A SiO2 supported RuO2@Pt bimetallic core-shell structure catalyst, a preparation method and application thereof

Abstract

The application relates to a SiO2-loaded RuO2@Pt bimetallic core-shell structure catalyst and a preparation method and application thereof. The catalyst takes SiO2 as a carrier, loads a bimetallic structure RuO2@Pt-2ML of a RuO2 core coated with 2-3 layers of Pt, wherein the RuO2 core is a RuO2 nanoparticle, and 2-3 layers of Pt are deposited on the surface of the RuO2 nanoparticle to form a shell layer. Compared with the prior art, the application utilizes interface strain / electron coupling to stabilize the recyclable Pt-O structure, and couples the C-H bond activation of alkane and the O2 activation process, breaks through the bottleneck of the competitive adsorption relationship of the two reactants on the traditional catalyst, and exhibits excellent low-temperature catalytic activity in the combustion reaction of methane, ethane, propane, butane, n-hexane and other alkane.

Description

Technical Field

[0001] This invention relates to the fields of industrial catalysis and nanomaterials technology, and in particular to the application of a SiO2-supported Pt-Ru bimetallic core-shell structure catalyst in the catalytic combustion of alkanes. Background Technology

[0002] Alkanes, as typical volatile organic compounds, are widely found in petrochemical, fine chemical, and motor vehicle exhaust, seriously endangering human health and the ecological environment. Catalytic combustion technology is an effective means of controlling low-carbon alkane pollution, converting them into harmless CO2 and H2O. The core of this technology lies in the development of high-performance catalysts. Catalytic combustion technology can completely oxidize alkanes to CO2 and H2O under low-temperature conditions and has advantages such as low energy consumption (reaction temperature is usually below 500℃), high treatment efficiency (≥99%), and no secondary pollution. It has become the preferred technical route for the treatment of low-carbon alkane pollution (especially propane, a typical recalcitrant low-carbon alkane in petrochemical exhaust with a CH bond energy as high as 410 kJ / mol). The key to the industrialization of this technology lies in overcoming the bottleneck of catalyst performance in terms of low-temperature activity, structural stability, and anti-interference ability.

[0003] Currently, catalysts used for propane catalytic combustion mainly include noble metal catalysts (such as Pt, Pd, Ru, etc.), transition metal oxide catalysts, and composite metal catalysts. Among them, Pt-based and Ru-based noble metal catalysts, due to their unique d-orbital electronic structures, can effectively activate the CH bonds of propane and the O=O bonds of oxygen, exhibiting excellent low-temperature catalytic activity (the complete propane conversion temperature T90 of existing Pt-based catalysts is typically 200-350℃), making them the core of research in this field. Regarding Pt-based catalysts, there is still some controversy regarding the active sites. Some studies indicate that metallic Pt is a highly active site for propane oxidation, while others have found that a mixture of metallic Pt and Pt in a certain oxidation state is a highly active site. Furthermore, recent studies have found that during propane oxidation, due to excess oxygen, metallic Pt is partially oxidized, forming Pt sites in a certain oxidation state. On the other hand, when Pt sites are in a metallic state, they readily adsorb oxygen, significantly inhibiting the adsorption and activation of propane by Pt sites. Therefore, constructing Pt-based active sites that combine high activity with stability in the reaction environment is a core technical challenge that needs to be addressed in existing Pt-based catalysts.

[0004] Atomic layer deposition (ALD) technology, with its self-confined layer-by-layer growth, can precisely control the size, composition, and structure of materials at the sub-nanometer scale (0.5-5 nm), providing an ideal platform for constructing well-defined metal catalysts. Previous studies have used ALD technology to prepare SiO2-supported monometallic or conventional bimetallic catalysts. For example, the team led by Lu Junling at the University of Science and Technology of China disclosed a core-shell bimetallic catalyst in *Nature Catalysis* (2021, Vol. 4, pp. 840-849). Using ALD technology, they first deposited an Au core on the SiO2 surface, then coated it with 1-3 layers of Pt shell to construct a core-shell bimetallic catalyst. This study confirmed that the catalytic performance of the catalyst is extremely sensitive to the thickness of the Pt shell; optimal activity is achieved only with a single atomic layer. As the shell thickness increases, the contact between the reactants and the Au core is hindered, leading to a significant decrease in activity. More importantly, the Pt single-atom shell prepared by the catalyst via ALD technology is only suitable for the reducing atmosphere of hydrogenation reactions, and its Pt (111) crystal plane has an electron density of 0.82 e / Å. 3 ) and surface energy (1.2 J / m 2 It cannot meet the synergistic requirements of O2 activation and CH bond breaking in the propane oxidation reaction, and the structure is prone to Pt shell oxidation and stripping in an oxidizing atmosphere, leading to catalyst deactivation.

[0005] Patent CN108993487A discloses a method for preparing Ru-Pt / TiO2 single-atom catalysts using atomic layer deposition (ALD). This method primarily utilizes pre-synthesized hexamethyl-methylcyclopentadiene platinum-ruthenium as a precursor, then simultaneously deposits Ru and Pt onto a TiO2 support using ALD technology, achieving single-atom dispersion of Ru and Pt. However, this method cannot separately modulate the structure and electronic state of Ru and Pt, making it unsuitable for enhancing activity in other reactions. Furthermore, the single-atom structure exhibits poor thermal stability under the medium-to-high temperature conditions required for catalytic combustion, limiting its application to low-temperature environments up to 25°C and thus lacking industrial applicability.

[0006] Patent CN113996291A discloses a Pt-Ru catalyst supported on a composite oxide support of CuO, TiO2, Al2O3 and SiO2, which exhibits high catalytic combustion activity for dichloromethane and bromomethane. The catalyst can be prepared by methods such as vapor deposition. Although the patent mentions vapor deposition in the specification, the four methods listed in the patent claims and description all use impregnation. According to the Pt and Ru precursors used in the examples, it is impossible to synthesize using ALD, let alone achieve precise design and control of the catalyst structure.

[0007] Patent CN119657119A discloses a platinum-based catalyst, its preparation method, and its application in the catalytic combustion of methane. This catalyst achieves a breakthrough by reducing the temperature for complete methane conversion to below 200°C and maintaining long-term stability. The technology uses rarely used nitrous oxide as the oxidant, whose oxidizing power is significantly stronger than that of commonly used oxygen, resulting in a significant increase in its activity. However, nitrous oxide is a hazardous chemical and cannot be used in actual industrial applications, rendering its high activity useless for practical use. Replacing nitrous oxide with oxygen as the oxidant cannot avoid the competitive adsorption of alkanes and O2 on traditional supported Pt catalysts, making it difficult to overcome the limitations of poor catalytic combustion performance of alkanes in existing technologies.

[0008] Therefore, developing Ru-Pt bimetallic catalysts with precise and controllable structures and optimized metal electronic states is an effective way to achieve efficient catalytic combustion of alkanes under low-temperature conditions. Summary of the Invention

[0009] The purpose of this invention is to solve at least one of the above-mentioned problems by providing a SiO2-supported RuO2@Pt bimetallic core-shell catalyst with precise and controllable structure, high activity, and high stability, as well as its preparation method and application.

[0010] To achieve the above objectives, this invention constructs a core-shell structure catalyst with silica (SiO2) as the support, rutile-phase ruthenium dioxide (RuO2) nanoparticles as the core, and a precisely controlled platinum (Pt) atomic layer as the shell. Specifically, this invention utilizes atomic layer deposition (ALD) technology to precisely control 2-3 Pt shell layers in a SiO2-supported Ru-Pt bimetallic core-shell structure catalyst, providing a new approach for developing alkane oxidation catalysts and achieving the aforementioned objectives.

[0011] The objective of this invention can be achieved through the following technical solution: a SiO2-supported RuO2@Pt bimetallic core-shell structure catalyst, wherein the catalyst uses SiO2 as a support and supports a RuO2 core coated with 2-3 layers of Pt to form a bimetallic structure RuO2@Pt-2ML, wherein the RuO2 core is RuO2 nanoparticles and 2-3 layers of Pt are deposited on the surface of the RuO2 nanoparticles to form a shell.

[0012] Furthermore, the RuO2 core is a rutile phase RuO2 nanoparticle with a valence state of +3 to +4 and a particle size of 3 to 5 nm; the shell is 2 to 3 Pt atomic layers with a valence state of 0 to +2.

[0013] Furthermore, the lattice constant of the outermost Pt atoms in the bimetallic structure RuO2@Pt-2ML is 0.380~0.385 nm, which is lattice compressed compared to the lattice constant of pure Pt metal of 0.392 nm.

[0014] Furthermore, the bimetallic RuO2@Pt bimetallic core-shell catalyst is characterized in that the RuO2 nanoparticles form a heterogeneous interface with the Pt shell, generating a global electron transfer effect through Ru-O-Pt bonding, causing the d-band center of the Pt atom to shift downward. This catalyst achieves a conversion rate of over 90% for propane combustion at 180-200 °C. Its apparent activation energy for CH bond dissociation, calculated using the Arrhenius equation fitted to programmed temperature rise data, is 24 kJ / mol, lower than the activation energy of the pure Pt catalyst. The CH bond dissociation energy barrier of the propane molecule, calculated using DFT, is 0.48 eV, indicating its intended activation capability.

[0015] This invention also provides a method for preparing a SiO2-supported RuO2@Pt bimetallic core-shell catalyst, which is prepared according to the following steps: S1. Preparation of SiO2 support by Stöber method: Silicon source, NH3·H2O, organic solvent and H2O are mixed and stirred. The precipitate is centrifuged, washed with organic solvent, dried and then calcined to obtain SiO2 support. S2. Loading Pt nanoparticles onto the surface of SiO2 support using a wet chemical method: The SiO2 support obtained in step S1 is dispersed in an ethanol solution of ruthenium source, calcined, continuously stirred, evaporated, and dried to obtain Ru / SiO2. S3. Deposit 2-3 layers of Pt on Ru nanoparticles using ALD technology: Place the Ru / SiO2 and Pt precursor obtained in step S2 in an ALD reaction chamber, use oxygen as the reaction gas, and perform ALD cycling at 100-200℃ to deposit Pt on the surface of Ru nanoparticles, forming a 2-3 atomic layer Pt shell, and obtain a bimetallic RuO2@Pt-2ML catalyst. S4. The deposited samples obtained in step S3 were heat-treated to obtain a RuO2@Pt-2ML catalyst with a bimetallic structure of RuO2 as the core and 2-3 layers of Pt supported.

[0016] Further, in step S1: the volume ratio of the silicon source, NH3·H2O, organic solvent and H2O is (10~25):(3~7):(300~400):(20~40), preferably 17.8:5.4:360:30; the stirring temperature is 25~30℃, the stirring time is 12~36h; the drying temperature is 70~100℃, the drying time is 12~48h; the calcination conditions are: calcination at 600~800℃ for 2~5 hours at a flow rate of 10~40 mL / min and 5~10 vol.% O2 / Ar. The silicon source is one or more of ethyl silicate, sodium silicate, tetraethoxysilane, and polyethoxysilane; the organic solvent includes one or more of ethanol, cyclohexane, and 1,2-dichloroethane.

[0017] Further, in step S2: the ruthenium source includes one or more of nitrosyl nitrate ruthenium, acetylacetone ruthenium, and bis(ethylcyclopentadiene)ruthenium; the mass percentage of metallic ruthenium in Ru / SiO2 is 2 1-3 wt%; the calcination temperature is 600~800℃, the calcination time is 2~4h, the drying temperature is 50~70℃, and the drying time is 12~48h.

[0018] Further, in step S3: the Pt precursor includes one or more of chloroplatinic acid hexahydrate, tetraammineplatinum nitrate, methylcyclopentadienyltrimethylplatinum, or (trimethyl)methylcyclopentadienylplatinum; the reaction gas is oxygen; the ALD cycle is as follows: ultra-high purity nitrogen or argon is used as the carrier gas at a flow rate of 100-300 mL / min. The Pt precursor is heated to 50-80 °C, and O2 is used as the oxidant at an oxygen flow rate of 10 mL / min; ruthenium ALD is performed at 120-180 °C for 10-12 cycles.

[0019] Furthermore, in step S4: the heat treatment temperature is 200~500 ℃, and the heat treatment time is 1~3h.

[0020] This invention also provides an application of a SiO2-supported RuO2@Pt bimetallic core-shell structure catalyst, wherein the RuO2@Pt-2ML catalyst is applied to the catalytic oxidation reaction of low-carbon alkanes, including methane, ethane, butane, and n-hexane, with propane catalytic combustion being preferred.

[0021] Furthermore, the conditions for the propane catalytic combustion reaction are: space velocity of 20,000~30,000 mL·g -1 ·h -1 The gas flow rate is 20-30 mL / min; the preferred space velocity is 30000 mL·g. -1 ·h -1 The gas flow rate is 25 mL / min.

[0022] When the aforementioned Pt-Ru bimetallic catalyst is applied to the propane catalytic combustion reaction, its unique RuO2@Pt-2ML hierarchical structure significantly enhances the coupling ability of Pt sites for oxygen activation and low-carbon alkane CH activation. Specifically, the outermost atoms of the 2-3 layer Pt shell possess strong O2 activation capabilities, enabling the in-situ generation of highly active Pt-O species. These species are the key active centers for the efficient activation of alkane CH bonds; they significantly lower the reaction energy barrier, promoting CH bond breaking and facilitating the generation of CO2 and H2O. In the propane catalytic combustion reaction, the RuO2@Pt-2ML catalyst exhibits superior performance. Experimental results show that the optimal reaction atmosphere is 0.2 vol.% C3H8, 2 vol.% O2, and 97.8 vol.% N2, with a space velocity of 30,000 mL·g. -1 ·h -1 At this time, the bimetallic catalyst exhibits excellent low-temperature activity, with an ignition temperature (T0). 10 The reaction can achieve complete combustion of propane at temperatures as low as 125 °C, and at 205 °C. Especially at 200 °C, the reaction rate reaches as high as 97 μmol / g. metal The catalyst exhibits significantly superior performance compared to single-metal Pt / SiO2 and Ru / SiO2 catalysts, as well as PtRu / SiO2 bimetallic alloy catalysts prepared by co-impregnation. More importantly, it demonstrates excellent reaction stability and broad adaptability to reaction conditions, maintaining its activity even after 500 hours of continuous reaction at 180 °C, fully demonstrating its great potential as a candidate material for industrial applications.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) Excellent catalytic activity and ultra-low activation energy: This invention (RuO2@Pt): RuO2 is a semiconductor oxide. Strong electronic coupling exists at the RuO2-Pt interface. This interaction drives the dynamic reconstruction of surface Pt sites under reaction conditions, forming special highly active Pt-O species (H2-TPR shows its reduction at -10°C). The RuO2@Pt-2ML catalyst of this invention exhibits optimal performance in the propane catalytic combustion reaction, with an apparent activation energy (E0) of very low... a The efficiency was as low as 24.4 kJ / mol, significantly lower than that of single-layer Pt shell catalysts (54.4 kJ / mol) and four-layer Pt shell catalysts (44.1 kJ / mol), and also far superior to catalyst systems reported in the literature. The temperature required to achieve 90% propane conversion (T0) was [not specified]. 90 It reduces the temperature by more than 80 °C compared to single-metal catalysts.

[0024] (2) Breakthrough Reaction Mechanism: This invention reveals a novel mechanism that surpasses traditional oxygen activation mechanisms. For the first time, it systematically reveals the dynamic reconstruction behavior, substrate stability, and shell thickness-dependent activity mechanism of Pt-shell catalysts constructed with oxide (RuO2) cores in alkane oxidation reactions. The RuO2 core is not only stable itself but also regulates the Pt shell through electronic coupling, promoting the cyclic generation of reactive oxygen species and achieving synergistic activation of CH bonds and O2. By precisely controlling the thickness of the Pt shell, strong electronic coupling between the RuO2 core and the Pt shell is achieved, driving the Pt surface to dynamically reconstruct into a highly active metallic state under reaction conditions and cyclically generating highly active Pt-O species. The effective hybridization of this Pt-O species with the propyl C 2p orbital directly lowers the CH bond dissociation energy barrier, breaks through the competitive adsorption bottleneck between alkanes and oxygen, and synergistically optimizes the two key steps of CH activation and O2 activation.

[0025] (3) Excellent versatility and stability: This catalyst is not only highly efficient for propane oxidation, but its excellent performance also extends to the oxidation reactions of other low-carbon alkanes such as methane, ethane, and butane, showing broad application prospects. In addition, the catalyst showed no activity decay after continuous reaction at 180 °C for 500 hours, demonstrating excellent stability for industrial applications.

[0026] (4) Precise atomic-scale design and guidance: This invention achieves atomic-level precise control of the electronic state and geometric effect of the core-shell structure interface through atomic layer deposition technology. For the first time, it establishes a direct correlation between the electronic state of metal, the hybridization of adsorbate orbitals and reaction kinetics in experiments and theory, providing an important basis for the rational design of high-performance catalysts at the atomic scale in the future. Attached Figure Description

[0027] Figure 1 This is a comparison diagram of the propane catalytic combustion activity of the RuO2@Pt-2ML catalyst prepared in Example 1 of the present invention and the catalysts of Comparative Examples 1-3; Figure 2 Dark-field scanning transmission electron microscopy (TEM) image and particle size distribution diagram of the RuO2@Pt-2ML catalyst prepared in Example 1 of this invention; Figure 3 This is a high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image of the RuO2@Pt-2ML catalyst prepared in Example 1 of this invention. Figure 4 The image shows the X-ray diffraction (XRD) pattern of the RuO2@Pt-2ML catalyst prepared in Example 1 of this invention. Figure 5 The Ru 3d X-ray photoelectron spectroscopy (XPS) of the RuO2@Pt-2ML catalyst prepared in Example 1 of this invention. Figure 6 The Pt 4f X-ray photoelectron spectroscopy (XPS) of the RuO2@Pt-2ML catalyst prepared in Example 1 of this invention. Figure 7 The Pt L3 X-ray absorption fine structure spectrum (XAFS) of the RuO2@Pt-2ML catalyst prepared in Example 1 of this invention. Figure 8 This is a graph showing the long-term stability test (conversion rate vs. time) of the RuO2@Pt-2ML catalyst prepared in Example 1 of this invention. Figure 9 The catalytic combustion performance of the RuO2@Pt-2ML catalyst prepared in Example 1 of this invention was tested for methane, ethane, butane, and n-hexane. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0029] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, each point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value, or combined with other lower or upper limits, to form a range not explicitly stated. In the description of this application, it should be noted that, unless otherwise stated, "above" includes the stated number, and "multiple" in "one or more" means two or more.

[0030] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0031] Numerous details are explored in the following description to provide a more thorough explanation of embodiments of this application; however, it will be apparent to those skilled in the art that embodiments of this application may be practiced without these specific details.

[0032] This invention constructs a core-shell structure catalyst with silica (SiO2) as the support, rutile ruthenium dioxide (RuO2) nanoparticles as the core, and a precisely controlled platinum (Pt) atomic layer as the shell. Specifically, this invention utilizes atomic layer deposition (ALD) technology to precisely control 2-3 Pt shell layers in a SiO2-supported Ru-Pt bimetallic core-shell structure catalyst, providing a new approach for the development of alkane oxidation catalysts.

[0033] To further understand the present invention, the following embodiments are provided. It is worth noting that, unless otherwise specified, all raw materials used in the present invention are commercially available; and all methods and equipment employed are common in the art.

[0034] Example 1: A Pt-Ru bimetallic catalyst for the catalytic combustion of propane is prepared using the following steps: (1) Preparation of SiO2 support Silica microspheres were prepared using the Stöber method. Specifically, 17.8 mL of silicon source (tetraethyl silicate (TEOS) in this example), 5.4 mL of NH3·H2O, 360 mL of organic solvent (C2H5OH in this example), and 30 mL of H2O were added to a 500 mL beaker. The solution mixture was then vigorously stirred at 25 °C for 24 h. Afterward, the precipitate was centrifuged, washed several times with ethanol, and dried overnight at 70 °C. Finally, it was calcined in a tube furnace at 800 °C for 5 h at a flow rate of 40 mL / min under 10 vol.% O2 / Ar to obtain the SiO2 support with an average particle size of 100 ± 10 nm.

[0035] (2) Loading of Ru nanoparticles The SiO2 support obtained in step (1) was calcined at 700°C for 3 hours under an oxygen flow. The calcined material was dispersed in 80 mL of ethanol in a 500 mL beaker and sonicated to obtain a SiO2 suspension. 157 mg of ruthenium source (ruthenium(III) acetylacetone (Ru(acac)3) in this example) was dissolved in 40 mL of ethanol. This solution was then added dropwise to the SiO2 suspension under vigorous stirring. The mixture was stirred continuously until the ethanol was completely evaporated. The resulting solid was dried overnight in a 60°C oven. Finally, the material was treated at 300°C under oxygen for 2 hours to obtain 4 nm Ru / SiO2.

[0036] (3) Deposition of Pt shell The Ru / SiO2 sample obtained in step (2) was held in the ALD reaction chamber and atomic layer deposition (ALD) was performed in a viscous flow ALD reactor using tetraammineplatinum(II) nitrate as a Pt precursor to synthesize the RuO2@Pt-2ML catalyst. Ultra-high purity N2 was used as the carrier gas at a flow rate of 200 mL / min. Tetraammineplatinum(II) nitrate was heated to 65 °C to obtain sufficient vapor pressure, and O2 was used as the oxidant. To accurately synthesize the RuO2@Pt-2ML catalyst, ALD of Pt was performed at 150 °C, selectively depositing Pt onto Ru nanoparticles in Ru / SiO2 for 10–12 cycles. During this process, Pt deposition on spherical SiO2 was suppressed.

[0037] (4) Post-processing The sample after deposition in step (3) was heat-treated in air at 300 °C for 2 h to remove the precursor ligands, obtain a pure metal surface, and further enhance the interaction between the metal and the support and the bimetallic site to obtain the final RuO2 core supported by 2-3 Pt shell bimetallic structure RuO2@Pt-2ML catalyst. Figure 3 and Figure 4 The images shown are high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray diffraction (XRD) patterns of the obtained RuO2@Pt-2ML catalyst. Figure 3 As can be seen, the obtained RuO2@Pt-2ML catalyst particles have a size of approximately 4–5 nm. The particles exhibit an irregular polyhedral outline with clear edges and a dense overall structure. Clear parallel striations are visible inside, which are projections of the atomic planes (crystal planes) of the crystal under an electron beam, indicating that the particles have good crystallinity. The contrast of HAADF-STEM is positively correlated with the atomic number (Z contrast), with Pt (Z=78) being brighter than Ru (Z=44) and O (Z=8). The contrast at the edge of the image is slightly higher than that in the interior, suggesting that Pt may be coated on the surface of the RuO2 core in the form of an ultrathin shell (approximately 2 atomic layers, 2ML), forming a core-shell structure.

[0038] from Figure 4 As can be seen, in the prepared SiO2-supported RuO2@Pt-2ML sample, the RuO2 core maintains a complete rutile structure, with clear and intact diffraction peaks. No obvious Pt diffraction peaks were detected, confirming that Pt is uniformly coated on the RuO2 surface in the form of an ultrathin layer (approximately 2-3 atomic layers). Compared with pure RuO2, the diffraction peaks of the RuO2@Pt-2ML sample show a slight shift / intensity change, indicating the existence of interfacial stress and electronic interactions between the Pt shell and the RuO2 core. Furthermore, the 2-3 atomic layers of Pt remain stable before and after the reaction. Figure 2This is a dark-field scanning transmission electron microscope (TEM) image of the RuO2@Pt-2ML catalyst. Figure 3 Further structural analysis revealed that RuO2@Pt-2ML exhibits a clear core-shell structure, with its shell consisting of 2-3 atomic layers, forming a mixed PtOx phase with poor crystallinity. Figure 5 The X-ray photoelectron spectroscopy (XPS) of the obtained RuO2@Pt-2ML catalyst shows that the substrate Ru exists in the +4 oxidation state. Figure 5 It can be seen that the Ru valence state of the obtained RuO2@Pt-2ML catalyst is highly consistent with that of the Ru / SiO2 catalyst, both exhibiting the Ru valence state. 4+ It exists in the form of (RuO2). Moreover, XPS comparison analysis before and after the reaction revealed that the valence state of Ru remained stable during the catalytic reaction; Figure 6 The Pt 4f X-ray photoelectron spectroscopy (XPS) of the RuO2@Pt-2ML catalyst prepared in this embodiment was obtained by... Figure 6 It can be seen that the obtained RuO2@Pt-2ML catalyst contains Pt. 0 Pt 2+ and Pt 4+ The three valence states of Pt, after calculation, show an overall valence of 1.4, which is obtained after peak fitting. In this example, the electronic state of Ru in the RuO2@Pt-2ML catalyst is basically consistent with that of a single metal, while Pt is intermediate between the metallic state (Pt...). 0 Between ) and +2.

[0039] Figure 7 X-ray absorption fine structure (XAFS) spectroscopy analysis was performed on the L3 edge of Pt. The spectral characteristics of the obtained RuO2@Pt-2ML catalyst were between those of Pt foil (metallic state) and PtO2 (oxidized state), indicating the coexistence of Pt-O and Pt-Pt bonds. EXAFS fitting yielded a Pt-Pt bond length of 2.73 Å, slightly shorter than the 2.76 Å of the bulk Pt foil, indicating lattice compression in the Pt shell. The white line peaks in the XANES spectrum, whose area is proportional to the number of unoccupied Pt 5d states, provide key insights into the electronic structure. The fitted average Pt oxidation state was approximately +1.2. This trend was strongly supported by X-ray photoelectron spectroscopy (XPS) results, which also showed a Pt oxidation state fitted value of +1.4, highly consistent with the XAFS analysis.

[0040] Example 2 Synthesis of RuO2@Pt-1ML catalyst: The only difference from Example 1 is that (in "Step (3) Pt shell deposition", 5 to 8 cycles are performed.) Example 3 Synthesis of RuO2@Pt-4ML catalyst: The only difference from Example 1 is that (in "step (3) Pt shell deposition", 15 to 18 cycles were performed).

[0041] Comparative Example 1: A Pt / SiO2 catalyst, the specific preparation steps are as follows: (1) Preparation of SiO2 support Silica microspheres were prepared using the Stöber method. Specifically, 17.8 mL of silicon source (tetraethyl silicate (TEOS) was used in this comparative example), 5.4 mL of NH3·H2O, 360 mL of organic solvent (C2H5OH was used in this comparative example), and 30 mL of H2O were added to a 500 mL beaker. The solution mixture was then vigorously stirred at 25 °C for 24 h. Afterward, the precipitate was centrifuged, washed several times with C2H5OH, and dried overnight at 70 °C. Finally, it was calcined in a tube furnace at 800 °C for 5 h at a flow rate of 40 mL / min under 10 vol.% O2 / Ar to obtain silica microspheres with an average particle size of 100 ± 10 nm.

[0042] (2) Load of Pt 2.0 g of SiO2 nanospheres were calcined at 700 °C for 3 hours under an oxygen flow. After cooling, the material was transferred to a 500 mL beaker and dispersed in 80 mL of ethanol, then sonicated to form a homogeneous suspension. Separately, 79 mg of platinum source (tetraammineplatinum(II)((NH3)4Pt·(NO3)2) was completely dissolved in 40 mL of deionized water. This solution was then added dropwise to the SiO2 suspension under continuous stirring. The mixture was stirred until the ethanol was completely evaporated. The resulting solid was dried overnight at 60 °C.

[0043] (3) Post-processing The deposited sample was heat-treated in air at 300 °C for 2 h to remove the precursor ligands, obtain a pure metal surface, and thus obtain the final Pt / SiO2 catalyst (Pt nanoparticles).

[0044] Comparative Example 2: A PtRu / SiO2 catalyst, the specific preparation steps are as follows: (1) Preparation of SiO2 support Silica microspheres were prepared using the Stöber method. Specifically, 17.8 mL of silicon source (tetraethyl silicate (TEOS) was used in this comparative example), 5.4 mL of NH3·H2O, 360 mL of organic solvent (C2H5OH was used in this comparative example), and 30 mL of H2O were added to a 500 mL beaker. The solution mixture was then vigorously stirred at 25 °C for 24 h. Afterward, the precipitate was centrifuged, washed several times with C2H5OH, and dried overnight at 70 °C. Finally, the precipitate was heated in a tube furnace at a flow rate of 40 mL / min at a concentration of 10 vol.% O2. 2 / Calcination at 800 ℃ for 5 hours under Ar yielded silica microspheres with an average particle size of 100±10 nm.

[0045] (2) Load of PtRu 2.0 g of SiO2 nanospheres were calcined at 700 °C for 3 hours under an oxygen flow. After cooling, the material was transferred to a 500 mL beaker and dispersed in 80 mL of ethanol, then sonicated to form a homogeneous suspension. Separately, 157 mg of ruthenium source (ruthenium(III) acetylacetone (Ru(acac)3) in this comparative example) and 79 mg of platinum source (platinum(II) tetraamminenitrate ((NH3)4Pt·(NO3)2) in this comparative example) were completely dissolved in 40 mL of ethanol. This solution was then added dropwise to the SiO2 suspension under continuous stirring. The mixture was stirred continuously until the ethanol was completely evaporated. The resulting solid was dried overnight at 60 °C.

[0046] (3) Post-processing The deposited sample was heat-treated in air at 300 °C for 2 h to remove the precursor ligands, obtain a pure metal surface, and thus obtain the final PtRu / SiO2 catalyst.

[0047] Propane catalytic combustion performance test: (1) Evaluation of propane catalytic combustion performance of the catalysts obtained in Examples 1-3 and Comparative Examples 1-2: The test was conducted using a fixed-bed reactor. 50 mg of catalyst was placed in a quartz tube and a reaction gas with the composition of 0.2 vol.% C3H8, 2.0 vol.% O2 (generally 1.0-4.0 vol.%) and 97.8 vol.% N2 (generally 98.8-95.8 vol.% as a balance gas) was introduced. The gas flow rate was 25 mL / min and the space velocity was 30,000 mL·g. -1 ·h -1 Once the system stabilizes, start from 30. Start at ℃ and gradually increase the temperature until propane is completely converted.

[0048] Test results are as follows Figure 1As shown, the ignition temperature (T) of the RuO2@Pt-2ML catalyst prepared in Example 1 of this invention is... 10 The reaction temperature (at which the conversion rate is 10%) is 125 °C, complete combustion of propane is achieved at 205 °C, and the reaction rate reaches 97 μmol / g at 200 °C. metal / s. Its low-temperature activity is significantly superior to other catalysts. Following closely behind is the PtRu / SiO2 catalyst prepared in Comparative Example 1, T 10 At approximately 200℃, complete propane combustion was achieved at 345℃, indicating a moderate level of activity. Examples 2-3 show the complete propane combustion using RuO2@Pt-1ML and RuO2@Pt-4ML catalysts, respectively. It can be seen that: (T 10 The temperatures were approximately 149 and 154 °C, respectively, and propane complete combustion was achieved at 230 and 245 °C. The activity was higher than that of the impregnated bimetallic PtRu / SiO2, but significantly lower than that of the RuO2@Pt-2ML catalyst. In contrast, as single-metal catalysts, the Ru / SiO2 prepared in Comparative Example 1 and the Pt / SiO2 prepared in Comparative Example 2 showed significantly lower activity: the T0 of Pt / SiO2 was... 10 The temperature is approximately 200℃, and the complete combustion temperature is approximately 350℃; while the T of Ru / SiO2 10 The temperature reaches as high as 250℃, and the complete combustion temperature exceeds 380℃. These results strongly demonstrate the crucial role of the synergistic effect of the core-shell bimetallic sites in the RuO2@Pt-2ML catalyst in enhancing the low-temperature activity of propane catalytic combustion, providing important experimental evidence for the design of high-performance low-carbon alkane combustion catalysts.

[0049] (2) Long-term stability test: The RuO2@Pt-2ML catalyst prepared in Example 1 was subjected to long-term stability testing. The test conditions were: catalyst dosage 50 mg, reaction gas composition: 0.2 vol.% C3H8, 2% O2, equilibrium gas: N2, and total space velocity (HSV): 30,000 mL·g. -1 ·h -1 The reaction temperature is 180°C. o C.

[0050] Test results are as follows Figure 8 As shown, the propane conversion rate remained at 79% after 500 h of continuous reaction, indicating that the RuO2@Pt-2ML catalyst has good reaction stability and can meet the requirements of industrial applications.

[0051] The stability of Examples 2-3 and each comparative example was tested using the same method, and the results are as follows: As can be seen from the table above, the activities of the three comparative catalysts, Pt / SiO2, Ru / SiO2 and RuO2@Pt-2ML, all decreased after 500 h of continuous reaction. However, the propane conversion rate of the RuO2@Pt-2ML catalyst remained at 79%, indicating that the RuO2@Pt-2ML catalyst not only has excellent activity but also better reaction stability.

[0052] (3) Performance testing of methane, ethane, butane, and n-hexane: The catalytic combustion performance of RuO2@Pt-2ML prepared in Example 1 was evaluated using a fixed-bed reactor. 50 mg of catalyst was placed in a quartz tube, and an atmosphere containing 0.2 vol.% CH4, C2H6, and C4H4 was introduced. 10 or C6H 14 The reaction gases consist of 2.0 vol.% O2 (typically 1.0-4.0 vol.%) and 97.8 vol.% N2 (typically 98.8-95.8 vol.%) as a balance gas, with a gas flow rate of 25 mL / min and a space velocity of 30,000 mL·g. -1 ·h -1 Once the system stabilizes, start from 30. Start at ℃ and gradually increase the temperature until propane is completely converted.

[0053] Test results are as follows Figure 9 As shown, from Figure 9 It can be seen from this that The three catalysts (Ru / SiO2, RuO2@Pt-2ML, and Pt / SiO2) showed a highly consistent activity order for the four reactants (methane, ethane, n-butane, and n-hexane): RuO2@Pt-2ML > Pt / SiO2 > Ru / SiO2. This indicates that the core-shell structure of the RuO2 core and the ultrathin Pt shell significantly enhances the catalytic performance, outperforming single-metal Ru and Pt catalysts. Specifically: Methane conversion (top left): RuO2@Pt-2ML achieves 100% conversion at 470°C, while Pt / SiO2 and Ru / SiO2 achieve only 75% and 35% methane conversion at 550°C, respectively. The core-shell structure provides the most significant improvement in low-temperature activity for methane conversion.

[0054] Ethane conversion (top right): RuO2@Pt-2ML is completely converted at 220°C, while Pt / SiO2 and Ru / SiO2 require 320°C and 405°C respectively.

[0055] n-Butane conversion (bottom left): RuO2@Pt-2ML achieved 100% conversion at 205°C, demonstrating extremely strong low-temperature activity, while Pt / SiO2 and Ru / SiO2 required 315°C and 370°C, respectively.

[0056] hexane conversion (bottom right): RuO2@Pt-2ML can be completely converted at 150°C, while Pt / SiO2 and Ru / SiO2 require 260°C and 330°C respectively.

[0057] The RuO2@Pt-2ML catalyst exhibits significantly better oxidation activity for methane, ethane, n-butane, and n-hexane than the Pt / SiO2 and Ru / SiO2 catalysts. This is attributed to the synergistic electronic effects and interfacial interactions between the RuO2 core and the Pt shell.

[0058] The foregoing has shown and described the basic process, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A SiO2-supported RuO2@Pt bimetallic core-shell structure catalyst, characterized in that, The catalyst uses SiO2 as a support and supports a bimetallic structure RuO2@Pt-2ML with a RuO2 core coated with 2-3 layers of Pt. The RuO2 core is a RuO2 nanoparticle, and 2-3 layers of Pt are deposited on the surface of the RuO2 nanoparticle to form a shell.

2. The SiO2-supported RuO2@Pt bimetallic core-shell catalyst according to claim 1, characterized in that, The RuO2 core is a rutile phase RuO2 nanoparticle with a Ru valence state of +3 to +4 and a particle size of 3 to 5 nm; the shell consists of 2 to 3 Pt atomic layers with a Pt valence state of 0 to +2.

3. The SiO2-supported RuO2@Pt bimetallic core-shell catalyst according to claim 1, characterized in that, The outermost Pt atom in the bimetallic structure RuO2@Pt-2ML has a lattice constant of 0.380~0.385 nm, which is lattice compressed compared to the lattice constant of 0.392 nm of pure Pt metal.

4. The SiO2-supported RuO2@Pt bimetallic core-shell catalyst according to claim 1, characterized in that, The RuO2 nanoparticles form a heterogeneous interface with the Pt shell, and a global electron transfer effect is generated through Ru-O-Pt bonding, causing the d-band center of the Pt atom to shift downward.

5. A method for preparing a SiO2-supported RuO2@Pt bimetallic core-shell structure catalyst as described in any one of claims 1 to 4, characterized in that, Prepare according to the following steps: S1. Preparation of SiO2 support by Stöber method: Silicon source, NH3·H2O, organic solvent and H2O are mixed and stirred. The precipitate is centrifuged, washed with organic solvent, dried and then calcined to obtain SiO2 support. S2. Loading Pt nanoparticles onto the surface of SiO2 support using a wet chemical method: The SiO2 support obtained in step S1 is dispersed in an ethanol solution of ruthenium source, calcined, continuously stirred, evaporated, and dried to obtain Ru / SiO2. S3. Deposit 2-3 layers of Pt on Ru nanoparticles using ALD technology: Place the Ru / SiO2 and Pt precursor obtained in step S2 in an ALD reaction chamber, use oxygen as the reaction gas, and perform ALD cycling at 100-200℃ to deposit Pt on the surface of Ru nanoparticles, forming a 2-3 atomic layer Pt shell, and obtain a bimetallic RuO2@Pt-2ML catalyst. S4. The deposited samples obtained in step S3 were heat-treated to obtain a RuO2@Pt-2ML catalyst with a bimetallic structure of RuO2 as the core and 2-3 layers of Pt supported.

6. The method for preparing a SiO2-supported RuO2@Pt bimetallic core-shell structure catalyst according to claim 5, characterized in that, In step S1, the volume ratio of silicon source, NH3·H2O, organic solvent, and H2O is (10~25):(3~7):(300~400):(20~40); the stirring temperature is 25~30℃, and the stirring time is 12~36h; the drying temperature is 70~100℃, and the drying time is 12~48h; the calcination conditions are: a flow rate of 10~40 mL / min at 5~10 vol.% O2 / Ar at 600~800℃ for 2~5 hours. The silicon source is one or more of ethyl silicate, sodium silicate, tetraethoxysilane, and polyethoxysilane; the organic solvent includes one or more of ethanol, cyclohexane, and 1,2-dichloroethane.

7. The method for preparing a SiO2-supported RuO2@Pt bimetallic core-shell structure catalyst according to claim 5, characterized in that, The ruthenium source in step S2 includes one or more of ruthenium nitrate nitrosyl nitrate, ruthenium acetylacetonate, and bis(ethylcyclopentadiene)ruthenium; the mass percentage of metallic ruthenium in Ru / SiO2 is 1~3 wt%; the calcination temperature is 600~800℃, the calcination time is 2~4h, the drying temperature is 50~70℃, and the drying time is 12~48h.

8. The method for preparing a SiO2-supported RuO2@Pt bimetallic core-shell structure catalyst according to claim 5, characterized in that, The Pt precursor in step S3 includes one or more of chloroplatinic acid hexahydrate, tetraammineplatinum nitrate, methylcyclopentadienyltrimethylplatinum, or (trimethyl)methylcyclopentadienylplatinum; the reaction gas is oxygen; and the Pt precursor deposition cycle is 10-12 times.

9. The method for preparing a SiO2-supported RuO2@Pt bimetallic core-shell structure catalyst according to claim 5, characterized in that, The heat treatment temperature in step S4 is 200~500 ℃, and the heat treatment time is 1~3h.

10. The application of a SiO2-supported RuO2@Pt bimetallic core-shell structure catalyst as described in any one of claims 1 to 4, characterized in that, The catalyst was applied to the catalytic oxidation of low-carbon alkanes.

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