A process for treating catalytic diesel and increasing production of light aromatics

Abstract

The present disclosure relates to a method for treating catalytic diesel and increasing the yield of light aromatic hydrocarbons, which comprises the following steps: subjecting catalytic diesel to hydrotreating to obtain hydrotreated catalytic diesel, and subjecting the hydrotreated catalytic diesel to a non-hydrogen catalytic cracking reaction, so that heavy aromatic hydrocarbons generated in the conversion of the hydrotreated catalytic diesel can be efficiently converted into light aromatic hydrocarbons. On the one hand, the method can avoid the problems of high hydrogen consumption, harsh operating conditions and aromatic hydrocarbon loss caused by using hydrotreating to produce light aromatic hydrocarbons. On the other hand, the method can solve the problem of difficult utilization of low-value heavy aromatic hydrocarbons and realize efficient utilization of resources. In addition, the heavy gasoline obtained is subjected to a second cracking reaction in a second cracking reactor, which is a dense-phase fluidized bed reactor, so that the heavy gasoline can be further converted into light aromatic hydrocarbons, thereby reducing the yield of heavy aromatic hydrocarbon components and increasing the yield of BTX products. In addition, the method of the present disclosure can also produce low-carbon olefins as by-products, further improving the utilization rate of raw materials.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of petroleum chemical industry, in particular, to a method for treating catalytic diesel and increasing production of light aromatic hydrocarbons. BACKGROUND

[0002] BTX (benzene, toluene, xylene) is an important petrochemical basic product, and is an important raw material for synthesizing rubber, synthetic fibers and synthetic resins and various chemical products. Toluene and xylene can also be used as gasoline octane number additives.

[0003] CN200710043941.3 discloses a method for producing light aromatic hydrocarbons and light alkanes from hydrocarbon raw materials. The hydrocarbon raw materials with a boiling point of 30-250℃ are reacted in the presence of a zeolite catalyst containing Pt or Pd. The heavy aromatic hydrocarbons in the hydrocarbon raw materials are dealkylated by hydrogenation and undergo transalkylation with light aromatic hydrocarbons. The light aromatic hydrocarbons are isomerized to form a component rich in BTX (B is benzene, T is toluene, and X is xylene) light aromatic hydrocarbons. Non-aromatic hydrocarbons are converted into light alkanes by hydrogenation cracking. In a distillation column, liquid products can be separated into benzene, toluene, xylene, and C9+ aromatic hydrocarbons according to different boiling points. Light alkanes can be separated from the gas phase product. This method solves the technical problems of complex process, high cost, and low utilization value of heavy aromatic hydrocarbons and non-aromatics in the traditional separation process of hydrocarbon raw materials.

[0004] CN116496814A discloses a method for producing light aromatic hydrocarbons from diesel. The diesel is hydrogenated and then catalytically cracked. The cracking products are separated to obtain a light aromatic hydrocarbon fraction and a heavy aromatic hydrocarbon fraction. The light aromatic hydrocarbon fraction is subjected to aromatic extraction, and the heavy aromatic hydrocarbon fraction is returned to the riser reactor for further reaction. The heavy aromatic hydrocarbon fraction and the hydrogenated diesel are layered and fed. However, this method only simply recycles the heavy aromatic hydrocarbon fraction, and does not provide a dedicated reaction zone and reaction environment most conducive to the conversion of the heavy aromatic hydrocarbon fraction, resulting in a low yield of light aromatic hydrocarbons in the conversion process. SUMMARY

[0005] The present disclosure provides a method for treating catalytic diesel and increasing production of light aromatic hydrocarbons to solve the problems of high production of low-value heavy aromatic hydrocarbons, difficulty in utilization, and low yield of light aromatic hydrocarbons in the prior art.

[0006] To achieve the above object, the present disclosure provides a method for processing catalytic diesel and increasing production of light aromatic hydrocarbons, which comprises: feeding catalytic diesel into a hydrogenation reaction unit for hydrogenation treatment to obtain hydrogenated catalytic diesel, and feeding the hydrogenated catalytic diesel into a first cracking reactor of a cracking reaction unit for first cracking reaction, and after gas-solid separation, obtaining a cracking reaction product; subjecting the cracking reaction product to product separation treatment to obtain other products, light gasoline components, heavy gasoline components and diesel components; returning the diesel components to the hydrogenation reaction unit; feeding the heavy gasoline components into a second cracking reactor of the cracking reaction unit for second cracking reaction, and feeding the obtained oil agent mixture into the first cracking reactor; subjecting the light gasoline components to aromatic hydrocarbon separation treatment to obtain benzene products, toluene products and xylene products; the second cracking reactor is a dense phase fluidized bed reactor, the bed density of the dense phase fluidized bed reactor is 180-700 kg / m 3 ; the catalyst activity of the catalyst in the second cracking reactor is 50-99.

[0007] Optionally, the initial boiling point of the light gasoline components is 20-50℃; the distillation cut point of the light gasoline components and the heavy gasoline components is 120-150℃; the distillation cut point of the diesel components and the heavy gasoline components is 200-250℃.

[0008] Optionally, the initial boiling point of the hydrogenated catalytic diesel is 150-250℃, and the final boiling point is 300-380℃.

[0009] Optionally, the reaction conditions of the first cracking reaction include: the reaction temperature is 520-680℃, preferably 560-600℃; the reaction time is 1-15s, preferably 1-8s; the catalyst / oil ratio is (1-100):1, preferably (1-30):1; the reaction conditions of the second cracking reaction include: the reaction temperature is 555-720℃, preferably 580-660℃; the catalyst / oil ratio is (1-100):1, preferably (5-30):1; the catalyst activity is 60-90.

[0010] Optionally, the catalysts of the first cracking reaction and the second cracking reaction are the same or different, and each independently comprises zeolite, inorganic oxide and optional clay; based on the total weight of the catalyst, the content of the zeolite is 5-70 wt%, the content of the inorganic oxide is 1-95 wt%, and the content of the clay is 1-50 wt%.

[0011] Optionally, the zeolite comprises large-pore zeolite and optional medium-pore zeolite; based on the total weight of the zeolite, the content of the large-pore zeolite is 60-100 wt%, and the content of the medium-pore zeolite is 0-40 wt%.

[0012] Optionally, the medium pore zeolite is selected from ZSM zeolite; the large pore zeolite is selected from one or more of beta zeolite and Y zeolite; the inorganic oxide comprises silicon dioxide and / or di-aluminum trioxide; and the clay is kaolin and / or halloysite.

[0013] Optionally, the catalyst contains rare earth elements, and preferably, the large pore zeolite is Y zeolite modified by rare earth elements.

[0014] Optionally, the method further comprises regenerating the spent catalyst from the first cracking reaction and returning the regenerated catalyst to the cracking reaction unit.

[0015] Optionally, the method further comprises adding fresh agent into the second cracking reactor.

[0016] Optionally, the ratio of the weight of the fresh agent to the total weight of the catalyst in the cracking reaction unit is 0.2 or less.

[0017] Optionally, the cracking reaction unit further comprises a regenerator, and the method further comprises feeding the spent catalyst into the regenerator for regeneration to obtain regenerated catalyst, and returning the regenerated catalyst to the first cracking reactor through a first regenerated inclined pipe and to the second cracking reactor through a second regenerated inclined pipe, and optionally, the second regenerated inclined pipe is provided with a fresh agent inlet.

[0018] Optionally, the dense phase fluidized bed reactor is an upflow reactor or a downflow reactor.

[0019] Optionally, the dense phase fluidized bed reactor has a bed density of 300-500 kg / m 3 and a bed linear velocity of 0.4-2 m / s.

[0020] Optionally, the first cracking reactor and the second cracking reactor are arranged in series and the first cracking reactor is arranged downstream of the second cracking reactor.

[0021] Optionally, the first cracking reactor and the second cracking reactor are arranged coaxially.

[0022] Optionally, the conditions of the hydroprocessing comprise a reaction temperature of 330-450℃, a hydrogen partial pressure of 6-25 MPa, a volume space velocity of 0.1-2 h -1 , and a hydrogen / oil volume ratio of 1000-2000 Nm 3 / m 3 .

[0023] Optionally, the first cracking reactor is a dilute phase transport bed reactor and / or a dense phase fluidized bed reactor.

[0024] Optionally, the first cracking reactor is a cracking reactor for heavy oil feedstock.

[0025] Optionally, the hydrocatalytic diesel is contacted with the catalyst in the first cracking reactor prior to the heavy oil feedstock.

[0026] By the above technical solution, the catalytic diesel is first subjected to hydroprocessing to obtain a hydrocatalytic diesel, and the hydrocatalytic diesel is subjected to a non-hydrogen catalytic cracking reaction, which can efficiently convert heavy aromatics generated in the conversion of the hydrocatalytic diesel into light aromatics. On the one hand, this can avoid the problems of high hydrogen consumption, harsh operating conditions, and loss of aromatics caused by using hydroprocessing to produce light aromatics. On the other hand, it can solve the problem of difficult utilization of low-value heavy aromatics and achieve efficient utilization of resources. In addition, the heavy gasoline obtained can be recycled in the second cracking reactor, which is a dense-phase fluidized bed reactor, to further convert the heavy gasoline into light aromatics, thereby reducing the yield of heavy aromatic components and increasing the yield of BTX products. In addition, the method of the present disclosure can also produce low-carbon olefins as by-products, further improving the utilization rate of the feedstock.

[0027] Other features and advantages of the present disclosure will be described in detail in the following detailed description section. BRIEF DESCRIPTION OF DRAWINGS

[0028] The accompanying drawings are included to provide a further understanding of the present disclosure, and constitute a part of the specification, and are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0029] Figure 1 is a schematic diagram of a method for processing catalytic diesel and increasing the yield of light aromatics according to the present disclosure.

[0030] Figure 2 is a schematic diagram of a specific embodiment of a cracking reaction unit used in the method according to the present disclosure.

[0031] Figure 3 is a schematic diagram of a second specific embodiment of a cracking reaction unit used in the method according to the present disclosure.

[0032] Figure 4 is a schematic diagram of a method for processing catalytic diesel and increasing the yield of light aromatics according to the present disclosure.

[0033] BRIEF DESCRIPTION OF DRAWINGS

[0034] 1 catalytic diesel; 2 hydrogenation reaction unit; 3 hydrogenation catalytic diesel; 4 cracking reaction unit; 5 cracking reaction product; 6 product separation device; 7 light gasoline component; 8 heavy gasoline component; 9 diesel component; 10 other product; 11 aromatic hydrocarbon separation device; 12 benzene product; 13 toluene product; 14 xylene product; 15 second cracking reactor; 16 first cracking reactor; 17 settler; 18 to-be-regenerated inclined pipe; 19 regenerator; 20 first regeneration inclined pipe; 21 second regeneration inclined pipe; 22 regeneration flue gas; 23 fresh agent; 24 fresh agent; 25 riser reactor. DETAILED DESCRIPTION

[0035] The specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0036] As shown in the Figure 1 The present disclosure provides a method for processing catalytic diesel and increasing production of light aromatic hydrocarbons, which comprises: feeding catalytic diesel 1 into a hydrogenation reaction unit 2 for hydrogenation treatment to obtain hydrogenation catalytic diesel 3, and feeding the hydrogenation catalytic diesel 3 into a first cracking reactor 16 of a cracking reaction unit 4 for first cracking reaction, and after gas-solid separation, obtaining a cracking reaction product 5; subjecting the cracking reaction product 5 to product separation treatment to obtain other products 10, a light gasoline component 7, a heavy gasoline component 8 and a diesel component 9; returning the diesel component 9 to the hydrogenation reaction unit 2; feeding the heavy gasoline component 8 into a second cracking reactor 15 of the cracking reaction unit 4 for second cracking reaction, and feeding the obtained oil agent mixture into the first cracking reactor 16; subjecting the light gasoline component 7 to aromatic hydrocarbon separation treatment to obtain benzene product 12, toluene product 13 and xylene product 14; the second cracking reactor 15 is a dense phase fluidized bed reactor, the bed density of the dense phase fluidized bed reactor is 180-700 kg / m 3 ; the catalyst activity of the catalyst in the second cracking reactor is 50-99.

[0037] Through the above technical solution, the catalytic diesel is first subjected to hydrogenation treatment to obtain hydrogenation catalytic diesel, and the hydrogenation catalytic diesel is subjected to non-hydrogen catalytic cracking reaction, which can efficiently convert heavy aromatic hydrocarbons generated in the hydrogenation catalytic diesel conversion process into light aromatic hydrocarbons. On the one hand, it can avoid the problems of high hydrogen consumption, harsh operating conditions and aromatic hydrocarbon loss caused by using hydrogenation treatment to produce light aromatic hydrocarbons; on the other hand, it can solve the problem of difficult utilization of low-value heavy aromatic hydrocarbons, and realize efficient utilization of resources. And the obtained heavy gasoline is backfired in the second cracking reactor, wherein the second cracking reactor is a dense phase fluidized bed reactor, which can further convert the heavy gasoline into light aromatic hydrocarbons, thereby reducing the yield of heavy aromatic hydrocarbon components and improving the yield of BTX products. In addition, the method of the present disclosure can also produce low-carbon olefins as by-products, further improving the utilization rate of raw materials.

[0038] In one embodiment, the initial boiling point of the hydrocatalytically cracked diesel is 150-250°C, preferably 190-220°C; and the final boiling point is 300-380°C, preferably 330-360°C.

[0039] In one embodiment, the catalysts for the first cracking reaction and the second cracking reaction are the same or different, each independently comprising a zeolite, an inorganic oxide, and optionally a clay; the content of the zeolite is 5-70% by weight, preferably 30-60% by weight, based on the total weight of the cracking catalyst; the content of the inorganic oxide is 1-95% by weight, preferably 30-70% by weight; and the content of the clay is 1-50% by weight, preferably 5-40% by weight.

[0040] In one embodiment, the zeolite comprises a large-pore zeolite and optionally a medium-pore zeolite; the medium-pore zeolite is preferably a ZSM series zeolite; and the large-pore zeolite is preferably one or more of β zeolite and Y zeolite. The content of the large-pore zeolite is 60-100% by weight, preferably 70-90% by weight, based on the total weight of the zeolite; and the content of the medium-pore zeolite is 0-40% by weight, preferably 10-30% by weight.

[0041] In one embodiment, the inorganic oxide is silicon dioxide and / or diatomic aluminum oxide; and the clay is kaolin and / or polyhydrous kaolin.

[0042] In one embodiment, the catalyst further comprises a rare earth element. The rare earth element used in the present disclosure is conventionally selected in the art, and no special requirement is made in the present application. Preferably, the rare earth element is present in the zeolite of the catalyst, and more preferably, the rare earth element in the catalyst is mainly derived from a Y-type zeolite modified by a rare earth element. In this embodiment, the addition of the rare earth element in the cracking catalyst can improve the catalytic activity of the cracking catalyst, thereby facilitating the improvement of the activity of the catalytic cracking reaction.

[0043] In one specific embodiment, the method for modifying the Y-type zeolite by a rare earth element comprises: contacting NaY molecular sieve with a rare earth solution or a mixed solution of a rare earth solution and an ammonium salt, performing filtration, water washing, and drying, and then performing first calcination to obtain a rare earth sodium Y molecular sieve; then slushing the rare earth sodium Y molecular sieve and contacting it with an acid solution, performing filtration, mixing with a rare earth solution, and adjusting the pH value of the slurry to 5-6 with ammonia water, and then performing second calcination after filtration or without filtration and drying to obtain a rare earth Y-type molecular sieve.

[0044] In one embodiment, the method for preparing the cracking catalyst comprises:

[0045] The inorganic oxide source, clay and deionized water are mixed and stirred to form a slurry, wherein the solid content of the slurry is 10-50% by weight; the pH of the slurry is adjusted to 1-4 with an inorganic acid (such as hydrochloric acid, nitric acid, phosphoric acid or sulfuric acid, etc.), and the aging treatment is carried out at this pH value, wherein the temperature of the aging treatment is 20-80℃, and the time is 0-2h; then inorganic oxide is added and stirred for 0.5-1.5h to form a colloid, and zeolite is added to form a catalyst slurry, wherein the content of the zeolite is 5-70% by weight, the content of the clay is 1-50% by weight, and the content of the inorganic oxide is 1-95% by weight, based on the total weight of the solid phase in the catalyst slurry, wherein the content of the large-pore zeolite in the zeolite is 40-100% by weight, and the content of the medium-pore zeolite is 0-60% by weight, based on the total weight of the zeolite; after continuous stirring, the microspherical catalyst is prepared by spray drying; then the microspherical catalyst is calcined at 400-600℃ for 0.5-2h, washed with ammonium sulfate at 30-80℃ until the sodium oxide content is less than 0.25% by weight, then leached with deionized water and filtered, and then dried at 100-200℃ to obtain a cracking catalyst; wherein the weight ratio of ammonium sulfate to microspherical catalyst to water is (0.1-1) : 1 : (5-15).

[0046] In one embodiment, the cracking reaction unit 4 used in the present disclosure comprises a first cracking reactor 16, a second cracking reactor 15, a regenerator 19 and a settler 17. The first cracking reactor 16 and the second cracking reactor 15 are arranged in series, and the first cracking reactor 16 is arranged downstream of the second cracking reactor 15, so that the material passing through the second cracking reactor 15 can enter the first cracking reactor 16.

[0047] The second cracking reactor 15 is a dense phase fluidized bed reactor, and the first cracking reactor 16 is a dense phase fluidized bed reactor, a dilute phase transport bed reactor, or a composite reactor comprising a dense phase fluidized bed reactor and a dilute phase transport bed reactor. The reactor type of the dense phase fluidized bed reactor used in the present disclosure is a bubbling bed reactor, a turbulent bed reactor or a fast bed reactor; the dilute phase transport bed reactor is a riser reactor.

[0048] In a preferred embodiment, the cracking reaction unit 4 comprises a dense phase fluidized bed reactor, which comprises the first cracking reactor 16 and the second cracking reactor 15, and the second cracking reactor 15 is arranged upstream of the first cracking reactor 16.

[0049] The bed density of the dense phase fluidized bed reactor is preferably 300-500 kg / m 3 , and the bed linear velocity is 0.1-4 m / s, preferably 0.4-2 m / s.

[0050] The first cracking reactor 16 is integrated in the interior of the settler 17, so that the material reacted in the first cracking reactor 16 can enter the settler 17. Alternatively, the first cracking reactor 16 and the settler 17 can be coaxially arranged or separately arranged according to actual use, preferably coaxially arranged.

[0051] The first cracking reactor 16 and the second cracking reactor 15 can be coaxially arranged or separately arranged according to actual production needs, preferably coaxially arranged.

[0052] In one embodiment, the method further comprises regenerating the spent catalyst obtained from the first cracking reaction, and returning the regenerated catalyst to the cracking reaction unit 4, preferably returning the regenerated catalyst to the first cracking reactor 16 and / or the second cracking reactor 15.

[0053] In one embodiment, the cracking reaction is carried out by using the cracking reaction unit 4 as shown in Figure 2 and Figure 3 to regenerate the spent catalyst obtained from the first cracking reaction, and returning the regenerated catalyst to the first cracking reactor 16 and / or the second cracking reactor 15.

[0054] In one specific embodiment, as shown in Figure 2 , the first cracking reactor 16 and the second cracking reactor 15 are coaxially arranged, and the second cracking reactor 15 is arranged upstream of the first cracking reactor 16. A spent catalyst outlet is arranged on the side wall of the settler 17; a spent catalyst inlet, a first regenerated agent outlet and a second regenerated agent outlet are arranged on the side wall of the regenerator 19; a first regenerated agent inlet and a hydrocatalytic diesel oil inlet are arranged on the first cracking reactor 16; a second regenerated agent inlet, a heavy gasoline inlet, a first fresh agent inlet and a pre-lift medium inlet are arranged on the second cracking reactor 15. The spent catalyst outlet of the settler 17 is communicated with the spent catalyst inlet of the regenerator 19 through the spent catalyst inclined pipe 18; the first regenerated agent outlet of the regenerator 19 is communicated with the first regenerated agent inlet of the first cracking reactor 16 through the first regenerated inclined pipe 20, and the second regenerated agent outlet of the regenerator 19 is communicated with the second regenerated agent inlet of the second cracking reactor 15 through the second regenerated inclined pipe 21; in addition, the hydrocatalytic diesel oil inlet of the first cracking reactor 16 is communicated with the hydrocatalytic diesel oil outlet of the hydrogenation reaction unit 2; the pre-lift medium inlet of the second cracking reactor 15 is used to communicate with a pre-lift medium source, and the first fresh agent inlet of the second cracking reactor 15 is used to communicate with a fresh agent source, so that the fresh agent 24 can enter the second cracking reactor 15 to react.

[0055] In a preferred embodiment, the heavy gasoline inlet is arranged downstream of the first fresh agent inlet, and the second regeneration agent inlet is arranged between the heavy gasoline inlet and the first fresh agent inlet.

[0056] In a preferred embodiment, a second fresh agent inlet is arranged on the second regeneration inclined pipe 21, and the fresh agent inlet is connected to a fresh agent source, so that fresh agent 23 can enter the second cracking reactor 15 with the second regeneration catalyst.

[0057] In a preferred embodiment, in order to flexibly adjust the flow rate of the feed and discharge of the regenerator 19, a flow regulating valve is arranged on the spent catalyst inclined pipe 18, the first regeneration inclined pipe 20 and the second regeneration inclined pipe 21.

[0058] In an embodiment, the pre-lift medium used by the present disclosure is conventionally selected in the art, and the present application does not make special requirements, for example, the pre-lift medium can be steam and / or dry gas.

[0059] In an embodiment, a steam inlet is further arranged at the outlet of the second cracking reactor 15, which is connected to a steam source, so that steam can enter the first cracking reactor 16.

[0060] In an embodiment, the method further comprises adding a fresh agent in the second cracking reactor.

[0061] In this embodiment, the spent catalyst produced by the first cracking reactor 16 is regenerated in the regenerator 19 to obtain regenerated catalyst, and the regenerated catalyst returns to the first cracking reactor and the second cracking reactor through the first regeneration inclined pipe 20 and the second regeneration inclined pipe 21 respectively, or the regenerated catalyst only returns to the second cracking reactor 15 through the second regeneration inclined pipe 21. Figure 2

[0062] In a specific embodiment, the cracking reaction unit is a cracking reactor. Figure 2 ​The method for processing catalytic diesel to increase the production of light aromatics includes: introducing fresh catalyst 24, a second regenerated catalyst, and heavy gasoline component 8 into a second cracking reactor 15 under the action of a pre-lifting medium to conduct a second cracking reaction, obtaining an oil-catalyst mixture; introducing the oil-catalyst mixture, the first regenerated catalyst, and hydrotreated catalytic diesel into a first cracking reactor 16 to conduct a first cracking reaction, obtaining a mixture containing cracking reaction products 5 and a spent catalyst. The mixture is then introduced into a settling tank 17 for separation. Most of the spent catalyst in the mixture moves downwards under gravity, while the cracking reaction products 5 and a small portion of the spent catalyst move upwards and enter a cyclone separator for separation, so that a small portion of the spent catalyst returns to the settling tank 17, and the cracking reaction products 5 exit the settling tank 17 through a gas collecting chamber. The catalyst to be recycled is introduced into the regenerator 19 through the prepared inclined tube 18 and regenerated under the action of oxygen-containing gas to obtain regenerated catalyst and regenerated flue gas 22, and the regenerated flue gas 22 is discharged. The regenerated catalyst is divided into a first regenerated catalyst and a second regenerated catalyst. The first regenerated catalyst is returned to the first cracking reactor 16 through the first regenerated inclined tube 20, and the second regenerated catalyst is returned to the second cracking reactor 15 through the second regenerated inclined tube 21 along with the fresh catalyst 23.

[0063] Another specific implementation, such as Figure 3 As shown, the first cracking reactor 16 and the second cracking reactor 15 are separately arranged, with the second cracking reactor 15 located upstream of the first cracking reactor 16. A catalyst outlet is provided on the side wall of the settling tank 17, and a catalyst inlet, a first regenerator outlet, and a second regenerator outlet are provided on the side wall of the regenerator. The first cracking reactor 16 has a first regenerator inlet, an oil-fuel mixture inlet, a hydrotreated catalytic diesel inlet, and a pre-lifting medium inlet; the second cracking reactor 15 has a second regenerator inlet, a heavy gasoline inlet, an oil-fuel mixture outlet, and a first freshener inlet; the catalyst outlet of the settling tank 17 is connected to the catalyst inlet of the regenerator; the first regenerator outlet of the regenerator 19 is connected to the first regenerator outlet of the first cracking reactor 16. The inlet is connected to the second regenerator outlet of the regenerator 19, which is connected to the second regenerator inlet of the second cracking reactor 15; the oil-to-fuel mixture outlet of the second cracking reactor 15 is connected to the oil-to-fuel mixture inlet of the first cracking reactor 16; the hydrotreated catalytic diesel inlet of the first cracking reactor 16 is connected to the hydrotreated catalytic diesel outlet of the hydrotreated reaction unit 2; the pre-lifting medium inlet of the first cracking reactor 16 is connected to the pre-lifting medium source; the heavy gasoline inlet of the second cracking reactor 15 is connected to the heavy gasoline outlet of the product separation device 6; and the first freshener inlet of the second cracking reactor 15 is connected to the freshener source.

[0064] In a preferred embodiment, the hydrogenated catalytic diesel oil inlet is arranged downstream of the first regenerator inlet and the oil agent mixture inlet; and the first regenerator inlet is arranged downstream of the oil agent mixture inlet.

[0065] In a preferred embodiment, a second fresh agent inlet is arranged on the second regenerator inclined pipe 21 of the second cracking reactor 15, and the fresh agent inlet is connected to a fresh agent source, so that the fresh agent can be mixed with the second regenerated catalyst and then enter the second cracking reactor 15.

[0066] In a preferred embodiment, in order to flexibly adjust the flow rates of the feed and the discharge of the regenerator 19, flow regulating valves are arranged on the spent catalyst inclined pipe 18, the first regenerator inclined pipe 20, the second regenerator inclined pipe 21 and the mixed material outlet pipeline.

[0067] In this embodiment, the cracking reaction is carried out by the cracking reaction unit Figure 3 , so that the spent catalyst produced by the first cracking reactor 16 can enter the regenerator 19 for regeneration to obtain regenerated catalyst; the regenerated catalyst returns to the first cracking reactor 16 and the second cracking reactor 15 through the first regenerator inclined pipe 20 and the second regenerator inclined pipe 21 respectively, and the reaction material in the second cracking reactor enters the first cracking reactor.

[0068] In another specific embodiment, the device Figure 3 for processing catalytic diesel oil to increase light aromatic hydrocarbons includes: the oil agent mixture at the outlet of the second cracking reactor, the first regenerated catalyst and the hydrogenated catalytic diesel oil enter the first cracking reactor 16 for the first cracking reaction under the action of the pre-lifting medium, to obtain a mixture containing the cracking reaction product 5 and the spent catalyst; the mixture enters the settler 17 for separation, most of the spent catalyst in the mixture runs downward under the action of gravity, the cracking reaction product 5 and a small part of the spent catalyst in the mixture run upward and enter the cyclone separator for separation, so that the small part of the spent catalyst returns to the settler 17, and the cracking reaction product 5 is discharged from the settler 17 through the gas collecting chamber; the spent catalyst enters the regenerator 19 through the spent catalyst inclined pipe 18 and is regenerated under the action of the oxygen-containing gas to obtain the regenerated catalyst and the regenerated flue gas 22; the regenerated flue gas 22 is discharged, the regenerated catalyst is divided into the first regenerated catalyst and the second regenerated catalyst, the first regenerated catalyst returns to the first cracking reactor 16 through the first regenerator inclined pipe 20; the second regenerated catalyst enters the second cracking reactor 15 through the second regenerator inclined pipe 21 to contact with the heavy gasoline component 8 and the fresh agent for the second cracking reaction, and the obtained oil agent mixture returns to the first cracking reactor 16.

[0069] In one embodiment, the first cracking reactor 16 and the second cracking reactor 15 can each independently be provided with a gas-solid separation device and a regeneration device, wherein the gas-solid separation device can be a settler and the regeneration device can be a regenerator, so that the products of the first cracking reactor 16 and the second cracking reactor 15 can be independently separated into spent catalyst and cracking reaction products, and the spent catalyst can be independently regenerated.

[0070] In one embodiment, in order to further improve the separation effect, a cyclone separator is arranged at the upper part of the settler 17 and the regenerator 19. The cyclone separator used in the present disclosure is a conventional selection in the art, and the present application does not make any requirements. The number of stages of the cyclone separator can be flexibly selected according to the actual production needs, and preferably, the number of stages of the cyclone separator is 2 stages.

[0071] In one embodiment, the settler 17 is provided with a gas collecting chamber at the top thereof, the inlet of the gas collecting chamber is in communication with the cracking reaction product outlet of the cyclone separator, and the outlet of the gas collecting chamber is used to communicate with the cracking reaction product outlet, so that the cracking reaction product can be buffered in the gas collecting chamber and then discharged out of the system through the cracking reaction product outlet.

[0072] In one embodiment, the regenerator 19 is further provided with an oxygen-containing gas distributor inside, and the inlet of the oxygen-containing gas distributor extends to the outside of the regenerator 19 to form an oxygen-containing gas inlet.

[0073] In the above embodiments, the catalyst refers to a cracking catalyst; the fresh agent refers to fresh cracking catalyst; the spent catalyst refers to the cracking catalyst after the first cracking reaction and / or the second cracking reaction; and the regenerated catalyst refers to the spent catalyst after the regeneration treatment.

[0074] In one embodiment, the catalyst used in the second cracking reactor 15 includes the second regenerated catalyst and the fresh agent. The ratio of the weight of the fresh agent to the total weight of the catalyst of the cracking reaction unit 4 is 0.2 or less, preferably 0.02-0.18, and further preferably 0.05-0.12.

[0075] In one embodiment, the reaction conditions of the first cracking reaction include a reaction temperature of 520-680℃, a reaction time of 1-15s, a reaction pressure of 130-450kPa, and a catalyst to oil ratio of (1-100):1; and preferably, the reaction conditions include a reaction temperature of 560-600℃, a reaction time of 1-8s, a reaction pressure of 150-300kPa, and a catalyst to oil ratio of (1-30):1; and the catalyst activity is 40-90, and preferably 50-80.

[0076] In an embodiment, the reaction conditions of the second cracking reaction include: a reaction temperature of 555-720℃, a reaction time of 1-20s, a reaction pressure of 130-450kPa, and a catalyst to oil ratio of (1-100):1; preferred reaction conditions include: a reaction temperature of 580-660℃, a reaction time of 3-15s, a reaction pressure of 150-300kPa, and a catalyst to oil ratio of (5-30):1; and the catalyst activity is preferably 60-90.

[0077] In an embodiment, the catalyst activity of the present disclosure refers to the micro-reactor activity index determined by the method of NB / SH / T 0952-2017.

[0078] In an embodiment, the product separation treatment device and method of the present disclosure are conventional choices in the art, and the present application does not make any requirements, as long as the cracking reaction products can be separated into other products, light gasoline components, heavy gasoline components, and diesel components.

[0079] In an embodiment, the main components of the other products include H2-C4 gas components, diesel and heavy oil fractions; the main component of the light gasoline components is C6-C8 components; and the main component of the heavy gasoline components is C9-C12 components.

[0080] In an embodiment, the initial boiling point of the light gasoline components is 20-50℃; the distillation cut point of the light gasoline components and the heavy gasoline components is 120-150℃; and the distillation cut point of the diesel components and the heavy gasoline components is 200-250℃.

[0081] In an embodiment, the device and method for aromatic hydrocarbon separation treatment are conventional choices in the art, and the present application does not make any requirements, as long as the gasoline light fraction can be separated into benzene products, toluene products, and xylene products, for example, the present application uses aromatic extraction technology for separation, and the aromatic raffinate can be returned to the catalytic cracking reactor for further reaction, and the back-refining position can be the same as the hydrogenated catalytic diesel.

[0082] In an embodiment, if the raw material of the first cracking reaction includes heavy oil raw material, the first cracking reactor 16 can be a heavy oil raw material cracking reactor; the method further includes: introducing the hydrogenated catalytic diesel and the heavy oil raw material into the first cracking reactor 16 to perform the first cracking reaction. In this embodiment, in order to make the hydrogenated catalytic diesel react with the catalyst before the heavy oil raw material, a heavy oil raw material inlet can be arranged above the hydrogenated catalytic diesel inlet of the first cracking reactor, and a first regenerated catalyst inlet can be arranged below the hydrogenated catalytic diesel inlet or between the hydrogenated catalytic diesel inlet and the heavy oil raw material inlet.

[0083] The following examples will further illustrate the present application without, however, restricting it. The properties of the hydrotreated hydrocatalytic diesel oil obtained in the examples and comparative examples are shown in Table 1. The heavy oil feedstock used in the examples is heavy oil, and the properties of the heavy oil are shown in Table 2.

[0084] Table 1 Properties of the hydrotreated hydrocatalytic diesel oil

[0085]

[0086]

[0087] Table 2 Properties of the heavy oil feedstock

[0088]

[0089] Preparation Example 1

[0090] The method for preparing the rare earth Y-type molecular sieve (REY) comprises: contacting a NaY molecular sieve with a rare earth solution or a mixed solution of a rare earth solution and an ammonium salt, and after filtration, water washing and drying, performing a first calcination treatment to obtain a rare earth sodium Y-type molecular sieve; then slurrying the rare earth sodium Y-type molecular sieve and contacting it with an acid solution, filtering, mixing with a rare earth solution, and adjusting the pH value of the slurry to 6 with ammonia water, and after filtration or without filtration, drying and performing a second calcination treatment to obtain the rare earth Y-type molecular sieve (REY).

[0091] The method for preparing the cracking catalyst C1 comprises: mixing an aluminum sol with kaolin, and using deionized water to prepare a slurry with a solid content of 40% by weight, uniformly stirring, adjusting the pH value of the slurry to 4 with an inorganic acid (such as hydrochloric acid, nitric acid, phosphoric acid or sulfuric acid), maintaining the pH value, adding aluminum sol at 60°C after standing and aging for 1 hour, stirring for 1 hour to form a colloid, adding a rare earth Y-type molecular sieve (REY) to form a catalyst slurry (with a solid content of 35% by weight), wherein the weight of REY: the weight of kaolin: the weight of aluminum sol = 50:34:16, continuing to stir and then spray drying to prepare a microspherical catalyst. Then the microspherical catalyst is calcined at 500°C for 1 hour, washed with ammonium sulfate at 60°C (wherein the weight of ammonium sulfate: the weight of the microspherical catalyst: the weight of water = 0.5:1:10) to a sodium oxide content of less than 0.25% by weight, then leached with deionized water and filtered, and then dried at 110°C to obtain the cracking catalyst C1.

[0092] Preparation Example 2

[0093] The method for preparing the rare earth Y-type molecular sieve (REY) is the same as that in Preparation Example 1;

[0094] The method for preparing the cracking catalyst C2 includes: mixing alumina sol with kaolin and preparing it into a slurry with a solid content of 40% by weight using decationized water, stirring evenly, adjusting the pH of the slurry to 4 with an inorganic acid (such as hydrochloric acid, nitric acid, phosphoric acid or sulfuric acid), maintaining this pH value, allowing it to stand and age at 60°C for 1 hour, adding alumina sol, stirring for 1 hour to form a colloid, adding ZSM-5 and REY to form a catalyst slurry (with a solid content of 35% by weight), wherein the weight of ZSM-5 molecular sieve: weight of REY: weight of kaolin: weight of alumina sol = 15:35:34:16, continuing to stir and then spray drying to prepare microsphere catalyst. The microsphere catalyst was then calcined at 500°C for 1 hour, and then washed with ammonium sulfate at 60°C (wherein the weight of ammonium sulfate: weight of microsphere catalyst: weight of water = 0.5:1:10) until the sodium oxide content was less than 0.25% by weight. After that, it was rinsed with deionized water and filtered, and then dried at 110°C to obtain the cracking catalyst C2.

[0095] Test Example 1

[0096] The micro-reaction activity index was determined according to the method for determining the micro-reaction activity index at 460℃ in NB / SH / T 0952-2017, and the obtained micro-reaction activity index is the catalyst activity of the cracking catalyst.

[0097] Example 1

[0098] use Figure 1 The system and Figure 2 The methods for increasing the production of light aromatics by processing catalytic diesel in cracking unit 4 include:

[0099] Catalytic diesel 1 and hydrogen are introduced into hydrogenation reaction unit 2 for hydrogenation treatment to obtain hydrogenated catalytic diesel 3. The hydrogenation conditions include a reaction temperature of 380℃, a hydrogen partial pressure of 10 MPa, and a volume hourly space velocity of 1 h⁻¹. -1 The hydrogen-to-oil volume ratio is 1200 Nm. 3 / m 3 .

[0100] The oil mixture from the second cracking reactor 15, the first regenerated catalyst and the hydrocracked diesel 3 are fed into the first cracking reactor 16 to perform the first cracking reaction, to obtain a mixture containing the cracking reaction product 5 and spent catalyst. The mixture is fed into the settler 17 to perform separation, most of the spent catalyst in the mixture runs downward under the action of gravity, the cracking reaction product 5 and a small part of the spent catalyst in the mixture run upward and are separated in the cyclone to return the small part of the spent catalyst to the settler 17, and the cracking reaction product 5 is discharged from the settler 17 through the gas collecting chamber. The spent catalyst is fed into the regenerator 19 through the spent catalyst inclined pipe 18 and is subjected to the regeneration treatment under the action of the oxygen-containing gas to obtain the regenerated catalyst and the regeneration flue gas 22, and the regeneration flue gas 22 is discharged; the regenerated catalyst is divided into the first regenerated catalyst and the second regenerated catalyst, the first regenerated catalyst is returned to the first cracking reactor 16 through the first regenerated catalyst inclined pipe 20, and the second regenerated catalyst is returned to the second cracking reactor 15 through the second regenerated catalyst inclined pipe 21;

[0101] The cracking reaction product 5 is fed into the product separation device 6 to perform the first separation, to obtain other products 10, a light gasoline component 7, a heavy gasoline component 8 and a diesel component 9; the fresh agent, the second regenerated catalyst and the heavy gasoline component 8 are fed into the second cracking reactor 15 to perform the second cracking reaction under the action of the pre-lift medium (water vapor), to obtain the oil mixture; the initial distillation of the light gasoline component 7 is 40°C, the distillation cut point of the light gasoline component 7 and the diesel component 9 is 150°C, and the distillation cut point of the heavy gasoline component 8 and the diesel component 9 is 210°C; the light gasoline component 7 is fed into the aromatic separation device 11 to perform the second separation, to obtain the benzene product 12, the toluene product 13 and the xylene product 14; the diesel component 9 is returned to the hydrogenation reaction unit, and the weight ratio of the fresh agent to the total weight of the catalyst in the cracking reaction unit 4 is 0.18:1; the other products are subjected to further separation, to obtain dry gas, ethylene, liquefied petroleum gas, propylene and gasoline. The cracking reaction conditions and product properties are shown in Table 3.

[0102] Example 2

[0103] The method for treating catalytic diesel and increasing the production of light aromatic hydrocarbons is the same as that in Example 1, except that the reaction temperature of the second cracking reaction is 620°C. The cracking reaction conditions and product properties are shown in Table 3.

[0104] Example 3

[0105] The method for treating catalytic diesel and increasing the production of light aromatic hydrocarbons is the same as that in Example 1, except that the agent-oil ratio of the second cracking reaction is 15:1. The cracking reaction conditions and product properties are shown in Table 3.

[0106] Example 4

[0107] The process for treating catalytic diesel and increasing production of light aromatic hydrocarbons is the same as that of Example 1, except that the system of Figure 1 is used for the cracking reaction, wherein the first cracking reactor and the second cracking reactor in the cracking reaction unit 4 are separately provided with gas-solid separation equipment and regeneration equipment, so that the source of the catalyst for the first cracking reaction is all regenerated catalyst, and the ratio of the weight of the fresh agent to the total weight of the catalyst in the cracking reaction unit 4 is 0.02:1; the cracking reaction conditions and product properties are shown in Table 3.

[0108] Example 5

[0109] The process for treating catalytic diesel and increasing production of light aromatic hydrocarbons is the same as that of Example 1, except that the first regeneration inclined pipe 20 is closed, so that the source of the catalyst for the first cracking reaction is all spent catalyst generated by the second cracking reaction, and the ratio of the weight of the fresh agent to the total weight of the catalyst in the cracking reaction unit 4 is 0.02:1. The cracking reaction conditions and product properties are shown in Table 3.

[0110] Example 6

[0111] The process for treating catalytic diesel and increasing production of light aromatic hydrocarbons is the same as that of Example 1, except that the cracking catalyst C1 is replaced by an equal weight of cracking catalyst C2, and the ratio of the weight of the fresh agent to the total weight of the catalyst in the cracking reaction unit 4 is 0.02:1. The cracking reaction conditions and product properties are shown in Table 3.

[0112] Example 7

[0113] The process for treating catalytic diesel and increasing production of light aromatic hydrocarbons is the same as that of Example 1, except that the bed density of the second cracking reactor is 250 kg / m 3 . The cracking reaction conditions and product properties are shown in Table 3.

[0114] Example 8

[0115] The process for treating catalytic diesel and increasing production of light aromatic hydrocarbons is the same as that of Example 1, except that the first cracking reactor is a cracking reactor for heavy oil feedstock, and the hydrogenated catalytic diesel is contacted with the catalyst before the heavy oil. The cracking reaction conditions and product properties are shown in Table 3.

[0116] Example 9

[0117] The process for treating catalytic diesel and increasing production of light aromatic hydrocarbons is the same as that of Example 1, except that the reaction conditions for the first cracking reaction are different. The reaction conditions and product properties are shown in Table 4.

[0118] Example 10

[0119] The method for processing catalytic diesel and increasing the production of light aromatics is the same as in Example 1, except that the weight ratio of the fresh catalyst to the total weight of the catalyst in cracking reaction unit 4 is 0.02:1. Reaction conditions and product properties are shown in Table 4.

[0120] Example 11

[0121] The method for processing catalytic diesel and increasing the production of light aromatics is the same as in Example 1, except that no freshener is added during the second cracking reaction in the second cracking reactor 15. Reaction conditions and product properties are shown in Table 4.

[0122] Comparative Example 1

[0123] use Figure 1 The system for processing catalytic diesel to increase the production of light aromatics is the same as in Example 1, except that it employs... Figure 4 The cracking reaction is carried out in cracking unit 4, which replaces the reactor consisting of a dense-phase fluidized bed reactor and a riser reactor connected in series with a riser reactor 25. The conditions for the cracking reaction and the properties of the products are shown in Table 4.

[0124] Comparative Example 2

[0125] The method for increasing the production of light aromatics from catalytic diesel is the same as in Example 5, except that the C1 cracking catalyst is replaced with an equal weight of CDOS cracking catalyst. The cracking reaction conditions and product properties are shown in Table 4.

[0126] Comparative Example 3

[0127] The method for increasing the production of light aromatics from catalytic diesel is the same as in Example 1, except that the heavy gasoline components are directly discharged. The conditions for the cracking reaction and the properties of the products are shown in Table 4.

[0128] Table 3 shows the conditions of the cracking reaction and the properties of the products in the examples.

[0129]

[0130]

[0131] Table 4. Conditions and product properties of the cracking reaction in the comparative examples.

[0132]

[0133]

[0134] From the table, according to the comparison of the data of Examples 1-11 and Comparative Examples 1-3, it can be seen that the technical scheme of the present disclosure can avoid the problems of high hydrogen consumption, harsh operating conditions and loss of aromatic hydrocarbons caused by using hydrogenation treatment to produce light aromatic hydrocarbons. According to the comparison of the data in Examples 1, 2 and 3, it can be seen that the second cracking reaction in the present application is a non-hydrogen catalytic cracking of heavy gasoline components at a temperature of 580-660℃ and a catalyst to oil ratio of (15-25):1, which can obtain a higher yield of BTX; according to the comparison of the data in Examples 1, 6 and Comparative Example 2, it can be seen that when the catalyst activity of the catalyst in the second cracking reactor is 50-99, a higher yield of BTX can be obtained; according to the comparison of the data in Examples 1, 7 and Comparative Example 1, it can be seen that when the bed density of the second cracking reactor is 180-700kg / m 3 , a higher yield of BTX can be obtained, and when the bed density of the dense phase fluidized bed reactor is 300-500kg / m 3 , the yield of BTX can be further improved; according to the comparison of the data in Examples 1, 10 and 11, it can be seen that adding fresh agent in the second cracking reactor can obtain a higher yield of BTX; according to the comparison of the data in Examples 1 and Comparative Example 3, it can be seen that making the heavy fraction first react in the second cracking reactor and then entering the first cracking reactor for further reaction can obtain a higher yield of BTX.

[0135] The preferred embodiments of the present disclosure are described in detail above in combination with the drawings, but the present disclosure is not limited to the specific details in the above-described embodiments, and various simple modifications can be made to the technical scheme of the present disclosure within the scope of the technical concept of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

[0136] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction, and in order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0137] In addition, various different embodiments of the present disclosure can also be combined in any manner, as long as they do not deviate from the idea of the present disclosure, and they should also be considered as disclosed by the present disclosure.

Claims

1. A process for treating catalytic diesel and increasing the production of light aromatics, characterized by, The method comprises: feeding the catalytic diesel into a hydrogenation reaction unit for hydrogenation treatment to obtain hydrogenation catalytic diesel, and feeding the hydrogenation catalytic diesel into a first cracking reactor of a cracking reaction unit for non-hydrogen first cracking reaction, and after gas-solid separation, obtaining a cracking reaction product; subjecting the cracking reaction product to product separation treatment to obtain other products, light gasoline components, heavy gasoline components and diesel components; returning the diesel components to the hydrogenation reaction unit; feeding the heavy gasoline components into a second cracking reactor of the cracking reaction unit for non-hydrogen second cracking reaction, and feeding the obtained oil agent mixture into the first cracking reactor; subjecting the light gasoline components to aromatic hydrocarbon separation treatment to obtain benzene products, toluene products and xylene products; the second cracking reactor is a dense phase fluidized bed reactor; the micro-reaction activity index of the catalyst in the second cracking reactor is 50-99; the reaction conditions of the non-hydrogen first cracking reaction include: the reaction temperature is 520-680℃, the reaction time is 1-15s, and the catalyst / oil ratio is (1-100):1; the reaction conditions of the non-hydrogen second cracking reaction include: the reaction temperature is 580-660℃; and the catalyst / oil ratio is (10-30):1; The bed density of the dense fluidized bed reactor is 300-500 kg / m 3 , and the bed linear velocity is 0.4-2 m / s.

2. The method of claim 1, wherein, the initial boiling point of the light gasoline components is 20-50℃; the distillation cut point of the light gasoline components and the heavy gasoline components is 120-150℃; and the distillation cut point of the diesel components and the heavy gasoline components is 200-250℃.

3. The method of claim 1, wherein, The initial boiling point of the hydrogenation catalytic diesel is 150-250℃, and the final boiling point is 300-380℃.

4. The method of claim 1, wherein, The reaction conditions of the non-hydrogen first cracking reaction include: the reaction temperature is 560-600℃, the reaction time is 1-8s, and the catalyst / oil ratio is (1-30):1; The micro-reaction activity index of the catalyst of the non-hydrogen second cracking reaction is 60-90.

5. The method of claim 1, wherein, The catalysts of the non-hydrogen first cracking reaction and the non-hydrogen second cracking reaction are the same or different, and each independently comprises a zeolite, an inorganic oxide and a clay; The content of the zeolite is 5-70% by weight, the content of the inorganic oxide is 1-95% by weight, and the content of the clay is 1-50% by weight, based on the total weight of the catalyst; the sum of the contents of the components in the catalyst of the non-hydrogen first cracking reaction is 100% by weight, and the sum of the contents of the components in the catalyst of the non-hydrogen second cracking reaction is 100% by weight.

6. The method of claim 5, wherein, The zeolite comprises a large-pore zeolite and optionally a medium-pore zeolite; The content of the large-pore zeolite is 60-100% by weight, and the content of the medium-pore zeolite is 0-40% by weight, based on the total weight of the zeolite; and the sum of the contents of the components in the zeolite is 100% by weight.

7. The method of claim 6, wherein, The medium-pore zeolite is selected from ZSM zeolite; and the large-pore zeolite is selected from β zeolite and / or Y zeolite; The inorganic oxide comprises silicon dioxide and / or aluminum sesquioxide; The clay is kaolin.

8. The method of claim 7, wherein, The clay is hydrous kaolin.

9. The method of claim 7, wherein, The catalyst contains rare earth elements.

10. The method of claim 9, wherein, The large-pore zeolite is Y zeolite modified by rare earth elements.

11. The method of claim 1, wherein, The method further comprises regenerating the spent catalyst from the first cracking reaction without hydrogen, and returning the regenerated catalyst to the cracking reaction unit.

12. The method of claim 1, wherein, The method further comprises adding fresh agent in the second cracking reactor.

13. The method of claim 12, wherein, The ratio of the weight of the fresh agent to the total weight of the catalyst in the cracking reaction unit is 0.2 or less.

14. The method of claim 11, wherein, The cracking reaction unit further comprises a regenerator; The method further comprises regenerating the spent catalyst in the regenerator to obtain regenerated catalyst, and returning the regenerated catalyst to the first cracking reactor through a first regenerated inclined pipe and to the second cracking reactor through a second regenerated inclined pipe, respectively. Optionally, the second regenerated inclined pipe is provided with a fresh agent inlet.

15. The method of claim 1, wherein, The dense phase fluidized bed reactor is an upflow reactor or a downflow reactor.

16. The method of claim 1, wherein, The first cracking reactor and the second cracking reactor are arranged in series and the first cracking reactor is arranged downstream of the second cracking reactor.

17. The method of claim 16, wherein, The first cracking reactor and the second cracking reactor are arranged coaxially.

18. The method of claim 1, wherein, The conditions of the hydroprocessing include: reaction temperature 330-450℃, hydrogen partial pressure 6-25MPa, volume space velocity 0.1-2h -1 , hydrogen to oil volume ratio 1000-2000Nm 3 / m 3 .

19. The method of claim 1, wherein, The first cracking reactor is a dilute phase transport bed reactor and / or a dense phase fluidized bed reactor.

20. The method of claim 1, wherein, The first cracking reactor is a cracking reactor for heavy oil feedstock. Optionally, the hydrogenated catalytic diesel is contacted with the catalyst in the first cracking reactor prior to the heavy oil feedstock.

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