KY molecular sieve supported Pt-Zn bimetallic composite material, preparation method thereof and straight-chain alkane aromatization method

Abstract

The invention provides a KY molecular sieve supported Pt-Zn bimetallic composite material as well as a preparation method and application thereof. According to the invention, an atomic layer deposition technology is combined, surface functional groups of the KY molecular sieve are modified by using an inhibitor, positioning and growth processes of metals Zn and Pt on the surface of the molecular sieve are regulated and controlled, and the microstructure of the composite material is controlled at an atomic level. The KY molecular sieve supported Pt-Zn bimetallic composite material provided by the invention is used for aromatization reaction of straight-chain alkanes, the reaction activity and the aromatic hydrocarbon selectivity are greatly improved, and the selectivity of small-molecule alkanes is effectively inhibited.

Description

Technical Field

[0001] This invention relates to the field of catalysts, and more particularly to a KY molecular sieve-supported Pt-Zn bimetallic composite material, its preparation method, and a method for aromatizing straight-chain alkanes. Background Technology

[0002] Pt / KL catalysts are supported catalysts with platinum (Pt) as the active component and KL-type molecular sieves as the support. They exhibit excellent hexane / heptane aromatization performance and have important applications in the field of catalysis. However, given their limitations in the aromatization of medium- and long-chain alkanes (C8+), researchers have recently conducted research on the application of noble metal catalysts supported by other types of molecular sieves in alkane aromatization reactions. They have found that Pt-based catalysts supported by KY molecular sieves have great potential for development in the aromatization of medium- and long-chain alkanes.

[0003] As the sole active center in the Pt / KY catalytic system, the electronic properties and dispersion of Pt are crucial factors influencing catalytic activity and product distribution. Adding a second metal (Sn / Zn / Ir / Fe / Ga) is an effective method for modulating the metallic properties of Pt. Researchers have found that the addition of Fe as a promoter can effectively improve the atom utilization and thermal stability of Pt species. The addition of Zn can inhibit alkane hydrogenolysis and improve the selectivity of target products. He (ACS Appl. Mater. Interfaces, Highly Selective Aromatization of Octane over Pt-Zn / UZSM-5: The Effect of Pt-Zn Interaction and Pt Position, 2020, 12, 28273-28287) studied a Pt-Zn bimetallic catalyst supported on ZSM-5 and found that it exhibited lower small molecule alkane selectivity compared to monometallic Pt-based catalysts, and significantly improved catalyst activity and aromatic selectivity in naphtha catalytic reforming. However, since the metal distribution is related to the chemical functional groups on the support surface, traditional methods are difficult to effectively control the microstructure of bimetallic catalysts, resulting in low utilization rates of active centers and second metal promoters in the KY molecular sieve catalytic system. Summary of the Invention

[0004] The technical problem solved by this invention is to provide a method for preparing a KY molecular sieve-supported Pt-Zn bimetallic composite material. The KY molecular sieve-supported Pt-Zn bimetallic composite material prepared in this application has high catalytic activity and aromatic selectivity as a catalyst for alkane aromatization reaction, and can effectively inhibit the selectivity of small molecule alkanes.

[0005] In view of this, this application provides a method for preparing a Pt-Zn bimetallic composite material supported on KY molecular sieves, comprising the following steps:

[0006] S1) Using atomic layer deposition technology, inhibitors are pulsed and deposited on KY molecular sieves, followed by purging, to obtain inhibitor-modified KY molecular sieves;

[0007] S2) Using atomic layer deposition technology, Zn source was pulsed and deposited on the inhibitor-modified KY molecular sieve. After purging, O3 was pulsed and deposited. After purging, Zn-supported composite material of KY molecular sieve was obtained.

[0008] Steps S1 and S2) are repeated 1 to 5 times;

[0009] S3) Using atomic layer deposition technology, an inhibitor is pulsed and deposited on the KY molecular sieve-supported Zn composite material, followed by purging, to obtain an inhibitor-modified KY molecular sieve-supported Zn composite material.

[0010] S4) Pt source was pulsed and deposited on the inhibitor-modified KY molecular sieve-supported Zn composite material using atomic layer deposition technology. After purging, O3 was pulsed and deposited. After purging, KY molecular sieve-supported Pt-Zn bimetallic composite material was obtained.

[0011] Repeat steps S3 and S4 1 to 5 times.

[0012] In some specific embodiments, in steps S1) and S3), the inhibitor independently includes one or more of methanol, ethanol, isopropanol, acetic acid, isobutyric acid, and 2-ethylbutyric acid.

[0013] In some specific embodiments, in step S1), the temperature of the inhibitor is 25-35°C, and / or the pulse time of the inhibitor is 0.1-1s, and / or the deposition time of the inhibitor is 1-10s, and / or the purge time after the inhibitor deposition is 80-150s.

[0014] In some specific embodiments, in step S2), the temperature of the Zn source is 50–80°C, and / or the Zn source includes one or more of diethylzinc, dimethylzinc, and zinc acetylacetonate.

[0015] In some specific embodiments, in step S2), the duration of the Zn source pulse is 0.1–3 s, and / or the Zn source deposition time is 50–100 s, and / or the purging time after Zn source deposition is 100–200 s; and / or the duration of the O3 pulse is 0.5–2 s, and / or the O3 deposition time is 80–150 s, and / or the purging time after O3 deposition is 90–120 s.

[0016] In some specific embodiments, in step S3), the temperature of the inhibitor is 25-35°C, and / or the pulse time of the inhibitor is 0.1-1s, and / or the deposition time of the inhibitor is 1-10s, and / or the purge time after the inhibitor deposition is 80-150s.

[0017] In some specific embodiments, in step S4), the Pt source includes one or more of (trimethyl)methylcyclopentadiene platinum, (trimethyl)pentamethylcyclopentadiene platinum, acetylacetone platinum, and p-cyclopentadiene (trimethyl) platinum; and / or, the duration of the Pt source pulse is 0.1–3 s, and / or, the duration of the Pt source deposition is 50–100 s, and / or, the purging time after the Pt source deposition is 100–200 s; and / or, the duration of the O3 pulse is 0.5–2 s, and / or, the duration of the O3 deposition is 80–150 s, and / or, the purging time after the O3 deposition is 90–120 s.

[0018] This application also provides a KY molecular sieve-supported Pt-Zn bimetallic composite material prepared by the aforementioned preparation method.

[0019] This application also provides a method for the aromatization of straight-chain alkanes, comprising:

[0020] Straight-chain alkanes are reacted in the presence of a catalyst;

[0021] The catalyst is prepared by the preparation method described above or the KY molecular sieve-supported Pt-Zn bimetallic composite material described above.

[0022] In some specific embodiments, the straight-chain alkane is C6 to C6. 10 One or more of the following, and / or, the reaction pressure is 0.1–0.5 MPa, and the reaction mass hourly space velocity is 0.3–1.5 h⁻¹. -1 The H2 flow rate of the reaction is 30-80 mL / min, the reaction temperature is 350-550 °C, and the molar ratio of H2 to the straight-chain alkane is (3-10):1.

[0023] This application provides a method for preparing a Pt-Zn bimetallic composite material supported on a KY molecular sieve. First, an inhibitor is pulse-deposited onto the molecular sieve using atomic layer deposition (ALD) to obtain an inhibitor-modified KY molecular sieve. Then, a zinc source is pulse-deposited onto the inhibitor-modified KY molecular sieve using ALD, allowing Zn atoms to be introduced into the sieve channels. Next, an inhibitor is pulse-deposited onto the Zn-supported KY molecular sieve composite material using ALD to passivate some Pt ​​source binding sites. Finally, a Pt source is pulse-deposited onto the inhibitor-modified KY molecular sieve Zn-supported composite material using ALD. Due to the steric hindrance of the inhibitor and the passivation of the binding sites, Pt atoms are not... The distribution of Zn near the atoms enables the regulation of the distribution of Pt and Zn in Pt-Zn bimetallic supported KY molecular sieves. The preparation method of KY-molecular sieve-supported Pt-Zn bimetallic composite material provided in this application utilizes atomic layer deposition technology to first deposit inhibitors, which can regulate the placement and growth process of Zn on the molecular sieve surface at the atomic level. The deposition of an appropriate amount of Zn can effectively inhibit the formation of small molecule alkanes and improve the selectivity of aromatics. The inhibitor deposition before Pt deposition can regulate the placement and growth of Pt on the surface of KY molecular sieve-supported Zn composite material at the atomic level. Zn deposition has a significant impact on the metallic properties of Pt species, effectively improving the aromatization performance and stability of the composite material as a catalyst. Attached Figure Description

[0024] Figure 1 SEM images of the KY molecular sieves used in comparative examples and Examples 1-4;

[0025] Figure 2 TEM image of the KY molecular sieve-supported Pt-Zn bimetallic composite material prepared in Example 3;

[0026] Figure 3 TEM image of the KY molecular sieve-supported Pt-Zn bimetallic composite material prepared for comparison. Detailed Implementation

[0027] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention.

[0028] Given the low utilization rate of active centers and second metal promoters in existing molecular sieve-supported Pt-Zn bimetallic composite materials used as catalysts for alkane aromatization, this application provides a method for preparing KY molecular sieve-supported Pt-Zn bimetallic composite materials. This method effectively improves the utilization rate of Pt and the second metal promoter Zn by introducing inhibitors and utilizing atomic layer deposition technology to control the deposition and growth of metals Pt and Zn on the surface of KY molecular sieves, thus preparing a highly efficient alkane aromatization catalyst with microscopically controllable structure. Specifically, this invention discloses a method for preparing KY molecular sieve-supported Pt-Zn bimetallic composite materials, including the following steps:

[0029] S1) Using atomic layer deposition technology, inhibitors are pulsed and deposited on KY molecular sieves, followed by purging, to obtain inhibitor-modified KY molecular sieves;

[0030] S2) Using atomic layer deposition technology, Zn source was pulsed and deposited on the inhibitor-modified KY molecular sieve. After purging, O3 was pulsed and deposited. After purging, Zn-supported composite material of KY molecular sieve was obtained.

[0031] Steps S1 and S2) are repeated 1 to 5 times;

[0032] S3) Using atomic layer deposition technology, an inhibitor is pulsed and deposited on the KY molecular sieve-supported Zn composite material, followed by purging, to obtain an inhibitor-modified KY molecular sieve-supported Zn composite material.

[0033] S4) Pt source was pulsed and deposited on the inhibitor-modified KY molecular sieve-supported Zn composite material using atomic layer deposition technology. After purging, O3 was pulsed and deposited. After purging, KY molecular sieve-supported Pt-Zn bimetallic composite material was obtained.

[0034] Repeat steps S3 and S4 1 to 5 times.

[0035] In the process of loading Pt-Zn bimetallic composite material onto KY molecular sieve, in step S1, an inhibitor is pulsed and deposited onto the KY molecular sieve using atomic layer deposition technology, followed by purging to obtain an inhibitor-modified KY molecular sieve. During this process, the KY molecular sieve can be prepared according to methods well known to those skilled in the art, and this application does not impose any particular limitations. In a specific embodiment, the preparation method of the KY molecular sieve is as follows:

[0036] Potassium source was dissolved in alcohol solvent to obtain potassium alkoxide solution, and then potassium alkoxide was dissolved in Y molecular sieve and mixed in a certain proportion. The mixture was stirred at room temperature, centrifuged and washed until neutral, and then dried and calcined to obtain KY molecular sieve.

[0037] Specifically, the concentration of the potassium alkoxide solution is 0.01–0.5 mol / L, the solid-liquid ratio of the potassium alkoxide solution to the molecular sieve is 100:1–10:1, the stirring time is 10 min–2 h, the calcination temperature is 350–650 °C, and the calcination time is 5–12 h.

[0038] The inhibitor includes one or more of methanol, ethanol, isopropanol, acetic acid, isobutyric acid, and 2-ethylbutyric acid. Specifically, the inhibitor is selected from one of methanol, ethanol, isopropanol, acetic acid, isobutyric acid, and 2-ethylbutyric acid. More specifically, the inhibitor is selected from methanol. The temperature of the inhibitor is 25–35°C, the pulse time of the inhibitor is 0.1–1 s, and the deposition time of the inhibitor is 1–10 s. Specifically, the pulse time of the inhibitor is 0.2–0.8 s, and the deposition time of the inhibitor is 2–8 s. More specifically, the pulse time of the inhibitor is 0.3–0.5 s, and the deposition time of the inhibitor is 3–5 s. The purging gas includes one or more of high-purity nitrogen, high-purity argon, and high-purity helium. The purging time is 80–150 s. Specifically, the purging time is 100–140 s, and more specifically, the purging time is 120–130 s. The reaction chamber temperature of the atomic layer deposition (ALD) technique is 150–300°C, specifically 180–250°C. This step involves depositing inhibitors on KY molecular sieves to obtain inhibitor-modified KY molecular sieves. The Si-OH groups on the surface of the KY molecular sieves are modified into Si-OR groups by the inhibitors (R depends on the type of inhibitor; for example, if the inhibitor is selected from methanol, R is -CH3; if the inhibitor is selected from ethanol, R is -CH2CH3), thus passivating some sites on the KY molecular sieves.

[0039] In step S2, a Zn source is pulse-deposited onto the inhibitor-modified KY molecular sieve using atomic layer deposition (ALD). After purging, O3 is pulse-deposited, and the resulting Zn-supported KY molecular sieve composite material is obtained. In this step, due to the modification effect of the inhibitor, Zn is introduced into the pores of the molecular sieve via ALD. After O3 treatment, the functional groups on the molecular sieve are Si-OH / Zn-OH. During the above process, the temperature of the Zn source is 50–80°C, specifically 65–75°C. The Zn source includes one or more of diethylzinc, dimethylzinc, and zinc acetylacetonate, specifically selected from diethylzinc, dimethylzinc, and zinc acetylacetonate. The Zn source pulse duration is 0.1–3 s, and the Zn source deposition time is 50–100 s. Specifically, the Zn source pulse duration is 0.2–1.5 s, and the Zn source deposition time is 60–90 s. More specifically, the Zn source pulse duration is 0.5–0.8 s, and the Zn source deposition time is 70–80 s. The purging time after Zn source deposition is 100–200 s. Specifically, the purging time is 110–180 s, and more specifically, the purging time is 120–150 s. The O3 pulse duration is 0.5–2 s, the O3 deposition time is 80–150 s, and the purging time after O3 deposition is 90–120 s. Specifically, the O3 pulse duration is 1–1.5 s, the O3 deposition time is 90–100 s, and the purging time after O3 deposition is 100–110 s. The reaction chamber temperature of the atomic layer deposition (ALD) technology is 150–300°C, specifically, the reaction chamber temperature of the ALD is 180–250°C.

[0040] In step S3, an inhibitor is pulsed and deposited on the above-mentioned KY molecular sieve-supported Zn composite material using atomic layer deposition (ALD), followed by purging to obtain an inhibitor-modified KY molecular sieve-supported Zn composite material. In this process, the inhibitor includes one or more of methanol, ethanol, isopropanol, acetic acid, isobutyric acid, and 2-ethylbutyric acid. Specifically, the inhibitor is selected from one of methanol, ethanol, isopropanol, acetic acid, isobutyric acid, and 2-ethylbutyric acid. The temperature of the inhibitor is 25–35°C, the pulse time of the inhibitor is 0.1–1 s, and the deposition time of the inhibitor is 1–10 s; specifically, the pulse time of the inhibitor is 0.2–0.5 s, and the deposition time of the inhibitor is 3–5 s. The purging gas includes one or more of high-purity nitrogen, high-purity argon, and high-purity helium; the purging time is 80–150 s, specifically, the purging time is 100–120 s. The reaction chamber temperature of the atomic layer deposition (ALD) technique is 150–300°C, specifically 180–250°C. This step deposits an inhibitor on a KY molecular sieve-supported Zn composite material, resulting in an inhibitor-modified KY molecular sieve-supported Zn composite material. This material can passivate some Pt ​​source binding sites. By selecting different inhibitors, the hydrocarbon chain length can be controlled to regulate the distribution of Pt and Zn sources in the Pt-Zn bimetallic compound.

[0041] In step S4, a Pt source is pulse-deposited onto the inhibitor-modified KY molecular sieve-supported Zn composite material using atomic layer deposition (ALD). After purging, O3 is pulse-deposited, resulting in a KY molecular sieve-supported Pt-Zn bimetallic composite material. In this step, with the addition of an inhibitor, Pt is passivated due to steric hindrance and binding sites, preventing it from distributing near Zn species. Otherwise, Pt might preferentially bind to Zn-OH (especially when Zn is distributed on the outer surface of the molecular sieve), depositing near Zn species and ultimately affecting the catalytic performance of the molecular sieve composite material. During the above process, the temperature of the Pt source is 50–80°C, specifically 65–75°C. The Pt source includes one or more of (trimethyl)methylcyclopentadiene platinum, (trimethyl)pentamethylcyclopentadiene platinum, acetylacetonate platinum, and p-cyclopentadiene (trimethyl)platinum, specifically selected from acetylacetonate platinum and (trimethyl)methylcyclopentadiene platinum. The duration of the Pt source pulse is 0.1–3 s, and the Pt source deposition time is 50–100 s. Specifically, the duration of the Pt source pulse is 0.3–0.5 s, and the Pt source deposition time is 60–80 s. The purge time after Pt source deposition is 100–200 s. Specifically, the purge time is 120–180 s. The duration of the O3 pulse is 0.5–2 s, the O3 deposition time is 80–150 s, and the purge time after O3 deposition is 90–120 s. Specifically, the duration of the O3 pulse is 1–1.5 s, the O3 deposition time is 90–100 s, and the purge time after O3 deposition is 100–110 s. The reaction chamber temperature of the atomic layer deposition (ALD) technique is 150–300 °C. Specifically, the reaction chamber temperature of the ALD technique is 180–250 °C.

[0042] In this application, steps S1 and S2 are repeated 1 to 5 times. For example, if steps S1 and S2 are repeated twice, they are performed in the order of S1, S2, S1, S2; if they are repeated three times, they are performed in the order of S1, S2, S1, S2, S1, S2. Similarly, steps S3 and S4 are repeated 1 to 5 times. For example, if steps S3 and S4 are repeated twice, they are performed in the order of S3, S4, S3, S4; if they are repeated three times, they are performed in the order of S1, S2, S1, S2. 3. Steps S4, S3, S4, S3, and S4 are performed sequentially. Further, the number of repetitions of steps S1 and S2 can be the same as or different from the number of repetitions of steps S3 and S4. For example, the composite material can be prepared in the order of steps S1, S2, S1, S2, S3, and S4, or in the order of steps S1, S2, S1, S2, S3, S4, S3, and S4. This application also provides a KY molecular sieve-supported Pt-Zn bimetallic composite material prepared by the above method.

[0043] Furthermore, this application also provides a method for the aromatization of straight-chain alkanes, comprising:

[0044] Straight-chain alkanes are reacted in the presence of a catalyst;

[0045] The catalyst is the KY molecular sieve-supported Pt-Zn bimetallic composite material described in the above scheme.

[0046] In the aromatization of straight-chain alkanes, the straight-chain alkanes are C6 to C6. 10 One or more straight-chain alkanes are used; in a specific embodiment, the straight-chain alkane is n-octane; the reaction pressure is 0.1–0.5 MPa, and the mass hourly space velocity (HHSV) is 0.3–1.5 h⁻¹. -1 The H2 gas velocity in the reaction is 30–80 mL / min, and the molar ratio of H2 to the straight-chain alkane is (3–10):1; specifically, the reaction pressure is 0.2–0.4 MPa, and the mass hourly space velocity (HSV) is 0.8–1.1 h⁻¹. -1 The H2 gas velocity in the reaction is 50-60 mL / min, and the molar ratio of H2 to the straight-chain alkane is (4.5-7):1.

[0047] This invention employs atomic layer deposition (ALD) technology to regulate the deposition and growth of Zn on the surface of molecular sieves at the atomic level. Appropriate Zn deposition can effectively suppress the formation of small molecule alkanes and improve the selectivity of aromatic products. ALD technology can also regulate the deposition and growth of Pt on the Zn species / molecular sieve surface at the atomic level. Zn deposition has a significant impact on the metallic properties of Pt species, effectively improving the aromatization performance and stability of the composite material. Furthermore, since the selective deposition of inhibitors can passivate some Pt ​​source binding sites, adjusting the hydrocarbon chain length in the inhibitor can regulate the distribution of Pt and Zn sources in the Pt-Zn bimetallic composite material.

[0048] To further understand the present invention, the following detailed description, in conjunction with embodiments, provides the KY molecular sieve-supported Pt-Zn bimetallic composite material, its preparation method, and the method for aromatizing straight-chain alkane. The scope of protection of the present invention is not limited by the following embodiments.

[0049] In the following examples and comparative examples, the KY molecular sieves were prepared according to the following method:

[0050] Dissolve 0.1020 g KOH in 120 mL ethanol to prepare a 0.15 mol / L potassium ethoxide solution. Then, place 2 g Y molecular sieve into the above potassium ethoxide solution and stir at room temperature for 1 h.

[0051] The system obtained above was centrifuged and washed repeatedly with ethanol until neutral. It was then dried in a 100°C oven for 8 hours and finally calcined in a muffle furnace at 600°C for 6 hours to obtain KY molecular sieve.

[0052] like Figure 1 As shown, Figure 1 The above-prepared KY molecular sieve is shown in the SEM image. Figure 1 It can be seen that K modification has little effect on the morphology of Y molecular sieve.

[0053] Example 1

[0054] 1) Take 3g of KY molecular sieve and ultrasonically disperse it in 120mL of ethanol. After mixing evenly, coat it on a quartz plate, dry it at room temperature, and place it in an ALD chamber at 200℃. Perform methanol pulse, deposition, and purging. The methanol temperature is room temperature, and the pulse, deposition, and purging times are 0.1s, 2s, and 90s, respectively, to obtain methanol-modified KY molecular sieve.

[0055] 2) The 3g methanol-modified KY molecular sieve was ground and ultrasonically dispersed in 120mL of ethanol. After being mixed evenly, it was coated onto a quartz plate, dried at room temperature, and then placed in an ALD chamber at 200℃ for ALD loading of Zn.

[0056] First, acetylacetone zinc was pulsed, deposited, and purged at a temperature of 65°C for 0.2 s, 60 s, and 100 s, respectively. Then, O3 was pulsed, deposited, and purged for 0.5 s, 80 s, and 90 s, respectively.

[0057] Steps S1 and S2 are repeated twice more using the above method to obtain the KY molecular sieve-supported Zn composite material.

[0058] 3) The above 3g of KY molecular sieve-supported Zn composite material was ground and ultrasonically dispersed in 120mL of ethanol. After being mixed evenly, it was coated on a quartz plate, dried at room temperature, and placed in an ALD chamber at 200℃. Methanol pulse, deposition and purging were performed. The methanol temperature was room temperature, and the pulse, deposition and purging times were 0.1s, 2s and 80s, respectively, to obtain methanol-modified KY molecular sieve-supported Zn composite material.

[0059] 4) The above-mentioned 3g methanol-modified KY molecular sieve-supported Zn composite material was ground and ultrasonically dispersed in 120mL of ethanol. After being mixed evenly, it was coated onto a quartz plate, dried at room temperature, and then placed in an ALD chamber at 200℃ for Pt ALD loading:

[0060] First, acetylacetone platinum was pulsed, deposited, and purged at a temperature of 60°C for 0.1 s, 60 s, and 100 s, respectively. Then, O3 was pulsed, deposited, and purged for 0.5 s, 80 s, and 90 s, respectively.

[0061] Steps S3 and S4 are performed twice more using the same method to obtain the KY molecular sieve-supported Pt-Zn composite material.

[0062] Example 2

[0063] 1) Take 3g of KY molecular sieve and ultrasonically disperse it in 120mL of ethanol. After mixing evenly, coat it on a quartz plate, dry it at room temperature, and place it in an ALD chamber at 200℃. Perform methanol pulse, deposition, and purging. The methanol temperature is room temperature, and the pulse, deposition, and purging times are 0.2s, 2s, and 100s, respectively, to obtain methanol-modified KY molecular sieve.

[0064] 2) The 3g methanol-modified KY molecular sieve was ground and ultrasonically dispersed in 120mL of ethanol. After mixing evenly, it was coated onto a quartz plate, dried at room temperature, and then placed in an ALD chamber at 200℃ for ALD loading of Zn.

[0065] First, diethylzinc was pulsed, deposited, and purged at a temperature of 65°C for 0.8 s, 80 s, and 110 s, respectively. Then, O3 was pulsed, deposited, and purged for 1 s, 90 s, and 100 s, respectively.

[0066] Steps 1) and 2) are repeated once more using the methods described above to obtain the KY molecular sieve-supported Zn composite material.

[0067] 3) The above 3g of KY molecular sieve-supported Zn composite material was ground and ultrasonically dispersed in 120mL of ethanol. After being mixed evenly, it was coated on a quartz plate, dried at room temperature, and placed in an ALD chamber at 200℃. The ethanol was pulsed, deposited and purged. The ethanol was used at room temperature, and the pulse, deposition and purging times were 0.2s, 5s and 100s, respectively, to obtain the ethanol-modified KY molecular sieve-supported Zn composite material.

[0068] 4) The 3g ethanol-modified KY molecular sieve-supported Zn composite material was ground and ultrasonically dispersed in 120mL ethanol. After being mixed evenly, it was coated onto a quartz plate, dried at room temperature, and then placed in an ALD chamber at 200℃ for Pt ALD loading:

[0069] First, (trimethyl)pentamethylcyclopentadiene platinum was pulsed, deposited, and purged at a temperature of 60°C for 0.3 s, 80 s, and 120 s, respectively. Then, O3 was pulsed, deposited, and purged for 1 s, 100 s, and 100 s, respectively.

[0070] Steps 3 and 4) are repeated twice more using the above method to obtain the KY molecular sieve-supported Pt-Zn composite material.

[0071] Example 3

[0072] 1) Take 3g of KY molecular sieve and ultrasonically disperse it in 120mL of ethanol. After mixing evenly, coat it on a quartz plate, dry it at room temperature, and place it in an ALD chamber at 200℃. Perform methanol pulse, deposition, and purging. The methanol temperature is room temperature, and the pulse, deposition, and purging times are 0.5s, 5s, and 120s, respectively, to obtain methanol-modified KY molecular sieve.

[0073] 2) The 3g methanol-modified KY molecular sieve was ground and ultrasonically dispersed in 120mL of ethanol. After mixing evenly, it was coated onto a quartz plate, dried at room temperature, and then placed in an ALD chamber at 200℃ for ALD loading of Zn.

[0074] First, dimethyl zinc was subjected to pulse deposition and purging at a temperature of 65°C for 0.5 s, 100 s, and 120 s, respectively. Subsequently, O3 was subjected to pulse deposition and purging for 2 s, 100 s, and 110 s, respectively, to obtain a KY molecular sieve-supported Zn composite material.

[0075] 3) The above 3g of KY molecular sieve-supported Zn composite material was ground and ultrasonically dispersed in 120mL of ethanol. After being mixed evenly, it was coated on a quartz plate, dried at room temperature, and placed in an ALD chamber at 200℃ for acetic acid pulse, deposition, and purging. The acetic acid was used at room temperature, and the pulse, deposition, and purging times were 0.5s, 3s, and 120s, respectively, to obtain the acetic acid-modified KY molecular sieve-supported Zn composite material.

[0076] 4) The above-mentioned 3g acetic acid-modified KY molecular sieve-supported Zn composite material was ground and ultrasonically dispersed in 120mL ethanol. After being mixed evenly, it was coated onto a quartz plate, dried at room temperature, and then placed in an ALD chamber at 200℃ for Pt ALD loading:

[0077] First, (trimethyl)methylcyclopentadiene platinum was pulsed, deposited, and purged at a temperature of 60°C for 0.5 s, 100 s, and 150 s, respectively. Then, O3 was pulsed, deposited, and purged for 1.5 s, 100 s, and 120 s, respectively.

[0078] Steps 3 and 4) are repeated twice more using the above method to obtain the KY molecular sieve-supported Pt-Zn composite material.

[0079] Example 4

[0080] 1) Take 3g of KY molecular sieve and ultrasonically disperse it in 120mL of ethanol. After mixing evenly, coat it on a quartz plate, dry it at room temperature, and place it in an ALD chamber at 200℃. Perform methanol pulse, deposition, and purging. The methanol temperature is room temperature, and the pulse, deposition, and purging times are 0.8s, 8s, and 150s, respectively, to obtain methanol-modified KY molecular sieve.

[0081] 2) The 3g methanol-modified KY molecular sieve was ground and ultrasonically dispersed in 120mL of ethanol. After mixing evenly, it was coated onto a quartz plate, dried at room temperature, and then placed in an ALD chamber at 200℃ for ALD loading of Zn.

[0082] First, dimethyl zinc was pulsed, deposited, and purged at a temperature of 65°C for 1.5 s, 100 s, and 150 s, respectively. Then, O3 was pulsed, deposited, and purged for 2 s, 100 s, and 110 s, respectively, to obtain KY molecular sieve-supported Zn composite material.

[0083] 3) The above 3g of KY molecular sieve-supported Zn composite material was ground and ultrasonically dispersed in 120mL of ethanol. After being mixed evenly, it was coated on a quartz plate, dried at room temperature, and placed in an ALD chamber at 200℃ for pulse, deposition and purging of 2-ethylbutyric acid. The temperature of 2-ethylbutyric acid was room temperature, and the pulse, deposition and purging times were 1s, 10s and 150s, respectively, to obtain KY molecular sieve-supported Zn composite material modified with 2-ethylbutyric acid.

[0084] 4) The 3g of 2-ethylbutyric acid-modified KY molecular sieve-supported Zn composite material was ground and ultrasonically dispersed in 120mL of ethanol. After being mixed evenly, it was coated onto a quartz plate, dried at room temperature, and then placed in an ALD chamber at 200℃ for Pt ALD loading.

[0085] First, (trimethyl)methylcyclopentadiene platinum was pulsed, deposited, and purged at a temperature of 60°C for 1 s, 100 s, and 180 s, respectively. Then, O3 was pulsed, deposited, and purged for 2 s, 120 s, and 120 s, respectively.

[0086] Steps 3 and 4) are repeated twice more using the above method to obtain the KY molecular sieve-supported Pt-Zn composite material.

[0087] Comparative Example

[0088] 1) Take 3g of KY molecular sieve and ultrasonically disperse it in 120mL of ethanol. After mixing evenly, coat it on a quartz plate, dry it at room temperature, and place it in an ALD chamber at 200℃. Perform methanol pulse, deposition, and purging. The methanol temperature is room temperature, and the pulse, deposition, and purging times are 0.8s, 8s, and 150s, respectively, to obtain methanol-modified KY molecular sieve.

[0089] 2) The 3g methanol-modified KY molecular sieve was ground and ultrasonically dispersed in 120mL of ethanol. After mixing evenly, it was coated onto a quartz plate, dried at room temperature, and then placed in an ALD chamber at 200℃ for ALD loading of Zn.

[0090] First, dimethyl zinc was pulsed, deposited, and purged at a temperature of 65°C for 2 s, 100 s, and 180 s, respectively. Then, O3 was pulsed, deposited, and purged for 2 s, 120 s, and 120 s, respectively, to obtain KY molecular sieve-supported Zn composite material.

[0091] 3) The above 3g of KY molecular sieve-loaded Zn composite material was ground and ultrasonically dispersed in 120mL of ethanol. After being mixed evenly, it was coated onto a quartz plate, dried at room temperature, and then placed in an ALD chamber at 200℃ for Pt ALD loading:

[0092] First, (trimethyl)methylcyclopentadiene platinum was pulsed, deposited, and purged at a temperature of 60°C for 2 s, 100 s, and 180 s, respectively. Then, O3 was pulsed, deposited, and purged for 2 s, 120 s, and 120 s, respectively.

[0093] Step S3) Repeat the above method twice more to obtain the KY molecular sieve-supported Pt-Zn composite material.

[0094] The composite materials finally prepared in the examples and comparative examples were used as catalysts in alkane aromatization, specifically as follows:

[0095] Using n-octane as a raw material, the composite materials prepared in the comparative examples and Examples 1-4 were evaluated for alkane aromatization performance. The specific reaction conditions were as follows: 0.5 g of the prepared composite material was mixed with quartz sand as a catalyst and then loaded into a fixed-bed reaction tube. The mixture was reduced at 500 °C for 1 h at an H2 flow rate of 50 mL / min. After the reduction was completed, the temperature of the reaction tube was lowered to the reaction temperature, and the H2 flow rate was adjusted to 8 mL / min. Subsequently, the liquid feed pump was turned on, and the liquid flow rate was 0.8 mL / h. All products were analyzed by online gas chromatography, as shown in Table 1.

[0096] Table 1. Evaluation data of the catalytic performance of composite materials in Examples 1-4 and Comparative Examples.

[0097]

[0098] As shown in Table 1, although the composite material prepared in Comparative Example 1 was loaded with a high content of Pt as a catalyst, its aromatic selectivity was lower than that of the examples, and its n-octane conversion rate was also lower.

[0099] Figure 2 TEM image of the KY molecular sieve-supported Pt-Zn bimetallic composite material prepared for the example; Figure 3 TEM images of the Pt-Zn bimetallic composite material supported on KY molecular sieves, prepared as a comparative example; by Figure 2and Figure 3 It is known that inhibitor modification can significantly improve the dispersion of active centers and adjust the distribution of active centers on KY molecular sieves.

[0100] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0101] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a KY molecular sieve supported Pt-Zn bimetallic composite material, comprising the following steps: S1) depositing an inhibitor on a KY molecular sieve by atomic layer deposition (ALD), and then purging to obtain an inhibitor-modified KY molecular sieve; S2) depositing a Zn source on the inhibitor-modified KY molecular sieve by ALD, and then purging, and then depositing O 3 by ALD to obtain a KY molecular sieve supported Zn composite material; repeating steps S1) and S2) 1-5 times; S3) depositing an inhibitor on the KY molecular sieve supported Zn composite material by ALD, and then purging to obtain an inhibitor-modified KY molecular sieve supported Zn composite material; S4) depositing a Pt source on the inhibitor-modified KY molecular sieve supported Zn composite material by ALD, and then purging, and then depositing O 3 by ALD to obtain a KY molecular sieve supported Pt-Zn bimetallic composite material; and repeating steps S3) and S4) 1-5 times. In steps S1) and S3), the inhibitor independently comprises one or more of methanol, ethanol, isopropanol, acetic acid, isobutyric acid and 2-ethylbutyric acid. In step S1), the temperature of the inhibitor is 25-35 ℃, and / or the pulse time of the inhibitor is 0.1-1 s, and / or the deposition time of the inhibitor is 1-10 s, and / or the purging time after deposition of the inhibitor is 80-150 s. In step S2), the temperature of the Zn source is 50-80 ℃, and / or the Zn source comprises one or more of diethyl zinc, dimethyl zinc and acetylacetonate zinc. In step S2), the pulse time of the Zn source is 0.1-3 s, and / or the deposition time of the Zn source is 50-100 s, and / or the purging time after deposition of the Zn source is 100-200 s; and / or the pulse time of O 3 is 0.5-2 s, and / or the deposition time of O 3 is 80-150 s, and / or the purging time after deposition of O 3 is 90-120 s. In step S3), the temperature of the inhibitor is 25-35 ℃, and / or the pulse time of the inhibitor is 0.1-1 s, and / or the deposition time of the inhibitor is 1-10 s, and / or the purging time after deposition of the inhibitor is 80-150 s. In step S4), the Pt source comprises one or more of (trimethyl) methylcyclopentadiene platinum, (trimethyl) pentamethylcyclopentadiene platinum, acetylacetonate platinum and п-cyclopentadiene (trimethyl) platinum; and / or the pulse time of the Pt source is 0.1-3 s, and / or the deposition time of the Pt source is 50-100 s, and / or the purging time after deposition of the Pt source is 100-200 s; and / or the pulse time of O 3 is 0.5-2 s, and / or the deposition time of O 3 is 80-150 s, and / or the purging time after deposition of O 3 is 90-120 s.

2. The production method according to claim 1, characterized by, ​ 3. The production method according to claim 1 or 2, characterized by, ​ 4. The production method according to claim 1 or 2, characterized by, ​ 5. The preparation method according to claim 4, characterized in that, ​ 6. The production method according to claim 1 or 2, characterized by, ​ 7. The production method according to claim 1 or 2, characterized by, ​ 8. The Pt-Zn bimetallic composite material of KY molecular sieve prepared by the preparation method of any one of claims 1-7.

9. A method for aromatization of linear alkanes, comprising: reacting linear alkanes in the presence of a catalyst; the catalyst is the Pt-Zn bimetallic composite material of KY molecular sieve prepared by the preparation method of any one of claims 1-7 or claim 8.

10. The method of claim 9, wherein, The straight-chain alkane is C6-C6. 10 One or more of the following, and / or, the reaction pressure is 0.1–0.5 MPa, and the reaction mass hourly space velocity is 0.3–1.5 h⁻¹. -1 The H2 flow rate of the reaction is 30-80 mL / min, the reaction temperature is 350-550 °C, and the molar ratio of H2 to the straight-chain alkane is (3-10):1.

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