A process for producing light aromatic hydrocarbons

Abstract

The present application relates to the technical field of petroleum chemical production, and discloses a method for producing light aromatic hydrocarbons. The method for producing light aromatic hydrocarbons comprises the following steps: (1) performing a hydrogenation reaction on catalytic diesel oil in the presence of hydrogen to obtain a liquid-phase hydrogenation product; (2) performing a selective conversion reaction on the liquid-phase hydrogenation product and C 10 + heavy aromatic hydrocarbons in the presence of hydrogen and a selective conversion catalyst to obtain light aromatic hydrocarbons and C 11 + heavy tail oil, wherein the selective conversion catalyst is arranged in the form of an n-stage grading, and n is a positive integer. The method can improve the purity and yield of light aromatic hydrocarbons, and hydrogen consumption is low.

Description

Technical Field

[0001] This invention relates to the technical field of petrochemical production, and specifically to a method for producing light aromatics. Background Technology

[0002] LCO feedstock has high sulfur and nitrogen content and is rich in polycyclic aromatic hydrocarbons, making its processing into automotive gasoline / diesel technically and economically unsustainable. In particular, with the further restrictions on aromatic content imposed by the China VI emission standard for gasoline / diesel upgrades, traditional technologies that convert LCO feedstock into gasoline blending components (FD2G, RLG, and LTAG) can no longer meet national environmental standards and market demands. Furthermore, with the increasing demand in the domestic aromatics market, aromatics co-production units are continuously expanding their capacity, and byproduct reforming C... 10 The production of heavy aromatics is also increasing, and its main components include monocyclic aromatics, bicyclic aromatics, and small amounts of tricyclic and tetracyclic fused-ring aromatics. In terms of composition, catalytic diesel and C... 10 Heavy aromatics are a relatively abundant aromatic resource, and are used to achieve the desired effect in low-quality catalytic diesel and C2C4. 10 Maximizing the value of heavy aromatics by utilizing their rich aromatic content to produce light aromatics is currently an effective approach.

[0003] Chinese patent application CN112322349A discloses a complete conversion method and apparatus for producing light aromatics from catalytic diesel fuel. The method involves hydrorefining the catalytic diesel fuel stream, separating impurities, and then subjecting it to a selective conversion reaction. The resulting mixed aromatics are then separated sequentially to obtain light aromatics such as benzene-toluene and xylene, C9A aromatics, and C6A aromatics. 10 Aromatics and heavy tail oil from the bottom of the tower; the heavy tail oil from the bottom of the tower enters the selective saturation reactor, where it is selectively hydrogenated and saturated under low temperature and low pressure conditions to obtain a product with a benzene ring, and then sent back to the selective conversion reactor to realize the full-fraction conversion from catalytic diesel to light aromatics.

[0004] Chinese patent application CN115595175A discloses a complete conversion method and apparatus for producing chemical feedstocks from catalytic diesel. The technical solution of this invention includes hydrorefining the catalytic diesel stream and a selective conversion reaction. The selective conversion catalyst includes β-zeolite, MWW-type zeolite with a sheet thickness ranging from 2-12 nm, group VIB metal sulfides, and a binder.

[0005] Chinese patent application CN112662428A discloses a C 10 +A method and system for hydrogenating heavy aromatics to lighter forms, employing a two-stage conversion scheme: C 10 Heavy aromatic feedstock is first subjected to selective hydrogenation saturation under mild conditions. The resulting hydrogenated saturated products are then subjected to hydrocracking to yield C6-C8 aromatics and C9 / C9 aromatics. 10 Heavy aromatics and C-containing hydrocarbons 10+Logistics of heavy aromatics.

[0006] Chinese patent application CN107376984A discloses a method for C 10 A method for preparing a non-precious metal catalyst for the lightening of heavy aromatics. The catalyst of this invention uses elemental nickel and nickel phosphide (Ni2P) as the active phases, and molecular sieves and alumina as supports. A competing adsorbent is used to address the problem that the reaction between alumina and phosphorus in the support to form aluminum phosphate, which significantly reduces the catalyst's activity. A low-boiling-point organic compound with strong reducing properties is used to lower the formation temperature of the nickel phosphide phase, reducing nickel phosphide particle aggregation and significantly improving catalyst activity. A non-precious metal hydrogenation active phase is used instead of precious metals to significantly reduce catalyst costs.

[0007] Chinese patent application CN104368373A discloses a C 10 A method for preparing a heavy aromatic alkyl transfer catalyst, wherein the catalyst is composed of 50-80% HY molecular sieve (crystal size 30-100 nm), 15-40% alumina as a binder component, and 1-8% a metal or its oxide as a modifier component. This catalyst is capable of operating at C9-C... 12 The non-hydrogen-dependent conversion of heavy aromatics into light aromatics.

[0008] Chinese patent application CN103897731A discloses a catalytic cracking diesel fuel and C 10 A method for producing light aromatics by blending distillate oils, firstly by mixing catalytic cracked diesel oil and C... 10 The distillate oil is mixed with hydrogen and then subjected to a hydrorefining reaction to remove sulfur and nitrogen, saturate olefins, and appropriately saturate aromatics. The hydrorefining product is then extracted with an extraction solvent to obtain an aromatic-rich extract oil and an alkane-rich raffinate oil. The raffinate oil is used as a component in clean diesel blending, while the extract oil is separated by distillation to obtain aromatic extract oil. This aromatic extract oil is then subjected to hydrocracking, and the hydrocracking products are further separated. The distillate oil with a temperature >195°C is used as a component in clean diesel blending, while the distillate oil with a temperature <195°C is fed into an aromatics processing unit to obtain light aromatics and a clean gasoline blending component. This invention increases the yield of light aromatics while obtaining high-quality clean fuel oil and achieving C... 10 +High-value utilization of distillate oils, but this implementation method will increase the hydrogen consumption of the reaction.

[0009] The above methods have, to some extent, achieved the production of catalytic diesel and reformed C. 10+ The high-value utilization of aromatics also has the following problems: (1) the raw materials are single; (2) the catalysts are single, aromatics are prone to oversaturation, and the selectivity of light aromatics is poor; (3) the equipment process is too complicated and the investment cost is high; (4) the raw materials are first purified by hydrogenation, which will inevitably lead to the oversaturation reaction of aromatics, high hydrogen consumption and low selectivity of aromatics. Summary of the Invention

[0010] The purpose of this invention is to overcome the problems existing in the prior art and provide a method for producing light aromatics, which can improve the purity and yield of light aromatics and has low hydrogen consumption.

[0011] To achieve the above objectives, the present invention provides a method for producing light aromatics, wherein the method includes the following steps:

[0012] (1) In the presence of hydrogen, catalytic diesel is hydrogenated to obtain liquid-phase hydrogenation product;

[0013] (2) In the presence of hydrogen and a selective conversion catalyst, the liquid-phase hydrogenation product is reacted with C 10 + Selective conversion of heavy aromatics yields light aromatics and C 11 +Heavy tail oil, wherein the selective conversion catalyst is present in an n-stage graded packing form, where n is a positive integer.

[0014] The method provided by this invention combines catalytic diesel and C 10 The production of light aromatics by combining heavy aromatics with catalytic diesel fuel solves the problem of existing technologies involving the production of light aromatics. 10 The separate production of light aromatics from heavy aromatics addresses the issue of limited feedstock availability and expands the production of catalytic diesel and C2C20. 10 + Process route for producing light aromatics from heavy aromatics.

[0015] Compared to existing technologies for catalytic diesel and C 10 Heavy aromatics all require hydrogenation to produce light aromatics. The method provided by this invention only requires hydrogenation of catalytic diesel, which reduces hydrogen consumption while improving the purity and yield of light aromatics. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the process flow of the present invention.

[0017] Explanation of reference numerals in the attached figures

[0018] 1-Catalytic diesel 2-Hydrogen

[0019] 3-Hydrogenation reactor 4-Hydrogenation products

[0020] 5-First separation system; 6-Streams of hydrogen sulfide and ammonia

[0021] 7-Liquid-phase hydrogenation products 8-Selective conversion reactor

[0022] 9-C 10 +Heavy aromatics 10-Selective conversion reaction products

[0023] 11-Second Separation System 12-Dry Gas and C3-C5 Light Hydrocarbons

[0024] 13-Benzene and Toluene, 14-Xylene

[0025] 15-C9A aromatics 16-C 10 Aromatic hydrocarbons

[0026] 17-C 11 Heavy tail oil Detailed Implementation

[0027] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0028] This invention provides a method for producing light aromatics, wherein the method includes the following steps:

[0029] (1) In the presence of hydrogen, catalytic diesel is hydrogenated to obtain liquid-phase hydrogenation product;

[0030] (2) In the presence of hydrogen and a selective conversion catalyst, the liquid-phase hydrogenation product is reacted with C 10 + Selective conversion of heavy aromatics yields light aromatics and C 11 +Heavy tail oil, wherein the selective conversion catalyst is present in an n-stage graded packing form, where n is a positive integer.

[0031] In this invention, catalytic diesel fuel undergoes desulfurization, denitrification, and selective saturation of polycyclic aromatic hydrocarbons via hydrogenation, reducing sulfur and nitrogen content and ensuring that the liquid-phase hydrogenation products are compatible with C. 10 The successful selective conversion reaction of heavy aromatics has made it possible to process different feedstocks into light aromatics using the same process route, opening up new process pathways; C 10 Heavy aromatics do not require hydrogenation, thus reducing hydrogen consumption while increasing the purity and yield of light aromatics. Furthermore, the method provided by this invention improves the purity and yield of light aromatics by selecting a specific catalyst gradient. In contrast, existing technologies directly convert C... 10The direct mixing and hydrorefining of heavy aromatics with catalytic diesel has drawbacks, including oversaturation of aromatics, increased hydrogen consumption, and low yield and purity of aromatics.

[0032] In this invention, the light aromatic hydrocarbons refer to light aromatic hydrocarbons with 6-10 carbon atoms, such as benzene, toluene, xylene, C9A aromatic hydrocarbons, and C6A aromatic hydrocarbons. 10 Aromatic hydrocarbons.

[0033] In this invention, the selective conversion catalyst being present in an n-stage graded packing form means that the selective conversion catalyst is packed in n catalyst beds connected in series. In this invention, there is no particular limitation on the arrangement of the catalyst beds. For example, n catalyst beds connected in series can be arranged in the same reactor, or n reactors can be connected in series to form a catalyst bed.

[0034] In this invention, there are no particular limitations on the property parameters of the catalytic diesel oil. Preferably, in step (1), the T of the catalytic diesel oil is... 95 The distillation range is 320-360℃, the sulfur content is 1000-4000ppm, and the nitrogen content is 200-1000ppm. In this invention, T 95 Distillation range refers to the distillation temperature at which catalytic diesel oil yields 95% of its volume fraction during distillation. The method provided by this invention can process T... 95 Inferior catalytic diesel with a distillation range within the aforementioned preferred range broadens the application range of feedstocks.

[0035] In this invention, preferably, in step (1), the hydrogenation reaction is carried out in the presence of a hydrogenation catalyst, which includes a hydrogenation support and a hydrogenation component.

[0036] In this invention, there is no particular limitation on the type of support in the hydrogenation catalyst. Preferably, the support is selected from at least one of alumina, silicon dioxide, and titanium dioxide, and more preferably alumina.

[0037] In this invention, there is no particular limitation on the type of hydrogenation component in the hydrogenation catalyst. Preferably, the hydrogenation component includes sulfides of Group VIII metals and / or sulfides of Group VIB metals, and more preferably sulfides of W, Mo, Ni, and Co.

[0038] In this invention, the content of each component in the hydrogenation catalyst is not particularly limited. Preferably, based on the total amount of the hydrogenation catalyst, the sulfide content of W is 5-20 wt%, the sulfide content of Mo is 5-20 wt%, the sulfide content of Ni is 1-15 wt%, and the sulfide content of Co is 1-15 wt%.

[0039] In this invention, the content of each component in the hydrogenation catalyst was determined by XRF (X-ray fluorescence) analysis. In this invention, the composition of Group VIB and Group VIII metal sulfides was determined by XPS (X-ray photoelectron spectroscopy).

[0040] In this invention, there is no particular limitation on the source of the hydrogenation catalyst. For example, it can be prepared by conventional methods defined in the art or it can be obtained commercially. Those skilled in the art can choose according to actual needs, as long as it can meet the needs of step (1) catalytic hydrogenation of diesel and subsequent selective conversion reaction.

[0041] In this invention, preferably, the conditions for the hydrogenation reaction include: a reaction temperature of 250-400℃, a reaction pressure of 2-10 MPa, and a weight hourly space velocity of 0.5-2 h⁻¹. -1 The hydrogen-to-oil volume ratio is 500-2000. It should be noted that when the reaction proceeds continuously, the "oil" in the hydrogen-to-oil volume ratio includes catalytic diesel and recycled C20. 11 +Heavy tail oil, in this invention, catalytic diesel and recycled C 11 There is no particular limitation on the amount of heavy tail oil used, as long as the total amount of both meets the requirements. Those skilled in the art can choose according to actual needs. The advantage of this preferred embodiment is that it can reduce the nitrogen content in the hydrogenation reaction products to below 20 ppm, the sulfur content to below 200 ppm, and the aromatics retention rate to greater than 90%, providing high-quality hydrogenation refining LCO feedstock for the selection of the conversion reaction stage.

[0042] In this invention, preferably, step (1) further includes gas-liquid separation and desulfurization treatment of the hydrogenation product obtained from the hydrogenation reaction to obtain a liquid-phase hydrogenation product and a stream containing hydrogen sulfide and ammonia. In this invention, the conditions for gas-liquid separation and desulfurization treatment are not particularly limited, and those skilled in the art can adjust them according to actual needs. In this invention, the equipment used for gas-liquid separation and desulfurization treatment is not particularly limited; for example, it can be carried out in a first separation system. Preferably, the first separation system includes a gas-liquid separation unit and optionally a desulfurization tower. In this invention, the specific operation method is not particularly limited, as long as the desired liquid-phase hydrogenation product can be obtained. For example, the hydrogenation catalyst product can be sequentially passed through a water cooler and a high-efficiency separator for gas-liquid separation.

[0043] In this invention, C 10 +The source of heavy aromatics is not particularly limited, and C is conventionally defined in this field. 10 Heavy aromatic hydrocarbons are all applicable to this invention. Preferably, in step (2), the C 10 Heavy aromatics are derived from at least one of the following: catalytic reforming unit, ethylene cracking unit, and coal coking by-products, preferably from the catalytic reforming unit.

[0044] In this invention, C 10 The properties of heavy aromatic hydrocarbons are not particularly limited. Preferably, in step (2), the C 10 +In heavy aromatics, the sulfur content is <10ppm and the nitrogen content is <10ppm.

[0045] In this invention, the composition of the selective conversion catalyst is not particularly limited, as long as it meets the requirements of the selective conversion reaction. Preferably, in step (2), the selective conversion catalyst includes oxides and / or sulfides of Group VIB metals, molecular sieves, binders, and elemental forms of Group VIII metals, more preferably oxides of Group VIB metals, molecular sieves, binders, and elemental forms of Group VIII metals. The advantage of this preferred embodiment is that the hydrogenation activity of the reaction is moderate, it will not be over-hydrogenated to saturation, and it can produce as many light aromatics as possible.

[0046] In this invention, preferably, the Group VIB metal is selected from at least one of chromium, molybdenum and tungsten, and more preferably molybdenum and / or tungsten.

[0047] In this invention, there is no particular limitation on the type of molecular sieve, and those skilled in the art can select it according to actual needs. Preferably, the molecular sieve is a β-zeolite molecular sieve and / or a ZSM-5 zeolite molecular sieve, and more preferably a β-zeolite molecular sieve and a ZSM-5 zeolite molecular sieve.

[0048] In this invention, preferably, based on a total molecular sieve content of 100 parts by weight, the content of β-zeolite molecular sieve is 30-100 parts by weight, and the content of ZSM-5 zeolite molecular sieve is 0-70 parts by weight; more preferably, based on a total molecular sieve content of 100 parts by weight, the content of β-zeolite molecular sieve is 40-80 parts by weight, and the content of ZSM-5 zeolite molecular sieve is 20-60 parts by weight. By controlling the type and content of molecular sieves, it is more beneficial to select the conversion reaction to proceed, producing more high-quality light aromatics.

[0049] In this invention, there is no particular limitation on the type of adhesive. Preferably, the adhesive is alumina and / or silicon oxide, and more preferably alumina.

[0050] In this invention, preferably, the Group VIII metal is selected from at least one of iron, cobalt, and nickel, and more preferably cobalt and / or nickel.

[0051] In this invention, preferably, based on 100 parts by weight of the selective conversion catalyst, the oxide and / or sulfide of the Group VIB metal is 0.5-15 parts by weight, the molecular sieve is 10-75 parts by weight, the binder is 10-75 parts by weight, and the elemental form of the Group VIII metal is 0.5-10 parts by weight; more preferably, based on 100 parts by weight of the selective conversion catalyst, the oxide of the Group VIB metal is 0.5-14 parts by weight, the sulfide of the Group VIB metal is 0-1 parts by weight, the molecular sieve is 35-60 parts by weight, the binder is 35-60 parts by weight, and the elemental form of the Group VIII metal is 0.5-5 parts by weight.

[0052] In this invention, the content of each metal in the conversion catalyst is determined by ICP (inductively coupled plasma) and XRF (X-ray fluorescence) methods, and the content of binder and molecular sieve is calculated by the amount of feed.

[0053] In this invention, the composition ratio of group VIB metal oxides and metal sulfides is determined using XPS (X-ray photoelectron spectroscopy).

[0054] In this invention, the preparation method of the selective conversion catalyst is not particularly limited. For example, it can be prepared by the following method: S1, mixing molecular sieves and binders, followed by a first drying and a first calcination to obtain a catalyst support; S2, impregnating the catalyst support of step S1 with a solution containing Group VIII metal precursors and Group VIB metal precursors, followed by a second drying and a second calcination to obtain a catalyst precursor; S3, subjecting the catalyst precursor obtained in step S2 to reduction treatment and optionally sulfidation treatment to obtain the selective conversion catalyst. It should be noted that in this invention, reduction treatment refers to reducing the catalyst precursor under a certain hydrogen partial pressure and temperature. In this invention, sulfidation treatment refers to sulfiding the reduced catalyst in a sulfidation reactor.

[0055] In this invention, the types and amounts of molecular sieves, binders, Group VIII metals, and Group VIB metals have been described above and will not be repeated here.

[0056] In this invention, there are no particular limitations on the conditions for the first drying in step S1. Preferably, the conditions for the first drying in step S1 include: a temperature of 80-120°C and a time of 12-24 hours.

[0057] In this invention, there are no particular limitations on the conditions for the first roasting in step S1. Preferably, the conditions for the first roasting in step S1 include: a temperature of 500-600℃ and a time of 2-6 hours.

[0058] In this invention, there is no specific limitation on the molding method. For example, the existing standard molding method can be used. Specifically, the molecular sieve and the binder can be mixed and the material can be added to an extruder with a mold installed to extrude the material in the form of a strip.

[0059] In this invention, there is no particular limitation on the type of Group VIII metal precursor. Preferably, the Group VIII metal precursor is selected from at least one of ferric nitrate, ferric chloride, nickel nitrate, basic nickel carbonate, nickel acetate, cobalt nitrate, and basic cobalt carbonate.

[0060] In this invention, there is no specific limitation on the type of Group VIB metal precursor. Preferably, the Group VIB metal precursor is selected from at least one of ammonium molybdate, ammonium phosphomolybdate, ammonium tungstate, ammonium metatungstate, and ethyl metatungstate.

[0061] In this invention, various metal components can be introduced using conventional impregnation methods in the art, such as at least one of equal-volume impregnation, co-impregnation, and stepwise impregnation. In a preferred embodiment, the present invention employs equal-volume impregnation to prepare a selective conversion catalyst. In a specific embodiment, the equal-volume impregnation method includes impregnating the catalyst support with a solution containing a Group VIII metal precursor and a Group VIB metal precursor.

[0062] In this invention, there are no particular limitations on the conditions for the second drying in step S2. Preferably, in step S1, the conditions for the second drying include: a temperature of 80-120°C and a time of 12-24 hours.

[0063] In this invention, there are no particular limitations on the conditions for the second calcination in step S2. Preferably, in step S1, the conditions for the second calcination include: a temperature of 500-600℃ and a time of 2-6 hours.

[0064] In this invention, the conditions for the reduction treatment in step S3 are not particularly limited. Preferably, the conditions for the reduction treatment in step S3 include: a temperature of 350-480℃ and a time of 2-6 hours. It should be noted that in this invention, the reduction treatment involves reducing the catalyst precursor under certain hydrogen partial pressure (1-10 MPa) and temperature (350-480℃) conditions for 2-6 hours.

[0065] In this invention, the method of sulfidation is not particularly limited; for example, it can be wet sulfidation or dry sulfidation, with wet sulfidation being preferred. Preferably, the sulfidation is carried out in the presence of a sulfiding agent. In this invention, the type of sulfiding agent is not particularly limited; for example, it can be a cyclohexane solution containing dimethyl disulfide. In one specific embodiment, the sulfidation treatment may include: selecting a conversion catalyst and carrying out sulfidation treatment in a cyclohexane solution containing dimethyl disulfide, with reaction conditions of: temperature 300-360℃, time 2-8h, and feed weight hourly space velocity 1-10h. -1 The hydrogen-to-oil volume ratio is 100-2000. The concentration of the sulfiding agent (preferably a cyclohexane solution containing dimethyl disulfide) is not particularly limited in this invention; those skilled in the art can select it according to actual needs.

[0066] In this invention, preferably, in step (2), n is 2-10, and more preferably 2-6. The advantage of this preferred embodiment is that an appropriate number of fractions can yield high yields of light aromatics and reduce hydrogen consumption. Too many fractions will increase investment costs and make the equipment more complex.

[0067] In this invention, preferably, based on the total loading amount of the n-stage graded selective conversion catalyst, the loading amount of each stage of selective conversion catalyst accounts for 10-70% by mass of the total loading amount. It should be noted that "the loading amount of each stage of selective conversion catalyst accounts for the total loading amount" refers to the proportion of the loading amount of selective conversion catalyst in a single catalyst bed to the total loading amount of the n-stage graded selective conversion catalyst. Furthermore, it should be noted that this invention does not impose any particular limitation on the loading ratio of selective conversion catalyst in adjacent catalyst beds, as long as the total loading amount requirement is met.

[0068] In this invention, preferably, two methods are used: increasing the zeolite molecular sieve content in the catalyst or adding a more acidic molecular sieve type to improve the catalyst's acidity, effectively preventing excessive cracking of the raw materials and reducing hydrogen consumption in the reaction. According to a preferred embodiment of the invention, the total amount of molecular sieves in each stage of the selective conversion catalyst gradually increases from top to bottom along the material flow direction. According to another preferred embodiment of the invention, the ZSM-5 zeolite molecular sieve content in each stage of the selective conversion catalyst gradually increases from top to bottom along the material flow direction.

[0069] In this invention, preferably, the increase in the total amount of molecular sieves in each stage of the selective conversion catalyst along the material flow direction from top to bottom is 10-50%, and more preferably 10-25%.

[0070] In this invention, preferably, compared to the selective conversion catalyst in the adjacent upstream bed, the content of ZSM-5 zeolite molecular sieve in the downstream bed is increased to 5-25%, more preferably to 8-20%, wherein the content of ZSM-5 zeolite molecular sieve in the downstream bed is based on 100 parts by weight of the selective conversion catalyst loaded in the upstream bed. The advantages of this preferred embodiment are that it effectively prevents excessive cracking of the feedstock, suppresses the formation of by-product methane, reduces hydrogen consumption, and increases the yield of light aromatics.

[0071] In this invention, hydrogenation activity is controlled by reducing the total amount of active metals or the content of active metal phases in the catalyst, thus avoiding over-hydrogenation. According to a preferred embodiment of the invention, the total amount of Group VIB metal oxides and / or Group VIB metal sulfides and Group VIII metal elements in each stage of the selective conversion catalyst gradually decreases from top to bottom along the stream flow direction. According to another preferred embodiment of the invention, the content of Group VIII metal elements and / or Group VIB metal oxides in each stage of the selective conversion catalyst gradually decreases from top to bottom along the stream flow direction.

[0072] In this invention, preferably, the reduction in the total amount of Group VIB metal oxides and / or Group VIB metal sulfides and Group VIII metal elements in each stage of the selective conversion catalyst is 5-30%, more preferably 8-20%.

[0073] In this invention, preferably, the content of Group VIII metal elements in each stage of the conversion catalyst decreases by 1-10% from top to bottom along the material flow direction, and more preferably by 5-10%.

[0074] In this invention, preferably, the content of group VIB metal oxides in each stage of the selective conversion catalyst decreases by 1-20% from top to bottom along the material flow direction, and more preferably by 3-16%.

[0075] The advantages of the above-described preferred embodiments are that they effectively reduce the excessive hydrogenation saturation of aromatics, reduce hydrogen consumption, and increase the yield of light aromatics.

[0076] In this invention, there are no particular limitations on the conditions for selecting the conversion reaction. Preferably, in step (2), the conditions for selecting the conversion reaction include: a reaction temperature of 300-500℃, a reaction pressure of 2-10 MPa, and a weight hourly space velocity of 0.5-2 h⁻¹. -1 The hydrogen-to-oil volume ratio is 500-4000; more preferably, in step (2), the conditions for selecting the conversion reaction include: a reaction temperature of 350-420℃, a reaction pressure of 6-9 MPa, and a weight hourly space velocity of 0.5-2 h⁻¹. -1 The hydrogen-to-oil volume ratio is 1000-4000.

[0077] In this invention, preferably, in step (2), the liquid-phase hydrogenation product and C 10 The mass ratio of heavy aromatics is 4-9:1, more preferably 6-9:1.

[0078] In this invention, preferably, the method further includes separating the selected conversion reaction product obtained in step (2) to obtain light aromatics and C 11 Heavy aromatics.

[0079] In this invention, the separation method in step (2) is not particularly limited. Preferably, the separation includes gas-liquid separation, liquid-liquid separation, and distillation. The gas-liquid separation yields a liquid phase heavy component (C6 and above aromatics), dry gas, and C3-C5 light hydrocarbons. The distillation includes depentane, deheptane, dexylene, and deheavy aromatics. The liquid-liquid separation includes extraction and separation of the C6-C7 fraction stream. Preferably, the separation is carried out in a second separation system. In this invention, the conditions for the separation in step (2) are not particularly limited, as long as the separation of the aforementioned components can be achieved. Those skilled in the art can adjust the conditions according to actual needs.

[0080] In this invention, preferably, the method further includes taking the C from step (2) 11 +Heavy tail oil is recycled to step (1). In this invention, when the reaction proceeds continuously, C is recycled to step (1). 11 + The heavy tail oil is recycled to step (1) for hydrogenation reaction to achieve continuous operation of the method.

[0081] The compositional analysis of the catalysts involved in this invention employs existing analytical methods in the art. The content of each metal in the selected conversion catalyst was analyzed using ICP (Inductively Coupled Plasma) and XRF (X-ray Fluorescence) methods, while the contents of binders and molecular sieves were calculated based on the feed amounts. The compositional ratio of Group VIB metal oxides and metal sulfides was determined using XPS (X-ray Photoelectron Spectroscopy). ICP testing conditions: Varian 700-ES series XPS instrument. XRF testing conditions: Rigaku ZSX 100e XRF instrument. XPS testing conditions: Perkin Elmer PHI 5000CESCA X-ray photoelectron spectrometer, using a MgK excitation source, operating voltage 10kV, current 40mA, vacuum degree 4.0×10⁻⁶. -8 Pa.

[0082] This invention uses an Agilent Technologies 7890A GC and a Snowscape Technology (Shanghai) Co., Ltd. SSM solid-state thermal modulator full two-dimensional gas chromatograph (GC×GC-FID) to analyze (multidimensional chromatographic analysis) the composition of catalytic diesel and liquid-phase hydrogenation products.

[0083] In this invention, the composition of the reaction stream was determined by gas chromatography. The chromatograph used was an Agilent 7890A, equipped with an FID detector. Separation was performed using an FFAP capillary column. The column was programmed with an initial temperature of 90°C, held for 15 minutes, and then increased to 220°C at a rate of 15°C / min, held for 45 minutes.

[0084] In this invention, the formulas for calculating the aromatic hydrocarbon retention rate, the yield of heavy aromatic hydrocarbons, and the hydrogen consumption in the hydrogenation reaction are as follows:

[0085]

[0086]

[0087]

[0088] The present invention will be described in detail below through embodiments. Unless otherwise specified, all raw materials used in the following embodiments are commercially available products.

[0089] The following embodiments all employ the following methods: Figure 1 The process flow shown involves mixing catalytic diesel 1 and hydrogen 2, which then enters the hydrogenation reactor 3. A hydrogenation reaction is carried out in the presence of a hydrogenation catalyst to obtain hydrogenation product 4. Hydrogenation product 4 undergoes gas-liquid separation and desulfurization treatment in the first separation system 5, yielding a stream of hydrogen sulfide and ammonia 6 and a liquid-phase hydrogenation product 7. The liquid-phase hydrogenation product 7, hydrogen 2, and C... 10 Heavy aromatics 9 enter the selective conversion reactor 8 and undergo selective conversion in the presence of a selective conversion catalyst to obtain selective conversion product 10. Selective conversion product 10 is then separated by a second separation system 11 to obtain dry gas and C3-C5 light hydrocarbons 12, benzene and toluene 13, xylene 14, C9A aromatics 15, and C... 10 Aromatic hydrocarbon 16 and C 11 +Heavy tail oil, during continuous reaction, C 11 Heavy tail oil is returned to hydrotreating reactor 3 for reuse.

[0090] Example of hydrogenation catalyst preparation

[0091] Preparation of hydrogenation catalyst HT-1

[0092] Using boehmite as raw material, guar gum powder and a binder were added, and the mixture was mechanically mixed, kneaded, and extruded to obtain a carrier. The carrier was then impregnated with a metal precursor solution containing the active components molybdenum, nickel, and tungsten. After aging at room temperature for 12 hours, drying at 120°C for 24 hours, and then calcining in a muffle furnace at 550°C for 3 hours, the oxidized catalyst was obtained.

[0093] The obtained oxidized catalyst was pre-sulfurized under the following conditions: wet sulfidation in a cyclohexane solution containing 2000 ppm dimethyl disulfide at a pressure of 3.0 MPa and a feed weight hourly space velocity of 2.8 h⁻¹. -1 The hydrogen-to-oil volume ratio is 500. Sulfation begins at 170℃, with the following temperature program: 230℃ for 4 hours, 280℃ for 6 hours, 320℃ for 10 hours, and 350℃ for 10 hours. The required hydrogenation catalyst HT has the following composition: 3.1wt% NiS, 10.2wt% MoS2, 13.2wt% WS2, and 73.5wt% Al2O3.

[0094] Example of Selected Conversion Catalyst Preparation

[0095] Preparation Example 1

[0096] Preparation of the selected conversion catalyst SC-1: 50% wt β-zeolite (SiO2 / Al2O3 molar ratio = 50) and 50% wt alumina were mixed, extruded, dried at 120℃ for 24 h, and calcined at 550℃ for 3 h to obtain catalyst support Z-1. Nickel nitrate and ammonium tungstate were then prepared into a clear solution, and the support was impregnated with an equal volume of the solution, followed by drying at 100℃ and calcination in air at 500℃ for 2 h to obtain the catalyst precursor, which was then subjected to reduction and sulfidation. The reduction conditions were: 450℃, 7.0 MPa, hydrogen atmosphere for 2 h, followed by cooling to 350℃ and then injection of a cyclohexane solution containing 2000 ppm dimethyl disulfide at a feed weight hourly space velocity (WHSV) of 2.8 h⁻¹. -1 With a hydrogen-to-oil volume ratio of 500, sulfidation was carried out for 4 hours to obtain the desired selective conversion catalyst SC-1.

[0097] Preparation Example 2

[0098] Preparation of selective conversion catalyst SC-2: 60 wt% β-zeolite (SiO2 / Al2O3 molar ratio = 50) and 40 wt% alumina were mixed, extruded, dried at 120℃ for 24 h, and calcined at 550℃ for 3 h to obtain catalyst support Z-2. Nickel nitrate and ammonium tungstate were then prepared into a clear solution, impregnated with an equal volume of the support, dried at 100℃, and calcined in air at 500℃ for 2 h to obtain the catalyst precursor. The catalyst precursor was then subjected to external reduction at 450℃, 7.0 MPa, and a hydrogen atmosphere for 2 h to obtain the desired selective conversion catalyst SC-2.

[0099] Preparation Example 3

[0100] Preparation of selective conversion catalyst SC-3: 35 wt% β-zeolite (SiO2 / Al2O3 molar ratio = 50), 15 wt% ZSM-5 zeolite (SiO2 / Al2O3 molar ratio = 50), and 50 wt% alumina were mixed, extruded, dried at 120℃ for 24 h, and calcined at 550℃ for 3 h to obtain catalyst support Z-3. Nickel nitrate and ammonium tungstate were then prepared into a clear solution, impregnated with an equal volume, dried at 100℃, and calcined in air at 500℃ for 2 h to obtain the catalyst precursor. The catalyst precursor was then subjected to external reduction at 450℃, 7.0 MPa, and a hydrogen atmosphere for 2 h to obtain the desired selective conversion catalyst SC-3.

[0101] Preparation Example 4

[0102] Preparation of selective conversion catalyst SC-4: 25 wt% β-zeolite (SiO2 / Al2O3 molar ratio = 50), 25 wt% ZSM-5 zeolite (SiO2 / Al2O3 molar ratio = 50), and 50 wt% alumina were mixed, extruded, dried at 120℃ for 24 h, and calcined at 550℃ for 3 h to obtain catalyst support Z-4. Nickel nitrate and ammonium tungstate were then prepared into a clear solution, impregnated with an equal volume, dried at 100℃, and calcined in air at 500℃ for 2 h to obtain the catalyst precursor. The catalyst precursor was then subjected to external reduction at 450℃, 7.0 MPa, and a hydrogen atmosphere for 2 h to obtain the desired selective conversion catalyst SC-4.

[0103] The composition of the conversion catalysts selected in the above preparation examples 1-4 is shown in Table 1.

[0104] Example 1

[0105] use Figure 1 In this process, catalytic diesel feedstock B is mixed with hydrogen and fed into a hydrorefining reactor where it comes into full contact with the hydrotreating catalyst (HT-1). The reaction temperature is 320°C and the weight hourly space velocity (WHSV) is 0.8 h⁻¹. -1 The reaction pressure was 6.5 MPa, and the hydrogen-to-oil volume ratio was 2000. After passing through the first separation system, water cooling, and high-precision separation tank, the liquid-phase hydrogenation product was obtained.

[0106] Control of liquid-phase hydrogenation products, C 10 Heavy aromatics at a mass ratio of 9:1 are mixed with hydrogen and fed into a selective conversion reactor to undergo selective conversion reaction in contact with the selective conversion catalyst. The selective conversion catalyst is graded, with two catalyst beds. The first bed is loaded with selective conversion catalyst SC-1, and the second bed is loaded with selective conversion catalyst SC-2, with a mass ratio of SC-1 to SC-2 of 1:1. The reaction conditions are: reaction temperature 380℃, reaction pressure 7.0 MPa, hydrogen-to-oil volume ratio 1800, and weight hourly space velocity 1.0 h⁻¹. -1After passing through the second separation system, benzene, toluene, xylene, C9A, and C were obtained. 10 A.

[0107] Example 2

[0108] The method is the same as in Example 1, except that there are two catalyst beds. The first bed is filled with conversion catalyst SC-2 and the second bed is filled with conversion catalyst SC-3. The mass ratio of SC-2 to SC-3 is 2:1.

[0109] Example 3

[0110] The method is the same as in Example 1, except that there are three catalyst beds: the first bed is filled with conversion catalyst SC-2, the second bed is filled with conversion catalyst SC-3, and the third bed is filled with conversion catalyst SC-4. The mass ratio of SC-2, SC-3 and SC-4 is 2:1:1.

[0111] Example 4

[0112] The method is the same as in Example 1, except that the reaction temperature for the conversion reaction is chosen to be 370°C.

[0113] Example 5

[0114] The method is the same as in Example 1, except that catalytic diesel A is selected as the feedstock.

[0115] Example 6

[0116] The method is the same as in Example 5, except that the liquid-phase hydrogenation product and C are controlled. 10 The mass ratio of heavy aromatics is 5:1.

[0117] Example 7

[0118] The method is the same as in Example 5, except that the same selective conversion catalyst SC-2 is used in each catalyst bed in the selective conversion reaction.

[0119] Example 8

[0120] The method is the same as in Example 1, except that the same selective conversion catalyst SC-1 is used in each catalyst bed in the selective conversion reaction.

[0121] Comparative Example 1

[0122] Catalytic diesel feedstocks B and C 10 Heavy aromatics are mixed with hydrogen and introduced into a hydrorefining reactor, where they come into full contact with the hydrorefining catalyst (HT-1). The reaction temperature is 320°C and the weight hourly space velocity (WHSV) is 0.8 h⁻¹. -1The reaction pressure was 6.5 MPa, and the hydrogen-to-oil volume ratio was 2000. After passing through the first separation system, water cooling, and high-precision separation tank, the liquid-phase hydrogenation product was obtained.

[0123] The liquid-phase hydrogenation product is mixed with hydrogen gas and fed into a selective conversion reactor to undergo selective conversion reaction in contact with a selective conversion catalyst. The selective conversion catalyst is graded, with two catalyst beds. The first bed is loaded with selective conversion catalyst SC-1, and the second bed is loaded with selective conversion catalyst SC-2, with a mass ratio of SC-1 to SC-2 of 1:1. The reaction conditions are: reaction temperature 380℃, reaction pressure 7.0 MPa, hydrogen-to-oil volume ratio 1800, and weight hourly space velocity 1.0 h⁻¹. -1 After passing through the second separation system, benzene, toluene, xylene, C9A, and C were obtained. 10 A.

[0124] Comparative Example 2

[0125] Following the method of Comparative Example 1, the difference is that catalytic diesel A is chosen to replace catalytic diesel B.

[0126] The catalytic diesel and C used in the above embodiments and comparative examples 10 The properties of heavy aromatic hydrocarbons are shown in Table 2, the liquid-phase hydrogenation products are shown in Table 3, and the reaction results are shown in Table 4.

[0127] Table 1

[0128]

[0129] Note: The content of each component in the conversion catalyst is selected based on 100 parts by weight of the total catalyst.

[0130] Table 2

[0131] Sulfur / ppm 1250 2563 <5.0 Nitrogen / ppm 460 282 <5.0 Non-aromatic hydrocarbons / wt% 17.3 15.51 0 Monocyclic aromatic hydrocarbons / wt% 21.7 17.25 31.37 Bicyclic aromatic hydrocarbons / wt% 56.3 53.38 64.89 Tricyclic aromatic hydrocarbons and above / wt% 4.7 13.86 3.74 <![CDATA[T 95 Distillation range 325 355 /

[0132] Table 3

[0133] Sulfur / ppm 95 126 Nitrogen / ppm 9.5 8.2 Non-aromatic hydrocarbons / wt% 25 22.95 Monocyclic aromatic hydrocarbons / wt% 63.7 68.20 Bicyclic aromatic hydrocarbons / wt% 9.9 8.69 Tricyclic aromatic hydrocarbons and above / wt% 1.1 0.16

[0134] Table 4

[0135]

[0136] As can be seen from the table above, by using the method of the present invention, catalytic diesel and C 10+ Combining heavy aromatics with light aromatics can reduce hydrogen consumption in the reaction while improving the purity and yield of light aromatics.

[0137] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for producing light aromatics, characterized in that, The method includes the following steps: (1) In the presence of hydrogen, catalytic diesel is hydrogenated to obtain liquid-phase hydrogenation products; (2) In the presence of hydrogen and a selective conversion catalyst, the liquid-phase hydrogenation product is reacted with C 10 + Selective conversion of heavy aromatics yields light aromatics and C 11 +Heavy tail oil, wherein the selective conversion catalyst is present in an n-stage graded packing form, where n is 2-10; In step (2), the selective conversion catalyst includes oxides and / or sulfides of Group VIB metals, molecular sieves, binders, and elemental Group VIII metals; the Group VIII metals are selected from at least one of iron, cobalt, and nickel. Wherein, the molecular sieve is a β zeolite molecular sieve and / or a ZSM-5 zeolite molecular sieve; Among them, along the logistics direction from top to bottom, the total amount of molecular sieves in the conversion catalysts at each stage gradually increases; Alternatively, along the logistics direction from top to bottom, the content of ZSM-5 zeolite molecular sieve in each stage of the selective conversion catalyst gradually increases.

2. The method according to claim 1, wherein, In step (1), the T of the catalytic diesel oil 95 The distillation range is 320-360℃, the sulfur content is 1000-4000ppm, and the nitrogen content is 200-1000ppm.

3. The method according to claim 1, wherein, In step (1), the hydrogenation reaction is carried out in the presence of a hydrogenation catalyst, which includes a hydrogenation support and a hydrogenation component.

4. The method according to claim 3, wherein, The carrier is selected from at least one of alumina, silicon dioxide, and titanium dioxide; And / or, the hydrogenated component includes sulfides of Group VIII metals and / or sulfides of Group VIB metals.

5. The method according to claim 4, wherein, The hydrogenated components are sulfides of W, sulfides of Mo, sulfides of Ni, and sulfides of Co.

6. The method according to claim 5, wherein, In the hydrogenation catalyst, based on the total amount of hydrogenation catalyst, the sulfide content of W is 5-20 wt%, the sulfide content of Mo is 5-20 wt%, the sulfide content of Ni is 1-15 wt%, and the sulfide content of Co is 1-15 wt%.

7. The method according to claim 1, wherein, The conditions for the hydrogenation reaction include: a reaction temperature of 250-400℃, a reaction pressure of 2-10 MPa, and a weight hourly space velocity of 0.5-2 h⁻¹. -1 The hydrogen-to-oil volume ratio is 500-2000.

8. The method according to claim 1, wherein, In step (2), the C 10 Heavy aromatics originate from at least one of the following: catalytic reforming unit, ethylene cracking unit, and coal coking byproducts.

9. The method according to claim 8, wherein, In step (2), the C 10 Heavy aromatics originate from catalytic reforming units.

10. The method according to claim 1, wherein, In step (2), the C 10 +In heavy aromatics, the sulfur content is <10ppm and the nitrogen content is <10ppm.

11. The method according to claim 1, wherein, In step (2), the selected conversion catalyst includes oxides of Group VIB metals, molecular sieves, binders, and elemental elements of Group VIII metals.

12. The method according to claim 1 or 11, wherein, The group VIB metal is selected from at least one of chromium, molybdenum, and tungsten.

13. The method according to claim 12, wherein, The Group VIB metal is molybdenum and / or tungsten.

14. The method according to claim 1, wherein, The molecular sieves are β-zeolite molecular sieves and ZSM-5 zeolite molecular sieves.

15. The method according to claim 14, wherein, Based on a total molecular sieve content of 100 parts by weight, the content of the β-zeolite molecular sieve is 30-100 parts by weight, and the content of the ZSM-5 zeolite molecular sieve is 0-70 parts by weight.

16. The method according to claim 15, wherein, Based on a total molecular sieve content of 100 parts by weight, the content of β-zeolite molecular sieve is 40-80 parts by weight, and the content of ZSM-5 zeolite molecular sieve is 20-60 parts by weight.

17. The method according to claim 1 or 11, wherein, The binder is aluminum oxide and / or silicon oxide.

18. The method according to claim 17, wherein, The adhesive is aluminum oxide.

19. The method according to claim 1, wherein, The Group VIII metal is cobalt and / or nickel.

20. The method according to claim 1 or 11, wherein, Based on 100 parts by weight of the selected conversion catalyst, the oxides and / or sulfides of Group VIB metals are 0.5-15 parts by weight, the molecular sieve is 10-75 parts by weight, the binder is 10-75 parts by weight, and the elemental group VIII metal is 0.5-10 parts by weight.

21. The method according to claim 20, wherein, Based on 100 parts by weight of the selected conversion catalyst, the oxides of Group VIB metals are 0.5-14 parts by weight, the sulfides of Group VIB metals are 0-1 parts by weight, the molecular sieve is 35-60 parts by weight, the binder is 35-60 parts by weight, and the elemental form of Group VIII metal is 0.5-5 parts by weight.

22. The method according to claim 1, wherein, In step (2), n is 2-6.

23. The method according to claim 1 or 22, wherein, Based on the total loading amount of selective conversion catalyst in n-stage gradation, the loading amount of each stage of selective conversion catalyst accounts for 10-70% of the total loading amount.

24. The method according to claim 1, wherein, Along the logistics direction from top to bottom, the total amount of molecular sieves in the selected conversion catalysts at each level increases by 10-50%.

25. The method according to claim 24, wherein, Along the logistics direction from top to bottom, the increase in the total amount of molecular sieves in the conversion catalysts at each level is 10-25%.

26. The method of claim 25, wherein, Compared to the selective conversion catalyst in the adjacent upstream bed, the content of ZSM-5 zeolite molecular sieve in the downstream bed increases to 5-25%, wherein the content of ZSM-5 zeolite molecular sieve in the downstream bed is based on 100 parts by weight of selective conversion catalyst loaded in the upstream bed.

27. The method according to claim 26, wherein, Compared to the selective conversion catalyst in the adjacent upstream bed, the content of ZSM-5 zeolite molecular sieve in the downstream bed increases to 8-20%.

28. The method according to claim 1, wherein, Along the logistics direction from top to bottom, the total amount of group VIB metal oxides and / or group VIB metal sulfides and group VIII metal elements in each stage of selective conversion catalyst gradually decreases. Alternatively, along the logistics direction from top to bottom, the content of Group VIII metal elements and / or the content of Group VIB metal oxides in each stage of the selective conversion catalyst gradually decreases.

29. The method according to claim 28, wherein, The reduction in the total amount of Group VIB metal oxides and / or Group VIB metal sulfides and Group VIII metal elements in each stage of selective conversion catalysts ranges from 5% to 30%.

30. The method according to claim 29, wherein, The reduction in the total amount of Group VIB metal oxides and / or Group VIB metal sulfides and Group VIII metal elements in each stage of selective conversion catalysts ranges from 8% to 20%.

31. The method according to claim 30, wherein, Along the logistics direction from top to bottom, the content of Group VIII metal elements in each stage of the selective conversion catalyst decreases by 1-10%; And / or, along the logistics direction from top to bottom, the content of Group VIB metal oxides in each stage of the selected conversion catalyst is reduced by 1-20%.

32. The method according to claim 31, wherein, Along the logistics direction from top to bottom, the content of Group VIII metal elements in each stage of the selective conversion catalyst decreases by 5-10%; And / or, along the logistics direction from top to bottom, the content of Group VIB metal oxides in each stage of the selective conversion catalyst decreases by 3-16%.

33. The method according to claim 1, wherein, In step (2), the conditions for selecting the conversion reaction include: a reaction temperature of 300-500℃, a reaction pressure of 2-10MPa, and a weight hourly space velocity of 0.5-2h. -1 The hydrogen-to-oil volume ratio is 500-4000.

34. The method according to claim 33, wherein, In step (2), the conditions for selecting the conversion reaction include: a reaction temperature of 380-420℃, a reaction pressure of 6-9 MPa, and a weight hourly space velocity of 0.5-1.5 h⁻¹. -1 The hydrogen-to-oil volume ratio is 1000-4000.

35. The method according to claim 1, wherein, In step (2), the liquid-phase hydrogenation product and C 10 The mass ratio of heavy aromatics is 4-9:

1.

36. The method according to claim 35, wherein, In step (2), the liquid-phase hydrogenation product and C 10 The mass ratio of heavy aromatics is 6-9:

1.

37. The method according to claim 1, wherein, The method further includes separating the selected conversion reaction product obtained in step (2) to obtain light aromatics and C. 11 +Heavy tail oil.

38. The method according to claim 37, wherein, The method also includes the C described in step (2) 11 +Recycle heavy tail oil to step (1).

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