CN108102704B

CN108102704B - Method for producing high-quality gasoline

Info

Publication number: CN108102704B
Application number: CN201611045496.XA
Authority: CN
Inventors: 王仲义; 彭冲; 崔哲; 刘昶; 吴子明; 孙士可
Original assignee: China Petroleum and Chemical Corp; Sinopec Fushun Research Institute of Petroleum and Petrochemicals
Current assignee: China Petroleum and Chemical Corp; Sinopec Fushun Research Institute of Petroleum and Petrochemicals
Priority date: 2016-11-24
Filing date: 2016-11-24
Publication date: 2020-06-09
Anticipated expiration: 2036-11-24
Also published as: CN108102704A

Abstract

The invention discloses a method for producing high-quality gasoline, which comprises the following steps: a) mixing a heavy oil raw material with hydrogen, and reacting in a reaction zone containing a wax oil hydroconversion catalyst; b) separating the reaction effluent obtained in the step a) to obtain converted gasoline and converted diesel oil; c) mixing the converted diesel oil obtained in the step b) with hydrogen, and reacting the mixture through a reactor containing a diesel oil hydrogenation modification catalyst bed; d) separating the reaction effluent obtained in the step c) to obtain modified gasoline and modified diesel oil; e) mixing the modified diesel oil obtained in the step d) with conventional catalytic cracking feed, then carrying out catalytic cracking reaction, and separating reaction effluent to obtain catalytic gasoline; f) blending the gasoline components obtained in the step b), the step d) and the step e) together to obtain a high-quality gasoline product or blended component. The invention can effectively process heavy raw oil, thereby obtaining high-quality gasoline products or gasoline blending components.

Description

Method for producing high-quality gasoline

Technical Field

The invention relates to a method for processing wax oil components, in particular to a method for processing a wax oil raw material to produce high-quality gasoline.

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 then the gasoline component is blended, and if necessary, a high-octane component needs to be added, and finally, a gasoline product meeting the national standard is 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. The method carries out hydrogenation conversion reaction on the conventional heavy raw materials, produces high-quality gasoline or blending components under the conditions of certain process condition limitation and special catalyst grading, simultaneously carries out modification reaction on the by-product diesel components to produce high-quality diesel components and gasoline blending components, furthest produces target products on the basis of realizing processing of heavy fractions, and simultaneously carries out targeted treatment on other by-product components.

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

a) under the condition of a hydro-conversion process, a heavy oil raw material is mixed with hydrogen and then reacts in a reaction zone containing a hydrofining and wax oil hydro-conversion catalyst bed layer;

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

c) under the condition of a hydrogenation modification process, the converted diesel oil obtained in the step b) is mixed with hydrogen and then reacts through a reactor containing a hydrogenation refining and diesel oil hydrogenation modification catalyst bed layer;

d) carrying out gas-liquid separation, fractionation and other processes on the reaction effluent obtained in the step c) to obtain modified gasoline and modified diesel oil;

e) mixing the modified diesel oil obtained in the step d) with other catalytic cracking feed materials, then feeding the mixture into a catalytic cracking unit for reaction, and separating reaction effluent to obtain catalytic gasoline, catalytic diesel oil and catalytic slurry oil;

f) blending the converted gasoline in the step b), the modified gasoline in the step d) and the catalytic gasoline in the step e) together to obtain a high-quality gasoline product or gasoline blending component.

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 0.92g/cm³Above, preferably 0.93g/cm³The above. The heavy distillate oil is one or more of vacuum wax oil, deasphalted oil, coked wax oil or catalytic slurry oil, and can be selected from the components obtained by processing middle east crude oil or Liaohe crude oil, and the properties of other impurities of the raw materials are common knowledge in the field and must meet the requirement of being used as the feed of a hydrocracking unit.

The hydroconversion process conditions in the step a) are as follows: the reaction pressure is 6.0-12.0 MPa, the volume ratio of hydrogen to oil is 200: 1-1000: 1, and the volume airspeed is 0.1-5.0 h^-1The reaction temperature is 260-455 ℃; the preferable operation conditions are that the reaction pressure is 7.0-11.0 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 300-440 ℃.

The hydrofining catalyst for hydrogenation in the steps a) and c) comprises a carrier and hydrogenation metal loaded. Based on the weight of the catalyst, the catalyst generally comprises a metal component of group VIB of the periodic table of elements, such as tungsten and/or molybdenum, accounting for 10-35 percent of oxide, preferably 15-30 percent; group VIII metals such as nickel and/or cobalt, in terms of oxides, are in the range of 1% to 7%, preferably 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 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 or upgrading catalyst.

The grading hydrogenation conversion catalyst in the step a) is at least two hydrocracking catalysts containing molecular sieves which are filled in a grading way according to the nitrogen content in the raw oil, and the catalysts are 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 comprises 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 catalysts which are specific for the present invention comprise, by weight, WO₃(or MoO)₃) 5-15 wt%, NiO (or CoO) 1-10 wt%, molecular sieve 30-70 wt% and alumina 20-50 wt%, wherein the molecular sieve can be Y type, β type or ZSM type molecular sieve, preferably Y type molecular sieve, the particle size of the Y type molecular sieve is 400-600 nm, and the unit cell parameter is 2.433-2.448 nm.

For the grading of the catalyst, the difficulty of removing nitrogen is high under the condition of the hydroconversion of the invention, so the nitrogen resistance of the hydroconversion catalyst is gradually reduced according to the flow direction of reaction materials. The main physical properties of the graded catalyst should be as described above, but there is a special way to process and modify the molecular sieve to distinguish its different nitrogen resistance. Wherein, the molecular sieve inside the catalyst filled in the material flow upstream has the following characteristics: unit cell parameterThe number is 2.433-2.438 nm, preferably more than or equal to 2.433 and less than 2.438 nm; infrared total acid 0.5-0.7 mmol/g, secondary pores of 1.7-10nm accounting for total pore volume (molecular sieve pore volume) over 70%, and strong acid center proportion of 50% (mmol/g)^-1/mmol·g^-1) The total molecular sieve content accounts for 30-40 wt% of the weight of the catalyst; and the internal molecular sieve of the catalyst filled in the downstream of the material flow has the following characteristics: the unit cell parameter is 2.438-2.448 nm, the infrared total acid is 0.8-1.0 mmol/g, the proportion of 1.7-10nm secondary pores in the total pore volume (molecular sieve pore volume) is more than 70%, the proportion of strong acid centers is more than 80%, and the total molecular sieve content accounts for 50-60 wt% of the weight of the catalyst. The special molecular sieve has a certain difference with a conventional molecular sieve, the conventional modified molecular sieve used in the hydro-conversion catalyst generally has the grain size of 800-1200 nm, and the proportion of secondary pores with the grain size of 1.7-10nm in the total pore volume is generally 20-40%.

In the present invention, the technical term "strong acid" is conventional 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.

In the step a), the grading volume ratio of the two hydroconversion catalysts with different nitrogen resistance is generally 1: 10-10: 1, and preferably 1: 5-5: 1.

The gas-liquid separation and fractionation processes described in step b) and step d) are well known to those skilled in the art. The gas-liquid separation is the separation process of products in the hydro-conversion and modification processes, 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.

Wherein the unconverted oil from step b) may be recycled back to step a) to be mixed with the heavy oil feedstock or fed to a catalytic cracking unit as feed.

The initial boiling point of the catalytic cracking feed in the steps b) and e) is generally 250-600 ℃, and preferably 280-500 ℃. The heavy distillate oil is selected from one or more of various heavy distillate oils obtained by processing crude oil, such as vacuum wax oil, coker wax oil, atmospheric residue, vacuum residue and cracking tail oil, and can be obtained by processing any crude oil.

The catalytic cracking described in steps b) and e) generally comprises three sections, a reaction-regeneration system, a fractionation system and an absorption-stabilization system, the reaction-regeneration system operating under the following conditions: the reaction pressure is 0.1-0.6 MPa, and the reaction temperature is 400-650 ℃; the preferable operation conditions are that the reaction pressure is 0.2-0.4 MPa and the reaction temperature is 450-600 ℃. The catalyst used is a conventional catalytic cracking catalyst in the field, and generally comprises a molecular sieve and a supporter, wherein the content of the molecular sieve is about 5-15%, and the molecular sieve can be an X-type or Y-type molecular sieve; the components of the supporter are natural argil, synthetic low-aluminum silicate or high-aluminum silicate.

The hydro-upgrading catalyst in the step c) is a hydrocracking catalyst containing a molecular sieve, and refers to a common hydrocracking catalyst or a hydro-upgrading catalyst special for the invention. The catalyst can realize the reaction of the open loop and the continuous chain of the diesel components by matching with the process conditions, and the cetane number of the diesel is improved to the maximum extent. The general hydrocracking catalyst consists of active metal components of Wo, Mo, Co, Ni, Fe, etc., molecular sieve component, alumina carrier, etc. and has hydrogenation component content of 5-40 wt%. The hydro-upgrading catalyst specially used in the invention comprises WO by weight₃(or MoO)₃) 13-25 wt%, NiO (or CoO) 3-10 wt%, molecular sieve 10-30 wt% and alumina 40-60 wt%, wherein the molecular sieve can be Y type, β type or ZSM type molecular sieve, the conventional hydrogenation modified catalyst can be selected from various existing commercial catalysts, such as 3963 catalyst developed by FRIPP, FC-18 catalyst and the like, and the specific hydrogenation modified catalyst can also be prepared according to the requirement according to the common knowledge in the field.

The operation conditions of the hydro-upgrading reaction zone in the step c) are as follows: the reaction pressure is 6.0-12.0 MPa, the volume ratio of hydrogen to oil is 200: 1-1000: 1, and the volume is emptyThe speed is 0.1-5.0 h^-1The reaction temperature is 260-455 ℃; the preferable operation conditions are that the reaction pressure is 7.0-10.0 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 300-400 ℃.

The catalytic diesel oil obtained in the step e) can be recycled to the step c) to be mixed with the converted diesel oil, and the obtained catalytic slurry oil can be recycled to the step a) to be mixed with the heavy raw material.

The converted gasoline in the step f) is a gasoline component obtained in a hydro-conversion process, the general sulfur content is less than 10 mug/g, and the research octane number is greater than 89, the modified gasoline is a gasoline component obtained in a hydro-modification process, the general sulfur content is less than 10 mug/g, and the research octane number is greater than 60, the catalytic gasoline is a gasoline component obtained in a catalytic cracking process, the general sulfur content is less than 600 mug/g, and the research octane number is greater than 91, and in an actual production process, conventional blending can be performed according to the requirements of the product, so that a high-quality gasoline product with low sulfur content and high octane number is obtained.

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

1. selecting proper heavy oil raw material, making it pass through the hydrogenation conversion selective saturation of special catalyst and ring-opening chain-breaking process, polycyclic aromatic hydrocarbon in the raw material is converted into gasoline or diesel oil component, the obtained gasoline component has the characteristics of low sulfur content and high octane number, can be used for blending high-quality gasoline, under the condition of the method, the properties of the obtained diesel components have no advantages, but after the diesel components are saturated and opened by hydrogenation modification, the diesel oil is converted into diesel oil with low sulfur content and higher cetane number and then enters a catalytic cracking device, can improve the yield of catalytic gasoline and reduce the sulfur content, the obtained unconverted oil can be used as catalytic cracking raw material through hydrogenation, the sulfur content in the catalytic product can be reduced, and in addition, according to the mechanism of catalytic reaction, the hydrogen-carbon ratio in the raw material is increased, and the yield and the property of the obtained catalytic gasoline are also improved to a certain extent after catalytic cracking; the poor quality catalytic diesel oil and catalytic slurry oil generated by the catalytic device can be selectively recycled to the conversion device or the modification device for continuous processing, an economical and feasible line is found for the treatment of the poor quality catalytic cracking fraction, and the method has great advantages.

2. The method deeply couples the heavy oil hydro-conversion, the diesel hydro-upgrading and the catalytic cracking in the process flow, and obtains ideal comprehensive processing effect on the basis of improving the product quality. In the process flow, the method combines different units, has the advantages of equipment saving, low operation cost and the like, and simultaneously reduces the energy consumption of the device and the investment to a certain extent due to the improvement of a heat exchange system caused by coupling, thereby having wide application prospect.

3. According to the method, a new heavy oil hydroconversion catalyst is developed on the basis of the original diesel hydroconversion catalyst, which is a great embodiment of technical progress and can widen the production path of high-quality gasoline. In addition, the newly developed hydro-conversion catalyst is purposefully graded, researched and filled according to the nitrogen content in the raw material, the problem that the catalyst is possibly poisoned by nitrogen due to the fact that the pressure is lower under the conversion working condition by the method can be solved, in the past, in the production process, for the hydrogenation process of the wax oil raw material, if light fractions are produced, only heavy naphtha raw material with high aromatic hydrocarbon potential can be provided for a catalytic reforming device, but high-quality gasoline cannot be directly produced, and by adopting the method, the wax oil raw material can be directly converted into a gasoline product required by the market, so that the method has great competitive advantage technically, more production flexibility is provided for enterprises, and visual economic benefits are brought. The catalyst has strong cracking performance and weaker hydrogenation performance, and can realize the directional conversion of polycyclic aromatic hydrocarbon into monocyclic aromatic hydrocarbon. The molecular sieve prepared by the conventional method has larger grain size, is not beneficial to uniform dispersion in a matrix, causes overhigh concentration of the molecular sieve at certain parts in the matrix, reduces the dispersity of a cracking active center in a catalyst, reduces the use efficiency of the catalyst and reduces the selectivity of a target product. The small-grain high-crystallinity high-silica-alumina-ratio molecular sieve is applied to cracking reaction, can relatively increase the active center, enables heavy oil macromolecules to be more easily close to the active center, improves the conversion capability of heavy oil, and has larger external surface area compared with a larger-grain molecular sieve, thereby showing more excellent performance in the aspect of macromolecule conversion. In addition, the catalyst has large proportion of secondary pores of the molecular sieve, and less non-framework structures in pore channels, thereby being more beneficial to macromolecular adsorption reaction and desorption and the reaction of polycyclic aromatic hydrocarbon.

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 figure 1, the combined process flow for producing high-quality gasoline of the invention is as follows: mixing a heavy raw material 1 with hydrogen 2, and then entering a hydrogenation reaction zone to sequentially contact and react with hydrogenation catalysts 3, 4 and 5; the reaction effluent 6 enters a separation and fractionation system 7, the upper part discharges conversion gasoline 8, the middle part obtains conversion diesel oil 9, and the bottom obtains unconverted oil 10; wherein, the converted diesel oil 9 is mixed with hydrogen 11 and then enters a hydrogenation reaction zone to be sequentially contacted with hydrogenation catalysts 12 and 13 for reaction; the reaction effluent 14 enters a separation and fractionation system 15, modified gasoline 16 is discharged from the upper part, and modified diesel oil 17 is obtained from the bottom; wherein the modified diesel oil 17 and the catalytic cracking feed 18 are mixed and then enter a catalytic cracking unit 19 for reaction, separation and fractionation, the upper part discharges catalytic gasoline 20, the middle part obtains catalytic diesel oil 21 which can be recycled to the hydrogenation reaction zone to be mixed with the converted diesel oil 9, the bottom obtains catalytic oil slurry 22 which can be recycled to the hydrogenation reaction zone to be mixed with the heavy raw material 1; the unconverted oil 10 can be recycled to the hydrogenation reaction zone to be mixed with the heavy feedstock 1 or can be mixed with the catalytic cracking feed 18 as a feed to a catalytic cracking unit; the converted gasoline 8, the modified gasoline 16 and the catalytic gasoline 20 are mixed together to obtain high-quality gasoline 23; catalysts 3 and 12 are hydrofining catalysts, catalysts 4 and 5 are graded hydro-conversion catalysts, and catalyst 13 is a hydro-upgrading catalyst.

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

Example 1

The combined technological process shown in figure 1 is adopted, straight-run wax oil is selected as a conversion raw material to be hydrogenated to produce gasoline, and a gasoline product is mixed with diesel modified gasoline and catalytic gasoline to obtain high-quality gasoline. The catalysts used in the examples were commercial catalyst FF-36 hydrotreating catalyst, specialty hydroconversion catalysts A and B, FC-18 hydro-upgrading catalyst, and LHO-1 catalytic cracking catalyst.

The properties of catalysts A and B 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 technological process shown in figure 1 is adopted, the mixed wax oil is selected as a conversion raw material to be hydrogenated to produce gasoline, and the gasoline product is mixed with diesel modified gasoline and catalytic gasoline to obtain high-quality gasoline. The catalysts used in the examples were commercial catalyst FF-36 hydrotreating catalyst, specialty hydroconversion catalysts A and B, FC-18 hydro-upgrading catalyst, and LHO-1 catalytic cracking catalyst.

Comparative example 1

Comparative example 1 is a hydrocracking process for processing a mixed wax oil, the comparative product is heavy naphtha, and the catalysts used in the comparative example are a commercial catalyst FF-36 hydrotreating catalyst, FC-24 hydrocracking catalyst.

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

Table 1 tailoring the main physicochemical properties of the conversion catalyst.

Table 2 raw oil properties table.

Table 3 reaction conditions.

Table 4 gasoline fraction main properties.

As can be seen from the above examples, the treatment of heavy oil feedstock using the present invention, compared to the comparative examples, can eliminate the catalytic reforming process and directly produce high octane, low sulfur gasoline products, with technical advantages.

It can be seen from the above examples and comparative examples that the gasoline produced in the hydroconversion of the heavy oil and the gasoline produced by the combined process are blended together, so that high-quality gasoline blending components meeting the national IV emission standards can be directly produced, and the technology for producing high-quality gasoline by hydroconversion of the heavy oil is developed.

In addition, the problem that the nitrogen poisoning of the catalyst is possibly caused by low pressure under the hydro-conversion working condition can be solved by the grading research and development and filling of the new catalyst, and the method is proved to have higher adaptability and applicability.

The heavy oil hydro-conversion, diesel hydro-upgrading and catalytic cracking are deeply coupled in the process flow, so that an ideal comprehensive processing effect is obtained on the basis of improving the product quality, the advantages of equipment saving, low operation cost and the like are achieved, and meanwhile, due to the improvement of a heat exchange system caused by coupling, the energy consumption of the device is reduced to a certain extent, the investment is reduced, and the method has a wide application prospect.

Claims

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

a) under the condition of a hydro-conversion process, a heavy oil raw material is mixed with hydrogen and then reacts in a reaction zone containing a hydrofining and graded wax oil hydro-conversion catalyst bed layer;

b) carrying out gas-liquid separation and fractionation on the reaction effluent obtained in the step a) to obtain converted gasoline, converted diesel oil and unconverted oil, and recycling the unconverted oil to the step a) to be mixed with the heavy oil raw material or to be supplied to a catalytic cracking unit as a feed;

d) carrying out gas-liquid separation and fractionation on the reaction effluent obtained in the step c) to obtain modified gasoline and modified diesel oil;

f) blending the converted gasoline in the step b), the modified gasoline in the step d) and the catalytic gasoline in the step e) together to obtain a high-quality gasoline product;

wherein, the wax oil hydrogenation conversion 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 unit cell parameter is 2.433-2.448 nm, and the proportion of secondary pores of 2-8nm in the total pore volume is more than 70%;

the wax oil hydroconversion catalyst in the step a) adopts a grading scheme: the Y-type molecular sieve of the upstream-loaded catalyst has the following characteristics: infrared total acid is 0.5-0.7 mmol/g, the proportion of strong acid centers is more than 50%, and the content of the total molecular sieve accounts for 30-40 wt% of the weight of the catalyst; the Y-type molecular sieve of the catalyst loaded at the downstream has the following characteristics: infrared total acid 0.8-1.0 mmol/g, strong acid center proportion over 80%, total molecular sieve content 50-60 wt% of catalyst weight.

2. The process according to claim 1, characterized in that the catalytic diesel obtained in step e) is recycled to step c) to be mixed with the converted diesel and the catalytic slurry oil obtained is recycled to step a) to be mixed with the heavy feedstock.

3. The process of claim 1 wherein said heavy oil feedstock has an end point of 450 to 580 ℃ and a density of 0.92g/cm³The above.

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

5. The method according to claim 3 or 4, wherein the heavy oil feedstock is one or more of vacuum wax oil, deasphalted oil, coker wax oil or catalytic slurry oil.

6. The process of claim 1, wherein the hydroconversion process conditions in step a) are: the reaction pressure is 6.0-12.0 MPa, the volume ratio of hydrogen to oil is 200: 1-1000: 1, and the volume airspeed is 0.1-5.0 h^-1The reaction temperature is 260-455 ℃.

7. The process of claim 6 wherein the hydroconversion process conditions in step a) are: the reaction pressure is 7.0-11.0 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 300-440 ℃.

8. The process of claim 1 wherein the hydrofinishing catalyst of steps a) and c) comprises a support and a hydrogenation metal supported thereon, comprising from 10% to 35% by weight on an oxide basis of tungsten and/or molybdenum and from 1% to 7% by weight on an oxide basis of nickel and/or cobalt; the carrier is an inorganic refractory oxide.

9. The process of claim 1, wherein the wax oil hydroconversion catalyst of step a) comprises, by weight, WO₃Or MoO₃5-15 wt%, NiO or CoO 1-10 wt%, Y-type molecular sieve 30-70 wt% and alumina 20-50 wt%.

10. The process of claim 1, wherein the wax oil hydroconversion catalyst employs a grading scheme: the nitrogen resistance of the catalyst gradually decreases in the direction of the reaction flow.

11. The process according to claim 1, characterized in that the Y-type molecular sieve of the catalyst loaded upstream has the following characteristics: the unit cell parameter is 2.433-2.438 nm; the Y-type molecular sieve of the catalyst loaded at the downstream has the following characteristics: the unit cell parameter is 2.438 to 2.448 nm.

12. The process of claim 11, wherein the two hydroconversion catalysts are present in a ratio of 1: 10 to 10: 1 by volume gradation.

13. The process of claim 1, wherein the initial boiling point of the catalytically cracked feedstock in step b) and step e) is in the range of 250 to 600 ℃.

14. The process of claim 13, wherein the catalytic cracking feed in step b) and step e) is one or more selected from vacuum wax oil, coker wax oil, atmospheric residue, vacuum residue, and cracked tail oil.

15. The process according to claim 1, characterized in that the catalytic cracking in step b) and step e) comprises three sections, a reaction-regeneration system, a fractionation system and an absorption-stabilization system.

16. The method of claim 15, wherein the reaction-regeneration system is operated under the following conditions: the reaction pressure is 0.1-0.6 MPa, and the reaction temperature is 400-650 ℃.

17. The process of claim 1, wherein the hydro-upgrading catalyst of step c) comprises, by weight, WO₃Or MoO₃13-25 wt%, NiO or CoO 3-10 wt%, molecular sieve 10-30 wt% and alumina 40-60 wt%.

18. The process of claim 1 wherein said hydro-upgrading reaction zone of step c) is operated under conditions selected from the group consisting of: the reaction pressure is 6.0-12.0 MPa, the volume ratio of hydrogen to oil is 200: 1-1000: 1, and the volume airspeed is 0.1-5.0 h^-1The reaction temperature is 260-455 ℃.

19. The method of claim 18, wherein the preferred operating conditions are a reaction pressure of 7.0 to 10.0MPa, a hydrogen-oil volume ratio of 300: 1 to 900: 1, and a volume space velocity of 1.0 to 3.0 h^-1The reaction temperature is 300-400 ℃.