A catalyst for dehydrogenating propane to produce propylene and its preparation method and application

Abstract

The present invention relates to the field of catalyst technology, and specifically to a catalyst for preparing propylene from propane by dehydrogenation, and a preparation method and application thereof. The present invention effectively improves the catalytic activity of the catalyst and the selectivity of the reaction by limiting the carrier, catalyst components and content. The catalyst of the present invention is used to prepare propylene from propane by dehydrogenation, and the selectivity of propylene is greater than 75%. The present invention uses a weak alkaline solution to modify γ-alumina, which reduces the acidity of the surface of the γ-alumina carrier and is beneficial to improving the selectivity of propylene. In addition, anhydrous ethanol is also used as a dissolving solution for SnCl2, which not only avoids the addition of acid, but also the anhydrous ethanol removed by decompression after the impregnation is completed can be recycled for multiple times, reducing the preparation cost of the catalyst.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts, and in particular to a catalyst for producing propylene by dehydrogenating propane, and a preparation method and application thereof. Background Art

[0002] Propylene is one of the important raw materials for various chemicals and intermediates (such as polypropylene, acrylonitrile, acetone, propylene oxide, etc.) in the production of modern petrochemical industry. In recent years, the global demand and production of propylene have increased. The production of propylene mainly relies on traditional catalytic cracking and steam cracking of naphtha or other petroleum by-products, which has a series of problems worthy of attention, such as high energy consumption, low propylene selectivity, lack of crude oil reserves, and large amounts of CO2 emissions.

[0003] At present, the main industrial technologies for catalytic dehydrogenation are Lummus' Catofin process (Cr2O3 / Al2O3 catalyst) and Honeywell UOP's Oleflex process (Pt-Sn / Al2O3 catalyst). x Compared with Pt-based catalysts, Pt-based catalysts have the advantages of environmental protection and high catalytic activity. With the development of shale gas and the increase in propane availability, propane dehydrogenation to propylene (PDH) has become an alternative way to reduce the dependence of propylene production on traditional processes. Since PDH has high endothermicity and thermodynamic limitations, relatively high temperature and low pressure are crucial to obtain a high propylene yield. In addition, due to strict environmental regulations, some countries also have certain restrictions on the preparation and application of chromium-based catalysts. Therefore, both academia and industry will pay more attention to the development of new PDH catalysts.

[0004] Pt has the function of activating the CH bond of alkanes in the eighth group and is often used as an active component for the dehydrogenation of alkanes. However, in the PDH process, the sintering of Pt species and the carbon deposition of Pt-based catalysts are the reasons for the gradual deterioration of the dehydrogenation performance. Therefore, by adding different additives (such as Sn, Ga, Zn, Cu, In, Mg, Ca, Pr, Nd, etc.) to platinum-based catalysts to form a bimetallic or multimetallic system and loading it onto a porous material carrier, the dispersibility, reducibility, structure and electronic properties of the Pt catalyst can be changed, and the catalytic activity and stability can be improved. There are already some catalysts for PDH in the prior art, but they all have some shortcomings.

[0005] Patent CN101411978A discloses a continuous equal volume impregnation method using Pt and Sn metals as main catalysts, Zn and rare earth metal elements as additives, and γ-Al2O3 as a carrier to prepare a propane dehydrogenation catalyst containing four components of metal elements. Nitrogen is used as a diluent gas during the reaction, and the prepared catalyst has high propylene selectivity and propane conversion rate. However, the preparation cycle of the catalyst is long, the energy consumption is high, and the use of nitrogen as a diluent gas increases the difficulty of subsequent separation and purification.

[0006] Patent CN101066532A reports a Sn-containing ZSM-5 molecular sieve, which exhibits high selectivity and stability in the catalytic process of propane dehydrogenation to propylene, but the conversion rate is relatively low. In addition, the preparation process of the Sn-containing ZSM-5 molecular sieve is cumbersome and energy-intensive, and the content of each metal component is relatively high, which increases the preparation cost of the catalyst. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a catalyst for dehydrogenating propane to produce propylene and a preparation method and application thereof. The present invention specifically includes the following contents:

[0008] A catalyst for preparing propylene by dehydrogenating propane comprises a γ-Al2O3 carrier and an active component loaded on the γ-Al2O3 carrier, wherein the active component comprises Pt accounting for 0.01-5% of the total mass of the catalyst, Sn accounting for 0.01-5% of the total mass of the catalyst, and a modified metal element accounting for 0.1-20% of the total mass of the catalyst; the modified metal element is one or more of an alkali metal, an alkaline earth metal, and a lanthanide metal element.

[0009] Furthermore, the modified metal element is one or more of K, Na, Rb, Mg, Ca, Sr, La, Ce, Pr, and Nd.

[0010] Furthermore, the modified metal element is one or more of K, Ca, La, and Ce.

[0011] Furthermore, the particle size of the γ-Al2O3 carrier is 40-600 mesh, preferably 100-400 mesh, and more preferably 100-200 mesh.

[0012] Furthermore, the active components include Pt accounting for 0.1-3% of the total mass of the catalyst, Sn accounting for 0.1-3% of the total mass of the catalyst, and modified metal elements accounting for 0.5-15% of the total mass of the catalyst.

[0013] Furthermore, the active components include Pt accounting for 0.3-1% of the total mass of the catalyst, Sn accounting for 0.3-1% of the total mass of the catalyst, and modified metal elements accounting for 1-5% of the total mass of the catalyst.

[0014] A method for preparing a catalyst for producing propylene by dehydrogenating propane, comprising: sequentially impregnating a γ-Al2O3 carrier in a weakly alkaline solution containing a modified metal auxiliary agent, an alcohol solution containing Sn, and a solution containing Pt, to finally obtain the catalyst for producing propylene by dehydrogenating propane.

[0015] Furthermore, in the weak alkaline solution containing modified metal additives: the modified metal additives are one or more of KNO3, Ca(NO3), La(NO3)3·6H2O, Ce(NO3)3·6H2O; and / or the weak base is one or more of urea, ammonia water, sodium citrate, sodium carbonate, and ammonium bicarbonate; and / or the molar ratio of the modified metal additive to the weak base in the solution is 1:(5-20), preferably 1:(3-8).

[0016] Further, the following steps are included:

[0017] S1, first impregnation: impregnating the γ-Al2O3 carrier in a weak alkaline solution containing a modified metal additive, followed by filtering, washing, drying and calcining to obtain a first catalyst precursor;

[0018] S2, second impregnation: impregnating the first catalyst precursor in an alcohol solution containing Sn, removing the solvent under reduced pressure and drying to obtain a second catalyst precursor;

[0019] S3, third impregnation: impregnating the second catalyst precursor in a solution containing Pt, and obtaining the catalyst for producing propylene by dehydrogenation of propane through drying and calcination.

[0020] Furthermore,

[0021] In step S1: the immersion temperature is 80-100°C; and / or, the washing uses 80-100°C deionized water as a detergent; and / or, the drying time is 12-24h; and / or, the roasting temperature is 450-650°C and the roasting time is 4-6h; and / or,

[0022] The Sn-containing alcohol solution in step S2 is an alcohol solution of SnCl2·2H2O; and / or, the solvent of the solution in step S2 is an anhydrous ethanol solution; and / or, the Pt-containing solution in step S3 is a solution of H2PtCl6·6H2O; and / or, the solvent of the solution in step S3 is deionized water; and / or,

[0023] The drying temperature in step S3 is 80-100° C. and the drying time is 12-24 hours; and / or the roasting temperature in step S3 is 450-650° C. and the roasting time is 4-6 hours.

[0024] An application of the catalyst for producing propylene by dehydrogenating propane in propane dehydrogenation.

[0025] Further, a fixed bed reactor, a moving bed reactor or a fluidized bed reactor is used for propane dehydrogenation; and / or, the temperature of the propane dehydrogenation reaction is 450-650° C.; and / or, the catalytic temperature is 550-700° C.; and / or, the propane gas volume space velocity is 500 h -1 -3800h -1 ; and / or, the flow ratio of hydrogen to propane is (1:3)-(4:1).

[0026] Beneficial effects of the present invention:

[0027] (1) The catalyst for preparing propylene by dehydrogenation of propane disclosed in the present invention comprises a γ-Al2O3 carrier and an active component, wherein the active component comprises 0.01-5% of Pt, 0.01-5% of a metal promoter Sn, and 0.1-20% of a modified metal element accounting for the total mass of the catalyst, wherein the modified metal element is one or more of an alkali metal, an alkaline earth metal, and a lanthanide metal element. The present invention effectively improves the catalytic activity and the selectivity of the reaction of the catalyst by limiting the carrier, the catalyst component and the content. When the catalyst of the present invention is used to prepare propylene by dehydrogenation of propane, the selectivity of propylene is greater than 75%.

[0028] (2) The method for preparing a catalyst for preparing propylene by dehydrogenating propane disclosed in the present invention uses a weak alkaline solution to modify γ-alumina, thereby reducing the acidity of the surface of the γ-alumina carrier, which is beneficial to improving the selectivity of propylene. In addition, anhydrous ethanol is used as a dissolving liquid for SnCl2·2H2O, which not only avoids the addition of acid, but also the anhydrous ethanol removed by decompression after the impregnation is completed can be recycled for multiple times, thereby reducing the preparation cost of the catalyst. DETAILED DESCRIPTION

[0029] The present invention is described in detail below in conjunction with specific embodiments. The embodiments shown below do not limit the invention content described in the claims. In addition, the entire contents of the structures represented by the following embodiments are not limited to those necessary as solutions to the invention described in the claims.

[0030] A catalyst for preparing propylene by dehydrogenating propane, comprising a γ-Al2O3 carrier and an active component loaded on the γ-Al2O3 carrier, wherein the active component comprises Pt accounting for 0.01-5% of the total mass of the catalyst, Sn accounting for 0.01-5% of the total mass of the catalyst, and a modified metal element accounting for 0.1-20% of the total mass of the catalyst; the modified metal element is one or more of alkali metals, alkaline earth metals, and lanthanide metal elements, preferably one or more of K, Na, Rb, Mg, Ca, Sr, La, Ce, Pr, and Nd, and more preferably one or more of K, Ca, La, and Ce; the particle size of the γ-Al2O3 carrier is 40-600 mesh, preferably 100-400 mesh, and more preferably 100-200 mesh. Preferably, the active components include 0.1-3% of Pt in total mass of the catalyst, 0.1-3% of Sn in total mass of the catalyst, and 0.5-15% of the total mass of the catalyst as modified metal elements; more preferably, the active components include 0.3-1% of Pt in total mass of the catalyst, 0.3-1% of Sn in total mass of the catalyst, and 1-5% of the total mass of the catalyst as modified metal elements.

[0031] A method for preparing a catalyst for producing propylene by dehydrogenating propane comprises the following steps:

[0032] S1, first impregnation: impregnate the γ-Al2O3 carrier in a weak alkaline solution containing a modified metal auxiliary agent at an immersion temperature of 80-100°C, then filter, wash with deionized water at 80-100°C, dry for 12-24 hours, and calcine at 450-650°C for 4-6 hours to obtain a first catalyst precursor; the modified metal auxiliary agent is one or more of KNO3, Ca(NO3), La(NO3)3·6H2O, Ce(NO3)3·6H2O; the weak base is one or more of urea, ammonia water, sodium citrate, sodium carbonate, and ammonium bicarbonate; the molar ratio of the modified metal auxiliary agent to the weak base in the solution is 1:(5-20), preferably 1:(3-8);

[0033] S2, second impregnation: impregnating the first catalyst precursor in an anhydrous ethanol solution of SnCl2·2H2O, removing the solvent under reduced pressure and drying to obtain a second catalyst precursor;

[0034] S3, third impregnation: the second catalyst precursor is impregnated in an aqueous solution of H2PtCl6·6H2O, dried at 80-100°C for 12-24h after the impregnation, and then calcined at 450-650°C for 4-6h to obtain the catalyst for dehydrogenation of propane to propylene.

[0035] An application of the catalyst for preparing propylene by dehydrogenating propane in propane dehydrogenation, wherein the propane dehydrogenation is carried out by using a fixed bed reactor, a moving bed reactor or a fluidized bed reactor; and / or the temperature of the propane dehydrogenation reaction is 450-650° C.; and / or the catalytic temperature is 550-700° C.; and / or the propane gas volume space velocity is 500 h / min. -1 -3800h -1 ; and / or, the flow ratio of hydrogen to propane is (1:3)-(4:1).

[0036] Example 1

[0037] In this example, catalyst 1, Pt-Sn-K / Al2O3, was prepared and its catalytic performance in propane dehydrogenation to propylene was tested. The preparation method comprises the following steps:

[0038] 1) At 60°C, 4.65g of KNO3 and 11.05g of urea were dissolved in 100mL of deionized water, and a clear solution was obtained after stirring. Subsequently, 100g of γ-Al2O3 (100-200 mesh) was added to the clear solution, sealed and immersed at 60°C for 12h, and then the aqueous solution was filtered out. The remaining γ-Al2O3 was washed with deionized water (120mL×3) three times, placed in a vacuum dryer at 100°C for 12h, and finally calcined at 600°C for 5h;

[0039] 2) At room temperature, 0.48 g of SnCl2·2H2O was dissolved in 100 mL of anhydrous ethanol, and a clear and transparent solution was obtained after stirring. Subsequently, the γ-Al2O3 calcined in step 1) was added to the transparent solution, sealed and immersed for 2 hours, and the anhydrous ethanol was removed under reduced pressure, and the remaining solid was placed at 100°C for vacuum drying for 12 hours; at room temperature, 1.60 g of H2PtCl6·6H2O was further dissolved in 100 mL of deionized water, and a yellow and transparent solution was obtained after stirring. Subsequently, the dried γ-Al2O3 was added to the transparent solution, sealed and immersed for 2 hours, and then placed at 100°C for vacuum drying for 12 hours, and finally calcined at 600°C for 5 hours to obtain the Pt-Sn-K / Al2O3 propane dehydrogenation catalyst.

[0040] Evaluation: 2.0 g of catalyst 1 was loaded into a micro fixed bed reactor and the propane gas volumetric space velocity was controlled to be 1000 h -1 , hydrogen / propane flow ratio 1:3, reaction pressure is atmospheric pressure, bed temperature is 600°C, and the reaction products are analyzed by Agilent 7890A gas chromatograph. The results are shown in Table 2.

[0041] Example 2

[0042] In this example, catalyst 2, Pt-Sn-Ca / Al2O3, was prepared and its catalytic performance in the dehydrogenation of propane to propylene was tested.

[0043] Preparation: 1) At 60°C, 7.37g of Ca(NO3) and 10.80g of urea were dissolved in 100mL of deionized water, and a clear and transparent solution was obtained after stirring. Subsequently, 100g of γ-Al2O3 (100-200 mesh) was added to the transparent solution, sealed and immersed at 60°C for 12h, and then the aqueous solution was filtered out. The remaining γ-Al2O3 was soaked and washed three times with deionized water (120mL×3), placed at 100°C for 12h in vacuum drying, and finally calcined at 600°C for 5h;

[0044] 2) Repeat step 2) in Example 1 to obtain a Pt-Sn-Ca / Al2O3 propane dehydrogenation catalyst.

[0045] Evaluation: 2.0 g of catalyst 1 was loaded into a micro fixed bed reactor and the propane gas volumetric space velocity was controlled to be 1000 h -1 , hydrogen / propane flow ratio 1:3, reaction pressure is atmospheric pressure, bed temperature is 600°C, and the reaction products are analyzed by Agilent 7890A gas chromatograph. The results are shown in Table 2.

[0046] Example 3

[0047] In this example, catalyst 3, Pt-Sn-La / Al2O3, was prepared and its catalytic performance in the dehydrogenation of propane to propylene was tested.

[0048] Preparation: 1) At 60°C, 5.61g of La(NO3)3·6H2O and 3.11g of urea were dissolved in 100mL of deionized water, and a clear and transparent solution was obtained after stirring. Subsequently, 100g of γ-Al2O3 (100-200 mesh) was added to the transparent solution, sealed and immersed at 60°C for 12h, and then the aqueous solution was filtered out. The remaining γ-Al2O3 was soaked and washed three times with deionized water (120mL×3), placed at 100°C for 12h in vacuum drying, and finally calcined at 600°C for 5h;

[0049] 2) Repeat step 2) in Example 1 to obtain a Pt-Sn-La / Al2O3 propane dehydrogenation catalyst.

[0050] Evaluation: 2.0 g of catalyst 1 was loaded into a micro fixed bed reactor and the propane gas volumetric space velocity was controlled to be 1000 h -1 , hydrogen / propane flow ratio 1:3, reaction pressure is atmospheric pressure, bed temperature is 600°C, and the reaction products are analyzed by Agilent 7890A gas chromatograph. The results are shown in Table 2.

[0051] Example 4

[0052] In this example, catalyst 4, Pt-Sn-Ce / Al2O3, was prepared and its catalytic performance in the dehydrogenation of propane to propylene was tested.

[0053] Preparation: 1) At 60°C, 5.58g of Ce(NO3)3·6H2O and 3.09g of urea were dissolved in 100mL of deionized water, and a clear and transparent solution was obtained after stirring. Subsequently, 100g of γ-Al2O3 (100-200 mesh) was added to the transparent solution, sealed and immersed at 60°C for 12h, and then the aqueous solution was filtered out. The remaining γ-Al2O3 was soaked and washed three times with deionized water (120mL×3), placed at 100°C for 12h in vacuum drying, and finally calcined at 600°C for 5h;

[0054] 2) Repeat step 2) in Example 1 to obtain a Pt-Sn-Ce / Al2O3 propane dehydrogenation catalyst.

[0055] Evaluation: 2.0 g of catalyst 1 was loaded into a micro fixed bed reactor and the propane gas volumetric space velocity was controlled to be 1000 h -1 , hydrogen / propane flow ratio 1:3, reaction pressure is atmospheric pressure, bed temperature is 600°C, and the reaction products are analyzed by Agilent 7890A gas chromatograph. The results are shown in Table 2.

[0056] Example 5

[0057] A method for preparing a catalyst for producing propylene by dehydrogenating propane comprises the following steps:

[0058] S1, first impregnation: impregnate the γ-Al2O3 carrier in a sodium carbonate solution containing Ca(NO3) at an impregnation temperature of 80°C, filter it, wash it with deionized water at 80°C, dry it for 12 hours, and calcine it at 600°C for 4 hours to obtain the first catalyst precursor; control the molar ratio of the modified metal additive Ca(NO3) to sodium carbonate in the solution to be 1:3;

[0059] S2, second impregnation: impregnating the first catalyst precursor in an anhydrous ethanol solution of SnCl2·2H2O, removing the solvent under reduced pressure and drying to obtain a second catalyst precursor;

[0060] S3, third impregnation: the second catalyst precursor was impregnated in an aqueous solution of H2PtCl6·6H2O, dried at 80°C for 12h after the impregnation, and then calcined at 6000°C for 4h to obtain catalyst 5. The composition of catalyst 5 is shown in Table 1. The catalytic performance of catalyst 5 was evaluated by the same method as in Example 4, and the results are shown in Table 2.

[0061] Example 6

[0062] A method for preparing a catalyst for producing propylene by dehydrogenating propane comprises the following steps:

[0063] S1, first impregnation: impregnate the γ-Al2O3 carrier in a sodium citrate solution containing KNO3, control the molar ratio of the modified metal additive KNO3 to the weak base sodium citrate in the solution to be 1:8, and the impregnation temperature to be 100°C, then filter, wash with deionized water at 100°C, dry for 24 hours, and calcine at 600°C for 6 hours to obtain the first catalyst precursor;

[0064] S2, second impregnation: impregnating the first catalyst precursor in an anhydrous ethanol solution of SnCl2·2H2O, removing the solvent under reduced pressure and drying to obtain a second catalyst precursor;

[0065] S3, third impregnation: the second catalyst precursor was impregnated in an aqueous solution of H2PtCl6·6H2O, dried at 100°C for 24h after the impregnation, and then calcined at 600°C for 6h to obtain catalyst 6. The composition of catalyst 6 is shown in Table 1. The catalytic performance of catalyst 6 was evaluated by the same method as in Example 4, and the results are shown in Table 2.

[0066] Example 7

[0067] A method for preparing a catalyst for producing propylene by dehydrogenating propane comprises the following steps:

[0068] S1, first impregnation: impregnate the γ-Al2O3 carrier in an ammonium bicarbonate solution containing Ce(NO3)3·6H2O, control the molar ratio of Ce(NO3)3·6H2O to ammonium bicarbonate to be 1:6, and the impregnation temperature to be 95°C, then filter, wash with deionized water at 85°C, dry for 15h, and calcine at 6000°C for 5h to obtain the first catalyst precursor;

[0069] S2, second impregnation: impregnating the first catalyst precursor in an anhydrous ethanol solution of SnCl2·2H2O, removing the solvent under reduced pressure and drying to obtain a second catalyst precursor;

[0070] S3, third impregnation: the second catalyst precursor was impregnated in an aqueous solution of H2PtCl6·6H2O, dried at 95°C for 15h after the impregnation, and then calcined at 600°C for 5h to obtain catalyst 7. The composition of catalyst 7 is shown in Table 1. The catalytic performance of catalyst 7 was evaluated by the same method as in Example 4, and the results are shown in Table 2.

[0071] Comparative Example 1

[0072] In this example, catalyst 8, Pt-Sn-K / Al2O3, was prepared and its catalytic performance in the dehydrogenation of propane to propylene was tested. This catalyst was a blank comparative example and weakly alkaline urea was not added.

[0073] Preparation: 1) Dissolve 4.65g of KNO3 in 100mL of deionized water at 60℃ and stir to obtain a clear and transparent solution. Then, add 100g of γ-Al2O3 (100-200 mesh) to the transparent solution, seal and immerse at 60℃ for 12h, and then filter out the aqueous solution. The remaining γ-Al2O3 is placed in a vacuum dryer at 100℃ for 12h, and finally calcined at 600℃ for 5h;

[0074] 2) Repeat step 2) in Example 1 to obtain a Pt-Sn-K / Al2O3 propane dehydrogenation catalyst.

[0075] Evaluation: 2.0 g of catalyst 1 was loaded into a micro fixed bed reactor and the propane gas volumetric space velocity was controlled to be 1000 h -1 , hydrogen / propane flow ratio 1:3, reaction pressure is atmospheric pressure, bed temperature is 600°C, and the reaction products are analyzed by Agilent 7890A gas chromatograph. The results are shown in Table 2.

[0076] The active components and additive contents of catalysts 1-8 are shown in Table 1, and the catalytic performance tests of the catalysts prepared in Examples 1-4 and Comparative Example 1 are shown in Table 2. The molar ratio of the modified metal additive to the weak base is 1:4.

[0077] Table 1 Contents of active components and additives of catalyst

[0078]

[0079]

[0080] Table 2 Catalytic performance of catalysts

[0081]

[0082] The test results in Table 1 and Table 2 show that: compared with the blank comparative example 1, the catalytic performance of the propane dehydrogenation catalyst can be effectively improved by modifying the alumina carrier with a weak alkaline aqueous solution (for example, a urea aqueous solution); the addition of modified metal elements can significantly improve the conversion rate of propane and the selectivity of propylene.

[0083] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A catalyst for producing propylene by dehydrogenating propane, characterized in that: The catalyst comprises a γ-Al2O3 carrier and an active component loaded on the γ-Al2O3 carrier, wherein the active component comprises 0.01-5% of Pt in the total mass of the catalyst, 0.01-5% of Sn in the total mass of the catalyst, and 0.1-20% of a modified metal element in the total mass of the catalyst; the modified metal element is one or more of an alkali metal, an alkaline earth metal, and a lanthanide metal element.

2. The catalyst for preparing propylene by dehydrogenating propane according to claim 1, characterized in that: The modified metal element is one or more of K, Na, Rb, Mg, Ca, Sr, La, Ce, Pr, and Nd.

3. A catalyst for preparing propylene by dehydrogenating propane according to claim 2, characterized in that: The modified metal element is one or more of K, Ca, La and Ce.

4. The catalyst for preparing propylene by dehydrogenating propane according to claim 1, characterized in that: The particle size of the γ-Al2O3 carrier is 40-600 mesh, preferably 100-400 mesh, and more preferably 100-200 mesh.

5. The catalyst for preparing propylene by dehydrogenating propane according to any one of claims 1 to 4, characterized in that: The active components include Pt accounting for 0.1-3% of the total mass of the catalyst, Sn accounting for 0.1-3% of the total mass of the catalyst, and a modifying metal element accounting for 0.5-15% of the total mass of the catalyst.

6. The catalyst for producing propylene by dehydrogenating propane according to claim 5, characterized in that: The active components include Pt accounting for 0.3-1% of the total mass of the catalyst, Sn accounting for 0.3-1% of the total mass of the catalyst, and a modifying metal element accounting for 1-5% of the total mass of the catalyst.

7. A method for preparing a catalyst for producing propylene by dehydrogenation of propane according to any one of claims 1 to 6, characterized in that: The γ-Al2O3 carrier is sequentially impregnated in a weak alkaline solution containing a modified metal auxiliary agent, an alcohol solution containing Sn, and a solution containing Pt, and finally the catalyst for producing propylene by dehydrogenating propane is obtained.

8. The method for preparing a catalyst for producing propylene by dehydrogenation of propane according to claim 7, characterized in that: In the weak alkaline solution containing modified metal additives: the modified metal additives are one or more of KNO3, Ca(NO3), La(NO3)3·6H2O, Ce(NO3)3·6H2O; and / or the weak base is one or more of urea, ammonia water, sodium citrate, sodium carbonate, and ammonium bicarbonate; and / or the molar ratio of the modified metal additive to the weak base in the solution is 1:(5-20), preferably 1:(3-8).

9. The method for preparing a catalyst for producing propylene by dehydrogenation of propane according to any one of claims 7 to 8, characterized in that: The following steps are involved: S1, first impregnation: impregnating the γ-Al2O3 carrier in a weak alkaline solution containing a modified metal additive, followed by filtering, washing, drying and calcining to obtain a first catalyst precursor; S2, second impregnation: impregnating the first catalyst precursor in an alcohol solution containing Sn, removing the solvent under reduced pressure and drying to obtain a second catalyst precursor; S3, third impregnation: impregnating the second catalyst precursor in a solution containing Pt, and obtaining the catalyst for producing propylene by dehydrogenation of propane through drying and calcination.

10. The method for preparing a catalyst for producing propylene by dehydrogenation of propane according to claim 9, characterized in that: In step S1: the immersion temperature is 80-100°C; and / or, the washing uses 80-100°C deionized water as a detergent; and / or, the drying time is 12-24h; and / or, the roasting temperature is 450-650°C and the roasting time is 4-6h; and / or, The Sn-containing alcohol solution in step S2 is an alcohol solution of SnCl2·2H2O; and / or, the solvent of the solution in step S2 is an anhydrous ethanol solution; and / or, the Pt-containing solution in step S3 is a solution of H2PtCl6·6H2O; and / or, the solvent of the solution in step S3 is deionized water; and / or, The drying temperature in step S3 is 80-100° C. and the drying time is 12-24 hours; and / or the roasting temperature in step S3 is 450-650° C. and the roasting time is 4-6 hours.

11. Use of the catalyst for producing propylene by dehydrogenating propane according to any one of claims 1 to 6 in propane dehydrogenation.

12. Use of the catalyst for preparing propylene by dehydrogenation of propane according to claim 11 in propane dehydrogenation, characterized in that: A fixed bed reactor, a moving bed reactor or a fluidized bed reactor is used for propane dehydrogenation; and / or, the temperature of the propane dehydrogenation reaction is 450-650°C; and / or, the catalytic temperature is 550-700°C; and / or, the propane gas volume space velocity is 500h -1 -3800h -1 ; and / or, the flow ratio of hydrogen to propane is (1:3)-(4:1).

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