Catalyst for increasing yield of benzene and p-xylene through toluene disproportionation as well as preparation method and application of catalyst

Abstract

The invention relates to the technical field of catalysts, in particular to a catalyst for high yield of benzene and p-xylene through toluene disproportionation as well as a preparation method and application thereof, and the catalyst for high yield of benzene and p-xylene through toluene disproportionation comprises the following raw materials: a silicon source, an aluminum source, an alkali source, a first template agent, a second template agent, water, a seed crystal and an inorganic substance containing modified elements. According to the present invention, the modification element is introduced by using the hydrothermal method, the ZSM-5 molecular sieve (MFI type molecular sieve) and the ZSM-11 molecular sieve (MEL molecular sieve) are subjected to ball milling eutectic, and finally the modification is performed by using the silicon coating modification mode to obtain the catalyst, the catalyst for increasing the yield of benzene and p-xylene through toluene disproportionation is appropriate in pore volume, specific surface area and particle size and good in catalytic performance, has a good shape-selective catalytic effect on a product of a toluene disproportionation reaction, and can not only increase the yield of benzene, but also improve the selectivity of p-xylene in xylene when being used in the toluene disproportionation reaction.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a catalyst for the disproportionation of toluene to produce benzene and p-xylene, its preparation method, and its application. Background Technology

[0002] The toluene disproportionation unit is a key component of aromatic hydrocarbon complexes. Toluene disproportionation technology is currently the most mature and widely used technology for producing xylene and benzene. Its principle is based on the methyl transfer reaction between aromatic hydrocarbons, transferring a methyl group from one toluene molecule to another, thereby producing benzene and xylene. The core research focus of traditional toluene disproportionation catalysts is to suppress the demethylation reaction and maximize xylene selectivity, aiming to maximize xylene production. However, traditional toluene disproportionation and alkyl transfer technologies can only yield mixed xylenes with a para-xylene content of approximately 24%. The product structure of traditional toluene disproportionation technologies, primarily focused on xylene production, is not adapted to market demands, necessitating the development of novel catalysts to improve the benzene selectivity of toluene disproportionation technology.

[0003] For the toluene disproportionation reaction to produce benzene, the conversion rate and selectivity of the toluene disproportionation reaction are directly related to the catalyst pore structure and acid strength. Precisely optimizing the structure and composition of molecular sieve catalysts is of great importance for obtaining high-performance catalysts with high selectivity, high aromatic hydrocarbon processing capacity, high conversion rate, low hydrogen consumption, and high benzene purity.

[0004] ZSM-5 molecular sieve is an MFI type molecular sieve, belonging to a two-dimensional channel system. It includes two channel structures: one is a 10-membered ring straight pore with a pore size of 0.53 nm × 0.56 nm, and the other is a 10-membered ring bent pore with a bend angle of approximately 150 degrees. ° The pore size is 0.51 nm × 0.55 nm. Although the pore sizes of the two types of channels are similar, the diffusion characteristics of molecules differ significantly. The diffusion energy barriers of aromatic hydrocarbon molecules in the straight pores, from smallest to largest, are benzene, p-xylene, toluene, o-xylene, and m-xylene. Among them, the diffusion energy barriers of benzene and p-xylene are similar and much smaller than those of other molecules. Therefore, after the toluene disproportionation reaction is completed, they will preferentially diffuse out of the pores, thus demonstrating that the ZSM-5 molecular sieve straight pores have good selectivity for benzene and p-xylene.

[0005] ZSM-11 molecular sieve is a MEL molecular sieve, belonging to a two-dimensional pore system with 10-membered ring straight pores and a pore size of 0.53 nm × 0.54 nm. The diffusion barriers of the various isomers of toluene, in ascending order, are p-xylene, o-xylene, and m-xylene. MEL molecular sieves also exhibit good shape-selective catalysis of the products of toluene disproportionation reaction.

[0006] Chinese patent document CN115710154A discloses a process for producing benzene by toluene disproportionation. It includes heating toluene, a toluene disproportionation reaction to produce benzene, and benzene separation. The toluene disproportionation catalyst used in this process features high toluene conversion, high benzene selectivity, and high stability. The toluene conversion rate of this process is 9% to 26% higher than similar processes, and the benzene selectivity is 5% to 12% higher.

[0007] Chinese patent document CN115709096A discloses a highly active catalyst for the disproportionation of toluene to benzene. It is composed of a hydrogen-form eutectic molecular sieve, a binder, an active metal or metal oxide, and an additive. It features high toluene conversion, high benzene selectivity, and high stability, exhibiting overall performance superior to single-component ordinary molecular sieve catalysts and catalysts using a simple mixture of two molecular sieves. The hydrogen-form eutectic molecular sieve obtained by modifying the eutectic molecular sieve eliminates the toxicity to the catalyst compared to the original eutectic molecular sieve, thus improving the overall catalyst performance. The hydrogen-form eutectic molecular sieve disclosed in this invention is mainly one of ZSM-5 / ZSM-12, ZSM-5 / β, MOR / β, MOR / ZSM-12, ZSM-5 / MOR, or Y / MCM-22, achieving a toluene conversion of 52.8% to 55.3% and a benzene selectivity of 44.2% to 44.8%.

[0008] Chinese patent document CN117160521A discloses a toluene disproportionation catalyst, its preparation method, and its application. The catalyst comprises a composite modified alumina and a modified molecular sieve. The composite modified alumina contains alkali metal K and / or Cs and / or alkaline earth metal Mg and / or Ca, transition metals Co, Cr, Mn, and alumina. The modified molecular sieve contains at least one molecular sieve selected from ZSM-5, mordenite, and β-zeolite, and a modified metal (at least one selected from Pt, Re, and Mo). This catalyst, used in the toluene disproportionation reaction, exhibits advantages such as high benzene selectivity, with a toluene conversion rate of 51.2% to 56.8%, a benzene selectivity of 50.2% to 58.7%, and a xylene selectivity of 33.7% to 41.5%.

[0009] The zeolite molecular sieves used in the above catalysts, including MOR, Y, β, and MCM-22, all belong to the twelve-membered ring molecular sieve category. When improving toluene conversion, the molar ratio of benzene to xylene in the product is low, and the selectivity for p-xylene in the product is low. Additionally, C9... + The problem of high yield of heavy aromatics. Summary of the Invention

[0010] This invention provides a catalyst for the disproportionation of toluene to produce benzene and p-xylene, its preparation method, and its application. It overcomes the shortcomings of existing technologies, effectively addressing the low molar ratio of benzene to xylene in the products and the low selectivity for p-xylene in existing toluene disproportionation catalysts. Simultaneously, C9... + The problem of high yield of heavy aromatics.

[0011] One of the technical solutions of the present invention is achieved through the following measures: a catalyst for the disproportionation of toluene to produce benzene and p-xylene, wherein the raw materials include a silicon source, an aluminum source, an alkaline source, a first template agent, a second template agent, and water in a molar ratio of 1:(0.01 to 0.07):(0 to 0.4):(0.01 to 1.0):(0.01 to 1.0):(5 to 40), the raw materials also include seed crystals and inorganic substances containing modifying elements, wherein the amount of seed crystals added is 0.5% to 20% of the mass of the silicon source, and the amount of inorganic substances containing modifying elements added is 0.5% to 15% of the mass of the silicon source.

[0012] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions: The silicon source mentioned above is tetraethyl orthosilicate or macroporous silica gel.

[0013] The aluminum source mentioned above is aluminum isopropoxide or sodium aluminate.

[0014] The above-mentioned alkaline source is sodium hydroxide.

[0015] The aforementioned seed crystals are ZSM-5 and ZSM-11.

[0016] The first template agent is tetrapropylammonium hydroxide, and the second template agent is tetrabutylammonium hydroxide. The molar ratio of the first template agent to the second template agent is (1 to 2):1.

[0017] The modifying element in the aforementioned inorganic compounds containing modifying elements is one or more of P, Ni, Co, Mo, Ru, Cu, Mg, and Fe.

[0018] The catalyst for the disproportionation of toluene to produce benzene and p-xylene, as described above, was obtained by the following method: The first step is to mix and stir the required amounts of silicon source, aluminum source, alkali source, first template agent, second template agent, seed crystal and deionized water until uniform to obtain a mixed solution; The second step is to stir the mixed solution and then perform dynamic crystallization to obtain the molecular sieve precursor. The third step is to add the required amount of inorganic material containing modified elements to the molecular sieve precursor and mix them to obtain a mixed slurry, and then adjust the pH value of the mixed slurry. The fourth step involves ball milling the mixed slurry to crystallize it, followed by solid-liquid separation, filtration, washing, drying, and calcination to obtain the modified eutectic molecular sieve. The fifth step involves adding an aqueous solution of ammonium chloride to the modified eutectic molecular sieve and stirring thoroughly to obtain a mixture. The mixture is then filtered, washed until neutral, dried, and calcined to obtain a hydrogen-form molecular sieve. Step 6: Add silica-coated modifier and solvent to hydrogen-type molecular sieve, stir and perform chemical liquid phase deposition to obtain product. After rotary evaporation, drying and calcination, the product is obtained as a composite modified eutectic molecular sieve. Step 7: Add γ-type alumina and Tianqing powder to the ground composite modified eutectic molecular sieve, mix well, add dilute nitric acid, extrude into strips, and then dry and calcine to obtain a catalyst for toluene disproportionation to produce benzene and p-xylene.

[0019] In the second step above, the stirring time is 2 to 3 hours.

[0020] In the second step above, dynamic crystallization is carried out in a homogeneous reactor with a rotating oven. The rotation speed of the rotating oven is 10 r / min to 100 r / min. During crystallization, the crystallization temperature is 80℃ to 100℃ and the crystallization time is 20h to 80h.

[0021] In the third step above, the pH of the mixed slurry is adjusted to 10.5 to 12.

[0022] In the fourth step above, ball milling crystallization is carried out in a heated ball mill. During crystallization, the ball mill speed is 6500 r / min to 7500 r / min, the crystallization temperature is 150℃ to 170℃, and the crystallization time is 72h to 96h.

[0023] In the fifth step above, the mass ratio of the modified eutectic molecular sieve to the ammonium chloride aqueous solution is 1:(8 to 12), and the mass concentration of the ammonium chloride aqueous solution is 1 mol / L to 1.2 mol / L.

[0024] In the fifth step above, the stirring temperature is 80℃ to 90℃ and the stirring time is 2h to 2.5h.

[0025] In step six above, the solvent is cyclohexane, and the silicone modifier is one or more of tetraethyl orthosilicate, dimethyl silicone oil, silane, and silicone resin.

[0026] In the sixth step above, the mass ratio of hydrogen molecular sieve to silica-coated modifier is 10:(1 to 2), and the volume ratio of solvent to silica-coated modifier is (4 to 6):1.

[0027] In the sixth step above, the deposition time for chemical liquid phase deposition is 6 to 72 hours.

[0028] In the seventh step above, the mass ratio of the composite modified eutectic molecular sieve to γ-alumina is (1 to 9): (1 to 9), and the amount of Tianqing powder added is 2% to 3% of the mass of the composite modified eutectic molecular sieve.

[0029] In step seven above, the mass concentration of dilute nitric acid is 2% to 4%.

[0030] In steps four, five, six and seven above, the drying temperature is 100℃ to 150℃ and the drying time is 2.5h to 3.5h; the calcination temperature is 500℃ to 600℃ and the calcination time is 4h to 8h.

[0031] The second technical solution of the present invention is achieved through the following measures: a method for preparing a catalyst for the disproportionation of toluene to produce benzene and p-xylene, which is carried out according to the following method: The first step is to mix and stir the required amounts of silicon source, aluminum source, alkali source, first template agent, second template agent, seed crystal and deionized water until uniform to obtain a mixed solution; The second step is to stir the mixed solution and then perform dynamic crystallization to obtain the molecular sieve precursor. The third step is to add the required amount of inorganic material containing modified elements to the molecular sieve precursor and mix them to obtain a mixed slurry, and then adjust the pH value of the mixed slurry. The fourth step involves ball milling the mixed slurry to crystallize it, followed by solid-liquid separation, filtration, washing, drying, and calcination to obtain the modified eutectic molecular sieve. The fifth step involves adding an aqueous solution of ammonium chloride to the modified eutectic molecular sieve and stirring thoroughly to obtain a mixture. The mixture is then filtered, washed until neutral, dried, and calcined to obtain a hydrogen-form molecular sieve. Step 6: Add silica-coated modifier and solvent to hydrogen-type molecular sieve, stir and perform chemical liquid phase deposition to obtain product. After rotary evaporation, drying and calcination, the product is obtained as a composite modified eutectic molecular sieve. Step 7: Add γ-type alumina and Tianqing powder to the ground composite modified eutectic molecular sieve, mix well, add dilute nitric acid, extrude into strips, and then dry and calcine to obtain a catalyst for toluene disproportionation to produce benzene and p-xylene.

[0032] The third technical solution of the present invention is achieved through the following measures: the application of a catalyst for the disproportionation of toluene to produce benzene and p-xylene in the toluene disproportionation reaction.

[0033] This invention provides a catalyst for the toluene disproportionation reaction that produces more benzene and p-xylene. The catalyst is obtained by introducing modifying elements via a hydrothermal method, followed by ball milling and co-crystallization of ZSM-5 molecular sieves (MFI type) and ZSM-11 molecular sieves (MEL type). Finally, it is modified using a silica-coating method. This catalyst exhibits suitable pore volume, specific surface area, and particle size, and demonstrates good catalytic performance. It shows good shape-selective catalysis for the products of the toluene disproportionation reaction. Using it in the toluene disproportionation reaction not only increases the production of benzene but also improves the selectivity for p-xylene in xylene. This effectively solves the problem of existing toluene-to-benzene catalysts, which use ZSM-5 molecular sieves co-crystallized with larger pore size (twelve-membered ring) molecular sieves, resulting in low molar ratios of benzene to xylene and low selectivity for p-xylene while improving toluene conversion. Furthermore, the C9... + The problem of high yield of heavy aromatics. Attached Figure Description

[0034] Figure 1 The image shows the XRD pattern of the toluene disproportionation catalyst prepared in Example 21 of this invention, which produces benzene and p-xylene.

[0035] Figure 2 This is a SEM image of the toluene disproportionation catalyst prepared in Example 21 of the present invention, which produces benzene and p-xylene. Detailed Implementation

[0036] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemicals mentioned in this invention are well-known and commonly used chemical reagents and chemicals in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are aqueous solutions with water as the solvent, for example, hydrochloric acid solution is an aqueous solution of hydrochloric acid; room temperature in this invention generally refers to a temperature between 15°C and 25°C, generally defined as 25°C.

[0037] The present invention will be further described below with reference to embodiments: Example 1: The catalyst for the disproportionation of toluene to produce benzene and p-xylene comprises a silicon source (calculated as SiO2), an aluminum source (calculated as Al2O3), an alkali source (calculated as Na2O), and a first template agent (calculated as N(C3H7)4) in a molar ratio of 1:(0.01 to 0.07):(0 to 0.4):(0.01 to 1.0):(0.01 to 1.0):(5 to 40). + (Calculation), second template agent (N(C4H9)4) +The raw materials include water and seed crystals and inorganic substances containing modified elements. The amount of seed crystals added is 0.5% to 20% of the mass of silicon source (SiO2), and the amount of inorganic substances containing modified elements added is 0.5% to 15% of the mass of silicon source (SiO2).

[0038] Example 2: As an optimization of the above example, the silicon source is tetraethyl orthosilicate or macroporous silica gel.

[0039] Example 3: As an optimization of the above examples, the aluminum source is aluminum isopropoxide or sodium aluminate.

[0040] Example 4: As an optimization of the above examples, the alkali source is sodium hydroxide.

[0041] Example 5: As an optimization of the above examples, the seed crystals are ZSM-5 seed crystals and ZSM-11 seed crystals.

[0042] Example 6: As an optimization of the above example, the first template agent is tetrapropylammonium hydroxide, the second template agent is tetrabutylammonium hydroxide, and the molar ratio of the first template agent to the second template agent is (1 to 2):1.

[0043] Example 7: As an optimization of the above examples, the modifying element in the inorganic compound containing the modifying element is one or more of P, Ni, Co, Mo, Ru, Cu, Mg and Fe.

[0044] Example 8: As an optimization of the above examples, a catalyst for the disproportionation of toluene to produce benzene and p-xylene was obtained by the following method: The first step is to mix and stir the required amounts of silicon source, aluminum source, alkali source, first template agent, second template agent, seed crystal and deionized water until uniform to obtain a mixed solution; The second step is to stir the mixed solution and then perform dynamic crystallization to obtain the molecular sieve precursor. The third step is to add the required amount of inorganic material containing modified elements to the molecular sieve precursor and mix them to obtain a mixed slurry, and then adjust the pH value of the mixed slurry. The fourth step involves ball milling the mixed slurry to crystallize it, followed by solid-liquid separation, filtration, washing, drying, and calcination to obtain the modified eutectic molecular sieve. The fifth step involves adding an aqueous solution of ammonium chloride to the modified eutectic molecular sieve and stirring thoroughly to obtain a mixture. The mixture is then filtered, washed until neutral, dried, and calcined to obtain a hydrogen-form molecular sieve. Step 6: Add silica-coated modifier and solvent to hydrogen-type molecular sieve, stir and perform chemical liquid phase deposition to obtain product. After rotary evaporation, drying and calcination, the product is obtained as a composite modified eutectic molecular sieve. Step 7: Add γ-type alumina and Tianqing powder to the ground composite modified eutectic molecular sieve, mix well, add dilute nitric acid, extrude into strips, and then dry and calcine to obtain a catalyst for toluene disproportionation to produce benzene and p-xylene.

[0045] Example 9: As an optimization of the above example, in the second step, the stirring time is 2 to 3 hours.

[0046] Example 10: As an optimization of the above example, in the second step, dynamic crystallization is carried out in a homogeneous reactor with a rotating oven. The rotation speed of the rotating oven is 10 r / min to 100 r / min. During crystallization, the crystallization temperature is 80°C to 100°C and the crystallization time is 20 h to 80 h.

[0047] Example 11: As an optimization of the above example, in the third step, the pH value of the mixed slurry is adjusted to 10.5 to 12.

[0048] Example 12: As an optimization of the above example, in the fourth step, the ball milling crystallization is carried out in a heated ball mill. During crystallization, the ball mill speed is 6500 r / min to 7500 r / min, the crystallization temperature is 150°C to 170°C, and the crystallization time is 72 h to 96 h.

[0049] Example 13: As an optimization of the above example, in the fifth step, the mass ratio of the modified eutectic molecular sieve to the ammonium chloride aqueous solution is 1:(8 to 12), and the mass concentration of the ammonium chloride aqueous solution is 1 mol / L to 1.2 mol / L.

[0050] Example 14: As an optimization of the above example, in the fifth step, the stirring temperature is 80°C to 90°C and the stirring time is 2h to 2.5h.

[0051] Example 15: As an optimization of the above example, in step 6, the solvent is cyclohexane, and the silicone modifier is one or more of tetraethyl orthosilicate, dimethyl silicone oil, silane, and silicone resin.

[0052] Example 16: As an optimization of the above example, in the sixth step, the mass ratio of hydrogen molecular sieve to silica-coated modifier is 10:(1 to 2), and the volume ratio of solvent to silica-coated modifier is (4 to 6):1.

[0053] Example 17: As an optimization of the above example, in step 6, the deposition time during chemical liquid phase deposition is 6h to 72h.

[0054] Example 18: As an optimization of the above example, in step 7, the mass ratio of composite modified eutectic molecular sieve to γ-alumina is (1 to 9): (1 to 9), and the amount of Tianqing powder added is 2% to 3% of the mass of composite modified eutectic molecular sieve.

[0055] Example 19: As an optimization of the above example, in step 7, the mass concentration of dilute nitric acid is 2% to 4%.

[0056] Example 20: As an optimization of the above example, in steps four, five, six and seven, the drying temperature is 100°C to 150°C and the drying time is 2.5h to 3.5h; the calcination temperature is 500°C to 600°C and the calcination time is 4h to 8h.

[0057] Compared with the prior art, the beneficial effects of the present invention are as follows: First, in the synthesis process of the catalyst for toluene disproportionation to produce benzene and p-xylene in this invention, the introducing method of the modifying element (inorganic material containing the modifying element) is a hydrothermal method. The inorganic material containing the modifying element is mixed with silicon and aluminum sources in a certain proportion, and under suitable pH conditions, the precipitation process of metal (non-metal) ions with silicon and aluminum sources and the crystallization of silica-alumina gel can be synchronized during the hydrothermal synthesis process. This ensures that the size of the metal (non-metal) salt hydrolysis and condensation products is small enough to enter the zeolite channels and combine with the molecular sieve, thereby modifying the acidity of the inner surface, the acidity of the pore opening, and the pore size of the molecular sieve channels, and improving the toluene conversion rate. At the same time, the metal (non-metal) ions are uniformly dispersed, eliminating the agglomeration of metal (non-metal) compounds. Secondly, in this invention, a ball milling crystallization method is used to co-crystallize ZSM-11 molecular sieve and ZSM-5 molecular sieve. The impact and shearing forces of the balls make it easier for ZSM-11 molecular sieve nanocrystals to enter the pores of ZSM-5 molecular sieve. At the same time, the surface of the molecular sieve is prone to forming new "growth points" due to the high-speed impact of the balls, thereby avoiding the independent growth of ZSM-11 molecular sieve and ZSM-5 molecular sieve. Third, in this invention, hydrogen-type molecular sieves are modified by silicon coating (silica modification) to obtain composite modified eutectic molecular sieves. This does not change the acid properties within the pores of the composite modified eutectic molecular sieves, and the acidity of the outer surface of the obtained composite modified eutectic molecular sieves is passivated, inhibiting the further isomerization of p-xylene to m-xylene and o-xylene. At the same time, the pore openings of the composite modified eutectic molecular sieves shrink, restricting the diffusion of m-xylene and o-xylene, while p-xylene diffuses preferentially. Therefore, by modifying the outer surface and pore diameter of the modified eutectic molecular sieves by silicon coating, this invention further exhibits better shape-selective catalytic activity for the products of toluene disproportionation reaction. Fourth, the catalyst for toluene disproportionation to produce benzene and p-xylene prepared by the preparation method provided by this invention has a pore volume of 0.22 cm³. 3 / g to 0.25cm 3 / g, specific surface area is 240m²2 / g to 350m 2 / g, with a particle size of 4μm to 10μm. When the catalyst of this invention, which produces benzene and p-xylene in the toluene disproportionation reaction, is applied to the toluene disproportionation reaction, the toluene conversion rate is high, ranging from 47.14% to 53.66% (mass percentage), the selectivity of benzene in the product is from 47.98% to 54.49% (mass percentage), the molar ratio of benzene to xylene in the product is from 1.37 to 1.83, and the selectivity of p-xylene in the product for xylene is from 37.72% to 60.23% (mass percentage).

[0058] Example 21: This catalyst for the disproportionation of toluene to produce benzene and p-xylene uses macroporous silica gel (80-100 mesh) as the silicon source, sodium aluminate (41% by mass) as the aluminum source, sodium hydroxide as the alkali source, tetrapropylammonium hydroxide (25% by mass) as the first template agent, and tetrabutylammonium hydroxide (25% by mass) as the second template agent. The raw materials are: silicon source (calculated as SiO2), aluminum source (calculated as Al2O3), alkali source (calculated as Na2O), and first template agent (calculated as N(C3H7)4). + (Calculation), second template agent (N(C4H9)4) + The molar ratio of silicon source (calculated as SiO2) to water is 1:0.033:0.04:0.1:0.05:40. The raw materials also include seed crystals and inorganic substances containing modifying elements. The seed crystals are ZSM-5 seed crystals and ZSM-11 seed crystals, with the addition amount of ZSM-5 seed crystals and ZSM-11 seed crystals being 5% of the mass of silicon source (calculated as SiO2). The inorganic substances containing modifying elements are ammonium phosphate, magnesium sulfate, and ferrous sulfate. The addition amount of ammonium phosphate (calculated as P) is 5% of the mass of silicon source (calculated as SiO2), the addition amount of magnesium sulfate (calculated as Mg) is 8% of the mass of silicon source (calculated as SiO2), and the addition amount of ferrous sulfate (calculated as Fe) is 2% of the mass of silicon source (calculated as SiO2). The raw materials are obtained by the following method: The first step is to mix the required amounts of silicon source, aluminum source, alkali source, first template agent, second template agent, seed crystal and deionized water thoroughly to obtain a mixed solution; The second step involves placing the mixed solution in a homogeneous reactor equipped with a rotary oven, stirring it at room temperature for 2 hours, and then dynamically crystallizing it at 100°C and a rotary oven speed of 50 r / min for 24 hours to obtain the molecular sieve precursor. The third step is to add the required amount of inorganic substances containing modifying elements (ammonium phosphate, magnesium sulfate and ferrous sulfate) to the molecular sieve precursor and mix them to obtain a mixed slurry. The pH value of the mixed slurry is adjusted to 11. The fourth step involves ball milling the mixed slurry at 170°C and 7000 r / min for 72 h. After the reaction is complete, the reaction vessel is rapidly cooled, and the product is separated into solid and liquid components. The obtained solid product is then filtered, washed, dried at 120°C for 3 h, and calcined at 550°C for 6 h to obtain the modified eutectic molecular sieve. Fifth step: Add ammonium chloride aqueous solution with a mass concentration of 1 mol / L to the modified eutectic molecular sieve, stir at 85℃ for 2 hours to obtain a mixture, filter and wash the mixture until neutral, dry at 120℃ for 3 hours, and then calcine at 550℃ for 6 hours to obtain hydrogen-form molecular sieve, wherein the mass ratio of modified eutectic molecular sieve to ammonium chloride aqueous solution is 1:10; Step 6: Add silica-coating modifier (tetraethyl orthosilicate) and solvent (cyclohexane) to the hydrogen-form molecular sieve, stir and perform chemical liquid phase deposition for 24 hours to obtain the product. Evaporate the solvent in a water bath at 90°C, dry at 120°C for 3 hours, and then calcine at 550°C for 6 hours. Repeat step 6 to perform secondary silica-coating modification to obtain a composite modified eutectic molecular sieve. The mass ratio of hydrogen-form molecular sieve to silica-coating modifier (tetraethyl orthosilicate, calculated as SiO2) is 10:1.6, and the volume ratio of solvent (cyclohexane) to silica-coating modifier (tetraethyl orthosilicate) is 5:1. Step 7: Add γ-alumina and Tianqing powder to the ground composite modified eutectic molecular sieve and mix well. Then add 4% dilute nitric acid and extrude into strips. Dry at 120℃ for 3 hours and then calcine at 550℃ for 6 hours to obtain a catalyst for toluene disproportionation to produce benzene and p-xylene. The mass ratio of composite modified eutectic molecular sieve to γ-alumina is 8:2, and the amount of Tianqing powder added is 2.5% of the mass of composite modified eutectic molecular sieve.

[0059] Example 22: The catalyst for the disproportionation of toluene to produce benzene and p-xylene differs from that in Example 21 of this invention in that the raw materials are silicon source (calculated as SiO2), aluminum source (calculated as Al2O3), alkali source (calculated as Na2O), and the first template agent (calculated as N(C3H7)4). + (Calculation), second template agent (N(C4H9)4) + The molar ratio of (calculated) to water is 1:0.033:0.04:0.1:0.066:40; The inorganic substances containing the modifying elements are ammonium phosphate, magnesium sulfate, and ferrous sulfate. The amount of ammonium phosphate (calculated as P) added is 5% of the mass of the silicon source (calculated as SiO2), the amount of magnesium sulfate (calculated as Mg) added is 10% of the mass of the silicon source (calculated as SiO2), and the amount of ferrous sulfate (calculated as Fe) added is 2% of the mass of the silicon source (calculated as SiO2). In step six, the mass ratio of hydrogen-type molecular sieve to silica-coated modifier (tetraethyl orthosilicate, calculated as SiO2) is 10:1.4, and the volume ratio of solvent (cyclohexane) to silica-coated modifier (tetraethyl orthosilicate) is 5:1; the remaining steps remain unchanged.

[0060] Example 23: The catalyst for the disproportionation of toluene to produce benzene and p-xylene differs from that in Example 21 of this invention in that the silicon source is tetraethyl orthosilicate and the aluminum source is aluminum isopropoxide; the raw materials are silicon source (calculated as SiO2), aluminum source (calculated as Al2O3), alkali source (calculated as Na2O), and the first template agent (calculated as N(C3H7)4). + (Calculation), second template agent (N(C4H9)4) + The molar ratio of (calculated) to water is 1:0.033:0.04:0.1:0.05:40; The seed crystals are ZSM-5 and ZSM-11, and the addition amount of ZSM-5 and ZSM-11 seed crystals is 8% of the mass of the silicon source (based on SiO2). The inorganic substances containing the modifying elements are ammonium phosphate, cobalt nitrate, and ferrous sulfate. The amount of ammonium phosphate (calculated as P) added is 10% of the mass of the silicon source (calculated as SiO2), the amount of cobalt nitrate (calculated as Co) added is 2% of the mass of the silicon source (calculated as SiO2), and the amount of ferrous sulfate (calculated as Fe) added is 1% of the mass of the silicon source (calculated as SiO2). In step six, the mass ratio of hydrogen-type molecular sieve to silica-coated modifier (dimethyl silicone oil, calculated as SiO2) is 10:1.8, and the volume ratio of solvent (cyclohexane) to silica-coated modifier (dimethyl silicone oil) is 5:1; the remaining steps remain unchanged.

[0061] Example 24: The catalyst for the disproportionation of toluene to produce benzene and p-xylene differs from that in Example 21 of this invention in that the silicon source is macroporous silica gel (80 to 100 mesh), and the aluminum source is aluminum isopropoxide; the raw materials are silicon source (calculated as SiO2), aluminum source (calculated as Al2O3), alkali source (calculated as Na2O), and the first template agent (calculated as N(C3H7)4). + (Calculation), second template agent (N(C4H9)4) + The molar ratio of (calculated) to water is 1:0.0165:0.04:0.1:0.05:40; The seed crystals are ZSM-5 and ZSM-11, and the addition amount of ZSM-5 and ZSM-11 seed crystals is 5% of the mass of the silicon source (based on SiO2); The inorganic substances containing the modifying elements are ammonium phosphate, magnesium sulfate, and ferrous sulfate. The amount of ammonium phosphate (calculated as P) added is 5% of the mass of the silicon source (calculated as SiO2), the amount of magnesium sulfate (calculated as Mg) added is 4% of the mass of the silicon source (calculated as SiO2), and the amount of ferrous sulfate (calculated as Fe) added is 1.5% of the mass of the silicon source (calculated as SiO2). In step six, the mass ratio of hydrogen-type molecular sieve to silica-coated modifier (tetraethyl orthosilicate, calculated as SiO2) is 10:1.5, and the volume ratio of solvent (cyclohexane) to silica-coated modifier (tetraethyl orthosilicate) is 5:1; the remaining steps remain unchanged.

[0062] Example 25: The catalyst for the disproportionation of toluene to produce benzene and p-xylene differs from that in Example 21 of this invention in that the silicon source is tetraethyl orthosilicate and the aluminum source is sodium aluminate; the raw materials are silicon source (calculated as SiO2), aluminum source (calculated as Al2O3), alkali source (calculated as Na2O), and the first template agent (calculated as N(C3H7)4). + (Calculation), second template agent (N(C4H9)4) + The molar ratio of (calculated) to water is 1:0.0165:0.04:0.1:0.05:40; The seed crystals are ZSM-5 and ZSM-11, and the addition amount of ZSM-5 and ZSM-11 seed crystals is 10% of the mass of silicon source (based on SiO2). The inorganic substances containing the modifying elements are ammonium phosphate, nickel nitrate, and ferrous sulfate. The amount of ammonium phosphate (calculated as P) added is 6% of the mass of the silicon source (calculated as SiO2), the amount of nickel nitrate (calculated as Ni) added is 5% of the mass of the silicon source (calculated as SiO2), and the amount of ferrous sulfate (calculated as Fe) added is 1% of the mass of the silicon source (calculated as SiO2). In step six, the mass ratio of hydrogen-type molecular sieve to silica-coated modifier (dimethyl silicone oil, calculated as SiO2) is 10:2, and the volume ratio of solvent (cyclohexane) to silica-coated modifier (dimethyl silicone oil) is 5:1; the remaining steps remain unchanged.

[0063] Example 26: The catalyst for the disproportionation of toluene to produce benzene and p-xylene differs from that in Example 21 of this invention in that the silicon source is tetraethyl orthosilicate and the aluminum source is aluminum isopropoxide; the raw materials are silicon source (calculated as SiO2), aluminum source (calculated as Al2O3), alkali source (calculated as Na2O), and the first template agent (calculated as N(C3H7)4). + (Calculation), second template agent (N(C4H9)4) + The molar ratio of (calculated) to water is 1:0.0165:0.04:0.1:0.066:40; The seed crystals are ZSM-5 and ZSM-11, and the addition amount of ZSM-5 and ZSM-11 seed crystals is 5% of the mass of the silicon source (based on SiO2); The inorganic substances containing the modifying elements are ammonium phosphate, cobalt nitrate, and ferrous sulfate. The amount of ammonium phosphate (calculated as P) added is 7% of the mass of the silicon source (calculated as SiO2), the amount of cobalt nitrate (calculated as Co) added is 2% of the mass of the silicon source (calculated as SiO2), and the amount of ferrous sulfate (calculated as Fe) added is 2% of the mass of the silicon source (calculated as SiO2). In step six, the mass ratio of hydrogen-type molecular sieve to silica-coated modifier (dimethyl silicone oil, calculated as SiO2) is 10:1.8, and the volume ratio of solvent (cyclohexane) to silica-coated modifier (dimethyl silicone oil) is 5:1; the remaining steps remain unchanged.

[0064] Comparative Example 1: This eutectic molecular sieve catalyst uses macroporous silica gel (80-100 mesh) as the silicon source, sodium aluminate (41% by mass) as the aluminum source, sodium hydroxide as the alkali source, tetrapropylammonium hydroxide (25% by mass) as the first template agent, and tetrabutylammonium hydroxide (25% by mass) as the second template agent. The raw materials are: silicon source (calculated as SiO2), aluminum source (calculated as Al2O3), alkali source (calculated as Na2O), and first template agent (calculated as N(C3H7)4). + (Calculation), second template agent (N(C4H9)4) + The molar ratio of silicon source (SiO2) to water is 1:0.033:0.04:0.1:0.05:40. The raw materials also include seed crystals, namely ZSM-5 seed crystals and ZSM-11 seed crystals. The addition amount of ZSM-5 seed crystals and ZSM-11 seed crystals is 5% of the mass of silicon source (SiO2), and they are obtained by the following method: S1. Mix the required amounts of silicon source, aluminum source, alkali source, first template agent, second template agent, seed crystal and deionized water thoroughly to obtain a mixed solution; S2, the mixed solution was placed in a homogeneous reactor with a rotary oven and stirred at room temperature for 2 hours. Then, it was dynamically crystallized at 100℃ and a rotary oven speed of 50 r / min for 24 hours to obtain the molecular sieve precursor. S3, the molecular sieve precursor was ball-milled and crystallized in a ball mill at 170℃ and 7000 r / min for 72 h. After the reaction was completed, the reaction vessel was rapidly cooled, the product was separated into solid and liquid, and the obtained solid product was filtered, washed, dried at 120℃ for 3 h, and then calcined at 550℃ for 6 h to obtain the modified eutectic molecular sieve. S4. Add a 1 mol / L ammonium chloride aqueous solution to the modified eutectic molecular sieve, stir at 85°C for 2 h to obtain a mixture, filter and wash the mixture until neutral, dry at 120°C for 3 h, and then calcine at 550°C for 6 h to obtain a hydrogen-form molecular sieve. The mass ratio of the modified eutectic molecular sieve to the ammonium chloride aqueous solution is 1:10. S5. After mixing γ-alumina and Tianqing powder with the ground hydrogen-type molecular sieve, 4% dilute nitric acid is added and extruded into strips. The strips are dried at 120°C for 3 hours and then calcined at 550°C for 6 hours to obtain a eutectic molecular sieve catalyst. The mass ratio of hydrogen-type molecular sieve to γ-alumina is 8:2, and the amount of Tianqing powder added is 2.5% of the mass of hydrogen-type eutectic molecular sieve.

[0065] Comparative Example 2: The ZSM-11 molecular sieve catalyst uses macroporous silica gel (80-100 mesh) as the silicon source, sodium aluminate (41% by mass) as the aluminum source, sodium hydroxide as the alkali source, and tetrabutylammonium hydroxide (25% by mass) as the template agent. The raw materials are: silicon source (calculated as SiO2), aluminum source (calculated as Al2O3), alkali source (calculated as Na2O), and template agent (calculated as N(C4H9)4). + The molar ratio of silicon source (SiO2) to water is 1:0.033:0.02:0.6:40. The raw materials also include seed crystals, specifically ZSM-11 seed crystals. The amount of ZSM-11 seed crystals added is 5% of the mass of the silicon source (SiO2), obtained according to the following method: S1. Mix the required amounts of silicon source, aluminum source, alkali source, template agent, seed crystal and deionized water thoroughly to obtain a mixed solution; S2, the mixed solution was placed in a homogeneous reactor with a rotary oven, and dynamically crystallized at 100℃ for 24h, and then dynamically crystallized at 170℃ for 72h. The rotation speed of the rotary oven was 80r / min. After the reaction was completed, the product was separated into solid and liquid, and the obtained solid product was filtered, washed, dried at 120℃ for 3h, and then calcined at 550℃ for 6h to obtain ZSM-11 molecular sieve. S3. After adding γ-alumina and Tianqing powder to the ground ZSM-11 molecular sieve and mixing well, 4% dilute nitric acid is added and extruded into strips. The strips are dried at 120℃ for 3 hours and then calcined at 550℃ for 6 hours to obtain the ZSM-11 molecular sieve catalyst. The mass ratio of ZSM-11 molecular sieve to γ-alumina is 8:2, and the amount of Tianqing powder added is 2.5% of the mass of ZSM-11 molecular sieve.

[0066] Comparative Example 3: The ZSM-5 molecular sieve catalyst uses macroporous silica gel (80-100 mesh) as the silicon source, sodium aluminate (41% by mass) as the aluminum source, sodium hydroxide as the alkali source, and tetrapropylammonium hydroxide (25% by mass) as the template agent. The raw materials are: silicon source (calculated as SiO2), aluminum source (calculated as Al2O3), alkali source (calculated as Na2O), and template agent (calculated as N(C3H7)4). + The molar ratio of silicon source (SiO2) to water is 1:0.033:0.02:0.6:40. The raw materials also include seed crystals, specifically ZSM-5 seed crystals, which are added at 5% of the mass of the silicon source (SiO2). The raw materials are obtained as follows: S1. Mix the required amounts of silicon source, aluminum source, alkali source, template agent, seed crystal and deionized water thoroughly to obtain a mixed solution; S2, the mixed solution was placed in a homogeneous reactor with a rotary oven, and dynamically crystallized at 100℃ for 24h, and then dynamically crystallized at 170℃ for 72h. The rotation speed of the rotary oven was 80r / min. After the reaction was completed, the product was separated into solid and liquid, and the obtained solid product was filtered, washed, dried at 120℃ for 3h, and then calcined at 550℃ for 6h to obtain ZSM-11 molecular sieve. S3. After adding γ-alumina and Tianqing powder to the ground ZSM-5 molecular sieve and mixing them evenly, 4% dilute nitric acid was added and extruded into strips. The strips were dried at 120℃ for 3 hours and then calcined at 550℃ for 6 hours to obtain the ZSM-5 molecular sieve catalyst. The mass ratio of ZSM-5 molecular sieve to γ-alumina was 8:2, and the amount of Tianqing powder added was 2.5% of the mass of ZSM-5 molecular sieve.

[0067] Experimental Example 1: The basic performance of the catalyst for the disproportionation of toluene to produce benzene and p-xylene in this invention was investigated.

[0068] Experimental Methods: The performance of the toluene disproportionation catalysts for producing benzene and p-xylene prepared in Examples 21 to 26 of this invention was tested using a Micromeritics ASAP2460 multifunctional adsorption analyzer (N2 adsorption-desorption method). Performance parameters included specific surface area, pore size, type of eutectic molecular sieve in the catalyst, and ZSM-5 content in the catalyst. Simultaneously, the toluene disproportionation catalyst for producing benzene and p-xylene prepared in Example 21 of this invention was analyzed by XRD using a Bruker AXS GmbH polycrystalline / D8 Advance X-ray diffractometer. The morphology of the toluene disproportionation catalyst for producing benzene and p-xylene prepared in Example 21 of this invention was analyzed using a Hitachi SU8010 SEM instrument.

[0069] Experimental Results: The basic properties of the toluene disproportionation catalyst for producing benzene and p-xylene of the present invention are shown in Table 1. As can be seen from Table 1, the pore volume of the toluene disproportionation catalysts for producing benzene and p-xylene prepared in Examples 21 to 26 of the present invention is less than 0.20 cm³. 3 / g to 0.25cm 3 Between / g, with a specific surface area of ​​240m² 2 / g to 320m 2 The particle size is between 4 μm and 10 μm, with suitable pore volume, specific surface area, and particle size. The XRD pattern of the toluene disproportionation catalyst prepared in Example 21 of this invention, which produces benzene and p-xylene, is shown below. Figure 1 As shown, the SEM image of the toluene disproportionation catalyst prepared in Example 21 of this invention, which produces benzene and p-xylene, is as follows. Figure 2 As shown, by Figures 1 to 2 It is known that the catalyst for the disproportionation of toluene to produce benzene and p-xylene in this invention is a ZSM-5 / ZSM-11 co-crystallized molecular sieve catalyst with a particle size between 4 μm and 10 μm.

[0070] Experimental Example 2: The application of the catalyst for the disproportionation of toluene to produce benzene and p-xylene according to the present invention was investigated.

[0071] Experimental Method: The toluene disproportionation catalysts for producing benzene and p-xylene prepared in Examples 21 to 26 of this invention were respectively loaded into 100 mL fixed reactors, with a catalyst loading of 80 mL. Toluene was used as the raw material, and the toluene disproportionation reaction was carried out under the action of the catalysts of this invention. The reaction conditions were: reaction temperature 460℃ and 480℃, reaction pressure 2.0 MPa, and toluene space velocity 2.0 h⁻¹. -1 The molar ratio of hydrogen to toluene was 2.2. The reaction products of the toluene disproportionation reaction were quantitatively analyzed by gas chromatography.

[0072] Experimental Results: The reaction products of the toluene disproportionation reaction are shown in Table 2. The PX / X selectivity represents the selectivity of p-xylene in xylene, and the benzene selectivity is the ratio of benzene produced to converted toluene in the reaction products. As shown in Table 2, compared to the data from Comparative Examples 1 to 3, the catalyst of this invention, which produces more benzene and p-xylene in the toluene disproportionation reaction, exhibits improved benzene selectivity and p-xylene / xylene selectivity, indicating that the catalyst of this invention has excellent catalytic performance.

[0073] In summary, the catalyst for toluene disproportionation yielding both benzene and p-xylene of this invention is obtained by introducing modifying elements via a hydrothermal method, followed by ball milling co-crystallization of ZSM-5 molecular sieves (MFI type molecular sieve) and ZSM-11 molecular sieves (MEL molecular sieve), and finally modification using a silica-coating method. This catalyst exhibits suitable pore volume, specific surface area, and particle size, along with good catalytic performance. It demonstrates good shape-selective catalysis for the products of toluene disproportionation. Using it in the toluene disproportionation reaction not only increases benzene production but also improves the selectivity for p-xylene in xylene. This effectively solves the problem of existing toluene-to-benzene catalysts, which use ZSM-5 molecular sieves co-crystallized with larger pore size (twelve-membered ring) molecular sieves, resulting in low molar ratios of benzene to xylene and low selectivity for p-xylene while improving toluene conversion. Furthermore, the C9... + The problem of high yield of heavy aromatics.

[0074] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A catalyst for the disproportionation of toluene to produce benzene and p-xylene, characterized in that... The raw materials include a silicon source, an aluminum source, an alkali source, a first template agent, a second template agent, and water in a molar ratio of 1:0.01 to 0.07:0 to 0.4:0.01 to 1.0:0.01 to 1.0:5 to 40. The raw materials also include seed crystals and inorganic substances containing modifying elements. The amount of seed crystals added is 0.5% to 20% of the mass of the silicon source, and the amount of inorganic substances containing modifying elements added is 0.5% to 15% of the mass of the silicon source.

2. The catalyst for toluene disproportionation to produce benzene and p-xylene according to claim 1, characterized in that... The silicon source is tetraethyl orthosilicate or macroporous silica gel; and / or the aluminum source is aluminum isopropoxide or sodium aluminate; and / or the alkali source is sodium hydroxide.

3. The catalyst for toluene disproportionation to produce benzene and p-xylene according to claim 1 or 2, characterized in that... The seed crystals are ZSM-5 and ZSM-11; or / and, the first template agent is tetrapropylammonium hydroxide, the second template agent is tetrabutylammonium hydroxide, and the molar ratio of the first template agent to the second template agent is 1 to 2:1; or / and, the modifying element in the inorganic compound containing the modifying element is one or more of P, Ni, Co, Mo, Ru, Cu, Mg and Fe.

4. The catalyst for toluene disproportionation to produce benzene and p-xylene according to claim 1, 2, or 3, characterized in that... Obtained using the following method: The first step is to mix and stir the required amounts of silicon source, aluminum source, alkali source, first template agent, second template agent, seed crystal and deionized water until uniform to obtain a mixed solution; The second step is to stir the mixed solution and then perform dynamic crystallization to obtain the molecular sieve precursor. The third step is to add the required amount of inorganic material containing modified elements to the molecular sieve precursor and mix them to obtain a mixed slurry, and then adjust the pH value of the mixed slurry. The fourth step is to ball mill the mixed slurry to crystallize it, and then after solid-liquid separation, filtration, washing, drying and calcination, the modified eutectic molecular sieve is obtained. The fifth step involves adding an aqueous solution of ammonium chloride to the modified eutectic molecular sieve and stirring thoroughly to obtain a mixture. The mixture is then filtered, washed until neutral, dried, and calcined to obtain a hydrogen-form molecular sieve. Step 6: Add silica-coated modifier and solvent to hydrogen-type molecular sieve, stir and perform chemical liquid phase deposition to obtain product. After rotary evaporation, drying and calcination, the product is obtained as a composite modified eutectic molecular sieve. Step 7: Add γ-type alumina and Tianqing powder to the ground composite modified eutectic molecular sieve, mix well, add dilute nitric acid, extrude into strips, and then dry and calcine to obtain a catalyst for toluene disproportionation to produce benzene and p-xylene.

5. The catalyst for toluene disproportionation to produce benzene and p-xylene according to claim 4, characterized in that... In the second step, the stirring time is 2 to 3 hours; or / and, in the second step, dynamic crystallization is carried out in a homogeneous reactor with a rotary oven, the rotation speed of the rotary oven is 10 to 100 r / min, the crystallization temperature is 80 to 100℃, and the crystallization time is 20 to 80 hours; or / and, in the third step, the pH value of the mixed slurry is adjusted to 10.5 to 12.

6. The catalyst for toluene disproportionation to produce benzene and p-xylene according to claim 4 or 5, characterized in that... In the fourth step, ball milling crystallization is carried out in a heated ball mill. During crystallization, the ball mill speed is 6500 r / min to 7500 r / min, the crystallization temperature is 150℃ to 170℃, and the crystallization time is 72 h to 96 h; or / and in the fifth step, the mass ratio of modified eutectic molecular sieve to ammonium chloride aqueous solution is 1:8 to 12, and the mass concentration of ammonium chloride aqueous solution is 1 mol / L to 1.2 mol / L; or / and in the fifth step, during stirring, the stirring temperature is 80℃ to 90℃, and the stirring time is 2 h to 2.5 h.

7. The catalyst for toluene disproportionation to produce benzene and p-xylene according to claim 4, 5, or 6, characterized in that... In step six, the solvent is cyclohexane, and the silicone modifier is one or more of tetraethyl orthosilicate, dimethyl silicone oil, silane, and silicone resin; or / and, in step six, the mass ratio of hydrogen-form molecular sieve to silicone modifier is 10:1 to 2, and the volume ratio of solvent to silicone modifier is 4 to 6:1; or / and, in step six, during chemical liquid phase deposition, the deposition time is 6 h to 72 h.

8. The catalyst for toluene disproportionation to produce benzene and p-xylene according to any one of claims 4 to 7, characterized in that... In step seven, the mass ratio of the composite modified eutectic molecular sieve to γ-alumina is 1 to 9:1 to 9, and the amount of Tianqing powder added is 2% to 3% of the mass of the composite modified eutectic molecular sieve; or / and, in step seven, the mass concentration of dilute nitric acid is 2% to 4%; or / and, in steps four, five, six and seven, the drying temperature is 100℃ to 150℃ and the drying time is 2.5h to 3.5h; during calcination, the calcination temperature is 500℃ to 600℃ and the calcination time is 4h to 8h.

9. A method for preparing a catalyst for the disproportionation of toluene to produce benzene and p-xylene according to any one of claims 1 to 3, 5 to 8, characterized in that... Perform it as follows: The first step is to mix and stir the required amounts of silicon source, aluminum source, alkali source, first template agent, second template agent, seed crystal and deionized water until uniform to obtain a mixed solution; The second step is to stir the mixed solution and then perform dynamic crystallization to obtain the molecular sieve precursor. The third step is to add the required amount of inorganic material containing modified elements to the molecular sieve precursor and mix them to obtain a mixed slurry, and then adjust the pH value of the mixed slurry. The fourth step is to ball mill the mixed slurry to crystallize it, and then after solid-liquid separation, filtration, washing, drying and calcination, the modified eutectic molecular sieve is obtained. The fifth step involves adding an aqueous solution of ammonium chloride to the modified eutectic molecular sieve and stirring thoroughly to obtain a mixture. The mixture is then filtered, washed until neutral, dried, and calcined to obtain a hydrogen-form molecular sieve. Step 6: Add silica-coated modifier and solvent to hydrogen-type molecular sieve, stir and perform chemical liquid phase deposition to obtain product. After rotary evaporation, drying and calcination, the product is obtained as a composite modified eutectic molecular sieve. Step 7: Add γ-type alumina and Tianqing powder to the ground composite modified eutectic molecular sieve, mix well, add dilute nitric acid, extrude into strips, and then dry and calcine to obtain a catalyst for toluene disproportionation to produce benzene and p-xylene.

10. The application of a catalyst for the disproportionation of toluene to produce benzene and p-xylene according to any one of claims 1 to 8 in the toluene disproportionation reaction.

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