A method for producing BTX from C9+ heavy aromatics

Abstract

The present invention discloses a method for producing BTX from C9+ heavy aromatics, comprising the following contents: C9+ heavy aromatics raw materials enter a dealkylation reaction zone and a transalkylation reaction zone in accordance with the direction of logistics, wherein the dealkylation reaction zone is loaded with a dealkylation catalyst having ZSM-5 molecular sieve as the main component, and the transalkylation reaction zone is loaded with a transalkylation catalyst having Beta molecular sieve as the main component, wherein the catalyst volume ratio of the dealkylation reaction zone and the transalkylation reaction zone is 1:9~6:4, preferably 3:7~5:5, and the fraction of 65~150°C obtained by separation of the reaction material is a product rich in BTX components, and the fraction greater than 150°C can be circulated to the dealkylation reaction zone and / or the transalkylation reaction zone, preferably to the transalkylation reaction zone. The method couples the dealkylation reaction zone with the transalkylation reaction zone to realize two reactions in succession, and the benzene and toluene produced by the dealkylation reaction can be used as reactants for subsequent transalkylation reactions. The method has a high conversion rate for both polymethylbenzenes and long alkyl side-chain substituted benzenes, can effectively avoid the condensation of macromolecules, delays carbon deposition, and improves the operating cycle of the device.

Description

Technical Field

[0001] The present invention belongs to the field of comprehensive utilization of C9+ heavy aromatics, and relates to a method for producing a high-value product BTX from C9+ heavy aromatics, and specifically relates to a method for producing a high-value product BTX by reforming C9+ heavy aromatics. Background Art

[0002] C9+ heavy aromatics, byproducts of catalytic reforming and steam cracking ethylene production plants, primarily include propylbenzene, ethylmethylbenzene, trimethylbenzene, and a small amount of C10 aromatics. With the expansion of aromatics complexes and ethylene plants in my country, their production is expected to increase significantly. However, with increasing environmental protection requirements and increasingly stringent requirements for aromatic content in gasoline, the utilization of these heavy aromatics has attracted widespread attention. Using lightweighting technologies to convert these aromatic-rich feedstocks into high-value BTX is an effective way to increase the value of these heavy aromatics.

[0003] CN200410066625.4 discloses a method for the hydrodealkylation and transalkylation of heavy aromatic hydrocarbons. Using C10 and / or C11 aromatic hydrocarbons as feedstock, the reaction proceeds in a fixed-bed reactor using a large-pore zeolite loaded with bismuth and molybdenum metals or oxides as a catalyst at temperatures between 300°C and 600°C and pressures between 1.0 and 4.0 MPa to produce mixed xylenes. This method boasts a simple process, high mixed xylene yield, and a low hydrogen-to-hydrocarbon ratio, and is suitable for the industrial production of mixed xylenes from heavy aromatic hydrocarbons. The catalyst exhibits good conversion efficiency for polymethylbenzenes, but has poor conversion efficiency for heavy aromatic hydrocarbons with long side chains, such as methyl, ethyl, and propylbenzenes.

[0004] CN104447159 B uses a transalkylation reactor to carry out a transalkylation reaction of heavy aromatics with light aromatics under non-hydrogenation conditions, maximizing the lightening of single-ring heavy aromatics while avoiding hydrogenation saturation of single-ring aromatics. The fraction with a boiling point ≥178°C in the transalkylation product enters a hydrogenation reactor for hydrogenation and lightening, ultimately achieving the goal of increasing the conversion rate and liquid yield of heavy aromatics while producing more high-value-added mixed xylenes and C9 aromatics fractions. The disadvantages of this method are that it requires additional benzene and toluene, which is not conducive to the lightening step to produce BTX, and there is also the possibility of hydrogenation saturation loss during the lightening reaction; heavy aromatics are very prone to coking under non-hydrogenation conditions in the first step, which makes the heavy aromatics distillation range heavier and more difficult to handle. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention provides a method for producing BTX from C9+ heavy aromatics. This method couples a dealkylation reaction zone with a transalkylation reaction zone, allowing the two reactions to proceed sequentially. The benzene and toluene produced by the dealkylation reaction can serve as reactants for the subsequent transalkylation reaction. This method achieves high conversion rates for both polymethylbenzenes and long-alkyl side-chain substituted benzenes, effectively preventing the condensation of macromolecules, delaying carbon deposition, and increasing the operating cycle of the device.

[0006] A method for producing BTX from C9+ heavy aromatics comprises the following steps: a C9+ heavy aromatics feedstock is sequentially fed into a dealkylation reaction zone and a transalkylation reaction zone according to a logistics direction; the dealkylation reaction zone is loaded with a dealkylation catalyst containing a ZSM-5 molecular sieve as a main component; and the transalkylation reaction zone is loaded with a transalkylation catalyst containing a Beta molecular sieve as a main component; the volume ratio of the catalysts loaded in the dealkylation reaction zone to the transalkylation reaction zone is 1:9-6:4, preferably 3:7-5:5; a fraction having a temperature of 65-150° C. obtained by separation of the reaction materials is a product rich in BTX components; and a fraction having a temperature greater than 150° C. can be circulated to the dealkylation reaction zone and / or the transalkylation reaction zone, preferably to the transalkylation reaction zone.

[0007] In the method of the present invention, the dealkylation reaction zone and the transalkylation reaction zone may be arranged in one reactor or in multiple reactors.

[0008] In the method of the present invention, the dealkylation reaction zone is filled with a dealkylation catalyst with modified ZSM-5 molecular sieve as the main component, and the transalkylation reaction zone is filled with a transalkylation catalyst with modified Beta molecular sieve as the main component.

[0009] In the method of the present invention, the dealkylation catalyst contains ZSM-5 molecular sieve (preferably modified ZSM-5 molecular sieve), a binder and a precious metal hydrogenation center. Based on the weight of the dealkylation catalyst, the precious metal content is 0.1wt% to 2.0wt% as a single substance, and the mass content of the ZSM-5 molecular sieve is 30wt% to 80wt%.

[0010] In the method of the present invention, the total acid content of the dealkylation catalyst is 0.05-0.12 mmol / g, the acid content outside the micropores is not higher than 5 μmol / g, preferably 0.1 μmol / g-2 μmol / g, and the pore volume is 0.18-0.30 cm 3 / g, of which the micropore volume is 0.03~0.09cm 3 / g.

[0011] In the method of the present invention, the transalkylation catalyst comprises a Beta molecular sieve (preferably a modified Beta molecular sieve), a binder, and a metal hydrogenation center. The Beta molecular sieve content is 20 wt% to 70 wt% based on the weight of the transalkylation catalyst. The metal hydrogenation center is preferably a noble metal, and the noble metal content is 0.1 wt% to 2.0 wt% on a unit basis.

[0012] In the method of the present invention, the total acid content of the transalkylation catalyst is 0.25-0.45 mmol / g, the external acid content of the micropore channel is not higher than 0.01 mmol / g, preferably 0.5 μmol / g-5 μmol / g, and the pore volume is 0.30-0.45 cm 3 / g, of which the micropore volume is 0.15~0.30cm 3 / g.

[0013] In the method of the present invention, the operating conditions for producing BTX from C9+ heavy aromatics are as follows: reaction pressure is 1.0-8.0 MPa, preferably 3.0-6.0 MPa; hydrogen-to-oil volume ratio is 50:1-600:1, preferably 200:1-400:1; liquid hourly volume space velocity is 0.3-3h -1 , preferably 0.5~2h -1 ; The reaction temperature is 350~500℃, preferably 350~500℃.

[0014] In the method of the present invention, the C9+ heavy aromatics are reformed C9+ heavy aromatics. The reformed C9+ heavy aromatics contain 30% to 50% by weight of trimethylbenzene, 3% to 10% by weight of propylbenzene, 20% to 30% by weight of methylethylbenzene, and 10% to 20% by weight of C10+ aromatics.

[0015] In the method of the present invention, the preparation method of the modified ZSM-5 molecular sieve or modified Beta molecular sieve comprises the following steps:

[0016] (1) Hydrothermal treatment of ZSM-5 molecular sieve or Beta molecular sieve raw powder;

[0017] (2) impregnating the material obtained in step (1) with a pore protection liquid;

[0018] (3) treating the material obtained in step (2) with a highly sterically hindered organic acid;

[0019] (4) mixing the material obtained in step (3) with a dealumination and siliconization reagent to carry out dealumination and siliconization;

[0020] (5) The material obtained in step (4) is filtered, washed, dried, and calcined to obtain a modified molecular sieve.

[0021] Furthermore, in step (1), the ZSM-5 molecular sieve can be a commercially available product or a ZSM-5 molecular sieve prepared according to existing technology. The properties of the ZSM-5 molecular sieve are as follows: a SiO2 / Al2O3 molar ratio of 30 to 100.

[0022] Furthermore, in step (1), the Beta molecular sieve can be a commercially available product or a Beta molecular sieve prepared according to existing technology. The properties of the Beta molecular sieve are as follows: a SiO2 / Al2O3 molar ratio of 20 to 40.

[0023] Furthermore, in step (1), the specific treatment process in the hydrothermal process is: placing the commercially available molecular sieve in a hydrothermal furnace, introducing water vapor, and treating it at a temperature of 400°C to 600°C and a pressure of 0.05 to 0.2 MPa for 1 hour to 3 hours.

[0024] Furthermore, 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.

[0025] Furthermore, in step (2), the impregnation is preferably equal volume impregnation. The impregnation temperature is room temperature, generally 20-25°C.

[0026] Furthermore, in step (3), the highly sterically hindered organic acid is one or more of 2,4-dimethylbenzenesulfonic acid and 2,5-dimethylbenzoic acid.

[0027] Furthermore, in step (3), the specific operation is as follows: first, the material obtained in step (2) is mixed with water, wherein the liquid-to-solid volume ratio of water to the material obtained in step (2) is 2:1 to 6:1, and then an organic acid is added until the pH value of the solution drops below 8, preferably 6.5 to 7.5.

[0028] Furthermore, in step (4), the dealuminized siliconizing agent is at least one of an ammonium hexafluorosilicate solution and an ethyl orthosilicate solution. The molar concentration of the dealuminized siliconizing agent is 0.3 to 1.0 mol / L. The mass ratio of the material obtained in step (4) to the dealuminized siliconizing agent is 1:1 to 1:5. The mixing temperature is 60 to 100°C.

[0029] Furthermore, the specific operation process of step (4) is as follows: the material obtained in step (3) is rapidly heated to 60-100°C, and continuously stirred, and the dealumination and siliconization reagent is added dropwise, and stirring is continued for 60-120 minutes after the addition is completed. The addition rate does not exceed 0.5 mL / min·g of the material obtained in step (3); preferably, it is 0.2-0.4 mL / min·g of the material obtained in step (3).

[0030] Furthermore, in step (5), the filtration and washing can be carried out by conventional methods in the art, the drying temperature is 100°C to 150°C, and the drying time is 2 to 4 hours; the roasting temperature is 400°C to 600°C; and the roasting time is 3 to 5 hours.

[0031] In the method of the present invention, the dealkylation catalyst or transalkylation catalyst is prepared as follows: first, a modified ZSM-5 molecular sieve or a modified Beta molecular sieve and a binder are mixed, kneaded, extruded, and formed into strips, followed by drying and calcination to obtain a carrier; then, the carrier is impregnated with a solution containing a precious metal, wherein the precious metal is platinum, palladium, ruthenium, or the like.

[0032] Compared with the prior art, the method for producing BTX from C9+ heavy aromatics of the present invention has the following advantages:

[0033] (1) The present invention couples dealkylation with a transalkylation catalyst to achieve two reactions in succession. The benzene and toluene produced by the dealkylation reaction can be used as reactants in the subsequent transalkylation reaction, further promoting the transalkylation reaction. At the same time, there is no need to introduce benzene or toluene into the raw materials as reactants for the transalkylation reaction.

[0034] (2) The present invention selectively masks the acidity outside the pores of ZSM-5 and Beta molecular sieves, thereby avoiding the adsorption and condensation of larger molecules in the mesopores and external surfaces, reducing carbon deposition, and increasing the service life of the catalyst;

[0035] (3) The present invention has a high conversion rate for both polymethylbenzenes and long alkyl side chain substituted benzenes, and the molecular sieve modification technology effectively avoids the condensation of large molecules, delays carbon deposition, and improves the operating cycle of the device. Implementation Method

[0036] The following examples and comparative examples are used to further illustrate the effects and benefits of the technical solutions of the present invention. However, the following examples do not limit the scope of protection of the present invention.

[0037] In the present invention, % involved in the embodiments and comparative examples are all mass percentages unless otherwise specified.

[0038] In the present invention, the total acid content is determined by pressing the powdered catalyst into pellets, evacuating the pellets, and then degassing at 450°C for 2 hours. After cooling to room temperature, a pyridine molecule with a kinetic diameter of 5Å is used as a probe molecule. The infrared spectrum of chemical desorption is measured and the adsorption amount is calculated. Because the diameter of the pyridine molecule is smaller than the micropores, this method can determine the total acid content.

[0039] In the present invention, the method for determining the amount of external acid in micropore channels is as follows: a powdered catalyst is pressed into a pellet, evacuated, and then degassed at 450°C for 2 hours. After the temperature is cooled to room temperature, a 2,6-di-tert-butylpyridine molecule is used as a probe molecule, and its chemical desorption infrared spectrum is measured to calculate the adsorption amount. Because the diameter of a 2,6-di-tert-butylpyridine molecule is larger than that of a micropore channel, this method can determine the amount of external acid in the micropore channel.

[0040] In this invention, pore volume and micropore volume were measured by physical adsorption using an ASAP 2420 low-temperature liquid nitrogen physical adsorption instrument manufactured by MICROMERITICS (USA). Prior to measurement, the sample was calcined at 550°C for 4 hours to remove the template. During testing, the sample was pretreated at 300°C for 3 hours and then subjected to nitrogen adsorption at 77K.

[0041] The Examples and Comparative Examples all used C9+ heavy aromatics from a refinery as raw materials, the composition of which is shown in Table 1.

[0042] Table 1 C9+ heavy aromatics feedstock of a refinery

[0043]

[0044] The properties of the commercially available hydrogen-type ZSM-5 molecular sieve raw powder used in the examples or comparative examples of the present invention are as follows: the specific surface area is 404.5 m 2 / g, pore volume 0.18 cm 3 / g, SiO2 / Al2O3 (mol) is 49, the properties of commercially available hydrogen-type Beta molecular sieve raw powder are as follows: specific surface area 627.8 m 2 / g, pore volume 0.319 cm 3 / g, SiO2 / Al2O3 (mol) is 25.

[0045] Example 1

[0046] CAT-1 was obtained according to the method of the present invention. Its properties are as follows: total acid content is 0.09 mmol / g, pore external acid content is 1.0 μmol / g, pore volume is 0.28 cm 3 / g, of which the micropore volume is 0.07cm 3 / g, the Pt content (as a single substance) is 0.5wt%, and the content of modified ZSM-5 molecular sieve is 80 wt%.

[0047] CAT-2 was obtained according to the method of the present invention. Its properties are as follows: total acid content is 0.43 mmol / g, pore external acid content is 1.4 μmol / g, pore volume is 0.43 cm 3 / g, of which the micropore volume is 0.26cm 3 / g, the Pt content (as a single substance) is 0.5wt%, and the modified Beta molecular sieve content is 30wt%.

[0048] CAT-3 was obtained according to the method of the present invention. Its properties are as follows: total acid content is 0.11 mmol / g, pore external acid content is 2.1 μmol / g, pore volume is 0.20 cm 3 / g, of which the micropore volume is 0.04cm 3 / g, the Pt content (as a single substance) is 0.5wt%, and the content of modified ZSM-5 molecular sieve is 40 wt%.

[0049] CAT-4 was obtained according to the method of the present invention. Its properties are as follows: total acid content is 0.27 mmol / g, pore external acid content is 4.5 μmol / g, pore volume is 0.32 cm 3 / g, of which the micropore volume is 0.17cm 3 / g, the Pt content (as a single substance) is 0.5wt%, and the modified Beta molecular sieve content is 70wt%.

[0050] Example 1-1

[0051] The dealkylation catalyst support CAT-1BS was obtained by rolling and mixing H-ZSM-5 raw powder and aluminum sol binder in a dry weight ratio of 80:20. The mixture was then extruded, dried, and calcined to obtain CAT-1BS. The support was then impregnated with ammonium chloroplatinate solution to obtain CAT-1B. Its properties are as follows: total acid content of 0.25 mmol / g, extra-pore acid content of 0.012 mmol / g, and a pore volume of 0.27 cm. 3 / g, of which the micropore volume is 0.12cm 3 / g, and the Pt content (as a single substance) is 0.5wt%.

[0052] The dealkylation catalyst support CAT-2BS was obtained by rolling and mixing H-Beta raw powder and aluminum sol binder in a dry weight ratio of 70:30, extruding, drying, and calcining. The support was impregnated with ammonium chloroplatinate solution to obtain CAT-2B. Its properties are as follows: total acid content of 0.57 mmol / g, extra-pore acid content of 0.027 mmol / g, and pore volume of 0.40 cm 3 / g, of which the micropore volume is 0.32cm 3 / g, and the Pt content (as a single substance) is 0.5wt%.

[0053] Example 2

[0054] The volume ratio of the dealkylation reaction zone to the transalkylation reaction zone was set to 1:9, the dealkylation reaction zone was filled with CAT1, the transalkylation reaction zone was filled with CAT2, the reaction pressure was 8.0 MPa, the hydrogen-to-oil volume ratio was 600:1, and the liquid hourly space velocity was 3.0 h -1 The reaction temperature was 500°C, and the fraction above 150°C was circulated to the reactor inlet. After 168 hours of operation, the single-pass conversion rate, BTX selectivity and the amount of carbon deposited on the unloaded catalyst were measured.

[0055] Example 3

[0056] The volume ratio of the dealkylation reaction zone to the transalkylation reaction zone was set to 7:3, the dealkylation reaction zone was filled with CAT1, the transalkylation reaction zone was filled with CAT2, the reaction pressure was 1.0 MPa, the hydrogen-to-oil volume ratio was 50:1, and the liquid hourly space velocity was 0.3 h -1 The reaction temperature was 350°C, and the fraction above 150°C was circulated to the reactor inlet. After 168 hours of operation, the single-pass conversion rate, BTX selectivity and the amount of carbon deposited on the unloaded catalyst were measured.

[0057] Example 4

[0058] The volume ratio of the dealkylation reaction zone to the transalkylation reaction zone was set to 2:8, the dealkylation reaction zone was filled with CAT3, the transalkylation reaction zone was filled with CAT4, the reaction pressure was 5.0 MPa, the hydrogen-to-oil volume ratio was 300:1, and the liquid hourly space velocity was 1.0 h -1 The reaction temperature was 400°C, and the fraction above 150°C was circulated to the reactor inlet. After 168 hours of operation, the single-pass conversion rate, BTX selectivity and the amount of carbon deposited on the unloaded catalyst were measured.

[0059] Example 5

[0060] The volume ratio of the dealkylation reaction zone to the transalkylation reaction zone was set to 3:7, the dealkylation reaction zone was filled with CAT1, the transalkylation reaction zone was filled with CAT4, the reaction pressure was 5.0 MPa, the hydrogen-to-oil volume ratio was 300:1, and the liquid hourly space velocity was 1.0 h -1 The reaction temperature was 400°C, and the fraction above 150°C was circulated to the reactor inlet. After 168 hours of operation, the single-pass conversion rate, BTX selectivity and the amount of carbon deposited on the unloaded catalyst were measured.

[0061] Example 6

[0062] The volume ratio of the dealkylation reaction zone to the transalkylation reaction zone was set to 4:6, the dealkylation reaction zone was filled with CAT3, the transalkylation reaction zone was filled with CAT2, the reaction pressure was 5.0 MPa, the hydrogen-to-oil volume ratio was 300:1, and the liquid hourly space velocity was 1.0 h -1The reaction temperature was 400°C, and the fraction above 150°C was circulated to the reactor inlet. After 168 hours of operation, the single-pass conversion rate, BTX selectivity and the amount of carbon deposited on the unloaded catalyst were measured.

[0063] Example 7

[0064] The volume ratio of the dealkylation reaction zone to the transalkylation reaction zone was set to 5:5, the dealkylation reaction zone was filled with CAT1, and the transalkylation reaction zone was filled with CAT2. The reaction pressure was 5.0 MPa, the hydrogen-to-oil volume ratio was 300:1, and the liquid hourly space velocity was 1.0 h -1 The reaction temperature was 400°C, and the fraction above 150°C was circulated to the reactor inlet. After 168 hours of operation, the single-pass conversion rate, BTX selectivity and the amount of carbon deposited on the unloaded catalyst were measured.

[0065] Example 8

[0066] The volume ratio of the dealkylation reaction zone to the transalkylation reaction zone was set to 5:5, the dealkylation reaction zone was filled with CAT3, the transalkylation reaction zone was filled with CAT4, the reaction pressure was 5.0 MPa, the hydrogen-to-oil volume ratio was 300:1, and the liquid hourly space velocity was 1.0 h -1 The reaction temperature was 400°C, and the fraction above 150°C was circulated to the inlet of the transalkylation reaction zone. After 168 hours of operation, the single-pass conversion rate, BTX selectivity and the amount of carbon deposited on the unloaded catalyst were measured.

[0067] Example 9

[0068] The volume ratio of the dealkylation reaction zone to the transalkylation reaction zone was set to 3:7, the dealkylation reaction zone was filled with CAT1, the transalkylation reaction zone was filled with CAT2, the reaction pressure was 5.0 MPa, the hydrogen-to-oil volume ratio was 300:1, and the liquid hourly space velocity was 1.0 h -1 The reaction temperature was 400°C, and the fraction above 150°C was circulated to the inlet of the transalkylation reaction zone. After 168 hours of operation, the single-pass conversion rate, BTX selectivity and the amount of carbon deposited on the unloaded catalyst were measured.

[0069] Example 10

[0070] The volume ratio of the dealkylation reaction zone to the transalkylation reaction zone was set to 1:9, the dealkylation reaction zone was filled with CAT1B, the transalkylation reaction zone was filled with CAT2B, the reaction pressure was 8.0 MPa, the hydrogen-to-oil volume ratio was 600:1, and the liquid hourly space velocity was 3.0 h -1 The reaction temperature was 500°C, and the fraction above 150°C was circulated to the reactor inlet. After 168 hours of operation, the single-pass conversion rate, BTX selectivity and the amount of carbon deposited on the unloaded catalyst were measured.

[0071] Table 2 Evaluation results of the examples

[0072]

Claims

1. A method for producing BTX from C9+ heavy aromatics, characterized in that: The method comprises the following steps: a C9+ heavy aromatic hydrocarbon feedstock enters a dealkylation reaction zone and a transalkylation reaction zone in sequence according to a logistics direction; the dealkylation reaction zone is loaded with a dealkylation catalyst mainly composed of a modified ZSM-5 molecular sieve; the transalkylation reaction zone is loaded with a transalkylation catalyst mainly composed of a modified Beta molecular sieve; the volume ratio of the catalysts loaded in the dealkylation reaction zone and the transalkylation reaction zone is 1:9 to 6:4; a fraction having a temperature of 65 to 150° C. obtained by separation of the material after the transalkylation reaction is a product rich in a BTX component; and a fraction having a temperature greater than 150° C. is recycled to the dealkylation reaction zone and / or the transalkylation reaction zone; The dealkylation catalyst has a total acid content of 0.05-0.12 mmol / g, an acid content outside the micropores of no more than 5 μmol / g, and a pore volume of 0.18-0.30 cm 3 / g, of which the micropore volume is 0.03~0.09cm 3 / g; The total acid content of the transalkylation catalyst is 0.25-0.45 mmol / g, the external acid content of the micropores is not higher than 0.01 mmol / g, and the pore volume is 0.30-0.45 cm 3 / g, of which the micropore volume is 0.15~0.30cm 3 / g; The preparation method of the modified ZSM-5 molecular sieve or modified Beta molecular sieve comprises the following steps: (1) Hydrothermal treatment of ZSM-5 molecular sieve or Beta molecular sieve raw powder; (2) impregnating the material obtained in step (1) with a pore protection liquid; (3) treating the material obtained in step (2) with a highly sterically hindered organic acid; (4) mixing the material obtained in step (3) with a dealumination and siliconization reagent to carry out dealumination and siliconization; (5) The material obtained in step (4) is filtered, washed, dried, and calcined to obtain a modified molecular sieve.

2. The method according to claim 1, wherein: The catalyst volume ratio of the dealkylation reaction zone and the transalkylation reaction zone is 3:7 to 5:5; the fraction with a temperature greater than 150° C. is circulated to the transalkylation reaction zone.

3. The method according to claim 1, wherein: The dealkylation reaction zone and the transalkylation reaction zone are arranged in one reactor, or are respectively arranged in multiple reactors.

4. The method according to claim 1, wherein: The dealkylation catalyst contains a modified ZSM-5 molecular sieve, a binder, and a noble metal hydrogenation center. Based on the weight of the dealkylation catalyst, the noble metal content is 0.1 wt% to 2.0 wt% as a single substance, and the modified ZSM-5 molecular sieve has a mass content of 30 wt% to 80 wt%.

5. The method according to claim 1, wherein: The amount of external acid in the micropores of the dealkylation catalyst is 0.1 μmol / g to 2 μmol / g.

6. The method according to claim 1, wherein: The transalkylation catalyst contains a modified Beta molecular sieve, a binder, and a metal hydrogenation center. Based on the weight of the transalkylation catalyst, the mass content of the modified Beta molecular sieve is 20wt% to 70wt%. The metal hydrogenation center is selected from noble metals, and the content of the noble metal is 0.1wt% to 2.0wt% on a simple basis.

7. The method according to claim 1, wherein: The amount of external acid in the micropores of the transalkylation catalyst is 0.5 μmol / g to 5 μmol / g.

8. The method according to claim 1, wherein: The operating conditions for producing BTX from C9+ heavy aromatics are as follows: reaction pressure of 1.0-8.0 MPa; hydrogen-to-oil volume ratio of 50:1-600:1; liquid hourly space velocity of 0.3-3 h -1 ; The reaction temperature is 350~500℃.

9. The method according to claim 8, characterized in that: The operating conditions for producing BTX from C9+ heavy aromatics are as follows: reaction pressure of 3.0-6.0 MPa; hydrogen-to-oil volume ratio of 200:1-400:1; liquid hourly space velocity of 0.5-2 h -1 ; The reaction temperature is 350~500℃.

10. The method according to claim 1, wherein: The C9+ heavy aromatics are reformed C9+ heavy aromatics.

11. The method according to claim 10, characterized in that: The mass content of trimethylbenzene in the reformed C9+ heavy aromatics is 30% to 50%, the mass content of propylbenzene is 3% to 10%, the mass content of methylethylbenzene is 20% to 30%, and the mass content of C10+ aromatics is 10% to 20%.

12. The method according to claim 1, wherein: The dealkylation catalyst or transalkylation catalyst preparation process is as follows: first, a modified ZSM-5 molecular sieve or a modified Beta molecular sieve and a binder are mixed, kneaded, extruded, and formed, and then dried and calcined to obtain a carrier; then, the carrier is impregnated with a solution containing a precious metal, wherein the precious metal is at least one of platinum, palladium, or ruthenium.

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