Aluminum Oxide Support, Preparation Method of Catalyst Containing Aluminum Oxide Support, and Application of Catalyst

Abstract

The present invention discloses an alumina support, a preparation method of a catalyst containing the alumina support, and the application of the catalyst. The raw materials of the alumina support include bauxite, methyl cellulose, and component one. A preparation method of the alumina support is also disclosed, as well as a catalyst containing the alumina support. The raw materials of the catalyst include: 40 to 55 parts by mass of the above alumina support, preferably 45 parts by mass, 10 to 30 parts by mass of component two, and 1 to 10 parts by mass of component three. A preparation method of the catalyst containing the alumina support is also disclosed. During the dehydrogenation reaction process, the catalyst of the present invention has the advantages of high dehydrogenation activity and selectivity, slow deactivation, and strong anti-coking ability.

Description

Technical Field

[0001] The present invention relates to the field of chemistry, and particularly to an alumina support, a preparation method of a catalyst containing the alumina support, and the application of the catalyst. Background Art

[0002] Light olefins are very important organic chemical raw materials. In particular, ethylene, propylene, and isobutene are considered the basic raw materials of modern petrochemical industry. Light olefins are generally obtained by co-production or by-production. For example, currently about 70% of the propylene globally comes from the co-production of steam cracking to produce ethylene, and 28% of the propylene comes from the by-production of the catalytic cracking unit in refineries. With the further development of the chemical industry and the plastics industry, the demand for light olefins has increased rapidly. However, the traditional naphtha cracking and catalytic cracking production processes and devices can no longer meet the demand for light olefins in the petrochemical industry. Therefore, it is very important to develop new technologies to replace the traditional olefin production methods. Using the dehydrogenation of low-carbon alkanes with rich sources and low prices to produce light olefins is one of the most promising methods. The catalytic dehydrogenation technology of low-carbon alkanes is an effective way to increase the production of C3-C4 olefins. Currently, the main low-carbon alkane dehydrogenation technologies in the world are: the Oleflex process of UOP Company, the Catofin process of ABB-Lummus Company, the Star process of ConocoPhillips (Uhde) Company, the FBD-4 process of Snamprogetti / Yarsintz Company, the PDH process of Linde / BASF Company, etc. In the existing industrial plants that have been put into operation, the Catofin and Oleflex processes have become the dominant processes. The Oleflex process uses a platinum-based catalyst, and the Catofin process uses a chromium-based catalyst. Compared with platinum-based noble metal catalysts, chromium-based non-noble metal catalysts have high activity, relatively low requirements for impurities in the raw materials, and low prices. However, the existing catalysts, especially chromium-based catalysts, have many problems. For example, their stability is not high, they deactivate quickly, the reaction cycle is only 15-30 minutes, and the catalyst needs to be carbonized and regenerated every 7-15 minutes. The operation is complex, which seriously affects the production efficiency. In a high-temperature and acidic support environment, side reactions such as polymerization, cyclization, and carbonization occur, causing rapid carbon deposition and deactivation on the catalyst surface. Therefore, improving the carbon deposition resistance and dehydrogenation stability of the catalyst is the focus of the research on chromium-based dehydrogenation catalysts. At the same time, obtaining chromium-based catalysts with high stability, high activity, and high selectivity is the goal that people have been pursuing. Summary of the Invention

[0003] The technical problem solved by the present invention is that the existing catalysts have low stability, deactivate quickly, have a short reaction cycle, require frequent regeneration, and are extremely prone to carbon deposition and deactivation in a high-temperature and acidic support environment, and their stability, activity, and selectivity cannot meet the increasingly demanding usage requirements.

[0004] To solve the above technical problems, a technical solution adopted in the present invention is: an alumina carrier, the raw materials of the alumina carrier including bauxite, methylcellulose, urea, and component one, where component one is selected from one or a mixture of starch, hexamethylenetetramine, polyacrylamide, and urea, and preferably a mixture of starch and hexamethylenetetramine.

[0005] The bauxite includes one or a mixture of pseudo-boehmite, gibbsite, and aluminum powder.

[0006] In the present invention, the raw materials of the alumina carrier include: 50 - 80 parts by mass of bauxite, preferably 60 parts by mass, 4 - 7 parts by mass of methylcellulose, preferably 6 parts by mass, and 2 - 10 parts by mass of urea, preferably 6 parts by mass.

[0007] In the present invention, the starch is 2 - 8 parts by mass, and the hexamethylenetetramine is 2 - 8 parts by mass. Preferably, the starch is 4 parts by mass and the hexamethylenetetramine is 4 parts by mass.

[0008] Furthermore, the present invention also provides a preparation method for the above alumina carrier, and the method includes the following steps:

[0009] ① Take bauxite, methylcellulose, urea, and component one, add an appropriate amount of deionized water and stir to form an alumina suspension, and continue stirring;

[0010] ② Add a 15 - 40 wt% nitric acid solution, preferably a 25 wt% nitric acid solution, in step ①, and stir at 30 - 50 °C, preferably 35 °C, to form an alumina slurry.

[0011] ③ Drop the alumina slurry into one or a mixture of liquid paraffin, vacuum pump oil, or transformer oil, preferably paraffin, and shape it at 75 - 100 °C, preferably 85 °C;

[0012] ④ Age the shaped material at 100 - 150 °C for 4 - 20 h, preferably age it at 120 °C for 12 h. After washing with water, dry it at 80 - 150 °C for 4 - 10 h, preferably dry it at 130 °C for 8 h;

[0013] ⑤ Heat the dried material to 950 - 1100 °C and keep it at a constant temperature for 4 - 10 h, preferably heat it to 1000 °C and keep it at a constant temperature for 8 h. Before heating to 950 - 1100 °C, preferably 1000 °C, keep it at a constant temperature of 200 - 300 °C, 400 - 500 °C, 600 - 700 °C, and 800 - 900 °C for 6 - 8 h, preferably keep it at a constant temperature of 300 °C, 450 °C, 650 °C, and 850 °C for 4 h.

[0014] Furthermore, the present invention also provides an alumina-supported catalyst. The raw materials of the catalyst include: 40-55 parts by mass, preferably 45 parts by mass, of the alumina support described in any one of claims 1-3, 10-30 parts by mass of component two, and 1-10 parts by mass of component three; component two is selected from one or a mixture of two of chromium trioxide and chromium nitrate; component three is selected from one or a mixture of more of potassium nitrate, potassium hydroxide, magnesium nitrate, and zinc nitrate.

[0015] In the present invention, component two is chromium trioxide, and the chromium trioxide is 10-30 parts by mass, preferably 14.75 parts by mass; component three is potassium nitrate, and the potassium nitrate is 0.5-5 parts by mass, preferably 2.0 parts by mass.

[0016] Furthermore, the present invention provides a method for preparing a catalyst, which includes the following steps:

[0017] ① Weigh 10-30 parts by mass of component one and 1-10 parts by mass of component two, add 15-35, preferably 28 parts by mass of water, and prepare a mixed solution.

[0018] ② Weigh 40-55 parts by mass of the above-mentioned alumina support and perform equal-volume impregnation with the mixed solution in step ①, place it at room temperature for 1-10 h, preferably 2 h, dry it at 100-150 °C for 4-8 h, preferably dry it at 120 °C for 4 h, and calcine it at 500-800 °C for 4-10 h, preferably calcine it in an air atmosphere at 650 °C for 6 h to obtain the catalyst.

[0019] The present invention also provides an application method of the catalyst. The catalyst is applied to dehydrogenation of light alkanes, and the light alkanes are alkanes with C1-C4, further selected from one or a mixture of two of propane and isobutane.

[0020] In the present invention, the conditions of the application are: reaction temperature 450 °C - 650 °C, pressure normal pressure, alkane mass space velocity 3.0 - 6.0 h -1 , the volume ratio of the dilution gas to the light alkane is 1:4 - 1:1, and the dilution gas includes one or a mixture of more of hydrogen, nitrogen, methane, and water vapor, preferably hydrogen or / and nitrogen.

[0021] Further, when applied to propane dehydrogenation, the propane mass space velocity is 3.5 h -1 , the pressure is normal pressure, and the reaction temperature is 590 °C. When applied to isobutane dehydrogenation, the propane mass space velocity is 3.5 h -1 , the pressure is normal pressure, and the reaction temperature is 570 °C.

[0022] In the present invention, the catalyst regeneration conditions in the application are: treatment for 4-10 h at 450-600 °C in an air, air and nitrogen atmosphere.

[0023] The dehydrogenation reaction is carried out at a relatively high temperature, and usually cracking, isomerization and deep dehydrogenation reactions occur. Due to the presence of acidity on the catalyst, the formation of coke on the catalyst is accelerated. Research shows that acidity is crucial for the initial activity and selectivity of the propane dehydrogenation reaction. If the acidity is too low, the activity of the catalyst will also decrease. Therefore, alumina with a certain acidity is usually selected as the catalyst support. To reduce the impact of carbon deposition on the catalyst activity, alkali metal or alkaline earth metal elements are generally added during the catalyst preparation process to synergistically act with the acidic centers on the catalyst, adjust the catalyst acidity, and improve the catalyst stability and activity. Or other modifying elements are added to improve the catalyst activity, selectivity and stability.

[0024] The dehydrogenation of light alkanes is restricted by the thermodynamic equilibrium and needs to be carried out under harsh conditions of high temperature and low pressure. Too high reaction temperature exacerbates the cracking and deep dehydrogenation activities of alkanes, resulting in a decrease in selectivity. At the same time, it accelerates the carbon deposition on the catalyst surface and causes the catalyst to deactivate quickly. Although the Cr2O3 / Al2O3 catalyst has relatively high dehydrogenation activity, due to the existence of a large number of acid centers on the alumina support, problems such as rapid coking of the catalyst and olefin cracking occur. Therefore, the prior art adopts adding alkali metals and / or alkaline earth metals to weaken the surface acidity of the alumina support. At the same time, in order to improve the catalyst performance, some promoter elements are also added to optimize the surface characteristics of the catalyst, especially the electronic characteristics, such as elements like P and Ga, to further improve the activity and stability of the Cr2O3 / Al2O3 catalyst. And adding promoters is also the simplest and easiest way to improve the catalyst activity and stability. Through these means, although the catalyst performance has been significantly improved, the prior art still has problems such as low catalyst conversion rate, or high conversion rate but low olefin selectivity, especially fast deactivation.

[0025] The catalyst of the present invention uses mesoporous alumina as the support, chromium oxide as the active component, and alkali metal and / or alkaline earth metal as the co-catalytic component. The active component and the promoter are loaded onto the support by the common equal-volume impregnation method.

[0026] The mesoporous alumina support adopted in the present invention has a specific pore size distribution, in which the pores with a pore diameter of 10 - 50 nm account for more than 90% of the total pore volume, and the pores with a pore diameter less than 10 nm and greater than 50 nm account for no more than 10% of the total pore volume. The specific surface area of the support is 100 - 300 m 2 / g, with a pore volume of 0.40 - 0.85 ml / g and an average pore diameter of 20 - 40 nm. The alumina crystal form is a mixed type, with the main crystal form being the θ-type, with a content of not less than 85%, and also containing 2 - 10% of the δ- and / or α-crystal forms. The carrier shape is strip-shaped, spherical or clover-shaped. Since there are almost no pores with a pore diameter less than 10 nm in the carrier, the catalyst has a strong carbon-holding capacity. The carbon deposition formed during the reaction will not quickly block the catalyst pores, which can provide more active surfaces for the reaction. At the same time, there are fewer macropores larger than 50 nm, ensuring that the catalyst has sufficient crushing strength and can withstand the requirements of repeated regeneration, thereby ensuring the stable performance of the catalyst. At the same time, the concentrated pore size distribution provides a good channel for the rapid diffusion of reactants and products.

[0027] To further improve the activity, selectivity and stability of the catalyst, during the catalyst preparation process, one or several metal elements selected from zirconium, gallium, niobium, copper, zinc, molybdenum, tungsten, nickel or tin can be added to modulate the surface properties of the catalyst, especially the electronic properties. These modifying elements can be introduced before or after the loading of the active component chromium and the promoter alkali metal and / or alkaline earth metal.

[0028] The present invention has the following beneficial effects: (1) The catalyst of the present invention is modified with alkali metal and / or alkaline earth metal and other modifying aids, so that the catalyst has appropriate surface acidity and basicity, improving the alkane dehydrogenation conversion rate and olefin selectivity; (2) The method for improving the activity and stability of the catalyst of the present invention is to use a mesoporous alumina with a specific pore size distribution as the carrier. The alumina carrier used does not have micropores with smaller pore diameters and macropores with larger pore diameters, ensuring that the catalyst has good carbon-holding capacity during the reaction and the crushing strength required for repeated regeneration, and prolonging the service life of the catalyst; (3) The catalyst preparation method of the present invention is simple and easy to implement, does not require hydrothermal treatment to expand the pores of the carrier, nor does it require special modification treatment of the carrier. The catalyst preparation process is simple and convenient for large-scale industrial production. (4) During the dehydrogenation reaction process, the catalyst of the present invention has the advantages of high dehydrogenation activity and selectivity, slow deactivation and strong anti-carbon deposition ability. Description of the Drawings

[0029] Figure 1 is the pore size distribution curve of the alumina carrier prepared in Example 1 of the present invention;

[0030] Figure 2 is the pore size distribution curve of the alumina carrier prepared in Example 2 of the present invention. Detailed Embodiments

[0031] Example 1

[0032] Support Preparation: Take 60 g of pseudo-boehmite, 6 g of methyl cellulose, 4 g of starch, 4 g of hexamethylenetetramine, and 6 g of urea. Add an appropriate amount of deionized water and stir to form a suspension with an alumina mass content of 25%. Continue stirring for 2 h, slowly add 21.5 g of a nitric acid solution with a mass concentration of 25%, and stir at 35 °C for 2 h to form an alumina sol slurry. Drop the alumina sol into a hot oil column with liquid paraffin as the oil phase and an oil bath temperature of 85 °C for shaping. Collect the shaped pellets under the oil column, transfer them to an aging kettle, age at 120 °C for 12 h, then wash with water and dry at 130 °C for 8 h. Place the dried shaped support in a high-temperature furnace, raise the temperature to 1000 °C at a heating rate of 1.5 °C / min and hold for 8 h. Before reaching 1000 °C, hold at 300 °C, 450 °C, 650 °C, and 850 °C for 4 h respectively. The prepared alumina support is a mixed crystal form of θ- and δ-, with a specific surface area of 145 m 2 / g, a pore volume of 0.56 ml / g, an average pore diameter of 24 nm, and the proportion of pores with a pore diameter of 15 - 50 nm in the total pore volume is 91.4%.

[0033] Catalyst Preparation: Weigh 14.75 g of chromium trioxide and 2.0 g of potassium nitrate, add 28 ml of deionized water to prepare an impregnation solution. Then weigh 45 g of the above alumina support for equal-volume impregnation, age at room temperature for 2 h, dry at 120 °C for 4 h, and calcine in an air atmosphere at 650 °C for 6 h to obtain the finished catalyst A.

[0034] Screening Example ①

[0035] Support Preparation: Take 60 g of pseudo-boehmite, 6 g of methyl cellulose, 4 g of starch, 4 g of hexamethylenetetramine, and 6 g of urea. Add an appropriate amount of deionized water and stir to form a suspension with an alumina mass content of 25%. Continue stirring for 2 h, slowly add 21.5 g of a nitric acid solution with a mass concentration of 25%, and stir at 35 °C for 2 h to form an alumina sol slurry. Drop the alumina sol into a hot oil column with liquid paraffin as the oil phase and an oil bath temperature of 85 °C for shaping. Collect the shaped pellets under the oil column, transfer them to an aging kettle, age at 120 °C for 12 h, then wash with water and dry at 130 °C for 8 h. Place the dried shaped support in a high-temperature furnace, raise the temperature to 1000 °C at a heating rate of 1.5 °C / min and hold for 8 h. Before reaching 1000 °C, hold at 300 °C, 450 °C, 650 °C, and 850 °C for 4 h respectively. The prepared alumina support is a mixed crystal form of θ- and δ-, with a specific surface area of 145 m 2 / g, a pore volume of 0.56 ml / g, an average pore diameter of 24 nm, and the proportion of pores with a pore diameter of 15 - 50 nm in the total pore volume is 91.4%.

[0036] Catalyst preparation: Weigh 14.75 g of chromium trioxide and 4.0 g of potassium nitrate, add 27 ml of deionized water to prepare an impregnation solution, then weigh 45 g of the above alumina support for equal-volume impregnation, age at room temperature for 2 hours, dry at 150 °C for 4 h, and calcine in an air atmosphere at 750 °C for 4 h to obtain the catalyst product A-1.

[0037] Screening Example ②

[0038] Take 60 g of pseudo-boehmite, 6 g of methylcellulose, 4 g of starch, 4 g of hexamethylenetetramine, and 6 g of urea, add an appropriate amount of deionized water and stir to form a suspension with an alumina mass content of 25%. Continue stirring for 2 h, slowly add 21.5 g of a nitric acid solution with a mass concentration of 25%, and stir at 35 °C for 2 h to form an alumina sol slurry. Drop the alumina sol into a hot oil column with liquid paraffin as the oil phase and an oil bath temperature of 85 °C for shaping. Collect the shaped spheres below the oil column, transfer them to an aging kettle for aging at 120 °C for 12 h, then wash with water and dry at 130 °C for 8 h. Place the dried shaped support in a high-temperature furnace, raise the temperature to 1000 °C at a heating rate of 1.5 °C / min and keep it constant for 8 h. Before reaching 1000 °C, keep it constant at 300 °C, 450 °C, 650 °C, and 850 °C for 4 h respectively. The prepared alumina support is a mixed crystal form of θ- and δ-, with a specific surface area of 145 m 2 / g, a pore volume of 0.56 ml / g, an average pore diameter of 24 nm, and the proportion of pores with a pore diameter of 15 - 50 nm in the total pore volume is 91.4%.

[0039] Catalyst preparation: Weigh 12.25 g of chromium trioxide and 2.0 g of potassium nitrate, add 31 ml of deionized water to prepare an impregnation solution, then weigh 45 g of the above alumina support for equal-volume impregnation, age at room temperature for 4 hours, dry at 130 °C for 8 h, and calcine in an air atmosphere at 550 °C for 10 h to obtain the catalyst product A-2.

[0040] Screening Example ③

[0041] Take 60 g of pseudo-boehmite, 6 g of methylcellulose, 4 g of starch, 4 g of hexamethylenetetramine, 6 g of urea, add an appropriate amount of deionized water and stir to form a suspension with an alumina mass content of 25%. Continue stirring for 2 h, slowly add 21.5 g of a nitric acid solution with a mass concentration of 25%, and stir at 35 °C for 2 h to form an alumina sol slurry. Drop the alumina sol into a hot oil column with liquid paraffin as the oil phase and an oil bath temperature of 85 °C for shaping. Collect the shaped spheres under the oil column, transfer them to an aging kettle, age at 120 °C for 12 h, then wash with water and dry at 130 °C for 8 h. Place the dried shaped carrier in a high-temperature furnace, raise the temperature to 1000 °C at a heating rate of 1.5 °C / min and keep it constant for 8 h. Before reaching 1000 °C, keep it constant at 300 °C, 450 °C, 650 °C, and 850 °C for 4 h respectively. The prepared alumina carrier is a mixed crystal form of θ- and δ-, with a specific surface area of 145 m 2 / g, a pore volume of 0.56 ml / g, an average pore diameter of 24 nm, and the proportion of pores with a pore diameter of 15 - 50 nm in the total pore volume is 91.4%.

[0042] Catalyst preparation: Weigh 21.45 g of chromium trioxide and 4.0 g of potassium nitrate, add 20 ml of deionized water to prepare an impregnation solution. Then weigh 45 g of the above alumina carrier for equal-volume impregnation, age at room temperature for 4 h, dry at 130 °C for 8 h, and calcine in an air atmosphere at 700 °C for 6 h to obtain the catalyst product A-3.

[0043] Example 2

[0044] Support preparation: Take 70 g of pseudo-boehmite, 5 g of polyacrylamide, 5 g of methylcellulose, 10 g of urea, add an appropriate amount of deionized water and stir to form a suspension with an alumina mass content of 35%. Continue stirring for 2 h, slowly add 10 g of a nitric acid solution with a mass concentration of 35%, and stir at 50 °C for 2 h to form an alumina sol slurry. Add 30 g of boehmite and 10 g of gibbsite to the alumina sol, mix evenly, then add 10 g of carob powder and 2 g of 35% nitric acid and knead, extrude into shape, and dry at 130 °C for 8 h. Place the dried shaped carrier in a high-temperature furnace, raise the temperature to 1050 °C at a heating rate of 2 °C / min and keep it constant for 4 h. Before reaching 1050 °C, keep it constant at 250 °C, 450 °C, 650 °C, and 850 °C for 6 h respectively. The prepared alumina carrier is a mixed crystal form of θ- and δ-, with a specific surface area of 125 m 2 / g, a pore volume of 0.65 ml / g, an average pore diameter of 34 nm, and the proportion of pores with a pore diameter of 15 - 50 nm in the total pore volume is 93.5%.

[0045] Catalyst Preparation: Weigh 14.75 grams of chromium trioxide, add 30 ml of deionized water to prepare an impregnation solution. Then weigh 45 g of the above alumina support for equal-volume impregnation, age at room temperature for 2 h, dry at 120 °C for 4 h, and calcine in an air atmosphere at 700 °C for 6 h to obtain a chromium-containing catalyst precursor. Weigh 1.11 grams of potassium hydroxide, add 40 ml of deionized water to prepare an impregnation solution, impregnate the chromium-containing catalyst precursor, age at room temperature for 2 h, dry at 120 °C for 4 h, and calcine in an air atmosphere at 700 °C for 6 h to obtain the finished catalyst B.

[0046] Example 3

[0047] Support Preparation: The support preparation is the same as in Example 1, except that the oil phase is transformer oil.

[0048] Catalyst Preparation: Weigh 0.29 grams of potassium hydroxide and 1.48 grams of potassium nitrate, add 40 ml of deionized water to prepare an impregnation solution. Then weigh 45 g of the above alumina support for equal-volume impregnation, age at room temperature for 2 h, dry at 120 °C for 4 h, and calcine in an air atmosphere at 600 °C for 6 h to obtain a potassium-containing catalyst precursor. Weigh 19 grams of chromium nitrate and 10 grams of chromium trioxide, add 13 ml of deionized water to prepare an impregnation solution to impregnate the potassium-containing catalyst precursor, age at room temperature for 2 h, dry at 120 °C for 4 h, and calcine in an air atmosphere at 600 °C for 6 h to obtain the finished catalyst C.

[0049] Example 4

[0050] Support Preparation: The support preparation is the same as in Example 1, except that the oil phase is vacuum pump oil.

[0051] Catalyst Preparation: Weigh 14.75 grams of chromium trioxide and 2.0 grams of potassium nitrate, add 26 ml of deionized water to prepare an impregnation solution. Then weigh 45 grams of the above alumina support for equal-volume impregnation, age at room temperature for 2 h, dry at 120 °C for 4 h, and calcine in an air atmosphere at 650 °C for 6 h to obtain a chromium- and potassium-containing catalyst precursor. Weigh 2.3 grams of zinc nitrate, add 38 ml of deionized water to prepare an impregnation solution, impregnate the chromium- and potassium-containing catalyst precursor, age at room temperature for 2 h, dry at 120 °C for 4 h, and calcine in an air atmosphere at 650 °C for 6 h to obtain the finished catalyst D.

[0052] Example 5

[0053] Support Preparation: Take 70 g of pseudoboehmite, 6 g of starch, 5 g of polyacrylamide, 5 g of methylcellulose, and 10 g of urea. Add appropriate deionized water and stir to form a suspension with an alumina mass content of 30%. Continue stirring for 2 h, and slowly add 10 g of a nitric acid solution with a mass concentration of 35%. Stir at 50 °C for 2 h to form an alumina sol slurry. Add 30 g of boehmite and 10 g of gibbsite to the alumina sol, mix evenly, then add 15 g of carob powder and 2 g of 35% nitric acid and knead. Extrude into pellets and dry at 120 °C for 8 h. Place the dried formed support in a high-temperature furnace, raise the temperature to 1080 °C at a heating rate of 1.5 °C / min and hold for 6 h. Before reaching 1080 °C, hold at 300 °C, 450 °C, 650 °C, and 900 °C for 6 h respectively. The prepared alumina support has a θ- and δ-mixed crystal form, with a specific surface area of 135 m 2 / g, a pore volume of 0.68 ml / g, an average pore diameter of 33.5 nm, and the proportion of pores with a pore diameter of 15 - 50 nm accounting for 92.8% of the total pore volume.

[0054] Catalyst Preparation: Weigh 14.75 g of chromium trioxide, 1.05 g of potassium nitrate, 4.5 g of magnesium nitrate, and 2.3 g of zinc nitrate. Add 25 ml of deionized water to prepare an impregnation solution. Then weigh 45 g of the above alumina support for equal-volume impregnation, age at room temperature for 2 h, dry at 120 °C for 4 h, and calcine in an air atmosphere at 650 °C for 6 h to obtain the finished catalyst E.

[0055] Comparative Example 1

[0056] Support Preparation: The support preparation is the same as in Example 1, except that the formed support is calcined by directly raising the temperature to 1000 °C at a heating rate of 1.5 °C / min and holding for 8 h. The prepared alumina support has a θ- and δ-mixed crystal form, with a specific surface area of 173 m 2 / g, a pore volume of 0.64 ml / g, an average pore diameter of 18 nm, and the proportion of pores with a pore diameter of 15 - 50 nm accounting for 75.4% of the total pore volume.

[0057] Catalyst Preparation: The catalyst preparation is the same as in Example 1 to obtain the finished catalyst F.

[0058] Comparative Example 2

[0059] Support Preparation: The support preparation is the same as in Example 1, except that the formed support is calcined by raising the temperature to 650 °C at a heating rate of 1.5 °C / min and holding for 8 h, and then treated in air with a water vapor volume content of 5% at 650 °C for 6 h. The prepared alumina support has a γ-crystal form, with a specific surface area of 265 m 2 / g, a pore volume of 0.42 ml / g, an average pore diameter of 14 nm, and the proportion of pores with a pore diameter of 15 - 50 nm accounting for 50.4% of the total pore volume.

[0060] Catalyst Preparation: The catalyst was prepared in the same manner as in Example 1.

[0061] Example 6

[0062] Catalyst Reaction Performance Test: A 10-ml fixed-bed micro-reactor evaluation device was used. 10 ml of the catalyst was loaded into a quartz tube reactor with an inner diameter of 15 mm for the dehydrogenation reaction performance test. The volume ratio of the dilution gas to the light alkane was 1:4 to 1:1. When evaluating propane dehydrogenation, the propane mass space velocity was 3.5 h -1 , the pressure was atmospheric, and the reaction temperature was 590 °C. When evaluating isobutane dehydrogenation, the propane mass space velocity was 3.5 h -1 , the pressure was atmospheric, and the reaction temperature was 570 °C. Samples were taken every 5 minutes for chromatographic analysis to calculate the raw material conversion rate and product selectivity. The catalyst evaluation results are shown in Tables 1 to 4.

[0063] As can be seen from Tables 1, 2, 3, and 4, when the catalyst of the present invention is used for propane and isobutane dehydrogenation, the conversion rate and selectivity are relatively high, especially the stability is good, the activity decay is slow, and the regeneration performance is excellent.

[0064] Conversion rate % = (alkane in raw material - alkane in product) / alkane in raw material * 100.

[0065] Table 1 Propane Dehydrogenation Evaluation Results

[0066]

[0067] Table 2 Isobutane Dehydrogenation Evaluation Results

[0068]

[0069]

[0070] Table 3 Isobutane Dehydrogenation Stability

[0071]

[0072] Table 4 Regeneration Performance of Catalyst A (Isobutane Dehydrogenation)

[0073] The catalyst regeneration conditions were: under atmospheric pressure, at 450 - 600 °C, in an air or air + nitrogen atmosphere for 4 - 10 h.

[0074]

[0075]

[0076] The above are only embodiments of the present invention, and thus do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the specification of the present invention, or directly or indirectly applied in other related technical fields, shall similarly be included within the patent protection scope of the present invention.

Claims

1. Alumina support, characterized in that, The raw materials of the alumina support include 50-80 parts by mass of bauxite, 4-7 parts by mass of methylcellulose, 2-10 parts by mass of urea, and Component 1, where Component 1 is a mixture of 2-8 parts by mass of starch and 2-8 parts by mass of hexamethylenetetramine; The preparation method of the alumina support includes the following steps: ① Take bauxite, methylcellulose, urea, and Component 1, add deionized water and stir to form an alumina suspension, and continue stirring; ② Add a 15-40 wt% nitric acid solution in step ①, and stir at 30-50 °C to form an alumina slurry; ③ Drop the alumina slurry into a mixture of one or more of liquid paraffin, vacuum pump oil, or transformer oil, and form it at 75-100 °C; ④ Age the formed material at 100-150 °C for 4-20 h, wash it with water, and then dry it at 80-150 °C for 4-10 h; ⑤ Heat the dried material to 950-1100 °C and keep it at a constant temperature for 4-10 h. Before heating to 950-1100 °C, keep it at a constant temperature of 200-300 °C, 400-500 °C, 600-700 °C, and 800-900 °C for 4 h respectively.

2. The alumina support according to claim 1, characterized in that, The raw materials of the alumina support include: 60 parts by mass of bauxite, 6 parts by mass of methylcellulose, and 6 parts by mass of urea.

3. The alumina support according to claim 1, wherein The starch is 4 parts by mass, and the hexamethylenetetramine is 4 parts by mass.

4. The preparation method of the alumina support according to any one of claims 1 to 3, characterized in that, The preparation method includes the following steps: ① Take bauxite, methylcellulose, urea, and Component 1, add deionized water and stir to form an alumina suspension, and continue stirring; ② Add a 25 wt% nitric acid solution in step ①, and stir at 35 °C to form an alumina slurry; ③ Drop the alumina slurry into liquid paraffin and form it at 85 °C; ④ Age the formed material at 120 °C for 12 h, wash it with water, and then dry it at 130 °C for 8 h; ⑤ Heat the dried material to 1000 °C and keep it at a constant temperature for 8 h. Before heating to 1000 °C, keep it at a constant temperature of 300 °C, 450 °C, 650 °C, and 850 °C for 4 h respectively.

5. Alumina-supported catalyst, characterized in that, The raw materials of the catalyst include: 40-55 parts by mass of the alumina support according to any one of claims 1-3, 10-30 parts by mass of Component 2, and 1-10 parts by mass of Component 3; Component 2 is selected from one or a mixture of two of chromium trioxide and chromium nitrate; Component 3 is selected from one or a mixture of several of potassium nitrate, potassium hydroxide, magnesium nitrate, and zinc nitrate.

6. The alumina-supported catalyst according to claim 5, wherein The raw materials of the catalyst include: 45 parts by mass of the alumina support according to any one of claims 1-3.

7. The catalyst according to claim 5, characterized in that, Component 2 is chromium trioxide, and the chromium trioxide is 10-30 parts by mass; Component 3 is potassium nitrate, and the potassium nitrate is 0.5-5 parts by mass.

8. The catalyst according to claim 7, characterized in that, Component 2 is chromium trioxide, and the chromium trioxide is 14.75 parts by mass; Component 3 is potassium nitrate, and the potassium nitrate is 2.0 parts by mass.

9. The preparation method of the catalyst according to any one of claims 5 to 8, characterized in that, This method includes the following steps: ① Weigh 10-30 parts by mass of Component 2 and 1-10 parts by mass of Component 3, add 15-35 parts by mass of water, and prepare a mixed solution, ② Weigh 40 - 55 parts by mass of the above-mentioned alumina support, impregnate it with the mixed solution in step ① in an equal-volume manner, leave it at room temperature for 1 - 10 h, dry it at 100 - 150 °C for 4 - 8 h, and calcine it at 500 - 800 °C for 4 - 10 h to obtain the catalyst.

10. The preparation method according to claim 9, characterized in that, This method comprises the following steps: ① Weigh 10 - 30 parts by mass of component two and 1 - 10 parts by mass of component three, add 28 parts by mass of water to prepare a mixed solution. ② Weigh 40 - 55 parts by mass of the above-mentioned alumina support, impregnate it with the mixed solution in step ① in an equal-volume manner, leave it at room temperature for 2 h, dry it at 120 °C for 4 h, and calcine it in an air atmosphere at 650 °C for 6 h to obtain the catalyst.

11. Use of the catalyst according to any one of claims 5 to 8, characterized in that, The catalyst is applied to dehydrogenation of light alkanes, and the light alkanes are alkanes with C1 - C4.

12. The application according to claim 11, wherein The catalyst is applied to dehydrogenation of a mixture of one or two of propane and isobutane.

13. The application according to claim 11 or 12, characterized in that, The conditions for the application are as follows: the volume ratio of the diluent gas to the lower-carbon alkane is 1:4 to 1:1, the reaction temperature is 450°C to 650°C, the pressure is atmospheric pressure, and the mass space velocity of the alkane is 3.0 to 6.0 h -1 , and the diluent gas is a mixture of one or more of hydrogen, nitrogen, methane, and water vapor.

14. The application according to claim 13, wherein The conditions for the application are as follows: when applied to propane dehydrogenation, the propane mass space velocity is 3.5 h -1 , the pressure is atmospheric, and the reaction temperature is 590 °C. When applied to isobutane dehydrogenation, the propane mass space velocity is 3.5 h -1 , the pressure is atmospheric, and the reaction temperature is 570 °C.

15. The application according to claim 13, characterized in that, The dilution gas is hydrogen or / and nitrogen.

16. The catalyst application according to claim 8, wherein The catalyst regeneration conditions in the application are: under the atmosphere of air or the atmosphere of air and nitrogen at 450 - 600 °C, treat for 4 - 10 h.

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