Lanthanum oxide carbonate catalyst, method for preparing same, and use thereof

Abstract

This invention relates to the field of methane oxidative coupling technology, and discloses a lanthanum oxycarbonate catalyst, its preparation method, and its application. The preparation method of the lanthanum oxycarbonate catalyst includes: (1) mixing a solid lanthanum salt and optionally a solid dopant with an alkaline solution to obtain a suspension; (2) allowing the suspension to stand, removing the supernatant, and then adding water to adjust the pH to 11-13; (3) subjecting the material obtained in step (2) to a hydrothermal reaction, separating the products of the hydrothermal reaction, and then calcining the separated solid under a carbon dioxide atmosphere. The lanthanum oxycarbonate catalyst prepared by this invention can improve the selectivity of C2 and above hydrocarbons when used for methane oxidative coupling.

Description

Technical Field

[0001] This invention relates to the field of methane oxidative coupling technology, specifically to a lanthanum oxycarbonate catalyst, its preparation method, and its application. Background Technology

[0002] Natural gas refers to all gases that exist naturally in the world, including gases formed by various natural processes in the atmosphere, hydrosphere, and lithosphere (including oilfield gas, gas field gas, mud volcano gas, coalbed methane, and biogenic gas). However, the commonly used definition of "natural gas" is a narrower definition from an energy perspective, referring to a mixture of hydrocarbon and non-hydrocarbon gases naturally occurring in geological formations. In petroleum geology, it usually refers to oilfield gas and gas field gas. Its composition is mainly hydrocarbons, but it also contains non-hydrocarbon gases. On May 6, 2020, China National Petroleum Corporation's Southwest Oil & Gas Field Company announced the discovery of a new natural gas-rich zone with estimated potential resources exceeding one trillion cubic meters. On February 28, 2023, the National Bureau of Statistics released the "Statistical Communiqué of the People's Republic of China on National Economic and Social Development in 2022," which, according to preliminary calculations, showed that natural gas consumption decreased by 1.2%, while clean energy consumption, including natural gas, hydropower, nuclear power, wind power, and solar power, accounted for 25.9% of total energy consumption, an increase of 0.4 percentage points. With the continuous development of extraction methods, the consumption of natural gas as a clean energy source will continue to rise, making the conversion and utilization of methane, a major component of natural gas, particularly important. Oxidative coupling of methane (OCM) technology refers to the reaction that directly converts methane into ethylene and ethane. Since its inception in the 1980s, it has been a research focus in the fields of catalysis, chemistry, and new energy. Numerous scientists have dedicated themselves to the development of catalysts for OCM reactions, studying over two thousand catalyst compositions that cover almost all elements in the periodic table. However, due to technical challenges in scale-up engineering, no industrial-scale plant has yet been established worldwide. Therefore, the development of catalysts and the research of reaction processes remain a long and arduous task. In recent years, research interest in OCM reactions has further increased, with catalysts exhibiting higher activity and selectivity being continuously discovered. It is worth noting that OCM reactions are highly exothermic, easily generating hot spots in the reactor. Sufficiently high product selectivity can effectively reduce the strong exothermic nature of the reaction process. Rare earth oxides and their composite catalysts with alkaline earth metals exhibit high catalytic activity and selectivity for the oxidative coupling reaction of methane, and also demonstrate good stability at high temperatures. The literature "Structure Sensitivity of La2O2CO3 Catalysts in the Oxidative Coupling of Methane" (ACS Catal. 2015, 5, 1663-1674) reports that different preparation methods result in different methane oxidative coupling reaction performances. To further improve the catalytic performance of lanthanum oxycarbonate catalysts, this invention prepares a lanthanum oxycarbonate catalyst and achieves good C2 hydrocarbon selectivity when applied to the methane oxidative coupling reaction. Summary of the Invention

[0003] The purpose of this invention is to further improve the catalytic performance of lanthanum oxycarbonate catalysts in the oxidative coupling reaction of methane, and to provide a lanthanum oxycarbonate catalyst, its preparation method, and its application.

[0004] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a lanthanum oxycarbonate catalyst, the method comprising:

[0005] (1) Mix solid lanthanum salt and optional solid doped element with alkaline solution to obtain suspension;

[0006] (2) After the suspension has stood, remove the supernatant and then add water to adjust the pH to 11-13;

[0007] (3) The material obtained in step (2) is subjected to hydrothermal reaction, the product of hydrothermal reaction is separated, and the separated solid is roasted in an atmosphere containing carbon dioxide.

[0008] A second aspect of the present invention provides a lanthanum oxycarbonate catalyst prepared by the method described.

[0009] The third aspect of the present invention provides a lanthanum oxycarbonate catalyst, which has a linear structure with a length of 1-50 μm, a diameter of 5-100 nm, and an aspect ratio of 50-500.

[0010] The fourth aspect of this invention provides the application of the above-described lanthanum oxycarbonate catalyst in the oxidative coupling reaction of methane to produce C2 and above hydrocarbons.

[0011] The fifth aspect of the present invention provides a method for preparing C2 and above hydrocarbons from methane, the method comprising: reacting methane with the above-described lanthanum oxycarbonate catalyst in the presence of oxygen and under the conditions of methane oxidative coupling reaction;

[0012] Alternatively, a lanthanum oxycarbonate catalyst can be prepared according to the method described above, and then methane can be reacted with the obtained lanthanum oxycarbonate catalyst in the presence of oxygen and under the conditions of methane oxidative coupling reaction.

[0013] This invention discloses a lanthanum oxycarbonate catalyst with a linear structure, prepared by controlling the contact method between lanthanum salt and alkaline solution—specifically, contacting the solid lanthanum salt with the alkaline solution and adjusting the pH of the lower particle settling layer with water before conducting a hydrothermal reaction. The lanthanum oxycarbonate catalyst prepared by this invention improves the selectivity for C2 and higher hydrocarbons when used in methane oxidative coupling. Furthermore, the lanthanum oxycarbonate catalyst of this invention can achieve high methane conversion and high selectivity for C2 and higher hydrocarbons at relatively low reaction temperatures. Attached Figure Description

[0014] Figure 1This is a scanning electron microscope image of the lanthanum oxycarbonate catalyst prepared in Example 1. Detailed Implementation

[0015] The endpoints and any values ​​of the ranges disclosed herein 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 the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] The first aspect of this invention provides a method for preparing a lanthanum oxycarbonate catalyst, the method comprising:

[0017] (1) Mix solid lanthanum salt and optional solid doped element with alkaline solution to obtain suspension;

[0018] (2) After the suspension has stood, remove the supernatant and then add water to adjust the pH to 11-13;

[0019] (3) The material obtained in step (2) is subjected to hydrothermal reaction, the product of hydrothermal reaction is separated, and the separated solid is roasted in an atmosphere containing carbon dioxide.

[0020] The inventors of this invention unexpectedly discovered that by directly mixing lanthanum salt with an alkaline solution to obtain a suspension, removing the supernatant, adjusting the pH with water, and then carrying out a hydrothermal reaction, a lanthanum oxycarbonate catalyst with a linear structure was prepared, and this lanthanum oxycarbonate catalyst exhibited good catalytic performance when used for methane oxidative coupling.

[0021] According to the present invention, the lanthanum salt can be a lanthanum salt commonly used in the art, preferably, the lanthanum salt is at least one of lanthanum nitrate (e.g., lanthanum nitrate hexahydrate), lanthanum chloride and lanthanum acetate.

[0022] According to the present invention, preferably, the alkaline solution is an aqueous solution of an alkali metal hydroxide, more preferably an aqueous solution of sodium hydroxide and / or an aqueous solution of potassium hydroxide. When the type of alkaline solution is limited to the above range, not only can a lanthanum oxycarbonate catalyst with a linear structure be obtained, but the lanthanum oxycarbonate catalyst can further improve the conversion rate of methane and the selectivity of C2 and above hydrocarbons when used for methane oxidative coupling.

[0023] According to the present invention, in order to further improve the conversion rate of methane and the selectivity of C2 and above hydrocarbons, preferably, the concentration of the alkaline solution is 1-3 mol / L. In the present invention, the concentration of the alkaline solution can be 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, or any combination of the above.

[0024] According to the present invention, preferably, the weight ratio of the lanthanum salt to the alkaline solution is 1:2-40, more preferably 1:5-30. In the present invention, the weight ratio of the lanthanum salt to the alkaline solution can be 1:2, 1:5, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, or any two of the above ratios.

[0025] According to the present invention, preferably, the mixing time is 10-100 min, more preferably 25-60 min.

[0026] According to the present invention, in order to ensure that the lanthanum salt reacts fully with the alkaline solution, the mixing is preferably carried out under stirring.

[0027] According to the present invention, the settling time is not particularly limited, as long as it allows the suspension to separate into an upper clear liquid layer and a lower particle sedimentation layer after settling. Preferably, to ensure sufficient sedimentation of the particles in the suspension, the settling time is preferably 10-100 hours. The settling time in the present invention can be 10 hours, 20 hours, 30 hours, 40 hours, 50 hours, 60 hours, 70 hours, 80 hours, 90 hours, 100 hours, or any range of two of the above.

[0028] According to the present invention, the settling temperature is not particularly limited, but preferably, the settling temperature is 25-50°C.

[0029] According to the present invention, preferably, in step (2), the process of adding water to adjust the pH is carried out under stirring.

[0030] According to the present invention, preferably, the substance containing the dopant element is at least one of alkaline earth metal compounds, more preferably at least one of magnesium nitrate, calcium nitrate, strontium nitrate and barium nitrate.

[0031] According to the present invention, preferably, the molar ratio of the lanthanum salt to the substance containing the dopant element is 1:0.01-1 (e.g., 1:0.01, 1:0.05, 1:0.09, 1:0.1, 1:0.11, 1:0.12, 1:0.13, 1:0.14, 1:0.15, 1:0.16, 1:0.17, 1:0.18, 1:0.19, 1:0.2, 1:0.3, 1:0.5, 1:0.8, 1:1, and any two of the above ranges), more preferably 1:0.05-0.5, and even more preferably 1:0.09-0.3.

[0032] According to the present invention, preferably, the hydrothermal conditions include: a temperature of 150-180°C and a time of 10-24 hours.

[0033] According to the present invention, preferably, in step (3), the separation method is centrifugal separation, more preferably, the conditions for centrifugal separation include: rotation speed of 8000-11000 rpm, temperature of 5-20℃, and time of 10-30 min.

[0034] According to the present invention, preferably, step (3) further includes drying the separated solid, more preferably, the drying conditions include: a temperature of 80-150°C and a time of 5-20h.

[0035] According to the present invention, preferably, the calcination conditions include: a temperature of 500-600°C and a time of 2-10 hours.

[0036] According to the present invention, preferably, the calcination is carried out at a heating rate of 1-5°C / min to the calcination temperature.

[0037] According to the present invention, preferably, the carbon dioxide-containing atmosphere is an air atmosphere.

[0038] A second aspect of the present invention provides a lanthanum oxycarbonate catalyst prepared by the method described.

[0039] The third aspect of the present invention provides a lanthanum oxycarbonate catalyst, which has a linear structure with a length of 1-50 μm, a diameter of 5-100 nm, and an aspect ratio of 50-500.

[0040] According to the present invention, preferably, the length of the linear structure is 2-10 μm, the diameter of the linear structure is 5-50 nm, and the aspect ratio is 100-400.

[0041] According to the present invention, preferably, the specific surface area of ​​the lanthanum oxycarbonate catalyst is 65-100 m². 2 / g, pore volume 0.2-0.5cm 3 / g, with an average pore size of 10-20 angstroms.

[0042] In this invention, E It is a unit of length, 10 angstroms = 1 nm.

[0043] According to the present invention, preferably, the lanthanum oxycarbonate catalyst further contains a dopant element, wherein the dopant element includes at least one selected from magnesium, calcium, strontium and barium.

[0044] According to the present invention, preferably, the molar ratio of lanthanum to dopant in the lanthanum oxycarbonate catalyst is 1:0.01-3. In this invention, the molar ratio of lanthanum to dopant in the lanthanum oxycarbonate catalyst is calculated based on the amount of raw materials fed.

[0045] The fourth aspect of this invention provides the application of the above-described lanthanum oxycarbonate catalyst in the oxidative coupling reaction of methane to produce C2 and above hydrocarbons.

[0046] The fifth aspect of the present invention provides a method for preparing C2 and above hydrocarbons from methane, the method comprising: reacting methane with the above-described lanthanum oxycarbonate catalyst in the presence of oxygen and under the conditions of methane oxidative coupling reaction;

[0047] Alternatively, a lanthanum oxycarbonate catalyst can be prepared according to the method described above, and then methane can be reacted with the obtained lanthanum oxycarbonate catalyst in the presence of oxygen and under the conditions of methane oxidative coupling reaction.

[0048] According to the present invention, preferably, the molar ratio of methane to oxygen (referred to as alkoxy ratio) is 5-8:1.

[0049] According to the present invention, preferably, the temperature of the contact reaction is 500-750°C.

[0050] According to the present invention, preferably, the space velocity of the methane is 40,000-140,000 mL / (g·h).

[0051] According to a particularly preferred embodiment of the present invention, the preparation method of the lanthanum oxycarbonate catalyst includes: adding 5.8-6 g of lanthanum nitrate hexahydrate and 0.3-0.2 g of barium nitrate to 100-120 g of sodium hydroxide solution (1.5-2 mol / L), and rapidly stirring for 50-60 min to obtain a suspension; after the suspension has stood for 50-60 h, it separates into layers (the upper layer is a clear liquid, and the lower layer is a particle sedimentation layer); the upper clear liquid is discarded, and then deionized water is added to the particle sedimentation layer while stirring, and the reaction solubility is measured. When the pH of the solution is 11-11.3, stop adding liquid dropwise, stir for 30-40 min, and react at 160-165℃ for 20-24 h. Wash and separate the solution using a centrifuge (centrifugation conditions include: speed 10000-11000 rpm, temperature 10-15℃, time 15-20 min). After washing with water and ethanol, dry at 120-140℃ for 10-12 h, and then heat to 620-650℃ at 1.5-2℃ / min in air atmosphere and hold for 2-3 h.

[0052] The present invention will be described in detail below through embodiments. In the following embodiments,

[0053] The process is carried out at room temperature (approximately 25°C).

[0054] The method for calculating methane conversion rate is as follows:

[0055] Methane conversion rate = Amount of methane consumed in the reaction / Initial amount of methane × 100%.

[0056] The method for calculating ethylene selectivity is as follows:

[0057] Ethylene selectivity = Amount of methane consumed to produce ethylene / Total methane consumption × 100%.

[0058] The method for calculating ethane selectivity is as follows:

[0059] Ethane selectivity = Amount of methane consumed to produce ethane / Total methane consumption × 100%.

[0060] The selectivity of C2 and above hydrocarbons includes ethylene, ethane, propylene, propane, and the sum of higher carbon hydrocarbons.

[0061] Example 1

[0062] 5.8 g of lanthanum nitrate hexahydrate was weighed and added to 100 g of sodium hydroxide solution (3 mol / L). The mixture was stirred rapidly for 30 min to obtain a suspension. After standing for 100 h, the suspension separated into two layers (a clear liquid on top and a sedimentation layer of particles on the bottom). The clear liquid was discarded, and deionized water was added to the sedimentation layer while stirring. The pH of the reaction solution was measured to be 12, at which point the addition was stopped. After stirring for 30 min, the mixture was placed in a high-pressure hydrothermal reactor lined with polytetrafluoroethylene (PTFE). The reactor was placed at 160 °C for 12 h. After cooling to room temperature, the reactor was opened, and the mixture was washed and separated using a centrifuge (centrifugation conditions: 10,000 rpm, 10 °C, 15 min). The mixture was washed three times with water and once with ethanol. It was then placed in a 120 °C oven for 12 h, and then transferred to a muffle furnace (calcination atmosphere: air). The temperature was increased to 550 °C at 2 °C / min and held for 2 h. Lanthanum oxycarbonate catalyst A1 was thus prepared. The XRD pattern of the lanthanum oxycarbonate catalyst prepared in Example 1 shows that it has the characteristic peaks of lanthanum oxycarbonate, indicating that the catalyst prepared in Example 1 is lanthanum oxycarbonate.

[0063] Example 2

[0064] Weigh 5.8g of lanthanum nitrate hexahydrate and 0.32g of barium nitrate and add them to 100g of sodium hydroxide solution (2mol / L). Stir rapidly for 60min to obtain a suspension. After the suspension stands for 50h, it separates into layers (the upper layer is a clear liquid and the lower layer is a particle sedimentation layer). Discard the upper clear liquid and then add deionized water to the particle sedimentation layer while stirring. The pH of the reaction solution is measured to be 11.3. Stop adding water and stir for 30min. Place the solution in a high-pressure hydrothermal reactor lined with polytetrafluoroethylene and react at 160℃ for 24h. After cooling to room temperature, open the hydrothermal reactor and wash and separate the solution using a centrifuge (centrifugation conditions: speed 11000rpm, temperature 10℃, time 15min). Wash three times with water and once with ethanol. Place the solution in a 120℃ oven for 12h and then transfer it to a muffle furnace (calcination atmosphere is air). Increase the temperature to 600℃ at 2℃ / min and hold for 2h. Lanthanum oxycarbonate catalyst A2 was prepared.

[0065] Example 3

[0066] Weigh 5.8g of lanthanum nitrate hexahydrate and 0.36g of strontium nitrate and add them to 100g of sodium hydroxide solution (3mol / L). Stir rapidly for 25min to obtain a suspension. After the suspension stands for 24h, it separates into layers (the upper layer is a clear liquid and the lower layer is a particle sedimentation layer). Discard the upper clear liquid and then add deionized water to the particle sedimentation layer while stirring. The pH of the reaction solution is measured to be 11.5. Stop adding water and stir for 30min. Place the solution in a high-pressure hydrothermal reactor lined with polytetrafluoroethylene and react at 180℃ for 12h. After cooling to room temperature, open the hydrothermal reactor and wash and separate the solution using a centrifuge (centrifugation conditions: speed 8500rpm, temperature 10℃, time 15min). Wash three times with water and once with ethanol. Place the solution in a 120℃ oven for 12h and then transfer it to a muffle furnace (calcination atmosphere is air). Increase the temperature to 600℃ at 2℃ / min and hold for 2h. Lanthanum oxycarbonate catalyst A3 was prepared.

[0067] Example 4

[0068] Weigh 5.8g of lanthanum nitrate hexahydrate and 0.4g of magnesium nitrate and add them to 150g of sodium hydroxide solution (3mol / L). Stir rapidly for 30min to obtain a suspension. After the suspension stands for 100h, it separates into layers (the upper layer is clear liquid and the lower layer is a particle sedimentation layer). Discard the upper clear liquid and then add deionized water to the particle sedimentation layer while stirring. The pH of the reaction solution is measured to be 11.5. Stop adding water and stir for 30min. Place the solution in a high-pressure hydrothermal reactor lined with polytetrafluoroethylene and react at 180℃ for 24h. After cooling to room temperature, open the hydrothermal reactor and wash and separate the solution using a centrifuge (centrifugation conditions: speed 9000rpm, temperature 15℃, time 15min). Wash three times with water and once with ethanol. Place the solution in a 120℃ oven for 12h and then transfer it to a muffle furnace (calcination atmosphere is air). Increase the temperature to 500℃ at 2℃ / min and hold for 2h. Lanthanum oxycarbonate catalyst A4 was prepared.

[0069] Comparative Example 1

[0070] 5.8 g of lanthanum nitrate hexahydrate was weighed and added to 100 g of deionized water. Sodium hydroxide solution (3 mol / L) was added dropwise to adjust the final pH to 12. After stirring thoroughly, the mixture was placed in a high-pressure reactor lined with polytetrafluoroethylene and allowed to stand at 160 °C for 12 h. The mixture was then washed three times with water and once with ethanol using a centrifuge. It was then placed in an oven at 120 °C for 12 h, and then transferred to a muffle furnace (calcination atmosphere: air). The temperature was increased to 500 °C at a rate of 2 °C / min and held for 5 h. Lanthanum oxycarbonate catalyst D1 was thus prepared.

[0071] Comparative Example 2

[0072] The procedure was carried out according to Example 1, except that the pH of the reaction solution was measured to be 9, at which point the addition was stopped.

[0073] Test Example 1

[0074] The results of the shape and size, specific surface area, pore volume, and average pore diameter of the above catalysts are shown in Table 1.

[0075] The shape of the lanthanum oxycarbonate catalyst was determined by scanning electron microscopy (SEM). The method for testing the size of the lanthanum oxycarbonate catalyst was as follows: 5-10 samples were selected from the field of view, and the length and diameter were measured using the measuring instrument on the SEM. The average length and average diameter of the 5-10 samples in the field of view were then calculated as the length and diameter data of the sample, and the length-to-diameter ratio was calculated based on the average length and average diameter of the sample.

[0076] The specific surface area, pore volume, and average pore size of the lanthanum oxycarbonate catalyst were determined using an ASAP2420 fully automated physical adsorption analyzer. 100 mg of sample was weighed and placed in a sample tube, which was then placed in the instrument's degassing station for degassing at 350°C for 4 hours. After natural cooling to room temperature, the sample tube was placed in the instrument's analysis station for analysis. A complete analysis of the nitrogen adsorption-desorption isotherm was performed at liquid nitrogen temperature. The specific surface area of ​​the sample was calculated using the BET (Brunauer, Emmett, Teller) method, and the pore volume and average pore size were calculated based on the desorption (adsorption) branch using the BJH (Barret, Joyner, Halenda) method.

[0077] Table 1

[0078]

[0079] Test Example 2

[0080] The above catalyst was tableted and sieved through a 40-60 mesh sieve. 100 mg of the tablet was then weighed and packed into a quartz tube fixed-bed reactor with an inner diameter of 4 mm. Methane and oxygen were introduced, with a methane space velocity of 140,000 mL / (g·h) and an alkane-to-oxygen ratio of 8. The reaction temperature is shown in Table 2. The product composition was determined online using an Agilent gas chromatograph, and the results are shown in Table 2.

[0081] Table 2

[0082]

[0083] As can be seen from the results in Table 2, the lanthanum oxycarbonate catalyst prepared by the method of the present invention has a high methane conversion rate and selectivity for C2 and above hydrocarbons.

[0084] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a lanthanum oxycarbonate catalyst, characterized in that, The method includes: (1) A solid lanthanum salt and an optional solid doped element are mixed with an alkaline solution to obtain a suspension; wherein the concentration of the alkaline solution is 1-3 mol / L; and the weight ratio of the solid lanthanum salt to the alkaline solution is 1:2-40. (2) After the suspension has stood, remove the supernatant and then add water to adjust the pH to 11-13; (3) The material obtained in step (2) is subjected to hydrothermal reaction, the product of hydrothermal reaction is separated, and the separated solid is roasted in an atmosphere containing carbon dioxide.

2. The method according to claim 1, wherein, The lanthanum salt is at least one of lanthanum nitrate, lanthanum chloride, and lanthanum acetate; And / or, the substance containing the doped element is at least one of the alkaline earth metal compounds; And / or, the alkaline solution is an aqueous solution of an alkali metal hydroxide.

3. The method according to claim 1, wherein, The substance containing the doped element is at least one of magnesium nitrate, calcium nitrate, strontium nitrate, and barium nitrate. And / or, the alkaline solution is an aqueous solution of sodium hydroxide and / or an aqueous solution of potassium hydroxide.

4. The method according to claim 1, wherein, The molar ratio of the lanthanum salt to the substance containing the doped element is 1:0.01-1; And / or, the weight ratio of the solid lanthanum salt to the alkaline solution is 1:5-30.

5. The method according to claim 1, wherein, The settling time is 10-100 hours.

6. The method according to claim 1, wherein, The hydrothermal conditions include: a temperature of 150-180℃ and a time of 10-24h; And / or, the calcination conditions include: a temperature of 500-600℃ and a time of 2-10h.

7. A lanthanum oxycarbonate catalyst prepared by the method according to any one of claims 1-6.

8. A lanthanum oxycarbonate catalyst, characterized in that, The lanthanum oxycarbonate catalyst has a linear structure with a length of 1-50 μm, a diameter of 5-100 nm, and an aspect ratio of 50-500.

9. The lanthanum oxycarbonate catalyst according to claim 8, wherein, The length of the linear structure is 2-10 μm, the diameter of the linear structure is 5-50 nm, and the aspect ratio is 100-400; And / or, the specific surface area of the lanthanum oxide carbonate catalyst is 65-100 m 2 / g, the pore volume is 0.2-0.5 cm 3 / g, and the average pore diameter is 10-20 angstroms.

10. The lanthanum oxycarbonate catalyst according to claim 8, wherein, The lanthanum oxycarbonate catalyst also contains doping elements, including at least one of magnesium, calcium, strontium, and barium.

11. The use of the lanthanum oxycarbonate catalyst according to any one of claims 7 and 8-10 in the oxidative coupling reaction of methane to produce C2 and above hydrocarbons.

12. A method for preparing C2 and above hydrocarbons from methane, characterized in that, The method comprises: reacting methane with the lanthanum oxycarbonate catalyst according to any one of claims 7 and 8-10 in the presence of oxygen and under conditions of methane oxidative coupling reaction; Alternatively, a lanthanum oxycarbonate catalyst may be prepared according to the method described in any one of claims 1-6, and then methane may be reacted with the obtained lanthanum oxycarbonate catalyst in the presence of oxygen and under the conditions of methane oxidative coupling reaction.

13. The method according to claim 12, wherein, The molar ratio of methane to oxygen is 5-8:1; And / or, the temperature of the contact reaction is 500-750°C; And / or, the space velocity of the methane is 40,000-140,000 mL / (g·h).

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