Lanthanum oxide polycrystalline material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of methane oxidative coupling, and discloses a lanthanum oxide polycrystalline material and a preparation method and application thereof.The lanthanum oxide polycrystalline material comprises lanthanum oxide of a p63 / mmc hexagonal crystal system, and the lanthanum oxide of the p63 / mmc hexagonal crystal system has an exposed crystal face (211). The method for preparing the lanthanum oxide polycrystalline material comprises the following steps: carrying out hydrothermal crystallization on an alkaline solution containing alcohol, C6-C15 phenol, C1-C6 aldehyde and a lanthanum source to obtain a solid product; and roasting the solid product. According to the lanthanum oxide polycrystalline material disclosed by the invention, methane and oxygen can react to generate C2 hydrocarbon at a relatively low temperature, so that the reaction temperature of oxidative coupling of methane is greatly reduced.

Description

Technical Field

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

[0002] Ethylene is a basic chemical raw material. In order to change the situation that the raw materials for ethylene production are overly dependent on petroleum resources, the technology of direct production of ethylene from natural gas (methane) has received widespread attention. However, the direct conversion of methane to ethylene is very difficult and challenging. The technology of direct production of ethylene from methane is divided into two categories: methane oxidative coupling and methane oxygen-free coupling. In terms of oxygen-free coupling, the temperature needs to be over 1000 degrees. Deven S.Baser et al. prepared a lithium-tungsten doped Mg-Mn-based oxygen carrier (Li, W)-Mg6MnO8. The designed co-doped oxygen carrier showed good OCM performance at 850°C. 2+ The hydrocarbon yield reached 28.6%, which is 80% higher than the total yield of a single oxygen carrier doped with Li and W. In the related research of Kim et al., TiO2 and Ce were used as carriers and promoters to promote CH4 conversion by providing more available oxygen in the Mn / Na2WO4 substrate catalyst. In terms of aerobic coupling, Siluria used a biological template to synthesize a nanowire catalyst, which achieved methane oxidative coupling to ethylene at 5-10 atmospheres, 200℃-300℃ lower than the operating temperature of the traditional steam cracking method. Despite more than three decades of extensive research, the reaction has not been able to be industrialized due to limited C2 hydrocarbon selectivity, insufficient catalyst activity and poor stability. Lanthanum oxide catalysts have become highly promising OCM catalysts due to their excellent catalytic performance and high temperature stability.

[0003] However, the existing lanthanum oxide-catalyzed methane oxidative coupling is mostly carried out at high temperatures and has almost no catalytic activity at low temperatures. This is because the activation energy of this reaction is high and a higher temperature is required to fully proceed. The catalytic activity of lanthanum oxide mainly comes from its special electronic structure and excellent oxygen ion conductivity. At high temperatures, lanthanum oxide can provide sufficient active oxygen species to promote the oxidative coupling reaction of methane. However, at low temperatures, due to the weakening of thermal motion, the migration rate of oxygen ions and the generation rate of active oxygen species will be significantly reduced, resulting in a decrease in catalytic activity. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem in the prior art that lanthanum oxide has low catalytic activity or even no catalytic activity at low temperatures, and to provide a lanthanum oxide polycrystalline material and a preparation method and application thereof.

[0005] In order to achieve the above-mentioned object, the first aspect of the present invention provides a lanthanum oxide polycrystalline material, wherein the lanthanum oxide polycrystalline material comprises p63 / mmc hexagonal lanthanum oxide, wherein the p63 / mmc hexagonal lanthanum oxide has a (211) exposed crystal plane.

[0006] The second aspect of the present invention provides a method for preparing a lanthanum oxide polycrystalline material, the method comprising: 15 The alkaline solution of phenol, C1-C6 aldehyde and lanthanum source is hydrothermally crystallized to obtain a solid product; and then the solid product is calcined.

[0007] The third aspect of the present invention provides a lanthanum oxide polycrystalline material prepared by the above method.

[0008] A fourth aspect of the present invention provides the use of the above-mentioned lanthanum oxide polycrystalline material in the oxidative coupling reaction of methane to produce C2 and higher hydrocarbons.

[0009] 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 methane oxidative coupling reaction, contacting and reacting methane with the above-mentioned lanthanum oxide polycrystalline material;

[0010] Alternatively, the lanthanum oxide polycrystalline material is prepared according to the method described above, and then methane is contacted with the obtained lanthanum oxide polycrystalline material in the presence of oxygen and under the conditions of methane oxidative coupling reaction.

[0011] Through the above technical solution, the present invention achieves the following beneficial effects:

[0012] (1) When the lanthanum oxide polycrystalline material with (211) exposed crystal plane of the present invention is used for methane oxidative coupling, methane and oxygen can react to generate carbon dihydrocarbons at a relatively low temperature. The lanthanum oxide polycrystalline material of the present invention greatly reduces the reaction temperature of methane oxidative coupling, starts to generate carbon dihydrocarbons at 450°C, and the selectivity of carbon dihydrocarbons increases with increasing temperature.

[0013] (2) The present invention prepares a lanthanum oxide polycrystalline material having (211) exposed crystal faces by a liquid phase template method. Preferably, the lanthanum oxide polycrystalline material of the present invention also has a larger grain size.

[0014] (3) The preparation method of the lanthanum oxide polycrystalline material of the present invention is simple, the raw materials are readily available, the process is simple, the operation is convenient, the cost is low, and the environment is friendly. The entire reaction process has low requirements on the preparation equipment, is conducive to industrial production, and has practical industrial significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is the BET diagram of the lanthanum oxide polycrystalline material prepared in Example 1;

[0016] Figure 2 is the XRD pattern of the lanthanum oxide polycrystalline material prepared in Example 1;

[0017] Figure 3 is a transmission electron microscope image of the lanthanum oxide polycrystalline material prepared in Example 1;

[0018] Figure 4 This is a transmission electron microscope image of the lanthanum oxide polycrystalline material prepared in Example 3. DETAILED DESCRIPTION

[0019] 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.

[0020] A first aspect of the present invention provides a lanthanum oxide polycrystalline material, wherein the lanthanum oxide polycrystalline material comprises p63 / mmc hexagonal lanthanum oxide, wherein the p63 / mmc hexagonal lanthanum oxide has a (211) exposed crystal plane.

[0021] The inventors of the present invention have found that when the lanthanum oxide polycrystalline material has a (211) exposed crystal plane, the starting reaction temperature of the oxidative coupling reaction can be greatly reduced. This may be because the (211) exposed crystal plane has a higher surface energy, which is more conducive to activating the reaction substrate, thereby reducing the energy required for the reaction and promoting the improvement of catalytic activity.

[0022] According to the present invention, preferably, the lanthanum oxide polycrystalline material further comprises cubic lanthanum oxide and / or monoclinic lanthanum oxide.

[0023] According to the present invention, preferably, the lattice width of the (211) exposed crystal plane of the p63 / mmc hexagonal lanthanum oxide is 0.3±0.05 nm.

[0024] According to the present invention, preferably, the specific surface area of ​​the lanthanum oxide polycrystalline material is 200-350m 2 / g.

[0025] According to the present invention, preferably, the average pore size of the lanthanum oxide polycrystalline material is 1-20 nm.

[0026] According to the present invention, preferably, the pore volume of the lanthanum oxide polycrystalline material is 20-50cm 3 / g.

[0027] According to the present invention, preferably, the average particle size of the lanthanum oxide polycrystalline material is 150-250 nm.

[0028] The second aspect of the present invention provides a method for preparing a lanthanum oxide polycrystalline material, the method comprising: 15 The alkaline solution of phenol, C1-C6 aldehyde and lanthanum source is hydrothermally crystallized to obtain a solid product; and then the solid product is calcined.

[0029] The present invention adopts alcohol, C6-C 15 Phenol and C1-C6 aldehyde are used as templates, and the solution is adjusted to alkalinity. Then, lanthanum oxide polycrystalline materials with specific exposed crystal faces are prepared through hydrothermal crystallization and calcination. The lanthanum oxide polycrystalline materials can significantly reduce the starting reaction temperature of methane oxidative coupling.

[0030] According to the present invention, preferably, the alcohol, C6-C 15 The molar ratio of phenol, C1-C6 aldehyde and lanthanum source is 500-1500:0.5-3:0.5-3:1, more preferably 600-1100:2-2.8:0.5-1.5:1, wherein the lanthanum source is calculated as lanthanum element. 15 The molar ratio of phenol, C1-C6 aldehyde and lanthanum source is limited to the above range, which can further reduce the initial reaction temperature of methane oxidative coupling.

[0031] In the present invention, the molar ratio of alcohol to lanthanum source in the alkaline solution is 500:1, 600:1, 700:1, 800:1, 900:1, 1000:1, 1100:1, 1200:1, 1300:1, 1400:1, 1500:1, and a range consisting of any two of the above points.

[0032] In the present invention, the molar ratio of C1-C6 aldehyde to lanthanum source in the alkaline solution is 0.5:1, 0.8:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 2:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 3:1, and a range consisting of any two of the above points.

[0033] In the present invention, the alkaline solution contains C6-C 15 The molar ratio of phenol to lanthanum source is 0.5:1, 0.8:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 2:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 3:1, and a range consisting of any two of the above points.

[0034] According to the present invention, in order to further reduce the initial reaction temperature of methane oxidative coupling and improve methane conversion rate and C2 hydrocarbon selectivity, preferably, the pH of the alkaline solution is 8-12, for example, it can be 8, 9, 10, 11, 12, and a range consisting of any two of the above points.

[0035] In the present invention, the pH of the alkaline solution is not particularly limited, and can be controlled by conventional methods in the art, such as in alcohol, C6-C 15 An alkali source is added to an aqueous solution of phenol, C1-C6 aldehyde and lanthanum source. According to the present invention, the type of the alkali source is not particularly limited, as long as the pH value of the alkaline solution can meet the requirements. Preferably, the alkali source is an alkali metal hydroxide, more preferably potassium hydroxide and / or sodium hydroxide. Usually, the alkali source is added to the alcohol, C6-C6 aldehyde and lanthanum source in the form of an aqueous solution. 15 In the aqueous solution of phenol, C1-C6 aldehyde and lanthanum source, the concentration of the aqueous solution of alkali source is 5-15wt%.

[0036] According to the present invention, preferably, the alcohol is a C1-C4 monohydric alcohol, more preferably at least one of methanol, ethanol and propanol.

[0037] According to the present invention, preferably, the C6-C 15 Phenol is C6-C 15 dihydric phenol, more preferably C6-C 10 The dihydric phenol is preferably at least one of resorcinol, catechol and hydroquinone.

[0038] According to the present invention, preferably, the C1-C6 aldehyde is a C1-C6 monoaldehyde, more preferably a C1-C3 monoaldehyde, and further preferably at least one of formaldehyde, paraformaldehyde, acetaldehyde and propionaldehyde.

[0039] According to the present invention, preferably, when formaldehyde is used, the formaldehyde is used in the form of an aqueous solution, and the concentration of the formaldehyde aqueous solution is 2-5 wt %.

[0040] According to a particularly preferred embodiment of the present invention, when ethanol, resorcinol and formaldehyde are used as templates, the initial reaction temperature of methane oxidative coupling can be further reduced, and the methane conversion rate and C2 hydrocarbon selectivity can be improved.

[0041] According to the present invention, the lanthanum source can be any substance that can provide lanthanum element. Preferably, the lanthanum source is a water-soluble salt of lanthanum, more preferably at least one of lanthanum nitrate, lanthanum sulfate and lanthanum hydroxide.

[0042] According to the present invention, preferably, the alkaline solution also includes water, and the water content is 30-70wt% (for example, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, and a range consisting of any two of the above points), more preferably 40-65wt%, and further preferably 45-60wt%.

[0043] According to a particularly preferred embodiment of the present invention, the 15 The alkaline solution of phenol, C1-C6 aldehyde and lanthanum source is obtained by:

[0044] (1-1) mixing alcohol and water and stirring at 25-80° C. for 10-120 min to obtain solution A;

[0045] (1-2) Add C6-C to solution A. 15 Phenol and C1-C6 aldehyde are stirred at 25-80°C for 60-720 min to obtain solution B;

[0046] (1-3) Lanthanum nitrate is dissolved in water to obtain a lanthanum nitrate aqueous solution; the lanthanum nitrate aqueous solution is added to solution B, and then a sodium hydroxide solution is added to adjust the pH to obtain an alkaline solution.

[0047] According to the present invention, preferably, in step (1-1), the weight ratio of alcohol to water is 1-5:1, more preferably 1-3:1.

[0048] According to the present invention, preferably, in step (1-3), the concentration of lanthanum nitrate in the lanthanum nitrate aqueous solution is 0.5-3wt%, more preferably 1-2wt%.

[0049] According to the present invention, preferably, the conditions for the hydrothermal crystallization include: a temperature of 120-180° C. and a time of 1-24 h.

[0050] According to the present invention, preferably, the calcination conditions include: a temperature of 600-800° C. and a time of 2-6 hours.

[0051] According to the present invention, preferably, the calcination is performed in an air atmosphere.

[0052] The third aspect of the present invention provides a lanthanum oxide polycrystalline material prepared by the above method.

[0053] A fourth aspect of the present invention provides the use of the above-mentioned lanthanum oxide polycrystalline material in the oxidative coupling reaction of methane to produce C2 and higher hydrocarbons.

[0054] 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 methane oxidative coupling reaction, contacting and reacting methane with the above-mentioned lanthanum oxide polycrystalline material;

[0055] Alternatively, the lanthanum oxide polycrystalline material is prepared according to the method described above, and then methane is contacted with the obtained lanthanum oxide polycrystalline material in the presence of oxygen and under the conditions of methane oxidative coupling reaction.

[0056] According to the present invention, preferably, the molar ratio of the methane to the oxygen (referred to as the alkoxygen ratio) is 5-100:1.

[0057] According to the present invention, preferably, the temperature of the contact reaction is 450-650°C.

[0058] According to the present invention, preferably, the space velocity of methane is 100000-150000 mL / (g·h).

[0059] According to a particularly preferred embodiment of the present invention, the method for preparing lanthanum oxide polycrystalline material comprises:

[0060] (1) Anhydrous ethanol and 30-35 mL of deionized water were mixed and stirred at 30-35° C. for 30-40 min to obtain solution A. Resorcinol and formaldehyde solution were then added to solution A, and then stirred at 30-35° C. for 8-8.5 h to obtain solution B. 0.65-0.7 g of lanthanum nitrate was dissolved in 40-45 mL of deionized water to obtain an aqueous solution of lanthanum nitrate; the aqueous solution of lanthanum nitrate was added to solution B, and then sodium hydroxide solution was added to adjust the pH to 11-11.5 to obtain solution C. Solution C was stirred for 50-60 min and then transferred to a reactor for hydrothermal crystallization at a temperature of 145-150° C. for 10-12 h. The solid product obtained by crystallization was washed by centrifugation with water and anhydrous ethanol, and dried at 80-85° C. for 10-12 h to obtain a powder sample. The molar ratio of ethanol, resorcinol, formaldehyde and lanthanum nitrate in the aqueous solution is 700-720:2.4-2.6:0.5-0.6:1.

[0061] (2) The powder sample obtained in step (1) is placed in air and calcined at 700-720° C. for 4-4.5 hours to obtain a lanthanum oxide polycrystalline material.

[0062] The present invention will be described in detail below by way of examples. In the following examples,

[0063] The concentration of the formaldehyde aqueous solution is 3wt%;

[0064] The concentration of the sodium hydroxide aqueous solution was 10 wt %.

[0065] The analysis of the reaction product components was carried out on a gas chromatograph model 7890A purchased from Agilent.

[0066] The calculation method of methane conversion rate is as follows:

[0067] Methane conversion rate = amount of methane consumed in the reaction / initial amount of methane × 100%.

[0068] The ethylene selectivity is calculated as follows:

[0069] Ethylene selectivity = amount of methane consumed by produced ethylene / total methane consumption x 100%.

[0070] The ethane selectivity is calculated as follows:

[0071] Ethane selectivity = amount of methane consumed by produced ethane / total methane consumption x 100%.

[0072] The calculation method of C2 hydrocarbon yield is as follows:

[0073] C2 hydrocarbon yield = methane conversion × (ethane selectivity + ethylene selectivity).

[0074] Example 1

[0075] (1) Anhydrous ethanol and 20 mL of deionized water were mixed and stirred at 30°C for 30 min to obtain solution A. Resorcinol and formaldehyde aqueous solution were then added to solution A, and then stirred at 30°C for 12 h to obtain solution B. 0.5 g of lanthanum nitrate was dissolved in 30 mL of deionized water to obtain a lanthanum nitrate aqueous solution; the lanthanum nitrate aqueous solution was added to solution B, and then sodium hydroxide aqueous solution was added to adjust the pH to 11.5 to obtain solution C. Solution C was stirred for 60 min and transferred to a reactor for hydrothermal crystallization at a temperature of 160°C and a time of 12 h. The solid product obtained by crystallization was washed three times by centrifugation with water and anhydrous ethanol, and dried at 80°C for 24 h to obtain a powder sample. The molar ratio of ethanol, resorcinol, formaldehyde and lanthanum nitrate in the aqueous solution was 669.02:2.36:1.12:1, and lanthanum nitrate was calculated as lanthanum element.

[0076] (2) The powder sample obtained in step (1) is calcined in air at 700° C. for 4 h to obtain a lanthanum oxide polycrystalline material.

[0077] The BET diagram of the lanthanum oxide polycrystalline material prepared in Example 1 is as follows: Figure 1 As shown, the specific surface area, pore volume and average pore size of lanthanum oxide polycrystalline materials can be obtained through BET analysis.

[0078] The XRD pattern of the lanthanum oxide polycrystalline material prepared in Example 1 is as follows: Figure 2As shown, the transmission electron microscopy (HRTEM) image of the lanthanum oxide polycrystalline material prepared in Example 1 is as follows Figure 3 As shown, through XRD and transmission electron microscopy analysis, it can be concluded that the lanthanum oxide polycrystalline material has p63 / mmc hexagonal lanthanum oxide, and the exposed crystal plane of the p63 / mmc hexagonal lanthanum oxide is the (211) crystal plane and the lattice width of the (211) crystal plane, as well as the crystallinity of the lanthanum oxide polycrystalline material.

[0079] Example 2

[0080] (1) Anhydrous ethanol and 30 mL of deionized water were mixed and stirred at 30°C for 30 min to obtain solution A. Resorcinol and formaldehyde aqueous solution were then added to solution A, and then stirred at 30°C for 8 h to obtain solution B. 0.7 g of lanthanum nitrate was dissolved in 40 mL of deionized water to obtain a lanthanum nitrate aqueous solution; the lanthanum nitrate aqueous solution was added to solution B, and then sodium hydroxide aqueous solution was added to adjust the pH to 11.5 to obtain solution C. Solution C was stirred for 60 min and transferred to a reactor for hydrothermal crystallization at a temperature of 150°C and a time of 12 h. The solid product obtained by crystallization was washed three times by centrifugation with water and anhydrous ethanol, and dried at 80°C for 12 h to obtain a powder sample. The molar ratio of ethanol, resorcinol, formaldehyde and lanthanum nitrate in the aqueous solution was 716.81:2.53:0.56:1, and lanthanum nitrate was calculated as lanthanum element.

[0081] (2) The powder sample obtained in step (1) is calcined in air at 700° C. for 4 h to obtain a lanthanum oxide polycrystalline material.

[0082] Example 3

[0083] The method of Example 1 was followed, except that the temperature of hydrothermal crystallization was 180°C.

[0084] The transmission electron microscopy image of the lanthanum oxide polycrystalline material prepared in Example 3 is as follows: Figure 4 As shown, it can be concluded from the analysis of XRD and transmission electron microscopy that the lanthanum oxide polycrystalline material has p63 / mmc hexagonal lanthanum oxide, and the exposed crystal plane of the p63 / mmc hexagonal lanthanum oxide is the (211) crystal plane, as well as the lattice width of the (211) crystal plane.

[0085] Example 4

[0086] (1) Anhydrous ethanol and 60 mL of deionized water were mixed and stirred at 30°C for 60 min to obtain solution A. Resorcinol and formaldehyde aqueous solution were then added to solution A, and then stirred at 60°C for 8 h to obtain solution B. 0.5 g of lanthanum nitrate was dissolved in 40 mL of deionized water to obtain an aqueous solution of lanthanum nitrate; the aqueous solution of lanthanum nitrate was added to solution B, and then sodium hydroxide aqueous solution was added to adjust the pH to 10.0 to obtain solution C. Solution C was stirred for 120 min and then transferred to a reactor for hydrothermal crystallization at a temperature of 150°C and a time of 12 h. The solid product obtained by crystallization was washed three times by centrifugation with water and anhydrous ethanol, and dried at 80°C for 12 h to obtain a powder sample. The molar ratio of ethanol, resorcinol, formaldehyde and lanthanum nitrate in the aqueous solution was 1075.2:2.53:1.12:1, and lanthanum nitrate was calculated as lanthanum element.

[0087] (2) The powder sample obtained in step (1) is calcined in air at 700° C. for 4 h to obtain a lanthanum oxide polycrystalline material.

[0088] Example 5

[0089] The method of Example 1 was followed, except that resorcinol was replaced with an equal molar amount of phenol.

[0090] Example 6

[0091] The method of Example 1 was followed, except that formaldehyde was replaced with an equal molar amount of glyoxal.

[0092] Example 7

[0093] The method of Example 1 was followed, except that ethanol was replaced with an equal molar amount of ethylene glycol.

[0094] Example 8

[0095] The method of Example 1 was followed, except that sodium hydroxide solution was added to adjust the pH to 8.0 to obtain Solution C.

[0096] Example 9

[0097] The method of Example 1 was followed, except that lanthanum nitrate was replaced with an equal molar amount of lanthanum sulfate.

[0098] Comparative Example 1

[0099] The preparation method reported in "Preparation and Characterization of Nano-lanthanum Oxide Powder" Chemical Industry Times, Vol. 19, No. 2, February 2005, 28-29 was adopted. LaCl3 was mixed with deionized water to form a solution with a concentration of 50 g / L, 200 mL of the LaCl3 aqueous solution was measured and added to a three-necked flask, and 10 mL of an ethanol aqueous solution (2 mol / L) was added to the three-necked flask. 30 wt% ammonia water was added dropwise under stirring until a white precipitate began to appear, and the addition of ammonia water was stopped. Stirring was continued for 30 min, and then the gel was filtered, washed, and dried. The filter cake was calcined at 700° C. for 3 h to obtain nano-La2O3 powder (white).

[0100] XRD characterization shows that the lanthanum oxide prepared in Comparative Example 1 has an irregular amorphous structure and has no exposed crystal faces.

[0101] Comparative Example 2

[0102] The method of Example 1 was followed, except that resorcinol was replaced with an equal molar amount of formaldehyde. XRD characterization showed that the lanthanum oxide prepared in Comparative Example 2 had an irregular amorphous structure and had no exposed crystal faces.

[0103] Test Example 1

[0104] The specific surface area, pore volume, average pore diameter and average particle size of the lanthanum oxide prepared in the above examples and comparative examples were tested. The test results are shown in Table 1.

[0105] The specific surface area, pore volume and average pore size of lanthanum oxide were obtained through BET testing.

[0106] The test method for the average particle size of lanthanum oxide is: select 5-10 samples in the field of view, measure the grain size using a measuring instrument provided with a scanning electron microscope, and then calculate the average particle size of the 5-10 samples in the field of view.

[0107] The crystallinity of lanthanum oxide and the lattice width of the exposed crystal plane (211) were analyzed by XRD and HRTEM tests.

[0108] Table 1

[0109]

[0110]

[0111] Test Example 2

[0112] 0.1 g of the lanthanum oxide prepared in the above examples and comparative examples was weighed, tableted, sieved and loaded into a quartz fixed bed reactor for performance testing. The product was measured by Agilent gas chromatograph 7890A. The reaction space velocity was 100000 ml / gh in terms of methane, the alkoxy ratio was 8, and methane and oxygen were introduced for reaction. The reaction temperature is shown in Table 2. The methane conversion rate, carbon two selectivity and carbon two yield were calculated according to the composition of the product, and the results are shown in Table 2.

[0113] Table 2

[0114]

[0115]

[0116] 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 polycrystalline material, characterized in that: The lanthanum oxide polycrystalline material comprises p63 / mmc hexagonal lanthanum oxide, wherein the p63 / mmc hexagonal lanthanum oxide has a (211) exposed crystal plane.

2. The lanthanum oxide polycrystalline material according to claim 1, wherein: The lattice width of the (211) exposed crystal plane of the p63 / mmc hexagonal lanthanum oxide is 0.3±0.05 nm.

3. The lanthanum oxide polycrystalline material according to claim 1, wherein: The specific surface area of ​​the lanthanum oxide polycrystalline material is 200-350m 2 / g, average pore size is 1-20nm, pore volume is 20-50cm 3 / g; And / or, the average particle size of the lanthanum oxide polycrystalline material is 150-250nm.

4. A method for preparing lanthanum oxide polycrystalline material, characterized in that: The method comprises: 15 The alkaline solution of phenol, C1-C6 aldehyde and lanthanum source is hydrothermally crystallized to obtain a solid product; and then the solid product is calcined.

5. The method according to claim 4, wherein: The alcohol, C6-C 15 The molar ratio of phenol, C1-C6 aldehyde and lanthanum source is 500-1500:0.5-3:0.5-3:1, preferably 600-1100:2-2.8:0.5-1.5:1, wherein the lanthanum source is calculated as lanthanum element; And / or, the pH of the alkaline solution is 8-12.

6. The method according to claim 4, wherein: The alcohol is a C1-C4 monohydric alcohol, preferably at least one of methanol, ethanol and propanol; And / or, the C6-C 15 Phenol is C6-C 15 dihydric phenol, more preferably C6-C 10 The dihydric phenol is further preferably at least one of resorcinol, catechol and hydroquinone; and / or, the C1-C6 aldehyde is a C1-C6 monoaldehyde, more preferably a C1-C3 monoaldehyde, further preferably at least one of formaldehyde, paraformaldehyde, acetaldehyde and propionaldehyde; And / or, the lanthanum source is a water-soluble salt of lanthanum, preferably lanthanum nitrate.

7. The method according to claim 4, wherein: The conditions of the hydrothermal crystallization include: temperature of 120-180° C. and time of 1-24 h.

8. The method according to claim 4, wherein: The calcination conditions include: in an air atmosphere, a temperature of 600-800° C., and a time of 2-6 hours.

9. Lanthanum oxide polycrystalline material prepared by the method according to any one of claims 4 to 8.

10. Use of the lanthanum oxide polycrystalline material according to any one of claims 1 to 3 and 9 in the oxidative coupling reaction of methane to produce C2 and higher hydrocarbons.

11. A method for preparing hydrocarbons with carbon content of two or more carbon atoms from methane, characterized in that: The method comprises: in the presence of oxygen and under the conditions of methane oxidative coupling reaction, contacting and reacting methane with the lanthanum oxide polycrystalline material according to any one of claims 1 to 3 and 9; Alternatively, a lanthanum oxide polycrystalline material is prepared according to the method described in any one of claims 4 to 8, and then methane is contacted with the obtained lanthanum oxide polycrystalline material to react in the presence of oxygen and under the conditions of a methane oxidative coupling reaction.

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