Elm leaf-like lanthanum oxide material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of methane oxidative coupling, and discloses an elm leaf-like lanthanum oxide material and a preparation method and application thereof, the lanthanum oxide material comprises elm leaf-like lanthanum oxide, the average length of the elm leaf-like lanthanum oxide is 2-6 [mu] m, the average width of the elm leaf-like lanthanum oxide is 1-5 [mu] m, and the average thickness of the elm leaf-like lanthanum oxide is 10-100 nm. The method for preparing the lanthanum oxide material comprises the steps that an alkaline solution containing a lanthanum precursor, urea, alcohol and water reacts for 2-50 h at the temperature of 80-180 DEG C, then separation and roasting are conducted, and the pH of the alkaline solution is 8.5-10. The lanthanum oxide material disclosed by the invention has relatively high methane conversion rate and selectivity of hydrocarbons with two or more carbons when being used for oxidative coupling reaction of methane.

Description

Technical Field

[0001] The invention relates to the technical field of methane oxidative coupling, and in particular to an elm leaf-shaped lanthanum oxide material and a preparation method and application thereof. Background Art

[0002] Lanthanum oxide is an inorganic compound with the chemical formula La2O3, and is a white powder. It is soluble in acid, ethanol, and ammonium chloride, but insoluble in water and ketone. The application of rare earth lanthanum oxide is very wide, and it plays an important role in the fields of glass, ceramics, electronics, etc. The preparation of lanthanum oxide nanopowders with specific morphology is of great significance. At present, a variety of preparation methods of nanopowders have been reported at home and abroad, including physical and chemical methods. The chemical methods mainly include: vapor deposition method, hydrothermal synthesis method, sol-gel method, solvent evaporation method, microemulsion method, precipitation method, electrochemical method, supercritical method and polymer protection method, etc. The influencing factors are relatively complex. Journal of Fuel Chemistry, "Oxidative Coupling of Methane on Lanthanum Oxide Catalysts-Comparison of Different Preparation Methods", five methods were used to prepare lanthanum oxide catalysts, and the evaluation was carried out under the same experimental conditions, and the chemical properties obtained were different. Literature Fern shaped La2O3 nanostructures as potential scaffold for efficient hydroquinone chemicalsensing application. Ceramics International 2020, 46 (4), 5141-5148. A fern-shaped nano lanthanum oxide was reported. Lanthanum nitrate solution (20 mL, 0.1 M) and hexamethylenetetramine solution (20 mL, 0.1 M) were mixed under stirring, and the pH value of the solution was adjusted to 10 by adding ammonia solution dropwise to the mixture; the resulting solution was then transferred to a 100 ml polytetrafluoroethylene-lined stainless steel autoclave and aged at 160-170°C for 6 hours; cooled to room temperature, the solid part was filtered and washed with deionized water and ethanol, and the resulting product was then dried at 80°C for 3 hours; subsequently, the material was calcined in air at 800°C for 4 hours. The obtained lanthanum oxide material shows a 3D fern-like structure with dendritic arms of different lengths, a triangular profile, connected to a long common trunk in a beaded pattern, and evenly arranged along the central trunk, and this material is used in electrochemical sensors for hydroquinone. The above lanthanum oxide has the disadvantage of poor performance in the methane oxidative coupling reaction. Summary of the invention

[0003] The purpose of the present invention is to overcome the problem of poor activity in the oxidative coupling reaction in the prior art, and to provide an elm leaf-shaped lanthanum oxide material and a preparation method and application thereof.

[0004] In order to achieve the above objectives, the first aspect of the present invention provides a lanthanum oxide material, which includes elm leaf-shaped lanthanum oxide, and the elm leaf-shaped lanthanum oxide has an average length of 2-6 μm, an average width of 1-5 μm, and an average thickness of 10-100 nm.

[0005] The second aspect of the present invention provides a method for preparing a lanthanum oxide material, the method comprising: reacting an alkaline solution containing a lanthanum precursor, urea, alcohol and water at 80-180°C for 2-50h, and then separating and calcining, wherein the pH of the alkaline solution is 8.5-10.

[0006] The third aspect of the present invention provides a lanthanum oxide material prepared by the method described above.

[0007] A fourth aspect of the present invention provides the use of the above-mentioned lanthanum oxide material in the oxidative coupling reaction of methane to produce C2 and higher hydrocarbons.

[0008] A fifth aspect of the present invention provides a method for preparing hydrocarbons having two or more carbon atoms from methane, the method comprising: in the presence of oxygen and under the conditions of a methane oxidative coupling reaction, contacting methane with the above-mentioned lanthanum oxide material for reaction;

[0009] Alternatively, the lanthanum oxide material is prepared according to the method described above, and then methane is contacted with the obtained lanthanum oxide material in the presence of oxygen and under the conditions of methane oxidative coupling reaction.

[0010] The invention prepares an elm leaf-shaped lanthanum oxide material by reacting an alkaline solution of a lanthanum precursor, urea, alcohol and water at a relatively low temperature. The lanthanum oxide material has a relatively high methane conversion rate and selectivity for C2 and above hydrocarbons when used in a methane oxidative coupling reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a scanning electron microscope image of the lanthanum oxide catalyst prepared in Example 1. DETAILED DESCRIPTION

[0012] 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.

[0013] A first aspect of the present invention provides a lanthanum oxide material, characterized in that the lanthanum oxide material comprises elm leaf-shaped lanthanum oxide, the elm leaf-shaped lanthanum oxide has an average length of 2-6 μm, an average width of 1-5 μm, and an average thickness of 10-100 nm.

[0014] In the present invention, unless otherwise specified, the thickness, length and width described herein are measured by scanning electron microscopy. The shape of the lanthanum oxide material is determined by scanning electron microscopy characterization. The test method for the size of the lanthanum oxide material is: select 5-10 samples in the visual field, measure the length, width and thickness with a measuring instrument provided by a scanning electron microscope, and then calculate the average length, average width and average thickness of the 5-10 samples in the visual field. Since the elm-like leaf shape is wide in the middle and narrow at both ends, the length of the longest part of the elm-like leaf structure is used as the length, and the width of the widest part of the elm-like leaf structure is used as the width.

[0015] In the present invention, the average length of the elm leaf-shaped lanthanum oxide can be 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, and a range consisting of any two of the above points.

[0016] In the present invention, the average width of the elm leaf-shaped lanthanum oxide can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, and a range consisting of any two of the above points.

[0017] In the present invention, the average thickness of the elm leaf-shaped lanthanum oxide can be 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, and a range consisting of any two of the above points. Preferably, the average thickness of the elm leaf-shaped lanthanum oxide is 20-90nm, more preferably 20-50nm.

[0018] According to the present invention, preferably, the specific surface area of ​​the lanthanum oxide material is 25-29m 2 / g, pore volume is 0.01-0.05cm 3 / g, and an average pore size of 100-500 angstroms, more preferably 100-250 angstroms. It is a unit of length, 10 angstroms = 1 nm.

[0019] According to the present invention, preferably, the lanthanum oxide material further comprises a doping element, and the doping element is selected from Group IA elements and / or Group IIA elements.

[0020] According to the present invention, preferably, the lanthanum oxide material further comprises a doping element, and the doping element is selected from at least one of Mg, Ca, Sr and Ba.

[0021] According to the present invention, preferably, the molar ratio of the doping element to the lanthanum element in the lanthanum oxide material is 0.01-0.2: 1. In the present invention, the molar ratio of the doping element to the lanthanum element is calculated based on the feed amount.

[0022] The second aspect of the present invention provides a method for preparing a lanthanum oxide material, the method comprising: reacting an alkaline solution containing a lanthanum precursor, urea, alcohol and water at 80-180°C for 2-50h, and then separating and calcining, wherein the pH of the alkaline solution is 8.5-10.

[0023] According to the present invention, the lanthanum precursor may be a conventional substance containing lanthanum element; preferably, the lanthanum precursor is a water-soluble salt of lanthanum (such as lanthanum nitrate, lanthanum chloride, etc.), preferably lanthanum nitrate.

[0024] According to the present invention, preferably, the alcohol is a C1-C4 monohydric alcohol and / or a C1-C4 dihydric alcohol, preferably at least one of methanol, ethanol, ethylene glycol and propylene glycol.

[0025] According to the present invention, preferably, the weight ratio of lanthanum precursor: urea: water: alcohol in the alkaline solution is (1-10): (3-15): (200-400): (1-10), more preferably (1.5-5): (3-6): (250-350): (4-9).

[0026] According to the present invention, preferably, the alkaline solution is obtained by mixing a lanthanum precursor and an aqueous solution of urea and alcohol to obtain a mixed solution, and then adjusting the pH of the mixed solution to alkaline (pH 8.5-10) with a base. More preferably, the base is ammonia water; further preferably, the mass percentage of ammonia water is 20-36wt%.

[0027] According to the method for obtaining the alkaline solution of the present invention, preferably, the weight ratio of the lanthanum precursor to urea is 1:0.5-5 (for example, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, and a range formed by any two of the above points), more preferably 1:1-4, and further preferably 1:1.5-3.8.

[0028] According to the method for obtaining the alkaline solution of the present invention, preferably, the alcohol content in the alcohol aqueous solution is 1-20 wt %, more preferably 1-3 wt %.

[0029] According to the method for obtaining the alkaline solution of the present invention, preferably, the weight ratio of the lanthanum precursor and the alcohol aqueous solution is 1:50-300 (for example, 1:50, 1:80, 1:100, 1:120, 1:150, 1:180, 1:200, 1:220, 1:250, 1:300, and a range consisting of any two of the above points), more preferably 1:60-250, and further preferably 1:80-200.

[0030] According to the present invention, preferably, the reaction method includes water bath reaction and / or hydrothermal reaction. That is, the reaction of the alkaline solution of the present invention can be carried out in a water bath or in a hydrothermal reactor, as long as the reaction temperature and reaction time can be met.

[0031] According to the present invention, preferably, the conditions of the water bath reaction include: reaction temperature of 80-100° C., and reaction time of 12-24 h.

[0032] According to the present invention, preferably, the conditions of the hydrothermal reaction include: reaction temperature of 80-180° C. and reaction time of 12-24 h.

[0033] According to the present invention, preferably, the method further comprises: standing the reaction solution obtained after the reaction at 15-40° C. for 8-24 hours, and then performing separation and roasting steps.

[0034] According to the present invention, preferably, the method further comprises: washing the separated solid with water and alcohol (ethanol) in sequence, and then drying. The number of water washings may be 2-4 times, and the number of alcohol washings may be 1-2 times.

[0035] According to the present invention, preferably, the method further comprises: before roasting, drying the separated solid, and the drying conditions include: temperature of 80-120° C. and time of 12-60 h.

[0036] According to the present invention, preferably, the calcination conditions include: heating to 700-850° C. at a heating rate of 2-5° C. / min, and then maintaining at the temperature for 2-5 h.

[0037] According to the present invention, preferably, the calcination atmosphere is an air atmosphere or an inert atmosphere. More preferably, the gas providing the inert atmosphere is selected from at least one of nitrogen, helium, neon, argon, krypton or xenon, preferably nitrogen.

[0038] According to the present invention, preferably, the method further comprises doping with doping elements, and the doping manner comprises: an impregnation method and / or a co-precipitation method.

[0039] According to the present invention, preferably, the co-precipitation method comprises: adding a doping element precursor to an alkaline solution; more preferably, the doping element is selected from Group IIA elements and / or Group IA elements; further preferably, the molar ratio of the doping element precursor calculated as the doping element to the lanthanum precursor calculated as the lanthanum element is 0.01-0.2:1.

[0040] According to the present invention, preferably, the impregnation method comprises: impregnating the calcined product with a solution containing a doping element precursor; more preferably, the doping element is selected from Group IIA elements and / or Group IA elements; further preferably, the molar ratio of the doping element precursor calculated as the doping element to the calcined product calculated as the lanthanum element is 0.01-0.2:1.

[0041] According to the present invention, preferably, the method further comprises solid-liquid separation, drying and roasting of the impregnated product; wherein the drying conditions include: temperature of 80-120°C and time of 12-60h. The roasting conditions include: heating to 700-850°C at a heating rate of 2-5°C / min, and then maintaining at this temperature for 2-5h.

[0042] The third aspect of the present invention provides a lanthanum oxide material prepared by the method described above.

[0043] A fourth aspect of the present invention provides the use of the above-mentioned lanthanum oxide material in the oxidative coupling reaction of methane to produce C2 and higher hydrocarbons.

[0044] A fifth aspect of the present invention provides a method for preparing hydrocarbons having two or more carbon atoms from methane, the method comprising: in the presence of oxygen and under the conditions of a methane oxidative coupling reaction, contacting methane with the above-mentioned lanthanum oxide material for reaction;

[0045] Alternatively, the lanthanum oxide material is prepared according to the method described above, and then methane is contacted with the obtained lanthanum oxide material in the presence of oxygen and under the conditions of methane oxidative coupling reaction.

[0046] According to the present invention, preferably, the molar ratio of the methane to the oxygen is 2-10:1.

[0047] According to the present invention, preferably, the temperature of the contact reaction is 650-800°C.

[0048] According to the present invention, preferably, the space velocity calculated as methane is 10000-100000 mL / (g·h).

[0049] According to a particularly preferred embodiment of the present invention, the method for preparing lanthanum oxide material comprises:

[0050] (1) Add 3.3-3.5g of lanthanum nitrate hexahydrate and 4.6-4.8g of urea to 300-320g of ethylene glycol aqueous solution (ethylene glycol content in the ethylene glycol aqueous solution is 1.5-2wt%), stir to completely dissolve, add ammonia water to adjust the pH to 8.5-9; then transfer to a water bath at 80-85°C and keep stirring for 2-3h, the stirring speed is 500-600rpm, and stand at 25-30°C overnight (about 10-12h); centrifuge the solid and liquid, wash with water and ethanol, dry at 110-120°C for 12-14h, transfer to a muffle furnace, heat to 750-760°C at a heating rate of 2-2.5°C / min and keep for 2-2.5h. A lanthanum oxide catalyst is prepared.

[0051] (2) The lanthanum oxide catalyst doped with strontium is prepared by impregnating the lanthanum oxide catalyst with an equal volume of strontium nitrate aqueous solution, drying and calcining the catalyst. The molar ratio of the doped strontium element to the lanthanum element is 0.1-0.15:1, and the drying conditions include: a temperature of 110-120°C for 12-14 hours; and the calcination conditions include: heating at a rate of 4.5-5°C / min to 720-750°C and maintaining for 4.5-4 hours.

[0052] The present invention will be described in detail below by way of examples. In the following examples,

[0053] Unless otherwise specified, the calcination atmosphere was air.

[0054] The mass percentage of ammonia water is 25wt%.

[0055] The calculation method of methane conversion rate is as follows:

[0056] Methane conversion rate = amount of methane consumed in the reaction / initial amount of methane × 100%.

[0057] The ethylene selectivity is calculated as follows:

[0058] Ethylene selectivity = amount of methane consumed by produced ethylene / total methane consumption x 100%.

[0059] The ethane selectivity is calculated as follows:

[0060] Ethane selectivity = amount of methane consumed by produced ethane / total methane consumption x 100%.

[0061] The selectivity of C2 and above hydrocarbons includes the sum of ethylene, ethane, propylene, propane and higher carbon hydrocarbons.

[0062] Example 1

[0063] This example is used to illustrate the use of water bath method to prepare lanthanum oxide material

[0064] 3.3g of lanthanum nitrate hexahydrate and 4.6g of urea were added to 300g of ethylene glycol aqueous solution (ethylene glycol content in ethylene glycol aqueous solution was 2wt%), stirred to completely dissolve, and ammonia water was added to adjust the pH to 8.5; then transferred to a water bath at 80°C for 2h, the stirring speed was 500rpm, and left to stand overnight at 25°C (about 12h); the solid and liquid were centrifuged, washed three times with water, washed once with ethanol, placed in an oven, dried at 120°C for 12h, moved to a muffle furnace, heated to 750°C at a heating rate of 2°C / min and kept for 2h. The elm leaf-shaped lanthanum oxide catalyst cat1 was prepared.

[0065] The scanning electron microscope image of the lanthanum oxide catalyst prepared in Example 1 is as follows: Figure 1 As shown by Figure 1 It can be seen that the lanthanum oxide catalyst has an elm leaf-like shape.

[0066] Example 2

[0067] This example is used to illustrate the use of water bath method to prepare lanthanum oxide material

[0068] 2g of lanthanum nitrate hexahydrate and 5.5g of urea were added to 300g of ethanol aqueous solution (ethanol content in ethanol aqueous solution was 2wt%), stirred to completely dissolve, and ammonia water was added to adjust the pH to 8.5; then transferred to a water bath at 90°C for 2h, stirring at 400rpm, and left to stand overnight at 30°C (about 12h); the solid and liquid were centrifuged, washed three times with water, washed once with ethanol, placed in an oven, dried at 80°C for 12h, moved to a muffle furnace, heated to 800°C at a heating rate of 5°C / min and kept for 5h. The elm leaf-shaped lanthanum oxide catalyst cat2 was prepared.

[0069] Example 3

[0070] This example is used to illustrate the use of water bath method to prepare lanthanum oxide material

[0071] 4.8g of lanthanum nitrate hexahydrate and 5.6g of urea were added to 300g of ethylene glycol aqueous solution (ethylene glycol content in ethylene glycol aqueous solution was 3wt%), stirred to completely dissolve, and ammonia water was added to adjust the pH to 9; then transferred to a water bath at 80°C for 4h, the stirring speed was 500rpm, and left to stand at 30°C overnight (about 12h); the solid and liquid were centrifuged, washed three times with water, washed once with ethanol, placed in an oven, dried at 120°C for 12h, moved to a muffle furnace, heated to 750°C at a heating rate of 5°C / min and kept for 4h. The elm leaf-shaped lanthanum oxide catalyst cat3 was prepared.

[0072] Example 4

[0073] The method of Example 1 was followed, except that ethylene glycol was replaced by an equal weight of propylene glycol to prepare an elm leaf-shaped lanthanum oxide catalyst cat4.

[0074] Example 5

[0075] The method of Example 1 was followed, except that ethylene glycol was replaced by an equal weight of n-octanol to prepare an elm leaf-shaped lanthanum oxide catalyst cat5.

[0076] Example 6

[0077] The method of Example 1 was followed, except that the ethylene glycol content in the ethylene glycol aqueous solution was 20 wt %, to prepare an elm leaf-shaped lanthanum oxide catalyst cat6.

[0078] Example 7

[0079] Weigh 2g of lanthanum oxide catalyst cat1, then use strontium nitrate aqueous solution to impregnate lanthanum oxide catalyst cat1 in equal volume, dry and calcine to prepare strontium-doped lanthanum oxide catalyst cat-7. The molar ratio of doped strontium to lanthanum is 0.1:1, and the drying conditions include: temperature 120℃, time 12h; calcination conditions include: heating at 5℃ / min to 750℃ and maintaining for 4h.

[0080] Example 8

[0081] This example is used to illustrate the use of hydrothermal method to prepare lanthanum oxide material

[0082] 3.3g of lanthanum nitrate hexahydrate and 4.6g of urea were added to 300g of ethylene glycol aqueous solution (ethylene glycol content in ethylene glycol aqueous solution was 2wt%), stirred to completely dissolve, and ammonia water was added to adjust the pH to 8.5; then transferred to a hydrothermal kettle and kept at 100°C for 12h; the solid and liquid were centrifuged, washed with water three times, washed with ethanol once, placed in an oven, dried at 120°C for 12h, moved to a muffle furnace, heated to 750°C at a heating rate of 2°C / min and kept for 2h. The elm leaf-shaped lanthanum oxide catalyst cat8 was prepared.

[0083] Comparative Example 1

[0084] The method of Example 1 was followed, except that urea was not added, to prepare lanthanum oxide that was not in the shape of an elm leaf.

[0085] Comparative Example 2

[0086] The method of Example 1 was followed, except that the ethylene glycol aqueous solution was replaced with an equal weight of water to prepare lanthanum oxide that was not in the shape of an elm leaf.

[0087] Comparative Example 3

[0088] Commercially available lanthanum oxide (purity 99.9%) was used to replace the elm leaf-shaped lanthanum oxide catalyst cat-1 prepared in Example 1.

[0089] Test Example 1

[0090] The specific surface area, pore volume, average pore diameter of the above catalyst and the thickness, length and width of the lanthanum oxide catalyst were tested. The test results are shown in Table 1.

[0091] The test method for the specific surface area, pore volume and average pore size of the lanthanum oxide catalyst is as follows: weigh 2000 mg of sample and put it into a sample tube, put the sample tube into the instrument degassing station for degassing, the degassing condition is 350 degrees for 4 hours, and after naturally cooling to room temperature, put the sample tube into the instrument analysis station for analysis, and perform a full analysis of the nitrogen adsorption and desorption isotherm at liquid nitrogen temperature. The specific surface area of ​​the sample is calculated by the BET (Brunauer, Emmett, Teller) method, and the pore volume and average pore size of the sample are calculated according to the desorption (adsorption) branch by the BJH (Barret, Joyner, Halenda) method. Instrument model: fully automatic physical adsorption instrument ASAP2420, Mack Instrument Company, USA.

[0092] The testing method for the thickness, length and width of the lanthanum oxide catalyst is as follows: the shape of the lanthanum oxide material is determined by scanning electron microscopy, 5-10 samples in the field of view are selected, the length, width and thickness are measured using the measuring instrument provided by the scanning electron microscope, and then the average length, average width and average thickness of the 5-10 samples in the field of view are calculated.

[0093] Table 1

[0094]

[0095] Test Example 2

[0096] After the catalyst tablets were sieved through 40-60 mesh, 100 mg was weighed and loaded into a quartz tube fixed bed reactor with an inner diameter of 4 mm, and methane and oxygen were introduced. The methane space velocity was 40000 mL / (g·h), the alkoxy ratio was 3, and the reaction temperature was 750°C. The methane conversion rate and the selectivity of C2 and above hydrocarbons were calculated based on the composition of the product. The results are shown in Table 2.

[0097] Table 2

[0098]

[0099]

[0100] 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 lanthanum oxide material, characterized in that The lanthanum oxide material comprises elm leaf-like lanthanum oxide, and the elm leaf-like lanthanum oxide has an average length of 2-6 μm, an average width of 1-5 μm, and an average thickness of 10-100 nm.

2. The lanthanum oxide material according to claim 1, wherein The specific surface area of ​​the lanthanum oxide material is 25-29m 2 / g, pore volume is 0.01-0.05cm 3 / g, and the average pore size is 100-500 angstroms, preferably 100-250 angstroms.

3. The lanthanum oxide material according to claim 1 or 2, wherein The lanthanum oxide material further comprises a doping element selected from Group IA elements and / or Group IIA elements.

4. The lanthanum oxide material according to claim 3, further comprising a doping element, wherein the doping element is selected from at least one of Mg, Ca, Sr and Ba; Preferably, the molar ratio of the doping element to the lanthanum element in the lanthanum oxide material is 0.01-0.2:

1.

5. A method for preparing lanthanum oxide material, characterized in that: The method comprises: reacting an alkaline solution containing a lanthanum precursor, urea, alcohol and water at 80-180° C. for 2-50 hours, and then separating and roasting, wherein the pH of the alkaline solution is 8.5-10.

6. The method according to claim 5, wherein: The lanthanum precursor is a water-soluble salt of lanthanum, preferably lanthanum nitrate; And / or, the alcohol is a C1-C4 monohydric alcohol and / or a C1-C4 dihydric alcohol, preferably at least one of methanol, ethanol, ethylene glycol and propylene glycol.

7. The method according to claim 5, wherein: The weight ratio of lanthanum precursor: urea: water: alcohol in the alkaline solution is (1-10): (3-15): (200-400): (1-10), preferably (1.5-5): (3-6): (250-350): (4-9); And / or, the reaction method includes water bath reaction and / or hydrothermal reaction; Preferably, the conditions of the water bath reaction include: reaction temperature of 80-100°C, reaction time of 12-24h; Preferably, the conditions of the hydrothermal reaction include: reaction temperature of 80-180° C. and reaction time of 12-24 h.

8. The method according to claim 5, wherein: The calcination conditions include: heating to 700-850° C. at a heating rate of 2-5° C. / min, and then maintaining the temperature for 2-5 hours.

9. The method according to claim 5, wherein: The method further comprises doping with a doping element, wherein the doping method comprises: an impregnation method and / or a coprecipitation method; Preferably, the coprecipitation method comprises: adding a doping element precursor to an alkaline solution; more preferably, the doping element is selected from Group IIA elements and / or Group IA elements; further preferably, the molar ratio of the doping element precursor calculated as the doping element to the lanthanum precursor calculated as the lanthanum element is 0.01-0.2:1; Preferably, the impregnation method comprises: impregnating the calcined product with a solution containing a doping element precursor; more preferably, the doping element is selected from Group IIA elements and / or Group IA elements; further preferably, the molar ratio of the doping element precursor calculated as the doping element to the calcined product calculated as the lanthanum element is 0.01-0.2:

1.

10. The lanthanum oxide material prepared by the method according to any one of claims 5 to 9.

11. Use of the lanthanum oxide material according to any one of claims 1 to 4 and 10 in the oxidative coupling reaction of methane to produce C2 and higher hydrocarbons.

12. A method for preparing hydrocarbons with carbon 2 or higher content from methane, characterized in that: The method comprises: in the presence of oxygen and under the conditions of methane oxidative coupling reaction, contacting methane with the lanthanum oxide material according to any one of claims 1 to 4 and 10 for reaction; Alternatively, the lanthanum oxide material is prepared according to the method described in any one of claims 5 to 9, and then methane is contacted with the obtained lanthanum oxide material to react 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 the methane to the oxygen is 2-10:1; And / or, the contact reaction temperature is 650-800°C; And / or, the space velocity calculated in terms of methane is 10000-100000 mL / (g·h).

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