CN114437791A

CN114437791A - Low-pressure long-period hydrocracking process for Fischer-Tropsch synthetic oil

Info

Publication number: CN114437791A
Application number: CN202011116518.3A
Authority: CN
Inventors: 柳伟; 杜艳泽; 秦波; 高杭; 张晓萍; 薛景杭
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: 2020-10-19
Filing date: 2020-10-19
Publication date: 2022-05-06
Anticipated expiration: 2040-10-19
Also published as: CN114437791B

Abstract

The invention discloses a low-pressure and long-period hydrocracking process for Fischer-Tropsch synthetic oil, which comprises the following steps: (1) the Fischer-Tropsch synthetic oil or the hydrogenated and pretreated Fischer-Tropsch synthetic oil enters a hydrocracking reactor, and a liquid-phase material flows to the lower part of the hydrocracking reactor, enters a hydrocracking catalyst bed layer filled in the lower part of the hydrocracking reactor, and is in countercurrent contact with hydrogen to carry out hydrocracking reaction; (2) allowing a gas phase material of part of the hydrocracking product in the step (1) and Fischer-Tropsch synthetic oil or Fischer-Tropsch synthetic oil subjected to hydrogenation pretreatment to enter a hydrocracking reactor to flow to the upper part of the hydrocracking reactor; enters a separation zone arranged at the upper part of the hydrocracking reactor, and is fractionated to obtain a diesel product, and the other part of the hydrocracking product is discharged from the bottom of the hydrocracking reactor to obtain a lubricating oil product. The Fischer-Tropsch synthetic oil hydrocracking process achieves the purpose of long-period operation under the low-pressure condition.

Description

Low-pressure long-period hydrocracking process for Fischer-Tropsch synthetic oil

Technical Field

The invention relates to a Fischer-Tropsch synthetic oil hydrocracking process, in particular to a Fischer-Tropsch synthetic oil low-pressure long-period hydrocracking process.

Background

China is rich in coal resources and deficient in petroleum resources, the technology for producing Fischer-Tropsch synthetic oil by taking coal as a raw material is mature and is rapidly developed, and in recent years, a plurality of Fischer-Tropsch synthetic oil production devices are built successively in Shanxi Luan, Nemonte Yitai and Ordos.

The Fischer-Tropsch synthetic oil is a substance taking normal paraffin as a main component, and the composition characteristics of the Fischer-Tropsch synthetic oil make the Fischer-Tropsch synthetic oil become a potential ideal raw material (high cetane number and high viscosity index) for producing diesel oil and lubricating oil base oil. Common processing methods for Fischer-Tropsch synthetic oil include physical and chemical methods: the physical method mainly adopts a solvent dewaxing method to remove the high pour point paraffin of the Fischer-Tropsch synthetic oil and produce the base oil of the lubricating oil, and the method has high energy consumption, large pollution and low yield of target products; the chemical method mainly comprises a hydrogenation method, mainly comprises hydrocracking or hydroisomerization, and produces high-quality diesel oil or lubricating oil products by hydrocracking or isomerizing Fischer-Tropsch synthetic oil.

The industrial device for producing diesel oil and lubricating oil by hydrocracking Fischer-Tropsch synthetic oil is usually carried out on a hydrogenation device with the pressure grade of more than 6.0MPa, the Fischer-Tropsch synthetic oil raw material and hydrogen are mixed and then enter a pretreatment reactor to remove impurities such as olefin, oxide and the like, the pretreated generated oil and hydrogen then enter a hydrocracking reactor to complete the cracking and isomerization reactions of the Fischer-Tropsch synthetic oil under the action of a hydrocracking catalyst, and the reaction generated oil is fractionated by a fractionating tower to obtain products such as naphtha, diesel oil, lubricating oil and the like.

CN201610365749.5 discloses a hydrogenation method of Fischer-Tropsch synthetic oil, which comprises the following steps: (1) mixing Fischer-Tropsch synthetic oil and hydrogen, feeding the mixture into a hydrocracking reactor, and reacting under the action of a hydrocracking catalyst, wherein the average pore size of the hydrocracking catalyst is in a decreasing trend along the flow direction of material flow; (2) separating the hydrogenation effluent in the step (1) into a gas phase and a liquid phase, recycling the gas phase, and enabling the liquid phase to enter a fractionating tower; (3) fractionating in a fractionating tower to obtain naphtha, aviation kerosene and diesel oilAnd tail oil; recycling tail oil to the hydrocracking reactor; the hydrocracking operating conditions were as follows: the reaction pressure is 5.0-35.0 MPa, preferably 6.0-19.0 MPa; the reaction temperature is 200-480 ℃, preferably 270-450 ℃; the volume space velocity is 0.1-15.0 h^-1Preferably 0.2 to 3.0 hours^-1(ii) a The volume ratio of hydrogen to oil is 100: 1-2500: 1, preferably 400: 1-2000: 1.

CN200510028649.5 discloses a method for producing diesel oil or diesel oil components from fischer-tropsch synthesis products, said production method at least comprising the following steps: (1) hydrotreating all or a lighter part of fractions of a Fischer-Tropsch synthesis product, wherein the hydrotreating conditions are as follows: the reaction temperature is 260-400 ℃, the hydrogen partial pressure is 4.0-18 MPa, and the liquid hourly space velocity is 0.1-15 h^-1The volume ratio of hydrogen to oil is 200-1600; (2) and (2) carrying out hydroisomerization cracking on part or all of the hydrotreated Fischer-Tropsch synthesis product and/or the heavier part fraction of the non-hydrotreated Fischer-Tropsch synthesis product, wherein the hydroisomerization cracking conditions are as follows: the reaction temperature is 280-440 ℃, the hydrogen partial pressure is 4.0-18 MPa, and the liquid hourly space velocity is 0.1-10 h^-1The volume ratio of hydrogen to oil is 400-2000; (3) fractionating the products obtained by hydrotreating and hydroisomerizing cracking or the mixture of the products to obtain gas, light fraction, middle fraction and heavy fraction; wherein the heavy fraction is returned to the hydroisomerization cracking reactor as cycle oil; the middle distillate produced is a high quality diesel or diesel component.

CN201610617631.7 discloses a processing method of Fischer-Tropsch synthetic oil, in the method, Fischer-Tropsch oil is firstly contacted with a first hydrocracking catalyst, the hydrogen partial pressure is 6-8MPa, the temperature is 300-390 ℃, and the volume space velocity is 0.8-1.2h^-1The volume ratio of hydrogen to oil is (600-800): 1 under the optimized technological conditions, the generated product is cut to obtain the fraction at 350-500 ℃, then the fraction at 350-500 ℃ is contacted with a second hydrocracking catalyst, the hydrogen partial pressure is 6-8MPa, the temperature is 300-390 ℃, and the volume space velocity is 0.8-1.2h^-1The volume ratio of hydrogen to oil is (600-800): 1 under the optimized technological condition to obtain the diesel oil with 150-370 deg.C and lubricating oil component with temp. greater than 370 deg.C. .

CN201510420352.7 discloses a method for producing Fischer-Tropsch synthetic oilThe method of the middle distillate oil, the separation and fractionation after the Fischer-Tropsch synthetic oil and hydrogen containing material flow react through the hydrofining reactor at first, get the first naphtha fraction, light diesel oil fraction and heavy oil fraction; introducing the heavy oil fraction into an isomerization hydrocracking reactor, wherein the hydrogen partial pressure is 2.0-15.0MPa, the reaction temperature is 300-450 ℃, and the volume ratio of hydrogen to oil is 300-1500: 1, the volume space velocity is 0.5-5.0h^-1Reacting under the operation condition, and then sequentially separating and fractionating the isomeric hydrocracking reaction effluent; at least two reaction zones are arranged in the isomerization hydrocracking reactor, and according to the flow direction of reactant flow, the cracking activity of the isomerization hydrocracking catalyst in unit volume in the adjacent two reaction zones is reduced in sequence.

CN201810016687.6 prehydrogenating the whole fraction of Fischer-Tropsch synthetic oil in the presence of hydrogen and a reduced-state prerefining catalyst, hydrorefining the product in the presence of hydrogen and a reduced-state hydrofining catalyst, and separating to obtain diesel oil-I, naphtha and heavy oil; heavy oil is subjected to hydrogen and hydroisomerization cracking catalyst under the conditions that the hydrogen partial pressure is 5-12MPa, the reaction temperature is 280-370 ℃ and the volume space velocity is 0.5-3h^-1The volume ratio of hydrogen to oil is (500-1500): 1, carrying out a hydroisomerization cracking reaction under the same operation conditions; carrying out hydrofining stabilization reaction on the isomerization product, and finally carrying out rectification separation to obtain diesel oil-II and lubricating oil base oil; and recycling the tail oil to carry out the hydroisomerization cracking reaction.

In summary, in the prior art, although the selectivity of the target products such as diesel oil and lubricating oil in the hydrocracking reaction process of the fischer-tropsch synthetic oil is improved through the reaction zone design and catalyst optimization, the hydrocracking process needs to be performed under a higher pressure so as to realize long-period operation. Although the pressure range disclosed in the literature is relatively low, the pressure range is limited by the requirement of long-period operation of an industrial device, in the prior art, the device still needs to be operated under medium and high pressures, generally above 5MPa, the industrial practical application process is generally performed under the reaction pressure above 8.0MPa, when the hydrocracking pressure level is lower than 5.0MPa, the catalyst carbon-collecting deactivation rate is accelerated, and the problem of the reduction of the operation period of the device occurs, and the higher operation and operation pressure makes the device construction and operation costs higher, and how to realize the hydrocracking of the fischer-tropsch synthetic oil under the low pressure and long period is a technical problem which is well to be solved by technical personnel in the field.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a Fischer-Tropsch synthetic oil hydrocracking process, which realizes the purpose of long-period operation under the condition of low pressure.

A low-pressure and long-period hydrocracking process for Fischer-Tropsch synthetic oil, which comprises the following steps:

(1) the Fischer-Tropsch synthetic oil or the hydrogenated and pretreated Fischer-Tropsch synthetic oil enters a hydrocracking reactor, liquid-phase materials flow to the lower part of the hydrocracking reactor and enter a hydrocracking catalyst bed layer filled at the lower part of the hydrocracking reactor, and are in countercurrent contact with hydrogen to carry out hydrocracking reaction, wherein the hydrocracking reaction has the following operation conditions: the reaction pressure is 1MPa-5MPa, preferably 1MPa-4MPa, more preferably 1.5MPa-3.5MPa, and specifically can be 2MPa, 2.5MPa or 3 MPa; the reaction temperature is 260-400 ℃, and the preferable temperature is 280-380 ℃; the liquid hourly volume airspeed measured by the Fischer-Tropsch synthetic oil in the step (1) is 0.2h^-1-4h^-1Preferably 0.5h^-1-1-3.0h^-1The hydrogen-oil ratio is 50: 1-500: 1;

(2) allowing a gas phase material of part of the hydrocracking product in the step (1) and Fischer-Tropsch synthetic oil or Fischer-Tropsch synthetic oil subjected to hydrogenation pretreatment to enter a hydrocracking reactor to flow to the upper part of the hydrocracking reactor; enters a separation zone arranged at the upper part of the hydrocracking reactor, and is fractionated to obtain a diesel product, and the other part of the hydrocracking product is discharged from the bottom of the hydrocracking reactor to obtain a lubricating oil product.

In the process, the Fischer-Tropsch synthesis oil raw material in the step (1) is Fischer-Tropsch synthesis oil with the distillation range of 220-750 ℃, and preferably, the ratio of the 220-350 ℃ fraction in the Fischer-Tropsch synthesis oil is less than 15%; wherein the mass content of the straight-chain alkane is 90-98%, preferably 93-98%, more preferably 95-98%, the mass content of the alkene is 1-10%, and the mass content of the oxygen is 0.1-5%.

In the process, the Fischer-Tropsch synthetic oil in the step (1) enters a hydrogenation pretreatment reactor and contacts with hydrogenation refining catalyst filled in the hydrogenation pretreatment reactor to carry out hydrogenation refining reaction.

In the process, the hydrogenation pretreatment in the step (1) is hydrofining pretreatment under the action of a hydrofining catalyst, the hydrofining catalyst can be a conventional hydrofining catalyst, and the adopted refining catalyst can be a commercially available product or can be prepared according to conventional knowledge in the field.

In the process, the hydrorefining catalyst in the step (1) takes VIB group and/or VIII group metals as active components, and takes alumina or silicon-containing alumina as a carrier. The group VIB metal is typically Mo and/or W and the group VIII metal is typically Co and/or Ni. Based on the weight of the catalyst, the content of the VIB group metal is 8-28 wt% calculated by oxide, and the content of the VIII group metal is 2-15 wt% calculated by oxide.

In the process, the hydrogenation pretreatment in the step (1) is hydrofining pretreatment under the action of a hydrofining catalyst, and the hydrofining reaction conditions are as follows: the reaction pressure is 1.0-5.0MPa, the reaction temperature is 180-^-1Hydrogen-oil volume ratio 50: 1-500: 1.

in the process of the present invention, the hydrocracking catalyst filled in the hydrocracking reactor in step (1) may be commercially available or prepared according to the prior art. The hydrocracking catalyst filled in the hydrocracking reactor generally contains a cracking component and a metal component, wherein the cracking component can use one or more molecular sieves in Y, beita, SAPO, ZSM and other types of molecular sieves, the metal component is VIB group and/or VIII group metal, and the hydrocracking catalyst can also comprise components such as alumina, amorphous silicon-aluminum and the like besides the metal component and the cracking component.

In one or more embodiments of the present invention, the hydrocracking catalyst packed in the hydrocracking reactor contains MoO by weight₃Or WO₃15-30%, NiO 2-15%, modified beita molecular sieve 2 &20%, preferably 4-15%; 20-60% of amorphous silicon-aluminum and/or aluminum oxide, preferably 30-50%; preferably contains MoO₃Or WO₃15～30％，NiO₂15 percent of modified Y-type molecular sieve, 5 to 15 percent of modified Beita-type molecular sieve, and preferably 2 to 8 percent of modified Beita-type molecular sieve; 20-60% of amorphous silicon aluminum and/or aluminum oxide, preferably 30-50%.

In the context of the present invention, the upper part of the hydrocracking reactor and the lower part of the hydrocracking reactor are distinguished by taking the position of the Fischer-Tropsch synthetic oil or the Fischer-Tropsch synthetic oil subjected to hydrogenation pretreatment entering the hydrocracking reactor as a reference.

In the context of the present invention, the stated pressures are absolute pressures unless otherwise specified and the% are percentages by mass unless otherwise specified.

In the context of the present invention, the amount of the fischer-tropsch synthesis oil or the hydrogenated and pretreated fischer-tropsch synthesis oil that forms a liquid phase material flow and a gas phase material flow after entering the hydrocracking reactor depends on the nature of the feed and the temperature and pressure at the feed location of the hydrocracking reactor.

In the process, the Fischer-Tropsch synthetic oil or the hydrogenated and pretreated Fischer-Tropsch synthetic oil in the step (1) is introduced from the middle part of the hydrocracking reactor, and the hydrogen is introduced from the lower part (preferably the bottom) of the hydrocracking reactor.

In the process, diesel oil is separated from the upper separation area side line of the hydrocracking reactor in the step (2), and tower top airflow enters a reflux tank to separate naphtha and hydrogen; optionally returning a part of naphtha to the reactor, and throwing the other part of naphtha outwards; the hydrogen is circulated back to the reactor from the top of the reflux tank through a recycle hydrogen compressor.

In the process, optional part or all of the reactor bottom material flow in the step (2) is recycled to the hydrocracking reactor, and the recycle ratio is full recycle-1: 10, preferably 1: 1-1: 5 (mass ratio of recycled back to reactor and external throwing part).

In the process of the invention, the temperature at the top of the hydrocracking reactor in the step (2) is 160-250 ℃, the pressure at the top of the hydrocracking reactor is 0.8-3.8 MPa, and the reflux ratio is 0.5-4.0.

In the process, the reaction depth is expressed by the conversion rate (X) of the raw material, the catalyst running period is expressed by the catalyst deactivation rate (K), the two are in a mutual restriction relation with the reaction pressure (P), and the RI is expressed by a restriction index RI, namely RI-X/(K P), and the RI range is 600-1500.

Through years of research, the applicant finds that in the traditional Fischer-Tropsch synthetic oil hydroisomerization/cracking reaction process, hydrogen and a Fischer-Tropsch oil raw material flow into a reactor in a parallel mode, the hydrogen concentration in the reactor gradually decreases from top to bottom along with the hydrogen consumption of the reaction, a large amount of long-chain paraffin is isomerized/cracked along with the reaction, more paraffin reaction products with low molecular weight are generated, the concentration of the reaction products is increased, meanwhile, due to the fact that the temperature of the lower portion of the reactor is higher and the reaction is more severe, the hydrogen solubility of the reaction products is reduced along with the reduction of molecules, the problems of reduction of hydrogen supply and increase of hydrogen demand occur at the middle lower portion of the reactor, the hydrogen supply at the middle lower portion is insufficient due to the superposition of the hydrogen supply and the hydrogen demand, and the carbon deposition of a catalyst is accelerated. The skilled person knows that the hydrogen required for the gas-liquid-solid three-phase hydrogenation reaction is hydrogen dissolved in the liquid phase, and that the hydrogen required for the reaction is insufficient, mainly insufficient. The main factors influencing the speed and the amount of hydrogen dissolved into the liquid phase in the gas phase are the properties, the temperature and the pressure of the liquid phase and whether the gas-liquid contact is sufficient, and under the aim of achieving the required reaction result, the space with adjustable temperature is small, the properties of a liquid phase system are basically determined, and the gas-liquid contact state cannot be changed, so that medium and high pressure conditions are required in the prior art to maintain sufficient hydrogen supply of the whole catalyst bed layer in the reaction process, and the long-period operation of the catalyst is ensured.

Those skilled in the art will appreciate that the rate of catalyst deactivation is related to the depth of the reaction, which is generally measured by conversion, the magnitude of the change in key properties of the desired product, and the like. For the fischer-tropsch synthesis oil hydroisomerization/cracking reaction process, it is usually expressed in terms of conversion. Namely, long-period operation is realized on the premise of ensuring higher conversion rate of the Fischer-Tropsch raw oil. In the prior art, although a wide range of reaction pressures is disclosed, including lower reaction pressures, the reaction depth and the stable operating cycle are contradictory under these conditions. Namely, the operation period is short when the reaction depth is deep under lower reaction pressure; in order to maintain a long run length, the reaction depth is insufficient and the product index is difficult to achieve.

According to the Fischer-Tropsch synthetic oil hydrocracking reaction, the reaction depth is expressed by the conversion rate (X) of the raw material, the catalyst running period is expressed by the catalyst deactivation rate (k), and a mutual restriction relation is formed between the catalyst deactivation rate (X) and the reaction pressure (P) and is expressed by a restriction index RI. RI ═ X/(K × P), in the present invention, RI is generally 600 or more, preferably 750 or more, and most preferably 900 or more, whereas RI in the prior art is generally 600 or less, and in the case of industrial application is generally as follows.

On the basis of the research result, the process adopts the hydroisomerization/cracking reactor with the upper part provided with the fractionation zone, hydrogen required by the reaction is introduced from the lower part of the catalyst bed layer, the hydrocarbon composition and the temperature distribution of the reactant flow of the whole reaction bed layer are more uniform in the process, and the hydrogen requirement in the whole reactor is more uniform. More importantly, the "hydrogen deficient" region of the reaction process is in the upper portion of the catalyst bed, i.e., the primary region where carbon deposition causes a reduction in the run length. In the scheme of the invention, the upper part of the reaction zone is provided with the fractionation zone, the fractionation zone is operated under the condition of distillation separation, and part of materials flow back to the upper part of the reaction zone, which causes two main changes, firstly, the part of the back-flowed materials are fully contacted with the gas phase containing hydrogen flowing upwards at the lower part of the fractionation zone, the amount of dissolved hydrogen is greatly increased, the back-flowed materials of hydrogen are fully dissolved, more dissolved hydrogen which can be utilized by reaction is provided for the reaction zone, and the problem of hydrogen deficiency of the upper reaction zone is relieved; and secondly, the part of reflux materials cause great changes to the fluid flowing state and the gas-liquid contact state of the upper reaction zone, the gas-liquid contact state is changed, the dissolution of hydrogen in the liquid phase materials is facilitated, the dissolved hydrogen which can be utilized in the reaction is increased, the change of the flowing state is helpful for the carbon deposit precursors to flow downwards along the material flow and be gradually hydrogenated and removed, and the tendency of further forming carbon deposit due to aggregation in the upper reaction zone is relieved. Therefore, the scheme of the invention can provide more dissolved hydrogen for hydrogenation reaction in the hydrogen-deficient reaction area under lower pressure, is beneficial to the hydrogenation removal of carbon deposit precursors, and realizes the result of ensuring the long-period stable operation of the catalyst under lower pressure on the premise that the reaction depth meets the performance index of the product.

Compared with the prior hydrocracking process, the invention has the following advantages:

1. the invention realizes the long-period stable operation of the Fischer-Tropsch synthetic oil hydrocracking process under the low-pressure condition, and the optimal pressure can be maintained at 2-3 MPa;

2. the process of the present invention can produce high quality diesel oil fraction.

Drawings

FIG. 1 shows a Fischer-Tropsch process employed in an embodiment of the present invention.

Wherein 1 is a raw oil feed pipeline; 2 is a hydrogen feed line; 3 is a pretreatment reactor; 4 is a pretreated produced oil outflow pipeline; 5 is a hydrocracking reactor; 6 is a hydrogen introduction line; 7 is a diesel oil extraction pipeline; 8 is naphtha and light hydrocarbon extraction pipeline; 9 is a tower top reflux tank; 10 is a naphtha recycle line; 11 is a naphtha withdrawal line; 12 is light hydrocarbon and hydrogen extraction pipeline; 13 is a hydrocracking unconverted oil extraction line; 14 is a pipeline for circulating the hydrocracking unconverted oil back to the hydrocracking reactor; 15 is a hydrocracking reactor cracking reaction zone; 16 is a hydrocracking reactor fractionation zone

Detailed Description

The hydrocracking process of the Fischer-Tropsch synthetic oil adopted by the embodiment of the invention comprises the following specific processes: the Fischer-Tropsch synthesis oil raw material is mixed with hydrogen introduced through a pipeline 1 and a pipeline 2 and enters a pretreatment reactor 3, the reaction generated oil enters from the middle of a hydrocracking reactor 5 through a pipeline 4 and reversely contacts and reacts with the hydrogen entering through a pipeline 6 on a hydrocracking catalyst in a cracking reaction zone 15, the diesel oil and naphtha generated by the reaction enter an upper fractionating zone 16 of the reactor along with the upward flow of the hydrogen, then the diesel oil product is discharged from the device through a pipeline 7, the naphtha and the hydrogen continuously flow upward and enter a reflux tank 9, the hydrogen flows out from the top of the reflux tank 9 through a pipeline 12 and is recycled, one part of the naphtha returns to the hydrocracking reactor through a pipeline 10, and the other part of the naphtha flows out through a pipeline 11. One part of unconverted oil flows out of the device through a pipeline 13, and the other part of unconverted oil is mixed with the oil generated by the pretreatment reactor through a pipeline 14 and then enters the hydrocracking reactor 5 for continuous reaction.

The action and effect of the method of the present invention will be further discussed with reference to the drawings and examples, but the following examples should not be construed as limiting the method of the present invention.

Example 1

The properties of the feedstock are shown in Table 1, the composition of the catalyst is shown in Table 2, and the operating conditions and reaction effects are shown in Table 3.

TABLE 1

Density, g/cm³	0.8072
		Distillation range, deg.C
IBP	240
		10％	386
30％	395
		50％	462
70％	560
		90％	590
FBP	700
		Content of olefin (a)%	5％
Oxygen content%	3％

TABLE 2

TABLE 3

	Pretreatment reactor	Hydrocracking reactor
			Reaction temperature of	250	350
Reaction pressure, MPa	2.0	2.5
			Volume ratio of hydrogen to oil	200	400
Volume space velocity, h^-1	2.0	1.5
			The temperature at the top of the column,. degree.C		180
Pressure at the top of the column, MPa		2.3
			Reflux ratio		2.5
The deactivation rate K of the hydrocracking catalyst is measured at DEG C/day		0.025
			Conversion rate X%		59.5
RI		952

Example 2

The properties of the feedstock are shown in Table 4, the composition of the catalyst is shown in Table 5, and the operating conditions and reaction effects are shown in Table 6.

TABLE 4

TABLE 5

	Pre-treatment catalyst	Hydrocracking reactor catalyst
			Active metal,% of
WO₃	24	22
			NiO	4	6
beita molecular sieve,%	-	15
			Aluminum oxide,% of	72
Alumina + amorphous silica-alumina%		57

TABLE 6

Example 3

The properties of the feedstock are shown in Table 7, the composition of the catalyst is shown in Table 8, and the operating conditions and reaction effects are shown in Table 9.

TABLE 7

TABLE 8

TABLE 9

Example 4

The properties of the feedstock are shown in Table 10, the composition of the catalyst is shown in Table 11, and the operating conditions and reaction effects are shown in Table 12.

Watch 10

TABLE 11

TABLE 12

Example 5

The properties of the feedstock are shown in Table 13, the composition of the catalyst is shown in Table 14, and the operating conditions and reaction effects are shown in Table 15.

Watch 13

TABLE 14

	Pre-treatment catalyst	Hydrocracking reactor catalyst
			Active metal,% of
WO₃	24	22
			NiO	4	6
Y molecular sieve,%	-	15
			Aluminum oxide,% of	72
Alumina + amorphous silica-alumina%	-	57

Watch 15

Example 6

The properties of the feedstock are shown in Table 16, the composition of the catalyst is shown in Table 17, and the operating conditions and reaction effects are shown in Table 18.

TABLE 16

TABLE 17

Watch 18

	Pretreatment reactor	Hydrocracking reactor
			Reaction temperature of	300	335
Reaction pressure, MPa	2.0	3.5
			Volume ratio of hydrogen to oil	200	300
Volumetric space velocity h^-1	2.0	0.8
			The temperature at the top of the column,. degree.C		215
Pressure at the top of the column, MPa		3.3
			Reflux ratio		2.8
The deactivation rate K of the hydrocracking catalyst is measured at DEG C/day		0.020
			Conversion rate X%		55
RI		785

Example 7

The properties of the feedstock are shown in Table 19, the composition of the catalyst is shown in Table 20, and the operating conditions and reaction effects are shown in Table 21.

Watch 19

Watch 20

	Pre-treatment catalyst	Hydrocracking reactor catalyst
			Active metal,% of
WO3	22	25
			NiO	4	8
beita molecular sieve,%	-	12
			Aluminum oxide,% of	74
Alumina + amorphous silica-alumina%		55

TABLE 21

	Pretreatment reactor	Hydrocracking reactor
			Reaction temperature of	280	365
Reaction pressure, MPa	2.0	1.8
			Volume ratio of hydrogen to oil	300	200
Volumetric space velocity h^-1	2.0	3.0
			The deactivation rate K of the hydrocracking catalyst is measured at DEG C/day		0.035
The temperature at the top of the column,. degree.C		165
			Pressure at the top of the column, MPa		1.5
Reflux ratio		1.5
			Unconverted oil recycle ratio		Full circulation
Conversion rate X%		67.8
			RI		1076

Example 8

The properties of the feedstock are shown in Table 22, the composition of the catalyst is shown in Table 23, and the operating conditions and reaction effects are shown in Table 24.

TABLE 22

TABLE 23

	Pre-treatment catalyst	Hydrocracking reactor catalyst
			Active metal,% of
WO₃	24	22
			NiO	4	6
beita molecular sieve,%	-	4
			Y molecular sieve		10
Aluminum oxide%	72
			Alumina + amorphous silica-alumina%		58

Watch 24

Table 25 shows the product distributions of examples 1 to 8

TABLE 25

	Example 1	Example 2	Example 3	Example 4
					Product yield
Diesel oil fraction%	55.1	53.2	55.8	55.5
					Freezing point, deg.C	-16	-12	-16	-18
A tail oil fraction of%	40.5	40.1	40.2	40.1

Continuation table 25

	Example 5	Example 6	Example 7	Example 8
					Product yield
Diesel oil fraction%	54.1	50.3	88	53.2
					Freezing point, deg.C	-2	-19	-18	-8
A tail oil fraction of%	41.0	45.0	-	40.1

Comparative example 1

By adopting a conventional process flow, the Fischer-Tropsch synthesis raw oil and hydrogen gas flow in parallel and enter refining and cracking reactions, the generated oil enters a fractionating tower to cut out components for reaction, and the table 26 shows the properties of the raw oil, the table 27 shows the composition of a catalyst, and the table 28 shows the operation conditions and the reaction effects.

Watch 26

Watch 27

	Pre-treatment catalyst	Hydrocracking reactor
			Active metal, wt.%
WO₃	24	22
			NiO	4	6
beita molecular sieve,%	-	15
			Aluminum oxide,% of	72
Alumina + amorphous silica-alumina%	-	57

Watch 28

	Pretreatment reactor	Hydrocracking reactor
			Reaction temperature, deg.C	300	355
Reaction pressure, MPa	2.0	2.5
			Volume ratio of hydrogen to oil	500	400
Volumetric space velocity h^-1	2.0	1.5
			The deactivation rate K of the hydrocracking catalyst is measured at DEG C/day		0.048
Conversion rate X%		59.5
			RI		495

Comparative example 2

By adopting a conventional process flow, the Fischer-Tropsch synthesis raw oil and hydrogen gas flow in parallel and enter refining and cracking reactions, the generated oil enters a fractionating tower to cut out components for reaction, and the table 29 shows the properties of the raw oil, the table 30 shows the composition of a catalyst, and the table 31 shows the operation conditions and the reaction effects.

29

Watch 30

Watch 31

	Pretreatment reactor	Hydrocracking reactor
			Reaction temperature of	300	348
Reaction pressure, MPa	7.0	7.0
			Volume ratio of hydrogen to oil	500	400
Volumetric space velocity h^-1	2.0	1.5
			The deactivation rate K of the hydrocracking catalyst is measured at DEG C/day		0.02
Conversion rate X%		59.8
			RI		427

Table 32 shows the distribution of products in comparative examples 1 to 2.

Watch 32

Claims

1. A low-pressure and long-period hydrocracking process for Fischer-Tropsch synthetic oil is characterized by comprising the following steps: the process comprises the following steps:

(1) the Fischer-Tropsch synthetic oil or the hydrogenated and pretreated Fischer-Tropsch synthetic oil enters a hydrocracking reactor, liquid-phase materials flow to the lower part of the hydrocracking reactor and enter a hydrocracking catalyst bed layer filled at the lower part of the hydrocracking reactor, and are in countercurrent contact with hydrogen to carry out hydrocracking reaction, wherein the hydrocracking reaction has the following operation conditions: the reaction pressure is 1MPa to 5MPa, preferably 1MPa to 4MPa, and further preferably 1.5MPa to 3.5 MPa; the reaction temperature is 260-400 ℃, and the preferable temperature is 280-380 ℃; the liquid hourly volume airspeed measured by the Fischer-Tropsch synthetic oil in the step (1) is 0.2h^-1-4h^-1Preferably 0.5h^-1-1-3.0h^-1The hydrogen-oil ratio is 50: 1-500: 1;

(2) allowing a gas phase material of part of the hydrocracking product in the step (1) and Fischer-Tropsch synthetic oil or Fischer-Tropsch synthetic oil subjected to hydrogenation pretreatment to enter a hydrocracking reactor to flow to the upper part of the hydrocracking reactor; the mixture enters a separation zone arranged at the upper part of the hydrocracking reactor, and is fractionated to obtain a diesel oil product, and the other part of the hydrocracking product is discharged from a device at the bottom of the hydrocracking reactor to obtain a lubricating oil product.

2. The method of claim 1, wherein: the Fischer-Tropsch synthesis oil raw material in the step (1) is Fischer-Tropsch synthesis oil with the distillation range of 220-750 ℃, and preferably, the ratio of the 220-350 ℃ fraction in the Fischer-Tropsch synthesis oil is less than 15%; wherein the mass content of the straight-chain alkane is 90-98%, preferably 93-98%, further preferably 95-98%, the mass content of the alkene is 1-10%, and the mass content of the oxygen is 0.1-5%.

3. The method of claim 1, wherein: and (2) enabling the Fischer-Tropsch synthetic oil in the step (1) to enter a hydrogenation pretreatment reactor, and contacting with hydrogenation refining catalyst filled in the hydrogenation pretreatment reactor to perform hydrogenation refining reaction.

4. The method of claim 1, wherein: the hydrogenation pretreatment in the step (1) is hydrofining pretreatment under the action of a hydrofining catalyst.

5. The method of claim 4, wherein: the hydrorefining catalyst takes VIB group and/or VIII group metals as active components and takes alumina or silicon-containing alumina as a carrier.

6. The method of claim 5, wherein: the VIB group metal is Mo and/or W, the VIII group metal is Co and/or Ni, and the weight of the catalyst is taken as the reference, the VIB group metal content is 8wt% -28 wt% calculated by oxide, and the VIII group metal content is 2wt% -15 wt% calculated by oxide.

7. The method of claim 1, wherein: the hydrogenation pretreatment reaction conditions in the step (1) are as follows: the reaction pressure is 1.0-5.0MPa, the reaction temperature is 180-The liquid hourly space velocity of the oil meter is 1.0-10.0h^-1Hydrogen-oil volume ratio 50: 1-500: 1.

8. the method of claim 1, wherein: the hydrocracking catalyst filled in the hydrocracking reactor in the step (1) contains a cracking component and a metal component, wherein the cracking component is one or more of Y, beita, SAPO and ZSM molecular sieves, and the metal component is a VIB group and/or VIII group metal.

9. The method of claim 1, wherein: the hydrocracking catalyst filled in the hydrocracking reactor contains MoO by weight₃Or WO₃15-30% of NiO 2-15% of modified beita type molecular sieve, preferably 4-15%; 20-60% of amorphous silicon-aluminum and/or aluminum oxide, preferably 30-50%; preferably contains MoO₃Or WO₃15～30%，NiO₂15 percent of modified Y-type molecular sieve, 5 to 15 percent of modified Beita-type molecular sieve, and preferably 2 to 8 percent of modified Beita-type molecular sieve; 20-60% of amorphous silicon aluminum and/or aluminum oxide, preferably 30-50%.

10. The method of claim 1, wherein: and (2) introducing the Fischer-Tropsch synthetic oil or the hydrogenated and pretreated Fischer-Tropsch synthetic oil in the step (1) from the middle part of the hydrocracking reactor, and introducing the hydrogen from the lower part of the hydrocracking reactor.

11. The method of claim 1, wherein: in the step (2), diesel oil is separated from the upper separation area of the hydrocracking reactor at the side line, and the gas flow at the top of the hydrocracking reactor enters a reflux tank to separate naphtha and hydrogen; optionally returning a part of naphtha to the reactor, and throwing the other part of naphtha out; the hydrogen is circulated back to the reactor from the top of the reflux tank through a recycle hydrogen compressor.

12. The method of claim 1, wherein: optionally recycling part or all of the reactor bottom material flow in the step (2) to the hydrocracking reactor, wherein the recycle ratio is full recycle-1: 10, preferably 1: 1-1: 5.

13. the method of claim 1, wherein: in the step (2), the temperature at the top of the hydrocracking reactor is 160-.

14. The method of claim 1, wherein: the reaction depth is expressed by the conversion rate (X) of raw materials, the catalyst running period is expressed by the deactivation rate (K) of the catalyst, the two are in a mutual constraint relation with the reaction pressure (P), and RI = X/(K P) is expressed by a constraint index RI, and the RI range is 600-1500.