Spherical catalyst as well as preparation method and application thereof

Abstract

The invention discloses a spherical catalyst as well as a preparation method and application thereof. The catalyst comprises Pt and aluminum oxide, and the preparation method of the catalyst comprises the following steps: mixing aluminum hydroxide sol with a Pt-containing aqueous solution, dropwise adding the obtained mixture into an oil-ammonia water-oil-water four-layer mixed column, molding, drying, and roasting to obtain the spherical catalyst. The catalyst disclosed by the invention is applied to propane dehydrogenation reaction and has relatively good stability and good reaction performance.

Description

Technical Field

[0001] The present invention relates to a spherical catalyst, a preparation method thereof and an application thereof, and particularly relates to a spherical noble metal catalyst suitable for a fluidized bed, a preparation method thereof and an application thereof. Background Art

[0002] The shape and size of catalyst particles are generally determined according to the requirements of reactors used in industrial production. At present, there are four common types of reactors in industry: fixed bed, fluidized bed (boiling bed), suspension bed and moving bed. Fixed bed reactors commonly use spherical, cylindrical bar, clover, four-leaf and flake catalysts. Moving bed reactors often use large particle spherical catalysts. Fluidized bed reactors generally use spherical or bar catalysts with smaller particles.

[0003] Spherical catalysts have the advantages of good fluidity, high packing factor, uniform fluid distribution, low resistance and small pressure drop, and are widely used in the technology of dehydrogenating lower alkanes to produce olefins.

[0004] Currently, the catalysts for dehydrogenating lower alkanes to produce olefins are mainly prepared by loading active component Pt and other additives on a γ-Al 2 O 3 support, such as EP100222A, CN1185994A, etc. However, since the dehydrogenation reaction is carried out at a high temperature of about 600 °C, 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 subjected to multiple high-temperature carbon burning regeneration treatments, resulting in the γ-Al 2 O 3 support is easily sintered and undergoes α-phase transformation, greatly reducing the specific surface area of the support and destroying the pore structure. Furthermore, the active components of the catalyst aggregate, and the activity of the catalyst drops severely. Therefore, it is necessary to further modify the γ-Al 2 O 3 support to make the catalyst have high thermal stability.

[0005] CN112973771A discloses a spherical catalyst support containing molecular sieve and alumina, its preparation and application. This catalyst support is obtained by precipitating an inorganic aluminum salt with ammonia water and acidifying to obtain a sol, adding a mixed solution of ball-milled pseudo-boehmite and molecular sieve and a sol modification additive to the sol, then dropping and forming and aging in an oil-ammonia column, and finally washing, drying and calcining to obtain a composite small ball with high strength and large specific surface area. This method is to redisperse the suspension slurry obtained by ball-milling pseudo-boehmite and molecular sieve and mix it with a dilute sol, which will result in the disadvantage of uneven dispersion of the molecular sieve. At the same time, the doping of solid molecular sieve will also lead to a decrease in the strength of the support.

[0006] CN105478100A discloses a method for preparing silicon-containing γ-Al 2 O 3 spheres. The method is to stir and slurry pseudoboehmite dry gel powder and deionized water, acidify with dilute nitric acid, 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 and form spheres in an oil-ammonia column, cure the wet spheres in ammonia water for 2 hours, then filter, wash with deionized water, dry and calcine to obtain silicon-containing γ-Al 2 O 3 spheres. The method for preparing γ-Al 2 O 3 spheres has a long curing time, difficult washing and low production efficiency. SUMMARY OF THE INVENTION

[0007] Aiming at the deficiencies of the prior art, the present invention provides a spherical catalyst, a preparation method and an application thereof. The spherical catalyst has the characteristics of good roundness, high crushing strength, large pore volume and pore diameter, uniform Pt loading, environmental protection and no peculiar smell of the product. The catalyst of the present invention is applied to propane dehydrogenation reaction and has good stability and good reaction performance.

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

[0009] Mix aluminum hydroxide sol with an aqueous solution containing Pt, and drop the obtained mixture into an oil-ammonia-oil-water four-layer mixing column for forming, drying and calcining to obtain a spherical catalyst.

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

[0011] Further, the preparation method of the aluminum hydroxide sol includes: mixing aluminum hydroxide and water to make a slurry, adding a peptizing agent, and stirring evenly to obtain aluminum hydroxide sol. 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 an inorganic acid, the mass concentration of the inorganic acid is 30% to 50%. When the peptizing agent contains an organic acid, the mass concentration of the organic acid is 30% to 50%. Further, the addition amount of the peptizing agent in terms of acid is 1 wt% to 10 wt% of the mass of aluminum hydroxide in terms of alumina, preferably 2 wt% to 8 wt%. Further, the aluminum hydroxide is preferably hydrated aluminum hydroxide, such as wet aluminum hydroxide material. Preferably, in the aluminum hydroxide, the water content is 17 wt% to 25 wt%. Preferably, the properties of the aluminum hydroxide after calcination are as follows: the specific surface area is 110 to 201 m 2 / g, the pore volume is 0.8 - 2.0 mL / g, and the average pore diameter is 15 - 17 nm. Among them, the calcination conditions are as follows: the temperature is 600 - 850 °C, the time is 2 - 12 h, and the oxygen-containing atmosphere is such as air. The aluminum hydroxide can be commercially purchased or prepared by a conventional method. The aluminum hydroxide is preferably macroporous pseudo-boehmite containing water, and the water content is 19 wt% - 23 wt%.

[0012] Further, the platinum-containing compound used in the Pt-containing aqueous solution is platinum chloride (PtCl 4 ), chloroplatinic acid (H 2 PtCl 6 ), or one or more of them, and preferably chloroplatinic acid. Further, the Pt-containing aqueous solution contains stannous chloride (SnCl 2 ) and hydrochloric acid.

[0013] Further, the concentration of the platinum-containing compound in the Pt-containing aqueous solution is 2 wt% - 6 wt%. The addition amount of the Pt-containing aqueous solution is 8% - 40% of the mass of the aluminum hydroxide sol calculated as alumina, preferably 15% - 30%.

[0014] Further, in the Pt-containing aqueous solution, the concentration of stannous chloride (SnCl 2 ) is 0.5 wt% - 3.5 wt%, and the concentration of hydrochloric acid is 5 wt% - 12 wt%.

[0015] Further, the oil-ammonia-oil-water four-layer mixing column is a straight column, preferably a cylinder.

[0016] Further, in the oil-ammonia-oil-water four-layer mixing column, four layers are arranged in sequence from top to bottom. The first layer is the first oil layer, the second layer is the ammonia water layer, the third layer is the second oil layer, and the fourth layer is the water layer.

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

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

[0019] Further, in the oil-ammonia-oil-water four-layer mixing column, the third layer is the second oil layer, that is, the liquid seal oil layer, with a density between the second ammonia water layer and the fourth water layer, and the kinematic viscosity at 40 °C is 60 mm2 One or more vegetable oils below / s, preferably a mixed oil of castor oil and soybean oil, wherein the volume ratio of castor oil to soybean oil is 1 / 4 to 1 / 6. The kinematic viscosity of the castor oil at 40 °C is 500 to 650 mm 2 / s, preferably 570 to 600 mm 2 / s; the kinematic viscosity of the soybean oil at 40 °C is 10 to 25 mm 2 / s, preferably 13 to 17 mm 2 / s. The height of the third layer is 30% to 50% of the height of the second layer, preferably 35% to 45%.

[0020] Furthermore, in the oil-ammonia water-oil-water four-layer mixing 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 the height of the second layer, preferably 1.2 to 1.5 times.

[0021] Furthermore, 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] Furthermore, the preparation method of the oil-ammonia water-oil-water four-layer mixing column includes:

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

[0024] (2) Slowly add the materials required for the third layer onto the fourth layer materials in step (1) and stabilize for 20 to 35 min;

[0025] (3) Slowly add the materials required for the second layer onto the third layer materials in step (2);

[0026] (4) Slowly add the materials required for the first layer onto the second layer materials in step (3) to obtain an oil-ammonia water-oil-water four-layer mixing column. Preferably, during the addition of the materials required for the first layer, slowly circulate up and down above the interface between the first layer and the second layer through a peristaltic pump to weaken the surface tension at the interface between the first layer and the second layer, and then let it stand for 30 to 60 min until it stabilizes. This can ensure that the aluminum hydroxide sol can quickly pass through the contact interface between the first layer and the second layer, prevent pauses from causing trailing and affecting the true roundness.

[0027] Furthermore, the spherical catalyst forming is carried out in the oil-ammonia water-oil-water four-layer mixing column, and a mixture of aluminum hydroxide sol and a Pt-containing aqueous solution is dropped into the oil-ammonia water-oil-water four-layer mixing column, wherein the inner diameter of the dropping head used is 1.0 mm to 1.6 mm.

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

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

[0030] The second aspect of the present invention 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 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 pores with a pore size of 2-50 nm accounts for 95.0%-99.2% of the total pore volume, preferably 97.0%-99.0%.

[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 / grain.

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

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

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

[0039] Further, the application includes: contacting a propane raw material with the catalyst for a dehydrogenation reaction to obtain a product propylene.

[0040] Further, before the catalyst is used, it needs to be reduced. The catalyst precursor is reduced in a reducing atmosphere. The reducing atmosphere is preferably H 2 , the reduction temperature is 450-600°C, 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 °C, the reaction pressure is 0 - 1 MPa, and the volume space velocity is 50 - 200 h -1 .

[0042] Compared with the prior art, the advantages of the present invention are as follows:

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

[0044] (2) The preparation process of the present invention is environmentally friendly. In the traditional oil-ammonia column ball-forming process, the volatilization of ammonia water brings serious environmental pollution problems and subsequent pollutant emission problems. The present invention separates the second layer of ammonia water layer from the fourth layer of water layer with the second oil layer, so that the ammonia water layer is sealed above the fourth layer of water layer, which can extend the service time and avoid environmental pollution caused by the product bringing out ammonia water. After long-term use, deionized water can be replaced to ensure the liquid seal effect, and the operation is simple and cost-saving in industry.

[0045] (3) The present invention uses a one-step method for synthesis, which is more convenient to operate, saves costs, and is conducive to industrial operation. The spherical catalyst of the present invention is used in the propane-to-propylene reaction, and has a high propane conversion rate and propylene selectivity. The catalyst with large pore diameter and pore volume can avoid carbon deposition after long-term operation, and has good stability and good reaction performance. Specific Embodiments

[0046] The following further illustrates the spherical catalyst, its preparation method and application effect in the present invention through examples. The examples are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

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

[0048] In the present invention, the nitrogen adsorption-desorption curve of the sample was tested at -196 °C using an ASAP2020 full-automatic physical adsorption instrument from Micromeritics, USA, to determine the specific surface area, pore volume, and pore size distribution.

[0049] In the present invention, the crushing strength was tested using a ZQJ-III intelligent particle strength testing machine manufactured by Dalian Zhiqu Testing Machine Factory, and the average value of crushing ten spherical catalysts was measured.

[0050] In the present invention, the roundness was tested using an electron microscope from Olympus, and the average value was calculated after testing 20 samples.

[0051] Example 1

[0052] Take 250 g of macroporous pseudo-boehmite filter cake with a moisture content of 22 wt% (calcined at 600 °C for 3 h in an air atmosphere, with the following properties: pore volume 0.87 ml / g, specific surface area 175 m 2 / g, average pore diameter 16 nm). After adding deionized water and stirring to make a uniform slurry, 26 g of a nitric acid solution with a mass concentration of 45% was added for peptization, and finally a pseudo-boehmite sol with an alumina mass content of 20% was prepared; take 300 g of the above sol (alumina content 20 wt%), add 12 g of a chloroplatinic acid solution with a chloroplatinic acid concentration of 3 wt%, which also contains 0.8% stannous chloride and 7% hydrochloric acid, and stir evenly to obtain a sol mixture;

[0053] Use a dropper with an inner diameter of 1.2 mm to drop the above sol into a four-layer mixing column (cylindrical) of (white oil with a kinematic viscosity of 32 mm 2 / s at 40 °C - ammonia water with a concentration of 25 wt% - mixed oil - deionized water) for forming, and the residence time in the four-layer mixing column is 8 s. 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 the volume of ammonia water; the mixed oil is composed of castor oil with a kinematic viscosity of 580 mm 2 / s at 40 °C and soybean oil with a kinematic viscosity of 15 mm 2 / s, and the volume ratio of the two is 1:5. Then dry at 130 °C for 8 hours and calcine at 800 °C for 3 hours to obtain the spherical catalyst A of the present invention, and its analysis results are shown in Table 1.

[0054] Example 2

[0055] Compared with Example 1, the difference lies in that the material in the fourth layer is changed from deionized water to a 5 wt% dilute acetic acid solution, obtaining the spherical catalyst B of the present invention, and its analysis results are shown in Table 1.

[0056] Example 3

[0057] Compared with Example 1, the difference lies in that the synthesis process of the sol mixture is as follows: 300 g of pseudoboehmite sol (aluminum oxide content is 20 wt%) is taken, and 15.6 g of chloroplatinic acid solution with a chloroplatinic acid concentration of 6% is added, which simultaneously contains 1.0% of stannous chloride and 9% of hydrochloric acid, obtaining the spherical catalyst C of the present invention, and its analysis results are shown in Table 1.

[0058] Example 4

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

[0060] Example 5

[0061] Compared with Example 1, the difference lies in 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 at the same time, the ammonia water concentration is changed to 28 wt%, obtaining the spherical catalyst E of the present invention, and its analysis results are shown in Table 1.

[0062] Example 6

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

[0064] Example 7

[0065] Compared with Example 1, the difference lies in that the addition amount of white oil is 42% of the volume of ammonia water, the addition amount of the mixed oil is 32% of the volume of ammonia water, and the addition amount of deionized water is 1.6 times the volume of ammonia water, obtaining the spherical catalyst G of the present invention, and its analysis results are shown in Table 1.

[0066] Comparative Example 1

[0067] The synthesis steps of the sol mixture are the same as those in Example 1.

[0068] Compared with Example 1, the difference lies in that the four-layer oil-ammonia water-oil-water mixing column is changed to a two-layer oil-ammonia column. The upper layer is white oil with a kinematic viscosity of 32 mm 2 / s at 40 °C, and the lower layer is ammonia water with a concentration of 25 wt%. The addition amount of white oil is 25% of the volume of ammonia water, obtaining the comparative spherical catalyst H of the present invention, and the analysis results are shown in Table 2.

[0069] Comparative Example 2

[0070] The synthesis steps of the sol mixture are the same as those in Example 1.

[0071] Compared with Example 1, the difference lies in that only the first-layer white oil column in the four-layer oil-ammonia water-oil-water mixing column is removed, and the three-layer mixing column is used to form spheres, obtaining the comparative spherical catalyst I of the present invention, and the analysis results are shown in Table 2.

[0072] Comparative Example 3

[0073] The synthesis steps of the sol mixture are the same as those in Example 1.

[0074] Compared with Example 1, the difference lies in that only the fourth-layer water column is removed, obtaining the comparative spherical catalyst J of the present invention, and the analysis results are shown in Table 2.

[0075] Comparative Example 4

[0076] The synthesis steps of the sol mixture are the same as those in Example 1.

[0077] Compared with Example 1, the difference lies in that only the third-layer castor oil and soybean oil mixing layer in the four-layer oil-ammonia water-oil-water mixing column is removed, obtaining the comparative spherical catalyst K of the present invention, and the analysis results are shown in Table 2.

[0078] Comparative Example 5

[0079] The synthesis method of the sol mixture is the same as that in Example 1.

[0080] Compared with Example 1, the difference lies in that the addition amount of white oil is 16% of the volume of ammonia water, the addition amount of mixed oil is 20% of the volume of ammonia water, and the addition amount of deionized water is 0.4 times the volume of ammonia water, obtaining the comparative spherical catalyst L of the present invention, and the analysis results are shown in Table 2.

[0081] Table 1 Physicochemical properties of the catalysts obtained in each example

[0082] Catalyst Number A B C D E F G Average Particle Diameter, mm 1.82 1.81 1.83 1.79 1.78 1.82 1.79 <![CDATA[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, % < 2nm 2.0 1.9 2.2 2.3 2.0 2.1 2.0 2 - 50nm 97.4 97.5 97.2 97.1 97.0 97.1 97.6 > 50nm 0.6 0.6 0.6 0.6 1.0 0.8 0.4 Average Pore Size, 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 Roundness, % 96.9 96.3 96.0 95.3 95.9 95.8 95.9

[0083] Table 2 Physicochemical properties of the catalysts obtained in each comparative example

[0084]

[0085]

[0086] Table 3 Composition of catalysts in each example

[0087] Catalyst Number A B C D E F G Aluminum Oxide (wt%) 99.6 99.6 99.1 99.7 99.6 99.4 99.6 <![CDATA[PtO 2 (wt%)]]> 0.3 0.3 0.7 0.2 0.3 0.5 0.3 <![CDATA[SnO 2 (wt%)]]> 0.1 0.1 0.2 0.1 0.1 0.1 0.1

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

[0089] Catalyst Number H I J K L Aluminum Oxide (wt%) 99.6 99.6 99.6 99.7 99.6 <![CDATA[PtO 2 (wt%)]]> 0.2 0.3 0.3 0.2 0.3 <![CDATA[SnO 2 (wt%)]]> 0.2 0.1 0.1 0.1 0.1

[0090] Catalyst evaluation

[0091] Take 5 g of each of the above catalysts, first reduce them at 520 °C for 1.5 h in a hydrogen atmosphere, and then load them into a fixed-bed reactor for the activity evaluation of propane dehydrogenation: the reaction temperature is 600 °C, atmospheric pressure, and the volume space velocity is 100 h -1 . The results of propane dehydrogenation are listed in Tables 5 - 8.

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

[0093]

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

[0095]

[0096] Table 7 Evaluation results of the stability of catalysts in each example for propane dehydrogenation

[0097]

[0098] Table 8 Evaluation results of the stability of catalysts in each comparative example for propane dehydrogenation

[0099]

[0100] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A preparation method of a spherical catalyst, wherein the catalyst comprises Pt and alumina, and the preparation method comprises: Mixing an aluminum hydroxide sol with an aqueous Pt-containing solution, dropping the resulting mixture into an oil-ammonia water-oil-water four-layer mixing column for shaping, drying, and calcining to obtain a spherical catalyst.

2. The preparation method according to claim 1, characterized in that: The platinum-containing compound in the aqueous Pt-containing solution is one or more of platinum chloride and chloroplatinic acid, preferably chloroplatinic acid; and / or, the aqueous Pt-containing solution contains stannous chloride and hydrochloric acid.

3. The preparation method according to claim 2, characterized in that: The concentration of the platinum-containing compound in the aqueous Pt-containing solution is 2 wt% to 6 wt%; and / or, in the aqueous Pt-containing solution, the concentration of stannous chloride is 0.5 wt% to 3.5 wt%, and the concentration of hydrochloric acid is 5 wt% to 12 wt%.

4. The preparation method according to claim 1, characterized in that: The alumina content in the aluminum hydroxide sol is 15 wt% to 26 wt%; and / or, the addition amount of the aqueous Pt-containing solution is 8% to 40% of the mass of the aluminum hydroxide sol calculated as alumina, preferably 15% to 30%.

5. The preparation method according to claim 1, characterized in that: In the oil-ammonia water-oil-water four-layer mixing column, four layers are arranged in sequence from top to bottom. The first layer is the first oil layer, the second layer is the ammonia water layer, the third layer is the second oil layer, and the fourth layer is the water layer; and / or, the oil-ammonia water-oil-water four-layer mixing column is a straight column, preferably a cylinder.

6. The preparation method according to claim 5, characterized in that: In the oil-ammonia water-oil-water four-layer mixing column, the first layer is the first oil layer, which is selected from one or more of white oil and diesel oil, preferably white oil, and the kinematic viscosity of the white oil at 40 °C is 20-40 mm 2 / s, preferably 25-35 mm 2 / s.

7. The preparation method according to claim 5, characterized in that: In the oil-ammonia water-oil-water four-layer mixing column, the second layer is the ammonia water layer, and the ammonia water concentration is 20 wt% to 28 wt%, preferably 22 wt% to 26 wt%.

8. The preparation method according to claim 5, characterized in that: In the oil-ammonia water-oil-water four-layer mixing column, the third layer is the second oil layer, i.e., the liquid-sealing oil layer, which is one or more vegetable oils with a density between that of the second ammonia water layer and the fourth water layer and a kinematic viscosity of 60 mm 2 / s or less at 40°C, preferably a mixed oil of castor oil and soybean oil; the volume ratio of castor oil to soybean oil is 1 / 4 to 1 / 6; Preferably, the kinematic viscosity of the castor oil at 40 °C is 500 to 650 mm 2 / s, preferably 570 to 600 mm 2 / s; the kinematic viscosity of the soybean oil at 40 °C is 10 to 25 mm 2 / s, preferably 13 to 17 mm 2 / s.

9. The preparation method according to claim 5, characterized in that: In the oil-ammonia water-oil-water four-layer mixing column, the fourth layer is the water layer, preferably deionized water or a dilute acid solution, more preferably 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%.

10. The preparation method according to claim 5, characterized in that: The height of the first layer is 30% to 50% of the height of the second layer; and / or, the height of the third layer is 30% to 50% of the height of the second layer, preferably 35% to 45%; and / or, the height of the fourth layer is 1.0 to 2.0 times the height of the second layer, preferably 1.2 to 1.5 times.

11. A spherical catalyst prepared by the preparation method according to any one of claims 1-10.

12. The catalyst according to claim 11, characterized in that: The specific surface area of the spherical catalyst is 70 to 110 m 2 / g; and / or, the pore volume of the spherical catalyst is 0.60 to 0.80 mL / g; and / or, the average diameter of the spherical catalyst particles is 1.6 to 1.9 mm; and / or, the average pore diameter of the spherical catalyst is 12 to 15 nm; and / or, the crushing strength of the spherical catalyst is 62 to 85 N / grain; and / or, the roundness of the spherical catalyst is 95.2% to 99.9%.

13. The catalyst according to claim 11, wherein: the pore size distribution of the spherical catalyst is as follows: the pore volume of pores with a pore size less than 2 nm accounts for 0.4% to 4.5% of the total pore volume, and the pore volume of pores with a pore size of 2 - 50 nm accounts for 95.0% to 99.2% of the total pore volume, preferably 97.0% to 99.0%.

14. The catalyst according to claim 11, wherein: in the catalyst, based on the mass of the catalyst and in terms of mass fraction, the content of Pt in terms of oxide is 0.2% to 1.0%, the content of Sn in terms of oxide is 0.02% to 0.82%, and the content of alumina is 98.1% to 99.8%.

15. Use of the catalyst according to any one of claims 11 - 14 in the propane dehydrogenation reaction.

16. The use according to claim 15, wherein: Before use, the catalyst needs to be reduced; preferably, the reducing atmosphere is preferably H 2 , the reduction temperature is 450-600 °C, and the reduction time is 1-3 h.

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