Pt-based dehydrogenation catalyst as well as preparation method and application thereof

Abstract

The invention discloses a Pt-based dehydrogenation catalyst as well as a preparation method and application thereof. 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 Pt-based dehydrogenation catalyst, wherein four layers are sequentially arranged in the mixing column 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, the fourth layer is a tin-containing water layer, the second oil layer is selected from modified transformer oil, and the tin-containing water layer comprises tin salt and hydrochloric acid. The catalyst is used for propane dehydrogenation reaction, and the activity and stability of the catalyst can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to a Pt-based dehydrogenation catalyst, a preparation method and an application thereof, and particularly to a Pt-based dehydrogenation catalyst suitable for a fluidized bed, a preparation method 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. Currently, 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 smaller spherical or bar-shaped catalysts.

[0003] Spherical catalysts have good fluidity, a high packing coefficient, uniform fluid distribution, low resistance, small pressure drop and other advantages, 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 being prone to sintering and α-phase transformation, greatly reducing the specific surface area of the support, damaging the pore structure, and then the active components of the catalyst aggregate, and the activity of the catalyst seriously decreases. 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 in an oil-ammonia column for aging, 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-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.

[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 spheres 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 spheres, and then immerse the γ-Al 2 O 3 spheres 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 spheres 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] Aiming at the deficiencies of the prior art, the present invention provides a Pt-based dehydrogenation catalyst, a preparation method and an application thereof. The catalyst prepared by this method has the characteristics of good roundness, high crushing strength, large pore volume and pore diameter, uniform Pt loading, high dispersion, and environmentally friendly and odorless products. When used in propane dehydrogenation reaction, it can significantly improve the activity and stability of the catalyst.

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

[0010] An aluminum hydroxide sol is mixed with an aqueous solution containing Pt, and the resulting mixture is dropped into an oil-ammonia water-oil-water four-layer mixing column to form a shape, followed by drying and calcination to obtain a Pt-based dehydrogenation catalyst. In the 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 a tin-containing water layer. Among them, the second oil layer is selected from modified transformer oil, and the tin-containing water layer includes a tin salt and hydrochloric acid. Preferably, the concentration of the tin salt is 0.5 wt% to 1.1 wt%, preferably 0.6 wt% to 0.8 wt%, and the concentration of hydrochloric acid is 5 wt% to 8 wt%.

[0011] Further, the alumina content in the aluminum hydroxide sol is 15 wt% to 26 wt%.

[0012] 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 the 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), 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, the water content in the aluminum hydroxide is 17 wt% to 25 wt%. Preferably, the properties of the aluminum hydroxide after calcination are as follows: specific surface area is 110 to 201 m 2 / g, pore volume is 0.8 to 2.0 mL / g, and average pore diameter is 15 to 17 nm. The calcination conditions are as follows: temperature is 600 to 850 °C, time is 2 to 12 h, and an oxygen-containing atmosphere 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% to 23 wt%.

[0013] Further, the platinum-containing compound in the aqueous solution containing Pt is one or more of platinum chloride (PtCl 4 ), chloroplatinic acid (H 2 PtCl 6 ), preferably chloroplatinic acid. The concentration of the platinum-containing compound in the aqueous solution containing Pt is 2 wt% to 6 wt%. The addition amount of the aqueous solution containing Pt is 8% to 40% of the mass of the aluminum hydroxide sol in terms of alumina, preferably 15% to 30%.

[0014] Further, the oil-ammonia water-oil-water four-layer mixing column is a straight column, preferably a cylinder.

[0015] 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.

[0016] 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%.

[0017] Further, in the oil-ammonia water-oil-water four-layer mixing column, the third layer is the second oil layer, i.e., the liquid seal oil layer. The density of the modified transformer oil used in the second oil layer is between that of ammonia water and water. Preferably, the density of the modified transformer oil at 20 °C is above 0.90 g / mL, preferably 0.93-0.96 g / mL, and further preferably 0.94-0.96 g / mL. The height of the third layer is 30%-50% of the height of the second layer, preferably 35%-45%.

[0018] Further, the modified transformer oil includes transformer oil and a water-soluble surfactant.

[0019] Further, the mass of the water-soluble surfactant is 6%-25% of the mass of the transformer oil, preferably 10%-18%.

[0020] Further, the water-soluble surfactant is one or more of lauroyl diethanolamine, nonylphenol polyoxyethylene ether (the polymerization degree is preferably 9, i.e., n = 9), and octylphenol polyoxyethylene ether (the polymerization degree is preferably 7, i.e., n = 7).

[0021] Further, the density (at 20 °C) of the transformer oil is 0.86-0.89 g / mL, and the kinematic viscosity at 40 °C is 9-15 mm 2 / s.

[0022] Further, the preparation process of the modified transformer oil is as follows:

[0023] Mix the water-soluble surfactant with the transformer oil, and the obtained mixture is subjected to heat treatment, i.e., sealed heating treatment and open heating treatment in sequence, and the above heat treatment is repeated 3-6 times to obtain the modified transformer oil.

[0024] Further, the conditions of the sealed heating treatment are as follows: the heating temperature is 80-120 °C, and the heating time is 6-20 h. Further, the conditions of the open heating treatment are as follows: the heating temperature is 80-120 °C, and the heating time is 6-20 h.

[0025] Further, in the oil-ammonia water-oil-water four-layer mixing column, 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. During the preparation of the Pt-based dehydrogenation catalyst, when the concentration of the tin salt is less than 0.5 wt%, the tin salt is supplemented by an external circulating pump to make the concentration meet the above requirements.

[0026] Further, the preparation method of the oil-ammonia water-oil-water four-layer mixing column includes:

[0027] (1) Pour the materials required for the fourth layer into a columnar container (preferably a plexiglass container) and ensure the uniformity of the solution;

[0028] (2) Slowly add the materials required for the third layer onto the fourth-layer materials in step (1) and stabilize for 20 to 35 minutes;

[0029] (3) Slowly add the materials required for the second layer onto the third-layer materials in step (2);

[0030] (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, slow up-and-down circulation is carried out 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 minutes 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 tailing, and affect the true roundness.

[0031] Further, the shaping of the spherical alumina catalyst is carried out in an oil-ammonia water-oil-water four-layer mixing column, and a mixture of aluminum hydroxide sol and Pt-containing aqueous solution is dropped into the oil-ammonia water-oil-water four-layer mixing column, wherein the inner diameter of the dropper used is 1.0 mm to 1.6 mm.

[0032] Further, the residence time of the mixture of aluminum hydroxide sol and Pt-containing aqueous solution in the oil-ammonia water-oil-water four-layer mixing column is 5 to 18 s, preferably 7 to 11 s.

[0033] 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.

[0034] The second aspect of the present invention provides a Pt-based dehydrogenation catalyst prepared by the above preparation method.

[0035] Further, the specific surface area of the Pt-based dehydrogenation catalyst is 62 to 114 m 2 / g, and the pore volume is 0.62 - 0.85 mL / g.

[0036] Further, the Pt-based dehydrogenation catalyst is in the form of spherical particles with an average particle diameter of 1.6 - 2.0 mm.

[0037] Further, the pore size distribution of the Pt-based dehydrogenation catalyst is as follows: the pore volume of pores with a pore size less than 2 nm accounts for 0.9% - 3.5% of the total pore volume, and the pore volume of pores with a pore size of 2 - 50 nm accounts for 96.5% - 99.1% of the total pore volume, preferably 97.0% - 99.0%.

[0038] Further, the average pore size of the Pt-based dehydrogenation catalyst is 15.2 - 19.2 nm.

[0039] Further, the crushing strength of the Pt-based dehydrogenation catalyst is 69 - 90 N / grain.

[0040] Further, the roundness of the Pt-based dehydrogenation catalyst is 98.0% - 99.9%.

[0041] Further, in the Pt-based dehydrogenation catalyst, based on the mass of the catalyst, by mass fraction, the content of Pt is 0.23% - 1.20%, the content of Sn is 0.03% - 0.87%, and the content of alumina is 97.93% - 99.74%.

[0042] The third aspect of the present invention provides the application of the above catalyst in the propane dehydrogenation reaction.

[0043] Further, the application includes: contacting a propane raw material with the catalyst for a dehydrogenation reaction to obtain a product propylene.

[0044] Further, before use, the propane dehydrogenation catalyst needs to be reduced. The catalyst precursor is reduced under 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.

[0045] 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 .

[0046] Compared with the prior art, the advantages of the present invention are:

[0047] (1) The present invention uses a one-step method to synthesize a Pt-based dehydrogenation catalyst. An aqueous solution containing Pt is added to an aluminum hydroxide sol, so that the metal is uniformly dispersed in the alumina support, and at the same time, it also plays a role in pore expansion. The four-layer oil-ammonia-water-oil mixed column used in the forming process is different from the two-layer oil-ammonia column or the hot oil column. The third oil layer is added as a liquid seal oil layer and the fourth tin-containing water layer, which can enable 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, it is not easy to break or shrink with the volatilization of the surface ammonia water, so that the alumina particle size and mechanical strength are significantly increased. At the same time, the metal and the support 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 pellets also causes the hydrophobicity of the colloid surface to rapidly decrease, the interaction force between the colloids to increase significantly, the distance between the colloids to become shorter, and part of the original structure to collapse, resulting in an increase in the mesoporous structure of the support in the range of 2-50 nm. By adjusting the hydrochloric acid concentration in the tin-containing water layer, the pore structure can be further optimized.

[0048] (2) In the four-layer mixed column used in the present invention, tin elements are introduced into the fourth water column. Since the surface potential of the spherical sol is negative, Sn 2+ ions can be quickly adsorbed when passing through the tin-containing water column. Metal elements are introduced in one step during the support synthesis process, and Sn-doped spherical alumina is obtained by subsequent calcination. This method is not only simple to operate, but also because the adsorption mainly occurs on the outer surface and does not block the pores. Moreover, the interaction between Sn and alumina is enhanced during the curing process, which is more beneficial to improving the stability and dispersion degree after noble metal loading, and thus improving the catalyst activity.

[0049] (3) The preparation process of the present invention is environmentally friendly. In the traditional oil-ammonia column pelletizing process, the problems of environmental pollution caused by ammonia volatilization and subsequent pollutant emissions are relatively serious. In the present invention, the second oil layer separates the second ammonia water layer and the fourth tin-containing water 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, the tin-containing water layer can be replaced to ensure the liquid seal effect, which is simple to operate and cost-saving in industry.

[0050] (4) In the four-layer hybrid column used in the present invention, since the density difference between ammonia water in the ammonia water layer and pure water in the tin-containing water layer is small, the density of the selected liquid-sealing oil (modified transformer oil) needs to be greater than that of ammonia water and less than that of pure water, and at the same time, the viscosity cannot be too high, otherwise it will affect the roundness of the sol. By adding a surfactant to the transformer oil in the present invention, the density can be increased without changing its viscosity to meet the requirements. The water-soluble surfactant slowly penetrates into the oil under heating conditions, and the intermolecular interaction force is enhanced. During the process of evaporating the water, the intermolecular distance shortens. After repeated operations, the stability of the modified oil can be ensured. At the same time, due to the addition of the surfactant, the surface tension at the oil-water interface is significantly reduced, and the pause of the sol sphere when passing through the oil-water interface is reduced, and it can quickly pass through the interface, reducing pulling, effectively improving the roundness of the spherical carrier.

[0051] (5) The Pt-based dehydrogenation catalyst obtained by the preparation method 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 Pt is not easily precipitated, having good stability and good reaction performance. Specific embodiments

[0052] The following examples are used to further illustrate the Pt-based dehydrogenation catalyst, its preparation method and application effect in the present invention. 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.

[0053] In the following examples, the experimental methods are all conventional methods in the art unless otherwise specified. The experimental materials used in the following examples are all purchased from conventional biochemical reagent stores unless otherwise specified.

[0054] In the present invention, the nitrogen adsorption-desorption curve of the sample is tested at -196 °C by using the ASAP2020 type fully automatic physical adsorption instrument of Micromeritics Company in the United States to measure the specific surface area, pore volume and pore size distribution.

[0055] In the present invention, the crushing strength is tested by using the ZQJ-Ⅲ intelligent particle strength testing machine manufactured by Dalian Zhiqu Testing Machine Factory, and the average value of crushing ten spherical carriers is tested.

[0056] In the present invention, the true roundness is tested by using the electron microscope of Olympus Company, and the average value is calculated after testing 20 samples.

[0057] Example 1

[0058] 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 m2 (16 nm average pore diameter), after adding deionized water and stirring to make a uniform slurry, 26 g of nitric acid solution with a mass concentration of 45% was added for peptization, and finally a pseudoboehmite sol with an alumina mass content of 20% was prepared; 300 g of the above sol (alumina content 20 wt%) was taken, and 12 g of chloroplatinic acid solution with a chloroplatinic acid concentration of 3% was added and stirred evenly to obtain a sol mixture;

[0059] 7 g of lauroyl diethanolamine and 7 g of nonylphenol polyoxyethylene ether (n = 9) were added to 100 g of transformer oil (density at 20 °C is 0.89 g / mL, kinematic viscosity at 40 °C is 12 mm 2 / s), after stirring evenly, it was sealed and placed in an oven at 100 °C for heating for 8 hours, then the sealing cover was removed and heating was continued for 4 hours, and the above steps were repeated 3 times to obtain modified transformer oil (density at 20 °C is 0.94 g / mL); using a dropper with an inner diameter of 1.2 mm to drip the above sol into a four-layer column of (white oil - 25 wt% ammonia water - modified transformer oil - stannous-containing aqueous solution) with a kinematic viscosity of 32 mm at 40 °C for shaping, and the residence time in the four-layer column was 8 s. Among them, the addition amount of white oil was 35% of the volume of ammonia water, the addition amount of modified transformer oil was 38% of the volume of ammonia water, and the addition amount of stannous-containing aqueous solution was 1.3 times the volume of ammonia water. The concentration of stannous chloride in the stannous-containing aqueous solution was 0.7%, and the hydrochloric acid concentration was 6 wt%. During the preparation of the catalyst, when the stannous chloride concentration was less than 0.5 wt%, the stannous chloride concentration in the stannous-containing aqueous solution was made the initial concentration by an external circulating pump. Then it was dried at 130 °C for 8 hours and calcined at 800 °C for 3 hours to obtain the catalyst A of the present invention, and its analysis results are shown in Table 1. 2 / s white oil - 25 wt% ammonia water - modified transformer oil - stannous-containing aqueous solution) four-layer column for shaping, and the residence time in the four-layer column was 8 s. Among them, the addition amount of white oil was 35% of the volume of ammonia water, the addition amount of modified transformer oil was 38% of the volume of ammonia water, and the addition amount of stannous-containing aqueous solution was 1.3 times the volume of ammonia water. The concentration of stannous chloride in the stannous-containing aqueous solution was 0.7%, and the hydrochloric acid concentration was 6 wt%. During the preparation of the catalyst, when the stannous chloride concentration was less than 0.5 wt%, the stannous chloride concentration in the stannous-containing aqueous solution was made the initial concentration by an external circulating pump. Then it was dried at 130 °C for 8 hours and calcined at 800 °C for 3 hours to obtain the catalyst A of the present invention, and its analysis results are shown in Table 1.

[0060] Example 2

[0061] Compared with Example 1, the difference is that the hydrochloric acid concentration in the fourth layer was changed to 8 wt% and the tin salt concentration was changed to 0.8% to obtain the catalyst B of the present invention, and its analysis results are shown in Table 1.

[0062] Example 3

[0063] Compared with Example 1, the difference is that 15.6 g of chloroplatinic acid solution with a concentration of 6% was added to obtain the catalyst C of the present invention, and its analysis results are shown in Table 1.

[0064] Example 4

[0065] Compared with Example 1, the difference is that in the preparation of the modified transformer oil, the surfactant used was changed to lauroyl diethanolamine, the addition amount was changed to 12 g, and the number of repetitions was changed to 4 times, and the density of the obtained modified transformer oil at 20 °C was 0.95 g / mL), to obtain the catalyst D of the present invention, and its analysis results are shown in Table 1.

[0066] Example 5

[0067] Compared with Example 1, the difference lies in that in the preparation of the modified transformer oil, 4 g of lauroyl diethanolamine and 4 g of nonylphenol polyoxyethylene ether (n = 9) are added to 100 g of transformer oil, and the density of the obtained modified transformer oil at 20 °C is 0.93 g / mL), obtaining the catalyst E of the present invention, and its analysis results are shown in Table 1.

[0068] Example 6

[0069] 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 modified transformer oil is 32% of the volume of ammonia water, and the addition amount of stannum-containing aqueous solution is 1.6 times the volume of ammonia water, obtaining the catalyst F of the present invention, and its analysis results are shown in Table 1.

[0070] Comparative Example 1

[0071] The synthesis step of the sol mixture is the same as that in Example 1.

[0072] 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, and the remaining forming steps remain unchanged. After calcination, 100 g of the carrier is taken and saturatedly impregnated into an aqueous solution containing 0.4 g of stannum tetrachloride. After impregnation for 30 min, it is dried in a drying oven at 90 °C for 10 h and calcined in a muffle furnace at 600 °C for 4 h, obtaining the comparative catalyst G of the present invention, and its analysis results are shown in Table 2.

[0073] Comparative Example 2

[0074] The synthesis step of the sol mixture is the same as that in Example 1.

[0075] Compared with Example 1, the difference lies in that only the first layer of white oil column is removed and the spheres are formed with a three-layer column, obtaining the comparative catalyst H of the present invention, and its analysis results are shown in Table 2.

[0076] Comparative Example 3

[0077] The synthesis step of the sol mixture is the same as that in Example 1.

[0078] Compared with Example 1, the difference lies in that the fourth layer of stannum-containing water column is removed. After calcination, 100 g of the carrier is taken and saturatedly impregnated into an aqueous solution containing 0.4 g of stannum tetrachloride. After impregnation for 30 min, it is dried in a drying oven at 90 °C for 10 h and calcined in a muffle furnace at 600 °C for 4 h, obtaining the comparative catalyst I of the present invention, and its analysis results are shown in Table 2.

[0079] Comparative Example 4

[0080] The synthesis step of the sol mixture is the same as that in Example 1.

[0081] Compared with Example 1, the difference is that only the modified transformer oil layer is removed to obtain the comparative catalyst J of the present invention, and the analysis results are shown in Table 2.

[0082] Comparative Example 5

[0083] The synthesis step of the sol mixture is the same as that in Example 1.

[0084] Compared with Example 1, the difference is that only the modified transformer oil is replaced by transformer oil, and the remaining forming steps remain unchanged. That is, the forming step is to use a dropper with an inner diameter of 1.2 mm to drop the above sol into a four-layer column of (white oil with a kinematic viscosity of 32 mm 2 / s - ammonia water with a concentration of 25 wt% - transformer oil - stannous-containing aqueous solution) for forming, and the residence time in the four-layer column is 8 s. Among them, the addition amount of white oil is 35% of the volume of ammonia water, the addition amount of transformer oil is 38% of the volume of ammonia water, and the addition amount of stannous-containing aqueous solution is 1.3 times the volume of ammonia water. The concentration of stannous chloride in the stannous-containing aqueous solution is 0.7%, and the concentration of hydrochloric acid is 6 wt%. During the preparation of the catalyst, when the concentration of stannous chloride is less than 0.5 wt%, the concentration of stannous chloride in the stannous-containing aqueous solution is made the initial concentration by an external circulating pump. Then it is dried at 130 °C for 8 hours and calcined at 800 °C for 3 hours to obtain the comparative catalyst K of the present invention, and 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 is that the addition amount of white oil is 16% of the volume of ammonia water, the addition amount of modified transformer oil is 20% of the volume of ammonia water, and the addition amount of stannous-containing aqueous solution is 0.4 times the volume of ammonia water, to obtain the comparative catalyst L of the present invention, and the analysis results are shown in Table 2.

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

[0089]

[0090]

[0091] Table 2 Physicochemical properties of the catalysts obtained in each comparative example

[0092] Catalyst Number G H I J K L Average Particle Diameter, mm 1.70 1.70 1.73 1.76 1.69 1.71 <![CDATA[Specific surface area, m 2 / g]]> 102 103 98 97 100 101 Pore Volume, mL / g 0.493 0.435 0.499 0.484 0.397 0.402 Pore Size Distribution, % <2nm 4.4 4.2 5.3 5.5 4.0 4.1 2 - 50nm 95.5 95.7 94.7 94.5 96.0 95.7 >50nm 0.1 0.1 - - - 0.2 Average Pore Size, nm 13.7 13.5 12.9 13.9 12.8 13.0 Crushing Strength, N / particle 52 55 53 45 29 47 Roundness, % 95.1 94.2 93.9 92.1 94.6 95.0

[0093] Table 3 Composition of the catalysts in each example

[0094] Catalyst Number A B C D E F Alumina (wt%) 99.5 99.4 99.2 99.5 99.5 99.5 Pt (wt%) 0.3 0.3 0.6 0.3 0.3 0.3 Sn (wt%) 0.2 0.3 0.2 0.2 0.2 0.2

[0095] Table 4 Composition of Catalysts in Each Comparative Example

[0096] Catalyst Number G H I J K L Alumina (wt%) 99.5 99.6 99.6 99.6 99.6 99.5 Pt (wt%) 0.3 0.2 0.2 0.3 0.3 0.3 Sn (wt%) 0.2 0.2 0.2 0.1 0.1 0.2

[0097] Catalyst Evaluation

[0098] 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 propane dehydrogenation activity evaluation: the reaction temperature is 530 °C, 0.2 MPa, and the volume space velocity is 80 h -1 . The results of propane dehydrogenation are listed in Tables 5 - 8.

[0099] Table 5 Evaluation Results of Catalysts in Each Example for Propane Dehydrogenation

[0100]

[0101] Table 6 Evaluation Results of Catalysts in Each Example for Propane Dehydrogenation

[0102]

[0103] Table 7 Evaluation Results of Catalysts in Each Example for Propane Dehydrogenation Stability

[0104]

[0105] Table 8 Evaluation Results of Catalysts in Each Comparative Example for Propane Dehydrogenation Stability

[0106]

[0107] 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. Preparation method of the described Pt-based dehydrogenation catalyst, including: Mix aluminum hydroxide sol with an aqueous solution containing Pt, and drop the obtained mixture into an oil-ammonia water-oil-water four-layer mixing column for shaping, followed by drying and calcination to obtain the Pt-based dehydrogenation catalyst; 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 tin-containing water layer. Among them, the second oil layer is selected from modified transformer oil, and the tin-containing water layer includes a tin salt and hydrochloric acid. Preferably, the concentration of the tin salt is 0.5 wt% to 1.1 wt%, preferably 0.6 wt% to 0.8 wt%, and the concentration of hydrochloric acid is 5 wt% to 8 wt%.

2. The preparation method according to claim 1, characterized in that: The platinum-containing compound in the aqueous solution containing Pt is one or more of platinum chloride and chloroplatinic acid, preferably chloroplatinic acid; and / or, the concentration of the platinum-containing compound in the aqueous solution containing Pt is 2 wt% to 6 wt%; and / or, the addition amount of the aqueous solution containing Pt is 8% to 40% of the mass of the aluminum hydroxide sol calculated as alumina, preferably 15% to 30%.

3. The preparation method according to claim 1, 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; the kinematic viscosity of the white oil at 40 °C is 20 to 40 mm 2 / s, preferably 25 to 35 mm 2 / s.

4. The preparation method according to claim 1, characterized in that: 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% to 28 wt%, preferably 22 wt% to 26 wt%.

5. The preparation method according to claim 1, characterized in that: 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 second ammonia water layer and the fourth water layer and a kinematic viscosity of 60 mm 2 / s or less at 40°C. Preferably, it is a mixed oil of castor oil and soybean oil. Among them, the volume ratio of castor oil to soybean oil is preferably 1 / 4 to 1 / 6; And / or, 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.

6. The preparation method according to claim 1, characterized in that: The oil-ammonia water-oil-water four-layer mixing column is a straight column, preferably a cylinder.

7. The preparation method according to claim 1, 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.

8. The preparation method according to claim 1, characterized in that: In the oil-ammonia water-oil-water four-layer mixing column, the density of the modified transformer oil used in the second oil layer is between that of ammonia water and water. Preferably, the density of the modified transformer oil at 20 °C is above 0.90 g / mL, further 0.93 to 0.96 g / mL. The modified transformer oil includes transformer oil and a water-soluble surfactant; Preferably, the mass of the water-soluble surfactant is 6% to 25% of the mass of the transformer oil, preferably 10% to 18%; Preferably, the water-soluble surfactant is one or more of lauroyl diethanolamine, nonylphenol polyoxyethylene ether, or octylphenol polyoxyethylene ether; Preferably, the density of the transformer oil at 20 °C is 0.86 to 0.89 g / mL, and the kinematic viscosity at 40 °C is 9 to 15 mm 2 / s.

9. The preparation method according to claim 1, characterized in that: The preparation process of the modified transformer oil is as follows: A water-soluble surfactant is mixed with transformer oil, and the resulting mixture is subjected to heat treatment, i.e., sealed heating treatment and open heating treatment in sequence, and the above heat treatment is repeated 3 to 6 times to obtain the modified transformer oil; Preferably, the conditions of the sealed heating treatment are as follows: the heating temperature is 80 to 120 °C, and the heating time is 6 to 20 h; Preferably, the conditions of the open heating treatment are as follows: the heating temperature is 80 to 120 °C, and the heating time is 6 to 20 h.

10. The Pt-based dehydrogenation catalyst prepared by the preparation method according to any one of claims 1-9.

11. The catalyst according to claim 10, wherein: The specific surface area of the Pt-based dehydrogenation catalyst is 62 to 114 m 2 / g, and the pore volume is 0.62 to 0.85 mL / g; and / or, the average diameter of the particles of the Pt-based dehydrogenation catalyst is 1.6 to 2.0 mm; and / or, the average pore diameter of the Pt-based dehydrogenation catalyst is 15.2 to 19.2 nm; and / or, the crushing strength of the Pt-based dehydrogenation catalyst is 69 to 90 N / grain; and / or, the true roundness of the Pt-based dehydrogenation catalyst is 98.0% to 99.9%; and / or, the pore size distribution of the Pt-based dehydrogenation catalyst is: the pore volume of pores with a pore size less than 2 nm accounts for 0.9% to 3.5% of the total pore volume, and the pore volume of pores with a pore size of 2-50 nm accounts for 96.5% to 99.1% of the total pore volume, preferably 97% to 99%.

12. The catalyst according to claim 10, wherein: In the Pt-based dehydrogenation catalyst, based on the mass of the catalyst and in terms of mass fraction, the content of Pt is 0.23% to 1.20%, the content of Sn is 0.03% to 0.87%, and the content of alumina is 97.93% to 99.74%.

13. The application of the catalyst according to any one of claims 10-12 in the propane dehydrogenation reaction.

14. The application according to claim 13, 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.

15. The application according to claim 14, wherein: The reaction conditions are 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 .

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