A process for isomerization of alkylaromatics and an alkylaromatic isomerization catalyst

Abstract

The application discloses an alkyl aromatic hydrocarbon isomerization method and an alkyl aromatic hydrocarbon isomerization catalyst. The alkyl aromatic hydrocarbon isomerization method comprises: making alkyl aromatic hydrocarbon contact with the alkyl aromatic hydrocarbon isomerization catalyst to perform an isomerization reaction under the reaction pressure of keeping liquid state and in the presence of nitrogen and / or hydrogen. The alkyl aromatic hydrocarbon isomerization catalyst comprises 24-99.9% of ten-membered ring molecular sieve and 0.1-76% of inert carrier based on the total weight of the alkyl aromatic hydrocarbon isomerization catalyst; wherein the ten-membered ring molecular sieve is a mixed molecular sieve of ZSM-5 molecular sieve and ZSM-11 molecular sieve or a mixed crystal structure of ZSM-5 molecular sieve and ZSM-11 molecular sieve. In the catalytic reaction process of the alkyl aromatic hydrocarbon isomerization method, nitrogen and / or hydrogen are introduced, so that the isomerization activity of the alkyl aromatic hydrocarbon isomerization catalyst and the xylene yield are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of aromatic hydrocarbon isomerization technology, specifically to an alkyl aromatic hydrocarbon isomerization method and an alkyl aromatic hydrocarbon isomerization catalyst. Background Technology

[0002] The xylene isomerization unit is an important component of aromatic hydrocarbon complexes. In recent years, the catalytic activity of the xylene isomerization unit has approached the upper limit of thermodynamic equilibrium. The key to further improving its quality and efficiency lies in enhancing the selectivity of the reaction process.

[0003] Analysis of the reaction mechanism of xylene isomerization shows that both isomerization and disproportionation are Brønsted acid-catalyzed reactions, differing only in the required pore space and the energy barrier of the elementary reaction. The energy barrier for disproportionation is higher than that for isomerization; therefore, to suppress the disproportionation side reaction, a lower reaction temperature should be selected.

[0004] With advancements in combined processes, various methods now exist for enriching ethylbenzene in mixed C8 aromatics, resulting in isomerization feeds that are essentially ethylbenzene-free. Therefore, while low temperatures reduce the deethylation activity of ethylbenzene, the extremely low ethylbenzene content minimizes the hydrogen consumption required for deethylation, effectively reducing the accumulation of ethylbenzene in the cycle. The advantage of low-temperature isomerization lies in the fact that dissolved hydrogen alone can maintain the catalyst's xylene isomerization activity, selectivity, and stability.

[0005] Taking into account the process design and power consumption of the equipment, selecting liquid phase conditions for the isomerization reaction unit is a technical solution with unique advantages.

[0006] US20170297977A1 ​​discloses a liquid-phase non-hydrogen-dependent xylene isomerization catalyst, using UZM-54 molecular sieve, preferably with a molecular sieve content of 70% by mass, and alumina as the binder, without the need for metal support. Under non-hydrogen-dependent conditions, the PX (para-xylene) generated by the xylene isomerization reaction can reach thermodynamic equilibrium.

[0007] US9809509 uses small-grained ZSM-23 molecular sieves with a silica / alumina molar ratio between 15 and 75 as the acidic component of a catalyst for a liquid-phase isomerization reaction at 260°C for 5.2 hours. -1 At an air velocity of 3.1 MPa, PX / X can be made greater than the gas phase equilibrium value of 24 mass.

[0008] The catalyst prepared using Ga-MFI molecular sieves in US7371913 can perform alkyl aromatic hydrocarbon isomerization in a completely hydrogen-free state, while retaining higher levels of ethylbenzene and C8 cycloalkanes in the feedstock when the isomerization achieves good performance.

[0009] US20110263918 A1 describes a xylene isomerization process using HZSM-5 or MCM-49 as the acidic catalyst. Under conditions of below 295°C and pressure ensuring the reactants remain liquid, a xylene fraction with a near-equilibrium composition can be obtained. This process can operate continuously when the feed only requires ppm-level dissolved hydrogen. It can also be recycled with non-hydrogen-dependent feeds, but the catalyst needs periodic regeneration with low-ppm-level hydrogen.

[0010] CN103201240A discloses a method for preparing p-xylene, in which C8... + Aromatic feedstock is separated into C8 aromatics and C9 aromatics. + Two types of aromatic hydrocarbons are used. After PX is separated from the C8 aromatic hydrocarbon material, the PX-depleted material is processed in parallel liquid-phase isomerization and gas-phase isomerization units. This process can better achieve energy-saving goals.

[0011] The literature "A Study on Xylene Liquid-Phase Isomerization Catalysts" (Petrochemical Technology, Vol. 7, No. 3, 1978) investigated the performance of xylene liquid-phase isomerization reaction on the ZSM-5 catalyst, synthesized from water glass, aluminum sulfate, sulfuric acid, and ethylamine. Experimental results showed that the ZSM-5 zeolite catalyst exhibits high activity and selectivity for xylene liquid-phase isomerization and is suitable for mixed xylene feedstocks containing ethylbenzene.

[0012] How to significantly improve the isomerization activity and para-alkyl aromatic selectivity in the catalytic process of alkyl aromatic isomerization is a technical problem that urgently needs to be solved. Summary of the Invention

[0013] The purpose of this invention is to provide an alkyl aromatic hydrocarbon isomerization method and an alkyl aromatic hydrocarbon isomerization catalyst, so as to significantly improve the isomerization activity and para-alkyl aromatic hydrocarbon selectivity in the catalytic process of alkyl aromatic hydrocarbon isomerization.

[0014] In a first aspect, the present invention provides a method for isomerizing alkyl aromatics, comprising: contacting an alkyl aromatic with an alkyl aromatic isomerization catalyst in the presence of nitrogen and / or hydrogen under a reaction pressure that maintains a liquid state to carry out an isomerization reaction.

[0015] Optionally, when the alkyl aromatic hydrocarbon is contacted with an alkyl aromatic hydrocarbon isomerization catalyst for isomerization reaction under a reaction pressure that maintains a liquid state, the ratio of the total amount of nitrogen and hydrogen to the amount of the alkyl aromatic hydrocarbon is (0.03-0.5):1, and the percentage of nitrogen in the total amount of nitrogen and hydrogen is 0.1-99.9%; preferably, the ratio of the total amount of nitrogen and hydrogen to the amount of the alkyl aromatic hydrocarbon is (0.05-0.4):1, and the percentage of nitrogen in the total amount of nitrogen and hydrogen is 50%-90%.

[0016] Optionally, when the alkyl aromatic hydrocarbon is contacted with an alkyl aromatic hydrocarbon isomerization catalyst for isomerization reaction under a reaction pressure that maintains a liquid state, in the presence of nitrogen or hydrogen, the ratio of the amount of nitrogen or hydrogen to the amount of the alkyl aromatic hydrocarbon is (0.03-0.5):1; preferably, the ratio of the amount of nitrogen or hydrogen to the amount of the alkyl aromatic hydrocarbon is (0.05-0.4):1.

[0017] Optionally, the reaction conditions for the isomerization reaction include: a reaction temperature of 240℃~310℃ and a weight hourly space velocity of 1h. -1 ~10h -1 .

[0018] Optionally, the alkyl aromatic isomerization catalyst comprises 24–99.9% by mass of a ten-membered ring molecular sieve and 0.1–76% by mass of an inert support, based on the total weight of the alkyl aromatic isomerization catalyst; wherein the ten-membered ring molecular sieve is a mixed molecular sieve of ZSM-5 and ZSM-11 molecular sieves or a mixed crystal structure of ZSM-5 and ZSM-11 molecular sieves.

[0019] Optionally, in the ten-membered ring molecular sieve, the ZSM-11 molecular sieve accounts for 0.1% to 70% of the mass, based on the total weight of the ten-membered ring molecular sieve; preferably, in the ten-membered ring molecular sieve, the ZSM-11 molecular sieve accounts for 10% to 50% of the mass, based on the total weight of the ten-membered ring molecular sieve.

[0020] Optionally, the molar ratio of SiO2 to Al2O3 in the ZSM-11 molecular sieve is 20 to 200, and the molar ratio of SiO2 to Al2O3 in the ZSM-5 molecular sieve is 20 to 200; preferably, the molar ratio of SiO2 to Al2O3 in the ZSM-11 molecular sieve is 30 to 100, and the molar ratio of SiO2 to Al2O3 in the ZSM-5 molecular sieve is 30 to 100.

[0021] Optionally, the preparation method of the ZSM-5 molecular sieve, the ZSM-11 molecular sieve, and the mixed crystal structure of the ZSM-5 and ZSM-11 molecular sieves includes: mixing a silicon source, an aluminum source, a template agent, and water to obtain a mixture to be crystallized, and subjecting the mixture to hydrothermal crystallization, washing, and drying; the silicon source is selected from water glass, silica sol, and solid silica gel; the aluminum source is aluminum sulfate or sodium aluminate; the template agent is a substance conforming to the general formula N(R)4X, wherein R is an alkyl group having 1 to 4 carbon atoms, and X is a carbon atom. The template agent is a hydroxide ion or a halide anion, where N is a nitrogen atom; the alkyl group is ethyl or propyl, and the halide anion is a bromide ion; when preparing the ZSM-5 molecular sieve, the template agent with R being ethyl is selected; when preparing the ZSM-11 molecular sieve, the template agent with R being butyl is selected; when preparing the mixed crystal structure of the ZSM-5 and ZSM-11 molecular sieves, at least two template agents are selected, wherein one template agent has R being ethyl and the other template agent has R being butyl.

[0022] Optionally, the silicon source is water glass, and the feeding ratio of the silicon source, the aluminum source, the template agent and water is (0.01~0.4):1:(0.005~0.05):(0.05~1):(10~60) based on the amount of Na2O, SiO2, Al2O3, template agent and H2O in the water glass.

[0023] Optionally, the concentration of the silica sol is 10-40% by mass, preferably 20-40% by mass; the particle size of the solid silica gel is 0.005-0.05 μm, preferably 0.01-0.03 μm.

[0024] Optionally, the hydrothermal crystallization reaction conditions include: a hydrothermal temperature of 130–190°C, preferably 140–180°C; and a hydrothermal time of 18–100 hours, preferably 20–96 hours.

[0025] Optionally, the preparation method of the alkyl aromatic hydrocarbon isomerization catalyst includes: mixing the ten-membered ring molecular sieve and the inert support to obtain a first mixture; adding a pectin solution to the first mixture and then kneading and extruding to obtain a strip; subjecting the strip to a first drying and a first calcination to obtain an intermediate; subjecting the intermediate to ammonium exchange to obtain an ammonium-exchanged intermediate; subjecting the ammonium-exchanged intermediate to a second drying and a second calcination to obtain the alkyl aromatic hydrocarbon isomerization catalyst; or, subjecting the ten-membered ring molecular sieve to ammonium exchange to obtain an ammonium-exchanged molecular sieve; subjecting the ammonium-exchanged molecular sieve to a second drying and a second calcination to obtain a hydrogen-form molecular sieve; mixing the hydrogen-form molecular sieve with the inert support to obtain a second mixture; adding a pectin solution to the second mixture and then kneading and extruding to obtain a strip; subjecting the strip to a first drying and a first calcination to obtain the alkyl aromatic hydrocarbon isomerization catalyst.

[0026] Optionally, the colloidal solvent contains at least one of nitric acid, phosphoric acid, and citric acid, and the concentration of the colloidal solvent solution is 1-5% by mass; the ammonium salt used in the ammonium exchange is ammonium chloride or ammonium nitrate, and the concentration of the ammonium salt is 1-30% by mass, preferably 3-10% by mass.

[0027] Optionally, the conditions for the first drying and the second drying each independently include: a temperature of 100–140°C and a time of 4–24 h; the conditions for the first roasting and the second roasting each independently include: a temperature of 520–550°C or 400–500°C and a roasting time of 2–24 h.

[0028] Optionally, the alkyl aromatic hydrocarbon is C8-C. 10 Aromatic hydrocarbons; the inert support is alumina and / or silicon dioxide.

[0029] Optionally, in the alkyl aromatic isomerization catalyst, based on the total weight of the alkyl aromatic isomerization catalyst, the content of the ten-membered ring molecular sieve is 30-70% by mass, and the sum of the percentages of the ten-membered ring molecular sieve and the inert support is 100% by mass.

[0030] In a second aspect, the present invention provides an alkyl aromatic hydrocarbon isomerization catalyst comprising 24–99.9% by mass of a ten-membered ring molecular sieve and 0.1–76% by mass of an inert support, based on the total weight of the alkyl aromatic hydrocarbon isomerization catalyst; wherein the ten-membered ring molecular sieve is a mixed molecular sieve of ZSM-5 and ZSM-11 molecular sieves or a mixed crystal structure of ZSM-5 and ZSM-11 molecular sieves.

[0031] The present invention has the following beneficial effects:

[0032] The alkyl aromatic hydrocarbon isomerization method of the present invention effectively improves the isomerization activity of the alkyl aromatic hydrocarbon isomerization catalyst and the xylene yield by introducing nitrogen and / or hydrogen during the catalytic reaction of alkyl aromatic hydrocarbon isomerization. Attached Figure Description

[0033] Figure 1 This is the XRD diffraction pattern of ZSM-5 molecular sieve Z-1 prepared in Example 1 of this invention;

[0034] Figure 2 This is the XRD diffraction pattern of ZSM-11 molecular sieve Z-2 prepared in Example 1 of this invention;

[0035] Figure 3 This is the XRD diffraction pattern of ZSM-5 / ZSM-11 mixed crystal molecular sieve Z-3 prepared in Example 2 of this invention;

[0036] Figure 4 This is the XRD diffraction pattern of ZSM-5 molecular sieve Z-4 ​​prepared in Example 3 of this invention;

[0037] Figure 5 This is the XRD diffraction pattern of ZSM-11 molecular sieve Z-5 prepared in Example 3 of this invention;

[0038] Figure 6 This is the XRD diffraction pattern of ZSM-5 / ZSM-11 mixed crystal molecular sieve Z-6 prepared in Example 4 of this invention. Detailed Implementation

[0039] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present application will become clearer and more apparent.

[0040] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0041] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0042] In a first aspect, the present invention provides a method for isomerizing alkyl aromatics, comprising: contacting an alkyl aromatic with an alkyl aromatic isomerization catalyst in the presence of nitrogen and / or hydrogen under a reaction pressure that maintains a liquid state to carry out an isomerization reaction.

[0043] It should be noted that the reaction pressure required to keep alkyl aromatics in a liquid state is not a fixed pressure value or pressure range. This is because the pressure that needs to be controlled is related to the reaction temperature. For example, at around 250°C, a pressure of around 2 MPa is sufficient to keep alkyl aromatics in a liquid state. When the controlled reaction temperature increases, the reaction pressure required to keep alkyl aromatics in a liquid state will also increase.

[0044] It should be noted that in the catalytic reaction of alkyl aromatic hydrocarbon isomerization, various alkyl aromatic hydrocarbon isomerization catalysts commonly used in the art can be used for catalysis. By introducing nitrogen and / or hydrogen, the isomerization activity of the alkyl aromatic hydrocarbon isomerization catalyst and the xylene yield can be effectively improved.

[0045] According to one embodiment, when the alkyl aromatic hydrocarbon is contacted with an alkyl aromatic hydrocarbon isomerization catalyst for isomerization reaction under a reaction pressure that maintains a liquid state, the ratio of the total amount of nitrogen and hydrogen to the amount of the alkyl aromatic hydrocarbon is (0.03-0.5):1, and the percentage of nitrogen in the total amount of nitrogen and hydrogen is 0.1-99.9%; preferably, the ratio of the total amount of nitrogen and hydrogen to the amount of the alkyl aromatic hydrocarbon is (0.05-0.4):1, and the percentage of nitrogen in the total amount of nitrogen and hydrogen is 50%-90%.

[0046] It should be noted that in the alkyl aromatics isomerization method of the present invention, nitrogen and hydrogen can be simultaneously introduced into the reaction system loaded with alkyl aromatics and alkyl aromatics isomerization catalyst, or a mixture of nitrogen and hydrogen can be introduced into the reaction system, or nitrogen and hydrogen can be introduced into the reaction system loaded with alkyl aromatics liquid feed together with the alkyl aromatics isomerization catalyst.

[0047] According to one embodiment, when the alkyl aromatic hydrocarbon is contacted with an alkyl aromatic hydrocarbon isomerization catalyst for isomerization reaction under a reaction pressure that maintains a liquid state, in the presence of nitrogen or hydrogen, the ratio of the amount of nitrogen or hydrogen to the amount of the alkyl aromatic hydrocarbon is (0.03-0.5):1; preferably, the ratio of the amount of nitrogen or hydrogen to the amount of the alkyl aromatic hydrocarbon is (0.05-0.4):1.

[0048] It should be noted that, as mentioned above, nitrogen or hydrogen can be introduced into the reaction system loaded with alkyl aromatics and alkyl aromatics isomerization catalysts, or nitrogen or hydrogen can be introduced into the reaction system loaded with alkyl aromatics isomerization catalysts together with the alkyl aromatics liquid feed.

[0049] In a preferred embodiment, during the above-mentioned isomerization reaction, the alkyl aromatic hydrocarbon is contacted with the alkyl aromatic hydrocarbon isomerization catalyst under a liquid reaction pressure in the presence of nitrogen to carry out the isomerization reaction. In the above-mentioned alkyl aromatic hydrocarbon isomerization system, nitrogen has better solubility and can dissolve more in the liquid reactant system. Therefore, carrying out the isomerization reaction in the presence of nitrogen can further improve the isomerization activity of the alkyl aromatic hydrocarbon isomerization catalyst and the xylene yield.

[0050] According to one embodiment, the reaction conditions for the isomerization reaction include: a reaction temperature of 240℃~310℃ and a weight hourly space velocity of 1h. -1 ~10h -1 .

[0051] According to a preferred embodiment, the alkyl aromatic isomerization catalyst comprises 24-99.9% by mass of a ten-membered ring molecular sieve and 0.1-76% by mass of an inert support, based on the total weight of the alkyl aromatic isomerization catalyst; wherein the ten-membered ring molecular sieve is a mixed molecular sieve of ZSM-5 molecular sieve and ZSM-11 molecular sieve or a mixed crystal structure of ZSM-5 molecular sieve and ZSM-11 molecular sieve.

[0052] In the alkyl aromatic hydrocarbon isomerization method of this embodiment, a mixed molecular sieve of ZSM-5 molecular sieve and ZSM-11 molecular sieve or a mixed crystal structure of ZSM-5 molecular sieve and ZSM-11 molecular sieve is used as a catalyst. During the catalytic reaction of alkyl aromatic hydrocarbon isomerization, the isomerization activity of the alkyl aromatic hydrocarbon isomerization catalyst and the xylene yield can be further improved more effectively by introducing nitrogen and / or hydrogen.

[0053] It should be noted that, in this preferred embodiment, the alkyl aromatic hydrocarbon is contacted with the alkyl aromatic hydrocarbon isomerization catalyst under a liquid reaction pressure and in the presence of nitrogen and / or hydrogen to carry out the isomerization reaction. By controlling the reaction conditions of the isomerization reaction, the isomerization activity of the catalyst and the selectivity of para-alkyl aromatic hydrocarbons in the isomerization reaction can be further improved.

[0054] In one embodiment, the ZSM-11 molecular sieve accounts for 0.1% to 70% of the mass of the ten-membered ring molecular sieve, based on the total weight of the ten-membered ring molecular sieve; preferably, the ZSM-11 molecular sieve accounts for 10% to 50% of the mass of the ten-membered ring molecular sieve, based on the total weight of the ten-membered ring molecular sieve.

[0055] It should be noted that if the ten-membered ring molecular sieve is a mixed crystal structure of ZSM-5 molecular sieve and ZSM-11 molecular sieve, then in the mixed crystal structure, the mass proportion of the crystal component with the microstructure of ZSM-11 molecular sieve crystal structure in the ten-membered ring molecular sieve is 0.1% to 70%, preferably 10% to 50%.

[0056] In one embodiment, the molar ratio of SiO2 to Al2O3 in the ZSM-11 molecular sieve is 20–200, and the molar ratio of SiO2 to Al2O3 in the ZSM-5 molecular sieve is 20–200; preferably, the molar ratio of SiO2 to Al2O3 in the ZSM-11 molecular sieve is 30–100, and the molar ratio of SiO2 to Al2O3 in the ZSM-5 molecular sieve is 30–100.

[0057] In the alkyl aromatic hydrocarbon isomerization method described above, ZSM-5 molecular sieve, ZSM-11 molecular sieve, or mixed crystal structure with a specific silicon-to-aluminum ratio are selected for preparation. During the catalyst preparation process, the mass ratio of ZSM-5 molecular sieve and ZSM-11 molecular sieve is controlled in a certain proportion. The resulting alkyl aromatic hydrocarbon isomerization catalyst allows for better selectivity for para-alkyl aromatic hydrocarbons when nitrogen and hydrogen are introduced during the alkyl aromatic hydrocarbon isomerization process while maintaining a liquid reaction pressure.

[0058] According to one embodiment, the preparation method of the ZSM-5 molecular sieve, the ZSM-11 molecular sieve, and the mixed crystal structure of the ZSM-5 and ZSM-11 molecular sieves includes: mixing a silicon source, an aluminum source, a template agent, and water to obtain a mixture to be crystallized; subjecting the mixture to hydrothermal crystallization, washing, and drying; wherein the silicon source is selected from water glass, silica sol, and solid silica gel; the aluminum source is aluminum sulfate or sodium aluminate; and the template agent is a substance conforming to the general formula N(R)4X, wherein R is an alkyl group having 1 to 4 carbon atoms. X is a hydroxide ion or a halide anion, etc., and N is a nitrogen atom; the alkyl group is ethyl or propyl, and the halide anion is a bromide ion; when preparing the ZSM-5 molecular sieve, the template agent with R being ethyl is selected; when preparing the ZSM-11 molecular sieve, the template agent with R being butyl is selected; when preparing the mixed crystal structure of the ZSM-5 molecular sieve and the ZSM-11 molecular sieve, at least two template agents are selected, wherein one template agent has R being ethyl and the other template agent has R being butyl.

[0059] In one embodiment, the silicon source is water glass, and the feeding ratio of the silicon source, the aluminum source, the template agent and water is (0.01~0.4):1:(0.005~0.05):(0.05~1):(10~60) based on the amount of Na2O, SiO2, Al2O3, template agent and H2O in the water glass.

[0060] It should be noted that when using water glass as the silicon source, the silicon source, aluminum source, template agent and water can be mixed according to the above-mentioned molar ratio of Na2O in water glass, SiO2, Al2O3 in water glass, template agent and H2O as (0.01~0.4):1:(0.005~0.05):(0.05~1):(10~60).

[0061] In one embodiment, the concentration of the silica sol is 10-40% by mass, preferably 20-40% by mass; the particle size of the solid silica gel is 0.005-0.05 μm, preferably 0.01-0.03 μm.

[0062] According to one embodiment, the hydrothermal crystallization reaction conditions include: a hydrothermal temperature of 130–190°C, preferably 140–180°C; and a hydrothermal time of 18–100 hours, preferably 20–96 hours.

[0063] It should be noted that if the ten-membered ring molecular sieve is a mixed molecular sieve of ZSM-5 molecular sieve and ZSM-11 molecular sieve, then ZSM-5 molecular sieve and ZSM-11 molecular sieve are prepared separately according to the above method, and then the ZSM-5 molecular sieve and ZSM-11 molecular sieve are mixed to obtain the ten-membered ring molecular sieve.

[0064] According to one embodiment, the preparation method of the alkyl aromatic hydrocarbon isomerization catalyst includes: a first method: mixing the ten-membered ring molecular sieve and the inert support to obtain a first mixture; adding a pectin solution to the first mixture and then kneading and extruding to obtain a strip; subjecting the strip to a first drying and a first calcination to obtain an intermediate; subjecting the intermediate to ammonium exchange to obtain an ammonium-exchanged intermediate; subjecting the ammonium-exchanged intermediate to a second drying and a second calcination to obtain the alkyl aromatic hydrocarbon isomerization catalyst; or, a second method: subjecting the ten-membered ring molecular sieve to ammonium exchange to obtain an ammonium-exchanged molecular sieve; subjecting the ammonium-exchanged molecular sieve to a second drying and a second calcination to obtain a hydrogen-form molecular sieve; mixing the hydrogen-form molecular sieve with the inert support to obtain a second mixture; adding a pectin solution to the second mixture and then kneading and extruding to obtain a strip; subjecting the strip to a first drying and a first calcination to obtain the alkyl aromatic hydrocarbon isomerization catalyst.

[0065] It should be noted that the alkyl aromatic hydrocarbon isomerization catalyst prepared by the above method has high isomerization activity and xylene yield. As a preferred embodiment, the alkyl aromatic hydrocarbon isomerization method of the present invention may further include a pretreatment step before the isomerization reaction: separating or removing ethylbenzene from the alkyl aromatic hydrocarbon. Thus, under liquid reaction pressure and in the presence of nitrogen and hydrogen, the ethylbenzene content in the alkyl aromatic hydrocarbon undergoing isomerization reaction in contact with the alkyl aromatic hydrocarbon isomerization catalyst is very low. Therefore, the alkyl aromatic hydrocarbon isomerization catalyst of the present invention does not need to be loaded with other metal components, thereby simplifying the catalyst preparation process, shortening the preparation cycle, and improving the preparation efficiency. The small amount of ethylbenzene remaining in the alkyl aromatic hydrocarbon can undergo ethyl transfer under the catalysis of the Brønsted acid active center of the alkyl aromatic hydrocarbon isomerization catalyst of the present invention, generating benzene and diethylbenzene, etc.

[0066] It should be noted that after the ZSM-5 molecular sieve, ZSM-11 molecular sieve, and mixed crystal structure of ZSM-5 molecular sieve and ZSM-11 molecular sieve are prepared by the method described in this invention, before preparing the alkyl aromatic hydrocarbon isomerization catalyst according to the first method described above, the ZSM-5 molecular sieve, ZSM-11 molecular sieve or mixed crystal structure can be washed with deionized water until neutral, such as pH range 6 to 8.

[0067] It should be noted that in the second method described above, if the ten-membered ring molecular sieve is a mixed molecular sieve of ZSM-5 and ZSM-11 molecular sieves, during ammonium exchange, the ZSM-5 and ZSM-11 molecular sieves can be added together to the ammonium salt solution for ammonium exchange, or the ZSM-5 and ZSM-11 molecular sieves can be added separately to different ammonium salt solutions for ammonium exchange and then mixed to obtain the ammonium-exchanged molecular sieve.

[0068] In one embodiment, the colloidal solvent contains at least one of nitric acid, phosphoric acid, and citric acid, and the concentration of the colloidal solvent solution is 1-5% by mass; the ammonium salt used in the ammonium exchange is ammonium chloride or ammonium nitrate, and the concentration of the ammonium salt is 1-30% by mass, preferably 3-10% by mass.

[0069] According to one embodiment, the conditions for the first drying and the second drying each independently include: a temperature of 100-140°C and a time of 4-24 hours; the conditions for the first roasting and the second roasting each independently include: a temperature of 520-550°C or 400-500°C and a roasting time of 2-24 hours.

[0070] It should be noted that the first and second calcinations can be carried out in an air atmosphere.

[0071] In one embodiment, the alkyl aromatic hydrocarbon is C8-C. 10Aromatic hydrocarbons; the inert support is alumina and / or silicon dioxide.

[0072] It should be noted that C8-C 10 Aromatic hydrocarbons can be aromatic hydrocarbons containing methyl and C2-substituted benzene.

[0073] According to a preferred embodiment, in the alkyl aromatic isomerization catalyst, based on the total weight of the alkyl aromatic isomerization catalyst, the content of the ten-membered ring molecular sieve is 30-70% by mass, and the sum of the percentages of the ten-membered ring molecular sieve and the inert support is 100% by mass.

[0074] In a second aspect, the present invention provides an alkyl aromatic hydrocarbon isomerization catalyst comprising 24–99.9% by mass of a ten-membered ring molecular sieve and 0.1–76% by mass of an inert support, based on the total weight of the alkyl aromatic hydrocarbon isomerization catalyst; wherein the ten-membered ring molecular sieve is a mixed molecular sieve of ZSM-5 and ZSM-11 molecular sieves or a mixed crystal structure of ZSM-5 and ZSM-11 molecular sieves.

[0075] It should be noted that the alkyl aromatic isomerization catalyst described in this invention can be used for C8 aromatic isomerization, which can increase the production of p-xylene and maintain good selectivity.

[0076] The present invention will be further described in detail below through examples.

[0077] In the following examples, materials conforming to the composition of Table 1 below were used as alkyl aromatic hydrocarbon feedstocks; the materials or reagents used in the examples were commercially available products.

[0078] Table 1

[0079]

[0080] Note: In Table 1 above, C8NA represents C8 non-aromatic hydrocarbons, B represents benzene, T represents toluene, and EB represents ethylbenzene.

[0081] Example 1

[0082] (1) Preparation of ZSM-5 molecular sieve Z-1

[0083] Add 58.5g of water glass (SiO2 content 24.01% by mass, Na2O content 7.08% by mass, Al2O3 content 0.2% by mass, the same below), 1.83g of aluminum sulfate octadechydrate, and 9.84g of tetraethylammonium bromide N(C2H5)4 to a 200mL reactor. + Br -As a template agent (T), 0.8g of deionized water was mixed evenly to obtain a mixture to be crystallized; the molar ratio of each material was Na2O:SiO2:Al2O3:T:H2O=0.28:1:0.017:0.2:10;

[0084] The mixture to be crystallized was hydrothermally crystallized at 170℃ for 36 hours. The solid obtained after crystallization was washed with excess deionized water until the pH of the washing solution was 6-8, which was neutral. Then it was dried at 120℃ for 6 hours to obtain ZSM-5 molecular sieve, denoted as Z-1, with a silica / alumina molar ratio of 60 (determined by XRF method, the same below).

[0085] (2) Preparation of ZSM-11 molecular sieve Z-2

[0086] The method for preparing ZSM-5 molecular sieve is the same as in step (1), except that the template agent tetraethylammonium bromide N(C2H5)4 in (1) is used instead. + Br - Replace with tetrabutylammonium bromide N(C4H9)4 + Br - .

[0087] Add 58.5g of water glass (SiO2 content 24.01% by mass, Na2O content 7.08% by mass, Al2O3 content 0.2% by mass, the same below), 1.83g of aluminum sulfate octadechydrate, and 15.09g of tetrabutylammonium bromide N(C4H9)4 to a 200mL reactor. + Br - As a template agent (T), 0.8g of deionized water was mixed evenly to obtain a mixture to be crystallized; the molar ratio of each material was Na2O:SiO2:Al2O3:T:H2O=0.28:1:0.017:0.2:10;

[0088] The mixture to be crystallized was hydrothermally crystallized at 160℃ for 48 hours. The solid obtained after crystallization was washed with excess deionized water until the pH of the washing solution was 6-8, which was neutral. Then it was dried at 120℃ for 6 hours to obtain ZSM-11 molecular sieve, denoted as Z-2, with a silica / alumina molar ratio of 60 (determined by XRF method, the same below).

[0089] (3) Preparation of catalyst C-1

[0090] Take ZSM-5 molecular sieve powder Z-1 prepared in step (1), ZSM-11 molecular sieve powder Z-2 prepared in step (2), and alumina and mix them thoroughly in a mass ratio of 4:3:3. Add nitric acid aqueous solution with a concentration of 5% by mass and knead evenly. The nitric acid aqueous solution used accounts for 40% by mass of the solid mixture. Then, extrude the mixture into strips. Dry the strips at 120°C for 6 hours, then cut them into granules and calcine them at 540°C for 4 hours. After calcination, the sample is subjected to ion exchange at 90°C for 2 hours with ammonium chloride aqueous solution with a concentration of 5% by mass. After washing until there are no chloride ions in the mother liquor, the sample is dried at 120°C for 6 hours and calcined at 500°C for 4 hours to obtain catalyst C-1.

[0091] (4) Alkyl aromatic isomerization

[0092] In a continuous flow small fixed-bed device, 3 grams of catalyst C-1 were loaded, and the catalyst performance was evaluated using alkyl aromatic hydrocarbon feedstock conforming to the composition in Table 1. The alkyl aromatic hydrocarbon feedstock was fed into the small fixed-bed device, and a mixture of nitrogen and hydrogen (nN2:nH2 = 8:2) was added to the feedstock through a high-pressure dissolved gas device. The molar ratio of the mixed gas to the alkyl aromatic hydrocarbon feedstock was controlled at 0.05:1. The device was operated at 250°C, 2 MPa, and a feed mass hourly space velocity of 2 h⁻¹. -1 The reaction takes place under specific conditions.

[0093] Example 2

[0094] (1) Preparation of ZSM-5 / ZSM-11 mixed crystal molecular sieve Z-3

[0095] Molecular sieve Z-3 was synthesized according to step (1) in Example 1, except that the template agent was replaced with a mixture of tetraethylammonium bromide and tetrabutylammonium bromide. The total amount of the two was equal to the amount of the template agent in step (1) of Example 1. The molar ratio of tetraethylammonium bromide to tetrabutylammonium bromide was 4:3, and the molar ratio of silicon dioxide to aluminum oxide in mixed crystal molecular sieve Z-3 was 61.

[0096] (2) Preparation of catalyst C-2

[0097] The mixed-crystal molecular sieve powder Z-3 obtained in step (1) was thoroughly mixed with alumina at a mass ratio of 7:3; a nitric acid aqueous solution with a concentration of 5% by mass was added and kneaded evenly, with the nitric acid aqueous solution accounting for 40% of the mass of the solid mixture; then extruded into strips; the strips were dried at 120°C for 6 hours, then granulated and calcined at 540°C for 4 hours; the calcined sample was subjected to ion exchange at 90°C for 2 hours with a 5% by mass ammonium chloride aqueous solution, washed until no chloride ions were present in the mother liquor, dried at 120°C for 6 hours, and calcined at 500°C for 4 hours to obtain catalyst C-2;

[0098] (3) Alkyl aromatic isomerization

[0099] In a continuous flow small fixed-bed device, 3 grams of catalyst C-2 were loaded. The catalyst performance was evaluated using alkyl aromatic hydrocarbon feedstock conforming to the composition in Table 1. The alkyl aromatic hydrocarbon feedstock was fed into the small fixed-bed device, and a mixture of nitrogen and hydrogen (nN2:nH2 = 8:2) was added to the feedstock through a high-pressure dissolved gas device. The molar ratio of the mixed gas to the alkyl aromatic hydrocarbon feedstock was controlled at 0.05:1. The device was tested at 250°C, 2 MPa, and a feed mass hourly space velocity of 2 h⁻¹. -1 The reaction takes place under specific conditions.

[0100] Example 3

[0101] (1) Preparation of ZSM-5 molecular sieve Z-4 ​​and ZSM-11 molecular sieve Z-5

[0102] Molecular sieve ZSM-5 was synthesized according to the method of step (1) in Example 1, and denoted as Z-4. The difference is that the molar ratio of each material is Na2O:SiO2:Al2O3:T:H2O=0.28:1:0.033:0.1:10, and the molar ratio of silicon oxide / alumina in ZSM-5 molecular sieve Z-4 ​​is 30.

[0103] Molecular sieve ZSM-11 was synthesized according to the method of step (2) in Example 1, and was designated as Z-5. The difference was that the molar ratio of each material was Na2O:SiO2:Al2O3:T:H2O = 0.28:1:0.033:0.1:10, and the molar ratio of silicon oxide to aluminum oxide in ZSM-11 molecular sieve Z-5 was 30.

[0104] (2) Preparation of catalyst C-3

[0105] Catalyst C-3 was prepared according to step (3) in Example 1, except that the molecular sieve was replaced with ZSM-5 molecular sieve Z-4 ​​and ZSM-11 molecular sieve Z-5;

[0106] (3) Alkyl aromatic isomerization

[0107] In a continuous flow small fixed-bed device, 3 grams of catalyst C-3 were loaded, and the catalyst performance was evaluated using alkyl aromatic hydrocarbon feedstock conforming to the composition in Table 1. The alkyl aromatic hydrocarbon feedstock was fed into the small fixed-bed device, and a mixture of nitrogen and hydrogen (nN2:nH2 = 8:2) was added to the feedstock through a high-pressure dissolved gas device. The molar ratio of the mixed gas to the alkyl aromatic hydrocarbon feedstock was controlled at 0.05:1. The device was operated at 250°C, 2 MPa, and a feed mass hourly space velocity of 2 h⁻¹. -1 The reaction takes place under specific conditions.

[0108] Example 4

[0109] (1) Preparation of ZSM-5 / ZSM-11 mixed crystal molecular sieve Z-6

[0110] ZSM-5 / ZSM-11 mixed-crystal molecular sieve Z-6 was synthesized according to step (1) of Example 2, except that the molar ratio of each material was Na2O:SiO2:Al2O3:T:H2O = 0.28:1:0.033:0.2:10. The template agent T was a mixture of tetraethylammonium bromide and tetrabutylammonium bromide, with a molar ratio of 4:3. The molar ratio of silicon oxide to aluminum oxide in the mixed-crystal molecular sieve Z-6 was 32.

[0111] (2) Preparation of catalyst C-4

[0112] Catalyst C-4 was prepared according to step (2) in Example 2, except that the molecular sieve was replaced with ZSM-5 / ZSM-11 mixed crystal molecular sieve Z-6;

[0113] (3) Alkyl aromatic isomerization

[0114] In a continuous flow small fixed-bed device, 3 grams of catalyst C-4 were loaded. The catalyst performance was evaluated using alkyl aromatic hydrocarbon feedstock conforming to the composition in Table 1. The alkyl aromatic hydrocarbon feedstock was fed into the small fixed-bed device, and a mixture of nitrogen and hydrogen (nN2:nH2 = 8:2) was added to the feedstock through a high-pressure dissolved gas device. The molar ratio of the mixed gas to the alkyl aromatic hydrocarbon feedstock was controlled at 0.05:1. The device was tested at 250°C, 2 MPa, and a feed mass hourly space velocity of 2 h⁻¹. -1 The reaction takes place under specific conditions.

[0115] Example 5

[0116] (1) ZSM-5 / ZSM-11 mixed crystal molecular sieve Z-6 was prepared according to the method of step (1) in Example 4;

[0117] (2) Catalyst C-4 was prepared according to the method in step (2) of Example 4;

[0118] (3) Alkyl aromatic isomerization

[0119] In a continuous flow small fixed-bed device, 3 grams of catalyst C-4 were loaded. The catalyst performance was evaluated using alkyl aromatic hydrocarbon feedstock conforming to the composition in Table 1. The alkyl aromatic hydrocarbon feedstock was fed into the small fixed-bed device, and nitrogen was added to the feedstock through a high-pressure dissolved gas device. The molar ratio of nitrogen to alkyl aromatic hydrocarbon feedstock was controlled at 0.05:1. The device was operated at 250°C, 2 MPa, and a feed mass hourly space velocity of 2 h⁻¹. -1 The reaction takes place under specific conditions.

[0120] Example 6

[0121] (1) ZSM-5 / ZSM-11 mixed crystal molecular sieve Z-6 was prepared according to the method of step (1) in Example 4;

[0122] (2) Catalyst C-4 was prepared according to the method in step (2) of Example 4;

[0123] (3) Alkyl aromatic isomerization

[0124] In a continuous flow small fixed-bed device, 3 grams of catalyst C-4 were loaded. The catalyst performance was evaluated using alkyl aromatic hydrocarbon feedstock conforming to the composition in Table 1. The alkyl aromatic hydrocarbon feedstock was fed into the small fixed-bed device, and hydrogen was added to the feedstock through a high-pressure dissolved gas device. The molar ratio of hydrogen to alkyl aromatic hydrocarbon feedstock was controlled at 0.05:1. The device was operated at 250°C, 2 MPa, and a feed mass hourly space velocity of 2 h⁻¹. -1 The reaction takes place under specific conditions.

[0125] Example 7

[0126] (1) ZSM-5 molecular sieve Z-4 ​​and ZSM-11 molecular sieve Z-5 were prepared according to the method of step (1) in Example 3;

[0127] (2) Preparation of catalyst C-5

[0128] Catalyst C-5 was prepared according to step (3) in Example 1, except that the mass ratio of molecular sieve powders Z-4 and Z-5 to alumina was 6:1:3.

[0129] (3) Alkyl aromatic isomerization

[0130] In a continuous flow small fixed-bed device, 3 grams of catalyst C-5 were loaded, and the catalyst performance was evaluated using alkyl aromatic hydrocarbon feedstock conforming to the composition in Table 1. The alkyl aromatic hydrocarbon feedstock was fed into the small fixed-bed device, and a mixture of nitrogen and hydrogen (nN2:nH2 = 8:2) was added to the feedstock through a high-pressure dissolved gas device. The molar ratio of the mixed gas to the alkyl aromatic hydrocarbon feedstock was controlled at 0.05:1. The device was operated at 250°C, 2 MPa, and a feed mass hourly space velocity of 2 h⁻¹. -1 The reaction takes place under specific conditions.

[0131] Comparative Example 1

[0132] (1) Beta molecular sieve with a silica-to-alumina ratio of 28 was used as an acidic material and was thoroughly mixed with alumina at a mass ratio of 7:3. A 5% by mass nitric acid aqueous solution was added and kneaded until uniform. The nitric acid aqueous solution accounted for 40% of the mass of the solid mixture. Then, the mixture was extruded into strips. The strips were dried at 120°C for 6 hours, then granulated and calcined at 540°C for 4 hours. The calcined sample was subjected to ion exchange at 90°C for 2 hours with a 5% by mass ammonium chloride aqueous solution. The sample was washed until there were no chloride ions in the mother liquor. The sample was dried at 120°C for 6 hours and calcined at 500°C for 4 hours to obtain catalyst D-1.

[0133] (2) Based on the catalyst D-1 obtained in step (1), alkyl aromatic hydrocarbon isomerization was carried out according to the method in step (4) of Example (1);

[0134] (3) Based on the catalyst D-1 obtained in step (1), alkyl aromatic hydrocarbon isomerization is carried out according to the method in step (4) of Example (1), except that nitrogen and hydrogen are not added to the feed.

[0135] Comparative Example 2

[0136] (1) ZSM-12 molecular sieve with a silicon-to-aluminum ratio of 30 was used as the acid material and was thoroughly mixed with alumina at a mass ratio of 7:3. A nitric acid aqueous solution with a concentration of 5% by mass was added and kneaded evenly. The nitric acid aqueous solution accounted for 40% of the mass of the solid mixture. Then, it was extruded into strips. The strips were dried at 120°C for 6 hours, then granulated and calcined at 540°C for 4 hours. The calcined sample was subjected to ion exchange with a 5% by mass ammonium chloride aqueous solution at 90°C for 2 hours. The sample was washed until there were no chloride ions in the mother liquor. It was dried at 120°C for 6 hours and calcined at 500°C for 4 hours to obtain catalyst D-2.

[0137] (2) Based on the catalyst D-2 obtained in step (1), alkyl aromatic hydrocarbon isomerization was carried out according to the method in step (4) of Example (1);

[0138] (3) Based on the catalyst D-2 obtained in step (1), alkyl aromatic hydrocarbon isomerization is carried out according to the method in step (4) of Example (1), except that nitrogen and hydrogen are not added to the feed.

[0139] Comparative Example 3

[0140] (1) ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 30 was used as the acid material and was thoroughly mixed with alumina at a mass ratio of 7:3. A nitric acid aqueous solution with a concentration of 5% by mass was added and kneaded evenly. The nitric acid aqueous solution accounted for 40% of the mass of the solid mixture. Then, it was extruded into strips. The strips were dried at 120°C for 6 hours, then granulated and calcined at 540°C for 4 hours. The calcined sample was subjected to ion exchange with a 5% by mass ammonium chloride aqueous solution at 90°C for 2 hours. The sample was washed until there were no chloride ions in the mother liquor. It was dried at 120°C for 6 hours and calcined at 500°C for 4 hours to obtain catalyst D-3.

[0141] (2) Based on the catalyst D-3 obtained in step (1), alkyl aromatic hydrocarbon isomerization was carried out according to the method in step (4) of Example (1);

[0142] (3) Based on the catalyst D-3 obtained in step (1), alkyl aromatic hydrocarbon isomerization was carried out according to the method in step (4) of Example (1), except that nitrogen and hydrogen were not added to the feed.

[0143] Comparative Example 4

[0144] (1) ZSM-11 molecular sieve with a silicon-to-aluminum ratio of 30 was used as an acidic material and was thoroughly mixed with alumina at a mass ratio of 7:3. A nitric acid aqueous solution with a concentration of 5% by mass was added and kneaded evenly. The nitric acid aqueous solution accounted for 40% of the mass of the solid mixture. Then, it was extruded into strips. The strips were dried at 120°C for 6 hours, then granulated and calcined at 540°C for 4 hours. The calcined sample was subjected to ion exchange with a 5% by mass ammonium chloride aqueous solution at 90°C for 2 hours. The sample was washed until there were no chloride ions in the mother liquor. It was dried at 120°C for 6 hours and calcined at 500°C for 4 hours to obtain catalyst D-4.

[0145] (2) Based on the catalyst D-4 obtained in step (1), alkyl aromatic hydrocarbon isomerization was carried out according to the method in step (4) of Example (1);

[0146] (3) Based on the catalyst D-4 obtained in step (1), alkyl aromatic hydrocarbon isomerization was carried out according to the method in step (4) of Example (1), except that nitrogen and hydrogen were not added to the feed.

[0147] Comparative Example 5

[0148] (1) EU-1 molecular sieve with a silicon-to-aluminum ratio of 30 was used as the acid material and was thoroughly mixed with alumina at a mass ratio of 7:3. A nitric acid aqueous solution with a concentration of 5% by mass was added and kneaded evenly. The nitric acid aqueous solution accounted for 40% of the mass of the solid mixture. Then, it was extruded into strips. The strips were dried at 120°C for 6 hours, then granulated and calcined at 540°C for 4 hours. The calcined sample was subjected to ion exchange with a 5% by mass ammonium chloride aqueous solution at 90°C for 2 hours. The sample was washed until there were no chloride ions in the mother liquor. It was dried at 120°C for 6 hours and calcined at 500°C for 4 hours to obtain catalyst D-5.

[0149] (2) Based on the catalyst D-5 obtained in step (1), alkyl aromatic hydrocarbon isomerization was carried out according to the method in step (4) of Example (1);

[0150] (3) Based on the catalyst D-5 obtained in step (1), alkyl aromatic hydrocarbon isomerization was carried out according to the method in step (4) of Example (1), except that nitrogen and hydrogen were not added to the feed.

[0151] Comparative Example 6

[0152] Alkyl aromatic hydrocarbon isomerization was performed using catalyst C-1 from Example 1, except that nitrogen and hydrogen were not added to the feed.

[0153] Comparative Example 7

[0154] Alkyl aromatic hydrocarbon isomerization was performed using catalyst C-2 from Example 2, except that nitrogen and hydrogen were not added to the feed.

[0155] Comparative Example 8

[0156] Alkyl aromatic hydrocarbon isomerization was performed using catalyst C-3 from Example 3, except that nitrogen and hydrogen were not added to the feed.

[0157] Comparative Example 9

[0158] Alkyl aromatic hydrocarbon isomerization was performed using catalyst C-4 from Example 4, except that nitrogen and hydrogen were not added to the feed.

[0159] Comparative Example 10

[0160] Alkyl aromatic hydrocarbon isomerization was performed using catalyst C-5 from Example 7, except that nitrogen and hydrogen were not added to the feed compared to Example 5.

[0161] Test Example 1

[0162] The p-xylene content and total xylene content in the products of Examples 1-7 and Comparative Examples 1-10 were detected by gas chromatography. The isomerization activity index of Examples 1-7 and Comparative Examples 1-10 was calculated using the following formula:

[0163]

[0164] The total amount of xylene in the raw materials and products of Examples 1-7 and Comparative Examples 1-10 was determined by gas chromatography, and the yield of xylene in Examples 1-7 and Comparative Examples 1-10 was calculated using the following formula:

[0165]

[0166] The calculation results are shown in Tables 2-4 below. The results of Examples 1-7 are shown in Table 1, the results of Comparative Examples 1-5 are shown in Table 2, and the results of Comparative Examples 6-10 are shown in Table 3.

[0167] Table 2

[0168]

[0169]

[0170] Table 3

[0171]

[0172] Table 4

[0173]

[0174] As shown in Tables 2-4, when isomerization is carried out using the methods of Examples 1-7 of this invention, the catalysts prepared in Examples 1-7 have higher isomerization activity (PX / ∑X) for the target product p-xylene and fewer by-products compared to the catalysts in Comparative Examples 1-5, while maintaining a higher xylene yield. The overall performance of the catalysts in Examples 1-7 is superior to that of the catalysts in Comparative Examples 1-5. This indicates that the catalysts using the method of this invention have high reactivity and selectivity. A comparison of Tables 2 and 4 shows that, for the same catalysts, using evaluation methods with and without gas, the addition of a small amount of nitrogen and / or hydrogen to the feed significantly improves the isomerization activity of all catalysts while maintaining a high xylene yield. This indicates that the alkyl aromatic hydrocarbon isomerization method of this invention can significantly improve the overall performance of the catalyst.

[0175] Test Example 2

[0176] X-ray powder diffraction analysis was performed on molecular sieves Z-1, Z-2, Z-3, Z-4, Z-5, and Z-6, respectively. The obtained XRD patterns are shown below. Figure 1-6The horizontal axis of the XRD spectrum represents the 2θ angle, and the vertical axis represents the X-ray diffraction intensity.

[0177] pass Figures 1-6 It can be seen that, Figure 1 and Figure 4 The characteristic spectrum of a typical ZSM-5 molecular sieve; Figure 2 and Figure 5 The characteristic spectrum of a typical ZSM-11 molecular sieve; Figure 3 and Figure 6 The spectrum of the mixed-crystal molecular sieves shows the unique peak structure of the mixed crystals.

[0178] The alkyl aromatic hydrocarbon isomerization method of the present invention is applicable to the liquid-phase isomerization reaction of aromatic hydrocarbons containing methyl and C2 or higher substituted benzenes. It exhibits high isomerization reaction performance of methyl and C2 or higher substituted alkylbenzenes and good reaction selectivity. During the isomerization process, adding a small amount of hydrogen and nitrogen in a certain proportion to the liquid-phase feed can significantly improve the performance of the catalyst.

[0179] In the description of this application, it should be noted that the terms "upper", "lower", "inner", "outer", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship in the working state of this application. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0180] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0181] The present application has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present application based on these embodiments, all of which fall within the protection scope of the present application.

Claims

1. A method for isomerization of alkyl aromatics, characterized in that, include: An alkyl aromatic hydrocarbon is brought into contact with an alkyl aromatic hydrocarbon isomerization catalyst under a reaction pressure maintained in a liquid state and in the presence of nitrogen to carry out an isomerization reaction, wherein the molar ratio of nitrogen to the molar ratio of the alkyl aromatic hydrocarbon is (0.03~0.5):

1. The alkyl aromatic hydrocarbon is C8-C. 10 The alkyl aromatic hydrocarbon isomerization catalyst comprises 24-99.9% by mass of a ten-membered ring molecular sieve and 0.1-76% by mass of an inert support, based on the total weight of the alkyl aromatic hydrocarbon isomerization catalyst; wherein the ten-membered ring molecular sieve is a mixed crystal structure of ZSM-5 molecular sieve and ZSM-11 molecular sieve.

2. The alkyl aromatic hydrocarbon isomerization method according to claim 1, characterized in that, The ratio of the amount of nitrogen to the amount of the alkyl aromatic hydrocarbon is (0.05~0.4):

1.

3. The alkyl aromatic hydrocarbon isomerization method according to claim 1 or 2, characterized in that, The reaction conditions for the isomerization reaction include: The reaction temperature was 240℃~310℃ and the weight hourly space velocity was 1h. -1 ~10h -1 .

4. The alkyl aromatic hydrocarbon isomerization method according to claim 1, characterized in that, In the ten-membered ring molecular sieve, the ZSM-11 molecular sieve accounts for 0.1% to 70% of the mass, based on the total weight of the ten-membered ring molecular sieve.

5. The alkyl aromatic hydrocarbon isomerization method according to claim 4, characterized in that, In the ten-membered ring molecular sieve, the ZSM-11 molecular sieve accounts for 10-50% of the mass, based on the total weight of the ten-membered ring molecular sieve.

6. The alkyl aromatic hydrocarbon isomerization method according to claim 4, characterized in that, The molar ratio of SiO2 to Al2O3 in the ZSM-11 molecular sieve is 20~200, and the molar ratio of SiO2 to Al2O3 in the ZSM-5 molecular sieve is 20~200.

7. The alkyl aromatic hydrocarbon isomerization method according to claim 6, characterized in that, The molar ratio of SiO2 to Al2O3 in the ZSM-11 molecular sieve is 30~100, and the molar ratio of SiO2 to Al2O3 in the ZSM-5 molecular sieve is 30~100.

8. The alkyl aromatic hydrocarbon isomerization method according to claim 6, characterized in that, The preparation method of the mixed crystal structure of the ZSM-5 molecular sieve and ZSM-11 molecular sieve includes: A mixture of silicon source, aluminum source, template agent and water is obtained to crystallize the mixture, which is then subjected to hydrothermal crystallization, washing and drying. The silicon source is selected from water glass, silica sol, and solid silica gel; the aluminum source is aluminum sulfate or sodium aluminate; the template agent is a substance conforming to the general formula N(R)4X, wherein R is an alkyl group with 1 to 4 carbon atoms, X is a hydroxide ion or a halide anion, and N is a nitrogen atom; the alkyl group is ethyl or propyl, and the halide anion is a bromide ion. When preparing the mixed crystal structure of the ZSM-5 molecular sieve and ZSM-11 molecular sieve, at least two template agents are selected and used. In one of the template agents, R is ethyl and R is butyl.

9. The alkyl aromatic hydrocarbon isomerization method according to claim 8, characterized in that, The silicon source is water glass. Based on the amount of Na2O, SiO2, Al2O3, template agent and H2O in the water glass, the molar ratio of Na2O, SiO2, aluminum source, template agent and water in the silicon source is (0.01~0.4):1:(0.005~0.05):(0.05~1):(10~60).

10. The alkyl aromatic hydrocarbon isomerization method according to claim 9, characterized in that, The concentration of the silica sol is 10-40% by mass; the particle size of the solid silica gel is 0.005-0.05 μm.

11. The alkyl aromatic hydrocarbon isomerization method according to claim 10, characterized in that, The concentration of the silica sol is 20-40% by mass.

12. The alkyl aromatic hydrocarbon isomerization method according to claim 10, characterized in that, The particle size of the solid silica gel is 0.01 ~ 0.03 μm.

13. The alkyl aromatic hydrocarbon isomerization method according to claim 10, characterized in that, The reaction conditions for the hydrothermal crystallization include: The hydrothermal temperature is 130~190℃; The hydrothermal time is 18 to 100 hours.

14. The alkyl aromatic hydrocarbon isomerization method according to claim 13, characterized in that, The hydrothermal temperature is 140~180℃.

15. The alkyl aromatic hydrocarbon isomerization method according to claim 13, characterized in that, The hydrothermal time is 20 to 96 hours.

16. The alkyl aromatic hydrocarbon isomerization method according to claim 13, characterized in that, The preparation method of the alkyl aromatic isomerization catalyst includes: The ten-membered ring molecular sieve and the inert support are mixed to obtain a first mixture. A peptide solution is added to the first mixture, and the mixture is kneaded and extruded to obtain a strip. The strip is then subjected to a first drying and a first calcination to obtain an intermediate. The intermediate is then subjected to ammonium exchange to obtain an ammonium-exchanged intermediate. The ammonium-exchanged intermediate is then subjected to a second drying and a second calcination to obtain the alkyl aromatic hydrocarbon isomerization catalyst. Alternatively, the ten-membered ring molecular sieve is subjected to ammonium exchange to obtain an ammonium-exchanged molecular sieve. The ammonium-exchanged molecular sieve is then subjected to a second drying and a second calcination to obtain a hydrogen-form molecular sieve. The hydrogen-form molecular sieve is mixed with the inert support to obtain a second mixture. A peptide solvent solution is added to the second mixture, and the mixture is kneaded and extruded to obtain a strip. The strip is then subjected to a first drying and a first calcination to obtain the alkyl aromatic hydrocarbon isomerization catalyst.

17. The alkyl aromatic hydrocarbon isomerization method according to claim 16, characterized in that, The adhesive solvent contains at least one of nitric acid, phosphoric acid, and citric acid, and the concentration of the adhesive solvent solution is 1-5% by mass. The ammonium salt used in the ammonium exchange is ammonium chloride or ammonium nitrate, and the concentration of the ammonium salt is 1 to 30% by mass.

18. The alkyl aromatic hydrocarbon isomerization method according to claim 17, characterized in that, The concentration of the ammonium salt is 3 to 10% by mass.

19. The alkyl aromatic hydrocarbon isomerization method according to claim 17, characterized in that, The conditions for the first drying and the second drying each independently include: a temperature of 100~140℃ and a time of 4~24h; the conditions for the first roasting and the second roasting each independently include: a temperature of 520~550℃ or 400~500℃ and a roasting time of 2~24h.

20. The alkyl aromatic hydrocarbon isomerization method according to claim 1, characterized in that, The inert carrier is aluminum oxide and / or silicon dioxide.

21. The alkyl aromatic hydrocarbon isomerization method according to claim 1, characterized in that, In the alkyl aromatic isomerization catalyst, based on the total weight of the alkyl aromatic isomerization catalyst, the content of the ten-membered ring molecular sieve is 30-70% by mass, and the sum of the percentages of the ten-membered ring molecular sieve and the inert support is 100% by mass.

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