A two-stage hydrocracking process and system

Abstract

The present invention provides a two-stage hydrocracking process and system, the process comprising the following steps: (1) separating catalytic diesel to obtain light catalytic diesel and heavy catalytic diesel; (2) the wax oil raw material enters a hydropretreatment reactor for reaction to obtain a hydropretreatment stream; (3) the hydropretreatment stream enters a first-stage hydrocracking reactor for reaction to obtain a first-stage hydrocracking stream, and the first-stage hydrocracking stream is separated to obtain a gas product, light naphtha, heavy naphtha, light tail oil, and heavy tail oil; (4) the light catalytic diesel, heavy catalytic diesel, light tail oil, and heavy tail oil enter a second-stage hydrocracking reactor for reaction to obtain a stream that is recycled to a separation unit for treatment. The provided two-stage hydrocracking system comprises a catalytic diesel separation unit, a hydropretreatment reactor, a separation unit, a first-stage hydrocracking reactor, and a second-stage hydrocracking reactor. The present invention provides a two-stage hydrocracking method that can process catalytic diesel in a two-stage hydrocracking process, while improving the long-term stability of the two-stage hydrocracking unit and the product yield of the high-quality reforming unit raw material heavy naphtha.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum refining, and in particular relates to a two-stage full-circulation hydrocracking process and system which can extend the operation cycle of a device and improve the yield of heavy naphtha. Background Art

[0002] In recent years, the refining and petrochemical market has undergone tremendous changes. Hydrocracking technology has attracted more and more attention due to its flexible target products. At present, the development direction of hydrocracking technology is mainly concentrated in the following two directions: (1) improving the yield of target products; (2) large-scale equipment.

[0003] The hydrocracking process usually includes a single-stage hydrocracking process and a two-stage hydrocracking process, wherein the single-stage hydrocracking can be divided into a single-stage two-dose hydrocracking process, a single-stage series one-pass process, and a single-stage series circulation process. Taking the single-stage series as an example, the crude oil is processed by the hydrofining reactor and the hydrocracking reactor, and the reaction product enters the separation unit to obtain a series of products; in the two-stage process, the crude oil is processed by the hydrofining reactor and the hydrocracking reactor, and the reaction product enters the separation unit, and part of the product is discharged while part of the unconverted oil enters the second-stage hydrocracking reactor, and the obtained second-stage hydrocracking product is circulated to the separation unit. Since its cracking function is dispersed to two reactors, its processing volume is significantly increased compared with the single-stage hydrocracking. Therefore, the two-stage hydrocracking process has a strong development prospect. During the research and development process, emphasis should be placed on improving the long-term operation stability of the device and the heavy naphtha yield.

[0004] Catalytic diesel is a relatively difficult fraction to utilize in the petroleum refining and chemical industry due to its intrinsic characteristics. The ability to blend catalytic diesel will certainly enrich the technical options of refining and chemical companies and increase economic benefits.

[0005] CN109988607A discloses a flexible two-stage hydrocracking process, which is characterized in that the flow obtained by the wax oil raw material through the first hydrogenation pretreatment catalyst bed is divided into two streams, one stream is mixed with catalytic diesel and passed through the hydrotreatment reactor as a catalytic cracking raw material, and the other stream continues to be subjected to the hydrocracking reactor. Although this process can process wax oil and catalytic diesel at the same time, the hydrocracking process is in the conventional single-stage hydrocracking process and cannot achieve the maximum production of reforming raw materials.

[0006] CN109777500A discloses a two-stage hydrocracking method with gas-liquid countercurrent. The patent separates the refined product into gas and liquid through a flash tank. The liquid phase enters the hydrocracking reactor from the top and the gas phase enters from different bed positions of the hydrocracking reactor. This can effectively solve the problem of matching cracking and refining temperatures and increase the naphtha yield to a certain extent. Summary of the invention

[0007] In view of the low yield of heavy naphtha in the existing conventional two-stage hydrocracking process and the shortened operation cycle due to the accumulation of aromatics in the circulating oil, combined with the practical problem that catalytic diesel is difficult to use with high added value. The main purpose of the present invention is to provide a two-stage hydrocracking method that can process catalytic diesel in the two-stage hydrocracking process, while improving the long-term stability of the two-stage hydrocracking unit and the product yield of heavy naphtha, the raw material of the high-quality reforming unit.

[0008] The existing two-stage hydrocracking process has the following technical bottlenecks: (1) In the two-stage full-cycle hydrocracking process, since the unconverted oil from the second-stage hydrocracking directly enters the separation system without going through the hydrotreating reaction zone, some polycyclic aromatic hydrocarbons that are difficult to undergo hydrocracking reactions will circulate in the system and accumulate to a certain amount, affecting the overall technical effect of the device; (2) The existing two-stage full-cycle process is difficult to break through the 70% mark of heavy naphtha selectivity by relying solely on catalyst performance upgrades. Increasing the reaction depth will lead to an increase in the yield of light naphtha and gas products, resulting in a decrease in the overall heavy naphtha selectivity.

[0009] During the research process, the applicant discovered that the hydrocracking reaction has a dynamic inhibition and guidance phenomenon in the cracking reaction area, that is, in the hydrocracking process of the full-fraction reactants, the introduction of substances with a distillation range of A to B°C will promote the substances with a distillation range of A to B°C to preferentially react with light components (<A°C), while inhibiting the reaction of substances with a distillation range of >B°C. Based on the above test, the applicant found that by optimizing the functional area of ​​the two-stage hydrocracking reaction and the hydrocracking reaction path, the selectivity of the target product can be significantly improved while extending the operation cycle of the device.

[0010] In order to solve the deficiencies of the prior art, the present invention provides a two-stage hydrocracking process, comprising the following steps:

[0011] (1) separating catalytic diesel to obtain light catalytic diesel and heavy catalytic diesel;

[0012] (2) Under the conditions of hydrogenation pretreatment, the wax oil feedstock enters the hydrogenation pretreatment reactor and reacts with hydrogen and a hydrogenation pretreatment catalyst to obtain a hydrogenation pretreatment stream;

[0013] (3) Under the condition of the first-stage hydrocracking, the hydrogenation pretreatment stream enters the first-stage hydrocracking reactor, reacts with hydrogen and a hydrocracking catalyst, and the first-stage hydrocracking stream enters the separation unit for separation to obtain gas products, light naphtha, heavy naphtha, light tail oil, and heavy tail oil;

[0014] (4) Under the conditions of the second-stage hydrocracking, the light catalytic diesel, the heavy catalytic diesel, the light tail oil, and the heavy tail oil enter the second-stage hydrocracking reactor, react with hydrogen and the catalyst therein, and the obtained second-stage hydrocracking stream is circulated back to the separation unit for treatment;

[0015] Wherein, a hydrocracking catalyst bed layer I, a hydrorefining catalyst bed layer and a hydrocracking catalyst bed layer II are sequentially arranged in the second-stage hydrocracking reactor according to the flow direction of the liquid phase material;

[0016] An inlet I is provided at the top of the reactor, and heavy catalytic diesel and heavy tail oil enter the second-stage hydrocracking reactor through the inlet I;

[0017] An inlet II is provided on the reactor shell between the hydrocracking catalyst bed I and the hydrofining catalyst bed, and the light catalytic diesel enters the second-stage hydrocracking reactor through the inlet II;

[0018] An inlet III is arranged on the reactor shell between the hydrorefining catalyst bed and the hydrocracking catalyst bed II; the light tail oil enters the second-stage hydrocracking reactor through the inlet III.

[0019] Preferably, according to a specific embodiment of the present invention, the distillation range of catalytic diesel is generally 150°C to 350°C, the mass content of aromatics is 40% to 80%, and preferably the mass content of aromatics is 50% to 70%; the sulfur content is not more than 1.0wt%, the nitrogen content is not more than 1000ppm, and preferably the nitrogen content is not more than 500ppm.

[0020] Preferably, according to a specific embodiment of the present invention, the processing amount of catalytic diesel is 2wt% to 55wt%, preferably 5wt% to 15wt% of the wax oil feedstock.

[0021] Preferably, according to a specific embodiment of the present invention, the splitting temperature of light catalytic diesel and heavy catalytic diesel is 200-340°C, preferably 280-320°C.

[0022] Preferably, according to a specific embodiment of the present invention, the initial distillation point of the wax oil raw material is generally controlled to be 180-250°C, preferably 210-235°C; the final distillation point is controlled to be 450-550°C, preferably 460-500°C.

[0023] Preferably, according to a specific embodiment of the present invention, the wax oil raw material can be selected from at least one of straight-run wax oil, ebullated bed wax oil, coking wax oil, etc. The requirements for the sulfur and nitrogen content of the wax oil raw material are relatively broad, and the sulfur content can usually be controlled to be no higher than 3.0wt% and the nitrogen content can be controlled to be no higher than 2000ppm.

[0024] Preferably, according to a specific embodiment of the present invention, in step (3), the first-stage hydrocracking flow enters the separation unit for separation to obtain gas products, light naphtha, heavy naphtha, light tail oil, and heavy tail oil. The specific process is as follows: the first-stage hydrocracking flow is first subjected to gas-liquid separation, and the separated gas phase is purified and compressed by a circulating hydrogen compressor to obtain hydrogen, which is used as circulating hydrogen. Specifically, in the present invention, it can be recycled back to the first-stage hydrocracking reactor and the second-stage hydrocracking reactor for use. The purification treatment refers to removing sulfides (including but not limited to hydrogen sulfide) in the gas phase. The purification treatment can adopt any of the existing processes for removing hydrogen sulfide; the separated liquid phase is separated to obtain light naphtha, heavy naphtha, light tail oil, and heavy tail oil.

[0025] Preferably, according to a specific embodiment of the present invention, light naphtha can partially or completely enter the second-stage hydrocracking reactor. When part of it enters the second-stage hydrocracking reactor, the rest can be used as a product outlet device; when it enters the second-stage hydrocracking reactor, it preferably enters the second-stage hydrocracking reactor through an inlet III on the reactor shell disposed between the hydrorefining catalyst bed and the hydrocracking catalyst bed II. The amount of light naphtha entering the second-stage hydrocracking reactor is 0% to 100% (wt) of the light naphtha product, preferably 10% to 50% (wt).

[0026] Preferably, according to a specific embodiment of the present invention, the volume proportion of the hydrotreating catalyst bed in the second-stage hydrocracking reactor is 20% to 60%, preferably 25% to 40%. The bottom of the hydrotreating catalyst bed is located at 30% to 90% of the height (from top to bottom) of the second-stage hydrocracking reactor, more preferably 55% to 85%.

[0027] Preferably, according to a specific embodiment of the present invention, at least one hydrocracking pretreatment catalyst is loaded in the hydrotreating reactor, preferably comprising 1 to 3 hydrocracking pretreatment catalysts. Generally, the hydrocracking pretreatment catalyst comprises a carrier and a hydrogenation metal component loaded on the carrier, and the hydrogenation metal component can be at least one selected from metal elements of Group VI, Group VII or Group VIII, preferably two or more metals of Co, Mo, Ni, and W as active components. Specifically, commercial hydrogenation catalysts such as FF-12, FF-56, FF-66, and FHUDS-8 developed by Dalian (Fushun) Petrochemical Research Institute of Sinopec can be selected, and can also be prepared according to common sense in the art as needed.

[0028] Preferably, according to a specific embodiment of the present invention, a first-stage hydrocracking reactor contains at least one hydrocracking catalyst, and the hydrocracking catalyst includes a carrier and a hydrogenation component supported on the carrier. The hydrogenation component can generally be selected from at least one of the metal elements of Group VIB and Group VIII, preferably two or more of Co, Mo, Ni, and W; the carrier can be selected from at least one of Y molecular sieve, β molecular sieve, modified Y molecular sieve, modified β molecular sieve, alumina, and amorphous silicon aluminum. In general, based on the weight of the catalyst, the content of the hydrogenation component calculated as oxide is 20% to 45% (wt), preferably 23% to 32% (wt). Specifically, commercial hydrocracking catalysts such as FC-52 and FC-32 developed by Fushun Petrochemical Research Institute (FRIPP) of Sinopec can be selected, and can also be prepared according to common sense in the art as needed.

[0029] Preferably, according to a specific embodiment of the present invention, the second-stage hydrocracking reactor comprises a hydrocracking catalyst bed I and a hydrocracking catalyst bed II, wherein:

[0030] The catalyst loaded in the hydrocracking catalyst bed I includes a carrier and an active metal component loaded on the carrier. The active metal component is generally selected from one or more of the metal elements of the VIB group and the VIII group, preferably two or more of Co, Mo, Ni, and W; the carrier is selected from at least one of Y molecular sieve, β molecular sieve, modified Y molecular sieve, modified β molecular sieve, alumina, and amorphous silicon aluminum. In general, based on the weight of the catalyst, the active metal component is calculated as oxide and the content is 18% to 38%, preferably 20% to 28%. The molecular sieve is preferably β molecular sieve, and the content is 15% to 35%, preferably 20% to 30%. Specifically, commercial hydrocracking catalysts such as FC-76 and FC-50 developed by Fushun Petrochemical Research Institute (FRIPP) of Sinopec can be selected, and can also be prepared according to common sense in the field as needed.

[0031] The catalyst loaded in the hydrocracking catalyst bed II includes a carrier and an active metal component loaded on the carrier. The active metal component is generally selected from one or more of the metal elements of the VIB group and the VIII group, preferably two or more of Co, Mo, Ni, and W; the carrier is selected from at least one of Y molecular sieve, β molecular sieve, modified Y molecular sieve, modified β molecular sieve, alumina, and amorphous silicon aluminum. In general, based on the weight of the catalyst, the active metal component is calculated as oxide and the content is 20% to 40%, preferably 22% to 30%. The molecular sieve is preferably Y molecular sieve, and the content is 18% to 38%, preferably 25% to 35%. Specifically, commercial hydrocracking catalysts such as FC-38 and FC-14 developed by Fushun Petrochemical Research Institute (FRIPP) of Sinopec can be selected, and can also be prepared according to common sense in the field as needed.

[0032] Preferably, according to a specific embodiment of the present invention, the hydrorefining catalyst bed in the second-stage hydrocracking reactor is filled with at least one hydrorefining catalyst, and the hydrorefining catalyst is at least one VIB group metal supported on amorphous alumina and / or silicon oxide, or at least one catalyst selected from group VIII metals or a combination thereof. The hydrorefining catalyst can be selected from commercial products or prepared according to common sense in the art as needed. Specifically, commercial hydrorefining catalysts such as FF-56, FF-66, FHUDS-7, FHUDS-8, and FTX developed by Fushun Research Institute of Petrochemicals (FRIPP) of Sinopec can be selected.

[0033] Preferably, according to a specific embodiment of the present invention, the operating conditions of the hydrogenation pretreatment reactor are generally as follows: the reaction pressure is 8.0 to 20.0 MPa, preferably 10.0 to 18.0 MPa, the reaction temperature is 340 to 430°C, preferably 350 to 425°C, and the volume space velocity is 0.2 to 10.0 h -1 , preferably 0.8~2.0h -1 , the volume ratio of hydrogen to oil is 100 to 3000, preferably 800 to 2000.

[0034] Preferably, according to a specific embodiment of the present invention, the operating conditions of the first stage hydrocracking reactor are generally as follows: reaction pressure is 8.0-20.0 MPa, preferably 10.0-18.0 MPa, reaction temperature is 330-425°C, preferably 360-410°C, volume space velocity is 0.6-8.0 h -1 , preferably 0.8~2.0h -1 , the volume ratio of hydrogen to oil is 100-2500, preferably 600-2200.

[0035] Preferably, according to a specific embodiment of the present invention, the operating conditions of the second-stage hydrocracking reactor are generally as follows: the reaction pressure is 8.0-18.0 MPa, preferably 10.0-17.0 MPa, the reaction temperature is 320-410°C, preferably 340-390°C, and the volume space velocity is 0.6-8.0 h -1 , preferably 1.0 to 2.5 hours -1 , the volume ratio of hydrogen to oil is 500-2500, preferably 600-2200.

[0036] Another aspect of the present invention provides a two-stage hydrocracking system, comprising a catalytic diesel separation unit, a hydrogenation pretreatment reactor, a first-stage hydrocracking reactor, a separation unit, and a second-stage hydrocracking reactor; wherein:

[0037] A catalytic diesel separation unit, which is used to receive and separate the catalytic diesel to obtain light catalytic diesel and heavy catalytic diesel;

[0038] A hydrogenation pretreatment reactor, which is used to receive the wax oil feedstock and hydrogen, and obtain a hydrogenation pretreatment stream after reacting with a hydrogenation pretreatment catalyst under hydrogenation pretreatment conditions;

[0039] A first-stage hydrocracking reactor is used to receive the hydropretreatment stream and hydrogen from the hydropretreatment reactor and react with the hydrocracking catalyst to obtain a first-stage hydrocracking stream;

[0040] The separation unit is used to receive the first hydrocracking flow from the first hydrocracking reactor, first enter the gas-liquid separation zone to obtain gas phase and liquid phase after gas-liquid separation, and the liquid phase is separated by a fractionating tower to obtain light naphtha, heavy naphtha, light tail oil, and heavy tail oil;

[0041] A two-stage hydrocracking reactor, in which a hydrocracking catalyst bed I, a hydrorefining catalyst bed and a hydrocracking catalyst bed II are sequentially arranged according to the flow direction of the liquid phase material;

[0042] An inlet I is provided at the top of the reactor, and heavy catalytic diesel and heavy tail oil enter the second-stage hydrocracking reactor through the inlet I;

[0043] An inlet II is provided on the reactor shell between the hydrocracking catalyst bed I and the hydrofining catalyst bed, and the light catalytic diesel enters the second-stage hydrocracking reactor through the inlet II;

[0044] An inlet III is arranged on the reactor shell between the hydrorefining catalyst bed and the hydrocracking catalyst bed II; the light tail oil enters the second-stage hydrocracking reactor through the inlet III.

[0045] Preferably, according to a specific embodiment of the present invention, the gas-liquid separation zone generally includes a hot high-pressure separator, a hot low-pressure separator, a cold high-pressure separator and a cold low-pressure separator according to actual conditions. The connection method between the separators and between the separators and the distillation tower can adopt the existing connection method in the field, and technical personnel in this field can freely choose according to actual needs.

[0046] Preferably, according to a specific embodiment of the present invention, light naphtha can partially or completely enter the second-stage hydrocracking reactor. When part of it enters the second-stage hydrocracking reactor, the rest can be used as a product outlet device; when it enters the second-stage hydrocracking reactor, it preferably enters the second-stage hydrocracking reactor through an inlet III on the reactor shell disposed between the hydrorefining catalyst bed and the hydrocracking catalyst bed II. The amount of light naphtha entering the second-stage hydrocracking reactor is 0% to 100% (wt) of the light naphtha product, preferably 10% to 50% (wt).

[0047] Compared with the prior art, the two-stage hydrocracking process provided by the present invention has the following advantages:

[0048] (1) The two-stage hydrocracking process of the present invention solves the problem of accumulation of polycyclic aromatics inherent in the traditional two-stage full-cycle wax oil hydrocracking process by setting a hydrorefining catalyst bed in the middle and lower part of the two-stage hydrocracking reactor to partially saturate the polycyclic aromatics in the two-stage hydrocracking reactor, while avoiding the problem that the hydrorefining catalyst bed is set at the top of the two-stage hydrocracking reactor, causing some light aromatics to be saturated first and then pass through the subsequent hydrocracking reaction zone to undergo excessive hydrocracking, resulting in an increase in the yield of gas and light naphtha products, thereby affecting the overall economic benefits. In the present invention, a hydrorefining catalyst bed is set in the middle and lower part of the two-stage hydrocracking reactor, and the yield of heavy naphtha is improved according to the gradual reaction law and combined with the use of dynamic inhibition phenomenon.

[0049] (2) In the two-stage hydrocracking process of the present invention, the catalytic diesel feedstock is cut into light and heavy components, the heavy catalytic diesel enters the second-stage hydrocracking reactor from the top inlet, and the light catalytic diesel enters the second-stage hydrocracking reactor from the inlet II, so that the processing load of the catalytic diesel at the top of the second-stage reactor is reduced, the heavy catalytic diesel that is difficult to react is fully reacted, and the light catalytic diesel is fed into the middle stage to reduce its tendency to produce light naphtha and gas products due to overreaction. At the same time, due to the introduction of light naphtha fraction, a high-density area of ​​diesel fraction and light naphtha fraction is formed below the refined catalyst in the second-stage hydrocracking reactor. According to the principle of chemical equilibrium, the reaction of diesel fraction to obtain heavy naphtha is intensified, while the reaction of heavy naphtha to light naphtha is inhibited, so that the yield of heavy naphtha is improved. In summary, combined with the reasonable catalyst grading setting in the second-stage hydrocracking reactor, different material inlets are set at the same time, and different materials are allowed to enter different positions of the reactor through different inlets for reaction, so as to achieve the positive effect of blending catalytic diesel, and according to the gradual reaction law and combined with the dynamic inhibition theory, the yield of heavy naphtha is improved.

[0050] (3) In summary, the two-stage hydrocracking process of the present invention proposes a novel two-stage hydrocracking process by rationally allocating the processing raw materials and combining the adjustment of the process route, based on the dynamic inhibition phenomenon discovered by the applicant. While improving the selectivity of the heavy naphtha product of the device, it also solves the inherent problem of the two-stage full-cycle hydrocracking process that easily leads to the accumulation of polycyclic aromatic hydrocarbons, and can process catalytic diesel raw materials that are currently difficult to reasonably and efficiently utilize, providing favorable technical support for the physical efficiency improvement of enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 The figure is a schematic flow diagram of a two-stage hydrocracking process in an embodiment of the present invention.

[0052] Among them, 1-wax oil feedstock; 2-hydrogenation pretreatment reactor; 3-hydrogenation pretreatment logistics; 4-first stage hydrocracking reactor; 5-first stage hydrocracking reaction logistics; 6-gas-liquid separator; 7-liquid phase; 8-gas phase; 9-gas product; 10-light naphtha; 11-heavy naphtha; 12-light tail oil; 13-heavy tail oil; 14-second stage hydrocracking reactor; 15-second stage hydrocracking reaction logistics; 16-catalytic diesel feedstock; 17-catalytic diesel separation unit; 18-light catalytic diesel; 19-heavy catalytic diesel; 20-circulating hydrogen compressor; 21-circulating hydrogen; 22-new hydrogen;

[0053] Figure 2 It is a schematic flow diagram of a two-stage hydrocracking process in a comparative example of the present invention.

[0054] Among them, 1-wax oil feedstock; 2-hydrogenation pretreatment reactor; 3-hydrogenation pretreatment logistics; 4-first-stage hydrocracking reactor; 5-gas-liquid separator; 6-liquid phase; 7-distillation tower; 8-gas; 9-light naphtha; 10-heavy naphtha; 11-tail oil; 12-second-stage hydrocracking reactor; 13-second-stage hydrocracking reaction logistics; 14-gas phase; 15-circulating hydrogen compressor; 16-first-stage hydrocracking reaction logistics; 17-circulating hydrogen; 18-new hydrogen. DETAILED DESCRIPTION

[0055] The technical scheme and technical effects of the present invention are further described below in conjunction with the accompanying drawings and specific implementation methods.

[0056] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0057] In this document, for the convenience of description, spatial relative terms such as "below", "below", "down", "above", "above", "upper", etc. may be used to describe the relationship between one element or feature and another element or feature in the accompanying drawings. It should be understood that the spatial relative terms are intended to include different directions of objects in use or operation in addition to the directions drawn in the drawings. For example, if the object in the figure is turned over, the elements described as being "below" or "below" other elements or features will be oriented "above" the elements or features. Therefore, the exemplary term "below" can include both below and above directions. Objects may also have other orientations (rotated 90 degrees or other orientations) and the spatial relative terms used in this document should be interpreted accordingly.

[0058] In this document, the terms "first", "second", etc. are used to distinguish two different elements or parts, and are not used to limit a specific position or relative relationship. In other words, in some embodiments, the terms "first", "second", etc. can also be interchangeable.

[0059]

[0043] All numerical values ​​for parameters (eg, amounts or conditions) herein are to be understood as being modified in all instances by the term "about", whether or not "about" actually appears before the numerical value.

[0060] by Figure 1 The specific implementation methods of the process and system provided by the present invention are further described as follows: Figure 1As shown, the specific process of the two-stage hydrocracking process provided by the present invention is as follows: the catalytic diesel feedstock 16 first enters the catalytic diesel separation unit 17, and after the light and heavy components are cut, a light catalytic diesel 18 and a heavy catalytic diesel 19 are obtained. The wax oil feedstock 1 is mixed with the circulating hydrogen 21 in the presence of new hydrogen 22 and enters the hydropretreatment reactor 2 for reaction to obtain a hydropretreatment stream 3, and the hydropretreatment stream 3 enters the first-stage hydrocracking reactor 4 for reaction. The first-stage hydrocracking reaction stream 5 obtained after the reaction enters the gas-liquid separator 6 for gas-liquid separation to obtain a gas phase 8 and a liquid phase 7, wherein the gas phase 8 is circulated back to the reaction system by the circulating hydrogen compressor 20, and the liquid phase 7 enters the fractionation tower for separation to obtain a gas 9, a light naphtha 10, a heavy naphtha 11, a light tail oil 12, and a heavy tail oil 13. Heavy catalytic diesel 19 and heavy tail oil 13 enter the second-stage hydrocracking reactor 14 through inlet I at the top of the second-stage hydrocracking reactor. In the second-stage hydrocracking reactor, a hydrocracking catalyst bed I, a hydrorefining catalyst bed and a hydrocracking catalyst bed II are arranged in sequence according to the flow direction of the liquid phase material; an inlet II is arranged on the reactor shell between the hydrocracking catalyst bed I and the hydrorefining catalyst bed, and the light catalytic diesel enters the second-stage hydrocracking reactor through inlet II; an inlet III is arranged on the reactor shell between the hydrorefining catalyst bed and the hydrocracking catalyst bed II; light tail oil and optional light naphtha enter the second-stage hydrocracking reactor through inlet III; the second-stage hydrocracking reaction flow 15 obtained after the reaction is circulated to the gas-liquid separator 6 of the separation unit for treatment.

[0061] The properties of the raw oil used in the examples of the present invention and the comparative examples are shown in Table 1.

[0062] Table 1 Raw oil properties

[0063]

[0064] Example 1

[0065] use Figure 1The two-stage hydrocracking process shown in the figure, the properties of the processed wax oil feedstock 1 and catalytic diesel are shown in Table 1, and the processing amount of catalytic diesel is 12wt% of the wax oil feedstock. The FF-66 catalyst is loaded in the hydropretreatment reactor, the FC-70 catalyst is loaded in the first hydrocracking reactor, and the hydrocracking catalyst FC-32, the hydrofining catalyst FF-66, and the hydrocracking catalyst FC-52 are loaded in the second hydrocracking reactor in the direction of liquid phase material flow. The volume of the hydrofining catalyst in the second hydrocracking reactor accounts for 25%, and the bottom position of the hydrofining catalyst bed is located at 85% of the height of the second hydrocracking reactor from top to bottom. The light-heavy splitting temperature of catalytic diesel is 320℃, and the amount of light naphtha entering the second hydrocracking reactor is 30wt% of the light naphtha product. The reaction conditions of the hydropretreatment reactor are as follows: the reaction pressure is 16.0 MPa, the reaction temperature is 360℃, and the volume space velocity is 1.0h -1 , the hydrogen-to-oil volume ratio is 1200. The reaction conditions of the first-stage hydrocracking reactor are as follows: reaction pressure is 16.0 MPa, reaction temperature is 360 °C, volume space velocity is 0.8 h -1 , the hydrogen-oil volume ratio is 1300. The reaction conditions of the second-stage hydrocracking reactor are as follows: reaction pressure is 16.0 MPa, reaction temperature is 340℃, volume space velocity is 1.2h -1 , the volume ratio of hydrogen to oil is 1000. The reaction results are shown in Table 2.

[0066] Example 2

[0067] use Figure 1 The two-stage hydrocracking process shown in the figure, the properties of the processed wax oil feedstock 2 and catalytic diesel are shown in Table 1, and the processing amount of catalytic diesel is 10wt% of the wax oil feedstock. The FF-36 / FF-56 catalyst is graded and loaded in the hydropretreatment reactor, the FC-52 catalyst is loaded in the first hydrocracking reactor, and the hydrocracking catalyst FC-14, the hydrofining catalyst FUDS-10, and the hydrocracking catalyst FC-46 are loaded in the second hydrocracking reactor in the direction of liquid phase material flow. The volume of the hydrofining catalyst in the second hydrocracking reactor accounts for 30%, and the bottom position of the hydrofining catalyst bed is located at 75% of the height of the second hydrocracking reactor from top to bottom. The light-heavy splitting temperature of catalytic diesel is 320℃, and the amount of light naphtha entering the second hydrocracking reactor is 30wt% of the light naphtha product. The reaction conditions of the hydropretreatment reactor are as follows: the reaction pressure is 12.0 MPa, the reaction temperature is 350℃, and the volume space velocity is 2.0 h -1 , the hydrogen-to-oil volume ratio is 800. The reaction conditions of the first-stage hydrocracking reactor are as follows: reaction pressure is 12.0 MPa, reaction temperature is 375 °C, volume space velocity is 2.0 h -1, the hydrogen-to-oil volume ratio is 1000. The reaction conditions of the second-stage hydrocracking reactor are as follows: reaction pressure is 12.0 MPa, reaction temperature is 350 °C, volume space velocity is 1.8 h -1 , the volume ratio of hydrogen to oil is 800. The reaction results are shown in Table 2.

[0068] Example 3

[0069] use Figure 1 The two-stage hydrocracking process shown in the figure, the properties of the processed wax oil feedstock 1 and catalytic diesel are shown in Table 1, and the processing amount of catalytic diesel is 8wt% of the wax oil feedstock. The FF-56 catalyst is loaded in the hydropretreatment reactor, the FC-46 catalyst is loaded in the first hydrocracking reactor, and the hydrocracking catalyst FC-28, the hydrofining catalyst FTX, and the hydrocracking catalyst FC-70 are loaded in the second hydrocracking reactor in the direction of liquid phase material flow. The volume of the hydrofining catalyst in the second hydrocracking reactor accounts for 40%, and the bottom position of the hydrofining catalyst bed is located at 65% of the height of the second hydrocracking reactor from top to bottom. The light-heavy splitting temperature of catalytic diesel is 280℃, and the amount of light naphtha entering the second hydrocracking reactor is 50wt% of the light naphtha product. The reaction conditions of the hydropretreatment reactor are as follows: the reaction pressure is 15.0 MPa, the reaction temperature is 370℃, and the volume space velocity is 1.0 h -1 , the hydrogen-to-oil volume ratio is 1500. The reaction conditions of the first-stage hydrocracking reactor are as follows: reaction pressure is 15.0 MPa, reaction temperature is 380 °C, volume space velocity is 1.8 h -1 , the hydrogen-to-oil volume ratio is 1600. The reaction conditions of the second-stage hydrocracking reactor are as follows: reaction pressure is 15.0 MPa, reaction temperature is 370 °C, volume space velocity is 2.0 h -1 , the volume ratio of hydrogen to oil is 1200. The reaction results are shown in Table 2.

[0070] Comparative Example 1

[0071] use Figure 2The wax oil two-stage hydrocracking method shown in the figure, the properties of the processed wax oil raw material 1 and catalytic diesel are shown in Table 1, the wax oil raw material and catalytic diesel enter from the entrance of the hydrogenation pretreatment reactor, and the specific process flow of the wax oil two-stage hydrocracking method is as follows: in the presence of new hydrogen 18, the wax oil raw material, catalytic diesel and circulating hydrogen 17 are mixed and enter the hydrogenation pretreatment reactor 2 for reaction, the hydrogenation pretreatment stream 3 obtained after the reaction enters the first-stage hydrocracking reactor 4 for reaction, the first-stage hydrocracking reaction stream 16 obtained after the reaction enters the gas-liquid separator 5 to obtain a gas phase 14 and a liquid phase 6 after gas-liquid separation, wherein the gas phase 14 is recycled as the circulating hydrogen 17 after the action of the circulating hydrogen compressor 15, the liquid phase 6 enters the fractionation tower 7 for separation to obtain gas 8, light naphtha 9, heavy naphtha 10, and tail oil 11, the tail oil 11 enters the second-stage hydrocracking reactor 12 from the feed port at the top of the second-stage hydrocracking reactor, and the second-stage hydrocracking reaction stream 13 obtained after the reaction is circulated back to the gas-liquid separator 5 for treatment.

[0072] The processing amount of catalytic diesel is 12wt% of the wax oil feedstock. The hydrotreating pretreatment reactor is filled with FF-66 catalyst, the first stage hydrocracking reactor is filled with FC-70 catalyst, and the second stage hydrocracking reactor is filled with FC-32. The reaction conditions of the hydrotreating pretreatment reactor are as follows: reaction pressure is 16.0 MPa, reaction temperature is 360℃, volume space velocity is 1.0 h -1 , the hydrogen-to-oil volume ratio is 1200. The reaction conditions of the first-stage hydrocracking reactor are as follows: reaction pressure is 16.0 MPa, reaction temperature is 360 °C, volume space velocity is 0.8 h -1 , the hydrogen-to-oil volume ratio is 1300. The reaction conditions of the second-stage hydrocracking reactor are as follows: reaction pressure is 16.0 MPa, reaction temperature is 340 °C, volume space velocity is 1.2 h -1 , the volume ratio of hydrogen to oil is 1000. The reaction results are shown in Table 2.

[0073] Comparative Example 2

[0074] use Figure 1The two-stage hydrocracking process shown in the figure is different in that no hydrorefining catalyst is loaded in the second-stage hydrocracking reactor, and light naphtha does not enter the second-stage hydrocracking reactor. The properties of the processed wax oil feedstock 1 and catalytic diesel are shown in Table 1. The processing amount of catalytic diesel is 10wt% of the wax oil feedstock. The FF-36 / FF-56 catalyst is loaded in the hydropretreatment reactor, and the FC-52 catalyst is loaded in the first-stage hydrocracking reactor. The upper hydrocracking catalyst in the second-stage hydrocracking reactor is FC-14 (75%V), and the lower hydrocracking catalyst is FC-46 (25%V). The light-heavy splitting temperature of catalytic diesel is 320℃. The heavy catalytic diesel enters from the top of the second-stage hydrocracking reactor, and the light catalytic diesel enters between the FC-14 and FC-46 catalyst beds. The reaction conditions of the hydropretreatment reactor are as follows: the reaction pressure is 12.0 MPa, the reaction temperature is 350℃, and the volume space velocity is 2.0 h -1 , the hydrogen-to-oil volume ratio is 800. The reaction conditions of the first-stage hydrocracking reactor are as follows: reaction pressure is 12.0 MPa, reaction temperature is 375 °C, volume space velocity is 2.0 h -1 , the hydrogen-to-oil volume ratio is 1000. The reaction conditions of the second-stage hydrocracking reactor are as follows: reaction pressure is 12.0 MPa, reaction temperature is 350 °C, volume space velocity is 1.8 h -1 , the volume ratio of hydrogen to oil is 800. The reaction results are shown in Table 2.

[0075] Comparative Example 3

[0076] use Figure 1 The two-stage hydrocracking process shown in the figure is different in that the catalytic diesel is not cut and directly enters from the top inlet of the second-stage hydrocracking reactor. The properties of the processed wax oil feedstock 1 and catalytic diesel are shown in Table 1. The processing amount of catalytic diesel is 8wt% of the wax oil feedstock. The hydropretreatment reactor is filled with FF-56 catalyst, the first-stage hydrocracking reactor is filled with FC-46 catalyst, and the second-stage hydrocracking reactor is filled with hydrocracking catalyst FC-28, hydrofining catalyst FTX, and hydrocracking catalyst FC-70 in the direction of liquid material flow. The volume of the hydrofining catalyst in the second-stage hydrocracking reactor accounts for 40%, and the bottom position of the hydrofining catalyst bed is located at 65% of the height of the second-stage hydrocracking reactor from top to bottom. The reaction conditions of the hydropretreatment reactor are as follows: the reaction pressure is 15.0 MPa, the reaction temperature is 370℃, and the volume space velocity is 1.0 h -1 , the hydrogen-to-oil volume ratio is 1500. The reaction conditions of the first-stage hydrocracking reactor are as follows: reaction pressure is 15.0 MPa, reaction temperature is 380 °C, volume space velocity is 1.8 h -1, the hydrogen-to-oil volume ratio is 1600. The reaction conditions of the second-stage hydrocracking reactor are as follows: reaction pressure is 15.0 MPa, reaction temperature is 370 °C, volume space velocity is 2.0 h -1 , the volume ratio of hydrogen to oil is 1200. The reaction results are shown in Table 2.

[0077] Table 2 Results of Examples and Comparative Examples

[0078]

[0079] The experimental results of the above embodiments and comparative examples show that the two-stage hydrocracking process of the present invention has a significantly increased heavy naphtha yield, and the potential content of heavy naphtha aromatics has been improved. At the same time, the problem of aromatics accumulation in circulating oil during long-term operation of the two-stage circulating hydrocracking is solved, and part of the catalytic diesel is processed with high value.

Claims

1. A two-stage hydrocracking process comprising the following steps: (1) Separating the catalytic diesel to obtain light catalytic diesel and heavy catalytic diesel, wherein the separation temperature of the light catalytic diesel and the heavy catalytic diesel is 200 to 340°C; (2) Under hydrogenation pretreatment conditions, the wax oil feedstock enters the hydrogenation pretreatment reactor and reacts with hydrogen and a hydrogenation pretreatment catalyst to obtain a hydrogenation pretreatment stream; (3) Under the condition of the first-stage hydrocracking, the hydrogenation pretreatment stream enters the first-stage hydrocracking reactor, reacts with hydrogen and a hydrocracking catalyst, and the first-stage hydrocracking stream enters the separation unit for separation to obtain gas products, light naphtha, heavy naphtha, light tail oil, and heavy tail oil; (4) Under the conditions of the second-stage hydrocracking, the light catalytic diesel, the heavy catalytic diesel, the light tail oil, and the heavy tail oil enter the second-stage hydrocracking reactor, react with hydrogen and the catalyst therein, and the obtained second-stage hydrocracking stream is circulated back to the separation unit for treatment; Wherein, a hydrocracking catalyst bed layer I, a hydrorefining catalyst bed layer and a hydrocracking catalyst bed layer II are sequentially arranged in the second-stage hydrocracking reactor according to the flow direction of the liquid phase material; An inlet I is provided at the top of the reactor, and heavy catalytic diesel and heavy tail oil enter the second-stage hydrocracking reactor through the inlet I; An inlet II is provided on the reactor shell between the hydrocracking catalyst bed I and the hydrofining catalyst bed, and the light catalytic diesel enters the second-stage hydrocracking reactor through the inlet II; An inlet III is provided on the reactor shell between the hydrorefining catalyst bed and the hydrocracking catalyst bed II; the light tail oil enters the second-stage hydrocracking reactor through the inlet III; Part or all of the light naphtha enters the second-stage hydrocracking reactor through an inlet III disposed on the reactor shell between the hydrorefining catalyst bed and the hydrocracking catalyst bed II.

2. The two-stage hydrocracking process according to claim 1, characterized in that: The distillation range of catalytic diesel is 150℃~350℃, and the mass content of aromatics is 40%~80%.

3. The two-stage hydrocracking process according to claim 2, characterized in that: The mass content of aromatics is 50% to 70%.

4. The two-stage hydrocracking process according to claim 1, characterized in that: The processing amount of catalytic diesel is 2wt% to 55wt% of the wax oil raw material.

5. The two-stage hydrocracking process according to claim 1, characterized in that: The processing amount of catalytic diesel is 5wt% to 15wt% of the wax oil raw material.

6. The two-stage hydrocracking process according to claim 1, characterized in that: The splitting temperature between light catalytic diesel and heavy catalytic diesel is 280-320°C.

7. The two-stage hydrocracking process according to claim 1, characterized in that: The initial distillation point of the wax oil raw material is controlled at 180-250°C, and the final distillation point is controlled at 450-550°C.

8. The two-stage hydrocracking process according to claim 1, characterized in that: The initial distillation point of the wax oil raw material is controlled at 210-235°C; the final distillation point is controlled at 460-500°C.

9. The two-stage hydrocracking process according to claim 1, characterized in that: The volume proportion of the hydrotreating catalyst bed in the second-stage hydrocracking reactor is 20% to 60%; the bottom end of the hydrotreating catalyst bed is located at 30% to 90% of the height of the second-stage hydrocracking reactor from top to bottom.

10. The two-stage hydrocracking process according to claim 1, characterized in that: The volume proportion of the hydrotreating catalyst bed in the second-stage hydrocracking reactor is 25% to 40%; the bottom end of the hydrotreating catalyst bed is located at 55% to 85% of the height of the second-stage hydrocracking reactor from top to bottom.

11. The two-stage hydrocracking process according to claim 1, characterized in that: The operating conditions of the hydrogenation pretreatment reactor are as follows: reaction pressure is 8.0-20.0 MPa, reaction temperature is 340-430°C, volume space velocity is 0.2-10.0 h -1 , the volume ratio of hydrogen to oil is 100 to 3000.

12. The two-stage hydrocracking process according to claim 1, characterized in that: The operating conditions of the hydrogenation pretreatment reactor are as follows: reaction pressure is 10.0-18.0 MPa, reaction temperature is 350-425°C, volume space velocity is 0.8-2.0 h -1 , the volume ratio of hydrogen to oil is 800~2000.

13. The two-stage hydrocracking process according to claim 1, characterized in that: The operating conditions of the first-stage hydrocracking reactor are as follows: reaction pressure is 8.0-20.0 MPa, reaction temperature is 330-425°C, volume space velocity is 0.6-8.0 h -1 , the volume ratio of hydrogen to oil is 100~2500.

14. The two-stage hydrocracking process according to claim 1, characterized in that: The operating conditions of the first stage hydrocracking reactor are as follows: reaction pressure is 10.0-18.0 MPa, reaction temperature is 360-410°C, volume space velocity is 0.8-2.0 h -1 , the volume ratio of hydrogen to oil is 600~2200.

15. The two-stage hydrocracking process according to claim 1, characterized in that: The operating conditions of the second-stage hydrocracking reactor are as follows: reaction pressure is 8.0-18.0 MPa, reaction temperature is 320-410°C, volume space velocity is 0.6-8.0 h -1 , the volume ratio of hydrogen to oil is 500~2500.

16. The two-stage hydrocracking process according to claim 1, characterized in that: The operating conditions of the second-stage hydrocracking reactor are as follows: reaction pressure is 10.0-17.0 MPa, reaction temperature is 340-390°C, volume space velocity is 1.0-2.5 h -1 , the volume ratio of hydrogen to oil is 600~2200.

17. A two-stage hydrocracking system, comprising a catalytic diesel separation unit, a hydrogenation pretreatment reactor, a first-stage hydrocracking reactor, a separation unit, and a second-stage hydrocracking reactor; wherein: A catalytic diesel separation unit, which is used to receive and separate the catalytic diesel to obtain light catalytic diesel and heavy catalytic diesel; A hydrogenation pretreatment reactor, which is used to receive the wax oil feedstock and hydrogen, and obtain a hydrogenation pretreatment stream after reacting with a hydrogenation pretreatment catalyst under hydrogenation pretreatment conditions; A first-stage hydrocracking reactor is used to receive the hydropretreatment stream and hydrogen from the hydropretreatment reactor and react with the hydrocracking catalyst to obtain a first-stage hydrocracking stream; The separation unit is used to receive the first hydrocracking flow from the first hydrocracking reactor, first enter the gas-liquid separation zone to obtain gas phase and liquid phase after gas-liquid separation, and the liquid phase is separated by a fractionating tower to obtain light naphtha, heavy naphtha, light tail oil, and heavy tail oil; A two-stage hydrocracking reactor, in which a hydrocracking catalyst bed I, a hydrorefining catalyst bed and a hydrocracking catalyst bed II are sequentially arranged according to the flow direction of the liquid phase material; Among them, an inlet I is arranged at the top of the second-stage hydrocracking reactor, and the heavy catalytic diesel and heavy tail oil enter the second-stage hydrocracking reactor through the inlet I; An inlet II is provided on the reactor shell between the hydrocracking catalyst bed I and the hydrofining catalyst bed, and the light catalytic diesel enters the second-stage hydrocracking reactor through the inlet II; An inlet III is provided on the reactor shell between the hydrorefining catalyst bed and the hydrocracking catalyst bed II; the light tail oil enters the second-stage hydrocracking reactor through the inlet III; Part or all of the light naphtha enters the second-stage hydrocracking reactor through an inlet III disposed on the reactor shell between the hydrorefining catalyst bed and the hydrocracking catalyst bed II.

18. The two-stage hydrocracking system according to claim 17, characterized in that: The gas-liquid separation zone includes a hot high-pressure separator, a hot low-pressure separator, a cold high-pressure separator and a cold low-pressure separator.

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