CN113122322A

CN113122322A - Method for reducing bromine index of hydrocracking heavy naphtha

Info

Publication number: CN113122322A
Application number: CN201911424161.2A
Authority: CN
Inventors: 曹均丰; 王仲义; 吴子明; 崔哲
Original assignee: China Petroleum and Chemical Corp; Sinopec Dalian Research Institute of Petroleum and Petrochemicals
Current assignee: Sinopec Dalian Petrochemical Research Institute Co ltd; China Petroleum and Chemical Corp
Priority date: 2019-12-31
Filing date: 2019-12-31
Publication date: 2021-07-16
Anticipated expiration: 2039-12-31
Also published as: CN113122322B

Abstract

The invention discloses a hydrocracking method for reducing the bromine index of heavy naphtha. The method comprises the following steps: (1) after being mixed with hydrogen, the hydrocracking raw material enters a hydrocracking pretreatment reactor for carrying out hydrofining reaction; (2) the effluent of the hydrorefining reaction enters a hydrocracking reactor, contacts with a high-activity hydrocracking catalyst, and undergoes a hydrocracking reaction at a higher severity; (3) the effluent obtained in the step (2) enters the bottom of a hydrocracking reactor and contacts with a weak hydrocracking activity cracking catalyst for reaction; (4) and (4) separating and fractionating the hydrocracking product obtained in the step (3) to obtain a heavy naphtha product with a reduced bromine index. The method can improve the quality of the heavy naphtha product on the premise of maintaining the yield of the light fraction product not to be reduced.

Description

Method for reducing bromine index of hydrocracking heavy naphtha

Technical Field

The invention relates to a method for improving the quality of a hydrocracking product through a catalyst adjustment scheme, in particular to a method for improving the quality of a hydrocracking heavy naphtha product.

Background

The hydrocracking process is a process for converting heavy distillate oil (VGO, CGO and DAO) into target products such as light oil, middle distillate oil and the like by hydrodesulfurization, hydrodenitrogenation, polycyclic aromatic hydrocarbon hydrosaturation and ring-opening cracking under the conditions of hydrogen presence, high temperature and high pressure and under the action of a catalyst, has the characteristics of flexible operation, good product quality and environmental friendliness, is one of the main processes for deep processing of the heavy distillate oil, not only is an important means for producing light oil products in the oil refining industry, but also becomes a key technology of petrochemical enterprises, exerts the irreplaceable effect of other processes, has become the standard configuration of various current large oil refining enterprises, and plays a key role in combination of oil, chemical and fiber and flow optimization configuration of the whole plant.

The hydrocracking device is used as a standard preparation device of an oil refining enterprise, plays a key linking transition role between oil refining-oil refining and oil refining-chemical engineering, the liquid product of the hydrocracking device can be light naphtha which can be used as a blending component to produce high-quality gasoline, heavy naphtha which can be used as a catalytic reforming unit to feed and produce reformed gasoline or aromatic hydrocarbon products, kerosene which can be used as aviation kerosene or low-freezing diesel oil products, diesel oil which can be used as high-quality fuel oil products, tail oil which can be used as lubricating oil base stock or ethylene cracking raw materials, and the yield and quality of each liquid product can be flexibly adjusted according to different used catalysts and process conditions, so the flexibility and the superiority of the hydrocracking device are self-evident.

At present, when the domestic hydrocracking device is in actual use, according to the difference of oil product balance of enterprises, target products or production modes of the hydrocracking device are different, but higher economic benefits are pursued in order to meet the market demands, and the adjustment mode of the hydrocracking device is generally stronger in pertinence and is produced according to the demands. At present, diesel oil products in domestic markets are excessive and are blocked in sales, so that the improvement of the diesel oil-gas ratio and the reduction of the diesel oil yield become the fundamental targets of optimization and upgrading of oil refining enterprises at present and even in recent years. The diesel-gasoline ratio is reduced, although the way and the method are not single, the high-activity hydrocracking catalyst is a preferred choice in catalyst selection, the high-activity catalyst is selected, the heavy naphtha can be produced at a lower reaction temperature, namely a large amount of raw materials are converted, the reaction process is more severe, the quality of the heavy naphtha product is slightly poor, and the problem also occurs in the process of the tail end of the operation of the low-activity catalyst, and the quality of the heavy naphtha product is reduced due to the increase of the reaction temperature.

The hydrocracking process simultaneously carries out a plurality of reactions. Cracking reactions typically involve the cleavage of carbon-carbon single bonds to lower molecular weight compounds, including olefins, and the cleavage of aromatic side chains of higher molecular weight compounds. Hydrogenation reactions also occur in the hydrocracking unit, including the hydrogenation of double bonds of aromatic and olefinic compounds. Therefore, in the reaction process, the existing hydrogenation process is accompanied by the dehydrogenation process, the two processes have certain difference in equilibrium constants under different reaction conditions, and the olefin generated in the reaction process is not beneficial to the stability of subsequent products, so that a certain amount of refined catalyst is always added to the bottommost part of a cracking reactor in the general hydrocracking process, namely, the refined catalyst is a post-treatment catalyst, and the function of the refined catalyst can be used for carrying out hydrogenation saturation on the olefin generated in the reaction process, so that the stability of the subsequent products is improved, and the trend of generating mercaptan is reduced, for example, the excessive standard of mercaptan in heavy naphtha and aviation kerosene products can be avoided, so that the quality of the products is ensured to be qualified, or the excessive standard of the olefin of the heavy naphtha, namely the excessive bromine index is avoided, so that the deactivation rate.

CN200610047864.4 describes a one-stage serial hydrocracking method, in which a one-stage serial hydrocracking pretreatment reactor is filled with a pretreatment catalyst and a hydrocracking catalyst, and in the hydrocracking reactor is filled with a hydrocracking catalyst and a post-hydrogenation treatment catalyst. Compared with the prior art, the method can improve the overall activity of the hydrocracking unit, increase the processing capacity of the unit or prolong the operation period, and simultaneously improve the product quality. CN200780020520.7 introduces a hydrocracking method for producing low-sulfur diesel, which can realize the production of low-sulfur diesel after the reaction is carried out in single-stage or two-stage hydrocracking and the optimized promotion of a catalyst and the proper treatment of the reaction process. However, both of them involve the phenomena that the temperature of the reaction zone of the post-treatment of hydrocracking is too high, the activity of the catalyst is not matched very well, the product quality is not stable, and the problems are more serious especially in the middle and later stages of the reaction.

CN201510604895.4 introduces a preparation method of a post-treatment type hydrocracking catalyst, which can realize the production of products with higher hydrogenation activity and selectivity by optimizing and limiting the preparation process of the catalyst, and the selectivity of middle distillate oil of the products is higher, thus being suitable for treating hydrocracking catalysts consisting of various metals. But still belongs to the hydrocracking catalyst category in principle, if used for hydrogenation after-treatment, the stability of product quality is difficult to guarantee, and after short-term operation, the problem that the content of olefin in a liquid phase product exceeds the standard or mercaptan exceeds the standard can occur.

CN02144950.3 introduces a hydrocracking post-treatment catalyst and a preparation method thereof, and the catalyst can realize the characteristics of hydrodemercaptan removal, high olefin saturation activity and good stability by improving the preparation of the catalyst, and is particularly suitable for the process of producing low-sulfur alcohol products by hydrocracking post-treatment. Although the preparation process of the catalyst is improved, the preparation process is not adapted to the actual reaction condition of aftertreatment, the characteristic that the product quality is difficult to stabilize in the middle and later stages of the reaction still exists, in addition, key indexes such as acidity of the catalyst are not explained, the improvement of hydrogenation performance and cracking performance is not involved, and the like, and the problem still exists in the practical application.

CN02144949.X introduces a hydrotreating catalyst and its preparation method, and the improvement of the catalyst preparation process can realize the features of high hydrogenation sweetening and olefin saturation activity, especially suitable for the sweetening process after hydrocracking. The method still belongs to a patent related to a catalyst in principle, a process is not limited and modified, the aim of completely and uniformly controlling the preparation and process application of the catalyst is not achieved, the optimization of the product quality cannot be thoroughly realized, in addition, the preparation method is not optimized for some key parameters, and after the reaction temperature is overhigh during application, the inactivation rate of the catalyst is accelerated, and the severity is increased, so that the condition that the quality of individual products does not reach the standard is caused.

Disclosure of Invention

Aiming at the technical problem that the quality of heavy naphtha is unqualified in the existing hydrocracking process, the invention provides an improved hydrocracking method.

A hydrocracking process for reducing the bromine index of heavy naphtha comprising the steps of:

(1) after being mixed with hydrogen, the hydrocracking raw material enters a hydrocracking pretreatment reactor for carrying out hydrofining reaction;

(2) the effluent of the hydrorefining reaction enters a hydrocracking reactor, contacts with a high-activity hydrocracking catalyst, and performs a hydrocracking reaction under the reaction condition with high severity;

(3) the effluent obtained in the step (2) enters the bottom of a hydrocracking reactor, and is contacted with a weak hydrogenation activity cracking catalyst for hydrogenation reaction;

(4) and (4) separating and fractionating the hydrocracking product obtained in the step (3) to obtain a hydrocracking heavy naphtha product with a reduced bromine index.

In the method of the present invention, the hydrocracking raw material may be a wax oil raw material or a diesel oil raw material, etc., preferably a wax oil raw material, especially a paraffin-based wax oil raw material. The initial boiling point of the wax oil raw material is generally 200-300 ℃, the dry point is generally 500-600 ℃, and the optimal dry point is 510-590 ℃; the nitrogen content is below 2500 mug/g, generally 500 mug/g-2000 mug/g, the sulfur content is not strictly limited, and the content of other impurities can meet the conventional requirements. The wax oil raw material can be various straight run or secondary processed wax oils obtained by processing naphthenic base crude oil, intermediate base crude oil or paraffin base crude oil, and the like, preferably straight run wax oil components or deasphalted oil of the paraffin base crude oil which is processed for the first time, and can be selected from various Vacuum Gas Oil (VGO) and deasphalted oil (DAO) obtained by processing the paraffin base crude oil, such as one or more of Daqing VGO, DAO, Changqing VGO and DAO. The hydrogen is the common feeding material with the impurity content meeting the requirement in the industry.

In the method of the present invention, the conditions of the hydrorefining reaction in step (1) are as follows: the reaction temperature is 300-420 ℃, preferably 310-405 ℃, and the pressure of a reaction inlet is 6-16 MPa, preferably 8-14 MPa; the volume space velocity is 0.5h^-1～3.0h^-1Preferably 0.6h^-1～2.5h^-1(ii) a The volume ratio of hydrogen to oil at the reaction inlet is 400-1200, preferably 500-1100.

In the method of the invention, the hydrocracking pretreatment reactor is filled with a hydrocracking pretreatment catalyst. The hydrocracking pretreatment catalyst comprises a carrier and hydrogenation metal loaded on the carrier, so thatThe catalyst generally comprises, by weight, a metal component of group VIB of the periodic Table of the elements, such as tungsten and/or molybdenum, in an amount of 10% to 35%, preferably 15% to 30%, calculated as the oxide; group VIII metals such as nickel and/or cobalt, in terms of oxides, ranging from 1% to 7%, preferably from 1.5% to 6%; the carrier is inorganic refractory oxide, and is generally selected from alumina, amorphous silica-alumina, silica, titanium oxide and the like. The preferable metal of the catalyst is Mo-Ni combination, and the specific surface area is not less than 160m²/g^-1Not less than 0.3mL/g^-1. Wherein the conventional hydrocracking pretreatment catalyst can be selected from various existing commercial catalysts, such as 3936, 3996, FF-16, FF-26, FF-36 and FF-46 catalysts developed by the Fushun petrochemical research institute (FRIPP); the desired catalyst may also be prepared as desired according to common knowledge in the art. The refining reaction is a process of removing impurities such as desulfurization, denitrification, aromatic saturation and the like.

In the method, the hydrocracking reaction conditions in the step (2) are as follows: the reaction temperature is 370-435 ℃, preferably 375-430 ℃, and the hydrocracking reaction temperature in the middle and later periods of operation is generally 390-425 ℃; the inlet pressure of the reactor is 6.0MPa to 16.0MPa, preferably 6.5MPa to 15.5 MPa; the volume space velocity is 0.5h^-1～5.0h^-1Preferably 0.8h^-1～2.81h^-1(ii) a The volume ratio of hydrogen to oil at the reaction inlet is 400-2000, preferably 500-1100.

In the method, the high-activity hydrocracking catalyst comprises a carrier component and a hydrogenation component. The cracking component in the carrier typically comprises amorphous silica alumina and/or molecular sieves such as Y-type, β -type or USY molecular sieves, and the binder is typically alumina or silica. The hydrogenation component is selected from metals, metal oxides or metal sulfides in groups VI, VII or VIII, and more preferably one or more of iron, chromium, molybdenum, tungsten, cobalt, nickel or sulfides or oxides thereof. Based on the weight of the catalyst, the content of the hydrogenation component is 5-40%, preferably 10-35%, the content of the molecular sieve is more than 40%, and the balance is amorphous silicon-aluminum and/or aluminum oxide components. The conventional hydrocracking catalyst can be selected from various commercial catalysts, such as FC-46 and FC-52 developed by FRIPP. The specific hydrocracking catalyst may also be prepared as required according to common general knowledge in the art.

The method aims at the conditions that the reaction severity is high, the quality of heavy naphtha is reduced, and the bromine index is increased. In the invention, the content of the catalyst molecular sieve and the reaction temperature are used as limiting indexes, so that the heavy naphtha bromine index is higher after the raw oil is in contact reaction with the high-activity hydrocracking catalyst at the reaction temperature. Under the severe reaction conditions, the yield of the hydrocracked heavy naphtha can generally reach more than 25 wt%. In addition, low pressure (8 MPa or less) is also a case of high severity, and the present invention will not be described in detail. According to the above reaction process, if the hydrocracking catalyst bed bottom continues to use the high-activity hydrocracking catalyst of the kind in combination with the conventional hydrocracking post-treatment catalyst, the bromine index of the heavy naphtha will rise, and in severe cases, the heavy naphtha will have difficulty in meeting the requirements of the downstream device for feeding.

In the method of the invention, compared with the hydrocracking pretreatment catalyst, the cracking catalyst with weak hydrocracking activity has lower hydrogenation and dehydrogenation activities. The weak hydrogenation activity cracking catalyst comprises a carrier component and a hydrogenation component. The cracking component in the carrier generally comprises amorphous silica-alumina and/or molecular sieve, the beta type molecular sieve is used in the invention, the binder is generally alumina or silica, the hydrogenation component is selected from metals, metal oxides or metal sulfides in groups VI, VII or VIII, and in view of weak hydrogenation activity and high-temperature activity stability, one or more of molybdenum, tungsten and cobalt sulfides or oxides are most preferred. Based on the weight of the catalyst, the content of the hydrogenation component is 5.1-22.1 percent, preferably 8.1-20.1 percent, the content of the molecular sieve is 1-20 percent, and the balance is a carrier component. The catalyst has a pore volume of 0.28-0.42 mL/g and a specific surface area of 180-250 m²(ii) in terms of/g. . The hydrocracking catalyst is a proprietary technical catalyst which can be prepared according to the general knowledge in the art in accordance with the above description.

In the step (3), the temperature of the hydrogenation reaction is basically consistent with the reaction temperature in the step (2), and is about 370-435 ℃.

In step (4), the subsequent product separation, fractionation process and various qualified products are conventional technical contents familiar to those skilled in the art, and will not be described herein in a repeated manner.

In view of the research on the hydrocracking process in the prior art, the inventors found that, in a hydrocracking apparatus with a severe reaction process, a high yield of light oil, or a high reaction temperature, the olefin content generated during the hydrocracking process is high, especially in light oil fractions such as heavy naphtha fractions. The hydrocracking post-treatment catalyst used in the prior art has strong hydrogenation performance, and the catalyst with strong hydrogenation performance has correspondingly strong dehydrogenation performance. And because the positions of the post-treatment catalysts are generally temperature extreme regions of the whole reaction process, higher temperature is favorable for hydrogenation reaction, but is also favorable for dehydrogenation reaction. Therefore, for a high-activity hydrocracking catalyst or a high-temperature reaction process, the problems of high heavy naphtha bromine index, high mercaptan and overproof sulfur of aviation kerosene products generally exist at present. In view of the above-identified technical problems, the present invention provides the hydrocracking process described above, and achieves a good result.

Compared with the prior art, the hydrocracking method has the following beneficial effects:

1. aiming at the hydrocracking reaction effluent under the harsh condition, the invention uses a hydrocracking catalyst with weak hydrogenation activity as a hydrocracking post-treatment catalyst at the lower part of a hydrocracking reactor. Compared with the conventional hydrocracking catalyst, the weak hydrocracking catalyst does not need to pursue overhigh hydrogenation performance due to the optimization of the use position and the difference of the reaction purpose, so the dehydrogenation performance is reduced. The excessive dehydrogenation reaction is inhibited while the upper effluent olefin is ensured to be subjected to hydrogenation saturation, the tendency of quality reduction of heavy naphtha in the running process is delayed, and particularly the tendency of olefin generation in a high-temperature reaction section is reduced; the stability and balance of hydrogenation and dehydrogenation are maintained; the method can reduce unsaturated hydrocarbons such as olefin and the like generated in the reaction process to the maximum extent and inhibit the dehydrogenation process of oil products in the reaction process, reduces the olefin as much as possible from multiple aspects, avoids the subsequent reaction with hydrogen sulfide to generate mercaptan sulfur or directly enters products, and has great effect on improving and stabilizing the product quality.

2. The invention utilizes the temperature difference of different reaction zones in the hydrocracking process and the fusion of dehydrogenation reaction zones, optimizes and adjusts the reaction conditions of the interbed hydrocracking catalyst, and transfers the reaction conditions from the original high-temperature section for hydrogenation post-treatment to the reaction section with wider temperature range, so that on one hand, a large amount of olefin generated in the upper reaction process is subjected to saturated hydrogenation so as to be removed, the reaction severity of the catalyst concentrated at the bottom for post-treatment is reduced, on the other hand, the coking tendency and the inactivation rate in the reaction process are delayed, the running stability of the hydrocracking device is improved, the running period of the device can be further prolonged, and the loss caused by unplanned shutdown is reduced for enterprises.

3. The method perfectly integrates the characteristics of the catalyst and the reasonable application of the process conditions, and can realize the purpose of improving the quality of the heavy naphtha product only by matching and filling the catalyst, changing the types and optimizing the conditions on the premise of not modifying a hydrocracking device.

4. Research results show that the conventional hydrocracking post-treatment catalyst is filled at the bottom of a cracking catalyst bed layer, has the function of reducing olefins generated in the reaction process, and can indeed play a good role in the initial stage and the middle stage of hydrocracking operation. However, the inventor of the present application found through research that, because the reaction temperature at the bottom of the hydrocracking reactor is relatively high and basically belongs to the highest temperature level in the whole hydrogenation reaction process, the occurrence probability of the dehydrogenation reaction is also high in the process of saturating olefins; with the extension of the running period, the reaction temperature is higher and higher, and the problem that the bromine index of heavy naphtha exceeds the standard frequently occurs. Particularly, for a hydrocracking device for producing chemical raw material heavy naphtha, the reaction temperature is higher due to the use of a high-activity hydrocracking catalyst; and even more if the activity of the hydrocracking catalyst is reduced, the reaction temperature thereof is further increased. Such problems occur not only in medium-pressure hydrocracking plants, but also frequently in high-pressure hydrocracking plants. Therefore, the heavy naphtha bromine index is higher, and the excessive mercaptan of the aviation kerosene product becomes the more serious problem in the middle and later stages of the current hydrocracking device, and needs to be solved urgently. Aiming at the defects existing in the reaction condition of the post-treatment catalyst, the method utilizes the catalyst bed layer to modify and replace the post-treatment catalyst, balances the relationship between hydrogenation and dehydrogenation, realizes the aims of olefin saturation and generation inhibition at a lower temperature position, reduces the content of olefin in the whole cracking reaction system, meanwhile, hydrogenation catalysts with different performances are graded and used, and through the adjustment of parameters such as activity, aperture and the like, so that the catalyst performance is more matched with the process conditions, and the method has the characteristics of simple operation, safety, controllability and convenience for implementation, can solve the problems of high bromine index and mercaptan in the heavy naphtha in the middle and later periods of operation and over standard mercaptan in the aviation kerosene product, not only improves the stability of the product quality in the operation process of the device and prolongs the operation period, the invention can be realized only by changing the grading of the catalyst without modifying the device.

Detailed Description

The process of the present invention will be described in more detail below with reference to specific examples and comparative examples.

The properties of the feedstock oils used in the following examples and comparative examples are shown in Table 1, and the main properties of the catalysts used in the examples and comparative examples are shown in Table 2.

TABLE 1 Primary Properties of the base oils

TABLE 2 catalyst key Properties

The examples are different from the comparative examples in that only the last hydrocracking catalyst bed is different, all the hydrocracking catalysts in the comparative examples are single cracking catalysts, and the last hydrocracking catalyst bed in the examples uses the catalyst specially prepared by the invention. In all cases, only the filling mode of the catalyst is different, and the rest of the cases do not need to be changed greatly.

Example 1

Adopts a conventional one-stage series process flow. A hydrocracking pretreatment catalyst is used, an upper cracking catalyst is used, B is used, a lower cracking catalyst is used, C is used, the yield of heavy naphtha is controlled to be 30%, and the bromine index of the heavy naphtha is sampled and analyzed.

Example 2

Adopts a conventional one-stage series process flow. A hydrocracking pretreatment catalyst is used, an upper cracking catalyst is used, B is used, a lower cracking catalyst is used, C is used, the yield of heavy naphtha is controlled to be 35%, and the bromine index of the heavy naphtha is sampled and analyzed.

Comparative example 1

Adopts a conventional one-stage series process flow. A hydrocracking pretreatment catalyst is used, a cracking catalyst is used, B is used, the yield of the heavy naphtha is controlled to be 30%, and the bromine index of the heavy naphtha is sampled and analyzed.

Comparative example 2

Adopts a conventional one-stage series process flow. A is used as a hydrocracking pretreatment catalyst, B is used as a cracking catalyst, and A is used as a hydrocracking post-treatment catalyst. And controlling the yield of the heavy naphtha to 35%, and sampling and analyzing the bromine index of the heavy naphtha.

The effects of the above examples and comparative examples were compared, and the results are shown in tables 3 and 4.

Table 3 (operation time 30 days)

Table 4 (running time 800 days)

The embodiment and the comparative example show that the method has the greatest characteristics that under a certain reaction condition, a single reaction temperature range of the original post-treatment catalyst is dispersed through the use of the special catalyst and the change of the filling position, the dehydrogenation capacity of the oil product is reduced and the high-temperature stability is improved while the saturation capacity of olefin is kept, so that the content of the olefin in the product is reduced, the purposes of improving the product quality and the stability are achieved, the operation period of the device can be prolonged, high-quality feeding is provided for a downstream device, the consumption of manpower and material resources is saved, considerable economic benefits and social benefits are brought to enterprises, and the method has great practical application advantages.

Claims

1. A hydrocracking process for reducing the bromine index of heavy naphtha comprising the steps of:

(2) the effluent of the hydrofining reaction enters a hydrocracking reactor, contacts with a high-activity hydrocracking catalyst, and undergoes a hydrocracking reaction at the temperature of 370-435 ℃;

2. The process of claim 1 wherein the hydrocracking feedstock is a waxy oil feedstock or a diesel feedstock.

3. The method according to claim 2, wherein the wax oil feedstock has a first boiling point of 200 ℃ to 300 ℃, a dry point of 500 ℃ to 600 ℃, and a nitrogen content of 2500 μ g/g or less.

4. The method according to claim 1, wherein the conditions of the hydrofinishing reaction in the step (1) are as follows: the reaction temperature is 300-420 ℃, preferably 310-405 DEG CThe inlet pressure is 6MPa to 16MPa, preferably 8MPa to 14 MPa; the volume space velocity is 0.5h^-1～3.0h^-1Preferably 0.6h^-1～2.5h^-1(ii) a The volume ratio of hydrogen to oil at the reaction inlet is 400-1200, preferably 500-1100.

5. The process of claim 1 wherein the yield of heavy naphtha from the hydrocracking reaction in step (2) is 25 wt.% or more.

6. The process of claim 1 wherein the hydrocracking pretreatment reactor is loaded with a hydrocracking pretreatment catalyst, said hydrocracking pretreatment catalyst comprising a support and a supported hydrogenation metal; based on the weight of the catalyst, the catalyst comprises 10-35% of VIB group metal and 1-7% of VIII group metal in the periodic table of elements by oxide; the carrier is an inorganic refractory oxide.

7. The process of claim 1, wherein the hydrocracking reaction conditions in step (2) are as follows: the reaction temperature is 370-435 ℃, preferably 375-430 ℃; the inlet pressure of the reactor is 6.0MPa to 16.0MPa, preferably 6.5MPa to 15.5 MPa; the volume space velocity is 0.5h^-1～5.0h^-1Preferably 0.8h^-1～2.81h^-1(ii) a The volume ratio of hydrogen to oil at the reaction inlet is 400-2000, preferably 500-1100.

8. The process of claim 1 wherein said high activity hydrocracking catalyst comprises a support and a hydrogenation component, said support comprising a molecular sieve; the content of the molecular sieve is more than 40 percent based on the weight of the catalyst.

9. The process of claim 8 wherein the hydrogenation component is selected from the group consisting of group VI, VII or VIII metals, metal oxides or metal sulfides and is present in an amount of from 5% to 40%.

10. A process according to claim 1, wherein the weakly hydrocracked catalyst comprises a support component and a hydrogenation component, the hydrogenation component being present in an amount of from 5.1% to 22.1%, preferably from 8.1% to 20.1% as oxide, based on the weight of the catalyst.

11. The method of claim 10, wherein the carrier component comprises a molecular sieve; based on the weight of the catalyst, the content of the molecular sieve is 1% -20%.

12. The process of claim 1, wherein the hydrogenation reaction of step (3) is carried out at a temperature of 370 ℃ to 435 ℃.