Method for producing high-purity p-methyl-ethylbenzene

Abstract

The invention discloses a method for producing high-purity p-methyl-ethylbenzene, which comprises the following steps: mixing an aromatic hydrocarbon raw material and an alkylating agent, introducing the mixture into a reaction unit, and obtaining a reaction product flow under the action of an alkylation-isomerization catalyst; introducing the reaction product flow into a separation unit, and separating to obtain a p-methyl-ethylbenzene / m-methyl-ethylbenzene mixture flow and a circulating flow; finally, the p-methyl-ethylbenzene / m-methyl-ethylbenzene mixture flow is separated through an adsorption separation unit to obtain p-methyl-ethylbenzene flow and m-methyl-ethylbenzene flow, and production of high-purity p-methyl-ethylbenzene is achieved. The p-methyl-ethylbenzene obtained by the method is high in purity and high in yield; the used catalyst is stable in performance, long in one-way service life and high in one-way conversion rate; a moderate shape-selective alkylation reaction, a moderate shape-selective isomerization reaction and an adsorption separation process are coupled, so that side reactions are few, and the utilization rate of raw materials is high; and p-methyl-ethylbenzene and m-methyl-ethylbenzene can be flexibly produced according to market demand conditions, and the product purity and the production efficiency are improved in industrial production.

Description

Technical Field

[0001] This invention belongs to the field of p-toluene preparation technology, specifically relating to a method for producing high-purity p-toluene. Background Technology

[0002] p-Toluene-ethylbenzene is mainly used in the synthesis of p-methylstyrene and poly(p-methylstyrene), and is an important chemical product. Compared with styrene, p-methylstyrene has the advantages of lower toxicity and lower volatility. Further polymerization of p-methylstyrene produces poly(p-methylstyrene), which, compared with polystyrene, has advantages such as lower density, better heat resistance, and shorter molding cycle. However, the production of high-purity p-methylstyrene is difficult, resulting in a persistently high price and limiting the further development of its downstream industries.

[0003] Currently, the production of p-toluene is mainly divided into physical separation and chemical synthesis. Physical separation directly separates p-toluene from C9 aromatic fractions; however, due to the complex composition of the raw materials and the similar boiling points of different components, special separation processes such as extractive distillation are required, resulting in high separation difficulty and energy consumption. Chemical synthesis generates p-toluene through shape-selective ethylation of toluene or shape-selective methylation of ethylbenzene. This requires modification of the catalyst pores and improving the purity of p-toluene in the product through product shape selection. However, the catalyst's single-pass lifetime is often short, requiring frequent regeneration.

[0004] CN102795957B and CN101077849B disclose a method for separating m-toluene and p-toluene by extractive distillation, which achieves the separation of m-toluene and p-toluene by introducing different extractants. Although extractive distillation can achieve the separation of m-toluene and p-toluene and obtain high-purity p-toluene, the extractants suffer from problems such as slow decomposition at high temperatures and difficulty in separating p-toluene / m-toluene.

[0005] CN116023221A discloses a method for adsorbing and separating high-purity p-ethylbenzene from heavy aromatic hydrocarbon feedstock, achieving the separation of high-purity p-ethylbenzene through an adsorption separation process. Since heavy aromatic hydrocarbons are generally byproducts of reforming units, ethylene cracking units, and catalytic cracking units, they suffer from low yields and low p-ethylbenzene content, thus limiting the production capacity of p-ethylbenzene using this method.

[0006] CN104276920B and CN104230632B disclose a method for preparing ethyltoluene from toluene and ethanol, which can adjust the ratio of ortho, meta, and para-ethyltoluenes to a certain extent. However, when the purity of para-ethyltoluene is high, the catalyst's single-pass life is significantly reduced, and the problem of long-term stability of the catalyst in the production of high-purity para-ethyltoluene cannot be solved.

[0007] CN119330803A proposes a method for synthesizing high-purity p-methylstyrene. This method involves alkylating toluene with catalytic dry gas to produce a mixture of methyl and ethylbenzene. The methyl and ethylbenzene mixture is then separated by adsorption to obtain high-purity p-methyl and ethylbenzene. Finally, the p-methyl and ethylbenzene undergoes a high-temperature dehydrogenation reaction under an iron-based catalyst to yield high-purity p-methylstyrene. This method addresses the short lifespan of alkylation catalysts to some extent; however, the proportion of m-methyl and ethylbenzene obtained from the alkylation reaction is relatively high and lacks a suitable utilization pathway, meaning it can only be collected as a low-value byproduct. Summary of the Invention

[0008] This invention is proposed to solve the problems of low conversion rate, poor catalyst stability and low product purity in the prior art, and its purpose is to provide a method for producing high-purity p-toluene.

[0009] This invention is achieved through the following technical solution: A method for producing high-purity p-toluene includes the following steps: S1. The aromatic raw material and alkylating agent are mixed and then introduced into the alkylation reaction unit. Under the action of the alkylation-isomerization catalyst, the reaction product stream is obtained. When the aromatic feedstock is toluene, the alkylating agent is at least one of ethanol, ethylene, or a mixture containing ethylene; when the aromatic feedstock is ethylbenzene, the alkylating agent is methanol. S2. Pass the reaction product stream from step S1 into the separation unit to separate the p-toluene / m-toluene mixture stream and the circulating stream. S3. The p-toluene / m-toluene mixture obtained in step S2 is fed into the adsorption separation unit to separate the p-toluene stream and the m-toluene stream.

[0010] In the above technical solution, the recycled stream obtained from the separation unit is returned to the alkylation reaction unit; the p-toluene stream obtained from the adsorption separation unit is directly collected to achieve the production of high-purity p-toluene; the m-toluene stream obtained from the adsorption separation unit is returned to the alkylation reaction unit or treated by the shape-selective isomerization unit before being returned to the adsorption separation unit; when the m-toluene stream is returned to the alkylation reaction unit, the m-toluene stream is mixed with the recycled stream obtained from step S2 and then split into two streams, one stream is used as a quench source, and the other stream is mixed with aromatic raw materials and alkylation reagents and then heated to the reaction temperature.

[0011] In the above technical solution, the molar ratio of aromatic raw material and alkylating agent in step S1 is 15:1 to 1:3, preferably 10:1 to 1:1.

[0012] In the above technical solution, the mass space velocity of the aromatic feedstock introduced into the alkylation reaction unit in step S1 is 0.5 h⁻¹. -1 ~10 h-1 Preferably 3 h -1 ~6 h -1 .

[0013] In the above technical solution, the aromatic raw material in step S1 is toluene or ethylbenzene; the alkylating agent is at least one of methanol, ethanol, ethylene or ethylene-containing mixed gas; the ethylene-containing mixed gas is a mixed gas with an ethylene mass content of more than 15%, generally referring to ethylene-containing mixed gas by-products of catalytic cracking units and other equipment.

[0014] In the above technical solution, the reaction conditions in the alkylation reaction unit are: reaction temperature of 300 ℃~500 ℃ and reaction pressure of 0.1 MPa~4.0 MPa.

[0015] In the above technical solution, the alkylation reaction unit is any one of a fixed bed, a moving bed, a fluidized bed, or a slurry bed.

[0016] In the above technical solution, the alkylation reaction unit is filled with an alkylation-isomerization catalyst.

[0017] In the above technical solution, the preparation method of the alkylation-isomerization catalyst is as follows: after mixing the active component with the binder and molding, the oxide is introduced into it by means of impregnation, ion exchange or deposition precipitation, and after drying and calcination, the alkylation-isomerization catalyst is obtained; the active component accounts for 20% to 70% of the mass of the alkylation-isomerization catalyst, the oxide accounts for 6% to 30%, and the remainder is the binder.

[0018] In the above technical solution, the active component is at least one of ZSM-5 molecular sieve, ZSM-11 molecular sieve or SAPO-11 molecular sieve; the oxide is at least one of magnesium oxide, silicon oxide, phosphorus oxide or boron oxide; and the binder is at least one of silica sol, boehmite, alumina or acid-treated clay.

[0019] In the above technical solution, the separation unit is a conventional separation facility; the separation unit is a distillation separation column; In the above technical solution, when the alkylating agent contains ethanol, the separation unit further includes an oil-water separator; when the alkylating agent contains a mixture of ethylene, the separation unit (2) further includes a gas-liquid separator.

[0020] In the above technical solution, the adsorption separation unit is a simulated moving bed.

[0021] In the above technical solution, the adsorption separation conditions in the adsorption separation unit are: adsorption temperature 40 ℃~180℃, pressure 0.1 MPa~1.5 MPa, and the mass flow rate ratio of the p-toluene / m-toluene mixture to the desorbent is 1:(1~3); the desorbent is at least one of toluene, xylene or diethylbenzene, with toluene being preferred; the mass flow rate ratio of the p-toluene / m-toluene mixture to the circulation volume is 1:(0.8~4).

[0022] In the above technical solution, when toluene is selected as the desorbent in the adsorption separation unit, the required separation accuracy of the distillation separation column in step S2 can be appropriately reduced, and the small amount of cost reduction in the bottom product has no impact on the separation of the simulated moving bed in the next step.

[0023] In the above technical solution, the adsorbent of the adsorption separation unit is an X-type zeolite that has been exchanged with any one of the metal ions of Li, K, Rb or Cs.

[0024] In the above technical solution, the metal ion exchange of the X-type zeolite adsorbent is carried out by column exchange or static exchange, the metal ion exchange temperature is 60℃~90℃, and the metal ion exchange time is 2h~12h; the concentration of metal ions (Li, K, Rb or Cs) in the ion exchange solution used for metal ion exchange is 0.03~0.2mol / L; the X-type zeolite is a commercially available product.

[0025] In the above technical solution, the reaction conditions within the shape-selective isomerization unit are: a reaction temperature of 200 ℃~400 ℃, a reaction pressure of 0.3 MPa~2.0 MPa, and a mass hourly space velocity (MHV) of 0.5 h⁻¹ for the m-toluene-ethylbenzene stream. -1 ~10 h -1 .

[0026] In the above technical solution, the shape-selective isomerization unit is a fixed bed.

[0027] In the above technical solution, the shape-selective isomerization unit is filled with a shape-selective isomerization catalyst.

[0028] In the above technical solution, the preparation method of the shape-selective isomerization catalyst is as follows: after mixing the active component with the binder and molding, the catalyst is then modified with oxide to obtain the shape-selective isomerization catalyst. The preparation method is the same as that of the alkylation-isomerization catalyst. The active component accounts for 25% to 65% of the mass of the shape-selective isomerization catalyst, the oxide accounts for 5% to 25%, and the remainder is binder.

[0029] In the above technical solution, the active component is at least one of ZSM-5 molecular sieve, ZSM-11 molecular sieve, MOR molecular sieve or EU-1 molecular sieve; the oxide is at least one of magnesium oxide, silicon oxide, phosphorus oxide or boron oxide; the binder is at least one of silica sol, boehmite, alumina or acid-treated clay.

[0030] The beneficial effects of this invention are: This invention provides a method for producing high-purity p-toluene-ethylbenzene, which yields p-toluene-ethylbenzene with high purity and high yield. The catalyst used has stable performance, long single-pass lifetime, and high single-pass conversion rate. By coupling moderate shape-selective alkylation and isomerization reactions with adsorption separation processes, side reactions are minimized and raw material utilization is high. The method allows for flexible production of p-toluene-ethylbenzene and m-toluene-ethylbenzene according to market demand, thereby improving product purity and production efficiency in industrial production. Attached Figure Description

[0031] Figure 1 These are schematic diagrams of the reaction systems in embodiments 1, 2, and 4 of the present invention. Figure 2 This is a schematic diagram of the reaction system in Embodiment 3 of the present invention.

[0032] in: 1. Alkylation reaction unit; 2. Separation unit; 3. Adsorption separation unit; 4. Shape-selective isomerization unit.

[0033] For those skilled in the art, other related figures can be obtained from the above figures without any creative effort. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0035] Example 1

[0036] like Figure 1 As shown, a method for producing high-purity p-toluene includes the following steps: S1. Toluene and ethanol are mixed at a molar ratio of 15:1 and then introduced into a fluidized bed. The mass hourly space velocity of toluene is 10 h⁻¹. -1 Under the action of an alkylation-isomerization catalyst, the reaction product stream is obtained; The operating conditions within the fluidized bed are: reaction temperature 400 ℃, reaction pressure 4.0 MPa; The alkylation-isomerization catalyst was formed by mixing ZSM-5 and ZSM-11 with an alumina binder and then modifying it with Mg-Si. Mg modification was introduced by impregnation with magnesium nitrate, and Si modification was introduced by deposition and precipitation of tetraethyl orthosilicate. The mass ratio of ZSM-5 is 45%, ZSM-11 is 25%, magnesium oxide is 2%, silicon oxide is 15%, and the remainder is binder.

[0037] S2. The reaction product stream from step S1 is fed into a distillation column. The circulating stream from the top of the distillation column is returned to the fluidized bed. The p-toluene / m-toluene mixture stream from the bottom of the distillation column is fed into a simulated moving bed. S3. The simulated moving bed separates the p-ethylbenzene / m-ethylbenzene mixture into p-ethylbenzene stream and m-ethylbenzene stream. The p-ethylbenzene stream is collected directly, while the m-ethylbenzene stream is returned to the fluidized bed.

[0038] The adsorbent in the simulated moving bed was Li-exchanged X-type zeolite, the adsorption temperature was 180℃, the adsorption pressure was 1.5MPa, the mass flow rate ratio of the p-toluene / m-toluene mixture to the desorbent was 1:1, the mass flow rate ratio of the feed to the circulating flow was 1:2, and the desorbent was toluene. The X-type zeolite metal ion exchange of the adsorbent is a static exchange, the ion exchange temperature is 60℃, the Li ion concentration in the ion exchange solution is 0.03mol / L, and the ion exchange time is 12h.

[0039] According to Example 1, the purity of the p-toluene product was 98.5 wt%, the catalyst single-pass life of the isomerization-alkylation reaction unit was 80 days, the alkylation reagent utilization rate was 99%, and the p-toluene yield was 96%.

[0040] Example 2

[0041] like Figure 1 As shown, a method for producing high-purity p-toluene includes the following steps: S1. Toluene and ethylene are mixed at a molar ratio of 5:1 and then introduced into a moving bed. The mass hourly space velocity of toluene is 5 h⁻¹. -1 Under the action of an alkylation-isomerization catalyst, the reaction product stream is obtained; The operating conditions inside the moving bed are: reaction temperature 500 ℃, reaction pressure 1.0 MPa; The alkylation-isomerization catalyst was formed by mixing ZSM-5 and SAPO-11 with a silica sol binder, and then modified with Mg-B after molding. Mg modification was introduced by ion exchange with magnesium nitrate solution, and B was introduced by boric acid impregnation. The composition is 45% ZSM-5, 15% SAPO-11, 4% magnesium oxide, 8% boron oxide, and the remainder is binder.

[0042] S2. The reaction product stream from step S1 is fed into a distillation column. The recycle stream obtained from the top of the distillation column is returned to the moving bed. The p-toluene / m-toluene mixture stream obtained from the bottom of the distillation column is fed into the simulated moving bed. S3. The simulated moving bed separates the p-ethylbenzene / m-ethylbenzene mixture stream into p-ethylbenzene stream and m-ethylbenzene stream. The p-ethylbenzene stream is collected directly, while the m-ethylbenzene stream is returned to the moving bed.

[0043] The adsorbent in the simulated moving bed was K-exchanged X-type zeolite, the adsorption temperature was 100℃, the adsorption pressure was 0.8 MPa, the mass flow rate ratio of the p-toluene / m-toluene mixture to the desorbent was 1:3, the mass flow rate ratio of the feed to the circulating flow was 1:4, and the desorbent was toluene. The X-type zeolite metal ion exchange of the adsorbent is carried out by column exchange, the ion exchange temperature is 90℃, the K ion concentration in the ion exchange solution is 0.2mol / L, and the ion exchange time is 2h.

[0044] In Example 2, the obtained p-toluene product had a purity of 99.5 wt%, a catalyst single-pass lifetime of 90 rpm in the isomerization-alkylation reaction unit, an alkylation reagent utilization rate of 98%, and a p-toluene yield of 97%.

[0045] Example 3

[0046] like Figure 2 As shown, a method for producing high-purity p-toluene includes the following steps: S1. Ethylbenzene and methanol are mixed at a molar ratio of 1:1 and then introduced into a fixed bed. The mass hourly space velocity (WHSV) of ethylbenzene is 0.5 h⁻¹. -1 Under the action of an alkylation-isomerization catalyst, the reaction product stream is obtained; The operating conditions in the fixed bed are: reaction temperature 350 ℃, reaction pressure 1.5 MPa; The alkylation-isomerization catalyst was formed by mixing ZSM-5 and pseudoboehmite, and then modified with Mg-Si-P after molding. Mg modification was introduced by impregnation with magnesium nitrate solution, Si modification was introduced by deposition of tetraethyl orthosilicate, and P modification was introduced by impregnation with phosphoric acid. The composition of ZSM-5 is 70% by mass, magnesium oxide is 2% by mass, silicon oxide is 10% by mass, phosphorus pentoxide is 8% by mass, and the remainder is binder.

[0047] S2. The reaction product stream from step S1 is fed into a distillation separation column. The product at the top of the distillation separation column is separated into a gas phase by a gas-liquid separator and the mixed gas exits the device. The liquid phase is returned to the moving bed as a circulating stream. The p-toluene / m-toluene mixture stream obtained from the bottom of the distillation separation column enters the simulated moving bed. S3. The simulated moving bed separates the p-ethylbenzene / m-ethylbenzene mixture stream into p-ethylbenzene stream and m-ethylbenzene stream. The p-ethylbenzene stream is collected directly, while the m-ethylbenzene stream enters the shape-selective isomerization unit. The resulting m-ethylbenzene / p-ethylbenzene mixture stream is returned to the simulated moving bed.

[0048] The adsorbent in the simulated moving bed was Rb-exchanged X-type zeolite, the adsorption temperature was 40℃, the adsorption pressure was 0.1 MPa, the mass flow rate ratio of the p-toluene / m-toluene mixture to the desorbent was 1:3, the mass flow rate ratio of the feed to the circulating flow was 1:4, and the desorbent was toluene. The X-type zeolite metal ion exchange of the adsorbent is a static exchange, the ion exchange temperature is 70℃, the Rb ion concentration in the ion exchange solution is 0.08mol / L, and the ion exchange time is 4h.

[0049] The operating conditions for the shape-selective isomerization unit are: m-toluene mass hourly space velocity (HHSV) of 5.0 h⁻¹. -1 The reaction temperature was 300 ℃, the reaction pressure was 1.0 MPa, and the reactor was a fixed bed.

[0050] The catalyst is a mixture of 70% ZSM-11 and 30% boehmite, which is then modified by Si-P after molding, with SiO2 content of 8% and P2O5 content of 12% (based on 100% support).

[0051] The shape-selective isomerization catalyst was formed by mixing ZSM-11 and pseudoboehmite, and then modified with Si-P after molding; Si modification is achieved through tetraethyl orthosilicate deposition and precipitation, while P modification is achieved through phosphoric acid impregnation. ZSM-11 accounts for 60% of the mass, silicon dioxide accounts for 8% of the mass, phosphorus pentoxide accounts for 12% of the mass, and the remainder is binder.

[0052] In Example 3, the obtained p-toluene product had a purity of 99.5 wt%, a single-pass catalyst lifetime of 95 days in the alkylation reaction unit, a single-pass catalyst lifetime of 90 days in the isomerization reaction unit, a utilization rate of 90% for the alkylation reagent, and a p-toluene yield of 95%.

[0053] Example 4

[0054] like Figure 1 As shown, a method for producing high-purity p-toluene includes the following steps: S1. Toluene and catalytic cracking dry gas (ethylene content 20%) are mixed at a molar ratio of 1:3 (toluene to ethylene in the catalytic cracking dry gas) and then introduced into a moving bed. The toluene mass hourly space velocity (HHSV) is 10 h⁻¹. -1 Under the action of an alkylation-isomerization catalyst, the reaction product stream is obtained; The operating conditions inside the moving bed are: reaction temperature 300 ℃, reaction pressure 0.1 MPa; The alkylation-isomerization catalyst was formed by mixing ZSM-5, ZSM-11 and alumina, and then modified with Mg-Si after molding. Mg modification was introduced by impregnation with magnesium nitrate solution, and Si modification was achieved by deposition and precipitation of tetraethyl orthosilicate. ZSM-5 accounts for 30% of the total mass, ZSM-11 accounts for 20%, magnesium oxide accounts for 2%, silicon oxide accounts for 1.5%, and the remainder is binder.

[0055] S2. The reaction product stream from step S1 is fed into a distillation separation column. The product at the top of the distillation separation column is separated into a gas phase by a gas-liquid separator and the mixed gas exits the device. The liquid phase is returned to the moving bed as a circulating stream. The p-toluene / m-toluene mixture stream obtained from the bottom of the distillation separation column enters the simulated moving bed. S3. The simulated moving bed separates the p-ethylbenzene / m-ethylbenzene mixture stream into p-ethylbenzene stream and m-ethylbenzene stream. The p-ethylbenzene stream is collected directly, while the m-ethylbenzene stream is returned to the moving bed.

[0056] The adsorbent in the simulated moving bed was Cs-exchanged X-type zeolite, the adsorption temperature was 80℃, the adsorption pressure was 0.5 MPa, the mass flow rate ratio of the p-toluene / m-toluene mixture to the desorbent was 1:1, the mass flow rate ratio of the feed to the circulating flow was 1:0.8, and the desorbent was toluene. The X-type zeolite metal ion exchange of the adsorbent is carried out by column exchange, the ion exchange temperature is 80℃, the Cs ion concentration in the ion exchange solution is 0.06mol / L, and the ion exchange time is 6h.

[0057] In Example 4, the obtained p-toluene product had a purity of 98.9 wt%, a single-pass catalyst lifetime of 85 days in the alkylation reaction unit, a utilization rate of alkylation reagent of 96% of the theoretical value, and a p-toluene yield of 98%.

[0058] The calculation methods for each indicator in this application are as follows: Alkylation reagent utilization rate = (Molar amount of methyl ethyl phenyl in feed A) / (Molar amount of alkylation reagent in feed) × 100% p-Toluene / Ethylene Yield = (Molar amount of p-toluene / Ethylene in feedstock D) / (Molar amount of aromatic feedstock in feedstock) × 100% The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for producing high-purity p-toluene, characterized in that: Includes the following steps S1. The aromatic raw material and alkylating agent are mixed and then introduced into the alkylation reaction unit (1). Under the action of the alkylation-isomerization catalyst, the reaction product stream is obtained. The aromatic raw material is toluene or ethylbenzene; When the aromatic feedstock is toluene, the alkylating agent is at least one of ethanol, ethylene, or a mixture containing ethylene; when the aromatic feedstock is ethylbenzene, the alkylating agent is methanol. S2. Pass the reaction product stream from step S1 into the separation unit (2) to separate the p-toluene / m-toluene mixture stream and the circulating stream. S3. The p-toluene / m-toluene mixture obtained in step S2 is fed into the adsorption separation unit (3) to separate the p-toluene stream and the m-toluene stream.

2. The method for producing high-purity p-toluene according to claim 1, characterized in that: The circulating stream obtained from the separation unit (2) is returned to the alkylation reaction unit (1); the p-toluene and m-toluene streams are separated by the adsorption separation unit (3); the m-toluene stream is returned to the alkylation reaction unit (1) or the m-toluene stream is processed by the shape selective isomerization unit (4) to obtain a p-toluene / m-toluene circulating stream which is returned to the adsorption separation unit (3).

3. The method for producing high-purity p-toluene according to claim 2, characterized in that: When the m-toluene stream obtained by the adsorption separation unit (3) is returned to the alkylation reaction unit (1), the m-toluene stream is mixed with the circulating stream obtained in step S2 and then divided into two streams. One stream is used as a quench source, and the other stream is introduced into the alkylation reaction unit (1) to be mixed with aromatic raw materials and alkylation reagents and heated to the reaction temperature.

4. The method for producing high-purity p-toluene according to claim 1, characterized in that: In step S1, the molar ratio of aromatic feedstock to alkylating agent is 15:1 to 1:3; the mass hourly space velocity (HHSV) of the aromatic feedstock entering the alkylation reaction unit (1) is 0.5 h⁻¹. -1 ~10 h -1 ; The reaction conditions in the alkylation reaction unit (1) are: reaction temperature of 300 ℃~500 ℃ and reaction pressure of 0.1 MPa~4.0 MPa; the alkylation reaction unit (1) is any one of fixed bed, moving bed, fluidized bed or slurry bed.

5. The method for producing high-purity p-toluene according to claim 1, characterized in that: The alkylation reaction unit (1) is filled with an alkylation-isomerization catalyst; the preparation method of the alkylation-isomerization catalyst is: after the active component is mixed with the binder and shaped, it is then modified with oxide to obtain the alkylation-isomerization catalyst.

6. The method for producing high-purity p-toluene according to claim 5, characterized in that: The active component is at least one of ZSM-5 molecular sieve, ZSM-11 molecular sieve, or SAPO-11 molecular sieve; the oxide is at least one of magnesium oxide, silicon oxide, phosphorus oxide, or boron oxide; and the binder is at least one of silica sol, boehmite, alumina, or acid-treated clay.

7. The method for producing high-purity p-toluene according to claim 1, characterized in that: The separation unit (2) is a conventional separation facility; the separation unit (2) is a distillation separation tower; when the alkylating agent contains ethanol or methanol, the separation unit (2) also includes an oil-water separation tank; when the alkylating agent contains a mixture of gases containing ethylene, the separation unit (2) also includes a gas-liquid separation tank.

8. The method for producing high-purity p-toluene according to claim 1, characterized in that: The adsorption separation unit (3) is a simulated moving bed; the adsorption separation conditions in the adsorption separation unit (3) are: adsorption temperature 40 ℃~180 ℃, pressure 0.1 MPa~1.5 MPa, and the mass flow rate ratio of the p-toluene / m-toluene mixture to the desorbent is 1:(1~3); the mass flow rate ratio of the p-toluene / m-toluene mixture obtained in step S2 to the circulation volume is 1:(0.8~4); the desorbent is at least one of toluene, xylene or diethylbenzene.

9. The method for producing high-purity p-toluene according to claim 1, characterized in that: The adsorbent of the adsorption separation unit (3) is an X-type zeolite exchanged with any one of the metal ions of Li, K, Rb or Cs.

10. The method for producing high-purity p-toluene according to claim 2, characterized in that: The reaction conditions within the shape-selective isomerization unit (4) are as follows: reaction temperature of 200 ℃~400 ℃, reaction pressure of 0.3 MPa~2.0 MPa, and mass hourly space velocity (MHV) of the m-toluene-ethylbenzene stream of 0.5 h⁻¹. -1 ~10 h -1 The shape-selective isomerization unit (4) is a fixed bed; the shape-selective isomerization unit (4) is filled with a shape-selective isomerization catalyst; the shape-selective isomerization catalyst is prepared by mixing the active component with a binder and molding it, and then modifying it with an oxide to obtain the shape-selective isomerization catalyst; the active component is at least one of ZSM-5 molecular sieve, ZSM-11 molecular sieve, MOR molecular sieve or EU-1 molecular sieve; the oxide is at least one of magnesium oxide, silicon oxide, phosphorus oxide or boron oxide; the binder is at least one of silica sol, boehmite, alumina or clay treated with acid.

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