Preparation method and application of high-stability catalyst for methanol-to-aryl aviation kerosene

Abstract

The invention relates to the technical field of catalysts, and discloses a preparation method and application of a high-stability catalyst for methanol-to-aryl aviation kerosene, and the preparation method comprises the following steps: S1, adding a silicon source, an aluminum source, tetrapropylammonium hydroxide and urea into water, carrying out a hydrothermal crystallization reaction, and carrying out aerobic roasting on a reaction product to obtain a lamellar ZSM-5 molecular sieve; s2, mixing the lamellar ZSM-5 molecular sieve and an alkali solution, heating and stirring, filtering and drying, and carrying out ammonia exchange to obtain a lamellar mesoporous ZSM-5 molecular sieve; and S3, mixing 50-80% by mass of the lamellar mesoporous ZSM-5 molecular sieve and 20-50% by mass of a graphite auxiliary agent, and carrying out ball milling. The lamellar mesoporous ZSM-5 molecular sieve and the graphite additive are compounded and ball-milled to form the catalyst with a molecular sieve-graphite additive alternate stacking structure, so that the molecular sieve and the graphite additive are in dual structure-property synergism, and the catalytic activity and stability of the catalyst are improved.

Description

Technical Field

[0001] This invention relates to the technical field of catalysts, and in particular to a method for preparing and applying a highly stable catalyst for methanol-to-aromatics-based jet fuel. Background Technology

[0002] Developing sustainable jet fuel (SAF) as an alternative to fossil jet fuel has become one of the core pathways for emission reduction in the aviation industry. Methanol, produced through renewable energy-driven CO2 hydrogenation or biomass conversion, possesses the potential for carbon neutrality throughout its entire life cycle. Therefore, the technological route for producing sustainable jet fuel using methanol as a feedstock has attracted widespread attention. The core process of methanol-to-sustainable jet fuel involves converting methanol into a hydrocarbon mixture rich in aromatics (primarily C8-C6) using a catalyst. 12 Aromatics are produced, and then hydrogenated to obtain fuel that meets aviation kerosene standards. However, the industrialization of this technology faces many challenges, with catalyst stability limiting its large-scale application.

[0003] Currently, most commonly used catalysts are molecular sieves (such as ZSM-5). For example, patent CN120483183A discloses a method for preparing mesoporous Zn-ZSM-5 molecular sieves for methanol-to-aromatics production. The method involves mixing zinc gluconate with aluminum source, silicon source, and template agent, then placing the mixture in a closed reaction vessel for hydrothermal crystallization, followed by washing, drying, and calcination to obtain a sodium-type molecular sieve. The sodium-type molecular sieve is then subjected to multiple ion exchanges with ammonium chloride solution, followed by filtration, washing, drying, and calcination to obtain the mesoporous Zn-ZSM-5 molecular sieve. However, traditional ZSM-5 molecular sieves (block or spherical morphology) have the following defects: (1) long micropore channels (diffusion distance 1~5μm), C8~C 12 (1) Aromatic products have a long residence time and are prone to forming polycyclic aromatic carbon deposits; (2) The specific surface area is low, the active sites are not exposed enough, and the by-product water is prone to corroding the skeleton aluminum, resulting in dealuminization and deactivation. As a result, the single-pass life of existing catalysts is generally short (usually less than 100 hours). Frequent regeneration not only increases energy consumption and operating costs, but also shortens the overall service life of the catalyst, which seriously hinders the economics and industrialization of methanol-to-aromatics-based sustainable jet fuel technology.

[0004] Therefore, developing catalyst systems with high stability and long lifespan through structure-property synergy has become an urgent need to promote breakthroughs in methanol-to-aromatics-based sustainable jet fuel technology. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing and applying a highly stable catalyst for methanol-to-aromatics-based jet fuel. By ball milling a composite of lamellar mesoporous ZSM-5 molecular sieve and graphite additive, a catalyst with an alternating stacked structure of molecular sieve and graphite additive is formed. This results in a dual synergistic effect of structure and property of the molecular sieve and graphite additive, thereby enhancing the catalytic activity and stability of the catalyst.

[0006] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for preparing a highly stable catalyst for methanol-to-aromatics-based jet fuel, comprising the following steps: S1: Add silicon source, aluminum source, tetrapropylammonium hydroxide and urea to water to carry out hydrothermal crystallization reaction. The reaction product is then calcined with oxygen to obtain sheet ZSM-5 molecular sieve. S2: After mixing the sheet-like ZSM-5 molecular sieve with an alkaline solution, heating and stirring, filtering and drying, and then performing ammonia exchange, a sheet-like mesoporous ZSM-5 molecular sieve is obtained; the sheet-like mesoporous ZSM-5 molecular sieve has a silicon-to-aluminum molar ratio of 20~80, an a-axis length of 1~3 μm, a b-axis length of 50~400 nm, and a c-axis length of 300~800 nm; S3: By mass percentage, 50-80% of lamellar mesoporous ZSM-5 molecular sieve and 20-50% of graphite additive are mixed and ball-milled to obtain a catalyst, wherein the catalyst has a structure with alternating stacking of molecular sieve and graphite additive.

[0007] The catalyst in this invention is a composite of layered mesoporous ZSM-5 molecular sieve and graphite additive. Both the ZSM-5 molecular sieve and the graphite additive have layered structures. Furthermore, the size of the layered mesoporous ZSM-5 molecular sieve is controlled, resulting in the lowest binding potential energy on its large surface area (the 010 crystal plane of the molecular sieve and the layered surface of the graphite). Its smooth surface also facilitates face-to-face contact during ball milling, forming a stable open framework of alternating stacked molecular sieve and graphite additive. In contrast, other additives (such as SiO2) have spherical structures, making it difficult to form face-to-face contact with the layered mesoporous ZSM-5 molecular sieve. They tend to form dense packing that blocks the molecular sieve's pore structure and cannot exert a synergistic structure-property effect.

[0008] The catalyst with its alternating molecular sieve-graphite promoter stacked structure has the following advantages: On the one hand, the layered structure of graphite additives partially covers or isolates strong acid sites on the surface and between particles of ZSM-5 molecular sieves, effectively weakening the locally excessively acidic environment. Simultaneously, the π-electron system of graphite can weakly interact with the Brønsted acid sites of the molecular sieve, further reducing acid strength and inhibiting excessive condensation reactions of olefins and aromatics. Therefore, the formation rate of polycyclic aromatic hydrocarbons and coke during aromatization is significantly reduced, the coke morphology is easier to regenerate and remove, and the catalyst deactivation rate is greatly slowed down. Moreover, controlling the silicon-aluminum molar ratio of ZSM-5 molecular sieves helps to further reduce coking. A low silicon-aluminum molar ratio accelerates coking, while increasing the ratio reduces acid sites and slows down coking. However, after increasing it to a certain extent, the weakened acidity leads to a decrease in methanol conversion.

[0009] On the other hand, since this invention requires the use of the acidic sites of ZSM-5 molecular sieves, the defined molecular sieve has a low silica-to-alumina ratio (20-80), and its hydrophobicity is much weaker than that of graphite. Low silica-to-alumina molecular sieves themselves have insufficient hydrothermal stability, necessitating timely removal of byproduct water to prevent framework collapse. The strong hydrophobicity of graphite additives (contact angle >120°) can form local drainage channels between ZSM-5 molecular sieve particles, reducing the retention and adsorption of water molecules in the pores, thereby effectively preventing the poisoning of acidic sites by byproduct water and the dealumination damage to the molecular sieve framework.

[0010] Therefore, graphite additives can form a synergistic effect of structure and property with the mesoporous ZSM-5 molecular sieve. While directly coating the surface of the mesoporous ZSM-5 molecular sieve with an S-1 shell can enhance the hydrophobicity of the molecular sieve surface, the diffusion restriction of the S-1 channels makes it difficult for macromolecular products to desorb, causing them to accumulate within the molecular sieve channels and leading to catalyst carbon deposition and deactivation. Moreover, this invention further improves catalytic stability by controlling the compound ratio of mesoporous ZSM-5 molecular sieve and graphite additive. When the proportion of mesoporous ZSM-5 molecular sieve is too large, the hydrophobicity of the graphite additive is insufficient, resulting in a lack of significant improvement in catalyst lifetime; while when the proportion of graphite additive is too large, the acidic sites of the molecular sieve are insufficient, causing a decrease in methanol conversion rate.

[0011] Preferably, in step S1, the silicon source is tetraethyl silicate (TEOS); the aluminum source is aluminum isopropoxide, aluminum sulfate, or boehmite.

[0012] Preferably, in step S1, the molar ratio of silicon to tetrapropylammonium hydroxide and urea in the silicon source is 1:0.1~0.5:0.1~2.5.

[0013] Preferably, in step S1, the molar ratio of silicon to water in the silicon source is 1:20~33.5.

[0014] Preferably, in step S1, the temperature of the hydrothermal crystallization reaction is 120~200℃ and the time is 24~80h.

[0015] Preferably, in step S1, the temperature of the aerobic roasting is 500~600℃ and the time is 3~5h.

[0016] Preferably, in step S2, the concentration of the alkaline solution is 0.1~0.3M; the alkaline solution is NaOH solution; the heating and stirring temperature is 70~90℃, and the stirring time is 1~2h.

[0017] Molecular sieves are selectively dissolved in alkaline solutions to form mesoporous structures. When the alkaline concentration is too low, the mesoporous content is insufficient, and the molecular sieve is prone to rapid carbon deposition. When the alkaline concentration is too high, the molecular sieve framework partially collapses, and the catalytic performance is greatly reduced.

[0018] Preferably, in step S2, the ammonia exchange involves ion exchange of the sheet-like ZSM-5 molecular sieve with an ammonium salt solution; the ammonium salt solution is an ammonium chloride solution; the ion exchange is performed by heating to 80-90°C, stirring for 1-2 hours, and repeating the ion exchange three or more times until Na is displaced. + H-type molecular sieves are generated.

[0019] Preferably, in step S3, the graphite additive is graphite and / or graphene; the length and width dimensions of the graphite additive are 2~10μm.

[0020] Preferably, in step S3, the ball mill rotates at a speed of 300-600 rpm for 1-3 hours.

[0021] Secondly, the present invention also provides an application of the catalyst prepared by the above method in the production of aromatic-based jet fuel from methanol.

[0022] Preferably, the aromatic-based jet fuel comprises aromatics having 8 to 12 carbon atoms.

[0023] Preferably, the reaction conditions for producing aromatic-based jet fuel from methanol include: being carried out in a fixed bed or fluidized bed under a mixed atmosphere of hydrogen and inert gas, at a temperature of 350-450°C, at atmospheric pressure, and with a methanol space velocity of 0.2-2 h⁻¹. -l .

[0024] Preferably, the inert gas is one or more of nitrogen, helium, and argon; the molar ratio of hydrogen to the inert gas is 0.1 to 0.5:1.

[0025] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses a combination of sheet-like mesoporous ZSM-5 molecular sieve and graphite additives to form a catalyst with an alternating stacked structure of molecular sieve and graphite additives by ball milling. This results in a dual synergistic effect of structure and property of molecular sieve and graphite additives, thereby improving the catalytic activity and stability of the catalyst. (2) By limiting the compounding ratio of lamellar mesoporous ZSM-5 molecular sieve and graphite additive and the silicon-aluminum ratio of molecular sieve, the present invention can balance the reaction performance of acidic sites of molecular sieve, diffusion performance of mesopore and hydrophobic performance of graphite, thereby further improving the stability of catalyst. (3) Under the same methanol-to-aromatics-based jet fuel reaction conditions, the catalyst in this invention can have higher catalytic stability and longer catalytic reaction life, reducing catalyst regeneration consumption. Attached Figure Description

[0026] Figure 1 This is a SEM image of the mesoporous ZSM-5 molecular sieve in Example 1.

[0027] Figure 2 This is a SEM image of the catalyst in Example 1.

[0028] Figure 3 This is a time-conversion graph of the catalyst in Example 1 in the methanol-to-aromatics-based jet fuel reaction.

[0029] Figure 4 This is a nitrogen adsorption-desorption curve of the mesoporous ZSM-5 molecular sieve in Example 2.

[0030] Figure 5 This is the gas chromatogram of the product in Example 3. Detailed Implementation

[0031] The technical solution of the present invention will be illustrated below with specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0032] Example 1 The catalyst composition by mass percentage is: 70% lamellar mesoporous ZSM-5 molecular sieve (silicon-aluminum molar ratio 40) and 30% graphite.

[0033] The preparation method of the catalyst includes the following steps: S1: According to the molar ratio of SiO2:Al:tetrapropylammonium hydroxide:urea:water of 1:0.25:0.1:2.5:20, silicon source (tetraethyl silicate), aluminum source (aluminum isopropoxide), tetrapropylammonium hydroxide and urea were added to water to form a mixed solution. Hydrothermal crystallization reaction was carried out in a closed container at 180℃ for 48 h. After the reaction was completed, the reaction product was calcined in air at 550℃ for 4 h to obtain sheet ZSM-5 molecular sieve with a sheet thickness of 80±10 nm. S2: Mix the sheet-like ZSM-5 molecular sieve and 0.1 M NaOH solution at a ratio of 1 g: 50 mL, heat and stir at 70 °C for 1 h; after stirring, filter and dry; perform ammonia exchange by mixing the sheet-like ZSM-5 molecular sieve and 1 M NH4Cl solution at a ratio of 1 g: 50 mL, heating to 80 °C, stirring for 2 h, and repeating three times; after completion, filter and dry to obtain the sheet-like mesoporous ZSM-5 molecular sieve. S3: By mass percentage, 70% of the lamellar mesoporous ZSM-5 molecular sieve and 30% of graphite are mixed and ground evenly, and then ball-milled at 400 rpm for 2 hours to obtain the catalyst.

[0034] The above catalyst was used in a fixed-bed reactor for the production of aromatic-based sustainable jet fuel from methanol. The reaction atmosphere was a hydrogen / nitrogen mixture (hydrogen / nitrogen molar ratio of 0.1:1), the reaction temperature was 450℃, and the methanol space velocity was 0.5 h⁻¹. -1 .

[0035] Example 2 The catalyst composition, by mass percentage, is: 80% lamellar mesoporous ZSM-5 molecular sieve (silicon-aluminum molar ratio 20) and 20% graphite.

[0036] The preparation method of the catalyst includes the following steps: S1: According to the molar ratio of SiO2:Al:tetrapropylammonium hydroxide:urea:water of 1:0.05:0.2:1:25, silicon source (tetraethyl silicate), aluminum source (aluminum isopropoxide), tetrapropylammonium hydroxide and urea were added to water to form a mixed solution. The solution was subjected to hydrothermal crystallization reaction in a closed container at 120°C for 80 h. After the reaction was completed, the reaction product was calcined in air at 550°C for 4 h to obtain sheet-like ZSM-5 molecular sieve with a sheet thickness of 200±10 nm. S2: The sheet-like ZSM-5 molecular sieve and 0.2 M NaOH solution were mixed at a ratio of 1 g: 50 mL and heated and stirred at 80 °C for 1.5 h. After stirring, the mixture was filtered and dried. For ammonia exchange, the sheet-like ZSM-5 molecular sieve and 1 M NH4Cl solution were mixed at a ratio of 1 g: 50 mL and heated to 80 °C for 2 h. This process was repeated three times. After the process was completed, the mixture was filtered and dried to obtain the sheet-like mesoporous ZSM-5 molecular sieve. S3: By mass percentage, 80% of the lamellar mesoporous ZSM-5 molecular sieve and 20% of graphite are mixed and ground evenly, and then ball-milled at 400 rpm for 2 hours to obtain the catalyst.

[0037] The above catalyst was used in a fixed-bed reactor to produce aromatic-based sustainable jet fuel from methanol. The reaction atmosphere was a hydrogen / nitrogen mixture (hydrogen / nitrogen molar ratio of 0.2:1), the reaction temperature was 450℃, and the methanol space velocity was 0.5 h⁻¹. -1 .

[0038] Example 3 The catalyst composition by mass percentage is: 50% lamellar mesoporous ZSM-5 molecular sieve (silicon-aluminum molar ratio 80) and 50% graphite.

[0039] The preparation method of the catalyst includes the following steps: S1: According to the molar ratio of SiO2:Al:tetrapropylammonium hydroxide:urea:water of 1:0.0125:0.5:0.1:33.5, silicon source (tetraethyl silicate), aluminum source (aluminum isopropoxide), tetrapropylammonium hydroxide and urea were added to water to form a mixed solution. The solution was subjected to hydrothermal crystallization reaction in a closed container at 200℃ for 24 h. After the reaction was completed, the reaction product was calcined in air at 550℃ for 4 h to obtain sheet-like ZSM-5 molecular sieve with a sheet thickness of 300±10 nm. S2: Mix the sheet-like ZSM-5 molecular sieve and 0.3 M NaOH solution at a ratio of 1 g: 50 mL, heat and stir at 90 °C for 2 h; after stirring, filter and dry; perform ammonia exchange by mixing the sheet-like ZSM-5 molecular sieve and 1 M NH4Cl solution at a ratio of 1 g: 50 mL, heating to 80 °C, stirring for 2 h, and repeating three times; after completion, filter and dry to obtain the sheet-like mesoporous ZSM-5 molecular sieve. S3: By mass percentage, 50% of the lamellar mesoporous ZSM-5 molecular sieve and 50% of graphite are mixed and ground evenly, and then ball-milled at a speed of 400 rpm for 2 hours to obtain the catalyst.

[0040] The above catalyst was used in a fixed-bed reactor to produce aromatic-based sustainable jet fuel from methanol. The reaction atmosphere was a hydrogen / helium mixture (hydrogen / helium molar ratio of 0.1:1), the reaction temperature was 450℃, and the methanol space velocity was 0.5 h⁻¹. -1 .

[0041] Example 4 The catalyst composition by mass percentage is: 60% lamellar mesoporous ZSM-5 molecular sieve (silicon-aluminum molar ratio 20) and 40% graphite.

[0042] The preparation method of the catalyst includes the following steps: S1: According to the molar ratio of SiO2:Al:tetrapropylammonium hydroxide:urea:water of 1:0.02:0.4:2.5:30, silicon source (tetraethyl silicate), aluminum source (aluminum isopropoxide), tetrapropylammonium hydroxide and urea were added to water to form a mixed solution. The solution was subjected to hydrothermal crystallization reaction in a closed container at 200℃ for 48 h. After the reaction was completed, the reaction product was calcined in air at 550℃ for 4 h to obtain sheet-like ZSM-5 molecular sieve with a sheet thickness of 100±10 nm. S2: Mix the sheet-like ZSM-5 molecular sieve and 0.1 M NaOH solution at a ratio of 1 g: 50 mL, heat and stir at 70 °C for 1 h; after stirring, filter and dry; perform ammonia exchange by mixing the sheet-like ZSM-5 molecular sieve and 1 M NH4Cl solution at a ratio of 1 g: 50 mL, heating to 80 °C, stirring for 2 h, and repeating three times; after completion, filter and dry to obtain the sheet-like mesoporous ZSM-5 molecular sieve. S3: By mass percentage, 60% of the lamellar mesoporous ZSM-5 molecular sieve and 40% of graphite are mixed and ground evenly, and then ball-milled at 400 rpm for 2 hours to obtain the catalyst.

[0043] The above catalyst was used in a fixed-bed reaction to produce aromatic-based sustainable jet fuel from methanol. The reaction atmosphere was a hydrogen / argon mixture (hydrogen / argon molar ratio of 0.5:1), the reaction temperature was 400℃, and the methanol space velocity was 0.8 h⁻¹. -1 .

[0044] Example 5 The catalyst composition, by mass percentage, is: 70% lamellar mesoporous ZSM-5 molecular sieve (silicon-aluminum molar ratio 20) and 30% graphite.

[0045] The preparation method of the catalyst includes the following steps: S1: According to the molar ratio of SiO2:Al:tetrapropylammonium hydroxide:urea:water of 1:0.05:0.5:1:33.5, silicon source (tetraethyl silicate), aluminum source (aluminum isopropoxide), tetrapropylammonium hydroxide and urea were added to water to form a mixed solution. The solution was subjected to hydrothermal crystallization reaction in a closed container at 180℃ for 48 h. After the reaction was completed, the reaction product was calcined in air at 550℃ for 4 h to obtain sheet ZSM-5 molecular sieve with a sheet thickness of 200±10 nm. S2: Mix the sheet-like ZSM-5 molecular sieve and 0.1 M NaOH solution at a ratio of 1 g: 50 mL, heat and stir at 70 °C for 2 h; after stirring, filter and dry; perform ammonia exchange by mixing the sheet-like ZSM-5 molecular sieve and 1 M NH4Cl solution at a ratio of 1 g: 50 mL, heating to 80 °C, stirring for 2 h, and repeating three times; after completion, filter and dry to obtain the sheet-like mesoporous ZSM-5 molecular sieve. S3: By mass percentage, 70% of the lamellar mesoporous ZSM-5 molecular sieve and 30% of graphite are mixed and ground evenly, and then ball-milled at 400 rpm for 2 hours to obtain the catalyst.

[0046] The above catalyst was used in a fixed-bed reactor for the production of aromatic-based sustainable jet fuel from methanol. The reaction atmosphere was a hydrogen / nitrogen mixture (hydrogen / nitrogen molar ratio of 0.5:1), the reaction temperature was 350℃, and the methanol space velocity was 0.2 h⁻¹. -1 .

[0047] Example 6 The catalyst composition by mass percentage is: 70% lamellar mesoporous ZSM-5 molecular sieve (silicon-aluminum molar ratio 40) and 30% graphite.

[0048] The preparation method of the catalyst includes the following steps: S1: According to the molar ratio of SiO2:Al:tetrapropylammonium hydroxide:urea:water of 1:0.25:0.1:2.5:20, silicon source (tetraethyl silicate), aluminum source (aluminum isopropoxide), tetrapropylammonium hydroxide and urea were added to water to form a mixed solution. Hydrothermal crystallization reaction was carried out in a closed container at 180℃ for 48 h. After the reaction was completed, the reaction product was calcined in air at 550℃ for 4 h to obtain sheet ZSM-5 molecular sieve with a sheet thickness of 80±10 nm. S2: Mix the sheet-like ZSM-5 molecular sieve and 0.1 M NaOH solution at a ratio of 1 g: 50 mL, heat and stir at 70 °C for 1 h; after stirring, filter and dry; perform ammonia exchange by mixing the sheet-like ZSM-5 molecular sieve and 1 M NH4Cl solution at a ratio of 1 g: 50 mL, heating to 80 °C, stirring for 2 h, and repeating three times; after completion, filter and dry to obtain the sheet-like mesoporous ZSM-5 molecular sieve. S3: By mass percentage, 70% of the lamellar mesoporous ZSM-5 molecular sieve and 30% of graphite are mixed and ground evenly, and then ball-milled at 400 rpm for 2 hours to obtain the catalyst.

[0049] The above catalyst was used in a fixed-bed reactor to produce aromatic-based sustainable jet fuel from methanol. The reaction atmosphere was a hydrogen / nitrogen mixture (hydrogen / nitrogen molar ratio of 0.3:1), the reaction temperature was 450℃, and the methanol space velocity was 2 h⁻¹. -1 .

[0050] Comparative Example 1 The difference from Example 1 is that the catalyst contains only lamellar mesoporous ZSM-5 molecular sieve (silicon-aluminum molar ratio 40).

[0051] The preparation method of the catalyst includes the following steps: S1: According to the molar ratio of SiO2:Al:tetrapropylammonium hydroxide:urea:water of 1:0.25:0.1:2.5:20, silicon source (tetraethyl silicate), aluminum source (aluminum isopropoxide), tetrapropylammonium hydroxide and urea were added to water to form a mixed solution. Hydrothermal crystallization reaction was carried out in a closed container at 180℃ for 48 h. After the reaction was completed, the reaction product was calcined in air at 550℃ for 4 h to obtain sheet ZSM-5 molecular sieve with a sheet thickness of 80±10 nm. S2: The sheet-like ZSM-5 molecular sieve and 0.1 M NaOH solution were mixed at a ratio of 1 g: 50 mL and heated and stirred at 70 °C for 1 h. After stirring, the mixture was filtered and dried. For ammonia exchange, the sheet-like ZSM-5 molecular sieve and 1 M NH4Cl solution were mixed at a ratio of 1 g: 50 mL and heated to 80 °C for 2 h. This process was repeated three times. After the process was completed, the mixture was filtered and dried to obtain the catalyst.

[0052] Comparative Example 2 The difference from Example 1 is that the catalyst was obtained by coating and growing an S-1 shell on the surface of a sheet-like mesoporous ZSM-5 molecular sieve (silicon-aluminum molar ratio 40).

[0053] The preparation method of the catalyst includes the following steps: S1: According to the molar ratio of SiO2:Al:tetrapropylammonium hydroxide:urea:water of 1:0.25:0.1:2.5:20, silicon source (tetraethyl silicate), aluminum source (aluminum isopropoxide), tetrapropylammonium hydroxide and urea were added to water to form a mixed solution. Hydrothermal crystallization reaction was carried out in a closed container at 180℃ for 48 h. After the reaction was completed, the reaction product was calcined in air at 550℃ for 4 h to obtain sheet ZSM-5 molecular sieve with a sheet thickness of 80±10 nm. S2: Mix the sheet-like ZSM-5 molecular sieve and 0.1 M NaOH solution at a ratio of 1 g: 50 mL, heat and stir at 70 °C for 1 h; after stirring, filter and dry; perform ammonia exchange by mixing the sheet-like ZSM-5 molecular sieve and 1 M NH4Cl solution at a ratio of 1 g: 50 mL, heating to 80 °C, stirring for 2 h, and repeating three times; after completion, filter and dry to obtain the sheet-like mesoporous ZSM-5 molecular sieve. S3: Using mesoporous ZSM-5 molecular sieve as seed crystal, an S-1 shell coating was formed on its surface by hydrothermal synthesis: according to the molar ratio of silicon element in silicon source: tetrapropylammonium hydroxide: water: silicon element in molecular sieve of 1:0.1:180:1, a mixed solution of silicon source (tetraethyl silicate), tetrapropylammonium hydroxide and water was formed and stirred at room temperature for 8 hours. Then, the mesoporous ZSM-5 molecular sieve was added and stirred for another 1 hour. Hydrothermal crystallization reaction was carried out in a closed container at 170℃ for 72 hours. After the reaction was completed, the resulting reaction product was calcined in air at 550℃ for 4 hours to obtain the catalyst.

[0054] Comparative Example 3 The difference from Example 1 is that the catalyst used is SiO2 micro powder.

[0055] The catalyst composition by mass percentage is: 70% lamellar mesoporous ZSM-5 molecular sieve (silicon-aluminum molar ratio 40) and 30% SiO2 micro powder (particle size 200~300nm).

[0056] The preparation method of the catalyst includes the following steps: S1: According to the molar ratio of SiO2:Al:tetrapropylammonium hydroxide:urea:water of 1:0.25:0.1:2.5:20, silicon source (tetraethyl silicate), aluminum source (aluminum isopropoxide), tetrapropylammonium hydroxide and urea were added to water to form a mixed solution. Hydrothermal crystallization reaction was carried out in a closed container at 180℃ for 48 h. After the reaction was completed, the reaction product was calcined in air at 550℃ for 4 h to obtain sheet ZSM-5 molecular sieve with a sheet thickness of 80±10 nm. S2: Mix the sheet-like ZSM-5 molecular sieve and 0.1 M NaOH solution at a ratio of 1 g: 50 mL, heat and stir at 70 °C for 1 h; after stirring, filter and dry; perform ammonia exchange by mixing the sheet-like ZSM-5 molecular sieve and 1 M NH4Cl solution at a ratio of 1 g: 50 mL, heating to 80 °C, stirring for 2 h, and repeating three times; after completion, filter and dry to obtain the sheet-like mesoporous ZSM-5 molecular sieve. S3: By mass percentage, 70% of the lamellar mesoporous ZSM-5 molecular sieve and 30% of SiO2 micro powder were mixed and ground evenly, and then ball-milled at 400 rpm for 2 hours to obtain the catalyst.

[0057] Comparative Example 4 The difference from Example 2 is that the mass proportion of lamellar mesoporous ZSM-5 molecular sieve in the catalyst is too high. Specifically, by mass percentage, the catalyst composition is: 90% lamellar mesoporous ZSM-5 molecular sieve (silicon-aluminum molar ratio 20) and 10% graphite.

[0058] Comparative Example 5 The difference from Example 3 is that the mass proportion of the mesoporous ZSM-5 molecular sieve in the catalyst is too small. Specifically, by mass percentage, the catalyst composition is: 30% mesoporous ZSM-5 molecular sieve (silicon-aluminum molar ratio 80) and 70% graphite.

[0059] Comparative Example 6 The difference from Example 2 is that the silica-alumina ratio of the lamellar mesoporous ZSM-5 molecular sieve in the catalyst is too high.

[0060] The catalyst composition by mass percentage is: 80% lamellar mesoporous ZSM-5 molecular sieve (silicon-aluminum molar ratio 150) and 20% graphite.

[0061] The preparation method of the catalyst includes the following steps: S1: According to the molar ratio of SiO2:Al:tetrapropylammonium hydroxide:urea:water of 1:0.0067:0.2:1:25, silicon source (tetraethyl silicate), aluminum source (aluminum isopropoxide), tetrapropylammonium hydroxide and urea were added to water to form a mixed solution. The solution was subjected to hydrothermal crystallization reaction in a closed container at 120℃ for 80 h. After the reaction was completed, the reaction product was calcined in air at 550℃ for 4 h to obtain sheet ZSM-5 molecular sieve with a sheet thickness of 150±10 nm. S2: The sheet-like ZSM-5 molecular sieve and 0.2 M NaOH solution were mixed at a ratio of 1 g: 50 mL and heated and stirred at 80 °C for 1.5 h. After stirring, the mixture was filtered and dried. For ammonia exchange, the sheet-like ZSM-5 molecular sieve and 1 M NH4Cl solution were mixed at a ratio of 1 g: 50 mL and heated to 80 °C for 2 h. This process was repeated three times. After the process was completed, the mixture was filtered and dried to obtain the sheet-like mesoporous ZSM-5 molecular sieve. S3: By mass percentage, 80% of the lamellar mesoporous ZSM-5 molecular sieve and 20% of graphite are mixed and ground evenly, and then ball-milled at 400 rpm for 2 hours to obtain the catalyst.

[0062] Table 1. Catalytic performance of the catalysts in Examples 1-6 and Comparative Examples 1-6 in the methanol-to-aromatics-based jet fuel reaction.

[0063] Note: The stable operating time of the catalyst refers to the time during which the fixed bed reaction continues until the catalyst shows obvious deactivation (the methanol conversion rate begins to decline).

[0064] like Figure 1 The image shown is an SEM image of the mesoporous ZSM-5 molecular sieve in Example 1. It can be seen that the a-axis length of the mesoporous ZSM-5 molecular sieve is 2±0.5 μm, the b-axis (sheet thickness) length is 100±10 nm, and the c-axis length is 500±10 nm. Figure 2 As shown, after ball milling the lamellar mesoporous ZSM-5 molecular sieve and graphite in Example 1, a structure of alternating stacked molecular sieve and graphite additives can be clearly seen. Figure 3 As shown, in Example 1, the catalyst only showed significant deactivation after 350 hours of continuous and stable operation, indicating that the catalyst has a long service life. Figure 4 The figure shows the nitrogen adsorption-desorption curve of the mesoporous ZSM-5 molecular sieve prepared in Example 2. It exhibits a typical type IV isotherm with a distinct hysteresis loop, indicating that the molecular sieve has a mesoporous structure. Figure 5 The image shows a gas chromatogram of the product obtained from the catalytic reaction in Example 3, indicating that the product is mainly aromatic-based sustainable jet fuel (C8~C4). 12 ).

[0065] As shown in Table 1, Comparative Example 1 and Example 1 demonstrate that, compared to pure molecular sieve catalysts, the addition of hydrophobic graphite additives significantly improves the stability of the methanol-to-aromatics-based sustainable jet fuel catalyst without affecting the selectivity of aromatic jet fuel. The reason for this is that the diffusion of water byproducts and the target aromatic product generated during the reaction is influenced by graphite. Due to the hydrophobic properties of graphite, the water byproduct can be accelerated to detach from the catalyst surface, pulling the reaction equilibrium and improving the catalyst's catalytic performance. Simultaneously, during the diffusion of the target aromatic product from the molecular sieve channels to the pore openings, the orderly coating of graphite on the outer surface provides ordered macropores, promoting its detachment from the channels and preventing carbon deposition, thereby increasing catalyst stability.

[0066] As can be seen from Comparative Example 2 and Example 1, compared to the catalyst composition of a combination of molecular sieve catalyst and hydrophobic graphite additive, directly coating the outer surface of the molecular sieve with an S-1 shell to form a classic core-shell structure does not improve catalyst stability. The reason is that methanol molecules react in the mesoporous sheet-like ZSM-5 molecular sieve to generate the target aromatic product, and its diffusion is restricted by the S-1 channels of the shell. Furthermore, compared to the mesoporous channels of the core layer, the ordered microporous structure of the shell significantly increases diffusion resistance, leading to rapid clogging of the pores of the core-layer mesoporous sheet-like ZSM-5 molecular sieve. The catalyst lifetime is even shorter than that of the pure mesoporous sheet-like ZSM-5 molecular sieve in Comparative Example 1. Therefore, it can be concluded that the hydrophobic additive modified on the outer surface of the active molecular sieve, on the one hand, can promote the desorption of byproduct water and the target aromatic product from the catalyst surface through its chemical oleophilic and hydrophobic properties; on the other hand, the ordered macroporous structure it constructs can accelerate the diffusion and mass transfer of these substances in the reaction system. These two effects synergistically promote the improvement of catalyst stability.

[0067] As can be seen from Comparative Example 3 and Examples 1 and 1, when silica microspheres are used as an additive, the catalyst stability is slightly improved compared to pure molecular sieve catalysts. This is because silica itself has similar physical properties to graphite, possessing oleophilic and hydrophobic properties, which can promote the discharge of byproduct water to a certain extent. However, due to its spherical structure, the contact area with the molecular sieve surface is very limited, and it cannot form an alternating stacked structure of molecular sieve and additive. Therefore, the improvement in catalytic performance is not significant, and the effect is far weaker than that of sheet graphite. This indicates that the morphology and structure of the additive are just as important as its oleophilic and hydrophobic properties.

[0068] As can be seen from Comparative Example 4 and Example 2, when the content of lamellar mesoporous ZSM-5 molecular sieve is too low, the catalytic efficiency of the catalyst drops rapidly, and the catalyst stability also decreases. This may be because the catalyst has limited acidic sites, leading to catalytic efficiency saturation and a decrease in methanol conversion; furthermore, the generated aromatic target product is prone to further alkylation, cyclization, and other side reactions with excess methanol, generating large molecular carbon precursors, which in turn reduces catalyst stability. Therefore, more graphite additives are not necessarily better; they need to be within a suitable ratio range with the molecular sieve catalyst to improve catalyst stability.

[0069] As can be seen from Comparative Example 5 and Example 3, when the content of graphite additive is too low, the catalyst lifetime is not significantly improved. This may be because the reaction performance of the acidic sites and the diffusion performance of the mesopores of the catalyst far exceed the hydrophobic performance of the corresponding graphite, making it difficult to exert the structure-property synergy between the graphite additive and the molecular sieve, and thus failing to further improve the stability of the catalyst.

[0070] As can be seen from Comparative Example 6 and Example 2, when the silica-to-alumina ratio of the molecular sieve is too high, the methanol conversion rate and the selectivity of aromatics and jet fuel decrease significantly. This is because the methanol aromatization reaction depends on the acidic sites of the molecular sieve. When the silica-to-alumina ratio is too high, there are insufficient acidic sites, leading to a decrease in methanol conversion rate. The lack of strong acidic sites causes the reaction route to deviate, significantly reducing the selectivity of aromatics and increasing the selectivity of alkanes and olefins, which improves the stability of the catalyst.

[0071] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a highly stable catalyst for methanol-to-aromatics-based jet fuel, characterized in that, Includes the following steps: S1: Add silicon source, aluminum source, tetrapropylammonium hydroxide and urea to water to carry out hydrothermal crystallization reaction. The reaction product is then calcined with oxygen to obtain sheet ZSM-5 molecular sieve. S2: After mixing the sheet-like ZSM-5 molecular sieve with an alkaline solution, heating and stirring, filtering and drying, and then performing ammonia exchange, a sheet-like mesoporous ZSM-5 molecular sieve is obtained; the sheet-like mesoporous ZSM-5 molecular sieve has a silicon-to-aluminum molar ratio of 20~80, an a-axis length of 1~3 μm, a b-axis length of 50~400 nm, and a c-axis length of 300~800 nm; S3: By mass percentage, 50-80% of lamellar mesoporous ZSM-5 molecular sieve and 20-50% of graphite additive are mixed and ball-milled to obtain a catalyst, wherein the catalyst has a structure with alternating stacking of molecular sieve and graphite additive.

2. The method for preparing the highly stable catalyst for methanol-to-aromatics-based jet fuel according to claim 1, characterized in that, In step S1, the molar ratio of silicon element to tetrapropylammonium hydroxide and urea in the silicon source is 1:0.1~0.5:0.1~2.

5.

3. The method for preparing the highly stable catalyst for methanol-to-aromatics-based jet fuel according to claim 1 or 2, characterized in that, In step S1, the molar ratio of silicon to water in the silicon source is 1:20~33.

5.

4. The method for preparing the highly stable catalyst for methanol-to-aromatics-based jet fuel according to claim 1, characterized in that, In step S1, the temperature of the hydrothermal crystallization reaction is 120~200℃ and the time is 24~80h.

5. The method for preparing the highly stable catalyst for methanol-to-aromatics-based jet fuel according to claim 1 or 4, characterized in that, In step S1, the temperature of the aerobic roasting is 500~600℃ and the time is 3~5h.

6. The method for preparing the highly stable catalyst for methanol-to-aromatics-based jet fuel according to claim 1, characterized in that, In step S2, the concentration of the alkaline solution is 0.1~0.3M; the heating and stirring temperature is 70~90℃, and the stirring time is 1~2h.

7. The method for preparing the highly stable catalyst for methanol-to-aromatics-based jet fuel according to claim 1 or 6, characterized in that, In step S2, the ammonia exchange is performed by ion exchange of the sheet-like ZSM-5 molecular sieve with an ammonium salt solution.

8. The method for preparing the highly stable catalyst for methanol-to-aromatics-based jet fuel according to claim 1, characterized in that, In step S3, the graphite additive is graphite and / or graphene; the ball milling speed is 300~600 rpm, and the time is 1~3 h.

9. The application of a catalyst prepared by any one of claims 1-8 in the production of aromatic-based jet fuel from methanol.

10. The application according to claim 9, characterized in that, The reaction conditions for producing aromatic-based jet fuel from methanol include: a temperature of 350-450°C, a pressure of atmospheric pressure, and a methanol space velocity of 0.2-2 h⁻¹ under a mixed atmosphere of hydrogen and inert gas. -l .

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