A high-aromatics-content catalytic diesel hydrocracking catalyst, a preparation method and application thereof

Abstract

The application discloses a high-aromatics-content catalytic diesel hydrocracking catalyst, which contains 40wt%-70wt%, preferably 50wt%-60wt% of La-Y heteroatomic molecular sieve based on the weight of the hydrocracking catalyst, the silicon-aluminum ratio (molar ratio of SiO2 / Al2O3) of the La-Y heteroatomic molecular sieve is 5.0-20.0, preferably 8.0-15.0; the content of La heteroatoms is <=5.0% in terms of the mass of the oxide, preferably <=3.0%, and further preferably 0.5-2% based on the weight; and the mass content of Na2O is <=0.5%, preferably <=0.3%. The catalyst is used in a catalytic diesel hydrocracking process, has good light aromatic (BTX) selectivity and high yield, simultaneously produces low-carbon alkanes (C1-C4) gas, and can realize the maximum utilization of the value of poor catalytic diesel raw materials.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology, specifically relating to a high aromatic content catalytic diesel hydrocracking catalyst, its preparation method, and its application. Background Technology

[0002] Catalytic cracking, as one of the main methods of heavy oil processing, accounts for about one-third of the primary crude oil processing capacity. This results in catalytic diesel accounting for approximately 30 wt.% of my country's diesel fuel, with an annual output exceeding 40 million tons. Catalytic diesel contains a significant amount of heteroatom compounds, aromatics, and olefins, especially polycyclic aromatic hydrocarbons (PAHs). The content of bicyclic and higher PAHs is generally above 50 wt.%, leading to poor complete combustion performance, high density, and low cetane number, becoming a limiting factor for product quality upgrades in refining enterprises. It is worth noting that efficiently converting aromatic-rich catalytic diesel into BTX (bicyclic aromatic hydrocarbons) rich in light aromatics could solve the processing problems of catalytic diesel, expand aromatic feedstock resources, and alleviate the tight supply of aromatics.

[0003] CN106853377A reports a catalyst for hydrotreating high-aromatic diesel, its preparation method, and its application. The catalyst, by weight, comprises: 20%-65% composite molecular sieve, 10%-50% alumina, 10%-30% Group VIB metals (based on oxides), and 3%-8% Group VIII metals (based on oxides). The composite molecular sieve is a small-crystal modified Y molecular sieve and a SAPO-11 molecular sieve, with a weight ratio of 2:1 to 10:1. The invention also discloses a method for preparing the small-crystal modified Y molecular sieve: using small-crystal high-silicon-aluminum ratio NaY molecular sieve with a SiO2 / Al2O3 molar ratio of 6.0-7.0 as raw material, the catalyst undergoes a series of processes including primary ammonium exchange, primary hydrothermal treatment, secondary ammonium exchange, secondary hydrothermal treatment, and primary acid treatment. This catalyst exhibits high liquid product yield and can be used to produce low-sulfur, olefin-free high-octane gasoline and ultra-low-sulfur clean diesel from high-aromatic diesel.

[0004] CN104549473A discloses a catalyst for converting sulfur-containing polycyclic aromatic hydrocarbons (PAHs) to monocyclic aromatic hydrocarbons (MOHs) and its preparation method. It mainly addresses the problems of low conversion depth of PAHs, low yield and selectivity of MOHs, and rapid catalyst deactivation rate in existing technologies. This invention effectively solves the above problems by employing a catalyst comprising, by weight percentage, 30%-65% of a mixture of FAU-type zeolite and ZSM-12 molecular sieve, 33.5%-69.8% of at least one selected from γ-alumina, η-alumina, or boehmite as a binder, and 0.1%-0.5% of at least one metal selected from Pt, Pd, or Ir, and 0.1%-1% of at least one metal selected from La, Ce, or Sn. This catalyst can be used in the industrial production of converting sulfur-containing PAHs to MOHs.

[0005] CN112322348A discloses a method and system for producing heavy naphtha rich in light aromatics from heavy aromatics. This invention involves hydrocracking a catalytic diesel stream after hydrorefining to separate impurities, yielding a fraction including light hydrocarbons, heavy naphtha rich in light aromatics, and heavy tail oil. The hydrocracking catalyst, by weight, comprises: a2) 5-80 parts solid acid zeolite; b2) 0.05-8 parts Group VIII metals; c2) 3-25 parts Group VIB metal oxides; d2) 0.1-2 parts Group VIB metal sulfides; e2) 20-95 parts a first binder.

[0006] Existing technologies have reported the use of various types of molecular sieve composite materials as acidic supports for catalytic diesel hydrocracking catalysts, but these generally suffer from problems such as poor selectivity and low yield of light aromatics (BTX). Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a high-aromatic-content catalytic diesel hydrocracking catalyst, its preparation method, and its application. The catalyst prepared by this method exhibits good selectivity and high yield of light aromatics (BTX) in the catalytic diesel hydrocracking process, while simultaneously producing low-carbon alkane (C1-C4) gases, thus maximizing the utilization of inferior catalytic diesel feedstock.

[0008] The first aspect of the present invention provides a high aromatic content catalytic diesel hydrocracking catalyst, wherein the hydrocracking catalyst contains 40%-70%, preferably 50%-60% La-Y heteroatom molecular sieves based on its weight.

[0009] In the hydrocracking catalyst of the present invention, the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of the La-Y heteroatom molecular sieve is 5.0-20.0, preferably 8.0-15.0; the La heteroatom content (in terms of oxide mass fraction) is ≤5.0% by weight, preferably ≤3.0%, more preferably 0.5-2%; and the Na2O mass content is ≤0.5%, preferably ≤0.3%.

[0010] In the hydrocracking catalyst of the present invention, the La-Y heteroatom molecular sieve exhibits a layered morphology formed by stacking plate-like molecular sieves, with a single layer of plate-like molecular sieve having a thickness of less than 200 nm, preferably less than 150 nm, and more preferably 60 nm-120 nm.

[0011] The hydrocracking catalyst of the present invention contains, by weight, 10%-25%, preferably 15%-20% of hydrocracking active metal (calculated as metal oxide).

[0012] In the hydrocracking catalyst of the present invention, the hydrocracking active metal is selected from Group VIII and / or Group VIB metals, wherein the Group VIII metal is Ni and / or Co, and the Group VIB metal is W and / or Mo. Based on the weight of the catalyst, the content of Group VIII metals, calculated as metal oxides, is 2%-8%, preferably 3%-5%, and the content of Group VIB metals, calculated as metal oxides, is 10%-20%, preferably 12%-15%.

[0013] The hydrocracking catalyst of the present invention contains 20%-50%, preferably 25%-40% γ-alumina by weight.

[0014] In the hydrocracking catalyst of the present invention, the hydrocracking catalyst includes a support and an active metal component supported on the support. Based on the weight of the hydrocracking catalyst, the mass ratio of each component is 40%-70%: 20%-50%: 10%-25% for La-Y heteroatom molecular sieve: γ-alumina: hydrogenated metal (calculated as oxide).

[0015] In the hydrocracking catalyst of this invention, the specific surface area of ​​the hydrocracking catalyst is 350 m². 2 / g-500m 2 / g, preferably 400m 2 / g-450m 2 / g, pore volume 0.30cm 3 / g-0.40cm 3 / g, preferably 0.33cm 3 / g-0.37cm 3 / g.

[0016] The second aspect of the present invention provides a method for preparing a high aromatic content catalytic diesel hydrocracking catalyst, the method comprising mixing La-Y heteroatom molecular sieve, γ-alumina and a hydrogenation active metal to obtain a hydrocracking catalyst, or first molding La-Y heteroatom molecular sieve and γ-alumina and then loading a hydrogenation active metal to obtain a hydrocracking catalyst.

[0017] The method of the present invention, a non-limiting method for preparing a hydrocracking catalyst, includes the following: (1) Mix La-Y heteroatom molecular sieve, γ-alumina and hydrogenated active metal in a certain proportion, and then add a peptizing solvent (e.g. nitric acid solution) to the mixture to make a slurry for kneading and extrusion molding; (2) The extruded product obtained in step (1) is dried and calcined to obtain a hydrocracking catalyst.

[0018] In the method of the present invention, in step (1), the mass fraction ratio of La-Y heteroatom molecular sieve, γ-alumina and hydrogenated active metal (calculated as metal oxide) in the solid mixture is 30%-50%: 25%-50%: 20%-30%; the concentration of the nitric acid solution is 5-30% by mass; the solid content of the slurry is suitable for extrusion molding to obtain a strip-shaped extruded product, preferably, the solid content of the slurry is 30-60% by mass.

[0019] In the method of this invention, the La-Y heteroatom molecular sieve in step (1) exhibits a layered morphology composed of stacked plate-like molecular sieves, with a single layer of plate-like molecular sieve having a thickness of less than 200 nm, preferably less than 150 nm; the average particle size of the La-Y heteroatom molecular sieve is 1.5 μm-3.0 μm, preferably 2.0 μm-2.5 μm; and the pore volume of the La-Y heteroatom molecular sieve is 0.38 cm³. 3 / g-0.5cm 3 / g, preferably 0.40cm 3 / g-0.45cm 3 / g, with a mesoporous pore volume ratio of 30%-50%, preferably 35%-45%; the specific surface area of ​​the La-Y heteroatom molecular sieve is 700m². 2 / g-900m 2 / g, preferably 750m 2 / g-850m 2 / g.

[0020] In the method of the present invention, the La-Y heteroatom molecular sieve in step (1) has a typical FAU type topology and a relative crystallinity of 90%-105%, preferably 95%-100%.

[0021] In the method of the present invention, in the La-Y heteroatom molecular sieve mentioned in step (1), the Na2O mass content is less than 0.5% by weight, preferably 0.05%-0.3%; the silicon-aluminum ratio (SiO2 / Al2O3 molar ratio) of the La-Y heteroatom molecular sieve is 5-20, preferably 8-15; and the La heteroatom content (in terms of oxide mass fraction) is ≤5.0% by weight, preferably ≤3.0%, and more preferably 0.5-2%.

[0022] In the method of the present invention, the pyridine infrared acid content of the La-Y heteroatom molecular sieve in step (1) is 0.5 mmol / g-1.2 mmol / g, preferably 0.7 mmol / g-1 mmol / g; wherein, the molar ratio of Brønsted acid to L-acid is 3.0-10.0, preferably 5.0-7.0; and the content of medium-strong acid accounts for 60%-75%, preferably 65%-70%.

[0023] In the method of this invention, the adhesive mentioned in step (1) is γ-alumina, characterized by a specific surface area of ​​200 m². 2 / g-600m 2 / g, preferably 300m 2 / g-500m 2 / g; pore volume 0.5cm 3 / g-1.5cm 3 / g, preferably 0.8cm 3 / g-1.2cm 3 / g.

[0024] In the method of the present invention, in step (2), the extruded product is dried at 80℃-120℃ for 6h-12h, and then calcined at 400℃-500℃ for 1h-5h.

[0025] In the method of this invention, the La-Y heteroatom molecular sieve in step (1) can be prepared by the following method: (a) Ammonium ion exchange on lamellar Y molecular sieves; (b) Perform hydrothermal treatment on the material obtained in step (a); (c) The material obtained in step (b) is processed by a mixed solution of ammonium fluorosilicate and La metal precursor, and then filtered, washed, dried and calcined to obtain La-Y heteroatom molecular sieve.

[0026] In the method for preparing La-Y heteroatom molecular sieves of the present invention, the lamellar Y molecular sieve in step (a) can be prepared according to existing publicly available technologies or by using commercially available products.

[0027] In the La-Y heteroatom molecular sieve preparation method of the present invention, the lamellar Y molecular sieve in step (a) presents a lamellar morphology formed by stacking lamellar Y molecular sieves, and the thickness of a single layer of lamellar Y molecular sieve is less than 200 nm, preferably less than 150 nm.

[0028] In the method for preparing La-Y heteroatom molecular sieves of the present invention, the average particle size of the lamellar Y molecular sieve in step (a) is 1.5 μm-3.0 μm, preferably 2.0 μm-2.5 μm.

[0029] In the method for preparing La-Y heteroatom molecular sieves of the present invention, the specific surface area of ​​the lamellar Y molecular sieve in step (a) is 750 m². 2 / g-900m 2 / g, preferably 800m 2 / g-850m 2 / g, total pore volume is 0.35cm³ 3 / g-0.42cm 3 / g, preferably 0.38cm 3 / g-0.40cm 3 / g.

[0030] In the method for preparing La-Y heteroatom molecular sieves of the present invention, the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of the lamellar Y molecular sieve in step (a) is 5.0-7.0, preferably 6.0-6.5; and the Na2O mass content in the lamellar Y molecular sieve is 8%-12% by weight, preferably 9%-11%.

[0031] In the method for preparing La-Y heteroatom molecular sieves of the present invention, in step (a), the lamellar Y molecular sieve is subjected to ion exchange with an ammonium salt solution at 30℃-100℃, preferably 60℃-90℃, for 1-3 hours, and the number of exchange times is 1-2.

[0032] In the method for preparing La-Y heteroatom molecular sieves of the present invention, the ammonium salt used in the ion exchange in step (a) is one or more of ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium acetate, and ammonium oxalate. The concentration of the ammonium salt solution is 0.5 mol / L-2 mol / L, preferably 1 mol / L-1.5 mol / L. The solid-liquid ratio of the lamellar Y molecular sieve to the ammonium salt solution is 1:5-15 (g:mL), preferably 1:8-10 (g:mL).

[0033] In the method for preparing La-Y heteroatom molecular sieves of the present invention, in step (a), the lamellar Y molecular sieve is controlled to contain an appropriate amount of sodium ions. Based on weight, the mass content of sodium ions, calculated as sodium oxide, is 2.8%-4.5%, preferably 3.5%-4.0%. An appropriate amount of Na ions has a stabilizing effect on the sodalite cages of the molecular sieve during the hydrothermal treatment of the Y molecular sieve, which is beneficial to the efficient retention of crystallinity of the molecular sieve in the subsequent hydrothermal process.

[0034] In the method for preparing La-Y heteroatom molecular sieves of the present invention, the hydrothermal treatment in step (b) is a steam heat treatment: the material obtained in step (a) is contacted with steam at a temperature of 550℃-700℃ and a pressure of 0.05MPa-0.3MPa for 1h-4h.

[0035] In the method for preparing La-Y heteroatom molecular sieves of the present invention, in step (c), the material obtained in step (b) is treated with a mixed solution of ammonium fluorosilicate and lanthanum atom precursor at 60℃-120℃, preferably 80℃-100℃, for 3h-5h. Then, the solid particles are filtered, washed, dried and calcined to obtain La-Y heteroatom molecular sieves.

[0036] In the method for preparing La-Y heteroatom molecular sieves of the present invention, the concentration of ammonium fluorosilicate in the mixed solution in step (c) is 0.02 mol / L-0.15 mol / L; and the concentration of lanthanum atom precursor is 0.01 mol / L-0.05 mol / L.

[0037] In the La-Y heteroatom molecular sieve preparation method of the present invention, the heteroatom precursor in step (c) is at least one of lanthanum nitrate and lanthanum chloride.

[0038] In the La-Y heteroatom molecular sieve preparation method of the present invention, the solid-liquid ratio of the molecular sieve material obtained in step (b) to the mixed solution in step (c) is 1:20-50 (g:mL).

[0039] In the method for preparing La-Y heteroatom molecular sieves of the present invention, the La-Y heteroatom molecular sieve product in step (c) is subjected to solid-liquid separation by filtration, washed with water until neutral, and the drying temperature is 80℃-120℃, and the drying time is 12h-24h; the calcination atmosphere is air, the calcination temperature is 400℃-500℃, and the calcination time is 2h-4h.

[0040] A La-Y heteroatom molecular sieve-based hydrocracking catalyst prepared by the above method is applied to the process of producing light aromatics (BTX) from catalytic diesel hydrocracking with high aromatic content. It has the advantages of high BTX selectivity and yield, and can also co-produce low-carbon alkane (C1-C5) gases, which can be further used as feedstock for the catalytic cracking of high-quality carbon nanotubes.

[0041] In the method of this invention, the properties of the high aromatic content catalytic diesel are as follows: the density (20°C) of the catalytic diesel ranges from 0.85 g / cm³. 3 -0.98g / cm 3 The preferred value is 0.90 g / cm³. 3 -0.97g / cm 3 The distillation range is 150℃-380℃, preferably 180℃-370℃; the alkanes are 8wt.%-18wt.%, the cycloalkanes are 5wt.%-16wt.%, and the aromatics are 70wt.%-85wt.%.

[0042] In the method of this invention, the hydrocracking reaction conditions are as follows: (i) after the catalytic diesel and hydrogen are mixed, they enter the hydrorefining reaction zone and react with the hydrorefining catalyst bed to obtain hydrorefined product oil and gaseous products; (ii) the obtained hydrorefined product oil and gaseous products enter the hydrocracking reaction zone and react with the La-Y heteroatom molecular sieve-based hydrocracking catalyst. The reaction effluent obtained from the hydrocracking reaction is separated into gas and liquid and fractionated to obtain gas, naphtha and tail oil.

[0043] In the above method, the hydrorefining catalyst in step (i) can be any type of commercial catalyst in the prior art, or it can be prepared according to common knowledge in the field as needed, as long as it can achieve the purpose of catalytic hydrorefining of diesel in step (i).

[0044] In the above method, the hydrorefined oil obtained after hydrorefining the catalytic diesel in step (i) has the following properties: nitrogen content <40ppm, preferably 10-30ppm; sulfur content <200ppm, preferably <100ppm; and aromatics retention rate of the hydrorefined oil >90wt.%.

[0045] In the above method, the reaction conditions in the hydrocracking reaction zone in step (ii) are: reaction pressure 5 MPa-10 MPa, preferably 6 MPa-8 MPa; reaction temperature 360℃-420℃, preferably 390℃-410℃; and hydrocracking catalyst volume hourly space velocity 1.0 h⁻¹. -1 -3.0h -1 The hydrogen-to-oil volume ratio is 500-1500, preferably 800-1200.

[0046] Compared with the prior art, the present invention has the following beneficial effects: The La-Y heteroatom molecular sieve prepared by this invention has a lamellar morphology, which has advantages over conventional octahedral Y molecular sieves in terms of reactant molecule mass transfer. The doping of La element in the molecular sieve can effectively increase the content of Brønsted acid and the proportion of medium-strong acid in the molecular sieve, which can promote the ring-opening and side-chain breaking process of polycyclic aromatic hydrocarbons in catalytic diesel. At the same time, La element can effectively reduce hydrogen transfer during the reaction process, which is beneficial to improving the selectivity and yield of BTX. Detailed Implementation

[0047] The present invention will be further described in detail below with reference to specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0048] Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following examples were purchased from conventional biochemical reagent stores.

[0049] In this invention, the thickness of a single layer of the layered molecular sieve was determined by SEM, and the average particle size of the molecular sieve was determined by a laser particle size analyzer (DLS). The crystal structure and relative crystallinity of the molecular sieve were determined by XRD characterization. The elemental composition of the molecular sieve and catalyst was determined by XRF characterization. The acidity characteristics of the molecular sieve were determined by pyridine adsorption infrared spectroscopy. Pore information was obtained by nitrogen adsorption-desorption testing of the Y molecular sieve at 77 K using an ASAP 2420 automatic physical adsorption instrument. In the embodiments and comparative examples of this invention, the reaction conversion rate was calculated using the actual boiling point cut data of the product. The formula for calculating the yield of BTX product was: BTX mass content in naphtha fraction × naphtha fraction yield × 100%; the formula for calculating the selectivity of BTX product was: BTX yield / conversion rate × 100%. The composition of BTX mass content in naphtha fraction was analyzed by gas chromatography-mass spectrometry. Example 1

[0050] (1) Layered Y molecular sieve (average particle size 2.2 μm, thickness of single layer of layered molecular sieve approximately 100 nm, silicon-to-aluminum ratio 6.2, specific surface area 863 m²) 2 / g, pore volume 0.38cm 3 A mixture of sodium-containing Y molecular sieve (containing 10.8% Na2O) and a 1.0 mol / L ammonium nitrate solution at a solid-liquid ratio of 1:10 was prepared and subjected to ammonium ion exchange at 80℃ for 2 hours to obtain sodium-removed Y molecular sieve with a Na2O content of 3.7%.

[0051] (2) The desodium-free Y molecular sieve was contacted with water vapor at a temperature of 600℃ and a pressure of 0.1MPa for 2 hours to obtain the dealuminized Y molecular sieve.

[0052] (3) A mixed solution of dealuminized Y molecular sieve and 0.05 mol / L ammonium fluorosilicate and 0.03 mol / L lanthanum nitrate was mixed at a solid-liquid ratio of 1:30 and treated at 80°C for 3 h. After filtration and separation, the solid was washed with water until neutral, dried at 100°C for 12 h, and calcined at 500°C for 2 h in air atmosphere to obtain La-Y heteroatom molecular sieve. The properties of La-Y heteroatom molecular sieve are as follows: La-Y heteroatom molecular sieve still maintains the lamellar morphology formed by stacking plate molecular sieves. The thickness of a single layer of plate Y molecular sieve is about 100 nm, the average particle size is 2.2 μm, and the specific surface area is 840 m². 2 / g, total pore volume is 0.43cm³ 3 / g, mesoporous pore volume accounts for 38.6% of the total pore volume; La-Y heteroatom molecular sieve exhibits typical FAU topological characteristic peaks, with lamellar Y molecular sieve as standard, the relative crystallinity of La-Y heteroatom molecular sieve is 101%; the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of La-Y heteroatom molecular sieve is 15.8, the mass content of Na2O in La-Y heteroatom molecular sieve is 0.06%, the content of La2O3 is 2.9%; the content of pyridine infrared acid in La-Y heteroatom molecular sieve is 0.905 mmol / g, of which the Brønsted acid / Low acid ratio is 5.5; the proportion of moderately strong acids is 71.1%.

[0053] (4) La-Y heteroatom molecular sieve and γ-alumina (specific surface area 460m²) 2 / g, pore volume 1.2cm 3 MoO3 powder and nickel nitrate were mixed in a dry mass ratio of molecular sieve: alumina: NiO: MoO3 of 55:25:5:15. Then, a 15% concentration of nitric acid solution was added to the mixture to prepare a catalyst slurry with a solid content of 50%, which was then kneaded and extruded into strips.

[0054] (5) The catalyst after molding was dried at 120°C for 3 hours and then calcined at 500°C for 3 hours in air to obtain a hydrocracking catalyst with strong ring-opening ability.

[0055] The hydrocracking catalyst provided in this embodiment, based on its weight, contains 55% La-Y heteroatom molecular sieve, 25% alumina, 5% NiO, and 15% MoO3, and is designated as A-1; the specific surface area of ​​the hydrocracking catalyst is 430 m². 2 / g, pore volume 0.35cm 3 / g. Example 2

[0056] (1) Layered Y molecular sieve (average particle size 2.2 μm, thickness of single layer of layered molecular sieve approximately 100 nm, silicon-to-aluminum ratio 6.2, specific surface area 863 m²) 2 / g, pore volume 0.38cm 3 A mixture of 1 g (Na2O content 10.8%) and a 1.0 mol / L ammonium nitrate solution at a solid-liquid ratio of 1:10 was prepared and subjected to ammonium ion exchange at 80 °C for 2 h. The above operation was repeated once to obtain desodium-free Y molecular sieve with a Na2O content of 2.8%.

[0057] (2) The desodium-free Y molecular sieve was contacted with water vapor at a temperature of 650℃ and a pressure of 0.2MPa for 1h to obtain the dealuminized Y molecular sieve.

[0058] (3) A mixed solution of dealuminated Y molecular sieve and 0.1 mol / L ammonium fluorosilicate and 0.05 mol / L lanthanum nitrate was mixed at a solid-liquid ratio of 1:20 and treated at 80°C for 3 h. After filtration and separation, the solid was washed with water until neutral, dried at 100°C for 12 h, and calcined at 500°C for 2 h in air atmosphere to obtain La-Y heteroatom molecular sieve. The properties of La-Y heteroatom molecular sieve are as follows: La-Y heteroatom molecular sieve still maintains the lamellar morphology formed by stacking plate molecular sieves. The thickness of a single layer of plate Y molecular sieve is about 100 nm, the average particle size is 2.2 μm, and the specific surface area is 812 m². 2 / g, total pore volume is 0.45cm³ 3 / g, mesoporous pore volume accounts for 42.2% of the total pore volume; La-Y heteroatom molecular sieve exhibits typical FAU topological characteristic peaks, with lamellar Y molecular sieve as standard, the relative crystallinity of La-Y heteroatom molecular sieve is 94%; the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of La-Y heteroatom molecular sieve is 21.1, the mass content of Na2O in La-Y heteroatom molecular sieve is 0.03%, the content of La2O3 is 4.3%; the content of pyridine infrared acid in La-Y heteroatom molecular sieve is 0.810 mmol / g, of which the Brønsted acid / Low acid ratio is 7.2; the proportion of moderately strong acids is 69.5%.

[0059] (4) La-Y heteroatom molecular sieve and γ-alumina (specific surface area 460m²) 2 / g, pore volume 1.2cm 3 MoO3 powder and nickel nitrate were mixed in a dry mass ratio of molecular sieve: alumina: NiO: MoO3 of 60:20:4:16. Then, a 15% concentration of nitric acid solution was added to the mixture to prepare a catalyst slurry with a solid content of 50%, which was then kneaded and extruded into strips.

[0060] (5) The catalyst after molding was dried at 120°C for 3 hours and then calcined at 500°C for 3 hours in air to obtain a hydrocracking catalyst with strong ring-opening ability.

[0061] The hydrocracking catalyst provided in this embodiment, based on its weight, contains 60% La-Y heteroatom molecular sieve, 20% alumina, 4% NiO, and 16% MoO3, and is designated as A-2; the specific surface area of ​​the hydrocracking catalyst is 442 m². 2 / g, pore volume 0.33cm 3 / g. Example 3

[0062] (1) Layered Y molecular sieve (average particle size 2.2 μm, thickness of single layer of layered molecular sieve approximately 100 nm, silicon-to-aluminum ratio 6.2, specific surface area 863 m²) 2 / g, pore volume 0.38cm 3 A mixture of sodium-containing Y molecular sieve (containing 10.8% Na2O) and 0.8 mol / L ammonium nitrate solution at a solid-liquid ratio of 1:8 was prepared and subjected to ammonium ion exchange at 80°C for 2 hours to obtain sodium-removed Y molecular sieve with a Na2O content of 4.4%.

[0063] (2) The desodium-free Y molecular sieve was contacted with water vapor at a temperature of 550℃ and a pressure of 0.1MPa for 1h to obtain the dealuminized Y molecular sieve.

[0064] (3) A mixed solution of dealuminized Y molecular sieve and 0.03 mol / L ammonium fluorosilicate and 0.01 mol / L lanthanum chloride was mixed at a solid-liquid ratio of 1:40 and treated at 80°C for 3 h. After filtration and separation, the solid was washed with water until neutral, dried at 100°C for 12 h, and calcined at 500°C for 2 h in air atmosphere to obtain La-Y heteroatom molecular sieve. The properties of La-Y heteroatom molecular sieve are as follows: La-Y heteroatom molecular sieve still maintains the lamellar morphology formed by stacking plate molecular sieves. The thickness of a single layer of plate Y molecular sieve is about 100 nm, the average particle size is 2.2 μm, and the specific surface area is 852 m². 2 / g, total pore volume is 0.42cm³ 3 / g, mesoporous pore volume accounts for 35.2% of the total pore volume; La-Y heteroatom molecular sieve exhibits typical FAU topological characteristic peaks, with lamellar Y molecular sieve as standard, the relative crystallinity of La-Y heteroatom molecular sieve is 104%; the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of La-Y heteroatom molecular sieve is 11.6, the mass content of Na2O in La-Y heteroatom molecular sieve is 0.08%, and the content of La2O3 is 1.2%; the content of pyridine infrared acid in La-Y heteroatom molecular sieve is 1.15 mmol / g, of which the Brønsted acid / Low acid ratio is 4.2; the proportion of moderately strong acids is 66.9%.

[0065] (4) La-Y heteroatom molecular sieve and γ-alumina (specific surface area 460m²) 2 / g, pore volume 1.2cm 3 / g), ammonium metatungstate and nickel nitrate were mixed in a dry mass ratio of molecular sieve: alumina: NiO: WO3 of 50:34:3:13. Then, a 10% concentration of nitric acid solution was added to the mixture to prepare a catalyst slurry with a solid content of 60%, which was then kneaded and extruded into strips.

[0066] (5) The catalyst after molding was dried at 120°C for 3 hours and then calcined at 500°C for 3 hours in air to obtain a hydrocracking catalyst with strong ring-opening ability.

[0067] The hydrocracking catalyst provided in this embodiment, based on its weight, contains 50% La-Y heteroatom molecular sieve, 34% alumina, 3% NiO, and 13% WO3, and is designated as A-3; the specific surface area of ​​the hydrocracking catalyst is 423 m². 2 / g, pore volume 0.38cm 3 / g. Example 4

[0068] The preparation process of the molecular sieve and hydrocracking catalyst is the same as in Example 1, except that in step (1), conventional NaY molecular sieves are used instead of layered Y molecular sieves. The properties of the NaY molecular sieve are as follows: the NaY molecular sieve has a typical FAU molecular sieve octahedral morphology, an average particle size of 1.8 μm, a silica-to-alumina ratio of 5.2, and a specific surface area of ​​835 m². 2 / g, pore volume 0.37cm 3 / g, Na2O content 11.6%. The properties of the prepared La-Y heteroatom molecular sieve are as follows: the La-Y heteroatom molecular sieve retains its octahedral morphology, with an average particle size of 1.8 μm; specific surface area is 795 m² / g. 2 / g, total pore volume is 0.44cm³ 3 / g, mesoporous pore volume accounts for 37.2% of the total pore volume; La-Y heteroatom molecular sieve exhibits typical FAU topological characteristic peaks, with NaY molecular sieve as standard, the relative crystallinity of La-Y heteroatom molecular sieve is 102%; the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of La-Y heteroatom molecular sieve is 14.5, the mass content of Na2O in La-Y heteroatom molecular sieve is 0.03%, and the content of La2O3 is 2.7%; the content of pyridine infrared acid in La-Y heteroatom molecular sieve is 0.957 mmol / g, of which the Brønsted acid / Low acid ratio is 5.3; the proportion of medium-strong acids is 69.8%.

[0069] The hydrocracking catalyst provided in this embodiment, based on its weight, contains 55% La-Y heteroatom molecular sieve, 25% alumina, 5% NiO, and 15% MoO3, and is designated as A-4; the specific surface area of ​​the hydrocracking catalyst is 421 m². 2 / g, pore volume 0.35cm 3 / g. Example 5

[0070] The preparation process of the molecular sieve and hydrocracking catalyst is the same as in Example 2, except that in step (1), conventional NaY molecular sieves are used instead of layered Y molecular sieves. The properties of the NaY molecular sieve are as follows: the NaY molecular sieve has a typical FAU molecular sieve octahedral morphology, an average particle size of 1.8 μm, a silica-alumina ratio of 5.2, and a specific surface area of ​​835 m². 2 / g, pore volume 0.37cm 3 / g, Na2O content 11.6%. The properties of the prepared La-Y heteroatom molecular sieve are as follows: the La-Y heteroatom molecular sieve retains its octahedral morphology, with an average particle size of 1.8 μm; specific surface area is 811 m² / g. 2 / g, total pore volume is 0.42cm³ 3 / g, mesoporous pore volume accounts for 40.8% of the total pore volume; La-Y heteroatom molecular sieve exhibits typical FAU topological characteristic peaks, with NaY molecular sieve as standard, the relative crystallinity of La-Y heteroatom molecular sieve is 96%; the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of La-Y heteroatom molecular sieve is 20.2, the mass content of Na2O in La-Y heteroatom molecular sieve is 0.01%, and the content of La2O3 is 4.1%; the content of pyridine infrared acid in La-Y heteroatom molecular sieve is 0.828 mmol / g, of which the Brønsted acid / Low acid ratio is 7.0; the proportion of moderately strong acids is 70.3%.

[0071] The hydrocracking catalyst provided in this embodiment, based on its weight, contains 60% La-Y heteroatom molecular sieve, 20% alumina, 4% NiO, and 16% MoO3, and is designated as A-5; the specific surface area of ​​the hydrocracking catalyst is 440 m². 2 / g, pore volume 0.32cm 3 / g. Example 6

[0072] The preparation process of the molecular sieve and hydrocracking catalyst is the same as in Example 3, except that in step (1), conventional NaY molecular sieves are used instead of layered Y molecular sieves. The properties of the NaY molecular sieve are as follows: the NaY molecular sieve has a typical FAU molecular sieve octahedral morphology, an average particle size of 1.8 μm, a silica-to-alumina ratio of 5.2, and a specific surface area of ​​835 m². 2 / g, pore volume 0.37cm 3 / g, Na2O content 11.6%. The properties of the prepared La-Y heteroatom molecular sieve are as follows: the La-Y heteroatom molecular sieve retains its octahedral morphology, with an average particle size of 1.8 μm; specific surface area is 825 m² / g. 2 / g, total pore volume is 0.41cm³ 3 / g, mesoporous pore volume accounts for 34.4% of the total pore volume; La-Y heteroatom molecular sieve exhibits typical FAU topological characteristic peaks, with NaY molecular sieve as standard, the relative crystallinity of La-Y heteroatom molecular sieve is 103%; the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of La-Y heteroatom molecular sieve is 11.1, the mass content of Na2O in La-Y heteroatom molecular sieve is 0.07%, and the content of La2O3 is 1.2%; the content of pyridine infrared acid in La-Y heteroatom molecular sieve is 1.16 mmol / g, of which the Brønsted acid / Low acid ratio is 4.1; the proportion of moderately strong acids is 65.5%.

[0073] The hydrocracking catalyst provided in this embodiment, based on its weight, contains 50% La-Y heteroatom molecular sieve, 34% alumina, 3% NiO, and 13% WO3, and is designated as A-6; the specific surface area of ​​the hydrocracking catalyst is 409 m². 2 / g, pore volume 0.39cm 3 / g.

[0074] Comparative Example 1 The preparation steps of the hydrocracking catalyst are the same as in Example 1, except that commercially available USY molecular sieves are used instead of La-Y heteroatom molecular sieves. The USY molecular sieves were purchased from Liaoning Tieling Desijie Chemical Co., Ltd., and have a traditional FAU octahedral morphology, an average particle size of 2.0 μm, and a specific surface area of ​​821 m². 2 / g, pore volume 0.41cm 3 / g, mesoporous content 33.8%, silicon-aluminum ratio (SiO2 / Al2O3 molar ratio) 14.2, based on weight, the USY molecular sieve has a Na2O mass content of 0.03%, the USY molecular sieve has a pyridine infrared acid content of 0.967 mmol / g, of which the Brønsted acid / Low acid ratio is 3.0, and the proportion of medium strong acid is 61.4%.

[0075] The hydrocracking catalyst provided in this comparative example, based on its weight, contains 55% USY molecular sieve, 25% alumina, 5% NiO, and 15% MoO3, and is designated as C-1; the specific surface area of ​​the hydrocracking catalyst is 425 m². 2 / g, pore volume 0.36cm 3 / g.

[0076] Comparative Example 2 The preparation steps of the La-Y heteroatom molecular sieve hydrocracking catalyst are the same as in Example 2, except that lanthanum nitrate is not added in step (3). The properties of the modified Y molecular sieve are as follows: the modified Y molecular sieve still maintains the lamellar morphology formed by stacking plate-like molecular sieves, with a single layer of plate-like Y molecular sieve thickness of about 100 nm and an average particle size of 2.2 μm; the specific surface area is 812 m². 2 / g, total pore volume is 0.45cm³ 3 / g, mesoporous pore volume accounts for 42.2% of the total pore volume; the modified Y molecular sieve exhibits typical FAU topological characteristic peaks, and with lamellar Y molecular sieve as standard, the relative crystallinity of the modified Y molecular sieve is 95%; the silica-alumina ratio (SiO2 / Al2O3 molar ratio) of the modified Y molecular sieve is 19.8, the Na2O mass content in the modified Y molecular sieve is 0.05%; the pyridine infrared acid content of the modified Y molecular sieve is 0.835 mmol / g, of which the Brønsted acid / Low acid ratio is 3.3, and the proportion of medium-strong acids is 64.2%.

[0077] The hydrocracking catalyst provided in this comparative example, based on its weight, contains 60% modified Y molecular sieve, 20% alumina, 4% NiO, and 16% WO3, and is designated as C-2; the specific surface area of ​​the hydrocracking catalyst is 438 m². 2 / g, pore volume 0.35cm 3 / g.

[0078] Comparative Example 3 The preparation steps of the hydrocracking catalyst are the same as in Example 3, except that La-USY was prepared by impregnating commercially available USY molecular sieves with La element using an equal-volume impregnation method instead of La-USY heteroatom molecular sieves. The resulting La-USY molecular sieve has a traditional FAU octahedral morphology, an average particle size of 2.0 μm, and a specific surface area of ​​803 m². 2 / g, pore volume 0.40cm 3 / g, mesoporous content 30.5%, silicon-aluminum ratio (SiO2 / Al2O3 molar ratio) 14.4, based on weight, the Na2O mass content in the La-USY molecular sieve is 0.02%, the pyridine infrared acid content in the USY molecular sieve is 0.933mmol / g, of which the B acid / L acid ratio is 3.5, and the proportion of medium strong acid is 65.5%.

[0079] The hydrocracking catalyst provided in this embodiment, based on its weight, contains 50% La-USY heteroatom molecular sieve, 34% alumina, 3% NiO, and 13% WO3, and is designated as C-3; the specific surface area of ​​the hydrocracking catalyst is 416 m². 2 / g, pore volume 0.37cm 3 / g.

[0080] Evaluation Example 1 The hydrocracking catalysts prepared in the examples and the catalysts in the comparative examples were successively tested in a small fixed-bed device for catalytic diesel hydrocracking evaluation. The properties of the feedstocks are shown in Table 1. The evaluation device adopted a single-stage series one-pass process flow. The first reactor was loaded with conventional refined catalyst, and the second reactor was loaded with hydrocracking catalyst. The specific process conditions and evaluation results are shown in Table 2.

[0081] Table 1 Properties of Catalytic Diesel Feedstock

[0082] Table 2 Evaluation results of the hydrocracking catalyst of the present invention

Claims

1. A high-aromatic-content catalytic diesel hydrocracking catalyst, characterized in that: The hydrocracking catalyst contains 40wt%-70wt%, preferably 50wt%-60wt% of La-Y heteroatom molecular sieves, based on its weight.

2. The hydrocracking catalyst according to claim 1, characterized in that: The SiO2 / Al2O3 molar ratio of the La-Y heteroatom molecular sieve is 5.0-20.0, preferably 8.0-15.0; the mass content of La heteroatoms, calculated as oxides, is ≤5.0%, preferably ≤3.0%, and more preferably 0.5-2%; the mass content of Na2O is ≤0.5%, preferably ≤0.3%.

3. The hydrocracking catalyst according to claim 1, characterized in that: The La-Y heteroatom molecular sieve exhibits a layered morphology formed by stacking plate-like molecular sieves, with a single layer of plate-like molecular sieve having a thickness of less than 200 nm, preferably less than 150 nm, and more preferably 60 nm-120 nm.

4. The hydrocracking catalyst according to claim 1, characterized in that: The hydrocracking catalyst contains, by weight, 10wt%-25wt%, preferably 15wt%-20wt% of hydrocracking active metal oxides.

5. The hydrocracking catalyst according to claim 1, characterized in that: The hydrogenation active metal is selected from Group VIII and / or Group VIB metals, wherein the Group VIII metal is Ni and / or Co, and the Group VIB metal is W and / or Mo. Based on the weight of the catalyst, the mass content of Group VIII metals, calculated as metal oxides, is 2%-8%, preferably 3%-5%, and the mass content of Group VIB metals, calculated as metal oxides, is 10%-20%, preferably 12%-15%.

6. The hydrocracking catalyst according to claim 1, characterized in that: The hydrocracking catalyst contains 20wt%-50wt%, preferably 25wt%-40wt% γ-alumina, based on its weight.

7. The hydrocracking catalyst according to claim 1, characterized in that: The specific surface area of ​​the hydrocracking catalyst is 350 m². 2 / g-500m 2 / g, preferably 400m 2 / g-450m 2 / g, pore volume 0.30cm 3 / g-0.40cm 3 / g, preferably 0.33cm 3 / g-0.37cm 3 / g.

8. The method for preparing any one of the hydrocracking catalysts according to claims 1-7, characterized in that: The method includes preparing a hydrocracking catalyst by mixing La-Y heteroatom molecular sieve, γ-alumina and hydrogenation active metal, or preparing a hydrocracking catalyst by first shaping La-Y heteroatom molecular sieve and γ-alumina and then loading hydrogenation active metal.

9. The method according to claim 8, characterized in that: The preparation method of hydrocracking catalyst includes the following: (1) Mix La-Y heteroatom molecular sieve, γ-alumina and hydrogenated active metal in a certain proportion, and then add a peptizing solvent to the mixture to make a slurry for kneading and extrusion molding; (2) The extruded product obtained in step (1) is dried and calcined to obtain a hydrocracking catalyst.

10. The method according to claim 9, characterized in that: The La-Y heteroatom molecular sieve in step (1) is prepared by the following method: (a) Ammonium ion exchange on lamellar Y molecular sieves; (b) Perform hydrothermal treatment on the material obtained in step (a); (c) The material obtained in step (b) is processed by a mixed solution of ammonium fluorosilicate and La metal precursor, and then filtered, washed, dried and calcined to obtain La-Y heteroatom molecular sieve.

11. The hydrocracking catalyst of any one of claims 1-7 is applied to the process of preparing light aromatics BTX by hydrocracking of high aromatic content catalytic diesel.

12. The application according to claim 11, characterized in that: The properties of the high aromatic content catalytic diesel are as follows: the density (20℃) of the catalytic diesel ranges from 0.85 g / cm³. 3 -0.98g / cm 3 The preferred value is 0.90 g / cm³. 3 -0.97g / cm 3 The distillation range is 150℃-380℃, preferably 180℃-370℃; the alkanes are 8wt.%-18wt.%, the cycloalkanes are 5wt.%-16wt.%, and the aromatics are 70wt.%-85wt.%.

13. The application according to claim 11, characterized in that: The reaction conditions are as follows: (i) After the catalytic diesel is mixed with hydrogen, it enters the hydrorefining reaction zone and reacts with the hydrorefining catalyst bed to obtain hydrorefined product oil and gas products; (ii) The obtained hydrorefined product oil and gas products enter the hydrocracking reaction zone and react with the La-Y heteroatom molecular sieve-based hydrocracking catalyst. The reaction effluent obtained from the hydrocracking reaction is separated into gas and liquid and fractionated to obtain gas, naphtha and tail oil.

14. The application according to claim 13, characterized in that: The properties of the hydrorefined oil obtained after hydrorefining the catalytic diesel in step (i) are as follows: nitrogen content <40ppm, preferably 10-30ppm; sulfur content <200ppm, preferably <100ppm; aromatics retention rate of the hydrorefined oil >90wt.%.

15. The application according to claim 13, characterized in that: The reaction conditions in the hydrocracking reaction zone in step (ii) are as follows: reaction pressure 5 MPa-10 MPa, preferably 6 MPa-8 MPa; reaction temperature 360℃-420℃, preferably 390℃-410℃; and hydrocracking catalyst volume hourly space velocity 1.0 h⁻¹. -1 -3.0h -1 The hydrogen-to-oil volume ratio is 500-1500, preferably 800-1200.

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