An alkylarene isomerization catalyst, its preparation method and use

Abstract

The present disclosure relates to an alkylaromatic isomerization catalyst, a preparation method and application thereof, wherein the alkylaromatic isomerization catalyst comprises 25-99.9 wt% of mixed ten-membered ring molecular sieve and 0.1-75 wt% of inert carrier, based on the total weight of the alkylaromatic isomerization catalyst; and the mixed ten-membered ring molecular sieve comprises ZSM-11 molecular sieve and ZSM-12 molecular sieve. The alkylaromatic isomerization catalyst provided by the present disclosure has higher isomerization activity and para-alkylaromatic selectivity.

Description

Technical Field

[0001] This disclosure relates to the field of alkyl aromatic hydrocarbon isomerization, specifically to an alkyl aromatic hydrocarbon isomerization catalyst, its preparation method, and its application. 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 Bronsted 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 disproportionation side reactions, a lower reaction temperature should be selected for the isomerization reaction.

[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-crystal 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 a reaction temperature of 260°C and a reaction time of 5.2 h. -1 At a space velocity of 3.1 MPa and a reaction pressure of 3.1 MPa, PX / X can be made greater than the gas phase equilibrium value of 24 by mass.

[0008] The catalyst prepared using Ga-MFI molecular sieves in US7371913 can carry out alkyl aromatic hydrocarbon isomerization reactions in a completely hydrogen-free state, and retains high amounts 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] However, the activity and selectivity of the catalysts used in the aforementioned patents and documents still need to be further improved. Summary of the Invention

[0013] The purpose of this disclosure is to provide an alkyl aromatic hydrocarbon isomerization catalyst, its preparation method, and its application. The alkyl aromatic hydrocarbon isomerization catalyst has high isomerization activity and para-alkyl aromatic hydrocarbon selectivity.

[0014] To achieve the above objectives, the first aspect of this disclosure provides an alkyl aromatic hydrocarbon isomerization catalyst, wherein, based on the total weight of the alkyl aromatic hydrocarbon isomerization catalyst, the alkyl aromatic hydrocarbon isomerization catalyst comprises 25 to 99.9% by weight of a mixed ten-membered ring molecular sieve and 0.1 to 75% by weight of an inert support; the mixed ten-membered ring molecular sieve comprises ZSM-11 molecular sieve and ZSM-12 molecular sieve.

[0015] Optionally, based on the total weight of the alkyl aromatic isomerization catalyst, the alkyl aromatic isomerization catalyst comprises 25 to 99.9% by weight of a mixed ten-membered ring molecular sieve and 0.1 to 75% by weight of an inert support.

[0016] Preferably, based on the total weight of the mixed ten-membered ring molecular sieve, the content of the ZSM-11 molecular sieve is 20-70% by weight, preferably 30-55% by weight; more preferably, the silicon-aluminum ratio of the ZSM-11 molecular sieve is 20-100, preferably 25-80; and the silicon-aluminum ratio of the ZSM-12 molecular sieve is 20-100, preferably 30-80.

[0017] Optionally, the alkyl aromatic isomerization catalyst further includes a Group VIII metal element; preferably, based on the total weight of the alkyl aromatic isomerization catalyst, the content of the Group VIII metal element is 0.001-0.5% by weight, preferably 0.003-0.4% by weight; preferably, the Group VIII metal element is selected from one or more of nickel, palladium, platinum and rhodium.

[0018] Optionally, the inert support is selected from one or more of alumina, silica, silica gel and activated carbon;

[0019] Optionally, the catalyst has an average particle size of 1–10 mm, preferably 2–7 mm; and a BET specific surface area of ​​300–450 m². 2 / g, preferably 330-420m 2 / g; the total pore volume is 0.1 to 0.45 ml / g, preferably 0.15 to 0.4 ml / g.

[0020] A second aspect of this disclosure provides a method for preparing an alkyl aromatic hydrocarbon isomerization catalyst, comprising the following steps:

[0021] S1. The ZSM-11 molecular sieve raw material and the ZSM-12 molecular sieve raw material are subjected to ammonium exchange treatment and organic ammonium salt modification treatment to obtain modified ZSM-11 molecular sieve and modified ZSM-12 molecular sieve.

[0022] S2. The modified ZSM-11 molecular sieve and the modified ZSM-12 molecular sieve are mixed with an inert support and subjected to molding treatment, first drying treatment and first calcination treatment.

[0023] Optionally, step S1 includes:

[0024] The ZSM-11 molecular sieve raw material is contacted with an aqueous solution of a first ammonium salt to perform a first ammonium exchange treatment; the product obtained from the first ammonium exchange treatment is contacted with a solution of a first organic ammonium salt to perform a first organic ammonium salt modification treatment to obtain a modified ZSM-11 molecular sieve.

[0025] The ZSM-12 molecular sieve raw material is contacted with a second ammonium salt aqueous solution to perform a second ammonium exchange treatment. The product obtained from the second ammonium exchange treatment is then contacted with a second organic ammonium salt solution to perform a second organic ammonium salt modification treatment, thereby obtaining a modified ZSM-12 molecular sieve.

[0026] Optionally, the conditions for the first and second ammonium exchange treatments each independently include: an ammonium salt aqueous solution concentration of 0.4–0.6 mol / L, a volume of 3–50 mL of ammonium salt aqueous solution relative to 1 g of molecular sieve raw material, an exchange temperature of 60–95 °C, a contact time of 0.5–8 h, and 1–3 exchange cycles; preferably, the ammonium salt aqueous solution concentration is 0.45–0.55 mol / L, a volume of 5–45 mL of ammonium salt aqueous solution relative to 1 g of molecular sieve raw material, an exchange temperature of 65–90 °C, and a contact time of 1–7 h; the exchanged molecular sieve is washed several times with excess deionized water until no halogen anions are detected in the washing solution, the pH range is 6–8, and the Na₂O molar content of the washed mixed crystal molecular sieve is 0.02–0.30%; optionally, the first and second ammonium salts are each independently selected from one or more of tetrabutylammonium hydroxide aqueous solution, tetraethylammonium hydroxide, and hexadecyltrimethylammonium bromide;

[0027] The conditions for the first organic ammonium salt modification treatment and the second organic ammonium salt modification treatment each independently include: the concentration of the organic ammonium salt solution is 0.05-0.5 mol / L, preferably 0.1-0.4 mol / L; the amount of organic ammonium salt solution used relative to 1 g of molecular sieve is 3-40 mL, preferably 5-35 mL; the treatment temperature is 110-190℃, preferably 120-180℃; and the treatment time is 2-8 h, preferably 3-7 h. Optionally, the first organic ammonium salt and the second organic ammonium salt are each independently selected from one or more of the following: an aqueous solution of tetrabutylammonium hydroxide, tetraethylammonium hydroxide, and hexadecyltrimethylammonium bromide.

[0028] Optionally, the ZSM-11 molecular sieve raw material and the ZSM-12 molecular sieve raw material mentioned in step S1 are each prepared independently by a method including the following steps:

[0029] a. Mix the silicon source, aluminum source, template agent and water to obtain the mixture to be crystallized;

[0030] b. Perform hydrothermal crystallization and drying treatment on the mixture to be crystallized;

[0031] Preferably, the silicon source is in the form of SiO2, and the molar ratio of silicon source: aluminum source: template agent: H2O in the mixture to be crystallized is 1:(0.01~0.05):(0.05~0.8):(10~80), more preferably 1:(0.02~0.04):(0.06~0.7):(10~75);

[0032] Optionally, the molar ratio of Na2O to SiO2 in the mixture to be crystallized is controlled to be (0.01 to 0.5):1, preferably (0.02 to 0.4):1.

[0033] Optionally, the silicon source is selected from one or more of water glass, liquid silica sol, and solid silica gel; preferably, the molar ratio of sodium oxide to silicon oxide in the water glass is (0.01-0.5):1; the concentration of the liquid silica sol is 10-40% by weight, preferably 20-40% by weight; and the particle size of the solid silica gel is 0.005μm-0.05μm, preferably 0.01μm-0.03μm.

[0034] Optionally, the aluminum source is selected from one or more of aluminum sulfate, sodium aluminate, aluminum nitrate, and aluminum isopropoxide;

[0035] Optionally, the template agent is selected from those having the general formula One or more of the compounds with the structure shown; wherein R1, R2, R3 and R4 are the same or different, and each is independently selected from alkyl groups having 1 to 4 carbon atoms, preferably ethyl or butyl; X- is a hydroxide ion or a halide anion, preferably a bromide ion, and N is a nitrogen atom; preferably, the silicon source is in the form of SiO2, and the molar ratio of X- to SiO2 in the template agent is 0.05 to 0.8, preferably 0.06 to 0.7;

[0036] More preferably, in the raw materials used to synthesize ZSM-11 molecular sieves, the template agent is selected from one or more of methyltributylammonium chloride, tetrabutylammonium bromide, and tetrabutylammonium hydroxide;

[0037] In the raw materials used to synthesize ZSM-12 molecular sieves, the template agent is selected from one or more of methyltriethylammonium bromide, tetraethylammonium bromide, and tetraethylammonium hydroxide.

[0038] Optionally, the hydrothermal crystallization treatment includes a first-stage hydrothermal crystallization treatment and a second-stage hydrothermal crystallization treatment performed sequentially.

[0039] Preferably, the conditions for the first stage of hydrothermal crystallization treatment include: a hydrothermal crystallization temperature of 40–90°C and a hydrothermal crystallization time of 6–18 h; the conditions for the second stage of hydrothermal crystallization treatment include: a hydrothermal crystallization temperature of 120–190°C and a hydrothermal crystallization time of 9–60 h.

[0040] Preferably, the conditions for the first stage of hydrothermal crystallization treatment include: a hydrothermal crystallization temperature of 50–80°C and a hydrothermal crystallization time of 7–17 h; the conditions for the second stage of hydrothermal crystallization treatment include: a hydrothermal crystallization temperature of 130–180°C and a hydrothermal crystallization time of 10–55 h.

[0041] Optionally, the temperature change rate from the first stage hydrothermal crystallization treatment to the second stage hydrothermal crystallization treatment is 0.5 to 5 °C / min, preferably 1 to 3 °C / min;

[0042] Optionally, the drying conditions include: a drying temperature of 80–120°C and a drying time of 2–6 hours.

[0043] Optionally, step S2 includes:

[0044] The modified ZSM-11 molecular sieve and the modified ZSM-12 molecular sieve are mixed with an inert support, and a solution of a peptide solvent is added for kneading treatment. Then, they are subjected to extrusion molding, first drying treatment and first calcination treatment.

[0045] Preferably, the mixing weight ratio of modified ZSM-11 molecular sieve: modified ZSM-12 molecular sieve: inert support is 1:0.4-4:1.05-3.3, and more preferably 1:0.8-2.3:1.2-2.2;

[0046] Optionally, the adhesive solvent is selected from one or more of nitric acid, phosphoric acid and citric acid, and the solution concentration of the adhesive solvent is 1 to 5% by weight; preferably, the volume of the adhesive solvent solution is 0.5 to 1.5 mL relative to 1 g of solid mixture.

[0047] Optionally, the conditions for the first drying treatment include: a drying temperature of 100–140°C and a drying time of 4–24 h; the conditions for the first calcination treatment include: a calcination temperature of 400–550°C and a calcination time of 4–24 h; preferably, the conditions for the first calcination treatment include: a calcination temperature of 110–130°C and a calcination time of 5–20 h; optionally, the atmosphere for the first calcination treatment is air.

[0048] Optionally, the method further includes the following steps:

[0049] S3. The product obtained from the first calcination treatment in step S2 is brought into contact with an active metal source for active metal loading treatment; then a second drying treatment, a second calcination treatment, and a reduction treatment are performed.

[0050] Optionally, the active metal source is selected from one or more group VIII metal salts, preferably, the active metal source is selected from one or more nickel, palladium, platinum and rhodium; preferably, the weight ratio of the product obtained from the first calcination treatment in step S2 to the active metal source is 1:0.0001 to 0.05, more preferably 1:0.0002 to 0.04.

[0051] Optionally, the conditions for active metal loading treatment include: a loading temperature of 10–40°C and a loading time of 4–24 h;

[0052] Optionally, the conditions for the second drying treatment include: a drying temperature of 80–140°C and a drying time of 4–12 hours;

[0053] Optionally, the conditions for the second calcination treatment include: a calcination temperature of 450–520°C and a calcination time of 4–8 h; preferably, a calcination temperature of 480–500°C and a calcination time of 5–7 h; and the atmosphere for the second calcination treatment is air.

[0054] Optionally, the conditions for the reduction treatment include: a reduction temperature of 450–520°C and a reduction time of 4–8 h; preferably, a reduction temperature of 480–500°C and a reduction time of 5–7 h; and the atmosphere for the reduction treatment is hydrogen or a mixture of nitrogen and hydrogen.

[0055] The third aspect of this disclosure provides an alkyl aromatic hydrocarbon isomerization catalyst prepared according to the method described in the second aspect of this disclosure.

[0056] This disclosure provides a fourth aspect of a liquid-phase alkyl aromatic hydrocarbon isomerization method, comprising the following steps:

[0057] An alkyl aromatic feedstock is brought into contact with a catalyst under liquid conditions to undergo an isomerization reaction; the catalyst includes the alkyl aromatic isomerization catalyst described in the first or third aspect of this disclosure; in the isomerization reaction, hydrogen and nitrogen are introduced to contact the catalyst.

[0058] Optionally, the alkyl aromatic raw material includes aromatics having 8 to 10 carbon atoms;

[0059] Preferably, the conditions for the isomerization reaction include: a reaction temperature of 240–310°C, a reaction pressure of 2–4 MPa, and a weight hourly space velocity (WHSV) of 1–10 h⁻¹ for the alkyl aromatic feedstock. -1 The molar ratio of hydrogen to feedstock is 0.01–1; the molar ratio of nitrogen to feedstock oil is 0.01–1. Preferably, the reaction temperature is 250–290°C, and the weight hourly space velocity (WHSV) of the alkyl aromatic feedstock is 2–6 h⁻¹. -1 The molar ratio of hydrogen to feed is 0.05–0.6; the molar ratio of nitrogen to feedstock is 0.06–0.6.

[0060] Through the above technical solution, this disclosure provides an alkyl aromatic hydrocarbon isomerization catalyst, its preparation method, and its application. The catalyst comprises ZSM-11 and ZSM-12 molecular sieves as a mixed ten-membered ring molecular sieve, which can improve the isomerization activity and xylene yield in the alkyl aromatic hydrocarbon isomerization reaction. The method provided in this disclosure can also improve the utilization rate of the catalyst's acid centers.

[0061] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0062] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0063] Figure 1 This is the XRD pattern of ZSM-11 molecular sieve Z-1 prepared in Example 1 of this disclosure;

[0064] Figure 2 This is the XRD pattern of ZSM-12 molecular sieve Z-2 prepared in Example 1 of this disclosure. Detailed Implementation

[0065] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure.

[0066] The first aspect of this disclosure provides an alkyl aromatic hydrocarbon isomerization catalyst, wherein, based on the total weight of the alkyl aromatic hydrocarbon isomerization catalyst, the alkyl aromatic hydrocarbon isomerization catalyst comprises 25 to 99.9% by weight of a mixed ten-membered ring molecular sieve and 0.1 to 75% by weight of an inert support; the mixed ten-membered ring molecular sieve comprises ZSM-11 molecular sieve and ZSM-12 molecular sieve.

[0067] This disclosure provides an alkyl aromatic hydrocarbon isomerization catalyst, wherein the catalyst comprises ZSM-11 and ZSM-12 molecular sieves as a mixed ten-membered ring molecular sieve, which can improve the isomerization activity and xylene yield in the alkyl aromatic hydrocarbon isomerization reaction. The catalyst provided in this disclosure is suitable for the liquid-phase isomerization reaction of aromatic hydrocarbons containing methyl and C2 or higher substituted benzenes (such as trimethylbenzene, tetramethylbenzene, ethylbenzene, and diethylbenzene), and has high isomerization reaction performance of methyl and C2 or higher substituted alkylbenzenes, and good reaction selectivity.

[0068] In a preferred embodiment, the alkyl aromatic isomerization catalyst comprises 25-99.9% by weight of a mixed ten-membered ring molecular sieve and 0.1-75% by weight of an inert support, based on the total weight of the alkyl aromatic isomerization catalyst.

[0069] In a preferred embodiment, based on the total weight of the mixed ten-membered ring molecular sieves, the content of the ZSM-11 molecular sieve is 0.1–70% by weight, preferably 10–50% by weight. When the content of ZSM-11 molecular sieve in the alkyl aromatic isomerization catalyst is within the optimized content range provided in this embodiment, the catalyst can obtain better catalytic performance.

[0070] In one specific embodiment, the silicon-to-aluminum ratio of the ZSM-11 molecular sieve is 20-100, preferably 25-80; the silicon-to-aluminum ratio of the ZSM-12 molecular sieve is 20-100, preferably 30-80.

[0071] In one embodiment, the alkyl aromatic isomerization catalyst further includes a Group VIII metal element; preferably, based on the total weight of the alkyl aromatic isomerization catalyst, the content of the Group VIII metal element is 0.001-0.5% by weight, more preferably 0.003-0.4% by weight; preferably, the Group VIII metal element is selected from one or more of nickel, palladium, platinum and rhodium;

[0072] Optionally, the inert support is selected from one or more of alumina, silicon dioxide, silica gel, and activated carbon.

[0073] In one specific embodiment, the catalyst has an average particle size of 1-10 mm, preferably 2-7 mm; a BET specific surface area of ​​300-450 m² / g, preferably 330-420 m² / g; and a total pore volume of 0.1-0.45 ml / g, preferably 0.15-0.4 ml / g.

[0074] A second aspect of this disclosure provides a method for preparing an alkyl aromatic hydrocarbon isomerization catalyst, comprising the following steps:

[0075] S1. The ZSM-11 molecular sieve raw material and the ZSM-12 molecular sieve raw material are subjected to ammonium exchange treatment and organic ammonium salt modification treatment to obtain modified ZSM-11 molecular sieve and modified ZSM-12 molecular sieve.

[0076] S2. The modified ZSM-11 molecular sieve and the modified ZSM-12 molecular sieve are mixed with an inert support and subjected to molding treatment, first drying treatment and first calcination treatment.

[0077] This disclosure provides a method for preparing an alkyl aromatic hydrocarbon isomerization catalyst, which combines ZSM-11 and ZSM-12 molecular sieve raw materials, followed by drying, calcination, ammonium exchange, and organic ammonium salt modification. The treated molecular sieves are then combined with an inert support to prepare the catalyst, which can effectively improve the utilization rate of the acid centers of the catalyst and obtain high isomerization activity and xylene yield in the catalytic liquid-phase alkyl aromatic hydrocarbon isomerization reaction.

[0078] In one specific embodiment, step S1 includes:

[0079] The ZSM-11 molecular sieve raw material is contacted with an aqueous solution of a first ammonium salt to perform a first ammonium exchange treatment; the product obtained from the first ammonium exchange treatment is contacted with a solution of a first organic ammonium salt to perform a first organic ammonium salt modification treatment to obtain a modified ZSM-11 molecular sieve.

[0080] The ZSM-12 molecular sieve raw material is contacted with a second ammonium salt aqueous solution to perform a second ammonium exchange treatment. The product obtained from the second ammonium exchange treatment is then contacted with a second organic ammonium salt solution to perform a second organic ammonium salt modification treatment, thereby obtaining a modified ZSM-12 molecular sieve.

[0081] This disclosure describes how ammonium exchange treatment and organic amine modification treatment can be applied to ZSM-11 molecular sieve raw materials and ZSM-12 molecular sieve raw materials, respectively, to improve the main reaction activity and reduce side reactions.

[0082] In one embodiment, the conditions for the first and second ammonium exchange treatments each independently include: the concentration of the ammonium salt aqueous solution is 0.4–0.6 mol / L, the amount of ammonium salt aqueous solution used is 3–50 mL relative to 1 g of molecular sieve raw material, the exchange temperature is 60–95 °C, the contact time is 0.5–8 h, and the number of exchange cycles is 1–3; preferably, the concentration of the ammonium salt aqueous solution is 0.45–0.55 mol / L, the amount of ammonium salt aqueous solution used is 5–45 mL relative to 1 g of molecular sieve raw material, the exchange temperature is 65–90 °C, and the contact time is 1–7 h; the exchanged molecular sieve is washed several times with excess deionized water until no halogen anions are detected in the washing solution, the pH range is 6–8, and the Na₂O molar content of the washed mixed crystal molecular sieve is 0.02–0.30%; optionally, the first and second ammonium salts are each independently selected from one or more of the following: an aqueous solution of tetrabutylammonium hydroxide, tetraethylammonium hydroxide, and hexadecyltrimethylammonium bromide.

[0083] In one embodiment, the conditions for the first organic ammonium salt modification treatment and the second organic ammonium salt modification treatment each independently include: the concentration of the organic ammonium salt solution is 0.05-0.5 mol / L, preferably 0.1-0.4 mol / L; the amount of organic ammonium salt solution used relative to 1 g of molecular sieve is 3-40 mL, preferably 5-35 mL; the treatment temperature is 110-190℃, preferably 120-180℃; and the treatment time is 2-8 h, preferably 3-7 h. Optionally, the first organic ammonium salt and the second organic ammonium salt are each independently selected from one or more of the following: an aqueous solution of tetrabutylammonium hydroxide, tetraethylammonium hydroxide, and hexadecyltrimethylammonium bromide.

[0084] The ZSM-11 and ZSM-12 molecular sieve raw materials used in this disclosure can be ZSM-11 and ZSM-12 molecular sieves specifically for liquid-phase isomerization reactions.

[0085] In one specific embodiment, the ZSM-11 molecular sieve raw material and the ZSM-12 molecular sieve raw material mentioned in step S1 are each prepared independently by a method including the following steps:

[0086] a. Mix the silicon source, aluminum source, template agent and water to obtain the mixture to be crystallized;

[0087] b. Perform hydrothermal crystallization and drying treatment on the mixture to be crystallized.

[0088] In a preferred embodiment, the silicon source is in the form of SiO2, and the molar ratio of silicon source: aluminum source: template agent: H2O in the mixture to be crystallized is 1:(0.01~0.05):(0.05~0.8):(10~80), preferably 1:(0.02~0.04):(0.06~0.7):(10~75);

[0089] Optionally, the molar ratio of Na2O to SiO2 in the mixture to be crystallized is controlled to be (0.01–0.5):1, preferably (0.02–0.4):1. The molecular sieve raw material prepared according to the optimized molar ratio in this embodiment is more suitable for preparing liquid-phase isomerization reaction catalysts and has better catalytic effects.

[0090] In one embodiment, the silicon source is selected from one or more of water glass, liquid silica sol, and solid silica gel; preferably, the molar ratio of sodium oxide to silicon oxide in the water glass is (0.01-0.5):1; the concentration of the liquid silica sol is 10-40% by weight, preferably 20-40% by weight; and the particle size of the solid silica gel is 0.005μm-0.05μm, preferably 0.01μm-0.03μm.

[0091] The aluminum source is selected from one or more of aluminum sulfate, sodium aluminate, aluminum nitrate, and aluminum isopropoxide;

[0092] The template agent is selected from those having the general formula. One or more of the compounds with the structures shown; wherein R1, R2, R3, and R4 are the same or different, and each is independently selected from alkyl groups having 1 to 4 carbon atoms, preferably ethyl or butyl; X - The template agent contains hydroxide ions or halide anions, preferably bromide ions, and N is a nitrogen atom; preferably, the silicon source is in the form of SiO2, and X in the template agent... - The molar ratio of SiO2 to SiO2 is 0.05 to 0.8, preferably 0.06 to 0.7.

[0093] This disclosure controls the synthesis of two molecular sieve structures by controlling the type of template agent and the synthesis process conditions. The synthesis process conditions include crystallization temperature and crystallization time.

[0094] More preferably, in the raw materials used to synthesize ZSM-11 molecular sieves, the template agent is selected from one or more of methyltributylammonium chloride, tetrabutylammonium bromide, and tetrabutylammonium hydroxide;

[0095] In the raw materials used to synthesize ZSM-12 molecular sieves, the template agent is selected from one or more of methyltriethylammonium bromide, tetraethylammonium bromide, and tetraethylammonium hydroxide.

[0096] In this disclosure, the synthesis temperature is controlled in two stages during the synthesis of ZSM-11 and ZSM-12 molecular sieve raw materials, which has the effect of improving the isomerization reaction activity of molecular sieves.

[0097] In a preferred embodiment, the conditions for the first-stage hydrothermal crystallization treatment include: a hydrothermal crystallization temperature of 40–90°C and a hydrothermal crystallization time of 6–18 h; the conditions for the second-stage hydrothermal crystallization treatment include: a hydrothermal crystallization temperature of 120–190°C and a hydrothermal crystallization time of 9–60 h; preferably, the conditions for the first-stage hydrothermal crystallization treatment include: a hydrothermal crystallization temperature of 50–80°C and a hydrothermal crystallization time of 7–17 h; the conditions for the second-stage hydrothermal crystallization treatment include: a hydrothermal crystallization temperature of 130–180°C and a hydrothermal crystallization time of 10–55 h;

[0098] Optionally, the temperature change rate from the first stage hydrothermal crystallization treatment to the second stage hydrothermal crystallization treatment is 0.5 to 5 °C / min, preferably 0.5 to 5 °C / min.

[0099] In one embodiment, step S2 includes: mixing the modified ZSM-11 molecular sieve and the modified ZSM-12 molecular sieve with an inert support, adding a solution of a peptide solvent and kneading until homogeneous, and then performing extrusion molding, a first drying process, and a first calcination process; preferably, the mixing weight ratio of modified ZSM-11 molecular sieve: modified ZSM-12 molecular sieve: inert support is 1:0.4~4:1.05~3.3, more preferably 1:0.8~2.3:1.2~2.2;

[0100] Optionally, the adhesive solvent is selected from one or more of nitric acid, phosphoric acid and citric acid, and the solution concentration of the adhesive solvent is 1 to 5% by weight; preferably, the volume of the adhesive solvent solution is 0.5 to 1.5 mL relative to 1 g of solid mixture.

[0101] Optionally, the conditions for the first drying treatment include: a drying temperature of 100–140°C and a drying time of 4–24 h; the conditions for the first calcination treatment include: a calcination temperature of 400–550°C and a calcination time of 4–24 h; preferably, the conditions for the first calcination treatment include: a calcination temperature of 110–130°C and a calcination time of 5–20 h; optionally, the atmosphere for the first calcination treatment is air.

[0102] In a preferred embodiment, the method further includes the following steps:

[0103] S3. The product obtained from the first calcination treatment in step S2 is brought into contact with an active metal source for active metal loading treatment; then a second drying treatment, a second calcination treatment, and a reduction treatment are performed.

[0104] In one specific embodiment, the active metal source is selected from one or more group VIII metal salts, preferably, the active metal source is selected from one or more nickel, palladium, platinum and rhodium; preferably, the weight ratio of the product obtained from the first calcination treatment in step S2 to the active metal source is 1:0.0001 to 0.05, more preferably 1:0.0002 to 0.04;

[0105] Optionally, the conditions for active metal loading treatment include: a loading temperature of 10–40°C and a loading time of 4–24 h;

[0106] Optionally, the conditions for the second drying treatment include: a drying temperature of 80–140°C and a drying time of 4–12 hours;

[0107] Optionally, the conditions for the second calcination treatment include: a calcination temperature of 450–520°C and a calcination time of 4–8 h; preferably, a calcination temperature of 480–500°C and a calcination time of 5–7 h; and the atmosphere for the second calcination treatment is air.

[0108] Optionally, the conditions for the reduction treatment include: a reduction temperature of 450–520°C and a reduction time of 4–8 h; preferably, a reduction temperature of 480–500°C and a reduction time of 5–7 h; and the atmosphere for the reduction treatment is hydrogen or a mixture of nitrogen and hydrogen.

[0109] The third aspect of this disclosure provides an alkyl aromatic hydrocarbon isomerization catalyst prepared according to the method described in the second aspect of this disclosure.

[0110] This disclosure provides a fourth aspect of a liquid-phase alkyl aromatic hydrocarbon isomerization method, comprising the following steps:

[0111] An alkyl aromatic feedstock is brought into contact with a catalyst under liquid conditions to undergo an isomerization reaction; the catalyst includes the alkyl aromatic isomerization catalyst described in the first or third aspect of this disclosure; in the isomerization reaction, hydrogen and nitrogen are introduced to contact the catalyst.

[0112] This disclosure provides a liquid-phase alkyl aromatic hydrocarbon isomerization method, which uses the aforementioned catalyst and introduces a mixed gas of hydrogen and nitrogen during the reaction process, which can effectively improve the performance of the catalyst.

[0113] In one specific embodiment, the alkyl aromatic raw material comprises aromatics having 8 to 10 carbon atoms;

[0114] The conditions for the isomerization reaction include: a reaction temperature of 240–310 °C, a reaction pressure of 2–4 MPa, and a weight hourly space velocity (WHSV) of 1–10 h⁻¹ for the alkyl aromatic feedstock. -1 The molar ratio of hydrogen to feedstock is 0.01–1; the molar ratio of nitrogen to feedstock oil is 0.01–1. Preferably, the reaction temperature is 250–290°C, and the weight hourly space velocity (WHSV) of the alkyl aromatic feedstock is 2–6 h⁻¹. -1 The molar ratio of hydrogen to feed is 0.05–0.6; the molar ratio of nitrogen to feedstock is 0.06–0.6.

[0115] The present disclosure is further described in detail below through examples.

[0116] The XRD pattern of the molecular sieve was measured using a Philips XPert X-ray diffractometer. The testing methods included: determining the crystal phase structure of the molecular sieve using Cu Kα rays, with a 2θ scan range of 5°–35°, and quantification using the external standard method.

[0117] Example 1

[0118] (1) Preparation of ZSM-11 molecular sieve

[0119] Add 58.5g of water glass (SiO2 content 24.01% by mass, Na2O content 7.08% by mass, Al2O3 content 0.2% by mass), aluminum sulfate octadecylhydrate, and tetrabutylammonium bromide N(C4H9)4 to a 200mL reactor. + Br - As a template agent (denoted as T, where the silicon source is in the form of SiO2), the anion X in the template agent T - The mixture of Na₂O (at a molar ratio of 0.2 to SiO₂) and deionized water was thoroughly mixed to obtain a crystallization mixture. The molar ratio of each material was Na₂O:SiO₂:Al₂O₃:T:H₂O = 0.28:1:0.033:0.2:20. The mixture was hydrothermally crystallized at 70℃ for 12 hours, then heated to 160℃ for 48 hours, with a temperature increase / decrease rate of 1℃ / min. The resulting solid was washed with excess deionized water until the pH of the wash solution was within the range of 6–8, and then dried at 120℃ for 6 hours to obtain ZSM-11 molecular sieve, denoted as Z-1. The XRD diffraction pattern is shown below. Figure 1 .Depend on Figure 1 It can be seen that the XRD diffraction pattern of this molecular sieve has characteristic diffraction peaks at positions of 7.92°, 8.8°, 23.12° and 23.92°, indicating that the molecular sieve has a ZSM-11 configuration.

[0120] (2) Preparation of ZSM-12 molecular sieve

[0121] Add 58.5g of water glass (SiO2 content 24.01% by mass, Na2O content 7.08% by mass, Al2O3 content 0.2% by mass), aluminum sulfate octadecylhydrate, and tetraethylammonium bromide N(C2H5)4 to a 200mL reactor. + Br - As a template agent (denoted as T, where the silicon source is in the form of SiO2), the anion X in the template agent T - The mixture of Na₂O (at a molar ratio of 0.2 to SiO₂) and deionized water was thoroughly mixed to obtain a crystallization mixture. The molar ratio of each material was Na₂O:SiO₂:Al₂O₃:T:H₂O = 0.28:1:0.033:0.2:20. The mixture was hydrothermally crystallized at 80℃ for 10 hours and then at 160℃ for 50 hours. The resulting solid was washed with excess deionized water until the pH of the wash solution was 6–8. It was then dried at 120℃ for 6 hours to obtain ZSM-12 molecular sieve, denoted as Z-2. The XRD diffraction pattern is shown below. Figure 2 .Depend on Figure 2 It can be seen that the XRD diffraction pattern of this molecular sieve has diffraction peaks at positions of 8.8°, 18.7°, 20.8° and 23.1°, indicating that the molecular sieve has the ZSM-12 configuration.

[0122] (3) Ammonium exchange treatment:

[0123] The obtained ZSM-11 and ZSM-12 molecular sieves were subjected to ammonium exchange. The ammonium exchange treatment for each molecular sieve included: an ammonium chloride aqueous solution concentration of 0.5 mol / L, an exchange liquid-to-solid ratio of 10 mL / g molecular sieve (i.e., the amount of ammonium salt aqueous solution used was 10 mL relative to 1 g of molecular sieve raw material), a temperature of 85℃, an exchange treatment contact time of 1 h, and two exchanges. The exchanged molecular sieves were washed with deionized water until no chloride ions were detected in the wash solution, and the washing was carried out until the pH range was 6-8. The Na2O molar content of the mixed crystal molecular sieve after washing was 0.02%.

[0124] (4) Organic amine modification treatment:

[0125] Then, the two molecular sieves were modified with organic ammonium salts. The modification process for each molecular sieve included: using an aqueous solution of 0.3 mol / L tetrabutylammonium hydroxide and hexadecyltrimethylammonium bromide (mass ratio 1:1), with a solution volume of 20 mL / g molecular sieve, a treatment temperature of 150℃, and a treatment time of 5 hours.

[0126] (5) Preparation of catalyst

[0127] The modified ZSM-11 and modified ZSM-12 molecular sieve powders prepared in the previous steps were thoroughly mixed with alumina at a mass ratio of 3:3:4 (i.e., 1:1:1.33). A 5% (w / w) nitric acid aqueous solution was added and kneaded until homogeneous. The volume of the peptide solution was 1 mL relative to 1 g of the solid mixture. The mixture was then extruded into strips. The strips were dried at 110 °C for 8 hours, then granulated and calcined at 500 °C for 6 hours to obtain catalyst C-1.

[0128] Example 2

[0129] This embodiment uses the catalyst C-1 prepared in Example 1 for active metal loading treatment, including the following steps:

[0130] 10 g of the C-1 catalyst obtained in Example 1 was impregnated with 15 mL of an aqueous solution of chloroplatinic acid containing 0.0025 g of platinum (the weight ratio of C-1 catalyst to active metal source was 1:0.00025). After drying at 110 °C, a catalyst containing 0.025% by mass of platinum was prepared. This was then activated at 490 °C for 6 hours in air to prepare an oxidized catalyst. Finally, it was reduced at 500 °C for 6 hours under hydrogen atmosphere to prepare catalyst C-2.

[0131] Example 3

[0132] This embodiment uses the catalyst C-1 prepared in Example 1 for active metal loading treatment, including the following steps:

[0133] 10 g of the C-1 catalyst obtained in Example 1 was impregnated with 15 mL of a nickel acetate aqueous solution containing 0.03 g of nickel (the weight ratio of C-1 catalyst to active metal source was 1:0.003). After drying at 110 °C, a catalyst containing 0.3% by mass of nickel was prepared. This was then activated at 490 °C for 4 hours in air to prepare an oxidized catalyst. Finally, it was reduced at 500 °C for 4 hours under hydrogen atmosphere to prepare catalyst C-3.

[0134] Example 4

[0135] This embodiment uses the catalyst C-1 prepared in Example 1 for active metal loading treatment, including the following steps:

[0136] 10 g of the C-1 catalyst prepared by the method in Example 1 was impregnated with 15 mL of an aqueous solution containing 0.02 g of nickel acetate (the weight ratio of C-1 catalyst to the active metal source nickel acetate was 1:0.002), and dried at 110 °C to prepare a catalyst containing 0.2% by mass of nickel. The catalyst was then impregnated with 15 mL of an aqueous solution containing 0.0015 g of platinum chloroplatinic acid (the weight ratio of C-1 catalyst to the active metal source chloroplatinic acid was 1:0.00015), and dried at 110 °C to prepare a catalyst containing 0.015% by mass of platinum. The catalyst was then activated at 490 °C for 4 hours in air to prepare an oxidized catalyst, which was then reduced at 500 °C for 4 hours under hydrogen atmosphere to obtain catalyst C-4.

[0137] Example 5

[0138] In this embodiment, Z-1 and Z-2 were obtained by preparing molecular sieves according to the method of Example 1. The difference from Example 1 is that after the molecular sieves were subjected to ammonium exchange treatment, the two types of molecular sieves were not modified with organic ammonium salts.

[0139] The catalyst preparation in this embodiment includes the following steps:

[0140] The ZSM-11 and ZSM-12 molecular sieve powders obtained above without organic ammonium salt modification were thoroughly mixed with alumina at a mass ratio of 3:3:4 (i.e., 1:1:1.33). A 5% by mass nitric acid aqueous solution was added and kneaded until homogeneous. The nitric acid aqueous solution accounted for 30% by mass of the solid mixture. The mixture was then extruded into strips. The strips were dried at 110°C for 8 hours, then granulated and calcined at 500°C for 6 hours to obtain catalyst C-5.

[0141] Example 6

[0142] The catalyst was prepared according to the preparation method in Example 1, but differed from that in that:

[0143] In step (5), the alumina content remains unchanged during extrusion, and the ratio of modified ZSM-11 to modified ZSM-12 molecular sieves becomes 3:7 (i.e., the weight ratio of modified ZSM-11 molecular sieve: modified ZSM-12 molecular sieve: alumina is 1.8:4.2:4, or 1:2.33:2.22). The rest of the process is the same as in Example 1, and catalyst C-6 is obtained.

[0144] Example 7

[0145] The catalyst was prepared according to the preparation method in Example 1, but differed from that in that:

[0146] In step (5), the alumina content remains unchanged during extrusion, and the ratio of modified ZSM-11 and modified ZSM-12 molecular sieves becomes 7:3 (the mixed weight ratio of modified ZSM-11 molecular sieve: modified ZSM-12 molecular sieve: alumina is 1:0.43:0.95). The rest of the process is the same as in Example 1, and catalyst C-7 is obtained.

[0147] Comparative Example 8

[0148] (1) Preparation of ZSM-11 molecular sieve (molecular sieve synthesis adopts one-step crystallization)

[0149] Add 58.5g of water glass (SiO2 content 24.01% by mass, Na2O content 7.08% by mass, Al2O3 content 0.2% by mass), aluminum sulfate octadecylhydrate, and tetrabutylammonium bromide N(C4H9)4 to a 200mL reactor. + Br - As a template agent (denoted as T, where the silicon source is in the form of SiO2), the anion X in the template agent T - The mixture of Na₂O (at a molar ratio of 0.03 to SiO₂) and deionized water was thoroughly mixed to obtain a mixture to be crystallized; the molar ratio of each material was Na₂O:SiO₂:Al₂O₃:T:H₂O = 0.28:1:0.033:0.007:5. The mixture was hydrothermally crystallized at 160℃ for 48 hours. The resulting solid was washed with excess deionized water until the pH of the wash solution was 6–8, and then dried at 120℃ for 6 hours to obtain ZSM-11 molecular sieve.

[0150] (2) Preparation of ZSM-12 molecular sieve (the molecular sieve synthesis adopts one-step crystallization)

[0151] Add 58.5g of water glass (SiO2 content 24.01% by mass, Na2O content 7.08% by mass, Al2O3 content 0.2% by mass), aluminum sulfate octadecylhydrate, and tetraethylammonium bromide N(C2H5)4 to a 200mL reactor. + Br - As a template agent (T, the silicon source is in the form of SiO2), the anion X in the template agent T - The mixture of Na₂O (at a molar ratio of 0.03 to SiO₂) and deionized water was thoroughly mixed to obtain a mixture to be crystallized; the molar ratio of each material was Na₂O:SiO₂:Al₂O₃:T:H₂O = 0.28:1:0.33:0.03:5. The mixture was hydrothermally crystallized at 160℃ for 50 hours. The resulting solid was washed with excess deionized water until the pH of the wash solution was 6-8, and then dried at 120℃ for 6 hours to obtain ZSM-12 molecular sieve.

[0152] (3) Ammonium exchange treatment:

[0153] The obtained ZSM-11 and ZSM-12 molecular sieves were subjected to ammonium exchange. The ammonium exchange treatment for each molecular sieve included: an ammonium chloride aqueous solution concentration of 0.5 mol / L, an exchange liquid-to-solid ratio of 10 mL / g molecular sieve (i.e., the amount of ammonium salt aqueous solution used was 10 mL relative to 1 g of molecular sieve raw material), a temperature of 85℃, an exchange treatment contact time of 1 h, and two exchanges. The exchanged molecular sieves were washed with deionized water until no chloride ions were detected in the wash solution, and the washing was carried out until the pH range was 6-8. The Na2O molar content of the mixed crystal molecular sieve after washing was 0.02%.

[0154] (4) Organic amine modification treatment:

[0155] Then, the two molecular sieves were modified with organic ammonium salts. The modification process for each molecular sieve included: using an aqueous solution of 0.3 mol / L tetrabutylammonium hydroxide and hexadecyltrimethylammonium bromide (mass ratio 1:1), with a solution volume of 20 mL / g molecular sieve, a treatment temperature of 150℃, and a treatment time of 5 hours.

[0156] (5) Preparation of catalyst: Same as in Example 1; catalyst C-8 was obtained.

[0157] Comparative Example 9

[0158] The preparation method is the same as in Example 1, except that the preparation conditions of ZSM-11 and ZSM-12 molecular sieves are changed, specifically including:

[0159] (1) Preparation of ZSM-11 molecular sieve

[0160] Add 58.5g of water glass (SiO2 content 24.01% by mass, Na2O content 7.08% by mass, Al2O3 content 0.2% by mass), aluminum sulfate octadecylhydrate, and tetrabutylammonium bromide N(C4H9)4 to a 200mL reactor. + Br - As a template agent (denoted as T, where the silicon source is in the form of SiO2), the anion X in the template agent T - The mixture of Na₂O (at a molar ratio of 0.03 to SiO₂) and deionized water was thoroughly mixed to obtain a crystallization mixture. The molar ratio of each material was Na₂O:SiO₂:Al₂O₃:T:H₂O = 0.28:1:0.033:0.03:5. The mixture was hydrothermally crystallized at 30℃ for 8 hours, then heated to 195℃ for 20 hours, with a temperature increase (decrease) rate of 1℃ / min each time. The resulting solid was washed with excess deionized water until the pH of the wash solution was 6–8, and then dried at 120℃ for 6 hours to obtain ZSM-11 molecular sieve.

[0161] (2) Preparation of ZSM-12 molecular sieve

[0162] Add 58.5g of water glass (SiO2 content 24.01% by mass, Na2O content 7.08% by mass, Al2O3 content 0.2% by mass), aluminum sulfate octadecylhydrate, and tetraethylammonium bromide N(C2H5)4 to a 200mL reactor. + Br - As a template agent (T, the silicon source is in the form of SiO2), the anion X in the template agent T - The mixture of Na₂O (at a molar ratio of 0.03 to SiO₂) and deionized water was thoroughly mixed to obtain a mixture to be crystallized; the molar ratio of each material was Na₂O:SiO₂:Al₂O₃:T:H₂O = 0.28:1:0.33:0.03:5. The mixture to be crystallized was subjected to hydrothermal crystallization at 30℃ for 10 hours and at 195℃ for 20 hours, with a temperature increase (decrease) rate of 1℃ / min each time. The solid obtained after crystallization was washed with excess deionized water until the pH of the washing solution was 6-8, and then dried at 160℃ for 6 hours to obtain ZSM-12 molecular sieve.

[0163] The remaining process is the same as in Example 1, and catalyst C-9 is prepared.

[0164] Comparative Example 10

[0165] The preparation method described in Example 1 differs from that in that the conditions for ammonium exchange treatment and organic ammonium salt modification treatment are changed, specifically including:

[0166] (3) Ammonium exchange treatment:

[0167] The obtained ZSM-11 and ZSM-12 molecular sieves were subjected to ammonium exchange. The ammonium exchange treatment for each molecular sieve included: an ammonium chloride salt aqueous solution concentration of 0.5 mol / L, an exchange liquid-to-solid ratio of 10 mL / g molecular sieve (i.e., the amount of ammonium salt aqueous solution used was 10 mL relative to 1 g of molecular sieve raw material), a temperature of 50℃, an exchange treatment contact time of 1 h, and two exchanges. The exchanged molecular sieves were washed with deionized water until no chloride ions were detected in the wash solution, and the pH range was adjusted to 6-8. The molar content of Na2O in the washed mixed crystal molecular sieves was 0.2%.

[0168] (4) Organic amine modification treatment:

[0169] Then, the two molecular sieves were modified with organic ammonium salts. The modification process for each molecular sieve included: using an aqueous solution of 0.3 mol / L tetrabutylammonium hydroxide and hexadecyltrimethylammonium bromide (mass ratio 1:1), with a solution volume of 10 mL / g molecular sieve, a treatment temperature of 100℃, and a treatment time of 10 hours.

[0170] The remaining process is the same as in Example 1, and catalyst C-10 is prepared.

[0171] Example 11

[0172] The preparation method described in Example 1 differs from that in Example 1 in that:

[0173] In the preparation of ZSM-11 molecular sieve, the molar ratio of Na2O:SiO2:Al2O3:T:H2O was 0.28:1:0.05:0.8:20.

[0174] In the preparation of ZSM-12, ZSM-12 molecular sieves were prepared according to the molar ratio of Na2O:SiO2:Al2O3:T:H2O = 0.28:1:0.05:0.8:10.

[0175] The remaining process is the same as in Example 1; catalyst C-11 was prepared.

[0176] Example 12

[0177] The preparation conditions in Example 2 differ from those in Example 2 in that:

[0178] The catalyst was activated at 490°C for 4 hours in air to prepare an oxidized catalyst, and then reduced at 500°C for 4 hours in hydrogen to prepare catalyst C-12.

[0179] Comparative Example 1

[0180] Beta molecular sieves (purchased from Fushun Catalyst Factory) with a silica-to-alumina ratio of 30 were used as the acidic material and thoroughly mixed with alumina at a mass ratio of 7:3. A 5% (w / w) aqueous nitric acid solution was added and kneaded until homogeneous, with the nitric acid solution accounting for 40% of the solid mixture mass. The mixture was then extruded into strips. The strips were dried at 110°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% (w / w) ammonium chloride aqueous solution at 90°C for 2 hours, washed until no chloride ions were present in the mother liquor, dried at 110°C for 8 hours, and calcined at 500°C for 6 hours to obtain catalyst D-1.

[0181] Comparative Example 2

[0182] ZSM-12 molecular sieve (self-made) with a silica-to-alumina ratio of 30 was used as the acidic material and thoroughly mixed with alumina at a mass ratio of 7:3. A 5% (w / w) aqueous nitric acid solution was added and kneaded until homogeneous, with the nitric acid solution accounting for 40% of the solid mixture mass. The mixture was 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 with a 5% (w / w) ammonium chloride aqueous solution at 90°C for 2 hours, washed until no chloride ions were present in the mother liquor, dried at 110°C for 8 hours, and calcined at 500°C for 6 hours to obtain catalyst D-2.

[0183] Comparative Example 3

[0184] ZSM-5 molecular sieve (purchased from Fushun Catalyst Factory) with a silica-to-alumina ratio of 30 was used as the acidic material and thoroughly mixed with alumina at a mass ratio of 7:3. A 5% (w / w) aqueous nitric acid solution was added and kneaded until homogeneous, with the nitric acid solution accounting for 40% of the solid mixture mass. The mixture was then extruded into strips. The strips were dried at 120℃ for 6 hours, then granulated and calcined at 540℃ for 4 hours. The calcined sample was subjected to ion exchange with a 5% (w / w) ammonium chloride aqueous solution at 90℃ for 2 hours, washed until no chloride ions were present in the mother liquor, dried at 110℃ for 8 hours, and calcined at 500℃ for 6 hours to obtain catalyst D-3.

[0185] Comparative Example 4

[0186] ZSM-11 molecular sieve (self-made) with a silica-to-alumina ratio of 30 was used as the acidic material and thoroughly mixed with alumina at a mass ratio of 7:3. A 5% (w / w) aqueous nitric acid solution was added and kneaded until homogeneous, with the nitric acid solution accounting for 40% of the solid mixture mass. The mixture was 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 with a 5% (w / w) ammonium chloride aqueous solution at 90°C for 2 hours, washed until no chloride ions were present in the mother liquor, dried at 110°C for 8 hours, and calcined at 500°C for 6 hours to obtain catalyst D-4.

[0187] Comparative Example 5

[0188] EU-1 molecular sieve (purchased from Changling Catalyst Factory) with a silica-to-alumina ratio of 30 was used as the acidic material and thoroughly mixed with alumina at a mass ratio of 7:3. A 5% (w / w) aqueous nitric acid solution was added and kneaded until homogeneous, with the nitric acid solution accounting for 40% of the solid mixture mass. The mixture was 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 with a 5% (w / w) ammonium chloride aqueous solution at 90°C for 2 hours, washed until no chloride ions were present in the mother liquor, dried at 110°C for 8 hours, and calcined at 500°C for 6 hours to obtain catalyst D-5.

[0189] Comparative Example 6

[0190] ZSM-5 and ZSM-12 molecular sieves (self-made) with a silica-to-alumina ratio of 30 were used as acidic materials and thoroughly mixed with alumina at a mass ratio of 3:3:4. A 5% (w / w) aqueous nitric acid solution was added and kneaded until homogeneous, with the nitric acid solution accounting for 40% of the solid mixture mass. The mixture was 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 with a 5% (w / w) ammonium chloride aqueous solution at 90°C for 2 hours, washed until no chloride ions were present in the mother liquor, dried at 110°C for 8 hours, and calcined at 500°C for 6 hours to obtain catalyst D-6.

[0191] Comparative Example 7

[0192] ZSM-11 and EU-1 molecular sieves (purchased from Changling Catalyst Factory) with a silica-to-alumina ratio of 30 were used as acidic materials and thoroughly mixed with alumina at a mass ratio of 3:3:4. A 5% (w / w) aqueous nitric acid solution was added and kneaded until homogeneous, with the nitric acid solution accounting for 40% of the solid mixture mass. The mixture was 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 with a 5% (w / w) ammonium chloride aqueous solution at 90°C for 2 hours, washed until no chloride ions were present in the mother liquor, dried at 110°C for 8 hours, and calcined at 500°C for 6 hours to obtain catalyst D-7.

[0193] The component content and other data of the catalysts prepared by the above examples, comparative examples and comparative examples are listed in Table 1 below.

[0194] Table 1

[0195]

[0196] Test Example 1 (No Gas)

[0197] In a small, continuously flowing fixed-bed apparatus, 3 grams of catalyst were loaded, and the catalyst performance was evaluated using the reagents listed in Table 2 as raw materials. The evaluation conditions were: 250℃, 2 MPa, and a feed mass hourly space velocity of 2 h⁻¹. -1 .

[0198] Test Example 2 (with gas)

[0199] In a small, continuously flowing fixed-bed reactor, 3 grams of catalyst were loaded, and the catalyst performance was evaluated using the reagents listed in Table 2 as feedstock. The evaluation conditions were: 250°C, 2 MPa, and a feed space velocity of 2 h⁻¹ for the alkyl aromatic hydrocarbon feedstock. -1The gas (nN2:nH2 = 3:7) is added to the feed through a high-pressure dissolved gas device. The molar ratio of the gas (total molar amount of hydrogen and nitrogen, calculated based on a standard volume of 22.4 L / mol) to the feed (molar amount of feed calculated based on 106 g / mol of C8 aromatics, liquid density 0.87 g / ml) is controlled at 0.2. The flow rate of hydrogen is 3 mL / min and the flow rate of nitrogen is 1.3 mL / min.

[0200] The catalysts used in test examples 1 and 2 and the reaction results are shown in Tables 3 and 4.

[0201] The catalytic effect indicators and their calculation methods include:

[0202] Isomerization activity indicators:

[0203] Xylene yield:

[0204] The substance content is the mass content.

[0205] Table 2

[0206] <![CDATA[C8NA]]> B T EB PX MX OX <![CDATA[C9 + ]]> 0.05 0.02 0.50 4.43 1.63 64.42 28.94 0.01

[0207] Table 3

[0208]

[0209] Table 4

[0210]

[0211] A comparison of the data in Tables 3 and 4 above shows that the catalyst prepared using the method of this disclosure has higher isomerization activity (PX / ∑X) for the target product p-xylene and fewer by-reaction products than the catalysts of Comparative Examples 1-7, exhibiting superior overall performance. This indicates that the catalyst prepared using the method of this disclosure possesses higher reactivity and selectivity.

[0212] Meanwhile, the evaluation methods for different catalysts, both with and without gas, were compared. The results showed that the isomerization activity of each catalyst was significantly improved after gas was added to the feed (Test Example 2). This indicates that the liquid-phase alkyl aromatic hydrocarbon isomerization method provided in this disclosure can significantly improve the performance of the catalyst.

[0213] Comparing Example 1 and Example 5, it can be seen that in the molecular sieve synthesis process, the molecular sieve in Example 1 underwent organic ammonium salt modification after ammonium exchange treatment, while in Example 5, the molecular sieve after ammonium exchange treatment was not modified with organic amine salt. Compared with the catalyst prepared from the unoptimized molecular sieve in Example 5, the catalyst prepared in Example 1 has higher isomerization activity and xylene yield in the alkyl aromatic hydrocarbon isomerization reaction (without gas test and with gas test).

[0214] Comparing Example 1 with Examples 6-7, it can be seen that, in the catalyst preparation process of Example 1, the mixing weight ratio of modified ZSM-11 molecular sieve: modified ZSM-12 molecular sieve: alumina within the optimized range provided in this disclosure, compared with the catalysts prepared in Examples 6-7, the catalyst prepared in Example 1 has higher isomerization activity and xylene yield in the alkyl aromatic hydrocarbon isomerization reaction (without gas test and with gas test).

[0215] Comparing Examples 1-7 with Comparative Example 8, it can be seen that Examples 1-7 all adopted a staged hydrothermal crystallization synthesis process in the molecular sieve synthesis process. Compared with Example 8, which adopted a one-step hydrothermal crystallization synthesis of molecular sieves, the catalysts prepared in Examples 1-7 and the catalyst prepared in Example 1 all have higher isomerization activity in the alkyl aromatic hydrocarbon isomerization reaction (without gas test and with gas test).

[0216] Comparing Example 1 with Comparative Examples 9-10, it can be seen that the molecular sieve and catalyst prepared in Example 1 according to the raw material addition amount and reaction conditions provided in this disclosure have higher isomerization activity and xylene yield in the alkyl aromatic hydrocarbon isomerization reaction (without gas test and with gas test) compared with the catalysts prepared in Comparative Examples 9-10.

[0217] Comparing Example 1 with Example 11, it can be seen that the molecular sieve synthesized in Example 1 according to the optimized raw material molar ratio provided in this disclosure has better catalytic performance than that in Example 11.

[0218] Comparing Example 2 with Example 12, it can be seen that the catalyst prepared in Example 2, which is prepared according to the preferred active metal loading treatment reaction conditions provided in this disclosure, has better catalytic performance than the catalyst prepared in Example 12.

[0219] Test Example 3 (with gas)

[0220] Referring to the test method in Test Example 2, the difference from Test Example 2 is as follows:

[0221] The evaluation conditions were: 240℃, 2MPa, and a feed mass hourly space velocity (MHSV) of 10h for the alkyl aromatics feedstock. -1 Gas (nN2:nH2 = 3:7) is added to the feed through a high-pressure dissolved gas device, and the molar ratio of gas to feed is controlled at 0.2, with the flow rate of hydrogen at 15 mL / min and the flow rate of nitrogen at 6.5 mL / min.

[0222] The catalyst used in test example 3 and the reaction results are listed in Table 5 below.

[0223] Table 5

[0224]

[0225] As can be seen from the data in Table 5, comparing Test Example 3 with Test Example 2, it can be seen that Test Example 2 was carried out under the preferred liquid-phase alkyl aromatic hydrocarbon isomerization reaction conditions provided in this disclosure. Under the same catalyst conditions, Test Example 2 can obtain higher isomerization activity.

[0226] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0227] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0228] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. An alkyl aromatic hydrocarbon isomerization catalyst, characterized in that, Based on the total weight of the alkyl aromatic isomerization catalyst, the alkyl aromatic isomerization catalyst comprises 25-99.9% by weight of a mixed ten-membered ring molecular sieve and 0.1-75% by weight of an inert support; the mixed ten-membered ring molecular sieve comprises ZSM-11 molecular sieve and ZSM-12 molecular sieve; based on the total weight of the mixed ten-membered ring molecular sieve, the content of ZSM-11 molecular sieve is 20-70% by weight; the silicon-to-aluminum ratio of ZSM-11 molecular sieve is 20-100, and the silicon-to-aluminum ratio of ZSM-12 molecular sieve is 20-100; The catalyst has a BET specific surface area of ​​366~450 m². 2 / g, with an average particle size of 2~7mm and a total pore volume of 0.15~0.4ml / g.

2. The alkyl aromatic hydrocarbon isomerization catalyst according to claim 1, characterized in that, Based on the total weight of the mixed ten-membered ring molecular sieve, the content of the ZSM-11 molecular sieve is 30~55% by weight; the silicon-aluminum ratio of the ZSM-11 molecular sieve is 25~80, and the silicon-aluminum ratio of the ZSM-12 molecular sieve is 30~80.

3. The alkyl aromatic hydrocarbon isomerization catalyst according to claim 1, characterized in that, The alkyl aromatic hydrocarbon isomerization catalyst further includes a Group VIII metal element; based on the total weight of the alkyl aromatic hydrocarbon isomerization catalyst, the content of the Group VIII metal element is 0.001~0.5% by weight%. The inert carrier is selected from one or more of alumina, silicon dioxide, silica gel, and activated carbon.

4. The alkyl aromatic hydrocarbon isomerization catalyst according to claim 3, characterized in that, Based on the total weight of the alkyl aromatic isomerization catalyst, the content of the Group VIII metal element is 0.003~0.4% by weight; the Group VIII metal element is selected from one or more of nickel, palladium, platinum and rhodium.

5. A method for preparing the alkyl aromatic hydrocarbon isomerization catalyst according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1. The ZSM-11 molecular sieve raw material and the ZSM-12 molecular sieve raw material are subjected to ammonium exchange treatment and optional organic ammonium salt modification treatment to obtain modified ZSM-11 molecular sieve and modified ZSM-12 molecular sieve. S2. The modified ZSM-11 molecular sieve and the modified ZSM-12 molecular sieve are mixed with an inert support and subjected to molding treatment, first drying treatment and first calcination treatment. The ZSM-11 molecular sieve raw material and the ZSM-12 molecular sieve raw material mentioned in step S1 are each prepared independently by a method including the following steps: a. Mix the silicon source, aluminum source, template agent and water to obtain the mixture to be crystallized; b. Perform hydrothermal crystallization and drying treatment on the mixture to be crystallized; The silicon source is in the form of SiO2. In the mixture to be crystallized, the molar ratio of silicon source: aluminum source: template agent: H2O is 1:(0.01~0.05):(0.05~0.8):(10~80). The hydrothermal crystallization treatment includes a first-stage hydrothermal crystallization treatment and a second-stage hydrothermal crystallization treatment performed sequentially.

6. The method according to claim 5, characterized in that, Step S1 includes: The ZSM-11 molecular sieve raw material is contacted with an aqueous solution of a first ammonium salt to perform a first ammonium exchange treatment; the product obtained from the first ammonium exchange treatment is contacted with a solution of a first organic ammonium salt to perform a first organic ammonium salt modification treatment to obtain a modified ZSM-11 molecular sieve. The ZSM-12 molecular sieve raw material is contacted with a second ammonium salt aqueous solution to perform a second ammonium exchange treatment. The product obtained from the second ammonium exchange treatment is then contacted with a second organic ammonium salt solution to perform a second organic ammonium salt modification treatment, thereby obtaining a modified ZSM-12 molecular sieve.

7. The method according to claim 6, characterized in that, The conditions for the first and second ammonium exchange treatments are each independent of the following: the concentration of the ammonium salt aqueous solution is 0.4~0.6 mol / L, the volume of the ammonium salt aqueous solution is 3~50 mL relative to 1 g of molecular sieve raw material, the exchange temperature is 60~95℃, the contact time is 0.5~8 h, and the number of exchange cycles is 1~3; the exchanged molecular sieve is washed several times with excess deionized water until no halogen anions are detected in the washing solution, the pH range is 6~8, and the Na2O molar content of the washed mixed crystal molecular sieve is 0.02~0.30%; The conditions for the first organic ammonium salt modification treatment and the second organic ammonium salt modification treatment each independently include: the concentration of the organic ammonium salt solution is 0.05~0.5mol / L, the amount of organic ammonium salt solution used relative to 1g of molecular sieve is 3~40mL, the treatment temperature is 110~190℃, and the treatment time is 2~8h.

8. The method according to claim 7, characterized in that, The concentration of the ammonium salt aqueous solution is 0.45~0.55mol / L. The amount of ammonium salt aqueous solution used relative to 1g of molecular sieve raw material is 5~45mL. The exchange temperature is 65~90℃ and the contact time is 1~7h. The first ammonium salt and the second ammonium salt are each independently selected from one or more of the following: aqueous solution of tetrabutylammonium hydroxide, tetraethylammonium hydroxide and hexadecyltrimethylammonium bromide. The conditions for the first organic ammonium salt modification treatment and the second organic ammonium salt modification treatment each independently include: the concentration of the organic ammonium salt solution is 0.1~0.4 mol / L, the amount of organic ammonium salt solution used relative to 1g of molecular sieve is 5~35mL, the treatment temperature is 120~180℃, and the treatment time is 3~7h; the first organic ammonium salt and the second organic ammonium salt are each independently selected from one or more of the following: aqueous solution of tetrabutylammonium hydroxide, tetraethylammonium hydroxide, and hexadecyltrimethylammonium bromide.

9. The method according to claim 5, characterized in that, In the mixture to be crystallized, the molar ratio of silicon source: aluminum source: template agent: H2O is 1:(0.02~0.04):(0.06~0.7):(10~75); The molar ratio of Na2O to SiO2 in the mixture to be crystallized is (0.01~0.5):

1.

10. The method according to claim 9, characterized in that, The molar ratio of Na2O to SiO2 in the mixture to be crystallized is (0.02~0.4):

1.

11. The method according to claim 5, characterized in that, The silicon source is selected from one or more of water glass, liquid silica sol, and solid silica gel; the molar ratio of sodium oxide to silicon oxide in the water glass is (0.01~0.5):1; the concentration of the liquid silica sol is 10~40% by weight; and the particle size of the solid silica gel is 0.005μm~0.05μm. The aluminum source is selected from one or more of aluminum sulfate, sodium aluminate, aluminum nitrate, and aluminum isopropoxide; The template agent is selected from those having the general formula. One or more of the compounds with the structure shown; wherein R1, R2, R3, and R4 are the same or different, and each is independently selected from alkyl groups having 1 to 4 carbon atoms, X - It is a hydroxide ion or a halide anion, and N is a nitrogen atom.

12. The method according to claim 11, characterized in that, The concentration of the liquid silica sol is 20-40% by weight, the particle size of the solid silica gel is 0.01μm-0.03μm, and the silicon source is water glass. R1, R2, R3, and R4 may be the same or different, and each is independently selected from ethyl or butyl; X - The silicon source is bromide ions; the silicon source is in the form of SiO2, and the X in the template agent... - The molar ratio with SiO2 is 0.05~0.8; In the raw materials used to synthesize ZSM-11 molecular sieves, the template agent is selected from one or more of methyltributylammonium chloride, tetrabutylammonium bromide, and tetrabutylammonium hydroxide.

13. The method according to claim 12, characterized in that, X in the template agent - The molar ratio with SiO2 is 0.06~0.7; In the raw materials used to synthesize ZSM-12 molecular sieves, the template agent is selected from one or more of methyltriethylammonium bromide, tetraethylammonium bromide, and tetraethylammonium hydroxide.

14. The method according to claim 5, characterized in that, The conditions for the first stage of hydrothermal crystallization treatment include: a hydrothermal crystallization temperature of 40~90℃ and a hydrothermal crystallization time of 6~18h; the conditions for the second stage of hydrothermal crystallization treatment include: a hydrothermal crystallization temperature of 120~190℃ and a hydrothermal crystallization time of 9~60h. The temperature change rate from the first stage of hydrothermal crystallization treatment to the second stage of hydrothermal crystallization treatment is 0.5~5℃ / min; The drying conditions described in step b include: a drying temperature of 80~120℃ and a drying time of 2~6h.

15. The method according to claim 14, characterized in that, The conditions for the first stage of hydrothermal crystallization treatment include: a hydrothermal crystallization temperature of 50~80℃ and a hydrothermal crystallization time of 7~17h; the conditions for the second stage of hydrothermal crystallization treatment include: a hydrothermal crystallization temperature of 130~180℃ and a hydrothermal crystallization time of 10~55h. The temperature change rate from the first stage of hydrothermal crystallization treatment to the second stage of hydrothermal crystallization treatment is 1~3℃ / min.

16. The method according to claim 5, characterized in that, Step S2 includes: The modified ZSM-11 molecular sieve and the modified ZSM-12 molecular sieve are mixed with an inert support, and a solution of a peptide solvent is added for kneading treatment. Then, they are subjected to extrusion molding, first drying treatment and first calcination treatment. The mixing weight ratio of modified ZSM-11 molecular sieve: modified ZSM-12 molecular sieve: inert support is 1:0.4~4:1.05~3.3; The adhesive solvent is selected from one or more of nitric acid, phosphoric acid, and citric acid, and the solution concentration of the adhesive solvent is 1-5% by weight. The conditions for the first drying treatment include: a drying temperature of 100~140℃ and a drying time of 4~24h; the conditions for the first calcination treatment include: a calcination temperature of 400~550℃ and a calcination time of 4~24h.

17. The method according to claim 16, characterized in that, In step S2, the mixing weight ratio of modified ZSM-11 molecular sieve: modified ZSM-12 molecular sieve: inert support is 1:0.8~2.3:1.2~2.2; The volume of the solution of the adhesive solvent is 0.5 to 1.5 mL relative to 1 g of the solid mixture; The conditions for the first calcination treatment include: a calcination temperature of 110~130℃ and a calcination time of 5~20h; The atmosphere for the first roasting process is air.

18. The method according to claim 5, characterized in that, The method also includes the following steps: S3. The product obtained from the first calcination treatment in step S2 is brought into contact with an active metal source for active metal loading treatment; then a second drying treatment, a second calcination treatment, and a reduction treatment are performed. The active metal source is selected from one or more group VIII metal salts, and the weight ratio of the product obtained from the first calcination treatment in step S2 to the active metal source is 1:0.0001~0.

05. The conditions for active metal loading treatment include: loading temperature of 10~40℃ and loading time of 4~24h; The conditions for the second drying process include: a drying temperature of 80~140℃ and a drying time of 4~12h; The conditions for the second calcination treatment include: a calcination temperature of 450~520℃ and a calcination time of 4~8h; the atmosphere for the second calcination treatment is air. The conditions for the reduction treatment include: a reduction temperature of 450~520℃ and a reduction time of 4~8h; the atmosphere for the reduction treatment is hydrogen or a mixture of nitrogen and hydrogen.

19. The method according to claim 18, characterized in that, The active metal source is selected from one or more of nickel, palladium, platinum and rhodium; the weight ratio of the product obtained from the first calcination treatment in step S2 to the active metal source is 1:0.0002~0.04; The conditions for the second calcination treatment include: a calcination temperature of 480~500℃ and a calcination time of 5~7h; The conditions for the reduction treatment include: a reduction temperature of 480~500℃ and a reduction time of 5~7h.

20. The alkyl aromatic hydrocarbon isomerization catalyst prepared by the method according to any one of claims 5 to 19.

21. A method for isomerization of alkyl aromatic hydrocarbons in liquid phase, characterized in that, Includes the following steps: An alkyl aromatic feedstock is brought into contact with a catalyst under liquid conditions to undergo an isomerization reaction; the catalyst includes the alkyl aromatic isomerization catalyst according to any one of claims 1 to 4 and claim 20; in the isomerization reaction, hydrogen and nitrogen are introduced to contact the catalyst.

22. The liquid-phase alkyl aromatic hydrocarbon isomerization method according to claim 21, characterized in that, The alkyl aromatic raw material includes aromatics with 8 to 10 carbon atoms; The conditions for the isomerization reaction include: a reaction temperature of 240-310℃, a reaction pressure of 2-4 MPa, and a weight hourly space velocity (WHSV) of 1-10 h⁻¹ for the alkyl aromatic feedstock. -1 The molar ratio of hydrogen to feed is 0.01~1; the molar ratio of nitrogen to feedstock oil is 0.01~1.

23. The liquid-phase alkyl aromatic hydrocarbon isomerization method according to claim 22, characterized in that, The conditions for the isomerization reaction include: a reaction temperature of 250-290°C and a weight hourly space velocity (WHSV) of 2-6 h⁻¹ for the alkyl aromatic feedstock. -1 The molar ratio of hydrogen to feed is 0.05~0.6; the molar ratio of nitrogen to feedstock is 0.06~0.6.

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