A catalyst for the catalytic separation of reformed heavy aromatics, its preparation method and application

Abstract

This invention discloses a catalyst for the catalytic separation of reformed heavy aromatics, its preparation method, and its application. The catalyst comprises a modified ZSM-5 molecular sieve and an active metal. The preparation of the catalyst includes the preparation of the modified ZSM-5 molecular sieve, the preparation of a ZSM-5 molecular sieve support, and the introduction of Group VIB and / or Group VIII metals onto the prepared ZSM-5 molecular sieve support. This catalyst, when used for the catalytic separation of reformed heavy aromatics, can simultaneously produce tricresylbenzene and BTX.

Description

Technical Field

[0001] This invention relates to the field of comprehensive utilization of reformed heavy aromatics, specifically to a catalyst for the catalytic separation of reformed heavy aromatics to simultaneously produce trimethylbenzene and BTX, its preparation method, and its application. Background Technology

[0002] Catalytic reforming units contain a significant amount of heavy aromatics. The composition of reformed heavy aromatics is very complex, typically consisting of C9+ aromatics. C9 aromatics usually include n-propylbenzene, isopropylbenzene, ethylbenzene, as well as methyltrimethylbenzene, pseudotrimethylbenzene, mesitylene, etc., as shown in Table 1. Mesitylene is the highest value-added component among C9 aromatics. Fully utilizing this valuable resource will not only improve the economic efficiency of the oil refining industry but also promote the development of my country's fine chemical industry.

[0003] The most abundant trimethylbenzenes in C9 aromatics can be produced astribenzene via isomerization. However, other long-chain alkylbenzenes, especially o-methylbenzene, have boiling points that differ from astribenzene by only 0.4°C, making direct separation of astribenzene using conventional methods very difficult. Existing technologies often employ multiple distillations to separate trimethylbenzenes. For example, CN1974500A uses a three-tower serial process to separate reformed heavy aromatics, producing high-purity pseudotrimethylbenzene and enriched astribenzene with a purity of over 35 wt%, but the purity of the astribenzene is low. Therefore, existing technologies for separating and producing astribenzene and pseudotrimethylbenzene involve long and complex processes with low yields, high production costs, and significant challenges for industrial application.

[0004] CN201110099991.X discloses a method for hydrogenating C9 heavy aromatics, removing methylbenzene components with boiling points close to trimethylbenzene, and then distilling the resulting products to obtain pseudotrimethylbenzene and mesitylene products with a purity of over 98%. This method uses a hydrogen-formed ZSM-5 molecular sieve impregnated with Pt and Zn as a catalyst for hydrogenation of heavy aromatics. The shape-selectivity of the ZSM-5 molecular sieve allows for the selective removal of o-methylbenzene and other compounds. However, due to the acidity of the ZSM-5 molecular sieve's outer surface, it lacks shape selectivity, leading to a significant amount of trimethylbenzene reacting. Furthermore, its microporous structure prevents the aromatic hydrocarbons from diffusing out of the pores in time, resulting in ring-opening reactions and the formation of chain hydrocarbons. For these reasons, nearly 20 wt% of the aromatics are converted into chain hydrocarbons during hydrogenation, resulting in substantial waste of aromatics. Additionally, a large amount of trimethylbenzene reacts, with trimethylbenzene accounting for only 27.3% of the product. Moreover, the use of the precious metal Pt as the hydrogenation component significantly increases the preparation cost. Therefore, developing hydrogenolysis catalysts with lower costs and higher retention rates of aromatics and tricresylene has become an urgent problem to be solved.

[0005] Table 1. Common Compositions of Reformed C9 Aromatics

[0006] Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a catalyst for the catalytic separation of reformed heavy aromatics to simultaneously produce trimethylbenzene and BTX, and a method for its preparation.

[0008] The first aspect of this invention provides a catalytic separation catalyst for reformed heavy aromatics, the catalyst comprising a modified ZSM-5 molecular sieve and an active metal, wherein the active metal comprises Group VIB and / or Group VIII metals, and based on the weight of the heavy aromatics catalytic separation catalyst, the content of the modified ZSM-5 molecular sieve is 30% to 90%, preferably 40% to 70%, the content of the Group VIB metal (calculated as oxides) is 5.0% to 30.0%, and the content of the Group VIB metal (calculated as oxides) is... The content of Group II metals, calculated as oxides, is 1.0% to 5.0%. The molar ratio of SiO2 / Al2O3 on the outer surface of the modified ZSM-5 molecular sieve is 200 to 1000, the molar ratio of SiO2 / Al2O3 in the bulk phase is 20 to 100, the total pyridine infrared acidity is 0.30 to 0.60 mmol / g, and the total pyridine infrared acidity is 0.00 to 0.02 mmol / g. The mesoporous pore volume of the modified ZSM-5 molecular sieve accounts for 10% to 20% of the total pore volume.

[0009] Furthermore, in the heavy aromatic hydrocarbon catalytic separation catalyst, the Group VIB metal is preferably molybdenum and / or tungsten, and the Group VIII metal is preferably cobalt and / or nickel.

[0010] Further, preferably, the molar ratio of SiO2 / Al2O3 on the outer surface of the modified ZSM-5 molecular sieve is 500~1000, and the molar ratio of SiO2 / Al2O3 in the bulk phase is 20~50, preferably 35~45.

[0011] Further, preferably, the modified ZSM-5 molecular sieve has a total pyridine infrared acidity of 0.35~0.45 mmol / g and a total di-tert-butylpyridine infrared acidity of 0.00~0.005 mmol / g.

[0012] Furthermore, the mesopores in the modified ZSM-5 molecular sieve are concentrated in the range of 2-10 nm, wherein the pore volume of mesopores in the range of 2-10 nm accounts for 20%-50% of the total mesopore volume. In this invention, mesopores refer to pores with a diameter of 2-50 nm.

[0013] A second aspect of the present invention provides a catalytic separation catalyst for reforming heavy aromatics, comprising the preparation of a modified ZSM-5 molecular sieve, the preparation of a ZSM-5 molecular sieve support, and the process of introducing a Group VIB and / or Group VIII metal onto the prepared ZSM-5 molecular sieve support, wherein the method for preparing the modified ZSM-5 molecular sieve includes the following steps:

[0014] (1) Hydrothermal treatment of ZSM-5 molecular sieve;

[0015] (2) Impregnate the material obtained in step (1) with a channel protection liquid;

[0016] (3) The material obtained in step (2) is treated with organic acids;

[0017] (4) Mix the material obtained in step (3) with the dealuminizing and silicon replenishing reagent to perform dealuminizing and silicon replenishment;

[0018] (5) The material obtained in step (4) is filtered, washed, dried and calcined to obtain modified ZSM-5 molecular sieve.

[0019] Further, in step (1), the ZSM-5 molecular sieve can be a commercially available product or a microporous hydrogen-form ZSM-5 molecular sieve prepared according to existing technology. The properties of the ZSM-5 molecular sieve are as follows: SiO2 / Al2O3 molar ratio 20~100, specific surface area 300~450m². 2 / g, pore volume 0.15~0.20cm³ 3 / g.

[0020] Further, in step (1), the specific treatment process in the hydrothermal process is as follows: place the commercially available ZSM-5 molecular sieve in a hydrothermal furnace, introduce steam, and treat it for 1h to 3h at a temperature of 400℃~500℃ and a pressure of 0.05~0.2MPa.

[0021] Further, in step (2), the pore protection solution is one or more of isopropylamine solution, tetraethylammonium hydroxide solution, tetrapropylammonium hydroxide solution, etc. The concentration of the pore protection solution is 0.8~2.0 mol / L, preferably 1.1~1.5 mol / L.

[0022] Furthermore, in step (2), the impregnation is preferably an equal-volume impregnation. The impregnation treatment temperature is room temperature, generally 20~25℃.

[0023] Further, in step (3), the organic acid is one or more of 2,4-dimethylbenzenesulfonic acid and 2,5-dimethylbenzoic acid.

[0024] Further, in step (3), the specific operation is as follows: first, the material obtained in step (2) is mixed with water, wherein the liquid-solid volume ratio of water to the material obtained in step (2) is 2:1 to 6:1, and then organic acid is added until the pH value of the solution drops below 8, preferably 6.5 to 7.5.

[0025] Further, in step (4), the dealuminizing and silicon-replenishing reagent is at least one of ammonium hexafluorosilicate solution, tetraethyl orthosilicate solution, etc. The molar concentration of the dealuminizing and silicon-replenishing reagent is 0.3~1.0 mol / L. The mass ratio of the material obtained in step (4) to the dealuminizing and silicon-replenishing reagent is 1:1~1:5. The mixing temperature is 60~100℃.

[0026] Further, the specific operation process of step (4) is as follows: rapidly heat the material obtained in step (3) to 60~100℃ and continuously stir, add the aluminum removal and silicon replenishment reagent dropwise, and continue stirring for 60~120min after the dropwise addition is completed. Among them, the dropwise addition rate does not exceed 0.5mL / min·g of the material obtained in step (3); preferably 0.2~0.4mL / min·g of the material obtained in step (3).

[0027] Furthermore, in step (5), the filtration and washing can be carried out using conventional methods in the art, the drying temperature is 100℃~150℃, the drying time is 2~4h, the calcination temperature is 400℃~600℃, and the calcination time is 3~5h.

[0028] Furthermore, the preparation of the ZSM-5 molecular sieve carrier involves mixing, extruding, and molding the modified molecular sieve with macroporous alumina and alumina sol binder, followed by drying and calcination to obtain the ZSM-5 molecular sieve carrier.

[0029] Furthermore, metals of Group VIB and / or Group VIII were introduced onto the prepared ZSM-5 molecular sieve support by impregnation, followed by drying and calcination to obtain a catalyst for the catalytic separation of reformed heavy aromatics.

[0030] A third aspect of the present invention provides the application of the above-mentioned catalyst in the catalytic separation process of reformed heavy aromatics.

[0031] The application includes: in the presence of hydrogen, the feedstock oil reacts under the action of the above-mentioned catalyst to obtain a mixture of trimethylbenzene and a mixture of BTX products.

[0032] Furthermore, in the aforementioned application, the reaction conditions are as follows: reaction pressure of 5.0~8.0 MPa, hydrogen-to-oil volume ratio of 50:1~600:1, and liquid hourly space velocity of 0.5~2 h⁻¹. -1 The reaction temperature is 350~450℃.

[0033] Furthermore, after the reaction products are separated by distillation to remove benzene, toluene, xylene, and other products, they are reintroduced into the top of the reactor and mixed with fresh raw materials to continue the reaction.

[0034] Compared with the prior art, the reforming heavy aromatics catalytic separation catalyst, its preparation method, and its application of the present invention have the following advantages:

[0035] 1. The heavy aromatic hydrocarbon catalyst of the present invention uses modified ZSM-5 molecular sieve as the acidic component. The modified ZSM-5 molecular sieve has a low total infrared acidity of di-tert-butylpyridine, which eliminates mesoporous acid and external surface acid while having a suitable mesoporous distribution. The catalyst prepared by using this modified ZSM-5 molecular sieve can significantly reduce the ring-opening rate of aromatic hydrocarbons and improve the retention rate of tricresyl in the catalytic separation of reformed heavy aromatic hydrocarbons.

[0036] 2. The preparation method of the modified ZSM-5 molecular sieve of the present invention first obtains a certain amount of mesopores through acid treatment technology, and then removes the acid centers in the non-zigzag channels at specific points. Most of the aluminum sites in the non-zigzag channels are replaced by non-acidic silicon atoms under the action of ammonium hexafluorosilicate, thus completely preserving the molecular sieve structure and the acid centers inside the channels. When heavy aromatics come into contact with the catalyst, molecules such as n-propylbenzene, isopropylbenzene, and ethylbenzene enter the molecular sieve channels and undergo dealkylation reactions to generate more valuable and easily removed molecules such as benzene, toluene, and xylene. At the same time, because the molecular sieve channels are more unobstructed, the product molecules leave the channels in time, avoiding ring-opening reactions. Meanwhile, because the acid sites outside the molecular sieve channels are masked, trimethylbenzene cannot enter the molecular sieve channels and is ultimately retained in the product. Detailed Implementation

[0037] The following examples and comparative examples further illustrate the role and effect of the technical solution of the present invention, but the following examples do not constitute a limitation on the scope of protection of the present invention.

[0038] In this invention, unless otherwise specified, all percentages (%) in the embodiments and comparative examples refer to mass fractions.

[0039] In this invention, the SiO2 / Al2O3 molar ratio on the outer surface was determined by X-ray photoelectron spectroscopy (XPS). The elemental composition and state of the catalyst surface were determined using a Thermofisher Multilab2000 electron spectrometer, with MgKa as the excitation source and a cathode voltage and current of 13 kV and 20 mA, respectively. The electron binding energy was calibrated using C1s (284.6 eV).

[0040] The bulk SiO2 / Al2O3 molar ratio was obtained by X-ray fluorescence spectroscopy (XRF) analysis using a ZSX100e X-ray fluorescence spectrometer with the spectral line Ka, the crystal being LiF1, the target material being Rh, the detector being SC scintillation, the timing being 20 s, and the optical path atmosphere being vacuum.

[0041] In this invention, the specific surface area, pore volume, and pore distribution were measured using the following method: an ASAP 2420 cryogenic liquid nitrogen physical adsorption instrument manufactured by Microlithics, Inc. was used, with a pretreatment temperature of 300°C and a pretreatment time of 4 hours.

[0042] In this invention, the pyridine infrared determination method is as follows: Powdered ZSM-5 molecular sieve is compressed into tablets, vacuumed, and degassed at 450°C for 2 hours. After the temperature drops to room temperature, pyridine molecules are used as probe molecules to measure the infrared spectrum of chemical desorption, and the adsorption amount is calculated.

[0043] In this invention, the total infrared acidity of di-tert-butylpyridine refers to the proton acid that a 2,6-di-tert-butylpyridine molecule with a kinetic diameter of 10.5 Å can contact. The infrared determination method for 2,6-di-tert-butylpyridine is as follows: Powdered ZSM-5 molecular sieve is compressed into tablets, vacuumed, and degassed at 450°C for 2 hours. After the temperature drops to room temperature, 2,6-di-tert-butylpyridine molecules are used as probe molecules to measure their chemical desorption infrared spectrum, and the adsorption amount is calculated.

[0044] The ZSM-5 involved in the embodiments and comparative examples of this invention is a commercially available product, specifically a microporous hydrogen-form ZSM-5 molecular sieve. The properties of the ZSM-5 are as follows: specific surface area of ​​405 m² / g. 2 / g, pore volume is 0.182cm³ 3 / g, water absorption rate is 55%, SiO2 / Al2O3 ratio (molar) is 31.2.

[0045] The heavy aromatic hydrocarbon compositions used in the examples are shown in Table 1.

[0046] Table 1 Composition of C9+ raw materials

[0047]

[0048] Example 1

[0049] 30g of commercially available ZSM-5 raw powder was placed in a hydrothermal furnace and treated at 400℃ and 0.1MPa pressure for 2h. The resulting material was impregnated with 16.5mL of 1.1 mol / L isopropylamine solution and allowed to stand for 10 min. 170mL of water was added, and 2,5-dibenzenesulfonic acid was added dropwise until the pH value reached 7.5. The mixture was stirred and heated to 60℃. 90mL of 0.3mol / L ammonium hexafluorosilicate solution was added dropwise at a rate of 0.2mL / min·g using a peristaltic pump, while maintaining the temperature at 60℃ and stirring continuously for 90min. The mixture was filtered while hot, and 300mL of water was added to the filter cake. The mixture was heated to 60℃ and maintained for 20min. The mixture was then filtered while hot, and the filter cake was dried at 120℃ for 24h and then calcined at 500℃ for 3h. The resulting modified molecular sieve was named Z-T1.

[0050] Example 2

[0051] 30g of commercially available ZSM-5 raw powder was placed in a hydrothermal treatment furnace and treated at 450℃ and 0.1MPa pressure for 2h. The resulting material was impregnated with 16.5mL of 1.1 mol / L isopropylamine solution and allowed to stand for 10 min. 170mL of water was added, and 2,5-dibenzenesulfonic acid was added dropwise until the pH value reached 7.0. The mixture was stirred and heated to 60℃. 90mL of 0.3mol / L ammonium hexafluorosilicate solution was added dropwise at a rate of 0.2mL / min·g using a peristaltic pump, while maintaining the temperature at 60℃ and stirring continuously for 90 min. The mixture was filtered while hot, and 300mL of water was added to the filter cake. The mixture was heated to 60℃ and maintained for 20 min. It was then filtered while hot, and the filter cake was dried at 120℃ for 24h and calcined at 500℃ for 3h. The resulting modified molecular sieve was named Z-T2.

[0052] Example 3

[0053] 30g of commercially available ZSM-5 raw powder was placed in a hydrothermal treatment furnace and treated at 500℃ and 0.1MPa pressure for 2h. The resulting material was impregnated with 16.5mL of 1.1 mol / L isopropylamine solution and allowed to stand for 10 min. 170mL of water was added, and 2,5-dibenzenesulfonic acid was added dropwise until the pH value reached 6.5. The mixture was stirred and heated to 60℃. 90mL of 0.3mol / L ammonium hexafluorosilicate solution was added dropwise at a rate of 0.2mL / min·g using a peristaltic pump, while maintaining the temperature at 60℃ and stirring continuously for 90 min. The mixture was filtered while hot, and 300mL of water was added to the filter cake. The mixture was heated to 60℃ and maintained for 20 min. The mixture was then filtered while hot, and the filter cake was dried at 120℃ for 24h and then calcined at 500℃ for 3h. The resulting modified molecular sieve was named Z-T3.

[0054] Example 4

[0055] 30g of commercially available ZSM-5 raw powder was placed in a hydrothermal treatment furnace and treated at 400℃ and 0.1MPa pressure for 2h. The resulting material was impregnated with 16.5mL of 1.1 mol / L isopropylamine solution and allowed to stand for 10 min. 170mL of water was added, and 2,5-dibenzenesulfonic acid was added dropwise until the pH value reached 7.5. The mixture was stirred and heated to 60℃. 90mL of 0.4mol / L ammonium hexafluorosilicate solution was added dropwise at a rate of 0.2mL / min·g using a peristaltic pump, while maintaining the temperature at 60℃ and stirring continuously for 90 min. The mixture was filtered while hot, and 300mL of water was added to the filter cake. The mixture was heated to 60℃ and maintained for 20 min. The mixture was then filtered while hot, and the filter cake was dried at 120℃ for 24h and then calcined at 500℃ for 3h. The resulting modified molecular sieve was named Z-T4.

[0056] Example 5

[0057] 30g of commercially available ZSM-5 raw powder was placed in a hydrothermal furnace and treated at 450℃ and 0.1MPa pressure for 2h. The resulting material was impregnated with 16.5mL of 1.1 mol / L isopropylamine solution and allowed to stand for 10 min. 170mL of water was added, and 2,5-dibenzenesulfonic acid was added dropwise until the pH value reached 7.0. The mixture was stirred and heated to 60℃. 90mL of 0.4mol / L ammonium hexafluorosilicate solution was added dropwise at a rate of 0.2mL / min·g using a peristaltic pump, while maintaining the temperature at 60℃ and stirring continuously for 90 min. The mixture was filtered while hot, and 300mL of water was added to the filter cake. The mixture was heated to 60℃ and maintained for 20 min. It was then filtered while hot, and the filter cake was dried at 120℃ for 24h and calcined at 500℃ for 3h. The resulting modified molecular sieve was named Z-T5.

[0058] Example 6

[0059] 30g of commercially available ZSM-5 raw powder was placed in a hydrothermal treatment furnace and treated at 500℃ and 0.1MPa pressure for 2h. The resulting material was impregnated with 16.5mL of 0.8 mol / L isopropylamine solution and allowed to stand for 10 min. 170mL of water was added, and 2,5-dibenzenesulfonic acid was added dropwise until the pH value reached 6.5. The mixture was stirred and heated to 60℃. 90mL of 0.4mol / L ammonium hexafluorosilicate solution was added dropwise at a rate of 0.2mL / min·g using a peristaltic pump, while maintaining the temperature at 60℃ and stirring continuously for 90min. The mixture was filtered while hot, and 300mL of water was added to the filter cake. The mixture was heated to 60℃ and maintained for 20min. The mixture was then filtered while hot, and the filter cake was dried at 120℃ for 24h and then calcined at 500℃ for 3h. The resulting modified molecular sieve was named Z-T6.

[0060] Example 7

[0061] 30g of commercially available ZSM-5 raw powder was placed in a hydrothermal treatment furnace and treated at 450℃ and 0.1MPa pressure for 2h. The resulting material was impregnated with 16.5mL of 1.5mol / L isopropylamine solution and allowed to stand for 10 min. 170mL of water was added, and 2,5-dibenzenesulfonic acid was added dropwise until the pH value reached 7.0. The mixture was stirred and heated to 60℃. 90mL of 0.4mol / L ammonium hexafluorosilicate solution was added dropwise at a rate of 0.2mL / min·g using a peristaltic pump, while maintaining the temperature at 60℃ and stirring continuously for 90min. The mixture was filtered while hot, and 300mL of water was added to the filter cake. The mixture was heated to 60℃ and maintained for 20min. The mixture was then filtered while hot, and the filter cake was dried at 120℃ for 24h and then calcined at 500℃ for 3h. The resulting modified molecular sieve was named Z-T7.

[0062] Example 8

[0063] 30g of commercially available ZSM-5 raw powder was placed in a hydrothermal treatment furnace and treated at 450℃ and 0.1MPa pressure for 2h. The resulting material was impregnated with 16.5mL of 2.0 mol / L isopropylamine solution and allowed to stand for 10 min. 170mL of water was added, and 2,5-dibenzenesulfonic acid was added dropwise until the pH value reached 7.0. The mixture was stirred and heated to 60℃. 90mL of 0.5mol / L ammonium hexafluorosilicate solution was added dropwise at a rate of 0.2mL / min·g using a peristaltic pump, while maintaining the temperature at 60℃ and stirring continuously for 90min. The mixture was filtered while hot, and 300mL of water was added to the filter cake. The mixture was heated to 60℃ and maintained for 20min. The mixture was then filtered while hot, and the filter cake was dried at 120℃ for 24h and then calcined at 500℃ for 3h. The resulting modified molecular sieve was named Z-T8.

[0064] Comparative Example 1

[0065] 30g of commercially available ZSM-5 raw powder was placed in a hydrothermal treatment furnace and treated at 450℃ and 0.1MPa pressure for 2h to obtain a modified molecular sieve, named ZB.

[0066] Comparative Example 2

[0067] 30g of commercially available ZSM-5 raw powder was placed in a hydrothermal treatment furnace and treated at 450℃ and 0.1MPa pressure for 2h. The resulting material was then uniformly added dropwise with 90 mL of 0.4 mol / L ammonium hexafluorosilicate solution using a peristaltic pump at a dropping rate of 0.3 mL / min·g, while maintaining the temperature at 65℃ and continuously stirring for 90min. The resulting modified molecular sieve was named ZC.

[0068] Table 2 Characterization results of the modified molecular sieves obtained in the examples and comparative examples

[0069]

[0070] Example 9

[0071] Catalysts were prepared using the modified molecular sieves obtained in Examples 1, 5, and 8. The preparation process involved mixing, extruding, and molding the modified molecular sieves with macroporous alumina (specific surface area of ​​302 m² / g and pore volume of 0.96 cm³ / g) and an alumina sol binder, followed by drying and calcination to obtain a support. The support was then impregnated with a metal-containing impregnation solution, followed by drying and calcination to obtain catalysts, denoted as C1, C5, and C8. The modified molecular sieve had a mass fraction of 60 wt%, the macroporous alumina had a mass fraction of 20 wt%, MoO₃ had a mass fraction of 10 wt%, NiO had a mass fraction of 5 wt%, and the remainder was binder.

[0072] 10g each of catalysts C1, C5, and C8 were placed in a fixed-bed reactor. The reaction was carried out at a pressure of 7.0 MPa, a hydrogen-to-oil volume ratio of 100:1, and a liquid hourly space velocity of 2.0 h⁻¹. -1 Catalytic dealkylation reaction was carried out at a reaction temperature of 420℃. The conversion of raw materials and the distribution of products are shown in Table 3.

[0073] Comparative Example 3

[0074] The modified molecular sieve obtained in Comparative Example 1 was used to prepare a catalyst. The preparation process was as follows: the modified molecular sieve was mixed with macroporous alumina (specific surface area of ​​302 m2 / g, pore volume of 0.96 cm3 / g) and an alumina sol binder, extruded, shaped, dried and calcined to obtain a support; the above support was impregnated with an impregnation solution containing metal, and then dried and calcined to obtain a catalyst, denoted as BC1; wherein the mass fraction of the modified molecular sieve was 60 wt%, the mass fraction of macroporous alumina was 20 wt%, the mass fraction of MoO3 was 10 wt%, the mass fraction of NiO was 5 wt%, and the remainder was binder.

[0075] 10g of catalyst BC1 was placed in a fixed-bed reactor. The reaction was carried out at a pressure of 7.0 MPa, a hydrogen-to-oil volume ratio of 100:1, and a liquid hourly space velocity of 2.0 h⁻¹. -1 Catalytic dealkylation reaction was carried out at a reaction temperature of 420℃. The conversion of raw materials and the distribution of products are shown in Table 3.

[0076] Comparative Example 4

[0077] The catalyst was prepared using the modified molecular sieve obtained in Comparative Example 2. The preparation process involved reacting the modified molecular sieve with macroporous alumina (with a specific surface area of ​​302 m²). 2 / g, pore volume 0.96 cm³ 3The carrier is obtained by mixing, extruding, and molding the aluminum sol binder (g), followed by drying and calcination. The carrier is then impregnated with a metal-containing impregnation solution, followed by drying and calcination to obtain the catalyst, denoted as BC2. The catalyst consists of 60 wt% modified molecular sieve, 20 wt% macroporous alumina, 10 wt% MoO3, 5 wt% NiO, and the remainder is binder.

[0078] 10g of catalyst BC2 was placed in a fixed-bed reactor. The reaction was carried out at a pressure of 7.0 MPa, a hydrogen-to-oil volume ratio of 100:1, and a liquid hourly space velocity of 2.0 h⁻¹. -1 The catalytic dealkylation reaction was carried out at a reaction temperature of 420℃, and the conversion of raw materials and the distribution of products are shown in Table 3.

[0079] Table 3. Composition of reformed C9+ heavy aromatic hydrocarbon feedstocks and products used in the experiment.

[0080]

Claims

1. A catalytic separation catalyst for reforming heavy aromatics, characterized by: The heavy aromatic catalytic separation catalyst comprises modified ZSM-5 molecular sieve and active metals, the active metals comprising metals of Group VIB and Group VIII, the content of the modified ZSM-5 molecular sieve being 30-90% by weight of the heavy aromatic catalytic separation catalyst, the content of the metal of Group VIB being 5.0-30.0% by weight of the oxide, the content of the metal of Group VIII being 1.0-5.0% by weight of the oxide, the molar ratio of SiO2 / Al2O3 on the external surface of the modified ZSM-5 molecular sieve being 200-1000, the molar ratio of SiO2 / Al2O3 in the bulk phase being 20-100, the total pyridine infrared acid amount being 0.30-0.60 mmol / g, and the total di-tert-butyl pyridine infrared acid amount being 0.00-0.02 mmol / g; and the mesopore volume of the modified ZSM-5 molecular sieve accounting for 10-20% of the total pore volume.

2. The catalyst of claim 1, wherein: The heavy aromatic catalytic separation catalyst, the metal of Group VIB being molybdenum and / or tungsten, and the metal of Group VIII being cobalt and / or nickel.

3. The catalyst of claim 1, wherein: The molar ratio of SiO2 / Al2O3 on the external surface of the modified ZSM-5 molecular sieve is 500-1000, and the molar ratio of SiO2 / Al2O3 in the bulk phase is 20-50.

4. The catalyst of claim 1, wherein: The total pyridine infrared acid amount of the modified ZSM-5 molecular sieve is 0.35-0.45 mmol / g, and the total di-tert-butyl pyridine infrared acid amount is 0.00-0.005 mmol / g.

5. The catalyst of claim 1, wherein: The mesopores in the modified ZSM-5 molecular sieve are concentrated in 2-10 nm, and the mesopore volume in 2-10 nm accounts for 20-50% of the total mesopore volume.

6. The process for the preparation of the catalytic separation catalyst for the catalytic reforming of heavy aromatic hydrocarbons according to any one of claims 1 to 5, characterized in that: The preparation of modified ZSM-5 molecular sieve, the preparation of a carrier containing the modified ZSM-5 molecular sieve, and the process of introducing metals of Group VIB and Group VIII onto the prepared modified ZSM-5 molecular sieve carrier, wherein the preparation method of the modified ZSM-5 molecular sieve comprises the following steps: (1) hydrothermally treating ZSM-5 molecular sieve; (2) impregnating the material obtained in step (1) with a channel protection solution; (3) treating the material obtained in step (2) with an organic acid; (4) mixing the material obtained in step (3) with a dealumination and silicon supplementation reagent to perform dealumination and silicon supplementation; (5) filtering, washing, drying, and calcining the material obtained in step (4) to obtain modified ZSM-5 molecular sieve; In step (2), the channel protection solution is one or more of isopropylamine solution, tetraethylammonium hydroxide solution, and tetrapropylammonium hydroxide solution, and the concentration of the channel protection solution is 0.8-2.0 mol / L; in step (3), the organic acid is 2,4-dimethylbenzenesulfonic acid and / or 2,5-dimethylbenzoic acid; in step (4), the dealumination and silicon supplementation reagent is ammonium hexafluorosilicate solution and / or tetraethyl orthosilicate solution, the molar concentration of the dealumination and silicon supplementation reagent is 0.3-1.0 mol / L, the mass ratio of the material obtained in step (3) to the dealumination and silicon supplementation reagent is 1:1-1:5, and the mixing temperature is 60-100°C.

7. The method of claim 6, wherein: The ZSM-5 molecular sieve in step (1) has the following properties: SiO2 / Al2O3 molar ratio 20-100, specific surface area 300-450 m 2 / g, pore volume 0.15-0.20 cm 3 / g.

8. The method of claim 6, wherein: In step (1), the hydrothermal treatment is specifically as follows: the ZSM-5 molecular sieve is placed in a hydrothermal furnace, water vapor is introduced, and the treatment is carried out at a temperature of 400-500°C and a pressure of 0.05-0.2 MPa for 1-3 h.

9. The method of claim 6, wherein: In step (2), the impregnation is isovolumetric impregnation; the impregnation treatment temperature is 20-25°C.

10. The method of claim 6, wherein: In step (3), the specific operation is as follows: the material obtained in step (2) is first mixed with water, wherein the liquid-solid volume ratio of water to the material obtained in step (2) is 2:1-6:1, and then an organic acid is added until the pH value of the solution is reduced to below 8.

11. The method of claim 6, wherein: In step (4), the specific operation process is as follows: the material obtained in step (3) is rapidly heated to 60-100°C and continuously stirred, and a dealumination and silicon supplementation reagent is added dropwise; after the dropwise addition is completed, the stirring is continued for 60-120 min, wherein the dropwise addition speed is not more than 0.5 mL / min·g of the material obtained in step (3).

12. The method of claim 6, wherein: In step (5), the drying temperature is 100-150°C, and the drying time is 2-4 h; the calcination temperature is 400-600°C; and the calcination time is 3-5 h.

13. The method of claim 6, wherein: The preparation of the modified ZSM-5 molecular sieve carrier is as follows: the modified molecular sieve is mixed with a macroporous alumina and an aluminum sol binder, extruded, shaped, and then dried and calcined to obtain the modified ZSM-5 molecular sieve carrier.

14. The method of claim 6, wherein: The Group VIB and Group VIII metals are introduced on the prepared modified ZSM-5 molecular sieve carrier by impregnation, and then dried and calcined to obtain the heavy aromatic reforming and catalytic separation catalyst.

15. A process for the catalytic separation of reforming heavy aromatics using the catalytic separation catalyst of claim 1, characterized in that: The heavy aromatic reforming and catalytic separation catalyst comprises a modified ZSM-5 molecular sieve and active metals, wherein the active metals comprise Group VIB and Group VIII metals; the content of the modified ZSM-5 molecular sieve is 30%-90% based on the weight of the heavy aromatic reforming and catalytic separation catalyst; the content of the Group VIB metal is 5.0%-30.0% as calculated in terms of oxides; the content of the Group VIII metal is 1.0%-5.0% as calculated in terms of oxides; the SiO2 / Al2O3 molar ratio of the outer surface of the modified ZSM-5 molecular sieve is 200-1000; the SiO2 / Al2O3 molar ratio of the bulk phase is 20-100; the total pyridine infrared acid amount is 0.30-0.60 mmol / g; the di-tert-butyl pyridine infrared total acid amount is 0.00-0.02 mmol / g; and the mesopore volume accounts for 10%-20% of the total pore volume.

16. The process of claim 15, wherein: The reaction products are separated by rectification, and benzene, toluene and xylene are removed, and then re-enter the top of the reactor to be mixed with fresh raw materials and continue to react.

17. The process of claim 15, wherein: The reaction conditions are as follows: the reaction pressure is 5.0-8.0 MPa, the hydrogen-oil volume ratio is 50:1-600:1, the liquid hourly space velocity is 0.5-2 h -1 , and the reaction temperature is 350-450 DEG C.

18. The heavy aromatic reforming and catalytic separation catalyst according to any one of claims 1 to 5 is used in a heavy aromatic reforming and catalytic separation process.

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