Catalyst for preparing propylene through propane dehydrogenation as well as preparation and application of catalyst

Abstract

The invention discloses a catalyst for preparing propylene through propane dehydrogenation as well as preparation and application of the catalyst. The catalyst comprises an active metal Pt, an auxiliary metal Sn and an alumina carrier, in the catalyst, based on the mass of the catalyst, the content of total Pt is 0.26%-1.40%, the content of Sn is 0.02%-0.90%, and the content of aluminum oxide is 97.70%-99.72% in percentage by mass; in the catalyst, the content of Pt on the surface of the catalyst is 0.40%-0.85%. The catalyst is applied to the propane dehydrogenation reaction process, and the propane conversion rate and the propylene selectivity can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to a catalyst for propane dehydrogenation to propylene, its preparation and application, in particular to a catalyst for propane dehydrogenation to propylene 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 strip, 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, and small pressure drop, and are widely used in the technology of dehydrogenating light alkanes to produce olefins.

[0004] Currently, 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 regenerated by high-temperature carbon burning treatment many times, resulting in the γ-Al 2 O 3 support being prone to sintering and α-phase transformation, causing a significant decrease in the specific surface area of the support and damage to the pore structure. Furthermore, the active components of the catalyst aggregate, and the activity of the catalyst drops severely. Therefore, it is necessary to further modify the γ-Al 2 O 3 support to make the catalyst have high thermal stability.

[0005] CN112973771A discloses a spherical catalyst support containing molecular sieve and alumina and its preparation and application. This catalyst support is prepared 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 composite small ball with high strength and large specific surface area. This method is to re-peptize the suspension slurry obtained by ball-milling pseudo-boehmite and molecular sieve with a dilute sol, 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 and then add dilute nitric acid to form a sol, then 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 and 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 period, complex process, need to regulate the pH value, and cannot guarantee product consistency. SUMMARY OF THE INVENTION

[0008] Aiming at the deficiencies of the prior art, the present invention provides a catalyst for propane dehydrogenation to propylene and its preparation and application. The catalyst has the characteristics of good roundness, high crushing strength, large pore volume and pore diameter, large Pt loading, and environmental protection and no peculiar smell of the product. When applied to the propane dehydrogenation reaction process, it can significantly improve the propane conversion rate and propylene selectivity.

[0009] The first aspect of the present invention provides a catalyst for propane dehydrogenation to propylene, which catalyst comprises an active metal Pt, a promoter metal Sn and an alumina support; in the catalyst, based on the mass of the catalyst and in terms of mass fraction, the total Pt content is 0.26% to 1.40%, the Sn content is 0.02% to 0.90%, and the alumina content is 97.70% to 99.72%; in the catalyst, the Pt content on the catalyst surface is 0.40% to 0.85%.

[0010] Further, the specific surface area of the catalyst is 85 - 110 m 2 / g, and the pore volume is 0.62 - 0.83 mL / g.

[0011] Further, the catalyst is in the form of spherical particles, and the average diameter of the particles is 1.7 - 1.9 mm.

[0012] Further, 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 1.3% 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 98.7% of the total pore volume, preferably 97.0% to 98.0%.

[0013] Further, the average pore size of the catalyst is 14.5 - 18.5 nm.

[0014] Further, the crushing strength of the catalyst is 65 - 85 N / grain.

[0015] Further, the true roundness of the catalyst is 97.6% to 99.9%.

[0016] The second aspect of the present invention provides a preparation method of a catalyst for propane dehydrogenation to propylene, comprising:

[0017] (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 catalyst precursor;

[0018] (2) Impregnating and loading Pt on the catalyst precursor obtained in step (1), drying and calcining to obtain the catalyst;

[0019] 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 the water layer. The second oil layer is selected from modified transformer oil.

[0020] Further, the alumina content in the aluminum hydroxide sol is 15 wt% to 26 wt%.

[0021] Further, the preparation method of the aluminum hydroxide sol includes: mixing aluminum hydroxide with water to make a slurry, adding a peptizing agent, and obtaining the aluminum hydroxide sol after stirring evenly. Further, the peptizing agent is selected from one or more of inorganic acids (such as nitric acid), organic acids (such as acetic acid, citric acid), and 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 1 wt% - 10 wt% of the mass of aluminum hydroxide calculated as alumina, and is preferably 2 wt% - 8 wt%. Further, the aluminum hydroxide is preferably hydrated aluminum hydroxide, such as wet aluminum hydroxide material. Preferably, in the aluminum hydroxide, the water content is 17 wt% - 25 wt%. Preferably, the properties of the aluminum hydroxide after calcination are as follows: the specific surface area is 110 - 201 m 2 / g, the pore volume is 0.8 - 2.0 mL / g, and the average pore diameter is 15 - 17 nm. The calcination conditions are as follows: the temperature is 600 - 850 °C, the time is 2 - 12 h, and the oxygen-containing atmosphere is such as air. The aluminum hydroxide can be commercially purchased or prepared by conventional methods. The aluminum hydroxide is preferably macroporous pseudo-boehmite with water content, and the water content is 19 wt% - 23 wt%.

[0022] Further, the organic Pt salt in the organic Pt salt solution is one or more of platinum acetylacetonate or platinum tetrakis(triphenylphosphine), and is preferably platinum acetylacetonate. The solvent used is preferably acetone. Further, the concentration of the organic Pt salt in the organic Pt salt solution is 1.0 wt% - 1.9 wt%. The addition amount of the organic Pt salt solution is 9% - 11% of the mass of the aluminum hydroxide sol calculated as alumina.

[0023] Further, the organic Pt salt solution contains stannous chloride, and the concentration of stannous chloride in the organic Pt salt solution is 0.4 wt% - 11 wt%.

[0024] Further, the oil-ammonia-oil-water four-layer mixing column is a straight column, and is preferably a cylinder.

[0025] Further, in the oil-ammonia-oil-water four-layer mixing column, the first layer is the first oil layer, which is selected from one or more of white oil or diesel oil, and is preferably white oil. The kinematic viscosity of the white oil at 40 °C is 20 - 40 mm 2 / s, and is preferably 25 - 35 mm 2 / s. The height of the first layer is 30% - 50% of the height of the second layer.

[0026] 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% to 28 wt%, preferably 22 wt% to 26 wt%.

[0027] 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 the ammonia water and water. Preferably, the density of the modified transformer oil at 20 °C is above 0.90 g / mL, preferably 0.93 to 0.96 g / mL, and more preferably 0.94 to 0.96 g / mL. The height of the third layer is 30% to 50% of the height of the second layer, preferably 35% to 45%.

[0028] Further, the modified transformer oil includes transformer oil and a water-soluble surfactant.

[0029] Further, the mass of the water-soluble surfactant is 6% to 25% of the mass of the transformer oil, preferably 10% to 18%.

[0030] 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), or octylphenol polyoxyethylene ether (the polymerization degree is preferably 7, i.e., n = 7).

[0031] Further, the density (at 20 °C) of the transformer oil is 0.86 to 0.89 g / mL, and the kinematic viscosity at 40 °C is 9 to 15 mm 2 / s.

[0032] Further, the preparation process of the modified transformer oil is as follows:

[0033] Mix the water-soluble surfactant with the transformer oil, and subject the obtained mixture to heat treatment, i.e., successively to sealed heating treatment and open heating treatment, and repeat the above heat treatment 3 to 6 times to obtain the modified transformer oil.

[0034] Further, 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. Further, 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.

[0035] 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 to 2.0 times the height of the second layer, preferably 1.2 to 1.5 times.

[0036] Further, the fourth layer preferably uses a dilute acid solution. In the dilute acid solution, the acid is selected from at least one of acetic acid and citric acid. The mass concentration of the dilute acid solution is 3% to 8%.

[0037] Further, the preparation method of the oil-ammonia water-oil-water four-layer mixing column includes:

[0038] (1) Pour the materials required for the fourth layer into a columnar container (preferably a plexiglass container) and ensure the solution is uniform;

[0039] (2) Slowly add the materials required for the third layer on top of the fourth layer materials in step (1), and stabilize for 20 to 35 minutes;

[0040] (3) Slowly add the materials required for the second layer on top of the third layer materials in step (2);

[0041] (4) Slowly add the materials required for the first layer on top of the second layer materials in step (3) to obtain an oil-ammonia water-oil-water four-layer mixing column. Preferably, during the addition of the materials required for the first layer, slowly circulate up and down above the interface between the first layer and the second layer through a peristaltic pump to weaken the surface tension at the interface between the first layer and the second layer, and then let it stand for 30 to 60 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.

[0042] Further, the shaping of the catalyst precursor is carried out in an oil-ammonia water-oil-water four-layer mixing column. A mixture of aluminum hydroxide sol and an organic Pt salt solution is dropped into the oil-ammonia water-oil-water four-layer mixing column, wherein the inner diameter of the dropping head used is 1.0 mm to 1.6 mm.

[0043] Further, the residence time of the mixture of aluminum hydroxide sol and the organic Pt salt solution in the oil-ammonia water-oil-water four-layer mixing column is 5 - 18 s, preferably 7 - 11 s.

[0044] 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.

[0045] Further, in the catalyst precursor obtained in step (1), Pt exists in the form of single atoms.

[0046] Further, the impregnation preferably uses the saturated impregnation method. Among them, the Pt precursor used in the impregnation solution is preferably PtCl 4 、H 2 PtCl 6At least one of them. 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.

[0047] Further, in the catalyst, based on the mass of the catalyst and in terms of mass fraction, the total Pt content is 0.26%-1.40%, the Sn content is 0.02%-0.90%, and the alumina content is 97.70%-99.72%; in the catalyst, the Pt content on the catalyst surface is 0.40%-0.85%.

[0048] Further, the specific surface area of the catalyst is 85-110 m 2 / g, and the pore volume is 0.62-0.83 mL / g.

[0049] Further, the catalyst is in the form of spherical particles, and the average diameter of the particles is 1.7-1.9 mm.

[0050] Further, 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 1.3%-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%-98.7% of the total pore volume, preferably 97.0%-98.0%.

[0051] Further, the average pore size of the catalyst is 14.5-18.5 nm.

[0052] Further, the crushing strength of the catalyst is 65-85 N / grain.

[0053] Further, the true roundness of the catalyst is 97.6%-99.9%.

[0054] The third aspect of the present invention provides the application of the above catalyst in the propane dehydrogenation reaction.

[0055] Further, the application includes: contacting a propane raw material with the catalyst for a dehydrogenation reaction to obtain a product propylene.

[0056] Further, before the propane dehydrogenation catalyst is used, it 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.

[0057] 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 .

[0058] Compared with the prior art, the advantages of the present invention are as follows:

[0059] (1) During the preparation process of the 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 have a large steric hindrance, and it is easy to form a single-atom Pt catalyst during the synthesis process. The metal Pt is uniformly dispersed in the alumina support, and at the same time, it also plays a role in expanding the pores. During the forming process, the four-layer oil-ammonia water-oil-water mixing column is different from the two-layer oil-ammonia column or the hot oil column. The third layer of oil layer is added as a liquid-sealing oil layer and the fourth layer of water layer, which can enable the sol to quickly enter the third layer and the fourth layer of water layer after passing through the second layer of ammonia water layer, and the pH value quickly drops to neutral. During the drying process of the small balls, it is not easy to break or shrink with the volatilization of the surface ammonia water, 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 loading is more uniform. In addition, the rapid decrease in the pH value on the surface of the sol small balls also causes a rapid decrease in the hydrophobicity of the colloid surface, a significant increase in the interaction force between the colloids, a shortening of the distance between the colloids, 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 layer of water layer, the pore structure can be further optimized. Subsequently, the precursor is impregnated with a chloroplatinic acid solution, which increases the metal loading amount. At the same time, the number of Pt sites of the outer-layer nanoparticles increases. After calcination, both single-atom Pt and nanoparticle Pt coexist in the catalyst, which can play a synergistic role. The Pt salt increases from the inside to the outside, which is beneficial to expose more active sites, accelerate the reaction, and reduce carbon deposition.

[0060] (2) In the four-layer oil-ammonia water-oil-water mixing column of the present invention, on the one hand, since the density difference between ammonia water and pure water is small, the selected liquid-sealing oil density 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 large, otherwise it will affect the roundness of the sol. By adding a surfactant to the transformer oil, 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 is shortened. After repeated operations, the stability of the modified oil can be ensured. On the other hand, by using the modified transformer oil for liquid sealing, due to the addition of the surfactant, the surface tension at the oil-water interface is significantly reduced, the pause of the sol small balls when passing through the oil-water interface is reduced, and it can quickly pass through the interface, reducing the pulling force, effectively improving the roundness of the spherical support.

[0061] (3) The preparation process of the present invention is environmentally friendly. In the traditional oil-ammonia column pelletizing process, ammonia volatilization causes serious environmental pollution problems and subsequent pollutant emission problems. In the present invention, the second oil layer separates the second ammonia water layer from the fourth water layer, so that the ammonia water layer is sealed above the fourth water layer, which can extend the service time, avoid environmental pollution caused by the product carrying out ammonia water, and after long-term use, deionized water can be replaced to ensure the liquid seal effect, which is simple to operate industrially and saves costs.

[0062] (4) The catalyst obtained by the preparation method of the present invention is used in the propane-to-propylene reaction, 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. Specific embodiments

[0063] The following examples are used to further illustrate the catalyst for propane dehydrogenation to propylene in the present invention, its preparation method and application effect. 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.

[0064] In the following examples, the experimental methods, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all purchased from conventional biochemical reagent stores.

[0065] In the present invention, the nitrogen adsorption and desorption curves of the samples are tested at -196 °C using an ASAP2020 full-automatic physical adsorption instrument from Micromeritics, USA, and the specific surface area, pore volume, and pore size distribution are measured.

[0066] In the present invention, the crushing strength is 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 carriers is tested.

[0067] In the present invention, the true roundness is tested using an electron microscope from Olympus, and the average value is calculated after testing 20 samples.

[0068] In the present invention, the metal Pt content on the catalyst surface is measured by XPS (the instrument is of the Kratos Axis Ultra DLD model).

[0069] Example 1

[0070] 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(16 nm in average pore size), after adding deionized water and stirring to make a homogeneous 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 6 g of acetylacetone platinum solution with a concentration of 1.2% of acetylacetone platinum, which also contained 2.4% of stannous chloride, was added and stirred evenly to obtain a sol mixture;

[0071] 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 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 mixing column (cylindrical) of (white oil with a kinematic viscosity of 32 mm at 40 °C - ammonia water with a concentration of 25 wt% - modified transformer oil - deionized water) for shaping, and the residence time in the four-layer mixing 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 deionized water was 1.3 times the volume of ammonia water. Then it was dried at 130 °C for 8 hours and calcined at 800 °C for 3 hours. 2 100 g of the catalyst precursor prepared above was taken and saturatedly impregnated into an aqueous solution containing 2.0 g of chloroplatinic acid. After impregnation for 30 min, it was dried in a drying oven at 90 °C for 10 h and calcined in a muffle furnace at 600 °C for 4 h to obtain the catalyst A of the present invention, and its analysis results are shown in Table 1.

[0072] Compared with Example 1, the difference is that the deionized water in the fourth layer of the four-layer mixing column was changed to 5 wt% dilute acetic acid solution to obtain the catalyst B of the present invention, and its analysis results are shown in Table 1.

[0073] Example 2

[0074] Compared with Example 1, the difference is that 5.4 g of acetylacetone platinum solution with a concentration of 1.8% of acetylacetone platinum, which also contained 0.8% of stannous chloride, was added to obtain the catalyst C of the present invention, and its analysis results are shown in Table 1.

[0075] Example 3

[0076] Compared with Example 1, the difference is that 5.4 g of acetylacetone platinum solution with a concentration of 1.8% of acetylacetone platinum, which also contained 0.8% of stannous chloride, was added to obtain the catalyst C of the present invention, and its analysis results are shown in Table 1.

[0077] Example 4

[0078] Compared with Example 1, the differences are as follows: In the preparation of the modified transformer oil, the surfactant used is changed to lauroyl diethanolamine, the addition amount is changed to 12 g, and the number of repetitions is changed to 4 times. The density of the obtained modified transformer oil at 20 °C is 0.95 g / mL), and the catalyst D of the present invention is obtained. The analysis results are shown in Table 1.

[0079] Example 5

[0080] Compared with Example 1, the differences are as follows: In the four-layer mixing column, the white oil 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 catalyst E of the present invention is obtained. The analysis results are shown in Table 1.

[0081] Example 6

[0082] Compared with Example 1, the differences are as follows: The ammonia water concentration is changed to 28 wt%; in the preparation of the modified transformer oil, the addition amounts of lauroyl diethanolamine and nonylphenol polyoxyethylene ether are changed to 4 g each. The density of the obtained modified transformer oil at 20 °C is 0.93 g / mL), and the catalyst F of the present invention is obtained. The analysis results are shown in Table 1.

[0083] Example 7

[0084] The difference from Example 1 is 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 deionized water is 1.6 times the volume of ammonia water. The catalyst G of the present invention is obtained. The analysis results are shown in Table 1.

[0085] Comparative Example 1

[0086] The synthesis steps of the sol mixture are the same as those in Example 1.

[0087] Compared with Example 1, the differences are as follows: 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. The comparative catalyst H of the present invention is obtained. The analysis results are shown in Table 2.

[0088] Comparative Example 2

[0089] The synthesis steps of the sol mixture are the same as those in Example 1.

[0090] Compared with Example 1, the difference is 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. The comparative catalyst I of the present invention is obtained. The analysis results are shown in Table 2.

[0091] Comparative Example 3

[0092] The synthesis procedure of the sol mixture is the same as that in Example 1.

[0093] Compared with Example 1, the difference is as follows: 1. Only the fourth water column is removed to obtain the comparative catalyst J of the present invention, and its analysis results are shown in Table 2.

[0094] Comparative Example 4

[0095] The synthesis procedure of the sol mixture is the same as that in Example 1.

[0096] Compared with Example 1, the difference is that only the modified transformer oil layer in the four-layer mixture is removed to obtain the comparative catalyst K of the present invention, and its analysis results are shown in Table 2.

[0097] Comparative Example 5

[0098] The synthesis procedure of the sol mixture is the same as that in Example 1.

[0099] Compared with Example 1, the difference is that only the modified transformer oil in the second oil layer is replaced with transformer oil, and the remaining forming steps remain unchanged to obtain the comparative catalyst L of the present invention, and its analysis results are shown in Table 2.

[0100] Comparative Example 6

[0101] The synthesis method of the sol mixture is the same as that in Example 1.

[0102] 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 deionized water is 0.4 times the volume of ammonia water to obtain the comparative catalyst M of the present invention, and its analysis results are shown in Table 2.

[0103] Table 1 Physicochemical properties of the catalysts obtained in each example

[0104]

[0105] Table 2 Physicochemical properties of the catalysts obtained in each comparative example

[0106] Catalyst number H I J K L M Average particle diameter, mm 1.73 1.79 1.70 1.72 1.73 1.72 <![CDATA[Specific surface area, m 2 / g]]> 100 109 101 104 102 101 Pore volume, mL / g 0.471 0.428 0.409 0.443 0.417 0.425 Pore size distribution, % <2nm 4.0 4.3 4.5 4.2 5.1 4.4 2 - 50nm 95.6 95.7 95.4 95.6 94.7 95.3 >50nm 0.4 - 0.1 0.2 0.2 0.3 Average pore diameter, nm 12.7 11.4 13.0 12.5 12.1 12.4 Crushing strength, N / grain 29 31 37 34 40 42 Roundness, % 95.6 95.9 93.4 93.7 92.4 93.6

[0107] Table 3 Compositions of the catalysts in each example

[0108] Catalyst number A B C D E F G Alumina (wt%) 98.9 98.9 99.0 98.9 98.9 98.9 98.9 Total Pt (wt%) 0.9 0.9 0.9 0.9 0.9 0.9 0.9 Sn (wt%) 0.2 0.2 0.1 0.2 0.2 0.2 0.2 Surface Pt (wt%) 0.72 0.70 0.71 0.71 0.70 0.72 0.72

[0109] Table 4 Compositions of the catalysts in each comparative example

[0110] Catalyst number H I J K L M Alumina (wt%) 99.0 99.0 99.0 98.9 98.9 98.9 Total Pt (wt%) 0.8 0.9 0.8 0.9 0.9 0.9 Sn (wt%) 0.2 0.1 0.2 0.2 0.2 0.2 Surface Pt (wt%) 0.79 0.77 0.72 0.73 0.70 0.74

[0111] Catalyst evaluation

[0112] 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 respectively for the activity evaluation of propane dehydrogenation: the reaction temperature is 500 °C, the pressure is 1 MPa, and the volume space velocity is 150 h -1 . The results of propane dehydrogenation are listed in Table 5-6.

[0113] Table 5 Evaluation results of the catalysts of each example for propane dehydrogenation

[0114]

[0115] Table 6 Evaluation results of the catalysts of each comparative example for propane dehydrogenation

[0116]

[0117]

[0118] 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 catalyst for propane dehydrogenation to propylene, the catalyst comprising active metal Pt, promoter metal Sn and an alumina support; in the catalyst, based on the mass of the catalyst and in terms of mass fraction, the total Pt content is 0.26% - 1.40%, the Sn content is 0.02% - 0.90%, and the alumina content is 97.70% - 99.72%; in the catalyst, the Pt content on the catalyst surface is 0.40% - 0.85%.

2. The catalyst according to claim 1, wherein: The specific surface area of the catalyst is 85-110 m 2 / g, and the pore volume is 0.62-0.83 mL / g; and / or, the catalyst is in the form of spherical particles with an average particle diameter of 1.7 - 1.9 mm; and / or, the pore size distribution of the catalyst is: the pore volume of pores with a pore size less than 2 nm accounts for 1.3% - 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% - 98.7% of the total pore volume, preferably 97.0% - 98.0%; and / or, the average pore size of the catalyst is 14.5 - 18.5 nm; and / or, the crushing strength of the catalyst is 65 - 85 N / grain; and / or, the true roundness of the catalyst is 97.6% - 99.9%.

3. A method for preparing a catalyst for propane dehydrogenation to propylene, comprising: (1) Mixing an aluminum hydroxide sol with an organic Pt salt solution, dropping the resulting mixture into an oil - ammonia - oil - water four - layer mixing column for shaping, drying, and calcining to obtain a catalyst precursor; (2) Impregnating the precursor obtained in step (1) with a Pt - containing impregnating solution, drying, and calcining to obtain the catalyst; in the 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 layer, the third layer is the second oil layer, and the fourth layer is the water layer, and the second oil layer is selected from modified transformer oil.

4. The preparation method according to claim 3, 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% - 1.9 wt%; and / or, the addition amount of the organic Pt salt solution is 9% - 11% of the mass of the aluminum hydroxide sol in terms of alumina.

5. The preparation method according to claim 3, 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% - 11 wt%.

6. The preparation method according to claim 3, wherein: the oil - ammonia - oil - water four - layer mixing column is a straight column, preferably a cylinder.

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

8. The preparation method according to claim 3, wherein: in the oil - ammonia - oil - water four - layer mixing column, the second layer is the ammonia layer, and the ammonia concentration is 20 wt% - 28 wt%, preferably 22 wt% - 26 wt%.

9. The preparation method according to claim 3, wherein: 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 0.90 g / mL or more, preferably 0.93 - 0.96 g / mL; Preferably, the modified transformer oil includes transformer oil and a water-soluble surfactant; Preferably, the mass of the water-soluble surfactant is 6% - 25% of the mass of the transformer oil, preferably 10% - 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.

10. According to the preparation method described in claim 3, It is characterized in that: The preparation process of the modified transformer oil is as follows: Mix the water-soluble surfactant with the transformer oil, and the obtained mixture is subjected to heat treatment, i.e., successively subjected to sealed heating treatment and open heating treatment, and the above heat treatment is repeated 3 - 6 times to obtain the modified transformer oil; Preferably, 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; Preferably, 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.

11. According to the preparation method described in claim 3, It is characterized in that: In the oil-ammonia water-oil-water four-layer mixing column, the fourth layer is the water layer, preferably deionized water or a dilute acid solution, more preferably a dilute acid solution; in the dilute acid solution, the acid is selected from at least one of acetic acid and citric acid; the mass concentration of the dilute acid solution is 3% - 8%.

12. According to the preparation method described in claim 3, It is characterized in that: The height of the first layer is 30% - 50% of the height of the second layer; And / or, the height of the third layer is 30% - 50% of the height of the second layer, preferably 35% - 45%; And / or, the height of the fourth layer is 1.0 - 2.0 times the height of the second layer, preferably 1.2 - 1.5 times.

13. According to the preparation method described in claim 3, It is characterized in that: 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 at least one of them.

14. Application of the catalyst according to any one of claims 1 - 2 or the catalyst prepared by the method according to any one of claims 3 - 13 in the propane dehydrogenation reaction.

15. According to the application described in claim 14, It is characterized in that: 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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