A catalyst for dehydrogenation of isobutane to isobutene and a preparation method and application thereof

Abstract

The present application relates to isobutane dehydrogenation to isobutene chemical technology field, provide a kind of isobutane dehydrogenation to isobutene catalyst and its preparation method, the catalyst includes first active component, first adjuvant, second adjuvant and carrier.The preparation method of the catalyst includes the following steps: first, with isopropyl alcohol aluminum and bismuth nitrate pentahydrate as raw material preparation supported first adjuvant carrier;Then with alcohol-water solution as solvent, under stirring, join the platinum salt containing first active component and the alkali metal salt containing second adjuvant, then join the supported first adjuvant carrier, ultrasonic dispersion after vacuum rotary evaporation, again through drying, finally placed in muffle furnace calcination, obtain catalyst.The catalyst prepared by the method of the present application has good stability at higher dehydrogenation to isobutene reaction temperature, the range of adaptive reaction temperature is wider, has high activity while having high selectivity.

Description

Technical Field

[0001] This invention relates to the field of catalysts for the dehydrogenation of alkanes to olefins, and specifically to a catalyst for the direct dehydrogenation of isobutane to isobutene and its preparation method. Background Technology

[0002] Isobutene, the dehydrogenation product of isobutane, is an important chemical intermediate raw material, widely used in the synthesis of polyisobutene, tert-butanol, methyl tert-butyl ether, butyl rubber, synthetic resins, and other organic chemicals. With the continuous development and use of downstream chemical products, the demand for isobutene is gradually increasing both domestically and internationally. A large portion of isobutane is directly burned in the production of civilian fuels, resulting in a significant waste of resources. Obtaining high-value-added isobutene through alkane dehydrogenation technology can not only meet the domestic and international market demand for isobutene but also greatly improve the resource utilization value of isobutane.

[0003] There are two main types of industrially available isobutane dehydrogenation catalysts: platinum-based catalysts and chromium-based catalysts. Chromium-based catalysts are relatively inexpensive, but their rapid deactivation and environmental impact limit their application. Platinum-based catalysts remain the primary alkane dehydrogenation catalysts, offering relatively high alkane conversion and olefin selectivity. However, they still suffer from problems such as poor dispersion, sintering during the reaction, and carbon deposition, which reduce the stability of the catalytic reaction and the selectivity for isobutene. To this end, researchers have conducted extensive research on improving the performance of platinum-based catalysts, such as adding promoters (Sn, In, Ga, etc.) (Industrial & Engineering Chemistry Research, 2018, 57(33):11265-11270; Applied Catalysis B: Environmental, 2022, 300:120731), or using different supports (Al2O3, SiO2, TiO2, CaO, MgO, etc.) (Nanomaterials, 2022, 12(3):417; Molecular Catalysis, 2022, 522:112235), or modifying the support to enhance the dispersion of platinum and the interaction between platinum and the support, thereby enhancing the activity and stability of the catalytic reaction. Although significant progress has been made in isobutane dehydrogenation catalysts, there is still room for improvement in catalyst activity and stability. By changing the morphology of the support, the type, addition method, and amount of promoters, relatively ideal isobutane dehydrogenation catalysts can still be obtained.

[0004] To address the aforementioned problems, this invention proposes a method for preparing a platinum-based catalyst supported on sheet-like Al2O3. This method increases the dispersion of platinum (Pt) and its interaction with the support by introducing highly dispersed metallic bismuth (Bi) into sheet-like Al2O3 with high specific surface area and high pore volume, thereby enhancing the stability of the catalytic reaction and the selectivity of olefins. Summary of the Invention

[0005] To address the problems of low activity, poor stability, and low selectivity of platinum-based catalysts in existing technologies, this invention provides a method for preparing a catalyst for the dehydrogenation of isobutane to isobutene. The method uses high-specific-surface-area, high-pore-volume sheet-like Al₂O₃ as a support. By introducing bismuth metal during the support preparation process, the dispersion of platinum and its interaction with the support are increased. Then, platinum metal is loaded to prepare the catalyst, thereby improving the dispersion of platinum metal and its interaction with the support, and increasing the activity, stability, and isobutene selectivity of the catalytic reaction.

[0006] The preparation method of this invention has a wide suitable temperature range for the reaction, exhibiting high stability and olefin selectivity at high temperatures, while maintaining a high conversion rate even at lower reaction temperatures. The raw materials used in this preparation method are readily available, the process is simple, easily scalable, and highly reproducible, making it of significant application value.

[0007] The present invention also provides a catalyst for the dehydrogenation of isobutane to isobutene, which is prepared by the aforementioned preparation method.

[0008] This invention also provides an application of a catalyst for the dehydrogenation of isobutane to isobutene.

[0009] This invention provides an isobutane dehydrogenation catalyst, which is a platinum-based catalyst using Al2O3 nanosheets as a support.

[0010] Furthermore, the thickness of the Al2O3 nanosheets is 3–20 nm.

[0011] Furthermore, the catalyst support is loaded with platinum, bismuth, and alkali metals.

[0012] Furthermore, the platinum nanoparticles supported on the catalyst support have a particle size of 0.3–15 nm, and the mass of platinum in the catalyst is 0.05%–10% of the total mass of platinum and Al2O3, the mass of bismuth is 0.05%–10% of the total mass of bismuth and Al2O3, and the mass of alkali metal is 0.1%–5% of the total mass of alkali metal and Al2O3.

[0013] The method for preparing the isobutane dehydrogenation catalyst of the present invention includes the following steps:

[0014] Step 1: Add the aluminum source to the alcohol, stir until homogeneous, heat and stir continuously, then reflux. Then, allow the oil bath to cool naturally, and slowly add the aqueous solution containing bismuth salt while stirring. After stirring, transfer the resulting mixture to a high-pressure reactor, heat and solvothermal reaction. Collect the product, filter under reduced pressure, wash the product with ethanol-water solution, and then dry it in an oven. After removal, grind thoroughly and then calcine in a muffle furnace to obtain the bismuth-supported Al2O3 (abbreviated as Bi-Al2O3) support.

[0015] Step 2: Using an alcohol-water solution as the solvent, with a water-to-alcohol volume ratio of 1:4 to 4:1, platinum salt and alkali metal salt are added while stirring, followed by the Bi-Al2O3 support. The mixture is ultrasonically dispersed for 0.5 to 4 hours, then vacuum rotary evaporated at 40 to 80°C for 5 to 12 hours, dried at 70 to 110°C, and finally calcined in air at 450 to 800°C for 1 to 6 hours to obtain the isobutane dehydrogenation catalyst.

[0016] Further, in step 1, the aluminum source is one or more of aluminum isopropoxide, aluminum trichloride, aluminum nitrate, and aluminum sulfate; the alcohol is one or more of ethanol, propanol, isopropanol, methanol, n-butanol, isobutanol, and ethylene glycol, and its amount is 8 to 15 times the mass of the aluminum source, preferably 10 to 12 times; the bismuth salt is one or more of bismuth nitrate, bismuth chloride, bismuth isooctanoate, bismuth laurate, bismuth neodecanoate, bismuth naphthenate, bismuth oxide, bismuth oxycarbonate, and bismuth oxynitrate, and the mass of bismuth element contained in the bismuth salt is 0.05% to 10% of the total mass of bismuth element and Al2O3 (Al2O3 is generated from aluminum contained in the aluminum source), preferably 0.07% to 2%; the volume ratio of water to ethanol in the ethanol-water solution is 1:1 to 1:10, preferably 1:4 to 1:8.

[0017] Further, in step 1, the heating is oil bath heating, with a heating temperature of 30–100°C, preferably 50–100°C, and more preferably 80°C; the reflux condensation time is 2–12 hours, preferably 3–10 hours, and more preferably 3 hours; the natural cooling is natural cooling to 40°C; the volume of the aqueous solution containing bismuth salt is 20–50 ml, preferably 20–40 ml, and more preferably 26.5 ml; the stirring time is 1–6 hours, preferably 2–4 hours, and more preferably 2 hours; in the high-pressure reactor, the heating is raised to 110–200°C. The temperature is preferably 120–150°C, more preferably 120°C, and the solvothermal reaction time is 6–72 h, preferably 6–24 h, more preferably 12 h; in the oven, the drying time is 6–24 h, preferably 6–12 h, more preferably 12 h, and the drying temperature is 90–160°C, preferably 100–120°C, more preferably 110°C; in the muffle furnace, the calcination temperature is 500–700°C, preferably 550–650°C, more preferably 600°C, and the calcination time is 3–8 h, preferably 4–6 h, more preferably 5 h.

[0018] Further, in step 2, the alcohol is one or more of ethanol, propanol, isopropanol, methanol, n-butanol, isobutanol, and ethylene glycol, and the mass ratio of water-alcohol solution to carrier is 10:1 to 30:1; the platinum salt is one or more of chloroplatinic acid, chloroplatinic acid aqueous solution, platinum dichloride, and platinum tetrachloride, and the mass of platinum element contained in the platinum salt is 0.05% to 10% of the total mass of platinum element and Al2O3 (Al2O3 is generated from aluminum contained in the aluminum source), preferably 0.1% to 2%; the alkali metal salt is one or more of potassium nitrate, sodium nitrate, rubidium nitrate, potassium chloride, sodium chloride, rubidium chloride, calcium nitrate, magnesium nitrate, calcium chloride, and magnesium chloride, and the mass of alkali metal element in the alkali metal salt is 0.1% to 5% of the total mass of alkali metal element and Al2O3 (Al2O3 is generated from aluminum contained in the aluminum source), preferably 0.3% to 1%.

[0019] Further, in step 2, the volume ratio of water to alcohol is preferably 1:4 to 4:1, more preferably 1:1; ultrasonic dispersion is preferably 1 to 2 hours, more preferably 1 hour; the vacuum rotary evaporation is preferably carried out at a temperature of 50 to 70°C, more preferably 60°C, and for a time of 6 to 10 hours, more preferably 10 hours; the drying is preferably carried out at a temperature of 80 to 100°C, more preferably 100°C, and for a time of 4 to 6 hours, more preferably 5 hours; the calcination is carried out in a muffle furnace at a temperature of 550 to 650°C, more preferably 550°C, and for a time of 2 to 3 hours, more preferably 3 hours.

[0020] The isobutane dehydrogenation catalyst of the present invention is applied to the isobutane dehydrogenation to isobutene reaction: activation and reaction are carried out in a fixed bed, the catalyst dosage is 0.1 mg; the activation conditions are: atmospheric pressure, H2 atmosphere, space velocity of 1-8 L·g -1 ·h -1 Preferably 3-6 L·g -1 ·h -1 More preferably 3L·g -1 ·h -1 The activation temperature is 400–800℃, preferably 500–600℃, more preferably 550℃; the activation time is 1–4 h, preferably 1–2 h, more preferably 1 h; the reaction conditions are: reaction temperature 400–800℃, preferably 450–550℃, more preferably 550℃, i-C4H 10 The N2 (volume ratio) is 1:8 to 2:1, preferably 1:6 to 1:1, more preferably 1:6, at atmospheric pressure, and the space velocity is 6-18 L·g. -1 ·h -1 Preferably 6–12 L·g -1 ·h -1 More preferably 12 L·g -1 ·h -1 The reaction tail gas was analyzed using an Agilent 7890A gas chromatograph, with nitrogen as an internal standard to calculate the conversion rate and product selectivity.

[0021] Compared with existing isobutane dehydrogenation catalysts, the isobutane dehydrogenation catalyst of the present invention has the following advantages and beneficial effects:

[0022] (1) The Al2O3 nanosheets prepared in this invention have higher specific surface area and pore volume, which can significantly improve the dispersion of platinum. Bismuth doping during the preparation of Al2O3 nanosheets can significantly improve the interaction between platinum and the support, thereby improving the stability of the catalyst at higher isobutane dehydrogenation to isobutene reaction temperatures (400-800℃).

[0023] (2) Under high temperature conditions (550~650℃), the isobutane dehydrogenation catalyst of the present invention can maintain high stability and has a wide range of suitable reaction temperatures for isobutane dehydrogenation to isobutene. Within the reaction temperature range of 400~600℃, it can maintain high isobutene selectivity and low selectivity for by-products such as CH4, ethane, propane, propylene, butane, and CO2.

[0024] (3) At a reaction temperature of 450–550 °C, the isobutane dehydrogenation catalyst of the present invention has high activity and isobutene selectivity of up to 97%.

[0025] (4) The preparation process of the isobutane dehydrogenation catalyst of the present invention is simple, the raw materials are readily available, it is easy to scale up and has good reproducibility. Attached Figure Description

[0026] Figure 1 The physical adsorption-desorption isotherms are those of the Al2O3 nanosheets prepared in Example 1 and the commercial Al2O3 nanoparticles.

[0027] Figure 2 This is a transmission electron microscope (TEM) image of the Al2O3 nanosheets prepared in Example 1;

[0028] Figure 3 Transmission electron microscopy (TEM) images of commercial Al2O3 nanoparticles;

[0029] Figure 4 This is a transmission electron microscope (TEM) image of the carrier C prepared in Example 3;

[0030] Figure 5 The image shows a scanning transmission electron microscope (STEM) image of the catalyst prepared in Example 3.

[0031] Figure 6 The surface distribution diagram (scanning transmission electron microscopy energy dispersive spectroscopy) of the Pt element contained in the catalyst prepared in Example 3 is shown.

[0032] Figure 7 The surface distribution diagram (scanning transmission electron microscopy energy dispersive spectroscopy) of the Bi element contained in the catalyst prepared in Example 3 is shown.

[0033] Figure 8 The image shows the surface distribution of K in the catalyst prepared in Example 3 (scanning transmission electron microscopy energy dispersive spectroscopy). Detailed Implementation

[0034] The present invention will be further illustrated below with reference to specific embodiments. However, these embodiments are not intended to limit the scope of the invention.

[0035] Example 1

[0036] Step 1: Add 50g of aluminum isopropoxide to 400ml of isopropanol, stir evenly, heat in an oil bath to 80℃, stir continuously, and reflux for 3h. Then, allow the oil bath to cool naturally to 40℃, and then slowly add 26.5ml of water while stirring at 40℃. Continue stirring for 2h, then transfer the resulting mixture to a high-pressure reactor, heat to 120℃, and solvothermal react for 12h. After removing the product, filter under reduced pressure, wash the product with an ethanol-water solution (volume ratio of water to ethanol is 1:5), and then place it in an oven to dry at 110℃ for 12h. After removing it, grind it thoroughly, and then calcine it in a muffle furnace at 600℃ for 5h to obtain a sheet-like Al2O3 support, denoted as support A.

[0037] Step 2: Using 20 ml of an ethanol-water solution with a volume ratio of 1:1 (water to ethanol) as the solvent, add 984 mg of 8 wt% chloroplatinic acid solution and 119 mg of potassium chloride while stirring. Then add 12.5 g of the carrier A obtained in Step 1, sonicate for 1 h, then vacuum rotary evaporate at 60 °C for 10 h, and dry the resulting powder at 100 °C for 5 h. Finally, calcine it in a muffle furnace at 550 °C for 3 h to obtain catalyst 0.3Pt0.5K / Al2O3, denoted as catalyst A-Cat.

[0038] In catalyst A-Cat, 0.3Pt refers to the mass of platinum being 0.3% of the total mass of platinum and Al2O3 (theoretical calculation value, the same in the following examples); 0.5K refers to the mass of potassium being 0.5% of the total mass of potassium and Al2O3 (theoretical calculation value, the same in the following examples).

[0039] Catalyst evaluation experiments were conducted in a fixed-bed reactor (TORCH) with a catalyst dosage of 0.1 mg. Activation conditions were: atmospheric pressure, H2 atmosphere, and space velocity of 3 L / g. -1 ·h -1 The activation temperature was 550℃, and the activation time was 1 hour; the reaction conditions were: reaction temperature 550℃, i-C4H 10 The N2 (volume ratio) is 1:6, at atmospheric pressure, and the space velocity is 12 L·g. -1 ·h -1 The reaction tail gas was analyzed using an Agilent 7890A gas chromatograph, with nitrogen as an internal standard to calculate the conversion rate and product selectivity. Average reaction data over 20 hours after the introduction of isobutane are shown in Table 2.

[0040] The specific surface area, pore volume, and pore size of carrier A and commercial Al2O3 nanoparticles in Example 1 were characterized using a nitrogen physical adsorption-desorption apparatus. The results are listed in Table 1, and the nitrogen physical adsorption-desorption isotherms are shown below. Figure 1 As shown.

[0041] Table 1. Nitrogen physisorption-desorption data for carrier A and commercial Al2O3 nanoparticles in Example 1.

[0042]

[0043] According to the appendix Figure 1 As shown in Table 1, the self-made support A has a higher specific surface area and pore volume compared with commercial Al2O3 nanoparticles, which is beneficial to the dispersion of active components, increases the distance between active component metal nanoparticles, and improves their catalytic activity and stability.

[0044] The carrier A and commercial Al2O3 nanoparticles in Example 1 were characterized using transmission electron microscopy (TEM), and the characterization images are shown below. Figure 2 and3 As shown, by Figure 2 It can be seen that the self-prepared carrier A is in the form of a thin sheet, with a thickness of approximately 4-6 nm; Figure 3 It can be seen that commercial Al2O3 exhibits relatively large granular structure.

[0045] Example 2

[0046] Step 1: Add 50g of aluminum isopropoxide to 400ml of isopropanol, stir evenly, heat in an oil bath to 80℃, and stir continuously for 3 hours under reflux. Then, allow the oil bath to cool naturally to 40℃. Next, slowly add 26.5ml of an aqueous solution containing 29mg of bismuth nitrate pentahydrate while stirring at 40℃. Continue stirring for 2 hours, then transfer the resulting mixture to a high-pressure reactor, heat to 120℃, and solvothermal react for 12 hours. After removing the product, filter under reduced pressure, wash the product with an ethanol-water solution (water and ethanol volume ratio of 1:5), and then place it in an oven to dry at 110℃ for 12 hours. After removing it, grind it thoroughly, and then calcine it in a muffle furnace at 600℃ for 5 hours to obtain a 0.1Bi-Al2O3 support with a bismuth element mass of 0.1% of the total mass of bismuth element and Al2O3 (theoretical calculation value, the same in the following examples), denoted as support B.

[0047] Step 2: Using 20 ml of ethanol-water solution (water to ethanol volume ratio of 1:1) as solvent, add 984 mg of 8 wt% chloroplatinic acid solution and 119 mg of potassium chloride while stirring. Then add 12.5 g of the support B obtained in Step 1, sonicate for 1 h, then vacuum rotary evaporate at 60 °C for 10 h, and dry the resulting powder at 100 °C for 5 h. Finally, calcine it in a muffle furnace at 550 °C in air for 3 h to obtain catalyst 0.3Pt0.5K / 0.1Bi-Al2O3, denoted as catalyst B-Cat.

[0048] In catalyst B-Cat, 0.3Pt refers to the mass of platinum being 0.3% of the total mass of platinum and Al2O3 (theoretical calculation); 0.5K refers to the mass of potassium being 0.5% of the total mass of potassium and Al2O3 (theoretical calculation).

[0049] Catalyst evaluation experiments were conducted in a fixed-bed reactor (TORCH) with a catalyst dosage of 0.1 mg. Activation conditions were: atmospheric pressure, H2 atmosphere, and space velocity of 3 L / g. -1 ·h -1 The activation temperature was 550℃, and the activation time was 1 hour; the reaction conditions were: reaction temperature 550℃, i-C4H 10 The N2 (volume ratio) is 1:6, at atmospheric pressure, and the space velocity is 12 L·g. -1 ·h -1The reaction tail gas was analyzed using an Agilent 7890A gas chromatograph, with nitrogen as an internal standard to calculate the conversion rate and product selectivity. Average reaction data over 20 hours after the introduction of isobutane are shown in Table 2.

[0050] Example 3

[0051] Step 1: Add 50g of aluminum isopropoxide to 400ml of isopropanol, stir evenly, heat in an oil bath to 80℃, stir continuously, and reflux for 3h. Then, allow the oil bath to cool naturally to 40℃, and then slowly add 26.5ml of an aqueous solution containing 58mg of bismuth nitrate pentahydrate while stirring at 40℃. Continue stirring for 2h, then transfer the resulting mixture to a high-pressure reactor, heat to 120℃, and solvothermal react for 12h. After removing the product, filter under reduced pressure, wash the product with an ethanol-water solution (volume ratio of water to ethanol is 1:5), and then place it in an oven to dry at 110℃ for 12h. After removing it, grind it thoroughly, and then calcine it in a muffle furnace at 600℃ for 5h to obtain a 0.2Bi-Al2O3 support with a bismuth element content of 0.2% of the total mass of bismuth element and Al2O3, denoted as support C.

[0052] Step 2: Using 20 ml of ethanol-water solution (water to ethanol volume ratio of 1:1) as solvent, add 984 mg of 8 wt% chloroplatinic acid solution and 119 mg of potassium chloride under stirring, then add 12.5 g of the support C obtained in Step 1, ultrasonically disperse for 1 h, then vacuum rotary evaporate at 60 °C for 10 h, and dry the resulting powder at 100 °C for 5 h; finally, calcine it in a muffle furnace at 550 °C in air for 3 h to obtain catalyst 0.3Pt0.5K / 0.2Bi-Al2O3, denoted as catalyst C-Cat.

[0053] In the catalyst C-Cat, 0.3Pt refers to the mass of platinum being 0.3% of the total mass of platinum and Al2O3 (theoretical calculation); 0.5K refers to the mass of potassium being 0.5% of the total mass of potassium and Al2O3 (theoretical calculation).

[0054] Catalyst evaluation experiments were conducted in a fixed-bed reactor (TORCH) with a catalyst dosage of 0.1 mg. Activation conditions were: atmospheric pressure, H2 atmosphere, and space velocity of 3 L / g. -1 ·h -1 The activation temperature was 550℃, and the activation time was 1 hour; the reaction conditions were: reaction temperature 550℃, i-C4H 10 The N2 (volume ratio) is 1:6, at atmospheric pressure, and the space velocity is 12 L·g. -1 ·h -1 The reaction tail gas was analyzed using an Agilent 7890A gas chromatograph, with nitrogen as an internal standard to calculate the conversion rate and product selectivity. Average reaction data over 20 hours after the introduction of isobutane are shown in Table 2.

[0055] The carrier C in Example 3 was characterized using transmission electron microscopy, such as... Figure 4 As shown, the carrier C loaded with Bi still maintains a good sheet-like structure with a thickness of about 4-6 nm.

[0056] The catalyst C-Cat prepared in Example 3 was characterized using scanning transmission electron microscopy. Figure 5 This is a STEM image of the C-Cat catalyst. Figure 6 This is a surface distribution map of Pt element in the C-Cat catalyst obtained by scanning transmission electron microscopy energy dispersive spectroscopy. Figure 7 This is a surface distribution map of Bi element in the C-Cat catalyst obtained by scanning transmission electron microscopy energy dispersive spectroscopy. Figure 8 This is a surface distribution map of potassium (K) in the C-Cat catalyst obtained using scanning transmission electron microscopy (STEM) energy dispersive spectroscopy. From... Figure 6 , Figure 7 and Figure 8 It can be seen that Pt, Bi, and K elements are uniformly dispersed on the self-made Al2O3 nanosheets.

[0057] Example 4

[0058] Step 1: Add 50g of aluminum isopropoxide to 400ml of isopropanol, stir evenly, heat in an oil bath to 80℃, stir continuously, and reflux for 3h. Then, allow the oil bath to cool naturally to 40℃, and then slowly add 26.5ml of an aqueous solution containing 116mg of bismuth nitrate pentahydrate while stirring at 40℃. Continue stirring for 2h, then transfer the resulting mixture to a high-pressure reactor, heat to 120℃, and solvothermal react for 12h. After removing the product, filter under reduced pressure, wash the product with an ethanol-water solution (water and ethanol volume ratio of 1:5), and then place it in an oven to dry at 110℃ for 12h. After removing it, grind it thoroughly, and then calcine it in a muffle furnace at 600℃ for 5h to obtain a 0.4Bi-Al2O3 support with a bismuth element mass of 0.4% and a total Al2O3 mass of 0.4%, denoted as support D.

[0059] Step 2: Using 20 ml of ethanol-water solution (water to ethanol volume ratio of 1:1) as solvent, add 984 mg of 8 wt% chloroplatinic acid solution and 119 mg of potassium chloride under stirring, then add 12.5 g of the support D obtained in Step 1, ultrasonically disperse for 1 h, then vacuum rotary evaporate at 60 °C for 10 h, and dry the resulting powder at 100 °C for 5 h; finally, calcine it in a muffle furnace at 550 °C in air for 3 h to obtain catalyst 0.3Pt0.5K / 0.4Bi-Al2O3, denoted as catalyst D-Cat.

[0060] In catalyst D-Cat, 0.3Pt refers to the mass of platinum being 0.3% of the total mass of platinum and Al2O3 (theoretical calculation); 0.5K refers to the mass of potassium being 0.5% of the total mass of potassium and Al2O3 (theoretical calculation).

[0061] Catalyst evaluation experiments were conducted in a fixed-bed reactor (TORCH) with a catalyst dosage of 0.1 mg. Activation conditions were: atmospheric pressure, H2 atmosphere, and space velocity of 3 L / g. -1 ·h -1 The activation temperature was 550℃, and the activation time was 1 hour; the reaction conditions were: reaction temperature 550℃, i-C4H 10 The N2 (volume ratio) is 1:6, at atmospheric pressure, and the space velocity is 12 L·g. -1 ·h -1 The reaction tail gas was analyzed using an Agilent 7890A gas chromatograph. Conversion and product selectivity were calculated using nitrogen as an internal standard. Average reaction data over 20 hours after the introduction of isobutane are shown in Table 2.

[0062] Example 5

[0063] Step 1: Add 50g of aluminum isopropoxide to 400ml of isopropanol, stir evenly, heat in an oil bath to 80℃, stir continuously, and reflux for 3h. Then, allow the oil bath to cool naturally to 40℃, and then slowly add 26.5ml of an aqueous solution containing 174mg of bismuth nitrate pentahydrate while stirring at 40℃. Continue stirring for 2h, then transfer the resulting mixture to a high-pressure reactor, heat to 120℃, and solvothermal react for 12h. After removing the product, filter under reduced pressure, wash the product with an ethanol-water solution (volume ratio of water to ethanol is 1:5), and then place it in an oven to dry at 110℃ for 12h. After removing it, grind it thoroughly, and then calcine it in a muffle furnace at 600℃ for 5h to obtain a 0.6Bi-Al2O3 support with a bismuth element content of 0.6% of the total mass of bismuth element and Al2O3, denoted as support E.

[0064] Step 2: Using 20 ml of ethanol-water solution (water to ethanol volume ratio of 1:1) as solvent, add 984 mg of 8 wt% chloroplatinic acid solution and 119 mg of potassium chloride under stirring, then add 12.5 g of the support E obtained in Step 1, ultrasonically disperse for 1 h, then vacuum rotary evaporate at 60 °C for 10 h, and dry the resulting powder at 100 °C for 5 h; finally, calcine it in a muffle furnace at 550 °C in air for 3 h to obtain catalyst 0.3Pt0.5K / 0.6Bi-Al2O3, denoted as catalyst E-Cat.

[0065] In catalyst E-Cat, 0.3Pt refers to the mass of platinum being 0.3% of the total mass of platinum and Al2O3 (theoretical calculation); 0.5K refers to the mass of potassium being 0.5% of the total mass of potassium and Al2O3 (theoretical calculation).

[0066] Catalyst evaluation experiments were conducted in a fixed-bed reactor (TORCH) with a catalyst dosage of 0.1 mg. Activation conditions were: atmospheric pressure, H2 atmosphere, and space velocity of 3 L / g. -1 ·h -1 The activation temperature was 550℃, and the activation time was 1 hour; the reaction conditions were: reaction temperature 550℃, i-C4H 10 The N2 (volume ratio) is 1:6, at atmospheric pressure, and the space velocity is 12 L·g. -1 ·h -1 The reaction tail gas was analyzed using an Agilent 7890A gas chromatograph. Conversion and product selectivity were calculated using nitrogen as an internal standard. Average reaction data over 20 hours after the introduction of isobutane are shown in Table 2.

[0067] Example 6

[0068] 0.1 mg of the catalyst C-Cat from Example 3 was used to test its reaction performance in a fixed-bed reactor (TORCH). The activation conditions were: atmospheric pressure, H2 atmosphere, and space velocity of 3 L·g⁻¹. -1 ·h -1 The activation temperature was 450℃, and the activation time was 1 hour; the reaction conditions were: reaction temperature 450℃, i-C4H 10 The N2 (volume ratio) is 1:6, at atmospheric pressure, and the space velocity is 12 L·g. -1 ·h -1 The reaction tail gas was analyzed using an Agilent 7890A gas chromatograph, and the conversion rate and product selectivity were calculated using nitrogen as an internal standard. The average reaction data within 20 hours after the introduction of isobutane are shown in Table 2.

[0069] Example 7

[0070] 0.1 mg of the catalyst C-Cat from Example 3 was used to test its reaction performance in a fixed-bed reactor (TORCH). The activation conditions were: atmospheric pressure, H2 atmosphere, and space velocity of 3 L·g⁻¹. -1 ·h -1 The activation temperature was 500℃, and the activation time was 1 hour; the reaction conditions were: reaction temperature 500℃, i-C4H 10 The N2 (volume ratio) is 1:6, at atmospheric pressure, and the space velocity is 12 L·g. -1 ·h -1The reaction tail gas was analyzed using an Agilent 7890A gas chromatograph, and the conversion rate and product selectivity were calculated using nitrogen as an internal standard. The average reaction data within 20 hours after the introduction of isobutane are shown in Table 2.

[0071] Example 8

[0072] 0.1 mg of the catalyst C-Cat from Example 3 was used to test its reaction performance in a fixed-bed reactor (TORCH). The activation conditions were: atmospheric pressure, H2 atmosphere, and space velocity of 3 L·g⁻¹. -1 ·h -1 The activation temperature was 600℃, and the activation time was 1 hour; the reaction conditions were: reaction temperature 600℃, i-C4H 10 The N2 (volume ratio) is 1:6, at atmospheric pressure, and the space velocity is 12 L·g. -1 ·h -1 The reaction tail gas was analyzed using an Agilent 7890A gas chromatograph, and the conversion rate and product selectivity were calculated using nitrogen as an internal standard. The average reaction data within 20 hours after the introduction of isobutane are shown in Table 2.

[0073] Example 9

[0074] Using 20 ml of ethanol-water solution (water to ethanol volume ratio of 1:1) as solvent, 984 mg of 8 wt% chloroplatinic acid solution and 71 mg of potassium chloride were added under stirring. Then, 12.5 g of the support C obtained in step 1 of Example 3 was added, and the mixture was ultrasonically dispersed for 1 h. After that, it was vacuum rotary evaporated at 60 °C for 10 h. The resulting powder was dried at 100 °C for 5 h. Finally, it was placed in a muffle furnace and calcined in air at 550 °C for 3 h to obtain the catalyst 0.3Pt0.3K / 0.2Bi-Al2O3, denoted as catalyst F-Cat.

[0075] In catalyst F-Cat, 0.3Pt refers to the mass of platinum being 0.3% of the total mass of platinum and Al2O3 (theoretical calculation); 0.3K refers to the mass of potassium being 0.3% of the total mass of potassium and Al2O3 (theoretical calculation).

[0076] Catalyst evaluation experiments were conducted in a fixed-bed reactor (TORCH) with a catalyst dosage of 0.1 mg. Activation conditions were: atmospheric pressure, H2 atmosphere, and space velocity of 3 L / g. -1 ·h -1 The activation temperature was 550℃, and the activation time was 1 hour; the reaction conditions were: reaction temperature 550℃, i-C4H 10 The N2 (volume ratio) is 1:6, at atmospheric pressure, and the space velocity is 12 L·g. -1 ·h -1The reaction tail gas was analyzed using an Agilent 7890A gas chromatograph, with nitrogen as an internal standard to calculate the conversion rate and product selectivity. Average reaction data over 20 hours after the introduction of isobutane are shown in Table 2.

[0077] Example 10

[0078] Using 20 ml of ethanol-water solution (water to ethanol volume ratio of 1:1) as solvent, 984 mg of 8 wt% chloroplatinic acid solution and 167 mg of potassium chloride were added under stirring. Then, 12.5 g of the support C obtained in step 1 of Example 3 was added, and the mixture was ultrasonically dispersed for 1 h. After that, it was vacuum rotary evaporated at 60 °C for 10 h. The resulting powder was dried at 100 °C for 5 h. Finally, it was calcined in a muffle furnace at 550 °C in air for 3 h to obtain the catalyst 0.3Pt0.7K / 0.2Bi-Al2O3, denoted as catalyst G-Cat.

[0079] In catalyst G-Cat, 0.3Pt refers to the mass of platinum being 0.3% of the total mass of platinum and Al2O3 (theoretical calculation); 0.7K refers to the mass of potassium being 0.7% of the total mass of potassium and Al2O3 (theoretical calculation).

[0080] Catalyst evaluation experiments were conducted in a fixed-bed reactor (TORCH) with a catalyst dosage of 0.1 mg. Activation conditions were: atmospheric pressure, H2 atmosphere, and space velocity of 3 L / g. -1 ·h -1 The activation temperature was 550℃, and the activation time was 1 hour; the reaction conditions were: reaction temperature 550℃, i-C4H 10 The N2 (volume ratio) is 1:6, at atmospheric pressure, and the space velocity is 12 L·g. -1 ·h -1 The reaction tail gas was analyzed using an Agilent 7890A gas chromatograph, with nitrogen as an internal standard to calculate the conversion rate and product selectivity. Average reaction data over 20 hours after the introduction of isobutane are shown in Table 2.

[0081] Comparative Example 1

[0082] Using 20 ml of ethanol-water solution (water to ethanol volume ratio of 1:1) as solvent, 984 mg of 8 wt% chloroplatinic acid solution, 119 mg of potassium chloride and 29 mg of bismuth nitrate pentahydrate were added under stirring. Then, 12.5 g of carrier A obtained in step 1 of Example 1 was added, and the mixture was ultrasonically dispersed for 1 h. After that, it was vacuum rotary evaporated at 60 °C for 10 h. The resulting powder was dried at 100 °C for 5 h. Finally, it was calcined in a muffle furnace at 550 °C in air for 3 h to obtain catalyst 0.3Pt0.5K0.2Bi / Al2O3, denoted as catalyst H-Cat.

[0083] In catalyst H-Cat, 0.3Pt refers to the mass of platinum being 0.3% of the total mass of platinum and Al2O3 (theoretical calculation); 0.5K refers to the mass of potassium being 0.5% of the total mass of potassium and Al2O3 (theoretical calculation); and 0.2Bi refers to the mass of bismuth co-impregnated with platinum and potassium being 0.2% of the total mass of bismuth and Al2O3 (theoretical calculation).

[0084] Catalyst evaluation experiments were conducted in a fixed-bed reactor (TORCH) with a catalyst dosage of 0.1 mg. Activation conditions were: atmospheric pressure, H2 atmosphere, and space velocity of 3 L / g. -1 ·h -1 The activation temperature was 550℃, and the activation time was 1 hour; the reaction conditions were: reaction temperature 550℃, i-C4H 10 The N2 (volume ratio) is 1:6, at atmospheric pressure, and the space velocity is 12 L·g. -1 ·h -1 The reaction tail gas was analyzed using an Agilent 7890A gas chromatograph, with nitrogen as an internal standard to calculate the conversion rate and product selectivity. Average reaction data over 20 hours after the introduction of isobutane are shown in Table 2.

[0085] Comparative Example 2

[0086] Using 20 ml of ethanol-water solution (water to ethanol volume ratio 1:1) as solvent, 984 mg of 8 wt% chloroplatinic acid solution, 119 mg of potassium chloride, and 29 mg of bismuth nitrate pentahydrate were added under stirring. Then, 12.5 g of commercial Al2O3 (abbreviated as S-Al2O3; MACKLIN, product number: A800207, nanoparticles, purity 99.9%) was added as a carrier. The mixture was ultrasonically dispersed for 1 h, followed by vacuum rotary evaporation at 60 °C for 10 h. The resulting powder was dried at 100 °C for 5 h. Finally, it was calcined in a muffle furnace at 550 °C in air for 3 h to obtain catalyst 0.3Pt0.5K0.2Bi / S-Al2O3, denoted as catalyst I-Cat.

[0087] In catalyst I-Cat, 0.3Pt refers to 0.3% of the total mass of platinum and commercial Al2O3 (theoretical calculation); 0.5K refers to 0.5% of the total mass of potassium and commercial Al2O3 (theoretical calculation); and 0.2Bi refers to 0.2% of the total mass of bismuth and commercial Al2O3 (theoretical calculation) co-impregnated with platinum and potassium.

[0088] Catalyst evaluation experiments were conducted in a fixed-bed reactor (TORCH) with a catalyst dosage of 0.1 mg. Activation conditions were: atmospheric pressure, H2 atmosphere, and space velocity of 3 L / g. -1 ·h -1The activation temperature was 550℃, and the activation time was 1 hour; the reaction conditions were: reaction temperature 550℃, i-C4H 10 The N2 (volume ratio) is 1:6, at atmospheric pressure, and the space velocity is 12 L·g. -1 ·h -1 The reaction tail gas was analyzed using an Agilent 7890A gas chromatograph, with nitrogen as an internal standard to calculate the conversion rate and product selectivity. Average reaction data over 20 hours after the introduction of isobutane are shown in Table 2.

[0089] Comparative Example 3

[0090] Using 20 ml of ethanol-water solution (water to ethanol volume ratio 1:1) as solvent, 984 mg of 8 wt% chloroplatinic acid solution, 119 mg of potassium chloride, and 29 mg of bismuth nitrate pentahydrate were added under stirring. Then, 12.5 g of commercial SiO2 (aladdin, product number: S433692, nanoparticles, purity 99.8%) was added as a support. The mixture was ultrasonically dispersed for 1 h, followed by vacuum rotary evaporation at 60 °C for 10 h. The resulting powder was dried at 100 °C for 5 h. Finally, it was calcined in a muffle furnace at 550 °C in air for 3 h to obtain the catalyst 0.3Pt0.5K0.2Bi / SiO2, denoted as catalyst J-Cat.

[0091] In catalyst J-Cat, 0.3Pt refers to 0.3% of the total mass of platinum and SiO2 (theoretical calculation); 0.5K refers to 0.5% of the total mass of potassium and SiO2 (theoretical calculation); and 0.2Bi refers to 0.2% of the total mass of bismuth and SiO2 (theoretical calculation) co-impregnated with platinum and potassium.

[0092] Catalyst evaluation experiments were conducted in a fixed-bed reactor (TORCH) with a catalyst dosage of 0.1 mg. Activation conditions were: atmospheric pressure, H2 atmosphere, and space velocity of 3 L / g. -1 ·h -1 The activation temperature was 550℃, and the activation time was 1 hour; the reaction conditions were: reaction temperature 550℃, i-C4H 10 The N2 (volume ratio) is 1:6, at atmospheric pressure, and the space velocity is 12 L·g. -1 ·h -1 The reaction tail gas was analyzed using an Agilent 7890A gas chromatograph, with nitrogen as an internal standard to calculate the conversion rate and product selectivity. Average reaction data over 20 hours after the introduction of isobutane are shown in Table 2.

[0093] Table 2 Performance of the catalyst in the direct dehydrogenation reaction of isobutane

[0094]

[0095]

[0096] Comparing Examples 1-5, it can be seen that as the Bi content in the support increases, the isobutane conversion rate and isobutene selectivity first increase and then decrease. The conversion rate and selectivity are highest when the Bi content is 0.2%, which are 55% and 97%, respectively.

[0097] Comparing Examples 3, 6, 7, and 8, according to the data in Table 2, it can be seen that as the catalytic reaction temperature increases, the isobutane conversion first increases and then decreases. The isobutene selectivity reaches its maximum at 550°C. Further increasing the reaction temperature, the isobutene selectivity decreases rapidly at 600°C.

[0098] Comparing Examples 3, 9, and 10, the data in Table 2 shows that increasing the K content significantly improves the isobutylene selectivity, but significantly reduces the isobutylene conversion rate.

[0099] According to Table 2, as can be seen from Comparative Example 1, the isobutane conversion and isobutene selectivity of the catalyst obtained by the Bi-doped Al2O3 support (catalyst C-Cat in Example 3) are higher than those of the catalyst H-Cat prepared by the impregnation method with metallic Bi.

[0100] The catalyst prepared by co-impregnation using commercial Al2O3 nanoparticles and SiO2 nanoparticles as supports exhibits relatively low isobutane conversion and isobutene selectivity.

Claims

1. A catalyst for the dehydrogenation of isobutane to isobutene, the catalyst comprising an active component Pt, a second auxiliary alkali metal, and a support, wherein the support is Al2O3 doped with a first auxiliary Bi, characterized in that: First, Bi-doped Al2O3 is prepared in alcohol using an aluminum source and a bismuth salt, and the Bi-doped Al2O3 is used as the support. Then, using an alcohol-water solution as a solvent, a platinum salt solution, an alkali metal salt, and the support are added sequentially, and the catalyst is obtained by calcination in air. The specific process for preparing Bi-doped Al2O3 from aluminum source and bismuth salt in alcohol is as follows: aluminum source is added to alcohol, stirred evenly, heated and stirred continuously, and refluxed; then, the oil bath is cooled naturally, and an aqueous solution containing bismuth salt is slowly added while stirring. After stirring, the resulting mixture is transferred to a high-pressure reactor, heated, and subjected to a solvothermal reaction. The product was collected, filtered under reduced pressure, washed with an ethanol-water solution, and then dried in an oven. After being removed, it was ground thoroughly and then calcined in a muffle furnace to obtain Bi-doped Al2O3, which is the support. The support is in the shape of a nanosheet; the platinum nanoparticles loaded on the support have a particle size of 0.3~15nm; in the final catalyst, the mass of platinum is 0.05%~10% of the total mass of platinum and Al2O3, the mass of bismuth is 0.05%~10% of the total mass of bismuth and Al2O3, and the mass of alkali metal is 0.1%~5% of the total mass of alkali metal and Al2O3, wherein the mass of Al2O3 is calculated based on the mass of aluminum contained in the aluminum source.

2. The catalyst according to claim 1, characterized in that, The aluminum source is one or more of aluminum isopropoxide, aluminum trichloride, aluminum nitrate, and aluminum sulfate.

3. The catalyst according to claim 1, characterized in that, The alcohol is one or more of ethanol, propanol, isopropanol, methanol, n-butanol, isobutanol, and ethylene glycol, and its amount is 8 to 15 times the mass of the aluminum source; the alcohol-water solution is an ethanol-water solution, wherein the volume ratio of water to ethanol is 1:1 to 1:

10.

4. The catalyst according to claim 3, characterized in that, The alcohol is one or more of ethanol, propanol, isopropanol, methanol, n-butanol, isobutanol, and ethylene glycol, and its amount is 10 to 12 times the mass of the aluminum source; the alcohol-water solution is an ethanol-water solution, wherein the volume ratio of water to ethanol is 1:4 to 1:

8.

5. The catalyst according to claim 4, characterized in that, The alcohol-water solution is an ethanol-water solution, wherein the volume ratio of water to ethanol is 1:

5.

6. The catalyst according to claim 1, characterized in that, The bismuth salt is one or more of bismuth nitrate, bismuth nitrate hydrate, bismuth chloride, bismuth chloride hydrate, bismuth isooctanoate, bismuth laurate, bismuth neodecanoate, bismuth naphthenate, bismuth oxide, bismuth oxide hydrate, bismuth oxycarbonate, bismuth oxycarbonate hydrate, and bismuth oxynitrate. The mass of bismuth element contained in the bismuth salt is 0.05% to 10% of the total mass of bismuth element and Al2O3.

7. The catalyst according to claim 6, characterized in that, The mass of bismuth in the bismuth salt is 0.07% to 2% of the total mass of bismuth and Al2O3.

8. The catalyst according to claim 7, characterized in that, The mass of bismuth in the bismuth salt is 0.1% to 0.4% of the total mass of bismuth and Al2O3.

9. The catalyst according to claim 1, characterized in that, The platinum salt is one or more of chloroplatinic acid, chloroplatinic acid aqueous solution, platinum dichloride and platinum tetrachloride, and the mass of platinum element in the platinum salt is 0.1% to 2% of the total mass of platinum element and Al2O3; the mass of alkali metal element in the alkali metal salt is 0.3% to 1% of the total mass of alkali metal element and Al2O3.

10. The catalyst according to claim 9, characterized in that, The platinum salt is one or more of chloroplatinic acid, chloroplatinic acid aqueous solution, platinum dichloride and platinum tetrachloride, and the mass of platinum element in the platinum salt is 0.3% of the total mass of platinum element and Al2O3; the mass of alkali metal element in the alkali metal salt is 0.3% to 0.7% of the total mass of alkali metal element and Al2O3.

11. The catalyst according to claim 10, characterized in that, The mass of alkali metal elements in alkali metal salts is 0.5% of the total mass of alkali metal elements and Al2O3.

12. A method for preparing the catalyst according to any one of claims 1-11, characterized in that, Includes the following steps: Step 1: Add the aluminum source to the alcohol, stir until homogeneous, heat while stirring continuously, and reflux. Then, allow the oil bath to cool naturally, and slowly add the aqueous solution containing bismuth salt while stirring. After stirring, transfer the resulting mixture to a high-pressure reactor, heat, and perform a solvothermal reaction. Collect the product, filter under reduced pressure, wash the product with an ethanol-water solution, and then dry it in an oven. After removal, grind thoroughly and calcine in a muffle furnace to obtain bismuth-doped Al2O3, which is the support. Step 2: Using an alcohol-water solution as the solvent, with a water-to-alcohol volume ratio of 1:4 to 4:1, platinum salt and alkali metal salt are added while stirring, followed by the Bi-Al2O3 support. The mixture is ultrasonically dispersed for 0.5 to 4 hours, then vacuum rotary evaporated at 40 to 80°C for 5 to 12 hours, dried at 70 to 110°C, and finally calcined in air at 450 to 800°C for 1 to 6 hours to obtain the isobutane dehydrogenation catalyst.

13. The preparation method according to claim 12, characterized in that: In step 1, the aluminum source is one or more of aluminum isopropoxide, aluminum trichloride, aluminum nitrate, and aluminum sulfate; the alcohol is one or more of ethanol, propanol, isopropanol, methanol, n-butanol, isobutanol, and ethylene glycol, and its amount is 8 to 15 times the mass of the aluminum source; the bismuth source is one or more of bismuth nitrate, bismuth chloride, bismuth isooctanoate, bismuth laurate, bismuth neodecanoate, bismuth naphthenate, bismuth oxide, bismuth oxycarbonate, and bismuth oxynitrate, and the mass of bismuth element contained in the bismuth source is 0.05% to 10% of the total mass of bismuth element and Al2O3; the volume ratio of water to ethanol in the ethanol-water solution is 1:1 to 1:

10.

14. The preparation method according to claim 13, characterized in that: In step 1, the aluminum source is one or more of aluminum isopropoxide, aluminum trichloride, aluminum nitrate, and aluminum sulfate; the alcohol is one or more of ethanol, propanol, isopropanol, methanol, n-butanol, isobutanol, and ethylene glycol, and its amount is 10 to 12 times the mass of the aluminum source; the bismuth source is one or more of bismuth nitrate, bismuth chloride, bismuth isooctanoate, bismuth laurate, bismuth neodecanoate, bismuth naphthenate, bismuth oxide, bismuth oxycarbonate, and bismuth oxynitrate, and the mass of bismuth element contained in the bismuth source is 0.07% to 2% of the total mass of bismuth element and Al2O3; the volume ratio of water to ethanol in the ethanol-water solution is 1:4 to 1:

8.

15. The preparation method according to claim 14, characterized in that: The volume ratio of water to ethanol in an ethanol-water solution is 1:

5.

16. The preparation method according to claim 12, characterized in that: In step 1, the heating is oil bath heating, and the heating temperature is 30~100℃; the condensation reflux time is 2~12h; the natural cooling is natural cooling to 40℃; when the mass of the aluminum source is 50g, the volume of the aqueous solution containing bismuth salt is 20~50ml; the stirring time is 1~6h; in the high-pressure reactor, the temperature is raised to 110~200℃, and the solvothermal reaction time is 6~72h; in the oven, the drying time is 6~24h, and the drying temperature is 90~160℃; in the muffle furnace, the calcination temperature is 500~700℃, and the calcination time is 3~8h.

17. The preparation method according to claim 16, characterized in that: In step 1, the heating is oil bath heating at a temperature of 50-100℃; the reflux condensation time is 3-10 hours; when the aluminum source mass is 50g, the volume of the aqueous solution containing bismuth salt is 20-40ml; the stirring time is 2-4 hours; in the high-pressure reactor, the temperature is raised to 120-150℃, and the solvothermal reaction time is 6-24 hours; in the oven, the drying time is 6-12 hours, and the drying temperature is 100-120℃; in the muffle furnace, the calcination temperature is 550-650℃, and the calcination time is 4-6 hours.

18. The preparation method according to claim 17, characterized in that: In step 1, the heating is oil bath heating at a temperature of 80°C; the reflux condensation time is 3 hours; the natural cooling is natural cooling to 40°C; when the aluminum source mass is 50g, the volume of the aqueous solution containing bismuth salt is 26.5ml; the stirring time is 2 hours; in the high-pressure reactor, the temperature is raised to 120°C, and the solvothermal reaction time is 12 hours; in the oven, the drying time is 12 hours, and the drying temperature is 110°C; in the muffle furnace, the calcination temperature is 600°C, and the calcination time is 5 hours.

19. The preparation method according to claim 12, characterized in that: In step 2, the alcohol is one or more of ethanol, propanol, isopropanol, methanol, n-butanol, isobutanol and ethylene glycol, and the mass ratio of water-alcohol solution to carrier is 10:1 to 30:

1. The platinum salt is one or more of chloroplatinic acid, aqueous solution of chloroplatinic acid, platinum dichloride, and platinum tetrachloride. The mass of platinum element in the platinum salt is 0.05% to 10% of the total mass of platinum element and Al2O3. The mass of alkali metal element in the alkali metal salt is 0.1% to 5% of the total mass of alkali metal element and Al2O3. The mass of Al2O3 is calculated based on the mass of aluminum element contained in the aluminum source.

20. The preparation method according to claim 19, characterized in that: The platinum salt is one or more of chloroplatinic acid, aqueous solution of chloroplatinic acid, platinum dichloride, and platinum tetrachloride. The mass of platinum element in the platinum salt is 0.1% to 2% of the total mass of platinum element and Al2O3. The mass of alkali metal element in the alkali metal salt is 0.3% to 1% of the total mass of alkali metal element and Al2O3. The mass of Al2O3 is calculated based on the mass of aluminum element contained in the aluminum source.

21. The preparation method according to claim 12, characterized in that: In step 2, the volume ratio of water to alcohol is 1:1; ultrasonic dispersion takes 1-2 hours; vacuum rotary evaporation takes 6-10 hours at a temperature of 50-70°C; drying takes 4-6 hours at a temperature of 80-100°C; and calcination takes 2-3 hours in a muffle furnace at a temperature of 550-650°C.

22. The preparation method according to claim 21, characterized in that: In step 2, ultrasonic dispersion is performed for 1 hour; vacuum rotary evaporation is performed at 60°C for 10 hours; drying is performed at 100°C for 5 hours; and calcination is performed in a muffle furnace at 550°C for 3 hours.

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