Dehydrogenation methods for hydrogen storage materials

Abstract

This invention relates to the field of catalytic dehydrogenation technology for hydrogen storage materials, and discloses a method for dehydrogenating hydrogen storage materials. The method includes: contacting the hydrogen storage material sequentially with a first dehydrogenation catalyst and a second dehydrogenation catalyst under dehydrogenation reaction conditions; wherein the hydrogen storage material includes a hydrogenated N-containing heterocyclic hydrogen storage material and an impurity component; the first dehydrogenation catalyst includes a first support and a first active component supported on the first support, the first active component being Cu; the second dehydrogenation catalyst includes a second support and a second active component supported on the second support, the second active component being at least one of noble metals; the volume ratio of the first dehydrogenation catalyst to the second dehydrogenation catalyst is 1:(1-9). The dehydrogenation method provided by this invention can adapt to hydrogen storage materials containing impurity components, exhibiting high reactivity and good long-term operational stability.

Description

Technical Field

[0001] This invention relates to the field of catalytic dehydrogenation technology for hydrogen storage materials, and specifically to a method for dehydrogenating hydrogen storage materials. Background Technology

[0002] With the rapid development of global industrialization, human demand for traditional fossil fuels such as coal, oil, and natural gas is constantly increasing, leading to a continuous rise in carbon dioxide emissions. This new era demands a shift in the energy structure from traditional fossil fuels to clean energy. In this transition, traditional coal-fired power plants will gradually be relegated to auxiliary power sources, while the proportion of clean energy sources such as wind and solar power will gradually increase. However, wind and solar energy are intermittent and fluctuating, resulting in significant power instability in their power systems. Therefore, it is necessary to develop energy storage systems corresponding to this energy transformation. Hydrogen energy, as a clean secondary energy source, has advantages such as abundant supply, high calorific value, and high conversion rate, and is widely used in fuel cells, hydrogen refueling reactions, and other technological fields. Developing hydrogen-electric coupling technology, using hydrogen energy as an energy carrier, is a crucial step in ensuring stable energy output.

[0003] However, due to the unique physicochemical properties of hydrogen, its storage and transportation have always been major technological barriers hindering the large-scale development and utilization of hydrogen energy. Current hydrogen storage methods mainly include high-pressure gaseous hydrogen storage, cryogenic liquid hydrogen storage, solid-material hydrogen storage, and organic liquid hydrogen storage. Among these different hydrogen storage technologies, organic liquid hydrogen storage technology utilizes unsaturated organic liquids to perform reversible addition and dehydrogenation reactions to achieve hydrogen storage and release. It boasts advantages such as technical safety, high hydrogen storage density, and compatibility with existing oil and gas transportation and storage equipment, enabling large-scale, long-distance transportation of hydrogen at ambient temperature and pressure.

[0004] Currently, organic liquid hydrogen storage supports mainly include dibenzyltoluene, toluene, and nitrogen-containing heterocyclic compounds. Nitrogen-containing heterocyclic hydrogen storage supports, especially 12H-nitrogen-ethylcarbazole, have attracted considerable attention due to their lower dehydrogenation temperature and higher hydrogen storage capacity. Existing technologies using nitrogen-containing heterocyclic carbazoles and their derivatives primarily utilize coal tar extraction, which contains trace amounts of impurities such as S, Cl, and Br. These impurities have a certain toxic effect on the catalyst, affecting its lifespan and requiring frequent shutdowns for regeneration, thus impacting industrial operating efficiency. Noble metal catalysts, in particular, while exhibiting high activity and selectivity, are limited in their large-scale commercial application due to their high cost and susceptibility to deactivation. Therefore, in practical industrial operations, ensuring high dehydrogenation efficiency of the catalyst, reducing side reactions of the hydrogen storage support, minimizing catalyst usage costs, and extending catalyst lifespan are of paramount importance. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of poor catalyst impurity resistance and short single-pass operation cycle in the dehydrogenation process of N-containing heterocyclic hydrogen storage materials in the prior art, and to provide a dehydrogenation method for hydrogen storage materials. This method has the characteristics of high dehydrogenation efficiency, good product hydrogen purity, and long single-pass operation cycle.

[0006] To achieve the above objectives, the present invention provides a method for dehydrogenation of a hydrogen storage material, the method comprising:

[0007] Under dehydrogenation reaction conditions, the hydrogen storage material is sequentially contacted with the first dehydrogenation catalyst and the second dehydrogenation catalyst;

[0008] The hydrogen storage material includes hydrogenated N-containing heterocyclic hydrogen storage materials and impurity components;

[0009] The first dehydrogenation catalyst includes a first support and a first active component supported on the first support, wherein the first active component is Cu;

[0010] The second dehydrogenation catalyst includes a second support and a second active component supported on the second support, wherein the second active component is at least one of noble metals;

[0011] The volume ratio of the first dehydrogenation catalyst to the second dehydrogenation catalyst is 1:(1-9).

[0012] Preferably, the impurity components are selected from at least one of S, Cl and Br; based on the total amount of the hydrogen storage material, the content of S is 3-7 ppm, the content of Cl is 1-4 ppm, and the content of Br is 2-5 ppm.

[0013] The nitrogen-containing heterocyclic carbazoles and their derivatives used in the existing technology are mainly extracted from coal tar. The raw materials contain trace amounts of impurities such as S, Cl, and Br. These impurities have a certain toxic effect on the catalyst, affecting its service life and requiring frequent shutdowns for regeneration, thus affecting the efficiency of industrial operation.

[0014] This invention grades a Cu catalyst and a noble metal catalyst at a specific loading ratio of 1:1-9, allowing the hydrogen storage material containing impurities to sequentially contact the first and second dehydrogenation catalysts for a dehydrogenation reaction. The graded catalysts exhibit more stable activity and higher product hydrogen purity during long-term lifetime testing. This is likely because the presence of copper, the active component in the Cu catalyst, can adsorb impurities such as S, Cl, and Br in the hydrogen storage material, reducing their poisoning effect on the noble metal catalyst. The dehydrogenation method provided by this invention is adaptable to hydrogen storage materials containing impurities. On the one hand, it improves reaction stability and avoids frequent catalyst regeneration; on the other hand, it expands the selection of hydrogen storage feedstock sources, saves on feedstock purification steps, and improves the overall economic efficiency of the process. Detailed Implementation

[0015] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] This invention provides a method for dehydrogenation of hydrogen storage materials, the method comprising:

[0017] Under dehydrogenation reaction conditions, the hydrogen storage material is sequentially contacted with the first dehydrogenation catalyst and the second dehydrogenation catalyst;

[0018] The hydrogen storage material includes hydrogenated N-containing heterocyclic hydrogen storage materials and impurity components;

[0019] The first dehydrogenation catalyst includes a first support and a first active component supported on the first support, wherein the first active component is Cu;

[0020] The second dehydrogenation catalyst includes a second support and a second active component supported on the second support, wherein the second active component is at least one of noble metals;

[0021] The volume ratio of the first dehydrogenation catalyst to the second dehydrogenation catalyst is 1:(1-9).

[0022] When performing dehydrogenation reactions alone, Cu catalysts exhibit low catalytic activity, while noble metal catalysts exhibit high catalytic activity. The inventors of this invention have surprisingly discovered in their research that by graded Cu catalysts and noble metal catalysts in a specific ratio and then performing dehydrogenation reactions on feedstocks containing impurities, the dehydrogenation activity can be maintained at a comparable level while exhibiting more stable activity and product hydrogen purity during long-term life tests.

[0023] In this invention, the selection range of sources for the hydrogen storage material is relatively wide. Hydrogen storage materials containing impurity components exhibit high dehydrogenation activity and stability, eliminating the need for raw material purification steps and improving the overall economic efficiency of the process. For example, the N-containing heterocyclic carbazole and its derivatives can be extracted from coal tar. Preferably, the impurity components are selected from at least one of S, Cl, and Br.

[0024] The present invention offers a wide range of options for the content of the impurity components. According to some preferred embodiments of the present invention, based on the total amount of the hydrogen storage material, the content of sulfur (S) is 3-7 ppm, the content of chloride (Cl) is 1-4 ppm, and the content of br (Br) is 2-5 ppm. The dehydrogenation method provided by the present invention exhibits superior dehydrogenation activity and operational stability compared to existing technologies for hydrogen storage materials with the aforementioned specific impurity compositions.

[0025] This invention does not specifically limit the type of N-containing heterocyclic hydrogen storage material; any known substance capable of hydrogenation and dehydrogenation can be used in this invention. Preferably, the N-containing heterocyclic hydrogen storage material is selected from substituted or unsubstituted carbazole compounds, preferably at least one of carbazole, N-ethylcarbazole, N-methylcarbazole, N-propylcarbazole, and N-butylcarbazole. The hydrogenated N-containing heterocyclic hydrogen storage material refers to the hydrogenation product of the N-containing heterocyclic hydrogen storage material. This invention does not have specific requirements on the degree of hydrogenation of the hydrogenation product. For example, depending on the degree of hydrogenation, the hydrogenation product of N-ethylcarbazole may include one or more of 4H-N-ethylcarbazole, 6H-N-ethylcarbazole, 8H-N-ethylcarbazole, and 12H-N-ethylcarbazole (i.e., perhydro-N-ethylcarbazole), which are well known to those skilled in the art.

[0026] In this invention, the volume ratio of the first dehydrogenation catalyst to the second dehydrogenation catalyst is 1:(1-9), preferably 1:(1.5-4), and can be, for example, specific but not limiting volume ratios such as 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, etc. Using the above-mentioned preferred volume ratio is beneficial for further improving dehydrogenation efficiency and stability.

[0027] According to some preferred embodiments of the present invention, the dehydrogenation reaction conditions include: a temperature of 160-250°C, preferably 170-230°C; a reaction pressure of 0-0.2 MPa, preferably 0.09-0.11 MPa; and a volume hourly space velocity (VHSV) of 0.2-2 h⁻¹ for the hydrogen storage material. -1 Preferably 0.4-1h -1 .

[0028] In this invention, the volume hourly space velocity of the hydrogen storage material is defined based on the total volume of the first dehydrogenation catalyst and the second dehydrogenation catalyst.

[0029] This invention does not impose any particular requirements on the contact method between the hydrogen storage material and the first and second dehydrogenation catalysts. The first and second dehydrogenation catalysts can be loaded into two reactors connected in series, or they can be loaded into two beds within the same reactor, as long as the hydrogen storage material first contacts the first dehydrogenation catalyst and then contacts the second dehydrogenation catalyst. Those skilled in the art can choose the appropriate method based on the specific circumstances. The conditions for the first and second contacts can be the same or different, both satisfying the aforementioned dehydrogenation reaction conditions.

[0030] In a further preferred embodiment, the conditions for the first contact and the second contact are the same.

[0031] The present invention has a wide range of choices for the first and second carriers. The types of the first and second carriers can be the same or different. Those skilled in the art can make the selection according to actual needs. Preferably, the first and second carriers are each independently selected from at least one of Al2O3, TiO2, SiO2 and MgO, and Al2O3 is preferred.

[0032] According to some preferred embodiments of the present invention, based on the total amount of the first dehydrogenation catalyst, the content of the first support is 70-95 wt%, preferably 75-92 wt%, and the content of the first active component by element is 5-30 wt%, preferably 8-25 wt%.

[0033] According to some preferred embodiments of the present invention, the specific surface area of ​​the first dehydrogenation catalyst is 150-250 m². 2 / g, preferably 170-230m 2 / g, with a bulk density of 0.4-0.7g / mL, preferably 0.45-0.65g / mL.

[0034] According to the present invention, the second active component is selected from at least one of noble metals. Any noble metal element known in the art that can be used for dehydrogenation of N-containing heterocyclic hydrogen storage materials can be applied to the present invention. Preferably, the second active component is Pd and / or Pt, and more preferably Pd.

[0035] Preferably, based on the total amount of the second dehydrogenation catalyst, the content of the second support is 99.2-99.8 wt%, more preferably 99.4-99.7 wt%; and the content of the second active component, calculated by element, is 0.2-0.8 wt%, more preferably 0.3-0.6 wt%.

[0036] According to some preferred embodiments of the present invention, the specific surface area of ​​the second dehydrogenation catalyst is 170-280 m². 2 / g, preferably 190-260m 2 / g; the bulk density is 0.38-0.6g / mL, preferably 0.42-0.55g / mL.

[0037] The present invention does not have any particular limitation on the source of the first dehydrogenation catalyst and the second dehydrogenation catalyst. They can be obtained from commercial purchases or prepared by any method known in the art, such as impregnation, which is well known to those skilled in the art.

[0038] By using the first dehydrogenation catalyst with the above-mentioned preferred composition and structure to grade the second dehydrogenation catalyst, the decomposition of hydrogen storage materials can be further reduced while ensuring activity stability.

[0039] According to the present invention, preferably, the method further includes: subjecting the first dehydrogenation catalyst to a first reduction treatment before the contact; and / or subjecting the second dehydrogenation catalyst to a second reduction treatment.

[0040] In this invention, the terms "first" and "second" in the first and second reduction processes are used only to distinguish different reduction processes and conditions, and do not indicate the actual processing order.

[0041] The present invention does not particularly limit the specific conditions of the first and second reduction treatments, and can be carried out in a manner conventional in the art, as long as at least a portion of the active components in the first and second dehydrogenation catalysts can be reduced to elemental form. Those skilled in the art can select specific reduction conditions according to actual needs. The first and second reduction treatments can be carried out inside or outside the reactor. Preferably, the first and second reduction treatments are carried out outside the reactor, and then the reduced catalyst is loaded into the reactor.

[0042] Preferably, the first reduction process and the second reduction process are each carried out independently in the presence of hydrogen.

[0043] According to some preferred embodiments of the present invention, the conditions for the first reduction treatment include: a reduction temperature of 200-350°C, preferably 200-260°C; and a reduction time of 4-12 hours, preferably 5-10 hours.

[0044] According to some preferred embodiments of the present invention, the conditions for the second reduction treatment include: a reduction temperature of 230-400°C, preferably 300-350°C; and a reduction time of 2-10 h, preferably 3-6 h.

[0045] According to some preferred embodiments of the present invention, when the first and second reduction treatments are carried out outside the reactor, the method further includes: purging the first and second dehydrogenation catalysts with a hydrogen-containing atmosphere before the contact. Hydrogen purging is beneficial for further improving the reaction activity of the catalysts.

[0046] Preferably, the hydrogen-containing atmosphere can be hydrogen or a mixture of hydrogen and an inert gas, wherein the inert gas can be, for example, nitrogen and / or argon. Preferably, the hydrogen content in the hydrogen-containing atmosphere is 75-100 vol%.

[0047] Preferably, the purging conditions include: a temperature of 180-230℃ and a purging time of 3-10 hours.

[0048] The present invention will be described in detail below through embodiments.

[0049] Unless otherwise specified, all raw materials used in the following embodiments are commercially available.

[0050] The dehydrogenation catalysts used in the following examples were prepared using a conventional impregnation method.

[0051] The catalyst Cu / Al2O3 contains 20wt% Cu and the remainder is Al2O3, with a specific surface area of ​​185m². 2 / g, with a bulk density of 0.54g / mL.

[0052] The catalyst Pd / Al2O3 contains 0.3 wt% Pd and the remainder is Al2O3, with a specific surface area of ​​212 m². 2 / g, with a bulk density of 0.47g / mL.

[0053] Before use, the catalyst is reduced in the presence of hydrogen.

[0054] The catalyst Cu / Al2O3 was reduced at 240℃ for 8 hours, the catalyst Pd / Al2O3 was reduced at 350℃ for 4 hours, and the catalyst Ni / Al2O3 was reduced at 450℃ for 4 hours.

[0055] The hydrogen storage feedstock used in the following examples and comparative examples is perhydro-N-ethylcarbazole containing impurity components. The content of impurity components is shown in Table 1 based on the total weight of the hydrogen storage feedstock.

[0056] Table 1

[0057]

[0058]

[0059] Example 1

[0060] The dehydrogenation reaction was carried out in a fixed-bed feed dehydrogenation reactor (2m high), with a total loading volume of 10mL for the first and second dehydrogenation catalysts.

[0061] The upper bed is loaded with a reduced first dehydrogenation catalyst, Cu / Al₂O₃, with a loading volume of 1 mL. The lower bed is loaded with a reduced second dehydrogenation catalyst, Pd / Al₂O₃, with a loading volume of 9 mL. The catalysts are packed using a dense-phase packing technique, and the catalyst particle size is 20-40 mesh. Hydrogen gas is introduced into the fixed bed and purged at 220℃ for 5 hours. When the temperature drops to 210℃ and the reactor pressure is 0.11 MPa, the feed pump is started, and the feed space velocity of the hydrogen storage feedstock is controlled at 0.5 h⁻¹. -1 The product composition after 30 h and 500 h of reaction was tested by gas chromatography, and the dehydrogenation rate was calculated. The results are shown in Table 2.

[0062] The formula for calculating the dehydrogenation rate is as follows:

[0063]

[0064] Wherein, NEC refers to N-ethylcarbazole, n1 is the molar amount of 12H-N-ethylcarbazole, n2 is the molar amount of 8H-N-ethylcarbazole, n3 is the molar amount of 4H-N-ethylcarbazole, and n4 is the molar amount of N-ethylcarbazole.

[0065] Example 2

[0066] The method is the same as in Example 1, except that the loading volume of the Cu / Al2O3 catalyst is 3 mL and the loading volume of the Pd / Al2O3 catalyst is 7 mL.

[0067] The reaction conditions are shown in Table 2. The dehydrogenation rate was tested by gas chromatography at 30 h and 500 h, and the results are shown in Table 3.

[0068] Example 3

[0069] The method is the same as in Example 1, except that the loading volume of Cu / Al2O3 catalyst is 5 mL and the loading volume of Pd / Al2O3 catalyst is 5 mL.

[0070] The reaction conditions are shown in Table 2. The dehydrogenation rate was tested by gas chromatography at 30 h and 500 h, and the results are shown in Table 3.

[0071] Example 4

[0072] Following the method of Example 1, the type and amount of active metal loaded were the same, except that the support for both dehydrogenation catalysts was replaced with SiO2. The Cu / SiO2 specific surface area was 195 m². 2 / g, bulk density is 0.55g / mL; Pd / SiO2 specific surface area is 230m². 2 / g, with a bulk density of 0.48g / mL. All the above catalysts were reduced under the same reduction conditions before use.

[0073] The reaction conditions are shown in Table 2. The dehydrogenation rate was tested by gas chromatography at 30 h and 500 h, and the results are shown in Table 3.

[0074] Example 5

[0075] The method is the same as in Example 1, except that hydrogen purging is not performed.

[0076] The reaction conditions are shown in Table 2. The dehydrogenation rate was tested by gas chromatography at 30 h and 500 h, and the results are shown in Table 3.

[0077] Example 6

[0078] The method is the same as in Example 1, except that the reaction conditions are shown in Table 2.

[0079] The dehydrogenation rate was tested by gas chromatography at 30 h and 500 h, respectively, and the results are shown in Table 3.

[0080] Comparative Example 1

[0081] The reduced Cu-based non-precious metal dehydrogenation catalyst Cu / Al₂O₃ was crushed to 20-40 mesh, and then 10 mL was packed into the isothermal zone of a fixed bed. The temperature was raised to 210℃, the reaction pressure was 0.11 MPa, and the feed pump was started, controlling the feed space velocity to 0.5 h⁻¹. -1 The dehydrogenation rate was tested by gas chromatography at 30 h and 500 h, respectively, and the results are shown in Table 3.

[0082] Comparative Example 2

[0083] The method is the same as in Comparative Example 1, except that the Cu / Al2O3 catalyst is replaced with a reduced Pd / Al2O3 catalyst.

[0084] The reaction conditions are shown in Table 2. The dehydrogenation rate was tested by gas chromatography at 30 h and 500 h, and the results are shown in Table 3.

[0085] Comparative Example 3

[0086] The method is the same as in Example 2, except that the catalyst Cu / Al2O3 and the catalyst Pd / Al2O3 are physically and uniformly mixed and then packed into the catalyst bed.

[0087] The reaction conditions are shown in Table 2. The dehydrogenation rate was tested by gas chromatography at 30 h and 500 h, and the results are shown in Table 3.

[0088] Comparative Example 4

[0089] The method is the same as in Example 2, except that the upper bed is filled with Pd / Al2O3 catalyst and the lower bed is filled with Cu / Al2O3 catalyst.

[0090] The reaction conditions are shown in Table 2. The dehydrogenation rate was tested by gas chromatography at 30 h and 500 h, and the results are shown in Table 3.

[0091] Comparative Example 5

[0092] The method is the same as in Example 3, except that the upper bed is filled with Pd / Al2O3 catalyst and the lower bed is filled with Cu / Al2O3 catalyst.

[0093] The reaction conditions are shown in Table 2. The dehydrogenation rate was tested by gas chromatography at 30 h and 500 h, and the results are shown in Table 3.

[0094] Comparative Example 6

[0095] The method is the same as in Example 5, except that the catalyst Cu / Al2O3 is replaced with an equal volume of Ni / Al2O3 (Ni content is 20wt%, specific surface area is 171m²). 2 / g, bulk density is 0.54g / mL).

[0096] The reaction conditions are shown in Table 2. The dehydrogenation rate was tested by gas chromatography at 30 h and 500 h, and the results are shown in Table 3.

[0097] Table 2

[0098]

[0099] Table 3

[0100]

[0101]

[0102] As can be seen from the results in Table 3, in the embodiments of the present invention, Cu catalyst and noble metal catalyst are graded according to a specific loading ratio, so that the hydrogen storage material containing impurity components is sequentially contacted with the first dehydrogenation catalyst and the second dehydrogenation catalyst to carry out the dehydrogenation reaction. The graded catalyst exhibits more stable activity in long-term life test. At the same time, the amount of noble metal used is reduced by catalyst gradation, which greatly reduces the cost of using the dehydrogenation catalyst.

[0103] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for dehydrogenating a hydrogen storage material, characterized in that, The method includes: Under dehydrogenation reaction conditions, the hydrogen storage material is sequentially contacted with the first dehydrogenation catalyst and the second dehydrogenation catalyst; The hydrogen storage material includes a hydrogenated N-containing heterocyclic hydrogen storage material and an impurity component; the N-containing heterocyclic hydrogen storage material is selected from carbazole compounds; the impurity component is selected from at least one of S, Cl, and Br. The first dehydrogenation catalyst includes a first support and a first active component supported on the first support, wherein the first active component is Cu; The second dehydrogenation catalyst includes a second support and a second active component supported on the second support, wherein the second active component is at least one of noble metals; The volume ratio of the first dehydrogenation catalyst to the second dehydrogenation catalyst is 1:(1-9).

2. The method according to claim 1, wherein, Based on the total amount of the hydrogen storage material, the content of sulfur is 3-7 ppm, the content of chlorine is 1-4 ppm, and the content of br is 2-5 ppm.

3. The method according to claim 1 or 2, wherein, The N-containing heterocyclic hydrogen storage material is at least one of carbazole, N-ethylcarbazole, N-methylcarbazole, N-propylcarbazole, and N-butylcarbazole.

4. The method according to claim 1, wherein, The volume ratio of the first dehydrogenation catalyst to the second dehydrogenation catalyst is 1:(1.5-4).

5. The method according to claim 1, wherein, The dehydrogenation reaction conditions include: a temperature of 160-250℃; a reaction pressure of 0-0.2 MPa; and a volume hourly space velocity (VHSV) of 0.2-2 h⁻¹ for the hydrogen storage material. -1 .

6. The method according to claim 5, wherein, The dehydrogenation reaction conditions include: a temperature of 170-230℃; a reaction pressure of 0.09-0.11 MPa; and a volume hourly space velocity (VHSV) of 0.4-1 h⁻¹ for the hydrogen storage material. -1 .

7. The method according to claim 1, wherein, The method further includes: subjecting the first dehydrogenation catalyst to a first reduction treatment prior to the contact; and / or, The second dehydrogenation catalyst is subjected to a second reduction treatment.

8. The method according to claim 7, wherein, The conditions for the first reduction treatment include: a reduction temperature of 180-300℃ and a reduction time of 4-12h.

9. The method according to claim 8, wherein, The conditions for the first reduction treatment include: a reduction temperature of 200-260℃ and a reduction time of 5-10h.

10. The method according to claim 7, wherein, The conditions for the second reduction treatment include: a reduction temperature of 300-450℃ and a reduction time of 2-10h.

11. The method according to claim 10, wherein, The conditions for the second reduction treatment include: a reduction temperature of 300-350℃ and a reduction time of 3-6h.

12. The method according to claim 1, wherein, The method further includes purging the first dehydrogenation catalyst and the second dehydrogenation catalyst with a hydrogen-containing atmosphere before the contact.

13. The method according to claim 12, wherein, The purging conditions include: a temperature of 180-230℃ and a purging time of 3-10 hours.

14. The method according to claim 1, wherein, The first and second supports are each independently selected from at least one of Al2O3, TiO2, SiO2 and MgO.

15. The method according to claim 14, wherein, The first and second carriers are Al2O3.

16. The method according to claim 1, wherein, Based on the total amount of the first dehydrogenation catalyst, the content of the first support is 70-95 wt%, and the content of the first active component by element is 5-30 wt%.

17. The method according to claim 1, wherein, The specific surface area of ​​the first dehydrogenation catalyst is 150-250 m². 2 / g, with a bulk density of 0.4-0.7g / mL.

18. The method according to claim 1, wherein, The second active component is Pd and / or Pt.

19. The method according to claim 18, wherein, The second active component is Pd.

20. The method according to claim 1, wherein, Based on the total amount of the first dehydrogenation catalyst, the content of the second support is 99.2-99.8 wt%, and the content of the second active component by element is 0.2-0.8 wt%.

21. The method according to claim 1, wherein, The specific surface area of ​​the second dehydrogenation catalyst is 170-280 m². 2 / g, with a bulk density of 0.38-0.6g / mL.

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