Process for reducing benzene content in gasoline and process for producing low benzene gasoline

Abstract

The present application relates to a method for reducing benzene content in gasoline and a method for producing low-benzene gasoline, wherein the benzene-rich gasoline is subjected to high-precision distillation to obtain a gasoline light fraction, a middle fraction and a heavy fraction, the benzene-rich gasoline middle fraction is introduced into a moving bed, a fluidized bed or a fixed bed reactor to be in contact with a medium-pore molecular sieve catalyst in a grading contact with a low-carbon olefin-rich stream for catalytic alkylation, so that benzene is efficiently converted into alkylbenzene, thereby converting the benzene-rich gasoline into high-octane low-benzene gasoline and liquefied gas. The method of the present application reduces the benzene content and the olefin content in gasoline, increases the octane rating of gasoline and increases the production of liquefied gas, solves the problem that the high benzene content in refinery gasoline is difficult to meet the national VI standard for motor gasoline, improves the quality of gasoline and increases the production of liquefied gas.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalytic conversion of benzene in gasoline, in particular to a method for reducing the content of benzene in benzene-rich gasoline and a method for producing low-benzene gasoline. BACKGROUND

[0002] In recent years, with the implementation of the national VI clean gasoline standard, the olefin content limit of motor gasoline is reduced from 24% in the national V to 18% in the national VI a stage and 15% in the national VI b stage, the aromatic hydrocarbon content limit is reduced from 40% in the national V to 35%, and the benzene content limit is further tightened from 1.0% in the national V to 0.8%, which is even stricter than the European Union 1.0%. The benzene in the gasoline pool mainly comes from the reforming gasoline and catalytic cracking gasoline which are not subjected to benzene extraction. The benzene content of reforming gasoline is relatively high, generally 2-10 wt%, while the benzene content of catalytic cracking gasoline with high olefin, high sulfur and high nitrogen content is relatively low, generally 0.4-1.0 wt%. The benzene content of straight-run naphtha and hydrocracking naphtha is as low as 0.1-0.5 wt%, and because of the low octane value, it is generally not used as a gasoline blending component. The benzene content of steam cracking gasoline is as high as 20-60 wt%, and because of the high benzene content, it is generally subjected to benzene extraction and used as a chemical material.

[0003] With the deterioration of catalytic cracking feedstock and the strong demand for producing liquefied gas and processing catalytic diesel, the reaction severity is continuously increased, which further leads to a high benzene content in catalytic cracking gasoline. For example, the catalytic cracking units of Tianjin Petrochemical and Jinan Refining process residual oil as feedstock to produce hydrocracking diesel and straight-run diesel, and when the liquefied gas production program is implemented, the benzene content of the stable gasoline produced is as high as 1.4 wt% or more, and the benzene volume fraction of the gasoline is higher than 1.2%. The benzene content of catalytic cracking gasoline exceeds the standard, which seriously restricts the catalytic cracking unit to process catalytic diesel and increase the production of liquefied gas according to market demand. Therefore, during the chemical transformation and structural adjustment of the refinery, it is urgent to upgrade the gasoline and reduce the benzene content of catalytic cracking gasoline.

[0004] At present, mature gasoline benzene reduction schemes mainly target reforming gasoline, such as distillation, extraction, adsorption and other physical separation methods, as well as benzene hydrogenation saturation and alkylation chemical methods. Because of the carcinogenicity of benzene, the United States and other North American countries have more stringent restrictions on benzene (<0.6 v%). They usually adopt physical separation + chemical conversion methods to reduce benzene. There are two technical routes for reducing benzene, one is to saturate the aromatic ring by hydrogenation to reduce benzene, and the other is to reduce benzene by alkylation.

[0005] Hydrogenation saturation benzene reduction technology has CD Tech company combined with hydrogenation reactor and product stripping column to implement catalytic distillation hydrogenation saturation benzene reduction (CD Hydro) process, UOP company Bensat process using Pt-based catalyst, IFP and Axens company Benfree process, GTC company GT-BenZapSM process and Neste company NExSAT process. Hydrogenation saturation benzene reduction route exists gasoline octane loss and high hydrogen consumption problem, need to be combined with isomerization to make up the octane loss. Hydrogenation saturation benzene reduction only has 20 or so device application.

[0006] Benzene-containing reforming gasoline alkylation benzene reduction technology mainly has MBR dense phase fluidized bed process developed by Mobil company, liquid phase alkylation BenzOUTTM process developed by Exxon Mobil. More than 90 commercial applications abroad use alkylation benzene reduction. Among them, hydrogenation saturation benzene reduction and liquid phase alkylation benzene reduction are not suitable for high olefin content catalytic cracking gasoline benzene reduction, and currently only MBR dense phase fluidized bed process can realize the mixing of benzene-rich fraction of reforming oil and catalytic cracking light gasoline feed. Adopting dense phase fluidized bed and special ZSM-5 catalyst, the raw material is benzene-rich fraction of reforming oil, and the olefin is catalytic cracking dry gas and other light olefin resources. Under typical gas phase alkylation conditions (operating pressure is 1.2-1.5 MPa, temperature is 350℃), the single-pass conversion rate of benzene is 60%-70%, and if the material is partially recycled, the total conversion rate can reach 90%. Because light olefins are converted into gasoline components, the gasoline yield increases by 7%, and the octane number increases by 5-10 units. There is also dry gas and benzene alkylation to prepare ethylbenzene technology in China, but it mainly uses pure benzene and ethylene in dry gas to produce ethylbenzene or styrene.

[0007] For benzene and low-carbon olefin alkylation benzene reduction patent technology, foreign countries mainly use MWW zeolite special catalyst in fixed bed reactor for alkylation of reforming gasoline. US62 / 084158, US61 / 209995 and US2011 / 023900 and US2011 / 023912 all disclose that benzene-containing gasoline is contacted with C4+ alkylating agent in the fixed bed of MWW zeolite catalyst, preferably MCM-22, and the alkylating agent adopts staged olefin injection operation, and the final distillate has reduced benzene content.

[0008] Most of the patents in China use ZSM zeolite specific catalysts for alkylation of reforming gasoline in fixed bed reactors. Patent CN201110109863.9 contacts the benzene-rich fraction of reformate with C2-C4 olefins in the presence of an alkylation catalyst to perform an alkylation reaction, and the resulting polyalkylbenzene fraction is then contacted with the benzene-rich fraction of reformate in the presence of an transalkylation catalyst to perform a transalkylation reaction. Patent CN200710140485.4 uses an ethylene and benzene in gasoline and ZSM5 / ZSM11 co-crystallized silicon-aluminum zeolite alkylation catalyst in a fixed bed or fluidized bed reactor to contact ethylene and benzene at a temperature of 300-450℃, a pressure of 0.2-1.5 MPa, a benzene to ethylene molar ratio of 1-12, and a benzene space velocity of 0.2-2.0 h-1 to produce ethylbenzene, with a benzene conversion rate of greater than 45%.

[0009] There are also patents that propose technologies for coupling benzene alkylation with catalytic cracking of FCC gasoline. Patents CN200810231560.2 and CN200710120108.4 both disclose catalytic cracking devices provided with an alkylation reaction zone to introduce dry gas and a gasoline fraction, which is converted into alkylbenzene by ZSM-5 molecular sieve and Y-type molecular sieve catalysts, with the benzene volume content reduced by more than 50%.

[0010] Domestic and foreign patents for reducing benzene, as well as foreign technologies for hydrogenation saturation and liquid phase alkylation to reduce benzene, are all directed at reducing benzene in reforming gasoline fractions that are low in olefins and do not contain sulfur, nitrogen, and water, and are not suitable for reducing benzene in catalytic cracking gasoline that is high in olefins and sulfur and nitrogen content and has a relatively low benzene content compared to reforming gasoline. At present, there is no mature and low-cost technology for efficiently reducing the benzene content of catalytic cracking gasoline. Therefore, catalytic cracking devices that process hydrogenation catalytic diesel or produce more liquefied gas all have the problem of excessive benzene content in the stabilized gasoline, which is as high as 1.2 v%, and there is an urgent need to develop a production method for reducing the benzene content of gasoline. SUMMARY

[0011] The present application aims to provide a method for catalytically converting benzene in gasoline into alkylbenzene and converting benzene-rich gasoline into high-octane low-benzene gasoline and liquefied gas, which improves the quality of gasoline and increases the production of liquefied gas, and also provides a method and system for producing low-benzene gasoline.

[0012] The first aspect of the present application provides a method for reducing the benzene content of gasoline, the method comprising:

[0013] (1) distillation and cutting of benzene-rich gasoline to obtain a benzene-rich gasoline intermediate fraction with a distillation range of 60-90℃;

[0014] (2) the benzene-rich gasoline intermediate fraction enters a first reactor to contact a catalyst under hydrogenation conditions with a staged-in low-carbon olefin-rich stream to perform a catalytic alkylation reaction, to obtain a first mixture of spent catalyst and first oil gas;

[0015] (3) the first mixture passes through an oil-gas separation filter of the first reactor to be separated, and the separated first oil gas enters an oil-gas separation system to be separated into products, to obtain products including dry gas, liquefied gas and gasoline;

[0016] (4) the separated first spent catalyst is stripped by a steam stripper and then enters a regenerator to be regenerated with oxygen, and the regenerated catalyst returns to the first reactor for recycling, and preferably, part or all of the flue gas after regeneration is recycled back to the regenerator;

[0017] Preferably, the benzene content of the benzene-rich gasoline is 0.8-40 wt%; and the low-carbon olefin is ethylene and / or propylene.

[0018] Preferably, the molar ratio of low-carbon olefin to benzene in step (2) is maintained at 3-9:1, preferably 4-8:1.

[0019] According to the method of the first aspect of the application, the low-carbon olefin content in the low-carbon olefin-rich stream is 20-50 wt%.

[0020] Preferably, the low-carbon olefin-rich stream is selected from one or more of the following: an ethylene stream, a propylene stream, dry gas rich in ethylene, and liquefied gas rich in propylene.

[0021] According to the method of the first aspect of the application, the catalytic alkylation reaction temperature is 250-450°C, preferably 300-400°C.

[0022] The reaction pressure is 0.1-5.0 MPa, preferably 0.5-4.0 MPa.

[0023] The weight ratio of catalyst to raw oil is 1.0-9.0:1, preferably 2.0-6.0:1; and / or

[0024] The weight hourly space velocity is 0.2-20.0 h -1 , preferably 1.0-5.0 h -1 .

[0025] According to the method of the first aspect of the application, the first reactor is selected from a fluidized bed reactor, a moving bed reactor or a fixed bed reactor, preferably a moving bed reactor; and / or

[0026] Three or more low-carbon olefin injection ports are arranged on the first reactor in sections.

[0027] The method according to the first aspect of the present application, wherein the distillation cut of the benzene-rich gasoline is carried out in one or more than one distillation column.

[0028] Preferably, the total number of theoretical plates of the distillation column is equal to or greater than 14.

[0029] The method according to the first aspect of the present application, wherein the catalyst comprises mesoporous molecular sieve, heat-resistant inorganic oxide and optional clay, wherein the mesoporous molecular sieve accounts for 40-80% by weight of the total catalyst.

[0030] Preferably, the mesoporous molecular sieve is selected from the group consisting of mordenite series and / or ZSM series mesoporous zeolite, more preferably ZSM series mesoporous zeolite; and / or

[0031] Preferably, the heat-resistant inorganic oxide is alumina and / or silica.

[0032] The method according to the first aspect of the present application, wherein the benzene-rich gasoline is catalytic cracking gasoline, hydrocracking gasoline, reforming gasoline and / or steam cracking gasoline with a boiling point of 30-220℃; and / or

[0033] The benzene-rich gasoline intermediate fraction is preheated to enter the first reactor, and the preheating temperature is 100-350℃, preferably 150-300℃.

[0034] The method according to the first aspect of the present application, wherein the oxygen-containing regeneration atmosphere is air and / or oxygen atmosphere, preferably oxygen-enriched and / or pure oxygen atmosphere.

[0035] The regeneration temperature of the regenerator is 450-750℃, preferably 500-700℃.

[0036] The regeneration pressure of the regenerator is 0.2-5.0 MPa, preferably 0.5-5.0 MPa; and / or

[0037] The flue gas temperature circulating back to the regenerator is 300-600℃.

[0038] The second aspect of the present application provides a method for producing low-benzene gasoline, which comprises:

[0039] (1) catalytically cracking heavy oil in the second reactor to obtain a second mixture comprising second spent catalyst and second oil gas;

[0040] (2) separating the second mixture in the oil gas separation system to obtain dry gas component, liquefied gas component and gasoline component;

[0041] (3) distilling the gasoline component in the gasoline distillation system to obtain self-produced gasoline benzene-rich fraction and low-benzene gasoline;

[0042] (4) the benzene-rich gasoline fraction and optionally other benzene-rich gasoline fraction are fed into a first reactor to contact with a staged injection of a low carbon olefin stream under non-hydrogen or hydrogen conditions to perform catalytic alkylation reaction to obtain a first mixture comprising a first spent catalyst and a first oil gas;

[0043] (5) the first mixture is separated by an oil separation filter of the first reactor, and the separated oil gas is fed into the oil gas separation system to perform oil gas separation;

[0044] (6) the separated first spent catalyst is mixed with a second spent catalyst in a second reactor, and after being stripped by a steam stripper of the second reactor, is fed into a regenerator to perform oxygen-containing regeneration, and the regenerated catalyst is returned to the first reactor and the second reactor for recycling, and preferably, part or all of the flue gas after regeneration is recycled back to the regenerator;

[0045] wherein the heavy oil is wax oil and / or residual oil.

[0046] According to the method of the second aspect of the present application, wherein the benzene-rich gasoline fraction is a benzene-rich gasoline intermediate fraction with a distillation range of 60-90℃ obtained by distillation cutting of the benzene-rich gasoline.

[0047] wherein the benzene content of the benzene-rich gasoline is 0.8-40 wt%.

[0048] Preferably, the benzene-rich gasoline is catalytic cracking gasoline, hydrocracking gasoline, reforming gasoline and / or steam cracking gasoline with a boiling point of 30-220℃.

[0049] Compared with the prior art, the present application has the following technical effects:

[0050] (1) The benzene-rich catalytic cracking gasoline is subjected to high-precision distillation cutting to obtain a benzene-rich gasoline intermediate fraction, which is then contacted with a staged injection of a low carbon olefin stream to perform catalytic alkylation on a medium pore molecular sieve, thereby achieving high benzene conversion rate, improving the octane number of gasoline, and increasing the production of liquefied gas.

[0051] (2) The regenerated catalyst after reaction is recycled or supplemented into a heavy oil catalytic cracking reactor, which not only realizes continuous production, but also maintains a relatively high activity of the catalyst at all times, thereby solving the problem of coke formation and deactivation of the catalyst in processing high olefin catalytic cracking gasoline or steam cracking gasoline.

[0052] (3) Part or all of the flue gas after heat exchange with the main air is recycled, which not only makes full use of the oxygen in the flue gas, but also solves the problem of heat carried out of the reaction-regeneration system by the flue gas, reduces the emission of waste gas such as carbon dioxide, and greatly saves energy and reduces emissions.

[0053] (4) Wide application range, not only suitable for benzene reforming gasoline with low olefin, low sulfur and low nitrogen content (benzene 2-10 wt%), but also suitable for catalytic cracking gasoline with high olefin, high sulfur and high nitrogen content and relatively low benzene content (benzene 0.8-3.0 wt%), and steam cracking gasoline with high olefin, high sulfur and high nitrogen content and also high benzene content (benzene 20-40 wt%). BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 The process flow diagram of the embodiment of the present application is shown in Figure 1, which illustrates the continuous process flow of fluidized bed catalytic alkylation of benzene-rich gasoline.

[0055] Figure 2 The process flow diagram of the embodiment of the present application is shown in Figure 2, which illustrates the coupled process flow of alkylation of benzene-rich gasoline middle distillate and catalytic cracking of heavy oil.

[0056] BRIEF DESCRIPTION OF DRAWINGS

[0057] I, reactor; II, regenerator; III, oil-gas separation system; IV, oil agent filter separator; V, gasoline rectification system; VI, heavy oil cracking reactor; VII, rectification column; 1, gasoline benzene-rich fraction; 1a, gasoline light fraction without aromatic hydrocarbon; 1b, gasoline middle fraction rich in benzene; 1c, gasoline heavy fraction rich in aromatic hydrocarbon; 2, low-carbon olefin stream I; 3, hydrogenation fluidization medium; 4, low-carbon olefin stream II; 5, low-carbon olefin stream III; 6, reaction oil gas pipeline dry gas; 7, dry gas; 8, liquefied gas; 9, gasoline; 10, spent agent delivery pipeline I; 11, spent agent delivery pipeline II; 12, regenerated agent delivery pipeline I; 13, regenerated agent delivery pipeline II; 14, stripping medium; 15, oxygen-containing regeneration gas; 16, flue gas; 17, flue gas circulation pipeline; 18, agent feeding pipeline; 19, heavy raw oil; 20, atomization medium; 21, pre-elevation medium; 22, diesel; 23, oil slurry; 24, gasoline feeding exchanger; 25, self-produced gasoline benzene-rich fraction; 26, low-benzene gasoline after rectification. DETAILED DESCRIPTION

[0058] The present application will be further described in detail by the accompanying drawings and examples. The features and advantages of the present application will become more apparent from these descriptions.

[0059] The term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. Unless specifically stated otherwise, the drawings are not drawn to scale and the depiction of an example in a drawing does not imply a certain orientation of the example in the drawing.

[0060] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0061] The inventors of the present application have found through years of research that: (1) the benzene content of high-benzene catalytic cracking gasoline is 0.8-2.0 wt%, which is mainly distributed in the gasoline intermediate fraction of 60-90℃, so the present application adopts distillation cutting of the benzene-rich intermediate fraction for separate processing; (2) in order to maintain a relatively high benzene conversion rate, the molar ratio of olefins to benzene needs to be maintained within a certain range, such as 3-9; (3) the benzene-rich intermediate fraction of catalytic cracking gasoline has a high olefin content, a low octane number, a high sulfur and nitrogen content, and a relatively low benzene content, so the present application adopts a mesoporous molecular sieve catalyst to catalyze the alkylation of benzene and low-carbon olefins in the benzene-rich intermediate fraction, which can not only reduce the benzene content of catalytic cracking gasoline, but also increase the octane number of gasoline and produce liquefied gas; (4) the benzene-rich intermediate fraction of catalytic cracking gasoline has a high olefin content, which is easy to coke and deactivate during alkylation, and the coked catalyst can be regenerated by burning in an oxygen atmosphere, and the regenerated catalyst can be recycled, which not only realizes continuous production, but also maintains a high activity of the catalyst; (5) the flue gas after regeneration of the coked catalyst is exchanged with the main air, which not only makes full use of the oxygen in the flue gas, but also solves the problem of heat carried out of the reaction-regeneration system by the flue gas, and reduces the emission of waste gas such as carbon dioxide.

[0062] Based on the above findings, the present application provides a method for reducing benzene in gasoline by catalytic alkylation of benzene, which comprises: (1) distillation cutting of benzene-rich gasoline to obtain a benzene-rich gasoline intermediate fraction with a distillation range of 60-90℃; (2) contacting the benzene-rich gasoline intermediate fraction with a low-carbon olefin-rich stream in a moving bed, fluidized bed or fixed bed reactor under suitable temperature and pressure, and in the presence of a mesoporous molecular sieve catalyst; (3) separating the oil and gas after the reaction to obtain dry gas, liquefied gas and gasoline; (4) further stripping the coked and deactivated catalyst to remove flammable gases such as oil and gas, and then regenerating the catalyst in an oxygen-containing regeneration system; (5) returning the regenerated catalyst after nitrogen stripping to remove oxygen and water to the reaction stage for recycling, and returning part and / or all of the high-temperature flue gas after regeneration to the regenerator, so as to realize self-heat balance of the gasoline benzene alkylation reaction, high conversion rate of benzene under high-activity catalyst, and efficient continuous production.

[0063] The present application provides a method for reducing the benzene content of benzene-rich gasoline, which comprises:

[0064] (1) distillation cutting of benzene-rich gasoline to obtain a benzene-rich gasoline intermediate fraction with a distillation range of 60-90℃;

[0065] (2) the benzene-rich gasoline intermediate fraction enters a first reactor to contact a catalyst under hydrogenation conditions with a staged-in low-carbon olefin-rich stream to perform catalytic alkylation to obtain a first mixture of spent catalyst and first oil gas;

[0066] (3) the first mixture passes through an oil agent separation filter of the first reactor to be separated, and the separated first oil gas enters an oil gas separation system to separate products to obtain products including dry gas, liquefied gas and gasoline;

[0067] (4) the separated first spent catalyst is stripped by a steam stripper and then enters a regenerator to perform oxygen-containing regeneration, and the regenerated catalyst returns to the first reactor for recycling, and preferably, part or all of the flue gas after regeneration is recycled back to the regenerator.

[0068] In step (1), the benzene content of the benzene-rich gasoline is 0.8-40 wt%, and the benzene-rich gasoline is catalytic cracking gasoline, hydrocracking gasoline, reforming gasoline and / or steam cracking gasoline with a boiling point of 30-220°C.

[0069] In the present application, the benzene-rich gasoline is mainly catalytic cracking gasoline with a boiling point of 30-220°C and / or gasoline fraction from a hydrocracking device and / or a reforming device and / or a steam cracking device and the like, and the benzene content is 0.8-40 wt%. The benzene-rich gasoline is cut by high-precision distillation to obtain an aromatic hydrocarbon-free gasoline light fraction, a benzene-rich gasoline intermediate fraction and an aromatic hydrocarbon-rich gasoline heavy fraction. The benzene-rich gasoline intermediate fraction is generally controlled to have a distillation range of 60-90°C and to enrich more than 50% of benzene in gasoline. In principle, the benzene content of the gasoline obtained by mixing the aromatic hydrocarbon-free gasoline light fraction and the aromatic hydrocarbon-rich gasoline heavy fraction meets the blending requirements of refinery gasoline, and benzene is maximally enriched at a lower energy consumption, and the yield of the benzene-rich gasoline intermediate fraction is low.

[0070] In an embodiment, the distillation cutting of the benzene-rich gasoline is performed by using one or more than one rectifying column.

[0071] Preferably, the total theoretical plate number of the rectifying column is greater than or equal to 14.

[0072] In step (2), the low-carbon olefin is ethylene and / or propylene.

[0073] Preferably, the molar ratio of the low-carbon olefin to benzene is maintained to be 3-9:1, preferably 4-8:1 in step (2).

[0074] In an embodiment, the benzene-rich gasoline intermediate fraction enters the first reactor after being preheated, and the preheating temperature is 100-350°C, preferably 150-300°C.

[0075] Since the equilibrium conversion of low carbon olefins with benzene is low, the present application maintains the molar ratio of olefin / benzene at 3-9:1 by injecting the low carbon olefin-rich stream in stages, thereby increasing the conversion of benzene.

[0076] The low carbon olefin-rich stream of the present application mainly refers to ethylene, propylene, dry gas rich in ethylene or liquefied gas rich in propylene from catalytic cracking device, and the content of low carbon olefin is 20-50 wt%.

[0077] In one embodiment, the first reactor is selected from fluidized bed reactor, moving bed reactor or fixed bed reactor, preferably moving bed reactor; and / or

[0078] The first reactor is provided with 3 or more than 3 low carbon olefin injection ports in stages.

[0079] In the present application, the gasoline intermediate fraction reaction oil gas rich in benzene is contacted with the low carbon olefin-rich stream in moving bed or fluidized bed or fixed bed reactor, and the low carbon olefin fraction is injected in stages to maintain the molar ratio of olefin / benzene in a certain range; the catalyst of moving bed reactor is in uniform downward moving state, and the catalyst and the reaction stream can be in co-current contact reaction or counter-current contact reaction, preferably counter-current contact reaction, and 3 or more than 3 low carbon olefin stream injection ports are provided in stages; the catalyst of fluidized bed reactor is in turbulent fluidization state, and the average linear velocity of oil gas is 0.2-2.0 m / s, the catalyst and the reaction stream can be in upflow bed or downflow bed, preferably upflow bed, and 3 or more than 3 low carbon olefin stream injection ports are provided in stages; the fixed bed reactor can be conventional radial flow fixed bed reactor, preferably tubular reactor, and the catalyst is loaded in at least 2 or more than 2 reaction zones, and low carbon olefin stream injection ports are provided upstream of each reaction zone.

[0080] In one embodiment, the catalyst comprises mesoporous molecular sieve, heat-resistant inorganic oxide and optional clay, wherein the mesoporous molecular sieve accounts for 40-80 wt% of the total amount of catalyst;

[0081] Preferably, the mesoporous molecular sieve is selected from the mesoporous zeolite of mordenite series and / or ZSM series, more preferably the mesoporous zeolite of ZSM series; and / or

[0082] Preferably, the heat-resistant inorganic oxide is alumina and / or silica.

[0083] The mesoporous molecular sieve catalyst in this invention is a catalyst composed of molecular sieves and heat-resistant inorganic oxides. The molecular sieve is optionally a mesoporous zeolite such as the mordenite series or ZSM series; the heat-resistant inorganic oxide is a binder such as alumina or silica and / or optionally a natural porous support material such as clay; preferably, it is a composite material composed of ZSM series mesoporous zeolite, alumina, silica and other binders and optionally a natural porous support material such as clay, wherein the mesoporous molecular sieve accounts for 40-80% of the total catalyst weight, and the remainder is the support component.

[0084] In one embodiment, the catalytic alkylation reaction temperature is 250–450°C, preferably 300–400°C;

[0085] The reaction pressure is 0.1–5.0 MPa, preferably 0.5–4.0 MPa;

[0086] The catalyst to feedstock oil weight ratio is 1.0–9.0:1, preferably 2.0–6.0:1; and / or

[0087] The weight hourly space velocity is 0.2–20.0 h⁻¹. -1 Preferably, it is 1.0 to 5.0 h. -1 .

[0088] In this invention, the reactor and regenerator can be arranged in parallel or overlapping, and the fluidized bed and settling tank of the fluidized bed reactor can be built-in or external; the catalyst can be stripped and lifted by nitrogen and / or water vapor, and the regenerated catalyst is returned to the reaction stage for recycling after nitrogen stripping for deoxygenation and dehydration.

[0089] In one embodiment, the oxygen-containing regeneration atmosphere is an air and / or oxygen atmosphere, preferably an oxygen-rich and / or pure oxygen atmosphere;

[0090] The regeneration temperature of the regenerator is 450–750°C, preferably 500–700°C;

[0091] The regeneration pressure of the regenerator is 0.2–5.0 MPa, preferably 0.5–5.0 MPa; and / or

[0092] The flue gas temperature of the recirculating regenerator is 300–600°C.

[0093] In this invention, the catalyst after reaction enters an oxygen-containing regeneration system for regeneration, which can be performed using air and / or oxygen; preferably, oxygen-enriched and / or pure oxygen regeneration. The regenerated flue gas is partially or completely recycled back to the regenerator. The high-temperature oxygen-containing flue gas, after only partial heat exchange (without heat exchange), has a temperature of 300-600°C and is partially or completely returned to the regenerator for reuse, fully utilizing the oxygen in the flue gas and maintaining a high regeneration temperature and a high regenerant temperature in the regenerator.

[0094] The benzene-rich gasoline alkylation and benzene removal of the present application can be coupled with catalytic cracking of heavy oil such as wax oil and residual oil, and the reactions are carried out in two different reactors, and the catalyst regeneration system and the oil-gas separation system are shared, and the integration degree is high, and the regenerated catalyst after the alkylation reaction is recycled or supplemented into the heavy oil catalytic cracking reactor, which not only realizes continuous production, but also can always maintain a relatively high activity of the catalyst, and solves the problem of easy coking and deactivation of the alkylation catalyst for processing high-olefin catalytic cracking gasoline or steam cracking gasoline.

[0095] The method for reducing the benzene content in gasoline by coupling with catalytic cracking of heavy oil of the present application comprises:

[0096] (1) catalytic cracking of the heavy oil in the second reactor to obtain a second mixture containing second spent catalyst and second oil gas;

[0097] (2) oil-gas separation of the second mixture in the oil-gas separation system to obtain dry gas component, liquefied gas component and gasoline component;

[0098] (3) rectification of the gasoline component in the gasoline rectification system to obtain self-produced benzene-rich gasoline fraction and low-benzene gasoline;

[0099] (4) the self-produced benzene-rich gasoline fraction and optional other benzene-rich gasoline fraction enter the first reactor to contact the catalyst under non-hydrogen or hydrogen conditions with the low-carbon olefin stream injected in stages to carry out catalytic alkylation reaction, and obtain a first mixture containing first spent catalyst and first oil gas;

[0100] (5) the first mixture passes through the oil catalyst separation filter of the first reactor for separation, and the separated oil gas enters the oil-gas separation system for oil-gas separation;

[0101] (6) the separated first spent catalyst is mixed with the second spent catalyst in the second reactor, and after stripping by the steam exchanger of the second reactor, it enters the regenerator for oxygen-containing regeneration, and the regenerated catalyst returns to the first reactor and the second reactor for recycling, and preferably, part or all of the flue gas after regeneration is recycled back to the regenerator;

[0102] The heavy oil is wax oil and / or residual oil.

[0103] The low-benzene gasoline has a benzene content of less than 1.0 wt%, preferably less than 0.8 wt%.

[0104] In one embodiment, the benzene-rich gasoline fraction is a benzene-rich gasoline intermediate fraction with a distillation cut of 60-90℃ obtained by distillation cutting of benzene-rich gasoline;

[0105] The benzene content of the benzene-rich gasoline is 0.8-40 wt.%;

[0106] Preferably, the benzene-rich gasoline is catalytic cracking gasoline, hydrocracking gasoline, reforming gasoline and / or steam cracking gasoline with a boiling point of 30-220°C.

[0107] The present application is further illustrated in detail by the following examples. The raw materials used in the examples can be obtained by commercial purchase.

[0108] The following examples will further illustrate the present method, but do not limit the present method.

[0109] In the examples, the whole fraction gasoline feedstock A is catalytic cracking gasoline from a certain refinery, the benzene-rich fraction feedstock B is obtained by distillation cutting of A, the low carbon olefin-rich stream is catalytic cracking concentrated dry gas from a certain refinery after deoxygenation and desulfurization, and the heavy feedstock is hydroresid from a certain refinery. The properties of the three feedstocks are shown in Table 1.

[0110] The catalyst used in the examples is the same, and its preparation method is briefly described as follows:

[0111] 1) 20.0 kg of MFI structure mesoporous ZRP-1 zeolite powder (an industrial product of Sinopec Catalyst Qilu Branch, SiO2 / Al2O3=30, phosphorus content P2O5=3.5 wt.%, solid content 91.75%) and 113.3 kg of 3 wt.% ammonium chloride aqueous solution are stirred at 70-80°C in a reaction kettle for 2 hours, and the ammonium exchange is performed twice. The mixture is cooled, the liquid is removed, and the ion exchange catalyst is obtained after washing with water. The ion exchange catalyst is dried at 120°C and calcined at 500°C for 3 hours to obtain H-type ZRP-1 molecular sieve.

[0112] 2) 5.1 kg of high water content kaolin (an industrial product of Suzhou Kaolin Company, solid content 71.6 wt.%) is slurried with 28.4 kg of de-cationic water, and 3.4 kg of pseudo-boehmite (an industrial product of Shandong Aluminum Factory, solid content 63 wt.%) is added to obtain a slurry with a solid content of 5-30 wt.%. The pH is adjusted to 2-4 with hydrochloric acid, and the mixture is stirred uniformly and aged at 60-70°C for 1 hour to obtain a mixed carrier slurry.

[0113] 3) Molding and drying: 18 kg of H-type ZRP-1 molecular sieve (solid content 91 wt.%) obtained in step 1) was mixed with 48 kg of de-cation water at a solid-liquid ratio of 1:1 to 1:10 to form a slurry, which was then added to the mixed carrier slurry obtained in step 2) and stirred uniformly. Then, 4.4 kg of aluminum sol (produced by SINOPEC Catalyst Qilu Branch, Al2O3 content 21.7 wt.%, catalyst solid content to aluminum sol solid content (calculated as Al2O3) ratio 10-50:1) was added and the mixture was continuously stirred in a binder until a uniform sol was formed. The sol was left to stand in air for 4 hours, and then was shaped into a ball using a ball-rolling machine and left to stand for 24 hours. The ball was then dried in a drying oven at 120°C for 3 hours, and then was washed to remove free Na+and K+ions. The ball was then calcined at 500-800°C for 3 hours to obtain a catalyst, which was designated as CAT-Z1. + CAT-Z1 was calcined at about 120°C for 3 hours, and then was calcined at 500-800°C for 3 hours to obtain a catalyst, which was designated as CAT-Z1.

[0114] CAT-Z1 had an average particle size of 2-4 mm and was used as a moving bed alkylation catalyst. The dry basis composition of the catalyst was 70.82 wt.% MFI structure medium pore zeolite, 9.26 wt.% pseudo-boehmite, 4.13 wt.% aluminum sol and 15.79 wt.% kaolin. The properties of the catalyst are listed in Table 2.

[0115] The heavy oil catalytic cracking catalyst was a commercial product CGP special agent produced by SINOPEC Catalyst Qilu Branch, which contained ZSM-5 molecular sieve and Y molecular sieve. The properties of the catalyst are listed in Table 2.

[0116] Example 1

[0117] This example was tested according to the procedure shown in Figure 1 , using the feed oil B, i.e. the benzene-rich fraction of catalytic cracking gasoline, in Table 1 as the raw material, and the CAT-Z1 catalyst was used for the alkylation reaction with the staged injection of ethylene in a moving bed reactor.

[0118] As shown in Figure 1 , in this example, the benzene-rich gasoline 1 was subjected to high-precision distillation cutting in the rectifying column VII to obtain an aromatic hydrocarbon-free gasoline light fraction la, a benzene-rich gasoline intermediate fraction lb and a benzene-rich gasoline heavy fraction lc. The benzene-rich gasoline intermediate fraction lb was generally controlled to have a distillation range of 60-90°C, and the benzene content in the gasoline was more than 50%.

[0119] The benzene-rich gasoline intermediate fraction lb was fed into the reactor at the lower part of the moving bed reactor I to contact the catalyst and to react with the low-carbon olefins injected from the bottom, middle and upper parts of the reactor to perform alkylation reaction. The spent catalyst after the reaction was separated from the oil gas and was regenerated, and the flue gas after the regeneration was partially recycled back to the regenerator. The process flow is as follows:

[0120] The benzene-rich gasoline fraction 1 is fed into the lower part of the reactor I to contact the catalyst, and is subjected to alkylation with the low-carbon olefin gas 2 fed from the bottom of the reactor, and a fluidizing medium 3 can be injected into the bottom of the reactor as needed for fluidization of the catalyst; after the first stage of reaction, the benzene-rich gasoline fraction 1 is further contacted with the low-carbon olefin gas 4 injected into the middle and upper parts of the reactor, and the low-carbon olefin gas 5 injected into the upper part of the reactor, to strengthen the alkylation of benzene; the spent catalyst after the reaction is separated from the oil gas by means of an oil catalyst separation device 6, and after the spent catalyst is settled, it is fed into a gasoline stripper 7 via a spent catalyst delivery line 8, and after stripping with nitrogen and / or steam, it is fed into a regenerator II via a spent catalyst delivery line 9; the spent catalyst is regenerated in the regenerator under an oxygen-containing atmosphere, and the oxygen-containing regeneration gas 10 includes air, oxygen, etc., the regeneration temperature is 450-550°C, and the regenerated catalyst is returned to the reactor I via a regenerated catalyst delivery line 10 and a regenerated catalyst delivery line 11 for recycling; part of the flue gas 12 after regeneration is circulated back to the regenerator via a flue gas circulation line 13; the separated reaction oil gas is fed into an oil gas separation system 14 via a reaction oil gas line 15, and product dry gas 16, liquefied gas 17, and gasoline 18 are obtained after separation.

[0121] The catalytically cracked gasoline feedstock A is subjected to distillation cutting in a rectifying column with 30 trays (theoretical tray number 18), and a benzene-rich 60-90°C middle fraction is obtained by withdrawing from the middle section of the column to obtain a feedstock B, and the yield is 16.0%. The cutting mode has an energy consumption of 21.59 kgEO / t of feedstock.

[0122] The feedstock B is preheated to 180°C and then fed into the lower part of the moving fluidized bed reactor I to perform alkylation with ethylene fed from the bottom of the reactor, hydrogen is used as the fluidizing medium, the fluidizing medium flows from bottom to top, ethylene is injected into the reactor in three stages in the lower, middle, and upper three regions, and the molar ratio of ethylene to benzene in the reaction system is maintained at 4.0, the alkylation reaction is performed under the conditions of a reaction temperature (the outlet temperature of the upper part of the reactor is used as the criterion, the same below) of 400°C, a weight ratio of catalyst to feedstock of 3.1, a weight hourly space velocity of 5.0 h -1 The spent catalyst after oil catalyst separation is sent into a regenerator after stripping with nitrogen to remove the oil gas adsorbed inside, and oxygen is used as the regeneration gas, and the regenerated catalyst is recycled, and part of the flue gas after regeneration is circulated, and the circulation flue gas temperature is 400°C, and the dense phase temperature of the regenerator is maintained at 500°C. The operating conditions and product distribution are listed in Table 3.

[0123] As can be seen from Table 3, in Example 1, the benzene content of the catalytically cracked gasoline rich in benzene fraction is 7.68%, the octane number RON is 83.6, the catalytically cracked gasoline is subjected to alkylation reaction with ethylene in a moving bed reactor, the conversion rate of benzene is 96.42%, the yield of gasoline is 81.25%, the benzene content of gasoline is reduced to 0.25%, the octane number RON is increased by 5.5 units, and the yield of liquefied gas is 15.55%.

[0124] Comparative Example 1

[0125] In Comparative Example 1, the catalytically cracked gasoline A is used as the raw material, the same catalyst and process conditions as in Example 1 are used, and the only difference is that: 1) a riser reactor is used in Comparative Example 1; 2) ethylene is only injected at the bottom of the reactor; 3) air is used as the regeneration gas, and the flue gas is not recycled; 4) in order to maintain the same process conditions as in Example 1, the combustion oil needs to be provided with heat in the regenerator. The operating conditions and product distribution are listed in Table 3.

[0126] As can be seen from Table 3, compared with Comparative Example 1 (riser reactor), the conversion rate of benzene in Example 1 (moving bed reactor) is increased by 63.33 percentage points, the benzene content of gasoline is reduced by 1.03 percentage points, the increase in octane number RON is 4.0 units, and the yield of liquefied gas is increased by 7.83 percentage points.

[0127] Example 2

[0128] This example is tested according to the process of Figure 2 , using heavy oil C in Table 1 as the raw material, and the catalytically cracked gasoline D obtained by cracking is subjected to high-precision distillation to obtain a gasoline rich in benzene fraction E. The heavy oil C and the gasoline rich in benzene fraction E are respectively subjected to tests in a riser reactor and a moving bed reactor, and catalysts CGP and CAT-Z1 are respectively used.

[0129] Figure 2 The process flow diagram of Example 2 is shown in FIG. 2. The same as in Example 1 is that the alkylation of the gasoline rich in benzene fraction uses a moving bed reactor I, and the different is that the heavy oil 19 enters a conventional riser reactor, and the catalyst after benzene alkylation reaction and the catalyst after heavy oil catalytic cracking reaction can each be stripped and then enter the same regenerator, or can share a settler for stripping. In this example, both of them use a settler. The process flow is as follows:

[0130] The heavy oil feedstock 19 is atomized by steam and fed into the lower part of the heavy oil cracking reactor VI to contact the catalytic cracking catalyst for cracking reaction. The separated reaction oil gas is fed into the oil gas separation system III through the reaction oil gas pipeline 6 to separate the product dry gas 7, liquefied gas 8, gasoline 9, diesel 22 and oil slurry 23. The gasoline 9 is separated into the self-produced gasoline rich in benzene fraction 25 and low benzene gasoline 26 after rectification by the gasoline rectification tower V. The self-produced gasoline rich in benzene fraction 25 is partially recycled or not returned to the reactor I as needed, and the low benzene gasoline 26 after rectification is discharged from the device for gasoline pool blending. The benzene-rich gasoline intermediate fraction 1b of the self-produced gasoline rich in benzene fraction 25 and the optional benzene-rich gasoline from the rectification tower is fed into the reactor to contact the catalyst at the lower part of the reactor I and is subjected to alkylation reaction with the low carbon olefin gas I2 fed from the bottom of the reactor. After the first stage of reaction, the low carbon olefin gas II 4 and the low carbon olefin gas III 5 injected from the middle and upper parts of the reactor are further contacted to strengthen the alkylation of benzene. The spent catalyst after the alkylation reaction is separated from the oil gas by the oil catalyst filter separator IV. After the separation, the catalyst is settled and fed into the heavy oil cracking reactor VI through the spent catalyst delivery pipeline I 10. After being stripped in the steam stripper 24 by nitrogen and / or steam 14, the catalyst is fed into the regenerator II through the spent catalyst delivery pipeline II 11. The spent catalyst is regenerated in the oxygen-containing atmosphere in the regenerator II. The oxygen-containing regeneration gas 15 includes air, oxygen and the like. The regeneration temperature is 600-700°C. The regenerated catalyst is recycled. The regenerated catalyst is fed into the heavy oil cracking reactor VI through the regenerated catalyst delivery pipeline I 12 and into the reactor I through the regenerated catalyst delivery pipeline II 13. The separated reaction oil gas is fed into the oil gas separation system III through the reaction oil gas pipeline 6 for product separation. It should be noted that the alkylation catalyst is supplemented into the reactor I through the catalyst supplement pipeline 18. Since the alkylation catalyst is also a propylene additive or octane improver for heavy oil cracking, the amount of the alkylation catalyst fed into the heavy oil cracking reactor needs to meet the demand for benzene alkylation and heavy oil cracking.

[0131] The heavy oil feedstock is preheated to 200°C and fed into the bottom of the riser reactor to contact the catalytic cracking catalyst for cracking reaction. The cracking reaction is carried out under the conditions of a reaction pressure of 0.35 MPa, steam as the fluidization and atomization medium, upward flow of the fluidization medium, a reaction temperature of 540°C (the temperature at the upper part of the reactor, i.e. the outlet temperature), a weight ratio of the catalyst to the oil feedstock of 7.4, a mass ratio of the atomized water to the oil feedstock of 11.8, a weight hourly space velocity of 20.0 h-1 -1 .

[0132] The gasoline D obtained by catalytic cracking of heavy feedstock oil was subjected to high-precision distillation cutting using a rectifying column 1 with 30 trays (15 theoretical trays) and a rectifying column 2 with 50 trays (25 theoretical trays). The light gasoline fraction at the bottom of the rectifying column 1 was introduced into the rectifying column 2, and a 60-90°C intermediate fraction rich in benzene, i.e., a gasoline fraction E rich in benzene, was withdrawn at the top of the rectifying column 2. The yield of the gasoline fraction E rich in benzene was 29.4% of the catalytic cracking gasoline D. The cutting mode had an energy consumption of 14.66 kg EO / t of feedstock. The properties of the catalytic cracking gasoline D and the gasoline fraction E rich in benzene are shown in Table 1.

[0133] The gasoline fraction E rich in benzene was introduced into the lower part of the moving fluidized bed reactor I after being preheated to 300°C, and was subjected to alkylation with dry gas rich in ethylene fed from the bottom of the reactor. The dry gas for alkylation provided low-carbon olefins and a hydrogen atmosphere. The alkylation was carried out under the following conditions: upward flow at a reaction pressure of 0.5 MPa, three times of injection of ethylene into the lower, middle and upper regions of the reactor, and a molar ratio of ethylene to benzene in the reaction system of 5.9. The alkylation was carried out at a reaction temperature of 350°C, a weight ratio of catalyst to feedstock oil of 4.7, a weight hourly space velocity of 2.0 h-1, and a reaction time of 1.5 h. -1 After the reaction, oil agent separation was carried out.

[0134] The separated reaction oil gas was introduced into an oil gas separation system through an oil gas line, and product dry gas, liquefied gas, gasoline, diesel and oil slurry were separated. The gasoline was separated into self-produced gasoline rich in benzene and gasoline low in benzene through a gasoline rectifying column, and the self-produced gasoline rich in benzene was recycled to the reactor.

[0135] The reaction oil gas after separation of the gasoline fraction E rich in benzene was introduced into a heavy oil cracking oil gas line, and the separated spent catalyst was introduced into the settling section of the heavy feedstock oil catalytic cracking reactor, and was sent to the regenerator after being stripped with steam to remove the oil gas adsorbed inside. Air was used as the regeneration gas, and the spent catalyst was regenerated at a dense phase temperature of 680°C. The regenerated catalyst was recycled, and the flue gas after regeneration was not recycled.

[0136] The operating conditions and product distribution are shown in Table 4.

[0137] As shown in Table 4, in Example 2, the benzene conversion rate after alkylation of the gasoline fraction E rich in benzene was 89.24%, the benzene content of the gasoline was reduced to 0.77%, the octane value RON was increased to 88.0, and the liquefied gas yield was as high as 8.55%. The alkylation of the gasoline fraction E rich in benzene was not included in the feedstock as a recycling material, and the liquefied gas yield of the heavy oil catalytic cracking was 28.75 wt%, the gasoline yield was 34.09 wt%, the olefin content of the gasoline was 8.54 wt%, the benzene content was 0.42 wt%, and the octane value RON was 98.3.

[0138] Comparative Example 2

[0139] The same heavy feed oil C as in Example 2 was used as the raw material, the same catalyst and process conditions as in Example 2 were used for the cracking reaction, except that: 1) the gasoline obtained by cracking of the heavy feed oil in Comparative Example 2 was not cut; 2) the gasoline was all fed into the upper part of the riser reactor for back- refining, and reacted with ethylene in the dry gas for alkylation. The operating conditions and product distribution are listed in Table 4.

[0140] As can be seen from Table 4, compared with Comparative Example 2 (gasoline not cut, riser reactor alkylation), the benzene content of the gasoline in Example 2 (gasoline cut, moving bed alkylation) was 1.21 percentage points lower, the octane value RON was increased by 1.8 units, and the liquefied gas yield was 7.3 percentage points higher.

[0141] The above describes the present application in combination with preferred embodiments, but these embodiments are only exemplary and are for illustrative purposes only. On this basis, various substitutions and improvements can be made to the present application, and these all fall within the protection scope of the present application.

[0142] Table 1

[0143]

[0144] Table 2

[0145]

[0146]

[0147] Table 3

[0148]

[0149]

[0150] Table 4

[0151]

[0152] # indicates data obtained by sampling and analyzing at the outlet of the catalyst oil separator of the riser reactor (based on the feed oil C)

[0153] ## indicates data obtained by sampling and analyzing at the outlet of the oil catalyst filter separator of the moving bed reactor (based on the gasoline benzene-rich fraction E)

[0154] ### indicates the overall data of Example 2 (based on the feed oil C).

Claims

1. A method of reducing the benzene content of gasoline, characterized in that, The method comprises: (1) distillation cutting benzene-rich gasoline to obtain a benzene-rich gasoline intermediate fraction with a distillation range of 60-90℃; (2) the benzene-rich gasoline intermediate fraction is introduced into a first reactor to contact a catalyst under a hydrogenation condition with a staged injection of a low-carbon olefin-rich stream to perform a catalytic alkylation reaction, to obtain a first mixture comprising a first spent catalyst and a first oil gas; (3) the first mixture is separated by an oil agent separation filter of the first reactor, and the separated first oil gas is introduced into an oil gas separation system to perform product separation, to obtain products including dry gas, liquefied gas and gasoline; (4) the separated first spent catalyst is introduced into a regenerator after steam stripping to perform oxygen-containing regeneration, and the regenerated catalyst is returned to the first reactor for recycling; wherein the benzene content of the benzene-rich gasoline is 0.8-40 wt%; the low-carbon olefin is ethylene and / or propylene; In step (2), the molar ratio of low-carbon olefin to benzene is maintained at 3-9:

1.

2. The method of claim 1, wherein, In step (4), part or all of the flue gas after regeneration is recycled back to the regenerator.

3. The method of claim 1, wherein, In step (2), the molar ratio of low-carbon olefin to benzene is maintained at 4-8:

1.

4. The method of claim 1, wherein, The low-carbon olefin content in the low-carbon olefin-rich stream is 20-50 wt%.

5. The method of claim 4, wherein, The low-carbon olefin-rich stream is selected from one or more of the following: an ethylene stream, a propylene stream, dry gas rich in ethylene, liquefied gas rich in propylene.

6. The method of claim 1, wherein, The catalytic alkylation reaction temperature is 250-450℃; The reaction pressure is 0.1-5.0 MPa; The weight ratio of catalyst to raw oil is 1.0-9.0:1; and / or Weight hourly space velocity is 0.2-20.0 h -1 .

7. The method of claim 6, wherein, The catalytic alkylation reaction temperature is 300-400℃; The reaction pressure is 0.5-4.0 MPa; The weight ratio of catalyst to raw oil is 2.0-6.0:1; and / or Weight hourly space velocity was 1.0 to 5.0 h -1 .

8. The method of claim 1, wherein, The first reactor is selected from a fluidized bed reactor, a moving bed reactor or a fixed bed reactor; and / or Three or more low-carbon olefin injection ports are arranged on the first reactor in sections.

9. The method of claim 8, wherein, The first reactor is a moving bed reactor.

10. The method of claim 1, wherein, The distillation cutting of the benzene-rich gasoline is performed by using one or more rectifying columns.

11. The method of claim 10, wherein, The total theoretical plate number of the rectifying column is greater than or equal to 14.

12. The method of claim 1, wherein, The catalyst comprises a mesoporous molecular sieve and a heat-resistant inorganic oxide, wherein the mesoporous molecular sieve accounts for 40-80 wt% of the total amount of the catalyst.

13. The method of claim 12, wherein, The mesoporous molecular sieve is selected from a mordenite series and / or a ZSM series of mesoporous zeolites; and / or The heat-resistant inorganic oxide is alumina and / or silicon oxide.

14. The method of claim 13, wherein, The mesoporous molecular sieve is a ZSM series of mesoporous zeolites.

15. The method of claim 1, wherein, The benzene-rich gasoline is catalytic cracking gasoline, hydrocracking gasoline, reforming gasoline and / or steam cracking gasoline with a boiling point of 30-220℃; and / or The benzene-rich gasoline intermediate fraction is preheated before being introduced into the first reactor, and the preheating temperature is 100-350℃.

16. The method of claim 15, wherein, The benzene-rich gasoline intermediate fraction is preheated before being introduced into the first reactor, and the preheating temperature is 150-300℃.

17. The method of claim 1, wherein, The oxygen-containing regeneration atmosphere is an air and / or oxygen atmosphere; The regeneration temperature of the regenerator is 450-750℃; The regeneration pressure of the regenerator is 0.2-5.0 MPa; and / or The regeneration pressure of the regenerator is 0.2-5.0 MPa; and / or The flue gas temperature circulating back to the regenerator is 300-600℃.

18. The method of claim 17, wherein, The oxygen-containing regeneration atmosphere is an oxygen-rich and / or pure oxygen atmosphere. The regeneration temperature of the regenerator is 500-700℃. The regeneration pressure of the regenerator is 0.5-5.0 MPa.

19. A method of producing low benzene gasoline, characterized by, The method comprises: (1) performing catalytic cracking on the heavy oil in a second reactor to obtain a second mixture comprising a second spent catalyst and a second oil gas; (2) performing oil-gas separation on the second mixture in an oil-gas separation system to obtain dry gas components, liquefied gas components and gasoline components; (3) performing distillation on the gasoline components in a gasoline distillation system to obtain self-produced gasoline benzene-rich fractions and low-benzene gasoline; (4) the self-produced gasoline benzene-rich fractions and other gasoline benzene-rich fractions enter the first reactor to contact the catalytic alkylation reaction with the low-carbon olefin stream injected in stages under non-hydrogen or hydrogen conditions, to obtain a first mixture comprising a first spent catalyst and a first oil gas, and the molar ratio of low-carbon olefins to benzene is maintained at 3-9:1; (5) the first mixture passes through the oil catalyst separation filter of the first reactor for separation, and the separated oil gas enters the oil-gas separation system for oil-gas separation; (6) the separated first spent catalyst is mixed with the second spent catalyst in the second reactor, and after being stripped by the steam exchanger of the second reactor, it enters the regenerator for oxygen-containing regeneration, and the regenerated regenerated catalyst is returned to the first reactor and the second reactor for recycling; The heavy oil is wax oil and / or residual oil, and the benzene-rich gasoline fraction is a benzene-rich gasoline intermediate fraction with a distillation range of 60-90℃ obtained by distillation cutting of benzene-rich gasoline. The benzene content of the benzene-rich gasoline is 0.8-40 wt%.

20. The method of claim 19, wherein, Part or all of the regenerated flue gas is circulated back to the regenerator.

21. The method of claim 19, wherein, The benzene-rich gasoline is catalytic cracking gasoline, hydrocracking gasoline, reforming gasoline and / or steam cracking gasoline with a boiling point of 30-220℃. The benzene-rich gasoline is catalytic cracking gasoline, hydrocracking gasoline, reforming gasoline and / or steam cracking gasoline with a boiling point of 30-220℃.

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