Toluene disproportionation catalyst precursor, catalyst and preparation method and application thereof

Abstract

The invention discloses a toluene disproportionation catalyst precursor, a toluene disproportionation catalyst and a preparation method and application of the toluene disproportionation catalyst. The toluene disproportionation catalyst precursor comprises the following components in parts by weight: (1) 10-90 parts of a zeolite molecular sieve with the SiO2 / Al2O3 molar ratio of 10-100; (2) 10 to 90 parts of pseudo-boehmite; (3) 0.01-1 part of metal elements selected from VIB group elements in the periodic table of elements; the pseudo-boehmite contains a beta-Al2O3. 3H2O crystal phase, and the crystal phase of the pseudo-boehmite is a crystal phase. The catalyst prepared from the precursor is used for toluene disproportionation reaction, and has the characteristics of high reaction conversion rate, high selectivity of products benzene and C8 aromatic hydrocarbon and the like under the condition of poor quality of raw materials.

Description

Technical Field

[0001] This invention relates to the field of catalysis technology, specifically to a toluene disproportionation catalyst precursor, the catalyst, its preparation method, and its application. Background Technology

[0002] p-Xylene is an important organic raw material, mainly used in the production of purified terephthalic acid (PTA), which is a raw material for polyester production. Major polyester varieties include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyarylates, with applications spanning the chemical fiber industry, packaging industry, electronics, medical and health industries, and construction. Due to the surge in demand for polyester, the added value of p-xylene, as a raw material for polyester, has also increased. Industrially, the toluene disproportionation unit is one of the most important processes for producing xylene in aromatic hydrocarbon complexes. This technology uses toluene, which has a relatively low added value but high yield, as a raw material. Under the action of a catalyst, toluene undergoes a disproportionation reaction to produce the main products, benzene and xylene, thus solving the problem of toluene overproduction and meeting market demand.

[0003] Currently, most catalysts used for toluene disproportionation are molecular sieves that provide catalytic activity. Reported molecular sieves include mordenite (MOR), ZSM-5, SSZ-33, and TNU-9. During catalyst synthesis, they are typically bonded with inorganic oxides and selectively loaded with metal components to improve catalyst activity and lifespan. CN101124186A uses nickel-modified mordenite as a catalyst. The catalyst first requires moderate sulfidation to passivate the active nickel before being used in the toluene disproportionation reaction. This catalyst contains the precious metal platinum, resulting in high production costs.

[0004] CN101898152B discloses a toluene disproportionation and alkyl transfer catalyst. The catalyst comprises a hydrogen-form Y / Beta / ZSM-12 composite molecular sieve and an inorganic refractory oxide, with a loaded metal active component. In this method, the composite molecular sieve is not simply mechanically mixed, but rather synthesized using a novel preparation method to simultaneously possess the three crystalline phases of Y / Beta / ZSM-12. The catalyst prepared by this method exhibits high toluene conversion and selectivity for benzene + C8A (B+C8A).

[0005] CN115190873A discloses a toluene disproportionation catalyst that uses a novel zeolite molecular sieve, UZM-44, as a support. Through ion exchange, metal loading, and support surface modification, the molar ratio of p-xylene to xylene in the product is enhanced, and the loss of benzene rings is reduced.

[0006] All of the above methods require modification of zeolite molecular sieves, or even the synthesis of novel zeolite materials, to achieve the goal of increasing xylene production. However, these preparation methods are relatively complex and have high production costs. Furthermore, given the increasing scarcity of petroleum resources, maximizing the utilization of inferior chemical raw materials has become one of the urgent problems to be solved in refinery upgrading and transformation. In the toluene disproportionation unit, crude toluene from the extraction unit has gradually replaced the reflux component of the toluene tower as the source of toluene feedstock for the disproportionation reaction. Crude toluene contains non-aromatic hydrocarbons (such as C8 alkanes, C9 alkanes, methyl ethyl cyclopentane, and dimethyl cyclohexane) with boiling points close to toluene. In the toluene disproportionation reaction, these hydrocarbons compete with toluene for catalyst active sites, reducing toluene conversion and hindering the long-term stable operation of the disproportionation catalyst, posing a significant challenge to existing disproportionation technologies.

[0007] Therefore, given the increasingly deteriorating quality of raw materials, there is a need for a catalyst that can be applied to the stringent reaction conditions where the disproportionation reaction feedstock contains heavy non-aromatic hydrocarbons, has a high toluene conversion rate, and exhibits good selectivity for benzene and C8 aromatic hydrocarbons. Summary of the Invention

[0008] The technical problem this invention aims to solve is to overcome the problems of poor catalyst activity and low selectivity of target products in existing toluene disproportionation technologies when the disproportionation feedstock contains non-aromatic hydrocarbons or other impurities with boiling points close to toluene. This invention provides a new toluene disproportionation catalyst precursor, catalyst, its preparation method, and its applications. The catalyst prepared from this precursor, when used in the toluene disproportionation reaction, exhibits high reaction conversion rate and high selectivity for benzene and C8 aromatic hydrocarbons, even under conditions of inferior feedstock.

[0009] The first aspect of the present invention provides a toluene disproportionation catalyst precursor, comprising, by weight parts:

[0010] (1) 10-90 parts of zeolite molecular sieve with a SiO2 / Al2O3 molar ratio of 10-100;

[0011] (2) 10-90 parts of pseudoboehmite;

[0012] (3) 0.01 to 1 part of metallic elements selected from Group VIB of the periodic table;

[0013] The pseudoboehmite contains the β-Al2O3·3H2O crystalline phase.

[0014] In the above technical solution, the zeolite molecular sieve is a silica-alumina molecular sieve with a ten-membered ring or twelve-membered ring structure, preferably at least one of mordenite, ZSM-5 molecular sieve, Beta molecular sieve, and Y molecular sieve.

[0015] In the above technical solution, the molar ratio of SiO2 / Al2O3 in the zeolite molecular sieve is 15 to 100, preferably 20 to 40.

[0016] In the above technical solution, the weight percentage of the zeolite molecular sieve is preferably 60-80 parts; the weight percentage of the pseudoboehmite is preferably 20-40 parts.

[0017] In the above technical solution, the β-Al2O3·3H2O crystalline phase content in the pseudoboehmite is 5-30%, preferably 10-20%, for example 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc., and any value within any range formed by any two of these values.

[0018] In the above technical solution, the XRD pattern of the pseudoboehmite contains at least two β-Al₂O₃·3H₂O characteristic peaks with 2θ values ​​of 18.61° (±0.05°) and 20.27° (±0.05°), preferably at least two β-Al₂O₃·3H₂O characteristic peaks with 2θ values ​​of 18.61° (±0.05°), 20.27° (±0.05°), 27.82° (±0.05°), 40.60° (±0.05°), and 53.14° (±0.05°), where 2θ represents the position of the diffraction peak in the XRD pattern.

[0019] In the above technical solution, preferably, the pseudoboehmite has a dual-pore distribution, wherein the most probable pore size of the small pore is 1-7 nm and the most probable pore size of the large pore is 8-50 nm. More preferably, the most probable pore size of the small pore is 3-6 nm and the most probable pore size of the large pore is 9-20 nm.

[0020] In the above technical solution, the metal element is selected from at least one of chromium, molybdenum, and tungsten.

[0021] A second aspect of the present invention provides a toluene disproportionation catalyst, wherein the catalyst is prepared by calcination of the toluene disproportionation catalyst precursor.

[0022] In the above technical solution, the catalyst has a dual-pore distribution, wherein the most probable pore size of the small pore is 1-4 nm and the most probable pore size of the large pore is 5-10 nm.

[0023] In the above technical solution, the calcination conditions are: temperature of 400-550℃ and time of 1-5 hours.

[0024] A third aspect of the present invention provides a method for preparing the above-mentioned toluene disproportionation catalyst precursor, comprising the following steps:

[0025] Molecular sieves, pseudoboehmite, and a metal source are mixed, shaped, and dried to obtain a toluene disproportionation catalyst precursor.

[0026] In the above preparation method, the zeolite molecular sieve is a silica-alumina molecular sieve with a ten-membered or twelve-membered ring structure, preferably at least one of mordenite, ZSM-5 molecular sieve, Beta molecular sieve, and Y molecular sieve.

[0027] In the above preparation method, the molar ratio of SiO2 / Al2O3 in the zeolite molecular sieve is 15 to 100, preferably 20 to 40.

[0028] In the above preparation method, the pseudoboehmite contains the β-Al2O3·3H2O crystalline phase.

[0029] In the above preparation method, the content of β-Al2O3·3H2O crystalline phase in the pseudoboehmite is 5-30%, preferably 10-20%.

[0030] In the above preparation method, the XRD pattern of the pseudoboehmite contains at least two β-Al₂O₃·3H₂O characteristic peaks with 2θ values ​​of 18.61° (±0.05°) and 20.27° (±0.05°), preferably at least two β-Al₂O₃·3H₂O characteristic peaks with 2θ values ​​of 18.61° (±0.05°), 20.27° (±0.05°), 27.82° (±0.05°), 40.60° (±0.05°), and 53.14° (±0.05°), where 2θ is the position of the diffraction peak in the XRD pattern.

[0031] In the above preparation method, preferably, the pseudoboehmite has a dual-pore distribution, wherein the most probable pore size of the small pore is 1-7 nm and the most probable pore size of the large pore is 8-50 nm. Preferably, the most probable pore size of the small pore is 3-6 nm and the most probable pore size of the large pore is 9-20 nm.

[0032] In the above preparation method, the metal source is selected from the soluble salt of the corresponding metal, wherein the metal is selected from at least one of chromium, molybdenum, and tungsten.

[0033] In the above preparation method, there is no special way to add the metal. It can be loaded onto the molecular sieve first and then formed with boehmite, or loaded onto the boehmite first and then formed with the molecular sieve, or the molecular sieve and boehmite can be mechanically mixed first and then the metal solution can be added for forming.

[0034] In the above preparation method, an acid solution may be added before the catalyst is formed, with a mass concentration of 10% or more, more preferably 50% or more. The acid solution is selected from at least one of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, citric acid, oxalic acid, formic acid, and acetic acid.

[0035] In the above preparation method, the drying conditions are: temperature 100-150℃, time 0.5-6 hours.

[0036] The fourth aspect of the present invention provides a method for preparing the above-mentioned toluene disproportionation catalyst, comprising: calcining the toluene disproportionation catalyst precursor to obtain the toluene disproportionation catalyst.

[0037] In the above preparation method, the calcination conditions are: temperature of 400-550℃ and time of 1-5 hours.

[0038] The fifth aspect of the present invention provides the application of the toluene disproportionation catalyst described in the second aspect or the catalyst prepared by the method provided in the fourth aspect for the synthesis of benzene and C8 aromatics by the toluene disproportionation reaction.

[0039] In the above technical solution, the application includes: under hydrogen-exposed conditions, toluene feedstock comes into contact with a catalyst to undergo a toluene disproportionation reaction to produce benzene and C8 aromatic hydrocarbons.

[0040] In the above technical solution, the reaction conditions are: reaction temperature 300–500℃, reaction pressure 0.1–5 MPa, hydrogen-to-hydrocarbon molar ratio 0.2–6, and feed space velocity 1–8 h⁻¹. -1 Preferably, the reaction temperature is 400–500℃, the reaction pressure is 1–3 MPa, the hydrogen / toluene molar ratio is 0.5–4, and the feed space velocity is 1–4 h⁻¹. -1 .

[0041] In the above technical solution, the toluene raw material contains non-aromatic hydrocarbons, specifically C7-C6 hydrocarbons with boiling points between toluene and ethylbenzene. 10 Non-aromatic hydrocarbons.

[0042] In the above technical solution, the weight content of non-aromatic hydrocarbons in the toluene raw material is 0.1-30%, preferably 0.1-10%.

[0043] Compared with the prior art, the present invention has the following advantages:

[0044] In existing toluene disproportionation technologies, the catalysts cannot operate under harsh conditions where the feedstock contains heavy non-aromatic hydrocarbons, and the selectivity for xylene is low due to side reactions, with C9 byproducts being produced. +A. High selectivity, but low yield of the target product. The inventors discovered that the β-Al₂O₃·3H₂O crystalline phase in the pseudoboehmite of the catalyst precursor provided by this invention, at a specific content of 5–30% (especially 10–20%), preferably combined with the specific biporous distribution properties of pseudoboehmite, and in conjunction with molecular sieves and metal phases, can significantly improve the catalytic activity of the resulting catalyst and reduce the residence time of the target product on the catalyst surface, thereby reducing the self-disproportionation of xylene to C₉. + A. The opportunity for byproducts increases the selectivity of benzene and C8 aromatics. Attached Figure Description

[0045] Figure 1 The image shows the XRD pattern of boehmite A from Example 1. Detailed Implementation

[0046] The technical solution of the present invention will be further illustrated below through embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0047] In this invention, the pseudoboehmite used in the embodiments was obtained through commercial procurement. The crystal phase structure and pore structure of the pseudoboehmite were obtained through characterization testing methods.

[0048] The crystal phase structure determination in this invention was performed using X-ray powder diffraction (XRD) on a Rigaku D / max-1400 X-ray diffractometer. Instrument operating conditions: Cu target, Kα radiation source, graphite monochromator, tube voltage 40 kV, tube current 40 mA, scanning range 5°–50°, and scanning speed 2° / min. The content of the β-Al₂O₃·3H₂O crystalline phase was determined as a percentage of the specific phase in the multiphase mixture using the quantitative phase method of X-ray diffraction.

[0049] The specific surface area and pore structure characterization in this invention are determined by nitrogen adsorption-desorption method. High-purity nitrogen is used as the adsorbate, and the test is carried out at -196℃. Before the test, a vacuum pretreatment at 350℃ for 4 hours is required. The specific surface area is calculated using the BET formula, the external surface area is calculated using the t-plot method, and the pore structure analysis is performed using the BJH method.

[0050] In this invention, the toluene conversion rate (T) of the reaction is... 转 (100%), selectivity of benzene and C8 aromatics (S B+C8A (100%) as follows:

[0051]

[0052] Example 1

[0053] Take 70g of ZSM-5 molecular sieve with a SiO2 / Al2O3 molar ratio of 25, mix it with 30g of pseudoboehmite A, add 3ml of 65wt% nitric acid and 60g of 0.3% ammonium heptamolybdate tetrahydrate solution, knead it evenly, and then extrude it into strips. Dry it at 120℃ for 4 hours and calcine it at 540℃ for 3 hours to obtain catalyst A.

[0054] The β-Al2O3·3H2O crystalline phase content in pseudoboehmite A is 14.69%. In terms of pore structure distribution, the most probable pore diameter of the micropores is 5.7 nm, and the most probable pore diameter of the macropores is 12 nm.

[0055] Figure 1 The image shows the XRD pattern of boehmite containing the β-Al₂O₃·3H₂O crystalline phase, with characteristic peaks of β-Al₂O₃·3H₂O at 18.64°, 20.25°, 27.82°, 40.59°, and 53.14°.

[0056] Regarding the pore structure distribution of catalyst A, the most probable pore diameter of the micropores is 3.5 nm, and the most probable pore diameter of the macropores is 5.8 nm.

[0057] Example 2

[0058] Take 70g of ZSM-5 molecular sieve with a SiO2 / Al2O3 molar ratio of 25, mix it with 30g of pseudoboehmite B, add 3ml of 65wt% nitric acid and 60g of 0.3% ammonium heptamolybdate tetrahydrate solution, knead it evenly, and then extrude it into strips. Dry it at 120℃ for 4 hours and calcine it at 540℃ for 3 hours to obtain catalyst B.

[0059] The β-Al₂O₃·3H₂O crystalline phase content in pseudoboehmite B is 16.98%. In terms of pore structure distribution, the most probable pore diameter for small pores is 5.5 nm, and the most probable pore diameter for large pores is 12.5 nm. The XRD pattern is similar to that of Example 1.

[0060] Regarding the pore structure distribution of catalyst B, the most probable pore diameter for the micropores is 3.9 nm, and the most probable pore diameter for the macropores is 6.5 nm.

[0061] Example 3

[0062] Take 70g of ZSM-5 molecular sieve with a SiO2 / Al2O3 molar ratio of 25, mix it with 30g of pseudoboehmite C, add 3ml of 65wt% nitric acid and 60g of 0.3% ammonium heptamolybdate tetrahydrate solution, knead it evenly, and then extrude it into strips. Dry it at 120℃ for 4 hours and calcine it at 540℃ for 3 hours to obtain catalyst C.

[0063] The β-Al₂O₃·3H₂O crystalline phase content in pseudoboehmite C is 12%. In terms of pore structure distribution, the most probable pore diameter of the micropores is 5.4 nm, and the most probable pore diameter of the macropores is 11.9 nm. The XRD pattern is similar to that of Example 1.

[0064] Regarding the pore structure distribution of catalyst C, the most probable pore diameter for micropores is 3.7 nm, and the most probable pore diameter for macropores is 6.0 nm.

[0065] Example 4

[0066] Take 70g of ZSM-5 molecular sieve with a SiO2 / Al2O3 molar ratio of 38, mix it evenly with 30g of pseudoboehmite A, add 3ml of 65wt% nitric acid and 60g of 0.3% ammonium heptamolybdate tetrahydrate solution, knead evenly, extrude into strips, dry at 120℃ for 4 hours and calcine at 540℃ for 3 hours to obtain catalyst D.

[0067] Regarding the pore structure distribution of catalyst D, the most probable pore diameter for the micropores is 3.5 nm, and the most probable pore diameter for the macropores is 5.5 nm.

[0068] Example 5

[0069] Take 60g of ZSM-5 molecular sieve with a SiO2 / Al2O3 molar ratio of 25, mix it evenly with 40g of pseudoboehmite A, add 3ml of 65wt% nitric acid and 60g of 0.15% ammonium heptamolybdate tetrahydrate solution, knead evenly, extrude into strips, dry at 120℃ for 4 hours and calcine at 540℃ for 3 hours to obtain catalyst E.

[0070] Regarding the pore structure distribution of catalyst E, the most probable pore diameter of the micropores is 3.5 nm, and the most probable pore diameter of the macropores is 5.8 nm.

[0071] Example 6

[0072] Take 65g of MOR molecular sieve with a SiO2 / Al2O3 molar ratio of 22, mix it with 35g of pseudoboehmite A, add 3ml of 65wt% nitric acid and 60g of 0.25% ammonium heptamolybdate tetrahydrate solution, knead it evenly, and then extrude it into strips. Dry it at 120℃ for 4 hours and calcine it at 540℃ for 3 hours to obtain catalyst F.

[0073] Regarding the pore structure distribution of catalyst F, the most probable pore diameter for micropores is 3.8 nm, and the most probable pore diameter for macropores is 6.2 nm.

[0074] Example 7

[0075] Take 70 g of Beta molecular sieve with a SiO2 / Al2O3 molar ratio of 26, mix it evenly with 30 g of pseudoboehmite A, add 3 mL of 65 wt% nitric acid and 60 g of 0.28% ammonium heptamolybdate tetrahydrate solution, knead evenly, extrude into strips, dry at 120℃ for 4 hours and calcine at 540℃ for 3 hours to obtain catalyst G.

[0076] Regarding the pore structure distribution of catalyst G, the most probable pore diameter for micropores is 3.5 nm, and the most probable pore diameter for macropores is 6.5 nm.

[0077] Example 8

[0078] Take 72g of Y molecular sieve with a SiO2 / Al2O3 molar ratio of 28, mix it with 28g of pseudoboehmite A, add 3ml of 65wt% nitric acid and 60g of 0.26% ammonium heptamolybdate tetrahydrate solution, knead it evenly, and then extrude it into strips. Dry it at 120℃ for 4 hours and calcine it at 540℃ for 3 hours to obtain catalyst H.

[0079] Regarding the pore structure distribution of catalyst H, the most probable pore diameter for micropores is 3.8 nm, and the most probable pore diameter for macropores is 7.0 nm.

[0080] Example 9

[0081] Take 70g of ZSM-5 molecular sieve with a SiO2 / Al2O3 molar ratio of 25, mix it with 30g of pseudoboehmite D, add 3ml of 65wt% nitric acid and 60g of 0.3% ammonium heptamolybdate tetrahydrate solution, knead it evenly, and then extrude it into strips. Dry it at 120℃ for 4 hours and calcine it at 540℃ for 3 hours to obtain catalyst I.

[0082] The β-Al₂O₃·3H₂O crystalline phase content in pseudoboehmite D is 5%. In terms of pore structure distribution, the most probable pore diameter for small pores is 4.9 nm, and the most probable pore diameter for large pores is 11.5 nm. The XRD pattern is similar to that of Example 1.

[0083] Regarding the pore structure distribution of catalyst I, the most probable pore diameter for the micropores is 3.4 nm, and the most probable pore diameter for the macropores is 5.9 nm.

[0084] Example 10

[0085] Take 70g of ZSM-5 molecular sieve with a SiO2 / Al2O3 molar ratio of 25, mix it with 30g of pseudoboehmite E, add 3ml of 65wt% nitric acid and 60g of 0.3% ammonium heptamolybdate tetrahydrate solution, knead it evenly, and then extrude it into strips. Dry it at 120℃ for 4 hours and calcine it at 540℃ for 3 hours to obtain catalyst J.

[0086] The β-Al₂O₃·3H₂O crystalline phase content in pseudoboehmite E is 30%. In terms of pore structure distribution, the most probable pore diameter of the micropores is 5.2 nm, and the most probable pore diameter of the macropores is 11.2 nm. The XRD pattern is similar to that of Example 1.

[0087] Regarding the pore structure distribution of catalyst J, the most probable pore diameter for the micropores is 3.7 nm, and the most probable pore diameter for the macropores is 6.0 nm.

[0088] Comparative Example 1

[0089] Take 70g of ZSM-5 molecular sieve with a SiO2 / Al2O3 molar ratio of 25, mix it with 30g of pseudoboehmite F, add 3ml of 65wt% nitric acid and 60g of 0.3% ammonium heptamolybdate tetrahydrate solution, knead it evenly, and then extrude it into strips. The catalyst K is obtained by drying at 120℃ for 4 hours and calcining at 540℃ for 3 hours.

[0090] The β-Al2O3·3H2O crystalline phase content in pseudoboehmite F is 0.50%. In terms of pore structure distribution, the most probable pore diameter of the micropores is 5.2 nm, and the most probable pore diameter of the macropores is 12.3 nm.

[0091] Regarding the pore structure distribution of catalyst K, the most probable pore diameter for micropores is 3.2 nm, and the most probable pore diameter for macropores is 5.8 nm.

[0092] Comparative Example 2

[0093] Take 70g of ZSM-5 molecular sieve with a SiO2 / Al2O3 molar ratio of 25, mix it with 30g of pseudoboehmite G, add 3ml of 65wt% nitric acid and 60g of 0.3% ammonium heptamolybdate tetrahydrate solution, knead it evenly, and then extrude it into strips. Dry it at 120℃ for 4 hours and calcine it at 540℃ for 3 hours to obtain catalyst L.

[0094] The β-Al2O3·3H2O crystalline phase content in pseudoboehmite G is 14%. In terms of pore structure distribution, the most probable pore diameter of the micropores is 5.5 nm, and there are no macropores.

[0095] Regarding the pore structure distribution of catalyst L, the most probable pore diameter of the micropores is 3.5 nm, and there is no macropore distribution.

[0096] The performance of catalysts A to L prepared in Examples 1-10 and Comparative Examples 1-2 was evaluated in a fixed-bed reactor for the toluene disproportionation reaction. The conditions were as follows: toluene containing n-octane was used as the feedstock, with a toluene content of 95 wt% and n-octane content of 5 wt%. The catalyst loading was 5 g, and the toluene feed weight hourly space velocity was 3 h⁻¹. -1The reaction hydrogen-to-hydrocarbon molar ratio was 3, and the reaction pressure was 3.0 MPa. The reaction temperature was adjusted to control the toluene conversion rate to approximately 50%, and the evaluation results are shown in Table 1.

[0097] Table 1 Catalytic performance of the examples and comparative examples

[0098]

[0099]

Claims

1. A toluene disproportionation catalyst precursor, comprising, by weight parts: (1) 10-90 parts of zeolite molecular sieve with a SiO2 / Al2O3 molar ratio of 10-100; (2) 10-90 parts of pseudoboehmite; (3) 0.01 to 1 part of metallic elements selected from Group VIB of the periodic table; The pseudoboehmite contains the β-Al2O3·3H2O crystalline phase.

2. The catalyst precursor according to claim 1, characterized in that, The zeolite molecular sieve is a silica-alumina molecular sieve with a ten-membered or twelve-membered ring structure, preferably at least one of mordenite, ZSM-5 molecular sieve, Beta molecular sieve, and Y molecular sieve. And / or, the molar ratio of SiO2 / Al2O3 in the zeolite molecular sieve is 15 to 100; And / or, the metallic element is selected from at least one of chromium, molybdenum, and tungsten.

3. The catalyst precursor according to claim 1, characterized in that, The content of β-Al2O3·3H2O crystalline phase in the pseudoboehmite is 5-30%, preferably 10-20%; And / or, the pseudoboehmite has a dual-pore distribution, wherein the most probable pore size of the small pore is 1-7 nm and the most probable pore size of the large pore is 8-50 nm.

4. A toluene disproportionation catalyst, characterized in that, It is prepared by calcination of the toluene disproportionation catalyst precursor according to any one of claims 1-3.

5. The catalyst according to claim 4, characterized in that, The catalyst has a dual-pore distribution, wherein the most probable pore size of the smaller pore is 1–4 nm and the most probable pore size of the larger pore is 5–10 nm.

6. A method for preparing the toluene disproportionation catalyst precursor according to any one of claims 1-3, comprising the following steps: Molecular sieves, pseudoboehmite, and a metal source are mixed, shaped, and dried to obtain a toluene disproportionation catalyst precursor.

7. A method for preparing a toluene disproportionation catalyst, characterized in that, The catalyst is prepared by calcination of the toluene disproportionation catalyst precursor according to claim 6.

8. The preparation method according to claim 6 or 7, characterized in that, The metal source is selected from the soluble salt of the corresponding metal, wherein the metal is selected from at least one of chromium, molybdenum, and tungsten; And / or, the drying conditions are: temperature 100-150°C, time 0.5-6 hours.

9. The preparation method according to claim 7, characterized in that, The roasting conditions are: temperature of 400-550℃ and time of 1-5 hours.

10. The toluene disproportionation catalyst according to any one of claims 4-5 or the toluene disproportionation catalyst prepared by any one of claims 7-9 is used for the synthesis of benzene and C8 aromatic hydrocarbons by toluene disproportionation reaction.

11. The application according to claim 10, characterized in that, The application includes: under hydrogen-exposed conditions, toluene feedstock comes into contact with a catalyst to undergo a toluene disproportionation reaction to produce benzene and C8 aromatic hydrocarbons.

12. The application according to claim 10, characterized in that, The reaction conditions are as follows: reaction temperature 300–500℃, reaction pressure 0.1–5 MPa, hydrogen-to-hydrocarbon molar ratio 0.2–6, and feed space velocity 1–8 h⁻¹. -1 ; And / or, the toluene feedstock contains non-aromatic hydrocarbons, preferably C7-C6 with boiling points between toluene and ethylbenzene. 10 Non-aromatic hydrocarbons; And / or, the toluene feedstock contains 0.1% to 30% by weight of non-aromatic hydrocarbons.

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