A spherical catalyst and a preparation method and application thereof

Abstract

The application discloses a spherical catalyst and a preparation method and application thereof. The catalyst comprises Pt and alumina, and the preparation method of the catalyst comprises the following steps: mixing an alumina hydroxide sol with a Pt-containing aqueous solution, dropping the obtained mixture into an oil-ammonia water-oil-water four-layer mixed column to form, drying and calcining, and obtaining the spherical catalyst. The catalyst is applied to a propane dehydrogenation reaction, and has good stability and good reaction performance.

Description

TECHNICAL FIELD

[0001] The present application relates to a spherical catalyst and a preparation method and application thereof, in particular to a spherical noble metal catalyst suitable for a boiling bed and a preparation method and application thereof. BACKGROUND

[0002] The shape and size of catalyst particles are generally determined according to the requirements of the reactor used in industrial production. Currently, there are four types of reactors commonly used in industry: fixed bed, fluidized bed (boiling bed), suspended bed and moving bed. The fixed bed reactor often uses spherical, cylindrical strip, three-leaf clover, four-leaf clover and sheet-shaped catalysts. The moving bed reactor often uses large-particle spherical catalysts. The fluidized bed reactor generally uses small-particle spherical or strip-shaped catalysts.

[0003] Spherical catalysts have good flow performance and high packing factor, uniform fluid distribution, low resistance and small pressure drop, and are widely used in the technology of dehydrogenation of low-carbon alkanes to produce olefins.

[0004] Currently, the catalyst for dehydrogenation of low-carbon alkanes to produce olefins is mainly prepared by loading active components Pt and other additives on a γ-Al2O3 carrier, such as EP100222A, CN1185994A, etc. However, since the dehydrogenation reaction is carried out at a high temperature of about 600℃, the high reaction temperature often causes a large amount of carbon deposition on the catalyst. As the use time of the catalyst increases, the catalyst needs to be treated by high-temperature carbon burning and regeneration multiple times, which causes the γ-Al2O3 carrier to easily sinter and α-phase change, greatly reduces the specific surface area of the carrier, destroys the pore structure, and further causes the active components of the catalyst to aggregate, thus seriously reducing the activity of the catalyst. Therefore, it is necessary to further modify the γ-Al2O3 carrier to make the catalyst have high thermal stability.

[0005] CN112973771A discloses a spherical catalyst carrier containing molecular sieve and alumina and a preparation and application thereof. The catalyst carrier is prepared by precipitating an inorganic aluminum salt with ammonia water and acidifying to obtain a sol, adding a mixed solution of ball-milled pseudoboehmite and molecular sieve and a sol modification additive to the sol, then drop-sphering and aging in an oil-ammonia column, and finally washing, drying and calcining to obtain a high-strength large-specific-surface-area composite pellet. The method is to mix the suspension slurry of the pseudoboehmite and the molecular sieve after ball milling with the dilute sol again, which will cause uneven dispersion of the molecular sieve. At the same time, the doping of solid molecular sieve will also cause the strength of the carrier to decrease.

[0006] CN105478100A discloses a method for preparing silicon-containing γ-Al2O3 pellets. The method is to stir and slurry pseudo-boehmite dry glue powder and deionized water, add dilute nitric acid for acidification, then add urea and a predetermined amount of sodium silicate solution, stir for 5 hours, add kerosene and fatty alcohol polyoxyethylene ether and stir for 5 hours, drop ball forming in an oil-ammonia column, solidify the wet ball in ammonia water for 2 hours, then filter, rinse with deionized water, dry, and calcine to obtain silicon-containing γ-Al2O3 pellets. The method has long solidification time, difficult washing, and low production efficiency. SUMMARY

[0007] In view of the deficiencies of the prior art, the present application provides a spherical catalyst, a preparation method thereof and an application thereof. The spherical catalyst has good roundness, high crushing strength, large pore volume and pore size, uniform Pt loading, and no peculiar smell, and the like. The catalyst has good stability and good reaction performance when applied to a propane dehydrogenation reaction.

[0008] The first aspect of the present application provides a preparation method of a spherical catalyst, wherein the catalyst comprises Pt and alumina, and the preparation method comprises:

[0009] The alumina hydroxide sol is mixed with a Pt-containing aqueous solution, and the obtained mixture is dropped into an oil-ammonia water-oil-water four-layer mixed column for forming, drying, and calcining to obtain the spherical catalyst.

[0010] Further, the alumina content in the alumina hydroxide sol is 15wt%-26wt%.

[0011] Further, the preparation method of the alumina hydroxide sol comprises: mixing alumina hydroxide with water to obtain a slurry, and adding a peptizing agent to obtain the alumina hydroxide sol after uniform stirring. Further, the peptizing agent is selected from one or more of inorganic acids (such as nitric acid), organic acids (such as acetic acid, citric acid), and preferably nitric acid. When the peptizing agent contains inorganic acid, the mass concentration of the inorganic acid is 30%-50%. When the peptizing agent contains organic acid, the mass concentration of the organic acid is 30%-50%. Further, the addition amount of the peptizing agent is 1wt%-10wt% of the mass of the alumina hydroxide in terms of acid, and preferably 2wt%-8wt%. Further, the alumina hydroxide is preferably water-containing alumina hydroxide, such as alumina hydroxide wet material. Preferably, the water content in the alumina hydroxide is 17wt%-25wt%. Preferably, the properties of the alumina hydroxide after calcination are as follows: specific surface area is 110-201 m 2 / g, pore volume is 0.8-2.0 mL / g, and average pore diameter is 15-17 nm. The calcination conditions are as follows: temperature is 600-850°C, time is 2-12 h, and oxygen-containing atmosphere is, for example, air. The aluminum hydroxide can be commercially available or prepared by a conventional method. The aluminum hydroxide is preferably hydrous macroporous pseudoboehmite, and the water content is 19 wt% to 23 wt%.

[0012] Further, the platinum-containing compound used in the Pt-containing aqueous solution is one or more of platinum chloride (PtCl4) and chloroplatinic acid (H2PtCl6), and is preferably chloroplatinic acid. Further, the Pt-containing aqueous solution contains stannous chloride (SnCl2) and hydrochloric acid.

[0013] Further, the concentration of the platinum-containing compound in the Pt-containing aqueous solution is 2 wt% to 6 wt%. The amount of the Pt-containing aqueous solution to be added is 8% to 40%, preferably 15% to 30%, of the mass of the aluminum hydroxide sol in terms of aluminum oxide.

[0014] Further, in the Pt-containing aqueous solution, the concentration of stannous chloride (SnCl2) is 0.5 wt% to 3.5 wt%, and the concentration of hydrochloric acid is 5 wt% to 12 wt%.

[0015] Further, the oil-ammonia water-oil-water four-layer mixed column is a straight column, and is preferably a cylindrical column.

[0016] Further, in the oil-ammonia water-oil-water four-layer mixed column, four layers are provided in order from top to bottom, the first layer is a first oil layer, the second layer is an ammonia water layer, the third layer is a second oil layer, and the fourth layer is a water layer.

[0017] Further, in the oil-ammonia water-oil-water four-layer mixed column, the first layer is a first oil layer, and is selected from one or more of white oil or diesel oil, and is preferably white oil. The white oil has a kinematic viscosity of 20 to 40 mm 2 / s at 40°C, and preferably 25 to 35 mm 2 / s at 40°C. The height of the first layer is 30% to 50% of the height of the second layer.

[0018] Further, in the oil-ammonia water-oil-water four-layer mixed column, the second layer is an ammonia water layer, and the concentration of the ammonia water is 20 wt% to 28 wt%, and preferably 22 wt% to 26 wt%.

[0019] Further, in the oil-ammonia water-oil-water four-layer mixed column, the third layer is a second oil layer, i.e., a liquid seal oil layer, and has a density between the second layer of ammonia water and the fourth layer of water, and a kinematic viscosity of 60 mm 2one or more plant oils, preferably a mixture of castor oil and soybean oil, wherein the volume ratio of castor oil to soybean oil is 1 / 4 to 1 / 6. The castor oil has a kinematic viscosity at 40°C of 500 to 650 mm 2 / s, preferably 570 to 600 mm 2 / s; and the soybean oil has a kinematic viscosity at 40°C of 10 to 25 mm 2 / s, preferably 13 to 17 mm 2 / s. The third layer has a height of 30% to 50%, preferably 35% to 45%, of the height of the second layer.

[0020] Further, in the oil-ammonia water-oil-water four-layer mixed column, the fourth layer is a water layer, preferably deionized water or a dilute acid solution. The height of the fourth layer is 1.0 to 2.0 times, preferably 1.2 to 1.5 times, the height of the second layer.

[0021] Further, the fourth layer preferably uses a dilute acid solution. In the dilute acid solution, the acid is selected from at least one of acetic acid and citric acid. The mass concentration of the dilute acid solution is 3% to 8%.

[0022] Further, the preparation method of the oil-ammonia water-oil-water four-layer mixed column comprises:

[0023] (1) Pour the required material of the fourth layer into a columnar container (preferably an organic glass container) and ensure uniform solution;

[0024] (2) Slowly add the required material of the third layer to the fourth layer material of step (1), and stabilize for 20 to 35 minutes;

[0025] (3) Slowly add the required material of the second layer to the third layer material of step (2);

[0026] (4) Slowly add the required material of the first layer to the second layer material of step (3) to obtain an oil-ammonia water-oil-water four-layer mixed column. Preferably, during the addition of the required material of the first layer, a peristaltic pump is used to slowly circulate up and down above the interface between the first layer and the second layer, so that the surface tension at the interface between the first layer and the second layer is reduced, and then it is left to stand for 30 to 60 minutes until it is stable. This can ensure that the aluminum hydroxide sol can quickly pass through the contact interface between the first layer and the second layer, preventing the generation of tailing due to stagnation and affecting the true circularity.

[0027] Further, the spherical catalyst is formed in the oil-ammonia water-oil-water four-layer mixed column, and the mixture of aluminum hydroxide sol and Pt-containing aqueous solution is dropped into the oil-ammonia water-oil-water four-layer mixed column, wherein the inner diameter of the drop head used is 1.0 mm to 1.6 mm.

[0028] Further, the residence time of the mixture of the aluminum hydroxide sol and the Pt-containing aqueous solution in the oil-ammonia water-oil-water four-layer mixing column is 5-18 s, preferably 7-11 s.

[0029] Further, the drying temperature is 100-150℃, and the drying time is 6-10 hours; the calcination temperature is 750-950℃, and the calcination time is 1-4 hours.

[0030] The second aspect of the present application provides a spherical catalyst prepared by the above preparation method.

[0031] Further, the specific surface area of the spherical catalyst is 70-110 m 2 / g, and the pore volume is 0.60-0.80 mL / g.

[0032] Further, the average diameter of the spherical catalyst particles is 1.6-1.9 mm.

[0033] Further, the pore size distribution of the spherical catalyst is as follows: the pore volume of the pores with a pore size less than 2 nm accounts for 0.4%-4.5% of the total pore volume, and the pore volume of the pores with a pore size of 2-50 nm accounts for 95.0%-99.2%, preferably 97.0%-99.0%, of the total pore volume.

[0034] Further, the average pore size of the spherical catalyst is 12-18 nm.

[0035] Further, the crushing strength of the spherical catalyst is 62-85 N / particle.

[0036] Further, the sphericity of the spherical catalyst is 95.2%-99.9%.

[0037] Further, in the spherical catalyst, the content of Pt as an oxide is 0.2%-1.0%, the content of Sn as an oxide is 0.02%-0.82%, and the content of alumina is 98.1%-99.8%, based on the mass of the catalyst.

[0038] The fourth aspect of the present application provides the use of the above catalyst in a propane dehydrogenation reaction.

[0039] Further, the use includes: contacting a propane raw material with the catalyst to perform a dehydrogenation reaction, and obtaining a product propylene.

[0040] Further, the catalyst needs to be reduced before use. The catalyst precursor is reduced under a reducing atmosphere. The reducing atmosphere is preferably H2, the reduction temperature is 450-600℃, and the reduction time is 1-3 h.

[0041] Further, the propane dehydrogenation reaction conditions are preferably as follows: the reaction temperature is 500-600 DEG C, the reaction pressure is 0-1 MPa, the volume space velocity is 50-200 h -1 .

[0042] Compared with the prior art, the present application has the advantages of:

[0043] (1) The present application adopts one-step synthesis of spherical catalyst, and Pt-containing aqueous solution is added into the aluminum hydroxide sol, so that the metal is uniformly dispersed in the catalyst, and also plays a role of hole expansion. The four-layer oil-ammonia water-oil-water mixed column is different from the two-layer oil-ammonia column or hot oil column, and the third layer of oil layer is added as a liquid seal oil layer and the fourth layer of water layer, so that the sol can quickly enter the third layer of second oil layer and the fourth layer of water layer after passing through the second layer of ammonia water layer, and the pH value is quickly reduced to neutral, so that the small ball is not easy to break or shrink during the drying process with the volatilization of the surface ammonia water, so that the catalyst particle size and mechanical strength are obviously increased, and at the same time, the metal and the carrier are in full contact, and the loading is more uniform. In addition, the rapid decrease of the pH value of the sol small ball surface also makes the hydrophobicity of the colloidal particle surface decrease rapidly, the interaction force between the colloidal particles increases obviously, the distance between the colloidal particles becomes shorter, and the original structure collapses partially, resulting in an increase in the mesoporous structure of the catalyst in the range of 2-50 nm. By adding an appropriate amount of acidic solution into the fourth layer of water layer, the pore structure can be further optimized.

[0044] (2) The preparation process of the present application is environmentally friendly. In the traditional oil-ammonia column balling process, the volatilization of ammonia water causes serious environmental pollution and subsequent pollutant emission problems. The present application separates the second layer of ammonia water layer from the fourth layer of water layer by the second oil layer, so that the ammonia water layer is sealed above the fourth layer of water layer, which can prolong the service time and avoid environmental pollution caused by the product taking out the ammonia water. After long-term use, the deionized water can be replaced to ensure the liquid sealing effect. The industrial operation is simple and cost-saving.

[0045] (3) The present application adopts one-step synthesis, which is more simple and cost-saving, and is beneficial to industrial operation. The spherical catalyst of the present application has high propane conversion rate and propylene selectivity in the reaction of propane to propylene, and the macroporous and pore volume catalyst can avoid carbon deposition after long-term operation, and has good stability and good reaction performance. DETAILED DESCRIPTION

[0046] The spherical catalyst and its preparation method and application effect will be further illustrated by the following examples. The examples are implemented on the premise of the technical scheme of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following examples.

[0047] The experimental methods in the following examples are the conventional methods in the art, unless otherwise specified. The experimental materials used in the following examples are purchased from the conventional biochemical reagent stores, unless otherwise specified.

[0048] In the present application, the nitrogen adsorption-desorption curve of the sample is tested at -196℃ by using the ASAP2020 full-automatic physical adsorption instrument of the American Micromeritics Company to determine the specific surface area, pore volume and pore size distribution.

[0049] In the present application, the crushing strength is tested by using the ZQJ-III intelligent particle strength tester manufactured by the Dalian Zhiqu Testing Machine Factory, and the average value of crushing ten spherical catalysts is tested.

[0050] In the present application, the true circularity is tested by using the electronic microscope of the Olympus Company, and the average value is calculated after testing 20 samples.

[0051] Example 1

[0052] Take 250g of the macroporous pseudoboehmite filter cake with a water content of 22wt% (calcined at 600℃ for 3h in air atmosphere, and the properties are as follows: pore volume 0.87ml / g, specific surface area 175m 2 / g, and average pore diameter 16nm), add deionized water to stir and uniformly pulp, then add 26g of a nitric acid solution with a mass concentration of 45% to peptize, and finally prepare a pseudoboehmite sol with an alumina mass content of 20%; take 300g of the above sol (alumina content 20wt%), add 12g of a chloroplatinic acid solution with a chloroplatinic acid concentration of 3wt%, which contains 0.8% of stannous chloride and 7% of hydrochloric acid at the same time, and stir uniformly to obtain a sol mixture;

[0053] Use a nozzle with an inner diameter of 1.2mm to drop the above sol into a four-layer mixed column (cylinder) of white oil (40℃ kinematic viscosity 32mm 2 / s) - ammonia water with a concentration of 25wt% - mixed oil - deionized water, and the residence time in the four-layer mixed column is 8s. Among them, the addition amount of white oil is 35% of the volume of ammonia water, the addition amount of mixed oil is 38% of the volume of ammonia water, and the addition amount of deionized water is 1.3 times of the volume of ammonia water; the mixed oil is mixed by castor oil with a kinematic viscosity of 580mm 2 / s at 40℃ and soybean oil with a kinematic viscosity of 15mm 2 / s at a volume ratio of 1:5. Then dry at 130℃ for 8 hours, calcine at 800℃ for 3 hours to obtain the spherical catalyst A of the present application, and the analysis results are shown in Table 1.

[0054] Example 2

[0055] The difference between Example 1 and Example 2 is that the material in the fourth layer is changed from deionized water to 5wt% dilute acetic acid solution to obtain spherical catalyst B of the present application, and the analysis results are shown in Table 1.

[0056] Example 3

[0057] The difference between Example 1 and Example 3 is that the sol mixture synthesis process is as follows: 300g of pseudo-boehmite sol (alumina content of 20wt%) is added with 15.6g of chloroplatinic acid solution with a chloroplatinic acid concentration of 6%, which contains stannous chloride with a concentration of 1.0% and hydrochloric acid with a concentration of 9% at the same time, to obtain spherical catalyst C of the present application, and the analysis results are shown in Table 1.

[0058] Example 4

[0059] The difference between Example 1 and Example 4 is that the white oil in the four-layer mixing column is changed to white oil with a kinematic viscosity of 23mm 2 / s at 40°C, the ammonia water concentration is changed to 21wt%, and the volume ratio of castor oil to soybean oil is changed to 1:4, to obtain spherical catalyst D of the present application, and the analysis results are shown in Table 1.

[0060] Example 5

[0061] The difference between Example 1 and Example 5 is that the white oil in the four-layer mixing column is changed to a mixture of diesel oil and white oil with a mixing mass ratio of 1:1, and the ammonia water concentration is changed to 28wt%, to obtain spherical catalyst E of the present application, and the analysis results are shown in Table 1.

[0062] Example 6

[0063] The difference between Example 1 and Example 6 is that the chloroplatinic acid concentration in the sol mixture is changed to 6wt%, and the white oil in the four-layer mixing column is changed to white oil with a kinematic viscosity of 28mm 2 / s at 40°C, the ammonia water concentration is changed to 23wt%, and the volume ratio of castor oil to soybean oil is changed to 1:4, to obtain spherical catalyst F of the present application, and the analysis results are shown in Table 1.

[0064] Example 7

[0065] The difference between Example 1 and Example 7 is that the amount of white oil added is 42% of the volume of ammonia water, the amount of mixed oil added is 32% of the volume of ammonia water, and the amount of deionized water added is 1.6 times the volume of ammonia water, to obtain spherical catalyst G of the present application, and the analysis results are shown in Table 1.

[0066] Comparative Example 1

[0067] The sol mixture synthesis step is the same as Example 1.

[0068] Comparative Example 1 except that the four-layer oil-ammonia water-oil-water mixed column was changed to a two-layer oil-ammonia column, the upper layer was white oil with a kinematic viscosity of 32 mm 2 / s at 40°C, and the lower layer was ammonia water with a concentration of 25 wt%, the amount of white oil added was 25% of the volume of ammonia water, to obtain a comparative spherical catalyst H of the application, the analysis results of which are shown in Table 2.

[0069] Comparative Example 2

[0070] The sol mixture synthesis step was the same as in Example 1.

[0071] Comparative Example 1 except that only the first layer of white oil in the four-layer oil-ammonia water-oil-water mixed column was removed, and a three-layer mixed column was used to form the ball, to obtain a comparative spherical catalyst I of the application, the analysis results of which are shown in Table 2.

[0072] Comparative Example 3

[0073] The sol mixture synthesis step was the same as in Example 1.

[0074] Comparative Example 1 except that only the fourth layer of water was removed, to obtain a comparative spherical catalyst J of the application, the analysis results of which are shown in Table 2.

[0075] Comparative Example 4

[0076] The sol mixture synthesis step was the same as in Example 1.

[0077] Comparative Example 1 except that only the third layer of castor oil and soybean oil mixture in the four-layer oil-ammonia water-oil-water mixed column was removed, to obtain a comparative spherical catalyst K of the application, the analysis results of which are shown in Table 2.

[0078] Comparative Example 5

[0079] The sol mixture synthesis method was the same as in Example 1.

[0080] Comparative Example 1 except that the amount of white oil added was 16% of the volume of ammonia water, the amount of mixed oil added was 20% of the volume of ammonia water, and the amount of deionized water added was 0.4 times the volume of ammonia water, to obtain a comparative spherical catalyst L of the application, the analysis results of which are shown in Table 2.

[0081] Table 1 Physical and chemical properties of the catalysts obtained in each example

[0082] Catalyst No. A B C D E F G Particle average diameter, mm 1.82 1.81 1.83 1.79 1.78 1.82 1.79 Specific surface area, m 2 / g]] 76 80 80 84 79 78 79 Pore volume, mL / g 0.769 0.779 0.771 0.744 0.759 0.764 0.753 Pore size distribution, % < 2 nm 2.0 1.9 2.2 2.3 2.0 2.1 2.0 2-50 nm 97.4 97.5 97.2 97.1 97.0 97.1 97.6 > 50 nm 0.6 0.6 0.6 0.6 1.0 0.8 0.4 Average pore diameter, nm 17.3 17.6 17.2 16.5 16.2 17.1 16.3 Crushing strength, N / particle 79 75 70 74 69 75 74 True circularity, % 96.9 96.3 96.0 95.3 95.9 95.8 95.9

[0083] Table 2 Physical and chemical properties of the catalysts obtained in each comparative example

[0084]

[0085]

[0086] Composition of catalysts of each example of Table 3

[0087] Catalyst No. A B C D E F G Alumina (wt%) 99.6 99.6 99.1 99.7 99.6 99.4 99.6 PtO2 (wt%) 0.3 0.3 0.7 0.2 0.3 0.5 0.3 SnO2 (wt%) 0.1 0.1 0.2 0.1 0.1 0.1 0.1

[0088] Composition of catalysts of each comparative example of Table 4

[0089] Catalyst No. H I J K L Alumina (wt%) 99.6 99.6 99.6 99.7 99.6 PtO2 (wt%) 0.2 0.3 0.3 0.2 0.3 SnO2 (wt%) 0.2 0.1 0.1 0.1 0.1

[0090] Catalyst evaluation

[0091] 5 g of each of the above catalysts were reduced at 520°C under hydrogen atmosphere for 1.5 h, and then were charged into a fixed bed reactor for evaluation of the dehydrogenation activity of propane: reaction temperature 600°C, normal pressure, volume space velocity 100 h -1 The results of the dehydrogenation of propane are shown in Tables 5-8.

[0092] Evaluation results of each example catalyst for dehydrogenation of propane of Table 5

[0093]

[0094] Evaluation results of each comparative example catalyst for dehydrogenation of propane of Table 6

[0095]

[0096] Evaluation results of each example catalyst for dehydrogenation of propane of Table 7

[0097]

[0098] Evaluation results of each comparative example catalyst for dehydrogenation of propane of Table 8

[0099]

[0100] The specific embodiments of the present application are 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 each technical feature in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A method of preparing a spherical catalyst, wherein the catalyst comprises Pt and alumina, the method comprising: The spherical catalyst is prepared by mixing aluminum hydroxide sol with a Pt-containing aqueous solution, dropping the obtained mixture into an oil-ammonia water-oil-water four-layer mixed column to form, drying and calcining.

2. The method of claim 1, wherein: The concentration of chloroplatinic acid in the Pt-containing aqueous solution is 2wt%-6wt%. And / or, the concentration of stannous chloride in the Pt-containing aqueous solution is 0.5wt%-3.5wt%, and the concentration of hydrochloric acid is 5wt%-12wt%.

3. The method of claim 1, wherein: The content of aluminum oxide in the aluminum hydroxide sol is 15wt%-26wt%. And / or, the addition amount of the Pt-containing aqueous solution is 8%-40% of the mass of the aluminum hydroxide sol in terms of aluminum oxide.

4. The method of claim 3, wherein: The addition amount of the Pt-containing aqueous solution is 15%-30% of the mass of the aluminum hydroxide sol in terms of aluminum oxide.

5. The method of claim 1, wherein: The oil-ammonia water-oil-water four-layer mixed column is a straight column.

6. The method of claim 5, wherein: The oil-ammonia water-oil-water four-layer mixed column is a cylindrical column.

7. The method of claim 1, wherein: The oil-ammonia water-oil-water four-layer mixed column, the first oil layer is white oil, the white oil has a kinematic viscosity of 20-40 mm 2 / s at 40°C.

8. The method of claim 7, wherein: The white oil has a kinematic viscosity at 40°C of 25-35 mm 2 / s.

9. The method of claim 1, wherein: The concentration of ammonia water in the oil-ammonia water-oil-water four-layer mixed column is 20wt%-28wt%.

10. The method of claim 9, wherein: The concentration of ammonia water is 22wt%-26wt%.

11. The method of claim 1, wherein: The oil-ammonia water-oil-water four-layer mixed column, the kinematic viscosity of the castor oil at 40℃ is 500~650mm 2 / s; the kinematic viscosity of the soybean oil at 40℃ is 10~25mm 2 / s.

12. The method of claim 11, wherein: The castor oil has a kinematic viscosity at 40°C of 570-600 mm 2 / s; and the soybean oil has a kinematic viscosity at 40°C of 13-17 mm 2 / s.

13. The method of claim 1, wherein: In the oil-ammonia water-oil-water four-layer mixed column, the water layer is a dilute acid solution; the acid in the dilute acid solution is at least one selected from acetic acid and citric acid; and the mass concentration of the dilute acid solution is 3%-8%.

14. The method of claim 1, wherein: The height of the third layer is 35%-45% of the height of the second layer. And / or, the height of the fourth layer is 1.2-1.5 times the height of the second layer.

15. The spherical catalyst prepared by the preparation method of any one of claims 1-14.

16. The catalyst of claim 15, wherein: The specific surface area of the spherical catalyst is 70-110 m 2 / g; And / or, the pore volume of the spherical catalyst is 0.60-0.80mL / g. And / or, the average diameter of the spherical catalyst particles is 1.6-1.9mm. And / or, the average pore diameter of the spherical catalyst is 12-15nm. And / or, the crushing strength of the spherical catalyst is 62-85 N / particle. And / or, the sphericity of the spherical catalyst is 95.2%-99.9%.

17. The catalyst of claim 15, wherein: The pore size distribution of the spherical catalyst is that the pore volume of pores with a pore size less than 2nm accounts for 0.4%-4.5% of the total pore volume, and the pore volume of pores with a pore size of 2-50nm accounts for 95.0%-99.2% of the total pore volume.

18. The catalyst of claim 17, wherein: The pore volume of pores with a pore size of 2-50nm accounts for 97.0%-99.0% of the total pore volume.

19. The catalyst of claim 15, wherein: The content of Pt in the catalyst is 0.2% to 1.0% by mass, the content of Sn is 0.02% to 0.82% by mass, and the content of alumina is 98.1% to 99.8% by mass.

20. Use of the catalyst according to any one of claims 15 to 19 in a dehydrogenation reaction of propane.

21. The use according to claim 20, characterized in that: The catalyst needs to be reduced before use.

22. The use according to claim 21, characterized in that: The reducing atmosphere is H2, the reducing temperature is 450 to 600℃, and the reducing time is 1 to 3 hours.

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