Hydrocracking method for producing propane from raffinate oil

Abstract

The invention relates to the technical field of light oil utilization and conversion, and discloses a hydrocracking method for producing propane from raffinate oil. The raffinate oil is sequentially introduced into a hydrocracking reaction zone I filled with a hydrocracking catalyst I and a hydrocracking reaction zone II filled with a hydrocracking catalyst II for a hydrocracking reaction, and a hydrocracking product is obtained; the content of paraffin in the raffinate oil is 48wt%-99wt%, and the content of total saturated hydrocarbon is not less than 90wt%; and separating the hydrocracking product to obtain a C3 / C4 product and light naphtha. According to the method provided by the invention, the raffinate oil fraction which is relatively low in additional value and hardly contains aromatic hydrocarbon can be used for producing gas products mainly containing propane and n-butane to the maximum extent under the low-pressure hydrogen condition.

Description

Technical Field

[0001] The invention relates to the technical field of light oil utilization and conversion, and in particular to a hydrocracking method for producing propane from raffinate oil. Background Art

[0002] The sustained development of the national economy has brought about a sustained increase in the demand for chemical products, and along with it the demand for chemical raw materials.

[0003] At present, more than 50% of the raw materials for my country's ethylene cracking units are naphtha, but the triene yields of isoalkanes and cycloalkanes in naphtha are low, and the ideal raw materials are normal alkanes; the main raw materials for dehydrogenation units are propane, butane, etc., which are currently largely dependent on imports.

[0004] Common raffinate oils in refineries include reforming raffinate oil, DCC hydrogenated gasoline raffinate oil, etc. With the development of oil conversion trends in the refining industry, the demand for gasoline blending has decreased. Therefore, these naphtha fractions are converted into low-carbon chemical light hydrocarbons such as propane and n-butane through hydrocracking to provide raw materials for chemical plants, which is of great significance to increasing the added value of oil products.

[0005] CN106062148A discloses a process for converting hydrocarbons into olefins, wherein a hydrocarbon raw material represented by naphtha is separated into multiple streams classified by carbon number through a hydrocracking unit, and the appropriate streams are fed to 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°C, a pressure of 0.6-3.0 MPa gauge pressure and a temperature of 0.2-10 h -1 Mass airspeed.

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

[0007] CN108368435A discloses a method for converting a raw material containing middle distillate oil into C2 and C3 in maximum amount, by setting a plurality of continuous hydrocracking reaction zones, the carbon number of the raw material is effectively reduced, wherein the boiling point range of the raw material required by the first hydrocracking zone is 180-360°C, the reaction conditions are a temperature of 300-400°C, 3-35MPa, the conditions of the second hydrocracking reaction zone are 300-450°C, 1200-4000kPa gauge pressure, and the mass space velocity is 0.1-15h -1 The molar ratio of hydrogen to hydrocarbon is 1:1-4:1, and the third hydrocracking reaction zone is carried out at a temperature of 425-580°C.

[0008] However, the methods of the prior art all have the disadvantages of insufficient raw material adaptability, harsh operating conditions, and limited propane yield. Summary of the invention

[0009] The purpose of the present invention is to provide a method for converting the raffinate oil fraction with lower added value into propane in the maximum amount in view of the problem of excess naphtha such as raffinate oil in some current refining enterprises.

[0010] In order to achieve the above object, the present invention provides a hydrocracking method for maximizing the production of propane from raffinate oil, the method comprising:

[0011] (1) under low-pressure hydrogen conditions, introducing the raffinate oil into a hydrocracking reaction zone I filled with a hydrocracking catalyst I and a hydrocracking reaction zone II filled with a hydrocracking catalyst II in sequence for hydrocracking reaction to obtain a hydrocracking product; the paraffin content in the raffinate oil is 48 wt% to 99 wt% and the total saturated hydrocarbon content is not less than 90 wt%;

[0012] The hydrocracking catalyst I and the hydrocracking catalyst II both contain an acidic component, and the acidic component in the hydrocracking catalyst I is selected from at least one of a β-type molecular sieve, a modified product of a β-type molecular sieve, a Y-type molecular sieve, and a modified product of a Y-type molecular sieve, and the acidic component in the hydrocracking catalyst II is selected from at least one of a ZSM-type molecular sieve and a modified product of a ZSM-type molecular sieve;

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

[0014] The conditions of the hydrocracking reaction are controlled so that the conversion rate I of the hydrocracking reaction zone I is 5% to 50%; and the conversion rate II of the overall hydrocracking reaction is 60% to 99%.

[0015] The method provided by the invention can produce gas products mainly composed of propane and normal butane in maximum amount from the raffinate oil fraction with low added value and almost no aromatic hydrocarbons under low-pressure hydrogen conditions.

[0016] The treatment method provided by the present invention can take into account the activity and stability of the hydrocracking catalyst, and convert the raffinate oil into high-quality chemical materials at a high conversion rate. Preferably, the catalyst grading scheme is adjusted according to the content of cycloalkanes in the raw material to achieve the selective conversion of cycloalkanes and paraffins in the raw material, so that the maximum amount of hydrocarbons in the raw material is converted into a propane-rich gas product. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a schematic flow diagram of a hydrocracking method for producing propane from raffinate oil.

[0018] Description of Reference Numerals

[0019] 1, 3, 5, 6, 8, 10, 12, 14, 15, 17, 18 are pipelines

[0020] 2: Raw oil pump

[0021] 4: Heating furnace

[0022] 7: Hydrocracking reaction zone I

[0023] 9: Hydrocracking reaction zone II

[0024] 11: High pressure separator

[0025] 13: Gas purification unit

[0026] 16: Fractionation unit DETAILED DESCRIPTION

[0027] The endpoints and any values ​​of the ranges disclosed in this article 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, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0028] As mentioned above, the present invention provides a hydrocracking method for producing propane from raffinate oil, the method comprising:

[0029] (1) under low-pressure hydrogen conditions, introducing the raffinate oil into a hydrocracking reaction zone I filled with a hydrocracking catalyst I and a hydrocracking reaction zone II filled with a hydrocracking catalyst II in sequence for hydrocracking reaction to obtain a hydrocracking product; the paraffin content in the raffinate oil is 48 wt% to 99 wt% and the total saturated hydrocarbon content is not less than 90 wt%;

[0030] The hydrocracking catalyst I and the hydrocracking catalyst II both contain an acidic component, and the acidic component in the hydrocracking catalyst I is selected from at least one of a β-type molecular sieve, a modified product of a β-type molecular sieve, a Y-type molecular sieve, and a modified product of a Y-type molecular sieve, and the acidic component in the hydrocracking catalyst II is selected from at least one of a ZSM-type molecular sieve and a modified product of a ZSM-type molecular sieve;

[0031] (2) separating the hydrocracking products to obtain C3 / C4 products and light naphtha;

[0032] The conditions of the hydrocracking reaction are controlled so that the conversion rate I of the hydrocracking reaction zone I is 5% to 50%; and the conversion rate II of the overall hydrocracking reaction is 60% to 99%.

[0033] In the present invention, the calculation method of the conversion rate I of the hydrocracking reaction zone I is: conversion rate I = (1-mass percentage of C5 or higher hydrocarbons in the liquid product of the hydrocracking reaction zone I * yield of the liquid product of the hydrocracking reaction zone I / mass percentage of C5 or higher hydrocarbons in the raffinate) * 100%; the calculation method of the conversion rate II of the overall hydrocracking reaction is: conversion rate II = conversion rate II = (1-mass percentage of C5 or higher hydrocarbons in the liquid product of the hydrocracking reaction zone II * yield of the liquid product of the hydrocracking reaction zone II / mass percentage of C5 or higher hydrocarbons generated in the hydrocracking reaction zone I) * 100%.

[0034] The yield of the liquid product is calculated as follows: yield of the liquid product = mass of the liquid product at the outlet of the reaction zone / mass of the raw material at the inlet of the reaction zone * 100%.

[0035] The method of the present invention can ensure that the mass yield of C3 in the product is not less than 45%, and the selectivity of C3 is not less than 55%.

[0036] The calculation method of the selectivity of C3 in the present invention is: selectivity of C3 = mass yield of C3 in the product / sum of mass yields of C3 and C4 in the product*100%.

[0037] The method of the present invention may also include, before the raffinate oil is introduced into the hydrocracking reaction zone for the hydrocracking reaction, preheating the raffinate oil alone or together with hydrogen, for example, introducing it into a heating furnace for preheating treatment; and then introducing the preheated material into the hydrocracking reaction zone for the hydrocracking reaction. The present invention has no special requirements for the preheating temperature, which can be the temperature required for the hydrocracking reaction, or slightly lower than the temperature required for the hydrocracking reaction.

[0038] Preferably, the conditions of the hydrocracking reaction are controlled so that the conversion rate I of the hydrocracking reaction zone I is 10% to 35%; and the conversion rate II of the overall hydrocracking reaction is 75% to 99%.

[0039] The raffinate oil of the present invention may be a refinery light oil rich in saturated hydrocarbons.

[0040] Preferably, the carbon number of the raffinate oil is C5-C12, the paraffin content is 48wt%-95wt%, the cycloparaffin content is 1wt%-50wt%, and the aromatic content is 0wt%-10wt%.

[0041] Particularly preferably, the content of the fraction with carbon numbers of C5 to C10 in the raffinate oil is ≮80wt%, and the content of aromatics in the raffinate oil is ≯3wt%. The inventors have found that in this preferred case, the propane yield and selectivity of the scheme of the present invention are higher.

[0042] Preferably, the raffinate oil is selected from at least one of reforming raffinate oil and DCC gasoline hydrogenation unit raffinate oil.

[0043] The method of the present invention can process feedstock oils with various nitrogen contents; in a particularly preferred case, the nitrogen content in the raffinate oil is ≯20 μg / g.

[0044] Preferably, the nitrogen content in the raffinate oil is not higher than 20 μg / g. In this preferred case, it is not necessary to set a hydrotreating catalyst in the solution of the present invention.

[0045] Preferably, the pressure of the hydrocracking reaction is ≯8.0 MPa.

[0046] Preferably, the temperature of the hydrocracking reaction zone I is 330-420°C, and the temperature of the hydrocracking reaction zone II is 280-420°C.

[0047] Preferably, the pressure of the hydrocracking reaction is 0.2-8.0 MPa, and the total volume space velocity of the feed is 0.1-20.0 h -1 , the volume ratio of hydrogen to oil is 100~2000.

[0048] According to a preferred specific embodiment, the hydrocracking catalyst I and the hydrocracking catalyst II each independently have the following characteristics: the hydrocracking catalyst contains a carrier and an active metal component, and the content of the active metal component calculated as oxide is 10wt% to 50wt% based on the weight of the hydrocracking catalyst as 100%; the content of the acidic component is 45wt% to 80wt% based on the weight of the carrier as 100%.

[0049] Preferably, based on the total volume of the catalyst in the hydrocracking reaction being 100%, the volume fraction of the hydrocracking catalyst I is 10% to 60%, and the volume fraction of the hydrocracking catalyst II is 20% to 90%.

[0050] Preferably, in the hydrocracking reaction zone I, a protective catalyst is also loaded upstream of the hydrocracking catalyst I according to the flow direction of the liquid phase flow in the hydrocracking reaction.

[0051] Preferably, based on the total volume of the catalyst in the hydrocracking reaction being 100%, the packing volume of the protection catalyst is ≯20%.

[0052] According to a preferred embodiment, the hydrocracking catalyst I and the hydrocracking catalyst II each independently have the following characteristics:

[0053] The carrier of the hydrocracking catalyst also contains a heat-resistant inorganic oxide, and the heat-resistant inorganic oxide is selected from at least one of silicon oxide and aluminum oxide.

[0054] In a particularly preferred case, the hydrocracking catalyst I and the hydrocracking catalyst II each independently have the following characteristics:

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

[0056] Preferably, the protection catalyst is selected from at least one of a hydrogenation protection catalyst, a hydroarsenication catalyst, a hydrodechlorination catalyst and a hydrodemetallization catalyst.

[0057] According to a preferred specific embodiment, the hydrogenation protection catalyst contains a protectant carrier and a protectant active metal component, the protectant carrier is alumina, and the protectant active metal component contains at least one element selected from Group VIII metal elements and at least one element selected from Group VIB metal elements.

[0058] Preferably, in the hydrogenation protection catalyst, based on the total weight of the hydrogenation protection agent, the content of the Group VIII metal element is 0.3 wt% to 5 wt%, and the content of the Group VIB metal element is 1 wt% to 30 wt% in terms of oxide.

[0059] Preferably, in the hydrogenation protection catalyst, the protective agent active metal component contains at least one of nickel and cobalt, and at least one of molybdenum and tungsten.

[0060] According to another preferred specific implementation, the arsenic content in the raffinate oil is 1 μg / g to 30 μg / g, and the protective catalyst contains the hydro-dearsenification catalyst.

[0061] Preferably, the carrier of the hydrodearsenicating catalyst is alumina, and the active metal component contains at least one of nickel and cobalt, and at least one of molybdenum and tungsten. Calculated as oxides, the total content of nickel and / or cobalt is 0.1wt% to 6wt%, and the total content of molybdenum and / or tungsten is 1wt% to 20wt%.

[0062] According to another preferred embodiment, the total metal content in the raffinate oil is 0.1 wt% to 2 wt%, and the protected catalyst contains a hydrodemetallization catalyst.

[0063] Preferably, the hydrodemetallization catalyst carrier is alumina, and the active metal component contains at least one of nickel and cobalt, and at least one of molybdenum and tungsten. Calculated as oxides, the total content of nickel and / or cobalt is 1wt% to 3wt%, and the total content of molybdenum and / or tungsten is 1wt% to 30wt%.

[0064] The present invention has no particular requirements for the specific separation method described in step (2). Those skilled in the art may adopt separation methods known in the art, such as gas-liquid separation, fractionation, etc. The examples of the present invention provide a specific separation method by way of example, and those skilled in the art should not interpret this as limiting the scope of protection of the present invention.

[0065] The separation of the present invention can be performed in a separator (e.g., a high-pressure separator) for gas-liquid separation. The gas 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 further fractionated to obtain the C3 / C4 product and the light naphtha.

[0066] The light naphtha product obtained in the present invention can be mixed with the raw oil as unconverted oil according to production needs, and then circulated to the reaction system for full conversion, or it can be led out of the device. The present invention has no special requirements for this.

[0067] The following combination Figure 1 The process flow diagram shown provides a preferred specific embodiment of a hydrocracking method for producing propane from raffinate oil of the present invention. Specifically, the method comprises:

[0068] (1) Under low-pressure hydrogen conditions, the raffinate oil is introduced into a heating furnace 4 through pipeline 1, a feed oil pump 2 and a pipeline 3 in sequence for preheating, and hydrogen is introduced into the heating furnace 4 through pipeline 5 to obtain a preheated material; the preheated material is introduced into a hydrocracking reaction zone I7 filled with a hydrocracking catalyst I through pipeline 6 for a hydrocracking reaction, and the stream obtained in the hydrocracking reaction zone I is introduced into a hydrocracking reaction zone II9 filled with a hydrocracking catalyst II through pipeline 8 for a hydrocracking reaction to obtain a hydrocracking product;

[0069] (2) The hydrocracking product is introduced into the high-pressure separator 11 via pipeline 10 for gas-liquid phase separation; the gas phase flowing out of the high-pressure separator 11 enters the gas purification unit 13 via pipeline 12, and the purified gas can be used as circulating hydrogen and mixed with new hydrogen from pipeline 5 via pipeline 14; the liquid phase flowing out of the high-pressure separator 11 enters the fractionation unit 16 via pipeline 15, and the propane-rich gas phase exits the device via pipeline 18; after fractionation by the fractionation unit, light naphtha containing components above C5 is drawn out from pipeline 17, and this part of light naphtha can also be used as unconverted oil according to production needs, mixed with the raw material oil from the pipeline via pipeline, and then circulated to the reaction system for full conversion. The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the raw materials used are all ordinary commercial products.

[0070] Unless otherwise specified, the following examples use Figure 1 The process flow shown is carried out.

[0071] The properties of the raffinate oil used below are listed in Table 1; the conditions of the catalyst used are listed in Table 2.

[0072] The catalysts provided in Table 2 are all prepared by methods known in the art, for example, they can be prepared by the preparation method provided in the document with publication number CN112742440A.

[0073] Table 1: Properties of Raffinate Oil

[0074]

[0075] Table 2: Catalyst conditions

[0076]

[0077]

[0078] Example 1

[0079] use Figure 1 The process flow shown in the figure is carried out, and no protective catalyst is set in the hydrocracking reaction zone. The process parameters and other information involved are listed in Table 3. The reaction product can be divided into gas and a small amount of light naphtha fraction by fractionation.

[0080] The distribution and properties of the obtained products are listed in Table 4.

[0081] Example 2

[0082] use Figure 1 The process flow shown in the figure is carried out, and no protective catalyst is set in the hydrocracking reaction zone. The process parameters and other information involved are listed in Table 3. The reaction product can be divided into gas and a small amount of light naphtha fraction by fractionation.

[0083] The distribution and properties of the obtained products are listed in Table 4.

[0084] Example 3

[0085] use Figure 1 The process flow shown in the figure is carried out, and the hydrodechlorination catalyst and the hydrocracking catalyst are set in the hydrocracking reaction zone. The process parameters and other information involved are listed in Table 3. The reaction product can be divided into gas and a small amount of light naphtha fraction by fractionation.

[0086] The distribution and properties of the obtained products are listed in Table 4.

[0087] Comparative Example 1

[0088] use Figure 1 The process flow shown is carried out, and no protective catalyst is set in the hydrocracking reaction zone. The process parameters and other information involved are listed in Table 3.

[0089] The reaction products can be divided into gas and a small amount of light naphtha fraction by fractionation.

[0090] Comparative Example 2

[0091] use Figure 1 The process flow shown is carried out, and no protective catalyst is set in the hydrocracking reaction zone. The process parameters and other information involved are listed in Table 3.

[0092] The reaction products can be divided into gas and a small amount of light naphtha fraction by fractionation.

[0093] Comparative Example 3

[0094] use Figure 1 The process flow shown is carried out, and no protective catalyst is set in the hydrocracking reaction zone. The process parameters and other information involved are listed in Table 3.

[0095] The reaction products can be divided into gas and a small amount of light naphtha fraction by fractionation.

[0096] Table 3

[0097]

[0098] The catalyst loading volume percentages in Table 3 are calculated based on the total catalyst loading volume for the hydrocracking reaction.

[0099] Table 4

[0100]

[0101] The method of the present invention selectively converts cycloalkanes and paraffins in the raw materials, can maximize the yield of propane, reduce the content of cycloalkanes, and enrich paraffins. In addition, a small amount of naphtha products can also be recycled to further increase the yield of propane.

[0102] In addition, it can be explained from Example 3 that if the raffinate oil raw material used contains chlorine after being processed by the upstream device, a hydrodechlorination catalyst can be used to remove the chlorine in the raw material to prevent corrosion of the device. After removal, the feed demand of the cracking stage is met, the production of propane can be maximized, and the product distribution can be consistent with the raw material that does not require dechlorination.

[0103] The present invention is capable of converting a maximum amount of feedstocks having a high content of saturated hydrocarbons.

[0104] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A hydrocracking method for maximizing propane production from raffinate oil, characterized in that: The method includes: (1) under low-pressure hydrogen conditions, introducing the raffinate oil into a hydrocracking reaction zone I filled with a hydrocracking catalyst I and a hydrocracking reaction zone II filled with a hydrocracking catalyst II in sequence for hydrocracking reaction to obtain a hydrocracking product; the paraffin content in the raffinate oil is 48 wt% to 99 wt% and the total saturated hydrocarbon content is not less than 90 wt%; The hydrocracking catalyst I and the hydrocracking catalyst II both contain an acidic component, and the acidic component in the hydrocracking catalyst I is selected from at least one of a β-type molecular sieve, a modified product of a β-type molecular sieve, a Y-type molecular sieve, and a modified product of a Y-type molecular sieve, and the acidic component in the hydrocracking catalyst II is selected from at least one of a ZSM-type molecular sieve and a modified product of a ZSM-type molecular sieve; (2) separating the hydrocracking products to obtain C3 / C4 products and light naphtha; The conditions of the hydrocracking reaction are controlled so that the conversion rate I of the hydrocracking reaction zone I is 5% to 50%; and the conversion rate II of the overall hydrocracking reaction is 60% to 99%.

2. The hydrocracking method according to claim 1, characterized in that: The conditions of the hydrocracking reaction are controlled so that the conversion rate I of the hydrocracking reaction zone I is 10% to 35%; and the conversion rate II of the overall hydrocracking reaction is 75% to 99%.

3. The hydrocracking method according to claim 1, characterized in that: The carbon number of the raffinate oil is C5-C12, the paraffin content is 48wt%-95wt%, the cycloparaffin content is 1wt%-50wt%, and the aromatic content is 0wt%-10wt%; Preferably, the content of the fraction with carbon number of C5 to C10 in the raffinate oil is ≮80wt%, and the content of aromatics in the raffinate oil is ≯3wt%; Preferably, the raffinate oil is selected from at least one of reforming raffinate oil and DCC gasoline hydrogenation unit raffinate oil.

4. The hydrocracking method according to claim 1, characterized in that: The nitrogen content in the raffinate oil is ≯20 μg / g.

5. The hydrocracking method according to any one of claims 1 to 4, characterized in that: The pressure of the hydrocracking reaction is ≯8.0 MPa.

6. The hydrocracking method according to any one of claims 1 to 4, characterized in that: The temperature of the hydrocracking reaction zone I is 330-420°C, and the temperature of the hydrocracking reaction zone II is 280-420°C.

7. The hydrocracking method according to any one of claims 1 to 6, characterized in that: The pressure of the hydrocracking reaction is 0.2-8.0 MPa, and the total volume space velocity of the feed is 0.1-20.0 h -1 , the volume ratio of hydrogen to oil is 100~2000.

8. The hydrocracking method according to any one of claims 1 to 7, characterized in that: The hydrocracking catalyst I and the hydrocracking catalyst II each independently have the following characteristics: the hydrocracking catalyst contains a carrier and an active metal component, and the content of the active metal component calculated as oxide is 10wt% to 50wt% based on the weight of the hydrocracking catalyst as 100%; the content of the acidic component is 45wt% to 80wt% based on the weight of the carrier as 100%.

9. The hydrocracking method according to any one of claims 1 to 8, characterized in that: Based on the total volume of the catalyst in the hydrocracking reaction being 100%, the volume fraction of the hydrocracking catalyst I is 10% to 60%, and the volume fraction of the hydrocracking catalyst II is 20% to 90%; Preferably, in the hydrocracking reaction zone I, according to the flow direction of the liquid phase stream in the hydrocracking reaction, a protective catalyst is also loaded upstream of the hydrocracking catalyst I; Preferably, based on the total volume of the catalyst in the hydrocracking reaction being 100%, the packing volume of the protection catalyst is ≯20%.

10. The hydrocracking method according to claim 8, characterized in that: The hydrocracking catalyst I and the hydrocracking catalyst II each independently have the following characteristics: The carrier of the hydrocracking catalyst also contains a heat-resistant inorganic oxide, and the heat-resistant inorganic oxide is selected from at least one of silicon oxide and aluminum oxide.

11. The hydrocracking method according to claim 8, characterized in that: The hydrocracking catalyst I and the hydrocracking catalyst II each independently have the following characteristics: In the carrier of the hydrocracking catalyst, the active metal elements in the active metal component are selected from at least two of the metal elements of Group VIB and the metal elements of Group VIII; based on the total weight of the hydrocracking catalyst, the content of the metal elements of Group VIB is 5wt% to 35wt%, and the content of the metal elements of Group VIII is 1wt% to 8wt% in terms of oxide.

12. The hydrocracking method according to claim 9, characterized in that: The protection catalyst is selected from at least one of a hydrogenation protection catalyst, a hydroarsenic removal catalyst, a hydrodechlorination catalyst and a hydrodemetallization catalyst.

13. The hydrocracking method according to claim 12, characterized in that: The hydrogenation protection catalyst contains a protection agent carrier and a protection agent active metal component, wherein the protection agent carrier is alumina, and the protection agent active metal component contains at least one element selected from the metal elements of Group VIII and at least one element selected from the metal elements of Group VIB; Preferably, in the hydrogenation protection catalyst, based on the total weight of the hydrogenation protection agent, the content of the metal element of Group VIII is 0.3wt% to 5wt%, and the content of the metal element of Group VIB is 1wt% to 30wt% in terms of oxide; Preferably, in the hydrogenation protection catalyst, the protective agent active metal component contains at least one of nickel and cobalt, and at least one of molybdenum and tungsten.

14. The hydrocracking method according to claim 12, characterized in that: The arsenic content in the raffinate oil is 1 μg / g to 30 μg / g, and the protective catalyst contains the hydro-arsenic removal catalyst; Preferably, the carrier of the hydrodearsenicating catalyst is alumina, and the active metal component contains at least one of nickel and cobalt, and at least one of molybdenum and tungsten. Calculated as oxides, the total content of nickel and / or cobalt is 0.1wt% to 6wt%, and the total content of molybdenum and / or tungsten is 1wt% to 20wt%.

15. The hydrocracking method according to claim 12, characterized in that: The total metal content in the raffinate oil is 0.1wt% to 2wt%, and the protective catalyst contains a hydrodemetallization catalyst; Preferably, the hydrodemetallization catalyst carrier is alumina, and the active metal component contains at least one of nickel and cobalt, and at least one of molybdenum and tungsten. Calculated as oxides, the total content of nickel and / or cobalt is 1wt% to 3wt%, and the total content of molybdenum and / or tungsten is 1wt% to 30wt%.

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