Cobalt-based catalyst and preparation method and application thereof

Abstract

The invention relates to a cobalt-based catalyst as well as a preparation method and application thereof. The catalyst comprises a carrier, an active component and an auxiliary agent, wherein the active component and the auxiliary agent are loaded on the carrier; the element in the active component comprises metal Co; the element in the auxiliary agent comprises metal Sn; the carrier is a dealumination molecular sieve. The active component Co and the assistant Sn are introduced into the framework structure of the dealumination molecular sieve, and the active component Co is uniformly distributed on the molecular sieve under the action of the assistant Sn, so that more active sites can be exposed, and the catalytic activity of the catalyst is improved; the propane conversion rate, the propylene selectivity and the propylene yield when the cobalt-based catalyst is used for propane dehydrogenation are obviously improved; the catalyst with the auxiliary Sn introduced still has high catalytic activity after long-time operation, and the high-temperature stability of the cobalt-based catalyst is improved.

Description

Technical Field

[0001] This invention belongs to the field of catalysts, specifically relating to a cobalt-based catalyst, its preparation method, and its application. Background Technology

[0002] Propylene is a crucial raw material for the production of downstream products such as polypropylene, polyacrylonitrile, and propylene oxide, and is widely used in organic chemicals, pharmaceuticals, plastics, and rubber. With the increasing production of downstream propylene products, the demand for propylene is robust. Due to the unstable supply of petroleum resources, technologies for producing propylene, such as olefin disproportionation, methanol-to-olefins (MTO), and heavy hydrocarbon cracking, have seen significant development. Compared to olefin disproportionation and cracking technologies, the direct dehydrogenation of propane to propylene offers advantages such as high selectivity and high yield, making it an important method for increasing propylene production capacity.

[0003] The direct dehydrogenation of propane refers to the process of directly dehydrogenating propane to produce propylene under high temperature and the action of a catalyst. However, in current industrial production, this reaction process mostly uses metal-based catalysts, such as the widely used Pt-based catalysts and Gr-based catalysts. However, due to the high cost of Pt-based catalysts and the environmental pollution caused by Gr-based catalysts, the application of these metal-based catalysts is relatively limited.

[0004] In recent years, cobalt-based catalysts have shown great industrial potential due to their high propane dehydrogenation activity. CN113318774A discloses a method for preparing propylene from propane using a modified Co-based catalyst. This catalyst uses Co as the active component and one or more of Mg, Zr, Nd, W, La, Ce, and Zn as promoters. By controlling the structural relationships such as the species composition, particle size, and dispersion degree on the catalyst surface, the catalytic performance can be adjusted, achieving an initial propane conversion of 17.1% and a propylene selectivity of 96.1%. However, this catalyst still suffers from problems such as low propane conversion and poor stability. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of low propane conversion and poor stability of existing cobalt-based catalysts used for propane dehydrogenation.

[0006] To achieve the above objectives, a first aspect of the present invention provides a cobalt-based catalyst, the catalyst comprising a support and an active component and an auxiliary agent supported on the support; the active component comprises metallic Co; the auxiliary agent comprises metallic Sn; and the support is a dealuminated molecular sieve.

[0007] Optionally, the content of the element in the active component is 1 to 10 wt% based on the weight of the carrier; and / or the content of the element in the adjuvant is 0.3 to 1 wt% based on the weight of the carrier.

[0008] Optionally, the dealuminized molecular sieve is an MFI type molecular sieve, preferably a ZSM-5 molecular sieve; the silica-to-alumina ratio of the ZSM-5 molecular sieve before dealuminization is 38~600, preferably 100~500; the specific surface area of ​​the dealuminized molecular sieve is 320~400 m². 2 / g; pore volume is 0.15~0.45 cm³ 3 / g.

[0009] Optionally, the cobalt-based catalyst has a particle size of 14-40 mesh.

[0010] The second aspect of the present invention provides a method for preparing the aforementioned catalyst, the method comprising the following steps: (1) mixing a dealuminated molecular sieve and a solvent to form a slurry, thereby obtaining a carrier slurry; (2) mixing the carrier slurry with an active component precursor and an auxiliary agent precursor, and drying and calcining the resulting mixture to obtain a cobalt-based catalyst.

[0011] Optionally, the mass ratio of the dealuminized molecular sieve, the active component precursor, and the auxiliary agent precursor is 1:0.025~0.3:0~0.04; the active component precursor is selected from at least one of cobalt nitrate, cobalt sulfate, and cobalt chloride; and the auxiliary agent precursor is selected from at least one of tin nitrate, tin sulfate, and tin chloride.

[0012] Optionally, in step (2), the drying temperature is 80~100 ℃ and the time is 8~12 h; the calcination temperature is 600~800 ℃ and the time is 4~8 hours.

[0013] Optionally, the dealuminolite molecular sieve is prepared by a method comprising the following steps: mixing the molecular sieve and an acid solution for acid treatment, allowing the mixture to stand and separate into layers, filtering, and then drying and calcining the filtered solid in sequence; the acid treatment conditions include: a temperature of 80-100 °C; a time of 12-24 h; the amount of acid solution used relative to 10 g of the molecular sieve is 50-400 mL; the concentration of the acid solution is 1-20 mol / L; the acid solution is selected from one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, and citric acid; the molecular sieve is an MFI type molecular sieve, preferably a ZSM-5 molecular sieve; the original silica-alumina ratio of the ZSM-5 molecular sieve is 38-600, preferably 100-500.

[0014] A third aspect of the present invention provides a method for propane dehydrogenation to propylene, the method comprising: contacting a propane-containing feed gas with the aforementioned cobalt-based catalyst in a reactor under a protective gas atmosphere to carry out a propane dehydrogenation to propylene reaction.

[0015] Optionally, the concentration of propane in the feed gas is 5-30% by volume; the reaction conditions for propane dehydrogenation to propylene include: a reaction temperature of 500-600 °C, a reaction pressure of 0-1 MPa, and a propane mass hourly space velocity of 0.5-8 h⁻¹. -1 .

[0016] Through the above technical solution, the present invention introduces the active component Co and the promoter Sn into the dealubilized molecular sieve framework structure. Under the action of the promoter Sn, the active component Co is uniformly distributed on the molecular sieve, which can expose more active sites, increase the catalytic activity of the catalyst, and significantly improve the propane conversion, propylene selectivity and propylene yield of the cobalt-based catalyst when used for propane dehydrogenation. The introduction of the promoter Sn enables the catalyst to still have high catalytic activity after long-term operation and improves the high-temperature stability of the cobalt-based catalyst.

[0017] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 The XRD patterns are of the cobalt-based catalysts obtained in Examples 1-3; Figure 2 SEM images of the cobalt-based catalysts obtained in Example 2 and Comparative Example 1; Figure 3 The image shows the EDS sequence of the cobalt-based catalyst obtained in Example 2 after 9 hours of propane dehydrogenation to propylene reaction. Detailed Implementation

[0019] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0020] To achieve the above objectives, a first aspect of the present invention provides a cobalt-based catalyst, the catalyst comprising a support and an active component and an auxiliary agent supported on the support; the active component comprises metal Co; the auxiliary agent comprises metal Sn; and the support is a dealuminated molecular sieve.

[0021] This invention introduces the active component Co and the promoter Sn into the framework structure of a dealuminized molecular sieve. Under the action of the promoter Sn, the active component Co is uniformly distributed on the molecular sieve, which can expose more active sites, increase the catalytic activity of the catalyst, significantly improve the propane conversion and propylene selectivity of the cobalt-based catalyst in propane dehydrogenation, and can also significantly improve the propylene yield. At the same time, the introduction of the promoter Sn enables the catalyst to maintain high catalytic activity after long-term operation, and improves the high-temperature stability of the cobalt-based catalyst.

[0022] In some embodiments of the present invention, the content of elements in the active component, calculated as elements, is 1 to 10 wt% based on the weight of the carrier; for example, the content of elements in the active component, calculated as elements, can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or any value within the aforementioned range, based on the weight of the carrier.

[0023] The present invention incorporates a small amount of additive Sn into the dealubilized molecular sieve, which can make the active components uniformly distributed on the dealubilized molecular sieve and improve the propylene selectivity and high-temperature stability of the catalyst.

[0024] In some embodiments of the present invention, the content of the element in the additive is 0.3 to 1 wt%, based on the weight of the carrier, and calculated by element. For example, it can be 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, or any value within the aforementioned range.

[0025] The dealuminolite molecular sieve is an MFI type molecular sieve, preferably a ZSM-5 molecular sieve. The silica-alumina ratio of the ZSM-5 molecular sieve can be changed within a wide range, and its three-dimensional straight channels can limit the formation of macromolecules. Furthermore, the active components are fully dispersed on the molecular sieve, which is beneficial for the full contact between propane and the active components, and has a significant impact on the propylene selectivity of the catalyst.

[0026] In some embodiments of the present invention, the silicon-to-aluminum ratio of the ZSM-5 molecular sieve before dealumination is 38-600. Preferably, in order to improve the conversion rate of propane in the propane dehydrogenation reaction catalyzed by the catalyst and to improve the thermal stability of the catalyst, so that the dealumination molecular sieve has a suitable acid content, the silicon-to-aluminum ratio of the ZSM-5 molecular sieve before dealumination is 100-500.

[0027] The cobalt-based catalyst has a particle size of 14-40 mesh. Preferably, the dealuminized molecular sieve has a specific surface area of ​​320-400 m². 2 / g; pore volume is 0.15~0.45 cm³ 3 / g. Dealuinated molecular sieves have a large specific surface area and abundant pore structure, and have sites suitable for loading active components and auxiliary components, which is beneficial to improving the catalytic activity of the support.

[0028] A second aspect of the present invention provides a method for preparing the aforementioned catalyst, the method comprising the following steps: (1) Mix the dealuminated molecular sieve and solvent to prepare a slurry, thereby obtaining a carrier slurry; (2) The active component precursor and the auxiliary precursor of the carrier slurry are mixed, and the resulting mixture is dried and calcined to obtain a cobalt-based catalyst.

[0029] In step (1), the solvent can be deionized water to mix the dealuminized molecular sieve with deionized water and slurry; specifically, the mass ratio of the dealuminized molecular sieve to the solvent is 1:15~32.

[0030] In order to obtain an appropriate content of active component and auxiliaries, the mass ratio of the dealuminized molecular sieve, the active component precursor and the auxiliaries precursor is 1:0.025~0.3:0~0.04; the active component precursor is selected from at least one of cobalt nitrate, cobalt sulfate and cobalt chloride; the auxiliaries precursor is selected from at least one of tin nitrate, tin sulfate and tin chloride.

[0031] In step (2), the drying temperature is 80~100 ℃ and the time is 8~12 h; the roasting temperature is 600~800 ℃ and the time is 4~8 hours.

[0032] Acid treatment of molecular sieves can adjust their specific surface area and pore structure. The dealuminized molecular sieve is prepared by a method including the following steps: mixing the molecular sieve with an acid solution for acid treatment, allowing it to stand and separate into layers, filtering, and then drying and calcining the filtered solid. The acid treatment conditions also affect the support, thereby influencing the catalytic performance of the catalyst. The acid treatment conditions include: a temperature of 80–100 °C and a time of 12–24 h.

[0033] Specifically, relative to 10 g of the molecular sieve, the amount of acid solution used is 50-400 mL; the concentration of the acid solution can be 1-20 mol / L.

[0034] Preferably, the acid solution is selected from one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, and citric acid.

[0035] The molecular sieve is an MFI type molecular sieve, preferably a ZSM-5 molecular sieve; the original silica-alumina ratio of the ZSM-5 molecular sieve is 38~600, preferably 100~500, in order to improve the catalytic activity of the catalyst, reduce side reactions such as propane cracking, and improve propylene selectivity.

[0036] A third aspect of the present invention provides a method for propane dehydrogenation to propylene, the method comprising: contacting a propane-containing feed gas with the aforementioned cobalt-based catalyst in a reactor under a protective gas atmosphere to carry out a propane dehydrogenation to propylene reaction.

[0037] The concentration of propane in the feed gas is 5-30% by volume; the cobalt-based catalyst provided by the present invention can achieve high propane conversion and propylene selectivity even at high feed concentrations.

[0038] The reaction conditions for propane dehydrogenation to propylene include: a reaction temperature of 500–600 °C, a reaction pressure of 0–1 MPa, and a propane mass hourly space velocity of 0.5–8 h⁻¹. -1 .

[0039] The present invention will be further described in detail below through examples, but the present invention is not limited thereto.

[0040] All raw materials used in the examples were commercially available. Specifically, the ZSM-5 molecular sieve, with a silica-to-alumina ratio of 300, was purchased from Tianjin Shenneng Technology Co., Ltd.

[0041] Example 1 This embodiment illustrates a method for preparing the cobalt-based catalyst of the present invention, which includes the following steps: (1) Preparation of dealubilized molecular sieve support: Weigh 10 g of ZSM-5 molecular sieve (silicon-to-aluminum ratio of 300) and dissolve it in 180 mL of nitric acid (concentration of 12 mol / L). Stir continuously for 12 h at 100 °C. Let the obtained mixed solution stand until it is completely separated into layers. Filter and centrifuge and wash the precipitate obtained by filtration with deionized water until it is neutral. Dry the washed precipitate at 100 °C until constant weight. Then calcine the dried solid powder in air at 600 °C for 2 h. The dealubilized molecular sieve support obtained is called DZ-12.

[0042] (2) Preparation of cobalt-based catalysts: S1. Take 1 g of dealuminized molecular sieve carrier DZ-12 and mix it with 25 mL of deionized water. Stir at room temperature for 60 min to obtain carrier slurry. S2. Add 0.148 g of cobalt precursor Co(NO3)2·6H2O and 0.0115 g of auxiliary precursor SnCl2·2H2O to the carrier slurry, stir continuously at room temperature for 6 h, and then continue stirring at 80 °C until the solvent is completely evaporated. S3. The obtained sample was dried thoroughly at 100 °C. After the sample cooled to room temperature, the obtained solid was ground. The ground powder was calcined in air at 600 °C for 6 h. The resulting cobalt-based catalyst was denoted as 3Co0.3Sn / DZ-12.

[0043] Example 2 This embodiment uses the method of Example 1 to prepare the cobalt-based catalyst, and the difference between it and Example 1 is: In step S2, the amount of the auxiliary precursor SnCl2·2H2O added was 0.0192 g. The resulting cobalt-based catalyst is designated as 3Co0.5Sn / DZ-12.

[0044] Example 3 This embodiment uses the method of Example 1 to prepare the cobalt-based catalyst, and the difference between it and Example 1 is: In step S2, the amount of the auxiliary precursor SnCl2·2H2O added was 0.0384 g. The resulting cobalt-based catalyst is designated as 3CoSn / DZ-12.

[0045] Example 4 This embodiment illustrates a method for preparing the cobalt-based catalyst of the present invention, which includes the following steps: (1) Preparation of dealubilized molecular sieve support: Weigh 10 g of ZSM-5 molecular sieve (silicon-to-aluminum ratio of 300) and dissolve it in 180 mL of nitric acid (concentration of 12 mol / L). Stir continuously for 24 h at 100 °C. Let the resulting mixed solution stand until it is completely separated into layers. Filter and centrifuge and wash the precipitate obtained by filtration with deionized water until it is neutral. Dry the washed precipitate at 100 °C until it reaches constant weight. Then calcine the dried solid powder in air at 600 °C for 2 h. The dealubilized molecular sieve support obtained is called DZ-24.

[0046] (2) Preparation of cobalt-based catalysts: S1. Take 1 g of dealuminized molecular sieve carrier DZ-24 and mix it with 25 mL of deionized water. Stir at room temperature for 60 min to obtain carrier slurry. S2. Add 0.148 g of cobalt precursor Co(NO3)2·6H2O and 0.0115 g of auxiliary precursor SnCl2·2H2O to the carrier slurry prepared in step S1, stir continuously at room temperature for 6 h, and then continue stirring at 80 °C until the solvent is completely evaporated. S3. The obtained sample was dried thoroughly at 100 °C. After the sample cooled to room temperature, the obtained solid was ground. The ground powder was calcined in air at 600 °C for 6 h. The resulting cobalt-based catalyst was denoted as 3Co0.3Sn / DZ-24.

[0047] Example 5 This embodiment uses the method of Example 4 to prepare the cobalt-based catalyst, and the difference between it and Example 4 is: In step S2, the amount of the auxiliary precursor SnCl2·2H2O added was 0.0192 g. The resulting cobalt-based catalyst is designated as 3Co0.5Sn / DZ-24.

[0048] Example 6 This embodiment uses the method of Example 4 to prepare the cobalt-based catalyst, and the difference between it and Example 4 is: In step S2, the amount of the auxiliary precursor SnCl2·2H2O added was 0.0384 g. The resulting cobalt-based catalyst is designated as 3CoSn / DZ-24.

[0049] Comparative Example 1 This comparative example uses the method of Example 1 to prepare a cobalt-based catalyst, but the difference between it and Example 1 is: In step S2, only 0.148 g of cobalt precursor was added; no auxiliary precursor was added. The resulting cobalt-based catalyst is designated 3Co / DZ-12.

[0050] The properties of the dealuminolite molecular sieves obtained in Examples 1 and 4 are shown in Table 1.

[0051] Table 1

[0052] Example 7 The cobalt-based catalysts prepared in Examples 1-6 and Comparative Example 1 were subjected to tableting, granulation, and sieving processes, respectively. 0.2 g of cobalt-based catalyst with a particle size of 14-40 mesh was loaded into a fixed-bed reactor, reactant gas was introduced, the temperature was raised to 550 °C, and after holding at that temperature for 50 min, the catalytic performance of the catalyst for propane dehydrogenation was evaluated under atmospheric pressure.

[0053] The mass ratio of propane to nitrogen in the reaction gas was 11:19 (i.e., the volume fraction of propane in the reaction gas was 26.92%), and the mass hourly space velocity (HSV) of propane was 4 h⁻¹. -1 The product was analyzed by gas chromatography after a reaction time of 60 min.

[0054] The catalytic performance results of the catalyst are shown in Table 2.

[0055] Table 2

[0056] Note: In Table 2, the part of the catalyst name that is not supported, the number before the element followed by a percentage sign indicates the content of that element based on the weight of the support. Taking the catalyst 3CoSn / DZ-12 in Example 3 as an example, it means that based on the weight of the support DZ-12, the content of Co in the catalyst is 3% by weight and the content of Sn is 1% by weight.

[0057] As shown in Table 2, the Sn-modified cobalt-based catalyst for direct dehydrogenation of propane to propylene provided by the present invention has high propane conversion rate and propylene selectivity, and can be applied to reaction systems with high propane content in the reaction gas, thus having high industrial production value.

[0058] The table above also shows that the acid treatment time and the content of the additive for ZSM-5 molecular sieve both affect the conversion rate of propane and the selectivity for propylene. The 3Co0.5Sn / DZ-12 catalyst exhibited the best catalytic performance, achieving an initial propane conversion of 40%, a propylene selectivity of 86%, and a propylene yield of 34.44 wt% when used for dehydrogenation to propylene. This indicates that the addition of the additive Sn significantly improved the catalyst's catalytic activity. With the dealulated molecular sieve DZ-12 as the support, the catalyst achieved the highest propylene yield when the Sn addition was 0.5 wt%.

[0059] Example 8 In this embodiment, the 3Co0.5Sn / DZ-12 catalyst prepared in Example 2 was used for propane dehydrogenation. The reaction conditions were the same as in Example 7, except that the reaction time was 9 hours. The EDS spectrum of the catalyst after the reaction is shown in [Figure 1]. Figure 3 .

[0060] The products were analyzed by gas chromatography. The conversion rate of propane was 36%, and the selectivity of propylene was 90%, indicating that the catalyst provided by this invention has excellent high-temperature stability, and the propylene selectivity significantly improves as the reaction proceeds.

[0061] Example 9 In this embodiment, the 3Co0.5Sn / DZ-12 catalyst prepared in Example 2 was used for propane dehydrogenation. The reaction conditions were the same as in Example 7, except that the volume fraction of propane in the reactants was 40%. Gas chromatography was used to analyze the products. The propane conversion rate was 30%, and the propylene selectivity was 92%.

[0062] Figure 1 The XRD patterns of the cobalt-based catalysts obtained in Examples 1-3 of this invention are shown below. Figure 1As shown, a comparison with the standard card PDF#44-0003 revealed that its characteristic peaks basically correspond to those of the ZSM-5 molecular sieve standard card, exhibiting the characteristic MFI-type structural features, indicating that acid treatment of the molecular sieve did not affect its framework structure. Furthermore, the small amounts of Co and Sn incorporated did not show characteristic peaks of their metal or metal oxide forms in the XRD pattern, indicating that both the active and auxiliary components were uniformly distributed on the acid-treated ZSM-5 molecular sieve support.

[0063] Figure 2 The images show SEM images of the catalysts obtained in Example 2 and Comparative Example 1. Figure 2 It can be seen that the addition of the promoter Sn significantly reduces the particle size of the active species Co and makes its distribution on the support more uniform, which is conducive to exposing more active sites and improving the catalytic performance of the catalyst.

[0064] Figure 3 The EDS diagram for the catalyst prepared in Example 2 after 9 hours of reaction (i.e., Example 8) is shown below. Figure 3 As shown, the active metals did not aggregate and remained uniformly distributed on the support surface, indicating that the catalyst has excellent high-temperature stability.

[0065] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0066] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0067] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A cobalt-based catalyst, characterized in that, The catalyst includes a support and an active component and an additive supported on the support; the active component includes metal Co; the additive includes metal Sn; and the support is a dealuminated molecular sieve.

2. The catalyst according to claim 1, wherein, Based on the weight of the carrier, the content of elements in the active component is 1~10 wt%; and / or Based on the weight of the carrier, the content of the elements in the additives is 0.3~1 wt%.

3. The catalyst according to claim 1, wherein, The dealuminized molecular sieve is an MFI type molecular sieve, preferably a ZSM-5 molecular sieve; The silicon-to-aluminum ratio of the ZSM-5 molecular sieve before dealuminization is 38-600, preferably 100-500; The specific surface area of ​​the dealuminized molecular sieve is 320~400 m². 2 / g; pore volume is 0.15~0.45 cm³ 3 / g.

4. The catalyst according to claim 1, wherein, The cobalt-based catalyst has a particle size of 14-40 mesh.

5. A method for preparing the catalyst according to any one of claims 1 to 4, characterized in that, The method includes the following steps: (1) Mix the dealuminated molecular sieve and solvent to prepare a slurry, thereby obtaining a carrier slurry; (2) The carrier slurry is mixed with the active component precursor and the auxiliary agent precursor, and the resulting mixture is dried and calcined to obtain a cobalt-based catalyst.

6. The method according to claim 5, wherein, The mass ratio of the dealuminized molecular sieve, the active component precursor, and the auxiliary agent precursor is 1:0.025~0.3:0~0.04; The active component precursor is selected from at least one of cobalt nitrate, cobalt sulfate, and cobalt chloride; The auxiliary precursor is selected from at least one of tin nitrate, tin sulfate, and tin chloride.

7. The method according to claim 5, wherein, In step (2), the drying temperature is 80~100 ℃ and the time is 8~12 h; the roasting temperature is 600~800 ℃ and the time is 4~8 hours.

8. The method according to claim 5, wherein, The dealulimed molecular sieve is prepared by a method comprising the following steps: The molecular sieve was mixed with an acid solution and subjected to acid treatment. After standing and separating into layers, the solid was filtered and then dried and calcined in sequence. The acid treatment conditions include: a temperature of 80~100 ℃ and a time of 12~24 h; The amount of acid solution used relative to 10 g of the molecular sieve is 50-400 mL; the concentration of the acid solution is 1-20 mol / L. The acid solution is selected from one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, and citric acid; The molecular sieve is an MFI type molecular sieve, preferably a ZSM-5 molecular sieve; the original silica-alumina ratio of the ZSM-5 molecular sieve is 38~600, preferably 100~500.

9. A method for producing propylene by dehydrogenation of propane, characterized in that, The method includes: Under a protective gas atmosphere, a propane-containing feed gas is brought into contact with the cobalt-based catalyst according to any one of claims 1-4 in a reactor to carry out a propane dehydrogenation to propylene reaction.

10. The method according to claim 9, wherein, The concentration of propane in the feed gas is 5-30% by volume. The reaction conditions for propane dehydrogenation to propylene include: a reaction temperature of 500-600 °C, a reaction pressure of 0-1 MPa, and a propane mass hourly space velocity of 0.5-8 h⁻¹. -1 .

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