A catalytic conversion process and system for producing lower carbon olefins and reducing the aromatic content of gasoline

Abstract

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

Description

Technical Field

[0001] This invention relates to the field of petrochemicals, specifically to a catalytic conversion method and system for producing low-carbon olefins and reducing the aromatic content of gasoline. Background Technology

[0002] Catalytic cracking is one of the main methods of secondary petroleum processing. Under high temperature and with the aid of a catalyst, heavy oil undergoes a cracking reaction, transforming it into cracked gas, gasoline, and diesel. The main reactions involved in catalytic cracking include decomposition, isomerization, hydrogen transfer, aromatization, condensation, and coking. Compared to thermal cracking, catalytic cracking yields higher light oils, produces gasoline with higher octane numbers, and offers better stability in diesel, while also producing liquefied petroleum gas (LPG) rich in olefins as a byproduct.

[0003] For example, CN112745901A discloses a catalytic conversion method for producing low-carbon olefins, comprising: contacting a first hydrocarbon feedstock with a cracking catalyst in a first riser reactor to obtain a first oil-catalyst mixture; contacting a second hydrocarbon feedstock with a cracking catalyst in a second riser reactor to obtain a second oil-catalyst mixture; and mixing the first oil-catalyst mixture and the second oil-catalyst mixture and then reacting them in a third reactor, wherein the cracking catalyst is converted into a spent catalyst after the reaction and enters a stripper, wherein a portion of the spent catalyst is introduced into the second riser reactor.

[0004] However, there is a need to further improve the yield of catalytic conversion to produce low-carbon olefins and further reduce the aromatic content of gasoline. Summary of the Invention

[0005] The purpose of this invention is to further improve the yield of low-carbon olefins produced by catalytic conversion and to further reduce the aromatic content of gasoline.

[0006] To achieve the above objectives, the present invention provides a catalytic conversion method for producing low-carbon olefins and reducing the aromatic content of gasoline. This catalytic conversion method includes the following steps: S1, introducing heavy feedstock oil and a first catalyst stream from the bottom into a first riser reactor to carry out a first catalytic conversion reaction, obtaining a first oil-catalyst mixture; introducing light feedstock oil and a second catalyst stream from the middle into a second riser reactor to carry out a second catalytic conversion reaction, obtaining a second oil-catalyst mixture; the first riser reactor and the second riser reactor are arranged side-by-side; S2, introducing the first oil-catalyst mixture into a catalyst separator to separate some of the solids, obtaining a first catalyst stream to be produced. S1. The first gas-solid mixture and the second oil-agent mixture are introduced into a fluidized bed reactor to carry out a third catalytic conversion reaction to obtain a third oil-agent mixture. The third oil-agent mixture is then subjected to gas-solid separation to obtain a second gas-agent mixture and oil and gas products. S2. The first gas-agent mixture and the second gas-solid mixture are stripped and regenerated to obtain a regenerated catalyst. The first and second regenerated catalysts are then drawn from the regenerated catalyst and returned to the operation of step S1.

[0007] The present invention also provides a catalytic conversion system for producing low-carbon olefins and reducing the aromatic content of gasoline. The catalytic conversion system includes a first riser reactor, a catalyst separator, a second riser reactor, a fluidized bed reactor, a settling tank, and a regenerator. The first riser reactor and the second riser reactor are arranged in parallel. The upper end of the reaction zone of the first riser reactor is connected to the 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 connected to the gas-solid mixture outlet and the upper end of the second riser reactor. The upper end of the fluidized bed reactor is connected to the lower end of the settling tank. The settling tank contains a gas-solid separator and a stripper. The stripper is connected to the regenerator via a catalyst delivery connection. The regenerator has a first regenerated catalyst outlet and a second regenerated catalyst outlet. The first regenerated catalyst outlet is connected to the first riser reactor via a first regenerated catalyst delivery connection. The second regenerated catalyst outlet is connected to the reaction zone of the second riser reactor via a second regenerated catalyst delivery connection.

[0008] Through the above technical solution, the present invention reduces the catalyst density in the fluidized bed reactor by separating part of the catalyst in the first oil-agent mixture; and the regenerated catalyst in the second riser reacts with the medium-quality feedstock first, which can produce some coke, covering the strongly acidic centers of the regenerated catalyst; therefore, the present invention inhibits hydrogen transfer reaction and aromatization reaction on the one hand, and promotes cracking reaction on the other hand, thereby further improving the yield of catalytic conversion to produce low-carbon olefins and further reducing the aromatic content of gasoline.

[0009] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0010] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0011] Figure 1 This is a schematic diagram of the structure of a catalytic conversion system according to one embodiment of the present invention.

[0012] Figure 2 This is a schematic diagram of one embodiment of the catalyst separator in this invention.

[0013] Figure 3 This is a schematic diagram of one embodiment of the catalyst separator in this invention.

[0014] Explanation of reference numerals in the attached figures

[0015] Figure 1 The reference numerals in the attached figures are explained as follows:

[0016] 1-First riser reactor

[0017] 11-Heavy feedstock oil; 12-First pre-lifting gas; 13-Recycle oil

[0018] 14-Catalyst Separator 15-Distributor

[0019] 2-Second riser reactor

[0020] 21-Medium-quality feedstock; 22-Second pre-lifting gas; 23-Light-quality feedstock

[0021] 24-Distributor

[0022] 3-Fluidized bed reactor

[0023] 4-Settling Device

[0024] 41, 42 - Cyclone separator; 43 - Gas collection chamber; 44 - Reaction oil and gas

[0025] 5-Stripper

[0026] 51-Catalyst delivery pipe; 52-Stripping gas; 53-Stripping baffle.

[0027] 6-Regenerator

[0028] 61-Main Wind

[0029] 62-Second regenerated catalyst delivery pipe

[0030] 63-First regenerated catalyst delivery pipe

[0031] 64, 65 - Cyclone separator; 66 - Gas collection chamber; 67 - Regenerated flue gas Detailed Implementation

[0032] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0033] refer to Figure 1 This invention provides a catalytic conversion method for producing low-carbon olefins and reducing the aromatic content of gasoline. The catalytic conversion method includes the following steps: S1, introducing heavy feedstock oil and a first catalyst stream from the bottom into a first riser reactor to carry out a first catalytic conversion reaction, obtaining a first oil-catalyst mixture; introducing light feedstock oil and a second catalyst stream from the middle into a second riser reactor to carry out a second catalytic conversion reaction, obtaining a second oil-catalyst mixture; the first riser reactor and the second riser reactor are arranged side-by-side; S2, introducing the first oil-catalyst mixture into a catalyst separator to separate some of the solids, obtaining a first unprocessed catalyst and a first... S3. The first gas-solid mixture is introduced into a fluidized bed reactor to carry out a third catalytic conversion reaction to obtain a third oil mixture, and the third oil mixture is subjected to gas-solid separation to obtain a second gas-solid mixture and oil and gas products; S4. The first gas-solid mixture and the second gas-solid mixture are stripped and regenerated to obtain a regenerated catalyst, and the first and second regenerated catalysts are drawn from the regenerated catalyst and returned to the operation of step S1.

[0034] In this invention, after the first catalytic conversion of the material (including the first catalyst, reaction oil and gas, and fluidizing medium) in the first riser reactor is partially separated from the catalyst, the material that has undergone the second catalytic conversion reaction in the second riser reactor then undergoes the third catalytic conversion reaction in the fluidized bed reactor. In other words, the first catalytic conversion reaction, the second catalytic conversion reaction, and the third catalytic conversion reaction can be carried out in succession.

[0035] Optionally, 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.

[0036] Optionally, the catalytic conversion method further includes: introducing medium feedstock oil from the bottom into the second riser reactor to participate in the second catalytic conversion reaction.

[0037] Optionally, the height of the inlet for introducing the light feedstock oil accounts for 30-70% of the total height of the second riser reactor, preferably 40-60%.

[0038] Optionally, 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.

[0039] Optionally, the first and second catalyst streams comprise unmodified or modified ZSM-5 molecular sieves, clay, and a binder. Based on the total weight of the catalysts, the content of the unmodified or modified ZSM-5 molecular sieves is 10–60% by weight, preferably 30–50% by weight; the content of clay is 10–70% by weight, preferably 15–45% by weight; and the content of the binder is 10–40% by weight, preferably 20–35% by weight. The unmodified or modified Y-type molecular sieves are selected from one or more of HY, USY, REUSY, REY, REHY, DASY, and REDASY, or Y-type molecular sieves obtained through treatment with various metal oxides. The clay is selected from various clays that can be used as catalyst components, such as kaolin, montmorillonite, and bentonite. The binder is selected from one or a mixture of two or three of silica sol, alumina sol, and boehmite, wherein a preferred binder is a double-alumina binder of alumina sol and boehmite.

[0040] Optionally, the reaction temperature of the first riser reactor is 520–620°C, preferably 540–600°C; the agent-to-oil ratio is 2–25, preferably 3–20; and the reaction time is 1–15 seconds, preferably 2–10 seconds.

[0041] Optionally, the reaction temperature in the reaction zone of the second riser is 560–660°C, preferably 580–640°C, the agent-to-oil ratio is 3–40, preferably 5–30, and the reaction time is 0.5–10 seconds, preferably 1–5 seconds.

[0042] Optionally, the reaction temperature of the fluidized bed reactor is 560–660°C, preferably 580–640°C, and the catalyst density is 20–300 kg / m³. 3 Preferred weight: 100-200 kg / m 3 Airspeed is 2–15 h -1 Preferably 5-10 hours -1 The residence time of oil and gas is 0.2 to 8 seconds, preferably 1 to 4 seconds.

[0043] Optionally, the heavy feedstock oil is selected from one or more of the following: vacuum wax oil, atmospheric residue oil, vacuum residue oil, coking wax oil, deasphalted oil, furfural refined residue oil, coal liquefaction oil, oil sands oil, shale oil, Fischer-Tropsch synthetic distillate oil, or bio-oil.

[0044] Optionally, the medium-quality feedstock oil is selected from one or more of kerosene, diesel oil, light cycle oil, heavy cycle oil and slurry oil, preferably a mixture of one or more of heavy cycle oil and slurry oil.

[0045] Optionally, the initial boiling point of the heavy feedstock oil is any temperature between 280 and 380°C.

[0046] Optionally, the initial boiling point of the medium-quality feedstock oil is any temperature between 150 and 220°C, and the final boiling point is any temperature between 260 and 350°C.

[0047] Optionally, the light raw material contains C4 to C8 hydrocarbons.

[0048] Optionally, the initial boiling point of the light feedstock oil is any temperature between 10 and 40°C, and the final boiling point is any temperature between 50 and 100°C.

[0049] Optionally, the regeneration temperature is 670–730℃, preferably 690–710℃, and the catalyst distribution density is 30–350 kg / m³. 3 Preferred weight is 80-250 kg / m³. 3 The dwell time of the main wind is 0.5 to 15 seconds, preferably 2 to 10 seconds.

[0050] Optionally, the catalytic conversion method further includes separating distillate oil from the oil and gas products of step S3 and returning it to step S1 as recycled oil, either by hydrogenation or without hydrogenation. Specifically, it can be returned from the middle to the first riser reactor.

[0051] Optionally, the method further includes introducing a pre-lifting gas into the bottom of the first riser reactor and the second riser reactor. The pre-lifting gas may be selected from one or more of water vapor, nitrogen, and dry gas, with water vapor being preferred.

[0052] The present invention also provides a catalytic conversion system for producing low-carbon olefins and reducing the aromatic content of gasoline. The catalytic conversion system includes a first riser reactor, a catalyst separator, a second riser reactor, a fluidized bed reactor, a settling tank, and a regenerator. The first riser reactor and the second riser reactor are arranged in parallel. The upper end of the reaction zone of the first riser reactor is connected to the 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 connected to the gas-solid mixture outlet and the upper end of the second riser reactor. The upper end of the fluidized bed reactor is connected to the lower end of the settling tank. The settling tank contains a gas-solid separator and a stripper. The stripper is connected to the regenerator via a catalyst delivery connection. The regenerator has a first regenerated catalyst outlet and a second regenerated catalyst outlet. The first regenerated catalyst outlet is connected to the first riser reactor via a first regenerated catalyst delivery connection. The second regenerated catalyst outlet is connected to the reaction zone of the second riser reactor via a second regenerated catalyst delivery connection.

[0053] Optionally, the catalyst separator is one or more of the following combinations: a cyclone rapid separator, a three-lobe rapid separator, a catapult rapid separator, a U-shaped tube separator, and a wall-mounted cutting rapid separator, with a cyclone rapid separator being preferred.

[0054] In one implementation, reference Figure 2 In the catalyst separator, the material inlet is located on the side of the catalyst separator, the outlet for the spent catalyst is located at the bottom of the catalyst separator, and the gas-solid mixture outlet is located at the top of the catalyst separator.

[0055] In one implementation, reference Figure 3 In the catalyst separator, the material inlet is located at the bottom of the catalyst separator, the catalyst to be generated is located on the side of the catalyst separator, and the gas-solid mixture outlet is located at the top of the catalyst separator.

[0056] According to a particularly preferred embodiment of the present invention, in this invention, heavy feedstock oil 11 is preheated to 180–340°C and then sprayed into the first riser reactor 1 through a nozzle. Under conditions of a reaction temperature of 520–620°C, preferably 540–600°C; a catalyst-to-oil ratio of 2–25, preferably 3–20; and a reaction time of 1–15 seconds, preferably 2–10 seconds, it undergoes a first catalytic conversion reaction with a first stream of regenerated catalyst entering the bottom of the first riser reactor 1 through the first regenerated catalyst pipeline 63. The resulting first oil-catalyst mixture is separated by a catalyst separation device 14 at the top of the first riser reactor 1, such that at least 50% of the regenerated catalyst in the first oil-catalyst mixture is separated as the first stream of regenerated catalyst and introduced into the stripper 5, preferably at least 80% of the regenerated catalyst is separated as the first stream of regenerated catalyst and introduced into the stripper 5. The first gas-solid mixture is introduced into the fluidized bed reactor 3 via a distributor 15. After the medium-grade feedstock oil 21 is preheated to 180–300°C, it is sprayed into the second riser reactor 2 through a nozzle, where it undergoes a second catalytic conversion reaction with the regenerated catalyst that enters the bottom of the second riser reactor 2 through the second regenerated catalyst pipeline 62 (more preferably, the light feedstock oil 21 is preheated to 100–150°C and then sprayed into the second riser reactor 2 through a nozzle located in the middle of the second riser reactor 2). The reaction temperature is 560–660°C, preferably 580–640°C, 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 resulting second oil-catalyst mixture is introduced into the fluidized bed reactor 3 through the distributor 24, where it reacts with the first gas-solid mixture from the distributor 15 at a reaction temperature of 560–660°C, preferably 580–640°C, and a catalyst density of 20–300 kg / m³. 3 Preferred weight: 100-200 kg / m 3 Airspeed is 2–15 h -1 Preferably 5-10 hours -1The third catalytic conversion reaction is carried out under conditions where the oil and gas residence time is 0.2 to 8 seconds, preferably 1 to 4 seconds. The resulting third oil-fuel mixture undergoes gas-solid separation in settler 4, yielding reacted oil and gas 44. The second stream of recycled catalyst is introduced into stripper 5. The recycled catalyst after stripping (including the first and second streams) is introduced into regenerator 6 via recycled catalyst delivery pipe 51 for regeneration and recycling. Reacted oil and gas 44 enters the subsequent product separation system. In the product separation system, catalytic cracking products are separated into dry gas, cracked gas, gasoline, light oil, and slurry. After subsequent product separation and refining, the cracked gas yields polymer-grade propylene and a mixture of C4-C8 hydrocarbons. Light oil and slurry are partially introduced into the bottom of the second riser reactor 2, while the mixture of C4-C8 hydrocarbons is partially or completely returned to the second riser reactor 2 for further reaction. The recycled catalyst separated by cyclone separators 41-42 enters stripper 5 for stripping. The stripping steam in stripper 5 can directly enter settling tank 5, and after being separated from other oil and gas by cyclone separators 41-42, it is introduced into the separation system pipeline 44 and exited from the reactor. The catalyst stripped in the stripper enters regenerator 6 for coke burn regeneration, and the regenerated flue gas is exited from the top space of regenerator 6 through regenerated flue gas outlet 66. The regenerated catalyst is returned to the pre-lifting section of the first riser reactor 1 and the second riser reactor 2 via the first regenerated catalyst pipeline 63 and the second regenerated catalyst pipeline 62, respectively, for recycling. In the above specific embodiment, lifting gas is introduced into the first riser reactor 1 and the second riser reactor 2 through the first pre-lifting gas pipeline 12 and the second pre-lifting gas pipeline 22, respectively.

[0057] The catalyst used in Examples 1-2 and Comparative Examples 1-2 was RAG-6, which is a catalyst containing 35% by weight of ZSM-5 molecular sieve. Its composition and properties are shown in Table 1. The light feedstock used was light gasoline fraction, the middle feedstock was cracked light oil, and the heavy feedstock was wax oil. Its specific properties are shown in Tables 2, 3 and 4.

[0058] Table 1. Composition and properties of catalysts

[0059] catalyst RAG-6 Chemical composition, % (w) <![CDATA[Al2O3]]> 51.2 <![CDATA[SiO2]]> 43.1 BET Full Analysis <![CDATA[BET total surface area / (m 2 ·g -1 )]]> 197.000 <![CDATA[Micropore area / (m 2 ·g -1 )]]> 98.000 <![CDATA[Total pore volume / (cm 3 ·g -1 )]]> 0.1500 <![CDATA[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

[0060] Table 2 Composition and Properties of Light Gasoline

[0061] project Light gasoline <![CDATA[Density (20 °C) / (kg / m 3 )]]> 635.1 Elemental mass composition / % carbon 84.76 hydrogen 15.24 Sulfur / (μg / g) 46.29 Nitrogen (μg / g) 32 Distillation range / ℃ Initial boiling point 12 10v％ 18 30v％ 30 50v％ 35 70v％ 57 90v％ 59 Final boiling point 60 Mass family composition / % Alkanes 37.19 Olefins 62.49 Cycloalkanes 0.32 Aromatics 0

[0062] Table 3 Composition and properties of pyrolysis light oil

[0063] project Cracked light oil <![CDATA[Density (20 °C) / (kg / m 3 )]]> 922.9 <![CDATA[Viscosity (at 20 °C) / (mm 2 / s)]]> 2.671 Refractive index at 20℃ 1.5345 Closed-cup flash point / ℃ 76 Residual carbon 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 family composition / % Alkanes 13.00 Total cycloalkanes 9.90 Total aromatics 77.10 gelatinous 0.00 Distillation range / ℃ Initial boiling point 191 10v％ 212 30v％ 226 50v％ 236 70v％ 255 90v％ 274 Final boiling point 286

[0064] Table 4 Composition and Properties of Wax Oils

[0065] project Wax oil <![CDATA[Density (20 °C) / (kg / m 3 )]]> 856.5 Residual carbon mass fraction / % 0.12 Elemental mass composition / % C 86.12 H 13.47 S 0.85 N 0.41 Mass family composition / % Saturated hydrocarbons 66.55 Aromatics 24.15 gelatinous 9.05 Asphalt 0.25 Metal mass composition (mg / kg) Fe 1.9 Ni 8.0 V 9.5 Na 3.1 Ca 1.8 Distillation range / ℃ Initial boiling point 284 10％ 342 30％ 390 50％ 420 70％ 449 90％ 497 Final boiling point 526

[0066] Examples 1-2

[0067] The experiment was conducted in Figure 1 The experiment was conducted on the apparatus shown. The apparatus includes two riser reactors and one fluidized bed reactor. The first riser reactor 1 has an inner diameter of 16 mm and a length of 3800 mm, the second riser reactor 2 has an inner diameter of 16 mm and a height of 3400 mm, and the fluidized bed reactor 3 has an inner diameter of 64 mm and a height of 500 mm.

[0068] Wax oil, as a heavy feedstock, is introduced into the bottom of the first riser reactor 1, where it contacts and reacts with the regenerated catalyst from the regenerator 6. The resulting first oil-solid mixture is separated by a catalyst separator, and the resulting first gas-solid mixture is introduced into the fluidized bed reactor 3. Light gasoline, as a light feedstock, is introduced into the middle of the second riser reactor 2, where it contacts and reacts with the regenerated catalyst from the regenerator 6. The resulting second oil-solid mixture is then introduced into the fluidized bed reactor 3. The first gas-solid mixture from the first riser reactor 1 and the second oil-solid mixture from the second riser reactor 2 react in the fluidized bed reactor 3. The resulting oil-solid mixture is separated by a cyclone separator, and the catalyst enters the stripper 5 and then the regenerator 6 for regeneration. The regenerated catalyst is returned to the riser reactor for recycling, and the oil and gas are introduced into the fractionation system for separation. The mass ratio of light gasoline to wax oil is 0.05:1. The reaction conditions and results are shown in Table 5.

[0069] Example 2

[0070] The method is the same as in Example 1, except that the cracked light oil obtained from fractionation is introduced as a medium-quality feedstock into the second riser reactor 2, and the mass ratio of light gasoline, cracked light oil and wax oil is 0.05:0.1:1. The reaction conditions and results are shown in Table 5.

[0071] Comparative Example 1

[0072] The method was carried out according to Example 1, except that a catalyst separator was not installed, and the entire first oil-agent mixture entered fluidized bed 3 for the third catalytic conversion reaction. The reaction conditions and results are shown in Table 5.

[0073] Comparative Example 2

[0074] The method was carried out according to Example 2, except that a catalyst separator was not installed, and the entire first oil-agent mixture entered fluidized bed 3 for the third catalytic conversion reaction. The reaction conditions and results are shown in Table 5.

[0075] As shown in Table 5, the method and system provided by this invention can achieve higher hydrocarbon conversion capacity, obtain higher low-carbon olefin yield, and reduce gasoline aromatics content.

[0076] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0077] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0078] Table 5. Reaction conditions and results of Examples 1-2 and Comparative Examples 1-2

[0079]

[0080] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A catalytic conversion method for producing low-carbon olefins and reducing the aromatic content of gasoline, characterized in that, The catalytic conversion method includes the following steps: S1. Heavy feedstock oil and a first catalyst are introduced from the bottom into a first riser reactor to carry out a first catalytic conversion reaction, yielding a first oil-catalyst mixture; light feedstock oil and a second catalyst are introduced from the middle into a second riser reactor to carry out a second catalytic conversion reaction, yielding a second oil-catalyst mixture; the first riser reactor and the second riser reactor are arranged side by side; S2. The first oil-based mixture is introduced into a catalyst separator to separate some of the solids, resulting in a first stream of unprocessed catalyst and a first gas-solid mixture; the first stream of unprocessed catalyst accounts for no less than 50% of the catalyst weight in the first oil-based mixture; S3. The second oil-based mixture and the first gas-solid mixture are introduced into a fluidized bed reactor to carry out a third catalytic conversion reaction to obtain a third oil-based mixture. The third oil-based mixture is then subjected to gas-solid separation to obtain a second stream of undeveloped catalyst and oil and gas products. S4. Strip and regenerate the first and second strands of the spent catalyst to obtain a regenerated catalyst, and then extract the first and second strands of the regenerated catalyst and return to step S1.

2. The catalytic conversion method according to claim 1, wherein, The first batch of undeveloped catalyst accounts for no less than 80% of the weight of the catalyst in the first oil mixture.

3. The catalytic conversion method according to claim 1, wherein, The weight ratio of the heavy feedstock oil to the light feedstock oil is 1:0.01 to 0.

3.

4. The catalytic conversion method according to claim 3, wherein, The weight ratio of the heavy feedstock oil to the light feedstock oil is 1:0.05 to 0.

15.

5. The catalytic conversion method according to any one of claims 1-4, wherein, The catalytic conversion method further includes introducing medium feedstock oil from the bottom into the second riser reactor to participate in the second catalytic conversion reaction.

6. The catalytic conversion method according to claim 5, wherein, The weight ratio of the heavy feedstock oil to the medium feedstock oil is 1:0.05 to 0.

5.

7. The catalytic conversion method according to claim 6, wherein, The weight ratio of the heavy feedstock oil to the medium feedstock oil is 1:0.1 to 0.

2.

8. The catalytic conversion method according to claim 5, wherein, The first and second catalyst streams comprise unmodified or modified ZSM-5 molecular sieves, clay, and a binder. Based on the total weight of the catalyst, the content of unmodified ZSM-5 molecular sieve or modified ZSM-5 molecular sieve is 10-60% by weight, the content of clay is 10-70% by weight, and the content of binder is 10-40% by weight.

9. The catalytic conversion method according to claim 8, wherein, Based on the total weight of the catalyst, the content of unmodified ZSM-5 molecular sieve or modified ZSM-5 molecular sieve is 30-50% by weight, the content of clay is 15-45% by weight, and the content of binder is 20-35% by weight.

10. The catalytic conversion method according to claim 1, wherein, The reaction temperature of the first riser reactor is 520–620°C; the agent-to-oil ratio is 2–25; and the reaction time is 1–15 seconds. The reaction temperature of the second riser reactor is 560-660℃, the agent-to-oil ratio is 3-40, and the reaction time is 0.5-10 seconds. The fluidized bed reactor has a reaction temperature of 560–660℃ and a catalyst density of 20–300 kg / m³. 3 Airspeed is 2–15 h -1 The residence time of oil and gas is 0.2 to 8 seconds.

11. The catalytic conversion method according to claim 10, wherein, The reaction temperature of the first riser reactor is 540–600℃; the agent-to-oil ratio is 3–20; and the reaction time is 2–10 seconds. The reaction temperature of the second riser reactor is 580–640°C, the agent-to-oil ratio is 5–30, and the reaction time is 1–5 seconds. The fluidized bed reactor has a reaction temperature of 580–640℃ and a catalyst density of 100–200 kg / m³. 3 Airspeed is 5-10 h -1 The residence time of oil and gas is 1 to 4 seconds.

12. The catalytic conversion method according to claim 5, wherein, The heavy feedstock oil is selected from one or more of the following: vacuum wax oil, atmospheric residue oil, vacuum residue oil, coking wax oil, deasphalted oil, furfural refined raffinate oil, coal liquefaction oil, oil sands oil, shale oil, Fischer-Tropsch synthetic distillate oil, or bio-oil. The medium-quality feedstock is selected from one or more of kerosene, diesel, light cycle oil, heavy cycle oil and oil slurry; The initial boiling point of the heavy feedstock oil is any temperature between 280 and 380°C; The light feedstock oil contains C4-C8 hydrocarbons; The initial boiling point of the light feedstock oil is any temperature between 10 and 40°C, and the final boiling point is any temperature between 50 and 100°C.

13. The catalytic conversion method according to claim 12, wherein, The medium-quality feedstock is selected from one or more of heavy cycle oil and oil slurry.

14. The catalytic conversion method according to claim 5, wherein, The initial boiling point of the medium-quality feedstock is any temperature between 150 and 220°C, and the final boiling point is any temperature between 260 and 350°C.

15. The catalytic conversion method according to claim 1, wherein, The regeneration temperature is 670–730℃, and the catalyst distribution density is 30–350 kg / m³. 3 The duration of the prevailing wind is 0.5 to 15 seconds.

16. The catalytic conversion method according to claim 15, wherein, The regeneration temperature is 690–710℃, and the catalyst distribution density is 80–250 kg / m³. 3 The duration of the prevailing wind is 2 to 10 seconds.

17. A catalytic conversion system for producing low-carbon olefins and reducing the aromatic content of gasoline, characterized in that, The catalytic conversion system includes 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 reactor is connected to the 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 connected to the outlet of the gas-solid mixture and the upper end of the second riser reactor; The upper end of the fluidized bed reactor is connected to the lower end of the settler; the settler is equipped with a gas-solid separator and a stripper. The stripper is connected to the regenerator via a catalyst delivery connection. The regenerator is provided with a first regenerated catalyst outlet and a second regenerated catalyst outlet; the first regenerated catalyst outlet is connected to the first riser reactor via a first regenerated catalyst transport connection; the second regenerated catalyst outlet is connected to the second riser reactor via a second regenerated catalyst transport connection.

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