CN109988651B

CN109988651B - Method for producing gasoline by catalyst grading technology

Info

Publication number: CN109988651B
Application number: CN201711469242.5A
Authority: CN
Inventors: 王仲义; 崔哲; 彭冲; 曹正凯; 孙士可; 吴子明
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: 2017-12-29
Filing date: 2017-12-29
Publication date: 2021-02-05
Anticipated expiration: 2037-12-29
Also published as: CN109988651A

Abstract

The invention discloses a method for producing gasoline by a catalyst grading technology. The method carries out restrictive hydrogenation saturation on a conventional heavy raw material, then carries out a hydro-conversion reaction, produces high-quality gasoline or blending components under the conditions of certain process condition limitation and special catalyst grading, and can also produce other high-quality fuel oils or high-quality ethylene cracking raw materials by carrying out a cracking reaction on a by-product liquid phase component. The method can produce the target product to the maximum extent on the basis of the selective processing of the heavy fraction.

Description

Method for producing gasoline by catalyst grading technology

Technical Field

The invention relates to a method for treating wax oil components, in particular to a method for producing high-quality gasoline and high-quality liquid phase products as by-products by processing wax oil raw materials through a catalyst grading technology.

Background

Gasoline is one of the most used light petroleum products, is an important fuel of an engine, can be obtained by different units for petroleum refining, and in the process of crude oil processing, units such as distillation, catalytic cracking, thermal cracking, hydrocracking, catalytic reforming and the like all produce gasoline components, but have different octane numbers, such as the octane number of straight-run gasoline is low, and the gasoline cannot be independently used as engine fuel; in addition, the sulfur content of impurities is different, so that the gasoline component with high sulfur content also needs to be desulfurized and refined, and finally, the gasoline component is blended, and if necessary, a high-octane component needs to be added, so that the gasoline product meeting the national standard is finally obtained.

At present, the main ways for producing gasoline in China are catalytic cracking and catalytic reforming. The catalytic cracking is the most important secondary processing process in the petroleum refining industry at present, and is also the core process for the heavy oil lightening, along with the increasing heavy oil of the world, the processing capacity of an FCC device is continuously improved, various heavy oils are used as raw materials, the main product, namely the high-octane gasoline, is obtained through catalytic cracking reaction, but because the emission standard of the gasoline at present is improved, the production of the catalytic cracking gasoline requires the pre-refining of the raw materials and the post-refining of the product; the catalytic reforming is a process for rearranging the molecular structure of hydrocarbons in gasoline fractions into a new molecular structure, is an important means for improving the quality of gasoline and producing petrochemical raw materials, is an essential process for producing gasoline at present, and has high requirements on the source and cleanliness of the raw materials due to the reaction process and the characteristic requirements of catalysts.

The hydrocracking technology has the advantages of strong raw material adaptability, flexible product scheme, high liquid product yield, good product quality and the like, and is favored by oil refining enterprises of various countries in the world for many years. Hydrocracking, which is one of the main processes for deep processing of heavy oil, can also indirectly produce gasoline components, and due to the characteristics of the processes, the produced heavy naphtha has extremely low impurity content and low octane number, which is exactly opposite to that of catalytic gasoline, and the heavy naphtha is used as a feed of a catalytic reforming unit to produce high-octane gasoline after molecular structure rearrangement.

CN104611029A discloses a catalytic cracking diesel oil hydro-conversion method, wherein catalytic diesel oil and hydrogen gas are mixed and then enter a hydrofining reactor for hydrofining reaction, and then enter a hydrocracking reactor for hydrocracking reaction. Although gasoline with high octane number is produced through a hydro-conversion process, catalytic cracking diesel oil is still used as a raw material essentially, and the range of the raw material for producing high-quality gasoline is not expanded, so that the method has certain limitation.

CN101724454A introduces a hydrocracking method for producing high-octane gasoline, raw oil and hydrogen are mixed and then enter a reactor to be sequentially subjected to hydrofining and hydrocracking reactions, although the method has the characteristics of capability of processing more inferior raw materials, long operation period of a catalyst, good quality of a hydrocracking product and the like. But the used raw material is still the diesel oil component, and heavy oil is not used for directly producing high-octane gasoline.

CN103184073A introduces a hydrocracking method for producing high-octane gasoline blending components, wherein raw oil is subjected to controlled hydrofining and hydro-conversion reaction, although the target product can be high-octane gasoline or blending components through process control, the selection range of the raw material is single, the production cannot be carried out by utilizing heavy oil products, and meanwhile, the catalyst is not effectively improved aiming at the process.

Disclosure of Invention

Aiming at the problems in the prior art, the technical problem to be solved by the invention is to provide a hydrocracking process method for processing heavy raw materials to produce high-octane gasoline. The method carries out restrictive hydrogenation saturation on a conventional heavy raw material and then carries out a hydro-conversion reaction, produces a certain amount of high-quality gasoline or blending components under the conditions of certain process condition limitation and special catalyst grading, simultaneously carries out cracking reaction on a by-product liquid phase component, can also produce other high-quality fuel oil products, can be used as a high-quality ethylene cracking raw material and the like, and furthest produces a target product on the basis of realizing selective processing on heavy fractions.

The invention provides a method for producing high-quality gasoline, which comprises the following steps:

a) under the condition of hydrofining, the heavy oil raw material and hydrogen are mixed and then pass through a reaction zone containing a hydrofining catalyst bed layer to carry out limited hydrofining reaction;

b) carrying out a limiting hydroconversion reaction on the reaction effluent obtained in the step a) through a reaction zone containing a graded wax oil hydroconversion catalyst bed under the hydroconversion process condition;

c) and c) carrying out gas-liquid separation, fractionation and other processes on the reaction effluent obtained in the step b) to obtain converted gasoline, converted diesel oil, unconverted oil and the like, wherein the converted diesel oil and the unconverted oil can be discharged as oil products and can also be subjected to a two-stage conventional hydrocracking reaction, so that a high-quality liquid-phase target product is obtained.

The final boiling point of the heavy oil raw material in the step a) is generally 450-580 ℃, preferably 480-570 ℃, and the density is generally 0.90g/cm³Above, preferably 0.93g/cm³Above, the total aromatic hydrocarbon in the raw material is above 40wt%, preferably above 45wt%, and the nitrogen content is 800mg g^-1Above, preferably 1000mg g^-1The above. Generally, the oil is one or more of vacuum wax oil, deasphalted oil or coker wax oil, and can be selected from the above-mentioned components obtained by processing middle east crude oil or Liaohe crude oil, and the other impurity properties of the raw material must be the common knowledge in the field, and must meet the requirements of that it can be used as feed of hydrocracking equipment.

The hydrofining process conditions in the step a) are as follows: the reaction pressure is 6.0-13.0 MPa, the volume ratio of hydrogen to oil is 200: 1-3000: 1, and the volume airspeed is 0.1-5.0 h^-1The reaction temperature is 260-435 ℃; the preferable operation conditions are that the reaction pressure is 7.0-12.0 MPa, the volume ratio of hydrogen to oil is 300: 1-900: 1, and the volume airspeed is 1.0-3.0 h^-1The reaction temperature is 300-430 ℃.

The limiting hydrofining reaction in the step a) is to control a certain hydrogenation saturation depth to avoid the influence of the over saturation of the aromatic hydrocarbon component in the heavy oil raw material on the octane number of a gasoline fraction product, and the nitrogen content of the refined oil (namely the reaction effluent obtained in the step a) is generally required to be controlled to be 50-250 mg g.g.^-1Preferably 100 to 200 mg/g^-1Thus, the nitrogen content of the refined oil can be reduced while the aromatic hydrocarbon component in the raw material can be retained to the maximum extent. It should be noted that, in the course of the hydrorefining reaction, by controlling the nitrogen content of the refined oil, the aromatic hydrocarbon component in the reaction effluent has a low content of tricyclic and higher aromatic hydrocarbon components, and the total content is generally 1 to 20wt%, preferably 2 to 15 wt%.

The hydroconversion process conditions in the step b) are as follows: the reaction pressure is 6.0-13.0 MPa, the volume ratio of hydrogen to oil is 300: 1-2000: 1, and the volume airspeed is 0.1-5.0 h^-1The reaction temperature is 280-455 ℃; the preferred operating conditions are the reverseThe reaction pressure is 7.0-12.0 MPa, the volume ratio of hydrogen to oil is 400: 1-1000: 1, and the volume airspeed is 1.0-3.0 h^-1The reaction temperature is 310-440 ℃.

The limiting hydroconversion reaction in the step b) is to control a certain hydroconversion depth, so that the octane number of a gasoline fraction product is prevented from being influenced by excessive cracking of non-aromatic hydrocarbon components in the reaction effluent in the step a), and the yield of high-quality gasoline fraction in the total product is generally required to be controlled to be 10-40 wt% according to the difference of the raw materials and the aromatic hydrocarbon in the reaction effluent in the step a), so that the aromatic hydrocarbon components in the raw materials can be retained to the maximum extent and converted into the gasoline fraction while the heavy oil raw materials are processed, and the octane number of the gasoline product is improved.

The hydrofining catalyst of step a) comprises a carrier and a hydrogenation metal loaded. Based on the weight of the catalyst, the catalyst generally comprises 10-35% of metal components in VIB group of the periodic table of elements, such as tungsten and/or molybdenum, calculated by oxide, and preferably 15-30%; group VIII metals such as nickel and/or cobalt are present in amounts of 1% to 7%, preferably 1.5% to 6%, calculated as oxides. The carrier is inorganic refractory oxide, and is generally selected from alumina, amorphous silica-alumina, silica, titanium oxide and the like. The conventional hydrocracking pretreatment catalyst can be selected from various conventional commercial catalysts, such as hydrogenation refining catalysts developed by the Fushu petrochemical research institute (FRIPP), such as 3936, 3996, FF-16, FF-26, FF-36, UDS-6 and the like; it can also be prepared according to the common knowledge in the field, if necessary. The purification catalyst should be loaded upstream of the conversion catalyst.

The grading hydrogenation conversion catalyst in the step b) is at least three hydrocracking catalysts containing molecular sieves, which are specially prepared according to the method, filled according to the difference of the types of aromatic hydrocarbons in the raw oil. And sequentially filling a heavy aromatic hydrocarbon hydrogenation conversion catalyst, a light aromatic hydrocarbon hydrogenation conversion catalyst and a monocyclic aromatic hydrocarbon retention catalyst from top to bottom according to the reactant flow direction.

The corresponding heavy aromatics hydroconversion catalyst is a hydroconversion catalyst containing a molecular sieve, and is a catalyst specially prepared according to the method. The hydroconversion catalyst comprisesHydrogen active metal, a molecular sieve component and an alumina carrier. The general hydrogenation conversion catalyst is composed of hydrogenation active metal components such as W, Mo, Co, Ni and the like, a Y-type molecular sieve component, an alumina carrier and the like. The heavy aromatics hydroconversion catalyst comprises WO by weight₃(or MoO)₃) 9-29 wt%, NiO (or CoO) 5-10 wt%, Y-type molecular sieve 15-45 wt% and alumina 20-50 wt%. In the heavy aromatics hydroconversion catalyst, the Y-type molecular sieve is a small-grain Y-type molecular sieve. The small crystal grain Y-type molecular sieve has a particle size of 400-600 nm, total infrared acid content of 0.3-0.7 mmol/g, and medium-strong acid content of more than 50% (mmol/g)^-1/mmol·g^-1) Cell parameters are 2.435-2.440 nm; the pore volume is 0.5-0.7 cm³The proportion of the 2-8nm secondary pore volume in the total pore volume is more than 60 percent. The Y-type molecular sieve has more accessible and exposed acid centers, is beneficial to the diffusion of hydrocarbon molecules, can improve the preferential conversion capability of cyclic hydrocarbons, particularly tricyclic and higher aromatic hydrocarbons, directionally saturates and breaks aromatic rings in the tricyclic aromatic hydrocarbons, and produces gasoline components with high octane number to the maximum extent. The hydroconversion catalyst containing the small-grain Y-shaped molecular sieve has the main function of performing selective reaction on tricyclic aromatic hydrocarbon in raw materials, and has poor selectivity on non-tricyclic two-ring and monocyclic aromatic hydrocarbon. The Y-type molecular sieve has a certain difference with the conventional Y-type molecular sieve, the grain size of the conventional modified molecular sieve is generally 800-1200 nm, and the pore volume is 0.35-0.50 cm³The proportion of secondary pore volume to total pore volume is generally 30-50%, and the proportion of medium strong acid is 50-70% (mmol. g)^-1/mmol·g^-1). The hydroconversion catalyst may be used to prepare a satisfactory catalyst in accordance with common general knowledge in the art, as described above.

The corresponding light aromatic hydrocarbon hydrogenation conversion catalyst is a hydrogenation conversion catalyst containing a molecular sieve, and is a catalyst specially prepared according to the method. The hydrogenation conversion catalyst comprises hydrogenation active metal, a molecular sieve component and an alumina carrier. The general hydro-conversion catalyst is composed of hydrogenation active metal components such as Wo, Mo, Co, Ni and the like, a molecular sieve component, an alumina carrier and the like. The hydroconversion promoter metal specific for the present invention is preferably Ni, which is selected fromThe weight is comprised of WO₃(or MoO)₃) 5-15 wt%, NiO (or CoO) 3-8 wt%, molecular sieve 50-60 wt% and alumina 5-30 wt%; the molecular sieve may be a Y-type molecular sieve. Further, the Y-type molecular sieve has the following properties: the particle size is 600-800 nm, the unit cell parameter is 2.438-2.442 nm, the infrared total acid is 0.6-0.8 mmol/g, and the proportion of the medium strong acid is 80% (mmol/g)^-1/mmol·g^-1) Wherein the proportion of the 2-8nm secondary pore volume in the total pore volume is more than 50%. The modified Y molecular sieve can be obtained by modifying by a conventional method in the field. The light aromatic hydrocarbon hydroconversion catalyst has the main function of performing selective reaction on bicyclic aromatic hydrocarbon in raw materials, and has poor selectivity on other aromatic hydrocarbon. The present hydroconversion catalyst is a proprietary technical catalyst that can be prepared according to the above description, following common general knowledge in the art.

The corresponding single-ring aromatic hydrocarbon retention catalyst is a hydroconversion catalyst containing a molecular sieve, and the hydroconversion catalyst comprises hydrogenation active metal, a molecular sieve component and an alumina carrier. The general hydro-conversion catalyst is composed of hydrogenation active metal components such as Wo, Mo, Co, Ni and the like, a molecular sieve component, an alumina carrier and the like. The hydroconversion catalyst metal composition specific for the present invention is preferably Mo-Co, which includes MoO by weight₃5-25 wt%, CoO 3-8 wt%, molecular sieve 20-40 wt% and alumina 30-50 wt%, wherein the molecular sieve can be a Y-type molecular sieve. Further, the preferred Y-type molecular sieve has the following properties: the particle size is 500-700 nm, the unit cell parameter is 2.438-2.440 nm, the infrared total acid is 0.6-0.7 mmol/g, and the proportion of the medium-strong acid is 70% (mmol/g)^-1/mmol·g^-1) And the proportion of the 2-8nm secondary pore volume to the total pore volume is 51-55%. The catalyst is characterized in that the preparation process of the molecular sieve adopts a modified Y-type molecular sieve which has moderate acid strength and more non-framework aluminum and is beneficial to retaining monocyclic aromatic hydrocarbon. The main function of the catalyst is to retain monocyclic aromatic hydrocarbons in the upper transfer stream and to selectively react other components than monocyclic aromatic hydrocarbons. The present hydroconversion catalysts may be prepared in accordance with common general knowledge in the art, as described above.

In the present invention, the technical term "strong acid" is used hereinConventional knowledge well known to those skilled in the art. In the field of catalyst preparation, both medium and strong acids adopt NH₃TPD was analyzed, with 150 ℃ desorption defined as weak acid, 250 ℃ desorption defined as medium strong acid, and 400 ℃ desorption defined as strong acid.

The three catalysts need to consider the excessive cracking performance in the grading process, namely, the heavy aromatic hydrocarbon hydroconversion catalyst at the top contacts the refined oil containing nitrogen and mainly reacts on the polycyclic aromatic hydrocarbon, so the cracking performance does not need to be excessively high; the light aromatic hydrocarbon hydrogenation conversion catalyst filled at the lower part of the catalyst has the task of producing high octane gasoline, and simultaneously, the reaction of bicyclic aromatic hydrocarbon is needed, and the cracking activity of the catalyst is higher than that of the heavy aromatic hydrocarbon hydrogenation conversion catalyst; the function of the single-ring aromatic hydrocarbon retaining catalyst at the lowest part is to retain the single-ring aromatic hydrocarbon and simultaneously prevent low-octane components from entering the gasoline fraction, so that the cracking activity of the catalyst is not too high and is close to or slightly lower than that of a heavy aromatic hydrocarbon hydro-conversion catalyst.

The gas-liquid separation and fractionation process described in step c) are well known to those skilled in the art. The gas-liquid separation is a separation process of products in the hydro-conversion process, and generally mainly comprises a high-low pressure separator, a circulating hydrogen system and the like; the fractionation process is a process for further refining a liquid-phase product of gas-liquid separation, and generally mainly comprises a stripping tower, a fractionating tower, a side-line tower and the like.

The converted gasoline in the step c) is a gasoline component obtained in the hydro-conversion process, generally the sulfur content is less than 10 mug/g, and the research octane number is more than 85.

The second-stage conventional hydrocracking reaction in step c) refers to the residual liquid phase component after the high-quality gasoline component is produced by the method, and because the aromatic hydrocarbon content is very low, the hydrocracking process for producing high-quality aviation kerosene or diesel oil products can be directly carried out or used as a raw material for preparing ethylene by steam cracking, and the process is well known by persons skilled in the art and is not described herein again.

Compared with the prior art, the method for producing the high-quality gasoline has the following advantages:

1. the method is characterized in that proper heavy oil raw materials are selected, and after selective saturation and ring-opening chain scission of hydroconversion of a special catalyst, polycyclic aromatic hydrocarbons in the raw materials are converted into high-quality gasoline components, the obtained gasoline components have the characteristics of low sulfur content and high octane number, and can be subjected to blending production. The heavy distillate oil can be converted into high-quality gasoline which is a target product to the utmost extent, an economical and feasible line is found for processing inferior raw materials and producing gasoline, and the method has great practical advantages.

2. The method carries out grading sectional processing on the heavy oil by hydro-conversion in the process flow, and obtains ideal comprehensive processing effect on the basis of improving the quality of gasoline products. In the process flow, the method does not need to modify the device, realizes the purpose of high-quality production only by the combination of the catalyst and the adjustment of physical properties, has the advantages of equipment saving, low operating cost and the like, reduces the investment, and has wide application prospect.

3. The method of the invention has certain limitation on the process condition, has rigid requirements on the reaction depth of a refining section and a conversion section, aims to convert polycyclic aromatic hydrocarbon in heavy raw oil into monocyclic aromatic hydrocarbon as much as possible, retain the monocyclic aromatic hydrocarbon in gasoline fraction, and simultaneously play a role in avoiding excessive cracking of low-octane number fraction, thereby causing the phenomenon of gasoline quality reduction, and can completely realize the purpose of processing heavy raw oil to produce high-quality gasoline to the maximum extent by matching with excessive gradation of a catalyst.

3. According to the method, a new hydroconversion catalyst is developed, which is a great embodiment of technical progress, the production way of high-quality gasoline can be widened, in addition, the newly developed hydroconversion catalyst is purposefully graded, researched and filled according to the content of aromatic hydrocarbon in the raw material, and the degree of main reaction under the conversion working condition of the method can be realized.

Drawings

FIG. 1 is a schematic flow diagram of the process of the present invention.

Detailed Description

The combined process of the present invention will be described in detail with reference to the accompanying drawings. Only the main description of the process flow is given in fig. 1, and some necessary equipment and vessels are also omitted from the schematic.

As shown in FIG. 1, the process flow of the invention is as follows: mixing a heavy raw material 1 and hydrogen 2, and then entering a hydrofining reaction zone to contact and react with a hydrofining catalyst 3; the reaction effluent 4 enters a hydro-conversion reaction zone to be in contact reaction with graded hydro-

conversion catalysts

5, 6 and 7; the product 10 obtained after the reaction effluent 8 enters the separation system 9 continuously enters a fractionation system 11, the upper part of the product discharges the converted gasoline 12, and the rest material flow 13 can be used as liquid fuel or special oil products to be discharged out of the system or enter a second-stage hydrocracking reaction area 14 for subsequent reaction. Catalyst 3 is a hydrofining catalyst, and 5, 6 and 7 are heavy aromatics, light aromatics and monocyclic aromatics respectively and retain a hydroconversion catalyst.

The combined process of the present invention is further illustrated by the following specific examples.

Example 1

The combined process flow shown in figure 1 is adopted, straight-run wax oil is selected as a conversion raw material to carry out hydrogenation to produce gasoline, and certain refining depth (nitrogen content 100 ppm) and conversion depth (gasoline yield 30%) are controlled. The catalysts used in the examples were a commercial catalyst FF-36 hydrotreating catalyst, a tailored hydroconversion catalyst A, B, and a C single ring aromatics retention hydroconversion catalyst.

The properties of catalyst A, B and C are shown in Table 1, the properties of the feed oil are shown in Table 2, and the operating conditions are shown in Table 3.

Example 2

The combined process flow shown in figure 1 is adopted, straight-run wax oil is selected as a conversion raw material to carry out hydrogenation to produce gasoline, and certain refining (nitrogen content of 200 ppm) and conversion depth (gasoline yield of 30%) are controlled. The catalysts used in the examples were a commercial catalyst FF-36 hydrotreating catalyst, a tailored hydroconversion catalyst A, B, and a C single ring aromatics retention hydroconversion catalyst.

Example 3

The combined process flow shown in figure 1 is adopted, straight-run wax oil is selected as a conversion raw material to carry out hydrogenation to produce gasoline, and certain refining (nitrogen content of 200 ppm) and conversion depth (gasoline yield of about 20%) are controlled. The catalysts used in the examples were a commercial catalyst FF-36 hydrotreating catalyst, a tailored hydroconversion catalyst A, B, and a C single ring aromatics retention hydroconversion catalyst.

Comparative example 1

Comparative example 1 is a hydrocracking process for processing straight-run wax oil, the naphtha yield is controlled to 20% according to the conventional hydrofining depth, the comparative product is heavy naphtha, and the catalysts used in the comparative example are a commercial catalyst FF-36 hydrotreating catalyst and an FC-24 hydrocracking catalyst.

The properties of the feed oil are shown in Table 2, and the operating conditions are shown in Table 3.

Comparative example 2

Comparative example 1 is a hydrocracking process for processing straight-run wax oil, the naphtha yield was controlled to 30% according to the conventional hydrofining depth, the comparative product was heavy naphtha, and the catalysts used in the comparative example were commercial catalysts FF-36 hydrotreating catalyst and FC-24 hydrocracking catalyst.

TABLE 1 tailoring the principal physicochemical properties of the conversion catalyst

TABLE 2 raw oil Properties Table

TABLE 3 reaction conditions

TABLE 4 Main Properties of the gasoline fraction

It can be seen from the above examples and comparative examples that the method of the present invention for treating heavy oil feedstock can omit the catalytic reforming process, directly produce gasoline products with high octane number and low sulfur, and has technical advantages compared with comparative examples.

Claims

1. A method for producing high quality gasoline, comprising the steps of:

a) under the condition of a hydrofining process, a heavy oil raw material and hydrogen are mixed and then subjected to a limited hydrofining reaction through a reaction zone containing a hydrofining catalyst bed; the limiting hydrofining means controlling the nitrogen content of refined oil to be 50-250 mu g.g^-1；

b) Carrying out a limiting hydroconversion reaction on the reaction effluent obtained in the step a) through a reaction zone containing a graded wax oil hydroconversion catalyst bed under the hydroconversion process condition; the limiting hydroconversion means that the yield of gasoline fractions in the total product is controlled to be 10-40 wt%;

c) carrying out gas-liquid separation and fractionation on the reaction effluent obtained in the step b) to obtain converted gasoline, converted diesel oil and unconverted oil; wherein,

the heavy oilThe total aromatic hydrocarbon content in the raw material is more than 40wt percent, and the nitrogen content is 800 mu g.g^-1The above;

the graded wax oil hydro-conversion catalyst sequentially comprises a heavy aromatic hydro-conversion catalyst, a light aromatic hydro-conversion catalyst and a monocyclic aromatic retention catalyst according to the direction of a reactant flow;

the heavy aromatics hydroconversion catalyst comprises hydrogenation active metal, a Y-type molecular sieve and an alumina carrier; the particle size of the Y-type molecular sieve is 400-600 nm, the infrared total acid is 0.3-0.7 mmol/g, the proportion of the medium-strong acid is more than 50%, and the unit cell parameter is 2.435-2.440 nm; the pore volume is 0.5-0.7 cm³The proportion of the 2-8nm secondary pore volume in the total pore volume is more than 60%;

the light aromatic hydrocarbon hydrogenation conversion catalyst comprises hydrogenation active metal, a Y-type molecular sieve and an alumina carrier; the unit cell parameter of the Y-type molecular sieve is 2.438-2.442 nm, the infrared total acid is 0.6-0.8 mmol/g, the proportion of the medium-strong acid is more than 80%, wherein the proportion of the secondary pore volume of 2-8nm in the total pore volume is more than 50%;

the monocyclic aromatic hydrocarbon retention catalyst comprises hydrogenation active metal, a Y-type molecular sieve and an alumina carrier; the particle size of the Y-type molecular sieve is 500-700 nm, the unit cell parameter is 2.438-2.440 nm, the infrared total acid is 0.6-0.7 mmol/g, the proportion of the medium strong acid is more than 70%, and the proportion of the secondary pore volume of 2-8nm in the total pore volume is 51-55%.

2. The process of claim 1 wherein said heavy oil feedstock has a total aromatics content of greater than 45 wt.% and a nitrogen content of 1000 mg-g^-1The above.

3. The process according to claim 2, wherein the heavy oil feedstock has an end point of 450 to 580 ℃ and a density of 0.90g/cm³The above.

4. The process according to any of claims 1 to 3, wherein the heavy feed oil is selected from one or more of vacuum wax oil, deasphalted oil or coker wax oil.

5. The process of claim 1, wherein the hydrofinishing conditions of step a) are: the reaction pressure is 6.0-13.0 MPa, the volume ratio of hydrogen to oil is 200: 1-3000: 1, and the volume airspeed is 0.1-5.0 h^-1The reaction temperature is 260-435 ℃.

6. The method according to claim 1, wherein the limited hydrofinishing of step a) is to control the nitrogen content of the refined oil obtained in step a) to be 100-200 μ g-g^-1。

7. The method according to claim 1 or 6, wherein the content of tricyclic and higher aromatic components in the aromatic hydrocarbon component in the reaction effluent obtained in step a) is 1 to 20 wt%.

8. The process of claim 1, wherein the hydroconversion process conditions in step b) are: the reaction pressure is 6.0-13.0 MPa, the volume ratio of hydrogen to oil is 300: 1-2000: 1, and the volume airspeed is 0.1-5.0 h^-1The reaction temperature is 280-455 ℃.

9. The process of claim 1 wherein said heavy aromatics hydroconversion catalyst comprises WO, by weight₃Or MoO₃9-29 wt%, NiO or CoO 5-10 wt%, Y-type molecular sieve 15-45 wt% and alumina 20-50 wt%.

10. The process of claim 1 wherein said light aromatic hydroconversion catalyst comprises WO₃Or MoO₃5-15 wt%, NiO or CoO 3-8 wt%, Y-type molecular sieve 50-60 wt% and alumina 5-30 wt%.

11. The method of claim 1, wherein the single ring aromatics retention catalyst comprises MoO by weight₃5-25 wt%, CoO 3-8 wt%, Y-type molecular sieve 20-40 wt% and alumina 30-50 wt%。

12. The method of claim 1, wherein the converted diesel oil and unconverted oil are discharged as oil products or subjected to conventional hydrocracking reaction.

13. The process according to claim 3, wherein the heavy oil feedstock has an end point of 480 to 570 ℃ and a density of 0.93g/cm³The above.

14. The method according to claim 7, wherein the content of tricyclic and higher aromatic components in the aromatic hydrocarbon component in the reaction effluent obtained in step a) is 2 to 15 wt%.