Catalytic conversion method of gasoline benzene, and method and system for producing gasoline with low benzene content

Abstract

The invention provides a gasoline benzene catalytic conversion method and a method and system for producing low-benzene-content gasoline. The method comprises the following steps: performing high-precision distillation cutting on benzene-rich gasoline to obtain a gasoline light fraction, a gasoline middle fraction and a gasoline heavy fraction; the benzene-rich gasoline middle fraction enters a moving bed or a fixed bed or a fluidized bed reactor to be in graded contact with low-carbon alcohol through a mesoporous molecular sieve catalyst for catalytic alkylation, and benzene is efficiently converted into alkylbenzene, so that the benzene-rich gasoline is converted into high-octane-number low-benzene gasoline and liquefied gas. The method provided by the invention reduces the benzene content and olefin content in gasoline, improves the octane number of gasoline and increases the yield of liquefied gas, not only solves the problem that refinery gasoline has high benzene content and is difficult to meet the national standard VI of motor gasoline, but also improves the quality of gasoline and increases the yield of liquefied gas.

Description

Technical Field

[0001] The invention relates to the field of catalytic conversion of gasoline to benzene, and in particular to a method for catalytic conversion of gasoline to benzene, a method for producing gasoline with low benzene content and a reaction system thereof. 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] Ethylene is a basic chemical material with a shortage of resources. Studies have found that low-carbon alcohols such as methanol can also undergo alkylation reactions with benzene. Regarding the patented technology of alkylation and benzene reduction of benzene with low-carbon alcohols, patent CN200910236630.8 discloses a catalytic conversion method for reducing the benzene content of gasoline. Benzene-containing gasoline and alcohol contact catalytic cracking catalysts in fluidized beds and / or riser reactors, and the benzene content in gasoline can be reduced by up to 60% by volume. CN200910043913.0 discloses a method for reducing the benzene content in benzene-containing gasoline. Benzene-containing gasoline and methanol undergo alkylation reactions in a fixed bed reactor equipped with a catalyst, and the benzene content in benzene-containing gasoline is reduced from 20 to 60 wt% to 3 to 7 wt%. CN201710342646.1 discloses a method for reducing the benzene content in benzene-rich gasoline. Benzene-rich gasoline, methanol and hydrogen react with modified ZSM-5 molecular sieves, MCM-56 molecular sieves and β molecular sieve alkylation catalysts to reduce benzene, thereby increasing the utilization rate of methanol by >99%. There are also patents proposing patented technologies for coupling the alkylation of FCC gasoline benzene with low-carbon alcohols with catalytic cracking. Patent CN201010296622.5 discloses a catalytic conversion method for reducing the benzene content in gasoline. Benzene-containing gasoline and alcohol are contacted with catalytic cracking catalysts in multiple reaction zones in turn, and the volume content of benzene can be reduced by more than 65%.

[0008] 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 high nitrogen content and 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 gasoline benzene content 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 catalytic cracking gasoline. Summary of the invention

[0009] The object of the present invention is to provide a method for catalytically converting gasoline benzene into alkylbenzene and converting benzene-rich gasoline into high-octane low-benzene gasoline and liquefied gas, thereby improving the quality of gasoline and increasing the production of liquefied gas. Specifically, a method is provided for producing low-benzene and low-olefin gasoline by catalytic alkylation of a gasoline intermediate fraction rich in benzene obtained by high-precision distillation cutting of benzene-rich gasoline and graded injection of low-carbon alcohol on a medium-pore molecular sieve catalyst, thereby improving the octane number of gasoline and increasing the production of liquefied gas.

[0010] A first aspect of the present invention provides a method for catalytic conversion of gasoline benzene, the method comprising:

[0011] (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.;

[0012] (2) the benzene-rich gasoline middle fraction enters the first reactor and contacts the catalyst with the graded injected low-carbon alcohol stream under non-hydrogenation or hydrogenation conditions to carry out a catalytic alkylation reaction, thereby obtaining a first mixed material comprising a first spent catalyst and a first oil gas;

[0013] (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;

[0014] (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;

[0015] The benzene content of the benzene-rich gasoline is 0.8 to 20% by weight; the low-carbon alcohol is a C1 to C3 alkyl alcohol, preferably methanol, ethanol and / or isopropanol;

[0016] Preferably, in step (2), the molar ratio of the lower alcohol to benzene is maintained at 0.2 to 7.0:1, more preferably 0.5 to 5.0:1.

[0017] According to the method of the first aspect of the present invention, the first reactor is provided with 3 or more low-carbon alcohol injection ports in sections; and / or

[0018] The content of low-carbon alcohol in the low-carbon alcohol stream is 50 to 100 weight %.

[0019] According to the method of the first aspect of the present invention, the catalytic alkylation reaction temperature is 400-550°C, preferably 420-520°C;

[0020] The reaction pressure is 0.1-1.0 MPa, preferably 0.2-0.8 MPa;

[0021] The weight ratio of catalyst to feedstock oil is 0.7 to 7.0:1, preferably 1.0 to 5.0:1; and / or

[0022] Weight hourly space velocity is 0.5~25.0h -1 , preferably 1.0~15.0h -1 .

[0023] 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.

[0024] 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;

[0025] Preferably, the total theoretical plate number of the distillation tower is greater than or equal to 14.

[0026] 6. The method according to claim 1, characterized in that 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 % of the total amount of the catalyst;

[0027] Preferably, the mesoporous molecular sieve is selected from β series, ZSM series and / or Y series mesoporous zeolite, more preferably a composite mesoporous zeolite of ZSM series and β series; and / or

[0028] Preferably, the heat-resistant inorganic oxide is aluminum oxide and / or silicon oxide.

[0029] 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

[0030] The benzene-rich gasoline middle fraction is preheated before entering the first reactor, and the preheating temperature is 50-350°C, preferably 100-300°C.

[0031] According to the method of the first aspect of the present invention, the atmosphere of oxygen-containing regeneration is air and / or oxygen atmosphere, preferably oxygen-enriched and / or pure oxygen atmosphere;

[0032] The regeneration temperature of the regenerator is 450-750°C, preferably 500-700°C;

[0033] The regeneration pressure of the regenerator is 0.2-1.5 MPa, preferably 0.2-1.0 MPa; and / or

[0034] The flue gas temperature circulating back to the regenerator is 300-600°C.

[0035] A second aspect of the present invention provides a method for producing low benzene content gasoline, the method comprising:

[0036] (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;

[0037] (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;

[0038] (3) distilling the gasoline components in a gasoline distillation system to obtain a self-produced gasoline benzene-rich fraction and a low-benzene gasoline;

[0039] (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 graded injected low-carbon alcohol stream under non-hydrogenation or hydrogenation conditions to perform a catalytic alkylation reaction to obtain a first mixed material comprising a first spent catalyst and a first oil gas;

[0040] (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;

[0041] (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.

[0042] Wherein, the heavy oil is wax oil and / or residual oil.

[0043] 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 gasoline middle fraction with a distillation range of 60 to 90°C;

[0044] Wherein, the benzene content of the benzene-rich gasoline is 0.8 to 20 weight %;

[0045] 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.

[0046] A third aspect of the present invention provides a system for producing low benzene content gasoline, comprising:

[0047] A catalytic cracking reaction unit, the catalytic cracking reaction unit comprising

[0048] - catalytic cracking reactor,

[0049] - Catalytic cracking oil separator, and

[0050] - steam exchanger;

[0051] The catalytic cracking oil agent separator is connected to the oil and gas outlet of the catalytic cracking reactor, and is used to separate the reaction oil agent from the catalytic cracking reactor, and allow the separated catalytic cracking spent catalyst to enter the steam exchanger for stripping;

[0052] A gasoline-benzene catalytic conversion unit, the gasoline-benzene catalytic conversion unit comprising

[0053] - a reactor for catalytic conversion of gasoline benzene, and

[0054] - Oil filter separator;

[0055] Wherein, the oil agent filter separator is connected to the oil and gas outlet of the gasoline-benzene catalytic conversion reactor, and is used to separate the reaction oil agent from the gasoline-benzene catalytic conversion reactor;

[0056] The lower part of the gasoline-benzene catalytic conversion reactor is connected to the steam exchanger of the catalytic cracking reaction unit, so that the gasoline-benzene catalytic conversion catalyst to be spent in the gasoline-benzene catalytic conversion reactor enters the steam exchanger for stripping;

[0057] The gasoline-benzene catalytic conversion reactor is provided with a gasoline benzene-rich fraction inlet and a plurality of low-carbon alcohol stream inlets. Preferably, the gasoline-benzene catalytic conversion reactor is provided with 3 or more low-carbon alcohol stream inlets;

[0058] A regenerator, wherein the regenerator is connected to the steam exchanger of the catalytic cracking reaction unit, so that the regenerated catalyst that has been stripped in the steam exchanger enters the regenerator for regeneration; the regenerator is also respectively connected to the catalytic cracking reactor of the catalytic cracking reaction unit and the gasoline-benzene catalytic conversion reactor of the gasoline-benzene catalytic conversion unit, so that the regenerated catalyst circulates back to the catalytic cracking reactor and the gasoline-benzene catalytic conversion reactor;

[0059] an oil-gas separation unit, the oil-gas separation unit being respectively connected to the catalytic cracking oil agent separator of the catalytic cracking reaction unit and the oil agent filter separator of the gasoline-benzene catalytic conversion unit, so that the oil and gas products from the catalytic cracking reaction unit and the gasoline-benzene catalytic conversion unit are separated in the oil-gas separation unit; and

[0060] A gasoline distillation unit, wherein the gasoline distillation unit is connected with the gasoline fraction outlet of the oil-gas separation unit, so that the gasoline fraction from the oil-gas separation unit is distilled in the gasoline distillation unit to obtain a gasoline benzene-rich fraction and a low-benzene gasoline after distillation; the gasoline benzene-rich fraction outlet of the gasoline distillation unit is connected with the gasoline benzene-rich fraction inlet of the gasoline-benzene catalytic conversion reactor, so that the gasoline benzene-rich fraction from the gasoline distillation unit enters the gasoline-benzene catalytic conversion reactor for catalytic conversion of benzene; wherein the gasoline distillation unit includes one or more distillation towers, and preferably, the total theoretical number of plates of the distillation towers is greater than or equal to 14.

[0061] Compared with the prior art, the present invention has the following technical effects:

[0062] (1) The benzene-rich catalytic cracking gasoline is cut by high-precision distillation to obtain a benzene-rich gasoline intermediate fraction, which is then contacted with a medium-pore molecular sieve for catalytic alkylation together with graded injection of low-carbon alcohols. The benzene conversion rate is high, the gasoline octane number is improved, and the production of liquefied gas is increased.

[0063] (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 keeps the catalyst activity high all the time, thus solving the problem of easy coking and deactivation of the alkylation catalyst in processing high-olefin catalytic cracking gasoline or steam cracking gasoline.

[0064] (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.

[0065] (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

[0066] Figure 1 The present invention is a schematic diagram of a process flow of a benzene alkylation moving bed reactor embodiment, which is used to illustrate the continuous process flow of the fluidized bed catalytic alkylation of benzene-rich gasoline.

[0067] Figure 2 The present invention is a process flow diagram of a combined implementation method of a benzene alkylation moving bed reactor and heavy oil catalytic cracking, which is used to illustrate the coupled processing process of benzene-rich gasoline intermediate fraction alkylation and heavy oil catalytic cracking.

[0068] Description of reference numerals:

[0069] I. Moving bed 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. Benzene-rich gasoline middle fraction; 1c. Heavy gasoline fraction rich in aromatics; 2. Low-carbon alcohol stream I; 3. Fluidizing medium; 4. Low-carbon alcohol stream II; 5. Low-carbon alcohol stream 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. Stripping 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. Slurry oil; 24. Steam exchanger; 25. Self-produced gasoline benzene-rich fraction; 26. Low-benzene gasoline after distillation. DETAILED DESCRIPTION

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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) for the alkylation of low-carbon alcohols and benzene, it is necessary to maintain the alcohol / benzene molar ratio within a certain range, such as an alcohol / benzene molar ratio of 0.2-7.0:1, in order to maintain a high benzene conversion rate; (3) for the catalytic cracking gasoline benzene-rich middle distillate, for reforming gasoline, not only the olefin content is high and the octane number is low, but also the sulfur and nitrogen content is high and the benzene content is relatively low. Therefore, the present invention uses a medium-pore molecular sieve catalyst to catalyze the benzene-rich middle distillate. The alkylation of benzene in the fraction with low-carbon alcohols can not only reduce the benzene content of catalytic cracking gasoline, but also improve the octane number of gasoline and increase the production of liquefied gas. (4) The benzene-rich intermediate fraction of catalytic cracking gasoline has a high olefin content and is easily coked and deactivated during the alkylation 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, 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.

[0074] Based on the above findings, the present invention provides a gasoline benzene reduction method in which a benzene-rich gasoline fraction is contacted with a low-carbon alcohol in a graded manner over a medium-pore molecular sieve catalyst for catalytic alkylation of benzene, that is, a benzene-rich gasoline intermediate fraction is obtained by high-precision distillation and cutting, and then enters a moving bed, fixed bed or fluidized bed reactor, and is contacted with a medium-pore molecular sieve catalyst in a non-hydrogen or hydrogen-containing manner with a graded injection of low-carbon alcohol to carry out a catalytic alkylation reaction under 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 alkylation reaction in a continuous regeneration, achieving a higher conversion rate of benzene under a high-activity catalyst, and achieving efficient and continuous production.

[0075] The present invention provides a method for catalytic conversion of gasoline benzene, comprising the following steps:

[0076] (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.;

[0077] (2) the benzene-rich gasoline middle fraction enters the first reactor and contacts the catalyst with the graded injected low-carbon alcohol stream under non-hydrogenation or hydrogenation conditions to carry out a catalytic alkylation reaction, thereby obtaining a first mixed material comprising a first spent catalyst and a first oil gas;

[0078] (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;

[0079] (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.

[0080] In step (1), the benzene content of the benzene-rich gasoline is 0.8-20% 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.

[0081] 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 0.8-20% by weight. The benzene-rich gasoline is cut by high-precision distillation to obtain a gasoline light fraction without aromatics, a gasoline middle fraction rich in benzene, and a gasoline heavy fraction rich in aromatics, wherein the gasoline middle fraction rich in benzene 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 gasoline heavy fraction rich in aromatics 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 gasoline middle fraction rich in benzene is lower.

[0082] In one embodiment, the distillation and cutting of the benzene-rich gasoline is performed using one or more distillation towers; preferably, the total theoretical plate number of the distillation tower is greater than or equal to 14.

[0083] The method of the present invention adopts one or more distillation towers to perform high-precision distillation cutting, and the total theoretical number of tower plates is at least 14 layers, so as to cut out a gasoline middle fraction rich in benzene with a distillation range of 60-90° C., and directly carry out alkylation. The cutting scheme is flexible and the enrichment efficiency is high. It is unnecessary to further hydrogenate, remove or other treatments on the fraction cut by the distillation, thereby simplifying the production process and improving the production efficiency.

[0084] In step (2), the low-carbon alcohol is a C1-C3 alkyl alcohol, preferably methanol, ethanol and / or isopropanol;

[0085] Preferably, in step (2), the molar ratio of the lower alcohol to benzene is maintained at 0.2 to 7.0:1, more preferably 0.5 to 5.0:1.

[0086] In one embodiment, the benzene-rich gasoline middle fraction is preheated before entering the first reactor, and the preheating temperature is 50-350°C, preferably 100-300°C.

[0087] In one embodiment, the first reactor is provided with 3 or more low-carbon alcohol injection ports in sections; and / or

[0088] The content of low-carbon alcohol in the low-carbon alcohol stream is 50 to 100 weight %.

[0089] The method of the present application injects the lower alcohol alkylating agent in stages and always maintains the alcohol / benzene molar ratio at 0.2 to 7.0:1, so that the conversion rate of benzene is higher, it is easier to implement, and the reactor operating conditions are easy to control.

[0090] 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.

[0091] In the present invention, the benzene-rich gasoline intermediate fraction reaction oil and gas enters a moving bed, fixed bed or fluidized bed reactor and contacts with low-carbon alcohols in stages, and low-carbon alcohols are injected in stages to maintain the alcohol / benzene molar ratio within a certain range; the catalyst in the moving bed reactor is in a uniform downward moving state, 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 three low-carbon alcohol flow injection ports are arranged in sections; the catalyst in the fluidized bed reactor is in a turbulent fluidization state, the oil and gas apparent average linear velocity 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 three low-carbon alcohol flow injection ports are arranged 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 three reaction zones, and a low-carbon alcohol flow injection port is arranged upstream of each reaction zone.

[0092] 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;

[0093] Preferably, the mesoporous molecular sieve is selected from β series, ZSM series and / or Y series mesoporous zeolite, more preferably a composite mesoporous zeolite of ZSM series and β series; and / or

[0094] Preferably, the heat-resistant inorganic oxide is aluminum oxide and / or silicon oxide.

[0095] The catalyst of the present invention is a mesoporous molecular sieve catalyst, which is a catalyst composed of molecular sieve and heat-resistant inorganic oxide, wherein the catalyst molecular sieve is an optional mesoporous zeolite of β 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 ZSM series and β composite mesoporous 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. The catalyst of the present invention is simple to prepare and has a high benzene conversion rate.

[0096] In one embodiment, the catalytic alkylation reaction temperature is 400-550°C, preferably 420-520°C;

[0097] The reaction pressure is 0.1-1.0 MPa, preferably 0.2-0.8 MPa;

[0098] The weight ratio of catalyst to feedstock oil is 0.7 to 7.0:1, preferably 1.0 to 5.0:1; and / or

[0099] Weight hourly space velocity is 0.5~25.0h -1 , preferably 1.0~15.0h -1 .

[0100] 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.

[0101] In one embodiment, the oxygen-containing regeneration atmosphere is air and / or oxygen atmosphere, preferably oxygen-enriched and / or pure oxygen atmosphere.

[0102] 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.

[0103] In one embodiment, the regeneration temperature of the regenerator is 450-750°C, preferably 500-700°C;

[0104] The regeneration pressure of the regenerator is 0.2-1.5 MPa, preferably 0.2-1.0 MPa; and / or

[0105] The flue gas temperature circulating back to the regenerator is 300-600°C.

[0106] The alkylation debenzenization of benzene-rich gasoline of the present invention can be coupled with the catalytic cracking of heavy oils such as wax oil and residual oil, and the reaction is carried out in two different reactors, and a catalyst regeneration system and an oil-gas separation system are shared, so the integration is high. Moreover, after the alkylation reaction, the catalyst is regenerated and recycled, or added into a heavy oil catalytic cracking reactor, so that not only continuous production is realized, but also a high activity of the catalyst can be always maintained, thereby solving the problem that the alkylation catalyst is easily coked and deactivated when processing high-olefin catalytic cracking gasoline or steam cracking gasoline.

[0107] The method for producing low-benzene gasoline by coupling the present invention with heavy oil catalytic cracking comprises:

[0108] (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;

[0109] (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;

[0110] (3) distilling the gasoline components in a gasoline distillation system to obtain a self-produced gasoline benzene-rich fraction and a low-benzene gasoline;

[0111] (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 graded injected low-carbon alcohol stream under non-hydrogenation or hydrogenation conditions to perform a catalytic alkylation reaction to obtain a first mixed material comprising a first spent catalyst and a first oil gas;

[0112] (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;

[0113] (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.

[0114] Wherein, the heavy oil is wax oil and / or residual oil.

[0115] 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 %.

[0116] In one embodiment, the gasoline benzene-rich fraction is obtained by distilling and cutting the benzene-rich gasoline to obtain a benzene-rich gasoline middle fraction with a distillation range of 60 to 90° C.

[0117] Wherein, the benzene content of the benzene-rich gasoline is 0.8 to 20 weight %;

[0118] 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.

[0119] The present invention also provides a system for producing low-benzene content gasoline, comprising:

[0120] A catalytic cracking reaction unit, the catalytic cracking reaction unit comprising

[0121] - catalytic cracking reactor,

[0122] - Catalytic cracking oil separator, and

[0123] - steam exchanger;

[0124] The catalytic cracking oil agent separator is connected to the oil and gas outlet of the catalytic cracking reactor, and is used to separate the reaction oil agent from the catalytic cracking reactor, and allow the separated catalytic cracking spent catalyst to enter the steam exchanger for stripping;

[0125] The heavy oil is catalytically cracked in the catalytic cracking reaction unit, and the catalytic cracking reactor is preferably a riser reactor; the gas exchanger can be arranged in the catalytic cracking reactor;

[0126] A gasoline-benzene catalytic conversion unit, the gasoline-benzene catalytic conversion unit comprising

[0127] - a reactor for catalytic conversion of gasoline benzene, and

[0128] - Oil filter separator;

[0129] The oil filter separator is connected to the oil and gas outlet of the gasoline-benzene catalytic conversion reactor and is used to separate the reaction oil from the gasoline-benzene catalytic conversion reactor;

[0130] The lower part of the gasoline-benzene catalytic conversion reactor is connected to the steam exchanger of the catalytic cracking reaction unit, so that the gasoline-benzene catalytic conversion catalyst to be spent in the gasoline-benzene catalytic conversion reactor enters the steam exchanger for stripping;

[0131] The gasoline-benzene catalytic conversion reactor is provided with a gasoline benzene-rich fraction inlet and a plurality of low-carbon alcohol stream inlets. Preferably, the gasoline-benzene catalytic conversion reactor is provided with 3 or more low-carbon alcohol stream inlets;

[0132] The gasoline benzene catalytic conversion reactor is selected from a fluidized bed reactor, a moving bed reactor or a fixed bed reactor, preferably a moving bed reactor;

[0133] The gasoline benzene catalytic conversion unit adopts the above-mentioned gasoline benzene catalytic conversion method to catalytically convert the benzene in the gasoline raw material to achieve the purpose of producing gasoline with low benzene content;

[0134] A regenerator, wherein the regenerator is connected to the steam exchanger of the catalytic cracking reaction unit, so that the regenerated catalyst that has been stripped in the steam exchanger enters the regenerator for regeneration; the regenerator is also respectively connected to the catalytic cracking reactor of the catalytic cracking reaction unit and the gasoline-benzene catalytic conversion reactor of the gasoline-benzene catalytic conversion unit, so that the regenerated catalyst circulates back to the catalytic cracking reactor and the gasoline-benzene catalytic conversion reactor;

[0135] The regenerator can be regenerated by air and / or oxygen; preferably, regenerated by oxygen-enriched and / or pure oxygen; the flue gas after regeneration can be partially or completely recycled back to the regenerator;

[0136] an oil-gas separation unit, the oil-gas separation unit being respectively connected to the catalytic cracking oil agent separator of the catalytic cracking reaction unit and the oil agent filter separator of the gasoline-benzene catalytic conversion unit, so that the oil and gas products from the catalytic cracking reaction unit and the gasoline-benzene catalytic conversion unit are separated in the oil-gas separation unit to obtain products including dry gas, liquefied gas and gasoline; and

[0137] A gasoline distillation unit, wherein the gasoline distillation unit is connected to the gasoline fraction outlet of the oil-gas separation unit, so that the gasoline fraction from the oil-gas separation unit is distilled in the gasoline distillation unit to obtain a self-produced gasoline benzene-rich fraction and a low-benzene gasoline after distillation; the self-produced gasoline benzene-rich fraction outlet of the gasoline distillation unit is connected to the gasoline benzene-rich fraction inlet of the gasoline-benzene catalytic conversion reactor, so that the self-produced gasoline benzene-rich fraction from the gasoline distillation unit enters the gasoline-benzene catalytic conversion reactor for benzene catalytic conversion; wherein the gasoline distillation unit comprises one or more distillation towers VII, preferably, the total theoretical plate number of the distillation tower is greater than or equal to 14;

[0138] The gasoline source of the gasoline-benzene catalytic conversion reactor can also come from other gasoline benzene-rich fractions, which are obtained by distilling and cutting the benzene-rich gasoline to obtain a benzene-rich gasoline middle fraction with a distillation range of 60-90°C.

[0139] 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.

[0140] The following examples will further illustrate the method, but are not intended to limit the method.

[0141] In the embodiment, the full-fraction gasoline raw material A is catalytic cracking gasoline from a refinery. A is distilled and cut to obtain a benzene-rich fraction raw material oil B. The low-carbon alcohols are qualified industrial methanol and industrial ethanol with a purity of more than 99% by weight. The heavy raw material oil is hydrogenated residue oil from a refinery. The properties of the three raw materials are shown in Table 1.

[0142] The catalysts used in the examples are the same, and their preparation methods are briefly described as follows:

[0143] 1) 15.0 kg of MFI structure mesoporous ZRP-1 zeolite powder (industrial product of Sinopec Catalyst Qilu Branch, SiO2 / Al2O3=17.4, phosphorus content P2O5=4.5% by weight, solid content 91.75%), 5.0 kg of mesoporous β zeolite powder (industrial product of Sinopec Catalyst Qilu Branch, SiO2 / Al2O3=11.7, solid content 90.68%), and 113.3 kg of 3% by weight ammonium chloride aqueous solution are stirred in a reactor at 70-80°C for 2 hours, and ammonium exchange is performed twice; the mixture is cooled, the liquid is removed, and an ion exchange catalyst is obtained after washing with water; the ion exchange catalyst is dried at 120°C and calcined at 500°C for 3 hours to obtain a ZRP-1 and β composite H-type molecular sieve.

[0144] 2) 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.

[0145] 3) Forming and drying: 18 kg of composite H-type molecular sieve (solid content is 91% by weight) obtained in step 1) is mixed with 48 kg of decationized water at a solid-liquid ratio of 1:1-1:10, and 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 is 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 the mixture is placed in a bonding machine and stirred continuously until a uniform sol is formed; the sol is placed in the air for 4 hours, formed by rolling with a rolling machine, and then placed for 24 hours, and then dried in a drying oven at 120°C for 3 hours, and free Na + , dried at about 120°C for 3 hours, and then calcined at 500-800°C for 3 hours to obtain a catalyst named CAT-A1.

[0146] CAT-A1 has an average particle size of 2-4 mm and is used as a moving bed alkylation catalyst. The catalyst is composed on a dry basis of 70.68 wt% of MFI structure medium pore zeolite, 9.32 wt% of pseudo-boehmite, 4.18 wt% of aluminum sol and 15.82% of kaolin. Its properties are listed in Table 2.

[0147] 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.

[0148] Example 1

[0149] 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 an alkylation reaction was carried out with staged injected methanol in a moving bed reactor using a CAT-A1 catalyst.

[0150] 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 gasoline middle fraction 1b rich in benzene and a gasoline heavy fraction 1c rich in aromatics, wherein the gasoline middle fraction 1b rich in benzene is generally controlled to have a distillation range of 60-90°C, and more than 50% of the benzene in the gasoline is enriched.

[0151] Using a moving bed reactor I, the benzene-rich gasoline middle fraction 1b is fed into the reactor at the bottom of the moving bed reactor to contact the catalyst, and is contacted with the low-carbon alcohol injected from the bottom, middle and upper parts of the reactor for alkylation 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:

[0152] The benzene-rich gasoline intermediate fraction 1b is fed into the reactor at the lower part of the reactor I to contact the catalyst, and undergoes an alkylation reaction with the low-carbon alcohol stream I2 fed from the bottom of the reactor I. 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 low-carbon alcohol stream II4 and the low-carbon alcohol stream III5 injected into the middle and upper parts of the reactor to strengthen the alkylation of benzene; 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 steam exchanger 24 through the spent catalyst delivery pipeline I10, and then passes through the spent catalyst delivery pipeline I10. After stripping with nitrogen and / or water vapor, the catalyst 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 500-600°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 recycled 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.

[0153] Catalytic cracking gasoline feedstock A is distilled and cut using a 30-plate distillation tower VII (theoretical plate number 18), and a 60-90°C middle fraction rich in benzene is extracted from the middle section of the tower to obtain feedstock B, with a yield of 16.0%. This cutting method consumes 21.59 kg EO / t feedstock.

[0154] After being preheated at 180° C., the feedstock B enters the lower part of the moving fluidized bed reactor I to undergo an alkylation reaction with methanol. Under a reaction pressure of 0.5 MPa, nitrogen is used as a fluidizing medium. As the fluidizing medium flows from bottom to top, methanol is injected into the lower, middle and upper regions of the reactor three times and the molar ratio of methanol to benzene in the reaction system is maintained at not less than 0.5. At a reaction temperature (based on the upper part of the reactor, i.e., the outlet temperature, the same below) of 500° C., a catalyst / feedstock mass ratio of 1.5, and a weight hourly space velocity of 10.0 h -1The alkylation 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 and gasoline products by the separation system; the spent catalyst after the oil agent separation 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 spent catalyst at the regeneration temperature of 500℃ for regeneration; the regenerated regenerated agent is recycled, and the regenerated flue gas is partially recycled, the circulating flue gas temperature is 400℃, and the regeneration dense phase temperature is maintained at 500℃. The operating conditions and product distribution are listed in Table 3.

[0155] 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 an alkylation reaction with graded injected methanol in a moving bed reactor, and the benzene conversion rate was 94.43%, the gasoline yield was 75.62 wt%, the benzene content of the gasoline was reduced to 0.54 wt%, the octane number RON 89.7 was increased by 6.1 units, and the liquefied gas yield was as high as 17.71 wt%.

[0156] Gasoline cutting - benzene-rich fraction moving bed alkylation, after the reaction and then mixed with the remaining gasoline, taking the full fraction catalytic cracking gasoline feedstock oil A as the benchmark, the benzene conversion rate is 67.85%, the benzene content of gasoline is reduced to 0.54% by weight, and the gasoline + liquefied gas yield is 98.90%.

[0157] Comparative Example 1

[0158] By using uncut catalytic cracking gasoline feedstock oil A as raw material and the same process conditions as in Example 1, the alkylation reaction is carried out, except that: 1) Comparative Example 1 uses a riser reactor, and methanol is only injected at the bottom of the reactor; 2) Comparative Example 1 uses a conventional catalytic cracking catalyst CGP; 3) the feedstock oil A-catalytic cracking gasoline in Comparative Example 1 is not cut, and the whole fraction is directly mixed with methanol for feeding; 4) air is used as the regeneration gas, and the flue gas is not circulated; 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.

[0159] As can be seen from Table 3, compared with Comparative Example 2 (alkylation of the gasoline without cutting the entire fraction in a riser reactor), Example 2 (gasoline cutting - benzene-rich fraction moving bed alkylation, and then mixing with the cut gasoline after the reaction) has a benzene conversion rate that is 29.99 percentage points higher, a gasoline benzene content that is 0.54 percentage points lower, and a gasoline+liquefied gas yield that is 3.18 percentage points higher.

[0160] Example 2

[0161] This embodiment follows Figure 2The 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 moving bed reactor, respectively, using catalysts CGP and CAT-A1, respectively.

[0162] Figure 2 This is a process flow diagram of Example 2 of the present invention. The same as Example 1 is that the gasoline benzene-rich fraction alkylation adopts a moving bed reactor I, and the difference is that the heavy crude oil 19 enters a conventional riser reactor, and the catalyst after the benzene alkylation reaction and the catalyst after the heavy oil catalytic cracking reaction can be stripped separately and then enter the same regenerator, or they can share a settler for stripping. In this embodiment, the two use a settler. The process flow is as follows:

[0163] The heavy crude oil 19 is atomized by atomizing steam and fed into the lower part of the heavy oil cracking reactor VI to contact the catalytic cracking catalyst for cracking reaction; the separated reaction oil 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 through a gasoline fractionating 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 is used for gasoline pool blending. The benzene-rich fraction 25 of the self-produced gasoline and the optional benzene-rich gasoline 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 undergo alkylation reaction with the low-carbon alcohol stream I2 fed from the bottom of the reactor; after a period of reaction, they are further contacted with the low-carbon alcohol stream II4 and low-carbon alcohol stream III5 injected into the middle and upper parts of the reactor to strengthen the alkylation of benzene; the spent catalyst after the alkylation 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 VI through the spent catalyst delivery pipeline I10, After stripping by nitrogen and / or water vapor 14 in the steam exchanger 24, the catalyst enters the regenerator II through the spent catalyst delivery pipeline II11; the spent catalyst is regenerated in an oxygen-containing atmosphere in the regenerator II, and the oxygen-containing regeneration gas 15 includes air, oxygen, etc. The regeneration temperature is 600-700°C, and the regenerated catalyst is recycled. The regenerated catalyst is delivered to the heavy oil cracking reactor VI through the regeneration agent delivery pipeline I12, and delivered 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 added to 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.

[0164] After being preheated at 200°C, the heavy crude oil is introduced into the bottom of the riser reactor to contact the catalytic cracking catalyst for cracking reaction. At a reaction pressure of 0.3 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 outlet temperature of the upper part of the reactor, the same below) is 540°C, the mass ratio of catalyst to crude oil is 7.4, the mass ratio of atomized water to crude oil is 11.8, and the weight hourly space velocity is 20.0 h. -1 The cracking reaction was carried out under the following conditions.

[0165] 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.

[0166] After being preheated at 300°C, the benzene-rich fraction E of gasoline enters the lower part of the moving fluidized bed reactor I to undergo alkylation reaction with ethanol. Hydrogen is used as the fluidizing medium and flows from bottom to top at a reaction pressure of 0.3 MPa. Ethanol is injected into the lower, middle and upper regions of the reactor three times and the molar ratio of ethanol to benzene in the reaction system is maintained at not less than 1.0. At a reaction temperature of 450°C, a catalyst / feedstock oil mass ratio of 1.5, and a weight hourly space velocity of 10.0 h -1 The alkylation reaction is carried out under the following conditions, and the oil agent is separated after the reaction.

[0167] 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 product dry gas, liquefied gas, gasoline, diesel and oil slurry. The gasoline is further separated into self-produced benzene-rich gasoline and low-benzene gasoline through the gasoline distillation tower, and the self-produced benzene-rich gasoline (i.e., gasoline benzene-rich fraction E) is circulated back to the reactor.

[0168] The reaction oil and gas after separation of the gasoline benzene-rich fraction alkylation oil agent are merged into the heavy oil cracking oil and gas pipeline. The separated catalyst enters the settling section of the heavy crude oil catalytic cracking reactor, and is 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 spent catalyst at a regeneration dense phase temperature of 650°C. The regenerated regenerated agent is recycled, but the regenerated flue gas is not recycled.

[0169] The operating conditions and product distribution are listed in Table 4.

[0170] As can be seen from Table 4, in Example 2, after alkylation of the gasoline benzene-rich fraction with a benzene content of 7.72% and an octane number RON 82.4, the benzene conversion rate is 83.60%, the benzene content of the gasoline is reduced to 1.19%, the octane number RON is increased to 87.0, and the liquefied gas yield is 2.78%; when the gasoline benzene-rich fraction is alkylated as a recycling and not included in the raw material, the liquefied gas yield of the heavy oil catalytic cracking is 28.19% by weight, the gasoline yield is 34.41% by weight, the gasoline olefin content is 8.38% by weight, the benzene content is 0.56% by weight, and the octane number RON is 97.8.

[0171] It can be seen from Example 1 and Example 2 that the method of the present invention can effectively reduce the benzene content in the gasoline benzene-rich fraction under both hydrogenation and non-hydrogenation conditions, and the benzene conversion rate is high, and a good benzene reduction effect is achieved.

[0172] Comparative Example 2

[0173] By using the same heavy crude oil C as the raw material, the same catalyst and process conditions as in Example 2 for cracking reaction, the gasoline obtained by cracking the heavy crude oil is cut to obtain a benzene-rich fraction which is also subjected to alkylation reaction with ethanol, except that: 1) the gasoline in Comparative Example 2 is cut to obtain a benzene-rich fraction which accounts for 13.17% of the heavy oil feed; 2) the benzene-rich fraction of gasoline is mixed with ethanol and fed to the upper part of the riser reactor for recycling. The operating conditions and product distribution are listed in Table 4.

[0174] As can be seen from Table 4, compared with Example 2 (alkylation of gasoline benzene-rich fraction with ethanol in a moving bed with staged injection) and Comparative Example 2 (alkylation of gasoline benzene-rich fraction with ethanol in the upper part of a riser reactor), the benzene content of gasoline is 1.09 percentage points lower, the octane number RON is 1.3 units, and the liquefied gas yield is 8.09 percentage points higher.

[0175] 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.

[0176] Table 1

[0177]

[0178] Table 2

[0179] Catalyst No. CAT-A1 CGP Chemical composition, weight % Rare Earth - 2.48 Phosphorus pentoxide 4.41 0.48 Sodium oxide 0.11 0.24 Alumina 44.30 53.74 Silicon oxide 49.90 43.06 <![CDATA[Apparent density, kg / m 3 > 825 830 Pore ​​volume, ml / g 0.18 0.18 <![CDATA[Specific surface area, m 2 / g]]> 185.0 139.47 <![CDATA[Wear index, wt% -1 > 1.35 1.3 Average particle size 3.2 mm 74.5 microns

[0180] Table 3

[0181]

[0182]

[0183] The * column represents the data obtained when the feedstock oil B is fed into the moving bed reactor and is based on the feedstock oil B;

[0184] The ** column represents the data obtained in Example 1 based on the feedstock oil B, which is converted to the feedstock oil A.

[0185] *** indicates the mixed gasoline obtained by mixing the crude oil B (i.e. the benzene-rich fraction of crude oil A) with the gasoline obtained by cutting the benzene-rich fraction of crude oil A (i.e. crude oil B) after reacting in a moving bed reactor

[0186] Table 4

[0187]

[0188]

[0189] 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)

[0190] 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)

[0191] The ### column represents the overall data of Example 2 (based on raw oil C).

Claims

1. A method for catalytic conversion of gasoline benzene, 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 intermediate fraction enters the first reactor and contacts the catalyst with the graded injected low-carbon alcohol stream under non-hydrogenation or hydrogenation conditions to carry out a catalytic alkylation 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 20% by weight; the low-carbon alcohol is a C1 to C3 alkyl alcohol, preferably methanol, ethanol and / or isopropanol; Preferably, in step (2), the molar ratio of the lower alcohol to benzene is maintained at 0.2 to 7.0:1, more preferably 0.5 to 5.0:

1.

2. The method according to claim 1, characterized in that The first reactor is provided with 3 or more low-carbon alcohol injection ports in sections; and / or The content of low-carbon alcohol in the low-carbon alcohol stream is 50 to 100 weight %.

3. The method according to claim 1, characterized in that The catalytic alkylation reaction temperature is 400-550°C, preferably 420-520°C; The reaction pressure is 0.1-1.0 MPa, preferably 0.2-0.8 MPa; The weight ratio of catalyst to feedstock oil is 0.7 to 7.0:1, preferably 1.0 to 5.0:1; and / or Weight hourly space velocity is 0.5~25.0h -1 , preferably 1.0~15.0h -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.

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 β series, ZSM series and / or Y series mesoporous zeolite, more preferably a composite mesoporous zeolite of ZSM series and β 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 gasoline middle fraction is preheated before entering the first reactor, and the preheating temperature is 50-350°C, preferably 100-300°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 450-750°C, preferably 500-700°C; The regeneration pressure of the regenerator is 0.2-1.5 MPa, preferably 0.2-1.0 MPa; and / or The flue gas temperature circulating back to the regenerator is 300-600°C.

9. A method for producing low benzene content gasoline, 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 graded injected low-carbon alcohol stream under non-hydrogenation or hydrogenation conditions to perform a catalytic alkylation reaction to obtain a first mixed material comprising a first spent catalyst and a first oil 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 gasoline benzene-rich fraction is obtained by distilling and cutting the benzene-rich gasoline to obtain a benzene-rich gasoline middle fraction with a distillation range of 60 to 90° C. Wherein, the benzene content of the benzene-rich gasoline is 0.8 to 20 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.

11. A system for producing low benzene content gasoline, comprising: A catalytic cracking reaction unit, the catalytic cracking reaction unit comprising - catalytic cracking reactor, - Catalytic cracking oil separator, and - steam exchanger; The catalytic cracking oil agent separator is connected to the oil and gas outlet of the catalytic cracking reactor, and is used to separate the reaction oil agent from the catalytic cracking reactor, and allow the separated catalytic cracking spent catalyst to enter the steam exchanger for stripping; A gasoline-benzene catalytic conversion unit, the gasoline-benzene catalytic conversion unit comprising - a reactor for catalytic conversion of gasoline benzene, and - Oil filter separator; The oil filter separator is connected to the oil and gas outlet of the gasoline-benzene catalytic conversion reactor and is used to separate the reaction oil from the gasoline-benzene catalytic conversion reactor; The lower part of the gasoline-benzene catalytic conversion reactor is connected to the steam exchanger of the catalytic cracking reaction unit, so that the gasoline-benzene catalytic conversion catalyst to be spent in the gasoline-benzene catalytic conversion reactor enters the steam exchanger for stripping; The gasoline-benzene catalytic conversion reactor is provided with a gasoline benzene-rich fraction inlet and a plurality of low-carbon alcohol stream inlets. Preferably, the gasoline-benzene catalytic conversion reactor is provided with 3 or more low-carbon alcohol stream inlets; A regenerator, wherein the regenerator is connected to the steam exchanger of the catalytic cracking reaction unit, so that the regenerated catalyst that has been stripped in the steam exchanger enters the regenerator for regeneration; the regenerator is also respectively connected to the catalytic cracking reactor of the catalytic cracking reaction unit and the gasoline-benzene catalytic conversion reactor of the gasoline-benzene catalytic conversion unit, so that the regenerated catalyst circulates back to the catalytic cracking reactor and the gasoline-benzene catalytic conversion reactor; an oil-gas separation unit, the oil-gas separation unit being respectively connected to the catalytic cracking oil agent separator of the catalytic cracking reaction unit and the oil agent filter separator of the gasoline-benzene catalytic conversion unit, so that the oil and gas products from the catalytic cracking reaction unit and the gasoline-benzene catalytic conversion unit are separated in the oil-gas separation unit; and A gasoline distillation unit, wherein the gasoline distillation unit is connected with the gasoline fraction outlet of the oil-gas separation unit, so that the gasoline fraction from the oil-gas separation unit is distilled in the gasoline distillation unit to obtain a self-produced gasoline benzene-rich fraction and a low-benzene gasoline after distillation; the self-produced gasoline benzene-rich fraction outlet of the gasoline distillation unit is connected with the gasoline benzene-rich fraction inlet of the gasoline-benzene catalytic conversion reactor, so that the self-produced gasoline benzene-rich fraction from the gasoline distillation unit enters the gasoline-benzene catalytic conversion reactor for benzene catalytic conversion; wherein the gasoline distillation unit includes one or more distillation towers, and preferably, the total theoretical number of plates of the distillation tower is greater than or equal to 14.

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