Process and system for producing mesitylene

Abstract

The application discloses a production method and system of durene, and the production method comprises the following steps: step 1, benzene and methanol are subjected to alkylation reaction under the action of a catalyst to obtain a reaction mixture containing durene; and step 2, the reaction mixture is separated to obtain durene. The application adopts benzene and methanol as raw materials to perform alkylation reaction, the properties of the raw materials are stable, the product composition is stable, durene can be produced, and xylene can be by-produced at the same time, and the total selectivity of durene and xylene can reach 85%. The application can adjust the proportion of methanol and benzene to achieve the purpose of adjusting the production amount of durene and xylene, and the product scheme is flexible and variable.

Description

Technical Field

[0001] This invention belongs to the field of organic chemical raw material production, specifically relating to a method and system for producing mesitylene. Background Technology

[0002] Mesitylene, also known as 1,2,4,5-tetramethylbenzene or Durone, is an important organic chemical raw material, mainly used in the production of pyromellitic dianhydride or pyromellitic anhydride, PMDA. Currently, mesitylene is primarily obtained from C10 aromatic hydrocarbons. Since C10 heavy aromatic hydrocarbons contain a relatively large number of components, mesitylene, the economically valuable component, accounts for only about 8%–9%. Synthetic methods for mesitylene include methanol alkylation of pseudotrimethylbenzene; isomerization and disproportionation of trimethylbenzene; chloromethylation of pseudotrimethylbenzene; isomerization of tetramethylbenzene; methanol to mesitylene; and methanol-xylene alkylation.

[0003] Chinese patent CN201510918420.2 discloses a catalyst for the highly selective preparation of mesitylene from methanol and its preparation method.

[0004] Chinese patent CN200310123203.1 discloses a method for simultaneously preparing mesitylene and mesitylene.

[0005] Chinese Patent 201810573387.8 discloses a catalyst for producing mesitylene from pseudotrimethylbenzene and its preparation method. The catalyst uses Na-ZSM-5 molecular sieve as the main component, with other types of molecular sieves as auxiliary agents, and is mixed with binders and pore-forming agents in a certain proportion. The mixture is then extruded, calcined, and subjected to ion exchange, high-temperature steam treatment, acid washing, and water washing. Finally, it undergoes halogen element and specific metal impregnation modification to obtain the catalyst. The resulting catalyst product exhibits high selectivity for mesitylene and few byproducts.

[0006] Chinese Patent 201610958726.5 discloses a one-step method for preparing mesitylene using syngas. The catalyst used is mainly HZSM-5, and mesitylene is obtained by catalytic reaction of syngas at 320-370℃ and 4.0-7.0 MPa.

[0007] Chinese Patent 201710461287.1 discloses a method for preparing BTX and co-producing mesitylene from C9+ heavy aromatics. First, C9+ heavy aromatics are catalytically cracked into a single-stage hydrocarbon mixture mainly composed of BTX and trimethylbenzene. After separation by a deethanizer, debutaneizer, dehexaneizer, BTX remover, and trimethylbenzene remover, the products are respectively identified as dry gas, liquefied petroleum gas, C5-C6 non-aromatics and BTX, trimethylbenzene, and C10+ heavy aromatics. The reaction is carried out under conditions where the molar ratio of trimethylbenzene to methanol is 1:1 to 5:1 to obtain dry gas, wastewater, and liquid hydrocarbons rich in mesitylene. The liquid hydrocarbon product is returned to the deethanizer for further separation. The C10+ heavy components are further separated by a crystallization separation system to obtain mesitylene and a residual liquid of the heavy components.

[0008] Chinese Patent 201910868346.6 discloses a method for producing mesitylene from methanol and xylene. The method involves mixing xylene with a portion of methanol, which enters the reactor via the top main feed line. The remaining methanol is fed into the reactor via a multi-stage side feed line. The material is converted into a mixed hydrocarbon component rich in mesitylene at a temperature of 250–400°C and a pressure of 0.5–2.0 MPa. After separation, heavy aromatics rich in mesitylene are obtained, which are then subjected to a multi-stage freeze crystallization and centrifugal pressing system to obtain high-purity mesitylene. Xylene and its mixed aromatics (C7–C9 aromatics and heavy aromatic residues) undergo repeated alkylation reactions with methanol, thereby increasing the selectivity of mesitylene in the oil phase products to 45%. The C7–C9 aromatics and heavy aromatic residues are returned to the feed storage tank, fully utilizing the reaction byproducts and increasing the mesitylene yield to 35%. Therefore, it can be seen that the actual reaction raw materials in this invention are toluene, xylene, trimethylbenzene and heavy aromatics reacting together with methanol. As the reaction proceeds, the mixed aromatics continuously circulate, and the heavy aromatics in the raw materials will continuously increase. The continuous change in the composition of the raw materials leads to the instability of the product composition.

[0009] As can be seen from the above, there are existing reports on the synthesis process and research of mesitylene, but there are still problems such as complex raw materials and unstable product composition, which require further improvement by those skilled in the art. Summary of the Invention

[0010] The main objective of this invention is to provide a method and system for producing mesitylene, so as to overcome the problems of complex raw materials and unstable product composition in the existing mesitylene synthesis process.

[0011] To achieve the above objectives, the present invention provides a method for producing mesitylene, comprising the following steps:

[0012] Step 1: Benzene and methanol are subjected to an alkylation reaction in the presence of a catalyst to obtain a reaction mixture containing mesitylene;

[0013] Step 2: Separate the reaction mixture to obtain mesitylene.

[0014] The method for producing mesitylene according to the present invention, wherein the separation of the reaction mixture includes:

[0015] The first separation step separates the reaction mixture into wastewater, C1-C4 hydrocarbons, and C5+ hydrocarbons;

[0016] The second separation step separates the C5+ hydrocarbons into light aromatics and heavy aromatics;

[0017] The third separation step separates the heavy aromatics into trimethylbenzene and C10+ aromatics;

[0018] The fourth separation step separates the C10+ aromatic hydrocarbons into mesitylene and other heavy aromatic hydrocarbons.

[0019] The method for producing mesitylene according to the present invention further includes a fifth separation step, in which the light aromatic hydrocarbon is separated into unreacted benzene, toluene and xylene, wherein the unreacted benzene is recycled for the alkylation reaction and the xylene is used as a by-product.

[0020] The method for producing mesitylene according to the present invention includes a process in which the toluene obtained in the fifth separation step is subjected to a disproportionation and alkyl transfer reaction with the trimethylbenzene obtained in the third separation step to obtain benzene and xylene, which are then recycled back to the second separation step for further separation.

[0021] The method for producing mesitylene according to the present invention, wherein the catalyst in step 1 is a molecular sieve, and the molecular sieve is at least one of β molecular sieve, ZSM-5 molecular sieve, ZSM-11 molecular sieve, and ZSM-35 molecular sieve.

[0022] The method for producing mesitylene according to the present invention, wherein the alkylation reaction in step 1 is carried out at a temperature of 350–480°C, a pressure of 0.5–4.0 MPa, a methanol to benzene molar ratio of 1:1–9:1, and a total feed space velocity of 0.1–5.0 h⁻¹. -1 .

[0023] To achieve the above objectives, the present invention also provides a mesitylene production system, comprising:

[0024] The reaction apparatus is equipped with a raw material inlet to allow benzene and methanol to be introduced into the reaction apparatus for alkylation reaction;

[0025] A separation unit, connected to the reaction apparatus, is used to input the reaction mixture into the separation unit for separation to obtain mesitylene.

[0026] The mesitylene production system of the present invention, wherein the separation unit comprises:

[0027] The first separation unit is connected to the reaction device to input the reaction mixture into the first separation unit for separation, thereby obtaining wastewater, C1-C4 hydrocarbons and C5+ hydrocarbons;

[0028] The second separation unit is connected to the first separation unit to input the C5+ hydrocarbon into the second separation unit for separation to obtain light aromatic hydrocarbons and heavy aromatic hydrocarbons;

[0029] The third separation unit is connected to the second separation unit to input the heavy aromatic hydrocarbon into the third separation unit for separation to obtain mesitylene.

[0030] The mesitylene production system of the present invention further includes a fourth separation unit connected to the third separation unit. The third separation unit separates the heavy aromatics into C10+ aromatics, and the fourth separation unit separates the C10+ aromatics into mesitylene and other heavy aromatics.

[0031] The mesitylene production system of the present invention further includes a fifth separation unit connected to the second separation unit, for inputting the light aromatic hydrocarbon into the fifth separation unit for separation to obtain unreacted benzene, toluene and xylene.

[0032] The mesitylene production system of the present invention further includes a reaction unit connected to the fifth separation unit and the third separation unit. The third separation unit further separates trimethylbenzene. The trimethylbenzene and the toluene obtained from the fifth separation unit are input into the reaction unit for disproportionation and alkyl transfer reactions to obtain benzene and xylene.

[0033] The present invention discloses a mesitylene production system, wherein the reaction unit is connected to the second separation unit to recycle the benzene and xylene back to the second separation unit for separation.

[0034] The mesitylene production system of the present invention includes a fifth separation unit connected to the reaction apparatus to recycle the unreacted benzene back to the reaction apparatus for alkylation reaction.

[0035] The beneficial effects of this invention are:

[0036] This invention uses benzene and methanol as raw materials for alkylation reaction. The raw materials are stable and the product composition is stable. Xylene can also be produced as a byproduct while producing mesitylene. The total selectivity of mesitylene and xylene can reach 85%.

[0037] This invention can adjust the production of mesitylene and xylene by adjusting the ratio of methanol to benzene, and the product scheme is flexible and variable. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of a mesitylene production system according to an embodiment of the present invention.

[0039] In the attached figures, the following labels are used:

[0040] I. Reaction apparatus

[0041] II. First Separation Unit

[0042] III. Second Separation Unit

[0043] IV. Fifth Separation Unit

[0044] V Third Separation Unit

[0045] VI Reaction Unit

[0046] VII. Fourth Separation Unit

[0047] 1. Benzene

[0048] 2 Methanol

[0049] 3. Reaction mixture

[0050] 4 Wastewater

[0051] 5 C1-C4 hydrocarbons

[0052] 6 C5+ hydrocarbons

[0053] 7. Light aromatics

[0054] 8. Toluene

[0055] 9 Unreacted benzene

[0056] 10 Xylene

[0057] 11 Heavy Aromatic Hydrocarbons

[0058] 12 Trimethylbenzene

[0059] 13 C10+ Aromatic Hydrocarbons

[0060] 14-Methoxylene

[0061] 15 Other heavy aromatics

[0062] 16. Benzene and xylene Detailed Implementation

[0063] The following provides a detailed description of the embodiments of the present invention. These embodiments are implemented based on the technical solution of the present invention and provide detailed implementation methods and processes. However, the scope of protection of the present invention is not limited to the following embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions.

[0064] In response to the current situation of excessive benzene production capacity and severe oversupply of methanol, and based on the in-depth implementation of the coal chemical and petrochemical coupled circular development strategy, this invention proposes a benzene and methanol alkylation to aromatics technology, with the aim of synthesizing xylene, mesitylene, and other basic organic chemical raw materials urgently needed by the market, which have higher added value.

[0065] Figure 1 This is a schematic diagram of a mesitylene production system according to an embodiment of the present invention, as shown below. Figure 1 As shown, the production system for methyltetramethylbenzene of the present invention includes a reaction device I and a separation unit.

[0066] The reaction apparatus I is equipped with a raw material inlet to allow benzene 1 and methanol 2 to be introduced into the reaction apparatus I for alkylation reaction. In one embodiment, the reaction apparatus I is a fixed-bed reactor or a moving-bed reactor, and a catalyst is provided in the reaction apparatus I. Benzene 1 and methanol 2 undergo alkylation reaction under the action of the catalyst to obtain reaction mixture 3. In another embodiment, the catalyst is a molecular sieve, such as at least one of β-methylene sieve, ZSM-5 molecular sieve, ZSM-11 molecular sieve, and ZSM-35 molecular sieve. The preparation of mesitylene from benzene requires the addition of four methyl groups, while the preparation of mesitylene from xylene only requires the addition of two methyl groups. Those skilled in the art tend to use pseudotrimethylbenzene to produce mesitylene because the reaction is easier to occur. This invention uses the reaction of benzene and methanol, and under the action of a specific catalyst, selectively inhibits the alkylation reaction, maximizing the utilization of the methyl groups provided by methanol in the raw materials to generate xylene and 1,2,4,5-mesitylene, rather than randomly generating toluene, xylene, trimethylbenzene, or more heavy aromatics.

[0067] The separation unit is connected to the reaction apparatus I to input the reaction mixture 3 into the separation unit for separation, thereby obtaining mesitylene.

[0068] In one embodiment, the separation unit includes a multi-stage separation unit, such as a first separation unit II, a second separation unit III, and a third separation unit V. The first separation unit II is connected to the reaction apparatus I to input the reaction mixture 3 for separation, yielding wastewater 4, C1-C4 hydrocarbons 5, and C5+ hydrocarbons 6. Wastewater 4 can be discharged from the system for further treatment, while C1-C4 hydrocarbons 5 can be utilized, for example, in other processes.

[0069] The second separation unit III is connected to the first separation unit II, so that C5+ hydrocarbons 6 are input into the second separation unit III for further separation to obtain light aromatics 7 and heavy aromatics 11. In one embodiment, light aromatics refer to C6-C8 aromatics, and heavy aromatics refer to C9 and above aromatics. Among them, heavy aromatics 11 include mesitylene 14.

[0070] The third separation unit V is connected to the second separation unit III, so that the heavy aromatic hydrocarbon 11 is input into the third separation unit V for separation to obtain mesitylene 14.

[0071] In another embodiment, the separation unit includes a first separation unit II, a second separation unit III, a third separation unit V, and a fourth separation unit VII. The third separation unit V first separates the heavy aromatic hydrocarbon 11 into trimethylbenzene 12 and C10+ aromatic hydrocarbon 13. The fourth separation unit VII is connected to the third separation unit V, and the C10+ aromatic hydrocarbon 13 is input into the fourth separation unit VII for further separation into mesitylene 14 and other heavy aromatic hydrocarbons 15.

[0072] In one embodiment, the production system for xylene of the present invention further includes a fifth separation unit IV, which is connected to the second separation unit III, to input light aromatic hydrocarbon 7 into the fifth separation unit IV for separation, yielding unreacted benzene 9, toluene 8, and xylene 10. Xylene 10 can be used as a byproduct in other processes.

[0073] In another embodiment, the fifth separation unit IV is connected to the reaction device I, and unreacted benzene 9 can be recycled back to the reaction device I to participate in the alkylation reaction again.

[0074] In one embodiment, the trimethylbenzene production system of the present invention further includes a reaction unit VI, which is connected to a fifth separation unit IV and a third separation unit V. Trimethylbenzene 12 separated from the third separation unit V and toluene 8 obtained from the fifth separation unit IV are input into the reaction unit VI for disproportionation and alkyl transfer reactions to obtain benzene and xylene 16. The disproportionation and alkyl transfer reactions of trimethylbenzene and toluene can be carried out according to conventional disproportionation and alkyl transfer reactions in the art, and the present invention is not particularly limited thereto. In another embodiment, the reaction unit VI is also connected to a second separation unit III to recycle benzene and xylene 16 back to the second separation unit III for separation.

[0075] The present invention does not limit the specific separation form of the above separation unit, such as atmospheric distillation, vacuum distillation, rectification, etc.

[0076] The method for producing mesitylene according to the present invention will be described in detail below.

[0077] The present invention provides a method for producing mesitylene, comprising the following steps:

[0078] Step 1: Benzene 1 and methanol 2 are subjected to an alkylation reaction under the action of a catalyst to obtain a reaction mixture 3 containing mesitylene;

[0079] Step 2: Separate the reaction mixture 3 to obtain mesitylene 14.

[0080] In one embodiment, the catalyst in step 1 is a molecular sieve, such as at least one selected from β-zeolite, ZSM-5 molecular sieve, ZSM-11 molecular sieve, and ZSM-35 molecular sieve, with a silica-to-alumina ratio of, for example, 20-200. The alkylation reaction is carried out at a temperature of 350-480°C, a pressure of 0.5-4.0 MPa, a methanol-to-benzene molar ratio of 1:1-9:1, and a total feed mass hourly space velocity of 0.1-5.0 h⁻¹. -1 .

[0081] In one embodiment, the separation of the reaction mixture of the present invention is performed in a fractional manner, for example including:

[0082] In the first separation step, the reaction mixture 3 is separated into wastewater 4, C1-C4 hydrocarbons 5 and C5+ hydrocarbons 6; wastewater 4 can be discharged from the system for further treatment before being discharged; C1-C4 hydrocarbons 5 can be comprehensively utilized.

[0083] In the second separation step, the C5+ hydrocarbon 6 is separated into light aromatic hydrocarbon 7 and heavy aromatic hydrocarbon 11; wherein, heavy aromatic hydrocarbon 11 includes mesitylene and light aromatic hydrocarbon 7 includes xylene.

[0084] The third separation step separates the heavy aromatic hydrocarbon 11 into trimethylbenzene 12 and C10+ aromatic hydrocarbon 13;

[0085] In the fourth separation step, the C10+ aromatic hydrocarbon 13 is separated into mesitylene 14 and other heavy aromatic hydrocarbons 15.

[0086] In another embodiment, the method for producing xylene of the present invention further includes a fifth separation step, in which light aromatic hydrocarbon 7 is separated into unreacted benzene 9, toluene 8 and xylene 10, the unreacted benzene 9 is recycled back to the reaction device I to undergo an alkylation reaction with methanol 2, and xylene 10 is collected as a by-product.

[0087] In another embodiment, the method for producing xylene of the present invention further includes disproportionation and alkyl transfer reaction of toluene 8 obtained in the fifth separation step and trimethylbenzene 12 obtained in the third separation step to obtain benzene and xylene 16 which are recycled back to the second separation step for separation.

[0088] Therefore, this invention provides a method for producing xylene and mesitylene from benzene. The resulting products have a stable composition, and xylene is produced concurrently with the formation of mesitylene. The overall selectivity for mesitylene and xylene can reach 85%.

[0089] The technical solution of the present invention will be further described below with reference to specific embodiments, but it is by no means limited thereto.

[0090] The reaction uses benzene and methanol as raw materials, and the specific product composition is shown in Table 1.

[0091] Example 1

[0092] The alkylation reaction was carried out using HZSM-5 molecular sieve with a silica-to-alumina ratio of 30 as a catalyst. The molar ratio of benzene to methanol in the alkylation reactor was 1:4, the reaction temperature was 380℃, the pressure was 0.5 MPa, and the total feed mass hourly space velocity was 1 h⁻¹. -1 The resulting hydrocarbon mixture rich in mesitylene and xylene is separated by a three-phase separator in separation unit II to obtain wastewater, C1-C4 hydrocarbons, and C5+ hydrocarbons. The wastewater exits the system. The C5+ hydrocarbons enter the primary product separation tower III, where the bottom temperature is maintained at 210°C to produce heavy aromatics rich in mesitylene, and the top temperature yields light aromatics rich in xylene. The light aromatics continue into the second-stage separation tower IV, where benzene is collected at the top temperature of 80°C and recycled back to reactor I to continue the reaction. Toluene is collected at the side stream temperature of 110°C, and xylene is collected from the bottom. The heavy aromatics are separated in the third-stage heavy aromatics separation tower V to obtain trimethylbenzene and C10+ aromatics rich in mesitylene. The C10+ heavy aromatics are then subjected to freeze crystallization, centrifugal separation, and pressing to obtain mesitylene with a purity of 98%. Toluene and xylene enter reaction unit VI for disproportionation and alkyl transfer reactions. The reaction temperature is 460℃, the reaction pressure is 2.0-3.3 MPa, the mass hourly space velocity is 2.0-4.0 h⁻¹, and the hydrogen-to-hydrocarbon molar ratio is ≥2.5. The resulting benzene and xylene enter the primary product separation tower III for separation.

[0093] The product distribution results under these conditions are shown in Table 1.

[0094] Example 2

[0095] The alkylation reaction was carried out using HZSM-5 molecular sieve with a silica-to-alumina ratio of 60 as a catalyst. The alkylation reactor employed a benzene to methanol molar ratio of 1:3, a reaction temperature of 400℃, a pressure of 1.0 MPa, and a total feed mass hourly space velocity (MHSV) of 1 h⁻¹. -1 The product separation steps are as shown in Example 1. The product distribution results under the stable operation of the catalyst under these conditions are shown in Table 1.

[0096] Example 3

[0097] An alkylation reaction was carried out using HZSM-5 molecular sieve (both with a silica-to-alumina ratio of 60) and ZSM-11 molecular sieve in a 1:1 mass ratio as catalysts. The alkylation reactor employed a benzene-to-methanol molar ratio of 1:5, a reaction temperature of 400℃, a pressure of 2.0 MPa, and a total feed mass hourly space velocity (WHSV) of 1 h⁻¹. -1 The product separation steps are as shown in Example 1. The product distribution results under the stable operation of the catalyst under these conditions are shown in Table 1.

[0098] Example 4

[0099] An alkylation reaction was carried out using HZSM-5 molecular sieve (both with a silica-to-alumina ratio of 60) and β-molecular sieve in a 1:1 mass ratio as catalysts. The alkylation reactor employed a benzene-to-methanol molar ratio of 1:5, a reaction temperature of 400℃, a pressure of 2.0 MPa, and a total feed mass hourly space velocity (WHSV) of 1 h⁻¹. -1 The product separation steps are as shown in Example 1. The product distribution results under the stable operation of the catalyst under these conditions are shown in Table 1.

[0100] Example 5

[0101] The alkylation reaction was carried out using HZSM-5 molecular sieve with a silica-to-alumina ratio of 80 as a catalyst. The alkylation reactor employed a benzene to methanol molar ratio of 1:5, a reaction temperature of 420℃, a pressure of 3.0 MPa, and a total feed space velocity of 1 h⁻¹. -1 The product separation steps are as shown in Example 1. The product distribution results under the stable operation of the catalyst under these conditions are shown in Table 1.

[0102] Example 6

[0103] The alkylation reaction was carried out using ZSM-35 molecular sieve with a silicon-to-aluminum ratio of 30 as a catalyst. The alkylation reactor employed a benzene to methanol molar ratio of 1:5, a reaction temperature of 400℃, a pressure of 2.5 MPa, and a total feed space velocity of 1 h⁻¹. -1 The product separation steps are as shown in Example 1. The product distribution results under the stable operation of the catalyst under these conditions are shown in Table 1.

[0104] Example 7

[0105] ZSM-5 molecular sieves with a silica-to-alumina ratio of 150 and ZSM-11 were mixed in a 1:1 mass ratio as catalysts for alkylation. The alkylation reactor used a benzene-to-methanol molar ratio of 1:6, a reaction temperature of 440℃, a pressure of 4.0 MPa, and a total feed mass hourly space velocity of 1 h⁻¹. -1 The product separation steps are as shown in Example 1. The product distribution results under the stable operation of the catalyst under these conditions are shown in Table 1.

[0106] Example 8

[0107] ZSM-5 molecular sieves with a silica-to-alumina ratio of 150 and ZSM-35 were mixed in a 1:1 mass ratio as catalysts for alkylation. The alkylation reactor used a benzene-to-methanol molar ratio of 1:6, a reaction temperature of 440℃, a pressure of 4.0 MPa, and a total feed mass hourly space velocity of 1 h⁻¹. -1 The product separation steps are as shown in Example 1. The product distribution results under the stable operation of the catalyst under these conditions are shown in Table 1.

[0108] Table 1. Distribution of reaction products (wt%)

[0109]

[0110] C5+ hydrocarbons are organic compounds obtained after separation of reaction mixture 3 by the first separation unit II, and then after removing C1-C4 hydrocarbons and C5+ non-aromatic hydrocarbons.

[0111] Therefore, the present invention provides a method for producing mesitylene, wherein increasing the proportion of methanol used is beneficial to the reaction, and increasing the catalyst activity is also beneficial to the reaction.

[0112] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for producing mesitylene, characterized in that, Includes the following steps: Step 1: Benzene and methanol are subjected to an alkylation reaction in the presence of a catalyst to obtain a reaction mixture containing mesitylene; Step 2, separating the reaction mixture, including: The first separation step separates the reaction mixture into wastewater, C1-C4 hydrocarbons, and C5+ hydrocarbons; The second separation step separates the C5+ hydrocarbons into light aromatics and heavy aromatics; The third separation step separates the heavy aromatics into trimethylbenzene and C10+ aromatics; The fourth separation step separates the C10+ aromatics into mesitylene and other heavy aromatics; In the fifth separation step, the light aromatic hydrocarbons are separated into unreacted benzene, toluene, and xylene. The unreacted benzene is recycled for the alkylation reaction, and the xylene is used as a byproduct. The toluene obtained in the fifth separation step is subjected to disproportionation and alkyl transfer reaction with the trimethylbenzene obtained in the third separation step to obtain benzene and xylene, which are then recycled back to the second separation step for further separation. The catalyst is a molecular sieve, which is at least one of β molecular sieve, ZSM-5 molecular sieve, ZSM-11 molecular sieve, and ZSM-35 molecular sieve, and the silica-alumina ratio of the molecular sieve is 20-200. The alkylation reaction is carried out at a temperature of 350–480 °C, a pressure of 0.5–4.0 MPa, a methanol to benzene molar ratio of 3:1–9:1, and a total feed mass hourly space velocity of 0.1–5.0 h⁻¹. -1 .

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