A dehydrogenation catalyst and a method for preparing the same

Abstract

This invention discloses a dehydrogenation catalyst and its preparation method. The dehydrogenation catalyst includes a honeycomb substrate, a modified silica-alumina coating on the surface of the honeycomb substrate, and an active component Pt, wherein the modified silica-alumina coating contains a mesoporous molecular sieve encapsulating a Group VIB metal carbide. The preparation method is as follows: (1) The precursor of the Group VIB metal carbide is encapsulated into the pores of the mesoporous molecular sieve to obtain a modified molecular sieve; (2) The pretreated honeycomb ceramic substrate is immersed in the coating slurry containing the modified molecular sieve for a period of time, and after removal, the residual liquid is blown out of the pores, dried, and calcined to obtain an integral catalyst support; (3) The support is immersed in a Pt-containing solution, and then ammonia is added. After standing at the reaction temperature for a period of time, it is removed, washed with water, dried, calcined, and reduced to obtain the dehydrogenation catalyst. The dehydrogenation catalyst of this invention has broad application prospects in the fields of selective oxidation and oxidative dehydrogenation.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation, specifically relating to a carbon dioxide-assisted dehydrogenation catalyst and its preparation method. Background Technology

[0002] Oxidative dehydrogenation of hydrocarbons can produce high-value-added olefin products. Compared with the traditional steam cracking method for obtaining olefins, oxidative dehydrogenation has low investment costs, single and easy-to-separate products, low energy consumption, no carbon buildup, and is not limited by thermodynamic equilibrium. Oxidative dehydrogenation generally uses oxygen as the oxidation source, but due to its strong oxidizing properties, it is easy to cause over-oxidation and reduce the selectivity of olefins. Therefore, the design of the reaction system is more complicated and the control is more difficult. For example, it is necessary to inject O2 at fixed points in the later stage of the pulse reactor. Compared with O2 as an oxidant, CO2 shows its unique advantages: (1) CO2 is a relatively mild oxidant. By controlling the reaction conditions, it can effectively inhibit the catalytic combustion of reactants (alkane) and the deep oxidation of intermediate products, thereby improving the selectivity of target products (olefins); (2) Using CO2 as an oxidant, direct mixing or co-feeding can be achieved in the existing direct dehydrogenation reactor, thereby saving equipment and process transformation costs, shortening the transformation cycle, and avoiding the uncertain start-up risks and possible pollution brought about by the transformation process.

[0003] CO2, as a relatively mild oxidant, has far less activity than O2. Therefore, how to activate CO2 in a catalytic system is a crucial issue that must be addressed when using it as an oxidant. CN115041208A discloses a method for forming honeycomb-shaped boron nitride and its application in the oxidative dehydrogenation of low-carbon alkanes. The honeycomb-shaped boron nitride prepared by this method has ordered axial channels, increasing the effective utilization area. The resulting product is lightweight, has high mechanical strength, and high mass transfer efficiency, exhibiting excellent catalytic activity and stability in the catalytic conversion of low-carbon alkanes. However, this method involves mixing boron nitride powder with a binder, resulting in a lack of slurry during synthesis and limiting the ability to continuously load active centers. This restricts the upper limit of dehydrogenation capacity, and using oxygen as an oxidation source can easily lead to over-oxidation, reducing the selectivity for olefins. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a dehydrogenation catalyst and its preparation method. The dehydrogenation catalyst of this invention has a dual function of activating the dissociation and adsorption of carbon dioxide and alkanes, and the active components are not easily aggregated or deactivated. It has broad application prospects in selective oxidation, oxidative dehydrogenation and other fields.

[0005] The dehydrogenation catalyst of the present invention comprises a honeycomb substrate, a modified silica-alumina coating on the surface of the honeycomb substrate, and a first active component Pt. The modified silica-alumina coating contains a mesoporous molecular sieve encapsulating a Group VIB metal carbide, preferably Mo and / or W. Pt is atomically supported on the surface of the Group VIB metal carbide and the molecular sieve surface. The average particle size of Pt on the molecular sieve surface is 2-5 nm. Pt exhibits a single-atom distribution on molybdenum carbide.

[0006] The dehydrogenation catalyst of the present invention comprises, by weight of total catalyst, 85% to 92% honeycomb ceramic matrix, 5% to 12% coating, and 0.1% to 0.5% Pt (by element). Based on the weight of coating, the coating contains 25% to 65% alumina, 25% to 65% mesoporous molecular sieve, 2% to 5% silica, 0.5% to 3% transition metal additives selected from one or more of cerium, lanthanum, zirconium, titanium, and vanadium, and 2% to 6% group VIB metal carbides.

[0007] In the dehydrogenation catalyst of the present invention, the mesoporous molecular sieve is SBA-15 and / or ZSM-5 molecular sieve.

[0008] The carbon dioxide-assisted dehydrogenation catalyst of the present invention may further include one or more of zinc, tin, iron, manganese and gallium. Based on the total weight of the catalyst, zinc, tin, iron, manganese and gallium are 0.3wt% to 1.5wt% as oxides, and the sum of the contents of each component of the catalyst is 100%.

[0009] The method for preparing the dehydrogenation catalyst of the present invention includes the following steps: (1) A group VIB metal is encapsulated inside the pores of a mesoporous molecular sieve to obtain a modified molecular sieve; (2) The pretreated honeycomb ceramic substrate is immersed in the coating slurry containing the modified molecular sieve of step (1) for a period of time. After taking it out, the residual liquid is blown out of the channel, dried and calcined to obtain an integral catalyst support. (3) The monolithic catalyst support is immersed in a Pt-containing solution, then ammonia is added, and it is left to stand at the reaction temperature for a period of time. After being taken out, it is washed with water, dried and calcined, and then reduced in a mixture of methane and hydrogen to obtain the dehydrogenation catalyst.

[0010] In the method of the present invention, the encapsulation method described in step (1) is the in-situ encapsulation method commonly used in the field, that is, water-soluble salts of Group VIB metals are added during the molecular sieve synthesis stage; the molecular sieve undergoes crystal growth, water washing, drying, calcination and other processes to obtain a molecular sieve encapsulating Group VIB metals, and the Group VIB metals are 1% to 5% in terms of oxides based on the total weight of the modified molecular sieve.

[0011] In the method of this invention, the pretreatment process described in step (2) is well known to those skilled in the art. Generally, the honeycomb ceramic substrate is acid-treated, then washed with water and dried for later use. The acid treatment generally involves soaking in dilute nitric acid or hydrochloric acid, preferably with simultaneous ultrasonic oscillation treatment for 10-60 minutes. In the method of this invention, the coating slurry in step (2) comprises, by total weight,: 40%~60% solvent, 15%~25% activated alumina powder, 5%~10% modified molecular sieve from step (1), 3%~5% boehmite, 0%~5% transition metal salt, 3%~5% surfactant, 3%~5% silicon source, and 0.5%~2% nitric acid or hydrochloric acid; the solvent is water and / or an alcohol solvent; the surfactant is one or more of polyethylene glycol, urea, sodium dodecylbenzenesulfonate, and stearic acid; the silicon source is one or more of tetraethyl orthosilicate, methyl orthosilicate, polysiloxane, and ethoxysiloxane. The alcohol is one or more of ethanol, ethylene glycol, or butanol; preferably, the mass ratio of alcohol to water is 1~2:20; the activated alumina powder has a specific surface area of ​​100~1000 m². 2 / g; the pseudoboehmite has a specific surface area of ​​150~300m². 2 / g; The transition metal salt is a soluble salt, and the transition metal is selected from one or more of lanthanum, zirconium, titanium, and vanadium.

[0012] The preparation method of the coating slurry involves mixing activated alumina powder, boehmite, and a transition metal salt solution, then adding a surfactant and a silicon source, and adjusting the pH to 3-4 or the viscosity to 10-100 mPa·s to obtain the slurry. Generally, a diluted inorganic acid solution is used to adjust the pH to obtain a slurry with a suitable viscosity; the inorganic acid is typically hydrochloric acid or nitric acid. The transition metal salt solution is generally obtained by dissolving the transition metal salt in water and then adding a certain proportion of alcohol; the concentration of the transition metal solution is 0.16-0.5 mol / L.

[0013] In the method of the present invention, the impregnation time in step (2) is 2 to 10 minutes. The drying temperature is 100 to 150°C and the time is 12 to 24 hours; the calcination temperature is 400 to 550°C and the time is 2 to 4 hours.

[0014] In the method of the present invention, the impregnation time in step (3) is 2 to 10 minutes. The concentration of the Pt-containing solution in step (3) is 0.01 to 0.03 mol / L. The drying temperature in step (3) is 100 to 150°C and the time is 12 to 24 hours; the calcination temperature is 400 to 550°C and the time is 2 to 4 hours.

[0015] In the method of the present invention, step (3) involves adding concentrated ammonia to adjust the pH to 8-9, letting it stand for 1-4 hours, raising the temperature to 60-70°C, and holding it at that temperature for 1-2 hours.

[0016] In the method of the present invention, one or more auxiliary metals of zinc, tin, iron, manganese and gallium can be loaded between steps (2) and (3). The loading process can be carried out by impregnation, which is well known to those skilled in the art.

[0017] In the method of this invention, in step (3), the methane and hydrogen mixture has a methane volume percentage of 5% to 15% and a space velocity of 100 to 1000 h⁻¹. -1 .

[0018] In the method of the present invention, the reduction process in step (3) is a programmed temperature rise process, which raises the temperature from room temperature to 550~650 ℃ at a rate of 1℃ / min, and the reduction time is 0.5~1.5 hours.

[0019] The dehydrogenation catalyst of this invention is used in the coupled reaction of carbon dioxide utilization and oxidative dehydrogenation. The general operating conditions are: reaction pressure of 0.1~1.5 MPa, reaction temperature of 400~650℃, and gas hourly space velocity (HSV) of 5~200 h⁻¹. -1 .

[0020] Compared with the prior art, the present invention has the following advantages: The catalyst of this invention has two forms of active metal Pt: one on a molecular sieve support, and the other on Group VIB metal carbide (such as molybdenum carbide) particles. The Pt-loaded metal particles on the mesoporous molecular sieve encapsulating Group VIB metal carbides are black particles with an average size of about 2-5 nm, composed of distinct parallel lines. Inside the encapsulated structure, there are molybdenum carbide particles (50-200 nm) with a size much larger than 5 nm. Dark-field images obtained using transmission electron microscopy are needed to observe the details. Figure 2 These molybdenum carbide particles, which are composed of parallel lines in the figure, can be identified by the lattice spacing (the particles on the 111 crystal plane in the figure have a spacing of 0.246 nm). At the same time, there are small particles with obvious differences in brightness on their surface. These particles are Pt atoms that have migrated to the surface of molybdenum carbide.

[0021] This invention introduces a molecular sieve encapsulating a Group VIB metal carbide precursor into the slurry formulation, while simultaneously loading Pt onto a honeycomb ceramic coating. After reduction with a methane and hydrogen mixture, dual active sites of Pt and Group VIB metal carbides are obtained. These active sites are located both within and on the coating support, with the Group VIB metal carbides particularly encapsulated within the molecular sieve, making them less prone to aggregation and deactivation during the reaction. Pt is responsible for alkane dehydrogenation, while the Group VIB metal carbides activate carbon dioxide. The synthesized catalyst shows broad application prospects in selective oxidation and other fields. Attached Figure Description

[0022] Figure 1 This is a TEM image of Pt loaded on a molecular sieve in the catalyst of Example 1.

[0023] Figure 2 This is a TEM image of Pt supported on molybdenum carbide in the catalyst of Example 1.

[0024] Figure 3 Comparison of MoC and PtZn-loaded molybdenum carbide H2-TPR in Example 1. Detailed Implementation

[0025] The technical solutions and effects of the present invention will be further illustrated below with reference to the embodiments, but the invention is not limited to the following embodiments.

[0026] This invention utilizes TEM to observe the relationship between Pt and Mo2C in a sample. A JEOL JEM-F200 field emission transmission electron microscope was used. Operating conditions: accelerating voltage 200 kV. Before testing, a small amount of powdered sample was ultrasonically dispersed in anhydrous ethanol and then dropped onto a copper grid using a capillary tube. After drying, the sample was tested.

[0027] This invention utilizes inductively coupled plasma (ICP) analysis to detect the elemental content in samples. The elemental composition of the samples was analyzed using an AVIO 500 (Perkin Elmer) spectrometer. 0.1 g of the sample was ultrasonically dissolved in a mixture of 2 mL concentrated hydrofluoric acid and 2 mL concentrated hydrochloric acid, then poured into a 100 mL volumetric flask and diluted to the mark. An appropriate amount of the sample solution was then used for testing.

[0028] The hydrogen temperature-programmed reduction (H2-TPR) in this invention was performed using a ChemBETPulsar chemisorption analyzer from Quanta Instruments, USA, to determine the reducing properties of the sample. Approximately 100 mg of sample was weighed and placed in a U-tube. Before testing, the sample was purged with He at 400°C for 40 min; then cooled to room temperature, switched to 5% H2 / Ar, and heated to 800°C at a rate of 10°C / min. The signal of hydrogen consumption was detected using a TCD detector.

[0029] The physical adsorption experiments of this invention were conducted on an autosorb-Q2 (Quantachrome) physical adsorption instrument. Approximately 0.05 g of sample was weighed and vacuum-treated at 300 °C for 8 h, followed by analysis at 77 K. The specific surface area was calculated using the BET method, the micropore volume was calculated using the t-plot method, the total pore volume was measured at P / P0 = 0.95, and the pore size distribution was calculated using the BJH method. Example 1

[0030] Dissolve 3g of cerium nitrate in 170g of water; Molybdenum was encapsulated in SBA-15 molecular sieves. In this process, 10 wt% Mo was impregnated onto the SBA-15 molecular sieve using an equal-volume impregnation method. Then, 2.5 parts TPAOH, 38.00 parts deionized water, and 6.00 parts 30% silica sol were added, and the mixture was stirred at 35°C for 30 min. Next, 3 parts of the previously prepared 10% Mo / SBA-15 masterbatch were added, and the mixture was stirred for another 30 min before being placed in a crystallization vessel. Crystallization was carried out at 180°C and 30 r / min for 24 h. After crystallization, the sample was centrifuged, then placed in an 80°C oven for 12 h, and finally calcined in a muffle furnace at 540°C in air for 6 h. The resulting sample was named Mo@SBA-15. (3) The cerium nitrate solution obtained in step (1) is mixed with the Mo@SBA-15, alumina powder, urea and boehmite obtained in step (2) at a mass ratio of 170:30:60:10:10 and stirred vigorously at 10,000 rpm for 6 hours to obtain a mixed slurry. (4) Add 18g butanol to the mixed slurry obtained in step (3), and then stir for 1 hour; (5) Add 10g of tetraethyl orthosilicate to the mixed slurry obtained in step (4), and then stir for 1 hour; add 5g of concentrated nitric acid, and then stir for 1 hour; (6) Place 100 mL of honeycomb ceramic into 200 mL of 1 mol / L nitric acid solution and vibrate in an ultrasonic oscillator for 1 hour; then rinse repeatedly with 500 mL of water and dry in an oven at 110 °C for 12 hours. (7) Immerse the honeycomb ceramic in step (6) in the slurry in step (5) for 5 minutes, take it out and blow the slurry residue out of the channel. The supported honeycomb ceramic is dried in an oven at 110°C for 12 hours and then calcined in a muffle furnace at 500°C for 2 hours to obtain an integral catalyst support. (8) The monolithic catalyst support in step (7) is immersed in a zinc acetate solution containing 0.4 mol / L for 5 minutes, then washed with water, then dried and purged with air for 2 hours, then dried in an oven at 110°C for 12 hours, and then calcined in a muffle furnace at 450°C for 4 hours to obtain the monolithic catalyst. (9) Prepare 150 mL of platinum nitrate solution with a concentration of 0.02 mol / L; (10) The monolithic catalyst obtained in step (8) is impregnated in the solution in step (9), concentrated ammonia is added to adjust the pH to 9, and then it is allowed to stand for 2 hours; dry air is purged for 2 hours, then dried in an oven at 110°C for 12 hours, and then calcined in a muffle furnace at 450°C for 4 hours; it is then transferred to a tube furnace and a mixture of methane and hydrogen is used (methane accounts for 10% by volume, the remainder is hydrogen, and the space velocity is 6000 h⁻¹). -1 The catalyst Pt-Mo2C@SBA-15 was obtained by temperature-programmed reduction, which was performed by increasing the temperature from room temperature to 550 °C at a rate of 1 °C / min. Example 2

[0031] Dissolve 3g of lanthanum nitrate in 170g of water; Molybdenum was encapsulated in ZSM-5 molecular sieves. In this process, 10 wt% Mo was impregnated onto the ZSM-5 molecular sieve using an equal-volume impregnation method. Then, 2.5 parts TPAOH, 38.00 parts deionized water, and 6.00 parts 30% silica sol were added and stirred at 35°C for 30 min. Three parts of the previously prepared 10% Mo / ZSM-5 master powder were added and stirred for another 30 min before being placed in a crystallization vessel and crystallized at 180°C and 30 r / min for 24 h. After crystallization, the sample was removed and centrifuged, then placed in an 80°C oven for 12 h, and finally calcined in a muffle furnace at 540°C in air for 6 h. The resulting sample was named Mo@ZSM-5. (3)~(11) The process of preparing the slurry is the same as in Example 1; (12) Transfer the honeycomb ceramic catalyst from step (11) to a tubular furnace, using a mixture of methane and hydrogen (methane volume percentage 10%, the remainder being hydrogen, space velocity 6000 h⁻¹). -1 The catalyst Pt-Mo2C@ZSM-5 was obtained by temperature-programmed reduction, which was carried out by temperature-programmed reduction, with the temperature increased from room temperature to 550 °C at a rate of 1 °C / min. Example 3

[0032] Dissolve 3g of lanthanum nitrate in 170g of water; Tungsten was encapsulated in ZSM-5 molecular sieves. In this process, 10 wt% W was impregnated onto the ZSM-5 molecular sieve using an equal-volume impregnation method. Then, 2.5 parts TPAOH, 38.00 parts deionized water, and 6.00 parts 30% silica sol were added and stirred at 35°C for 30 min. Three parts of the previously prepared 10% W / ZSM-5 master powder were added and stirred for another 30 min before being placed in a crystallization vessel and crystallized at 180°C and 30 r / min for 24 h. After crystallization, the sample was removed and centrifuged, then placed in an 80°C oven for 12 h, and finally calcined in a muffle furnace at 540°C in air for 6 h. The resulting sample was named W@ZSM-5. (3)~(11) The process of preparing the slurry is the same as in Example 1; (12) Transfer the honeycomb ceramic catalyst from step (11) to a tubular furnace, using a mixture of methane and hydrogen (methane volume percentage 10%, the remainder being hydrogen, space velocity 6000 h⁻¹). -1 The temperature was increased by programmed reduction, which was carried out at a rate of 1℃ / min from room temperature to 550℃ to obtain the catalyst Pt-WC@ZSM-5.

[0033] Comparative Example 1 The rest is the same as in Example 1, except that molybdenum was not encapsulated in step (2); thus, the catalyst Pt-SBA-15 was obtained.

[0034] Comparative Example 2 The rest is the same as in Example 2, except that in step (12) the gas is pure nitrogen instead of a mixture of methane and hydrogen; thus, the catalyst Pt-Mo@ZSM-5 is obtained.

[0035] Comparative Example 3 The rest is the same as in Example 1, except that in step (2), molybdenum is not encapsulated inside the molecular sieve but is impregnated on the surface of the molecular sieve; thus, the catalyst Pt-Mo2C@SBA-15-2 is obtained. Example 4

[0036] The catalysts from Examples 1, 2, and 3, and Comparative Examples 1, 2, and 3 were applied to the catalytic oxidation of ethane in a fixed-bed reactor within a medium-sized reaction evaluation apparatus. The catalyst loading was 100 mL, the bed height was 10 cm, the initial propane concentration was 25% (v / v), the initial carbon dioxide concentration was 25% (v / v), the carrier gas was nitrogen, the reaction pressure was 0.1 MPa, the reaction temperature was 550 °C, and the space velocity was 50 h⁻¹. -1Propane and propylene were measured using an Agilent 7890A gas chromatograph, and the results are shown in Table 1.

[0037] Table 1 Catalyst Evaluation Results

[0038] Figure 1 The Pt particles on the molecular sieve are very small, averaging about 2-5 nm. These small particles can be identified as Pt particles based on the lattice spacing. Another characteristic is that Pt exhibits a single-atom distribution on molybdenum carbide, such as... Figure 2 As shown, the identification of single atoms needs to be observed from the changes in brightness. It can be seen that in the thinner areas on the right, the lattice brightness of MoC generally changes with the lattice itself, but there are some obvious bright spots, which are single-atom Pt.

[0039] at the same time, Figure 3 The results show that the amount of O on the surface of molybdenum carbide loaded with PtZn is significantly reduced, and therefore the reduction peak area of ​​its H2-TPR is significantly reduced, with the characteristic decrease exceeding 80%.

Claims

1. A dehydrogenation catalyst, characterized in that: It includes a honeycomb substrate, a modified silicon-aluminum coating on the surface of the honeycomb substrate, and an active component Pt, wherein the modified silicon-aluminum coating contains a mesoporous molecular sieve encapsulating a Group VIB metal carbide, the Group VIB metal being preferably Mo and / or W; Pt is atomically loaded on the surface of the Group VIB metal carbide and the surface of the molecular sieve.

2. The catalyst according to claim 1, characterized in that: The average particle size of Pt on the surface of the molecular sieve is 2-5 nm.

3. The catalyst according to claim 1, characterized in that: Pt exhibits a single-atom distribution on molybdenum carbide.

4. The catalyst according to claim 1, characterized in that: Based on the total weight of the catalyst, the honeycomb ceramic matrix accounts for 85%~92%, the coating accounts for 5%~12%, and Pt accounts for 0.1%~0.5% by element. Based on the weight of the coating, the coating contains 25%~65% alumina, 25%~65% mesoporous molecular sieve, 2%~5% silica, 0.5%~3% transition metal additives selected from one or more of cerium, lanthanum, zirconium, titanium, and vanadium, and 2%~6% group VIB metal carbides.

5. The catalyst according to claim 1, characterized in that: The mesoporous molecular sieve is SBA-15 and / or ZSM-5 molecular sieve.

6. The catalyst according to claim 1, characterized in that: The catalyst also includes one or more of zinc, tin, iron, manganese and gallium. Based on the total weight of the catalyst, zinc, tin, iron, manganese and gallium are 0.3wt% to 1.5wt% as oxides, and the sum of the contents of each component of the catalyst is 100%.

7. A method for preparing a dehydrogenation catalyst according to any one of claims 1 to 6, characterized in that... The process includes the following: (1) Encapsulating a Group VIB metal into the pores of a mesoporous molecular sieve to obtain a modified molecular sieve; (2) Immersing a pretreated honeycomb ceramic substrate in a coating slurry containing the modified molecular sieve of step (1) for a period of time, removing it, blowing the residual liquid out of the pores, drying and calcining it to obtain an integral catalyst support; (3) Immersing the integral catalyst support in a Pt-containing solution, then adding ammonia, letting it stand at the reaction temperature for a period of time, removing it, washing it with water, drying and calcining it, and then reducing it in a mixture of methane and hydrogen to obtain a dehydrogenation catalyst.

8. The method according to claim 7, characterized in that: The encapsulation method described in step (1) is the in-situ encapsulation method commonly used in the field, which involves adding a water-soluble salt of a Group VIB metal during the molecular sieve synthesis stage; the molecular sieve undergoes crystal growth, water washing, drying, and calcination processes to obtain a molecular sieve encapsulating a Group VIB metal, with the Group VIB metal accounting for 1% to 5% of the total weight of the modified molecular sieve as an oxide.

9. The method according to claim 7, characterized in that: The pretreatment process described in step (2) involves acid treatment of the honeycomb ceramic substrate, followed by washing with water and drying for later use.

10. The method according to claim 7, characterized in that: The coating slurry described in step (2) comprises, by total weight: 40%~60% solvent, 15%~25% activated alumina powder, 5%~10% modified molecular sieve from step (1), 3%~5% boehmite, 0%~5% transition metal salt, 3%~5% surfactant, 3%~5% silicon source, and 0.5%~2% nitric acid or hydrochloric acid; the solvent is water and / or an alcohol solvent; the surfactant is one or more of polyethylene glycol, urea, sodium dodecylbenzenesulfonate, and stearic acid; the silicon source is one or more of tetraethyl orthosilicate, methyl orthosilicate, polysiloxane, and ethoxysiloxane; the alcohol is one or more of ethanol, ethylene glycol, or butanol; and the activated alumina powder has a specific surface area of ​​100~1000 m². 2 / g; the pseudoboehmite has a specific surface area of ​​150~300m². 2 / g; The transition metal salts are all soluble salts, and the transition metals are selected from one or more of cerium, lanthanum, zirconium, titanium, and vanadium.

11. The method according to claim 7 or 10, characterized in that: The preparation method of the coating slurry includes the following steps: mixing activated alumina powder, boehmite, and transition metal salt solution, then adding surfactant and silicon source, adjusting the pH value to 3-4 or the viscosity to 10-100 mpa·s to obtain the slurry.

12. The method according to claim 7, characterized in that: The soaking time in step (2) is 2 to 10 minutes; the drying temperature is 100 to 150°C and the time is 12 to 24 hours; the calcination temperature is 400 to 550°C and the time is 2 to 4 hours.

13. The method according to claim 7, characterized in that: The soaking time in step (3) is 2 to 10 minutes; the concentration of the Pt-containing solution in step (3) is 0.01 to 0.03 mol / L; the drying temperature in step (3) is 100 to 150°C and the time is 12 to 24 hours; the calcination temperature is 400 to 550°C and the time is 2 to 4 hours.

14. The method according to claim 7, characterized in that: In step (3), the pH is adjusted to 8-9 by adding concentrated ammonia, the standing time is 1-4 hours, the temperature is raised to 60-70℃, and the temperature is kept constant for 1-2 hours.

15. The method according to claim 7, characterized in that: Between steps (2) and (3), one or more auxiliary metals of zinc, tin, iron, manganese, and gallium are loaded by impregnation.

16. The method according to claim 7, characterized in that: In step (3), the methane and hydrogen mixture has a methane volume percentage of 5% to 15% and a space velocity of 100 to 1000 h⁻¹. -1 .

17. The method according to claim 7, characterized in that: In step (3), the reduction process is a programmed temperature rise process, which raises the temperature from room temperature to 550~650 ℃ at a rate of 1℃ / min, and the reduction time is 0.5~1.5 hours.

18. The application of a dehydrogenation catalyst according to any one of claims 1 to 6 in a coupled reaction of carbon dioxide utilization and oxidative dehydrogenation.

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