A method of hydrocracking

Abstract

The present application relates to the field of light oil utilization conversion, and discloses a hydrocracking method, comprising: introducing light oil into a hydrocracking reaction zone under low-pressure hydrogen-approaching conditions to carry out a hydrocracking reaction, to obtain a hydrocracking product; and separating the hydrocracking product to obtain C3 / C4 product and naphtha product. The hydrocracking method provided by the present application can produce propane, butane and naphtha product rich in aromatic hydrocarbons under low-pressure hydrogen-approaching conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of light oil conversion technology, and in particular to a hydrocracking method. BACKGROUND

[0002] The continuous development of economy brings about the continuous growth of demand for chemical products, and the demand for chemical raw materials also increases.

[0003] The main devices for producing olefins include ethylene cracking and propane dehydrogenation, and the main raw materials are propane and n-paraffin. Since most of the refinery naphtha contains naphthenes and aromatics, and the content of isomeric paraffin is higher, the triene yield is lower when used as cracking raw material. In addition, the naphthenes and aromatics in the naphtha are also important raw materials for the production of BTX in the reforming device.

[0004] Therefore, if straight-run naphtha, coking naphtha or DCC device hydrogenated gasoline, etc. can be used as raw materials, and the isomeric hydrocarbon and naphthenic hydrocarbon-based saturated hydrocarbon is converted into propane and other olefin materials with as little loss of aromatics as possible, the utilization value of naphtha can be greatly improved, the supply chain of olefins and BTX can be connected, and the problem of excess resources of part of the low-value-added naphtha fraction in the refinery can be solved.

[0005] CN106062148A discloses a process for converting hydrocarbons into olefins. The hydrocarbon raw material represented by naphtha is separated into multiple streams classified by carbon number through a hydrocracking unit, and suitable streams are fed into subsequent steam cracking, propane dehydrogenation and butane dehydrogenation units to produce olefins. The conditions of the hydrocracking unit in the method include a temperature of 470-550℃, a pressure of 0.6-3.0 MPa gauge, and a mass space velocity of 0.2-10 h -1 -1.

[0006] CN12409121A discloses a method for converting light naphtha into low-carbon olefins and aromatics. Light naphtha with a C5, C6 paraffin content of 99% is subjected to normal-isomer separation, the isomer component is fed into a hydrocracking unit, and refinery dry gas, propane, n-butane and isobutane are obtained by separation, and these components are further converted into ethylene and propylene through steam cracking or propane dehydrogenation units. The conditions of the hydrocracking unit in the method include a temperature of 330-360℃ and a pressure of 6-8 MPa gauge. After separation through the hydrocracking unit, the proportions of refinery dry gas, propane, n-butane and isobutane are 6%, 31%, 29% and 34%, respectively.

[0007] CN13307717A discloses a method for producing propane from light hydrocarbons under hydrogen conditions, the light hydrocarbon raw material, hydrogen-rich gas and recycled light hydrocarbons are heated and then catalytically cracked under the condition of an acidic catalyst, and the reaction products can be obtained after cooling and fractionation, respectively, dry gas, propane and aromatic gasoline components. The raw material of the method is an alkane content of more than 50wt%, the carbon number range is C4~C13, the reaction temperature is 250~550℃, the pressure is 0.01~5.0MPa, the mass space velocity is 0.1~5.0h-1, the hydrogen / oil ratio is 30~800:1, and the catalyst contains HZSM-5 type molecular sieve.

[0008] CN110951500A discloses a method for producing propane and gasoline from paraffin, which comprises contacting the hydrocarbon with a hydrocarbon conversion catalyst under non-hydrogen, 0.1~3.0MPa, 400~550℃, and feed mass space velocity of 0.1~10.0h -1 The hydrocarbon conversion catalyst comprises 20~85wt% ZSM series zeolite and 15~80wt% binder, the ZSM series zeolite is ZSM-5 and / or ZSM-35, the α value of the catalyst is 60~80, and the paraffin is selected from one or more of C5~C12 paraffin. The method can produce propane under non-hydrogen conditions, and by-product high-octane gasoline blending component.

[0009] WO2021236149A1 discloses a method for producing high-value chemical components from light naphtha, which adopts a two-stage reaction zone, the raw material is mixed with hydrogen and preheated, then enters the first reaction zone, and after hydrogenation reaction, BTEX and products such as ethane, propane and butane obtained from cracked naphtha can be obtained by fractionation. The raw material of the method is light raw material with boiling point of 200 to 315°F, the hydrogenation reaction zone temperature of the method is 400~650℃, the pressure is 1~50bar, and the liquid hourly space velocity is 0.1~15h -1 . The method can obtain 45~55wt% of liquid product and 45~55wt% of gas product, and the yield of BTEX is 20~30wt%. SUMMARY

[0010] The purpose of the present application is to convert light oil raw materials under low pressure and hydrogen conditions to produce propane and naphtha products rich in aromatics.

[0011] In order to achieve the above purpose, the present application provides a hydrogenation cracking method, which comprises:

[0012] (1) introducing a light oil into a hydrocracking reaction zone under low pressure and hydrogen-approaching conditions to perform a hydrocracking reaction, and obtaining a hydrocracking product; the light oil has an aromatic hydrocarbon content of 5wt% to 40wt% and an olefin content of 0.1wt% to 20wt%;

[0013] (2) separating the hydrocracking product to obtain a C3 / C4 product and a naphtha product;

[0014] wherein the conditions of the hydrocracking reaction are controlled so that the total conversion rate of the hydrocracking reaction zone is 38% to 75%;

[0015] According to the flow direction of the liquid phase material, the hydrocracking reaction zone is sequentially filled with a hydrocracking catalyst I and a hydrocracking catalyst II; the carriers of the hydrocracking catalyst I and the hydrocracking catalyst II both contain an acidic component; in the hydrocracking catalyst I, the acidic component is at least one of a β-type molecular sieve and a modified product of a β-type molecular sieve; in the hydrocracking catalyst II, the acidic component is at least one of a ZSM-type molecular sieve and a modified product of a ZSM-type molecular sieve;

[0016] The total conversion rate = (1 - mass percentage content of C5+ hydrocarbons in the naphtha product * total yield of liquid products / mass percentage content of C5+ hydrocarbons in the light oil) * 100%.

[0017] The method of hydrocracking provided by the application can produce propane, butane and naphtha products rich in aromatic hydrocarbons under low pressure and hydrogen-approaching conditions.

[0018] The method of hydrocracking of the application can solve the problem that some naphtha fractions of a refinery are difficult to directly use, and can convert saturated hydrocarbons in a raw material into propane and low-carbon alkanes while retaining aromatic hydrocarbons in the naphtha fractions.

[0019] By using the treatment method provided by the application, the activity and stability of the hydrocracking catalyst can be considered, sulfur and nitrogen compounds can be removed, and large-molecular-chain alkanes and cycloalkanes can be converted into low-carbon alkanes such as propane under the condition of minimizing the loss of aromatic hydrocarbons in the raw material. Preferably, the catalyst grading scheme is adjusted according to the content of cycloalkanes in the raw material to realize the selective conversion of cycloalkanes and alkanes in the raw material in different zones. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a process flow diagram of a preferred embodiment of the method of hydrocracking of the application.

[0021] REFERENCE SIGNS

[0022] 1, 3, 5, 6, 8, 10, 12, 14, 15, 17, 19, 20, 21 are pipelines;

[0023] 2, raw oil pump

[0024] 4, heating furnace

[0025] 7, first cracking reaction zone

[0026] 9, second cracking reaction zone

[0027] 11, high pressure separator

[0028] 13, gas purification unit

[0029] 16, fractionation unit

[0030] 18, extraction unit DETAILED DESCRIPTION

[0031] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not considered critical for the purposes of the application. The ranges disclosed herein are understood to include all values from and between the recited ranges. For values having only one independent variable, the endpoints of the ranges are understood to include all values between the recited endpoints. For values having two independent variables, the endpoints of the ranges are understood to include all values between the recited endpoints.

[0032] As described previously, the present application provides a method for hydrocracking, which comprises:

[0033] (1) introducing a light oil into a hydrocracking reaction zone under low pressure and hydrogen conditions to perform a hydrocracking reaction, to obtain a hydrocracking product; the light oil has an aromatic hydrocarbon content of 5wt% to 40wt% and an olefin content of 0.1wt% to 20wt%;

[0034] (2) separating the hydrocracking product to obtain a C3 / C4 product and a naphtha product;

[0035] wherein the conditions of the hydrocracking reaction are controlled so that the total conversion rate of the hydrocracking reaction zone is 38% to 75%;

[0036] According to the flow direction of the liquid phase material, the hydrocracking reaction zone is sequentially filled with a hydrocracking catalyst I and a hydrocracking catalyst II; the carriers of the hydrocracking catalyst I and the hydrocracking catalyst II both contain an acidic component; in the hydrocracking catalyst I, the acidic component is at least one of a β-type molecular sieve and a modified product of a β-type molecular sieve; in the hydrocracking catalyst II, the acidic component is at least one of a ZSM-type molecular sieve and a modified product of a ZSM-type molecular sieve;

[0037] The total conversion rate = (1 - mass percentage of C5+ hydrocarbons in the naphtha product * total yield of liquid product / mass percentage of C5+ hydrocarbons in the light oil) * 100%.

[0038] The total yield of the liquid product = (1 - total mass of the gaseous product obtained after separation of the hydrocracking product) / mass of the light oil * 100%.

[0039] The method of the present application can further comprise, before introducing the light oil into the hydrocracking reaction zone for hydrocracking reaction, preheating the light oil alone or together with hydrogen, for example, introducing into a heating furnace for preheating treatment; and then introducing the preheated material into the hydrocracking reaction zone for the hydrocracking reaction. The present application does not have a specific requirement for the temperature of preheating, which can be the temperature required for the hydrocracking reaction or slightly lower than the temperature required for the hydrocracking reaction.

[0040] The present application does not have a specific requirement for the specific method of separation in step (2), which can be performed by a person skilled in the art using a separation method known in the art, for example, by using gas-liquid separation, fractionation, etc. The examples of the present application exemplarily provide a specific separation method, which should not be understood as limiting the protection scope of the present application.

[0041] The separation of the present application can be performed by gas-liquid separation in a separator (for example, a high-pressure separator). The gaseous product obtained after the gas-liquid separation can be recycled back to the device for the hydrocracking reaction after purification. The liquid product obtained after the gas-liquid separation is preferably subjected to further fractionation treatment, and the liquid phase product obtained after fractionation is preferably subjected to extraction treatment, and the naphtha product obtained is preferably sent to a reforming device, and a small amount of raffinate can be recycled back to the hydrocracking reaction for back refining or discarded.

[0042] The raw oil (i.e., light oil) used in the method of the present application does not need to be subjected to extraction treatment and can be directly converted.

[0043] Further preferably, the conditions of the hydrocracking reaction are controlled such that the total conversion rate of the hydrocracking reaction zone is 45% to 60%. More preferably, the conditions of the hydrocracking reaction are controlled such that the total conversion rate of the hydrocracking reaction zone is 50% to 60%.

[0044] Preferably, the light oil is selected from the group consisting of straight-run naphtha, DCC gasoline, and coker naphtha.

[0045] According to one preferred specific embodiment, the nitrogen content in the light oil is ≯ 20 μg / g.

[0046] Preferably, the pressure of the hydrocracking reaction is ≯ 8.0 MPa.

[0047] According to one particularly preferred embodiment, the temperature of the hydrocracking reaction is 280-420°C, the pressure is 0.2-8.0 MPa, the volume space velocity is 0.1-20.0 h -1 , and the hydrogen to oil volume ratio is 100-2000.

[0048] Preferably, a hydrofining catalyst is further packed upstream of the hydrocracking catalyst I according to the flow direction of the liquid phase material.

[0049] The hydrocracking catalyst I and the hydrocracking catalyst II of the present application can be packed in different hydrocracking reactors, respectively, or in different hydrocracking reaction zones of the same hydrocracking reactor, respectively, and the present application does not have a particular limitation in this regard, and the person skilled in the art should not understand this as a limitation on the scope of the present application.

[0050] Particularly preferably, the total amount of the acid component in the hydrocracking catalyst I and the hydrocracking catalyst II is each independently 45wt%-80wt% based on the total weight of the respective carrier.

[0051] "The total amount of the acid component is each independently 45wt%-80wt%" means that, in the hydrocracking catalyst I, the total amount of the acid component contained therein is 45wt%-80wt% based on the total weight of the carrier contained therein; similarly, in the hydrocracking catalyst II, the total amount of the acid component contained therein is 45wt%-80wt% based on the total weight of the carrier contained therein.

[0052] Preferably, the hydrocracking catalyst I and the hydrocracking catalyst II each contain an active metal element, and the total amount of the active metal element is each independently 10wt%-50wt% based on the oxide, with the balance being the carrier.

[0053] "The total amount of the active metal element is each independently 10wt%-50wt%" means that, in the hydrocracking catalyst I, the total amount of the active metal element contained therein is 10wt%-50wt% based on the total weight of the hydrocracking catalyst I based on the oxide; similarly, in the hydrocracking catalyst II, the total amount of the active metal element contained therein is 10wt%-50wt% based on the total weight of the hydrocracking catalyst II based on the oxide.

[0054] According to one particularly preferred embodiment, the hydrocracking catalyst I and the hydrocracking catalyst II are each independently selected from at least one of catalysts A having the following characteristics:

[0055] In the catalyst A, the active metal elements are selected from at least two of a Group VIB metal element and a Group VIII metal element; the content of the Group VIB metal element is 5 to 35 wt% and the content of the Group VIII metal element is 1 to 8 wt% in terms of oxides, based on the total weight of the catalyst A.

[0056] Preferably, the hydrocracking catalyst I and the hydrocracking catalyst II each further contain a heat-resistant inorganic oxide selected from at least one of silicon oxide and aluminum oxide.

[0057] More preferably, in the hydrocracking catalyst I and the hydrocracking catalyst II, the total amount of the heat-resistant inorganic oxide is each independently 20 to 55 wt%, based on the total weight of the respective support.

[0058] The "total amount of the heat-resistant inorganic oxide is each independently 20 to 55 wt%" means that, in the hydrocracking catalyst I, the total amount of the heat-resistant inorganic oxide contained therein is 20 to 55 wt%, based on the total weight of the support of the hydrocracking catalyst I; likewise, in the hydrocracking catalyst II, the total amount of the heat-resistant inorganic oxide contained therein is 20 to 55 wt%, based on the total weight of the support of the hydrocracking catalyst II.

[0059] Preferably, in the hydrocracking catalyst, the packed volume of the hydrofining catalyst is 0 to 20%, the packed volume of the hydrocracking catalyst I is 10 to 60%, and the packed volume of the hydrocracking catalyst II is 20 to 90%, based on 100% of the total volume of the catalyst in the hydrocracking reaction zone.

[0060] According to one preferred embodiment, the hydrofining catalyst is selected from at least one of a hydrodesulfurization catalyst, a hydrodechlorination catalyst, and a hydrodesulfurization and denitrification catalyst.

[0061] Preferably, the hydrofining catalyst contains a support and an active metal component, the support is aluminum oxide, and the active metal component contains at least one Group VIII metal element and at least one Group VIB metal element.

[0062] Preferably, in the hydrofining catalyst, the Group VIII metal element is nickel and / or cobalt, and the Group VIB metal element is selected from molybdenum and / or tungsten.

[0063] Preferably, the content of the Group VIII metal element is 0.3wt% to 5wt% and the content of the Group VIB metal element is 1wt% to 30wt% based on the total weight of the hydrofining catalyst.

[0064] The source of the aforementioned catalyst is not particularly required in the present application, and the catalyst with corresponding characteristics can be prepared by methods known in the art or purchased commercially. The present application will not be described in detail here, and the person skilled in the art should not understand it as a limitation of the present application.

[0065] The process flow diagram shown below provides a preferred embodiment of a hydrocracking method of the present application, which specifically comprises: Figure 1 The process flow diagram shown below provides a preferred embodiment of a hydrocracking method of the present application, which specifically comprises:

[0066] The (light oil) from pipeline 1 enters the heating furnace 4 through the raw oil pump 2 and pipeline 3, mixes with hydrogen from pipeline 5, enters the first cracking reaction zone 7 through pipeline 6, and mainly undergoes refining and primary cracking reaction, then enters the second cracking reaction zone 9 through pipeline 8, and mainly undergoes hydrocracking reaction; the product of the second cracking reaction zone enters the high-pressure separator 11 through pipeline 10 for gas-liquid phase separation; the gas phase from the high-pressure separator enters the gas purification unit 13 through pipeline 12, and the purified gas can be mixed with new hydrogen as circulating hydrogen through pipeline 14; the liquid phase from the high-pressure separator enters the fractionation unit 16 through pipeline 15, and after fractionation by the fractionation unit, the liquid phase product enters the extraction unit 18 through pipeline 17, the aromatic hydrocarbon material enters the reforming device through pipeline 19, a small amount of raffinate can be recycled to the first cracking reaction zone and / or the second cracking reaction zone through pipeline 20 or discarded, and the gas product rich in propane obtained from the high-pressure separator is discharged from the device through pipeline 21.

[0067] The present application will be described in detail below by way of examples. In the following examples, the raw materials used are all ordinary commercially available products unless otherwise specified.

[0068] In the following examples, the process flow shown in Figure 1 is used unless otherwise specified. The specific process steps are described in the description of the specific embodiment part, and the present application will not be described hereinafter.

[0069] The properties of the light oil used in the following examples (catalytic naphtha for light oil A, straight-run naphtha for light oil B, and coking naphtha for C) are listed in Table 1; the conditions of the catalyst used are listed in Table 2.

[0070] The catalyst used in the following examples is prepared by methods known in the art, for example, the method provided in CN112742440A can be used.

[0071] Table 1: Properties of Light Oils

[0072]

[0073]

[0074] Table 2: Catalyst Information

[0075]

[0076] Example 1

[0077] use Figure 1 The process flow shown is illustrated, and the relevant process parameters are listed in Table 3. In this embodiment, the reaction product can be fractionated into gaseous and naphtha fractions.

[0078] The distribution and properties of the obtained products are listed in Table 4.

[0079] Example 2

[0080] use Figure 1 The process flow shown is illustrated, and the relevant process parameters are listed in Table 3. In this embodiment, the reaction product can be fractionated into gaseous and naphtha fractions.

[0081] The distribution and properties of the obtained products are listed in Table 4.

[0082] Example 3

[0083] use Figure 1 The process flow shown is illustrated, and the relevant process parameters are listed in Table 3. In this embodiment, the reaction product can be fractionated into gaseous and naphtha fractions.

[0084] The distribution and properties of the obtained products are listed in Table 4.

[0085] Example 4

[0086] use Figure 1 The process flow shown is illustrated, and the relevant process parameters are listed in Table 3. In this embodiment, the reaction product can be fractionated into gaseous and naphtha fractions.

[0087] The distribution and properties of the obtained products are listed in Table 4.

[0088] Comparative Example 1

[0089] use Figure 1 The process flow shown is illustrated, and the relevant process parameters are listed in Table 3. In this comparative example, the reaction product can be fractionated into gas and naphtha fractions.

[0090] The distribution and properties of the obtained products are listed in Table 4.

[0091] Comparative Example 2

[0092] The process flow shown in Table 3 was used, and the process parameters and other information involved are listed in Table 3. In this comparative example, the reaction product can be separated into gas and naphtha fractions by fractionation. Figure 1

[0093] The distribution and properties of the products obtained are listed in Table 4.

[0094] Comparative Example 3

[0095] The process flow shown in Table 3 was used, and the process parameters and other information involved are listed in Table 3. In this comparative example, the reaction product can be separated into gas and naphtha fractions by fractionation. Figure 1

[0096] The distribution and properties of the products obtained are listed in Table 4.

[0097] Comparative Example 4

[0098] The process flow shown in Table 3 was used, and the process parameters and other information involved are listed in Table 3. In this comparative example, the reaction product can be separated into gas and naphtha fractions by fractionation. Figure 1

[0099] The distribution and properties of the products obtained are listed in Table 4.

[0100] Comparative Example 5

[0101] The process flow shown in Table 3 was used, and the process parameters and other information involved are listed in Table 3. Figure 1 In this comparative example, the reaction product can be separated into gas and naphtha fractions by fractionation.

[0102]

[0103] The distribution and properties of the products obtained are listed in Table 4.

[0104] Table 3

[0105]

[0106] Note: The reaction temperatures shown are the average temperatures of the loading zones of the hydrofining catalyst, the hydrocracking catalyst I, and the hydrocracking catalyst II, respectively.

[0107] Table 3 (continued)

[0108]

[0109]

[0110] Note: The reaction temperatures shown are the average temperatures of the loading zones of the hydrofining catalyst, the hydrocracking catalyst I, and the hydrocracking catalyst II, respectively.​​​​

[0111] Table 4

[0112]

[0113] The method of the present application can realize the conversion of the saturated hydrocarbon in the raw material to small molecule hydrocarbons, while retaining the aromatic components in the raw material as much as possible. With different types of raw materials, high-quality ethylene and aromatic raw materials can be obtained.

[0114] In addition, as can be seen from the results in Example 4 of the present application, when the raw material contains chlorine, a hydrogenation dechlorination catalyst can be used to remove the chlorine in the raw material to prevent device corrosion. After removal, the cracking section feed requirements can be met, propane and aromatic-rich naphtha products can be produced, and the product distribution can be consistent with the raw material without dechlorination.

[0115] The results of the comparative examples show that when not within the scope of the present application, the adsorption of aromatic hydrocarbons will have a greater restriction on saturated hydrocarbons, and will also reduce the retention of aromatic hydrocarbons, which cannot meet the production requirements of the target product.

[0116] The above describes the preferred embodiments of the present application, 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 the combination of various technical features 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 of hydrocracking, characterized by, The method comprises: (1) introducing a light oil into a hydrocracking reaction zone under low-pressure hydrogen conditions to perform a hydrocracking reaction, to obtain a hydrocracking product; the light oil has an aromatic hydrocarbon content of 5wt%-40wt% and an olefin content of 0.1wt%-20wt%; the hydrocracking reaction has a pressure of ≯8.0MPa; (2) separating the hydrocracking product to obtain a C3 / C4 product and a naphtha product; wherein the conditions of the hydrocracking reaction are controlled so that the total conversion rate of the hydrocracking reaction zone is 38%-75%; According to the flow direction of the liquid-phase material, the hydrocracking reaction zone is sequentially filled with a hydrocracking catalyst I and a hydrocracking catalyst II; the carriers of the hydrocracking catalyst I and the hydrocracking catalyst II both contain an acidic component; in the hydrocracking catalyst I, the acidic component is at least one of a β-type molecular sieve and a modified product of a β-type molecular sieve; in the hydrocracking catalyst II, the acidic component is at least one of a ZSM-type molecular sieve and a modified product of a ZSM-type molecular sieve; The total conversion rate = (1 - mass percentage content of C5+ hydrocarbons in the naphtha product * total yield of liquid product / mass percentage content of C5+ hydrocarbons in the light oil) * 100%; The total yield of liquid product = (1 - total mass of the gaseous product obtained after separation of the hydrocracking product) / mass of the light oil * 100%.

2. The method of claim 1, wherein, The light oil has a carbon number of C5-C12, a paraffin content of 20wt%-70wt%, and a naphthene content of 5wt%-60wt%.

3. The method of claim 2, wherein, The light oil is selected from the group consisting of straight-run naphtha, DCC gasoline, and coking naphtha.

4. The method of any of claims 1-3, wherein, The nitrogen content in the light oil is ≯20μg / g.

5. The method of any of claims 1-3, wherein, The temperature of the hydrocracking reaction is 280-420℃, the pressure is 0.2-8.0MPa, the volume space velocity is 0.1-20.0h -1 , and the hydrogen-oil volume ratio is 100-2000.

6. The method of any of claims 1-3, wherein, According to the flow direction of the liquid-phase material, a hydrofining catalyst is also filled upstream of the hydrocracking catalyst I.

7. The method of any of claims 1-3, wherein, In the hydrocracking catalyst I and the hydrocracking catalyst II, the total amount of the acidic component is each independently 45wt%-80wt%, based on the total weight of the respective carrier.

8. The method of any of claims 1-3, wherein, The hydrocracking catalyst I and the hydrocracking catalyst II each independently contain an active metal element, and the total amount of the active metal element is each independently 10wt%-50wt%, based on the oxide, with the balance being the carrier.

9. The method of claim 8, wherein, The hydrocracking catalyst I and the hydrocracking catalyst II are each independently selected from at least one of a catalyst A having the following characteristics: In the catalyst A, the active metal element is selected from at least one Group VIB metal element and at least one Group VIII metal element; the content of the Group VIB metal element is 5wt%-35wt% and the content of the Group VIII metal element is 1wt%-8wt%, based on the total weight of the catalyst A, as oxides.

10. The method of any of claims 1-3, wherein, The hydrocracking catalyst I and the hydrocracking catalyst II each also contain at least one heat-resistant inorganic oxide selected from silicon oxide and aluminum oxide.

11. The method of claim 10, wherein, The total amount of the heat-resistant inorganic oxides is independently 20wt%-55wt% based on the total weight of the respective carrier.

12. The method of any one of claims 1-3, wherein, In the hydrocracking reaction zone, the packing volume of the hydrofining catalyst is 0%-20%, the packing volume of the hydrocracking catalyst I is 10%-60%, and the packing volume of the hydrocracking catalyst II is 20%-90%, based on 100% of the total volume of the catalysts in the hydrocracking reaction zone.

13. The method of claim 6, wherein, The hydrofining catalyst is selected from at least one of a hydro-dearsonation catalyst, a hydro-dechlorination catalyst, and a hydro-desulfurization and denitrification catalyst.

14. The method of claim 13, wherein, The hydrofining catalyst contains a carrier and an active metal component, the carrier is alumina, and the active metal component contains at least one Group VIII metal element and at least one Group VIB metal element.

15. The method of claim 14, wherein, In the hydrofining catalyst, the Group VIII metal element is nickel and / or cobalt, and the Group VIB metal element is selected from molybdenum and / or tungsten.

16. The method of claim 14, wherein, The content of the Group VIII metal element is 0.3wt%-5wt% and the content of the Group VIB metal element is 1wt%-30wt% based on the total weight of the hydrofining catalyst in terms of oxides.

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