A catalyst for diesel hydrocracking, its preparation method and application
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2023-10-26
- Publication Date
- 2026-06-30
Smart Images
Figure CN119897149B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of hydrocracking catalyst technology, specifically relating to a diesel-catalyzed hydrocracking catalyst, its preparation method, and its application. Background Technology
[0002] In recent years, refining and chemical enterprises have experienced a massive surplus of low-quality, rich aromatic oil products, primarily catalytic diesel. Catalytic diesel is one of the main products of the catalytic cracking process, with an annual national output of approximately 50 million tons. Although its boiling point is in the diesel fraction, its high content of polycyclic aromatic hydrocarbons makes it uneconomical to process into diesel, forcing some enterprises to use it only as fuel oil. Hydrocracking technology is one of the important means of secondary crude oil processing and the conversion of heavy oil into lighter products. Due to its strong adaptability to feedstocks, flexible operation and product formulation, and high product quality, it has become an important way to produce high-quality light oil products and solve the problem of chemical feedstock sources.
[0003] In existing processes, light oil-based hydrocracking catalysts target gasoline or naphtha as the product, but suffer from problems such as low aromatics yield and purity, and excessively high diesel yield. Related research institutions have developed technologies that can convert catalytic diesel into high-octane gasoline blending components. For example, the technologies disclosed in Chinese patents CN101724454A and CN102839018A yield heavy naphtha fractions with aromatics content between 50-65%, which can be used as high-octane gasoline blending components. The catalysts used contain 20-75 wt% Y-type zeolite. However, due to the open pores of Y-type zeolite, it lacks the shape-selective effect for cracking non-aromatics, resulting in C8, C9, and C6 hydrocarbons. 10 The fraction has a low aromatic content and a high non-aromatic content, which makes it difficult to meet the requirements for reformed oil. As a result, it is difficult for the fraction to be used as a feedstock for the production of benzene and paraxylene in the aromatics complex.
[0004] The technology of producing light aromatics from catalytic diesel fuel is attracting increasing attention from the industry. Chinese patent CN112570016A discloses a nitrogen-resistant aromatics-type hydrocracking catalyst, its preparation method, and its application. In this type of hydrocracking catalyst, mordenite and β-zeolite play a dominant cracking role, and the pore shape-selective effect selectively converts tetrahydronaphthalene hydrocarbons into light aromatics, further cracking alkanes and cycloalkanes within the light aromatic fraction. The resulting heavy naphtha has an aromatic purity that meets the requirements of aromatics complexes. Chinese patent CN105435836A discloses a hydrocracking catalyst, its preparation, and its application, using a mixture of ZSM-5 molecular sieves and molybdenum-containing β-molecular sieves as the solid acid component, which can achieve efficient conversion of polycyclic aromatic hydrocarbons and high yield of light aromatics.
[0005] Maximizing the conversion of catalytic diesel into light aromatics that meet the quality standards of aromatics complexes and producing high-quality light hydrocarbons that can be used as feedstock for olefins, directly providing raw materials for aromatics, olefins, and other chemical plants, the development of high-performance hydrocracking catalysts is a key issue. Therefore, it is necessary to develop hydrocracking catalysts with stronger shape-selective effects and non-aromatic cracking capabilities to efficiently produce high-quality light aromatics from catalytic diesel. Summary of the Invention
[0006] The technical problem this invention aims to solve is the low selectivity and purity of light aromatics obtained from catalytic diesel hydrocracking. This invention provides a catalytic diesel hydrocracking catalyst for use in the hydrocracking reaction of feedstock oil rich in polycyclic aromatic hydrocarbons, characterized by high aromatic selectivity and purity, enabling efficient chemical utilization of catalytic diesel.
[0007] One objective of this invention is to provide a catalytic diesel hydrocracking catalyst, comprising: aluminum-rich ZSM-5 type zeolite, a hydrogenation functional component, an optional metal functional regulating component, and a binder; wherein the aluminum-rich ZSM-5 type zeolite has a silicon-to-aluminum molecular ratio between 5 and 15 and the average length of the zeolite particles in at least one dimension is less than 20 nm, and the hydrogenation functional component is a sulfided metal component.
[0008] According to the present invention, in the catalytic diesel hydrocracking catalyst:
[0009] In the aforementioned aluminum-rich ZSM-5 zeolite, the skeletal aluminum content accounts for more than 90% of the total aluminum content, preferably more than 95%;
[0010] The hydrogenation functional component is selected from group VIB metal sulfides, preferably from at least one of molybdenum sulfide and tungsten sulfide; the group VIB metal sulfide can continuously exert hydrogenation effects in a high-sulfur atmosphere;
[0011] The metal functional modifier is selected from at least one Group VIII metal component, preferably from at least one nickel component and / or at least one cobalt component; wherein the metal functional modifier exists in the catalyst in the form of a metal sulfide, a metal oxide, or a metal element. The aforementioned metal functional modifier can improve the hydrogenation capacity of Group VIB metal sulfides. The Ni and Co components can exist as compounds, such as sulfides or oxides, chemically combined with one or more other components in the final catalyst composition, or as metal elements in the catalyst.
[0012] The binder can be any catalyst binder commonly used in the art to provide good mechanical and textural properties, preferably at least one of an alumina-containing component and a silica-containing component. The alumina-containing component can specifically be boehmite, and the silica-containing component can specifically be a combination of porous silica powder and ammonia-type silica sol. The binder can be incorporated into the catalyst in any suitable manner, for example, by mixing with zeolite, extruding, curing, drying, and calcining to obtain the catalyst support.
[0013] According to the present invention, based on a total weight of 100 parts by weight of the aluminum-rich ZSM-5 zeolite and the binder, the ZSM-5 zeolite comprises 5 to 95 parts, preferably 10 to 90 parts, more preferably 15 to 80 parts; the hydrogenation functional component comprises 1 to 30 parts, preferably 2 to 20 parts, more preferably 3 to 18 parts; and the metal functional regulating component comprises 0 to 10 parts, preferably 0.2 to 8 parts, more preferably 0.5 to 6 parts.
[0014] The catalyst described in this invention may also include conventional components of catalysts in the art, such as diatomaceous earth, activated clay, etc., and the amount used may be the usual amount.
[0015] The second objective of this invention is to provide a method for preparing the above-mentioned catalytic diesel hydrocracking catalyst.
[0016] The hydrocracking catalyst of this invention can be prepared using any method of catalyst preparation in the art, without particular limitation. For example, the preparation of the catalyst of this invention may include the steps of shaping a catalyst support containing the zeolite, loading components including the hydrogenation functional component and optional metal functional adjustment component, calcining and activating the catalyst to obtain a catalyst precursor, and then sulfiding the catalyst precursor. The support shaping can be carried out by using conventional methods in the art, such as extrusion, ball rolling, or oil column forming, together with the binder; the loading of the metal-containing component can be carried out by conventional methods in the art, such as co-precipitation, co-gelling, kneading, ion exchange, or impregnation, with the catalyst support containing the metal compound.
[0017] According to the present invention, the preparation method of the catalytic diesel hydrocracking catalyst includes: loading a catalytic system comprising a hydrogenation functional component and an optional metal functional regulating component onto a support comprising the aluminum-rich ZSM-5 zeolite and a binder to obtain the catalytic diesel hydrocracking catalyst. Specifically, the preparation method includes the following steps:
[0018] Step 1) After mixing and molding the components including aluminum-rich ZSM-5 zeolite and binder, the catalyst support is dried and calcined to obtain the catalyst support.
[0019] Step 2) Prepare an aqueous solution of a metal compound by adding the hydrogenated functional component precursor compound and optionally the metal functional modifier precursor compound;
[0020] Step 3) The catalyst support obtained in Step 1) is immersed in the aqueous solution of the metal compound obtained in Step 2), taken out, dried, and calcined to obtain the catalyst precursor;
[0021] Step 4) Sulfide the catalyst precursor obtained in Step 3) to obtain the aforementioned catalytic hydrocracking catalyst.
[0022] According to the present invention, in the preparation method of the catalytic hydrocracking catalyst:
[0023] The hydrogenation functional component precursor compound is selected from soluble Group VIB metal compounds, preferably from at least one of soluble molybdenum compounds and soluble tungsten compounds, and more preferably from at least one of ammonium tungstate and ammonium molybdate.
[0024] The metal functional regulating component precursor compound is selected from at least one soluble Group VIII metal compound, preferably from at least one soluble nickel compound and / or at least one soluble cobalt compound, more preferably from at least one of nickel nitrate, nickel sulfate, nickel halide, nickel oxalate, nickel acetate, cobalt nitrate, cobalt chloride, and cobalt oxalate.
[0025] According to the present invention, in the preparation method of the catalytic hydrocracking catalyst:
[0026] In step 1), both drying and calcination can be carried out using commonly used drying and calcination processes in the art. For example, the drying temperature is 50-150℃, preferably 60-120℃; the calcination temperature is 500-600℃, preferably 520-580℃; and the calcination time is 1-6h, preferably 2-5h.
[0027] In step 2), the concentration of the aqueous solution of the metal compound is 3-50 wt%, preferably 5-40 wt%; an appropriate amount of ammonia can be added to the aqueous solution of the metal compound to obtain a homogeneous solution.
[0028] In step 3), both drying and calcination can be carried out using commonly used drying and calcination processes in the art. For example, the drying temperature is 50–150°C, preferably 60–120°C; the calcination temperature is 450–600°C, preferably 480–580°C; and the calcination time is 0.5–8 h, preferably 1–6 h. The impregnation can be carried out using commonly used impregnation processes in the art, such as equal-volume impregnation.
[0029] The sulfidation in step 4) can be carried out using a sulfidation method commonly used in the art, such as adding carbon dioxide solution to complete the sulfidation. Preferably, the concentration of the carbon disulfide solution is 0.1-10 wt%, more preferably 0.2-8 wt%. The solvent in the carbon disulfide solution is selected from aromatic solvents, preferably at least one of toluene and C8 aromatics, which can prevent violent cracking reactions during the sulfidation process. The sulfidation conditions are as follows: the sulfidation heating rate is 10-20℃ / h, preferably 5-10℃ / h; the sulfidation endpoint temperature is 300-370℃, preferably 320-360℃; and the endpoint temperature is maintained for 1-24h, preferably 4-18h.
[0030] According to the present invention, the aluminum-rich ZSM-5 type zeolite is obtained by the following preparation method:
[0031] a) Obtain a colloid comprising a silicon source, a first aluminum source, an alkali source, a template agent, and a solvent;
[0032] b) The colloid obtained in step a) is pre-crystallized and hydrothermally crystallized once to obtain a slurry;
[0033] c) Add a second aluminum source to the slurry obtained in step b);
[0034] d) Repeat the pre-crystallization and hydrothermal crystallization for secondary crystallization to obtain the aluminum-rich ZSM-5 type zeolite;
[0035] Optionally, it also includes e) calcining the aluminum-rich ZSM-5 zeolite once, then performing ion exchange, and then calcining a second time.
[0036] According to the present invention, in the preparation method of the aluminum-rich ZSM-5 type zeolite:
[0037] The first aluminum source and the second aluminum source may be the same or different, and each is independently selected from at least one of sodium aluminate, aluminum hydroxide, and aluminum sulfate; and / or,
[0038] The alkali source includes alkali metal hydroxides and / or ammonia; preferably, the alkali metal includes at least one of Na and K; and / or,
[0039] The silicon source is selected from at least one of silica gel, silica sol, and silica fume; and / or,
[0040] The template agent is selected from organic amines, preferably from at least one of tetrapropylammonium hydroxide, tetrapropylammonium bromide, and n-propylamine; and / or,
[0041] The solvent is water.
[0042] According to the present invention, in the preparation method of the aluminum-rich ZSM-5 type zeolite:
[0043] In step a), the molar ratio of silica source, template agent, alumina source, sodium hydroxide, and water is (20-50):(2-10):1:(0.01-0.20):(120-500), wherein the silica source is SiO2 and the alumina source is Al2O3.
[0044] In step a), halides with a salt effect, such as sodium bromide or sodium chloride, can be added as needed to promote the crystallization of aluminum-rich zeolite. There is no particular limitation on the amount of metal salt added; it can be added according to the usual amount as needed.
[0045] The precrystallization conditions in steps b) and d) are independently: precrystallization at 50–100°C for 3–60 h, preferably precrystallization at 60–95°C for 5–30 h;
[0046] The hydrothermal crystallization conditions in steps b) and d) are independently: crystallization at 110–180°C for 12–240 h, preferably pre-crystallization at 120–170°C for 24–200 h;
[0047] In the system obtained in step c), the molar ratio of silica source, template agent, alumina source, sodium hydroxide, and water is (8-18):(0.5-2):1:(0.005-0.015):(40-150), wherein the silica source is calculated as SiO2 and the alumina source is calculated as Al2O3.
[0048] After the secondary crystallization, the process further includes filtration, washing, and drying steps; preferably, the drying temperature is 30–200°C.
[0049] The aluminum-rich ZSM-5 zeolite obtained in step e) further requires ammonium ion exchange and calcination treatment. According to the present invention, sodium-type aluminum-rich ZSM-5 zeolite obtained by the above preparation method needs to be exchanged into ammonium-type aluminum-rich ZSM-5 zeolite before preparing the catalyst support, and then calcined to obtain hydrogen-type aluminum-rich ZSM-5 zeolite. Both the exchange treatment and the calcination treatment can employ commonly used exchange treatment and calcination treatment processes in the art. Specifically, the ion exchange includes ammonium exchange, preferably, the ammonium exchange reagent includes at least one of ammonium nitrate, ammonium chloride, ammonium oxalate, and ammonium sulfate; the ammonium exchange is carried out at a temperature of 10–120°C for 0.1–1000 h; the concentration of the ammonium exchange reagent aqueous solution is 0.01–5 mol / L; the volume-to-mass ratio of the ammonium exchange reagent aqueous solution to ZSM-5 molecular sieve is 4–10 mL:1 g; the number of ion exchanges is 1–20; after the ion exchange, the ion is first filtered, washed, and dried, and then calcined a second time.
[0050] The conditions for the first roasting are: the temperature of the first roasting is 200-980℃, and the roasting time is 0.1-250h;
[0051] The conditions for the secondary roasting are: the temperature of the secondary roasting is 400-650℃, and the time of the secondary roasting is 1-10h.
[0052] In this invention, the aluminum-rich ZSM-5 zeolite and its preparation method can be referred to patent ZL202311219634.1, and the relevant content disclosed in the aforementioned document is incorporated herein by reference.
[0053] The third objective of this invention is to provide an application of the above-mentioned catalytic diesel hydrocracking catalyst or the catalytic diesel hydrocracking catalyst prepared by the above-mentioned preparation method in the hydrocracking reaction of rich aromatic diesel. Preferably, it includes the following steps: loading the hydrorefining catalyst and the catalytic diesel hydrocracking catalyst into a first reactor and a second reactor connected in series in a single stage, and then adding rich aromatic diesel to carry out hydrorefining and hydrocracking reactions.
[0054] According to the present invention,
[0055] The aromatic diesel fuel contains no less than 50% aromatic hydrocarbons.
[0056] The aromatic diesel oil is selected from at least one of catalytic diesel oil, coking diesel oil, and ethylene tar.
[0057] The aromatic diesel oil, after hydrorefining, has a nitrogen content of ≤50ppm and a sulfur content of ≤800ppm; preferably, the nitrogen content is ≤20ppm and the sulfur content is ≤500ppm.
[0058] The hydrorefining process can employ catalytic diesel hydrorefining technology known in the art, and the hydrorefining reaction conditions can be those known in the art for catalytic diesel hydrorefining. The hydrorefining catalyst can be any type of hydrorefining catalyst already available in the art, as long as it can achieve the purpose of catalytic diesel hydrorefining. Preferably, the hydrorefining reaction conditions include: a reaction temperature of 280–400°C, a hydrogen partial pressure of 2.0–15.0 MPa, and a liquid hourly space velocity of 0.2–4.0 h⁻¹. -1 The hydrogen-to-hydrogen volume ratio is 500–4000; preferably, the reaction temperature is 300–380℃, the hydrogen partial pressure is 5.0–12.0 MPa, and the liquid hourly space velocity is 0.5–2.0 h⁻¹. -1 The hydrogen-to-hydrogen volume ratio is 1000–3000;
[0059] The hydrocracking reaction conditions include: a reaction temperature of 300–450 °C, a hydrogen partial pressure of 2.0–15.0 MPa, and a liquid hourly space velocity of 0.2–4.0 h⁻¹. -1The hydrogen-to-hydrogen volume ratio is 500–4000; preferably, the reaction temperature is 320–420°C, the hydrogen partial pressure is 5.0–12.0 MPa, and the liquid hourly space velocity is 0.5–2.0 h⁻¹. -1 The hydrogen-to-hydrogen volume ratio is 1000–3000;
[0060] The single-pass conversion rate of the hydrocracking reaction is greater than 80%.
[0061] In the hydrocracking reaction products, the benzene content in C6 hydrocarbons is greater than 30%, and the toluene content in C7 hydrocarbons is greater than 80%. Specifically, the C6 hydrocarbons are a mixture of benzene and C6 non-aromatic hydrocarbons, and the C7 hydrocarbons are a mixture of toluene and C7 non-aromatic hydrocarbons.
[0062] The catalytic diesel hydrocracking catalyst provided by this invention can be used to produce light aromatics and light hydrocarbons with chemical applications, realizing the conversion of low-value aromatic oil products such as catalytic diesel into chemical products such as aromatics and olefins. In the catalytic diesel hydrocracking catalyst of this invention, ZSM-5 zeolite with a silicon-to-aluminum ratio between 5 and 15 and an average length of less than 20 nm in at least one dimension is used as the acidic functional component. The high-aluminum-content ZSM-5 provides abundant Brønsted acid centers, and because the average length in at least one dimension is less than 20 nm, tetrahydronaphthalene hydrocarbons can contact the open outer surface and Brønsted acid centers near the pores to undergo cracking reactions. Compared with ordinary ZSM-5 catalysts, its conversion activity is significantly improved, and the single-pass conversion rate is high. Moreover, the ten-membered ring channels of ZSM-5 zeolite are more likely to exert shape-selective effects and have a stronger ability to convert non-aromatic hydrocarbons. Simultaneously, the use of sulfide-state metal components, combined with the hydrorefining and hydrocracking reactions in a single-stage series reactor, avoids deactivation caused by sulfur loss in other reaction processes. The hydrocracking catalyst provided in this application exhibits higher selectivity and purity for the conversion of light aromatics in catalytic cracking. Attached Figure Description
[0063] Figure 1 SEM image of the aluminum-rich ZSM-5 zeolite prepared in Example 1. Detailed Implementation
[0064] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.
[0065] The testing instruments and conditions used in this embodiment are as follows:
[0066] 1. The content of elements such as Si and Al in the test sample was determined by ICP (inductively coupled plasma atomic emission spectrometry) and the SiO2 / Al2O3 (SAR) was calculated. The instrument was Thermo IR IS Intrepid II XSP. The sample amount was 20-40 mg. The sample was fully dissolved in 40-80 mL of 40% hydrofluoric acid solution before detection.
[0067] 2. The composition of the hydrocracking catalyst was determined by XRF (X-ray fluorescence spectroscopy) using an S4 Explorer X-ray fluorescence spectrometer manufactured by Bruker GmbH, Germany.
[0068] 3. 27 Al MAS NMR measurements were performed on a VARIAN VNMRS-400WB NMR spectrometer at a frequency of 104.18 MHz, a rotation speed of 10000 r / s, and a relaxation time of 4 s. KAl(SO4)2.12H2O was used as the standard. The chemical shift signal peaks of ~60 ppm corresponded to skeletal aluminum, and the chemical shift signal peaks of ~0 ppm corresponded to non-skeletal aluminum.
[0069] 4. SEM test: The morphology of ZSM-5 zeolite crystals was observed using a Hitachi S-4800 cold field emission high-resolution scanning electron microscope (SEM) from Japan.
[0070] 5. The composition of the crude oil and light chemical products was determined by gas chromatography. The chromatograph was an Agilent 7890A, equipped with an FID detector. Separation was performed using an FFAP capillary column. The column was programmed with an initial temperature of 90°C, held for 15 minutes, and then increased to 220°C at a rate of 15°C / min, held for 45 minutes.
[0071] The calculation basis for the main result data involved in the specific implementation of this invention is as follows:
[0072] 1. The formula for calculating the total conversion rate is:
[0073]
[0074] 2. The formula for calculating the selectivity of light aromatics is:
[0075]
[0076] 3. In hydrocracking products, the benzene content in C6 hydrocarbons and the toluene content in C7 hydrocarbons are used as indicators of aromatic hydrocarbon purity.
[0077] The following are examples of catalytic cracking feedstocks and hydrorefining catalysts involved in the embodiments:
[0078] 1. To illustrate the effects of the present invention, the raw material composition is shown in Table 1.
[0079] Table 1. Composition of Catalyst Raw Materials
[0080]
[0081] 2. The hydrorefining catalyst involved in the embodiments and comparative examples of this invention is commercially available catalyst HT-1, with a composition of 5.73wt% NiO, 35.15wt% MoO3, 4.66% P2O5, and 54.46% Al2O3. Hydrorefining catalysts with similar composition and performance indicators can meet the requirements of this technical solution.
[0082] 3. All other raw materials involved in the embodiments and comparative examples of this invention are commercially available products.
[0083] Comparative Example 1
[0084] Preparation of hydrocracking catalysts:
[0085] Hydrogen-form USY zeolite (SAR=12) was obtained from the Catalyst Division of Sinopec, with an average particle size of 1.7 micrometers. 43g of USY, 72.3g of pseudoboehmite, and 2g of guar gum powder were uniformly mixed, and 12ml of nitric acid and 90ml of water were added. The mixture was kneaded into a dough, extruded, cured at room temperature for 24 hours, dried at 110℃ for 12 hours, and calcined in air at 550℃ for 3 hours to obtain a hydrocracking catalyst support. 4.34g of nickel nitrate, 5.75g of ammonium molybdate, and 20ml of ammonia were dissolved in water to obtain a 50ml aqueous solution. 50g of the hydrocracking catalyst support was impregnated with an equal volume of the solution in 50ml of water, allowed to stand for 3 hours, dried at 110℃ for 12 hours, and calcined in air at 500℃ for 4 hours to obtain a hydrocracking catalyst precursor.
[0086] Catalyst pre-sulfurization: A cyclohexane solution containing 0.5% carbon disulfide was injected into a fixed-bed reactor packed with hydrocracking catalyst precursors. The temperature was increased from room temperature to the final sulfidation temperature of 340℃ at a rate of 10℃ / h, and held at this temperature for 12h to complete the pre-sulfurization of the hydrocracking catalyst. After sulfidation, the CO composition of the hydrocracking catalyst was 2.4wt% NiS-9.2wt% MoS2 / 39.3wt% USY (SAR=12)-49.1wt% Al2O3, as shown in Table 2.
[0087] Catalyst evaluation:
[0088] The evaluation was conducted using a series microreactor unit. The hydrorefining catalyst HT-1 was charged into the pre-reactor, and the hydrocracking catalyst CO was charged into the series post-reactor. A catalytic diesel feedstock was used, the reaction pressure was 6.5 MPa, and the hydrogen-to-oil ratio was 2400. The HT-1 hydrorefining catalyst space velocity (LHSV) was 0.8 h⁻¹. -1The reaction temperature was 315℃; the catalyst space velocity (LHSV) for C1 hydrocracking was 1.0 h⁻¹. -1 The reaction temperature is 375℃.
[0089] A high-pressure separator was installed at the outlet of the hydrocracking reactor. After 48 hours of stable operation, the gaseous and liquid products were metered and analyzed for composition. The reaction products were classified as CH4, C2-C5 light hydrocarbons, and C6-C4 light hydrocarbons. 10 The total conversion rate and the selectivity of light aromatics were calculated using the aforementioned formula, and the data are summarized in Table 3.
[0090] The single-pass conversion rate was 58.6 wt%, the selectivity for light aromatics was 36.9%, and the benzene content in C6 hydrocarbons and the toluene content in C7 hydrocarbons were 19.4% and 56.8%, respectively.
[0091] Comparative Example 2
[0092] Preparation of hydrocracking catalysts:
[0093] Hydrogen-form ZSM-5 zeolite (SAR=38) was obtained from the Catalyst Division of Sinopec, with an average particle size of 1.5 micrometers. 43g of hydrogen-form ZSM-5 zeolite (SAR=38), 72.3g of pseudoboehmite, and 2g of guar gum powder were uniformly mixed, and 12ml of nitric acid and 90ml of water were added. The mixture was kneaded into a dough, extruded, cured at room temperature for 24 hours, dried at 110℃ for 12 hours, and calcined in air at 550℃ for 3 hours to obtain a hydrocracking catalyst support. 4.34g of nickel nitrate, 5.75g of ammonium molybdate, and 20ml of ammonia were dissolved in water to obtain a 50ml aqueous solution. 50g of the hydrocracking catalyst support was impregnated with the 50ml solution by equal volume and allowed to stand for 3 hours. It was then dried at 110℃ for 12 hours and calcined in air at 500℃ for 4 hours to obtain a hydrocracking catalyst precursor.
[0094] Catalyst pre-sulfurization: A cyclohexane solution containing 0.5% carbon disulfide was injected into a fixed-bed reactor packed with hydrocracking catalyst precursors. The temperature was increased from room temperature to the final sulfidation temperature of 340℃ at a rate of 10℃ / h, and held at this temperature for 12h to complete the pre-sulfurization of the hydrocracking catalyst. After sulfidation, the composition of the Cl in the hydrocracking catalyst was 2.4wt% NiS-9.2wt% MoS2 / 39.3wt% ZSM-5 (SAR=38)-49.1wt% Al2O3, as shown in Table 2.
[0095] Catalyst evaluation:
[0096] The evaluation was conducted using a series microreactor unit. Hydrorefining catalyst HT-1 was charged into the pre-reactor, and hydrocracking catalyst C1 was charged into the series post-reactor. A catalytic diesel feedstock was used, the reaction pressure was 6.5 MPa, and the hydrogen-to-oil ratio was 2400. The HT-1 hydrorefining catalyst space velocity (LHSV) was 0.8 h⁻¹. -1 The reaction temperature was 315℃; the catalyst space velocity (LHSV) for C2 hydrocracking was 1.0 h⁻¹. -1 The reaction temperature is 380℃.
[0097] A high-pressure separator was installed at the outlet of the hydrocracking reactor. After 48 hours of stable operation, the gaseous and liquid products were metered and analyzed for composition. The reaction products were classified as CH4, C2-C5 light hydrocarbons, and C6-C4 light hydrocarbons. 10 The total conversion rate and the selectivity of light aromatics were calculated using the aforementioned formula, and the data are summarized in Table 3.
[0098] The single-pass conversion rate was 35.5 wt%, the selectivity for light aromatics was 57.7%, and the benzene content in C6 hydrocarbons and the toluene content in C7 hydrocarbons were 74.8% and 96.2%, respectively.
[0099]
Example 1
[0100] Preparation of aluminum-rich ZSM-5 zeolite:
[0101] First, NaOH, sodium bromide, and sodium aluminate are dissolved in deionized water. Then, a template agent is added, followed by 25% tetrapropylammonium hydroxide (OSDA). The molar ratio of SiO2, OSDA, Al2O3, NaOH, and deionized water is 40:5:1:3.5:200, and the molar ratio of NaOH to NaBr is 2:1. After stirring evenly, a milky white gelling solution is obtained. The gelling solution is then placed in a polytetrafluoroethylene-lined pressure steel autoclave and pre-crystallized at 90°C for 6 hours. After that, it is placed in a rotary oven at 150°C and 20 r / min for further hydrothermal crystallization for 160 hours. Finally, it is cooled to room temperature with tap water to obtain a highly crystalline ZSM-5 slurry.
[0102] An appropriate amount of sodium aluminate and solvent were directly added to the ZSM-5 slurry. The molar ratio of SiO2, OSDA, Al2O3, (NaOH and sodium bromide) and deionized water was 40:5:3.2:0.03:240. The above crystallization procedure was repeated for secondary crystallization. The resulting product was filtered, washed, and dried, and then calcined in air at 550°C for 3 hours to obtain aluminum-rich ZSM-5 molecular sieve. XRD characterization showed that it was a pure-phase MFI configuration. 27Al MAS NMR results showed that 98 wt% of aluminum species were in a four-coordinate state. ICP analysis revealed a silica-to-alumina ratio of 13 for the ZSM-5 molecular sieve. Its SEM image is shown below. Figure 1 It appears as irregularly shaped particles with a diameter between 100-300 nm, and these particles are loosely aggregated from basic particles with a diameter of less than 20 nm.
[0103] The obtained aluminum-rich ZSM-5 molecular sieve was added to a 1 mol / L ammonium nitrate solution at 90 °C and exchanged three times to exchange the sodium-type aluminum-rich ZSM-5 (SAR=13) into the ammonium-type aluminum-rich ZSM-5 (SAR=13). Then, it was calcined at 550 °C to obtain the hydrogen-type aluminum-rich ZSM-5 (SAR=13).
[0104] Preparation of hydrocracking catalysts:
[0105] 43g of hydrogen-type aluminum-rich ZSM-5 (SAR=13), 72.3g of pseudoboehmite, and 2g of guar gum powder were uniformly mixed, and 12ml of nitric acid and 90ml of water were added. The mixture was kneaded into a dough, extruded, and cured at room temperature for 24 hours. It was then dried at 110℃ for 12 hours and calcined in air at 550℃ for 3 hours to obtain a hydrocracking catalyst support. 4.34g of nickel nitrate, 5.75g of ammonium molybdate, and 20ml of ammonia were dissolved in water to obtain a 50ml aqueous solution. 50g of the hydrocracking catalyst support was impregnated with the 50ml solution in an equal volume manner, allowed to stand for 3 hours, dried at 110℃ for 12 hours, and calcined in air at 500℃ for 4 hours to obtain a hydrocracking catalyst precursor.
[0106] Catalyst pre-sulfurization: A cyclohexane solution containing 1.0% carbon disulfide was injected into a fixed-bed reactor packed with hydrocracking catalyst precursors. The temperature was increased from room temperature to the final sulfidation temperature of 360℃ at a rate of 10℃ / h, and held at this temperature for 12h to complete the pre-sulfurization of the hydrocracking catalyst. Catalyst C2 was obtained. Its composition by weight is: 2.4wt% NiS - 9.2wt% MoS2 / 39.3wt% ZSM-5 (SAR=13) - 49.1wt% Al2O3 (see Table 3).
[0107] The evaluation was conducted using a series microreactor unit. Hydrorefining catalyst HT-1 was charged into the pre-reactor, and hydrocracking catalyst C2 was charged into the series-connected post-reactor. Catalytic diesel feedstock was used, the reaction pressure was 6.5 MPa, and the hydrogen-to-oil ratio was 2400. The HT-1 hydrorefining catalyst space velocity (LHSV) was 0.8 h⁻¹. -1 The reaction temperature was 315℃; the catalyst space velocity (LHSV) for C2 hydrocracking was 1.0 h⁻¹. -1 The reaction temperature is 380℃.
[0108] A high-pressure separator was installed at the outlet of the hydrocracking reactor. After 48 hours of stable operation, the gaseous and liquid products were metered and analyzed for composition. The reaction products were classified as CH4, C2-C5 light hydrocarbons, and C6-C4 light hydrocarbons. 10 The total conversion rate and the selectivity of light aromatics were calculated using the aforementioned formula, and the data are summarized in Table 3.
[0109] The single-pass conversion rate was 81.5 wt%, the selectivity for light aromatics was 51.6%, and the benzene content in C6 hydrocarbons and the toluene content in C7 hydrocarbons were 49.3% and 90.8%, respectively.
[0110]
Example 2
[0111] Preparation of hydrocracking catalysts:
[0112] The hydrocracking catalyst support was prepared according to the method in [Example 1]. 4.34 g of nickel nitrate, 8.78 g of ammonium tungstate, and 20 ml of ammonia were dissolved in water to obtain 50 ml of aqueous solution. 50 g of the hydrocracking catalyst support was added to the 50 ml solution by an equal-volume impregnation method and allowed to stand for 6 hours. It was then dried at 90°C for 24 hours and calcined at 510°C in air for 3 hours to obtain the hydrocracking catalyst precursor.
[0113] Catalyst pre-sulfurization: A cyclohexane solution containing 1.0% carbon disulfide was injected into a fixed-bed reactor packed with hydrocracking catalyst precursors. The temperature was increased from room temperature to the final sulfidation temperature of 320℃ at a rate of 10℃ / h, and held at this temperature for 18h to complete the pre-sulfurization of the hydrocracking catalyst. Catalyst C3 was obtained. Its composition by weight is: 2.3wt% NiS - 13.6wt% WS2 / 37.4wt% ZSM-5 (SAR=13) - 46.7wt% Al2O3 (see Table 3).
[0114] The evaluation was conducted using a series microreactor unit. Hydrorefining catalyst HT-1 was charged into the pre-reactor, and hydrocracking catalyst C3 was charged into the series post-reactor. A catalytic diesel feedstock was used, with a reaction pressure of 6.5 MPa and a hydrogen-to-oil ratio of 2400. The low-space velocity (LHSV) of the HT-1 hydrorefining catalyst was 0.8 h⁻¹. -1 The reaction temperature was 315℃; the catalyst space velocity (LHSV) for C2 hydrocracking was 1.0 h⁻¹. -1 The reaction temperature is 380℃.
[0115] A high-pressure separator was installed at the outlet of the hydrocracking reactor. After 48 hours of stable operation, the gaseous and liquid products were metered and analyzed for composition. The reaction products were classified as CH4, C2-C5 light hydrocarbons, and C6-C4 light hydrocarbons. 10 The total conversion rate and the selectivity of light aromatics were calculated using the aforementioned formula, and the data are summarized in Table 3.
[0116] The single-pass conversion rate was 86.7 wt%, the selectivity for light aromatics was 49.4%, and the benzene content in C6 hydrocarbons and the toluene content in C7 hydrocarbons were 45.4% and 86.6%, respectively.
[0117]
Example 3
[0118] Preparation of aluminum-rich ZSM-5 zeolite:
[0119] First, NaOH, sodium bromide, and sodium aluminate are dissolved in deionized water. Then, a template agent is added, followed by 25% tetrapropylammonium hydroxide (OSDA). The molar ratio of SiO2, OSDA, Al2O3, (NaOH and sodium bromide), and deionized water is 25:3:1:0.02:135. After stirring evenly, a milky white gelling solution is obtained. The gelling solution is then placed in a polytetrafluoroethylene-lined pressure steel autoclave and pre-crystallized at 70°C for 12 hours. After that, it is placed in a rotary oven at 165°C and 20 r / min for 36 hours of hydrothermal crystallization. Finally, it is cooled to room temperature with tap water to obtain a highly crystalline ZSM-5 slurry.
[0120] An appropriate amount of aluminum hydroxide and deionized water were directly added to the ZSM-5 slurry. The molar ratio of SiO2, OSDA, Al2O3 (NaOH and sodium bromide) to the solvent deionized water was 25:3:2.8:0.02:135. The above crystallization procedure was repeated for secondary crystallization. The resulting product was filtered, washed, and dried, and then calcined in air at 550°C for 3 hours to obtain aluminum-rich ZSM-5 molecular sieve. XRD characterization showed that it was a pure-phase MFI configuration. 27 Al MAS NMR results showed that 96 wt% of aluminum species were in a four-coordinate state. ICP analysis revealed that the silica-alumina ratio of the ZSM-5 molecular sieve was 8.6. The obtained aluminum-rich ZSM-5 molecular sieve was composed of loosely aggregated basic particles with a particle size of less than 20 nm.
[0121] The obtained aluminum-rich ZSM-5 molecular sieve was added to a 1 mol / L ammonium nitrate solution at 90 °C and exchanged three times to convert sodium-type aluminum-rich ZSM-5 (SAR=8.6) into ammonium-type aluminum-rich ZSM-5 (SAR=8.6). Then, it was calcined at 550 °C to obtain hydrogen-type aluminum-rich ZSM-5 (SAR=8.6).
[0122] Preparation of hydrocracking catalysts:
[0123] 60g of hydrogen-type aluminum-rich ZSM-5 (SAR=8.6), 57g of pseudoboehmite, and 2g of guar gum powder were uniformly mixed, and 6ml of nitric acid and 85ml of water were added. The mixture was kneaded into a dough, extruded, and cured at room temperature for 24h. It was then dried at 110℃ for 24h and calcined in air at 550℃ for 3h to obtain a hydrocracking catalyst support. 6.06g of cobalt nitrate, 5.75g of ammonium molybdate, 2.64g of ammonium tungstate, and 20ml of ammonia were dissolved in water to obtain a 50ml aqueous solution. 50g of the hydrocracking catalyst support was impregnated with the 50ml solution by equal volume and allowed to stand for 3 hours. It was then dried at 90℃ for 24h and calcined in air at 480℃ for 6h to obtain a hydrocracking catalyst precursor.
[0124] Catalyst pre-sulfurization: A cyclohexane solution containing 1.0% carbon disulfide was injected into a fixed-bed reactor packed with hydrocracking catalyst precursors. The temperature was increased from room temperature to the final sulfidation temperature of 330℃ at a rate of 10℃ / h, and held at this temperature for 12h to complete the pre-sulfurization of the hydrocracking catalyst. Catalyst C4 was obtained. Its composition by weight is: 3.2wt% CoS - 8.8wt% MoS2 - 4.1wt% WS2 / 50.4wt% ZSM-5 (SAR = 8.6) - 33.5wt% Al2O3 (see Table 3).
[0125] The evaluation was conducted using a series microreactor unit. Hydrorefining catalyst HT-1 was charged into the pre-reactor, and hydrocracking catalyst C2 was charged into the series-connected post-reactor. Catalytic diesel feedstock was used, the reaction pressure was 6.5 MPa, and the hydrogen-to-oil ratio was 2400. The HT-1 hydrorefining catalyst space velocity (LHSV) was 0.8 h⁻¹. -1 The reaction temperature was 315℃; the catalyst space velocity (LHSV) for C2 hydrocracking was 1.0 h⁻¹. -1 The reaction temperature is 380℃.
[0126] A high-pressure separator was installed at the outlet of the hydrocracking reactor. After 48 hours of stable operation, the gaseous and liquid products were metered and analyzed for composition. The reaction products were classified as CH4, C2-C5 light hydrocarbons, and C6-C4 light hydrocarbons. 10 The total conversion rate and the selectivity of light aromatics were calculated using the aforementioned formula, and the data are summarized in Table 3.
[0127] The single-pass conversion rate was 94.3 wt%, the selectivity for light aromatics was 52.7%, and the benzene content in C6 hydrocarbons and the toluene content in C7 hydrocarbons were 60.5% and 95.4%, respectively.
[0128] Table 2. Catalyst composition obtained in Comparative Examples 1-2 and Examples 1-3
[0129]
[0130] Table 3. Product yields from Comparative Examples 1-2 and Examples 1-3
[0131]
[0132] As can be seen from the results in Table 3, the aluminum-rich ZSM-5 zeolite catalytic hydrocracking catalysts with a silicon-aluminum molecule ratio between 5 and 15 used in Examples 1 to 3 of this invention have a higher single-pass conversion rate.
Claims
1. A catalytic diesel hydrocracking catalyst, comprising: The composition comprises: aluminum-rich ZSM-5 zeolite, a hydrogenated functional component, an optional metal functional modifier, and a binder; wherein the aluminum-rich ZSM-5 zeolite has a silica-alumina molecular weight ratio between 5 and 15 and the average length of the zeolite particles in at least one dimension is less than 20 nm; and the aluminum-rich ZSM-5 zeolite contains skeletal aluminum content of more than 90 wt% of the total aluminum content; the hydrogenated functional component is selected from group VIB metal sulfides. The aluminum-rich ZSM-5 zeolite is obtained by the following preparation method: a) obtaining a colloid comprising a silicon source, a first aluminum source, an alkali source, a template agent, and a solvent; b) performing a first crystallization of the colloid obtained in step a) by pre-crystallization and hydrothermal crystallization to obtain a slurry; c) adding a second aluminum source to the slurry obtained in step b); d) performing a second crystallization by repeating the pre-crystallization and hydrothermal crystallization to obtain the aluminum-rich ZSM-5 zeolite; optionally, the method further includes e) calcining the aluminum-rich ZSM-5 zeolite once, then performing ion exchange, and then performing a second calcination; the pre-crystallization conditions in steps b) and d) are independently: pre-crystallization at 50~100℃ for 3~60h; the hydrothermal crystallization conditions in steps b) and d) are independently: crystallization at 110~180℃ for 12~240h.
2. The catalyst according to claim 1, characterized in that, In the aforementioned aluminum-rich ZSM-5 zeolite, the skeletal aluminum content accounts for more than 95 wt% of the total aluminum; and / or, The hydrogenation functional component is selected from at least one of molybdenum sulfide and tungsten sulfide; and / or, The metal functional modulating component is selected from at least one component containing a Group VIII metal; and / or, The adhesive is selected from at least one of aluminum oxide-containing components and silicon dioxide-containing components.
3. The catalyst according to claim 2, characterized in that, The metal functional regulating component is selected from at least one nickel-containing component and / or at least one cobalt-containing component.
4. The catalyst according to claim 1, characterized in that, Based on a total weight of 100 parts by weight of the aluminum-rich ZSM-5 zeolite and binder, the aluminum-rich ZSM-5 zeolite comprises 5 to 95 parts, the hydrogenation functional component comprises 1 to 30 parts, and the metal functional regulating component comprises 0 to 10 parts.
5. The catalyst according to claim 4, characterized in that, Based on a total weight of 100 parts by weight of the aluminum-rich ZSM-5 zeolite and binder, the aluminum-rich ZSM-5 zeolite comprises 10 to 90 parts, the hydrogenation functional component comprises 2 to 20 parts, and the metal functional regulating component comprises 0.2 to 8 parts.
6. The catalyst according to claim 5, characterized in that, Based on a total weight of 100 parts by weight of the aluminum-rich ZSM-5 zeolite and binder, the aluminum-rich ZSM-5 zeolite comprises 15 to 80 parts, the hydrogenation functional component comprises 3 to 18 parts, and the metal functional regulating component comprises 0.5 to 6 parts.
7. A method for preparing the catalytic diesel hydrocracking catalyst according to any one of claims 1 to 6, comprising: A catalytic system containing hydrogenation functional components and optional metal functional adjustment components is loaded onto a support containing the aforementioned aluminum-rich ZSM-5 zeolite and a binder to obtain the aforementioned catalytic diesel hydrocracking catalyst. The aluminum-rich ZSM-5 zeolite is obtained by the following preparation method: a) obtaining a colloid comprising a silicon source, a first aluminum source, an alkali source, a template agent, and a solvent; b) performing a first crystallization of the colloid obtained in step a) by pre-crystallization and hydrothermal crystallization to obtain a slurry; c) adding a second aluminum source to the slurry obtained in step b); d) performing a second crystallization by repeating the pre-crystallization and hydrothermal crystallization to obtain the aluminum-rich ZSM-5 zeolite; optionally, the method further includes e) calcining the aluminum-rich ZSM-5 zeolite once, then performing ion exchange, and then performing a second calcination; the pre-crystallization conditions in steps b) and d) are independently: pre-crystallization at 50~100℃ for 3~60h; the hydrothermal crystallization conditions in steps b) and d) are independently: crystallization at 110~180℃ for 12~240h.
8. The preparation method according to claim 7, characterized in that, The preparation method includes the following steps: Step 1) After mixing and molding the components including aluminum-rich ZSM-5 zeolite and binder, the catalyst support is dried and calcined to obtain the catalyst support. Step 2) Prepare an aqueous solution of a metal compound by adding the hydrogenated functional component precursor compound and optionally the metal functional modifier precursor compound; Step 3) Impregnate the catalyst support obtained in Step 1) in the aqueous solution of the metal compound obtained in Step 2), remove it, dry it, and calcine it to obtain the catalyst precursor; Step 4) Sulfide the catalyst precursor obtained in Step 3) to obtain the aforementioned catalytic hydrocracking catalyst.
9. The preparation method according to claim 8, characterized in that, The hydrogenated functional component precursor compound is selected from soluble Group VIB metal compounds; and / or, The metal functional modulating component precursor compound is selected from at least one soluble Group VIII metal compound.
10. The preparation method according to claim 9, characterized in that, The hydrogenated functional component precursor compound is selected from at least one of soluble molybdenum compounds and soluble tungsten compounds; and / or, The metal functional modulating component precursor compound is selected from at least one soluble nickel compound and / or at least one soluble cobalt compound.
11. The preparation method according to claim 10, characterized in that, The hydrogenation functional component precursor compound is selected from at least one of ammonium tungstate and ammonium molybdate; and / or, The metal functional regulating component precursor compound is selected from at least one of nickel nitrate, nickel sulfate, nickel halide, nickel acetate, cobalt nitrate, and cobalt chloride.
12. The preparation method according to claim 8, characterized in that, In step 1), the drying temperature is 50-150℃, the calcination temperature is 500-600℃, and the calcination time is 1-6 hours; and / or, In step 2): the concentration of the aqueous solution of the metal compound is 3~50 wt%; and / or, In step 3), the drying temperature is 50-150℃, the calcination temperature is 450-600℃, and the calcination time is 0.5-8 hours; and / or, The conditions for vulcanization in step 4) are as follows: the vulcanization heating rate is 10~20℃ / h, the vulcanization endpoint temperature is 300~370℃, and the endpoint temperature is maintained for 1~24h.
13. The preparation method according to claim 12, characterized in that, In step 1), the drying temperature is 60~120℃, the calcination temperature is 520~580℃, and the calcination time is 2~5h; and / or, In step 2): the concentration of the aqueous solution of the metal compound is 5~40 wt%; and / or, In step 3), the drying temperature is 60~120℃, the calcination temperature is 480~580℃, and the calcination time is 1~6h; and / or, The conditions for vulcanization in step 4) are as follows: the vulcanization heating rate is 10℃ / h, the vulcanization endpoint temperature is 320~360℃, and the endpoint temperature is maintained for 4~18h.
14. The preparation method according to claim 7, characterized in that, The first aluminum source and the second aluminum source may be the same or different, and each is independently selected from at least one of sodium aluminate, aluminum hydroxide, and aluminum sulfate; and / or, The alkali source includes alkali metal hydroxides and / or ammonia; and / or, The silicon source is selected from at least one of silica gel, silica sol, and silica fume; and / or, The template agent is selected from organic amines; and / or, The solvent is water.
15. The preparation method according to claim 14, characterized in that, The alkali metal includes at least one of Na and K; and / or, The template agent is selected from at least one of tetrapropylammonium hydroxide, tetrapropylammonium bromide, and n-propylamine.
16. The preparation method according to claim 7, characterized in that, In step a), the molar ratio of silicon source, template agent, aluminum source, alkali source, and water is (20~50):(2~10):1:(0.01~0.20):(120~500), where the silicon source is calculated as SiO2 and the aluminum source is calculated as Al2O3; and / or, Following the secondary crystallization, the process further includes filtration, washing, and drying steps; and / or, In the system obtained in step c), the molar ratio of silicon source, template agent, aluminum source, alkali source, and water is (8~18):(0.5~2):1:(0.005~0.015):(40~150), where the silicon source is represented by SiO2 and the aluminum source by Al2O3; and / or, Step e) The ion exchange includes ammonium exchange; and / or, The conditions for the first roasting are: a roasting temperature of 200~980℃ and a roasting time of 0.1~250h; and / or, The conditions for the secondary roasting are: the temperature of the secondary roasting is 400~650℃, and the time of the secondary roasting is 1~10h.
17. The preparation method according to claim 16, characterized in that, The pre-crystallization conditions in steps b) and d) are independently: pre-crystallization at 60–95°C for 5–30 h; and / or, The hydrothermal crystallization conditions in steps b) and d) are independently: crystallization at 120~170℃ for 24~200h; and / or, After the secondary crystallization, the drying temperature is 30~200℃; and / or, The ammonium exchange reagent includes at least one of ammonium nitrate, ammonium chloride, ammonium oxalate, and ammonium sulfate; and / or, the ammonium exchange is performed at a temperature of 10-120℃ for 0.1-1000 h; and / or, the concentration of the aqueous solution of the ammonium exchange reagent is 0.01-5 mol / L; and / or, the volume-to-mass ratio of the aqueous solution of the ammonium exchange reagent to ZSM-5 molecular sieve is 4-10 mL:1 g; and / or, the number of ion exchanges is 1-20; and / or, after the ion exchange, the mixture is first filtered, washed, and dried, and then subjected to a second calcination.
18. The application of a catalytic diesel hydrocracking catalyst according to any one of claims 1 to 6 or a catalytic diesel hydrocracking catalyst prepared by any one of claims 7 to 17 in the hydrocracking reaction of aromatic diesel fuel, wherein the aromatic diesel fuel contains not less than 50% aromatic hydrocarbons.
19. The application according to claim 18, characterized in that, The process includes the following steps: the hydrorefining catalyst and the aforementioned catalytic diesel hydrocracking catalyst are respectively loaded into the first and second reactors connected in a single-stage series, and then aromatic diesel fuel is added to carry out hydrorefining and hydrocracking reactions.
20. The application according to claim 19, characterized in that, The aromatic diesel oil is selected from at least one of catalytic diesel oil, coking diesel oil, and ethylene tar; and / or, The aromatic diesel oil, after hydrorefining, has a nitrogen content of ≤50ppm and a sulfur content of ≤800ppm. And / or, The reaction conditions for the hydrorefining include: a reaction temperature of 280–400 °C, a hydrogen partial pressure of 2.0–15.0 MPa, and a liquid hourly space velocity of 0.2–4.0 h⁻¹. -1 The hydrogen-to-hydrogen volume ratio is 500~4000; and / or, The hydrocracking reaction conditions include: a reaction temperature of 300–450 °C, a hydrogen partial pressure of 2.0–15.0 MPa, and a liquid hourly space velocity of 0.2–4.0 h⁻¹. -1 The hydrogen-to-hydrogen volume ratio is 500~4000; and / or, Based on a fraction above 200°C, the single-pass conversion rate of the hydrocracking reaction is greater than 80%; and / or, In the hydrocracking reaction products, the benzene content in C6 hydrocarbons is greater than 30%, and the toluene content in C7 hydrocarbons is greater than 80%.
21. The application according to claim 20, characterized in that, The aromatic diesel fuel, after hydrorefining, has a nitrogen content ≤20ppm and a sulfur content ≤500ppm; and / or, The reaction conditions for the hydrorefining include: a reaction temperature of 300~380℃, a hydrogen partial pressure of 5.0~12.0MPa, and a liquid hourly space velocity of 0.5~2.0h. -1 The hydrogen-to-hydrogen volume ratio is 1000~3000; and / or, The hydrocracking reaction conditions include: a reaction temperature of 320–420 °C, a hydrogen partial pressure of 5.0–12.0 MPa, and a liquid hourly space velocity of 0.5–2.0 h⁻¹. -1 The hydrogen-to-hydrogen volume ratio is 1000~3000.