Lanthanum oxycarbonate catalyst, preparation method therefor and use thereof

Abstract

The present invention relates to the technical field of lanthanum oxycarbonate. Disclosed are a lanthanum oxycarbonate catalyst, a preparation method therefor and a use thereof. The lanthanum oxycarbonate catalyst comprises hexagonal crystal phase lanthanum oxycarbonate and hexagonal crystal phase lanthanum oxycarbonate containing a doping element R. The method comprises: (1) adding alkali liquor into a lanthanum source solution, and then performing solid-liquid separation and drying to obtain lanthanum hydroxide; (2) enabling the solution of a compound containing the doping element R to be in contact with lanthanum hydroxide, and then drying; and (3) roasting the dried product in Step (2) in a carbon-containing atmosphere to obtain the lanthanum oxycarbonate catalyst. The catalyst prepared in the present invention has a relatively high yield of C2 hydrocarbons when being used for an oxidative coupling reaction of methane.

Description

30 BET analysis shows that the lanthanum dioxide carbonate catalyst has a specific surface area of 38 m2 / g, a pore volume of 0.2 cm3 / g, and an average pore diameter of 13.3 nm. 2023350438   09 Oct 2026 Only the characteristic peaks of the hexagonal crystalline phase are seen in the XRD spectrum (similar to Example 1, not shown again), and no characteristic peaks of the doping element in the form of metal salts appear. The total content of the hexagonal crystalline lanthanum dioxide carbonate 5 and the hexagonal crystalline lanthanum dioxide carbonate containing a doping element in the product was 99.6wt% as determined by the XRD spectrum. From the transmission scanning electron microscopy image (similar to Example 1, not shown again), it can be seen that the lanthanum dioxide 10 carbonate catalyst has a fibrous nanostructure, and it is calculated to have an average diameter of 21 nm and an average length-to-diameter ratio of 17:1. Example 12 (1) 15 g of lanthanum nitrate hexahydrate was dissolved in 155 g of 15 deionized water, and was stirred at 25°C and at a rotation speed of 900 rpm for 30 min. Then, a sodium hydroxide solution was added dropwise to the lanthanum nitrate aqueous solution (the concentration of the sodium hydroxide solution was 10wt%, calculated as the compound of the Group IA metal, the addition rate of the alkali solution was 10 mL / min per kilogram 20 of the solution of lanthanum source; and the utilization amount of the alkali solution was such that the final pH value of the mixed system of the alkali solution and the solution of lanthanum source was 10). After the dropadding was completed, the mixture was stirred at 25°C and at a rotation speed of 9000 rpm for 10 min. Then the temperature was raised to 100°C 25 and the condensation reflux was maintained with continuous stirring for 15 h. After the solution was cooled to room temperature, the solid material was separated by centrifugation at 9000 rpm in a centrifuge and washed with deionized water until the pH value of the washing liquid was neutral. The obtained solid was sequentially subjected to a first drying and a second 30 drying. The first drying conditions included: a temperature of 80°C and a time of 15 h; the second drying conditions included: a relative pressure of 40kPa, a temperature of 140°C, and a time of 5 h. 2023350438   09 Oct 2026 the saturated water absorption amount of the lanthanum hydroxide after the second drying was determined: under nitrogen protection, 1g of the lanthanum hydroxide after the second drying was taken and placed in a round-bottom flask, deionized water was added dropwise to the roundbottom flask by using a syringe, and was mixed with the lanthanum hydroxide by using a vortex mixer until the lanthanum hydroxide did not absorb further water significantly, and the drop-adding the deionized water was stopped , and the addition amount of deionized water was recorded at this time. The saturated water absorption amount of lanthanum hydroxide was determined to be 1.9 mL / g. (2) 0.24 g of ferric nitrate was dissolved in 1.52 mL of deionized water to obtain a strontium nitrate aqueous solution. Under nitrogen protection, 0.9 g of the lanthanum hydroxide after the second drying was weighed and placed in a round-bottom flask. Then, at 35°C, the ferric nitrate aqueous solution was added dropwise into the round-bottom flask by using a syringe (the addition rate of the solution containing a compound of doping element was 1.5 mL / min per gram of the lanthanum hydroxide), and fully mixed by a vortex mixer, the mixing time was 3 hours. Then, the obtained mixture was dried at 80°C for 15 h. (3) A lanthanum dioxide carbonate catalyst was prepared by calcining at 500°C for 2h in an air atmosphere. The molar ratio of lanthanum element to the ferric element in the catalyst was 1:0.13. BET analysis shows that the lanthanum dioxide carbonate catalyst has a specific surface area of 48 m2 / g, a pore volume of 0.36 cm3 / g, and an average pore diameter of 13.8 nm. Only the characteristic peaks of the hexagonal crystalline phase are seen in the XRD spectrum (similar to Example 1, not shown again), and no characteristic peaks of the doping element in the form of metal salts appear. The total content of the hexagonal crystalline lanthanum dioxide carbonate and the hexagonal crystalline lanthanum dioxide carbonate containing a doping element in the product was 98.1wt% as determined by the XRD - 28- 2023350438   09 Oct 2026 spectrum. It can be seen from the transmission scanning electron microscopy image (similar to Example 1, not shown again) that the lanthanum dioxide carbonate catalyst has a fibrous nanostructure, and it is calculated to have an average diameter of 20 nm and an average length-to-diameter ratio of 20:1. Example 13 (1) 5g of lanthanum nitrate hexahydrate was dissolved in 210g of deionized water, and stirred at 25°C and a rotation speed of 900rpm for 30min; then sodium hydroxide solution was added dropwise into the lanthanum nitrate aqueous solution (the concentration of the sodium hydroxide solution was 10wt%, the addition rate of the alkali solution was 7mL / min per kilogram of the solution of lanthanum source, and the utilization amount of the alkali solution was such that the final pH value of the mixed system of the alkali solution and the solution of lanthanum source was 11.6 ), and stirring at 25°C and 9000rpm was continued for 10min after the drop-adding was completed. Then, the temperature was raised to 90°C, and the condensation reflux was maintained with stirring for 12h. After the solution was cooled to room temperature, the solid material was separated by centrifugation at 1000rpm by a centrifuge, and washed with deionized water until the pH value of the washing liquid was neutral. The obtained solid was sequentially subjected to a first drying and a second drying. The first drying conditions included: a temperature of 80°C and a time of 12h; the second drying conditions included: a relative pressure of 60kPa, a temperature of 140°C and a time of 5h. The saturated water absorption amount of the lanthanum hydroxide after the second drying was determined: under nitrogen protection, 1g of the lanthanum hydroxide after the second drying was taken and placed in a round-bottom flask, deionized water was added dropwise to the roundbottom flask by using a syringe, and was mixed with the lanthanum hydroxide by using a vortex mixer until the lanthanum hydroxide did not - 29- 2023350438   09 Oct 2026 absorb further water significantly, and the drop-adding the deionized water was stopped , and the addition amount of deionized water was recorded at this time. The saturated water absorption amount of lanthanum hydroxide was determined to be 2mL / g. 5      (2) 0.06 g of calcium nitrate was dissolved in 1.5 mL of deionized water to obtain a calcium nitrate aqueous solution. Under nitrogen protection, 1.0 g of the lanthanum hydroxide after the second drying was weighed and placed in a round-bottom flask. Then, at 25°C, the calcium nitrate aqueous solution was added dropwise into the round-bottom flask by using a syringe 10 (the addition rate of the solution of the compound containing doping elemental calcium was 1 mL / min per gram of the lanthanum hydroxide), and was fully mixed by a vortex mixer for 5 h. Then, the obtained mixture was dried at 80°C for 12 hours. (3) A lanthanum dioxide carbonate catalyst was prepared by calcining 15 at 500°C for 2h in an air atmosphere. The molar ratio of lanthanum element to calcium element in the catalyst was 1:0.11. BET analysis shows that the lanthanum dioxide carbonate catalyst has a specific surface area of 49 m2 / g, a pore volume of 0.3 cm3 / g, and an 20 average pore diameter of 10.2 nm. Only the characteristic peaks of the hexagonal crystalline phase are seen in the XRD spectrum (similar to Example 1, not shown again), and no characteristic peaks of the doping element in the form of metal salts appear. The total content of the hexagonal crystalline lanthanum dioxide carbonate 25 and the hexagonal crystalline lanthanum dioxide carbonate containing a doping element in the product was 99.3wt% as determined by the XRD spectrum. It can be seen from the transmission scanning electron microscopy image (similar to Example 1, not shown again) that the lanthanum dioxide 30 carbonate catalyst has a fibrous nanostructure, and it is calculated to have an average diameter of 18 nm and an average length-to-diameter ratio of 20:1. 2023350438   09 Oct 2026 Comparative Example 1 (1) 5g of lanthanum nitrate hexahydrate was dissolved in 210g of deionized water, stirred at 25°C and a rotation speed of 900rpm for 30min, then sodium hydroxide solution was added dropwise into the lanthanum nitrate aqueous solution (the concentration of the sodium hydroxide solution was 10wt%, the addition rate of the alkali solution was 7mL / min per kilogram of the solution of lanthanum source, and the utilization amount of the alkali solution was such that the final pH value of the mixed system of the alkali solution and the solution of lanthanum source was 11.6), and after the drop-adding was completed, stirring was continued at 25°Cand a rotation speed of 9000rpm for 10min. Then, temperature was raised to 90°C and condensation reflux was maintained with stirring for 12h. After the solution was cooled to room temperature, the solid material by centrifugation was separated at 10000rpm in a centrifuge, and was washed with deionized water until the pH value of the washing liquid was neutral. The obtained solid was sequentially subjected to a first drying and a second drying. The first drying conditions included: a temperature of 80°C and a time of 12h; the second drying conditions included: a relative pressure of 60kPa, a temperature of 140°C and a time of 5h. A lanthanum dioxide carbonate catalyst was prepared by calcining at 500°C for 2h in air atmosphere. BET analysis shows that the lanthanum dioxide carbonate catalyst has a specific surface area of 68 m2 / g, a pore volume of 6 cm3 / g, and an average pore diameter of 42 nm. Only the characteristic peaks of the hexagonal crystalline phase are seen in the XRD spectrum (similar to Example 1, not shown again), and no characteristic peaks of the doping element in the form of metal salts appear. The total content of hexagonal crystalline lanthanum dioxide carbonate in the product was 98.2wt% as determined by the XRD spectrum. From the transmission scanning electron microscopy image (similar to Example 1, not shown again), it can be seen that the lanthanum dioxide carbonate catalyst has a fibrous nanostructure, and it is calculated to have - 31- 2023350438   09 Oct 2026 an average diameter of 12 nm and an average length-to-diameter ratio of 15:1. Comparative Example 2 (1) Lanthanum hydroxide was prepared according to the method of step (1) of Example 1; (2) 0.08 g of strontium nitrate was calcined at 500°C for 2h in an air atmosphere; (3) 0.8 g of lanthanum hydroxide was calcined at 500°C for 2h in an air atmosphere; (4) then, the product obtained in step (2) and the product obtained in step (3) were mixed evenly to obtain a catalyst. BET analysis shows that the lanthanum dioxide carbonate catalyst has a specific surface area of 40 m2 / g, a pore volume of 2.3 cm3 / g, and an average pore diameter of 14.2 nm. Only the characteristic peaks of the hexagonal crystalline phase are seen in the XRD spectrum (similar to Example 1, not shown again), and no characteristic peaks of the doping element in the form of metal salts appear. The total content of the hexagonal crystalline lanthanum dioxide carbonate and the hexagonal crystalline lanthanum dioxide carbonate containing a doping element in the product was 82.3wt% as determined by the XRD spectrum. Comparative Example 3 (1) 5g of lanthanum nitrate hexahydrate was dissolved in 210g of deionized water, stirred at 25°C and a rotation speed of 900rpm for 30min, then sodium hydroxide solution was added dropwise into the lanthanum nitrate aqueous solution (the concentration of the sodium hydroxide solution was 10wt%, the addition rate of the alkali solution was 7mL / min per kilogram of the solution of lanthanum source, and the utilization amount of the alkali solution was such that the final pH value of the mixed system of the alkali solution and the solution of lanthanum source was 11.6), and - 32- 2023350438   09 Oct 2026 stirring at 25°C and a rotation speed of 9000rpm was continued for 10min after the drop-adding was completed. Then, the temperature was raised to 90°C and condensation reflux was kept with stirring for 12h. After the solution was cooled to room temperature, the solid material was separated by centrifugation at 10000rpm in a centrifuge, and was washed with deionized water until the pH value of the washing liquid was neutral. The obtained solid was sequentially subjected to a first drying and a second drying. The first drying conditions included: a temperature of 80°C and a time of 12h; the second drying conditions included: a relative pressure of 60kPa, a temperature of 140°C and a time of 5h. The saturated water absorption amount of the lanthanum hydroxide after the second drying was determined: under nitrogen protection, 1g of the lanthanum hydroxide after the second drying was taken and placed in a round-bottom flask, deionized water was added dropwise to the roundbottom flask by using a syringe, and was mixed with the lanthanum hydroxide by using a vortex mixer until the lanthanum hydroxide did not absorb further water significantly, and adding deionized water was stopped; and the addition amount of deionized water was recorded at this time. The saturated water absorption amount of lanthanum hydroxide was determined to be 2mL / g. (2) 0.08 g of strontium nitrate was dissolved in 1.5 mL of deionized water to obtain a strontium nitrate aqueous solution. Under nitrogen protection, 0.8 g of the lanthanum hydroxide after the second drying was weighed, and then the lanthanum hydroxide solid was added directly to the strontium nitrate solution at 25°C. Then the obtained mixture was dried at 80°C for 12 h. (3) A lanthanum dioxide carbonate catalyst was prepared by calcining at 500°C for 2h in an air atmosphere. Comparative Example 4 0.26 g of barium nitrate was dissolved in 10 mL of deionized water and was stirred to dissolve it completely. 2g of the prepared hexagonal - 33- 2023350438   09 Oct 2026 crystalline lanthanum dioxide carbonate was weighed, the barium nitrate aqueous solution was dropwise added into the hexagonal crystalline lanthanum dioxide carbonate, was stirred to mix it evenly and placed in an 80°C oven for24 h, then it is transferred to a muffle furnace, heated to 500°C 5 at 2°C / min, and maintained for 2h to prepare Ba / La2O2CO3. FIG.3 is an XRD spectrum of the lanthanum dioxide carbonate catalyst prepared in Comparative Example 4, from which it can be seen that: XRD results show that in addition to the peaks of lanthanum dioxide carbonate, a characteristic peak of BaCO4 is also obtained in the sample. 10 Comparative Example 5 0.3 g of nickel nitrate hexahydrate was dissolved in 10 mL of deionized water and stirred to dissolve it completely. 2g of the prepared hexagonal crystalline lanthanum dioxide carbonate was weighed, the nickel nitrate 15 aqueous solution was added dropwise into the hexagonal crystalline lanthanum dioxide carbonate, and was stirred to mix them evenly, placed in an oven at 80°C for 24 h, and then transferred to a muffle furnace; the temperature was raised to 500°C at 2°C / min, and maintained for 2h to prepare Ni / La2O2CO3. 20 Test Example 1 The catalysts prepared in the above examples and comparative examples were tableted and sieved through 40-60 meshes, and then 0.1g was taken and loaded into an Inconel fixed-bed reactors. Under normal pressure, 25 methane and oxygen (the molar ratio of methane to oxygen was 3:1) were introduced to react. Other reaction conditions and results were shown in Table 1. Table 1 Reaction temperature Methane space velocity Methane conversion rate C2 hydrocarbons selectivity Yield of C2 hydrocarbons °C mL / g<h % % % Example 1 500 40000 30.8 48.7 15.00 550 40000 31.8 52.7 16.76 600 40000 33.5 52.3 17.52 2023350438   09 Oct 2026 Example 2 500 40000 26.1 54.7 14.28 550 40000 29.8 47.8 14.24 600 40000 30.7 48.9 15.01 Example 3 500 40000 31.5 44.6 14.05 550 40000 32.1 46.3 14.86 600 40000 33.5 52.3 17.52 Example 4 500 80000 27.3 56.2 15.34 550 80000 28.4 57.6 16.36 600 80000 29.8 60.5 18.03 Example 5 500 50000 26.9 57.6 15.49 550 50000 30.9 53.1 16.41 600 50000 31.3 51.1 15.99 Example 6 500 50000 32.4 39.6 12.83 550 50000 33.7 41.1 13.85 600 50000 34.6 42.3 14.64 Example 7 500 50000 24.8 47.4 11.76 550 50000 26.7 46.7 12.47 600 50000 31.7 43.7 13.85 Example 8 500 50000 27.5 56.3 15.48 550 50000 28.3 47.7 13.50 600 50000 31 50.3 15.59 Example 9 500 50000 23.6 45.6 10.76 550 50000 27.9 46.2 12.89 600 50000 28.2 47.1 13.28 Example 10 500 50000 26.3 43.1 11.34 550 50000 28.3 46.8 13.24 600 50000 28.6 46.9 13.41 Embodiment 11 500 50000 25.6 43.1 11.03 550 50000 26.6 45.9 12.21 600 50000 27.6 46.9 12.94 Example 12 500 50000 25.4 48 12.19 550 50000 26.5 48.4 12.83 600 50000 27.4 47.9 13.12 Example 13 500 40000 27.4 56.2 15.3 550 40000 32.8 45.4 14.9 600 40000 29.7 53.5 15.9 Comparative Example 1 500 50000 21 43.4 9.11 550 50000 23.6 43.1 10.17 600 50000 24.6 44.2 10.87 Comparative Example 2 500 50000 18 43.6 7.85 550 50000 20 44.2 8.84 600 50000 20 44.3 8.86 Comparative Example 3 500 50000 19.4 44.3 8.59 550 50000 22.1 44.5 9.83 600 50000 22.1 43.5 9.61 Comparative Example 4 500 50000 2.3 1.6 0.04 550 50000 19 46.7 8.87 600 50000 20 49.9 9.98 Comparative Example 5 500 40000 30.2 10.2 3.1 550 40000 33.7 8.0 2.7 2023350438   09 Oct 2026 600 40000 40.0 3.9 1.6 It can be seen from the results in Table 1 that, compared with Comparative Example 1, the utilization of the lanthanum dioxide carbonate catalyst containing a doping element R of the present invention produces a 5 higher yield of C2 hydrocarbons at 500-650°C. Particularly preferably, the yield of C2 hydrocarbons using the catalysts of Examples 1-5 is higher than 15% at 550-650°C. In Comparative Example 2, the yield of C2 hydrogens produced by the catalyst obtained by directly mixing lanthanum dioxide carbonate and 10 strontium oxide is less than 10%, while the yield of C2 hydrogens produced by the catalyst prepared by the method of Example 1 of the present invention is 16.8%. Therefore, compared with the direct mixing method of Comparative Example 2, the element doping method of the present invention can improve the yield of C2 hydrogens. 15 In Comparative Example 3, solid lanthanum hydroxide was added to a strontium nitrate solution instead of dropwise adding the strontium nitrate aqueous solution to the solid lanthanum hydroxide according to the present invention. The yield of C2 hydrocarbons produced by the obtained catalyst was less than 10%. 20 Comparative Example 4 uses a conventional impregnation method to conduct the doping, and the obtained catalyst has lower methane conversion rate, C2 hydrocarbons selectivity and yield. In particular, the performance of the catalyst obtained by this method is greatly affected by temperature, especially at 500°C, the three important indicators of conversion rate, 25 selectivity and yield are very low. Comparative Example 5 uses Ni instead of the specific doping element of the present invention to conduct the doping, which obviously causes the production of the target product C2 hydrocarbons to fail to achieve the desired purpose, and the selectivity and yield of C2 hydrocarbons at various 30 temperatures are very low. The preferred embodiments of the present invention are described in 2023350438   09 Oct 2026 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 combinations of various technical features in any other 5 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 lanthanum dioxide carbonate catalyst, characterized in that the catalyst comprises hexagonal crystalline lanthanum dioxide carbonate and hexagonal crystalline lanthanum dioxide carbonate containing a doping element R, and the total content of hexagonal crystalline lanthanum dioxide carbonate and hexagonal crystalline lanthanum dioxide carbonate containing a doping element R in the catalyst is not less than 98wt%, wherein the molar ratio of the lanthanum element to the doping element R is 1:0.01 to 1:0.3; and the doping element R is selected from at least one of Mg, Ca, Sr, Ba, Fe and Zn elements.

2. The lanthanum dioxide carbonate catalyst according to claim 1, wherein the doping element R is Sr and / or Ba.

3. The lanthanum dioxide carbonate catalyst according to claim 1, wherein the total content of hexagonal crystalline lanthanum dioxide carbonate and hexagonal crystalline lanthanum dioxide carbonate containing a doping element R in the lanthanum dioxide carbonate catalyst is not less than 99wt%; and / orthe molar ratio of the lanthanum element to the doping element R in the lanthanum dioxide carbonate catalyst is 1:0.03 to 1:0.2, preferably from 1:0.04 to 1:0.15.

4. The lanthanum dioxide carbonate catalyst according to any one of claims 1 to 3, wherein the lanthanum dioxide carbonate catalyst has a fibrous nanostructure; the diameter of the lanthanum dioxide carbonate catalyst is 10 nm to 30 nm, preferably 10 nm to 20 nm, and the length-to-diameter ratio is 5:1 to 50:1, preferably 15:1 to 40:1; and / or,the lanthanum dioxide carbonate catalyst has a specific surface area of 35 m2 / g-90 m2 / g, preferably 50 m2 / g-60 m2 / g, a pore volume of 0.15 cm3 / g-0.5 cm3 / g, preferably 0.26 cm3 / g- 0.4 cm3 / g, and an average pore diameter of 8 nm-16 nm, preferably 10 nm-13.5 nm.

5. The lanthanum dioxide carbonate catalyst according to any one of claims 1 to 3, wherein the XRD spectrum of the lanthanum dioxide - 38-2023350438   09 Oct 2026carbonate catalyst has no characteristic peak of the doping element in the form of metal salt.

6. A method for preparing the lanthanum dioxide carbonate catalyst according to any one of the preceding claims, characterized in that the method comprises:(1) adding an alkali solution to a solution of lanthanum source, and then performing a solid-liquid separation and a drying to obtain solid lanthanum hydroxide; wherein the drying comprises a first drying and a second drying, wherein the first drying conditions comprise: a temperature of 70-90°C and a time of 10-20 hours, and the second drying is performed at a higher temperature and for a shorter time than the first drying;determining the saturated water absorption amount of the lanthanum hydroxide after the second drying: under nitrogen protection, taking 1g of the lanthanum hydroxide after the second drying and placing it in a container, adding water to evenly mix it with the lanthanum hydroxide, until the lanthanum hydroxide has no obvious further water absorption, and recording the addition amount of water at this time as the saturated water absorption amount of the lanthanum hydroxide;(2) adding a solution of a compound containing the doping element R to the solid lanthanum hydroxide obtained in step (1) so that the solution in an amount less than or equal to the saturated water absorption amount of the lanthanum hydroxide is contacted with the lanthanum hydroxide, and then performing a drying; wherein the contacting method is selected from lattice doping, surface precipitation, atomic layer deposition and single atomic layer plating;(3) calcining the dried product of step (2) in a carbon-containing atmosphere to obtain a lanthanum dioxide carbonate catalyst.

7. The method according to claim 6, wherein the alkali in the alkali solution is a compound of a Group IA metal, and preferably the concentration of the alkali solution is 3wt%-25wt%; and / or,the amount of the alkali solution is such that the final pH value of the mixed system of the alkali solution and the solution of lanthanum source is- 39-2023350438   09 Oct 202610-12.5; and / or,the lanthanum source is a water-soluble salt of lanthanum, preferably at least one of lanthanum nitrate, lanthanum chloride and lanthanum acetate, preferably, the concentration of the solution of lanthanum source is 5 0.01wt%-10wt%.

8. The method according to claim 6, wherein in step (1), an aging is performed before the solid-liquid separation, and the aging conditions include: a temperature of 80-100°C and a time of 10-50h; and / or,preferably, the second drying conditions include: a relative pressure of 10 10kPa-91kPa, preferably 20kPa-70kPa, a temperature of 120-160°C, and a time of 2-10 h.

9. The method according to claim 6, wherein step (2) is carried out under a protective atmosphere provided by an inert gas and / or nitrogen; and / or15 the concentration of the solution of a compound containing the doping element R is 0.01-0.2 g / mL; and / or,the molar ratio of the lanthanum element to the doping element R in the lanthanum hydroxide is 1:0.01 to 1:1; and / or,the compound containing the doping element R is selected from a 20 compound of at least one element of Mg, Ca, Sr, Ba, Fe and Zn, preferably a compound of Sr and / or Ba; and / or,the contact conditions include: a temperature of 15-50°C and a time of 2-5h.

10. The method according to claim 6, wherein in step (2), the addition 25 rate of the solution of a compound containing the doping element R is 0.1 mL / min-10 mL / min, preferably 0.1 mL / min-8 mL / min, per gram of the lanthanum hydroxide; and / or, the drying conditions include: a temperature of 60-100°C and a time of 10-24 hours.

11. The method according to claim 6, wherein in step (3), the carbon-30 containing atmosphere is an atmosphere containing CO and / or CO2; and / orthe calcination conditions include: a temperature of 450-550°C and a time of 2-8h.2023350438   09 Oct 202612. The method according to claim 6, wherein the amount of the solution of a compound containing the doping element R contacted with the lanthanum hydroxide is equal to or substantially equal to the saturated water absorption amount of the lanthanum hydroxide.5       13. Use of the lanthanum dioxide carbonate catalyst according to anyone of claims 1 to 5 in the methane oxidative coupling reaction to prepare C2 or higher hydrocarbons.

14. A method for preparing C2 or higher hydrocarbons from methane, characterized in that the method comprises:10 in the presence of oxygen and under the conditions of methane oxidative coupling reaction, contacting methane with the lanthanum dioxide carbonate catalyst according to any one of claims 1 to 5 for reaction; or, preparing a lanthanum dioxide carbonate catalyst according to the method of any one of claims 6 to 12, and then contacting methane with the15 obtained lanthanum dioxide carbonate catalyst for reaction in the presence of oxygen and under the conditions of methane oxidative coupling reaction.

15. The method according to claim 14, wherein the molar ratio of methane to oxygen is 2:1 to 9:1; and / or,the contact reaction temperature is 500-650°C; and / or, the methane20 space velocity is 5000 mL / (g^h)-200000 mL / (g^h).

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