CN107008509B - Improved diesel hydrocracking catalyst carrier and preparation method thereof - Google Patents

Abstract

The invention discloses an improved diesel hydrocracking catalyst carrier and a preparation method thereof. The carrier raw material includes the following components and weight percentages: 3-35% molecular sieve, 5-75% γ-Al ₂ O ₃ , 15-35% γ-Al 2 O 3 75% of amorphous silicon-alumina and 7-40% of binder; the carrier has a specific surface area of 200-450 m ² /g, and a total pore volume of 0.35-0.75 cm ³ /g. In the present invention, the molecular sieve that does not remove the template agent is added in the process of preparing the molecular sieve and the alumina composite material. In the mixed solution, the NH4 ⁺ generated by the reaction of the aluminum salt and the ammonia water is exchanged with the alkali Na+ that balances the negative charge of the molecular sieve framework. During the roasting process, The organic template agent and NH ₄ ⁺ in the molecular sieve are removed, so that the ammonium exchange and the template removal agent of the zeolite molecular sieve are completed in the process of preparing the composite material. The structure has the function of support and protection, and the hydrocracking catalyst prepared by the carrier can obviously lower the freezing point of diesel fraction and increase the cetane number of diesel under the premise of ensuring high yield of diesel.

Description

Improved diesel hydrocracking catalyst carrier and preparation method thereof

technical field

The present invention relates to a catalyst carrier, in particular to an improved diesel hydrocracking catalyst carrier and a preparation method thereof.

Background technique

With the rapid development of the economy, the demand for petroleum products has grown rapidly, and my country's hydrocracking processing capacity has also achieved rapid development. However, as the quality of processed raw materials in my country gradually becomes heavier and worse, the processing volume of high-sulfur crude oil increases year by year, and environmental protection has increasingly strict requirements on the refining process itself and the quality of petroleum products, which puts forward higher requirements for the level of hydrocracking technology , and the catalyst plays a central role in the hydrocracking reaction, and the key to the hydrocracking technology lies in the development and improvement of the catalyst.

The conventional preparation methods of hydrocracking catalysts mainly include impregnation method, co-precipitation method, kneading method, etc. Among them, the kneading method is the simplest preparation process, and the requirements for the process and catalyst ingredients are not high, but due to its extensive preparation process, the catalyst The dispersibility of each component is not good, and some metal hydrogenation active centers are covered, which cannot give full play to its activity. It is usually used for catalysts with low hydrogenation performance requirements; the preparation process of co-precipitation method is the most complicated. , but the dispersion of each component in the catalyst is good, the matching relationship between the components is good, and the hydrogenation and cracking active centers are evenly distributed in the catalyst, so that the catalyst hydrogenation and cracking The active center has a higher synergistic effect; The impregnation method is the most widely used method for preparing hydrocracking catalysts. First, a carrier with shape, mechanical strength, specific surface and acidity that meets the requirements of catalyst performance needs to be prepared, and then the saturated or supersaturated impregnation method is used to support metal components. The components are enriched in the catalyst, which makes the catalyst have higher mechanical strength and give full play to its hydrogenation performance. Therefore, the carrier plays a crucial role in the catalyst. The mechanical function of the carrier is to act as the skeleton of the active component, play the role of dispersing the active component, and increase the strength and thermal stability of the catalyst. Activity and selectivity have a great impact.

US Patent US4738767 discloses a hydrocracking catalyst, the main acidic component is amorphous silica-alumina, and the preparation method of the amorphous silica-alumina used for the carrier is to precipitate aluminum into a silica gel, which results in a specific surface area of the silica-alumina. The pore volume and pore volume are small, the acid content is low and the distribution is uneven, and the catalyst activity is not high. CN1351121A discloses a hydrocracking catalyst containing modified beta molecular sieve and amorphous silica-alumina and a preparation method thereof. In the method, the modified beta molecular sieve is to directly perform ammonium exchange on the synthesized molecular sieve slurry, and then calcine to remove ammonium and acid. The modified β molecular sieve was obtained by treatment and hydrothermal treatment, because a large amount of non-framework aluminum was retained in the molecular sieve pores, which affected the acidity and diffusion properties of the modified molecular sieve, and finally affected the yield and properties of diesel products. CN1393521A discloses a medium oil type hydrocracking catalyst and a preparation method thereof. The carrier used in the catalyst is a composite molecular sieve of amorphous silica-alumina, alumina, Y and β molecular sieve, wherein the composite molecular sieve is to burn the original powder of β molecular sieve to remove the template agent After mixing with modified Y molecular sieve, it is obtained by ammonium exchange treatment. The catalytic activity of this catalyst is not high, and the product quality of middle distillate oil of jet fuel and diesel oil is general and needs to be further improved. However, the above-mentioned hydrocracking catalyst support components are simply mechanically mixed, and each component in the catalyst is easily agglomerated into secondary particles, which makes the dispersibility of the active components poor, and the prepared catalyst is difficult to exert optimal performance. .

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an improved diesel hydrocracking catalyst carrier and a preparation method thereof. The hydrocracking catalyst prepared by using the catalyst carrier has high catalytic activity, and can significantly reduce the diesel fuel yield on the premise of ensuring the diesel yield. The freezing point of the distillate increases the cetane number of diesel fuel.

In order to achieve the above purpose, the technical scheme adopted in the present invention is: an improved diesel hydrocracking catalyst carrier, the carrier raw material includes the following components and their weight percentages: 3-35% molecular sieve, 5-75% γ -Al ₂ O ₃ , 15-75% amorphous silicon-alumina and 7-40% binder; the carrier has a specific surface area of 200-450 m ² /g, and a total pore volume of 0.35-0.75 cm ³ /g .

Further, the carrier material includes the following components and their weight percentages: 3.4-7.6% molecular sieve, 27.3-47.7% γ-Al ₂ O ₃ , 28.3-46.9% amorphous silicon-alumina and 18-20% Binder; the carrier has a specific surface area of 362-383 m ² /g, and a total pore volume of 0.52-0.63 cm ³ /g; the carrier is columnar and has a length of 3-8 mm.

Further, the molecular sieve is one or more of beta molecular sieve, Y-type molecular sieve, MOR molecular sieve, ZSM-5 molecular sieve, ZSM-22 molecular sieve and ZSM-23 molecular sieve.

Further, the amorphous silica-alumina pore volume is 0.5-1.0 cm ³ /g, and the specific surface area is 300-500 m ² /g.

Further, the binder contains 10-40% by mass of small-pore alumina, and the rest is acid; the pore volume of the small-pore alumina is 0.3-0.5 cm ³ /g, and the specific surface area is 200-350 m ² /g, the mass ratio of the acid to the small-pore alumina is 0.1-0.5.

Further, the specific surface area of the beta molecular sieve is 624-643 m ² /g, and the total pore volume is 0.32-0.35 cm ³ /g.

A preparation method of the above-mentioned improved diesel hydrocracking catalyst carrier, comprising the following steps:

1) tetraethylammonium bromide solution, sodium hydroxide, aluminum source and water are mixed and stirred to a clear solution, then silicon source is added, and the stirring is continued to obtain silica-alumina gel;

2) crystallizing the silica-alumina gel obtained in step 1), then washing with water and drying to obtain molecular sieves;

3) adding the molecular sieve obtained in step 2) into the mixed solution of aluminum salt and ammonia water to carry out precipitation, and after sufficient precipitation, take the slurry and carry out evaporation, drying and roasting treatment in turn to obtain molecular sieve and alumina composite material;

4) The molecular sieve obtained in step 3) is mixed with alumina composite material, amorphous silicon-alumina and binder according to the ratio of the raw materials, and the hydrocracking catalyst carrier can be obtained after molding.

Further, in the step 1), the silicon source, aluminum source, sodium hydroxide, tetraethylammonium bromide solution and water are in a molar ratio of SiO ₂ : Al ₂ O ₃ : Na ₂ O: tetraethyl bromide Ammonium: H ₂ O is added in a ratio of 50-70: 1: 5-8: 15-20: 1000-1200.

Further, in the step 3), the aluminum salt is 0.5-3.0 mol/L of aluminum chloride, and the concentration of the ammonia water is 0.5-4 mol/L.

Further, in the step 3), the pore volume of the molecular sieve and the alumina composite material is 0.4-0.9 cm ³ /g, and the specific surface area is 350-500 m ² /g.

Further, in the step 2), the molecular sieve is β molecular sieve, the crystallization temperature is 135-145°C; the washing solution is washed with water until the pH is 6.5-7.5; the drying temperature is 90-110°C, and the drying time is 22-26h.

Further, in the step 3), in the precipitation process, the temperature is 60-80°C, the pH is 3-7; the drying temperature is 90-120°C, and the drying time is 2-3 hours; the roasting temperature is 300-600°C , the calcination time is 2 to 8 hours.

Further, in the step 4), drying and activation treatment are performed in sequence after molding, the drying temperature is 100-120° C., the drying time is 18-22 hours, the activation temperature is 450-600° C., and the activation time is 4-6 hours .

Further, in the step 3), the concentration of the ammonia water is 1.0-2.0 mol/L.

Further, in the described step 1), the aluminum source is one or more of pseudo-boehmite, aluminum sulfate and sodium metaaluminate; the silicon source is one or more of white carbon black, silica sol and water glass. species or several.

Compared with the prior art, the present invention has the following advantages:

First, in the process of preparing the molecular sieve and alumina composite material, the molecular sieve that does not remove the template agent is added in the present invention, and in the mixed solution, the NH4 ⁺ generated by the reaction of the aluminum salt and the ammonia water is exchanged with the alkali Na+ that balances the negative charge of the molecular sieve framework. During the calcination process, the organic template agent and NH ₄ ⁺ in the molecular sieve are removed at the same time. The removed template agent is mainly TEA ⁺ , which fills the interior of the pores and balances the negative charge of the molecular sieve framework, while NH ₄ ⁺ is in the form of NH ₃ . Remove the H-β molecular sieve to obtain the H-β molecular sieve, so that the ammonium exchange and the template removal agent of the zeolite molecular sieve are completed in the process of preparing the composite material. The pore structure of the molecular sieve has the functions of support and protection, so that the pore structure of the molecular sieve is not easily damaged, and the mechanical strength of the catalyst carrier is greatly improved.

Second, the molecular sieve dispersion in the catalyst carrier of the present invention is high, the carrier has more uniform acid sites, and the alumina and the molecular sieve are in closer contact, which is conducive to the rapid transfer of reactants and product molecules between the acid center and the cracking center, and cracking. The components and the hydrogenation components are optimally matched, and the hydrocracking catalyst prepared by using it has a good synergistic effect on the hydrogenation activity and the cracking activity.

Thirdly, the hydrocracking catalyst prepared by the carrier of the present invention has suitable cracking effect and good isomerization effect on long-chain alkanes, aromatic hydrocarbons and long side chain alkyl groups of naphthenic hydrocarbons, and its hydrogenation active center and cracking active center. The matching is more reasonable, and the hydrocracking catalyst prepared by using it has good selectivity of middle distillate oil, can produce high-quality middle distillate oil products, and has high catalytic activity, which can significantly reduce diesel oil fraction under the premise of ensuring high diesel yield. It is suitable for the catalytic process of hydrocracking of vacuum distillate oil to produce high-quality diesel oil.

Detailed ways

The present invention will be further described in detail below with reference to specific embodiments, so as to facilitate a clearer understanding of the present invention, but they do not constitute a limitation of the present invention.

In the following examples, the specific surface area and pore volume were determined by low-temperature N ₂ physical adsorption method, the molar ratio of silicon to aluminum was determined by chemical method, the amount of infrared acid, B acid amount and L acid amount were determined by pyridine adsorption infrared spectroscopy, and molecular sieves were relatively crystalline The degree was measured by XRD method.

The preparation of the hydrocracking catalyst carrier in the following examples is carried out as follows:

The crystallized molecular sieve slurry is directly filtered, washed and dried, and is not treated with a template release agent after drying, and its SiO ₂ /Al ₂ O ₃ (molar ratio) is 20 to 60; the aluminum salt solution and the alkali precipitant are mixed, The above-mentioned molecular sieve that does not remove the template agent is added to the mixed solution, stirred, the temperature is controlled at 60～80 ℃, the pH value is controlled at 3～7, evaporated under the temperature condition of 50～90 ℃, dried at 100 ℃, and the precipitation is roasted , calcination temperature is 300～600 ℃, calcination time is 2～6 hours, obtains molecular sieve and alumina composite material; The pore volume of small-pore alumina in the binder is 0.3-0.5 cm ³ /g, the specific surface area is 200-350 m ² /g, the ratio of acid to alumina in the binder is 0.1-0.5, and the acid is HNO ₃ or H ₃ PO ₄ ) Mixing, rolling in a wheel mill for 20-60 minutes, extruding strips into columns, the length of the carrier is 3-8nm, and then drying the strips at 100-120°C for 10-20 hours at 450-600°C Lower calcination for 4 to 6 hours to obtain a hydrocracking catalyst carrier.

Example 1

Weigh 201.3g tetraethylammonium bromide (98wt%, technical grade), 27.39g sodium hydroxide, 7.2g pseudoboehmite (70wt%, technical grade), 870g water and mix and stir until a clear solution, then in Add 180 g of white carbon black (98 wt %, technical grade) to the solution under constant stirring, and continue to stir to obtain a uniform silica-alumina gel. The silica-alumina gel was dynamically crystallized at 145° C. for 7 days. After washing and drying, beta molecular sieve is obtained, numbered as B1, and the main properties of the beta molecular sieve are shown in Table 1.

Add 3000ml aluminum chloride solution (concentration is 1.5mol/L) into a 5000ml beaker, add 19g B1 molecular sieve (dry basis 99%) into the mixed solution, keep constant temperature at 70°C, and continuously add 2mol/L ammonia water until the pH value is 4 , evaporated at 80 ℃ (evaporation temperature can be 50 ~ 90 ℃), the sucked white solid was dried at 100 ℃ for 3 hours, calcined at 500 ℃ for 4 hours to obtain molecular sieve and alumina composite material 273.7g (dry basis 93% ), the conversion rate was 72.5%, and the number was C1.

Mix 183.7g (dry basis 93%) C1, amorphous silica-alumina 172.7g (dry basis 88%), and binder 240g (dry basis 30%), and roll it in a wheel mill for 40 minutes. It is extrudable paste, extruded into strips, the shape of the carrier is columnar, and the length is 3-8nm, and then the strip-shaped carrier is dried at 120 ℃ for 20 hours, and calcined at 550 ℃ for 5 to 6 hours to obtain the catalyst carrier Z-1, which is See Table 2 for properties.

Example 2

Weigh 201.3g tetraethylammonium bromide (98wt%, technical grade), 27.39g sodium hydroxide, 7.2g pseudoboehmite (70wt%, technical grade), 870g water and mix and stir until a clear solution, then in Add 180 g of white carbon black (98 wt %, technical grade) to the solution under constant stirring, and continue to stir to obtain a uniform silica-alumina gel. The silica-alumina gel was dynamically crystallized at 145° C. for 7 days. After washing and drying, beta molecular sieve is obtained, numbered as B1, and the main properties of the beta molecular sieve are shown in Table 1.

Add 3000ml aluminum chloride solution (concentration is 1.5mol/L) into 5000ml beaker, add 28g B1 molecular sieve (dry basis 99%) into the mixture, keep constant temperature at 70℃, and continuously add 2mol/L ammonia water until the pH value is 4.3 , evaporated at 85°C, the sucked out white solid was dried at 100°C for 3 hours, and calcined at 500°C for 4 hours to obtain 276.2g of molecular sieve and alumina composite material (dry basis 93%), the conversion rate was 73%, numbered as C2.

Mix 225.1g (dry basis 93%) C2, amorphous silica-alumina 126.8g (dry basis 88%), and binder 240g (dry basis 30%), and roll it in a wheel mill for 40 minutes. It is extrudable paste, extruded into strips, the shape of the carrier is columnar, and the length is 3-8nm, and then the strip-shaped carrier is dried at 120 ° C for 20 hours, and calcined at 550 ° C for 5 to 6 hours to obtain the catalyst carrier Z-2. See Table 2 for properties.

Example 3

Weigh 185.3g tetraethylammonium bromide (98wt%, technical grade), 22.65g sodium hydroxide, 10.3g pseudoboehmite (70wt%, technical grade), 870g water and mix and stir until a clear solution, then in Add 180 g of white carbon black (industrial grade) to the solution under constant stirring, and continue to stir to obtain a uniform silica-alumina gel. The silica-alumina gel was dynamically crystallized at 145°C for 7 days. After solid-liquid separation, washing and drying The beta molecular sieve was obtained, numbered as B2, and the main properties of the beta molecular sieve are shown in Table 1.

Add 3000ml aluminum chloride solution (concentration is 1.5mol/L) into 5000ml beaker, add 60.5g B2 molecular sieve (dry basis 99%) into the mixture, keep constant temperature at 70℃, and continuously add 2mol/L ammonia water until the pH value is 4. Evaporate at 85 DEG C, dry the sucked white solid at 100 DEG C for 3 hours, and calcinate at 500 DEG C for 4 hours to obtain 296.4g of molecular sieve and alumina composite material (dry basis 93%), conversion rate 78.4%, number for C3.

Mix 145.7g (dry basis 93%) C3, amorphous silica-alumina 210.7g (dry basis 88%), and binder 240g (dry basis 30%), and roll it in a wheel mill for 40 minutes. It is extrudable paste, extruded into strips, the shape of the carrier is columnar, and the length is 3-8nm, and then the strip-shaped carrier is dried at 120 ° C for 20 hours, and calcined at 550 ° C for 5 to 6 hours to obtain the catalyst carrier Z-3, which is See Table 2 for properties.

Example 4

Weigh 185.3g tetraethylammonium bromide (98wt%, technical grade), 22.65g sodium hydroxide, 10.3g pseudoboehmite (70wt%, technical grade), 870g water and mix and stir until a clear solution, then in Add 180 g of white carbon black (industrial grade) to the solution under constant stirring, and continue to stir to obtain a uniform silica-alumina gel. The silica-alumina gel was dynamically crystallized at 145°C for 7 days. After solid-liquid separation, washing and drying The beta molecular sieve was obtained, numbered as B2, and the main properties of the beta molecular sieve are shown in Table 1.

Add 3000ml of aluminum chloride solution (with a concentration of 1.5mol/L) into a 5000ml beaker, add 34.3g of B2 molecular sieves (dry basis 99%) into the mixture, keep the temperature at 70°C, and continuously add 2mol/L of ammonia until the pH value is 4.8, evaporated at 85°C, dried the suctioned white solid at 100°C for 3 hours, and calcined at 500°C for 4 hours to obtain 285.3g of molecular sieve and alumina composite material (dry basis 93%), conversion rate 75.6%, No. for C4.

Mix 196.4g (dry basis 93%) C4, amorphous silica-alumina 159.6g (dry basis 88%), and binder 240g (dry basis 30%), and roll it in a wheel mill for 40 minutes. It is extrudable paste, extruded into strips, the shape of the carrier is columnar, and the length is 3-8nm, and then the strip-shaped carrier is dried at 120 ° C for 20 hours, and calcined at 550 ° C for 5 to 6 hours to obtain the catalyst carrier Z-4, which is See Table 2 for properties.

The catalyst carriers obtained in Example 3 and Example 4 were carried out by supersaturated impregnation method to support hydrogenation metal, and the hydrogenation metal used tungsten-nickel system. The prepared catalyst numbers were CZ-3 and CZ-4 respectively, and their properties were shown in Table 2 .

The catalytic activities of catalysts CZ-3 and CZ-4 prepared by the carriers obtained in Example 3 and Example 4 were evaluated on a fixed-bed hydrogenation experimental device. The evaluation conditions were: the total reaction pressure was 10MPa, and the volume ratio of hydrogen to oil was 1000. , the volume space velocity was 1.0h ^-1 , and vacuum distillate oil (VGO) was used as the feedstock oil. The properties of the feedstock oil are shown in Table 3. The catalysts CZ-3 and CZ-4 were evaluated under the same process conditions, and the evaluation results are shown in Table 4. As can be seen from the data in Table 4, under the same process conditions, the catalyst prepared by the carrier of the present invention has good selectivity of middle distillate oil, and on the premise of ensuring the yield of diesel oil, the freezing point of diesel oil fraction is obviously reduced, and the alkane number.

Table 1

Molecular sieve B1 B2 Molar ratio of silicon to aluminum (Si/Al) 31.5 22.6 Relative crystallinity, % 96 105 Specific surface, m²/g 624 643 Total pore volume, ml/g 0.32 0.35 Infrared acid content, mmol/g 0.29 0.31 B acid/L acid 0.56 0.48

Table 2

table 3

raw oil vacuum distillate oil Density (20℃), kg/m³ 912.3 Distillation range, °C IBP/10% 315/403 30%/50% 442/461 70%/90% 495/526 95%/EBP 532/544 Freezing point, °C 32 Nitrogen, μg/g 1568 Carbon, wt% 84.53 Hydrogen, wt% 11.72 Carbon residue, wt% 0.32 BMCI value 43

Table 4

Claims (11)

1. an improved diesel hydrocracking catalyst carrier is characterized in that: The carrier material includes the following components and their weight percentages: 3.4-7.6% molecular sieve, 27.3-47.7% γ-Al ₂ O ₃ , 28.3-46.9% amorphous silicon-alumina and 18-20% binder ; The specific surface area of the carrier is 362-383 m ² /g, and the total pore volume is 0.52-0.63 cm ³ /g; the carrier is columnar, and the length is 3-8 mm; The molecular sieve is one or more of β molecular sieve, Y-type molecular sieve, MOR molecular sieve, ZSM-5 molecular sieve, ZSM-22 molecular sieve and ZSM-23 molecular sieve; The binder contains 10-40% by mass of small-pore alumina, and the rest is acid; the small-pore alumina has a pore volume of 0.3-0.5 cm ³ /g, and a specific surface area of 200-350 m ² /g , the mass ratio of the acid to the small-pore alumina is 0.1 to 0.5; The amorphous silica-alumina has a pore volume of 0.5-1.0 cm ³ /g, and a specific surface area of 300-500 m ² /g. 2 . The improved diesel hydrocracking catalyst carrier according to claim 1 , wherein the beta molecular sieve has a specific surface area of 624-643 m ² /g, and a total pore volume of 0.32-0.35 cm ³ /g. 3 . 3. the preparation method of the described improved diesel hydrocracking catalyst carrier of claim 1, is characterized in that: comprises the following steps: 1) tetraethylammonium bromide solution, sodium hydroxide, aluminum source and water are mixed and stirred to a clear solution, then silicon source is added, and the stirring is continued to obtain silica-alumina gel; 2) crystallizing the silica-alumina gel obtained in step 1), then washing with water and drying to obtain molecular sieves; 3) adding the molecular sieve obtained in step 2) into the mixed solution of aluminum salt and ammonia water to carry out precipitation, and after sufficient precipitation, take the slurry and carry out evaporation, drying and roasting treatment in turn to obtain molecular sieve and alumina composite material; 4) The molecular sieve obtained in step 3) is mixed with alumina composite material, amorphous silicon-alumina and binder according to the ratio of the raw materials, and the hydrocracking catalyst carrier can be obtained after molding. 4. the preparation method of the improved diesel hydrocracking catalyst carrier according to claim 3, is characterized in that: in described step 1), silicon source, aluminium source, sodium hydroxide, tetraethylammonium bromide solution and water It is added according to the molar ratio of SiO ₂ : Al ₂ O ₃ : Na ₂ O: tetraethylammonium bromide: H ₂ O of 50-70: 1: 5-8: 15-20: 1000-1200. 5. The method for preparing an improved diesel hydrocracking catalyst carrier according to claim 3, wherein in the step 3), the aluminum salt is 0.5-3.0 mol/L of aluminum chloride, and the concentration of ammonia water is 0.5 ~4mol/L. 6. The preparation method of the improved diesel hydrocracking catalyst carrier according to claim 3 or 4 or 5, wherein in the step 3), the pore volume of the molecular sieve and the alumina composite material is 0.4-0.9 cm ³ /g, and the specific surface area is 350 to 500 m ² /g. 7. The preparation method of the improved diesel hydrocracking catalyst carrier according to claim 3, 4 or 5, characterized in that: in the step 2), the molecular sieve is β molecular sieve, and the crystallization temperature is 135-145 °C; The pH of the washing solution is 6.5-7.5; the drying temperature is 90-110°C, and the drying time is 22-26h. 8. The preparation method of the improved diesel hydrocracking catalyst carrier according to claim 3, 4 or 5, characterized in that: in the step 3), in the precipitation process, the temperature is 60～80°C, and the pH is 3～80°C 7; the drying temperature is 90-120°C, and the drying time is 2-3 hours; the roasting temperature is 300-600°C, and the roasting time is 2-8 hours. 9. The preparation method of the improved diesel hydrocracking catalyst carrier according to claim 3, 4 or 5, characterized in that: in the step 4), drying and activation treatment are carried out successively after molding, and the drying temperature is 100-120 °C. °C, the drying time is 18-22 hours, the activation temperature is 450-600 °C, and the activation time is 4-6 hours. 10 . The method for preparing an improved diesel hydrocracking catalyst carrier according to claim 3 , wherein in the step 3), the concentration of ammonia water is 1.0-2.0 mol/L. 11 . 11. according to the preparation method of the described improved diesel hydrocracking catalyst carrier of claim 3 or 4 or 5, it is characterized in that: in described step 1), aluminium source is pseudo-boehmite, aluminium sulfate and metaaluminate One or more of sodium; silicon source is one or more of white carbon black, silica sol and water glass.