Alumina support, its preparation and use

Abstract

The application discloses an alumina carrier and a preparation and application thereof. The preparation method of the alumina carrier comprises the following steps: mixing an aluminum hydroxide sol with an acidic silicon sol, dropping the obtained mixture into an oil-ammonia water-oil-water four-layer mixed column for shaping, drying and calcining to prepare alumina; and the oil-ammonia water-oil-water four-layer mixed column is sequentially provided with a first oil layer, an ammonia water layer, a second oil layer and a water layer from top to bottom, wherein 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 the ammonia water and the water. The alumina carrier has the characteristics of good roundness, high crushing strength, large pore volume and pore size, no peculiar smell and environmental protection, and is suitable for being used as a precious metal catalyst carrier.

Description

TECHNICAL FIELD

[0001] The present application relates to an alumina carrier and a preparation method and application thereof, in particular to a spherical alumina carrier for a boiling bed and a noble metal catalyst and a preparation 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. Currently, there are four types of reactors commonly used 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 factor, 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] Currently, 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 the γ-Al2O3 carrier to easily sinter and α-phase change, greatly reduces the specific surface area of the carrier, destroys the pore structure, and further causes the active components of the catalyst to aggregate, thus 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 strength of the carrier to decrease.

[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, acidify by adding 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 ball forming in an oil-ammonia column, wet ball is solidified in ammonia water for 2 hours, then filtered, washed with deionized water, dried, calcined, to obtain silicon-containing γ-Al2O3 pellets. The method has long solidification time, difficult washing and 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 an 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, then add a silicon source, stir, filter, age for 10-48 hours, drop ball forming, then dry and calcine to obtain Si-containing γ-Al2O3 pellets. Alternatively, the aluminum source is added to an alkaline aqueous solution, stirred, the pH of the mixed solution is adjusted to 7-14 by continuously adding an alkaline aqueous solution, filtered, washed with deionized water, then dilute nitric acid is added to form a sol, stirred, filtered, aged for 10-48 hours, drop ball forming, then dried and calcined to obtain γ-Al2O3 pellets, then the γ-Al2O3 pellets are immersed in a silicon source aqueous solution or ethanol solution at 60-120℃ for 2-6 hours, then dried and calcined to obtain Si-containing γ-Al2O3 pellets. The method has long preparation period, complex process, pH value needs to be adjusted, and product consistency cannot be guaranteed. SUMMARY

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

[0009] The first aspect of the present application provides a method for preparing an alumina carrier, comprising:

[0010] The alumina carrier is prepared by mixing the aluminum hydroxide sol with the acidic silicon sol, dropping the obtained mixture into an oil-ammonia water-oil-water four-layer mixed column for forming, drying and calcining. In the oil-ammonia water-oil-water four-layer mixed column, the first oil layer, the ammonia water layer, the second oil layer and the 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, and the second oil layer is selected from modified transformer oil. 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℃ is 0.90g / mL or more, further 0.93-0.96g / mL.

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

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

[0013] Further, the method for preparing the aluminum hydroxide sol comprises: mixing aluminum hydroxide with 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%-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 in terms of acid is 1wt%-10wt% of the mass of the aluminum hydroxide in terms of alumina, and is preferably 2wt%-8wt%. Further, the aluminum hydroxide is preferably hydrous aluminum hydroxide, such as hydrous aluminum hydroxide wet material. Preferably, the water content in the aluminum hydroxide is 17wt%-25wt%. Preferably, the properties of the aluminum hydroxide after calcination are as follows: the specific surface area is 110-201 m 2 / g, the pore volume is 0.8-2.0 mL / g, and the average pore size is 15-17 nm. The calcination conditions are as follows: the temperature is 600-850℃, the time is 2-12 h, 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 19wt%-23wt%.

[0014] Further, the concentration of the acidic silica sol is 5-45 g SiO2 / L, the pH value of the acidic silica sol is controlled to be 3-5 by using acid (such as at least one of nitric acid and acetic acid), and the addition amount of the acidic silica sol in terms of SiO2 is 0.2%-8.0% of the mass of the aluminum hydroxide in terms of alumina, and is preferably 2.5%-7.5%.

[0015] Further, the oil-ammonia water-oil-water four-layer mixed column is a straight column, and is preferably a circular column.

[0016] Further, in the oil-ammonia water-oil-water four-layer mixed column, the first oil layer 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℃ is 20-40 mm 2 / s, and is 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 mixed column, the concentration of the ammonia water is 20wt% to 28wt%, preferably 22wt% to 26wt% in the ammonia water layer. Further, in the oil-ammonia water-oil-water four-layer mixed column, the height of the second oil layer, i.e. the liquid seal oil layer, is 30% to 50%, preferably 35% to 45% of the height of the ammonia water layer.

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

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

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

[0021] Further, the density (20°C) of the transformer oil is 0.86 to 0.89 g / mL, and the kinematic viscosity at 40°C is 9 to 15 mm 2 / s.

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

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

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

[0025] Further, in the oil-ammonia water-oil-water four-layer mixed column, the water layer is preferably deionized water or 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 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 mixed column comprises:

[0028] (1) Pour the required material of the water layer into a columnar container (preferably an organic glass container) and ensure uniform solution;

[0029] (2) Slowly add the required material of the second oil layer to the water layer material of step (1) and stabilize for 20-35 min;

[0030] (3) Slowly add the required material of the ammonia layer to the second oil layer material of step (2);

[0031] (4) Slowly add the required material of the first oil layer to the ammonia 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 oil layer, slow up-and-down circulation is performed above the interface between the first oil layer and the ammonia layer by a peristaltic pump to weaken the surface tension at the interface between the first oil layer and the ammonia layer, and then stand for 30-60 min until it is stable, which can ensure that the aluminum hydroxide sol can quickly pass through the contact interface between the first oil layer and the ammonia layer and prevent the generation of tailing due to stagnation, thereby affecting the roundness.

[0032] Further, the spherical alumina carrier is formed in the oil-ammonia water-oil-water four-layer mixed column, and the mixture of the aluminum hydroxide sol and the acidic silica 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.

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

[0034] 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.

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

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

[0037] Further, the alumina carrier is a spherical particle, and the average diameter of the particle is 1.7-2.0 mm.

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

[0039] Further, the crushing strength of the alumina carrier is 59-78 N / particle.

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

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

[0042] Further, in the alumina carrier, the content of silicon oxide is 0.15wt%-7.5wt% of the mass of the alumina, and preferably 3.0wt%-6.0wt%.

[0043] The third aspect of the present application provides a propane dehydrogenation catalyst, which comprises the above alumina carrier and noble metals Pt and Sn.

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

[0045] Further, the preparation method of the propane dehydrogenation catalyst can adopt an impregnation method, preferably a saturated impregnation method. Pt and Sn can be impregnated by a step-by-step impregnation method or a 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 a SnCl4 solution. The drying conditions after impregnation are preferably as follows: the drying temperature is 80-120℃, and the drying time is 8-12h. The calcination conditions after impregnation are preferably as follows: the calcination temperature is 500-700℃, and the calcination time is 2-6h.

[0046] 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 450-600℃, and the reduction time is 1-3h.

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

[0048] Further, the use comprises: contacting a propane raw material with the catalyst to perform a dehydrogenation reaction, so as to obtain a product propylene.

[0049] Further, the propane dehydrogenation reaction conditions are preferably as follows: the reaction temperature is 500-600℃, the reaction pressure is 0-1MPa, the volume space velocity is 50-200h-1, and the reaction time is 0.1-2h. -1 .

[0050] Compared with the prior art, the present application has the following advantages:

[0051] (1) The four-layer oil-ammonia water-oil-water mixed column used in the preparation process of the alumina carrier of the present application is different from the two-layer oil-ammonia column or the hot oil column, and the second oil layer (liquid seal oil layer) and the water layer are added, so that the sol can quickly enter the second oil layer and the water layer after passing through the ammonia water layer, and the pH value is quickly reduced to neutral, so that the pellets 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 significantly increased. In addition, the rapid decrease of the pH value of the sol pellet surface also causes the rapid decrease of the hydrophobicity of the colloidal particle surface, the interaction force between the colloidal particles is significantly increased, the distance between the colloidal particles is shortened, and the original structure is partially collapsed, resulting in an increase in the mesoporous structure of the carrier in the range of 2-50 nm. By adding an appropriate amount of acidic solution to the fourth layer of water, the pore structure can be further optimized.

[0052] (2) In the four-layer oil-ammonia water-oil-water mixed column of the present application, the density difference between the ammonia water in the second layer and the pure water in the fourth layer is small, and the density of the liquid seal oil (modified transformer oil) in the second oil layer needs to be greater than that of the ammonia water and less than that of the pure water, and the viscosity cannot be too large. The present application can increase the density without changing the viscosity by adding a surfactant to the transformer oil, so that it meets the requirements. Among them, the water-soluble surfactant slowly penetrates into the oil under heating conditions, the intermolecular interaction force is enhanced, and the intermolecular distance is shortened during the evaporation of water. After repeated several times, the stability of the modified transformer oil can be ensured. The use of the modified transformer oil liquid seal of the present application can significantly reduce the surface tension at the oil-water interface due to the addition of the surfactant, reduce the pause of the sol pellets when passing through the oil-water interface, and quickly pass through the interface, reduce the pulling, and effectively improve the roundness of the spherical carrier.

[0053] (3) The preparation process of the present application is environmentally friendly. In the traditional oil-ammonia column balling process, the volatilization of ammonia water causes serious environmental pollution and subsequent pollutant emission problems. The present application separates the ammonia water layer from the water layer by the second oil layer, so that the ammonia water layer is sealed above the water layer, the use time can be prolonged, and the environmental pollution caused by the product carrying out ammonia water can be avoided. After long-term use, the deionized water can be replaced to ensure the liquid sealing effect, which is simple to operate and cost-saving in industry. DETAILED DESCRIPTION

[0054] The present application will be further illustrated by the following examples. The examples are implemented on the premise of the technical scheme of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following examples.

[0055] The experimental methods in the following examples are the conventional methods in the art, unless otherwise specified. The experimental materials used in the following examples are purchased from the conventional biochemical reagent stores, unless otherwise specified.

[0056] In the present 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.

[0057] In the present application, the crushing strength is tested by using the ZQJ-III intelligent particle strength tester manufactured by the Dalian Zixu Test Machine Factory, and the average value of crushing ten spherical carriers is tested.

[0058] In the present 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.

[0059] Example 1

[0060] Take 250g of the macroporous pseudo-boehmite filter cake with a water content of 22wt% (calcined at 600℃ for 3h in air atmosphere, and the properties are as follows: pore volume 0.87mL / g, specific surface area 175m 2 / g, average pore diameter 16nm), add deionized water to stir and uniformly pulp, then add 26g of 45wt% nitric acid solution for peptization, and finally prepare a pseudo-boehmite sol with an alumina mass content of 20%; take 300g of the above sol (alumina content 20wt%), add 100mL of acid silica sol with a pH value of 4, and the silica sol concentration is 30g SiO2 / L, stir uniformly, and obtain a sol mixture;

[0061] Add 7g of lauryl diethanolamide and 7g of nonylphenol polyoxyethylene ether (n=9) into 100g of transformer oil (20℃ density 0.89g / mL, 40℃ kinematic viscosity 12mm 2 / s), stir uniformly, seal and put into a 100℃ oven for heating for 8h, remove the sealing cover and continue heating for 4h, and repeat the above heat treatment steps for 3 times to obtain modified transformer oil (20℃ density 0.94g / mL). Use a nozzle with an inner diameter of 1.2mm to drop into (40℃ kinematic viscosity 32mm 2The sol mixture was added dropwise into a four-layer mixed column (cylinder) of white oil, modified transformer oil, and deionized water, with a residence time of 8 s in the four-layer mixed column. The white oil was added in an amount of 35% of the volume of the ammonia water, the modified transformer oil was added in an amount of 38% of the volume of the ammonia water, and the deionized water was added in an amount of 1.3 times the volume of the ammonia water. The resulting product was dried at 130°C for 8 hours and then calcined at 800°C for 3 hours to obtain the alumina carrier A of the present application. 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 was changed from deionized water to a 5wt% dilute acetic acid solution to obtain the alumina carrier B of the present application. 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 acid silicon sol was changed to 15g SiO2 / L, the pH of the acid silicon sol was adjusted to 5, the drying temperature after shaping was changed to 140°C, and the calcination temperature was changed to 850°C to obtain the alumina carrier C of the present application. The physicochemical properties of the obtained carrier are shown in Table 1.

[0066] Example 4

[0067] Compared with Example 1, the difference is that in the preparation of the modified transformer oil, the surfactant used was changed to lauryl diethanolamide, the amount added was changed to 12g, the repeated heat treatment step was performed 4 times, and the 20°C density of the obtained modified transformer oil was 0.95g / mL; and at the same time, the concentration of the ammonia water was changed to 22wt% to obtain the alumina carrier D of the present application. The physicochemical properties of the obtained carrier are shown in Table 1.

[0068] Example 5

[0069] Compared with Example 1, the difference is that the concentration of the acid silicon sol was changed to 25g SiO2 / L, and the concentration of the ammonia water was changed to 23wt% to obtain the alumina carrier E of the present application. The physicochemical properties of the obtained carrier are shown in Table 1.

[0070] Example 6

[0071] Compared with Example 1, the difference is that in the preparation of the modified transformer oil, the amounts of lauryl diethanolamide and nonylphenol polyoxyethylene ether were changed to 4g each, and the 20°C density of the obtained modified transformer oil was 0.93g / mL. The alumina carrier F of the present application was obtained. The physicochemical properties of the obtained carrier are shown in Table 1.

[0072] Example 7

[0073] The difference between the example 1 and the comparative example 1 is that the white oil is added in the amount of 42% of the volume of the ammonia water, the modified transformer oil is added in the amount of 32% of the volume of the ammonia water, and the deionized water is added in the amount of 1.6 times of the volume of the ammonia water, to obtain the inventive alumina carrier G, and the analysis results are shown in Table 1.

[0074] Comparative example 1

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

[0076] The difference between the example 1 and the comparative example 1 is that the four-layer oil-ammonia water-oil-water mixed column is changed into a two-layer oil-ammonia column, the upper layer is the white oil with the kinematic viscosity of 32 mm 2 / s at 40℃, the lower layer is the ammonia water with the concentration of 25wt%, the white oil is added in the amount of 25% of the volume of the ammonia water, and the remaining forming steps are unchanged, to obtain the inventive comparative alumina carrier H. The physicochemical properties of the obtained carrier are shown in Table 2.

[0077] Comparative example 2

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

[0079] The difference between the example 1 and the comparative example 2 is that only the first layer of the white oil column in the four-layer oil-ammonia water-oil-water mixed column is removed, and the three-layer column is used to form the balls, to obtain the inventive comparative alumina carrier I. The physicochemical properties of the obtained carrier are shown in Table 2.

[0080] Comparative example 3

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

[0082] The difference between the example 1 and the comparative example 3 is that only the fourth layer of the water column is removed, to obtain the inventive comparative alumina carrier J. The physicochemical properties of the obtained carrier are shown in Table 2.

[0083] Comparative example 4

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

[0085] The difference between the example 1 and the comparative example 4 is that the modified transformer oil in the second oil layer in the four-layer oil-ammonia water-oil-water mixed column is replaced by the transformer oil, and the remaining forming steps are unchanged, that is, the forming step is that the inner diameter of the drop head is 1.2 mm, the white oil with the kinematic viscosity of 32 mm 2The sol mixture was shaped by dropping into a four-layer mixed column (cylinder) of white oil, ammonia water with a concentration of 25 wt%, transformer oil, and deionized water. The residence time in the four-layer mixed column was 8 s. The white oil was added in an amount of 35% of the volume of the ammonia water, the transformer oil was added in an amount of 38% of the volume of the ammonia water, and the deionized water was added in an amount of 1.3 times the volume of the ammonia water. The shaped product was dried at 130°C for 8 h and then calcined at 800°C for 3 h to obtain comparative alumina carrier K of the present application. The physicochemical properties of the obtained carrier are shown in Table 2.

[0086] Comparative Example 5

[0087] The sol mixture was synthesized by the same method as in Example 1.

[0088] Comparative Example 5

[0089] Table 1 Physicochemical properties of the spherical alumina carriers obtained in the Examples

[0090] Support No. A B C D E F G Particle average diameter, mm 1.80 1.81 1.80 1.79 1.81 1.81 1.80 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 Sphericity, % 98.6 98.3 98.2 98.1 98.4 98.2 98.1

[0091] Table 2 Physicochemical properties of the spherical alumina carriers obtained in the Comparative Examples

[0092] Support No. H I J K L Particle average diameter, mm 1.79 1.75 1.60 1.59 1.70 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 Sphericity, % 95.6 94.2 90.2 85.2 91.2

[0093] Catalyst evaluation

[0094] Each of the spherical alumina carriers obtained in the above Examples and Comparative Examples was saturated with impregnation in an aqueous solution containing 0.8 g of chloroplatinic acid and 0.4 g of tin tetrachloride, and then dried in a drying oven at 90°C for 10 h and calcined in a muffle furnace at 600°C for 4 h, and then reduced at 520°C for 1.5 h under a hydrogen atmosphere. The compositions of the obtained catalysts are shown in Tables 3-4.

[0095] Each of 5 g of the above catalysts was charged into a fixed bed reactor for evaluation of the dehydrogenation activity of propane: the reaction temperature was 560°C, the pressure was 0.6 MPa, the volume space velocity was 160 h -1 The results of the dehydrogenation of propane are shown in Tables 5-6.

[0096] Table 3 Compositions of the catalysts of the Examples

[0097] Support No. A B C D E F G Alumina (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 SiO2(wt%) 4.0 4.1 3.3 4.0 3.6 3.9 4.0

[0098] Table 4 Compositions of the catalysts of the Comparative Examples

[0099] Support No. H I J K L Alumina (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 SiO2 (wt%) 4.0 4.2 3.9 4.1 4.0

[0100] Table 5 Evaluation results of each example catalyst for propane dehydrogenation

[0101]

[0102] Table 6 Evaluation results of each comparative catalyst for propane dehydrogenation

[0103]

[0104] 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 an alumina carrier, comprising: mixing an aluminum hydroxide sol with an acidic silica sol, and dropping the mixture into an oil-ammonia water-oil-water four-layer mixed column to form a spherical alumina carrier, and drying and calcining the spherical alumina carrier; in the oil-ammonia water-oil-water four-layer mixed column, from top to bottom, a first oil layer, an ammonia water layer, a second oil layer and a water layer are arranged in sequence, wherein 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, the density of the modified transformer oil is between that of ammonia water and water, the density of the modified transformer oil at 20℃ is 0.90 g / mL or more, the modified transformer oil comprises transformer oil and a water-soluble surfactant, the water-soluble surfactant is one or more of lauryl diethanolamide, nonylphenol polyoxyethylene ether or octylphenol polyoxyethylene ether, the water layer is deionized water or a dilute acid solution, the height of the first oil layer is 30% to 50% of the height of the ammonia water layer, the height of the second oil layer is 30% to 50% of the height of the ammonia water layer, and the height of the water layer is 1.0 to 2.0 times the height of the ammonia water layer.

2. The method of claim 1, wherein: The density of the modified transformer oil at 20℃ is 0.93 to 0.96 g / mL.

3. The method of claim 1, wherein: The mass of the water-soluble surfactant is 6% to 25% of the mass of the transformer oil. The transformer oil has a density of 0.86-0.89 g / mL at 20°C and a kinematic viscosity of 9-15 mm 2 / s at 40°C.

4. The method of claim 3, wherein: The mass of the water-soluble surfactant is 10% to 18% of the mass of the transformer oil.

5. The method of claim 1, wherein: The modified transformer oil is prepared by mixing the water-soluble surfactant with the transformer oil, and then heat treating the mixture, i.e., sequentially performing sealed heat treatment and open heat treatment, and repeating the heat treatment 3 to 6 times to obtain the modified transformer oil.

6. The method of claim 5, wherein: The sealed heat treatment is performed at a temperature of 80 to 120℃ for 6 to 20 hours.

7. The method of claim 5, wherein: The open heat treatment is performed at a temperature of 80 to 120℃ for 6 to 20 hours.

8. The method of claim 1, wherein: The aluminum hydroxide sol contains 15wt% to 26wt% of alumina. And / or, the concentration of the acidic silica sol is 5 to 45 g SiO2 / L in terms of SiO2. And / or, the pH value of the acidic silica sol is 3 to 5. And / or, the amount of the acidic silica sol added is 0.2% to 8.0% of the mass of the aluminum hydroxide sol in terms of alumina.

9. The method of claim 8, wherein: The amount of the acidic silica sol added is 2.5% to 7.5% of the mass of the aluminum hydroxide sol in terms of alumina.

10. The production method according to claim 1, wherein the first oil layer in the oil-ammonia water-oil-water four-layer mixed column is white oil having a kinematic viscosity of 20 to 40 mm2 / s at 40°C. 2 / s at 40°C.

11. The production method according to claim 10, wherein the white oil has a kinematic viscosity at 40 °C of 25 to 35 mm2 / s. 2 / s.

12. The method of claim 1, wherein: In the ammonia water layer, the concentration of the ammonia water is 20wt% to 28wt%.

13. The method of claim 12, wherein: The concentration of the ammonia water is 22wt% to 26wt%.

14. The method of claim 1, wherein: In the oil-ammonia water-oil-water four-layer mixed column, the water layer is a dilute acid solution.

15. The method of claim 14, wherein: In the dilute acid solution, the dilute acid is at least one of acetic acid or citric acid, and the mass concentration of the dilute acid solution is 3% to 8%.

16. The method of claim 1, wherein: The height of the second oil layer is 35% to 45% of the height of the ammonia water layer. And / or, the height of the water layer is 1.2 to 1.5 times the height of the ammonia water layer. 17.An alumina carrier prepared by the method of any one of claims 1 to 16.

18. The alumina support of claim 17, wherein: The pore size distribution of the alumina carrier is: 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.

19. The alumina support of claim 18, wherein: The pore volume of pores with a pore size of 2-50 nm accounts for 97.0% to 99.0% of the total pore volume.

20. The alumina support of claim 17, wherein: The specific surface area of the alumina support is between 80 and 105 m 2 / g; And / or, the pore volume of the alumina carrier is 0.45 to 0.79 mL / g; And / or, the average diameter of the alumina carrier particles is 1.7 to 2.0 mm; And / or, the average pore size of the alumina carrier is 13.5 to 17.5 nm; And / or, the crushing strength of the alumina carrier is 59 to 78 N / particle; And / or, the roundness of the alumina carrier is 97.5% to 99.9%.

21. The alumina support of claim 17, wherein: In the alumina carrier, the mass fraction of silicon oxide in the alumina is 0.15wt% to 7.5wt%.

22. The alumina support of claim 21, wherein: In the alumina carrier, the mass fraction of silicon oxide in the alumina is 3.0wt% to 6.0wt%.

23. A propane dehydrogenation catalyst comprising the alumina carrier of any one of claims 17-22 and noble metals Pt and Sn.

24. The catalyst of claim 23, wherein: In the propane dehydrogenation catalyst, the mass fraction of Pt is 0.25% to 1.70%, the mass fraction of Sn is 0.06% to 0.70%, and the mass fraction of the alumina carrier is 97.6% to 99.69%, based on the mass of the catalyst.

25. The catalyst of claim 23 or 24, wherein: The propane dehydrogenation catalyst needs to be reduced before use.

26. The catalyst of claim 25, wherein: The reduction atmosphere is H2, the reduction temperature is 450-600°C, and the reduction time is 1-3h.

27. Use of the catalyst of any one of claims 23-26 in a propane dehydrogenation reaction.

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