A method for lightening reformed heavy aromatics

Abstract

This invention discloses a method for lightening reformed heavy aromatics. The method involves the lightening of reformed heavy aromatics under the action of a catalyst, with the following operating conditions: reaction pressure of 1.0~5.0 MPa, hydrogen-to-oil volume ratio of 50:1~600:1, and liquid hourly space velocity of 0.5~2 h⁻¹. ‑1 The reaction temperature is 380~450℃, and the catalyst uses modified ZSM-5 molecular sieve and Y molecular sieve as acid cracking components. This method exhibits high conversion rates for polymethylbenzene and long alkyl side-chain substituted benzenes, effectively avoids macromolecular condensation, delays carbon deposition, and improves the operating cycle of the unit.

Description

Technical Field

[0001] This invention relates to the field of comprehensive utilization of reformed heavy aromatics, and specifically to a method for lightening reformed heavy aromatics, and more particularly to a method for producing BTX from lightened reformed heavy aromatics. Background Technology

[0002] Light aromatics such as BTX (benzene, toluene, xylene) are important basic petrochemical products and crucial raw materials for various chemical products, including synthetic rubber, synthetic fibers, and synthetic resins. Toluene and xylene can also be used as octane additives for gasoline. Aromatics production typically involves catalytic reforming. Catalytic reforming units and steam cracking ethylene production units both generate large quantities of heavy aromatics (C9 and above) as byproducts. Heavy aromatics have very complex compositions, are difficult to utilize, and have low value. Converting C9 and above aromatics into BTX is undoubtedly an effective method for fully utilizing resources and improving enterprise efficiency. This not only promotes the economic benefits of the refining industry but also contributes to the development of my country's fine chemical industry.

[0003] CN114057533A discloses a method for producing light aromatics and low-carbon olefins. This method can efficiently convert C9 and above aromatics into light aromatics and low-carbon olefins while achieving long-term stable operation. However, the reaction process generates a large amount of carbon deposits and the yield of non-aromatic components is high, resulting in a waste of aromatic resources.

[0004] CN200410066625.4 discloses a method for the hydrogenation dealkylation and alkyl transfer of heavy aromatics. Using C10 or / and C11 aromatics as raw materials, a macroporous zeolite supported on bismuth and molybdenum metals or oxides is used as a catalyst in a fixed-bed reactor at a temperature of 300–600 °C and a pressure of 1.0–4.0 MPa to produce mixed xylenes. This method features a simple process, high yield of mixed xylenes, and a low hydrogen-to-hydrogen ratio, making it suitable for industrial production of mixed xylenes from heavy aromatics. The catalyst shows good conversion of polymethylbenzene, but poor conversion of long-chain heavy aromatics such as ethylbenzene and propylbenzene. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for the lightening of reformed heavy aromatics. This method exhibits high conversion rates for both polymethylbenzene and long alkyl side-chain substituted benzenes, effectively avoids the condensation of large molecules, delays carbon deposition, and improves the operating cycle of the equipment.

[0006] A method for lightening reformed heavy aromatics involves using a catalyst to achieve this process. The operating conditions are as follows: reaction pressure 1.0–5.0 MPa, hydrogen-to-oil volume ratio 50:1–600:1, and liquid hourly space velocity (LISH) 0.5–2 h⁻¹. -1The reaction temperature is 380~450℃, and the catalyst uses modified ZSM-5 molecular sieve and Y molecular sieve as acid cracking components.

[0007] Furthermore, the reformed heavy aromatic hydrocarbon contains 30% to 50% by mass of tricresylbenzene, 3% to 10% by mass of propylbenzene, 20% to 30% by mass of ethylbenzene, and 10% to 20% by mass of C10+ aromatic hydrocarbons.

[0008] Furthermore, the modified ZSM-5 molecular sieve has an outer surface SiO2 / Al2O3 molar ratio of 100-500, a bulk SiO2 / Al2O3 molar ratio of 20-50, a pyridine infrared total acidity of 0.20-0.50 mmol / g, a di-tert-butylpyridine infrared total acidity of 0.01-0.05 mmol / g, and a mesoporous content accounting for 20%-60% of the total pore volume, of which 2-10 nm pore volume accounts for 10%-40% of the total mesoporous pore volume.

[0009] Further, preferably, the molar ratio of SiO2 / Al2O3 on the outer surface of the modified ZSM-5 molecular sieve is 200~400, and the molar ratio of SiO2 / Al2O3 in the bulk phase is 30~40.

[0010] Further, preferably, the modified ZSM-5 molecular sieve has a total pyridine infrared acidity of 0.30~0.45 mmol / g and a total di-tert-butylpyridine infrared acidity of 0.02~0.04 mmol / g.

[0011] Further, preferably, the mesoporous content of the modified ZSM-5 molecular sieve accounts for 30% to 50% of the total pore volume, of which the 2 to 10 nm pore volume accounts for 20% to 30% of the total mesoporous pore volume.

[0012] Furthermore, based on the weight of the catalyst, the content of the hydrogenation active metal component, calculated as oxide, is 14% to 38%, and the content of the acid cracking component support is 62% to 85%.

[0013] Furthermore, the catalyst also includes a binder, such as microporous alumina, and the content of the binder is less than 5% based on the weight of the catalyst, and more specifically 0.1% to 5%.

[0014] Furthermore, in the catalyst, the content of modified ZSM-5 molecular sieve is 25%–35% by weight of the support, the content of Y molecular sieve is 27%–50%, and the content of macroporous alumina is 10%–33%; preferably, the content of modified ZSM-5 molecular sieve is 27%–32%, the content of Y molecular sieve is 35%–45%, and the content of macroporous alumina is 20%–30%.

[0015] Further, the active metal is a Group VIB and / or Group VIII metal, preferably molybdenum and / or tungsten, and preferably cobalt and / or nickel. Preferably, the active metal is a Group VIB and a Group VIII metal, with the content of the Group VIB metal (calculated as oxide) being 10.0% to 30.0% and the content of the Group VIII metal (calculated as oxide) being 4.0% to 8.0% based on the weight of the catalyst.

[0016] Furthermore, the properties of the Y molecular sieve are as follows: specific surface area of ​​860–940 m². 2 The total pore volume is 0.43–0.55 mL / g, the SiO2 / Al2O3 molar ratio is 20–150, the cell parameter is 2.425–2.433 nm, and the infrared acidity is 0.1–0.4 mmol / g.

[0017] Furthermore, the macroporous alumina can be conventional macroporous alumina in the art. Its properties are as follows: pore volume of 0.8~2.0 mL / g, specific surface area of ​​350~500 m² / g. 2 / g.

[0018] Furthermore, the catalyst has the following properties: a specific surface area of ​​220–420 m². 2 / g, with a pore volume of 0.22~0.45mL / g.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] In this invention, the modified ZSM-5 molecular sieve and Y-type molecular sieve are used together as cracking centers in the hydrocracking catalysis. Polymethyl substituted aromatic hydrocarbons such as trimethylbenzene and tetramethylbenzene enter the supercage of the Y-type molecular sieve and undergo a "peeling reaction" to obtain BTX. However, the Y-type molecular sieve has poor dealkylation activity for long side chains such as ethylbenzene, diethylbenzene, propylbenzene and butylbenzene.

[0021] Modified ZSM-5 molecular sieves exhibit higher dealkylation activity for long-chain heavy aromatic hydrocarbons such as ethylbenzene, diethylbenzene, propylbenzene, and butylbenzene. Pore-expansion treatment of ZSM-5 molecular sieves significantly improves the accessibility of acidic sites, further enhancing activity while allowing product molecules to diffuse out of the pores quickly, preventing excessive reaction and the formation of chain hydrocarbons. Selective masking of acidity outside the ZSM-5 molecular sieve pores avoids the adsorption and condensation of larger molecules on the mesopores and outer surfaces, reducing carbon buildup and extending the catalyst's service life.

[0022] In this invention, the two molecular sieves not only fully utilize their respective performance characteristics, but also enable the synergistic catalytic effect of the two molecular sieves to ultimately complete the lightening of all components of the reformed heavy aromatics, obtaining chemical raw materials such as BTX. In addition, this invention controls the aromatic hydrogenation reaction within the thermodynamic region by regulating the reaction temperature, further reducing the occurrence of exothermic aromatic saturation reactions and improving the BTX yield. Attached Figure Description

[0023] Figure 1 This is a chromatogram of C9+ aromatic hydrocarbons. Implementation

[0024] A method for preparing a catalyst according to the present invention includes the preparation of a support and the loading of an active metal component; wherein the preparation process of the support is as follows: a modified ZSM-5 molecular sieve, a Y molecular sieve, and macroporous alumina are mixed, shaped, dried, and calcined to prepare a support.

[0025] Furthermore, during the preparation of the carrier, an adhesive is added during mixing and molding.

[0026] Furthermore, the preparation method of the modified ZSM-5 molecular sieve includes the following steps:

[0027] (1) Hydrothermal treatment of ZSM-5 molecular sieve;

[0028] (2) Impregnate the material obtained in step (1) with a channel protection liquid;

[0029] (3) Mix the material obtained in step (2) with the dealuminization and silicon replenishment reagent to perform dealuminization and silicon replenishment;

[0030] (4) The material obtained in step (3) is filtered, washed, dried and calcined to obtain modified ZSM-5 molecular sieve.

[0031] Further, in step (1), the ZSM-5 molecular sieve can be a commercially available product or a microporous hydrogen-form ZSM-5 molecular sieve prepared according to existing technology. The properties of the ZSM-5 molecular sieve are as follows: SiO2 / Al2O3 molar ratio 20~100, specific surface area 300~450m². 2 / g, pore volume 0.15~0.20cm³ 3 / g.

[0032] Further, in step (1), the specific treatment process in the hydrothermal process is as follows: place the commercially available ZSM-5 molecular sieve in a hydrothermal furnace, introduce steam, and treat it for 1h to 3h at a temperature of 560℃~650℃ and a pressure of 0.05~0.2MPa.

[0033] Further, in step (2), the pore protection solution is one or more of isopropylamine solution, tetraethylammonium hydroxide solution, tetrapropylammonium hydroxide solution, etc. The concentration of the pore protection solution is 0.8~2.0 mol / L, preferably 1.1~1.5 mol / L.

[0034] Furthermore, in step (2), the impregnation is preferably an equal-volume impregnation. The impregnation treatment temperature is room temperature, generally 20~25℃.

[0035] Further, in step (3), the dealuminizing and silicon-replenishing reagent is at least one of ammonium hexafluorosilicate solution, tetraethyl orthosilicate solution, etc. The molar concentration of the dealuminizing and silicon-replenishing reagent is 0.3~1.0 mol / L. The mass ratio of the material obtained in step (3) to the dealuminizing and silicon-replenishing reagent is 1:1~1:5. The mixing temperature is 60~100℃.

[0036] Further, the specific operation process of step (3) is as follows: rapidly heat the material obtained in step (2) to 60~100℃ and continuously stir, add the aluminum removal and silicon replenishment reagent dropwise, and continue stirring for 60~120min after the dropwise addition is completed. Among them, the dropwise addition rate does not exceed 0.5mL / min·g of the material obtained in step (2); preferably it is 0.2~0.4mL / min·g of the material obtained in step (2).

[0037] Furthermore, in step (4), the filtration and washing can be carried out using conventional methods in the art, the drying temperature is 100℃~150℃, the drying time is 2~4h, the calcination temperature is 400℃~600℃, and the calcination time is 3~5h.

[0038] Furthermore, the Y molecular sieve can be prepared using existing technologies.

[0039] Furthermore, in the carrier preparation method, the drying and calcination can be carried out under conventional conditions, generally drying at 100℃~150℃ for 1~12 hours, and then calcining at 450℃~550℃ for 2.5~6.0 hours.

[0040] Furthermore, the catalyst support is loaded with active metal components using conventional methods, such as kneading or impregnation. In this invention, impregnation is preferred to load the hydrogenation active metal components, followed by drying and calcination to obtain the hydrocracking catalyst. The impregnation method can be saturated impregnation, excess impregnation, or complex impregnation; that is, the catalyst support is impregnated with a solution containing the desired active component. The impregnated support is then dried at 100°C–150°C for 1–12 hours, and then calcined at 450°C–550°C for 2.5–6.0 hours to obtain the final catalyst.

[0041] The following examples and comparative examples further illustrate the role and effect of the technical solution of the present invention, but the following examples do not constitute a limitation on the scope of protection of the present invention.

[0042] In this invention, unless otherwise specified, all percentages (%) in the embodiments and comparative examples refer to mass fractions.

[0043] In this invention, the SiO2 / Al2O3 molar ratio on the outer surface was determined by X-ray photoelectron spectroscopy (XPS). The elemental composition and state of the catalyst surface were determined using a Thermofisher Multilab2000 electron spectrometer, with MgKa as the excitation source and a cathode voltage and current of 13 kV and 20 mA, respectively. The electron binding energy was calibrated using C1s (284.6 eV).

[0044] The bulk SiO2 / Al2O3 molar ratio was obtained by X-ray fluorescence spectroscopy (XRF) analysis using a ZSX100e X-ray fluorescence spectrometer with the spectral line Ka, the crystal being LiF1, the target material being Rh, the detector being SC scintillation, the timing being 20 s, and the optical path atmosphere being vacuum.

[0045] In this invention, the specific surface area, pore volume, and pore distribution were measured using the following method: an ASAP 2420 cryogenic liquid nitrogen physical adsorption instrument manufactured by Microlithics, Inc. was used, with a pretreatment temperature of 300°C and a pretreatment time of 4 hours.

[0046] In this invention, the pyridine infrared determination method is as follows: Powdered ZSM-5 molecular sieve is compressed into tablets, vacuumed, and degassed at 450°C for 2 hours. After the temperature drops to room temperature, pyridine molecules are used as probe molecules to measure the infrared spectrum of chemical desorption, and the adsorption amount is calculated.

[0047] In this invention, the total infrared acidity of di-tert-butylpyridine refers to the proton acid that a 2,6-di-tert-butylpyridine molecule with a kinetic diameter of 10.5 Å can contact. The infrared determination method for 2,6-di-tert-butylpyridine is as follows: Powdered ZSM-5 molecular sieve is compressed into tablets, vacuumed, and degassed at 450°C for 2 hours. After the temperature drops to room temperature, 2,6-di-tert-butylpyridine molecules are used as probe molecules to measure their chemical desorption infrared spectrum, and the adsorption amount is calculated.

[0048] The ZSM-5 involved in the embodiments and comparative examples of this invention is a commercially available product, specifically a microporous hydrogen-form ZSM-5 molecular sieve. The properties of the ZSM-5 are as follows: specific surface area of ​​405 m² / g. 2 / g, pore volume is 0.182cm³ 3 / g, water absorption rate is 55%, SiO2 / Al2O3 ratio (molar) is 31.2.

[0049] Example 1

[0050] 30g of commercially available ZSM-5 raw powder was placed in a hydrothermal furnace and treated at 560℃ and 0.1MPa pressure for 2h. The resulting material was impregnated with 16.5mL of 1.1 mol / L isopropylamine solution and allowed to stand for 10 min. 170mL of water was added, stirred, and heated to 60℃. 90mL of 0.3mol / L ammonium hexafluorosilicate solution was added dropwise using a peristaltic pump at a rate of 0.2mL / min·g, while maintaining the temperature at 60℃ and stirring continuously for 90 min. The mixture was filtered while hot, and 300mL of water was added to the filter cake. The mixture was heated to 60℃ and maintained for 20 min, then filtered while hot. The filter cake was dried at 120℃ for 24h and then calcined at 500℃ for 3h. The resulting modified molecular sieve was named Z-T1.

[0051] Example 2

[0052] 30g of commercially available ZSM-5 raw powder was placed in a hydrothermal furnace and treated at 580℃ and 0.1MPa pressure for 2h. The resulting material was impregnated with 16.5mL of 1.2 mol / L isopropylamine solution and allowed to stand for 10 min. 170mL of water was added, stirred, and heated to 60℃. 90mL of 0.4mol / L ammonium hexafluorosilicate solution was added dropwise using a peristaltic pump at a rate of 0.2mL / min·g, while maintaining the temperature at 60℃ and stirring continuously for 90 min. The mixture was filtered while hot, and 300mL of water was added to the filter cake. The mixture was heated to 60℃ and maintained for 20 min, then filtered while hot. The filter cake was dried at 120℃ for 24h and then calcined at 500℃ for 3h to obtain the modified molecular sieve, named Z-T2.

[0053] Example 3

[0054] 30g of commercially available ZSM-5 raw powder was placed in a hydrothermal furnace and treated at 600℃ and 0.1MPa pressure for 2h. The resulting material was impregnated with 16.5mL of 1.2 mol / L isopropylamine solution and allowed to stand for 10 min. 170mL of water was added, stirred, and heated to 60℃. 90mL of 0.3mol / L ammonium hexafluorosilicate solution was added dropwise using a peristaltic pump at a rate of 0.2mL / min·g, while maintaining the temperature at 60℃ and stirring continuously for 90 min. The mixture was filtered while hot, and 300mL of water was added to the filter cake. The mixture was heated to 60℃ and maintained for 20 min, then filtered while hot. The filter cake was dried at 120℃ for 24h and then calcined at 500℃ for 3h to obtain the modified molecular sieve, named Z-T3.

[0055] Example 4

[0056] 30g of commercially available ZSM-5 raw powder was placed in a hydrothermal treatment furnace and treated at 620℃ and 0.1MPa pressure for 2h. The resulting material was impregnated with 16.5mL of 1.1mol / L isopropylamine solution and allowed to stand for 10 min. 170mL of water was added, stirred, and heated to 60℃. 90mL of 0.4mol / L ammonium hexafluorosilicate solution was added dropwise using a peristaltic pump at a rate of 0.2mL / min·g, while maintaining the temperature at 60℃ and stirring continuously for 90 min. The mixture was filtered while hot, and 300mL of water was added to the filter cake. The mixture was heated to 60℃ and maintained for 20 min, then filtered while hot. The filter cake was dried at 120℃ for 24h and then calcined at 500℃ for 3h to obtain the modified molecular sieve, named Z-T4.

[0057] Example 5

[0058] 30g of commercially available ZSM-5 raw powder was placed in a hydrothermal treatment furnace and treated at 640℃ and 0.1MPa pressure for 2h. The resulting material was impregnated with 16.5mL of 1.2 mol / L isopropylamine solution and allowed to stand for 10 min. 170mL of water was added, stirred, and heated to 60℃. 90mL of 0.5mol / L ammonium hexafluorosilicate solution was added dropwise using a peristaltic pump at a rate of 0.2mL / min·g, while maintaining the temperature at 60℃ and stirring continuously for 90min. The mixture was filtered while hot, and 300mL of water was added to the filter cake. The mixture was heated to 60℃ and maintained for 20min, then filtered while hot. The filter cake was dried at 120℃ for 24h and then calcined at 500℃ for 3h. The resulting modified molecular sieve was named Z-T5.

[0059] Comparative Example 1

[0060] 30g of commercially available ZSM-5 raw powder was placed in a hydrothermal treatment furnace and treated at 600℃ and 0.1MPa pressure for 2h. The resulting material was then uniformly added dropwise with 90 mL of 0.4mol / L ammonium hexafluorosilicate solution using a peristaltic pump at a dropping rate of 0.3 mL / min·g, while maintaining the temperature at 65℃ and continuously stirring for 90min. The resulting modified molecular sieve was named ZA.

[0061] Table 1. Characterization results of the modified molecular sieves obtained in the examples and comparative examples.

[0062]

[0063] Example 9

[0064] The modified molecular sieve obtained in Example 3 was used to prepare a catalyst. The preparation process was as follows: modified Z-T3 molecular sieve, Y-type molecular sieve and macroporous alumina (specific surface area of ​​302 m2 / g, pore volume of 0.96 cm3 / g) and alumina sol binder were mixed, extruded and shaped, and then dried and calcined to obtain a support. The above support was impregnated with nickel nitrate impregnation solution, and then dried and calcined to obtain a catalyst. The catalysts were C1, C2 and C3 according to different proportions of each component. The proportions of each component are shown in Table 2.

[0065] Comparative Example 2

[0066] The modified molecular sieve obtained in Comparative Example 1 was used to prepare a catalyst. The preparation process was as follows: modified Z-T3 molecular sieve, Y-type molecular sieve, macroporous alumina (specific surface area of ​​302 m2 / g, pore volume of 0.96 cm3 / g), and alumina sol binder were mixed, extruded, and shaped, and then dried and calcined to obtain a support. The above support was impregnated with nickel nitrate impregnation solution, and then dried and calcined to obtain catalyst BC1. The proportions of each component are shown in Table 2.

[0067] Table 2 Catalyst Composition of Examples and Comparative Examples

[0068]

[0069] Example 10

[0070] 10g of catalyst C1 was placed in a fixed-bed reactor. The reaction was carried out at a pressure of 4.0 MPa, a hydrogen-to-oil volume ratio of 100:1, and a liquid hourly space velocity of 2.0 h⁻¹. -1 The catalytic dealkylation reaction was carried out at a reaction temperature of 420℃. The conversion rate of reformed heavy aromatics, the aromatic saturation rate and the yield of BTX are shown in Table 3.

[0071] Example 11

[0072] 10g of catalyst C2 was placed in a fixed-bed reactor. The reaction was carried out at a pressure of 4.0 MPa, a hydrogen-to-oil volume ratio of 100:1, and a liquid hourly space velocity of 2.0 h⁻¹. -1 The catalytic dealkylation reaction was carried out at a reaction temperature of 420℃. The conversion rate of reformed heavy aromatics, the aromatic saturation rate and the yield of BTX are shown in Table 3.

[0073] Example 12

[0074] 10g of catalyst C3 was placed in a fixed-bed reactor. The reaction was carried out at a pressure of 4.0 MPa, a hydrogen-to-oil volume ratio of 100:1, and a liquid hourly space velocity of 2.0 h⁻¹. -1 The catalytic dealkylation reaction was carried out at a reaction temperature of 420℃. The conversion rate of reformed heavy aromatics, the aromatic saturation rate and the yield of BTX are shown in Table 3.

[0075] Comparative Example 3

[0076] 10g of catalyst BC1 was placed in a fixed-bed reactor. The reaction was carried out at a pressure of 4.0 MPa, a hydrogen-to-oil volume ratio of 100:1, and a liquid hourly space velocity of 2.0 h⁻¹. -1 The catalytic dealkylation reaction was carried out at a reaction temperature of 420℃. The conversion rate of reformed heavy aromatics, the aromatic saturation rate and the yield of BTX are shown in Table 3.

[0077] Comparative Example 4

[0078] 10g of catalyst C2 was placed in a fixed-bed reactor. The reaction was carried out at a pressure of 4.0 MPa, a hydrogen-to-oil volume ratio of 100:1, and a liquid hourly space velocity of 2.0 h⁻¹. -1 The catalytic dealkylation reaction was carried out at a reaction temperature of 360℃. The conversion rate of reformed heavy aromatics, the aromatic saturation rate and the yield of BTX are shown in Table 3.

[0079] Table 3. Conversion status of the Implementation Examples and Comparative Examples

[0080]

[0081] Example 13

[0082] 10g of catalyst C2 was placed in a fixed-bed reactor. The reaction was carried out at a pressure of 4.0 MPa, a hydrogen-to-oil volume ratio of 100:1, and a liquid hourly space velocity of 2.0 h⁻¹. -1 The reaction was carried out at a reaction temperature of 420℃. The product was distilled through a fractionation tower and the component with a temperature greater than 145℃ was recycled to the top of the reactor. After three months of operation, the initial and final BTX yields and catalyst carbon deposition were shown in Table 4.

[0083] Comparative Example 5

[0084] 10g of catalyst BC1 was placed in a fixed-bed reactor and reacted at a pressure of 4.0 MPa, a hydrogen-to-oil volume ratio of 100:1, and a liquid hourly space velocity of 2.0 h⁻¹. -1 The reaction was carried out at a reaction temperature of 420℃. The product was distilled through a fractionation tower and the component with a temperature greater than 145℃ was recycled to the top of the reactor. After three months of operation, the initial and final BTX yields and catalyst carbon deposition were shown in Table 4.

[0085] Table 4. Conversion status of the Implementation Examples and Comparative Examples

[0086]

Claims

1. A method for lightening reformed heavy aromatics, characterized in that: The reforming of heavy aromatics to lighter forms was carried out under the action of a catalyst, with the following operating conditions: reaction pressure 1.0–5.0 MPa, hydrogen-to-oil volume ratio 50:1–600:1, and liquid hourly space velocity 0.5–2 h⁻¹. -1 The reaction temperature is 380–450℃; The catalyst contains, by weight, 14% to 38% hydrogenation active metal components (calculated as oxides) and 62% to 85% support, wherein the support contains acidic cracking components. The catalyst uses modified ZSM-5 molecular sieve and Y molecular sieve as acid cracking components; The modified ZSM-5 molecular sieve has a total pyridine infrared acidity of 0.30–0.45 mmol / g, a total di-tert-butylpyridine infrared acidity of 0.01–0.05 mmol / g, and a mesoporous content of 20%–60% of the total pore volume, of which pores of 2–10 nm account for 10%–40% of the total mesoporous pore volume. The modified ZSM-5 molecular sieve has an outer surface SiO2 / Al2O3 molar ratio of 100 to 500 and a bulk SiO2 / Al2O3 molar ratio of 20 to 50. In the catalyst, the content of modified ZSM-5 molecular sieve is 25%–35% by weight of the support, the content of Y molecular sieve is 27%–50%, and the content of macroporous alumina is 10%–33%. The reformed heavy aromatics contain 30%–50% by mass of methylbenzene, 3%–10% by mass of propylbenzene, 20%–30% by mass of ethylbenzene, and 10%–20% by mass of C10+ aromatics.

2. The method according to claim 1, characterized in that: The properties of the Y molecular sieve are as follows: specific surface area of ​​860–940 m² 2 The total pore volume is 0.43–0.55 mL / g, the SiO2 / Al2O3 molar ratio is 20–150, the cell parameter is 2.425–2.433 nm, and the infrared acidity is 0.1–0.4 mmol / g.

3. The method according to claim 1, characterized in that: The modified ZSM-5 molecular sieve has an outer surface SiO2 / Al2O3 molar ratio of 200–400 and a bulk SiO2 / Al2O3 molar ratio of 30–40.

4. The method according to claim 1, characterized in that: The total tert-butylpyridine content of the modified ZSM-5 molecular sieve is 0.02–0.04 mmol / g.

5. The method according to claim 1, characterized in that: The modified ZSM-5 molecular sieve has a mesoporous content of 30% to 50% of the total pore volume, of which 2 to 10 nm pores account for 20% to 30% of the total mesoporous pore volume.

6. The method according to claim 1, characterized in that: The catalyst also includes a binder, and the binder content is less than 5% based on the weight of the catalyst.

7. The method according to claim 6, characterized in that: The catalyst also includes a binder, with the binder content ranging from 0.1% to 5% based on the weight of the catalyst.

8. The method according to claim 1, characterized in that: The modified ZSM-5 molecular sieve content is 27%–32%, the Y molecular sieve content is 35%–45%, and the macroporous alumina content is 20%–30%.

9. The method according to claim 1, characterized in that: The hydrogenation active metal is a metal from Group VIB and / or Group VIII.

10. The method according to claim 9, characterized in that, The active metals for hydrogenation are Group VIB and Group VIII metals. Based on the weight of the catalyst, the content of Group VIB metals as oxides is 10.0% to 30.0%, and the content of Group VIII metals as oxides is 4.0% to 8.0%.

11. The method according to claim 9, characterized in that: Group VIB metals are molybdenum and / or tungsten, and Group VIII metals are cobalt and / or nickel.

12. The method according to claim 1, characterized in that: The macroporous alumina has a pore volume of 0.8–2.0 mL / g and a specific surface area of ​​350–500 m² / g. 2 / g.

13. The method according to claim 1, characterized in that: The catalyst has the following properties: specific surface area of ​​220–420 m². 2 / g, with a pore volume of 0.22~0.45mL / g.

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