A catalyst for selective hydrogenation and dealkylation of aromatics, its preparation method and application

Abstract

This invention discloses a catalyst for the selective hydrogenation and dealkylation of aromatics, its preparation method, and its applications. The catalyst comprises a composite-modified alumina support, a Group VIII transition metal oxide, and a rare earth metal oxide. Using this catalyst, selective hydrogenation and dealkylation of alkyl aromatics at C2... + Side chain substituents are used for selective end-position removal, effectively utilizing C2. + Side chain substituents increase the production of methyl groups, thereby increasing the yield of polymethyl aromatic hydrocarbons in the product.

Description

Technical Field

[0001] This invention relates to the field of aromatic catalytic conversion, and more specifically to an aromatic selective hydrogenation and dealkylation catalyst, its preparation method, and its application. Background Technology

[0002] Aromatics is an important pillar of the national economy, with a long industrial chain and a wide range of products, serving both the oil and chemical markets. In recent years, China's aromatics industry has experienced rapid development and has become a global center for aromatics investment and production.

[0003] In petrochemical production processes, aromatics mainly originate from catalytic reforming, steam cracking, catalytic cracking, and light hydrocarbon aromatization. Besides producing common light aromatics such as benzene (B), toluene (T), and xylene (X), these processes also produce some C9 / C10 aromatics as byproducts. 10 Aromatics). This part of C9 / C 10 Aromatic hydrocarbons are monocyclic aromatic hydrocarbons containing side-chain substituents. Based on the number of carbon atoms in the substituent, the side-chain substituents can be classified as methyl or C2. + Substituents, such as trimethylbenzene, ethylbenzene, propylbenzene, tetramethylbenzene, etc. C9 / C 10 In addition to polymethyl substituents, aromatic hydrocarbons also contain a large number of C2 substituents. + Side chain substituents, such as in C9 aromatics produced by catalytic reforming, contain 53-54% methylbenzene, 27-28% ethylbenzene, and 8-10% propylbenzene.

[0004] At this stage, this part of C9 / C 10 The main use of aromatics is to increase the production of light aromatics such as BTX. Commonly used technologies include, but are not limited to: (1) Toluene disproportionation and alkyl transfer technology: This technology uses toluene and C9 / C 10 Using aromatics as raw materials, benzene and xylene are produced through methyl transfer reactions and aromatic side-chain hydrogenation and dealkylation reactions. In this technology, the methyl group mainly undergoes inter-aromatic transfer reactions, while the C2 group... + Side chain substituents are removed by hydrogenation dealkylation reaction (Aromatics Technology [M]. Beijing: China Petrochemical Press, 2014: 156-191.), and the common catalyst is metal-modified molecular sieve; (2) Aromatics catalytic hydrogenation dealkylation technology: This technology uses toluene and above alkyl aromatics as raw materials, and removes all side chain substituents, including methyl, through side chain catalytic hydrogenation dealkylation reaction, and C2 + The removal rate of side chain substituents is higher than that of methyl groups, and common catalysts include Cr2O3 / Al2O3 and MoO3 / Al2O3. (Research Progress on Catalysts for Hydrogen Dealkylation of Alkyl Aromatic Hydrocarbons, Industrial Catalysis, 2004, 12(11):1-6.)

[0005] Therefore, it can be seen that in the above-mentioned catalytic conversion of alkyl aromatics, C2 + All side chain substituents are removed by overall hydrogenation to generate the corresponding C2. + Alkanes, if we can target this C2 portion + Selective removal of side-chain substituents at the terminal position, such as selective demethylation of ethyl groups to produce methyl and methane, and selective dealkylation of propyl groups to produce methyl and ethane, can fully utilize the C2 substituent. + Side chain substituents increase the number of methyl groups in the aromatic stream, and the resulting polymethyl aromatics can be introduced into an aromatic complex to increase xylene production and improve the unit's PX output. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention aims to develop a selective hydrogenation dealkylation catalyst for aromatics, its preparation method, and its applications. The catalyst of this invention can selectively hydrogenate and dealkylate alkyl aromatics at C2... + Side chain substituents are used for selective end-position removal, effectively utilizing C2. + Side chain substituents increase the production of methyl groups, thereby increasing the yield of polymethyl aromatic hydrocarbons in the product.

[0007] The first aspect of the present invention provides a catalyst for selective hydrogenation and dealkylation of aromatics, the catalyst comprising a composite modified alumina support, a group VIII transition metal oxide, and a rare earth metal oxide.

[0008] Furthermore, in the catalyst, based on the mass of the catalyst, the mass content of Group VIII transition metal oxide is 0.01% to 1%, the mass content of rare earth metal oxide is 1% to 5%, and the mass content of composite modified alumina support is 94% to 98%.

[0009] Furthermore, the metal in the group VIII transition metal oxide is preferably at least one of Ru, Ir, and Rh; the metal in the rare earth metal oxide is preferably La and / or Ce.

[0010] Furthermore, the composite modified alumina carrier comprises modified alumina and metal oxides.

[0011] Furthermore, the most probable mesopore diameter of the modified alumina in the composite modified alumina carrier is 8–12 nm, and the most probable macropore diameter is 1000–2000 nm. The most probable mesopore diameter of the modified alumina is 30%–200% higher than that of conventional unmodified alumina, while the most probable macropore diameter of the modified alumina is only 20%–70% of that of conventional unmodified alumina.

[0012] Furthermore, the metal oxide in the composite modified alumina carrier is an oxide of an alkali metal and / or an alkaline earth metal, preferably magnesium oxide and / or potassium oxide.

[0013] Furthermore, the mass content of metal oxide in the composite modified alumina carrier is 1% to 5%, and the mass content of modified alumina is 95% to 99%.

[0014] A second aspect of this invention provides a method for preparing the above-mentioned selective hydrogenation and dealkylation catalyst for aromatics, comprising the following steps:

[0015] (1) Preparation of composite modified alumina carrier;

[0016] (2) Take the composite modified alumina support described in step (1), introduce group VIII transition metal salts and rare earth metal salts, dry and calcine to obtain an aromatic selective hydrogenation dealkylation catalyst.

[0017] Further, the preparation method of the composite modified alumina carrier in step (1) includes: treating alumina with steam, then mixing it with a metal salt, and then molding, drying and calcining to obtain the composite modified alumina carrier.

[0018] Further, the molding process described in step (1) can employ conventional molding methods, preferably extrusion molding. During extrusion molding, molding aids, such as at least one of guar gum powder and cellulose, can be added as needed. The amount of the molding aid added is 0.1% to 10% of the mass of alumina. After molding, the composite modified alumina carrier can be obtained by processing under conventional drying and calcination conditions in the art. Preferably, the drying temperature is 90–150°C, and the drying time is 2–10 hours; the calcination temperature is 400–600°C, and the calcination time is 2–10 hours.

[0019] Furthermore, the alumina used in step (1) is preferably γ-Al2O3. The mesoporous most probable pore size of γ-Al2O3 is 4-6 nm, and the macroporous most probable pore size is 3000-5000 nm.

[0020] Furthermore, the temperature of the steam treatment in step (1) is 300-500°C, and the treatment time is 2-5 hours.

[0021] Further, the metal salt in step (1) is an alkali metal and / or alkaline earth metal salt, preferably at least one of magnesium nitrate and potassium nitrate. The amount of the metal salt added, calculated as oxide, is 1% to 5% of the mass of the composite modified alumina carrier.

[0022] Furthermore, the method of introducing Group VIII transition metal salts and rare earth metal salts in step (2) can be a conventional method in the art, preferably an equal volume impregnation method.

[0023] Further, the Group VIII transition metal mentioned in step (2) is selected from at least one of Ru, Ir and Rh.

[0024] Furthermore, the rare earth metals mentioned in step (2) are preferably La and / or Ce.

[0025] Further, in step (2), the drying temperature is 90-150℃ and the drying time is 2-10 hours; the calcination temperature is 400-600℃ and the calcination time is 2-10 hours.

[0026] Further, in the aromatic selective hydrogenation dealkylation catalyst obtained in step (2), the group VIII transition metal salt, calculated as metal oxide, accounts for 0.01% to 1% of the catalyst mass, and the rare earth metal salt, calculated as metal oxide, accounts for 1% to 5% of the catalyst mass.

[0027] The third aspect of this invention provides the application of the above-mentioned aromatic selective hydrogenation dealkylation catalyst in the selective hydrogenation dealkylation reaction of alkyl aromatics.

[0028] Furthermore, the reaction conditions for the selective hydrogenation and dealkylation reaction of the aromatics are: a temperature of 350–550 °C, a pressure of 2–5 MPa, and a mass hourly space velocity (HSV) of alkyl aromatics of 1–10 h⁻¹. -1 The molar ratio of hydrogen to alkyl aromatics is 2 to 6.

[0029] Furthermore, the alkyl aromatic hydrocarbon is C2-containing. + Aromatic hydrocarbons with side-chain substituents (C2 and above side-chain substituents), preferably ethylbenzene.

[0030] Compared with the prior art, the advantages of this invention are:

[0031] The aromatic selective hydrogenation dealkylation catalyst provided by this invention can fully utilize C2 + Side-chain substituents increase methyl production, significantly improving the methyl / benzene ring ratio in the product. Introducing the produced polymethyl aromatics into an aromatics complex can increase xylene production and improve PX yield. Specifically, the modified alumina of this invention exhibits increased mesoporous structure and reduced macroporous structure, which improves the diffusion properties of raw materials and products and reduces side-chain demethylation side reactions.

[0032] In the preparation method of this invention, treating the alumina support with steam can open up the pores and improve the catalyst diffusion performance. Introducing metals into the steam-modified alumina can modify the acidity of the catalyst and suppress C2. + The side chain is completely removed from the side reaction. Detailed Implementation

[0033] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0034] The raw materials used in the embodiments and comparative examples of this invention are commercially available and have an analytical grade (AR) purity.

[0035] The most probable mesopore size of the catalyst was determined by measuring the nitrogen physical adsorption-desorption isotherm using a physical adsorption instrument (such as the TriStar 3000 physical adsorption instrument from Micron Instruments, USA), and then calculated using the BJH method for desorption curves. The experimental conditions for the catalyst were: measurement temperature -196℃, and the molecular sieve pretreated under vacuum at 300℃ for 10 hours before measurement. The most probable macropore size was determined using a mercury porosimeter (such as the PoreMaster mercury porosimeter from Anton Pacanta, USA). Based on the Washburn equation, which states that the size of the pore into which mercury can enter conforms to the pore size, different pressures can be controlled to measure the volume of mercury injected into the pore, thus obtaining the cumulative distribution curve or differential curve corresponding to different pressures.

[0036] Example 1

[0037] 100g of γ-Al₂O₃ (mesoporous most probable pore size 4.3nm, macroporous most probable pore size 4368nm) was treated with steam at 450℃ for 5 hours to obtain steam-treated modified alumina (mesoporous most probable pore size 8.5nm, macroporous most probable pore size 1530nm). 100g of the steam-treated modified alumina was then mixed with 2g of guar gum powder, 7.36g of magnesium nitrate, and an appropriate amount of deionized oil. After kneading and extrusion, the mixture was dried at 120℃ for 3 hours and calcined at 550℃ for 5 hours to obtain a composite modified alumina carrier. The magnesium oxide content in the composite modified alumina carrier was 2.5% by mass.

[0038] Take 100g of the above-mentioned composite modified alumina support, introduce rhodium chloride and lanthanum nitrate by equal volume impregnation, dry at 90℃ for 5 hours, calcine at 550℃ for 5 hours, and obtain aromatic selective hydrogenation dealkylation catalyst A1, wherein the mass content of rhodium oxide is 0.5% and the mass content of lanthanum oxide is 1.5%.

[0039] The aromatic selective hydrogenation dealkylation catalyst A1 in the example was used in the aromatic selective hydrogenation dealkylation reaction, wherein the reactant was ethylbenzene, the reaction temperature was 500℃, the reaction pressure was 3MPa, and the ethylbenzene feed mass hourly space velocity was 2h. -1 The molar ratio of hydrogen to aromatics was 6 / 1. The evaluation results of the reaction performance are shown in Table 1.

[0040] Example 2

[0041] 100g of γ-Al₂O₃ (mesoporous most probable pore size 5.8nm, macroporous most probable pore size 3870nm) was treated with steam at 500℃ for 2 hours to obtain steam-treated modified alumina (mesoporous most probable pore size 11.4nm, macroporous most probable pore size 1590nm). 100g of the steam-treated modified alumina was then mixed with 2g of guar gum powder, 14.72g of magnesium nitrate, and an appropriate amount of deionized oil. After kneading and extrusion, the mixture was dried at 120℃ for 3 hours and calcined at 550℃ for 5 hours to obtain a composite modified alumina carrier. The magnesium oxide content in the composite modified alumina carrier was 4.5% by mass.

[0042] Take 100g of the above-mentioned composite modified alumina support, introduce iridium chloride and cerium nitrate by equal volume impregnation, dry at 120℃ for 3 hours, calcine at 550℃ for 3 hours, and obtain aromatic selective hydrogenation dealkylation catalyst A2, wherein the mass content of iridium oxide is 1.0% and the mass content of cerium oxide is 5.0%.

[0043] The aromatic selective hydrogenation dealkylation catalyst A2 in the example was used in the aromatic selective hydrogenation dealkylation reaction, wherein the reactant was ethylbenzene, the reaction temperature was 400℃, the reaction pressure was 5MPa, and the ethylbenzene feed mass hourly space velocity was 1h. -1 The molar ratio of hydrogen to aromatics was 3 / 1. The evaluation results of the reaction performance are shown in Table 1.

[0044] Example 3

[0045] 100g of γ-Al₂O₃ (mesoporous maximum probable pore size 5.8nm, macroporous maximum probable pore size 4680nm) was treated with steam at 400℃ for 5 hours to obtain steam-treated modified alumina (mesoporous maximum probable pore size 8.2nm, macroporous maximum probable pore size 1850nm). 100g of the steam-treated modified alumina was then mixed with 2g of guar gum powder, 2.58g of potassium nitrate, and an appropriate amount of deionized water. After kneading and extrusion, the mixture was dried at 120℃ for 3 hours and calcined at 550℃ for 5 hours to obtain a composite modified alumina carrier. The potassium oxide content in the composite modified alumina carrier was 1.2% by mass.

[0046] Take 100g of the above-mentioned composite modified alumina support, introduce iridium chloride and lanthanum nitrate by equal volume impregnation, dry at 90℃ for 5 hours, calcine at 550℃ for 5 hours, and obtain aromatic selective hydrogenation dealkylation catalyst A3, wherein the mass content of iridium oxide is 1.0% and the mass content of lanthanum oxide is 2.5%.

[0047] The aromatic selective hydrogenation dealkylation catalyst A3 in the example was used in the aromatic selective hydrogenation dealkylation reaction, wherein the reactant was ethylbenzene, the reaction temperature was 500℃, the reaction pressure was 3MPa, and the ethylbenzene feed mass hourly space velocity was 1h.-1 The molar ratio of hydrogen to aromatics was 3 / 1. The evaluation results of the reaction performance are shown in Table 1.

[0048] Example 4

[0049] 100g of γ-Al₂O₃ (mesoporous most probable pore size 6.0nm, macroporous most probable pore size 3180nm) was treated with steam at 300℃ for 5 hours to obtain steam-treated modified alumina (mesoporous most probable pore size 8.5nm, macroporous most probable pore size 1990nm). 100g of the steam-treated modified alumina was then mixed with 2g of guar gum powder, 8.16g of potassium nitrate, and an appropriate amount of deionized water. After kneading and extrusion, the mixture was dried at 120℃ for 3 hours and calcined at 550℃ for 5 hours to obtain a composite modified alumina carrier. The potassium oxide content in the composite modified alumina carrier was 3.5% by mass.

[0050] Take 100g of the above-mentioned composite modified alumina support, introduce ruthenium chloride and lanthanum nitrate by equal volume impregnation, dry at 90℃ for 5 hours, calcine at 550℃ for 5 hours, and obtain aromatic selective hydrogenation dealkylation catalyst A4, wherein the mass content of ruthenium oxide is 0.65% and the mass content of lanthanum oxide is 4.0%.

[0051] The aromatic selective hydrogenation dealkylation catalyst A4 in the example was used in the aromatic selective hydrogenation dealkylation reaction, wherein the reactant was ethylbenzene, the reaction temperature was 500℃, the reaction pressure was 3MPa, and the ethylbenzene feed mass hourly space velocity was 1h. -1 The molar ratio of hydrogen to aromatics was 4 / 1. The evaluation results of the reaction performance are shown in Table 1.

[0052] Comparative Example 1

[0053] 100g of γ-Al₂O₃ (mesoporous most probable pore size 4.3nm, macroporous most probable pore size 4368nm) was treated with steam at 450℃ for 5 hours to obtain steam-treated modified alumina (mesoporous most probable pore size 8.5nm, macroporous most probable pore size 1530nm). 100g of the steam-treated modified alumina was then mixed with 2g of guar gum powder and an appropriate amount of deionized oil. After kneading and extruding, the mixture was dried at 120℃ for 3 hours and calcined at 550℃ for 5 hours to obtain alumina support T1.

[0054] Take 100g of the above alumina support T1, introduce rhodium chloride and lanthanum nitrate by equal volume impregnation, dry at 90℃ for 5 hours, calcine at 550℃ for 5 hours, and obtain aromatic selective hydrogenation dealkylation catalyst D1, wherein the mass content of rhodium oxide is 0.5% and the mass content of lanthanum oxide is 1.5%.

[0055] The aromatic selective hydrogenation dealkylation catalyst D1 in the example was used in the aromatic selective hydrogenation dealkylation reaction, wherein the reactant was ethylbenzene, the reaction temperature was 500℃, the reaction pressure was 3MPa, and the ethylbenzene feed mass hourly space velocity was 2h. -1 The molar ratio of hydrogen to aromatics was 6 / 1. The evaluation results of the reaction performance are shown in Table 1.

[0056] Comparative Example 2

[0057] Take 100g of γ-Al2O3 (mesoporous most probable pore size 4.3nm, macroporous most probable pore size 4368nm), add 2g of guar gum powder, 7.36g of magnesium nitrate and an appropriate amount of deionized oil, knead and extrude into strips, dry at 120℃ for 3 hours and calcine at 550℃ for 5 hours to obtain alumina carrier T2, wherein the magnesium oxide mass content is 2.5%.

[0058] Take 100g of alumina support T2, introduce rhodium chloride and lanthanum nitrate by equal volume impregnation, dry at 90℃ for 5 hours, calcine at 550℃ for 5 hours, and obtain aromatic selective hydrogenation dealkylation catalyst D2, wherein the mass content of rhodium oxide is 0.5% and the mass content of lanthanum oxide is 1.5%.

[0059] The aromatic selective hydrogenation dealkylation catalyst D2 from the example was used in the aromatic selective hydrogenation dealkylation reaction, wherein the reactant was ethylbenzene, the reaction temperature was 500℃, the reaction pressure was 3MPa, and the ethylbenzene feed mass hourly space velocity was 2h⁻¹. -1 The molar ratio of hydrogen to aromatics was 6 / 1. The evaluation results of the reaction performance are shown in Table 1.

[0060] Comparative Example 3

[0061] Take 100g of γ-Al2O3 (the most probable pore size of mesopores is 4.3nm, and the most probable pore size of macropores is 4368nm), add 2g of guar gum powder and an appropriate amount of deionized oil, knead and extrude the mixture, dry it at 120℃ for 3 hours, and calcine it at 550℃ for 5 hours to obtain alumina carrier T3.

[0062] Take 100g of the above alumina support T3, introduce rhodium chloride and lanthanum nitrate by equal volume impregnation, dry at 90℃ for 5 hours, calcine at 550℃ for 5 hours, and obtain aromatic selective hydrogenation dealkylation catalyst D3, wherein the mass content of rhodium oxide is 0.5% and the mass content of lanthanum oxide is 1.5%.

[0063] The aromatic selective hydrogenation dealkylation catalyst D3 from the example was used in the aromatic selective hydrogenation dealkylation reaction, wherein the reactant was ethylbenzene, the reaction temperature was 500℃, the reaction pressure was 3MPa, and the ethylbenzene feed mass hourly space velocity was 2h. -1 The molar ratio of hydrogen to aromatics was 6 / 1. The evaluation results of the reaction performance are shown in Table 1.

[0064] Comparative Example 4

[0065] 100g of γ-Al₂O₃ (mesoporous most probable pore size 4.3nm, macroporous most probable pore size 4368nm) was treated with steam at 450℃ for 5 hours to obtain steam-treated modified alumina (mesoporous most probable pore size 8.5nm, macroporous most probable pore size 1530nm). 100g of the steam-treated modified alumina was then mixed with 2g of guar gum powder, 7.36g of magnesium nitrate, and an appropriate amount of deionized oil. After kneading and extrusion, the mixture was dried at 120℃ for 3 hours and calcined at 550℃ for 5 hours to obtain a composite modified alumina carrier. The magnesium oxide content in the composite modified alumina carrier was 2.5% by mass.

[0066] Take 100g of the above-mentioned composite modified alumina support, introduce rhodium chloride by equal volume impregnation, dry at 90℃ for 5 hours, calcine at 550℃ for 5 hours, and obtain the aromatic selective hydrogenation and dealkylation catalyst D4, wherein the mass content of rhodium oxide is 0.5%.

[0067] The catalyst D4 for the selective hydrogenation and dealkylation of aromatics in the example was used in the selective hydrogenation and dealkylation reaction of aromatics, wherein the reactant was ethylbenzene, the reaction temperature was 500℃, the reaction pressure was 3MPa, and the mass hourly space velocity of the ethylbenzene feed was 2h. -1 The molar ratio of hydrogen to aromatics was 6 / 1. The evaluation results of the reaction performance are shown in Table 1.

[0068] Comparative Example 5

[0069] 100g of γ-Al₂O₃ (mesoporous most probable pore size 5.8nm, macroporous most probable pore size 3870nm) was treated with steam at 500℃ for 2 hours to obtain steam-treated modified alumina (mesoporous most probable pore size 11.4nm, macroporous most probable pore size 1590nm). 100g of the steam-treated modified alumina was then mixed with 2g of guar gum powder, 14.72g of magnesium nitrate, and an appropriate amount of deionized oil. After kneading and extrusion, the mixture was dried at 120℃ for 3 hours and calcined at 550℃ for 5 hours to obtain a composite modified alumina carrier. The magnesium oxide content in the composite modified alumina carrier was 4.5% by mass.

[0070] Take 100g of the above-mentioned composite modified alumina support, introduce cerium nitrate by equal volume impregnation, dry at 120℃ for 3 hours, calcine at 550℃ for 3 hours, and obtain the aromatic selective hydrogenation dealkylation catalyst D5 with a cerium oxide mass content of 5%.

[0071] The catalyst D5 for the selective hydrogenation and dealkylation of aromatics in the example was used in the selective hydrogenation and dealkylation reaction of aromatics, wherein the reactant was ethylbenzene, the reaction temperature was 400℃, the reaction pressure was 5MPa, and the mass hourly space velocity of the ethylbenzene feed was 1h. -1 The molar ratio of hydrogen to aromatics was 3 / 1. The evaluation results of the reaction performance are shown in Table 1.

[0072] Table 1. Performance of selective hydrodealkylation of aromatics in the examples and comparative examples.

[0073]

[0074] The specific embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A catalyst for selective hydrogenation and dealkylation of aromatics, the catalyst comprising a composite modified alumina support, a Group VIII transition metal oxide, and a rare earth metal oxide; In the catalyst, based on the mass of the catalyst, the mass content of Group VIII transition metal oxides is 0.01% to 1%, the mass content of rare earth metal oxides is 1% to 5%, and the mass content of composite modified alumina support is 94% to 98%. The composite modified alumina carrier comprises modified alumina and metal oxides; The most probable pore size of the mesopores in the composite modified alumina carrier is 8–12 nm, and the most probable pore size of the macropores is 1000–2000 nm; the metal oxides in the composite modified alumina carrier are oxides of alkali metals and / or alkaline earth metals.

2. The catalyst according to claim 1, characterized in that, The metal in the group VIII transition metal oxide is selected from at least one of Ru, Ir, and Rh; the metal in the rare earth metal oxide is La and / or Ce.

3. The catalyst according to claim 1 or 2, characterized in that, The metal oxides in the composite modified alumina carrier are magnesium oxide and / or potassium oxide.

4. A method for preparing the aromatic selective hydrogenation dealkylation catalyst according to any one of claims 1-3, comprising the following steps: (1) Preparation of composite modified alumina carrier; (2) Take the composite modified alumina support described in step (1), introduce group VIII transition metal salts and rare earth metal salts, dry and calcine to obtain an aromatic selective hydrogenation dealkylation catalyst.

5. The preparation method according to claim 4, characterized in that, The preparation method of the composite modified alumina carrier in step (1) includes: treating alumina with steam, then mixing it with metal salt, and then molding, drying and calcining to obtain the composite modified alumina carrier.

6. The preparation method according to claim 5, characterized in that, The temperature of the steam treatment in step (1) is 300-500℃, and the treatment time is 2-5 hours.

7. The preparation method according to claim 5, characterized in that, The metal salt in step (1) is an alkali metal and / or alkaline earth metal salt.

8. The preparation method according to claim 7, characterized in that, The metal salt mentioned in step (1) is at least one of magnesium nitrate and potassium nitrate.

9. The preparation method according to claim 4, characterized in that, The group VIII transition metal in step (2) is selected from at least one of Ru, Ir and Rh.

10. The preparation method according to claim 9, characterized in that, The rare earth metal in step (2) is La or / and Ce.

11. The application of the aromatic selective hydrogenation dealkylation catalyst according to any one of claims 1-3 in the selective hydrogenation dealkylation reaction of alkyl aromatics.

12. The application according to claim 11, characterized in that, The reaction conditions for the selective hydrogenation and dealkylation of aromatics are: temperature 350–550 °C, pressure 2–5 MPa, and alkyl aromatic mass hourly space velocity (HHSV) 1–10 h⁻¹. -1 The molar ratio of hydrogen to alkyl aromatics is 2 to 6.

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