Hydrocracking method of middle distillate

Abstract

The present invention relates to the field of hydrocracking processes, and discloses a middle distillate hydrocracking method, which comprises: in the presence of a hydrogen-rich gas, introducing middle distillate into a hydrocracking reaction unit sequentially containing a protection bed layer and a cracking bed layer, and carrying out hydrotreating to obtain a reaction effluent, and separating the reaction effluent. The method provided by the invention can obtain a product which can be used as military diesel oil and / or high-specific-gravity jet fuel.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hydrocracking process, in particular to a hydrocracking method of middle distillate oil. BACKGROUND

[0002] The apparent consumption of finished diesel oil has reached a peak and is showing a downward trend year by year. In the future, the implementation of hydrogen energy and new energy vehicles will lead to further shrinkage of the market demand for traditional fuel oil. Straight-run diesel oil, hydrocracked diesel oil and hydro-upgraded diesel oil, etc. are important components of the diesel pool. If they are directly used as diesel blending components, the added value is low, and the market demand is shrinking year by year.

[0003] Military diesel oil and high-specific-gravity jet fuel have the characteristics of good low-temperature performance and high volumetric heat value, and can be used at low ambient temperature and improve the range of transportation tools. At present, they are mainly obtained by deep hydrofining process of secondary processing oil rich in cyclic hydrocarbons, which has a complex processing flow and high hydrogen consumption. Conventional middle distillate oil cannot meet the property index requirements of military diesel oil and high-specific-gravity jet fuel due to poor low-temperature flowability and low volumetric heat value. Therefore, it is of important practical significance to develop a method for converting middle distillate oil into military diesel oil and high-specific-gravity jet fuel and other special-purpose fuels, which can alleviate the overcapacity of vehicle diesel oil and improve the added value.

[0004] CN110540875A discloses a method for producing high-density jet fuel and clean diesel oil. The method first performs aromatic extraction on poor-quality diesel oil to obtain extracted oil and raffinate oil. The raffinate oil is reacted in a hydrofining reaction zone to obtain clean diesel oil. The extracted oil is reacted in a hydrocracking reaction zone loaded with a phosphorus-containing Y-type molecular sieve to obtain naphtha, high-density jet fuel and unconverted diesel oil. The yield of the high-density jet fuel fraction is 30% to 58%.

[0005] CN105733670A discloses a method for producing high-specific-gravity aviation kerosene by hydroprocessing catalytic recycling oil. The catalytic recycling oil is sequentially contacted with a hydrofining catalyst, a hydro-upgrading catalyst containing amorphous silicon aluminum and modified Y zeolite, and a post-treatment catalyst to obtain a high-specific-gravity aviation kerosene fraction and a low-condensation diesel oil fraction. However, the method does not disclose the heat value properties of the high-specific-gravity aviation kerosene.

[0006] CN103789034A discloses a method for producing high-specific-gravity aviation kerosene by hydroprocessing medium and low-temperature coal tar. The method first cuts the medium and low-temperature coal tar into light and heavy fractions. The light fraction is directly reacted in a hydroprocessing reaction zone. The reaction product is separated by a fractionating column to obtain a 140℃ to 290℃ kerosene fraction which is reacted in a hydro-upgrading reaction zone with a catalyst containing amorphous silicon aluminum and modified Y zeolite, and then separated and fractionated to obtain high-specific-gravity aviation kerosene.

[0007] CN113528181A discloses a combined method for producing heavy aviation kerosene, wherein hydrogen is mixed with heavy feedstock and then introduced into a hydrotreating reaction zone for contact reaction, the reaction effluent is controlled to have an organic nitrogen content of 50-600 μg / g, the hydrotreating effluent is contacted with a phosphorus-containing molecular sieve hydrocracking catalyst in a hydrocracking reaction zone for contact reaction, and the reaction effluent is cut to obtain a 180-215℃ fraction, so that aviation kerosene with a density of about 0.830 g / cm 3 , but the kerosene fraction cannot meet the requirement of the property index of No. 6 heavy jet fuel.

[0008] Overall, the prior art in the production of special oils including heavy jet fuel needs multiple processes to treat secondary processing oil rich in cyclic hydrocarbons, the device investment cost is high, and the production process is long. Secondly, Y-type molecular sieve cracking agent is mainly used, and the overall heavy aviation kerosene fraction yield is not high.

[0009] Therefore, it is of great practical significance to develop a method for converting middle distillate oil into special fuels including heavy jet fuel and military diesel to alleviate the overcapacity of vehicle diesel and improve the added value. SUMMARY

[0010] The purpose of the present application is to solve the problems of the prior art in the production of special fuel products such as military diesel and heavy jet fuel, such as complex production process, high investment and operation cost, and low yield.

[0011] In order to achieve the above-mentioned purpose, the present application provides a middle distillate oil hydrocracking method, which comprises: introducing middle distillate oil into a hydrocracking reaction unit containing a protective bed and a cracking bed in sequence in the presence of hydrogen-rich gas for hydroprocessing to obtain a reaction effluent; separating the reaction effluent to obtain a product that can be used as military diesel and / or heavy jet fuel; wherein,

[0012] At least two kinds of hydrogenation protective catalysts with different average particle sizes are loaded in the protective bed, and the average particle size of the hydrogenation protective catalysts loaded gradually decreases along the flow direction of the liquid phase material;

[0013] The cracking bed is loaded with a hydrocracking catalyst; the hydrocracking catalyst contains a mesoporous molecular sieve with a pore size in the range of 0.35 nm-0.60 nm, the crystallinity of the mesoporous molecular sieve is 78%-95%, the silicon-aluminum ratio is 20-60, and the specific surface area is 270 g / m 2 -380 g / m 2 ;

[0014] The ratio of the total loading volume of the hydrogenation protective catalyst in the protective bed to the loading volume of the hydrocracking catalyst is 1:7 to 1:20.

[0015] Control the reaction conditions of the hydrocracking reaction unit such that the yield of naphtha fraction below 175 °C in the reaction effluent is 2 wt% - 8 wt%.

[0016] In the present invention, middle distillate oil and hydrogen-rich gas are mixed and then enter the hydrocracking reaction unit, and are respectively contacted and reacted with a hydrotreating catalyst and a hydrocracking catalyst containing mesoporous molecular sieve. After the reaction products are separated and hydrogen sulfide is removed, military diesel or high-density jet fuel products can be obtained.

[0017] Moreover, in the present invention, by loading more than two kinds of hydrotreating catalysts with gradually decreasing average particle size in the hydrogenation process, and controlling the loading ratio of the hydrotreating catalyst and the hydrocracking catalyst, it is possible to effectively avoid the adverse impact of metal deposition in the feedstock oil on the activity of the hydrocracking catalyst during the operation of the unit, and optimize the reaction stream distribution.

[0018] In addition, the method of the present invention can also improve the low-temperature fluidity and volume calorific value of middle distillate oil through the synergistic effect of technical features. By applying a hydrocracking catalyst containing mesoporous molecular sieve with a pore diameter in the range of 0.35 nm - 0.60 nm, and requiring the crystallinity of the mesoporous molecular sieve to be 78% - 95%, the silicon-aluminum ratio to be 20 - 60, and the specific surface area to be 270 g / m 2 - 380 g / m 2 When, the scheme of the present invention can selectively convert n-alkanes and polycyclic hydrocarbons in middle distillate oil.

[0019] Furthermore, the method of the present invention can obtain target products with qualified properties and high yields by optimizing the reaction conditions of the hydrogenation reaction and the grading mode of the catalyst. Detailed Embodiments

[0020] In the ranges disclosed herein, the endpoints and any values are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0021] In the present invention, the definition of the naphtha fraction yield is: the weight percentage of the fraction below T1 °C cut by the fractionation tower from the whole fraction product to the whole fraction product.

[0022] In the present application, "in the range of" means including the end point values of the range, for example, in the range of 0.35 nm-0.60 nm means including both end point values of 0.35 nm and 0.60 nm.

[0023] The average particle diameter in the present application means the weight particle average particle diameter.

[0024] The silicon-aluminum ratio means the molar ratio of silicon oxide to aluminum oxide.

[0025] As described above, the present application provides a method for hydrocracking middle distillate oil, which comprises: introducing the middle distillate oil into a hydrocracking reaction unit containing a guard bed and a cracking bed in sequence in the presence of hydrogen-rich gas to perform hydroprocessing, to obtain a reaction effluent; separating the reaction effluent to obtain a product which can be used as military diesel oil and / or high specific gravity jet fuel; wherein,

[0026] The guard bed is packed with at least two kinds of hydrogenation guard catalysts with different average particle diameters, and the average particle diameter of the hydrogenation guard catalysts packed gradually decreases along the flow direction of the liquid phase material;

[0027] The cracking bed is packed with a hydrocracking catalyst; the hydrocracking catalyst contains mesoporous molecular sieve with a pore size in the range of 0.35 nm-0.60 nm, the mesoporous molecular sieve has a crystallinity of 78%-95%, a silicon-aluminum ratio of 20-60, and a specific surface area of 270 g / m 2 -380 g / m 2 ;

[0028] The ratio of the total packing volume of the hydrogenation guard catalysts in the guard bed to the packing volume of the hydrocracking catalyst is 1:7 to 1:20;

[0029] The reaction conditions of the hydrocracking reaction unit are controlled so that the yield of <175℃ naphtha fraction in the reaction effluent is 2wt%-8wt%.

[0030] Preferably, in the guard bed, the average particle diameter of the hydrogenation guard catalysts is in the range of 1.3 mm-18 mm.

[0031] Preferably, in the guard bed, the average particle diameter of the hydrogenation guard catalysts packed upstream is 1 mm-13 mm larger than the average particle diameter of the hydrogenation guard catalysts packed adjacently downstream.

[0032] According to a particularly preferred specific embodiment, the guard bed is packed with three kinds of hydrogenation guard catalysts with different average particle diameters, and the packing volume ratio of the hydrogenation guard catalysts packed upstream, the hydrogenation guard catalysts packed in the middle, and the hydrogenation guard catalysts packed downstream is 1:1-2:1-4.

[0033] More preferably, in the aforementioned particularly preferred specific embodiment, the difference between the average particle size of the upstream packed hydrogen protection catalyst and the average particle size of the midstream packed hydrogen protection catalyst is 5mm-12mm; the difference between the average particle size of the midstream packed hydrogen protection catalyst and the average particle size of the downstream packed hydrogen protection catalyst is 1mm-3mm.

[0034] Preferably, the hydrogen protection catalysts are each independently selected from at least one of the following catalysts A:

[0035] The catalyst A comprises a carrier and an active metal component, the carrier is alumina, the active metal component contains at least one Group VIII metal element and at least one Group VIB metal element, the Group VIII metal element is nickel and / or cobalt, and the Group VIB metal element is molybdenum and / or tungsten; the content of the Group VIII metal element is 0.3wt%-5wt% and the content of the Group VIB metal element is 1wt%-10wt% based on the total weight of the catalyst A in terms of oxides.

[0036] Preferably, the reaction conditions of the guard bed include: hydrogen partial pressure is 2.0MPa-8.0MPa, reaction temperature is 250℃-380℃, liquid hourly space velocity is 3.0h -1 -25.0h -1 , hydrogen to oil volume ratio is 300-2000.

[0037] Preferably, the mesoporous molecular sieve is selected from at least one of ZSM series molecular sieve, SAPO series molecular sieve, IM-5 molecular sieve and MCM-22 molecular sieve.

[0038] According to a particularly preferred specific embodiment, the mesoporous molecular sieve is ZSM-5 molecular sieve.

[0039] Preferably, the hydrogen cracking catalyst further contains a heat-resistant inorganic oxide and an active metal component, the heat-resistant inorganic oxide is selected from at least one of silicon oxide, aluminum oxide and amorphous aluminum silicate; the active metal component contains at least one Group VIII metal element and at least one Group VIB metal element; the content of the Group VIB metal element is 15wt%-35wt% and the content of the Group VIII metal element is 2wt%-8wt% based on the total weight of the hydrogen cracking catalyst in terms of oxides.

[0040] Preferably, in the hydrogen cracking catalyst, the content of the mesoporous molecular sieve is 20wt%-65wt% based on the total weight of the heat-resistant inorganic oxide and the mesoporous molecular sieve, and the balance is heat-resistant inorganic oxide.

[0041] In a preferred embodiment, the reaction conditions of the cracking bed include: a hydrogen partial pressure of 2.0 MPa-8.0 MPa, a reaction temperature of 280℃-380℃, and a liquid hourly space velocity of 0.3 h⁻¹. -1 -5h -1 The hydrogen-to-oil volume ratio is 300-2000. The inventors discovered that by adjusting the hydrocracking reaction temperature within the range of 280℃ to 380℃, the synergistic effect of the technical features in this invention enables a yield of 2wt%-8wt% of the <175℃ naphtha fraction in the reaction effluent.

[0042] Preferably, the middle distillate oil has an initial boiling point of D-86 of ≥175℃, a final boiling point of D-86 of 300-325℃, an aromatic content of 3wt%-20wt%, and a nitrogen content of ≤100μg / g.

[0043] In a preferred embodiment, the middle distillate oil is selected from at least one of hydrotreated diesel, straight-run diesel, hydrocracked diesel, and hydrotreated modified diesel.

[0044] Preferably, the hydrogen component in the hydrogen-rich gas is 80%-99.99%.

[0045] Particularly preferably, the hydrogen sulfide concentration in the hydrogen-rich gas is 150 μL / L to 10000 μL / L.

[0046] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the raw materials used are all commercially available products.

[0047] In the following examples and comparative examples, unless otherwise specified, the hydrogenation protection catalysts were sequentially loaded with RG-200, RG-30A, and RG-30B in a volume ratio of 1:1:1. All three grades of protection catalysts were manufactured by Changling Catalyst Branch. The average particle size of RG-200 was 16 mm, that of RG-30A was 6 mm, and that of RG-30B was 3 mm.

[0048] In the following examples, unless otherwise specified, the ratio of the total packing volume of the hydroprotection catalyst to the total packing volume of the hydrocracking catalyst is 1:10.

[0049] In the following example, the hydrocracking catalyst CAT-1 contains a ZSM-5 molecular sieve with a specific surface area of ​​291 m². 2 / g, the crystallinity of the molecular sieve is 80.6%, the silica-alumina ratio is 40.4, and the pore size range is 0.51 nm-0.56 nm; the hydrocracking catalyst CAT-1 also contains a heat-resistant inorganic oxide and an active metal component, the heat-resistant inorganic oxide is alumina, the content of the active metal element in the hydrocracking catalyst CAT-1 is 29.2 wt% (of which the content of nickel element in the form of oxide is 4.5 wt%, the content of molybdenum element in the form of oxide is 24.7 wt%), and the balance is the carrier; the content of the mesoporous molecular sieve is 35 wt% based on the total weight of the carrier, and the balance is the heat-resistant inorganic oxide.

[0050] The property parameters of the middle distillate oils are shown in Table 1. The property indexes of No. 6 heavy jet fuel are shown in Table 4. The property indexes of military diesel oil according to GJB3075-1997 are shown in Table 5.

[0051] Table 1: Properties of middle distillate oils

[0052] Item Feed oil 1 Feed oil 2 Density (20°C) / (g / cm 3 )]]> 0.8434 0.8458 Sulfur mass fraction / (μg / g) 48.4 110 Nitrogen content / (μg / g) 3.1 25 Hydrocarbon composition, wt% Paraffins 26.6 27.6 Naphthenes 65.3 62.4 Aromatics 8.1 9.0 ASTM D-86 distillation range / °C IBP 203.4 205.1 50％ 270.3 275 FBP 316.4 325

[0053] Example 1, Example 2 and Comparative Example 1

[0054] Process flow:

[0055] The middle distillate oil is mixed with hydrogen-rich gas (in which the concentration of hydrogen sulfide is 1200 μL / L, and the rest are the same as the examples) and then enters the hydrocracking reactor to contact with the hydroprotection catalyst and the hydrocracking catalyst, respectively. The reaction product is separated and fractionated to obtain the naphtha at the top of the column and the heavy jet fuel product at the bottom of the column. The corresponding process condition parameters, product yield and property data are shown in Table 2.

[0056] Table 2

[0057]

[0058] From the data in Table 2, the reaction temperature of the hydroprotection catalysts in Example 1 and Example 2 is 300℃, the reaction temperature of the hydrocracking catalysts is 310℃ and 320℃, respectively, the <175℃ naphtha fraction yield (raw material conversion rate) is 2.33 wt% and 4.23 wt%, respectively, the weight yield of the heavy jet fuel fraction is 97.67% and 95.77%, respectively, the density is 0.8454 g / cm 3 and 0.8458 g / cm 3 , the smoke point is 23.4 mm and 23.9 mm, respectively, the freezing point meets <-47℃, and the net calorific value is 42.93 MJ / kg and 42.90 MJ / kg, respectively.

[0059] The above results show that the method provided by the present application can obtain a large specific gravity jet fuel fraction with a weight yield of >95% and qualified properties.

[0060] It can be seen from the data in Table 2 that the <175℃ naphtha fraction yield of the comparative example 1 is 1.0 wt%, and the yield of the corresponding large specific gravity jet fuel fraction is 99.0 wt%, but the freezing point of the product is only -44℃, and the net calorific value is only 42.82 MJ / kg, which cannot meet the property index requirements of the large specific gravity jet fuel.

[0061] Example 3, Example 4

[0062] Examples 3 and 4 use the raw oil 2, and the same catalyst scheme as Example 1 is used. The raw oil 2 is mixed with hydrogen-rich gas and then enters the hydrocracking reactor to react with the hydrogen protection catalyst and the hydrocracking catalyst. The reaction product is separated and fractionated to obtain the naphtha and the military diesel product. The corresponding process condition parameters, product yield and property data are listed in Table 3.

[0063] Table 3

[0064] Item Example 3 Example 4 Process condition parameters Reaction hydrogen partial pressure / MPa 5.7 5.7 Hydrogenation guard catalyst reaction temperature / °C 310 310 Hydrocracking catalyst reaction temperature / °C 325 335 Hydroprotection catalyst / hydrocracking catalyst volume space velocity / h -1 ]]> 10.0 / 1.4 10.0 / 1.4 Hydrogen to oil volume ratio 1200 1200 Product distribution / wt% <175 °C naphtha fraction 4.25 6.80 > 175 °C military diesel fraction 95.75 93.20 Military diesel fraction product properties Density (20°C) / (g / cm 3 )]]> 0.8456 0.8458 Sulfur content / (μg / g) 0.4 0.3 Nitrogen content / (μg / g) 0.2 0.3 Flash point (closed) / °C 65 65 Freezing point / °C -44 -52 Kinematic viscosity (20°C) / (mm 2 / s) 4.885 5.105 ASTM D-86 distillation range / °C 10％ 221 221 50％ 266 266 90％ 300 303 Cetane index (ASTM D-4737) 46.6 46.6

[0065] It can be seen from Table 3 that the reaction temperature of the hydrogen protection catalyst in Examples 3 and 4 is 310℃, and the reaction temperature of the hydrocracking catalyst is 325℃ and 335℃ respectively. The corresponding <175℃ naphtha fraction yield is 4.25% and 6.80%, the bottom military diesel product fraction yield is 95.75% and 93.20% respectively, the sulfur content and nitrogen content of the military diesel product both meet <1 μg / g, the freezing point is -44℃ and -52℃ respectively, the kinematic viscosity at 20℃ is 4.885 mm 2 / s and 5.105 mm 2 / s respectively, and the cetane index is 46.6, which meets the property index requirements of the -35 and -50 military diesel respectively.

[0066] Therefore, the method of the present application can obtain a low freezing military diesel product with a yield of more than 90%.

[0067] Table 4: Property index of No. 6 large specific gravity jet fuel

[0068] Item 6# jet fuel Density (20°C) / (kg / m3) 3 )] ≮835 Flash point (closed) / °C ≮38 Freezing point / °C ≯-47 Aromatics volume fraction / % ≯10 Sulfur mass fraction / % ≯0.05 Mercaptan sulfur mass fraction / % ≯0.0010 Smoke point / mm ≮20 Naphthalene series hydrocarbon volume fraction / % ≯0.5 Net heat value / (MJ / kg) ≮42.9 Distillation range (D-86) / °C Initial boiling point ≮195 10％ ≯220 50％ ≯255 90％ ≯300 Final boiling point ≯315

[0069] Table 5: Property index of GJB 3075-1997 military diesel

[0070]

[0071] Example 5

[0072] Example 5 uses the same process as Example 1, but the catalyst loading scheme is different. In Example 5, the hydrogenation guard catalysts are loaded in the order RG-30T, RAM-100 and RCS-30, and the volume ratio of the three catalysts is 1:1:1. The three types of guard catalysts are all produced by Changling Catalyst Branch. The average particle size of RG-30T is 30 mm, the average particle size of RAM-100 is 1.8 mm, and the average particle size of RCS-30 is 1.3 mm. The specific process condition parameters, product yield and property data of this example are listed in Table 6.

[0073] Example 6

[0074] Example 6 uses the same process as Example 1, but the catalyst loading scheme is different. In Example 6, the hydrogenation guard catalysts are loaded in the order RG-30S, RG-200 and RG-30B, and the volume ratio of the three catalysts is 1:1:1. The three types of guard catalysts are all produced by Changling Catalyst Branch. The average particle size of RG-30S is 25 mm, the average particle size of RG-200 is 16 mm, and the average particle size of RG-30B is 3 mm. The specific process condition parameters, product yield and property data of this example are listed in Table 6.

[0075] Example 7

[0076] Example 7 uses the same process as Example 1, but the catalyst loading scheme is different. In Example 7, the hydrogenation guard catalysts are loaded in the order RG-30S, RG-200 and RG-30B, and the volume ratio of the three catalysts is 2:1:1. The three types of guard catalysts are all produced by Changling Catalyst Branch. The average particle size of RG-30S is 25 mm, the average particle size of RG-200 is 16 mm, and the average particle size of RG-30B is 3 mm.

[0077] The specific process condition parameters, product yield and property data of the examples are listed in Table 6.

[0078] Table 6

[0079]

[0080] As can be seen from Table 6, qualified high-gravity jet fuel can be obtained in Example 5, Example 6 and Example 7, but the flow distribution of the cracking catalyst bed is uneven during operation, resulting in a decrease in the utilization efficiency of the catalyst.

[0081] Comparative Example 2

[0082] The same hydrogen protection catalyst as in Example 1 was used in Comparative Example 2, but the particle size of the hydrogen protection catalyst was the same and all 16 mm, and the hydrogen cracking catalyst was packed and the rest was the same as in Example 1. The specific process condition parameters and product yield and property data of this comparative example are listed in Table 7.

[0083] As can be seen from Table 7, the liquid phase flow distribution in Comparative Example 2 is poor, which in turn leads to a decrease in the utilization efficiency of the cracking catalyst bed, resulting in a decrease in the yield of heavy jet fuel and a decrease in the net calorific value.

[0084] Comparative Example 3

[0085] The hydrogen cracking catalyst in Comparative Example 3 was prepared from a MCM-22 mesoporous molecular sieve with a pore size range of 0.4 nm to 0.59 nm, a crystallinity of the molecular sieve of 65%, a silicon-aluminum ratio of 20.5, a specific surface area of 438 g / m 2 The hydrogen protection catalyst and the reaction process conditions were the same as in Example 2. The specific process condition parameters and product yield and property data of this comparative example are listed in Table 7.

[0086] As can be seen from Table 7, under similar reaction conditions as in the example, the density of the product jet fuel fraction in Comparative Example 3 is low, and the freezing point is unqualified, and a qualified heavy jet fuel product cannot be obtained.

[0087] Comparative Example 4

[0088] In Comparative Example 4, the sum of the packing volumes of the hydrogen protection catalyst and the hydrogen cracking catalyst was the same as the sum of the packing volumes of the hydrogen protection catalyst and the hydrogen cracking catalyst in Example 2; the packing types of the hydrogen protection catalyst and the ratio of the packing volumes between the various types were the same as in Example 2; the difference was that the ratio of the total packing volume of the hydrogen protection catalyst to the total packing volume of the hydrogen cracking catalyst in this comparative example was 1:1. The rest of the specific process condition parameters and product yield and property data of this comparative example are listed in Table 7.

[0089] As can be seen from Table 7, the heat value of the jet fuel fraction in Comparative Example 4 decreases, and the product properties cannot meet the requirements of qualified products.

[0090] Table 7

[0091]

[0092]

[0093] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A method for hydrocracking middle distillate oil, characterized in that, The method includes: introducing middle distillate oil into a hydrocracking reactor unit containing a protective bed and a cracking bed in the presence of hydrogen-rich gas for hydrocracking to obtain a reaction effluent; separating the reaction effluent to obtain a product that can be used as military diesel and / or high-density jet fuel; wherein, The protective bed is filled with at least two hydrogenation protection catalysts with different average particle sizes, and the average particle size of the hydrogenation protection catalysts gradually decreases along the flow direction of the liquid phase material. The cracking bed is packed with a hydrocracking catalyst; the hydrocracking catalyst contains a mesoporous molecular sieve with a pore size in the range of 0.35 nm to 0.60 nm, the mesoporous molecular sieve having a crystallinity of 78% to 95%, a silica-alumina ratio of 20 to 60, and a specific surface area of ​​270 g / m². 2 -380g / m 2 ; The ratio of the total loading volume of the hydrogenation protective catalyst in the protective bed to the loading volume of the hydrocracking catalyst is 1:7 to 1:20; The reaction conditions of the hydrocracking unit are controlled such that the yield of the naphtha fraction at <175°C in the reaction effluent is 2wt%-8wt%.

2. The hydrocracking method according to claim 1, characterized in that, In the protective bed, the average particle size of the hydrogenation protective catalyst is in the range of 1.3 mm to 18 mm.

3. The hydrocracking method according to claim 1 or 2, characterized in that, In the protective bed, the average particle size of the upstream hydrogenation protective catalyst is 1 mm to 13 mm larger than the average particle size of the adjacent downstream hydrogenation protective catalyst.

4. The hydrocracking method according to any one of claims 1-3, characterized in that, The protective bed is filled with three hydrogenation protective catalysts with different average particle sizes, and the packing volume ratio of the upstream hydrogenation protective catalyst, the midstream hydrogenation protective catalyst and the downstream hydrogenation protective catalyst is 1:1-2:1-4. Preferably, the difference between the average particle size of the upstream hydrogenation protection catalyst and the average particle size of the midstream hydrogenation protection catalyst is 5 mm to 12 mm; the difference between the average particle size of the midstream hydrogenation protection catalyst and the average particle size of the downstream hydrogenation protection catalyst is 1 mm to 3 mm.

5. The hydrocracking method according to any one of claims 1-4, characterized in that, Each of the hydrogenation protection catalysts is independently selected from at least one of catalyst A having the following characteristics: The catalyst A comprises a support and an active metal component. The support is alumina, and the active metal component contains at least one Group VIII metal element and at least one Group VIB metal element. The Group VIII metal element is nickel and / or cobalt, and the Group VIB metal element is molybdenum and / or tungsten. Based on the total weight of the catalyst A, the content of the Group VIII metal element, calculated as oxides, is 0.3wt%-5wt%, and the content of the Group VIB metal element is 1wt%-10wt%.

6. The hydrocracking method according to any one of claims 1-5, characterized in that, The reaction conditions for the protective bed include: hydrogen partial pressure of 2.0 MPa-8.0 MPa, reaction temperature of 250℃-380℃, and liquid hourly space velocity of 3.0 h⁻¹. -1 -25.0h -1 The hydrogen-to-oil volume ratio is 300-2000.

7. The hydrocracking method according to any one of claims 1-6, characterized in that, The mesoporous molecular sieve is selected from at least one of ZSM series molecular sieves, SAPO series molecular sieves, IM-5 molecular sieves, and MCM-22 molecular sieves; Preferably, the mesoporous molecular sieve is a ZSM-5 molecular sieve.

8. The hydrocracking method according to any one of claims 1-7, characterized in that, The hydrocracking catalyst also contains heat-resistant inorganic oxides and active metal components. The heat-resistant inorganic oxides are selected from at least one of silicon oxide, aluminum oxide, and amorphous aluminum silicate. The active metal components contain at least one Group VIII metal element and at least one Group VIB metal element. Based on the total weight of the hydrocracking catalyst, the content of the Group VIB metal element is 15wt%-35wt% and the content of the Group VIII metal element is 2wt%-8wt% based on the oxide content.

9. The hydrocracking method according to claim 8, characterized in that, In the hydrocracking catalyst, based on the total weight of the heat-resistant inorganic oxide and the mesoporous molecular sieve, the content of the mesoporous molecular sieve is 20wt%-65wt%, and the balance is heat-resistant inorganic oxide.

10. The hydrocracking method according to any one of claims 1-9, characterized in that, The reaction conditions of the cracking bed include: hydrogen partial pressure of 2.0 MPa-8.0 MPa, reaction temperature of 280℃-380℃, and liquid hourly space velocity of 0.3 h⁻¹. -1 -5h -1 The hydrogen-to-oil volume ratio is 300-2000.

11. The hydrocracking method according to any one of claims 1-10, characterized in that, The middle distillate oil has an initial boiling point of D-86 of ≥175℃, a final boiling point of D-86 of 300-325℃, an aromatic content of 3wt%-20wt%, and a nitrogen content of ≤100μg / g.

12. The hydrocracking method according to any one of claims 1-11, characterized in that, The middle distillate oil is selected from at least one of hydrotreated diesel, straight-run diesel, hydrocracked diesel, and hydrotreated modified diesel.

13. The hydrocracking method according to any one of claims 1-12, characterized in that, The hydrogen content in the hydrogen-rich gas is 80%-99.99%; Preferably, the hydrogen sulfide concentration in the hydrogen-rich gas is 150 μL / L to 10000 μL / L.

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