Preparation method and application of catalyst for catalyzing the production of mesitylene from unsimilar trimethylbenzene

Abstract

The present invention relates to a preparation method and application of a catalyst for catalyzing the production of mesitylene from trimethylbenzene. The method comprises the following steps: firstly preparing a multi-level pore Hβ zeolite molecular sieve, then mixing the multi-level pore Hβ zeolite molecular sieve with a hydrogen-type mordenite molecular sieve and a binder, adding a nitric acid solution and water, extruding the zeolite molecular sieve into strips, drying the strips and then calcining the strips at 500-750°C to obtain an unmodified catalyst I; performing impregnation modification on the unmodified catalyst I, then drying and calcining the strips to obtain a modified catalyst; and reducing the modified catalyst in a hydrogen atmosphere at 0.3-1MPa and 350-450°C to obtain a catalyst for isomerization of trimethylbenzene to mesitylene. The present invention utilizes a multi-level pore Hβ zeolite molecular sieve and a hydrogen-type mordenite molecular sieve to form a composite molecular sieve catalyst, then adding rare earth metals, Group VIII, Group IIIB and Group IVB as modifying elements, and reducing the catalyst with hydrogen to improve the selectivity and thermal stability of the catalyst, while increasing the life of the catalyst and improving the economic efficiency of the device.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and particularly relates to a preparation method and application of a catalyst for catalyzing the production of mesitylene from unsymmetrical trimethylbenzene. Background Art

[0002] Mesitylene is a valuable fine chemical raw material. As an organic chemical raw material, it is used to produce synthetic resins, M acid, mesitylene antioxidant 330, high-efficiency wheat field herbicide, polyester resin stabilizer, alkyd resin plasticizer, etc. It can also be used to produce dye intermediates such as Reactive Brilliant Blue and K-3R, and has broad market prospects.

[0003] Currently, mesitylene is produced primarily through synthesis and separation and purification. The synthesis method is divided into isomerization and alkylation. The isomerization method uses paratrimethylbenzene as a raw material, undergoing an isomerization reaction to produce mesitylene. The alkylation method uses a C9 aromatic mesitylene-rich solution and propylene through multiple alkylation reactions, or a combined alkylation of propylene and isobutylene to produce mesitylene. The separation and purification method uses C9 mixed aromatics, a byproduct of catalytic reforming, ethylene, and paraxylene production in petrochemical processes, as a raw material, and directly separates and extracts the mesitylene contained within them through distillation. The large amount of C9 mixed aromatics produced as a byproduct generally contains 6-12% mesitylene.

[0004] Tianjin University used Ni-Mo / HM catalyst with a Mo content of 1.25%. At a reaction temperature of 260°C, a reaction pressure of 1.2 MPa, and a mass space velocity of 1.0 h -1 Under the condition of hydrogen-to-oil ratio of 5, mesitylene was prepared, the conversion rate of partial trimethylol was 49.17%, the yield of mesitylene was 23.10%, and the selectivity of mesitylene was 46.98%.

[0005] The Nanjing Refinery Research Institute used nickel-molybdenum mordenite as a catalyst. Using a mixed tower bottoms oil of trimethylol and trimethylol as feedstock in the presence of hydrogen, they produced mesitylene with a near-thermodynamic equilibrium distribution. The process conditions were: temperature 320-380°C, pressure 0.1-1.5 MPa, and space velocity 1.0-2.0 h / min. -1 Under the condition of high temperature, the yield of mesitylene can reach 25%.

[0006] Patent CN1510017 discloses a catalyst for the simultaneous preparation of mesitylene and durene. The catalyst is an acid catalyst of crystalline metal silicate containing beta zeolite, and the temperature is 210-400℃, the pressure is 1.5MPa, and the mass space velocity is 0.1-2.0h -1 Under the appropriate conditions, mesitylene and durene were catalytically produced using trimethylol as raw material, with the selectivity of mesitylene being 35%.

[0007] Patent CN102746092A discloses a method for producing mesitylene by hydrocracking and separation of heavy aromatics. Using a hydrogen-type binderless ten-membered ring zeolite loaded with 0.005-0.5% by mass of platinum or palladium as a catalyst, hydrogen and heavy aromatics are used as raw materials for hydrocracking, which can increase the production of BTX aromatics and separate the production of mesitylene.

[0008] The aforementioned catalyst for producing mesitylene uses only a molecular sieve catalyst modified with mordenite and rare earth metals. Consequently, the raw material single-pass conversion rate and mesitylene selectivity are low, and there are many side reactions. This results in a large circulation volume for the device, increased investment, and low economic benefits, which cannot generate optimal returns for the enterprise. Summary of the Invention

[0009] To address technical deficiencies in catalyst technology for the isomerization of paratrimethylbenzene to mesitylene, the present invention provides a method for preparing and applying a catalyst for catalyzing the production of mesitylene from paratrimethylbenzene. The composite molecular sieve catalyst is formed using a hierarchical pore Hβ zeolite molecular sieve and a hydrogen-type mordenite molecular sieve. Rare earth metals, Group VIII, Group IIIB, and Group IVB elements are then added as modifying metal elements. This improves the conversion rate of the raw material and the selectivity of mesitylene. Hydrogen reduction further enhances the catalyst's selectivity and thermal stability, while also increasing the catalyst's lifespan and improving the economic efficiency of the device. The catalytic reaction produces few byproducts, resulting in a stable finished product and enhanced economic benefits.

[0010] The present invention is specifically achieved through the following technical solutions. According to the present invention, a method for preparing a catalyst for catalyzing the production of mesitylene from unsymmetrical trimethylbenzene comprises the following steps:

[0011] (1) Preparation of multi-level pore Hβ zeolite molecular sieve: a certain amount of Hβ molecular sieve raw powder is added to 0.05 mol / L sodium hydroxide solution, and stirred continuously at 65°C for 40 to 60 min; the obtained solid-liquid mixture is cooled and filtered, and the filtered solid matter is washed with distilled water until neutral, dried at 110°C for 1 hour, and then calcined at 550°C for 6 hours to obtain Naβ molecular sieve; the obtained Naβ molecular sieve is ion exchanged with ammonium chloride solution, filtered, and dried, and the process is repeated 3 times; the dried molecular sieve is washed with deionized water, filtered, and dried, and the process is repeated 3 times, and then calcined at 550°C for 6 hours to obtain multi-level pore Hβ zeolite molecular sieve raw powder;

[0012] The silicon-aluminum molar ratio of the hierarchical pore Hβ zeolite molecular sieve raw powder is 25;

[0013] (2) Take a certain amount of hydrogen-type mordenite molecular sieve, the prepared multi-level pore Hβ zeolite molecular sieve raw powder, and a binder, mix the three evenly, add nitric acid solution and water, stir thoroughly, and then extrude into strips;

[0014] (3) drying the wet strips prepared in step (2) at 110-120°C for 2-10 hours, and then calcining at 500-750°C for 2-12 hours to obtain unmodified catalyst I;

[0015] (4) impregnating the unmodified catalyst I prepared in step (3) for 6-12 hours, drying at 110-120°C for 2-8 hours, and then calcining at 500-750°C for 2-12 hours to obtain a modified catalyst;

[0016] (5) The modified catalyst prepared in step (4) is loaded into a fixed bed reactor and reduced in a hydrogen atmosphere at 0.3-1 MPa and 350-450°C for 4 h to obtain a catalyst for isomerization of trimethylbenzene to mesitylene.

[0017] In the aforementioned method for preparing a catalyst for catalyzing the production of mesitylene from unsymmetrical trimethylbenzene, in step (1), the volume ratio of the Hβ molecular sieve raw powder to the sodium hydroxide solution is 1 (g):2 (mL) (solid-to-liquid ratio is 1g:2mL).

[0018] The specific steps of the ion exchange include: mixing Naβ molecular sieve with 1 mol / L ammonium chloride solution, stirring at 80°C for 2 hours and then filtering, drying the filtered molecular sieve and then performing a second ion exchange, and repeating this three times.

[0019] Furthermore, during the ion exchange process, a certain volume concentration of 1 mol / L ammonium chloride solution was prepared according to the ratio of the mass of the Hβ molecular sieve raw powder to the volume ratio of the ammonium chloride solution of 1 (g):4 (mL). The prepared ammonium chloride solution was used three times and ion exchange was carried out three times with the Naβ molecular sieve.

[0020] In the aforementioned method for preparing a catalyst for catalyzing the production of mesitylene from unsimilar trimethylbenzene, the contents of hydrogen-type mordenite, hierarchical pore Hβ zeolite molecular sieve, and binder in step (2) are as follows in terms of weight percentage:

[0021] Hydrogen-type mordenite, 20%-70%;

[0022] Hierarchical pore Hβ zeolite molecular sieve, content 20%-70%;

[0023] Binder, content 10-20%;

[0024] The silicon-aluminum molar ratio of the hydrogen-type mordenite is 25.

[0025] The binder is selected from at least one of aluminum sol, silica sol, and pseudo-boehmite, preferably pseudo-boehmite (SB powder).

[0026] In the aforementioned method for preparing a catalyst for catalyzing the production of mesitylene from para-trimethylbenzene, the mass fraction of the nitric acid solution in step (2) is 4%, and the ratio of its added mass to the total mass of the hydrogen-type mordenite molecular sieve, the multi-level pore Hβ zeolite molecular sieve and the binder is 2:5.

[0027] In the aforementioned method for preparing a catalyst for catalyzing the production of mesitylene from unsimilar trimethylbenzene, in step (4), a salt solution of a modified metal is used for the impregnation modification, and the modified metal is at least one of a rare earth metal, a Group VIII element, a Group IIIB element, and a Group IVB element, preferably Ni, La, and Zr. In other embodiments, the modified metal may also be two or more of Ni, La, Zr, and W. The loaded mass of the modified metal accounts for 0.05 to 5.0% of the total mass of the hydrogen-type mordenite molecular sieve, the multi-level pore Hβ zeolite molecular sieve, and the binder.

[0028] The present invention also provides an application of the catalyst prepared according to the above method in catalyzing the production of mesitylene from paratrimethylbenzene. Paratrimethylbenzene is used as a raw material and is fed into a fixed bed reactor filled with a catalyst and porcelain balls for reaction to prepare mesitylene. Under hydrogen conditions, the reaction temperature is 240-340°C, preferably 260-300°C; the pressure is 1.0-1.5MPa, preferably 1.2-1.4MPa; the mass space velocity is 0.5-2.0h -1 , preferably 0.8-1.3 h-1; hydrogen-to-oil volume ratio 50-1000 V / V, preferably 500-800 V / V; reaction time 250-600 h. The selectivity of mesitylene is greater than 45%.

[0029] Compared with the prior art, the present invention has obvious advantages and beneficial effects. By means of the above technical solution, the present invention can achieve considerable technological advancement and practicality, and has a wide range of utilization value. It has at least the following advantages:

[0030] (1) The present invention treats Hβ molecular sieve raw powder with a low-concentration sodium hydroxide solution to obtain a multi-level pore Hβ zeolite molecular sieve with a large specific surface area and abundant micropores and mesopores. In the catalytic reaction of macromolecules, it can effectively shorten the diffusion length of reactants and products and increase the effective diffusion rate, thereby significantly reducing the occurrence of carbon deposition and improving the utilization efficiency and service life of the catalyst.

[0031] (2) A composite molecular sieve is prepared by mixing hydrogen-type mordenite molecular sieve and multi-level pore Hβ zeolite molecular sieve. The active sites of the two molecular sieves are rationally utilized, which has an inhibitory effect and high selectivity on the disproportionation reaction and alkylation reaction of toluene, trimethylbenzene and C9; the acidity and appropriate pore volume of the composite zeolite molecular sieve can produce isomerization, thereby improving the stability of the catalyst and the conversion rate of the raw material.

[0032] (3) The composite molecular sieve further improves the activity and selectivity of the catalyst through metal modification treatment. Zr and W can inhibit the disproportionation reaction and thus improve the selectivity of the target product, mesitylene.

[0033] (4) The activity and selectivity of the catalyst were further improved by hydrogen reduction treatment. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0035] The calcination in the following examples was carried out in a muffle furnace, and the hydrogen reduction process was carried out in a fixed bed reactor.

[0036] Example 1

[0037] 500g of Hβ molecular sieve powder with a silicon-aluminum molar ratio of 25 was placed in a container. 1000mL of a 0.05mol / L sodium hydroxide solution was added to cover the catalyst. The mixture was stirred continuously at 65°C for 40 minutes. The resulting solid-liquid mixture was cooled and filtered. The filtered solid was washed with distilled water until neutral, dried at 110°C for 1 hour, and then calcined at 550°C for 6 hours to obtain Naβ molecular sieve. 2000mL of a 1mol / L ammonium chloride solution was prepared and used in three batches. The Naβ molecular sieve was ion-exchanged with the 1mol / L ammonium chloride solution three times: 600-700mL of ammonium chloride solution was added to the Naβ molecular sieve, stirred at 80°C for 2 hours, filtered, and the filtered molecular sieve was dried. A second ion exchange was performed, repeated three times. The dried molecular sieve was washed with deionized water, filtered, and dried three times, and then calcined at 550°C for 6 hours. This yielded the multi-level pore Hβ zeolite molecular sieve powder.

[0038] Example 2

[0039] 60g of hydrogen-type mordenite molecular sieve, 20g of hierarchical pore Hβ zeolite molecular sieve powder, and 20g of SB powder were weighed and mixed uniformly. 40g of 4% nitric acid solution and an appropriate amount of deionized water were added, kneaded, and then extruded into bars. The mixture was dried at 120°C for 3h and calcined at 550°C for 5h to produce unmodified catalyst A1. A modified metal salt solution was prepared by adding 0.452g of nickel nitrate hexahydrate, 0.383g of lanthanum nitrate hexahydrate, and 0.193g of zirconium nitrate pentahydrate to 15mL of deionized water. 10g of unmodified catalyst A1 was evenly immersed in the modified metal salt solution. The mixture was allowed to stand for 12h, then dried at 120°C for 4h and calcined at 550°C for 6h to produce modified catalyst A2. Modified catalyst A2 was reduced at 450°C for 4h in a hydrogen atmosphere at 0.3-1MPa to obtain catalyst A.

[0040] Example 3

[0041] 20g of hydrogen-type mordenite molecular sieve, 60g of hierarchically porous Hβ zeolite molecular sieve powder, and 20g of SB powder were weighed and mixed uniformly. 40g of 4% nitric acid solution and an appropriate amount of deionized water were added, kneaded, and then extruded into bars. The mixture was dried at 120°C for 3h and calcined at 550°C for 5h to produce unmodified catalyst B1. A modified metal salt solution was prepared by adding 0.452g of nickel nitrate hexahydrate, 0.383g of lanthanum nitrate hexahydrate, and 0.193g of zirconium nitrate pentahydrate to 15mL of deionized water. 10g of unmodified catalyst B1 was evenly immersed in the modified metal salt solution. The mixture was allowed to stand for 12h, then dried at 120°C for 4h and calcined at 550°C for 6h to produce modified catalyst B2. Modified catalyst B2 was reduced at 450°C for 4h in a hydrogen atmosphere at 0.3-1MPa to obtain catalyst B.

[0042] Example 4

[0043] 40g of hydrogen-type mordenite molecular sieve, 40g of hierarchically porous Hβ zeolite molecular sieve powder, and 20g of SB powder were weighed and mixed uniformly. 40g of 4% nitric acid solution and an appropriate amount of deionized water were added, kneaded, and then extruded into bars. The mixture was dried at 120°C for 3h and calcined at 550°C for 5h to produce unmodified catalyst C1. A modified metal salt solution was prepared by adding 0.452g of nickel nitrate hexahydrate, 0.383g of lanthanum nitrate hexahydrate, and 0.193g of zirconium nitrate pentahydrate to 15mL of deionized water. 10g of unmodified catalyst C1 was evenly immersed in the modified metal salt solution. The mixture was allowed to stand for 12h, then dried at 120°C for 4h and calcined at 550°C for 6h to produce modified catalyst C2. Modified catalyst C2 was reduced at 450°C for 4h in a hydrogen atmosphere at 0.3-1MPa to obtain catalyst C.

[0044] Example 5

[0045] 60g of hydrogen-type mordenite molecular sieve, 20g of multi-level pore Hβ zeolite molecular sieve powder, and 20g of SB powder were weighed and mixed uniformly. 40g of 4% nitric acid solution and an appropriate amount of deionized water were added, kneaded, and then extruded into bars. The mixture was dried at 120°C for 3h and calcined at 550°C for 5h to produce unmodified catalyst D1. A modified metal salt solution was prepared by adding 0.3g of nickel nitrate hexahydrate and 0.38g of lanthanum nitrate hexahydrate to 15mL of deionized water. 10g of unmodified catalyst D1 was evenly immersed in the modified metal salt solution. The mixture was allowed to stand for 12h, then dried at 120°C for 4h and calcined at 550°C for 6h to produce modified catalyst D2. Modified catalyst D2 was reduced at 450°C for 4h in a hydrogen atmosphere at 0.3-1MPa to obtain catalyst D.

[0046] Example 6

[0047] 60g of hydrogen-type mordenite molecular sieve, 20g of hierarchical pore Hβ zeolite molecular sieve powder, and 20g of SB powder were weighed and mixed uniformly. 40g of 4% nitric acid solution and an appropriate amount of deionized water were added, kneaded, and then extruded into bars. The mixture was dried at 120°C for 3h and calcined at 550°C for 5h to produce unmodified catalyst E1. A modified metal salt solution was prepared by adding 0.298g of nickel nitrate hexahydrate and 0.19g of zirconium nitrate pentahydrate to 15mL of deionized water. 10g of unmodified catalyst E1 was evenly immersed in the modified metal salt solution. The mixture was allowed to stand for 12h, then dried at 120°C for 4h and calcined at 550°C for 6h to produce modified catalyst E2. Modified catalyst E2 was reduced at 450°C for 4h in a hydrogen atmosphere at 0.3-1MPa to obtain catalyst E.

[0048] Example 7

[0049] 60g of hydrogen-type mordenite molecular sieve, 20g of multi-level pore Hβ zeolite molecular sieve powder, and 20g of SB powder were weighed and mixed uniformly. 40g of 4% nitric acid solution and an appropriate amount of deionized water were added, kneaded, and then extruded into bars. The mixture was dried at 120°C for 3 hours and then calcined at 550°C for 5 hours to produce unmodified catalyst F1. A modified metal salt solution was prepared by adding 0.297g of nickel nitrate hexahydrate to 15mL of deionized water. 10g of unmodified catalyst F1 was evenly immersed in the modified metal salt solution. The mixture was allowed to stand for 12 hours, then dried at 120°C for 4 hours and calcined at 550°C for 6 hours to produce modified catalyst F2. Modified catalyst F2 was reduced at 450°C for 4 hours in a hydrogen atmosphere at 0.3-1MPa to obtain catalyst F.

[0050] Example 8

[0051] Weigh 60g of hydrogen-type mordenite molecular sieve, 20g of multi-level pore Hβ zeolite molecular sieve raw powder and 20g of SB powder, mix them evenly, add 40g of 4% nitric acid solution and an appropriate amount of deionized water, knead them evenly, and then extrude them into strips. Dry them at 120℃ for 3h and then calcine them at 550℃ for 5h to prepare catalyst G.

[0052] Comparative Example 1

[0053] Take HM type mordenite with a silicon-aluminum molar ratio of 25; take 0.4g of lanthanum nitrate hexahydrate and 0.32g of nickel nitrate hexahydrate, add 15mL of deionized water to prepare a modified metal salt solution; weigh 10g of HM type mordenite and evenly immerse it in the above modified metal salt solution, let it stand for 12h, then dry it at 120℃ for 4h, and then calcine it at 600℃ for 6h to obtain a modified catalyst Ni-La-HM, named H.

[0054] Comparative Example 2

[0055] Take HM type mordenite catalyst with a silicon-aluminum ratio of 25 and name it I.

[0056] Example 9

[0057] Catalyst A was loaded into a 10ml adiabatic fixed-bed laboratory reactor, and the reaction product was analyzed offline. The starting material was mesitylene (98% purity). The conversion of mesitylene and selectivity to mesitylene under different reaction conditions are shown in Table 1.

[0058] Table 1. Conversion rate of trimethylol and selectivity of mesitylene under different experimental conditions

[0059]

[0060] Example 10

[0061] The catalysts prepared in Examples 2 to 8 and Comparative Examples 1 and 2 were loaded into a 10 ml adiabatic fixed-bed reactor in the laboratory, and the reaction products were analyzed by offline liquid collection. The raw material was trimethylol (98% purity), and the reaction conditions were: temperature 290°C, pressure 1.4 MPa, and mass space velocity 1.0 h-1. -1 The hydrogen-to-oil ratio was 500 v / v, and the reaction time was 600 h. The product compositions of mesitylene produced from unsaturated trimethylbenzene using different catalysts are shown in Table 2 below, and the reaction performance is shown in Table 3.

[0062] Table 2. Product composition of mesitylene produced by different catalysts catalyzed by para-trimethylbenzene

[0063]

[0064] Table 3. Reaction performance of different catalysts for the production of mesitylene from para-trimethylbenzene

[0065]

[0066] The present invention treats the Hβ molecular sieve raw powder with a low-concentration sodium hydroxide solution, and the resulting multi-level pore Hβ zeolite molecular sieve has a large specific surface area and abundant micropores and mesoporous channels. It can effectively shorten the diffusion length of reactants and products in the catalytic reaction of macromolecules, increase the effective diffusion rate, and thus significantly reduce the occurrence of carbon deposition, thereby improving the utilization efficiency and service life of the catalyst. The composite molecular sieve prepared by mixing hydrogen-type mordenite molecular sieve and multi-level pore Hβ zeolite molecular sieve has an inhibitory effect and high selectivity on the disproportionation reaction and alkylation reaction of toluene, trimethylbenzene and C9; the acidity and appropriate pore volume of the composite zeolite molecular sieve can produce an isomerization effect, thereby improving the stability of the catalyst and the conversion rate of the raw material. The composite molecular sieve is further improved in activity and selectivity of the catalyst through metal modification treatment and hydrogen reduction treatment.

[0067] The above description is merely an embodiment of the present invention and does not constitute any form of limitation to the present invention. The present invention may also have other forms of embodiments based on the above structures and functions, which are not listed here one by one. Therefore, any simple modification, equivalent changes, and modifications made to the above embodiments by any person skilled in the art in accordance with the technical essence of the present invention without departing from the scope of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a catalyst for catalyzing the production of mesitylene from unsymmetrical trimethylbenzene, characterized in that The following steps are involved: (1) Preparation of multi-level pore Hβ zeolite molecular sieve: Add Hβ molecular sieve raw powder to 0.05 mol / L sodium hydroxide solution and stir continuously at 65°C for 40-60 min. The volume ratio of Hβ molecular sieve raw powder to sodium hydroxide solution is 1 g:2 mL. The obtained solid-liquid mixture is cooled and filtered. The filtered solid matter is washed with distilled water until neutral, dried at 110°C for 1 h, and then calcined at 550°C for 6 h to obtain Naβ molecular sieve. The obtained Naβ molecular sieve is ion-exchanged with ammonium chloride solution, filtered, and dried, and the process is repeated three times. The dried molecular sieve is washed with deionized water, filtered, and dried, and the process is repeated three times. The dried molecular sieve is then calcined at 550°C for 6 h to obtain multi-level pore Hβ zeolite molecular sieve raw powder. (2) taking a certain amount of hydrogen-type mordenite molecular sieve, the prepared multi-level pore Hβ zeolite molecular sieve raw powder, and the binder pseudo-boehmite, mixing the three evenly, adding nitric acid solution and water, stirring thoroughly, and then extruding into strips; in terms of weight percentage, the contents of hydrogen-type mordenite, multi-level pore Hβ zeolite molecular sieve raw powder, and binder pseudo-boehmite are as follows: hydrogen-type mordenite 60%, multi-level pore Hβ zeolite molecular sieve raw powder 20%, and binder pseudo-boehmite 20%, and the silicon-aluminum molar ratio of the hydrogen-type mordenite is 25; (3) drying the wet strips prepared in step (2) at 110-120°C for 2-10 hours, and then calcining at 550°C for 2-12 hours to obtain unmodified catalyst I; (4) The unmodified catalyst I prepared in step (3) is impregnated with a salt solution of a modified metal for 6-12 hours, dried at 110-120°C for 2-8 hours after impregnation, and then calcined at 550°C for 2-12 hours to obtain a modified catalyst; the modified metal is Ni, La and Zr, and the loading mass of the modified metal accounts for 0.05-5.0% of the total mass of the hydrogen-type mordenite molecular sieve, the multi-level pore Hβ zeolite molecular sieve and the binder; (5) The modified catalyst prepared in step (4) is loaded into a fixed bed reactor and reduced at 450°C for 4 h in a hydrogen atmosphere of 0.3-1 MPa to obtain a catalyst for isomerization of trimethylbenzene to mesitylene.

2. The method for preparing a catalyst for producing mesitylene from unsymmetrical trimethylbenzene as claimed in claim 1, wherein The specific steps of ion exchange in step (1) include: mixing Naβ molecular sieve with 1 mol / L ammonium chloride solution, stirring at 80°C for 2 hours and then filtering, drying the filtered molecular sieve and then performing a second ion exchange, and repeating this three times.

3. The preparation method of the catalyst for producing mesitylene from unsymmetrical trimethylbenzene as claimed in claim 1, characterized in that The mass fraction of the nitric acid solution in step (2) is 4%, and the ratio of the added mass to the total mass of the hydrogen-type mordenite molecular sieve, the multi-level pore Hβ zeolite molecular sieve and the binder is 2:

5.

4. Use of the catalyst prepared by the preparation method according to claim 1 in catalyzing the production of mesitylene from paratrimethylbenzene, wherein the raw material paratrimethylbenzene is fed into a fixed-bed reactor filled with the catalyst and porcelain balls for reaction to produce mesitylene, under hydrogen conditions, at a reaction temperature of 240-340°C, a pressure of 1.0-1.5 MPa, and a mass space velocity of 0.5-2.0 h -1 , hydrogen-to-oil volume ratio 50-1000.

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