CN104611050B

CN104611050B - A kind of catalytic cracking diesel oil method for transformation

Info

Publication number: CN104611050B
Application number: CN201310540463.2A
Authority: CN
Inventors: 柳伟; 杜艳泽; 王凤来; 刘昶; 秦波; 张晓萍
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: 2013-11-05
Filing date: 2013-11-05
Publication date: 2016-08-17
Anticipated expiration: 2033-11-05
Also published as: CN104611050A

Abstract

The invention discloses a kind of catalytic cracking diesel oil method for transformation.Catalytic diesel oil is introduced into hydrofining reactor and carries out hydrofining reaction after mixing with hydrogen；Hydrofining reaction effluent is directly entered hydrocracking reactor, with the beds haptoreaction of grating in cracker；Wherein arranging at least two Cracking catalyst bed in hydrocracking reactor, according to the flow direction of reaction mass, the hydrogenation activity of hydrocracking catalyst is in reducing trend；Hydrocracking reaction effluent, through separating and fractionation, obtains naphtha and diesel oil.The inventive method while ensureing H-G hydrocracking effect, can reduce excessive hydrogenation and the second pyrolysis of pressure naphtha, reduces chemical hydrogen consumption, thus improves octane number and the liquid yield of naphtha.

Description

A kind of catalytic cracking diesel oil method for transformation

Technical field

The present invention relates to a kind of hydrocarbon hdyrotreating method, a kind of catalytic cracking diesel oil method for transformation.

Background technology

Since entering the new century, along with the enhancing day by day of people's environmental consciousness, the increasingly strict of national environmental protection regulation and the fast development of national economy, the demand of cleaning automotive fuel is all being continuously increased by countries in the world.Catalytic cracking (FCC) technology is one of main technique means of heavy oil lighting, the status that all occupation ratio is more important in the oil refining enterprise of countries in the world.China's catalytic cracking unit annual working ability alreadys more than 100,000,000 tons at present, is only second to the U.S..In petrol and diesel oil product are constituted, catalytically cracked gasoline accounts for about 80%, and catalytic diesel oil accounts for about 30%.In recent years, heaviness day by day along with domestic processed crude quality, the raw material that catalytic cracking is processed heaviness the most increasingly and in poor quality, in addition many enterprises are in order to reach to improve the purpose of quality of gasoline or propylene enhancing, catalytic cracking unit is carried out transformation or has improve the operating severity of catalytic cracking unit, the quality causing the product of catalytic cracking, particularly catalytic diesel oil more deteriorates.

For improving the utilization rate of petroleum resources, improve the total quality level of petrol and diesel oil fuel, realize product blending to optimize and the maximized target of value of the product, meeting domestic to cleaning fuel increasing need, high aromatics diesel hydro-conversion produces the novel technique that is hydrocracked of high added value naphtha component and low-sulfur cleaning diesel fuel and has good application prospect.Researcher has been also carried out substantial amounts of research work both at home and abroad.Abroad use hydrocracking process technology that catalytic cracking light cycle oil is converted into the relevant report of ultra-low-sulphur diesel and high octane value gasoline blending component.As: the meeting of nineteen ninety-five NPRA, David A.Pappal et al. describes by Mobil, Akzo Nobel/Nippon Ketjen and a kind of single-stage hydrocracking technology of M.W.Kellogg company exploitation；NPRA meeting in 2005, Vasant P. Thakkar et al. describes the LCO UnicrackingTM technology of Uop Inc.'s exploitation.It is reported, the catalytic cycle oil ingredient of low value all can be converted into high octane gasoline component and fine-quality diesel oil blending component by both the above technology.But at present, prior art there is also some problems, high aromatics diesel transformation technology main purpose is that high aromatics diesel is converted into high octane gasoline component, simultaneously, reduce the sulfur content of diesel oil and improve diesel cetane-number, the hydrogenation of gasoline component and diesel component also exists contradiction, when cracking zone catalyst hydrogenation hyperenergia, the gasoline component excessive hydrogenation that cracking generates, product octane number is relatively low, and during cracking zone catalyst hydrogenation scarce capacity, diesel product is second-rate, meanwhile, catalyst carbon deposition speed can be made to accelerate, affect long-term operation.In the process, the problem having related to selective hydrogenation, the hydrogenation selectivity improving gasoline component and diesel component becomes the problem faced by this kind of hydrocracking process needs.

Summary of the invention

It is converted into problem present in high-knock rating gasoline technology for catalytic cracking diesel oil, a kind of method that the invention provides filling hydrocracking catalyst at different stages, preferably diesel oil distillate and gasoline fraction are carried out selective hydrogenation, improve productivity and the octane number of the gasoline component that hydrocracking process generates, meanwhile, reactive hydrogen consumption is reduced.

A kind of catalytic cracking diesel oil method for transformation of the present invention, including herein below:

(1) under the conditions of hydrofining technology, the mixed material of catalytic cracking diesel oil and hydrogen is introduced into hydrogenation reactor and carries out hydrofining reaction；

(2) hydrofining reaction effluent is directly entered cracker, mixed catalyst bed haptoreaction with two or more grading loading, flow direction according to reaction mass, the hydrogenation activity of mixed catalyst bed is on a declining curve, and wherein said mixed catalyst bed is formed with hydrocracking catalyst mixed packing by the body phase method Hydrobon catalyst of high hydrogenation activity；The cracking activity of preferred mixed catalyst bed also reduces along Flow of Goods and Materials direction；

(3) step (2) obtains that hydrocracking reaction effluent is separated and fractionation obtains naphtha component and diesel component, wherein naphtha component directly goes out device as high-knock rating gasoline blend component, diesel component can directly go out device blended diesel, it is possible to loops back cracker and reacts further.

In the hydrogenating conversion process of the present invention, in step (2), in hydrocracking reactor, the adjustment of mixed catalyst bed hydrogenation activity can be realized by the mixed proportion changing body phase method catalyst for refining and hydrocracking catalyst.Generally according to the flow direction of reaction mass, body phase method Hydrobon catalyst ratio in difference mixing beds is gradually reduced.In different mixed catalyst beds, body phase method Hydrobon catalyst can be 0～5:1 with the ratio of hydrocracking catalyst.It is 1:10～10:1 that two of arbitrary neighborhood are hydrocracked the volume ratio of mixed catalyst bed

In the hydrocracking process of the present invention, in addition to above-mentioned suitable mixed catalyst grading distribution scheme, can further include herein below: gas phase is set between the mixed catalyst bed that at least two is adjacent in step (2) and draws pipeline, partial gas phase logistics can be drawn pipeline via gas phase and be led to high-pressure separator, and liquid phase and residue gas phase mixture proceed hydrocracking reaction.

Generally, at reaction conditions after raw material reaction rate of gasification (rate of gasification refers at reaction conditions, the raw material being converted into gas phase accounts for the ratio of raw material gross mass, not hydrogen) more than 30 mass %, gas phase is set between the Cracking catalyst bed of preferably greater than 50 mass % and draws pipeline.

Described gas phase is drawn pipeline and is preferably provided at catalyst bed interlayer gas-liquid partition tray or the lower section of cold hydrogen box, and gas phase is drawn pipeline and is provided with flow control valve.During normal operating, a gas-phase space can be formed at the bottom of gas-liquid partition tray or cold hydrogen box, and gas phase is drawn pipeline opening in reactor and is arranged in this gas-phase space, and liquid phase material does not the most enter gas phase and draws pipeline.The present invention preferably draws pipeline opening part in gas phase baffle plate is set, draw pipeline to prevent liquid phase from entering gas phase further.

The hydrogen to oil volume ratio drawing the beds above pipeline in gas phase is generally 700:1～3000:1, preferably 800:1～1500:1；Gas phase is drawn the hydrogen to oil volume ratio of beds below pipeline and is generally 220:1～2000:1, preferably 300:1～1000:1.Preferably the hydrogen-oil ratio of hydrocracking reactor is higher than the hydrogen to oil volume ratio 200～800 of hydrofining reactor, most preferably exceeds 300～600.

Described gas phase is drawn the gas gas-phase objects doses of pipeline extraction and is generally the 20%～70% of recycle hydrogen tolerance (by volume), preferably 30%～60%.

Method in the present invention, the refining stage pretreatment catalyst of selection and cracking segment body phase method refining agent and cracking agent can use commercially available prod, it is also possible to prepare according to this area Conventional wisdom.Refining stage pretreatment agent used by the present invention can use conventional hydrocracking pretreatment catalyst, typically with VI B race and/or group VIII metal as active component, with aluminum oxide or silicon-containing alumina as carrier.Group VIB metal is generally Mo and/or W, and group VIII metal is generally Co and/or Ni.On the basis of the weight of catalyst, group VIB tenor is calculated as 8wt% ~ 28wt% with oxide, and group VIII metal content is calculated as 2wt% ~ 15wt% with oxide.The body phase method catalyst for refining that cracking zone is selected contains tri-kinds of active components of W, Mo, Ni, and in catalyst, W, Ni are with composite oxides Ni_xW_yO_z, z=x+3y, Mo are with oxide M oO₃Presented in.Compound Ni_xW_yO_zThe atomic molar of x and y is than for 1:8 ~ 8:1, preferably 1:4 ~ 4:1.Compound Ni_xW_yO_zWith MoO₃Weight ratio 1:10 ~ 10:1, preferably 1:5 ~ 5:1.Ni in bulk phase catalyst_xW_yO_zWith MoO₃Gross weight content be 40% ~ 100%, preferably 50% ~ 80%.Hydrocracking catalyst is the hydrocracking catalyst containing Modified Zeolite Y, and catalyst contains WO by weight₃15 ~ 30%, NiO or CoO 2 ~ 15%, modified Y molecular sieve 30 ~ 90%, preferably 50 ~ 80%.Carrier is aluminum oxide or amorphous silica-alumina.

In the inventive method, described weighted BMO spaces segment process condition includes: reaction temperature is 320 DEG C～440 DEG C, preferably 340 DEG C～420 DEG C；Reaction pressure is 4.0 MPa～15.0 MPa, preferably 6.0 MPa～12.0 MPa；During liquid, volume space velocity is 0.2h^-1～6.0h^-1, preferably 0.5h^-1～3.0h^-1；Hydrogen to oil volume ratio is 100～2000, preferably 500～1500.

In the present invention in method, described hydrocracking process condition includes: reaction temperature is 340 DEG C～440 DEG C, preferably 360 DEG C～430 DEG C；Reaction pressure is 4.0 MPa～15.0 MPa, preferably 6.0 MPa～12.0 MPa；During liquid, volume space velocity is 0.2h^-1～6.0h^-1, preferably 0.5h^-1～3.0h^-1；Hydrogen to oil volume ratio is 100～2000, preferably 500～1500.

In the hydrogenating conversion process of the present invention, the character of described catalytic cracking diesel oil: density 0.88～0.95g/cm³, boiling range 150～380 DEG C, sulfur content 2000～20000ppm, nitrogen content 500ppm～2000ppm, arene content 50 ~ 90m%.

Compared with prior art, the advantage of the method for the catalytic cracking diesel oil hydro-conversion of the present invention is:

1, in hydrocracking reactor, from top to bottom along with the intensification of cracking level, the naphtha content being cracked to form in reactant composition in cracker is from top to bottom gradually increased, and non-cracked diesel oil part is from top to bottom gradually reduced.Therefore, using the inventive method, cracking zone beds hydrogenation activity is from top to bottom gradually reduced, and while ensure that catalytic cracking diesel oil hydrogenation effect, decreases the hydrogenation of naphtha, reduces hydrogen consumption, improve naphtha product octane number.Additionally, different hydrogenation activity distributions combine cracking activity and are gradually lowered from top to bottom, and being gradually increased of catalyst aperture reduces the naphtha that reaction generates and is cracked into the probability of lighter hydrocarbons further, improves the yield of naphtha.Owing to the cracking activity of bottom unconverted catalytic diesel oil component is higher than the cracking activity of the naphtha component that reaction generates, therefore, Cracking catalyst relatively low cracking activity in bottom is while meeting the further cracking of unconverted catalytic diesel oil, reduce the probability of the further cracking of the naphtha that reaction generates, and Cracking catalyst bigger aperture in bottom also reduces naphtha diffusional resistance on a catalyst, shorten the time of contact of naphtha and Cracking catalyst, avoid the further cracking of the naphtha that reaction generates, add the selectivity of naphtha.

2, the inventive method is on the basis of hydrocracking catalyst mixed bed layer grading loading, gas phase is set between adjacent mixed catalyst bed and draws pipeline, equally the most cracked gas phase of part (mainly include gas light and naphtha component) is directly led out hydrocracking catalyst bed, hydrogenation or the cracking reaction further of naphtha can also be further reduced to a certain extent, on the one hand can improve the fragrant potential content of naphtha, the liquid product yield being hydrocracked can also be improved simultaneously.

3, by improving the hydrogen-oil ratio of cracker, carrying light component more and discharge reactor, can reduce secondary or the repeatedly cracking reaction of light component further, and then increase hydrocracking reaction liquid receipts, the virtue improving heavy naphtha is dived.

4, the secondary of light component or repeatedly cracking reaction minimizing in hydrocracking reactor lower catalyst bed layer, is also beneficial to reduce the carbon deposit of beds, the service cycle of extension fixture.

Accompanying drawing explanation

Fig. 1 is a kind of principle process chart of the catalytic diesel oil hydrogenating conversion process of the present invention.

Fig. 2 is the another kind of principle process chart of the catalytic diesel oil hydrogenating conversion process of the present invention.

Detailed description of the invention

With specific embodiment, the method for the catalytic diesel oil hydro-conversion of the present invention is specifically described below in conjunction with the accompanying drawings.

As shown in Figure 1: catalytic cracking diesel oil raw material through pipeline 1 with introduce after hydrogen mixes through pipeline 2, enter weighted BMO spaces reactor 3 and carry out weighted BMO spaces reaction, reaction effluent is entered cracker 5 by pipeline 4 without isolation and carries out hydrocracking reaction.At least two hydrocracking catalyst mixing bed is set in hydrocracking reactor.Hydrocracking reactor reaction effluent enters gas-liquid separator 10 through pipeline 9 and carries out gas-liquid separation.Separating obtained gaseous products through pipeline 11, and mixes Posterior circle with the hydrogen make-up of pipeline 18 and returns preatreating reactors after compressor boosts；Liquid phase effluent enters fractionating column 13 through pipeline 12 and isolates lighter hydrocarbons, heavy naphtha and hydrocracking tail oil respectively through pipeline 14,15 and 17 ejector, and the midbarrel that fractionation obtains can loop back hydrocracking reactor 5 through pipeline 16 and continue reaction.

In the present invention, in embodiment 1 ~ 3, refining stage uses conventional Hydrobon catalyst, is 30ppm by adjust refining stage reaction condition controlling refining stage effluent oil nitrogen content.Cracking zone has selected the different gradation mode of three kinds of Cracking catalyst of same vehicle, different metal content respectively, and the physico-chemical property of the different cracking agent of cracking zone three kinds is as shown in table 1 below.

Below by embodiment and comparative example, the solution of the present invention and effect are described.

Embodiment 1 ~ 3

Embodiment 1 ~ 3 uses flow process such as Fig. 1 of the present invention.

Body phase method catalyst and hydrocracking catalyst according to beds order grading loading different proportion respectively from top to bottom in filling FF-36 catalyst, hydrocracking reactor in weighted BMO spaces reactor in embodiment 1-3.In three embodiments, in three mixed catalyst beds, body phase method catalyst is respectively 3:1:0,1:1:1,0:1:2 with the ratio of Cracking catalyst 1 and Cracking catalyst 2.

The composition of catalyst and character are shown in Table 1, and raw materials used character is shown in Table 2, and embodiment 1 ~ 3 reaction condition and reaction result see table 3 and table 4.

Embodiment 4

Use flow process shown in Fig. 2.Feedstock oil and used catalyst are with embodiment 3.Wherein arranging gas between Cracking catalyst bed second and the 3rd and draw pipeline, other are with embodiment 3.Gas phase draws gas gas-phase objects doses is recycle hydrogen tolerance 30% that pipeline is drawn.

The composition of table 1 embodiment used catalyst and main character.

Project	FTX	Cracking catalyst 1	Cracking catalyst 2	Cracking catalyst 3
					Chemical composition, quality %
MoO₃	16	—	—
					NiO	18	4	4	6
WO₃	42	18	18	22
					Surplus	Aluminum oxide	Aluminum oxide+molecular sieve	Aluminum oxide+molecular sieve
Carrier	Aluminum oxide	Aluminum oxide	Aluminum oxide
					Cracking Component	—	Y molecular sieve	Y molecular sieve	Y molecular sieve
Content, m%	—	70	40	70

Table 2 Feedstock oil character.

Feedstock oil	Feedstock oil
		Density, g/cm³	0.9324
Boiling range, DEG C	192～350
		S, m%	1.54
N, ppm	800
		Aromatic hydrocarbons, m%	72
Cetane number	18

The used operating condition of table 3 embodiment 1-4.

	Embodiment 1	Embodiment 2	Embodiment 3	Embodiment 4
					Reaction temperature, DEG C	380	390	405	405
Reaction pressure, MPa	8.0	6.0	8.0	8.0
					Volume space velocity, h^-1	1.0	2.0	1.5	1.5
Hydrogen to oil volume ratio	1200	1200	1200	1500
					Cracking zone feed nitrogen content, ppm	30	30	30	30
Conversion per pass, m%	65	65	80	81
					Chemical hydrogen consumption, m%	3.32	3.37	3.64	3.44

Table 4 Embodiment 1-4 evaluation result.

	Embodiment 1	Embodiment 2	Embodiment 3	Embodiment 4
					Product slates, m%
Naphtha cut cut (＜ 210 DEG C)	59	58	72	74
					Diesel oil distillate (＞ 210 DEG C)	35	35	20	19
Product property
					Naphtha (＜ 210 DEG C)
Density, g/cm^-3	0.7600	0.7610	0.7602	0.7603
					S, ppm	<0.5	<0.5	<0.5	<0.5
N, ppm	<0.5	<0.5	<0.5	<0.5
					Octane number	92	93	91.5	92.5
Diesel oil (＞ 210 DEG C)
					Density, g/cm^-3	0.8802	0.8830	0.8750	0.8740
Sulfur content, ppm	7	10	5	5
					Cetane number	27	30	33	34

Comparative example 1-2

Comparative example 1-2 uses the technological process identical with embodiment 1-3, the pretreatment catalyst that in comparative example 1-2 weighted BMO spaces reactor, filling is identical with embodiment 1-3, and the nitrogen content adjusting refining stage effluent oil by controlling operating condition is 30ppm, cracking zone Catalyst packing Cracking catalyst 3, the feedstock oil used in comparative example 1-2 is identical with implementing 1-4.Comparative example 1-2 operating condition and product property are listed in table 5, table 6.

The used operating condition of table 5 comparative example 1-2.

	Comparative example 1	Comparative example 2
			Reaction temperature, DEG C	372	398
Reaction pressure, MPa	8.0	8.0
			Volume space velocity, h^-1	1.0	1.5
Hydrogen to oil volume ratio	1200	1200
			Cracking zone feed nitrogen content, ppm	30	30
Conversion per pass, %	65	80
			Chemical hydrogen consumption, m%	3.72	4.16

Table 6 comparative example 1-2 result of the test.

	Comparative example 1	Comparative example 2
			Product slates, m%
Naphtha cut cut (＜ 210 DEG C)	58	71
			Diesel oil distillate (＞ 210 DEG C)	35	20
Product property
			Naphtha (＜ 210 DEG C)
Density, g/cm^-3	0.7600	0.7602
			S, ppm	<0.5	<0.5
N, ppm	<0.5	<0.5
			Octane number	88	86
Diesel oil (＞ 210 DEG C)
			Density, g/cm^-3	0.8802	0.8750
Sulfur content, ppm	7	5
			Cetane number	28	34

By embodiment 1, embodiment 3 finds with comparative example 1 and comparative example 2 contrast, in using same process condition processing table 2 during raw material, comparative example 1 and comparative example 2 use the cracking agent A of high hydrogenation activity and cracking activity, controlling and in the case of embodiment same conversion, owing to comparative example 1 and the higher hydrogenation activity of comparative example 2 catalyst make comparative example 1 and comparative example 2 in the case of diesel oil character and naphtha yield are close with embodiment 1 and embodiment 3, reactive hydrogen consumption will be apparently higher than embodiment 1 and embodiment 3, its chemical hydrogen consumption increases by 0.4 and 0.52 unit respectively, and the gasoline component octane number generated reduces by 4 and 5.5 units respectively.

Claims

1. a catalytic cracking diesel oil method for transformation, including herein below:

(2) hydrofining reaction effluent is directly entered cracker, mixed catalyst bed haptoreaction with two or more grading loading, flow direction according to reaction mass, the hydrogenation activity of mixed catalyst bed is on a declining curve, and wherein said mixed catalyst bed is formed with hydrocracking catalyst mixed packing by the body phase method Hydrobon catalyst of high hydrogenation activity；

(3) step (2) obtains that hydrocracking reaction effluent is separated and fractionation obtains naphtha component and diesel component.

The most in accordance with the method for claim 1, it is characterised in that along the direction of Flow of Goods and Materials, the cracking activity of described hydrocracking catalyst also reduces along the flow direction of reaction mass.

The most in accordance with the method for claim 1, it is characterised in that the grating of the hydrogenation activity of described mixed catalyst is realized by the mixed proportion changing body phase method Hydrobon catalyst and hydrocracking catalyst.

The most in accordance with the method for claim 2, it is characterised in that the cracking activity of the cracking activity of described hydrocracking catalyst content and molecular sieve by adjusting Cracking catalyst Middle molecule sieve adjusts.

The most in accordance with the method for claim 1, it is characterised in that in step (2), the volume ratio of two mixed catalyst beds of arbitrary neighborhood is 1:10～10:1.

The most in accordance with the method for claim 1, it is characterized in that, gas phase is set between the mixed catalyst bed that at least two is adjacent in step (2) and draws pipeline, partial gas phase logistics is drawn pipeline via gas phase and is led to high-pressure separator, and liquid phase and residue gas phase mixture proceed hydrocracking reaction.

The most in accordance with the method for claim 6, it is characterised in that after raw material reaction, rate of gasification draws pipeline more than arranging gas phase between the Cracking catalyst bed of 30 mass % at reaction conditions.

The most in accordance with the method for claim 6, it is characterised in that described gas phase is drawn pipeline and is arranged on catalyst bed interlayer gas-liquid partition tray or the lower section of cold hydrogen box, gas phase is drawn pipeline and is provided with flow control valve.

The most in accordance with the method for claim 6, it is characterised in that draw pipeline opening part in gas phase and arrange baffle plate, to prevent liquid phase from entering gas phase extraction pipeline further.

The most in accordance with the method for claim 6, it is characterised in that the hydrogen to oil volume ratio drawing pipeline uppermost catalyst bed in gas phase is 700:1～3000:1, gas phase draws the hydrogen to oil volume ratio of beds below pipeline is 220:1～2000:1.

11. in accordance with the method for claim 6, it is characterised in that the hydrogen-oil ratio of described hydrocracking reactor is higher than the hydrogen-oil ratio 200～800 of hydrofining reactor.

12. in accordance with the method for claim 6, it is characterised in that described gas phase draws gas gas-phase objects doses is recycle hydrogen tolerance by volume 20%～70% that pipeline is drawn.

13. in accordance with the method for claim 1, it is characterised in that described hydrocracking catalyst is the hydrocracking catalyst containing Modified Zeolite Y, and catalyst contains WO by weight₃15%～30%, NiO or CoO 2%～15%, modified Y molecular sieve 30%～90%；The character of Y molecular sieve used is as follows: specific surface area 700m²/ g～900m²/ g, total pore volume 0.35mL/g～0.48mL/g, relative crystallinity 90%～130%, cell parameter 2.437～2.460, meleic acid amount 0.5～1.5mmol/g, carrier is aluminum oxide or amorphous silica-alumina.

14. in accordance with the method for claim 1, it is characterised in that described body phase method Hydrobon catalyst contains tri-kinds of active components of W, Mo, Ni, and in catalyst, W, Ni are with composite oxides Ni_xW_yO_z, z=x+3y, Mo are with oxide M oO₃Presented in；Composite oxides Ni_xW_yO_zThe atomic molar of x and y is than for 1:8 ~ 8:1, composite oxides Ni_xW_yO_zWith MoO₃Weight ratio 1:10 ~ 10:1, Ni in catalyst_xW_yO_zWith MoO₃Gross weight content be 40% ~ 100%.

15. in accordance with the method for claim 2, it is characterised in that along the flow direction of reaction mass, the average pore diameter of hydrocracking catalyst is also gradually reduced.

16. in accordance with the method for claim 7, it is characterised in that after raw material reaction, rate of gasification draws pipeline more than arranging gas phase between the Cracking catalyst bed of 50 mass % at reaction conditions.

17. in accordance with the method for claim 10, it is characterised in that the hydrogen to oil volume ratio drawing pipeline uppermost catalyst bed in gas phase is 800:1～1500:1；It is 300:1～1000:1 that gas phase draws the hydrogen to oil volume ratio of beds below pipeline.

18. in accordance with the method for claim 11, it is characterised in that the hydrogen-oil ratio of described hydrocracking reactor is higher than the hydrogen-oil ratio 300～600 of hydrofining reactor.

19. in accordance with the method for claim 12, it is characterised in that described gas phase draws gas gas-phase objects doses is recycle hydrogen tolerance by volume 30%～60% that pipeline is drawn.