CN117942874A

CN117942874A - Catalytic conversion method and system for producing low-carbon olefin and reducing aromatic hydrocarbon content of gasoline

Info

Publication number: CN117942874A
Application number: CN202211352509.3A
Authority: CN
Inventors: 朱根权; 马文明; 杨超
Original assignee: Sinopec Petrochemical Research Institute Co ltd; China Petroleum and Chemical Corp
Current assignee: Sinopec Petrochemical Research Institute Co ltd; China Petroleum and Chemical Corp
Priority date: 2022-10-31
Filing date: 2022-10-31
Publication date: 2024-04-30

Abstract

The invention provides a catalytic conversion method for producing low-carbon olefin and reducing the aromatic hydrocarbon content of gasoline, which comprises the following steps: introducing heavy raw oil and a first strand of catalyst into a first riser reactor from the bottom to perform a first catalytic conversion reaction to obtain a first oil mixture; introducing the first oil mixture into a catalyst separator to separate part of solids in the first oil mixture, so as to obtain a first stream of spent catalyst and a first gas-solid mixture; introducing the light raw oil and a second catalyst into a second riser reactor from the middle part to perform a second catalytic conversion reaction to obtain a second oil mixture; the first riser reactor and the second riser reactor are arranged in parallel. The invention also provides a catalytic conversion system. The invention can further improve the yield of the low-carbon olefin produced by catalytic conversion and further reduce the aromatic hydrocarbon content of the gasoline.

Description

Catalytic conversion method and system for producing low-carbon olefin and reducing aromatic hydrocarbon content of gasoline

Technical Field

The invention relates to the field of petrochemical industry, in particular to a catalytic conversion method and a catalytic conversion system for producing low-carbon olefin and reducing the aromatic hydrocarbon content of gasoline.

Background

Catalytic cracking is one of the main methods for secondary processing of petroleum, and it makes heavy oil undergo the process of cracking reaction under the action of high temperature and catalyst, and can be converted into cracked gas, gasoline and diesel oil, etc.. Catalytic cracking involves the main reactions of decomposition, isomerization, hydrogen transfer, aromatization, condensation, coking, and the like. Compared with thermal cracking, the catalytic cracking light oil has high yield, high gasoline octane number, better diesel stability and byproducts of liquefied gas rich in olefin.

For example, CN112745901a discloses a catalytic conversion process for producing lower olefins comprising: contacting a first hydrocarbon feedstock with a cracking catalyst in a first riser reactor to produce a first oil mixture; contacting the second hydrocarbon feedstock with a cracking catalyst in a second riser reactor to produce a second oil mixture; and mixing the first oil mixture and the second oil mixture, then entering a third reactor for reaction, and converting the cracking catalyst into a spent catalyst after reaction and entering a stripper, wherein part of the spent catalyst is introduced into the second riser reactor.

However, there is a need to further increase the yield of low olefins produced by catalytic conversion and to further reduce the aromatics content of gasoline.

Disclosure of Invention

The invention aims to further improve the yield of low-carbon olefin produced by catalytic conversion and further reduce the aromatic hydrocarbon content of gasoline.

In order to achieve the above object, the present invention provides a catalytic conversion method for producing light olefins and reducing the aromatic hydrocarbon content of gasoline, comprising the steps of: s1, introducing heavy raw oil and a first stream of catalyst into a first riser reactor from the bottom to perform a first catalytic conversion reaction to obtain a first oiling agent mixture; introducing the light raw oil and a second catalyst into a second riser reactor from the middle part to perform a second catalytic conversion reaction to obtain a second oil mixture; the first riser reactor and the second riser reactor are arranged in parallel; s2, introducing the first oil solution mixture into a catalyst separator to separate part of solids in the first oil solution mixture, so as to obtain a first stream of spent catalyst and a first gas-solid mixture, wherein the weight ratio of the first stream of spent catalyst to the catalyst in the first oil solution mixture is not less than 50%, preferably not less than 80%; s3, introducing the second oil agent mixture and the first gas-solid mixture into a fluidized bed reactor, performing a third catalytic conversion reaction to obtain a third oil agent mixture, and performing gas-solid separation on the third oil agent mixture to obtain a second stream of spent catalyst and a gas-oil product; and S4, stripping and regenerating the first strand of spent catalyst and the second strand of spent catalyst to obtain regenerated catalyst, and leading the first strand of regenerated catalyst and the second strand of regenerated catalyst out of the regenerated catalyst to return to the operation of the step S1.

The invention also provides a catalytic conversion system for producing low-carbon olefin and reducing the aromatic hydrocarbon content of gasoline, which comprises a first riser reactor, a catalyst separator, a second riser reactor, a fluidized bed reactor, a settler and a regenerator; the first riser reactor and the second riser reactor are arranged in parallel; the upper end of the first riser reaction zone is communicated with a material inlet of the catalyst separator; the catalyst separator has a solid material outlet and a gas-solid mixture outlet; the lower end of the fluidized bed reactor is communicated with the gas-solid mixture outlet and the upper end of the second riser reactor; the upper end of the fluidized bed reactor is communicated with the lower end of the settler; a gas-solid separator and a stripper are arranged in the settler; the stripper is in spent catalyst transfer connection with the regenerator; the regenerator is provided with a first regenerated catalyst outlet and a second regenerated catalyst outlet; a first regenerated catalyst delivery connection is provided between the first regenerated catalyst outlet and the first riser reactor; and a second regenerated catalyst conveying connection is arranged between the second regenerated catalyst outlet and the second riser reaction zone.

By the technical scheme, the catalyst density in the fluidized bed reactor is reduced by separating part of the catalyst in the first oil mixture; the regenerated catalyst of the second riser is contacted and reacted with the medium raw material to generate partial coke which is covered on the strong acid center of the regenerated catalyst; therefore, the invention suppresses the hydrogen transfer reaction and the aromatization reaction on one hand and promotes the cracking reaction on the other hand, thereby further improving the yield of the low-carbon olefin produced by catalytic conversion and further reducing the aromatic hydrocarbon content of the gasoline.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate the invention and together with the description serve to explain, without limitation, the invention. In the drawings:

Fig. 1 is a schematic structural view of a catalytic conversion system according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of one embodiment of a catalyst separator of the present invention.

FIG. 3 is a schematic diagram of one embodiment of a catalyst separator of the present invention.

Description of the reference numerals

In fig. 1, reference numerals are explained as follows:

1-first riser reactor

11-Heavy raw oil 12-first pre-lifting gas 13-cycle oil

14-Catalyst separator 15-distributor

2-Second riser reactor

21-Medium feedstock 22-second pre-lift gas 23-light feedstock

24-Distributor

3-Fluidized bed reactor

4-Settler

41. 42-Cyclone separator 43-plenum 44-reaction oil and gas

5-Stripper

51-Spent catalyst transfer tube 52-stripping gas 53-stripping baffle

6-Regenerator

61-Main wind

62-Second regenerated catalyst conveying pipe

63-First regenerated catalyst delivery pipe

64. 65-Cyclone separator 66-plenum 67-regenerated flue gas

Detailed Description

The following describes specific embodiments of the present invention in detail. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.

Referring to fig. 1, the present invention provides a catalytic conversion method for producing light olefins and reducing the aromatic hydrocarbon content of gasoline, the catalytic conversion method comprising the steps of: s1, introducing heavy raw oil and a first stream of catalyst into a first riser reactor from the bottom to perform a first catalytic conversion reaction to obtain a first oiling agent mixture; introducing the light raw oil and a second catalyst into a second riser reactor from the middle part to perform a second catalytic conversion reaction to obtain a second oil mixture; the first riser reactor and the second riser reactor are arranged in parallel; s2, introducing the first oil solution mixture into a catalyst separator to separate part of solids in the first oil solution mixture, so as to obtain a first stream of spent catalyst and a first gas-solid mixture, wherein the weight ratio of the first stream of spent catalyst to the catalyst in the first oil solution mixture is not less than 50%, preferably not less than 80%; s3, introducing the second oil agent mixture and the first gas-solid mixture into a fluidized bed reactor, performing a third catalytic conversion reaction to obtain a third oil agent mixture, and performing gas-solid separation on the third oil agent mixture to obtain a second stream of spent catalyst and a gas-oil product; and S4, stripping and regenerating the first strand of spent catalyst and the second strand of spent catalyst to obtain regenerated catalyst, and leading the first strand of regenerated catalyst and the second strand of regenerated catalyst out of the regenerated catalyst to return to the operation of the step S1.

In the invention, the material (comprising a first strand of catalyst, reaction oil gas and a fluidization medium) which is subjected to the first catalytic conversion in the first riser reactor is separated into a part of catalyst, and then the material which is subjected to the second catalytic conversion with the second riser reactor is subjected to the third catalytic conversion in the fluidized bed reactor, namely the first catalytic conversion, the relay of the second catalytic conversion and the third catalytic conversion can be realized.

Wherein, optionally, the weight ratio of the heavy raw oil to the light raw oil is 1:0.01 to 0.3, preferably 1:0.05 to 0.15.

Wherein, optionally, the catalytic conversion method further comprises: and introducing medium raw oil into the second riser reactor from the bottom to participate in the second catalytic conversion reaction.

Wherein optionally the height of the feed inlet for introducing the light feed oil is 30-70%, preferably 40-60% of the total height of the second riser reactor.

Wherein, optionally, the weight ratio of the heavy raw oil to the medium raw oil is 1:0.05 to 0.5, preferably 1:0.1 to 0.2.

Wherein, optionally, the first and second catalysts comprise unmodified ZSM-5 molecular sieve or modified ZSM-5 molecular sieve, clay and binder, the content of unmodified ZSM-5 molecular sieve or modified ZSM-5 molecular sieve is 10 to 60wt%, preferably 30 to 50wt%, the content of clay is 10 to 70wt%, preferably 15 to 45 wt%, and the content of binder is 10 to 40 wt%, preferably 20 to 35 wt%, based on the total weight of the catalyst. The unmodified Y-type molecular sieve or modified Y-type molecular sieve may be selected from one or more of HY, USY, REUSY, REY, REHY, DASY, REDASY or Y-type molecular sieves obtained by treatment with various metal oxides. The clay is selected from various clays which can be used as catalyst components, such as kaolin, montmorillonite, bentonite, etc. The binder is selected from one or two or three of silica sol, alumina sol and pseudo-boehmite, wherein the preferred binder is a double-aluminum binder of alumina sol and pseudo-boehmite.

Wherein, optionally, the reaction temperature of the first riser reactor is 520-620 ℃, preferably 540-600 ℃; the ratio of the agent to the oil is 2-25, preferably 3-20; the reaction time is 1 to 15 seconds, preferably 2 to 10 seconds.

Wherein, the reaction temperature of the second riser reaction zone is 560-660 ℃, preferably 580-640 ℃, the catalyst-to-oil ratio is 3-40, preferably 5-30, and the reaction time is 0.5-10 seconds, preferably 1-5 seconds.

Wherein, alternatively, the reaction temperature of the fluidized bed reactor is 560-660 ℃, preferably 580-640 ℃, the catalyst density is 20-300 kg/m ³, preferably 100-200 kg/m ³, and the space velocity is 2-15 h ^-1, preferably 5-10 h ^-1. The residence time of the oil gas is 0.2 to 8 seconds, preferably 1 to 4 seconds.

Wherein, optionally, the heavy raw oil is selected from one or more than one of vacuum wax oil, atmospheric residuum, vacuum residuum, coking wax oil, deasphalted oil, furfural refined raffinate oil, coal liquefied oil, oil sand oil, shale oil, fischer-Tropsch synthesis distillate oil or biological grease.

Wherein, optionally, the medium raw oil is selected from one or more of kerosene, diesel oil, light cycle oil, heavy cycle oil and slurry oil, preferably one or more of the heavy cycle oil and slurry oil.

Wherein, optionally, the initial distillation point of the heavy raw oil is any temperature between 280 ℃ and 380 ℃.

Wherein, optionally, the initial distillation point of the medium raw oil is any temperature between 150 ℃ and 220 ℃ and the final distillation point is any temperature between 260 ℃ and 350 ℃.

Wherein, optionally, the light feedstock contains C4-C8 hydrocarbons.

Wherein, optionally, the initial distillation point of the light raw oil is any temperature between 10 and 40 ℃ and the final distillation point is any temperature between 50 and 100 ℃.

Wherein, the regeneration temperature is 670-730 ℃, preferably 690-710 ℃, the catalyst distribution density is 30-350 kg/m ³, preferably 80-250 kg/m ³, and the main air residence time is 0.5-15 s, preferably 2-10 s.

Optionally, the catalytic conversion method further includes separating distillate oil from the oil gas product in step S3, and returning the distillate oil to step S1 as recycle oil after hydrogenation or no hydrogenation, and specifically may return to the first riser reactor from the middle part.

Wherein optionally the process further comprises introducing a pre-lift gas to the bottoms of the first riser reactor and the second riser reactor, said pre-lift gas may be selected from one or more of steam, nitrogen, dry gas, preferably steam.

Wherein, optionally, the catalyst separator is one or more of a rotational flow type rapid separator, a three-blade type rapid separator, an ejection type rapid separator, a U-shaped pipe type separator, a wall-attached cutting type rapid separator and the like, and is preferably a rotational flow type rapid separator.

In one embodiment, referring to fig. 2, in the catalyst separator, the material inlet is located at the side of the catalyst separator, the spent catalyst outlet is located at the bottom of the catalyst separator, and the gas-solid mixture outlet is located at the upper portion of the catalyst separator.

In one embodiment, referring to fig. 3, in the catalyst separator, the material inlet is located at the bottom of the catalyst separator, the spent catalyst is located at the side of the catalyst separator, and the gas-solid mixture outlet is located at the upper portion of the catalyst separator.

According to a particularly preferred embodiment of the present invention, in the present invention, after the heavy raw oil 11 is preheated to 180 to 340 ℃, it is sprayed into the first riser reactor 1 through a nozzle at a reaction temperature of 520 to 620 ℃, preferably 540 to 600 ℃; the ratio of the agent to the oil is 2-25, preferably 3-20; the first catalytic conversion reaction is carried out with the first stream of regenerated catalyst entering the bottom of the first riser reactor 1 through the first regenerated catalyst line 63 for a reaction time of 1 to 15 seconds, preferably 2 to 10 seconds. The first oil mixture obtained after the reaction is separated by the catalyst separation device 14 at the top of the first riser reactor 1, so that not less than 50% of the spent catalyst in the first oil mixture is introduced into the stripper 5 after being separated as a first spent catalyst, and preferably not less than 80% of the spent catalyst is introduced into the stripper 5 after being separated as a first spent catalyst. The first gas-solid mixture is introduced into the fluidized-bed reactor 3 via a distributor 15. The medium feed oil 21 is preheated to 180-300 ℃ and then sprayed into the second riser reactor 2 through a nozzle, and then undergoes a second catalytic conversion reaction with the regenerated catalyst entering the bottom of the second riser reactor 2 through a second regenerated catalyst pipeline 62 (more preferably, the light feed oil 21 is preheated to 100-150 ℃ and then sprayed into the second riser reactor 2 through a nozzle arranged in the middle of the second riser reactor 2). The reaction temperature is 560-660 ℃, preferably 580-640 ℃, the catalyst-oil ratio is 3-40, preferably 5-30, and the reaction time is 0.5-10 seconds, preferably 1-5 seconds. The reacted second oil mixture is introduced into the fluidized bed reactor 3 through a distributor 24, and is contacted with the first gas-solid mixture from the distributor 15 under the conditions that the reaction temperature is 560-660 ℃, preferably 580-640 ℃, the catalyst density is 20-300 kg/m ³, preferably 100-200 kg/m ³, the airspeed is 2-15 h ^-1, preferably 5-10 h ^-1, the oil gas residence time is 0.2-8 seconds, preferably 1-4 seconds to carry out a third catalytic conversion reaction, the gas-solid separation is carried out on the third oil mixture obtained after the reaction in a settler 4 to obtain a reaction oil gas 44 extraction device, the second stream of spent catalyst is introduced into a stripper 5, and the stripped spent catalyst (comprising the first stream of spent catalyst and the second stream of spent catalyst) is introduced into a regenerator 6 through a spent catalyst conveying pipe 51 to be regenerated for recycling. The reaction oil and gas 44 enters a subsequent product separation system. In the product separation system, the catalytic cracking products are separated into dry gas, cracked gas, gasoline, light oil, slurry oil and other products. The cracked gas can be separated and refined to obtain the mixture of the polymerization grade propylene product and the C4-C8 hydrocarbon. The light oil and the slurry oil are partially introduced into the bottom of the second riser reactor 2, and the mixture of C4-C8 hydrocarbons is partially or completely returned to the second riser reactor 2 for reaction. The spent agent separated by the cyclone separators 41-42 enters the stripper 5 for stripping. The stripping steam in the stripper 5 can directly enter the settler 5, and is separated together with other oil gas by cyclone separators 41-42, and then is led out of the reactor by a reaction oil gas lead-in separation system pipeline 44. The catalyst stripped in the stripper enters the regenerator 6 for coke burning regeneration, and regeneration flue gas is led out from the top space of the regenerator 6 through a regeneration flue gas outlet 66. The regenerated catalyst is returned to the pre-riser sections of the first riser reactor 1 and the second riser reactor 2 for recycling via the first regenerated catalyst line 63 and the second regenerated catalyst line 62, respectively. In the course of the above embodiments, lift gas is introduced into the first riser reactor 1 and the second riser reactor 2 through the first pre-lift gas line 12 and the second pre-lift gas line 22, respectively.

The catalyst used in examples 1-2 and comparative examples 1-2 was RAG-6, and RAG-6 was a catalyst containing 35 wt% ZSM-5 molecular sieve, the composition and properties are shown in Table 1; the light raw oil used is light gasoline fraction, medium fraction oil is pyrolysis light oil, and heavy fraction oil is wax oil, and the specific properties are shown in tables 2, 3 and 4.

TABLE 1 composition and Properties of the catalysts

Catalyst	RAG-6
		Chemical composition,% (w)
Al₂O₃	51.2
		SiO₂	43.1
BET total analysis
		BET total area/(m ²·g^-1)	197.000
Micropore area/(m ²·g^-1)	98.000
		Total pore volume/(cm ³·g^-1)	0.1500
Micropore volume/(cm ³·g^-1)	0.0450
		Particle size distribution,% (w)
0-20μm	0.5
		0-40μm	32.6
0-80μm	87.3
		0-105μm	98.5
＞105μm	1.5

TABLE 2 composition and Properties of light gasoline

Project	Light gasoline
		Density (20 ℃ C.)/(kg/m ³)	635.1
Elemental mass composition/%
		Carbon (C)	84.76
Hydrogen gas	15.24
		Sulfur/(μg/g)	46.29
Nitrogen/(μg/g)	32
		Distillation range/. Degree.C
Initial point of distillation	12
		10v％	18
30v％	30
		50v％	35
70v％	57
		90v％	59
End point of distillation	60
		Mass group composition/%
Alkanes	37.19
		Olefins	62.49
Cycloalkane (CNS)	0.32
		Aromatic hydrocarbons	0

TABLE 3 composition and Properties of pyrolysis light oil

Project	Cracking light oil
		Density (20 ℃ C.)/(kg/m ³)	922.9
Viscosity (20 ℃ C.)/(mm ²/s)	2.671
		Refractive index at 20 DEG C	1.5345
Closed flash point/°c	76
		Carbon residue mass fraction/%	0.13
Elemental mass composition/%
		C	90.13
H	9.87
		S/(μg/g)	976
N/(μg/g)	444
		Cetane number	43.7
Mass group composition/%
		Paraffin hydrocarbons	13.00
Total cycloalkane	9.90
		Total aromatic hydrocarbon	77.10
Colloid	0.00
		Distillation range/. Degree.C
Initial point of distillation	191
		10v％	212
30v％	226
		50v％	236
70v％	255
		90v％	274
End point of distillation	286

TABLE 4 composition and Properties of wax oil

Project	Wax oil
		Density (20 ℃ C.)/(kg/m ³)	856.5
Carbon residue mass fraction/%	0.12
		Elemental mass composition/%
C	86.12
		H	13.47
S	0.85
		N	0.41
Mass group composition/%
		Saturated hydrocarbons	66.55
Aromatic hydrocarbons	24.15
		Colloid	9.05
Asphaltenes	0.25
		Metal mass composition/(mg/kg)
Fe	1.9
		Ni	8.0
V	9.5
		Na	3.1
Ca	1.8
		Distillation range/. Degree.C
Initial point of distillation	284
		10％	342
30％	390
		50％	420
70％	449
		90％	497
End point of distillation	526

Examples 1 to 2

The test was performed on the test apparatus shown in fig. 1. The apparatus comprises two riser reactors and a fluidized bed reactor. The first riser reactor 1 had an inner diameter of 16mm and a length of 3800mm, the second riser reactor 2 had an inner diameter of 16mm and a height of 3400mm, and the fluidized bed reactor 3 had an inner diameter of 64mm and a height of 500mm.

Wax oil is introduced into the bottom of a first riser reactor 1 as heavy raw oil, contacts and reacts with regenerated catalyst from a regenerator 6, the reacted first oil mixture is separated by a catalyst separator, and the obtained first gas-solid mixture is introduced into a fluidized bed reactor 3; introducing light gasoline as light raw oil into the middle part of a second riser reactor 2, contacting and reacting with regenerated catalyst from a regenerator 6, and introducing a reacted second oil mixture into a fluidized bed reactor 3; the first gas-solid mixture from the first riser reactor 1 and the second oil mixture from the second riser reactor 2 are contacted and reacted in the fluidized bed reactor 3, the reacted oil mixture is separated by a cyclone separator, the catalyst enters a stripper 5 and then enters a regenerator 6 for regeneration, the regenerated catalyst returns to the riser reactor for recycling, and the oil gas is introduced into a fractionation system for separation. Wherein the mass ratio of the light gasoline to the wax oil is 0.05:1. The reaction conditions and results are shown in Table 5.

Example 2

The process according to example 1 is further followed, except that the fractionated cracked light oil is introduced into the second riser reactor 2 as a medium feedstock, the mass ratio of light gasoline, cracked light oil to wax oil being 0.05:0.1:1. The reaction conditions and results are shown in Table 5.

Comparative example 1

The procedure of example 1 was followed except that no catalyst separator was provided and that the entire first oil mixture was fed to the fluidized bed 3 to perform the third catalytic conversion reaction. The reaction conditions and results are shown in Table 5.

Comparative example 2

The procedure of example 2 was followed, except that no catalyst separator was provided, and the entire first oil mixture was fed into the fluidized bed 3 to perform the third catalytic conversion reaction. The reaction conditions and results are shown in Table 5.

As can be seen from Table 5, the method and system provided by the invention can realize higher hydrocarbon conversion capability, obtain higher low-carbon olefin yield, and reduce the aromatic hydrocarbon content of gasoline.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the scope of the technical concept of the present invention, and all the simple modifications belong to the protection scope of the present invention.

In addition, the specific features described in the above embodiments may be combined in any suitable manner without contradiction. The various possible combinations of the invention are not described in detail in order to avoid unnecessary repetition.

TABLE 5 reaction conditions and reaction results for examples 1-2 and comparative examples 1-2

Moreover, any combination of the various embodiments of the invention can be made without departing from the spirit of the invention, which should also be considered as disclosed herein.

Claims

1. A catalytic conversion process for producing light olefins and reducing the aromatic content of gasoline, comprising the steps of:

s1, introducing heavy raw oil and a first stream of catalyst into a first riser reactor from the bottom to perform a first catalytic conversion reaction to obtain a first oiling agent mixture; introducing the light raw oil and a second catalyst into a second riser reactor from the middle part to perform a second catalytic conversion reaction to obtain a second oil mixture; the first riser reactor and the second riser reactor are arranged in parallel;

S2, introducing the first oil mixture into a catalyst separator to separate part of solids in the first oil mixture, so as to obtain a first stream of spent catalyst and a first gas-solid mixture; the first stream of spent catalyst comprises not less than 50%, preferably not less than 80% by weight of the catalyst in the first oil mixture;

S3, introducing the second oil agent mixture and the first gas-solid mixture into a fluidized bed reactor, performing a third catalytic conversion reaction to obtain a third oil agent mixture, and performing gas-solid separation on the third oil agent mixture to obtain a second stream of spent catalyst and a gas-oil product;

And S4, stripping and regenerating the first strand of spent catalyst and the second strand of spent catalyst to obtain regenerated catalyst, and leading the first strand of regenerated catalyst and the second strand of regenerated catalyst out of the regenerated catalyst to return to the operation of the step S1.

2. The catalytic conversion process of claim 1, wherein the weight ratio of the heavy feedstock oil to the light feedstock oil is 1:0.01 to 0.3, preferably 1:0.05 to 0.15.

3. The catalytic conversion process according to claim 1 or 2, wherein the catalytic conversion process further comprises: and introducing medium raw oil into the second riser reactor from the bottom to participate in the second catalytic conversion reaction.

4. The catalytic conversion process according to claim 3, wherein the weight ratio of the heavy feedstock oil to the medium feedstock oil is 1:0.05 to 0.5, preferably 1:0.1 to 0.2.

5. The catalytic conversion process according to claim 3, wherein the first and second catalysts comprise unmodified ZSM-5 molecular sieve or modified ZSM-5 molecular sieve, clay, and binder,

The unmodified ZSM-5 molecular sieve or modified ZSM-5 molecular sieve is present in an amount of 10 to 60 wt%, preferably 30 to 50 wt%, the clay is present in an amount of 10 to 70 wt%, preferably 15 to 45 wt%, and the binder is present in an amount of 10 to 40 wt%, preferably 20 to 35 wt%, based on the total weight of the catalyst.

6. The catalytic conversion process according to claim 1, wherein the reaction temperature of the first riser reactor is 520-620 ℃, preferably 540-600 ℃; the ratio of the agent to the oil is 2-25, preferably 3-20; the reaction time is 1 to 15 seconds, preferably 2 to 10 seconds;

The reaction temperature of the second riser reaction zone is 560-660 ℃, preferably 580-640 ℃, the catalyst-to-oil ratio is 3-40, preferably 5-30, and the reaction time is 0.5-10 seconds, preferably 1-5 seconds;

The reaction temperature of the fluidized bed reactor is 560-660 ℃, preferably 580-640 ℃, the catalyst density is 20-300 kg/m ³, preferably 100-200 kg/m ³, the space velocity is 2-15 h ^-1, preferably 5-10 h ^-1. The residence time of the oil gas is 0.2 to 8 seconds, preferably 1 to 4 seconds.

7. The catalytic conversion process according to claim 1, wherein the heavy feedstock oil is selected from one or more of vacuum wax oil, atmospheric residuum, vacuum residuum, coker wax oil, deasphalted oil, furfural refining raffinate oil, coal liquefaction oil, oil sand oil, shale oil, fischer-tropsch distillate oil, or bio-oil;

The medium raw oil is selected from one or more of kerosene, diesel oil, light cycle oil, heavy cycle oil and slurry oil, preferably one or more of the heavy cycle oil and slurry oil;

the initial boiling point of the heavy raw oil is any temperature between 280 ℃ and 380 ℃;

the light raw oil contains C4-C8 hydrocarbon;

The initial distillation point of the light raw oil is any temperature between 10 and 40 ℃, and the final distillation point is any temperature between 50 and 100 ℃.

8. The catalytic conversion process according to claim 3, wherein the medium feedstock oil has an initial boiling point of any temperature between 150 and 220 ℃ and a final boiling point of any temperature between 260 and 350 ℃.

9. The catalytic conversion process according to claim 1, wherein the regeneration temperature is 670-730 ℃, preferably 690-710 ℃, the catalyst distribution density is 30-350 kg/m ³, preferably 80-250 kg/m ³, and the main wind residence time is 0.5-15 s, preferably 2-10 s.

10. A catalytic conversion system for producing low-carbon olefin and reducing the aromatic hydrocarbon content of gasoline, which is characterized by comprising a first riser reactor, a catalyst separator, a second riser reactor, a fluidized bed reactor, a settler and a regenerator; the first riser reactor and the second riser reactor are arranged in parallel;

The upper end of the first riser reaction zone is communicated with a material inlet of the catalyst separator; the catalyst separator has a solid material outlet and a gas-solid mixture outlet;

The lower end of the fluidized bed reactor is communicated with the gas-solid mixture outlet and the upper end of the second riser reactor;

the upper end of the fluidized bed reactor is communicated with the lower end of the settler; a gas-solid separator and a stripper are arranged in the settler;

the stripper is in spent catalyst transfer connection with the regenerator;

The regenerator is provided with a first regenerated catalyst outlet and a second regenerated catalyst outlet; a first regenerated catalyst delivery connection is provided between the first regenerated catalyst outlet and the first riser reactor; and a second regenerated catalyst conveying connection is arranged between the second regenerated catalyst outlet and the second riser reaction zone.