tm-X obtained by arc melting, induction furnace melting, or solid-state melting also requires annealing.

[0049] In some embodiments, A is an alkali metal, alkaline earth metal, or rare earth metal. It is readily and selectively removed by an etchant. Specifically, it can be Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu. From the perspective of self-assembly of the nanoconfined structure, La and Ce are preferred. From the perspective of catalytic activity and subsequent catalyst optimization, La is particularly preferred.

[0050] In some embodiments, acid etching specifically includes immersing the powdered intermetallic compound A-Tm-X in a concentrated acid (concentrated hydrochloric acid, concentrated sulfuric acid, concentrated nitric acid, preferably concentrated hydrochloric acid) and then stirring for 6-24 hours.

[0051] Of course, after soaking, it still needs to be centrifuged, washed, and dried.

[0052] In some embodiments, the inert or reducing atmosphere is Ar, H2, He, or N2. H2 is particularly preferred considering the self-assembly efficiency of the metal particles.

[0053] In some embodiments, the heat treatment temperature is 200-800℃ (e.g., 200℃, 300℃, 400℃, 500℃, 600℃, 700℃, 800℃), and the time is 6-16 hours (e.g., 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours). Considering subsequent catalytic performance, 300-400℃ (e.g., 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, 400℃) is preferred, and 8-12 hours is particularly preferred. The gas purity is preferably 99.9999%, and the flow rate is not particularly limited, but 40 mL / min is preferred. -1 There is no specific limit to the gas pressure, which is usually between 1 bar and 10 bar.

[0054] In some embodiments, the exothermic power density of the exothermic reaction is 0.5–50 W·g. -1 (For example, 0.5 W·g) -1 1W·g -1 10W·g -1 20W·g -1 30W·g -1 40W·g -1 50W·g -1 , preferably 15-30 W·g -1 (For example, 15 W·g) -1 20W·g -1 25W·g -1 30W·g -1 ), such as 24 W·g -1 .

[0055] This embodiment also provides the application of the aforementioned amorphous oxide confined metal catalyst in the catalytic production of methane, ethane, and ethylene from CO2 and H2.

[0056] Specifically, in the preparation of methane, the amorphous oxide confined metal catalyst (Tm@XO) of the present invention is used. y The method of producing methane, ethane, and ethylene by reacting CO2 and H2 on a surface is not particularly limited, as long as CO2 and H2 are brought into contact on the above-mentioned catalyst. It can be carried out according to known synthesis methods.

[0057] This catalytic process can be carried out in a heated furnace or under ambient conditions. Specifically, the catalytic reaction pressure is 1-10 bar. To simplify the experimental equipment and optimize energy efficiency, 1 bar is preferred. The heating temperature of the catalytic reaction is from room temperature to 220°C, with room temperature being preferred to increase energy efficiency. Here, room temperature refers to ambient temperature, which is between 15°C and 30°C.

[0058] During the catalytic reaction, the molar ratio of CO2 to H2 in contact with the amorphous oxide-confined metal catalyst is not particularly limited, but typically the H2:CO2 molar ratio is 0.5-10:1, preferably 3-6:1. The total mass flow rate of the gas is typically 10-100 L·g. -1 ·h -1 In the manufacturing method of this invention, the form of the reaction vessel is not particularly limited, and a reaction vessel commonly used in ammonia synthesis reactions can be used. To highlight the self-heating driven catalytic reaction process, a catalytic reaction vessel set under ambient conditions can be used.

[0059] The methane production method of this invention requires no external heat source. This is because the amorphous oxide confined metal catalyst possesses high activity at low temperatures and extremely low thermal conductivity, giving it a Tm hotspot characteristic during CO2 methanation. Even without an external heat source, the catalyst bed temperature can reach between 100-400°C, and the Tm hotspot temperature can reach between 300-500°C. The self-heating catalytic process of this invention exhibits strong environmental resistance; by using a fan to increase convection cooling, the self-heating process can still be maintained for a long time. The self-heating catalytic process of this invention can be triggered by simple ignition methods, such as traditional lighters, industrial hot air guns, or even focused natural sunlight. These simple activation methods make the system very suitable for resource-constrained applications.

[0060] The present invention will be further described below through specific embodiments.

[0061] Example 1 I. A method for preparing an amorphous oxide confined metal catalyst, comprising the following steps: 1. Mix La, Ru, and Si in stoichiometric ratio, and then melt them five times by electric arc melting, with a weight loss of less than 0.1%. Then grind the resulting intermetallic compound into powder using an agate mortar in an Ar-filled glove box. Since the obtained La-Ru-Si intermetallic compound is not a single phase, it is annealed at 1000℃ for 10 days to eliminate impurity phases.

[0062] 2. Immerse 0.25 g of powdered La-Ru-Si intermetallic compound (after impurity phase removal) in a centrifuge tube containing 100 mL of 3M HCl to perform acid etching to remove La. Stir for 12 h, then centrifuge to separate the solid, wash five times with distilled water, and vacuum dry at room temperature for 12 h to obtain Ru / SiO. y Two-dimensional superlattice materials.

[0063] 3. The obtained Ru / SiO y Two-dimensional superlattice materials, at a temperature of 400℃ and a flow rate of 40 mL·min -1 In-situ reduction at a flow rate of H2 for 2 hours, followed by cooling to 25°C, partially yielded the amorphous oxide confined metal catalyst Ru@SiO. y Experiments revealed that the above-mentioned amorphous oxide-confined metal catalyst Ru@SiO2... y Heating the material to 230°C in a gas-free vacuum or inert environment does not result in a significant change in the material morphology.

[0064] 4. Then, a mixture of CO2 and H2 in a molar ratio of 1:4 is introduced into the above product. This generates high localized heat within the material, and the intense thermal shock drives the partial fracture and reorganization of the Ru layered structure into granular form. Simultaneously, it promotes the formation of amorphous SiO₂ on the periphery. y The carrier undergoes local migration driven by heat, thus transforming from the original two-dimensional superlattice structure into amorphous SiO. y Coated nano-Ru structure.

[0065] The above structural changes are as follows Figure 1 The powder diffraction pattern of a is shown in Figure 1. At the bottom is the La-Ru-Si intermetallic compound (LaRuSi) obtained in step 1 of this embodiment, and in the middle is the amorphous oxide confined metal catalyst Ru@SiO2 that was partially obtained in step 3. y However, the content is not very high. After step 4, the Ru@SiO2 catalyst, which is completely converted into an amorphous oxide confined metal catalyst, is obtained. y As shown in the top diagram. Figure 1 b is a confined metal catalyst Ru@SiO y The TEM-EDS images further validated the pudding-like microstructure of the catalyst: the bright-field TEM image showed that the catalyst has a nanoscale confined morphology; the EDS elemental mapping showed that the Ru active component (red) is present in SiO₂. y The Ru active sites are uniformly distributed in a banded pattern within the green matrix, without obvious agglomeration, and highly coincide with the Si elemental signal, directly confirming that the Ru active sites are uniformly confined within the amorphous SiO₂ matrix. y The structural features in the matrix provide the structural basis for the excellent performance of the catalyst.

[0066] II. Desorption via programmed temperature rise: The confined metal catalyst Ru@SiO obtained by using 50 mg y The sample was placed in a chemical adsorption-desorption tester and subjected to the following steps: First, it underwent pretreatment at 400℃ (including 2 hours of He gas treatment, 2 hours of H2 gas treatment, and then 2 hours of He gas treatment again to thoroughly remove surface adsorbates). Then, CO2 gas was introduced and treated at 50℃ for 2 hours, followed by He gas purging for 1 hour, to conduct a programmed temperature-progression gas desorption experiment. The results are as follows: Figure 2 As shown. Figure 2 In the middle, 'a' represents Ru@SiO. y The H2-TPD curve of the confined metal catalyst shows that the main desorption peak of the m / z=2 signal is located at approximately 200℃, indicating that Ru@SiO y Confined metal catalysts have a large number of active hydrogen species with moderate adsorption strength on their surface, providing a highly active hydrogen source for hydrogenation reactions; Figure 2 Figure b shows the CO2-TPD curve, where the m / z=44 (CO2) signal is effectively adsorbed by the catalyst during the 50℃ pretreatment stage, and a significant desorption peak appears at approximately 200℃ during the heating process, directly verifying the sample's strong activation ability for CO2. Simultaneously, the signals at m / z=28, 16, and 12 (intensity amplified by 3 times) appear synchronously with the CO2 desorption peak, indicating that some CO2 undergoes CO bond breaking and preliminary activation on the catalyst surface, generating active intermediates containing C and O. This further confirms the highly efficient activation effect of the Ru active sites in the confined structure on CO2. This is consistent with the H2-TPD results, indicating that the catalyst possesses excellent activation abilities for both H2 and CO2, and the synergy of the two provides a key foundation for the subsequent CO2 hydrogenation reaction.

[0067] 0.1 g of the confined metal catalyst obtained in Example 1 was loaded into a fixed-bed reactor, and then a mixture of CO2 and H2 gas (flow rate of 100 mL / min, CO2:H2 = 1:4) was introduced. Catalytic tests under different external heat dissipation conditions demonstrated the catalyst's excellent heat retention capabilities. When the furnace temperature approached the set value of 220°C, the catalyst temperature suddenly spiked to approximately 350°C. After external heating was stopped, the bed temperature slowly decreased to approximately 290°C and stabilized at approximately 220°C after the furnace was completely dismantled. Under zero external heating conditions, the catalyst maintained a CO2 conversion rate of over 80%, a CH4 selectivity of nearly 100%, and stability for over 500 hours.

[0068] The space-time yield (STY) of CH4 from the confined metal catalyst obtained in Example 1 was compared with that of an existing Ru-based catalyst under a stoichiometric CO2 to H2 ratio of 1:4. The results are as follows: Figure 3As shown.

[0069] Figure 3 In the middle, 'a' represents Ru@SiO. y Results of thermal management and long-term stability tests of confined catalysts in CO2 methanation reaction: During the furnace controlled heating stage, the catalyst temperature rapidly increased with the start of the reaction. When the furnace temperature approached the set value of 220℃, the bed temperature spontaneously jumped to about 350℃, demonstrating the strong self-heating effect of the exothermic reaction on the catalyst bed. After external heating was stopped, the bed temperature slowly dropped and stabilized at about 220℃ after the furnace was removed. Under these zero external heating conditions, the catalyst could still maintain a CO2 conversion rate of over 80% and a CH4 selectivity of nearly 100%, and this stability could be maintained continuously for over 500 hours, fully demonstrating the excellent heat preservation ability, strong self-heating maintenance characteristics, and ultra-high stability of the confined structure. Figure 3 In Figure b, the CH4 space-time yield (STY) of this catalyst is compared with that of previously reported Ru-based catalysts: Within a wide temperature window of 0–400 °C, the STY of this catalyst is significantly superior to that of existing reported systems, especially in the low-temperature range. While most reported catalysts exhibit no significant catalytic activity below 150 °C, this catalyst still maintains a high space-time yield, directly verifying the effectiveness of confined Ru@SiO₂ catalysts. y The catalyst exhibits high activation efficiency and low-temperature catalytic performance in the CO2 methanation reaction under mild conditions. Among the reported Ru-based catalysts are those obtained from the following four comparative documents: 1. DENG S, WANG X, FANG X, et al. Oxyphilic Ru-O-Mn 2+Interfaces on Ru / MnO Catalysts: Unprecedented Activity for Low-Temperature CO2Methanation[J]. Angewandte Chemie International Edition, 2026: e6087744.2, LóPEZ-RODRíGUEZ S, DAVó-QUIñONERO A, BAILóN-GARCíA E, et al. Effect of Ru loading on Ru / CeO2catalysts for CO2methanation[J]. MolecularCatalysis, 2021, 515: 111911.3, LI M, YAN W, LIU M, et al. Improved Activity of Ru / CeO2Catalyst for CO2Methanation by Enhanced Electronic Metal–SupportInteraction[J]. Energy&Fuels, 2025, 39(1): 604-613.4, LIAO W, TANG C, ZHENG H,et al. Tuning activity and selectivity of CO2hydrogenation via metal-oxideinterfaces over ZnO-supported metal catalysts[J]. Journal of Catalysis, 2022,407: 126-140. The Ru@SiO in this embodiment y The strong self-driven nature of confined catalysts makes them compatible with highly flexible and low-energy activation strategies. This spontaneous and continuous methanation process can be rapidly triggered by easily accessible local heat sources, such as conventional lighters, industrial heat guns, or even focused natural sunlight. These simple activation methods make the system well-suited for resource-constrained applications. Related results are as follows... Figure 4 As shown. Figure 4 The Ru@SiO2 model is visually demonstrated. yThe confined catalyst demonstrates its ability to achieve self-driven and stable operation of CO2 methanation under various low-energy and easily achievable external triggering conditions: the catalyst bed can be rapidly triggered and enter a stable self-heating reaction state under three different initial activation methods: brief local heating with a lighter, local purging heating with an industrial hot air gun, and focused sunlight irradiation. Furthermore, even after the external heating / light irradiation stops, the bed temperature can remain stably maintained within the required operating range for an extended period, enabling a continuous CO2 methanation process. This result fully verifies the catalyst's excellent self-heating maintenance characteristics; its spontaneous reaction exothermics are sufficient to support the continuous reaction without the need for additional continuous energy supply. It is highly compatible with low-cost and readily available local heat sources such as lighters, industrial hot air guns, and focused sunlight, breaking through the dependence of traditional CO2 methanation reactions on continuous high-temperature external heating systems. This provides a low-energy and highly flexible CO2 conversion solution for resource-constrained and power-inconvenient scenarios (such as remote areas and emergency scenarios).

[0070] In summary, this invention provides an amorphous oxide-confined metal catalyst, its preparation, and its application. This invention utilizes acid etching of the intermetallic compound A-Tm-X (where A is an alkali metal, alkaline earth metal, or rare earth metal; Tm is a transition metal; and X is a p-block element forming the amorphous oxide), combined with heat treatment and exothermic reaction structural reconstruction to form a pudding-like amorphous oxide-confined metal catalyst, which includes amorphous XO. y Nanolayers, and discretely distributed on amorphous XO y Tm nanoparticles in the nanolayer. Experiments showed that this amorphous oxide-confined metal catalyst can serve as a self-heating methanation catalyst. This amorphous oxide-confined metal catalyst (Tm@XO) y It has extremely low effective thermal conductivity, ranging from 0.05 to 1.5 W / m. -1 K -1 This allows for the preservation of the catalyst and the self-heating-driven reaction process. Furthermore, the amorphous oxide confined metal catalyst (Tm@XO) obtained in this embodiment... y It possesses extremely strong activation capabilities for CO2 and H2, and can reversibly adsorb / desorb CO2 and H2 below 100℃. It can efficiently adsorb CO2 and H2 and produce CH4 at room temperature and atmospheric pressure, thus it can be selected as a CO2 methanation catalyst.

[0071] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. An amorphous oxide confined metal catalyst, characterized in that, include: Amorphous XO y Nanolayers, and discretely distributed on amorphous XO y Tm nanoparticles in the nanolayer; Wherein, Tm is a transition metal with CO2 reduction activity; The amorphous XO y X in the nanolayer is a p-block element that readily forms amorphous oxides; The amorphous XO y In the nanolayer, 0 < y ≤ 2.

2. The amorphous oxide confined metal catalyst according to claim 1, characterized in that, The Tm nanoparticles are spherical, ellipsoidal, or rod-shaped, with a size of 2-100 nm.

3. The amorphous oxide confined metal catalyst according to claim 1, characterized in that, The macroscopic particle size of the amorphous oxide confined metal catalyst is 5 nm-1 μm; The specific surface area of ​​the amorphous oxide confined metal catalyst is 10-300 m². 2 / g, the amorphous oxide confined metal catalyst has pores, wherein the specific surface area outside the pores accounts for between 20% and 95%.

4. The amorphous oxide confined metal catalyst according to claim 1, characterized in that, The Tm is Ru, Pd, Rh, Pt, Ni, Co, Fe, Cu or Mn.

5. The amorphous oxide confined metal catalyst according to claim 1, characterized in that, The amorphous XO y X in the nanolayer is Si, Ge, B or Al.

6. The amorphous oxide confined metal catalyst according to claim 1, characterized in that, Tm in Tm nanoparticles and amorphous XO y The molar ratio of X in the nanolayer is between 0.2 and 3.

7. A method for preparing an amorphous oxide confined metal catalyst according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Prepare intermetallic compound A-Tm-X, and then grind it into powder form. S2. Etch the powdered intermetallic compound A-Tm-X with acid to remove A, obtaining self-assembled Tm-XO. y Two-dimensional superlattice materials; S3, the obtained self-assembled Tm-XO y Two-dimensional superlattice materials are heat-treated in an inert or reducing atmosphere; S4. The product obtained by heat treatment is placed in an exothermic reaction. The heat released during the exothermic reaction drives the product obtained by heat treatment to undergo structural reconstruction in situ, forming the amorphous oxide confined metal catalyst. Wherein, Tm is a transition metal with CO2 reduction activity; the amorphous XO y X in the nanolayer is a p-block element that readily forms amorphous oxides; the amorphous XO y In the nanolayer, 0 < y ≤ 2; A is an active metal.

8. The method for preparing the amorphous oxide confined metal catalyst according to claim 7, characterized in that, The A is an alkali metal, alkaline earth metal, or rare earth metal, including Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

9. The method for preparing the amorphous oxide confined metal catalyst according to claim 7, characterized in that, The acid etching specifically includes: immersing the powdered intermetallic compound A-Tm-X in concentrated acid, and then stirring for 6-24 hours; The heat treatment is performed at a temperature of 200-800℃ for 6-16 hours. The exothermic power density of the exothermic reaction is 0.5–50 W·g. -1 .

10. The application of the amorphous oxide confined metal catalyst according to any one of claims 1-6 in the catalytic production of methane, ethane, and ethylene from CO2 and H2.

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