A diesel hydro-upgrading catalyst, its preparation method and application

Abstract

The application discloses a diesel oil hydro-upgrading catalyst and a preparation method and application thereof. The catalyst takes alumina as a carrier, Y type molecular sieve as an acid component, and VIB group metal and VIII group metal as active components. The catalyst is prepared by the following steps: preparing a solution containing active component compounds, then adding alumina precursors to prepare a slurry or suspension, drying, mixing with Y molecular sieve, shaping, and drying and calcining. According to the application, the active metal-alumina composite is prepared first, and then combined with Y molecular sieve, so that the acid center is avoided from being covered by the active metal, the acid amount of the catalyst is increased, the matching of the hydrogenation capacity and the ring-opening capacity of the catalyst is effectively improved, the secondary reactions such as chain breaking of the paraffin are reduced, the paraffin can be retained in the upgraded diesel oil in the maximum degree, the BMCI of the upgraded diesel oil is greatly reduced, and the maximum production of straight-run diesel oil and high-quality ethylene cracking raw materials is realized.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation, specifically relating to a diesel hydrotreating catalyst, its preparation method, and its application. Background Technology

[0002] Ethylene is one of the world's largest-produced chemical products and an important indicator of a country's petrochemical development level. With the increase in domestic production capacity, my country's ethylene self-sufficiency rate has gradually rebounded, but the market gap remains significant. Refining and chemical enterprises need to diversify and broaden their feedstock sources for ethylene production via steam cracking.

[0003] In recent years, my country's diesel-to-gasoline ratio has shown a continuous downward trend, and the oversupply problem in the diesel market will become increasingly prominent. Therefore, finding a market for diesel has become an urgent issue for refineries. In my country's diesel fuel pool, straight-run diesel accounts for 59%. Straight-run diesel has a large volume, and its conversion can significantly reduce the diesel-to-gasoline ratio, achieving high-value utilization of diesel. Hydrogenating straight-run diesel, converting aromatics and cycloalkanes into alkanes through hydrogenation and ring-opening, and enriching them in diesel products, can make it a high-quality feedstock for ethylene. This approach can reduce the diesel-to-gasoline ratio, solving the diesel market for refineries, and also increase the production of ethylene cracking feedstock, which is of great significance for refining enterprises to achieve "reducing oil consumption and increasing chemical production," thereby improving the economic efficiency of refineries.

[0004] Patent CN201610289569.3 discloses a hydrocracking method. This method uses straight-run diesel as feedstock, which is contacted with a hydrocracking catalyst to undergo a hydrocracking reaction, yielding heavy naphtha, diesel, jet fuel, and hydrocracking tail oil. The hydrocracking catalyst used employs modified Y-type molecular sieves, amorphous silica-alumina, and alumina as supports. The modified Y-type molecular sieve is rich in mesopores and has a concentrated effective pore size distribution. This invention is particularly suitable for the hydrocracking process of straight-run diesel hydroconverting to produce jet fuel, exhibiting high catalytic activity and high jet fuel product yield, while also improving product quality.

[0005] Patent CN201911046230.0 discloses a hydrotreating catalyst, its preparation method, and its application. The hydrotreating catalyst includes a support and an active metal component loaded on the support. The support comprises a matrix and a Y-type molecular sieve, wherein the Y-type molecular sieve requires three hydrothermal treatments and four dealumination treatments, making the preparation process relatively complex. The catalyst is mainly used for hydrotreating inferior catalytic diesel to improve its cetane number.

[0006] Patent CN202011115312.9 discloses a hydrotreating catalyst, its preparation method, and its application. The preparation method includes the preparation of a support and the loading of a hydrotreating active metal component. The support preparation method comprises mixing and molding Al-SBA-15 / Y shell-core composite molecular sieve, macroporous alumina, and a binder, followed by drying and calcination to obtain the catalyst support. The catalyst is mainly used for the hydrotreating of inferior catalytic diesel to improve its cetane number.

[0007] Patent CN 202110100233.9 discloses a hydrorefining catalyst and its application. The catalyst comprises a catalyst support, an acidic component, and an active component. The catalyst support comprises mesoporous alumina and mesoporous amorphous silica-alumina. The acidic component is a Y-type molecular sieve. The active component comprises at least one metal from Group VIB and Group VIII. The mesoporous alumina has a pore volume of 0.36–0.60 mL / g in the 12–20 nm range, and the mesoporous amorphous silica-alumina has a pore volume of 0.51–0.70 mL / g in the 12–20 nm range. This hydrorefining catalyst is mainly used to process low-quality catalytic diesel feedstock, producing high-cetane diesel and high-aromatic naphtha.

[0008] Patent CN202111269679.0 discloses a catalyst for the hydroreconstitution of straight-run diesel. The catalyst, based on its weight, comprises: 70-98 wt% support; and 2-30 wt% active metal (based on oxides). The support, based on its mass, comprises: 10-20% Al-SBA-15 / β core-shell composite molecular sieve, 35-70% amorphous silica-alumina, and 20-45% binder components. This catalyst is suitable for the hydroreconstitution of straight-run diesel to produce jet fuel, exhibiting high jet fuel yield and good product quality, particularly a high smoke point.

[0009] Patent CN202111681480.9 discloses a selective hydrocracking catalyst for diesel fuel, its preparation method, and its application. This catalyst comprises a support and a metal hydrocracking active component, wherein the support includes a (USY+HMS) composite mesoporous molecular sieve. This diesel fuel selective hydrocracking catalyst can effectively and efficiently convert straight-run diesel fuel into ethylene cracking feedstock, and has significant industrial application value in integrated refining and chemical enterprises.

[0010] Patent CN201410603740.4 discloses a preparation method of a catalytic diesel hydrogenation conversion catalyst and a hydrogenation process, including the following contents: (1) impregnating Y zeolite with an impregnating solution containing active metal; (2) uniformly mixing the Y zeolite obtained in step (1) with amorphous silica-alumina and / or alumina, adding dilute nitric acid to form a slurry, extruding and forming, drying and calcining to obtain a catalytic diesel conversion catalyst. The method of the present invention improves the effective utilization rate of the active metal, controls the overall hydrogenation ability of the catalyst, and at the same time improves the hydrogenation reaction selectivity and stability of the catalyst. The present invention also provides a hydrogenation process配套 with the hydrogenation conversion catalyst. This hydrogenation process reduces the further hydrogenation or cracking reaction of gasoline to a certain extent, and can improve the octane number of gasoline and the liquid product yield of hydrocracking.

[0011] From the content disclosed in the above prior art, it can be seen that in the relevant research on domestic diesel hydrogenation upgrading catalysts, Y zeolite, β zeolite, amorphous silica-alumina and alumina are all used respectively, and Y zeolite usually needs to be subjected to various modification treatments. At the same time, the catalyst preparation generally adopts the traditional method of first preparing the carrier and then impregnating the active metal. The active metal will enter the zeolite pores during the impregnation process, covering the acid centers, resulting in a decrease in the ring-opening ability of the catalyst, and causing the mismatch between the hydrogenation ability and the ring-opening ability of the catalyst. In addition, secondary calcination is required after impregnation, which has the disadvantages of long process and high energy consumption. In addition, most of the raw materials targeted by these catalysts are heavy catalytic diesel, and the products are mainly naphtha and diesel, or jet fuel is produced from straight-run diesel, and it is not mentioned whether it can be used as an ethylene raw material. Although patent CN202111681480.9 uses straight-run diesel as a raw material to produce ethylene cracking raw materials, the obtained naphtha and tail oil aromatics index (BMCI) is relatively high, the reforming effect is limited, and the catalyst preparation also adopts the impregnation method, which has the disadvantages of insufficient ring-opening ability of the catalyst and high preparation cost. Patent CN201410603740.4 loads the active metal onto the Y zeolite, which will block the pores of the Y zeolite, making it不利于 for the products after ring-opening to diffuse quickly from the acid centers, resulting in a deeper cracking degree and a low tail oil yield. Therefore, it is necessary to improve the performance of the catalyst to produce the highest amount of high-quality ethylene cracking raw materials, realize the high-value utilization of straight-run diesel, solve the problem of current diesel surplus and ethylene raw material shortage in China, and help refineries achieve "reducing oil and increasing chemicals". Summary of the Invention

[0012] The purpose of this invention is to address the shortcomings of existing technologies by providing a diesel hydrotreating catalyst capable of producing high-quality ethylene feedstock, along with its preparation method and applications. This invention involves first preparing an active metal-alumina composite, then mixing it with a Y molecular sieve and molding it to obtain the catalyst. This avoids the active metal covering the acid centers, thus increasing the acid content of the catalyst. This method has the advantages of simple process and low energy consumption, and effectively improves the matching between the catalyst's hydrogenation capacity and ring-opening capacity, reducing secondary reactions such as alkane chain breaking. It can retain alkanes in the treated diesel to the greatest extent, significantly reducing the BMCI of the treated diesel and achieving maximum production of high-quality ethylene cracking feedstock from straight-run diesel.

[0013] To achieve the above objectives, the present invention adopts the following technical solution:

[0014] A diesel hydrotreating catalyst includes a support, an acidic component, and an active metal component; the support is alumina, the acidic component is a Y-type molecular sieve, and the active component includes Group VIB metals and Group VIII metals.

[0015] Furthermore, based on a total mass of 100 wt%, the obtained catalyst contains 30-70 wt% alumina, 5-40 wt% Y molecular sieve, 10-30 wt% group VIB metal oxides, and 1-10 wt% group VIII metal oxides.

[0016] The preparation method of the diesel hydrotreating catalyst includes the following steps:

[0017] (1) Prepare a solution of a compound containing metals from Group VIB and Group VIII;

[0018] (2) Add the alumina precursor to the solution prepared in step (1) under stirring to form a slurry or suspension;

[0019] (3) The slurry or suspension obtained in step (2) is dried to obtain an active metal-alumina composite.

[0020] (4) The active metal-alumina composite obtained in step (3) is mixed with Y molecular sieve, shaped, dried and calcined to obtain the catalyst.

[0021] Furthermore, the compound containing group VIB metal elements used in step (1) is one or more of molybdic acid, secondary molybdic acid, ammonium molybdate, ammonium secondary molybdate, molybdenum trioxide, tungstic acid, metatungstic acid, ammonium tungstate, ammonium metatungstate, and tungsten trioxide.

[0022] Furthermore, the compound containing a Group VIII metal element used in step (1) is derived from one or more inorganic or organic acid salts containing a Group VIII metal element. Among them, the inorganic acid salt can be a basic carbonate, nitrate, phosphate, carbonate, or halide; the organic acid salt can be an acetate, oxalate, citrate, formate, or tartrate.

[0023] Further, the alumina precursor in step (2) is selected from one or more of boehmite, activated p-alumina powder, amorphous aluminum hydroxide, gibbsite, boehmite, and boehmite. It can be a commercially available product or a product prepared by any method in the prior art. Boehmite is preferred.

[0024] Further, in step (2), the mixture is stirred for 0.5 to 4 hours.

[0025] Furthermore, the drying temperature in step (3) is 80~200 ℃. The drying method can be static drying or dynamic drying, with dynamic drying being preferred, such as drying under stirring conditions, or rotary evaporation or spray drying.

[0026] Furthermore, the water content of the active metal-alumina composite obtained in step (3) is 10~40 wt%.

[0027] Furthermore, the Y molecular sieve mentioned in step (4) can be a commercially available product or prepared using conventional methods.

[0028] Furthermore, the molding method described in step (4) can employ various conventional techniques known in the art, such as extrusion, tableting, and pelletizing. However, none of these molding methods constitute a limitation on the diesel reforming catalyst of the present invention.

[0029] Furthermore, molding aids, such as adhesives and / or extrusion aids, may be added during the molding process described in step (4). The types and amounts of adhesives and extrusion aids are known to those skilled in the art. For example, the adhesive can be an inorganic acid and / or an organic acid solution. The inorganic acid can be one or more of nitric acid, phosphoric acid, hydrochloric acid, and sulfuric acid, and the organic acid can be one or more of oxalic acid, acetic acid, and citric acid. The extrusion aid can be one or more of guar gum powder, methylcellulose, starch, polyvinyl alcohol, and polyethylene glycol.

[0030] Furthermore, the drying temperature in step (4) is 80~150 ℃ and the time is 1~24 h.

[0031] Furthermore, the roasting temperature in step (4) is 400~700 ℃ and the time is 2~8 h.

[0032] The catalyst obtained by this invention can be applied to diesel hydrotreating. It is suitable for diesel fractions at 180~410 °C, especially straight-run diesel, and the target product is low-BMCI purified diesel, which can be used as a high-quality feedstock for ethylene cracking.

[0033] When using the catalyst of this invention for diesel hydrotreating, a commercial hydrorefining catalyst or a hydrorefining catalyst prepared according to existing technology should be loaded before the refining catalyst to maintain the nitrogen content of the refined oil ≤15 mg / kg. The catalyst should be pre-sulfurized before application. The reaction conditions for hydrotreating after sulfidation are: reaction temperature 330~380℃, hydrogen partial pressure 8~12 MPa, hydrogen-to-oil volume ratio 500~800, and liquid hourly space velocity 1.0~3.0 h⁻¹. -1 .

[0034] This invention prepares a high-performance diesel hydrotreating catalyst by first preparing an active metal-alumina composite, then mixing and molding it with a Y molecular sieve. Specifically, the active metal is preferentially dispersed on an alumina support to avoid covering the acid sites, thereby increasing the acid content of the catalyst. This effectively improves the matching between the catalyst's hydrogenation capacity and ring-opening capacity, significantly reducing the BMCI of the modified diesel. Simultaneously, the dispersion of the active metal on the alumina prevents clogging of the Y molecular sieve channels, keeping the channels open and allowing the ring-opening products to diffuse rapidly from the acid sites.

[0035] The significant advantages of this invention are:

[0036] (1) Compared with existing catalyst preparation technologies, the catalyst prepared by the method of the present invention has excellent performance. It can effectively reduce excessive cracking reaction and lower the BMCI of the modified diesel during the straight-run diesel reforming process, while ensuring a high yield of the modified diesel, thereby achieving the maximum production of high-quality ethylene cracking feedstock.

[0037] (2) The amount of acid in the catalyst of the present invention can be flexibly controlled. Compared with the conventional method of first preparing the support and then impregnating the active metal, the amount of Y molecular sieve can be reduced under the same acid conditions, thus reducing the raw material cost of the catalyst.

[0038] (3) The preparation method of the present invention is simple, the process is short, and no secondary roasting is required, which reduces the energy consumption in the catalyst production process. Detailed Implementation

[0039] A diesel hydrotreating catalyst is prepared by the following steps:

[0040] (1) Prepare a solution of a compound containing metals from Group VIB and Group VIII;

[0041] (2) Add the alumina precursor to the solution prepared in step (1) under stirring, and stir and mix for 0.5~4 h to form a slurry or suspension;

[0042] (3) The slurry or suspension obtained in step (2) is dried at 80~200 °C to obtain an active metal-alumina composite with a water content of 10~40 wt%.

[0043] (4) The active metal-alumina composite obtained in step (3) is mixed with Y molecular sieve, shaped, and dried at 80~150 ℃ for 1~24 h and calcined at 400~700 ℃ for 2~8 h to obtain the catalyst.

[0044] In step (1), the compound containing a Group VIB metal element is one or more of the following: molybdic acid, secondary molybdic acid, ammonium molybdate, ammonium secondary molybdate, molybdenum trioxide, and tungstic acid, metatungstic acid, ammonium tungstate, ammonium metatungstate, and tungsten trioxide. The compound containing a Group VIII metal element is derived from one or more inorganic or organic acid salts containing a Group VIII metal element. The inorganic acid salt can be a basic carbonate, nitrate, phosphate, carbonate, or halide; the organic acid salt can be an acetate, oxalate, citrate, formate, or tartrate.

[0045] The alumina precursor in step (2) is selected from one or more of the following: boehmite, active ρ alumina powder, amorphous aluminum hydroxide, gibbsite, soft boehmite, and boehmite.

[0046] Based on a total mass of 100 wt%, the obtained catalyst contains 30-70 wt% alumina, 5-40 wt% Y molecular sieve, 10-30 wt% group VIB metal oxides, and 1-10 wt% group VIII metal oxides.

[0047] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0048] Example 1

[0049] (1) Weigh 17.8 g of nickel nitrate and 26.4 g of ammonium metatungstate, and add them to 200 mL of water to dissolve them to obtain an active metal solution;

[0050] (2) Weigh 79.7 g of boehmite (71.0 wt% on dry basis) and add it to the active metal solution prepared in step (1) under stirring. Continue stirring for 1 h to obtain a suspension.

[0051] (3) The obtained suspension was transferred to a flask and dynamically dried at 120 °C using a rotary evaporator to obtain an active metal-alumina composite with a water content of 25.0 wt%.

[0052] (4) Weigh 19.1 g of Y-type molecular sieve (78.7 wt% on dry basis), mix it with active metal-alumina composite, add 1.0 wt% nitric acid solution as a glue solvent for kneading, use an extruder to extrude the kneaded material into shape, dry the extrudate at 120 ℃ for 6 h, and finally calcine at 550 ℃ for 4 h to obtain catalyst C1.

[0053] Example 2

[0054] (1) Weigh 15.8 g of nickel nitrate and 25.0 g of ammonium metatungstate, and add them to 200 mL of water to dissolve them to obtain an active metal solution.

[0055] (2) Weigh 86.5 g of boehmite (71.0 wt% on dry basis) and add it to the active metal solution prepared in step (1) under stirring. Continue stirring for 1 h to obtain a suspension.

[0056] (3) The obtained suspension was transferred to a flask and dynamically dried at 120 °C using a rotary evaporator to obtain an active metal-alumina composite with a water content of 27.2 wt%.

[0057] (4) Weigh 15.2 g of Y-type molecular sieve (78.7 wt% on dry basis), mix it with active metal-alumina composite, add 1.0 wt% nitric acid solution as a binder for kneading, use an extruder to extrude the kneaded material into shape, dry the extrudate at 120 ℃ for 6 h, and finally calcine at 550 ℃ for 4 h to obtain catalyst C2.

[0058] Example 3

[0059] (1) Weigh 9.0 g of basic nickel carbonate and 23.8 g of molybdenum trioxide, and add them sequentially to 200 mL of water containing 6.5 g of phosphoric acid and heat to dissolve them to obtain an active metal solution.

[0060] (2) Weigh 74.1 g of boehmite (71.0 wt% on dry basis) and add it to the active metal solution prepared in step (1) under stirring. Continue stirring for 1 h to obtain a suspension.

[0061] (3) The obtained suspension was transferred to a flask and dynamically dried at 120 °C using a rotary evaporator to obtain an active metal-alumina composite with a water content of 28.7 wt%.

[0062] (4) Weigh 19.1 g of Y-type molecular sieve (78.7 wt% on dry basis), mix it with active metal-alumina composite, add 1.0 wt% nitric acid solution as a binder for kneading, use an extruder to extrude the kneaded material into shape, dry the extrudate at 120 ℃ for 6 h, and finally calcine at 550 ℃ for 4 h to obtain catalyst C3.

[0063] Comparative Example 1

[0064] (1) Weigh 38.2 g of Y-type molecular sieve (78.7 wt% on dry basis) and 159.4 g of boehmite (71.0 wt% on dry basis), mix them evenly, add 1.0 wt% nitric acid solution as a binder and knead them, use an extruder to extrude the kneaded material into shape, dry the extrudate at 120 ℃ for 6 h, and then calcine at 550 ℃ for 4 h to obtain the catalyst support, and determine the water absorption rate of the support.

[0065] (2) Weigh 71.6 g of catalyst support and calculate the required volume of active metal solution based on its water absorption rate. Weigh 17.8 g of nickel nitrate and 26.4 g of ammonium metatungstate, dissolve them in an appropriate amount of water and bring the volume to the required level. Load the active metal onto the catalyst support using the impregnation method.

[0066] (3) The wet catalyst strips obtained in step (2) are dried at 120 °C for 6 h and then calcined at 550 °C for 4 h to obtain catalyst D1.

[0067] Comparative Example 2

[0068] (1) Weigh 17.8 g of nickel nitrate and 26.4 g of ammonium metatungstate, add them to 40 mL of water to dissolve them, and then add ammonia solution to adjust the pH to 5.5 to obtain an active metal solution.

[0069] (2) Weigh 19.1 g of Y-type molecular sieve (78.7 wt% on dry basis), immerse the active metal solution on the Y-type molecular sieve, and dry at 120 ℃ for 4 h.

[0070] (3) Weigh 79.7 g of pseudoboehmite (71.0 wt% on dry basis), mix it with the Y molecular sieve containing active metal obtained in step (2), add 1.0 wt% nitric acid solution as a glue solvent for kneading, use an extruder to extrude the kneaded material into shape, dry the extrudate at 120 ℃ for 6 h, and finally calcine at 550 ℃ for 4 h to obtain catalyst D2.

[0071] Comparative Example 3

[0072] (1) Weigh 17.8 g of nickel nitrate and 26.4 g of ammonium metatungstate, and add them to 40 mL of water to dissolve them to obtain an active metal solution.

[0073] (2) Weigh 79.7 g of boehmite (71.0 wt% on dry basis), immerse the boehmite in the active metal solution, and dry at 120 °C for 4 h.

[0074] (3) Weigh 19.1 g of Y-type molecular sieve (78.7 wt% on dry basis), mix it with the pseudoboehmite containing active metal obtained in step (2), add 1.0 wt% nitric acid solution as a glue solvent for kneading, use an extruder to extrude the kneaded material into shape, dry the extrudate at 120 ℃ for 6 h, and finally calcine at 550 ℃ for 4 h to obtain catalyst D3.

[0075] The physicochemical properties of the catalysts obtained in the examples and comparative examples are listed in Table 1. The acidity of the catalysts was determined by the NH3-TPD method (see Research Methods for Solid Catalysts, Petrochemical Technology, 30(12), 2001: 952).

[0076] Table 1 Physicochemical properties of catalysts

[0077]

[0078] As shown in Table 1, compared with the catalyst prepared in the comparative example, the catalyst prepared in the example has a larger pore volume and specific surface area, as well as a higher total acid content.

[0079] Application Examples

[0080] The catalyst was evaluated in a 200 mL fixed-bed hydrogenation pilot-scale apparatus. Prior to evaluation, the catalyst underwent wet presulfurization. Evaluation conditions were: 350 °C for the commercial hydrorefining catalyst, 360 °C for the hydroreforming catalyst, 10 MPa partial pressure of hydrogen, and 2.4 h⁻¹ liquid hourly space velocity. -1 The hydrogen-to-oil volume ratio is 650. The properties of the feedstock oil are shown in Table 2.

[0081] Table 2 Properties of Crude Oil

[0082]

[0083] The properties of the modified diesel obtained by treating with the catalysts prepared in the examples and comparative examples are shown in Table 3.

[0084] Table 3 Properties of modified diesel obtained by different catalyst treatments

[0085]

[0086] The results in Table 3 show that, compared with the comparative example, the catalyst prepared in the examples has superior performance, higher modified diesel yield, and lower BMCI, and can produce high-quality ethylene cracking feedstock in the largest quantities.

[0087] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing a diesel hydrotreating catalyst, characterized in that: Includes the following steps: (1) Prepare a solution of a compound containing group VIB and group VIII metal elements; (2) Add the alumina precursor to the solution prepared in step (1) under stirring to form a slurry or suspension; (3) The slurry or suspension obtained in step (2) is dried to obtain an active metal-alumina composite. (4) The active metal-alumina composite obtained in step (3) is mixed with Y molecular sieve, shaped, dried and calcined to obtain the catalyst.

2. The method for preparing a diesel hydrotreating catalyst according to claim 1, characterized in that: The compound containing group VIB metal elements used in step (1) is one or more of the following: molybdic acid, ammonium molybdate, ammonium paramolybdate, molybdenum trioxide, tungstic acid, metatungstic acid, ammonium tungstate, ammonium metatungstate, and tungsten trioxide. The compounds containing Group VIII metal elements used are derived from one or more inorganic or organic acid salts containing Group VIII metal elements.

3. The method for preparing a diesel hydrotreating catalyst according to claim 1, characterized in that: The alumina precursor in step (2) is selected from one or more of the following: boehmite, active ρ alumina powder, amorphous aluminum hydroxide, gibbsite, soft boehmite, and boehmite.

4. The method for preparing a diesel hydrotreating catalyst according to claim 1, characterized in that: The drying temperature in step (3) is 80~200 ℃.

5. The method for preparing a diesel hydrotreating catalyst according to claim 1, characterized in that: The water content of the active metal-alumina composite obtained in step (3) is 10~40 wt%.

6. The method for preparing a diesel hydrotreating catalyst according to claim 1, characterized in that: The drying temperature in step (4) is 80~150 ℃ and the time is 1~24 h; the calcination temperature is 400~700 ℃ and the time is 2~8 h.

7. The method for preparing a diesel hydrotreating catalyst according to claim 1, characterized in that: Based on a total mass of 100 wt%, the obtained catalyst contains 30-70 wt% alumina, 5-40 wt% Y molecular sieve, 10-30 wt% group VIB metal oxides, and 1-10 wt% group VIII metal oxides.

8. A method for diesel hydrotreating using the diesel hydrotreating catalyst prepared by the method of claim 1, characterized in that: The diesel fuel has a distillation range of 180~410 ℃.

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