Method for reducing benzene content in gasoline and method for producing gasoline with low benzene content

Abstract

The invention provides a method for reducing benzene content in gasoline by catalyzing transalkylation and a method for producing gasoline with low benzene content. The method comprises the following steps: performing high-precision distillation cutting on benzene-rich gasoline to obtain gasoline light fraction, middle fraction and heavy fraction; a gasoline middle fraction rich in benzene and gasoline and diesel oil fractions rich in C9 and C10 monocyclic heavy aromatics which are injected in a graded manner enter a fluidized bed or moving bed or fixed bed reactor to be in contact with a mesoporous molecular sieve catalyst for catalytic transalkylation reaction, so that benzene and heavy aromatics are efficiently converted into xylene and the like; therefore, the benzene-rich gasoline and the catalytic cracking light diesel oil are converted into the high-octane-number low-benzene gasoline. According to the method, the benzene content and the olefin content in the gasoline are reduced, meanwhile, the octane number of the gasoline is increased, the problem that refinery gasoline is high in benzene content and difficult to meet the national VI standard of automotive gasoline is solved, the diesel-gasoline ratio of a catalytic cracking device is reduced, and the yield of high-quality gasoline is increased.

Description

Technical Field

[0001] The invention relates to the field of catalytic conversion of gasoline to benzene, and in particular to a method for reducing the benzene content in gasoline by catalytic alkyl transfer and a method for producing gasoline with low benzene content. Background Art

[0002] In recent years, with the implementation of the National VI clean gasoline standard, not only has the olefin content limit of automotive gasoline been reduced from 24v% of National V to 18v% in National VI a stage and 15v% in National VI b stage, and the aromatic content limit has been reduced from 40v% of National V to 35v%, but the benzene content limit has also been tightened, from 1.0v% of National V to 0.8v%, even stricter than the EU 1.0v%. The benzene in the gasoline pool mainly comes from reformed gasoline and catalytic cracking gasoline that have not been extracted with benzene. The benzene content of reformed gasoline is relatively high, generally 2-10% by weight, 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% 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. Because of the high benzene content, benzene is generally extracted and used as a chemical material.

[0003] With the deterioration of catalytic cracking raw materials and the strong demand for producing more liquefied gas and processing catalytic diesel, the severity of the reaction has continued to increase, further leading to a high benzene content in catalytic cracking gasoline. Taking Tianjin Petrochemical and Jinan Refining as examples, their catalytic cracking units are processing residual oil raw materials while processing hydrogenated catalytic diesel and straight-run diesel. When implementing the high-production liquefied gas plan, the benzene content of the stable gasoline produced is as high as 1.4% by weight, and the volume fraction of gasoline benzene is higher than 1.2v%. The excessive benzene content in catalytic cracking gasoline has seriously restricted the catalytic cracking unit from processing catalytic diesel and increasing the production of liquefied gas according to market demand. Therefore, in the process of chemical transformation and structural adjustment, refineries need to deal with gasoline upgrades and reduce benzene in catalytic cracking gasoline without delay.

[0004] At present, mature gasoline benzene reduction schemes are mainly carried out on reformed gasoline, such as physical separation methods such as distillation, extraction, and adsorption, as well as chemical methods such as benzene hydrogenation saturation and alkylation. North American countries such as the United States have stricter restrictions on benzene (<0.6v%) because benzene is carcinogenic, and usually use physical separation + chemical conversion methods to reduce benzene. There are usually two technical routes for reducing benzene by hydrogenation saturation of aromatic rings in reformed gasoline benzene fractions and alkylation.

[0005] Hydrogenation saturation aromatic ring benzene reduction technologies include CD Tech's catalytic distillation hydrogenation saturation benzene reduction (CD Hydro) process that combines a hydrogenation reactor with a product stripper, UOP's Bensat process using a Pt-based catalyst, IFP and Axens' Benfree process, GTC's GT-BenZapSM process, and Neste's NExSAT process. The hydrogenation saturation route for benzene-containing fractions has problems with gasoline octane number loss and high hydrogen consumption, and needs to be combined with isomerization to compensate for the octane number loss. Only about 20 sets of hydrogenation saturation benzene reduction units are in use.

[0006] The main technologies for alkylation benzene reduction in reformed gasoline containing benzene include the MBR dense phase fluidized bed process developed by Mobil and the liquid phase alkylation BenzOUTTM process developed by ExxonMobil. The alkylation benzene reduction is more mainstream abroad, with more than 90 commercial applications. Among them, hydrogenation saturation benzene reduction and liquid phase alkylation benzene reduction are not suitable for benzene reduction in catalytic cracking gasoline with high olefin content. Currently, only the MBR dense phase fluidized bed process can achieve mixed feed of reformed oil benzene-rich fraction and catalytic cracking light gasoline. Using a dense phase fluidized bed and a dedicated ZSM-5 catalyst, the raw material is the reformed oil benzene-rich fraction, and the olefin is a light olefin resource such as catalytic cracking dry gas. Under typical gas phase alkylation conditions (operating pressure of 1.2-1.5MPa and temperature of 350℃), the single-pass conversion rate of benzene is 60%-70%. If the material is partially recycled, the total conversion rate can reach 90%. Since 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 technology for producing ethylbenzene by alkylation of dry gas and benzene in China, but it mainly utilizes pure benzene and ethylene in dry gas to produce ethylbenzene or styrene.

[0007] Transalkylation reactions are mostly used to produce xylenes from toluene and heavy aromatics. For example, CN00119767.3 published a method for the disproportionation of toluene and the transalkylation of heavy aromatics. CN201510674618.0 published a method for increasing the production of xylene by lightening heavy aromatics over two supported metal catalysts under hydrogen conditions. CN01131953.4 and AU2002344025A1 published methods for the selective disproportionation of toluene and the disproportionation and transalkylation of toluene and C9 and above aromatics. There are few patent technologies for the transalkylation of benzene and heavy aromatics. CN01105840.4 discloses a method for the transalkylation of benzene and heavy aromatics. In a fixed bed reactor, hydrogen-type mordenite, β-zeolite or Y-zeolite loaded with bismuth and at least one metal or oxide selected from iron, cobalt, nickel or molybdenum is used as a catalyst to react at a temperature of 300-600°C and a pressure of 1.5-6.0 MPa to produce C7-C9 aromatics and C1-C4 paraffins.

[0008] Patent CN201110109863.9 is directed to a method of contacting a benzene-rich fraction of reformed oil with C2-C4 olefins in the presence of an alkylation catalyst to carry out a transalkylation reaction, and then the polyalkylbenzene fraction obtained by the reaction is subjected to a transalkylation reaction with the benzene-rich fraction of reformed oil in the presence of a transalkylation catalyst.

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

[0010] Domestic and foreign patents for reducing benzene, as well as existing technologies for reducing benzene by hydrogenation saturation and liquid phase alkylation, are all aimed at reducing benzene in reformed gasoline fractions that are low in olefins and do not contain sulfur, nitrogen, or water. They are not suitable for reducing benzene in catalytic cracking gasoline that has high olefins, high sulfur, and nitrogen content, and has a lower benzene content than reformed gasoline. At present, there is no mature, low-cost, and efficient technology for reducing the benzene content in catalytic cracking gasoline at home and abroad. Therefore, the catalytic cracking unit has a problem of exceeding the stable benzene content in gasoline when executing the processing of hydrogenation catalytic diesel or the production of more liquefied gas, which is as high as 1.2v%. There is an urgent need to develop a production method for reducing the benzene content in gasoline. Summary of the invention

[0011] The object of the present invention is to provide a method for reducing benzene by alkylation of gasoline benzene and heavy aromatic hydrocarbons, thereby reducing the benzene content of gasoline while increasing the gasoline octane number and increasing the production of high-quality gasoline. Specifically, the present invention provides a method for producing low-benzene and low-olefin gasoline by catalytic alkylation of a gasoline intermediate fraction rich in benzene obtained by high-precision distillation and cutting and graded injection of heavy aromatic hydrocarbon fractions on a medium-pore molecular sieve catalyst, thereby increasing the gasoline octane number and increasing the production of xylene and high-quality gasoline.

[0012] A first aspect of the present invention provides a method for reducing the benzene content in gasoline by catalytic transalkylation, the method comprising:

[0013] (1) distilling and cutting the benzene-rich gasoline to obtain a benzene-rich gasoline middle distillate with a distillation range of 60 to 90° C.;

[0014] (2) the benzene-rich gasoline middle fraction enters the first reactor and contacts the catalyst with the graded injected heavy aromatics-rich fraction under non-hydrogenation or hydrogenation conditions to carry out a catalytic transalkylation reaction, thereby obtaining a first mixed material comprising a first spent catalyst and a first oil gas;

[0015] (3) allowing the first mixed material to pass through the oil separation filter of the first reactor for separation, and 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;

[0016] (4) the separated first catalyst to be regenerated is stripped in a steam exchanger and then enters a regenerator for oxygen-containing regeneration. The regenerated catalyst is returned to the first reactor for recycling. Preferably, part or all of the flue gas after regeneration is recycled back to the regenerator;

[0017] The benzene content of the benzene-rich gasoline is 0.8 to 40 weight percent; the content of carbon nine and carbon ten single-ring heavy aromatics in the heavy aromatics-rich fraction is 20 to 100 weight percent;

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

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

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

[0021] The reaction pressure is 0.1 to 5.0 MPa, preferably 0.5 to 4.0 MPa;

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

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

[0024] According to the method of the first aspect of the present invention, 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] The first reactor is provided with three or more heavy aromatic hydrocarbon injection ports in sections.

[0026] According to the method of the first aspect of the present invention, the distillation and cutting of the benzene-rich gasoline is carried out by using one or more distillation towers;

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

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

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

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

[0031] According to the method of the first aspect of the present invention, the benzene-rich gasoline is catalytic cracking gasoline, hydrocracking gasoline, reforming gasoline and / or steam cracking gasoline with a boiling point of 30 to 220° C.; and / or

[0032] The benzene-rich middle fraction is preheated before entering 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 invention, the atmosphere for oxygen-containing regeneration is air and / or oxygen atmosphere, preferably 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 to 5.0 MPa, preferably 0.5 to 5.0 MPa; and / or

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

[0037] A second aspect of the present invention provides a method for producing low-benzene gasoline by catalytic transalkylation, the method comprising:

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

[0039] (2) performing oil-gas separation on the second mixed material 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 components in a gasoline distillation system to obtain a self-produced gasoline benzene-rich fraction and a low-benzene gasoline;

[0041] (4) the self-produced gasoline benzene-rich fraction and any other gasoline benzene-rich fraction enter the first reactor and contact the catalyst with the fraction rich in heavy aromatics injected in stages under non-hydrogenation or hydrogenation conditions to perform a catalytic transalkylation reaction, thereby obtaining a first mixed material comprising a first spent catalyst and a first oil and gas;

[0042] (5) allowing the first mixed material to pass through the oil separation filter of the first reactor for separation, and the separated oil and gas enter the oil and gas separation system for oil and gas separation;

[0043] (6) The separated first catalyst to be regenerated enters the second reactor and is mixed with the second catalyst to be regenerated. After being stripped by the steam exchanger of the second reactor, it enters the regenerator for oxygen-containing regeneration. 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.

[0044] Wherein, the heavy oil is wax oil and / or residual oil.

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

[0046] Wherein, the benzene content of the benzene-rich gasoline is 0.8 to 40 weight %;

[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 to 220°C.

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

[0049] (1) The benzene-rich catalytic cracking gasoline is cut by high-precision distillation to obtain a benzene-rich gasoline intermediate fraction, which is then transalkylated with the graded injected catalytic cracking light diesel rich in monocyclic heavy aromatics on a medium-pore molecular sieve catalyst. The benzene conversion rate is high, the gasoline octane number is improved, the diesel-gasoline ratio of the catalytic cracking unit is reduced, and the production of high-quality gasoline is increased.

[0050] (2) After the reaction, the catalyst is regenerated and recycled, or fed into the heavy oil catalytic cracking reactor, which not only realizes continuous production but also can always maintain a high activity of the catalyst, thus solving the problem of catalyst deactivation caused by coking when processing high-olefin catalytic cracking gasoline or steam cracking gasoline.

[0051] (3) The regenerated flue gas is partially or completely circulated after heat exchange with the main air, which not only makes full use of the oxygen in the flue gas, but also solves the problem of the flue gas carrying heat out of the regeneration system, and reduces the emission of waste gases such as carbon dioxide, thus greatly saving energy and reducing emissions.

[0052] (4) It has a wide range of applications. It is not only suitable for benzene-containing reforming gasoline (benzene 2-10 wt%) with low olefin, low sulfur and low nitrogen content, but also can be used for catalytic cracking gasoline (benzene 0.8-3.0 wt%) with high olefin, high sulfur and high nitrogen content and relatively low benzene content, and steam cracking gasoline (benzene 20-40 wt%) with high olefin, high sulfur and high nitrogen content and also relatively high benzene content. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 The present invention is a schematic diagram of a process flow of a fluidized bed reactor for transalkylation of benzene and heavy aromatics, which is used to illustrate the continuous process of fluidized bed catalytic transalkylation of benzene-rich gasoline.

[0054] Figure 2 The present invention is a process flow diagram of a combined implementation method of a fluidized bed reactor for transalkylation of benzene and heavy aromatics and catalytic cracking of heavy oil, which is used to illustrate the coupled processing process of transalkylation of benzene-rich gasoline intermediate fraction and catalytic cracking light diesel and catalytic cracking of heavy oil.

[0055] Description of reference numerals:

[0056] I. Reactor; II. Regenerator; III. Oil-gas separation system; IV. Oil filter separator; V. Gasoline distillation system; VI. Heavy oil cracking reactor; VII. Distillation tower; 1. Benzene-rich gasoline; 1a. Light gasoline fraction without aromatics; 1b. Middle fraction rich in benzene; 1c. Heavy fraction rich in aromatics; 2. Single-ring heavy aromatics logistics I; 3. Fluidizing medium; 4. Single-ring heavy aromatics logistics II; 5. Single-ring heavy aromatics logistics III; 6. Reaction oil and gas pipeline dry gas; 7. Dry gas; 8. Liquefied gas; 9. Gasoline; 10. Regenerated agent delivery pipeline I; 11. Regenerated agent delivery pipeline II; 12. Regeneration agent delivery pipeline I; 13. Regeneration agent delivery pipeline II; 14. Gas lift medium; 15. Oxygen-containing regeneration gas; 16. Flue gas; 17. Flue gas circulation pipeline; 18. Additive pipeline; 19. Heavy crude oil; 20. Atomizing medium; 21. Pre-lifting medium; 22. Diesel; 23. Oil slurry; 23. Gasoline exchanger; 25. Self-produced gasoline benzene-rich fraction; 26. Low-benzene gasoline after distillation. DETAILED DESCRIPTION

[0057] The present application is further described in detail below through the accompanying drawings and embodiments. Through these descriptions, the characteristics and advantages of the present application will become clearer and more specific.

[0058] The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise noted.

[0059] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0060] The inventors of the present invention have found through years of research that: (1) the benzene content of high-benzene catalytic cracking gasoline is 0.8-2.0% by weight, which is mainly distributed in the gasoline middle distillate at 60-90°C. Therefore, the present invention uses distillation to cut the benzene-rich middle distillate for separate processing; (2) the heavy aromatics and benzene alkyl transfer requires maintaining a molar ratio of heavy aromatics to benzene of 0.3-5.0 to maintain a high benzene conversion rate; (3) the benzene-rich middle distillate of catalytic cracking gasoline has not only a high olefin content and a low octane number for reformed gasoline, but also a high sulfur and nitrogen content and a relatively low benzene content. Therefore, the present invention uses a medium-pore molecular sieve catalyst to catalyze the benzene and gasoline and diesel fractions of the benzene-rich middle distillate. The alkyl transfer of C9 and C10 heavy aromatics in the catalytic cracking gasoline can not only reduce the benzene content of the catalytic cracking gasoline, but also improve the gasoline octane number and increase the production of xylene. (4) The benzene-rich intermediate fraction of catalytic cracking gasoline has a high olefin content and is easily coked and deactivated during the alkyl transfer process. The coked catalyst can be regenerated by burning it in an oxygen atmosphere. After the reaction, the catalyst can be regenerated and recycled, which not only realizes continuous production but also keeps the catalyst at a high activity. (5) The flue gas after the regeneration of the coked catalyst is exchanged with the main air for heat, which not only makes full use of the oxygen in the flue gas, but also further solves the problem of the flue gas carrying heat out of the regeneration system and reduces the emission of waste gases such as carbon dioxide.

[0061] Based on the above findings, the present invention provides a method for reducing benzene by transalkylation by contacting a benzene-rich gasoline fraction with a gasoline and diesel fraction rich in carbon nine and carbon ten heavy aromatics with a medium-porous molecular sieve catalyst, that is, high-precision distillation and cutting of the benzene-rich gasoline obtains a benzene-rich gasoline intermediate fraction, which then enters a fluidized bed, moving bed or fixed bed reactor, contacts the medium-porous molecular sieve catalyst in the absence of hydrogen or in the presence of hydrogen, and performs a catalytic transalkylation reaction at a suitable temperature and pressure; the coked deactivated catalyst is regenerated in an oxygen-containing regeneration system, and part and / or all of the regenerated high-temperature flue gas is returned to the regenerator; thereby achieving the self-thermal balance of the gasoline benzene transalkylation reaction regeneration continuously, achieving a higher conversion rate of benzene under a high-activity catalyst, and achieving efficient and continuous production.

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

[0063] (1) distilling and cutting the benzene-rich gasoline to obtain a benzene-rich gasoline middle distillate with a distillation range of 60 to 90° C.;

[0064] (2) the benzene-rich gasoline middle fraction enters the first reactor and contacts the catalyst with the graded injected heavy aromatics-rich fraction under non-hydrogenation or hydrogenation conditions to carry out a catalytic transalkylation reaction, thereby obtaining a first mixed material comprising a first spent catalyst and a first oil gas;

[0065] (3) allowing the first mixed material to pass through the oil separation filter of the first reactor for separation, and 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;

[0066] (4) The separated first catalyst to be regenerated is stripped in a steam exchanger and then enters a regenerator for oxygen-containing regeneration. The regenerated catalyst is returned to the first reactor for recycling. 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% by weight, 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] The benzene-rich gasoline in the present invention is mainly catalytic cracking gasoline with a boiling point of 30-220°C and / or gasoline fractions from other sources such as hydrocracking units and / or reforming units and / or steam cracking units, and its benzene content is 0.8-40% by weight. The benzene-rich gasoline is cut by high-precision distillation to obtain a gasoline light fraction without aromatics, a benzene-rich middle fraction and an aromatics-rich heavy fraction, wherein the benzene-rich middle fraction is generally controlled to have a distillation range of 60-90°C, and more than 50% of the benzene in the gasoline is enriched. In principle, the benzene content of the gasoline obtained by mixing the gasoline light fraction and the aromatics-rich heavy fraction is controlled to meet the gasoline blending requirements of the refinery, and the benzene is enriched in the maximum amount with lower energy consumption, and the yield of the benzene-rich middle fraction is lower.

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

[0070] Preferably, the total theoretical plate number of the distillation tower is greater than or equal to 14.

[0071] The method of the present invention adopts one distillation tower and / or more than one distillation tower Jining high-precision distillation cutting, the total theoretical number of tower plates is at least 14 layers, and a 60-90°C middle fraction rich in benzene can be extracted in the middle and directly transalkylated. The cutting scheme is flexible and the enrichment efficiency is high. There is no need to further hydrogenate, remove or other treatments on the distillation cut fractions, thereby simplifying the production process and improving the production efficiency.

[0072] In step (2), the heavy aromatics-rich fraction is a catalytic cracking gasoline fraction, a catalytic cracking diesel fraction, a hydrocracking gasoline fraction, a hydrocracking diesel fraction, a reformed gasoline fraction, a reformed diesel fraction, a steam cracking gasoline fraction and / or a steam cracking diesel fraction with a boiling point of 150 to 240° C.; the content of carbon nine and carbon ten monocyclic heavy aromatics in the heavy aromatics-rich fraction is 20 to 100 weight %;

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

[0074] The gasoline and diesel fractions rich in heavy aromatics used in the present invention mainly refer to gasoline fractions and / or diesel fractions at 150-240°C from catalytic cracking and / or from hydrocracking units and / or reforming units and / or steam cracking units, and their carbon nine and carbon ten monocyclic heavy aromatic content is 20-100 weight %.

[0075] The present invention maintains the mass ratio of benzene to heavy aromatics within a certain range by injecting the fraction rich in heavy aromatics 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] The first reactor is provided with three or more heavy aromatic hydrocarbon injection ports in sections.

[0078] In the present invention, the benzene-rich gasoline intermediate fraction reaction oil and gas enter a fluidized bed or a moving bed or a fixed bed reactor. The catalyst of the fluidized bed reactor is in a turbulent fluidized state, and the apparent average linear velocity of the oil and gas is 0.2-2.0 m / s. The catalyst and the reaction flow can be an ascending bed or a descending bed, preferably an ascending bed, and more than two heavy aromatic hydrocarbon fraction injection ports are provided in sections; the catalyst of the moving bed reactor is in a uniform downward moving state, and the catalyst and the reaction flow can be contacted and reacted in a co-current manner or in a counter-current manner, preferably in a counter-current manner, and more than two heavy aromatic hydrocarbon fraction injection ports are provided in sections; the fixed bed reactor can be a conventional radial flow fixed bed reactor, preferably a tubular reactor, and the catalyst is loaded in at least two reaction zones, and a heavy aromatic hydrocarbon stream injection port is provided upstream of each reaction zone.

[0079] The method of the invention reacts in a non-hydrogen or hydrogen atmosphere, has low hydrogen consumption, and the xylene component generated by alkyl transfer has a high octane number.

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

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

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

[0083] The mesoporous molecular sieve catalyst of the present invention is a catalyst composed of molecular sieve and heat-resistant inorganic oxide, wherein the catalyst molecular sieve is an optional mesoporous zeolite of the mercerized series, ZSM series and Y series; the heat-resistant inorganic oxide is a binder such as aluminum oxide, silicon oxide and / or an optional natural porous carrier material such as clay; preferably, a composite composed of a mesoporous zeolite of the mercerized series or a composite molecular sieve containing mercerized zeolite, a binder such as aluminum oxide, silicon oxide and an optional natural porous carrier material such as clay, wherein the mesoporous molecular sieve accounts for 30-80% by weight of the total amount of the catalyst, and the rest is a carrier. The catalyst of the present invention is simple to prepare, does not need to add precious metals, has low cost and high benzene conversion rate.

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

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

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

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

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

[0089] In the present invention, the reactor and the regenerator can be arranged in parallel or overlapped, and the fluidized bed and the settler of the fluidized bed reactor can be internal or external; the spent catalyst can be stripped and lifted by nitrogen and / or water vapor and other media when entering the regenerator, and the regenerated catalyst is stripped, deoxygenated and dehydrated by nitrogen, and then returned to the reaction stage for recycling.

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

[0091] In the present invention, the catalyst after the reaction enters the oxygen-containing regeneration system for regeneration, and air and / or oxygen can be used for regeneration; preferably, oxygen-enriched and / or pure oxygen is used for regeneration. The flue gas after regeneration is partially or completely circulated back to the regenerator, and the oxygen-containing high-temperature flue gas is not heat exchanged or partially heat exchanged, and its temperature is 300-600°C, and partially and / or completely returned to the regenerator for recycling, making full use of the oxygen in the flue gas and maintaining a high regeneration temperature of the regenerator and a high regeneration agent temperature.

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

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

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

[0095] The benzene-rich gasoline transalkylation debenzenization method provided by the present invention can be coupled with the catalytic cracking of heavy oils such as wax oil and residual oil, and the benzene-rich gasoline middle distillate and the heavy oil are reacted in two different reactors; the benzene-rich gasoline middle distillate adopts a fluidized bed, a moving bed or a fixed bed reactor, and the catalyst after the reaction is introduced into the 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 invention provides a method for producing low-benzene gasoline by catalytic transalkylation, comprising:

[0097] (1) catalytically cracking the heavy oil in a second reactor to obtain a second mixed material comprising a second spent catalyst and a second oil and gas;

[0098] (2) performing oil-gas separation on the second mixed material in an oil-gas separation system to obtain a dry gas component, a liquefied gas component, and a gasoline component;

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

[0100] (4) the self-produced gasoline benzene-rich fraction and any other gasoline benzene-rich fraction enter the first reactor and contact the catalyst with the fraction rich in heavy aromatics injected in stages under non-hydrogenation or hydrogenation conditions to perform a catalytic transalkylation reaction, thereby obtaining a first mixed material comprising a first spent catalyst and a first oil and gas;

[0101] (5) allowing the first mixed material to pass through the oil separation filter of the first reactor for separation, and the separated oil and gas enter the oil and gas separation system for oil and gas separation;

[0102] (6) The separated first catalyst to be regenerated enters the second reactor and is mixed with the second catalyst to be regenerated. After being stripped by the steam exchanger of the second reactor, it enters the regenerator for oxygen-containing regeneration. 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] Wherein, the heavy oil is wax oil and / or residual oil.

[0104] The low benzene content gasoline of the present invention has a benzene content of less than 1.0 weight %, preferably less than 0.8 weight %.

[0105] The heavy aromatics in the heavy aromatics-rich fraction of the present invention refer to carbon nine-carbon ten-monocyclic heavy aromatics.

[0106] In one embodiment, the gasoline benzene-rich fraction is obtained by distilling and cutting the benzene-rich gasoline to obtain a benzene-rich middle fraction with a distillation range of 60 to 90° C.

[0107] Wherein, the benzene content of the benzene-rich gasoline is 0.8 to 40 weight %;

[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 to 220°C.

[0109] The present invention is further described in detail by way of examples. The raw materials used in the examples can be obtained through commercial sources.

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

[0111] The full-fraction gasoline feedstock A1 used in the embodiment is catalytic cracking gasoline from a certain refinery. A1 is distilled and cut to obtain a benzene-rich fraction feedstock oil B. The monocyclic heavy aromatics-rich fraction feedstock A2 is catalytic cracking light diesel from a certain refinery. The heavy feedstock oil C is hydrogenated residue oil from a certain refinery. The properties of the four feedstock oils are shown in Table 1.

[0112] The catalysts used in the examples are the same, and their preparation methods are briefly described as follows:

[0113] 1) 5.1 kg of halloysite (industrial product of Suzhou Clay Company, solid content 71.6 wt%) was slurried with 28.4 kg of decationized water, and then 3.4 kg of pseudo-boehmite (industrial product of Shandong Aluminum Plant, solid content 63 wt%) was added to slurry to obtain a slurry with a solid content of 5-30 wt%; the pH was adjusted to 2-4 with hydrochloric acid, stirred evenly, and aged at 60-70°C for 1 hour to obtain a mixed carrier slurry.

[0114] 2) Spray molding: 18 kg of MOR hydrogen-type mordenite powder (industrial product of Yingkou Zhongbao Molecular Sieve Co., Ltd., SiO2 / Al2O3=22-25, solid content of 91.9%) and 48 kg of decationized water are mixed and slurried at a solid-liquid ratio of 1:1-1:10, added to the mixed carrier slurry obtained in step 2), stirred evenly, and 4.4 kg of aluminum sol (produced by Sinopec Catalyst Qilu Branch, Al2O3 content of 21.7% by weight, wherein the ratio of catalyst solid content to aluminum sol solid content (calculated as alumina) is 10-50:1) is added, and placed in a bonding machine and stirred until a uniform sol is formed; the sol is placed in the air for 4 hours and spray dried to form. Generally, the tail gas temperature is controlled at 250-300°C, and the spray pressure is 50-60 atmospheres to obtain a microspherical catalyst.

[0115] 3) Calcination of microsphere catalyst: The microsphere catalyst is formed by spray drying. (If the residual sodium of the molecular sieve is high after ammonium exchange, the free Na is removed by washing with ammonium chloride solution. + ), dried at about 120°C for 3 hours, and then calcined at 500-800°C for 3 hours to obtain a catalyst, which is recorded as CAT-A.

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

[0117] The heavy oil catalytic cracking catalyst is a CGP special agent produced by Sinopec Catalyst Qilu Branch, containing ZSM-5 molecular sieve and Y molecular sieve. Its properties are listed in Table 2.

[0118] Example 1

[0119] This embodiment follows Figure 1 The process was tested using the feedstock B in Table 1, i.e., the benzene-rich fraction of catalytic cracking gasoline, as the feedstock, and a transalkylation reaction was carried out with a graded injection of a heavy aromatic fraction in a dense phase fluidized bed reactor using a CAT-A catalyst.

[0120] like Figure 1 As shown, in this embodiment, benzene-rich gasoline 1 is subjected to high-precision distillation cutting in distillation tower VII to obtain a gasoline light fraction 1a without aromatics, a benzene-rich middle fraction 1b and an aromatics-rich heavy fraction 1c, wherein the benzene-rich middle fraction 1b is generally controlled to have a distillation range of 60-90°C, and more than 50% of the benzene in the gasoline is enriched.

[0121] Using a dense phase fluidized bed reactor I, the benzene-rich gasoline middle fraction 1b is fed into the reactor at the bottom of the fluidized bed reactor to contact the catalyst, and is contacted with the monocyclic heavy aromatics injected from the bottom, middle and upper parts of the reactor to undergo transalkylation reaction. The spent catalyst after the reaction is separated from the oil and gas and then regenerated, and the regenerated flue gas is partially recycled back to the regenerator. The process flow is as follows:

[0122] The gasoline benzene-rich fraction 1 is fed into the reactor at the lower part of the reactor I to contact the catalyst, and undergoes an alkylation translocation reaction with the monocyclic heavy aromatic hydrocarbon stream I2 fed from the bottom of the reactor. According to the catalyst fluidization requirements, a fluidizing medium 3 can be injected into the bottom of the reactor; after a period of reaction, it is further contacted with the monocyclic heavy aromatic hydrocarbon stream II4 and the monocyclic heavy aromatic hydrocarbon stream III5 injected into the middle and upper parts of the reactor to strengthen the alkylation translocation of benzene and heavy aromatic hydrocarbons; the spent catalyst after the reaction is separated from the oil and gas by the oil filter separator IV, and the separated catalyst is settled and then enters the gas feed exchanger 24 through the spent catalyst delivery pipeline I10. , and then after nitrogen and / or water vapor stripping, it enters the regenerator II through the regenerated catalyst delivery pipeline II11; the regenerated catalyst is regenerated in an oxygen-containing atmosphere in the regenerator, and the oxygen-containing regeneration gas 15 includes air, oxygen, etc., and the regeneration temperature is 500-700°C. The regenerated catalyst returns to the reactor I for recycling through the regeneration agent delivery pipeline I12 and the regeneration agent delivery pipeline II13; part of the regenerated flue gas 16 is circulated back to the regenerator through the flue gas circulation pipeline 17; the separated reaction oil and gas enter the oil and gas separation system III through the reaction oil and gas pipeline 6, and the product dry gas 7, liquefied gas 8, and gasoline 9 are separated.

[0123] Catalytic cracking gasoline feedstock A1 was distilled and cut using a 30-plate distillation tower (theoretical plate number 18), and a 60-90°C middle fraction rich in benzene was extracted from the middle section of the tower to obtain feedstock B, with a yield of 16.0%. This cutting method consumed 21.59 kg EO / t feedstock.

[0124] After being preheated at 250° C., the feedstock B enters the lower part of the dense phase fluidized bed reactor I and undergoes an alkylation reaction with the heavy aromatic fraction fed from the bottom of the reactor. At a reaction pressure of 1.5 MPa, nitrogen is used as a fluidizing medium. As the fluidizing medium flows from bottom to top, the heavy aromatic fraction A2 is injected into the lower, middle and upper regions of the reactor three times and the molar ratio of heavy aromatics to benzene in the reaction system is maintained to be not less than 1:1. At a reaction temperature (based on the upper part of the reactor, i.e., the outlet temperature, the same below) of 300° C., a weight ratio of catalyst to feedstock of 3.1, and a weight hourly space velocity of 5.0 h. -1The alkyl transfer reaction is carried out under the following conditions; the oil agent is separated after the reaction, and the separated reaction oil and gas are separated into dry gas, liquefied gas, gasoline and diesel products by the separation system; the catalyst to be regenerated after the oil agent is separated is stripped by nitrogen to remove the oil and gas adsorbed inside it, and then sent to the regenerator, and oxygen is used as the regeneration gas to contact with the catalyst to be regenerated at a regeneration temperature of 550°C; the regenerated regenerated agent is recycled, and the flue gas after regeneration is partially recycled, the circulating flue gas temperature is 400°C, and the regeneration dense phase temperature is 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 a benzene content of 7.68% and an octane number RON 83.6 was subjected to a transalkylation reaction with a catalytic cracking light diesel oil rich in heavy aromatics in a dense phase fluidized bed reactor, and the benzene conversion rate was 97.09%, the gasoline yield was 61.99% by weight, the benzene content of the gasoline was reduced to 0.18% by weight, the octane number RON 88.5 was increased by 4.9 units, and the gasoline yield growth ratio (calculated by the formula (gasoline yield-gasoline percentage in the feedstock) / gasoline percentage in the feedstock*100%, the same below) reached 23.98% by weight.

[0126] Comparative Example 1

[0127] By using the benzene-rich fraction B obtained by cutting catalytic cracking gasoline and the heavy aromatic fraction A2 as raw materials, the same catalyst and process conditions as in Example 1 are used to carry out transalkylation reaction, except that: 1) Comparative Example 1 uses a riser reactor; 2) the benzene-rich fraction is only injected once at the bottom of the reactor; 3) air is used as the regeneration gas, and the flue gas is not circulated; 4) in order to maintain the same process conditions as in Example 1 for the operation of the reverse regeneration system, it is necessary to spray combustion oil 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 Example 2 (the benzene-rich fraction after gasoline cutting and the heavy aromatic fraction injected in stages are transalkylated in a dense fluidized bed) and Comparative Example 2 (the benzene-rich fraction after gasoline cutting and the heavy aromatic fraction are mixed at one time in a riser reactor for transalkylation), the benzene conversion rate of Example 2 is 70.28 percentage points higher, the benzene content of gasoline is 4.63 percentage points lower, and the gasoline yield is 7.22 percentage points higher.

[0129] Example 2

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

[0131] Figure 2 The process flow diagram of Example 2 is the same as that of Example 1 in that the gasoline benzene-rich fraction and the heavy aromatic fraction are transalkylated using a dense phase fluidized bed reactor 1, but the difference is that the heavy crude oil 19 enters a conventional riser reactor, and the catalyst after the transalkylation reaction of benzene and heavy aromatics and the catalyst after the heavy oil catalytic cracking reaction can be gas-lifted separately and then enter the same regenerator, or can share a settler for gas-lifting. In this embodiment, the two use a settler. The process flow is as follows:

[0132] The heavy crude oil 19 is atomized by atomizing steam and fed into the lower part of the cracking reactor VI to contact the catalytic cracking catalyst for cracking reaction; the separated reaction oil and gas enter the oil and gas separation system III through the reaction oil and 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 a self-produced gasoline benzene-rich fraction 25 and a low-benzene gasoline 26 after distillation through a gasoline distillation tower V. 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 distillation is discharged from the device for gasoline pool blending. The benzene-rich fraction 25 of the self-produced gasoline and the benzene-rich middle fraction 1b of the benzene-rich gasoline from the distillation tower are fed into the reactor at the lower part of the reactor I to contact the catalyst, and are transalkylated with the single-ring heavy aromatics stream I2 fed from the bottom of the reactor; after a period of reaction, they are further contacted with the single-ring heavy aromatics stream II4 and the single-ring heavy aromatics stream III5 injected into the middle and upper parts of the reactor to strengthen the transalkylation of benzene; the spent catalyst after the transalkylation reaction is separated from the oil and gas by the oil agent filter separator IV, and the separated catalyst is settled and then enters the heavy oil cracking reactor through the spent catalyst delivery pipeline I10 VI, and then after nitrogen and / or water vapor 14 is stripped in the gas exchanger 24, it enters the regenerator II through the regenerator delivery pipeline II11; the regenerator is regenerated in an oxygen-containing atmosphere in the regenerator II, and the oxygen-containing regeneration gas 15 includes air, oxygen, etc., and the regeneration temperature is 600-800°C. The regenerated catalyst is recycled, and the regenerated catalyst is transported to the heavy oil cracking reactor VI through the regeneration agent delivery pipeline I12, and transported to the reactor I through the regeneration agent delivery pipeline II13; the separated reaction oil and gas enter the oil and gas separation system III through the reaction oil and gas pipeline 6 for product separation. It should be noted that the alkylation catalyst is supplemented into the reactor I through the dosing pipeline 18, and since the alkylation catalyst is also a propylene additive or octane improver for heavy oil cracking, the amount of the alkylation catalyst entering the heavy feedstock oil cracking reactor needs to meet the requirements of benzene alkylation and heavy oil cracking.

[0133] After being preheated at 200°C, the heavy crude oil rises to the bottom of the reactor and contacts the catalytic cracking catalyst for cracking reaction. At a reaction pressure of 0.35 MPa, water vapor is used as the fluidizing and atomizing medium. As the fluidizing medium flows from bottom to top, the reaction temperature (based on the reactor top, i.e., the outlet temperature, the same below) is 540°C, the weight ratio of catalyst to crude oil is 7.4, and the weight hourly space velocity is 20.0 hours. -1 The cracking reaction was carried out under the following conditions.

[0134] Gasoline D obtained by catalytic cracking of heavy crude oil is subjected to high-precision distillation cutting using a distillation tower 1 with 30 plates (theoretical plate number 15) and a distillation tower 2 with 50 plates (theoretical plate number 25). The light gasoline fraction at the bottom of distillation tower 1 enters distillation tower 2, and a 60-90°C middle fraction rich in benzene, i.e. gasoline benzene-rich fraction E, is extracted at the top of distillation tower 2, with a yield of 29.4% of catalytic cracking gasoline D. This cutting method consumes 14.66 kg EO / t of raw material. The properties of catalytic cracking gasoline D and gasoline benzene-rich fraction E are shown in Table 1.

[0135] The gasoline benzene-rich fraction E is preheated at 300°C and enters the lower part of the dense phase fluidized bed reactor I. Hydrogen is used as the fluidizing medium to carry out transalkylation reaction with the diesel fraction rich in heavy aromatics fed from the bottom of the reactor. It flows from bottom to top at a reaction pressure of 0.5 MPa. The heavy aromatic fraction is injected into the lower, middle and upper regions of the reactor three times and the molar ratio of heavy aromatics to benzene in the reaction system is maintained at not less than 1:1. The reaction temperature is 350°C, the weight ratio of catalyst to feed oil is 3.1, and the weight hourly space velocity is 2.5 hours. -1 The alkyl transfer reaction is carried out under the following conditions, and the oil agent is separated after the reaction.

[0136] The separated reaction oil and gas enter the oil and gas separation system through the reaction oil and gas pipeline, and are separated to obtain dry gas, liquefied gas, gasoline, diesel and oil slurry. The gasoline is separated into self-produced benzene-rich gasoline and low-benzene gasoline through a gasoline distillation tower. The self-produced benzene-rich gasoline can be partially recycled or not returned to the reactor as needed.

[0137] The reaction oil and gas after separation of the gasoline benzene-rich fraction and the heavy aromatics alkyl transfer reaction oil enter the sedimentation section of the heavy crude oil catalytic cracking reactor, and are sent to the regenerator after being stripped by steam to remove the oil and gas adsorbed inside. Air is used as the regeneration gas and is regenerated by contact with the regenerated agent at a regeneration dense phase temperature of 680°C. The regenerated regenerated agent is recycled, and the regenerated flue gas is not recycled.

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

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

[0140] Comparative Example 2

[0141] The same heavy crude oil C as in Example 2 was used as the raw material, and the same heavy oil cracking catalyst and process conditions as in Example 2 were used to carry out the cracking reaction, except that: 1) the gasoline obtained by cracking the heavy crude oil in Example 2 was not cut; 2) the heavy aromatic fraction and the heavy oil were mixed at one time in the riser reactor for reaction. The operating conditions and product distribution are listed in Table 4.

[0142] As can be seen from Table 4, compared with Example 2 (the benzene-rich fraction after cutting of gasoline obtained by heavy oil cracking and the heavy aromatic fraction injected in stages in a dense phase fluidized bed are transalkylated), and Comparative Example 2 (the heavy oil and the heavy aromatic fraction are mixed at one time and reacted in a riser reactor), the benzene content of gasoline is 1.70 percentage points lower.

[0143] The present application has been described above in conjunction with preferred embodiments, but these embodiments are only exemplary and serve only as an illustration. On this basis, various replacements and improvements may be made to the present application, all of which fall within the scope of protection of the present application.

[0144] Table 1

[0145]

[0146]

[0147] Table 2

[0148]

[0149]

[0150] Table 3

[0151] Example 1 Comparative Example 1 Crude oil B A Reactor type dense phase fluidized bed Riser Catalyst name CAT-A CAT-A Reaction operating conditions Raw oil preheating temperature, ℃ 250 250 Reactor bottom temperature, °C 300 300 Reactor middle temperature, °C 300 300 Reactor upper temperature, °C 300 300 Reaction pressure, MPa 1.5 1.5 Catalyst / Feedstock Weight Ratio 3.1 3.1 Heavy aromatics / benzene molar ratio 0.5*3 1.5 <![CDATA[Weight hourly space velocity, h-1 -1 > 5.0 5.0 Regenerator dense phase temperature, ℃ 550 550 Regeneration pressure, MPa 1.5 1.5 Regeneration flue gas circulation ratio, % 50 - Circulating flue gas temperature, ℃ 400 - Product yield, weight % Dry gas 0.19 0.28 Liquefied gas 0.93 0.20 gasoline 61.99 58.38 diesel fuel 33.51 35.74 Coke 3.38 5.41 Gasoline properties Olefin content, weight % 3.79 3.43 Aromatic content, weight % 40.51 41.72 Benzene content, weight % 0.18 4.81 RON 88.5 88.4 MON 83.1 82.9 Benzene conversion rate, % 97.09 26.81 Gasoline yield growth rate, % 23.98 16.76

[0152] Table 4

[0153]

[0154] The # column represents the data obtained by sampling and analyzing at the outlet of the catalytic cracking oil separator of the riser reactor (based on crude oil C)

[0155] The ## column represents the data obtained by sampling and analyzing at the outlet of the oil filter separator of the moving bed reactor (based on the gasoline benzene-rich fraction E)

[0156] The ### column represents the overall data of Example 2 (based on raw oil C).

Claims

1. A method for reducing the benzene content in gasoline by catalytic transalkylation, characterized in that: The method comprises: (1) distilling and cutting the benzene-rich gasoline to obtain a benzene-rich gasoline middle distillate with a distillation range of 60 to 90° C.; (2) the benzene-rich gasoline middle fraction enters the first reactor and contacts the catalyst with the graded injected heavy aromatics-rich fraction under non-hydrogenation or hydrogenation conditions to carry out a catalytic transalkylation reaction, thereby obtaining a first mixed material comprising a first spent catalyst and a first oil gas; (3) allowing the first mixed material to pass through the oil separation filter of the first reactor for separation, and 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 separated first catalyst to be regenerated is stripped in a steam exchanger and then enters a regenerator for oxygen-containing regeneration. The regenerated catalyst is returned to the first reactor for recycling. Preferably, part or all of the flue gas after regeneration is recycled back to the regenerator; The benzene content of the benzene-rich gasoline is 0.8 to 40 weight percent; the content of carbon nine and carbon ten single-ring heavy aromatics in the heavy aromatics-rich fraction is 20 to 100 weight percent; Preferably, in step (2), the molar ratio of the heavy aromatics to benzene is maintained at 0.3 to 5.0, preferably 0.5 to 2.

0.

2. The method according to claim 1, characterized in that The heavy aromatics-rich fraction is a catalytic cracking gasoline fraction, a catalytic cracking diesel fraction, a hydrocracking gasoline fraction, a hydrocracking diesel fraction, a reformed gasoline fraction, a reformed diesel fraction, a steam cracking gasoline fraction and / or a steam cracking diesel fraction with a boiling point of 150 to 240°C.

3. The method according to claim 1, characterized in that The catalytic transalkylation reaction temperature is 200-450°C, preferably 250-400°C; The reaction pressure is 0.1 to 5.0 MPa, preferably 0.5 to 4.0 MPa; The weight ratio of catalyst to feedstock oil is 2.0 to 12.0:1, preferably 3.0 to 9.0:1; and / or Weight hourly space velocity is 1.0~20.0h -1 , preferably 2.0~10.0h -1 .

4. 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, preferably a moving bed reactor; and / or The first reactor is provided with three or more heavy aromatic hydrocarbon injection ports in sections.

5. The method according to claim 1, characterized in that The distillation and cutting of the benzene-rich gasoline is carried out by using one or more distillation towers; Preferably, the total theoretical plate number of the distillation tower is greater than or equal to 14.

6. The method according to claim 1, characterized in that The catalyst comprises a mesoporous molecular sieve, a heat-resistant inorganic oxide and optional clay, wherein the mesoporous molecular sieve accounts for 30 to 80 weight percent of the total amount of the catalyst; Preferably, the mesoporous molecular sieve is selected from the group consisting of the mesoporous zeolites of the mordenite series, the ZSM series and / or the Y series, more preferably the mesoporous zeolites of the mordenite series or the composite molecular sieves containing the mesoporous zeolites of the mordenite series; and / or Preferably, the heat-resistant inorganic oxide is aluminum oxide and / or silicon oxide.

7. The method according to claim 1, characterized in that The benzene-rich gasoline is catalytic cracking gasoline, hydrocracking gasoline, reforming gasoline and / or steam cracking gasoline with a boiling point of 30 to 220° C.; and / or The benzene-rich middle fraction is preheated before entering the first reactor, and the preheating temperature is 200-400°C, preferably 220-380°C.

8. The method according to claim 1, characterized in that: The oxygen-containing regeneration atmosphere is air and / or oxygen atmosphere, preferably oxygen-enriched and / or pure oxygen atmosphere; The regeneration temperature of the regenerator is 500-800°C, preferably 550-700°C; The regeneration pressure of the regenerator is 0.2 to 5.0 MPa, preferably 0.5 to 5.0 MPa; and / or The flue gas temperature circulating back to the regenerator is 300-600°C.

9. A method for producing low-benzene gasoline by catalytic transalkylation, characterized in that: The method comprises: (1) catalytically cracking the heavy oil in a second reactor to obtain a second mixed material comprising a second spent catalyst and a second oil and gas; (2) performing oil-gas separation on the second mixed material in an oil-gas separation system to obtain a dry gas component, a liquefied gas component, and a gasoline component; (3) distilling the gasoline components in a gasoline distillation system to obtain a self-produced gasoline benzene-rich fraction and a low-benzene gasoline; (4) the self-produced gasoline benzene-rich fraction and any other gasoline benzene-rich fraction enter the first reactor and contact the catalyst with the fraction rich in heavy aromatics injected in stages under non-hydrogenation or hydrogenation conditions to perform a catalytic transalkylation reaction, thereby obtaining a first mixed material comprising a first spent catalyst and a first oil and gas; (5) allowing the first mixed material to pass through the oil separation filter of the first reactor for separation, and the separated oil and gas enter the oil and gas separation system for oil and gas separation; (6) The separated first catalyst to be regenerated enters the second reactor and is mixed with the second catalyst to be regenerated. After being stripped by the steam exchanger of the second reactor, it enters the regenerator for oxygen-containing regeneration. 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. Wherein, the heavy oil is wax oil and / or residual oil.

10. The method according to claim 9, characterized in that The benzene-rich gasoline fraction is obtained by distilling and cutting the benzene-rich gasoline to obtain a benzene-rich middle fraction with a distillation range of 60 to 90° C. Wherein, the benzene content of the benzene-rich gasoline is 0.8 to 40 weight %; Preferably, the benzene-rich gasoline is catalytic cracking gasoline, hydrocracking gasoline, reforming gasoline and / or steam cracking gasoline with a boiling point of 30 to 220°C.

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