Preparation method of Pt-based alloy catalyst for preparing propylene through propane dehydrogenation

Abstract

The invention discloses a preparation method of a Pt-based alloy catalyst for preparing propylene through propane dehydrogenation, and belongs to the technical field of chemical catalysis. According to the catalyst, a silicalite-1 (S1) molecular sieve is used as a carrier, PtX alloy is used as an active component, the active component is Pt and any one of Sn, Zn, La, Fe, Cu, In and Ga to form an alloy phase, the molar ratio of tetraethyl orthosilicate (TEOS, 98%) to tetrapropylammonium hydroxide of a template agent is (1: 1)-(1: 3), the loading capacity of Zn is 0.2-1.8 wt%, and the loading capacity of Pt is 0.1-1.0 wt%. PtX alloy nano-particles are packaged in pores of the silicalite-1 molecular sieve, and sintering and carbon deposition phenomena of the PtX alloy nano-particles, especially PtZn-coated silicalite-1, are remarkably inhibited by utilizing a confinement effect of the molecular sieve, so that the stability of the catalyst is greatly improved, and the service life of the catalyst is greatly prolonged. Experimental results show that the method can realize higher propylene yield and selectivity, and is efficient, stable and environment-friendly.

Description

Technical Field

[0001] The present invention relates to the field of chemical catalysis, and more particularly, to a method for preparing a Pt-based alloy catalyst for propane dehydrogenation to propylene. Background Art

[0002] As a key petrochemical basic raw material, propylene plays an irreplaceable role in the production of chemical products such as polypropylene, acrylonitrile, and propylene oxide. With the continuous growth of the market demand for propylene, propane dehydrogenation to propylene technology (Propane Dehydrogenation, PDH) has become an important way to increase propylene production due to its advantages such as wide raw material sources and simple process routes.

[0003] Currently, the PDH catalysts widely used in industry are mainly divided into two categories: Pt-based catalysts and Cr-based catalysts.

[0004] Although Cr-based catalysts have cost advantages, their toxicity problems and potential environmental pollution during the reaction process limit their wide application. In addition, the activity and selectivity of Cr-based catalysts are generally low, and their stability is poor, which further restricts their further development in industrial applications.

[0005] Pt-based catalysts exhibit excellent activity and selectivity. Pt has excellent C-H bond activation ability, which can significantly reduce the activation energy of the propane dehydrogenation reaction, thereby increasing the reaction rate. At the same time, Pt-based catalysts show high propylene selectivity in the propane dehydrogenation reaction, which can effectively inhibit the occurrence of side reactions and improve the yield of the target product.

[0006] However, Pt-based catalysts also have some significant disadvantages: (1) High cost: As a precious metal, the high price of Pt limits the wide application of the catalyst; (2) Easy sintering: Under high-temperature reaction conditions, Pt particles are prone to sintering, resulting in a reduction in active sites and a decrease in catalytic performance; (3) Carbon deposition problem: The carbon deposition generated during the reaction will cover the catalyst active sites, hinder the contact between the reactants and the catalyst, and thus reduce the catalytic efficiency.

[0007] Despite the above disadvantages of Pt-based catalysts, their excellent catalytic performance still makes them irreplaceable in the field of propane dehydrogenation. Therefore, how to overcome the defects of Pt-based catalysts and develop high-efficiency, stable and economical Pt-based catalysts has become a hot and difficult point in current research. Developing high-efficiency, stable and environmentally friendly Pt-based catalysts has important practical significance for promoting the industrial application of PDH technology.

[0008] The process of producing propylene by dehydrogenation of propane has been industrialized, but existing catalysts still have problems such as low propane conversion rate and easy deactivation. Therefore, it is of great practical significance to develop propane dehydrogenation catalysts with excellent performance. In order to improve the reaction performance of propane dehydrogenation catalysts, a large number of studies have focused on catalyst optimization.

[0009] For example, patent CN108855066B discloses a catalyst with Pt, metal promoter Sn and metal promoter Na as active components, which are loaded on a spherical three-mesoporous chlorite composite carrier. However, the preparation process of the catalyst is complicated, and its best performance is only 26.2% propane conversion and 86.1% propylene selectivity. In contrast, the PtZn alloy @silicalite-1 catalyst in this patent has significant advantages such as simple preparation process, high propane conversion, high propylene selectivity, low precious metal loading, and low cost.

[0010] In addition, patent CN103420769B discloses a method for preparing propylene by dehydrogenating propane, wherein the dehydrogenation catalyst used comprises an active component selected from Pt group metals, IIB group elements, rare earth metals and IIA group metals, and the carrier is selected from at least one of α-Al2O3, γ-Al2O3, δ-Al2O3, θ-Al2O3 or spinel. Although the catalyst has a good conversion effect, its noble metal loading is high, resulting in a significant increase in cost.

[0011] In summary, the propane dehydrogenation catalysts in the prior art generally have the problems of complex preparation process, high precious metal loading, high cost, etc. Therefore, developing a catalyst with simple preparation process, low precious metal loading, low cost, high propane conversion rate, selectivity and stability has become a technical problem to be solved in the field. Summary of the invention

[0012] The purpose of the present invention is to provide an efficient, stable and environmentally friendly Pt-based alloy catalyst, in particular a method for preparing a PtZn alloy@silicalite-1 catalyst, so as to solve the problems of complex catalyst preparation process, high precious metal loading, high cost, and insufficient propane conversion rate and selectivity in the prior art.

[0013] The catalyst of the present invention is prepared by a one-step synthesis method and has the following significant advantages:

[0014] (1) Simple preparation process: The preparation of Pt-based alloy catalysts is achieved through a one-step synthesis method, which simplifies the complex process of traditional multi-step synthesis;

[0015] (2) Low precious metal loading: The loading of the optimal catalyst is 0.2%, and the loading of Pt is significantly reduced, thereby greatly reducing the catalyst cost;

[0016] (3) Excellent catalytic performance: The propane conversion rate, propylene selectivity, and stability of the optimal catalyst are significantly higher than those of the catalysts in the prior art.

[0017] (4) Environmentally friendly and pollution-free, meeting the requirements of green chemistry.

[0018] The preparation method of the Pt-based alloy catalyst for propane dehydrogenation to propylene provided by the present invention has the characteristics of high efficiency, stability, and environmental friendliness, and can effectively overcome the deficiencies of the prior art.

[0019] The present invention adopts the following technical solutions:

[0020] The present invention provides a preparation method of a Pt-based alloy catalyst for propane dehydrogenation to propylene. Propane, H2, and helium (volume ratio of propane:H2 = 1:1) are introduced into a fixed-bed reactor loaded with the metal catalyst at a gas velocity of 20 mL / min, and a catalytic reaction is carried out at 600 °C and atmospheric pressure. Among them, the metal catalyst is composed of a silicalite-1 support and a metal active component, and the metal active component is an alloy phase composed of Pt and any one of Sn, Zn, La, Fe, Cu, In, and Ga. The loading amount of the metal active component Pt accounts for 0.2% of the total mass of the metal catalyst, and the metal active components Sn, Zn, La, Fe, Cu, In, and Ga account for 0.2 - 1.8 wt% of the total mass of the metal catalyst.

[0021] Furthermore, in the reaction gas, the content of propane is 4 vol% - 20 vol%, the content of H2 is 4 vol% - 20 vol%, and the content of helium is 60 vol% - 92 vol%.

[0022] Furthermore, in the PtX@silicalite-1 metal, X is preferably Zn.

[0023] Furthermore, the molar ratio of the template agent is tetraethyl orthosilicate (TEOS):tetrapropylammonium hydroxide (TPAOH) = 1:1 - 1:3, and the preferred ratio of the template agent is 1:2.

[0024] Furthermore, the loading amount of Zn is 0.2 - 1.8 wt%, preferably 1.0 wt%.

[0025] Furthermore, the loading amount of Pt is 0.1 - 1.0 wt%, preferably 0.2 wt%.

[0026] Furthermore, in the metal catalyst, the loading amount of Zn is preferably 1.0 wt%, and the loading amount of Pt is preferably 0.2 wt%. When the metal catalyst is Pt 0.2％ Zn 1.0％When using silicalite-1, at 600 °C, the initial conversion rate of C3H8 can reach 70.3%, and the selectivity of C3H6 is as high as 97.3%. Even after continuous reaction for 36 hours, the conversion rate of propane can still be stably maintained at 61.4%.

[0027] Through the catalyst evaluation experiment of the present invention, it can be clearly confirmed that Pt 0.2％ Zn 1.0％ @The synergistic effect between Pt and Zn in the S1 catalyst. This synergy not only significantly improves the activity and stability of the catalyst but also effectively maintains the high conversion rate of propane. The introduction of Zn finely adjusts the dehydrogenation ability of Pt, thereby effectively suppressing the occurrence of side reactions and significantly enhancing the selectivity of propylene. Therefore, Pt 0.2％ Zn 1.0％ @The S1 bimetallic alloy catalyst exhibits excellent catalytic activity, stability, and selectivity in the propane dehydrogenation reaction, and its comprehensive performance is significantly superior to that of the monometallic catalysts Pt 0.2％ @S1 and Zn 1.0％ @S1.

[0028] Furthermore, the present invention provides a preparation method for a Pt-based alloy catalyst for propane dehydrogenation to propylene, comprising the following steps:

[0029] S1: Calculate the masses of chloroplatinic acid hexahydrate and X metal hydrate required on PtX@S1, where X is any one of Sn, Zn, La, Fe, Cu, In, and Ga;

[0030] S2: Using a one-step synthesis method, tetraethyl orthosilicate (TEOS): tetrapropylammonium hydroxide (TPAOH) with a molar ratio of 1:2 is mixed and added to a tetrafluorine inner liner. Subsequently, the required masses of metal chloroplatinic acid hexahydrate and X metal hydrate are added, and the mixture is stirred at room temperature for 1 hour;

[0031] S3: Transfer the stirred mixture to a hydrothermal reaction kettle, heat and stir it at 180 °C for 24 hours;

[0032] S4: Take out the reacted mixture from the hydrothermal reaction kettle and wash it by centrifugation three times with ethanol;

[0033] S5: Place the washed sample in an oven at 60 °C for drying;

[0034] S6: Put the dried sample into a muffle furnace and calcine it at 550 °C for 6 hours to obtain the PtX@silicalite-1 catalyst.

[0035] S7: Tablet the prepared sample and screen out a particle size of 40 - 60 mesh for subsequent use

[0036] Furthermore, the present invention provides a performance testing method for a Pt-based alloy catalyst for propane dehydrogenation to propylene. The specific process is as follows:

[0037] S1: Open the evaluation device panel of the fixed-bed reactor and start the hydrogen-air generator and gas chromatograph (GC).

[0038] S2: Fill the metal catalyst into the fixed-bed reactor and pre-treat the catalyst with 10 vol% H2 / He at a temperature of 600 °C for 60 minutes of purging.

[0039] S3: Introduce the reaction gas into the fixed-bed reactor. The reaction gas includes propane, hydrogen, and helium, with a gas flow rate of 20 mL / min. Perform the catalytic reaction at a reaction temperature of 600 °C and atmospheric pressure, where the content of propane is 4 vol% - 20 vol%, the content of H2 is 4 vol% - 20 vol%, and the content of helium is 60 vol% - 92 vol%.

[0040] S4: Use the gas chromatograph to detect the components of the tail gas after the reaction, and calculate the conversion rate of propane and the selectivity of propylene based on the measured concentration data.

[0041] The beneficial effects of the present invention are as follows:

[0042] (1) Simple preparation process: The Pt-based alloy@silicalite-1 catalyst is prepared by a one-step synthesis method, avoiding the complexity of traditional multi-step synthesis processes, and significantly reducing the preparation cost and time.

[0043] (2) Low noble metal loading: By optimizing the loading ratio of Pt and Zn, while ensuring high catalytic activity, the usage amount of the noble metal Pt is significantly reduced, thereby greatly reducing the catalyst cost.

[0044] (3) Unique catalyst structure design: By encapsulating PtZn alloy nanoparticles in the pores of silicalite-1 zeolite and utilizing the confinement effect of the zeolite, the sintering and carbon deposition of PtZn alloy nanoparticles are effectively inhibited, thereby improving the stability and service life of the catalyst.

[0045] (3) Excellent catalytic performance: The catalyst provided by the present invention exhibits excellent propane conversion rate, propylene selectivity, and stability in the propane dehydrogenation reaction, significantly superior to the catalysts in the prior art.

[0046] (4) High environmental friendliness: No harmful reagents are required during the catalyst preparation process, and the amount of by-products generated during the reaction is small, which is environmentally friendly. It also avoids the environmental pollution problems caused by Cr-based catalysts, and is an environmentally friendly catalyst for propane dehydrogenation to propylene.

[0047] (5) Wide application: The preparation process of this catalyst is simple and the cost is low, making it suitable for industrial production and application. This catalyst is not only applicable to the propane dehydrogenation reaction to produce propylene, but can also be extended to other light alkane dehydrogenation reactions, showing broad application prospects. Description of the drawings

[0048] Figure 1 is Pt 0.2％ Sn 0.6％ @S1, Pt 0.2％ Zn 0.6％ @S1, Pt 0.2％ La 0.6％ @S1, Pt 0.2％ Fe 0.6％ @S1, Pt 0.2％ Cu 0.6％ @S1, Pt 0.2％ In 0.6％ @S1, Pt 0.2％ Ga 0.6％ Evaluation test results of @S1. Reaction conditions: 600 °C, gas velocity 20 mL·min -1 , C3H8:H2:He = 10%:10%:80%, mass space velocity is 12000 mL·g cat -1 ·h -1 .

[0049] Figure 2 is under different molar ratios of template agents (tetraethyl orthosilicate: tetrapropylammonium hydroxide = 1:1 to 1:3), Pt 0.2％ Zn 0.6％ @S1(1:1), Pt 0.2％ Zn 0.6％ @S1(1:2) and Pt 0.2％ Zn 0.6％ Evaluation test results of @S1(1:3). Reaction conditions: 600 °C, gas velocity 20 mL·min -1 , C3H8:H2:He = 10%:10%:80%, mass space velocity is 12000 mL·g cat -1 ·h -1 .

[0050] Figure 3 is under different Zn loadings, Pt 0.2％ Zn 0.2％ @S1, Pt 0.2％ Zn 0.6％ @S1, Pt 0.2％ Zn 1.0％ @S1, Pt 0.2％ Zn 1.4％@S1 and Pt 0.2％ Zn 1.8％ Evaluation test results of @S1. Reaction conditions: 600 °C, gas velocity 20 mL·min -1 , C3H8:H2:He = 10%:10%:80%, mass space velocity is 12000 mL·g cat -1 ·h -1 .

[0051] Figure 4 For different Pt loadings, Pt 0.1％ Zn 1.0％ @S1, Pt 0.2％ Zn 1.0％ @S1, Pt 0.3％ Zn 1.0％ @S1, Pt 0.5％ Zn 1.0％ @S1 and Pt 1.0％ Zn 1.0％ Evaluation test results of @S1. Reaction conditions: 600 °C, gas velocity 20 mL·min -1 , C3H8:H2:He = 10%:10%:80%, mass space velocity is 12000 mL·g cat -1 ·h -1 .

[0052] Figure 5 and Figure 6 For the bimetallic catalyst Pt 0.2％ Zn 1.0％ @S1 and the monometallic catalyst Pt 0.2％ @S1 and Zn 1.0％ Comparison of the evaluation test results of @S1. Reaction conditions: 600 °C, gas velocity 20 mL·min -1 , C3H8:H2:He = 10%:10%:80%, mass space velocity is 12000 mL·g cat -1 ·h -1 .

[0053] Figure 7 For Pt 0.2％ Zn 1.0％ Stability test of @S1 within 36 h. Reaction conditions: 600 °C, gas velocity 20 mL·min -1 , C3H8:H2:He = 10%:10%:80%, mass space velocity is 12000 mL·g cat -1 ·h -1 .

[0054] Figure 8 For Pt0.2％ Zn 1.0％ @S1 and R-Pt prepared by the traditional impregnation method 0.2％ Zn 1.0％ / S1 evaluation test result comparison. Reaction conditions: 600 °C, gas velocity 20 mL·min -1 , C3H8:H2:He = 10%:10%:80%, mass space velocity is 12000 mL·g cat -1 ·h -1 .

[0055] Figure 9 is Pt 0.2％ Zn 1.0％ @S1, Pt 0.2％ @S1, Zn 1.0％ @S1 and R-Pt prepared by the traditional impregnation method 0.2％ Zn 1.0％ / S1 XRD pattern.

[0056] Figure 10 Pt 0.2％ Zn 1.0％ @S1 HRTEM image. Specific implementation manners

[0057] The following further illustrates the present invention in conjunction with embodiments, but the protection scope of the present invention is not limited to the scope shown in the embodiments.

[0058] Example 1 Preparation of Pt 0.2％ Sn 0.6％ @S1

[0059] Comprises the following steps:

[0060] S1: Calculate the mass of chloroplatinic acid hexahydrate and stannous chloride dihydrate required on Pt 0.2％ Sn 0.6％ @S1;

[0061] S2: Using a one-step synthesis method, 10.0 g of tetraethyl orthosilicate is dropped into a tetrafluoro inner liner of an aqueous solution containing 17.7 g of tetrapropylammonium hydroxide (25 wt%), and then 1.53 mL of an aqueous solution of metal chloroplatinic acid hexahydrate (0.01 g / mL) and 3.31 mL of an aqueous solution of stannous chloride dihydrate (0.01 g / mL) are added, and stirred at room temperature for 1 hour;

[0062] S3: Transfer the stirred mixture to a hydrothermal reaction kettle, heat and stir at 180 °C for 24 hours;

[0063] S4: Take out the reacted mixture from the hydrothermal reaction kettle and wash it by centrifugation three times with ethanol;

[0064] S5: Place the washed sample in an oven at 60 °C for drying;

[0065] S6: Put the dried sample into a muffle furnace and calcine it at 550 °C for 6 hours to obtain the Pt 0.2％ Sn 0.6％ @S1 catalyst;

[0066] S7: Press the prepared sample and screen out a particle size of 40 - 60 mesh for subsequent use.

[0067] Example 2 Pt 0.2％ Zn 0.6％ Preparation of @S1 (template molar ratio is 1:1)

[0068] It includes the following steps:

[0069] S1: Calculate the masses of chloroplatinic acid hexahydrate and zinc nitrate hexahydrate required for Pt 0.2％ Zn 0.6％ @S1;

[0070] S2: Using the one-step synthesis method, add 10.0 g of tetraethyl orthosilicate dropwise to an aqueous solution containing 9.8 g of tetrapropylammonium hydroxide (25 wt%) in a Teflon liner, then add 1.53 mL of an aqueous solution of metal chloroplatinic acid hexahydrate (0.01 g / mL) and 0.08 g of zinc nitrate hexahydrate, and stir at room temperature for 1 hour;

[0071] S3: Transfer the stirred mixture to a hydrothermal reaction kettle, heat and stir at 180 °C for 24 hours;

[0072] S4: Take out the reacted mixture from the hydrothermal reaction kettle and wash it by centrifugation three times with ethanol;

[0073] S5: Place the washed sample in an oven at 60 °C for drying;

[0074] S6: Put the dried sample into a muffle furnace and calcine it at 550 °C for 6 hours to obtain the Pt 0.2％ Zn 1.0％ @S1 catalyst;

[0075] S7: Press the prepared sample and screen out a particle size of 40 - 60 mesh for subsequent use.

[0076] Example 3 Pt 0.2％ Zn 0.6％ Preparation of @S1 (template molar ratio is 1:2)

[0077] It includes the following steps:

[0078] S1: Calculate Pt0.2％ Zn 0.6％ The mass of chloroplatinic acid hexahydrate and zinc nitrate hexahydrate required on @S1;

[0079] S2: Using a one-step synthesis method, 10.0 g of tetraethyl orthosilicate was added dropwise to a Teflon-lined container containing an aqueous solution (25 wt%) of 17.7 g of tetrapropylammonium hydroxide. Subsequently, 1.53 mL of an aqueous solution of metal chloroplatinic acid hexahydrate (0.01 g / mL) and 0.08 g of zinc nitrate hexahydrate were added, and the mixture was stirred at room temperature for 1 hour;

[0080] S3: Transfer the stirred mixture to a hydrothermal reaction kettle, heat and stir at 180 °C for 24 hours;

[0081] S4: Take out the reacted mixture from the hydrothermal reaction kettle and wash it three times by centrifugation with ethanol;

[0082] S5: Place the washed sample in an oven at 60 °C for drying;

[0083] S6: Put the dried sample into a muffle furnace and calcine it at 550 °C for 6 hours to obtain Pt 0.2％ Zn 0.6％ @S1 catalyst;

[0084] S7: Press the prepared sample into tablets and screen out particles with a particle size of 40 - 60 mesh for subsequent use.

[0085] Example 4 Pt 0.2％ Zn 1.0％ Preparation of @S1

[0086] Comprises the following steps:

[0087] S1: Calculate Pt 0.2％ Zn 1.0％ The mass of chloroplatinic acid hexahydrate and zinc nitrate hexahydrate required on @S1;

[0088] S2: Using a one-step synthesis method, 10.0 g of tetraethyl orthosilicate was added dropwise to a Teflon-lined container containing an aqueous solution (25 wt%) of 17.7 g of tetrapropylammonium hydroxide. Subsequently, 1.53 mL of an aqueous solution of metal chloroplatinic acid hexahydrate (0.01 g / mL) and 0.13 g of zinc nitrate hexahydrate were added, and the mixture was stirred at room temperature for 1 hour;

[0089] S3: Transfer the stirred mixture to a hydrothermal reaction kettle, heat and stir at 180 °C for 24 hours;

[0090] S4: Take out the reacted mixture from the hydrothermal reaction kettle and wash it three times by centrifugation with ethanol;

[0091] S5: Place the washed sample in an oven at 60 °C for drying;

[0092] S6: Put the dried sample into a muffle furnace and calcine it at 550 °C for 6 hours to obtain the Pt 0.2％ Zn 1.0％ @S1 catalyst;

[0093] S7: Press the prepared sample and screen out a particle size of 40 - 60 mesh for subsequent use.

[0094] Example 5 Preparation of Pt 0.2％ @S1

[0095] It includes the following steps:

[0096] S1: Calculate the mass of chloroplatinic acid hexahydrate required on the Pt 0.2％ @S1;

[0097] S2: Using a one-step synthesis method, add 10.0 g of tetraethyl orthosilicate dropwise to a tetrafluoro inner lining in an aqueous solution (25 wt%) containing 17.7 g of tetrapropylammonium hydroxide, then add 1.53 mL of an aqueous solution of metal chloroplatinic acid hexahydrate (0.01 g / mL), and stir at room temperature for 1 hour;

[0098] S3: Transfer the stirred mixture to a hydrothermal reaction kettle, heat and stir at 180 °C for 24 hours;

[0099] S4: Take out the reacted mixture from the hydrothermal reaction kettle and wash it by centrifugation with ethanol three times;

[0100] S5: Place the washed sample in an oven at 60 °C for drying;

[0101] S6: Put the dried sample into a muffle furnace and calcine it at 550 °C for 6 hours to obtain the Pt 0.2％ @S1 catalyst;

[0102] S7: Press the prepared sample and screen out a particle size of 40 - 60 mesh for subsequent use.

[0103] Example 6 Preparation of Zn 1.0％ @S1

[0104] It includes the following steps:

[0105] S1: Calculate the mass of chloroplatinic acid hexahydrate and zinc nitrate hexahydrate required on the Zn 1.0％ @S1;

[0106] S2: Using the one-step synthesis method, 10.0 g of tetraethyl orthosilicate was added dropwise to a tetrafluoro inner lining containing an aqueous solution (25 wt%) of 17.7 g of tetrapropylammonium hydroxide, and then 0.13 g of zinc nitrate hexahydrate was added, and the mixture was stirred at room temperature for 1 hour;

[0107] S3: The stirred mixture was transferred to a hydrothermal reactor and heated and stirred at 180 °C for 24 hours;

[0108] S4: The reacted mixture was taken out from the hydrothermal reactor and centrifugally washed three times with ethanol;

[0109] S5: The washed sample was placed in an oven at 60 °C for drying;

[0110] S6: The dried sample was placed in a muffle furnace and calcined at 550 °C for 6 hours to obtain the Zn 1.0％ @S1 catalyst;

[0111] S7: The prepared sample was tableted, and particles with a particle size of 40 - 60 mesh were screened for subsequent use.

[0112] Example 7 Preparation of R-Pt by impregnation method 0.2％ Zn 1.0％ / S1

[0113] It includes the following steps:

[0114] S1: Calculate the masses of chloroplatinic acid hexahydrate and zinc nitrate hexahydrate required on Pt 0.2％ Zn 1.0％ @S1;

[0115] S2: 10.0 g of tetraethyl orthosilicate was added dropwise to a tetrafluoro inner lining containing an aqueous solution (25 wt%) of 17.7 g of tetrapropylammonium hydroxide, and the mixture was stirred at room temperature for 1 hour;

[0116] S3: The stirred mixture was transferred to a hydrothermal reactor and heated and stirred at 180 °C for 24 hours;

[0117] S4: The reacted mixture was taken out from the hydrothermal reactor and centrifugally washed three times with ethanol;

[0118] S5: The washed sample was placed in an oven at 60 °C for drying;

[0119] S6: The dried sample was placed in a muffle furnace and calcined at 550 °C for 6 hours to obtain the silicalite-1 catalyst.

[0120] S7: Weigh 2.88 g of silicalite-1 powder and place it in an eggplant-shaped flask. Then, sequentially add 1.53 mL of an aqueous solution of chloroplatinic acid hexahydrate (concentration: 0.01 g / mL), 0.13 g of zinc nitrate hexahydrate, and 200 mL of deionized water. Place the mixture in a water bath at 100 °C and continuously stir for 4 hours to ensure thorough mixing;

[0121] S8: Transfer the mixture obtained in step S7 to a rotary evaporator. Set the rotation speed to 400 rpm and perform rotary evaporation at 60 °C until the liquid is completely evaporated to obtain a solid mixture;

[0122] S9: Place the eggplant-shaped flask containing the solid mixture in an oven at 60 °C and dry for 12 hours to completely remove residual moisture;

[0123] S10: Use a long-handled spatula to scrape the dried sample from the wall of the eggplant-shaped flask and transfer it to a crucible. Place the crucible in a muffle furnace and calcine at 550 °C for 6 hours to finally obtain the R-Pt 0.2％ Zn 1.0％ / S1 catalyst;

[0124] S11: Press the prepared sample into tablets and screen out particles with a particle size of 40 - 60 mesh for subsequent use.

[0125] Metal catalyst activity evaluation test

[0126] The test procedure for the Pt-based alloy catalyst prepared above in the propane dehydrogenation reaction is as follows:

[0127] S1: Open the panel of the fixed-bed reactor evaluation device and start the hydrogen-air generator and gas chromatograph (GC);

[0128] S2: Fill 0.1 g of the metal catalyst into the fixed-bed reactor and pre-treat the catalyst with 10 vol% H2 / He at a temperature of 600 °C for 60 minutes;

[0129] S3: Feed the reaction gas into the fixed-bed reactor. The reaction gas contains propane, hydrogen, and helium, with a gas flow rate of 20 mL / min. Perform the catalytic reaction at a reaction temperature of 600 °C and atmospheric pressure. The content of propane is 10 vol%, the content of H2 is 10 vol%, and the content of helium is 80 vol%.

[0130] S4: Use the gas chromatograph to detect the components of the tail gas after the reaction, and calculate the conversion rate of C3H8 and the selectivity of propylene based on the measured concentration data.

[0131] Test example 1

[0132] In Pt 0.2％ Sn0.6％ @S1, Pt 0.2％ Zn 0.6％ @S1, Pt 0.2％ La 0.6％ @S1, Pt 0.2％ Fe 0.6％ @S1, Pt 0.2％ Cu 0.6％ @S1, Pt 0.2％ In 0.6％ @S1 and Pt 0.2％ Ga 0.6％ The propane dehydrogenation activity evaluation test was carried out on the @S1 catalyst, and the conversion rate of C3H8 at 600 °C was plotted in Figure 1 it.

[0133] It can be seen from Figure 1 that compared with other catalysts, Pt 0.2％ Zn 0.6％ @S1 catalyst showed the best catalytic activity. At 600 °C, the conversion rate of propane was 59.7% at 60 min of reaction, and it dropped to 52.5% after 240 min of reaction. Secondly, Pt 0.2％ Sn 0.6％ @S1 also had good catalytic activity. The conversion rate of propane was 29.2% at 60 min of reaction and dropped to 18.3% after 240 min. The conversion rates of propane on the remaining catalysts (Pt 0.2％ La 0.6％ @S1, Pt 0.2％ Fe 0.6％ @S1, Pt 0.2％ Cu 0.6％ @S1, Pt 0.2％ In 0.6％ @S1 and Pt 0.2％ Ga 0.6％ @S1) were all relatively low, and the conversion rate of propane within 4 h of reaction was less than 20%.

[0134] It can be seen from Figure 1 that the propane dehydrogenation activity of the Pt 0.2％ Zn 0.6％ @S1 catalyst was significantly better than that of other bimetallic catalysts, indicating that the introduction of Zn had a significant effect on improving the catalytic performance.

[0135] Test Example 2

[0136] To investigate the effect of the template agent molar ratio (tetraethyl orthosilicate (TEOS): tetrapropylammonium hydroxide (TPAOH) = 1:1 - 1:3) on the catalytic activity during the synthesis of the Pt 0.2％ Zn 0.6％ @S1 catalyst, Pt 0.2％ Zn0.6％ @S1(1:1), Pt 0.2％ Zn 0.6％ @S1(1:2) and Pt 0.2％ Zn 0.6％ @S1(1:3) catalyst and its propane dehydrogenation activity was evaluated. The test results are as Figure 2 shown.

[0137] During the synthesis of molecular sieve, the template ratio (TEOS:TPAOH) can significantly regulate the structure and properties of the molecular sieve, and thus affect the activity of the catalyst. When TEOS:TPAOH = 1:2, Pt 0.2％ Zn 0.6％ @S1(1:2) exhibits the optimal catalytic activity: when the reaction time is 60 min, the propane conversion rate reaches 59.7%. At other ratios, the catalytic activity is relatively low: Pt 0.2％ Zn 0.6％ @S1(1:1) and Pt 0.2％ Zn 0.6％ @S1(1:3) have propane conversion rates lower than those of Pt 0.2％ Zn 0.6％ @S1(1:2), and the propane conversion rates are 14.3% and 55.7% respectively when the reaction time is 60 min. The experimental results show that TEOS:TPAOH = 1:2 is an optimized template ratio, and the Pt 0.2％ Zn 0.6％ @S1(1:2) catalyst prepared at this ratio has the best propane dehydrogenation activity.

[0138] Test Example 3

[0139] To investigate the effect of Zn loading on the performance of Pt 0.2％ Zn x％ @S1 catalyst, catalysts with different Zn loadings (Pt 0.2％ Zn 0.2％ @S1, Pt 0.2％ Zn 0.6％ @S1, Pt 0.2％ Zn 1.0％ @S1, Pt 0.2％ Zn 1.4％ @S1 and Pt 0.2％ Zn 1.8％ @S1) were prepared at the same Pt loading (0.2 wt%), and their propane dehydrogenation activity was evaluated. The test results are as Figure 3 shown.

[0140] When the Zn loading increases from 0.2 wt% to 1.0 wt%, the activity of the catalyst gradually increases. When the Zn loading is 0.2 wt%, Pt0.2％ Zn 0.2％ @S1 has very poor catalytic activity and stability: at 60 min of reaction, the propane conversion rate reaches 37.7%; at 240 min of reaction, the propane conversion rate drops to 23.7%. When the Zn loading is 1.0 wt%, Pt 0.2％ Zn 1.0％ @S1 exhibits the optimal catalytic activity and stability: at 60 min of reaction, the propane conversion rate reaches 70.3%; at 240 min of reaction, the propane conversion rate still remains at 69.4%. When the Zn loading is further increased to 1.4 wt% and 1.8 wt%, the activity of the catalyst begins to decline again. This phenomenon may be due to the uneven distribution of active centers or the weakening of the Pt-Zn synergistic effect caused by the excessive Zn loading, thereby reducing the catalytic performance. The experimental results show that the Zn loading has a significant impact on the performance of Pt 0.2％ Zn x％ @S catalyst. When the Zn loading is 1.0 wt%, the catalyst exhibits the best propane dehydrogenation activity and stability, while the excessive Zn loading will have a negative impact on its performance.

[0141] Test Example 4

[0142] To explore the effect of Pt loading on the performance of Pt x％ Zn 1.0％ @S1 catalyst, catalysts with different Pt loadings (Pt 0.1％ Zn 1.0％ @S1, Pt 0.2％ Zn 1.0％ @S1, Pt 0.3％ Zn 1.0％ @S1, Pt 0.5％ Zn 1.0％ @S1 and Pt 1.0％ Zn 1.0％ @S1) were prepared under the same Zn loading (1.0 wt%), and their propane dehydrogenation activity evaluation tests were carried out. The test results are as Figure 4 shown.

[0143] From Figure 4It can be seen that at the same Zn loading (1.0 wt%), when the Pt loading is 0.1 wt%, the activity of the catalyst is the worst, and the propane conversion rate at 60 min of the reaction is 47.1%. The reason may be that the Pt loading is too low, and the number of active centers is insufficient to effectively activate the C-H bond in the propane molecule. When the Pt loading is 0.2 wt%, the catalytic activity of the catalyst is the highest. At 60 min of the reaction, the propane conversion rate is 70.3%; at 240 min of the reaction, the propane conversion rate still remains at 69.4%, showing good stability. When the Pt loading is further increased to 0.3 wt%, 0.5 wt% and 1.0 wt%, the catalytic activity decreases slightly. Although the catalytic activity of Pt 0.3％ Zn 1.0％ @S1, Pt 0.5％ Zn 1.0％ @S1 and Pt 1.0％ Zn 1.0％ @S1 is still relatively high, but the increase in Pt loading does not significantly improve the performance, but instead increases the cost of the catalyst. The experimental results show that the Pt loading has a significant impact on the performance of the Pt x％ Zn 1.0％ @S1 catalyst. When the Pt loading is 0.2 wt%, the catalyst exhibits the best propane dehydrogenation activity and stability, and at the same time has a relatively low cost, which is suitable for industrial applications.

[0144] Test Example 5

[0145] Figure 5 and Figure 6 shows the comparison results of the propane dehydrogenation performance of the bimetallic catalyst Pt 0.2％ Zn 1.0％ @S1 with the monometallic catalysts Pt 0.2％ @S1 and Zn 1.0％ @S1.

[0146] Figure 5 compares the catalytic activity of the bimetallic catalyst Pt 0.2％ Zn 1.0％ @S1 with the monometallic catalysts Pt 0.2％ @S1 and Zn 1.0％ @S1. The bimetallic catalyst Pt 0.2％ Zn 1.0％ @S1 shows a significant catalytic activity advantage. Pt 0.2％ Zn 1.0％ @S1 has a propane conversion rate of 70.3% at 60 min of the reaction; at 240 min of the reaction, the propane conversion rate still remains at 69.4%, showing excellent stability. The monometallic catalyst Pt 0.2％@The catalytic activity of S1 is relatively low. At 60 min of the reaction, the propane conversion rate is 10.8%; at 240 min of the reaction, the propane conversion rate further drops to 5.4%. The single-metal catalyst Zn 1.0％ @The catalytic activity of S1 is better than that of Pt 0.2％ @S1, but it is still much lower than that of the bimetallic catalyst. At 60 min of the reaction, the propane conversion rate is 35.1%; at 240 min of the reaction, the propane conversion rate drops to 27.7%.

[0147] Figure 6 In [reference] compared the bimetallic catalyst Pt 0.2％ Zn 1.0％ @S1 with the single-metal catalyst Pt 0.2％ @S1 and Zn 1.0％ @The propylene selectivity on S1. The bimetallic catalyst Pt 0.2％ Zn 1.0％ @The propylene selectivity of S1 is as high as 97.3%, indicating that the Pt-Zn bimetallic synergistic effect significantly improves the selectivity of the target product. In contrast, the propylene selectivity of the single-metal catalyst Pt 0.2％ @S1 is 85.9% and there are more side reactions. The propylene selectivity on Zn 1.0％ @S1 is 97.0%, but its catalytic activity is relatively low. This shows that the addition of Zn regulates the dehydrogenation ability of Pt, reduces side reactions, and increases the selectivity of propylene.

[0148] Therefore, Pt 0.2％ Zn 1.0％ @In the S1 catalyst, the synergistic effect of Pt and Zn significantly improves the catalytic activity and stability, while maintaining a high propane conversion rate. The addition of Zn regulates the dehydrogenation ability of Pt, reduces side reactions, and significantly improves the propylene selectivity. In summary, Pt 0.2％ Zn 1.0％ @The S1 bimetallic catalyst exhibits excellent catalytic activity, stability and selectivity in the propane dehydrogenation reaction, significantly superior to the single-metal catalysts Pt 0.2％ @S1 and Zn 1.0％ @S1.

[0149] Test Example 6

[0150] As mentioned above, Pt 0.2％ Zn 1.0％ @The S1 catalyst exhibits excellent catalytic activity and stability. Specifically, at 60 min of the reaction, the propane conversion rate is as high as 70.3%; even when the reaction is extended to 240 min, the propane conversion rate still remains stable at 69.4%. In addition, Figure 7Further shows the long-term stability test results of the catalyst at 600 °C for 36 h. In the initial stage, the propane conversion rate was 70.3%; after 28 h of reaction, the conversion rate slightly decreased to 6.9%; and after 28 h, the activity decline rate slightly accelerated, and the conversion rate dropped to 61.4% at 36 h. This result indicates that Pt 0.2％ Zn 1.0％ @S1 catalyst can still maintain high catalytic activity during long-term reaction, further verifying its excellent stability.

[0151] Comparative example

[0152] Figure 8 Shows the comparison results of the propane dehydrogenation performance between Pt 0.2％ Zn 1.0％ @S1 catalyst and the R-Pt 0.2％ Zn 1.0％ -S1 catalyst prepared by the traditional impregnation method.

[0153] As previously shown, Pt 0.2％ Zn 1.0％ @S1 catalyst has excellent catalytic activity and stability: at 60 min of reaction, the propane conversion rate is 70.3%; at 240 min of reaction, the propane conversion rate still remains at 69.4%. In contrast, Figure 8 the R-Pt 0.2％ Zn 1.0％ / S1 catalyst prepared by the traditional impregnation method in [reference] has significantly lower activity and stability: at 60 min of reaction, the propane conversion rate is only 17.9%; at 240 min of reaction, the propane conversion rate further drops to 5.5%. In addition, the R-Pt 0.2％ Zn 1.0％ / S1 catalyst prepared by the traditional impregnation method has the disadvantages of long preparation cycle, complex process, and poor catalytic performance.

[0154] In summary, Pt 0.2％ Zn 1.0％ @S1 catalyst not only exhibits excellent catalytic performance, but also has the advantages of simple preparation process and high economic benefit, further highlighting its technological advancement and application potential.

[0155] The above is only a preferred embodiment of the present invention, and it is not intended to limit the present invention in any other form. Any modification or equivalent change made according to the technical essence of the present invention still belongs to the scope protected by the present invention.

Claims

1. A preparation method of a Pt-based alloy catalyst for propane dehydrogenation to propylene, characterized in that, Propane, H2, and helium were introduced into a fixed-bed reactor loaded with the metal catalyst at a gas flow rate of 20 mL / min, and a catalytic reaction was carried out at a reaction temperature of 600 °C and atmospheric pressure. Among them, the metal catalyst consisted of a silicalite-1 support and a metal active component. The metal active component was an alloy phase composed of Pt and any one of Sn, Zn, La, Fe, Cu, In, and Ga. The loading amount of the metal active component Pt accounted for 0.1-1.0 wt% of the total mass of the metal catalyst, and the metal active components Sn, Zn, La, Fe, Cu, In, and Ga accounted for 0.2-1.8 wt% of the total mass of the metal catalyst.

2. The method according to claim 1, wherein In the reaction gas, the content of propane was 4 vol% - 20 vol%, the content of H2 was 4 vol% - 20 vol%, and the content of helium was 60 vol% - 92 vol%; and the volume ratio of propane:H2 = 1:

1.

3. The preparation method according to claim 1, characterized in that, In the synthesis of PtZn@silicalite-1, the molar ratio of tetraethyl orthosilicate to tetrapropylammonium hydroxide as the template agent was 1:1 - 1:

3.

4. The preparation method according to claim 1, characterized in that, The loading amount of Zn was 1.0 wt%.

5. The preparation method according to claim 1, characterized in that, The loading amount of Pt was 0.2 wt%.

6. The preparation method of the Pt-based alloy catalyst according to any one of claims 1 to 5, characterized in that, It includes the following steps: S1: Calculate the masses of chloroplatinic acid hexahydrate and X metal hydrate, where X is any one of Sn, Zn, La, Fe, Cu, In, and Ga; S2: Using a one-step synthesis method, tetraethyl orthosilicate:tetrapropylammonium hydroxide were mixed in a molar ratio of 1:2 and added to a Teflon liner. Subsequently, the required masses of metal chloroplatinic acid hexahydrate and X metal hydrate were added, and the mixture was stirred at room temperature for 1 hour; S3: Transfer the stirred mixture to a hydrothermal reaction kettle, heat and stir it at 180 °C for 24 hours; S4: Take out the reacted mixture from the hydrothermal reaction kettle and perform centrifugal washing three times with ethanol; S5: Place the washed sample in an oven at 60 °C for drying; S6: Put the dried sample into a muffle furnace and calcine it at 550 °C for 6 hours to obtain the catalyst; S7: Press the prepared sample and screen out a particle size of 40 - 60 mesh.

7. A test method for the Pt-based alloy catalyst obtained by the method according to any one of claims 1 to 6 in propane dehydrogenation, characterized in that, It includes the following steps: S1: Open the evaluation device panel of the fixed-bed reactor and start the hydrogen-air generator and gas chromatograph; S2: Fill 0.1 g of the Pt-based alloy catalyst into the fixed-bed reactor and pre-treat it with 10 vol% H2 / He at a temperature of 600 °C for 60 minutes of purging; S3: Pass the reaction gas into the fixed-bed reactor. The reaction gas contains propane, hydrogen, and helium, with a gas flow rate of 20 mL / min. A catalytic reaction is carried out at a reaction temperature of 600 °C and atmospheric pressure conditions. Among them, the content of propane is 4 vol% - 20 vol%, the content of H2 is 4 vol% - 20 vol%, the content of helium is 60 vol% - 92 vol%, and the volume ratio of propane:H2 = 1:1; S4: Use the gas chromatograph to detect the components of the tail gas after the reaction, and calculate the conversion rate of C3H8 and the selectivity of propylene based on the measured concentration data.

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