Pt-based supported catalyst as well as preparation method and application thereof

Abstract

The invention relates to a Pt-based supported catalyst and a preparation method and application thereof, the catalyst comprises a carrier and an active component dispersed on the carrier, and the element in the active component comprises Pt; the carrier is a V-modified dealumination molecular sieve. The V element is introduced into the framework structure of the dealumination molecular sieve, and the V element is coordinated with the hydroxyl on the surface of the dealumination molecular sieve, so that the charge distribution on the surface of the dealumination molecular sieve carrier can be improved, and the electron adsorption effect of the carrier on a Pt precursor is enhanced, so that Pt nanoparticles are highly dispersed on the carrier, more active sites can be exposed, and the dealumination molecular sieve is more stable in performance. The catalytic activity and the carbon deposition resistance of the catalyst are improved, and the catalyst has relatively high stability.

Description

Technical Field

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

[0002] Propylene plays a vital role in the chemical industry, and its downstream products, such as acrylonitrile, propylene oxide, and polypropylene, are important basic organic chemical products. With increasing market demand for propylene, traditional petrochemical methods for producing propylene can no longer meet the production needs, making the propane dehydrogenation route for propylene production a focus of attention in recent years.

[0003] Currently, the main catalysts used in propane dehydrogenation are Pt-based and Cr-based catalysts. Cr-based catalysts have certain toxicity and are therefore gradually being replaced by Pt-based catalysts. Pt-based catalysts are widely used in the industrial catalysis of propane dehydrogenation because they have superior activity for catalyzing the CH bond of alkanes but lower activity for CC cracking.

[0004] Chen et al. (Catalysis Science & Technology, 2020, 10: 5973-5982) found that, compared with SiO2, the Ti / Nb modified SiO2 support exhibited a significantly enhanced metal-support interaction with Pt nanoparticles, resulting in a significantly improved propylene selectivity for the modified platinum-based catalyst in propane dehydrogenation. However, most of the Pt nanoparticles in this catalytic system were covered by SMSI oxide, which inhibited the catalyst activity. Meanwhile, more strategies for optimizing the interaction between the metal and the support have been proposed. CN112138656A discloses a method for modifying the spherical mesoporous material SBA-15 with Mg and Ti, and a catalyst support prepared using this method. The catalyst prepared using this support showed a coking amount of less than 1.00 wt% after 50 h of operation under propane dehydrogenation conditions. CN111992207A discloses a method for modifying Sn alumina supports with potassium ethylenediaminetetraacetate. By allowing the inorganic acid to interact with metallic Pt, more Pt can be anchored at Sn sites, thereby achieving Pt dispersion and stabilization. Fan et al. (Journal of Catalysis, 2020, 389: 450–460) disclosed a method for surface modification of dendritic mesoporous silica nanoparticles (DMSN) using Mn, utilizing highly dispersed MnO on the DMSN. x The site enhances the dispersion and stability of Pt clusters.

[0005] However, existing platinum-based catalysts for propane dehydrogenation still suffer from low propylene selectivity and easy coking. Summary of the Invention

[0006] The purpose of this invention is to further improve the propylene selectivity and anti-coking ability in the existing propane dehydrogenation to propylene process.

[0007] To achieve the above objectives, a first aspect of the present invention provides a Pt-based supported catalyst comprising a support and an active component dispersed on the support, wherein the active component comprises Pt; the support is a V-modified dealuminated molecular sieve.

[0008] Optionally, based on the total weight of the catalyst, the Pt content is 0.3-1.5 wt% by element; and based on the total weight of the support, the V content is 0.5-3.5 wt% by element.

[0009] Optionally, the specific surface area of ​​the dealuminized molecular sieve is 350-420 m². 2 / g; pore volume is 0.20-0.30 cm³ 3 / g.

[0010] Optionally, the carrier is a Beta molecular sieve; the silicon-to-aluminum ratio of the Beta molecular sieve before dealumination is 18-75.

[0011] The second aspect of the present invention provides a method for preparing the aforementioned catalyst, the method comprising the following steps: (1) mixing a dealuminized molecular sieve, a solvent and a V precursor for a first impregnation treatment, and subjecting the obtained solid to a first drying and a first calcination to obtain a V-modified molecular sieve; (2) mixing the V-modified molecular sieve and a Pt precursor solution for a second impregnation treatment, and subjecting the obtained solid to a second drying, a second calcination and reduction to obtain a modified Pt-based catalyst.

[0012] Optionally, the mass ratio of the dealuminized molecular sieve, the V precursor, and the Pt precursor is 1:0.006-0.035:0.01-0.085; preferably, the V precursor is selected from at least one of ammonium metavanadate, sodium metavanadate, and vanadium oxalate; and the Pt precursor is selected from at least one of chloroplatinic acid, platinum nitrate, and platinum acetate.

[0013] Optionally, in step (1), the conditions for the first impregnation treatment include: a temperature of 25-60 ℃ and a time of 6-12 h; a first drying temperature of 80-100 ℃ and a time of 12-24 h; a first calcination temperature of 500-800 ℃, a heating rate of 2-10 ℃ / min, and a time of 5-10 h; in step (2), the conditions for the second impregnation treatment include: a temperature of 25-60 ℃ and a time of 6-12 h; a second drying temperature of 80-100 ℃ and a time of 12-24 h; a second calcination temperature of 500-800 ℃, a heating rate of 2-10 ℃ / min, and a time of 5-10 h; the reduction includes: reducing the solid after the second calcination in a hydrogen-containing atmosphere; the reduction temperature is 500-700 ℃ and the time is 1-2 h.

[0014] Optionally, the method further includes: mixing the molecular sieve with an acid solution under heating conditions to perform acid treatment, thereby obtaining a dealuminized molecular sieve; the acid treatment conditions include: a temperature of 80-120 ℃; a time of 6-18 h; a volume of acid solution of 50-500 mL relative to 10 g of the molecular sieve; and a concentration of acid solution of 1-20 mol / L; preferably, the molecular sieve is a Beta molecular sieve; the original silica-to-alumina ratio of the Beta molecular sieve is 18-75; and the acid solution is selected from one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, and citric acid.

[0015] A third aspect of the present invention provides a method for producing propylene by propane dehydrogenation, the method comprising: contacting a propane-containing feed gas with a Pt-based supported catalyst provided in the first aspect of the present invention to carry out a propane dehydrogenation reaction.

[0016] Optionally, the conditions for propane dehydrogenation include: a reaction temperature of 450-700 °C, a reaction pressure of 0-1 MPa, and a propane mass hourly space velocity of 1.0-3.0 h⁻¹. -1 .

[0017] The present invention has the following beneficial effects: 1. Introducing the V element from the framework structure of the dealubilized molecular sieve and coordinating it with the hydroxyl groups on the surface of the dealubilized molecular sieve can improve the charge distribution on the surface of the dealubilized molecular sieve support, enhance the electron adsorption of Pt precursor on the support, and disperse Pt nanoparticles on the support, thereby improving the catalytic activity and anti-coking ability of the catalyst. At the same time, the highly dispersed V element on the support has better stability. Through the interaction between the V element and Pt nanoparticles, the interaction between the reactive sites on the catalyst and the support can be further enhanced, so that the catalyst also has good stability. 2. This invention introduces V element into the dealuminolite molecular sieve, which can form more coordinated unsaturated V on the surface of the dealuminolite molecular sieve.3+ / V 4+ As a Lewis acid center, it can further promote the activation of propane, thereby improving the catalyst's adsorption and activation capacity for propane.

[0018] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0019] 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 images show X-ray powder diffraction patterns of the dealuated molecular sieve S1, the V-modified dealuated molecular sieve S2, the V-modified Pt-based supported catalyst A1, and the unmodified Pt-based catalyst C1 prepared in Comparative Example 1.

[0020] Figure 2 This is a transmission electron microscope (TEM) image of the V-modified Pt-based supported catalyst A1 prepared in Example 1. Detailed Implementation

[0021] 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.

[0022] A first aspect of the present invention provides a Pt-based supported catalyst comprising a support and an active component dispersed on the support, wherein the active component comprises Pt; the support is a V-modified dealuminated molecular sieve.

[0023] This invention introduces the element V into the framework structure of the dealubilized molecular sieve. The V element coordinates with the hydroxyl groups on the surface of the dealubilized molecular sieve, which can improve the charge distribution on the surface of the dealubilized molecular sieve support and enhance the electron adsorption of Pt precursors on the support. This allows Pt nanoparticles to be dispersed on the support, exposing more active sites, and can reduce the side reactions caused by the interaction between the target product and Pt nanoparticles, thereby improving the catalytic activity and anti-coking ability of the catalyst.

[0024] In catalysts used for propane dehydrogenation to propylene, the strong adsorption energy between Pt nanoparticles and propylene molecules easily induces side reactions such as deep dehydrogenation or cracking, leading to a decrease in propylene selectivity. In this invention, the V-modified dealubilized molecular sieve exhibits high stability, and the interaction between V and Pt nanoparticles enhances the interaction between metallic Pt and the support, thereby improving catalyst selectivity and resistance to coking while simultaneously enhancing catalyst stability.

[0025] Furthermore, the highly dispersed V element on the catalyst support provided by this invention has superior stability. Through the interaction between the V element and Pt nanoparticles, the interaction between the reactive sites on the catalyst and the support can be further enhanced, thus giving the catalyst good stability as well.

[0026] In this invention, the carrier is a V-modified dealubilized molecular sieve. Because the surface acidity is removed, the dealubilized molecular sieve can avoid deep dehydrogenation or cracking reactions caused by strong Brønsted acids.

[0027] In some embodiments of the present invention, the Pt content, based on the total weight of the catalyst and in terms of elemental composition, is 0.3-1.5 wt%, 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%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, or any value within the aforementioned range.

[0028] Based on the total weight of the carrier, the content of V, in terms of elements, is 0.5-3.5 wt%, for example, it can be 0.5 wt%, 0.6 wt%, 0.8 wt%, 1.0 wt%, 1.2 wt%, 1.5 wt%, 2.0 wt%, 2.2 wt%, 2.5 wt%, 2.8 wt%, 3.0 wt%, 3.5 wt%, or any value within the aforementioned range.

[0029] In some embodiments of the present invention, the specific surface area of ​​the dealuminized molecular sieve is 350-420 m². 2 / g; pore volume is 0.20-0.30 cm³ 3 / g. Therefore, the dealuminolite molecular sieve with the above structure facilitates the high dispersion of the active component Pt on the support.

[0030] In this invention, the active component is confined within the pore structure of the molecular sieve. The characteristics of the support affect the form and stability of the active component in the catalyst. In some embodiments of this invention, the support is a Beta molecular sieve; the silicon-to-aluminum ratio of the Beta molecular sieve before dealumination is 18-75.

[0031] Introducing V into the framework of the dealuminolite molecular sieve in this invention can, on the one hand, reduce the strong Brønsted acid in traditional molecular sieves, thereby avoiding deep dehydrogenation or cracking reactions of propylene on the support; on the other hand, by modifying the Pt-based catalyst with V, more coordinated unsaturated V can be formed on the support surface compared to other methods of modifying the support surface with metals. 3+ / V 4+As a Lewis acid center, it further promotes the activation of propane and enhances the catalyst's adsorption and activation capabilities for propane.

[0032] The second aspect of the present invention provides a method for preparing the aforementioned catalyst, the method comprising the following steps: (1) mixing a dealuminized molecular sieve, a solvent and a V precursor for a first impregnation treatment, removing the solvent, and first drying and first calcining the resulting solid to obtain a V-modified molecular sieve; (2) mixing the V-modified molecular sieve and a Pt precursor solution for a second impregnation treatment, and second drying, second calcining and reduction of the resulting solid to obtain a modified Pt-based catalyst.

[0033] In some embodiments of the present invention, the mass ratio of the dealuminized molecular sieve, the V precursor, and the Pt precursor is 1:0.006-0.035:0.01-0.085.

[0034] Specifically, the V precursor is a soluble salt of V, preferably at least one of ammonium metavanadate, sodium metavanadate, and vanadium oxalate.

[0035] Specifically, the Pt precursor is a soluble salt of Pt, preferably at least one of chloroplatinic acid, platinum nitrate, and platinum acetate.

[0036] In some embodiments of the present invention, in step (1), the conditions for the first impregnation treatment include: a temperature of 25-60 ℃ and a time of 6-12 h; a first drying temperature of 80-100 ℃ and a time of 12-24 h; and a first calcination temperature of 500-800 ℃, a heating rate of 2-10 ℃ / min, and a time of 5-10 h.

[0037] In some embodiments of the present invention, in step (2), the conditions for the second impregnation treatment include: a temperature of 25-60 ℃ and a time of 6-12 h; a second drying temperature of 80-100 ℃ and a time of 12-24 h; and a second calcination temperature of 500-800 ℃, a heating rate of 2-10 ℃ / min, and a time of 5-10 h.

[0038] In some embodiments of the present invention, the reduction includes: reducing the solid after the second calcination in a hydrogen-containing atmosphere; the reduction temperature is 500-700 °C, and the time is 1-2 h. The hydrogen content in the hydrogen-containing atmosphere is 5% by volume or more, preferably 10% by volume or more.

[0039] In some embodiments of the present invention, the solvent used to prepare the Pt precursor solution in step (1) and step (2) can be deionized water. In step (1) and / or step (2), the solvent can be removed before the solid is dried. The solvent can be removed by evaporating the solvent at 60-100 °C.

[0040] In this invention, the dealuminized molecular sieve is a molecular sieve obtained by treating a silicon-aluminum-containing molecular sieve with an acid solution.

[0041] In some embodiments of the present invention, the preparation method of the catalyst further includes: mixing the molecular sieve with an acid solution under heating conditions for acid treatment to obtain a dealuminated molecular sieve.

[0042] The acid treatment conditions include: a temperature of 80-120 ℃ and a time of 6-18 h.

[0043] The amount of acid solution used is 50-500 mL relative to 10 g of the molecular sieve; the concentration of the acid solution is 1-20 mol / L.

[0044] This process also includes washing the solid obtained from acid treatment, followed by drying and calcining the washed solid. Specifically, the centrifuged solid is washed with deionized water until the pH reaches 4-7. The washed solid is dried at 80-100 °C for 12-24 h; the calcination temperature is 500-800 °C, the heating rate is 2-10 °C / min, and the time is 5-10 h. In some embodiments of the present invention, the molecular sieve is a Beta molecular sieve; the original silica-to-alumina ratio of the Beta molecular sieve is 18-75. By performing dealumination treatment on the Beta molecular sieve support, surface acidity is removed, avoiding deep dehydrogenation or cracking reactions caused by the strong Brønsted acid of traditional molecular sieve supports.

[0045] The acid solution may be an organic acid or an inorganic acid. In some specific embodiments of the present invention, the acid solution is selected from nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid and citric acid, preferably nitric acid.

[0046] A third aspect of the present invention provides a method for producing propylene by propane dehydrogenation, the method comprising: contacting a propane-containing feed gas with a Pt-based supported catalyst provided in the first aspect of the present invention to carry out a propane dehydrogenation reaction.

[0047] In some embodiments of the present invention, the conditions for propane dehydrogenation include: a reaction temperature of 450-700 °C, a reaction pressure of 0-1 MPa, and a propane mass hourly space velocity of 1.0-3.0 h⁻¹. -1 .

[0048] The present invention will be further described in detail below through examples, but the present invention is not limited thereto.

[0049] All raw materials used in the embodiments and comparative examples of this invention can be obtained commercially. Specifically, the Beta molecular sieve, with a silica-to-alumina ratio of 50, was purchased from Sinopec Catalyst Company; the H2PtCl6 solution, an 8 wt% aqueous solution, was purchased from Tianjin Guangfu Fine Chemical Co., Ltd.

[0050] Example 1 This embodiment illustrates the preparation method of the Pt-based supported catalyst and the propane dehydrogenation method of the present invention. The preparation method of the Pt-based supported catalyst includes the following steps: (1) Preparation of dealuminized molecular sieve support: 10 g of Beta molecular sieve (silicon-to-aluminum ratio of 50) was weighed and dissolved in 200 mL of nitric acid (concentration of 2 mol / L). The mixture was stirred continuously at 100°C for 12 h. The resulting suspension was cooled to room temperature and then centrifuged. The solid fraction after centrifugation was washed with distilled water until neutral. The resulting solid was dried until constant weight, and then the resulting solid powder was calcined at a heating rate of 3 °C / min, a calcination temperature of 550 °C, and a calcination time of 6 h. The dealuminized molecular sieve was obtained and denoted as S1.

[0051] (2) Preparation of V-modified support: 1 g of dealubilized molecular sieve S1 was mixed with 25 mL of deionized water to obtain a dealubilized molecular sieve slurry. 0.23 g of ammonium metavanadate was added to the dealubilized molecular sieve slurry and stirred continuously at room temperature for 6 h. Stirring was continued at 80 °C until the solvent was completely evaporated. The mixture was dried to constant weight and then calcined at 600 °C for 6 h to obtain V-modified dealubilized molecular sieve, denoted as S2.

[0052] Based on the total mass of the V-modified dealuminolite molecular sieve, the mass percentage of V in the V-modified dealuminolite molecular sieve S2 is 1.00%.

[0053] (3) Preparation of Pt-based catalysts: Take 2 g of the above-mentioned V-modified dealubilized molecular sieve S2 and mix it with 50 mL of deionized water. Stir at room temperature for 2 hours to obtain a V-modified dealubilized molecular sieve slurry. Slowly add 0.63 mL of H2PtCl6 solution to the V-modified dealubilized molecular sieve slurry and stir continuously at room temperature for 6 hours. Then continue stirring at 80 °C until the solvent is completely evaporated. Dry to constant weight and then calcine at 600 °C for 6 hours. The solid obtained by calcination is then reduced at 600 °C for 1.5 hours in an H2 / N2 atmosphere with a hydrogen content of 10% by volume to obtain a V-modified Pt-based supported catalyst, denoted as A1.

[0054] Based on the total mass of catalyst A1, the mass percentage of Pt is 0.30%.

[0055] The properties of dealuminolite molecular sieve S1 and catalyst A1 are shown in Table 1.

[0056] Table 1

[0057] Performance testing of propane dehydrogenation to propylene: Catalyst A1 was subjected to tableting, granulation, and sieving. 200 mg of catalyst A1 with a particle size of 14-40 mesh was loaded into a fixed-bed reactor, reactant gas was introduced, and the temperature was raised to 600 °C. The catalytic performance of catalyst A1 was evaluated under atmospheric pressure. The volume ratio of propane to nitrogen in the reactant gas was 1:19 (i.e., the propane content in the reactant gas was 5% by volume), and the mass hourly space velocity (WHSV) of propane was 1 h⁻¹. -1 The products were analyzed by gas chromatography, and the results are shown in Table 2.

[0058] Table 2

[0059] As can be seen from the table above, the Pt-based supported catalyst provided by this invention has a high initial propane conversion rate and propylene selectivity when used for propane dehydrogenation to propylene, and the catalyst has high activity; moreover, it still has high propylene selectivity and good stability after long-term operation.

[0060] Examples 2-5 Examples 2-5 prepared Pt-based catalysts using the method of Example 1, the difference being that the mass fraction of V in the V-modified dealuminolite molecular sieve support was 0.50 wt%, 0.60 wt%, 1.50 wt%, and 3.00 wt%, respectively.

[0061] The obtained Pt-based catalyst was used for propane dehydrogenation to propylene test. The reaction conditions were the same as in Example 1, and the reaction time was 120 min. The evaluation results are shown in Table 3.

[0062] Examples 6-7 Examples 6-7 prepared Pt-based catalysts using the method of Example 1, the difference being that the mass fraction of Pt element in the Pt-supported catalysts was 0.60 wt% and 1.20 wt%, respectively.

[0063] The obtained Pt-based catalyst was used for propane dehydrogenation to propylene test. The reaction conditions were the same as in Example 1, and the reaction time was 120 min. The evaluation results are shown in Table 3.

[0064] Comparative Example 1 This comparative example uses the method of Example 1 to prepare a Pt-based catalyst. The difference between this example and Example 1 is that ammonium metavanadate is not added to modify the support during the preparation process. Instead, H2PtCl6 solution is slowly added directly to the slurry of the dealuminolite molecular sieve S1 to obtain a Pt-loaded dealuminolite molecular sieve. The resulting catalyst is denoted as C1.

[0065] The obtained Pt-based catalyst C1 was used for propane dehydrogenation to propylene test. The reaction conditions were the same as in Example 1, and the reaction time was 120 min. The evaluation results are shown in Table 3.

[0066] Table 3

[0067] As can be seen from the table above, the Pt-based supported catalyst provided by this invention has high propane conversion and propylene selectivity.

[0068] Based on the results of Examples 1-5, it can be seen that the content of V element on the catalyst has a certain influence on the propane conversion rate and propylene selectivity during propane dehydrogenation. When the V element content on the catalyst is between 0.50-1.00 wt%, the dehydrogenation activity of the catalyst increases with the increase of V element content. When the V element content on the catalyst exceeds 1.00 wt%, the dehydrogenation activity of the catalyst tends to stabilize.

[0069] Based on the results of Examples 1, 6 and 7, it can be seen that, while keeping the V element content on the catalyst constant, the dehydrogenation activity of the catalyst decreases with the increase of the Pt element content.

[0070] Catalyst coke content analysis: After 120 min of propane dehydrogenation test reaction, thermogravimetric analysis was used to analyze the coke content of catalysts A1 and C1. The results are shown in Table 4.

[0071] Table 4

[0072] As shown in the table above, compared with the Pt-supported catalyst of the dealubilizing molecular sieve without V modification, the V-modified Pt-based catalyst has a significantly enhanced ability to resist coking.

[0073] Figure 1 The images show X-ray powder diffraction patterns of the dealuitized molecular sieve S1, the V-modified dealuitized molecular sieve S2, the V-modified Pt-based supported catalyst A1, and the unmodified Pt-based catalyst C1 prepared in Comparative Example 1, obtained by the method of Example 1 of this invention. Figure 1 It can be observed that the d of the dealuminolite modified with V... 302The significantly increased spacing indicates that V species were successfully introduced into the framework structure of the dealuminolite molecular sieve S1. Compared to the unmodified Pt-based catalyst C1, no Pt diffraction peaks were observed in the V-modified Pt-based supported catalyst A1, indicating that metallic Pt is highly dispersed on the support surface.

[0074] Figure 2 This is a transmission electron microscope (TEM) image of the V-modified Pt-based supported catalyst A1 prepared in Example 1. Figure 2 It can be seen that metallic Pt does not form obvious particles in the catalyst, further proving that metallic Pt is highly dispersed in the support.

[0075] 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.

[0076] 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.

[0077] 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 Pt-based supported catalyst, characterized in that, The catalyst comprises a support and an active component dispersed on the support, wherein the active component includes Pt; the support is a V-modified dealuminolite molecular sieve.

2. The catalyst according to claim 1, wherein, Based on the total weight of the catalyst, the Pt content, by elemental calculation, is 0.3-1.5 wt%; and / or Based on the total weight of the carrier, the content of V, in terms of elements, is 0.5-3.5 wt%.

3. The catalyst according to claim 1, wherein, The specific surface area of ​​the dealuminized molecular sieve is 350-420 m². 2 / g; pore volume is 0.20-0.30 cm³ 3 / g.

4. The catalyst according to claim 1, wherein, The carrier is a Beta molecular sieve, and the silicon-to-aluminum ratio of the Beta molecular sieve before dealumination is 18-75.

5. A method for preparing the catalyst according to any one of claims 1-4, characterized in that, The method includes the following steps: (1) Mix the dealuminolized molecular sieve, solvent and V precursor for a first impregnation treatment, and then perform a first drying and a first calcination on the resulting solid to obtain V modified molecular sieve; (2) The V-modified molecular sieve and the Pt precursor solution are mixed and subjected to a second impregnation treatment, and the resulting solid is subjected to a second drying, a second calcination and reduction to obtain a modified Pt-based catalyst.

6. The method according to claim 5, wherein, The mass ratio of the dealuminized molecular sieve, the V precursor, and the Pt precursor is 1:0.006-0.035:0.01-0.085; Preferably, the V precursor is selected from at least one of ammonium metavanadate, sodium metavanadate, and vanadium oxalate; the Pt precursor is selected from at least one of chloroplatinic acid, platinum nitrate, and platinum acetate.

7. The method according to claim 5, wherein, In step (1), the conditions for the first impregnation treatment include: a temperature of 25-60 ℃ and a time of 6-12 h; a first drying temperature of 80-100 ℃ and a time of 12-24 h; and a first calcination temperature of 500-800 ℃, a heating rate of 2-10 ℃ / min, and a time of 5-10 h. In step (2), the conditions for the second impregnation treatment include: a temperature of 25-60 ℃ and a time of 6-12 h; a second drying temperature of 80-100 ℃ and a time of 12-24 h; and a second calcination temperature of 500-800 ℃, a heating rate of 2-10 ℃ / min, and a time of 5-10 h. The reduction includes: reducing the solid after the second calcination in a hydrogen-containing atmosphere; the reduction temperature is 500-700℃ and the time is 1-2 h.

8. The method according to claim 5, wherein, The method further includes: mixing the molecular sieve with an acid solution under heating conditions to perform acid treatment, thereby obtaining a dealuminized molecular sieve; The acid treatment conditions include: a temperature of 80-120 °C; a time of 6-18 h; a volume of acid solution of 50-500 mL relative to 10 g of the molecular sieve; and a concentration of acid solution of 1-20 mol / L. Preferably, the molecular sieve is a Beta molecular sieve; the original silica-to-alumina ratio of the Beta molecular sieve is 18-75; the acid solution is selected from one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, and citric acid.

9. A method for producing propylene by dehydrogenation of propane, characterized in that, The method includes: Propane-containing feed gas is contacted with the Pt-based supported catalyst according to any one of claims 1-4 to carry out propane dehydrogenation reaction.

10. The method according to claim 9, wherein, The conditions for propane dehydrogenation include: a reaction temperature of 450-700 °C, a reaction pressure of 0-1 MPa, and a propane mass hourly space velocity of 1.0-3.0 h⁻¹. -1 .

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