Spherical alumina carrier, and preparation method and application thereof

Abstract

The application discloses a spherical alumina carrier and a preparation method and application thereof. The preparation method of the spherical alumina carrier comprises the following steps: mixing an aluminum hydroxide sol and an acidic silicon sol, dropping the obtained mixture into an oil-ammonia water-oil-water four-layer mixed column for shaping, and drying and calcining to obtain the spherical alumina carrier. The spherical alumina carrier prepared by the method has good roundness, high crushing strength, large pore volume and large pore size, and is suitable for being used as a noble metal catalyst carrier.

Description

TECHNICAL FIELD

[0001] The present application relates to a spherical alumina carrier and a preparation method and application thereof, in particular to a spherical alumina carrier suitable for a boiling bed, a noble metal catalyst and a preparation method and application thereof. BACKGROUND

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

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

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

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

[0006] CN105478100A discloses a method for preparing silicon-containing γ-Al2O3 pellets. The method is to stir and slurry pseudo-boehmite dry glue powder and deionized water, add dilute nitric acid to acidify, then add urea and a predetermined amount of sodium silicate solution, stir for 5 hours, add kerosene and fatty alcohol polyoxyethylene ether and stir for 5 hours, drop ball forming in an oil-ammonia column, solidify the wet ball in ammonia water for 2 hours, then filter, rinse with deionized water, dry and calcine to obtain silicon-containing γ-Al2O3 pellets. The method has a long solidification time for preparing γ-Al2O3 pellets, is difficult to wash, and has low production efficiency.

[0007] CN104289220A discloses a method for preparing and use of a high-thermal-stability low-carbon alkane dehydrogenation catalyst. The carrier preparation method is to add an aluminum source to an alkaline aqueous solution, stir, continue to add the alkaline aqueous solution to adjust the pH of the mixed solution to 7-14, filter, wash with deionized water, then add dilute nitric acid to form a sol, add a silicon source, stir, filter, age for 10-48 hours, drop ball forming, then dry and calcine to obtain γ-Al2O3 pellets containing Si element; or add an aluminum source to an alkaline aqueous solution, stir, continue to add the alkaline aqueous solution to adjust the pH of the mixed solution to 7-14, filter, wash with deionized water, then add dilute nitric acid to form a sol, stir, filter, age for 10-48 hours, drop ball forming, then dry and calcine to obtain γ-Al2O3 pellets, then immerse the γ-Al2O3 pellets in a silicon source aqueous solution or ethanol solution at 60-120℃ for 2-6 hours, then dry and calcine to obtain γ-Al2O3 pellets containing Si element. The method has the disadvantages of long preparation period, complex process, pH value adjustment, and inability to guarantee product consistency. SUMMARY

[0008] In view of the deficiencies of the prior art, the application provides a spherical alumina carrier, a preparation method and application thereof. The spherical alumina carrier prepared by the method has the characteristics of good roundness, high crushing strength, large pore volume and pore size, and no peculiar smell, and is suitable for use as a noble metal catalyst carrier.

[0009] The first aspect of the application provides a preparation method of a spherical alumina carrier, comprising:

[0010] The aluminum hydroxide sol is mixed with the acidic silicon sol, the obtained mixture is dropped into an oil-ammonia water-oil-water four-layer mixed column for forming, and the spherical alumina carrier is prepared by drying and calcining.

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

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

[0013] Further, the concentration of the acidic silica sol is 5 to 45 g SiO2 / L in terms of SiO2, the pH value of the silica sol is adjusted to 3 to 5 by using an acid (such as at least one of nitric acid and acetic acid), and the addition amount of the acidic silica sol is 0.2% to 8.0% by mass of the aluminum hydroxide sol in terms of SiO2, and is preferably 2.5% to 7.5% by mass.

[0014] Further, in the oil-ammonia water-oil-water four-layer mixed column, four layers are sequentially arranged from top to bottom, the first layer is a first oil layer, the second layer is an ammonia water layer, the third layer is a second oil layer, and the fourth layer is a water layer. The oil-ammonia water-oil-water four-layer mixed column is a straight column, and is preferably a cylindrical column.

[0015] Further, in the oil-ammonia water-oil-water four-layer mixed column, the first layer is a first oil layer, and 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 to 40 mm 2 / s, and is preferably 25 to 35 mm 2 / s. The height of the first layer is 30% to 50% of the height of the second layer.

[0016] Further, in the oil-ammonia water-oil-water four-layer mixed column, the second layer is an ammonia water layer, and the concentration of the ammonia water is 20% to 28% by mass, and is preferably 22% to 26% by mass.

[0017] Further, in the oil-ammonia water-oil-water four-layer mixed column, the third layer is the second oil layer, i.e., the liquid seal oil layer, which has a density between that of the second layer of ammonia water and the fourth layer of water, and a kinematic viscosity of 60 mm 2 / s or more of one or more plant oils, preferably a mixture of castor oil and soybean oil, wherein the volume ratio of castor oil to soybean oil is 1 / 4 to 1 / 6. The castor oil has a kinematic viscosity of 500 to 650 mm 2 / s, preferably 570 to 600 mm 2 / s. The soybean oil has a kinematic viscosity of 10 to 25 mm 2 / s, preferably 13 to 17 mm 2 / s. The third layer has a height of 30% to 50%, preferably 35% to 45%, of the height of the second layer.

[0018] Further, in the oil-ammonia water-oil-water four-layer mixed column, the fourth layer is a water layer, preferably deionized water or a dilute acid solution. The fourth layer has a height of 1.0 to 2.0 times, preferably 1.2 to 1.5 times, the height of the second layer.

[0019] 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%.

[0020] Further, the preparation method of the oil-ammonia water-oil-water four-layer mixed column comprises:

[0021] (1) Pour the required material of the fourth layer into a columnar container (preferably an organic glass container) and ensure uniform solution;

[0022] (2) Slowly add the required material of the third layer to the fourth layer material of step (1), and stabilize for 20 to 35 minutes;

[0023] (3) Slowly add the required material of the second layer to the third layer material of step (2);

[0024] (4) Slowly add the required material of the first layer to the second layer material of step (3) to obtain an oil-ammonia water-oil-water four-layer mixed column. Preferably, during the addition of the required material of the first layer, a peristaltic pump is used to slowly circulate up and down above the interface between the first layer and the second layer, so that the surface tension at the interface between the first layer and the second layer is reduced, and then it is left to stand for 30 to 60 minutes until it is stable. This can ensure that the aluminum hydroxide sol can quickly pass through the contact interface between the first layer and the second layer, preventing the generation of tailing due to stagnation, which affects the roundness.

[0025] Further, the spherical alumina carrier is formed in an oil-ammonia water-oil-water four-layer mixed column, and the mixture of the aluminum hydroxide sol and the acidic silicon sol is dropped into the oil-ammonia water-oil-water four-layer mixed column, wherein the inner diameter of the drop head used is 1.0 mm-1.6 mm.

[0026] Further, the residence time of the mixture of the aluminum hydroxide sol and the acidic silicon sol in the oil-ammonia water-oil-water four-layer mixed column is 5-18 s, preferably 7-11 s.

[0027] Further, the drying temperature is 100℃-150℃, and the drying time is 6-10 hours; the calcination temperature is 550℃-950℃, and the calcination time is 1-4 hours.

[0028] The second aspect of the present application provides a spherical alumina carrier prepared by the above preparation method.

[0029] Further, in the spherical alumina carrier, the silicon oxide accounts for 0.1wt%-6.9wt% of the mass of the alumina, preferably 2.5wt%-5.0wt%.

[0030] Further, the specific surface area of the spherical alumina carrier is 70-192 m 2 / g.

[0031] Further, the pore volume of the spherical alumina carrier is 0.50-0.75 mL / g.

[0032] Further, the average diameter of the spherical alumina carrier particles is 1.8-2.0 mm.

[0033] Further, the pore size distribution of the spherical alumina carrier is that the pore volume of the pores with a pore size less than 2 nm accounts for 0.5%-5.0% of the total pore volume, the pore volume of the pores with a pore size of 2-50 nm accounts for 94.0%-99.0%, preferably 95.0%-99.0%, of the total pore volume.

[0034] Further, the average pore size of the spherical alumina carrier is 14-17 nm.

[0035] Further, the crushing strength of the spherical alumina carrier is 55-75 N / particle.

[0036] Further, the sphericity of the spherical alumina carrier is 94.5%-99.9%.

[0037] Further, the spherical alumina carrier can be used as a noble metal catalyst carrier, and can be used in processes such as propane dehydrogenation and carbon two selective hydrogenation.

[0038] The third aspect of the present application provides a propane dehydrogenation catalyst, comprising the spherical alumina carrier and the noble metal Pt and Sn.

[0039] Further, in the propane dehydrogenation catalyst, the content of Pt is 0.20% to 1.50% by mass fraction, the content of Sn is 0.05% to 0.80% by mass fraction, and the content of the spherical alumina carrier is 97.70% to 99.75% by mass fraction.

[0040] Further, the preparation method of the propane dehydrogenation catalyst can adopt the impregnation method, preferably the saturated impregnation method. The Pt and Sn can adopt the step-by-step impregnation method or the co-impregnation method. The Pt precursor in the impregnation solution is preferably at least one of PtCl4 and H2PtCl6, and the Sn precursor is preferably SnCl4. The drying condition after impregnation is preferably as follows: the drying temperature is 80 to 120℃, and the drying time is 8 to 12h. The calcination condition after impregnation is preferably as follows: the calcination temperature is 500 to 700℃, and the calcination time is 2 to 6h.

[0041] Further, the propane dehydrogenation catalyst needs to be reduced before use. The catalyst precursor is reduced in a reducing atmosphere. The reducing atmosphere is preferably H2, the reduction temperature is 450 to 600℃, and the reduction time is 1 to 3h.

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

[0043] Further, the application includes: the propane raw material is contacted with the catalyst to perform the dehydrogenation reaction, and the product propylene is obtained.

[0044] Further, the propane dehydrogenation reaction condition is preferably as follows: the reaction temperature is 500 to 600℃, the reaction pressure is 0 to 1MPa, the volume space velocity is 50 to 200h -1 .

[0045] Compared with the prior art, the present application has the following advantages:

[0046] (1) The four-layer oil-ammonia water-oil-water mixed column used in the preparation process of the spherical alumina carrier in the application is different from the two-layer oil-ammonia column or the hot oil column, a third layer of oil layer is added as a liquid seal oil layer and a fourth layer of water layer, which can make the sol 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 is quickly reduced to neutral, so that the small balls are not easy to break or shrink during the drying process due to the volatilization of the surface ammonia water, and the alumina particle size and mechanical strength are obviously increased. In addition, the rapid decrease of the pH value of the sol small ball surface also makes the hydrophobicity of the colloidal particle surface decrease rapidly, the interaction force between the colloidal particles increases obviously, the distance between the colloidal particles becomes shorter, and the original structure collapses partially, so that the mesoporous structure of the carrier in the range of 2-50 nm is increased, and by adding an appropriate amount of acidic solution into the fourth layer of water layer, the pore structure can be further optimized.

[0047] (2) The preparation process of the application belongs to the environment-friendly type. In the traditional oil-ammonia column balling process, the volatilization of ammonia water brings about serious environmental pollution problems and subsequent pollutant emission problems. The second oil layer in the application separates the second layer of ammonia water layer and the fourth layer of water layer, so that the ammonia water layer is sealed on the fourth layer of water layer, the use time can be prolonged, the environmental pollution caused by the product taking out ammonia water can be avoided, and after long-term use, the deionized water can be replaced to ensure the liquid sealing effect. The operation is simple and convenient in industry, and the cost is saved. DETAILED DESCRIPTION

[0048] The following examples further illustrate the spherical alumina carrier and the preparation method and application effect thereof in the application. The examples are implemented on the premise of the technical scheme of the application, and detailed implementation modes and specific operation processes are given, but the protection scope of the application is not limited to the following examples.

[0049] In the following examples, the experimental methods are conventional methods in the art unless otherwise specified. The experimental materials used in the following examples are purchased from conventional biochemical reagent stores unless otherwise specified.

[0050] In the application, the nitrogen adsorption-desorption curve of the sample is tested at-196℃ by using the ASAP2020 full-automatic physical adsorption instrument of the American Micromeritics Company to determine the specific surface area, pore volume and pore size distribution.

[0051] In the application, the crushing strength is tested by using the ZQJ-III intelligent particle strength tester manufactured by the Dalian Ziqie Testing Machine Factory, and the average value of ten spherical carriers is tested.

[0052] In the application, the true circularity is tested by using the electronic microscope of the Olympus Company, and the average value is calculated after testing 20 samples.

[0053] Example 1

[0054] A macroporous pseudo-boehmite filter cake 250 g (calcined at 600°C for 3 h in air atmosphere, properties as follows: pore volume 0.87 mL / g, specific surface area 175 m 2 / g, average pore diameter 16 nm) with a water content of 22 wt% was taken, and after stirring and uniformly slurring with deionized water, 26 g of a 45 wt% nitric acid solution was added to perform peptization, and finally a pseudo-boehmite sol with an alumina mass content of 20% was prepared; 300 g of the above sol (alumina content of 20 wt%) was taken, and 100 mL of an acidic silica sol with a pH value of 4 was added, and the silica sol concentration was 30 g SiO2 / L as calculated based on SiO2, and after stirring and uniformity, a sol mixture was obtained;

[0055] The sol mixture was added dropwise to a four-layer mixed column (cylinder) of white oil (40°C kinematic viscosity of 32 mm 2 / s, ammonia water (concentration of 25 wt%), mixed oil, and deionized water) through a nozzle with an inner diameter of 1.2 mm, and the residence time in the four-layer mixed column was 8 s. Among them, the amount of white oil added was 35% of the volume of ammonia water, the amount of mixed oil added was 38% of the volume of ammonia water, and the amount of deionized water added was 1.3 times the volume of ammonia water; the mixed oil was mixed with castor oil with a 40°C kinematic viscosity of 580 mm 2 / s and soybean oil with a kinematic viscosity of 15 mm 2 / s in a volume ratio of 1:5. Then dried at 130°C for 8 hours, and calcined at 800°C for 3 hours to obtain the spherical alumina carrier A of the present application, and the analysis results are shown in Table 1.

[0056] Example 2

[0057] 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, and the spherical alumina carrier B of the present application is obtained, and the analysis results are shown in Table 1.

[0058] Example 3

[0059] Compared with Example 1, the difference is that the concentration of the acidic silica sol used is changed to 15 g SiO2 / L, the pH value of the acidic silica sol is adjusted to 5, the drying temperature after molding is changed to 140°C, and the calcination temperature is changed to 850°C, and the spherical alumina carrier C of the present application is obtained, and the analysis results are shown in Table 1.

[0060] Example 4

[0061] Compared with Example 1, the difference is that the white oil in the four-layer mixed column is changed to white oil with a 40°C kinematic viscosity of 23 mm 2 / s, the concentration of ammonia water is changed to 21 wt%, and the volume ratio of castor oil to soybean oil is changed to 1:4, and the spherical alumina carrier D of the present application is obtained, and the analysis results are shown in Table 1.

[0062] Example 5

[0063] Compared with Example 1, the difference is that the white oil in the four-layer mixing column is replaced by a mixture of diesel oil and white oil with a mixing mass ratio of 1:1, and the ammonia water concentration is changed to 28wt%, to obtain the spherical alumina carrier E of the application, and the analysis results are shown in Table 1.

[0064] Example 6

[0065] Compared with Example 1, the difference is that the acid silica sol concentration is changed to 25g SiO2 / L, the white oil in the four-layer mixing column is replaced by white oil with a kinematic viscosity of 28mm 2 / s at 40℃, the ammonia water concentration is changed to 23wt%, and the volume ratio of castor oil to soybean oil is changed to 1:4, to obtain the spherical alumina carrier F of the application, and the analysis results are shown in Table 1.

[0066] Example 7

[0067] Compared with Example 1, the difference is that in the four-layer mixing column, the amount of white oil added is 42% of the volume of ammonia water, the amount of mixed oil added is 32% of the volume of ammonia water, and the amount of deionized water added is 1.6 times the volume of ammonia water, to obtain the spherical alumina carrier G of the application, and the analysis results are shown in Table 1.

[0068] Comparative Example 1

[0069] The sol mixture synthesis step is the same as Example 1.

[0070] Compared with Example 1, the difference is that the four-layer oil-ammonia water-oil-water mixing column is replaced by a two-layer oil-ammonia column, the upper layer is white oil with a kinematic viscosity of 32mm 2 / s at 40℃, and the lower layer is ammonia water with a concentration of 25wt%, the amount of white oil added is 25% of the volume of ammonia water, and the remaining forming steps remain unchanged, to obtain the comparative spherical alumina carrier H of the application, and the analysis results are shown in Table 2.

[0071] Comparative Example 2

[0072] The sol mixture synthesis method is the same as Example 1.

[0073] Compared with Example 1, the difference is that only the first layer of white oil column in the four-layer oil-ammonia water-oil-water mixing column is removed, and a three-layer column is used to form a ball, to obtain the comparative spherical alumina carrier I of the application, and the analysis results are shown in Table 2.

[0074] Comparative Example 3

[0075] The sol mixture synthesis method is the same as Example 1.

[0076] Comparative Example 1 was repeated, except that only the fourth layer of water was removed from the four-layer oil-ammonia water-oil-water mixture column to obtain the comparative spherical alumina support J of the present application, the analysis results of which are shown in Table 2.

[0077] Comparative Example 4

[0078] The sol mixture was synthesized in the same manner as in Example 1.

[0079] Comparative Example 1 was repeated, except that only the third layer of castor oil and soybean oil mixture was removed from the four-layer oil-ammonia water-oil-water mixture column to obtain the comparative spherical alumina support K of the present application, the analysis results of which are shown in Table 2.

[0080] Comparative Example 5

[0081] The sol mixture was synthesized in the same manner as in Example 1.

[0082] Comparative Example 1 was repeated, except that in the four-layer mixture column, the amount of white oil added was 16% of the volume of ammonia water, the amount of mixed oil added was 20% of the volume of ammonia water, and the amount of deionized water added was 0.4 times the volume of ammonia water to obtain the comparative spherical alumina support L of the present application, the analysis results of which are shown in Table 1.

[0083] Table 1 Physical and chemical properties of the spherical alumina support obtained in each example

[0084]

[0085]

[0086] Table 2 Physical and chemical properties of the spherical alumina support obtained in each comparative example

[0087] Support No. H I J K L Particle average diameter, mm 1.73 1.50 1.81 1.70 1.71 Specific surface area, m 2 / g]] 93 94 91 94 95 Pore volume, mL / g 0.593 0.484 0.591 0.585 0.594 Pore size distribution, % < 2 nm 6.1 9.3 6.2 7.2 6.4 2-50 nm 93.2 90.1 93.0 92.1 93.2 > 50 nm 0.7 0.6 0.8 0.7 0.4 Average pore diameter, nm 13.2 11.3 12.4 11.7 11.9 Crushing strength, N / particle 53 30 47 37 45 True sphericity, % 93.2 70.9 93.7 89.3 92.1

[0088] Catalyst evaluation

[0089] 100 g of the spherical alumina support prepared in the above examples and comparative examples was respectively saturated and impregnated in an aqueous solution containing 0.8 g of chloroplatinic acid and 0.4 g of tin tetrachloride, impregnated for 30 min, dried in a drying oven at 90°C for 10 h, calcined in a muffle furnace at 600°C for 4 h, and reduced at 520°C under a hydrogen atmosphere for 1.5 h. The composition of the obtained catalysts is shown in Tables 3-4.

[0090] 5 g of the above catalysts were respectively taken and loaded into a fixed bed reactor for evaluation of the dehydrogenation activity of propane: reaction temperature 600°C, atmospheric pressure, volume space velocity 100 h -1 The results of propane dehydrogenation are shown in Tables 5-6.

[0091] Table 3 Composition of the catalysts of each example

[0092]

[0093]

[0094] Table 4 Composition of each comparative catalyst

[0095] Support No. H I J K L Al2O3 (wt%) 97.2 98.06 97.3 97.1 97.4 SiO2(wt%) 2.2 1.6 2.2 2.3 2.0 Pt (wt%) 0.4 0.3 0.4 0.4 0.4 Sn (wt%) 0.2 0.04 0.1 0.2 0.2

[0096] Table 5 Evaluation results of each example catalyst for propane dehydrogenation

[0097]

[0098] Table 6 Evaluation results of each comparative catalyst for propane dehydrogenation

[0099]

[0100] The specific embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A method for preparing a spherical alumina support, comprising: Aluminum hydroxide sol and acidic silica sol are mixed, and the resulting mixture is dripped into a four-layer oil-ammonia-oil-water mixing column to form a spherical alumina carrier after drying and calcination. The four-layer oil-ammonia-oil-water mixing column consists of four layers arranged sequentially from top to bottom: a first oil layer, a second ammonia layer, a third second oil layer, and a fourth water layer. The first oil layer is selected from one or more types of white oil or diesel oil. The second oil layer is a mixture of castor oil and soybean oil, with a volume ratio of castor oil to soybean oil of 1 / 4 to 1 / 6. The density of the second oil layer is between that of the second ammonia layer and the fourth water layer. The water layer is deionized water or a dilute acid solution. The height of the first layer is 30% to 50% of the height of the second layer, the height of the third layer is 30% to 50% of the height of the second layer, and the height of the fourth layer is 1.0 to 2.0 times the height of the second layer.

2. The preparation method according to claim 1, characterized in that: The aluminum hydroxide sol contains 15wt%~26wt% aluminum oxide. And / or, the concentration of the acidic silica sol is 5~45 g SiO2 / L, calculated as SiO2; And / or, the pH value of the acidic silica sol is 3 to 5; And / or, the amount of acidic silica sol added is 0.2wt% to 8.0wt% of the mass of aluminum hydroxide sol (calculated as aluminum oxide), based on SiO2.

3. The preparation method according to claim 2, characterized in that: The amount of acidic silica sol added is 2.5wt% to 7.5wt% of the mass of aluminum hydroxide sol (calculated as aluminum oxide), based on SiO2.

4. The preparation method according to claim 1, characterized in that: The four-layer mixed column of oil-ammonia-oil-water is a straight column.

5. The preparation method according to claim 4, characterized in that: The four-layer mixed column of oil-ammonia-oil-water is cylindrical.

6. The preparation method according to claim 1, characterized in that: In the oil-ammonia-oil-water four-layer mixed column, the first oil layer is white oil, and the kinematic viscosity of the white oil at 40°C is 20~40 mmHg. 2 / s.

7. The preparation method according to claim 6, characterized in that: The kinematic viscosity of the white oil at 40°C is 25~35 mm. 2 / s.

8. The preparation method according to claim 1, characterized in that: In the oil-ammonia-oil-water four-layer mixed column, the concentration of ammonia is 20wt%~28wt%.

9. The preparation method according to claim 8, characterized in that: The concentration of ammonia water is 22wt%~26wt%.

10. The preparation method according to claim 1, characterized in that: In the oil-ammonia-oil-water four-layer mixed column, the kinematic viscosity of castor oil at 40°C is 500~650 mmHg. 2 / s; and / or, the kinematic viscosity of the soybean oil at 40°C is 10~25mm. 2 / s.

11. The preparation method according to claim 10, characterized in that: The kinematic viscosity of the castor oil at 40°C is 570~600 mmHg. 2 / s; and / or, the kinematic viscosity of the soybean oil at 40°C is 13~17 mm. 2 / s.

12. The preparation method according to claim 1, characterized in that: In the oil-ammonia-oil-water four-layer mixed column, the water layer is a dilute acid solution; the acid in the dilute acid solution is selected from at least one of acetic acid and citric acid; the mass concentration of the dilute acid solution is 3%~8%.

13. The preparation method according to claim 1, characterized in that: The height of the third layer is 35% to 45% of the height of the second layer; And / or, the height of the fourth layer is 1.2 to 1.5 times the height of the second layer.

14. The spherical alumina carrier prepared by any of the preparation methods described in claims 1-13.

15. The spherical alumina carrier according to claim 14, characterized in that: In the spherical alumina carrier, silicon oxide accounts for 0.1 wt% to 6.9 wt% of the mass of alumina; And / or, the specific surface area of ​​the spherical alumina carrier is 70~192m². 2 / g; And / or, the pore volume of the spherical alumina support is 0.50~0.75mL / g; And / or, the average diameter of the spherical alumina carrier particles is 1.8~2.0 mm; And / or, the average pore size of the spherical alumina support is 14~17 nm; And / or, the crushing strength of the spherical alumina carrier is 55~75 N / particle; And / or, the spherical alumina carrier has a sphericality of 94.5% to 99.9%.

16. The spherical alumina carrier according to claim 15, characterized in that: In the spherical alumina carrier, silicon oxide accounts for 2.5wt% to 5.0wt% of the mass of alumina.

17. The spherical alumina carrier according to claim 15, characterized in that: The pore size distribution of the spherical alumina carrier is as follows: the pore volume of pores with a pore size of less than 2 nm accounts for 0.5% to 5.0% of the total pore volume, and the pore volume of pores with a pore size of 2-50 nm accounts for 94.0% to 99.0% of the total pore volume.

18. The spherical alumina carrier according to claim 17, characterized in that: The pore volume of pores with a diameter of 2-50 nm accounts for 95.0% to 99.0% of the total pore volume.

19. A propane dehydrogenation catalyst comprising the spherical alumina support as described in any one of claims 14-18 and the noble metals Pt and Sn.

20. The catalyst according to claim 19, characterized in that: In the propane dehydrogenation catalyst, based on the mass of the catalyst, the content of Pt is 0.20%~1.50% by mass fraction, the content of Sn is 0.05%~0.80%, and the content of the spherical alumina support is 97.70%~99.75%.

21. The catalyst according to claim 19, characterized in that: The propane dehydrogenation catalyst needs to be reduced before use.

22. The catalyst according to claim 21, characterized in that: The reducing atmosphere is H2, the reduction temperature is 450~600℃, and the reduction time is 1~3h.

23. The use of the catalyst according to any one of claims 19-21 in the propane dehydrogenation reaction.

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