Process for the preparation of light aromatic hydrocarbons

Abstract

The present application relates to the field of poor quality aromatic-rich distillate oil hydroprocessing, and discloses a preparation method of light aromatic hydrocarbon. The method comprises the following steps: (1) contacting aromatic-rich distillate oil and hydrogen with a hydrofining catalyst to perform a hydrofining reaction, to obtain a hydrofining product; (2) contacting the hydrofining product and hydrogen with a hydrocracking catalyst to perform a hydrocracking reaction, to obtain a hydrocracking product; (3) performing gas-liquid separation on the hydrocracking product, to obtain a gas phase product and a liquid phase product, wherein the content of methane in the gas phase product is not higher than 1 wt%; (4) separating the gas phase product to obtain recycled hydrogen, and then returning the recycled hydrogen to the hydrocracking reaction in step (2) for recycling. The method provided by the present application can achieve high BTX yield and long-period stable operation of the device.

Description

Technical Field

[0001] This invention relates to the field of hydrogenation treatment of inferior aromatic-rich distillate oils, and specifically to a method for preparing light aromatic hydrocarbons. Background Technology

[0002] In petroleum refining, a large amount of heavy aromatic components with high aromatic content are often produced as a byproduct. These heavy aromatics contain a large number of polycyclic aromatic compounds (PACs) and are mainly used as low-value diesel blending components. With the accelerated pace of oil product upgrading in recent years, there is an urgent need to develop technologies that can convert low-quality heavy aromatic components into other high-value chemical products. Currently, selective partial hydrogenation of PACs, followed by ring-opening and cracking reactions of saturated rings to produce monocyclic aromatics, is one of the effective conversion pathways for PACs, mainly used to produce light aromatics (BTX) components that are in high demand in the market. Hydrogenation to saturate the first ring of PACs is relatively easy, but ring-opening through cracking of saturated rings is more difficult and the reaction process is complex. Once one or more saturated rings are formed, the next step is to open these saturated rings and further crack them into smaller molecules, such as monocyclic aromatics. This step is often more challenging because it involves the breaking of C-C bonds, which are usually quite stable. In addition, to ensure high selectivity and yield, it is also necessary to avoid over-hydrogenation or other side reactions. In the gaseous products of hydrocracking, methane tends to accumulate in the system, reducing the circulating hydrogen concentration and affecting reaction performance. To ensure the purity of the circulating hydrogen, the decision to discharge waste hydrogen is generally based on the concentration of hydrogen in the circulating hydrogen analysis sample, which increases costs.

[0003] CN1117404A discloses a catalyst for the production of BTX from heavy aromatics. This catalyst uses 30–70 wt% ZSM-5 zeolite and 30–70 wt% γ- or η-Al₂O₃ as a support, and supports 0.1–0.5 wt% rhenium, 0.1–0.5 wt% tin, 0.05–0.3 wt% platinum, or 0.2–0.8 wt% palladium. The catalyst operates at 350–450 °C, 0.5–3.5 MPa, and a weight hourly space velocity (WHSV) of 1–5. -1 Under operating conditions with a hydrogen / hydrocarbon (volume ratio) of 500–1200, the BTX production is only 25.2 wt%.

[0004] CN104383961A discloses a catalyst and preparation method for producing high-purity BTX aromatics by hydrogenation cracking of heavy aromatics. The catalyst is composed of amorphous silica-alumina or molecular sieves and alumina, and the active components are platinum metal, rare earth and transition metals. The BTX content in the liquid phase product is 41.9 wt%.

[0005] Existing technologies have low BTX yields and poor catalyst stability, which are not conducive to long-term operation of the unit. Researching efficient and stable hydrocracking processes and catalysts is key. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem of low efficiency in converting rich aromatic heavy components into light aromatics in existing technologies, and to provide a method for preparing light aromatics. The method provided by this invention can achieve high BTX yield and long-term stable operation of the equipment.

[0007] To achieve the above objectives, the present invention provides a method for preparing light aromatic hydrocarbons, the method comprising the following steps:

[0008] (1) Aromatic distillate oil and hydrogen are contacted with a hydrorefining catalyst to carry out a hydrorefining reaction to obtain a hydrorefined product.

[0009] (2) The hydrorefined product and hydrogen are contacted with a hydrocracking catalyst to carry out a hydrocracking reaction to obtain a hydrocracking product;

[0010] (3) The hydrocracking product is subjected to gas-liquid separation to obtain a gas phase product and a liquid phase product, wherein the methane content in the gas phase product is not higher than 1 wt%.

[0011] (4) Separate the gaseous products to obtain recycled hydrogen, and then return the recycled hydrogen to the hydrocracking reaction in step (2) for recycling.

[0012] The beneficial effects of the present invention through the above technical solution include:

[0013] In the method provided by this invention, the content of methane in the gaseous products obtained by hydrocracking is controlled. When hydrogen in the gaseous products is recycled, it is beneficial to improve the stability of the hydrocracking catalyst, so that it can operate for a long period of time without significantly reducing the BTX yield. Attached Figure Description

[0014] Figure 1 This is the XRD pattern of the ZSM-5 molecular sieve prepared in Example 1 of this invention;

[0015] Figure 2 This is a SEM image of the ZSM-5 molecular sieve prepared in Example 1 of this invention;

[0016] Figure 3 Here is a SEM image of the ZSM-5 molecular sieve prepared in Example 2 of this invention;

[0017] Figure 4 This is a SEM image of the ZSM-5 molecular sieve prepared in Comparative Preparation Example 1 of this invention;

[0018] Figure 5 This is a SEM image of the ZSM-5 molecular sieve prepared in Comparative Preparation Example 2 of this invention;

[0019] Figure 6This is a SEM image of the ZSM-5 molecular sieve prepared in Comparative Preparation Example 3 of this invention;

[0020] Figure 7 This is a TEM image of the catalyst prepared in Example 1 of this invention;

[0021] Figure 8 This is a TEM image of the catalyst prepared in Comparative Preparation Example 1 of the present invention;

[0022] Figure 9 This is a TEM image of the catalyst prepared in Comparative Preparation Example 2 of the present invention;

[0023] Figure 10 This is a TEM image of the catalyst prepared in Comparative Preparation Example 3 of the present invention. Detailed Implementation

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] This invention provides a method for preparing light aromatic hydrocarbons, the method comprising the following steps:

[0026] (1) Aromatic distillate oil and hydrogen are contacted with a hydrorefining catalyst to carry out a hydrorefining reaction to obtain a hydrorefined product.

[0027] (2) The hydrorefined product and hydrogen are contacted with a hydrocracking catalyst to carry out a hydrocracking reaction to obtain a hydrocracking product;

[0028] (3) The hydrocracking product is subjected to gas-liquid separation to obtain a gas phase product and a liquid phase product, wherein the methane content in the gas phase product is not higher than 1 wt%.

[0029] (4) Separate the gaseous products to obtain recycled hydrogen, and then return the recycled hydrogen to the hydrocracking reaction in step (2) for recycling.

[0030] The present invention does not particularly limit the hydrorefining catalyst, and any conventional choice in the art can be used. Preferably, the hydrorefining catalyst comprises a first support and a first active component, wherein the first active component is selected from at least one group VIB metal and a group VIII metal.

[0031] According to the present invention, preferably, based on the total mass of the hydrorefining catalyst, the mass content of Group VIII metals, calculated as oxides, is 2-15% and the mass content of Group VIB metals is 3-30%.

[0032] The present invention has a wide range of choices for the group VIB metals. Preferably, the group VIB metals are Mo and / or W, with Mo being the most preferred.

[0033] The present invention has a wide range of choices for the group VIII metals. Preferably, the group VIII metals are Ni and / or Co, with Ni being the most preferred.

[0034] The present invention has a wide range of choices for the type of the first carrier. Preferably, the first carrier is selected from at least one of the following: alumina-mordenite composite carrier, alumina carrier, silica carrier, alumina-silica composite carrier, and alumina-beta zeolite composite carrier.

[0035] The hydrorefining catalyst used in this invention can be prepared using conventional methods in the art or can be obtained commercially.

[0036] The present invention has a wide range of choices for the hydrocracking catalyst. Preferably, the hydrocracking catalyst includes a second support and a second active component. The second support is ZSM-5 molecular sieve, and the second active component is selected from at least one of Group VIB metals and Group VIII metals.

[0037] Preferably, the ZSM-5 molecular sieve has a cage-like structure formed by stacked plate-like primary crystals. The catalyst prepared using the ZSM-5 zeolite with the specific structure described in this invention has good catalytic performance, which is beneficial for improving the BTX yield, and at the same time, it is beneficial for controlling the methane content in the gaseous products to be no higher than the above-mentioned range.

[0038] The morphology of the molecular sieve described in this invention was measured using SEM. The overall morphology of the molecular sieve resembles a lantern with internal cavities, hence it is termed a cage-like structure. This cage-like structure is formed by the stacking of layered primary crystals, as can be seen from [reference needed]. Figure 1 .

[0039] The cage-like structure described in this invention can be regular or not completely regular, both of which are within the protection scope of this invention.

[0040] The size of the plate-shaped primary grains of the present invention is relatively small. Preferably, the average size of the plate-shaped primary grains is (40-170)×(20-100)×(30-100)nm, and more preferably (100-140)×(40-70)×(30-50)nm.

[0041] In this invention, the average size of the primary grain is given in the form of length × width × height.

[0042] The method for testing the average size of the lamellar primary grains of the present invention includes: measuring the length, width and height of 20-40 primary grains in the SEM image using a NanoMeasurer and taking the average value.

[0043] The molecular sieve of this invention has a high specific surface area, which is beneficial for increasing the reaction contact area. Preferably, the specific surface area of ​​the ZSM-5 molecular sieve is 300-500 m² / g. 2 / g, preferably 300-400m 2 / g.

[0044] According to the present invention, preferably, the ratio of the external specific surface area of ​​the ZSM-5 molecular sieve to its total surface area is 30-55%, specifically 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, and any two of these values, preferably 35-50%. This preferred embodiment provides more active centers, promotes chemical reactions, and improves reaction efficiency.

[0045] It is understood that in this invention, the specific surface area is the sum of the external specific surface area and the internal specific surface area.

[0046] The specific surface area parameter of the molecular sieve described in this invention was measured by the BET method.

[0047] According to the present invention, preferably, the SiO2 / Al2O3 molar ratio of the ZSM-5 molecular sieve is 15-50, more preferably 20-40.

[0048] The SiO2 / Al2O3 molar ratio of the molecular sieve described in this invention was measured by inductively coupled plasma atomic emission spectrometry (ICP).

[0049] According to the present invention, preferably, after sulfidation, the catalyst has an average number of stacked layers of active centers of 1-5 layers, specifically 1, 2, 3, 4, or 5 layers, and a range of any two of these values, preferably 2-5 layers. This preferred embodiment demonstrates that the active metal component has good dispersibility, which is beneficial for improving the activity of the catalyst.

[0050] According to the present invention, preferably, after sulfidation, the average lamellar length of the active center of the catalyst is no greater than 8 nm, specifically it can be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, and any two of these values ​​within a range, preferably 2-8 nm. This preferred embodiment is more conducive to improving the activity of the catalyst.

[0051] It should be noted that the "lamella length and number of stacked layers of the active center" here refers to the lamellar length and number of stacked layers of MoS2.

[0052] The average number of stacked layers and the average lamellar length of the active centers in the catalyst of this invention were measured by transmission electron microscopy (TEM). The instrument model was a Tecnai20S-TWIN from ThemoFisher Scientific, USA. Technical specifications: lattice resolution: 0.14 nm; point resolution: 0.24 nm; maximum voltage: 200 kV. Specifically, the lattice length and number of stacked layers of the active centers in 10-20 catalyst samples were measured, and the average value was taken.

[0053] Before transmission electron microscopy (TEM) testing, the prepared catalyst was pre-sulfurized using aviation kerosene containing 3% (w / v) dimethyl disulfide as the sulfiding oil. The sulfidation conditions were: sulfidation temperature 270℃, and liquid hourly space velocity (LHSV) of the sulfiding oil 1.0 h⁻¹. -1 The hydrogen pressure is 6 MPa, the volume ratio of hydrogen to sulfurized oil is 1000, and the sulfurization time is 24 hours.

[0054] According to the present invention, preferably, based on the total weight of the hydrocracking catalyst, the mass content of Group VIII metals is 0.5-4% and the mass content of Group VIB metals is 5.5-13.5% in terms of oxides.

[0055] The present invention has a wide range of choices for the group VIB metals, and preferably, the group VIB metals are Mo and / or W.

[0056] The present invention has a wide range of choices for the group VIB metals. Preferably, the group VIII metals are Ni and / or Co.

[0057] This invention does not impose any particular limitation on the preparation method of the hydrocracking catalyst, as long as a hydrocracking catalyst with the above-mentioned composition and characteristic parameters can be obtained. To further improve the performance of the hydrocracking catalyst, and also to better illustrate the preparation of the hydrocracking catalyst, this invention also provides a method for preparing the hydrocracking catalyst.

[0058] According to the present invention, preferably, the preparation method of the hydrocracking catalyst includes the following steps:

[0059] (1) Aluminum source, silicon source, alkali source, structure directing agent, fluoride and water are gelled to obtain a colloidal solution; the molar ratio of silicon source to alkali source is 1:0.2-0.9, and the molar ratio of silicon source to fluoride is 1:0.08-0.3, wherein the silicon source is calculated as SiO2;

[0060] (2) The colloidal solution is dynamically crystallized, and then subjected to a first drying and a first calcination to obtain ZSM-5 molecular sieve;

[0061] (3) The impregnation solution containing the second active component compound is brought into contact with ZSM-5 molecular sieve, and then subjected to second drying and second calcination.

[0062] The method for preparing ZSM-5 molecular sieve provided by this invention involves adding a structure-directing agent, an alkali source, and a fluoride to the system without adding seed crystals, followed by a one-step dynamic crystallization process to obtain the sieve.

[0063] According to the present invention, the molar ratio of silicon source to alkali source is 1:0.2-0.9, specifically 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, and any two of these values ​​within a range, preferably 1:0.3-0.7, wherein the silicon source is SiO2. In the present invention, controlling the amount of alkali source within the above-mentioned preferred range is beneficial for inducing the formation of the cage-like molecular sieve structure.

[0064] According to the present invention, the molar ratio of silicon source to fluoride is 1:0.08-0.3, specifically 1:0.08, 1:0.09, 1:0.1, 1:0.11, 1:0.12, 1:0.13, 1:0.14, 1:0.15, 1:0.16, 1:0.17, 1:0.18, 1:0.19, 1:0.2, 1:0.21, 1:0.22, 1:0.23, 1:0.24, 1:0.25, 1:0.26, 1:0.27, 1:0.28, 1:0.29, 1:0.3, and any two of these values ​​forming a range, preferably 1:0.08-0.24, wherein the silicon source is SiO2. In the present invention, controlling the amount of fluoride within the above-mentioned preferred range is beneficial for forming a specific zeolite framework structure.

[0065] According to the present invention, preferably, the molar ratio of silicon source, aluminum source and water is 1:0.01-0.07:50-80, more preferably 1:0.02-0.06:50-75, wherein the silicon source is calculated as SiO2 and the aluminum source is calculated as Al2O3.

[0066] According to the present invention, preferably, the molar ratio of silicon source to structure directing agent is 1:0.3-0.8, more preferably 1:0.4-0.7, wherein the silicon source is SiO2.

[0067] The present invention does not impose any particular limitation on the type of aluminum source, and any conventional choice in the art can be made. Preferably, the aluminum source is selected from at least one of sodium aluminate, aluminum sulfate, aluminum powder, and boehmite.

[0068] The present invention does not impose any particular limitation on the type of silicon source, and any conventional choice in the art can be used. Preferably, the silicon source is selected from at least one of silicic acid, silica sol, silica fume, and water glass.

[0069] The present invention does not impose any particular limitation on the type of alkali source, and any conventional choice in the art can be made. Preferably, the alkali source is selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and ammonia water.

[0070] The present invention has a wide range of choices for the type of structure directing agent. Preferably, the structure directing agent is selected from at least one of ethylenediamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide and hexadecyltrimethylammonium bromide.

[0071] The present invention has a wide range of choices for the types of fluorides. Preferably, the fluorides are selected from at least one of sodium fluoride, potassium fluoride, calcium fluoride and magnesium fluoride.

[0072] According to the present invention, preferably, the gelation conditions in step (1) include: a gelation temperature of 10-60°C, preferably 20-50°C; and a gelation time of 2-10 h, preferably 3-8 h.

[0073] The present invention does not impose any particular limitation on the order of adding the aluminum source, silicon source, alkali source, structure directing agent, fluoride, and water in step (1), and can make appropriate adjustments according to the actual situation. Moreover, during the addition of the above substances, conventional operations such as stirring or ultrasonication can be performed to achieve uniform mixing. According to a preferred embodiment of the present invention, step (1) includes: first adding the aluminum source aqueous solution to the aqueous solution containing the silicon source and alkali source, then adding the fluoride aqueous solution, and finally adding the structure directing agent aqueous solution.

[0074] According to a particularly preferred embodiment of the present invention, step (1) includes: first, adding an aqueous solution of aluminum source dropwise to an aqueous solution containing silicon source and alkali source, stirring for 20-40 min, then adding an aqueous solution of fluoride, stirring for 60-120 min, and finally adding an aqueous solution of structure guiding agent, stirring for 3-6 h to obtain a colloidal solution.

[0075] The dynamic crystallization process described in this invention does not require temperature-variable crystallization and has a short crystallization time. Preferably, the conditions for dynamic crystallization in step (2) include: a crystallization temperature of 150-220℃ and a crystallization time of 18-40h.

[0076] The present invention does not particularly limit the method of achieving dynamic crystallization, and conventional methods in the art can be used. Preferably, the dynamic crystallization in step (2) is carried out under stirring conditions.

[0077] Preferably, the stirring speed is 1-60 r / min, more preferably 10-40 r / min. This preferred embodiment facilitates gel conversion and crystallization, and also helps to obtain small-diameter primary crystals.

[0078] The present invention does not have any particular limitation on the conditions for the first drying in step (2), and can refer to conventional methods in the art.

[0079] According to the present invention, preferably, the conditions for the first roasting in step (2) include: a roasting temperature of 300-700℃, preferably 350-600℃; and a roasting time of 2-10h, preferably 3-8h.

[0080] Preferably, the method further includes: performing solid-liquid separation and washing before the dynamic crystallization product described in step (2) undergoes a first drying.

[0081] The present invention does not particularly limit the method of solid-liquid separation, and conventional technical means in the art can be used.

[0082] The present invention does not have any particular limitation on the washing method, and conventional methods in the art can be used.

[0083] In step (3) of this invention, a second active component is introduced onto the ZSM-5 molecular sieve using an impregnation method.

[0084] The present invention does not specifically limit the method of impregnation. The method of impregnation can be impregnation with excess liquid or impregnation with equal volume, depending on the amount of impregnation liquid used.

[0085] The present invention does not have a particular limitation on the number of impregnations; impregnation can be performed once or multiple times, as long as the mass content of the second active component in the hydrocracking catalyst is within the above-mentioned range.

[0086] The present invention does not impose a particular limitation on the impregnation temperature, and it can be carried out according to conventional methods, such as at room temperature. The present invention also does not impose a particular limitation on the impregnation time, as long as the required amount of the second active component is loaded onto the carrier. Once the required impregnation amount and conditions are determined, a suitable impregnation time can be easily selected. The present invention does not impose a particular limitation on the impregnation environment, and it can be carried out under sealed conditions or in an open environment according to conventional methods in the art.

[0087] The present invention has a wide range of choices for the second active component compound, as long as it contains a second active component compound, it can be any kind of second active component compound commonly found in the art.

[0088] According to the present invention, preferably, a dispersant is also added to the impregnation solution in step (3), wherein the dispersant is selected from at least one of laurylamidopropylamine oxide, octadecylamidopropylamine oxide, cocamidopropylamine oxide, hexadecyl dihydroxyethylamine oxide and hexadecyl dimethylamine oxide.

[0089] The inventors of this invention have discovered that adding a specific type of dispersant to the impregnation solution is more conducive to improving the dispersion of the active component, thereby improving the reaction activity of the catalyst and at the same time improving the stability of the catalyst.

[0090] According to the present invention, preferably, the mass fraction of the dispersant in the impregnation solution is 1-5%, more preferably 1.5-3.5%.

[0091] According to the present invention, preferably, an auxiliary agent is also added to the impregnation solution in step (3). The auxiliary agent of the present invention can be a conventional choice in the art. Preferably, the auxiliary agent is selected from at least one of phosphoric acid, hydrochloric acid, citric acid, and nitric acid.

[0092] According to the present invention, preferably, the mass fraction of the auxiliary agent in the impregnation solution is 2-18%, more preferably 3.5-16%.

[0093] According to a more preferred embodiment of the present invention, the auxiliary agent is citric acid and phosphoric acid. This preferred embodiment further improves the stability of the catalyst.

[0094] More preferably, the mass ratio of citric acid to phosphoric acid is 0.5-2.5, specifically 0.5:1, 1:1, 1:1.5, 1:2, 1:2.5, and any two of these values ​​forming a range.

[0095] The present invention does not particularly limit the specific conditions for the second drying and the second calcination, and can refer to conventional methods in the art.

[0096] The present invention does not particularly limit the conditions for the hydrogenation refining reaction, and can refer to conventional methods in the art. Preferably, the conditions for the hydrogenation refining reaction in step (1) include: a reaction inlet temperature of 200-350℃, preferably 200-300℃; a reaction pressure of 3.5-7.5MPa, preferably 4-7MPa; and a weight hourly space velocity of 0.5-3h. -1 Preferably 0.5-2h -1 The hydrogen-to-oil volume ratio is 600-4000:1, preferably 800-3000:1.

[0097] According to the present invention, preferably, the conditions for the hydrocracking reaction in step (2) include: a reaction inlet temperature of 250-450°C, preferably 280-400°C; a reaction pressure of 3.5-7.5 MPa, preferably 4-7 MPa; and a weight hourly space velocity of 0.5-2.5 h⁻¹. -1 Preferably 0.6-2h -1 The hydrogen-to-oil volume ratio is 600-3500:1, preferably 700-2500:1.

[0098] In existing technologies, a large amount of hydrogen is used in the hydrocracking process. Due to hydrogenation efficiency issues, a significant portion of the hydrogen remains after the hydrocracking reaction, and it is typically recycled to avoid waste. However, small-molecule hydrocarbons are generated during hydrocracking, and many byproduct hydrocarbon compounds are recovered along with the hydrogen. The inventors of this invention discovered that methane, among the byproduct hydrocarbon compounds, tends to accumulate in the system, affecting reaction performance. Further research revealed that by controlling the methane content in the gaseous products obtained from hydrocracking, and when the recycled hydrogen obtained from the gaseous product separation is reused, it is beneficial to the stability of the hydrocracking catalyst, allowing it to operate over long periods without a significant decrease in BTX yield. According to this invention, the methane content in the gaseous products is no higher than 1 wt%, preferably no higher than 0.5 wt%.

[0099] The amount of circulating hydrogen used in this invention can be adjusted appropriately according to actual conditions. Preferably, in step (4), the hydrogen circulation ratio is 1-6:1.

[0100] In this invention, the hydrogen recycling ratio refers to the mass ratio of recycled hydrogen to fresh hydrogen.

[0101] The separation described in step (4) of this invention can be carried out using conventional methods in the art, as long as the circulating hydrogen can be separated. This invention will not elaborate further here.

[0102] According to the present invention, preferably, the initial boiling point of the aromatic-rich distillate oil is 150-250℃, and the final boiling point is 300-380℃.

[0103] According to the present invention, preferably, the aromatic content in the aromatic-rich distillate oil is >70 wt%, more preferably >80 wt%.

[0104] Preferably, the sulfur content in the aromatic distillate oil is 500-7000 ug / mL, more preferably 800-5000 ug / mL; and the nitrogen content is 100-1000 ug / mL, more preferably 200-800 ug / mL.

[0105] This invention does not particularly limit the source of the aromatic-rich distillate oil; it can be an aromatic-rich distillate oil obtained by various means, as long as the above conditions are met. Preferably, the aromatic-rich distillate oil is selected from at least one of ethylene tar, coal tar, catalytic cracking diesel oil, and coking diesel oil.

[0106] The present invention will be described in detail below through embodiments.

[0107] In the following examples, the specific surface area of ​​the molecular sieve was measured using the nitrogen physical adsorption-desorption method (BET method): the nitrogen physical adsorption-desorption isotherm of the molecular sieve was measured using a Micromeretic ASAP2020M physical adsorption instrument, and then calculated using the BET equation and t-plot equation. The experimental conditions for this molecular sieve were: measurement temperature -196℃, and before measurement, the molecular sieve was heat-treated at 550℃ in air for 6 hours, and then pretreated in vacuum at 350℃ for 4 hours.

[0108] The content of each element in the molecular sieve was determined by inductively coupled plasma atomic emission spectrometry (ICP) using a Varian 725-ES instrument. Before testing, the sample was dissolved in hydrofluoric acid, and the content was expressed in moles.

[0109] The content of the active component in the hydrocracking catalyst of the present invention was measured by inductively coupled plasma atomic emission spectrometry (ICP).

[0110] The size and distribution of the active centers of the sample can be studied by transmission electron microscopy. (1) Instrument model: Tecnai20S-TWIN by ThemoFisher Scientific, USA; (2) Technical specifications: lattice resolution: 0.14nm; point resolution: 0.24nm; maximum voltage: 200kV; (3) Experimental conditions: the sample is ultrasonically dispersed in ethanol solution and then dropped onto a copper grid. After the ethanol evaporates, the sample is observed.

[0111] The preparation examples described in this invention are used to illustrate the preparation of hydrocracking catalysts.

[0112] Preparation Example 1

[0113] The ZSM-5 molecular sieve was prepared using a cage-like ZSM-5 molecular sieve as a carrier. The preparation method of the ZSM-5 molecular sieve was as follows: sodium hydroxide, silica sol (containing 40% by weight of SiO2) and deionized water were prepared into solution A; aluminum sulfate octadechydrate and deionized water were prepared into solution B; potassium fluoride dihydrate and deionized water were prepared into solution C; and tetraethylammonium hydroxide and deionized water were prepared into solution D.

[0114] While stirring, solution B was added dropwise to solution A, and the mixture was stirred at room temperature for 30 minutes. Then solution C was added, and the mixture was stirred at room temperature for 80 minutes. Finally, solution D was added to the above solutions, and the mixture was stirred at 30°C for 5 hours to obtain a mixed solution. The final material ratio (molar ratio) is:

[0115] SiO2 / Al2O3 = 33.28;

[0116] NaOH / SiO2 = 0.67;

[0117] Structure directing agent / SiO2 = 0.5;

[0118] Fluoride / SiO2 = 0.22;

[0119] H2O(total) / SiO2 = 56.29.

[0120] The above mixed solution was placed in a stainless steel reactor and crystallized at 190°C with a stirring speed of 20 rpm for 26 hours. After crystallization, the crystallized product was filtered, washed with deionized water, dried in an oven at 105°C overnight, and calcined in air at 550°C for 6 hours to obtain ZSM-5 molecular sieve.

[0121] The XRD pattern of the molecular sieve prepared in Example 1 is shown below. Figure 1 As shown. (Through) Figure 1 It can be seen that the characteristic diffraction peaks of the typical MFI-type framework structure appear at 2θ = 7.9°, 8.8°, 23.1°, 23.8° and 24.3°, and there are no other impurity phase peaks, indicating that the synthesized ZSM-5 molecular sieve is a pure phase with high crystallinity.

[0122] An exemplary SEM image of the molecular sieve prepared in Example 1 is shown below. Figure 2 As shown. (Through) Figure 2 As can be seen, the molecular sieve of the present invention has an overall cage-like structure, and the molecular sieve is composed of multiple plate-like primary crystals stacked together.

[0123] Weigh out 42g of nickel nitrate hexahydrate, 165g of ammonium molybdate, 15g of phosphoric acid, 12g of citric acid, 12g of lauramide propylamine oxide, and 254g of deionized water, and stir at room temperature for 4 hours to prepare an impregnation solution. Mix the above impregnation solution with 1kg of the above hydrogen-form ZSM-5 molecular sieve, impregnate at room temperature for 8 hours, dry at 110℃ for 4 hours, and calcine at 500℃ for 4 hours to prepare a hydrocracking catalyst, wherein the mass content of NiO is 0.95% and the mass content of MoO3 is 10.71%.

[0124] An exemplary TEM image of the catalyst prepared in Example 1 is shown below. Figure 7 As shown. (Through) Figure 7 It can be seen that the active centers are evenly distributed, with an average lamellar length of 6.32 nm and an average number of stacked layers of 3.6.

[0125] Preparation Example 2

[0126] The ZSM-5 molecular sieve was prepared using a cage-like ZSM-5 molecular sieve as a carrier. The preparation method of the ZSM-5 molecular sieve was as follows: sodium hydroxide, silica sol (containing 40% by weight of SiO2) and deionized water were prepared into solution A, aluminum sulfate octadecylhydrate and deionized water were prepared into solution B, sodium fluoride and deionized water were prepared into solution C, and tetraethylammonium hydroxide and deionized water were prepared into solution D.

[0127] While stirring, solution B was added dropwise to solution A, and the mixture was stirred at room temperature for 30 minutes. Then, solution C was added, and the mixture was stirred at room temperature for 90 minutes. Finally, solution D was added to the above solutions, and the mixture was stirred at 40°C for 4 hours to obtain a mixed solution. The final material ratio (molar ratio) is:

[0128] SiO2 / Al2O3 = 22.18;

[0129] NaOH / SiO2 = 0.56;

[0130] Structure directing agent / SiO2 = 0.62;

[0131] Fluoride / SiO2 = 0.16;

[0132] H2O(total) / SiO2 = 71.11.

[0133] The above mixed solution was placed in a stainless steel reactor and crystallized at 200°C with a stirring speed of 18 rpm for 24 hours. After crystallization, the crystallized product was filtered, washed with deionized water, dried in an oven at 110°C overnight, and calcined in air at 550°C for 6 hours to obtain ZSM-5 molecular sieve.

[0134] An exemplary SEM image of the molecular sieve prepared in Example 2 is shown below. Figure 3 As shown. (Through) Figure 3As can be seen, the molecular sieve of the present invention has an overall cage-like structure, and the molecular sieve is composed of multiple plate-like primary crystals stacked together.

[0135] Weigh out 40g of nickel nitrate hexahydrate, 140g of ammonium molybdate, 30g of phosphoric acid, 16g of citric acid, 12g of octadecylammonium oxychloride, and 262g of deionized water, and stir at room temperature for 4 hours to prepare an impregnation solution. Mix the above impregnation solution with 1kg of the above hydrogen-form ZSM-5 molecular sieve, impregnate at room temperature for 8 hours, dry at 110℃ for 4 hours, and calcine at 500℃ for 4 hours to prepare a hydrocracking catalyst, wherein the mass content of NiO is 0.93% and the mass content of MoO3 is 9.24%.

[0136] The TEM of the catalyst was similar to that of Preparation Example 1, with a uniform distribution of active centers, an average lamellar length of 5.72 nm, and an average number of stacked layers of 3.7.

[0137] Preparation Example 3

[0138] The ZSM-5 molecular sieve was prepared using a cage-like ZSM-5 molecular sieve as a carrier. The preparation method of the ZSM-5 molecular sieve was as follows: sodium hydroxide, silica sol (containing 40% by weight of SiO2) and deionized water were prepared into solution A; aluminum sulfate octadechydrate and deionized water were prepared into solution B; potassium fluoride dihydrate and deionized water were prepared into solution C; and tetraethylammonium hydroxide and deionized water were prepared into solution D.

[0139] While stirring, solution B was added dropwise to solution A, and the mixture was stirred at room temperature for 30 minutes. Then, solution C was added, and the mixture was stirred at room temperature for 100 minutes. Finally, solution D was added to the above solutions, and the mixture was stirred at 36°C for 5 hours to obtain a mixed solution. The final material ratio (molar ratio) is:

[0140] SiO2 / Al2O3 = 26.10;

[0141] NaOH / SiO2 = 0.47;

[0142] Structure directing agent / SiO2 = 0.55;

[0143] Fluoride / SiO2 = 0.21;

[0144] H2O(total) / SiO2 = 69.48.

[0145] The above mixed solution was placed in a stainless steel reactor and crystallized at 170°C and 30 rpm for 30 hours. After crystallization, the crystallized product was filtered, washed with deionized water, dried in an oven at 100°C overnight, and calcined in air at 550°C for 6 hours to obtain ZSM-5 molecular sieve.

[0146] Weigh out 45g of nickel nitrate hexahydrate, 142g of ammonium molybdate, 9g of phosphoric acid, 10g of citric acid, 9g of cocamidopropylamine oxide, and 285g of deionized water, and stir at room temperature for 4 hours to prepare an impregnation solution. Mix the above impregnation solution with 1kg of the above hydrogen-form ZSM-5 molecular sieve, impregnate at room temperature for 8 hours, dry at 110℃ for 4 hours, and calcine at 500℃ for 4 hours to prepare a hydrocracking catalyst, wherein the mass content of NiO is 1.04% and the mass content of MoO3 is 9.35%.

[0147] The TEM of the catalyst was similar to that of Preparation Example 1, with a uniform distribution of active centers, an average lamellar length of 6.13 nm, and an average number of stacked layers of 3.5.

[0148] Preparation Example 4

[0149] Using cage-like ZSM-5 molecular sieve as a carrier, the ZSM-5 molecular sieve is prepared as follows: sodium hydroxide, silica sol (containing 40% by weight of SiO2) and deionized water are prepared into solution A, aluminum sulfate octadechydrate and deionized water are prepared into solution B, magnesium fluoride and deionized water are prepared into solution C, and tetraethylammonium hydroxide and deionized water are prepared into solution D.

[0150] While stirring, add solution B dropwise to solution A and stir at room temperature for 30 minutes. Then add solution C and stir at room temperature for 80 minutes. Finally, add solution D to the above solutions and stir at 22°C for 5 hours to obtain a mixed solution. The final material ratio (molar ratio) is:

[0151] SiO2 / Al2O3 = 29.58;

[0152] NaOH / SiO2 = 0.39;

[0153] Structure directing agent / SiO2 = 0.54;

[0154] Fluoride / SiO2 = 0.12;

[0155] H2O(total) / SiO2 = 68.71.

[0156] The above mixed solution was placed in a stainless steel reactor and crystallized at 180°C with a stirring speed of 12 rpm for 28 hours. After crystallization, the crystallized product was filtered, washed with deionized water, dried overnight in an oven at 110°C, and calcined in air at 550°C for 6 hours to obtain ZSM-5 molecular sieve.

[0157] Weigh out 95g of nickel nitrate hexahydrate, 102g of ammonium molybdate, 20g of phosphoric acid, 19g of citric acid, 14g of hexadecyl dihydroxyethylamine oxide, and 250g of deionized water, and stir at room temperature for 4 hours to prepare an impregnation solution. Mix the above impregnation solution with 1kg of the above hydrogen-form ZSM-5 molecular sieve, impregnate at room temperature for 8 hours, dry at 110℃ for 4 hours, and calcine at 500℃ for 4 hours to prepare a hydrocracking catalyst, wherein the mass content of NiO is 2.22% and the mass content of MoO3 is 6.81%.

[0158] The TEM of the catalyst was similar to that of Preparation Example 1, with a uniform distribution of active centers, an average lamellar length of 6.21 nm, and an average number of stacked layers of 3.5.

[0159] Preparation Example 5

[0160] The ZSM-5 molecular sieve was prepared using a cage-like ZSM-5 molecular sieve as a carrier. The preparation method of the ZSM-5 molecular sieve was as follows: sodium hydroxide, silica sol (containing 40% by weight of SiO2) and deionized water were prepared into solution A, aluminum sulfate octadecylhydrate and deionized water were prepared into solution B, sodium fluoride and deionized water were prepared into solution C, and tetraethylammonium hydroxide and deionized water were prepared into solution D.

[0161] While stirring, solution B was added dropwise to solution A, and the mixture was stirred at room temperature for 30 minutes. Then, solution C was added, and the mixture was stirred at room temperature for 100 minutes. Finally, solution D was added to the above solutions, and the mixture was stirred at 28°C for 4 hours to obtain a mixed solution. The final material ratio (molar ratio) is:

[0162] SiO2 / Al2O3 = 28.99;

[0163] NaOH / SiO2 = 0.32;

[0164] Structure directing agent / SiO2 = 0.47;

[0165] Fluoride / SiO2 = 0.13;

[0166] H2O(total) / SiO2 = 61.55.

[0167] The above mixed solution was placed in a stainless steel reactor and crystallized at 160°C with a stirring speed of 35 rpm for 38 hours. After crystallization, the crystallized product was filtered, washed with deionized water, dried overnight in an oven at 100°C, and calcined in air at 550°C for 6 hours to obtain ZSM-5 molecular sieve.

[0168] Weigh out 140g of nickel nitrate hexahydrate, 86g of ammonium molybdate, 18g of phosphoric acid, 16g of citric acid, 15g of lauramide propylamine oxide, and 225g of deionized water, and stir at room temperature for 4 hours to prepare an impregnation solution. Mix the above impregnation solution with 1kg of the above hydrogen-form ZSM-5 molecular sieve, impregnate at room temperature for 8 hours, dry at 110℃ for 4 hours, and calcine at 500℃ for 4 hours to prepare a hydrocracking catalyst, wherein the mass content of NiO is 3.28% and the mass content of MoO3 is 5.75%.

[0169] The TEM of the catalyst was similar to that of Preparation Example 1, with a uniform distribution of active centers, an average lamellar length of 5.83 nm, and an average number of stacked layers of 3.6.

[0170] Preparation Example 6

[0171] Using cage-like ZSM-5 molecular sieve as a carrier, the ZSM-5 molecular sieve is prepared as follows: sodium hydroxide, silica sol (containing 40.0% by weight of SiO2) and deionized water are prepared into solution A, aluminum sulfate octadecylhydrate and deionized water are prepared into solution B, calcium fluoride and deionized water are prepared into solution C, and tetraethylammonium hydroxide and deionized water are prepared into solution D.

[0172] While stirring, add solution B dropwise to solution A, and stir at room temperature for 30 minutes. Then add solution C, stir at room temperature for 100 minutes, and then add solution D to the above solutions. Stir at 42°C for 3 hours to obtain a mixed solution. The final material ratio (molar ratio) is:

[0173] SiO2 / Al2O3 = 28;

[0174] NaOH / SiO2 = 0.42;

[0175] Structure directing agent / SiO2 = 0.49;

[0176] Fluoride / SiO2 = 0.11;

[0177] H2O (total) / SiO2 = 66.95.

[0178] The above mixed solution was placed in a stainless steel reactor and crystallized at 210°C with a stirring speed of 32 rpm for 20 hours. After crystallization, the crystallized product was filtered, washed with deionized water, dried overnight in an oven at 120°C, and calcined in air at 550°C for 6 hours to obtain ZSM-5 molecular sieve.

[0179] Weigh out 41g of nickel nitrate hexahydrate, 150g of ammonium molybdate, 20g of phosphoric acid, 16g of hexadecyl dimethylamine oxide, and 273g of deionized water, and stir at room temperature for 4 hours to prepare an impregnation solution. Mix the above impregnation solution with 1kg of the above hydrogen-form ZSM-5 molecular sieve, impregnate at room temperature for 8 hours, dry at 110℃ for 4 hours, and calcine at 500℃ for 4 hours to prepare a hydrocracking catalyst, wherein the mass content of NiO is 0.94% and the mass content of MoO3 is 9.83%.

[0180] The TEM of the catalyst was similar to that of Preparation Example 1, with a uniform distribution of active centers, an average lamellar length of 5.94 nm, and an average number of stacked layers of 3.6.

[0181] Preparation Example 7

[0182] The ZSM-5 molecular sieve was prepared using a cage-like ZSM-5 molecular sieve as a carrier. The preparation method of the ZSM-5 molecular sieve was as follows: sodium hydroxide, silica sol (containing 40% by weight of SiO2) and deionized water were prepared into solution A, aluminum sulfate octadecylhydrate and deionized water were prepared into solution B, sodium fluoride and deionized water were prepared into solution C, and tetraethylammonium hydroxide and deionized water were prepared into solution D.

[0183] While stirring, solution B was added dropwise to solution A, and the mixture was stirred at room temperature for 30 minutes. Then, solution C was added, and the mixture was stirred at room temperature for 100 minutes. Finally, solution D was added to the above solutions, and the mixture was stirred at 45°C for 3 hours to obtain a mixed solution. The final material ratio (molar ratio) is:

[0184] SiO2 / Al2O3 = 26.90;

[0185] NaOH / SiO2 = 0.42;

[0186] Structure directing agent / SiO2 = 0.54;

[0187] Fluoride / SiO2 = 0.10;

[0188] H2O (total) / SiO2 = 72.10.

[0189] The above mixed solution was placed in a stainless steel reactor and crystallized at 180°C and 26 rpm for 26 hours. After crystallization, the crystallized product was filtered, washed with deionized water, dried overnight in an oven at 115°C, and calcined in air at 550°C for 6 hours to obtain ZSM-5 molecular sieve.

[0190] Weigh out 40g of nickel nitrate hexahydrate, 146g of ammonium molybdate, 20g of citric acid, 16g of lauramide propylamine oxide, and 278g of deionized water, and stir at room temperature for 4 hours to prepare an impregnation solution. Mix the above impregnation solution with 1kg of the above hydrogen-form ZSM-5 molecular sieve, impregnate at room temperature for 8 hours, dry at 110℃ for 4 hours, and calcine at 500℃ for 4 hours to prepare a hydrocracking catalyst, wherein the mass content of NiO is 0.92% and the mass content of MoO3 is 9.6%.

[0191] The TEM of the catalyst was similar to that of Preparation Example 1, with a uniform distribution of active centers, an average lamellar length of 6.95 nm, and an average number of stacked layers of 3.8.

[0192] Preparation Example 8

[0193] Following the method of Preparation Example 1, except that 42g of nickel nitrate hexahydrate, 165g of ammonium molybdate, 12g of lauramide propylamine oxide, and 281g of deionized water were weighed and stirred at room temperature for 4 hours to prepare an impregnation solution. This impregnation solution was mixed with 1kg of the aforementioned hydrogen-form ZSM-5 molecular sieve, impregnated at room temperature for 8 hours, dried at 110°C for 4 hours, and calcined at 500°C for 4 hours to prepare a hydrocracking catalyst, wherein the NiO mass content was 0.96% and the MoO3 mass content was 10.71%.

[0194] The TEM of the catalyst was similar to that of Preparation Example 1, with a relatively uniform distribution of active centers, an average lamellar length of 7.53 nm, and an average number of stacked layers of 4.1.

[0195] Preparation Example 9

[0196] Following the method of Preparation Example 2, except that 40g of nickel nitrate hexahydrate, 140g of ammonium molybdate, 30g of phosphoric acid, 16g of citric acid, and 274g of deionized water were weighed and stirred at room temperature for 4 hours to prepare an impregnation solution. This impregnation solution was mixed with 1kg of the aforementioned hydrogen-form ZSM-5 molecular sieve, impregnated at room temperature for 8 hours, dried at 110°C for 4 hours, and calcined at 500°C for 4 hours to prepare a hydrocracking catalyst. The catalyst contained 0.93% NiO and 9.24% MoO3 by mass.

[0197] The TEM of the catalyst was similar to that of Preparation Example 1, with a relatively uniform distribution of active centers, an average lamellar length of 7.66 nm, and an average number of stacked layers of 4.3.

[0198] Comparative Preparation Example 1

[0199] Sodium hydroxide, silica sol (containing 40% by weight of SiO2), and deionized water were prepared to form solution A; aluminum sulfate octadecylhydrate was prepared to form solution B; and tetraethylammonium hydroxide and deionized water were prepared to form solution C.

[0200] While stirring, solution B was added dropwise to solution A. The mixture was stirred at room temperature for 30 minutes. Then, solution C was added to the above solution, and the mixture was stirred at 38°C for 2 hours to obtain a mixed solution. The final material ratio (molar ratio) is:

[0201] SiO2 / Al2O3 = 22.18;

[0202] NaOH / SiO2 = 0.56;

[0203] Structure directing agent / SiO2 = 0.62;

[0204] Fluoride / SiO2 = 0;

[0205] H2O(total) / SiO2 = 71.11.

[0206] The above mixed solution was placed in a stainless steel reactor and crystallized at 200°C with a stirring speed of 18 rpm for 24 hours. After crystallization, the crystallized product was filtered, washed with deionized water, dried in an oven at 110°C overnight, and calcined in air at 550°C for 6 hours to obtain ZSM-5 molecular sieve.

[0207] SEM images of the molecular sieve prepared in Comparison Example 1 are shown below. Figure 4 As shown. (Through) Figure 4 It can be seen that the molecular sieve described in this invention is a spherical structure formed by primary crystal stacking, rather than a cage-like structure.

[0208] Weigh out 40g of nickel nitrate hexahydrate, 140g of ammonium molybdate, 30g of phosphoric acid, 16g of citric acid, 12g of octadecylammonium oxychloride, and 262g of deionized water, and stir at room temperature for 4 hours to prepare an impregnation solution. Mix the above impregnation solution with 1kg of the above hydrogen-form ZSM-5 molecular sieve, impregnate at room temperature for 8 hours, dry at 110℃ for 4 hours, and calcine at 500℃ for 4 hours to prepare a hydrocracking catalyst, wherein the mass content of NiO is 0.93% and the mass content of MoO3 is 9.24%.

[0209] TEM images of the catalyst prepared in Comparison Example 1 are shown below. Figure 8 As shown. (Through) Figure 8 It can be seen that the active centers are unevenly dispersed, and the average lamellar length and the average number of stacked layers are increasing. The average lamellar length is 8.45 nm, and the average number of stacked layers is 7.8.

[0210] Comparative Preparation Example 2

[0211] The preparation method was followed as in Example 3, except that no stirring was performed during crystallization. ZSM-5 molecular sieve was obtained.

[0212] SEM images of the molecular sieves prepared in Comparative Example 2 are shown below. Figure 5 As shown. (Through) Figure 5 As can be seen, the molecular sieve of the present invention has a flat spherical structure, not a cage-like structure, and has no primary crystals.

[0213] TEM images of the catalyst prepared in Comparison Example 2 are shown below. Figure 9 As shown. (Through) Figure 9 It can be seen that the active centers are unevenly dispersed, and the average lamellar length and the average number of stacked layers are increasing. The average lamellar length is 8.53 nm, and the average number of stacked layers is 6.1.

[0214] Comparative preparation example 3

[0215] The preparation method was followed as in Example 1, except that the amount of sodium hydroxide was adjusted so that the molar ratio of NaOH / SiO2 in the resulting mixed solution was 0.95. ZSM-5 molecular sieve was thus obtained.

[0216] SEM images of the molecular sieve prepared in Comparison Example 3 are shown below. Figure 6 As shown. (Through) Figure 6 It can be seen that the molecular sieve is formed by stacking primary crystals. Many primary crystals have grown in the original cage-like structure, filling the hollow structure, and it is no longer a cage-like structure.

[0217] TEM images of the catalyst prepared in Comparison Example 3 are shown below. Figure 10 As shown. (Through) Figure 10 It can be seen that the active centers are unevenly dispersed and exhibit agglomeration, with an increased average lamellar length and an increased average number of stacked layers. The average lamellar length is 11.02 nm, and the average number of stacked layers is 10.9.

[0218] Table 1

[0219]

[0220] The embodiments described in this invention illustrate the preparation of light aromatic hydrocarbons.

[0221] Example 1

[0222] 1. Hydrogenation purification reaction

[0223] 25 ml of hydrorefining catalyst was packed into a fixed-bed reactor. The hydrorefining catalyst was a Ni-Mo / Al2O3 catalyst containing 4% NiO and 12% MoO3 by mass.

[0224] Aviation kerosene containing 3% (mass concentration) dimethyl disulfide was used as the sulfiding oil to sulfide the hydrorefining catalyst. The sulfidation conditions were: sulfidation temperature 270℃, and liquid hourly space velocity (LHSV) of the sulfiding oil 1.0 h⁻¹. -1 The hydrogen pressure is 6 MPa, the volume ratio of hydrogen to sulfurized oil is 1000, and the sulfurization time is 24 hours.

[0225] The sulfidated hydrorefining catalyst was used for the hydrorefining reaction of aromatic-rich distillate oil. The aromatic-rich distillate oil had the following composition: N content 400 μg / mL, S content 4000 μg / mL, distillation range 150-340℃, and aromatic content >80 wt%. The reaction conditions were: reaction temperature 280℃, reaction pressure 5.8 MPa, and liquid hourly space velocity (LHSV) of the aromatic-rich distillate oil 0.8 h⁻¹. -1 The volume ratio of hydrogen to aromatic distillate oil is 1200, yielding hydrotreated product I.

[0226] 2. Hydrocracking reaction

[0227] The hydrocracking catalyst of Preparation Example 1 was loaded into a fixed-bed reactor and subjected to hydrocracking with the hydrorefined product I obtained above, yielding gaseous and liquid products. The gaseous product was separated to obtain recycled hydrogen, which was then returned to the hydrocracking reaction for reuse. The reaction conditions were: reaction temperature 340℃, reaction pressure 6MPa, and volume hourly space velocity 1h. -1 With a hydrogen / oil volume ratio of 1200 and a hydrogen recirculation ratio of 2:1, product II was obtained through hydrocracking. The results after 50 hours of reaction are shown in Table 2.

[0228] Examples 2-9, Comparative Examples 1-3

[0229] The procedure was carried out according to Example 1, except that the hydrocracking catalysts of Preparation Examples 2-9 and Comparative Preparation Examples 1-3 were used respectively. The results after 50 h of reaction are shown in Table 2.

[0230] Example 10

[0231] The method was the same as in Example 1, except that the conditions for the hydrocracking reaction were: reaction temperature 370°C, reaction pressure 5.5 MPa, and volume hourly space velocity 1.2 h⁻¹. -1 With a hydrogen / oil volume ratio of 1000 and a hydrogen recycle ratio of 4:1, product II was obtained by hydrocracking.

[0232] Example 11

[0233] The method is the same as in Example 1, except that the reaction conditions for the hydrocracking reaction are: reaction temperature 280°C, reaction pressure 6.5 MPa, and volume hourly space velocity 0.8 h⁻¹. -1 With a hydrogen / oil volume ratio of 1500 and a hydrogen recycle ratio of 3:1, product II was obtained through hydrocracking.

[0234] Table 2

[0235] Example number BTX in liquid products, wt% Methane in the gas phase, wt% Example 1 84.42 0.32 Example 2 84.15 0.36 Example 3 83.16 0.37 Example 4 82.54 0.37 Example 5 83.14 0.35 Example 6 82.05 0.36 Example 7 81.57 0.38 Example 8 78.56 0.49 Example 9 77.64 0.49 Example 10 82.46 0.41 Example 11 81.71 0.42 Comparative Example 1 41.37 2.06 Comparative Example 2 33.41 2.84 Comparative Example 3 31.04 3.04

[0236] As can be seen from the results in Table 2, the method of the present invention has a significantly higher BTX yield and a lower methane content.

[0237] Test Example 1

[0238] The long-term operation experimental data of Examples 1, 10, Comparative Example 1, and Comparative Example 3 are shown in Table 3.

[0239] Table 3

[0240]

[0241] As can be seen from the results in Table 3, the method provided by the present invention controls the content of methane in the gaseous products obtained by hydrocracking. When hydrogen in the gaseous products is recycled, the catalyst can operate for a long period of time without a significant decrease in BTX yield.

[0242] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing light aromatic hydrocarbons, characterized in that, The method includes the following steps: (1) Aromatic distillate oil and hydrogen are contacted with a hydrorefining catalyst to carry out a hydrorefining reaction to obtain a hydrorefined product. (2) The hydrorefined product and hydrogen are contacted with a hydrocracking catalyst to carry out a hydrocracking reaction to obtain a hydrocracking product; (3) The hydrocracking product is subjected to gas-liquid separation to obtain a gas phase product and a liquid phase product, wherein the methane content in the gas phase product is not higher than 1 wt%. (4) Separate the gaseous products to obtain recycled hydrogen, and then return the recycled hydrogen to the hydrocracking reaction in step (2) for recycling.

2. The method according to claim 1, wherein, The hydrorefining catalyst includes a first support and a first active component, wherein the first active component is selected from at least one group VIB metal and a group VIII metal. Preferably, based on the total mass of the hydrorefining catalyst, the mass content of Group VIII metals, calculated as oxides, is 2-15% and the mass content of Group VIB metals is 3-30%. Preferably, the Group VIB metal is Mo; Preferably, the Group VIII metal is Ni; Preferably, the first carrier is selected from at least one of alumina-mordenite composite carrier, alumina carrier, silica carrier, alumina-silica composite carrier, and alumina-beta zeolite composite carrier.

3. The method according to claim 1, wherein, The hydrocracking catalyst includes a second support and a second active component. The second support is ZSM-5 molecular sieve, and the second active component is selected from at least one group VIB metal and group VIII metal. Preferably, the ZSM-5 molecular sieve has a cage-like structure formed by stacking plate-like primary crystals; Preferably, the average size of the lamellar primary grains is (40-170)×(20-100)×(30-100)nm, and more preferably (100-140)×(40-70)×(30-50)nm; Preferably, the specific surface area of ​​the ZSM-5 molecular sieve is 300-500 m². 2 / g, preferably 300-400m 2 / g; Preferably, the ratio of the external specific surface area of ​​the ZSM-5 molecular sieve to the total surface area is 30-55%, more preferably 35-50%. Preferably, the SiO2 / Al2O3 molar ratio of the ZSM-5 molecular sieve is 15-50, more preferably 20-40.

4. The method according to claim 3, wherein, After sulfidation, the catalyst has an average number of 1-5 active center layers, preferably 2-5 layers. Preferably, after sulfidation, the average lamellar length of the active center of the catalyst is not greater than 8 nm, and more preferably 2-8 nm; Preferably, based on the total weight of the hydrocracking catalyst, the mass content of Group VIII metals, calculated as oxides, is 0.5-4% and the mass content of Group VIB metals is 5.5-13.5%. Preferably, the Group VIB metal is Mo and / or W; Preferably, the Group VIII metal is Ni and / or Co.

5. The method according to any one of claims 1-4, wherein, The preparation method of the hydrocracking catalyst includes the following steps: (1) Aluminum source, silicon source, alkali source, structure directing agent, fluoride and water are gelled to obtain a colloidal solution; the molar ratio of silicon source to alkali source is 1:0.2-0.9, and the molar ratio of silicon source to fluoride is 1:0.08-0.3, wherein the silicon source is calculated as SiO2; (2) The colloidal solution is dynamically crystallized, and then subjected to a first drying and a first calcination to obtain ZSM-5 molecular sieve; (3) The impregnation solution containing the second active component compound is brought into contact with ZSM-5 molecular sieve, and then subjected to second drying and second calcination.

6. The method according to claim 5, wherein, The molar ratio of silicon source to alkali source is 1:0.3-0.7, where the silicon source is SiO2. Preferably, the molar ratio of silicon source to fluoride is 1:0.08-0.24, wherein the silicon source is SiO2; Preferably, the molar ratio of silicon source, aluminum source and water is 1:0.01-0.07:50-80, more preferably 1:0.02-0.06:50-75, wherein the silicon source is calculated as SiO2 and the aluminum source is calculated as Al2O3; Preferably, the molar ratio of silicon source to structure directing agent is 1:0.3-0.8, more preferably 1:0.4-0.7, wherein the silicon source is SiO2.

7. The method according to claim 5 or 6, wherein, The aluminum source is selected from at least one of sodium aluminate, aluminum sulfate, aluminum powder, and boehmite. Preferably, the silicon source is selected from at least one of silicic acid, silica sol, silica fume, and water glass; Preferably, the alkali source is selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and ammonia water; Preferably, the structure-directing agent is selected from at least one of ethylenediamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and hexadecyltrimethylammonium bromide; Preferably, the fluoride is selected from at least one of sodium fluoride, potassium fluoride, calcium fluoride, and magnesium fluoride.

8. The method according to any one of claims 5-7, wherein, The gelation conditions in step (1) include: a gelation temperature of 10-60℃, preferably 20-50℃; and a gelation time of 2-10h, preferably 3-8h. Preferably, the conditions for dynamic crystallization in step (2) include: a crystallization temperature of 150-220℃ and a crystallization time of 18-40h; Preferably, the dynamic crystallization in step (2) is carried out under stirring conditions, and the stirring speed is 1-60 r / min, preferably 10-40 r / min; Preferably, the conditions for the first roasting in step (2) include: a roasting temperature of 300-700℃, preferably 350-600℃; and a roasting time of 2-10h, preferably 3-8h.

9. The method according to any one of claims 5-8, wherein, In step (3), a dispersant is also added to the impregnation solution, wherein the dispersant is selected from at least one of laurylamidopropylamine oxide, octadecylamidopropylamine oxide, cocamidopropylamine oxide, hexadecyl dihydroxyethylamine oxide, and hexadecyl dimethylamine oxide; Preferably, the dispersant has a mass fraction of 1-5% in the impregnation solution, more preferably 1.5-3.5%; Preferably, an auxiliary agent is also added to the impregnation solution in step (3), the auxiliary agent being selected from at least one of phosphoric acid, hydrochloric acid, citric acid and nitric acid; Preferably, the mass fraction of the additive in the impregnation solution is 2-18%, more preferably 3.5-16%.

10. The method according to any one of claims 1-9, wherein, The conditions for the hydrorefining reaction in step (1) include: a reaction inlet temperature of 200-350℃, preferably 200-300℃; a reaction pressure of 3.5-7.5 MPa, preferably 4-7 MPa; and a weight hourly space velocity of 0.5-3 h⁻¹. -1 Preferably 0.5-2h -1 The hydrogen-to-oil volume ratio is 600-4000:1, preferably 800-3000:

1.

11. The method according to any one of claims 1-10, wherein, The conditions for the hydrocracking reaction in step (2) include: a reaction inlet temperature of 250-450℃, preferably 280-400℃; a reaction pressure of 3.5-7.5MPa, preferably 4-7MPa; and a weight hourly space velocity of 0.5-2.5h⁻¹. -1 Preferably 0.6-2h -1 The hydrogen-to-oil volume ratio is 600-3500:1, preferably 700-2500:

1. Preferably, the methane content in the gaseous product is not higher than 0.5 wt%. Preferably, in step (4), the hydrogen recycling ratio is 1-6:

1.

12. The method according to any one of claims 1-11, wherein, The initial boiling point of the aromatic-rich distillate oil is 150-250℃, and the final boiling point is 300-380℃; Preferably, the aromatic-rich distillate oil has a sulfur content of 500-7000 ug / mL, more preferably 800-5000 ug / mL; a nitrogen content of 100-1000 ug / mL, more preferably 200-800 ug / mL; and an aromatic content of >70 wt%, more preferably >80 wt%. Preferably, the aromatic-rich distillate oil is selected from at least one of ethylene tar, coal tar, catalytic cracked diesel oil, and coking diesel oil.

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