Dehydrogenation catalyst as well as preparation method and application thereof

Abstract

The invention discloses a dehydrogenation catalyst as well as a preparation method and application thereof. The preparation method of the catalyst comprises the following steps: mixing aluminum hydroxide sol with a Pt-containing aqueous solution and an organic Pt salt solution, and dropwise adding the obtained mixture into an oil-ammonia water-oil-water four-layer mixed column for molding, drying and roasting to obtain the dehydrogenation catalyst, four layers are sequentially arranged in the mixing column 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, the fourth layer is a water layer, the second oil layer is selected from modified transformer oil, and the modified transformer oil comprises transformer oil and a water-soluble surfactant. The catalyst is used in a propane dehydrogenation reaction, and has high propane conversion rate, high propylene selectivity and good stability.

Description

Technical Field

[0001] The present invention relates to a dehydrogenation catalyst, a preparation method thereof and an application thereof, and particularly relates to a dehydrogenation catalyst suitable for a fluidized bed, a preparation method thereof and an application thereof. 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 bed, fluidized bed (boiling bed), suspension bed and moving bed. Fixed bed reactors commonly use spherical, cylindrical bar, clover, four-leaf and flake catalysts. Moving bed reactors often use large particle spherical catalysts. Fluidized bed reactors generally use smaller spherical or bar-shaped catalysts.

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

[0004] At present, the catalysts for dehydrogenating lower alkanes to produce olefins are mainly prepared by loading active component Pt and other additives on a γ-Al 2 O 3 support, such as EP100222A, CN1185994A, etc. However, since the dehydrogenation reaction is carried out at a high temperature of about 600 °C, the high reaction temperature often causes a large amount of carbon deposition on the catalyst. As the use time of the catalyst increases, the catalyst needs to be subjected to multiple high-temperature carbon burning regeneration treatments, resulting in the γ-Al 2 O 3 support being easily sintered and undergoing α-phase transformation, greatly reducing the specific surface area of the support and destroying the pore structure. Furthermore, the active components of the catalyst aggregate, and the activity of the catalyst drops severely. Therefore, it is necessary to further modify the γ-Al 2 O 3 support to make the catalyst have high thermal stability.

[0005] CN112973771A discloses a spherical catalyst support containing molecular sieve and alumina, and its preparation and application. 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 mix the suspension slurry obtained by ball-milling pseudo-boehmite and molecular sieve with a dilute sol and then peptize again, which will have the disadvantage of uneven dispersion of the molecular sieve. At the same time, the doping of solid molecular sieve will also lead to a decrease in the strength of the support.

[0006] CN105478100A discloses a method for preparing silicon-containing γ-Al2 O 3 A method for preparing small balls. This method involves stirring and slurrying pseudo-boehmite dry gel powder and deionized water, acidifying with dilute nitric acid, adding urea and a predetermined amount of sodium silicate solution, stirring for 5 hours, adding kerosene and fatty alcohol polyoxyethylene ether and stirring for 5 hours, dropping and forming balls in an oil-ammonia column, curing the wet balls in ammonia water for 2 hours, then filtering, rinsing with deionized water, drying, and calcining to obtain silicon-containing γ-Al 2 O 3 small balls. The method for preparing γ-Al 2 O 3 small balls has a long curing time, is difficult to wash, and has low production efficiency.

[0007] CN104289220A discloses a preparation method and use of a high thermal stability dehydrogenation catalyst for light alkanes. 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, add dilute nitric acid to form a sol, then add a silicon source, stir, filter, age for 10-48 hours, drop and form balls, and then dry and calcine to obtain γ-Al 2 O 3 small balls; or add an aluminum source to an alkaline aqueous solution, stir, continue to drop the alkaline aqueous solution to adjust the pH of the mixed solution to 7-14, filter, wash with deionized water, add dilute nitric acid to form a sol, stir, filter, age for 10-48 hours, drop and form balls, and then dry and calcine to obtain γ-Al 2 O 3 small balls, and then impregnate the γ-Al 2 O 3 small balls in an aqueous solution or ethanol solution of a silicon source at 60-120 °C for 2-6 hours, and then dry and calcine to obtain γ-Al 2 O 3 small balls containing Si element. The disadvantages of this method are long preparation cycle, complex process, need to regulate the pH value, and cannot guarantee product consistency. Summary of the Invention

[0008] In view of the deficiencies of the prior art, the present invention provides a dehydrogenation catalyst, its preparation method and application. The catalyst has good roundness, high crushing strength, large pore volume and pore diameter, Pt is not easy to agglomerate, the product is environmentally friendly and odorless, and is used in propane dehydrogenation reaction, having high propane conversion rate, high propylene selectivity and good stability.

[0009] The first aspect of the present invention provides a preparation method of a dehydrogenation catalyst, including:

[0010] An aluminum hydroxide sol is mixed with an aqueous Pt solution and an organic Pt salt solution, and the resulting mixture is dropped into an oil-ammonia-oil-water four-layer mixing column to form a shape, followed by drying and calcination to obtain a dehydrogenation catalyst; in the 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 second oil layer is selected from modified transformer oils, and the modified transformer oil includes transformer oil and a water-soluble surfactant.

[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 and water to make a slurry, adding a peptizing agent, and stirring evenly to obtain the aluminum hydroxide sol. Further, the peptizing agent is selected from one or more of inorganic acids (such as nitric acid), organic acids (such as acetic acid, citric acid), 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: 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 h, and the oxygen-containing atmosphere is such as air. The aluminum hydroxide can be commercially purchased or prepared by a conventional method. The aluminum hydroxide is preferably macroporous pseudo-boehmite with water content, and the water content is 19 wt% to 23 wt%.

[0013] Further, the platinum-containing compound in the aqueous Pt solution is platinum chloride (PtCl 4 ), chloroplatinic acid (H 2 PtCl 6 ), or one or more of them, preferably chloroplatinic acid.

[0014] Further, the concentration of the platinum-containing compound in the aqueous Pt solution is 2 wt% to 6 wt%. The addition amount of the aqueous Pt solution is 8% to 40% of the mass of the aluminum hydroxide sol in terms of alumina, preferably 15% to 30%.

[0015] Further, the aqueous Pt solution contains stannous chloride (SnCl 2) and hydrochloric acid. Further, in the Pt-containing aqueous solution, the concentration of stannous chloride (SnCl 2 ) is 0.5 wt% to 3.5 wt%, and the concentration of hydrochloric acid is 5 wt% to 12 wt%.

[0016] Further, the organic Pt salt in the organic Pt salt solution is one or more of platinum acetylacetonate or tetrakis(triphenylphosphine)platinum, preferably platinum acetylacetonate, and the solvent used is preferably acetone. The concentration of the organic Pt salt in the organic Pt salt solution is 1.0 wt% to 1.9 wt%. The addition amount of the organic Pt salt solution is 9% to 11% of the mass of the aluminum hydroxide sol calculated as alumina.

[0017] Further, the oil-ammonia-oil-water four-layer mixing column is a straight column, preferably a cylinder.

[0018] Further, in the oil-ammonia-oil-water four-layer mixing column, the first layer is the first oil layer, selected from one or more of white oil or diesel oil, preferably white oil, and the kinematic viscosity of the white oil at 40 °C is 20 to 40 mm 2 / s, preferably 25 to 35 mm 2 / s. The height of the first layer is 30% to 50% of the height of the second layer.

[0019] Further, in the oil-ammonia-oil-water four-layer mixing column, the second layer is the ammonia water layer, and the concentration of the ammonia water is 20 wt% to 28 wt%, preferably 22 wt% to 26 wt%.

[0020] Further, in the oil-ammonia-oil-water four-layer mixing column, the third layer is the second oil layer, i.e., the liquid seal oil layer. The density of the modified transformer oil used in the second oil layer is between that of ammonia water and water. Preferably, the density of the modified transformer oil at 20 °C is above 0.90 g / mL, preferably 0.93 to 0.96 g / mL, and further preferably 0.94 to 0.96 g / mL. The height of the third layer is 30% to 50% of the height of the second layer, preferably 35% to 45%.

[0021] Further, the mass of the water-soluble surfactant is 6% to 25% of the mass of the transformer oil, preferably 10% to 18%.

[0022] Further, the water-soluble surfactant is one or more of lauroyl diethanolamine, nonylphenol polyoxyethylene ether (the degree of polymerization is preferably 9, i.e., n = 9), or octylphenol polyoxyethylene ether (the degree of polymerization is preferably 7, i.e., n = 7).

[0023] Further, the density of the transformer oil at 20 °C is 0.86 to 0.89 g / mL, and the kinematic viscosity at 40 °C is 9 to 15 mm 2 / s.

[0024] Further, the preparation process of the modified transformer oil is as follows:

[0025] Mix a water-soluble surfactant with transformer oil, and subject the resulting mixture to heat treatment, i.e., successively to sealed heating treatment and open heating treatment, and repeat the above heat treatment 3 to 6 times to obtain the modified transformer oil.

[0026] Further, the conditions of the sealed heating treatment are as follows: the heating temperature is 80 to 120 °C, and the heating time is 6 to 20 h. Further, the conditions of the open heating treatment are as follows: the heating temperature is 80 to 120 °C, and the heating time is 6 to 20 h.

[0027] Further, the oil-ammonia-oil-water four-layer mixing column is a straight column, preferably a cylinder.

[0028] Further, in the oil-ammonia-oil-water four-layer mixing column, the fourth layer is a water layer, preferably deionized water or a dilute acid solution. The height of the fourth layer is 1 to 2 times the height of the second layer, preferably 1.2 to 1.5 times.

[0029] 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%.

[0030] Further, the preparation method of the oil-ammonia-oil-water four-layer mixing column includes:

[0031] (1) Pour the materials required for the fourth layer into a columnar container (preferably a plexiglass container) and ensure the solution is uniform;

[0032] (2) Slowly add the materials required for the third layer on top of the fourth layer materials in step (1), and stabilize for 20 to 35 min;

[0033] (3) Slowly add the materials required for the second layer on top of the third layer materials in step (2);

[0034] (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-oil-water four-layer mixing column. Preferably, during the addition of the materials required for the first layer, slowly circulate up and down above the interface between the first layer and the second layer through a peristaltic pump 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 min 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, preventing pauses from causing trailing and affecting the true roundness.

[0035] Furthermore, the dehydrogenation catalyst is formed in an oil-ammonia water-oil-water four-layer mixing column. A mixture of aluminum hydroxide sol, an aqueous Pt solution, and an organic Pt salt solution is dropped into the oil-ammonia water-oil-water four-layer mixing column. The inner diameter of the dropping head used is 1.0 mm to 1.6 mm.

[0036] Furthermore, the residence time of the mixture of aluminum hydroxide sol, the aqueous Pt solution, and the organic Pt salt solution in the oil-ammonia water-oil-water four-layer mixing column is 5 - 18 s, preferably 7 - 11 s.

[0037] Furthermore, the drying temperature is 100°C to 150°C, and the drying time is 6 to 10 hours; the calcination temperature is 750°C to 950°C, and the calcination time is 1 to 4 hours.

[0038] The second aspect of the present invention provides a dehydrogenation catalyst prepared by the above preparation method.

[0039] Furthermore, the specific surface area of the dehydrogenation catalyst is 80 - 110 m 2 / g, and the pore volume is 0.55 - 0.80 mL / g.

[0040] Furthermore, the dehydrogenation catalyst is spherical particles, and the average diameter of the particles is 1.6 - 1.9 mm.

[0041] Furthermore, the pore size distribution of the dehydrogenation catalyst is as follows: the pore volume of pores with a pore size less than 2 nm accounts for 0.9% - 4.3% of the total pore volume, and the pore volume of pores with a pore size of 2 - 50 nm accounts for 95.7% - 99.1% of the total pore volume, preferably 96.0% - 98.0%.

[0042] Furthermore, the average pore size of the dehydrogenation catalyst is 14 - 18 nm.

[0043] Furthermore, the crushing strength of the dehydrogenation catalyst is 66 - 88 N / grain.

[0044] Furthermore, the true roundness of the dehydrogenation catalyst is 97.5% - 99.9%.

[0045] Furthermore, in the dehydrogenation catalyst, based on the mass of the catalyst, by mass fraction, the total Pt content is 0.16% - 1.20%, the Sn content is 0.03% - 0.90%, and the alumina content is 97.90% - 99.81%.

[0046] Furthermore, in the dehydrogenation catalyst, the Pt content on the catalyst surface is 0.001% - 0.025%.

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

[0048] Further, the application includes: contacting a propane raw material with the catalyst to carry out a dehydrogenation reaction to obtain a product propylene.

[0049] Further, before the propane dehydrogenation catalyst is used, it needs to be reduced. The catalyst precursor is reduced in a reducing atmosphere. The reducing atmosphere is preferably H 2 , the reduction temperature is 450 - 600 °C, and the reduction time is 1 - 3 h.

[0050] 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 .

[0051] Compared with the prior art, the advantages of the present invention are as follows:

[0052] (1) The present invention adopts a one-step method to synthesize a dehydrogenation catalyst. By adding an aqueous Pt solution and an organic Pt salt solution to an aluminum hydroxide sol, the metal is uniformly dispersed in the alumina support, and at the same time, it also plays a role in pore expansion. During the forming process, the four-layer oil-ammonia water-oil-water mixing column is different from the two-layer oil-ammonia column or the hot oil column. The third-layer oil layer is added as a liquid seal oil layer and the fourth-layer water layer, which can enable the sol to quickly enter the third-layer and fourth-layer water layers after passing through the second-layer ammonia water layer, and the pH value quickly drops to neutral. As a result, during the drying process of the small balls, it is not easy to break or shrink with the volatilization of the surface ammonia water, which significantly increases the alumina particle size and mechanical strength. At the same time, it enables full contact between the metal and the support, and the loading is more uniform. 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 surface, a significant increase in the interaction force between the colloids, a shorter distance between the colloids, and partial collapse of the original structure, resulting in an increase in the mesoporous structure of the support within the range of 2 - 50 nm. By adding an appropriate amount of acidic solution to the fourth-layer water layer, the pore structure can be further optimized.

[0053] (2) During the preparation of the catalyst of the present invention, an organic Pt salt solution is added. Since the organic Pt has low solubility and a relatively large molecular weight, the organic molecules connected to the Pt atoms occupy a large steric hindrance, and it is easy to form a single-atom Pt catalyst during the synthesis process. The four-layer oil-water mixing column makes it difficult for the organic Pt to precipitate, and it contacts more fully with pseudo-boehmite, with stronger interaction forces. After calcination, both single-atom Pt and nano-particle Pt coexist in the catalyst, which can play a synergistic role and improve the catalyst activity. In the four-layer mixing column of the present invention, on the one hand, since the density difference between ammonia water and pure water is relatively small, the selected liquid-sealing oil density needs to be greater than that of ammonia water and less than that of pure water, and the viscosity cannot be too large, otherwise it will affect the roundness of the sol. By adding a surfactant to the transformer oil, the density can be increased without changing its viscosity to meet the requirements. The water-soluble surfactant slowly penetrates into the oil under heating conditions, and the intermolecular interaction forces are enhanced. During the process of evaporating the water, the intermolecular distance shortens. After repeated operations, the stability of the modified oil can be ensured. On the other hand, with the liquid sealing of the modified transformer oil, due to the addition of the surfactant, the surface tension at the oil-water interface is significantly reduced, the pause of the sol spheres when passing through the oil-water interface is reduced, and they can quickly pass through the interface, reducing pulling, effectively improving the roundness of the spherical carrier.

[0054] (3) The preparation process of the present invention is environmentally friendly. In the traditional oil-ammonia column ball-forming process, the volatilization of ammonia water brings serious environmental pollution problems and subsequent pollutant emission problems. The present invention separates the second ammonia water layer from the fourth water layer with the second oil layer, so that the ammonia water layer is sealed above the fourth water layer, which can extend the service time, avoid the product from carrying out ammonia water and causing environmental pollution. After long-term use, deionized water can be replaced to ensure the liquid-sealing effect. It is simple to operate industrially and saves costs.

[0055] (4) The dehydrogenation catalyst obtained by the preparation method of the present invention is used in the propane-to-propylene reaction, and has a high propane conversion rate and propylene selectivity. The catalyst with large pore diameter and pore volume can avoid carbon deposition after long-term operation. The Pt loading is mainly inside the catalyst and is not easy to precipitate, having good stability and good reaction performance. Detailed Embodiments

[0056] The following further illustrates the dehydrogenation catalyst, 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.

[0057] The experimental methods in the following examples are all conventional methods in the art unless otherwise specified. The experimental materials used in the following examples are all purchased from conventional biochemical reagent stores unless otherwise specified.

[0058] In the present invention, a nitrogen adsorption / desorption curve of a sample was tested at -196 °C using an ASAP 2020 full-automatic physical adsorption analyzer produced by Micromeritics Company in the United States, and the specific surface area, pore volume, and pore size distribution were determined.

[0059] In the present invention, the crushing strength was tested using a ZQJ-Ⅲ intelligent particle strength testing machine manufactured by Dalian Zhiqu Testing Machine Factory, and the average value of crushing ten spherical carriers was tested.

[0060] In the present invention, the true roundness was tested using an electron microscope of Olympus Company, and the average value was calculated after testing 20 samples.

[0061] In the present invention, the Pt content on the catalyst surface was measured by XPS (the instrument is of the Kratos Axis Ultra DLD model).

[0062] Example 1

[0063] 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), add deionized water and stir to make a uniform slurry, then add 26 g of nitric acid solution with a mass concentration of 45% for peptization, and finally make a pseudo-boehmite sol with an alumina mass content of 20%; take 300 g of the above sol (alumina content 20 wt%), add 12 g of chloroplatinic acid solution with a chloroplatinic acid concentration of 3%, which also contains stannous chloride with a concentration of 0.8% and hydrochloric acid with a concentration of 7%, stir evenly and then continue to add 6 g of platinum acetylacetonate solution with a concentration of 1.2%, and continue to stir to obtain a sol mixture;

[0064] Add 7 g each of lauroyl diethanolamine and nonylphenol polyoxyethylene ether (n = 9) to 100 g of transformer oil (density at 20 °C is 0.89 g / mL, kinematic viscosity at 40 °C is 12 mm 2 / s), stir evenly, seal and place in an oven at 100 °C and heat for 8 hours, remove the sealing cover and continue to heat for 4 hours, repeat the above steps 3 times, and the final density of the modified transformer oil is 0.94 g / mL; use a dropper with an inner diameter of 1.2 mm to (kinematic viscosity at 40 °C is 32 mm 2The above-mentioned sol was dropped and formed in a four-layer mixed column (cylindrical column) of white oil - ammonia water with a concentration of 25 wt% - modified transformer oil - deionized water at a rate of / s, and the residence time in the four-layer mixed column was 8 s. Among them, the addition amount of white oil was 35% of the volume of ammonia water, the addition amount of modified transformer oil was 38% of the volume of ammonia water, and the addition amount of deionized water was 1.3 times the volume of ammonia water. Then it was dried at 130 °C for 8 hours and calcined at 800 °C for 3 hours to obtain the catalyst A of the present invention, and its analysis results are shown in Table 1.

[0065] Example 2

[0066] Compared with Example 1, the difference is that the deionized water in the fourth layer of the four-layer mixed column was changed to a 5 wt% dilute acetic acid solution to obtain the catalyst B of the present invention, and its analysis results are shown in Table 1.

[0067] Example 3

[0068] Compared with Example 1, the difference is that 15.6 g of chloroplatinic acid solution with a concentration of 6% of chloroplatinic acid was added, which simultaneously contained 1.0% of stannous chloride and 9% of hydrochloric acid. After stirring evenly, 6.4 g of platinum acetylacetonate solution with a concentration of 1.8% of platinum acetylacetonate was continuously added to obtain the catalyst C of the present invention, and its analysis results are shown in Table 1.

[0069] Example 4

[0070] Compared with Example 1, the difference is that in the preparation of the modified transformer oil, the surfactant used was changed to lauroyl diethanolamine, the addition amount was changed to 12 g, and the number of repetitions was changed to 4 times. The density of the obtained modified transformer oil at 20 °C was 0.95 g / mL) to obtain the catalyst D of the present invention, and its analysis results are shown in Table 1.

[0071] Example 5

[0072] Compared with Example 1, the difference is that 5.4 g of platinum acetylacetonate solution with a concentration of 1.8% of platinum acetylacetonate was added to obtain the catalyst E of the present invention, and its analysis results are shown in Table 1.

[0073] Example 6

[0074] Compared with Example 1, the difference is that the addition amount of white oil was 42% of the volume of ammonia water, the addition amount of modified transformer oil was 32% of the volume of ammonia water, and the addition amount of deionized water was 1.6 times the volume of ammonia water to obtain the catalyst F of the present invention, and its analysis results are shown in Table 1.

[0075] Comparative Example 1

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

[0077] 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 2 / s at 40 °C, and the lower layer is ammonia water with a concentration of 25 wt%. The addition amount of white oil is 25% of the volume of ammonia water. The remaining forming steps remain unchanged, obtaining Comparative Catalyst G of the present invention, and its analysis results are shown in Table 2.

[0078] Comparative Example 2

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

[0080] Compared with Example 1, the difference is that only the first-layer white oil column in the four-layer mixing column is removed, and spherical forming is carried out with a three-layer column, obtaining Comparative Catalyst H of the present invention, and its analysis results are shown in Table 2.

[0081] Comparative Example 3

[0082] The synthesis step of the sol mixture is the same as that in Example 1.

[0083] Compared with Example 1, the difference is that only the fourth-layer water column is removed, obtaining Comparative Catalyst I of the present invention, and its analysis results are shown in Table 2.

[0084] Comparative Example 4

[0085] The synthesis step of the sol mixture is the same as that in Example 1.

[0086] Compared with Example 1, the difference is that only the modified transformer oil layer in the four-layer mixing column is removed, obtaining Comparative Catalyst J of the present invention, and its analysis results are shown in Table 2.

[0087] Comparative Example 5

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

[0089] Compared with Example 1, the difference is that only the modified transformer oil in the four-layer mixing is replaced with transformer oil, and the remaining forming steps remain unchanged. That is, the forming step is to use a dropper with an inner diameter of 1.2 mm to drop the above sol 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% - transformer oil - deionized water) for forming, and the residence time in the four-layer mixing column is 8 s. Among them, the addition amount of white oil is 35% of the volume of ammonia water, the addition amount of transformer oil is 38% of the volume of ammonia water, and the addition amount of deionized water is 1.3 times the volume of ammonia water. Then it is dried at 130 °C for 8 hours and calcined at 800 °C for 3 hours, obtaining Comparative Catalyst K of the present invention, and its analysis results are shown in Table 2.

[0090] Comparative Example 6

[0091] The synthesis method of the sol mixture is the same as that in Example 1.

[0092] Compared with Example 1, the differences are as follows: the addition amount of white oil is 16% of the volume of ammonia water, the addition amount of modified transformer oil is 20% of the volume of ammonia water, and the addition amount of deionized water is 0.4 times the volume of ammonia water, obtaining the comparative catalyst L of the present invention, and its analysis results are shown in Table 2.

[0093] Table 1 Physicochemical properties of the catalysts obtained in each example

[0094]

[0095]

[0096] Table 2 Physicochemical properties of the catalysts obtained in each comparative example

[0097] Catalyst number G H I J K L Average particle diameter, mm 1.79 1.77 1.75 1.75 1.76 1.76 <![CDATA[Specific surface area, m 2 / g]]> 98 107 99 101 105 99 Pore volume, mL / g 0.454 0.401 0.423 0.421 0.397 0.402 Pore size distribution, % <2 nm 4.9 4.5 4.7 5.3 6.0 5.1 2 - 50 nm 95.0 95.3 95.3 94.5 94.0 94.6 >50 nm 0.1 0.2 - 0.2 - 0.3 Average pore diameter, nm 13.1 13.0 13.6 11.2 10.5 11.4 Crushing strength, N / grain 37 22 39 41 37 38 Roundness, % 95.1 95.3 94.2 95.8 93.9 95.2

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

[0099] Catalyst number A B C D E F Alumina (wt%) 99.6 99.6 99.0 99.6 99.6 99.6 Total Pt (wt%) 0.3 0.3 0.8 0.3 0.3 0.3 Sn (wt%) 0.1 0.1 0.2 0.1 0.1 0.1 Surface Pt (wt%) 0.01 0.01 0.02 0.01 0.01 0.01

[0100] Table 4 Compositions of the catalysts in each comparative example

[0101] Catalyst number G H I J K L Alumina (wt%) 99.6 99.7 99.6 99.6 99.6 99.6 Total Pt (wt%) 0.3 0.2 0.3 0.3 0.3 0.3 Sn (wt%) 0.1 0.1 0.1 0.1 0.1 0.1 Surface Pt (wt%) 0.01 0.01 0.01 0.01 0.01 0.01

[0102] Catalyst evaluation

[0103] Take 5 g of each of the above catalysts, first reduce them at 520 °C for 1.5 h in a hydrogen atmosphere, and then load them into a fixed-bed reactor for propane dehydrogenation activity evaluation: the reaction temperature is 600 °C, the pressure is 0.5 MPa, and the volume space velocity is 140 h -1 . The propane dehydrogenation results are listed in Tables 5 - 8.

[0104] Table 5 Evaluation results of the catalysts in each example for propane dehydrogenation

[0105]

[0106] Table 6 Evaluation results of the catalysts in each comparative example for propane dehydrogenation

[0107]

[0108] Table 7 Evaluation results of the stability of the catalysts in each example for propane dehydrogenation

[0109]

[0110] Table 8 Evaluation results of the stability of the catalysts in each comparative example for propane dehydrogenation

[0111]

[0112] 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 solutions of the present invention, including the combination of each technical feature in any other suitable manner. 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 dehydrogenation catalyst, comprising mixing an aluminum hydroxide sol with an aqueous Pt-containing solution and an organic Pt salt solution, dropping the obtained mixture into an oil-ammonia water-oil-water four-layer mixing column for shaping, drying, and calcining to obtain the dehydrogenation catalyst; in the mixing column, four layers are sequentially arranged 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 second oil layer is selected from modified transformer oils, and the modified transformer oil includes transformer oil and a water-soluble surfactant.

2. The preparation method according to claim 1, wherein: the platinum-containing compound in the aqueous Pt-containing solution is one or more of platinum chloride and chloroplatinic acid, preferably chloroplatinic acid; and / or, the concentration of the platinum-containing compound in the aqueous Pt-containing solution is 2 wt% to 6 wt%; and / or, the addition amount of the aqueous Pt-containing solution is 8% to 40% of the mass of the aluminum hydroxide sol calculated as alumina, preferably 15% to 30%.

3. The preparation method according to claim 1 or 2, wherein: the aqueous Pt-containing solution contains stannous chloride and hydrochloric acid; and / or, in the aqueous Pt-containing solution, the concentration of stannous chloride is 0.5 wt% to 3.5 wt%, and the concentration of hydrochloric acid is 5 wt% to 12 wt%.

4. The preparation method according to claim 1, wherein: the organic Pt salt in the organic Pt salt solution is one or more of platinum acetylacetonate and tetrakis(triphenylphosphine)platinum, preferably platinum acetylacetonate, and the solvent used is preferably acetone; and / or, the concentration of the organic Pt salt in the organic Pt salt solution is 1.0 wt% to 1.9 wt%; and / or, the addition amount of the organic Pt salt solution is 9% to 11% of the mass of the aluminum hydroxide sol calculated as alumina.

5. The preparation method according to claim 1, wherein: the alumina content in the aluminum hydroxide sol is 15 wt% to 26 wt%.

6. The preparation method according to claim 1, wherein: and / or, the oil-ammonia water-oil-water four-layer mixing column is a straight column, preferably a cylinder.

7. The preparation method according to claim 1, wherein: In the oil-ammonia water-oil-water four-layer mixing column, the first oil layer is selected from one or more of white oil and diesel oil, preferably white oil, and the kinematic viscosity of the white oil at 40 °C is 20-40 mm 2 / s, preferably 25-35 mm 2 / s.

8. The preparation method according to claim 1, wherein: in the oil-ammonia water-oil-water four-layer mixing column, the ammonia concentration in the ammonia water layer is 20 wt% to 28 wt%, preferably 22 wt% to 26 wt%.

9. The preparation method according to claim 1, wherein: in the oil-ammonia water-oil-water four-layer mixing column, the third layer is the second oil layer, i.e., the liquid seal oil layer. The density of the modified transformer oil used in the second oil layer is between that of ammonia water and water. Preferably, the density of the modified transformer oil at 20 °C is above 0.90 g / mL, preferably 0.93 to 0.96 g / mL; preferably, the mass of the water-soluble surfactant is 6% to 25% of the mass of the transformer oil, preferably 10% to 18%; preferably, the water-soluble surfactant is one or more of lauroyl diethanolamine, nonylphenol polyoxyethylene ether, and octylphenol polyoxyethylene ether; Preferably, the density of the transformer oil at 20 °C is 0.86 to 0.89 g / mL, and the kinematic viscosity at 40 °C is 9 to 15 mm 2 / s.

10. The preparation method according to claim 1, It is characterized in that: The preparation process of the modified transformer oil is as follows: Mix a water-soluble surfactant with transformer oil, and subject the resulting mixture to heat treatment, that is, successively carry out sealed heating treatment and open heating treatment, and repeat the above heat treatment 3 to 6 times to obtain the modified transformer oil; Preferably, the conditions of the sealed heating treatment are as follows: the heating temperature is 80 to 120 °C, and the heating time is 6 to 20 h; Preferably, the conditions of the open heating treatment are as follows: the heating temperature is 80 to 120 °C, and the heating time is 6 to 20 h.

11. According to the preparation method described in claim 1, It is characterized in that: In the oil-ammonia water-oil-water four-layer mixing column, the fourth layer is a water layer, preferably deionized water or a dilute acid solution, and 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%.

12. According to the preparation method described in claim 1, It is 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.

13. A dehydrogenation catalyst prepared by the preparation method described in any one of claims 1-12.

14. According to the catalyst described in claim 13, It is characterized in that: The specific surface area of the dehydrogenation catalyst is 80 to 110 m 2 / g, and the pore volume is 0.55 to 0.80 mL / g; And / or, the dehydrogenation catalyst is spherical particles, and the average diameter of the particles is 1.6 to 1.9 mm; And / or, the average pore diameter of the dehydrogenation catalyst is 14 to 18 nm; And / or, the crushing strength of the dehydrogenation catalyst is 66 to 88 N / particle; And / or, the true roundness of the dehydrogenation catalyst is 97.5% to 99.9%; And / or, the pore size distribution of the dehydrogenation catalyst is: the pore volume of pores with a pore diameter less than 2 nm accounts for 0.9% to 4.3% of the total pore volume, and the pore volume of pores with a pore diameter of 2-50 nm accounts for 95.7% to 99.1% of the total pore volume, preferably 96.0% to 98.0%.

15. According to the catalyst described in claim 13, It is characterized in that: In the catalyst, based on the mass of the catalyst, by mass fraction, the total Pt content in the catalyst is 0.16% to 1.20%, the Sn content is 0.03% to 0.90%, and the alumina content is 97.90% to 99.81%; Preferably, the Pt content on the surface of the catalyst is 0.001% to 0.025%.

16. Application of the catalyst described in any one of claims 13-15 in propane dehydrogenation reaction.

17. According to the application described in claim 16, It is characterized in that: Before use, the catalyst needs to be reduced; preferably, the reducing atmosphere is preferably H 2 , the reduction temperature is 450-600 °C, and the reduction time is 1-3 h.

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