Pt-based catalyst as well as preparation and application thereof

Abstract

The invention discloses a Pt-based catalyst as well as preparation and application thereof. The preparation method of the Pt-based catalyst comprises the following steps: (1) mixing aluminum hydroxide sol with an organic Pt salt solution, and dropwise adding the obtained mixture into an oil-ammonia water-oil-water four-layer mixed column for molding, drying and roasting to obtain a spherical Pt-based catalyst precursor; and (2) impregnating the precursor obtained in the step (1) with Pt-containing impregnation liquid, drying, and roasting to obtain the Pt-based catalyst. The catalyst disclosed by the invention is applied to propane dehydrogenation reaction and has relatively high propane conversion rate and propylene selectivity.

Description

Technical Field

[0001] The present invention relates to a Pt-based catalyst and its preparation and application, in particular to a Pt-based catalyst suitable for a fluidized bed and its preparation and application. Background Art

[0002] The shape and size of catalyst particles are generally determined according to the requirements of the 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 clover, and flake catalysts. Moving bed reactors often use large particle spherical catalysts. Fluidized bed reactors generally use small particle spherical or bar catalysts.

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

[0004] Currently, the catalysts for dehydrogenating light 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 catalyst is used for a longer time, the catalyst needs to be subjected to multiple high-temperature carbon burning and regeneration treatments, resulting in the γ-Al 2 O 3 support being easily sintered and undergoing α-phase transformation, greatly reducing the specific surface area of the support, destroying the pore structure, and then causing the aggregation of the active components of the catalyst and a serious decline in the catalyst activity. 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 and its preparation and application. The 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 high-strength and large-specific-surface composite sphere. This method is to mix the suspension slurry obtained by ball-milling pseudo-boehmite and molecular sieve with a dilute sol and then peptize again, which will have 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-Al2 O 3 A method for preparing spherical particles. The method is to stir and pulp pseudoboehmite dry gel 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 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 spherical particles. The method for preparing γ-Al 2 O 3 spherical particles has a long curing time, is difficult to wash, and has low production efficiency.

[0007] CN104289220A discloses a preparation method and use of a high thermal stability low-carbon alkane dehydrogenation catalyst. The method for preparing the carrier is to add an aluminum source to an alkaline aqueous solution, stir, continue to drop the alkaline aqueous solution to adjust the pH of the mixed solution to 7-14, filter, wash with deionized water, then add dilute nitric acid to form a sol, add a silicon source, stir, filter, age for 10-48 hours, drop and form spheres, and then dry and calcine to obtain γ-Al 2 O 3 spherical particles containing Si element; or add an aluminum source to an alkaline aqueous solution, stir, continue to drop the alkaline aqueous solution to adjust the pH of the mixed solution to 7-14, filter, wash with deionized water, then add dilute nitric acid to form a sol, stir, filter, age for 10-48 hours, drop and form spheres, and then dry and calcine to obtain γ-Al 2 O 3 spherical particles, and then immerse the γ-Al 2 O 3 spherical particles in an aqueous solution or ethanol solution of a silicon source at 60-120 °C for 2-6 hours, and then dry and calcine to obtain γ-Al 2 O 3 spherical particles containing Si element. The disadvantages of this method are long preparation cycle, complex process, need to regulate the pH value, and cannot ensure product consistency. SUMMARY OF THE INVENTION

[0008] In view of the deficiencies of the prior art, the present invention provides a Pt-based catalyst and its preparation and application. The catalyst prepared by this method has the characteristics of good roundness, high crushing strength, large pore volume and pore diameter, large Pt loading, and the product is environmentally friendly and odorless. When applied to propane dehydrogenation reaction, it has high propane conversion rate and propylene selectivity.

[0009] The first aspect of the present invention provides a preparation method of a Pt-based catalyst, including:

[0010] (1) Mix the aluminum hydroxide sol with the organic Pt salt solution, and drop the obtained mixture into an oil-ammonia water-oil-water four-layer mixing column to form a shape. After drying and calcination, a spherical Pt-based catalyst precursor is obtained;

[0011] (2) Impregnate the Pt-based catalyst precursor obtained in step (1) with an impregnating solution containing Pt, and after drying and calcination, a Pt-based catalyst is obtained.

[0012] Furthermore, the alumina content in the aluminum hydroxide sol is 15 wt% to 26 wt%.

[0013] Furthermore, the preparation method of the aluminum hydroxide sol includes: mixing aluminum hydroxide with water to make a slurry, adding a peptizing agent, and stirring evenly to obtain the aluminum hydroxide sol. Furthermore, 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%. Furthermore, 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%. Furthermore, the aluminum hydroxide is preferably hydrated aluminum hydroxide, such as wet aluminum hydroxide material. Preferably, in the aluminum hydroxide, the moisture 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 to 2.0 mL / g, and the average pore diameter is 15 to 17 nm. The calcination conditions are as follows: the temperature is 600 to 850 °C, the time is 2 to 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 moisture content is 19 wt% to 23 wt%.

[0014] Furthermore, the organic Pt salt in the organic Pt salt solution is one or more of platinum acetylacetonate or tetrakis(triphenylphosphine)platinum, preferably platinum acetylacetonate, and the solvent used is preferably acetone. Furthermore, the concentration of the organic Pt salt in the organic Pt salt solution is 1.0 wt% to 1.9 wt%. The addition amount of the organic Pt salt solution is 9% to 11% of the mass of the aluminum hydroxide sol in terms of alumina.

[0015] Furthermore, the organic Pt salt solution contains stannous chloride; preferably, the concentration of stannous chloride in the organic Pt salt solution is 0.4 wt% to 11 wt%.

[0016] Furthermore, the oil-ammonia water-oil-water four-layer mixing column is a straight column, preferably a cylinder.

[0017] Further, in the oil-ammonia water-oil-water four-layer mixing column, four layers are sequentially arranged 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.

[0018] Further, 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. 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.

[0019] Further, in the oil-ammonia water-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%.

[0020] Further, in the oil-ammonia water-oil-water four-layer mixing column, the third layer is the second oil layer, namely the liquid seal oil layer, which is one or more vegetable oils with a density between the ammonia water layer of the second layer and the water layer of the fourth layer and a kinematic viscosity at 40 °C of 60 mm 2 / s or less, preferably a mixed oil of castor oil and soybean oil, wherein the volume ratio of castor oil to soybean oil is 1 / 4-1 / 6. The kinematic viscosity of the castor oil at 40 °C is 500-650 mm 2 / s, preferably 570-600 mm 2 / s; the kinematic viscosity of the soybean oil at 40 °C is 10-25 mm 2 / s, preferably 13-17 mm 2 / s. The height of the third layer is 30%-50% of the height of the second layer, preferably 35%-45%.

[0021] Further, 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. The height of the fourth layer is 1.0-2.0 times the height of the second layer, preferably 1.2-1.5 times.

[0022] 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%-8%.

[0023] Further, the preparation method of the oil-ammonia water-oil-water four-layer mixing column includes:

[0024] (1) Pour the materials required for the fourth layer into a columnar container (preferably an organic glass container) and ensure that the solution is uniform;

[0025] (2) Slowly add the materials required for the third layer on top of the fourth layer of materials in step (1), and stabilize for 20 - 35 min;

[0026] (3) Slowly add the materials required for the second layer on top of the third layer of materials in step (2);

[0027] (4) Slowly add the materials required for the first layer on top of the second layer of materials in step (3) to obtain an oil - ammonia - oil - water four - layer mixing column. Preferably, during the addition of the materials required for the first layer, slowly circulate up and down through a peristaltic pump above the interface between the first layer and the second layer to weaken the surface tension at the interface between the first layer and the second layer, and then let it stand for 30 - 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.

[0028] Further, the shaping of the Pt - based catalyst precursor is carried out in the oil - ammonia - oil - water four - layer mixing column. The mixture of aluminum hydroxide sol and organic Pt salt solution is dropped into the oil - ammonia - oil - water four - layer mixing column, wherein the inner diameter of the dropper used is 1.0 mm - 1.6 mm.

[0029] Further, the residence time of the mixture of aluminum hydroxide sol and organic Pt salt solution in the oil - ammonia - oil - water four - layer mixing column is 5 - 18 s, preferably 7 - 11 s.

[0030] Further, the drying temperature is 100°C - 150°C, and the drying time is 6 - 10 hours; the calcination temperature is 750°C - 950°C, and the calcination time is 1 - 4 hours.

[0031] Further, in the Pt - based catalyst precursor obtained in step (1), Pt exists in the form of single atoms.

[0032] Further, in step (2), the impregnation preferably adopts the saturated impregnation method. Among them, the Pt precursor used in the impregnation solution is preferably at least one of PtCl 4 、H 2 PtCl 6 . The drying conditions after impregnation are as follows: the drying temperature is 80 - 120°C, and the drying time is 8 - 12 h. The calcination conditions after impregnation are as follows: the calcination temperature is 500 - 700°C, and the calcination time is 2 - 6 h.

[0033] The second aspect of the present invention provides a Pt - based catalyst prepared by the above - mentioned preparation method.

[0034] Further, the specific surface area of the catalyst is 70 - 115 m 2 / g, and the pore volume is 0.60 - 0.85 mL / g.

[0035] Furthermore, the catalyst is in the form of spherical particles with an average particle diameter of 1.6 - 1.9 mm.

[0036] Furthermore, the pore size distribution of the catalyst is as follows: the pore volume of pores with a pore size less than 2 nm accounts for 1.0% - 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% - 98.9% of the total pore volume, preferably 96.0% - 98.0%.

[0037] Furthermore, the average pore size of the catalyst is 13 - 17 nm.

[0038] Furthermore, the crushing strength of the catalyst is 65 - 85 N / grain.

[0039] Furthermore, the true roundness of the catalyst is 96.2% - 99.9%.

[0040] Furthermore, in the catalyst, based on the mass of the catalyst and in terms of mass fraction, the total Pt content is 0.5% - 1.9%, the Sn content is 0.02% - 0.70%, and the alumina content is 97.4% - 99.48%. Further, the Pt content on the catalyst surface is 0.3% - 0.8%.

[0041] The third aspect of the present invention provides the application of the above catalyst in the propane dehydrogenation reaction.

[0042] Furthermore, the application includes: contacting a propane raw material with the catalyst for a dehydrogenation reaction to obtain a product propylene.

[0043] Furthermore, before the propane dehydrogenation 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.

[0044] Furthermore, 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 .

[0045] Compared with the prior art, the advantages of the present invention are:

[0046] (1) During the preparation of the Pt-based catalyst of the present invention, an organic Pt salt solution is added to the aluminum hydroxide sol. Since the organic Pt has low solubility and a relatively large molecular weight, the organic molecules connected to the Pt atoms occupy a large steric hindrance and are prone to form a single-atom Pt catalyst precursor during the synthesis process. Subsequently, the catalyst precursor is impregnated with a Pt-containing impregnating solution, which increases the metal Pt loading. At the same time, the Pt sites on the outer-layer nanoparticles increase. After calcination, both single-atom Pt and nanoparticle Pt coexist in the catalyst, which can play a synergistic role. The Pt increases from the inside to the outside, which is beneficial to expose more active sites, accelerate the reaction, and reduce carbon deposition. During the forming process, the four-layer oil-ammonia-oil-water mixing column is different from the two-layer oil-ammonia column or the hot oil column. The third oil layer is added as a liquid-sealing oil layer and the fourth water layer, which enables the sol to quickly enter the third and fourth water layers after passing through the second ammonia water layer, and the pH value quickly drops to neutral. During the drying process of the pellets, they are not easily broken or shrunk with the volatilization of the surface ammonia water, which significantly increases the alumina particle size and mechanical strength. At the same time, it enables full contact between the metal and the support, and the metal is not easily agglomerated. In addition, the rapid decrease in the pH value on the surface of the sol pellets also causes a rapid decrease in the hydrophobicity of the colloidal particles, a significant increase in the interaction force between the colloidal particles, a shortening of the distance between the colloidal particles, and partial collapse of the original structure, resulting in an increase in the mesoporous structure of the support in the range of 2-50 nm. By adding an appropriate amount of acidic solution to the fourth water layer, the pore structure can be further optimized.

[0047] (2) The preparation process of the present invention is environmentally friendly. In the traditional oil-ammonia column pelletizing process, the volatilization of ammonia water brings serious environmental pollution problems and subsequent pollutant emission problems. The present invention separates the second ammonia water layer from the fourth water layer with the second oil layer, so that the ammonia water layer is sealed above the fourth water layer, which can extend the service time and avoid environmental pollution caused by the product carrying out ammonia water. After long-term use, deionized water can be replaced to ensure the liquid-sealing effect, and the operation is simple and cost-saving in industry.

[0048] (3) The spherical Pt-based catalyst obtained by the preparation method of the present invention is used in the propane-to-propylene reaction, which has a high propane conversion rate and propylene selectivity, makes full use of the inner space of the catalyst, reduces carbon deposition, and has better catalytic activity. Detailed Embodiments

[0049] The Pt-based catalyst, its preparation method and application effects in the present invention will be further described below 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.

[0050] The experimental methods in the following examples are all conventional methods in the art unless otherwise specified. The experimental materials used in the following examples are all purchased from regular biochemical reagent stores unless otherwise specified.

[0051] In the present invention, the nitrogen adsorption - desorption curve of the sample was tested at - 196 °C using a Micromeritics ASAP2020 full - automatic physical adsorption instrument in the United States to determine the specific surface area, pore volume, and pore size distribution.

[0052] 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.

[0053] In the present invention, the true roundness was tested using an electron microscope of Olympus Corporation, and the average value was calculated after testing 20 samples.

[0054] In the present invention, the metal Pt content on the catalyst surface was measured by XPS (the instrument model is Kratos Axis Ultra DLD).

[0055] Example 1

[0056] (1) Take 250 g of macroporous pseudo - boehmite filter cake with a water 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 of 16 nm). After adding deionized water and stirring to make a uniform slurry, add 26 g of nitric acid solution with a mass concentration of 45% for peptization to finally make a pseudo - boehmite sol with an alumina mass content of 20%; take 300 g of the above sol (alumina content of 20 wt%), add 6 g of platinum acetylacetonate solution with a platinum acetylacetonate concentration of 1.2%, which also contains 2.4% of stannous chloride, and stir evenly to obtain a sol mixture;

[0057] 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 shaping, 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 a Pt - based catalyst precursor.

[0058] (2) Take 100 g of the obtained Pt-based catalyst precursor, and saturate it by impregnation into an aqueous solution containing 2 g of chloroplatinic acid. After impregnation for 30 min, dry it in a drying oven at 90 °C for 10 h, and calcine it in a muffle furnace at 600 °C for 4 h to obtain the Pt-based catalyst A of the present invention, and its analysis results are shown in Table 1.

[0059] Example 2

[0060] Compared with Example 1, the difference is that deionized water in the fourth layer of the four-layer mixture is changed to a 5 wt% dilute acetic acid solution to obtain the Pt-based catalyst B of the present invention, and its analysis results are shown in Table 1.

[0061] Example 3

[0062] Compared with Example 1, the difference is that 5.4 g of an acetylacetone platinum solution with an acetylacetone platinum concentration of 1.8% is added, which simultaneously contains stannous chloride with a concentration of 0.9%, to obtain the Pt-based catalyst C of the present invention, and its analysis results are shown in Table 1.

[0063] Example 4

[0064] Compared with Example 1, the difference is 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. 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 to obtain the Pt-based catalyst D of the present invention, and its analysis results are shown in Table 1.

[0065] Example 5

[0066] Compared with Example 1, the difference 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. At the same time, the ammonia water concentration is changed to 28 wt% to obtain the Pt-based catalyst E of the present invention, and its analysis results are shown in Table 1.

[0067] Example 6

[0068] Compared with Example 1, the difference is that the acetylacetone platinum concentration is changed to 1.8%, 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 to obtain the Pt-based catalyst F of the present invention, and its analysis results are shown in Table 1.

[0069] Example 7

[0070] Compared with Example 1, the difference is 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 to obtain the Pt-based catalyst G of the present invention, and its analysis results are shown in Table 1.

[0071] Comparative Example 1

[0072] The synthesis step of the sol mixture is the same as that in Example 1.

[0073] 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. The remaining forming steps remain unchanged, and the comparative Pt-based catalyst H of the present invention is obtained. The analysis results are shown in Table 2.

[0074] Comparative Example 2

[0075] The synthesis step of the sol mixture is the same as that in Example 1.

[0076] Compared with Example 1, the difference lies in that only the first white oil column in the four-layer mixing column is removed, and the spheres are formed with a three-layer column, obtaining the comparative Pt-based catalyst I of the present invention. The analysis results are shown in Table 2.

[0077] Comparative Example 3

[0078] The synthesis step of the sol mixture is the same as that in Example 1.

[0079] Compared with Example 1, the difference lies in that only the fourth water layer is removed, obtaining the comparative Pt-based catalyst J of the present invention. The analysis results are shown in Table 2.

[0080] Comparative Example 4

[0081] The synthesis step of the sol mixture is the same as that in Example 1.

[0082] Compared with Example 1, the difference lies in that only the mixed layer of castor oil and soybean oil in the third layer of the four-layer mixing column is removed, obtaining the comparative Pt-based catalyst K of the present invention. The analysis results are shown in Table 2.

[0083] Comparative Example 5

[0084] The synthesis method is the same as that in Example 1, except that the process of impregnating the catalyst precursor with the Pt-containing impregnating solution in step (2) is not carried out, obtaining the comparative Pt-based catalyst L of the present invention. The analysis results are shown in Table 2.

[0085] Comparative Example 6

[0086] The synthesis method of the sol mixture is the same as that in Example 1.

[0087] 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 the 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 Pt-based catalyst M of the present invention. The analysis results are shown in Table 1.

[0088] Table 1 Physicochemical properties of the Pt-based catalysts obtained in each example

[0089] Catalyst Number A B C D E F G Average Particle Diameter, mm 1.83 1.82 1.81 1.82 1.80 1.82 1.81 <![CDATA[Specific surface area, m 2 / g]]> 77 81 84 82 78 80 81 Pore Volume, mL / g 0.722 0.725 0.711 0.688 0.685 0.716 0.699 Pore Size Distribution, % <2 nm 3.6 3.4 3.9 3.7 3.7 3.9 3.4 2 - 50 nm 96.2 96.4 95.5 95.4 95.5 95.7 96.5 >50 nm 0.2 0.2 0.6 0.9 0.8 0.4 0.1 Average Pore Size, nm 15.8 16.0 15.4 14.4 14.3 15.5 14.5 Crushing Strength, N / particle 79 70 75 72 74 70 72 Roundness, % 97.4 97.2 96.9 96.5 96.9 97.2 96.8

[0090] Table 2 Physicochemical properties of the Pt-based catalysts obtained in each comparative example

[0091] Catalyst Number H I J K L M Average Particle Diameter, mm 1.79 1.78 1.75 1.80 1.77 1.78 <![CDATA[Specific surface area, m 2 / g]]> 83 87 84 85 82 85 Pore Volume, mL / g 0.594 0.591 0.472 0.563 0.725 0.583 Pore Size Distribution, % <2 nm 6.8 6.3 6.1 5.7 3.4 5.1 2 - 50 nm 92.1 92.9 93.5 94.1 96.3 94.6 >50 nm 1.1 0.8 0.4 0.2 0.3 0.3 Average Pore Size, nm 13.4 14.4 14.2 13.2 15.9 14.5 Crushing Strength, N / particle 41 56 69 59 69 62 Roundness, % 85.2 78.4 88.2 79.4 97.7 89.5

[0092] Table 3 Compositions of the catalysts in each example

[0093] Catalyst Number A B C D E F G Aluminum Oxide (wt%) 98.85 98.75 98.95 98.85 98.84 98.86 98.85 Total Pt (wt%) 1.0 1.1 1.0 1.0 1.0 1.1 1.0 Surface Pt (wt%) 0.69 0.69 0.67 0.67 0.69 0.70 0.69 Sn (wt%) 0.15 0.15 0.05 0.15 0.16 0.14 0.15

[0094] Table 4 Compositions of the catalysts in each comparative example

[0095] Catalyst Number H I J K L M Aluminum Oxide (wt%) 98.84 98.94 98.95 99.05 99.78 98.85 Total Pt (wt%) 1.0 0.9 0.9 0.8 0.05 1.0 Surface Pt (wt%) 0.65 0.67 0.67 0.66 - 0.67 Sn (wt%) 0.16 0.16 0.15 0.15 0.17 0.15

[0096] Catalyst evaluation

[0097] 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 evaluation of propane dehydrogenation activity: 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 - 6.

[0098] Table 5 Evaluation results of the catalysts in each example for propane dehydrogenation

[0099]

[0100] Table 6 Evaluation results of the catalysts in each comparative example for propane dehydrogenation

[0101]

[0102] 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 Pt-based catalyst, comprising: (1) Mixing an aluminum hydroxide sol with an organic Pt salt 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 Pt-based catalyst precursor; (2) Impregnating the precursor obtained in step (1) with an impregnating solution containing Pt, drying, and calcining to obtain a Pt-based catalyst.

2. The preparation method according to claim 1, wherein: the organic Pt salt in the organic Pt salt solution is one or more of platinum acetylacetonate or tetrakis(triphenylphosphine)platinum, preferably platinum acetylacetonate, and the solvent used is preferably acetone; and / or, the concentration of the organic Pt salt in the organic Pt salt solution is 1.0 wt% to 1.9 wt%; and / or, the addition amount of the organic Pt salt solution is 9% to 11% of the mass of the aluminum hydroxide sol calculated as alumina.

3. The preparation method according to claim 1 or 2, wherein: the organic Pt salt solution contains stannous chloride; preferably, the concentration of stannous chloride in the organic Pt salt solution is 0.4 wt% to 11 wt%.

4. The preparation method according to claim 1, wherein: 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.

5. The preparation method according to claim 4, wherein: 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. The kinematic viscosity of the white oil at 40 °C is 20-40 mm 2 / s, preferably 25-35 mm 2 / s.

6. The preparation method according to claim 4, wherein: 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%.

7. The preparation method according to claim 4, wherein: 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 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.

8. The preparation method according to claim 4, wherein: 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%.

9. The preparation method according to claim 4, wherein: 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.

10. The preparation method according to claim 1, wherein: In step (2), the impregnation is preferably the saturated impregnation method; and / or, the Pt precursor used in the impregnation liquid is preferably PtCl 4 , H 2 PtCl 6 or at least one of them.

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

12. The catalyst according to claim 11, wherein: The specific surface area of the catalyst is 70 to 115 m 2 / g, and the pore volume is 0.60 to 0.85 mL / g; and / or, the average diameter of the catalyst particles is 1.6 to 1.9 mm; and / or, the average pore diameter of the catalyst is 13 to 17 nm; and / or, the crushing strength of the catalyst is 65 to 85 N / grain; And / or, the true roundness of the catalyst is 96.2% to 99.9%.

13. The catalyst according to claim 11, wherein: The pore size distribution of the catalyst is as follows: the pore volume of pores with a pore size less than 2 nm accounts for 1.0% 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 98.9% of the total pore volume, preferably 96.0% to 98.0%.

14. The catalyst according to claim 11, wherein: In the catalyst, based on the mass of the catalyst and calculated by mass fraction, the total Pt content is 0.5% to 1.9%, the Sn content is 0.02% to 0.70%, and the alumina content is 97.4% to 99.48%; Preferably, the Pt content on the surface of the catalyst is 0.3% to 0.8%.

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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