A dichlorotoluene isomerization catalyst

Abstract

The application discloses a 2,5-dichlorotoluene isomerization catalyst, wherein the carrier of the catalyst is a multi-stage pore hydrogen type molecular sieve, the active component is zirconium oxide, the cocatalyst is alkaline earth metal oxide, the total loading amount of the zirconium oxide and the alkaline earth metal oxide is 1-5 wt%, the molar ratio of zirconium and the alkaline earth metal is 10:0-0:10, and the multi-stage pore hydrogen type molecular sieve is obtained by modifying a hydrogen type molecular sieve with an organic acid. Through the organic acid dealumination modification, mesoporous channels can be effectively constructed in the molecular sieve crystal, the specific surface area, mesoporous pore size and pore volume of the molecular sieve are increased, the diffusion of macromolecules in the channels is greatly enhanced, and the carbon deposition inactivation of the catalyst is inhibited; the active component can provide more catalytic active sites, improve the catalytic activity of the catalyst, and the cocatalyst has a positive influence on the acidity, carbon deposition and other properties of the catalyst; the highest conversion rate of 2,5-dichlorotoluene reaches 59.14%, and the total selectivity of dichlorotoluene reaches 37.77%.

Description

Technical Field

[0001] This invention belongs to the fields of isomerization of chlorotoluene derivatives and application of metal-molecular sieve bifunctional catalysts, and relates to a dichlorotoluene isomerization catalyst, specifically a catalyst for the isomerization reaction of 2,5-dichlorotoluene. Background Technology

[0002] Among the dichlorotoluene isomers, 2,5-dichlorotoluene has a narrower application range and is inexpensive, while 2,4-dichlorotoluene is an important fine chemical intermediate widely used in the pesticide, pharmaceutical, and dye industries. It can be used to synthesize herbicides such as pyrazolite, fungicides such as tebuconazole and ciprofloxacin, and antimalarial drugs such as azithromycin. Common preparation methods for 2,4-dichlorotoluene include direct chlorination of p-chlorotoluene and diazotization of 3-chloro-p-toluidine, but these methods have drawbacks such as producing numerous byproducts, complex processes, and significant pollution.

[0003] 2,6-Dichlorotoluene is an important fine chemical raw material widely used in the fields of pesticides, pharmaceuticals, and dyes to manufacture insecticides, fungicides, dyes, pharmaceuticals, and other chemical products. For example, 2,6-dichlorotoluene can be used as a reaction intermediate to synthesize 2,6-dichlorobenzonitrile, 2,6-dichlorobenzamide, 2,6-dichlorophenol, and some asymmetric biphenyl derivatives, which are raw materials for fine chemical products.

[0004] Currently, there are various methods for synthesizing 2,6-dichlorotoluene both domestically and internationally. The main methods include the o- or p-nitrotoluene method, the o- or p-methanesulfonyl chloride method, the direct chlorination of toluene, the o-chlorotoluene method, and the dichlorotoluene isomerization method. Among these, the direct chlorination of toluene and the o-chlorotoluene method use toluene and o-chlorotoluene as raw materials, respectively, to directly produce 2,6-dichlorotoluene in a one-step process. While these methods are simple and conducive to industrialization, they also produce 2,5-dichlorotoluene and 2,4-dichlorotoluene as byproducts. Furthermore, because the boiling points of 2,5-dichlorotoluene and 2,4-dichlorotoluene are extremely close, the byproduct containing 2,5-dichlorotoluene cannot be separated and can only be used as a solvent, significantly reducing its added value. Isomerizing 2,5-dichlorotoluene into dichlorotoluene with other structures is a feasible route to increase the added value of 2,5-dichlorotoluene.

[0005] Isomerization is a method that uses 2,5-dichlorotoluene isomers as raw materials, employing suitable catalysts and optimal reaction processes to prepare other isomers such as 2,6-dichlorotoluene. Therefore, to maintain the healthy and sustainable development of my country's fine chemical industry, screening suitable catalysts and process parameters, and strengthening the research and development of synthetic routes and production processes for isomers such as 2,6-dichlorotoluene, is of significant research importance and has broad application prospects.

[0006] Patent JPS6393739A discloses a method for isomerizing aromatic chlorides using the acidic form of ω-type zeolite as a catalyst, revealing superior catalytic activity and reaction selectivity, and the ability to increase the concentration of certain isomers in dichlorotoluene mixtures. When using the acidic form of ω-type zeolite as a catalyst, the reaction temperature is 300°C and the mass hourly space velocity is 0.6 hr. -1 Under optimal conditions, the content of 2,5-dichlorotoluene in the component decreased from 60.3% to 54.4%, while the content of 2,6-dichlorotoluene increased from 0.92% to 5.99%.

[0007] Chinese patent application CN105198696 A discloses a method for preparing 2,6-dichlorotoluene from 2,5-dichlorotoluene using H-type molecular sieve catalysis. Under normal pressure conditions, when using Hβ molecular sieve, the reaction temperature is 350℃ and the volume hourly space velocity (HHSV) of 2,5-dichlorotoluene is 0.6 hr⁻¹. -1 When the nitrogen carrier gas flow rate is 10 mL / min, the conversion rate of 2,5-dichlorotoluene is 30.9%, and the selectivity of 2,6-dichlorotoluene is 45.7%.

[0008] Chinese patent CN 112705186 A uses a heteroatom-doped modified carbon source as a catalyst for the isomerization of 2,5-dichlorotoluene, at a reaction temperature of 360℃ and a 2,5-dichlorotoluene volume hourly space velocity of 0.44hr. -1 When the nitrogen carrier gas flow rate is 20 mL / min, the conversion rate of 2,5-dichlorotoluene is 44.6%, and the selectivity of 2,6-dichlorotoluene is 32.2%.

[0009] Most of the above methods use hydrogen-type molecular sieves as catalysts to convert low-value-added 2,5-dichlorotoluene into high-value-added 2,4-dichlorotoluene or 2,6-dichlorotoluene, but the conversion rate is generally low.

[0010] Supported catalysts typically consist of a molecular sieve support and an active component, with metal species being a common active component. Supported metal catalysts exhibit high catalytic activity, selectivity, and stability, low corrosivity, and can be continuously recovered and reused, making them widely used in petroleum refining and petrochemical processes. They are important catalytic materials in hydrogenation, dehydrogenation, and isomerization reactions. However, the relatively small pore size of microporous molecular sieves hinders the diffusion of large molecular reactants and products within the pores, easily leading to coking and deactivation of the molecular sieve, thereby reducing the catalyst's catalytic activity and lifespan. Summary of the Invention

[0011] The purpose of this invention is to develop a 2,5-dichlorotoluene isomerization catalyst that has low production costs and is easy to industrialize.

[0012] The objective of this invention is achieved through the following technical solution:

[0013] A 2,5-dichlorotoluene isomerization catalyst, wherein the catalyst support is a hierarchical porous hydrogen-type molecular sieve, the active component is zirconium oxide, the co-catalyst is an alkaline earth metal oxide, the total loading of zirconium oxide and alkaline earth metal oxide (the percentage of the mass of the metal oxide to the total mass of the molecular sieve) is 1-5 wt%, and the molar ratio of zirconium to alkaline earth metal is 10:0 to 0:10.

[0014] The aforementioned hierarchical porous hydrogen-type molecular sieve is a multi-level porous hydrogen-type molecular sieve obtained by modifying a hydrogen-type molecular sieve with an organic acid.

[0015] The hierarchical porous hydrogen-form molecular sieve is prepared by the following method: the hydrogen-form molecular sieve is immersed in an aqueous solution of organic acid and reacted at a temperature of 70-90℃ for 1-3 hours. After filtration, the resulting solid is washed with deionized water until neutral, dried at a temperature of 100-120℃, and calcined at a temperature of 550℃ for 2-4 hours to obtain the hierarchical porous hydrogen-form molecular sieve.

[0016] The hydrogen-form molecular sieve is an Hβ molecular sieve, preferably an Hβ molecular sieve with SiO2 / Al2O3 = 30. The particle size of the hydrogen-form molecular sieve is 30-60 mesh.

[0017] The concentration of the organic acid aqueous solution is 5-40 wt%, preferably 15 wt%.

[0018] The organic acid is any one of acetic acid, citric acid, and oxalic acid, preferably oxalic acid.

[0019] The ratio of the hydrogen-type molecular sieve impregnation to the organic acid aqueous solution is 1:10 g / mL.

[0020] The alkaline earth metal is Ca; the alkaline earth metal oxide is CaO.

[0021] Preferably, the total loading of zirconium oxide and alkaline earth metal oxide is 3 wt%.

[0022] Preferably, the molar ratio of zirconium to alkaline earth metal is 7:3 to 3:7.

[0023] More preferably, the molar ratio of zirconium to alkaline earth metal is 7:3 to 5:5.

[0024] Most preferably, the molar ratio of zirconium to alkaline earth metal is 7:3.

[0025] Specifically, the molar ratio of zirconium to alkaline earth metal is 10:0, 7:3, 5:5, 3:7, or 0:10.

[0026] Another object of the present invention is to provide a method for preparing the 2,5-dichlorotoluene isomerization catalyst, comprising the following steps:

[0027] Step (1): Immerse the hydrogen molecular sieve in an aqueous organic acid solution and react at 70-90℃ for 1-3 hours. Filter the solution, wash the resulting solid with deionized water until neutral, dry it at 100-120℃, and calcine it at 550℃ for 2-4 hours to obtain a multi-level porous hydrogen molecular sieve.

[0028] Step (2): Dissolve Zr(NO3)4·5H2O and alkaline earth metal nitrate in deionized water to obtain a mixed solution; mix the mixed solution with a hierarchical porous hydrogen molecular sieve, impregnate for 12-24 h, filter, dry the solid at 110-120℃, and calcine at 450-550℃ for 3-5 h to obtain a 2,5-dichlorotoluene isomerization catalyst.

[0029] The alkaline earth metal nitrate is Ca(NO3)2·4H2O.

[0030] The impregnation temperature is room temperature.

[0031] Another object of the present invention is to provide the application of the catalyst described above in the isomerization of dichlorotoluene to prepare 2,4-dichlorotoluene and 2,6-dichlorotoluene.

[0032] A method for preparing 2,4-dichlorotoluene and 2,6-dichlorotoluene by catalytic isomerization of 2,5-dichlorotoluene, comprising: using 2,5-dichlorotoluene as a raw material, using N2 as a carrier gas, using the aforementioned 2,5-dichlorotoluene isomerization catalyst, and the mass hourly space velocity (HHSV) of the raw material being 0.3–1.0 hr. -1 The carrier gas flow rate is 6.5–20 mL / min / gcat, and 2,5-dichlorotoluene undergoes an isomerization reaction to produce 2,4-dichlorotoluene and 2,6-dichlorotoluene at a reaction temperature of 330–370 °C.

[0033] Preferably, the reaction temperature is 340–360°C.

[0034] Most preferably, the reaction temperature is 350°C.

[0035] Preferably, the mass hourly space velocity (MHSV) of the raw material is 0.4–0.8 hr. -1 .

[0036] Most preferably, the mass hourly space velocity (MHSV) of the raw material is 0.4 hr. -1 .

[0037] Preferably, the flow rate of the carrier gas is 6.5–7 mL / min / gcat.

[0038] Feed mass space velocity = Feed mass flow rate / Catalyst mass.

[0039] The beneficial effects of this invention are:

[0040] This invention utilizes organic acid dealumination modification to effectively construct mesoporous channels within Hβ molecular sieve crystals, expanding the pore size of the Hβ molecular sieve and thereby increasing its specific surface area, mesopore diameter, and pore volume. This significantly enhances macromolecular diffusion within the channels and inhibits catalyst deactivation due to coking. The metal active component supported on the catalyst provides more catalytic active sites, thus improving the catalyst's catalytic activity. Simultaneously, the addition of alkaline earth metal oxides as a co-catalyst positively impacts the catalyst's acidity and coking properties, further enhancing its catalytic activity.

[0041] Using the catalyst of this invention to catalyze the isomerization reaction of 2,5-dichlorotoluene, the highest conversion rate of 2,5-dichlorotoluene can reach 59.14%, and the total selectivity of dichlorotoluene reaches 37.77%. Detailed Implementation

[0042] The technical solution of the present invention will be further described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto, and the data shown does not represent a limitation on the feature scope of the present invention.

[0043] Example 1

[0044] The preparation of hierarchical porous hydrogen-form molecular sieves includes the following steps:

[0045] 20g of solid organic acid (acetic acid, citric acid, or oxalic acid) was added to 80g of deionized water and stirred until homogeneous to prepare an organic acid aqueous solution with a concentration of 20wt%. 10g of Hβ molecular sieve (SiO2 / Al2O3 = 30, hereinafter referred to as Hβ30, particle size 30-60 mesh) was immersed in the above organic acid aqueous solution and stirred under reflux at 80℃ for 2h. After filtration, the obtained solid was washed with deionized water until the filtrate was neutral, then dried at 110℃ for 12h, and finally calcined at 550℃ for 3h to obtain hierarchical porous hydrogen-type molecular sieves (denoted as acetic acid-modified Hβ, citric acid-modified Hβ, and oxalic acid-modified Hβ, respectively).

[0046] Using 2,5-dichlorotoluene (2,5-DCT) as a starting material, a gas-phase isomerization reaction of 2,5-dichlorotoluene was carried out to investigate the effect of organic acid type on the Hβ molecular sieve-catalyzed isomerization reaction of 2,5-dichlorotoluene. The reaction conditions were: feed mass hourly space velocity (HHSV) of 0.8 hr. -1 The carrier gas N2 flow rate was 10.87 mL / min / gcat, the reaction temperature was 350℃, and the reaction time was 1 h.

[0047] The reaction results are shown in Table 1. It can be seen that, compared with Hβ molecular sieve, the selectivity of 2,6-dichlorotoluene and 2,4-dichlorotoluene was improved by using catalysts modified with organic acids as acid sources. In particular, the catalytic effect was best when using oxalic acid as an acid source, with a conversion rate of 41.19% for 2,5-dichlorotoluene, a selectivity of 18.99% for 2,6-dichlorotoluene, and a selectivity of 12.71% for 2,4-dichlorotoluene.

[0048] Table 1. Effects of organic acid type on feed conversion rate and product selectivity

[0049]

[0050]

[0051] Note: CB stands for chlorobenzene, o-CT stands for o-chlorotoluene, DCB stands for dichlorobenzene, DCX stands for dichloroxylene, 2,3-DCT stands for 2,3-dichlorotoluene, 2,4-DCT stands for 2,4-dichlorotoluene, 2,6-DCT stands for 2,6-dichlorotoluene, and 3,4-DCT stands for 3,4-dichlorotoluene.

[0052] Example 2

[0053] The preparation of hierarchical porous hydrogen-form molecular sieves includes the following steps:

[0054] Solid oxalic acid was added to deionized water and stirred until homogeneous to obtain aqueous solutions of oxalic acid with concentrations of 5, 10, 15, 20, 25, and 30 wt%. 10 g of Hβ molecular sieve (SiO2 / Al2O3 = 30, particle size 30-60 mesh) was immersed in the aqueous oxalic acid solution (solid-liquid ratio 1:10 g / mL) and stirred under reflux at 80 °C for 2 h. After filtration, the solid was washed with deionized water until the filtrate was neutral to remove oxalic acid. The obtained solid was dried at 110 °C for 12 h and then calcined at 550 °C for 3 h to obtain a hierarchical porous hydrogen-type molecular sieve, denoted as C-Hβ-x (x represents the concentration of the oxalic acid solution).

[0055] Using 2,5-dichlorotoluene (2,5-DCT) as a starting material, the effect of oxalic acid concentration on the Hβ molecular sieve-catalyzed isomerization reaction of 2,5-dichlorotoluene was investigated. The reaction conditions were: feed mass hourly space velocity (HHSV) of 0.8 hr. -1 The carrier gas N2 flow rate was 10.87 mL / min / gcat, the reaction temperature was 350℃, and the reaction time was 1 h.

[0056] The reaction results are shown in Table 2. It can be seen that, compared with Hβ molecular sieves, the catalyst modified with oxalic acid as the acid source showed improved conversion of 2,5-dichlorotoluene and selectivity for 2,6-dichlorotoluene and 2,4-dichlorotoluene. With increasing oxalic acid concentration, the conversion of 2,5-dichlorotoluene first increased and then decreased, while the selectivity for 2,4-dichlorotoluene and 2,6-dichlorotoluene first decreased and then increased, the opposite trend to the conversion rate increase. Specifically, the catalyst exhibited optimal catalytic performance when the oxalic acid concentration was 15%, at which point the conversion of 2,5-dichlorotoluene was 43.33%, the selectivity for 2,6-dichlorotoluene was 19.45%, and the selectivity for 2,4-dichlorotoluene was 12.72%.

[0057] Table 2. Effects of oxalic acid concentration on feed conversion rate and product selectivity

[0058]

[0059] Example 3

[0060] The preparation of bimetallic modified hierarchical porous hydrogen-form molecular sieves includes the following steps:

[0061] Using the hierarchical porous hydrogen-type molecular sieve C-Hβ-15 prepared at the optimal oxalic acid concentration in Example 2 as the catalyst support, Zr(NO3)4·5H2O and calcium nitrate were dissolved in deionized water in a certain proportion. After complete dissolution, a mixed solution of zirconium nitrate and calcium nitrate was obtained. The mixed solution of zirconium nitrate and calcium nitrate was mixed with 10g of hierarchical porous hydrogen-type molecular sieve and impregnated at room temperature for 24h. After filtration, the obtained solid was dried at 110℃ for 12h and then calcined at 550℃ for 4h to obtain a bimetallic modified hierarchical porous molecular sieve. The total loading of zirconium oxide and calcium oxide on the catalyst was 3wt%. The molar ratio of Zr and Ca is shown in Table 3.

[0062] The isomerization reaction conditions for 2,5-dichlorotoluene were the same as those in Example 1. The effect of the metal molar ratio in the catalyst on the isomerization reaction of 2,5-dichlorotoluene catalyzed by bimetallic modified hierarchical hydrogen molecular sieves was investigated by changing the metal molar ratio in the catalyst. The results are shown in Table 3. It can be seen that, compared with C-Hβ-15, the supported bimetallic Zr-Ca can effectively improve the catalytic activity of the catalyst. With the decrease of the Zr / Ca molar ratio, the conversion of 2,5-dichlorotoluene first increases and then decreases; among them, when the Zr and Ca molar ratio is 7:3, the catalyst has the best catalytic performance, with a conversion rate of 49.81% for 2,5-dichlorotoluene, a selectivity of 19.83% for 2,6-dichlorotoluene, and a selectivity of 13.02% for 2,4-dichlorotoluene.

[0063] Table 3. Effect of metal molar ratio on feed conversion rate and product selectivity

[0064]

[0065] Note: A Zr:Ca molar ratio of 10:0 indicates a zirconium oxide loading of 3 wt%, and a Zr:Ca molar ratio of 0:10 indicates a calcium oxide loading of 3 wt%.

[0066] Example 4

[0067] The isomerization reaction conditions for 2,5-dichlorotoluene were the same as those in Example 1, using a 7Zr:3Ca-Hβ catalyst (a bimetallic modified hierarchical porous hydrogen molecular sieve with a Zr:Ca molar ratio of 7:3 prepared in Example 3), and a mass hourly space velocity (HHSV) of 0.8 hr for 2,5-dichlorotoluene. -1 When the carrier gas N2 flow rate was 10.87 mL / min / gcat, the reaction temperature was changed to 330℃, 340℃, 350℃, 360℃ and 370℃ to investigate the effect of reaction temperature on the isomerization reaction of 2,5-dichlorotoluene catalyzed by modified Hβ molecular sieve. The reaction results are shown in Table 4.

[0068] The results show that with increasing reaction temperature, the conversion of 2,5-dichlorotoluene initially increases and then decreases, while the selectivity for 2,4-dichlorotoluene and 2,6-dichlorotoluene gradually decreases. Specifically, the modified Hβ molecular sieve catalyst exhibits the best catalytic activity for the isomerization reaction of 2,5-dichlorotoluene at a reaction temperature of 350℃, achieving the highest conversion rate of 49.72% for 2,5-dichlorotoluene, a selectivity of 19.73% for 2,6-dichlorotoluene, and a selectivity of 13.06% for 2,4-dichlorotoluene.

[0069] Table 4. Effect of reaction temperature on feed conversion rate and product selectivity

[0070]

[0071] Example 5

[0072] The isomerization reaction conditions for 2,5-dichlorotoluene were the same as those in Example 1, using a 7Zr:3Ca-Hβ catalyst, a N2 carrier gas flow rate of 10.87 mL / min / gcat, and a reaction temperature of 350 °C. The mass hourly space velocity (WHSV) of the 2,5-dichlorotoluene feedstock was varied to 0.3 hr. -1 0.4hr -1 0.6hr -1 0.8hr -1 1.0hr -1 The effect of feed mass hourly space velocity on the isomerization reaction of 2,5-dichlorotoluene catalyzed by modified Hβ molecular sieve was investigated. The reaction results are shown in Table 5.

[0073] Experimental results show that when the mass hourly space velocity of the raw material increases from 0.3 hr...-1 Increase to 1.0hr -1 At that time, the conversion rate of 2,5-dichlorotoluene gradually decreased from 60.21% to 39.29%. This was because the increase in feed mass hourly space velocity (MHSV) shortened the contact time between the feed and the catalyst, leading to a decrease in conversion rate. Meanwhile, the selectivity of 2,6-dichlorotoluene, 2,4-dichlorotoluene, and dichlorotoluene all increased with increasing feed MHSV. This indicates that while a lower feed MHSV results in a higher 2,5-dichlorotoluene conversion, it also exacerbates side reactions, reducing the degree of isomerization of 2,5-dichlorotoluene and the number of dichlorotoluene isomers, thus generating more dichlorobenzene and other byproducts.

[0074] When the mass hourly space velocity of the raw material is 0.4 hr -1 At this point, it exhibits good catalytic activity. The conversion rate of 2,5-dichlorotoluene is 57.47%, the selectivity for 2,6-dichlorotoluene is 18.77%, and the selectivity for 2,4-dichlorotoluene is 13.31%.

[0075] Table 5. Effects of feedstock mass hourly velocity on feedstock conversion rate and product selectivity

[0076]

[0077]

[0078] Example 6

[0079] The isomerization reaction conditions for 2,5-dichlorotoluene were the same as those in Example 1, using a 7Zr:3Ca-Hβ catalyst and a mass hourly space velocity (WHSV) of 0.4 hr for the 2,5-dichlorotoluene feedstock. -1 The reaction temperature was 350℃. The effect of the carrier gas N2 flow rate on the isomerization reaction of 2,5-dichlorotoluene catalyzed by modified Hβ molecular sieve was investigated when the carrier gas flow rate was changed to 6.52 mL / min / gcat, 10.87 mL / min / gcat, 15.22 mL / min / gcat, and 19.57 mL / min / gcat. The reaction results are shown in Table 6.

[0080] Experimental results show that when the carrier gas N2 flow rate increases from 6.52 mL / min / gcat to 19.57 mL / min / gcat, the conversion rate of 2,5-dichlorotoluene gradually decreases from 59.14% to 45.73%, while the selectivity for 2,6-dichlorotoluene, 2,4-dichlorotoluene, and dichlorotoluene increases with increasing carrier gas flow rate. This indicates that a higher carrier gas flow rate is more conducive to the isomerization reaction and inhibits side reactions, thus generating more dichlorotoluene isomers. However, excessively high carrier gas flow rates can also significantly reduce the catalytic activity of the catalyst.

[0081] When the carrier gas N2 flow rate is 6.52 mL / min / gcat, good catalytic activity is observed. At this rate, the conversion rate of 2,5-dichlorotoluene is 59.14%, the selectivity for 2,6-dichlorotoluene is 17.91%, and the selectivity for 2,4-dichlorotoluene is 14.15%.

[0082] Table 6. Effect of carrier gas flow rate on feed conversion rate and product selectivity

[0083]

Claims

1. A process for the catalytic isomerization of 2,5-dichlorotoluene to produce 2,4-dichlorotoluene and 2,6-dichlorotoluene, characterized in that: The carrier of the 2,5-dichlorotoluene isomerization catalyst is a hierarchical pore hydrogen type molecular sieve, the active component is zirconium oxide, the cocatalyst is an alkaline earth metal oxide, the total loading of the zirconium oxide and the alkaline earth metal oxide is 1-5 wt%, the molar ratio of zirconium to the alkaline earth metal is 10:0-0:10, and neither is 0; the hierarchical pore hydrogen type molecular sieve is a hierarchical pore hydrogen type molecular sieve obtained by modifying a hydrogen type molecular sieve with an organic acid; and the alkaline earth metal is Ca. The isomerization of 2,5-dichlorotoluene is carried out at a reaction temperature of 330-370℃, using 2,5-dichlorotoluene as raw material, N2 as carrier gas, 2,5-dichlorotoluene isomerization catalyst as catalyst, the mass space velocity of raw material being 0.3-1.0 h -1 -1, and the flow rate of carrier gas being 6.5-20 mL / min / gcat, to produce 2,4-dichlorotoluene and 2,6-dichlorotoluene. The hierarchical pore hydrogen type molecular sieve is prepared by the following method: immersing a hydrogen type molecular sieve in an organic acid aqueous solution at a temperature of 70-90°C for 1-3 h, filtering, washing the obtained solid with deionized water until neutral, drying at a temperature of 100-120°C, and calcining at a temperature of 550°C for 2-4 h to obtain the hierarchical pore hydrogen type molecular sieve.

2. The process for the catalytic isomerization of 2,5-dichlorotoluene to produce 2,4-dichlorotoluene and 2,6-dichlorotoluene according to claim 1, characterized in that: The hydrogen type molecular sieve is Hß molecular sieve.

3. The process for the catalytic isomerization of 2,5-dichlorotoluene to produce 2,4- dichlorotoluene and 2,6-dichlorotoluene according to claim 1, characterized in that: The concentration of the organic acid aqueous solution is 5-40 wt%; and the organic acid is any one of acetic acid, citric acid, and oxalic acid.

4. The process for the catalytic isomerization of 2,5-dichlorotoluene to produce 2,4- dichlorotoluene and 2,6-dichlorotoluene according to claim 1, characterized in that: The concentration of the organic acid aqueous solution is 15 wt%.

5. The process for the catalytic isomerization of 2,5-dichlorotoluene to produce 2,4-dichlorotoluene and 2,6-dichlorotoluene according to claim 4, characterized in that: The organic acid is oxalic acid.

6. The process for the catalytic isomerization of 2,5-dichlorotoluene to produce 2,4- dichlorotoluene and 2,6-dichlorotoluene according to claim 4, characterized in that: The total loading of the zirconium oxide and the alkaline earth metal oxide is 3 wt%; and the molar ratio of zirconium to the alkaline earth metal is 7:3-3:

7.

7. The process for the catalytic isomerization of 2,5-dichlorotoluene to produce 2,4- dichlorotoluene and 2,6-dichlorotoluene according to claim 1, characterized in that: The molar ratio of zirconium to the alkaline earth metal is 7:3-5:

5.

8. The process for the catalytic isomerization of 2,5-dichlorotoluene to produce 2,4- dichlorotoluene and 2,6-dichlorotoluene according to claim 7, characterized in that: The molar ratio of zirconium to the alkaline earth metal is 7:

3.

9. Process for the catalytic isomerization of 2,5-dichlorotoluene to produce 2,4- dichlorotoluene and 2,6-dichlorotoluene according to claim 8, characterized in that: The alkaline earth metal oxide is CaO.

10. The process for the catalytic isomerization of 2,5-dichlorotoluene to produce 2,4- dichlorotoluene and 2,6-dichlorotoluene according to claim 1, characterized in that: The preparation method of the 2,5-dichlorotoluene isomerization catalyst comprises the following steps:

11. The process for the catalytic isomerization of 2,5-dichlorotoluene to produce 2,4-dichlorotoluene and 2,6-dichlorotoluene according to claim 1, characterized in that: Step (1), immersing a hydrogen type molecular sieve in an organic acid aqueous solution at a temperature of 70-90°C for 1-3 h, filtering, washing the obtained solid with deionized water until neutral, drying at a temperature of 100-120°C, and calcining at a temperature of 550°C for 2-4 h to obtain a hierarchical pore hydrogen type molecular sieve; Step (2), dissolving Zr(NO3)4·5H2O and an alkaline earth metal nitrate in deionized water to obtain a mixed solution; mixing the mixed solution with the hierarchical pore hydrogen type molecular sieve, impregnating for 12-24 h, filtering, drying the solid at a temperature of 110-120°C, and calcining at a temperature of 450-550°C for 3-5 h to obtain a 2,5-dichlorotoluene isomerization catalyst. The reaction temperature is 340-360°C.

12. The process for the catalytic isomerization of 2,5-dichlorotoluene to produce 2,4- dichlorotoluene and 2,6-dichlorotoluene according to claim 1, characterized in that: The reaction temperature is 350°C.

13. The process for the catalytic isomerization of 2,5-dichlorotoluene to produce 2,4-dichlorotoluene and 2,6-dichlorotoluene according to claim 12, characterized in that: ​ 14. The process for the catalytic isomerization of 2,5-dichlorotoluene to produce 2,4- dichlorotoluene and 2,6-dichlorotoluene according to claim 1, characterized in that: The mass space velocity of the raw material is 0.4-0.8 h -1 ; the flow rate of the carrier gas is 6.5-7 mL / min / gcat.

15. The process for the catalytic isomerization of 2,5-dichlorotoluene to produce 2,4-dichlorotoluene and 2,6-dichlorotoluene according to claim 14, characterized in that: The mass space velocity of the raw material is 0.4 h -1 ; the flow rate of the carrier gas is 6.5-7 mL / min / gcat.

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