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

Abstract

The invention discloses a catalyst for producing propylene through propane dehydrogenation as well as preparation and application of the catalyst. The catalyst comprises a tin-containing alumina carrier and an active metal Pt, and the pore size distribution of the tin-containing alumina carrier is as follows: the pore volume of pores with the pore size less than 2 nm accounts for 1.5%-5.0% of the total pore volume, and the pore volume of pores with the pore size of 2-50 nm accounts for 95.0%-98.5% of the total pore volume. When the catalyst is applied to propylene preparation reaction through propane dehydrogenation, the activity of the catalyst can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to a catalyst for propane dehydrogenation to produce propylene, its preparation and application. 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 clover, 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, the catalysts for dehydrogenating light alkanes to produce olefins are mainly prepared by loading active component Pt and other additives on a γ-Al 2 O 3 support, such as EP100222A, CN1185994A, etc. However, since the dehydrogenation reaction is carried out at a high temperature of about 600 °C, the high reaction temperature often causes a large amount of carbon deposition on the catalyst. As the catalyst is used for a longer time, the catalyst needs to be subjected to multiple high-temperature carbon burning 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, destroying the pore structure, and then causing the aggregation of the active components of the catalyst and a serious decline in the catalyst activity. Therefore, it is necessary to further modify the γ-Al 2 O 3 support to make the catalyst have high thermal stability.

[0005] CN112973771A discloses a spherical catalyst support containing molecular sieve and alumina and its preparation and application. 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 obtaining a high-strength and large specific surface composite sphere through washing, drying, and calcination. 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 molecular sieve dispersion. 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 3Method for small balls. This method involves stirring and slurrying pseudoboehmite dry gel powder with deionized water, acidifying with dilute nitric acid, adding urea and a predetermined amount of sodium silicate solution, stirring for 5 hours, adding kerosene and fatty alcohol polyoxyethylene ether and stirring for 5 hours, dropping and forming balls in an oil-ammonia column, curing the wet balls in ammonia water for 2 hours, then filtering, rinsing with deionized water, drying, and calcining to obtain silicon-containing γ-Al 2 O 3 small balls. This method for preparing γ-Al 2 O 3 small balls has a long curing time, is difficult to wash, and has low production efficiency.

[0007] CN104289220A discloses a preparation method and use of a high thermal stability low-carbon alkane dehydrogenation catalyst. The method for preparing the carrier is to add an aluminum source to an alkaline aqueous solution, stir, continue to drop the alkaline aqueous solution to adjust the pH of the mixed solution to 7-14, filter, wash with deionized water, then add dilute nitric acid to form a sol, add a silicon source, stir, filter, age for 10-48 hours, drop and form balls, and then dry and calcine to obtain γ-Al 2 O 3 small balls; 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 balls, and then dry and calcine to obtain γ-Al 2 O 3 small balls, and then immerse the γ-Al 2 O 3 small balls 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 silicon-containing γ-Al 2 O 3 small balls. The disadvantages of this method are long preparation cycle, 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 produce propylene and its preparation and application. This catalyst is used in the reaction of propane dehydrogenation to produce propylene, and the catalytic activity is significantly improved.

[0009] In the first aspect of the present invention, a catalyst for propane dehydrogenation to produce propylene is provided. The catalyst includes a tin-containing alumina carrier and an active metal Pt. Among them, the pore size distribution of the tin-containing alumina carrier is as follows: the pore volume of pores with a pore size less than 2 nm accounts for 1.5% - 5.0% of the total pore volume, and the pore volume of pores with a pore size of 2-50 nm accounts for 95.0% - 98.5% of the total pore volume, preferably 95.5% - 98.0%.

[0010] Further, in the catalyst for propane dehydrogenation to produce propylene, based on the mass of the catalyst and in terms of mass fraction, the content of Pt calculated as Pt is 0.2% to 1.6%, and the content of the tin-containing alumina support is 98.4% to 99.8%.

[0011] Further, the specific surface area of the tin-containing alumina support is 65 to 120 m 2 / g, and the pore volume is 0.50 to 0.86 mL / g.

[0012] Further, the tin-containing alumina support is in the form of spherical particles, and the average diameter of the particles is 1.8 to 2.0 mm.

[0013] Further, the average pore diameter of the tin-containing alumina support is 14 to 18 nm.

[0014] Further, the crushing strength of the tin-containing alumina support is 62 to 79 N / grain.

[0015] Further, the true roundness of the tin-containing alumina support is 97.7% to 99.9%.

[0016] Further, in the tin-containing alumina support, the content of Sn is 0.08% to 0.89%, the content of SiO 2 is 3.0% to 5.1%, and the content of alumina is 94.01% to 96.92%.

[0017] The second aspect of the present invention provides a method for preparing the above-mentioned catalyst for propane dehydrogenation to produce propylene, wherein the method for preparing the tin-containing alumina support includes:

[0018] Mixing aluminum hydroxide sol and acidic silica sol, dropping the obtained mixture into an oil-ammonia-oil-water four-layer mixing column for shaping, drying, and calcining to obtain a tin-containing spherical alumina support; in the oil-ammonia-oil-water four-layer mixing column, a first oil layer, an ammonia layer, a second oil layer, and a tin-containing water layer are sequentially arranged from top to bottom, wherein the second oil layer is selected from modified transformer oil, and the tin-containing water layer includes a tin salt and hydrochloric acid.

[0019] Further, in the tin-containing water layer, the tin salt is at least one of stannous chloride or tin tetrachloride, preferably stannous chloride. Further, in the tin-containing water layer, 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%.

[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 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), 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 calculated as acid is 1wt% - 10wt% of the mass of aluminum hydroxide calculated as alumina, preferably 2wt% - 8wt%. Further, the aluminum hydroxide is preferably hydrated aluminum hydroxide, such as wet aluminum hydroxide material. Preferably, in the aluminum hydroxide, the water content 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 - 2.0 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 a conventional method. The aluminum hydroxide is preferably macroporous pseudo-boehmite containing water, and the water content is 19wt% - 23wt%.

[0022] Further, the concentration of the acidic silica sol is 5 - 45 g SiO 2 / L calculated as SiO 2 , and the pH value of the silica sol is adjusted to 3 - 5 with an acid (such as at least one of nitric acid and acetic acid). The addition amount of the acidic silica sol calculated as SiO 2 is 0.2wt% - 8.0wt% of the mass of the aluminum hydroxide sol calculated as alumina, preferably 2.5wt% - 7.5wt%.

[0023] Further, the oil-ammonia-oil-water four-layer mixing column is a straight column, preferably a cylinder.

[0024] Further, in the oil-ammonia-oil-water four-layer mixing column, the first oil layer 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 oil layer is 30% - 50% of the height of the ammonia water layer.

[0025] Further, in the oil-ammonia-oil-water four-layer mixing column, in the ammonia water layer, the concentration of the ammonia water is 20wt% - 28wt%, preferably 22wt% - 26wt%.

[0026] Further, in the oil-ammonia water-oil-water four-layer mixing column, in the second oil layer, i.e., the liquid-sealing oil layer, the density of the modified transformer oil 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, and more preferably 0.94 - 0.96 g / mL. Further, the height of the second oil layer is 30% - 50% of the height of the ammonia water layer, preferably 35% - 45%.

[0027] Further, the modified transformer oil includes transformer oil and a water-soluble surfactant.

[0028] Further, the mass of the water-soluble surfactant is 6% - 25% of the mass of the transformer oil, preferably 10% - 18%.

[0029] Further, the water-soluble surfactant is one or more of lauroyl diethanolamine, nonylphenol polyoxyethylene ether (preferably with a polymerization degree of 9, i.e., n = 9), or octylphenol polyoxyethylene ether (preferably with a polymerization degree of 7, i.e., n = 7).

[0030] Further, the density of the transformer oil (at 20 °C) is 0.86 - 0.89 g / mL, and the kinematic viscosity at 40 °C is 9 - 15 mm 2 / s.

[0031] Further, the preparation process of the modified transformer oil is as follows:

[0032] Mix the water-soluble surfactant with the 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 - 6 times to obtain the modified transformer oil.

[0033] 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.

[0034] 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.

[0035] Further, in the oil-ammonia water-oil-water four-layer mixing column, the tin-containing water layer is prepared by dissolving a tin salt in hydrochloric acid. The height of the fourth layer is 1.0 - 2.0 times that of the second layer, preferably 1.2 - 1.5 times. During the preparation process of the tin-containing spherical alumina support, when the concentration of the tin salt is less than 0.5 wt%, a tin salt is supplemented through an external circulating pump to make the concentration meet the above requirements.

[0036] Further, the preparation method of the oil-ammonia water-oil-water four-layer mixing column includes:

[0037] (1) Pour the materials required for the stannous-containing water layer into a columnar container (preferably a plexiglass container) and ensure the solution is uniform;

[0038] (2) Slowly add the materials required for the second oil layer on top of the stannous-containing water layer materials in step (1), and stabilize for 20 - 35 min;

[0039] (3) Slowly add the materials required for the ammonia water layer on top of the second oil layer materials in step (2);

[0040] (4) Slowly add the materials required for the first oil layer on top of the ammonia water layer materials in step (3) to obtain an oil - ammonia water - oil - water four - layer mixed column. Preferably, during the addition of the materials required for the first oil layer, slowly circulate up and down above the interface between the first oil layer and the ammonia water layer through a peristaltic pump to weaken the surface tension at the interface between the first oil layer and the ammonia water layer, and then let it stand for 30 - 60 min until it stabilizes. This can ensure that the aluminum hydroxide sol can quickly pass through the contact interface between the first oil layer and the ammonia water layer, prevent pauses from causing trailing, and affect the roundness.

[0041] Further, the forming of the stannous-containing alumina support is carried out in the oil - ammonia water - oil - water four - layer mixed column. The mixture of aluminum hydroxide sol and acidic silica sol is dropped into the oil - ammonia water - oil - water four - layer mixed column. Among them, the inner diameter of the dropping head used is 1.0 mm - 1.6 mm.

[0042] Further, the residence time of the mixture of aluminum hydroxide sol and acidic silica sol in the oil - ammonia water - oil - water four - layer mixed column is 5 - 18 s, preferably 7 - 11 s.

[0043] Further, the drying temperature is 100°C - 150°C, and the drying time is 6 - 10 hours; the calcination temperature is 550°C - 950°C, and the calcination time is 1 - 4 hours.

[0044] Further, in the catalyst for propane dehydrogenation to produce propylene, the active metal Pt can be loaded by the impregnation method, preferably the saturated impregnation method. Among them, the Pt precursor used in the impregnating solution is preferably at least one of PtCl 4 、H 2 PtCl 6 . The drying conditions after impregnation are preferably as follows: the drying temperature is 80 - 120°C, and the drying time is 8 - 12 h. The calcination conditions after impregnation are preferably as follows: the calcination temperature is 500 - 700°C, and the calcination time is 2 - 6 h.

[0045] Further, before the catalyst for propane dehydrogenation to produce propylene is used, it needs to be reduced. The catalyst precursor is reduced under a reducing atmosphere. The reducing atmosphere is preferably H 2 , the reducing temperature is 450 - 600°C, and the reducing time is 1 - 3 h.

[0046] The third aspect of the present invention provides the application of the above catalyst in the propane dehydrogenation reaction.

[0047] Furthermore, the application includes: contacting the propane raw material with the catalyst for dehydrogenation reaction to obtain the product propylene.

[0048] Furthermore, the propane dehydrogenation reaction conditions are preferably as follows: the reaction temperature is 500 - 600 °C, the reaction pressure is 0 - 1 MPa, and the volume space velocity is 50 - 200 h -1 .

[0049] Compared with the prior art, the advantages of the present invention are as follows:

[0050] (1) In the preparation process of the tin - containing alumina support of the present invention, the four - layer oil - ammonia - water - oil mixed column adopted is different from the two - layer oil - ammonia column or the hot oil column. By adding a second oil layer as a liquid - sealing oil layer and a tin - containing water layer, the sol can quickly enter the second oil layer and the tin - containing water layer after passing through the ammonia - water layer, and the pH value quickly drops to neutral or acidic. During the drying process of the pellets, it is not easy to break or shrink with the volatilization of the surface ammonia - water, resulting in a significant increase in the alumina particle size and mechanical strength. In addition, the rapid decrease in the pH value on the surface of the sol pellets simultaneously causes a rapid decrease in the hydrophobicity of the colloidal particles, a significant increase in the intermolecular interaction force between the colloidal particles, a shortening of the distance between the colloidal particles, and partial collapse of the original structure, resulting in an increase in the mesoporous structure within the range of 2 - 50 nm of the support. By adjusting the hydrochloric acid concentration in the fourth - layer tin - containing water layer, the pore structure can be further optimized.

[0051] (2) In the four - layer oil - ammonia - water - oil mixed column adopted in the present invention, since the density difference between ammonia - water in the ammonia - water layer and pure water in the water layer is small, the density of the liquid - sealing oil (modified transformer oil) in the second oil layer selected needs to be greater than that of ammonia - water and less than that of pure water, and the viscosity should not be too high. 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 transformer oil can be ensured. 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 pellets when passing through the oil - water interface is reduced, and they can quickly pass through the interface, reducing pulling and effectively improving the roundness of the spherical support.

[0052] (3) In the four - layer oil - ammonia - water - oil mixed column adopted in the present invention, by introducing tin elements into the fourth - layer water layer, since the surface potential of the spherical sol is negative, it can quickly adsorb Sn when passing through the tin - containing water layer 2+Ions are used to introduce metal elements in one step during the synthesis of the support. Through subsequent calcination, an Sn-doped spherical alumina support is obtained. This method is not only simple to operate, but also, since adsorption mainly occurs on the outer surface, it will not block the pores. Moreover, during the curing process, the interaction between Sn and alumina is enhanced, which is more conducive to improving the stability and dispersion after noble metal loading, and thus improving the catalyst activity.

[0053] (4) The preparation process of the present invention is environmentally friendly. In the traditional oil-ammonia column pelletizing process, the volatilization of ammonia water brings serious environmental pollution problems and subsequent pollutant emission problems. In the present invention, the ammonia water layer and the tin-containing water layer are separated by the second oil layer, so that the ammonia water layer is sealed above the tin-containing 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. Detailed implementation manners

[0054] The catalyst for propane dehydrogenation to produce propylene, its preparation method and application effect in the present invention will be further described below through examples. The examples are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0055] 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.

[0056] In the present invention, the nitrogen adsorption-desorption curve of the sample is tested at -196 °C using an ASAP2020 type fully automatic physical adsorption instrument of Micromeritics Company, USA, to measure the specific surface area, pore volume, and pore size distribution.

[0057] 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 supports is measured.

[0058] In the present invention, the true roundness is tested using an electron microscope of Olympus Company, and the average value is calculated after testing 20 samples.

[0059] Example 1

[0060] 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 average pore size), deionized water was added and stirred to make a uniform slurry. Then, 26 g of a 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 100 mL of an acidic silica sol with a pH of 4 was added. The concentration of the silica sol was 30 g SiO 2 calculated as 30 g SiO 2 / L. After stirring evenly, a sol mixture was obtained.

[0061] 7 g each of lauroyl diethanolamine and nonylphenol polyoxyethylene ether (n = 9) were added to 100 g of transformer oil (density at 20 °C was 0.89 g / mL, kinematic viscosity at 40 °C was 12 mm 2 / s). After stirring evenly, it was sealed and placed in an oven at 100 °C for 8 hours. The seal was removed and heating continued for 4 hours. The above steps were repeated 3 times to obtain modified transformer oil (density at 20 °C was 0.94 g / mL). Using a dropper with an inner diameter of 1.2 mm, the above sol was dropped into a four-layer mixing column (cylindrical) of (white oil with a kinematic viscosity of 32 mm 2 / s - ammonia water with a concentration of 25 wt% - modified transformer oil - stannous chloride-containing aqueous solution) 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 stannous chloride-containing aqueous solution was 1.3 times the volume of ammonia water. The concentration of stannous chloride in the stannous chloride-containing aqueous solution was 0.7%, and the hydrochloric acid concentration was 6 wt%. During the preparation of the tin-containing spherical alumina support, when the concentration of stannous chloride was less than 0.5 wt%, stannous chloride was replenished through an external circulation pump to make the concentration of stannous chloride in the stannous chloride-containing aqueous solution the initial concentration. Then, it was dried at 130 °C for 8 hours and calcined at 800 °C for 3 hours to obtain the tin-containing alumina support A of the present invention, and its analysis results are shown in Table 1.

[0062] Example 2

[0063] Compared with Example 1, the difference is that the hydrochloric acid concentration in the fourth layer of stannous chloride-containing water layer was changed to 8 wt% and the stannous salt concentration was changed to 0.8% to obtain the tin-containing alumina support B of the present invention, and its analysis results are shown in Table 1.

[0064] Example 3

[0065] Compared with Example 1, the difference is that the concentration of the acidic silica sol used was changed to 15 g SiO 2 / L, the pH value of the acidic silica sol was adjusted to 5, the drying temperature was changed to 140 °C, and the calcination temperature was changed to 850 °C to obtain the tin-containing alumina support C of the present invention, and its analysis results are shown in Table 1.

[0066] Example 4

[0067] Compared with Example 1, the differences are as follows: The surfactant used in the second oil layer 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), obtaining the tin-containing alumina support D of the present invention, and its analysis results are shown in Table 1.

[0068] Example 5

[0069] Compared with Example 1, the difference is that in the preparation of the modified transformer oil, 4 g of lauroyl diethanolamine and 4 g of nonylphenol polyoxyethylene ether are added to 100 g of transformer oil. The density of the obtained modified transformer oil at 20 °C is 0.93 / mL), obtaining the tin-containing alumina support E of the present invention, and its analysis results are shown in Table 1.

[0070] Example 6

[0071] Compared with Example 1, the differences are as follows: The addition amount of white oil is 42% of the volume of ammonia water, the addition amount of the modified transformer oil is 32% of the volume of ammonia water, and the addition amount of the tin-containing aqueous solution is 1.6 times the volume of ammonia water, obtaining the tin-containing alumina support F of the present invention, and its analysis results are shown in Table 1.

[0072] Comparative Example 1

[0073] The synthesis step of the sol mixture is the same as that of Example 1.

[0074] 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, obtaining the comparative alumina support G of the present invention, and its analysis results are shown in Table 2.

[0075] Comparative Example 2

[0076] The synthesis step of the sol mixture is the same as that of Example 1.

[0077] Compared with Example 1, the difference is that only the first white oil column in the four-layer mixing column is removed, and the ball is formed with a three-layer column, obtaining the comparative tin-containing alumina support H of the present invention, and its analysis results are shown in Table 2.

[0078] Comparative Example 3

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

[0080] Compared with Example 1, the difference is that only the fourth tin-containing water layer is removed, obtaining the comparative alumina support I of the present invention, and its analysis results are shown in Table 2.

[0081] Comparative Example 4

[0082] The synthesis steps of the sol mixture are the same as those in Example 1.

[0083] Compared with Example 1, the difference lies in that only the second oil layer modified transformer oil layer is removed to obtain the comparative tin-containing alumina support J of the present invention, and the analysis results are shown in Table 2.

[0084] Comparative Example 5

[0085] The synthesis steps of the sol mixture are the same as those in Example 1.

[0086] Compared with Example 1, the difference lies in that only the second oil layer modified transformer oil layer is replaced with transformer oil, and the remaining forming steps remain unchanged. That is, the forming steps are as follows: using a dropper with an inner diameter of 1.2 mm to drop the above sol into a four-layer mixing column (cylindrical column) of (white oil with a kinematic viscosity of 32 mm 2 / s - ammonia water with a concentration of 25 wt% - transformer oil - tin-containing aqueous solution) for forming, and the residence time in the four-layer mixing column is 8 s. Among them, the addition amount of white oil is 35% of the volume of ammonia water, the addition amount of 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 6 wt%. During the preparation of the tin-containing spherical alumina support, when the concentration of stannous chloride is less than 0.5 wt%, stannous chloride is replenished by an external circulating pump to make the concentration of stannous chloride in the tin-containing aqueous solution the initial concentration. Then it is dried at 130 °C for 8 hours and calcined at 800 °C for 3 hours to obtain the comparative alumina support K of the present invention, and the analysis results are shown in Table 2.

[0087] Comparative Example 6

[0088] The synthesis method of the sol mixture is the same as that in Example 1.

[0089] Compared with Example 1, the difference lies in that the addition amount of white oil is 16% of the volume of ammonia water, the addition amount of 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 tin-containing alumina support L of the present invention, and the analysis results are shown in Table 2.

[0090] Table 1 Physical and chemical properties of the tin-containing alumina supports obtained in each example

[0091]

[0092]

[0093] Table 2 Physical and chemical properties of the tin-containing alumina supports obtained in each comparative example

[0094] Carrier number G H I J K L Average particle diameter, mm 1.76 1.76 1.77 1.64 1.72 1.73 <![CDATA[Specific surface area, m 2 / g]]> 89 91 96 87 89 92 Pore volume, mL / g 0.431 0.435 0.492 0.395 0.401 0.411 Pore size distribution, % < 2nm 6.2 3.6 7.7 7.1 6.3 6.1 2 - 50nm 93.6 96.2 92.2 92.8 93.6 93.8 > 50nm 0.2 0.1 0.1 0.1 0.1 0.1 Average pore diameter, nm 13.7 12.9 12.3 12.5 10.4 11.2 Crushing strength, N / particle 35 41 37 44 23 30 Roundness, % 93.2 95.7 91.4 90.4 90.2 91.4

[0095] Catalyst evaluation

[0096] 100 g of the tin-containing alumina supports prepared in Examples 1-6 and Comparative Examples 2, 4, and 5 were respectively taken and saturatedly impregnated into an aqueous solution containing 0.8 g of chloroplatinic acid. After impregnation for 30 min, they were dried in an oven at 90 °C for 10 h, calcined in a muffle furnace at 600 °C for 4 h, and reduced in a hydrogen atmosphere at 520 °C for 1.5 h. 100 g of the spherical alumina supports prepared in Comparative Examples 1 and 3 were respectively taken and saturatedly impregnated into an aqueous solution containing 0.8 g of chloroplatinic acid and 0.4 g of tin tetrachloride. After impregnation for 30 min, they were dried in an oven at 90 °C for 10 h, calcined in a muffle furnace at 600 °C for 4 h, and reduced in a hydrogen atmosphere at 520 °C for 1.5 h. The compositions of the obtained catalysts are listed in Table 3-4.

[0097] 5 g of each of the above catalysts were respectively taken and loaded into a fixed-bed reactor for the activity evaluation of propane dehydrogenation: the reaction temperature was 590 °C, the pressure was atmospheric, and the volume space velocity was 110 h -1 . The results of propane dehydrogenation are listed in Table 5-6.

[0098] Table 3 Compositions of the catalysts in each example

[0099]

[0100]

[0101] Table 4 Compositions of the catalysts in each comparative example

[0102] Carrier number G H I J K L Aluminum oxide (wt%) 95.3 95.5 96.2 96.5 95.5 95.5 Pt (wt%) 0.4 0.4 0.4 0.4 0.4 0.4 Sn (wt%) 0.2 0.2 0.2 0.1 0.1 0.1 <![CDATA[SiO 2 (wt%)]]> 4.1 3.9 3.2 3.0 4.0 4.0

[0103] Table 5 Evaluation results of the catalysts in each example for propane dehydrogenation

[0104]

[0105] Table 6 Evaluation results of the catalysts in each comparative example for propane dehydrogenation

[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 solution 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 the production of propylene by propane dehydrogenation, the catalyst comprising a tin-containing alumina support and an active metal Pt, wherein, the pore size distribution of the tin-containing alumina support is as follows: the pore volume of pores with a pore size less than 2 nm accounts for 1.5% - 5.0% of the total pore volume, and the pore volume of pores with a pore size of 2 - 50 nm accounts for 95.0% - 98.5% of the total pore volume, preferably 95.5% - 98.0%.

2. The catalyst according to claim 1, characterized in that: in the catalyst, based on the mass of the catalyst, in terms of mass fraction, the content of Pt in terms of Pt is 0.2% - 1.6%, and the content of the tin-containing alumina support is 98.4% - 99.8%; Preferably, in the tin-containing alumina support, the content of Sn is 0.08% to 0.89%, and the content of SiO 2 is 3.0% to 5.1%, and the content of alumina is 94.01% to 96.92%.

3. The catalyst according to claim 1, characterized in that: The specific surface area of the tin-containing alumina support is 65 to 120 m 2 / g; and / or, the pore volume of the tin-containing alumina support is 0.50 - 0.86 mL / g; and / or, the average diameter of the tin-containing alumina support is 1.8 - 2.0 mm; and / or, the average pore size of the tin-containing alumina support is 14 - 18 nm; and / or, the crushing strength of the tin-containing alumina support is 62 - 79 N / grain; and / or, the true roundness of the tin-containing alumina support is 97.7% - 99.9%.

4. A preparation method of the catalyst according to any one of claims 1 - 3, characterized in that: the preparation method of the tin-containing alumina support includes: mixing aluminum hydroxide sol and acidic silica sol, dropping the obtained mixture into an oil - ammonia - oil - water four - layer mixing column for shaping, drying and calcining to obtain a tin-containing spherical alumina support; in the oil - ammonia - oil - water four - layer mixing column, a first oil layer, an ammonia layer, a second oil layer and a tin-containing water layer are arranged in sequence from top to bottom, wherein the second oil layer is selected from modified transformer oil, and the tin-containing water layer includes a tin salt and hydrochloric acid.

5. The preparation method according to claim 4, characterized in that: in the tin-containing water layer, the tin salt is at least one of stannous chloride or stannic chloride, preferably stannous chloride; and / or, in the tin-containing water layer, the concentration of the tin salt is 0.5 wt% - 1.1 wt%, preferably 0.6 wt% - 0.8 wt%, and the concentration of hydrochloric acid is 5 wt% - 8 wt%.

6. The preparation method according to claim 4, characterized in that: the alumina content in the aluminum hydroxide sol is 15 wt% - 26 wt%; And / or, the concentration of the acidic silica sol is 5 to 45 g SiO 2 calculated as / L; 2 / L; and / or, the pH value of the acidic silica sol is 3 - 5; And / or, the addition amount of the acidic silica sol is 0.2 wt% to 8.0 wt%, preferably 2.5 wt% to 7.5 wt% of the mass of the aluminum hydroxide sol based on alumina in terms of SiO 2 calculated as.

7. The preparation method according to claim 4, characterized in that: In the oil-ammonia water-oil-water four-layer mixing column, the first oil layer is selected from one or more of white oil and diesel oil, preferably white oil, and the kinematic viscosity of the white oil at 40 °C is 20-40 mm 2 / s, preferably 25-35 mm 2 / s.

8. The preparation method according to claim 4, characterized in that: in the oil - ammonia - oil - water four - layer mixing column, in the ammonia layer, the concentration of ammonia is 20 wt% - 28 wt%, preferably 22 wt% - 26 wt%.

9. The preparation method according to claim 4, characterized in that: the density of the modified transformer oil is between that of ammonia 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; Preferably, in the oil - ammonia - oil - water four - layer mixing column, 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.

10. According to the preparation method described in claim 4, 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 heat-treated, that is, sequentially subjected to sealed heating treatment and open heating treatment, 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.

11. According to the preparation method described in claim 4, It is characterized in that: The height of the first oil layer is 30% to 50% of the height of the ammonia water layer; and / or, the height of the second oil layer is 30% to 50% of the height of the ammonia water layer, preferably 35% to 45%; and / or, the height of the tin-containing water layer is 1.0 to 2.0 times the height of the ammonia water layer, preferably 1.2 to 1.5 times.

12. The application of the catalyst according to any one of claims 1-3 in the propane dehydrogenation reaction.

13. According to the application described in claim 12, 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 to 600 °C, and the reduction time is 1 to 3 h.

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