Lanthanum oxide particles, their preparation methods and applications

Abstract

This invention relates to the field of powder forming technology, and discloses a lanthanum oxide particle, its preparation method, and its application. The purity of the lanthanum oxide particle is ≥95%, and the crushing strength of the lanthanum oxide particle is 80-150 N / particle. The lanthanum oxide particles provided in this invention have high mechanical strength, smooth surface, regular shape, and are easy to store. When used to prepare methane oxidative coupling catalysts, they can significantly improve the catalytic activity of the catalyst.

Description

Technical Field

[0001] This invention relates to the field of powder forming technology, specifically to a lanthanum oxide particle, its preparation method, and its application. Background Technology

[0002] Lanthanum is a rare earth element, and lanthanum oxide, as an important lanthanum compound, is widely used in catalysis, especially in the oxidative coupling catalysis of methane. Lanthanum oxide generally exists in powder form, and when preparing lanthanum oxide oxidative coupling catalysts for methane, the lanthanum oxide powder usually needs to be pressed into shape. To improve the purity of lanthanum oxide in the catalyst, the lanthanum oxide powder can be mixed with an organic polymer binder, pressed into shape, and then calcined at high temperature to remove the organic polymer binder, obtaining high-purity lanthanum oxide particles. However, the lanthanum oxide particles prepared by this method generally suffer from poor strength and easy crushing, making them difficult to implement industrially. Summary of the Invention

[0003] The purpose of this invention is to overcome the problems of poor mechanical strength and easy crushing of high-purity lanthanum oxide particles in the prior art, and to provide lanthanum oxide particles, their preparation method and application.

[0004] To achieve the above objectives, a first aspect of the present invention provides lanthanum oxide particles, wherein the purity of the lanthanum oxide particles is ≥95%, and the crushing strength of the lanthanum oxide particles is 80-150 N / particle.

[0005] A second aspect of the present invention provides a method for preparing lanthanum oxide particles, the method comprising the following steps:

[0006] (1) Lanthanum oxide powder, soluble starch, polyethylene glycol and water are mixed and granulated to obtain granular semi-finished product;

[0007] (2) The granular semi-finished product is roasted to obtain the roasted product;

[0008] (3) The calcined product is cooled in an air-isolated environment to obtain lanthanum oxide particles.

[0009] A third aspect of the present invention provides the application of lanthanum oxide particles as described in the first aspect of the present invention or lanthanum oxide particles prepared by the method described in the second aspect of the present invention in catalysts, preferably in methane oxidative coupling catalysts.

[0010] The beneficial technical effects achieved by the present invention through the above technical solution are as follows:

[0011] 1) The method for preparing lanthanum oxide particles provided in this invention can significantly improve the crushing strength of lanthanum oxide particles by cooling them in the absence of air.

[0012] 2) The method for preparing lanthanum oxide particles provided in this invention involves cooling in paraffin, which can reduce production costs. At the same time, a layer of paraffin can be coated on the outer surface of the lanthanum oxide particles to improve the surface smoothness of the lanthanum oxide particles and reduce the difficulty of storage and transportation.

[0013] 3) The lanthanum oxide particles provided in this invention have high mechanical strength, smooth surface, regular shape, and are easy to store. When used to prepare methane oxidative coupling catalysts, they can significantly improve the catalytic activity of the catalysts. Detailed Implementation

[0014] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0015] A first aspect of the present invention provides lanthanum oxide particles, wherein the purity of lanthanum oxide in the lanthanum oxide particles is ≥95%, and the crushing strength of the lanthanum oxide particles is 80-150 N / particle.

[0016] In this invention, the shape of the lanthanum oxide particles is not particularly limited; they can be spherical or strip-shaped, such as solid or hollow columnar. When the lanthanum oxide particles are spherical, their crushing strength is the point crushing strength; when the lanthanum oxide particles are strip-shaped, their crushing strength is the axial crushing strength.

[0017] In a preferred embodiment, the purity of lanthanum oxide in the lanthanum oxide particles is 97-99.9999%, and the crushing strength of the lanthanum oxide particles is 110-140 N / particle.

[0018] In a preferred embodiment, the lanthanum oxide is in the form of strip-shaped particles, preferably solid columnar particles or hollow columnar particles.

[0019] In this invention, the solid columnar particles have a height of 4-18 mm and a diameter of 4-20 mm; the hollow columnar particles have a height of 4-18 mm, a column diameter of 4-20 mm, and a hollow diameter of 1.5-2.5 mm.

[0020] In a preferred embodiment, the outer surface of the lanthanum oxide particles is coated with a layer of paraffin wax. The amount of paraffin wax used is not specifically limited in this invention, as long as it completely coats the lanthanum oxide particles. In this invention, coating the outer surface of the lanthanum oxide particles with a layer of paraffin wax serves two purposes: firstly, it provides a seal, preventing the lanthanum oxide particles from absorbing moisture and becoming damp during storage; secondly, it prevents the lanthanum oxide particles from being worn down due to contact and collision.

[0021] A second aspect of the present invention provides a method for preparing lanthanum oxide particles, the method comprising the following steps:

[0022] (1) Lanthanum oxide powder, soluble starch, polyethylene glycol and water are mixed and granulated to obtain granular semi-finished product;

[0023] (2) The granular semi-finished product is roasted to obtain the roasted product;

[0024] (3) The calcined product is cooled in an air-isolated environment to obtain lanthanum oxide particles.

[0025] In step (1),

[0026] In a preferred embodiment, the average particle size of the lanthanum oxide powder is 10 nm-100 μm, preferably 10 nm-50 μm. The lanthanum oxide powder in this invention can be a commercially available product, such as analytical grade lanthanum oxide powder, or lanthanum oxide powder with a purity of 3N-6N.

[0027] In a preferred embodiment, the soluble starch is selected from one or more of rice starch, corn starch, millet starch, and potato starch. In this invention, the soluble starch and polyethylene glycol work synergistically to increase the adhesiveness of the granular semi-finished product and improve the molding effect.

[0028] In a preferred embodiment, the present invention does not specifically limit the polyethylene glycol; any polyethylene glycol commonly used in the art can be used in the present invention. Preferably, the molecular weight of the polyethylene glycol is 500-40000 g / mol.

[0029] In a preferred embodiment, the mass ratio of lanthanum oxide, soluble starch, and polyethylene glycol is 1:(0.1-1):(0.01-0.8), preferably 1:(0.3-0.8):(0.05-0.5).

[0030] In this invention, by limiting the amounts of lanthanum oxide powder, soluble starch, and polyethylene glycol, the bonding and molding of lanthanum oxide powder can be promoted.

[0031] In a preferred embodiment, the mass ratio of the sum of the masses of lanthanum oxide, soluble starch, and polyethylene glycol to water is 1:0.1-0.4, preferably 1:0.15-0.3.

[0032] In this invention, in order to promote the uniformity of mixing of lanthanum oxide powder, soluble starch and polyethylene glycol, the soluble starch and polyethylene glycol can be prepared into aqueous solutions first, and then mixed with lanthanum oxide powder.

[0033] In a preferred embodiment, the granulation is compression granulation; wherein the operating conditions for compression granulation include: a compression pressure of 20-50 kN, preferably 25-35 kN, and a tableting time of 20-80 s, preferably 30-60 s.

[0034] In this invention, the granulated semi-finished product obtained by pressing under the above-mentioned pressing granulation operation conditions has good formability, which can prevent the granulated semi-finished product from cracking during the roasting process and further improve the crushing strength of the roasted lanthanum oxide granules.

[0035] In step (2),

[0036] In a preferred embodiment, the granular semi-finished product is dried before calcination, preferably at 60-150°C.

[0037] In this invention, drying the granular semi-finished product can improve the internal structure uniformity of the prepared lanthanum oxide granules.

[0038] In a preferred embodiment, the calcination operating conditions include: a calcination heating rate of 1-10℃ / min, preferably 3-7℃ / min; a calcination temperature of 1000-1400℃, preferably 1150-1350℃; and a calcination time of 1-6h, preferably 2-4h.

[0039] In step (3),

[0040] In a preferred embodiment, the calcined product is cooled in an inert gas, inert liquid, or inert solid to obtain lanthanum oxide particles.

[0041] In this invention, "inert" refers to not reacting chemically with lanthanum oxide. The inert gas can be selected from one or more of nitrogen, argon, and helium; the inert liquid can be selected from high-boiling-point solvent oil; and the inert solid is paraffin wax, preferably paraffin wax with a melting point below 70°C.

[0042] When the calcined product is cooled in an inert gas or inert liquid, the calcined product after calcination is directly transferred to an inert gas or inert liquid at the calcination temperature and slowly cooled to room temperature to obtain high-purity (purity ≥ 95%) lanthanum oxide particles.

[0043] When the calcined product is cooled in an inert solid, it is directly transferred to the inert solid at the calcination temperature. The high temperature carried by the calcined product instantly liquefies the inert solid, and the product is surrounded by the liquefied inert solid, allowing for cooling in an air-isolated environment. A rapid temperature drop occurs the instant the calcined product comes into contact with the inert solid; this drastic temperature change further enhances the mechanical strength of the lanthanum oxide particles. When the calcined product cools in the inert solid to near its melting point, the cooled particles are separated from the inert solid, preferably individually, and then further cooled in air to obtain lanthanum oxide particles encapsulated in inert solid.

[0044] In a preferred embodiment, the melting point of the paraffin wax is preferably 50-60°C. In this invention, the paraffin wax is selected to cool and calcine the product, allowing the calcined product to be coated with a layer of paraffin wax. When lanthanum oxide particles coated with paraffin wax are used as a catalyst for methane oxidative coupling, since the paraffin wax is easily volatilized at the reaction temperature and its content is very small, it is not necessary to remove the paraffin wax before use, and it can be used directly as a catalyst.

[0045] A third aspect of the present invention provides the application of lanthanum oxide particles as described in the first aspect of the present invention or lanthanum oxide particles prepared by the method described in the second aspect of the present invention in catalysts, preferably in methane oxidative coupling catalysts.

[0046] The present invention will be described in detail below through embodiments.

[0047] In the examples and comparative examples, lanthanum oxide powder was a commercially available product with a purity of 5N and an average particle size of 10 μm; polyethylene glycol was purchased from Beijing Bailingwei Technology Co., Ltd., with an average molecular weight of 20,000 g / mol and CAS: 25322-68-3; and paraffin wax was purchased from Zhonghai Nanlian, with a melting point of 60°C.

[0048] The tablet compression molding machine, model DP30, was purchased from Beijing Xinlongli Technology Co., Ltd. Particle strength was tested using a particle strength tester, model KC-2A, purchased from Jiangsu Jiangyan Analytical Instrument Factory. Seven lanthanum oxide particles were randomly selected, and their axial crushing strength was tested. The average value was taken as the test result.

[0049] Example 1

[0050] (1) Mix 40g of lanthanum oxide powder, 20g of soluble starch, 6g of polyethylene glycol and 14g of water evenly and put them into a tablet press for tableting. Press at 30kN for 45s to obtain solid cylindrical granules with a height of 5mm and a diameter of 5mm.

[0051] (2) The obtained granular semi-finished product was dried at 120℃ for 4 hours. The dried granular semi-finished product was placed in a muffle furnace and heated to 1350℃ at 5℃ / min. After calcination for 2 hours, it was quickly transferred to paraffin wax, cooled to 60℃ in the absence of air, and then removed one by one from the paraffin wax and cooled to room temperature to obtain lanthanum oxide granules coated with paraffin wax.

[0052] Example 2

[0053] (1) Mix 40g of lanthanum oxide powder, 30g of soluble starch, 3g of polyethylene glycol and 20g of water evenly and put them into a tablet press for tableting. Press at 25kN for 60s to obtain a semi-finished product of granules with a height of 5mm, a diameter of 5mm and a hollow diameter of 2mm.

[0054] (2) The obtained granular semi-finished product was dried at 120℃ for 4 hours. The dried granular semi-finished product was placed in a muffle furnace and heated to 1100℃ at 7℃ / min. After calcination for 4 hours, it was quickly transferred to paraffin wax, cooled to 60℃ in the absence of air, and then removed one by one from the paraffin wax and cooled to room temperature to obtain lanthanum oxide granules coated with paraffin wax.

[0055] Example 3

[0056] (1) Mix 40g of lanthanum oxide powder, 14g of soluble starch, 15g of polyethylene glycol and 18g of water evenly and put them into a tablet press for tableting. Press at 35kN for 30s to obtain a semi-finished product of granules with a height of 5mm, a diameter of 5mm and a hollow diameter of 2mm.

[0057] (2) The obtained granular semi-finished product was dried at 120℃ for 4 hours. The dried granular semi-finished product was placed in a muffle furnace and heated to 1250℃ at 3℃ / min. After calcination for 3 hours, it was quickly transferred to paraffin wax, cooled to 60℃ in the absence of air, and then removed one by one from the paraffin wax and cooled to room temperature to obtain lanthanum oxide granules coated with paraffin wax.

[0058] Example 4

[0059] (1) Mix 40g of lanthanum oxide powder, 20g of soluble starch, 6g of polyethylene glycol and 14g of water evenly and put them into a tablet press for tableting. Press at 30kN for 45s to obtain solid cylindrical granules with a height of 5mm and a diameter of 5mm.

[0060] (2) The obtained granular semi-finished product was dried at 120℃ for 4h. The dried granular semi-finished product was placed in a muffle furnace and heated to 1350℃ at 5℃ / min. After calcination for 2h, it was cooled to room temperature under nitrogen protection to obtain lanthanum oxide granules.

[0061] Comparative Example 1

[0062] (1) Mix 40g of lanthanum oxide powder, 20g of soluble starch, 6g of polyethylene glycol and 14g of water evenly and put them into a tablet press for tableting. Press at 30kN for 45s to obtain solid cylindrical granules with a height of 5mm and a diameter of 5mm.

[0063] (2) The obtained granular semi-finished product was dried at 120℃ for 4 hours. The dried granular semi-finished product was placed in a muffle furnace and heated to 1350℃ at 5℃ / min. After calcination for 2 hours, it was cooled to room temperature in air to obtain lanthanum oxide granules.

[0064] Test Example 1

[0065] The performance of the lanthanum oxide particles prepared in Examples 1-4 and Comparative Example 1 was characterized, and the test results are shown in Table 1:

[0066] Table 1

[0067]

[0068] Note: The purity of lanthanum oxide particles was tested using an X-ray fluorescence spectrometer (manufacturer: Panaco, Germany; specification: ZETIUM). When the lanthanum oxide particles were coated with paraffin, the paraffin shell was removed at high temperature before purity testing. When testing the axial crushing strength of lanthanum oxide particles, if the particles were coated with paraffin, it was not necessary to remove the paraffin shell; the test could be performed directly.

[0069] As can be seen from the results in Table 1, the preparation method provided in this invention can yield lanthanum oxide particles with high purity and high strength, and the obtained lanthanum oxide particles can be directly used as a methane oxidative coupling catalyst.

[0070] The lanthanum oxide particles prepared in Example 1 were pulverized, passed through a 20-40 mesh sieve, and packed into a fixed-bed quartz reactor with an inner diameter of 8 mm for evaluation of the catalytic activity of methane oxidative coupling. The catalyst loading was 0.1 g, the reaction temperature was 700 °C, the volume ratio of methane to oxygen was 3, the space velocity of methane and oxygen was 50000 mL / gh, and after 1 h of reaction, a C2 hydrocarbon yield of 17.6% could be obtained.

[0071] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing lanthanum oxide particles, characterized in that, The method includes the following steps: (1) Lanthanum oxide powder, soluble starch, polyethylene glycol and water are mixed and granulated to obtain granular semi-finished product; (2) The granular semi-finished product is roasted to obtain the roasted product; (3) The calcined product is cooled in an air-isolated environment to obtain lanthanum oxide particles; The average particle size of the lanthanum oxide powder is 10 nm-100 μm; The mass ratio of lanthanum oxide, soluble starch, and polyethylene glycol is 1:(0.1-1):(0.01-0.8). The mass ratio of the sum of the masses of lanthanum oxide, soluble starch, and polyethylene glycol to water is 1:0.1-0.

4.

2. The preparation method according to claim 1, wherein, The average particle size of the lanthanum oxide powder is 10 nm-50 μm.

3. The preparation method according to claim 1, wherein, The soluble starch is selected from one or more of rice starch, corn starch, millet starch, and potato starch.

4. The preparation method according to claim 1, wherein, The molecular weight of the polyethylene glycol is 500-40000 g / mol.

5. The preparation method according to claim 1, wherein, The mass ratio of lanthanum oxide, soluble starch, and polyethylene glycol is 1:(0.3-0.8):(0.05-0.5).

6. The preparation method according to claim 1, wherein, The mass ratio of the sum of the masses of lanthanum oxide, soluble starch, and polyethylene glycol to water is 1:0.15-0.

3.

7. The preparation method according to claim 1, wherein, The granulation is compression granulation; wherein, the operating conditions for compression granulation include: compression pressure of 20-50KN and tableting time of 20-80s.

8. The preparation method according to claim 7, wherein, The granulation is compression granulation; wherein, the operating conditions for compression granulation include: compression pressure of 25-35KN and tableting time of 30-60s.

9. The preparation method according to claim 1, wherein, The roasting operating conditions include: a roasting heating rate of 1-10℃ / min; a roasting temperature of 1000-1400℃; and a roasting time of 1-6h.

10. The preparation method according to claim 9, wherein, The roasting operating conditions include: a roasting heating rate of 3-7℃ / min; a roasting temperature of 1150-1350℃; and a roasting time of 2-4h.

11. The preparation method according to claim 1, wherein, The calcined product is cooled in an inert gas, inert liquid, or inert solid to obtain lanthanum oxide particles.

12. The preparation method according to claim 11, wherein, The calcined product is placed in an inert solid and cooled to obtain lanthanum oxide particles, wherein the inert solid is selected from paraffin wax.

13. The preparation method according to claim 12, wherein, The inert solid is selected from paraffin wax with a melting point of 47-64℃.

14. Lanthanum oxide particles prepared by the method according to any one of claims 1-13, characterized in that, The purity of the lanthanum oxide particles is ≥95%, and the crushing strength of the lanthanum oxide particles is 86-150 N / particle.

15. The lanthanum oxide particles according to claim 14, wherein, The purity of lanthanum oxide in the lanthanum oxide particles is 97%-99.9999%, and the crushing strength of the lanthanum oxide particles is 110-140 N / particle.

16. The lanthanum oxide particles according to claim 14 or 15, wherein, The outer surface of the lanthanum oxide particles is coated with a layer of paraffin.

17. The use of lanthanum oxide particles prepared by any one of claims 1-13 or lanthanum oxide particles according to any one of claims 14-16 in a catalyst.

18. The use of lanthanum oxide particles prepared by any one of claims 1-13 or lanthanum oxide particles according to any one of claims 14-16 in methane oxidative coupling catalysts.

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