Preparation method and application of a spherical TS-1 molecular sieve loaded with a PtZn bimetallic propane dehydrogenation to propylene catalyst

Abstract

The application discloses a preparation method and application of a spherical TS-1 molecular sieve loaded with PtZn bimetallic propane dehydrogenation propylene catalyst. The catalyst is prepared by hydrothermal synthesis, a template agent is mixed with water, and then a silicon source and a titanium source are added after being uniformly stirred, hydrothermal crystallization is carried out at 120 DEG C, filtration, washing, drying and calcination are carried out, and the spherical TS-1 molecular sieve is obtained; then, the metal PtZn bimetallic is loaded by an impregnation method, and the PtZn / TS-1 catalyst is obtained. The spherical TS-1 molecular sieve is used as a carrier, Pt is used as an active metal component, Zn is used as an additive, the PtZn bimetallic is formed into Pt1Zn1 alloy after reduction, and is highly dispersed in the TS-1 carrier. The catalyst prepared by the application has the advantages of high activity, high stability, strong anti-sintering capacity and the like, and the preparation method of the catalyst provides a new idea for structure design and performance optimization of a new Pt-based dehydrogenation catalyst.

Description

Technical Field

[0001] This invention belongs to the field of propane dehydrogenation to propylene catalyst technology, specifically involving a method for preparing PtZn bimetal supported on a small-particle-size spherical TS-1 molecular sieve, and applying it to the production of propylene from propane dehydrogenation catalyst. Background Technology

[0002] Propylene, a crucial raw material in the global petrochemical industry, is widely used in the production of polypropylene, acrylic acid, acrolein, and propylene oxide. With the explosive growth of shale gas technology, propane prices have become low and supply abundant, allowing the direct propane dehydrogenation to propylene (PDH) process to stand out from other propylene production processes due to its price advantage. Pt-based catalysts, exemplified by the Oleflex process, exhibit high activity and selectivity, but are prone to carbon deposition and sintering at high temperatures, leading to catalyst deactivation.

[0003] Currently, by controlling the support and constructing defect sites on the support surface to enhance the interaction between the metal and the support, the sintering of Pt species in the catalyst can be effectively suppressed. For example, Angew. Chem. Int. Ed. 2015, 54, 13994-13998 and J. Energy Chem. 2022, 65, 293-301 report unsaturated five-coordinate Al 3+ It can effectively anchor PtSn clusters and inhibit Pt sintering; for example, ACS Catal. 2015, 5, 438-447 and JACS Au 2023, 3, 1939-1951 report defective titanium species TiO2. x It can also enhance the interaction between the metal and the support, which is beneficial to the dispersion of Pt species and inhibits their sintering. However, although the catalysts reported above inhibit the sintering of Pt species to a certain extent, the reaction conditions of their catalysts are relatively mild, and the reaction activity (based on the propylene formation rate) still needs to be further improved.

[0004] Based on the above considerations, this invention provides a method for preparing and applying a PtZn bimetallic propane dehydrogenation catalyst supported on spherical TS-1 molecular sieves. The aim is to improve the catalyst's resistance to sintering while enhancing its reactivity, enabling stable operation even under ultra-high mass space velocity reaction conditions. Furthermore, the influence of TS-1 molecular sieve morphology on catalyst performance is investigated. Summary of the Invention

[0005] The purpose of this invention is to improve the anti-sintering ability and reactivity of catalysts, enabling stable operation even under high mass space velocity (HHSV) reaction conditions. This invention provides a method for preparing a catalyst using spherical TS-1 molecular sieves as the catalyst support and Pt1Zn1 intermetallic compounds as the active component, and its application in PDH reactions. The catalyst has a Pt loading of 0.5 wt% and a Zn loading of 1.7 wt%. TS-1 molecules possess an ordered porous structure, low acidity, and high thermal stability, making them excellent catalyst supports. Furthermore, the prepared TS-1 has a small grain size, and its resulting stacked mesoporous structure can more effectively promote mass transfer and improve catalytic performance. In addition, the titanium atoms in the TS-1 molecular sieve framework can effectively anchor the Pt1Zn1 intermetallic compounds, improving the dispersion of Pt species to enhance the catalyst's reactivity and anti-sintering ability, enabling stable operation even under ultra-high mass space velocity (HHSV) reaction conditions.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A PtZn bimetallic propane dehydrogenation catalyst for propylene production uses spherical TS-1 molecular sieves as the catalyst support and Pt1Zn1 intermetallic compounds as the active component. Based on the mass of the support in the catalyst (100%), the Pt loading is 0.5 wt% and the Zn loading is 1.7 wt%. TS-1 is prepared via hydrothermal synthesis, and the silicon-to-titanium molar ratio is 25-100. The specific preparation method includes the following steps:

[0008] (1) Mix the template agent and water to dissolve and stir to form a transparent solution;

[0009] (2) Add silicon source dropwise to the solution in step (1), stir continuously for 3-5 h, then add a certain amount of titanium source, stir continuously for 24 h, perform hydrothermal crystallization, after crystallization, filter, wash, dry and calcine the product to obtain TS-1 molecular sieve.

[0010] (3) The obtained TS-1 molecular sieve was mixed with water, a precursor containing Pt and Zn was added, ultrasonicated for 1 h, stirred for 12 h, the water was removed by rotary evaporation, dried, calcined, and then reduced to obtain the PtZn / TS-1 catalyst.

[0011] Furthermore, the template agent used in step (1) is tetrapropylammonium hydroxide.

[0012] Furthermore, the silicon source used in step (2) is tetraethyl silicate, and the titanium source used is tetrabutyl titanate.

[0013] Furthermore, in step (2), the molar ratio of each substance in the crystallization liquid satisfies the following: silicon source: template agent: titanium source = 1: 0.3: 0.01-0.04, where the number of moles of silicon source is calculated based on the number of moles of SiO2.

[0014] Furthermore, in step (2), the hydrothermal crystallization temperature is 120 °C and the crystallization time is 96 h.

[0015] Furthermore, in step (2), the product drying temperature is 60 ℃-100 ℃, the drying time is 12-24 h, the calcination temperature is 550 ℃, and the calcination time is 6 h.

[0016] Further, in step (3), the mass ratio of water to TS-1 molecular sieve is 20:1, the Pt precursor used is chloroplatinic acid hexahydrate with a Pt loading of 0.5 wt%, and the Zn precursor used is zinc nitrate hexahydrate with a Zn loading of 1.7 wt%, based on the mass of TS-1 molecular sieve.

[0017] Further, in step (3), the rotary evaporation temperature is 80 ℃-100 ℃, the drying temperature is 60-80 ℃, the drying time is 12-24 h, the calcination temperature is 550 ℃, and the calcination time is 2 h; the reduction is carried out under a reducing atmosphere, the reducing atmosphere is hydrogen, the flow rate is 20 mL / min, the reduction treatment temperature is 550-600 ℃, and the treatment time is 2 h.

[0018] The PtZn bimetallic propane dehydrogenation catalyst prepared by this invention is suitable for PDH reactions in a fixed-bed reactor. Specific applications include the following steps:

[0019] (1) The PtZn bimetallic propane dehydrogenation catalyst was packed into a quartz tube reactor with an outer diameter of 12 mm, and the quartz tube reactor was placed in the constant temperature zone of the fixed bed reactor heater.

[0020] (2) A mixture of hydrogen and nitrogen gas with a volume ratio of 1:1 is introduced and heated to 600 ℃ at 5 ℃ / min for 2 h. The mixture is then cooled to the reaction temperature of 550-600 ℃ and a reaction gas is introduced to carry out the reaction. The molar ratio of propane to hydrogen in the reaction gas is 2:1, and nitrogen is used as the equilibrium gas. The mass hourly space velocity of propane is 6-40 h⁻¹. -1 .

[0021] Furthermore, the PtZn bimetallic propane dehydrogenation catalyst shown in step (1) is loaded with a mass of 0.02-0.1 g.

[0022] Furthermore, in step (2), the flow rate of propane introduced is 0-10 mL / min (not 0).

[0023] Furthermore, the PDH reaction time in step (3) is 5-50 h.

[0024] The significant advantages of this invention are:

[0025] This invention synthesizes spherical TS-1 molecular sieves via hydrothermal synthesis. These sieves possess an ordered pore structure, low acidity, and high thermal stability, making them excellent catalyst supports. Furthermore, their small grain size and the resulting stacked mesoporous structure effectively promote mass transfer and improve catalytic performance. More importantly, the titanium atoms in the TS-1 molecular sieve framework effectively anchor the Pt1Zn1 alloy, enhancing the interaction between the metal and the support, improving Pt species dispersion, and promoting the catalyst's reactivity and anti-sintering ability, enabling stable operation even under high mass space velocity (MHS) reaction conditions. Attached Figure Description

[0026] Figure 1 The performance evaluation graph for application example 4 is shown.

[0027] Figure 2 Scanning electron microscope (SEM) images (a, b) of the TS-1-50-spheres prepared in Example 2 and (c, d) of the TS-1-50-sheets prepared in Comparative Example 2.

[0028] Figure 3 The N2 adsorption-desorption characterization diagrams are for the TS-1-50-sheet (a) prepared in Comparative Example 2 and the TS-1-50-sphere (b) prepared in Example 2.

[0029] Figure 4 The images show the X-ray diffraction (XRD) patterns and magnified views (38°-42°) of the 0.5Pt1.7Zn / TS-1-50-sphere catalyst after loading and reaction in Example 2. Detailed Implementation

[0030] To make the technical problems, technical solutions and beneficial effects of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0031] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased commercially. Specifically, tetraethyl silicate (TEOS) and zinc nitrate hexahydrate were purchased from Sinopharm Chemical Reagent Co., Ltd., tetrabutyl titanate (TBOT), tetrapropylammonium hydroxide (25 wt%, TPAOH), N,N-dimethylformamide (DMF), and chloroplatinic acid hexahydrate were purchased from Aladdin Reagent Co., Ltd., and deionized water was obtained from the laboratory's ultrapure water system.

[0032] In the embodiments, the catalyst is named xPtyZn / TS-1-z-spheres (sheets), where TS-1 is the support, Pt is the active metal component, Zn is the promoter, x is the loading of Pt, y is the loading of Zn, z is the silicon-titanium molar ratio, and the metal loading is based on the mass of TS-1 (100%).

[0033] Example 1

[0034] (1) Weigh 5.4665 g of TPAOH template agent aqueous solution (concentration 25wt%) and add it to 8.0066 g of water, and stir evenly.

[0035] (2) Weigh 5.0 g of TEOS and add it dropwise to the mixed solution in step (1). After stirring vigorously for 3 h, add 0.0817 g of TBOT dropwise and continue stirring for 24 h. Transfer the resulting clear and transparent solution to a hydrothermal reactor. The molar ratio of each substance in the crystallization solution satisfies the following conditions: silicon source: template agent: titanium source = 1:0.3:0.01. Crystallize at 120 ℃ for 96 h. After hydrothermal treatment, cool naturally to room temperature, wash with ultrapure water by centrifugation until neutral, and dry at 80 ℃ overnight. After drying, grind into powder and calcine in a muffle furnace at 550 ℃ for 6 h with a heating rate of 2 ℃ / min. The resulting support is designated as TS-1-100-sphere, where the silicon-titanium molar ratio is Si / Ti = 100.

[0036] (3) Take 0.5 g of the TS-1-100-balls obtained in step (2) and add them to 10.0 g of water. Then add 6.6 mg of chloroplatinic acid hexahydrate and 38.1 mg of zinc nitrate hexahydrate. Sonicate for 1 h and stir for 12 h. After stirring, remove the water by rotary evaporation at 80 °C. Dry in an oven at 80 °C for 12 h. Calcine at 550 °C for 2 h with a heating rate of 2 °C / min. Then reduce at 600 °C for 2 h with a heating rate of 5 °C / min under a hydrogen atmosphere to obtain 0.5Pt1.7Zn / TS-1-100-ball catalyst (Pt=0.5 wt%, Zn=1.7 wt%).

[0037] Example 2

[0038] (1) Weigh 5.4665 g of TPAOH template agent aqueous solution (concentration 25wt%) and add it to 8.0066 g of water, and stir evenly.

[0039] (2) Weigh 5.0 g of TEOS and add it dropwise to the mixed solution in step (1). After stirring vigorously for 3 h, add 0.1634 g of TBOT dropwise and continue stirring for 24 h. Transfer the resulting clear and transparent solution to a hydrothermal reactor. The molar ratio of each substance in the crystallization solution satisfies the following conditions: silicon source: template agent: titanium source = 1:0.3:0.02. Crystallize at 120 ℃ for 96 h. After hydrothermal treatment, cool naturally to room temperature, wash with ultrapure water by centrifugation until neutral, and dry at 80 ℃ overnight. After drying, grind into powder and calcine in a muffle furnace at 550 ℃ for 6 h with a heating rate of 2 ℃ / min. The resulting support is designated as TS-1-50-sphere, where the silicon-titanium molar ratio is Si / Ti = 50.

[0040] (3) Take 0.5 g of the TS-1-50-balls obtained in step (2) and add them to 10.0 g of water. Then add 6.6 mg of chloroplatinic acid hexahydrate and 38.1 mg of zinc nitrate hexahydrate. Sonicate for 1 h and stir for 12 h. After stirring, remove the water by rotary evaporation at 80 °C. Dry in an oven at 80 °C for 12 h. Calcine at 550 °C for 2 h with a heating rate of 2 °C / min. Then reduce at 600 °C for 2 h with a heating rate of 5 °C / min under a hydrogen atmosphere to obtain 0.5Pt1.7Zn / TS-1-50-ball catalyst (Pt=0.5 wt%, Zn=1.7 wt%).

[0041] Example 3

[0042] (1) Weigh 5.4665 g of TPAOH template agent aqueous solution (concentration 25wt%) and add it to 8.0066 g of water, and stir evenly.

[0043] (2) Weigh 5.0 g of TEOS and add it dropwise to the mixed solution in step (1). After stirring vigorously for 3 h, add 0.3268 g of TBOT dropwise and continue stirring for 24 h. Transfer the resulting clear and transparent solution to a hydrothermal reactor. The molar ratio of each substance in the crystallization solution satisfies the following conditions: silicon source: template agent: titanium source = 1:0.3:0.04. Crystallize at 120 ℃ for 96 h. After hydrothermal treatment, cool naturally to room temperature, wash with ultrapure water by centrifugation until neutral, and dry at 80 ℃ overnight. After drying, grind into powder and calcine in a muffle furnace at 550 ℃ for 6 h with a heating rate of 2 ℃ / min. The resulting support is designated as TS-1-25-sphere, where the silicon-titanium molar ratio is Si / Ti = 25.

[0044] (3) Take 0.5 g of TS-1-25 obtained in step (2) and add it to 10.0 g of water, then add 6.6 mg of chloroplatinic acid hexahydrate and 38.1 mg of zinc nitrate hexahydrate, sonicate for 1 h, stir for 12 h, remove water by rotary evaporation at 80 ℃ after stirring, dry in an oven at 80 ℃ for 12 h, calcine at 550 ℃ for 2 h with a heating rate of 2 ℃ / min, and then reduce at 600 ℃ for 2 h with a heating rate of 5 ℃ / min under a hydrogen atmosphere to obtain 0.5Pt1.7Zn / TS-1-25-sphere catalyst (Pt=0.5 wt%, Zn=1.7 wt%).

[0045] Example 4

[0046] 0.5Pt0.85Zn / TS-1-50-spheres (Pt=0.5 wt%, Zn=0.85 wt%) were prepared using the method of Example 2, the only difference being that the mass of zinc nitrate hexahydrate added in step (3) was 19.1 mg.

[0047] Example 5

[0048] 0.5Pt2.5Zn / TS-1-50-spheres (Pt=0.5 wt%, Zn=2.5 wt%) were prepared using the method of Example 2, the only difference being that the mass of zinc nitrate hexahydrate added in step (3) was 57.2 mg.

[0049] Comparative Example 1 (PtZn bimetallic sheet supported on TS-1)

[0050] (1) Weigh 5.4665 g of TPAOH template agent aqueous solution (concentration 25wt%) and add it to 8.0066 g of water, and stir evenly.

[0051] (2) Weigh 5.0 g TEOS and add it dropwise to the mixed solution in step (1). After stirring vigorously for 5 h, add 0.3268 g TBOT dropwise and stir for 3 h. Then add 0.4737 g DMF and continue stirring for 24 h. Transfer the resulting clear and transparent solution to a hydrothermal reactor. The molar ratio of each substance in the crystallization solution satisfies the following conditions: silicon source: template agent: titanium source = 1:0.3:0.04. Crystallize at 120 ℃ for 96 h. After hydrothermal treatment, cool naturally to room temperature, wash with ultrapure water until neutral, and dry at 80 ℃ overnight. After drying, grind into powder and calcine in a muffle furnace at 550 ℃ for 6 h with a heating rate of 2 ℃ / min. The resulting carrier is designated as TS-1-25-sheet, where the silicon-titanium molar ratio is Si / Ti = 25.

[0052] (3) Take 0.5 g of TS-1-25 obtained in step (2) and add it to 10.0 g of water, then add 6.6 mg of chloroplatinic acid hexahydrate and 38.1 mg of zinc nitrate hexahydrate, sonicate for 1 h, stir for 12 h, remove water by rotary evaporation at 80 ℃ after stirring, dry in an oven at 80 ℃ for 12 h, calcine at 550 ℃ for 2 h with a heating rate of 2 ℃ / min, and then reduce at 600 ℃ for 2 h with a heating rate of 5 ℃ / min under a hydrogen atmosphere to obtain 0.5Pt1.7Zn / TS-1-25-sheet catalyst (Pt=0.5 wt%, Zn=1.7 wt%).

[0053] Comparative Example 2

[0054] 0.5Pt1.7Zn / TS-1-50- tablets were prepared using the method of Comparative Example 1, the difference being that 0.1634 g of TBOT was added.

[0055] Comparative Example 3

[0056] 0.5Pt1.7Zn / TS-1-25- tablets were prepared using the method of Comparative Example 1, the difference being that 0.0817 g of TBOT was added.

[0057] Performance evaluation of catalysts in PDH reaction

[0058] The catalyst activity is expressed as propane conversion, propylene selectivity, and deactivation rate, and the calculation formulas for these three are as follows:

[0059] Propane conversion rate:

[0060]

[0061] Propylene selectivity:

[0062]

[0063] Deactivation rate:

[0064]

[0065] In the formula, This represents the molar flow rate of propane in the feed. and These represent the molar flow rates of propane and propylene in the product, respectively. and These represent the propane conversion rates at the beginning and end of the reaction, respectively. This represents the reaction time.

[0066] Application Example 1

[0067] (1) Take 0.025 g of the 0.5Pt1.7Zn / TS-1-100-sphere catalyst prepared in Example 1 and pack it into a quartz tube reactor with an outer diameter of 12 mm. Place the quartz tube reactor in the constant temperature zone of the fixed bed reactor heater.

[0068] (2) A mixture of hydrogen and nitrogen gas with a volume ratio of 1:1 was introduced and heated to 600 °C at a rate of 5 °C / min for 2 h. After treatment, a mixture of propane gas was introduced for reaction, wherein the volume flow rates of propane and hydrogen were 8 mL / min and 4 mL / min, respectively, based on a propane mass hourly space velocity of 37.7 h. -1 The reaction time is 7 hours.

[0069] Application Example 2

[0070] The performance evaluation process is the same as in Application Example 1, except that the catalyst used is the 0.5Pt1.7Zn / TS-1-50-sphere catalyst from Example 2.

[0071] Application Example 3

[0072] The performance evaluation process is the same as in Application Example 1, except that the catalyst used is the 0.5Pt1.7Zn / TS-1-25-sphere catalyst from Example 3.

[0073] Application Example 4

[0074] Its performance evaluation process is the same as that of Application Example 2, except that the reaction time is 50 h.

[0075] Application Example 5

[0076] The performance evaluation process was the same as in Application Example 2, except that the catalyst used was 0.1 g, the reaction gas was a mixture of propane, hydrogen, and nitrogen, with volumetric flow rates of 5 mL / min, 2.5 mL / min, and 22.5 mL / min, respectively, and a mass hourly space velocity (WHSV) of 6 h⁻¹. -1 .

[0077] Application Example 6

[0078] The performance evaluation process was the same as in Application Example 2, except that the catalyst used was 0.05 g, the reaction gas was a mixture of propane, hydrogen, and nitrogen, with volumetric flow rates of 5 mL / min, 2.5 mL / min, and 22.5 mL / min, respectively, and a mass hourly space velocity (WHSV) of 12 h⁻¹. -1 .

[0079] Application Example 7

[0080] The performance evaluation process was the same as in Application Example 2, except that the catalyst used was 0.03 g, the reaction gas was a mixture of propane, hydrogen, and nitrogen, with volumetric flow rates of 5 mL / min, 2.5 mL / min, and 22.5 mL / min, respectively, and a mass hourly space velocity (WHSV) of 20 h⁻¹. -1 .

[0081] Application Example 8

[0082] Its performance evaluation process is the same as that of Application Example 7, except that the catalyst used is the 0.5Pt0.85Zn / TS-1-50-sphere from Example 4.

[0083] Application Example 9

[0084] The performance evaluation process is the same as that in Application Example 7, except that the catalyst used is the 0.5Pt2.5Zn / TS-1-50-sphere catalyst from Example 5.

[0085] Application Example 10

[0086] Its performance evaluation process is the same as that of Application Example 7, except that the catalyst used is the 0.5Pt1.7Zn / TS-1-25-sheet catalyst used in Comparative Example 3.

[0087] Application Example 11

[0088] Its performance evaluation process is the same as that of Application Example 7, except that the catalyst used is the 0.5Pt1.7Zn / TS-1-50-piece catalyst from Comparative Example 2.

[0089] Application Example 12

[0090] Its performance evaluation process is the same as that of Application Example 7, except that the catalyst used is the 0.5Pt1.7Zn / TS-1-100-piece catalyst used in Comparative Example 1.

[0091] Application Example 13

[0092] Its performance evaluation process is the same as that of Application Example 4, except that the catalyst used is the 0.5Pt1.7Zn / TS-1-50-piece catalyst used in Comparative Example 2.

[0093] The specific results of the catalyst performance evaluation are shown in Tables 1 and 2.

[0094] From the comparison of the PDH reaction performance of different PtZn bimetallic catalysts in Table 1, compared with Application Examples 1-3, it can be seen that the 0.5Pt1.7Zn / TS-1-50-spheres have the best reaction activity compared to the 0.5Pt1.7Zn / TS-1-100-spheres and 0.5Pt1.7Zn / TS-1-25-spheres. That is, when the silicon-to-titanium ratio in the TS-1 support is 50, the reaction is most favorable. When the titanium content is too high or too low, the catalyst activity will be inhibited. As can be seen from Examples 7-9, the Zn content has a significant impact on the construction of Pt1Zn1 alloys. Too low a Zn content is not conducive to the dispersion of Pt, and the initial activity of 0.5Pt0.85Zn / TS-1-50 is much lower than that of 0.5Pt1.7Zn / TS-1-50 spheres. Too high a Zn content will cause some Zn species to cover the active sites of Pt, which is also not conducive to the formation of Pt1Zn1 alloys, resulting in the initial activity of 0.5Pt2.5Zn / TS-1-50 spheres being lower than that of 0.5Pt1.7Zn / TS-1-50 spheres.

[0095] Comparing the results of Application Example 7 and Application Example 11, it can be seen that the morphology of TS-1 has a relatively small impact on the initial activity of the catalyst, but a significant impact on the stability of the catalyst. Further comparison of Application Example 4 and Application Example 13 reveals that the 0.5Pt1.7Zn / TS-1-50-sphere catalyst exhibits significantly higher stability than the 0.5Pt1.7Zn / TS-1-50-sheet catalyst. This indicates that spherical molecular sieves can more effectively suppress the sintering of active sites and possess stronger carbon-holding capacity.

[0096] Furthermore, the effect of different mass hourly space velocities (MHSVs) on catalyst activity was investigated. Through applications 5-7, it was found that with increasing MHSV, the conversion rate of the 0.5Pt1.7Zn / TS-1-50-sphere catalyst did not decrease significantly, but its propylene formation rate increased significantly, indicating that the prepared catalyst possesses excellent activity and can operate stably even at high MHSVs. Further, the 0.5Pt1.7Zn / TS-1-50-sphere catalyst was subjected to reactions under even more severe conditions. As shown in application example 4, the 0.5Pt1.7Zn / TS-1-50-sphere catalyst reacted under 600 °C and a MHSV of 37.7 h⁻¹. -1 It can still operate stably under these conditions, with an initial propylene formation rate as high as 47.1 mol C3H6·g Pt -1 ·h -1 Furthermore, the inactivation rate constant is only 0.0046 h. -1 This indicates that the 0.5Pt1.7Zn / TS-1-50-sphere catalyst possesses excellent activity and extremely strong anti-sintering ability.

[0097] Table 1. Comparison of PDH reaction performance evaluation of different PtZn bimetallic catalysts

[0098]

[0099] Note: The reaction temperature for the application examples used was 600 ℃; the reaction time for application examples 1-3 was 7 h, the reaction time for application examples 4 and 13 was 50 h, and the feed volume ratio C3H8 / H2 = 8 / 4; the reaction time for application examples 5-12 was 7 h, and the feed volume ratio C3H8 / H2 = 5 / 2.5 / 22.5.

[0100] Depend on Figure 2 It can be seen that the prepared TS-1-sphere molecular sieve is spherical with small and uniform crystal size, about 140 nm; while the TS-1-sheet molecular sieve has a sheet structure with larger crystal size than the TS-1-sphere, and a thickness of 133 nm.

[0101] And by Figure 3 The pore size distribution diagram shows that TS-1-50-spheres have a higher specific surface area and intercrystalline mesoporous structure, which is beneficial to improve the dispersion of catalyst metals. Furthermore, the intercrystalline mesoporous structure can effectively improve mass transfer efficiency and enhance the carbon-holding capacity of the catalyst, thus significantly improving the stability of the catalyst.

[0102] Depend on Figure 4It can be seen that the prepared TS-1 molecular sieves all have their unique MFI microporous structure, and a weak diffraction peak can be detected on the Pt1Zn1 alloy (PDF#06-0604) (111) crystal plane at 40.8° for the 0.5Pt1.7Zn / TS-1-50-sphere catalyst after the reaction, confirming that the PtZn bimetal constitutes the Pt1Zn1 alloy.

[0103] The above fully demonstrates that the prepared spherical TS-1 molecular sieve is an excellent support for propane dehydrogenation catalysts. Impregnation and reduction of PtZn bimetals on this support can construct Pt1Zn1 intermetallic compounds, providing high catalyst activity. Compared to plate-shaped TS-1 molecular sieves, spherical molecular sieves have a higher specific surface area, which is beneficial for metal dispersion; furthermore, their intercrystalline mesoporous structure enhances the catalyst's carbon-holding capacity and significantly improves its stability. This catalyst preparation method provides a new approach for the structural design and performance optimization of novel Pt-based dehydrogenation catalysts.

[0104] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing a spherical TS-1 molecular sieve-supported PtZn bimetallic propane dehydrogenation catalyst for propylene production, characterized in that, The catalyst uses Pt as the active component, Zn as the promoter, and spherical TS-1 molecular sieve as the support. The specific preparation method includes the following steps: (1) Mix the template agent and water to dissolve and stir to form a transparent solution; (2) Add silicon source dropwise to the solution in step (1), stir continuously for 3-5 h, then add a certain amount of titanium source, stir continuously for 24 h, perform hydrothermal crystallization, after crystallization, filter, wash, dry and calcine the product to obtain TS-1 molecular sieve. (3) The obtained TS-1 molecular sieve was mixed with water evenly, a precursor containing Pt and Zn was added, ultrasonicated for 1 h, stirred for 12 h, water was removed by rotary evaporation, dried, calcined, and then reduced to obtain the catalyst.

2. The preparation method according to claim 1, characterized in that, The template agent used in step (1) is tetrapropylammonium hydroxide.

3. The preparation method according to claim 1, characterized in that, The silicon source used is tetraethyl silicate, and the titanium source used is tetrabutyl titanate; the molar ratio of each substance in the crystallization solution satisfies silicon source: template agent: titanium source = 1:0.3:0.01-0.04, where the number of moles of silicon source is calculated based on the number of moles of SiO2.

4. The preparation method according to claim 1, characterized in that, In step (2), the crystallization temperature is 120 °C and the crystallization time is 96 h.

5. The preparation method according to claim 1, characterized in that, In step (2), the product drying temperature is 60 ℃-100℃, the drying time is 12-24 h, the calcination temperature is 550 ℃, and the calcination time is 6 h.

6. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of water to TS-1 molecular sieve is 20:

1. The Pt precursor used is chloroplatinic acid hexahydrate, and the Zn precursor used is zinc nitrate hexahydrate.

7. The preparation method according to claim 1, characterized in that, In step (3), the rotary evaporation temperature is 80 ℃-100 ℃, the drying temperature is 60-80 ℃, the drying time is 12-24 h, the calcination temperature is 550 ℃, and the calcination time is 2 h; the reduction is carried out under a reducing atmosphere, the reducing atmosphere is hydrogen, the flow rate is 20 mL / min, the reduction treatment temperature is 550-600 ℃, and the treatment time is 2 h.

8. A spherical TS-1 molecular sieve-supported PtZn bimetallic propane dehydrogenation catalyst for propylene prepared by the method according to any one of claims 1-7, characterized in that, Based on the mass of the support in the catalyst, the Pt loading was 0.5 wt% and the Zn loading was 1.7 wt%.

9. The application of the catalyst according to claim 8 in the propane dehydrogenation reaction, characterized in that, The propane dehydrogenation to propylene is carried out in a fixed-bed reactor, specifically including the following steps: (1) The catalyst is packed into a quartz tube reactor with an outer diameter of 12 mm, and the quartz tube reactor is placed in the constant temperature zone of the fixed bed reactor heater. (2) A mixture of hydrogen and nitrogen in a molar ratio of 1:1 is introduced and heated to 600 °C at a rate of 5 °C / min for 2 h. The mixture is then cooled to the reaction temperature of 550-600 °C and a reaction gas is introduced to carry out the reaction. The molar ratio of propane to hydrogen in the reaction gas is 2:1, and nitrogen is used as the equilibrium gas. The mass hourly space velocity of propane is 6-40 h⁻¹. -1 .

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