Catalyst, process for its preparation and use

Abstract

The application relates to the technical field of methane oxidation coupling reaction catalysts, and discloses a lanthanum oxide series catalyst and a preparation method and application thereof, which are characterized in that (1) doping elements selected from Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Al, Ga, In, Zn, Ce are loaded on lanthanum oxide powder to obtain a doped powder; (2) the doped powder and inorganic forming aids are granulated to obtain a granular semi-finished product, and then the granular semi-finished product is extruded into a strip to obtain a formed granule; (3) the formed granule is calcined and cooled under nitrogen protection to obtain the lanthanum oxide series catalyst; wherein the calcining comprises one-stage calcining and two-stage calcining. The preparation method of the lanthanum oxide series catalyst provided in the application can obtain a catalyst which is excellent in mechanical properties and methane oxidation coupling reaction catalytic performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of methane oxidation coupling reaction catalyst, in particular to a lanthanum oxide catalyst and its preparation method and application. BACKGROUND

[0002] The preparation of ethylene by methane oxidation coupling reaction is one of the most challenging processes, and there is no commercial plant in the world at present. The research and development of catalysts are still in the laboratory or small test stage.

[0003] The active component of the methane oxidation coupling catalyst is mainly lanthanum oxide. In order to improve the catalytic activity of lanthanum oxide, some elements can be doped in the lanthanum oxide. The lanthanum oxide powder and the doping elements can be pressed into shape under the action of inorganic forming aids. However, the connection performance of the lanthanum oxide powder and the inorganic forming aids is poor. The mechanical strength of the catalyst particles obtained by this method is small, which is easy to wear and tear, and it is difficult to meet the requirements of the mechanical strength of the catalyst particles for the fixed bed reactor. SUMMARY

[0004] The purpose of the present application is to solve the problem of poor formability of lanthanum oxide powder and poor connection strength with inorganic forming aids, and to provide a lanthanum oxide catalyst and its preparation method and application.

[0005] In order to achieve the above purpose, the first aspect of the present application provides a preparation method of a lanthanum oxide catalyst, which comprises the following steps:

[0006] (1) loading the doping elements on the lanthanum oxide powder to obtain a doped powder; wherein the doping elements are selected from one or more of Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Al, Ga, In, Zn, Ce;

[0007] (2) first mixing the doped powder and inorganic forming aids and then granulating to obtain a granular semi-finished product, and then extruding the granular semi-finished product to obtain a shaped particle;

[0008] (3) calcining and cooling the shaped particle under nitrogen protection to obtain a lanthanum oxide catalyst; wherein the calcining comprises one-stage calcining and two-stage calcining, the one-stage calcining has a one-stage heating rate of 2-5℃ / min, a one-stage calcining temperature of 500-700℃, and a one-stage calcining time of 2-6h; the two-stage calcining has a two-stage heating rate of 3-8℃ / min, a two-stage calcining temperature of 750-1350℃, and a two-stage calcining time of 2-4h.

[0009] The second aspect of the present application provides a lanthanum oxide-based catalyst, the catalyst comprising lanthanum oxide, a doping element and a molding aid; wherein the molar ratio of lanthanum element to the doping element in the catalyst is 1:0.1-1, preferably 1:0.1-0.5; the mass ratio of the lanthanum oxide to the molding aid is 1:0.1-0.6, preferably 1:0.2-0.4; and the molding aid is selected from silica and / or alumina.

[0010] Preferably, the radial mechanical strength of the lanthanum oxide-based catalyst is 35-60 N / particle, preferably 45-55 N / particle.

[0011] The third aspect of the present application provides the use of the catalyst of the second aspect of the present application in a methane oxidative coupling reaction.

[0012] Through the above technical solution, the present application has the following beneficial technical effects:

[0013] 1) The preparation method of the lanthanum oxide-based catalyst provided in the present application can obtain a catalyst with good mechanical properties and methane oxidative coupling reaction catalytic performance.

[0014] 2) The preparation method of the lanthanum oxide-based catalyst provided in the present application is simple to operate and mild in conditions, and is suitable for industrial promotion. DETAILED DESCRIPTION

[0015] The endpoints of the ranges and any values disclosed herein are not to be construed as limiting. The disclosure should be understood to encompass all values falling within the range, including the range limits (and sub-ranges) established by the endpoints. Ranges can be expressed as from about one particular value to about another; however, when such a range is broader than or includes within its scope the values stated, the term encompasses the broader range as well as the narrower specified ranges within the broader ranges. All numerical values are "about" the indicated value, and allow for variations that include the tolerance in measuring the value, and round off error associated with the measurement of the value. Numeric ranges are inclusive of the numbers at the endpoints.

[0016] The first aspect of the present application provides a preparation method of a lanthanum oxide-based catalyst, the method comprising the following steps:

[0017] (1) loading a doping element on lanthanum oxide powder to obtain a doped powder; wherein the doping element is selected from one or more of Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Al, Ga, In, Zn, Ce;

[0018] (2) first mixing the doped powder and an inorganic molding aid, then granulating to obtain a granular semi-finished product, and then extruding the granular semi-finished product to obtain a molded granule;

[0019] (3) calcining and cooling the shaped particles under nitrogen protection to obtain a lanthanide oxide catalyst; wherein the calcining comprises a first-stage calcining and a second-stage calcining, the first-stage calcining has a first-stage heating rate of 2-5℃ / min, a first-stage calcining temperature of 500-700℃, and a first-stage calcining time of 2-6h; the second-stage calcining has a second-stage heating rate of 3-8℃ / min, a second-stage calcining temperature of 750-1350℃, and a second-stage calcining time of 2-4h.

[0020] In step (1),

[0021] In a preferred embodiment, the doping element is selected from one or more of Mg, Ca, Sr, Ba, Al, Zn, and Ce.

[0022] In the present application, the inventors have found that the doping element can not only improve the catalytic activity of the lanthanide oxide powder, but also improve the connection strength between the inorganic binder and the lanthanide oxide after multi-stage calcining, thereby improving the shaping property of the catalyst particles and improving the mechanical strength of the catalyst particles.

[0023] In a preferred embodiment, the loading comprises dissolving the doping element precursor in water, then adding the lanthanide oxide powder, uniformly mixing at room temperature, and then drying to obtain the doped powder. The doping element precursor contains a soluble compound corresponding to the doping element, including but not limited to nitrate, sulfate, chloride, etc. corresponding to the doping element.

[0024] In a preferred embodiment, the purity of the lanthanide oxide powder is ≥95%, preferably ≥98%. The lanthanide oxide powder in the present application can be a commercially available product, such as a general analytical pure and / or higher 6N grade lanthanide oxide.

[0025] In a preferred embodiment, the molar ratio of the lanthanide oxide powder to the doping element is 1:0.03-0.5, preferably 1:0.08-0.25, based on the molar amount of lanthanum in the lanthanide oxide powder.

[0026] In step (2),

[0027] In a preferred embodiment, the inorganic shaping aid is selected from silica sol and / or alumina sol, preferably silica sol.

[0028] In the present application, the silica sol and alumina sol are not specially limited, and commercially available silica sol and alumina sol can be used in the present application. For example, silica sol with a silica content of 15-30%, preferably 20-30%, or alumina sol with an alumina content of 15-30%, preferably 20-30%, can be used.

[0029] In a preferred embodiment, the mass ratio of lanthanum oxide and inorganic forming aid in the doped powder is 1:0.1-0.6, preferably 1:0.2-0.4, based on the mass of the effective components in the inorganic forming aid. In the present application, the effective components in the inorganic forming aid are silicon dioxide and / or aluminum oxide.

[0030] In a preferred embodiment, in order to improve the mixing uniformity of the doped powder and the inorganic forming aid, the mixed powder after mixing of the doped powder and the inorganic forming aid is ground before granulation.

[0031] In a preferred embodiment, the particle size of the granular semi-finished product is 20-120 mesh, preferably 40-120 mesh.

[0032] In the present application, the doped powder and the inorganic binder are prepared into small particles in a granulator, which can improve the flowability and uniformity of the extrusion material in the extruder in subsequent extrusion, further improving the extrusion effect and the mechanical strength of the shaped particles.

[0033] In a preferred embodiment, the shape of the shaped particles is selected from one of cylindrical, hollow cylindrical, clover-shaped, four-leaf clover-shaped, and gear-shaped.

[0034] In step (3),

[0035] In a preferred embodiment, the heating rate of the second-stage calcination is 1-3℃ / min higher than that of the first-stage calcination.

[0036] In the present application, the inventors have found that two-stage calcination of the shaped particles can allow the doped elements to fully react at the calcination temperature, improve the connection strength between the lanthanum oxide powder and the inorganic binder, and optimize the catalytic activity of the catalyst. When the heating rate of the second-stage calcination is higher than that of the first-stage calcination, the improvement effect on the mechanical strength is better.

[0037] The second aspect of the present application provides a lanthanum oxide-based catalyst, which comprises lanthanum oxide, a doped element, and a forming aid; wherein the molar ratio of lanthanum element to doped element in the catalyst is 1:0.1-1, preferably 1:0.1-0.5; and the mass ratio of lanthanum oxide to forming aid is 1:0.1-0.6, preferably 1:0.2-0.4.

[0038] In a preferred embodiment, the forming aid is selected from silicon dioxide and / or aluminum oxide.

[0039] In a preferred embodiment, the radial mechanical strength of the lanthanum oxide-based catalyst is 35-60 N / particle, preferably 45-55 N / particle.

[0040] In a preferred embodiment, the catalyst is prepared by the method of the first aspect of the application.

[0041] The third aspect of the application provides the use of the catalyst of the second aspect of the application in a methane oxidative coupling reaction.

[0042] The application will be described in detail below by way of examples.

[0043] In the examples and comparative examples, the lanthanum oxide powder is a commercially available product with a purity of 5N, and the silica content in the silica sol is 30wt%. The ball mill is purchased from Nanjing Nan Yi Experiment Instrument Co., Ltd., and the model is XQM-2L.

[0044] Example 1

[0045] (1) 2g of barium nitrate was dissolved in 50g of deionized water, and after stirring until the barium nitrate was completely dissolved, 40g of lanthanum oxide powder was added, and the mixture was continuously stirred until it was uniformly mixed, and then the mixture was heated at 120°C for 2h to obtain a doped powder;

[0046] (2) The doped powder was first placed in a ball mill and ball milled for 20min, and then mixed with 40g of silica sol and put into a granulator to perform granulation, to obtain a granular semi-finished product with a particle size of 80-120 mesh; then the obtained granular semi-finished product was put into an extrusion molding machine to perform extrusion, to obtain a clover-shaped long strip;

[0047] (3) The clover-shaped long strip was placed in a muffle furnace, and under the protection of nitrogen, the temperature was first raised to 650°C at a rate of 2°C / min, and calcined for 2h to complete the first-stage calcination, and then the temperature was raised to 1350°C at a rate of 5°C / min, and calcined for 2h to complete the second-stage calcination, and then cooled to room temperature under the protection of nitrogen, to obtain a lanthanum oxide-based catalyst.

[0048] Example 2

[0049] (1) 4g of zinc nitrate hexahydrate was dissolved in 50g of deionized water, and after stirring until the barium nitrate was completely dissolved, 40g of lanthanum oxide powder was added, and the mixture was continuously stirred until it was uniformly mixed, and then the mixture was heated at 120°C for 2h to obtain a doped powder;

[0050] (2) The doped powder was first placed in a ball mill and ball milled for 20min, and then mixed with 30g of silica sol and put into a granulator to perform granulation, to obtain a granular semi-finished product with a particle size of 80-120 mesh; then the obtained granular semi-finished product was put into an extrusion molding machine to perform extrusion, to obtain a gear-shaped long strip;

[0051] (3) The obtained gear-shaped long strip is placed in a muffle furnace, and first heated to 500°C at a heating rate of 5°C / min under nitrogen protection, baked for 6h to complete the first-stage baking, then heated to 1110°C at a heating rate of 8°C / min, baked for 4h to complete the second-stage baking, and then cooled to room temperature under nitrogen protection to obtain a lanthanum oxide-based catalyst.

[0052] Example 3

[0053] (1) 6g of cerium nitrate hexahydrate is dissolved in 50g of deionized water, and after stirring until the barium nitrate is completely dissolved, 40g of lanthanum oxide powder is added, and the mixture is continuously stirred until uniform, and then heated at 120°C for 2h to obtain a doped powder;

[0054] (2) The doped powder is first placed in a ball mill and ball milled for 20min, then mixed with 50g of silica sol and placed in a granulator to perform granulation, to obtain a granular semi-finished product of 80-120 mesh; then the obtained granular semi-finished product is placed in an extrusion molding machine to perform extrusion, to obtain a gear-shaped long strip;

[0055] (3) The obtained gear-shaped long strip is placed in a muffle furnace, and first heated to 550°C at a heating rate of 5°C / min under nitrogen protection, baked for 4h to complete the first-stage baking, then heated to 1250°C at a heating rate of 8°C / min, baked for 3h to complete the second-stage baking, and then cooled to room temperature under nitrogen protection to obtain a lanthanum oxide-based catalyst.

[0056] Example 4

[0057] (1) 2g of barium nitrate is dissolved in 50g of deionized water, and after stirring until the barium nitrate is completely dissolved, 40g of lanthanum oxide powder is added, and the mixture is continuously stirred until uniform, and then heated at 120°C for 2h to obtain a doped powder;

[0058] (2) The doped powder is first placed in a ball mill and ball milled for 20min, then mixed with 40g of silica sol and placed in a granulator to perform granulation, to obtain a granular semi-finished product of 80-120 mesh; then the obtained granular semi-finished product is placed in an extrusion molding machine to perform extrusion, to obtain a clover-shaped long strip;

[0059] (3) The obtained clover-shaped long strip is placed in a muffle furnace, and first heated to 650°C at a heating rate of 5°C / min under nitrogen protection, baked for 2h to complete the first-stage baking, then heated to 1350°C at a heating rate of 5°C / min, baked for 2h to complete the second-stage baking, and then cooled to room temperature under nitrogen protection to obtain a lanthanum oxide-based catalyst.

[0060] Comparative Example 1

[0061] (1) 40 g of lanthanum oxide powder was placed in a ball mill and ball-milled for 20 min, then mixed with 40 g of silica sol and put into a granulator to be granulated, to obtain granular semi-finished products of 20-120 mesh; then the obtained granular semi-finished products were put into an extrusion molding machine to be extruded, to obtain clover-shaped long strips;

[0062] (2) The obtained clover-shaped long strips were placed in a muffle furnace, under nitrogen protection, first heated to 650℃ at a heating rate of 2℃ / min, calcined for 2 h to complete the first-stage calcination, then heated to 1350℃ at a heating rate of 5℃ / min, calcined for 2 h to complete the second-stage calcination, then cooled to room temperature under nitrogen protection, to obtain a lanthanum oxide-based catalyst.

[0063] Comparative Example 2

[0064] (1) 2 g of barium nitrate was dissolved in 50 g of deionized water, after stirring until the barium nitrate was completely dissolved, 40 g of lanthanum oxide powder was added, and the mixture was continuously stirred until uniform, then heated at 120℃ for 2 h, to obtain a doped powder;

[0065] (2) The above doped powder was first placed in a ball mill and ball-milled for 20 min, then mixed with 40 g of silica sol and put into a granulator to be granulated, to obtain granular semi-finished products of 20-120 mesh; then the obtained granular semi-finished products were put into an extrusion molding machine to be extruded, to obtain clover-shaped long strips;

[0066] (3) The obtained clover-shaped long strips were placed in a muffle furnace, under air atmosphere, heated to 1350℃ at a heating rate of 2℃ / min, calcined for 4 h, and cooled to room temperature, to obtain a lanthanum oxide-based catalyst.

[0067] Comparative Example 3

[0068] (1) 2 g of barium nitrate was dissolved in 50 g of deionized water, after stirring until the barium nitrate was completely dissolved, 40 g of lanthanum oxide powder was added, and the mixture was continuously stirred until uniform, then heated at 120℃ for 2 h, to obtain a doped powder;

[0069] (2) The above doped powder was first placed in a ball mill and ball-milled for 20 min, then mixed with 40 g of silica sol and put into an extrusion molding machine to be extruded, to obtain clover-shaped long strips;

[0070] (3) The obtained clover-shaped long strips were placed in a muffle furnace, under nitrogen atmosphere, heated to 1350℃ at a heating rate of 2℃ / min, calcined for 4 h, and cooled to room temperature, to obtain a lanthanum oxide-based catalyst.

[0071] Test Example 1

[0072] The radial mechanical strength of the lanthanum oxide series catalysts in Examples 1-4 and Comparative Examples 1-3 was tested by using a particle strength tester, Model KC-2A, purchased from Jiangyan City, Jiangsu Province, China. Seven lanthanum oxide series catalysts were randomly selected, and the radial mechanical strength of each was tested. The average value of the radial mechanical strength of the seven lanthanum oxide series catalysts was taken as the test result. The test results are shown in Table 1.

[0073] Test Example 2

[0074] The catalytic activity of the lanthanum oxide series catalysts in Examples 1-4 and Comparative Examples 1-3 was tested in a fixed bed reactor. The fixed bed reactor had an inner diameter of 4 mm. The lanthanum oxide series catalysts were crushed and sieved to 40-60 mesh. The catalyst loading was 0.1 g. The reaction temperature was 760°C. The space velocity of methane was 30,000 mL / g-h. The volume ratio of methane to oxygen was 3. After 1 h of reaction, the reaction product was collected and analyzed. The analysis results are shown in Table 1.

[0075] Table 1

[0076]

[0077] As can be seen from the results in Table 1, the preparation method of the lanthanum oxide series catalysts provided in the present application can produce a catalyst having both good mechanical properties and good catalytic properties for the methane oxidative coupling reaction.

[0078] The preferred embodiments of the present application have been described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as disclosed in the present application and fall within the protection scope of the present application.

Claims

1. A method for preparing a lanthanide oxide catalyst, characterized in that, The method includes the following steps: (1) Loading a doping element onto lanthanum oxide powder to obtain doped powder; wherein the doping element is selected from one or more of Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Al, Ga, In, Zn, Ce; (2) First, the doped powder and inorganic molding aid are mixed and then granulated to obtain a semi-finished particle product. Then, the semi-finished particle product is extruded to obtain shaped particles. (3) The shaped particles are calcined and cooled under nitrogen protection to obtain lanthanide catalyst; wherein the calcination includes a first stage calcination and a second stage calcination, the first stage calcination heating rate is 2-5℃ / min, the first stage calcination temperature is 500-700℃, and the first stage calcination time is 2-6h; the second stage calcination heating rate is 3-8℃ / min, the second stage calcination temperature is 750-1350℃, and the second stage calcination time is 2-4h.

2. The preparation method according to claim 1, wherein, The purity of the lanthanum oxide powder is ≥95%.

3. The preparation method according to claim 1, wherein, The purity of the lanthanum oxide powder is ≥98%.

4. The preparation method according to claim 1, wherein, The molar ratio of lanthanum oxide powder to dopant element is 1:0.03-0.5, based on the molar amount of lanthanum in the lanthanum oxide powder.

5. The preparation method according to claim 1, wherein, The molar ratio of lanthanum oxide powder to dopant element is 1:0.08-0.25, based on the molar amount of lanthanum in the lanthanum oxide powder.

6. The preparation method according to any one of claims 1-5, wherein, The inorganic molding aid is selected from silica sol and / or aluminum sol.

7. The preparation method according to any one of claims 1-5, wherein, The inorganic molding aid is silica sol.

8. The preparation method according to any one of claims 1-5, wherein, Based on the mass of the effective component in the inorganic forming aid, the mass ratio of lanthanum oxide to inorganic forming aid in the doped powder is 1:0.1-0.

6.

9. The preparation method according to any one of claims 1-5, wherein, Based on the mass of the effective component in the inorganic forming aid, the mass ratio of lanthanum oxide to inorganic forming aid in the doped powder is 1:0.2-0.

4.

10. The preparation method according to any one of claims 1-5, wherein, The particle size of the semi-finished granules is 20-120 mesh.

11. The preparation method according to any one of claims 1-5, wherein, The particle size of the semi-finished granules is 80-120 mesh.

12. The preparation method according to any one of claims 1-5, wherein, The shape of the molded granules is selected from one of the following: cylindrical, hollow cylindrical, clover-shaped, four-leaf clover-shaped, and gear-shaped.

13. The preparation method according to any one of claims 1-5, wherein, The heating rate of the second-stage roasting is 1-6℃ / min higher than that of the first-stage roasting.

14. A lanthanide oxidation catalyst, characterized in that, The catalyst comprises lanthanum oxide, a dopant element, and a forming aid; wherein, in the catalyst, the molar ratio of lanthanum to the dopant element is 1:0.1-1; the mass ratio of lanthanum oxide to the forming aid is 1:0.1-0.6; and the forming aid is selected from silicon dioxide and / or aluminum oxide. The lanthanide oxide catalyst is prepared by the method according to any one of claims 1-13.

15. The lanthanide oxide catalyst according to claim 14, wherein, In the catalyst, the molar ratio of lanthanum to dopant is 1:0.1-0.

5.

16. The lanthanide oxide catalyst according to claim 14, wherein, The mass ratio of lanthanum oxide to molding aid is 1:0.2-0.

4.

17. The lanthanide oxide catalyst according to claim 14, wherein, The radial mechanical strength of the lanthanide oxide catalyst is 35-60 N / particle.

18. The lanthanide oxide catalyst according to claim 14, wherein, The radial mechanical strength of the lanthanide oxide catalyst is 45-55 N / particle.

19. The use of the catalyst according to any one of claims 14-18 in the oxidative coupling reaction of methane.

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