Methane oxidative coupling catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of methane oxidative coupling, and discloses a methane oxidative coupling catalyst as well as a preparation method and application thereof. In the methane oxidative coupling catalyst provided by the invention, the active component forms a monatomic active site on the carrier, so that the dispersity and the atom utilization rate of the active component are greatly improved, and the selectivity and the yield of C2 hydrocarbon are promoted to be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of methane oxidative coupling, and in particular to a methane oxidative coupling catalyst and a preparation method and application thereof. Background Art

[0002] The high temperature of the methane oxidative coupling reaction leads to rapid deactivation of the catalyst, which is one of the reasons why the current methane oxidative coupling technology is difficult to achieve industrial production. Although researchers have made improvements in many aspects and reduced the reaction temperature from over 800°C to 500-600°C, the reaction effect is still unsatisfactory, especially the selectivity and yield of carbon dihydrocarbons are difficult to meet industrial needs.

[0003] In addition, existing methane oxidative coupling catalysts have problems such as insufficient dispersion of active components, low atomic utilization efficiency, and easy coking, which pose huge challenges to the industrial application of methane oxidative coupling reactions. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems of insufficient selectivity and yield of carbon dihydrocarbons in the existing methane oxidative coupling reaction catalyst in the prior art, and to provide a methane oxidative coupling catalyst and its preparation method and application. The metal active component sites in the catalyst provided by the present invention exist in the form of single atoms, which effectively improves the dispersibility and catalytic activity of the active components in the catalyst compared to ordinary supported catalysts.

[0005] In order to achieve the above object, the present invention provides a methane oxidative coupling catalyst, characterized in that the catalyst comprises a carrier and an active component supported on the carrier;

[0006] Wherein, the carrier is an oxide carrier; the active component is selected from any one of Group IIA metals, Group IIIB metals and Group VIIB metals; and the catalyst has a single metal atom active site.

[0007] The second aspect of the present invention provides a method for preparing a methane oxidative coupling catalyst, characterized in that the method comprises: sequentially drying and calcining a carrier loaded with an active component precursor and a ligand;

[0008] Wherein, the carrier is an oxide carrier; the active component is selected from any one of Group IIA metals, Group IIIB metals and Group VIIB metals; and the catalyst has a single metal atom active site.

[0009] The third aspect of the present invention provides a catalyst prepared by the method described in the second aspect.

[0010] The fourth aspect of the present invention provides a method for preparing C2H, the method comprising contacting a raw gas with the catalyst described in the first aspect or the third aspect to carry out a methane oxidative coupling reaction, wherein the raw gas comprises CH4 and O2.

[0011] The fifth aspect of the present invention provides the use of the catalyst described in the first aspect or the third aspect, or the method described in the second aspect or the fourth aspect, in improving the selectivity of carbon dihydrocarbons in the methane oxidative coupling reaction, especially in improving the selectivity of carbon dihydrocarbons in the methane oxidative coupling reaction at a reaction temperature of not less than 500°C.

[0012] Through the above technical solution, the present invention can at least achieve the following beneficial effects:

[0013] (1) The catalyst provided by the present invention has a single metal atom site, which can greatly improve the dispersibility and atomic utilization of the active component. Moreover, the catalyst can effectively improve the adjustable ability in the methane oxidative coupling reaction through the synergistic effect between the carrier and the loaded active component.

[0014] (2) The preparation method of the catalyst provided by the present invention is simple and easy, the raw materials are easily available, and large-scale production can be achieved.

[0015] (3) When the catalyst provided by the present invention is used in the methane oxidative coupling reaction, it can improve the selectivity of carbon dihydrocarbons while maintaining a low methane activation temperature, and a high methane conversion rate and carbon dihydrocarbon selectivity can be obtained at a low reaction temperature, thereby reducing the energy consumption of the methane oxidative coupling reaction and laying a foundation for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figures 1A to 1C All are XAFS spectra of catalyst CAT-1 prepared in Example 1. Figure 1A , Figure 1B , Figure 1C Different fitting parameters were used in the experiments, but all showed good fitting results, indicating that CAT-1 has single-atom characteristics;

[0017] Figure 2 Mapping and TEM images of catalyst CAT-1 prepared in Example 1. DETAILED DESCRIPTION

[0018] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0019] The inventors of the present invention cleverly discovered in their research that the electronic structure and energy level orbit of the metal atom in the active site formed by a single metal atom in the single atom catalyst are different from those of traditional metal nanoparticles. The application of the single atom catalyst in the methane oxidative coupling reaction can largely inhibit the formation of coke, and the selectivity of carbon dihydrocarbons is greatly improved. "Single atom catalyst" refers to a special supported catalyst with isolated metal atoms as active sites on the carrier, which are anchored by the coordination sites of the surrounding solid phase carrier.

[0020] Based on the above findings, the first aspect of the present invention provides a methane oxidative coupling catalyst, the catalyst comprising a carrier and an active component supported on the carrier;

[0021] Wherein, the carrier is an oxide carrier; the active component is selected from any one of Group IIA metals, Group IIIB metals and Group VIIB metals; and the catalyst has a single metal atom active site.

[0022] In the present invention, the existence form of the active components in the single-atom catalyst can be characterized by using a synchrotron radiation method (such as XAFS, etc.), and the test results can be fitted and measured.

[0023] According to a preferred embodiment of the present invention, the carrier is selected from at least one of lanthanum oxide, silicon oxide and titanium oxide. In the present invention, the carrier can be in a crystalline form or in an amorphous state. The carrier is preferably a metal oxide carrier, more preferably lanthanum oxide.

[0024] In the catalyst provided by the present invention, the active component refers to all active component metal components loaded on the carrier, which includes both active components on single metal atom active sites and active components on non-single atom active sites (for example, active sites with two or more active component metal atoms).

[0025] According to a preferred embodiment of the present invention, the active component is selected from any one of Sr, Ba, Mn, Mg, Ce, Ca and Fe.

[0026] For the convenience of description, the catalyst provided by the present invention can be recorded as A / S, wherein A represents the active component and S represents the carrier.

[0027] In the present invention, there is no particular restriction on the loading amount of the active component in the catalyst. In order to obtain better catalytic performance, according to some preferred embodiments of the present invention, the molar ratio of the active component A to the carrier S is 1:1-20, preferably 1:5-10, in terms of metal elements. For example, it can be 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, or any intermediate ratio within the range of any two of the above ratios. It should be understood that the active component A includes active components of single-atom active sites and non-single-atom active sites.

[0028] The second aspect of the present invention provides a method for preparing a methane oxidative coupling catalyst, the method comprising: sequentially drying and calcining a carrier loaded with an active component precursor and a ligand;

[0029] Wherein, the carrier is an oxide carrier; the active component is selected from any one of Group IIA metals, Group IIIB metals and Group VIIB metals; and the catalyst has a single metal atom active site.

[0030] According to some preferred embodiments of the present invention, the carrier is selected from at least one of lanthanum oxide, silicon oxide and titanium oxide.

[0031] Preferably, the support is a metal oxide support, preferably lanthanum oxide.

[0032] According to some preferred embodiments of the present invention, the active component is selected from any one of Sr, Ba, Mn, Mg, Ce, Ca and Fe.

[0033] In the present invention, there is no particular limitation on the specific method and conditions for preparing the carrier loaded with active component precursors and ligands, and any method for preparing supported (single atom) catalysts in the art can be applied to the present invention. According to a preferred embodiment of the present invention, the method for obtaining the carrier loaded with active component precursors and ligands includes: contacting the carrier S with a solution D containing active component precursors and ligands.

[0034] Preferably, the active ingredient precursor is selected from water-soluble salts of the active ingredient, preferably nitrates and / or chlorides.

[0035] Preferably, the ligand is selected from a linear or heterocyclic compound containing 1-10 N atoms, preferably a heterocyclic compound containing 30-90 C atoms and 5-10 N atoms.

[0036] Preferably, the ligand is selected from at least one of diethylenetriamine, ethylenediaminetetraacetic acid, bipyridine, porphyrin and phthalocyanine, more preferably porphyrin and / or phthalocyanine.

[0037] Preferably, the solvent used in the solution D is water or an organic solvent.

[0038] More preferably, the solvent used in solution D is at least one of water, an alcohol having a carbon number not exceeding 5, and a ketone having a carbon number not exceeding 5. More preferably, it is at least one of water, methanol, ethanol, and acetone.

[0039] More preferably, in the solution D, the molar ratio of the active component calculated as metal ions to the solvent is 1:10-50. For example, it can be 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50, or any intermediate ratio within the range formed by any two of the above ratios.

[0040] Preferably, in solution D, the molar concentration ratio of the ligand to the active component precursor calculated as metal ions is 2-5:1. For example, it can be 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, or any intermediate ratio within the range of any two of the above ratios.

[0041] In order to produce defects on the carrier surface that facilitate the loading and dispersion of ligands and metal atoms, according to a preferred embodiment of the present invention, the carrier is pretreated before contacting with solution D. Any method that can produce the above-mentioned defects on the carrier surface can be applied to the present invention. According to some preferred embodiments of the present invention, the pretreatment method can be heat-treating the carrier under a reducing atmosphere.

[0042] Preferably, the reducing atmosphere is provided by H2 and / or CO.

[0043] Preferably, the heat treatment conditions include: temperature 300-500° C., time 0.5-5 h.

[0044] According to a preferred embodiment of the present invention, the amount of the carrier is such that the molar ratio of the carrier to the active component precursor is 5-10:1, calculated as metal ions, for example, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, or any intermediate ratio within the range of any two of the above ratios.

[0045] The inventors found in their research that ultrasonic treatment can further improve the dispersion of ions and promote the formation of more single metal atom active sites in the catalyst. Therefore, according to a preferred embodiment of the present invention, the contacting method includes: ultrasonic treatment followed by heating.

[0046] Preferably, the ultrasonic treatment conditions include: ultrasonic frequency 24-100MHz, ultrasonic time 0.5-3h, preferably stirring during the ultrasonic treatment. The purpose of stirring is mainly to further improve the dispersion uniformity, and any stirring conditions that can achieve this purpose can be applied to the present invention. For example, relative to a 250mL treatment system, a stirring speed of 200-500rpm can be used for stirring.

[0047] Preferably, the conditions of the heating treatment include: temperature 40-90°C, time 1-10h, preferably stirring is performed during the heating treatment (to improve dispersion uniformity). For example, relative to a 250mL treatment system, a stirring speed of 200-500rpm can be used for stirring.

[0048] According to a preferred embodiment of the present invention, the drying conditions are such that the water content in the carrier loaded with the active component precursor and the ligand does not exceed 0.5% by weight, preferably 0-0.3% by weight. "Water content" refers to the content of the solvent used in the solution D remaining in the carrier loaded with the active component precursor and the ligand, and when an organic solvent is used, "water content" refers to the amount of the residual organic solvent.

[0049] Preferably, the drying conditions include: temperature 80-120° C., time 12-24 h.

[0050] According to a preferred embodiment of the present invention, the calcination method includes: calcining at 100-600° C. for 30-300 min.

[0051] Preferably, the calcination atmosphere is at least one of air, nitrogen, argon and hydrogen. For example, the calcination can be carried out in an atmosphere of air, nitrogen, argon or hydrogen, or a mixed gas such as argon and hydrogen can be used to provide the calcination atmosphere.

[0052] The third aspect of the present invention provides a catalyst prepared by the method described in the second aspect.

[0053] The present invention further provides the use of the catalyst described in the first aspect or the third aspect, or the method described in the second aspect, in a methane oxidative coupling reaction. "Use in a methane oxidative coupling reaction" can be understood as using the catalyst of the present invention for a methane oxidative coupling reaction (of any scale), which can also include using the method of the present invention to prepare the catalyst and using the catalyst to carry out a reaction when methane oxidative coupling is used for industrial production (such as production of carbon dihydrocarbons, etc.).

[0054] The fourth aspect of the present invention provides a method for preparing C2H, the method comprising contacting a raw gas with the catalyst described in the first aspect or the third aspect to carry out a methane oxidative coupling reaction, wherein the raw gas comprises CH4 and O2.

[0055] According to a preferred embodiment of the present invention, the molar ratio of CH4 to O2 in the raw gas is 2-10:1, preferably 5-10:1.

[0056] According to a preferred embodiment of the present invention, the conditions of the methane oxidative coupling reaction include: a reaction temperature of not less than 500°C, preferably 500-750°C; a raw gas space velocity in terms of CH4 of 10,000-200,000 mL / (g·h), preferably 20,000-180,000 mL / (g·h). The unit "mL / (g·h)" refers to the total amount (mL) of raw gas (CH4) passing through a unit amount (1g) of catalyst within a unit time (1h).

[0057] For example, the temperature of the methane oxidative coupling reaction can be 500°C, 525°C, 550°C, 575°C, 600°C, 625°C, 650°C, 675°C, 700°C, 725°C, 750°C, or any intermediate value in the range formed by any two of the above values.

[0058] For example, the raw gas space velocity (in terms of CH4) of the methane oxidative coupling reaction can be 20000 mL / (g·h), 30000 mL / (g·h), 40000 mL / (g·h), 50000 mL / (g·h), 60000 mL / (g·h), 70000 mL / (g·h), 80000 mL / (g·h), 90000 mL / (g·h), 100000 mL / (g·h), 110000 mL / (g·h), 115000 mL / (g·h), 12 The abovementioned value can be any intermediate value in the range formed by any two of the above mentioned values.

[0059] The inventors of the present invention have also found in their research that when the catalyst provided by the present invention is used for methane oxidative coupling reaction, the selectivity of C2 hydrocarbons can be effectively improved, and at a specific reaction temperature, the selectivity performance of C2 hydrocarbons is further improved.

[0060] Based on this, the fifth aspect of the present invention provides the use of the catalyst described in the first aspect or the third aspect, or the method described in the second aspect or the fourth aspect in improving the selectivity of carbon dihydrocarbons in the methane oxidative coupling reaction, especially in improving the selectivity of carbon dihydrocarbons in the methane oxidative coupling reaction with a reaction temperature of not less than 500°C.

[0061] Preferably, the reaction temperature is 500-750° C. For example, it may be 500° C., 525° C., 550° C., 575° C., 600° C., 625° C., 650° C., 675° C., 700° C., 725° C., 750° C., or any intermediate value in the range formed by any two of the above values.

[0062] The present invention will be described in detail below by way of examples. It should be understood that the following examples are only used to further explain and illustrate the content of the present invention by way of example, and are not intended to limit the present invention.

[0063] In the following examples, unless otherwise specified, all reagents used were commercial products purchased from regular chemical suppliers and were of analytical grade.

[0064] Example 1

[0065] The single-atom methane oxidative coupling catalyst was prepared by the following method:

[0066] Carrier pretreatment: Place lanthanum oxide at 300°C and reduce it with H2 for 1 hour to create defects on its surface to facilitate the loading and dispersion of ligands and metal atoms.

[0067] Active component and ligand loading: Weigh barium nitrate as the active component precursor and dissolve the active component precursor in methanol aqueous solution (concentration 10 volume %) at a molar ratio of Ba to solvent of 1:20. 2+ Weigh phthalocyanine at a molar ratio of 3:1 and dissolve it in the above solution. Weigh the pretreated lanthanum oxide at a molar ratio of La to Ba of 7:1 in terms of metal ions and add it to the above solution. Ultrasonic dispersion is carried out at 250 rpm for 1 hour with an ultrasonic frequency of 45 MHz. After the ultrasonic dispersion is completed, heat and stir at 50°C (200 rpm) for 5 hours. Centrifuge to remove the carrier loaded with active components and ligands, which is recorded as catalyst precursor A1.

[0068] Catalyst preparation: The catalyst precursor A1 was dried at 85°C until the total content of methanol and water was 0.5% by weight. It was then moved to a tube furnace and calcined at 600°C for 300 min in an air atmosphere. After calcination, it was naturally cooled to room temperature to obtain a lanthanum oxide-supported Ba single-atom catalyst CAT-1.

[0069] The catalyst CAT-1 was detected by XAFS, and the obtained XAFS spectrum is as follows: Figures 1A-1C As shown in the figure, it can be seen that the catalyst CAT-1 has obvious single-atom characteristics.

[0070] The catalyst CAT-1 was observed using a transmission electron microscope and the distribution of different elements in it was detected. The results are as follows: Figure 2 As shown in the figure, it can be seen that the Ba distribution in catalyst CAT-1 is relatively uniform.

[0071] Example 2

[0072] The single-atom methane oxidative coupling catalyst was prepared by the following method:

[0073] Carrier pretreatment: Lanthanum oxide was placed at 350°C and reduced with H2 for 1 hour to create defects on its surface to facilitate the loading and dispersion of ligands and metal atoms.

[0074] Active component and ligand loading: Strontium nitrate was weighed as the active component precursor, and the active component precursor was dissolved in an ethanol aqueous solution (concentration 25 volume %) at a molar ratio of Sr to solvent of 1:30. 2+ Weigh phthalocyanine at a molar ratio of 3:1 and dissolve it in the above solution. Weigh the pretreated lanthanum oxide at a molar ratio of La to Sr of 7:1 in terms of metal ions and add it to the above solution. Ultrasonic dispersion is carried out at 400 rpm for 1 hour with an ultrasonic frequency of 80 MHz. After the ultrasonic dispersion is completed, heat and stir at 50°C (250 rpm) for 5 hours. Centrifuge to remove the carrier loaded with active components and ligands, which is recorded as catalyst precursor A2.

[0075] Catalyst preparation: The catalyst precursor A2 was dried at 100°C until the total content of ethanol and water was 0.2% by weight. It was then moved to a tube furnace and calcined at 400°C for 300 min in an air atmosphere. After calcination, it was naturally cooled to room temperature to obtain the lanthanum oxide-loaded Sr single-atom catalyst CAT-2.

[0076] The XAFS spectrum of catalyst CAT-2 is similar to that of CAT-1, and also shows obvious single-atom characteristics. Sr is evenly dispersed on the carrier. The catalyst CAT-2 was observed by transmission electron microscopy, and the results were similar to those of Figure 2 Similar to .

[0077] Example 3

[0078] The method in Example 1 was used, except that the pretreatment temperature was 380°C; cerium nitrate was selected as the active component precursor, and during the active component and ligand loading process, the amount of the pretreated carrier was adjusted so that the molar ratio of La to Ce was 5:1 in terms of metal ions; and the calcination temperature was adjusted to 500°C. The remaining operations and conditions were the same as those in Example 1, and a single-atom catalyst CAT-3 loaded with Ce on lanthanum oxide was obtained.

[0079] The XAFS spectrum of catalyst CAT-3 is similar to that of CAT-1, and also shows obvious single-atom characteristics. Ce is evenly dispersed on the carrier. The catalyst CAT-3 was observed by transmission electron microscopy, and the results were similar to those of Figure 2 Similar to .

[0080] Example 4

[0081] The method in Example 1 was used, except that the pretreatment temperature was 450°C. During the loading of active components and ligands, ethanol was used as a solvent, the amount of barium nitrate was adjusted so that the molar ratio of Ba to the solvent was 1:10, and the amount of the pretreated carrier was adjusted so that the molar ratio of La to Ba was 5:1 based on metal ions; the calcination temperature was adjusted to 650°C. The remaining operations and conditions were the same as those in Example 1, and a single-atom catalyst CAT-4 loaded with Ba on lanthanum oxide was obtained.

[0082] The XAFS spectrum of catalyst CAT-4 is similar to that of CAT-1, and also shows obvious single-atom characteristics. Ba is evenly dispersed on the carrier. The catalyst CAT-4 was observed by transmission electron microscopy, and the results were similar to those of Figure 2 Similar to .

[0083] Example 5

[0084] The method in Example 1 was used, except that the active component precursors (active component precursors were all nitrates or chlorides of the active component) were weighed according to the types and molar ratios with the carrier in Table 1. The remaining operations and conditions were the same as in Example 1.

[0085] Table 1

[0086] Catalyst No. Active ingredients Molar ratio of active ingredient to carrier CAT-5 Ti 1:10 CAT-6 Cr 1:10

[0087] Example 6

[0088] The method in Example 1 was used, except that the calcination was performed at the temperature shown in Table 2. The remaining operations and conditions were the same as those in Example 1.

[0089] Table 2

[0090] Catalyst No. Calcination temperature / ℃ CAT-7 650 CAT-8 200

[0091] Example 8

[0092] The method in Example 1 was adopted, except that the carrier was not pretreated. The remaining operations and conditions were the same as those in Example 1. Catalyst CAT-9 was obtained.

[0093] Comparing the XAFS spectrum of catalyst CAT-9 with that of CAT-1, it was found that the amount of single atoms in CAT-9 was less distributed. The catalyst CAT-9 was observed by transmission electron microscopy, and the results showed that the active components loaded in the form of single atoms were less.

[0094] Comparative Example 1

[0095] The method in Example 1 was used, except that a strontium nitrate aqueous solution was prepared with a molar ratio of Sr to water of 1:10 as the impregnation solution, and the pretreated lanthanum oxide was weighed and added to the solution in an amount of 7:1 in terms of metal ions, and stirred at 300 rpm for 5 hours. The remaining operations and conditions were the same as those in Example 1. Catalyst CAT-D1 was obtained.

[0096] The XAFS spectrum of catalyst CAT-D1 was compared with that of CAT-1, and it was found that CAT-D1 did not have single-atom active sites. Catalyst CAT-D1 was observed by transmission electron microscopy, and the results showed that there were no active components loaded in the form of single atoms.

[0097] Comparative Example 2

[0098] The method in Example 1 was used, except that no ligand was added to the solution during the loading of the active component and the ligand. The remaining operations and conditions were the same as those in Example 1. Catalyst CAT-D2 was obtained.

[0099] Comparison of the XAFS spectrum of catalyst CAT-D2 with CAT-1 revealed that no single-atom active sites were generated in CAT-D2. Observation of catalyst CAT-D2 by transmission electron microscopy showed that no active components were loaded in the form of single atoms.

[0100] Test Example 1

[0101] The element contents in the catalysts obtained in the above examples were analyzed by EDS. The results are shown in Table 3.

[0102] Table 3

[0103]

[0104] Test Example 2

[0105] This test example is used to illustrate the catalytic performance of the catalyst obtained in the above examples in the methane oxidative coupling reaction.

[0106] 0.1g of catalyst was loaded into a fixed bed quartz reactor. Under normal pressure, the molar ratio of methane to oxygen was 5:1 and the space velocity of methane was 140000ml / gh. The activation temperature of the reaction was tested, and the methane conversion rate and C2 and above hydrocarbons (C 2+ ) selectivity, the results are shown in Table 4. Wherein, the activation temperature refers to the lowest temperature at which methane contacts oxygen to produce ethylene and / or ethane.

[0107] The specific detection method is as follows: TPSR is used and MS is used for real-time monitoring.

[0108] The components of the reaction products were analyzed using an Agilent 7890A gas chromatograph, and the methane conversion rate and the selectivity of C2 and above hydrocarbons were calculated based on the analysis results.

[0109] Methane conversion rate = methane conversion rate = amount of methane consumed in the reaction / total amount of methane introduced × 100%.

[0110] C2 selectivity = amount of ethylene produced and amount of methane consumed by ethylene / total methane consumption x 100%.

[0111] Table 4

[0112]

[0113] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A methane oxidative coupling catalyst, characterized in that: The catalyst comprises a carrier and an active component supported on the carrier; Wherein, the carrier is an oxide carrier; the active component is selected from any one of Group IIA metals, Group IIIB metals and Group VIIB metals; and the catalyst has a single metal atom active site.

2. The catalyst according to claim 1, wherein The carrier is selected from at least one of lanthanum oxide, silicon oxide and titanium oxide; And / or, the active component is selected from any one of Sr, Ba, Mn, Mg, Ce, Ca and Fe; Preferably, the molar ratio of the active component to the carrier is 1:1-20, preferably 1:5-10, calculated on the basis of the metal element.

3. A method for preparing a methane oxidative coupling catalyst, characterized in that: The method comprises: sequentially drying and calcining a carrier loaded with an active component precursor and a ligand; Wherein, the carrier is an oxide carrier; the active component is selected from any one of Group IIA metals, Group IIIB metals and Group VIIB metals; and the catalyst has a single metal atom active site.

4. The method according to claim 3, wherein: The carrier is selected from at least one of lanthanum oxide, silicon oxide and titanium oxide; And / or, the active component is selected from any one of Sr, Ba, Mn, Mg, Ce, Ca and Fe; Preferably, the method of obtaining the carrier loaded with the active component precursor and the ligand comprises: contacting the carrier with a solution D containing the active component precursor and the ligand; Preferably, the active component precursor is selected from water-soluble salts of the active component, preferably nitrates and / or chlorides of the active component; Preferably, the ligand is selected from linear or heterocyclic compounds containing 1-10 N atoms; More preferably, the ligand is selected from at least one of diethylenetriamine, ethylenediaminetetraacetic acid, bipyridine, porphyrin and phthalocyanine; Preferably, the solvent used in the solution D is water or an organic solvent, preferably at least one of water, an alcohol with a carbon number not exceeding 5, and a ketone with a carbon number not exceeding 5, more preferably at least one of water, methanol, ethanol, and acetone; More preferably, in the solution D, the molar ratio of the active component calculated as metal ions to the solvent is 1:10-50; More preferably, in the solution D, the molar concentration ratio of the ligand to the active component precursor calculated as metal ions is 2-5:

1.

5. The method according to claim 4, wherein: The carrier is pretreated before contacting with the solution D, and the pretreatment method is preferably to heat treat the carrier under a reducing atmosphere; Preferably, the reducing atmosphere is provided by H2 and / or CO; Preferably, the heat treatment conditions include: temperature 300-500°C, time 0.5-5h; and / or, the amount of the carrier used is such that the molar ratio of the active component precursor to the carrier is 5-10:1, calculated as metal ions; And / or, the contacting method includes: ultrasonic treatment followed by heating treatment; Preferably, the ultrasonic treatment conditions include: ultrasonic frequency 24-100 MHz, ultrasonic time 0.5-3 h, preferably stirring during the ultrasonic treatment Preferably, the conditions of the heating treatment include: temperature 40-90° C., time 1-10 h, and preferably stirring is performed during the heating treatment.

6. The method according to claim 3, wherein: The drying conditions are such that the water content in the carrier loaded with the active component precursor and the ligand does not exceed 0.5% by weight, preferably 0-0.3% by weight; Preferably, the drying conditions include: temperature 80-120°C, time 12-24h; And / or, the calcination conditions include: temperature 300-600°C, time 30-300min; Preferably, the calcination atmosphere is at least one of air, nitrogen, argon and hydrogen.

7. The catalyst prepared by the method according to any one of claims 3 to 6.

8. A method for preparing carbon dihydrocarbons, characterized in that: The method comprises contacting a raw gas with the catalyst described in claim 1, 2 or 7 to carry out a methane oxidative coupling reaction, wherein the raw gas comprises CH4 and O2.

9. The method according to claim 8, wherein: In the raw gas, the molar ratio of CH4 to O2 is 2-10:1, preferably 5-10:1; And / or, the conditions of the methane oxidative coupling reaction include: the reaction temperature is not less than 500°C, preferably 500-750°C; the raw gas space velocity calculated as CH4 is 10000-200000 mL / (g·h), preferably 20000-180000 mL / (g·h).

10. Use of the catalyst according to claim 1, 2 or 7, or the method according to any one of claims 3-6 or 8-9, in improving the selectivity of dihydrocarbons in the oxidative coupling of methane, especially in improving the selectivity of dihydrocarbons in the oxidative coupling of methane at a reaction temperature of not less than 500°C.

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