Tin-doped S-1 molecular sieve platinum-based catalyst for preparing olefin through alkane dehydrogenation as well as preparation method and application of tin-doped S-1 molecular sieve platinum-based catalyst

Abstract

The invention provides a tin-doped S-1 molecular sieve platinum-based catalyst for preparing olefin through alkane dehydrogenation as well as a preparation method and application of the tin-doped S-1 molecular sieve platinum-based catalyst, the platinum-based catalyst is a Pt-coated Sn-S-1 catalyst, and the Pt-coated Sn-S-1 catalyst comprises a Sn-S-1 molecular sieve framework doped with Sn and Pt packaged in a Sn-S-1 molecular sieve crystal; the Pt content in the Pt (at) Sn-S-1 catalyst is 0.04 to 0.3 wt% and does not include 0.3 wt%; pt in the Pt (at) Sn-S-1 catalyst is dispersed in an atomic scale or a sub-nano cluster. The catalyst provided by the invention is used in the olefin preparation reaction through alkane dehydrogenation, and has excellent alkane conversion rate, olefin selectivity and catalytic stability.

Description

Technical Field

[0001] The present invention relates to the technical field of catalytic materials, and in particular to a tin-doped S-1 molecular sieve platinum-based catalyst for dehydrogenating alkanes to olefins, and a preparation method and application thereof. Background Art

[0002] Propylene is one of the most important chemical raw materials and intermediates in the petrochemical industry and organic synthesis. Currently, propylene is primarily sourced from steam cracking, catalytic cracking, methanol to propylene (MTP), and propane dehydrogenation (PDH). In recent years, PDH has become a key method for increasing propylene production, while also producing hydrogen as a by-product.

[0003] As is known to all, PDH is a reversible endothermic reaction with increasing molecular weight and is subject to thermodynamic equilibrium. Its equation is shown below:

[0004]

[0005] High temperature and low pressure are conducive to the PDH reaction. Studies have shown that the typical operating conditions of PDH are 550-750℃ and 0.1-1.0bar. Currently, the catalysts that have been industrialized are mainly divided into platinum-based (Pt) and chromium-based (CrO x ) catalysts. However, chromium-based catalysts deactivate quickly and require frequent regeneration (every 12 minutes) during use. They are also toxic, making them unsuitable for environmental friendliness and sustainable development. Therefore, non-toxic, highly efficient platinum-based catalysts have attracted extensive attention and development in both industrial applications (UOPOleflex) and academic research.

[0006] Studies have shown (see Chem. Rev. 2014, 114, 10613-10653; ACS Catal. 2015, 5, 6310-6319; ACS Catal. 2020, 10, 21, 12932–12942; Chem. Soc. Rev., 2021, 50, 3315-3354; ACS Catal. 2023, 13, 11, 7383–7394) that in the propane dehydrogenation reaction to produce propylene, the Pt particle size and dispersion directly determine the propane conversion rate and propylene selectivity; enhancing the dispersion of Pt active sites on Pt-based catalysts and reducing the size of Pt particles are effective strategies to improve the catalytic activity of Pt-based catalysts for propane dehydrogenation reactions. The addition of a secondary metal promoter (Sn, Zn, Ga, Co, Y, Mn, etc.) and the enhancement of metal-support interactions have been shown to be effective strategies for improving the propane dehydrogenation activity and prolonging the catalytic stability of single-metal Pt-based catalysts. Sn is the most widely used Pt-based metal promoter, which improves the dehydrogenation activity and propylene selectivity of Pt-based catalysts by regulating "geometric effect" and "electronic effect". Suljo Linic et al. reported that Pt1Sn1 / SiO2 (metal nanoparticles <2.0nm, 1.0wt% Pt) catalyzed pure propane (C3H8) to achieve a propane equilibrium conversion of 40.2% (reaction conditions: 580℃, WHSV=470g[C3H8]·g[Pt]) -1 ·h -1 , 720min), while having excellent propylene selectivity (>99%)

[0007] [Science.2021.373,217-222]. Compared with traditional Al2O3 supports, Pt and Sn nanoparticles impregnated on SiO2 to achieve near-atomic mixing can effectively inhibit Pt-Sn separation and SnOx formation, resulting in excellent catalytic activity and operational stability.

[0008] In recent years, molecular sieve materials have been widely used as Pt-based catalyst supports to catalyze PDH reactions due to their unique pore structure, adjustable acidity and excellent hydrothermal stability. Encapsulating subnanoscale PtM (such as PtZn, PtGa, PtSn) clusters into molecular sieves (such as Sn-Beta, S-1, ZSM-5) has become one of the most effective methods to achieve high activity and low deactivation rate and high propylene selectivity in propane dehydrogenation reactions. For example, Sun et al. found that direct hydrogen reduction with ligand protection can improve the subnano bimetallic Pt-Zn species in S-1 and developed PtZn4@S-1-H with high propylene selectivity and excellent catalytic stability, in which the Pt loading was 0.74wt% and no obvious deactivation occurred after 13000min of operation at 550°C [Angew.Chem.Int.Ed.2020.59,19540-19459]. In addition to conventional silica-alumina molecular sieves and pure silicon molecular sieves, metal heteroatoms are doped into the molecular sieve framework to construct unique heteroatom framework sites, which is beneficial to enhance the interaction between the metal and the support. Yue et al. reported that the Lewis acid sites in Sn-Beta zeolite containing framework Sn sites can effectively activate the C-H bond of propane and show excellent catalytic performance. Characterization methods such as XRD, STEM, and XPS confirmed that the Sn species was incorporated into the zeolite framework and had a strong interaction with the zeolite framework. Lewis acid is the active site of the dehydrogenation reaction, and The acid is responsible for the cracking reaction. Na-Sn-Beta-30 catalyst has the highest Lewis acid site content and the lowest / Lewis ratio, exhibiting the best PDH performance, achieving 40% propane conversion and 92% propylene selectivity. These Sn-Beta zeolites are extremely stable under harsh reaction conditions, with no obvious deactivation within 72 hours (see Journal of Catalysis 395 (2021) 155–167). In addition, the framework Sn sites can also anchor Pt, thereby improving the dispersion and stability of Pt. Wang et al. prepared an ultra-large-pore ECNU-46 zeolite containing framework Sn sites through post-treatment and introduced Pt species by impregnation. On the one hand, the framework Sn species ((SiO)Sn–OH) at the open sites on the zeolite framework can act as anchors for interaction with Pt species, which is conducive to the high dispersion of Pt. On the other hand, the framework Sn species acts as a second metal to regulate the geometric and electronic environment of the Pt species, thereby inhibiting Pt agglomeration (Chinese Journal of Structural Chemistry, 43 (2024) 100248).

[0009] However, the Pt loading in these prior art catalysts is much higher than that of industrial catalysts (0.3 wt%), resulting in high production costs. Developing low-cost Pt-based PDH catalysts that achieve high propane conversion, high propylene selectivity, and strong resistance to sintering and deactivation remains a major challenge. Summary of the Invention

[0010] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a tin-doped S-1 molecular sieve platinum-based catalyst for dehydrogenation of alkanes to olefins, as well as its preparation method and use, which can have better catalytic performance for propane dehydrogenation on the basis of low Pt loading.

[0011] To achieve this object, the present invention adopts the following technical solutions:

[0012] In the first aspect, the present invention provides a tin-doped S-1 molecular sieve platinum-based catalyst for the dehydrogenation of alkanes to olefins, wherein the tin-doped S-1 molecular sieve platinum-based catalyst is a Pt@Sn-S-1 catalyst, wherein the Pt@Sn-S-1 includes a Sn-S-1 molecular sieve skeleton doped with Sn and Pt encapsulated in the Sn-S-1 molecular sieve crystals; the Pt content in the Pt@Sn-S-1 catalyst is 0.04 to 0.3 wt% and does not include 0.3 wt%; the Pt in the Pt@Sn-S-1 catalyst is dispersed at the atomic level or in sub-nano clusters; the tin-doped S-1 molecular sieve platinum-based catalyst is used for the dehydrogenation of alkanes to olefins.

[0013] The platinum-based catalyst of the tin-doped S-1 molecular sieve provided by the present invention has the following advantages: first, the low Pt loading can reduce the cost of the catalyst, and the low Pt loading also promotes the atomic-level or sub-nano cluster dispersion of Pt; second, the present invention uses tin silicon molecular sieve as a carrier, wherein the doping of Sn in the Sn-S-1 molecular sieve framework will be beneficial to the subsequent dispersion of Pt, and the application of the ultra-small sub-nano cluster Pt@Sn-S-1 catalyst in the propane dehydrogenation to propylene reaction of propane dehydrogenation to propylene has excellent propane dehydrogenation conversion rate, propylene selectivity and catalytic stability, and has broad application prospects.

[0014] Specifically, the Pt content in the Pt@Sn-S-1 catalyst is 0.04-0.3wt% and does not include 0.3wt%. For example, it can be 0.04wt%, 0.05wt%, 0.08wt%, 0.11wt%, 0.14wt%, 0.18wt%, 0.21wt%, 0.24wt%, 0.27wt% or 0.29wt%, etc., but is not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0015] Preferably, the doping amount of Sn in the Pt@Sn-S-1 catalyst is 0.5 to 4 wt%, for example, it can be 0.5 wt%, 0.9 wt%, 1.3 wt%, 1.7 wt%, 2.1 wt%, 2.5 wt%, 2.9 wt%, 3.3 wt%, 3.7 wt% or 4 wt%, etc., but is not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0016] The tin silicon molecular sieve of the present invention is Sn-S-1, which has an MFI topological structure. The Sn-S-1 molecular sieve can be prepared by methods well known to those skilled in the art, such as conventional hydrothermal synthesis, or can be purchased commercially.

[0017] Optionally, the catalyst has an MFI topology.

[0018] Preferably, the maximum line width of the Pt@Sn-S-1 catalyst grains is 100 to 400 nm, for example, it can be 100 nm, 130 nm, 160 nm, 200 nm, 2304 nm, 260 nm, 300 nm, 330 nm, 360 nm or 400 nm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0019] Preferably, the size of Pt in the Pt@Sn-S-1 catalyst is less than 1 nm, for example, it can be 0.9 nm, 0.85 nm, 0.80 nm, 0.78 nm, 0.75 nm, 0.70 nm, 0.68 nm, 0.65 nm or 0.6 nm, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0020] The present invention can prepare a catalyst with a small Pt size by adopting tin silicon molecular sieve, obtain a higher propane conversion rate and propylene yield under the condition of low Pt loading, and has broad application prospects.

[0021] In a second aspect, the present invention provides a method for preparing the tin-doped S-1 molecular sieve platinum-based catalyst for dehydrogenation of alkanes to olefins according to the first aspect, the preparation method comprising the following steps:

[0022] Sn-S-1 molecular sieve, a structure directing agent, a platinum source and water are mixed and subjected to a hydrothermal crystallization reaction. The resulting reaction material is sequentially subjected to solid-liquid separation, drying, calcination and reduction to obtain a tin-doped S-1 molecular sieve platinum-based catalyst.

[0023] The preparation method provided in the second aspect of the present invention uses Sn-S-1 molecular sieve as a carrier, and encapsulates Pt in the catalyst by hydrothermal crystallization. The Pt nanoparticles have high dispersion and the final catalyst has excellent catalytic performance.

[0024] Preferably, the structure directing agent is selected from any one of triethylamine, tributylamine, diisopropylamine, diisobutylamine, isobutylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetramethylethyldiammonium or dimethyldiethylammonium hydroxide, or a combination of at least two thereof, wherein typical but non-limiting combinations are a combination of triethylamine and tributylamine, a combination of diisopropylamine and tributylamine, a combination of triethylamine and diisopropylamine, a combination of diisobutylamine and tributylamine, a combination of triethylamine and diisobutylamine, a combination of tetraethylammonium hydroxide and tributylamine, and a combination of tetraethylammonium hydroxide and dimethyldiethylammonium hydroxide.

[0025] Preferably, the platinum source is a solution of a complex of a platinum salt and ethylenediamine.

[0026] Preferably, the platinum salt comprises platinum nitrate and / or chloroplatinic acid.

[0027] Preferably, the concentration of ethylenediamine in the platinum source is 0.15 to 1.0 mg / mL, for example, 0.15 mg / mL, 0.25 mg / mL, 0.34 mg / mL, 0.44 mg / mL, 0.53 mg / mL, 0.63 mg / mL, 0.72 mg / mL, 0.82 mg / mL, 0.91 mg / mL or 1.0 mg / mL, but is not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0028] Preferably, the concentration of platinum ions in the platinum source is 0.2 to 0.8 mg / mL, for example, 0.2 mg / mL, 0.3 mg / mL, 0.4 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL or 0.8 mg / mL, but is not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0029] Preferably, the molar ratio of the structure directing agent to SiO2 in Sn-S-1 molecular sieve is 0.05 to 0.15:1, for example, it can be 0.05:1, 0.06:1, 0.07:1, 0.07:1, 0.08:1, 0.08:1, 0.09:1, 0.09:1, 0.1:1, 0.1:1, 0.12:1, 0.14:1 or 0.15:1, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0030] Preferably, the molar ratio of platinum in the platinum source to SiO2 in the Sn-S-1 molecular sieve is 0.0003 to 0.0005:1, for example, it can be 0.0003:1, 0.00033:1, 0.00035:1, 0.00037:1, 0.00039:1, 0.00042:1, 0.00044:1, 0.00046:1, 0.00048:1 or 0.0005:1, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0031] The present invention preferably has a molar ratio of Pt to Si within the above range. When the Pt content is too high, there are problems of large Pt particle size, poor dispersion and high cost; when the Pt content is too low, there are problems of insufficient active sites and poor dehydrogenation activity.

[0032] Preferably, the Sn / SiO2 molar ratio in the Sn-S-1 molecular sieve is 0.0025 to 0.02:1, for example, it can be 0.0025:1, 0.0030:1, 0.0035:1, 0.0040:1, 0.0045:1, 0.0050:1, 0.0060:1, 0.0069:1, 0.0070:1, 0.0080:1, 0.0085:1, 0.01:1, 0.0123:1, 0.0177:1 or 0.02:1, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0033] The present invention preferably has a molar ratio of Si:Sn within the above range. When the Sn content is too high, there are problems such as a small relative proportion of skeleton Sn sites and shielding of Pt active sites. When the Sn content is too low, there are problems such as insufficient skeleton Sn sites, poor dispersibility of Pt particles, and weak interaction between Pt and Sn.

[0034] Preferably, the temperature of the hydrothermal crystallization reaction is 150-180°C, for example, it can be 150°C, 155°C, 160°C, 165°C, 170°C, 175°C or 180°C, but is not limited to the listed values. Other values ​​not listed in this range are also applicable.

[0035] Preferably, the pressure during the hydrothermal crystallization reaction comes from the autogenous pressure during the synthesis process in the crystallization kettle.

[0036] Preferably, the hydrothermal crystallization reaction time is 8 to 24 hours, for example, it can be 8 hours, 9 hours, 10 hours, 12 hours, 15 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0037] Preferably, the calcination is performed in an inert atmosphere.

[0038] Preferably, the inert atmosphere comprises nitrogen and / or argon.

[0039] Preferably, the calcination temperature is 400-700°C, for example, it can be 400°C, 435°C, 460°C, 500°C, 530°C, 560°C, 600°C, 630°C, 660°C or 700°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0040] The present invention preferably controls the calcination temperature within the above range. When the calcination temperature is too high, there is a problem of sintering of platinum nanoparticles. When the calcination temperature is too low, there is a problem of incomplete removal of the structure directing agent.

[0041] Preferably, the calcination time is 4 to 12 hours, for example, it can be 4 hours, 4.5 hours, 5.0 hours, 5.5 hours, 6.0 hours, 6.5 hours, 7.0 hours, 7.5 hours, 8.0 hours, 8.5 hours, 9.0 hours, 9.5 hours, 10.0 hours, 10.5 hours, 11.0 hours, 11.5 hours or 12 hours, etc., but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0042] Preferably, the inert atmosphere is formed by introducing an inert gas.

[0043] Preferably, the inert gas flow rate is 50 to 200 mL / min, for example, 50 mL / min, 65 mL / min, 85 mL / min, 100 mL / min, 115 mL / min, 130 mL / min, 150 mL / min, 167 mL / min, 185 mL / min or 200 mL / min, but is not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0044] Preferably, the reduction temperature is 400-600°C, for example, it can be 400°C, 420°C, 450°C, 480°C, 500°C, 512°C, 523°C, 534°C, 545°C, 556°C, 567°C, 578°C, 589°C or 600°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0045] Preferably, the reduction is carried out in a hydrogen atmosphere.

[0046] Preferably, the reduction time is 1 to 4 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours, etc., but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0047] Preferably, the flow rate of hydrogen in the reduction is 50 to 150 mL / min, for example, 50 mL / min, 62 mL / min, 73 mL / min, 84 mL / min, 95 mL / min, 106 mL / min, 117 mL / min, 128 mL / min, 139 mL / min or 150 mL / min, but is not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0048] In a third aspect, the present invention provides a use of the platinum-based catalyst of the tin-doped S-1 molecular sieve described in the first aspect in the dehydrogenation of alkanes to olefins.

[0049] Preferably, the alkane is propane.

[0050] Preferably, the reaction temperature of the alkane dehydrogenation to olefins is 450-650°C, for example, it can be 450°C, 473°C, 495°C, 517°C, 539°C, 562°C, 584°C, 606°C, 628°C or 650°C, but is not limited to the listed values. Other values ​​not listed within this range are also applicable, preferably 450-580°C.

[0051] Preferably, the reaction pressure of the alkane dehydrogenation to olefins is 0.01 to 0.3 MPa, for example, it can be 0.01 MPa, 0.04 MPa, 0.06 MPa, 0.08 MPa, 0.1 MPa, 0.12 MPa, 0.16 MPa, 0.18 MPa, 0.2 MPa, 0.25 MPa or 0.3 MPa, but is not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0052] Preferably, the mass space velocity of alkanes in the alkane dehydrogenation to olefins is 2 to 20 h -1 , for example, it can be 2h -1 , 4h -1 , 6h -1 , 8h -1 , 10h -1 , 12h -1 , 14h -1 , 16h -1 , 18h -1 or 20h -1 The above values ​​are not limited to the above values, and other values ​​not listed in the above values ​​are also applicable.

[0053] Compared with the prior art, the present invention has at least the following beneficial effects:

[0054] (1) The tin-doped S-1 molecular sieve platinum-based catalyst provided by the present invention uses tin silicon molecular sieve Sn-S-1 as the silicon source and adopts a post-processing encapsulation method to synthesize a tin-doped S-1 molecular sieve encapsulated platinum Pt@Sn-S-1 catalyst, successfully achieving the encapsulation of highly dispersed sub-nanometer size and even unit point size Pt in the tin silicon molecular sieve Sn-S-1;

[0055] (2) The preparation method of the tin-doped S-1 molecular sieve platinum-based catalyst provided by the present invention adopts inert atmosphere calcination instead of traditional air atmosphere calcination, thereby forming and stabilizing the ultra-small sub-nano clusters of Pt@Sn-S-1 catalyst; wherein the Pt encapsulation amount is 0.04-0.3wt%, and the Sn encapsulation amount is 0.5-4.0wt%. Compared with other Pt-based catalysts used in the propane dehydrogenation to propylene process, the catalyst has an extremely low Pt dosage, which significantly reduces the ultra-small sub-nano metal clusters uniformly encapsulated in the Sn-S-1 crystal. On the one hand, it reduces the cost of the Pt-based catalyst for the propane dehydrogenation to propylene reaction, and on the other hand, it effectively controls the metal sub-nano clusters and significantly increases the catalytic stability.

[0056] (3) The present invention provides a method for preparing a tin-doped S-1 molecular sieve platinum-based catalyst, wherein Pt is encapsulated in a tin-silicon molecular sieve Sn-S-1. The post-processing encapsulation method includes: by changing the amount of Sn loaded in Sn-S-1, the Pt metal particle size can be directly regulated from the subnanometer level to the single-point platinum dispersion; this greatly improves the utilization rate of Pt, and the Pt@Sn-S-1 catalyst is used in the propane dehydrogenation reaction to produce propylene, showing excellent catalytic effect. Under preferred conditions, the initial propane conversion rate is greater than 35%, the propylene selectivity is greater than 99%, and the propylene production rate is greater than 40.0 mol[C3H6]·g[Pt]. -1 ·h -1 . BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a SEM image of the Pt@Sn-S-1 catalyst prepared in Example 1 of the present invention.

[0058] Figure 2 This is the XPS chart of the Pt@Sn-S-1 catalyst prepared in Example 1 of the present invention.

[0059] Figure 3 This is a TEM image of the Pt@Sn-S-1 catalyst prepared in Example 1 of the present invention.

[0060] Figure 4 This is a SEM image of the Pt@Sn-S-1 catalyst prepared in Example 4 of the present invention.

[0061] Figure 5 This is a TEM image of the Pt@Sn-S-1 catalyst prepared in Example 4 of the present invention.

[0062] Figure 6 This is a SEM image of the Pt@Sn-S-1 catalyst prepared in Example 5 of the present invention.

[0063] Figure 7 This is a TEM image of the Pt@Sn-S-1 catalyst prepared in Example 5 of the present invention.

[0064] Figure 8 It is a TEM image of the catalyst prepared in Comparative Example 1 of the present invention.

[0065] Figure 9 1 is a graph showing the conversion rates of the catalysts prepared in Example 1 of the present invention and Comparative Example 1 when catalyzing propane dehydrogenation reaction.

[0066] Figure 10 1 is a graph showing the propylene selectivity data of the catalysts prepared in Example 1 of the present invention and Comparative Example 1 when catalyzing propane dehydrogenation reaction.

[0067] Figure 11 1 is a graph showing the propylene yield data of the catalysts prepared in Example 1 of the present invention and Comparative Example 1 when catalyzing propane dehydrogenation reaction.

[0068] Figure 12 This is a data chart showing the conversion rates of the catalysts prepared in Example 1 and Examples 4-5 of the present invention when catalyzing propane dehydrogenation reactions.

[0069] Figure 13 This is a data diagram of propylene selectivity when the catalysts prepared in Example 1 and Examples 4-5 of the present invention catalyze propane dehydrogenation reaction.

[0070] Figure 14 This is a data chart showing the propylene yield of the catalysts prepared in Example 1 and Examples 4-5 of the present invention when catalyzing propane dehydrogenation reaction. DETAILED DESCRIPTION

[0071] To facilitate understanding of the present invention, the present invention is listed below with reference to the following embodiments.

[0072] It should be apparent to those skilled in the art that the embodiments are only intended to help understand the present invention and should not be considered as specific limitations of the present invention.

[0073] For comparative experiments, the Sn-S-1 molecular sieve frameworks in the following examples and comparative examples were prepared using the method reported by Xia et al. (see Catalysis Today 316 (2018) 193–198). Specifically, 4.16 g of TEOS was mixed with 2.67 g of a 25 wt% TPAOH aqueous solution, 5 g of deionized water, and x mL of anhydrous SnCl₄ to obtain a clear mixed solution. After aging for 4 h, the mixture was heated at 90°C with continuous stirring for 8 h to remove the alcohol vapor generated during the TEOS hydrolysis. The hydrolyzed gel was then transferred to a hydrothermal crystallization reactor lined with 100 mL of polytetrafluoroethylene and crystallized at 170°C for 72 h. The resulting product was filtered, washed with water, and dried, and then air-calcined at 550°C for 3 h to remove the organic template, thereby obtaining the Sn-S-1 support. The Sn content in the Sn-S-1 can be adjusted adaptively based on the value of x, which will not be further described.

[0074] Example 1

[0075] The present embodiment provides a tin-doped S-1 molecular sieve platinum-based catalyst for dehydrogenating alkanes to olefins and a preparation method thereof, wherein the tin-doped S-1 molecular sieve platinum-based catalyst is a Pt@Sn-S-1 catalyst, wherein the Pt@Sn-S-1 comprises a Sn-S-1 molecular sieve framework doped with Sn and Pt encapsulated in the Sn-S-1 molecular sieve framework; the Pt content in the Pt@Sn-S-1 catalyst is 0.19wt%; the Pt in the Pt@Sn-S-1 catalyst is dispersed in atomic-level or sub-nanometer clusters. The Sn doping amount in the Pt@Sn-S-1 catalyst is 1.6wt%; the maximum line width of the grains of the Pt@Sn-S-1 catalyst is 200nm; and the size of the Pt in the Pt@Sn-S-1 catalyst is 0.5nm.

[0076] The preparation method of the tin-doped S-1 molecular sieve platinum-based catalyst comprises the following steps:

[0077] (1) Hydrothermal crystallization: Sn-S-1 molecular sieve, platinum source (solution of platinum nitrate and / or chloroplatinic acid complexed with ethylenediamine), structure directing agent (tetrapropylammonium hydroxide) and water are mixed to obtain a mixed gel; the molar ratio of the components in the mixed gel is Si:TPAOH:H2O:Pt:Sn=1:0.1:10:0.0004:0.008; the mixed gel is transferred to a hydrothermal crystallization kettle, crystallized at 170°C for 12 hours, filtered, washed with water until the pH value is close to 7, taken out and placed in an oven at 105°C for 12 hours to obtain a catalyst raw powder.

[0078] (2) Calcination in an inert atmosphere: The catalyst powder obtained in step (1) was calcined in a nitrogen atmosphere at a nitrogen flow rate of 50 mL / min, a calcination temperature of 500° C., and a calcination time of 10 h to obtain a calcined catalyst.

[0079] (3) The calcined catalyst obtained in step (2) was placed in a tubular furnace and reduced at 550°C for 2 h in a pure hydrogen atmosphere with a hydrogen flow rate of 50 mL / min to obtain a Pt@Sn-S-1 catalyst, which was named A-1.

[0080] The SEM of the Pt@Sn-S-1 catalyst obtained in this example is as follows Figure 1 As shown, the Pt@Sn-S-1 catalyst has a uniform grain morphology and a maximum line width of about 200 nm.

[0081] The XPS analysis of the Pt@Sn-S-1 catalyst obtained in this example is as follows: Figure 2 As shown in the figure, the Sn peak in the Pt@Sn-S-1 catalyst is located at 487.5 eV, indicating that the catalyst contains skeleton Sn species; the Pt signal value is weak, indicating that the Pt in the catalyst is encapsulated inside the catalyst.

[0082] The TEM images of the Pt@Sn-S-1 catalyst obtained in this example are as follows: Figure 3 As shown, the average particle size of the Pt sub-nanoclusters encapsulated in the Pt@Sn-S-1 catalyst is 0.5 nm.

[0083] Example 2

[0084] The present embodiment provides a tin-doped S-1 molecular sieve platinum-based catalyst for dehydrogenating alkanes to olefins and a preparation method thereof, wherein the tin-doped S-1 molecular sieve platinum-based catalyst is a Pt@Sn-S-1 catalyst, wherein the Pt@Sn-S-1 comprises a Sn-S-1 molecular sieve framework doped with Sn and Pt encapsulated in the Sn-S-1 molecular sieve framework; the Pt content in the Pt@Sn-S-1 catalyst is 0.16wt%; the Pt in the Pt@Sn-S-1 catalyst is dispersed in atomic-level or sub-nanometer clusters. The Sn doping amount in the Pt@Sn-S-1 catalyst is 0.7wt%; the maximum line width of the grains of the Pt@Sn-S-1 catalyst is 100nm; and the size of the Pt in the Pt@Sn-S-1 catalyst is 0.9nm.

[0085] The preparation method of the tin-doped S-1 molecular sieve platinum-based catalyst comprises the following steps:

[0086] (1) Hydrothermal crystallization: Sn-S-1 molecular sieve, platinum source (solution of platinum nitrate and / or chloroplatinic acid complexed with ethylenediamine), structure directing agent (tetrapropylammonium hydroxide) and water are mixed to obtain a mixed gel; the molar ratio of the components in the mixed gel is Si:TPAOH:H2O:Pt:Sn=1:0.15:11:0.0005:0.004; the mixed gel is transferred to a hydrothermal crystallization kettle, crystallized at 160°C for 16 hours, filtered, washed with water until the pH value is close to 7.2, taken out and placed in an oven at 110°C for drying for 10 hours to obtain a catalyst raw powder.

[0087] (2) Calcination in an inert atmosphere: The catalyst powder obtained in step (1) was calcined in a nitrogen atmosphere at a nitrogen flow rate of 200 mL / min, a calcination temperature of 700° C., and a calcination time of 4 h to obtain a calcined catalyst.

[0088] (3) The calcined catalyst obtained in step (2) was placed in a tubular furnace and reduced at 500°C for 4 h in a pure hydrogen atmosphere with a hydrogen flow rate of 150 mL / min to obtain a Pt@Sn-S-1 catalyst, which was named A-2.

[0089] Example 3

[0090] The present embodiment provides a tin-doped S-1 molecular sieve platinum-based catalyst for dehydrogenating alkanes to olefins and a preparation method thereof, wherein the tin-doped S-1 molecular sieve platinum-based catalyst is a Pt@Sn-S-1 catalyst, wherein the Pt@Sn-S-1 comprises a Sn-S-1 molecular sieve framework doped with Sn and Pt encapsulated in the Sn-S-1 molecular sieve framework; the Pt content in the Pt@Sn-S-1 catalyst is 0.1wt%; the Pt in the Pt@Sn-S-1 catalyst is dispersed in atomic-level or sub-nanometer clusters. The Sn doping amount in the Pt@Sn-S-1 catalyst is 4.0wt%; the maximum line width of the grains of the Pt@Sn-S-1 catalyst is 400nm; and the size of the Pt in the Pt@Sn-S-1 catalyst is 0.6nm.

[0091] The preparation method of the tin-doped S-1 molecular sieve platinum-based catalyst comprises the following steps:

[0092] (1) Hydrothermal crystallization: Sn-S-1 molecular sieve, platinum source (solution of platinum nitrate and / or chloroplatinic acid complexed with ethylenediamine), structure directing agent (tetrapropylammonium hydroxide) and water are mixed to obtain a mixed gel; the molar ratio of the components in the mixed gel is Si:TPAOH:H2O:Pt:Sn=1:0.09:9:0.0003:0.02; the mixed gel is transferred to a hydrothermal crystallization kettle, crystallized at 180°C for 8 hours, filtered, washed with water until the pH value is close to 6.8, taken out and placed in an oven at 95°C for drying for 15 hours to obtain a catalyst raw powder.

[0093] (2) Calcination in an inert atmosphere: The catalyst powder obtained in step (1) was calcined in a nitrogen atmosphere at a nitrogen flow rate of 100 mL / min, a calcination temperature of 400° C., and a calcination time of 12 h to obtain a calcined catalyst.

[0094] (3) The calcined catalyst obtained in step (2) was placed in a tubular furnace and reduced at 600°C for 1 h in a pure hydrogen atmosphere with a hydrogen flow rate of 100 mL / min to obtain a Pt@Sn-S-1 catalyst, which was named A-3.

[0095] Example 4

[0096] This embodiment provides a tin-doped S-1 molecular sieve platinum-based catalyst for dehydrogenation of alkanes to olefins and a preparation method thereof. The preparation method is the same as Example 1, except that the molar ratio of the components in the mixed gel is Si:TPAOH:H2O:Pt:Sn=1:0.1:10:0.0004:0.006, and is named A-4. The final Sn doping amount in the Pt@Sn-S-1 catalyst is 1.1wt%, the maximum line width of the catalyst grains is approximately 150nm, and the sub-nanometer size of the metal encapsulated inside the molecular sieve is approximately 0.83nm.

[0097] The SEM image of the Pt@Sn-S-1 catalyst obtained in this example is shown in FIG. Figure 4 As shown in Figure 1, the catalyst has a uniform morphology, a smooth surface, and is nearly tetragonal; the maximum line width of the catalyst grains is about 150nm. Figure 5 , the sub-nano size of the metal encapsulated inside the molecular sieve is about 0.83nm.

[0098] Example 5

[0099] This embodiment provides a tin-doped S-1 molecular sieve platinum-based catalyst for dehydrogenation of alkanes to olefins and a preparation method thereof. The preparation method is the same as that in Example 1, except that the molar ratio of the components in the mixed gel is Si:TPAOH:H2O:Pt:Sn=1:0.1:10:0.0004:0.016. The catalyst is named A-5. The final Sn doping amount in the Pt@Sn-S-1 catalyst is 3.0wt%, the maximum line width of the catalyst grains is about 250nm, and the metal encapsulated inside the molecular sieve is dispersed at the atomic level.

[0100] The SEM image of the Pt@Sn-S-1 catalyst obtained in this example is shown in FIG. Figure 6 As shown in Figure 1, the catalyst has a uniform morphology and a rough surface; the maximum line width of the catalyst grains is about 250nm. The TEM image of the Pt@Sn-S-1 catalyst obtained in this example is shown in Figure 1. Figure 7As shown, the metal species encapsulated inside the molecular sieve are in a unit-site distribution state.

[0101] Example 6

[0102] This example provides a tin-doped S-1 molecular sieve platinum-based catalyst for the dehydrogenation of alkanes to olefins and its preparation method. The preparation method is identical to Example 1, except that the molar ratio of the components in the mixed gel is Si:Sn = 1:0.05. The catalyst is designated A-6 and will not be further described here. The final Sn doping level in the Pt@Sn-S-1 catalyst is 9.9 wt %, the maximum linewidth of the catalyst grains is approximately 300 nm, and the subnanometer size of the metal encapsulated within the molecular sieve is approximately 1.1 nm.

[0103] Compared with Example 1, the Sn content in the catalyst obtained in this example is relatively high, which makes the catalyst surface rough, the grain size increases, and irregular layered SnO2 crystals dispersed on the catalyst surface, which reduces the relative proportion of skeleton Sn sites.

[0104] Example 7

[0105] This example provides a tin-doped S-1 molecular sieve platinum-based catalyst for the dehydrogenation of alkanes to olefins and its preparation method. The preparation method is identical to Example 1, except that the molar ratio of the components in the mixed gel is Si:Sn = 1:0.001. The catalyst is designated A-7 and will not be further described here. The final Sn doping level in the Pt@Sn-S-1 catalyst is 0.2 wt %, the maximum linewidth of the catalyst grains is approximately 150 nm, and the metal nanoparticles encapsulated within the molecular sieve are approximately 2 nm in size.

[0106] Compared with Example 1, the Sn content in this example is relatively low, resulting in insufficient Sn sites in the catalyst framework and poor dispersibility of Pt particles. The size of the metal nanoparticles encapsulated inside the molecular sieve increases significantly, with an average particle size of 2 nm.

[0107] Example 8

[0108] This example provides a tin-doped S-1 molecular sieve platinum-based catalyst for the dehydrogenation of alkanes to olefins and its preparation method. The preparation method is identical to that of Example 1, except for the calcination temperature of 800°C. This method, designated A-8, is not further described here. The maximum linewidth of the final catalyst grains is approximately 200 nm, and the subnanometer size of the metal encapsulated within the molecular sieve is approximately 1.5 nm.

[0109] Compared with Example 1, the calcination temperature in the preparation method described in this example is relatively high, which easily causes the problem of sintering of platinum nanoparticles. The metal particles encapsulated inside the molecular sieve in the obtained catalyst are large in size, about 1.5 nm.

[0110] Comparative Example 1

[0111] This comparative example provides a Pt / Sn-S-1 impregnated catalyst and a preparation method thereof, the preparation method comprising:

[0112] (1) The molar ratio of Si to Sn components in Sn-S-1 tin silicon molecular sieve is the same as that described in Example 1, that is, Si:Sn=1:0.008.

[0113] (2) Preparation of impregnation solution: The platinum source (the same as in Example 1) was mixed with water to obtain a mixed solution, wherein the concentration of Pt in the mixed solution was 0.5 mg / mL.

[0114] (3) Synthesis of impregnated catalyst Pt / Sn-S-1: 3 mL of the mixed solution obtained in step (2) was taken and impregnated on 1 g of the tin-silicon molecular sieve described in step (1). The impregnated sample was dried in an oven at 105°C for 12 h.

[0115] (4) The calcination and reduction conditions of the sample obtained in step (3) were the same as those in Example 1, and the resulting Pt / Sn-S-1 catalyst was named D-1.

[0116] The TEM results of the obtained catalyst are shown in Figure 8 As shown in Figure 2, the average particle size of the PtSn nanoclusters encapsulated in the catalyst is about 2.1 nm.

[0117] Comparative Example 2

[0118] This comparative example provides a PtSn / S-1 impregnated catalyst and a preparation method thereof, the preparation method comprising:

[0119] (1) Synthesis of S-1 molecular sieve by hydrothermal crystallization: Tetraethyl orthosilicate, a structure directing agent, an alkali source and water are mixed to obtain a mixed solution; the molar ratio of the components in the mixed solution is Si:TPAOH:H2O=1:0.1:10; the mixed solution is heated and stirred at 80°C for 8 hours, the gel is transferred to a hydrothermal crystallization kettle, crystallized at 170°C for 12 hours, filtered, washed with water until the pH value is close to 7, taken out and placed in an oven for drying at 105°C for 12 hours to obtain S-1 molecular sieve.

[0120] (2) The catalyst powder obtained in step (1) was calcined in an air atmosphere at a temperature of 500° C. for 10 h.

[0121] (3) Preparation of impregnation solution: Mix the platinum precursor, anhydrous SnCl4 and deionized water to obtain mixed solution 3, in which the concentration of Pt is 0.5 mg / mL and the concentration of Sn is 5 mg / mL.

[0122] (4) Synthesis of impregnated catalyst PtSn / S-1: 3 mL of the mixed solution 3 obtained in step (3) was taken and impregnated on 1 g of the S-1 molecular sieve described in step (2). The impregnated sample was dried in an oven at 105° C. for 12 h.

[0123] (5) Calcination and hydrogen reduction: The calcination and reduction conditions of the sample obtained in step (4) were the same as those in Example 1, and the obtained PtSn / S-1 catalyst was named D-2.

[0124] Comparative Example 3

[0125] This comparative example provides a tin-doped S-1 molecular sieve platinum-based catalyst for the dehydrogenation of alkanes to olefins and its preparation method. The preparation method is identical to Example 1, except that the molar ratio of the components in the mixed gel is Si:Pt = 1:0.0001. The catalyst is designated A-9 and will not be further described here. The final Pt loading in the Pt@Sn-S-1 catalyst is 0.03wt%, the maximum line width of the catalyst grains is approximately 200nm, and the metal subnanometer size encapsulated within the molecular sieve is approximately 0.3nm.

[0126] Compared with Example 1, the Pt content in the catalyst of this comparative example is relatively low, which easily leads to the problem of insufficient Pt active sites, thereby resulting in low propane conversion rate of the catalyst and rapid deactivation, as shown in Table 1.

[0127] Application Example 1

[0128] This application example provides a method for preparing propylene by dehydrogenating propane, which includes the following steps:

[0129] A-1 catalyst with a particle size of 20-40 mesh was placed in the middle of the fixed bed reactor, and propane and nitrogen were introduced to carry out dehydrogenation reaction under the action of A-1 catalyst. The dehydrogenation reaction temperature was 550 ° C, the pressure was 0.1 MPa, and the mass space velocity of propane was 10h -1 , the volume ratio of nitrogen to propane is 7:3.

[0130] Application Example 2

[0131] This application example provides a method for preparing propylene by dehydrogenating propane, which includes the following steps:

[0132] A-2 catalyst with a particle size of 20-40 mesh was placed in the middle of the fixed bed reactor, and propane and nitrogen were introduced to carry out dehydrogenation reaction under the action of A-2 catalyst. The dehydrogenation reaction temperature was 650 ° C, the pressure was 0.1 MPa, and the mass space velocity of propane was 15h -1 , the volume ratio of nitrogen to propane is 7:3.

[0133] Application Example 3

[0134] This application example provides a method for preparing propylene by dehydrogenating propane, which includes the following steps:

[0135] A-3 catalyst with a particle size of 20-40 mesh was placed in the middle of the fixed bed reactor, and propane and nitrogen were introduced to carry out dehydrogenation reaction under the action of A-3 catalyst. The dehydrogenation reaction temperature was 580 ° C, the pressure was 0.01 MPa, and the mass space velocity of propane was 2h -1 , the volume ratio of nitrogen to propane is 1:1.

[0136] Application Examples 4 to 8 and Comparative Application Examples 1 to 2

[0137] Application Examples 4 to 8 and Comparative Examples 1 to 2 provide a method for preparing propylene by dehydrogenating propane. Except for using the catalysts in Examples 4 to 9 and Comparative Examples 1 to 2, the rest of the method for preparing propylene by dehydrogenating propane is the same as that in Application Example 1, and will not be repeated here.

[0138] Application Examples 9-11

[0139] Application Examples 9 to 11 provide a method for preparing propylene by dehydrogenating propane, wherein the mass space velocity of propane is 7.25h -1 , 10.87h -1 and 18.1h -1 Except for this, the rest are the same as those in Application Example 1 and will not be described again here.

[0140] Application Examples 12-14

[0141] Application Examples 12 to 14 provide a method for preparing propylene by dehydrogenating propane. The method for preparing propylene by dehydrogenating propane is the same as Application Examples 9 to 11 except that nitrogen is not fed and pure propane is used as feed, and the rest is not repeated here.

[0142] Application Example 15

[0143] Application Example 15 provides a method for preparing propylene by dehydrogenating propane. The method for preparing propylene by dehydrogenating propane is the same as Application Example 1 except that the temperature of the dehydrogenation reaction is 600°C, and is not described again here.

[0144] In the examples and comparative examples, the SEM spectra were tested using a Quanta200F scanning electron microscope produced by FEI Company. The test conditions were as follows: after the sample was dried, it was vacuum evaporated to increase the conductivity and contrast effect. The accelerating voltage of the analysis electron microscope was 20.0 kV and the magnification was 1-30K.

[0145] TEM spectra were measured using a JEOL JEM2010F field emission transmission electron microscope. The test conditions were as follows: the sample was dried and then vacuum evaporated to increase conductivity and contrast. The accelerating voltage of the electron microscope was 20.0 kV, and the magnification was 1-20K.

[0146] The data graphs of the conversion rate, propylene selectivity and propylene yield of the catalyst in the propane dehydrogenation reaction of Application Example 1 and Comparative Example 1 are shown as follows: Figures 9-12 As shown, from Figures 9-12 It can be seen that the catalyst provided in Application Example 1 has significantly better conversion rate and propylene selectivity. The data graphs of conversion rate, propylene selectivity and propylene yield of the catalysts in Application Examples 1 and Application Examples 4-5 when catalyzing propane dehydrogenation reaction are shown in Figures 1 and 10, respectively. Figures 12-14 As shown, from Figures 12-14 It can be seen that propane conversion is significantly affected by Sn content. Catalyst A-5 has the highest initial propane conversion, approaching the PDH thermodynamic equilibrium conversion (45%). Catalyst A-1 has an initial propane conversion of 36.03% and a propane conversion of 34.6% after 480 min of operation, demonstrating stable operation throughout the reaction. Catalyst A-4, with a Sn doping level of 1.1 wt%, has a lower initial propane conversion of 33.9%. Propylene selectivity for all three catalysts is greater than 99%. This indicates that increasing the framework Sn doping level is beneficial for improving the propane conversion of the catalyst. However, the effect of Sn doping on catalyst stability is the opposite. At higher Sn doping levels, catalyst A-5 exhibits poor stability, with the conversion decreasing to 41.62% after 480 min of operation. Catalyst 0.2Pt@Sn-S-1-1# exhibits a conversion of 33.2% after 480 min of operation, a decrease of only 0.7% compared to the initial propane conversion. This demonstrates that an appropriate Sn doping level is beneficial for balancing catalyst conversion and operational stability.

[0147] The calculation formula of the inactivation coefficient is as follows:

[0148]

[0149] Among them, Conv. Final is the propane conversion rate after long-term operation; Conv. Initial is the propane conversion during initial operation.

[0150] The conversion rates and selectivities in the above application examples and comparative application examples were calculated, and the test results of the above application examples and comparative application examples are shown in Table 1.

[0151] Table 1

[0152]

[0153]

[0154] As can be seen from Table 1, when the catalyst of the present invention is used in the reaction process of catalyzing the dehydrogenation of propane to propylene, the conversion rate and reaction stability of propane are significantly higher than those of the catalysts obtained in Comparative Examples 1 and 2. In addition, the product has extremely high selectivity for propylene, which can reach more than 99%, thereby reducing the cost of product separation and having significant economic benefits.

[0155] As can be seen from Table 1 above, the catalyst of the present invention is used in the process of catalytic propane dehydrogenation to propylene. The catalyst of Example 1 has excellent stability in long-term operation. The deactivation coefficient is very low, less than 0.005h after 102.5h (6150min) of operation. -1 The catalyst described in Example 1 did not show any obvious deactivation phenomenon when operated under the harsh reaction conditions of pure propane feed.

[0156] The above results show that in the synthesis method of the catalyst described in the present invention, sub-nanoclusters or even single-site Pt are encapsulated in the tin silicon molecular sieve Sn-S-1. The resulting low-Pt catalyst catalyzes the propane dehydrogenation to propylene reaction with excellent characteristics of high propane conversion rate, high propylene selectivity, and high operational stability, thereby achieving the goal of high propylene yield at a low Pt content and improving the economic benefits of the catalyst.

[0157] The present invention uses the above-described embodiments to illustrate the detailed features of the present invention. However, the present invention is not limited to the above-described detailed features, which does not mean that the present invention must rely on the above-described detailed features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for the selected technical features of the present invention, additions to auxiliary technical features, and selections of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A tin-doped S-1 molecular sieve platinum-based catalyst for dehydrogenation of alkanes to olefins, characterized in that: The tin-doped S-1 molecular sieve platinum-based catalyst is a Pt@Sn-S-1 catalyst, wherein the Pt@Sn-S-1 comprises a Sn-S-1 molecular sieve framework doped with Sn and Pt encapsulated in the Sn-S-1 molecular sieve crystals; The Pt content in the Pt@Sn-S-1 catalyst is 0.04 to 0.3 wt % and does not include 0.3 wt %; In the Pt@Sn-S-1 catalyst, Pt is dispersed in atomic or sub-nano clusters; The tin-doped S-1 molecular sieve platinum-based catalyst is used for dehydrogenating alkanes to produce olefins.

2. The tin-doped S-1 molecular sieve platinum-based catalyst according to claim 1, characterized in that The doping amount of Sn in the Pt@Sn-S-1 catalyst is 0.5-4 wt%; Preferably, the maximum line width of the Pt@Sn-S-1 catalyst grains is 100 to 400 nm; Preferably, the size of Pt in the Pt@Sn-S-1 catalyst is less than 1 nm.

3. A method for preparing a tin-doped S-1 molecular sieve platinum-based catalyst for dehydrogenation of alkanes to olefins according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: Sn-S-1 molecular sieve, a structure directing agent, a platinum source and water are mixed and subjected to a hydrothermal crystallization reaction. The resulting reaction material is sequentially subjected to solid-liquid separation, drying, calcination and reduction to obtain a tin-doped S-1 molecular sieve platinum-based catalyst.

4. The preparation method according to claim 3, characterized in that The structure directing agent is selected from any one of triethylamine, tributylamine, diisopropylamine, diisobutylamine, isobutylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetramethylethyldiammonium or dimethyldiethylammonium hydroxide, or a combination of at least two thereof; Preferably, the platinum source is a solution of a complex of a platinum salt and ethylenediamine; Preferably, the platinum salt comprises platinum nitrate and / or chloroplatinic acid.

5. The preparation method according to claim 3 or 4, characterized in that The molar ratio of the structure directing agent to SiO2 in the Sn-S-1 molecular sieve is 0.05 to 0.15:1; Preferably, the molar ratio of platinum in the platinum source to SiO2 in the Sn-S-1 molecular sieve is 0.0003-0.0005:

1.

6. The preparation method according to any one of claims 3 to 5, characterized in that The Sn-S-1 molecular sieve has a Sn / SiO2 molar ratio of 0.0025 to 0.02:

1.

7. The preparation method according to any one of claims 3 to 6, characterized in that The temperature of the hydrothermal crystallization reaction is 150-180°C; Preferably, the hydrothermal crystallization reaction time is 8 to 24 hours.

8. The preparation method according to any one of claims 3 to 7, characterized in that The calcination is carried out in an inert atmosphere; Preferably, the inert atmosphere comprises nitrogen and / or argon; Preferably, the calcination temperature is 400-700°C; Preferably, the roasting time is 4 to 12 hours; Preferably, the inert atmosphere is formed by introducing an inert gas; Preferably, the inert gas flow rate is 50 to 200 mL / min; Preferably, the reduction temperature is 400-600°C; Preferably, the reduction is carried out in a hydrogen atmosphere; Preferably, the reduction time is 1 to 4 hours; Preferably, the flow rate of hydrogen during the reduction is 50 to 150 mL / min.

9. Use of the platinum-based catalyst of the tin-doped S-1 molecular sieve according to claim 1 or 2 in the dehydrogenation of alkanes to olefins.

10. The use according to claim 9, characterized in that The alkane is propane; Preferably, the reaction temperature of the alkane dehydrogenation to olefins is 450-650°C; Preferably, the reaction pressure of the alkane dehydrogenation to olefins is 0.01 to 0.3 MPa; Preferably, the mass space velocity of alkanes in the alkane dehydrogenation to olefins is 2 to 20 h -1 .

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