A process for producing light aromatic hydrocarbons

Abstract

The application provides a method for producing light aromatic hydrocarbons, comprising: cutting the crude gasoline from a catalytic cracking unit fractionating column to obtain light fraction gasoline and heavy fraction gasoline; feeding the light fraction gasoline and the catalytic cracking unit fractionating column overhead rich gas into a fluidized bed reactor together to carry out deep desulfurization and light aromatization on a composite function catalyst to obtain light aromatization products; the composite function catalyst is characterized by a TEM-EDS method, and the proportion of the amount of ZSM-5 / β composite molecular sieve directly reacting with the group VIB metal sulfide to the total amount of the molecular sieve is 60-100% in terms of silicon element; the light aromatization products pass through an aromatic hydrocarbon extraction system to obtain light aromatic hydrocarbons (BTX) and light fraction gasoline products. The method uses the catalytic cracking unit fractionating column overhead rich gas and the crude gasoline as raw materials, can realize simultaneous reduction of gasoline production, production of high-value light aromatic hydrocarbons (benzene, toluene and p-xylene) and clean gasoline components, and can save the conventional rich gas alkali washing mercaptan removal process, and reduce the environmental pollution problems caused by waste lye.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of petroleum refining, and particularly relates to a method for producing high-value light aromatics from low-value poor-quality gasoline and refinery rich gas. BACKGROUND

[0002] China's economy has now entered a period of high-quality growth, and the oil refining industry is facing overcapacity problems. The demand for finished oil (gasoline, diesel) is growing at a much slower rate, and it is expected that the demand for gasoline will also enter a plateau period around 2025. Refining enterprises are facing the challenge of transforming from "fuel type" to "energy chemical type". At the same time, since 2019, China has implemented more stringent national VI clean gasoline standards, and the requirements for sulfur, especially olefin and aromatic content in gasoline, are becoming increasingly stringent. Therefore, "oil if suitable, olefin if suitable, and aromatic if suitable" has become an inevitable development trend for clean refining.

[0003] China is a big country in catalytic cracking (FCC), and the gasoline components produced by the catalytic cracking unit account for about 80% of the total national gasoline product. The sulfur and olefin content of FCC gasoline is relatively high, and it is the main source of sulfur and olefin in the finished gasoline pool. The catalytic cracking process generally consists of a reaction-regeneration system, a fractionation system, and an absorption-stabilization system. The purpose of the absorption-stabilization system is to separate and separate the overhead gas (C1-C4 hydrocarbons) from the fractionation section and the crude gasoline containing a small amount of C3 and C4 components to obtain dry gas, liquefied gas, and catalytic cracking stable gasoline with qualified vapor pressure. After desulfurization treatment, most refineries directly sell dry gas and liquefied gas as fuel, which has low economic benefits. In some refineries, the desulfurized liquefied gas is separated to obtain propylene as a polypropylene raw material, and C4 hydrocarbons as a raw material for producing MTBE, and the desulfurized stable gasoline is used as a blending component for clean gasoline. However, due to the full implementation of E10 vehicle ethanol gasoline in China in 2020, there is no need to add MTBE, and the development of MTBE is hindered. The outlet of C4 hydrocarbons, the raw material for producing MTBE, is a problem that refining enterprises need to solve. At the same time, the current industrialized liquefied gas desulfurization method is a two-step method represented by the Merox desulfurization process, which extracts hydrogen sulfide and mercaptan with alcohol amine and alkali liquor. However, a large amount of alkali liquor is used in the desulfurization process, which causes the problem of alkali residue discharge, and brings great pressure to environmental protection.

[0004] CN101492610B discloses a method for deep desulfurization and olefin reduction of gasoline, which comprises contacting gasoline feedstock and hydrogen with a hydroadsorption desulfurization catalyst and an olefin aromatization catalyst in sequence to remove sulfur in the gasoline and reduce the olefin content of the product. This method performs aromatization reaction on full-range gasoline, which increases side reactions such as cracking and polymerization, leading to easy carbon deposition and catalyst deactivation, affecting the operation cycle, reducing the liquid yield of gasoline product, affecting indicators such as vapor pressure and benzene content, and causing large loss of octane number. If the olefin content is required to be ≯15.0 v%, the above shortcomings will be more prominent.

[0005] CN110184089B discloses a method for treating low-sulfur catalytic cracking gasoline. The method cuts the low-sulfur catalytic cracking gasoline into a light fraction, a middle fraction and a heavy fraction; the sulfur content in the low-sulfur catalytic cracking gasoline is not more than 10 mg / kg; the aromatic potential content in the middle fraction is not less than 35% by weight, and the C9 aromatic hydrocarbon content is not higher than 8% by volume; and the benzene content in the light fraction is not higher than 0.8% by volume. The method can produce chemical materials, produce national VI gasoline and national VI ethanol gasoline blending components, but the method has high requirements for raw materials, is highly dependent, cannot produce light aromatic hydrocarbons, the aromatic hydrocarbon content in the raw material directly determines the amount of light aromatic hydrocarbons and other chemical materials that can be obtained, and the applicability range is narrow.

[0006] CN108315049B discloses a method for producing aromatic hydrocarbons from catalytic cracking gasoline, which comprises the following steps: pre-hydrogenation of catalytic cracking gasoline to obtain pre-hydrogenated catalytic cracking gasoline; cutting the pre-hydrogenated catalytic cracking gasoline into a light fraction and a heavy fraction; solvent extraction of the light fraction to obtain olefin-rich raffinate oil and aromatic hydrocarbon-rich extract oil; mild aromatization of the raffinate oil to obtain aromatization products; light olefin recovery of the extract oil to obtain light olefins and sulfur-rich oil; returning part of the light olefins to the solvent extraction, and performing mild aromatization on another part of the light olefins; selective hydrodesulfurization of the heavy fraction and sulfur-rich oil to obtain desulfurized heavy fraction; and aromatic hydrocarbon extraction or extractive distillation of the aromatization products and desulfurized heavy fraction. The method has a complex process flow, high energy consumption, high olefin content of the gasoline blending component, and cannot meet the national VI clean gasoline standard.

[0007] CN107201254B discloses a mixed liquefied petroleum gas desulfurization refining method. The method passes coking liquefied petroleum gas into the riser reactor of the catalytic cracking device to occur cracking reaction with the catalytic cracking raw material, sends the mixed liquefied petroleum gas fractionated out into the hydrogen sulfide extraction unit and mercaptan extraction unit to remove hydrogen sulfide and mercaptan, and the sulfur content of the liquefied petroleum gas product after desulfurization is not more than 10 μg / g. The mixed liquefied petroleum gas after refining can be fractionated to obtain propylene products meeting the sulfur content requirements, and can be used as MTBE raw material for producing low-sulfur MTBE. However, in the process of removing hydrogen sulfide and mercaptan, the method still uses the conventional alkali extraction method, which will produce a large amount of alkali residue discharge, which is not conducive to environmental protection.

[0008] CN110628476B discloses a liquefied gas pretreatment desulfurization method, which uses a purifying agent for purification pretreatment before liquefied gas desulfurization, catalytically oxidizes hydrogen sulfide and mercaptan and other light sulfur compounds in the refinery rich gas, and then through subsequent absorption, desorption and rectification processes, high-boiling sulfur compounds are removed to obtain crude liquefied gas with significantly reduced hydrogen sulfide concentration and almost completely removed mercaptan sulfur. The crude liquefied gas is then subjected to conventional alcohol amine desulfurization and alkali desulfurization to obtain low-sulfur liquefied gas products. The method has a long process flow and still produces a certain amount of alkali residue.

[0009] In the face of increasingly stringent environmental protection requirements and the problem of excess production capacity of finished gasoline, both existing liquefied gas desulfurization technology and poor gasoline desulfurization technology have certain problems. In the current liquefied petroleum gas desulfurization process, there are environmental problems caused by alkali residue and the problem of insufficient desulfurization depth, and further desulfurization is required in the subsequent process; in the existing poor gasoline desulfurization technology, the aromatization reaction of gasoline components is mainly to reduce the octane loss caused by olefin saturation, and there is no in-depth study on the selectivity of light aromatic hydrocarbons in the reaction products, which also leads to the inability to directly utilize existing technology to produce clean gasoline components while producing more high-value chemical products such as light aromatic hydrocarbons (BTX). In view of the high sulfur content and high olefin content of liquefied gas and poor gasoline components, both have the need for deep desulfurization and the potential to produce high-value light aromatic hydrocarbons. Therefore, how to effectively clean and deeply desulfurize high-sulfur and high-olefin liquefied gas and poor gasoline components, and at the same time effectively convert part of them into high-value light aromatic hydrocarbons (BTX), is an effective technical solution to effectively solve the increasingly stringent environmental protection requirements and the economic and effective technical solution to the problem of gasoline quality upgrading and excess production capacity in China. SUMMARY

[0010] In order to solve the problems of the prior art, the present application provides a method for producing light aromatic hydrocarbons, which uses the overhead gas and the crude gasoline from a catalytic cracking unit fractionating column as raw materials, can realize simultaneous reduction of gasoline production, production of high-value light aromatic hydrocarbons (benzene, toluene and p-xylene) and clean gasoline components, and can save the conventional rich gas caustic washing process for removing mercaptans, and reduce the environmental pollution problems caused by waste lye.

[0011] In order to achieve the above technical purpose, the present application provides a method for producing light aromatic hydrocarbons, comprising the following steps:

[0012] (1) cutting the crude gasoline from the catalytic cracking unit fractionating column to obtain light fraction gasoline and heavy fraction gasoline;

[0013] (2) sending the light fraction gasoline and the overhead gas from the catalytic cracking unit fractionating column into a fluidized bed reactor together, and performing deep desulfurization and light aromatization on a composite functional catalyst to obtain light aromatization products;

[0014] The composite functional catalyst is a sulfided hydrogenation catalyst, which comprises a carrier, an active component and a ZSM-5 / β composite molecular sieve, the active component comprises at least one of group VIII metal elements and at least one of group VIB metal elements, and the composite functional catalyst is characterized by TEM-EDS method, and the proportion of the amount of the ZSM-5 / β composite molecular sieve directly interacting with the group VIB metal sulfide to the total amount of the molecular sieve is 60-100% in terms of silicon element.

[0015] (3) the light aromatization products are subjected to an aromatic hydrocarbon extraction system to obtain light aromatic hydrocarbons (BTX) and light fraction gasoline products.

[0016] In the present application, the proportion of the amount of the molecular sieve directly interacting with the Group VIB metal sulfide in the total amount of the molecular sieve is the proportion of the amount of the molecular sieve directly interacting with the Group VIB metal sulfide in the total amount of the molecular sieve (calculated by the amount of silicon element) in the catalyst. The amount of the molecular sieve directly interacting with the Group VIB metal sulfide refers to the content of the molecular sieve (calculated by the amount of silicon element) within 2 nm from the outermost layer of the Group VIB metal sulfide crystal. The proportion of the amount of the molecular sieve directly interacting with the Group VIB metal sulfide in the total amount of the molecular sieve is obtained by the TEM-EDS (transmission electron microscope-energy dispersive X-ray spectroscopy) method. The instrument used is a transmission electron microscope of Model JEM2200FS produced by JEOL, Japan, which is equipped with a scanning transmission accessory and an X-ray energy spectrum accessory produced by EDAX, USA. The accelerating voltage of the electron microscope is 200 KV, the condenser aperture is 2 in the STEM mode, and the Spote size is 0.5 nm. The determination process is as follows: the catalyst particles are ground, the sample is prepared by the suspension method, 0.1 g of the catalyst sample is placed in a 2 mL container, ultrasonic dispersion is performed with anhydrous ethanol, the supernatant is taken, two to three drops of the supernatant are taken by a dropper and dropped on a sample net with a diameter of 3 mm, and then the sample to be tested is obtained after drying. Then, the sample to be tested is observed and analyzed by TEM, and then the Si content at the end point of the active phase within 2 nm from the edge is counted and analyzed by EDS. The proportion of the amount of the molecular sieve directly interacting with the Group VIB metal sulfide in the total amount of the molecular sieve is obtained by the corresponding peak area of Si. The proportion of the amount of the molecular sieve directly interacting with the Group VIB metal sulfide in the total amount of the molecular sieve in the present application is obtained by averaging the data obtained by selecting 40 TEM images and combining EDS analysis.

[0017] The above method further includes a process of treating the heavy fraction gasoline obtained in step (1) to obtain clean gasoline, which includes: feeding the heavy fraction gasoline obtained in step (1) into a hydrodesulfurization reactor to react with a selective hydrodesulfurization catalyst to obtain a heavy fraction gasoline desulfurization product; and mixing the light fraction gasoline product of step (3) and the heavy fraction gasoline desulfurization product to obtain a clean gasoline component with low sulfur and low olefin content.

[0018] The clean gasoline component produced by the method of the present application meets the standards of the World Wide Fuel Charter V standard clean gasoline: sulfur content ≯ 10.0 μg / g, olefin content ≯ 10.0%, aromatic content ≯ 35.0%, benzene content ≯ 0.8 v%, and dry point distillation range ≯ 205°C.

[0019] Further, the composition of the crude gasoline is generally C3-C 12 hydrocarbons, olefin volume content ≮ 20 v%, preferably 20 v%-45 v%, aromatic volume content ≯ 30 v%, preferably 15 v%-25 v%, and sulfur mass content ≯ 500 μg / g, preferably 100 μg / g-500 μg / g.

[0020] Further, the cutting point of the cutting of the crude gasoline is 60-90℃.

[0021] Further, the composition of the overhead gas of the catalytic cracking unit fractionating column is generally C1-C4 hydrocarbons. The content of liquefied gas components (i.e. C3-C4 hydrocarbons) accounts for 80v%-90v% of the total amount of the overhead gas, preferably 85v%-90v%, and the typical composition is propylene content of 20.0v%-40.0v% and butene content of 10.0v%-30v%; the total sulfur content is 100-5000mg / m 3 , the mercaptan sulfur content is 50-200mg / m 3 .

[0022] Further, the overhead gas of the catalytic cracking unit fractionating column is preferably first subjected to amine liquid absorption to remove hydrogen sulfide, and then is sent into the fluidized bed reactor.

[0023] Further, the mass ratio of the overhead gas and the light distillate gasoline in the reaction raw material is 1:3-1:1, preferably 1:2-1:1.

[0024] Further, in the composite functional catalyst used in step (2), the content of the ZSM-5 / β composite molecular sieve is 5-25wt% based on the total weight of the catalyst, preferably 5-15wt%, and more preferably 5-10wt%. In the ZSM-5 / β composite molecular sieve, the weight content of the ZSM-5 molecular sieve is 30wt%-75wt%, preferably 40wt%-70wt%.

[0025] Further, in the composite functional catalyst, the Group VIB metal element is Mo and / or W, and the Group VIII metal element is Co and / or Ni. The content of the Group VIB metal sulfide is 10-30wt% based on the sulfide, preferably 15-28wt%, and the content of the Group VIII metal sulfide is 2-10wt% based on the sulfide, preferably 4-8wt%. The Group VIB metal sulfide can refer to MoS2 and WS2, and the Group VIII metal sulfide can refer to CoS and NiS.

[0026] In the present application, the content of the Group VIB metal sulfide and the Group VIII metal sulfide can be jointly characterized by inductively coupled plasma ICP and XPS spectroscopy. Specifically, first, the total content of the Group VIB metal and the total content of the Group VIII metal in the catalyst are characterized by ICP, and then the content of different valence metal elements in the catalyst is quantitatively characterized by XPS spectrometer. The measurement conditions of the XPS spectrum include: the vacuum degree of the analysis chamber is ≤5×10 -10 mbar; the vacuum degree of the preparation chamber is ≤1×10-7 mbar; double anode sensitivity 4.5 x 10 6 , energy resolution 1.0 eV; monochromator sensitivity 1.4 x 10 5 , energy resolution 0.5 eV. Mo3d, W4f, Co2p, Ni2p spectra were fitted by XPSPEAK Version 4.0, and the content of different valence state metal elements in the catalyst was calculated according to the peak area.

[0027] Further, the carrier in the composite functional catalyst is selected from at least one of alumina, silica, titania and zirconia, and preferably is alumina. The carrier can further contain a doping element, which can be one or more of phosphorus, silicon, boron, fluorine, sodium and the like. The addition amount of the doping element can be a conventional addition amount, and preferably is 0.5% to 6% by mass of the carrier. The carrier is a microspherical carrier, and the particle size of the carrier is 20 to 100 μm particles, which can be prepared by a conventional industrial method such as spray drying and the like.

[0028] In addition, the composite functional catalyst is a sulfided hydrogenation catalyst, and most of the active components are in the form of sulfides. The catalyst provided in the present application can not exclude a small amount of Group VIB metal oxide and Group VIII metal oxide. It can be known that the sum of the content of all components in the composite functional catalyst is 100%.

[0029] Further, the composite functional catalyst can be prepared by the following method:

[0030] (a) impregnating the carrier with a solution containing an organic auxiliary agent, drying and calcining under an inert atmosphere to obtain a pretreated carrier;

[0031] (b) introducing Group VIB metal salt and Group VIII metal salt into the pretreated carrier by impregnation method, and sulfidizing to obtain a catalyst precursor;

[0032] (c) preparing a ZSM-5 / β composite molecular sieve precursor;

[0033] (d) hydrothermally treating the catalyst precursor and the composite molecular sieve precursor, drying and calcining under an inert atmosphere to obtain the composite functional catalyst.

[0034] In the preparation method of the composite functional catalyst in the present application, the carrier is pretreated to form a C inert surface layer on the surface of the carrier, which can weaken the interaction between the metal and the carrier, and on the other hand, because the surface of the carrier is covered with a C layer which is non-polar, the molecular sieve will interact more with the metal, thereby increasing the proportion of direct interaction between the molecular sieve and the active metal.

[0035] The carbon content in the pretreated carrier is 3-20 wt%, preferably 5-10 wt%.

[0036] Further, in the above preparation method, the organic additive in step (a) is selected from at least one of hydrocarbons, alcohols, carboxylic acids, preferably glycol, glycerol, butanediol, pentanediol, acetic acid, citric acid, glucose, malonic acid, succinic acid, glutaric acid, naphthalene and C9 aromatic hydrocarbons.

[0037] The solution containing the organic additive optionally further contains a solvent. When the organic additive is a solid, the solution containing the organic additive preferably further contains a solvent. When the organic additive is a liquid, the solution containing the organic additive can or can not contain a solvent. The solvent in the solution containing the organic additive can be selected from a wide range, and is not particularly limited as long as it can dissolve the organic additive (for example, water or ethanol), and can be appropriately selected by those skilled in the art according to the specific type of the organic additive. When the organic additive is a solid, the content of the organic additive is 10-30 wt%. When the organic additive is a liquid, the content of the organic additive is 50-100 wt%.

[0038] The inert atmosphere in step (a) refers to an atmosphere that does not participate in the reaction, and can be provided by an inert gas, which includes but is not limited to at least one of nitrogen, helium, argon and neon.

[0039] The drying conditions in step (a) preferably include a temperature of 20-90°C and a time of 4-16 hours.

[0040] The calcination conditions in step (a) preferably include a temperature of 200-400°C and a time of 3-8 hours, and more preferably a temperature of 250-350°C and a time of 3-5 hours.

[0041] The impregnation method in step (b) is not particularly limited, and can be isovolumetric impregnation or supersaturation impregnation. The Group VIB metal salt and the Group VIII metal salt can be introduced into the pretreated carrier simultaneously by co-impregnation, or introduced into the pretreated carrier separately by stepwise impregnation, and the order of introduction is not particularly limited. Preferably, the Group VIB metal salt and the Group VIII metal salt are introduced into the pretreated carrier simultaneously by co-impregnation. Preferably, step (b) includes impregnating the pretreated carrier with an impregnation solution containing the Group VIB metal salt and the Group VIII metal salt, and then drying. The preparation method of the impregnation solution is well known to those skilled in the art. The drying is preferably performed under an inert atmosphere. The inert atmosphere can be selected from the same range as above, and is not described here again. The drying conditions include a temperature of 20-90°C and a time of 4-16 hours.

[0042] The sulfidation in step (b) can be carried out by using conventional methods in the art, as long as the active metal in the oxidation state hydrogenation catalyst is converted into the sulfidation state, and the sulfidation can be carried out by using a known sulfidation method, preferably the sulfidation is dry sulfidation or wet sulfidation. The dry sulfidation and wet sulfidation in the present application have the conventional interpretation in the art.

[0043] The dry sulfidation agent used in the dry sulfidation is hydrogen sulfide. Specifically, the sulfidation gas used in the dry sulfidation includes hydrogen sulfide and hydrogen. Preferably, the volume content of hydrogen sulfide in the sulfidation gas is 1-10%.

[0044] The wet sulfidation agent used in the wet sulfidation is at least one of carbon disulfide, dimethyl disulfide, methyl sulfide and n-butyl sulfide. Specifically, the sulfidation liquid used in the wet sulfidation includes the wet sulfidation agent and an organic solvent. Preferably, the organic solvent is selected from at least one of cyclohexane, n-heptane and straight-run naphtha. The mass fraction of the wet sulfidation agent in the sulfidation liquid is selected in a wide range, preferably 2%-7%, more preferably 4%-6%. Preferably, the flow rate of the sulfidation liquid is 0.5-5 mL·h -1 ·g -1 , preferably 1-4 mL·h -1 ·g -1 .

[0045] The conditions of the sulfidation include: the sulfidation pressure is 1.0-6.0 MPa, the sulfidation temperature is 250-400℃, the sulfidation time is 4-12 h, and the flow rate of hydrogen is 2-25 mL·min -1 ·g -1 .

[0046] The preparation method of the ZSM-5 / β composite molecular sieve precursor in step (c) can be prepared by the following steps:

[0047] 1) Mix the silicon source, the aluminum source, the template agent (an aqueous solution of TPAOH) and deionized water in a certain proportion to form a ZSM-5 synthesis system, denoted as A solution;

[0048] 2) Mix the silicon source, the aluminum source, the template agent (tetraethylammonium hydroxide) and deionized water in a certain proportion to form a β synthesis system (B solution);

[0049] 3) After the A solution is crystallized at 90-150℃ for 3-24 h, centrifugal separation is carried out to obtain ZSM-5 nanoparticles, and the ZSM-5 nanoparticles are dispersed in the β synthesis system (B solution) to form a homogeneous slurry after stirring for 1-30 min, thereby obtaining the ZSM-5 / β composite molecular sieve precursor.

[0050] The addition amount of the reaction raw materials in the A solution should be such that the molar ratio of the components in the system is: A1203: Si02: tetrapropylammonium hydroxide: water = 1: 20-200: 3-10: 500-1000.

[0051] The addition amount of the reaction raw materials in the B solution should be such that the molar ratio of the components in the system is: A1203: Si02: tetraethylammonium hydroxide: water = 1: 20-200: 1-20: 500-1000.

[0052] The silicon source is one or more of tetraethyl orthosilicate, silica sol, and water glass seed.

[0053] The addition amount of the ZSM-5 particles is 25-75% of the final ZSM-5 / β composite molecular sieve production.

[0054] The hydrothermal treatment conditions in step (d) include: temperature 90-200℃, pressure 0.1-2 MPa, and time 8-72 hours.

[0055] The drying conditions in step (d) include: temperature 20-90℃, and time 4-16 hours.

[0056] The calcination conditions in step (d) include: temperature 300-500℃, and time 2-5 hours.

[0057] The specific selection of the inert atmosphere in step (d) can be as described above.

[0058] Further, the deep desulfurization and light aromatization reaction in step (2) refers to a deep desulfurization and aromatization reaction of the light distillate gasoline and the gas-rich component under high temperature and low space velocity aromatization reaction conditions, and the desulfurization and aromatization product mainly contains C6-C8 BTX aromatic hydrocarbons.

[0059] Further, the deep desulfurization and light aromatization reaction in step (2) is carried out under the following conditions: reaction pressure 1.0 MPa-2.5 MPa, reaction temperature 300℃-500℃, total liquid hourly space velocity 0.1h -1 -3.0h -1 , and hydrogen / oil volume ratio 50:1-300:1; and the preferred reaction conditions are as follows: reaction pressure 1.5 MPa-2.5 MPa, reaction temperature 350℃-450℃, total liquid hourly space velocity 0.5h -1 -1.5h -1 , and hydrogen / oil volume ratio 50-150:1.

[0060] In the method, the sulfur content in the light aromatization product in step (2) is ≯1 μg / g, the aromatic hydrocarbon content is ≮60.0 v%, and the bromine value is less than 0.5 gBr / 100g, which meets the requirements of aromatic hydrocarbon extraction device for feed.

[0061] In the method, the selectivity of BTX component in the light aromatization product in step (2) is ≮90.0%.

[0062] In the method, the aromatic hydrocarbon extraction in step (3) realizes accurate separation of aromatic hydrocarbon and non-aromatic hydrocarbon to meet the needs of production of high value-added chemical products such as PX. The method for aromatic hydrocarbon extraction is not strictly limited in the application, as long as it can realize accurate separation of aromatic hydrocarbon and non-aromatic hydrocarbon, and a mature method in industry can be used.

[0063] In the method, the light aromatic hydrocarbon (BTX) obtained in step (3) can be used as a raw material for production of chemical products such as PX.

[0064] Further, in the method, the selective hydrodesulfurization catalyst is a non-noble metal catalyst loaded with Group VIB metal such as Mo and / or W, and / or Group VIII metal such as Co and / or Ni on amorphous Al2O3 and / or aluminum silicate carrier, and various conventional gasoline selective hydrodesulfurization catalysts in prior art can also be used, such as FGH-21 / FGH-31 combined catalyst, ME-1 catalyst developed by Fushun Petrochemical Research Institute of Sinopec, or prepared according to the prior method in the field.

[0065] Further, the reaction conditions for the selective hydrodesulfurization reaction are as follows: reaction pressure 1.0-3.0 MPa, reaction temperature 200-300℃, liquid hourly space velocity 1.0-5.0 h-1, and hydrogen / oil volume ratio 150:1-450:1. -1 -5.0h -1 The preferred reaction conditions are as follows: reaction pressure 1.5-2.0 MPa, reaction temperature 250-300℃, liquid hourly space velocity 2.0-4.0 h-1, and hydrogen / oil volume ratio 250:1-350:1. The sulfur content in the product after hydrodesulfurization treatment of heavy distillate gasoline is ≯10 μg / g. -1 -4.0h -1

[0066] In the method, the sulfur content in the clean gasoline component is ≯10 μg / g, the olefin content is ≯10.0%, the aromatic hydrocarbon content is ≯35.0%, the benzene content is ≯0.8 v%, and the dry point of distillation range is ≯205℃.

[0067] Compared with the prior art, the application has the following advantages:

[0068] ​(1) The method of the present application uses catalytic cracking unit fractionating column overhead gas and crude gasoline as raw materials, can realize simultaneous reduction of gasoline production, production of high value light aromatics (benzene, toluene and p-xylene) and clean gasoline components, and can save the conventional overhead gas caustic washing mercaptan removal process, and reduce the environmental pollution problems caused by waste lye.

[0069] (2) The method of the present application uses overhead gas and light distillate gasoline as raw materials, carries out deep hydrogenation desulfurization and light aromatization reaction in a fluidized bed reactor, uses a specific composite functional catalyst to realize deep desulfurization and light aromatization reaction of overhead gas and light gasoline components in one step, the sulfur content in the light aromatization product is low and the selectivity of high value BTX components is high, thereby realizing directional conversion of low value overhead gas and light poor gasoline into clean components and high value chemical raw materials.

[0070] (3) In the method of the present application, the composite functional catalyst is prepared by the sequence of carrier pretreatment, loading active metal, sulfidation and loading molecular sieve, which makes more molecular sieve directly act on the active metal, the utilization rate of molecular sieve and active metal is higher, the active effect is better, the desulfurization depth is high, and the aromatization reaction process can be precisely controlled to avoid the production of large molecular aromatics and realize directional conversion of BTX components. Using this preparation method can reduce the amount of molecular sieve and reduce the cost of the catalyst. After impregnating the active metal, drying and direct sulfidation, the calcination process can be omitted, which not only reduces the interaction between the metal oxide and the carrier, but also simplifies the process.

[0071] (4) The present application produces low sulfur, low olefin gasoline components while increasing the production of high value light aromatics (BTX) from overhead gas and part of gasoline components, which not only solves the problem of upgrading of gasoline quality in China and the environmental pollution problem caused by the traditional overhead gas mercaptan removal process, but also is an economic and effective technical solution to solve the problem of excess refining capacity in China in the future, and promotes the transformation and upgrading of refining enterprises from "fuel type" to "energy chemical type". BRIEF DESCRIPTION OF DRAWINGS

[0072] Figure 1 The figure is a flowchart of a method for producing light aromatics according to the present application. DETAILED DESCRIPTION

[0073] The method and effects of the present application will be further illustrated below in combination with the drawings and examples, but the protection scope of the present application is not limited thereto.

[0074] A method for producing light aromatics, the process flow is as follows Figure 1As shown: the catalytic cracking crude gasoline 1 is fractionated into light fraction gasoline 2 and heavy fraction gasoline 3 by the fractionating column A; the light fraction gasoline 2, the rich gas 4 from which hydrogen sulfide is removed by amine washing and hydrogen 5 enter the fluidized bed reactor B from the bottom to carry out deep hydrodesulfurization and light aromatization reaction; the reaction product 6 is discharged from the top of the fluidized bed reactor B, separated by the high pressure separator C to separate hydrogen 7 containing hydrogen sulfide and separation product 8; the separation product 8 is separated by the stripping column D to separate liquefied gas 9 and light aromatization product 10; the light aromatization product 10 is separated by the aromatic extraction unit E to separate light gasoline fraction product 11 and light aromatic hydrocarbon (BTX) 12; the heavy fraction gasoline 3 and hydrogen 5 enter the hydrodesulfurization reactor F to carry out deep hydrodesulfurization reaction to obtain heavy fraction gasoline desulfurization product 13, which is then subjected to the high pressure separator G to obtain hydrogen 14 containing hydrogen sulfide and heavy fraction gasoline desulfurization product 15; the light gasoline fraction product 11 and the heavy fraction gasoline desulfurization product 15 are subjected to the mixer H to obtain clean gasoline component 16.

[0075] The schemes and effects of the present application are further illustrated by the following examples, but the present application is not limited by the examples.

[0076] Example 1

[0077] In this example, the composite functional catalyst F-1 is prepared, and the weight percentage of each component in the catalyst F-1 is as follows: MoS2 is 18%, CoS is 4.8%, ZSM-5 / β composite molecular sieve is 10%, wherein ZSM-5 accounts for 70% of the total weight of the composite molecular sieve, and the rest is an alumina carrier.

[0078] Preparation process of the composite functional catalyst F-1:

[0079] (a) A water solution containing 20wt% glucose is impregnated into the microspherical alumina carrier, and then dried at 80℃ in N2 atmosphere for 5 hours and calcined at 350℃ for 4 hours to obtain a pretreated microspherical carrier, and the carbon content in the pretreated microspherical carrier is shown in Table 1.

[0080] (b) The solution of cobalt nitrate and ammonium heptamolybdate is impregnated into the pretreated microspherical carrier prepared in step (a) by pore saturation impregnation, and then dried at 90℃ in nitrogen atmosphere for 3h, and then subjected to sulfidation treatment by hydrogen containing 1.5% by volume H2S, the flow rate of hydrogen is 10mL·min -1 ·g -1 , the sulfidation temperature is 300℃, the sulfidation pressure is 2.0MPa, and the sulfidation time is 4h, and then cooled to room temperature in N2 atmosphere to obtain a catalyst precursor.

[0081] (c) Sodium meta-aluminate, silica sol, tetrapropylammonium hydroxide were added into deionized water and stirred to form a uniform precursor solution A, in which the molar ratio of each component was n(Al2O3):n(SiO2):n(tetrapropylammonium hydroxide):n(H2O) = 1:50:7:600. The solution was transferred into a reaction kettle with a polytetrafluoroethylene lining and sealed. The solution was statically crystallized at 120°C for 15 hours. After washing and filtering, ZSM-5 particles were obtained. Sodium meta-aluminate, silica sol, tetraethylammonium hydroxide were added into deionized water and stirred to form a uniform precursor solution B, in which the molar ratio of each component was n(Al2O3):n(SiO2):n(tetraethylammonium hydroxide):n(H2O) = 1:100:15:800. The obtained ZSM-5 particles were uniformly dispersed into the solution B and stirred for 30 minutes to form a uniform ZSM-5 / β composite molecular sieve precursor. The amount of ZSM-5 particles added was 70% of the weight of the finally obtained ZSM-5 / β composite molecular sieve.

[0082] (d) The ZSM-5 / β composite molecular sieve precursor was mixed with the catalyst precursor prepared in step (b) and hydrothermally treated at 160°C, 1.5 MPa, and pH = 8.0 for 10 hours. Then, the mixture was filtered, washed with deionized water three times, dried at 90°C under a nitrogen atmosphere for 4 hours, and calcined at 400°C for 3 hours to obtain the composite functional catalyst F-1.

[0083] Example 2

[0084] In this example, the composite functional catalyst F-2 was prepared. The weight percentage of each component in the catalyst F-2 was as follows: MoS2 was 22%, NiS was 5.6%, and ZSM-5 / β composite molecular sieve was 8%, in which ZSM-5 accounted for 70% of the total weight of the composite molecular sieve, and the rest was an alumina carrier.

[0085] Preparation process of the composite functional catalyst F-2:

[0086] (a) A solution containing 60 wt% glycerol was impregnated into the microspherical alumina carrier, and then dried at 90°C under a nitrogen atmosphere for 6 hours and calcined at 300°C for 5 hours to obtain a pretreated microspherical carrier. The carbon content in the pretreated microspherical carrier is shown in Table 1.

[0087] (b) The solution of nickel nitrate and ammonium heptamolybdate was impregnated into the pretreated microspherical carrier prepared in step (a) by pore saturation impregnation, and then dried at 90°C under a nitrogen atmosphere for 3 hours. Then, the carrier was subjected to sulfidation treatment using hydrogen containing 1.5 vol% H2S, with a hydrogen flow rate of 10 mL·min-1, a sulfidation temperature of 300°C, a sulfidation pressure of 2.0 MPa, and a sulfidation time of 4 hours. Then, the carrier was cooled to room temperature under a nitrogen atmosphere to obtain a catalyst precursor. -1 ·g -1 ​

[0088] (c) Sodium meta-aluminate, silica sol, tetrapropylammonium hydroxide were added into deionized water and stirred to form a uniform precursor solution A, with the molar ratio of n(Al2O3) : n(SiO2) : n(tetrapropylammonium hydroxide) : n(H2O) = 1 : 50 : 7 : 600. The solution was transferred into a Teflon-lined autoclave and sealed. The autoclave was statically crystallized at 120°C for 15 hours. After washing and filtering, ZSM-5 particles were obtained. Sodium meta-aluminate, silica sol, tetraethylammonium hydroxide were added into deionized water and stirred to form a uniform precursor solution B, with the molar ratio of n(Al2O3) : n(SiO2) : n(tetraethylammonium hydroxide) : n(H2O) = 1 : 100 : 15 : 800. The obtained ZSM-5 particles were uniformly dispersed into the solution B and stirred for 30 minutes to form a uniform ZSM-5 / β composite molecular sieve precursor. The amount of ZSM-5 particles added was 70% of the weight of the final ZSM-5 / β composite molecular sieve,

[0089] (d) The ZSM-5 / β composite molecular sieve precursor was mixed with the catalyst precursor prepared in step (b) and hydrothermally treated at 160°C, 1.5 MPa, and pH = 8.0 for 10 hours. Then, the mixture was filtered, washed with deionized water three times, dried at 90°C under a nitrogen atmosphere for 4 hours, and calcined at 400°C for 3 hours to obtain the composite functional catalyst F-2.

[0090] Example 3

[0091] In this example, the composite functional catalyst F-3 was prepared. The weight percentage of each component in the catalyst F-3 was as follows: WoS2 was 16%, CoS was 5.2%, and ZSM-5 / β composite molecular sieve was 9%, wherein ZSM-5 accounted for 70% of the total weight of the composite molecular sieve, and the rest was an alumina carrier.

[0092] Preparation process of the composite functional catalyst F-3:

[0093] (a) A 70wt% ethylene glycol aqueous solution was impregnated into the microspherical alumina carrier, and then dried at 90°C under a nitrogen atmosphere for 5 hours and calcined at 350°C for 4 hours to obtain a pretreated microspherical carrier. The carbon content in the pretreated microspherical carrier is shown in Table 1.

[0094] (b) The solution of cobalt nitrate and ammonium metatungstate was impregnated into the pretreated microspherical carrier prepared in step (a) by pore saturation impregnation, and then dried at 90°C under a nitrogen atmosphere for 3 hours. Then, the catalyst precursor was obtained by sulfidation treatment using hydrogen containing 1.5% by volume H2S, with a hydrogen flow rate of 10 mL·min-1, a sulfidation temperature of 300°C, a sulfidation pressure of 2.0 MPa, and a sulfidation time of 4 hours, and then cooled to room temperature under a nitrogen atmosphere. -1 ·g -1 ,

[0095] (c) Sodium metaaluminate, silica sol, tetrapropylammonium hydroxide were added into deionized water and stirred to form a uniform precursor solution A, in which the molar ratio of each component was n(Al2O3):n(SiO2):n(tetrapropylammonium hydroxide):n(H2O) = 1:50:7:600. The solution was transferred into a reaction kettle with polytetrafluoroethylene as the inner liner and sealed. The static crystallization was carried out at 120°C for 15 hours. After washing and filtering, ZSM-5 particles were obtained. Sodium metaaluminate, silica sol, tetraethylammonium hydroxide were added into deionized water and stirred to form a uniform precursor solution B, in which the molar ratio of each component was n(Al2O3):n(SiO2):n(tetraethylammonium hydroxide):n(H2O) = 1:100:15:800. The obtained ZSM-5 particles were uniformly dispersed into the solution B and stirred for 30 minutes to form a uniform precursor of ZSM-5 / β composite molecular sieve. The amount of ZSM-5 particles added was 70% of the weight of the finally obtained ZSM-5 / β composite molecular sieve,

[0096] (d) The precursor of ZSM-5 / β composite molecular sieve was mixed with the catalyst precursor prepared in step (b), and hydrothermally treated at 160°C, 1.5 MPa, and pH = 8.0 for 10 hours. Then, the mixture was filtered, washed with deionized water for three times, dried at 90°C under nitrogen atmosphere for 4 hours, and calcined at 400°C for 3 hours to obtain the composite functional catalyst F-3.

[0097] Example 4

[0098] In this example, the composite functional catalyst F-4 was prepared. The weight percentage of each component in the catalyst F-4 was as follows: WoS2was 15%, NiS was 4.2%, and ZSM-5 / β composite molecular sieve was 9%, in which ZSM-5 accounted for 70% of the total weight of the composite molecular sieve, and the rest was an alumina carrier.

[0099] Preparation process of the composite functional catalyst F-4:

[0100] (a) A solution containing 50wt% butanediol was impregnated into the microspherical alumina carrier, and then dried at 90°C under N2atmosphere for 5 hours and calcined at 350°C for 4 hours to obtain a pretreated microspherical carrier. The carbon content in the pretreated microspherical carrier was shown in Table 1.

[0101] (b) The solution of cobalt nitrate and ammonium metatungstate was impregnated into the pretreated microspherical carrier prepared in step (a) by pore saturation impregnation, and then dried at 90°C under nitrogen atmosphere for 3 hours. Then, the sulfidation treatment was carried out by using hydrogen containing 1.5% by volume of H2S, and the flow rate of hydrogen was 10 mL·min -1 ·g -1, the sulfuration temperature is 300℃, the sulfuration pressure is 2.0 MPa, and the sulfuration time is 4h, and then the temperature is decreased to room temperature in N2 atmosphere to obtain a catalyst precursor.

[0102] (c) Sodium aluminite, silica sol and tetrapropylammonium hydroxide are added into deionized water to be stirred and mixed, wherein the molar ratio of each component is n(Al2O3):n(SiO2):n(tetrapropylammonium hydroxide):n(H2O) = 1:50:7:600, and the mixture is stirred to form a uniform precursor solution A, which is then transferred into a reaction kettle with polytetrafluoroethylene as the inner liner and sealed. The solution is statically crystallized at 120℃ for 15h, and then ZSM-5 particles are obtained by washing and filtering. Sodium aluminite, silica sol and tetraethylammonium hydroxide are added into deionized water to be stirred and mixed, wherein the molar ratio of each component is n(Al2O3):n(SiO2):n(tetraethylammonium hydroxide):n(H2O) = 1:100:15:800, and the mixture is stirred to form a uniform precursor solution B. The obtained ZSM-5 particles are uniformly dispersed into the solution B and stirred for 30 minutes to form a uniform precursor of ZSM-5 / β composite molecular sieve. The amount of ZSM-5 particles added is 70% of the weight of the finally obtained ZSM-5 / β composite molecular sieve,

[0103] (d) The precursor of ZSM-5 / β composite molecular sieve is mixed with the catalyst precursor prepared in step (b), and then hydrothermally treated at 160℃, 1.5 MPa and pH = 8.0 for 10h. Then, the mixture is filtered, washed with deionized water for three times, dried at 90℃ in nitrogen atmosphere for 4h, and calcined at 400℃ for 3h to obtain a composite functional catalyst F-4.

[0104] Comparative Example 1

[0105] The composite functional catalyst C-1 is prepared in this comparative example. The weight percentage of each component in the catalyst C-1 is as follows: MoS2 is 21%, CoS is 4.9%, ZSM-5 molecular sieve is 20%, and the rest is alumina carrier.

[0106] Preparation process of the composite functional catalyst C-1:

[0107] (a) ZSM-5 molecular sieve and pseudo-boehmite are mixed to prepare a microspherical ZSM-5-Al2O3 carrier according to the component content of the catalyst C-1.

[0108] (b) The solution of cobalt nitrate and ammonium heptamolybdate is impregnated into the microspherical carrier prepared in step (a) by pore saturation impregnation, dried at 100℃ in nitrogen atmosphere for 4h, and calcined at 450℃ for 4h to obtain an oxidized catalyst.

[0109] (c) The oxidized catalyst obtained in step (b) is sulfided with hydrogen containing 1.5% by volume of H2S, and the flow rate of hydrogen is 10 mL·min -1 ·g-1 The sulfuration temperature was 300°C, the sulfuration pressure was 2.0 MPa, the sulfuration time was 4 h, and then the temperature was decreased to room temperature in a N2 atmosphere to obtain the composite functional catalyst C-1.

[0110] Comparative Example 2

[0111] The composite functional catalyst C-2 was prepared in this comparative example, and the weight percentage of each component in the catalyst C-2 was as follows: MoS2 was 25%, NiS was 4.2%, ZSM-5 molecular sieve was 20%, β molecular sieve was 5%, and the rest was an alumina carrier.

[0112] Preparation process of the composite functional catalyst C-2:

[0113] (a) According to the component content of the C-2 catalyst, ZSM-5 molecular sieve, β molecular sieve and pseudo-boehmite were mixed to prepare a microspherical ZSM-5 / β-Al2O3 carrier.

[0114] (b) The solution of nickel nitrate and ammonium heptamolybdate was impregnated into the microspherical carrier prepared in step (a) by pore saturation impregnation, dried at 100°C in a nitrogen atmosphere for 4 h, and calcined at 450°C for 4 h to obtain an oxidized catalyst.

[0115] (c) The oxidized catalyst obtained in step (b) was sulfided with hydrogen containing 1.5% by volume of H2S, and the flow rate of hydrogen was 10 mL·min -1 ·g -1 The sulfuration temperature was 300°C, the sulfuration pressure was 2.0 MPa, the sulfuration time was 4 h, and then the temperature was decreased to room temperature in a N2 atmosphere to obtain the composite functional catalyst C-2.

[0116] Example 5

[0117] This example is a process method for producing light aromatics (BTX) and clean gasoline components using a composite functional catalyst F-1, and the properties of the catalytic cracking overhead gas raw material and the crude gasoline raw material used are shown in Tables 2 and 3, and the specific steps are as follows:

[0118] (1) The raw material crude gasoline was distilled in a fractionating column to cut into light fraction gasoline and heavy fraction gasoline, and the cutting temperature was controlled at 75°C, and the yield of the light fraction gasoline and the heavy fraction gasoline was 36.3wt% and 63.4wt%, respectively. The gas-rich raw material was removed of hydrogen sulfide by an alcohol amine extraction tower, diethanol amine was used as the absorption solvent, the volume ratio of diethanol amine to reaction product was 4:1, and the operating temperature of the extraction tower was 40°C.

[0119] (2) F-1 catalyst 40 mL was loaded into a small continuous fluidized bed reactor, the mass ratio of the reaction raw material of rich gas and light distillate gasoline was 1:1, the reaction raw material was subjected to deep desulfurization and light aromatization reaction in the fluidized bed to obtain light aromatization product, the reaction process conditions were: the reaction pressure was 2.0 MPa, the reaction temperature was 450 ℃, the liquid hourly space velocity was 0.8 h -1 , and the hydrogen to oil volume ratio was 150:1.

[0120] (3) The light aromatization product was subjected to aromatic extraction, and a mixed solvent of sulfolane and N-formyl morpholine was used for extraction, the extraction temperature was 90 ℃, the volume content ratio of sulfolane and N-formyl morpholine in the mixed extractant was 8:1, and BTX product and light distillate gasoline product were obtained.

[0121] (4) The heavy distillate gasoline was subjected to hydrodesulfurization reaction in a small fixed bed reactor, and a commercial CoMo / Al2O3 type ME-1 hydrodesulfurization catalyst was used, the reaction process conditions were: the reaction pressure was 2.0 MPa, the reaction temperature was 270 ℃, the liquid hourly space velocity was 2.5 h -1 , and the hydrogen to oil volume ratio was 350:1.

[0122] (5) The light distillate gasoline product and the heavy distillate desulfurized gasoline product were mixed to obtain clean gasoline components.

[0123] The properties of the BTX product and the clean gasoline components obtained by the above process are shown in Table 4.

[0124] Example 6

[0125] This example is a process method for producing light aromatics (BTX) and clean gasoline components using a composite functional catalyst F-2, and the properties of the feedstock of catalytic cracking tower top rich gas and the feedstock of crude gasoline are shown in Tables 2 and 3, and the specific steps are as follows:

[0126] (1) The feedstock of crude gasoline was distilled in a fractionating column to cut into light distillate gasoline and heavy distillate gasoline, and the cutting temperature was controlled at 75 ℃, and the yield of light distillate gasoline and heavy distillate gasoline was 36.3 wt% and 63.4 wt% respectively. The rich gas feedstock was subjected to removal of hydrogen sulfide in an alcohol amine extraction tower, diethanol amine was used as the absorption solvent, and the volume ratio of diethanol amine to reaction product was 4:1, and the operation temperature of the extraction tower was 40 ℃.

[0127] (2) F-2 catalyst 40 mL was loaded into a small continuous fluidized bed reactor, the mass ratio of the reaction raw material of rich gas and light distillate gasoline was 1:1, the reaction raw material was subjected to deep desulfurization and light aromatization reaction in the fluidized bed to obtain light aromatization product, the reaction process conditions were: the reaction pressure was 1.5 MPa, the reaction temperature was 420 ℃, the liquid hourly space velocity was 0.5 h -1 , and the hydrogen to oil volume ratio was 120:1.

[0128] (3) The light aromatic product is extracted with aromatic hydrocarbon, using a mixed solvent of sulfolane and N-formyl morpholine, the extraction temperature is 90°C, the volume content ratio of sulfolane and N-formyl morpholine in the mixed extractant is 8:1, and BTX product and light distillate gasoline product are obtained.

[0129] (4) The heavy distillate gasoline is subjected to hydrodesulfurization reaction in a small fixed bed reactor, using a commercial CoMo / Al2O3 type ME-1 hydrodesulfurization catalyst, the reaction process conditions are: reaction pressure is 2.0 MPa, reaction temperature is 280°C, liquid hourly space velocity is 2.5 h -1 , and hydrogen to oil volume ratio is 350:1.

[0130] (5) The light distillate gasoline product and the heavy distillate desulfurized gasoline product are mixed to obtain clean gasoline component.

[0131] The properties of the BTX product and the clean gasoline component obtained by the above process are shown in Table 4.

[0132] Example 7

[0133] The difference between this example and Example 5 is that the composite functional catalyst used is F-3.

[0134] Example 8

[0135] The difference between this example and Example 6 is that the composite functional catalyst used is F-4.

[0136] Comparative Example 3

[0137] In this comparative example, C-1 catalyst 40 mL is loaded into a small continuous fluidized bed reactor, the reaction raw material is the same as in Example 5, the reaction raw material is subjected to deep desulfurization and light aromatization reaction in the fluidized bed to obtain light aromatization product, the reaction process conditions are: reaction pressure is 2.0 MPa, reaction temperature is 450°C, liquid hourly space velocity is 0.8 h -1 , and hydrogen to oil volume ratio is 150:1. The reaction product is shown in Table 5.

[0138] Comparative Example 4

[0139] In this comparative example, C-2 catalyst 40 mL is loaded into a small continuous fluidized bed reactor, the reaction raw material is the same as in Example 5, the reaction raw material is subjected to deep desulfurization and light aromatization reaction in the fluidized bed to obtain light aromatization product, the reaction process conditions are: reaction pressure is 1.5 MPa, reaction temperature is 420°C, liquid hourly space velocity is 0.5 h -1 , and hydrogen to oil volume ratio is 120:1.

[0140] From the results of the reaction products below, it can be seen that the proportion of the molecular sieve directly interacting with the Group VIB metal sulfide in the composite functional catalyst prepared according to the present application is high and has better desulfurization and light aromatization performance, the selectivity of the BTX components in the light aromatization product is high, and the product can meet the requirements of aromatic extraction raw materials, and can realize the production of low-sulfur, low-olefin gasoline components while increasing the production of high-value light aromatics (BTX) from the gas and part of the gasoline components.

[0141] Table 1 Catalyst properties

[0142]

[0143] Table 2 Raw material crude gasoline properties

[0144]

[0145]

[0146] Table 3 Raw material gas properties

[0147] Properties Rich gas feed Ethylene, v% 1.44 Propylene, v% 39.2 Butylenes, v% 22.4 Total sulfur, pg / g 2870 Mercaptan sulfur, pg / g 168

[0148] Table 4 Example reaction product properties

[0149]

[0150] Table 5 Comparative example reaction product properties

[0151] Comparative example 3 Comparative example 4 Light aromatization product Sulfur, pg / g 13.2 11.5 Aromatics content, v% 45.2 41.3 BTX content, v% 37.4 32.1 Bromine number, g Br / 100 g 2.1 1.8 BTX product composition Benzene, v% 3.2 3.5 Toluene, v% 16.9 14.8 Xylenes, v% 79.9 81.7

Claims

1. A method for producing light aromatic hydrocarbons, comprising the following steps: (1) cutting the raw gasoline from a catalytic cracking unit fractionating column, the cutting point for cutting the raw gasoline being 60-90°C, to obtain light fraction gasoline and heavy fraction gasoline; (2) feeding the light fraction gasoline and the overhead gas of the catalytic cracking unit fractionating column into a fluidized bed reactor together to perform deep desulfurization and light aromatization on a composite functional catalyst to obtain light aromatization products; wherein the composite functional catalyst is a sulfided hydrogenation catalyst comprising a carrier, an active component and ZSM-5 / β composite molecular sieve, the active component comprising at least one of Group VIII metal elements and at least one of Group VIB metal elements, and the composite functional catalyst is characterized by TEM-EDS method, wherein the proportion of ZSM-5 / β composite molecular sieve directly interacting with Group VIB metal sulfide to the total amount of molecular sieve is 60-100% in terms of silicon element; (3) subjecting the light aromatization products to an aromatic extraction system to obtain light aromatic hydrocarbons and light fraction gasoline products.

2. The method of claim 1, wherein, The method further comprises a process for treating the heavy fraction gasoline obtained in step (1) to obtain clean gasoline, which comprises: feeding the heavy fraction gasoline obtained in step (1) into a hydrodesulfurization reactor to react with a selective hydrodesulfurization catalyst to obtain heavy fraction gasoline desulfurization products; and mixing the light fraction gasoline products of step (3) and the heavy fraction gasoline desulfurization products to obtain clean gasoline components with low sulfur and low olefins.

3. The method of claim 1, wherein, The composition of the crude gasoline is: olefin volume content ≮20v%, aromatic hydrocarbon volume content ≯30v%, sulfur mass content ≯500µg / g; the composition of the overhead gas of the fractionating column of the catalytic cracking device is: C3-C4 hydrocarbon content accounting for 80v%-90v% of the total amount of the overhead gas, total sulfur content being 100-5000mg / m 3 .

4. The method of claim 1, wherein, The overhead gas of the catalytic cracking unit fractionating column is first subjected to amine liquid absorption to remove hydrogen sulfide, and then fed into the fluidized bed reactor.

5. The method of claim 1, wherein, The mass ratio of the overhead gas of the catalytic cracking unit fractionating column to the light fraction gasoline in the reaction raw material is 1:3-1:

1.

6. The method of claim 1, wherein, In the composite functional catalyst used in step (2), the content of ZSM-5 / β composite molecular sieve is 5-25 wt% based on the total weight of the catalyst, and the weight content of ZSM-5 molecular sieve in the ZSM-5 / β composite molecular sieve is 30 wt%-75 wt%.

7. The method of claim 1, wherein, In the composite functional catalyst, the content of Group VIB metal sulfide is 10-30 wt% based on the total weight of the catalyst, and the content of Group VIII metal sulfide is 2-10 wt% based on the total weight of the catalyst.

8. The method of claim 1, wherein, In the composite functional catalyst, the carrier is selected from at least one of alumina, silica, titania and zirconia.

9. The method of claim 1, wherein, The composite functional catalyst is prepared by the following method: (a) impregnating the carrier with a solution containing an organic additive, drying and calcining under an inert atmosphere to obtain a pretreated carrier; (b) introducing Group VIB metal salt and Group VIII metal salt into the pretreated carrier by impregnation method, and sulfidizing to obtain a catalyst precursor; (c) preparing a ZSM-5 / β composite molecular sieve precursor; (d) hydrothermally treating the catalyst precursor and the composite molecular sieve precursor, drying and calcining under an inert atmosphere to obtain the composite functional catalyst.

10. The method of claim 9, wherein, The organic additive in step (a) is at least one selected from ethylene glycol, glycerol, butanediol, pentanediol, acetic acid, citric acid, glucose, malonic acid, succinic acid, glutaric acid, naphthalene and C9 aromatic hydrocarbon.

11. The method of claim 9, wherein, The drying condition in step (a) includes temperature of 20-90℃ and time of 4-16 hours, and the calcination condition includes temperature of 200-400℃ and time of 3-8 hours.

12. The method of claim 9, wherein, The ZSM-5 / β composite molecular sieve precursor in step (c) is prepared by the following steps: 1) uniformly mixing a silicon source, an aluminum source, a template agent tetrapropyl ammonium hydroxide and deionized water in a certain proportion to form a ZSM-5 synthesis system, denoted as A solution; 2) uniformly mixing a silicon source, an aluminum source, a template agent tetraethyl ammonium hydroxide and deionized water in a certain proportion to form a β synthesis system, denoted as B solution; 3) after the A solution is crystallized at 90-150℃ for 3-24 hours, ZSM-5 particles are obtained by centrifugal separation, the ZSM-5 particles are dispersed in the β synthesis system B solution, stirring is performed to form a homogeneous slurry, and a ZSM-5 / β composite molecular sieve precursor is obtained.

13. The method of claim 12, wherein, The addition amount of the reaction raw materials in the A solution should make the molar ratio of the components in the system be A12O3:SiO2: tetrapropyl ammonium hydroxide: water = 1:20-200:3-10:500-1000; the addition amount of the reaction raw materials in the B solution should make the molar ratio of the components in the system be A12O3:SiO2: tetraethyl ammonium hydroxide: water = 1:20-200:1-20:500-1000; the silicon source is one or more of tetraethyl orthosilicate, silica sol and water glass; the aluminum source is one or more of aluminum sulfate, aluminum chloride, aluminum isopropyl alcohol and sodium metaaluminate; and the addition amount of the ZSM-5 particles is 25-75% of the final ZSM-5 / β composite molecular sieve yield.

14. The method of claim 9, wherein, The hydrothermal treatment condition in step (d) includes temperature of 90-200℃, pressure of 0.1-2MPa and time of 8-72 hours, the drying condition includes temperature of 20-90℃ and time of 4-16 hours, and the calcination condition includes temperature of 300-500℃ and time of 2-5 hours.

15. The method of claim 1, wherein, The deep desulfurization and light aromatization reaction in step (2) is carried out under the following conditions: reaction pressure 1.0-2.5 MPa, reaction temperature 300-500°C, total liquid hourly space velocity 0.1-3.0 h -1 -3.0 h -1 , hydrogen to oil volume ratio 50:1-300:

1.

16. The method of claim 2, wherein, The selective hydrodesulfurization catalyst is a VIB group metal and / or VIII group metal supported on amorphous Al2O3 and / or aluminum silicate carrier, the VIB group metal is Mo and / or W, and the VIII group metal is Co and / or Ni.

17. The method of claim 2, wherein, The reaction conditions for the selective hydrodesulfurization reaction are: reaction pressure 1.0-3.0 MPa, reaction temperature 200-300°C, liquid hourly space velocity 1.0-5.0 h -1 -1 -1 , hydrogen to oil volume ratio 150:1-450:1.

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