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

Abstract

The present application provides a method for reducing benzene content in gasoline by catalytic transalkylation and a method for producing low-benzene-content gasoline. Benzene-rich gasoline is cut into light distillate, middle distillate and heavy distillate by high-precision distillation. The benzene-rich middle distillate and the gasoline or diesel distillate enriched with C9 and C10 monocyclic heavy aromatics by staged injection are introduced into a fluidized bed or moving bed or fixed bed reactor to contact a mesoporous molecular sieve catalyst to perform catalytic transalkylation reaction, so that benzene and heavy aromatics are efficiently converted into xylene, etc., thereby converting benzene-rich gasoline and catalytic cracking light diesel into high-octane low-benzene gasoline. The method of the present application reduces the benzene content and olefin content in gasoline while increasing the octane value of gasoline. Not only does it solve the problem of high benzene content in refinery gasoline which is difficult to meet the national VI standard for motor gasoline, but also reduces the diesel-gasoline ratio of the catalytic cracking unit and increases the production of high-quality gasoline.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalytic conversion of benzene in gasoline, in particular to a method for catalytically transalkylating to reduce the content of benzene in gasoline and a method for producing low-benzene-content 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 standard 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 standard to 35%, and the benzene content limit is further tightened from 1.0% in the national V standard to 0.8%, which is even stricter than the European Union standard of 1.0%. The benzene in the gasoline pool mainly comes from reforming gasoline and catalytic cracking gasoline that have not been subjected to benzene extraction. The benzene content of reforming gasoline is relatively high, generally 2-10% by weight, while the benzene content of catalytic cracking gasoline with high olefin, sulfur and nitrogen content is relatively low, generally 0.4-1.0% by weight. The benzene content of straight-run naphtha and hydrocracking naphtha is as low as 0.1-0.5% by weight, and because of the low octane number, it is generally not used as a gasoline blending component. The benzene content of steam cracking gasoline is as high as 20-60% by weight, 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 petroleum 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 are processing residual oil feedstock while processing hydrocracking diesel and straight-run diesel, and when the program of producing stable gasoline is implemented, the benzene content of the produced gasoline is as high as 1.4% by weight 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 processing of catalytic diesel and the production of liquefied petroleum gas according to market demand. Therefore, during the process of chemical transformation and structural adjustment, the upgrading of gasoline by the refinery is urgent, and the reduction of benzene in catalytic cracking gasoline cannot be delayed.

[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% by volume), and usually adopt physical separation + chemical conversion methods to reduce benzene. There are two technical routes for reducing benzene, i.e., hydrogenation saturation of benzene-containing fraction of reforming gasoline to reduce benzene and alkylation to reduce benzene.

[0005] Hydrogenation saturation benzene technology has CD Tech company hydrogenation reactor and product stripping tower combined catalytic distillation hydrogenation saturation benzene (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 fraction contains gasoline octane loss and hydrogen consumption problem, need to be combined with isomerization to make up for the loss of octane. Hydrogenation saturation benzene only has 20 or so device application.

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

[0007] Alkyl transfer reaction is mainly used for producing dimethylbenzene from toluene and heavy aromatics, such as CN00119767.3 discloses toluene disproportionation and heavy aromatics alkyl transfer method, CN201510674618.0 discloses lightening and increasing dimethylbenzene production of heavy aromatics under hydrogenation condition through two kinds of supported metal catalysts, CN01131953.4 and AU2002344025A1 disclose toluene selective disproportionation and toluene and C9 and above aromatics disproportionation and alkyl transfer method. There are few patents on benzene and heavy aromatics alkyl transfer benzene reduction, CN01105840.4 discloses benzene and heavy aromatics alkyl transfer method, in a fixed bed reactor, under hydrogenation condition, using hydrogen type mordenite, β-zeolite or Y-zeolite supported with bismuth and at least one metal or oxide selected from iron, cobalt, nickel or molybdenum as catalyst, under the condition of temperature 300-600 ℃, pressure 1.5-6.0 MPa, C7-C9 aromatics and C1-C4 paraffin are generated.

[0008] Patent CN201110109863.9 is directed to the benzene-rich fraction of reformate and C2-C4 olefins in the presence of an alkylation catalyst to contact for transalkylation reaction, and the reaction product of multi-alkyl benzene fraction is contacted with the benzene-rich fraction of reformate in the presence of an alkylation catalyst for transalkylation reaction.

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

[0010] Domestic and foreign benzene reduction patents and foreign hydrogen saturation benzene reduction and liquid phase alkylation benzene reduction technologies are all directed to the benzene reduction of reforming gasoline fraction with low olefins and without sulfur, nitrogen and water, and are all not applicable to the benzene reduction of catalytic cracking gasoline with high olefins, high sulfur and nitrogen content and low benzene content relative to reforming gasoline. At present, there is no mature and low-cost high-efficiency benzene content reduction technology for catalytic cracking gasoline at home and abroad. Therefore, the catalytic cracking device has the problem of exceeding the standard of stable gasoline benzene content when processing hydrogenated catalytic diesel or producing more liquefied gas, and the benzene content is as high as 1.2v% or more, and it is urgent to develop a production method for reducing the benzene content of gasoline. SUMMARY

[0011] The purpose of the present application is to provide a method for reducing the benzene content of gasoline by transalkylation of benzene and heavy aromatics, reducing the benzene content of gasoline while increasing the octane number of gasoline, and increasing the production of high-quality gasoline. Specifically, the present application provides a method for producing low-benzene and low-olefin gasoline by catalytic transalkylation of benzene-rich gasoline intermediate fraction obtained by high-precision distillation cutting of benzene-rich gasoline and fractionally injected heavy aromatic fraction on a medium pore molecular sieve catalyst, while increasing the octane number of gasoline and increasing the production of xylene and high-quality gasoline.

[0012] The first aspect of the present application provides a method for reducing the benzene content of gasoline by catalytic transalkylation, which comprises:

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

[0014] (2) the benzene-rich gasoline intermediate fraction enters the first reactor to contact the fractionally injected heavy aromatic-rich fraction under non-hydrogen or hydrogen conditions to carry out catalytic transalkylation reaction on the catalyst to obtain a first mixture containing first spent catalyst and first oil gas;

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

[0016] (4) passing the separated first spent catalyst into a steam stripper to strip steam, and then passing the stripped first spent catalyst into a regenerator to perform oxygen-containing regeneration, and returning the regenerated catalyst 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 content of C9-C10 monocyclic heavy aromatic hydrocarbons in the heavy aromatic hydrocarbon-rich fraction is 20-100 wt%.

[0018] Preferably, the molar ratio of the heavy aromatic hydrocarbons to benzene in step (2) is maintained at 0.3-5.0, preferably 0.5-2.0.

[0019] According to the method of the first aspect of the present application, the heavy aromatic hydrocarbon-rich fraction is a catalytic cracking gasoline fraction, a catalytic cracking diesel fraction, a hydrocracking gasoline fraction, a hydrocracking diesel fraction, a reforming gasoline fraction, a reforming diesel fraction, a steam cracking gasoline fraction and / or a steam cracking diesel fraction having a boiling point of 150-240°C.

[0020] According to the method of the first aspect of the present application, the temperature of the catalytic transalkylation reaction is 200-450°C, preferably 250-400°C.

[0021] The reaction pressure is 0.1-5.0 MPa, preferably 0.5-4.0 MPa.

[0022] The weight ratio of the catalyst to the raw oil is 2.0-12.0:1, preferably 3.0-9.0:1; and / or

[0023] The weight hourly space velocity is 1.0-20.0 h -1 , preferably 2.0-10.0 h -1 .

[0024] According to the method of the first aspect of the present 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

[0025] Three or more heavy aromatic hydrocarbon injection ports are arranged on the first reactor in sections.

[0026] According to the method of the first aspect of the present application, the benzene-rich gasoline is distilled and cut using one or more rectifying columns.

[0027] Preferably, the total theoretical plate number of the rectifying column is greater than or equal to 14.

[0028] According to the method of the first aspect of the present application, wherein the catalyst comprises a mesoporous molecular sieve, a heat-resistant inorganic oxide and optionally a clay, wherein the mesoporous molecular sieve accounts for 30-80% by weight of the total catalyst;

[0029] Preferably, the mesoporous molecular sieve is selected from the group consisting of mordenite series, ZSM series and / or Y series mesoporous zeolite, more preferably a mordenite series mesoporous zeolite or a composite molecular sieve containing a mordenite series mesoporous zeolite; and / or

[0030] Preferably, the heat-resistant inorganic oxide is alumina and / or silica.

[0031] According to the method of the first aspect of the present application, wherein the benzene-rich gasoline is catalytically cracked gasoline, hydrocracked gasoline, reformed gasoline and / or steam-cracked gasoline with a boiling point of 30-220°C; and / or

[0032] The benzene-rich middle distillate is preheated to enter the first reactor, and the preheating temperature is 200-400°C, preferably 220-380°C.

[0033] According to the method of the first aspect of the present application, wherein the oxygen-containing regeneration atmosphere is an air and / or oxygen atmosphere, preferably an oxygen-enriched and / or pure oxygen atmosphere;

[0034] The regeneration temperature of the regenerator is 500-800°C, preferably 550-700°C;

[0035] The regeneration pressure of the regenerator is 0.2-5.0 MPa, preferably 0.5-5.0 MPa; and / or

[0036] The flue gas temperature circulating back to the regenerator is 300-600°C.

[0037] The second aspect of the present application provides a method for producing low-benzene-content gasoline by catalytic transalkylation, which comprises:

[0038] (1) catalytically cracking heavy oil in a second reactor to obtain a second mixture comprising a second spent catalyst and a second oil gas;

[0039] (2) separating the oil gas from the second mixture in an oil gas separation system to obtain a dry gas component, a liquefied gas component and a gasoline component;

[0040] (3) distilling the gasoline component in a gasoline distillation system to obtain a self-produced gasoline benzene-rich fraction and a low-benzene-content gasoline;

[0041] (4) the benzene-rich gasoline fraction and optionally other benzene-rich gasoline fraction are fed into the first reactor to contact with the staged-in heavy aromatic-rich fraction under non-hydrogen or hydrogen conditions to perform catalytic transalkylation reaction on the catalyst to obtain a first mixture of first spent catalyst and first oil gas;

[0042] (5) the first mixture is separated by an oil agent separation filter of the first reactor, and the separated oil gas is fed into the oil gas separation system to separate the oil gas;

[0043] (6) the separated first spent catalyst is mixed with the second spent catalyst in the second reactor, is stripped by a steam stripper of the second reactor, and is then 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;

[0044] The heavy oil is wax oil and / or residual oil.

[0045] According to the method of the second aspect of the present application, the benzene-rich gasoline fraction is a benzene-rich intermediate fraction with a distillation range of 60-90°C obtained by distillation cutting of the benzene-rich gasoline.

[0046] The benzene content of the benzene-rich gasoline is 0.8-40 wt%.

[0047] 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.

[0048] Compared with the prior art, the present application has the following technical effects:

[0049] (1) The benzene-rich catalytic cracking gasoline is subjected to high-precision distillation cutting to obtain a benzene-rich intermediate fraction, which is then subjected to transalkylation on a medium pore molecular sieve catalyst with the staged-in catalytic cracking light diesel oil rich in monocyclic heavy aromatics, so that the benzene conversion rate is high, the gasoline octane number is improved, the diesel-gasoline ratio of the catalytic cracking device is reduced, and the production of high-quality gasoline is increased.

[0050] (2) The regenerated catalyst after the 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 catalyst for processing high-olefin catalytic cracking gasoline or steam cracking gasoline.

[0051] (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.

[0052] (4) Wide application range, not only suitable for benzene-containing 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

[0053] Figure 1 Figure 2 is a schematic diagram of a process flow of a benzene and heavy aromatic alkyl transfer fluidized bed reactor embodiment of the present application, which is used to illustrate the continuous process flow of fluidized bed catalytic alkyl transfer of benzene-rich gasoline.

[0054] Figure 2 Figure 3 is a schematic diagram of a process flow of a benzene and heavy aromatic alkyl transfer fluidized bed reactor combined with catalytic cracking of heavy oil embodiment of the present application, which is used to illustrate the coupled processing process flow of benzene-rich gasoline intermediate fraction and catalytic cracking of light diesel oil alkyl transfer and catalytic cracking of heavy oil.

[0055] BRIEF DESCRIPTION OF DRAWINGS

[0056] 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, benzene-rich gasoline; 1a, gasoline light fraction without aromatic hydrocarbon; 1b, benzene-rich intermediate fraction; 1c, heavy fraction rich in aromatic hydrocarbon; 2, single ring heavy aromatic hydrocarbon stream I; 3, fluidization medium; 4, single ring heavy aromatic hydrocarbon stream II; 5, single ring heavy aromatic hydrocarbon 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 material oil; 20, atomization medium; 21, pre-lifting medium; 22, diesel oil; 23, oil slurry; 23, gas exchanger; 25, self-produced gasoline benzene-rich fraction; 26, low benzene gasoline after rectification. DETAILED DESCRIPTION

[0057] The present application will be further described in detail by the accompanying drawings and examples. Through these descriptions, the features and advantages of the present application will become more apparent.

[0058] 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. Although various aspects of an implementation can be described herein as being a preferred or advantageous implementation, no inference should be drawn that other aspects necessarily are inferior or inferior to other aspects or implementations.

[0059] 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 there is no conflict.

[0060] 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 high benzene conversion rate, the molar ratio of heavy aromatics to benzene needs to be maintained at 0.3-5.0 for benzene transalkylation; (3) the benzene-rich intermediate fraction of catalytic cracking gasoline has not only a high olefin content and a low octane number, but also 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 benzene in the benzene-rich intermediate fraction and the C9-C10 heavy aromatics in the gasoline and diesel fractions for transalkylation, which can not only reduce the benzene content of catalytic cracking gasoline, but also increase the octane number of gasoline and the production of dimethylbenzene; (4) the benzene-rich intermediate fraction of catalytic cracking gasoline has a high olefin content, which is easy to coke and deactivate during transalkylation, 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 further 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.

[0061] Based on the above findings, the present application provides a method for reducing benzene by contacting a benzene-rich gasoline fraction with a C9-C10 heavy aromatics-rich gasoline and diesel fraction with a mesoporous molecular sieve catalyst for transalkylation, i.e. high-precision distillation cutting of benzene-rich gasoline to obtain a benzene-rich gasoline intermediate fraction, which is then introduced into a fluidized bed, moving bed or fixed bed reactor, and non-hydrogen or hydrogen is contacted with a mesoporous molecular sieve catalyst for catalytic transalkylation at a suitable temperature and pressure; the coked and deactivated catalyst is regenerated in an oxygen-containing regeneration system, and part and / or all of the high-temperature flue gas after regeneration is returned to the regenerator; thereby realizing self-heat balance of the gasoline benzene transalkylation reaction and continuous regeneration, achieving a high conversion rate of benzene on a high-activity catalyst, and realizing high-efficiency continuous production.

[0062] The present application provides a method for reducing the benzene content in gasoline by catalytic transalkylation, which comprises:

[0063] (1) distillation cutting of benzene-rich gasoline to obtain a benzene-rich gasoline intermediate fraction with a distillation range of 60-90℃;

[0064] (2) the benzene-rich gasoline intermediate fraction enters a first reactor to contact a catalyst under non-hydrogen or hydrogen conditions with a staged-in heavy aromatic-rich fraction to perform catalytic transalkylation, to obtain a first mixture of a first spent catalyst and a first oil gas;

[0065] (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;

[0066] (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.

[0067] 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.

[0068] 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 unit and / or a reforming unit and / or a steam cracking unit and other sources, and the benzene content is 0.8-40 wt%. The benzene-rich gasoline is cut by high-precision distillation to obtain an aromatic-free gasoline light fraction, a benzene-rich intermediate fraction and an aromatic-rich heavy fraction. The benzene-rich 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 gasoline light fraction and the aromatic-rich 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 intermediate fraction is low.

[0069] In one embodiment, the distillation cutting of the benzene-rich gasoline is performed by using one or more than one rectifying column;

[0070] Preferably, the total number of theoretical plates of the rectifying column is greater than or equal to 14.

[0071] The method of the present application uses one rectifying column and / or more than one rectifying column for high-precision distillation cutting, and the total number of theoretical plates is at least more than 14, and the benzene-rich 60-90°C intermediate fraction can be directly subjected to transalkylation, the cutting scheme is flexible, the enrichment efficiency is high, and the distillation cut fraction does not need to be further treated by hydrogenation and removal, thereby simplifying the production process and improving the production efficiency.

[0072] In step (2), the heavy aromatic hydrocarbon-rich fraction is a catalytically cracked gasoline fraction with a boiling point of 150-240°C, a catalytically cracked diesel fraction, a hydrocracked gasoline fraction, a hydrocracked diesel fraction, a reformed gasoline fraction, a reformed diesel fraction, a steam-cracked gasoline fraction and / or a steam-cracked diesel fraction; the content of C9-C10 monocyclic heavy aromatic hydrocarbons in the heavy aromatic hydrocarbon-rich fraction is 20-100 wt.%;

[0073] Preferably, the molar ratio of the heavy aromatic hydrocarbons to benzene in step (2) is maintained at 0.3-5.0, preferably 0.5-2.0.

[0074] The heavy aromatic hydrocarbon-rich gasoline and diesel fractions used in the present application refer mainly to gasoline fractions and / or diesel fractions with a boiling point of 150-240°C from catalytic cracking and / or from a hydrocracking device and / or a reforming device and / or a steam-cracking device, with a content of C9-C10 monocyclic heavy aromatic hydrocarbons of 20-100 wt.%.

[0075] The present application maintains the mass ratio of benzene to heavy aromatic hydrocarbons within a certain range by injecting the heavy aromatic hydrocarbon-rich fraction in stages, thereby improving the conversion rate of benzene.

[0076] In one embodiment, 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

[0077] Three or more heavy aromatic hydrocarbon injection ports are provided on the first reactor in stages.

[0078] In the present application, the heavy aromatic hydrocarbon-rich gasoline intermediate fraction reaction oil gas enters a fluidized bed reactor, a moving bed reactor or a fixed bed reactor. The catalyst in the fluidized bed reactor is in a turbulent fluidization state, the average linear velocity of the oil gas is 0.2-2.0 m / s, the catalyst and the reactant flow can be an upflowing bed or a downflowing bed, preferably an upflowing bed, and two or more heavy aromatic hydrocarbon fraction injection ports are provided in stages. The catalyst in the moving bed reactor is in a uniform downflowing moving state, the catalyst and the reactant flow can be in a co-current contact reaction or a counter-current contact reaction, preferably a counter-current contact reaction, and two or more heavy aromatic hydrocarbon fraction injection ports are provided in stages. The fixed bed reactor can be a conventional radial flow fixed bed reactor, preferably a tubular reactor, and the catalyst is loaded in two or more reaction zones, and a heavy aromatic hydrocarbon stream injection port is provided upstream of each reaction zone.

[0079] The method of the present application is carried out in a non-hydrogen or hydrogen atmosphere, the hydrogen consumption is low, and the octane value of the xylene component generated by transalkylation is high.

[0080] In one embodiment, the catalyst comprises a mesoporous molecular sieve, a heat-resistant inorganic oxide and optionally a clay, wherein the mesoporous molecular sieve accounts for 30-80 wt.% of the total catalyst;

[0081] Preferably, the mesoporous molecular sieve is selected from the group consisting of mordenite, ZSM series and / or Y series mesoporous zeolite, more preferably mordenite or a composite molecular sieve containing mordenite; and / or

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

[0083] The mesoporous molecular sieve catalyst in the present application is a catalyst composed of a molecular sieve and a heat-resistant inorganic oxide, the catalyst molecular sieve is a mesoporous zeolite selected from the group consisting of mordenite, ZSM series and Y series, the heat-resistant inorganic oxide is a binder such as alumina and / or silica and / or a natural porous carrier material such as clay, preferably a composite composed of mordenite or a composite molecular sieve containing mordenite, a binder such as alumina and / or silica and a natural porous carrier material such as clay, wherein the mesoporous molecular sieve accounts for 30-80 wt% of the total catalyst, and the rest is the carrier. The catalyst of the present application is simple to prepare, does not need to add noble metal, has low cost and high benzene conversion rate.

[0084] In one embodiment, the catalytic transalkylation reaction temperature is 200-450°C, preferably 250-400°C;

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

[0086] The weight ratio of catalyst to raw oil is 2.0-12.0:1, preferably 3.0-9.0:1; and / or

[0087] The weight hourly space velocity is 1.0-20.0 h -1 , preferably 2.0-10.0 h -1 .

[0088] The benzene-rich middle distillate is preheated to enter the first reactor, and the preheating temperature is 200-400°C, preferably 220-380°C.

[0089] In the present application, the reactor and the regenerator can be arranged in parallel or overlapped, and the fluidized bed of the fluidized bed reactor and the settler can be built-in or built-out; the spent catalyst can be stripped and lifted by using nitrogen and / or steam medium, and after the regenerated catalyst is stripped by nitrogen to remove oxygen and water, it is returned to the reaction stage for recycling.

[0090] In one embodiment, the oxygen-containing regeneration atmosphere is an air and / or oxygen atmosphere, preferably an oxygen-enriched and / or pure oxygen atmosphere.

[0091] The catalyst after reaction in the present application enters an oxygen-containing regeneration system for regeneration, and air and / or oxygen can be used for regeneration; preferably, oxygen-rich and / or pure oxygen regeneration. The flue gas after regeneration is partially or totally recycled back to the regenerator, and the high-temperature flue gas containing oxygen is not subjected to heat exchange or is subjected to partial heat exchange, and the temperature thereof is 300-600 DEG C, and part and / or all of the flue gas is returned to the regenerator for recycling, so that the oxygen in the flue gas is fully utilized, and the high regeneration temperature and high regenerator temperature are maintained.

[0092] In one embodiment, the regeneration temperature of the regenerator is 500-800 DEG C, preferably 550-700 DEG C;

[0093] The regeneration pressure of the regenerator is 0.2-5.0 MPa, preferably 0.5-5.0 MPa; and / or

[0094] The flue gas temperature recycled back to the regenerator is 300-600 DEG C.

[0095] The method for producing low-benzene-content gasoline by catalytic transalkylation provided by the present application can be coupled with catalytic cracking of heavy oil such as wax oil and residual oil, and the benzene-rich gasoline intermediate fraction is reacted with the heavy oil in two different reactors; the benzene-rich gasoline intermediate fraction is reacted in a fluidized bed reactor, a moving bed reactor or a fixed bed reactor, and the catalyst after reaction is introduced into a heavy oil catalytic cracking riser fluidized bed reactor, and the two different reactions use the same regenerator and oil gas separation system.

[0096] The present application provides a method for producing low-benzene-content gasoline by catalytic transalkylation, comprising:

[0097] (1) catalytic cracking of heavy oil in a second reactor to obtain a second mixture containing second spent catalyst and second oil gas;

[0098] (2) oil gas separation of the second mixture in an oil gas separation system to obtain dry gas component, liquefied gas component and gasoline component;

[0099] (3) distillation of the gasoline component in a gasoline distillation system to obtain self-produced gasoline benzene-rich fraction and low-benzene-content gasoline;

[0100] (4) self-produced gasoline benzene-rich fraction and optional other gasoline benzene-rich fraction are introduced into a first reactor to contact with a fraction rich in heavy aromatic hydrocarbons injected in stages under non-hydrogen or hydrogen conditions to perform catalytic transalkylation reaction, and a first mixture containing first spent catalyst and first oil gas is obtained;

[0101] (5) the first mixture passes through an 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;

[0102] (6) the separated first spent catalyst is mixed with the second spent catalyst in a second reactor, and after being stripped by a steam stripper of the second reactor, is introduced into a regenerator for oxygen-containing regeneration, and the regenerated catalyst is returned to the first reactor and the second reactor for recycling, preferably, part or all of the flue gas after regeneration is recycled back to the regenerator;

[0103] The heavy oil is wax oil and / or residual oil.

[0104] The benzene content of the low-benzene-content gasoline is less than 1.0 wt%, preferably less than 0.8 wt%.

[0105] The heavy aromatics in the heavy-aromatics-rich fraction refer to C9-C10 monocyclic heavy aromatics.

[0106] In one embodiment, the benzene-rich gasoline fraction is an intermediate fraction with a distillation range of 60-90 DEG C obtained by distillation cutting of the benzene-rich gasoline;

[0107] The benzene content of the benzene-rich gasoline is 0.8-40 wt%.

[0108] 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 DEG C.

[0109] The application will be further described in detail by way of examples. The raw materials used in the examples can be obtained by commercial purchase.

[0110] The following examples will further illustrate the method, but do not limit the method.

[0111] The full-range gasoline raw material A1 used in the examples is catalytic cracking gasoline from a certain refinery, the benzene-rich fraction raw material oil B is obtained by distillation cutting of A1, the heavy-aromatics-rich fraction raw material A2 is catalytic cracking light diesel oil from a certain refinery, and the heavy raw material oil C is hydrocracking residual oil from a certain refinery. The properties of the four raw material oils are shown in Table 1.

[0112] The catalyst used in the examples is the same, and its preparation method is briefly described as follows:

[0113] 1) 5.1 kg of high-water-content kaolin (Suzhou Porcelain Clay Company industrial product, solid content 71.6 wt%) is slurried with 28.4 kg of de-cationic water, and then 3.4 kg of pseudo-boehmite (Shandong Aluminum Factory industrial product, solid content 63 wt%) is added to be slurried, to obtain a slurry with a solid content of 5-30 wt%; then the PH is adjusted to 2-4 with hydrochloric acid, and stirred uniformly, and then aged at 60-70 DEG C for 1 hour to obtain a mixed carrier slurry.

[0114] 2) Spray forming: 18 kg of MOR hydrogen type mordenite powder (industrial product of Yingkou Zhongbao Molecular Sieve Co., Ltd., SiO2 / Al2O3 = 22-25, solid content 91.9%) and 48 kg of de-cation water were mixed with a solid-liquid ratio of 1:1-1:10 to form a slurry, which was added to the mixed carrier slurry obtained in step 2), stirred uniformly, and 4.4 kg of aluminum sol (produced by SINOPEC Qilu Catalyst Co., Ltd., Al2O3 content 21.7 wt%, wherein the ratio of catalyst solid content to aluminum sol solid content (calculated as Al2O3) was 10-50:1) was added, and the mixture was placed in a binder to continue stirring until a uniform sol was formed; the sol was left in the air for 4 hours and spray dried to form microspheres. The tail gas temperature was generally controlled at 250-300°C, and the spray pressure was 50-60 atm to obtain a microspherical catalyst.

[0115] 3) Calcination of microspherical catalyst: the microspherical catalyst formed by spray drying was calcined at 500-800°C for 3 hours to obtain a catalyst, which was denoted as CAT-A. +

[0116] The average particle size of CAT-A was 40-100 μm, which was used as a fluidized bed transalkylation catalyst. The dry basis composition of the catalyst was 71.51 wt% MOR structure medium pore zeolite, 9.09 wt% pseudo-boehmite, 4.05 wt% aluminum sol, and 15.35 wt% kaolin. The properties are listed in Table 2.

[0117] The heavy oil catalytic cracking catalyst was a CGP special catalyst produced by SINOPEC Qilu Catalyst Co., Ltd., which contained ZSM-5 molecular sieve and Y molecular sieve. The properties are listed in Table 2.

[0118] Example 1

[0119] This example was tested according to the process shown in Figure 1 , using the feed oil B in Table 1, i.e., a benzene-rich fraction of catalytic cracking gasoline, as the raw material, and the CAT-A catalyst was used for the transalkylation reaction with the heavy aromatic fraction injected in stages in a dense phase fluidized bed reactor.

[0120] 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 a gasoline light fraction la containing no aromatic hydrocarbons, an intermediate fraction lb rich in benzene, and a heavy fraction lc rich in aromatic hydrocarbons, wherein the intermediate fraction lb rich in benzene was generally controlled to have a distillation range of 60-90°C, and the benzene content in the gasoline was enriched to more than 50%.

[0121] ​The benzene-rich gasoline intermediate fraction lb is fed into the lower part of the fluidized bed reactor I to contact the catalyst and undergo transalkylation with the single-ring heavy aromatics injected from the bottom, middle and upper parts of the reactor. The spent catalyst is separated from the oil gas and regenerated. The flue gas from the regeneration is partially recycled back to the regenerator. The process flow is as follows:

[0122] The benzene-rich gasoline fraction 1 is fed into the lower part of the reactor I to contact the catalyst and undergo transalkylation with the single-ring heavy aromatics stream I2 fed from the bottom of the reactor. A fluidizing medium 3 can be injected into the bottom of the reactor as needed for catalyst fluidization. After the first stage of reaction, the single-ring heavy aromatics stream II 4 and the single-ring heavy aromatics stream III 5 are injected into the middle and upper parts of the reactor to further contact the benzene-rich gasoline fraction 1 and strengthen the transalkylation of benzene and heavy aromatics. The spent catalyst is separated from the oil gas through the oil catalyst filter separator IV. After settling, the separated catalyst is fed into the gas stripper 24 through the spent catalyst delivery line I 10, stripped with nitrogen and / or steam, and then fed into the regenerator II through the spent catalyst delivery line II 11. The spent catalyst is regenerated in the regenerator under an oxygen-containing atmosphere. The oxygen-containing regeneration gas 15 includes air, oxygen, etc. The regeneration temperature is 500-700°C. The regenerated catalyst is returned to the reactor I through the regenerated catalyst delivery line I 12 and the regenerated catalyst delivery line II 13 for recycling. Part of the flue gas 16 from the regeneration is recycled back to the regenerator through the flue gas circulation line 17. The separated reaction oil gas is fed into the oil gas separation system III through the reaction oil gas line 6 to obtain the product dry gas 7, liquefied gas 8 and gasoline 9.

[0123] The FCC gasoline feedstock oil A1 is distilled in a rectifying column with 30 trays (theoretical tray number 18) to obtain the benzene-rich 60-90°C intermediate fraction as the feedstock oil B with a yield of 16.0%. The cutting method has an energy consumption of 21.59 kgEO / t of feedstock.

[0124] The feedstock oil B is preheated to 250°C and then fed into the lower part of the dense-phase fluidized bed reactor I to undergo transalkylation with the heavy aromatics fraction fed from the bottom of the reactor. Under a reaction pressure of 1.5 MPa, nitrogen is used as the fluidizing medium, which flows from bottom to top. The heavy aromatics fraction A2 is injected into the lower, middle and upper parts of the reactor in three stages to maintain the molar ratio of heavy aromatics to benzene in the reaction system at no less than 1:1. The reaction temperature is 300°C, the weight ratio of catalyst to feedstock oil is 3.1, the weight hourly space velocity is 5.0 h-1, and the transalkylation reaction time is 30 minutes. The reaction oil gas is separated from the spent catalyst through the oil catalyst filter separator IV. After settling, the separated catalyst is fed into the gas stripper 24 through the spent catalyst delivery line I 10, stripped with nitrogen and / or steam, and then fed into the regenerator II through the spent catalyst delivery line II 11. The spent catalyst is regenerated in the regenerator under an oxygen-containing atmosphere. The oxygen-containing regeneration gas 15 includes air, oxygen, etc. The regeneration temperature is 500-700°C. The regenerated catalyst is returned to the reactor I through the regenerated catalyst delivery line I 12 and the regenerated catalyst delivery line II 13 for recycling. Part of the flue gas 16 from the regeneration is recycled back to the regenerator through the flue gas circulation line 17. The separated reaction oil gas is fed into the oil gas separation system III through the reaction oil gas line 6 to obtain the product dry gas 7, liquefied gas 8 and gasoline 9. -1The alkyl transfer reaction was carried out under the conditions; after the reaction, the oil separation was carried out, the separated reaction oil gas was subjected to product separation through the separation system to obtain dry gas, liquefied gas, gasoline and diesel products; the spent catalyst after the oil separation was subjected to stripping with nitrogen to remove the oil gas adsorbed in the spent catalyst, and then was sent into the regenerator, and the oxygen was used as the regeneration gas to contact with the spent catalyst at the regeneration temperature of 550°C to carry out the regeneration; the regenerated catalyst was recycled, and the flue gas after the regeneration was partially recycled, the circulating flue gas temperature was 400°C, and the dense phase temperature of the regeneration was maintained at 550°C. The operating conditions and product distribution are listed in Table 3.

[0125] As can be seen from Table 3, in Example 1, the benzene-rich fraction of the catalytic cracking gasoline with the benzene content of 7.68% and the octane value RON 83.6 was subjected to the alkyl transfer reaction with the catalytic cracking light diesel oil rich in heavy aromatics in the dense phase fluidized bed reactor, the benzene conversion rate was 97.09%, the gasoline yield was 61.99%, the benzene content of the gasoline was reduced to 0.18%, the octane value RON 88.5 was increased by 4.9 units, and the gasoline yield growth rate (the calculation formula (the gasoline yield-the percentage of gasoline in the raw material) / the percentage of gasoline in the raw material*100%, the same below) reached 23.98%.

[0126] Comparative Example 1

[0127] The alkyl transfer reaction was carried out by using the benzene-rich fraction B and the heavy aromatics fraction A2 obtained by cutting the catalytic cracking gasoline as the raw materials, using the same catalyst and process conditions as in Example 1, different in that: 1) the riser reactor was used in Comparative Example 1; 2) the benzene-rich fraction was only injected once at the bottom of the reactor; 3) the air was used as the regeneration gas, and the flue gas was not recycled; 4) in order to maintain the same process conditions as in Example 1, the combustion oil needed to be sprayed in the regenerator to provide heat. The operating conditions and product distribution are listed in Table 3.

[0128] As can be seen from Table 3, compared with Comparative Example 2 (the benzene-rich fraction after the gasoline cutting was mixed with the heavy aromatics fraction in the riser reactor for the alkyl transfer), in Example 2 (the benzene-rich fraction after the gasoline cutting was mixed with the heavy aromatics fraction injected in stages in the dense phase fluidized bed for the alkyl transfer), the benzene conversion rate was increased by 70.28 percentage points, the benzene content of the gasoline was reduced by 4.63 percentage points, and the gasoline yield was increased by 7.22 percentage points.

[0129] Example 2

[0130] This example was tested according to the process of Figure 2 The heavy raw material oil C in Table 1 was used as the raw material, the catalytic cracking gasoline D obtained by cracking the heavy raw material oil C was subjected to high-precision distillation cutting to obtain the gasoline benzene-rich fraction E, and the heavy raw material oil C and the gasoline benzene-rich fraction E were respectively subjected to tests in the riser reactor and the dense phase fluidized bed reactor, and the catalysts CGP and CAT-A were respectively used.

[0131] Figure 2 The process flow of Example 2 is shown in the figure, which is the same as that of Example 1 in that the gasoline benzene-rich fraction and the heavy aromatic fraction are subjected to transalkylation in the dense phase fluidized bed reactor I, and different from that of Example 1 in that the heavy oil feedstock 19 enters the conventional riser reactor, and the catalysts after the benzene and heavy aromatic transalkylation and the catalysts after the heavy oil catalytic cracking can each be subjected to gas stripping and then enter the same regenerator, or can share a settler for gas stripping, and in this example, both of them use one settler. The process flow is as follows:

[0132] The heavy oil feedstock 19 is subjected to steam atomization and then enters the lower part of the cracking reactor VI to contact the catalytic cracking catalyst for cracking reaction; the separated reaction oil gas enters the oil gas separation system III through the oil gas pipeline 6 for product separation to obtain dry gas 7, liquefied gas 8, gasoline 9, diesel 22 and oil slurry 23; the gasoline 9 is separated into the self-produced gasoline benzene-rich fraction 25 and the low-benzene gasoline 26 after rectification in the gasoline rectification tower V, and the self-produced gasoline benzene-rich fraction 25 is partially recycled or not returned to the reactor I as needed, and the low-benzene gasoline 26 after rectification is taken out of the device for use in the gasoline pool blending. The benzene-rich middle fraction 1b of the self-produced gasoline benzene-rich fraction 25 and the optional benzene-rich gasoline from the rectification tower is fed into the reactor I at the lower part of the reactor to contact the catalyst and the single-ring heavy aromatic stream I2 fed from the bottom of the reactor for transalkylation; after the first stage of reaction, it is further contacted with the single-ring heavy aromatic stream II 4 and the single-ring heavy aromatic stream III 5 injected from the middle and upper parts of the reactor to strengthen the transalkylation of benzene; the spent catalyst and the oil gas after the transalkylation reaction are separated by the oil catalyst filter separator IV, the separated catalyst is settled and then enters the heavy oil cracking reactor VI through the spent catalyst conveying pipeline I 10, and then is subjected to gas stripping in the gas stripping exchanger 24 by nitrogen and / or steam 14 and then enters the regenerator II through the spent catalyst conveying pipeline II 11; the spent catalyst is regenerated in the regenerator II in an oxygen-containing atmosphere, the oxygen-containing regeneration gas 15 includes air, oxygen and the like, the regeneration temperature is 600-800°C, and the regenerated catalyst is recycled for use, the regenerated catalyst is conveyed to the heavy oil cracking reactor VI through the regenerated catalyst conveying pipeline I 12 and to the reactor I through the regenerated catalyst conveying pipeline II 13; the separated reaction oil gas enters the oil gas separation system III through the oil gas pipeline 6 for product separation. It is to be noted that the transalkylation catalyst is supplemented into the reactor I through the catalyst supplementing pipeline 18, and since the transalkylation catalyst is also a propylene agent or octane improver for heavy oil cracking, the amount of the transalkylation catalyst entering the heavy oil cracking reactor needs to meet the requirements of benzene transalkylation and heavy oil cracking.

[0133] The heavy feed oil, preheated to 200°C, is introduced into the bottom of the riser reactor and contacted with the catalytic cracking catalyst to perform the cracking reaction. The water vapor is used as the fluidizing and atomizing medium. The fluidizing medium flows upward at a reaction pressure of 0.35 MPa. The cracking reaction is performed at a reaction temperature of 540°C (the temperature at the upper part of the reactor, i.e. the outlet temperature, is the same below), a weight ratio of the catalyst to the feed oil of 7.4, and a weight hourly space velocity of 20.0 h -1 The heavy feed oil, preheated to 200°C, is introduced into the bottom of the riser reactor and contacted with the catalytic cracking catalyst to perform the cracking reaction. The water vapor is used as the fluidizing and atomizing medium. The fluidizing medium flows upward at a reaction pressure of 0.35 MPa. The cracking reaction is performed at a reaction temperature of 540°C (the temperature at the upper part of the reactor, i.e. the outlet temperature, is the same below), a weight ratio of the catalyst to the feed oil of 7.4, and a weight hourly space velocity of 20.0 h

[0134] The gasoline D obtained by catalytic cracking of the heavy feed oil is subjected to high-precision distillation cutting in a rectifying column 1 with 30 trays (theoretical tray number 15) and a rectifying column 2 with 50 trays (theoretical tray number 25). The light gasoline fraction at the bottom of the rectifying column 1 is introduced into the rectifying column 2, and the 60-90°C middle fraction rich in benzene, i.e. the gasoline benzene-rich fraction E, is drawn out at the top of the rectifying column 2. The yield of the gasoline benzene-rich fraction E accounts for 29.4% of the catalytic cracking gasoline D. The cutting mode consumes 14.66 kg EO / t of feed. The properties of the catalytic cracking gasoline D and the gasoline benzene-rich fraction E are shown in Table 1.

[0135] The gasoline benzene-rich fraction E, preheated to 300°C, is introduced into the lower part of the dense-phase fluidized bed reactor I, and the hydrogen is used as the fluidizing medium to perform the transalkylation reaction with the diesel fraction rich in heavy aromatic hydrocarbons from the feed at the bottom of the reactor. The fluidizing medium flows upward at a reaction pressure of 0.5 MPa. The heavy aromatic hydrocarbon fraction is injected into the lower, middle and upper three regions of the reactor in three times, and the molar ratio of the heavy aromatic hydrocarbons to benzene in the reaction system is maintained to be not less than 1:1. The transalkylation reaction is performed at a reaction temperature of 350°C, a weight ratio of the catalyst to the feed oil of 3.1, and a weight hourly space velocity of 2.5 h -1 The transalkylation reaction is performed under the above conditions, and the oil-agent separation is performed after the reaction.

[0136] The separated reaction oil gas is introduced into the oil-gas separation system through the oil-gas pipeline to obtain the product dry gas, liquefied gas, gasoline, diesel and oil slurry. The gasoline is separated into the self-produced benzene-rich gasoline and the low-benzene gasoline in the gasoline rectifying column, and part of the self-produced benzene-rich gasoline is recycled or not recycled into the reactor as needed.

[0137] The reaction oil gas after the transalkylation reaction of the gasoline benzene-rich fraction and the heavy aromatic hydrocarbons is introduced into the settling section of the heavy feed oil catalytic cracking reactor, and is sent into the regenerator after being stripped by the water vapor to remove the oil gas adsorbed inside. The air is used as the regeneration gas to perform the regeneration with the spent catalyst at a regeneration dense-phase temperature of 680°C. The regenerated catalyst is recycled, and the flue gas after the regeneration is not recycled.

[0138] The operating conditions and product distribution are shown in Table 4.

[0139] As can be seen from Table 4, in Example 2, the benzene content of the gasoline is 7.72%, the octane number RON of the gasoline is 82.4, the benzene conversion rate is 96.85% after the benzene-rich fraction of the gasoline is subjected to the staged transalkylation with the heavy aromatic diesel fraction, the benzene content of the gasoline is reduced to 0.20%, the octane number RON of the gasoline is increased to 88.5, and the gasoline yield is as high as 60.31%; the gasoline benzene-rich fraction and the heavy aromatic diesel fraction are subjected to the transalkylation as a recycle, which is not included in the raw material, then the liquefied gas yield of the heavy oil catalytic cracking is 28.13 wt%, the gasoline yield is 37.29 wt%, the olefin content of the gasoline is 8.88 wt%, the benzene content of the gasoline is 0.27 wt%, and the octane number RON is 100.1.

[0140] Comparative Example 2

[0141] By using the same heavy oil C as the raw material, the same heavy oil cracking catalyst and process conditions as in Example 2, the only difference is that: 1) the gasoline obtained by cracking the heavy oil raw material in Comparative Example 2 is not cut; 2) the heavy aromatic fraction is mixed with the heavy oil in the riser reactor at one time. The operating conditions and product distribution are listed in Table 4.

[0142] As can be seen from Table 4, the benzene content of the gasoline in Example 2 (the benzene-rich fraction of the gasoline obtained by cutting the heavy oil cracking is subjected to the staged transalkylation with the heavy aromatic fraction injected in the dense phase fluidized bed) is 1.70 percentage points lower than that in Comparative Example 2 (the heavy oil is mixed with the heavy aromatic fraction in the riser reactor at one time).

[0143] The above describes the present application in combination with the preferred embodiments, but these embodiments are only exemplary and are used for illustration 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.

[0144] Table 1

[0145]

[0146]

[0147] Table 2

[0148]

[0149]

[0150] Table 3

[0151] Example 1 Comparative Example 1 Feed oil B A Reactor type Dense fluidized bed Riser Catalyst name CAT-A CAT-A Reaction operating conditions Feed oil preheating temperature, °C 250 250 Lower part of reactor temperature, °C 300 300 Middle part of reactor temperature, °C 300 300 Upper part of reactor temperature, °C 300 300 Reaction pressure, MPa 1.5 1.5 Weight ratio of catalyst / feed oil 3.1 3.1 Molar ratio of heavy aromatics / benzene 0.5*3 1.5 Hourly space velocity, h -1 ]] 5.0 5.0 Regenerator dense phase temperature, °C 550 550 Regeneration pressure, MPa 1.5 1.5 Regeneration flue gas circulation ratio, % 50 - Circulation flue gas temperature, °C 400 - Product yield, wt% Dry gas 0.19 0.28 Liquefied gas 0.93 0.20 Gasoline 61.99 58.38 Diesel oil 33.51 35.74 Coke 3.38 5.41 Gasoline properties Olefin content, wt% 3.79 3.43 Aromatic content, wt% 40.51 41.72 Benzene content, wt% 0.18 4.81 RON 88.5 88.4 MON 83.1 82.9 Benzene conversion, % 97.09 26.81 Gasoline yield increase ratio, % 23.98 16.76

[0152] Table 4

[0153]

[0154] Table 1 indicates data obtained from samples taken at the outlet of the catalytic cracking oil agent separator of the riser reactor and analyzed (on a feed oil C basis)

[0155] Table 2 indicates data obtained from samples taken at the outlet of the oil agent filtering separator of the moving bed reactor and analyzed (on a gasoline rich in benzene fraction E basis)

[0156] Table 3 indicates the overall data of Example 2 (on a feed oil C basis).

Claims

1. A method for reducing the benzene content in gasoline by catalytic alkyl transfer, characterized in that, The method includes: (1) Distillation of benzene-rich gasoline yields a benzene-rich gasoline middle fraction with a distillation range of 60~90℃; (2) The benzene-rich gasoline middle fraction enters the first reactor and is contacted with the fraction rich in heavy aromatics injected in stages under non-hydrogen or hydrogen-containing conditions to carry out a catalytic alkyl transfer reaction, thereby obtaining a first mixture containing the first catalyst and the first oil and gas; (3) The first mixture is separated by passing it through the oil separation filter of the first reactor. The separated first oil and gas enter the oil and gas separation system for product separation to obtain products including dry gas, liquefied gas and gasoline. (4) The first catalyst to be generated is stripped by a steam exchanger and then enters a regenerator for oxygen regeneration. The regenerated catalyst is returned to the first reactor for recycling. The benzene-rich gasoline has a benzene content of 0.8-40 wt%; the heavy aromatics-rich fraction contains 20-100 wt% C9-C10 monocyclic heavy aromatics. In step (2), the molar ratio of the heavy aromatic hydrocarbon to benzene is maintained at 0.3 to 5.

0.

2. The method according to claim 1, characterized in that, In step (2), the molar ratio of the heavy aromatic hydrocarbon to benzene is maintained at 0.5 to 2.

0.

3. The method according to claim 1, characterized in that, In step (4), the regenerated flue gas is partially or completely recycled back to the regenerator.

4. The method according to claim 1, characterized in that, The fractions rich in heavy aromatics are catalytic cracking gasoline fractions, catalytic cracking diesel fractions, hydrocracking gasoline fractions, hydrocracking diesel fractions, reformed gasoline fractions, reformed diesel fractions, steam cracking gasoline fractions, and / or steam cracking diesel fractions with boiling points of 150~240℃.

5. The method according to claim 1, characterized in that, The catalytic alkyl transfer reaction temperature is 200~450℃; The reaction pressure is 0.1~5.0 MPa; The catalyst to feedstock weight ratio is 2.0~12.0:1; and / or The weight hourly space velocity is 1.0~20.0 h. -1 .

6. The method according to claim 5, characterized in that, The catalytic alkyl transfer reaction temperature is 250~400℃; The reaction pressure is 0.5~4.0 MPa; The catalyst to feedstock weight ratio is 3.0~9.0:1; and / or The weight hourly space velocity is 2.0~10.0 h. -1 .

7. The method according to claim 1, characterized in that, The first reactor is selected from a fluidized bed reactor, a moving bed reactor, or a fixed bed reactor; and / or The first reactor is equipped with three or more heavy aromatic hydrocarbon injection ports in sections.

8. The method according to claim 7, characterized in that, The first reactor is a moving bed reactor.

9. The method according to claim 1, characterized in that, The distillation and cutting of benzene-rich gasoline is carried out using one or more distillation columns.

10. The method according to claim 9, characterized in that, The total theoretical number of plates in the distillation column is greater than or equal to 14.

11. The method according to claim 1, characterized in that, The catalyst comprises mesoporous molecular sieves and heat-resistant inorganic oxides, wherein the mesoporous molecular sieves account for 30-80% of the total catalyst weight.

12. The method according to claim 11, characterized in that, The mesoporous molecules are screened from the mordenite series, ZSM series, and / or Y series mesoporous zeolites; and / or The heat-resistant inorganic oxide is aluminum oxide and / or silicon oxide.

13. The method according to claim 12, characterized in that, The mesoporous molecular sieve is a mordenite series mesoporous zeolite or a composite molecular sieve containing mordenite series mesoporous zeolite.

14. The method according to claim 1, characterized in that, The benzene-rich gasoline is catalytic cracked gasoline, hydrocracking gasoline, reformed gasoline, and / or steam cracking gasoline with a boiling point of 30~220℃; and / or The benzene-rich intermediate fraction is preheated before entering the first reactor at a temperature of 200-400°C.

15. The method according to claim 14, characterized in that, The benzene-rich intermediate fraction is preheated before entering the first reactor at a temperature of 220-380°C.

16. The method according to claim 1, characterized in that, The oxygen-containing regeneration atmosphere is an air and / or oxygen atmosphere; The regeneration temperature of the regenerator is 500~800℃; The regeneration pressure of the regenerator is 0.2~5.0 MPa; and / or The flue gas temperature of the recirculating regenerator is 300~600℃.

17. The method according to claim 16, characterized in that, The oxygen-containing regeneration atmosphere is an oxygen-rich and / or pure oxygen atmosphere; The regeneration temperature of the regenerator is 550~700℃; The regeneration pressure of the regenerator is 0.5~5.0MPa.

18. A method for producing low-benzene-content gasoline by catalytic alkyl transfer, characterized in that, The method includes: (1) Catalytic cracking of heavy oil in the second reactor to obtain a second mixture containing the second catalyst and the second oil gas; (2) The second mixture is separated into dry gas, liquefied gas and gasoline components in an oil-gas separation system. (3) The gasoline components are distilled in a gasoline distillation system to obtain a benzene-rich fraction of self-produced gasoline and a low-benzene gasoline; (4) The benzene-rich fraction of self-produced gasoline and other benzene-rich fractions of gasoline enter the first reactor and are contacted with the fraction rich in heavy aromatics injected in stages under non-hydrogen or hydrogen-containing conditions to carry out catalytic alkyl transfer reaction, so as to obtain the first mixture containing the first catalyst and the first oil and gas, and the molar ratio of the heavy aromatics to benzene is maintained at 0.3~5.

0. (5) The first mixture is separated by passing it through the oil separation filter of the first reactor, and the separated oil and gas enter the oil and gas separation system for oil and gas separation; (6) The first catalyst to be generated separated enters the second reactor and is mixed with the second catalyst to be generated. After being stripped by the steam exchanger of the second reactor, it enters the regenerator for oxygen regeneration. The regenerated catalyst is returned to the first reactor and the second reactor for recycling. The heavy oil is wax oil and / or residue oil, and the benzene-rich gasoline fraction is obtained by distillation and cutting of benzene-rich gasoline to obtain a benzene-rich middle fraction with a distillation range of 60~90℃. The benzene-rich gasoline has a benzene content of 0.8 to 40 wt%.

19. The method according to claim 18, characterized in that, In step (6), the regenerated flue gas is partially or completely recycled back to the regenerator.

20. The method according to claim 18, characterized in that, The benzene-rich gasoline is catalytic cracking gasoline, hydrocracking gasoline, reformed gasoline, and / or steam cracking gasoline with a boiling point of 30~220℃.

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