Process for catalytic conversion of benzene in gasoline, process and system for producing gasoline with low benzene content

Abstract

The present application provides a method for catalytic conversion of benzene in gasoline, a method and system for producing low-benzene gasoline, and a method for producing low-benzene gasoline. The benzene-rich gasoline is cut into light distillate, middle distillate and heavy distillate by high-precision distillation. The benzene-rich middle distillate is contacted with a low-carbon alcohol fractionation medium pore molecular sieve catalyst in a moving bed, fixed bed or fluidized bed reactor to perform catalytic alkylation, thereby efficiently converting benzene into alkylbenzene, and converting the benzene-rich gasoline into high-octane low-benzene gasoline and liquefied gas. The method of the present application reduces the benzene content and olefin content in gasoline, while increasing the octane rating of gasoline and increasing the production of liquefied gas. Not only does the method solve the problem of high benzene content in refinery gasoline, which is difficult to meet the national VI standard for motor gasoline, but it also improves the quality of gasoline and increases the production of liquefied gas.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalytic conversion of benzene in gasoline, in particular to a method for catalytic conversion of benzene in gasoline, a method for producing gasoline with low benzene content and a reaction system thereof. BACKGROUND

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

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

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

[0005] Hydrogenation saturation benzene reduction technology has CD Tech company hydrogenation reactor with product stripping column combined and implemented catalytic distillation hydrogenation saturation reduction benzene(CD Hydro) process, UOP company using Pt-based catalyst Bensat process, IFP and Axens company Benfree process, GTC company GT-BenZapSM process and Neste company NExSAT process. Hydrogenation saturation benzene reduction only has 20 or so device application.

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

[0007] Ethylene as a basic chemical material, resource shortage. After research found that methanol and other low carbon alcohol can also be with benzene alkylation reaction. For benzene and low carbon alcohol alkylation reduce benzene patent technology, patent CN200910236630.8 published a kind of catalytic conversion method for reducing the benzene content of gasoline, benzene containing gasoline and alcohol are contacted with catalytic cracking catalyst in fluidized bed and / or riser reactor, the benzene content of gasoline can be reduced by more than 60% by volume. CN200910043913.0 published a kind of method for reducing the benzene content of benzene containing gasoline, benzene containing gasoline and methanol are subjected to alkylation reaction in the fixed bed reactor with catalyst, the benzene content of benzene containing gasoline is reduced from 20-60wt% to 3-7wt%. CN201710342646.1 published a kind of method for reducing the benzene content of benzene rich gasoline, benzene rich gasoline, methanol and hydrogen are reacted with modified ZSM-5 molecular sieve, MCM-56 molecular sieve and beta molecular sieve alkylation catalyst to reduce benzene, improve the utilization rate of methanol > 99%. There are also patents that FCC gasoline benzene and low carbon alcohol alkylation and catalytic cracking coupling patent technology, patent CN201010296622.5 published a kind of catalytic conversion method for reducing the benzene content of gasoline, benzene containing gasoline and alcohol are contacted with catalytic cracking catalyst in multiple reaction zones, the volume content of benzene can be reduced by more than 65%.

[0008] Domestic and foreign benzene reduction patents and foreign hydrogen saturation benzene reduction and liquid phase alkylation benzene reduction technology are all aimed at reducing benzene in reforming gasoline fraction with low olefin and without sulfur, nitrogen and water, and are not suitable for reducing benzene in catalytic cracking gasoline with high olefin, high sulfur and nitrogen content and relatively low benzene content. At present, there is no mature and low cost efficient method for reducing benzene content of catalytic cracking gasoline at home and abroad. Therefore, the catalytic cracking unit in the execution of processing hydrogenation catalytic diesel or high yield of liquefied gas production scheme all have the problem of exceeding the standard of stable gasoline benzene content, as high as 1.2v% or more, and it is urgent to develop a production method for reducing the benzene content of catalytic cracking gasoline. SUMMARY

[0009] The purpose of the present application is to provide a method for catalytically converting gasoline benzene into alkylbenzene while converting benzene rich gasoline into high octane low benzene gasoline and liquefied gas, which improves the quality of gasoline and increases the yield of liquefied gas. Specifically, a method for producing low benzene and low olefin gasoline by catalytically alkylating benzene rich gasoline intermediate fraction obtained by high precision distillation cutting of benzene rich gasoline with low carbon alcohol on a mesoporous molecular sieve catalyst is provided, which improves the octane number of gasoline and increases the yield of liquefied gas.

[0010] The first aspect of the present application provides a method for catalytically converting gasoline benzene, which comprises:

[0011] (1) distillation cutting of benzene rich gasoline to obtain benzene rich gasoline intermediate fraction with a distillation range of 60-90℃;

[0012] (2) the benzene-rich gasoline intermediate fraction enters a first reactor to contact a catalytic alkylation catalyst under non-hydrogen or hydrogen conditions with a staged injection of a low carbon alcohol stream to obtain a first mixture of spent catalyst and first oil gas;

[0013] (3) the first mixture passes through an oil separation filter of the first reactor to separate the first oil gas, which enters an oil gas separation system to separate products including dry gas, liquefied gas, and gasoline;

[0014] (4) the separated first spent catalyst is stripped in a stripper and then enters a regenerator for oxygen-containing regeneration, and the regenerated catalyst returns to the first reactor for recycling, and preferably, part or all of the flue gas after regeneration is recycled back to the regenerator;

[0015] Preferably, the benzene content of the benzene-rich gasoline is 0.8-20 wt%; the low carbon alcohol is a C1-C3 alkyl alcohol, preferably methanol, ethanol, and / or isopropyl alcohol;

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

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

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

[0019] According to the method of the first aspect of the application, 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 raw oil is 0.7-7.0:1, preferably 1.0-5.0:1; and / or

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

[0023] According to the method of the first aspect of the application, the first reactor is selected from a fluidized bed reactor, a moving bed reactor, or a fixed bed reactor, preferably a moving bed reactor.

[0024] The method according to the first aspect of the present application, wherein the distillation cut of the benzene-rich gasoline is carried out by using one or more than one rectifying column.

[0025] Preferably, the total number of theoretical plates of the rectifying column is greater than or equal to 14.

[0026] 6. The method according to claim 1, wherein the catalyst comprises mesoporous molecular sieve, heat-resistant inorganic oxide and optional clay, wherein the mesoporous molecular sieve accounts for 30-80 wt% of the total amount of the catalyst.

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

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

[0029] The method according to the first aspect of the present application, wherein the benzene-rich gasoline is catalytically cracked gasoline, hydrocracked gasoline, reformed gasoline and / or steam-cracked gasoline with a boiling point of 30-220℃; and / or

[0030] The benzene-rich gasoline intermediate fraction is preheated to enter the first reactor, and the preheating temperature is 50-350℃, preferably 100-300℃.

[0031] The method according to the first aspect of the present application, wherein the oxygen-containing regeneration atmosphere is air and / or oxygen atmosphere, preferably oxygen-enriched and / or pure oxygen atmosphere.

[0032] The regeneration temperature of the regenerator is 450-750℃, preferably 500-700℃.

[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℃.

[0035] The second aspect of the present application provides a method for producing low-benzene-content gasoline, which comprises:

[0036] (1) catalytically cracking heavy oil in a second reactor to obtain a second mixture comprising second spent catalyst and second oil gas;

[0037] (2) separating the second mixture in an oil gas separation system to obtain dry gas component, liquefied gas component and gasoline component;

[0038] (3) distilling the gasoline component in a gasoline rectification system to obtain self-produced gasoline benzene-rich fraction and low-benzene-content gasoline.

[0039] (4) the gasoline benzene-rich fraction and optionally other gasoline benzene-rich fraction are fed into a first reactor to contact with a staged-in low carbon alcohol stream under non-hydrogen or hydrogen conditions to perform catalytic alkylation reaction to obtain a first mixture comprising a first spent catalyst and a first oil gas;

[0040] (5) the first mixture is separated by an oil agent separation filter of the first reactor, and the separated oil gas is fed into the oil gas separation system to perform oil gas separation;

[0041] (6) the separated first spent catalyst is mixed with a second spent catalyst in a second reactor, and after being stripped by a steam stripper of the second reactor, is fed into a regenerator to perform oxygen-containing regeneration, and the regenerated catalyst is returned to the first reactor and the second reactor for recycling, and preferably, part or all of the flue gas after regeneration is recycled back to the regenerator;

[0042] The heavy oil is wax oil and / or residual oil.

[0043] According to the method of the second aspect of the present application, the gasoline benzene-rich fraction is a benzene-rich gasoline intermediate fraction with a distillation cut of 60-90°C obtained by distillation cutting of the benzene-rich gasoline.

[0044] The benzene content of the benzene-rich gasoline is 0.8-20 wt%.

[0045] Preferably, the benzene-rich gasoline is catalytic cracking gasoline, hydrocracking gasoline, reforming gasoline and / or steam cracking gasoline with a boiling point of 30-220°C.

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

[0047] a catalytic cracking reaction unit, which comprises

[0048] a catalytic cracking reactor,

[0049] a catalytic cracking oil agent separator, and

[0050] a steam stripper;

[0051] The catalytic cracking oil agent separator is connected to the oil gas outlet of the catalytic cracking reactor for separating the reaction oil agent from the catalytic cracking reactor and allowing the separated catalytic cracking spent catalyst to enter the steam stripper for stripping.

[0052] a gasoline benzene catalytic conversion unit, which comprises

[0053] a gasoline benzene catalytic conversion reactor, and

[0054] - an oil agent filtering separator;

[0055] wherein the oil agent filtering separator is connected with the oil gas outlet of the gasoline benzene catalytic conversion reactor for separating reaction oil agent from the gasoline benzene catalytic conversion reactor;

[0056] the lower part of the gasoline benzene catalytic conversion reactor is communicated with the gasoline stripping column of the catalytic cracking reaction unit, so that the gasoline benzene catalytic conversion spent catalyst of the gasoline benzene catalytic conversion reactor enters the gasoline stripping column 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 communicated with the gasoline stripping column of the catalytic cracking reaction unit, so that the spent catalyst stripped in the gasoline stripping column enters the regenerator for regeneration; the regenerator is also communicated with the catalytic cracking reactor of the catalytic cracking reaction unit and the gasoline benzene catalytic conversion reactor of the gasoline benzene catalytic conversion unit respectively, so that the regenerated catalyst is circulated back to the catalytic cracking reactor and the gasoline benzene catalytic conversion reactor;

[0059] an oil gas separation unit, which is communicated with the catalytic cracking oil agent separator of the catalytic cracking reaction unit and the oil agent filtering separator of the gasoline benzene catalytic conversion unit respectively, so that the oil 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 rectification unit, which is communicated with the gasoline fraction outlet of the oil gas separation unit, so that the gasoline fraction from the oil gas separation unit is rectified in the gasoline rectification unit to obtain a gasoline benzene-rich fraction and a low-benzene gasoline after rectification; the gasoline benzene-rich fraction outlet of the gasoline rectification unit is communicated with the gasoline benzene-rich fraction inlet of the gasoline benzene catalytic conversion reactor, so that the gasoline benzene-rich fraction from the gasoline rectification unit enters the gasoline benzene catalytic conversion reactor for benzene catalytic conversion; wherein the gasoline rectification unit comprises one or more rectification columns, preferably, the total theoretical plate number of the rectification column is greater than or equal to 14.

[0061] Compared with the prior art, the present application 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 low-carbon alcohol injected in stages to perform mesoporous molecular sieve catalytic alkylation, so that the benzene conversion rate is high, the gasoline octane number is improved, and liquefied gas production is increased.

[0063] (2) The regenerated catalyst is recycled for use, or is added to the heavy oil catalytic cracking reactor, so that continuous production is realized, and the high activity of the catalyst can be maintained, and the problem of easy coking and deactivation of the catalyst for processing high olefin catalytic cracking gasoline or steam cracking gasoline alkylation is solved.

[0064] (3) The flue gas after heat exchange with the main air is partially or totally recycled, so that the oxygen in the flue gas is fully utilized, the heat carried out of the reactor and regenerator system by the flue gas is solved, and the emission of waste gas such as carbon dioxide is reduced, and energy saving and emission reduction are greatly realized.

[0065] (4) The application range is wide, and it is not only suitable for benzene-containing reforming gasoline with low olefin, low sulfur and low nitrogen content (benzene 2-10 wt%), but also can be used for catalytic cracking gasoline with high olefin, high sulfur and high nitrogen content and relatively low benzene content (benzene 0.8-3.0 wt%), and steam cracking gasoline with high olefin, high sulfur and high nitrogen content and also high benzene content (benzene 20-40 wt%). BRIEF DESCRIPTION OF DRAWINGS

[0066] Figure 1 It is a process flow schematic diagram of a mobile bed reactor for benzene alkylation of the present application, which is used to illustrate the continuous process flow of fluidized bed catalytic alkylation of benzene-rich gasoline.

[0067] Figure 2 It is a process flow schematic diagram of a mobile bed reactor for benzene alkylation combined with catalytic cracking of heavy oil of the present application, which is used to illustrate the process flow of coupling processing of alkylation of benzene-rich gasoline middle distillate and catalytic cracking of heavy oil.

[0068] BRIEF DESCRIPTION OF DRAWINGS

[0069] I, mobile bed reactor; II, regenerator; III, oil-gas separation system; IV, oil agent filter separator; V, gasoline rectification system; VI, heavy oil cracking reactor; VII, rectification column; 1, benzene-rich gasoline; 1a, gasoline light fraction without aromatic hydrocarbon; 1b, gasoline middle distillate rich in benzene; 1c, gasoline heavy fraction rich in aromatic hydrocarbon; 2, low carbon alcohol stream I; 3, fluidization medium; 4, low carbon alcohol stream II; 5, low carbon alcohol stream III; 6, reaction oil gas pipeline dry gas; 7, dry gas; 8, liquefied gas; 9, gasoline; 10, spent agent conveying pipeline I; 11, spent agent conveying pipeline II; 12, regenerated agent conveying pipeline I; 13, regenerated agent conveying pipeline II; 14, stripping medium; 15, oxygen-containing regeneration gas; 16, flue gas; 17, flue gas circulation pipeline; 18, agent feeding pipeline; 19, heavy raw material oil; 20, atomization medium; 21, pre-lifting medium; 22, diesel; 23, oil slurry; 24, gasoline stripping exchanger; 25, self-produced gasoline benzene-rich fraction; 26, low benzene gasoline after rectification. DETAILED DESCRIPTION

[0070] The application will be further described in detail by the accompanying drawings and examples. The features and advantages of the application will become more apparent through these descriptions.

[0071] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. Unless specifically stated otherwise, the drawings are not drawn to scale and the depiction of an embodiment in a drawing does not imply a certain orientation of the embodiment in use or operation.

[0072] Furthermore, the technical features involved in the different embodiments of the application described below can be combined with each other as long as there is no conflict.

[0073] The inventors of the present application have found through years of research that: (1) the benzene content of high-benzene catalytic cracking gasoline is 0.8-2.0 wt%, which is mainly distributed in the intermediate gasoline fraction of 60-90℃, so the present application adopts distillation cutting to obtain the benzene-rich intermediate fraction for separate processing; (2) in the alkylation of benzene with low-carbon alcohol, it is necessary to maintain the alcohol / benzene molar ratio within a certain range, such as 0.2-7.0:1, in order to maintain a relatively high benzene conversion rate; (3) the benzene-rich intermediate fraction of catalytic cracking gasoline has not only a high olefin content and a low octane number, but also a high content of sulfur and nitrogen and a relatively low benzene content, so the present application adopts a mesoporous molecular sieve catalyst to catalyze the alkylation of benzene in the benzene-rich intermediate fraction with low-carbon alcohol, which can not only reduce the benzene content of catalytic cracking gasoline, but also increase the octane number of gasoline and produce more liquefied gas; (4) the benzene-rich intermediate fraction of catalytic cracking gasoline has a high olefin content, which is easy to coke and deactivate during alkylation, so the coked catalyst can be regenerated by burning in an oxygen atmosphere, and the regenerated catalyst can be recycled for use, which not only realizes continuous production, but also maintains a relatively high activity of the catalyst; (5) the flue gas after regeneration of the coked catalyst is exchanged with the main air, which not only makes full use of the oxygen in the flue gas, but also further solves the problem of heat carried out of the reaction-regeneration system by the flue gas, and reduces the emission of waste gas such as carbon dioxide.

[0074] Based on the above findings, the present application provides a method for reducing benzene in gasoline by catalytically alkylating benzene in a benzene-rich gasoline fraction with low-carbon alcohol using a graded mesoporous molecular sieve catalyst, i.e. the benzene-rich intermediate fraction is obtained by high-precision distillation cutting of benzene-rich gasoline, and then introduced into a moving bed, fixed bed or fluidized bed reactor, and contacted with low-carbon alcohol non-hydrogen or hydrogen in the presence of a graded mesoporous molecular sieve catalyst at a suitable temperature and pressure to perform catalytic alkylation; the coked and deactivated catalyst is regenerated in an oxygen-containing regeneration system, and part and / or all of the high-temperature flue gas after regeneration is returned to the regenerator; thus realizing self-heat balance of the gasoline benzene alkylation reaction and continuous regeneration, achieving a high conversion rate of benzene in the presence of a highly active catalyst, and realizing efficient continuous production.

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

[0076] (1) distillation cutting of benzene-rich gasoline to obtain a benzene-rich gasoline intermediate fraction with a distillation range of 60-90°C;

[0077] (2) the benzene-rich gasoline intermediate fraction is introduced into a first reactor to contact a catalyst under non-hydrogen or hydrogen conditions with a staged injection of a low-carbon alcohol stream to perform a catalytic alkylation reaction, to obtain a first mixture of spent catalyst and first oil gas;

[0078] (3) the first mixture is separated by an oil agent separation filter of the first reactor, and the separated first oil gas is introduced into an oil gas separation system to separate products, to obtain products including dry gas, liquefied gas and gasoline;

[0079] (4) the separated first spent catalyst is introduced into a regenerator after stripping by a steam stripper to perform oxygen-containing regeneration, and the regenerated catalyst is returned to the first reactor for recycling, and 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 wt%, and the benzene-rich gasoline is catalytic cracking gasoline, hydrocracking gasoline, reforming gasoline and / or steam cracking gasoline with a boiling point of 30-220°C.

[0081] In the present application, the benzene-rich gasoline is mainly catalytic cracking gasoline with a boiling point of 30-220°C and / or gasoline fraction from a hydrocracking unit and / or a reforming unit and / or a steam cracking unit and other sources, and the benzene content is 0.8-20 wt%. The benzene-rich gasoline is subjected to high-precision distillation cutting to obtain an aromatic hydrocarbon-free gasoline light fraction, a benzene-rich gasoline intermediate fraction and an aromatic hydrocarbon-rich gasoline heavy fraction. The benzene-rich gasoline intermediate fraction is generally controlled to have a distillation range of 60-90°C, and to enrich more than 50% of benzene in gasoline. In principle, the benzene content of the gasoline obtained by mixing the gasoline light fraction and the aromatic hydrocarbon-rich gasoline heavy fraction meets the blending requirements of refinery gasoline, and the benzene is maximally enriched at a lower energy consumption, and the yield of the benzene-rich gasoline intermediate fraction is low.

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

[0083] The method of the present application adopts one or more than one rectification tower to carry out high-precision distillation cutting, and the total theoretical plate number is at least 14 or more, so as to cut a benzene-rich gasoline intermediate fraction with a distillation range of 60-90°C, and directly carry out alkylation, the cutting scheme is flexible, the enrichment efficiency is high, and the fraction cut by rectification does not need to be further treated by hydrogenation and removal, so that the production process is simplified and the production efficiency is improved.

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

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

[0086] In an embodiment, the benzene-rich gasoline intermediate fraction is preheated to enter the first reactor, and the preheating temperature is 50-350°C, preferably 100-300°C.

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

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

[0089] The method of the present application grades the injection of low-carbon alcohol alkylation agent, and always maintains the molar ratio of alcohol to benzene at 0.2-7.0:1, 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 an 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 application, the benzene-rich gasoline intermediate fraction reaction oil gas enters a moving bed or a fixed bed or a fluidized bed reactor to be contacted with low-carbon alcohol in sections, the low-carbon alcohol is injected in sections to maintain the molar ratio of alcohol to benzene within a certain range; the catalyst of the moving bed reactor is in a uniform downward moving state, the catalyst and the reactant stream can be in a concurrent contact reaction or in a countercurrent contact reaction, preferably in a countercurrent contact reaction, and there are 3 or more low-carbon alcohol stream injection ports in sections; the catalyst of the fluidized bed reactor is in a turbulent fluidization state, the average linear velocity of the oil gas is 0.2-2.0 m / s, the catalyst and the reactant stream can be in an upward bed or in a downward bed, preferably in an upward bed, and there are 3 or more low-carbon alcohol stream injection ports 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 3 or more reaction zones, and a low-carbon alcohol stream injection port is provided upstream of each reaction zone.

[0092] In one embodiment, the catalyst comprises a mesoporous molecular sieve, a heat-resistant inorganic oxide, and optionally a clay, wherein the mesoporous molecular sieve accounts for 30-80 wt% of the total catalyst.

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

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

[0095] The catalyst of the present application is a mesoporous molecular sieve catalyst, which is composed of a molecular sieve and a heat-resistant inorganic oxide. The catalyst molecular sieve is a mesoporous zeolite selected from the group consisting of a β series, a ZSM series, and a Y series, and the heat-resistant inorganic oxide is a binder such as alumina and / or silica and / or a natural porous carrier material such as clay. Preferably, the catalyst is a composite of a ZSM series and a β series composite mesoporous zeolite, a binder such as alumina and / or silica, and a natural porous carrier material such as clay, wherein the mesoporous molecular sieve accounts for 30-80 wt% of the total catalyst. The catalyst of the present application 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 the catalyst to the raw oil is 0.7-7.0:1, preferably 1.0-5.0:1; and / or

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

[0100] In the present application, the reactor and the regenerator can be arranged in parallel or overlapped, and the fluidized bed of the fluidized bed reactor and the settler can be built-in or built-out. The spent catalyst can be stripped and lifted by using nitrogen and / or steam as the medium, and the regenerated catalyst is deoxidized and dehydrated by nitrogen stripping and then returned to the reaction stage for recycling.

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

[0102] The catalyst after reaction in the present application enters an oxygen-containing regeneration system for regeneration, and air and / or oxygen can be used for regeneration; preferably, oxygen-rich and / or pure oxygen is used for regeneration. The flue gas after regeneration is partially or totally recycled back to the regenerator, and the high-temperature flue gas containing oxygen is not subjected to heat exchange or is subjected to partial heat exchange, and the temperature thereof is 300-600 DEG C, and part and / or all of the flue gas is returned to the regenerator for recycling, so that the oxygen in the flue gas is fully utilized, and the high regeneration temperature of the regenerator and the high temperature of the regenerant are maintained.

[0103] In one embodiment, the regeneration temperature of the regenerator is 450-750 DEG C, preferably 500-700 DEG 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 recycled back to the regenerator is 300-600 DEG C.

[0106] The de-benzene of the benzene-rich gasoline in the present application can be coupled with catalytic cracking of heavy oil such as wax oil and residual oil, and the reactions are carried out in two different reactors, and a catalyst regeneration system and an oil-gas separation system are shared, so that the integration degree is high, and the catalyst after the alkylation reaction is regenerated and recycled, or is supplemented into a heavy oil catalytic cracking reactor, so that not only continuous production is realized, but also the high activity of the catalyst can be maintained all the time, and the problem of easy coking and deactivation of the alkylation catalyst for processing high-olefin catalytic cracking gasoline or steam cracking gasoline is solved.

[0107] The method for producing low-benzene-content gasoline coupled with catalytic cracking of heavy oil in the present application comprises:

[0108] (1) catalytic cracking of the heavy oil in the second reactor to obtain a second mixture comprising a second spent catalyst and a second oil gas;

[0109] (2) oil-gas separation of the second mixture in an oil-gas separation system to obtain a dry gas component, a liquefied gas component and a gasoline component;

[0110] (3) rectification of the gasoline component in a gasoline rectification system to obtain a self-produced gasoline benzene-rich fraction and a low-benzene-content gasoline;

[0111] (4) the self-produced gasoline benzene-rich fraction and optionally other gasoline benzene-rich fractions are introduced into the first reactor to contact the catalyst under non-hydrogen or hydrogen conditions to carry out catalytic alkylation reaction with a staged injection of a low-carbon alcohol stream, and a first mixture comprising a first spent catalyst and a first oil gas is obtained;

[0112] (5) the first mixture is separated by an oil-catalyst separation filter of the first reactor, and the separated oil gas is introduced into the oil-gas separation system for oil-gas separation;

[0113] (6) the separated first spent catalyst is mixed with the second spent catalyst in a second reactor, stripped by a gas stripping device of the second reactor, and then enters a regenerator for oxygen-containing regeneration, and the regenerated catalyst is returned to the first reactor and the second reactor for recycling, and preferably, part or all of the flue gas after regeneration is recycled back to the regenerator;

[0114] The heavy oil is wax oil and / or residual oil.

[0115] The low-benzene-content gasoline has a benzene content of less than 1.0 wt%, preferably less than 0.8 wt%.

[0116] In one embodiment, the benzene-rich gasoline fraction is a distillation cut benzene-rich gasoline to obtain a benzene-rich gasoline intermediate fraction with a distillation range of 60-90°C.

[0117] The benzene content of the benzene-rich gasoline is 0.8-20 wt%.

[0118] Preferably, the benzene-rich gasoline is catalytic cracking gasoline, hydrocracking gasoline, reforming gasoline and / or steam cracking gasoline with a boiling point of 30-220°C.

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

[0120] a catalytic cracking reaction unit, which comprises

[0121] a catalytic cracking reactor,

[0122] a catalytic cracking oil agent separator, and

[0123] a gas stripping device;

[0124] The catalytic cracking oil agent separator is connected to the oil gas outlet of the catalytic cracking reactor for separating the reaction oil agent from the catalytic cracking reactor and allowing the separated catalytic cracking spent catalyst to enter the gas stripping device 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; and the gas stripping device can be arranged in the catalytic cracking reactor;

[0126] a gasoline benzene catalytic conversion unit, which comprises

[0127] a gasoline benzene catalytic conversion reactor, and

[0128] an oil agent filtering separator;

[0129] The oil agent filter separator is connected with the oil gas outlet of the gasoline benzene catalytic conversion reactor, and is used for separating reaction oil agent from the gasoline benzene catalytic conversion reactor.

[0130] The lower part of the gasoline benzene catalytic conversion reactor is communicated with the gasoline stripping column of the catalytic cracking reaction unit, so that the gasoline benzene catalytic conversion spent catalyst of the gasoline benzene catalytic conversion reactor enters the gasoline stripping column for stripping.

[0131] The gasoline benzene catalytic conversion reactor is provided with a gasoline rich benzene 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 method of gasoline benzene catalytic conversion to catalytically convert benzene in a gasoline raw material, so as to produce low-benzene-content gasoline.

[0134] A regenerator, wherein the regenerator is communicated with the gasoline stripping column of the catalytic cracking reaction unit, so that the spent catalyst stripped in the gasoline stripping column is regenerated in the regenerator; the regenerator is also communicated with the catalytic cracking reactor of the catalytic cracking reaction unit and the gasoline benzene catalytic conversion reactor of the gasoline benzene catalytic conversion unit respectively, so that the regenerated catalyst is circulated 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, oxygen-rich and / or pure oxygen regeneration; the flue gas after regeneration can be partially or wholly circulated back to the regenerator.

[0136] An oil gas separation unit, which is communicated with 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 respectively, so that the oil 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 rectification unit, which is connected with a gasoline fraction outlet of the oil-gas separation unit, so that the gasoline fraction from the oil-gas separation unit is rectified in the gasoline rectification unit to obtain a self-produced gasoline benzene-rich fraction and a low-benzene gasoline after rectification; a self-produced gasoline benzene-rich fraction outlet of the gasoline rectification unit is connected with a gasoline benzene-rich fraction inlet of the gasoline benzene catalytic conversion reactor, so that the self-produced gasoline benzene-rich fraction from the gasoline rectification unit enters the gasoline benzene catalytic conversion reactor for benzene catalytic conversion; wherein the gasoline rectification unit comprises one or more than one rectification column VII, preferably, the total theoretical plate number of the rectification column 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 benzene-rich gasoline intermediate fractions with a distillation range of 60-90°C obtained by distillation cutting of the benzene-rich gasoline.

[0139] The application will be further described in detail through the following examples. The raw materials used in the examples can be obtained through commercial channels.

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

[0141] In the examples, the full-range gasoline raw material A is a certain refinery catalytic cracking gasoline, the benzene-rich fraction raw material oil B is obtained by distillation cutting of A, the low-carbon alcohol is qualified industrial methanol and industrial ethanol with a purity of more than 99 wt%, and the heavy raw oil is a certain refinery hydroresid, and the properties of the three raw oils are shown in Table 1.

[0142] The catalyst used in the examples is the same, and the preparation method thereof is briefly described as follows:

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

[0144] 2) 5.1 kg of hydrous kaolin (Suzhou porcelain clay company industrial product, solid content 71.6 wt%) was slurried with 28.4 kg of deionized water, and then 3.4 kg of pseudo-boehmite (Shandong aluminum plant industrial product, solid content 63 wt%) was added to the slurry. The solid content of the slurry was 5-30 wt%. The pH of the slurry was adjusted to 2-4 with hydrochloric acid, and the slurry was stirred uniformly and aged at 60-70°C for 1 hour to obtain a mixed carrier slurry.

[0145] 3) Drying: 18 kg of the composite H-type molecular sieve (solid content 91 wt%) obtained in step 1) was mixed with 48 kg of deionized water at a solid to liquid ratio of 1:1-1:10, and then added to the mixed carrier slurry obtained in step 2). 4.4 kg of aluminum sol (produced by SINOPEC Catalyst Qilu Branch, Al2O3 content 21.7 wt%, catalyst solid content to aluminum sol solid content (calculated as Al2O3) ratio 10-50:1) was added, and the mixture was stirred until a uniform sol was formed. The sol was placed in air for 4 hours, and then shaped into a ball using a ball rolling machine and placed for 24 hours. The ball was dried in a drying oven at 120°C for 3 hours, and then washed to remove free Na + , and then dried at 120°C for 3 hours. The catalyst was calcined at 500-800°C for 3 hours to obtain a catalyst, which is referred to as CAT-A1.

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

[0147] The heavy oil catalytic cracking catalyst was a CGP special catalyst produced by SINOPEC Catalyst Qilu Branch, and contained ZSM-5 molecular sieve and Y molecular sieve. The properties of the catalyst are listed in Table 2.

[0148] Example 1

[0149] This example was tested according to the procedure shown in Figure 1 , using the feedstock oil B in Table 1, i.e. a benzene-rich fraction of catalytic cracking gasoline, as the raw material, and performing alkylation reaction with fractional injection of methanol in a moving bed reactor, using CAT-A1 catalyst.

[0150] As shown in Figure 1 , in this example, benzene-rich gasoline 1 was subjected to high-precision distillation cutting in rectifying column VII to obtain an aromatic hydrocarbon-free gasoline light fraction la, a benzene-rich gasoline intermediate fraction lb, and a benzene-rich gasoline heavy fraction lc. The benzene-rich gasoline intermediate fraction lb was generally controlled to have a distillation range of 60-90°C, and to have more than 50% benzene in the gasoline.

[0151] The benzene-rich gasoline intermediate fraction lb is fed into the lower part of the moving bed reactor I to contact the catalyst and react with the low carbon alcohol injected from the bottom, middle and upper parts of the reactor, and the spent catalyst is separated from the oil gas and regenerated, and the flue gas from the regeneration is partially recycled back to the regenerator. The process flow is as follows:

[0152] The benzene-rich gasoline intermediate fraction lb is fed into the lower part of the reactor I to contact the catalyst and react with the low carbon alcohol stream I2 fed from the bottom of the reactor I, and a fluidizing medium 3 can be injected into the bottom of the reactor according to the need for fluidization of the catalyst; after the first stage of reaction, the low carbon alcohol stream II 4 and the low carbon alcohol stream III 5 injected from the middle and upper parts of the reactor are further contacted to strengthen the alkylation of benzene; the spent catalyst is separated from the oil gas through the oil catalyst filter separator IV, and after settling, the separated catalyst is fed into the gasoline exchanger 24 through the spent catalyst delivery line I 10, and after stripping with nitrogen and / or steam, it is fed into the regenerator II through the spent catalyst delivery line II 11; the spent catalyst is regenerated in the regenerator under an oxygen-containing atmosphere, and the oxygen-containing regeneration gas 15 includes air, oxygen, etc., and the regeneration temperature is 500-600°C; the regenerated catalyst is returned to the reactor I through the regenerated catalyst delivery line I 12 and the regenerated catalyst delivery line II 13 for recycling; part of the flue gas 16 from the regeneration is recycled back to the regenerator through the flue gas circulation line 17; the separated reaction oil gas is fed into the oil gas separation system III through the reaction oil gas line 6, and the products dry gas 7, liquefied gas 8 and gasoline 9 are obtained by separation.

[0153] The catalytically cracked gasoline feedstock A is distilled and cut using a rectifying column VII with 30 trays (theoretical tray number 18), and a benzene-rich 60-90°C intermediate fraction is obtained by withdrawing from the middle section of the column to obtain feedstock B, with a yield of 16.0%. This cutting method consumes 21.59 kg EO / t of feedstock.

[0154] The feedstock B is preheated to 180°C and then fed into the lower part of the moving fluidized bed reactor I to react with methanol, under a reaction pressure of 0.5 MPa, nitrogen is used as the fluidizing medium, which flows from bottom to top, methanol is injected three times in the lower, middle and upper regions of the reactor, and the molar ratio of methanol to benzene in the reaction system is maintained at not less than 0.5, the reaction temperature (the outlet temperature of the upper part of the reactor is used as the criterion, the same below) is 500°C, the mass ratio of catalyst to feedstock oil is 1.5, the weight hourly space velocity is 10.0 h -1The alkylation reaction was carried out under the conditions; after the reaction, the oil agent was separated, the separated reaction oil gas was subjected to product separation through a separation system to obtain dry gas, liquefied gas and gasoline product; the spent catalyst after oil agent separation was subjected to nitrogen stripping to remove the oil gas adsorbed therein and then was sent to the regenerator, oxygen was used as the regeneration gas, and the spent catalyst was contacted at a regeneration temperature of 500°C to carry out regeneration; the regenerated catalyst was recycled, and part of the flue gas after regeneration was recycled, the circulating flue gas temperature was 400°C, and the dense phase temperature in the regeneration was maintained at 500°C. 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 catalytic cracking gasoline with a benzene content of 7.68% and an octane value RON 83.6 was subjected to alkylation reaction with graded injection of methanol in a moving bed reactor, the benzene conversion rate was 94.43%, the gasoline yield was 75.62%, the benzene content of gasoline was reduced to 0.54%, the octane value RON 89.7 was increased by 6.1 units, and the liquefied gas yield was as high as 17.71%.

[0156] The gasoline was cut, the benzene-rich fraction was subjected to moving bed alkylation, and then was mixed with the cut residual gasoline, taking the full-range catalytic cracking gasoline raw oil A as a benchmark, the benzene conversion rate was 67.85%, the benzene content of gasoline was reduced to 0.54%, and the gasoline + liquefied gas yield was 98.90%.

[0157] Comparative Example 1

[0158] By using the catalytic cracking gasoline raw oil A without cutting as the raw material, and using the same process conditions as in Example 1 to carry out alkylation reaction, the differences are as follows: 1) the riser reactor is used in Comparative Example 1, and methanol is only injected at the bottom of the reactor; 2) the conventional catalytic cracking catalyst CGP is used in Comparative Example 1; 3) the raw oil A-catalytic cracking gasoline is not cut, and the full-range fraction is directly mixed with methanol for feeding; 4) air is used as the regeneration gas, and the flue gas is not recycled; in order to maintain the same process conditions as in Example 1 in the operation of the reaction-regeneration system, it is necessary to provide heat by spraying combustion oil in the regenerator. The operating conditions and product distribution are listed in Table 3.

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

[0160] Example 2

[0161] This example was carried out according to the process conditions in Example 2. Figure 2The process flow of Example 2 was tested using heavy feedstock oil C in Table 1 as the raw material, and the catalytic cracking gasoline D obtained by cracking was cut into a gasoline benzene-rich fraction E by high-precision distillation. The heavy feedstock oil C and the gasoline benzene-rich fraction E were respectively tested in the riser reactor and the moving bed reactor, and catalysts CGP and CAT-A1 were respectively used.

[0162] Figure 2 The process flow of Example 2 is shown in the figure, and the same as Example 1 is that the benzene-rich fraction of gasoline is alkylated in the moving bed reactor I, and different from Example 1 is that the heavy feedstock oil 19 enters the conventional riser reactor, and the catalyst after the benzene alkylation reaction and the catalyst after the heavy oil catalytic cracking reaction can each be stripped and then enter the same regenerator, or can share a settler for stripping. In this example, both of them use a settler. The process flow is as follows:

[0163] The heavy feedstock oil 19 is atomized by steam and then fed into the lower part of the heavy oil cracking reactor VI to contact the catalytic cracking catalyst for cracking reaction. The separated reaction oil gas enters the oil gas separation system III through the reaction oil gas pipeline 6, and the products dry gas 7, liquefied gas 8, gasoline 9, diesel 22 and oil slurry 23 are obtained by separation. The gasoline 9 is separated into the self-produced gasoline benzene-rich fraction 25 and the low-benzene gasoline 26 by the gasoline rectification 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 discharged from the device for use in the gasoline pool blending. The benzene-rich gasoline intermediate fraction 1b of the self-produced gasoline benzene-rich fraction 25 and the optional benzene-rich gasoline from the rectification tower is fed into the reactor I at the lower part of the reactor to contact the catalyst, and is subjected to alkylation reaction with the low-carbon alcohol stream I2 fed from the bottom of the reactor. After the first stage of reaction, it is further contacted with the low-carbon alcohol stream II 4 and the low-carbon alcohol stream III 5 injected from the middle and upper parts of the reactor to strengthen the alkylation of benzene. The spent catalyst and oil gas after the alkylation reaction are separated by the oil catalyst filter separator IV, and the separated catalyst is settled and then fed into the heavy oil cracking reactor VI through the spent catalyst conveying pipeline I 10. After being stripped in the steam exchanger 24 by nitrogen and / or steam 14, the spent catalyst is fed into the regenerator II through the spent catalyst conveying pipeline II 11. The spent catalyst is regenerated in the oxygen-containing atmosphere in the regenerator II, and the oxygen-containing regeneration gas 15 includes air, oxygen and the like. The regeneration temperature is 600-700℃. The regenerated catalyst is recycled. The regenerated catalyst is conveyed to the heavy oil cracking reactor VI through the regenerated catalyst conveying pipeline I 12 and to the reactor I through the regenerated catalyst conveying pipeline II 13. The separated reaction oil gas enters the oil gas separation system III through the reaction oil gas pipeline 6 for product separation. It should be noted that the alkylation catalyst is supplemented into the reactor I through the catalyst supplementing 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 demand for benzene alkylation and heavy oil cracking.

[0164] The heavy feed oil preheated to 200°C was lifted to the bottom of the riser reactor, contacted with the catalytic cracking catalyst to perform the cracking reaction, under the reaction pressure of 0.3 MPa, water vapor was used as the fluidizing and atomizing medium, and the fluidizing medium flowed from bottom to top, under the reaction temperature (the temperature at the upper part of the reactor, i.e. the outlet temperature, the same below) of 540°C, the mass ratio of catalyst to feed oil of 7.4, the mass ratio of atomizing water to feed oil of 11.8, the weight hourly space velocity of 20.0 h -1 The cracking reaction was performed under the above conditions.

[0165] The gasoline D obtained by catalytic cracking of the heavy feed oil was subjected to high-precision distillation cutting by using the rectifying column 1 with 30 layers of plates (theoretical plate number 15) and the rectifying column 2 with 50 layers of plates (theoretical plate number 25), the light gasoline fraction at the bottom of the rectifying column 1 was introduced into the rectifying column 2, and the 60-90°C middle fraction rich in benzene, i.e. the gasoline fraction E rich in benzene, was extracted at the top of the rectifying column 2, and the yield of the gasoline fraction E rich in benzene accounted for 29.4% of the catalytic cracking gasoline D. The cutting mode had the energy consumption of 14.66 kg EO / t of feed. The properties of the catalytic cracking gasoline D and the gasoline fraction E rich in benzene are shown in Table 1.

[0166] The gasoline fraction E rich in benzene was preheated to 300°C and introduced into the lower part of the moving fluidized bed reactor I, and subjected to alkylation reaction with ethanol, hydrogen was used as the fluidizing medium, and the fluidizing medium flowed from bottom to top under the reaction pressure of 0.3 MPa, ethanol was injected in three times in the lower, middle and upper three regions of the reactor, and the molar ratio of ethanol to benzene in the reaction system was maintained to be not less than 1.0, the alkylation reaction was performed under the reaction temperature of 450°C, the mass ratio of catalyst to feed oil of 1.5, and the weight hourly space velocity of 10.0 h -1 After the reaction, oil agent separation was performed.

[0167] The separated reaction oil gas was introduced into the oil gas separation system through the reaction oil gas pipeline, and product dry gas, liquefied gas, gasoline, diesel and oil slurry were separated, the gasoline was further separated into the self-produced benzene-rich gasoline and the low-benzene gasoline through the gasoline rectifying column, and the self-produced benzene-rich gasoline (i.e. the gasoline fraction E rich in benzene) was recycled back to the reactor.

[0168] The gasoline fraction E rich in benzene after the alkylation oil agent separation was introduced into the heavy oil cracking oil gas pipeline, the separated catalyst was introduced into the settling section of the heavy feed oil catalytic cracking reactor, and after the stripping of the oil gas adsorbed inside by water vapor, the catalyst was sent into the regenerator; air was used as the regeneration gas, and the regenerated catalyst was contacted with the spent catalyst to perform the regeneration under the dense phase temperature of 650°C in the regenerator; the regenerated catalyst was recycled, and the flue gas after the regeneration was not recycled.

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

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

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

[0172] Comparative Example 2

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

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

[0175] The above describes the present application in combination with preferred embodiments, but these embodiments are only exemplary and are used for illustrative purposes. On this basis, various substitutions and improvements can be made to the present application, and these all fall within the protection scope of the present application.

[0176] Table 1

[0177]

[0178] Table 2

[0179] Catalyst No. CAT-A1 CGP Chemical composition, wt% Rare earths - 2.48 Phosphorus pentoxide 4.41 0.48 Sodium oxide 0.11 0.24 Aluminium oxide 44.30 53.74 Silicon oxide 49.90 43.06 Apparent density, kg / m 3 ]] 825 830 Pore volume, ml / g 0.18 0.18 Specific surface area, m2 / g 2 / g 185.0 139.47 Wear index, % by weight -1 ]] 1.35 1.3 Average particle size 3.2 mm 74.5 μm

[0180] Table 3

[0181]

[0182]

[0183] *Columns represent data obtained using feedstock B as a reference when feeding feedstock B into the moving bed reactor;

[0184] **The column represents the data obtained in Example 1 based on feedstock B, after conversion based on feedstock A.

[0185] *** indicates the blended gasoline obtained by mixing feedstock B (i.e., the benzene-rich fraction of feedstock A) with gasoline obtained by cutting the benzene-rich fraction of feedstock A (i.e., feedstock B) in a moving bed reactor.

[0186] Table 4

[0187]

[0188]

[0189] The # column represents data obtained from analysis of samples taken at the outlet of the catalytic cracking oil separator in the riser reactor (based on feedstock C).

[0190] The ## column represents data obtained from sampling and analysis at the outlet of the oil filter separator in a moving bed reactor (based on the benzene-rich fraction E of gasoline).

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

Claims

1. A process for the catalytic conversion of benzene in gasoline, characterized in that, The method comprises: (1) distillation cutting of benzene-rich gasoline to obtain a benzene-rich gasoline intermediate fraction with a distillation range of 60-90℃; (2) the benzene-rich gasoline intermediate fraction is introduced into a first reactor to contact a catalyst under non-hydrogen or hydrogen conditions with a staged injection of a low-carbon alcohol stream to perform catalytic alkylation to obtain a first mixture comprising a first spent catalyst and a first oil gas; (3) the first mixture is separated by an oil agent separation filter of the first reactor, and the separated first oil gas is introduced into an oil gas separation system to separate products to obtain products including dry gas, liquefied gas and gasoline; (4) the separated first spent catalyst is introduced into a regenerator after stripping by a steam stripper to perform oxygen-containing regeneration, and the regenerated catalyst is returned to the first reactor for recycling; wherein the benzene content of the benzene-rich gasoline is 0.8-20 wt%; the low-carbon alcohol is C1-C3 alkyl alcohol; in step (2), the molar ratio of the low-carbon alcohol to benzene is maintained at 0.2-7.0:1, and the catalytic alkylation reaction temperature is 400-550℃.

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

3. The method of claim 1, wherein, the low-carbon alcohol is methanol, ethanol and / or isopropyl alcohol.

4. The method of claim 1, wherein, in step (2), the molar ratio of the low-carbon alcohol to benzene is maintained at 0.5-5.0:

1.

5. The method of claim 1, wherein, the first reactor is provided with 3 or more low-carbon alcohol injection ports in sections; and / or the low-carbon alcohol content in the low-carbon alcohol stream is 50-100 wt%.

6. The method of claim 1, wherein, the catalytic alkylation; the reaction pressure is 0.1-1.0 MPa; the weight ratio of the catalyst to the raw oil is 0.7-7.0:1; and / or Weight hourly space velocity is 0.5~25.0h -1 .

7. The method of claim 6, wherein, the catalytic alkylation reaction temperature is 420-520℃; the reaction pressure is 0.2-0.8 MPa; the weight ratio of the catalyst to the raw oil is 1.0-5.0:1; and / or Weight hourly space velocity was 1.0 to 15.0 h -1 .

8. The method of claim 1, wherein, the first reactor is selected from a fluidized bed reactor, a moving bed reactor or a fixed bed reactor.

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

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

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

12. The method of claim 1, wherein, the catalyst comprises mesoporous molecular sieve and heat-resistant inorganic oxide, wherein the mesoporous molecular sieve accounts for 30-80 wt% of the total amount of the catalyst.

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

14. The method of claim 13, wherein, the mesoporous molecular sieve is ZSM series and β series composite mesoporous zeolite.

15. The method of claim 1, wherein, the benzene-rich gasoline is catalytic cracking gasoline, hydrocracking gasoline, reforming gasoline and / or steam cracking gasoline with a boiling point of 30-220℃; and / or the benzene-rich gasoline intermediate fraction is preheated before being introduced into the first reactor, and the preheating temperature is 50-350℃.

16. The method of claim 15, wherein, the benzene-rich gasoline intermediate fraction is preheated before being introduced into the first reactor, and the preheating temperature is 100-300℃.

17. The method of claim 1, wherein, the oxygen-containing regeneration atmosphere is air and / or oxygen atmosphere; the regeneration temperature of the regenerator is 450-750℃; the regeneration pressure of the regenerator is 0.2-1.5 MPa; and / or the flue gas temperature recycled back to the regenerator is 300-600℃.

18. The method of claim 17, wherein, The oxygen-containing regeneration atmosphere is an oxygen-rich and / or pure oxygen atmosphere; The regeneration temperature of the regenerator is 500-700℃; The regeneration pressure of the regenerator is 0.2-1.0 MPa.

19. A method of producing a low benzene content gasoline characterized by, The method comprises: (1) performing catalytic cracking of heavy oil in a second reactor to obtain a second mixture comprising second spent catalyst and second oil gas; (2) performing oil gas separation on the second mixture in an oil gas separation system to obtain dry gas component, liquefied gas component and gasoline component; (3) performing rectification on the gasoline component in a gasoline rectification system to obtain self-produced gasoline benzene-rich fraction and low-benzene gasoline; (4) the self-produced gasoline benzene-rich fraction and other gasoline benzene-rich fraction enter the first reactor to contact the catalytic alkylation reaction with the staged injection of low-carbon alcohol stream under non-hydrogen or hydrogen conditions to obtain a first mixture comprising first spent catalyst and first oil gas; the molar ratio of low-carbon alcohol to benzene is maintained at 0.2-7.0:1, and the catalytic alkylation reaction temperature is 400-550℃; (5) the first mixture passes through the oil agent separation filter of the first reactor for separation, and the separated oil gas enters the oil gas separation system for oil gas separation; (6) the separated first spent catalyst enters the second reactor to mix with the second spent catalyst, is stripped by the gasoline stripper of the second reactor, and then enters the regenerator for oxygen-containing regeneration; the regenerated catalyst returns to the first reactor and the second reactor for recycling; wherein the heavy oil is wax oil and / or residual oil, and the gasoline benzene-rich fraction is a benzene-rich gasoline intermediate fraction with a distillation range of 60-90℃ obtained by distillation cutting of benzene-rich gasoline; wherein the benzene content of the benzene-rich gasoline is 0.8-20 wt%.

20. The method of claim 19, wherein, In step (6), part or all of the flue gas after regeneration is recycled back to the regenerator.

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

22. A system for producing low-benzene gasoline, comprising: a catalytic cracking reaction unit, which comprises a catalytic cracking reactor, a catalytic cracking oil agent separator, and a gasoline stripper; wherein the catalytic cracking oil agent separator is connected with the oil gas outlet of the catalytic cracking reactor for separating the reaction oil agent from the catalytic cracking reactor and allowing the separated catalytic cracking spent catalyst to enter the gasoline stripper for stripping; a gasoline benzene catalytic conversion unit, which comprises a gasoline benzene catalytic conversion reactor, and an oil agent filter separator; wherein the oil agent filter separator is connected with the oil gas outlet of the gasoline benzene catalytic conversion reactor for separating the reaction oil agent from the gasoline benzene catalytic conversion reactor; the lower part of the gasoline benzene catalytic conversion reactor is in communication with the gasoline stripper of the catalytic cracking reaction unit, so that the gasoline benzene catalytic conversion spent catalyst of the gasoline benzene catalytic conversion reactor enters the gasoline stripper 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; a regenerator, wherein the regenerator is in communication with a stripper of the catalytic cracking reaction unit, such that the stripped spent catalyst in the stripper is regenerated in the regenerator; the regenerator is also in communication with a catalytic cracking reactor of the catalytic cracking reaction unit and a gasoline benzene catalytic conversion reactor of the gasoline benzene catalytic conversion unit, respectively, such that the regenerated catalyst is recycled back to the catalytic cracking reactor and the gasoline benzene catalytic conversion reactor; an oil-gas separation unit, wherein the oil-gas separation unit is in communication with an oil-gas separation unit of the catalytic cracking reaction unit and an oil-gas separation unit of the gasoline benzene catalytic conversion unit, respectively, such that the oil-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 rectification unit, wherein the gasoline rectification unit is in communication with a gasoline fraction outlet of the oil-gas separation unit, such that the gasoline fraction from the oil-gas separation unit is rectified in the gasoline rectification unit to obtain a self-produced gasoline benzene-rich fraction and a low-benzene gasoline after rectification; a self-produced gasoline benzene-rich fraction outlet of the gasoline rectification unit is in communication with a gasoline benzene-rich fraction inlet of the gasoline benzene catalytic conversion reactor, such that the self-produced gasoline benzene-rich fraction from the gasoline rectification unit is introduced into the gasoline benzene catalytic conversion reactor for benzene catalytic conversion; wherein the gasoline rectification unit comprises one or more than one rectification column.

23. The system of claim 22, wherein, The gasoline benzene catalytic conversion reactor is provided with three or more than three low-carbon alcohol stream inlets.

24. The system of claim 22, wherein, The total number of theoretical plates of the rectification column is greater than or equal to 14.

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