A high-entropy oxide catalyst, its preparation method and application

Abstract

This invention discloses a high-entropy oxide catalyst, its preparation method, and its application, belonging to the field of catalytic materials technology. It solves the problems of existing technologies where precious metal catalysts require large quantities and are costly, and multi-element catalysts are prone to component segregation under synthesis and high-temperature reaction conditions, which disrupts the high-entropy effect and affects catalyst lifespan; and addresses the challenges posed by CO, HC, and NO in complex exhaust gas environments. x Competitive adsorption exists on the catalyst surface, making it difficult for traditional catalysts with single active sites to achieve simultaneous and efficient removal of all pollutants. The method involves mixing a solution of noble metals, rare earth metals, two or more 3d transition metals, and a refractory metal salt selected from groups IVB, VB, or VIB with a complexing agent, followed by stirring, evaporation, and calcination to obtain a high-entropy oxide catalyst with a spinel structure. This invention has the advantages of low noble metal usage, high synergistic catalytic efficiency for multiple pollutants, excellent thermal stability, and strong structural stability.

Description

Technical Field

[0001] This invention relates to the field of catalytic materials technology, and in particular to a high-entropy oxide catalyst, its preparation method, and its application. Background Technology

[0002] Currently, mobile sources have become a significant source of air pollution emissions. Statistics show that diesel vehicles emit CO, HC, and NO... x The emissions of PM2.5, PM10, PM2.5 ...

[0003] In the search for alternatives or reductions to precious metals, rare earth metals and 3d transition metals have shown unique potential. Rare earth metal ions (such as Ce, La, and Sm) possess unfilled 4f orbitals and strong polarization capabilities, exhibiting a variety of stable valences. Their oxide surfaces readily form oxygen vacancies, resulting in high oxygen storage capacity and excellent oxygen mobility. 3d transition metals (such as Mn, Co, and Fe) possess unfilled 3d electron orbitals, allowing for flexible bonding and facilitating electron transfer processes.

[0004] In recent years, multi-element oxide (MEO) nanoparticles composed of three or more cations, especially high-entropy oxides, have attracted much attention due to their unique multi-element synergistic effect and maximized configurational entropy. The high-entropy effect makes these materials tend to form thermodynamically stable single solid solution phases, maintaining excellent structural integrity even under harsh operating conditions. Therefore, they are considered a potential strategy for simultaneously improving the reactivity and stability of noble metal sites in DOC applications. However, despite the significant theoretical advantages of high-entropy oxides, their practical application in the DOC field still faces serious challenges: for example, multi-element systems are prone to component segregation under synthesis and high-temperature reaction conditions, leading to the formation of impurity phases, disrupting the high-entropy effect, and affecting catalyst lifetime; in complex exhaust gas environments, CO, HC, and NO...x Competition for adsorption exists on the catalyst surface, and the single active site of traditional catalysts makes it difficult to achieve simultaneous and efficient removal of all pollutants.

[0005] Therefore, developing a novel DOC catalyst that can balance high activity, excellent stability, synergistic purification capabilities for multiple pollutants, and low precious metal content remains a pressing technical challenge in this field. Summary of the Invention

[0006] In view of the above, the present invention aims to provide a high-entropy oxide catalyst and its preparation method and application, in order to solve the problems existing in the prior art: (1) reducing the loading of noble metals usually significantly sacrifices catalytic activity and durability; (2) in complex exhaust gas environments, CO, HC and NO x There is competitive adsorption on the catalyst surface, and the single active site of the traditional catalyst is difficult to achieve simultaneous and efficient removal of all pollutants; (3) Multi-element systems are prone to component segregation under synthesis and high temperature reaction conditions, resulting in the generation of impurity phases, destroying the high entropy effect, and affecting the catalyst life.

[0007] The objective of this invention is mainly achieved through the following technical solutions: The first aspect of this invention provides a high-entropy oxide catalyst, the catalyst comprising oxides of five different metal elements, the metal elements comprising: a) At least one precious metal; b) At least one rare earth metal; c) At least two 3d transition metals; d) At least one refractory metal selected from groups IVB, VB and VIB; The catalyst has a spinel structure.

[0008] Furthermore, the precious metal is a platinum group element.

[0009] Furthermore, the rare earth metal is a lanthanide element.

[0010] Furthermore, the 3d transition metal is selected from at least two of Mn, Co, Fe, and Ni.

[0011] Furthermore, the refractory metal is selected from Nb and / or Mo.

[0012] Furthermore, the platinum group elements are selected from Pt and / or Pd.

[0013] Furthermore, the rare earth metal is Sm.

[0014] Furthermore, the 3d transition metal is selected from Mn and Co.

[0015] Furthermore, the refractory metal is selected from Nb.

[0016] Further, the 3d transition metal includes a first 3d transition metal and a second 3d transition metal. In the catalyst, with the molar amount of rare earth metal elements as 1, the molar ratio of noble metal elements, first 3d transition metal elements, second 3d transition metal elements, and refractory metal elements is (0.008-0.015):(0.8-1.2):(0.8-1.2):(0.8-1.2).

[0017] Furthermore, the mass fraction of the noble metal in the catalyst is 0.3~0.8%.

[0018] A second aspect of the present invention provides a method for using the high-entropy oxide catalyst described in the first aspect, the method comprising: S1. Dissolve noble metal salts, rare earth metal salts, 3d transition metal salts, and refractory metal salts selected from Group IVB, Group VB, and Group VIB in deionized water and mix them evenly to obtain a mixed solution. S2. Under stirring conditions, a complexing agent is added to the above mixed solution, and after mixing evenly, it is evaporated and calcined to obtain the high-entropy oxide catalyst.

[0019] Furthermore, the noble metal salt is selected from at least one of chloroplatinic acid, platinum nitrate, chloropalladium acid, palladium nitrate, rhodium chloride, or rhodium nitrate.

[0020] Furthermore, the rare earth metal salt is at least one of the corresponding nitrate, chloride, or acetate.

[0021] Furthermore, the 3d transition metal salt is at least one of the corresponding nitrate, chloride, or acetate.

[0022] Furthermore, the refractory metal salt is at least one of niobium oxalate, niobium chloride, zirconium nitrate, zirconium oxychloride, ammonium molybdate, or ammonium heptamolybdate.

[0023] Further, the 3d transition metal salt includes a first 3d transition metal salt and a second 3d transition metal salt, and the molar ratio of the rare earth metal salt, noble metal salt, first 3d transition metal salt, second 3d transition metal salt, and refractory metal salt is 1:(0.008-0.015):(0.8-1.2):(0.8-1.2):(0.8-1.2).

[0024] Furthermore, the stirring conditions include: a stirring rate of 400-700 rpm and a stirring time of 2-6 h.

[0025] Furthermore, the evaporation conditions include: an evaporation temperature of 40-90℃ and an evaporation time of 12-36h.

[0026] Furthermore, the calcination conditions include: a calcination temperature of 300-550℃ and a calcination time of 2-5 hours.

[0027] A third aspect of the present invention provides a high-entropy oxide catalyst as described in the first aspect or a high-entropy oxide catalyst obtained by the method described in the second aspect for the catalytic oxidation of CO, HC and NO. x Applications of [the technology / method].

[0028] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: (1) The high-entropy oxide described in this invention has a unique spinel structure, exhibiting excellent thermal stability and structural integrity. More importantly, by atomically dissolving noble metals as lattice components in the oxide, rather than traditionally loading them onto the surface in the form of nanoparticles, the migration, sintering, and deactivation of noble metals under harsh high-temperature environments are fundamentally suppressed. While achieving a significant reduction in noble metal content, the durability and stability of active sites during long-term use are ensured, successfully resolving the contradiction between cost and durability that is difficult to balance in traditional catalysts.

[0029] (2) This invention creates multiple complementary active sites in a high-entropy spinel structure through a carefully designed combination of five components (noble metals, rare earth metals, 3d transition metals, and refractory metals selected from Groups IVB, VB, and VIB). Among these, noble metals provide high intrinsic activity, rare earth metals contribute excellent oxygen storage and migration capabilities, transition metals impart flexible valence characteristics to promote redox cycles, and refractory metals act as structural stabilizers. The electronic synergistic effect among these components enables the catalyst to simultaneously and efficiently catalyze the oxidation of three major pollutants with different properties in diesel vehicle exhaust: CO, HC, and NO. x Experiments show that it is effective against CO, HC and NO. x The ignition temperature (T50 / T100) is significantly lower than that of traditional Pt / Pd catalysts and comparative samples lacking any key component, achieving broad-spectrum and efficient removal of a variety of pollutants. Attached Figure Description

[0030] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts. Figure 1 The structure of the high-entropy oxide catalyst prepared in Example 1 is shown in Figure (a), which is the XRD pattern of the high-entropy oxide catalyst, Figure (b) is the HRTEM pattern of the high-entropy oxide catalyst, Figure (c) is the intensity distribution map of the corresponding region of the high-entropy oxide catalyst, Figure (d) is the SEAD pattern of the high-entropy oxide catalyst, and Figure (e) is the EDX elemental distribution map of the high-entropy oxide catalyst. Figure 2 The DOC performance test graph shows the high-entropy oxide catalyst oxide prepared in Example 1. Figure 3 The DOC performance test results of the high-entropy oxide catalyst oxide prepared in Comparative Example 1 are shown in the figure. Figure 4 The XRD pattern of the high-entropy oxide catalyst oxide prepared in Comparative Example 2 is shown. Figure 5 The DOC performance test results of the high-entropy oxide catalyst oxide prepared in Comparative Example 2 are shown in the figure. Figure 6 The performance change curve of the catalyst prepared in Example 1 during cycle testing; Figure 7 The performance change curve of the catalyst prepared for comparative example 2 during cycle testing. Detailed Implementation

[0031] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of the present invention and, together with the embodiments of the present invention, serve to illustrate the principles of the present invention.

[0032] Current commercial diesel oxidation catalysts (DOC) rely heavily on highly loaded precious metals such as platinum and palladium, resulting in high costs. Furthermore, traditional catalysts have a single active site, making it difficult to effectively target CO, hydrocarbons (HC), and nitrogen oxides (NOx). x Synergistic and efficient purification of multiple pollutants such as α and β. Although emerging high-entropy oxide materials theoretically possess excellent thermal stability and synergistic catalytic potential, they are prone to component segregation during actual preparation, making it difficult to form a stable single-phase structure, thus leading to sintering deactivation.

[0033] Therefore, in order to overcome the above-mentioned defects, the first aspect of the present invention provides a high-entropy oxide catalyst, the catalyst comprising oxides of five different metal elements, wherein the metal elements include: a) At least one precious metal; b) At least one rare earth metal; c) At least two 3d transition metals; d) At least one refractory metal selected from groups IVB, VB and VIB; The catalyst has a spinel structure.

[0034] In this invention, the high-entropy oxide catalyst possesses a spinel structure, and the oxides of the five different metal elements are uniformly mixed to form a stable solid solution. Simultaneously, the high-entropy spinel structure creates multiple complementary active sites, providing excellent catalytic activity. Specifically, noble metals provide high intrinsic activity, rare earth metals contribute excellent oxygen storage and migration capabilities, transition metals impart flexible valence characteristics to promote redox cycles, and refractory metals act as structural stabilizers. The electronic synergistic effect among these different components enables the catalyst to not only reduce the amount of noble metals used but also to simultaneously and efficiently catalyze the oxidation of three major pollutants with different properties in diesel vehicle exhaust: CO, HC, and NO. x .

[0035] According to some embodiments of the present invention, the precious metal element is a platinum group element.

[0036] In this invention, on the one hand, platinum group elements have a unique electronic structure, namely unfilled d electron orbitals, which makes them exhibit extremely high intrinsic activity in catalytic oxidation. On the other hand, the adsorption strength of platinum group elements for CO, O2 and NO is just right, which can effectively activate these molecules and allow reaction products (such as CO2) to be desorbed smoothly, thereby maintaining the continuous availability of active sites. For example, the platinum group elements in this invention are preferably Pt and / or Pd.

[0037] According to some embodiments of the present invention, the rare earth element is a lanthanide element.

[0038] In this invention, the inventors discovered that the unique microscopic electronic structure of lanthanides enables them to maintain catalytic stability in catalytic oxidation reactions while flexibly gaining and losing electrons, exhibiting rich valence state changes. They can reversibly store and release oxygen atoms according to fluctuations in oxygen concentration in the reaction environment, solving the problem of reaction rate decline under transient oxygen-deficient conditions in traditional catalysts. At the same time, it inhibits the sintering of other components in the catalyst, providing a strong guarantee for maintaining high catalytic activity of noble metals and catalyst stability.

[0039] According to some embodiments of the present invention, considering the formation of a five-element high-entropy system, the realization of high-entropy stabilization effect, and the suppression of segregation of other components during the reaction process, thereby ensuring the long lifespan of the catalyst, the 3d transition metal element is selected from at least two of Mn, Co, Fe and Ni.

[0040] According to some embodiments of the present invention, the refractory metal element is selected from at least one of Nb and / or Mo.

[0041] In this invention, the refractory metal element is selected from the aforementioned elements, which can greatly hinder the migration and diffusion of other elements (such as 3d transition metal elements) and noble metals, making the entire oxide framework more stable at high temperatures, effectively suppressing component segregation, and ensuring the long-term stability of the spinel structure of the high-entropy oxide catalyst. Simultaneously, it can also regulate the electronic environment of the noble metal, thereby synergistically enhancing the catalyst activity.

[0042] According to some embodiments of the present invention, the molar ratio of the five metallic elements is 0.01:0.8-1.2:0.8-1.2:0.8-1.2:0.8-1.2.

[0043] In this invention, the inventors discovered through extensive creative work that controlling the molar ratio of the four metal elements (excluding the noble metal) within the aforementioned range is key to maximizing configurational entropy and forming a single, stable spinel solid solution phase. When the elements coexist in the above proportions, the system exhibits the highest mixing entropy, which is thermodynamically most favorable for forming a homogeneous high-entropy phase, rather than a mixture of multiple simple oxides. This proportion range effectively suppresses the segregation of certain components during synthesis and high-temperature reactions, ensuring the long-term stability of the catalyst structure and fully leveraging the synergistic effect of each component. If the proportion of any element exceeds or falls below the above range, it will disrupt the homogeneity of the high-entropy structure, leading to a decrease in catalytic performance.

[0044] A second aspect of the present invention provides a method for preparing the high-entropy oxide catalyst described in the first aspect, the method comprising: S1. Dissolve noble metal salts, rare earth metal salts, 3d transition metal salts, and refractory metal salts selected from Group IVB, Group VB, and Group VIB in deionized water and mix them evenly to obtain a mixed solution. S2. Under stirring conditions, a complexing agent is added to the above mixed solution, and then the mixture is stirred, evaporated, and calcined to obtain the high-entropy oxide catalyst.

[0045] In this invention, atomic-level uniform mixing is achieved through the sol-gel method described above, laying the foundation for the subsequent formation of high-entropy oxides. Furthermore, the complexing agent can simultaneously form stable complexes with the various metal ions mentioned above, effectively preventing preliminary phase separation or precipitation caused by differences in hydrolysis rates of different metal ions during subsequent stirring and evaporation processes, thereby ensuring highly uniform mixing and avoiding component segregation.

[0046] According to some specific embodiments of the present invention, the complexing agent is selected from at least one of citric acid, ethylenediaminetetraacetic acid, tartaric acid, oxalic acid, succinic acid, gluconic acid, and amino acids.

[0047] In this invention, the amount of the complexing agent is 1-1.5 times the total molar amount of the noble metal salt, rare earth metal salt, 3d transition metal salt, and refractory metal salt selected from Group IVB, Group VB, and Group VIB.

[0048] According to some specific embodiments of the present invention, considering that it can exist stably in aqueous solution and decompose completely during calcination without introducing new impurity ions, specifically, the noble metal salt is selected from at least one of chloroplatinic acid, platinum nitrate, chloropalladium acid, palladium nitrate, rhodium chloride, or rhodium nitrate; the rare earth metal salt is at least one of the corresponding nitrate, chloride, or acetate; and the 3d transition metal salt is at least one of the corresponding nitrate, chloride, or acetate.

[0049] According to some embodiments of the present invention, taking into account stability and operability in aqueous solutions, specifically, the refractory metal salt is at least one of niobium oxalate, niobium chloride, zirconium nitrate, zirconium oxychloride, ammonium molybdate, or ammonium heptamolybdate.

[0050] According to some embodiments of the present invention, in order to form a single spinel phase with maximized configurational entropy, thereby fundamentally avoiding the precipitation of impurity phases, specifically, the 3d transition metal salt includes a first 3d transition metal salt and a second 3d transition metal salt, and the molar ratio of the rare earth metal salt, noble metal salt, first 3d transition metal salt, second 3d transition metal salt and refractory metal salt is 1:(0.008-0.015):(0.8-1.2):(0.8-1.2):(0.8-1.2).

[0051] According to some embodiments of the present invention, the stirring conditions include: a stirring rate of 400-700 rpm and a stirring time of 2-6 h.

[0052] In this invention, it should be noted that if the stirring speed is too low (less than 400 rpm), sufficient shear force cannot be provided to mix the solution and disperse the added complexing agent, resulting in excessively high local concentrations and precipitation. If the stirring speed is too high (greater than 700 rpm), too many air bubbles will be introduced, increasing unnecessary solvent evaporation and interfering with the gelation process. For example, the stirring speed is 400-700 rpm.

[0053] In this invention, when the stirring time meets the above-mentioned range and is combined with a specific stirring rate, the complexation reaction can be fully carried out, and the system can achieve molecular-level homogeneity. If the time is too short (less than 2 seconds), the complexation is incomplete, and phase separation is easy during subsequent evaporation; if the time is too long (more than 6 seconds), the improvement in homogeneity is limited, and production efficiency is reduced instead.

[0054] It should be noted that, considering the thermodynamic and kinetic factors of the complexation reaction, the stirring is carried out at 60-90°C.

[0055] According to some embodiments of the present invention, the evaporation conditions include: an evaporation temperature of 40-90°C and an evaporation time of 12-36 hours.

[0056] In this invention, the inventors discovered that if the evaporation temperature is less than 40°C, the evaporation rate will be slow and the efficiency will be low; if the temperature is greater than 90°C, it will cause premature decomposition or hydrolysis of certain metal complexes, thereby disrupting the uniform distribution of elements and causing the solvent to boil, thus destroying the formed gel network structure.

[0057] It should be noted that the method of the present invention further includes drying the evaporated product, wherein the drying conditions include a drying temperature of 90~120℃ and a drying time of 12~48h.

[0058] According to some embodiments of the present invention, considering the uniformity of heat transfer inside the catalyst during calcination, it is preferable to grind the evaporated product before calcination.

[0059] According to some embodiments of the present invention, the calcination conditions include: a calcination temperature of 300-550°C and a calcination time of 2-5 hours.

[0060] In this invention, the inventors discovered that when the temperature is below 300℃, the organic matter decomposes incompletely, resulting in poor crystallinity and low catalytic activity; while temperatures above 550℃ increase crystallinity, they lead to phase separation and damage to the high-entropy structure. Through extensive experimentation, the inventors found that satisfying the above-mentioned calcination temperature balances the relationship between crystallinity, specific surface area, and phase purity, thereby improving catalytic activity. Simultaneously, the calcination time, within the aforementioned range, ensures that the organic matter in the precursor is fully oxidized and removed.

[0061] A third aspect of the present invention provides a high-entropy oxide catalyst as described in the first aspect or a high-entropy oxide catalyst obtained by the method described in the second aspect for the catalytic oxidation of CO, HC and NO. x Applications of [the technology / method].

[0062] The high-entropy catalyst provided in the first aspect of this invention is effective against CO, HC and NO. x All samples exhibited low ignition temperatures. Their performance was significantly superior to comparative samples lacking key components (e.g., Comparative Example 1 lacked Nb) or with non-high entropy structures (e.g., Comparative Example 2 had phase separation). This demonstrates that the catalyst can simultaneously and efficiently purify multiple pollutants with different properties, solving the competitive adsorption problem faced by traditional catalysts due to their single active site, and has broad application prospects in the field of diesel vehicle exhaust purification.

[0063] The advantages of the method of the present invention will be illustrated below through examples. In the following embodiments, T50 : This refers to the temperature at which the conversion rate of reactants reaches 50%; T 100 : This refers to the temperature at which the conversion rate of reactants reaches 100%.

[0064] The percentage content of noble metals in the catalyst was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Unless otherwise specified, all raw materials used in the following examples are commercially available products.

[0065] Example 1 S1, 4.44g of Sm(NO3)3·6H2O (10mmol), 2.45g of (CH3COO)2Mn·4H2O (10mmol), 2.91g of Co(NO3)2·6H2O (10mmol), and 5.38g of C 10 H5NbO 20 10 mmol and 0.04 g of Pt(NO3)2 were dissolved in 100 mL of deionized water and allowed to dissolve completely to obtain a mixed solution; S2. Add 10.37 g of citric acid to the mixed solution at a stirring rate of 600 rpm, stir at 60 °C for 2 h, and then evaporate the solvent at 90 °C for 24 h to obtain a viscous gel precursor. Dry at 100 °C for 24 h to obtain a fluffy amorphous precursor. Calcine the ground powder in a muffle furnace at 450 °C for 3 h to obtain a pentagonal PtSmMnCoNb high-entropy oxide.

[0066] Tests showed that the catalyst contained 0.5% noble metals by mass.

[0067] Figure 1 The structure of the PtSmMnCoNb high-entropy nano-oxide prepared in Example 1 is shown. XRD patterns reveal a simple spinel structure (PDF NO. 73-1701) without impurity peaks. HRTEM and selected area electron diffraction further confirm the formation of the spinel structure. Mapping patterns indicate uniform elemental dispersion. These analyses demonstrate that the catalyst prepared by the synthetic method described in this invention exhibits the characteristics of a high-entropy oxide.

[0068] Example 2 S1, 8 mmol of Sm(NO3)3·6H2O, 8 mmol of (CH3COO)2Mn·4H2O, 12 mmol of Co(NO3)2·6H2O, and 12 mmol of C 10 H5NbO 20 Dissolve 0.1 mmol of Pt(NO3)2 in 100 mL of deionized water until fully dissolved to obtain a mixed solution; S2. Add 10.37 g of citric acid to the mixed solution at a stirring rate of 600 rpm, stir at 70 °C for 1.5 h, and then evaporate the solvent at 100 °C for 24 h to obtain a viscous gel precursor. Dry at 120 °C for 20 h to obtain a fluffy amorphous precursor. Calcine the ground powder in a muffle furnace at 450 °C for 3 h to obtain a pentagonal PtSmMnCoNb high-entropy oxide.

[0069] Tests showed that the catalyst contained 0.5% noble metals by mass.

[0070] Example 3 Replace Sm with an equimolar amount of La Tests showed that the catalyst contained 0.5% noble metals by mass.

[0071] Example 4 The method is the same as in Example 1, except that the amount of Pt(NO3)2 used is 0.023g.

[0072] Tests showed that the mass fraction of precious metals in the catalyst was 0.3%.

[0073] Example 5 The 3d transition metal is not limited to two types; for example, 8 mmol of Fe(NO3)3·9H2O can be added to prepare a six-membered metal oxide.

[0074] Tests showed that the catalyst contained 0.5% noble metals by mass.

[0075] Example 6 The method is the same as in Example 1, except that 20 mmol of Sm(NO3)3·6H2O, 6.7 mmol of (CH3COO)2Mn·4H2O, 6.7 mmol of Co(NO3)2·6H2O, and 6.7 mmol of C are used. 10 H5NbO 20 Dissolve 0.1 mmol of Pt(NO3)2 in 100 mL of deionized water until fully dissolved to obtain a mixed solution.

[0076] Tests showed that the catalyst contained 0.5% noble metals by mass.

[0077] Comparative Example 1 S1. Dissolve 6.67g of Sm(NO3)3·6H2O (13.33mmol), 3.68g of (CH3COO)2Mn·4H2O (13.33mmol), 4.37g of Co(NO3)2·6H2O (13.33mmol), and 0.04g of Pt(NO3)2 in 100mL of deionized water until fully dissolved to obtain a mixed solution. S2, Same as in Example 1, and then obtain quaternary PtSmMnCo oxide.

[0078] Tests showed that the catalyst contained 0.5% noble metals by mass.

[0079] like Figure 3 As shown, the DOC performance of the PtSmMnCo oxide catalyst is significantly lower than that of the PtSmMnCoNb oxide catalyst. For CO, the T100 is 250°C, which is 130°C higher than the sample in Example 1. C3H6 and NO... x The T50 values ​​were 247℃ and 251℃, respectively.

[0080] Comparative Example 2 A phase-separated five-membered PS-PtSmMnCoNb oxide was synthesized by a coprecipitation method. The oxide consisted of 4.44 g of Sm(NO3)3·6H2O, 2.45 g of (CH3COO)2Mn·4H2O, 2.91 g of Co(NO3)2·6H2O, and 5.38 g of C. 10 H5NbO 20 Dissolve 0.04 g of Pt(NO3)2 in 100 mL of deionized water until fully dissolved to obtain a mixed solution; S2. Under vigorous stirring, add 0.3M NaOH solution (96%, Sinopharm Chemical Reagent) dropwise until the pH of the solution reaches 10. After stirring thoroughly for 2 hours, transfer the mixture to a stainless steel high-pressure reactor lined with polytetrafluoroethylene (PTFE) and carry out a hydrothermal reaction at 160°C for 3 hours. The resulting precipitate is filtered, washed with deionized water, dried at 100°C for 24 hours, and finally calcined at 450°C in air for 3 hours to obtain the catalyst.

[0081] Tests showed that the catalyst contained 0.5% noble metals by mass.

[0082] like Figure 4 As shown, the XRD results clearly indicate the presence of the impurity phase, demonstrating that the sample does not possess high-entropy characteristics. Although the catalyst composition is the same in Example 1 and Comparative Example 2, differences in phase structure can significantly affect the conversion rate of the reactants. Figure 5 As shown, for CO, T100 is 240°C, which is 120°C lower than the sample in the example. C3H6 and NOx The T50 values ​​were 238℃ and 254℃, respectively.

[0083] Comparative Example 3 5 g of γ-Al₂O₃ was added to 20 mL of deionized water and heated to 80 °C at 400 rpm. 0.04 g of Pt(NO₃)₂ was dissolved in 10 mL of deionized water and added dropwise to the γ-Al₂O₃ suspension. After stirring for 2 h, the suspension was evaporated at 40 °C for 12 h to remove excess deionized water. The resulting powder was calcined at 650 °C for 3 h.

[0084] Tests showed that the catalyst contained 0.5% noble metals by mass.

[0085] Comparative Example 4 The method is the same as in Example 1, except that C is... 10 H5NbO 20 Replace with an equimolar amount of Zr(NO3)4·5H2O.

[0086] Tests showed that the catalyst contained 0.5% noble metals by mass.

[0087] Comparative Example 5 The method is the same as in Example 1, except that (CH3COO)2Mn·4H2O is replaced with an equimolar amount of Fe(NO3)3·9H2O, and Co(NO3)2·6H2O is replaced with an equimolar amount of Cu(NO3)2·6H2O.

[0088] Tests showed that the catalyst contained 0.5% noble metals by mass.

[0089] Comparative Example 6 Replace Pt with an equimolar amount of Pd.

[0090] Tests showed that the catalyst contained 0.5% noble metals by mass.

[0091] Comparative Example 7 The method is the same as in Example 1, except that 2.45g of (CH3COO)2Mn·4H2O (10mmol) and 2.91g of Co(NO3)2·6H2O (10mmol) are replaced with 20mmol of Zr(NO3)4·5H2O.

[0092] Tests showed that the catalyst contained 0.5% noble metals by mass.

[0093] Test case The catalysts prepared in the examples and comparative examples were tested for catalytic effect and ignition temperature. Specifically, the DOC performance of the catalysts was tested in a fixed-bed quartz reactor with an inner diameter of 6 mm. The catalysts prepared in the examples and comparative examples were tableted and granulated, and sieved to 40-60 mesh. The simulated feed gas consisted of 1000 ppm CO, 500 ppm C3H6, 200 ppm NO, 10 vol% O2, and 6 vol% H2O, with the remainder being N2. The gas hourly space velocity (GHSV) was 100,000 h⁻¹. -1 The catalyst loading mass was 0.28g. The ignition temperature test results are shown in Table 1.

[0094] The catalytic effect of Example 1 is as follows: Figure 2 As shown, the PtSmMnCoNb high-entropy oxide catalyst exhibits excellent DOC performance. Especially for CO, T... 100 Only 120℃. C3H6 and NO x T 50 At 192℃ and 204℃ respectively, they are a class of oxidation catalysts with great application potential.

[0095]

[0096] from Figure 2 As can be seen from the results, the DOC performance of the PtSmMnCoNb high-entropy oxide catalyst prepared in Example 1 shows that this catalyst exhibits good DOC performance against CO, C3H6, and NO. x All exhibited excellent catalytic activity: CO conversion reached 100% at 120℃ (T100=120℃); C3H6 conversion reached 50% at 192℃ (T50=192℃); NO... x The conversion rate reaches 50% at 204℃ (T50=204℃), which indicates that the catalyst can simultaneously and efficiently catalyze the oxidation of the three main pollutants in diesel vehicle exhaust, and has the ability to synergistically purify multiple pollutants.

[0097] Figure 3 The DOC performance test results of the PtSmMnCo (lacking refractory metal Nb) catalyst prepared in Comparative Example 1 show that the activity of the catalyst is significantly reduced compared with Example 1. This indicates that the lack of refractory metal Nb leads to a decrease in catalyst structural stability and a weakening of the synergistic effect of active sites, thereby affecting the overall catalytic performance.

[0098] Figure 4The image shows the XRD pattern of the PtSmMnCoNb-PS catalyst prepared by coprecipitation in Comparative Example 2. Multiple impurity peaks appear, indicating the presence of various crystalline phases in the sample, failing to form a single spinel structure and lacking high-entropy characteristics. This demonstrates that the synthesis method is crucial for the formation of high-entropy structures, and that coprecipitation easily leads to component segregation and impurity phase formation.

[0099] Figure 5 The results of DOC performance testing of the PtSmMnCoNb-PS catalyst prepared in Comparative Example 2 show that although its chemical composition is the same as that in Example 1, its catalytic activity is significantly reduced due to the presence of phase separation.

[0100] To test the stability of the catalysts, DOC cycling tests were performed on Example 1 (PtSmMnCoNb) and Comparative Example 1 (PtSmMnCo). The results showed that the catalyst in Example 1 maintained stable performance against CO, C3H6, and NO after 10 cycles. x The oxidation capacity did not show a significant decrease. Figure 6 The conversion rate curve basically overlapped with the initial test, and the ignition temperature (T50 / T100) did not change significantly, indicating that its activity remained stable during repeated use.

[0101] The performance changes of the phase-separated catalyst prepared in Comparative Example 2 after the second cycle test are as follows: Figure 7 As shown. From Figure 7 As can be seen, the catalyst activity decreased significantly in the second test compared to the first test, specifically in the reduction of CO, C3H6, and NO. x The ignition temperature increased significantly, and the conversion rate curve shifted to the right overall, indicating that the catalyst has poor stability during recycling and is prone to rapid deactivation.

[0102] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for the simultaneous catalytic oxidation of CO, HC and NO x The high-entropy oxide catalyst is characterized by, The catalyst comprises oxides of five different metal elements, including: a) A precious metal; b) A rare earth metal; c) Two 3d transition metals; d) A refractory metal selected from the VB group; The catalyst has a spinel structure; The noble metal is Pt, the rare earth metal is Sm or La, the two 3d transition metals are Mn and Co, and the refractory metal selected from group VB is Nb. In the catalyst, with the molar amount of rare earth metal elements as 1, the molar ratio of noble metal elements, Mn, Co, and refractory metal elements is (0.008-0.015):(0.8-1.2):(0.8-1.2):(0.8-1.2).

2. The catalyst according to claim 1, characterized in that, The catalyst contains 0.3-0.8% noble metal by mass.

3. A method for preparing the simultaneous catalytic oxidation of CO, HC and NO as described in claim 1 or 2. x The method using high-entropy oxide catalysts is characterized by... The method includes: S1. Dissolve the noble metal salt, rare earth metal salt, 3d transition metal salt, and refractory metal salt selected from group VB in deionized water and mix them evenly to obtain a mixed solution; S2. Under stirring conditions, a complexing agent is added to the above mixed solution, and after mixing evenly, it is evaporated and calcined to obtain the high-entropy oxide catalyst.

4. The method according to claim 3, characterized in that, The precious metal salt is selected from platinum nitrate; And / or, the rare earth metal salt is at least one of the corresponding nitrate, chloride or acetate; And / or, the 3d transition metal salt is at least one of the corresponding nitrate, chloride or acetate; And / or, the refractory metal salt is niobium oxalate and / or niobium chloride.

5. The method according to claim 3 or 4, characterized in that, The stirring conditions include: a stirring rate of 400-700 rpm and a stirring time of 2-6 h.

6. The method according to claim 3 or 4, characterized in that, The evaporation conditions include: an evaporation temperature of 40-90℃ and an evaporation time of 12-36h.

7. The method according to claim 3 or 4, characterized in that, The calcination conditions include: a calcination temperature of 300-550℃ and a calcination time of 2-5 hours.

8. The high-entropy oxide catalyst according to claim 1 or 2, or the high-entropy oxide catalyst obtained by the method of any one of claims 3-7, in the simultaneous catalytic oxidation of CO, HC and NO. x Applications in [the field].

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