M1 / manganese oxide support catalyst, preparation and use in catalyzing ethylene epoxidation

Abstract

The present application relates to a kind of M1 / manganese oxide carrier catalyst, preparation and the application of catalytic ethylene epoxidation.M selected from noble metal, preferably Ag, Ir, Ru, Rh, Pd, Pt and Au, M metal is supported on carrier in single atom site state;Carrier is manganese oxide MnO x Or the substance converted into manganese oxide, preferably α-MnO2.The single-atom noble metal catalytic system of the application shows excellent catalytic activity and selectivity in the reaction of ethylene selective oxidation to ethylene oxide compared with the widely used silver nanoparticle catalyst system, and has high industrial application prospect.

Description

Technical Field

[0001] This invention relates to a noble metal single-atom catalysis and its application in the catalytic epoxidation of ethylene to produce ethylene oxide, belonging to the field of industrial catalysis. Background Technology

[0002] Single-atom catalysts (SACs) are a novel class of heterogeneous catalysts that have recently attracted widespread attention. Compared to traditional nanocatalysts, SACs often exhibit unexpected chemical and reaction pathways, likely due to their unique local chemical environment, which determines their electronic structure, oxidation state, and charge distribution, thereby influencing their catalytic activity and selectivity. More notably, the spatially uniform metal active sites in SACs provide an ideal platform for identifying the precise structure of individual sites, determining catalytically active sites under actual reaction conditions, and elucidating potential reaction mechanisms at the molecular level.

[0003] The selective oxidation of ethylene to ethylene oxide (EO) is one of the most important industrial processes because EO is an irreplaceable chemical intermediate widely used in the synthesis of pharmaceuticals, antifreeze, detergents, and plastics. To date, silver is considered the most effective catalyst for ethylene epoxidation and has been extensively studied. Only with the aid of promoters (Cs, Re, C2H4Cl, Cu) can the selectivity of EO reach 90%. The most common pathway for ethylene epoxidation follows the ER mechanism. Despite significant efforts, many key issues involving this reaction remain unresolved. Furthermore, there is a lack of research on the application of quantum chemical calculations and in-situ spectroscopy in the ethylene epoxidation process due to the absence of novel catalytic systems with excellent performance and well-defined structures.

[0004] Manganese oxide, with its ordered array of MnO6 units sharing edges and vertices, has been used in fields such as industrial catalysis and energy storage. The Mn(IV) in manganese oxide possesses a unique d-electron structure (with at least one pair of unpaired electrons), making it easier for oxygen to interact with foreign adsorbed metal atoms and form structures favorable for catalytic reactions. Therefore, combining individual metal atoms with manganese oxide could potentially lead to a major breakthrough in the epoxidation of ethylene.

[0005] The industry needs a better catalyst for the preparation of ethylene oxide. Summary of the Invention

[0006] This invention provides a catalyst with an M1 / manganese oxide support structure, wherein M is selected from noble metals, preferably Ag, Ir, Ru, Rh, Pd, Pt, and Au, and the metal M is supported on the support in a single-atom site state; the manganese oxide support is manganese oxide or a substance converted to manganese oxide, and the chemical formula of the manganese oxide is MnO. xx = 1-4, the average pore size of the manganese oxide is 1-20 nm, more preferably 1-8 nm, and the loading of noble metal M is 0.01-10 wt% based on the total weight of the catalyst.

[0007] The manganese oxide or MnO x This includes pyrolusite (MnO2), pyrolusite (MnO·MnO2·nH2O), metamanganese ore (MnO2·nH2O), hygroscopicite (MnO2·Mn(OH)2), limonite (Mn2O3), and malachite. The substances that are converted into manganese oxide refer to compounds or mixtures that are converted into manganese oxide through heating or chemical reaction, such as MnCO3, KMnO4, MnSO4, basic manganese carbonate, or a mixture of potassium permanganate and manganese sulfate.

[0008] Further optimization of x=2, more preferably MnO x It is α-MnO2; M is selected from Ag or Ir.

[0009] This invention also discloses a method for preparing the aforementioned M1 / manganese oxide catalyst, comprising the following steps:

[0010] S1: Add water to the obtained or prepared manganese oxide powder to form a first dispersion;

[0011] S2: Take a soluble noble metal salt compound, mix it with a solvent, and prepare a second solution containing the noble metal;

[0012] S3: Mix the first dispersion and the second solution, and continue stirring to separate the solid and liquid components;

[0013] S4: Heat the resulting solid powder under oxygen or an oxygen-containing atmosphere;

[0014] in,

[0015] The manganese oxide powder mentioned in step S1 can be commercially available, or prepared by the following method: A mixture of potassium permanganate and manganese sulfate is heated to remove water by evaporation, yielding a brown powder, which is then calcined at a high temperature to obtain manganese oxide powder. The high temperature is 300-900℃, preferably 400-550℃, and the calcination time is preferably 2-6 hours.

[0016] In step S1, the water is preferably deionized water.

[0017] In step S2, the soluble noble metal salt compound is a soluble salt or soluble complex of a noble metal, preferably a soluble salt of a noble metal nitrate, chloride, chlorate, or acetylacetone salt. This invention implements AgNO3, H2IrCl6, H2PtCl6, HAuCl4, PdCl2, and RhCl3, with a total molar concentration of the noble metal salt of 0.001-0.3 mol / L. The solvent is water or ammonia, preferably deionized water or ammonia.

[0018] In this invention, ammonia is used as a solvent, and the noble metal salt is dissolved in the ammonia solvent.

[0019] In step S3, solid-liquid separation is a conventional separation method, including filtration and centrifugation.

[0020] Further, the solid matter after solid-liquid separation in S3 is washed and dried to obtain a dry solid powder. The washing can be performed using conventional methods; however, this invention employs a suspension centrifugation washing method, using ethanol and water as solvents. The drying is performed using a conventional drying method; this invention employs a vacuum drying method. The vacuum drying temperature is 20-60℃.

[0021] In step S3, if the soluble metal salt in step S2 is AgNO3, stirring should be carried out under light-protected conditions to prevent AgNO3 from decomposing in the light.

[0022] The stirring time is 2-24 hours and can be carried out at room temperature.

[0023] The heating temperature described in S4 is between 200-600℃. The oxygen or oxygen-containing gas is a fluid atmosphere. The oxygen-containing gas can be air. An air atmosphere promotes thermal diffusion of the material during heating. The heating temperature is 200-600℃, and the heating reaction time is not limited and can be selected according to actual needs. The preferred heating reaction time is 1-6 hours.

[0024] The present invention further provides a method for epoxidation of olefins, the method comprising: using C 2-8 The reaction of olefins and oxygen is carried out under the catalyst of the aforementioned M1 / manganese oxide support at 20℃ to 350℃ and 0.01MPa to 10.0MPa for a reaction time of 0.1 hours to 1000 hours.

[0025] Wherein, the M1 / manganese oxide supported catalyst is defined as described above, and the C 2-8 The olefin is selected from chain olefins or cycloalkenes, including substituted or unsubstituted ethylene, propylene, butene, pentene, cyclopentene, cyclohexene, etc., wherein the substituent is C. 1-6 Alkanes.

[0026] Preferably, in the method, C2-8 The molar ratio of olefin to oxygen is 1:2 to 1000, with C being preferred. 2-8 The olefin is ethylene.

[0027] The dispersion state, including single-atom site dispersion, single-atom state, single-atom distribution, single-atom morphology, and single-atom level dispersion states, as described in this invention refers to the state in which the active metal elements exhibit independent separation between metal atoms (ions), without direct metal-metal bonds connecting the active metal atoms, and are dispersed at the atomic level or at single-atom sites. Metals dispersed at single-atom sites may exist in an atomic state, or in an ionic state, but more likely in a state between the two (valence state between two valence states). In contrast, in metallic nanoparticles, the metal atoms within the same particle are bonded to each other and do not fall under the single-atom state or single-atom dispersion state defined in this invention. Theoretically, the single-atom site state of metals protected by this invention is completely independent of each other. However, random deviations in the control of preparation conditions between different batches may result in the presence of a small amount of agglomerated metal species in the product, such as clusters containing a single number of atoms or ions; it is also possible that some metals may exist in a nanoparticle state. In other words, the catalyst of this invention may contain active metals in a single-atom site dispersion state, while some may contain clusters containing aggregated metal atoms, and / or some metals may exist in a nanocrystalline state. Furthermore, with changes in the external environment, the single-atom state transforms into a cluster and / or nano-state. The single-atom state protected in this application requires that the single-atom noble metal in the catalyst, whether in different forms such as single-atom noble metal atoms, noble metal clusters, or noble metal nanocrystals, constitute a certain proportion, for example, higher than 10%, preferably higher than 20%, and particularly preferably higher than 50%.

[0028] In this invention, the subscript 1 in M1 indicates that the metal M exists in a single-atom site state.

[0029] The manganese oxide or manganese oxide MnO x (x = 1-4), including manganese dioxide, pyrolusite (MnO2), pyrolusite (MnO·MnO2·nH2O), metamanganese ore (MnO2·nH2O), hygroscopicite (MnO2·Mn(OH)2), leucite (Mn2O3), malachite, MnCO3, KMnO4, MnSO4, and basic manganese carbonate. Any manganese oxide capable of forming defect vacancies can be used as a support for the catalyst of this invention because the vacancies in manganese oxides can be used to anchor individual metal atoms, allowing them to be uniformly dispersed on the manganese oxide support in the form of single atoms.

[0030] Complexes, also known as coordination compounds, include complexes formed by noble metals or transition metals and ligands. Common ligands include halogens (fluorine, chlorine, bromine, iodine), nitro groups, nitroso groups, cyanide groups, ammonia, water molecules, or organic groups. Common complexes include chloride complexes, ammonia complexes, and cyanide complexes, such as chloroplatinic acid, chloroplatinate, and chloroplatinic acid hydrate. See *Handbook of Synthesis of Noble Metal Compounds and Complexes (Deluxe Edition)* (Yu Jianmin, 2009, Chemical Industry Press).

[0031] Beneficial effects

[0032] The advantages of the single-atom catalytic material of this invention and its application in catalyzing the production of ethylene oxide from ethylene are as follows:

[0033] 1. The catalyst preparation process is simple, can be mass-produced, low-cost, environmentally friendly, and has good reproducibility.

[0034] 2. This catalyst combines the synergistic catalytic advantages of noble metal single-atom sites and manganese oxide support.

[0035] 3. Compared with the silver nanoparticle catalyst system widely used in industry, the single-atom noble metal catalytic system of this application exhibits excellent catalytic activity, selectivity and structural stability in the selective oxidation of ethylene to ethylene oxide, and has high industrial application prospects. Attached Figure Description

[0036] Figure 1 Aberration-corrected high-angle annular dark-field scanning transmission electron microscope (AC-HAADF-STEM) image of 0.98% single-atom catalyst material supported on manganese oxide.

[0037] Figure 2 Aberration-corrected high-angle annular dark-field scanning electron microscope (AC-HAADF-STEM) image of a 2.21% manganese oxide-supported single-atom catalyst.

[0038] Figure 3 This is a graph showing the catalytic oxidation activity of ethylene.

[0039] Figure 4 Selectivity diagrams for the catalytic oxidation of ethylene to ethylene oxide (Figure a, Figure b).

[0040] Figure 5 This is a graph showing the stability of ethylene catalytic oxidation.

[0041] Figure 6 This is a transmission electron microscope (TEM) image of the manganese oxide-supported silver nanoparticle catalytic material in Comparative Example 1 of the present invention. Detailed Implementation

[0042] The following will provide a more detailed description, in conjunction with the accompanying drawings and specific embodiments, of the preparation method of the wide loading capacity (0.01wt%-10wt%) single-atom catalytic material and its catalytic epoxidation of ethylene to ethylene oxide provided by the present invention.

[0043] In this embodiment, the pore size of manganese oxide is approximately 5 nm. In this wide-loading (0.01 wt%-10 wt%) single-atom catalytic material, the mass percentage of single atoms is 0.1-10%, and the noble metal is dispersed in the single-atom catalytic material in the form of individual atoms, which are also fixed to the manganese oxide in the form of individual atoms. This invention further provides a heterogeneous catalytic reaction for the selective oxidation of ethylene to ethylene oxide (EO), in which the aforementioned wide-loading (0.01 wt%-10 wt%) single-atom catalytic material is used as the catalyst. The wide loading range (0.01 wt%-10 wt%) and ultra-high loading of the aforementioned wide-loading (0.01 wt%-10 wt%) single-atom catalytic material are not common among single-atom catalysts, making it more suitable for the industrial application of ethylene epoxidation.

[0044] The following will use specific examples to describe in detail the preparation method of the wide loading (0.01wt%-10wt%) single-atom catalytic material and the ethylene epoxidation performance testing method provided by the present invention.

[0045] Example 1

[0046] A. Synthesis of manganese oxide

[0047] a. Dissolve 5g of potassium permanganate and mix it with 5g of manganese sulfate solution to form solution A (first solution).

[0048] b. Treat the above mixture at 100°C for about 3 hours to allow it to react fully and obtain a brown powder.

[0049] c. Heat the resulting powder to 550°C at a rate of 3°C / min, and then treat it at 550°C for 5 hours.

[0050] Synthesis of B.Ag1 / manganese oxide

[0051] a. Dissolve 7.8 mg AgNO3 in 10 mL ammonia water to form solution B (second solution).

[0052] b. Add solution B dropwise to 100 mL of aqueous solution containing 500 mg manganese oxide under light-shielding and vigorous stirring, and stir continuously for 12 hours to form solution C (third solution).

[0053] c. Centrifuge the above solution C, then wash with H2O and ethanol, and finally dry under vacuum at 25°C.

[0054] d. The obtained powder was heated to 350°C at a rate of 5°C / min, and then treated at 350°C for 2 hours in a flowing air atmosphere to obtain a single-atom silver catalyst material supported on manganese oxide, with a silver mass loading of 0.98%.

[0055] See the aberration-corrected high-angle annular dark-field scanning electron microscope (HAADF-STEM) image of the wide loading range (0.01wt%-10wt%) single-atom silver catalyst with a mass loading of 0.65%. Figure 1 .

[0056] Example 2

[0057] A. Synthesis of manganese oxide

[0058] a. Dissolve 5g of potassium permanganate and mix it with 5g of manganese sulfate solution to form solution A (first solution).

[0059] b. Treat the above mixture at 100°C for about 3 hours to allow it to react fully and obtain a brown powder.

[0060] c. Heat the obtained powder to 550°C at a rate of 5°C / min, and then treat it at 550°C for 4 hours.

[0061] Synthesis of B.Ir1 / manganese oxide

[0062] a. Dissolve 17.8 mg of H2IrCl6 in 10 mL of ammonia water to form solution B (second solution).

[0063] b. Add solution B dropwise to 100 mL of aqueous solution containing 500 mg manganese oxide under light-shielding and vigorous stirring, and stir continuously for 12 hours to form solution C (third solution).

[0064] c. Centrifuge the above solution C, then wash with H2O and ethanol, and finally dry under vacuum at 25°C.

[0065] d. The obtained powder was heated to 350°C at a rate of 5°C / min, and then treated at 350°C for 2 hours in a flowing air atmosphere to obtain a manganese oxide-supported single-atom iridium catalyst with an iridium mass loading of 1.31%.

[0066] See the aberration-corrected high-angle annular dark-field scanning electron microscope (HAADF-STEM) image of the wide loading range (0.01wt%-10wt%) single-atom iridium catalyst with a mass loading of 1.31%. Figure 2 .

[0067] Example 3

[0068] Synthesis of Au1 / MnO2

[0069] a. Dissolve 11.5 mg of HAuCl4 in 10 mL of ammonia water to form solution B (second solution).

[0070] b. Add solution B dropwise to 100 mL of aqueous solution containing 500 mg manganese oxide under light-shielding and vigorous stirring, and stir continuously for 12 hours to form solution C (third solution).

[0071] c. Centrifuge the above solution C, then wash with H2O and ethanol, and finally dry under vacuum at 25°C.

[0072] d. The obtained powder was heated to 350°C at a rate of 5°C / min, and then treated at 350°C for 2 hours in a flowing air atmosphere to obtain a manganese oxide-supported single-atom gold catalyst with a gold mass loading of 1.31%.

[0073] Example 4

[0074] Synthesis of Pt1 / MnO2

[0075] a. Dissolve 17.6 mg of chloroplatinic acid in 10 mL of ammonia water to form solution B (second solution).

[0076] b. Add solution B dropwise to 100 mL of aqueous solution containing 500 mg manganese oxide under light-shielding and vigorous stirring, and stir continuously for 12 hours to form solution C (third solution).

[0077] c. Centrifuge the above solution C, then wash with H2O and ethanol, and finally dry under vacuum at 25°C.

[0078] d. The obtained powder was heated to 350°C at a rate of 5°C / min, and then treated at 350°C for 2 hours in a flowing air atmosphere to obtain a single-atom platinum catalyst material supported on manganese oxide, with a platinum mass loading of 1.31%.

[0079] Example 5

[0080] Synthesis of Pd1 / MnO2

[0081] a. Dissolve 11.1 mg of PdCl2 in 10 mL of ammonia water to form solution B (second solution).

[0082] b. Add solution B dropwise to 100 mL of aqueous solution containing 500 mg manganese oxide under light-shielding and vigorous stirring, and stir continuously for 12 hours to form solution C (third solution).

[0083] c. Centrifuge the above solution C, then wash with H2O and ethanol, and finally dry under vacuum at 25°C.

[0084] d. The obtained powder was heated to 350°C at a rate of 5°C / min, and then treated at 350°C for 2 hours in a flowing air atmosphere to obtain a single-atom palladium catalyst supported on manganese oxide, with a palladium mass loading of 1.31%.

[0085] Example 6

[0086] Synthesis of Ru1 / MnO2

[0087] a. Dissolve 13.6 mg RuCl3 in 10 mL of ammonia water to form solution B (second solution).

[0088] b. Add solution B dropwise to 100 mL of aqueous solution containing 500 mg manganese oxide under light-shielding and vigorous stirring, and stir continuously for 12 hours to form solution C (third solution).

[0089] c. Centrifuge the above solution C, then wash with H2O and ethanol, and finally dry under vacuum at 25°C.

[0090] d. The obtained powder was heated to 350°C at a rate of 5°C / min, and then treated at 350°C for 2 hours in a flowing air atmosphere to obtain a manganese oxide-supported single-atom ruthenium catalyst with a ruthenium mass loading of 1.31%.

[0091] Example 7

[0092] Synthesis of Rh1 / MnO2

[0093] a. Dissolve 13.5 mg of RhCl3 in 10 mL of ammonia water to form solution B (second solution).

[0094] b. Add solution B dropwise to 100 mL of aqueous solution containing 500 mg manganese oxide under light-shielding and vigorous stirring, and stir continuously for 12 hours to form solution C (third solution).

[0095] c. Centrifuge the above solution C, then wash with H2O and ethanol, and finally dry under vacuum at 25°C.

[0096] d. The obtained powder was heated to 350°C at a rate of 5°C / min, and then treated at 350°C for 2 hours in a flowing air atmosphere to obtain a single-atom rhodium catalyst material supported on manganese oxide, with a rhodium mass loading of 1.31%.

[0097] Comparative Example 1

[0098] Preparation method of Ag NPs / α-Al2O3

[0099] Ag NPs / α-Al2O3 was prepared by a conventional impregnation method.

[0100] a. Dissolve 17.8 mg AgNO3 in 10 mL of water to form solution A.

[0101] b. Add solution A dropwise onto 500 mg of aluminum oxide under light-shielding conditions.

[0102] c. Dry the above sample under vacuum at 75°C.

[0103] d. The obtained powder was heated to 350°C at a rate of 5°C / min, and then treated at 350°C for 2 hours in a flowing air atmosphere to obtain alumina-supported silver nanoparticle catalytic material with a silver mass loading of 2.21%. Its transmission electron microscopy (TEM) image is shown below. Figure 6 .

[0104] Comparative Example 2

[0105] Preparation method of Ag NPs / MnO2 catalyst

[0106] Ag NPs / MnO2 was prepared using a conventional impregnation method.

[0107] a. Dissolve 17.8 mg AgNO3 in 10 mL of water to form solution A.

[0108] b. Add solution A dropwise to 500 mg of manganese oxide under light-shielding conditions.

[0109] c. Dry the above sample under vacuum at 75°C.

[0110] d. The obtained powder was heated to 350°C at a rate of 5°C / min, and then treated at 350°C for 2 hours in a flowing air atmosphere to obtain manganese oxide-supported silver nanoparticle catalytic material with a silver mass loading of 2.21%.

[0111] Comparative Example 3

[0112] Preparation method of Ir NPs / MnO2

[0113] Ir NPs / MnO2 were prepared using a conventional impregnation method.

[0114] a. Dissolve 17.8 mg of H2IrCl6 in 10 mL of water to form solution A.

[0115] b. Add solution A dropwise to 500 mg of manganese oxide under light-shielding conditions.

[0116] c. Dry the above sample under vacuum at 75°C.

[0117] d. The obtained powder was heated to 350°C at a rate of 5°C / min, and then treated at 350°C for 2 hours in a flowing air atmosphere to obtain manganese oxide-supported iridium nanoparticle catalytic material with an iridium mass loading of 1.31%.

[0118] Application Test Examples

[0119] To obtain the rate, selectivity, and stability of the catalyst in the ethylene epoxidation reaction, the catalyst activity was tested in a fixed-bed reactor. The reactor used quartz tubes with an inner diameter of 9.5 mm. Before loading the reactor tubes, the catalyst was pressed into tablets and sieved to achieve a size of 40-60 mesh and a mass of 0.3 g. Prior to the reaction, the catalyst was reduced at 250 °C for 1 h in a mixture of 5% H₂ and 95% Ar (heating rate: 1 °C / min). The reaction pressure was atmospheric pressure, and the reaction gas composition was 2% C₂H₄, 1% O₂, and equilibrium He. Finally, the content analysis of the reaction products was performed by gas chromatography (HP-PLOT-U packed column, using a flame ionization detector). The catalytic performance of the catalyst for ethylene epoxidation under O₂ oxidant conditions is shown in the figure. Figure 3 .

[0120] The conversion and selectivity of ethylene were calculated using the following methods:

[0121] Ethylene conversion rate = [C C2H4(in) -C C2H4(out) ] / C C2H4(in) ×100%

[0122] Ethylene oxide selectivity = C C2H4O( out) / [C C2H4O( out)+C CO2(out) ]×100%

[0123] In the formula C C2H4(in) C C2H4(out) C C2H4O(out)和 C CO2(out) These represent the concentrations of the components of the introduced ethylene gas, the outflowing ethylene gas, the outflowing ethylene oxide gas, and the outflowing carbon dioxide gas, respectively.

[0124] The catalysts tested in this experiment included: Ag1 / α-MnO2, Ir1 / α-MnO2, Ir NPs / α-MnO2, and Ag NPs / Al2O3. The test results are shown in [link to results]. Figure 3-4 .

[0125] The Ir1 / α-MnO2 catalyst can achieve complete ethylene conversion at 250℃, and after 16 h of reaction, there are no significant changes in ethylene conversion rate and ethylene oxide selectivity. (See test results for details.) Figure 5 .

[0126] in conclusion

[0127] In summary, we have developed a novel ethylene epoxidation catalyst, namely a single atom anchored on MnO2 nanorods (M1 / α-MnO2), exhibiting catalytic performance distinct from nanoparticles (M NPs / α-MnO2, Ag NPs / α-Al2O3). Ir1 / α-MnO2 demonstrates superior ethylene oxidation activity, achieving a conversion 7.6 times higher than Ag NPs / α-Al2O3, with a 99% selectivity for EO. In-situ diffuse reflectance infrared Fourier transform spectroscopy and in-situ X-ray absorption spectroscopy, along with quantum chemical calculations, aided in exploring the mechanism of ethylene epoxidation on M1 / α-MnO2 at the molecular level, and helped identify the active center and track the evolution of individual iridium sites during the reaction. Our work here provides a deep understanding of the local structure of single atoms on oxide supports under practical catalytic conditions, which may guide the design of novel advanced catalysts.

Claims

1. A type of C 2-8 A method for epoxidation of olefins, the method comprising, using C 2-8 The reaction of olefins with oxygen, under a catalyst supported on M1 / manganese oxide, occurs at temperatures ranging from 20°C to 350°C and pressures from 0.01 MPa to 10.0 MPa, with reaction times ranging from 0.1 h to 1000 h. (C) 2-8 Alkenes are selected from C 2-8 Alkenes or C 2-8 Cycloalkanes and alkenes; The catalyst supported on M1 / manganese oxide has the noble metal M being Ir, which is loaded on the support in a single-atom site state; the manganese oxide support is α-MnO2, with an average pore size of 1-20 nm. Based on the total weight of the catalyst, the loading of the noble metal M is 0.01-10 wt%.

2. The method as described in claim 1, characterized in that, The catalyst is Ir1 / α-MnO2, and the manganese oxide support has an average pore size of 1-8 nm.

3. The method as described in claim 1, characterized in that, The catalyst is prepared by the following method, including: S1: Add water to manganese oxide powder to prepare the first dispersion; S2: Take a soluble noble metal salt compound, mix it with a solvent, and prepare a second solution containing the noble metal; S3: Mix the first dispersion and the second solution, and continue stirring to separate the solid and liquid components; S4: Heat the resulting solid powder under oxygen or an oxygen-containing atmosphere; In step S1, manganese oxide is either commercially available or prepared. When it is prepared, the manganese oxide powder is prepared as follows: a mixture of potassium permanganate and manganese sulfate is heated to remove water by evaporation, resulting in a brown powder. This powder is then calcined at a high temperature of 400-550 °C for 2-6 hours to obtain manganese oxide powder. The water used is deionized water. In step S2, the soluble noble metal salt compound is a soluble salt of a noble metal nitrate, chloride, chlorate, or acetylacetone salt; the total molar concentration of the noble metal salt is 0.001-0.3 mol / L; and the solvent is deionized water or ammonia. In step S3, the solid-liquid separation is achieved through filtration or centrifugation. In step S4, the temperature of the heat treatment is between 200-600 ℃.

4. The method of claim 3, wherein, In step S2, the noble metal salt is selected from H2IrCl6, and ammonia is used as the solvent.

5. The method of claim 3, wherein, Further, the solid matter after solid-liquid separation in S3 is washed and dried to obtain a dry solid powder; the washing is a suspension centrifugal washing method, and the solvents used for washing are ethanol and water, respectively.

6. The method of claim 3, wherein, The oxygen or oxygen-containing gas is a fluid atmosphere.

7. The method of claim 6, wherein the oxygen-containing gas is selected from air.

8. The method according to any one of claims 1-7, wherein, C 2-8 The olefin is ethylene; C 2-8 The molar ratio of olefins to oxygen is 1:2 to 1000.

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