Pt-based dehydrogenation catalyst, preparation method and application thereof

Abstract

The application discloses a Pt-based dehydrogenation catalyst and a preparation method and application thereof. The preparation method of the catalyst comprises the following steps: mixing an aluminum hydroxide sol with a Pt-containing aqueous solution, dropping the obtained mixture into an oil-ammonia water-oil-water four-layer mixed column for molding, drying and calcining, and thus a Pt-based dehydrogenation catalyst is prepared; wherein, four layers are sequentially arranged from top to bottom in the mixed column, the first layer is a first oil layer, the second layer is an ammonia water layer, the third layer is a second oil layer, and the fourth layer is a tin-containing water layer; the second oil layer is selected from modified transformer oil; and the tin-containing water layer comprises a tin salt and hydrochloric acid. The catalyst can be used for a propane dehydrogenation reaction, and can significantly improve the catalyst activity and stability.

Description

TECHNICAL FIELD

[0001] The present application relates to a Pt-based dehydrogenation catalyst, a preparation method and application thereof, in particular to a Pt-based dehydrogenation catalyst suitable for a boiling bed, a preparation method and application thereof. BACKGROUND

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

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

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

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

[0006] CN105478100A discloses a method for preparing silicon-containing γ-Al2O3 pellets. The method is to stir and slurry pseudo-boehmite dry glue powder and deionized water, acidify by adding 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 ball forming in an oil ammonia column, solidify the wet ball in ammonia water for 2 hours, then filter, rinse with deionized water, dry and calcine to obtain silicon-containing γ-Al2O3 pellets. The method has long solidification time, difficult washing and low production efficiency.

[0007] CN104289220A discloses a method for preparing and use of a high-thermal-stability low-carbon alkane dehydrogenation catalyst. The carrier preparation method is to add an aluminum source to an alkaline aqueous solution, stir, continue to add 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 ball forming, then dry and calcine to obtain Si-containing γ-Al2O3 pellets; or add an aluminum source to an alkaline aqueous solution, stir, continue to add 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 ball forming, then dry and calcine to obtain γ-Al2O3 pellets, then immerse the γ-Al2O3 pellets in a silicon source aqueous solution or ethanol solution at 60-120℃ for 2-6 hours, then dry and calcine to obtain Si-containing γ-Al2O3 pellets. The method has the disadvantages of long preparation period, complex process, pH value adjustment and inconsistent product. SUMMARY

[0008] In view of the deficiencies of the prior art, the present application provides a Pt-based dehydrogenation catalyst, a preparation method and application thereof. The catalyst prepared by the method has the characteristics of good roundness, high crushing strength, large pore volume and pore size, uniform Pt loading, high dispersion, environmental protection and no odor, etc., and can significantly improve the catalyst activity and stability when used for propane dehydrogenation reaction.

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

[0010] The Pt-based dehydrogenation catalyst is prepared by mixing the aluminum hydroxide sol with the Pt-containing aqueous solution, dropping the obtained mixture into an oil-ammonia water-oil-water four-layer mixed column to form, drying and calcining.

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

[0012] Further, the preparation method of the aluminum hydroxide sol comprises: mixing the aluminum hydroxide with water to obtain a slurry, and adding a peptizing agent to obtain the aluminum hydroxide sol after uniform stirring. Further, the peptizing agent is selected from one or more of inorganic acids (such as nitric acid) and organic acids (such as acetic acid and citric acid), and is preferably nitric acid. When the peptizing agent contains an inorganic acid, the mass concentration of the inorganic acid is 30%-50%. When the peptizing agent contains an organic acid, the mass concentration of the organic acid is 30%-50%. Further, the addition amount of the peptizing agent is 1wt%-10wt% of the mass of the aluminum hydroxide (calculated as aluminum oxide), and is preferably 2wt%-8wt%. Further, the aluminum hydroxide is preferably hydrous aluminum hydroxide, such as hydrous aluminum hydroxide material. Preferably, the water content in the aluminum hydroxide is 17wt%-25wt%. Preferably, the properties of the aluminum hydroxide after calcination are as follows: the specific surface area is 110-201m 2 / g, the pore volume is 0.8-2.0mL / g, and the average pore size is 15-17nm. The calcination conditions are as follows: the temperature is 600-850℃, the time is 2-12h, and the oxygen-containing atmosphere is air. The aluminum hydroxide can be commercially available or prepared by a conventional method. The aluminum hydroxide is preferably hydrous large-pore pseudoboehmite, and the water content is 19wt%-23wt%.

[0013] Further, the platinum-containing compound in the Pt-containing aqueous solution is one or more of platinum chloride (PtCl4) and chloroplatinic acid (H2PtCl6), and is preferably chloroplatinic acid. The concentration of the platinum-containing compound in the Pt-containing aqueous solution is 2wt%-6wt%. The addition amount of the Pt-containing aqueous solution is 8%-40% of the mass of the aluminum hydroxide sol (calculated as aluminum oxide), and is preferably 15%-30%.

[0014] Further, the oil-ammonia water-oil-water four-layer mixed column is a straight column, and is preferably a cylindrical column.

[0015] Further, in the oil-ammonia water-oil-water four-layer mixed column, the first layer is a first oil layer, which is selected from one or more of white oil or 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 mixed column, the second layer is an ammonia water layer, the concentration of the ammonia water is 20wt%-28wt%, preferably 22wt%-26wt%.

[0017] Further, in the oil-ammonia water-oil-water four-layer mixed column, the third layer is a second oil layer, i.e., a liquid seal oil layer, the modified transformer oil used in the second oil layer has a density between that of ammonia water and water, preferably, the modified transformer oil has a density of 0.90 g / mL or more at 20°C, preferably 0.93-0.96 g / mL, 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 comprises 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 lauryl diethanolamide, nonylphenol polyoxyethylene ether (the degree of polymerization is preferably 9, i.e., n = 9), or octylphenol polyoxyethylene ether (the degree of polymerization is preferably 7, i.e., n = 7).

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

[0022] Further, the modified transformer oil is prepared as follows:

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

[0024] Further, the sealed heat treatment is performed under the following conditions: a heating temperature of 80-120°C, and a heating time of 6-20 h. Further, the open heat treatment is performed under the following conditions: a heating temperature of 80-120°C, and a heating time of 6-20 h.

[0025] Further, in the oil-ammonia water-oil-water four-layer mixed column, the height of the fourth layer is 1.0-2.0 times, preferably 1.2-1.5 times of the height of the second layer. In the preparation of the Pt-based dehydrogenation catalyst, when the concentration of the tin salt is less than 0.5wt%, the tin salt is added by an external circulating pump to make the concentration reach the above requirement.

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

[0027] (1) Pour the required material of the fourth layer into a columnar container (preferably an organic glass container) and ensure that the solution is uniform;

[0028] (2) Slowly add the required material of the third layer to the fourth layer material of step (1) and stabilize for 20-35min;

[0029] (3) Slowly add the required material of the second layer to the third layer material of step (2);

[0030] (4) Slowly add the required material of the first layer to the second layer material of step (3) to obtain an oil-ammonia water-oil-water four-layer mixed column. Preferably, during the addition of the required material of the first layer, a peristaltic pump is used to slowly circulate up and down above the interface between the first layer and the second layer to weaken the surface tension at the interface between the first layer and the second layer, and then stand for 30-60min until it is stable, which can ensure that the aluminum hydroxide sol can quickly pass through the contact interface between the first layer and the second layer, prevent the generation of tailing due to stagnation, and affect the true roundness.

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

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

[0033] Further, the drying temperature is 100℃-150℃, and the drying time is 6-10 hours; the calcination temperature is 750℃-950℃, and the calcination time is 1-4 hours.

[0034] The second aspect of the present application 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 62-114m 2 / g, and the pore volume is 0.62-0.85mL / g.

[0036] Further, the Pt-based dehydrogenation catalyst is a spherical particle, and the average diameter of the particle is 1.6-2.0 mm.

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

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

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

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

[0041] Further, in the Pt-based dehydrogenation catalyst, 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%, all based on the mass of the catalyst.

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

[0043] Further, the use comprises: contacting a propane raw material with the catalyst to perform a dehydrogenation reaction, and obtaining a product propylene.

[0044] Further, the Pt-based dehydrogenation catalyst needs to be reduced before use. The catalyst precursor is reduced under a reducing atmosphere. The reducing atmosphere is preferably H2, the reduction temperature is 450-600 ℃, and the reduction time is 1-3 h.

[0045] Further, the propane dehydrogenation reaction conditions are preferably as follows: the reaction temperature is 500-600 ℃, the reaction pressure is 0-1 MPa, the volume space velocity is 50-200 h -1 .

[0046] Compared with the prior art, the present application has the following advantages:

[0047] (1) The present application adopts one-step synthesis of Pt-based dehydrogenation catalyst, adding Pt-containing aqueous solution in aluminum hydroxide sol, so that the metal is uniformly dispersed in the alumina carrier, and also plays a pore expansion role. The four-layer oil-ammonia water-oil-water mixed column used in the molding process is different from the two-layer oil-ammonia column or hot oil column, which increases the third oil layer as a liquid seal oil layer and the fourth tin-containing water layer, so that the sol quickly enters the third and fourth water layers after passing through the second ammonia water layer, and the pH value quickly decreases to neutral, so that the pellets are not easy to break or shrink during the drying process with the volatilization of surface ammonia water, so that the alumina particle size and mechanical strength increase significantly, and at the same time, the metal and the carrier are in full contact, and the loading is more uniform. In addition, the rapid decrease of the pH value of the sol pellet surface also makes the hydrophobicity of the colloidal particle surface decrease rapidly, the interaction force between the colloidal particles increases significantly, the distance between the colloidal particles becomes shorter, and the original structure collapses partially, resulting in an increase in the mesoporous structure of the carrier in the range of 2-50 nm. By adjusting the concentration of hydrochloric acid 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 application, tin is introduced in 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. The metal element is introduced in the carrier synthesis process by one-step method, and Sn-doped spherical alumina is prepared by subsequent calcination. The operation is simple, and since the adsorption mainly occurs on the outer surface, it will not block the pore channel, and the interaction between Sn and alumina is enhanced during the solidification process, which is more conducive to improving the stability and dispersion of noble metal after loading, and thus improving the catalyst activity.

[0049] (3) The preparation process of the present application is environmentally friendly. In the traditional oil-ammonia column balling process, ammonia water volatilization brings environmental pollution problems and subsequent pollutant emission problems are more serious. The present application separates the second ammonia water layer and the fourth tin-containing water layer with the second oil layer, so that the ammonia water layer is sealed above the fourth water layer, which can prolong the use time and avoid environmental pollution caused by the product taking out ammonia water. After long-term use, the tin-containing water layer can be replaced to ensure the liquid sealing effect, which is simple to operate in industry and saves cost.

[0050] (4) The density of the liquid seal oil (modified transformer oil) used in the four-layer mixing column of the present application needs to be greater than that of ammonia water and less than that of pure water, and the viscosity cannot be too large, otherwise the roundness of the sol will be affected. The present application can improve the density without changing the viscosity by adding a surfactant to the transformer oil, so that it meets the requirements. The water-soluble surfactant slowly penetrates into the oil under heating conditions, the intermolecular interaction force is enhanced, the intermolecular distance is shortened during the evaporation of water, and the stability of the modified oil can be ensured after repeated multiple times. At the same time, due to the addition of the surfactant, the surface tension at the oil-water interface is significantly reduced, the sol small ball stops at the oil-water interface, and the roundness of the spherical carrier is effectively improved.

[0051] (5) The Pt-based dehydrogenation catalyst prepared by the preparation method of the present application has high propane conversion rate and propylene selectivity in the propane-to-propylene reaction, the large pore size and pore volume catalyst can avoid carbon deposition after long-term operation, Pt is not easy to precipitate, and has good stability and good reaction performance. DETAILED DESCRIPTION

[0052] The following examples further illustrate the Pt-based dehydrogenation catalyst and its preparation method and application effect in the present application. The examples are implemented on the premise of the technical solutions of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following examples.

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

[0054] In the present application, the nitrogen adsorption-desorption curve of the sample is tested at-196℃ by using the ASAP2020 full-automatic physical adsorption instrument of the American Micromeritics company, and the specific surface area, pore volume and pore size distribution are determined.

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

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

[0057] Example 1

[0058] Take 250g of large-pore pseudo-boehmite filter cake with a water content of 22wt% (600℃ calcination for 3h under air atmosphere, properties as follows: pore volume 0.87ml / g, specific surface area 175m2 / g, and the average pore size is 16 nm), and then adding 26 g of a 45% nitric acid solution to perform peptization, and finally preparing pseudo-boehmite sol with an alumina mass content of 20%; taking 300 g of the above sol (alumina content of 20 wt%), adding 12 g of a chloroplatinic acid solution with a chloroplatinic acid concentration of 3%, and stirring uniformly to obtain a sol mixture;

[0059] Lauryl diethanolamide and nonylphenol polyoxyethylene ether (n=9) were each added to 100 g of transformer oil (20 °C density of 0.89 g / mL, 40 °C kinematic viscosity of 12 mm 2 / s) in an amount of 7 g, and after stirring uniformly, the mixture was sealed and placed in a 100 °C oven for heating for 8 hours, the sealing cover was removed and the mixture was continuously heated for 4 hours, and the above steps were repeated three times to obtain modified transformer oil (20 °C density of 0.94 g / mL); the sol was added dropwise to a four-layer column (40 °C kinematic viscosity of 32 mm 2 / s) white oil-ammonia water with a concentration of 25 wt%-modified transformer oil-tin-containing aqueous solution) to form a catalyst, and the residence time in the four-layer column was 8 s. The white oil was added in an amount of 35% of the volume of the ammonia water, the modified transformer oil was added in an amount of 38% of the volume of the ammonia water, and the tin-containing aqueous solution was added in an amount of 1.3 times the volume of the ammonia water. The stannous chloride concentration in the tin-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 tin-containing aqueous solution was maintained at the initial concentration by connecting an external circulating pump. Then, drying was performed at 130 °C for 8 hours, and calcination was performed at 800 °C for 3 hours to obtain the catalyst A of the present application, and the analysis results are shown in Table 1.

[0060] Example 2

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

[0062] Example 3

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

[0064] Example 4

[0065] Compared with Example 1, the difference lies in that in the preparation of the modified transformer oil, the surfactant used is changed to lauryl diethanolamide, the amount added is changed to 12 g, and the number of repetitions is changed to 4 times, and the 20 °C density of the modified transformer oil obtained is 0.95 g / mL, to obtain the catalyst D of the present application, and the analysis results are shown in Table 1.

[0066] Example 5

[0067] Comparing with Example 1, the difference is that 4g of lauryl diethanolamide and 4g of nonylphenol polyoxyethylene ether (n=9) are added into 100g of transformer oil in the preparation of modified transformer oil, the density of the obtained modified transformer oil is 0.93g / mL at 20℃, catalyst E of the application is obtained, and the analysis results are shown in Table 1.

[0068] Example 6

[0069] Comparing with Example 1, the difference is that the amount of white oil added is 42% of the volume of ammonia water, the amount of modified transformer oil added is 32% of the volume of ammonia water, and the amount of tin-containing aqueous solution added is 1.6 times of the volume of ammonia water, catalyst F of the application is obtained, and the analysis results are shown in Table 1.

[0070] Comparative Example 1

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

[0072] Comparing with Example 1, the difference is that the four-layer oil-ammonia water-oil-water mixed column is changed to a two-layer oil-ammonia column, the upper layer is white oil with a kinematic viscosity of 32mm 2 / s at 40℃, and the lower layer is ammonia water with a concentration of 25wt%, the amount of white oil added is 25% of the volume of ammonia water, and the remaining molding steps remain unchanged, after calcination, 100g of the carrier is saturated and immersed in an aqueous solution containing 0.4g of tin tetrachloride, dried in a drying oven at 90℃ for 10h after immersion for 30min, and calcined in a muffle furnace at 600℃ for 4h, to obtain comparative catalyst G of the application, and the analysis results are shown in Table 2.

[0073] Comparative Example 2

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

[0075] Comparing with Example 1, the difference is that only the first layer of white oil column is removed, and a three-layer column is used to form a ball, to obtain comparative catalyst H of the application, and the analysis results are shown in Table 2.

[0076] Comparative Example 3

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

[0078] Comparing with Example 1, the difference is that the fourth layer of tin-containing water column is removed, after calcination, 100g of the carrier is saturated and immersed in an aqueous solution containing 0.4g of tin tetrachloride, dried in a drying oven at 90℃ for 10h after immersion for 30min, and calcined in a muffle furnace at 600℃ for 4h, to obtain comparative catalyst I of the application, and the analysis results are shown in Table 2.

[0079] Comparative Example 4

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

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

[0082] Comparative Example 5

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

[0084] Compared with Example 1, the difference is that only the modified transformer oil is replaced by transformer oil, and the remaining molding steps remain unchanged, i.e., the molding step is to drop the above sol into the four-layer column of white oil (40℃ kinematic viscosity is 32mm 2 / s) - ammonia water with a concentration of 25wt% - transformer oil - tin-containing aqueous solution) with a drop head with an inner diameter of 1.2mm, and the residence time in the four-layer column is 8s. 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 tin-containing aqueous solution is 1.3 times the volume of ammonia water. The concentration of stannous chloride in the tin-containing aqueous solution is 0.7%, and the concentration of hydrochloric acid is 6wt%. During the preparation of the catalyst, when the concentration of stannous chloride is less than 0.5wt%, the concentration of stannous chloride in the tin-containing aqueous solution is made to be the initial concentration by connecting an external circulating pump. Then dried at 130℃ for 8 hours, calcined at 800℃ for 3 hours to obtain the comparative catalyst K of the present application, and the analysis results are shown in Table 2.

[0085] Comparative Example 6

[0086] The sol mixture synthesis method is the same as that of 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 tin-containing aqueous solution is 0.4 times the volume of ammonia water, to obtain the comparative catalyst L of the present application, and the analysis results are shown in Table 2.

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

[0089]

[0090]

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

[0092] Catalyst No. G H I J K L Particle average diameter, mm 1.70 1.70 1.73 1.76 1.69 1.71 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, % < 2 nm 4.4 4.2 5.3 5.5 4.0 4.1 2-50 nm 95.5 95.7 94.7 94.5 96.0 95.7 > 50 nm 0.1 0.1 - - - 0.2 Average pore diameter, nm 13.7 13.5 12.9 13.9 12.8 13.0 Crushing strength, N / particle 52 55 53 45 29 47 True circularity, % 95.1 94.2 93.9 92.1 94.6 95.0

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

[0094] Catalyst No. 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 Compositions of the catalysts of the respective comparative examples

[0096] Catalyst No. 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%) Catalyst No. Alumina (wt%) Pt (wt%) Sn (wt%) Catalyst No. Alumina (wt%) Pt (wt%) Sn (wt%) Catalyst No. Alumina (wt%) Pt (wt%) Sn (wt%) Catalyst No. Alumina (wt%) Pt (wt%) Sn (wt%) Catalyst No. Alumina (wt%) Pt (wt%) Sn (wt%) Catalyst No. Alumina (wt%) Pt (wt%) Sn (wt%) Catalyst No. Al 0.2 0.2 0.2 0.1 0.1 0.2

[0097] Catalyst evaluation

[0098] 5 g of the above catalysts were separately reduced at 520°C for 1.5 h under a hydrogen atmosphere, and then were separately charged into a fixed bed reactor for evaluation of the dehydrogenation activity of propane: reaction temperature 530°C, 0.2 MPa, volumetric space velocity 80 h -1 The results of the dehydrogenation of propane are shown in Tables 5 to 8.

[0099] Table 5 Evaluation results of the respective catalysts of the examples for dehydrogenation of propane

[0100]

[0101] Table 6 Evaluation results of the respective catalysts of the examples for dehydrogenation of propane

[0102]

[0103] Table 7 Evaluation results of the respective catalysts of the examples for stability in dehydrogenation of propane

[0104]

[0105] Table 8 Evaluation results of the respective catalysts of the comparative examples for stability in dehydrogenation of propane

[0106]

[0107] The specific embodiments of the present application have been described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A method for preparing a Pt-based dehydrogenation catalyst, comprising: mixing an aluminum hydroxide sol with a Pt-containing aqueous solution, and dropping the obtained mixture into an oil-ammonia water-oil-water four-layer mixed column to form a shape, and drying and calcining to obtain the Pt-based dehydrogenation catalyst; in the oil-ammonia water-oil-water four-layer mixed column, four layers are arranged from top to bottom, the first layer is a first oil layer, the second layer is an ammonia water layer, the third layer is a second oil layer, and the fourth layer is a tin-containing water layer, wherein the second oil layer is selected from modified transformer oil, and the tin-containing water layer comprises a tin salt and hydrochloric acid; the platinum compound in the Pt-containing aqueous solution is chloroplatinic acid; the first oil layer is selected from one or more of white oil or diesel oil; the density of the second oil layer is between the second layer of ammonia water and the fourth layer of water; the modified transformer oil comprises transformer oil and a water-soluble surfactant, and the water-soluble surfactant is one or more of lauryl diethanolamine, nonylphenol polyoxyethylene ether or octylphenol polyoxyethylene ether; the height of the first layer is 30%-50%of the height of the second layer; the height of the third layer is 30%-50%of the height of the second layer; and the height of the fourth layer is 1.0-2.0 times the height of the second layer.

2. The method of claim 1, wherein: In the tin-containing water layer, the concentration of the tin salt is 0.5wt%-1.1wt%, and the concentration of hydrochloric acid is 5wt%-8wt%.

3. The method of claim 2, wherein: In the tin-containing water layer, the concentration of the tin salt is 0.6wt%-0.8wt%.

4. The method of claim 1, wherein: The concentration of the platinum compound in the Pt-containing aqueous solution is 2wt%-6wt%. And / or, the amount of the Pt-containing aqueous solution added is 8%-40%of the mass of the aluminum hydroxide sol calculated as aluminum oxide.

5. The method of claim 4, wherein: The amount of the Pt-containing aqueous solution added is 15%-30%of the mass of the aluminum hydroxide sol calculated as aluminum oxide.

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

7. The method of claim 6, wherein: The white oil has a kinematic viscosity at 40°C of 25-35 mm 2 / s.

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

9. The method of claim 8, wherein: The concentration of ammonia water is 22wt%-26wt%.

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

11. The method of claim 10, wherein: The oil-ammonia water-oil-water four-layer mixed column is a cylindrical column. 12.The method according to claim 1, characterized in that: And / or, the height of the third layer is 35%-45%of the height of the second layer. And / or, the height of the fourth layer is 1.2-1.5 times the height of the second layer.

13. The method of claim 1, wherein: In the oil-ammonia water-oil-water four-layer mixed column, the density of the modified transformer oil at 20℃ is 0.90 g / mL or more.

14. The method of claim 13, wherein: The density of the modified transformer oil at 20℃ is 0.93-0.96 g / mL.

15. The method of claim 1, wherein: The mass of the water-soluble surfactant is 6%-25%of the mass of the transformer oil.

16. The method of claim 15, wherein: The mass of the water-soluble surfactant is 10%-18%of the mass of the transformer oil.

17. The method of claim 1, wherein: The transformer oil has a density of 0.86-0.89 g / mL at 20°C and a kinematic viscosity of 9-15 mm 2 / s at 40°C.

18. The method of claim 1, wherein: The preparation process of the modified transformer oil is as follows: mixing the water-soluble surfactant with the transformer oil, and heat-treating the obtained mixture, i.e. sequentially carrying out sealed heat treatment and open heat treatment, and repeating the above heat treatment 3-6 times to obtain the modified transformer oil.

19. The method of claim 18, wherein: The conditions of the sealed heat treatment are as follows: the heating temperature is 80-120℃, and the heating time is 6-20 h.

20. The method of claim 18, wherein: The conditions of the open heat treatment are as follows: the heating temperature is 80-120℃, and the heating time is 6-20 h.

21. The Pt-based dehydrogenation catalyst prepared by the method of any one of claims 1-20.

22. The catalyst of claim 21, wherein: The Pt-based dehydrogenation catalyst has a specific surface area of 62-114 m 2 / g, and a pore volume of 0.62-0.85 mL / g. and / or, the Pt-based dehydrogenation catalyst has an average diameter of 1.6-2.0 mm; and / or, the Pt-based dehydrogenation catalyst has an average pore size of 15.2-19.2 nm; and / or, the Pt-based dehydrogenation catalyst has a crushing strength of 69-90 N / particle; and / or, the Pt-based dehydrogenation catalyst has a roundness of 98.0%-99.9%; and / or, the Pt-based dehydrogenation catalyst has a pore size distribution of: a pore volume of pores with a pore size of less than 2 nm accounts for 0.9%-3.5% of the total pore volume, and a pore volume of pores with a pore size of 2-50 nm accounts for 96.5%-99.1% of the total pore volume.

23. The catalyst of claim 22, wherein: a pore volume of pores with a pore size of 2-50 nm accounts for 97%-99% of the total pore volume.

24. The catalyst of claim 21, wherein: In the Pt-based dehydrogenation catalyst, 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%, all based on the mass of the catalyst.

25. The use of the catalyst of any one of claims 21-24 in a propane dehydrogenation reaction.

26. The use according to claim 25, characterized in that: Before use, the catalyst needs to be reduced.

27. The use according to claim 26, characterized in that: The reduction atmosphere is H2, the reduction temperature is 450-600°C, and the reduction time is 1-3 h.

28. The use of claim 25, wherein: The reaction conditions are as follows: the reaction temperature is 500-600℃, the reaction pressure is 0-1 MPa, the volume space velocity is 50-200h -1 .

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