Alumina carrier as well as preparation and application thereof

Abstract

The invention discloses an alumina carrier as well as preparation and application thereof. The preparation method of the alumina carrier comprises the following steps: mixing aluminum hydroxide sol with acidic silica sol, dropwise adding the obtained mixture into an oil-ammonia water-oil-water four-layer mixed column, molding, drying and roasting to obtain alumina; a first oil layer, an ammonia water layer, a second oil layer and a water layer are sequentially arranged in the oil-ammonia water-oil-water four-layer mixing column from top to bottom, the first oil layer is selected from one or more of white oil or diesel oil, the second oil layer is selected from modified transformer oil, and the density of the modified transformer oil is between that of ammonia water and that of water. The alumina carrier has the characteristics of good roundness, high crushing strength, large pore volume and pore diameter, environmental protection, no peculiar smell and the like, and is suitable for being used as a noble metal catalyst carrier.

Description

Technical Field

[0001] The present invention relates to an alumina support and its preparation method and application, and particularly to a spherical alumina support suitable for fluidized beds and noble metal catalysts, and 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. At present, there are four common types of reactors in industry: fixed beds, fluidized beds (boiling beds), suspension beds, and moving beds. Fixed bed reactors commonly use spherical, cylindrical strip, cloverleaf, four-leaf, and flake catalysts. Moving bed reactors often use large particle spherical catalysts. Fluidized bed reactors generally use small particle spherical or bar-shaped catalysts.

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

[0004] Currently, catalysts for dehydrogenating lower alkanes to produce olefins are mainly prepared by loading active component Pt and other additives on a γ-Al 2 O 3 support, such as EP100222A, CN1185994A, etc. However, since the dehydrogenation reaction is carried out at a high temperature of about 600 °C, the high reaction temperature often causes a large amount of carbon deposition on the catalyst. As the use time of the catalyst increases, the catalyst needs to be subjected to multiple high-temperature carbon burning regeneration treatments, resulting in the γ-Al 2 O 3 support being prone to sintering and α-phase transformation, greatly reducing the specific surface area of the support and destroying 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 obtained by precipitating an inorganic aluminum salt with ammonia water and acidifying to obtain a sol, adding a mixed solution of ball-milled pseudo-boehmite and molecular sieve and a sol modification additive to the sol, then dropping and forming and aging in an oil-ammonia column, and finally washing, drying, and calcining to obtain a composite small ball with high strength and large specific surface area. This method is to remix the suspension slurry obtained by ball-milling pseudo-boehmite and molecular sieve with a dilute sol, which will result in the disadvantage of uneven dispersion of the molecular sieve. At the same time, the doping of solid molecular sieve will also cause 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 pseudo-boehmite 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 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 an alumina carrier and its preparation and application. The alumina carrier prepared by this method has the characteristics of good roundness, high crushing strength, large pore volume and pore diameter, and the product is environmentally friendly and odorless, and is suitable as a noble metal catalyst carrier.

[0009] The first aspect of the present invention provides a preparation method of an alumina carrier, including:

[0010] The aluminum hydroxide sol is mixed with the acidic silica sol, and the resulting mixture is dropped into an oil-ammonia-oil-water four-layer mixing column for shaping, followed by drying and calcination to obtain an alumina support. In the oil-ammonia-oil-water four-layer mixing column, a first oil layer, an ammonia water layer, a second oil layer, and a water layer are sequentially arranged from top to bottom. The first oil layer is selected from one or more of white oil or diesel oil. The second oil layer is selected from modified transformer oil, and 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, and further is 0.93 - 0.96 g / mL.

[0011] Further, the density of the modified transformer oil at 20 °C is preferably 0.94 - 0.96 g / mL.

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

[0013] 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 1 wt% - 10 wt% of the mass of aluminum hydroxide calculated as alumina, and 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: specific surface area is 110 - 201 m 2 / g, pore volume is 0.8 - 2.0 mL / g, and average pore diameter is 15 - 17 nm. The calcination conditions are as follows: temperature is 600 - 850 °C, time is 2 - 12 h, and an oxygen-containing atmosphere such as air. The aluminum hydroxide can be commercially purchased or prepared by a conventional method. The aluminum hydroxide is preferably macroporous pseudo-boehmite containing water, and the water content is 19 wt% - 23 wt%.

[0014] 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 acidic 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 0.2% - 8.0% of the mass of aluminum hydroxide calculated as alumina, and preferably 2.5% - 7.5%.

[0015] Further, the oil-ammonia water-oil-water four-layer mixing column is a straight column, preferably a cylinder.

[0016] Further, 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. 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.

[0017] Further, in the oil-ammonia water-oil-water four-layer mixing column, in the ammonia water layer, the concentration of the ammonia water is 20 wt%-28 wt%, preferably 22 wt%-26 wt%. Further, in the oil-ammonia water-oil-water four-layer mixing column, the height of the second oil layer, i.e., the liquid seal oil layer, is 30%-50% of the height of the ammonia water layer, preferably 35%-45%.

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

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

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

[0021] Further, the density 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.

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

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

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

[0025] Further, in the oil-ammonia water-oil-water four-layer mixing column, the water layer is preferably deionized water or a dilute acid solution. The height of the water layer is 1.0 to 2.0 times, preferably 1.2 to 1.5 times, the height of the ammonia water layer.

[0026] 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%.

[0027] Further, the preparation method of the oil-ammonia water-oil-water four-layer mixing column includes:

[0028] (1) Pour the materials required for the water layer into a columnar container (preferably a plexiglass container) and ensure the solution is uniform;

[0029] (2) Slowly add the materials required for the second oil layer on top of the water layer materials in step (1) and stabilize for 20 to 35 minutes;

[0030] (3) Slowly add the materials required for the ammonia water layer on top of the second oil layer materials in step (2);

[0031] (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 mixing 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 to 60 minutes 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, preventing pauses from causing tailing and affecting the true roundness.

[0032] Further, the forming of the spherical alumina carrier is carried out in the oil-ammonia water-oil-water four-layer mixing column. A mixture of aluminum hydroxide sol and acidic silica sol is dropped into the oil-ammonia water-oil-water four-layer mixing column, where the inner diameter of the dropper used is 1.0 mm to 1.6 mm.

[0033] Further, the residence time of the mixture of aluminum hydroxide sol and acidic silica sol in the oil-ammonia water-oil-water four-layer mixing column is 5 - 18 s, preferably 7 - 11 s.

[0034] Further, the drying temperature is 100°C to 150°C, and the drying time is 6 to 10 hours; the calcination temperature is 550°C to 950°C, and the calcination time is 1 to 4 hours.

[0035] The second aspect of the present invention provides an alumina support prepared by the above method. Preferably, the pore size distribution of the alumina support is as follows: the pore volume of pores with a pore size less than 2 nm accounts for 0.5% to 3.5% of the total pore volume, and the pore volume of pores with a pore size of 2 - 50 nm accounts for 96.5% to 99.5% of the total pore volume, preferably 97.0% to 99.0%.

[0036] Further, the specific surface area of the alumina support is 80 - 105 m 2 / g, and the pore volume is 0.45 - 0.79 mL / g.

[0037] Further, the alumina support is spherical particles, and the average diameter of the particles is 1.7 - 2.0 mm.

[0038] Further, the average pore diameter of the alumina support is 13.5 - 17.5 nm.

[0039] Further, the crush strength of the alumina support is 59 - 78 N / grain.

[0040] Further, the true roundness of the alumina support is 97.5% - 99.9%.

[0041] Further, the alumina support can be used as a noble metal catalyst support in reaction processes such as propane dehydrogenation and carbon - two selective hydrogenation.

[0042] Further, in the alumina support, silica accounts for 0.15 wt% - 7.5 wt% of the mass of alumina, preferably 3.0 wt% - 6.0 wt%.

[0043] The third aspect of the present invention provides a propane dehydrogenation catalyst, comprising the above alumina support, noble metal Pt and Sn.

[0044] Further, in the propane dehydrogenation catalyst, based on the mass of the catalyst, by mass fraction, the content of Pt calculated as Pt is 0.25% - 1.70%, the content of Sn calculated as Sn is 0.06% - 0.70%, and the content of the alumina support is 97.60% - 99.69%.

[0045] Further, the preparation method of the propane dehydrogenation catalyst can adopt the impregnation method, preferably the saturated impregnation method. Among them, Pt and Sn can adopt the step - by - step impregnation method or the co - impregnation method. The Pt precursor used in the impregnation solution is preferably PtCl 4 、H 2 PtCl 6 at least one of them, and the Sn precursor is preferably SnCl 4Solution. 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.

[0046] Furthermore, 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.

[0047] The fourth aspect of the present invention provides the application of the above catalyst in the propane dehydrogenation reaction.

[0048] Furthermore, the application includes: the propane raw material contacts with the catalyst for dehydrogenation reaction to obtain the product propylene.

[0049] 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 .

[0050] Compared with the prior art, the advantages of the present invention are as follows:

[0051] (1) The four - layer oil - ammonia - water - oil mixing column adopted in the preparation process of the alumina carrier of the present invention is different from the two - layer oil - ammonia column or the hot oil column. The second oil layer (liquid - sealing oil layer) and the water layer are added, which can enable the sol to quickly enter the second oil layer and the water layer after passing through the ammonia water layer, and the pH value quickly drops to neutral. During the drying process of the spheres, 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 spheres simultaneously causes a rapid decrease in the surface hydrophobicity of the colloidal particles, a significant increase in the interaction force between the colloidal particles, a shorter 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 carrier. By adding an appropriate amount of acidic solution to the fourth - layer water layer, the pore structure can be further optimized.

[0052] (2) In the oil-ammonia water-oil-water four-layer mixing column of the present invention, since the density difference between the ammonia water in the second layer and the pure water in the fourth layer is relatively 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 at the same time, the viscosity cannot 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. Among them, 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 transformer oil can be ensured. Using the modified transformer oil for liquid sealing in the present invention, due to the addition of the surfactant, the surface tension at the oil-water interface is significantly reduced, the pause of the sol spheres 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 carrier.

[0053] (3) The preparation process of the present invention is environmentally friendly. In the traditional oil-ammonia column spheroidization process, the problems of environmental pollution caused by the volatilization of ammonia water and subsequent pollutant emissions are relatively serious. The present invention separates the ammonia water layer and the water layer with the second oil layer, so that the ammonia water layer is sealed above the water layer, which can extend the service life, avoid environmental pollution caused by the product carrying out ammonia water. After long-term use, deionized water can be replaced to ensure the liquid sealing effect, and the operation is simple in industry and the cost is saved. Specific Embodiments

[0054] The following further illustrates the alumina carrier, its preparation method and application effect in the present invention through examples. The examples are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0055] 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.

[0056] In the present invention, the nitrogen adsorption and desorption curves of the samples are tested at -196 °C using the ASAP2020 type full-automatic physical adsorption instrument of Micromeritics Company in the United States to measure the specific surface area, pore volume and pore size distribution.

[0057] In the present invention, the crushing strength is tested using the ZQJ-III intelligent particle strength testing machine manufactured by Dalian Zhiqu Testing Machine Factory, and the average value of crushing ten spherical carriers is 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 250g of macroporous pseudo-boehmite filter cake with a water content of 22wt% (calcined at 600℃ for 3h in air atmosphere, with the following properties: pore volume 0.87mL / g, specific surface area 175m 2 / g, average pore size of 16nm), add deionized water to stir and slurry evenly, then add 26g of nitric acid solution with a mass concentration of 45% for peptization, and finally prepare pseudo-boehmite sol with an alumina content of 20%; take 300g of the above sol (alumina content of 20wt%), add 100mL of acidic silica sol with a pH value of 4, and the silica sol concentration is SiO 2 Calculated as 30g SiO 2 / L, after stirring evenly, a sol mixture is obtained;

[0061] 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 was 0.89 g / mL, kinematic viscosity at 40 °C was 12 mm 2 / s), stir evenly, seal and place in a 100℃ oven for 8 hours, remove the sealing cover and continue heating for 4 hours. Repeat the above heat treatment steps 3 times to obtain modified transformer oil (density at 20℃ is 0.94g / mL). Use a dripper with an inner diameter of 1.2mm to drip (kinematic viscosity at 40℃ is 32mm 2 The above sol mixture is added dropwise into a four-layer mixing column (cylinder) of white oil with a concentration of 25wt% ammonia water, modified transformer oil, and deionized water for molding, and the residence time in the four-layer mixing column is 8s. Among them, the amount of white oil added is 35% of the volume of ammonia water, the amount of modified transformer oil added is 38% of the volume of ammonia water, and the amount of deionized water added is 1.3 times the volume of ammonia water. Then it is dried at 130°C for 8 hours and calcined at 800°C for 3 hours to obtain the alumina carrier A of the present invention. The physicochemical properties of the obtained carrier are shown in Table 1.

[0062] Example 2

[0063] Compared with Example 1, the difference is that the material in the fourth layer is changed from deionized water to 5 wt% dilute acetic acid solution to obtain the aluminum oxide carrier B of the present invention. The physicochemical properties of the obtained carrier 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 is changed to 15g SiO 2 / L, the pH value of the acidic silica sol was adjusted to 5, the drying temperature after molding was changed to 140°C, and the calcination temperature was changed to 850°C to obtain the alumina carrier C of the present invention. The physicochemical properties of the obtained carrier are shown in Table 1.

[0066] Example 4

[0067] 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 heat treatment step is repeated 4 times. The density of the obtained modified transformer oil at 20 °C is 0.95 g / mL; at the same time, the ammonia water concentration is changed to 22 wt%, and the alumina support D of the present invention is obtained. The physicochemical properties of the obtained support are shown in Table 1.

[0068] Example 5

[0069] Compared with Example 1, the differences are as follows: the concentration of acidic silica sol is changed to 25 g SiO 2 / L, and the ammonia water concentration is changed to 23 wt%, and the alumina support E of the present invention is obtained. The physicochemical properties of the obtained support are shown in Table 1.

[0070] Example 6

[0071] Compared with Example 1, the differences are as follows: in the preparation of the modified transformer oil, the addition amounts of lauroyl diethanolamine and nonylphenol polyoxyethylene ether are changed to 4 g each, and the density of the obtained modified transformer oil at 20 °C is 0.93 g / mL). The alumina support F of the present invention is obtained. The physicochemical properties of the obtained support are shown in Table 1.

[0072] Example 7

[0073] 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 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, and the alumina support G of the present invention is obtained, and its analysis results are shown in Table 1.

[0074] Comparative Example 1

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

[0076] 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, and the comparative alumina support H of the present invention is obtained. The physicochemical properties of the obtained support are shown in Table 2.

[0077] Comparative Example 2

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

[0079] Compared with Example 1, the differences are as follows: only the first-layer white oil column in the four-layer oil-ammonia water-oil-water mixing column is removed, and the ball is formed with a three-layer column, and the comparative alumina support I of the present invention is obtained. The physicochemical properties of the obtained support are shown in Table 2.

[0080] Comparative Example 3

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

[0082] Compared with Example 1, the difference is that only the fourth water column is removed to obtain the comparative alumina support J of the present invention. The physicochemical properties of the obtained support are shown in Table 2.

[0083] Comparative Example 4

[0084] The synthesis method of the sol mixture is the same as that of Example 1.

[0085] Compared with Example 1, the difference is that the modified transformer oil in the second oil layer of the four-layer oil-ammonia water-oil-water mixing column is replaced with transformer oil, and the remaining forming steps remain unchanged. That is, the forming step is to use a dropper with an inner diameter of 1.2 mm to drip the above sol mixture 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%, transformer oil, deionized water) 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 deionized water is 1.3 times the volume of ammonia water. 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. The physicochemical properties of the obtained support are shown in Table 2.

[0086] Comparative Example 5

[0087] The synthesis method of the sol mixture is the same as that of Example 1.

[0088] 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 alumina support L of the present invention, and its analysis results are shown in Table 2.

[0089] Table 1 Physicochemical properties of the spherical alumina supports obtained in each example

[0090] Carrier number A B C D E F G Average particle diameter, mm 1.80 1.81 1.80 1.79 1.81 1.81 1.80 <![CDATA[Specific surface area, m 2 / g]]> 86 84 87 87 86 90 85 Pore volume, mL / g 0.604 0.611 0.601 0.602 0.598 0.576 0.574 Pore size distribution, % <2 nm 2.6 2.2 2.6 2.9 2.7 2.6 2.5 2 - 50 nm 97.2 97.4 97.2 97.0 97.2 97.3 97.4 >50 nm 0.2 0.4 0.2 0.1 0.1 0.1 0.1 Average pore diameter, nm 16.5 16.8 16.2 16.0 16.3 15.4 15.3 Crushing strength, N / particle 69 68 64 67 62 63 62 Roundness, % 98.6 98.3 98.2 98.1 98.4 98.2 98.1

[0091] Table 2 Physicochemical properties of the spherical alumina supports obtained in each comparative example

[0092] Carrier number H I J K L Average particle diameter, mm 1.79 1.75 1.60 1.59 1.70 <![CDATA[Specific surface area, m 2 / g]]> 92 106 99 86 90 Pore volume, mL / g 0.426 0.409 0.395 0.387 0.412 Pore size distribution, % <2 nm 5.4 4.6 6.7 7.9 4.9 2 - 50 nm 94.3 95.3 93.1 92.0 95.0 >50 nm 0.3 0.1 0.2 0.1 0.1 Average pore diameter, nm 13.5 12.1 10.6 10.3 11.2 Crushing strength, N / particle 39 40 35 32 38 Roundness, % 95.6 94.2 90.2 85.2 91.2

[0093] Catalyst evaluation

[0094] 100 g of the spherical alumina supports prepared in the above examples and comparative examples were respectively taken and saturatedly impregnated into an aqueous solution containing 0.8 g of chloroplatinic acid and 0.4 g of stannic chloride. 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 at 520 °C in a hydrogen atmosphere for 1.5 h. The compositions of the obtained catalysts are listed in Table 3-4.

[0095] 5 g of each of the above catalysts were respectively taken and loaded into a fixed-bed reactor for the evaluation of propane dehydrogenation activity: the reaction temperature was 560 °C, the pressure was 0.6 MPa, and the volume space velocity was 160 h -1 . The results of propane dehydrogenation are listed in Table 5-6.

[0096] Table 3 Compositions of the catalysts in each example

[0097] Carrier number A B C D E F G Aluminum oxide (wt%) 95.3 95.2 96.1 95.3 95.7 95.4 95.3 Pt (wt%) 0.4 0.4 0.4 0.4 0.4 0.4 0.4 Sn (wt%) 0.3 0.3 0.3 0.3 0.3 0.3 0.3 <![CDATA[SiO 2 (wt%)]]> 4.0 4.1 3.3 4.0 3.6 3.9 4.0

[0098] Table 4 Compositions of the catalysts in each comparative example

[0099] Carrier number H I J K L Aluminum oxide (wt%) 95.3 95.3 95.6 95.3 95.3 Pt (wt%) 0.4 0.3 0.3 0.4 0.4 Sn (wt%) 0.3 0.2 0.2 0.2 0.3 <![CDATA[SiO 2 (wt%)]]> 4.0 4.2 3.9 4.1 4.0

[0100] Table 5 Evaluation results of the catalysts in each example for propane dehydrogenation

[0101]

[0102] Table 6 Evaluation results of the catalysts in each comparative example for propane dehydrogenation

[0103]

[0104] 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 preparation method of an alumina carrier, comprising: mixing an aluminum hydroxide sol with an 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 spherical alumina carrier; in the oil-ammonia-oil-water four-layer mixing column, a first oil layer, an ammonia layer, a second oil layer and a water layer are sequentially arranged from top to bottom, wherein the first oil layer is selected from one or more of white oil or diesel oil, preferably white oil, and the second oil layer is selected from modified transformer oil, and 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 above 0.90 g / mL, and further is 0.93 - 0.96 g / mL.

2. The preparation method according to claim 1, characterized in that: the modified transformer oil comprises 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.

3. The preparation method according to claim 2, characterized in that: the preparation process of the modified transformer oil is as follows: mixing the water-soluble surfactant with the transformer oil, and subjecting the obtained mixture to heat treatment, that is, sequentially performing sealed heating treatment and open heating treatment, and repeating the above heat treatment 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.

4. The preparation method according to claim 1, 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 of 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% to 8.0%, preferably 2.5% to 7.5% of the mass of the aluminum hydroxide sol calculated as alumina in terms of SiO 2 counting.

5. According to the preparation method described in claim 1, 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.

6. The preparation method according to claim 1, characterized in that: in the ammonia layer, the ammonia concentration is 20 wt% - 28 wt%, preferably 22 wt% - 26 wt%.

7. The preparation method according to claim 1, characterized in that: in the oil-ammonia-oil-water four-layer mixing column, the water layer is preferably deionized water or a dilute acid solution, and further preferably a dilute acid solution; preferably, 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%.

8. The preparation method according to claim 1, characterized in that: the height of the first oil layer is 30% - 50% of the height of the ammonia layer; and / or, the height of the second oil layer is 30% - 50% of the height of the ammonia layer, preferably 35% - 45%; and / or, the height of the water layer is 1.0 - 2.0 times the height of the ammonia layer, preferably 1.2 - 1.5 times.

9. An alumina carrier prepared by the preparation method according to any one of claims 1 - 8.

10. The alumina carrier according to claim 9, characterized in that: The pore size distribution of the alumina support is as follows: the pore volume of pores with a pore size less than 2 nm accounts for 0.5% to 3.5% of the total pore volume, the pore volume of pores with a pore size of 2 - 50 nm accounts for 96.5% to 99.5% of the total pore volume, preferably 97.0% to 99.0%.

11. The alumina support according to claim 9, wherein: The specific surface area of the alumina support is 80 to 105 m 2 / g; and / or, the pore volume of the alumina support is 0.45 - 0.79 mL / g; and / or, the average diameter of the alumina support particles is 1.7 - 2.0 mm; and / or, the average pore size of the alumina support is 13.5 - 17.5 nm; and / or, the crush strength of the alumina support is 59 - 78 N / grain; and / or, the roundness of the alumina support is 97.5% - 99.9%.

12. The alumina support according to claim 9, wherein: in the alumina support, silica accounts for 0.15 wt% to 7.5 wt% of the mass of alumina, preferably 3.0 wt% to 6.0 wt%.

13. A propane dehydrogenation catalyst, comprising the alumina support according to any one of claims 9 - 12, noble metal Pt, and Sn.

14. The catalyst according to claim 13, wherein: in the propane dehydrogenation catalyst, based on the mass of the catalyst and by mass fraction, the content of Pt is 0.25% to 1.70%, the content of Sn is 0.06% to 0.70%, and the content of the alumina support is 97.6% to 99.69%.

15. The catalyst according to claim 13 or 14, wherein: before the propane dehydrogenation catalyst is used, it 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.

16. Use of the catalyst according to any one of claims 13 - 15 in a propane dehydrogenation reaction.

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