Spherical alumina carrier as well as preparation method and application thereof

Abstract

The invention discloses a spherical alumina carrier as well as a preparation method and application thereof. The preparation method of the spherical alumina carrier comprises the following steps: mixing aluminum hydroxide sol and 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 the spherical alumina carrier. The spherical alumina carrier prepared by the method has the advantages of good roundness, high crushing strength and large pore volume and pore diameter, and is suitable for being used as a noble metal catalyst carrier.

Description

Technical Field

[0001] The present invention relates to a spherical 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 method and application. Background Art

[0002] The shape and size of catalyst particles are generally determined according to the requirements of the reactors used in industrial production. At present, there are four common types of reactors in industry: fixed beds, fluidized beds (boiling beds), suspension beds, and moving beds. Fixed bed reactors commonly use spherical, cylindrical bars, clovers, four-leaf clovers, 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 and a high packing coefficient, with 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 and regeneration treatments, resulting in the γ-Al 2 O 3 support being easily sintered and undergoing 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. The 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 it is impossible to ensure product consistency. Summary of the Invention

[0008] In view of the deficiencies of the prior art, the present invention provides a spherical alumina carrier, a preparation method and an application thereof. The spherical 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 method for preparing a spherical 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 a spherical alumina support.

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

[0012] Further, the preparation method of the aluminum hydroxide sol includes: mixing aluminum hydroxide with 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), 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 in terms of acid is 1 wt% to 10 wt% of the mass of aluminum hydroxide in terms of alumina, preferably 2 wt% to 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% to 25 wt%. Preferably, the properties of the aluminum hydroxide after calcination are as follows: specific surface area is 110 to 201 m 2 / g, pore volume is 0.8 to 2.0 mL / g, and average pore diameter is 15 to 17 nm. The calcination conditions are as follows: temperature is 600 to 850 °C, time is 2 to 12 h, and an oxygen-containing atmosphere such as air. The aluminum hydroxide can be commercially purchased or prepared by conventional methods. The aluminum hydroxide is preferably macroporous pseudo-boehmite with water content of 19 wt% to 23 wt%.

[0013] Further, the concentration of the acidic silica sol is 5 to 45 g SiO 2 calculated as SiO 2 / L, and the pH value of the silica sol is adjusted to 3 to 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 wt% to 8.0 wt% of the mass of the aluminum hydroxide sol calculated as alumina, preferably 2.5 wt% to 7.5 wt%.

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

[0015] Further, in the oil-ammonia water-oil-water four-layer mixing column, the first layer is the first oil layer, which is selected from one or more of white oil and diesel oil, preferably white oil. The kinematic viscosity of the white oil at 40 °C is 20-40 mm 2 / s, preferably 25-35 mm 2 / s. The height of the first layer is 30%-50% of the height of the second layer.

[0016] Further, in the oil-ammonia water-oil-water four-layer mixing column, the second layer is the ammonia water layer, and the concentration of the ammonia water is 20 wt%-28 wt%, preferably 22 wt%-26 wt%.

[0017] Further, in the oil-ammonia water-oil-water four-layer mixing column, the third layer is the second oil layer, namely the liquid seal oil layer, which is one or more vegetable oils with a density between the second ammonia water layer and the fourth water layer and a kinematic viscosity at 40 °C of 60 mm 2 / s or less, preferably a mixed oil of castor oil and soybean oil, wherein the volume ratio of castor oil to soybean oil is 1 / 4-1 / 6. The kinematic viscosity of the castor oil at 40 °C is 500-650 mm 2 / s, preferably 570-600 mm 2 / s. The kinematic viscosity of the soybean oil at 40 °C is 10-25 mm 2 / s, preferably 13-17 mm 2 / s. The height of the third layer is 30%-50% of the height of the second layer, preferably 35%-45%.

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

[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%-8%.

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

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

[0022] (2) Slowly add the materials required for the third layer on top of the fourth layer materials in step (1) and stabilize for 20-35 min;

[0023] (3) Slowly add the materials required for the second layer on top of the third layer materials in step (2);

[0024] (4) Slowly add the materials required for the first layer on top of the second-layer materials in step (3) to obtain an oil-ammonia water-oil-water four-layer mixing column. Preferably, during the addition of the materials required for the first layer, slowly circulate up and down through a peristaltic pump above the interface between the first layer and the second layer to weaken the surface tension at the interface between the first layer and the second layer, and then let it stand for 30 to 60 minutes until it stabilizes. This can ensure that the aluminum hydroxide sol can quickly pass through the contact interface between the first layer and the second layer, prevent pauses from causing trailing, and affect the true roundness.

[0025] Further, the forming of the spherical alumina support is carried out in an oil-ammonia water-oil-water four-layer mixing column, and a mixture of aluminum hydroxide sol and acidic silica sol is dropped into the oil-ammonia water-oil-water four-layer mixing column, wherein the inner diameter of the dropping head used is 1.0 mm to 1.6 mm.

[0026] 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 to 18 s, preferably 7 to 11 s.

[0027] 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.

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

[0029] Further, in the spherical alumina support, silica accounts for 0.1 wt% to 6.9 wt% of the mass of alumina, preferably 2.5 wt% to 5.0 wt%.

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

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

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

[0033] Further, the pore size distribution of the spherical alumina support is as follows: the pore volume of pores with a pore size 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, preferably 95.0% to 99.0%.

[0034] Further, the average pore diameter of the spherical alumina support is 14 to 17 nm.

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

[0036] Further, the roundness of the spherical alumina support is 94.5% - 99.9%.

[0037] Further, the spherical alumina support can be used as a noble metal catalyst support in reaction processes such as propane dehydrogenation and C2 selective hydrogenation.

[0038] The third aspect of the present invention provides a propane dehydrogenation catalyst, comprising the above-mentioned spherical alumina support, noble metal Pt and Sn.

[0039] Further, in the propane dehydrogenation catalyst, based on the mass of the catalyst, by mass fraction, the content of Pt calculated as Pt is 0.20% - 1.50%, the content of Sn calculated as Sn is 0.05% - 0.80%, and the content of the spherical alumina support is 97.70% - 99.75%.

[0040] 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 stepwise impregnation method or the co-impregnation method. The Pt precursor used in the impregnation solution is preferably at least one of PtCl 4 、H 2 PtCl 6 ; the Sn precursor is preferably SnCl 4 . 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.

[0041] Further, before the propane dehydrogenation catalyst is used, it needs to be reduced. The catalyst precursor is reduced under a reducing atmosphere. The reducing atmosphere is preferably H 2 , the reducing temperature is 450 - 600 °C, and the reducing time is 1 - 3 h.

[0042] The fourth aspect of the present invention 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 for dehydrogenation reaction to obtain the product propylene.

[0044] Further, the propane dehydrogenation reaction conditions are preferably as follows: the reaction temperature is 500 - 600 °C, the reaction pressure is 0 - 1 MPa, and the volume space velocity is 50 - 200 h -1 .

[0045] Compared with the prior art, the advantages of the present invention are as follows:

[0046] (1) In the preparation process of the spherical alumina carrier of the present invention, the four-layer oil-ammonia-water mixed column adopted is different from the two-layer oil-ammonia column or the hot oil column. The third layer of oil layer is added as a liquid seal oil layer and the fourth layer of water layer, which enables the sol to quickly enter the third and fourth water layers after passing through the second ammonia water layer, and the pH value quickly drops to neutral. During the drying process of the small balls, it is not easy to break or shrink with the volatilization of the surface ammonia water, 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 small balls also causes a rapid decrease in the hydrophobicity of the colloid particles, a significant increase in the interaction force between the colloid particles, a shortening of the distance between the colloid 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 water layer, the pore structure can be further optimized.

[0047] (2) The preparation process of the present invention is environmentally friendly. In the traditional oil-ammonia column spheroidization process, the environmental pollution problem caused by ammonia water volatilization and the subsequent pollutant emission problem are relatively serious. In the present invention, the second oil layer separates the second ammonia water layer from the fourth water layer, so that the ammonia water layer is sealed above the fourth water layer, which can extend the service life and avoid environmental pollution caused by the product carrying out ammonia water. After long-term use, deionized water can be replaced to ensure the liquid seal effect, and the operation is simple and cost-saving in industry. Specific embodiments

[0048] The following further illustrates the spherical 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.

[0049] 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 regular biochemical reagent stores unless otherwise specified.

[0050] In the present invention, the nitrogen adsorption and desorption curves of the samples are tested at -196 °C using the ASAP2020 full-automatic physical adsorption instrument of Micromeritics Company in the United States to measure the specific surface area, pore volume and pore size distribution.

[0051] 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.

[0052] 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.

[0053] Example 1

[0054] Take 250 g of macroporous pseudo-boehmite filter cake with a moisture 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 / g, average pore diameter 16 nm). After adding deionized water and stirring to make a homogeneous slurry, add 26 g of a nitric acid solution with a mass concentration of 45% for peptization, and finally prepare a pseudo-boehmite sol with an alumina mass content of 20%; take 300 g of the above sol (alumina content 20 wt%), add 100 mL of acidic silica sol with a pH of 4, and the concentration of the silica sol is 30 g SiO 2 calculated as 30 g SiO 2 / L. After stirring evenly, a sol mixture is obtained;

[0055] Use a dropper with an inner diameter of 1.2 mm to drop the above sol mixture into a four-layer mixing column (cylindrical) of (white oil with a kinematic viscosity of 32 mm 2 / s at 40 °C - ammonia water with a concentration of 25 wt% - mixed oil - deionized water) for shaping, 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 mixed 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; the mixed oil is composed of castor oil with a kinematic viscosity of 580 mm 2 / s at 40 °C and soybean oil with a kinematic viscosity of 15 mm 2 / s, and the volume ratio of the two is 1:5. Then dry at 130 °C for 8 hours and calcine at 800 °C for 3 hours to obtain the spherical alumina support A of the present invention, and its 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 a 5 wt% dilute acetic acid solution to obtain the spherical alumina support B of the present invention, and its 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 SiO 2 / L, the pH value of the acidic silica sol is adjusted to 5, the drying temperature after shaping is changed to 140 °C, and the calcination temperature is changed to 850 °C to obtain the spherical alumina support C of the present invention, and its 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 mixing column is changed to a kinematic viscosity of 23 mm at 40 °C 2White oil of / s, while changing the ammonia water concentration to 21 wt%, and changing the volume ratio of castor oil to soybean oil added to 1:4, spherical alumina support D of the present invention is obtained, and its analysis results are shown in Table 1.

[0062] Example 5

[0063] Compared with Example 1, the differences are as follows: changing the white oil in the four-layer mixing column to a mixture of diesel oil and white oil with a mixing mass ratio of 1:1, and at the same time changing the ammonia water concentration to 28 wt%, spherical alumina support E of the present invention is obtained, and its analysis results are shown in Table 1.

[0064] Example 6

[0065] Compared with Example 1, the differences are as follows: changing the concentration of acidic silica sol to 25 g SiO 2 / L, changing the white oil in the four-layer mixing column to white oil with a kinematic viscosity of 28 mm at 40°C 2 / s, changing the ammonia water concentration to 23 wt%, and at the same time changing the volume ratio of castor oil to soybean oil to 1:4, spherical alumina support F of the present invention is obtained, and its analysis results are shown in Table 1.

[0066] Example 7

[0067] Compared with Example 1, the differences are as follows: in the four-layer mixing column, the addition amount of white oil is 42% of the volume of ammonia water, the addition amount of mixed 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, spherical alumina support G of the present invention is obtained, and its analysis results are shown in Table 1.

[0068] Comparative Example 1

[0069] The synthesis steps of the sol mixture are the same as those in Example 1.

[0070] Compared with Example 1, the difference is that 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 at 40°C 2 / s, 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 comparative spherical alumina support H of the present invention is obtained, and its analysis results are shown in Table 2.

[0071] Comparative Example 2

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

[0073] Compared with Example 1, the difference is that only the first white oil column in the four-layer oil-ammonia water-oil-water mixing column is removed, and a three-layer column is used for ball forming, and comparative spherical alumina support I of the present invention is obtained, and its analysis results are shown in Table 2.

[0074] Comparative Example 3

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

[0076] Compared with Example 1, the difference is that only the fourth water layer in the four-layer mixed column is removed to obtain the comparative spherical alumina support J of the present invention, and the analysis results are shown in Table 2.

[0077] Comparative Example 4

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

[0079] Compared with Example 1, the difference is that only the third mixed layer of castor oil and soybean oil in the four-layer oil-ammonia-oil-water mixed column is removed to obtain the comparative spherical alumina support K of the present invention, and the analysis results are shown in Table 2.

[0080] Comparative Example 5

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

[0082] Compared with Example 1, the difference is that in the four-layer mixed column, the addition amount of white oil is 16% of the volume of ammonia water, the addition amount of the mixed 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 spherical alumina support L of the present invention, and the analysis results are shown in Table 1.

[0083] Table 1 Physicochemical properties of the spherical alumina supports obtained in each example

[0084]

[0085]

[0086] Table 2 Physicochemical properties of the spherical alumina supports obtained in each comparative example

[0087] Carrier number H I J K L Average particle diameter, mm 1.73 1.50 1.81 1.70 1.71 <![CDATA[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, % < 2nm 6.1 9.3 6.2 7.2 6.4 2 - 50nm 93.2 90.1 93.0 92.1 93.2 > 50nm 0.7 0.6 0.8 0.7 0.4 Average pore size, nm 13.2 11.3 12.4 11.7 11.9 Crushing strength, N / particle 53 30 47 37 45 Roundness, % 93.2 70.9 93.7 89.3 92.1

[0088] Catalyst evaluation

[0089] 100 g of the spherical alumina supports prepared in the above examples and comparative examples were respectively saturated and 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 in a hydrogen atmosphere at 520 °C for 1.5 h. The compositions of the obtained catalysts are listed in Tables 3-4.

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

[0091] Table 3 Compositions of the catalysts in each example

[0092]

[0093]

[0094] Table 4 Composition of Catalysts for Each Comparative Ratio

[0095] Carrier number H I J K L <![CDATA[Al 2 O 3 (wt%)]]> 97.2 98.06 97.3 97.1 97.4 <![CDATA[SiO 2 (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 Catalysts for Propane Dehydrogenation in Each Example

[0097]

[0098] Table 6 Evaluation Results of Catalysts for Propane Dehydrogenation in Each Comparative Ratio

[0099]

[0100] 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 a spherical alumina support, comprising: Mixing aluminum hydroxide sol and acidic silica sol, dropping the obtained mixture into an oil-ammonia water-oil-water four-layer mixing column for shaping, drying, and calcining to obtain a spherical alumina support.

2. The preparation method according to claim 1, characterized in that: the alumina content in the aluminum hydroxide sol is 15 wt% to 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 to 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 calculated as alumina in terms of SiO 2 count.

3. The preparation method according to claim 1, characterized in that: the oil-ammonia water-oil-water four-layer mixing column is a straight column, preferably a cylinder; and / or, in the oil-ammonia water-oil-water four-layer mixing column, four layers are arranged in sequence from top to bottom, the first layer is the first oil layer, the second layer is the ammonia water layer, the third layer is the second oil layer, and the fourth layer is the water layer.

4. The preparation method according to claim 3, characterized in that: In the oil-ammonia water-oil-water four-layer mixing column, the first layer is the first oil layer, which is selected from one or more of white oil and diesel oil, preferably white oil. The kinematic viscosity of the white oil at 40 °C is 20 to 40 mm 2 / s, preferably 25 to 35 mm 2 / s.

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

6. The preparation method according to claim 3, characterized in that: In the oil-ammonia water-oil-water four-layer mixing column, the third layer is the second oil layer, namely the liquid-sealing oil layer, which is one or more vegetable oils with a density between the second ammonia water layer and the fourth water layer and a kinematic viscosity of 60 mm 2 / s or less at 40°C, preferably a mixed oil of castor oil and soybean oil; the volume ratio of castor oil to soybean oil is 1 / 4 to 1 / 6; Preferably, the kinematic viscosity of the castor oil at 40 °C is 500 to 650 mm 2 / s, preferably 570 to 600 mm 2 / s; and / or, the kinematic viscosity of the soybean oil at 40 °C is 10 to 25 mm 2 / s, preferably 13 to 17 mm 2 / s.

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

8. The preparation method according to claim 3, characterized in that: the height of the first layer is 30% to 50% of the height of the second layer; and / or, the height of the third layer is 30% to 50% of the height of the second layer, preferably 35% to 45%; and / or, the height of the fourth layer is 1.0 to 2.0 times the height of the second layer, preferably 1.2 to 1.5 times.

9. A spherical alumina support prepared by the preparation method according to any one of claims 1-8.

10. The spherical alumina support according to claim 9, characterized in that: in the spherical alumina support, silica accounts for 0.1 wt% to 6.9 wt% of the mass of alumina, preferably 2.5 wt% to 5.0 wt%; and / or, the specific surface area of the spherical alumina carrier is 70 to 192 m 2 / g; and / or, the pore volume of the spherical alumina support is 0.50 to 0.75 mL / g; and / or, the average diameter of the spherical alumina support particles is 1.8 to 2.0 mm; and / or, the average pore diameter of the spherical alumina support is 14 to 17 nm; and / or, the crush strength of the spherical alumina support is 55 to 75 N / grain; and / or, the true roundness of the spherical alumina support is 94.5% to 99.9%.

11. The spherical alumina support according to claim 9, characterized in that: the pore size distribution of the spherical alumina support is: the pore volume of pores with a pore size 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, preferably 95.0% to 99.0%.

12. A propane dehydrogenation catalyst comprising the spherical alumina support according to any one of claims 9-11, noble metal Pt and Sn.

13. The catalyst according to claim 12, wherein: in the propane dehydrogenation catalyst, based on the mass of the catalyst and in terms of mass fraction, the content of Pt is 0.20% to 1.50%, the content of Sn is 0.05% to 0.80%, and the content of the spherical alumina support is 97.70% to 99.75%.

14. The catalyst according to claim 12, 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.

15. Use of the catalyst according to any one of claims 12-14 in propane dehydrogenation reaction.

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