A hydrocracking catalyst carrier and a method for preparing the same

Abstract

This invention relates to the field of hydrocracking catalysis technology, and discloses a hydrocracking catalyst support and its preparation method. The invention uses hexadecyltrimethylammonium bromide as a soft template, and grows a silica isolation layer in situ on the surface of a molecular sieve via the hydrolysis and condensation of tetraethyl orthosilicate to prepare a modified USY molecular sieve. Subsequently, the modified USY molecular sieve is mixed with boehmite, extruded, and calcined at high temperature to obtain the support. During high-temperature calcination, the silica isolation layer in the support effectively blocks the solid-phase diffusion path of active aluminum atoms from the alumina matrix to the molecular sieve surface, inhibits the formation of amorphous and non-selective strongly acidic species at the interface between the molecular sieve and alumina phases, reduces random over-cracking and aromatic condensation side reactions, and significantly improves the selectivity of middle distillate oil in the hydrocracking reaction.

Description

Technical Field

[0001] This invention relates to the field of hydrocracking catalysis technology, and more specifically, to a hydrocracking catalyst support and its preparation method. Background Technology

[0002] Hydrocracking is mainly used for the deep processing of heavy oil and the production of clean middle distillate oils. It can convert heavy distillate oils into high-value-added products such as aviation kerosene and diesel oil under the action of hydrogen and catalysts. Hydrocracking catalysts are typical bifunctional catalysts. The support plays a key role in providing acidic cracking centers, dispersing hydrogenation active metals, and constructing reaction mass transfer channels, which directly determines the catalyst's reactivity, product selectivity, and operational stability.

[0003] Currently, industrial hydrocracking catalyst supports generally use Y-type molecular sieves as the core component for acid cracking, and γ-Al₂O₃ generated by calcining boehmite as a binder and matrix component. The catalysts are prepared by mixing, extruding, and then calcining at high temperatures. High-temperature calcination is a necessary step in the preparation of the support, which decrystalline aluminum hydroxide into γ-Al₂O₃ with a certain strength, while simultaneously removing molding aids and enhancing the mechanical strength of the support.

[0004] However, during the high-temperature calcination process at 500-600℃, a large number of unsaturated coordinated active aluminum atoms exist on the surface of γ-Al₂O₃. These atoms can migrate to the outer surface of the Y-zeolite via solid-phase diffusion and undergo bonding reactions with the silanol groups (Si-OH) on the zeolite surface, generating a large number of amorphous aluminosilicate species at the zeolite-alumina interface. These amorphous species lack the regular pore structure of zeolite crystals, have no shape-selective catalytic ability, and their acidity is dominated by strong Lewis acid centers. Their acid strength and properties differ from the Br₂ framework of the zeolite bulk. nsted acid center.

[0005] These acidic sites are not confined by the molecular sieve channels, which can trigger irregular and excessive cracking reactions, leading to an increase in the content of low-value light hydrocarbons in the cracking products and a decrease in the selectivity of middle distillate oils. Moreover, strong Lewis acid centers can catalyze the condensation reaction of polycyclic aromatic hydrocarbons, accelerate the formation and deposition of coke precursors, cause catalyst channel blockage and coverage of active sites, and accelerate the deactivation rate of the catalyst.

[0006] Therefore, the present invention proposes a hydrocracking catalyst support and its preparation method, which has important practical significance. Summary of the Invention

[0007] In view of this, the present invention proposes a method for preparing a hydrocracking catalyst support, which solves the problem of interfacial aluminum-silicon interdiffusion and generation of non-selective amorphous strong acidic species during the high-temperature calcination of molecular sieves and alumina in the preparation of hydrocracking supports in existing methods.

[0008] This invention proposes a method for preparing a hydrocracking catalyst support, comprising the following steps: NaY molecular sieve powder was added to ammonium nitrate solution for an exchange reaction to obtain ammonium-exchangeable Y molecular sieve. The ammonium-exchangeable Y molecular sieve was subjected to hydrothermal treatment. After the treatment, dilute hydrochloric acid solution was added and stirred. Then, the mixture was filtered, washed and dried to obtain USY molecular sieve. The USY molecular sieve was ultrasonically dispersed in an ethanol-water solution to obtain a molecular sieve suspension. Hexadecyltrimethylammonium bromide was added to the molecular sieve suspension for a first stirring reaction. After the reaction, the pH of the system was adjusted to between 9 and 9.4. Then, tetraethyl orthosilicate-ethanol dilution was added for a second stirring reaction. After the reaction, the solid product was separated by centrifugation, washed, dried, and then calcined to obtain a modified USY molecular sieve with a SiO2 isolation layer. The modified USY molecular sieve coated with SiO2 isolation layer is mixed with pseudoboehmite powder, guar gum powder is added and mixed further, and then dilute nitric acid solution is added for kneading to obtain a paste material. The paste material is extruded and then post-processed to obtain the hydrocracking catalyst support.

[0009] Furthermore, the exchange reaction specifically involves adding the NaY molecular sieve powder to a 1 mol / L ammonium nitrate solution at a solid-liquid ratio of 1 g to 10 ml, stirring and exchanging at 90°C for 2 h, filtering and washing, repeating the exchange reaction twice, and then drying the product at 120°C for 4 h.

[0010] Furthermore, the hydrothermal treatment temperature is 600℃, and the treatment time is 4 hours.

[0011] Furthermore, the first stirring reaction specifically involves adding 18% by mass of the USY molecular sieve, along with cetyltrimethylammonium bromide, to the molecular sieve suspension and stirring at 40°C for 30 minutes.

[0012] Furthermore, the second stirring reaction specifically involves: maintaining the system at a constant temperature of 45°C, and adding a tetraethyl orthosilicate-ethanol diluent dropwise at a stirring speed of 250 r / min at a rate of 0.2 mL / min. The volume ratio of tetraethyl orthosilicate to anhydrous ethanol in the tetraethyl orthosilicate-ethanol diluent is 1:2. The mass of tetraethyl orthosilicate added is controlled to be 10% of the mass of the USY molecular sieve. After the addition is completed, the temperature is maintained at 45°C and the stirring speed is maintained at 250 r / min for 6 hours.

[0013] Furthermore, the calcination temperature of the calcination treatment is 550℃, the heating rate is 1℃ / min, and the calcination time is 4h.

[0014] Furthermore, the mass ratio of the modified USY molecular sieve coated with the SiO2 isolation layer to the pseudoboehmite powder is (55~75):(25~45).

[0015] Furthermore, the mass of the guar gum powder is 3% of the total mass of the modified USY molecular sieve coated with a SiO2 isolation layer and the pseudoboehmite powder; The dilute nitric acid solution comprises 5% of the total mass of the modified USY molecular sieve coated with a SiO2 isolation layer and pseudoboehmite powder, and the concentration of the dilute nitric acid solution is 0.5 mol / L.

[0016] Furthermore, the post-processing specifically involves: air-drying the extruded material at room temperature for 2 hours, drying it at 120°C for 6 hours, and then heating it to 580°C at a rate of 2°C / min and calcining it at a constant temperature for 4 hours.

[0017] The present invention also provides a hydrocracking catalyst support as described above.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. In this invention, USY molecular sieves are first treated with tetraethyl orthosilicate-ethanol dilution to form a silica isolation layer on the surface of the USY molecular sieves. Then, the modified USY molecular sieves are mixed with boehmite binder, extruded into strips, and calcined at high temperature to prepare a hydrocracking catalyst support. During the high-temperature calcination process, the silica isolation layer can effectively block the solid-phase diffusion path of active aluminum atoms in the alumina matrix to the surface of the molecular sieve, inhibit the formation of non-selective amorphous strong acid species at the interface between the molecular sieve and alumina phases, reduce irregular over-cracking and aromatic condensation side reactions, and significantly improve the selectivity of middle distillate oil in hydrocracking reaction. Detailed Implementation

[0019] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0020] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0021] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0022] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0023] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0024] This invention provides a method for preparing a hydrocracking catalyst support, comprising the following steps: NaY molecular sieve powder was added to ammonium nitrate solution for an exchange reaction to obtain ammonium-exchangeable Y molecular sieve. The ammonium-exchangeable Y molecular sieve was subjected to hydrothermal treatment. After the treatment, dilute hydrochloric acid solution was added and stirred. Then, the mixture was filtered, washed and dried to obtain USY molecular sieve. The USY molecular sieve was ultrasonically dispersed in an ethanol-water solution to obtain a molecular sieve suspension. Hexadecyltrimethylammonium bromide was added to the molecular sieve suspension for a first stirring reaction. After the reaction, the pH of the system was adjusted to between 9 and 9.4. Then, tetraethyl orthosilicate-ethanol dilution was added for a second stirring reaction. After the reaction, the solid product was separated by centrifugation, washed, dried, and then calcined to obtain a modified USY molecular sieve with a SiO2 isolation layer. The modified USY molecular sieve coated with SiO2 isolation layer is mixed with pseudoboehmite powder, guar gum powder is added and mixed further, and then dilute nitric acid solution is added for kneading to obtain a paste material. The paste material is extruded and then post-processed to obtain the hydrocracking catalyst support.

[0025] Specifically, the silicon-aluminum molar ratio in the NaY molecular sieve raw powder is 5.

[0026] Understandably, this invention first treats the USY molecular sieve with a tetraethyl orthosilicate-ethanol diluent to form a silica isolation layer on the surface of the USY molecular sieve. Then, the modified USY molecular sieve is mixed with a pseudoboehmite binder, extruded into strips, and calcined at high temperature to prepare a hydrocracking catalyst support. During the high-temperature calcination process, the silica isolation layer can effectively block the solid-phase diffusion path of active aluminum atoms in the alumina matrix to the surface of the molecular sieve, inhibit the formation of non-selective amorphous strong acid species at the interface between the molecular sieve and alumina phases, reduce irregular over-cracking and aromatic condensation side reactions, and significantly improve the selectivity of the middle distillate oil in the hydrocracking reaction.

[0027] In this invention, the exchange reaction specifically refers to: The NaY molecular sieve raw powder was added to a 1 mol / L ammonium nitrate solution at a solid-liquid ratio of 1 g to 10 ml. After stirring and exchanging the mixture at 90 °C for 2 h, the mixture was filtered and washed. The exchange process was repeated twice. The product was then dried at 120 °C for 4 h.

[0028] Specifically, the NaY molecular sieve raw powder was added to a 1 mol / L ammonium nitrate solution according to a solid-liquid ratio of NaY molecular sieve raw powder: ammonium nitrate solution = 1 g: 10 ml. After stirring and exchanging at 90 °C for 2 h, the mixture was filtered and washed until no nitrate ions were detected in the filtrate. This process was repeated twice, and the product was dried at 120 °C for 4 h to obtain ammonium exchange Y molecular sieve.

[0029] Understandably, the ammonium ions in the ammonium nitrate solution undergo a cation exchange reaction with the sodium ions in the NaY molecular sieve powder, replacing the sodium ions with ammonium ions to remove sodium from the molecular sieve and prevent residual sodium ions from damaging the molecular sieve framework structure and reducing hydrothermal stability during subsequent high-temperature hydrothermal treatment. Simultaneously, after subsequent high-temperature treatment, the ammonium ions decompose to release hydrogen protons, forming a catalytically active framework Br. The acidic centers of nsted can be repeatedly exchanged to ensure sufficient ion exchange depth.

[0030] In this invention, the hydrothermal treatment temperature is 600°C and the treatment time is 4 hours.

[0031] Specifically, the ammonium-exchange Y molecular sieve was placed in a tubular hydrothermal furnace, and 100% saturated steam was introduced. The mixture was hydrothermally treated at 600°C for 4 hours. After the hydrothermal treatment, the product was added to a 0.3 mol / L dilute hydrochloric acid solution at a solid-liquid ratio of 1 g: 15 mL. The mixture was stirred at 90°C for 2 hours. The mixture was then filtered and washed until the pH of the filtrate was neutral. Finally, the mixture was dried at 120°C for 4 hours to obtain the USY molecular sieve.

[0032] Understandably, under high-temperature saturated steam conditions, ammonium ions in the ammonium-exchange Y molecular sieve decompose upon heating, releasing hydrogen protons. Simultaneously, the molecular sieve framework undergoes a dealumination reaction and silicon atom migration and rearrangement. Some framework aluminum detaches from the framework to form non-framework aluminum species, and silicon atoms fill the framework vacancies created by dealumination, increasing the framework silicon-to-aluminum ratio and causing cell shrinkage, thus forming the USY molecular sieve. This significantly improves the framework hydrothermal stability and structural thermal stability of the molecular sieve, while simultaneously regulating Br. The number of nsted acid centers is related to the acid strength.

[0033] In this invention, the first stirring reaction specifically comprises: Add 18% by mass of hexadecyltrimethylammonium bromide of the USY molecular sieve to the molecular sieve suspension and stir at 40°C for 30 min.

[0034] Specifically, the USY molecular sieve was added to a 70% volume fraction of ethanol aqueous solution at a solid-liquid ratio of 1g:50mL and ultrasonically dispersed for 30min to obtain a molecular sieve suspension. 18% by mass of hexadecyltrimethylammonium bromide of USY molecular sieve was added to the molecular sieve suspension and stirred at 40℃ for 30min.

[0035] Understandably, the use of an ethanol-water solution followed by ultrasonic dispersion treatment allows the USY molecular sieve particles to be fully deagglomerated and uniformly dispersed in the system, eliminating particle agglomeration and ensuring that the outer surface of the molecular sieve is fully exposed. Subsequently, the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) is added and stirred at a constant temperature, allowing CTAB to be uniformly adsorbed onto the outer surface of the molecular sieve particles through electrostatic interaction, forming ordered micelle assemblies as soft templates.

[0036] In this invention, the second stirring reaction specifically comprises: Maintain a constant temperature of 45℃ in the system, and add tetraethyl orthosilicate-ethanol diluent dropwise at a stirring speed of 250 r / min at a rate of 0.2 mL / min. The volume ratio of tetraethyl orthosilicate to anhydrous ethanol in the tetraethyl orthosilicate-ethanol diluent is 1:2. The mass of tetraethyl orthosilicate added is controlled to be 10% of the mass of USY molecular sieve. After the addition is completed, maintain the temperature of 45℃ and the stirring speed of 250 r / min and continue stirring for 6 h.

[0037] Specifically, the pH of the system was adjusted to between 9 and 9.4 using 25% ammonia water. The system was then heated to 45°C and kept at a constant temperature. While stirring at 250 r / min, a tetraethyl orthosilicate-ethanol dilution was added dropwise at a rate of 0.2 mL / min. The volume ratio of tetraethyl orthosilicate to anhydrous ethanol in the tetraethyl orthosilicate-ethanol dilution was 1:2. The mass of tetraethyl orthosilicate added was controlled to be 10% of the mass of the USY molecular sieve. After the addition was completed, the temperature was maintained at 45°C and the stirring speed at 250 r / min for 6 hours. After the reaction was completed, the solid product was separated by centrifugation.

[0038] Understandably, adjusting the system to a weakly alkaline environment and maintaining a constant reaction temperature with ammonia provides suitable catalytic conditions for the hydrolysis and condensation reaction of tetraethyl orthosilicate. Subsequently, the silicon source supply rate is controlled by slowly and uniformly adding tetraethyl orthosilicate-ethanol diluent, ensuring that the system maintains a low silicon source concentration. This drives the silicon-oxygen precursor generated by hydrolysis to preferentially undergo heterogeneous nucleation and condensation growth on the outer surface of the molecular sieve with adsorbed CTAB soft template, avoiding the formation of free silica particles within the system. This results in a uniformly thick and completely coated silica precursor isolation layer on the surface of the molecular sieve.

[0039] In this invention, the calcination temperature is 550°C, the heating rate is 1°C / min, and the calcination time is 4h.

[0040] Specifically, the solid product was washed three times with anhydrous ethanol to remove residual template agent and unreacted raw materials, dried at 120°C for 6 hours, and then heated to 550°C in a muffle furnace at a rate of 1°C / min and calcined at a constant temperature for 4 hours to remove the CTAB template agent, thereby obtaining the modified USY molecular sieve coated with a SiO2 isolation layer.

[0041] Understandably, the solid product is separated by centrifugation, and the unreacted silicon source, free template agent and impurity ions remaining on the surface of the molecular sieve are removed by washing with anhydrous ethanol multiple times. Then, the solvent and adsorbed water in the system are removed by drying. Subsequently, the CTAB soft template is slowly decomposed and completely removed by slow heating and calcination. At the same time, the silica precursor is further promoted to undergo silanol condensation reaction to form a pure silica layer with a stable framework.

[0042] In this invention, the mass ratio of the modified USY molecular sieve coated with SiO2 isolation layer to pseudoboehmite powder is (55~75):(25~45).

[0043] Specifically, the preferred mass ratio of the modified USY molecular sieve coated with the SiO2 isolation layer to the pseudo-boehmite powder is 65:35.

[0044] In this invention, the mass of the guar gum powder is 3% of the total mass of the modified USY molecular sieve coated with a SiO2 isolation layer and the pseudoboehmite powder; The dilute nitric acid solution comprises 5% of the total mass of the modified USY molecular sieve coated with a SiO2 isolation layer and pseudoboehmite powder, and the concentration of the dilute nitric acid solution is 0.5 mol / L.

[0045] Specifically, the modified USY molecular sieve with SiO2 isolation layer and pseudoboehmite powder are placed in a kneader and mixed dry for 10 min at a mass ratio of (55~75):(25~45). Then, guar gum powder (3% of the total mass of the modified USY molecular sieve with SiO2 isolation layer and pseudoboehmite powder) is added and mixed for another 5 min. Finally, 0.5 mol / L dilute nitric acid solution (5% of the total mass of the modified USY molecular sieve with SiO2 isolation layer and pseudoboehmite powder) is added and kneaded for 15 min to obtain a paste material.

[0046] Understandably, guar gum powder, as an extrusion aid, can improve the plasticity and lubricity of the material, reduce the resistance of subsequent extrusion molding, and reduce cracking defects in the molded body. At the same time, it can remove pores during the subsequent calcination process, and help regulate the pore structure and porosity of the carrier. Dilute nitric acid, as a colloidal solvent, can promote the colloidal reaction of boehmite, dissociate it into a binding aluminum sol component, form a bonding bridge between molecular sieve particles, significantly improve the mechanical strength of the carrier after molding, and at the same time, nitric acid can regulate the rheological properties of the material, so that after sufficient kneading, the material can form a paste with suitable plasticity.

[0047] In this invention, the post-processing specifically involves: air-drying the extruded material at room temperature for 2 hours, drying it at 120°C for 6 hours, and then heating it to 580°C at a rate of 2°C / min and calcining it at a constant temperature for 4 hours.

[0048] Specifically, the paste material is fed into a twin-screw extruder and extruded into cylindrical strips with a diameter of 1.8 mm. After being air-dried at room temperature for 2 hours, it is placed in a 120°C oven for 6 hours. Then, it is transferred to a muffle furnace and heated to 580°C at a rate of 2°C / min. It is then calcined at a constant temperature for 4 hours and then naturally cooled.

[0049] Understandably, slow air drying at room temperature removes free moisture from the surface of the wet strips, avoiding uneven surface shrinkage and cracking caused by rapid drying, thus ensuring the appearance and internal structural integrity of the molded body. Oven drying at 120℃ further removes adsorbed water and residual solvents from the material, allowing the green body to initially solidify and shape, stabilizing the precursor skeleton structure for subsequent high-temperature calcination. Subsequently, the temperature is programmed to rise to 580℃ at a rate of 2℃ / min for constant-temperature calcination. The gradual heating rate avoids pore collapse and carrier breakage caused by the rapid decomposition and volatilization of components such as guar gum powder and nitrate. During the constant-temperature process, organic extrusion aids and residual adhesives can be completely decomposed and removed. The pores formed by the escape of components help regulate the pore structure and pore distribution of the carrier. It also promotes the dehydration phase transformation of boehmite into a γ-alumina binder phase, building a stable binder skeleton between molecular sieve particles, significantly improving the mechanical strength and structural stability of the carrier.

[0050] The present invention also proposes a hydrocracking catalyst support.

[0051] Example 1 S1. Add the NaY molecular sieve raw powder to a 1 mol / L ammonium nitrate solution according to the solid-liquid ratio of NaY molecular sieve raw powder: ammonium nitrate solution = 1 g: 10 ml. Stir and exchange at 90 °C for 2 h, then filter and wash until no nitrate ions are detected in the filtrate. Repeat twice and then dry the product at 120 °C for 4 h to obtain ammonium exchange Y molecular sieve. S2. The ammonium-exchange Y molecular sieve was placed in a tubular hydrothermal furnace and 100% saturated steam was introduced. The mixture was hydrothermally treated at 600°C for 4 hours. After the hydrothermal treatment, the product was added to a 0.3 mol / L dilute hydrochloric acid solution at a solid-liquid ratio of 1 g: 15 mL. The mixture was stirred at 90°C for 2 hours. The mixture was then filtered and washed until the pH of the filtrate was neutral. Finally, the mixture was dried at 120°C for 4 hours to obtain the USY molecular sieve. S3. The USY molecular sieve was added to a 70% (v / v) ethanol aqueous solution at a solid-liquid ratio of 1g:50mL and ultrasonically dispersed for 30min to obtain a molecular sieve suspension. 18% (w / w) of hexadecyltrimethylammonium bromide of USY molecular sieve was added to the molecular sieve suspension, and the mixture was stirred at 40℃ for 30min. The pH of the system was adjusted to between 9 and 9.4 with 25% (w / w) ammonia water. The system was heated to 45℃ and kept at a constant temperature. At a stirring speed of 250r / min, tetraethyl orthosilicate-ethanol dilution was added dropwise at 0.2mL / min. The volume ratio of tetraethyl orthosilicate to anhydrous ethanol in the tetraethyl orthosilicate-ethanol dilution was 1:2. The mass of tetraethyl orthosilicate added was controlled to be 10% of the mass of USY molecular sieve. After the addition was completed, the temperature was maintained at 45℃ and the stirring speed at 250r / min and the stirring was continued for 6h. After the reaction was completed, the solid product was separated by centrifugation.

[0052] S4. The solid product was washed three times with anhydrous ethanol to remove residual template agent and unreacted raw materials, dried at 120℃ for 6h, and then heated to 550℃ in a muffle furnace at a rate of 1℃ / min and calcined at a constant temperature for 4h to remove CTAB template agent, thereby obtaining modified USY molecular sieve coated with SiO2 isolation layer. S5. The modified USY molecular sieve with SiO2 isolation layer and pseudoboehmite powder are put into a kneader and mixed dry for 10 min at a mass ratio of 55:45. Then, guar gum powder (3% of the total mass of the modified USY molecular sieve with SiO2 isolation layer and pseudoboehmite powder) is added and mixed for another 5 min. Then, 0.5 mol / L dilute nitric acid solution (5% of the total mass of the modified USY molecular sieve with SiO2 isolation layer and pseudoboehmite powder) is added and kneaded for 15 min to obtain a paste material. S6. The paste material is fed into a twin-screw extruder and extruded into cylindrical strips with a diameter of 1.8 mm. After being air-dried at room temperature for 2 hours, it is placed in a 120°C oven for 6 hours. Then it is transferred to a muffle furnace and heated to 580°C at a rate of 2°C / min. It is then calcined at a constant temperature for 4 hours and then naturally cooled to obtain a hydrocracking catalyst support.

[0053] Example 2 S1. Add the NaY molecular sieve raw powder to a 1 mol / L ammonium nitrate solution according to the solid-liquid ratio of NaY molecular sieve raw powder: ammonium nitrate solution = 1 g: 10 ml. Stir and exchange at 90 °C for 2 h, then filter and wash until no nitrate ions are detected in the filtrate. Repeat twice and then dry the product at 120 °C for 4 h to obtain ammonium exchange Y molecular sieve. S2. The ammonium-exchange Y molecular sieve was placed in a tubular hydrothermal furnace and 100% saturated steam was introduced. The mixture was hydrothermally treated at 600°C for 4 hours. After the hydrothermal treatment, the product was added to a 0.3 mol / L dilute hydrochloric acid solution at a solid-liquid ratio of 1 g: 15 mL. The mixture was stirred at 90°C for 2 hours. The mixture was then filtered and washed until the pH of the filtrate was neutral. Finally, the mixture was dried at 120°C for 4 hours to obtain the USY molecular sieve. S3. The USY molecular sieve was added to a 70% (v / v) ethanol aqueous solution at a solid-liquid ratio of 1g:50mL and ultrasonically dispersed for 30min to obtain a molecular sieve suspension. 18% (w / w) of hexadecyltrimethylammonium bromide of USY molecular sieve was added to the molecular sieve suspension, and the mixture was stirred at 40℃ for 30min. The pH of the system was adjusted to between 9 and 9.4 with 25% (w / w) ammonia water. The system was heated to 45℃ and kept at a constant temperature. At a stirring speed of 250r / min, tetraethyl orthosilicate-ethanol dilution was added dropwise at 0.2mL / min. The volume ratio of tetraethyl orthosilicate to anhydrous ethanol in the tetraethyl orthosilicate-ethanol dilution was 1:2. The mass of tetraethyl orthosilicate added was controlled to be 10% of the mass of USY molecular sieve. After the addition was completed, the temperature was maintained at 45℃ and the stirring speed at 250r / min and the stirring was continued for 6h. After the reaction was completed, the solid product was separated by centrifugation.

[0054] S4. The solid product was washed three times with anhydrous ethanol to remove residual template agent and unreacted raw materials, dried at 120℃ for 6h, and then heated to 550℃ in a muffle furnace at a rate of 1℃ / min and calcined at a constant temperature for 4h to remove CTAB template agent, thereby obtaining modified USY molecular sieve coated with SiO2 isolation layer. S5. The modified USY molecular sieve with SiO2 isolation layer and pseudoboehmite powder are placed in a kneader and mixed dry for 10 min at a mass ratio of 65:35. Then, guar gum powder (3% of the total mass of the modified USY molecular sieve with SiO2 isolation layer and pseudoboehmite powder) is added and mixed for another 5 min. Finally, 0.5 mol / L dilute nitric acid solution (5% of the total mass of the modified USY molecular sieve with SiO2 isolation layer and pseudoboehmite powder) is added and kneaded for 15 min to obtain a paste material. S6. The paste material is fed into a twin-screw extruder and extruded into cylindrical strips with a diameter of 1.8 mm. After being air-dried at room temperature for 2 hours, it is placed in a 120°C oven for 6 hours. Then it is transferred to a muffle furnace and heated to 580°C at a rate of 2°C / min. It is then calcined at a constant temperature for 4 hours and then naturally cooled to obtain a hydrocracking catalyst support.

[0055] Example 3 S1. Add the NaY molecular sieve raw powder to a 1 mol / L ammonium nitrate solution according to the solid-liquid ratio of NaY molecular sieve raw powder: ammonium nitrate solution = 1 g: 10 ml. Stir and exchange at 90 °C for 2 h, then filter and wash until no nitrate ions are detected in the filtrate. Repeat twice and then dry the product at 120 °C for 4 h to obtain ammonium exchange Y molecular sieve. S2. The ammonium-exchange Y molecular sieve was placed in a tubular hydrothermal furnace and 100% saturated steam was introduced. The mixture was hydrothermally treated at 600°C for 4 hours. After the hydrothermal treatment, the product was added to a 0.3 mol / L dilute hydrochloric acid solution at a solid-liquid ratio of 1 g: 15 mL. The mixture was stirred at 90°C for 2 hours. The mixture was then filtered and washed until the pH of the filtrate was neutral. Finally, the mixture was dried at 120°C for 4 hours to obtain the USY molecular sieve. S3. The USY molecular sieve was added to a 70% (v / v) ethanol aqueous solution at a solid-liquid ratio of 1g:50mL and ultrasonically dispersed for 30min to obtain a molecular sieve suspension. 18% (w / w) of hexadecyltrimethylammonium bromide of USY molecular sieve was added to the molecular sieve suspension, and the mixture was stirred at 40℃ for 30min. The pH of the system was adjusted to between 9 and 9.4 with 25% (w / w) ammonia water. The system was heated to 45℃ and kept at a constant temperature. At a stirring speed of 250r / min, tetraethyl orthosilicate-ethanol dilution was added dropwise at 0.2mL / min. The volume ratio of tetraethyl orthosilicate to anhydrous ethanol in the tetraethyl orthosilicate-ethanol dilution was 1:2. The mass of tetraethyl orthosilicate added was controlled to be 10% of the mass of USY molecular sieve. After the addition was completed, the temperature was maintained at 45℃ and the stirring speed at 250r / min and the stirring was continued for 6h. After the reaction was completed, the solid product was separated by centrifugation.

[0056] S4. The solid product was washed three times with anhydrous ethanol to remove residual template agent and unreacted raw materials, dried at 120℃ for 6h, and then heated to 550℃ in a muffle furnace at a rate of 1℃ / min and calcined at a constant temperature for 4h to remove CTAB template agent, thereby obtaining modified USY molecular sieve coated with SiO2 isolation layer. S5. The modified USY molecular sieve with SiO2 isolation layer and pseudoboehmite powder are put into a kneader and mixed dry for 10 min at a mass ratio of 75:25. Then, guar gum powder (3% of the total mass of the modified USY molecular sieve with SiO2 isolation layer and pseudoboehmite powder) is added and mixed for another 5 min. Then, 0.5 mol / L dilute nitric acid solution (5% of the total mass of the modified USY molecular sieve with SiO2 isolation layer and pseudoboehmite powder) is added and kneaded for 15 min to obtain a paste material. S6. The paste material is fed into a twin-screw extruder and extruded into cylindrical strips with a diameter of 1.8 mm. After being air-dried at room temperature for 2 hours, it is placed in a 120°C oven for 6 hours. Then it is transferred to a muffle furnace and heated to 580°C at a rate of 2°C / min. It is then calcined at a constant temperature for 4 hours and then naturally cooled to obtain a hydrocracking catalyst support.

[0057] Comparative Example 1 S1. Add the NaY molecular sieve raw powder to a 1 mol / L ammonium nitrate solution according to the solid-liquid ratio of NaY molecular sieve raw powder: ammonium nitrate solution = 1 g: 10 ml. Stir and exchange at 90 °C for 2 h, then filter and wash until no nitrate ions are detected in the filtrate. Repeat twice and then dry the product at 120 °C for 4 h to obtain ammonium exchange Y molecular sieve. S2. The ammonium-exchange Y molecular sieve was placed in a tubular hydrothermal furnace and 100% saturated steam was introduced. The mixture was hydrothermally treated at 600°C for 4 hours. After the hydrothermal treatment, the product was added to a 0.3 mol / L dilute hydrochloric acid solution at a solid-liquid ratio of 1 g: 15 mL. The mixture was stirred at 90°C for 2 hours. The mixture was then filtered and washed until the pH of the filtrate was neutral. Finally, the mixture was dried at 120°C for 4 hours to obtain the USY molecular sieve. S3. The USY molecular sieve and pseudoboehmite powder are placed in a kneader at a mass ratio of 65:35 and mixed dry for 10 min. Then, 3% of the total mass of the mixed molecular sieve and pseudoboehmite powder is added and the mixture is continued for 5 min. Finally, 5% of the total mass of the mixed molecular sieve and pseudoboehmite powder is added and the mixture is kneaded for 15 min to obtain a paste material. S4. The paste material is fed into a twin-screw extruder and extruded into cylindrical strips with a diameter of 1.8 mm. After being air-dried at room temperature for 2 hours, it is placed in a 120°C oven for 6 hours. Then it is transferred to a muffle furnace and heated to 580°C at a rate of 2°C / min. It is then calcined at a constant temperature for 4 hours and then naturally cooled to obtain a hydrocracking catalyst support.

[0058] Comparative Example 2 S1. Add the NaY molecular sieve raw powder to a 1 mol / L ammonium nitrate solution according to the solid-liquid ratio of NaY molecular sieve raw powder: ammonium nitrate solution = 1 g: 10 ml. Stir and exchange at 90 °C for 2 h, then filter and wash until no nitrate ions are detected in the filtrate. Repeat twice and then dry the product at 120 °C for 4 h to obtain ammonium exchange Y molecular sieve. S2. The ammonium-exchange Y molecular sieve was placed in a tubular hydrothermal furnace and 100% saturated steam was introduced. The mixture was hydrothermally treated at 600°C for 4 hours. After the hydrothermal treatment, the product was added to a 0.3 mol / L dilute hydrochloric acid solution at a solid-liquid ratio of 1 g: 15 mL. The mixture was stirred at 90°C for 2 hours. The mixture was then filtered and washed until the pH of the filtrate was neutral. Finally, the mixture was dried at 120°C for 4 hours to obtain the USY molecular sieve. S3. The USY molecular sieve and fumed nano-SiO2 are mixed at a ratio of 9:1 to obtain a mixed molecular sieve. The mixed molecular sieve and boehmite powder are placed in a kneader at a mass ratio of 65:35 and mixed dry for 10 minutes. Then, 3% of the total mass of the mixed molecular sieve and boehmite powder is added to guar gum powder and the mixture is continued to be mixed for 5 minutes. Finally, 5% of the total mass of the mixed molecular sieve and boehmite powder is added to a 0.5 mol / L dilute nitric acid solution and the mixture is kneaded for 15 minutes to obtain a paste material. S4. The paste material is fed into a twin-screw extruder and extruded into cylindrical strips with a diameter of 1.8 mm. After being air-dried at room temperature for 2 hours, it is placed in a 120°C oven for 6 hours. Then it is transferred to a muffle furnace and heated to 580°C at a rate of 2°C / min. It is then calcined at a constant temperature for 4 hours and then naturally cooled to obtain a hydrocracking catalyst support.

[0059] Effect test 1. Carrier characterization test Test samples: Carriers prepared in Example 2, Comparative Example 1, and Comparative Example 2.

[0060] Test method: The Br content of the sample was determined using a pyridine adsorption infrared spectroscopy (Py-IR) instrument. The amounts of Brønsted acid (B acid) and Lewis acid (L acid) were measured and quantitatively calculated using spectra acquired at 200℃ and 350℃, respectively; a solid-state nuclear magnetic resonance spectrometer was used. 27 Al MAS NMR was used to determine the relative content of amorphous non-framework aluminum in the sample, characterizing the degree of aluminum-silicon interdiffusion at the interface.

[0061] The test results are shown in Table 1: Table 1. Acidity of different carriers and the structural characterization results of aluminum species

[0062] As shown in Table 1, compared with Comparative Example 1 without an isolation layer, the amount of strong L-acid in the carrier of Example 2 of the present invention decreased from 121 μmol / g to 52 μmol / g, a decrease of approximately 57%; the relative content of amorphous non-framework aluminum decreased from 21.3% to 6.8%, a reduction of 68%. This demonstrates that the pure SiO2 isolation layer grown in situ in the present invention can effectively block the solid-phase diffusion of alumina to aluminum atoms on the surface of the molecular sieve during high-temperature calcination, significantly inhibiting the formation of non-selective amorphous strong acidic species at the interface. Simultaneously, the total Brønsted acid content of the three groups of samples is similar, indicating that the isolation layer does not damage the framework acidic centers of the molecular sieve body, and the basic cracking activity remains unaffected.

[0063] 2. Catalytic performance test Test samples: Using the supports prepared in Example 2, Comparative Example 1 and Comparative Example 2 as the matrix, W-Ni hydrogenation active components were loaded by the equal volume impregnation method. The loading amount was 24% WO3 and 4% NiO by mass of oxides. After impregnation, the samples were dried at 120°C for 4 hours and calcined at 500°C for 3 hours to obtain the corresponding catalysts.

[0064] Test method: Performance evaluation was conducted using catalysts with different supports in a fixed-bed microreactor. The feedstock was vacuum gas oil (VGO). Key properties: density 0.921 g / cm³. 3(20℃), sulfur content 1.2wt%, nitrogen content 0.12wt%, distillation range 350~520℃. Reaction conditions: reaction temperature 380℃, reaction pressure 14MPa, hydrogen-to-oil volume ratio 1200:1, liquid hourly space velocity 1.0h. -1 After the device has been running stably for 24 hours, product samples are collected. The product fraction distribution is analyzed by simulated distillation. After 100 hours of continuous operation, the catalyst is taken out and the amount of carbon deposit is determined by thermogravimetric analysis (TG). The activity retention rate is calculated (the ratio of the conversion rate after 100 hours to the initial conversion rate).

[0065] The test results are shown in Table 2: Table 2. Hydrocracking Reaction Performance Results of Different Catalysts

[0066] As shown in Table 2, the initial conversion rates of the three catalyst groups were basically the same, indicating that the presence of the SiO2 isolation layer did not reduce the reaction activity. The middle distillate yield of Example 2 reached 62.5%, which was 5.8 percentage points higher than that of Comparative Example 1. At the same time, the yield of C1-C4 light hydrocarbons decreased from 10.6% to 7.3%, indicating that the random over-cracking side reactions at the interface were effectively suppressed, and the products were directionally distributed towards high-value middle distillate oil.

[0067] After 100 hours of continuous operation, the catalyst carbon deposition in Example 2 was only 2.18%, a decrease of 32.7% compared to Comparative Example 1; the activity retention rate reached 92.4%, an increase of 8.7 percentage points compared to Comparative Example 1. These results indicate that reducing the number of strong Lewis acid sites at the interface significantly suppressed the side reaction of aromatic condensation and coking, slowed down the catalyst coking and deactivation rate, and greatly improved operational stability.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a hydrocracking catalyst support, characterized in that, Includes the following steps: NaY molecular sieve powder was added to ammonium nitrate solution for an exchange reaction to obtain ammonium-exchangeable Y molecular sieve. The ammonium-exchangeable Y molecular sieve was subjected to hydrothermal treatment. After the treatment, dilute hydrochloric acid solution was added and stirred. Then, the mixture was filtered, washed and dried to obtain USY molecular sieve. The USY molecular sieve was ultrasonically dispersed in an ethanol-water solution to obtain a molecular sieve suspension. Hexadecyltrimethylammonium bromide was added to the molecular sieve suspension for a first stirring reaction. After the reaction, the pH of the system was adjusted to between 9 and 9.

4. Then, tetraethyl orthosilicate-ethanol dilution was added for a second stirring reaction. After the reaction, the solid product was separated by centrifugation, washed, dried, and then calcined to obtain a modified USY molecular sieve with a SiO2 isolation layer. The modified USY molecular sieve coated with SiO2 isolation layer is mixed with pseudoboehmite powder, guar gum powder is added and mixed further, and then dilute nitric acid solution is added for kneading to obtain a paste material. The paste material is extruded and then post-processed to obtain the hydrocracking catalyst support.

2. The method for preparing the hydrocracking catalyst support according to claim 1, characterized in that, The exchange reaction is specifically as follows: The NaY molecular sieve raw powder was added to a 1 mol / L ammonium nitrate solution at a solid-liquid ratio of 1 g to 10 ml. After stirring and exchanging the mixture at 90 °C for 2 h, the mixture was filtered and washed. The exchange process was repeated twice. The product was then dried at 120 °C for 4 h.

3. The method for preparing the hydrocracking catalyst support according to claim 1, characterized in that, The hydrothermal treatment temperature is 600℃, and the treatment time is 4 hours.

4. The method for preparing the hydrocracking catalyst support according to claim 1, characterized in that, The first stirring reaction is specifically as follows: Add 18% by mass of hexadecyltrimethylammonium bromide of the USY molecular sieve to the molecular sieve suspension and stir at 40°C for 30 min.

5. The method for preparing the hydrocracking catalyst support according to claim 1, characterized in that, The second stirring reaction is specifically as follows: Maintain a constant temperature of 45℃ in the system, and add tetraethyl orthosilicate-ethanol diluent dropwise at a stirring speed of 250 r / min at a rate of 0.2 mL / min. The volume ratio of tetraethyl orthosilicate to anhydrous ethanol in the tetraethyl orthosilicate-ethanol diluent is 1:

2. The mass of tetraethyl orthosilicate added is controlled to be 10% of the mass of USY molecular sieve. After the addition is completed, maintain the temperature of 45℃ and the stirring speed of 250 r / min and continue stirring for 6 h.

6. The method for preparing the hydrocracking catalyst support according to claim 1, characterized in that, The roasting temperature for the roasting treatment is 550℃, the heating rate is 1℃ / min, and the roasting time is 4h.

7. The method for preparing the hydrocracking catalyst support according to claim 1, characterized in that, The mass ratio of the modified USY molecular sieve coated with SiO2 isolation layer to pseudoboehmite powder is (55~75):(25~45).

8. The method for preparing the hydrocracking catalyst support according to claim 1, characterized in that, The mass of the guar gum powder is 3% of the total mass of the modified USY molecular sieve coated with a SiO2 isolation layer and the pseudoboehmite powder; The dilute nitric acid solution comprises 5% of the total mass of the modified USY molecular sieve coated with a SiO2 isolation layer and pseudoboehmite powder, and the concentration of the dilute nitric acid solution is 0.5 mol / L.

9. The method for preparing the hydrocracking catalyst support according to claim 1, characterized in that, The post-processing specifically involves: air-drying the extruded material at room temperature for 2 hours, then drying it at 120°C for 6 hours, and then heating it to 580°C at a rate of 2°C / min and calcining it at a constant temperature for 4 hours.

10. The hydrocracking catalyst support prepared by the method for preparing the hydrocracking catalyst support according to any one of claims 1 to 9.

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