Method for producing more light aromatics

Abstract

The method for producing more light aromatic hydrocarbons comprises 1) contacting a raw material containing C9+ paraffins with a first catalyst in the presence of hydrogen in a first reaction zone to react, so that at least part of the C9 + Alkanes undergo dehydrogenation and cyclization to give C9 + Aromatics, including C9 + 2) separating the first stream obtained in step 1) to obtain C9 + Distillate stream and C6-C8 non-aromatic stream; the C9 + The fraction stream contains C9 + Aromatic hydrocarbons, the C6-C8 non-aromatic stream contains C6-C8 alkanes and cycloalkanes; 3) the C9 + The fraction stream and the C6-C8 non-aromatic stream are contacted with a second catalyst in the presence of hydrogen in a second reaction zone to make at least part of the C9 + Aromatic hydrocarbons undergo dealkylation to obtain light aromatic hydrocarbons, thereby obtaining a second stream, wherein the second catalyst comprises KL zeolite and platinum and a modified metal supported thereon, wherein the modified metal is selected from the group consisting of Group IA metals, Group IIA metals and rare earth metals. + Paraffin raw materials mostly produce light aromatics.

Description

Technical Field

[0001] The present application relates to the technical field of catalytic conversion of aromatic hydrocarbons, and specifically to a method for converting C9 + A method for producing more light aromatic hydrocarbons from paraffinic raw materials. Background Art

[0002] Naphtha usually contains C6-C12 alkanes, cycloalkanes and aromatic components. Its mainstream processing scheme is to convert alkane and cycloalkanes molecules into aromatics or high-octane gasoline blending components through catalytic reforming and other technologies, while producing high value-added hydrogen. In addition to light aromatics such as BTX, the liquid product of the reforming reaction also contains unconverted light alkanes below C7 and heavy aromatics above C9.

[0003] The main reactions occurring during the catalytic reforming reaction process include six major types of reactions: dehydrogenation of hexacyclic alkanes, dehydrogenation isomerization of pentacyclic alkanes, isomerization of alkanes, cycloalkanes and aromatics, dehydrogenation cyclization of alkanes, hydrogenolysis and hydrocracking of alkanes. Traditional catalytic reforming reaction chemistry follows the principle of "converting naphtha components with the same carbon number into products with the same carbon number", and the product distribution follows the laws of chemical thermodynamics and kinetics. Therefore, after the reforming catalyst and process technology are determined, the aromatics yield and product distribution depend on the composition of the feedstock, and the ratio of benzene, toluene and xylene isomers and the ratio of heavy aromatics in the product remain basically unchanged. Under the existing catalyst system, the space for regulating the distribution of each product by changing the reaction conditions is very limited.

[0004] Since the above-mentioned main reforming reactions follow the principle that the carbon number of reactants and products is the same (except for alkane hydrogenolysis and hydrocracking reactions), the content of heavy aromatics above C9 in the reforming oil is relatively high, usually up to 20% by mass or more. Limited by the terminal distillation point of finished gasoline, heavy aromatics cannot all be used as gasoline blending components. Although some heavy aromatics can be sold as products after distillation separation, the market capacity is limited. The dehydrogenation cyclization reaction rate of C6 and C7 light alkanes is slow, and a method of increasing the severity of the reforming operation is usually adopted to increase its conversion rate. However, increasing the severity has the problem of poor reaction selectivity, aggravated reactions such as hydrocracking, resulting in a decrease in liquid yield, and the consumption of hydrogen.

[0005] CN101570698B discloses a catalytic conversion method for naphtha with a boiling range of 40 to 260°C, comprising: (1) hydrotreating the naphtha in the presence of a hydrotreating catalyst, and then fractionating and cutting the hydrotreating naphtha into a light fraction, an intermediate fraction and a heavy fraction; (2) discharging the light fraction from a device or contacting it with a light hydrocarbon isomerization catalyst to carry out a light hydrocarbon isomerization reaction; (3) separating the intermediate fraction into one or more fractions for a staged reforming reaction; and (4) contacting the heavy fraction with a lightening catalyst to carry out a lightening reaction.

[0006] CN110358577A discloses a method for converting naphtha into high-octane gasoline and aromatics, wherein C5-C6 normal alkanes in naphtha are separated and isomerized, and the obtained isomerized products are aromatized under the action of a Pt / KL zeolite catalyst to convert the normal alkanes and monomethylalkanes in the isomerization equilibrium product into aromatics.

[0007] CN104711016A discloses a method for producing high-octane gasoline and aromatics from naphtha containing paraffins and cycloalkanes, the method comprising the following steps: a) sending a naphtha fraction to a first catalytic reforming unit, wherein the naphtha fraction is contacted with a reforming catalyst to convert at least a portion of the paraffins and / or cycloalkanes into aromatic compounds and produce hydrogen; b) taking out a first effluent and a hydrogen stream from the first catalytic reforming unit; c) sending the first effluent to an aromatic separation unit to separate a first aromatic fraction and a raffinate containing unconverted cycloalkanes and / or paraffins; d) sending the raffinate to a second catalytic reforming unit, wherein the raffinate is contacted with a reforming catalyst to convert unconverted cycloalkanes and / or paraffins into aromatic compounds and produce hydrogen; e) taking out a hydrogen stream and a reformate rich in aromatic compounds from the second catalytic reforming unit. The catalytic reforming catalyst used in steps a) and d) preferably comprises an alumina carrier and platinum.

[0008] WO2019105766A1 discloses a method for producing C6-C7 aromatics from naphtha, wherein the raw material naphtha is sent to a first fractionation unit to obtain an upper stream mainly containing C6 and C7 hydrocarbon compounds and a lower stream mainly containing C8-C10 hydrocarbon compounds; the upper stream and the stream mainly containing C6-C7 aromatic compounds obtained in the reforming separation section are sent to a unit for extracting aromatic compounds to obtain aromatics and a liquid effluent rich in alkanes; the liquid effluent rich in alkanes is sent to a first catalytic reforming unit to obtain a first reforming product effluent; the first reforming product effluent is sent to a reforming product separation section to obtain a first stream mainly containing C5 hydrocarbon compounds and a second stream mainly containing C6 and C7 aromatic compounds; the second stream mainly containing C6 and C7 aromatic compounds is at least partially recycled to the unit for extracting aromatic compounds. The catalyst used in the first reforming unit contains binder silica, active component platinum and L zeolite.

[0009] The catalysts for the lightweighting of heavy aromatics reported so far are mainly one or more of the molecular sieves such as ZSM-5, HZSM-5, HY, USY, NaY, β-zeolite, MCM-41, ZSM-12, MOR, NU-87, MFI, etc. The above molecular sieves can be used directly or modified, using alumina or other oxides as carriers. Some catalysts are added with platinum, palladium, iridium or their compounds. The reaction raw materials are C9+ or C 10 + Heavy aromatics, or C9 heavy aromatics or C 10 Narrower fractions such as heavy aromatics.

[0010] L-type molecular sieve (International Molecular Sieve Association code: LTL) is an alkaline macroporous molecular sieve developed by Union Carbide in 1965. No equivalent has been found in nature so far. Since Bernard (Proc. 5th Int. Conf. on Zeolites, Wiley, New York, 1980, 68) found that PtKL has much higher activity and selectivity for aromatization of n-hexane than traditional bifunctional catalysts, platinum-loaded L molecular sieves have received extensive attention as catalysts for dehydrogenation and cyclization of normal alkanes. Subsequently, Pt / KL molecular sieve catalysts have been used for dehydrogenation and reforming reactions to achieve industrial applications, but there have been no reports on the use of such catalysts for lightweighting of heavy aromatics.

[0011] Chinese patent application CN108236964A discloses a bimetallic catalytic reforming catalyst containing an LTL-type molecular sieve, comprising: a catalyst carrier composed of an LTL-type molecular sieve and a binder, and an active component containing a VIIIB group metal, Sn or Re element. The cations in the LTL-type molecular sieve are partially or completely replaced by lanthanide metal ions. In the embodiment of the patent application, Liaoyang Petrochemical reforming crude oil is used as a raw material, and the reaction temperature is 500°C, the pressure is 0.5MPa, and the volume space velocity is 3h -1 , the reaction was carried out for 10 hours under the condition of hydrogen-oil volume ratio of 800, and the aromatic yield was between 60-72%, C5 + The liquid yield is between 80-92%.

[0012] Chinese patent application CN106391098A discloses a naphtha reforming catalyst and a preparation method thereof, wherein the catalyst comprises a carrier, a metal and carbon. By adding a certain amount of monosaccharide during the preparation of the Pt / KL reforming catalyst, the dispersion of the metal Pt is improved and the carbon deposition rate of the catalyst during the reaction is reduced, thereby improving the reforming reaction performance of the Pt / KL catalyst. In the embodiment of the patent application, Fischer-Tropsch straight-run naphtha is used as a raw material for catalytic reforming at a reaction temperature of 500°C, a pressure of 0.7-1.0MPa, and a volume space velocity of 1.0h -1 , the reaction was carried out under the condition of hydrogen-to-oil molar ratio of 6, the aromatic yield was between 49.97-74.33%, C5 + The liquid yield was between 71.81-83.04%. Summary of the invention

[0013] The purpose of this application is to provide a method for producing more light aromatics, which can make C9 + Paraffin raw materials mostly produce light aromatics.

[0014] In order to achieve the above-mentioned object, the method for producing more light aromatics provided in the present application comprises the following steps:

[0015] 1) Include C9 + The paraffinic hydrocarbon feedstock is contacted with a first catalyst in the presence of hydrogen in a first reaction zone to react, so that at least part of the C9 + Alkanes undergo dehydrogenation and cyclization to give C9 + Aromatics, including C9 + a first stream of aromatic hydrocarbons, wherein the first catalyst comprises alumina and a Group VIII metal, a Group IVA metal, optionally a Group IA metal and a halogen supported thereon or comprises alumina and a Group VIII metal, a Group VIIB metal, a rare earth metal and a halogen supported thereon;

[0016] 2) Separating the first stream obtained in step 1) to obtain C9 + Distillate stream and C6-C8 non-aromatic stream; the C9 + The fraction stream contains C9 + Aromatic hydrocarbons, the C6-C8 non-aromatic stream contains C6-C8 alkanes and cycloalkanes;

[0017] 3) C9 obtained in step 2) + The fraction stream and the C6-C8 non-aromatic stream are contacted with a second catalyst in the presence of hydrogen in a second reaction zone to make at least part of the C9 + Aromatic hydrocarbons undergo dealkylation to obtain light aromatic hydrocarbons, thereby obtaining a second stream, wherein the second catalyst comprises KL zeolite and platinum and a modifying metal supported thereon, wherein the modifying metal is selected from Group IA metals, Group IIA metals and rare earth metals.

[0018] This method is implemented by including C9 + C9 in paraffinic raw materials + The paraffin undergoes a directional dehydrogenation cyclization reaction in the first reaction zone to obtain C9 + Aromatic hydrocarbons, and the products of the first reaction zone are separated, and the separated C6-C8 non-aromatic hydrocarbons and C9 + The fraction is subjected to C9 + Aromatic dealkylation reaction can convert C9 + Paraffins are efficiently converted into light aromatics, such as BTX, to increase their utilization value.

[0019] The method for producing more light aromatics provided by the present application, on the other hand, comprises the following steps: +The aromatic hydrocarbon raw material is contacted with a catalyst to carry out a dealkylation reaction, and the product is separated to obtain a C6-C8 non-aromatic stream and C6-C8 light aromatic hydrocarbons. The catalyst includes KL zeolite and platinum and a modified metal loaded thereon, wherein the modified metal is selected from Group IA metals, Group IIA metals and rare earth metals. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The following drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the following specific implementations, they are used to explain the present application but do not constitute a limitation to the present application.

[0021] Figure 1 The figure is a flow chart of a preferred embodiment of the method of the present application.

[0022] Figure 2 This is a flow chart showing the process of allowing the product from the moderate reforming zone to enter the zeolite reforming zone without separation.

[0023] Figure 3 This is a schematic diagram of the conventional reforming reaction process.

[0024] Figure 4 The present invention is a flow chart of another preferred embodiment of the method of the present application. DETAILED DESCRIPTION

[0025] The specific implementation of the present application is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present application, and is not used to limit the present application.

[0026] Any specific numerical value disclosed herein (including the endpoint of the numerical range) is not limited to the exact value of the numerical value, but should be understood to also cover values ​​close to the exact value, such as all possible numerical values ​​within the range of ±5% of the exact value. In addition, for the disclosed numerical range, the endpoint values ​​of the range, the endpoint values ​​and the specific point values ​​in the range, and the specific point values ​​can be arbitrarily combined to obtain one or more new numerical ranges, and these new numerical ranges should also be regarded as specifically disclosed herein.

[0027] Unless otherwise specified, the terms used herein have the same meaning as commonly understood by those skilled in the art. If a term is defined herein and its definition is different from the commonly understood meaning in the art, the definition herein shall prevail.

[0028] In this application, the term "C9 + “Alkanes” refer to straight-chain or branched alkanes with more than 9 carbon atoms, including but not limited to n-nonane, 2-methyloctane, 2,3,5-trimethylhexane, etc.; the term “C9 +“Aromatic hydrocarbons” refers to aromatic hydrocarbons with more than 9 carbon atoms, including but not limited to n-propylbenzene, m-ethylbenzene, 1,3,5-trimethylbenzene, etc.; the term “C7 - The term "chain alkane" refers to a chain alkane having 7 or less carbon atoms, including but not limited to n-hexane, 2-methylpentane, 2,3-dimethylpentane, etc.

[0029] In the present application, the term "light aromatics" refers to aromatics having 6 to 8 carbon atoms, including benzene, toluene, various xylene isomers and ethylbenzene, such as BTX.

[0030] In the present application, the term "naphtha" refers to various light oil products with a distillation range of 30-220°C obtained by processing crude oil or other hydrocarbon-containing raw materials. For example, the naphtha can be straight-run naphtha, hydrocracked heavy naphtha, hydrogenated coker gasoline, ethylene cracking gasoline raffinate, catalytic cracking gasoline, or a mixture of several thereof. Preferably, the naphtha contains cycloalkanes with a carbon number of 6-12, paraffins with a carbon number of 6-12, and aromatics with a carbon number of 6-12, with an initial distillation point of 80-95°C and a final distillation point of 135-180°C.

[0031] In this application, unless otherwise indicated, all pressures given are absolute pressures.

[0032] In this application, except for the contents clearly stated, any matters or items not mentioned are directly applicable to those known in the art without any changes. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, and the technical solutions or technical ideas formed thereby are deemed to be part of the original disclosure or original record of this application, and should not be regarded as new contents not disclosed or anticipated herein, unless a person skilled in the art considers that the combination is obviously unreasonable.

[0033] All patent and non-patent literature, including but not limited to textbooks and journal articles, mentioned herein are incorporated herein by reference in their entirety.

[0034] Traditionally, it is believed that L molecular sieves have small pores and aromatic hydrocarbons above C8 cannot be generated or converted in their pores. Therefore, L molecular sieves are mainly used as catalysts for the selective dehydrogenation and cyclization of C6-C7 paraffins. However, the inventors of this application unexpectedly discovered that C9 + Aromatic hydrocarbons can be efficiently dealkylated from side chains in the presence of hydrogen and a KL zeolite-based catalyst containing platinum and specific modified metals to be converted into light aromatic hydrocarbons such as BTX, thereby obtaining the present invention.

[0035] As described above, in the first aspect, the present application provides a method for producing more light aromatics, comprising the following steps:

[0036] 1) Include C9+ The paraffinic hydrocarbon feedstock is contacted with a first catalyst in the presence of hydrogen in a first reaction zone to react, so that at least part of the C9 + Alkanes undergo dehydrogenation and cyclization to give C9 + Aromatics, including C9 + a first stream of aromatic hydrocarbons, wherein the first catalyst comprises alumina and a Group VIII metal, a Group IVA metal, optionally a Group IA metal and a halogen supported thereon or comprises alumina and a Group VIII metal, a Group VIIB metal, a rare earth metal and a halogen supported thereon;

[0037] 2) Separating the first stream obtained in step 1) to obtain C9 + Distillate stream and C6-C8 non-aromatic stream; the C9 + The fraction stream contains C9 + Aromatic hydrocarbons, the C6-C8 non-aromatic stream contains C6-C8 alkanes and cycloalkanes;

[0038] 3) C9 obtained in step 2) + The fraction stream and the C6-C8 non-aromatic stream are contacted with a second catalyst in the presence of hydrogen in a second reaction zone to make at least part of the C9 + Aromatic hydrocarbons undergo dealkylation to obtain light aromatic hydrocarbons, thereby obtaining a second stream, wherein the second catalyst comprises KL zeolite and platinum and a modifying metal supported thereon, wherein the modifying metal is selected from Group IA metals, Group IIA metals and rare earth metals.

[0039] In a preferred embodiment, the reaction conditions of step 1) include: a temperature of 400-500°C, preferably 450-480°C, a pressure of 0.1-4.0 MPa, preferably 0.1-2.0 MPa, more preferably 0.1-0.5 MPa, and the C9 + The mass space velocity of the paraffin raw material is 1-50h -1 , preferably 1-20h -1 , more preferably 1-10h -1 , the hydrogen / hydrocarbon molar ratio is 0.5-20:1, preferably 1-10:1.

[0040] In certain preferred embodiments, the first reaction zone comprises one reactor or a plurality of reactors (e.g., 2-5 reactors connected in series), preferably one reactor or 2-4 reactors connected in series, wherein the first reaction zone comprises C9 + The mass space velocity of the paraffin raw material can be 1-50h -1 , preferably 1-20h -1 , more preferably 1-10h -1, the hydrogen / hydrocarbon molar ratio is 0.5-20:1, preferably 1-10:1, wherein when multiple reactors are used, the mass space velocity is calculated relative to the total amount of catalyst in all reactors in the first reaction zone, and the hydrogen / hydrocarbon molar ratio is the hydrogen / hydrocarbon molar ratio at the inlet of the first reactor.

[0041] According to the present application, step 1) can make C9 + Alkanes undergo dehydrogenation and cyclization to give C9 + Aromatic hydrocarbons. At the same time, if C6-C8 cycloalkanes are also present in the raw material, step 1) can also cause the cycloalkanes to undergo a dehydrogenation reaction to be directional converted into light aromatic hydrocarbons with the same carbon number. Preferably, in the first catalyst used in step 1), the VIII group metal is selected from platinum, palladium and iridium, the IVA group metal is selected from tin, germanium and silicon, the IA group metal is selected from potassium, sodium, rubidium and cesium, the halogen is selected from chlorine, fluorine, bromine and iodine, the VIIB group metal is selected from rhenium, and the rare earth metal is selected from yttrium or samarium. In order to control the reaction in step 1), it is preferred to use a catalyst with lower acidity to suppress the C7 - Dehydrogenation cyclization and hydrocracking reactions of light alkanes. In a preferred embodiment, the first catalyst comprises an alumina carrier and 0.1-2.0 mass % of a Group VIII metal, preferably platinum, 0.1-2.0 mass % of a Group IVA metal, preferably tin, 0-0.2 mass %, preferably 0.02-0.2 mass % of a Group IA metal, preferably potassium and 0.3-5 mass % of a halogen, preferably chlorine, based on the carrier, or comprises an alumina carrier and 0.1-2.0 mass %, preferably 0.1-1.0 mass % of a Group VIII metal, such as platinum, 0.1-3.0 mass %, preferably 0.1-2.0 mass % of a Group VIIB metal, such as rhenium, 0.01-3.0 mass %, preferably 0.1-1.0 mass % of a rare earth metal, such as yttrium and 0.3-5 mass %, preferably 0.5-1.5 mass % of a halogen, such as chlorine, based on the alumina carrier, wherein the contents of the metals and halogens are all calculated as elements.

[0042] In a further preferred embodiment, based on the alumina carrier, the first catalyst has a platinum content of 0.1-1.0 mass %, a tin content of 0.1-1.0 mass %, a potassium content of 0.02-0.1 mass %, and a chlorine content of 0.5-1.5 mass %.

[0043] In a preferred embodiment, the specific surface area of ​​the alumina carrier is 120-220 m 2 / g, more preferably 140-190m 2 / g. The alumina carrier may be in various shapes, such as strip and sphere, preferably sphere, and the diameter of the spherical carrier is preferably 1.5-2.0 mm. The alumina is preferably γ-alumina.

[0044] The first catalyst can be prepared by conventional methods in the art. In a preferred embodiment, the first catalyst can be prepared by the following method: an alumina carrier containing a Group IVA metal (such as tin) is impregnated with an aqueous solution of a platinum-containing compound and an optional Group IA metal halide (such as chloride), and the solid after impregnation is dried, activated with water and chlorine, and reduced to obtain the target catalyst. Preferably, the platinum-containing compound is chloroplatinic acid.

[0045] In a further preferred embodiment, the impregnation temperature in the catalyst preparation method is 10-50°C, the drying temperature is 90-150°C, and the drying time is preferably 8-24 hours. The water-chlorine activation is to treat the dried solid in air containing water and HCl, the water-chlorine activation temperature is preferably 460-540°C, the time is preferably 2-12 hours, and the molar ratio of water / HCl is preferably 10-100:1. The reducing gas used for the reduction is preferably hydrogen, the reduction temperature is preferably 480-520°C, and the time is preferably 2-12 hours.

[0046] According to the present application, it is preferred that the first product stream obtained in step 1) is mixed with the second product stream obtained in step 3) and then separated in step 2). In step 2), the first product stream obtained in step 1) is separated to obtain C9 + Distillate logistics, C5 - fraction logistics, C6-C8 non-aromatic logistics and C6-C8 light aromatic logistics; the C9 + The fraction stream contains C9 + Aromatic hydrocarbons, the C6-C8 non-aromatic hydrocarbon stream contains C6-C8 alkanes and cycloalkanes, and the C6-C8 light aromatic hydrocarbons discharge device; the first stream separation method comprises the steps of rectifying the first stream in a rectifying tower, and obtaining C5 - The distillate stream and C6-C8 distillate stream, C9 is obtained at the bottom of the tower + The fraction logistics is separated, and the C6-C8 fraction logistics is separated to obtain C6-C8 non-aromatic logistics and C6-C8 light aromatic logistics. The operating conditions of the distillation tower are: the top pressure is 0.3-2.5MPa, the top temperature is 50-300°C, and the reflux ratio is 2-8; the distillation tower is preferably a plate tower. The C6-C8 fraction logistics separation method includes liquid-liquid extraction or extractive distillation, and the extraction solvent or extraction solvent used is selected from at least one of cyclopentane sulfone, dimethyl sulfoxide, dimethylformamide, N-methylpyrrolidone, N-formylmorpholine, triethylene glycol, tetraethylene glycol, pentaethylene glycol, methanol and acetonitrile, preferably cyclopentane sulfone, and the extraction is carried out under conventional operating conditions in the art.

[0047] According to the present application, step 3) can make the C9-containing + C9 in distillate stream+ Aromatic hydrocarbons are converted into light aromatic hydrocarbons by removing side chain alkyl groups. At the same time, C6-C8 chain alkanes and cycloalkanes in non-aromatic streams are subjected to dehydrogenation cyclization reaction or dehydrogenation reaction to be converted into light aromatic hydrocarbons with the same carbon number.

[0048] In a preferred embodiment, the reaction conditions of step 3) include: a temperature of 350-490°C, preferably 450-480°C, a pressure of 0.1-4.0 MPa, preferably 0.1-2.0 MPa, more preferably 0.1-0.5 MPa, and the C9 + The mass space velocity of the aromatics flow is 1-20h -1 , preferably 1-10h -1 , the hydrogen / hydrocarbon molar ratio is 0.5-20:1, preferably 1-10:1.

[0049] In a further preferred embodiment, the second reaction zone comprises one reactor or a plurality of (e.g., 2-3) reactors connected in series, preferably one reactor or two reactors connected in series, and the C9 + The mass space velocity of the aromatics flow can be 1-20h -1 , preferably 1-10h -1 , more preferably 1-5h -1 , the hydrogen / hydrocarbon molar ratio is 0.5-20:1, preferably 1-10:1, wherein when multiple reactors are used, the mass space velocity is calculated relative to the total amount of catalyst in all reactors in the second reaction zone, and the hydrogen / hydrocarbon molar ratio is the hydrogen / hydrocarbon molar ratio at the inlet of the first reactor.

[0050] In a preferred embodiment, the second catalyst used in step 3) comprises KL zeolite and 0.1-1.5 mass %, preferably 0.3-1.2 mass % of platinum supported thereon, based on the KL zeolite, and 0.02-4.0 mass %, preferably 0.1-3.0 mass % of the modified metal, wherein the content of platinum and the modified metal is calculated as metal. Further preferably, the IA group metal is selected from cesium, the IIA group metal is selected from barium and calcium, and the rare earth metal is selected from one or more of La, Ce, Gd, Y, Sm and Yb metals. Particularly preferably, the average crystallite diameter of the KL zeolite is 0.1-2 μm.

[0051] The second catalyst can be prepared by conventional methods in the art. In a preferred embodiment, the second catalyst can be prepared by a method comprising the following steps: impregnating KL zeolite with an aqueous solution containing a platinum compound and a compound containing a Group IA metal, a Group IIA metal and / or a rare earth metal, and then drying and calcining. The platinum-containing compound is preferably a compound containing a Pt cation, such as Pt(NH3)2Cl2; the compound containing a Group IA metal, a Group IIA metal and a rare earth metal is preferably a soluble hydroxide, chloride or nitrate of the corresponding metal, such as BaCl2. The drying temperature is preferably 90-150°C, the time is preferably 8-24 hours, and the calcination temperature is preferably 300-400°C, and the time is preferably 2-8 hours.

[0052] In a preferred embodiment, the mass ratio of the first catalyst used in step 1) to the second catalyst used in step 3) is 1:(0.25-5), preferably 1:(1.2-3).

[0053] In the method of the present application, the reaction of converting hydrocarbons into aromatics in the above-mentioned step 1) and step 3) is an endothermic reaction. In order to maintain the temperature required for the reaction, an intermediate heating furnace is preferably provided between the first and second reaction zones, and between the series reactors provided in the corresponding reaction zones. The reactor suitable for step 1) and step 2) of the method of the present application can be a fixed bed reactor or a moving bed reactor, preferably a fixed bed reactor.

[0054] In certain preferred embodiments of the method of the present application, the C9 + The raw material of paraffin is naphtha, for example, it can be selected from straight run naphtha, hydrocracking heavy naphtha, hydrogenated coker gasoline, ethylene cracking gasoline raffinate, catalytic cracking gasoline, or any mixture thereof. In a further preferred embodiment, the naphtha contains cycloalkanes with a carbon number of 6-12, paraffins with a carbon number of 6-12, and aromatics with a carbon number of 6-12, with an initial boiling point of 80-95°C and a final boiling point of 135-180°C. Due to the limitation of the separation accuracy of distillation, the naphtha may also contain a small amount of C5 hydrocarbons, the proportion of which is usually not more than 0.5% by mass. In order to make the final boiling point of the reaction product meet the requirements of gasoline blending, the naphtha has a carbon number higher than C 11 Hydrocarbons (C 11 + ) is usually not more than 1 mass %.

[0055] In certain preferred embodiments of the method of the present application, the C9 + C9 of paraffinic raw materials + The paraffin content is 10% by mass or more, preferably 20% by mass or more, and more preferably 30% by mass or more.

[0056] In such a preferred embodiment, naphtha is introduced into the first reaction zone, and in step 1), the reaction conditions are controlled to perform a moderate dehydrogenation conversion reaction, so that the cycloalkanes therein undergo a dehydrogenation reaction to generate aromatic hydrocarbons with the same carbon number, C9 + The alkanes undergo dehydrogenation and cyclization reactions and are also converted into aromatic hydrocarbons with the same carbon number, while minimizing the amount of C7 - The paraffin undergoes a dehydrogenation cyclization or cracking reaction; then, the reaction product of the first reaction zone is separated to obtain a C9 + Aromatic C9 + The fraction stream and the non-aromatic stream containing C6-C8 alkanes and cycloalkanes are passed into the second reaction zone, and in step 3), the C9 + The aromatic hydrocarbons are dealkylated to convert them into light aromatic hydrocarbons, such as BTX, and the unreacted C6-C8 paraffins are dehydrogenated and cyclized to generate aromatic hydrocarbons with corresponding carbon numbers. The method of this preferred embodiment can convert more paraffins in naphtha into aromatic hydrocarbons through directional reaction, and make C9 + Aromatics undergo dealkylation to generate light aromatics, such as BTX, thereby increasing the yield of light aromatics.

[0057] In such a preferred embodiment, step 1) mainly performs a dehydrogenation conversion reaction of naphtha, during which the cycloalkanes in the naphtha that are easily reactive are dehydrogenated to generate aromatics, and the conversion of paraffins is controlled to make the C9 + Alkanes undergo dehydrogenation cyclization, C7 - The paraffins are not converted as much as possible. In the dehydrogenation reaction process of step 1), the C7 - The conversion of paraffins can also control the cracking reaction of light hydrocarbons, thereby maintaining the content of C6-C8 paraffins and increasing the content of light aromatics in the final reaction product.

[0058] In certain further preferred embodiments, the naphtha is subjected to a hydrotreating treatment before entering the first reaction zone to remove impurities such as arsenic, lead, copper, sulfur, and nitrogen. After the hydrotreating treatment, the naphtha generally does not contain olefins.

[0059] In certain further preferred embodiments, in step 1), the conversion rate of cycloalkanes in naphtha is controlled to be not less than 90% by mass, C9 + The conversion rate of paraffin is 70-95% by mass. Preferably, the control can be achieved by selecting appropriate reaction conditions, such as adjusting the reaction temperature or the mass space velocity of the naphtha feed, or by changing the content of the IA group metal, such as potassium, in the first catalyst to adjust the reaction selectivity of the first catalyst.

[0060] In a further preferred embodiment, in step 1), the conversion rate of cycloalkanes in naphtha is controlled to be not less than 90% by mass, wherein the conversion rates of both C7 and C8 cycloalkanes are not less than 95% by mass, and the conversion rate of C6 cycloalkanes is not less than 70% by mass. Preferably, the control can be achieved by selecting a suitable reaction temperature or a suitable naphtha feed space velocity.

[0061] In a further preferred embodiment, in step 1), the conversion rate of paraffins in naphtha is controlled to be no more than 60% by mass, wherein the conversion rate of C6 paraffins is no more than 18% by mass, the conversion rate of C7 paraffins is no more than 30% by mass, the conversion rate of C8 paraffins is no more than 70% by mass, and the conversion rate of C9 paraffins is no more than 10% by mass. + The conversion rate of paraffin is 70-95% by mass. Preferably, the control can be achieved by changing the content of Group IA metal, such as potassium, in the first catalyst to adjust the selectivity of the dehydrogenation cyclization reaction.

[0062] In a second aspect, the present application provides a method comprising: + A method for producing light aromatic hydrocarbons from aromatic hydrocarbon raw materials, comprising: reacting C9 + Aromatic hydrocarbons are contacted with a catalyst for dealkylation reaction, and the products are separated to obtain C6-C8 non-aromatic stream and C6-C8 light aromatic hydrocarbons. The catalyst includes KL zeolite and platinum and modified metal loaded thereon, wherein the modified metal is selected from Group IIA metals and rare earth metals.

[0063] In a preferred embodiment, the various features of the catalyst used in the method are as described in the first aspect above and will not be repeated here.

[0064] In a preferred embodiment, the dealkylation reaction conditions include: a temperature of 350-490°C, preferably 450-480°C, a pressure of 0.1-4.0 MPa, preferably 0.1-2.0 MPa, more preferably 0.1-0.5 MPa, and a raw material mass space velocity of 1-20 h -1 , preferably 1-10h -1 , the hydrogen / raw material molar ratio is 0.5-20:1, preferably 1-10:1.

[0065] In a further preferred embodiment, the dealkylation reaction can be carried out in one reactor or multiple (e.g., 2-3) reactors connected in series, preferably one reactor or two reactors connected in series, and the mass space velocity of the raw material is 1-20h -1 , preferably 1-10h -1 , more preferably 1-5h -1, the hydrogen / feedstock molar ratio is 0.5-20:1, preferably 1-10:1, wherein when multiple reactors are used, the mass space velocity is calculated relative to the total amount of catalyst in all reactors, and the hydrogen / feedstock molar ratio is the hydrogen / hydrocarbon molar ratio at the inlet of the first reactor.

[0066] The method according to the second aspect of the present invention is applicable to various + Aromatic feedstocks produce light aromatics, such as C9 + The aromatic hydrocarbon content is 10% by mass or more, preferably 20% by mass or more, more preferably 50% by mass or more, more preferably 80% by mass or more, and more preferably 90% by mass or more.

[0067] The preferred implementation modes of the present application are further described below in conjunction with the accompanying drawings.

[0068] Figure 1 This is a flow chart of a preferred embodiment of the method of the first aspect of the present application. Figure 1 As shown, the pre-hydrogenated naphtha is mixed with hydrogen and then heat-exchanged in the heat exchanger through pipeline 101, and then enters the first reaction zone 102 to contact with the first catalyst to perform a mild reforming reaction, so that the cycloalkanes in the naphtha are dehydrogenated into aromatics, C9 + Dehydrogenation and cyclization of heavy paraffins to produce C9 + Aromatic hydrocarbons. The first stream 103 produced by the first reaction zone 102 is mixed with the second stream 104 produced by the second reaction zone 109 to form a stream 105 which enters the distillation tower 106 to obtain C5 - The distillate stream 110 and the C6-C8 distillate stream 111 are used to obtain C9 at the bottom of the tower. + Fraction stream 107; C5 - The fraction stream 110 is discharged from the device, and the C6-C8 fraction stream 111 enters the aromatic separation unit 112 to obtain a C6-C8 light aromatic stream 114 and a C6-C8 non-aromatic stream 113. The C6-C8 light aromatic stream 114 is used as a product discharge device, and the C6-C8 non-aromatic stream 113 and the C9 obtained at the bottom of the distillation tower 106 are separated. + The fraction stream 107 is mixed to form stream 108, which enters the second reaction zone 109 and contacts the second catalyst. + Aromatic hydrocarbons are dealkylated to generate C6-C8 light aromatic hydrocarbons, and C6-C8 non-aromatic hydrocarbons are aromatized to generate C6-C8 light aromatic hydrocarbons, thereby obtaining a second stream 104.

[0069] Figure 2 FIG. 1 is a flow diagram of the first reaction product directly entering the second reaction zone without separation. Figure 2As shown, the pre-hydrogenated naphtha is mixed with hydrogen and then enters the first reaction zone 202 to contact the first catalyst after heat exchange through pipeline 201, and undergoes a mild reforming reaction to dehydrogenate the cycloalkanes in the naphtha into aromatics, C9 + Dehydrogenation and cyclization of heavy paraffins to produce C9 + Aromatic hydrocarbons. The stream 203 produced by the first reaction zone 202 enters the second reaction zone 204 and contacts with the second catalyst. + Aromatic hydrocarbons are dealkylated to generate C6-C8 light aromatic hydrocarbons. C6-C8 paraffins are aromatized to generate C6-C8 light aromatic hydrocarbons. The stream 205 produced by the second reaction zone 204 enters the distillation tower 206. The top of the distillation tower 206 obtains C5 - The distillate stream 207 and the C6-C8 distillate stream 208 are used to obtain C9 at the bottom of the tower. + Fraction stream 209, C5 - Distillate stream 207 and C9 + The fraction stream 209 is discharged from the device, and the C6-C8 fraction stream enters the aromatic separation unit 210 to be separated to obtain a C6-C8 non-aromatic stream 211 and a C6-C8 light aromatic stream 212.

[0070] Figure 3 The schematic diagram of the conventional reforming reaction process is shown in FIG. 3. The pre-hydrogenated naphtha is mixed with hydrogen and then enters the conventional reforming reaction zone 302 after heat exchange with the heat exchanger through pipeline 301. A series of reforming reactions occur in the conventional reforming reaction zone. The reaction product 303 of the conventional reforming reaction zone 302 enters the distillation tower 304. The C5 - The distillate stream 305 and the C6-C8 distillate stream 306 are used to obtain C9 at the bottom of the tower. + Fraction stream 307, C5 - Distillate stream 305 and C9 + The fraction stream 307 is discharged from the device, and the C6-C8 fraction stream 306 enters the aromatic separation unit 308 to be separated to obtain a C6-C8 non-aromatic stream 309 and a C6-C8 light aromatic stream 310.

[0071] Figure 4 This is a flow diagram of another preferred embodiment of the method of the present application, that is, a flow diagram of the method of the second aspect of the present application. The pre-hydrogenated naphtha enters the zeolite reforming reaction zone 402 through pipeline 401, and a series of reactions such as cycloalkane dehydrogenation, paraffin aromatization, and heavy aromatic lightening occur in the zeolite reforming reaction zone. The reaction product 403 of the zeolite reforming reaction zone 402 enters the distillation tower 404, and the top of the distillation tower 404 obtains C5 - The distillate stream 405 and the C6-C8 distillate stream 406 are used to obtain C9 at the bottom of the tower. + Fraction stream 407, C5 -Distillate stream 405 and C9 + The fraction stream 407 is discharged from the device, and the C6-C8 fraction stream 406 enters the aromatic separation unit 408 to be separated to obtain a C6-C8 non-aromatic stream 409 and a C6-C8 light aromatic stream 410.

[0072] To simplify the process notation, other equipment used in the above preferred embodiment of the method of the present application, such as naphtha feed pump, reaction product air cooler, gas-liquid separator, etc., are shown in FIG. Figures 1 to 4 Not shown in the figure.

[0073] Example

[0074] The present application will be further described below by way of examples, but the present application is not limited thereby.

[0075] Catalyst Preparation Example

[0076] Example I-1

[0077] This example illustrates the preparation of the first catalyst used in this application.

[0078] (1) Preparation of tin-containing γ-Al2O3 spheres with uniform tin distribution

[0079] Take 100 grams of aluminum hydroxide powder (produced by Sasol Germany, brand SB, aluminum oxide content of 72% by mass) and an appropriate amount of deionized water, stir and slurry to obtain a slurry with a liquid / solid mass ratio of 2.0. Add 7.5 ml of dilute nitric acid with a volume ratio of 1:1, 30 grams of urea and a predetermined amount of SnCl2 hydrochloric acid solution to the slurry, so that the Sn content in the solution is 0.30% by mass relative to the dry basis aluminum oxide, stir for 1 hour, add 30 grams of kerosene and 3 grams of fatty alcohol polyoxyethylene ether and stir for 1 hour, and drop into the oil-ammonia column to form a ball. The wet ball solidifies in ammonia water for 1 hour, then filters, rinses with deionized water 2-3 times, dries at 60°C for 6 hours, 120°C for 10 hours, and roasts in air at 680°C for 4 hours. The water content in the roasting atmosphere is 15% by volume to obtain a Sn-containing γ-Al2O3 spherical carrier with an average diameter of 1.62 mm and a specific surface area of ​​165 m determined by the BET method. 2 / g.

[0080] (2) Preparation of target catalyst

[0081] 0.5882 g of chloroplatinic acid, 0.1526 g of potassium chloride, 5.40 g of 37% hydrochloric acid and 175 g of deionized water were prepared into a solution, wherein the content of HCl was 2.0% by mass relative to the dry basis alumina carrier. The prepared solution was used as an impregnation liquid to impregnate the Sn-containing γ-Al2O3 small ball carrier prepared in step (1) at 25°C for 4 hours, and the liquid / solid ratio of the impregnation was 1.8 mL / g. After impregnation, the impregnation system was evaporated to dryness using a rotary evaporator, and the obtained solid was dried at 120°C for 12 hours, activated with water chlorine at 510°C for 4 hours, and the molar ratio of water to HCl in the air used for water chlorine activation was 40:1, and then reduced with hydrogen at 500°C for 4 hours to obtain the first catalyst A.

[0082] The component contents of catalyst A calculated based on the alumina carrier are: 0.27 mass % Pt, 0.30 mass % Sn, 0.08 mass % K, 1.0 mass % Cl, and the contents of each element are determined by X-ray fluorescence analysis.

[0083] Example I-2

[0084] This example illustrates the preparation of the second catalyst Pt-Cs / KL used in this application.

[0085] (1) Preparation of directing agent for synthesizing KL zeolite

[0086] 12.08g of Al(OH)3 (produced by Aluminum Corporation of China, brand H-WF-10, the same below) was added to 264.12ml of a solution containing 77.57g of KOH (purity 85.7% by mass, the same below), and heated to dissolve to obtain an aluminum sol. The aluminum sol was added to 435.6g of silica sol (containing 30% by mass SiO2, pH value 9, the same below) preheated to 50°C under stirring, and stirred for 0.5 hours to form a white gel. The white gel was aged at 30°C for 72 hours to obtain a translucent sol, which is a target-directing agent, wherein the molar ratio of each component is K2O:Al2O3:SiO2:H2O=7.9:1:29:430.

[0087] (2) Preparation of KL zeolite carrier

[0088] 107 g of Al(OH)3 was added to 1100 mL of a solution containing 210 g of KOH, and heated to dissolve to obtain an aluminum sol. The obtained aluminum sol and the directing agent prepared in step (1) were added to a reaction kettle containing 1200 mL of silica sol under stirring, wherein the molar ratio of Al2O3 contained in the added directing agent to Al2O3 contained in the material without the directing agent was 5:95, and the mixture was stirred for 0.5 hours to form a white reaction mixture gel, wherein the molar ratio of each component was K2O:Al2O3:SiO2:H2O=2.68:1:10:178.

[0089] The white gel was heated to 150°C with stirring, and the stirring was stopped. The crystallization was statically carried out for 72 hours. The crystallized product was rapidly cooled to 40°C, separated by centrifugation, and the upper liquid was taken out. The solid was then washed with deionized water until the pH value of the liquid phase was 9-10. The obtained solid was dried at 120°C for 10 hours to obtain KL zeolite, in which the molar ratio of each component was K2O:Al2O3:SiO2=1.2:1:5.6, and the average grain diameter was 0.3-1.2 μm.

[0090] (3) Preparation of Pt-CsKL Catalyst

[0091] The KL zeolite obtained in step (2) was supersaturatedly impregnated with a mixed solution containing Pt(NH3)2Cl2 and CsOH, wherein the mixed solution contained 1.0 mass% Pt and 1.0 mass% Cs (both relative to the mass of the KL zeolite), and the liquid / solid volume ratio during the impregnation was 1.5:1. After impregnation for 6 hours, the solid was dried at 120°C for 12 hours and calcined in air at 350°C for 4 hours to prepare Pt-Cs / KL zeolite, which was recorded as the second catalyst B. The Pt content of catalyst B was 1.0 mass% and the Cs content was 1.0 mass% based on the KL zeolite.

[0092] Example I-3

[0093] This example illustrates the preparation of the second catalyst Pt-Ca / KL used in this application.

[0094] 1.54 g of Pt(NH3)2Cl2 and 2.78 g of CaCl2 were dissolved in 150 g of deionized water and stirred to obtain an impregnation solution. The impregnation solution was added to 100 g of the KL zeolite carrier prepared in Example I-2, and the mixture was rotary evaporated after impregnation for 6 hours. The obtained solid was dried at 120°C for 12 hours and calcined in air at 350°C for 4 hours to prepare Pt-Ca / KL zeolite, which was recorded as catalyst B1. The Pt content of catalyst B1 was 1.0% by mass and the Ca content was 1.0% by mass based on KL zeolite.

[0095] Example I-4

[0096] This example illustrates the preparation of the second catalyst Pt-La / KL used in this application.

[0097] Take 1.54g Pt(NH3)2Cl2 and 1.77g LaCl3 and dissolve them in 150g deionized water, stir them thoroughly and evenly to obtain an impregnation solution. Add the above impregnation solution to 100g of the KL zeolite carrier prepared in Example I-2, impregnate for 6 hours and then evaporate to dryness by rotary evaporation. The obtained solid is dried at 120°C for 12 hours and calcined in air at 350°C for 4 hours to prepare Pt-La / KL zeolite, which is recorded as catalyst B2. The Pt content in catalyst B2 is 1.0% by mass and the La content is 1.0% by mass based on KL zeolite.

[0098] Application Examples

[0099] Examples II-1 to II-3

[0100] This example illustrates the application of the method according to the first aspect of the present application.

[0101] according to Figure 1 The process shown uses naphtha having the properties and composition described in Table II-1 and Table II-2 as the raw material for the reaction.

[0102] 3000 g of the first catalyst A prepared in Example I-1 was loaded into the fixed bed reactor used in the first reaction zone 102, and 6000 g of the second catalyst B prepared in Example I-2 was loaded into the fixed bed reactor used in the second reaction zone 109. Naphtha was passed into the first reaction zone. The reaction conditions and results of each example are shown in Table II-4.

[0103] The operating conditions of the distillation tower 106 are: the tower top pressure is 1.2 MPa, the tower top temperature is 250° C., and the reflux ratio is 3.

[0104] The aromatic separation unit 112 is a liquid-liquid extraction tower, the extraction solvent used is sulfolane, the solvent ratio (to feed) is 4, the tower top pressure is 0.2 MPa, the tower top temperature is 90°C, and the tower bottom temperature is 75°C.

[0105] Table II-1 Properties of naphtha used in the examples

[0106] project Initial distillation point 10% by volume 50% by volume 90% by volume Final distillation point Distillation temperature, °C 84 106 121 153 170

[0107] Table II-2 Composition of naphtha used in the examples

[0108] Hydrocarbon carbon number Alkanes, mass % Cycloalkanes, mass % Aromatics, mass% <![CDATA[C5]]> 0.15 0.03 - <![CDATA[C6]]> 3.43 3.17 0.38 <![CDATA[C7]]> 9.34 10.46 2.76 <![CDATA[C8]]> 15.92 13.95 6.51 <![CDATA[C9]]> 10.83 11.37 2.92 <![CDATA[C 10 ]]> 6.40 1.84 0.16 <![CDATA[C 11 + ]]> 0.38 0 0 total 46.45 40.82 12.73

[0109] Example II-4

[0110] According to the method of Example II-1, the same naphtha as in Example II-1 was introduced into the reaction zone, except that the second catalyst was replaced with catalyst B1 prepared in Example I-4. The reaction conditions and results are shown in Table II-4.

[0111] Example II-5

[0112] This example illustrates the application of the method according to the second aspect of the present application.

[0113] according to Figure 4 In the process shown in FIG. 1 , the fixed bed reactor 402 is loaded with 6000 g of the second catalyst B2 prepared in Example I-4, which contains C9 + Aromatic raw materials were reacted, and the reaction conditions and results are shown in Table II-4.

[0114] The operating conditions of the distillation tower 404 are: the tower top pressure is 1.2 MPa, the tower top temperature is 250° C., and the reflux ratio is 3.

[0115] The aromatic separation unit 408 is a liquid-liquid extraction tower, the extraction solvent used is sulfolane, the solvent ratio (to the feed) is 4, the tower top pressure is 0.2 MPa, the tower top temperature is 90°C, and the tower bottom temperature is 75°C.

[0116] Table II-3 C9 used in the examples + Composition of aromatic feedstock

[0117] Hydrocarbon carbon number Alkanes, mass % Cycloalkanes, mass % Aromatics, mass% <![CDATA[C5]]> 0.3 0 0 <![CDATA[C6]]> 8.7 0.9 5.5 <![CDATA[C7]]> 8.5 0.6 17.9 <![CDATA[C8]]> 3.1 0.4 22.8 <![CDATA[C9]]> 2 0.4 19.1 <![CDATA[C 10 ]]> 1.1 0.2 7.4 <![CDATA[C 11 + ]]> 0.8 0.1 0.2 total 24.5 2.6 72.9

[0118] Comparative Example II-1

[0119] This comparative example illustrates the result of directly entering the product of the first reaction zone into the second reaction zone for reaction without separation.

[0120] according to Figure 2 The process shown in the figure uses naphtha with the properties and composition described in Tables 1 and 2 as the raw material for the reaction. The catalyst used and the loading amount are the same as those in Example II-1. The reaction conditions and results are shown in Table II-4.

[0121] The operating conditions of the distillation tower 206 are: the tower top pressure is 1.2 MPa, the tower top temperature is 250° C., and the reflux ratio is 3.

[0122] The aromatic separation unit 210 is a liquid-liquid extraction tower, the extraction solvent used is sulfolane, the solvent ratio (to feed) is 4, the tower top pressure is 0.2 MPa, the tower top temperature is 90°C, and the tower bottom temperature is 75°C.

[0123] Comparative Example II-2

[0124] This comparative example illustrates the reaction results using a conventional reforming catalyst.

[0125] according to Figure 3 In the process shown in FIG. 1 , 6000 g of reforming catalyst C (produced by Hunan Jianchang Petrochemical Co., Ltd., brand RC011) containing C9 as described in Table II-3 is loaded into the moving bed reactor 302.+ The carrier of the reforming catalyst C is a γ-Al2O3 pellet, wherein the Pt content calculated based on the carrier is 0.28 mass%, the Sn content is 0.31 mass%, and the chlorine content is 1.10 mass%. The reaction conditions and results are shown in Table II-4.

[0126] The operating conditions of the distillation tower 304 are: the tower top pressure is 1.2 MPa, the tower top temperature is 250° C., and the reflux ratio is 3.

[0127] The aromatic separation unit 308 is a liquid-liquid extraction tower, the extraction solvent used is sulfolane, the solvent ratio (to the feed) is 4, the tower top pressure is 0.2 MPa, the tower top temperature is 90°C, and the tower bottom temperature is 75°C.

[0128] Table II-4 Reaction results of Examples II-1 to II-5 and Comparative Examples II-1 to II-2

[0129]

[0130] It can be seen from the results in Table II-4 that under the same reaction conditions, compared with the comparative example II-1 in which the product of the first reaction zone is not separated and directly introduced into the second reaction zone, in the method of the first aspect of the example II-2 of the present application, after the naphtha passes through the first reaction zone, the product is separated to obtain C9 + The C6-C8 non-aromatic stream in the fraction stream and the second reaction zone product is introduced into the second reaction zone for conversion reaction, thereby increasing the BTX yield and C9 + The yield of aromatics is reduced, achieving the goal of producing as much light aromatics as possible from naphtha, and the resulting gas still contains more hydrogen.

[0131] At the same time, compared with the reaction of comparative example II-2 using a conventional reforming catalyst, the BTX yield of method example II-5 according to the second aspect of the present application is greatly improved, and C9 + The aromatics yield is greatly reduced, and the goal of producing as much light aromatics as possible from naphtha can also be achieved, and the resulting gas still contains a lot of hydrogen.

[0132] The preferred embodiments of the present application are described in detail above; however, the present application is not limited to the specific details in the above embodiments. Within the technical concept of the present application, a variety of simple modifications can be made to the technical solution of the present application, and these simple modifications all fall within the protection scope of the present application.

[0133] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this application will not further describe various possible combinations.

[0134] In addition, the various implementation modes of the present application may be arbitrarily combined, and as long as they do not violate the concept of the present application, they should also be regarded as the contents disclosed in the present application.

Claims

1. A method for producing more light aromatics, comprising the following steps: 1) Include C9 + The paraffinic hydrocarbon feedstock is contacted with a first catalyst in the presence of hydrogen in a first reaction zone to react, so that at least part of the C9 + Alkanes undergo dehydrogenation and cyclization to give C9 + Aromatics, including C9 + A first stream of aromatic hydrocarbons, wherein the first catalyst comprises alumina and a Group VIII metal, a Group IVA metal, a halogen and an optional Group IA metal supported thereon; or comprises alumina and a Group VIII metal, a Group VIIB metal, a rare earth metal and a halogen supported thereon; 2) Separating the first stream obtained in step 1) to obtain C9 + Distillate stream and C6-C8 non-aromatic stream; the C9 + The fraction stream contains C9 + Aromatic hydrocarbons, the C6-C8 non-aromatic stream contains C6-C8 alkanes and cycloalkanes; 3) C9 obtained in step 2) + The fraction stream and the C6-C8 non-aromatic stream are contacted with a second catalyst in the presence of hydrogen in a second reaction zone to make at least part of the C9 + Aromatic hydrocarbons undergo dealkylation to obtain light aromatic hydrocarbons, and a second stream product is obtained in the second reaction zone, wherein the second catalyst comprises KL zeolite and platinum and a modified metal supported thereon, wherein the modified metal is selected from Group IA metals, Group IIA metals and rare earth metals, and the average crystallite diameter of the KL zeolite is 0.1-2 μm, and the reaction conditions include: The temperature is 350-490℃, the pressure is 0.1-4.0MPa, and the mass space velocity of the raw material is 1-20h -1 , the hydrogen / hydrocarbon molar ratio is 0.5-20:

1.

2. The method according to claim 1, characterized in that The first stream obtained in step 1) is mixed with the second stream obtained in step 3) and then the separation described in step 2) is performed.

3. The method according to claim 1, wherein the first stream separation in step 2) comprises fractionating the first stream to obtain C9 + Fraction flow, C 5- The C6-C8 fraction logistics is separated into a C6-C8 non-aromatic logistics and a C6-C8 light aromatic logistics.

4. The method according to claim 3, wherein the C6-C8 fraction stream separation method comprises liquid-liquid extraction or extractive distillation.

5. The method according to claim 1, wherein the second catalyst in step 3) comprises KL zeolite and 0.1-1.5 mass % of platinum and 0.02-4.0 mass % of the modifying metal based on the KL zeolite.

6. The method according to claim 5, wherein the platinum content is 0.3-1.2% by mass, and the modified metal content is 0.1-3.0% by mass.

7. The method of any one of claims 1, 5 or 6, wherein the second catalyst has one or more of the following characteristics: The Group IA metal is selected from potassium, sodium, rubidium and cesium; The Group IIA metal is selected from barium and calcium; The rare earth metal is selected from La, Ce, Gd, Y, Sm and Yb.

8. The method according to claim 1, wherein: In the first catalyst used in step 1), the Group VIII metal is selected from platinum, palladium and iridium, the Group IVA metal is selected from tin, germanium and silicon, the Group IA metal is selected from potassium, sodium, rubidium and cesium, the halogen is selected from chlorine, fluorine, bromine and iodine, the Group VIIB metal is selected from rhenium, and the rare earth metal is selected from yttrium or samarium.

9. The method according to claim 1, wherein: The first catalyst described in step 1) comprises an alumina carrier and 0.1-2.0 mass % of a Group VIII metal, 0.1-2.0 mass % of a Group IVA metal, 0-0.2 mass % of a Group IA metal and 0.3-5 mass % of a halogen, based on the alumina carrier; or comprises an alumina carrier and 0.1-2.0 mass % of a Group VIII metal, 0.1-3.0 mass % of a Group VIIB metal, 0.01-3.0 mass % of a rare earth metal and 0.3-5 mass % of a halogen, based on the alumina carrier.

10. The method of claim 1, wherein: The first catalyst described in step 1) comprises an alumina carrier and 0.1-1.0 mass % of a Group VIII metal, 0.1-1.0 mass % of a Group IVA metal, 0.02-0.1 mass % of a Group IA metal and 0.5-1.5 mass % of a halogen, based on the alumina carrier; or comprises an alumina carrier and 0.1-1.0 mass % of a Group VIII metal, 0.1-2.0 mass % of a Group VIIB metal, 0.1-1.0 mass % of a rare earth metal and 0.5-1.5 mass % of a halogen, based on the alumina carrier.

11. The method according to claim 1, wherein: The Group VIII metal is platinum, the Group IVA metal is tin, the Group IA metal is potassium, the halogen is chlorine, the Group VIIB metal is rhenium, and the rare earth metal is yttrium.

12. The method according to claim 11, wherein the alumina carrier is a γ-alumina carrier, and based on the alumina carrier, the first catalyst has a platinum content of 0.1-1.0 mass%, a tin content of 0.1-1.0 mass%, a potassium content of 0.02-0.1 mass%, and a chlorine content of 0.5-1.5 mass%.

13. The method according to claim 1, wherein the reaction conditions of step 1) include: The reaction temperature is 400-500°C, the reaction pressure is 0.1-4.0MPa, and the C9 + The mass space velocity of the paraffin raw material is 1-50h -1 , the hydrogen / hydrocarbon molar ratio is 0.5-20:

1.

14. The method according to claim 1, wherein the reaction conditions of step 1) include: The reaction temperature is 450-480°C, the reaction pressure is 0.1-2.0MPa, and the C9 + The mass space velocity of the paraffin raw material is 1-20h -1 , the hydrogen / hydrocarbon molar ratio is 1-10:

1.

15. The method according to claim 1, wherein the reaction conditions of step 3) include: The temperature is 450-480℃, the pressure is 0.1-2.0MPa, and the mass space velocity of the raw material is 1-10h -1 , the hydrogen / hydrocarbon molar ratio is 1-10:

1.

16. The method according to claim 1, wherein the mass ratio of the first catalyst used in step 1) to the second catalyst used in step 3) is 1:(0.25-5).

17. The method according to claim 16, wherein the mass ratio of the first catalyst to the second catalyst used in step 3) is 1:(1.2-3).

18. The method according to claim 1, wherein the C9 + The raw material for paraffins is naphtha.

19. The method according to claim 18, wherein the naphtha is selected from straight run naphtha, hydrocracked heavy naphtha, hydrogenated coker gasoline, ethylene pyrolysis gasoline raffinate, catalytic cracking gasoline or a mixture thereof.

20. The method according to claim 18, wherein the naphtha comprises cycloalkanes with a carbon number of 6-12, paraffins with a carbon number of 6-12 and aromatics with a carbon number of 6-12, an initial distillation point of 80-95°C, and a final distillation point of 135-180°C.

21. The method according to any one of claims 18 to 20, further comprising the step of subjecting the naphtha to hydrofining treatment before step 1) to remove arsenic, lead, copper, sulfur and nitrogen impurities contained therein.

22. The method according to claim 1, wherein the C9 + C9 of paraffinic raw materials + The paraffin content is 10% by mass or more.

23. The method according to claim 22, wherein the C9 + C9 of paraffinic raw materials + The paraffin content is 20% by mass or more.

24. The method according to claim 23, wherein the C9 + C9 of paraffinic raw materials + The paraffin content is 30% by mass or more.

25. The method according to any one of claims 18 to 20, wherein the reaction in step 1) is controlled so that the conversion rate of cycloalkanes in the naphtha is not less than 90% by mass, C9 + The conversion rate of paraffins is 70-95% by mass.

26. The method according to any one of claims 18 to 20, wherein the reaction in step 1) is controlled so that the conversion rate of cycloalkanes in the naphtha is not less than 90% by mass, wherein the conversion rates of both C7 and C8 cycloalkanes are not less than 95% by mass, and the conversion rate of C6 cycloalkanes is not less than 70% by mass.

27. The method according to any one of claims 18 to 20, wherein the reaction in step 1) is controlled so that the conversion rate of the paraffins in the naphtha is not more than 60% by mass, wherein the conversion rate of C6 paraffins is not more than 18% by mass, the conversion rate of C7 paraffins is not more than 30% by mass, the conversion rate of C8 paraffins is not more than 70% by mass, and the conversion rate of C9 paraffins is not more than 10% by mass. + The conversion rate of paraffins is 70-95% by mass.

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